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Biomedical subjects

A Andersson

Publications and source records attributed to A Andersson.

At least 199 records · Page 11Linked to original sources
PubMed1993

Human autoantibodies react with glutamic acid decarboxylase antigen in human and rat but not in mouse pancreatic islets.

The presence of one of the major targets for autoantibodies in Type 1 (insulin-dependent) diabetes mellitus, the enzyme glutamic acid decarboxylase, was studied in human, rat and mouse pancreatic tissue using immunoprecipitation and immunohistochemical techniques. Immunoprecipitation of glutamic acid decarboxylase was attempted with lysates of [35S]-methionine-labelled rat or mouse pancreatic islets using two different glutamic acid decarboxylase antisera, one mouse monoclonal antibody raised against the 65 kDa isoform of the enzyme, sera from six patients with Type 1 diabetes, one patient with stiff-man syndrome and sera from 19 non-obese diabetic mice. The same sera were used for immunoperoxidase staining of cryosections of human, rat or mouse pancreas. Using patient sera glutamic acid decarboxylase was detected by immunoprecipitations from isolated rat islets but not from islets of five different mouse strains tested, including the non-obese diabetic mouse. When using the non-obese diabetic mouse sera, glutamic acid decarboxylase could not be detected in either rat or mouse tissue. Immunoperoxidase staining demonstrated high levels of glutamic acid decarboxylase in human and rat pancreatic islets but low levels in mouse islets. Direct measurements of enzyme activity showed glutamic acid decarboxylase to be present in mouse islets at a level of about 40% of that in rat islets, and subsequent Western blot analyses indicated that mouse islets express the 67 kDa isoform, whereas as in rat islets both the 67 and 65 kDa isoforms are present.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Exposure of rat pancreatic islets to RS-61443 inhibits beta-cell function.

In this study, the long-term effects of the immunosuppressive drug RS-61443 on pancreatic beta-cell function have been evaluated. For this purpose, isolated rat pancreatic islets were precultured for 6 to 7 days in RPMI 1640 medium + 10% FCS and then cultured for another 6 days in the absence or presence of RS-61443 (15, 60, 120, and 240 mg/L). The islet DNA content was decreased by 20-30% after culture at all concentrations of the drug. At the highest drug concentration, there were disarrangements in the islet architecture. This was probably not confined to only beta-cells, since the ratio of insulin to DNA was not decreased. On day 6, glucose-stimulated insulin secretion was inhibited by 75-90%, whereas rates of islet (pro)insulin biosynthesis and glucose oxidation were not or only slightly affected. After 48 hr of culture in the absence of the drug, the decrease in islet DNA content remained, but the impaired insulin secretion was partly restored. In acute in vitro experiments, RS-61443 initially enhanced glucose-stimulated insulin secretion, but during a second hour of incubation, there was an inhibition. In variance to this latter finding, islet glucose oxidation was inhibited already during the first hour. The present results suggest that long-term exposure to RS-61443 in vitro impairs beta-cell function and this might be due to an inhibition of formation of guanosine metabolites. In other experiments, rats and mice were treated for 6 days with intraperitoneal injections of RS-61443 (70 mg/kg body wt). The pancreatic insulin concentration was not changed, but during glucose tolerance tests, minor impairments were observed. In conclusion, the present data suggest that RS-61443 is potentially harmful to beta-cells.

Animals↗
PubMed1993

Effects of an oral dose of isosorbide dinitrate on platelet function and fibrinolysis in healthy volunteers.

1. A randomised double-blind placebo-controlled study was performed to investigate the effects of isosorbide dinitrate (ISDN; 20 mg orally) on various aspects of platelet function and fibrinolysis in vivo in 12 healthy volunteers. 2. Measurements were performed at rest (before and after tablet ingestion) and during platelet activation by adrenaline (0.4 nmol kg-1 min-1; 30 min infusion). 3. At rest, ISDN did not alter plasma concentrations of beta-thromboglobulin (beta TG). EC50 values for ADP induced aggregation in vitro (Born aggregometry) or ex vivo filtragometry readings. Adrenaline markedly increased platelet aggregability in vivo as measured by filtragometry and elevated levels of beta TG in plasma. ISDN treatment did not affect these responses in the group as a whole. 4. Individuals responding to ISDN with more pronounced vasodilatation at rest showed a lesser increase in aggregability during the ensuing adrenaline infusion (r = -0.66, P = 0.02) despite higher adrenaline levels during ISDN. In individuals showing a significant decrease in systolic blood pressure (n = 8) ISDN tended to attenuate the adrenaline induced increase in platelet aggregability (filtragometry; P = 0.08), despite higher plasma adrenaline and noradrenaline levels after ISDN ingestion. 5. Plasma concentrations of ISDN and its active metabolites isosorbide-5-mononitrate and isosorbide-2-mononitrate were not correlated to haemodynamic or platelet variables. 6. Fibrinolytic activity (t-PA antigen and activity, PAI-1 antigen and activity) increased similarly during the adrenaline infusion following ISDN and placebo. 7. It is concluded that ISDN may affect platelet aggregation responses to adrenaline in vivo, but only in individuals showing significant haemodynamic responses to ISDN.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Elevated plasma homocysteine in alcoholics.

A significantly higher concentration of plasma homocysteine compared with controls was noted in a group of alcoholics (n = 42) hospitalized for detoxication. Normal concentrations of plasma homocysteine were reached within 1 or 2 weeks after admission to the hospital. In another group of abstinent alcoholics (n = 16) plasma homocysteine did not deviate from that of controls. Since hyperhomocysteinemia has been associated with premature vascular disease, we speculate that the increased plasma homocysteine in alcoholics might cause the increased incidence of stroke found in these patients.

Adult↗
PubMed1993

15-Deoxyspergualin prolongs pancreatic islet allo- and xenograft survival in mice.

The new immunosuppressant 15-deoxyspergualin was evaluated in allogeneic and xenogeneic pancreatic islet transplantation. In the allograft study 500 collagenase-isolated C57BL/6 mouse islets were transplanted under the renal capsule of alloxan-diabetic C57BL/Ks mice that were either 15-deoxyspergualin-treated (n = 15) or given saline only (n = 8). When 15-deoxyspergualin was given (5 mg/kg b.wt. intraperitoneally) until day 28 after transplantation in a special dosage schedule, 10 out of 15 animals were normoglycaemic one week after transplantation and 6 were still normoglycaemic after ten weeks. All 8 control animals were hyperglycaemic after 18 days. Light microscopy showed graft rejection in hyperglycaemic mice, but only mild infiltration of lymphocytes in the grafts of normoglycaemic animals. In the xenograft study C57BL/Ks mice were transplanted under the renal capsule with 500-750 foetal porcine islet-like cell clusters. The grafts were examined for evidence of rejection with light microscopy at different time points after implantation. In the control animals given saline only (n = 37) there was progressive evidence of rejection starting on day seven. In 15-deoxyspergualin treated animals (2.5 mg/kg intraperitoneally; n = 27) there was significantly less infiltration at days 7, 14 and 21. After 32 days there was, however, no difference between controls and 15-deoxyspergualin treated mice. A doubling of the 15-deoxyspergualin dose (5.0 mg/kg intraperitoneally; n = 5) did not further improve the survival of the xenografted islet-like cell clusters. There was no synergistic effect when cyclosporine A (12.5 mg/kg intraperitoneally) was added to the 15-deoxyspergualin therapy (n = 34).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Mapping of glutathione transferase (GST) genes in the rat.

Glutathione transferases (GST) make up a large group of related enzymes in mammalian tissues. The enzyme molecules are dimeric and at least 13 different subunits occur in the rat. Each subunit appears to be coded for by a distinct gene, and thus there is a large GST gene family in the rat. Recently, there have been several reports of the mapping of rat GST genes. In the present communication we confirm the previous assignments and extend the data with the mapping to rat chromosome 2 of a previously unmapped GST gene (Gstm1), and with the regional mapping of seven Gstp genes. These mappings provide further evidence for conservation of syntenic gene relationships among mammals. The human homologs of Gstm1 map to chromosome 1, and belong to a group of 9 genes that show conserved synteny on rat chromosome 2. The corresponding murine genes in most cases map to mouse chromosome 3. Similarly, the human homolog of Gstp maps to chromosome 11, and is one of 10 genes that exhibit conserved synteny on rat chromosome 1. The corresponding mouse genes map to mouse chromosome 7. Previously only one gene on rat chromosome 8 had a human homolog on chromosome 6, and rat Gsta1 is the second instance. Based on these mappings it appears that a new group of genes will exhibit conserved synteny on rat chromosome 8, human chromosome 6 and mouse chromosome 9. Interestingly, each of the three groups of conserved synteny seems to span the region across the centromeres of the human chromosomes.

Animals↗
PubMed1993

Adherence of group B streptococci to human endothelial cells in vitro.

A model using human umbilical vein endothelial cells was developed to study the adhesion of group B streptococci. Ten clinical isolates of serotypes Ia, Ib and III, including six blood isolates from neonates with early-onset disease, were studied. Isogenic variants with different ability to express capsule substance were also included. Clinical isolates of serotype III adhered significantly better than other serotypes. Strains with high ability to adhere to endothelial cells also had high ability to bind to plastic. Isogenic variants of serotype III with low amounts of capsule substance adhered significantly better to cells than variants expressing high amounts of capsule substance. These results show that the higher adherence of serotype III strains may be a virulence factor and contribute to the finding that this serotype dominates in invasive group B streptococcal disease.

Bacterial Adhesion↗
PubMed1993

Differences in the vascular response to terbutaline in the native and transplanted rat pancreas.

Syngeneic pancreaticoduodenal transplantations were performed in Wistar-Furth rats. Fourteen days after implantation, blood perfusion of the whole native and transplanted pancreas, the pancreatic islets and the native and transplanted duodenum was measured with a microsphere technique 5 min after an intravenous injection of 0.5 ml of either saline (n = 6) or terbutaline (1 mg/kg BW; n = 9). Terbutaline decreased the mean arterial blood pressure by approximately 30% (p < 0.001). The substance also decreased the whole pancreatic blood flow of the native pancreas (p < 0.05), but not of the transplanted gland. However, the vascular conductance of the whole pancreas was unchanged after terbutaline administration in both the native and transplanted gland. Islet blood flow (p < 0.001) and islet vascular conductance (p < 0.01) were markedly decreased in the native pancreas. In the transplanted gland, there was, however, no change in islet vascular conductance and only a slight decrease in islet blood flow (p < 0.05). Both the native and transplanted duodenal blood flows were unaffected by terbutaline. One likely explanation for the different effects of terbutaline on the blood perfusion of the native and transplanted pancreas may be that the latter gland is devoid of any physiologically relevant exogenous innervation.

Animals↗
PubMed1993

DNA replication in pancreatic islets and adrenals in diabetic Chinese hamsters.

The diabetic syndrome in Chinese hamsters is progressive and there is a decrease in the size of the pancreatic islets. To what extent this is due to impaired DNA replication in their islet cells is unknown. Therefore 3H-thymidine incorporation into islet cells was studied in genetically diabetic (subline L) male hamsters aged 17-20 days, 6 weeks, 3, 6 and 12 months. Because adrenal weight was decreased at almost all ages, studies of adrenal morphology and function were also performed. Age- and sex-matched normal (subline M) hamsters served as controls. Autoradiography showed progressively falling labeling with increasing age in both normal and diabetic animals in both islets and adrenals. At the earliest age studied, the diabetic subline animals were normoglycemic but showed hyperinsulinemia. DNA replication was reduced both in the islet cells and the adrenal cortex. From 6 weeks of age and onwards, the diabetic hamsters were hyperglycemic and usually hyperinsulinemic but DNA replication in both islets and adrenals was not different from that in normals. Histomorphometry showed reduced volume in both the adrenal medulla and cortex in 3-month-old diabetic hamsters. In 12-month-old male and female diabetic hamsters plasma cortisol and aldosterone and 24-hour urinary epinephrine were normal, but urinary norepinephrine and dopamine levels were excessive. Thus, in contrast to what is found in the obese-hyperglycemic mouse, there was no increased islet cell DNA replication in response to the increased functional demand in the diabetic Chinese hamster.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1993

Treatment with an interleukin-1 receptor antagonist protein prolongs mouse islet allograft survival.

An interleukin-1 receptor antagonist protein was evaluated with regard to its efficacy in allogeneic and xenogeneic islet transplantation. Alloxan-induced diabetic C57BL/6 (H-2b) mice were transplanted under the kidney capsule with 500 C57BL/Ks (H-2d) mouse islets. Alzet osmotic pumps, which release their content over an 11- to 13-day period, were implanted subcutaneously for continuous infusion of interleukin-1 receptor antagonist protein (1.0, 5.0, 8.0 mg.kg-1 x day-1) or phosphate-buffered saline. Blood glucose determinations were performed every second or third day; at death, the islet-bearing kidneys were morphologically evaluated. Mice treated initially with the higher interleukin-1 receptor antagonist protein concentrations were followed for an additional period after cessation of the drug release to evaluate whether a transitory interleukin-1 receptor antagonist protein treatment would induce tolerance to the graft. All phosphate-buffered saline-treated mice were hyperglycemic 11 days after islet allotransplantation. Most of their grafts were heavily infiltrated with mononuclear cells. In the various interleukin-1 receptor antagonist protein-treated groups, 60-80% of the mice were normoglycemic after 11 days. Moreover, light microscopic examinations showed that most mice treated with interleukin-1 receptor antagonist protein had normal islet grafts or grafts infiltrated with only a few mononuclear cells. After interruption of interleukin-1 receptor antagonist protein infusion (8.0 mg.kg-1 x day-1), all animals developed hyperglycemia within 2-9 days. In xenogeneic experiments, 500-750 fetal porcine islet-like cell clusters were transplanted under the kidney capsule of normoglycemic C57BL/6 mice. These animals were treated either with interleukin-1 receptor antagonist protein (8.0 mg.kg-1 x day-1) or phosphate-buffered saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

In vitro screening of putative compounds inducing fetal porcine pancreatic beta-cell differentiation: implications for cell transplantation in insulin-dependent diabetes mellitus.

Successful transplantation of fetal pancreatic beta-cells to diabetic recipients requires that differentiation of the immature beta-cells is achieved. Animal experiments have shown that this can occur in vivo, but it would be desirable to induce beta-cell maturation in vitro prior to transplantation. For that purpose the effect of several putative inducers of beta-cell differentiation and/or replication in explant cultures of fetal porcine pancreatic islet-like cell clusters (ICC) were investigated. Initial screening experiments indicated that dexamethasone (DEX; 200 ng/ml) and sodium butyrate (BUT; 2 mM) might promote beta-cell differentiation as evidenced by increased insulin/DNA contents in the ICC. In subsequent experiments these two substances, and also nicotinamide (NIC; 10 mM) which previously has been found to promote fetal beta-cell differentiation, were added alone or in combinations to the basal control medium consisting of RPMI 1640 + 1% human serum. All three test agents alone or in combinations increased the insulin content/DNA of the ICC compared with that of the control group. The combination of NIC+DEX increased the insulin mRNA levels of the ICC. No significant stimulation of insulin release was observed in any test group after short-term incubation with high glucose alone. Addition of 5 mM theophylline to high glucose stimulation, however, increased the insulin secretion in most groups of ICC. Finally, ICC in groups of about 600, which had developed in the presence of NIC or NIC+DEX, were transplanted under the kidney capsule of alloxan-diabetic nude mice. However, neither the time for reversal of diabetes (4 weeks) nor the amount of insulin secretion during perfusion from the grafted ICC were further affected by adding DEX to the NIC supplemented medium. The marked increase of the insulin content of the ICC cultured with DEX supplementation, appeared transient and was not manifested after transplantation. In conclusion, the present study demonstrated that some compounds can stimulate porcine fetal beta-cells in an in vitro system, but in order to attain terminal differentiation of the beta-cells including glucose-sensitive insulin secretion, longer observation periods might be required than used herein. Alternatively, an in vivo environment like that after transplantation is mandatory for this process.

Animals↗
PubMed1993

Reinnervation of transplanted pancreatic islets. A comparison among islets implanted into the kidney, spleen, and liver.

Islets transplanted beneath the kidney capsule become reinnervated during the first 3-4 months after implantation by both afferent and efferent nerve fibers. To evaluate the importance of the implantation organ for this process, the present study compared both the degree and the types of nerve fibers reinnervating islets transplanted into the liver, kidney, and spleen. For this purpose, 150 syngeneic islets were grafted under the kidney capsule of C57BL/6 mice. In addition, the same animals were injected with 150 islets into the spleen or liver. All animals were killed 14 weeks after transplantation, after which the graft-bearing organs were processed for indirect immunofluorescence for neuropeptides and tyrosine hydroxylase (TH), and with acetyl cholinesterase (AchE) staining to visualize nerve fibers. Both afferent (containing substance P and/or calcitonin gene-related peptide) and parasympathetic (containing vasoactive intestinal peptide or AchE) nerve fibers were absent from islets implanted into the spleen; an occasional CGRP fiber was seen in islets implanted into the liver; and all these fibers were regularly seen in islets implanted beneath the renal capsule. The islets implanted into the liver or spleen contained a dense network of sympathetic (containing neuropeptide Y and TH) nerve fibers that was often more dense than in the islet grafts under the kidney capsule. One-fifth of islets implanted into the liver were, however, completely devoid of demonstrable nerve fibers. In conclusion, there are marked differences with regard to the pattern of reinnervation of islets transplanted to different implantation sites.

Acetylcholinesterase↗
PubMed1993

Plasma homocysteine in renal failure.

Plasma homocysteine in three different groups of patients with chronic renal failure (one group without dialysis, one with CAPD and one with hemodialysis) was increased compared to controls. Another group of patients with slightly reduced renal dysfunction (normal serum creatinine but reduced glomerular filtration rate) did not, however, show increase of plasma homocysteine. The clearance of homocysteine as a percentage of creatinine clearance in the three different groups of patients with chronic renal failure was also significantly increased compared to controls. Thus the clearance of homocysteine was not affected to the same extent as that of creatinine in renal failure. This may be attributed to the fact that, besides the reduced glomerular filtration rate, a depressed tubular uptake of homocysteine may occur in chronic renal failure. We were also able to show that neither in patients with varying renal function nor in controls were there any significant diurnal variation of plasma homocysteine, despite the intake of a protein-rich meal. However, after methionine loading in eight patients with severe chronic renal failure, a slight but significant increase of plasma homocysteine was noted. This indicates a disturbed metabolism with high amounts of homocysteine, which might be mainly attributed to an impaired transulphuration pathway.

Adult↗
PubMed1993

The effect of high-dose pyridoxine and folic acid supplementation on serum lipid and plasma homocysteine concentrations in dialysis patients.

Pyridoxine and folic acid supplementation in dialysis patients is a matter of debate. This study was performed to estimate the effects of pharmacologic doses of these vitamins on serum lipid and plasma homocysteine concentrations, which are known to be high in dialysis patients. Both hemodialysis and continuous ambulatory peritoneal dialysis patients were included in the study. Pyridoxine supplementation had a mild but significant cholesterol-lowering effect (7%). Folic acid supplementation significantly lowered plasma homocysteine concentrations by a mean of 30%. There was a strong, inverse correlation between blood folate and plasma homocysteine concentrations. These results indicate that daily supplementation with pyridoxine 300 mg and folic acid 5 mg has a beneficial effect on the cardiovascular risk profile in dialysis patients.

Adult↗
PubMed1993

Homocysteine and other thiols determined in plasma by HPLC and thiol-specific postcolumn derivatization.

We describe a versatile high-performance liquid-chromatographic method for determining homocysteine and other plasma sulfhydryls. Using three different procedures for preparation of plasma, we determined total, free (non-protein-bound), and reduced forms of homocysteine, cysteine, glutathione, cysteinylglycine, and gamma-glutamylcysteine in human plasma. Sample preparation involves disulfide reduction with dithiothreitol and protein precipitation with sulfosalicylic acid. The assay utilizes isocratic reversed-phase ion-pair liquid chromatography at pH 2.4, postcolumn derivatization with 4,4'-dithiodipyridine, and colorimetric detection at 324 nm. The intra-assay precision (CV) of the method for total homocysteine is 1.5%; the interassay precision over 2.5 months is 2.5%. The detection limit for homocysteine is < 50 nmol/L plasma.

Chromatography, High Pressure Liquid↗
PubMed1993

Total homocysteine in plasma or serum: methods and clinical applications.

Total homocysteine is defined as the sum of all homocysteine species in plasma/serum, including free and protein-bound forms. In the present review, we compare and evaluate several techniques for the determination of total homocysteine. Because these assays include the conversion of all forms into a single species by reduction, the redistribution between free and protein-bound homocysteine through disulfide interchange does not affect the results, and total homocysteine can be measured in stored samples. Total homocysteine in whole blood increases at room temperature because of a continuous production and release of homocysteine from blood cells, but artificial increase is low if the blood sample is centrifuged within 1 h of collection or placed on ice. Different methods correlate well, and values between 5 and 15 mumol/L in fasting subjects are considered normal. Total homocysteine in serum/plasma is increased markedly in patients with cobalamin or folate deficiency, and decreases only when they are treated with the deficient vitamin. Total homocysteine is therefore of value for the diagnosis and follow-up of these deficiency states and may compensate for weaknesses of the traditional laboratory tests. In addition, total homocysteine is an independent risk factor for premature cardiovascular diseases. These disorders justify introduction of the total homocysteine assay in the routine clinical chemistry laboratory.

Blood Chemical Analysis↗
PubMed1993

Pretreatment of fetal porcine pancreas in culture with nicotinamide accelerates reversal of diabetes after transplantation to nude mice.

Successful transplantation of fetal pancreatic beta-cells to recipients with diabetes requires that differentiation of the immature beta-cells is induced. In this study isletlike cell clusters (ICC) were produced from fetal porcine pancreas in tissue culture, in medium RPMI-1640 supplemented with 10% human serum and in the presence or absence of 10 mmol/L nicotinamide. Light microscopy of immunostained ICC on day 4 of culture showed that nicotinamide caused a more than doubling in the frequency of insulin-positive cells, whereas no stimulatory effect by nicotinamide on DNA replication was found. Transplantation of ICC into nude mice with alloxan diabetes revealed that ICC formed in nicotinamide normalized the hyperglycemia faster than did control ICC (3 to 4 weeks compared with 6 to 8 weeks). The DNA content of the transplanted ICC increased two to three times over an 8-week period, whereas the insulin content increased 100-fold. The total insulin, total DNA content, and the insulin concentration of the grafts were significantly higher in the nicotinamide grafts in comparison with control grafts. In fact, the insulin concentration in the nicotinamide grafts was almost identical to that normally observed in fully differentiated mouse islets. Furthermore, perfusion in vitro of the graft-bearing kidneys 18 weeks after transplantation showed that the total amount of insulin released from the nicotinamide grafts on stimulation with glucose was more than five times higher than the amount from the control grafts. The perfusion of grafts from the nicotinamide group revealed a marked biphasic insulin response to glucose, which was less obvious in the control grafts. We conclude that nicotinamide induces beta-cell differentiation in porcine ICC and that this effect is beneficial when such explants are used for transplantation to recipients with diabetes.

Alloxan↗