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Biomedical subjects

A Prakash

Publications and source records attributed to A Prakash.

At least 37 records · Page 2Linked to original sources
PubMed2002

Genes encoding chimeras of Neurospora crassa erg-3 and human TM7SF2 proteins fail to complement Neurospora and yeast sterol C-14 reductase mutants.

The human gene TM7SF2 encodes a polypeptide (SR-1) with high sequence similarity to sterol C-14 reductase, a key sterol biosynthetic enzyme in fungi, plants and mammals. In Neurospora and yeast this enzyme is encoded by the erg-3 and erg24 genes respectively. In an effort to demonstrate sterol C-14 reductase activity for SR-1 we constructed six recombinant genes coding for chimeras of the Neurospora erg-3 and SR-1 protein sequences and tested them for complementation of the Neurospora erg-3 mutant. To our surprise, all the chimeras failed to complement erg-3. A few of the chimeric proteins were also tested against the yeast erg24 mutant, but again there was no complementation. We discuss some reasons that might account for these unexpected findings.

Amino Acid Sequence↗
PubMed2002

Effect of gamma irradiation on Listeria monocytogenes in frozen, artificially contaminated sandwiches.

Gamma irradiation has been shown to effectively control L monocytogenes in uncooked meats but has not been extensively studied in ready-to-eat foods. The presence of Listeria in ready-to-eat foods is often due to postprocess contamination by organisms in the food-manufacturing environment. Because gamma irradiation is applied after products are packaged, the treated foods are protected from environmental recontamination. Currently, a petition to allow gamma irradiation of ready-to-eat foods is under review by the Food and Drug Administration. This study was conducted to determine if gamma irradiation could be used to control L. monocytogenes in ready-to-eat sandwiches. Ham and cheese sandwiches were contaminated with L. monocytogenes, frozen at -40 degrees C, and exposed to gamma irradiation. Following irradiation, sandwiches were assayed for L. monocytogenes. A triangle test was performed to determine if irradiated and nonirradiated sandwiches differed in sensory quality. We found that the D10-values ranged from 0.71 to 0.81 kGy and that a 5-log reduction would require irradiation with 3.5 to 4.0 kGy. The results of a 39-day storage study of sandwiches inoculated with 10(7) CFU of L monocytogenes per g indicated that counts for nonirradiated sandwiches remained fairly constant. Counts for sandwiches treated with 3.9 kGy decreased by 5 log units initially and then decreased further during storage at 4 degrees C. Sensory panelists could distinguish between irradiated and nonirradiated sandwiches but were divided on whether irradiation adversely affected sandwich quality. Our results suggest that manufacturers of ready-to-eat foods could use gamma irradiation to control L. monocytogenes and improve the safety of their products.

Animals↗
PubMed2001

The sterol C-14 reductase encoded by the Neurospora crassa erg-3 gene: essential charged and polar residues identified by site-specific mutagenesis.

Sterol C-14 reductase catalyses the reduction of the Delta(14,15) bond in intermediates in the sterol biosynthesis pathway using NADPH as a cofactor. We have undertaken a systematic site-directed mutational analysis of all the conserved charged and potentially proton-donating residues of the sterol C-14 reductase from Neurospora crassa. The effect of each mutation was determined using an in vivo assay based on the complementation of the corresponding N. crassa mutant ( erg-3). The non-complementing mutations were also tested in the erg24 mutant of Saccharomyces cervisiae. The results are discussed with reference to the predicted topology of the enzyme and to its proposed catalytic mechanism, which involves addition of a proton from an appropriately positioned charged or polar residue to the substrate double bond, followed by addition of hydride ion from NADPH.

Amino Acid Sequence↗
PubMed2001

Right and left atrial activation during external direct-current cardioversion shocks delivered for termination of atrial fibrillation in humans.

We examined the regional electrophysiologic effects of successful and unsuccessful direct-current cardioversion shocks on different right and left atrial regions in patients with sustained atrial fibrillation (AF). Patients with sustained AF undergoing external cardioversion underwent simultaneous mapping of the right and left atria. Electrogram changes after shock delivery, regional atrial activation, and effects of shock intensity were analyzed. Twenty-two patients with sustained AF received 52 shocks (mean 2.4/patient, 22 successful and 30 unsuccessful). The efficacy of 50, 100, 200, and 300 J was 18%, 39%, 100%, and 100%, respectively. In all 22 successful shocks, there was virtually simultaneous termination of electrical activity in all right and left atrial regions mapped. Unsuccessful shocks resulted in a significant increase in mean atrial cycle length at lateral right atrium, superior left atrium, and proximal, mid, and distal coronary sinus (p = 0.01), but not at the interatrial septum (p >0.2), which often disappeared before the next shock. This cycle length prolongation was accompanied by reduction in fragmented and chaotic electrograms (p <0.03) and emergence of discrete electrograms at all right and left atrial regions that persisted until the next shock. The changes in electrogram morphology failed to alter the surface electrocardiographic appearance of AF. There was no correlation between the shock intensity and the magnitude of these effects. We conclude that termination of AF with external cardioversion shocks is associated with the widespread extinction of regional atrial wave fronts. Unsuccessful shocks are associated with a temporary slowing of atrial activation at all regions except at the interatrial septum and emergence of organized and/or rapidly propagating wave fronts.

Adult↗
PubMed2001

Lens regeneration in mice under the influence of vitamin A.

The effect of vitamin A has been studied on lens regeneration in young (7 days old) as well as adult mice. A longitudinal slit was made under local anesthesia in the cornea over the lens. The lens was extracted intact through the incision. Intraperitonial injection of vitamin A (0.05 ml of 30 IU/ml in young and 0.05 ml of 50 IU/ml in adult) was given to the operated animals. Vitamin A was found to induce lens regeneration in not only young but also in adult mice. Regenerated lenses were similar in shape, size, transparency and histological features to normal intact lenses.

Animals↗
PubMed2001

Homeotic regeneration of eye in amphibian tadpoles and its enhancement by vitamin A.

After removal of both the lateral eyes of external gill stage tadpoles of the toad Bufo melanostictus, the pineal organ gets transformed into a median eye. This type of transformation occurs in tadpoles of both control and vitamin A treated groups. However, vitamin A increases the likelihood of homeotic regeneration (57% in the control group and 71% in the vitamin A treated group). Histological studies showed that the newly transformed median eye developed from the pineal organ. The pineal eye so developed possessed all components of a normal eye such as a retina, sensory cells and lens.

Animals↗
PubMed2001

Estimation of vectorial capacity of Anopheles dirus (Diptera: Culicidae) in a forest-fringed village of Assam (India).

To estimate the vectorial capacity of Anopheles dirus, the main vector of forest malaria in the northeastern region of India, in order to gain an understanding of entomological factors related to malaria transmission in forest-fringe areas of Assam, India, an isolated village in the tropical rain forest-fringed area in the district of Dibrugarh, Assam, under the influence of An. dirus alone was studied. Data on various entomological variables required for computation of the vectorial capacity were generated in each month from June 1999 to May 2000 in the field using standard techniques. Malaria prevalence was also studied during the same period in the study village and correlated with the estimated vectorial capacity of An. dirus. Vectorial capacity of An. dirus was highest, 0.779 for Plasmodium vivax (Pv) and 0.649 for Plasmodium falciparum (Pf), during the hot-monsoon season (June-September) and decreased to 0.08 (Pv) and 0.07(Pf) in the temperate postmonsoon season (October-November) before attaining zero values in the cool-dry season (December-February). With increasing temperature in the temperate premonsoon season (March-May), vectorial capacity recorded was 0.119 and 0.82 for Pv and Pf, respectively. Significant positive correlation was seen between the estimated vectorial capacity of An. dirus and the number of new Pf (r = 0.86, p < 0.001) and Pv (r = 0.69, p < 0.02) cases in the study village in different months. Thus, this study highlights the pattern of malaria transmission by An. dirus in a forest-fringe area of Assam that begins in March, peaks in July/August, subsides by November, and remains interrupted between December and February. Measures for controlling malaria in forest-fringe areas should be scheduled accordingly.

Animals↗
PubMed2001

Effect of prophylactic ondansetron on postoperative nausea and vomiting after elective craniotomy.

This prospective, randomized, placebo-controlled, double-blind study was designed to evaluate the efficacy of ondansetron, a 5-HT3 antagonist, in preventing postoperative nausea and vomiting (PONV) after elective craniotomy in adult patients. The authors also tried to discover certain predictors for postcraniotomy nausea and vomiting. We studied 170 ASA physical status I and II patients, aged 15 to 70 years, undergoing elective craniotomy for resecting various intracranial tumors and vascular lesions. A standardized anesthesia technique and postoperative analgesia were used for all patients. Patients were divided into two groups and received either saline placebo (Group 1) or ondansetron 4 mg (Group 2) intravenously at the time of dural closure. Patients were extubated at the end of surgery and episodes of nausea and vomiting were noted for 24 hours postoperatively in the neurosurgical intensive care unit. Demographic data, duration of surgery, and anesthesia and analgesic requirements were comparable in both groups. Overall, a 24-hour incidence of postoperative emesis was significantly reduced in patients who received ondansetron compared with those who received a saline placebo (39% in Group 1 and 11% in Group 2, P = .001). There was a significant reduction in the frequency of emetic episodes and rescue antiemetic requirement in patients treated with ondansetron; however, ondansetron did not significantly reduce the incidence of nausea alone (14% in Group 2 vs 5% in Group 1, P = .065). Prophylactic ondansetron had a favorable influence on PONV outcome measures such as patient satisfaction and number needed to prevent emesis (3.5). Side effects were similar in both groups. We conclude that ondansetron 4 mg given at the time of dural closure is safe and effective in preventing emetic episodes after elective craniotomy in adult patients.

Adolescent↗
PubMed2000

IRF3 and IRF7 phosphorylation in virus-infected cells does not require double-stranded RNA-dependent protein kinase R or Ikappa B kinase but is blocked by Vaccinia virus E3L protein.

Induction of interferon-alpha (IFNalpha) gene expression in virus-infected cells requires phosphorylation-induced activation of the transcription factors IRF3 and IRF7. However, the kinase(s) that targets these proteins has not been identified. Using a combined pharmacological and genetic approach, we found that none of the kinases tested was responsible for IRF phosphorylation in cells infected with Newcastle disease virus (NDV). Although the broad-spectrum kinase inhibitor staurosporine potently blocked IRF3 and -7 phosphorylation, inhibitors for protein kinase C, protein kinase A, MEK, SAPK, IKK, and protein kinase R (PKR) were without effect. Both IkappaB kinase and PKR have been implicated in IFN induction, but cells genetically deficient in IkappaB kinase, PKR, or the PKR-related genes PERK, IRE1, or GCN2 retained the ability to phosphorylate IRF7 and induce IFNalpha. Interestingly, PKR mutant cells were defective for response to double-stranded (ds) RNA but not to virus infection, suggesting that dsRNA is not the only activating viral component. Consistent with this notion, protein synthesis was required for IRF7 phosphorylation in virus-infected cells, and the kinetics of phosphorylation and viral protein production were similar. Despite evidence for a lack of involvement of dsRNA and PKR, vaccinia virus E3L protein, a dsRNA-binding protein capable of inhibiting PKR, was an effective IRF3 and -7 phosphorylation inhibitor. These results suggest that a novel cellular protein that is activated by viral products in addition to dsRNA and is sensitive to E3L inhibition is responsible for IRF activation and reveal a novel mechanism for the anti-IFN effect of E3L distinct from its inhibition of PKR.

Animals↗
PubMed2000

Entamoeba histolytica: rapid detection of indian isolates by cysteine proteinase gene-specific polymerase chain reaction.

Amoebiasis, caused by Entamoeba histolytica, is still one of the major problems for developing countries like India. Early detection of the parasite is a must for its prevention and control. In this study, PCR analysis of the cysteine proteinase gene from clinical isolates of symptomatic intestinal and amoebic liver abscess (ALA) cases has been compared with the stool microscopy, serology, and ultrasonography methods. The clinical isolates negative for E. histolytica by stool microscopy demonstrated the presence of the cysteine proteinase gene by PCR amplification. Also the gene copy number was increased in ALA samples compared with intestinal cases. Hence an accurate, early, and easier detection was possible by cysteine proteinase gene amplification directly from the clinical samples.

Adult↗
PubMed2000

Catheter mapping of spontaneous and induced atrial fibrillation in man.

The clinical electrophysiologic study of atrial fibrillation [AF] has recently progressed from static characterization of the substrate to the dynamic investigation of both induced and spontaneous AF in man. Prior studies have demonstrated inhomogeneity and greater dispersion of atrial refractoriness in patients with AF, but recently atrial electrical remodeling with consequent abbreviation of atrial refractory periods has also been reported. Yet further experimental observations have suggested the existence of additional arrhythmogenic mechanisms for certain AF subsets. These include studies that have demonstrated a stable atrial flutter circuit in one atrium with fibrillatory conduction or a focal atrial tachyarrhythmia arising commonly in the left atrium. Efforts at catheter mapping of AF are now in progress. New mapping techniques and novel devices are currently being employed. We have performed catheter mapping simultaneously in right and left atrial sites at onset and during sustained pacing-induced and spontaneous AF in patients with ischemic and/or hypertensive heart disease. Atrial premature complexes that initiated spontaneous AF typically had coupling intervals ranging from 260 to 400 ms and most frequently arose in the crista terminalis, right atrioventricular junction or superior left atrium. AF at onset showed discrete electrograms at virtually all right and left atrial regions mapped and the region of earliest atrial activation during AF was in close proximity to the premature complexes in over 90% of patients. The regional atrial activation sequence for the first 10 AF beats demonstrated stable or unstable patterns in individual patients. In contrast to spontaneous AF, the initial arrhythmia of induced AF was seen to have a significantly different site of earliest atrial activation but similar discrete electrograms in different atrial regions. However, as with spontaneous AF, the site of extrastimulus delivery was in close proximity to the first induced beat. We conclude that regional catheter mapping of AF is feasible and safe in man and organized electrical activity is frequently observed at AF onset in patients with heart disease. Both right and left atrial regions can be the source of atrial premature complexes and at the onset of spontaneous AF. Induced AF may have differing activation patterns than spontaneous AF but both demonstrate earliest activation in proximity to the initiating atrial premature complex. These findings may help explain therapeutic benefits of right and left atrial interventions and pacing therapies in AF.

Atrial Fibrillation↗
PubMed2000

Antioxidant content of whole grain breakfast cereals, fruits and vegetables.

BACKGROUND: Considerable scientific evidence suggests that whole grains, as commonly consumed in the United States and Europe, reduce risk for chronic disease including cancer and heart disease. Whole grains provide a wide range of nutrients and phytochemicals that may work synergistically to optimize human health. Fruits and vegetables provide protection against age related diseases. It is believed their high content of antioxidant compounds is key to such protection. OBJECTIVE: This research compares the antioxidant activity of whole grain, ready-to-eat (RTE) breakfast cereals to that of fruits and vegetables. METHOD: Antioxidant activity was determined by dispersing finely ground samples in a 50% aqueous methanol solution of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). DPPH, which forms a deep purple solution, reacts with antioxidants and color loss at 515 nm correlates to antioxidant content, which is expressed as Trolox equivalents/100 grams (TE). RESULTS: Whole grain breakfast cereals analyzed in this study contained from 2,200-3,500 TE. By comparison, fruits generally ranged from 600-1,700 TE, with a high of 2,200 TE for red plums. Berries averaged 3,700 TE and. vegetables averaged 450 TE with a high of 1,400 TE for red cabbage. A 41 gram average serving of RTE breakfast cereal provides 1,120 TE, while an average 85 gram serving of vegetables or fruits provides 380 and 1,020 TE, respectively. CONCLUSION: Whole grain breakfast cereals, fruits and vegetables are all important dietary sources of antioxidants.

Antioxidants↗
PubMed2000

Phosphorylation-induced dimerization of interferon regulatory factor 7 unmasks DNA binding and a bipartite transactivation domain.

Interferon regulatory factor 7 (IRF7) is an interferon (IFN)-inducible transcription factor required for activation of a subset of IFN-alpha genes that are expressed with delayed kinetics following viral infection. IRF7 is synthesized as a latent protein and is posttranslationally modified by protein phosphorylation in infected cells. Phosphorylation required a carboxyl-terminal regulatory domain that controlled the retention of the active protein exclusively in the nucleus, as well as its binding to specific DNA target sequences, multimerization, and ability to induce target gene expression. Transcriptional activation by IRF7 mapped to two distinct regions, both of which were required for full activity, while all functions were masked in latent IRF7 by an autoinhibitory domain mapping to an internal region. A conditionally active form of IRF7 was constructed by fusing IRF7 with the ligand-binding and dimerization domain of estrogen receptor (ER). Hormone-dependent dimerization of chimeric IRF7-ER stimulated DNA binding and transcriptional transactivation of endogenous target genes. These studies demonstrate the regulation of IRF7 activity by phosphorylation-dependent allosteric changes that result in dimerization and that facilitate nuclear retention, derepress transactivation, and allow specific DNA binding.

Animals↗
PubMed2000

Metoprolol: a review of its use in chronic heart failure.

UNLABELLED: Metoprolol, a relatively selective beta1-blocker, is devoid of intrinsic sympathomimetic activity and possesses weak membrane stabilising activity. The drug has an established role in the management of essential hypertension and angina pectoris, and more recently, in patients with chronic heart failure. The effects of metoprolol controlled-release/extended-release (CR/XL) in patients with stable, predominantly mild to moderate (NYHA functional class II to III) chronic heart failure have been evaluated in the large Metoprolol CR/XL Randomised Intervention Trial in Congestive Heart Failure (MERIT-HF) trial and the much smaller Randomized Evaluation of Strategies for Left Ventricular Dysfunction (RESOLVD) pilot study. Treatment with metoprolol CR/XL was initiated at a low dosage of 12.5 to 25 mg once daily and gradually increased at 2-weekly intervals until the target dosage (200 mg once daily) or maximal tolerated dosage had been attained in patients receiving standard therapy for heart failure. At 12 months, metoprolol CR/XL was associated with a 34% reduction in relative risk of all-cause mortality in patients with chronic heart failure due to ischaemic or dilated cardiomyopathy in the MERIT-HF trial. The incidence of sudden death and death due to progressive heart failure were both significantly decreased with metoprolol CR/XL. Similarly, a trend towards decreased mortality in the metoprolol CR/XL group compared with placebo was observed in the RESOLVD trial. Data from small numbers of patients with severe (NYHA functional class IV) heart failure indicate that metoprolol CR/XL is effective in this subset of patients. However, no firm conclusions can yet be drawn. Improvement from baseline values in NYHA functional class, exercise capacity and some measures of quality of life with metoprolol CR/XL or immediate-release metoprolol were significantly greater than those with placebo. The drug is well tolerated when treatment is initiated in low dosages and gradually increased at intervals of 1 to 2 weeks. CONCLUSIONS: Metoprolol CR/XL effectively decreases mortality and improves clinical status in patients with stable mild to moderate (NYHA functional class II or III) chronic heart failure due to left ventricular systolic dysfunction, and the drug is effective in patients with ischaemic or dilated cardiomyopathy. Although limited data indicate that metoprolol CR/XL is effective in patients with severe (NYHA functional class IV) chronic heart failure, more data are needed to confirm these findings. Treatment with metoprolol CR/XL significantly reduced the incidence of sudden death and death due to progressive heart failure.

Adrenergic beta-Antagonists↗
PubMed2000

Insecticide susceptibility status of Culex tritaeniorhynchus giles, vector of Japanese encephalitis in Delhi.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10. 0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT50 and LT95 values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin - 0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC50 and LC90 values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC90 values were compared with diagnostic dosages of temephos and fenthion, respectively.

Animals↗
PubMed2000

Epidemiology of malaria outbreak (April/May, 1999) in Titabor Primary Health Centre, district Jorhat (Assam).

An investigation was undertaken of a malaria outbreak in the Primary Health Centre Titabor, district Jorhat, Assam during May/June 1999. The fever rate in the community since March 1999, was 44.4 per cent with an average case load of 2.5 per family. The fever cases peaked in the third week of May. Slide positive and slide falciparum rates in mass blood survey, in the study village were 16.1 and 14.5 per cent respectively with 90 per cent infection of Plasmodium falciparum. Males (SPR 17.5%) suffered relatively more than females (SPR 14.7%). Malaria prevalence was significantly less in individuals above 15 yr of age (SPR 11.0%) as compared to those below 15 yr (SPR 22.9%). Prevalence of malaria as well as mosquito densities in different clusters of the village were inversely related to the distance from the forested Naga hills. Anopheles minimus and A. dirus were collected in good numbers with comparatively higher densities of the former. Several factors like unusual climatic conditions, inadequate surveillance, unsatisfactory laboratory services and inadequate indoor residual insecticide spray were instrumental for the outbreak.

Adolescent↗