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E R Trimble

Publications and source records attributed to E R Trimble.

At least 73 records · Page 4Linked to original sources
PubMed1990

Underestimation of glucose turnover determined using [6-3H]glucose tracer in non-steady state. The role of a tritiated tracer impurity.

The use of tritiated glucose tracers may result in underestimation of glucose turnover during hyperinsulinaemic clamps giving paradoxical negative endogenous glucose production rates. While mathematical modelling errors in the analysis of tracer data are major determinants of this underestimate in the non-steady state, the relative importance of tracer contamination under these conditions remains in doubt. We have used high performance liquid chromatography to assess the possible contribution to this problem of a labelled tracer impurity found in [6-3H]glucose. In conventional 4 h hyperinsulinaemic clamps performed in six normal subjects, labelled impurity increased as a percentage of the neutral plasma radioactivity fraction from 5.3 +/- 0.9% after a 2 h equilibration period (0 min) to 13.5 +/- 2.2% at 120 min and 15.4 +/- 2.4% at 240 min, as plasma glucose specific activities fell following the infusion of insulin. Negative endogenous glucose production rates were observed both at 90-120 min (-8.8 +/- 1.6 mumol.kg-1min-1) and at 210-240 min (-8.5 +/- 1.4 mumol.kg-1min-1) implying a persistent underestimate in isotopically determined glucose appearance rate. Using chromatography data to correct for impurity increased glucose appearance rates by 7.9 +/- 2.1% at 120 min and 11.0 +/- 2.5% at 240 min. Purified tracer was then used for a further six clamps. When the conventional protocol was used with unlabelled glucose infusion an obvious negative error persisted only at 90-120 min. In contrast, labelled infusions gave exclusively positive values for endogenous glucose production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Beta-adrenergic stimulation of cyclic AMP is defective in cultured dermal fibroblasts of psoriatic subjects.

Epidermal cells from psoriatic lesions demonstrate a very low cAMP response to beta-adrenergic stimuli. We have shown that a similar abnormality occurs in dermal fibroblasts from affected areas of skin. The cells, after 5-12 passages in tissue culture, had a much reduced response to 10(-8) M and 10(-6) M isoproterenol when compared with fibroblasts from control subjects. The abnormality was not abolished by the addition of the phosphodiesterase inhibitor, 3-isobutyl-I-methylxanthine. Other putative agonists tested were vasoactive intestinal peptide and peptide histidine methionine. Neither of these had an effect on dermal fibroblasts from either normal controls or from lesions of psoriasis.

1-Methyl-3-isobutylxanthine↗
PubMed1990

Erythropoietic protoporphyria. The problem of a suitable screening test.

Erythropoietic protoporphyria (EPP) is characterized by increased red cell protoporphyrins and is included in the differential diagnosis of children presenting with photosensitivity. In the past 20 years, using the traditional solvent extraction qualitative screening test for blood porphyrins, the diagnosis of EPP had been missed in 9 out of 10 patients but recently, using fluorescence microscopy of erythrocytes, no patients with EPP have been missed. All 14 patients in Northern Ireland known to have EPP were recalled and it was found that fluorescence microscopic determination was positive in all cases. We recommend fluorescence microscopy as the screening test of choice for the detection of increased red cell porphyrins.

Child↗
PubMed1989

Apolipoprotein E phenotype determined by agarose gel electrofocusing and immunoblotting.

Polymorphism at the apolipoprotein E (ApoE) locus is an important factor in the development of remnant (Type III) hyperlipidemia and also influences the distribution of cholesterol concentrations in the population. The new method for ApoE phenotyping described here gives good results with simple apparatus. Serum (10 microL) is digested with sialidase (EC 3.2.1.18), delipidated, and redissolved in 6 mol/L urea. Electrofocusing is carried out in agarose, followed by immunoblotting with a monoclonal antibody to ApoE and an anti-immunoglobulin-peroxidase conjugate. Sialidase-catalyzed digestion effectively removes sialated forms of ApoE, which eases interpretation. This method can be used in nonspecialist laboratories and is particularly suited for assay of large numbers of samples.

Antibodies, Monoclonal↗
PubMed1987

Changes in individual rates of pancreatic enzyme and isoenzyme biosynthesis in the obese Zucker rat.

Both alterations of enzyme content and a markedly decreased secretory response to selected physiological stimuli have been demonstrated previously in the pancreas of the obese Zucker rat. The purpose of the present investigation was to determine the degree to which alterations of enzyme content could be attributed to changes in enzyme biosynthesis. Amylase content of obese rats was decreased by 50%, whereas lipase and trypsinogens were significantly increased. However, the decrease in amylase content was less than might have been predicted from the rate of amylase biosynthesis (80% decrease), and the increases in content of trypsinogen(s) and lipase were greater than would have been predicted from alterations in the absolute rates of biosynthesis. In view of the rapid turnover of pancreatic enzymes under normal conditions, it seems probable that a markedly decreased secretory response to various stimuli leads to an increased content of some enzymes in the pancreas of the obese rat. Ciglitazone treatment, which decreases insulin resistance in obese animals and leads to normalization of glucose metabolism in their pancreatic tissue, restored the enzyme-synthesis rates towards normal, showing that the abnormalities of enzyme synthesis were linked to the insulin resistance rather than to the obese genotype itself. Lipid inclusion bodies were found in acinar cells of obese rats. These bodies have previously been described in acinar cells of starved animals, which, in common with the acinar tissue of the obese Zucker rat, have decreased glucose metabolism.

Amino Acids↗
PubMed1987

Rapid increases in inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate and cytosolic free Ca2+ in agonist-stimulated pancreatic acini of the rat. Effect of carbachol, caerulein and secretin.

We compared the time course of increases in isomers of inositol trisphosphate [Ins(1,4,5)P3] and Ins(1,3,4)P3] and the tetrakisphosphate [Ins(1,3,4,5)P4] with changes in cytosolic free Ca2+ [( Ca2+]i) in dispersed pancreatic acini of the rat. There were rapid (5s) increases in Ins(1,4,5)P3 and Ins(1,3,4,5)P4 in response to carbachol, caerulein and secretin, whereas Ins(1,3,4)P3 increased more slowly. All three secretagogues induced increases in [Ca2+]i, which reached a peak at 15-20 s. Our results indicate that the very rapid formation of Ins(1,4,5)P3 is compatible with its second-messenger role in the initial elevation of [Ca2+]i.

Animals↗
PubMed1987

Direct stimulation of enzyme secretion from rat exocrine pancreas by neurotensin and its naturally occurring fragments.

Neurotensin stimulates amylase release from dispersed pancreatic acini at concentrations as low as 10(-15) M. The naturally occurring fragments of neurotensin (NT), NT 1-8 and NT 1-11, also stimulate amylase secretion at concentrations that occur in peripheral plasma (10(-11) M). The analogue D-Phe11 neurotensin was as potent as neurotensin itself with respect to stimulation of amylase secretion. Basal plasma neurotensin levels were approximately 10 pmol/L, a concentration that stimulates the exocrine pancreas in vitro. Increases in plasma neurotensin levels induced by infusion of neurotensin caused greater increases in secretion of pancreatic amylase than did similar changes of neurotensin concentration in vitro. These results suggest that in addition to its direct action, other factors are involved in modulation of the effects of neurotensin on pancreatic exocrine function in vivo.

Amylases↗
PubMed1987

Secretin stimulates cyclic AMP and inositol trisphosphate production in rat pancreatic acinar tissue by two fully independent mechanisms.

In rat pancreatic acinar tissue adenylate cyclase is stimulated by low concentrations of secretin, while higher concentrations also activate phosphatidylinositol bisphosphate hydrolysis. By the use of the secretin analogues [Tyr10,13]secretin and [Tyr10,13,Phe22,Trp25]secretin, we have shown that substitution of tyrosine for leucine at positions 10 and 13 was sufficient to reduce the ability of the peptide to stimulate the production of inositol trisphosphate and the increases in cytosolic free calcium, while the ability to stimulate cAMP is little affected and the peptide remained a full agonist. Incubation with cholera toxin caused increases in cAMP, which were maximal after 30 min. Cholera toxin treatment also resulted in a marked reduction of secretin-stimulated inositol trisphosphate production, but this required a much more prolonged treatment (150-240 min), suggesting that different cholera toxin substrates were involved. Activation of protein kinase C with the phorbol ester phorbol 12-myristate 13-acetate had no effect on secretin-induced cAMP formation, nor was secretin-stimulated inositol trisphosphate formation altered by further increases in cAMP. These results indicate that the mechanisms by which secretin stimulates adenylate cyclase and activates phospholipase C in acinar tissue are completely independent.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Regulation of pancreatic exocrine function: a role for cell-to-cell communication?

The effect of heptanol, an alkanol which decreases gap junctional permeability, was investigated in the perfused rat pancreas. Under basal conditions, heptanol (3.5 mM) caused a three- to fourfold increase of pancreatic juice, protein, and amylase outputs. The effect on enzyme secretion was fully reversible upon removal of the alkanol and was not secondary to the release of acetylcholine from nerve endings, since it was not prevented by addition of atropine (10(-6) M) to the perfusate. By contrast, another alkanol, hexanol (3 mM), which does not decrease coupling between acinar cells in spite of anesthetic properties analogous to those of heptanol, did not alter pancreatic secretion. The effect of heptanol was not mediated by a significant stimulation of cyclic AMP, nor did the alkanol increase the secretion of lactic dehydrogenase, a cytosolic marker. Analysis of the numerical density of freeze-fractured and immunolabeled gap junctions between acinar cells did not show differences between heptanol-perfused and control pancreases. In addition, heptanol did not alter carbachol (10(-6) M and 10(-5) M)-evoked amylase release. Since heptanol blocks cell coupling, apparently without interfering with the main intracellular pathways triggering enzyme release, we suggest that downregulation of direct cell-to-cell communications increases pancreatic exocrine secretion. Thus, cell coupling is probably involved in the regulation of the secretory activity of acinar cells.

Alcohols↗
PubMed1986

Secretin induces rapid increases in inositol trisphosphate, cytosolic Ca2+ and diacylglycerol as well as cyclic AMP in rat pancreatic acini.

Previous studies have shown that the dose-response relationship for secretin-stimulated cyclic AMP accumulation is different from that for secretin-stimulated enzyme secretion in the rat exocrine pancreas. Here we show that secretin concentrations of 10(-10) M and higher stimulated a rise in cyclic AMP levels, with maximum effect on cyclic AMP accumulation being achieved already with 10(-8) M-secretin. However, at this concentration of secretin, enzyme secretion rates were approximately half-maximal. Unexpectedly, at concentrations of secretin greater than 10(-8) M there was evidence suggestive of phosphatidylinositol bisphosphate hydrolysis with rapid increases in inositol trisphosphate, cytosolic free calcium and diacylglycerol content of rat pancreatic acini. Furthermore, there was a dose-response relationship among secretin concentration (in the range 10(-8) M-2 X 10(-6) M), increases in inositol trisphosphate and increases in cytosolic free calcium ([Ca2+]i). Contrary to what has been previously believed, these results clearly indicate that in rat pancreatic acini secretin not only stimulates cyclic AMP accumulation but also raises inositol trisphosphate, [Ca2+]i and diacylglycerol. Thus, two second messenger systems may play a role in the regulation of secretin-induced amylase release.

Animals↗
PubMed1986

Insulin resistance is accompanied by impairment of amylase-gene expression in the exocrine pancreas of the obese Zucker rat.

Insulin plays a major role in the control of pancreatic amylase biosynthesis. In this study we determined glucose metabolism by pancreatic acini as well as the pancreatic content of both amylase protein and amylase mRNA during development of insulin resistance in the obese Zucker rat. At age 4 weeks there were no abnormalities detected in the above parameters, although the obese animals were already hyperinsulinaemic. At 6 weeks glucose metabolism was decreased by 50% in acini from obese rats, whereas pancreatic amylase-gene expression was only slightly impaired. At 22 weeks glucose metabolism was decreased by 50%, amylase content by 55% and amylase mRNA by 60% in acinar tissue of obese rats. As expected, hyperinsulinaemia increased markedly with age. Thus development of severe insulin resistance was associated with impairment of amylase-gene expression. To decrease insulin resistance, one group of adult obese rats was treated with Ciglitazone for 4 weeks. A lowered plasma insulin concentration without alteration of food intake was taken as evidence of decreased insulin resistance. This was associated with normalization of glucose metabolism and a marked increase of both amylase content of pancreatic tissue and amylase mRNA. In conclusion, both the increase of insulin resistance with age and its partial reversal by Ciglitazone treatment appear to modulate pancreatic amylase-gene expression in the obese Zucker rat.

Amylases↗
PubMed1986

Abnormalities of pancreatic exocrine function in obesity: studies in the obese mouse.

Insulin is known to play a specific role in the biosynthesis of pancreatic amylase. In the insulin resistant adult C57 BL/6J--ob/ob mouse there is a reduction of pancreatic amylase content. The differences of enzyme content could not be explained by differences of food intake between obese and lean mice, but are more likely to be the consequence of insulin resistance at the level of the exocrine pancreas. By contrast, greater pancreatic content of amylase and lipase seen in young obese mice (less than 2-months old) was associated with the greater food intake of these mice with respect to lean controls.

Aging↗
PubMed1986

Differences in pancreatic enzyme release from ventral and dorsal areas of the rat pancreas.

The exocrine secretory function of the ventral and dorsal areas of the rat pancreas was investigated separately. In the isolated perfused rat pancreas, caerulein (10(-12), 10(-11), and 10(-10) M) and carbachol (10(-7) and 10(-6) M) caused a greaterfold increase in pancreatic secretion from the dorsal than the ventral area. Caerulein (10(-9) M) and carbachol (10(-5) M) were supramaximal concentrations with respect to secretion from the dorsal area, but this was not the case in the ventral area. Similar findings were also observed when ventral and dorsal secretions were studied in vivo in anesthetized animals. By contrast, in dispersed acini the sensitivity and responsiveness of tissue from the dorsal and ventral areas were similar to both secretagogues. The possible influence of the endocrine pancreas via the insuloacinar portal system was studied in the perfused pancreas of diabetic rats treated with insulin in vivo. Carbachol (10(-6) M)-stimulated secretion from the ventral area was similar (except for amylase) to that of controls, while a significantly reduced (P less than 0.001) output was measured from the dorsal pancreas. These results demonstrate that in the intact pancreas differences of exocrine secretion exist between the ventral and dorsal areas and suggest that insulin may contribute, at least in part, to the expression of such differences.

Amylases↗
PubMed1985

A new, rapid, method for preparation of dispersed pancreatic acini.

A new method for the preparation of pancreatic acini is described. The method is simple and much more rapid than previously described techniques, the time required for preparation of pancreatic acini being 20 min from removal of the pancreas. Acini prepared with this method perform in a superior manner when stimulated by either caerulein or secretin. Thus this new technique would be ideal for use in binding and secretion studies.

Amylases↗
PubMed1985

Abnormalities of caerulein- and carbamylcholine-stimulated pancreatic enzyme secretion in the obese Zucker rat.

The secretory function of the exocrine pancreas has been studied in dispersed pancreatic acini from obese and homozygous lean Zucker rats at 6 and 22 wk. No abnormality was found in acini from young rats. Acini from 22 wk obese and lean rats were equally responsive to secretagogues which stimulate cAMP, i.e. vasoactive intestinal peptide (VIP) and secretin. By contrast, there was a reduction in the maximum responsiveness to caerulein and carbamylcholine in acini from obese rats. These latter secretagogues act through mobilization of intracellular Ca2+. Since obese animals are insulin resistant and amylase release is modulated by insulin, the role of insulin resistance in the secretory defect was then investigated. A group of 22 wk obese rats received treatment with Ciglitazone (a drug which reduces insulin resistance in obese laboratory animals) for 4 wk before the secretion study. Despite the expected reduction in insulin resistance there was no improvement of the secretory defect seen with caerulein and carbamylcholine stimulation. Thus, the secretory abnormality in the exocrine pancreas of adult obese Zucker rats does not appear to be directly associated with insulin resistance. Furthermore, the secretory defect is linked to those secretagogues which induce Ca2+-independent phosphoinositide hydrolysis and Ca2+ mobilization in the target cell.

Amylases↗
PubMed1985

Activity of the insulo-acinar axis in the isolated perfused rat pancreas.

The object of the present investigation was to determine whether insulin secreted by the endocrine pancreas and carried in the insulo-acinar portal system has a direct effect on pancreatic enzyme secretion. For this purpose, the isolated rat pancreas was perfused in a nonrecirculating system. The perfusate contained 3 mM glucose, and either caerulein or vaso-active intestinal polypeptide was used to stimulate exocrine secretion. The amount of insulin reaching the exocrine pancreas was reduced by two different experimental procedures. In the first, use was made of streptozotocin-diabetic rats treated with insulin in vivo. Treatment was such that the contents of amylase and lipase, vastly altered in the untreated diabetic state, were normalized before the perfusion studies. In the second procedure, insulin reaching the exocrine pancreas was reduced by antiinsulin serum in the perfusate. In these procedures, the reduced insulin bioavailability was associated with a reduction in caerulein- and vasoactive intestinal polypeptide-stimulated enzyme release, which was shown as a reduction of maximum responsiveness to caerulein without alteration of sensitivity. By contrast, in dispersed pancreatic acini where the insulo-acinar axis was completely disrupted, amylase secretion from diabetic and nondiabetic tissue was identical over a wide range of caerulein concentrations, showing that the secretory defect seen in the perfusion studies was not inherent to the exocrine tissue. The results show that basal insulin secretion has a direct effect on pancreatic enzyme output and that the insulo-acinar axis may play an important role in the regulation of acinar cell function.

Amylases↗
PubMed1985

Sulfonylureas in insulin-dependent (type I) diabetes: evidence for an extrapancreatic effect in vivo.

The effect of glibenclamide treatment on insulin-mediated glucose disposal was studied in eight C-peptide-negative type I diabetic patients. The patients were studied twice by the euglycemic insulin clamp technique. One of the two experiments was preceded by glibenclamide treatment at the dose of 5 mg, three times daily for 15 days; half of the patients had the first test before and the second test after sulfonylurea treatment, and vice versa. Insulin was infused for four periods of 2 h each sequentially at 0.5, 1.0, 2.0, and 5.0 mU kg-1 min-1; for each insulin infusion period, the steady state plasma free insulin levels were comparable with or without glibenclamide. The mean +/- SEM plasma glucose concentration was 88 +/- 2 mg/dl in both experiments. The insulin-mediated glucose disposal rate was greater with glibenclamide during the first insulin infusion period (which generated plasma free insulin levels within the physiological range) 2.68 +/- 0.32 mg kg-1 min-1 with glibenclamide vs. 1.97 +/- 0.20 mg kg-1 min-1 without glibenclamide (P less than 0.005). However, glucose disposal rates did not differ in the diabetic patients with or without glibenclamide treatment during the second, third, and fourth insulin infusion periods, which generated plasma free insulin levels in the supraphysiological range. These results provide evidence for an extrapancreatic effect of glibenclamide at low insulin concentrations during euglycemic clamping in patients with insulin-dependent diabetes mellitus. However, this effect was not reflected clinically in either an increased rate of hypoglycemic reactions or decreased insulin needs during the short term period of treatment.

Adult↗