The authors thank members of the Shapiro lab and Erin Schrader for comments on the manuscript. The authors acknowledge financial support from: NIH postdoctoral fellowship F32 GM100732 to JMS and NIH grants R01 GM51426 and R01 GM32506 to LS.

1. Groß Synchrony - Optimal für Western Blot, Microarray / RNA-Seq und Sonstiges Material Intensive Tests <ol><li> Von einem Gefrierschrank Lager oder eine Platte, wachsen einem 5 ml O / N-Kultur des Stammes NA1000 durch Schütteln bei 28 ° C in PYE Medium. </li><li> Beimpfen von 0,5 ml der Zellen aus Schritt 1 in 25 ml M2G (Tabellen 1-2) und schüttelt bei 28 ° C, bis die Kultur eine OD 600 zwischen 0,5 und 0,6 erreicht. </li><li> Impfen Sie die Zellen in 1 l M2G und schütteln bei 28 ° C. </li><li> Sobald OD 600 erreicht 0,5 bis 0,6, bestätigen das Vorhandensein von Zellen mit Hilfe swarmer montiert flüssigen Phase Mikroskopie. Spot 1 ul der Zellen auf einen Objektträger, Deckel mit einem Deckglas und Bild durch Phasenmikroskopie. Bestätigen des Vorhandenseins von swarmer Zellen durch Visualisierung schneller schwimmen Zellen in der Population. </li><li> Spin-Zellen für 15 min bei 7 KXG bei 4 ° C in einem JA-10-Rotor. </li><li> Überstand verwerfen und fügen Sie 180 ml kaltes M2 (Tabellen 1-2) und sanft resuspend alle Zellen mit einer serologischen Pipette. Entsorgen Sie lose pelletierten Zellen; sie sind predivisional und stolzierte Zellen. </li><li> 60 ml kalte Kolloidales Siliciumdioxid-Lösung (unbedingt die Kolloidales Siliciumdioxid-Suspension auch vor der Zugabe zu den Zellen mischen) und mischen Sie die Zellsuspension gut. </li><li> Gießen Sie die Zellsuspension in acht 30-ml-Röhrchen und Spin für 30 min bei 6,4 KXG bei 4 ° C in einem JA-20 Rotor. HINWEIS: Man sollte zwei verschiedenen Bands zu sehen; die swarmer Band ist das untere Band während stolzierte / predivisional Zellen sind in der Top-Band (Abbildung 1B). </li><li> Die Top-Band vorsichtig absaugen und entfernen Sie die Flüssigkeit auf ca. 1 cm über dem swarmer Band (das untere Band). </li><li> (Kritisch) Mit einer Pasteur-Pipette, entfernen Sie vorsichtig die swarmer Band aufnehmen und in ein sauberes Röhrchen. Abzuwaschen Kolloidales Siliciumdioxid, oben das Rohr mit kaltem M2 und Schleudern für 10 min bei 6,4 KXG bei 4 ° C in einem JA-20-Rotor. </li><li> Vorsichtig den Überstand verwerfen und Resuspendieren derZellen in 20 ml kaltem M2 und Schleudern für 10 min bei 6,4 KXG bei 4 ° C in einem JA-20-Rotor. </li><li> Resuspendieren alle Pellets in 30 ml kaltem M2 und messen Sie die OD 600 mit einem Spektralphotometer und leere mit kaltem M2 Medium. Sparen Sie 1 ul für Phase-Bildgebung für swarmer Zellen überprüfen; 90-95% der Zellen sollten Schwärmer sein. </li><li> Anzentrifugieren die Zellen für 5 min bei 6,4 KXG bei 4 ° C in einem JA-20-Rotor. Zellen in 28 ° C M2G Medium, so dass der A 600 ist ~ 0,3-0,4 und beginnen bei 28 ° C schüttelnd. HINWEIS: Typische Ausbeuten zwischen 30 und 60 ml swarmer Zellkultur von 1L unsynchronisierten Zellen. </li><li> Fangen Sie an, Zeitpunkte (Wildtyp-Kultur wird in etwa 135 bis 140 Minuten in Anspruch nehmen zu teilen) 8,9. Zu jedem Zeitpunkt, messen Sie die OD 600. Prüfen, ob die OD 600 nach der Teilung ist ungefähr 2X die Anfangs-OD 600. </li><li> Für Western-Blot oder Genexpressionsassays entfernen 1 ml Aliquots der culture zu den gewünschten Zeitpunkten, Spin-down bei max Geschwindigkeit in einer Tischzentrifuge für 30 Sekunden, schnell Dekantieren des Mediums, und Flash Einfrieren des Zellpellets in flüssigem Stickstoff. Bewahren Sie die Zellen bei -80 ° C bis Downstream-Analyse. </li></ol> 2. Kleines Synchrony - Optimal für die Mikroskopie <ol><li> Von einem Gefrierschrank Lager oder eine Platte, wachsen ein 5 ml O / N-Kultur unter Schütteln bei 28 ° C im M2G. </li><li> Verdünnen Sie in 15 ml M2G (Tabellen 1-2) und wachsen, bis mid-log (OD 600 = 0,5-0,6). </li><li> Spin 6,4 KXG für 10 min bei 4 ° C in einem JA-20-Rotor und Resuspension in 1 ml kaltem M2 (Tabellen 1-2) und in ein 2 ml-Mikrozentrifugenröhrchen. </li><li> Spin bei 15 KXG für 3 min in ein Mikrozentrifugenröhrchen Zellen zu pelletieren, absaugen Überstand, legen Sie die Tablette auf Eis, und resuspendieren in 900 ul kaltem M2. </li><li> Hinzufügen 900 ul kaltem PVP beschichtet kolloidales Siliciumdioxid und Spin für 20 min bei 15 KXG bei 4 ° C in einem Mikrofonrocentrifuge Rohr. </li><li> (Critical) Verwerfen Sie pipettieren aus der Spitze marschierte / predivisional Zellband und sammeln Sie die unten swarmer Band in ein neues Mikrozentrifugenröhrchen. </li><li> Waschen der swarmer Zellen zwei Mal in 1 ml kaltem M2 während der Zentrifugation bei 15 KXG für 3 min. </li><li> Vor dem letzten Spin, verschieben Sie die Zellen in eine vorgekühlte 1 ml Reagenzglas und messen Sie die OD 600 der Zellen im Vergleich zu einem Rohling aus M2. </li><li> Resuspendieren die endgültige Zellpellet in 28 ° C M2G bei einer OD von 0,3 bis 0,4 und schütteln / Roll-Zellen bei 28 ° C. Anmerkung: Typische Ausbeuten liegen zwischen 2 und 4 ml swarmer Zellkultur. </li><li> Für die Mikroskopie Experimente, zum gewünschten Zeitpunkt Punkten Platz 1 ul der Zellen auf eine M2G Agarose-Pad für die Bildgebung. </li></ol>

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The authors have nothing to disclose.

The bacterial cell cycle is a fundamental process in life and is important for the study of growth and as a target for next generation antibiotics. Here, we detailed the rapid synchronization procedures for C. crescentus NA1000, a model organism for the study of the bacterial cell cycle and asymmetric cell division. This method is amendable to western blot, gene expression profiling, and fluorescence microscopy assays to investigate the spatiotemporal regulation of the bacterial cell cycle. 
The protocol is quick and yields healthy synchronized cells. Other synchronization methods require long starvation of cells and rely on the stringent response to arrest the cell cycle in the same state, leading to cells that are dissimilar to cultures in logarithmic growth 13. While &#8220;baby machines&#8221; and other surface attachment methods have been used successfully14,15, they typically have low yields of synchronized cells. The density centrifugation protocols presented here allow higher purity and yields of synchronized C. crescentus NA1000 swarmer cells.
Additional complications can lead to potential problems throughout the synchrony procedure. Have a liquid mount phase microscope handy to optically check the purity of cells before synchronization and to check the purity of swarmers. A good synchrony will yield >95% swarmer cells. Check the OD600 on a spectrophotometer to ensure the cells are doubling during the time course of the synchrony. 
Cells don&#8217;t synchronize as well in the presence of antibiotics or some mutations. If the strain does not carry a replicating plasmid, try to remove the antibiotics from the growth medium to improve swarmer cell yield. Cells grown in the presence of antibiotics or mutant strains will also have a slower cell cycle, so it is important to check the division time by microscopy for comparison to healthy strains. 
Avoid vortexing the cells, as this will shear off the flagella and lower the quality of the synchrony. In preparation for the synchrony protocol don&#8217;t grow the cells above OD600 0.5. This ensures healthy growth that isn&#8217;t altered by high cell density. Be careful when aspirating/pipetting off supernatants containing the stalked and predivisional cell populations. In particular, do not to touch the swarmer band which may lead to contamination and/or a loss in yield of the swarmer cells. The cell pellet will be very loose in the first wash of cells after removing them from the Colloidal silica. Be careful when removing the supernatant not to disrupt the pellet.
Occasionally NA1000 cells can lose synchronization capacity due to a loss of DNA in the prophage region of the genome 7. In this case, no swarmer band is observed or the swarmer band intensity is dramatically reduced. If possible, collect cells if present in the swarmer band and streak onto a PYE plate to re-isolate the synchronizable cells. If working with a mutant strain, it is often useful to reintroduce the mutation into a fresh batch of NA1000. Conversely, mutation of critical cell cycle regulatory proteins can, in some cases, disrupt the ability of cells to synchronize16.
M2G medium was initially described with a higher 20 mM phosphate concentration 8,17; however, current studies use a lower 10 mM concentration as presented in Table 1 18,19. Alternative to the standard M2G medium, it is possible to use richer PYE medium. Here the unsynchronized growth and growth after synchronization can be substituted for PYE.
C. crescentus NA1000 provides a valuable experimental tool to study the bacterial cell cycle. Additionally, due to the single copy of the chromosome in the swarmer cell, this bacterium has also become a powerful model to study the structure of the bacterial chromosome.

Die bakterielle Zellzyklus steuert sowohl die Replikation des Genoms und die Teilung der Tochterzellen. Wichtig ist, wie Antibiotika-Resistenz ist eine wachsende Bedrohung der öffentlichen Gesundheit stellt der bakteriellen Zellzyklus eine ungenutzte Ziel für Antibiotika-Entwicklung. In dem Bakterium Caulobacter crescentus, führt jede Zellzyklus in einer asymmetrischen Teilung, wodurch zwei Tochterzellen unterschiedlicher Schicksal (1A) 1,2. Eine Tochterzelle erbt eine Geißel und ist beweglich, während die andere Tochter erbt einen Stiel und sitzend. Eine integrierte genetische Schaltung steuert Zellzyklus und Zellschicksal von Transkriptionsregulation, Phospho-Signalisierung und regulierte Proteolyse 3. Zusätzlich Chromosomenreplikation und gleichzeitige Trennung Ausbeute Tochterzellen, die genau eine Kopie des Chromosoms 4 enthalten. Wichtig ist, dass diese beiden Zelltypen schnell durch collo getrennt werdenidal Silicateilchen Dichtezentrifugation im synchronisierbar NA1000 Stamm 5-7 ermöglicht die Isolierung der swarmer Zellen aus dem Rest der Population mit hohen Ausbeuten (1B). Isoliert swarmer Zellen dann synchron gehen durch asymmetrische Zellteilung. Hier haben wir ausführlich das Protokoll für die Synchronisierung von Caulobacter Belastung NA1000. Wir bieten Protokolle und gemeinsame Tipps zur Fehlerbehebung für Klein- und angelegte Synchronisationen. Das experimentelle Verfahren bietet ein leistungsfähiges Werkzeug, um die räumlich-zeitliche Kontrolle der Caulobacter Zellzyklus und Zellschicksal zu verhören.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Name of Material/ Equipment</td>
			<td style="width:71px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td style="width:167px;">Comments/Description</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">PVP Coated Colloidal Silica (Percoll)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">P4937</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Colloidal Silica (Ludox AS-40)</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">420840</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">JA10 Rotor</td>
			<td style="width:71px;">Beckman-Coulter</td>
			<td style="width:119px;">369687</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">JA20 Rotor</td>
			<td style="width:71px;">Beckman-Coulter</td>
			<td style="width:119px;">334831</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Ferrous Sulfate Chelate Solution</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td>F0518</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">30 mL Centrifuge Tubes</td>
			<td style="width:71px;">Corning</td>
			<td style="width:119px;">8445</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">Na2HPO4</td>
			<td style="width:71px;">EMD</td>
			<td style="width:119px;">SX0720-1</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">KH2PO4</td>
			<td style="width:71px;">VWR</td>
			<td style="width:119px;">BDH9268-500G</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:216px;">NH4Cl</td>
			<td style="width:71px;">Amresco</td>
			<td style="width:119px;">0621-500g</td>
			<td></td>
		</tr>
	</tbody>
</table>

synchronization of caulobacter crescentus for investigation of the bacterial cell cycle

The cell cycle is important for growth, genome replication, and development in all cells. In bacteria, studies of the cell cycle have focused largely on unsynchronized cells making it difficult to order the temporal events required for cell cycle progression, genome replication, and division. Caulobacter crescentus provides an excellent model system for the bacterial cell cycle whereby cells can be rapidly synchronized in a G0 state by density centrifugation. Cell cycle synchronization experiments have been used to establish the molecular events governing chromosome replication and segregation, to map a genetic regulatory network controlling cell cycle progression, and to identify the establishment of polar signaling complexes required for asymmetric cell division. Here we provide a detailed protocol for the rapid synchronization of Caulobacter NA1000 cells. Synchronization can be performed in a large-scale format for gene expression profiling and western blot assays, as well as a small-scale format for microscopy or FACS assays. The rapid synchronizability and high cell yields of Caulobacter make this organism a powerful model system for studies of the bacterial cell cycle.

Synchronisations ergibt typischerweise zwei Banden von Zellen (1B): der swarmer Band, das eine höhere Dichte hat, und eine gestielte / predivisional Zellenband mit geringerer Dichte. Um sicherzustellen, dass effiziente Synchronisation gemeinsame Kontrollen umfassen die Überwachung der OD 600 und Messung der Konzentrationen von Ctra Protein durch Western-Blot auf verschiedene Zellzykluszeitpunkten. Die OD 600 sollte um etwa 2-fach im Verlauf des Zellzyklus (Figur 2) zu erhöhen. Die Western-Blot für die Zellzyklushauptregulator Ctra ist eine sinnvolle Kontrolle, um eine gute Synchronität (Abbildung 2) zu überprüfen. Ctra im swarmer Zelle verwendet, um die DNA-Replikation zu blockieren und ist beim Einsetzen der DNA-Replikation 10 abgebaut. Ctra wird dann später in den Zellzyklus synthetisiert und aktiviert die Transkription einer Reihe von Entwicklungsgenen, einschließlich vieler Komponenten des Flagellums 11,12. Eine erfolgreiche Synchronisation wird tseine oszillierende Muster der Ctra Protein-Ebene. <img alt="Abbildung 1" src="/files/ftp_upload/52633/52633fig1.jpg" /> Abbildung 1. Der Zellzyklus von Caulobacter crescentus. (A) Eine Karikatur Schema des swarmer Zellzyklus. Die swarmer Zellen differenzieren sich in replikationskompetentem stolzierte Zellen durch Zurückziehen Pili, Auswerfen Geißeln und Initiierung der DNA-Replikation. Die Kreise und Theta im Inneren der Zelle Umrissen gezeigten Strukturen darstellen Ruhe und Replikation von Chromosomen. Zellen dann durch den Zellzyklus ein einheitliches, Geißel an der Stange gegenüber dem Stiel Fortschritt. Bei der Division, zwei einzigartige Zelltypen erzeugt werden, blockiert ein Replikations beweglichen swarmer Zelle und einer replikationskompetentem stationären stolzierte Zelle. (B) Repräsentative Ergebnisse für Dichtezentrifugation. Geringere Dichte gestielt und Predivisional Zellen schwimmen in der Nähe der Spitze des Gradienten, während dichte swarmer Zellen am Ende in Richtung der Unterseite des Rohres. Maßstabsbalken sind 1 &amp; mgr; m in der Phase-Mikroskopie-Aufnahmen. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52633/52633fig1large.jpg" target="_blank">Bitte klicken Sie hier, um eine größere Version dieses Bild anzuzeigen.</a> <img alt="Abbildung 2" src="/files/ftp_upload/52633/52633fig2.jpg" /> Abbildung 2. Repräsentative Ergebnisse für eine erfolgreiche swarmer Zelle synchron. Die Zellmasse durch OD 600 gemessen, sollte langsam zunehmen und schließlich im Verlauf des Assays zu verdoppeln. 1 ml Aliquots wurden in Kunststoffküvetten aus einer großen Zelle Synchronität und die OD 600 gemessen mit einem Spektrophotometer bei den angegebenen Zeitpunkten pipettiert. Zusätzlich sollte das Ctra Zellzyklusmaster regulatorisches Protein in der swarmer Zelle vorhanden sein, um die DNA-Replikation, gefolgt von einem schnellen Abbau blockierenübereinstimmend mit der Initiation der DNA-Replikation. Ctra wird dann später in den Zellzyklus regeneriert werden, um die Expression vieler Entwicklungsgenen, einschließlich kritischer Flagella und Pili Komponenten zu aktivieren. Western-Blots für die Zellzyklus-Regulatorprotein Master Ctra wurden hergestellt, indem 1 ml Aliquots einer großen Gleichtakt durchgeführt. Die Zellen wurden in 250 ul Probenpuffer Laemmlli pro OD 600 resuspendiert, auf einem 10% Tris-Gly-PAGE, auf PVDF übertragen getrennt und mit Anti-Ctra Antikörper geblottet. Fehlgeschlagen Synchronität Verfahren führen zu Ctra Western Blots ohne Veränderung der Protein-Ebene. α-Ctra Antikörper 12 wurde bei einer 1: 10.000-Verdünnung für 1,5 h in 3% Milch TBST und 3-mal gewaschen, in TBST. Goat-α-Kaninchen-Sekundär wurde dann bei 1 hinzugefügt: 10.000 Verdünnung in 3% Milch TBST 1 Stunde, 3 mal mit TBST gewaschen und auf Film aufgenommen mit einer Chemilumineszenznachweis Kit. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52633/52633fig2large.jpg" target="_blank">Bitte</a>Klicken Sie hier, um eine größere Version dieser Figur zu sehen. <table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td> Na 2 HPO 4 </td><td> 17,4 g </td></tr><tr><td> KH 2 PO 4 </td><td> 10,6 g </td></tr><tr><td> NH 4 Cl </td><td> 10 g </td></tr><tr><td> H 2 O </td><td> Resuspendieren in 1 L &amp; Autoklav </td></tr></tbody></table> Tabelle 1 20X M2 Salze Rezept. <table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td> 20X M2 Salze </td><td> 50 ml </td><td></td></tr><tr><td> 0,5 M MgSO 4 </td><td> 1 ml </td><td></td></tr><tr><td> 20% Glucose </td><td> 10 ml </td><td> Ersatz für H 2 O in M2 </td></tr><tr><td> Eisensulfat Chelatlösung </td><td> 1 ml </td><td></td></tr><tr><td> 0,1 M CaCl &amp; sub2; </td><td> 5 ml </td><td> In letzter avoid Niederschlag </td></tr><tr><td> H 2 O </td><td> Füllen Sie bis zu 1 L </td><td></td></tr><tr><td> Sterilfilter mit 0,22 &amp; mgr; </td><td></td><td></td></tr></tbody></table> Tabelle 2. M2 und M2G Rezept.

Watch this Scientific Journal Video about Synchronization of Caulobacter Crescentus for Investigation of the Bacterial Cell Cycle at JoVE.com

Synchronization of Caulobacter Crescentus for Investigation of the Bacterial Cell Cycle

Synchronization of bacterial cells is essential for studies of the bacterial cell cycle and development. Caulobacter crescentus is synchronizable through density centrifugation allowing a rapid and powerful tool for studies of the bacterial cell cycle. Here we provide a detailed protocol for the synchronization of Caulobacter cells.

Synchronisation<em&gt; Caulobacter crescentus</em&gt; Für die Untersuchung der Bakterienzellzyklus

The cell cycle is important for growth, genome replication, and development in all cells.  In bacteria, studies of the cell cycle have focused largely on ...

synchronization-caulobacter-crescentus-for-investigation-bacterial

Nanyang Technological University

Research

JoVE Journal

Biology

Synchronization of Caulobacter Crescentus for Investigation of the Bacterial Cell Cycle

11.8K Aufrufe.  Stanford University School of Medicine. Synchronization of bacterial cells is essential for studies of the bacterial cell cycle and development. Caulobacter crescentus is synchronizable through density centrifugation allowing a rapid and powerful tool for studies of the bacterial cell cycle. Here we provide a detailed protocol for the synchronization of Caulobacter cells.

Serie: Synchronization of Caulobacter Crescentus for Investigation of the Bacterial Cell Cycle

Electroporation of Mycobacteria

High efficiency transformation is a major limitation in the study of mycobacteria. The genus Mycobacterium can be difficult to transform; this is mainly caused by the thick and waxy cell wall, but is compounded by the fact that most molecular techniques have been developed for distantly-related species such as Escherichia coli and Bacillus subtilis. In spite of these obstacles, mycobacterial plasmids have been identified and DNA transformation of many mycobacterial species have now been described. The most successful method for introducing DNA into mycobacteria is electroporation. Many parameters contribute to successful transformation; these include the species/strain, the nature of the transforming DNA, the selectable marker used, the growth medium, and the  conditions for the electroporation pulse. Optimized methods for the transformation of both slow- and fast-grower are detailed here. Transformation efficiencies for different mycobacterial species and with various selectable markers are reported.

Mycobacterial pathogenic strategies remain poorly understood. The slow growth rate of most species, the impenetrable nature of the cell-wall, and the hazards of working with pathogens make mycobacteria difficult to study and are largely responsible for our poor understanding of these organisms. In this video we will demonstrate the technique of electroporation, which involves subjecting cells to a brief high electrical impulse to allow the entry of DNA. It is the most widely used method for introducing DNA into mycobacterial cells.

Elektroporation von Mykobakterien

High efficiency transformation is a major limitation in the study of mycobacteria. The genus Mycobacterium can be difficult to transform; this is mainly ...

Forschung

Biologie

Monitoring Kinase and Phosphatase Activities Through the Cell Cycle by Ratiometric FRET

F&ouml;rster resonance energy transfer (FRET)-based reporters1 allow the assessment of endogenous kinase and phosphatase activities in living cells. Such probes typically consist of variants of CFP and YFP, intervened by a phosphorylatable sequence and a phospho-binding domain. Upon phosphorylation, the probe changes conformation, which results in a change of the distance or orientation between CFP and YFP, leading to a change in FRET efficiency (Fig 1). Several probes have been published during the last decade, monitoring the activity balance of multiple kinases and phosphatases, including reporters of PKA2, PKB3, PKC4, PKD5, ERK6, JNK7, Cdk18, Aurora B9 and Plk19. Given the modular design, additional probes are likely to emerge in the near future10. 
Progression through the cell cycle is affected by stress signaling pathways 11. Notably, the cell cycle is regulated differently during unperturbed growth compared to when cells are recovering from stress12.Time-lapse imaging of cells through the cell cycle therefore requires particular caution. This becomes a problem particularly when employing ratiometric imaging, since two images with a high signal to noise ratio are required to correctly interpret the results. Ratiometric FRET imaging of cell cycle dependent changes in kinase and phosphatase activities has predominately been restricted to sub-sections of the cell cycle8,9,13,14.
Here, we discuss a method to monitor FRET-based probes using ratiometric imaging throughout the human cell cycle. The method relies on equipment that is available to many researchers in life sciences and does not require expert knowledge of microscopy or image processing.

FRET-based reporters are increasingly used to monitor kinase and phosphatase activities in live cells. Here we describe a method on how to use FRET-based reporters to assess cell cycle-dependent changes in target phosphorylation.

Überwachung Kinase und Phosphatase-Aktivitäten durch den Zellzyklus durch Ratiometric FRET

F&ouml;rster resonance energy transfer (FRET)-based reporters1 allow the assessment of endogenous kinase and phosphatase activities in living cells. Such ...

Analysis of Cell Cycle Position in Mammalian Cells

The regulation of cell proliferation is central to tissue morphogenesis during the development of multicellular organisms. Furthermore, loss of control of cell proliferation underlies the pathology of diseases like cancer. As such there is great need to be able to investigate cell proliferation and quantitate the proportion of cells in each phase of the cell cycle. It is also of vital importance to indistinguishably identify cells that are replicating their DNA within a larger population. Since a cell&prime;s decision to proliferate is made in the G1 phase immediately before initiating DNA synthesis and progressing through the rest of the cell cycle, detection of DNA synthesis at this stage allows for an unambiguous determination of the status of growth regulation in cell culture experiments.
DNA content in cells can be readily quantitated by flow cytometry of cells stained with propidium iodide, a fluorescent DNA intercalating dye. Similarly, active DNA synthesis can be quantitated by culturing cells in the presence of radioactive thymidine, harvesting the cells, and measuring the incorporation of radioactivity into an acid insoluble fraction. We have considerable expertise with cell cycle analysis and recommend a different approach. We Investigate cell proliferation using bromodeoxyuridine/fluorodeoxyuridine (abbreviated simply as BrdU) staining that detects the incorporation of these thymine analogs into recently synthesized DNA. Labeling and staining cells with BrdU, combined with total DNA staining by propidium iodide and analysis by flow cytometry1 offers the most accurate measure of cells in the various stages of the cell cycle. It is our preferred method because it combines the detection of active DNA synthesis, through antibody based staining of BrdU, with total DNA content from propidium iodide. This allows for the clear separation of cells in G1 from early S phase, or late S phase from G2/M. Furthermore, this approach can be utilized to investigate the effects of many different cell stimuli and pharmacologic agents on the regulation of progression through these different cell cycle phases.
In this report we describe methods for labeling and staining cultured cells, as well as their analysis by flow cytometry. We also include experimental examples of how this method can be used to measure the effects of growth inhibiting signals from cytokines such as TGF-&beta;1, and proliferative inhibitors such as the cyclin dependent kinase inhibitor, p27KIP1. We also include an alternate protocol that allows for the analysis of cell cycle position in a sub-population of cells within a larger culture5. In this case, we demonstrate how to detect a cell cycle arrest in cells transfected with the retinoblastoma gene even when greatly outnumbered by untransfected cells in the same culture. These examples illustrate the many ways that DNA staining and flow cytometry can be utilized and adapted to investigate fundamental questions of mammalian cell cycle control.

Determining the cell cycle position of a population of cells, or understanding how signals affect proliferation, can be readily measured by flow cytometry using this protocol. We report a simple experimental approach to staining cells and quantifying their position in the cell cycle.

Analyse des Zellzyklus Position in Säugerzellen

The regulation of cell proliferation is central to tissue morphogenesis during the development of multicellular organisms. Furthermore, loss of control of ...

The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity

The isolated microvessel preparation is an ex vivo preparation that allows for examination of the different contributions of factors that control vessel diameter, and thus, perfusion resistance1-5. This is a classic experimental preparation that was, in large measure, initially described by Uchida et al.15 several decades ago. This initial description provided the basis for the techniques that was extensively modified and enhanced, primarily in the laboratory of Dr. Brian Duling at the University of Virginia6-8, and we present a current approach in the following pages. This preparation will specifically refer to the gracilis arteriole in a rat as the microvessel of choice, but the basic preparation can readily be applied to vessels isolated from nearly any other tissue or organ across species9-13. Mechanical (i.e., dimensional) changes in the isolated microvessels can easily be evaluated in response to a broad array of physiological (e.g., hypoxia, intravascular pressure, or shear) or pharmacological challenges, and can provide insight into mechanistic elements comprising integrated responses in an intact, although ex vivo, tissue. The significance of this method is that it allows for facile manipulation of the influences on the integrated regulation of microvessel diameter, while also allowing for the control of many of the contributions from other sources, including intravascular pressure (myogenic), autonomic innervation, hemodynamic (e.g., shear stress), endothelial dependent or independent stimuli, hormonal, and parenchymal influences, to provide a partial list. Under appropriate experimental conditions and with appropriate goals, this can serve as an advantage over in vivo or in situ tissue/organ preparations, which do not readily allow for the facile control of broader systemic variables. 
The major limitation of this preparation is essentially the consequence of its strengths. By definition, the behavior of these vessels is being studied under conditions where many of the most significant contributors to the regulation of vascular resistance have been removed, including neural, humoral, metabolic, etc. As such, the investigator is cautioned to avoid over-interpretation and extrapolation of the data that are collected utilizing this preparation. The other significant area of concern with regard to this preparation is that it can be very easy to damage cellular components such as the endothelial lining or the vascular smooth muscle, such that variable source of error can be introduced. It is strongly recommended that the individual investigator utilize appropriate measurements to ensure the quality of the preparation, both at the initiation of the experiment and periodically throughout the course of a protocol.

The ex vivo Isolated Skeletal Microvessel Preparation for Investigation of Vascular Reactivity

An ex vivo preparation is described for isolation of the largest gracilis muscle resistance arterioles for interrogation of both vascular responses to vasoactive stimuli and the assessment of basic structural properties via passive wall mechanics.

Die Ex vivo Isoliert Skeletal Mikrogefäßdichte Vorbereitung für Untersuchung der vaskulären Reaktivität

The isolated  microvessel preparation is an ex vivo preparation that allows for examination of the different contributions of  factors that control vessel ...

Basic Caenorhabditis elegans Methods: Synchronization and Observation

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has since been used extensively as a model organism 1. C. elegans possesses key attributes such as simplicity, transparency and short life cycle that have made it a suitable experimental system for fundamental biological studies for many years 2. Discoveries in this nematode have broad implications because many cellular and molecular processes that control animal development are evolutionary conserved 3.
C. elegans life cycle goes through an embryonic stage and four larval stages before animals reach adulthood. Development can take 2 to 4 days depending on the temperature. In each of the stages several characteristic traits can be observed. The knowledge of its complete cell lineage 4,5 together with the deep annotation of its genome turn this nematode into a great model in fields as diverse as the neurobiology 6, aging 7,8, stem cell biology 9 and germ line biology 10. 
An additional feature that makes C. elegans an attractive model to work with is the possibility of obtaining populations of worms synchronized at a specific stage through a relatively easy protocol. The ease of maintaining and propagating this nematode added to the possibility of synchronization provide a powerful tool to obtain large amounts of worms, which can be used for a wide variety of small or high-throughput experiments such as RNAi screens, microarrays, massive sequencing, immunoblot or in situ hybridization, among others. 
Because of its transparency, C. elegans structures can be distinguished under the microscope using Differential Interference Contrast microscopy, also known as Nomarski microscopy. The use of a fluorescent DNA binder, DAPI (4',6-diamidino-2-phenylindole), for instance, can lead to the specific identification and localization of individual cells, as well as subcellular structures/defects associated to them.

Basic Caenorhabditis elegans Methods: Synchronization and Observation

The easiness of maintaining and propagating the nematode C. elegans make it a nice model organism to work with. The possibility of synchronizing worms allows the work with a significant amount of subjects at the same developmental stage, what facilitates the study of one particular process in many animals.

Grundlegende<em&gt; Caenorhabditis elegans</em&gt; Methoden: Synchronisation und Observation

Research into the molecular and developmental biology of the nematode Caenorhabditis elegans was begun in the early seventies by Sydney Brenner and it has ...

Temporal Tracking of Cell Cycle Progression Using Flow Cytometry without the Need for Synchronization

This protocol describes a method to permit the tracking of cells through the cell cycle without requiring the cells to be synchronized. Achieving cell synchronization can be difficult for many cell systems. Standard practice is to block cell cycle progression at a specific stage and then release the accumulated cells producing a wave of cells progressing through the cycle in unison. However, some cell types find this block toxic resulting in abnormal cell cycling, or even mass death. Bromodeoxyuridine (BrdU) uptake can be used to track the cell cycle stage of individual cells. Cells incorporate this synthetic thymidine analog, while synthesizing new DNA during S phase. By providing BrdU for a brief period it is possible to mark a pool of cells that were in S phase while the BrdU was present. These cells can then be tracked through the remainder of the cell cycle and into the next round of replication, permitting the duration of the cell cycle phases to be determined without the need to induce a potentially toxic cell cycle block. It is also possible to determine and correlate the expression of both internal and external proteins during subsequent stages of the cell cycle. These can be used to further refine the assignment of cell cycle stage or assess effects on other cellular functions such as checkpoint activation or cell death.

This protocol describes the use of bromodeoxyuridine (BrdU) uptake to permit the temporal tracking of cells that were in S phase at a specific point in time. Addition of DNA dyes and antibody labeling facilitates detailed analysis of the fate of the S phase cells at later times.

Zeitliche Verfolgung von Zellzyklus mittels Durchflusszytometrie, ohne die Notwendigkeit für die Synchronisation

This protocol describes a method to permit the tracking of cells through the cell cycle without requiring the cells to be synchronized. Achieving cell ...

Contractility Measurements on Isolated Papillary Muscles for the Investigation of Cardiac Inotropy in Mice

Papillary muscle isolated from adult mouse hearts can be used to study cardiac contractility during different physiological/pathological conditions. The contractile characteristics can be evaluated independently of external influences such as vascular tonus or neurohumoral status. It depicts a scientific approach between single cell measurements with isolated cardiac myocytes and in vivo studies like echocardiography. Thus, papillary muscle preparations serve as an excellent model to study cardiac physiology/pathophysiology and can be used for investigations like the modulation by pharmacological agents or the exploration of transgenic animal models. Here, we describe a method of isolating the murine left anterior papillary muscle to investigate cardiac contractility in an organ bath setup. In contrast to a muscle strip preparation isolated from the ventricular wall, the papillary muscle can be prepared in toto without damaging the muscle tissue severely. The organ bath setup consists of several temperature-controlled, gassed and electrode-equipped organ bath chambers. The isolated papillary muscle is fixed in the organ bath chamber and electrically stimulated. The evoked twitch force is recorded using a pressure transducer and parameters such as twitch force amplitude and twitch kinetics are analyzed. Different experimental protocols can be performed to investigate the calcium- and frequency-dependent contractility as well as dose-response curves of contractile agents such as catecholamines or other pharmaceuticals. Additionally, pathologic conditions like acute ischemia can be simulated.

Murine left ventricular papillary muscle can be used to investigate cardiac contractility in vitro. This article describes in detail the isolation and experimental protocols to study cardiac contractile characteristics.

Kontraktilität Messungen auf isolierte Papillarmuskeln für die Untersuchung von Herz Inotropie bei Mäusen

Papillary muscle isolated from adult mouse hearts can be used to study cardiac contractility during different physiological/pathological conditions. The ...

Efficient Mammalian Cell Expression and Single-step Purification of Extracellular Glycoproteins for Crystallization

Production of secreted mammalian proteins for structural and biophysical studies can be challenging, time intensive, and costly. Here described is a time and cost efficient protocol for secreted protein expression in mammalian cells and one step purification using nickel affinity chromatography. The system is based on large scale transient transfection of mammalian cells in suspension, which greatly decreases the time to produce protein, as it eliminates steps, such as developing expression viruses or generating stable expressing cell lines. This protocol utilizes cheap transfection agents, which can be easily made by simple chemical modification, or moderately priced transfection agents, which increase yield through increased transfection efficiency and decreased cytotoxicity. Careful monitoring and maintaining of media glucose levels increases protein yield. Controlling the maturation of native glycans at the expression step increases the final yield of properly folded and functional mammalian proteins, which are ideal properties to pursue X-ray crystallography. In some cases, single step purification produces protein of sufficient purity for crystallization, which is demonstrated here as an example case.

This is a quick, cost-efficient protocol for the production of secreted, glycosylated mammalian proteins and subsequent single-step purification with sufficient yields of homogenous protein for X-ray crystallography and other biophysical studies.

Effiziente Mammalian Cell Expression und Single-step Reinigung der extrazellulären Glykoproteinen für die Kristallisation

Production of secreted mammalian proteins for structural and biophysical studies can be challenging, time intensive, and costly. Here described is a time ...

Measurement of Survival Time in Brachionus Rotifers: Synchronization of Maternal Conditions

Rotifers are microscopic cosmopolitan zooplankton used as models in ecotoxicological and aging studies due to their several advantages such as short lifespan, ease of culture, and parthenogenesis that enables clonal culture. However, caution is required when measuring their survival time as it is affected by maternal age and maternal feeding conditions. Here we provide a protocol for powerful and reproducible measurement of the survival time in Brachionus rotifers following a careful synchronization of culture conditions over several generations. Empirically, poor synchronization results in early mortality and a gradual decrease in survival rate, thus resulting in weak statistical power. Indeed, under such conditions, calorie restriction (CR) failed to significantly extend the lifespan of B. plicatilis although CR-induced longevity has been demonstrated with well-synchronized rotifer samples in past and present studies. This protocol is probably useful for other invertebrate models, including the fruitfly Drosophila melanogaster and the nematode Caenorhabditis elegans, because maternal age effects have also been reported in these species.

Measurement of Survival Time in Brachionus Rotifers: Synchronization of Maternal Conditions

Rotifers are microscopic zooplankton used as models in ecotoxicological and aging studies. Here we provide a protocol for powerful and reproducible measurement of survival time in Brachionus rotifers. Synchronization of culture conditions over several generations is of particular importance because maternal condition affects life history of offspring.

Die Messung der Überlebensdauer in<em&gt; Brachionus</em&gt; Rotifers: Synchronisation von Maternal Bedingungen

Rotifers are microscopic cosmopolitan zooplankton used as models in ecotoxicological and aging studies due to their several advantages such as short ...

Combining Mitotic Cell Synchronization and High Resolution Confocal Microscopy to Study the Role of Multifunctional Cell Cycle Proteins During Mitosis

Study of the various regulatory events of the cell cycle in a phase-dependent manner provides a clear understanding about cell growth and division. The synchronization of cell populations at specific stages of the cell cycle has been found to be very useful in such experimental endeavors. Synchronization of cells by treatment with chemicals that are relatively less toxic can be advantageous over the use of pharmacological inhibitory drugs for the study of consequent cell cycle events and to obtain specific enrichment of selected mitotic stages. Here, we describe the protocol for synchronizing human cells at different stages of the cell cycle, including both in S phase and M phase with a double thymidine block and release procedure for studying the functionality of mitotic proteins in chromosome alignment and segregation. This protocol has been extremely useful for studying the mitotic roles of multifunctional proteins which possess established interphase functions. In our case, the mitotic role of Cdt1, a protein critical for replication origin licensing in G1 phase, can be studied effectively only when G2/M-specific Cdt1 can be depleted. We describe the detailed protocol for depletion of G2/M-specific Cdt1 using double thymidine synchronization. We also explain the protocol of cell fixation, and live cell imaging using high resolution confocal microscopy after thymidine release. The method is also useful for analyzing the function of mitotic proteins under both physiological and perturbed conditions such as for Hec1, a component of the Ndc80 complex, as it enables one to obtain large sample sizes of mitotic cells for fixed and live cell analysis as we show here.&#160;&#160;

We present a protocol for double thymidine synchronization of HeLa cells followed by analysis using high resolution confocal microscopy. This method is key to obtaining large number of cells that proceed synchronously from S phase to mitosis, enabling studies on mitotic roles of multifunctional proteins which also possess interphase functions.

Kombination von mitotische Zelle Synchronisation und hochauflösenden konfokalen Mikroskopie zur Untersuchung der Rolle von multifunktionalen Zelle Zyklus Proteine während der Mitose

Study of the various regulatory events of the cell cycle in a phase-dependent manner provides a clear understanding about cell growth and division. The ...