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Biomedical subjects

S Das

Publications and source records attributed to S Das.

At least 271 records · Page 15Linked to original sources
PubMed1998

Adsorption of Phosphate from Aqueous Solution Using Activated Red Mud.

Adsorption of phosphate (PO3-4) from aqueous solution on activated red mud (ARM) was studied as a function of time, pH, temperature, concentration of adsorbent and adsorbate in acetic acid-sodium acetate buffer medium. The adsorption of phosphate follows Langmuir as well as Freundlich adsorption isotherms. The process efficiency was found to be 80-90% at room temperature. This can be extended to the treatment of industrial effluents containing phosphates like that from phosphatic fertilizer plants. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Increased NMDA current and spine density in mice lacking the NMDA receptor subunit NR3A.

The NMDA (N-methyl-D-aspartate) subclass of glutamate receptor is essential for the synaptic plasticity thought to underlie learning and memory and for synaptic refinement during development. It is currently believed that the NMDA receptor (NMDAR) is a heteromultimeric channel comprising the ubiquitous NR1 subunit and at least one regionally localized NR2 subunit. Here we report the characterization of a regulatory NMDAR subunit, NR3A (formerly termed NMDAR-L or chi-1), which is expressed primarily during brain development. NR3A co-immunoprecipitates with receptor subunits NR1 and NR2 in cerebrocortical extracts. In single-channel recordings from Xenopus oocytes, addition of NR3A to NR1 and NR2 leads to the appearance of a smaller unitary conductance. Genetic knockout of NR3A in mice results in enhanced NMDA responses and increased dendritic spines in early postnatal cerebrocortical neurons. These data suggest that NR3A is involved in the development of synaptic elements by modulating NMDAR activity.

Animals↗
PubMed1998

Neurocytoma/rhabdomyoma (myoneurocytoma) of the cerebellum.

An unusual case of cerebellar neurocytoma with rhabdomyomatous differentiation in a 6-year-old boy is reported. Immunocytochemical and ultrastructural features of the tumour were studied. Abortive synapse formation, the presence of clear vesicles and synaptophysin immunoreactivity of the tumour cells indicated its intermediate neuronal differentiation, while the presence of myoblasts and myotubes and immunolabelling by desmin confirmed the rhabdomyomatous differentiation. In addition, the mesenchymal cells variably expressed neurofilament protein and glial fibrillary acidic protein, suggesting inductive interaction between the neuroectodermal and ectomesenchymal elements and persistence of the pleuripotential nature of the cells along the rhombic area of the brain stem.

Cerebellar Neoplasms↗
PubMed1998

Retroperitoneal and pelvic extraperitoneal laparoscopy: an international perspective.

OBJECTIVES: To assess technical preferences and current practice trends of retroperitoneal and pelvic extraperitoneal laparoscopy. METHODS: A questionnaire survey of 36 selected urologic laparoscopic centers worldwide was performed. RESULTS: Twenty-four centers (67%) responded. Overall, 3988 laparoscopic procedures were reported: transperitoneal approach (n = 2945) and retroperitoneal/extraperitoneal approach (n = 1043). Retroperitoneoscopic/extraperitoneoscopic procedures included adrenalectomy (n = 74), nephrectomy (n = 299), ureteral procedures (n = 166), pelvic lymph node dissection (n = 197), bladder neck suspension (n = 210), varix ligation (n = 91), and lumbar sympathectomy (n = 6). Mean number of total laparoscopic procedures performed in 1995 per center was 41 (range 5 to 86). Major complications occurred in 49 (4.7%) patients and included visceral complications in 26 (2.5%) patients and vascular complications in 23 (2.2%). Open conversion was performed in 69 (6.6%) patients, electively in 41 and emergently in 28 (visceral injuries, n = 16; vascular injuries, n = 1 2). Retroperitoneoscopy/extraperitoneoscopy is gaining in acceptance worldwide: in 1993, the mean estimated ratio of transperitoneal laparoscopic cases versus retroperitoneoscopic/ extraperitoneoscopic cases per center was 74:26; however, in 1996 the ratio was 49:51. CONCLUSIONS: Retroperitoneoscopy and pelvic extraperitoneoscopy are important adjuncts to the laparoscopic armamentarium in urologic surgery. The overall major complication rate associated with retroperitoneoscopy/extraperitoneoscopy was 4.7%.

Humans↗
PubMed1998

Estimation of spatiotemporal neural activity using radial basis function networks.

We report a method using radial basis function (RBF) networks to estimate the time evolution of population activity in topologically organized neural structures from single-neuron recordings. This is an important problem in neuroscience research, as such estimates may provide insights into systems-level function of these structures. Since single-unit neural data tends to be unevenly sampled and highly variable under similar behavioral conditions, obtaining such estimates is a difficult task. In particular, a class of cells in the superior colliculus called buildup neurons can have very narrow regions of saccade vectors for which they discharge at high rates but very large surround regions over which they discharge at low, but not zero, levels. Estimating the dynamic movement fields for these cells for two spatial dimensions at closely spaced timed intervals is a difficult problem, and no general method has been described that can be applied to all buildup cells. Estimation of individual collicular cells' spatiotemporal movement fields is a prerequisite for obtaining reliable two-dimensional estimates of the population activity on the collicular motor map during saccades. Therefore, we have developed several computational-geometry-based algorithms that regularize the data before computing a surface estimation using RBF networks. The method is then expanded to the problem of estimating simultaneous spatiotemporal activity occurring across the superior colliculus during a single movement (the inverse problem). In principle, this methodology could be applied to any neural structure with a regular, two-dimensional organization, provided a sufficient spatial distribution of sampled neurons is available.

Algorithms↗
PubMed1998

Spinal extradural cysticercosis: a case report.

An extremely rare case of extradural spinal cysticercosis in an adult male is presented. The patient had evidence of extradural granulation tissue with associated destruction of C4 and C5 pedicles and laminae, causing tetraparesis. Histopathological examination revealed evidence of a degenerated cysticercal cyst with host tissue reaction. The patient made a gradual and marked improvement after decompression. Though rare, cysticercosis as a possible etiology of extradural spinal compression may be considered in endemic area.

Adult↗
PubMed1998

Comparison of six respirator fit-test methods with an actual measurement of exposure in a simulated health care environment: Part I--Protocol development.

Quantitative fit tests (QNFT) have been assumed to be predictive of the protection respirators would provide to a wearer in the workplace. Workplace studies have consistently found no correlation between quantitative fit factors and workplace protection factors. This article is the first in a series of three describing a study designed to compare the fit factors from six QNFT methods against the actual dose of 1,1,2 trichloro-1,2,2 trifluoroethane (Freon-113) received under the same laboratory conditions. Five preliminary studies conducted to develop the protocol to assess the respirator wearer's dose through end-exhaled air analysis are described in this article: (1) chamber characterization, (2) end-exhaled air sampling, (3) skin absorption testing, (4) pharmacokinetic modeling, and (5) subject characterization. It was established that the concentration of corn oil aerosol and Freon-113 could be generated simultaneously in the chamber. It was ascertained that the optimum time to sample the exhaled breath was 30 minutes after the subject exited the chamber. It was also found that in a chamber concentration of 500 ppm, without any respiratory exposure, Freon-113 was still present in the end-exhaled air. This was attributed to skin absorption. The end-exhaled air of subjects exposed to 0.5, 3, 5, 25, 50, and 100 ppm (30 minute time-weighted average) of Freon-113 was evaluated at 30 minutes postexposure. This characterization was then used to predict the actual dose of Freon-113 received during the method comparison and validation testing to be described in subsequent articles.

Adult↗
PubMed1998

Lipoarabinomannan induced cytotoxic effects in human mononuclear cells.

Mycobacteria produce large quantities of lipoarabinomannan, a cell wall associated glycolipid, which confers virulence in many of the disease causing members of the genus. We studied the lipoarabinomannan induced altered signaling mechanism in human peripheral mononuclear cells. Lipoarabinomannan isolated from Mycobacterium smegmatis (a non-pathogenic species) at concentrations of 2, 5 and 10 microg ml(-1) was used for the study. It was found that protein kinase C activity of human mononuclear cells was significantly inhibited by lipoarabinomannan at these concentrations in a dose dependent manner. Calcium, phosphatidyl serine and diglyceride dependent phosphorylation of endogenous proteins (mainly 90-, 80-, 66-, 38-, 36- and 34-kDa proteins) were also inhibited. Potentially cytotoxic superoxide anions generated by peripheral blood mononuclear cells were scavenged by lipoarabinomannan. It was also observed that incubation of peripheral blood mononuclear cells with lipoarabinomannan at concentrations of 5 and 10 microg ml(-1) for 6 h directed the cells towards apoptotic cell death, confirmed by DNA degradation analysis, microscopic observation of Wright-Giemsa as well as DAPI stained nuclei. These results clearly demonstrate that lipoarabinomannan from M. smegmatis may exert its cytotoxic activity via inhibition of protein kinase C, a key signaling molecule inside the mononuclear cells, which ultimately affects the phosphorylation of various proteins imperative for cellular defence and survival.

Adult↗
PubMed1998

Onset of acute psychotic states in India: a study of sociodemographic, seasonal and biological factors.

This is a comparative study of patients with acute-onset, non-affective, non-organic, remitting psychoses and with non-remitting or schizophrenic psychoses in India. Two groups of patients with acute remitting and non-remitting or schizophrenic psychoses were compared with regard to the following variables: month of onset of psychosis; presence of stress, particularly fever, within 4 weeks preceding the onset of psychosis; childbirth within 12 weeks preceding the onset of psychosis; gender differences. It was found that the acute remitting psychoses showed an overrepresentation of females, a higher frequency of associated stress preceding the onset of psychosis, more often had onset during the summer months, i.e. between May and September, and had fever and childbirth preceding the onset of psychosis in a significantly higher proportion of patients, compared to acute non-remitting psychoses or schizophrenia. The implications of the findings which point towards biological factors in the aetiology of acute remitting psychoses are discussed.

Acute Disease↗
PubMed1998

Granulocytic ehrlichiosis in tick-immune guinea pigs.

We investigated whether Ixodes scapularis-mediated host immunity interrupts transmission of the agent of human granulocytic ehrlichiosis (aoHGE) to guinea pigs. Ticks infected with aoHGE readily transmitted aoHGE to tick-immune guinea pigs, despite incomplete tick engorgement and host attachment. Although tick immunity can prevent Lyme borreliosis, protection is not afforded against granulocytic ehrlichiosis.

Animals↗
PubMed1998

A small yeast RNA blocks hepatitis C virus internal ribosome entry site (HCV IRES)-mediated translation and inhibits replication of a chimeric poliovirus under translational control of the HCV IRES element.

Hepatitis C virus (HCV) infection frequently leads to chronic hepatitis and cirrhosis of the liver and has been linked to development of hepatocellular carcinoma. We previously identified a small yeast RNA (IRNA) capable of specifically inhibiting poliovirus (PV) internal ribosome entry site (IRES)-mediated translation. Here we report that IRNA specifically inhibits HCV IRES-mediated translation both in vivo and in vitro. A number of human hepatoma (Huh-7) cell lines expressing IRNA were prepared and characterized. Constitutive expression of IRNA was not detrimental to cell growth. HCV IRES-mediated cap-independent translation was markedly inhibited in cells constitutively expressing IRNA compared to control hepatoma cells. However, cap-dependent translation was not significantly affected in these cell lines. Additionally, Huh-7 cells constitutively expressing IRNA became refractory to infection by a PV-HCV chimera in which the PV IRES is replaced by the HCV IRES. In contrast, replication of a PV-encephalomyocarditis virus (EMCV) chimera containing the EMCV IRES element was not affected significantly in the IRNA-producing cell line. Finally, the binding of the La autoantigen to the HCV IRES element was specifically and efficiently competed by IRNA. These results provide a basis for development of novel drugs effective against HCV infection.

Autoantigens↗
PubMed1998

Intracellular uptake of recombinant superoxide dismutase after intratracheal administration.

We have previously demonstrated that recombinant human copper-zinc superoxide dismutase (rhCu,ZnSOD) is rapidly incorporated into cells of airways, respiratory bronchioles, and alveoli after intratracheal administration. The present study examines whether this cellular uptake is specific for rhCu,ZnSOD or whether other proteins are similarly incorporated into lung cells. Twenty-two newborn piglets (2-3 days old, 1.2-2.0 kg) were intubated and mechanically ventilated. Eight piglets received fluorescently labeled recombinant human manganese superoxide dismutase (rhMnSOD), six received fluorescently labeled albumin, two received free (unbound) fluorescent label intratracheally, and two piglets served as untreated controls. To determine whether endogenous surfactant was important in the process of intracellular uptake, four additional piglets were made surfactant deficient by repeated bronchoalveolar lavage and then given rhCu,ZnSOD intratracheally. All animals were killed after 30-60 min. Lung sections were examined blindly by laser confocal microscopy. Similar to our previous observations with rhCu,ZnSOD, intracellular uptake of rhMnSOD and albumin was noted throughout the lung. The free label did not localize intracellularly. The uptake of proteins did not appear to be affected by surfactant deficiency. rhMnSOD administration was associated with a greater than twofold increase in lung MnSOD activity. Data suggest that the cellular uptake of antioxidants and other proteins in the lung may reflect a nonspecific host defense system for clearing proteins from the lumen of airways and alveoli.

Animals↗
PubMed1998

Two-dimensional saccade-related population activity in superior colliculus in monkey.

The two-dimensional distribution of population activity in the superior colliculus (SC) during saccadic eye movements in the monkey was estimated using radial basis functions. To make these ensemble activity estimates, cells in the deeper layers of the SC were recorded over much of the rostrocaudal (caudal to 3.8 mm from the rostral tip), mediolateral extent of this structure. The dynamic movement field of each cell was determined at 2-ms intervals around the time of saccades for a wide variety of horizontal and oblique movements. Collicular neurons were divided into partially overlapping dorsal and ventral cell layers on the basis of recorded depth in SC. The pattern of presaccadic activity was used as an additional discriminant to sort the cells in the two layers into separate burst (dorsal) and buildup (ventral) cell classes. Rostrocaudal and medioventral cell location on the colliculus was estimated from the optimal target vector for a cell's visual response rather than from the optimal motor vector. The former technique was more reliable for locating some buildup neurons because it produced locations that compared better with the locations suggested by electrical stimulation. From the movement field data and from the estimates of each cell's anatomic location, a similar algorithm was used to compute the two-dimensional population activity in the two layers of the SC during horizontal and oblique saccades. A subset of the sample of neurons, located near the horizontal meridian of the SC, first was used to compute one-dimensional dynamic population activity estimates for horizontal saccades to allow partial comparison to previous studies. Statistical analyses on the one-dimensional data were limited to saccades of </=20 degrees. The analyses indicated that while there was a small rostrally directed shift in the center of gravity of the distributed activity in the buildup cell layer, there was little support for the theory of a systematic rostrally directed spread of the leading edge of the activity. The two-dimensional results extend the previous one-dimensional estimates of collicular activity during saccades. Discharge in the burst layer was invariant in size for all saccade vectors and symmetrically arranged about a center of gravity that did not move during saccades. The size of the active area in the buildup layer grew modestly with saccade amplitude, whereas the distribution of activity was skewed toward the rostral end of the SC for saccades larger than 10 degrees. There was a small, but consistent shift in the center of gravity of the two-dimensional activity that was directed along the horizontal meridian (for horizontal movements) or an oblique meridian (for oblique movements) of the SC. However, the spread of activity during a saccade was as large or larger in the mediolateral direction as it was in the rostral direction. The results indicate that changes in activity occur in an extended zone on the SC, and in all directions but caudal, in the buildup layer during saccades and do not support the idea of a rostrally directed spread of activity as a dynamic control mechanism for saccades. Our results and those of previous investigators of collicular population activity may be limited by stationarity concerns in that the cells used to estimate population activity were recorded in several monkeys over an extended period of time to obtain a sufficient spatial sample.

Algorithms↗
PubMed1998

Association between right ventricular function and perfusion abnormalities in hemodynamically stable patients with acute pulmonary embolism.

BACKGROUND/OBJECTIVES: Patients presenting with acute pulmonary embolism associated with hemodynamic compromise exhibit right ventricular enlargement and dysfunction on transthoracic echocardiogram. However, the degree of echocardiographic abnormalities among hemodynamically stable patients without preexisting cardiopulmonary disease during the acute stage of pulmonary embolism, and following treatment, is unknown. Therefore, this study was designed to assess the extent of right ventricular abnormalities detected on transthoracic echocardiogram in patients following acute pulmonary embolism and during treatment with anticoagulation or vena caval interruption. The extent of pulmonary vascular obstruction and complication rate on follow-up were also assessed. DESIGN/INTERVENTIONS: Sixty-four consecutive hemodynamically stable patients without preexisting known cardiopulmonary disorder presenting with acute pulmonary embolism and undergoing treatment with anticoagulation or inferior vena caval interruption were studied. All subjects underwent a two-dimensional transthoracic echocardiogram within 24 h of diagnosis. The degree of perfusion abnormality on lung scan was quantified. Twenty-six patients underwent follow-up echocardiogram and lung scan at 6 weeks. The echocardiographic findings were compared with those obtained from a group of normal control subjects matched for gender and age. RESULTS: Although the mean right ventricular end-diastolic areas did not differ (21.9+/-5.2 cm2 vs 20.1+/-2.9 cm2 for control subjects; p=not significant), the right ventricular end-systolic area was larger in comparison to our series of control subjects (14.6+/-5.1 cm2 vs 11.7+/-2.0 cm2; p=0.025). Fractional right ventricular area change was reduced in the patient group compared with the control subjects (34.3+/-9.0% vs 41.3+/-7.0%; p=0.003). The extent of right ventricular end-systolic area enlargement and decrease in fractional area change did not correlate with the degree of pulmonary vascular obstruction. Patients who were restudied at 6 weeks showed minimal improvement in echocardiographic findings, despite almost complete resolution of perfusion defects on lung scan. CONCLUSIONS: The extent of right ventricular dysfunction in hemodynamically stable, previously normal patients with acute pulmonary embolism does not reflect the extent of the perfusion abnormalities. Further, right ventricular enlargement and systolic dysfunction are present and persistent despite treatment with heparin and warfarin therapy or vena caval interruption.

Acute Disease↗
PubMed1998

Prevention of Borrelia burgdorferi transmission in guinea pigs by tick immunity.

We examined the effect of repeated infestation of guinea pigs with Ixodes scapularis on the capacity of ticks to transmit Borrelia burgdorferi infection. Repeated challenges with nymphs or larvae lead to a reduction in duration of nymphal tick attachment and weight of recovered ticks consistent with the development of tick immunity. Only one of 18 I. scapularis-immune guinea pigs challenged with B. burgdorferi-infected nymphal ticks became infected, whereas 10 of 18 naive guinea pigs similarly challenged became infected. We conclude that tick immunity interferes with borrelial transmission.

Animals↗