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M H Navarrete

Publications and source records attributed to M H Navarrete.

26 records · Page 2Linked to original sources
PubMed1981

Protein synthesis during the onset of cell proliferation in root meristems.

Dormant meristems of Allium cepa L. root begin to sprout as soon as the water and temperature conditions are right. These cell systems offer many advantages when studying the earliest metabolic events related with the onset of the cell proliferating activity. By electrophoresis in SDS polyacrylamide gels the soluble protein fraction from meristems with increasing imbibition times was analysed. There are qualitative constancy and quantitative differences between electrophoretic patterns from dormancy to steady state conditions. It is suggested that polypeptide 8a, approximately 80,000 daltons in molecular weight, be considered an indicator of proliferative activity in the meristem.

Cell Division↗
PubMed1981

Soluble polypeptides from root meristems growing at different temperatures.

Soluble polypeptides and their biosynthesis rate have been studied in root meristems of Allium cepa L. bulbs by electrophoresis in SDS polyacrylamide gels. The second mm of the root was chosen in all cases. The polypeptide composition of root meristems growing with a steady state kinetics at 15 degrees C and 25 degrees C appears to be roughly constant. The quantitative differences observed may be due to the different proportion of proliferative cells in the root segments studied, being higher at 15 degrees C than at 25 degrees C. One important fact is the existence of a polypeptide, approximately 80,000 daltons in molecular weight, which appears as an indicator of active proliferation in onion root cells.

Electrophoresis, Polyacrylamide Gel↗
PubMed1979

Dynamics of the nuclear envelope during cell cycle in plants.

Stereology of Allium cepa root meristem cells was done to evaluate changes in the nuclear envelope during cell cycle. A naturally synchronous population was labelled as binucleate by caffeine inhibition of cytokinesis. Growth of the nuclear envelope preferentially occurs from mid G2 to the next mid G1, most probably in relation to the reforming sister nuclei after mitosis. On the other hand, the number of nuclear pores doubles from mid G1 to mid G2, their growth rate being higher in the first half of interphase (from mid G1 to mid S). Hence, the new nuclear envelope probably lacks nuclear pores, which appear later.

Cell Cycle↗
PubMed1978

Compartmentalizing the S period.

In order to increase the resolution of interphase analysis we have developed a method which is an alternative to cytofluometric techniques for tissues where cell flow is not applicable. The method combines the estimation of cell frequency in G1, S, G2 and mitosis after a 3H-thymidine pulse with the grouping of interphase cells according to their DNA content, as estimated by cytophotometry in Feulgen stained nuclei. By superimposing both sets of data we get three different artificial compartments within the S period. As a biological test of the resolution reached, the method readily confirmed that hydroxyurea, after one cycle time, accumulates cycling cells of Allium cepa L. root meristems in early S.

Cell Compartmentation↗