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Biomedical subjects

N Singh

Publications and source records attributed to N Singh.

At least 415 records · Page 23Linked to original sources
PubMed1994

Circadian and power spectral changes of RR and QT intervals during treatment of patients with angina pectoris with nadolol providing evidence for differential autonomic modulation of heart rate and ventricular repolarization.

This study evaluates the effects of autonomic manipulation by chronic beta blockade with nadolol on the circadian and power spectral changes of heart rate and QT interval. It was hypothesized that differential innervation of the atria and ventricles by sympathetic and parasympathetic fibers may produce differential effects on heart rate and QT interval variabilities. Holter recordings of 12 male patients (age 63 +/- 7 years) with stable angina were analyzed before and after 3 weeks of nadolol therapy. The QT intervals were individually normalized by an exponential formula to study the circadian variation of QTc. Power spectra of RR and uncorrected QT intervals were obtained by fast-Fourier analysis from 256 consecutive sinus beats during the day at maximal heart rate and during the night at minimal heart rate. Frequency-specific variability was determined from areas under the spectral plots. Both heart rate and QTc exhibited significant circadian patterns (p < 0.01) in opposite phase with each other. Mean heart rate was significantly reduced with nadolol (81 +/- 12 vs 67 +/- 12 beats/min, p < 0.001), with greater reduction during daytime. The mean QTc was unexpectedly reduced after nadolol treatment, with borderline significance (p = 0.06). The RR variability in the frequency range of 0.05 to 0.25 Hz was significantly increased with nadolol at 3:00 A.M. (p < 0.01) but not at 1:00 P.M. The QT variability in the same frequency range of was not significantly increased with nadolol. The power spectra of RR and QT intervals were dissimilar except at the lower frequencies around 0.05 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1994

High-dose acyclovir compared with short-course preemptive ganciclovir therapy to prevent cytomegalovirus disease in liver transplant recipients. A randomized trial.

OBJECTIVE: To assess the efficacy of high-dose oral acyclovir therapy compared with preemptive, short-course ganciclovir therapy (administered only if cytomegalovirus [CMV] shedding occurred) to prevent CMV disease in liver transplant recipients. DESIGN: A randomized controlled trial. SETTING: Liver transplant center at a university-affiliated Veterans Affairs Medical Center. PATIENTS: 47 consecutive patients having liver transplantation. INTERVENTION: Patients were stratified by their CMV antibody status and the CMV antibody status of the donor and were randomly assigned to one of two treatment groups. Surveillance cultures for CMV (buffy coat and urine) were done every 2 to 4 weeks for 24 weeks in all patients. One group received high-dose oral acyclovir (800 mg four times daily). The experimental group received no acyclovir, but if surveillance cultures were positive, ganciclovir (5 mg/kg intravenously twice daily) was administered for 7 days. MEASUREMENTS: Cytomegalovirus shedding and CMV disease were measured in the two groups. RESULTS: Cytomegalovirus shedding before the onset of CMV disease occurred in 25% (6 of 24) of patients in the acyclovir group compared with 22% (5 of 23) in the experimental group. Cytomegalovirus disease developed in 29% (7 of 24) of the acyclovir group and in 4% (1 of 23) of the experimental group (P < 0.05). No hematologic toxicity occurred with ganciclovir. CONCLUSION: Oral acyclovir is ineffective prophylaxis against CMV in liver transplant recipients. Preemptive, short-course ganciclovir therapy in patients with CMV shedding was well tolerated and provided effective prophylaxis against subsequent CMV disease; this protocol targets the patients at risk for CMV disease and minimizes toxicity and expense.

Acyclovir↗
PubMed1994

Nodular lepromatous leprosy: report of a case diagnosed by FNA.

Lepromatous leprosy can present with skin nodules which can be misdiagnosed as soft tissue tumors or infected cysts. FNA can be diagnostic if unstained, refractile, intracellular mycobacteria are recognized on Romanowsky stained smears. Fite stain for Mycobacterium leprae confirms the diagnosis. Awareness of the differential diagnosis of skin nodules yielding foamy histiocytes on FNA, briefly discussed, should help avoid error.

Axilla↗
PubMed1994

Protein-ligand interactions as a driving force for a high-enthalpy two-state transition in glutamate dehydrogenase: the opposing roles of phosphate and acetate ions.

It is known that the binding of the reduced coenzyme (NADPH) to bovine liver glutamate dehydrogenase is controlled by the presence of phosphate, acetate, and other anions as well as the pH of the medium. These effectors mediate this binding by lowering the pK (8.5) of an ionizable group on the enzyme, and this pK shift is linked to a high enthalpy E <--> E' transition in the protein. In this study, we have measured enthalpy changes and proton transfer for enzyme-NADPH binding under a variety of combinations of phosphate, acetate, and hydrogen in the pairs acetate-NADPH and H(+)-phosphate, and negative interactions are seen in the pairs H(+)-NADPH, phosphate-NADPH, acetate-phosphate, and H(+)-acetate. We present a general model to account for all of these effects. This model incorporates a newly defined coenzyme binding subsite. The observed phenomena are interpreted in terms of the extent of loading of the specific anion-binding site on the enzyme that regulates the ionization of an enzyme group of pK 8.5. A proton is cooperatively shared with two phosphate groups at this site. Furthermore, we conclude that this cooperative trimolecular binding to the enzyme constitutes an allosteric driving force for the high enthalpy two-state transition observed in the ligand binding reactions of this enzyme.

Acetates↗
PubMed1994

Effect of detoxification of castor seed (Ricinus communis) protein isolate on its nutritional quality.

Nutritional quality of the castor meal protein isolate detoxified using boiling and lime cum heat treatments was evaluated in experiments with rats. Chemical scores of both the treated isolates were similar, threonine being the first limiting amino acid. The calculated nutritional indices (essential amino acid index) and PER were higher for the boiled isolate (1.3) than that was for lime-cum-heat treated (0.86). Though, necropsy examination of organs did not reveal any abnormalities, histopathological changes were observed in the organs-liver, kidney, intestine that could be attributed to the deficiency of essential amino acids in the detoxified castor protein isolates.

Amino Acids↗
PubMed1994

Decreased incidence of viral infections in liver transplant recipients. Possible effects of FK506?

Cytomegalovirus (CMV) is a major infectious complication of organ transplantation and its incidence is influenced by the type and intensity of immunosuppressive therapy employed. Using a new immunosuppressive agent FK506, CMV infection was observed in 30% and CMV disease in 15% of the 26 liver transplant recipients. Delayed onset of CMV disease was noted; the mean time to the occurrence of CMV disease being 137 days posttransplantation. No graft loss or mortality could be attributed to CMV infection. Mucocutaneous herpes simplex virus (HSV) infections were encountered in 19% of the patients, while no disease could be attributed to varicella zoster virus or Epstein-Barr virus (EBV). The contribution of FK506 to a decrease in viral morbidity and associated mortality bears further investigation.

Cytomegalovirus Infections↗
PubMed1994

Relevance of platelet serotonergic mechanisms in pregnancy induced hypertension.

Platelet functions are becoming the useful tool for delineating the etiology of pregnancy induced hypertension. Electronmicroscopic studies, efflux and content of 5-HT in platelets and platelet aggregation responses towards various aggregating agents have been measured in 25 normotensive pregnant subjects and 31 PIH subjects. Marked decrease changes have been noted in aggregation parameters with transformation from discoid to "spiny sphere" of platelets with long pseudopods along with prolonged time for spontaneous aggregation by platelets in PIH. Serotonin release from platelets was decreased and reserpine-induced release-reaction showed enhanced kinetics in PIH. Platelet serotonin content was raised and was inversely related to platelet count with severity of syndrome. Hence, a check and balance for platelet activation and aggregation in PIH might be crucial in the development of PIH.

Adolescent↗
PubMed1994

Improved detection of spontaneous bacterial peritonitis with Bactec as compared with conventional culture methods. A prospective study.

Bacteriologic diagnosis of spontaneous bacterial peritonitis is difficult due to the low yield of isolating the bacteria from the ascitic fluid. We prospectively compared the conventional culture method with the nonradiometric Bactec culture system for the detection of bacteria in 20 episodes of spontaneous bacterial peritonitis. The ascitic fluid culture was positive by the conventional culture method in 25% and by Bactec in 79% of the episodes of spontaneous bacterial peritonitis (P = 0.004). Of culture-positive episodes, Gram-negative bacteria were detected by conventional cultures in 20% and by Bactec in 47%. Bactec culture system was significantly better than the conventional cultures for the detection of streptococci (viridans streptococci and Enterococcus fecalis), 33% versus 0 (P < 0.05). Conventional cultures did not detect bacteria that were not also detected by Bactec cultures. In conclusion, the Bactec nonradiometric culture method is superior to conventional cultures for the diagnosis of spontaneous bacterial peritonitis.

Ascitic Fluid↗
PubMed1994

Central nervous system lesions in adult liver transplant recipients: clinical review with implications for management.

Our review shows that a wide array of neurologic complications can occur after liver transplantation. Clinical correlation of the neuropathologic lesions may be difficult, as multiple lesions of variable etiologies may coexist, and significant systemic and metabolic complications may obscure the symptoms related to an underlying lesion in the central nervous system. Nevertheless, a reasoned approach to the recognition and diagnosis of these lesions is offered. In the early post-transplantation period, noninfectious lesions predominated. Of these, anoxic-ischemic changes and vascular events (hemorrhages and/or infarcts) occurred most frequently. Anoxic events occurred a mean of 10 days after transplantation and were often preceded by transient or varying degrees of hypotension. Hemorrhagic events and infarcts occurred a median of 27 and 5 days, respectively, after transplantation. It should be noted, however, that the projected onset of these events may vary somewhat, e.g., a brain infarct developed 47 days after liver transplantation in case 2. Although defects in coagulation may predispose to hemorrhagic lesions, a source for the infarct is usually not apparent. Central pontine myelinolysis is also an early-occurring lesion: most cases are seen within 10 days of transplantation. Extrapontine involvement frequently coexisted with or was present without pontine lesions. Hyponatremia or wide variations in serum sodium generally preceded the CNS lesion. Focal areas of high signal density by CT scan in the pons was highly suggestive of central pontine myelinolysis. Cyclosporine may cause white matter changes in the brain despite normal serum cyclosporine levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

The utility of autopsies in a pediatric emergency department.

The role of the autopsy in verifying clinical diagnosis and as a quality assurance tool in pediatric emergency medicine has not been studied. We reviewed the charts of all children who died soon after arriving at to the pediatric emergency department between October 1985 and December 1989. Opinions as to clinical diagnoses and cause of death were obtained by presenting a summary of patient data, in a blinded fashion, to three emergency pediatricians. Clinical diagnoses were then compared with autopsy diagnoses using the Class Error System. Major diagnostic errors (Class I, Class II) were examined to determine if the autopsy was more useful in any particular patient group. There were 69 children: 36 (52%) were female, and 30 (43%) were infants. Autopsies were performed on 52 (75%) patients. Autopsy diagnoses were categorized as follows: sudden infant death syndrome (SIDS) 14 (27%); underlying disease 15 (29%); trauma 13 (25%); sepsis 8 (16%); and aspiration 2 (4%). No errors were made in 67% of cases. The autopsy confirmed the major clinical diagnosis in 85% of patients. There were no Class I errors. Class II error rate was 15%. Most Class II errors occurred in patients between one and five years of ate (57%), and in patients who had sepsis or underlying disease (95%). Our data show that autopsy is useful in determining the cause of death and may be useful for education and quality assurance in pediatric emergency medicine.

Autopsy↗
PubMed1994

Addition of lipid substituents of mammalian protein glycosylphosphoinositol anchors.

A single metabolic path leading to synthesis of ether lipids is known in animal cells, the major products of which are plasmalogens. To learn whether this peroxisomal path is also responsible for the synthesis of base-resistant lipid components of glycosylphosphoinositol (GPI)-anchored membrane proteins, we have investigated the structure of anchor precursor mannolipids both in wild-type cells (CHO-K1 and a macrophage-like line, RAW 264.7) and in two corresponding mutant cells in which ether lipid biosynthesis is severely impaired. We observe that the precursor mannolipids of both the wild-type and mutant cells do not include alkylglycerol. Nevertheless, both wild-type and mutant cells express cell surface GPI-anchored placental alkaline phosphatase (AP) which includes alkali-resistant hydrophobic chains in its anchor moiety. Thus, (i) in normal AP GPI anchor synthesis, any ether-linked substituents must be added either immediately before, during, or after anchor addition to AP, and (ii) the classical peroxisomal path for ether lipid synthesis appears not to contribute to the synthesis of GPI anchors.

Alkaline Phosphatase↗
PubMed1994

Myocardial alterations during hemodialysis: insights from new noninvasive technology.

Eighteen patients with chronic renal failure had their cardiac status monitored during hemodialysis (HD). Ten studies were carried out using an ambulatory nuclear vest to assess ejection fraction (EF), heart rate (HR), relative end-systolic (ESV) and end-diastolic (EDV) volumes every 60 s. A total of 36 episodes of EF falls occurred in 9 patients, all asymptomatic. These EF falls were associated with a rise in ESV, while HR, BP, and EDV remained unchanged. The EF falls correlated best with the volume of ultrafiltrate removed. Ten patients had on-line ST-segment monitoring with sestamibi injection either at the time of ST depression (STD) or at the end of dialysis, if no STD occurred, in order to detect the presence of transient ischemia. Seven of ten patients had perfusion defects after dialysis, with STD occurring in 3 of 10 patients. Predialysis imaging was available in only 8 of 10 patients, and 6 of these patients had perfusion defects. Changes in perfusion defects were not significantly different in the 3 patients with STD compared with those without STD. EF falls and perfusion defects are common in HD patients even in the absence of known coronary artery disease; however, ST segment monitoring is not a sensitive tool for its detection. These changes in function and perfusion may represent myocardial ischemia and contribute to the high incidence of cardiovascular morbidity and mortality in this patient population.

Electrocardiography↗