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Biomedical subjects

K Purvis

Publications and source records attributed to K Purvis.

At least 73 records · Page 4Linked to original sources
PubMed1986

Homologous up-regulation of the prolactin receptor in rat prostatic explants.

Exposure of explants of rat ventral prostates and a rat Leydig cell tumour to ovine prolactin for 20 h caused alterations of the subsequent membrane binding of 125I-human prolactin to an extent and in a direction dependent on the dose of hormone used. Low prolactin concentrations (1-10 micrograms/2 ml) were associated with an increase in binding (up-regulation) which was 75% in the case of the prostatic tissue and 500% in the case of the tumour tissue above control levels. Higher concentrations caused a dose-dependent decrease in binding to below control levels (down-regulation), alterations which could not be explained by receptor occupancy. Time studies with an up-regulatory dose of hormone (3 micrograms/2 ml) indicated that the effects of prolactin on its receptor did not begin to become manifest until after 6-12 h of culture. The results suggest that homologous up-regulation of prolactin binding may be a general feature of prolactin target organs and that explant cultures of prostatic tissue may provide a convenient model for exploring its mechanisms.

Animals↗
PubMed1986

Time- and temperature-related alterations in seminal plasma constituents after ejaculation.

The effects of temperature and incubation time were examined on the concentrations of the following seminal plasma constituents in ejaculates from seven healthy volunteers: prostatic acid phosphate (PAP), citric acid, testosterone, prostaglandin E (PGE), fructose, protein, putrescine and the polyamines spermidine and spermine. The results indicated that the majority of glandular products were stable up to 3 h after ejaculation when stored at room temperature, with the exception of the prostatic diamine putrescine, which appeared to undergo rapid metabolism. Prolonged periods of incubation resulted in a gradual reduction in the levels of fructose and a significant increase in the activity of PAP and the levels of spermidine. On the basis of these findings it appears that an evaluation of the functional integrity of the accessory sex glands can be carried out on semen up to 3 h after ejaculation.

Acid Phosphatase↗
PubMed1986

Ejaculate composition after masturbation and coitus in the human male.

The levels of fructose, acid phosphatase, citric acid, zinc, maltase, testosterone, prostaglandin E, putrescine, spermidine and spermine were compared in ejaculates collected by masturbation and after coitus in the same individuals. Coitus was associated with a significantly larger semen volume and increased concentrations and total amounts of prostaglandin E and polyamines in the ejaculate. In contrast, the concentrations of the conventional glandular parameters remained relatively unaffected, although a slight dilution of the seminal vesicle contribution to the ejaculate occurred after coitus. In the majority of cases, ejaculates provided by masturbation were significantly enriched in spermatozoa, but the total contributions under both conditions remained the same. It is concluded that the assessment of semen quality in male individuals using the conventional parameters of accessory gland function can be made with ejaculates provided by masturbation or coitus.

Acid Phosphatase↗
PubMed1986

Short-term effects of mating on the accessory sex glands of the male rat.

Mating in the rat was associated with a significant reduction in the tissue concentrations of the presumptive secretory products of the male accessory sex glands: prostatein and the amines, putrescine, spermidine and spermine (ventral prostate lobe), zinc (lateral prostate lobe) and fructose (coagulating gland). The amount of secretory product discharged and the time taken to restore precopulatory levels differed for the different lobes. Within 12-24 h of the mating period, the activity of ornithine decarboxylase and cytosolic oestrogen binding in the ventral prostate lobe underwent a transient increase which lasted 2-3 days. No change was observed in prolactin binding. Circulating testosterone concentrations were significantly elevated above control values 12 h after the start of mating but were significantly lower than control values at 24 h. A gradual recovery to concentrations in controls occurred over the next 2-3 days. None of these changes could be explained by alterations in gonadotrophin or prolactin release.

Androgen-Binding Protein↗
PubMed1986

Biochemical correlates of asthenozoospermia: a lesion at the level of the sperm adenylyl cyclase.

Studies of the adenylyl cyclase in spermatozoa from 10 asthenozoospermic and 10 normal men revealed major differences with regard to the activation of the enzyme by various drugs and metal ions. While the response to acetate ions was normal, activation of the enzyme by forskolin and the GTP analogue [Gpp(NH)p] was uniformly impaired. In addition, in 4 of the patients the ratios of the Mn2+- and Mg2+-dependent activities of the enzyme were significantly higher than normal, suggesting a delay in the transformation of the enzymes catalytic unit from the soluble to the membrane-bound form. No differences could be recorded in a variety of seminal plasma components including prostatic acid phosphatase, citric acid, zinc, putrescine, spermidine, spermine, fructose, prostaglandin E, and testosterone. Furthermore, the DNA fluorescence patterns of the spermatozoa measured by flow cytometry were within the range of control variations, suggesting that chromatin condensation, and thus nuclear maturation, proceeded normally. The study suggests that a lesion in the adenylyl cyclase system of the germ cells may explain at least some of the motility disturbances seen in infertile males.

Acetates↗
PubMed1985

Circadian rhythms in accessory sex gland function in the male rat.

Alterations in various parameters of accessory sex gland function were monitored during two separate 24 h periods in adult male rats, and compared to fluctuations in the circulating levels of testosterone, prolactin, corticosterone and LH. Bimodal circadian rhythms in ventral prostate prolactin binding, cytosolic oestrogen binding and seminal vesicle weight could be discerned which appeared to be related to a similar rhythmicity in circulating testosterone levels, but with a phase shift of 3 h. Prostatic membrane bound adenylyl cyclase activities (basal and hormone stimulated) and prostatein concentrations followed different patterns possibly correlated to other endocrine changes.

Adenylyl Cyclases↗
PubMed1985

Short-term effects of prolactin on prostatic function in rats with lisuride-induced hypoprolactinaemia.

The effects of a single injection of ovine prolactin on prostatic function were monitored in intact, intact androgenized and castrated-androgenized rats rendered hypoprolactinaemic after 7 days of treatment with a potent dopamine agonist, lisuride. Hypoprolactinaemia was associated with reductions in ventral prostate weight, polyamine levels, lateral lobe zinc and the concentration of the ventral prostate protein prostatein, but an elevation in the level of cytosolic oestradiol binding. Whether these differences attained statistical significance depended on whether the animals were intact, intact-androgenized or castrated-androgenized. With the exception of ventral prostate weight and lateral lobe zinc concentrations, a single injection of prolactin restored or reversed these changes towards control levels within 12 h, which could not be explained by an indirect effect of the hormone on adrenal or testicular function. No effects of lisuride or prolactin were observed with regard to the content of fructose in the coagulating gland or in the degree of prolactin binding to prostatic membranes.

Androgen-Binding Protein↗
PubMed1985

Testicular and glandular contributions to the prolactin pool in human semen.

The immunoreactive prolactin in human seminal plasma originates predominantly from two sources, the seminal vesicles and the testicular-epididymal axis. The following evidence supported a testicular-epididymal origin: Vasectomy reduced the content of prolactin in the ejaculates by 50%; the concentration of seminal prolactin was highly correlated (r = 0.54, p less than 0.003) with the concentration of sperm in a normal population of young and middle-aged men; and prolactin concentrations in the split ejaculates of normospermic men revealed a profile that corresponded to the sperm distribution pattern. Evidence supporting an additional contribution from the seminal vesicles included the following. The split ejaculate of an azoospermic individual coincided more with the distribution of the vesicular parameter fructose; vasectomy did not cause the disappearance of prolactin from the ejaculate; and split-ejaculate analyses weakened the possibility of a major prostatic source.

Acid Phosphatase↗
PubMed1985

Estrogen receptors in stromal and epithelial fractions of the ventral prostate of rats.

The cytosol from rat ventral prostates contains two estrogen-binding components that can be separated in a glycerol gradient: a high-affinity (KD = 4.2 X 10(-10) M), low-capacity (110 fmole/mg DNA) species that runs in the 8S region of the gradient, and a lower-affinity (KD = 2.4 X 10(-9) M), higher-capacity (410 fmole/mg DNA) 4S protein. Separation of prostate tissue into stromal- and epithelial-enriched fractions was associated with the disappearance of the latter component. When compared per milligram DNA stromal- and epithelial-enriched fractions contained similar amounts of the high-affinity 8S-binding protein. In vivo estrogen treatment caused a time-related disappearance of the protein from the intact cytosol presumably as a result of translocation. No major differences in the degree of binding to the high-affinity component were observed in rats of different ages. Estrogens seem to exert direct effects on both stromal and epithelial tissues of the prostate.

Aging↗
PubMed1984

Thyrotropin-releasing hormone (TRH) activates the adenylyl cyclase of nonsecretory cells in the rat ventral prostate.

Prostatic secretory and basal or stem cells were isolated from rat ventral prostate lobes by collagenase dispersion and density centrifugation in a Percoll gradient. The membrane-bound adenylyl cyclase of secretory cells could be activated in a dose-dependent manner by vasoactive intestinal peptide (VIP ED50 10(-7)M) but not thyrotropin-releasing hormone (TRH). Conversely, only TRH could significantly stimulate the adenylyl cyclase in basal cell membranes (ED50 5 X 10(-7). In two separate studies enzyme activity was stimulated seven- and 13-fold by this peptide. This action of TRH on prostatic basal cells supports previous reports that high levels of immunologically active TRH have been found in prostate tissue and that TRH stimulates the growth of prostatic cancer cells in vitro.

Adenylyl Cyclases↗
PubMed1984

Prolactin desensitizes the prostaglandin E1-dependent adenylyl cyclase in the rat prostate gland.

Prior exposure of the rat ventral prostate to a high dose of ovine prolactin in vivo or in vitro caused the specific desensitization of the prostaglandin E1-dependent adenylyl cyclase. Maximal desensitization was achieved in vivo 6 h after exposure to 100 micrograms prolactin and complete resensitization occurred after 7 days. No heterologous desensitization of the response of the cyclase to other hormones tested was observed. Incubation of isolated secretory cells with prolactin and prostaglandin E1 desensitized the subsequent response to the same prostaglandin. Simultaneous exposure of the cells to indomethacin prevented the prolactin-induced effect. Prolactin could also induce similar changes in the prostaglandin E1-dependent cyclase of rat Leydig cell tumour cells in vivo, suggesting that this may represent a phenomenon shared by other prolactin target organs. This study supports the hypothesis that prostaglandins may constitute second messengers for prolactin effects on the prostate gland.

Adenylyl Cyclases↗
PubMed1984

Seminal plasma characteristics during frequent ejaculation.

Seven young men provided a semen sample every 8 h for 2 days. Citric acid, zinc, acid phosphatase , spermine, fructose and protein were measured in the samples. Despite a dramatic reduction in semen volume, the concentration of the majority of the parameters remained constant during the period of study. The protein profile of the ejaculates, as assessed by 2-dimensional electrophoresis, also did not change. Levels of citric acid, zinc and acid phosphatase were closely correlated, while spermine, which is also believed to be of prostatic origin, showed no correlation with these other parameters. The spermine concentration of the ejaculates increased significantly during the period of high ejaculation frequency and returned to normal levels after a 3 day abstinence period. In view of the fact that spermine accumulation in tissues appears to be associated with growth and protein synthesis this increase in seminal spermine may reflect a stimulation of prostatic cell activity.

Acid Phosphatase↗
PubMed1984

Two-dimensional electrophoresis of proteins in various fractions of the human split ejaculate.

Two-dimensional electrophoresis of six fractions of split ejaculates from normal men (median age 23 years, n = 6) revealed large differences in the pattern of proteins found between the prostate-enriched fractions and secretions associated with the seminal vesicles. The glandular contributions were assessed using the concentrations of spermine, zinc and prostatic acid phosphatase (PAP) for prostatic secretion, and fructose and prostaglandin E for seminal vesicle secretion in the various fractions. Aside from PAP, four additional proteins were apparently associated with the prostatic fraction, one of which shared the biochemical characteristics of the specific ventral lobe protein of the rat prostate, prostatein (molecular mass 16 000, pI 4.8). The presumptive vesicular fractions contained a large number of low molecular mass proteins (10-20 000), with widely varying pI-values. The concentration of albumin and transferrin appeared to be highest in the sperm cell enriched fractions, indicating a major contribution to the ejaculate of testicular/epididymal origin.

Adult↗
PubMed1984

Current approaches to research on prostatic function and pathology.

This article describes some of the techniques and approaches currently in use in prostatic research which hopefully will provide new information and perspectives on the etiology of prostatic pathology. These techniques include a variety of methods for visualizing and quantitating protein hormone receptors, protein electrophoresis of prostatic tissue and fluids for protein markers, cell separation of the different cell populations of the prostate so that their interaction can be evaluated, and tests for the influence of low molecular weight peptides on prostatic function. Examples of the type of information which can be derived from each of the approaches are included and discussed.

Adenylyl Cyclases↗
PubMed1984

Human sperm characteristics during frequent ejaculation.

Sperm concentration, morphology, DNA condensation and nuclear protein pattern as well as sperm adenylate cyclase were evaluated in semen samples provided by 7 volunteers every 8 h for 2 days. During the observation period, sperm concentration and total sperm number decreased but began to return towards normal after a 3-day abstinence period. No increase in the proportion of immature sperm cells was observed by light microscopy. Total adenylate cyclase (EC 4.6.1.1) increased significantly per cell, due to an increase in the soluble component while the particulate component remained relatively constant. Microflow fluorometry revealed no consistent alterations in the DNA or nuclear protein distribution. We conclude that although a high frequency of ejaculation does not disturb the conventional measures of sperm integrity, such as DNA condensation, there are major changes in at least one biochemical measurement, the activity of soluble adenylate cyclase.

Adenylyl Cyclases↗
PubMed1984

Testicular gonadotropin receptors, testicular testosterone, dihydrotestosterone and androstenedione in the developing bull.

The testis homogenate from Red bull (3-17 months of age) show specific binding of hLH and hFSH with Kd of 1.3 +/- 0.1 X 10(-10)M and 1.5 +/- 0.1 X 10(-9)M, respectively. Prepubertal bulls (3-5 3/4 months) exhibit the highest binding capacity of both LH and FSH, revealing the fact that LH and FSH receptors are present in high concentrations prior to the first rise in plasma T. The testicular T concentration was significantly higher in the four prepubertal bulls than in the four older animals in spite of the fact that circulating T is lower before puberty. Thus, local androgen effects within the testis may occur before peripheral androgenization. The prepubertal bull Leydig cell also displayed steroidogenic capacity. The ratio of biologically active (testosterone, dihydrotestosterone) to inactive androgens (androstenedione) increased as the animals approached puberty. Such qualitative changes in steroid production may be one of the factors responsible for peripheral androgenization.

Androgens↗
PubMed1983

A systematic study of biochemical differences between the lobes of the rat prostate.

The present study constitutes a systematic search for biochemical parameters which could be used to monitor the isolated function of various prostate lobes and accessory sex glands in the rat. Various parameters were measured in the 105 000 X g supernatants of the ventral, lateral and dorsal prostate lobes, and in the coagulating glands and seminal vesicles. These included spermine, citric acid, acid phosphatase, fructose and zinc, as well as the pattern of proteins in both cytosols and secretions, which were determined using one dimensional SDS, polyacrylamide gel electrophoresis. The results suggest that several parameters can be used including: Ventral lobe--spermine or prostatein; Lateral lobe--zinc or a 15 000 dalton protein; Dorsal lobe--spermine or a 60 000 dalton protein; and coagulating gland--fructose.

Acid Phosphatase↗