Kimmo K. Vihko

Cell Interactions during the Seminiferous Epithelial Cycle

Publisher Summary This chapter discusses the cell interactions during the seminiferous epithelial cycle. Spermatozoa belong to the most differentiated cells of the body. Their special features are a haploid number of chromosomes, a tightly packed inactive form of the chromatin, a small amount of cytoplasm, and an ability of independent movement by a flagellum. The development of spermatozoa in the seminiferous epithelium includes three main phases: (1) spermatogonial multiplication, (2) meiosis, and (3) spermiogenesis. Cells in these phases are called spermatogonia, spermatocytes, and spermatids, respectively. The stage-dependent variation of the hormone responses in the seminiferous epithelium strongly suggests an existence of local paracrine regulation and cell interaction mechanisms in the seminiferous epithelium, that are dependent on spermatogenic cells associated with the Sertoli cells at each stage of the cycle of the seminiferous epithelium. The nature of this interaction is obscure; however some advances have been made. The secretion of a proteolytic enzyme, urokinase-type plasminogen activator, seems to be dependent on both cellular and hormonal regulation in the seminiferous epithelium. Testicular GnRH-like factors and proopiomelanocortin-derived peptides may play a role in seminiferous tubule-Leydig cell interaction. In the seminiferous epithelium, a Sertoli cell-derived growth factor is suggested to have a role in local regulation together with other factors, such as meiosis-inducing and -preventing substances, a somatomedin-like compound, and the spermatogonial chalone.

Effects of ospemifene and raloxifene on hormonal status, lipids, genital tract, and tolerability in postmenopausal women.

Objective: To compare ospemifene and raloxifene regarding their effects on hormones, lipids, genital tract, and tolerability in postmenopausal women. Design: A randomized, double-blind study in which 118 healthy postmenopausal women received 30 (n = 29), 60 (n = 30), or 90 mg (n = 30) of ospemifene or 60 mg (n = 29) of raloxifene for 3 months. Results: There were no significant differences in the baseline characteristics between study groups. In comparison with raloxifene, follicle-stimulating hormone levels decreased significantly more in the 90-mg ospemifene group and sex hormone-binding globulin levels increased more in all ospemifene groups. Total cholesterol and low-density lipoprotein cholesterol levels decreased more in raloxifene than in ospemifene groups, although the difference in low-density lipoprotein cholesterol between 90-mg ospemifene and raloxifene was not significant. Endometrial thickness did not change in any study group and endometrial biopsies showed atrophy in the majority of subjects at 3 months. All ospemifene groups demonstrated a clear estrogenic effect on the vaginal epithelium, as seen in Pap smears. This was in sharp contrast to the raloxifene group, which had no effect on the vaginal epithelium. Kupperman index decreased in all study groups during treatment. The adverse events were mild, mainly single cases, and no clustering of events was observed. There were no clinically significant abnormal findings in laboratory safety parameters. Conclusions: Ospemifene, at the dose of 90 mg/day, was more estrogenic than raloxifene, as shown by changes in serum follicle-stimulating hormone and sex hormone-binding globulin levels. Neither agent stimulated endometrium, but in contrast to raloxifene, ospemifene had a clear estrogenic effect in the vagina. Further studies with ospemifene are needed in subjects with vaginal atrophy.

Immunohistochemical localization of urokinase-type plasminogen activator in sertoli cells and tissue-type plasminogen activator in spermatogenic cells in the rat seminiferous epithelium

The occurrence of plasminogen activators of the urokinase-type (u-PA) and tissue-type (t-PA) at various stages of the epithelial cycle was studied immunohistochemically in rat seminiferous tubule segments. u-PA immunoreactivity was detected exclusively at stages VII and VIII in Sertoli cells, displaying a distinct granular cytoplasmic staining. t-PA immunoreactivity was found during mid- and late pachytene and diakinesis (stages VII-XIII) in spermatogenic cells, displaying a granular cytoplasmic staining with maximal intensity in stages IX-XIII. The specificity of the stainings was supported by staining controls, including absorption of the antibodies with purified preparations of the activators. It was also supported by zymographic studies of the occurrence of u-PA and t-PA in extracts of tubular segments at different stages of the cycle, isolated by transillumination-assisted microdissection. The possible functions of the two types of plasminogen activators in the seminiferous epithelium are discussed.

A rat seminiferous epithelial factor that inhibits Leydig cell cAMP and testosterone production: mechanism of action, stage-specific secretion, and partial characterization.

To elucidate further the seminiferous tubule-Leydig cell interaction we studied the effect of spent medium from 20 h rat seminiferous tubule cultures (STCM) on cyclic adenosine monophosphate (cAMP) and testosterone (T) production of Percoll-purified Leydig cells. 8% of STCM inhibited the human chorionic gonadotropin (hCG)-stimulated cAMP production by 30% in a 3 h, and 33% of STCm by 60% in a 20 h incubation. Likewise, a 40% decrease was found in the presence of 8% of STCM in the hCG-stimulated T production in a 3 h incubation. A similar inhibitory activity could be demonstrated in steroid-free rat interstitial fluid. STCM did not affect the viability of the Leydig cells (90-95% after a 20 h incubation) as judged by trypan blue exclusion and the adenosine triphosphate (ATP) content of the cells. Heating (80 degrees C for 10 min) abolished the inhibiting activity, and fractionation with Millipore Ultrafree filters showed that the inhibiting factor had an Mr of 30,000-100,000. When media from different stages of the seminiferous epithelial cycle were analyzed, only stages IX-I showed inhibition of T production (P less than 0.05). The cAMP production inhibiting activity was present in all stages, but stages IX-I showed significantly (P less than 0.05) greater inhibition than stages II-VI. STCM (16%) also inhibited cholera toxin- and forskolin-stimulated cAMP formation (approximately 50 and 60%, respectively; P less than 0.01), and the inhibitory activity persisted after a 3 h preincubation of Leydig cells with 100 micrograms/l pertussis toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Endometrial thermoablation for treatment of menorrhagia: comparison of two methods in outpatient setting

Background. Menorrhagia is one of the commonest reasons for gynecologic consultations. Inhibitors of fibrinolysis and non‐steroidal anti‐inflammatory drugs (NSAIDs) are generally used as therapy for the condition with an acceptable response in some patients. Endometrial ablation is one choice in patients suffering from menorrhagia. It can be performed in patients with no endometrial histological or anatomical pathology. In this method, the functional endometrial tissue is ablated under general anesthesia in an outpatient setting.

Protein kinase C and Gi-protein mediated modulation of cAMP production in different stages of the rat seminiferous epithelium

The modulatory role of protein kinase C (PK-C)- and Gi-protein-mediated signal transduction systems was studied in the cyclic variation of follicle-stimulating hormone (FSH)-stimulated cAMP production of rat seminiferous tubules. FSH (Metrodin, Serono, 30 mg/l) stimulated cAMP production 10-fold (p less than 0.01) in a 3 h incubation of 5 mm segments of seminiferous tubules of stages II-VI of the epithelial cycle, but only 2-fold (p less than 0.01) in stages VII-VIII. The PK-C activator 12-O-tetradecanoylphorbol 13-acetate (TPA, 100 nmol/l) suppressed the FSH effect on cAMP output by 50-70% (p less than 0.01) in stages II-VI, but had no effect in stages VII-VIII. If the tubular segments were preincubated for 3 h in the presence of pertussis toxin (PT, 100 micrograms/l), the FSH-stimulated cAMP production of stages VII-VIII increased by 100-200% (p less than 0.01), and now they also became responsive to the TPA suppression. Conversely, no effect of PT was observed in stages II-VI. Cholera toxin (CT, 100 micrograms/l) and forskolin (Fk, 100 mumol/l) nearly similarly stimulated the cAMP production in both stages studied (about 10-fold, p less than 0.01), and TPA and PT potentiated the effects in a non-additive fashion. In conclusion, both Gi-protein and PK-C-mediated mechanisms modulate cAMP production of rat seminiferous tubules. A clear cyclic variation can only be demonstrated in FSH-stimulated cAMP production, but not if the Gs-protein or adenylate cyclase are directly stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Activin B in patients with granulosa cell tumors: serum levels in comparison to inhibin

Background.  Activins and inhibins are polypeptide hormones/growth factors of primarily gonadal origin. In the ovary, activins and inhibins are primarily synthesized by granulosa cells. Serum inhibin measurements have been used for the follow‐up of patients with granulosa‐cell tumors (GCT) after surgery.

Regulation of ovarian UT-OC-2 carcinoma cells by cytokines: Effects on cell proliferation, activation of transcription factors and apoptosis

Background. It is known that immunologic factors are involved in the regulation of the growth of ovarian carcinoma and that granulocytes are often found on the site of ovarian cancer. Therefore, we chose to investigate the effects of cytokines on UT‐OC‐2 ovarian endometrioid adenocarcinoma cells in vitro. In order to investigate the molecular mechanisms involved, the activation of two key DNA‐binding proteins, AP‐1 and transcription factor NF‐κB (NF‐κB), was studied. Since DNA extracted from the UT‐OC‐2 cells showed fragmentation typical of apoptosis, we also studied the effects of cytokines on this event. Methods. The effects of the studied cytokines on the proliferation of UT‐OC‐2 cells were investigated by 125I‐deoxyuridine incorporation. The activation of DNA‐binding proteins was studied by electrophoretic mobility shift assay. Statistical analyses were performed by Students t‐test. Results. Interferon α (IFN‐α), transforming growth factor β1 (TGF‐β1), tumor necrosis factor α (TNF‐α) and interferon γ (IFN‐γ) all had a significant inhibitory effect on cell proliferation. Granulocyte colony stimulating factor (GM‐CSF) did not alter cell proliferation significantly. Transcription factors AP‐1 and NF‐κB were both found to be constitutively active in UT‐OC‐2 ovarian carcinoma cells. We were able to show that IFN‐γ, TGF‐β1 and TNF‐α all increased the binding activity of transcription factor AP‐1 (AP‐1). The binding activity of transcription factor NF‐κB was not altered by any of the cytokines studied, with the exception of IFN‐γ. IFN‐γ had also a clear inhibitory effect on the apparent magnitude of apoptosis, whereas TNF‐α and TGF‐β1 showed no effect. Conclusion. The results of this study show that TNF‐α, TGF‐β1, and IFN‐γ are able to inhibit the proliferation of UT‐OC‐2 ovarian carcinoma cells. Activation of AP‐1 seems to be involved in the growth‐regulating processes induced by IFN‐γ, TGF‐β1 and TNF‐α; IFN‐γ is also able to increase the binding activity of NF‐κB and inhibited apoptosis in ovarian cancer cells.