The influence of feeding crimped kernel maize silage on broiler production, nutrient digestibility and meat quality.

Two experiments were carried out in parallel with male Ross 308 broilers over 37 d. An experiment with a total of 736 broilers was performed to study the effect of dietary inclusion of crimped kernel maize silage (CKMS) on broiler production and meat quality. Another study with 32 broilers was carried out from 21 to 25 d to investigate the inclusion of CKMS on nutrient digestibility. In both trials, 4 dietary treatments were used: wheat-based feed (WBF), maize-based feed (MBF), maize-based feed supplemented with 15% CKMS (CKMS-15) and maize-based feed supplemented with 30% CKMS (CKMS-30). Compared with MBF, the dry matter (DM) intakes of broilers receiving CKMS-15 and CKMS-30, respectively, were numerically 7.5 and 6.2% higher and feed conversion ratio 6 and 12% poorer (significant for 30% CKMS), although there were no significant differences in AME content between the three diets. At 37 d, the body weight of birds receiving 15% CKMS was similar to birds fed with MBF. However, the inclusion of 30% CKMS decreased broiler growth. Dietary supplementation with CKMS significantly reduced the apparent digestibility of phosphorus. The fat digestibility was significantly lower for CKMS-30 than for the other three diets. Broiler mortality decreased significantly when CKMS was added to the diet. The consumption of drinking water was significantly lower in all maize-based diets as compared to WBF and was lowest in broilers fed with CKMS-30. An improved litter quality in terms of DM content and a lower frequency of foot pad lesions was observed with broilers supplemented with both dietary levels of CKMS. The addition of CKMS to maize-based diets increased juiciness, tenderness and crumbliness of the meat. In conclusion, the dietary supplementation of 15% CKMS had no negative effect on broiler growth and positively influenced bird welfare in terms of mortality and foot pad health. Therefore, the addition of 15% CKMS to maize-based diets is considered an advantageous feeding strategy in broiler production.

Effects of 12 weeks' treatment with a proton pump inhibitor on insulin secretion, glucose metabolism and markers of cardiovascular risk in patients with type 2 diabetes: a randomised double-blind prospective placebo-controlled study.

AIMS/HYPOTHESIS: Recent studies suggest that proton pump inhibitor treatment may increase insulin secretion and improve glucose metabolism in type 2 diabetes. In a randomised double-blind prospective placebo-controlled 2 × 2 factorial study, we examined the effect of esomeprazole on insulin secretion, HbA(1c) and cardiovascular risk factors in type 2 diabetes. METHODS: Forty-one patients with type 2 diabetes using dietary control or oral glucose-lowering treatment were randomised to receive add-on esomeprazole 40 mg (n = 20) or placebo (n = 21) for 12 weeks. Randomisation was carried out prior to inclusion on the basis of a computer-generated random-number list. The allocation sequence was concealed in sealed envelopes from the researcher enrolling and assessing participants. The study was undertaken at Steno Diabetes Center, Gentofte, Denmark. The primary outcome was change in AUC for insulin levels during a meal test. Secondary outcomes were the levels of HbA(1c) and biochemical markers of cardiovascular risk, including lipids, coagulation factors, inflammation markers, markers of endothelial function and 24 h ambulatory BP measurements. RESULTS: Forty-one participants were analysed. In the esomeprazole-treated group the AUC for insulin did not change (before vs after treatment: 28,049 ± 17,659 vs 27,270 ± 32,004 pmol/l × min (p = 0.838). In the placebo group AUC for insulin decreased from 27,392 ± 14,348 pmol/l × min to 22,938 ± 11,936 pmol/l × min (p = 0.002). Esomeprazole treatment (n = 20) caused a ninefold increase in the AUC for gastrin. HbA(1c) increased from 7.0 ± 0.6% (53 ± 5 mmol/mol) to 7.3 ± 0.8% (56 ± 6 mmol/mol) in the esomeprazole-treated group and from 7.0 ± 0.6% (53 ± 5 mmol/mol) to 7.4 ± 0.8% (57 ± 6 mmol/mol) in the placebo group (n = 21) (p for difference in change >0.05). Except for BP, there were no differences between the groups in the markers of cardiovascular risk (p > 0.05). Monitoring of 24 h ambulatory BP showed a significant decrease in daytime systolic BP, daytime diastolic BP and 24 h diastolic BP in the placebo group (p < 0.05). No change in BP was seen in the patients treated with esomeprazole. CONCLUSIONS/INTERPRETATION: Treatment with esomeprazole over 12 weeks did not improve insulin secretion, glycaemic control or cardiovascular disease biomarkers in patients with type 2 diabetes.

Treatment with a proton pump inhibitor improves glycaemic control in Psammomys obesus, a model of type 2 diabetes.

AIMS/HYPOTHESIS: Gastrin has been implicated in islet growth/neogenesis, and proton pump inhibitors (PPIs) have been shown to increase endogenous gastrin levels in animals and humans. Therefore, we investigated the effect of PPIs in a model of type 2 diabetes, Psammomys obesus. METHODS: P. obesus (morning blood glucose [mBG] 16.9 +/- 0.6 mmol/l) were treated with vehicle or different doses (1-15 mg/kg) of lansoprazole for 17 days. RESULTS: Treatment with lansoprazole resulted in up to ninefold dose-dependent increases in endogenous gastrin levels (p < 0.05 for 10 mg/kg lansoprazole vs vehicle). There was a significant reduction in mBG levels in all animals in the high-dose lansoprazole groups during the 17 day treatment period, whereas there was no significant improvement in mBG in animals in the vehicle groups. The mBG at end of study was 18.2 +/- 2.1, 8.7 +/- 2.2 (p < 0.01), and 6.1 +/- 2.3 (p < 0.001) mmol/l for vehicle and lansoprazole 10 and 15 mg/kg, respectively. The animals treated with 15 mg/kg lansoprazole, compared with vehicle, had a 2.3-fold increase in the intensity of insulin staining in beta cells (p=0.0002) and 50% higher beta cell mass (p=0.04). CONCLUSIONS/INTERPRETATIONS: The PPI lansoprazole had significant glucose-lowering effects in an animal model of type 2 diabetes, an effect that is most likely mediated through an increase in endogenous gastrin levels.

Advances in pemphigus research, signaling, and acantholysis.

Pemphigus is a family of human autoimmune blistering diseases in which pathogenic autoantibodies induce blistering in skin and mucosa. The mechanisms by which pemphigus autoantibodies induce disease in the skin is under active investigation. A large number of cellular events induced in the target keratinocytes by pemphigus IgG have been described and suggest that pemphigus IgG binding to desmogleins trigger a complicated cascade of intracellular signaling and regulatory events. Targeting these intracellular events may prove useful therapeutically.

ZP120 causes relaxation by pre-junctional inhibition of noradrenergic neurotransmission in rat mesenteric resistance arteries.

BACKGROUND AND PURPOSE: ZP120 (Ac-RYYRWKKKKKKK-NH(2)), is a new partial nociceptin/orphanin FQ (NOP) receptor agonist with sodium-potassium sparing aquaretic effects. The mechanisms of vasodilatation of ZP120 were examined in rat mesenteric resistance arteries. EXPERIMENTAL APPROACH: Arterial segments (internal diameters 206+/-4 microm, n=224) were mounted in microvascular myographs for isometric tension recordings and electrical field stimulation (EFS). KEY RESULTS: ZP120 and the endogenous NOP receptor ligand, N/OFQ, did not relax arteries contracted with noradrenaline or adenosine-triphosphate. EFS-evoked contractions were inhibited by a purinoceptor antagonist, suramin, and the alpha(1)-adrenoceptor antagonist prazosin. N/OFQ inhibited, concentration-dependently, EFS-evoked contractions with a maximal effect of 52+/-3% (n=8) at 1 microM. The maximal effect of 1 microM ZP120 was lower (27+/-5%, P<0.05, n=9) than for N/OFQ. Endothelial removal or pretreatment with capsaicin did not influence the vasodilator effects of ZP120 and N/OFQ. ZP120 and N/OFQ responses were preserved in the presence of suramin. The alpha(2)-adrenoceptor antagonist, rauwolscine, antagonized the effect of clonidine and brimonidine, but ZP120 and N/OFQ inhibition of EFS-evoked contraction was unaltered. The competitive NOP receptor antagonist, UFP-101 (10 microM), prevented the inhibitory effect of N/OFQ, but not ZP120 suggesting that N/OFQ and ZP120 have distinct modes of interaction with the NOP receptor. CONCLUSIONS AND IMPLICATIONS: Our findings suggest that the vasodilator effect of ZP120 and N/OFQ in rat mesenteric resistance arteries is mediated by prejunctional inhibition of adrenergic neurotransmission. These properties, that promote diuresis and attenuate the cardiovascular consequences of increased sympathetic nerve activity, make ZP120 a promising drug candidate.

Quantitative assay using recombinant human islet glutamic acid decarboxylase (GAD65) shows that 64K autoantibody positivity at onset predicts diabetes type.

At and before onset, most insulin-dependent diabetics (IDDM) have islet GAD65 autoantibodies (GAD65Ab). Since IDDM also occurs in older patients where non-insulin-dependent diabetes is common, we studied GAD65Ab at onset to classify diabetes type. Our quantitative immunoprecipitation assay uses recombinant human islet GAD65 stably expressed in hamster fibroblasts. Electrophoretic mobility was identical to native islet GAD65. Like native antigen, recombinant GAD65 migrated as two bands during electrophoresis, but converted to one under stronger reduction. Immunoprecipitation was linear with respect to antibody or antigen concentration. In 120 population-based diabetic patients of all ages grouped by treatment at onset and after 18 mo, GAD65Ab were present in 70% on insulin (n = 37), 10% on oral agent (n = 62, P < 0.0001), 69% changing from oral agent to insulin (n = 16, P < 0.001), and 1 of 33 controls. 65% with GAD65Ab, versus 8% without, changed from oral agent to insulin (P < 0.01). The GAD65Ab quantitative index was remarkably stable, and only 2 of 32 patients changed antibody status during follow-up. Concordance between GAD65Ab and islet cell antibodies was 93%. Quantitative correlation was approximate but significant. This highly sensitive, quantitative, high capacity assay for GAD65Ab reveals treatment requirements better than clinical criteria, perhaps guiding immunomodulatory therapy.

Prediction of insulin-dependent diabetes mellitus in siblings of children with diabetes. A population-based study. The Childhood Diabetes in Finland Study Group.

An unselected population of 755 siblings of children with insulin-dependent diabetes mellitus (IDDM) was studied to evaluate the predictive characteristics of islet cell antibodies (ICA), antibodies to the IA-2 protein (IA-2A), antibodies to the 65-kD isoform of glutamic acid decarboxylase (GADA), insulin autoantibodies (IAA), and combinations of these markers. We also evaluated whether the histochemical ICA test could be replaced by the combined detection of other markers. 32 siblings progressed to IDDM within 7.7 yr of the initial sample taken at or close to the diagnosis of the index case (median follow-up, 9.1 yr). The positive predictive values of ICA, IA-2A, GADA, and IAA were 43, 55, 42, and 29%, and their sensitivities 81, 69, 69, and 25%, respectively. In contrast to the other three antibody specificities, GADA levels were not related to the risk for IDDM. The risk for IDDM in siblings with four, three, two, one, or no antibodies was 40, 70, 25, 2, and 0.8%, respectively. Combined screening for IA-2A and GADA identified 70% of all ICA-positive siblings, and all of the ICA-positive progressors were also positive for at least one of the three other markers. The sensitivity of the combined analysis of IA-2A and GADA was 81%, and the positive predictive value was 41%. In conclusion, combined screening for IA-2A and GADA may replace the ICA assay, giving comparable sensitivity, specificity, and positive predictive value. Accurate assessment of the risk for IDDM in siblings is complicated, as not even all those with four antibody specificities contract the disease, and some with only one or no antibodies initially will progress to IDDM.

Neonatal tolerization with glutamic acid decarboxylase but not with bovine serum albumin delays the onset of diabetes in NOD mice.

To test the role of glutamic acid decarboxylase (GAD65) or bovine serum albumin (BSA) autoimmunity in the pathogenesis of diabetes, GAD65 or BSA was injected intraperitoneally into neonatal female NOD mice (100 micrograms/mouse of each protein). Treatment with GAD65, but not with BSA, significantly delayed the onset of diabetes compared with control mice (P < 0.05). At 18 weeks, 6 of 10 control mice compared with 0 of 10 GAD65-treated mice (P = 0.005) and 7 of 14 BSA-treated mice had developed diabetes. However, after 79 weeks, 6 of 10 of the GAD65-treated mice were diabetic compared with 9 of 10 of the control mice and 12 of 14 of the BSA-treated mice. In GAD65-treated mice without diabetes, insulitis was markedly reduced compared with control or BSA-treated mice (P < 10(-4)). To further elucidate why GAD becomes an autoantigen, the expression in NOD mice islets was studied. Quantitative immunohistochemistry revealed that islet cell expression of GAD was increased in 5-week-old NOD mice compared with BALB/c mice (P = 0.02). With the occurrence of insulitis (9-15 weeks), the GAD expression was further increased relative to 5-week-old NOD mice (P < 0.02). In conclusion, GAD, but not BSA, autoimmunity is important for the development of diabetes in NOD mice. Furthermore, concordant with the appearance of insulitis, the GAD expression increased in NOD mouse islets, which could possibly potentiate the beta-cell-directed autoimmunity.

Glutamic acid decarboxylase (GAD65) autoantibodies in prediction of beta-cell function and remission in recent-onset IDDM after cyclosporin treatment. The Canadian-European Randomized Control Trial Group.

We have investigated whether glutamic acid decarboxylase (GAD) autoantibodies (GAD65 Ab) were affected by cyclosporin therapy and were related to subsequent non-insulin-requiring remission and loss of glucagon-stimulated C-peptide response in 132 recent-onset insulin-dependent diabetes mellitus (IDDM) patients treated with cyclosporin or placebo for 12 months. GAD65 Ab were detected in a quantitative radioligand assay using as tracer recombinant, in vitro translated, human islet [35S]methionine-labeled GAD65. GAD65 Ab were found at onset in 66% (87 of 132) of IDDM patients and in 1% (1 of 100) of healthy control subjects. The prevalence of GAD65 Ab and median GAD65 Ab levels did not change in serum samples taken 3, 6, 9, and 12 months after study entry in either the cyclosporin- or the placebo-treated groups. The presence or absence of GAD65 Ab at study entry did not predict non-insulin-requiring remission in either cyclosporin- or placebo-treated patients. However, the relative (compared with 0 months) glucagon-stimulated C-peptide response was more than 30% lower in GAD65 Ab+ patients receiving placebo at 9 and 12 months compared with the GAD65 Ab- placebo patients (P < 0.035). Islet cell cytoplasmic antibody (ICA) and GAD65 Ab+ placebo-treated patients showed no significant differences in stimulated C-peptide levels compared with those who were ICA- and GAD65 Ab+, suggesting that ICA was not independently associated with loss of beta-cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

High prevalence of autoantibodies to glutamic acid decarboxylase in long-standing IDDM is not a marker of symptomatic autonomic neuropathy.

Immune reactivity to the enzyme glutamic acid decarboxylase (GAD), a pancreatic islet autoantigen, is present at the diagnosis of insulin-dependent diabetes mellitus (IDDM). Because GAD is also highly expressed in the nervous system, we investigated the presence of autoantibodies to the isoform GAD65 in patients with diabetic neuropathy, which is a debilitating complication of the disease. We studied 39 patients with autonomic and somatic neuropathy, 28 patients matched for age and IDDM duration, and 13 patients with a shorter duration of IDDM, all with no diabetic complications, as well as 50 recently diagnosed diabetic patients, 23 neurologic patients with idiopathic autonomic failure unrelated to IDDM, and 72 healthy subjects. An immunoprecipitation radioligand assay was used to detect anti-GAD65 autoantibodies with in vitro transcribed and translated human islet GAD65 as antigen. Autoantibodies to GAD65 were present in 56% of the diabetic patients with neuropathy, 57% of the long-duration and 69% of the short-duration diabetic control subjects, 78% of the recently diagnosed patients, and 13% of the nondiabetic neuropathic patients. Among the diabetic patients with neuropathy, there was no correlation between the presence of anti-GAD65 antibodies and the presence of autoantibodies to sympathetic ganglia, vagus nerve, or adrenal medulla structures identified by immunofluorescence. Our study shows that anti-GAD65 antibodies are present in a high proportion of patients with diabetic neuropathy but are not exclusively associated with it, rendering it unlikely that they have a role as a disease marker or that they are pathogenetic.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential expression of glutamic acid decarboxylase in rat and human islets.

The GABA synthesizing enzyme GAD is a prominent islet cell autoantigen in type I diabetes. The two forms of GAD (GAD64 and GAD67) are encoded by different genes in both rats and humans. By in situ hybridization analysis of rat and human pancreases, expression of both genes was detected in rat islets, whereas only GAD64 mRNA was detected in human islets. Immunocytochemical analysis of rat and human pancreatic sections or isolated islets with antibodies to GAD64 and GAD67 in combination with antibodies to insulin, glucagon, or SRIF confirmed that a GAD64 and GAD67 expression were beta-cell specific in rat islets. In contrast, only GAD64 was detected in human islets and was, in addition to beta-cells, also surprisingly localized to some alpha-cells, delta-cells, and PP-cells. In long-term (4 wk) monolayer cultures of newborn rat islet cells, GAD64 expression remained beta-cell specific as observed in vivo, whereas GAD67 was localized not only to the beta-cells but also in the alpha-cells and delta-cells. A small but distinct fraction of GAD positive cells in these monolayer cultures did not accumulate GABA immunoreactivity, which may indicate cellular heterogeneity with respect to GABA catabolism or GAD enzyme activity. In a rat insulinoma cell line (NHI-6F) producing both glucagon and insulin depending on the culture conditions, GAD64 expression was detected only in cultures in which the insulin producing phenotype dominated. In conclusion, these data demonstrate that the two GAD isoforms are differentially expressed in rat and human islets but also that the expression differs according to culture conditions. These findings emphasize the need to consider both the species and culture conditions of islets.

Recombinant glutamic acid decarboxylase (representing the single isoform expressed in human islets) detects IDDM-associated 64,000-M(r) autoantibodies.

GAD is an autoantigen in IDDM. Molecular cloning and specific antibodies allowed us to demonstrate that only the lower M(r) GAD64 isoform is expressed in human islets, in contrast to human brain, rat islets, and rat brain, all of which express both GAD64 and GAD67. Expression of the human islet GAD64 isoform in COS-7 and BHK cells resulted in an enzymatically active rGAD64, which is immunoreactive with diabetic sera comparable with that of the islet 64,000-M(r) autoantigen. Immunoprecipitation analyses showed that 21/28 (75%) IDDM sera had rGA D64 antibodies compared with only 1/59 (1.7%) of the healthy control sera. In immunoblot analyses, an SMS serum--but only 1/10 randomly selected IDDM sera--recognized the blotted rGAD64 without relation to immunoprecipitation titers. In conclusion, only the GA D64 isoform is expressed in human islets, in contrast to rat islets, which also express the GAD67 isoform. The immunological properties of human rGAD64 are comparable with the native 64,000-M(r) islet autoantigen, allowing further studies of the immunopathogenesis of IDDM.

Strain-dependent differences in sensitivity of rat beta-cells to interleukin 1 beta in vitro and in vivo: association with islet nitric oxide synthesis.

The aim of this study was to investigate whether strain-dependent differences in beta-cell sensitivity to interleukin (IL) 1 beta exist in vitro and in vivo and if so, whether these differences correlate to variations in IL-1 beta-induced islet inducible nitric oxide synthase (iNOS) mRNA expression and nitrite production in vitro and islet iNOS protein content in vivo. Isolated islets of Langerhans in vitro from Wistar-Kyoto/Møllegården (WK/Mol) rats were sensitive to the inhibitory effect of IL-1 beta on accumulated and acute insulin secretion, whereas islets from Brown Norway/Charles River (BN/CR) rats were resistant. Furthermore, IL-1 beta induced higher islet iNOS mRNA expression and nitric oxide production from WK/Mol islets compared with BN/CR islets. WK/Mol, WK/CR, BN/Mol, BN/CR, and Lewis-Scripps/Mol (LS/Mol) rats received one daily injection of recombinant human IL-1 beta (4.0 microg/kg) or vehicle for 5 days. All the strains investigated were susceptible to IL-1 beta-induced changes in body weight, food intake, temperature, and plasma glucagon and corticosterone. However, IL-1 beta induced hyperglycemia and impairment of beta-cell glucose responsiveness in WK/Mol and LS/Mol rats, but not in BN rats. Furthermore, IL-l beta-induced islet iNOS expression in vivo determined by immunostaining was greater in WK/Mol rats compared with WK/CR and BN/CR rats. No restriction fragment length polymorphisms, using 20 restriction enzymes, were identified in the iNOS gene in six rat strains including BioBreeding rats. In conclusion, the relative resistance of BN rat islets to IL-1 beta-induced inhibition of beta-cell function in vitro was associated with lower islet iNOS mRNA expression and nitrite production in this strain. Further, the resistance of BN rats to IL-1 beta-induced hyperglycemia was associated with a lower islet iNOS expression in vivo.

Detection of GAD65 antibodies in diabetes and other autoimmune diseases using a simple radioligand assay.

Autoantibodies to glutamic acid decarboxylase (GAD) are frequent at or before the onset of insulin-dependent diabetes mellitus (IDDM). We have developed a simple, reproducible, and quantitative immunoprecipitation radioligand assay using as antigen in vitro transcribed and translated [35S]methionine-labeled human islet GAD65. By using this assay, 77% (77 of 100) of serum samples from recent-onset IDDM patients were positive for GAD65 antibodies compared with 4% (4 of 100) of serum samples from healthy control subjects. In competition analysis with unlabeled purified recombinant human islet GAD65, binding to tracer was inhibited in 74% (74 of 100) of the GAD65-positive IDDM serum samples compared with 2% of the control samples. The levels of GAD antibodies expressed as an index value relative to a standard serum, analyzed with or without competition, were almost identical (r = 0.991). The intra- and interassay variations of a positive control serum sample were 2.9 and 7.6%, respectively (n = 4). The frequency of GAD antibodies was significantly higher with IDDM onset before the age of 30 (80%, 59 of 74) than after the age of 30 (48%, 10 of 21) (P < 0.01). The prevalence of islet cell antibodies showed a similar pattern relative to age at onset. Because simultaneous occurrences of multiple autoimmune phenomena are common, we analyzed sera from patients with other autoimmune diseases. The frequency of GAD antibodies in sera positive for DNA autoantibodies (8% [2 of 25] and 4% [1 of 25] in competition analysis) or rheuma factor autoantibodies [12% (4 of 35) and 3% (1 of 35) in competition analysis] was not different from that in control samples. In contrast, in sera positive for ribonucleoprotein antibodies the frequency of GAD antibodies was significantly increased (73% [51 of 70] and 10% [7 of 70] in competition analysis [P < 0.025]). In conclusion, even large numbers of serum samples can now be tested for GAD65 antibodies in a relatively short time, allowing screening of individuals without a family history of IDDM for the presence of this marker.

Cloning and expression of cytokine-inducible nitric oxide synthase cDNA from rat islets of Langerhans.

An inducible nitric oxide (NO) synthase isoform (iNOS) is specifically induced in the beta-cells of interleukin (IL)-1 beta-exposed rat islets, suggesting a role for NO in the pathogenesis of type I diabetes. The aim of this study was to clone and characterize iNOS cDNA from cytokine-exposed islets. Neither NO production nor iNOS transcription could be detected in rat islets or in rat insulinoma RIN-5AH beta-cells cultured in the absence of cytokines. Addition of IL-1 beta alone or in combination with tumor necrosis factor-alpha induced a concentration- and time-dependent expression of the iNOS gene and associated NO production (measured as nitrite) from both islets and RIN cells. iNOS transcripts were cloned by reverse transcriptase-polymerase chain reaction from the cytokine-exposed rat islets and RIN cells, and DNA sequence analysis revealed a near 100% identity to the recently published iNOS cDNA cloned from cytokine-exposed rat hepatocytes and smooth muscle cells. Recombinant rat islet iNOS was transiently and stably expressed in human kidney 293 fibroblasts, and the high enzymatic activity was inhibited by addition of the L-arginine analogs, N omega-nitro-L-arginine methyl ester and aminoguanidine. Two-dimensional gel electrophoresis revealed the recombinant iNOS as a series of spots with the expected molecular mass of 131 kDa and pI values in the range of 6.8 to 7.0. In conclusion, the IL-1 beta-induced iNOS cloned and expressed from rat islets and RIN cells is encoded by the same transcript as the iNOS induced in other cell types.

Immature transformed rat islet beta-cells differentially express C-peptides derived from the genes coding for insulin I and II as well as a transfected human insulin gene.

Synthetic peptides representing unique sequences in rat proinsulin C-peptide I and II were used to generate highly specific antisera, which, when applied on sections of normal rat pancreas, confirm a homogeneous coexpression of the two C-peptides in all islet beta-cells. Insulin gene expression is induced in the transformed heterogeneous rat islet cell clone, NHI-6F, by transient in vivo passage. During this process a transfected human insulin gene is coactivated with the endogenous nonallelic rat insulin I and II genes. Newly established cultures from NHI-6F insulinomas having a high frequency of insulin-producing cells showed highly differential expression at the cellular level of the three proinsulin C-peptide immunoreactivities, as follows: C-peptide I greater than human C-peptide greater than C-peptide II. The fractions of cells expressing human C-peptide and C-peptide II decreased in time and were absent after more than 50 successive passages, while a C-peptide I-producing population was still present. Double-labeling experiments revealed a heterogeneous distribution of the three different C-peptides. Surprisingly, in the early passages a large fraction of cells would express only a single species of proinsulin-C-peptide immunoreactivity but still at high levels. However, rat C-peptide II and human C-peptide were often colocalized, even in later passages. In situ hybridization studies combined with the immunocytochemical data suggest that the differential expression occurs at the level of transcription.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of glutamic acid decarboxylase diabetes autoantigen expression in highly purified isolated islets from Macaca nemestrina.

Macaca nemestrina, which may have larger and more numerous pancreatic islets than other species, was used for large scale islet isolation by ductal collagenase perfusion and Ficoll gradient centrifugation. The average yield was 51,000 islet equivalents per pancreas, or 8,750 islets equivalents per g. The average purity was 91%, often exceeding 95%. These are the highest reported size, purity, and yield per g of any nonautomated primate islet series. Perifusion with glucose, arginine, and isobutylmethylxanthine showed appropriate biphasic insulin secretion. Unlike that in the rat, human islet glutamic acid decarboxylase (GAD) isoform expression is restricted. However, glycemic regulation of GAD expression has been shown only in rats. We, therefore, tested hypotheses that M. nemestrina islets also have restricted GAD expression, that GAD expression in primates is stimulated by glucose, and that this stimulation remains restricted to the 64,000 mol wt (GAD65) isoform. Immunoprecipitation of labeled islet extracts showed that GAD65 expression increased 16.7 +/- 0.6-fold during high glucose in vitro culture. After controlling for observed increases in protein synthesis, specific glucose stimulation was still 4.2 +/- 0.2-fold. Specific antisera revealed no GAD67 expression under basal conditions, and isoform restriction was maintained during stimulation. Increased GAD65 synthesis thus accounts for glucose stimulation of 64K expression. These time- and concentration-dependent effects of glucose suggest that hyperglycemia increases autoantigenicity and may accelerate beta-cell destruction in primates, supporting a role for beta-cell rest in insulin-dependent diabetes mellitus prevention.

Ganglionic blockade with tetraethylammonium in conscious rats.

The sympathetic ganglionic blocking agent tetraethylammonium has been used as a clearance marker for the measurement of renal plasma flow, but the sympathetic ganglionic blocking dose in rats is unknown. In light of differential reflex activation of sympathetic nerve activity to heart and kidney, we compared the effect of tetraethylammonium on renal nerve activity, mean arterial pressure, and heart rate. Conscious rats were infused with either vehicle (isotonic saline) or tetraethylammonium (n = 7 in both groups). Tetraethylammonium was infused cumulatively (35 minutes per dose) in the following doses: 10(-5), 10(-4), 10(-3), 10(-2), and 10(-1) g/kg body wt per hour. Doses for 15% reduction were 10(-1) for mean arterial pressure, 0.55 x 10(-1) for heart rate, and 0.055 x 10(-1) g/kg body wt per hour for renal nerve activity. Renal nerve activity was abolished at 10(-1) g/kg body wt per hour; mean arterial pressure and heart rate were unchanged at doses lower than 10(-1) g/kg body wt per hour. The lethal dose was 1 g/kg body wt per hour. No changes were observed in vehicle-treated animals. Tetraethylammonium at 10(-1) g/kg body wt per hour resulted in an attenuated increase in renal nerve activity during acetylcholine-induced reduction in mean arterial pressure, reflecting arterial baroreceptor inhibition. We conclude that renal nerve activity is 10- and 18-fold more sensitive to sympathetic ganglionic blockade than heart rate and mean arterial pressure, respectively. When tetraethylammonium is used as a clearance marker for measurement of renal plasma flow in rats, it should be administered in doses less than 10(-2) g/kg body wt per hour.

Acute sympathoinhibitory actions of metformin in spontaneously hypertensive rats.

Chronic treatment with the antihyperglycemic agent metformin prevents hypertension in spontaneously hypertensive rats. This effect has been ascribed to normalization of plasma insulin levels. However, whether metformin affects arterial pressure via changes in sympathetic nerve activity is unknown. Therefore, the objective of this study was to examine whether acute administration of metformin produces changes in mean arterial pressure, heart rate, or efferent renal sympathetic nerve activity in spontaneously hypertensive rats. Rats were anesthetized with alphaxalone-alphadolone (Saffan), paralyzed with pancuronium, and artificially ventilated. Intravenous administration of metformin (0, 1, 10, 100 mg/kg) produced dose-dependent reversible decreases in mean arterial pressure, heart rate, and efferent renal sympathetic nerve activity that were not affected by arterial or cardiopulmonary baroreceptor denervation, nitric oxide synthase inhibition by N(omega)-nitro-L-arginine methyl ester, or cyclooxygenase inhibition by indomethacin. Metformin given into the lateral cerebral ventricle (250, 500, 1000 microg) produced dose-dependent decreases in mean arterial pressure, heart rate, and efferent renal sympathetic nerve activity in doses that caused no changes when given intravenously. The sympathoinhibitory response to intracerebroventricular administration of metformin was not affected by alpha2-adrenoceptor blockade by intracerebroventricular yohimbine. We conclude that metformin has acute sympathoinhibitory effects (decreased arterial pressure, heart rate, and efferent renal sympathetic nerve activity) that are produced by a direct central nervous system site of action.

Furosemide elicits nonuniform reflex responses via cardiac sympathetic afferents.

To examine whether furosemide elicits a cardiorenal reflex response via stimulation of cardiac afferents, furosemide was administered intrapericardially in sinoaortic denervated rats. The role of vagal afferents was evaluated by intrapericardial (IPC) administration of furosemide before and after bilateral vagotomy. The role of cardiac sympathetic afferents was examined by IPC administration of furosemide before and after IPC lidocaine blockade in rats with bilateral vagotomy. Low-dose furosemide (10 micrograms) elicited renal sympathoinhibition, whereas high-dose furosemide (1000 micrograms) produced a rapid and transient change in efferent renal sympathetic nerve activity of either inhibitory (19/49, or 39%) or excitatory (30/49, or 61%) nature. The responses were not affected by vagotomy but were abolished by IPC lidocaine blockade. In rats with a renal sympathoinhibitory response to IPC administration of 1000 micrograms furosemide, both the hypotensive and sympathoinhibitory responses were inhibited by indomethacin, whereas indomethacin did not affect reflex responses in rats showing a renal sympathoexcitatory response to IPC injection of 1000 micrograms furosemide. We conclude that furosemide elicits a nonuniform reflex response mediated via cardiac sympathetic afferents of which the renal sympathoinhibitory response is dependent on intact cyclooxygenase function.