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Biomedical subjects

J Bhattacharya

Publications and source records attributed to J Bhattacharya.

At least 37 records · Page 2Linked to original sources
PubMed2001

Rapid alveolar liquid removal by a novel convective mechanism.

Although alveoli clear liquid by active transport, the presence of surface-active material on the alveolar surface suggests that convective mechanisms for rapid liquid removal may exist. To determine such mechanisms, we held the isolated blood-perfused rat lung at a constant alveolar pressure (PA). Under videomicroscopy, we micropunctured a single alveolus to infuse saline or Ringer solution in approximately 10 adjacent alveoli. Infused alveoli were lost from view. However, as the infused liquid cleared, the alveoli reappeared and their diameters could be quantified. Hence the time-dependent determination of alveolar diameter provided a means for quantifying the time to complete liquid removal (C(t)) in single alveoli. All determinations were obtained at an PA of 5 cmH(2)O. C(t), which related inversely to alveolar diameter, averaged 4.5 s in alveoli with the fastest liquid removal. Injections of dye-stained liquid revealed that the liquid flowed from the injected alveoli to adjacent air-filled alveoli. Lung hyperinflations instituted by cycling PA between 5 and 15 cmH(2)O decreased C(t) by 50%. Chelation of intracellular Ca(2+) prolonged C(t) and abolished the inflation-induced enhancement of liquid removal. We conclude that when liquid is injected in a few alveoli, it rapidly flows to adjacent air-filled alveoli. The removal mechanisms are dependent on alveolar size, inflation, and intracellular Ca(2+). We speculate that removal of liquid from the alveolar surface is determined by the curvature and surface-active properties of the air-liquid interface.

Animals↗
PubMed2001

The impact of state policy on the costs of HIV infection.

There is substantial variation in the generosity of public assistance programs that affect HIV+ patients, and these differences should affect the economic outcomes associated with HIV infection. This article uses data from a nationally representative sample of HIV+ patients to assess how differences across states in Medicaid and AIDS Drug Assistance Programs (ADAP) affect costs and labor market outcomes for HIV+ patients in care in that state. Making ADAP programs more generous in terms of drug coverage would reduce per patient total monthly costs, mainly through a reduction in hospitalization costs. In contrast, expanding ADAP eligibility by increasing the income threshold would increase the total cost of care. Expanding eligibility for Medicaid through the medically needy program would increase per patient total costs, but full-time employment would increase and so would monthly earnings. The authors conclude that more generous state policies toward HIV+ patients--especially those designed to provide access to efficacious treatment--could improve the economic outcomes associated with HIV.

Adult↗
PubMed2001

Health plan choice and information about out-of-pocket costs: an experimental analysis.

Many consumers are offered two or more employer-sponsored health insurance plans, and competition among health plans for subscribers is promoted as a mechanism for balancing health care costs and quality. Yet consumers may not receive the information necessary to make informed health plan choices. This study tests the effects on health plan choice of providing supplemental decision-support materials to inform consumers about expected health plan costs. Our main finding is that such information induces consumers to bear more risk, especially those in relatively good health. Thus our results suggest that working-age, privately insured consumers currently may be over-insuring for medical care.

Adolescent↗
PubMed2001

Reduced degree of long-range phase synchrony in pathological human brain.

In this paper multivariate spontaneous EEG signals from three broad groups of human subjects--control, seizure, and mania--were studied with the aim of investigating the possible effect of these pathologies on the degree of phase synchronization between cortical areas. The degree of phase synchrony was measured by two recently developed measures which are more suitable than classical indices like correlation or coherence when dealing with nonlinear and non-stationary signals like the EEG. Signals were reduced to seven frequency bands (delta, theta, alpha-1, alpha-2, beta-1, beta-2 and gamma) which were statistically compared between the normal and the other two groups. It was found that the degree of long-range synchrony was significantly reduced for both pathological groups as compared with the control group. No clear differences were found in the degrees of short-range synchrony.

Bipolar Disorder↗
PubMed2001

Escherichia coli heat stable enterotoxin receptors & guanylyl cyclase activity in the intestinal brush border membrane of hamsters & guinea pigs.

BACKGROUND & OBJECTIVES: Although Escherichia coli heat stable enterotoxin (STa) causes diarrhoea in laboratory animals, no studies were done to find out the species specific variation of distribution of the STa receptors in laboratory animals. The present investigation evaluates the density of STa receptors and the guanylyl cyclase (GC) activity in the small intestinal epithelial cells of hamsters and guinea pigs. METHODS: Brush border membrane (BBM) was prepared from the small intestines of hamsters and guinea pigs. Receptor binding assay, GC assay and autoradiography were performed to determine the density of STa receptors, the GC activity and molecular weights of the STa binding proteins respectively. RESULTS: The receptor densities, per mg BBM protein at equilibrium, were found to be 4.1 x 10(9) and 1.5 x 10(12) in hamsters and guinea pigs respectively. The GC activity was found to be lower in STa treated hamster BBM compared to that of guinea pig. Scatchard analysis of the stoichiometric data showed a linear plot, and STa bound with association constants of 0.31 x 10(12) M-1 and 1.04 x 10(12) M-1 in hamsters and guinea pigs respectively. Autoradiographic analysis of the SDS-PAGE, revealed that 125I-STa bound apparently to a 45 kDa membrane protein in hamster and a 115 kDa membrane protein in guinea pig. INTERPRETATION & CONCLUSIONS: It appears that a lower density of STa receptor exists in hamsters compared to that in guinea pigs. STa binds with a single population of STa receptors in each species with different ligand binding affinities. Also, the molecular weights of the STa binding proteins differ in these species. Moreover, the GC activity was found to be lower in hamsters than in guinea pigs.

Animals↗
PubMed2000

alpha(v)beta(3) integrin induces tyrosine phosphorylation-dependent Ca(2+) influx in pulmonary endothelial cells.

The endothelial alpha(v)beta(3) integrin occurs luminally, where its ligation by soluble agents may induce inflammatory signaling. We tested this hypothesis in bovine pulmonary artery endothelial cell monolayers with the use of vitronectin and cross-linking antibodies to ligate and aggregate the integrin. We quantified the endothelial cytosolic Ca(2+) concentration ([Ca(2+)](i)) according to the Fura 2 ratio imaging method in single cells of confluent monolayers. At baseline, endothelial [Ca(2+)](i) levels remained steady at 86 nmol/L for >20 minutes. Cross-linking of the alpha(v)beta(3) integrin through the sequential exposure of monolayers to anti-alpha(v)beta(3) monoclonal antibody LM609 and secondary IgG resulted in a [Ca(2+)](i) increase of 100% above baseline. This increase commenced in <0.5 minute, peaked in <2 minutes, and decayed to baseline in approximately 5 minutes. Similar responses occurred after the addition of vitronectin (400 microg/mL). In contrast, external Ca(2+) depletion blunted the cross-linking-induced [Ca(2+)](i) increase by 60%, a response that was completely inhibited when the monolayers were also pretreated with thapsigargin. Thus, the [Ca(2+)](i) increase was attributable in part to the release of Ca(2+) from endosomal stores but mostly to Ca(2+) influx across the plasma membrane. Induced aggregation of the alpha(v)beta(3) integrin enhanced tyrosine phosphorylation of phospholipase C-gamma1 and increased the accumulation of inositol-1, 4,5-trisphosphate. Genistein, a broad-spectrum tyrosine kinase inhibitor, abrogated both of these effects, as well as the alpha(v)beta(3)-induced [Ca(2+)](i) increases. We conclude that aggregation of the endothelial alpha(v)beta(3) integrin induces a rapid tyrosine phosphorylation-dependent increase in [Ca(2+)](i). This response may subserve the inflammatory role of alpha(v)beta(3) integrin in blood vessels.

Animals↗
PubMed2000

Decomposition of posterior alpha rhythm.

The classical posterior alpha rhythm has been decomposed into regular and irregular components using orthogonal transformation. A periodicity generator is considered, which has three characteristic control parameters: the periodicity, the amplitudes or scaling factors and the pattern associated with successive periodic segments. The regular component is shown to be equivalent to an oscillator or periodicity generator whose parameters are dynamically varying and, thus, producing both amplitude- and frequency-modulation. The irregular component is devoid of such modulating behavior. Electroencephalogram signals from normal, maniac and epileptic subjects are studied. Through analytic signal-based analysis, it is shown that for the regular component, healthy brain possesses universal scaling behavior, whereas heterogeneous scaling or absence of universality is observed for the diseased brain.

Adolescent↗
PubMed2000

Vascular expression of the alpha(v)beta(3)-integrin in lung and other organs.

The expression of the alpha(v)beta(3)-integrin in nonproliferating vascular beds remains unclear. To determine possible organ-specific differences, we compared alpha(v)beta(3)-integrin expression in the lung and other organs. Paraffin-embedded tissue sections of lung, liver, brain, muscle and skin obtained from rats were processed for immunohistochemistry with a monoclonal (LM609) and a polyclonal antibody (AB1903) against the alpha(v)beta(3)-integrin. Immunogold electron microscopy was used to localize alpha(v)beta(3)-integrin in rat lung microvasculature. With the use of custom-designed primers, lung sections were subjected to in situ PCR in a thermal cycler to amplify alpha(v) or beta(3) mRNA. To confirm specific amplification, PCR products were further hybridized in situ with an alpha(v) or beta(3) cDNA probe. In the lung, the alpha(v)beta(3)-integrin protein as well as alpha(v) and beta(3) mRNAs was extensively evident in the endothelium of extra-alveolar and alveolar microvessels, in vascular smooth muscle, and in large bronchial epithelium but not in the epithelium of alveolar ducts or alveoli. Ultrastructural immunogold labeling showed the presence of the integrin on the luminal and abluminal faces of the lung microvascular endothelium but not on the apical surface of the alveolar epithelium. Staining for the integrin was generally negative in blood vessels of several systemic organs, although weak staining was evident in branches of the hepatic portal vein. The constitutive presence of the alpha(v) and beta(3) mRNAs and the alpha(v)beta(3)-integrin in the lung microvascular bed suggests that gene transcription for the integrin is ongoing in lung vessels. Because it binds vitronectin, the lung vascular alpha(v)beta(3)-integrin may play a role in ligation of bloodborne, vitronectin-containing macromolecular complexes formed in inflammation.

Animals↗
PubMed2000

[Ca(2+)](i) oscillations regulate type II cell exocytosis in the pulmonary alveolus.

Pulmonary surfactant, a critical determinant of alveolar stability, is secreted by alveolar type II cells by exocytosis of lamellar bodies (LBs). To determine exocytosis mechanisms in situ, we imaged single alveolar cells from the isolated blood-perfused rat lung. We quantified cytosolic Ca(2+) concentration ([Ca(2+)](i)) by the fura 2 method and LB exocytosis as the loss of cell fluorescence of LysoTracker Green. We identified alveolar cell type by immunofluorescence in situ. A 15-s lung expansion induced synchronous [Ca(2+)](i) oscillations in all alveolar cells and LB exocytosis in type II cells. The exocytosis rate correlated with the frequency of [Ca(2+)](i) oscillations. Fluorescence of the lipidophilic dye FM1-43 indicated multiple exocytosis sites per cell. Intracellular Ca(2+) chelation and gap junctional inhibition each blocked [Ca(2+)](i) oscillations and exocytosis in type II cells. We demonstrated the feasibility of real-time quantifications in alveolar cells in situ. We conclude that in lung expansion, type II cell exocytosis is modulated by the frequency of intercellularly communicated [Ca(2+)](i) oscillations that are likely to be initiated in type I cells. Thus during lung inflation, type I cells may act as alveolar mechanotransducers that regulate type II cell secretion.

Animals↗
PubMed2000

Mechanisms regulating endothelial cell barrier function.

Endothelium forms a physical barrier that separates blood from tissue. Communication between blood and tissue occurs through the delivery of molecules and circulating substances across the endothelial barrier by directed transport either through or between cells. Inflammation promotes macromolecular transport by decreasing cell-cell and cell-matrix adhesion and increasing centripetally directed tension, resulting in the formation of intercellular gaps. Inflammation may also increase the selected transport of macromolecules through cells. Significant progress has been made in understanding the molecular and cellular mechanisms that account for constitutive endothelial cell barrier function and also the mechanisms activated during inflammation that reduce barrier function. Current concepts of mechanisms regulating endothelial cell barrier function were presented in a symposium at the 2000 Experimental Biology Conference and are reviewed here.

Animals↗
PubMed2000

A novel signaling mechanism between gas and blood compartments of the lung.

Propagation of inflammatory signals from the airspace to the vascular space is pivotal in lung inflammation, but mechanisms of intercompartmental signaling are not understood. To define signaling mechanisms, we microinfused single alveoli of blood-perfused rat lung with TNF-alpha, and determined in situ cytosolic Ca(2+) concentration ([Ca(2+)](i)) by the fura-2 ratio method, cytosolic phospholipase A(2) (cPLA(2)) activation and P-selectin expression by indirect immunofluorescence. Alveolar TNF-alpha increased [Ca(2+)](i) and activated cPLA(2) in alveolar epithelial cells, and increased both endothelial [Ca(2+)](i) and P-selectin expression in adjoining perialveolar capillaries. All responses were blocked by pretreating alveoli with a mAb against TNF receptor 1 (TNFR1). Crosslinking alveolar TNFR1 also increased endothelial [Ca(2+)](i). However, the endothelial responses to alveolar TNF-alpha were blocked by alveolar preinjection of the intracellular Ca(2+) chelator BAPTA-AM, or the cPLA(2) blockers AACOCF(3) and MAFP. The gap-junction uncoupler heptanol had no effect. We conclude that TNF-alpha induces signaling between the alveolar and vascular compartments of the lung. The signaling is attributable to ligation of alveolar TNFR1 followed by receptor-mediated [Ca(2+)](i) increases and cPLA(2) activation in alveolar epithelium. These novel mechanisms may be relevant in the alveolar recruitment of leukocytes.

Animals↗
PubMed2000

Aberrant internal carotid artery in the middle-ear space.

The incidence of an aberrant internal carotid artery in the middle ear is approximately one per cent and most patients are asymptomatic. We present two patients with an aberrant internal carotid artery who presented with pulsatile tinnitus and an intra-tympanic mass. Here we discuss the clinical presentation, relevant radiographic investigations and further management of these patients.

Adolescent↗
PubMed2000

Complexity analysis of spontaneous EEG.

The aim of the present paper is the assessment of the overall complexity of spontaneous and non-paroxysmal EEG signals obtained from three groups of human subjects, e.g., healthy, seizure and mania. Linear complexity measure suitable for multi-variate signals, along with nonlinear measures such as approximate entropy (ApEn) and Taken's estimator are considered. The degree of linear complexity is significantly reduced for the pathological groups compared with healthy group. The nonlinear measures of complexity are significantly decreased in the seizure group for most of the electrodes, whereas a distinct discrimination between the maniac and healthy groups based on these nonlinear measures is not evident.

Adolescent↗
PubMed1999

Morphological and cytoskeletal changes caused by non-membrane damaging cytotoxin of Vibrio cholerae on int 407 and HeLa cells.

Vibrio cholerae produces a non-membrane damaging cytotoxin (NMDCY), also known as cell rounding factor, which causes rapid rounding of cultured cells like HeLa, CHO and Vero and reportedly elicits enterotoxic activity in the rabbit ileal loop assay. Pursuing the concept that NMDCY might be an accessory factor contributing to the diarrhea caused by V. cholerae, we investigated the effect of NMDCY on Int 407 (intestinal cell line) and HeLa (non-intestinal cell line) cells using light, fluorescent and electron microscopy to gain insight into the cellular response evoked by NMDCY. Binding assays showed that NMDCY has affinity for both Int 407 and HeLa cells. Changes in the internal organelles and cytoskeletal structures of the cell lines were documented indicating changes in the secretory and metabolic function of the toxin-treated cells. Toxin-treated cells visualized under the electron microscope revealed retraction of cell body, formation of blebs on cell surface, changes in mitochondria having dilated and rarefied matrix and an extensively developed Golgi apparatus, endoplasmic reticulum and lysosomes compared to those in normal cells. Immunofluorescence study showed restructuring of microfilament network represented by actin, filamin and vinculin, as also of the microtubular component, tubulin and the intermediate filament, vimentin. Immunogold study further revealed that the toxin is internalized even within the nucleus. Moreover, a rise in the intracellular calcium level of the NMDCY-treated cells leads us to hypothesize that a cascade of events results in the final impairment of the cell machinery.

Calcium↗
PubMed1999

Revisited measles and chickenpox dynamics through orthogonal transformation.

The question addressed is whether or not childhood epidemics such as measles and chickenpox are characterized by low-dimensional chaos. We propose a new method for the detection and extraction of hidden periodic components embedded in an irregular cyclical series, and study the characterization of the epidemiological series in terms of the characteristic features or periodicity attributes of the extracted components. It is shown that the measles series possesses two periodic components each having a period of one year. Both the periodic components have time-varying pattern, and the process is nonlinear and deterministic; there is no evidence of strong chaoticity in the measles dynamics. The chickenpox series has one seasonal component with stable pattern, and the process is deterministic but linear, and hence non-chaotic. We also propose surrogate generators based on null hypotheses relating to the variability of the periodicity attributes to analyse the dynamics in the epidemic series. The process dynamics is also studied using seasonally forced SEIR epidemic model, and the characterization performance of the proposed schemes is assessed.

Chickenpox↗
PubMed1999

Killed oral Shigella vaccine made from Shigella flexneri 2a protects against challenge in the rabbit model of shigellosis.

The protective efficacy of an orally administered heat-killed virulent strain of Shigella flexneri 2a (5 weekly oral doses) was evaluated in 25 rabbits (14 immunized and 11 non-immunized controls) against challenge with the same strain of Shigella using the rabbit model of shigellosis. All 11 non-immunized rabbits developed bloody diarrhoea following challenge and 6 (54%) died. None of the 14 immunized rabbits developed diarrhoea (all had pellet stools) but 3 (21%) died from causes not associated with diarrhoea. Protection from diarrhoea and dysentery following oral immunization with a killed Shigella species was 100% and highly significant. Death following challenge was 2.5-fold higher in the non-immunized group (p = 0.115) but was not significant. These promising results suggest that further studies should be undertaken to develop a killed oral vaccine against shigellosis.

Administration, Oral↗