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C Sernia

Publications and source records attributed to C Sernia.

87 records · Page 5Linked to original sources
PubMed1984

Separation of radioiodinated angiotensins by chromatofocusing in minicolumns.

Angiotensins I, II, and III (AI, AII, AIII) and Saralasin (Sar1-Ala8-AII) were labeled with 125I and separated from the nonlabeled forms on minicolumns (a Pasteur pipet ) of chromatofocusing medium. At low ionic strength, 125I-labeled angiotensins could be eluted with Polybuffer or a piperazine-histidine buffer at their approximate isoelectric points, while nonlabeled angiotensins remained adsorbed to the column and required 1 mol X liter-1 NaCl for elution. The 125I-labeled angiotensins prepared by this method were bound by antibodies (AI) and adrenal receptors (AII, Saralasin) to an extent similar to angiotensins prepared by DEAE-Sephadex A-25 chromatography. This new method of preparing radioiodinated angiotensins is rapid (15 min), inexpensive, and requires no fraction-collecting equipment.

Adrenal Glands↗
PubMed1983

Brain angiotensinogen: in vitro synthesis and chromatographic characterization.

The capacity of rat brain to synthesize angiotensinogen (renin substrate) was examined in vitro using brain slices (300 micrometers thick) incubated in minimum essential medium (Eagles) at pH 7.4 and 37 degrees C for 2 h. The concentration of angiotensinogen (measured as equivalents of angiotensin I;AI) increased from 5.2 +/- 1.1 ng AI/g of incubated tissue to 40 +/- 4 ng AI/g at 2 h. In the presence of cycloheximide (10 micrograms/ml) or vinblastine sulfate (10 micrograms/ml) the values at the 2 h interval were 24.5 +/- 3.5 ng AI/g and 10.5 +/- 3.5 ng AI/g respectively. The angiotensinogen released by brain slices was pooled and some of its physicochemical properties examined and compared to those of angiotensinogen from plasma and saline-perfused brains. Chromatography on Sephacryl S-200 showed brain and plasma angiotensinogen to be similar in size (mol. wt. approximately 59,000) but large differences in binding activity to Concanavalin A were found. Only 31% of plasma angiotensinogen bound to the affinity medium compared to 63% for the pooled incubation medium. It was concluded that de novo synthesis of angiotensinogen occurs in the rat brain and that the brain protein may differ in its glycoside composition from hepatic angiotensinogen.

Angiotensin I↗
PubMed1982

Search for a progesterone-binding protein in secretory granules of the ovine corpus luteum.

The hypothesis that electron-dense granules present in the corpus luteum contain progesterone in a protein-bound form was examined using differential and sucrose gradient centrifugation. Ovine luteal tissue was fractionated by differential centrifugation at 1,000 X g (P1 pellet), 10,000 X g (P2), and 82,000 X g (P3; supernatant S3). Samples of P2, P3, and S3 were further fractionated o 20-40% (P2 and P3) or 5-25% (S3) sucrose gradients and examined for progesterone-binding activity by measuring the progesterone content and/or the specific binding of [3H]progesterone of sucrose gradient samples. In addition, saturation binding assays were performed with steroid-free samples of P2 and S3. Saturable binding of progesterone was not found in P2, the fraction containing electron-dense granules. In S3, two progesterone-binding proteins with sedimentation rates of 3.2S and 8.6S and an affinity of 7.1 X 10(5) M-1 for progesterone were detected. The sedimentation behavior of these proteins was distinct from that of ovine plasma transcortin, a 4S protein. The view that a binding protein is released into the interstitial fluid during the exocytosis of granules was examined by measuring the progesterone-binding activity of protein released by slices of corpus luteum in vitro. No binding activity was found. The results of this investigation do not support the hypothesis that putative progesterone-secreting granules observed in luteal tissue contain a binding protein

Alpha-Globulins↗
PubMed1981

Secretion of aldosterone in the monotreme mammal, Tachyglossus aculeatus.

The secretion of aldosterone and its regulation by ACTH and angiotensin II were investigated in conscious, unrestrained echidnas with chronically implanted jugular catheters. Aldosterone was measured by radioimmunoassay after extraction and isolation by silica gel thin-layer chromatography. The mean concentration of aldosterone in blood plasma of five male and three female echidnas was only 5.4 +/- 1.3 (S.E.M.) pg/ml. During stress (surgery and anaesthesia) the mean concentration increased to 17.6 +/- 3.8 pg/ml. Infusion of beta 1-24 ACTH at a rate of 5 units/kg per h increased the plasma concentration of aldosterone to 53.8 +/- 9.8 pg/ml. Infusion of angiotensin II at rates of 100 and 500 ng/kg per h also increased aldosterone concentration, to 24.1 +/- 8.6 and 35.1 +/- 10.9 pg/ml respectively. Production and metabolic clearance rates were measured by the constant-rate infusion of [3H]aldosterone and found to be 5.0 +/- 2.2 ng/kg per h and 14.3 +/- 1.3 ml/kg per min respectively in the unstimulated state. Production rate was increased approximately sevenfold by the infusion of ACTH at 5 units/kg per h and fourfold and sixfold by infusion of angiotensin II at 100 and 500 ng/kg per h respectively. Metabolic clearance decreased following the infusion of ACTH or angiotensin II. Direct measurement of secretion rate by the collection of adrenal venous blood from three anaesthetized, laparotomized echidnas gave values of 9.4, 15.6 and 8.8 mg/kg per h. It is concluded that the adrenal secretion of aldosterone in the echidna is extremely low compared with that in other mammals but the response to stress, ACTH and angiotensin II indicates the presence of typical mammalian control mechanisms for its secretion.

Adrenocorticotropic Hormone↗
PubMed1980

Stimulation of angiotensinogen production: a dose-related effect of angiotensin II in the conscious dog.

The hypothesis that angiotensin II (AII) provides a positive feedback stimulus for production of angiotensinogen was examined in conscious dogs. AII was infused intravenously for 24 h at 5, 20, and 50 ng x kg-1 x min-1 and blood pressure, plasma renin activity (PRA), and the concentrations of AII, angiotensinogen, corticosteroids, and total protein in plasma were measured 0, 2, 4, and 24 h after the start of infusion. In addition, the liver content of angiotensinogen and the release of angiotensinogen by liver slices in vitro were measured after the 24-h sampling period. AII infusion increased blood pressure in a dose-related manner. PRA was markedly decreased by all doses of AII. Plasma corticosteroids were increased only at the highest dose of AII and did not bear any relationship to changes in the concentration of angiotensinogen. Plasma protein concentration and hematocrit were unchanged. Plasma angiotensinogen concentration was unchanged at 2 and 4 h but was increased significantly at 24 h by the two highest doses of AII. A linear relationship was found between the dose of AII and plasma angiotensinogen concentration, the liver content of angiotensinogen, and the release from liver slices during a 2-h incubation. These results provide further evidence that AII has a role in angiotensinogen production but suggest that it is of minor importance in physiological conditions.

Adrenal Cortex Hormones↗
PubMed1979

Prolactin receptors in the mammary gland, corpus luteum and other tissues of the tammar wallaby, Macropus eugenii.

Specific binding of radio-iodinated ovine prolactin to subcellular tissue fractions of the tammar wallaby (Macropus eugenii) was investigated. Specific binding was found, in order of decreasing binding activity, in the lactating mammary gland, corpus luteum, corpus albicans, adrenal gland and ovary. Specific binding was absent in kidney, liver, brain and inactive mammary gland. The mean association constant (Ka at 23 degrees C) was determined as 0.90 x 10(9), 2.20 x 10(9), 2.44 x 10(9), 3.38 x 10(9) and 10.98 x 10(9) l/mol for mammary gland, adrenal, corpus albicans, corpus luteum and ovary respectively. The mean receptor concentration (N) varied from 92.87 x 10(-14) mol/mg protein for the mammary gland to 1.03 x 10(-14) mol/mg protein for the ovary. The concentration in the corpus luteum varied between tissue pools collected at different times of the annual breeding cycle. The specificity for prolactin was shown in the mammary gland and corpus luteum by the failure of ovine FSH, LH, GH and TSH to displace 125I-labelled ovine prolactin, whereas it was displaced readily by both ovine and bovine prolactin.

Animals↗
PubMed1977

Adrenocortical function in a prototherian mammal, Tachyglossus aculeatus (Shaw).

The peripheral plasma concentrations and production rates of corticosterone and cortisol were measured in the conscious, unrestrained echidna (Tachyglossus aculeatus) under basal conditions and during maximal ACTH stimulation. Using Sephadex LH-20 column chromatography and radioligand assay, only cortisol and corticosterone could be detected in the peripheral blood plasma at very low concentrations of 0-07 +/- 0-03 (S.E.M.) mug/100 ml and 0-14 +/- 0-07 mug/100 ml respectively. Two-hourly sampling over periods of 36-48 h disclosed a diurnal periodicity in the combined plasma concentration of these corticosteroids, the high concentrations corresponding to periods of behavioural activity. Marked, short-term fluctuations in plasma corticosteroid concentration were also observed during periods of more frequent (20 min) sampling. Constant rate i.v. infusion of synthetic ACTH increased the plasma concentrations of both steroids to maximal values of 0-42 +/- 0-23 mug cortisol/100 ml and 1-06 +/- 0-56 mug corticosterone/100 ml at infusion rates of 1 i.u. ACTH/kg/h. This is approximately 1/160 of the potency of this ACTH in man. The production rates of corticosterone and cortisol, measured by isotope dilution during constant rate i.v. infusion of 3H-labelled tracers, were only 0-35 +/- 0-21 and 0-56 +/- 0-26 mug/kg/h respectively during saline infusion, and increased to 2-86 +/- 3-47 and 2-74 +/- 2-07 mug/kg/h during the infusion of 1 i.u. ACTH/kg/h. The metabolic clearance rate of cortisol was greater than that of corticosterone and both were depressed by ACTH. Plasma corticosteroid concentrations were increased after surgery during ether anaesthesia and in sick animals with heavy worm infestation. It is concluded that the adrenal cortex of echidnas responds to ACTH stimulation and stress in a similar way to eutherians, but the level of activity is much lower.

Adrenal Cortex↗
PubMed1977

Metabolic effects of cortisol, corticosterone and adrenocorticotrophin in a prototherian mammal Tachyglossus aculeatus (Shaw).

The effects of injections of cortisol, corticosterone and ACTH on indices of carbohydrate, fat and protein metabolism were investigated in the conscious echidna, Tachyglossus aculeatus. Intravenous infusion of cortisol and corticosterone for 2 h at rates of 3 and 30 microgram/kg/h respectively did not cause significant changes in the plasma concentrations of glucose, urea or amino acids during a 12.5 h observation period. In contrast, a dose-related increase in plasma free fatty acid (FFA) concentration was observed. Infusion of synthetic ACTH at 2 i.u./kg/h for 2 h caused a minor, short-lived increase in FFA concentration. Daily i.m. injections of 0.2 mg cortisol or corticosterone acetates/kg, which raised plasma total corticosteroid concentrations to levels characteristic of maximal ACTH stimulation, did not cause glycosuria nor was there any change in body weight, nitrogen intake or urinary nitrogen excretion. However, there was a minor, but significant, increase in plasma glucose concentration. The liver glycogen content of 24 h fasted, corticosteroid-treated animals was similar to that of fasted control animals. It is concluded that cortisol, corticosterone and ACTH have only minor effects on carbohydrate and protein metabolism and that the main action of these hormones may be to mobilize fat reserves.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

Arginine vasopressin- and oxytocin-like peptides in the testis of two Australian marsupials.

High performance liquid chromatography (HPLC) and specific radioimmunoassay (RIA) for arginine vasopressin (AVP), mesotocin (MT), and oxytocin (OT) were used to identify and quantify these peptides in the testis of the brushtail possum (Trichosurus vulpecula) and the northern brown bandicoot (Isoodon macrourus). Arginine vasopressin (0.092 +/- 0.041 ng/g) and MT (0.198 +/- 0.089 ng/g), but not OT, were found in the possum testis, while the bandicoot testis contained AVP (0.061 ng/g), MT (0.108 +/- 0.024 ng/g), and OT (0.114 +/- 0.053 ng/g). The values correlate well with those reported for AVP- and OT-like peptides in the testis of eutherian mammals. It was concluded that there are neurohypophysial peptides present in the marsupial testis.

Animals↗