Swallowing reflex and brain stem neurons activated by superior laryngeal nerve stimulation in the mouse

The purpose of the present study was to identify vagal subnuclei that participate in reflex swallowing in response to electrical stimulation of the left superior laryngeal nerve (SLN). SLN stimulation at 10 Hz evoked primary peristalsis, including oropharyngeal and esophageal peristalsis, and LES relaxation. It also induced c-fos expression in interneurons in the interstitial (SolI), intermediate (SolIM), central (SolCe), dorsomedial (SolDM) and commissural (SolC) solitary subnuclei. Neurons in parvicellular reticular nucleus (PCRt) and area postrema (AP) and motoneurons in the semicompact (NAsc), loose (NAl), and compact (NAc) formations of the nucleus ambiguus and both rostral (DMVr) and caudal (DMVc) parts of the dorsal motor nucleus of vagus were also activated. The activated neurons represent all neurons concerned with afferent SLN-mediated reflexes, including the swallowing-related neurons. SLN stimulation at 5 Hz elicited oropharyngeal and LES but not esophageal responses and evoked c-fos expression in neurons in SolI, SolIM, SolDM, PCRt, AP, NAsc, NAl, and DMVc but not in SolCe, NAc, or DMVr. These data are consistent with the role of SolI, SolIM, SolDM, NAsc, NAl, and DMVc circuit in oropharyngeal peristalsis and LES relaxation and SolCe, NAc, DMVc, and DMVr in esophageal peristalsis and LES responses.

An overview of pathophysiology and treatment of insulin resistance

Insulin resistance has emerged out as a concept linking diabetes mellitus and hypertension. Clinically it is characterized by hyperinsulinemia, hypertension, central obesity, abnormal lipid profile and cardiovascular complications. Insulin resistance is often associated with presence of anti-insulin antibodies and absent or dysfunctional insulin receptors. At molecular level insulin resistance appears to occur at the level of G-protein, kinase activation, glucose carriers (GLUT) and gene expression. Although with advent or research, the molecular mechanisms of insulin resistance are becoming more clear and there is development of new therapeutic agents like insulin sensitizers (thizolidinediones), in clinical practice, as of today, a patient with insulin resistance is looked upon as hypertensive or having diabetes mellitus. Accordingly he is taking either antihypertensives or antidiabetic drugs or both. It is thus essential to look into effects of these agents on insulin sensitivity. In recent years some scattered studies have been conducted to evaluate the effect of various antihypertensives and antidiabetics on insulin sensitivity. An antihypertensive or antidiabetic drug should directly benefit the cardiovascular risk profile of these patients. Although various newer approaches are explored to have a therapeutic benefit in insulin resistance, it is still a long way in the research, when a suitable pharmacological agent with least untoward effects will be available for the treatment of insulin residence.

Phenotype of Barrett's esophagus and intestinal metaplasia of the distal esophagus and gastroesophageal junction: an immunohistochemical study of cytokeratins 7 and 20, Das-1 and 45 MI

The pathogenesis of short segment Barrett's esophagus (SSBE) and intestinal metaplasia (IM) of the gastroesophageal junction (IMGEJ) are poorly understood. Also, these conditions are difficult to distinguish from one another based solely on endoscopic and pathologic criteria. Therefore, the aim of this study was to evaluate the immunophenotypic features of SSBE and IMGEJ and to compare the results with lesions of known etiologies: long segment BE (LSBE) caused by reflux disease and Helicobacter pylori-induced IM of the gastric antrum (IMGA). Routinely processed mucosal biopsy specimens from 11 patients with LSBE, 17 with SSBE, 10 with IMGEJ, 16 with IMGA, 17 with a normal nonmetaplastic GEJ, and 7 patients with a normal gastric antrum were immunohistochemically stained with monoclonal antibodies to: Das1, an antibody shown to react specifically with colonic goblet cells; 45M1, an antibody that recognizes the M1 gastric mucin antigen; and cytokeratin (CK) 7 and 20, antibodies that have previously been reported to show specific staining patterns in BE versus IMGA. Also evaluated was nonintestinalized mucinous epithelium from LSBE, SSBE, and also the normal GEJ and gastric antrum. LSBE, SSBE, and IMGEJ showed similar prevalences of Das1 (91% versus 88% versus 100%) and 45M1 reactivity (100% versus 100% versus 100%), and a similar pattern of CK7/20 reactivity (diffuse strong CK7 staining of the surface and crypt epithelium, and strong surface and superficial crypt CK20 staining) (91% versus 94% versus 90%). In contrast, although 45M1 reactivity in IMGA (93%) was similar to that of the other three groups, IMGA showed a significantly lower prevalence of Das positivity (13%, p < 0.001), and only a 14% prevalence of the CK7/20 staining pattern that was predominant in the other three groups (p < 0.001). Das1, 45M1, and CK7/20 staining were similar in nonintestinalized "cardia-type" mucinous epithelium from LSBE, SSBE, and the GEJ, but all were distinct from the normal gastric antrum. In summary, the immunophenotypic features of SSBE and IMGEJ are similar and closely resemble those seen in classic LSBE, but are distinct from IMGA. This may indicate that IM in LSBE, SSBE and at the GEJ have similar biologic properties. Based on our data, SSBE and IMGEJ cannot be distinguished on the basis of their immunophenotype.

Molecular characterization of mutations in Indian children with congenital adrenal hyperplasia due to steroid 21-hydroxylase deficiency

Congenital adrenal hyperplasia (CAH) is the commonest cause of female pseudohermaphroditism. It is most often due to steroid 21-hydroxylase deficiency resulting from mutations in the CYP21 gene. This study was conducted to characterize mutations in the CYP21 gene, determine their frequency and correlate genotype with phenotype in Indian children with CAH. Twenty-eight patients with salt-wasting (SW) or simple-virilizing (SV) forms of the disease as well as parents and siblings were studied. Allele specific PCR was carried out and rapid characterization of six mutations was achieved in 23 patients. Twelve patients were homozygous for the mutations and 11 were heterozygous, of whom eight were compound heterozygotes and three were hemizygotes; no mutation was found in five patients. The homozygosity of the mutations was found to be high in our population. The most common mutation was Ile173Asn (31.8%), followed by intron2 splice (27.2%), Gln319stop (22.7%), gene deletion (15.9%) and Pro31Leu (2.2%). Genotype-phenotype correlations showed that the most frequent mutations in the SW group were intron2 splice and Gln319stop mutations (33.3% each) and Ile173Asn (71.4%) in the SV group.

Lower esophageal sphincter relaxation and activation of medullary neurons by subdiaphragmatic vagal stimulation in the mouse

BACKGROUND & AIMS

Isolated lower esophageal sphincter (LES) relaxation associated with belching and vomiting and the transient LES relaxation associated with gastroesophageal reflux are gastric afferent-mediated vagovagal reflexes. We aimed to identify the brain stem vagal subnuclei involved in these reflexes.

METHODS

In anesthetized mice, LES pressures were recorded using a manometric technique and response to electrical stimulation of the ventral trunk of subdiaphragmatic vagus was investigated. Anatomy of the vagal subnuclei was defined, and activated subnuclei with ventral subdiaphragmatic vagus stimulation were detected by c-fos immunohistochemical staining.

RESULTS

Ventral subdiaphragmatic vagal stimulation elicited frequency-dependent LES relaxation without evoking esophageal contractions and induced c-fos expression in interneurons in medial, dorsomedial, and commissural subnuclei along with outer shell of area postrema and motoneurons in the caudal dorsal motor nucleus of vagus. Brain stem subnuclei including interstitial, intermediate, and central subnuclei, and nucleus ambiguous, which have been reported to be involved in the response to swallowing, were not activated.

CONCLUSIONS

Stimulation of the ventral subdiaphragmatic vagus causes isolated LES relaxation and activates neurons in select vagal subnuclei that may represent the brain stem circuit involved in the abdominal vagal-afferent-evoked isolated LES relaxation. These observations suggest that different brain stem circuits are involved in swallow-induced and gastric afferent-mediated isolated LES relaxations.

Effect of galanin and galanin antagonists on peristalsis in esophageal smooth muscle in the opossum

Galanin, a neuropeptide that is widely distributed in the esophageal nerves, is known to exert a neuromodulatory action in the gut. These studies examined the effect of galanin and galanin antagonists on esophageal peristalsis in anesthetized opossums in vivo. Intraluminal esophageal pressures were recorded at 1, 3, 5, 7, and 9 cm above the lower esophageal sphincter. Esophageal peristaltic contractions were induced by swallow and short- (1-s) and long-train (10-s) vagal stimulation (VS). Galanin (1 nmol/kg) inhibited the amplitude of swallow-induced peristaltic contractions and increased peristaltic velocity by enlarging the latency periods in the upper part of the esophagus and reducing them in the lower part. Galinin nearly abolished esophageal contractions caused by short-train VS at 5 Hz and inhibited the contractions at 10 Hz. Galanin increased latency periods induced by short-train VS with little change in the velocity of peristalsis and reduced the amplitude of both A (cholinergic) and B (noncholinergic) contractions due to long-train VS. However, the decrease in amplitude of B contractions was more marked. Galantide (3 nmol/kg) antagonized the inhibitory action of exogenous galanin on esophageal contractions elicited by short-train VS, but by itself galantide had no significant effect on esophageal contractions. In conclusion, exogenous galanin inhibits the amplitude of swallow-induced peristaltic contractions and converts them into nonperistaltic contractions by inhibiting both the cholinergic and noncholinergic components.

Gastric stasis in neuronal nitric oxide synthase-deficient knockout mice

BACKGROUND & AIMS

Nitric oxide (NO) is a major inhibitory neurotransmitter in the gut. This study aimed to identify the effect of chronic deprivation of NO derived from neuronal (nNOS) or endothelial (eNOS) nitric oxide synthase on gastric emptying.

METHODS

nNOS-deficient (knockout) mice were compared with wild-type mice for gastric size, fluoroscopic appearance after gavage of contrast, and histology of the pyloric sphincter. Wild-type mice treated with the NOS inhibitor N(omega)-nitro L-arginine (L-NA) and eNOS-deficient mice were also compared with wild-type and nNOS-deficient mice for liquid and solid gastric emptying.

RESULTS

nNOS-deficient mice showed gastric dilation. Fluoroscopy showed delayed gastric emptying of radiologic contrast. There was no marked localized hypertrophy or luminal narrowing at the pyloric sphincter by histology of relaxed wild-type, nNOS-deficient, and eNOS-deficient tissues. Gastric emptying of both solids (28% +/- 27%) and liquids (22% +/- 18%) was significantly delayed in nNOS-deficient mice compared with control wild-type mice (82% +/- 22% for solids; 48% +/- 17% for liquids). eNOS-deficient mice showed no significant difference from wild-type mice (74% +/- 28% for solids; 47% +/- 23% for liquids). Wild-type mice treated acutely with L-NA showed delay in emptying of solids (43% +/- 31%) but not liquids (39% +/- 15%).

CONCLUSIONS

Chronic depletion of NO from nNOS, but not eNOS, results in delayed gastric emptying of solids and liquids.

Oculohypotensive effect of angiotensin-converting enzyme inhibitors in acute and chronic models of glaucoma

We have studied the effects of various angiotensin-converting enzyme (ACE) inhibitors on intraocular pressure (IOP) of rabbits with experimentally induced ocular hypertension and their mechanism of action. Acute ocular hypertension was induced by infusion of 5% glucose (15 ml/kg) through marginal ear vein, whereas chronic glaucoma was induced by injection of alpha-chymotrypsin into the posterior chamber of the eye. IOP was measured by tonometer. All ACE inhibitors were instilled topically in the eye in a sterile solution. The effect of ACE inhibitors also was studied on serum cholinesterase (true and pseudo) and the enzyme ACE in vitro. Enalaprilat, ramiprilat, and fosinopril produced a time-dependent decrease of IOP in both acute and chronic models of ocular hypertension in rabbits. The decrease in IOP was observed for >4 h, and the extent of decrease was comparable to that with both pilocarpine and betaxolol. Prodrugs enalapril and ramipril failed to produced any change in IOP. Losartan also produced a significant decrease in IOP in the chronic model of ocular hypertension in rabbits. All the three ACE inhibitors were found to inhibit ACE activity in aqueous humor. The enzyme cholinesterase was found to be inhibited by enalaprilat, ramiprilat, and fosinopril. However, atropine did not alter the IOP-lowering effect of enalaprilat in rabbits. Indomethacin pretreatment produced slight but significant inhibition of the IOP-lowering effect of enalaprilat in rabbits. Our data suggest that ACE inhibitors enalaprilat, ramiprilat, and fosinopril produce a significant ocular hypotensive effect in acute and chronic models of ocular hypertension in rabbits. Inhibition of ACE in aqueous humor, and in ocular tissues, resulting in reduced angiotensin II formation, could be one of the major mechanisms responsible for the IOP reduction by ACE inhibitors in rabbits.

Serum insulin assay: an important therapeutic tool in management of freshly diagnosed type 2 diabetes mellitus

OBJECTIVES

The study was performed to see that, whether metabolic control and response to treatment in freshly diagnosed patients of type 2 diabetes mellitus is affected by primary pathology (hyperinsulinemia/inappropriate insulin secretion).

METHODS

One hundred and eight freshly diagnosed patients of type 2 diabetes mellitus with age range from 30-65 years were followed for a period of three months. The blood glucose, serum triglyceride, and serum insulin levels were determined in each patient. Patients were found to have either higher or normal to low serum insulin values at fasting, and accordingly patients were distributed into two groups; group one (normal to low initial fasting serum insulin level i.e. < or = 30 microU/ml) and group two (high fasting serum insulin level i.e. > or = 30 microU/ml). Each group was further divided into two subgroups A and B. Subgroup A was treated with glipizide and B with metformin.

RESULTS

Diabetic patients who had fasting hyperinsulinemia (n = 53, 100%) had blood pressure > or = 140/90 at the time of presentation. Patients who had fasting serum insulin within normal range only 30% (n = 17) had hypertension. Patients of group one had good recovery from hyperglycemia and reduction in triglyceride values when treated with sulphonylurea (subgroup A) as compared to patients treated with biguanide (subgroup B). On the contrary patients of group two showed poor glycemic control, increase in blood pressure and rise in serum triglyceride titre when treated with sulphonylurea (subgroup A) while in the same group biguanide effectively produced euglycemia with normalization of blood pressure and decrease in triglyceride levels (subgroup B).

CONCLUSION

Assessment of initial serum insulin levels is helpful guide to decide about the type of oral hypoglycemic agent to be used in freshly diagnosed patients to type 2 diabetes mellitus.

Antiulcer activity and the mechanism of action of magaldrate in gastric ulceration models of rat

The present study was undertaken to investigate the mechanism of cytoprotective effects of magaldrate in aspirin plus pylorus-ligation model and ethanol-induced gastric ulcer model in rats. Magaldrate (60 mg/kg, p.o.) produced a significant reduction in the ulcer index and significant increase in mucus content in ethanol-induced gastric ulceration in rats. In aspirin plus pylorus-ligation model magaldrate produced significant decrease in ulcer index, total acidity and protein content (PR). It did not produce any significant change in volume of gastric secretion. However, it produced significant increase in total carbohydrate (TC) level but not in ratio between TC and proteins. It also produced a significant decrease in lipid peroxidation (as expressed by thiobarbituric acid reactive substance). Our data suggests the cytoprotective action of magaldrate on gastric mucosal cells which may be due to protection of gastric mucosa from lipid peroxidation.

Role of losartan therapy in the management of diabetic hypertension

The management of diabetic hypertension requires meticulous selection of agents in the antihypertension armamentorium. There may be several associated factors to be considered while treating a hypertensive diabetic. These include hyperglycemia, dyslipidemia, proteinuria, left ventricular hypertrophy and heart failure to name a few. Losartan is the first of a new class of agents in the list of antihypertensive drugs. By its selective angiotension II receptor (subtype AT1) blocking action it is postulated to bring about a more complete inhibition of the renin-angiotensin system. Thus, it might produce all the benefits of angiotensin converting enzyme (ACE) inhibitor therapy with the freedom from cough so commonly seen with the use of ACE inhibitors. This review attempts to analyze the possible benefits of losartan therapy in diabetes.

Comparative evaluation of different rat models with co-existing diabetes-mellitus and hypertension

We have evaluated the suitability of different rat models for the study of effects of antihypertensives on cardiovascular and metabolic complications of diabetes mellitus and hypertension. IDDM was induced in Wistar and spontaneously hypertensive (SH) rats by single tail vein injection of STZ (45 mg/kg, i.v.). Neonatal STZ-diabetes (nSTZ) was induced by administering STZ, 70 mg/kg (i.p.) to 5 day old Wistar rat pups. DOCA-hypertension was induced in Wistar and STZ-diabetic rats using deoxycorticosterone acetate (DOCA, 5 mg/kg, s.c.) and NaCl (2%) in drinking water. Intravenous injection of STZ produced cardinal signs of diabetes mellitus including hyperglycemia, loss of body weight, polyphagia and polydipsia. STZ-diabetic rats also showed hyperlipidemia and hypoinsulinemia. STZ-treated rats developed hypertension and bradycardia. nSTZ rats were found to have mild hyperglycemia and were hypertensive and hyperinsulinemic. The OGTT and ITT revealed that nSTZ rats are insulin resistant. SH rats were also found to be hyperinsulinemic and hypertensive. Although, these rats were found to be insulin resistant, they did not demonstrate hyperglycemia. DOCA-treated STZ-diabetic rats were found to have milder hyperglycemia when compared to STZ-diabetic rats not treated with DOCA. Although, DOCA treatment was not found to alter serum levels of glucose and insulin, results of OGTT revealed enhanced glucose disposal in DOCA-treated Wistar rats, suggesting that DOCA probably produces some effect on glucose homeostasis in rats. The present data also suggest that STZ-diabetic rat may be considered a suitable model for IDDM. On the other hand, nSTZ and SH rats were hyperinsulinemic and insulin resistant and may be used as models to study insulin sensitivity. DOCA-hypertensive rat may not be a suitable model for studying the effects of various drug interventions on glucose homeostasis and insulin sensitivity as DOCA itself appears to influence these factors.

Functional anatomy and physiology of the upper esophageal sphincter

Upper esophageal sphincter (UES) refers to the high-pressure zone located in between the pharynx and the cervical esophagus. The physiological role of this sphincter is to protect against reflux of food into the airways as well as prevent entry of air into the digestive tract. UES is a musculocartilaginous structure with its anterior wall being formed by the full extent of the posterior surface of the cricoid cartilage and arytenoid and interarytenoid muscles in the upper part. Posteriorly and laterally the cricopharyngeus (CP) muscle is a definitive component of the UES. CP has many unique characteristics: it is tonically active, has a high degree of elasticity, does not develop maximal tension at basal length, and is composed of a mixture of slow- and fast-twitch fibers, with the former predominating. These features enable the cricopharyngeus to maintain a resting tone and yet be able to stretch open by distracting forces, such as a swallowed bolus and hyoid and laryngeal excursion. CP, however, constitutes only the lower one third of the entire high-pressure zone. The thyropharyngeus (TP) muscle accounts for the remaining upper two thirds of the UES. The UES pressure is not entirely the result of myogenic activity, as a component of the pressure is the result of passive elasticity of the tissues. The opening of the UES involves relaxation of CP and TP muscles and forward movement of the larynx by the contraction of hyoid muscles. The UES function is controlled by a variety of reflexes that involve afferent inputs to the motorneurons innervating the sphincter. These physiological reflexes elicit either contraction or opening of the UES. Inability of the sphincter to open leads to difficulty in swallowing. Opening of the sphincter without associated CP relaxation leads to the clinical syndrome of cricopharyngeal bar.

Nitric oxide: a molecule of the millennium

Recognition of Nitric oxide (NO) as the chemical entity of endothelium-derived relaxing factor (EDRF) has renewed the interest of the scientific community in the last decade. The outcome of research the world over is that the dreaded environmental pollutant is found to be a fundamental physiological mediator and effector. NO is synthesized endogenously by enzymes nitric oxide synthase (NOS) in specialized tissues from its precursor L-arginine. The L-arginine-NO biosynthetic pathway is involved in physiological processes such as vasodilation, memory, neuroprotection, peristalsis, penile erection, immune defense, various endocrine and exocrine secretions in various systems such as cardiovascular, CNS, reproductive and immune system. Small quantities of NO produced by constitutive enzymes mediate these physiological effects. The expression of inducible enzyme or overstimulation of constitutive enzymes leading to production of large quantities of NO is implicated in the cytotoxic effects observed in various disorders like AIDS, cancer, Alzheimer's, arthritis etc. In conclusion, NO is a 'double edged sword' and the challenge before the scientific community is to develop strategies for using it to our advantage.

Tuberculous liver abscess

Tuberculosis (TB) of liver is rare but may have a variety of presenting features similar to other more common conditions. A case of tuberculosis liver abscess with right sided pleural effusion is reported.

Insulin secretory response in healthy adult offspring of hypertensive parents

OBJECTIVES

The present study was done to observe the insulin secretory response in healthy adult offspring of normotensive and hypertensive parents as the etiology of essential hypertension is largely treated as unknown.

METHODS

The insulin secretary response was observed in 20 healthy adult offspring of normotensive parents (Group I) and 25 healthy adult offspring of hypertensive parents (Group II). The mean serum insulin levels were assessed at fasting, 30, 60, 90 and 120 minutes after 75 grams of oral glucose load in both groups.

RESULTS

The mean serum insulin levels in fasting state was higher in group II (32.40 +/- 18.59) than group I (17.90 +/- 11.98) (p < 0.01). After 30 minutes mean serum insulin levels were higher in group II than group I (88.00 +/- 56.04, 40.5 +/- 15.15 respectively, p < 0.001). There was no statistically significant difference after 60, 90 and 120 minutes of oral glucose load (p > 0.05).

CONCLUSIONS

Our observations suggest that the insulin secretory response in fasting and 30 minutes after oral glucose load was earliest metabolic abnormality in subjects at high risk for developing hypertension i.e. offspring of hypertensive parents.

Clinical and manometric features of the lower esophageal muscular ring

OBJECTIVE

In contrast to the well-recognized Schatzki's ring, the lower esophageal muscular ring remains a poorly defined entity. The purpose of this study is to report on the clinical features of three patients with lower esophageal muscular rings and review the literature on this disorder, to better understand its importance as a cause of dysphagia.

METHODS

Three patients presenting to the West Roxbury VA Medical Center were identified as having a contractile, focal narrowing in the distal esophagus by upper GI series. Clinical histories were obtained and endoscopic and manometric evaluations were performed.

RESULTS

The three patients had symptoms consisting of chronic, intermittent dysphagia for both liquids and solids. The results of barium swallows and upper endoscopic examinations were similar and revealed a focal, thick constriction of variable luminal diameter located a few centimeters above the squamocolumnar junction. Esophageal motility testing revealed peristaltic, high-amplitude, long-duration, and multiple peaked contractions. Lower esophageal sphincter function was normal. The patients derived partial or only temporary relief of dysphagia with esophageal dilation with rigid dilators. All three patients had significant symptomatic responses to anticholinergic agents.

CONCLUSIONS

Lower esophageal muscular rings are an uncommon but important cause of dysphagia. Significant esophageal motility abnormalities can be found in symptomatic patients. Distinguishing the lower esophageal muscular ring from the Schatzki's ring is important because of differences in the treatment and outcome of the two conditions.

Role of HERG-like K(+) currents in opossum esophageal circular smooth muscle

An inwardly rectifying K(+) conductance closely resembling the human ether-a-go-go-related gene (HERG) current was identified in single smooth muscle cells of opossum esophageal circular muscle. When cells were voltage clamped at 0 mV, in isotonic K(+) solution (140 mM), step hyperpolarizations to -120 mV in 10-mV increments resulted in large inward currents that activated rapidly and then declined slowly (inactivated) during the test pulse in a time- and voltage- dependent fashion. The HERG K(+) channel blockers E-4031 (1 microM), cisapride (1 microM), and La(3+) (100 microM) strongly inhibited these currents as did millimolar concentrations of Ba(2+). Immunoflourescence staining with anti-HERG antibody in single cells resulted in punctate staining at the sarcolemma. At membrane potentials near the resting membrane potential (-50 to -70 mV), this K(+) conductance did not inactivate completely. In conventional microelectrode recordings, both E-4031 and cisapride depolarized tissue strips by 10 mV and also induced phasic contractions. In combination, these results provide direct experimental evidence for expression of HERG-like K(+) currents in gastrointestinal smooth muscle cells and suggest that HERG plays an important role in modulating the resting membrane potential.

Lessons from genetically engineered animal models. IV. Nitric oxide synthase gene knockout mice

Nitric oxide is a ubiquitous molecule implicated in a variety of biological processes. The specific action of nitric oxide depends on its enzymatic sources, namely neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS), each having distinct tissue localization. Conventional pharmacological antagonists could not distinguish these enzymes or provide models of chronic nitric oxide depletion in whole animals. Several lines of knockout mice have been generated to distinguish the roles of nitric oxide from each enzyme: nitric oxide from nNOS is a major inhibitory neurotransmitter, nitric oxide from eNOS regulates blood flow under physiological conditions, and nitric oxide from iNOS causes hypotension during severe inflammatory conditions. Moreover, the nitric oxides from each isoform have different roles in tissue injury and inflammation. Studies of NOS-deficient animals have also identified redundant and compensatory pathways and revealed the consequences of life-long deficiency of these enzymes. The nNOS-deficient mice develop gastric dilation and stasis, the eNOS-deficient mice develop hypotension and lack vasodilatory responses to injury, and iNOS-deficient mice are more susceptible to inflammatory damage but more resistant to septic shock.

Neuronal NOS provides nitrergic inhibitory neurotransmitter in mouse lower esophageal sphincter

To identify the enzymatic source of nitric oxide (NO) in the lower esophageal sphincter (LES), studies were performed in wild-type and genetically engineered endothelial nitric oxide synthase [eNOS(-)] and neuronal NOS [nNOS(-)] mice. Under nonadrenergic noncholinergic (NANC) conditions, LES ring preparations developed spontaneous tone in all animals. In the wild-type mice, electrical field stimulation produced frequency-dependent intrastimulus relaxation and a poststimulus rebound contraction. NOS inhibitor N(omega)-nitro-L-arginine methyl ester (100 microM) abolished intrastimulus relaxation and rebound contraction. In nNOS(-) mice, both the intrastimulus relaxation and rebound contraction were absent. However, in eNOS(-) mice there was no significant difference in either the relaxation or rebound contraction from the wild-type animal. Both nNOS(-) and eNOS(-) tissues showed concentration-dependent relaxation to NO donor diethylenetriamine-NO and there was no difference in the sensitivity to the NO donor in nNOS(-), eNOS(-), or wild-type animals. These results indicate that in mouse LES, nNOS rather than eNOS is the enzymatic source of the NO that mediates NANC relaxation and rebound contraction.

Ajuba, a novel LIM protein, interacts with Grb2, augments mitogen-activated protein kinase activity in fibroblasts, and promotes meiotic maturation of Xenopus oocytes in a Grb2- and Ras-dependent manner

LIM domain-containing proteins contribute to cell fate determination, the regulation of cell proliferation and differentiation, and remodeling of the cell cytoskeleton. These proteins can be found in the cell nucleus, cytoplasm, or both. Whether and how cytoplasmic LIM proteins contribute to the cellular response to extracellular stimuli is an area of active investigation. We have identified and characterized a new LIM protein, Ajuba. Although predominantly a cytosolic protein, in contrast to other like proteins, it did not localize to sites of cellular adhesion to extracellular matrix or interact with the actin cytoskeleton. Removal of the pre-LIM domain of Ajuba, including a putative nuclear export signal, led to an accumulation of the LIM domains in the cell nucleus. The pre-LIM domain contains two putative proline-rich SH3 recognition motifs. Ajuba specifically associated with Grb2 in vitro and in vivo. The interaction between these proteins was mediated by either SH3 domain of Grb2 and the N-terminal proline-rich pre-LIM domain of Ajuba. In fibroblasts expressing Ajuba mitogen-activated protein kinase activity persisted despite serum starvation and upon serum stimulation generated levels fivefold higher than that seen in control cells. Finally, when Ajuba was expressed in fully developed Xenopus oocytes, it promoted meiotic maturation in a Grb2- and Ras-dependent manner.

Abnormalities of cytokine receptor signalling contributing to diseases of red blood cell production

The production of erythroid cells is a dynamic and exquisitely regulated process. The mature red cell is only the final phase of a complex but orderly series of genetic events that are initiated at the time a multipotent stem cell becomes committed to expressing the erythroid programme. Aberrations either in the intrinsic generation and/or amplification of functional erythroid cells or in the regulatory influences of microenvironment or cytokines form the basis for a number of blood diseases. In this review we focus upon abnormalities in red blood cell production and discuss how alterations in cytokine regulation of red blood cell production may contribute to these disease processes. We discuss clinical states in which blood red cell numbers are altered, including primary familial and congenital polycythaemia, the myeloproliferative disorder polycythaemia vera, erythroleukaemia, and Diamond-Blackfan anaemia. These disorders are briefly described and evidence supporting a potential role of specific cytokine receptor signalling defects as contributing to these phenotypes is discussed.

Pharmacology of sildenafil citrate

Erectile dysfunction is a common and multi-factorial disease that strongly impairs the quality of life in men. During the past decade, many new therapeutic strategies have become available. But the need for oral treatment was strongly felt. This need appears to have been fulfilled with the introduction of sildenafil. The drug acts by enhancing smooth muscle relaxant effect of nitric oxide. A number of clinical studies have now proved its safety and efficacy. The drug has shaken social life all over the world and to accept this "magic pill" or not remains the question of individual choice.

Calponin binds to the 20-kilodalton regulatory light chain of myosin

Calponin (CaP) is a 34 kDa smooth muscle-specific protein that has been implicated in regulation of smooth muscle contractility. Two CaP binding sites on smooth muscle myosin rod have been recently described [Szymanski and Tao (1997) J.Biol.Chem. 272, 11142-11146]. We used a combination of cosedimentation, overlay, and fluorescence assays to determine the interaction between CaP and both subfragment 1 of myosin and isolated 20 kDa regulatory light chain of myosin (RLC). Subfragment 1, which was generated by cleavage of myosin with Staphylococcus aureus protease (myosin S1SA) inhibits cosedimentation of CaP with myosin filaments. Fluorescence assay showed that CaP labeled with fluorescent label (DAN-CaP) interacts with myosin S1SA in solution via a single class of binding sites. The binding constant (kaff) of this interaction at 50 mM NaCl is (2. 1 +/- 0.2) x 10(6) M-1 (n = 3). The interaction between DAN-CaP and myosin S1SA depends on ionic strength, and the EC50 of inhibition of this interaction occurs at about 130 mM NaCl. In contrast, the subfragment 1 that was generated by papain digestion (myosin S1PA), which cleaves RLC 4 kDa away from the NH2-terminal end of the molecule, does not interact with DAN-CaP. Overlay and fluorescent assay in solution showed that CaP binds to isolated RLC, suggesting that the interaction between CaP and subfragment 1 of myosin is due to a direct binding of CaP to RLC. CaP binding to myosin S1SA is stronger than to subfragment 2 in physiological salt concentrations. CaP binding to myosin head strengthened upon phosphorylation of RLC by Ca2+/calmodulin-dependent myosin light chain kinase. We suggest that CaP binds to subfragment 1 of myosin, exclusively via the NH2-terminal end of RLC, and this interaction could play a role in regulation of the actin-myosin interaction in smooth muscle contractility.

Characterization of dopamine receptor subtypes involved in experimentally induced gastric and duodenal ulcers in rats

There are conflicting reports about the role of dopamine in gastric and duodenal ulcers. This investigation was undertaken to characterize the specific subtypes of dopamine receptor involved in gastric and duodenal ulceration. Administration of dopamine D1 agonist fenoldopam and dopamine D2 antagonist sulpiride elicited a significant decrease in acid secretion, total acid output, pepsin output and histamine content in the gastric juice, and reduced ulcer-index values, in pylorus-ligated rats. However, dopamine D1 receptor antagonist SCH 39166 ((-)-trans-6,7,7a,8,9,13b-hexahydro-3-chloro-2-hydroxy-N-methyl-5H -benzo (d) naptho -(2,1-b) azepine) and the D2 receptor agonist quinpirole led to significant augmentation of these parameters compared with respective controls. In the restraint plus water-immersion stress model the score for intraluminal bleeding and the cumulative gastric lesion length was significantly lower for rats treated with fenoldopam and sulpiride. The opposite effects were observed after pretreatment of rats with SCH 39166 and quinpirole. In the cysteamine-induced duodenal ulcer model the mean ulcer area and the score for intensity were significantly lower for fenoldopam and sulpiride and higher for SCH 39166 and quinpirole. Our data suggest that the dopamine D1 and D2 receptors have opposite effects on gastric and duodenal ulcers. Whereas stimulation of dopamine D1 receptors inhibits the formation of gastric and duodenal ulcers, stimulation of dopamine D2 receptors has a pro-ulcerogenic effect.

Effect of nifedipine and enalapril on insulin-induced glucose disposal in spontaneous hypertensive and diabetic rats

Hypertension and diabetes mellitus are associated with hyperinsulinemia and insulin resistance. The present work was undertaken to study the effects of enalapril and nifedipine on insulin sensitivity in spontaneously hypertensive (SH) rats and diabetic rats. Insulin sensitivity was measured by insulin tolerance test using K(ITT) as an index of insulin mediated glucose metabolism. The time to produce 50% fall in initial blood sugar level (T1/2) was significantly higher in non-insulin dependent diabetes mellitus (NIDDM) and SH rats as compared to Wistar control. The mean K(ITT) values were significantly lower in NIDDM and SH rats as compared to Wistar control. Treatment with nifedipine (10 mg/kg) and enalapril (5 mg/kg) for 15 days produced a significant reduction in T1/2. Further, K(ITT) value was found to be significantly increased in SH rats treated with nifedipine or enalapril as compared to control. Our data indicate that NIDDM and SH rats are not only hyperinsulinemic but also insulin resistant. Nifedipine and enalapril treatment produced increase in insulin sensitivity in these animals.

Hyperinsulinemia and insulin resistance in hypertension: differential effects of antihypertensive agents

Both hypertension and diabetes mellitus are multifaceted dynamic expressions of pathophysiological disequilibrium that are closely related with and even intermingled by a number of common factors. Hyperinsulinaemia and insulin resistance may be possible links between hypertension and diabetes mellitus. While working on the effect of different antihypertensive agents in several animal models of simultaneously occurring diabetes-mellitus and hypertension it was found that most antihypertensives prevented streptozotocin (STZ)-induced hypertension in rats. Hydralazine, angiotensin converting enzyme (ACE) inhibitors, calcium channel blockers (CCB) and clonidine prevented STZ-induced cardiomyopathy, hyperlipidaemia and glucose tolerance. It was further demonstrated that atenolol produced many unfavourable effects like hyperlipidaemia and decreased cardiac functions. We also used other animal models of simultaneously occurring diabetes-mellitus and hypertension such as genetically hypertensive or spontaneously hypertensive (SH), Deoxycorticosterone acetate (DOCA)-hypertensive and neonatal streptozotocin-induced NIDDM rats. Results of our studies suggest that SH, neonatal STZ-induced NIDDM, and fructose hypertensive rat models may be considered as models for insulin resistance - the concept that has come into limelight in recent years. DOCA may have some influence on glucose homeostasis and insulin sensitivity and some sort of counteraction to STZ-induced cardiovascular and metabolic changes occur with DOCA. Hence, it may not be considered as an ideal model to study the metabolic and cardiovascular complications of hypertension associated with diabetes-mellitus. Among ACE inhibitors, perindopril, spirapril, and among calcium channel blockers (CCB) used in our study amlodipine and nifedipine were found to produce an increase in insulin sensitivity. Enalapril, ramipril, lisinopril and nitrendipine failed to alter insulin sensitivity as far as the glycaemic control is concerned. Extension of the results of these experiments to the clinical practice substantiated many of the findings and a good correlation between results obtained from experimental studies and clinical data was found.

New classes of antihypertensive drugs: therapeutic potentials

A number of new classes of antihypertensive drugs have become available in the recent years which appear to hold therapeutic potential for better management of hypertension. Losartan, an angiotensin II receptor antagonist, does not produce cough which is classically seen with ACE inhibitors. Fenoldopam, a dopamine D1-receptor agonist, has a rapid and short duration of action and is ideally suited by intravenous infusion for quick control of BP in hypertensive emergencies. Kentaserin, a serotonin (5-HT2A) receptor antagonist, has a long duration of action and can be given once daily. It has the added benefit of having antiplatelet effect. Monatepil, a dual alpha-receptor and calcium channel blocker, has potent antihypertensive effect, lowers serum cholesterol and also has antiatherosclerotic effect. Dual ACE and endopeptidase inhibitor, such as alatriopril, has a "broad spectrum" antihypertensive effect and may be effective in majority of hypertensive patients. Many other classes of antihypertensive drugs are still in the investigative stage, and their therapeutic potentials and safety need to be ascertained in long-term controlled clinical trials.

Evidence for NO. redox form of nitric oxide as nitrergic inhibitory neurotransmitter in gut

A nitric oxide (NO)-like product of the L-arginine NO synthase pathway has been shown to be a major inhibitory neurotransmitter that is involved in the slow component of the inhibitory junction potential (IJP) elicited by stimulation of nonadrenergic, noncholinergic nerves. However, the exact nature of the nitrergic transmitter, the role of cGMP, and the involvement of a potassium or a chloride conductance in the slow IJP remain unresolved. We examined the effects of soluble guanylate cyclase inhibitors LY-83583 and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), potassium-channel blockers and putative chloride-channel blockers diphenylamine-2-carboxylate (DPC) and niflumic acid (NFA) on the hyperpolarization elicited by an NO. donor, diethylenetriamine/NO adduct (DNO), NO in solution, and an NO+ donor, sodium nitroprusside (SNP), in the guinea pig ileal circular muscle. Effects of these blockers on purinergic (fast) and nitrergic (slow) IJP were also examined. DNO-induced hyperpolarization and nitrergic slow IJP were suppressed by LY-83583 or ODQ and DPC or NFA but not by the potassium-channel blocker apamin. In contrast, hyperpolarization caused by SNP or solubilized NO gas and purinergic fast IJP were antagonized by apamin but not by inhibitors of guanylate cyclase or chloride channels. These results demonstrate biological differences in the actions of different redox states of NO and suggest that NO. is the nitrergic inhibitory neurotransmitter.

Oral zinc therapy in diabetic neuropathy

The present double blind randomized study was conducted on 50 subjects; 20 age and sex matched healthy controls (Group--I); 15 patients of diabetes mellitus with neuropathy who received placebo for 6 weeks (Group--IIA); and 15 patients of diabetes mellitus with neuropathy who were given supplemental zinc sulphate (660 mg) for 6 weeks (Group--IIB). Serum zinc level, fasting blood sugar (FBS) and post prandial blood sugar (PPBS) levels and motor nerve conduction velocity (MNCV) were estimated on day 0 and after 6 weeks in all subjects. Serum zinc levels were significantly low (p < 0.001) in group IIA and IIB as compared to healthy controls (Group--I) at baseline. After 6 weeks the change in pre and post therapy values of FBS, PPBS and MNCV (median and common peroneal nerve) were highly significant (P = < 0.001) for group IIB alone with insignificant change (P = > 0.05) in group IIA. No improvement (P = > 0.05) in autonomic dysfunction was observed in either groups. Therefore, oral zinc supplementation helps in achieving better glycemic control and improvement in severity of peripheral neuropathy as assessed by MNCV.

Gastroesophageal reflux disease versus Helicobacter pylori infection as the cause of gastric carditis

To explore the potential contributions of gastroesophageal reflux disease, as opposed to Helicobacter pylori infection, to the development of gastric carditis, we evaluated gastric carditis (using the criteria of the updated Sydney system for the classification of gastritis), clinical and morphologic features of esophagitis, and H. pylori infection (evaluation of Steiner stains) in biopsy specimens from the gastroesophageal squamocolumnar junction. We correlated clinical, endoscopic, and histologic features in an unselected group of 116 patients. Some degree of carditis was found in 107 (92%) of the patients. The mean age of the patients increased with increasing severity of carditis (P < .05). The various groups of patients with different degrees of carditis did not differ significantly in sex ratio, ethnic background, presence of obesity, percentage having symptoms of gastroesophageal reflux disease (such as heartburn, regurgitation, dysphagia, or odynophagia), endoscopic evidence of esophagitis and columnar epithelium in the distal esophagus, or histologic evidence of active esophagitis. The presence, however, of active gastritis and H. pylori infection in the distal stomach and/or in the cardia was significantly associated with carditis. In patients without carditis, H. pylori was not detected in any cardiac or distal gastric biopsy specimen. In contrast, H. pylori was demonstrated in gastric tissue samples (either from the cardia or distally) of patients with carditis, with the prevalence rate increasing with greater degrees of cardiac inflammation. The H. pylori prevalence rate was 12% in the group with mild carditis, 40% in those with moderate carditis, and 57% in patients with marked carditis (P = .0001). In summary, carditis is commonly found in patients with symptoms related to upper gastrointestinal diseases. From analysis of our study cohort, we concluded that carditis was significantly associated with H. pylori infection and active gastritis but not with symptoms or signs of gastroesophageal reflux disease. These findings suggest that carditis with histologic features similar to those of gastritis in the distal stomach was a sequel of H. pylori infection and represented a part of an H. pylori--associated gastric inflammation.

Differences in contractile protein content and isoforms in phasic and tonic smooth muscles

The basis of tonic vs. phasic contractile phenotypes of visceral smooth muscles is poorly understood. We used gel electrophoresis and quantitative scanning densitometry to measure the content and isoform composition of contractile proteins in opossum lower esophageal sphincter (LES), to represent tonic muscle, and circular muscle of the esophageal body (EB), to represent phasic smooth muscle. The amount of protein in these two types of muscles is similar: approximately 27 mg/g of frozen tissue. There is no difference in the relative proportion of myosin, actin, calponin, and tropomyosin in the two muscle types. However, the EB contains approximately 2.4-times more caldesmon than the LES. The relative ratios of alpha- to gamma-contractile isoforms of actin are 0.9 in the LES and 0.3 in EB. The ratio between acidic (LC17a) and basic (LC17b) isoforms of the 17-kDa essential light chain of myosin is 0.7:1 in the LES, compared with 2.7:1 in the EB. There is no significant difference in the ratios of smooth muscle myosin SM1 and SM2 isoforms in the two muscle types. The level of the myosin heavy chain isoform, which contains the seven-amino acid insert in the myosin head, is about threefold higher in the EB compared with LES. In conclusion, the esophageal phasic muscle in contrast to the tonic LES contains proportionally more caldesmon, LC17a, and seven-amino acid-inserted myosin and proportionally less alpha-actin. These differences may provide a basis for functional differences between tonic and phasic smooth muscles.

Effect of long-term treatment with enalapril in streptozotocin diabetic and DOCA hypertensive rats

We studied the effects of long-term treatment with enalapril (5 mg/kg/day orally) on various biochemical and cardiovascular complications in streptozotocin (STZ) diabetic and deoxycorticosterone acetate (DOCA) hypertensive rats. Female Wistar rats made diabetic or hypertensive or both by streptozotocin (STZ; 45 mg/kg) or deoxycorticosterone acetate (DOCA; 10 mg/kg, p.o., daily) or both. Enalapril (5 mg/kg) was administered daily by the oral route for 6 weeks. At the end of 6 weeks, blood samples were taken to analyze glucose, insulin, and lipids. Blood pressure and heart rate were recorded by a noninvasive technique, and cardiac functions were recorded by Neely's working heart preparation. Injection of STZ produced severe glycosuria (>2%), hyperglycemia, hypoinsulinemia, and loss of body weight. It also produced hypercholesterolemia, hypertriglyceridemia, hypertension, bradycardia, and decreased left ventricular developed pressure (LVDP) and increase in angiotensin-converting enzyme (ACE) in left ventricular tissue. DOCA by itself did not produce any change in blood glucose but reduced serum insulin levels in nondiabetic animals. However, in the diabetic group, DOCA reduced blood sugar levels. Treatment with enalapril prevented an increase in the blood pressure and the heart weight. Decrease in the heart rate, reduction in LVDP, and increase in intracardiac activity were observed in diabetic rats; these were also prevented by enalapril treatment. Enalapril had no effect on plasma glucose and did not modify plasma insulin levels in diabetic animals. The effects of STZ and DOCA together were not additive on the investigated parameters, and enalapril was similarly efficient in diabetic and diabetic hypertensive animals.

Effect of chronic treatment with amlodipine in non-insulin-dependent diabetic rats

We have investigated the effects of amlodipine on streptozotocin-(STZ) induced neonatal non-insulin-dependent diabetes mellitus (NIDDM) rats. NIDDM was induced by intraperitoneal injection of STZ (70 mg kg-1) to 5-day-old rat pups. The animals were weaned at 30 days and maintained with food and water ad libitum for 3 months. Amlodipine (5 mg kg-1 p.o.) was administered for 6 weeks after the animals were confirmed diabetic (3 months after the STZ injection). A group of control animals were also maintained and this group received citrate buffer 5 days after birth. Fasting- and fed-glucose levels in NIDDM rats were significantly higher than control rats. Treatment with amlodipine reduced the elevated fasting- and fed-glucose levels significantly. Results of the oral glucose tolerance test (OGTT) revealed the glucose tolerance is impaired in the NIDDM rats. There was a marked increase in glucose levels after oral administration of glucose in the control NIDDM rats. Increased glucose levels were found to be associated with increased insulin levels. Treatment with amlodipine in the NIDDM rats caused a decrease in insulin release, however, glucose levels were found to be lowered significantly indicating that amlodipine causes an increase in insulin sensitivity. In conclusion, our data indicated that amlodipine increases insulin sensitivity in neonatal-STZ NIDDM rats.

An intermediate conductance K+ channel in the cell membrane of mouse intestinal smooth muscle

Single channel currents were recorded from cell-attached and inside-out patches in smooth muscle cells of the mouse ileum in order to identify TEA-sensitive Ca2+-dependent K+ channels. Cells were bathed in high-K+ (150 mM) solution with [Ca2+] buffered to 80-150 nM with EGTA and patch pipettes were filled with low-K+ (2.5 mM) physiological solution. Two distinct TEA-sensitive unitary outward current levels were identified at a holding potential (Vh) of 0 mV, corresponding to intermediate conductance (IK, approximately 40 pS) and large conductance (BK, >200 pS) K+ channels. The open probability (Po) of IK channels increased with depolarization, the voltage for half-maximal activation averaging +12 mV in 80 nM Cabath2+. Raising the [Ca2+] in the high-K+ solution from 80 nM to 150 nM increased the Po of IK channels at Vh=0 mV from 0.078 to 0.21. Likewise, the open probability of BK channels at 0 mV was increased from 0.003 to 0.026. Unlike BK channels, IK channels inactivated with maintained depolarization with a voltage for half-maximal inactivation of -66 mV. IK channels were blocked by 2-5 mM external TEA and were sensitive to both charybdotoxin (100 nM) and apamin (500 nM). Our results suggest that IK channels contribute significantly to the Ca2+-dependent K+ conductance in visceral smooth muscle.

Nitric oxide suppresses a Ca(2+)-stimulated Cl- current in smooth muscle cells of opossum esophagus

Nitric oxide (NO) hyperpolarizes visceral smooth muscles. Using the patch-clamp technique, we investigated the possibility that NO-mediated hyperpolarization in the circular muscle of opossum esophagus results from the suppression of a Ca(2+)-stimulated Cl- current. Smooth muscle cells were dissociated from the circular layer and bathed in high-K+ Ca(2+)-EGTA-buffered solution. Macroscopic ramp currents were recorded from cell-attached patches. Contaminating K(+)-channel currents were blocked with tetrapentylammonium chloride (200 microM) added to all solutions. Raising bath Ca2+ concentration above 150 nM in the presence of A-23187 (10 microM) activated a leak current (IL-Ca) with an EC50 of 1.2 microM at -100 mV. The reversal potential (Erev) of IL-Ca (-8.5 +/- 1.8 mV, n = 8) was significantly different (P < 0.05) from Erev of the background current (+4.2 +/- 1.2 mV, n = 8). Equimolar substitution of 135 mM Cl- in the pipette solution with gluconate significantly shifted Erev of IL-Ca to +16.6 +/- 3.4 mV (n = 4) (P < 0.05 compared with background), whereas replacement of total Na+ with Tris+ suppressed IL-Ca but did not affect Erev (-15 +/- 3 mV, n = 3; P > 0.05). IL-Ca was inhibited by DIDS (500 microM). Diethylenetriamine-NO adduct (200 microM), a NO donor, and 8-bromo-cGMP (200 microM) suppressed IL-Ca by 59 +/- 15% (n = 5) and 62 +/- 21% (n = 4) at -100 mV, respectively. We conclude that in opossum esophageal smooth muscle NO-mediated hyperpolarization may be produced by suppression of a Ca(2+)-stimulated Cl(-)-permeable conductance via formation of cGMP.

Effect of chronic treatment with spirapril on biochemical parameters in streptozotocin-diabetic and spontaneously hypertensive rats

Present investigation was undertaken to study the effects of 6 week treatment with spirapril (2 mg/kg po) on insulin sensitivity, and serum lipid levels in streptozotocin (STZ)-diabetic and spontaneously hypertensive (SH) rats. Treatment of rats with spirapril in diabetic and diabetic with hypertensive animals significantly prevented STZ-induced loss of body weight, hypertension, and bradycardia. It also partially but significantly prevented STZ-induced hyperglycaemia in both diabetic Wistar and SH animals. Insulin level was not altered by spirapril treatment. There was significant reduction in cholesterol levels in the diabetic rats. In conclusion, the present investigation presents a number of beneficial effects of spirapril treatment in diabetic and/or hypertensive rats. Spirapril may be considered as one of the drugs of choice in treatment of hypertension when associated with diabetes

Beneficial effects of clonidine in streptozotocin-induced diabetes and DOCA-hypertensive rats

This investigation was undertaken to study the effects of chronic treatment with clonidine on cardiovascular complications in streptozotocin-induced diabetes and DOCA-hypertensive rats. Injection of streptozotocin induced glucosuria, hyperglycaemia, hypoinsulinaemia, hypothyroidism, hypercholesterolaemia, hypertriglyceridaemia, bradycardia and a decrease in left ventricular developed pressure (LVDP). DOCA by itself did not induce any change in blood-glucose levels in non-diabetic animals. However, in diabetic animals DOCA significantly reduced blood-glucose levels. Treatment of diabetic and diabetic hypertensive animals with clonidine (25 micrograms kg-1 every day for six weeks) significantly prevented diabetes-induced loss of body weight, bradycardia, cardiac hypertrophy and hypothyroidism. It also partially, but significantly, prevented diabetes-induced hyperglycaemia and hypoinsulinaemia in both diabetic and diabetic-hypertensive animals. There was a significant reduction in diabetes-induced elevation of cholesterol and triglyceride levels and an improvement in LVDP at higher filling pressure in diabetic and diabetic hypertensive animals. This investigation shows that chronic treatment with clonidine produces a number of beneficial effects such as prevention of hyperlipidaemia and hypothyroidism and improvement in cardiomyopathy and glycaemic control in diabetic and diabetic hypertensive rats.

Effects of chronic ramipril treatment in streptozotocin-induced diabetic rats

The present investigation was undertaken to study the effects of chronic oral ramipril (1 mg/kg) treatment in streptozotocin (STZ) induced diabetic rats. Single tail vein injection of STZ (45 mg/kg, i.v.) produced a diabetic state exhibiting all the cardinal symptoms such as loss of body weight, polydipsia, polyuria, glucosuria, polyphagia, hypoinsulinaemia and hyperglycaemia. The diabetic state was also found to be associated with bradycardia, hypothyroidism, cardiac depression and cardiomyopathy. Ramipril treatment prevented STZ-induced hypertension, bradycardia, hypothyroidism, hyperchosesterolaemia and partially the cardiomayopathy. Ramipril treatment could not, however prevent STZ-induced loss of body weight, polyuria, polydipsia, polyphagia, hyperglycaemia, hypoinsulinaemia, hypertriglyceridaemia and cardiac depression. Our data suggests that ramipril has a few beneficial effects in the STZ-treated diabetic rats.

Mechanism of the antihyperlipaemic activity and pharmacokinetics of 2-chloromethyl-5,6,7,8-tetrahydrobenzo(b)thieno[2,3-d]pyrimidin-4(3H)-o ne

The pharmacokinetics and the mechanism of action of the antihyperlipaemic compound 2-chloromethyl-5,6,7,8-tetrahydrobenzo(b)thieno[2,3-d]pyrimidin-4(3H)-on e (CAS 89587-03-3, LM-1554) have been studied. Serum concentrations were determined by reverse phase HPLC using methanol : water (60 : 40) as the solvent system. The results of pharmacokinetic studies suggest that the compound LM-1554 is poorly absorbed from the gastrointestinal tract after the oral administration in dogs and rabbits. The volume of distribution (Vd) was found to be low. The poor bioavailability (3-4%) and low volume of distribution of the compound LM-1554 suggest the gastrointestinal tract as the site of action for the antihyperlipaemic activity. This hypothesis is substantiated by the observations that the compound was found active in rabbits only when administered orally and found inactive by the parenteral route. Further, the cholesterol levels were found to increase in blood samples collected from the portal vein after oral administration of cholesterol in coconut oil to rats. This increase was found to be prevented by the compound LM-1554. In conclusion, the compound LM-1554 has a potential to be developed as an antihyperlipaemic agent. The mechanism of action of the compound LM-1554 appears to consist in the inhibition of cholesterol absorption in the gastrointestinal tract.

Evidence for alpha 2-adrenoceptor agonist activity of minoxidil

The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations. Minoxidil (4.7 x 10(-6) M to 4.7 x 10(-4) M) produced a concentration-dependent inhibition of field stimulation-evoked responses in rat anococcygeus muscle and vas deferens. The inhibition produced by minoxidil was antagonized by yohimbine (2.5 x 10(-7) M). Minoxidil (1.4 x 10(-5) M to 4.7 x 10(-4) M) also produced a concentration-dependent relaxation in oestrogen-primed potassium chloride-depolarized rat uterus. These responses were blocked not only by yohimbine but also by glibenclamide (2.02 x 10(-8) M). Our results suggest that minoxidil possesses alpha 2-adrenoceptor agonist activity in addition to potassium-channel-opening activity.

Activation of small conductance Ca(2+)-dependent K+ channels by purinergic agonists in smooth muscle cells of the mouse ileum

1. Whole-cell and single-channel K+ currents were recorded at room temperature (22-24 degrees C), from smooth muscle cells enzymatically dispersed from the mouse ileum, using variations of the patch-clamp technique. 2. Net outward K+ currents recorded through amphotericin-B-perforated patches in response to step depolarizations positive to -50 mV from a holding potential of -80 mV were decreased by up to 70% by external apamin (0.5 microM). Apamin-sensitive whole-cell currents were also recorded from cells perfused internally with 150 nM Ca2+ but not from cells perfused internally with 85 nM Ca2+. 3. Three types of non-inactivating Ca(2+)-sensitive K+ channels were identified in cell-attached and excised patches under an asymmetrical K+ gradient: (i) large conductance (BKCa; approximately 200 pS) channels blocked by 2 mM external TEA; (ii) intermediate conductance (IKCa; approximately 39 pS) channels blocked by 2 mM external TEA and inhibited by external apamin (0.5 microM); and (iii) small conductance (SKCa; approximately 10 pS) channels that were not blocked by 5 mM external TEA but were sensitive to extracellular apamin (0.5 microM). 4. The TEA-resistant SKCa channels were activated by an increase in [Ca2+]i with an EC50 of 1.5 microM and a Hill coefficient of 1.3. 5. P2 purinoceptor agonists 2-methylthioATP (2-MeSATP), 2-chloroATP and ATP (10-50 microM) increased an apamin-sensitive whole-cell outward K+ current. Extrapatch application of 2-MeSATP (20-100 microM) stimulated the apamin-sensitive IKCa and SKCa channels and activated an apamin-sensitive steady outward current at 0 mV. 6. Smooth muscle cells from the mouse ileum possess two apamin-sensitive K+ channels (IKCa and SKCa); of these, the IKCa channels are TEA sensitive while the SKCa channels are TEA resistant. These channels, along with an apamin-sensitive but TEA-resistant steady outward current, may mediate membrane hyperpolarization elicited by purinergic agonists.

Tyrosine phosphorylation in contraction of opossum esophageal longitudinal muscle in response to SNP

Sodium nitroprusside (SNP) has been shown to elicit a guanosine 3',5'-cyclic monophosphate (cGMP)-mediated, indomethacin-sensitive contraction of the opossum esophageal longitudinal muscle. We examined the role of tyrosine phosphorylation in the signal transduction pathway of contractions induced by SNP and cGMP in longitudinal muscle strips in vitro. Force of isometric contractions was expressed as the percentage of responses to KCl (73 mM). SNP (100 microM)-induced contractions were 75 +/- 5% before and 3 +/- 2% after 50 microM genistein (P < 0.005) and 86 +/- 16% before and 0 +/- 0% after 50 microM tyrphostin B46. Contractions in response to 8-bromo-cGMP (8-BrcGMP; 1 mM) were 74 +/- 15% before and 3 +/- 2% after genistein (P < 0.01) and 63 +/- 15% before and 18 +/- 4% after tyrphostin B46 (P < 0.05). In contrast, KCl-induced contractions were 82 +/- 8% and 96 +/- 9% of the control value after genistein and tyrphostin B46 treatments, respectively (P > 0.05 for both). Carbachol contractions were partially suppressed by genistein (106 +/- 8% vs. 79 +/- 8%; P < 0.05) but unaffected by tyrphostin B46 (114 +/- 10% vs. 107 +/- 12%; P > 0.05). Western blot analysis revealed a 116-kDa phosphotyrosine protein in the control muscle strips. The level of this protein was increased to 206 +/- 15% of control after SNP treatment. Both genistein and tyrphostin B46 blocked this increase. These studies show that contractions of the esophageal longitudinal muscle induced by SNP and cGMP utilize a signal transduction pathway different from that used by the depolarizing agent KCl and the muscarinic agonist carbachol. Contractions induced by SNP and cGMP involve tyrosine phosphorylation of a protein, possibly identified as a 116-kDa protein, as a key step in the signaling pathway.

Effects of chronic treatment with amlodipine in streptozotocin-diabetic and spontaneously hypertensive rats

Calcium antagonists have been reported to alter insulin secretion and insulin sensitivity. However, there still exists a controversy over the benefits of calcium antagonists in the conditions when diabetes mellitus and hypertension coexist. In the present study the effects of six-week chronic amlodipine treatment (5 mg kg-1 p.o.) on insulin sensitivity and serum lipid levels in streptozotocin (STZ)-diabetic and spontaneously hypertensive (SH) rats were investigated. Intravenous injection of STZ produced glucosuria (> 2%). hyperglycaemia, hypoinsulinemia, polydipsia, polyphagia, loss of body weight, hypercholesterolemia, hypertriglyceridaemia, hypertension and bradycardia. SH rats were found to have significantly higher insulin levels compared to their Wistar controls. Treatment of rats with amlodipine in diabetic and diabetic-hypertensive animals significantly prevented STZ-induced loss of body weight, hypertension and bradycardia. It also significantly prevented STZ-induced hyperglycaemia in both STZ-diabetic Wistar and SH rats. The insulin levels were decreased in the non-diabetic treated Wistar rats but were unaltered in the non-diabetic SH and the diabetic Wistar and SH rats. There was a significant reduction in cholesterol levels in diabetic Wistar and SH rats. In conclusion the present study revealed beneficial effects of amlodipine treatment in hyperinsulinemic, diabetic and/or hypertensive rats.