Biomedical subjects

G Selstam

Publications and source records attributed to G Selstam.

At least 55 records · Page 3Linked to original sources

PubMed1985

Acute increase of noradrenaline on vascular resistance in the corpus luteum of the pseudopregnant rat.

Noradrenaline infusion for 2 min (0.4 microgram/min) in anaesthetized rats increased the vascular resistance in 6-day-old corpora lutea, but had no significant effect on the vascular resistance in young (2-day-old) or old corpora lutea (11 days old). The luteal blood flow of the control rats was higher in 6-day-old corpora lutea than in those of 2 and 11 days. The luteal blood flow apparently lacks autoregulation, since a linear relationship between blood flow and arterial blood pressure was registered. The present study shows that, besides the well known metabolic effects of catecholamines on corpus luteum function, catecholamines can exert acute vascular effects, but only on the corpus luteum of pseudopregnancy in the middle of its life span.

Animals↗

PubMed1985

Plasma 20 alpha-OH-progesterone in women with malignant epithelial 'non-endocrine' ovarian tumors.

The production of 20 alpha-OH-progesterone (20 alpha-OH-P) in women with malignant epithelial ovarian tumors was investigated. The study material comprised 51 postmenopausal and/or oophorectomized women with ovarian carcinoma, including the histological types Ic, IIc, IIIc and V and FIGO stages I-IV. Their tumor volumes were evaluated once a month using bimanual recto-vaginal palpation under anesthesia. Blood samples were drawn for 20 alpha-OH-P radio-immunoassay at monthly intervals for 3 months. The plasma levels were compared with those of a control group of postmenopausal women. The results show a relationship between tumor volume and plasma 20 alpha-OH-P level. Another finding is that endometrioid ovarian cancer (histologically IIIc) showed a significantly lower 20 alpha-OH-P production than the other types. The reason for this is discussed.

20-alpha-Dihydroprogesterone↗

PubMed1985

Direct inhibitory effects of natural and synthetic oestrogens on testosterone release from human testicular tissue in vitro.

Human testicular slices were incubated in vitro in order to examine the direct effects of natural and synthetic oestrogens on testosterone secretion. In the presence of human chorionic gonadotrophin (10 IU per ml), oestradiol-17 beta (1 or 10 micrograms per ml) and ethinyl oestradiol (0.1, 1 or 10 micrograms per ml) inhibited testosterone release into the media in a dose dependent manner. The addition of estramustine phosphate, estromustine, diethylstilboestrol or diethylstilboestrol diphosphate in comparable concentrations produced no significant effects on testosterone release.

Adenocarcinoma↗

PubMed1984

Toxic effects of the antifertility agent gossypol in male rats.

In the present investigation the influence of gossypol on the male sex function and toxicology in the rat have been studied. Gossypol was injected daily for 5 weeks to adult male rats of the Sprague-Dawley strain with 1 or 10 mg/kg body wt. The low dose of gossypol (1 mg/kg body wt.) did not have any effect on the following parameters: plasma testosterone concentrations, body growth, kidney weights, sex organ weights (ventral prostate, seminal vesicle, epididymis), testicular weights, blood flow to testes, epididymides and ventral prostate as measured with the microsphere technique, intraarterial blood pressure and morphology of testis and epididymis. The plasma testosterone response to acute LH-injection was not significantly different in gossypol-treated rats when compared to control rats. The high dose of gossypol (10 mg/kg body wt) caused signs of tubular degeneration, retarded body growth, markedly reduced testosterone concentrations, involutions of the ventral prostate and seminal vesicles and gastrointestinal disturbances. After 5 weeks of treatment the mortality rate was 13%. It is concluded that gossypol is a very toxic substance in rats, since only a 10-fold increase of a non-effective dose caused serious side effects in addition to its antifertility effects.

Animals↗

PubMed1984

Beta-adrenergic receptor concentration in corpora lutea of different ages obtained from pregnant mare serum gonadotropin-treated rats.

We have measured the beta-adrenergic receptor content in 1- to 10-day-old corpora lutea. Corpora lutea of defined ages were obtained by sc injection of 8 IU PMSG to 26-day-old rats, leading to ovulation and formation of corpora lutea in the early morning of day 29. Membrane fractions of isolated corpora lutea were incubated with various concentrations of the beta-adrenergic antagonist [125I]iodohydroxybenzylpindolol [125I]iodo-HYP, 12.5-2500 pM) for 60 min at 22 C. Alprenolol (10(-5) M) was used to determine nonspecific binding. Bound and free [125I]iodo-HYP was separated by filtration and washing on Whatman GF/C filters under vacuum. There was a 3-fold increase in beta-adrenergic receptor concentration during the first 2-3 days of corpus luteum formation, followed by a decline in the beta-adrenergic receptor content with luteal age. The rat luteal beta-adrenergic receptor seems to be of the beta 2-subtype as determined from adenylate cyclase stimulation as well as from displacement of [125I]iodo-HYP binding by various beta-adrenergic agonists.

5-alpha-Dihydroprogesterone↗

PubMed1984

Steroid biosynthesis and Leydig cell morphology in adult unilaterally cryptorchid rats.

Unilateral cryptorchidism was induced in newborn rats and when the rats reached adult age Leydig cell morphology and steroid biosynthesis were compared in scrotal and abdominal testes. The cell profile area of abdominal Leydig cells was reduced, the cytoplasm contained an increased number of lipid droplets and the endoplasmatic reticulum was more sparse than in scrotal Leydig cells. The intratesticular concentrations of progesterone, 20 alpha-dihydroprogesterone, 17 alpha-hydroxyprogesterone and testosterone were measured both basally and after LH stimulation. The synthesis of testosterone was subnormal in the abdominal testes. The data on basal steroid concentrations suggest a block at the 17 alpha-hydroxylase level, but observations after LH stimulation suggest that earlier steps are also involved. When studied in vitro the steroid biosynthesis in abdominal testes was also disturbed. The conversion mediated by 17 alpha-hydroxylase and 17 beta-ketosteroid reductase was lower and the conversion mediated by 20 alpha-dehydrogenase was higher in the abdominal testis. The reason for the disturbed steroid biosynthesis in abdominal testes is unknown. It may be related to the increased concentration of oestradiol in abdominal testes. Other possibilities are altered paracrine influence from the damaged tubules or changes in the microcirculation of the testis.

17-alpha-Hydroxyprogesterone↗

PubMed1983

Prostaglandin F2 alpha inhibition of epinephrine stimulated cyclic AMP and progesterone production by rat corpora lutea of various ages.

Epinephrine can mimic the stimulatory effects of LH in vitro on cyclic AMP (cAMP) and progesterone production by isolated rat corpora lutea. The aim of the present study was to test whether the effects of epinephrine in vitro on the rat corpus luteum, as with LH, can be inhibited by prostaglandin F2 alpha (PGF2 alpha). The stimulatory effect of epinephrine on tissue levels of cAMP in 1-day-old corpora lutea was not inhibited by PGF2 alpha. A dose-dependent inhibition by PGF2 alpha (0.5-50 microM) was seen for 3-day-old corpora lutea and this inhibition could not be overcome by higher concentrations of epinephrine (0.165-165 microM). The stimulation by epinephrine on progesterone production was inhibited by PGF2 alpha (5 microM) in 3- and 5-day-old, but not in 1-day-old corpora lutea. Thus, PGF2 alpha can inhibit the stimulatory effect of epinephrine in 3- and 5-day-old corpora lutea, but not in the newly formed corpora lutea (1-day-old) and PGF2 alpha shows in this respect the same age dependent inhibitory pattern as in relation to LH stimulation.

Aging↗

PubMed1983

The acute effect of oestrogens on testosterone production appears not to be mediated by testicular oestrogen receptors.

Scatchard binding analysis was performed to measure the cytoplasmic oestrogen receptor in the testis of rats. After treatment of rats with the antioestrogen tamoxifen no oestrogen receptor binding was found in testicular low speed supernatant between 12 and 96 h after treatment. Such tamoxifen-treated rats were used to study the acute effect of oestrogens on testosterone secretion, both in vivo and in vitro. Injection of oestradiol benzoate (50 microgram, 24 h prior to experiment) resulted in a significant depression of basal and LH-stimulated plasma testosterone levels in control rats and this effect was unchanged in tamoxifen-pretreated rats. In vitro, oestradiol-17 beta also inhibited the LH-induced rise in testosterone secretion by isolated testicular interstitial cells. This inhibition was not affected if the rats had been pretreated with tamoxifen. These results indicate that the inhibitory effects of exogenous oestrogens on testicular testosterone production are probably not mediated by the oestrogen receptor.

Animals↗

PubMed1983

Rhythmical oscillations in rat testicular microcirculation as recorded by laser Doppler flowmetry.

We have earlier reported that local testicular blood flow, recorded by laser Doppler flowmetry, shows large oscillations with a frequency of 5-10 min-1. In the present study it is proposed that the recorded oscillations represent mainly local microvascular blood flow variations rather than variations in total testicular blood flow or tissue movements. The reasons for this are: (a) Blood flow simultaneously measured at two separate sites showed oscillations with different frequencies. (b) A local subcapsular injection of room-tempered saline under one probe site eradicated oscillations under that probe but not under another adjacent probe. (c) When the testicular capsule was split open, recordings of blood flow continued to show oscillations. (d) The amplitude of the oscillations was rather large (peak to peak value about 50% of mean flow value). No movements of the testicular surface were seen. A 20 min continuous infusion of 0.4 microgram/min noradrenaline did induce a decrease in plasma testosterone concentration, but did not change the mean blood flow. However, the oscillations nearly completely disappeared during the infusion period. The present study also shows that laser Doppler flowmetry is a versatile method and the rat testis provides a suitable organ in the study of the origin and functional importance of these oscillations.

Animals↗

PubMed1983

In vivo effect of noradrenaline on the cyclic AMP level in rat corpora lutea.

Under in vitro conditions adrenaline and noradrenaline can stimulate the production of cyclic AMP in rat corpora lutea to a similar extent as a maximal dose of LH. The present study was undertaken to compare the effects of noradrenaline and LH under in vivo conditions. Anaesthetized rats bearing 2 days old corpora lutea were either infused intraarterially with noradrenaline (0.4 microgram/min) or given a single intraarterial injection of 5 micrograms LH. The cAMP levels in whole ovaries had increased already after 30 sec of noradrenaline infusion. These levels remained high for a few minutes and, thereafter the effect decreased with time. No effect was seen after 20 min of infusion. Infusion of noradrenaline for 20 min increased cAMP in corpora lutea, but not in non-luteal tissue. LH was effective both in luteal and non-luteal tissue. The results show that noradrenaline in vivo can increase the cAMP content only in corpus luteum and within a rather short time period (5 min). This effect is different from that seen with LH which, instead, acts on both corpus luteum and stromal tissue.

Animals↗

PubMed1983

Measurement of blood flow to the ventral prostate in the rat with radioactive microspheres: effects of estradiol-17 beta and human chorionic gonadotrophin.

The function and size of the rat ventral prostate are stimulated by androgens and inhibited by estrogens. In order to test whether the blood flow in prostate is influenced in a similar fashion prostatic blood flow was measured after administration of human chorionic gonadotrophin (hCG) in rats with and without pretreatment of estradiol-17 beta (E2) and in rats castrated for five days with and without treatment with E2. Prostatic blood flow was measured with the microsphere technique, which allows blood flow measurement without any interference with the organ. E2 treatment resulted in a decreased prostatic blood flow in both intact and castrated rats, and blood flow was restored to normal in intact rats after hCG-injection. It was concluded that the E2 induced decrement of prostatic blood flow was at least in part mediated by a direct effect on the prostate.

Animals↗

PubMed1983

Estrogen receptor and aromatase activity in the testes of the unilateral cryptorchid rat.

The intratesticular concentration of estradiol-17 beta (E2) is increased in the abdominal testis of rats made unilaterally cryptorchid at birth. To elucidate this observation testicular aromatase activity and testicular estrogen receptor concentration were studied. Aromatase activity was lower while the concentration of estrogen receptor was higher in the abdominal testis. Treatment of cryptorchid rats with the anti-estrogen Tamoxifen did not change testicular concentration of testosterone. However, Tamoxifen induced a significant reduction of E2 in the abdominal testis. The main factor responsible for the increased E2 concentration in the abdominal testis appears to be increased binding of estrogen.

Aging↗

PubMed1982

Carbohydrate metabolism and concentration profiles of solutes in the canine lumbar intervertebral disc.

Utilization of glucose and oxygen by the cells as well as concentration profiles of solutes were studied in the canine intervertebral disc. Cell metabolism in this avascular tissue, being predominantly anaerobic, was found to be dependent on oxygen tension (this being especially pronounced in the region of 0.13-0.4 kPa (1-3 mmHg). A high production rate of lactic acid was found in the nucleus pulposus, whereas towards the periphery of the annulus fibrosus this rate gradually decreased. In the centrally located areas of the disc tissue, far away from the blood circulation, the highest concentrations of lactic acid were found. For the normal disc the energy demands seem to be met as even small amounts of oxygen account for a large energy source, whereas the cellular requirements are balanced up predominantly by glucose. In regions with extremely low oxygen tensions large amounts of glucose are consumed, but an additional potential energy pool of glycogen seems to be available.

Animals↗

PubMed1982

Testicular blood flow measured with a laser Doppler flowmeter: acute effects of catecholamines.

Laser Doppler flowmetry was used to continuously measure testicular blood flow in rats. The method was found applicable on surgically exposed testes. Regular oscillations in blood flow, with a periodicity of 8.6 +/- 0.7 cycles per minute (mean +/- SD), were observed in recordings from 22 to 23 rats. Clamping of the testicular artery reduced the blood flow signal to background values. Effects of catecholamines administered into the tail artery on testicular blood flow together with systemic effects on mean arterial blood pressure and heart rate were measured. It was found that noradrenaline as well as adrenaline caused a significant decrease in blood flow when 10 micrograms was injected. Only noradrenaline decreased the blood flow when 1 microgram was given. The large oscillations detected in the blood flow recordings disappeared quickly when 10 or 1 micrograms of both hormones was administered. It was concluded that catecholamines can exert rapid effects on testicular blood flow.

Animals↗

PubMed1982

Ioglycamide induced release of testosterone and estradiol from protein bound stores.

With the use of an aqueous two-phase system the effect of ioglycamide (Bilivistan) on the binding of testosterone and estradiol to albumin and testosterone-estradiol-binding globulin was investigated using whole human serum. Reduced binding capacity was recorded for TeBG and a reduced apparent association constant for the testosterone-albumin binding was recorded in the presence of ioglycamide in high concentration. The significance of reduced binding of testosterone and estradiol to albumin and TeBG was discussed in relation to side-effects of radiographic contrast media.

Estradiol↗

PubMed1982

Catecholamine stimulation of cyclic AMP and progesterone production in rat corpora lutea of different ages.

In vitro effects of catecholamines (adrenaline and noradrenaline) and adrenergic antagonists on adenosine 3',5'-cyclic monophosphate (cAMP) and progesterone production by rat corpora lutea (CL) of different ages (1-8 days old) were studied. To obtain defined ages of CL a pregnant mare's serum gonadotrophin (PMSG) model was used. The effect of catecholamines on cAMP decreased with luteal age while the effect on progesterone production was maximal on 5 day old CL. The beta-blocker propranolol inhibited the effects of catecholamines in concentrations around 10-(5) M. The effects of LH could only be inhibited with higher doses of propranolol known to exert unspecific effects. These results support the theory that LH and catecholamine effects on rat corpora lutea are mediated through different receptors.

Age Factors↗

PubMed1982

A comparative longitudinal study on sex hormone binding globulin capacity during estrogen replacement therapy.

An aqueous two-phase equilibrium partition system was used to assay SHBG-binding capacity. Sera from groups of postmenopausal women before and during unopposed estrogen replacement therapy were analyzed. The induction of SHBG showed considerable differences between different estrogens. Ethinyl-estradiol in a daily dose of 0.05 mg gave a 70% increase in the serum concentration of this liver derived protein. Estradiol-17 beta, 2 mg daily and estrone sulphate 1.25 mg gave moderate changes, whereas estriol in different doses had no effect. SHBG induction may reflect estrogen overtreatment.

Estradiol↗

PubMed1982

Oxygen tension alterations in the intervertebral disc as a response to changes in the arterial blood.

Measurements of oxygen tension in the canine lumbar intervertebral disc, by the use of a polarographic oxygen electrode, were performed. The oxygen tension in the arterial blood was changed by regulating the oxygen concentration in the inspired air. The alterations in oxygen tension in the nucleus pulposus, as a function of distance to the vertebral endplate were determined. The response times registered in the disc matrix were relatively short (within five min.), which implies an efficient solute transport from the vertebral blood pool underneath the hyaline cartilage into the avascular intervertebral disc.

Animals↗