Changes in adrenergic and peptidergic nerves in the submucous plexus of streptozocin-diabetic rat ileum.

The effect of streptozocin diabetes on the distribution of adrenergic and peptidergic nerves in the submucous plexus of rat ileum was investigated and compared with the changes in the myenteric plexus of the same region of ileum. There was an increase in the intensity of immunoreactivity in vasoactive intestinal polypeptide- and neuropeptide Y-like immunoreactive nerve fibers and neurons and a decrease in calcitonin gene-related peptide-like immunoreactivity but no change in substance P- and dopamine beta-hydroxylase-like immunoreactivity in the nerve fibers and neurons of the submucous plexus of both 8- and 16-wk streptozocin-diabetic rat ileum. However, in the myenteric plexus of the diabetic rat ileum, there was enlargement of varicosities and an increase followed by a slight decrease in the intensity of immunoreactivity of vasoactive intestinal polypeptide- and dopamine beta-hydroxylase-like immunoreactive nerve fibers and neurons, increased substance P-like immunoreactivity in diabetes at 16 wk, and an initial decrease (at 8 wk) followed by a recovery of calcitonin gene-related peptide-like immunoreactivity at 16 wk, but no change in neuropeptide Y-like immunoreactivity. The markedly different changes in peptidergic and adrenergic nerves between the two enteric plexuses show that diabetic neuropathy induced by streptozocin is not selective and involves factors other than neurotransmitter types.     

Progressive and concurrent deterioration of vagus-stimulated and hypoglycemia-induced glucagon secretion in streptozotocin-diabetic rats.

The effects of left cervical vagus nerve stimulation on glucagon secretion were studied in streptozotocin-diabetic and age-matched control adult male rats. At two-week intervals, after the induction of streptozotocin-diabetes, streptozotocin-diabetic and age-matched control rats were anesthetized with chloral hydrate (350 mg/kg, ip). Left cervical vagus nerves were electrically stimulated via a Grass stimulator with 5-volt monophasic pulses of 3 msec duration at a frequency of 20 Hz for 1, 2, and 4 min. Arginine-induced glucagon secretion was also determined. Vagus nerve-stimulated (2 and 4 min) glucagon secretion deteriorated as the duration of streptozotocin-diabetes increased. Glucagon secretion in response to vagus nerve stimulation was virtually absent by 12 weeks of streptozotocin-diabetes. However, arginine-induced glucagon secretion was unaffected. Subsequent experiments showed that the defect in glucagon secretion from vagal stimulation occurred concurrently with that seen from insulin-induced hypoglycemia. These results indicate that the impaired hypoglycemia-induced glucagon secretion in long-term streptozotocin-diabetic rats may be correlated with the deterioration of the parasympathetic nervous system transmission in streptozotocin-diabetes.     

Hepatic morphological changes and oxidative stress in chronic streptozotocin-diabetic rats

Oxidative stress (OS) is a biological entity quoted as responsible for several pathologies including diabetes. Diabetes mellitus (DM) has been also associated to human cirrhosis. The present work was designed to study the occurrence of OS as well as morphologic alterations in rat livers following induction of DM. Two groups of rats were used: Control and Diabetic. DM was induced in the second group by streptozotocin (STZ) in a single dose of 60 mg/kg, injected i.p. The occurrence of OS was determined in liver homogenates by measuring the hydroperoxide-initiated chemiluminescence and the activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase). Liver sinusoids were morphometrically analyzed. In conclusion, livers from the diabetic group did not show evidence of the occurrence of OS, as it would be expected, but dilation of hepatic sinusoids was documented and it was significantly different from control group.     

Distribution and development of peptidergic nerves and gut endocrine cells in mice with congenital aganglionic colon, and their normal littermates

Studies were made of the distribution of gut hormones and neuropeptides in the gastrointestinal tract of mice with hereditary aganglionic colon (s1/s1) and their normal littermates. Antisera to substance P, vasoactive intestinal polypeptide, and enkephalins demonstrated markedly diminished numbers of immunofluorescent nerve fibers in the aganglionic segment of colon; in contrast, in proximal colon and small intestine the distribution of peptidergic nerve fibers was essentially normal. Mucosal endocrine cells were demonstrated in the colon by antisera to substance P, somatostatin, glucagon, and cholecystokinin; in each case there were similar numbers of cells in s1/s1 and normal mice. Radioimmunoassays for vasoactive intestinal polypeptide and bombesin showed diminished concentrations of immunoreactive material in the aganglionic segment of colon of 16-17-day-old animals. However, assays for CCK--which is predominantly located in endocrine cells--showed similar concentrations of immunoreactive material throughout the gut of s1/s1 and normal mice. It was of interest that the concentrations of immunoreactive substance P were lower than normal not only in the aganglionic segment of colon, but also in proximal colon and distal small intestine, and that at all ages the development of substance P in the intestine was delayed in the s1/s1 mice. The results are consistent with the idea that the constriction of the aganglionic segment of colon develops as a consequence of lack of intrinsic inhibitory neurons, possibly those containing vasoactive intestinal polypeptide. The presence of an aganglionic segment is attributable to delayed migration of the neuroblasts from the neural crest. Thus the findings of normal populations of gut endocrine cells in the aganglionic segment is further support for the view that the embryologic origin of gut endocrine cells is different to that of gut neurons.     

Loss of regulation by sympathetic hepatic nerves of liver metabolism and haemodynamics in chronically streptozotocin-diabetic rats

Summary The consequences of autonomic diabetic neuropathy, a common complication of chronic diabetes mellitus, have been studied mainly with regard to heart and stomach function. Since the autonomic nervous system also regulates liver carbohydrate metabolism and haemodynamics via hepatic nerves, it was the purpose of this study to examine the function of hepatic nerves in chronically diabetic rats. Diabetes was induced by i.p. injection of streptozotocin. Rat livers were perfused via both portal vein and hepatic artery. Hepatic nerves were stimulated for 2 min using a platinum electrode placed around the portal vein and the hepatic artery; in an additional stimulation phase noradrenaline was infused into the portal vein. Stimulation of hepatic nerves as well as portal noradrenaline infusion increased hepatic glucose output and reduced flow in control and in acutely (48-h) diabetic animals, which still had almost normal glycogen content. In addition stimulation also caused an overflow of noradrenaline into the caval vein. However, nerve stimulation neither increased glucose output nor decreased flow in 4-month diabetic rats. In these rats noradrenaline overflow was nearly completely abolished and hepatic glycogen content was markedly depleted. Portal noradrenaline infusion in chronically diabetic rats reduced flow to a similar extent as in controls, yet the increase in glucose output was diminished. The lack of nerve stimulation-dependent glucose output, flow reduction and noradrenaline overflow is indicative of a profound loss of function of hepatic autonomic nerves in chronically diabetic rats.Abbreviations IDDM Insulin-dependent diabetes mellitus - NIDDM non-insulin-dependent diabetes mellitus - IVC inferior vena cava - BSA bovine serum albumin     

Extrinsic denervation causes a transient proabsorptive adrenergic hypersensitivity in the canine proximal colon

Our aim was to determine if extrinsic denervation alters the absorptive response of the colon to proabsorptive and prosecretory stimuli. Ten dogs underwent enteric isolation of a 50-cm proximal colonic segment; five were also randomized to undergo extrinsic denervation (DEN). At 2 and 13 wk postoperatively, net absorptive fluxes (mean ± sem) of water and electrolytes were determined during basal conditions and during proabsorptive low-dose (0.3 g/kg/min) or high-dose (3 g/kg/min) norepinephrine or prosecretory VIP (500 pg/kg/min). The net absorptive flux of water under basal conditions was decreased in DEN versus neurally intact controls at two weeks (4.0 ± 0.6 vs 6.6 ± 0.7 l/min/cm, P = 0.03) but did not differ at 13 weeks (5.0 ± 1.0 vs 5.7 ± 0.9, P > 0.05). Low- and high-dose norepinephrine increased water absorption in both groups at two weeks; the change in flux for high-dose norepinephrine was greater in DEN versus controls (4.1 ± 1 vs 2.1 ± 0.6 l/min/cm, P = 0.04). Net absorptive fluxes of Na⁺ and Cl^– followed these trends. VIP did not alter absorption of water or electrolytes. Extrinsic denervation of the proximal colon causes a decrease in net colonic absorption and a transient, proabsorptive adrenergic hypersensitivity in colonic absorption of water and electrolytes. VIP does not have a net secretory effect in the proximal canine colon.     

Enhanced 5-hydroxytryptamine release from vascular adrenergic nerves in spontaneously hypertensive rats

The release of 5-hydroxytryptamine from the vascular adrenergic nerve by periarterial nerve stimulation in spontaneously hypertensive rats (SHR) was compared with that in normotensive Wistar-Kyoto rats (WKY). The isolated mesenteric vascular bed was perfused at a constant flow rate of 5 ml/min. Vasoconstrictor responses to periarterial nerve stimulation (4, 8, 12, and 16 Hz for 30 seconds) and 5-hydroxytryptamine (1 microM), but not norepinephrine (1 nmol), were significantly greater in SHR than in WKY. After treatment with 5-hydroxytryptamine (1 microM) for 15 minutes, vasoconstrictor responses to periarterial nerve stimulation previously reduced by prazosin (50 nM) were restored and a frequency-dependent pressor response reappeared. However, 5-HT treatment did not significantly affect the pressor response to exogenously administered norepinephrine (1 nmol), which was previously inhibited by prazosin. The degree of the restoration in SHR was significantly greater than that in WKY at all frequencies used. The restoration of the pressor response to periarterial nerve stimulation after 5-hydroxytryptamine treatment did not occur in the presence of the selective 5-hydroxytryptamine2 receptor antagonists ketanserin (10 nM) or LY53857 (10 nM). In the perfused mesenteric vascular bed of both WKY and SHR prelabeled with [3H]5-hydroxytryptamine, periarterial nerve stimulation (4-16 Hz) evoked a frequency-dependent increase in tritium efflux that was abolished by Ca2+-free Krebs-Ringer solution or tetrodotoxin (100 nM) and treatment with 6-hydroxydopamine. The tritium efflux evoked by periarterial nerve stimulation was significantly greater in SHR than in WKY at all frequencies used. These results suggest that the release of 5-hydroxytryptamine from adrenergic nerve endings by periarterial nerve stimulation is enhanced in the mesenteric vascular bed of the SHR.     

The influence of cholinergic, adrenergic, and serotonergic drugs on the afternoon surge of plasma prolactin in ovariectomized, estrogen-treated rats.

The effects of systemic administration of cholinergic, adrenergic, and serotonergic drugs on the afternoon surge of plasma prolactin was investigated using ovariectomized, polyestradiol phosphate (PEP)-injected rats bearing aortic catheters. Basal prolactin levels were elevated and similar after PEP administration for a period of 5 weeks, and an afternoon surge in plasma prolactin persisted for a period of 3 weeks before the magnitude of the surge diminished. The plasma estradiol levels were significantly higher for the 1100 and 1300 h samples than for the 1500 and 1700 h samples. Cornified vaginal epithelia were predominant in the vaginal smears of all animals throughout the 49-day experimental period. The cholinergic agonists arecoline, nicotine, and carbachol significantly inhibited the afternoon surge of prolactin. The muscarinic antagonist atropine resulted in a partial inhibition of the surge while the nicotinic antagonist mecamylamine did not have any inhibitory effect. The alpha-adrenergic blockers phenoxybenzamine and phentolamine and the beta-blocker propranolol inhibited the prolactin surge, with phenoxybenzamine being most effective. The administration of the serotonergic antagonist methysergide resulted in only a partial blockade of the afternoon prolactin surge. The data suggest that both the adrenergic and serotonergic systems may have a positive input in the afternoon surge of plasma prolactin. It appears that the cholinergic system does not play a significant role in the afternoon surge.     

Noradrenergic and peptidergic nerves in the synovial membrane of the Sprague-Dawley rat

This immunohistochemical study of nerves in the synovial tissue of Sprague-Dawley rats demonstrated the occurrence of 4 neuropeptides and 2 enzymes that are involved in the synthesis of catecholamines. Substance P and calcitonin gene-related peptide were colocalized in fibers that terminated as varicosal endings in the synoviocyte layer. Similarly, tyrosine hydroxylase and dopamine beta-hydroxylase, which reflect the presence of noradrenaline, were colocalized with neuropeptide Y. These fibers were predominantly found adjacent to and within blood vessel walls. Immunoreactivity to vasoactive intestinal polypeptide was seen in varicose nerve terminals in the synoviocyte layer. Many were localized in vessel walls. There is accumulating evidence of an involvement of substance P and noradrenaline in the pathogenesis of inflammatory joint disease and nociception. The role of these colocalized neuropeptides, namely, calcitonin gene-related peptide and neuropeptide Y, in the pathophysiology of such conditions warrants further analysis.     

Lack of release of vasoactive intestinal polypeptide and calcitonin gene-related peptide during electrical stimulation of enteric nerves in streptozotocin-diabetic rats

The simultaneous release of endogenous acetylcholine, serotonin, vasoactive intestinal polypeptide, substance P, and calcitonin gene-related peptide was measured during electrical field stimulation of isolated preparations of rat ileum from control and 8-wk streptozotocin-treated diabetic rats. Electrical field stimulation of the control rat ileum caused a significant increase in the release of all the above substances from the enteric nerves. The electrically evoked, but not the basal, release of these substances was inhibited by tetrodotoxin. In the diabetic rat ileum, however, there was no increase in the release of vasoactive intestinal polypeptide and calcitonin gene-related peptide during electrical stimulation, whereas endogenous release of acetylcholine, serotonin, and substance P was unaffected by the diabetic state. This was surprising in view of the increased fluorescence intensity and tissue content of vasoactive intestinal polypeptide-like immunoreactivity in the same tissue reported previously. The lack of increase in evoked release of vasoactive intestinal polypeptide in the diabetic preparations might be due to an impaired mechanism of release at the terminal site or to defective axonal transport of the peptide, whereas in the case of calcitonin gene-related peptide, it might be the result of the low level of the peptide present in the enteric nerve fibers of the diabetic rat ileum. The differential effect of diabetes on enteric nerves is discussed.     

The maximal activity of phosphate-dependent glutaminase and glutamine metabolism in the colon and the small intestine of streptozotocin-diabetic rats

Summary The effects of short- and long-term diabetes on the maximal activities of phosphate-dependent glutaminase and glutamine metabolism were studied in the colon and the small intestine of streptozotocin-diabetic rats. The maximal activity of colonic phosphate-dependent glutaminase was decreased [44% in mucosal scrapings (p<0.01); 29% in whole colon (p<0.001)] or unchanged in short- or long-term diabetes respectively. That of the small intestine was increased in both short- (110%) and long-term (200%–500%) diabetes; insulin treatment corrected this increase. Acute insulin-deficiency (using anti-insulin serum) resulted in the increase (18%, p<0.05) of the activity of only intestinal glutaminase. Chemically-induced acidosis and alkalosis decreased (46%, p<0.001) and increased (24%, p<0.001), respectively, the activity of intestinal glutaminase, but had no effect on the colonic enzyme. Changes in glutaminase of the enlarged colon and small intestine were only detectable when activities were measured in whole organ. Arteriovenous-difference measurements showed diminished metabolism of plasma glutamine by the gut which correlated with the duration of the state of diabetes, and was accompanied by enhanced release by skeletal muscle and increased uptake by both kidney and liver. It is concluded that insulin is directly or indirectly involved in the regulation of glutamine metabolism of the gut.     

Progressive inflammatory and structural changes in the pulmonary vasculature of monocrotaline-treated rats

The progression of changes in the bronchus-associated and intraacinar pulmonary arteries of rats treated with a single dose of monocrotaline (60 mg/kg) was evaluated by quantitative light and electron microscopy. The relative volume of vessel wall components was normalized to the surface area of the adventitial sheath. An increased relative volume of media was evident in intraacinar pulmonary arteries by 4 hr post-treatment. This increase may represent vascular smooth muscle contraction. Significant increases in adventitial mononuclear inflammatory cells were evident by 8-16 hr post-treatment in intraacinar pulmonary arteries and veins but not until 14 days post-treatment in major, bronchus-associated pulmonary arteries. Inflammatory cell influxes were associated with increased relative volume of adventitia, largely due to increased extracellular space. By 22 days posttreatment, there was right ventricular hypertrophy and a marked mononuclear vasculitis in major and intraacinar pulmonary arteries as well as intraacinar veins (confirmed as such by vascular perfusion of carbon/gelatin). There was increased relative medial volume in both major and intraacinar pulmonary arteries associated with increased extracellular matrix composed largely of collagen. Intraacinar veins developed intimal plaques of smooth muscle in a collagenous matrix. We conclude that (1) adventitial inflammation precedes morphologic evidence of medial changes in monocrotaline-induced pulmonary hypertension, (2) involvement of intraacinar arteries precedes that of major bronchus associated arteries, and (3) both pulmonary arteries and veins are involved in monocrotaline-induced pulmonary vascular disease in the rat.     

Further studies on the effects of adrenergic, serotonergic and cholinergic drugs on the afternoon surge of plasma prolactin in ovariectomized, estrogen-treated rats.

The involvement of adrenergic, serotonergic and cholinergic mechanisms in the diurnal surge of plasma prolactin (Prl) secretion has been examined using ovariectomized, polyestradiol phosphate-treated (PEP) rats bearing aortic catheters. An afternoon surge in plasma Prl was observed to peak at 15.00 h and 17.00 h followed by declining levels at 19.00 and 21.00 h. This pattern was observed between 5 and 21 days after PEP administration. The alpha-adrenergic blocker, phenoxybenzamine (Phenox), completely prevented the Prl surge. The beta-blocker, propranolol (Propra), appeared to delay the onset and intensity of the diurnal Prl surge so that maximum levels were observed at 19.00 and 21.00 h. The serotonergic blocker, methysergide (MES), delayed the maximum diurnal Prl level until 21.00 h, while cyproheptadine (Cypro), another serotonergic blocker, significantly inhibited the surge. The muscarinic cholinergic agonist, arecoline (Arec), when administered at 12.00 h, delayed the surge, while the repeated administration of Arec completely blocked the surge. Atropine (Atro) (10 m/kg at 12.00 h and 5 mg/kg every 2 h thereafter) did not have any effect on the Prl surge, but when administered simultaneously with Arec, prevented the inhibitory effect of Arec on Prl release. The data suggested that the adrenergic and serotonergic systems have a positive input in the occurrence and magnitude of the surge and that the cholinergic system does not appear to have a physiologic role in tonically inhibiting Prl release, but may function under certain special conditions.     

The development of retinopathy in sucrose-fed and streptozotocin-diabetic rats

Summary Normal and streptozotocin-diabetic rats have been maintained for 6–11 months on completely balanced, reconstituted diets in which the sole source of carbohydrate was either 68% corn starch or 68% sucrose. The retinal vascular system was isolated by trypsin digestion and examined histologically for the presence of tortuosity and irregularity of capillary diameter, increased PAS-positive deposits, microaneurysms, loss of pericytes, endothelial proliferation, acellularity and strand formation. None of these pathological changes occurred in normal rats fed a starch-rich diet, but all developed to a similar extent in the sucrose-fed normal rats and the starch-fed diabetic group. The changes were more severe in sucrose-fed diabetic rats after 6 months. In all groups the retinopathy progressed with time. The possibility that a factor common to both the ingestion of a sucrose-rich diet and streptozotocin diabetes in rats has been considered since, histologically, the retinopathy observed was identical both with respect to severity and rate of development in normoglycaemic, sucrose-fed and hyperglycaemic, starch-fed diabetic rats.     

Variability of cell proliferation in the proximal and distal colon of normal rats and rats with dimethylhydrazine induced carcinogenesis

AIM：To investigate the patterns of cell proliferation in proximal and distal colons in normal rats and rats with1,2-dimethylhydrazine(DMH)induced carcinogenesis using the thymidine analogue bromodeoxyuridine.METHODS:Colonic crypt cell proliferation was immunohistochemically detected using the anti-bromodeoxyuridine Bu20a monoclonal antibody.RESULTS:Marked regional differences were found in both groups.Total labelling index(LI)and proliferative zone size in both normal(8.65&#177;0.34vs7.2&#177;0.45,27.74&#177;1.07vs16.75&#177;1.45)andDMH groups(13.13&#177;0.46vs11.55&#177;0.45,39.60&#177;1.32vs35.52&#177;1.58)were significantly higher in distal than in proximal colon(P&lt;0.05).although the number of cells per proxmal crypt was greater(31.45&#177;0.20vs34.45&#177;0.39,42.68&#177;0.53vs49.09&#177;0.65,P&lt;0.001).Crypt length,total LT and proliferative zone size all increased in both proximal and distal regions of DMH rats compared to normal controls(P&lt;0.0001).In DMH-treated rat colon a shift of labelled cells to higher crypt cell positions was demonstrated distally whist a bi-directional shift was evident proximally(P&lt;0.05).CONCLUSION:Our results show that changes in cell proliferation patterns,as assessed by bromodeoxyuridine uptake,can act as a reliable intermediate marker of colonic cancer formation.Observed differences between proliferation patterns in distal and proximal colon may be associated with the higher incidence of tumors in t he distal colon.     

Variability of cell proliferation in the proximal and distal colon of normal rats and rats with dimethylhydrazine induced carcinogenesis

AIM: To investigate the patterns of cell proliferation inproximal and distal colons in normal rats and rats with 1,2-dimethylhydrazine (DMH) induced carcinogenesis using thethymidine analogue bromodeoxyuridine.METHODS: Colonic crypt cell proliferation wasimmunohistochemically detected using the anti-bromodeoxyuridine Bu20a monoclonal antibody.RESULTS: Marked regional differences were found in bothgroups. Total labelling index (LI) and proliferative zone sizein both normal (8.65±0.34 vs 7.2±0.45, 27.74±1.07 vs16.75±1.45) and DMH groups (13.13±0.46 vs 11.55±0.45,39.60±1.32 vs35.52±1.58) were significantly higher in distalthan in proximal colon (P＜0.05), although the number ofcells per proximal crypt was greater (31.45±0.20 vs34.45±0.39, 42.68±0.53 vs49.09±0.65, P＜0.0001). Crypt length,total LI and proliferative zone size all increased in both proximaland distal regions of DMH rats compared to normal controls(P＜0.0001). In DMH-treated rat colon a shift of labelled cellsto higher crypt cell positions was demonstrated distally whilsta bi-directional shift was evident proximally (P＜0.05).CONCLUSION: Our results show that changes in cellproliferation patterns, as assessed by bromodeoxyuridineuptake, can act as a reliable intermediate marker of coloniccancer formation. Observed differences between proliferationpatterns in distal and proximal colon may be associated withthe higher incidence of tumors in the distal colon.     

Development of renal hypertrophy and increased renal Na,K-ATPase in streptozotocin-diabetic rats

The effects of experimental diabetes on renal tubular Na,K-ATPase activity were measured 4, 7, 14, 21, 28, and 56 days after ip injection of streptozotocin (STZ; 60 mg/kg) in rats. Significant increases in serum and urinary glucose levels as well as urinary volume and electrolyte output were observed 24 h after STZ injection. The elevated serum and urinary glucose levels were maintained during the entire 8-week experimental period, while urinary volume and electrolyte output showed an initial rising phase, reaching a peak at approximately 2-3 weeks, followed by a stabilization phase at a level lower than the peak effect, but still significantly higher than that in the saline-citrate-treated controls. A significant increase (+25.3%) in renal outer medullary Na,K-ATPase activity was observed 4 days after the induction of STZ-diabetes, while similar increases were not observed in the cortical regions until after 7 days of experimental diabetes. These elevated renal cortical and outer medullary enzyme activities, however, were subsequently maintained during the entire 8-week experimental period. In addition, a similar time course of development of renal hypertrophy, as indicated by increases in kidney weights and kidney protein to DNA ratios, was observed after the induction of STZ-diabetes in rats. Therefore, the present data indicate that renal hypertrophy and increased renal Na,K-ATPase develop early and with a similar time course after induction of STZ diabetes in rats and may mediate the gradual amelioration of excessive renal electrolyte loss seen in this experimental condition. Since Na,K-ATPase-mediated ion transport is the major consumer of metabolic energy in the kidney and is centrally important to renal function, it is suggested that the early and pronounced increase in renal Na,K-ATPase seen in diabetes is an essential component of the renal hypertrophy and hyperfunction seen in this disease and may represent an important adaptive change in the kidneys in response to glucose osmotic diuresis in the experimental diabetic animals.     

Regional differences in the nitrergic innervation between the proximal and the distal colon in rats

Background & Aims: Functional differences in the inhibitory neural pathway between the proximal and the distal colon are unknown. Methods: We investigated the nonadrenergic, noncholinergic (NANC) relaxation, nitric oxide synthase (NOS) synthesis, and NOS messenger RNA (mRNA) expression of the myenteric plexus in the proximal and the distal colon in rats. Results: Transmural nerve stimulation of the neuromuscular preparations from the proximal colon showed greater NANC relaxations than those from the distal colon. NANC relaxations were abolished by the NO biosynthesis inhibitor (N^G-nitro-L-arginine methyl ester) in the proximal and the distal colon, suggesting mediation by NO released from the myenteric plexus. The average number of NOS-immunoreactive cells was significantly higher in the tissue from the proximal colon than in the tissue from the distal colon. Western and Northern blot analyses showed a higher density of the immunoreactive NOS band and the NOS mRNA band in the tissue from the proximal colon than in that from the distal colon. Conclusions: These observations indicate that the number of NOS-containing neurons and the NOS activity are increased in the myenteric plexus of the proximal colon compared with the distal colon, resulting in greater NANC relaxation in the proximal colon. These findings may explain the physiological role of the proximal colon as an organ for fecal storage and absorption of excess fluid.GASTROENTEROLOGY 1998;115:1504-1512     

Progressive histopathological changes in pancreatic islets of Zucker Diabetic Fatty rats.

Thus far, histopathological changes in the pancreatic islets of Zucker Diabetic Fatty (ZDF) rats, an animal model of type 2 diabetes mellitus (or non-insulin-dependent diabetes mellitus), have only been studied in male rats and in 18-weeks old rats or younger. In this study, we have examined in both male and female ZDF rats the histopathological changes longitudinally, from 6 to 32 weeks of age. We studied islet architecture and cellular distribution of the various islet hormones both in ZDF and control rats. In the ZDF rats, aging was initially associated with an enlargement of the islets. From 18 weeks onwards, no further enlargement was noted but islet boundaries became increasingly irregular, leading to the appearance of projections of endocrine cells into the surrounding exocrine tissue. At the islet boundaries as well as within the islets progressive fibrosis was observed with increasing amounts of collagen and reticular fibers. In the islets, staining intensity of both insulin and islet amyloid polypeptide (IAPP) increased slightly till 10 weeks of age and thereafter decreased rapidly. In contrast, the staining intensities of glucagon, somatostatin, and pancreatic polypeptide (PP) did not change. Even at the age of 32 weeks, just the beta-cells and not the other endocrine islet cells appear to be affected. In control rats, aging evoked only minor changes. Thus, we observed that during prolonged development of diabetes mellitus in both male and female ZDF rats histopathological changes in the pancreatic islets became progressively more severe, eventually leading to disintegration of the islets.     

Relevance of plasma,glandular and urinary kallikrein in renal hypertrophy in streptozotocin-diabetic rats

Summary The relevance of plasma, glandular and renal kallikrein as an intrarenal hemodynamic regulator, in renal hypertrophy, in 1–5 weeks streptozotocin diabetic rats has been investigated. The fasting plasma glandular kallikrein level significantly decreased with increasing duration of diabetes (p<0.05). Glandular kallikrein correlated negatively with kidney weight (r=0.76, p=0.05). The 24 hour urinary kallikrein excretion significantly increased with increasing duration of diabetes (p<0.05), but this level was not correlated with glucose level, nor with kidney weight. Aprotinin (a kallikrein inhibitor) injected (10×10³ KIU/kg) twice daily for 2 weeks in diabetic rats, significantly decreased plasma glucose levels by 28%, 24 hour urinary kallikrein by 37% (p<0.05) and kidney weight by 6%. These results suggest that plasma, glandular and renal kallikrein did not play an important role in the renal hypertrophy observed in streptozotocin diabetic rats.