Biomedical subjects

J C Dunbar

Publications and source records attributed to J C Dunbar.

At least 37 records · Page 2Linked to original sources

PubMed1998

Regional blood flow dynamics in response to insulin and IGF-1 in diabetic animals.

Vascular changes in diabetes characterized by increased contractile or decreased dilator responses have been demonstrated in isolated blood vessels as well as in vivo systems. Previous studies in our laboratory have demonstrated that insulin and insulin like growth factor-1 (IGF-1) can decrease mean arterial pressure (MAP) and increase blood flow in vascular beds. In this study we evaluated the regional hemodynamic responses to insulin and IGF-1 in normal and diabetic rats. Normal male rats were made diabetic with streptozotocin (55 mg/kg) i.v. and maintained 60 to 70 days. On the day of the study the rats were anesthetized with urethane/chloralose, the femoral artery and vein cannulated for blood pressure monitoring and blood sampling or infusion, respectively. Pulsed-Doppler flow probes were placed around the iliac artery, renal artery and superior mesenteric artery to monitor blood flow. Insulin (16 nmol/kg) was infused as a bolus via the femoral vein and it decreased the MAP approximately 17% in both normal and diabetic rats. Insulin enhanced vascular flow (expressed as conductance) in the iliac and renal vascular bed but not the superior mesenteric vascular bed in normals. In diabetic rats the flow response to insulin compared to normals was attenuated in the iliac and renal vascular beds and increased in the superior mesenteric vascular bed. A bolus infusion of IGF-1 (16 nmol/kg) also decreased the MAP in normals and diabetics. IGF-1 increased vascular flow in all three vascular beds in normals but in the diabetics the response to IGF-1 was attenuated in the iliac, increased in the renal vascular bed and suppressed in the superior mesenteric vasculature. From these studies we conclude that diabetes is associated with an attenuated vascular response to insulin and IGF-1 in the iliac and renal vessels while insulin augments and IGF-1 decreases blood flow in the superior mesenteric vasculature.

Analysis of Variance↗

PubMed1998

The co-existence of insulin-mediated decreased mean arterial pressure and increased sympathetic nerve activity is not mediated by the baroreceptor reflex and differentially by hypoglycemia.

In this study we measured simultaneously and sequentially the lumbar sympathetic nerve activity (LSNA) or renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP), and heart rate (HR) in response to insulin with co-existing hypoglycemia or with glucose replacement in normal rats. Sinoaortic denervation (SAD) was used to evaluate the influence of the baroreflex. LSNA, RSNA, MAP and HR were determined using an acquisition processor and computer software. Bolus insulin infusion where the blood glucose was allowed to decrease resulted in an immediate decrease in MAP. The HR decreased for approximately 15 min and subsequently increased. The LSNA increased immediately after insulin infusion peaking at 25 minutes and then recovered toward baseline. Insulin infusion with glucose replacement resulted in a decrease in MAP and HR. The LSNA progressively increased and was maintained throughout the experimental period. Insulin infusion with hypoglycemia increased RSNA and when hypoglycemia was prevented the RSNA decreased. SAD attenuated the decrease in MAP and LSNA response to insulin. Thus, insulin acts to decrease MAP while simultaneously increasing HR, LSNA and RSNA when hypoglycemia is allowed to occur. However, insulin acts to decrease HR and RSNA when euglycemia is maintained. The insulin-induced increase in LSNA is modulated by the baroreflex mechanism. We conclude that insulin has independent direct and indirect effects on LSNA, RSNA, MAP and HR that are modulated by glycemia and the baroreflex.

Animals↗

PubMed1997

Impaired insulin but normal pentagastrin effect on gastric acid secretion in diabetic rats: a role for nitric oxide.

Significant changes in gastrointestinal function, decreased gastric secretion and motility in particular, are often observed in patients with chronic diabetes. The mechanisms leading to those remain unclear. In these studies we evaluated the gastric acid secretory response to insulin and pentagastrin in normal Wistar and streptozotocin diabetic rats. We also sought to determine the role of nitric oxide (NO) in this process. The animals were anesthetized with sodium pentobarbital. Warm saline was perfused through a polyethylene tube placed in the oesophagus and collected from the duodenum at 10 min intervals. Following a 50 min equilibration period, a bolus intra-jugular infusion of insulin (4.0 U/kg), 2-deoxyglucose (200 mg/kg) or pentagastrin 4.0 (ug/kg) was started and samples of the gastrointestinal perfusate were collected for an additional 80 min. Insulin-stimulated acid secretion peaked 60 min after bolus infusion in normal animals; a response that was significantly decreased in the diabetic rats. Similarly, 2-deoxyglucose-induced glucopenia increased gastric acid secretion to a lower extent in diabetic versus normal rats. The stimulatory response to pentagastrin was prompt and essentially equal in normal and diabetic animals. However, when hypoglycemia was prevented by glucose infusion, insulin did not stimulate gastric acid secretion in normal rats. Further, glucose infusion in these animals actually enhanced the secretory response to pentagastrin. Nitro-L-arginine methyl ester (L-NAME 20 mg/kg i.v.), an inhibitor of NO synthetase, also prevented the secretory response to insulin but not to pentagastrin. Preinfusion of arginine (100 mg/kg i.v.) in diabetic rats restored the gastric secretory response to insulin toward that of normal animals. We conclude that the gastric acid secretory response to insulin, but not to pentagastrin, is decreased in diabetic animals, that this response may operate through a NO mediated mechanism possibly set in motion by central nervous system glucopenia and that this NO-mediated mechanism is attenuated in diabetes.

Animals↗

PubMed1997

Regional vascular and cardiac responses to systemic neuropeptide-Y in normal and diabetic rats.

Diabetes is associated with altered autonomic activity, and both the peripheral and central nervous content of NPY is altered in diabetes suggesting that part of the cardiovascular dysfunction of diabetes may be associated with altered responses to NPY. We evaluated the mean arterial pressure (MAP), heart rate (HR) and regional blood flow (BF) in response to NPY in normal and diabetic rats. Male Wistar rats were made diabetic using streptozotocin and maintained without insulin treatment for 28-30 days. Normal and diabetic animals were anesthetized, the femoral artery cannulated, and flow probes placed around the iliac, renal and superior mesenteric arteries. Dose dependent responses to NPY infusion were determined for MAP, HR and BF. Conductance was calculated from BF/MAP. In normal rats NPY increased the MAP in a dose-dependent fashion but did not alter the HR. NPY decreased the BF in the iliac artery in a dose-dependent fashion while the renal BF was decreased only at the highest dose, and the superior mesenteric BF was not affected. The conductances in all vascular beds were decreased dose dependently. NPY in diabetic rats also increased MAP and did not affect HR. In diabetic rats NPY also decreased BF in iliac and renal arteries but contrastingly increased BF in the superior mesenteric artery. Again conductances in all three vascular beds were decreased by NPY. When comparing diabetic response to NPY to normals we noted that the MAP response was less in the diabetic, but the HR and regional BF were not different. The vascular conductances in response to NPY were attenuated in the diabetic vessels especially the iliac and superior mesenteric. We conclude that systemic NPY increases MAP as a result of decreased vascular conductance and this vasopressive effect of NPY is diminished in diabetics.

Animals↗

PubMed1997

Intracerebroventricular administration of NPY increases sympathetic tone selectively in vascular beds.

NPY is widely distributed and has broad regulatory actions in the peripheral and central nervous system (CNS) and is especially important in the regulation of cardiovascular responses. CNS administered NPY has been demonstrated to produce both increases and decreases in cardiovascular tone. In this study we evaluated the effect of intracerebroventricular (ICV) administered NPY on cardiovascular tone, regional blood flow dynamics, as well as the mechanism of this action in normal animals. Male rats were instrumented with ICV cannulas and allowed to recover. At the time of the experiment the rats were anesthetized with urethane/chloralose and the femoral artery cannulated for blood pressure determinations. The abdomen was opened and Doppler flow probes were placed around the iliac, renal, and superior mesenteric artery. Mean arterial pressure (MAP), heart rate (HR), iliac, renal, and superior mesenteric flow, as well as the calculated iliac, renal, and superior mesenteric conductance were determined. ICV administered NPY resulted in an increase in MAP and HR, which was associated with decreased flows in the iliac and superior mesenteric vessels while increasing renal flow. Conductance was decreased in the iliac and superior mesenteric vascular beds but not the renal artery. ICV administration of NPY in the presence of a systemically administered alpha1-adrenergic inhibitor, prazosin, attenuated the NPY-mediated effects on MAP as well as vascular conductance in the iliac and superior mesenteric vessels. Additionally, ICV administration of NPY in the presence of a systemically administered beta1-adrenergic inhibition, atenolol, also attenuated the NPY-mediated increase in HR and MAP. Blood flow responses and iliac and superior mesenteric vascular conductance were also attenuated by atenolol pretreatment. In these studies we conclude that lateral ventricular administration of NPY acts to increase systemic MAP and HR and the response is mediated by an increase in sympathetic tone to the heart and especially the splanchnic and skeletal muscle vasculature.

Animals↗

PubMed1997

Intracerebroventricular leptin increases lumbar and renal sympathetic nerve activity and blood pressure in normal rats.

Obesity and hyperinsulinism are known to be major stimuli of leptin production by adipose tissue, leading to increased leptin levels in the circulation. It has also been demonstrated that increased leptin production leads to satiety, possibly by decreasing the levels of neuropeptide Y (NPY) in the central nervous system (CNS). Because obesity and hyperinsulinism are also frequently associated with hypertension, we studied the effect of the intracerebroventricular (ICV) administration of leptin on mean arterial pressure (MAP), heart rate, vascular flows, and lumbar and renal sympathetic nerve activity (SNA). Normal Wistar rats were implanted with an ICV cannula and allowed to recover. On the day of the study, the animals were fasted and anesthetized with chloralose/urethane. Catheters were placed in a femoral artery and vein, and Doppler flow probes were placed around the iliac, renal, and superior mesenteric arteries for measurement of MAP, heart rate, and blood flows. In other experiments, lumbar SNA and renal SNA were recorded. ICV leptin administration resulted in an MAP that was slowly but progressively increasing. Blood flows decreased in the iliac and superior mesenteric arteries, but not in the renal artery. Leptin injection increased the lumbar SNA and renal SNA. The plasma glucose and insulin levels were not changed. We concluded that ICV leptin increases MAP by decreasing arterial blood flow to the skeletal muscle and the splanchnic vascular bed. This increased peripheral resistance is the result of an increased activity of the sympathetic nerves. We suggest that increased leptin may serve as a link in the triad of obesity and hyperinsulinism and hypertension.

Animals↗

PubMed1997

Insulin-like growth factor-I decreases sympathetic nerve activity: the effect is modulated by glycemic status.

Insulin-like growth factor-I (IGF-I) has been demonstrated to exert metabolic as well as cardiovascular actions similar to those of insulin. In previous studies, we have demonstrated that IGF-I acts both peripherally and centrally to increase muscle and renal blood flow and to decrease mean arterial pressure (MAP). Insulin has similar cardiovascular actions and has also been demonstrated to increase sympathetic nerve activity that may or may not play a role in blood flow or arterial pressure regulation. In this study, we evaluated the effect of IGF-I on lumbar sympathetic nerve activity (LSNA) and renal sympathetic nerve activity (RSNA), and correlated these responses with MAP and glycemic status. Normal rats were anesthetized with chloralose/urethane, the femoral artery and vein were cannulated to monitor MAP or heart rate (HR), or for infusions. The lumbar sympathetic nerve or renal nerve was isolated and placed on electrodes embedded in silicone gel for recording of nerve activity. Cardiovascular and nerve activity responses to IGF-I were recorded using a Dasy Lab Acquisition System. The infusion of IGF-I resulted in a decrease in plasma glucose that was accompanied by a decrease in MAP and an increased LSNA. However, when IGF-I was infused and euglycemia was maintained by glucose replacement, the LSNA was decreased. Renal nerve recording demonstrated that the RSNA was decreased both when hypoglycemia was allowed to occur and when euglycemia was maintained. We conclude that IGF-I acts to decrease LSNA and RSNA, and that the activity of the LSNA to skeletal muscle can be increased by hypoglycemia.

Animals↗

PubMed1996

Mechanisms mediating insulin-induced hypotension in rats. A role for nitric oxide and autonomic mediators.

The mechanisms associated with insulin-induced cardiovascular inhibitory responses were evaluated in untreated normal rats and in normal rats pretreated with an antagonist of nitric oxide (NO) production (L-NAME), with cholinergic, alpha- and beta-adrenergic antagonists, or after ganglionic blockade. Male Wistar rats were anesthetized with a mixture of urethane and alpha-chloralose and placed on a electric heating pad. The femoral artery and vein were cannulated for measurements of mean arterial pressure (MAP), heart rate, plasma glucose, blood sampling, and intravenous injections. Intravenous injection of insulin (5.0 U/kg) in untreated rats resulted in a significant and sustained decrease in arterial blood pressure (average 24%) and in a slight decrease in heart rate. These cardiovascular responses were blocked by L-NAME and by the cholinergic antagonist atropine, suggesting an involvement of NO and the cholinergic receptors, or an effect of insulin on the central nervous system parasympathetic center. The ganglionic blocker hexamethonium attenuated the insulin-induced response. On the other hand, the hypotensive effect of insulin persisted after sympathetic blockade with the alpha-1 antagonist prazosin and the beta-1 antagonist atenolol. We conclude that the insulin-induced decrease in blood pressure is due to both increased cholinergic outflow and to NO production and that an enhanced sympathetic activity possibly mediated by a reactive release of norepinephrine or epinephrine modulates this response.

Animals↗

PubMed1996

The lymphocyte and macrophage profile in the pancreas and spleen of NOD mice: percentage of interleukin-2 and prolactin receptors on immunocompetent cell subsets.

The NOD mouse is a model for autoimmune diabetes that develops symptoms similar to Type I diabetes. The incidence of diabetes is greater in females but the degree of insulitis is comparable in both sexes. The purpose of this study was to assess the populations of lymphocytes and macrophages in the pancreas and spleen of NOD mice. Comparisons were made between male and female; young (32-40 days old) and old (197-297 days old); diabetic and non-diabetic mice. Using analytical fluorescent cell cytometry we quantitated the percentages of CD4, and CD8 T-cells, B-cells and macrophages and the percentages of these subsets expressing interleukin-2 (IL-2R), prolactin (PRLR) and Hi-intensity PRL (Hi-PRLR) receptors. Evaluation of T-splenocytes indicated a 2:1 ratio of CD4 to CD8 T-lymphocytes in the spleen. The pancreas had higher percentages of all of the subsets in the old male and female groups compared to their young counterparts. Pancreatic immunocompetent cell subsets expressed lower percentages of IL-2R, PRLR and Hi-PRLR compared to splenocytes. The results did not demonstrate any dramatic differences in the immunocompetent cell populations of the spleen or pancreas between male and female animals, however we were able to establish the percentage of immunocompetent cells with IL-2R, PRLR and Hi-PRLR as a reference for future studies.

Animals↗

PubMed1996

Variable subcellular localization of a neuron-specific protein during NTera 2 differentiation into post-mitotic human neurons.

The current report describes the molecular characterization of the human (the D4S234 locus) and mouse (the m234) homologs of a gene that was isolated during our genomic analysis of the Huntington disease gene region. Sequence comparisons of full-length cDNA clones revealed that the mouse and human homologs encoded evolutionarily conserved 21-kDa proteins with greater than 90% amino acid sequence identity. Extensive sequence identity between the D4S234 gene and the rat p1A75 gene (a previously identified rat neuron-specific gene) showed that these genes are interspecies homologs. Furthermore, the D4S234 protein exhibited significant amino acid similarity to a 19-kDa mouse protein that localizes to the Golgi apparatus of embryonic neurons. However, nonconservative sequence differences suggested that these genes are independent members of a multigene family. Northern analyses revealed that rodent D4S234 expression occurred predominantly in the brain and included all brain regions. Neuron-specific expression was demonstrated using Northern analysis of cultured glial cells and quinolinic acid-treated rat brain samples. Minimal amounts of the rodent D4S234 mRNA were detected prenatally; however, elevated adult levels were detected within 1 month of birth. Sequence analyses of the human and mouse D4S234 proteins identified an evolutionarily conserved hydrophobic sequence and a consensus nuclear localization signal in both genes. Immunofluorescence microscopy, using an antipeptide antibody, established that the human D4S234 protein preferentially localized to the nucleus of mitotic cultured cells. Since the rat p1A75 protein was previously mapped to the neuronal cytoplasm by in situ hybridization, the subcellular localization of the D4S234 protein was subsequently examined during differentiation of the NTera 2 (NT2) cell line. Following differentiation into postmitotic NT2-N neurons, the D4S234 protein demonstrated cytoplasmic staining and reduced or undetectable nuclear staining in many cells. The variation in the intracellular localization of the D4S234 protein in mitotic and nonmitotic cells suggests that the subcellular localization of this protein is developmentally regulated and provides clues about the biochemical function of this protein.

Amino Acid Sequence↗

PubMed1996

Central IGF-1 decreases systemic blood pressure and increases blood flow in selective vascular beds.

IGF-1 and its receptors have been identified in many tissues including the central nervous system (CNS). We have previously demonstrated that injection of insulin directly into the cerebral ventricles (ICV) is followed by a drop in mean arterial pressure (MAP) associated with an increase in skeletal muscle blood flow. Given the similarities between the IGF-1 and insulin molecules and their respective receptors, we have investigated the effect of ICV administration of IGF-1 on systemic blood pressure and blood flow in selected vascular beds. ICV cannulas were implanted into normal rats and the animals were allowed to recover for 3 to 4 days. The femoral artery and vein were cannulated for blood pressure monitoring and blood sampling and blood flow probes placed around the iliac, the renal and the superior mesenteric artery were used to assess regional blood flow. ICV injection of IGF-1 resulted in a significant decrease in MAP with a nadir at 15 minutes and a gradual return to baseline by 60 minutes; heart rate increased 40 minutes after the injection. IGF-1 significantly enhanced vascular flow and conductance in the iliac, but not in the renal and superior mesenteric arteries. The effects of IGF-1 were much smaller than those observed previously with equimolar amounts of insulin. We conclude that IGF-1 can decrease MAP by selectively increasing blood flow to skeletal muscle through a direct action on the central nervous system.

Animals↗

PubMed1996

Insulin-like growth factor I diminishes in vivo and in vitro vascular contractility: role of vascular nitric oxide.

Although most insulin-like growth factor I (IGF-I) in the circulation is generated by the liver, the hormone is also produced locally by the vasculature, suggesting its potential importance in regulation of regional blood flow. Accordingly, we studied the effects of in vivo exposure to IGF-I (5.1 nmol, i.v.) as well as in vitro incubation (100 nM) on endothelium-intact rat tail artery contractile responses to KCl and norepinephrine (NE). Systemic administration of IGF-I resulted in transient lowering of blood pressure, with maximal reduction occurring at 15 min and a return to baseline by 60 min. Maximal contractility of rings removed from animals 90 min after a bolus injection of IGF-I, when blood pressure had returned to normal, was significantly reduced for both KCl (58%) and NE (51%) without a change in sensitivity. Similar data were obtained when rings from untreated animals were preincubated in vitro for 90 min; maximal contractility in response to KCl was decreased by 31% and that to NE by 22%. L-Nitroarginine methyl ester, an inhibitor of nitric oxide (NO) production, administered in vivo before IGF-I or added to the bath buffer reversed the attenuation. The nearly identical in vivo and in vitro results suggest that the observed diminution in contractility is a direct effect of IGF-I on the vasculature, probably mediated in large part by the release of NO. This idea is supported by our observation that IGF-I stimulates NO production in intact vessels. Further, the latency required indicates that rather complex mechanisms involving actions common on both receptor- and nonreceptor-mediated events are initiated by IGF-I and/or NO.

Animals↗

PubMed1996

Insulin-like growth factor-I decreases mean blood pressure and selectively increases regional blood flow in normal rats.

The insulin-like growth factor-I (IGF-I) and its receptors are widely distributed in peripheral vascular tissue, yet their role in the regulation of blood pressure and blood flow remains unknown. This study investigated the effect of IGF-I on blood pressure and selected regional blood flow in normal Wistar rats anesthetized with chloralose/urethane. The femoral artery was cannulated and used to monitor arterial blood pressure. Electromagnetic flow probes were placed around the left common iliac artery, left renal artery, and the superior mesenteric artery, and used to measure blood flow. IGF-I (2.6 micrograms, 5.1 or 10.3 nmol/animal Iv) was injected as a bolus into the femoral vein. Following the injection of IGF-I (10.3 nmol), we observed a significant decrease of plasma glucose (57%) and a significant decrease of mean arterial pressure (MAP) that continued to decline throughout the 60-min experimental period. IGF-I (5.1 nmol) significantly decreased blood glucose by 44% and decreased the MAP by 14% with a nadir at 15 min and recovery after 60 min. A smaller dose of IGF-I (2.6 nmol) did not significantly decrease the blood glucose but resulted in a slight but significant decrease in MAP. The heart rate was increased by 10.3 and 5.1 but not 2.5 nmol of IGF-I. IGF-I (10.3 nmol) was associated with regional vascular responses with a preferential increase in flow of the iliac and superior mesenteric vessels, measured as vascular conductance. IGF-I (5.1 and 2.6 nmol) increased preferentially renal vascular conductance. Preinfusion with L-NAME, a nitric oxide inhibitor, inhibited the effects of IGF-I on flow. We conclude that IGF-I can selectively dilate vascular beds leading to a decrease in blood pressure and that the response to IGF-I is mediated by nitric oxide.

Animals↗

PubMed1995

DNA determinants in sequence-specific recognition by XmaI endonuclease.

The XmaI endonuclease recognizes and cleaves the sequence C decreases CCGGG. Magnesium is required for catalysis, however, the enzyme forms stable, specific complexes with DNA in the absence of magnesium. An association constant of 1.2 x 10(9)/M was estimated for the affinity of the enzyme for a specific 195 bp fragment. Competition assays revealed that the site-specific association constant represented an approximately 10(4)-fold increase in affinity over that for non-cognate sites. Missing nucleoside analyses suggested an interaction of the enzyme with each of the cytosines and guanines within the recognition site. Recognition of each of the guanines was also indicated by dimethylsulfate interference footprinting assays. The phosphates 5' to the guanines within the recognition site appeared to be the major sites of interaction of XmaI with the sugar-phosphate backbone. No significant interaction of the protein was observed with phosphates flanking the recognition sequence. Comparison of the footprinting patterns of XmaI with those of the neoschizomer SmaI (CCC decreases GGG) revealed that the two enzymes utilize the same DNA determinants in their specific interaction with the CCCGGG recognition site.

Alkylation↗

PubMed1995

Sequence-specific DNA recognition by the SmaI endonuclease.

SmaI endonuclease recognizes and cleaves the sequence CCC decreases GGG. The enzyme requires magnesium for catalysis; however, equilibrium binding assays revealed that the enzyme binds specifically to DNA in the absence of magnesium. A specific association constant of 0.9 x 10(8) M-1 was determined for SmaI binding to a 22-base duplex oligonucleotide. Furthermore, the KA was a function of the length of the DNA substrate and the enzyme exhibited an affinity of 1.2 x 10(9) M-1 for a 195-base pair fragment and which represented a 10(4)-fold increase in affinity over binding to nonspecific sequences. A Km of 17.5 nM was estimated from kinetic assays based on cleavage of the 22-base oligonucleotide and is not significantly different from the KD estimated from the thermodynamic analyses. Footprinting (dimethyl sulfate and missing nucleoside) analyses revealed that SmaI interacts with each of the base pairs within the recognition sequence. Ethylation interference assays suggested that the protein contacts three adjacent phosphates on each strand of the recognition sequence. Significantly, a predicted protein contact with the phosphate 3' of the scissile bond may have implications in the mechanism of catalysis by SmaI.

Base Sequence↗

PubMed1995

The identification of a functional nuclear localization signal in the Huntington disease protein.

Positional cloning has shown that the Huntington disease (HD) mutation is an expanded trinucleotide repeat in the IT15 gene. Although this mutation clearly produces the HD phenotype, the function of the Huntington disease protein remains undefined. One recent immunocytochemical study suggested that the IT15 protein preferentially localizes to the nucleus of affected neuronal cells. If this result is accurate, it could link the biochemical function of this protein to nuclear activities such as gene regulation. To examine the nuclear transport of the Huntington disease protein, we searched for basic peptide motifs that could produce nuclear localization. One peptide (RRKGKEK) was identified that is highly homologous to a consensus nuclear localization signal. When fused to the cytoplasmic reporter protein, beta-galactosidase, nuclear localization was observed in stably transformed human cell lines. In a complementary study, an anti-peptide polyclonal antibody, raised against a sequence adjacent to the putative nuclear localization sequence, detected the IT15 protein in the nucleus of human cells. These results extend and confirm the previous localization studies and identify an IT15 peptide motif that can function for nuclear localization.

Amino Acid Sequence↗

PubMed1995

Effect of insulin and clonidine on the evoked release of norepinephrine and serotonin from the nucleus tractus solitarius of the diabetic rat.

Dorsal medullary brain slices containing primarily the nucleus tractus solitarius (NTS) were obtained from normal or 40- to 50-day streptozotocin-diabetic rats and employed for superfusion studies of evoked transmitter release. Electrically stimulated (25 mA, 2-ms pulses, 3 Hz, 1 min) release of [3H]norepinephrine ([3H]NE) or [3H]5-hydroxytryptamine ([3H]5-HT) from 400-microns NTS slices stimulated at 75 min (S1) and 130 min (S2) resulted in S2/S1 release ratios that were not different between normal controls or diabetic control groups. Perfusion of normal [3H]NE-loaded slices with 0.1 mumol/l clonidine reduced the S2/S1 ratio by 23% (p < 0.05) which was uniform in the caudal, subpostremal, and intermediate segment levels of the NTS. In diabetic NTS slices, the S2/S1 ratio was significantly less reduced by clonidine in both the subpostremal (-3%) and intermediate (-11%) slice regions. Blockade of alpha 2-adrenoceptors with yohimbine (0.1 mumol/l) enhanced (p < 0.05) [3H]NE release (S2/S1 ratios) in slices from both normal and diabetic rats. Perfusion of [3H]NE-loaded slices with 5 mU/ml insulin did not affect S2 release. Evoked S2/S1 release ratios from NTS slices loaded with [3H]5-HT did not differ between normal control and diabetic control groups. Clonidine (0.1 mumol/l) reduced S2-evoked release in both normal (-30%) and diabetic (-44%) slices, but the groups were not different from each other. Superfusion with 5 mU/ml insulin did not alter S2/S1 ratios in normal [3H]5-HT loaded slices, but did increase the diabetic NTS slice S2/S1 ratio to 1.40 +/- 0.06 (p < 0.01). In summary, it appears that alpha 2-adrenoceptor-mediated inhibition of [3H]NE release in the NTS was selectively attenuated in a regionally specific manner in diabetic animals. Release inhibition may be associated with receptor downregulation in NTS regions associated with cardiovascular reflex transmission. Insulin superfusion augmented [3H]5-HT release in the diabetic NTS slices, possibly through increased transmitter synthesis or improved synaptic release.

Adrenergic alpha-Agonists↗

PubMed1995

Effects of acetaldehyde on the isolated papillary muscle of diabetic rats.

The effects of acetaldehyde (ACA) were examined in isolated electrically driven papillary muscle preparations from normal and streptozotocin-treated diabetic rats. Muscles from diabetic rats developed greater tension than those from normal rats. In muscles from both groups, ACA caused concentration-dependent negative inotropic effects that were independent of cholinergic or purinergic mechanisms and were not attributable to nitric oxide (NO) release. ACA was three to five times more potent with regard to its negative inotropic effect in diabetic than in normal rat muscles. A propranolol-sensitive, sympathetically mediated positive inotropic effect occurred at certain concentrations. Decreasing [Ca2+]o from 2.7 to 0.5 mM reduced basal developed force to a significantly greater extent in muscles from normal rats than in those from diabetic rats. In low [Ca2+]o, concentration-response curves to CaCl2 in diabetic muscles were displaced to the left of that in normal muscles, suggesting that diabetic muscles are more sensitive to the positive inotropic effect of added CaCl2 at low [Ca2+]o, whereas at higher [Ca2+]o (> 1 mM), normal muscles developed more force in response to added CaCl2. ACA 10 and 30 mM more readily inhibited CaCl2-induced positive inotropic effect in normal than in diabetic muscles. Force-frequency curves, (negative staircase response) were recorded in both normal and diabetic muscles. In diabetic muscles, the curve exhibited a positive component at the lowest frequencies applied and was displaced to the right of that in normal muscle. ACA concentration-dependently inhibited force development, and diabetic muscles were more susceptible to the negative inotropic effect of ACA, when the stimulation frequency was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗