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Biomedical subjects

A Mehta

Publications and source records attributed to A Mehta.

At least 127 records · Page 7Linked to original sources
PubMed1998

Rapid quantitation of free fatty acids in human plasma by high-performance liquid chromatography.

We report a rapid and sensitive method for separation and quantitation of free fatty acids (FFAs) in human plasma using high-performance liquid chromatography (HPLC). Two established techniques of lipid extraction were investigated and modified to achieve maximal FFA recovery in a reasonably short time period. A modified Dole extraction method exhibited greater recovery (approximately 90%) and short processing times (30 min) compared to the method of Miles et al. Reversed-phase HPLC using UV detection was used for plasma FFA separation and quantitation. Two phenacyl ester derivatives, phenacyl bromide and p-bromophenacyl bromide, were investigated in order to achieve optimal separation of individual plasma FFAs (saturated and unsaturated) with desirable detection limits. Different chromatographic parameters including column temperature, column type and elution profiles (isocratic and gradient) were tested to achieve optimal separation and recovery of fatty acids. Phenacyl bromide esters of plasma fatty acids were best resolved using an octadecylsilyl column with endcapped silanol groups. An isocratic elution method using acetonitrile-water (83:17) at 2 ml/min with UV detection at 242 nm and a column temperature of 45 degrees C was found to optimally resolve the six major free fatty acids present in human plasma (myristic [14:0], palmitic [16:0], palmitoleic [16:1], stearic [18:0], oleic [18:1] and linoleic [18:2]), with a run time of less than 35 min and detection limits in the nmol range. The entire process including plasma extraction, pre-column derivatization, and HPLC quantitation can be completed in approximately 90 min with plasma samples as small as 50 microl. Over a wide physiological range, plasma FFA concentrations determined using our HPLC method agree closely with measurements using established TLC-GC methods (r2 < or = 0.95). In addition, by measuring [14C] or [3H] radioactivity in eluent fractions following HPLC separation of plasma FFA, this method can also quantitate rates of FFA turnover in vivo in human metabolic studies employing isotopic tracers of one or more fatty acids.

Chromatography, High Pressure Liquid↗
PubMed1998

Alpha-glucosidase inhibitors as potential broad based anti-viral agents.

N-Linked oligosaccharides play many roles in the fate and functions of glycoproteins. One function is to assist in the folding of proteins by mediating interactions of the lectin-like chaperone proteins calnexin and calreticulin with nascent glycoproteins. These interactions can be prevented by inhibitors of the alpha-glucosidases and this causes some proteins to be misfolded and retained within the endoplasmic reticulum. In human immunodeficiency virus (HIV) and hepatitis B virus (HBV) the misfolding of key viral envelope glycoproteins interferes with the viral life cycle. It has been demonstrated in an animal model of chronic HBV that glucosidase inhibitors can alter glycosylation and have anti-viral activity. As the mechanism of action of alpha-glucosidase inhibitors is the induction of misfolded or otherwise defective viral glycoproteins, such inhibitors may be useful therapeutics for many viruses, especially those which bud from the endoplasmic reticulum (where protein folding takes place). For example bovine viral diarrhea virus, a pestivirus akin to hepatitis C virus, is also extremely sensitive to glucosidase inhibition.

Animals↗
PubMed1998

Left atrial abnormality by electrocardiogram predicts left ventricular hypertrophy by echocardiography in the presence of right bundle-branch block.

BACKGROUND: Left ventricular hypertrophy (LVH) on the electrocardiogram (ECG) may be masked in the presence of complete right bundle-branch block (RBBB). Left bundle-branch block on the ECG is associated with LVH at autopsy in 93% of hearts studied. However, RBBB does not predict LVH and the usual ECG criteria applied for LVH may not be reliable in the presence of RBBB. HYPOTHESIS: The study was undertaken to evaluate left atrial (LA) abnormality as a criterion for the diagnosis of LVH in the presence of RBBB. METHODS: Left atrial abnormality in the ECG was assessed by two independent observers as a criterion of LVH in the presence of RBBB in 100 patients, and data were compared with those of 50 patients without LA abnormality. RESULTS: Left ventricular hypertrophy was confirmed by echocardiographic determination of left ventricular (LV) mass in both groups. Observers reliably differentiated between hypertrophied and normal-sized LV in the presence of RBBB by using LA abnormality as an ECG criterion when correlated with LV mass determined by echocardiography. Observer 1 correctly detected LVH in 88% and Observer 2 in 82% of patients. False positive diagnosis was made in 12 and 18% of patients by Observers 1 and 2, respectively. Observers' performance of recognition of LA abnormality in the present study was 94%. Results showed sensitivity of 76 and 70% and specificity of 84 and 92% for Observers 1 and 2, respectively. Left ventricular mass increased significantly and was diagnostic of LVH in 92% of patients with LA abnormality. Left ventricular mass was high in 84% of patients when corrected by body surface area. LVH in the presence of RBBB by the ECG was found in only seven patients (5%) when six commonly used conventional criteria of diagnosis of LVH by ECG were employed. Regression analysis found LA abnormality to be a strong independent predictor of increased LV mass. Multiple regression analysis revealed that age, body mass index, body surface area, and frontal axis are also significant predictors of LV mass. CONCLUSION: The results obtained by the correlation of LA abnormality by ECG and LVH by echocardiography conclude that LA abnormality by ECG was significantly diagnostic of LV hypertrophy in the presence of RBBB.

Adolescent↗
PubMed1998

Filmless medical imaging: experiences of the Massachusetts General Hospital.

As the concept of picture archival communication systems (PACS) gathers momentum, the vision of a filmless digital department and digital image management has become a reality. This report will discuss the experiences of a major health-care institution with implementation of a large-scale PACS. Specifically, we discuss success with a modular, nonproprietary, multivendor solution that offers flexibility and state of the art functionality at our institution.

Hospitals, General↗
PubMed1998

The primary interpretation workstation: information beyond image data.

With the advent of picture archival and communication systems (PACS), the importance of design surrounding primary review workstations has become apparent. To help acceptance of filmless medical imaging, workstations must be developed that serve the needs of both radiologists and referring clinicians. This report will discuss integral requirements of workstation design, including information creation, medical management, medical knowledge, and enabling technologies.

Data Display↗
PubMed1998

Voice recognition--an emerging necessity within radiology: experiences of the Massachusetts General Hospital.

Voice recognition represents a technology that is finally ready for prime time use. As radiology services continue to acquire a larger percentage of the shrinking health-care dollar, decreasing operating costs and improved services will become a necessity. The benefits of voice recognition implementation are significant, as are the challenges. This report will discuss the technology, experiences of major health-care institution with implementation, and potential benefits for the radiology practice.

Humans↗
PubMed1998

Intestinal mucosal lipid peroxidation and absorptive function in Salmonella typhimurium mediated intestinal infection.

S. typhimurium infection is associated with neutrophil infiltration within the intestinal mucosa. Neutrophil activation provides a major source of reactive oxygen species (ROS). The mucosal pathology of S. typhimurium infection may be in part due to the excessive production of these reactive species. This study was carried out to investigate if ROS play a role in mediating the changes in the structural components and functional properties of brush border membrane (BBM) in rats during S. typhimurium infection. This was done by determining the changes in the BBM extent of lipid peroxidation and absorptive function. A significant increase in the extent of lipid peroxidation of BBM during S. typhimurium infection was observed as judged by malondialdehyde (MDA) and conjugated diene formation and depletion of alpha-tocopherol and protein associated thiol groups. A significant decrease in the BBMV (brush border membrane vesicle) transport of amino acids was also observed. However there was no change in the transport of D-glucose. The decrease in amino acid transport further led to a significant decrease in the enterocyte level of protein synthesis. Exposure of BBMV to a free radical donor, cumene hydroperoxide, also led to an increase in the extent of lipid peroxidation and a decrease in the amino acid transport. Possibly ROS might play a significant role in mediating the mucosal damage during S. typhimurium infection.

Alanine↗
PubMed1998

Impairment of intestinal mucosal antioxidant defense system during Salmonella typhimurium infection.

The mucosal pathology of Salmonella typhimurium infection may in part be due to the excessive production of reactive oxygen species (ROS). The influence of S. typhimurium infection on the intestinal mucosal antioxidant defense system was investigated. We injected ligated rat ileal loops with Salmonella live culture or toxin. After 18 hr of infection, the animals were killed and enterocytes isolated from the ileal loops. The enterocyte-reduced glutathione (GSH) content and activities of the enzymes superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase, glutathione-S-transferase (GST), glutathione reductase (GR), and glucose-6-phosphate dehydrogenase (G6PDH) were spectrophotometrically estimated. The vitamin E and A contents were determined by high-performance liquid chromatography (HPLC). In both the Salmonella live culture and toxin-treated groups, the enterocyte GSH and vitamin E contents and activities of the enzymes SOD, GSH-Px, catalase, GR, and G6PDH were significantly decreased as compared to the control group. However there was a significant increase in the enterocyte activity of GST. There was no change in the vitamin A content of the enterocytes. These findings might indicate a decreased endogenous intestinal protection against ROS in S. typhimurium-mediated infection, which could contribute to the pathogenesis of the disease.

Animals↗
PubMed1998

Review article: the diagnosis and treatment of haematinic deficiency in gastrointestinal disease.

Deficiency of any of the vitamins and minerals essential for normal erythropoiesis (haematinics), including iron, copper, cobalt, vitamins A, B12, B6, C, E, folic acid, riboflavin and nicotinic acid, may be associated with defective erythropoiesis and anaemia. Iron, vitamin B12 and folate are the haematinics for which deficiency states manifest most often clinically and are the focus of this review. The normal absorption of these haematinics and gastrointestinal causes of their deficiency are described. Investigations, including the use of homocysteine metabolite levels and new techniques such as serum transferrin receptor assays, and treatment of haematinic deficiency are discussed in detail.

Deficiency Diseases↗
PubMed1998

Role of reactive oxygen species in Salmonella typhimurium-induced enterocyte damage.

BACKGROUND: Reactive oxygen species (ROS) are potent mediators of inflammatory cell-mediated tissue destruction and may be of pathophysiologic importance in Salmonella typhimurium-induced tissue damage. METHODS: In this study the ligated rat ileal loops were injected with Salmonella live culture or toxin. The ROS generation was detected by measuring the mucosal myeloperoxidase (MPO) activity; the enterocyte xanthine oxidase (XO) activity, and the chemiluminescence response of gut macrophages. The enterocyte damage was estimated by measuring the extent of lipid peroxidation and cell viability. RESULTS: Treatment with Salmonella live culture or toxin resulted in an increase in the mucosal MPO activity, the enterocyte XO activity, and the chemiluminescence response of macrophages. Treated loop enterocytes had an increased extent of lipid peroxidation and decreased cell viability. Cell viability was also decreased when the enterocytes were co-cultured with macrophages isolated from the treated loops. Lipid peroxidation decreased, and cell viability increased in the presence of superoxide dismutase (SOD) or catalase. CONCLUSIONS: The S. typhimurium-mediated intestinal infection is accompanied by an increased generation of ROS, which may induce the lipid peroxidation of the enterocyte membrane, thereby leading to a loss of cell viability.

Animals↗
PubMed1998

Cytomegalovirus infection is a risk factor for invasive aspergillosis in lung transplant recipients.

Invasive aspergillosis (IA) remains a major cause of morbidity and mortality following solid organ transplantation. To assess the incidence of IA following lung transplantation and to identify risk factors for its occurrence, we performed a case-control study involving 101 patients undergoing lung transplantation at our institution from 1990 to 1995 and reviewed the findings. Fourteen patients (14%) developed IA. The mean time from transplantation to diagnosis was 15 months. Nine patients died; the mean time to death from diagnosis was 13 days. Risk factors associated with developing IA included concomitant cytomegalovirus (CMV) pneumonia or viremia and culture isolation of Aspergillus species from a respiratory tract specimen after lung transplantation. Optimal strategies to prevent IA in lung transplant recipients remain to be determined, but prevention of aspergillus airway colonization and CMV viremia and disease after transplantation may be important targets for prophylactic interventions.

Aspergillosis↗
PubMed1998

A sequence-specific RNA-binding protein complements apobec-1 To edit apolipoprotein B mRNA.

The editing of apolipoprotein B (apo-B) mRNA involves the site-specific deamination of cytidine to uracil. The specificity of editing is conferred by an 11-nucleotide mooring sequence located downstream from the editing site. Apobec-1, the catalytic subunit of the editing enzyme, requires additional proteins to edit apo-B mRNA in vitro, but the function of these additional factors, known as complementing activity, is not known. Using RNA affinity chromatography, we show that the complementing activity binds to a 280-nucleotide apo-B RNA in the absence of apobec-1. The activity did not bind to the antisense strand or to an RNA with three mutations in the mooring sequence. The eluate from the wild-type RNA column contained a 65-kDa protein that UV cross-linked to apo-B mRNA but not to the triple-mutant RNA. This protein was not detected in the eluates from the mutant or the antisense RNA columns. Introduction of the mooring sequence into luciferase RNA induced cross-linking of the 65-kDa protein. A 65-kDa protein that interacted with apobec-1 was also detected by far-Western analysis in the eluate from the wild-type RNA column but not from the mutant RNA column. For purification, proteins were precleared on the mutant RNA column prior to chromatography on the wild-type RNA column. Silver staining of the affinity-purified fraction detected a single prominent protein of 65 kDa. Our results suggest that the complementing activity may function as the RNA-binding subunit of the holoenzyme.

APOBEC-1 Deaminase↗
PubMed1998

Prediction of lung function in the inadequately nourished.

BACKGROUND: In animal models, nutritional deficiency leads to profound qualitative changes in the lung beyond an effect on organ size. Although lung growth is non-isotropic, predictive values for spirometric lung function in children are corrected for height alone. Prediction of lung function should consider isotropic growth and nutritional status concurrently. AIM: To establish whether nutritional status influences lung function following the exclusion of the effect of isotropic growth. METHODS: Nutritional status (weight, body mass index, mid-upper arm circumference, and subscapular and triceps skinfold thicknesses) was assessed, and lung function (forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow rate (PEFR) was measured in 391 healthy school age children with normal respiratory history and examination in a rural setting in West Bengal, India. RESULTS: Lung function normalised for sitting height and stature correlated significantly with indices of nutrition in both sexes. Adding weight as an independent variable to sitting height, new reference prediction equations for FEV1, FVC, and PEFR were calculated. CONCLUSIONS: Nutritional differences influence qualitative aspects of lung development in childhood beyond simple isotropic lung growth. Prediction of lung function must take account of these differences if change as a result of disease is to be accurately measured. The identification and correction of relevant dietary deficiencies might help to improve lung function in children.

Body Height↗
PubMed1998

Nucleoside diphosphate kinase and Cl(-)-sensitive protein phosphorylation in apical membranes from ovine airway epithelium.

We have previously shown that nucleotide species (adenosine triphosphate [ATP] or guanosine triphosphate [GTP]), [Cl-], and anion species determine the steady-state phosphorylation of apical membrane proteins within human airway epithelium in vitro. We found that a Cl(-)-regulated 37-kD protein (p37) principally phosphorylated with GTP but not ATP as substrate. Here we show that apical membranes from sheep tracheal epithelium also contain a Cl(-)-regulated 37-kD phosphoprotein (p37s) and characterize one of the kinases involved in the regulation of p37s. Analysis of phosphorylation of apical membrane proteins with gamma[32P]GTP in the presence of MgCl2 showed that two proteins circa 19 and 21 kD (p19s and p21s) were transiently phosphorylated before p37s. Renaturation of apical membrane proteins within polyacrylamide gels showed that p19s and p21s autophosphorylated with either gamma[32P]GTP or gamma[32P]ATP as substrates, suggesting that the two proteins were kinases. Immunoblotting and immunoprecipitation with a specific polyclonal antibody showed that p21s was a membrane-bound isoform of nucleoside diphosphate kinase (NDPK, EC 2.7.4.6), a protein kinase which catalyzes transfer of terminal phosphate from ATP to diphosphate nucleotides and is, among other functions, essential for cell secretion. Incubation of apical membrane proteins in the presence of gamma[32P]ATP and guanosine diphosphate (GDP) (but not GDPbetaS) resulted in enhancement of phosphorylation of p37s. Dephosphorylation of NDPK was stimulated by the addition of Mg2+, Mn2+, and Co2+ (but not Zn2+ or Ca2+). Our data show that ovine trachea is a good model for further characterization of the chloride-dependent cascade in airway epithelium.

Adult↗
PubMed1998

The impact of infection control on intensive care unit microbial isolates.

In todays world, good infection control practices in high pressure intensive care units is of vital importance. Endogenous infections from the patients own microbial flora now cause the majority of nosocomial infections as the exogenous infections are curtailed to a large extent with aggressive surveillance and prevention of infection. We analysed absolute numbers of microbial isolates as an indirect reflection of infection rate in the intensive care unit (ICU) for 6 months in 1992, 1994 and 1996. We demonstrated that inspite of the total admission to the ICU increasing, the impact of infection control is certainly felt with strict inforcement of protocols.

Cross Infection↗