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H D Nicholson

Publications and source records attributed to H D Nicholson.

31 records · Page 2Linked to original sources
PubMed1994

The effect of germ cell complement on the presence of oxytocin in the interstitial and seminiferous tubule fluid of the rat testis.

In the rat testis oxytocin has been localized to the Leydig cells, and these cells have been shown to produce oxytocin in vitro. The present study was performed to determine whether oxytocin is present in the interstitial fluid (IF) and seminiferous tubule fluid (TF) of the rat and whether concentrations of the peptide vary within the two compartments following germ cell destruction. In order to destroy germ cells adult male rats were anaesthetized and their scrotal regions placed in a water bath at 43 degrees C for 20 min. Control animals were subjected to anaesthesia alone. Groups of 6 animals were killed 3, 7 and 21 days after heat treatment and their testes removed for histological examination or fluid extraction. IF and TF were separated and the oxytocin content of the fluids measured by radioimmunoassay. Immunoreactive oxytocin was detected in both the IF (100 +/- 11 pg/ml) and TF (27 +/- 4 pg/ml) of control rats and this immunoreactivity co-eluted with the authentic peptide following HPLC. Three days after heat treatment IF levels of oxytocin were significantly reduced but TF levels of the peptide were significantly increased. These changes were associated with a lack of pachytene spermatocytes in the histological sections. Seven and 21 days after heat treatment the levels of oxytocin in the IF and TF were not significantly different from control levels. Similar changes in IF and TF oxytocin levels were seen in a second experiment when pachytene spermatocytes were removed using the testicular toxicant methoxyacetic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1993

Oxytocin, a male intragonadal hormone.

It is now well recognised that oxytocin is not confined to the hypothalamo-neurohypophysial system but present elsewhere in the body. However, the significance of the peptide in these peripheral sites is still unclear. This paper considers the evidence for oxytocin to be a male gonadal hormone and focusses on three of the criteria which need to be fulfilled for it to earn this title: oxytocin must be produced within the gonads; have a physiological action and be regulated by factors which alter gonadal function.

Animals↗
PubMed1992

A novel, [tyrosyl-3,5-3H]oxytocin binding, uterine cell population in the rat.

The cellular localization of uterine oxytocin binding sites in the rat was studied by means of in vitro receptor autoradiography. Using [tyrosyl-3,5-3H]oxytocin as ligand, binding sites were localized in tissue sections from uteri of estrous, mated, and artificially cervically stimulated rats (n = 4 per group), and specificity of binding was investigated by means of simultaneous incubations with oxytocin, [Gly4,Thr7]oxytocin and [Arg]vasopressin. A previously unidentified type of cell was densely labelled by tritiated oxytocin. The labelled cells were preferentially localized near the endomyometrial border and at the interface of the circular and longitudinal muscle layers. In addition, these cells were found in the muscle layers. The dense labelling of these cells, which did not constitute part of the endometrial epithelium or blood vessels, was abolished when oxytocin or [Arg]vasopressin, but not [Gly4,Thr7]oxytocin, was added to the incubation medium. Binding of the radioligand was also found on muscle cells of the circular and longitudinal layers of the myometrium and cells of the endometrial luminal and glandular epithelium. Whereas incubation with oxytocin and [Gly4,Thr7]oxytocin diminished the labelling in both myometrium and endometrium, incubation with [Arg]vasopressin reduced labelling only in the myometrium. Similar results were obtained in tissues from rats in different reproductive states. This study demonstrates the presence of oxytocin binding sites in three different types of cell in the uterus of the rat. While the sites in the myometrium may be associated with the contractile response of this type of tissue to oxytocin, the functional significance of oxytocin binding sites on the endometrial epithelium and in the densely labelled, scattered cells remains to be elucidated.

Animals↗
PubMed1992

Luteinizing hormone differentially regulates the secretion of testicular oxytocin and testosterone by purified adult rat Leydig cells in vitro.

The aims of the present study were to determine whether Leydig cells in vitro synthesize oxytocin, and whether LH modulates the secretion of oxytocin by Leydig cells. Highly purified adult Leydig cells were prepared from adult rats and cultured for 3 days in the presence or absence of 0.1 ng/ml ovine LH, and media were changed daily. The total amount of oxytocin present in the culture was estimated by RIA of cell extracts before culture (day 0) and at the end of day 3 of culture and in media on days 1-3. The content of immunoreactive oxytocin in cell extracts on day 0 (3.4 +/- 1.2 pg/10(6) cells) was significantly lower than the total amount that had been released into the medium and was present in the cell extracts at the end of day 3 (+LH, 27.8 +/- 3.3; -LH, 16.5 +/- 2.7 pg/10(6) cells), suggesting that Leydig cells are able to synthesize and secrete oxytocin. This hypothesis was supported by the observation that oxytocin release into the medium was significantly reduced during a 3-h treatment of Leydig cells with the protein synthesis inhibitor cycloheximide (5 micrograms/ml for 3 h). The role of LH in regulating testosterone production by Leydig cells is well defined, but whether LH also regulates oxytocin is unknown. Therefore, the effects of LH on oxytocin and testosterone production by Leydig cells were compared. The production of both hormones was stimulated by increasing doses of LH (0.001-100 ng/ml), but no further rise in oxytocin release could be elicited with amounts of LH greater than 0.1 ng/ml. Testosterone production, however, continued to increase with doses of LH up to 100 ng/ml. Furthermore, the two hormones differed in the rate of their responses to both 3- and 12-h exposures to LH; testosterone secretion increased more rapidly than that of oxytocin. These data provide direct evidence that adult Leydig cells produce immunoreactive oxytocin, and that their production of this peptide is regulated by LH.

Animals↗
PubMed1991

Testicular oxytocin: effects of intratesticular oxytocin in the rat.

The long-term effects of oxytocin administration on the testis were studied using intratesticular implants. Adult male rats had an Accurel device containing 20 micrograms oxytocin (releasing approximately 200 ng/day) implanted into the parenchyma of each testis; control animals received empty devices. The animals were killed at weekly intervals for 4 weeks. Some animals were perfused and the testes processed for light and electron microscopy. Blood was collected from the remaining animals for the measurement of testosterone, dihydrotestosterone, LH, FSH and oxytocin; epididymal sperm counts were measured and the testes were extracted and radioimmunoassayed for testosterone, dihydrotestosterone and oxytocin. Long-term administration of oxytocin resulted in a significant reduction in testicular and plasma testosterone levels throughout the 4-week period examined and, after 14 days of treatment, lipid droplets were seen in the Leydig cells of treated but not control animals. Concentrations of dihydrotestosterone in the plasma and testes of the oxytocin-treated animals, however, were significantly elevated after 7 and 14 days and at no time fell below control values. Plasma FSH levels were also lower in the oxytocin-treated animals. Intratesticular oxytocin treatment did not affect LH or oxytocin concentrations in the plasma, epididymal sperm counts or the number of Leydig cells in the testis. Empty Accurel devices had no effect on testicular morphology. This study provides the first evidence that oxytocin in vivo can modify steroidogenesis in the testis.

Animals↗
PubMed1988

Two vasopressin-like peptides in the pig testis?

Vasopressin (VP)-like immunoreactivity (IR) has been located in the testes of several species of mammal. There is evidence that most of this IR in the rat does not represent authentic arginine vasopressin (AVP) and that a second AVP-like peptide may exist. We have studied testis samples from the pig, which produces lysine vasopressin (LVP) in its pituitary, and have found both LVP- and AVP-like IR. High-performance liquid chromatography (HPLC) of testis extracts showed two peaks of VP-IR. The first peak co-eluted with authentic LVP and was recognized only by antisera which cross-reacted with LVP. The second peak co-eluted with authentic AVP and was recognized by antisera raised against AVP. Both VP-like peptides bound to a neurophysin affinity column and the HPLC elution profiles of the bound peptides were similar to those of the authentic hormones. When the LVP-like material was oxidized with performic acid, a peak of IR running in the same position as oxidized authentic LVP on HPLC was produced. Similarly, the performic acid-oxidized AVP-like material co-eluted with oxidized authentic AVP. The presence of both LVP- and AVP-like peptides in the pig testis may mean that more than one gene is involved. A second VP-like gene could also explain the anomalies of VP-IR in other species.

Animals↗
PubMed1987

Ethan-1,2-dimethanesulphonate reduces testicular oxytocin content and seminiferous tubule movements in the rat.

An oxytocin-like peptide is present in the interstitial cells of the testis, and testicular concentrations of oxytocin have been shown to increase seminiferous tubule movements in vitro. We have used the drug ethan-1,2-dimethanesulphonate (EDS), which depletes the Leydig cell population of the adult rat testis, to examine further the relationships between the Leydig cell, testicular oxytocin and tubular movements. Adult rats were injected i.p. with a single dose of EDS (75 mg/kg) or of vehicle (25% dimethyl sulphoxide). Histological study 3 and 10 days after treatment with EDS showed a reduction in the number of interstitial cells, and levels of oxytocin immunoreactivity were undetectable by radioimmunoassay. Immunostaining revealed very few oxytocin-reactive cells. Spontaneous contractile activity of the seminiferous tubules in vitro was also dramatically reduced, but could be restored by the addition of oxytocin to the medium. Four weeks after EDS treatment, the interstitial cells were similar to those in the control animals both in number and in immunostaining; immunoassayable oxytocin was present and tubular movements were normal. The EDS effect, seen at 3 and 10 days, was not altered by daily treatment with testosterone. However, repopulation of the testes with oxytocin-immunoreactive cells was not seen until 6 weeks in the testosterone-treated animals. We suggest that the Leydig cells are the main source of oxytocin immunoreactivity in the testis and that this oxytocin is involved in modulating seminiferous tubule movements and the resultant sperm transport. The results also imply that testosterone does not play a major role in controlling tubular activity in the mature rat.

Animals↗
PubMed1986

LH and testosterone cause the development of seminiferous tubule contractile activity and the appearance of testicular oxytocin in hypogonadal mice.

Immunoreactive oxytocin is present in the testis and it has been shown that this hormone increases the contractility of seminiferous tubules. We have investigated the relationship between testicular oxytocin, tubular movements and the effects of LH and testosterone using, as a model, the hypogonadal (hpg/hpg) mouse, which is deficient in hypothalamic LH-releasing hormone (LHRH). Whilst both testicular oxytocin and seminiferous tubule movements, resembling those seen in the rat, can be found in normal adult mice, neither can be found in hypogonadal mice. After 2 weeks of treatment with LH (200 ng to 100 micrograms daily) low levels of testicular oxytocin and tubular movements were observed. Treatment with large doses of testosterone for 2-12 weeks led to higher concentrations of testicular oxytocin and tubular movements resembling those seen in the normal adult mouse. The results support the evidence that testicular oxytocin modulates seminiferous tubule movements. We suggest that testosterone may play a part in the accumulation of oxytocin in the testis.

Animals↗
PubMed1984

Identification of oxytocin and vasopressin in the testis and in adrenal tissue.

Oxytocin, vasopressin and neurophysin-like immunoreactivity have been identified and measured by radioimmunoassay in extracts of human and rat testis and human fetal adrenal tissue. The authenticity of these polypeptides has been confirmed by their behaviour on high performance liquid chromatography. The concentrations of the hormone were too great to be explained by known circulating levels of the polypeptides, and their presence in steroid secreting organs suggests a possible role for them in steroidogenesis. The peptides may be taken up and concentrated by the tissues but the co-localisation of neurophysins with the hormones points towards local synthesis.

Adrenal Glands↗
PubMedDate not supplied

A comparison of different embalming fluids on the quality of histological preservation in human cadavers.

There are significant problems in obtaining normal human material for histology for teaching or research purposes. This study shows that tissue from cadavers embalmed for teaching can be used for routine histology. Twelve cadavers embalmed with four different formalin-containing embalming fluids were used (n = 3 per fluid): (1) formalin mix (10% formalin); (2) Dunedin mix (an alcohol-based fluid containing phenol); (3) Michigan mix (a water-based fluid); and (4) phenoxyethanol mix (an alcohol-based fluid containing phenoxyethanol). Tissue blocks of liver, heart, kidney, skin and skeletal muscle were taken from each cadaver, paraffin embedded, sectioned and stained with haematoxylin and eosin (H & E), Periodic Acid Schiff (PAS), or Mallory trichrome (Malt). Each section was assigned an overall score based on the histological quality of the cellular components of the tissue. Sections were scored from 1 to 3 (1 = poor, 2 = satisfactory, 3 = good). Satisfactory sections were obtained from all cadavers except those embalmed with the Dunedin mix. The Michigan and phenoxyethanol fluids resulted in consistently good quality sections. No significant differences in tissue morphology were observed between the different stains. The clearest morphology was observed in the skin and skeletal muscle sections, and in tissues embalmed with fluids which do not contain phenol.

Cadaver↗
PubMedDate not supplied

Evidence for the regulation of prostatic oxytocin by gonadal steroids in the rat.

Oxytocin and its receptor are present in the mammalian prostate, and the peptide has been shown to increase prostatic growth, 5alpha-reductase activity, and contractility. This study was performed to investigate whether local concentrations of the peptide were regulated by gonadal steroids in order to establish whether oxytocin has a physiological role in the prostate. Both intact and castrated adult Wistar rats were treated daily for 7 days with either testosterone propionate or the antiandrogen cyproterone acetate. Animals were then killed, and plasma hormone and prostatic oxytocin concentrations were measured. A separate group of rats was treated with the 5alpha-reductase inhibitor finasteride to investigate whether testosterone or dihydrotestosterone (DHT) was involved in regulating oxytocin concentrations. In a further series of experiments, rats were treated with diethylstilbestrol (DES) or the antiestrogen tamoxifen. Treatment with testosterone significantly decreased prostatic oxytocin, whereas reduction of androgens by castration or by administration of cyproterone acetate increased prostatic peptide concentrations without altering circulating levels of the peptide. Treatment with finasteride increased plasma testosterone but decreased DHT concentrations. Prostatic oxytocin concentrations were higher in finasteride-treated animals than in control animals with comparable testosterone levels. The data suggest that both testosterone and DHT are capable of decreasing prostatic oxytocin concentrations. Treatment with DES did not significantly alter prostatic oxytocin, but administration of tamoxifen decreased concentrations of the peptide, suggesting that low levels of estrogen may be necessary for oxytocin production. These data provide evidence that oxytocin is regulated by androgens, and we hypothesize that this regulatory mechanism may be involved in controlling prostatic growth.

5-alpha Reductase Inhibitors↗