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A Mayerhofer

Publications and source records attributed to A Mayerhofer.

At least 19 recordsLinked to original sources
PubMed2006

Non-neuronal acetylcholine and choline acetyltransferase in oviductal epithelial cells of cyclic and pregnant pigs.

Certain female reproductive tissues are known to express the non-neuronal cholinergic system. Using different experimental approaches, we tested the hypothesis that acetylcholine (ACh) in the porcine oviduct may also be derived from non-neuronal structures. Immunohistochemistry was performed to detect acetylcholine synthesizing enzyme choline acetyltransferase (ChAT) in different segments of the oviduct of cyclic and pregnant sows. Immunohistochemical experiments revealed strong immunoexpression of ChAT in the entire oviductal epithelium at metoestrus. Thereby, a particular pronounced staining was found in the supranuclear region of almost all epithelial cells. Immunostaining of ChAT decreased markedly during dioestrus and prooestrus stages, respectively. At prooestrus, ChAT immunoreactivity was confined to ciliated cells. Furthermore, we found elevated level of staining intensity of ChAT in the pregnant oviduct at day 13. Using the same ChAT antibody for Western blot analyses, we detected immunoreactive bands of MW 69,000 and 46,000 mainly in ampulla, while MW 58,000 and 30,000 forms were present mainly in infundibulum and isthmus. Furthermore ACh was detected by HPLC and fluorimetric methods in oviductal epithelium. In conclusion, we show expression of ChAT in oviductal epithelial cells at different stages of the oestrus cycle and pregnancy, indicating that these cells can synthesize ACh in a cycle-dependent manner. These results suggest as yet unexplored roles of epithelial ACh in the oviduct.

Acetylcholine↗
PubMed2005

Divergent effects of the major mast cell products histamine, tryptase and TNF-alpha on human fibroblast behaviour.

Fibroblast proliferation is a key process in tissue remodeling and mast cells (MCs) are thought to play a crucial role. Having established that the three major MC products, tryptase, histamine and TNF-alpha (TNF) are normally present in human skin MCs, which are in close proximity to dermal fibroblasts, we studied their individual effects on cell cycle-controlled human dermal fibroblasts (HFFF2). These cells express receptors (H1, PAR2, TNFR1/2) for the major MC mediators, but only tryptase or a PAR2 agonist peptide stimulated proliferation and gene expression. TNF was antimitotic, and histamine, while elevating intracellular Ca2+ levels at high concentrations, did not affect proliferation. We conclude that MC products but also composition and numbers of respective receptors on fibroblasts are crucially responsible for fibroproliferative events.

Cell Cycle↗
PubMed2004

Tryptase inhibits motility of human spermatozoa mainly by activation of the mitogen-activated protein kinase pathway.

BACKGROUND: We previously localized protease-activated receptor 2 (PAR-2) on human spermatozoa and demonstrated that activation of PAR-2 by the mast cell (MC) product tryptase inhibits sperm motility. Importantly, tryptase-secreting MCs are encountered in the male and female genital tract, implying that MC-spermatozoa interactions may be as yet unrecognized factors affecting sperm fertilizing ability. In order to elucidate how tryptase via activation of PAR-2 acts in human spermatozoa, we studied intracellular signal transduction events. METHODS AND RESULTS: Impairment of sperm motility by tryptase was not dependent on the presence of extracellular Ca2+ and tryptase did not alter intracellular Ca2+ levels. Pre-incubation with pertussis toxin (PTX) failed to prevent tryptase effects on sperm motility. Western blot analyses revealed that tryptase increased phosphorylation of the mitogen-activated protein kinases (MAPK) ERK1/2, an effect which was blocked by the MAPK pathway inhibitor PD98059. Pre-treatment of spermatozoa with this inhibitor also blocked the inhibtion of sperm motility evoked by tryptase. CONCLUSIONS: These results indicate that tryptase acts via the ERK1/2 pathway to inhibit motility of human spermatozoa.

Calcium↗
PubMed2004

The neurobehavioral changes induced by bilateral rotenone lesion in medial forebrain bundle of rats are reversed by L-DOPA.

Rotenone (an inhibitor of mitochondrial complex I) has been proposed as a model of Parkinson's disease (PD) as it induces nigrostriatal degeneration associated with alpha-synuclein inclusions. So far, only peripherally administered rotenone has been used as a model of PD. There has not been any investigation on the neurobehavioral changes induced by bilateral lesions of dopaminergic neurons by rotenone in rats. In the present study, rotenone (3 microg) was administered bilaterally stereotaxically into the medial forebrain bundle (MFB) to produce parkinsonian symptoms. Behavioural and biochemical data showed a strong increase in catalepsy, a decrease in locomotor activity and a significant depletion of dopamine levels in the striatum as compared to sham-lesioned animals. If the locomotor deficits are caused by the depletion of dopaminergic neurons, then L-DOPA should counteract motor deficits because L-DOPA therapy reverses mostly all motor deficits in human Parkinsonian patients. To examine the effectiveness of L-DOPA in reversing the motor deficit in rats, two different doses of L-DOPA (5 and 10 mg/kg) in combination with the peripheral amino acid decarboxylase inhibitor benserazide were daily administrated intraperitonially for a period of 31 days lesioned animals. L-DOPA plus benserazide counteracted catalepsy dose-dependently and increased locomotor activity. The results indicate that rotenone infused into the MFB destroys dopaminergic neurons, induces pakinsonian symptoms that are reversed by the clinically effective anti-parkinsonian drug L-DOPA. Therefore, sterotaxically infused rotenone may be useful for screening drugs for the treatment of PD.

Analysis of Variance↗
PubMed2004

Ovarian function and morphology after deletion of the DARPP-32 gene in mice.

A plethora of systemic and local signaling molecules regulate ovarian function, but how different signaling molecules interact within an ovarian target cell is not known. Here we report that endocrine cells of the ovary express a phosphoprotein, DARPP-32 (dopamine and cyclic AMP-regulated phosphoprotein of Mr 32,000), which integrates signaling molecules in neurons. We thus hypothesized that DARPP-32 might act in a similar way in ovarian endocrine cells and therefore studied whether DARPP-32 gene deletion has consequences for ovarian functions in mice. Reproductive performance of adult mutants did not differ from wild-type females, as judged from numbers of litters and pups delivered. Similar steroid levels in mutant and wild-type mice ruled out gross abnormalities in the hypothalamic-pituitary-ovarian axis. However, an analysis of ovarian morphology, using serially sectioned ovaries, revealed several differences. Ovaries of young adult mutant mice at 2 - 3 months contained luteinized follicles, but fewer corpora lutea. At 5 - 6 months, large cysts were found in mutant mice, as well as reduced numbers of preantral follicles and antral follicles. Interstitial cell hypertrophy and degeneration was marked in all mutant ovaries at this age. Thus, while the lack of DARPP-32 does not overtly alter reproductive performance in adult mice, it is associated with progressive alterations and derangements of growth and development of ovarian follicles, suggesting premature ovarian ageing. This implies that ovarian DARPP-32 is involved in follicular development, presumably by integrating effects of signaling molecules, which act together to ensure efficient follicular development.

Animals↗
PubMed2003

Is the Ecstasy-induced ipsilateral rotation in 6-hydroxydopamine unilaterally lesioned rats dopamine independent?

3,4-Methylenedioxymethamphetamine (MDMA) has recently been hypothesized to be effective against the symptoms of Parkinson's disease. Therefore we tested the effects of MDMA-derivatives in the rotational behavioural model. Male Sprague Dawley rats were lesioned unilaterally with 6-hydroxydopamine at the medial forebrain bundle. MDMA was administered at doses of 2.5, 5.0 and 10.0 mg/kg, its derivatives N-Methyl-1-(1,3-benzodioxol-5-yl)-2-butananamine (MBDB), 3,4-Methylenedioxy-N-ethylamphetamine (MDE) and 3,4-Methylenedioxyamphetamine (MDA) at 5.0 mg/kg respectively. All substances induced ipsilateral rotations, MDA being the most effective. MDMA induced rotations were attenuated by the selective serotonin reuptake inhibitor Citalopram but were only slightly reduced by pre-treatment with the selective serotonin synthesis inhibitor PCPA (para-chlorophenylalanine). The effects of MDMA can therefore not fully be explained by serotonin release or by dopaminergic activity of the drugs.

3,4-Methylenedioxyamphetamine↗
PubMed2003

Mast cell-sperm interaction: evidence for tryptase and proteinase-activated receptors in the regulation of sperm motility.

BACKGROUND: The detection of significant levels of tryptase in human seminal plasma and follicular fluid and of tryptase-positive mast cells (MCs) in the wall of human Fallopian tubes lead us to hypothesize that tryptase may exert regulatory actions on human spermatozoa. METHODS AND RESULTS: Immunoelectronmicroscopy revealed proteinase-activated receptor 2 (PAR-2) in the membranes of the acrosomal region and midpiece of human spermatozoa. These PAR-2 were functional, as exposure of spermatozoa from healthy men (n = 12) with regular standard semen parameters to human recombinant tryptase significantly decreased motility in a dose- and time-dependent fashion. Motile spermatozoa (WHO a + b) were significantly decreased within 10 min of incubation with 1.000 ng/ml tryptase (P = 0.045). After 30 and 60 min, significant reduction of motility was also observed in the presence of lower tryptase concentrations (100 ng/ml, P = 0.037; 10 ng/ml, P = 0.046). The inhibitory effects of tryptase progressed throughout an observation period of 180 min. Furthermore, tryptase effects were reversible after washing procedures and could be inhibited by pretreatment with anti-tryptase antibody or anti-PAR-2 antiserum. CONCLUSIONS: The observations presented raise the possibility that tryptase directly interacts with human spermatozoa during their migration through the female genital tract. Genital tract MCs and their products may be as yet unrecognized factors involved in human fertility/sterility.

Acrosome↗
PubMed2002

Changes in sympathetic nerve activity of the mammalian ovary during a normal estrous cycle and in polycystic ovary syndrome: Studies on norepinephrine release.

Although it has been known for many years that the ovary is innervated by catecholaminergic nerve fibers and much experimental evidence has strengthened the notion that catecholamines are physiologically involved in the control of ovarian function, scarce evidence has been presented as to the role of sympathetic activity in ovarian pathologies that affect reproductive function. The purpose of this article is to provide a succinct overview of the findings in this area and discuss them relative to the pathology of polycystic ovary syndrome, the most common ovarian pathology in women during their reproductive years.

Animals↗
PubMed2002

Protein kinase inhibitors modulate time-dependent effects of UV and ionizing irradiation on ICAM-1 expression on human hepatoma cells.

PURPOSE: To investigate modulation of the expression of the adhesion protein ICAM-1 by UV and ionizing irradiation. MATERIALS AND METHODS: HepG2 hepatoma cells were irradiated in vitro with UVB (20 mJ cm(-2)) or X-rays (5 Gy), respectively. Gene expression of ICAM-1 after irradiation was quantified by RT-PCR. Cell surface density of ICAM-1 was determined by flow cytometry. Protein or lipid kinase inhibitors were used to clarify radiation-induced transduction pathways that control ICAM-1 expression. Immuno-electron microscopy and dot-blot analysis were used to examine localization of ICAM-1. RESULTS: The study showed time-dependent effects of ionizing and UV irradiation on ICAM-1 expression of HepG2 cells. After an immediate transient decrease of ICAM-1 cell surface expression within minutes to hours, ICAM-1 expression increased up to 1.35-fold over normal level at 48 h post-irradiation. Irradiation caused ICAM-1 to become internalized into lysosomes. Additionally, ICAM-1 together with parts of the cell were pinched off. Finally, ICAM-1 levels were down- and up-regulated by decreased or increased gene expression. The early decrease of ICAM-1 expression could be blocked by a potent PKC inhibitor (BisX), whereas the increase of ICAM-1 after 24 h was prevented by addition of the p38 MAP kinase inhibitor SB 203580. CONCLUSION: The data suggest that ICAM-1 expression is modulated by UV, as well as ionizing radiation, in a time-dependent way involving PKC and p38 MAP kinase pathways.

Carcinoma, Hepatocellular↗
PubMed2002

Development of an experimental ovarian tumor: immunocytochemical analysis.

OBJECTIVE: The aim of the present work was to study whether immunocytochemical parameters present in the normal ovary were altered after tumor development under high gonadotropin levels. METHODS: Ovarian tumors (luteoma): castrated female rats had an ovary grafted into the spleen; tumors were left to develop for 1, 2, 3 or 7 months. The presence of apoptotic cells (TUNEL method) and the expression of proliferating cell nuclear antigen (PCNA), gap junction protein (Cx43), steroidogenic acute regulatory protein (StAR), aromatase and synaptosome-associated protein of 25 kDa (SNAP-25) were determined by immunocytochemistry. Some of these findings were confirmed by RT-PCR (Cx43, StAR, SNAP-25). Inhibin subunit mRNAs were investigated by Northern blot. RESULTS: PCNA staining of tumors was mainly found in granulosa cells of transforming follicles and was absent from luteinized follicles. A nearly complete absence of apoptosis was observed. Cx43 was mainly found in follicles, while it was very weakly expressed or absent in luteinized follicles. StAR protein expression, indicating active steroidogenesis, was demonstrated only in luteinized follicles and in thecal cells, but was absent from granulosa cells. Aromatase immunoreactivity was very intense in granulosa and also present in luteal cells. Membrane-associated and cytoplasmic SNAP-25 immunostaining was determined in patches of endocrine cells in the follicles, as well as in the luteinized follicles. The expression of mRNAs for Cx43, StAR and SNAP-25 (RT-PCR) and inhibin subunits (Northern blots) were confirmed in 1-, 3- and 7-month-old tumors. CONCLUSIONS: These results indicated that luteoma most likely develop from unruptured follicles by hypertrophy and proliferation of follicular cells. Circulating gonadotropins seem to play a fundamental role in maintaining the expression of proteins typically expressed in normal ovary, while avoiding apoptosis in this tissue.

Animals↗
PubMed2001

Changes in serotonin, dopamine and noradrenaline levels in striatum and nucleus accumbens after repeated administration of the abused drug MDMA in rats.

The selective neurotoxic action of the abused drug 3,4-methylenedioxymethamphetamine (MDMA) on the serotonergic axons ascending from the dorsal raphe nucleus (DRN) is well known. The present study examined the long-term effects of subchronic MDMA treatment on rat brain tissue contents of catecholaminergic neurotransmitters. Two and four weeks after cessation of repeated MDMA treatment (ten consecutive days, 20 mg/kg/day), the tissue neurotransmitter concentrations were measured by means of electrochemical detected HPLC in several forebrain areas and DRN. We found reduced serotonin levels in the whole forebrain at both instants of time. In nucleus accumbens (NAC), the noradrenaline levels were also decreased, whereas dopamine levels were increased 4 weeks after treatment. It is concluded that MDMA causes changes of monoamine transmitter levels outlasting cessation of drug intake for at least 4 weeks. Decreased noradrenaline and/or serotonin may subsequently cause the augmentation of dopamine in NAC, a structure crucially involved in motivation circuits. With exception of transmitter alterations in the NAC, the post drug effects are opposite to the acute effects of MDMA and may underlie the psychiatric changes after MDMA intake in humans.

Animals↗
PubMed2001

StAR protein is increased by muscarinic receptor activation in human luteinized granulosa cells.

Cultured human luteinized granulosa cells (GC) are a unique model to study regulation of the human corpus luteum, e.g. by local factors, including acetylcholine (ACh). GC express functional ACh-receptors of the M1-type (M1R). Priming with the cholinergic agonist carbachol for 24 h, followed by a 24 h stimulation with human chorionic gonadotrophin (hCG), significantly increased progesterone levels (up to 2-fold), compared with hCG stimulation alone. This is likely due to the effect of carbachol, observed after 24 h, to increase the levels of steroid acute regulatory (StAR) protein, as found in Western blots. StAR protein was increased (2-10-fold), while P450 side chain cleavage (SCC) enzyme was unaffected. Thus, one role of muscarinic receptor activation in human GC is regulation of StAR protein and, subsequently, progesterone production.

Carbachol↗
PubMed2001

Expression of muscarinic receptor types in the primate ovary and evidence for nonneuronal acetylcholine synthesis.

The presence of muscarinic receptors (MR) in the ovary of different species has been recognized, but the identity of these receptors as well as ovarian sources of their natural ligand, acetylcholine (ACh), have not been determined. Because luteinized human granulosa cells (GC) in culture express functional MR, we have determined whether the group of the related MR subtypes, M1R, M3R, and M5R, are present in vivo in human and rhesus monkey ovaries. To this end, ribonucleic acids (RNAs) of different human and monkey ovaries as well as RNAs from human GC and monkey oocytes were reverse transcribed and subjected to PCR amplification, followed by sequencing of the amplified complementary DNAs. Results obtained showed that M1R, M3R, and M5R messenger RNAs are present in adult human and monkey ovaries; oocytes express exclusively the M3R subtype, whereas GC express M1R and M5R. To determine the ovarian source(s) of the natural ligand of these ACh receptors, we attempted to localize the enzyme responsible for its synthesis with the help of a monoclonal antibody recognizing choline acetyltransferase for immunohistochemistry. In neither human nor monkey sections did we detect immunoreactive choline acetyltransferase-positive fibers or nerve cells, but, surprisingly, GC of antral follicles showed prominent staining. To determine whether GC can produce ACh, human cultured GC derived from preovulatory follicles were analyzed using a high pressure liquid chromatography technique. The results showed that these cells contained ACh in concentrations ranging from 4.2-11.5 pmol/10(6) cells. Samples of a rat granulosa cell line likewise contained ACh. Thus, the ovary contains multiple MR, and GC of antral follicles are able to synthesize ACh, the ligand of MR. We propose that ACh may serve as an as yet unrecognized factor involved in the complex regulation of ovarian function in the primate, e.g. regulation of cell proliferation or progesterone production.

Acetylcholine↗
PubMed2000

Human testicular mast cells contain tryptase: increased mast cell number and altered distribution in the testes of infertile men.

OBJECTIVE: To determine whether human testicular mast cells contain the potent fibroblast growth factor tryptase and to examine changes in mast cell morphology and intratesticular distribution in testes with normal spermatogenesis versus abnormal spermatogenesis. DESIGN: Retrospective evaluation of testicular biopsies with the use of immunohistochemistry, morphometry, and electron microscopy. SETTING: University research and clinical institutes. PATIENT(S): Infertile men (total of 24) with severe hypospermatogenesis, germ cell arrest syndrome, or Sertoli cell only syndrome, and men without pathologies. INTERVENTION(S): Diagnostic testicular biopsy. MAIN OUTCOME MEASURE(S): Location, number, and distribution of testicular mast cells. RESULT(S): All groups showed tryptase-positive mast cells. In specimens with normal spermatogenesis, mast cells were round and located mainly in the interstitial spaces close to Leydig cells. In germ cell arrest syndrome, a 2-fold increase was evident, and in Sertoli cell only syndrome, a >3-fold increase of tryptase-immunoreactive mast cells became evident. Moreover, there was a statistically significant shift of the cells from the interstitium to the tubular walls in Sertoli cell only syndrome and germ cell arrest syndrome. Mast cells in specimens of Sertoli cell only syndrome and germ cell arrest syndrome were heterogeneous, with rounded or elongated shapes and signs of degranulation. The thickness of the tubular walls was doubled in specimens of germ cell arrest syndrome and Sertoli cell only syndrome in comparison with normal specimens, and this increase was positively correlated with the number of mast cells in these patients. CONCLUSION(S): Our results suggest that mast cell products, including the potent fibroblast growth factor tryptase, are involved in the thickening of the tubular wall and other changes in infertile testes.

Adult↗
PubMed2000

Synaptosome-associated protein of 25 kilodaltons in oocytes and steroid-producing cells of rat and human ovary: molecular analysis and regulation by gonadotropins.

The synaptosome-associated protein of 25 kDa (SNAP-25) is crucially involved in exocytosis in neurons. The aim of this study was to investigate whether it is present in the ovary. We found SNAP-25 to be expressed in nonneuronal cells of the rat and human ovary, namely in all oocytes and in steroidogenic cells, including granulosa cells (GC) of large antral follicles and luteal cells. Both isoforms, SNAP-25a and b, were found in the ovary. Oocytes obtained by laser capture microdissection were shown to express SNAP-25b, whereas SNAP-25a was found in rat GC and human luteinized GC. Immunohistochemical observations of strong SNAP-25 staining in GC of large growing antral follicles compared with absent or weak staining in small follicles suggested a role in folliculogenesis. To study a presumed regulation of SNAP-25, we used a rat GC line (GFSHR-17), which expresses FSH receptors, and luteinizing human GC, which express LH receptors. FSH elevated SNAP-25 mRNA and protein levels about fivefold within 24 h in GFSHR-17 cells. The cAMP analogue dibutyryl-cAMP (db-cAMP) mimicked this action of FSH. The effects of both db-cAMP and FSH were inhibited by the protein kinase A (PKA) inhibitor H89. In contrast, SNAP-25 protein and mRNA-levels were not altered by LH/hCG in luteinized human GC. Our results for the first time identify SNAP-25b in oocytes and SNAP-25a in steroidogenic cells of the mammalian ovary. SNAP-25a and b may be involved in different exocytotic processes in these cell types.

Animals↗
PubMed2000

Gap junction communication and connexin 43 gene expression in a rat granulosa cell line: regulation by follicle-stimulating hormone.

Follicle-stimulating hormone is the major regulator of growth and development of antral follicles in the ovary. Granulosa cells (GCs) in these follicles are coupled via gap junctions (GJs) consisting of connexin 43 (Cx 43). Because we and others have found that Cx 43 and GJs, respectively, are more abundant in large antral follicles compared with small antral and preantral follicles, we hypothesized that FSH may control Cx 43 gene expression, GJ formation, and intercellular communication. To directly address these points, we chose a rat GC line (GFSHR-17) expressing the FSH receptor and the Cx 43 gene. The functionality of FSH receptors was shown by the effects of porcine FSH, namely cell rounding, reduced cellular proliferation, and stimulation of progesterone production of GFSHR-17 cells, which are effects that were detectable within hours. Treatment with FSH also statistically significantly increased Cx 43 mRNA levels, as shown after 6 to 9 h in Northern blots. These effects were antedated by altered GJ communication, which was observed within seconds. Using a single-cell/whole-cell patch clamp technique, we showed that FSH rapidly and reversibly enhanced electrical cell coupling of GFSHR-17 cells. Increased GJ communication was associated with statistically significantly decreased phosphorylation of Cx 43, which was observed within 10 min after FSH addition, during immunoprecipitation experiments. Our results demonstrate, to our knowledge for the first time, that the gonadotropin FSH acutely and directly stimulates intercellular communication of GFSHR-17 cells through existing GJs. Moreover, FSH also increases levels of Cx 43 mRNA. These changes are associated with reduced proliferation and enhanced differentiation of GFSHR-17 cells. In vivo factors in addition to FSH may be involved in the regulation of GJ/GJ communication between GCs in the follicle, but our results suggest that improved cell-to-cell coupling, enhanced Cx 43 gene expression, and possibly, formation of new GJs are direct consequences of FSH receptor activation and may antedate and/or initiate the pivotal effects of FSH on GCs.

Animals↗
PubMed2000

Neuronal elements in the testis of the rhesus monkey: ontogeny, characterization and relationship to testicular cells.

Intrinsic neuron-like cells expressing the catecholamine-biosynthetic enzyme tyrosine hydroxylase (TH) were recently identified in the testis of the prepubertal rhesus monkey. In this study, we characterized the neuron-like nature of these cells and examined distribution and frequency of neuronal elements in the testes of monkeys during postnatal development, puberty and adulthood. Using immunohistochemical methods, we detected both nerve fibers and cell bodies, immunoreactive for the neuronal markers neurofilament 200 (NF-200) and synaptosomal associated protein of 25 kDa (SNAP-25), TH and neuropeptide Y (NPY) in perivascular locations, intermingled with interstitial cells and close to the wall of seminiferous tubules. Marked age-related differences in the numbers of these neuronal elements became apparent, when we quantified NF-200-immunoreactive neuronal elements. Thus, intrinsic neuron-like cell bodies were found only in the testes from immature animals (i.e. , until about 3 years of age). Conversely, nerve fibers, presumably representing mainly the extrinsic innervation, were observed at all ages although they became more prominent after the pubertal increase in LH and testosterone levels. Interestingly, another testicular cell type known to contain potent regulatory substances, mast cells, was found to be in close anatomical proximity to nerve fibers. The number of these cells, positively identified with an antibody to tryptase, increased significantly after puberty following the same pattern as nerve fibers. These results confirm that the testicular nervous system of the monkey is composed of two components, intrinsic nerve cells and extrinsic fibers, both of which are catecholaminergic and peptidergic in nature. Furthermore, both components show a marked degree of plasticity during development, especially around the time of puberty. The intratesticular locations of neuron-like cells and fibers suggest that catecholamines and neuropeptides are likely to have multiple sites of actions, and may affect Leydig cells, cells of the tubular wall and vascular cells directly and/or indirectly via intermediation of mast cells.

Age Factors↗