A team approach to emergency portable cardiopulmonary support.
Explore the source record for details and available documents.
Accidental Falls↗
Biomedical subjects
J A Parsons
Publications and source records attributed to J A Parsons.
Adaptation of islets of Langerhans to pregnancy: increased islet cell proliferation and insulin secretion correlates with the onset of placental lactogen secretion.
To elucidate the temporal profile of adaptive changes of the islets of Langerhans to the increased insulin demands of pregnancy, we have studied islet cell proliferation and insulin secretion during gestation in the rat. 5-Bromo-2'-deoxyuridine incorporation into dividing islet cells was significantly (P less than 0.05) increased over age-matched controls by day 10, rose continuously to a peak at day 14, and then returned to control levels by day 18. By day 20, cell division was significantly inhibited (P less than 0.05). The pattern of changes in insulin secretory profiles observed with perfused pancreata of pregnant animals was similar to that obtained for islet cell proliferation. Both the threshold of glucose-stimulated insulin secretion and the amount of above threshold insulin secretion began to diverge from controls by day 10. By day 12, the glucose-stimulation threshold was significantly decreased from 5.7 mM glucose to 3.3 mM (P less than 0.05), remained at this low level through day 15, and returned toward normal by day 20. Concomitant with the increased sensitivity of B cells to glucose, the above threshold insulin secretion was significantly increased by day 12 (P less than 0.05), peaked at day 15, and returned to control levels by day 20. This insulin secretory data demonstrates that the increased sensitivity of B cells to glucose is an important component of the adaptation of islets during pregnancy to the increased demand for insulin at physiological concentrations of plasma glucose. To correlate the above changes in islet cell proliferation and insulin secretion with levels of placental lactogen (PL), serum lactogenic hormone activity was measured by Nb2 lymphoma cell replication assays. This analysis revealed the expected biphasic pattern: a midpregnancy peak at day 12, followed by a nadir at day 14, and then continuously elevated levels until term. The bioassay data agreed with the known secretory profiles of rat (r) PL-I (midpregnancy) and rPL-II (late pregnancy). Our results provide the first systematic evaluation of changes in islet function during pregnancy in the rat. In addition, they provide evidence that rPL-I may be the critical hormonal signal which triggers the primary adaptive changes in islet function characteristic of pregnancy. The return to normal values of insulin secretion and inhibition of cell division observed at day 20 in the presence of high concentrations of rPL-II suggests that other inhibitory influences become dominant in the later stages of rat pregnancy.(ABSTRACT TRUNCATED AT 400 WORDS)
Animals↗
Detection of bacteria by ion mobility spectrometry.
Explore the source record for details and available documents.
Bacteria↗
Histochemical and immunocytochemical localization of prolactin receptors on Nb2 lymphoma cells: applications of confocal microscopy.
We studied prolactin (PRL) binding sites on Nb2 lymphoma cells using two different light microscopic methods. First, histochemical detection was accomplished by using an aminomethyl coumarin-acetic acid-conjugated ovine prolactin molecule (AMCA-oPRL) on both glutaraldehyde-fixed and unfixed Nb2 lymphoma cells. Binding of AMCA-oPRL was studied after UV illumination and appeared as punctate fluorescence associated with many but not all cells. Binding was abolished when tissue sections were treated with excess unlabeled lactogenic hormones and was unchanged when a non-lactogenic hormone was used for displacement. Counting revealed significant differences between the number of labeled cells in populations known to exhibit up- or down-regulated PRL receptors. Second, indirect immunocytochemistry of Nb2 PRL receptors was accomplished by immunological detection of exogenously added ovine PRL using two antisera directed against ovine PRL. Visualization of the ligand-antibody complexes was accomplished by confocal laser scanning microscopy. Staining was restricted to a subpopulation of cells. The morphological results presented here add to the previous physiological and biochemical data on the presence of lactogenic hormone receptors on Nb2 lymphoma cells.
Animals↗
Plasma concentrations of pituitary hormones in 2,3,7,8-tetrachlorodibenzo-p-dioxin-treated male rats.
Experiments were conducted to test the hypothesis that acute TCDD toxicity is associated with pituitary hypofunction. Sexually mature male Sprague-Dawley rats were given graded doses of TCDD (0-100 micrograms/kg) and evaluated 7 days later. Despite pronounced hypophagia and body weight loss, plasma concentrations of growth hormone (GH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were not significantly affected by any dose of TCDD. Only prolactin (PRL) concentrations were reduced, while, as previously reported, thyroid-stimulating hormone concentrations were elevated. Also, plasma LH, PRL, and adrenocorticotropic hormone (ACTH) concentrations were not significantly affected 1, 2, 3, 4, 5, or 7 days after a single dose of TCDD (50 micrograms/kg). We conclude that (1) pituitary hypofunction is not a major cause of the initial stages of acute TCDD toxicity, (2) growth retardation in TCDD-treated rats is not the result of a deficiency of GH, (3) alterations in plasma corticosterone concentrations are due to altered responsiveness of the adrenal to ACTH stimulation rather than to changes in plasma ACTH concentrations, and (4) that impaired spermatogenesis is not associated with a decrease in plasma FSH concentrations. In addition, the lack of a consistent effect on plasma PRL concentrations suggests that alterations in plasma PRL concentrations do not play a critical role in the toxicity of TCDD. Finally, because TCDD treatment causes a serious androgenic deficiency without increasing the rates at which androgens are catabolized or excreted, the fact that plasma LH concentrations were unaffected indicates that TCDD treatment must reduce the responsiveness of the testis to LH stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenocorticotropic Hormone↗
Histochemical demonstration of prolactin binding sites.
We have developed a new probe for histochemical demonstration of prolactin binding sites. Ovine prolactin (oPRL) was conjugated with the N-hydroxy-succinimide ester derivative of the fluorochrome 7-amino-4-methylcoumarin-3-acetic acid. Under mild reaction conditions the ester derivative reacted with available NH2 groups of the prolactin molecule to form stable bonds. The coupling reaction yielded products that co-migrated with oPRL but had slightly decreased isoelectric points. The receptor binding and bioactivity of the flurochrome-hormone derivatives were decreased essentially proportional to the extent of conjugation. The derivatives were further tested for their ability to label PRL binding sites, using frozen sections of mammary gland and brain tissue of lactating rats. The results presented in this report describe the validation of this probe with regard to labeling of PRL binding sites at the light microscopic level in known target organs (mammary gland and choroid plexus). In addition, this fluorescent probe was used to demonstrate the presence of PRL binding sites at a novel site, the ependymal lining of the third ventricle.
Animals↗
Characterization of a biotin-conjugated ovine prolactin ligand.
Ovine prolactin was biotinylated with N-hydroxysuccinimidobiotin. Biotinylation was proportional to the molar ratio of reactants. Gel electrophoresis of the biotinylated derivative revealed little or no change in migration, but isoelectric focusing showed an acidic shift when compared to oPRL. Biotinylated ovine prolactin (B-oPRL) was detected by anti-oPRL antiserum and avidin-fluorescein-isothiocyanate (FITC) on protein blots. Competitive binding assays using 125I-B-oPRL and 125I-oPRL revealed: (a) similar dissociation constants and ID50 values for binding to anti-oPRL antibodies; (b) similar dissociation constants and maximum binding values for binding to liver membrane preparations; and (c) similar dissociation curves for displacement by several pituitary hormones. In contrast, binding of biotinylated oPRL to Nb2 node cells was reduced by approximately 70% and its bioreactivity was only 10% of that of oPRL. Our results indicate that biotinylation of oPRL does not alter its binding characteristics as measured by radioimmunoassay and radioreceptor assay using hepatic lactogenic receptors, but decreases its binding and bioreactivity when measured in Nb2 lymphoma cells. Assuming that N-hydroxysuccinimidobiotin interacts with reactive free amino groups of oPRL, our results suggest that these groups are essential for binding and bioreactivity of the molecule in the Nb2 lymphoma cell system.
Animals↗
Increased dye coupling in pancreatic islets from rats in late-term pregnancy.
Our previous studies have suggested that elevated lactogen, increased glucose-stimulated insulin secretion, and increased beta-cell coupling are associated. To determine whether this association occurs under conditions of physiologically increased lactogen, we have studied the extent of dye coupling in rat islets during the later stage of pregnancy. These animals have high plasma lactogen levels in the form of placental lactogen, increased plasma insulin, and decreased plasma glucose. The fluorescent tracer, Lucifer yellow CH, was microinjected into central cells of islets from both pregnant and virgin rats, and the extent of transfer was quantitated by determining the projected area of dye spread. Two area measurements were made for each injection, one around the entire discernible fluorescent region ("outer") and another around the distinct brighter region of cells surrounding the injected cell ("inner"). Pregnancy increased dye transfer, as determined by both measurements. The outer area of dye transfer was 9047 +/- 775 microns2 for the islets from pregnant rats and 4699 +/- 391 microns2 for the islets from virgin rats (P less than .001). Similarly, pregnancy increased the inner area of dye transfer, 1447 +/- 161 microns2 for the islets from pregnant rats and 795 +/- 80 microns2 for the islets from virgin rats (P less than .001). These results support the hypothesis that elevated lactogen, increased glucose-stimulated insulin secretion, and increased beta-cell dye coupling are associated under physiological conditions. The study indicates that enhanced beta-cell coupling is part of the structural and functional adaptation that the islets undergo during a subject's pregnancy and demonstrates that the extent of beta-cell coupling is regulated by a physiological condition.
Animals↗
Decreased glucose stimulation threshold, enhanced insulin secretion, and increased beta cell coupling in islets of prolactin-treated rats.
In order to determine the effect of lactogen on insulin secretion and junctional coupling among islet beta cells, ovine prolactin (oPRL) was infused by Alzet minipumps into female rats for 4 days. This treatment produced an oPRL level of 994 +/- 122 ng/ml which, combined with residual rat PRL (rPRL) (12 +/- 2 ng/ml), represented nearly a 20-fold increase from control (rPRL: 53 +/- 17 ng/ml). In addition, plasma insulin was increased nearly 50% (control: 21.9 +/- 3 microU/ml; experimental: 30.3 +/- 3 microU/ml; p less than 0.05). When pancreata from lactogen-treated and control animals were perfused with linear 30-200 mg/dl glucose gradients, the apparent glucose threshold for insulin secretion in the experimental group was nearly 33% lower than that of the controls (i.e., 70 +/- 4.6 mg/dl vs. 104 +/- 7.5 mg/dl; p less than 0.01). The oPRL treatment also increased dye coupling among beta cells. Central cells in islets isolated from lactogen-treated and control animals were injected with Lucifer Yellow CH to estimate the extent of gap junctional coupling. There was nearly a twofold increase in the projected area of dye transfer per injection in the experimental vs. the controls: 4,607 +/- 575 micron 2 vs. 2,302 +/- 474 micron 2, respectively; p less than 0.02. The effects of oPRL decreased the apparent glucose threshold for insulin release, increased the above-threshold glucose-induced insulin secretion, and increased the extent of dye coupling among beta cells. These changes in insulin secretion and dye coupling closely resemble those observed in islets from pregnant rats.
Animals↗
Prolactin enhances cell-to-cell communication among beta-cells in pancreatic islets.
To determine the role of prolactin in increasing junctional communication among islet beta-cells, we studied dye coupling in pancreatic islets exposed to elevated levels of prolactin in vivo and in vitro. Islets were isolated from rats immediately after lactation or from rats bearing mammosomatotropic tumors (MtTW15), conditions involving high levels of prolactin (either 5-fold or 1000-fold control levels, respectively). When beta-cells were microinjected with the gap junction permeant dye Lucifer yellow CH, the mean number of dye-coupled cells per injection was approximately 10-fold greater than in islets from virgin control rats. As a more direct test of the effects of prolactin on beta-cell coupling, islets isolated from virgin rats were treated for 90 min with 500 ng/ml rat prolactin in the presence of low glucose (2.8 mM) and were microinjected with dye. The mean number of dye-coupled cells per injection increased by 6.7-fold over controls with low glucose, demonstrating a direct effect of prolactin on beta-cell coupling. In vitro treatment with high glucose (16.7 mM) resulted in a 2.7-fold increase in dye-coupled cells per injection. We discuss the possible relationship between the effects of glucose and of prolactin on coupling.
Animals↗
Radiation therapy for local-regional recurrent breast carcinoma.
One hundred seven women with recurrent breast carcinoma involving the chest wall and/or regional lymph node regions were treated with radiotherapy between 1970 and 1979. Local-regional tumor was the initial and only evidence of recurrent breast carcinoma in all cases. Forty-seven patients had their disease confined to the chest wall alone and sixty (56%) patients had chest wall involvement as some component of their local-regional recurrent disease. Within five years after the initial mastectomy, 80.5% of recurrences were manifested. All patients had radiotherapy to at least the site of involvement. Eighty-four patients (78.5%) had a complete response. The absolute 5-year survival of all patients following local-regional recurrence was 34.6%. Five year survival was 29% in those patients who had recurrence within 5 years of the original mastectomy. For those patients whose local-regional recurrence occurred after a 5-year disease-free interval, the subsequent 5-year survival was 57%. For patients with recurrence confined to the chest wall, subsequent 5-year survival was 48.9%. Patients who had supraclavicular involvement as part of their local-regional recurrence had only a 16.1% 5-year survival. The majority of patients developed distant metastasis. Twenty-two patients developed carcinoma of the contralateral breast following local-regional recurrence. Five year survival following local-regional recurrence was only 4.3% for patients whose initial treatment for their primary breast carcinoma was surgery and adjuvant chemotherapy. For those patients whose primary breast carcinoma was treated by surgery alone or surgery and post-operative radiotherapy, the 5-year survival following local-regional recurrence was over 40%.
Breast Neoplasms↗
Comparison between bioactivity and immunoreactivity of serum prolactin in uraemia.
The lactogenic potency of sera from 24 male uraemic patients on regular haemodialysis and 14 control subjects was measured by Nb2 node rat lymphoma cell bioassay, and was compared to serum prolactin levels measured by radioimmunoassay. Sera with immunoreactive growth hormone levels exceeding 5 ng/ml were excluded from comparisons. The uraemic patients had a higher serum immunoreactive prolactin (48.2 +/- 10.5 ng/ml) than controls (13.3 +/- 1.3 ng/ml (P less than 0.01). Similarly the lactogenic potency of uraemic serum was higher than that of the control sera (25.5 +/- 3.9 vs 12.6 +/- 1.4 ng/ml, P less than 0.02). The ratio of immunoreactive serum prolactin to the lactogenic potency of the serum was significantly higher in the uraemic group (1.80 +/- 0.14 vs 1.10 +/- 0.10, P less than 0.01) suggesting decreased bioactivity of prolactin in uraemic serum. To examine whether low molecular weight inhibitory molecules were responsible for this discrepancy, the lactogenic potency of 8 uraemic sera was studied before and after 4 h of dialysis against 1 litre of haemodialysis medium. Two of the eleven sera studied showed a significant increment in lactogenic potency after dialysis (47% and 57%). We conclude that there is a disparity between the bioactive and the immunoreactive serum prolactin concentrations in patients with chronic renal failure and that a dialysable factor may be partly responsible for this discrepancy in some cases.
Adult↗
Insulin secretion in mammosomatotropic tumor-bearing and pregnant rats. A role for lactogens.
The experiments reported here investigate the effects of two conditions of elevated lactogen activity on the threshold of glucose stimulation of insulin secretion and suprathreshold, glucose-stimulated insulin secretion in the isolated, perfused rat pancreas. In both the tumor-bearing animals and pregnant animals, the glucose threshold for insulin release was markedly reduced and the suprathreshold insulin release was elevated over that observed in control pancreata. There was no change on the glucose threshold or extent of release of somatostatin secretion. Altered insulin secretion appears to be readily reversible, since the secretion profile from postlactating animals was not different from the controls. The possible mechanistic role of lactogens is discussed.
Adenoma, Islet Cell↗
Effect of intraportal and peripheral insulin on glucose turnover and recycling in diabetic dogs.
The effects of peripheral and portal intravenous infusions of insulin on hepatic glucose production and glucose recycling have been compared in conscious diabetic dogs. Glucose turnover (Ra) was estimated using a priming dose of [3-3H]glucose and [1-14C]-glucose followed by constant intravenous infusion. Glucose recycling was calculated from 3H-Ra - 14C-Ra. In eight normal dogs, mean 3H-Ra was 3.0 mg X kg-1 X min-1 and recycling 19%. When these dogs were made diabetic with alloxan and streptozotocin the 3H-Ra rose to 6.2 mg X kg-1 X min-1 (P less than 0.001) and recycling to 24% (P less than 0.05). Insulin infusion for 2.5 h at 0.006 U X kg-1 X h-1 intraportally decreased 3H-Ra to 4.0 mg X kg-1 X min-1 (P less than 0.01 compared with untreated diabetic), whereas peripheral infusion at this rate had no significant effect. Insulin infusion at 0.05 U X kg-1 X h-1 by the peripheral and portal circulations reduced 3H-Ra to the normal range: 3.1 and 2.8 mg X kg-1 X min-1, respectively. Glucose recycling was also normalized by portal insulin infusion (20%) but was significantly decreased by peripheral infusion (11%, P less than 0.01). Thus the liver responds to lower infusion rates of insulin by the intraportal route, and only this mode of administration normalizes both hepatic glucose output and glucose recycling.
Animals↗
Metabolic responses to intraduodenal glucose loading in insulin-infused diabetic dogs.
The hormonal and metabolic responses to an intraduodenal glucose load (0.5 g/kg) were first determined in eight normal dogs before diabetes (alloxan/streptozotocin) was induced and then comparison made of the responses to the glucose load when normal plasma glucose profiles were recreated by preprogrammed infusion of insulin via the portal or peripheral circulations. Basal intraportal and peripheral insulin infusions at 0.021 +/- 0.001 and 0.022 +/- 0.000 U . kg-1 . h-1, respectively, for 16 h to fasting diabetic dogs normalized peripheral plasma levels of glucose (5.5 +/- 0.3 and 5.6 +/- 0.6 mmol/liter, respectively), immunoreactive insulin (IRI) (11.5 +/- 1.2 and 16.4 +/- 1.6 microU/ml), glucagon (65 +/- 7 and 62 +/- 5 pg/ml), lactate (0.63 +/- 0.04 and 0.54 +/- 0.03 mmol/liter), and alanine (0.236 +/- 0.037 and 0.191 +/- 0.008 mmol/liter). However, peripheral but not intraportal infusion of insulin depressed levels of glycerol, nonesterified fatty acids (NEFA), and 3-hydroxybutyrate (0.074 +/- 0.006 vs. 0.109 +/- 0.013, P less than 0.01; 0.67 +/- 0.04 vs. 0.84 +/- 0.09, P less than 0.05; and 0.018 +/- 0.004 vs. 0.059 +/- 0.015 mmol/liter, P less than 0.01, respectively). With the preprogrammed insulin infusions used to normalize plasma glucose profiles to the intraduodenal glucose load, all hormonal and metabolic responses were normalized during intraportal infusion (IRI, 72.5 +/- 4.2 microU/ml; glucagon, 66 +/- 10 pg/ml; lactate, 1.06 +/- 0.10 mmol/liter; alanine, 0.251 +/- 0.042 mmol/liter; glycerol, 0.043 +/- 0.013 mmol/liter; NEFA, 0.24 +/- 0.03 mmol/liter; and 3-hydroxybutyrate, 0.012 +/- 0.007 mmol/liter) but marked hyperinsulinemia (103.2 +/- 6.1 microU/ml) and depressed glycerol, NEFA, and 3-hydroxybutyrate responses at 2 h (0.056 +/- 0.005, 0.52 +/- 0.10, and 0.019 +/- 0.010 mmol/liter, respectively) resulted during peripheral infusion. Therefore, only the portal route of insulin infusion achieved complete metabolic normalization during glucose loading in diabetic dogs.
3-Hydroxybutyric Acid↗
Effect of MtTW15 mammosomatotropic tumors on pancreatic islet hormones.
The effects of hypersecretion of growth hormone and prolactin on islet endocrine cells have been studied by radioimmunoassays, immunocytochemistry, and morphometry in randomized samples of pancreata from MtTW15 mammosomatotropic tumor-bearing and control rats. The randomized sampling procedure, validated by immunoassays, allowed evaluation of both hormone content (immunoassay) and endocrine cell population (immunocytochemistry) on samples derived from the same origin. Hyperinsulinemia (2x) and non-fasting hypoglycemia in 10-wk-tumor rats were normalized 3 wk after tumor removal. Pancreatic weight was doubled, but proportional to body weight increases. Islet/pancreas ratio was constant (1.29 +/- 0.05%) and the same in tumor, tumor-removed, and control animals, but average islet dimensions were increased by 30% and average area doubled in tumor animals. Frequency analysis showed fewer small (less than 70 micrometers) and more large (greater than 140 micrometers) islets in tumor animals, but no change in average islet shape shown by average axis ratios of 1.4 in all groups. Pancreatic content of insulin and glucagon was doubled, while that of somatostatin was constant. These changes were not completely reversed in tumor-removed animals. Similarly, a significant doubling in islet-derived mass was mainly due to a doubling of the B-cell mass as the average proportion of endocrine cells per islet shifted from 66%, 26%, and 18% to 81%, 18%, and 3% for B-, A-, and D-cells of control and tumor-bearing rats, respectively. Immunocytochemically detectable insulin was found in duct cells of tumor animals, but not controls. Whether such cells represent a functional reserve remains to be determined.
Animals↗
In vitro studies on an antagonist of parathyroid hormone [Nle-8, Nle-18, Tyr-34]bPTH-(3-34)amide.
1 The actions of parathyroid hormone (PTH) are antagonized in vitro by the peptide [Nle-8, Nle-18, Tyr-34]-bPTH-(3-34)amide, an analogue of PTH. In this paper, the actions of the inhibitory peptide were investigated in vivo. 2 Native parathyroid hormone (bPTH-(1-84)), administered i.v. (0.17-1.51 nmol in volume of 0.3 ml) to 7 day old chicks produced hypercalcaemia but administration of the analogue in doses up to 173 nmol was ineffective in this respect. 3 The analogue failed to antagonize the hypercalcaemia produced by bPTH-(1-34) when injected, in 10 fold molar excess, 2 min before or simultaneously with bPTH-(1-34). 4 Normocalcaemia was restored in parathyroidectomized rats by intravenous infusion of bPTH-(1-84) at 32 pmol kg-1 h-1. Addition of the analogue to the infusion fluid in a 200 fold molar excess did not affect the concentrations of calcium and phosphate in the plasma, cyclic adenosine 3',5'-monophosphate (cyclic AMP) in the urine or phosphate clearance but produced a significant (P less than 0.05) rise in urinary calcium clearance. 5 The results suggest that the peptide [Nle-8, Nle-18, Tyr-34]-bPTH-(3-34)amide does not antagonize the actions of PTH in vivo and demonstrate an important dichotomy between in vitro and in vivo biological properties of the PTH analogue.
Animals↗
Sulfur-free parathyroid hormone analogues containing D-amino acids: biological properties in vitro and in vivo.
Three sulfur-free analogues of bovine parathyroid hormone (bPTH) containing D-amino acids were synthesized by the solid-phase method and their biological properties compared in an in vitro bioassay (rat renal adenylate cyclase assay), a receptor assay for parathyroid hormone (PTH) (canine renal membranes), and an in vivo bioassay (chick hypercalcemia assay). The analogue [Nle8,Nle18,D-Tyr34]-bPTH-(1-34)-amide, which was found to be more than 4 times as potent in vitro as unsubstituted PTH, is the most potent analogue of PTH yet synthesized. The enhanced potency was largely attributable to increased affinity for the PTH receptor. In vivo, however, this analogue was only one-third as potent as bPTH-(1-34). Cumulative evidence suggests that the nearly 15-fold decline in the relative potency when the compound was assayed in vivo is due to the substitution of norleucine for methionine. The other analogues, [D-Val2,Nle8,D-Tyr34]bPTH-(1-34)-amide and [D-Val2,Nle8,Nle18,D=Tyr34]bPTH-(2-34)-amide, were only weakly active in vitro and in vivo, indicating that substitution with D-amino acids at the NH2 terminus of PTH causes markedly diminished receptor affinity. In fact, the placement of a D-amino acid at the NH2 terminus is more deleterious to biological activity than is omission of amino acids at positions 1 and 2.
Adenylyl Cyclases↗