Developing sea urchin eggs (Strongylocentrotus purpuratus),
reared at 15° C, were subjected to single 15-minute treatments with
disodium versenate in calcium-free sea water, applied at 10-minute
intervals, from 4 minutes after insemination to the second cleavage.
These versene pulses produced specific degrees of retardation in
the mitotic process and delayed...
The spermiogenesis of Mytilus edulis (a marine mussel) has
been studied, employing techniques of light and electron microscopy
and cytochemical preparations. The observations trace the development
of the acrosomal complex, the nucleus, the mitochondrial
middle-piece, and the flagellum.
In early spermatids numerous membrane-bounded proacrosomal
vesicles arise from several Golgi complexes...
In the rat thymus, four stages of development have been distinguished:
(1) a newborn stage (Stage I), (2) an accelerated growth
stage (Stage II), (3) an involuting stage (Stage III), and (4) an involuted
stage (Stage IV) . There were three major types of thymic
lymphoid cells: small (STL), medium...
The present study was undertaken to determine, by measurement
of nuclear DNA, the degrees and frequencies of ploidy in the
last larval instar of the moth Galleria mellonella Linnaeus. While
such data have been amassed for a wide variety of vertebrate tissues,
few studies have been concerned with invertebrates and...
(Brandt) were surveyed for the presence of polyploid cells.
Large polyploid cells were found in the hepatic cecum, gut
and sheath of the testis.
The relative DNA content of the polyploid nuclei was
measured by means of two wavelength cytophotometry. Histograms
plotted from the data provide information on the level...