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M Davidoff

Publications and source records attributed to M Davidoff.

At least 19 recordsLinked to original sources
PubMed2002

Steroidogenic and structural differentiation of new Leydig cell population following exposure of adult rats to ethane dimethanesulphonate.

EDS alkylating agent has been shown to selectively and temporarily kill LCs in adult rats. The first newly formed single LCs appeared at 14th day post ESD and showed detectable activity for 3beta-HSD and NADH2-diaphorase, which became progressively stronger with time after treatment The ultrastructural study revealed that the progenitor LCs differentiated into immature LCs within a week, and two weeks later they were transformed into mature LCs. Therefore, the restoration of new LC population after EDS treatment repeated the dynamics of normal LC development within a similar time range. The dynamics of enzyme activity correlated with structural differentiation of the new LC population.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Degeneration and restoration of spermatogenesis in relation to the changes in Leydig cell population following ethane dimethanesulfonate treatment in adult rats.

OBJECTIVE: To investigate degeneration and restoration patterns of spermatogenesis in relation to the changes in Leydig cells (LCs) after treatment with ethane dimethanesulfonate (EDS). MATERIALS AND METHODS: Adult Wistar male rats were treated with EDS at a dose 75 mg/kg body weight and the testes were sampled at 7, 14, 21, 35 and 49 days after treatment for histological and ultrastructural studies. RESULTS: During the first two weeks after treatment stage dependent loss of germ cells was found within seminiferous tubules that led to a profound disturbance of spermatogenesis. The restoration of seminiferous epithelium followed also in stage specific manner and in relation to development of a new LC population (third week). The development of new LCs after EDS treatment repeats the normal dynamics of postnatal LC development within a similar time range. CONCLUSION: EDS treatment of rats causes a temporary germ cell degeneration in the testis. The kinetics of disappearance of germ cells and their regeneration broadly follows the changes in LC population.

Animals↗
PubMed1999

Identification of urotensin II as the endogenous ligand for the orphan G-protein-coupled receptor GPR14.

Urotensin II (UII) is a neuropeptide with potent cardiovascular effects. Its sequence is strongly conserved among different species and has structural similarity to somatostatin. No receptor for UII has been molecularly identified from any species so far. GPR14 was cloned as an orphan G protein-coupled receptor with similarity to members of the somatostatin/opioid receptor family. We have now demonstrated that GPR14 is a high affinity receptor for UII and designate it UII-R1a. HEK293 cells and COS-7 cells transfected with rat GPR14 showed strong, dose-dependent calcium mobilization in response to fish, frog, and human UII. Radioligand binding analysis showed high affinity binding of UII to membrane preparations isolated from HEK293 cells stably expressing rat GPR14. In situ hybridization analysis showed that GPR14 was expressed in motor neurons of the spinal cord, smooth muscle cells of the bladder, and muscle cells of the heart. The identification of the first receptor for UII will allow better understanding of the physiological and pharmacological roles of UII.

Amino Acid Sequence↗
PubMed1999

Immunocytochemical expression of p75LNGFR and trkA in Leydig cells of the human testis.

The authors demonstrate for the first time the immunocytochemical expression of the low-affinity neurotrophic growth factor (NGF) receptor p75LNGFR and the high-affinity NGF receptor trkA in the human testis. Employing the polyclonal anti-p75LNGFR antibody and the polyclonal anti-trkA antibody they report strong immunoreactivity for those antigens in the interstitial Leydig cells. Sertoli cells and some cellular elements of the germinative epithelium were also trkA-positive. These findings implicate the neurotrophic factor NGF and its receptors p75LNGFR and trkA in the autocrine and paracrine regulation of the steroidogenic activity of Leydig cells of the human testis.

Adult↗
PubMed1996

Capillaries in the lamina propria of human seminiferous tubules are partly fenestrated.

The three capillary parts of the microvasculature of the human testis, namely the arterial side inter-Leydig cell capillaries, the intramural capillaries, and the venous side inter-Leydig cell capillaries, were studied in detail by dual detection of alkaline phosphatase enzyme activity and endothelial marker immunoreactivity, and by means of light- and transmission-electron microscopy. Alkaline phosphatase enzyme activity was seen in intertubular arterioles, capillaries, and venules, and in intramural capillaries of the human testis, whereas the lamina propria of human seminiferous tubules showed no staining. Alkaline phosphatase enzyme activity and the endothelial marker detected by the Qbend 30 antibody co-existed within the endothelial cells of the microvasculature. Electron-microscopically, the endothelial cells of the arterial and venous side inter-Leydig cell capillaries, and of the intertubular capillaries free of Leydig cells were of the continuous type without fenestrations (A-1-alpha type). The intramural capillaries consisted of non-fenestrated (A-1-alpha type) and fenestrated sections (A-2-alpha type). The fenestrations faced the germinal epithelium. Capillaries with a continuous non-fenestrated endothelium contained a large number of transcytotic vesicles and channels. These were numerous in the endothelial cells of the inter-Leydig cell capillaries and the non-fenestrated part of the intramural capillaries. Capillaries partly ran in between the layers of the lamina propria and therefore represented the capillarization of the seminiferous tubules. Thus the multilayered lamina propria probably requires its own capillary supply to allow rapid exchange between the microvasculature and the epithelium of the human seminiferous tubules.

Arterioles↗
PubMed1996

Expression of C-type natriuretic peptide in the bovine pineal gland.

Recent studies have pointed to membrane-bound guanylyl cyclases (GCs) type A and type B in the rat pineal gland, which augment levels of cyclic GMP (cGMP) in response to atrial natriuretic peptide (ANP), brain-type natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). The present report demonstrates for the first time the expression of CNP in the bovine pineal gland. The CNP prohormone transcript (unlike pre-pro-ANP) was found by reverse transcriptase (RT)-PCR in bovine pineal extracts. CNP immunoreactivity (ir) was revealed in a subpopulation of pinealocytes in situ and in nearly all pinealocytes in culture. Electron microscopic immunohistochemical investigations showed the presence of CNP-ir in cytoplasmic vesicles, providing evidence for the potential secretion of this peptide by pineal cells. Furthermore, the CNP receptor (GC-B) and GC-A (receptor for ANP and BNP) were identified by RT-PCR. Although melatonin secretion was unaffected, natriuretic peptides were able to elevate markedly cGMP production in cultured bovine pinealocytes with a rank order of potency of CNP > BNP = ANP. These findings describe a tissue CNP system in the bovine pineal gland and suggest that CNP may be a local auto- or paracrine modulator of pineal function.

Animals↗
PubMed1994

Post-transcriptional block in oxytocin gene expression within the seminiferous tubules of the bovine testis.

Northern blot hybridization showed that bovine and sheep testis, unlike testes from other mammals, contain moderate levels of an apparently normal oxytocin gene transcript. In situ hybridization localized this mRNA to within the seminiferous tubules, possibly in the Sertoli cells. Conflicting with this result, immunohistochemistry showed that both oxytocin and the syngeneic neurophysin I epitopes are both clearly restricted to the Leydig cells, being expressed here at a low level. Since illegitimate transcription from spurious start sites can lead to a lack of translation product, the integrity of the major ruminant testicular transcripts of the oxytocin gene was checked using differential hybridization. RNase protection and multiple polymerase chain reaction assays. All tests showed the transcripts to have a normal, translatable composition and to be transcribed from the conventional 5' initiation site. Therefore, the block in oxytocin gene expression within the tubules is probably due to a lesion at the post-transcriptional level. The low level peptide expression in the Leydig cells can probably be attributed to the presence of functional transcripts in these cells, which are below the level of significant detection for the in situ hybridization assay.

Animals↗
PubMed1993

Localization and partial characterization of a rat ovarian granulosa cell protein with a monoclonal antibody.

Hybridoma cell lines were obtained from mouse splenocytes sensitized to granulosa cells collected from rat ovaries after gonadotropin stimulation. A monoclonal antibody (5G5) was obtained which reacted with granulosa cells and showed a positive reaction with serum-free conditioned medium containing granulosa cell secreted proteins. Immunoblotting of the conditioned medium and light- and electron-microscopic immunocytochemistry of rat ovary show that mAb 5G5 is directed against a 59-kDa protein which is located on the plasma membrane of granulosa cells. Furthermore, the immunoreactivity of the granulosa cells depends both on the degree of follicle development and on the position of the granulosa cells within the follicles. Strong immunoreactivity was observed in the innermost granulosa cell layers, close to the oocyte and the antral cavity. The results obtained show that mAb 5G5 is a useful marker of a 59-kDa granulosa cell protein which might be of importance for the development of the follicle and the oocyte maturation.

Animals↗
PubMed1992

Age-related changes in serotonin-immunoreactive neurons in the rat nucleus raphe dorsalis and nucleus centralis superior: a light microscope study.

Comparison of serotonin-immunoreactive (SER-IR) neurons in the nucleus raphe dorsalis (NRD) and the nucleus centralis superior (NCS) of 3-month-old and 28-month-old rats was made using qualitative and quantitative immunohistochemical analysis. Significant age-related changes in size and density of the SER-IR somata as well as in the length and number of their processes were demonstrated. A different vulnerability of the SER-IR neurons in both raphe nuclei to aging was observed that may be related to their different structural and functional features.

Aging↗
PubMed1992

Age-related morphological and morphometrical changes in parvalbumin- and calbindin-immunoreactive neurons in the rat hippocampal formation.

Parvalbumin (PV)- and calbindin (CaBP)-immunostaining in the hippocampal formation of 3-, 11- and 28-month-old Wistar rats was studied using monoclonal antibodies. A quantitative analysis of the densities, cross-sectional areas, length and number of processes of PV-immunoreactive neurons in the hippocampal dentata and CA1 areas of the three age groups was employed. Marked age-related changes in the morphological appearance and in the quantitative parameters characterizing the PV-immunoreactive neurons in both hippocampal regions were observed. The intensity of CaBP-immunostaining of the hippocampal principle cells and interneurons remained the same but the immunoreactive fibers were structurally altered in aging.

Aging↗
PubMed1992

Age-related changes in cholinergic and noradrenergic transmission in the rat cerebellum. A histochemical and immunocytochemical study.

The histochemical and immunocytochemical distribution of some cholinergic and noradrenergic markers was compared in the cerebellum of young adult (3-month old) and aged (24-month old) Wistar rats. A decrease in the density and staining of acetyl cholinesterase (AChE) positive fibers, puncta and Golgi cells was found in both the cerebellar cortex and nuclei of aged rats. The age-related changes in choline acetyltransferase immunoreactivity were less pronounced than the changes in AChE activity. A reduction in the density of catecholamine fluorescent fibers and puncta was observed in the cerebellar cortex during aging. In aged rats the increase in monoamine oxidase (MAO)-A activity was more pronounced than the increase in MAO-B activity.

Acetylcholinesterase↗
PubMed1991

Substance P- and neuron-specific enolase-like immunoreactivity of rodent Leydig cells in tissue section and cell culture.

Comparative immunocytochemical studies concerning the presence of a neurotransmitter (substance P), and a marker of neuroendocrine cells (neuron-specific enolase), in the Leydig cells of 3 mammalian species (golden hamster, guinea pig, and rat) were carried out on tissue sections and cell cultures. Substance P(SP)-like immunoreactivity (-LI) was found to be present in both fetal and adult generation of Leydig cells in hamster and guinea pig, while neuron-specific enolase (NSE)-LI was detected in Leydig cells of the 3 species at all stages studied: fetal, neonatal and adult. In primary cultures of Leydig cells isolated from adult hamster testes, SP- and NSE-LI was also established. This result was considered as an indirect evidence for the synthesis of the substances under study by the steroidogenic cells of the testis. A comparison of these results with data obtained in vivo suggests that Leydig cells may be related to the APUD- or the diffuse neuroendocrine system.

Animals↗
PubMed1991

Tachykinin (substance-P) gene expression in Leydig cells of the human and mouse testis.

Specific substance-P immunoreactivity can be detected in the Leydig cells, particularly of human testes, and to a lesser degree in mouse Leydig cells, but not in the rat. Using a modified polymerase chain reaction (PCR) assay, preprotachykinin-A (substance-P) mRNA could be detected in extracts of human, mouse, and bovine testes, but not in rat or boar testes or in bovine thyroid or corpus luteum used as negative controls. This assay is able to discriminate among the alpha, beta, and gamma transcripts of the gene and shows that only the beta and gamma transcripts are present in the testes. Sequencing analysis of the PCR products from bovine hypothalamus, mouse brain, and human testis confirmed the structure of these transcripts, which encode both substance-P and neurokinin-A (substance-K) neuropeptide hormones. Using a variant of this assay it was possible to identify tachykinin transcripts in as few as 500 freshly prepared purified mouse Leydig cells. In parallel studies PCR analysis was also able to confirm the presence of mRNA for both substance-P and neurokinin-A receptors in human testes. Thus, the tachykinins substance-P and neurokinin-A must now be added to the list of potentially paracrine substances regulating intratesticular function.

Aged↗
PubMed1991

Substance P: immunocytochemical localization and biological role in hamster gonads during ontogenesis.

The cellular localization of substance P immunoreactivity was demonstrated at light microscopy level in hamster gonads during foetal and postnatal development. Selective immunostaining was observed in both the foetal and the adult generation of Leydig cells, but only in the luteal and interstitial cells of the adult ovary. To date there have been few studies dealing with the potential role of substance P in the control of gonadal functions. To examine whether it exerts an effect on gonadal steroidogenesis, the gonads of newborn, prepuberal and adult hamsters were cultured in vitro in the presence of substance P (10(-7) M), HCG (5 IU/ml) or substance P + HCG. Production of the sex steroid hormones testosterone, oestradiol-17 beta and progesterone was measured by radioimmunoassay. Substance P was observed to have a modulatory effect on steroid production by foetal, immature and mature gonads of both sexes.

Animals↗
PubMed1991

Changes in GABA-immunoreactivity and GABA-transaminase activity in rat amygdaloid complex in aging.

The distribution of gamma-aminobutyric acid (GABA), gamma-aminobutyric acid-transaminase (GABA-T) and glial fibrillary acid protein (GFAP) in the amygdaloid complex of young adult (3-month old) and aged (26-month old) Wistar rats was compared by using histo- and immunohistochemical techniques. The study revealed a heterogeneous distribution of GABA-immunoreactive and GABA-T positive nerve cells, fibers and terminals in various amygdaloid nuclei of young adult rats. A significant reduction in the density of GABA-immunoreactive neurons was demonstrated in the amygdala of aged rats. Reduced density and staining of GABA- and GABA-T-positive fibers and terminals were also seen in aged rat amygdala. Heavily GABA- and GABA-T-stained aberrant fibers and coarse puncta were clustered around blood vessels as well as under the pial and ependymal surfaces. GFAP-immunostaining demonstrated numerous hypertrophic astrocytes in these areas.

4-Aminobutyrate Transaminase↗
PubMed1990

Combination of the peroxidase anti-peroxidase (PAP)- and avidin-biotin-peroxidase complex (ABC)-techniques: an amplification alternative in immunocytochemical staining.

A combination of the PAP- and ABC-techniques was developed to enhance the intensity of the immunocytochemical staining with monoclonal antibodies at light and electron microscopical levels. This amplification technique could be performed in 4 (single PAP + ABC) or 6 (double PAP + ABC) sequential steps depending on the quality of the primary antibodies used and the processing of the tissue before the immunocytochemical reaction: First step--Incubation of the tissue sections with the monoclonal primary antibodies; Second step--biotinylated anti-rat or anti-mouse IgG; Third step--monoclonal PAP complex; Fourth step--ABC complex which binds to the biotinylated secondary antibody. If stronger enhancement of the immunostaining has required the steps 2 and 3 could be repeated followed by the 6th step--the ABC complex. Choline acetyltransferase-like immunoreactivity of the rat hypoglossal nucleus and desmin- and vimentin-like immunoreactivity of human testis were studied. After the 4- and more pronounced the 6-step reaction a significant increase of the staining intensity was observed for all the reactions under study. ChAT-like immunoreactivity was observed to longer distances of the nerve cell dendrites after their emerging from the perikarya and within a greater number of structures in the neuropil as compared to the standard techniques. At electron microscopical level the technique permits longer fixation of the tissue which is important for the better preservation of the ultrastructure as well as for the easier recognition of the reaction product even in the smallest dendrite branches and the axons of the nerve cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗