Biomedical subjects
Publications and source records attributed to M J Watson.
The dexamethasone suppression test was carried out on 44 children to assess agreement with diagnosis of depression. No significant association was found between suppression of plasma cortisol and depression diagnosed clinically or by cluster analysis.
In this study we examined the effects of insulin on protein kinase C (PKC) activity in cultured fetal chick neurons. PKC activity, measured as 32P incorporation into histone H1 in the presence of calcium (500 microM), phosphatidylserine (100 micrograms/ml), and diolein (3.3 micrograms/ml) minus the incorporation in the presence of calcium alone, was detected in neuronal cytosolic (207 +/- 33 pmol/min/mg) and membrane (33 +/- 8 pmol/min/mg) fractions. Insulin added to intact neurons increased the activity of PKC in both cytosolic and membrane fractions by about 40%. Neurons preincubated with cycloheximide (10 micrograms/ml) 30 min prior to insulin treatment showed the same degree of stimulation of PKC activity by insulin. The activation of PKC was maximal within 5-10 min of insulin exposure and was sustained for at least 60 min. Insulin stimulated PKC in a dose-dependent manner, with a maximal response obtained at 100 ng/ml. Addition of phosphatidylserine and diolein to neuronal cell extracts resulted in the phosphorylation of four major cytosolic proteins (70, 57, 18, and 16 kDa) and one major membrane protein (75 kDa). Phosphorylation of all five proteins was increased 2-fold in extracts from insulin-treated neurons. Immunoblot analysis of whole cell extracts using antibodies against PKC-alpha, PKC-beta, PKC-gamma, PKC-delta, and PKC-epsilon revealed that cultured fetal chick neurons contained only one of these PKC isoforms, the epsilon-isoform. The enzyme was mostly cytosolic. Insulin had no effect on either the amount of distribution of PKC-epsilon in cultured neurons but induced a small change in the mobility of PKC-epsilon on sodium dodecyl sulfate-polyacrylamide gels. When assay conditions were designed to measure specifically the activity of PKC-epsilon, using a synthetic peptide substrate in the absence of calcium, activity was 50 +/- 12% higher in insulin-treated cells (p less than 0.005). PKC activity in control and insulin treated-neurons was almost completely inhibited when assays included a peptide identical to the pseudo-substrate binding site of PKC-epsilon. We conclude that PKC-epsilon is the major PKC isoform present in cultured fetal chick neurons. Insulin stimulates PKC-epsilon activity by a mechanism that does not involve translocation of the enzyme from cytosol to membrane.
Other laboratories have reported biphasic effects of heavy metals on protein kinase C activity: stimulation followed by inhibition at higher concentrations. We demonstrate that these earlier findings most likely resulted from a combination of the effect of the heavy metals to liberate Ca2+ from Ca2+-EGTA buffer systems and the direct inhibitory effects of the metals on protein kinase C. Simulations of such interactions substantiate this conclusion. When soluble protein kinase C is prepared without the addition of Ca2+ or chelator, heavy metals (Cd2+, Cu2+, Hg2+, Zn2+, in the 10 microM range) inhibit the activity of, and the binding of regulatory ligands to, protein kinase C. Heavy metals inhibit the extent of [3H]phorbol dibutyrate binding without affecting the affinity of the interaction, an inhibition that is not surmounted by excess phospholipid. Heavy metals also inhibit the phospholipid-dependent catalytic activity of protein kinase C in a manner that excess phosphatidylserine can overcome. The inhibition of enzyme activity by heavy metals cannot be surmounted by excess Ca2+ or Mg2+. The inhibitory effects of heavy metals are not confined to protein kinase C. Heavy metals also inhibit cyclic AMP binding to cyclic AMP-dependent protein kinase and the catalytic activity of that kinase, but in a distinctly different pattern.
We selected a group of male dialysis patients complaining of sexual dysfunction in whom penile vascular insufficiency and drug-induced impotence had been excluded. Monitoring of nocturnal penile tumescence was used to confirm organic disturbance. Patients with normal serum prolactin concentrations (n = 18) had significantly lower serum zinc values than normal controls (P less than 0.001) and were entered in a 6-month double-blind study comparing oral zinc acetate with placebo. Patients with elevated prolactin concentrations (n = 8) were entered in a 3-month double-blind crossover study comparing oral pergolide mesylate with placebo. In the zinc study, serum zinc concentrations increased (P less than 0.05) in the zinc-treated but not the placebo-treated group. One of nine patients receiving zinc reported improved sexual function, as did two of nine patients receiving placebo. There were no significant changes in sperm counts, nocturnal penile tumescence, testosterone, sex hormone binding globulin or gonadotrophin concentrations in either treatment group. In the pergolide study, serum prolactin values decreased (P less than 0.01) in the pergolide but not in the placebo treatment period. One patient reported improved sexual function during the pergolide treatment period and two during the placebo period. There were no significant changes in sperm counts, nocturnal penile tumescence, testosterone, sex hormone binding globulin or gonadotrophin concentrations after pergolide. These studies show no benefit of zinc or pergolide compared with placebo in the treatment of uraemic impotence.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The value of bromocriptine in the treatment of hirsutism in polycystic ovary syndrome (PCO) was assessed subjectively and photographically in a double-blind trial in 22 women studied for 1 year. Menstrual frequency was recorded. Circulating concentrations of oestradiol, oestrone, testosterone, androstenedione, and sex hormone binding globulin (SHBG) were determined before treatment and after 6 and 12 months therapy. On the same occasions gonadotrophin concentrations (mean of 24 samples) and their response to 100 micrograms LHRH were determined. No evidence was found to support a therapeutic role for bromocriptine in the treatment of hirsutism or menstrual regulation in PCO. No biochemical changes were seen specific to bromocriptine therapy.
The long-term sequelae of external pituitary irradiation alone or in combination with surgery and/or bromocriptine therapy have been studied in 14 patients with large prolactinomas over an observation period of 6-22 years (mean 13 years). Galactorrhoea was abolished in four of the five females with this symptom, but menstrual disturbance persisted in five of six patients. Sexual function was normal without sex hormone replacement in only one of the eight males after treatment. Neurological deficits were abolished or improved by treatment in all 9 patients with this presentation. Serum prolactin levels declined after treatment (P less than 0.001) and fell to within the normal range off bromocriptine therapy in six of the 14 patients at a mean of 9 years (range 5-17 years) after radiotherapy. All patients had anterior pituitary deficiency of some degree at reassessment, and 13 required replacement treatment. Serial skull radiographs revealed remineralization of the fossa floor in five patients and a decrease in fossa size in three. All five patients who did not also have surgery had evidence of tumour shrinkage without bromocriptine treatment (on CT scan or metrizamide cisternography). Fourth generation CT scans on completion of the study revealed a decrease in tumour mass in all patients, with varying degrees of empty sella in 13 and a cystic intrasellar tumour in the remaining one. Residual tumour was demonstrated in 10 patients, three of whom had normal serum prolactin levels, while one patient without visible tumour had persistent hyperprolactinaemia. Radiotherapy, alone or in combination with surgery and bromocriptine, effectively decreases prolactin secretion and tumour size in patients with large prolactinomas at the expense of other anterior pituitary function. Circulating prolactin levels are a poor marker of residual tumour volume.
Cortisol, prolactin, and growth hormone responses to insulin-induced hypoglycemia were measured in 20 patients undergoing continuous ambulatory peritoneal dialysis or intermittent hemodialysis. The plasma cortisol responses were normal; however, the increments in serum prolactin and growth hormone concentrations were impaired in most patients. The growth hormone responses were lower (p less than 0.05) in those patients treated by continuous ambulatory peritoneal dialysis, but there were no other significant differences between the two patient groups. These results show that anterior pituitary dysfunction persists in some patients with chronic renal failure despite maintenance dialysis therapy.
Sixty-six per cent of a group of 21 renal transplant recipients with chronic renal failure were shown to have adrenal suppression due to glucocorticoid treatment. Gradual withdrawal of steroids in these patients returning to maintenance dialysis therapy was achieved with few symptoms of hypoadrenalism. Adrenal recovery occurred in 52 per cent of patients after three months and 71 per cent after six months. However, the plasma cortisol response to insulin-induced hypoglycaemia, studied in patients in whom adrenal recovery had been demonstrated, was impaired in 46 per cent of cases. These results indicate that corticosteroids in renal transplant recipients induce profound hypothalamic-pituitary-adrenal suppression which is slow to recover. Such patients returning to maintenance dialysis are at risk of acute adrenocortical insufficiency for several months. Although withdrawal of steroids can be achieved safely, cover during periods of stress should be given until the hypothalamic-pituitary-adrenal axis has been shown to respond normally.
Avian red cells rapidly and extensively metabolize prostaglandin A1 (PGA1) to a polar form that extracts into 80% ethanol and is quantitatively desalted and recovered over a Waters C18 Sep-Pak. This material co-chromatographs with synthetic PGA1-GSH and with the human red cell PGA1 metabolite on cellulose and silica gel thin layer plates and on normal phase high performance liquid chromatography. Quantitation of the amino acid composition by [35S]cysteine incorporation and by fluorometric amino acid analysis of the material eluting from high performance liquid chromatography indicates the presence of PGA1, cysteine, glutamate, and glycine in equimolar ratios. Base sensitivity of the metabolite indicates that it exists largely (80%) in the 9-hydroxyl form. We conclude that the polar metabolite of PGA1 that acts intracellularly to inhibit cyclic AMP efflux by avian red cells is a glutathione conjugate of PGA1.
Osmoregulation of vasopressin secretion was studied in eight healthy women in the follicular and luteal phases of the menstrual cycle. Basal plasma osmolality in the luteal phase was significantly lower than in the follicular period (282.4 +/- 0.6, 285.6 +/- 1.1mmol/kg, respectively, P less than 0.05). Plasma AVP (pAVP) and plasma osmolality (pOsm) were measured during the infusion of 850 mmol/l saline in both phases of the cycle, and linear regression analyses of these data gave the following regression equations (i) follicular, pAVP = 0.43 (pOsm - 284), r = + 0.93, (ii) luteal, pAVP = 0.31 (pOsm - 279), r = + 0.95. Both the slope and abscissal intercept were significantly different (P less than 0.01). Osmotic threshold for thirst sensation in the luteal phase was lower than the follicular (293 +/- 2,297 +/- 1 mmol/kg, P less than 0.005). We conclude that, in the luteal phase, the threshold for AVP release and the gain or sensitivity of the osmostat are reduced together with lowering of the thirst threshold, which account for the lower basal luteal plasma osmolality.
Eight patients who had received megavoltage therapy for Cushing's disease 5-12 years previously have been reviewed. The long term response to this therapy was assessed with respect to efficacy of treatment in inducing continued remission and disturbance of hypothalamic-pituitary function. One patient showed clear evidence of relapse of Cushing's disease. One patient had unequivocal hypopituitarism. Basal levels of growth hormone (GH), TSH, LH, and FSH were not statistically different from controls, but provocative testing revealed significant abnormalities of response of cortisol/ACTH, GH, prolactin and LH. Six out of eight patients had absent diurnal cortisol variation and five patients had elevated serum prolactin levels. Thus, in this group of patients normal pituitary-adrenal function has not been satisfactorily restored. It is clear that significant disturbances of hypothalamic-pituitary function follow mega-voltage therapy and these may progress to overt hypopituitarism.
A boy aged two years presenting with advanced development of the genitalia, but with prepubertal testes, and accelerated growth is described. Investigation indicated pseudo-precocious puberty, due to idiopathic interstitial cell hyperplasia. Difficulties in interpretation of the hormonal studies were encountered due to an aberrant left testicular vein. This rare condition which has been called Testotoxicosis is probably due to an inborn error of metabolism not yet identified.
The investigation is described of a 62-year-old female patient who presented with severe virilisation; her plasma testosterone concentration was grossly elevated at 37.9 nmol/L. Measurement of plasma androstenedione, dehydroepiandrosterone (DHEA) and DHEA-sulphate, urinary 17-oxosteroids and urinary 'free' cortisol suggested an ovarian source of androgens. An ultrasound scan indicated the presence of an ovarian mass which was removed and classified as a Sertoli-Leydig cell tumour (arrhenoblastoma) combined with a mucinous cystadenoma. Following operation plasma testosterone levels returned to normal. The excessive pre-operative testosterone production appeared to have had little effect on the plasma level of SHBG, since levels remained similar before and after removal of the tumour. Serum LH and FSH levels were higher post-operatively.
The role of serotonin in the prolactin, growth hormone, ACTH and cortisol responses to hypoglycaemia has been investigated in normal subjects using a selective serotonin (5HT2) receptor antagonist, ketanserin. Circulating concentrations of these hormones were measured after administration of insulin (0.1 units/kg body weight iv) to eight normal male subjects with and without simultaneous iv ketanserin (10 mg). Plasma glucose fell to less than 2.0 mmol/1 in all subjects and was unaffected by ketanserin. Ketanserin induced a 50% decrease in the serum prolactin response to hypoglycaemia, 45 and 60 min after administration of insulin (increase in serum prolactin at 60 min: 1145 +/- 295 mU/l without ketanserin; 558 +/- 176 mU/l with ketanserin, P less than 0.05). The peak ACTH response was reduced by 30% (95.3 +/- 33.6 ng/l without ketanserin; 60.0 +/- 22.9 ng/l with ketanserin, P less than 0.05) but the plasma cortisol response was not significantly altered. The serum growth hormone response was unaffected by serotonin blockade. These findings suggest that serotonin, probably acting through 5HT2 receptors, is involved in the stimulation of prolactin and ACTH release but not in the release of growth hormone, during insulin induced hypoglycaemia.