Biomedical subjects

P Mali

Publications and source records attributed to P Mali.

23 records · Page 2Linked to original sources

PubMed1988

Localization of protamine 1 mRNA in different stages of the cycle of the rat seminiferous epithelium.

A mouse protamine 1 cDNA probe was used to study P1 protamine gene expression during the cycle of the seminiferous epithelium in the rat. In situ hybridization experiments showed that transcription of the P1 protamine mRNA starts in the middle of step 7 of spermiogenesis during substage VIIc. The mRNA levels stay high in steps 7-14 spermatids but decrease during steps 15-16 and are virtually undetectable in steps 17-19 spermatids. Northern blot analyses of RNAs isolated from microdissected pools of seminiferous tubules show high P1 protamine mRNA concentrations during stages VIIc-XIV-III of the cycle and lower levels during stages IV-VIIb. Owing to a post-transcriptional shortening of the poly(A) tail by 130 bases, a decrease in the size of protamine 1 mRNA from approximately 580 to 450 nucleotides was observed in stages XIII-XIV suggesting an initiation of protamine 1 synthesis in step 13-14 spermatids. In stages II-VI (steps 16-18 spermatids), only the smaller size protamine 1 mRNA was detectable. The expression of protamine 1 mRNAs has been localized in the very last phase of the haploid gene activity. Although the in situ hybridization suggests a disappearance of protamine 1 mRNA after step 16 of spermiogenesis, Northern blot analysis shows that low levels of mRNA are present during the period of final condensation of the chromatin, reflecting the association of protamine with DNA.

Animals↗

PubMed1988

Expression of a testis-specific hsp70 gene-related RNA in defined stages of rat seminiferous epithelium.

Changes in the level of a testis-specific hsp70 gene-related transcript (hst70 RNA) and its cellular localization during the cycle of rat seminiferous epithelium have been investigated. Segments of seminiferous tubules at defined stages of the cycle were isolated in living condition by transillumination-assisted microdissection and the exact stages identified by phase-contrast microscopy of live cell squashes. The levels of the hst70 RNA were determined by Northern and slot blotting of whole cell lysates. High levels were found in stages XII-XIV and I to early VII of the cycle, and low levels were found in other stages, i.e., late VII (VIId) through VIII-XI of the cycle. The in situ hybridization revealed that the hst70 gene was activated in late pachytene primary spermatocytes during stage XII of the cycle, and that mRNA was then present in cells during differentiation through diakinesis, meiotic divisions, and early spermiogenesis (steps 1 through early 7). The activation of the gene coding for hst70 RNA shortly before meiotic divisions may indicate that the gene product is needed either during differentiation of late spermatocytes into spermatids or later during spermiogenesis, and that the mRNA may be stored in early spermatids.

Animals↗

PubMed1986

Rat spermatogenesis in vitro traced by quantitative flow cytometry.

In vitro differentiation of germ cells in rat seminiferous tubule segments at stages II-III of the epithelial cycle was studied. DNA flow cytometry was used for quantitation of absolute cell numbers from the cultured tubule segments that were compared to freshly isolated stages of the cycle, as identified by transillumination stereomicroscopy of the seminiferous tubules and phase-contrast microscopy of live cell squashes. Spermatogonia and spermatocytes from stages II-III showed normal morphological differentiation during 7 days in vitro. Round spermatids differentiated to Step 7 of spermiogenesis but Step 16 spermatids failed to develop. Acid phosphatase activity in the spermatogenic cells changed normally during the culture. As compared with freshly isolated control tubule segments, 35% of round spermatids and 42% of pachytene spermatocytes were present in culture after 7 days. The cell numbers recovered from defined stages by DNA flow cytometry were close to those found in morphometric studies. Flow cytometry is an efficient quantitation method for cells liberated from seminiferous epithelium. Spermatogonia, spermatocytes, and early spermatids are able to differentiate in vitro, but spermatids approaching the elongation (acrosome) phase, and particularly the maturation phase, fail to differentiate under present culture conditions.

Acid Phosphatase↗

PubMed1986

Cell interactions in the rat seminiferous epithelium with special reference to the cellular distribution of calmodulin.

Spermatogenesis is dependent on stimulation by pituitary gonadotropins, FSH and LH. Targets for these hormones are Sertoli and Leydig cells, respectively. The effect of LH on spermatogenesis is mediated by testosterone. In addition to hormones, interactions between neighbouring cells seem to regulate spermatogenesis. This is reflected by cyclic secretion of several proteins by the seminiferous epithelium, of which plasminogen activator is a good example. While it is controlled by FSH a factor in preleptotene spermatocytes may also influence its cyclic secretion pattern. Both testosterone and FSH have a cyclic action in the seminiferous epithelium. The androgens seem to predominate in stages where spermiation, onset of meiosis and the highest rate of RNA transcription occur (VII-XI). FSH is most active in stages that contain meiotic divisions and early spermiogenesis (XIII-V), greatly stimulating the production of cyclic AMP. To investigate further the "second messengers" of FSH action in the seminiferous epithelium, the cellular distribution of calmodulin was analyzed using an indirect immunocytochemical method. In addition to their clear cyclic distribution in primary spermatocytes and in spermatids, Sertoli cells also showed a bright calmodulin immunofluorescence that was apparently cyclic. These observations suggest a local calmodulin and calcium regulation of spermatogenesis.

Androgens↗

PubMedDate not supplied

Vimentin expression in spermatogenic and Sertoli cells is stage-related in rat seminiferous epithelium.

Monoclonal and polyclonal antibodies were used in indirect immunofluorescence microscopy to localize vimentin intermediate filaments in the rat seminiferous epithelium. During stages XII-V of the epithelial cycle, the Sertoli cells showed a reaction in the perinuclear area and vimentin-positive extensions, projecting toward the developing spermatid bundles, were also seen. During stages VI-XI these extensions were small and narrow. Monoclonal antibody to vimentin gave a granular reaction in the peripheral region of the flagella of steps 16-19 spermatids. Western blotting indicated a specific reaction with a Mr 58,000 polypeptide in isolated seminiferous tubules and in epididymal spermatozoa. Our results suggest that vimentin filaments in Sertoli cells may be regulated cyclically in a stage-dependent manner. The granular reaction in the spermatid flagellum with the monoclonal antibody suggests that vimentin in germ cells is organized differently from that in somatic Sertoli cells.

Animals↗