Anti-ischemic effects of angiotensin- converting enzyme inhibition in hypertension

OBJECTIVES

We investigated whether augmentation of bradykinin (BK) bioavailability with angiotensin-converting enzyme (ACE) inhibition is associated with reduced exercise-induced myocardial ischemia in hypertension.

BACKGROUND

Bradykinin responses are depressed in hypertension, and endothelial dysfunction contributes to myocardial ischemia by promoting abnormal coronary vasomotion during stress.

METHODS

Fourteen hypertensive (HT) and 17 normotensive (NT), mildly symptomatic patients with coronary artery disease (CAD) and ST-segment depression during exercise were studied before and after seven days of oral enalapril (EN), which was titrated from 2.5 to 20 mg daily. Patients underwent two treadmill exercise tests and determination of forearm vasodilator response to BK.

RESULTS

Despite receiving a lower dose of EN (7.8 vs. 14.8 mg, p < 0.001), NT patients had a significant reduction in blood pressure compared to HT patients. Compared to pre-EN, the ischemic threshold, defined as the rate-pressure product at the onset of 1-mm ST depression (p = 0.045), the duration of exercise to 1-mm ST depression (180 +/- 54 s, p = 0.007) and the maximum exercise duration (94 +/- 18 s, p < 0.001) were greater after EN in HT patients, but not in NT subjects (all p > or = 0.3). Patients with a greater drop in blood pressure experienced no improvement in exercise-induced ischemia. Forearm blood flow responses to BK were improved with EN in all patients to a similar extent. Moreover, no correlation was observed between the basal response to BK or the magnitude of its improvement with EN and with either the dose of EN or the improvement in exercise ischemic threshold.

CONCLUSIONS

Exercise-induced myocardial ischemia is ameliorated in HT patients with CAD by ACE inhibition.

Angiotensin type 1 receptor antagonism reverses abnormal coronary vasomotion in atherosclerosis

OBJECTIVES

This study was performed to determine whether angiotensin type 1 (AT1) receptor inhibition improves abnormal coronary vasomotion and endothelial dysfunction in patients with atherosclerosis or its risk factors.

BACKGROUND

Endothelial dysfunction, an early feature of atherosclerosis, contributes to abnormal vasomotion during stress. Angiotensin II may contribute to endothelial dysfunction in atherosclerosis.

METHODS

In 25 patients, mean age 59 +/- 2 years, with atherosclerosis or its risk factors, we measured coronary vasomotion during flow-mediated dilation (FMD) in response to adenosine, cold pressor test (CPT) and exercise before and after AT1 receptor blockade with intracoronary losartan (5 mg).

RESULTS

Losartan did not alter resting coronary vascular tone, but epicardial FMD improved from 5.6 +/- 1.5% to 8.9 +/- 1.8% (p = 0.02). Abnormal epicardial vasomotion during CPT and exercise also improved with losartan from -1.7 +/- 0.8% to 1.5 +/- 0.1% (p = 0.02) and -0.6 +/- 0.9% to 3.4 +/- 1.2% (p = 0.009), respectively. Improvement in epicardial vasomotion was most prominent in segments with baseline endothelial dysfunction evidenced as constriction during stress. Microvascular dilation during adenosine, an endothelium-independent response, was unchanged with losartan.

CONCLUSIONS

Inhibition of the coronary vascular AT1 receptors in patients with atherosclerosis improves epicardial vasomotion during stress, probably by improving endothelial dysfunction. Whether AT1 receptor blockade will provide long-term therapeutic benefits in atherosclerosis needs further investigation.

Antimicrobial susceptibility testing in India - a status survey

Resistance to a variety of antimicrobial agents is emerging in bacterial pathogens throughout the world. Since the accuracy of the antimicrobial susceptibility data is associated with the performance standard of the test, strict adherence to the standard procedures is essential. The Kirby-Bauer disc diffusion susceptibility test, performed in accordance to NCCLS method gives reliable results and hence predicts clinical efficacy of the antibiotic tested. To assess the standard of performance of the antimicrobial susceptibility test, a survey was conducted by National Institute of Biologicals during 1999-2000. The findings indicated an urgent need of setting up a national quality control laboratory to provide the performance standards, reference Q.C. strains and quality antibiotic discs to ensure reproducible and reliable results.

Role of angiotensin II type 1 receptor in the regulation of cellular adhesion molecules in atherosclerosis

BACKGROUND

Inflammation is a central feature of coronary artery disease (CAD) that is characterized by increased expression of cellular adhesion molecules with the exception of L-selectin. L-selectin is a leukocyte adhesion molecule that is rapidly shed after leukocyte activation so that it appears to be decreased in CAD. The renin-angiotensin system (RAS) is implicated in atherogenesis and up-regulates these molecules.

OBJECTIVES

The aim of this study was to investigate the effect of angiotensin type 1 (AT1) receptor antagonism on serum and leukocyte adhesion molecule expression in patients with CAD. Blood samples were collected from 31 patients before and after 8 weeks of treatment with losartan (44 +/- 2 mg/d, mean +/- SE), an AT1 receptor antagonist. We measured serum intercellular adhesion molecule-1, vascular cell adhesion molecule-1, endothelial-leukocyte adhesion molecule, and C-reactive protein (CRP). By flow cytometry, we also measured the expression of leukocyte CD11a, CD11b, CD11c, CD18, CD31, CD49d, and CD62L (L-selectin) in 13 patients.

RESULTS

Treatment with losartan decreased systolic blood pressure (141 +/- 3 vs 135 +/- 4 mm Hg, P =.04) and increased plasma renin activity (1.2 +/- 0.4 vs 2.7 +/- 0.5 ng/mL/h, P =.001). There was a significant increase in L-selectin expression on monocytes (86 +/- 6 vs 118 +/- 10 MESF units, P =.007), lymphocytes (52 +/- 10 vs 79 +/- 8, P =.01), and granulocytes (124 +/- 7 vs 156 +/- 18, P =.056). However, there were no changes in the other leukocyte and serum adhesion molecules or CRP.

CONCLUSIONS

These findings suggest that AT1 receptor antagonism selectively modulates L-selectin expression on leukocytes and that endogenous stimulation of AT1 receptors by the RAS contributes to the activation of leukocytes and decreased expression of L-selectin in CAD.

Tuberculous biliary strictures: uncommon cause of obstructive jaundice

Tuberculous biliary stricture is a very rare cause of obstructive jaundice. A case of a man who had had pulmonary tuberculosis 20 years ago is reported. He now presented with obstructive jaundice due to multiple strictures just below the confluence of the hepatic ducts and in the right hepatic duct. At surgery these turned out to be tuberculous in origin. There was also tuberculous involvement of the gall bladder and cystic duct. The commonest differential diagnosis in such cases is cholangiocarcinoma (as in the present case). Imaging helps in defining the extent of bile duct obstruction. Suspicion of the disease and establishing a tissue diagnosis is very important in treating this potentially curable condition, especially with the worldwide resurgence of tuberculosis.

Pulmonary blastoma

A three-and-half-year-old boy presented with recurrent chest infections, fever and weight loss of three month duration not responding to antibiotics. The chest X-ray and CT scan revealed a large well-circumscribed mass in right upper thorax with collapse of right upper lobe. A preoperative diagnosis could not be made even after fine needle aspiration cytology. Thoracotomy and right upper lobectomy was done and the biopsy report was an inflammatory pseudotumor. The child remained well for three months after which his symptoms and the mass recurred. The histopathology slides were reviewed and revealed a biphasic malignant tumor suggestive of Pulmonary Blastoma (PB). Patient received four cycles of chemotherapy followed by re-exploration. The recurrent tumour could only be excised partly and the child succumbed to persistent shock postoperatively. The final histopathological diagnosis was confirmed as PB. Primary pulmonary neoplasms in children are rare and of these PB which is even rarer, constitutes less than 15%. The report highlights that the lack of familiarity with this entity still causes error in the diagnosis of PB.

Ca2+ signaling in the transformation of promastigotes to axenic amastigotes of Leishmania donovani

The present study is an attempt to look into the role of Ca2+ in signaling the transformation of promastigotes to axenic amastigotes. An estimation of intracellular free calcium concentration at 6 h intervals during the conversion of promastigotes to axenic amastigotes (72 h) revealed a 10 fold increase in [Ca2+]i at the initial 6-12 h during the conversion. This was followed by declining levels till 60 h and the concentration thereafter remained constant. Axenic amastigotes (72 h) had a 5 fold higher [Ca+]i as compared to the promastigotes. A 30-40% decrease in [Ca2+]i after pretreatment of cells with dentrolene and a gradual rise of intracellular Ca2+ in [Ca2+] free medium indicates the role of intracellular calcium pools in the elevation of [Ca2+]i. A sudden increase in [Ca2+]i on addition of NH4Cl (20 mM) in the cells grown in Ca2+ free medium indicates the presence of acidocalcisomes, as intracellular Ca2+ storing pool, in L. donovani. To study the role of Ca2+ influx from the external medium in the morphogenetic transformation and in the elevation of [Ca2+]i a 45Ca2+ uptake study was performed. Maximum uptake of 45Ca2+ was observed in the initial 24 h of transformation and maximum Ca2+ ATPase activity was also observed between 24-42 h. So the presence of low Ca2+ in the cytosol, existence of intracellular Ca2+ pools and presence of mechanisms to maintain the Ca2+ homeostasis in the cells suggests that Ca2+ can be an appropriate candidate for a second messenger during the morphogenetic transformation of L. donovani.

Endoscopic retrograde cholangiopancreatography in the management of pancreaticobiliary disorders in children

BACKGROUND AND AIM

The role of endoscopic retrograde cholangiopancreatography (ERCP) is not yet fully established in children. The purpose of this study was to assess the use of ERCP in the diagnosis and management of various pancreaticobiliary disorders in children.

METHODS

Eighty-four ERCPs were performed over 5.5 years in 72 children with suspected pancreaticobiliary tract disorders with an adult-type duodenoscope. In all cases, indications, procedure time, ERCP findings, complications, patients course and therapeutic intervention (if any) were recorded.

RESULTS

The mean (+/- SD) age of these children was 8.8 +/- 3.3 years. Successful cannulation was possible in 70 (97%) cases. Of the 44 cases with suspected biliary tract disease, 14 had a choledochal cyst, 13 had portal biliopathy, two each had CBD stones, primary sclerosing cholangitis and a bile leak, one had biliary ascariasis, eight had a normal cholangiogram, and CBD cannulation failed in two. Eight of the 28 children with suspected pancreatic disorders had chronic pancreatitis, five had pancreatic duct disruption, three had pancreas divisum and the rest had a normal pancreatogram (including all eight children with unexplained abdominal pain). Therapeutic ERCP was performed in 22 children, endoscopic nasobiliary or a nasocystic drain was placed in 16, biliary stenting was conducted in two, pancreatic duct stenting was conducted in three, and minor papilla dilation was conducted in one child. Six children had mild procedure-related complications.

CONCLUSION

Endoscopic retrograde cholangiopancreatography is very useful in the treatment of cholangitis, bile leak, pseudocyst and pancreatic fistulae in children. However, its role in unexplained abdominal pain is doubtful.

Cholecystogastric fistula: laparoscopic repair

We describe a patient with a cholecystogastric fistula treated by the laparoscopic approach. The use of intracorporeal suturing allows laparoscopic management of cholecystogastric fistulae without the need for an endoscopic transecting stapler.

Bronchoconstriction following nebulised colistin in cystic fibrosis

Nebulised colistin is regularly used as antipseudomonal therapy in children with cystic fibrosis. We assessed bronchoconstriction in response to nebulised colistin in 58 children. Nebulised colistin significantly reduced FEV(1), MEF(25%), and SaO(2) for 15 minutes. In 20 children the reduction was greater than 10% from baseline FEV(1), and was still at that level in five at 30 minutes. Subjective assessment, baseline FEV(1), and serum IgE were unable to identify susceptible children. It is recommended that children receiving colistin should be carefully assessed for bronchoconstriction.

Propofol and midazolam in the treatment of refractory status epilepticus

PURPOSE

To explore outcome differences between propofol and midazolam (MDL) therapy for refractory status epilepticus (RSE).

METHODS

Retrospective chart review of consecutive patients treated for RSE between 1995 and 1999.

RESULTS

We found 14 patients treated primarily with propofol and six with MDL. Propofol and MDL therapy achieved 64 and 67% complete clinical seizure suppression, and 78 and 67% electrographic seizure suppression, respectively. Overall mortality, although not statistically significant, was higher with propofol (57%) than with MDL (17%) (p = 0.16). Subgroup mortality data in propofol and MDL patients based on APACHE II (Acute Physiology and Chronic Health Evaluation) score did not show statistically significant differences except for propofol-treated patients with APACHE II score > or = 20, who had a higher mortality (p = 0.05). Reclassifying the one patient treated with both agents to the MDL group eliminated this statistically significant difference (p = 0.22).

CONCLUSIONS

In our small sample of RSE patients, propofol and MDL did not differ in clinical and electrographic seizure control. Seizure control and overall survival rates, with the goal of electrographic seizure elimination or burst suppression rather than latter alone, were similar to previous reports. In RSE patients with APACHE II score > or = 20, survival with MDL may be better than with propofol. A large multicenter, prospective, randomized comparison is needed to clarify these data. If comparable efficacy of these agents in seizure control is borne out, tolerance with regard to hemodynamic compromise, complications, and mortality may dictate the choice of RSE agents.

Neurocysticercal serodiagnosis--updated

For diagnosis of neurocysticercosis the gold standard would be a stereotactic biopsy and histological confirmation which are not universally available or acceptable to patients, hence the necessity of immunodiagnosis. The authors have narrated beautifully the serodiagnostic aspects of neurocysticercosis in its updated form and have discussed the subject with proper references.

N-acetylcysteine improves coronary and peripheral vascular function

OBJECTIVES

We investigated whether N-acetylcysteine (NAC), a reduced thiol that modulates redox state and forms adducts of nitric oxide (NO), improves endothelium-dependent vasomotion.

BACKGROUND

Coronary atherosclerosis is associated with endothelial dysfunction and reduced NO activity.

METHODS

In 16 patients undergoing cardiac catheterization, seven with and nine without atherosclerosis, we assessed endothelium-dependent vasodilation with acetylcholine (ACH) and endothelium-independent vasodilation with nitroglycerin (NTG) and sodium nitroprusside (SNP) before and after intracoronary NAC. In 14 patients femoral vascular responses to ACH, NTG and SNP were measured before and after NAC.

RESULTS

Intraarterial NAC did not change resting coronary or peripheral vascular tone. N-acetylcysteine potentiated ACH-mediated coronary vasodilation; coronary blood flow was 36 +/- 11% higher (p < 0.02), and epicardial diameter changed from -1.2 +/- 2% constriction to 4.7 +/- 2% dilation after NAC (p = 0.03). Acetylcholine-mediated femoral vasodilation was similarly potentiated by NAC (p = 0.001). Augmentation of the ACH response was similar in patients with or without atherosclerosis. N-acetylcysteine did not affect NTG-mediated vasodilation in either the femoral or coronary circulations and did not alter SNP responses in the femoral circulation. In contrast, coronary vasodilation with SNP was significantly greater after NAC (p < 0.05).

CONCLUSIONS

Thiol supplementation with NAC improves human coronary and peripheral endothelium-dependent vasodilation. Nitroglycerin responses are not enhanced, but SNP-mediated responses are potentiated only in the coronary circulation. These NO-enhancing effects of thiols reflect the importance of the redox state in the control of vascular function and may be of therapeutic benefit in treating acute and chronic manifestations of atherosclerosis.

Host response to cytomegalovirus infection as a determinant of susceptibility to coronary artery disease: sex-based differences in inflammation and type of immune response

BACKGROUND

Positive and negative associations between cytomegalovirus (CMV) infection and coronary artery disease (CAD) have been reported. We postulated that the susceptibility to CMV-induced CAD might relate to patterns of inflammatory and immune responses to CMV infection and that sex might have an effect on these responses.

METHODS AND RESULTS

In 151 men and 87 women being evaluated for CAD, blood samples were tested for humoral (Ab+) and cellular (Tc+) responses to CMV and for C-reactive protein (CRP). In men, an elevated CRP level was a significant determinant of CAD even after adjustment for CAD risk factors (OR, 3.1; 95% CI, 1.21 to 7. 97). CMV seropositivity was associated with elevated CRP levels on multivariate analysis (P:=0.006). In contrast, in women, CMV seropositivity was independently predictive of CAD (OR, 41.8; 95% CI, 4.12 to 423.74). CRP level in women with CAD was >25% higher than those without CAD, but the difference did not reach statistical significance. Importantly, compared with CMV Ab-/Tc- women, CAD prevalence was higher in Ab+/Tc- and Ab+/Tc+ (13% versus 68% and 64%, both P:<0.005) but not in Ab-/Tc+ women (25%). There were no differences in age, smoking, diabetes, hypertension, and hypercholesterolemia among women with different types of immune responses to CMV infection.

CONCLUSIONS

The mechanisms by which CMV predisposes to CAD in men and women may be different. In men, CMV appears to contribute to CAD risk, insofar as it predisposes to inflammation. In women, other mechanisms, possibly related to the type of immune response generated by the host, appear to be responsible for the proatherogenic effects of CMV.

Contribution of bradykinin receptor dysfunction to abnormal coronary vasomotion in humans

OBJECTIVES

The aim of our study was to investigate coronary vascular kinin receptor function in patients with atherosclerosis or its risk factors.

BACKGROUND

Although acetylcholine (ACH) is used as a probe for testing vascular function in vivo, endogenous bradykinin (BK) regulates resting and flow-mediated epicardial tone.

METHODS

In 53 patients with mild atherosclerosis or its risk factors and 9 control subjects, endothelium-dependent vasomotion was tested with intracoronary ACH (30 microg/min) and BK (62.5 ng/min and 4 microg/min), and endothelium-independent function with sodium nitroprusside. Metabolic vasodilation was assessed during cardiac pacing (n = 19). Correlation with serum angiotensin-converting enzyme (ACE) levels and the ACE insertion/deletion genotype was performed.

RESULTS

There was progressive impairment in ACH-mediated microvascular dilation with increasing numbers of risk factors (p = 0.025, analysis of variance). By contrast, BK- and sodium nitroprusside-mediated microvascular dilation was similar in all groups. Similarly, there was no correlation between epicardial coronary responses to ACH and BK; segments that constricted or dilated with ACH had similar dilator responses with BK. Bradykinin, but not ACH-mediated vasomotion, was depressed in epicardial segments that constricted with pacing. Finally, epicardial BK responses were depressed in patients with high ACE levels and in those with the ACE DD genotype.

CONCLUSIONS

Endothelial dysfunction in atherosclerosis appears to be receptor-specific, involving the muscarinic receptor with relative sparing of the kinin receptor pathways. Abnormal reactivity of epicardial coronary arteries during physiologic stress is better represented by BK and not by ACH responses. Bradykinin activity and, hence, physiologic coronary vasomotion appears to be influenced by serum ACE levels and the ACE insertion/deletion genotype.

The insertion/deletion polymorphism of the angiotensin-converting enzyme gene determines coronary vascular tone and nitric oxide activity

OBJECTIVES

We investigated whether the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene modulates vasomotor tone and endothelial function.

BACKGROUND

The deletion allele of the ACE I/D polymorphism has been associated with increased incidence of cardiovascular pathology. The risk is synergistically increased in patients who also possess the C allele at position 1,166 of the angiotensin type I (AT1) receptor gene.

METHODS

In 177 patients with coronary atherosclerosis or its risk factors, we investigated endothelial function with intracoronary acetylcholine (ACH), endothelium-independent smooth muscle function with sodium nitroprusside (SNP) and basal nitric oxide activity with L-NG monomethyl arginine.

RESULTS

Compared with ACE II genotype, patients with the ACE DD genotype had lower coronary microvascular and epicardial responses with SNP (coronary blood flow increase 196 +/- 26% vs. 121 +/- 11%, p = 0.003, and diameter increase 21.9 +/- 2% vs. 17 +/- 1%, p = 0.03, ACE II vs. DD, respectively). L-NG monomethyl arginine induced greater constriction in patients with the ACE DD compared with ACE II genotype (coronary blood flow -10 +/- 4% vs. 11 +/- 5%, p = 0.003, ACE DD vs. II and diameter constriction -6.3 +/- 1.2% vs. -1.9 +/- 1.2%, p = 0.01, respectively, in patients with atherosclerosis). No difference in ACH-mediated vasomotion was detected between the three ACE genotypes. The AT1 receptor polymorphism did not influence responses to either SNP or ACH.

CONCLUSIONS

Patients possessing the D allele of the ACE gene have increased vascular smooth muscle tone. The enhanced tone appears to be counterbalanced by an increase in basal nitric oxide activity in patients with atherosclerosis.

Regional and developmental expression of the Npc1 mRNA in the mouse brain

Niemann-Pick type C (NP-C) disease is a fatal, autosomal recessive disorder of cholesterol metabolism that results in progressive central nervous system deterioration and premature death. Recently, a gene mutated in NP-C disease (NPC1) was identified in both human patients and in the npc(nih) mouse model. Although the function of the NPC1 gene is at present unknown, determining the pattern of its expression in the brain may facilitate identification of the mechanisms underlying the neuropathology of this disease and in identifying relevant targets for any potential therapeutic intervention. We have used in situ hybridization techniques to characterize the pattern of Npc1 mRNA expression in both the wild-type and the npc(nih) mutant mouse brain. In adult animals of both genotypes, the Npc1 mRNA was detected in the majority of neurons in nearly all regions, but at significantly higher levels in the cerebellum and in specific pontine nuclei. Analysis of Npc1 mRNA levels during development in the wild-type mouse indicated that this transcript was expressed in neurons as early as embryonic day 15 and that a significant region-specific pattern of expression was established by postnatal day 7. Our data suggest that whereas the NPC1 gene is widely expressed in neurons of the brain, the higher levels of expression in the cerebellum and pontine structures established by early postnatal ages may make these regions more susceptible to neuronal dysfunction in NP-C disease.

Dealloying and electroformation in high-Pd dental alloys

OBJECTIVE

The corrosion of high-Pd dental alloys, depending on their composition, is postulated to be associated with dealloying and electroformation. The aim of this study was to obtain additional information to support these postulations.

METHODS

The corrosion characteristics of two commercial high-Pd alloys, Naturelle (79Pd-10Cu-2Au-9Ga wt%) and Rx 91 (54Pd-37Ag-9Sn), and their elemental components were evaluated in a phosphated buffer saline (PBS) solution. Indium, a common element in high-Pd alloys, was also included. The corrosion characteristics measured for each material were the 24 h open circuit potential (OCP) and the potentiodynamic anodic polarization curve. Additionally, the surface composition of the two alloys, before and after immersion corrosion in PBS for 2 months, was analyzed by X-ray photo electron spectroscopy (XPS).

RESULTS

Of the pure metals, Ga had the most electroactive OCP followed in order by In, Sn, Cu, Ag, Au, and Pd. The anodic polarization data showed all base metals to be unstable in PBS. The electroformation of AgCl was evidenced in the polarization curve of pure Ag. Both electrochemical characteristics of the PdCu-based alloy were very similar to that of pure Pd. The PdAg-based alloy displayed corrosion behavior resembling that of Ag. XPS data showed that the corrosion of the PdCu-based alloy was associated with a decrease in surface content of Cu and Ga but an increase in Pd and Au. The PdAg-based alloy surface during corrosion showed a decrease in Sn, an increase in Ag, and an unaltered Pd content. The behavior of the PdCu-based alloy is attributed to the operation of a galvanic interaction that causes dissolution of base metals and surface enrichment with primarily Pd. Dealloying, Ag-enrichment, and AgCl formation are thought to have contributed to the observed behavior of the PdAg-based alloy. These mechanisms are consistent with data from published ion release studies.

SIGNIFICANCE

The allergenic potential of any Pd alloy is dependent on its propensity to develop a Pd-rich surface and thus release Pd+2 ions. The present study, though limited, has shown that electrochemical characteristics, namely OCP and polarization curves, can be used to identify such alloys. Further studies are warranted to evaluate the widespread applicability of these characteristics in distinguishing between Pd alloys that are biologically safe and those that are not.