Strain differences in susceptibility to streptozotocin-induced diabetes: effects on hypertriglyceridemia and cardiomyopathy

OBJECTIVE

Streptozotocin (STZ)-induced diabetes in Wistar rats results in severe hyperlipidemia and a characteristic cardiomyopathy. However, Wistar-Kyoto (WKY) rats made diabetic with a similar dose of STZ did not develop heart dysfunction or hypertriglyceridemia at 12 weeks post-STZ. We investigated whether an apparent resistance of the WKY strain to develop diabetic cardiomyopathy and hypertriglyceridemia following chronic diabetes could be due to a reduced susceptibility to the diabetogenic effects of STZ.

METHODS

Adult male WKY and Wistar rats were made diabetic with a moderate (55 mg/kg) or high (75 mg/kg) dose of STZ. At 6 weeks of diabetes, glucose tolerance, cardiac function, pancreatic insulin content and basal and post-heparin plasma lipolytic activity were determined.

RESULTS

Administration of a moderate dose of STZ produced cardiac dysfunction in Wistar but not WKY rats at 6 weeks after diabetes induction. The same dose of STZ in WKY rats also resulted in a lesser degree of hyperglycemia and glucose intolerance, and significantly higher pancreatic insulin content relative to Wistar rats. Following a high dose of STZ, the apparent resistance to developing cardiomyopathy was lost in the WKY rats. As well, the WKY rats demonstrated an equal degree of hyperglycemia and glucose intolerance as Wistar rats. However, unlike the Wistar strain, WKY rats did not demonstrate either hypertriglyceridemia or a reduced heparin-releasable plasma lipoprotein lipase (LPL) activity following a high dose of STZ.

CONCLUSIONS

These results suggest that the incidence of diabetes-related cardiomyopathy and hypertriglyceridemia in rats may be independently influenced by strain-dependent susceptibilities to the beta-cytotoxic effects of STZ. The absence of hypertriglyceridemia in severely diabetic WKY rats may be linked to the maintenance of a critical level of plasma LPL activity.

Value of cytology in detecting intestinal metaplasia and associated dysplasia at the gastroesophageal junction

Tissue sampling is essential for detecting intestinal metaplasia in the distal esophagus (Barrett's esophagus), because symptoms and endoscopy are not reliable in making this diagnosis. The utility of cytology in this process is unknown. All adult patients having elective upper gastrointestinal endoscopy over a 6-month period were invited to participate in a prospective study whose aim was to determine the prevalence of intestinal metaplasia in the distal esophagus in an adult population with diverse upper gastrointestinal symptoms. Clinical data and endoscopic findings were recorded. Brush cytology and biopsy specimens were obtained from both sides of the apparent squamocolumnar junction. The cytology specimens were processed routinely, stained with the Papanicolaou technique, and reviewed blinded to the clinical information and the histological findings in the corresponding biopsy specimens. One hundred fifty-five patients (81 women, 74 men; 137 whites, 11 blacks, 7 others; mean age, 52 years) were included. Glandular epithelium/cells were present on both histology and cytology in 147 specimens. Thirty-two patients (22%) showed intestinal metaplasia on histology. Of the cytology specimens from these 32 patients, 6 contained definite goblet cells (19%), 7 probable goblet cells, and 19 no goblet cells. Goblet cells and probable goblet cells were observed on cytology in 7 and 11 additional specimens, respectively. One was from a patient known to have intestinal metaplasia in the esophagus. Follow-up endoscopy with biopsy was performed in two of these latter 18 patients and did not show intestinal metaplasia. One case of high-grade dysplasia, two of low-grade dysplasia, and three indefinite for dysplasia were diagnosed on histology. All three cases of dysplasia were also identified on cytology. The three indefinite cases on histology were considered reactive in two and unremarkable in one on cytology. Low-grade dysplasia was diagnosed on cytology alone on two cases. Follow-up endoscopy with biopsy was performed in one patient, and low-grade dysplasia was found. Cytology using the Papanicolaou stain is not as sensitive and specific as histology for detecting intestinal metaplasia in the distal esophagus. However, it may be at least as useful as tissue sampling in detecting dysplasia.

Pathogenesis of peptic ulcer disease and current trends in therapy

Traditionally drugs used in peptic ulcer have been directed mainly against a single luminal damaging agent i.e. hydrochloric acid and a plethora of drugs like antacids, anticholinergics, histamine H2-antagonists etc. have flooded the market. An increase in 'aggressive' factors like acid and pepsin is found only in a minority of peptic ulcer patients. These factors do not alter during or after spontaneous healing. It is well-known that the gastric mucosa can resist auto-digestion though it is exposed to numerous 'insults' like high concentration of hydrochloric acid, pepsin, reflux of bile, spicy food, microorganisms and at times alcohol and irritant drugs. It is thus evident that the integrity of the gastric mucosa is maintained by defense mechanisms against these 'aggressive' damaging factors. Recently, attention has been focused more on gastroduodenal defense mechanisms leading to the concept of 'Cytoprotection'. The old dictum "no acid--no ulcer" now extends to "if acid--why ulcer"? as a fundamental question. During last decade more information has poured in about the prevalence and changing pattern of the disease, the influence of environmental factors and speculation on the role of a recently characterized bacterial organism, Helicobacter pylori which colonizes in the gastric mucosa, particularly the antral region. This review briefly describes current knowledge about the pathogenesis of peptic ulcer disease and discusses strategies for its treatment.

Prevalence and significance of pancreatic acinar metaplasia at the gastroesophageal junction

Pancreatic acinar metaplasia (PAM), defined as nodules of glandular tissue forming acini composed of cells with coarse apical eosinophilic granules, with or without mucous cells, was recently recognized in gastric mucosa, but its significance is not known. As part of a study on intestinal metaplasia at the gastroesophageal junction (GEJ), we evaluated the prevalence and clinical and histologic correlates of PAM in biopsy specimens from the gastroesophageal squamocolumnar junction. All adult patients having elective upper gastrointestinal endoscopy over a 6-month period were invited to participate. Clinical data and endoscopic findings were recorded. Biopsy specimens, obtained from both sides of the apparent squamocolumnar junction, were processed routinely and reviewed (without knowledge of the clinical data) to evaluate types of epithelium, types and degree of inflammation, and the presence of PAM. The presence or absence of PAM was then correlated with the other histologic findings and with the clinical and endoscopic data. The study comprised 155 patients (79 women, 76 men; 139 white patients, nine black patients, and seven patients of other ethnic groups). Their mean age was 52 years (range: 18-89 years). PAM was present in 37 patients (24%). PAM was not associated with any of the reported symptoms, endoscopic evidence of esophagitis or columnar epithelium in the distal esophagus, or any of the histologic features evaluated, including active esophagitis, intestinal metaplasia at the GEJ, active and chronic gastritis, intestinal metaplasia in the stomach, and Helicobacter infection. Although PAM is present in a considerable proportion (24%) of patients with mucosal biopsy specimens from the squamocolumnar junction, it appears to be an incidental finding unrelated to clinical or histologic abnormalities. We therefore suggest a congenital, rather than an acquired, origin for this entity.

Effects of chronic treatment with lisinopril on cardiovascular complications in streptozotocin diabetic and DOCA hypertensive rats

The present study was undertaken to study the effects of chronic treatment with lisinopril on the cardiovascular complications in streptozotocin (STZ) diabetic and deoxycorticosteroneacetate (DOCA) hypertensive rats. Injection of STZ produced severe glycosuria (> 2%), hyperglycemia, hypoinsulnaemia, polydypsia, polyphagia and loss of body weight. It also produced hypothyroidism, hypercholesterolaemia, hypertriglyceridaemia, hypertension, bradycardia and decreased left ventricular developed pressure (LVDP). Elevation in serum creatinine level and increased activity of liver enzymes were also found in STZ treated animals. DOCA by itself did not produce any change in blood glucose but reduced serum insulin levels in non-diabetic animals. However, in the diabetic group, DOCA reduced blood sugar levels. Treatment of STZ-diabetic rats with DOCA did not aggravate cardiac depression or hyperglycaemia. Treatment of rats with lisinopril (1 mg kg-1, p.o. daily for six weeks), in diabetic and diabetic hypertensive animals prevented STZ induced loss of body weight and hypertension, bradycardia and hypothyroidism. It also prevented STZ induced hyperglycemia and hypoinsulinaemia in both diabetic and diabetic hypertensive animals. There was a reduction in cholesterol, triglyceride, and LDL levels; the ratio between total cholesterol to HDL and LDL to HDL and an improvement in LVDP at higher filling pressure in diabetic as well as diabetic hypertensive animals. Treatment with lisinopril also prevented hypertrophy and elevated levels of serum creatinine, SGOT and SGPT in diabetic animals. In conclusion, the present data suggests that STZ-DOCA model may not be considered as the ideal model for the study of cardiovascular complications of combined treatment hypertension and diabetes. However, the present investigation presents a number of beneficial effects of lisinopril treatment in diabetic with or without hypertensive rats and it may be considered as one of the drugs of choice in treatment of hypertension when it is associated with diabetes mellitus.

Hodgkin disease after renal transplantation in childhood

PURPOSE

Hodgkin disease (HD) has rarely been described in organ transplant recipients. We herewith report two cases of Epstein Barr virus (EBV)-associated HD that occurred in renal transplant recipients during childhood.

PATIENTS

A 19-year-old who had a renal transplant at 12 years of age developed mixed cellularity HD 1 year following diagnosis of an EBV-associated lymphoproliferative disorder. The second case is an 18-year-old man who developed nodular sclerosing HD 7 years after renal transplantation.

RESULTS

EBV latent membrane protein-1 antigen was strongly expressed in the Hodgkin Reed-Sternberg cells in both cases. These patients achieved complete remission with standard chemotherapy without unusual toxicity.

CONCLUSIONS

Renal transplant recipients on immunosuppressive therapy can develop Hodgkin disease. A review of literature on this subject with emphasis on recent molecular studies on EBV-associated cases and observed increase in incidence of HD in HIV seropositive individuals is presented.

Caffeine- and carbachol-induced Cl- and cation currents in single opossum esophageal circular muscle cells

Cl- and cation currents may play important roles in esophageal smooth muscle membrane potential changes and contraction. We studied Ca2+ release-activated cell-shortening and membrane currents in single cells freshly dispersed from the circular muscle of the opossum esophagus using the standard patch-clamp whole cell recording method. Caffeine (10-20 microM) and carbachol (10-100 microM) shortened the single smooth muscle cells by releasing intracellular Ca2+. At a holding potential of 0 mV, spontaneous transient outward currents STOCs, representing spontaneous Ca(2+)-activated K+ currents) were recorded. Caffeine, carbachol, or ionomycin evoked large outward currents (up to 1,650 pA) and subsequently abolished STOCs. At a holding potential of -50 mV in K(+)-containing solutions, an outward current in response to the agonists was observed; in some cells, the outward current followed an inward current. In K(+)-free solutions, the agonists induced only an inward current whose reversal potential was shifted by alteration of the anion gradient but not by that of the cation. With a low-Cl- pipette solution (Cl- substituted by glucuronate or glutamate), the inward currents were dependent mainly on the external cation gradient. This cation channel was permeable to Ba2+. Inclusion of 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid in the pipette solution abolished all these currents. These data suggest that in the opossum esophageal circular muscle 1) Ca2+ released from the intracellular stores by caffeine and carbachol is sufficient to induce single smooth muscle cell contraction and 2) the caffeine-, carbachol-, and ionomycin-induced membrane currents consist of Ca(2+)-activated K+, Cl-, and cation conductances.

Effect of chronic treatment with atenolol and prazosin in streptozotocin induced diabetic rats

Diabetes-mellitus was induced in rats by single intravenous injection of (45 mg/kg) streptozotocin (STZ). STZ diabetic rats showed hypertension, decreased cardiac functions, cardiomyopathy and hypercholesterolemia observed at the end of six weeks. Chronic treatment with atenolol (10 mg/kg) for six weeks in the diabetic rats reduced the elevated blood pressure, but failed to prevent STZ induced other complications. Chronic treatment with prazosin (1 mg/kg, po) in the diabetic rats, reduced the elevated blood pressure and also partially prevented hypercholesterolemia, cardiac dysfunctions and in particular the cardiomyopathy. The results suggest that prazosin may be a better option as compared to atenolol in hypertension when it is associated with diabetes mellitus.

Neuronal constitutive nitric oxide synthase is involved in murine enteric inhibitory neurotransmission

Mice lacking neuronal nitric oxide synthase gene (ncNOS) were used to determine the enzymatic source of nitric oxide (NO) and its relationship with other putative inhibitory neurotransmitters. Inhibitory junction potentials (IJP) of circular smooth muscle of gastric fundus were studied. The IJP in the wild-type mice consists of overlapping components, the fast and slow IJPs. NOS inhibitor L-NA or VIP receptor antagonist VIP(10-28), blocks the slow IJP but not the fast IJP. The fast UP is blocked by alpha-beta methylene ATP tachyphylaxis, by reactive blue 2, and by apamin. The IJP in the ncNOS-deficient [ncNOS(-)] mutant is of short duration and is abolished by blockers of the fast IJP, but is unaffected by blockers of the slow UP. Exogenous VIP produces membrane hyperpolarization in strips from wild-type but not ncNOS(-) mice. The hyperpolarizing action of VIP is resistant to nifedipine but is sensitive to omega-conotoxin GVIA.

IN CONCLUSION

(a) NO derived from ncNOS is an inhibitory neurotransmitter rather than a postjunctional mediator; (b) VIP is a prejunctional neurotransmitter that causes release of evanescent NO; and (c) ATP acts in parallel with the VIP/NO pathway.

Tyrosine kinase-dependent modulation of calcium entry in rabbit colonic muscularis mucosae

We studied the role of tyrosine kinase in the regulation of Ca2+ entry in single smooth muscle cells of the rabbit colonic muscularis mucosae using the whole cell patch-clamp technique. Step depolarization to +10 mV from a holding potential of -60 mV produced inward currents that were abolished by 1 microM nifedipine, consistent with the activation of L-type Ca2+ channels. The tyrosine kinase inhibitors, genistein and tyrphostin B42, dose dependently inhibited these Ca2+ currents. The inactive analogue of tyrphostins, tyrphostin A1, did not affect the currents at concentrations of up to 100 microM. Conversely, the tyrosine phosphatase inhibitor, orthovanadate, enhanced peak Ca2+ currents by 30%. Spontaneous transient outward currents (STOCs) (50-600 pA) were elicited with high K+ in the pipette and at 0-mV holding potential. STOCs were activated due to release of Ca2+ from intracellular stores, required the presence of extracellular Ca2+ concentration, and were insensitive to nifedipine. Genistein abolished STOCs; however, in its presence, outward currents activated by caffeine or carbachol were not affected. The refilling of the Ca2+ stores was studied by first depleting intracellular Ca2+ with carbachol in Ca(2+)-free media followed by reperfusing with a Ca(2+)-containing solution for 3-5 min. Under these conditions, a second application of carbachol evoked an outward current due to Ca2+ release. However, this effect was abolished when the refilling of the stores was carried out in the presence of genistein. Carbachol-evoked currents were not attenuated when the refilling was examined in the presence of orthovanadate. Epidermal growth factor (200 ng/ml) enhanced Ca2+ currents by 60% and markedly increased STOCs by over 200%. Western blot analysis, using an anti-phosphotyrosine antibody, showed a tyrosine phosphorylated protein of 60 kDa in control conditions. This was markedly increased after treatment with epidermal growth factor and carbachol. These results suggest that 1) tyrosine kinase modulates the entry of Ca2+ through L-type channels and through nifedipine-resistant pathways involved in refilling of intracellular stores and 2) stimulation of the kinase by agonists enhances Ca2+ entry in the smooth muscle cells of the rabbit colonic muscularis mucosae.

Synthesis and quantitative structure-activity relationships of antihyperlipaemic 2-substituted thieno[3,2-d]pyrimidin-4(3H)-ones

The synthesis, antihyperlipaemic evaluation and quantitative structure-activity relationships (QSAR) of two series of thieno[3,2-d]pyrimidin-4-one derivatives are reported. While most of the compounds in these series were found to exhibit antihyperlipaemic activity, the QSAR study of these two series indicated a positive influence of only the electronic nature of the 2-substitutents on the biological activity. The lipophilic and the steric parameters did not appear to be significant.

Effect of chronic treatment with hydralazine on various in vitro preparations of rat

Effect of chronic treatment with hydralazine (40 mg/kg/day) on isolated heart, anococcygeus muscle and myometrial preparations from rats has been studied. The treatment for 6 weeks caused a significant increase in isoprenaline induced positive inotropic response in rat heart. However, isoprenaline induced positive chronotropic effects were not altered significantly by chronic hydralazine treatment. Chronic hydralazine treatment also failed to alter noradrenaline induced contractile effects on rat anococcygeus muscle. However, on myometrial preparations from hydralazine treated rats showed an increase in adrenaline induced relaxations. The results of the present study can be explained on the basis of the effect of hydralazine on adenylate cyclase-cyclic adenosine monophosphate (cAMP).

Effects of enalapril on lipid profile in diabetic and non-diabetic essential hypertensive patients

Effectiveness of enalapril was studied in hypertensive patients with or without diabetes-mellitus. All the patients received enalapril, 5-20 mg per day for 9 months. Enalapril effectively controlled the blood pressure and favourably altered the lipid levels and did not affect the glucose level in diabetics as well as non-diabetics. Enalapril may be considered as a better therapeutic option for the treatment of hypertension associated with diabetes mellitus.

Investigation into the possible mechanisms involved in altered digoxin levels in diabetic patients

The present study was undertaken to investigate the possible factors which may contribute to the altered digoxin levels in diabetic patients. The digoxin levels were found to be significantly higher in diabetics (1.74 +/- 0.09 ng/ml) as compared to non-diabetics (0.76 +/- 0.07 ng /ml). There was a positive correlation between digoxin levels and glycosylated haemoglobin levels. All diabetic patients had serum creatinine, urea and potassium levels within normal limits. However, serum TSH levels were found to be significantly higher in diabetics as compared to controls. Serum tri-iodo-1-thyronine (T3) levels were found to be lower in diabetics as compared to non-diabetics. Our data suggests that diabetes-mellitus causes alteration of digoxin levels. One of the causes of this increase in digoxin levels may be a tendency towards mild hypothyroidism associated with diabetes mellitus.

Heartburn in patients with achalasia

Heartburn, the main symptom of gastrooesophageal reflux disease (GORD), might be expected to occur infrequently in achalasia, a disorder characterised by a hypertensive lower oesophageal sphincter (LOS) that fails to relax. Nevertheless, it is often described by patients with achalasia. The medical records of 32 patients with untreated achalasia who complained of heartburn, and of 35 similar patients who denied the symptom, were reviewed to explore the implications of heartburn in this condition. Data on endoscopic and manometric findings, and on the onset and duration of oesophageal symptoms were collected. Three patterns of heartburn were observed: (1) in 8 patients (25%) the onset of heartburn followed the onset of dysphagia, (2) in 15 patients (47%) heartburn preceded the onset of dysphagia and persisted as dysphagia progressed, and (3) in 9 patients (28%), heartburn preceded the onset of dysphagia and stopped as dysphagia progressed. The mean (SD) basal LOS pressure in the patients with heartburn (38 (16) mm Hg) was significantly lower than that in patients without the symptom (52 (26) mm Hg); the lowest LOS pressure (29 (11) mm Hg) was observed in the subset of patients whose heartburn preceded the onset of dysphagia and then stopped. It is concluded that patients who have achalasia with heartburn have lower basal LOS pressures than patients who have achalasia without this symptom. In some patients with achalasia, the appearance of dysphagia is heralded by the disappearance of longstanding heartburn. For these patients, it is speculated that achalasia develops in the setting of underlying GORD.

Gastric and duodenal anti-ulcer activity of SKF 38393, a dopamine D1-receptor agonist in rats

The effect of SKF 38393 (1-phenyl-7,8-diol-2,3,4,5-tetrahydro-1H-3-benzazepine), a specific dopamine D1-receptor agonist, was studied on pylorus-ligation and water immersion plus restraint stress-induced gastric ulcers, and cysteamine-induced duodenal ulcers in rats. Repeated administration of SKF 38393 (5 and 10 mg kg-1, p.o.) for six days was found to be effective in the prevention of gastric ulceration induced by water immersion plus restraint stress in rats. In 19-h pylorus-ligated rats, repeated treatment with SKF 38393 showed a significant reduction in the number and severity of ulcers. SKF 38393 did not alter the total gastric-mucosal carbohydrates:protein ratio; however, the gastric content volume and the free and total acidity were significantly reduced. In cysteamine-induced duodenal ulcers, the treatment with SKF 38393 for 6 days prevented the duodenal lesions. Our data suggests the involvement of dopamine D1 receptors in the anti-ulcer activity of SKF 38393, which could be largely attributed to its anti-secretory effect. Its anti-ulcer activity against water immersion plus restraint, also points towards a central mode of action, but its failure to alter the carbohydrate:protein ratio rules out any protective effect through the strengthening of the gastric mucosal barrier.

Effects of chronic nifedipine treatment on streptozotocin-induced diabetic rats

We studied the effects of 6-week treatment with nifedipine (35 mg/kg/day orally, p.o.) on streptozotocin (STZ)-induced diabetic rats. Injection of STZ [45 mg/kg intravenously, (i.v.) single dose] produced a significant increase in blood pressure (BP), bradycardia, hyperglycemia, hypoinsulinemia, hyperlipidemia, hypothyroidism, depression in left ventricular developed pressure (LVDP), cardiomyopathy, and nephropathy. Treatment of diabetic rats with nifedipine normalized the BP and prevented bradycardia. Insulin levels were decreased after nifedipine treatment in diabetic as well as nondiabetic rats. However, serum glucose levels were also partially decreased in diabetic animals by nifedipine treatment. In control animals as well, glucose levels were in the normal range despite lower insulin levels observed after nifedipine treatment. Nifedipine treatment significantly prevented STZ-induced increase in cholesterol and triglyceride levels. Nifedipine treatment significantly prevented STZ-induced hypothyroidism and also prevented STZ-induced cardiac depression and cardiomyopathy. Our data indicate that nifedipine increases insulin sensitivity and has some beneficial effects on cardiovascular parameters. It may therefore be considered a preferred drug in the treatment of hypertension associated with diabetes mellitus.

Comparative effects of atenolol versus nifedipine on serum lipids and other biochemical parameters in diabetic and non-diabetic hypertensive subjects

A controlled clinical trial on 65 patients was performed to compare the effects of nifedipine and atenolol in diabetic and non-diabetic hypertensive patients. Patients were from 45 to 70 years in age. The diabetic hypertensive patients and non-diabetic essential hypertensive patients randomly received atenolol (50-100 mg per day) or nifedipine (10-20 mg per day) for 9 months. Both the drugs effectively controlled the blood pressure throughout the therapy. Atenolol treatment significantly increased triglyceride levels and decreased the HDL-cholesterol levels after 9 months in both groups. However, nifedipine therapy did not alter lipid levels to any significant extent. Both drugs did not alter blood glucose, serum creatinine and blood urea levels. It may be concluded from the present study that nifedipine is preferable to atenolol as it does not alter lipid profile to any significant extent in diabetic and non-diabetic hypertensive patients.

Transient outward current in opossum esophageal circular muscle

The whole cell patch-clamp technique was used to record a transient outward K+ current (ITO) from single smooth muscle cells isolated from opossum esophageal circular muscle. The threshold for its activation was -50 mV from holding potentials negative to -70 mV. The current peaked within 10 ms and decayed completely in 200 ms between test depolarization of -40 and -10 mV. ITO was recorded at room temperature in the presence of 5 mM internal ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid. Both activation and inactivation kinetics of ITO were markedly changed when recordings were made at higher temperatures (32 degrees C). 4-Amino-pyridine (4-AP, 3 mM) abolished the fast component of the outward current. Tetraethylammonium ion (TEA, 1-30 mM) reduced the sustained component but did not affect ITO. In the presence of TEA and nifedipine, the voltage dependence of the steady-state inactivation data was well fitted by a Boltzmann distribution with a half-inactivation potential of -57 mV. The half-inactivation potential was shifted to a more positive potential in the presence of Cd2+ (-35 mV). The steady-state inactivation and activation data overlap between -50 and -30 mV, suggesting the presence of a "window" current in this potential range. In current-clamp mode, 4-AP depolarized single esophageal cells by approximately 8 mV and shifted the upstroke of the action potential to the left. These results indicate that, in the esophageal circular muscle, ITO is involved in the resting membrane potential and modulation of the onset of action potential.

Acyclovir-induced neutropenia in an infant with herpes simplex encephalitis: case report

A newborn infant whose condition was diagnosed as herpes simplex encephalitis and who had subsequent recurrences of skin disease had repeated episodes of neutropenia while receiving therapy with intravenous (30 mg/[kg.d]) or oral (30 mg/]kg.d]) acyclovir. The neutropenia did not recur when the dosage of oral acyclovir was reduced to 10 mg/(kg.d). This case represents the first well-documented report of acyclovir-induced neutropenia.

Involvement of K+ channels in the relaxant responses to various agonists in estrogen primed rat uterus

The present investigation was undertaken to study the effects of K+ channel openers in the relaxant responses to various agonists in estrogen primed rat uterus. Adrenaline and isoprenaline produced a dose-dependent relaxation in the estrogen primed rat uterus. The relaxant responses were found to be significantly potentiated when the preparations were exposed to PSS devoid of calcium. The responses to isoprenaline were found to be greater in the preparations depolarized with 40 mM KCl instead of 80 mM KCl. KCl failed to produce any contractile effect in the presence of D-600. Further, the addition of D-600 completely relaxed the KCl depolarized rat uterus. Pinacidil and cromakalim failed to relax 80 mM KCl depolarized rat uterus. However, they produced dose-dependent relaxation in the preparations depolarized with 40 mM KCl. The relaxant responses to pinacidil and cromakalim were competitively blocked by procaine. However, they were not altered by either propranolol or cimetidine. The relaxant responses to isoprenaline and histamine were found to be potentiated by pinacidil and cromakalim. These results indicate that in rat uterus in addition to adenylate cyclase c-AMP, potassium channels are also involved in the relaxant responses to isoprenaline and histamine.

Muscarinic suppression of ATP-sensitive K+ channel in rabbit esophageal smooth muscle

Smooth muscle cells from the rabbit esophageal muscularis mucosae were studied for the presence of ATP-sensitive K+ channel (KATP) and its inhibition by carbachol. Lemakalim (10 microM), a synthetic K+ channel opener, increased whole cell currents by -174 +/- 15 pA with 0.1 mM intracellular ATP concentration ([ATP]i) and -70 +/- 11 pA with 5 mM [ATP]i. Glibenclamide (10 microM) completely abolished the lemakalim-induced currents. These currents were therefore denoted as KATP. Carbachol (10 microM) suppressed KATP by 74 +/- 4% with 10 mM intracellular ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) concentration and 100% when EGTA was omitted from the pipette solution. Carbachol suppression was attenuated to 23 +/- 16% by the M3 receptor antagonist, p-flurohexahydrosiladifenidol (0.1 microM). KATP was also suppressed by phorbol 12-myristate 13-acetate (PMA; 100 nM) by 63 +/- 9%. The effects of both PMA and carbachol were significantly reduced by inhibitors of protein kinase C and tyrosine kinase. These results suggest that carbachol suppression of KATP is via M3 receptor subtype and the signaling pathway involves Ca2+, protein kinase C, and tyrosine kinase.

Prevalence of metaplasia at the gastro-oesophageal junction

Specialised columnar epithelium (SCE), a form of intestinal metaplasia usually found in Barrett's oesophagus, cannot be distinguished endoscopically from normal gastric epithelium. Endoscopists seldom obtain biopsy specimens from a normal-appearing gastro-oesophageal junction, and therefore short segments of SCE in this region may go unrecognised. We studied patients who had short segments of SCE at the gastro-oesophageal junction. All patients scheduled for elective endoscopic examinations in our general endoscopy unit, irrespective of indication, were questioned for symptoms of gastro-oesophageal reflux disease. At endoscopy, severity of oesophagitis was graded, and biopsy specimens obtained from the squamocolumnar junction, irrespective of its appearance or location in the oesophagus. Among 142 patients without endoscopically apparent Barrett's oesophagus, 26 (18%) were found to have SCE. All patients with SCE were white, and the male/female ratio was 1.9. In contrast, non-whites accounted for 14% of the 114 patients without SCE and the male/female ratio was 0.8. The groups did not differ significantly in the frequency of symptoms and endoscopic signs of gastrooesophageal reflux. We conclude that adults frequently have unrecognised segments of SCE at the gastro-oesophageal junction; this may underlie the rising frequency of cancer of the gastrooesophageal junction in the USA and Europe.

Nitrinergic and peptidergic innervation of the human oesophagus

The distribution, colocalisation, and interconnections of nitrinergic and peptidergic neurons and nerves in the human oesophagus were examined. Cryosections of surgically resected tissues from eight subjects were studied with indirect immunofluorescence for the presence of 11 neuropeptides and neuron specific enolase. After immunohistochemistry, nitric oxide synthase was shown on the same sections with the beta nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemical reaction. The histochemical findings were verified immunohistochemically on other sections with an antiserum against nitric oxide synthase. Most myenteric neurons (55%) were nitrinergic. Most (96%) received terminations positive for vasoactive intestinal polypeptide (VIP), calcitonin gene related peptide (CGRP) (80%), and galanin (59%). The neuronal somata of 14% also contained VIP, while 10% had galanin. Of the NADPH-diaphorase containing fibers seen in the muscle layers, many had closely associated VIP and galanin, but only rarely CGRP and substance P. Thus, despite abundant representation of both peptidergic and nitrinergic systems in oesophageal smooth muscle, only VIP and galanin colocalised to any significant extent with the nitrinergic elements. These findings provide morphological support for the role of nitric oxide as the non-adrenergic non-cholinergic inhibitory mediator in the human oesophagus and for its possible interactive role with the peptidergic system.

Innervation of the larynx, pharynx, and upper esophageal sphincter of the rat

We identified a 'semicircular' compartment of the rat thyropharyngeus muscle at the pharyngoesophageal junction and used the glycogen depletion method to determine how the fibers of this muscle (as well as all others of the pharynx and larynx) are innervated by different cranial nerve branches. The semicircular compartment appears anatomically homologous to the human cricopharyngeus muscle, an important component of the upper esophageal sphincter. While we found very little overlap in the muscle targets of the pharyngeal, superior laryngeal and recurrent laryngeal nerves within the pharynx and larynx, the semicircular muscle receives a dual, interdigitating innervation from two vagal branches: the pharyngeal nerve and a branch of the superior laryngeal nerve we call the dorsal accessory branch. After applying horseradish peroxidase to either of these two nerves, we compared the distribution and number of cells labeled in the brainstem. The dorsal accessory branch conveys a more heterogeneous set of efferent fibers than does the pharyngeal nerve, including the axons of pharyngeal and esophageal motor neurons and parasympathetic preganglionic neurons. The observed distribution of labeled motor neurons in nucleus ambiguus also leads us to suggest that the semicircular compartment is innervated by two subsets of motor neurons, one of which is displaced ventrolateral to the main pharyngeal motor column. This arrangement raises the possibility of functional differences among semicircular compartment motor neurons correlated with the observed differences in brainstem location of cell bodies.

Hypozincemia in diabetes mellitus

The present study was conducted on 20 age and sex matched healthy controls and 30 patients of diabetes mellitus. Serum zinc levels in diabetics were found to be significantly (p < 0.001) reduced as compared to healthy controls. There was no significant sex difference (P > 0.05) in serum zinc levels amongst diabetic patients and healthy controls. Hypozincema in diabetes mellitus may be due to altered zinc metabolism and oral zinc may have a role in therapy.

Evidence for catecholamine-depleting action of fluoxetine

The present investigation was undertaken to study the interaction of fluoxetine with 5-hydroxytryptamine (5-HT) and noradrenaline (NA) in rat anococcygeus muscle and vas-deferens. In rat anococcygeus muscle responses to NA were significantly potentiated after 30 min and 60 min incubation with fluoxetine (2.9 x 10(-9) M). The responses to 5-HT were however, inhibited after 30 min incubation with fluoxetine in this preparation. On rat vas-deferens also, the responses to NA were potentiated after 30 min incubation with fluoxetine. The response to 5-HT were not altered significantly. In rats pretreated with fluoxetine (5 mg/kg, ip) for seven days, the responses to NA were significantly potentiated in rat anococcygeus muscle. Whereas the responses to 5-HT and tyramine were significantly inhibited. The inhibited responses to 5-HT restored back to normal when the anococcygeus muscle was pre-incubated with NA for 30 min.

Effect of sodium nitroprusside on Ca2+ currents in opossum esophageal circular muscle cells

The effects of sodium nitroprusside (SNP) on ionic currents in single opossum esophageal circular muscle cells were examined. In voltage clamp, Ca2+ currents were studied after K+ currents were blocked with Cs+ in the patch pipette. The threshold for inward Ca2+ currents was -30 mV with peak current between 0 and +10 mV from holding potentials of -90 mV. The Ca2+ currents had both transient and sustained phases. The transient phase was partially resistant to nifedipine (1 microM). SNP (100 microM) reversibly decreased both the transient and sustained phases of the Ca2+ currents by approximately 20%. In cells dialyzed with high-K+ solutions, voltage-clamp recordings demonstrated the presence of an inward current followed by an outward current at potentials positive to -30 mV. SNP under these conditions resulted in a decrease in the Ca2+ current and decreased the outward current during test depolarizations. Action potentials were evoked during current-clamp recordings that consisted of multiple spikes, depending on the stimulus strength. The threshold for spike generation was close to -30 mV and was blocked by Cd2+, suggesting that the upstroke of the action potential was dependent on Ca2+ influx. SNP significantly attenuated action potentials and produced a small hyperpolarization (5-7 mV). These results suggest that SNP has a direct inhibitory effect on Ca2+ currents and thereby decreases evoked action potentials, and that SNP hyperpolarization is not due to Ca(2+)-activated K+ channels.

Effects of hydralazine on cardiac responsiveness to adrenergic agonists in streptozotocin-induced diabetic rats

The present investigation was undertaken to study the effects of hydralazine treatment (50 mg/kg/day, p.o.) on methoxamine and isoproterenol-induced responses in cardiac preparations of control and streptozotocin (STZ)-induced diabetic rats. Triiodothyronine (T3) and thyroxine (T4) levels were found to be significantly decreased in diabetic rats and this decrease was prevented by hydralazine treatment. Methoxamine and isoproterenol produced a dose-dependent positive chronotropic and positive inotropic effect in right and left atrium respectively. These responses to methoxamine were significantly increased, whereas, those to isoproterenol were significantly decreased in preparations obtained from diabetic rats. Hydralazine treatment did not alter the isoproterenol-induced chronotropic effect in right atrium. However, it prevented the diabetes-induced increase in responsiveness to methoxamine in this preparation. Hydralazine increased significantly the inotropic response to methoxamine and isoproterenol in left atrium of control and diabetic rats. Both the pD2 value and maximum response were increased. The studies indicates that hydralazine-induced alterations in the responsiveness to methoxamine could partly be due to its ability to prevent diabetes-induced hypothyroidism. The effects of hydralazine on isoproterenol-induced responses appear to be independent of hypothyroidism, and some post-receptor mechanisms and metabolic derangements might be responsible for this effect.

Biphasic effect of SNP on opossum esophageal longitudinal muscle: involvement of cGMP and eicosanoids

Effects of nitric oxide (NO)-containing compounds on opossum esophageal longitudinal smooth muscle in vitro were examined. Sodium nitroprusside (SNP) and authentic NO produced a biphasic concentration-dependent relaxation-contraction sequence in the esophageal longitudinal muscle (ELM) but only a concentration-dependent relaxation of the lower esophageal sphincter (LES) and no effect in the esophageal circular muscle. A cell membrane-permeable analogue of guanosine 3',5'-cyclic monophosphate (cGMP), 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) also produced relaxation-contraction sequence in the ELM and relaxation of the LES. The guanylate cyclase inhibitors methylene blue (MB) and LY-83583 increased resting tone and had no significant effect on SNP-induced relaxation of ELM. However, they abolished the SNP- and NO-induced contraction of ELM. The cyclooxygenase inhibitor indomethacin had no effect on ELM relaxation and abolished the contractions due to SNP, NO, and 8-BrcGMP. These studies show that in the ELM 1) SNP, authentic NO, and 8-BrcGMP cause a biphasic relaxation-contraction sequence; 2) MB and LY-83583 blocked contraction but not the relaxation associated with SNP and NO; and 3) indomethacin blocked contractions but not the relaxation due to SNP, NO, and 8-BrcGMP. These results suggest that in the ELM, NO donors exert an inhibitory action that is largely cGMP independent and an excitatory action via a cGMP-dependent pathway involving endogenous eicosanoids of the cyclooxygenase pathway.

The role of cricopharyngeus muscle in pharyngoesophageal disorders

The cricopharyngeus muscle is generally thought to be responsible for the high pressure zone of the pharyngoesophageal (upper esophageal) sphincter. In this review we critically examined the evidence for the role of the cricopharyngeus muscle in the manometric pharyngoesophageal sphincter. The available studies show disparities between the anatomic location of the cricopharyngeus muscle and the manometric high pressure zone of the pharyngoesophageal sphincter. The cricopharyngeus muscle seems to correspond to the distal 1/3 of the sphincteric high pressure zone and the peak high pressure zone appears to be located proximal to the cricopharyngeus muscle. The discrepancy between the upper high pressure zone and the anatomic cricopharyngeus is important in understanding the role of the cricopharyngeus muscle in the pathophysiology and treatment of clinical disorders of the pharyngoesophageal sphincter.

Nitric oxide involvement in the peptide VIP-associated inhibitory junction potential in the guinea-pig ileum

1. Intracellular membrane potential recordings were made from circular smooth muscle cells of the guinea-pig ileum in the presence of atropine (1 microM) and nifedipine (0.1 microM) at 30 degrees C. 2. Electrical field stimulation with one or four pulses produced a fast inhibitory junction potential (IJP) which lasted around 1 s. It was abolished by tetrodotoxin (1 microM), apamin (0.3 microM), and alpha, beta-methylene ATP tachyphylaxis. 3. Nitric oxide synthase inhibitor N-nitro-L-arginine (L-NNA; 200 microM) had no effect on the resting membrane potential or the fast IJP. 4. Electrical field stimulation in the presence of apamin and substance P desensitization produced a slow IJP which was abolished by tetrodotoxin (1 microM). 5. L-NNA significantly reduced the amplitude of the slow IJP (P < 0.01). The antagonistic effect of L-NNA was reversed by L-arginine but not by D-arginine. 6. Injections of alpha, beta-methylene ATP, nitric oxide (NO), and vasoactive intestinal polypeptide (VIP) into the recording chamber caused tetrodotoxin-resistant hyperpolarizations of the smooth muscle membrane. Substance P desensitization did not modify the amplitudes of the hyperpolarizing response to ATP or NO, but increased the VIP hyperpolarization by 150% (P < 0.01). 7. L-NNA did not modify the amplitude of hyperpolarization due to ATP or NO; however, it antagonized VIP-induced hyperpolarization (P < 0.01). 8. These studies show that in the guinea-pig ileum circular muscle: (a) NO is not involved in the fast IJP which is mediated by ATP; (b) NO is involved in the slow IJP which is mediated by VIP and NO acting in series, and (c) the hyperpolarizing effects of VIP and the slow IJP are normally masked by overlapping depolarization due to concomitant release of substance P by the peptide VIP.

Differential sensitivity to bradykinin of esophageal distension-sensitive mechanoreceptors in vagal and sympathetic afferents of the opossum

1. Single-unit activity was recorded from afferent fibers in the cervical vagus and thoracic sympathetic nerves in the opossum. Seventy-six fibers that responded to balloon distension (100 mmHg for 10 s) of the smooth muscle portion of the esophagus were selected for further study. 2. Forty-nine distension-sensitive afferents were identified in the vagus nerve. The stimulus response function (SRF) of 41 fibers behaved as "low-threshold mechanoreceptors" (LTM), with mean threshold value of 0.29 +/- 0.17 mmHg and saturation pressure of 50-70 mmHg. All fibers demonstrated background activity, with a mean rate of 8.83 +/- 0.93 imp/s (range 0.5-31.25). 3. Twenty-seven distension-sensitive afferents were identified in the thoracic sympathetic chain (T6-T8) and splanchnic nerve. The SRF study revealed two types of fibers: 1) a wide-dynamic-range mechanonociceptor (WDRMN) with a mean response threshold of 3.43 +/- 0.90 mmHg (n = 15) and 2) a "high-threshold mechanonociceptor" (HTMN) with a mean response threshold of 34.93 +/- 2.70 mmHg (n = 12). The mean background activities of WDRMN and HTMN fibers were 0.5 +/- 0.13 and 0.20 +/- 0.08 imp/s, respectively. Both of these fibers had saturation pressures of > 120 mmHg. 4. The conduction velocities were measured in 14 LTM, 10 WDRMN, and seven HTMN fibers. The mean conduction velocity of LTM fibers was 5.03 +/- 1.35 m/s (range 0.97-18.00), with five unmyelinated "C"-fibers (< 2.5 m/s) and nine A-delta fibers (> 2.5 m/s). The mean conduction velocity of WDRMN fibers was 3.64 +/- 0.84 m/s (range 1.10-8.25), consisting of five C-fibers and five A-delta fibers. The mean conduction velocity of HTMN fibers was 6.22 +/- 2.35 m/s (range 1.73-24.66); three fibers were unmyelinated C-fibers, and four fibers were A-delta fibers. 5. The sensitivity to bradykinin (BK) administered systemically (1-300 micrograms/kg) was tested in LTM (n = 34), WDRMN (n = 15), and HTMN (n = 8) fibers. Twenty-six (66%) LTM fibers responded to BK, and eight (34%) fibers were insensitive to BK. All 15 WDRMN and eight HTMN fibers tested responded to BK. 6. Tachyphylaxis to repeated application of BK was tested in all three classes of fibers. The vagal LTM fibers did not exhibit tachyphylaxis when BK was given at an intervals of 10 min. The sympathetic WDRMN and HTMN fibers demonstrated partial tachyphylaxis when BK was injected at 10-min intervals, but not when BK was injected at 20-min intervals.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of nitric oxide in esophageal peristalsis in the opossum

To explore the involvement of NO in normal peristalsis, the effects of inhibitors of NO synthase, including N omega-nitro-L-arginine (L-NNA) and N omega-nitro-L-arginine methyl ester (L-NAME), on esophageal peristaltic contractions induced by diverse stimuli that may involve different neuronal circuits were studied. Studies were performed in opossums. Experimental conditions in vivo included primary peristalsis (P) induced by pharyngeal stroking, short-train (1 second) electrical stimulation of the vagus nerve which caused peristaltic (S) contractions, and long-train (10 second) electrical stimulation of the vagus nerves which caused contractions at the onset of (A contractions) and after (B contractions) the stimulation period. In vitro experiments were performed on strips of esophageal circular muscle using electrical field stimulation which caused contractions at the onset of (on contractions) and after (off contractions) the stimulation period. The administration of L-NAME significantly decreased the latency period and reduced the latency gradient for P contractions, thereby increasing the velocity of peristalsis. Concomitant administration of atropine prolonged the latency period but did not restore the latency gradient. L-NAME abolished B contractions in a dose-dependent fashion. In vitro, L-NAME caused dose-dependent inhibition of off contractions and augmentation of on contractions. These studies support the hypothesis that NO may be involved in (a) both the latency period and the latency gradient, as well as in the contraction amplitude of esophageal peristalsis; and (b) esophageal B and off contractions.

Role of chloride ions in lower esophageal sphincter tone and relaxation

Studies were performed in strips of opossum lower esophageal sphincter (LES) muscle in vitro. External Cl(-)-free Krebs solution (0[Cl-]o) inhibited resting tone. Treatment with the Cl- channel blocker diphenylamine-2-carboxylate (DPC, 0.3-100 microM) caused a concentration-dependent relaxation of LES muscle, as did treatment with 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS, 1 microM-3 mM), a Cl(-)-HCO3- exchange blocker, and bumetanide (0.3-100 microM), a blocker of the Na(+)-K(+)-2Cl- cotransport. DIDS and bumetanide are also known to cause Cl- channel block. The calculated pD2 and Emax values for DPC, DIDS, and bumetanide were 5.24 +/- 0.28 (n = 5), 3.38 +/- 0.16 (n = 5), and 4.49 +/- 0.23 M (n = 5), and 78.80 +/- 5.38, 74.80 +/- 6.54, and 83.70 +/- 10.20%, respectively. The neuronal Cl- channel activators gamma-aminobutyric acid and glycine had no effect on the resting tone. DPC, DIDS, and bumetanide appear to have acted directly on smooth muscle rather than indirectly through the release of inhibitory neurotransmitters because LES relaxation by these agents was not influenced by tetrodotoxin (10 microM), which blocks action potentials in nerves, or by omega-conotoxin (1 microM), which inhibits the release of neurotransmitters from nerve terminals. LES muscle relaxed by exposure to 0[Cl-]o, DPC, DIDS, and bumetanide contracted with the addition of carbachol (30 microM); muscle so treated was resistant to the inhibitory neurotransmitter-mediated relaxation ordinarily induced by electrical field stimulation (EFS, 0.12-32 Hz). This effect was not nonselective, as the EFS-resistant muscle relaxed fully with isoproterenol (0.1-100 microM). HCO(3-)-free Krebs in the nominal absence of CO2 did not affect the resting tone and its relaxation. The Ca2+ channel blocker nifedipine decreased resting tone but did not antagonize the relaxation of carbachol-contracted muscle induced by either EFS or isoproterenol. These studies suggest that Cl- may play an important role in LES tone and relaxation due to inhibitory neurotransmitter released from intramural nerves.

Both ATP and the peptide VIP are inhibitory neurotransmitters in guinea-pig ileum circular muscle

1. Intracellular membrane potential recordings were made from circular smooth muscle cells of the guinea-pig ileum in the presence of atropine (1 microM) and nifedipine (0.1 microM) at 30 degrees C. 2. Perfusion with adenosine triphospate (ATP, 100 microM) and vasoactive intestinal peptide (VIP, 2 microM) resulted in membrane hyperpolarizations of 6.4 +/- 0.3 and 6.8 +/- 0.3 mV, respectively. Picospritzes of ATP (10 mM in pipette) and VIP (100 microM in pipette) resulted in membrane hyperpolarizations of 6.9 +/- 0.4 and 6.3 +/- 0.4 mV, respectively. 3. The ATP-induced hyperpolarizations were antagonized by alpha, beta-methylene ATP desensitization (100 microM for 30 min) and the ATP antagonist Reactive Blue 2 (200 microM), but were unaffected by the VIP antagonist VIP 10-28 (1 microM). 4. The VIP-induced hyperpolarizations were antagonized by VIP 10-28, but unaffected by alpha, beta-methylene ATP desensitization and Reactive Blue 2. 5. A single pulse of transmural nerve stimulation (2 ms, 15 mA) resulted in an inhibitory junction potential (IJP) that reached a maximal amplitude of 12.9 +/- 0.5 mV at 378 +/- 20 ms from the stimulus. This fast IJP was abolished by apamin (2 microM) or tetrodotoxin (1 microM), antagonized by alpha, beta-methylene ATP desensitization or Reactive Blue 2, but unaffected by VIP 10-28. 6. In the presence of apamin (1 microM), four pulses of transmural stimulation (2 ms, 20 Hz, 15 mA) resulted in an IJP that reached a maximal amplitude of 4.8 +/- 0.2 mV at 1.4 +/- 0.1 s from the stimulus. This slow IJP was antagonized by tetrodotoxin (1 microM) or VIP 10-28 (1 microM), augmented by Reactive Blue 2 (200 microM), and unaffected by alpha, beta-methylene ATP desensitization. 7. These findings provide evidence that both ATP and VIP are inhibitory neurotransmitters in the circular muscle layer of the ileum and that ATP may be the neurotransmitter responsible for the fast IJP and VIP the neurotransmitter responsible for the slow IJP.

Role of nitric oxide in lower esophageal sphincter relaxation to swallowing

Studies were performed in the opossum to define the role of the L-arginine-nitric oxide (NO) pathway in lower esophageal sphincter (LES) relaxation to swallowing and vagal stimulation in viv and intramural nerve stimulation in vitro. In vivo, L-NAME, a water soluble NO synthase (NOS) inhibitor, caused antagonism of LES relaxation due to reflex-induced swallowing. L-NAME (20 mg/kg i.v.) reduced the amplitude of swallow induced relaxation from 88% to 28%. LES relaxation due to electrical stimulation of peripheral end of decentralized vagus nerve was also antagonized. The effects of L-NAME were reversed by L-arginine, but not by D-arginine. L-NAME treatment did not antagonize LES relaxation to intravenous administration of isoproterenol. In vitro, NO and sodium nitroprusside (SNP) caused a decrease in the sphincter tone. The relaxing effect caused by NO and SNP was not antagonized by tetrodotoxin or omega-conotoxin. Inhibitors of NO synthase, L-NMMA and L-NNA, caused slight increase in the spontaneous resting LES tone and concentration-dependent antagonism of electrical field stimulation (EFS) induced LES relaxation. L-NNA (10(-4)M) abolished EFS induced LES relaxation at low frequencies (less than 5 Hz) and antagonized the relaxation to a value 20% of the control at 20 Hz. The antagonistic action of L-NMMA and L-NNA was unaffected by D-arginine but was reversed by L-arginine. The inhibitory effect of NO, SNP, or two other putative inhibitory neurotransmitters (VIP and CGRP) on the LES was not antagonized by L-NNA. These studies show that inhibitors of NO synthase selectively antagonize LES relaxation to all three modes of intramural inhibitory nerve stimulation including physiological swallowing. These studies suggest that the L-arginine-nitric oxide pathway is involved in physiological relaxation of the LES.

Peptidergic innervation of the human esophageal smooth muscle

Studies were performed to define the peptidergic nature of intramural nerves in the human esophagus. Cryosections of uninvolved surgically resected tissues from 14 individuals were studied by immunofluorescence for the localization of 10 neuropeptides. Myenteric neurons showed bombesin-, calcitonin gene-related peptide-, galanin-, substance P-, vasoactive intestinal polypeptide-, leucine-enkephalin-, methionine-enkephalin-, neuropeptide Y-, and somatostatin-like immunoreactivity. Submucous neurons had all the above except neuropeptide Y, methionine-enkephalin, leucine-enkephalin, and bombesin. Both groups of neurons received nerve terminations positive for calcitonin gene-related peptide, galanin, neuropeptide Y, substance P, and vasoactive intestinal polypeptide. Myenteric neurons additionally received terminations positive for neuropeptide Y, methionine-enkephalin, and somatostatin. All muscle layers had varicose fibers that reacted for calcitonin gene-related peptide, galanin, neuropeptide Y, and substance P. Longitudinal and circular muscle received few nerves reactive for leucine-enkephalin, whereas methionine-enkephalin was localized in a few nerve endings in the circular muscle. Somatostatin- and bombesin-reactive nerves occurred in longitudinal muscle. No cholecystokinin-reactive nerves were found. This study extends the results of previous studies and shows the previously undescribed presence of calcitonin gene-related peptide- and galanin-reactive nerves in the human esophagus and identifies neuropeptides that may serve as motor, sensory, and modulatory neurotransmitters of esophageal nerves.

Chloride-mediated inhibitory junction potentials in opossum esophageal circular smooth muscle

Intracellular recordings were made from circular smooth muscle cells of the opossum esophagus. Inhibitory junction potentials (IJPs) 8.3 +/- 0.7 mV in amplitude were observed in response to a single pulse (1 ms, 15 mA) of transmural nerve stimulation. Potassium channel blockers apamin (1 microM), tetraethylammonium (10 mM), 4-aminopyridine (250 microM), and cesium chloride (10 mM) did not reduce IJP amplitude. Conditioning hyperpolarizations to the equilibrium potential for potassium were associated with a significant increase in IJP amplitude. A small increase in membrane resistance was observed during the IJP. Changes in external potassium concentration had no significant effect on IJP amplitude acutely. However, prolonged perfusion with potassium-free Krebs solution resulted in a marked decrease in IJP amplitude as did prolonged perfusion with ouabain (0.1 mM). Low-chloride solution (12.4 mM) resulted acutely in an increase in IJP amplitude. Prolonged low-chloride perfusion resulted in a significant decrease in IJP amplitude. The anion exchange chloride channel inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (600 microM) significantly reduced IJP amplitude. These findings suggest that the IJP observed in opossum esophageal circular smooth muscle in response to a single pulse of stimulation is due to a decrease in membrane chloride conductance. The ability of prolonged application of Na-K pump inhibitors to abolish the IJP appears to be due to known secondary effects of these agents in depleting intracellular chloride.

Chloride-mediated junction potentials in circular muscle of the guinea pig ileum

Junction potentials were recorded from circular muscle cells of the guinea pig ileum at various sites oral and anal to a transmural stimulus in the presence of atropine, apamin, and substance P antagonism (desensitization) at 30 degrees C. A short train of pulses produced an inhibitory junction potential (slow IJP), which preceded an excitatory junction potential (slow EJP). The slow IJP was observed up to 56.4 +/- 2.9 mm oral and 65.4 +/- 2.2 mm anal to the stimulus. The slow EJP was observed up to 50.4 +/- 1.9 mm oral and 58.3 +/- 2.1 mm anal to the stimulus. Hexamethonium (400 microM) decreased the amplitudes of the slow IJP and slow EJP at all sites. After hexamethonium, the slow IJP was observed up to 37.3 +/- 2.3 mm oral and 39.8 +/- 2.1 mm anal to the stimulus and the slow EJP was 44.2 +/- 2.5 mm oral and 43.3 +/- 2.6 mm anal to the stimulus. The slow IJP and slow EJP were associated with an increase and decrease in membrane resistance, respectively. Conditioning depolarizations of the circular muscle cells reduced the amplitudes of the slow IJP and slow EJP. Both were abolished at a membrane potential of approximately -25 mV. Conditioning hyperpolarizations increased the amplitude of both the slow IJP and slow EJP. Ionic substitution experiments with low external chloride solution (12.4 mM) resulted in an immediate increase in slow IJP and slow EJP amplitudes, whereas more prolonged perfusion resulted in a significant decrease in slow IJP and slow EJP amplitudes. 4,4'-Diisothiocyanostilbene-2,2'-disulfonic acid (400 microM) resulted in decreases in slow IJP and slow EJP amplitudes. These results suggest that the slow IJP and slow EJP are due to a decrease and increase in membrane chloride conductance, respectively. The noncholinergic neural pathways responsible for the slow IJP and slow EJP extend approximately 40 mm orally and anally along the longitudinal axis of the guinea pig ileum.

Effects of bradykinin and bradykinin analogs on the opossum lower esophageal sphincter: characterization of an inhibitory bradykinin receptor

Bradykinin (BK) caused the circular muscle of opossum lower esophageal sphincter to relax and then contract in vitro. The effects of BK were not modified by indomethacin, tetrodotoxin, omega-conotoxin, atropine, propranolol, phentolamine, haloperidol, methysergide, pyrilamine or cimetidine. Apamin but not tetraethylammonium antagonized the inhibitory effect of BK and nifedipine antagonized its excitatory effect. Structure-activity relationships of 10 BK analogs known to be active on BK receptors were studied. Six analogs had distinct excitatory response profile and the rank order of potency of these agonists according to pD2 (shown in parentheses) was D-Arg-[Hyp3Thi5,8D-Phe7]-BK (6.49 +/- 0.19) greater than [Thi5,8D-Phe7]-BK (5.61 +/- 0.26) greater than Lys-Lys-[Hyp3-Thi5,8D-Phe7]-BK (5.45 +/- 0.14) greater than BK (5.16 +/- 0.20) greater than [des-Arg9]-BK (4.95 +/- 0.08) greater than [D-Phe7]-BK (4.73 +/- 0.10). However, only BK was fully efficacious (100%) and Emax values of all the analogs were less than that of BK. On the inhibitory response BK was the only agonist (pD2 = 5.48 +/- 0.08) and none of the BK analogs were agonist. All the BK analogs were also inactive as antagonists except Lys-Lys-[Hyp3-Thi5,8D-Phe7]-BK and Lys-Lys-[Hyp2,3-Thi5,8D-Phe7]-BK which competitively and selectively antagonized the BK inhibitory response. The pA2 value of Lys-Lys-[Hyp3-Thi5,8D-Phe7]-BK was 6.92 +/- 0.17.(ABSTRACT TRUNCATED AT 250 WORDS)

The nature of noncholinergic membrane potential responses to transmural stimulation in guinea pig ileum

The effect of substance P antagonism on membrane potential responses to transmural nerve stimulation in the presence of atropine was examined in circular smooth muscle of the guinea pig ileum. Intracellular recordings of membrane potential responses recorded 3-5 mm oral to the transmural stimulus consisted of an inhibitory junction potential followed by two distinct depolarizations referred to as early and late excitatory junction potentials. Substance P antagonism was achieved by desensitization with high doses of substance P or use of the antagonist Spantide (Sigma Chemical Co., St. Louis, MO). Substance P antagonism had no effect on the amplitude of the inhibitory junction potential, caused an increase in the latter portion of the early excitatory junction potential, and abolished the late excitatory junction potential. The excitatory junction potential potentiated by substance P receptor antagonism was associated with a decrease in membrane resistance, increased in amplitude with conditioning hyperpolarizations to the estimated equilibrium potential for K+, and was blocked by the Cl-/HCO3- exchange inhibitor DIDS or prolonged perfusion with low-chloride solution. These studies suggest that a noncholinergic, non-substance P neurotransmitter is released from enteric motoneurons that produces excitation through an increase in smooth muscle chloride conductance.

Localization of calcitonin gene-related peptide in human esophageal Langerhans cells

Previously undescribed calcitonin gene-related peptide-immunoreactive intraepithelial cells were seen in specimens of esophageal mucosa obtained by biopsy or surgical resection from 14 individuals. These calcitonin gene-related peptide-immunoreactive cells were sparsely seen in normal mucosa but increased markedly in esophagitis. They were inaccessible to routine histological stains, but osmication showed them as dendritic forms resembling Langerhans cells of the skin. Their cytological identity was determined with immunocytochemical tests for human antigenic markers such as Ia, HLA-DR, and OKT6 for Langerhans cells, Leu-M5 and Leu-M3 for intraepithelial macrophages, CD3 and TCR-1 for T-lymphocytes, Leu-14 for B-lymphocytes, S-100 for Merkel cells, and chromogranin for amine precursor uptake and decarboxylation cells. Double localization showed that calcitonin gene-related peptide immunoreactivity colocalized with Ia, HLA-DR, and OKT6 but not with the other markers. These studies show that intraepithelial Langerhans cells in the esophageal mucosa contain calcitonin gene-related peptide, which may serve as an immunomodulator.