Search PubMed⌕ Search

Biomedical subjects

S Majumdar

Publications and source records attributed to S Majumdar.

At least 199 records · Page 11Linked to original sources
PubMed1996

Experimental extrahepatic obstruction of portal vein: documentation of histopathological alterations in liver and extrahepatic tissues.

The histopathology of the portal vein in human extrahepatic portal vein obstruction (EHPVO) in the form of cavernomatous transformation of the portal vein is well documented. However, a similar detailed histopathology has not been documented in experimental EHPVO, even though the model has been in existence for many years. An experimental model of EHPVO was created by partial ligation of the portal vein in 20 rats. A control group of 11 sham operated (SO) rats was also studied. Development of portal hypertension was confirmed by measurement of intrasplenic pulp pressure (19.7 + 7.1 cm normal saline vs 12.9 + 1.1 cm of normal saline in SO rats). Histopathological evidence included varices in the oesophagus and congestion in the submucosa and mucosa of the stomach and capillarization of sinusoids in the spleen. Animals were killed at 22-265 days post-ligation. While SO animals showed mild focal sinusoidal congestion and a normal portal vein, the experimental group of animals with EHPVO showed oedema around the portal vein, multiple dilated vascular channels near the hilum resembling cavernomatous transformation and severe sinusoidal congestion. Jejunum and kidneys showed congested veins in the experimental group. None of the SO animals showed this change. Thus experimental EHPVO does reproduce some histological changes observed in human EHPVO.

Animals↗
PubMed1996

Distal radius: in vivo assessment with quantitative MR imaging, peripheral quantitative CT, and dual X-ray absorptiometry.

PURPOSE: To evaluate in vivo the relationship between magnetic resonance (MR) imaging relaxation time and bone mineral density (BMD) at the distal radius. MATERIALS AND METHODS: The 1/T2* MR imaging relaxation rates and dual X-ray absorptiometry (DXA) measurements were evaluated in the trabecular bone of the distal 5 cm of the radius in 14 healthy premenopausal women and 11 healthy postmenopausal women and in 11 women with osteoporosis. Trabecular and total BMD were measured with peripheral quantitative computed tomography (CT). RESULTS: In healthy women, 1/T2* values and trabecular BMD at peripheral quantitative CT were significantly correlated but 1/T2* and total BMD were not. Statistically significant (P = .03) correlations between 1/T2* and DXA were found only in the most distal area covered with DXA. The 1/T2* values were more closely correlated with age and showed higher relative annual decreases (0.47%-0.81%) than peripheral quantitative CT (0.20%-0.59%) or DXA (0.10%-0.39%). Pre- and postmenopausal healthy subjects could be distinguished only with MR imaging, and postmenopausal healthy and osteoporotic subjects only with CT and DXA. CONCLUSION: MR imaging relaxation rates correlate well with trabecular BMD in vivo.

Absorptiometry, Photon↗
PubMed1996

Coincident expression of Menkes gene with copper efflux in human placental cells.

BeWo cells, a human choriocarcinoma cell line, have a high-affinity system for transporting copper ions into the cell (Km = 0.21 microM) but are sluggish in releasing copper back into the medium from preloaded cells. The slow efflux rate has recently been shown to correlate with a failure of BeWo cells to express the Menkes transcript [Y. Qian, E. Tiffany-Castiglioni, and E. D. Harris. Am. J. Physiol. 271 (Cell Physiol. 40). In press]. We have now determined that only when BeWo cells were grown on plastic surfaces such as petri dishes or flasks did they display negligible release and enhanced retention of 67Cu. Reverse transcriptase-polymerase chain reaction with the use of primers selective for the Menkes gene failed to show any evidence of a Menkes transcript in cells cultured on plastic surfaces. In contrast, cells grown on porous filters previously shown to allow apical and basolateral surfaces to develop did display the transcript and showed significant copper release with normal retention. Release of copper from filter-grown cells was blocked with p-chloromercuribenzoate, thus confirming sulfhydryl group involvement. Absorption of the 67Cu, either as a free ion or bound to ceruloplasmin, was unaffected by the different culture conditions. The data link the Menkes gene product with the ability of cells to release copper ions. They also suggest that the expression of the Menkes gene may be regulated by the development of polarized cell membranes.

Base Sequence↗
PubMed1996

Pulmonary infection caused by Mycobacteria other than M. tuberculosis in and around Calcutta.

A study was undertaken to determine the prevalence rate of atypical mycobacteria in indolent fibrocavitary pulmonary diseases. 450 sputum specimens were examined and cultured, of which 15 were identified as atypical mycobacteria on repeated culture. No previous study was recorded from Calcutta. Compared to the results of previous workers from different regions of India, the prevalence rate seems high in this part of the country.

Adult↗
PubMed1995

MRI of bone marrow in the distal radius: in vivo precision of effective transverse relaxation times.

The effective transverse relaxation time T2* is influenced by the presence of trabecular bone, and can potentially provide a measure of bone density as well as bone structure. We determined the in vivo precision of T2* in repeated bone marrow measurements. The T2* measurements of the bone marrow of the distal radius were performed twice within 2 weeks in six healthy young volunteers using a modified water-presaturated 3D Gradient-Recalled Acquisition at Steady State (GRASS) sequence with TE 7, 10, 12, 20, and 30; TR 67; flip angle (FA) 90 degrees. An axial volume covering a length of 5.6 cm in the distal radius was measured. Regions of interest (ROIs) were determined manually and consisted of the entire trabecular bone cross-section extending proximally from the radial subchondral endplate. Reproducibility of T2* and area measurements was expressed as the absolute precision error (standard deviation [SD] in ms or mm2) or as the relative precision error (SD/mean x 100, or coefficient of variation [CV] in %) between the two-point measurements. Short-term precision of T2* and area measurements varied depending on section thickness and location of the ROI in the distal radius. Absolute precision errors for T2* times were between 1.3 and 2.9 ms (relative precision errors 3.8-9.5 %) and for area measurements between 20 and 55 mm2 (relative precision errors 5.1-16.4%). This MR technique for quantitative assessment of trabecular bone density showed reasonable reproducibility in vivo and is a promising future tool for the assessment of osteoporosis.

Adult↗
PubMed1995

A review of the recent advances in magnetic resonance imaging in the assessment of osteoporosis.

Osteoporosis is a common metabolic disorder with considerable associated morbidity and mortality. The loss of bone mineral integrity and the resultant occurrence of atraumatic fractures are typically symptomatic of the disease. Currently skeletal status is commonly assessed using non-invasive conventional radiography and scintigraphy as well as densitometric techniques such as quantitative computed tomography and dual-energy X-ray absorptiometry. But, apart from gross bone mineral density, the fine structure of trabecular bone also plays an important role in defining the biomechanical competence of the skeleton. Recently attention has been focused on deriving measures that provide information about not only trabecular bone density but also microstructure. Magnetic resonance imaging (MRI) is one such new technique which potentially may provide information pertaining to bone density and structure as well as to occult fracture detection. Cortical bone produces a signal void in MR images, due to the fact that it contains very few mobile protons that give rise to a signal in MRI; also the MR relaxation time T2 of these protons is very short which produces a very fast decay of the MR signal during image acquisition. However, the trabecular bone network affects the MR properties of bone marrow. The difference in the magnetic properties of trabecular bone and bone marrow generates local imperfections in the magnetic field. The MR signal from bone marrow is modified due to these imperfections and the MR relaxation time T2 of marrow is shortened. The extent of relaxation time shortening and hence loss of signal intensity is proportional to the density of trabecular bone and marrow interfaces and their spatial architecture. Recent investigation in this area include studies aimed at quantifying marrow relaxation times and establishing their relationship to trabecular bone density and structure. In addition, with advances in imaging software and hardware, MR images at in-plane resolutions of 78-200 microns may be obtained. The trabecular bone structure is clearly revealed in such images and studies aimed at the development of high-resolution MRI techniques combined with quantitative image analysis techniques are currently under way. These potentially useful techniques for assessing osteoporosis and predicting fracture risk are reviewed in this paper.

Bone Density↗
PubMed1995

Evaluation of technical factors affecting the quantification of trabecular bone structure using magnetic resonance imaging.

High resolution magnetic resonance (MR) techniques combined with standard techniques of stereology and texture analysis have been used to quantify trabecular structure. Using dried excised specimens from the tibia (n = 10) and radius (n = 2) we evaluate the impact of using volumetric gradient-echo (GE) and spin-echo (SE) MR imaging sequences, the relative importance of echo time in gradient-echo MR imaging, and the impact of different threshold values to segment the bone and bone marrow on the estimation of trabecular bone structure. We also investigate the inter-relationships between the different structural parameters derived from MR images. Images were obtained using fast gradient-echo and spin-echo imaging sequences, with TE values ranging from 7 to 17 ms using 4.7 and 1.5 Tesla imaging systems. In-plane image resolution ranged from 128 to 156 microns, and slice thickness ranged from 128 to 1000 microns. We derived stereological measures such as the mean intercept length, trabecular width, fractional area of trabecular bone, trabecular number, and trabecular spacing, the fractal dimension as a texture-related parameter and the Euler number as a measure of connectivity from these images. We found that the mean intercept length as a function of angle traced an ellipse with the orientation of the principal axis of the ellipse, a measure of trabecular orientation, identical when measured from the spin-echo or gradient-echo MR images. Absolute measures such as the fractional area, trabecular width, trabecular number, and fractal dimension as measured from gradient echo images were 28%, 30%, 1.3%, and 0.6% greater, respectively, than those calculated from spin-echo images, while the trabecular spacing was 14% less when calculated from gradient-echo images compared to spin-echo images. The structural parameters also depended on the echo time used to obtain the MR image. The choice of the threshold used to segment the high resolution images also affected the estimated structural parameters significantly. Our results indicate that MR may be used to visualize and quantify trabecular bone architecture; however, the different technical factors that could affect the appearance of MR images must be understood and considered in the data analysis and interpretation.

Absorptiometry, Photon↗
PubMed1995

Interleukin-8. Differential expression in lone fibrosing alveolitis and systemic sclerosis.

Fibrosing alveolitis may occur alone (CFA) or in association with systemic sclerosis (FASSc). FASSc was recently shown to have a prognostic advantage over CFA. Because interleukin-8 (IL-8) is likely to be a major determinant of neutrophil alveolitis, we evaluated IL-8 expression in patients with CFA and FASSc and compared it with that in normal individuals and sarcoidosis and systemic sclerosis patients without pulmonary involvement (SSc no FA). IL-8 protein in bronchoalveolar lavage fluid (BALF) was assessed by immunoassay, and IL-8 mRNA expression was assessed using Northern analysis and reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization of lung parenchyma. Compared with normal subjects, IL-8 concentration was significantly greater in both CFA (p < 0.001) and FASSc groups (p < 0.05) but no different in sarcoidosis. The IL-8 concentration in CFA was higher than in FASSc (p < 0.01) and was related to BAL % neutrophils (rs = 0.48, p < 0.01). IL-8 mRNA expression evaluated by Northern analysis was seen only in patients with CFA and FASSc and was related to BAL % neutrophils (rs = 0.63, p < 0.01). We suggest that IL-8 is a key factor in the pathogenesis of fibrosing alveolitis and that the poorer prognosis of CFA compared with FASSc is related to higher levels of IL-8 within the lower respiratory tract.

Adult↗
PubMed1995

Fibrosing alveolitis in systemic sclerosis: increase in memory T-cells in lung interstitium.

Despite the large numbers of T-cells present in the lungs in fibrosing alveolitis, their pathogenetic role is poorly understood. If these cells are involved in pathogenesis, they are more likely to express the CD45RO+ memory phenotype. To test this hypothesis, open lung biopsies from patients with fibrosing alveolitis associated with systemic sclerosis (FASSc) were compared with grossly normal lung taken from the periphery of lobes resected for lung cancer. Biopsies from eight patients with FASSc were compared with tissue from seven cancer controls. Paraffin sections were stained with a polyclonal anti-CD3 antibody for T-lymphocytes, monoclonal anti-CD45 antibody for leucocyte common antigen, and monoclonal anti-CD45RO antibody for primed T-lymphocytes. Staining was assessed quantitatively by computerized image analysis: in each case, the number of immunopositive cells was related to alveolar wall area and alveolar wall length. Mean alveolar wall thickness was increased in patients with FASSc (60.7 +/- 24.0 microns) compared with cancer controls (15.7 +/- 5.3 microns). Patients with FASSc had greater numbers of CD45+, CD3+ and CD45RO+ cells.mm-1 alveolar wall length compared with the controls. CD45RO+ cells made up 77% (median) of the CD3+ cells in FASSc, and their numbers per unit alveolar wall length were positively associated with alveolar wall thickness (r = 0.61). In conclusion, in fibrosing alveolitis of systemic sclerosis, most interstitial T-lymphocytes express the phenotype of memory cells; these cells are likely to be involved in the persistent inflammatory process.

Adult↗
PubMed1995

Physiology of fatigue in amyotrophic lateral sclerosis.

We investigated the mechanisms of muscle fatigue in ALS. In the muscles of ALS patients and healthy control subjects, we examined (1) fatigue using measurements of muscle force, (2) energy metabolism using phosphorus-31 magnetic resonance spectroscopy, and (3) activation using neurophysiologic measures and MRI. During 25 minutes of intermittent isometric exercise of the tibialis anterior muscle, both maximum voluntary and tetanic force declined more in patients than in controls, indicating greater fatigability in ALS. There was a similar decline of voluntary and tetanic force, suggesting that much of the fatigue was not central. Evoked compound muscle action potential amplitudes were preserved during exercise in both groups, indicating no failure of neuromuscular transmission; this result suggests that the source of fatigue was not at the neuromuscular junction or within the muscle membrane. In spite of greater fatigability, changes during exercise in energy metabolites and proton signal intensity tended to be less in ALS patients compared with controls, suggesting impaired muscular activation. We conclude that the greater muscle fatigue in ALS patients results from activation impairment, due in part to alterations distal to the muscle membrane.

Action Potentials↗
PubMed1995

51Cr-labelled ethylenediaminetetraacetic acid and D-xylose absorption test in Escherichia coli enterotoxin-induced diarrhoea in mice.

BACKGROUND AND METHODS: D-Xylose and 51Cr-labelled ethylenediaminetetraacetic acid (EDTA) absorption tests were evaluated in control and Escherichia coli heat-stable, heat-labile, and both heat-stable and heat-labile enterotoxin-induced diarrhoea in mice. RESULTS: The absorption of D-xylose was greatest 45 min after its ingestion in both control and enterotoxin-treated groups. There was a significant (p < 0.01) decrease in xylose absorption at 45 min in all the three experimental groups as compared with the control group, which may be due to change in membrane fluidity and hence change in membrane permeability, whereas 51Cr-EDTA absorption was at its maximum 15 min after its ingestion in both control and experimental groups. And there was a significant (p < 0.05) increase in 51Cr-EDTA absorption in enterotoxin-treated groups as compared with the control group. CONCLUSIONS: These results suggest a change in tight junctional permeability which may be due to change in the cytoskeletal microfilaments. Both these tests hence show that E. coli enterotoxin-induced diarrhoea results in absorption and permeability changes.

Animals↗
PubMed1995

Current methods and advances in bone densitometry.

Bone mass is the primary, although not the only, determinant of fracture. Over the past few years a number of noninvasive techniques have been developed to more sensitively quantitate bone mass. These include single and dual photon absorptiometry (SPA and DPA), single and dual X-ray absorptiometry (SXA and DXA) and quantitative computed tomography (QCT). While differing in anatomic sites measured and in their estimates of precision, accuracy, and fracture discrimination, all of these methods provide clinically useful measurements of skeletal status. It is the intent of this review to discuss the pros and cons of these techniques and to present the new applications of ultrasound (US) and magnetic resonance (MRI) in the detection and management of osteoporosis.

Absorptiometry, Photon↗
PubMed1995

Airway and lung elastic fibre is not reduced in asthma nor in asthmatics following corticosteroid treatment.

By morphometric investigation of the relative content of elastic and collagen fibres, we have tested the hypothesis that loss of elastic fibres in the conducting airways and lung parenchyma may reduce tissue elastic recoil, resulting in increased airway maximal closure and apparent increased responsiveness. The study groups comprised: Group A (n = 11) with relatively mild atopic asthma using inhaled bronchodilators prn (i.e. short-term corticosteroids users); Group B (n = 9) with more severe asthma requiring inhaled bronchodilators regularly, and daily inhaled glucocorticosteroids (i.e. longterm corticosteroid users); Group C (n = 12) normal healthy workers. Bronchial biopsy samples were taken from three sites from the left lung. Group A biopsy samples were taken before and after a 4 wk treatment period with inhaled corticosteroids (200 micrograms b.i.d.) and the relative elastic and collagen fibre content of a subepithelial zone was determined from electron micrographs. In a parallel study, the relative proportion of elastic fibre in post mortem lung tissue samples (inner aspect of the bronchial wall, alveolar wall, and points of attachment of surrounding alveoli to intrapulmonary bronchi) from subjects suffering a fatal asthma attack (n = 11), and non-asthmatic suffering sudden death (n = 9), were determined using Miller's elastic and eosin counterstain for light microscopy. In bronchial biopsies of normal subjects, 4.6 (SEM 1.1)% of subepithelial connective tissue was elastic fibre, similar to mild asthmatic subjects, 1.9 (SEM 0.48)%. Neither short-term (4 weeks) inhaled corticosteroid (200 micrograms b.i.d.) nor long-term (< 6 months) treatment with variable doses of inhaled steroids (100-1000 micrograms b.i.d.) significantly altered the elastic or collagen content of the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

The relationship of sonographic placental grading, biochemical pulmonary maturity and neonatal outcome in pregnancy-induced hypertension.

In a prospective study, the accuracy of placental grade in predicting pulmonary maturity was evaluated in 50 cases of pregnancy-induced hypertension (PIH) between 28 and 41 weeks of gestation. Pulmonary maturity was measured by lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) in amniotic fluid and by clinical development of respiratory distress syndrome (RDS) in the neonates. Fifty normotensive healthy primigravidae, who were matched for age and period of gestation, served as control. No difference (p > 0.05) in the placental grading was observed between normotensive and hypertensive pregnancies. The advancement of placental grade was found to be associated with an increase in L/S ratio and PG level in amniotic fluid. A mature placental grade (grade III) identified by real-time sonography corresponded to foetal lung maturity (L/S > or = 2.0, PG > or = 0.36 mg/dl) and absence of RDS in all cases. Hence, in PIH a grade III placenta appeared to be a reliable predictor of foetal lung maturity in the population examined.

Amniotic Fluid↗
PubMed1995

Effect of Ca(2+)-channel blockers, Ca(2+)-ionophore and increased pyrene excimer formation on the microsomal glucose-6-phosphatase.

The dependence of microsomal glucose-6-phosphatase (G-6-Pase) activity on Ca2+ as well as the membrane lipid microviscosity was studied by the effect of Ca(2+)-channel blockers (namely verapamil and nifedipine), Ca(2+)-ionophore, A23187 and pyrene excimer formation. Channel blockers depressed the G-6-Pase and Ca(2+)-ATPase while the ionophore increased these activities. Dimethyl sulfoxide, a known membrane surface active agent showed no change. Ca(2+)-uptake into the membrane has expectedly been lowered by the channel blockers while the ionophores facilitated the ion flux. Excimer formation of the fluorescent probe, pyrene as an indicator of increased membrane fluidity, and microviscosity calculated from there on, showed that Ca(2+)- and lipid microenvironment in the membrane significantly influenced the activity of G-6-Pase. Membrane lipid composition such as phospholipid/cholesterol molar ratio which also indicates an increased membrane fluidity is markedly increased with the ionophore but decreased with the channel blockers, while protein/phospholipid ratio remained unchanged. Microsomal G-6-Pase is a multicomponent multifunctional protein. It is argued that Ca2+ may play the role of an obligatory cofactor not only for the hydrolysis of G-6-P (catalytic part of the enzyme) but also involved in the regulation of substrate and product transport in or out of the endoplasmic reticulum lumen.

Animals↗
PubMed1994

Bovine parainfluenza-3 virus selectively depletes a calcium-independent, phospholipid-dependent protein kinase C and inhibits superoxide anion generation in bovine alveolar macrophages.

Bovine parainfluenza-3 (PI-3) virus inhibits oxygen-dependent bacterial killing by phagocytes, a key pulmonary defense, thus predisposing the host to intrapulmonary bacterial superinfection. PI-3 virus inhibited opsonized zymosan or PMA-activated superoxide anion (O2-) generation in bovine alveolar macrophages. The respiratory virus influenza also inhibits O2- generation by phagocytes, however, the mechanisms(s) of viral inhibition differs from PI-3. PI-3 did not trigger O2- generation before inhibition, whereas influenza triggered O2- generation before desensitization of ligand-initiated respiratory burst. PI-3 modified the twin signals of calcium and protein kinase C in alveolar macrophages. PI-3 infection increased macrophage membrane permeability to extracellular calcium, but did not inhibit calcium mobilization triggered by opsonized zymosan. These effects further distinguish bovine PI-3 from human influenza, which triggers mobilization of cell-associated calcium and inhibits calcium mobilization activated by physiologic ligands. Macrophages possessed two classes of PKC activity, a calcium/phosphatidylserine/diglyceride (Ca/PS/DG))-dependent activity and a Ca-independent, PS/DG-dependent histone IIIS phosphorylating activity. PI-3 infection selectively depleted the Ca-independent, PS/DG-dependent kinase activity but not the classical Ca/PS/DG-dependent activity. Inhibition of Ca-independent, PS/DG-dependent kinase activity and inhibition of O2- generation by PI-3 occurred at a similar viral dose and time frame, suggesting a role for this kinase in activating the respiratory burst. Inhibition of the oxygen-dependent bactericidal function of alveolar macrophages and disturbances in signal transduction may contribute to the immunosuppression and bacterial superinfection accompanying viral respiratory disease.

Animals↗