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Biomedical subjects

B Chowdhury

Publications and source records attributed to B Chowdhury.

13 recordsLinked to original sources
PubMed1997

Isolation and properties of an ATP transporter from a strain of Aspergillus niger.

A purified ATP transporter from Aspergillus niger did not show release or uptake for any of the nucleotides (ADP or UTP) except ATP. The release and uptake did not result from non-specific binding, but appeared to be concentration-dependent processes. ATP was shown by a double-isotopic technique to be transported across membrane vesicles without degradation. The ATP-transport protein was purified to near homogeneity from the membrane vesicles of a strain of A. niger and its apparent Mr was approximately 60000. The purified protein showed the properties of a membrane-bound protein in that the carrier protein was shown, during the liposome-preparative process, to translocate from the aqueous phase into the lipid bilayer of the liposome, unlike the cytosolic protein glucose-6-phosphate dehydrogenase, which remained confined to the aqueous compartment. Mycobacillin, a lipid-reactive antibiotic, was bound to the transport protein at a site other than the ATP-binding site, leading to its enhanced release or uptake, which was very feeble in absence of the antibiotic.

Adenosine Triphosphate↗
PubMed1996

Computed tomography-determined body composition in relation to cardiovascular risk factors in Indian and matched Swedish males.

Relationships between cardiovascular risk factors, body composition, and tissue distributions were examined in 10 Indian and 10 Swedish males matched by age, height, and weight. The body was divided into 29 compartments by means of a multiscan computed tomography (CT) technique. Fasting glucose, insulin, and triglycerides (TG) were higher in Indians than in Swedes. During the oral glucose tolerance test (OGTT), the glucose area was similar in both groups, whereas the insulin area was 80% larger in Indians. Adipose tissue (AT) and skin volumes were larger and remaining lean tissues were smaller in Indians. Indians had proportionally less muscle and more skeleton in the legs, but no ethnic difference could be demonstrated with respect to AT distribution. The visceral AT to total AT volume ratio was positively related to insulin and TG, and with higher risk factors for Indians at any given ratio. TG and glucose were negatively related to the leg muscle to total muscle volume ratio, and this ratio was smaller in Indians. It is concluded that the metabolic disturbances of Indians are not necessarily dependent on a preponderance of visceral AT, and also that an upper-body muscle distribution-recognized as a new phenotypic companion to the metabolic syndrome-is statistically related to cardiovascular risk factors.

Adipose Tissue↗
PubMed1994

Post-mortem limitations of body composition analysis by computed tomography.

Few of the indirect methods for measuring body composition have every been validated against direct human cadaver evidence. Computed tomography (CT), like NMR, has proved to be an important diagnostic tool and they appear to be the techniques of the future for body composition studies. The purpose of the present study (Cadaver Analysis Study III), undertaken at the Vrije Universiteit Brussel in a joint venture with the University of Göteborg, Sweden, was to validate tomographic measurements of volumes and areas from different tissues using data from CT-scanning of unembalmed deep-frozen cadavers and data collected by dissection of the same cadavers. Six Belgian adults were extensively measured and dissected. The body was divided into several slices for comparison of the CT image with photography of the same slice and comparison of tissue-volumes per segment for the whole body. Due to post-mortem changes and the frozen state of the cadavers, the CT measurements were greatly affected by artefacts disturbing adipose tissue (AT) and muscle area determinations. Only the bone area measurements were similar between the two techniques. However, when the volumes (per segment) of the same tissues were considered, no apparent difference was found between CT and dissection data for the muscle volume.

Aged↗
PubMed1994

A multicompartment body composition technique based on computerized tomography.

The objective of this study was to develop a body composition method based on computerized tomography (CT) which would make it possible to divide the body into multiple compartments at the tissue and organ level. Eight healthy males (21-42 years old) with BMIs ranging from 18.6 to 25.3 kg/m2 were used for the methodological development. Areas of tissues, organs and air/gas were measured in 28 cross-sectional scans having defined and identical positions in all examined subjects. The area determinations were performed with the following attenuation intervals (given in Hounsfield units, HU): air, gas and lungs: -1001 to -191 HU; adipose tissue (AT): -190 to -30 HU; all other soft tissues and organs: -29 to +151 HU; skeleton: 152 to 2500 HU. Various tissue and organ areas in the -29 to +151 HU interval were obtained by means of cursor circumscriptions, while area determinations in other intervals were based on the number of pixels fulfilling given attenuation criteria. Volumes of tissues, organs and gas were obtained from corresponding areas and the distances between the scans. The body was divided into 12 main volumes of tissues, organs and gas that could be further subdivided by region. The main volumes observed (in litres; mean +/- s.d.) were: skeleton (subdivisible into dense skeleton, red and yellow bone marrow): 8.7 +/- 0.9; skeletal muscle: 31.9 +/- 5.1; visceral AT (subdivisible into intra- and retroperitoneal, cardiac, other thoracic AT): 3.0 +/- 1.7; intra- and retroperitoneal organs other than AT: 4.6 +/- 0.8; gastrointestinal gas: 0.25 +/- 0.09; heart: 0.61 +/- 0.12; lungs and bronchial air: 5.1 +/- 1.1; other thoracic organs: 0.32 +/- 0.08; mammary glands: 0.001 +/- 0.004; CNS (subdivisible into brain and contents of spinal channel): 1.6 +/- 0.15; air in sinuses and trachea: 0.19 +/- 0.05; subcutaneous AT: 11.6 +/- 2.8; skin: 2.4 +/- 0.39. Precision errors as determined from double analyses of different tissue volumes ranged from 0.01 to 0.3 litres. For validation purposes, CT-estimated organ weights were obtained by multiplying organ volumes by their assumed densities. The sums of all organ weights were then compared with the measured body weights. The error calculated from the individual differences between these weights was 0.6 kg (0.85%). The multicompartmentation technique described has a high validity and reproducibility and is applicable over a wide range of medical fields which require body composition measurements at the tissue and organ level.

Abdomen↗
PubMed1993

CT-determined changes in adipose tissue distribution during a small weight reduction in obese males.

Nine obese males of Scandinavian origin were examined with a multiscan (n = 22) computerized tomography (CT) technique before and after a small weight reduction (4.4 kg). The total adipose tissue (AT) volume was reduced by 2.6 litres. Expressed as a percentage of initial depot volume, there were significant reductions (P < 0.02) in the AT depots of viscera (9.6%), upper limbs (7.0%), subcutaneous trunk (6.0%) and lower limbs (4.9%), while the AT of head and neck (1.9%) did not decrease significantly (P = 0.08). These results indicated a changed fat patterning and evidence for this was obtained by expressing the AT volume of each depot as a percentage of the total AT volume both before and after the weight reduction. Visceral AT constituted 21.7% of the total AT before and 20.9% after weight reduction. Thus, the fraction of AT in viscera was changed by -0.8 +/- 0.9% units which was significantly different from the change in leg AT (+0.5 +/- 1.1% units) (P < 0.02) and tended to be different from the change of subcutaneous AT (+0.2 +/- 1.0% units) (P < 0.07). Thus, the AT distribution was changed in a favourable direction by weight reduction. Changes in visceral/total AT area ratios of different trunk scans were not consistent and, in a stricter sense, fat patterning cannot be studied with area determinations since AT areas cannot be expressed as fractions of the total AT volume.

Adipose Tissue↗
PubMed1992

The morphology and metabolism of intraabdominal adipose tissue in men.

Mass, morphology, and metabolism of total adipose tissue and its subcutaneous, visceral, and retroperitoneal subcompartments were examined in 16 men with a wide variation of total body fat. Computerized tomography (CT) scans showed that the intraabdominal fat mass comprised approximately 20% of total fat mass. Visceral and retroperitoneal fat masses were approximately 80% and 20% of total intraabdominal fat mass, respectively. Enlargement of intraabdominal fat depots was due to a parallel adipocyte enlargement only. Direct significant correlations were found between these adipose tissue masses and blood glucose and plasma insulin levels, blood pressure, and liver function tests, while glucose disposal rate during euglycemic glucose clamp measurements at submaximal insulin concentrations (GDR), plasma testosterone, and sex hormone-binding globulin concentrations correlated negatively. The correlations for glucose, insulin, and GDR were strongest with visceral fat mass. Adipose tissue lipid uptake, measured after oral administration of labeled oleic acid in triglyceride, was approximately 50% higher in omental than in subcutaneous adipose tissues. Adipocytes from omental fat also showed a higher lipolytic sensitivity and responsiveness to catecholamines. Furthermore, these adipocytes were less sensitive to the antilipolytic effects of insulin. Both lipid uptake and lipolytic sensitivity and responsiveness showed strong correlations (r = 0.8 to 0.9) to blood glucose and plasma insulin concentrations and also to the GDR (negative), while no such correlations were found with lipid uptake in subcutaneous or retroperitoneal abdominal adipose tissues. Taken together, these results suggest a higher turnover of lipids in visceral than in the other fat depots, which is closely correlated to systemic insulin resistance and glucose metabolism in men.

Abdomen↗
PubMed1988

Total and visceral adipose-tissue volumes derived from measurements with computed tomography in adult men and women: predictive equations.

Total and visceral adipose-tissue (AT) volumes were determined by computed tomography (CT) by a multiscan technique in 17 men and 10 women with a wide range of body weights. In these primary materials, weight, height, and various diameters, circumferences, and subcutaneous AT thicknesses of the trunk were examined for their relationships to CT-determined total and visceral AT volumes. Predictive AT equations from the primary materials were then tested on two cross-validation groups consisting of another 7 men and 9 women. For the prediction of the total AT volume, weight/height was the superior single predictor, with errors less than 11% in primary and cross-validation materials. For the prediction of visceral AT volume, simple equations based entirely on the sagittal diameter of the trunk at the L3-L5 level resulted in errors less than 21% in both sexes.

Adipose Tissue↗
PubMed1988

Adipose tissue volume determination in males by computed tomography and 40K.

Seventeen healthy male volunteers with weights ranging from 54 to 145 kg were examined with a Philips Tomoscan 310. The upper attenuation limit of adipose tissue was determined to be -30 HU. The lower attenuation limit was set to -190 HU. Regional and total adipose tissue volumes were calculated from the adipose tissue areas of 22 scans and from the distances between these scans. Three different mathematical formulas were used, which all gave similar results. The adipose tissue area of several trunk scans, as well as the elbow, showed very high correlations (r greater than 0.96) versus the volume determinations based on 22 scans. The visceral adipose tissue area of scan L2-L3 showed a higher correlation (r = 0.986) than any other single scan versus the visceral adipose tissue volume. Total adipose tissue volume determinations with ten selected scans correlated very closely with the results obtained from 22 scans (r = 0.997). The adipose tissue volume of the head and neck region was 1.9 +/- 1.0 per cent of the total volume. Corresponding figures for other regions were: arms 6.8 +/- 1.0 per cent, legs 29.0 +/- 7.3 per cent, subcutaneous part of the trunk 41.4 +/- 7.4 per cent and the visceral region 20.9 +/- 7.0 per cent. With greater total adipose tissue volumes the percentage of the subcutaneous adipose tissue of the trunk increased (r = 0.686; P less than 0.005). There was a very strong negative relationship between the fractional amount of adipose tissue in the legs and in the trunk (r = 0.993, P less than 0.001). The potassium contents of fat-free mass and lean body mass were deduced to be 64.7 and 71.0 mmol/kg, respectively. These calculations were based on adipose tissue volume determinations by computed tomography, on 40K measurements and on the assumption that the volume proportions of fat, water and protein in adipose tissue were 85:13.7:1.3. By using computed tomography (CT) as a standard an optimal weight (W) for height (H) index was constructed by using an iterative correlation technique. The optimal index, i.e. highest correlation and lowest error versus ATCT was found for W/H0.9.

Adipose Tissue↗