The J-helix of Escherichia coli DNA polymerase I (Klenow fragment) regulates polymerase and 3'- 5'-exonuclease functions

To assess the functional importance of the J-helix region of Escherichia coli DNA polymerase I, we performed site-directed mutagenesis of the following five residues: Asn-675, Gln-677, Asn-678, Ile-679, and Pro-680. Of these, the Q677A mutant is polymerase-defective with no change in its exonuclease activity. In contrast, the N678A mutant has unchanged polymerase activity but shows increased mismatch-directed exonuclease activity. Interestingly, mutation of Pro-680 has a Q677A-like effect on polymerase activity and an N678A-like effect on the exonuclease activity. Mutation of Pro-680 to Gly or Gln results in a 10-30-fold reduction in k(cat) on homo- and heteropolymeric template-primers, with no significant change in relative DNA binding affinity or K(m)((dNTP)). The mutants P680G and P680Q also showed a nearly complete loss in the processive mode of DNA synthesis. Since the side chain of proline is generally non-reactive, mutation of Pro-680 may be expected to alter the physical form of the J-helix itself. The biochemical properties of P680G/P680Q together with the structural observation that J-helix assumes helical or coiled secondary structure in the polymerase or exonuclease mode-bound DNA complexes suggest that the structural alteration in the J-helix region may be responsible for the controlled shuttling of DNA between the polymerase and the exonuclease sites.

Syntheses and biological evaluation of 3-substituted amino-1-aryl-6-hydroxy-hex-2-ene-1-ones as antioxidant and hypolipidemic agents

A new series of compounds belonging to 3-substituted amino-1-aryl-6-hydroxy-hex-2-ene-1-ones (4-12a-e) have been synthesized and evaluated for antioxidant and hypolipidemic activities. Amongst all the synthesized compounds, seven compounds, namely 5b, 5d, 6e, 8a, 8b, 10b and 11a, exhibit better antioxidant activity than probucol. Two compounds, 5d and 10b, have been evaluated in detail for antioxidant and hypolipidemic activities and show comparable activity profile to that of probucol and guggulipid. From the present study it may be postulated that the mechanism of action of these compounds could be through activation of lecithin cholesterol acyltransferase (LCAT), liver lipolytic activity, increased faecal bile acid secretion and inhibition of hepatic cholesterol biosynthesis.

Reversible portal hypertension due to tuberculosis

Presentation of abdominal tuberculosis with portal hypertension is rare. We report a 25-year-old man with portal hypertension due to compression of the portal vein by tuberculous lymph nodes at the hepatic hilum. After antitubercular therapy, features of portal hypertension disappeared as the nodes regressed.

A carboxylate triad is essential for the polymerase activity of Escherichia coli DNA polymerase I (Klenow fragment). Presence of two functional triads at the catalytic center

The catalytic roles of two essential active-site aspartates at positions 705 and 882 of Escherichia coli DNA polymerase I have been well established (Steitz, T. A. (1998) Nature 391, 231-232). We now demonstrate that the participation of at least one additional carboxylate, a glutamate at position 710 or 883, is obligatory for catalysis. This conclusion has been drawn from our investigation of the properties of single (E710D, E710A, E883D, and E883A) and double (E710D/E883D and E710A/E883A) substitutions of residues Glu(710) and Glu(883). While single substitutions of either of the glutamates resulted in some reduction in polymerase activity, the mutant enzyme with simultaneous substitution of both glutamates with alanine exhibited a nearly complete loss of activity. Interestingly, substitution with two aspartates in place of the glutamates resulted in an enzyme species that catalyzed DNA synthesis in a strictly distributive mode. Pyrophosphorolytic activity of the mutant enzymes reflected their polymerase activity profiles, with markedly reduced pyrophosphorolysis by the double mutant enzymes. Moreover, an evaluation of Mg(2+) and salt optima for all mutant enzymes of Glu(710) and Glu(883) revealed significant deviations from that for the wild type, implying a possible role of these glutamates in metal coordination as well as in maintaining the structural integrity of the active site.

p38 mitogen-activated protein kinase pathway protects adult rat ventricular myocytes against beta -adrenergic receptor-stimulated apoptosis. Evidence for Gi-dependent activation

We have shown that stimulation of beta-adrenergic receptors (beta-AR) by norepinephrine (NE) increases apoptosis in adult rat ventricular myocytes (ARVMs) via a cAMP-dependent mechanism that is antagonized by activation of G(i) protein. The family of mitogen-activated protein kinases (MAPKs) is involved in the regulation of cardiac myocyte growth and apoptosis. Here we show that beta-AR stimulation activates p38 kinase, c-jun N-terminal kinases (JNKs), and extracellular signal-regulated kinase (ERK1/2) in ARVMs. Inhibition of p38 kinase with SB-202190 (10 micrometer) potentiated beta-AR-stimulated apoptosis as measured by flow cytometry and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining. SB-202190 at this concentration specifically blocked beta-AR-stimulated activation of p38 kinase and its downstream substrate MAPK-activated protein kinase-2 (MAPKAPK2). Pertussis toxin, an inhibitor of G(i)/G(o) proteins, blocked the activation of p38 kinase and potentiated beta-AR-stimulated apoptosis. Activation of G(i) protein with the muscarinic receptor agonist carbachol protected against beta-AR-stimulated apoptosis. Carbachol also activated p38 kinase, and the protective effect of carbachol was abolished by SB-202190. PD-98059 (10 micrometer), an inhibitor of ERK1/2 pathway, blocked beta-AR-stimulated activation of ERK1/2 but had no effect on apoptosis. These data suggest that 1) beta-AR stimulation activates p38 kinase, JNKs, and ERK1/2; 2) activation of p38 kinase plays a protective role in beta-AR-stimulated apoptosis in cardiac myocytes; and 3) the protective effects of G(i) are mediated via the activation of p38 kinase.

Optical encryption by double-random phase encoding in the fractional Fourier domain

We propose an optical architecture that encodes a primary image to stationary white noise by using two statistically independent random phase codes. The encoding is done in the fractional Fourier domain. The optical distribution in any two planes of a quadratic phase system (QPS) are related by fractional Fourier transform of the appropriately scaled distribution in the two input planes. Thus a QPS offers a continuum of planes in which encoding can be done. The six parameters that characterize the QPS in addition to the random phase codes form the key to the encrypted image. The proposed method has an enhanced security value compared with earlier methods. Experimental results in support of the proposed idea are presented.

Comparison of seven and fourteen days of lansoprazole, clarithromycin, and amoxicillin therapy for eradication of Helicobacter pylori: a report from India

BACKGROUND

In developed countries, a 1-week regimen of combined proton pump inhibitors and two antibiotics is considered adequate for Helicobacter pylori eradication. However, there is a paucity of reports from developing countries on treatment duration of less than 14 days. We compared efficacy of 7 and 14 days of lansoprazole (L), clarithromycin (C), and amoxicillin (A) combinations for eradication of H. pylori.

PATIENTS AND METHODS

Forty-six consecutive patients who presented with upper gastrointestinal symptoms and tested positive for H. pylori infection were included in the study. In every patient, after performance of upper gastrointestinal endoscopy, antral biopsies were obtained. H. pylori infection was diagnosed by positive rapid urease test and identification of organisms on antral histology. Patients were randomly selected to receive lansoprazole, 30 mg once daily, plus clarithromycin, 250 mg twice daily, plus amoxicillin, 500 mg three times daily for 2 weeks (group 1; n = 24; age, 36 +/- 12 years; 18 men) or 1 week (group 2; n = 22; age, 45 +/- 15 years; 12 men). One month after completion of treatment, repeat upper gastrointestinal endoscopy was performed. H. pylori eradication was defined as absence of organism on histopathological examination of both antrum and body of stomach and negative rapid urease test.

RESULTS

Eradication rate was higher in group 1 (23 of 24; 96%) as compared to group 2 (12 of 22; 54%; p <.05). One patient in group 1 had diarrhea, and one patient in group two had skin rash and itching.

CONCLUSIONS

Fourteen-day therapy with lansoprazole, clarithromycin, and amoxicillin is highly effective in eradication of H. pylori. Reducing duration of therapy to 7 days significantly lowers eradication rates.

Endoscopic dilation for treatment of anastomotic leaks following transhiatal esophagectomy

BACKGROUND AND STUDY AIMS

Anastomotic leak is a known complication after transhiatal esophagectomy (THE) and cervical esophagogastric anastomosis. Conservative management takes a long time to heal such leaks. We assessed the role of endoscopic dilation in patients with anastomotic leak following THE.

PATIENTS AND METHODS

Eight consecutive patients (seven men, one woman; mean age 51) with anastomotic leak following THE were subjected to endoscopic dilation using Savary Gilliard dilators of 7-15 mm diameter. The mean interval between surgery and detection of leak was 9 days (range 5-22 days) and dilation was performed at a mean interval of 11.4 days (range 1-20 days) after detection of the leak.

RESULTS

Drainage from fistulas stopped completely after 1-8 days (mean 3 days). X-ray with water soluble contrast showed closure of the fistula in all cases. Duration of follow-up ranged from 2 to 12 months. Anastomotic strictures developed in three patients. These patients required three sessions each of repeat dilation, and were alive at follow-up periods of 2, 4, and 12 months, respectively. One patient developed recurrence of growth at an anastomotic site. Four patients died because of distant metastasis.

CONCLUSIONS

Bougie dilation of anastomotic sites is a safe and effective technique for the healing of anastomotic leaks following THE. However there is a need for a prospective randomized trial comparing endoscopic dilation with no dilation in patients with anastomotic leaks following THE.

Adrenergic overload and apoptosis in heart failure: implications for therapy

Sympathetic nervous system activity to the myocardium is increased in patients with heart failure. It is now appreciated that norepinephrine (NE), the primary sympathetic neurotransmitter, can exert direct adverse effects on cardiac myocytes and might thereby contribute to pathological remodeling, a chronic process which leads to progressive left ventricular (LV) chamber dilation and loss of contractile function. The demonstration of apoptosis in failing human hearts has led to the thesis that continuing loss of viable myocytes is a mechanism for progressive myocardial failure. For many years it has been appreciated that chronic exposure to catecholamines can exert a toxic effect on the myocardium. In vitro studies in cultured cardiac myocytes show that tonic exposure to NE increases the number of apoptotic myocytes via stimulation of the beta-adrenergic receptor (beta-AR) pathway. Interestingly, a beta1-AR selective antagonist completely prevented NE-stimulated apoptosis, whereas a beta2-AR selective antagonist increased the amount of apoptosis, suggesting that beta1- versus beta2-AR may couple to different signaling pathways. In rats, isoproterenol infusion for as little as 12 hours increased the frequency of terminal deoxynucleotidyltransferase-mediated nick end-labeling (TUNEL)-positive myocytes. Likewise, mice that overexpress beta1-AR or G alpha s in the myocardium develop left ventricular dilation, contractile dysfunction and apoptosis. Although the link between apoptosis and myocardial failure remains to be proven, these in vitro and in vivo observations provide a rational mechanism by which beta-AR antagonists may help to prevent or slow LV remodeling and failure in patients.

Gynaecology in the new millennium

Great challenges await the gynaecologist in the 21st century. While advances in medical technology necessitate that gynaecology move more towards a medical discipline than a surgical one, gynaecologists will be expected to play an increasingly important role in the modern woman's life. This fundamental change is influenced by four main factors, namely, the world's aging population, spread of information technology, advances in molecular based medical therapy, and the changing lifestyle of the woman in the next century. Our role cannot get any lesser as we continue to advise, educate and facilitate the lives of women, and we must aspire a new generation of responsible gynaecologists to continue this ambition.

Budd-Chiari syndrome: our experience of 71 patients

BACKGROUND

Hepatic venous outflow obstruction (Budd-Chiari syndrome) is frequently encountered as a cause of portal hypertension at our centre.

METHODS AND RESULTS

We studied the clinical presentation, therapeutic modalities and outcome of 71 patients with hepatic venous outflow obstruction between 1992 and 1997. Twenty-seven patients presented with acute disease, while 44 had chronic presentation. Abdominal pain, distension, jaundice and upper gastrointestinal bleeding were the commonest presenting symptoms. The majority of patients had distended veins, hepatomegaly, splenomegaly, ascites and ankle oedema. The diagnosis was made on the basis of inferior vena cavography/functional hepatography and pulsed Doppler ultrasonography and/or liver biopsy in 39 patients and pulsed Doppler ultrasonography and/or liver biopsy in 32 patients. Pulsed Doppler ultrasonography accurately detected the site of the block in 31 of 39 patients (79.4%). The obstruction was in the hepatic vein in 20 patients, in the inferior vena cava in 10, and in both in 41 patients. Aetiologically, four had pregnancy-related disease, four tumour-related, three hypercoagulable states, 18 inferior vena cava membranes and 42 were idiopathic. Of 30 patients in whom liver biopsy was carried out, eight had centrizonal congestion and necrosis, 13 had mixed features and nine had established cirrhosis. Seven patients underwent a shunt operation and surgical membranotomy was carried out in one. Three patients (4.2%) died in the hospital.

CONCLUSIONS

Hepatic venous outflow obstruction is a common problem; patients present with abdominal pain, distension, jaundice, distended veins, ascites and ankle oedema. Chronic presentation is more frequent. Pulsed Doppler ultrasound, venography and liver biopsy are very helpful in diagnosis.

Myocardial-directed overexpression of the human beta(1)-adrenergic receptor in transgenic mice

The beta(1)-adrenergic receptor (AR) is the dominant subtype in non-failing and failing myocardium. beta(1)-AR signaling, by the endogenous neurotransmitter norepinephrine, is central to the regulation of myocardial contractility. In heart failure, the beta(1)-AR undergoes subtype-selective downregulation which may protect against the increased cardiac adrenergic drive associated with this pathophysiological state. To examine the hypothesis that chronically increased beta(1)-AR mediated signaling has adverse myocardial effects, transgenic mice overexpressing the human beta(1)-AR in a cardiac-selective context were produced, utilizing an alpha-myosin heavy chain (MHC) promoter. In these mice, beta(1)-AR protein abundance was approximately 24-46-fold (1-2 pmol/mg protein) that of wild-type mice. Histopathological examination of young (4 months old) and old (approximately 9 months old) transgenic mouse hearts consistently demonstrated large areas of interstitial replacement fibrosis, marked myocyte hypertrophy and myofibrilar disarray. In addition, increased expression of the pre-apoptotic marker, Bax, was observed coincident with regions of fibrosis accompanied by an increased apoptotic index, as measured by TUNEL assay. Older non-transgenic mice exhibited a slight tendency towards a decreased fractional shortening, whereas older beta(1)-AR transgenic mice had a marked reduction in fractional shortening (%FS approximately 30) as determined by echocardiography. Additionally, older beta(1)-AR transgenic mice had an increased left ventricular chamber size. In summary, cardiac-directed overexpression of the human beta(1)-AR in transgenic mice leads to a significant histopathological phenotype with no apparent functional consequence in younger mice and a variable degree of cardiac dysfunction in older animals. This model system may ultimately prove useful for investigating the biological basis of adrenergically-mediated myocardial damage in humans.

Protective efficacy of trypsin inhibitor on the the gut following rotavirus infection in malnourished infant mice

Epidemiologic data suggest a close relationship between protein energy malnutrition (or protein energy malnourished) (PEM) and development of infectious diarrheal diseases. In the present studies, the impact of trypsin inhibitor (TI) on the gut following rotavirus (RV) infection was investigated in PEM young growing inbred balb/c mice. The animals were divided into four groups: (1) control; (2) PEM; (3) PEM+RV and (4) PEM+ RV+TI. Control and PEM animals were orally inoculated with normal saline, PEM+RV animals were given 50 microl RV (100ID50) and PEM+RV+TI animals were inoculated with 0.6 mg TI/g body weight + 50 micronl RV. The body weight of each animal was recorded. Six animals from each group were sacrificed on days 0, 1, 3, 5, 7 and 10 post inoculation by cervical dislocation. The intestines were removed, everted and homogenized in ice-cold saline. Leucine aminopeptidase (LAP), glutathione (GSH) levels and L-leucine uptake were determined in the jejunum and ileum. Body weight was decreased in PEM and PEM+RV groups compared to the controls. LAP and leucine uptake levels were elevated in the PEM group but decreased in the PEM+RV group. GSH levels were decreased in the PEM+RV group. Enzyme activity, GSH and LAP uptake levels were restored in the PEM+RV+TI group. The study shows the protective role of soybean TI against RV infection in malnourished mice.

Helicobacter pylori infection in chronic smokers with non ulcer dyspepsia

BACKGROUND/AIMS

Both H. pylori infection and smoking are risk factors for acid peptic disorders. There is paucity of data on relationship between smoking and H. pylori infection. Therefore, we studied prevalence of H. pylori infection in smokers with non-ulcer dyspepsia (NUD).

PATIENTS AND METHODS

30 smokers with NUD (age 29.5 +/- 1.2 years; all men) and 30 non-smokers with NUD (age 29.2 +/- 1.6 years; all men) were included. None was on antiulcer drugs or antibiotics for more than 2 weeks. Upper gastrointestinal endoscopy was performed and antral biopsies obtained were subjected to rapid urease test, Gram's staining, culture and histopathology. Patient was considered H. pylori positive, if culture was positive or combination of histopathology plus rapid urease test or Gram's staining plus rapid urease test was positive.

RESULTS

24 of 30 (80%) smokers and 13 of 30 (43%) non smokers were positive for H. pylori infection (p < 0.001). There was no significant difference in the positivity of H. pylori in light (78%), moderate (81%) and heavy smokers (80%). All the 37 patients who were positive for H. pylori had histological gastritis compared to 65% in H. pylori negative patients. However there was no difference in presence of histological gastritis among H. pylori negative smokers (33%) and non smokers (70%; p = NS).

CONCLUSIONS

H. pylori infection is more common in smokers with NUD than in non-smokers. However duration and amount of smoking has no relationship with H. pylori positivity.

Intestinal pseudo-obstruction due to neurofibromatosis responding to cisapride

Gastrointestinal involvement in neurofibromatosis presenting with mechanical obstruction, hemorrhage or intussusception is known. Small bowel dysmotility and intestinal pseudo-obstruction due to neurofibromatosis is rare. A 23-year-old man with classical neurofibromatosis presented with intermittent episodes of intestinal pseudo-obstruction, small bowel bacterial overgrowth and steatorrhea. The patient had good symptomatic improvement with cisapride.

Gastrointestinal bleeding due to worm infestation, with negative upper gastrointestinal endoscopy findings: impact of enteroscopy

BACKGROUND AND STUDY AIMS

In cases of hookworm and roundworm infestation, chronic occult bleeding is well known, but acute gastrointestinal bleeding is rarely described. We report five patients with worm infestation who presented with acute massive gastrointestinal bleeding.

PATIENTS AND METHODS

Over 1 year, we have encountered 15 patients with obscure gastrointestinal bleeding. All the patients had normal findings on upper gastrointestinal endoscopy. Push enteroscopy was performed in each patient and evaluation of the proximal 40-50 cm of the jejunum was done.

RESULTS

Five patients (four men, one woman; average age 50 yr, range 40-60) had worm infestation (two hookworm, three roundworm). All the patients had gastrointestinal bleeding (five had melena, one hematemesis, and two hematochezia) for a duration of 7-14 days. Hemoglobin ranged from 2.8 to 9 g/dl. Push enteroscopy revealed fresh blood in the jejunum, multiple erosions, and hookworms in two patients and roundworms in three patients. Hookworms were retrieved endoscopically in two patients whereas roundworms could be retrieved in only one patient. All the patients were treated with mebendazole (100 mg twice a day for 3 days), iron, and folic acid. Gastrointestinal bleeding subsided in all the patients.

CONCLUSIONS

In developing countries, worm infestation should be considered an important cause of obscure acute gastrointestinal bleeding. Evaluation of the jejunum using an enteroscope will result in more frequent diagnosis of worms as a cause of acute gastrointestinal bleeding which might have been classified as obscure gastrointestinal bleeding.

Race-related stress among Asian American veterans: a model to enhance diagnosis and treatment

This article addresses theoretical principles and clinical descriptions of the phenomenon of race-related stress and trauma experienced by Asian American Vietnam veterans. A conceptual model of race-based stress is presented, comprised of five principles, by which to understand mental health difficulties that can arise in regard to race-based stressors. The model describes (a) the relationship between life threat and physical similarity to the "enemy," (b) the relationship between fear and prejudice, (c) dehumanization as it impacts race hate and combat indoctrination, (d) additive life threat related to exploitation of one's physical similarity to the "enemy," and (e) race-based remorse. The article delineates factors affecting treatment seeking and disclosure of race-based stresses, guidelines for interviewing veterans about race-related events and ethnic self-worth, and the harmful effects of race hate.

Immunohistochemical localization and correlation of p53 and PCNA expression in breast carcinoma

The object of the present study is to detect the p53 tumour suppressor gene and proliferation cell nuclear antigen (PCNA) expression in breast carcinoma by immunohistochemistry and correlate them with the prognostic parameters. Total 35 cases of primary breast carcinoma were studied and classified histologically. Paraffin sections were stained by using monoclonal antibody D07 for p53 protein and PC-10 for PCNA. Out of 35 cases, 16 (45.7%) were p53 positive and 25 (71.4%) were PCNA positive. The mean PCNA labelling index (PCNA LI +/- SD) was 58.97 +/- 22.72 in tumors positive for both p53+ and PCNA+ while cases negative for p53- and positive for PCNA+ has higher PCNA LI +/- SD (59.24 +/- 18.97). The difference in the two groups was not significant. Most cases were positive for both p53+ and PCNA+ in the age group < 30 with higher mean PCNA LI +/- SD (62.20 +/- 27.13) than in the group > 30 (57.88 +/- 18.47). In the pre-menopausal group 57.1% cases were positive for p53+ with higher PCNA LI +/- SD (59.94 +/- 24.22). Maximum p53 and PCNA positivity was observed in grade III tumors (63.2% and 84.2%). The mean PCNA LI +/- SD was also highest in grade III carcinomas (66.83 +/- 13.97). No significant correlation was found between p53 and PCNA status with morphological type and tumour size except that logistic regression showed a positive correlation with tumour grade. Therefore the present study suggests that both p53 expression and PCNA are markers of poor differentiation in breast cancer.