Biomedical subjects

Y Nishimune

Publications and source records attributed to Y Nishimune.

At least 127 records · Page 7Linked to original sources

PubMed1989

Isolation of mutants showing temperature-sensitive cell growth from embryonal carcinoma cells: control of stem cell differentiation by incubation temperatures.

Embryonal carcinoma(EC) cells, the undifferentiated stem cells of teratocarcinomas, have many properties in common with pluripotent embryonic cells, and thus provide an excellent system for studying the early events involved in embryonic development and stem cell differentiation. We have isolated three novel mutants with temperature-sensitive(ts) cell growth that were able to differentiate at a non-permissive temperature for cell growth. These mutations affect the progression of the cell cycle, leading to the transient accumulation of cells in a specific phase, the S phase, of the cell cycle, which is likely to be the primary cause of stem cell differentiation of EC cells at non-permissive temperature. Isolation of these mutants strongly supports the notion that there is a close association between the inhibition of DNA synthesis and EC cell differentiation.

Animals↗

PubMed1989

Inhibition of DNA synthesis causes stem cell differentiation: induction of teratocarcinoma F9 cell differentiation with nucleoside analogues of DNA-synthesis inhibitors and their inducing abilities counterbalanced specifically by normal nucleosides.

Nucleoside analogues inhibiting DNA synthesis can induce cell differentiation in teratocarcinoma cells. We have examined how their abilities to induce F9 cell differentiation were specifically counterbalanced by their corresponding normal nucleosides. We have also compared the differentiation inducing ability of the wild type F9 cells with that of its thymidine kinase-less mutant using plasminogen activator, as a differentiation marker, which is expressed at a very early stage of endodermal cell differentiation and can be assayed quantitatively. The results obtained were clearly explainable by the conventionally accepted action mechanisms of the nucleoside analogues, thus strongly suggesting that their abilities to induce cell differentiation were direct consequences of the inhibition of DNA synthesis; thus this confirms the notion that a close association exists between the inhibition of DNA synthesis and the induction of teratocarcinoma stem cell differentiation.

Animals↗

PubMed1989

Differentiation of germ cells in seminiferous tubules transplanted to testes of germ cell-deficient mice of W/Wv and Sl/Sld genotypes.

(WB X C57BL/6)F1-W/Wv (hereafter, WBB6F1-W/Wv) mice and (WC X C57BL/6)F1-Sl/Sld (hereafter, WCB6F1-Sl/Sld) mice are sterile due to the deficient spermatogenesis in the testes. The cause of deficient spermatogenesis in WBB6F1-W/Wv mice is considered to be a defect in germ cells themselves, whereas that in WCB6F1-Sl/Sld mice is considered to be a defect in tissue environment necessary for differentiation of germ cells. Seminiferous tubules isolated from cryptorchid testes of C57BL/6- +/+ mice were transplanted into the testes of WBB6F1-W/Wv and WCB6F1-Sl/Sld mice to clarify that the extratubular environment of these mice was intact or not. Type A spermatogonia in the transplanted tubules normally differentiated into spermatids, suggesting that the extratubular environment is intact in both WBB6F1-W/Wv and WCB6F1-Sl/Sld mice.

Animals↗

PubMed1989

Identification of peanut agglutinin receptors on mouse testicular germ cells.

Peanut agglutinin receptors expressed specifically in mouse testicular germ cells have been identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and lectin blotting techniques. Two major components were estimated to have molecular weights of 86,000 and isoelectric points of 6.1 +/- 0.3 and 6.2 +/- 0.3. Minor components with molecular weights of 71,000-74,000 and isoelectric points of 6.1 +/- 0.3 were also detected. Specific expression of these receptors on testicular germ cells was confirmed using the testes of mutant mice, Sld/Sld, devoid of germ cells.

Animals↗

PubMed1989

DNA and RNA synthesis by postpubertal undescended testis in vitro.

To study the spermatogenic potential of postpubertal undescended testis, the 3H-thymidine and 14C-uridine incorporations into normally descended and inguinal undescended testes were examined. The results suggest that DNA synthesis by the inguinal undescended testis is remarkably inhibited but, on the contrary, RNA synthesis is not. The cell-proliferative ability of postpubertal undescended testis may be impaired in spite of the retention of cell viability in the testis.

Adult↗

PubMed1989

Impaired DNA synthesis by early pubertal cryptorchid testis in vitro.

To study the spermatogenic potential of the early pubertal cryptorchid testis, testicular DNA synthesis was examined in vitro. DNA synthesis by early pubertal cryptorchid testis was inhibited and lost its normal temperature sensitivity. The spermatogenic potential of the cryptorchid testis may be impaired as early as puberty.

Cryptorchidism↗

PubMed1989

In vitro responsiveness of human testicular DNA synthesis to gonadotropins.

To evaluate the responsiveness of spermatogenesis in the normal human testis to human menopausal gonadotropin (hMG) and human chorionic gonadotropin (hCG), the DNA synthesis of spermatogonia was investigated using 3H-thymidine uptake by cultured tissue fragments of human testis with or without treatment with hCG and/or hMG. Two groups treated with different concentrations of hCG showed no difference in 3H-thymidine incorporation into testicular tissue compared with untreated control. In two other groups treatment with combined hMG/hCG in different concentrations induced significant changes in 3H-thymidine incorporation compared with control (p less than 0.01, p less than 0.01). Combined hMG/hCG treatment was effective in inducing spermatogenesis by normal human testicular tissue.

Chorionic Gonadotropin↗

PubMed1989

Effectiveness of hMG-hCG treatment for DNA/RNA syntheses in subfertile human testis in vitro.

To evaluate the effect of hMG-hCG treatment on spermatogenic impairment, DNA/RNA syntheses were measured in 25 patients with idiopathic male infertility by estimating the values of 3H-thymidine and 14C-uridine incorporation into the testicular tissue cultured with or without the hormonal treatment. Without the hormonal treatment, the levels of 3H-thymidine incorporation were in inverse correlation with the progress of spermatogenic impairment, whereas disturbances in responsiveness to the hormonal treatment directly correlated with spermatogenic impairment. Although the 14C-uridine incorporation increased both with and without the hormonal treatment, the values showed different patterns from those of 3H-thymidine incorporation. It would appear that the DNA synthesis in testicular tissue cultured with or without hMG-hCG treatment might predict the responsiveness to hormonal treatment for patients with idiopathic male infertility.

Chorionic Gonadotropin↗

PubMed1989

Induction of testicular DNA synthesis in vitro by hCG and hMG treatments in men with hypogonadotropic hypogonadism.

To study the effectiveness of hCG and hMG administration on spermatogenesis of patients with hypogonadotropic hypogonadism (HH), the DNA synthesis of spermatogonia was investigated by the method of 3H-thymidine uptake by cultured tissue fragments of human testis with or without treatment with hCG and/or hMG. Although in two groups treated with different concentrations of hCG the value of 3H-thymidine incorporation into testicular tissue showed no significant difference compared with the untreated control group, treatment with both hCG and hMG induced significant changes in the value of 3H-thymidine incorporation compared with the untreated control group. Combined hCG and hMG therapy was effective for induction of spermatogenesis in patients with HH.

Adolescent↗

PubMed1989

Plasminogen activator activity of testicular cells of subfertile men and FSH in vitro.

SDS-polyacrylamide gel electrophoresis followed by enzymography of a human testicular cell culture medium demonstrated that the molecular weight of plasminogen activator (PA) secreted was similar to that of human urokinase and it was also confirmed that follicle-stimulating hormone (FSH) stimulated PA secretion. To further investigate the correlation between spermatogenic impairment and secretory potential of PA in human testicular cells in vivo, the maximum increment in PA activity as a result of treatment with ovine FSH was measured for two groups of patients with different degrees of spermatogenic impairment. The mean value of maximum increment in PA activity in one group with severely impaired testes was remarkably lower than that in another group with slightly impaired testes. Protein biosynthesis in human testicular cells dependent on FSH appears to be impaired with the progression of spermatogenic impairment.

Cells, Cultured↗

PubMed1988

Male sterility of transgenic mice carrying exogenous mouse interferon-beta gene under the control of the metallothionein enhancer-promoter.

As an approach to elucidating the roles of interferon (IFN) in the normal physiology and diseases of animals, transgenic mice carrying extra mouse IFN-beta genes under the control of a mouse metallothionein I enhancer-promoter were constructed. Upon induction with Cd2+, IFN activity (15-430 IU/ml) was detected in the sera of six out of ten transgenic mouse lines so far obtained. Synthesis of mRNA of the transgene was observed in the liver, the testis and less abundantly in the brain. Interestingly, IFN mRNA was constitutively synthesized in the testis where substantial levels of IFN accumulated without heavy metal induction, whereas synthesis in the liver was mostly dependent on induction by CD2+. Since IFN activity in the serum also depended on heavy metal induction, the IFN in the serum may be produced mainly in the liver. All males expressing the IFN gene in the testis were found to be sterile. Testes were involuted and contained few mature sperm, and degeneration of spermatocytes and spermatids was observed. These findings suggest that high levels of IFN are harmful to spermatogenesis and can cause male sterility.

Animals↗

PubMed1988

Studies of Sl/Sld in equilibrium with +/+ mouse aggregation chimaeras. II. Effect of the steel locus on spermatogenesis.

Mutant mice of Sl/Sld genotype are deficient in melanocytes, erythrocytes, mast cells and germ cells. Deficiency of melanocytes, erythrocytes and mast cells is not attributable to an intrinsic defect in their precursor cells but to a defect in the tissue environment that is necessary for migration, proliferation and/or differentiation. We investigated the mechanism of germ cell deficiency in male Sl/Sld mice by producing aggregation chimaeras from Sl/Sld and +/+ embryos. Chimaeric mice with apparent white stripes were obtained. Two of four such chimaeras were fertile and the phenotypes of resulting progenies showed that some Sl/Sld germ cells had differentiated into functioning sperms in the testis of the chimaeras. In cross sections of the testes of chimaeras, both differentiated and nondifferentiated tubules were observed. However, the proportions of type A spermatogonia to Sertoli cells in both types of tubules were comparable to the values observed in differentiated tubules of normal +/+ mice. We reconstructed the whole length of four tubules from serial sections. Differentiated and nondifferentiated segments alternated in a single tubule. The shortest differentiated segment contained about 180 Sertoli cells and the shortest nondifferentiated segment about 150 Sertoli cells. These results suggest that Sertoli cells of either Sl/Sld or +/+ genotype make discrete patches and that differentiation of type A spermatogonia does not occur in patches of Sl/Sld Sertoli cells.

Animals↗

PubMed1988

Optimal temperature for synthesis of DNA, RNA, and protein by human testis in vitro.

To determine the optimal temperature for DNA, RNA, and protein syntheses in the human testis, the levels of incorporation of 3H-thymidine, 14C-uridine, and 14C-leucine into testicular tissue were studied at 28 degrees C, 31 degrees C, 34 degrees C, and 37 degrees C in vitro. The results suggest that the DNA synthesis is at a maximum at 31 degrees C and shows delicate temperature sensitivity, whereas the RNA and protein syntheses are at a maximum at 34 degrees C or 37 degrees C and are temperature-dependent. It is concluded that the temperature sensitivity of DNA synthesis may be one of the primary causes of delicate thermal inhibition of human spermatogenesis.

Cells, Cultured↗

PubMed1987

Influence of temperature on the function of Sertoli and Leydig cells of human testes.

The influence of temperature on Leydig and Sertoli cell functions was investigated in two experiments. One experiment was performed with testes of men with or without varicocele, because the temperature differs between right and left testes of men with left varicocele and right testes of men without varicocele. There were no significant differences in follicle-stimulating hormone (FSH), human chorionic gonadotropin (hCG) receptors, and testosterone (T) concentrations among the testes. The other experiment was performed with the use of testicular organ culture. Specific binding sites for FSH, hCG, and T production were similar in cultured testes maintained at 33 degrees and 37 degrees C for 7 days. It is concluded that high temperature may not disturb Leydig and Sertoli cell functions in the short term.

Adult↗

PubMed1987

Effects of a gonadotropin-releasing hormone agonist analog (ICI 118630) on endocrine functions of human testis in vivo and in vitro.

Six prostatic cancer patients were treated with a gonadotropin-releasing hormone agonist analog (ICI 118630, ICI Pharmaceutical Division, Macclesfield, England) for 4 weeks, and serum testosterone (T) had fallen to the castration level in all patients. Subsequently, three of the patients were orchiectomized. There were no significant differences in follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) receptors between the testes treated with ICI 118630 and testes obtained from untreated prostatic cancer patients. In the other three patients, testicular responsiveness evaluated using hCG stimulation was similar before and after 4 weeks of treatment. In vitro studies testes removed from untreated prostatic cancer patients were cultured in a medium with or without ICI 118630 for 5 days. There were no significant differences in FSH and hCG receptors and T production between the two groups. In conclusion, ICI 118630 had no direct inhibitory effect on human testes.

Aged↗

PubMed1987

Identification of the specific proteins associated with differentiation of spermatogonia in mice by two-dimensional gel electrophoresis.

Protein synthesis in testicular germ cells was studied during the differentiation of Type A spermatogonia in testes from adult cryptorchid mice to Intermediate and Type B spermatogonia in organ culture by two-dimensional gel electrophoresis. By comparing the patterns of Type A spermatogonia with those of differentiated (Intermediate and Type B) spermatogonia, we found two newly synthesized protein spots that correlated with differentiation. The isoelectric points (pIs) and molecular weights (MWs) of these proteins were estimated to be approximately pI 5.4, MW 67,000, and pI 5.8, MW 28,000, respectively.

Animals↗

PubMed1987

Reduction of human and rat testicular follicle stimulating hormone receptors by human menopausal gonadotrophin in vivo and in vitro.

Reduction of human and rat testicular FSH receptors by hMG was studied in vivo and in vitro. After a single injection of hMG, the number of high affinity FSH receptors were significantly reduced for 5 and 3 d in human and rat testes, respectively, without affecting their affinity. FSH receptor numbers recovered to pretreatment values by 14 d after the injection. Radioactivity in rat testes found 48 h after a s.c. injection of 125I-labelled human FSH was less than 10% of the maximum found 10 h after the injection, showing that the prolonged reduction of FSH receptors after hMG injection was not due to occupancy of the binding sites. Occupied FSH receptors measured in rat testes accounted for about 15% of all receptors on the day after an injection of hMG and for less than 5% after the third day. In experiments in vitro using organ culture techniques, an exposure to hMG for 24 h induced a dose-related significant loss of the specific FSH binding sites for 7 and 5 d in human and rat testes, respectively. Thereafter, the loss was gradually recovered. These findings suggest that the reduction in FSH receptors in human and rat testes by hMG is mainly due to down-regulation of the binding sites and that the testicular organ culture method used in the present study is useful to study hormonal regulation of testicular function, especially in human testes.

Animals↗

PubMed1987

Temperature sensitivity of human spermatogonia and spermatocytes in vitro.

To study the effect of temperature on human spermatogenesis, both the number and DNA synthesis of germ cells were investigated in tissue fragments of human testes cultured for 22 h at 31 degrees C and 37 degrees C. The number of differentiated germ cells such as spermatids and spermatozoa cultured at 37 degrees C was significantly smaller than that cultured at 31 degrees C. The number of spermatogonia and resting primary spermatocytes was not significantly different between these two temperatures, but the functional ability of DNA synthesis in these cells was significantly lower at 37 degrees C than at 31 degrees C. It seems that in normal body temperature (37 degrees C) differentiated germ cells such as spermatids and spermatozoa are fragile and the DNA synthesis of spermatogonia and resting primary spermatocytes is retarded.

Culture Techniques↗