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Biomedical subjects

M Dym

Publications and source records attributed to M Dym.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of Sertoli cell perinuclear filaments.

Sertoli cell nuclei are characterized by deep invaginations and, in addition, the orientation of the nuclei with respect to the wall of the seminiferous tubules varies during the cycle of the seminiferous epithelium. These events may be the result of cytoplasmic filaments acting at the level of the nuclear capsule and may represent significant changes in Sertoli cell activity. Thus, a study was performed to characterize the nature of the perinuclear filaments of Sertoli cells in vivo and in vitro. In Sertoli cells in vivo, microtubules and microfilaments were often detected in the perinuclear cytoplasm, and these cytoskeletal components were observed to course either parallel to, or abut at, the nuclear capsule. In Sertoli cells in vitro, the nuclear infoldings are retained and the perinuclear cytoskeleton was shown to contain microtubules, f-actin, and intermediate filaments. A fixation-permeabilization protocol employing tannic acid-saponin was used and it significantly enhanced the preservation of cytoskeletal components. The presence of f-actin was demonstrated by using the S1 fragment of muscle myosin to decorate the microfilaments. Treatment of the cultured cells with either microtubule or f-actin depolymerizing agents had no effect on nuclear shape. Thus, at present, the function of the prominent perinuclear cytoskeletal components remains unknown.

Actins↗
PubMed1992

Glandular-like morphogenesis of the human submandibular tumor cell line A253 on basement membrane components.

We have studied the interaction of a human tumor cell line, A253, derived from a submandibular gland carcinoma with a differentiation promoting reconstituted basement membrane extract, Matrigel. When cultured on plastic, these cells maintain a flat, cobblestone, epithelial morphology. On Matrigel, A253 cells initially form a honeycomb network of cords of cells which subsequently thickens. With time, these cords of cells become discontinuous and blunted, whereupon multilobular clusters of cells develop. These clusters possess a lumen with polarized, PAS(+) cells containing numerous desmosomes and an abundance of glycogen. Culture of the cells on laminin, the most abundant protein found in Matrigel, also induces this morphologic differentiation. Using synthetic laminin-derived peptides, the biologically active IKVAV-containing site of laminin was most active in attachment assays, as well as in inhibiting glandular-like morphogenesis when added to the media of cells cultured on Matrigel. Antibodies to the cell surface 67- and 32-kDa laminin binding proteins partially inhibited the glandular-like morphogenesis, suggesting that multiple interactions with laminin are likely required for the differentiation process. Our data demonstrate that A253 cells can undergo glandular-like morphogenesis on basement membrane and that laminin appears to be the major initiating factor.

Blotting, Western↗
PubMed1991

cAMP promotes branching of laminin-induced neuronal processes.

Laminin is a potent stimulator of neurite outgrowth. We have examined the signal transduction events involved in the neuronal cell response to laminin. Cyclic nucleotides, calcium, and sodium-proton exchange do not appear to be required for the transduction of the laminin signal during neurite outgrowth. Direct measurement of cAMP and cGMP levels shows no changes in NG108-15 cells when cultured on laminin. Exogenous cAMP alone had no effect on either the rate of process formation or process length, but did alter the morphology of laminin-induced neurites. A four-fold increase in the number of branches per neurite and a two-to-three-fold increase in the number of neurites per cell were observed in both NG108-15 and PC12 cells cultured on laminin when either 8-BrcAMP or forskolin was added. The cAMP-induced branching was also observed when PC12 cells were cultured on a laminin-derived synthetic peptide (PA22-2), which contains the neurite-promoting amino acid sequence IKVAV. By immunofluorescence analysis with axonal or dendritic markers, the PC12 processes on laminin and PA22-2 were axonal, not dendritic, and the cAMP-induced morphological changes were due to axonal branching. These data demonstrate that changes in cAMP are not involved in laminin-mediated neurite outgrowth, but cAMP can modulate the effects of laminin.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1991

Localization of pregnancy-specific beta 1-glycoprotein in the male reproductive tract of the rat by in situ hybridization.

Human pregnancy-specific beta 1-glycoprotein (PSG) is found in high concentrations in the serum of pregnant women, but also has been found in the serum of males and nonpregnant females. Northern slot-blot analysis has demonstrated the presence of PSG mRNA in a variety of tissues in the rat, with the highest levels being found in the testis. Therefore, we have investigated further the expression of PSG in the rat male reproductive tract using in situ hybridization. In testes from immature and adult rats, PSG mRNA was localized in Leydig and peritubular cells, and in the walls of the interstitial blood vessels. PSG transcripts were noted also in the tunica albuginea and in the stromal tissue of the caput and cauda epididymis, prostate, and seminal vesicle from adult rats. The function of PSG is unknown, but it has been speculated that PSG may have immunosuppressive properties or that it may serve as a paracrine regulator of growth and differentiation. It is possible, then, that PSG could contribute to the immunological privilege of the testis or that it plays a role in the cellular interactions which increasingly are being shown to be important in the regulation of male reproductive tract tissues.

Animals↗
PubMed1991

Basement membrane increases G-protein levels and follicle-stimulating hormone responsiveness of Sertoli cell adenylyl cyclase activity.

On a basement membrane substrate, Sertoli cells in culture have been shown to assume a phenotype similar to that of the in vivo differentiated cells. Sertoli cells from 10-day-old rats were cultured on plastic and on different extracellular matrix substrates [laminin, a reconstituted basement membrane (Matrigel), and a synthetic laminin peptide containing the arginine-glycine-aspartic acid (RGD) tripeptide sequence] to investigate the effects of the extracellular matrix on FSH responsiveness. Both laminin and Matrigel markedly enhanced the cAMP response to FSH and cholera toxin, indicating modifications at the level of guanine nucleotide-binding regulatory (G) proteins. Furthermore, Sertoli cell grown on either of these two substrates responded to physiological levels of FSH (25-50 ng/ml), whereas pharmacological levels of FSH (500 ng/ml) were required for cells grown on either plastic or on the RGD-containing laminin peptide. Immunoblotting of Sertoli cell plasma membranes with antibodies directed against the alpha-subunit of the stimulatory G-protein (Gs alpha) of adenylyl cyclase indicated that Sertoli cell culture on either laminin or Matrigel increased the amounts of Gs alpha. These results were further confirmed by immunoprecipitating the Gs alpha protein from the particulate fraction of [35S]methionine metabolically labeled Sertoli cells. However, Northern blot analysis using a cDNA probe for Gs alpha did not demonstrate changes in gene expression when Sertoli cells were grown on the various substrates. Immunofluorescent studies revealed that the Gs complex of adenylyl cyclase was preferentially located at the base of the Sertoli cells at the site of contact with the extracellular matrix. These data suggest that culture of epithelial Sertoli cells on basement membrane substrates enhances the Gs complex of adenylyl cyclase and the cAMP response to FSH, consistent with the more differentiated morphology and function of the cells.

Adenylyl Cyclases↗
PubMed1990

Differential expression of extracellular matrix components in rat Sertoli cells.

We studied expression of laminin, fibronectin, and Type IV collagen in the testis by means of immunofluorescence and immunoblot analysis and also examined gene expression of fibronectin using the ribonuclease protection assay. By immunofluorescence on sections from 20-day-old rats, laminin, fibronectin, and Type IV collagen were found in the basement membrane of the seminiferous tubules and in the interstitial regions of the testis. No localization of any extracellular matrix components was found inside the sectioned cells. However, when Sertoli cells were cultured on glass coverslips, laminin and Type IV collagen were both found inside the cells, suggesting new synthesis. In cultured peritubular cells, Type IV collagen, laminin, and fibronectin were found within the cells. When examined by immunoblot analysis, freshly isolated Sertoli and peritubular cells from 20-day-old rats did not demonstrate production of laminin or fibronectin. After 5 days in culture, peritubular cells produced both laminin and fibronectin, whereas cultured Sertoli cells produced only laminin. In contrast, freshly isolated and cultured Sertoli and peritubular cells all produced Type IV collagen. Moreover, the ribonuclease protection assay indicated that the bulk of fibronectin gene expression occurs within the first 10 days of postnatal development, with lower maintenance levels occurring thereafter. These results indicate that in the testis the highest levels of expression of laminin and fibronectin occur during development and in primary cell culture, whereas expression of Type IV collagen is higher at later stages.

Animals↗
PubMed1979

Testicular testosterone concentration following testicular vein ligation.

UNLABELLED: A rat model to study the local effects of testicular vein ligation is described. One hour after unilateral testicular vein ligation, the testicular concentration of testosterone was significantly greater (P less than 0.01) on the side that was ligated than in the contralateral testis (177.1 +/- 19.7 [SEM] ng/gm of tissue as compared with 108.8 +/- 11.8 ng/gm of tissue, respectively). This effect was not seen 1 week after the testicular vein ligation. The testosterone concentration in the ligated testis was also higher than that in sham-operated animals. These differences in testicular testosterone concentration were not associated with changes in peripheral serum testosterone levels. CONCLUSION: ligation of the testicular vein causes an acute rise in the testicular concentration of testosterone and may thus mediate changes in testicular function.

Animals↗
PubMed1979

Protein carboxyl-methylation in rat testes: a study of inherited and X-ray-induced seminiferous tubule failure.

Protein carboxyl-methylase (PCM), the enzyme that transfers methyl groups from S-adenosyl-methionine to free carboxyl groups on proteins, is highly localized in testes. The cellular distribution of PCM and its substrates, the methyl acceptor proteins, was investigated. Separation of testicular cells on an albumin gravity gradient revealed the preferential localization of both enzyme and substrates in spermatids. In young rats, PCM activity increases with age coincidently with germ cell maturation. Rats which are heterozygous for the Hre gene (Hre/+) are infertile as a result of germ cell depletion. In these animals, testicular PCM specific activity and total activity were, respectively, 4--6 and 40--50 times lower than in normal testes. Enzyme activity in testes from animals with x-ray-induced germ cell depletion was also very low. These observations suggest that PCM is located in germ cells.

Animals↗
PubMed1979

Is FSH required for maintenance of spermatogenesis in adult rats?

Administration of FSH antiserum to adult rats for 14 or 30 days had no or little effect on body, testis or accessory sex gland weights, androgen-binding protein, testosterone levels, germ cell numbers or fertility, thus indicating a relative insensitivity of the testis to withdrawal of FSH. Unlike immature rats, therefore, which do require FSH to initiate spermatogenesis, adult rats do not need this hormone to maintain spermatogenesis.

Age Factors↗
PubMed1978

Unusual features of the nuclear envelope in human spermatogenic cells.

Different types of human germ cells show unusual features of the nuclear envelope. Spermatogonial nuclei demonstrate two kinds of modifications. The first one is a series of intranuclear flattened cisterns, parallel to each other and to the inner aspect of the nuclear envelope. The second one is a nuclear envelope protrusion into the cytoplasm occupied by a double membrane-limited vesicle. Pores are found on the membrane of the vesicle facing the interior of the nucleus. In spermatocytes the nuclear pores are concentrated over certain areas and completely absent from others. In the regions where they are absent a single cytoplasmic cistern of rough endoplasmic reticulum is closely apposed to the outer membrane of the nuclear envelope. Early modifications of the nuclear surface appear in spermatids before the attachment of the acrosomic vesicle and may indicate an active role of the nuclear envelope in the morphogenesis of the acrosome. In round spermatids nuclear pores are absent from the area which is first related to the Golgi and later covered by the acrosomal cap. Single or multiple layers of cytoplasmic annulate lamellae are closely associated with the nuclear envelope over the pore rich areas. Frequently there are intranuclear accumulations of dense material adjacent to the annulate lamellae-nuclear pore complex. The chromatoid body is usually present on the cytoplasmic side of this complex. In the elongating spermatids most annulate lamellae are free in the cytoplasm, often in relation with Golgi and chromatoid body remnants near the axial filament. Few stacks of annulate lamellae are noted adjacent to the pore rich nuclear regions. It is suggested that the described modifications are related to an active nuclear-cytoplasmic interaction.

Adult↗