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M Parvinen

Publications and source records attributed to M Parvinen.

172 records · Page 10Linked to original sources
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RNA synthesis in different stages of rat seminiferous epithelial cycle.

In vitro RNA synthesis has been analyzed using autoradiographic and electrophoretic methods in isolated 1-2 mm segments of rat seminiferous tubules. The cellular composition of each segment was accurately identified using microscopic analysis of the transillumination pattern of the freshly isolated, unstained, seminiferous tubules combined with phase-contrast microscopy of the living spermatogenic cells. The RNA synthesized in the seminiferous tubules was found to be mostly heterogenous nuclear RNA (HnRNA), which appeared to have a long lifetime. It was most actively formed in the stages which contain mid-pachytene spermatocytes. Formation of rRNA was slow in all stages and it was first observed when a 2-h pulse with [3H]uridine was followed by a 6-h chase. A very low RNA synthetic rate was observed in the stage containing the meiotic reduction divisions. The function of the meiotic RNA in regulation of spermiogenesis is discussed.

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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.

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Superoxide dismutase activity along rat seminiferous epithelial wave: effects of ethane dimethanesulphonate and 3.0 Gy of X-irradiation.

Changes in generation of reactive oxygen species and antioxidant enzyme activities are associated with differentiation processes. The authors have studied the activity of superoxide dismutase (SOD) in sequentially cut stage-defined segments of rat seminiferous tubules. Great variation was observed in SOD activity along the seminiferous epithelial wave. At its highest, four-fold increases were observed in individual tubules. However, these changes showed no clear correlation to the stages of the cycle. To determine the effect of testosterone withdrawal, rats treated with ethane dimethanesulphonate (EDS) were studied. This treatment had no effect on the pattern of SOD activity along the seminiferous epithelial wave. Testes of other rats were exposed to local 3.0 Gy X-irradiation to cause selective loss of germ-cell populations. SOD activity in the seminiferous epithelium was not affected at 30 min or 7 d after X-irradiation. On day 31 post-irradiation, SOD activity increased at stages XIV-VI, peaking at stage III (P < 0.01 for comparison of stages XIV-VI with the other stages). The data presented here suggest that the activity of SOD in seminiferous epithelium is regulated over a wide range during spermatogenesis. Testosterone plays no major role in the control of seminiferous tubule SOD activity. The loss of spermatocytes and early spermatids by day 31 after X-irradiation revealed a stage-specific increase in SOD activity, which may be associated with the differentiation of elongated spermatids.

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Combined bleomycin treatment and radiation therapy in squamous cell carcinoma of the head and neck region.

Forty-six patients with squamous cell carcinoma of the head and neck region were randomized to either irradiation or irradiation plus bleomycin. If possible, the patients later underwent radical surgery. In the bleomycin group, significantly fewer patients had remaining tumour cells in the tissue removed at operation, and a longer time elapsed before recurrences occurred. However, bleomycin had no significant effect on the 3-and 5-year survival rates, and it did not significantly reduce the incidence of local recurrences.

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Basal and FSH-stimulated steady state levels of SGP-2, alpha 2-macroglobulin, and testibumin in culture media of rat seminiferous tubules at defined stages of the epithelial cycle.

Production of several proteins by rat Sertoli cells is dependent on the stage of the cycle of the seminiferous epithelium. The authors have determined steady state levels and follicle-stimulating hormone responsiveness of three Sertoli cell products in culture media of rat seminiferous tubule segments at different stages of the epithelial cycle: SGP-2 (sulfated glycoprotein-2), alpha 2-macroglobulin, and testibumin. Basal SGP-2 levels were twofold higher in stages VII through VIII compared with stages XIII to I to VI (P less than 0.05). Highest basal alpha 2-macroglobulin levels were found in stages II through VIII; this was about 35% greater than in stages XIII through I of the cycle (P less than 0.05). Basal testibumin levels were twofold higher in stages II through VI compared with stages IX through XII of the cycle. Follicle-stimulating hormone had no effect on SGP-2, but by contrast it (50 mg/L) increased the level of alpha 2-macroglobulin significantly (P less than 0.05) in stages XIII through I. Follicle-stimulating hormone treatment (10 mg/L) elevated testibumin levels at each stage-pool by about 40% (P less than 0.05). The current results using staged tubular segments in vitro demonstrate cyclic basal steady-state levels of the three proteins along the seminiferous tubules and follicle-stimulating hormone regulation of alpha 2-macroglobulin and testibumin.

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Cellular regulation of follicle-stimulating hormone (FSH) binding in rat seminiferous tubules.

Stage-specific binding of follicle-stimulating hormone (FSH) was measured in rat seminiferous tubules. The binding in single-point assays was over 3-fold higher (P less than 0.05) in stages XIII to I than in stages VI to VII of the epithelial cycle. No difference was found between the equilibrium association constants (Ka) of FSH binding in stages XIV to IV (10 +/- 1.9 X 10(9) 1/mol) and VII to VIII (9.2 +/- 0.6 X 10(9) 1/mol, mean +/- SEM, n = 5). In another experiment, the testes were dosed locally with 3 Gy of 4 MV x-irradiation to selectively lower the number of spermatogonia. After irradiation, FSH binding in staged seminiferous tubule segments was measured when the desired types of spermatogenic cells were reduced in number. Seven days after irradiation when differentiating spermatogonia and preleptotene spermatocytes were reduced in number, FSH binding was decreased in all stages of the cycle, but the cyclic variation remained. Seventeen days after irradiation when intermediate and type B spermatogonia and spermatocytes up to diplotene of stage XIII showed low numbers, FSH binding was decreased in all stages of the cycle and the stage-dependent variation disappeared. At 38 days when pachytene spermatocytes and early spermatids were reduced in number, similar results were found. But at 52 days postirradiation when all spermatids were low in number, FSH binding was slightly elevated compared with days 17 and 38. There were no significant differences in serum FSH or LH levels between irradiated and non-irradiated animals. These findings suggest that all spermatogenic cell types may stimulate FSH binding in the Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)

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DNA-flow cytometry of defined stages of rat seminiferous epithelium: effects of 3 Gy of high-energy X-irradiation.

Testes of adult Sprague-Dawley rats were irradiated locally by 3 Gy of 4 MeV X-rays produced by a linear accelerator. This type and dose of radiation gives an even distribution through the testis and selectively kills the proliferating spermatogonia. The seminiferous tubular cells were quantified by DNA flow cytometry at defined stages of the epithelial cycle at 7, 17, 22, 38, 52, and 80 days after irradiation. The flow cytometric technique was modified by using frozen instead of fresh samples. Freezing did not alter cell numbers when compared with fresh samples. At 7 days post-irradiation no significant changes were observed in any cell population by DNA flow cytometry, whereas histological analysis revealed a reduction in intermediate and type B spermatogonia. At 17 and 22 days post-irradiation, the number of cells at meiotic prophase (4C) was decreased, particularly in stages II-V of the cycle. In stages VII-VIII, cell numbers were 40 and 31%, and in stages IX-XIII, 24 and 43% of that in non-irradiated controls at 17 and 22 days, respectively. At 38 days after irradiation, both 4C and 1C (haploid) cells were decreased in number. The 4C cells were reduced to 24, 17, and 13% of that in non-irradiated controls in stages II-V, VII-VIII, and IX-XIII of the cycle, respectively. The corresponding numbers of 1C cells were 5, 17, and 4%. At 52 days after irradiation, 1C cells had declined to 38 and 19% of control values in stages II-V and IX-XIII, respectively. In stages II-V, 1C' cells (haploid cells with condensed nuclei) declined to 28% of controls at 52 days. The present data provide a quantitative basis for the use of X-ray-irradiated rat testes as a model system in experiments pursuing interactions between Sertoli cells and spermatogenic cells.

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Comparison of effects of 0.5 and 3.0 Gy X-irradiation on lipid peroxidation and antioxidant enzyme function in rat testis and liver.

The prooxidant effect of X-irradiation on rat testis and liver tissue was studied with doses of 0.5 and 3.0 Gy; the latter dose kills the proliferating spermatogonia and causes a maturation-depletion process in the germ cells. The level of lipid peroxidation, measured by the formation of diene conjugates and thiobarbituric acid-reactive substances (TBARS) and the activities of the antioxidant enzymes were determined 0.5 hours, 1 day, 7 days, and 31 days after the exposure. In the liver, increased levels of diene conjugation (+36%, P < 0.05) in the group of 3.0 Gy at 0.5 hours indicated increased lipid peroxidation. At the same time, TBARS were increased (+25%, P < 0.05) in the group of 0.5 Gy, but not in the 3.0-Gy group. In the testis, diene conjugation was not determined at 0.5 hours postirradiation, and at day 1 it was at the control level. The level of TBARS in the testis was below control (-11%, P < 0.01) in the 3.0-Gy group at day 1. At day 31 after 3.0 Gy in the testis, an increase in the amount of conjugated dienes (+24%, P < 0.01) was observed in parallel with a decreased level of TBARS (-15%, P < 0.01). The activity of superoxide dismutase (SOD) was decreased in the testis at 0.5 hours postirradiation (-28%, P < 0.05, and -29%, P < 0.05, in the groups of 0.5 and 3.0 Gy), whereafter it returned to normal by day 7. In the liver, such inactivation of SOD was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

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Stage-specific apoptosis in the rat seminiferous epithelium: quantification of irradiation effects.

The effects of 3 Gy local X-irradiation on the adult rat testis were studied together with exact determination of the radiation dose distribution in the testis. Seminiferous tubule segments were isolated 8-66 hours postirradiation (p.i.), squashed between a microscope slide and a coverslip, and the exact stage of the seminiferous epithelial cycle was identified under a phase-contrast microscope. The squash preparations were subjected to in situ end labeling (ISEL) for visualization and quantification of apoptotic cells. In controls, the highest numbers of apoptotic cells were scored in stages XII-XIV and I. In situ end-label staining of cells was observed in A3-A4 spermatogonia, spermatocytes at zygotene, pachytene, and meiotic division phases, as well as in early spermatids. In irradiated testes, from 8 hours p.i. and onward, intermediate- and B-type spermatogonia were sensitive at stages II-VI. At 42 hours, in stage I, elevated numbers of degenerating spermatocytes were seen. Most of them had not undergone meiotic divisions at stage XIV and showed an apoptotic type of degeneration at stage I. At the time of irradiation, the cells were in stage XIII, suggesting that diakinetic spermatocytes are particularly sensitive to irradiation. Also, preleptotene-zygotene spermatocytes in stages VII-XII were sensitive to irradiation. Apoptotic-type of cell degeneration was confirmed by living cell squash preparations, electron microscopy, and DNA electrophoresis. In conclusion, irradiation may provide a useful model system for studying apoptosis, and its control in spermatogonia and meiotically dividing cells.

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