PubMed Health⌕ Search

Biomedical subjects

K Mashiter

Publications and source records attributed to K Mashiter.

At least 55 records · Page 3Linked to original sources
PubMed1982

Effect of phentolamine on the metabolic response to gynaecological surgery.

The effect of the infusion of phentolamine 0.5 mg min-1 on the metabolic response to gynaecological surgery was investigated. In comparison with the control group of patients, phentolamine was associated with a significant increase in plasma insulin concentration after 30 and 60 min of surgery. The glycaemic response to surgery was decreased by alpha-adrenergic blockade, but this was only significant after 120 min of surgery. The hypotension produced by the administration of phentolamine was well tolerated.

Adult↗
PubMed1982

Childhood acromegaly successfully treated with interstitial irradiation using yttrium-90.

A child with a growth hormone producing tumour presented at the age of 4 1/2 years. The onset of the disease was at 18 months of age. Treatment was given with three doses of interstitial irradiation using yttrium-90 implants. There were no local complications from the procedures. Now, 11 years after diagnosis, she is asymptomatic, of normal appearance, and her height and the size of the pituitary fossa are normal. Growth hormone levels are almost normal, thyroid function is intact, and she is maintained on prednisone and sex hormones.

Adenoma, Acidophil↗
PubMed1982

Bombesin: action on gut hormones and calcium in man.

Bombesin, a peptide with widespread biological actions, has been demonstrated in human tissues by immunological methods. To investigate its effect in man, synthetic bombesin was infused at low doses in six male volunteers. Bombesin at 2.4 pmol kg-1 min-1 produced significant rises in plasma insulin, glucagon, pancreatic polypeptide, gastrin, cholecystokinin, motilin, glucose-dependent insulinotropic polypeptide, neurotensin, enteroglucagon, vasoactive intestinal polypeptide, and serum calcium. In contrast, bombesin caused a profound fall in parathyroid hormone levels and reduced plasma glucose concentrations. A late rise in plasma calcitonin was also observed. Bombesin had no significant effect on the pituitary hormones, TSH, GH, PRL, or cortisol. No hormonal changes or alterations in calcium were noted during saline infusions. Bombesin has a marked stimulatory effect on gastrointestinal hormones, which is unique and opposite to the effect of somatostatin, a potent inhibitor of gut hormone release. Bombesin also influences calcium-regulating hormones, either directly or through its action on gut hormones. The bombesin concentrations achieved with the dosages used were low enough to indicate a possible physiological role for the endogenous peptide.

Adult↗
PubMed1982

Vasoactive intestinal peptide stimulates adrenocorticotropin release from human corticotropinoma cells in culture: interaction with arginine vasopressin and hydrocortisone.

The effect of vasoactive intestinal peptide (VIP), cholecystokinin octapeptide (CCK), bombesin, arginine vasopressin (AVP), and hydrocortisone (HC) on ACTH release from human corticotropinoma cells in culture has been studied. Tumor tissue was obtained from 6 patients with pituitary corticotropinomas. Eleven to 21 cultures yielding 0.7-2.0 X 10(6) cells/culture, were obtained from each tumor and maintained for periods of 4 weeks to longer than 6 months. VIP (500 ng/ml) significantly (P less than 0.005) stimulated ACTH release from all tumors studied, and a dose (5-500 ng/ml)-response effect was observed in 3 of 5 tumors. Stimulation by VIP was seen at 2,4, and 24 h and was maximal at 4 h. CCK and bombesin were without effect on ACTH release from 4 tumors studies at 4 h. AVP (1-10 mU/ml) stimulated ACTH from 4 tumors studied at 60 min or 4 h. Coincubation of cultures with VIP (50-500 ng/ml) and AVP (1-10 mU/ml) resulted in at least an additive effect. HC (100 ng/ml) significantly (P less than 0.025) inhibited basal ACTH secretion from 2 of 4 tumors at 4 h and from 3 of 4 (P less than 0.005) at 24 h. Simultaneous coincubation of cultures with VIP (50 ng/ml) and HC (100 ng/ml) resulted in an attenuation or blockade of the VIP-stimulated ACTH release, whereas prior incubation of cultures with HC for 28 h before exposure to VIP did not. The results demonstrate that VIP is a potent ACTH secretagogue from human corticotropinoma cells in culture; its effects are additive to those of AVP and modulated by HC.

Adenoma↗
PubMed1982

Reassessment of the human chorionic gonadotropin stimulation test in hypogonadal males.

Eight normal and 17 hypogonadal males were injected with human chorionic gonadotropin (hCG). In normal males at 48 hr testosterone and estradiol became, respectively, 160% and 338% of basal values. In hypogonadal males at 48 hr testosterone and estradiol became respectively, 211% and 127% of basal values. No changes occurred in serum thyroid stimulating hormone (TSH), serum thyroxine (T4), and tri-iodothyronine (T3). The success of long-term therapy with hCG in five patients was predicted by the test.

Adult↗
PubMed1981

Analytical subcellular fractionation of rat pituitary homogenates, with special reference to prolactin proteolysis by lysosomes.

Prolactin proteolysis by rat pituitary homogenates was assayed by measuring the release of trichloroacetic acid-soluble peptides from 125I-labelled rat prolactin. There was a distinct optimum at pH 4.3, with only trace amounts of activity at neutral and alkaline pH. Rat pituitary homogenates were subjected to analytical subcellular fractionation by sucrose density gradient centrifugation in a Beaufay automatic zonal rotor. The principal organelles were characterized by their respective marker enzymes, including: cytosol (lactate dehydrogenase); plasma membrane (5'-nucleotidase); lysosomes (N-acetyl-beta-glucosaminidase, beta-glucuronidase); mitochondria (particulate malate dehydrogenase); endoplasmic reticulum (neutral alpha-glucosidase); prolactin granules (radioimmunoassayable prolactin). Acid prolactin protease had a similar distribution to the lysosomal marker enzymes. A localisation of the activity to lysosomes was confirmed by subcellular fractionation experiments in which the lysosomes were selectively disrupted with low concentrations of the membrane perturbant, digitonin. Experiments with specific inhibitors of the lysosomal cathepsins indicate that both cathepsins B and D are implicated in pituitary prolactin proteolysis.

Animals↗
PubMed1981

Heterogeneity of prolactin responses to oestradiol benzoate in women with prolactinomas.

Serum prolactin concentrations were measured for 72 h after intramuscular injection of 1 mg of oestradiol benzoate in six normoprolactinaemic women and nineteen with a prolactinoma (eleven with an obviously enlarged pituitary fossa and eight with a normal pituitary fossa). The group with an obvious tumour showed a rise in mean serum prolactin at 48 h to 122% of basal concentrations (p less than 0.05), and at 72 h to 137% of basal concentrations (p less than 0.01). Individual responses were variable, but in four patients serum prolactin rose to 165% or more of basal concentrations. In the group with a prolactinoma and a normal pituitary fossa serum prolactin at 72 h was 121% of basal concentrations (p less than 0.05). Normoprolactinaemic women showed no significant change in serum prolactin at any time. This study demonstrated a heterogeneity of serum prolactin responses to acute oestradiol administration in women with prolactinomas. Some patients with large tumours had a hypersensitive response to oestradiol. This heterogeneity of response could account for the present unpredictability of expansion of prolactinomas during pregnancy.

Adolescent↗
PubMed1981

Effect of hyperprolactinaemia due to pituitary tumour on serum albumin, protein and oncotic pressure.

1. Serum albumin, total protein, oncotic pressure and osmolality were measured in a group of patients with hyperprolactinaemia due to a prolactin secreting tumour, normal subjects and normoprolactinaemic acromegalic patients. 2. A significant increase in albumin, total protein and oncotic pressure was found in the prolactinoma patients when compared with those of the other two groups. 3. There was no difference in serum osmolality between the three groups. 4. These studies provide further evidence that prolactin may have anabolic effects.

Acromegaly↗
PubMed1981

Gonadotrophin levels in women with Cushing's syndrome before and after treatment.

Basal serum concentrations of LH and FSH and their response to LHRH were studied in twelve pre- and ten post-menopausal women with Cushing's syndrome before and after treatment. Subnormal basal concentrations of LH were found in twelve out of twenty-two, and of FSH in ten of the twenty untreated patients. There was a correlation between the urinary free cortisol (UFC) and basal LH values, r = -0.59 (P less than 0.05), and UFC and basal FSH values, r = -0.76 (P less than 0.02) in the premenopausal women. All seven patients with a UFC value greater than 1080 nmol/24 h (normal range less than 270) had both a subnormal basal gonadotrophin level and a subnormal response of at least one gonadotrophin to the releasing hormone. In those patients in whom successful remission was obtained and who did not require replacement therapy, subnormal basal gonadotrophins were usually restored towards or into the normal range. It is concluded that while gonadotrophin levels may be normal in women with Cushing's syndrome, they are subnormal in those with the highest cortisol values. This may be due to a direct suppressive effect of cortisol on the release of stored pituitary hormone, and/or on LHRH release from the hypothalamus.

Adult↗
PubMed1981

Secretion of LH, FSH, and PRL shown by cell culture and immunocytochemistry of human functionless pituitary adenomas.

Hormone secretion by ten functionless human pituitary adenomas in cell culture has been measured, and compared with tissue immunocytochemistry and electron microscopy, as well as results with a normal pituitary. Patients presented following routine x-ray and had no clinical or biochemical endocrine abnormality apart form one male with raised serum FSH and PRL, normal LH, and low testosterone. Of the ten adenomas, nine secreted both LH and FSH in cell culture and five of these also secreted PRL, one did not secrete any anterior pituitary hormones (ACTH was not measured). No GH or TSH was detectable in the cultures of the nine LH/FSH secretors excluding the possibility of contamination by normal anterior pituitary. The normal pituitary cells secreted all anterior pituitary hormones: the amounts of FSH/LH being comparable with those of the adenomas. Immunostaining confirmed the cell culture results and showed the adenoma FSH/LH cells to be scattered singly or in small groups of two to five cells with both hormones usually being in the same cell. PRL where found was in separate cells. Hormone granules were small (50-160nm), round or irregular and scattered in the cytoplasm of rounded cell of low secretory activity. The negatively staining cells were not different ultrastructurally to those staining positively. It is concluded that a significant proportion of functionless pituitary adenomas have detectable low levels of LH/FSH secretion often accompanied by PRL when examined by cell culture or immunocytochemistry. Although these adenomas were endocrinologically quiescent activity could have been masked because of post-menopausal secretion and one male probably had and FSH-secreting adenoma.

Adenoma, Chromophobe↗
PubMed1981

Bromocriptine suppresses ACTH secretion from human pituitary tumour cells in culture by a dopaminergic mechanism.

Bromocriptine (0.13-13 microM) significantly inhibited ACTH secretion in a dose-dependent manner when added to cell cultures of a human corticotrophic adenoma for 24 h. Haloperidol (13 microM), but not serotonin (13 microM), blocked this inhibition but had no significant effect when added alone. In addition, dopamine (10 microM) reduced ACTH secretion during a 4-h incubation, whereas serotonin (0.01-10 microM) was ineffective. An ectopic ACTH secreting lung carcinoid was non-responsive to doses of bromocriptine up to 13 microM. These results demonstrate a direct suppressive action of bromocriptine on a human pituitary corticotrophic adenoma through dopaminergic rather than serotoninergic mechanisms.

Adenoma↗