Biomedical subjects

M Parvinen

Publications and source records attributed to M Parvinen.

At least 73 records · Page 4Linked to original sources

PubMed1995

Testosterone inhibits and induces apoptosis in rat seminiferous tubules in a stage-specific manner: in situ quantification in squash preparations after administration of ethane dimethane sulfonate.

The quantitative effects of ethane dimethane sulfonate (EDS), a Leydig cell toxin, on apoptosis in adult rat seminiferous epithelium were studied by the improved transillumination method. Nonradioactive in situ end labeling of fragmented DNA in squash preparations revealed significant increases in apoptotic cells in stages II-XI, whereas controls showed 0.5-2.3 apoptotic cells/mm tubule. Seven days post-EDS treatment, the highest numbers of apoptotic cells were scored in stages VIIab and VIIcd (74.7 +/- 23.8 and 61.3 +/- 16.0 cells/mm, respectively). The effects were suppressed by testosterone (T) supplementation, except in stages II-III and VIIcd. An opposite effect was found in stage XII, where the number of apoptotic cells decreased 1, 3, and 7 days after EDS treatment and returned to control levels in T-supplemented rats. Electrophoretic analysis of internucleosomal DNA fragmentation revealed a biphasic apoptotic process after 1 and 5-7 days due to Leydig and germ cell apoptosis, respectively. The specific germ cell apoptosis was also confirmed by electron microscopic analysis. The results suggest that T withdrawal induces apoptotic cell death in most stages of the cycle and that the effects are largely preventable. In stage XII, however, T seems to promote apoptosis in premeiotic cells.

Animals↗

PubMed1995

In-situ quantification of stage-specific apoptosis in the rat seminiferous epithelium: effects of short-term experimental cryptorchidism.

Two techniques have been combined for quantification of apoptotic germ cells in defined stages of the cycle of the seminiferous epithelium: the improved transillumination method and nonradioactive in-situ end-labelling of DNA (ISEL). Segments of rat seminiferous tubules were squashed between a microscope slide and coverslip, and the stage identified under a phase-contrast microscope. After fixation, apoptotic cells were detected by ISEL and scored per 1 mm tubule. In the normal testis apoptotic cells were found in all stages, the highest frequency occurring in stages XII-XIV (19 cells/mm). In short-term (24 and 48 h) experimentally cryptorchid testes, a significant increase in number of apoptotic germ cells was evident in all stages, except for VI and VIII. Apoptosis of germ cells was confirmed by electrophoresis of radioactively labelled DNA from stages VII-VIII and XIII-I. It is proposed that apoptosis is a means of eliminating the most sensitive germ cells after short-term experimental cryptorchidism.

Analysis of Variance↗

PubMed1994

Localization of urokinase- and tissue-type plasminogen activator mRNAs in rat testes.

The expressions of urokinase (uPA) and tissue-type plasminogen activators (tPA) in different stages of the rat seminiferous epithelial cycle were analyzed by in situ and Northern hybridizations combined with zymographic analysis. Irradiated rat testes were used to assess the cell localization. Both of the plasminogen activators were expressed in a strictly stage specific manner. Maximal expression of uPA mRNA was seen in Sertoli cells during stages VII-VIII of the cycle. The same expression in the basal compartment of the tubules was detected at 7 days post-irradiation (p-i), during a selective reduction of spermatogonia and preleptotene spermatocytes. Levels of tPA mRNA started to accumulate in Sertoli cells at stage VIII and were high during stages IX-XII and detectable during stages XIII-XIV. At 26 days p-i, reduction of pachytene spermatocytes, which are shown to be immunoreactive for tPA, did not have an effect on tPA mRNA expression. Catalytic activities of uPA and tPA changed concomitantly to their RNA levels in different stages of the cycle. However, at 7 days p-i, uPA activity was decreased at stages VII-VIII of the cycle suggesting that germ cell Sertoli cell interaction is important for uPA activity.

Animals↗

PubMed1994

MIP-1 alpha is a regulator of mitotic and meiotic DNA synthesis during spermatogenesis.

To find out whether macrophage inflammatory protein-1 alpha (MIP-1 alpha) has a role in the regulation of germ cell development, we studied its effects on spermatogenic stage-specific DNA synthesis in vitro. MIP-1 alpha increased the DNA synthesis of primitive type A2-4 spermatogonia and of premeiotic cells, whereas the DNA synthesis of more differentiated intermediate and type B spermatogonia was inhibited when cultured in the presence of MIP-1 alpha. An antibody against MIP-1 alpha cross-reacted with a protein of 15 kDa from every spermatogenic stage of rat seminiferous epithelium. Immunohistochemical studies with the same antibody revealed a complex pattern of MIP-1 alpha localization both in primitive and advanced spermatogenic cells. These observations suggest that MIP-1 alpha is a local regulator of mitotic and meiotic DNA synthesis.

Animals↗

PubMed1994

Stage-specific expression of pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA in the rat seminiferous tubules.

We have used in situ hybridization and Northern blot analysis with oligonucleotide probe to characterize the site of pituitary adenylate cyclase-activating polypeptide (PACAP) synthesis in the rat testis. We observed strong hybridization signal in one third of the cross-sections of the seminiferous tubules, whereas some tubules were devoid of hybridization signal, thus suggesting that PACAP mRNA is expressed in a stage-specific manner. More detailed analysis showed that PACAP mRNA was present in round spermatids at stages III-VII of the cycle. Northern blot hybridization to RNAs extracted from samples of seminiferous tubules at different stages of the epithelial cycle confirmed that expression of PACAP mRNA is restricted to specific stages of the cycle. The highest amount of PACAP mRNA was detected at stages V to early -VII of the cycle, whereas very low levels of mRNA were present at stages I-II and IX-XIV. The present results demonstrate that PACAP mRNA is expressed in the developing germ cells. This suggests that PACAP may function as a paracrine or autocrine regulatory factor for the Sertoli and germ cells, with a specific function during early spermiogenesis, shortly before the onset of nuclear elongation, at the last period of haploid gene activity.

Animals↗

PubMed1994

Expression of inhibin alpha, beta A and beta B messenger ribonucleic acids in the normal human ovary and in polycystic ovarian syndrome.

We studied the cellular distribution of inhibin alpha, beta A and beta B mRNAs in the normal human ovary and in polycystic ovarian syndrome (PCOS) by in situ hybridization. Our results show that human granulosa cells express inhibin alpha, beta A and beta B subunit mRNAs, and theca cells express inhibin alpha and beta A subunit mRNAs. The co-localization of alpha and beta A mRNAs in theca cells supports the hypothesis that inhibin also has an autocrine function in these cells. We did not detect any inhibin subunit mRNA in the granulosa cells of atretic follicles, while theca cells also expressed alpha subunit mRNA in those follicles. The present findings suggest that the expression of inhibin subunits is regulated differently in human follicular granulosa and theca cells. It has been speculated that inhibin may be involved in the development of PCOS. Our results show that the cellular localization of inhibin subunit mRNAs is not disturbed in PCOS ovaries.

Female↗

PubMed1993

Role of transforming growth factor beta in testicular immunosuppression.

The potential role of transforming growth factor beta (TGF beta) in the regulation of the immunological milieu of the testis was investigated. Antibodies neutralizing TGF beta reversed the previously observed suppression of rat peripheral blood lymphocyte proliferation induced by rat abdominal testis extract. Recombinant TGF beta 1 dose-dependently inhibited testicular interleukin-1-like factor-driven proliferation of murine thymocytes and ConA-stimulated rat peripheral blood mononuclear cells. Extracts of seminiferous tubules contained a M(r) approximately 25 K TGF beta-like growth inhibitor of the CLL-64 mink lung epithelial cell line. The present findings suggest an important role for TGF beta in testicular immunosuppression.

Animals↗

PubMed1993

Effects of etoposide on stage-specific DNA synthesis during rat spermatogenesis.

The stage-specific effect of etoposide on spermatogenic DNA synthesis was measured 1, 3 and 18 days after a single intraperitoneal injection of etoposide. Etoposide inhibited premitotic DNA synthesis most effectively at stages II-III and IV-V of the seminiferous epithelial cycle in which DNA synthesis of late spermatogonia takes place. Compared with control levels, DNA synthesis at stages II-III was maximally inhibited 43% and 57% at doses of 5 and 10 mg/kg, respectively, and at stages IV-V the maximal inhibition was 67% and 62%, at doses of 5 and 10 mg/kg respectively. Premeiotic DNA synthesis was not as vulnerable to the etoposide action as premitotic DNA synthesis, the maximal inhibition of premeiotic DNA synthesis was 39% and 41% compared with control at doses of 5 and 10 mg/kg, respectively. Induction of most probably repair-type DNA synthesis was demonstrated in stages I-III, VIIa-b and XII of the cycle. All the effects of etoposide were most apparent 1 and 3 days after treatment but had not totally disappeared 18 days after the treatment.

Analysis of Variance↗

PubMed1993

Localization of the glucocorticoid receptor in testis and accessory sexual organs of male rat.

Localization of glucocorticoid receptor-like immunoreactivity (GR-LI) was studied in adult rat testis, epididymis, ejaculatory duct, seminal vesicle and prostate by light and electron microscopic immunocytochemistry. In the interstitium of the testis GR-LI was seen in the nuclei of Leydig cells, macrophages, fibroblasts, smooth muscle cells and endothelial cells of blood vessels. Furthermore, GR-LI was observed in zygotene and early pachytene primary spermatocytes of some seminiferous tubules during stages XIII-XIV and I-III of the spermatogenic cycle. Other spermatogenic cells and Sertoli cells were devoid of staining. GR-LI was also found in peritubular myoid cells, fibroblasts and basal cells of the epididymis, vas deferens and prostate. Localization of GR-LI in primary spermatocytes and Leydig cells suggests that glucocorticoids directly affect spermato- and steroidogenesis in the testis. The absence of GR-LI from functional, stromal cells of the male accessory sexual organs suggests that they are not targets for glucocorticoid hormones.

Animals↗

PubMed1993

Interleukin-1 bioactivity and DNA synthesis in X-irradiated rat testes.

Stage-specific DNA synthesis and interleukin-1 (IL-1) bioactivity were measured in the rat testis at 2, 6, 12 and 25 days after local irradiation with 3 Gy to investigate whether there was any correlation between germ cell DNA synthesis during repopulation and IL-1-like bioactivity in the seminiferous epithelium. DNA synthesis by intermediate and type-B spermatogonia was reduced significantly at 2, 6 and 12 days after irradiation in seminiferous tubules at stages II-III and IV-V. IL-1 bioactivity was increased significantly at 6 and 25 days after irradiation at stages II-VI during repopulation of spermatogonia. At 2, 6 and 25 days after irradiation at stages VIIa-c a significant increase in IL-1 bioactivity was observed that correlated with repair synthesis of DNA. Increased IL-1 bioactivity was also observed at stages IX-XII at 6 days post-irradiation. These observations support the concept that IL-1 is a spermatogonial growth factor which might also stimulate repair synthesis of DNA.

Animals↗

PubMed1993

Identification, ontogeny, and regulation of an interleukin-6-like factor in the rat seminiferous tubule.

The present study's aims are to search for the presence of interleukin-6 bioactivity (IL-6) in medium conditioned by various testicular cell types and to investigate the cellular and hormonal regulation of testicular IL-6 production. Sertoli cells prepared from rats of increasing ages (20, 35, and 45 days) secreted IL-6 in vitro, whereas medium conditioned by pachytene spermatocytes, early spermatids, and peritubular cells showed no activity. Lipopolysaccharide (LPS) and latex beads, two known stimulators of monocyte/macrophage IL-6 production, markedly stimulated IL-6 secretion by Sertoli cells at all the ages investigated. Maximum levels of IL-6 were reached after 6 h of culture of Sertoli cells with LPS and after 24 h with latex beads. When Sertoli cells were cocultured with pachytene spermatocytes, early spermatids, or fractions containing residual bodies and cytoplasts from elongated spermatids, only the latter significantly stimulated IL-6 levels. Maximum levels of IL-6 were attained by adding 2 x 10(6) residual bodies to Sertoli cells; a significant increase in IL-6 secretion was seen after 6 h, and maximum levels were observed after 24 h. The levels of IL-6 varied throughout different stages of the seminiferous epithelium cycle; highest levels were observed in stages II-VI and lowest in stages VII-VIII. IL-6 bioactivities induced by LPS and residual bodies and cytoplasts from elongated spermatids could be totally neutralized with a specific monoclonal antibody at all of the ages studied. FSH, phorbol myristate acetate, and IL-1 alpha augmented Sertoli cell IL-6 secretion in a dose-dependent manner. Furthermore, FSH and (Bu)2cAMP differentially stimulated IL-6 secretion during the seminiferous epithelial cycle. It is concluded that the release of IL-6 from Sertoli cells is regulated by a complex interplay between residual bodies and humoral factors.

Aging↗

PubMed1993

Localization of activin receptor (ActR-IIB2) mRNA in the rat seminiferous epithelium.

In situ hybridization was used to localize the mRNA expression of the high affinity activin receptor (ActR-IIB2) in the rat seminiferous epithelium. ActR-IIB2 mRNA was expressed maximally in stages IX-XI of the seminiferous epithelial cycle. The mRNA signal was detected basally in the epithelium in type A1 and A2 spermatogonia and in Sertoli cells. In the pubertal rat testis the expression was localized in Sertoli cells around primary spermatocytes and around meiotically dividing cells. The localization of ActR-IIB2 mRNA in spermatogonia lends support to the hypothesis that activin is a spermatogonial growth factor. The expression of activin receptor mRNA in pubertal rat testis suggests that activin may have a function during meiotic maturation.

Activin Receptors↗

PubMed1993

Effects of activin-A, inhibin-A, and transforming growth factor-beta 1 on stage-specific deoxyribonucleic acid synthesis during rat seminiferous epithelial cycle.

Activin and inhibin are members of the transforming growth factor-beta (TGF beta) gene family. They are expressed in various organ systems, where they possess regulatory functions. Inhibin, activin, and TGF beta have been reported to also be expressed in the adult rat testis. We studied in vitro the action of these growth factors on premitotic and premeiotic DNA synthesis during the rat seminiferous epithelial cycle. Two-millimeter rat seminiferous tubule segments were isolated by transillumination-assisted microdissection from stages V, VIIa, VIII-IX, and I of the cycle and incubated in vitro in the presence of activin-A, inhibin-A, or TGF beta 1. During 24-, 48-, and 72-h incubation spontaneous progression of spermatogenesis was noted. The staged samples allowed us to selectively quantitate DNA synthetic activity of specific germ cell types. At the end of the culture, the tubules were pulse labeled with [3H]thymidine, and DNA synthesis was quantified by liquid scintillation counting, and the activated cells were detected by autoradiography. Activin-A stimulated preleptotene spermatocyte DNA synthesis in a dose-dependent manner. DNA synthesis of intermediate spermatogonia was also stimulated by activin-A, whereas inhibin-A inhibited DNA synthesis of these cells. TGF beta 1 had a small, but significant, stimulatory effect on DNA synthetic activity at stage VII. These results support the view that activin-A, inhibin-A, and TGF beta 1 take part in the regulation of DNA synthesis during rat spermatogenesis.

Activins↗

PubMed1993

Polyamines and regulation of spermatogenesis: selective stimulation of late spermatogonia in transgenic mice overexpressing the human ornithine decarboxylase gene.

Polyamines are believed to participate in the induction of cell growth, differentiation, and proliferation, but their role in spermatogenesis has remained obscure. Two transgenic mouse lines (K2 and K15) that overexpress the human ornithine decarboxylase (ODC) gene coding for a rate-controlling enzyme in polyamine biosynthesis and, hence, contain high levels of tissue putrescine have been used to study the stage-specific role of ODC in spermatogenesis. In K2 mice with 30-fold testicular ODC overexpression, [3H]thymidine incorporation at stages I-VI of the cycle of the seminiferous epithelium was significantly above the control level. This may reflect a specific stimulation of DNA synthesis in type A4, intermediate, and type B spermatogonia. The K15 mice that have about 70-fold ODC overexpression showed an elevation of DNA synthesis only at stage V of the cycle, suggesting a specific dependence of type B spermatogonia on putrescine. In K15 mice, [3H]thymidine incorporation of stage VIII tubule segments was decreased, suggesting that excess amounts of putrescine selectively inhibit meiotic DNA synthesis. We propose that putrescine has strictly selective local stimulatory and inhibitory actions during spermatogenic DNA synthesis, and that its excess amounts ultimately may lead to decreased fertility.

Animals↗

PubMed1992

Immunosuppressive activity in the rat seminiferous tubules.

Rat seminiferous tubule segments in defined stages of the epithelial cycle were isolated by transillumination-assisted microdissection. The segments were cultured together with ConA-stimulated peripheral blood lymphocytes (PBL) and incorporation of 3H-labelled thymidine was measured. Tubule segments in stages II-VIII of the seminiferous epithelial cycle inhibited PBL proliferation significantly more than stages IX-I. Inhibition was lowest in stages IX-XII and increased progressively to reach a maximum in stages II-VIII. In a more detailed analysis, tubules in stages V and VI inhibited PBL proliferation significantly less than stage II tubules. No significant difference was observed between stages II and VII. The immunosuppressive activity had molecular weights of approximately 25 kDa and approximately 65 kDa in stage II-VIII seminiferous tubules. In stage II-VI seminiferous tubules activity was present also at approximately 10 kDa. The results suggest that the seminiferous tubules produce high-molecular weight immunosuppressive activity in a stage-dependent way. In addition to its contribution to the immunologically privileged milieu of the testis this activity may also be involved in the physiological regulation of DNA synthesis in the seminiferous epithelium.

Animals↗

PubMed1992

FSH receptor mRNA is expressed stage-dependently during rat spermatogenesis.

In situ hybridization was performed on testicular tissue from adult male Sprague-Dawley rats using cRNA antisense and sense probe of the monkey FSH receptor (FSHR) cDNA to determine the cellular site of synthesis, and possible stage-dependent expression of FSHR mRNA during the cycle of the seminiferous epithelium. Using antisense probe specific binding was first detected in Sertoli cells just prior to sperm release at stage VIII. The strongest specific hybridization signal was found during stages IX and X followed by a decrease of signal intensity in stages XI-XII. No specific binding was found in stages XIII-VII. The sequence of events with the maximum expression of FSHR mRNA in Sertoli cells in stages IX and X, before FSH-binding and FSH-stimulated cAMP production reach maximum values, coincides with a new wave of spermatogenesis and indicates an effect of FSH and spermatogenic cells on the regulation of FSHR mRNA expression.

Animals↗

PubMed1992

Expression of beta-nerve growth factor and its receptor in rat seminiferous epithelium: specific function at the onset of meiosis.

beta-Nerve growth factor (NGF) is expressed in spermatogenic cells and has testosterone-downregulated low-affinity receptors on Sertoli cells suggesting a paracrine role in the regulation of spermatogenesis. An analysis of the stage-specific expression of NGF and its low affinity receptor during the cycle of the seminiferous epithelium in the rat revealed NGF mRNA and protein at all stages of the cycle. Tyrosine kinase receptor (trk) mRNA encoding an essential component of the high-affinity NGF receptor was also present at all stages. In contrast, expression of low affinity NGF receptor mRNA was only found in stages VIIcd and VIII of the cycle, the sites of onset of meiosis. The low-affinity NGF receptor protein was present in the plasma membrane of the apical Sertoli cell processes as well as in the basal plasma membrane of these cells at stages VIIcd to XI. NGF was shown to stimulate in vitro DNA synthesis of seminiferous tubule segments with preleptotene spermatocytes at the onset of meiosis while other segments remained nonresponsive. We conclude that NGF is a meiotic growth factor that acts through Sertoli cells.

Animals↗

PubMed1992

Stage- and cell-specific expression of cyclic adenosine 3',5'-monophosphate-dependent protein kinases in rat seminiferous epithelium.

Expression of mRNAs in the rat testis encoding cyclic AMP (cAMP)-dependent protein kinases (PKAs) was studied. A microdissection method was used to isolate 10 pools of seminiferous tubules representing various stages of the cycle of the seminiferous epithelium in combination with Northern blots and in situ hybridization. The results showed a differential expression of the four isoforms of the regulatory subunits (PKA-R) at various stages of the cycle. RI alpha mRNA was detected at approximately the same levels at all stages while expression of RI beta mRNA was low at stages XIII-III, started to increase at stages IV-V, and reached a maximum at stages VIII-XI. The level of RII alpha mRNA was low at stages II-VI, increased markedly at stage VIIa,b, and reached maximal levels at stages VIIc,d and VIII, followed by a reduced expression at later stages, RII beta mRNA levels increased significantly at stage VI with maximal levels at stages VII and VIII. In situ hybridization of sections from the adult rat testis revealed RI alpha mRNA in the layers of pachytene spermatocytes and round spermatids of all stages. RI beta mRNA was detected over late pachytene spermatocytes and round spermatids of stages VII-XIII. RII alpha mRNA was seen in the layers of round spermatids of stages VII-VIII and elongating spermatids of later stages while RII beta mRNA was detected only in the round spermatid region of stages VII-VIII and in some tubules of stages I-VI. These data show that mRNAs encoding PKA-R are expressed in a stage-specific manner in differentiating male germ cells with different patterns of expression for each subunit; this suggests specific roles for these protein kinases at different times of spermatogenesis.

Animals↗