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Biomedical subjects

S Bose

Publications and source records attributed to S Bose.

At least 109 records · Page 6Linked to original sources
PubMed1996

Involvement of mercury in platelet aggregation--probable mechanism of action.

Both in vivo and in vitro Hg2+ caused dose dependent inhibition of rat platelet aggregation. However, as low a dose as 88.8 pM Hg2+ could initiate ADP-induced aggregation even in the absence of added calcium. The action of Hg2+ was found to be unaffected by antagonists such as cAMP and theophylline either alone or in combination. Hg2+ induced platelet aggregation was inhibited completely by pre-incubation with aspirin (1 mmol.L-1), but it was ineffective when added after Hg2+. The results also indicate that the normal platelet function is affected by both high and low concentrations of Hg2+.

Adenosine Diphosphate↗
PubMed1996

Basopenia as an indicator of ovulation (a short term clinical study).

In the present study 60 cases age ranging from 18-40 years were studied for variation in the absolute basophil count on the different days of menstrual cycle. At the time of ovulation a statistically significant decrease in the number of basophil count was noted. The decrease in the number of basophil at mid cycle coincided with the irregular follicle seen by sonography, which indicated ovulation. The basophil count then increased during the luteal phase. Basopenia at the time of ovulation was probably due to migration of these cells from the peripheral blood towards the rupturing follicle for the release of histamine required for ovulation.

Adolescent↗
PubMed1995

The classification of anatomic- and symptom-based low back disorders using motion measure models.

STUDY DESIGN: This study observed the trunk angular motion features of healthy subjects and those experiencing chronic low back disorders as they flexed and extended their trunks in five symmetric and asymmetric planes of motion. Trunk angular position, velocity, and acceleration were evaluated during several cycles of motion. OBJECTIVE: The trunk angular motion features of the low back disorder group were normalized relative to the healthy subjects and used to 1) evaluate the repeatability and reliability of trunk motion as a measure of trunk musculoskeletal status, 2) quantify the extent of the disorder, 3) determine the extent to which trunk motion measures might be used as quantifiable means to help classify low back disorders. SUMMARY OF BACKGROUND DATA: Given the magnitude of the low back disorder problem, it is problematic that there are few quantitative methods for objectively documenting the extent of a disorder. Impairment ratings of low back disorders can vary by as much as 70% using current systems. Diagnoses and classification schemes are rarely based upon quantitative indicators and we are unable to easily assess and diagnose low back disorders. It is important to quantitatively evaluate low back disorders so that proper treatment can be administered and the risk of exacerbating the problem can be minimized. METHODS: Three-hundred-thirty-nine men and women between 20 and 70 years old who had not experienced significant back pain were recruited as the healthy subjects in this study. One hundred-seventy-one patients with various chronic low back disorders also were recruited and compared with the healthy group of subjects. All subjects wore a triaxial goniometer on their trunks that documented the angular position, velocity, and acceleration of the trunk as the subjects flexed and extended their trunks in each of five planes of motion. Trunk motion features first were normalized for subject gender and age. Several two-stage eight-variable models that account for trunk motion interactions were developed to classify the 510 healthy and low back injured subjects into one of 10 anatomic and symptom-based low back disorder classification categories. RESULTS: Using conservative cross-validation measures, it was found that the stage one eight-variable model could correctly classify more than 94% of the subjects as either healthy or having a low back disorder. One of the stage two eight-variable models was able to reasonably classify the patients with low back disorders into one of 10 low back disorder classification groups. CONCLUSION: The motion-related parameters may relate to biomechanical or learned sensitivities to spinal loading. This study suggests that higher-order trunk motion characteristics hold great promise as a quantitative indicator of the trunk's musculoskeletal status and may be used as a measure of the extent of a disorder and as a measure of rehabilitative progress. Furthermore, once the interactive nature of these trunk motion characteristics is considered, the model could help diagnose low back disorders. However, independent data sets are needed to validate these findings.

Adult↗
PubMed1995

Regulation of expression of transcobalamin II receptor in the rat.

Surface and intracellular membrane distribution and hormonal regulation of transcobalamin II receptor (TC II-R) activity and protein levels have been studied in an effort to understand its regulation of expression in the rat. TC II-R activity and the levels of the 62 kDa monomeric and 124 kDa dimeric forms of TC II-R were highest in the rat kidney and intestine, and in these tissues the receptor expression was not dependent upon the postnatal development of the rat. TC II-R expression was uniform in the various regions of the gut. Surface membrane distribution of TC II-R in the kidney revealed the expression of the 124 kDa dimer form of TC II-R in the apical and basolateral membranes in the ratio of 1:10. Further subcellular distribution of TC II-R in the kidney revealed the expression of the 124 kDa dimer in the intermicrovillar clefts and clathrin-coated vesicles and the 62 kDa monomer in the microsomes. Neither the monomer nor the dimer could be detected in the early endosomes or lysosomes. Membrane TC II-R activity and TC II-R protein levels and cobalamin (Cbl; vitamin B12) transport in vivo were inhibited by about 90% in adrenalectomized rats and all three returned to normal levels by oral treatment of these animals with cortisone acetate. In contrast, thyroidectomy or experimentally induced diabetes had no effect on TC II-R activity or Cbl transport. Based on these observations, we suggest that TC II-R expression is not developmentally or regionally regulated in rat renal and intestinal membranes and its expression in the kidney is asymmetrically distributed between the apical (10%) and basolateral (90%) membranes. In addition, our results also show that the dimerization of TC II-R is a post-microsomal event and that the expression of TC II-R and plasma Cbl transport is regulated by cortisone.

Adrenalectomy↗
PubMed1995

The ability of actinic light to modify the bacteriorhodopsin photocycle. Heterogeneity and/or photocooperativity?

The focus of this paper is on the established observation that the bacteriorhodopsin (BR) photocycle responds to the level of actinic light by altering the proportions of two forms of the M intermediate. The first form of M, called M-fast or MF, decays to the O intermediate. In contrast, the second form of M, called M-slow or MS, decays directly to the ground state, and its decay rate is slower than that of MF. Any proposed scheme for the BR photocycle must account for this light-dependent phenomenon. Several papers have attempted to explain the observation on the basis of photocooperativity, or on the basis of heterogeneous populations. In this paper, we test previously proposed cooperative models with experimental data, and find those models to be inadequate. We show that two new models, one purely cooperative, the other purely heterogeneous, can both fit the data, hence such modelling will not resolve the mechanism. Taking into account the demonstration of heterogeneity, the trimer structure of BR, and certain experimental evidence in favor of cooperativity, it appears likely that both heterogeneity and cooperativity are involved in the adaptation of the BR photocycle to different levels of actinic light.

Bacteriorhodopsins↗
PubMed1995

Membrane expression and interactions of human transcobalamin II receptor.

Antiserum raised to purified 62-kDa human placental transcobalamin II receptor (TC II-R) has been used to study its synthesis and membrane expression. The antiserum immunoprecipitated a 45-kDa protein from the cell-free translation using human kidney mRNA and recognized a single 124-kDa band on immunoblotting of placental and other human tissue membranes, and quantitation of the blots revealed high levels of TC II-R expression in the human kidney followed by placenta, intestine, and liver. Triton X-100 extraction of placental membranes resulted in the complete (100%) solubilization of the receptor, and immunoblotting of the Triton X-100-soluble fraction revealed a single band of 62 kDa. Lipid extraction of placental membranes with a mixture of chloroformmethanol (2:1) followed by immunoblotting revealed a single band of molecular mass 62 kDa. The molecular mass of the pure Triton X-100-bound receptor increased on SDS-polyacrylamide gel electrophoresis from 62 to 124 kDa upon its insertion in liposomes prepared using egg phosphatidylcholine and cholesterol. Chemical cross-linking of native membrane-or lipid vesicle-bound TC II-R or detergent-soluble extracts of the membrane with 125I-TC II-cobalamin revealed that both the 124- and 62-kDa forms of the receptor were active in ligand binding. Based on these results we suggest that TC II-R is synthesized as a single polypeptide of 45 kDa, and following its maturation (involving N- and O-glycosylation) the 62-kDa mature receptor is expressed in plasma membranes as a noncovalent dimer of 124 kDa. The dimerization of TC II-R in the plasma membranes is due to its interactions with annular lipids.

Biopolymers↗
PubMed1995

Nimodipine, a centrally active calcium antagonist, exerts a beneficial effect on contrast sensitivity in patients with normal-tension glaucoma and in control subjects.

BACKGROUND/PURPOSE: The use of calcium antagonists in patients with normal-tension glaucoma (NTG) currently is under investigation. The aim of this study is to evaluate the effect of an acute dose of oral nimodipine, a centrally active calcium antagonist, on spatial contrast sensitivity in patients with NTG and in age-matched control subjects. METHODS: Spatial contrast sensitivity was measured using the Pelli-Robson and the Vistech 6000 charts in 14 patients with NTG and in 17 control subjects. Testing was performed at baseline and at two subsequent sessions. Measurements were recorded 2 hours after oral administration of either nimodipine or placebo in a randomized, double-masked manner. Data were analyzed using unpaired, two-tailed Student's t test for between-group comparisons and repeated measures analysis of variance for within-group comparisons. RESULTS: Using the Pelli-Robson charts, baseline contrast sensitivity was significantly lower in patients with NTG compared with control subjects (P < 0.05, unpaired Student's t test). There was a significant increase in log contrast sensitivity after administration of nimodipine compared with baseline and placebo in patients with NTG (baseline, 1.39 +/- 0.38; placebo, 1.41 +/- 0.40; nimodipine, 1.51 +/- 0.39) and in control subjects (baseline, 1.62 +/- 0.11; placebo, 1.64 +/- 0.10; nimodipine, 1.81 +/- 0.14) (P < 0.05, repeated measures analysis of variance). A similar trend was observed using the Vistech charts. CONCLUSION: These results suggest that central visual function as measured by Pelli-Robson and Vistech contrast sensitivity is impaired in eyes with NTG. An acute, oral administration of nimodipine, a calcium antagonist, improved contrast sensitivity in patients with NTG and in control subjects. The mechanism of this improvement is not fully understood. Further studies are needed to evaluate the effect of long-term administration in glaucoma.

Aged↗
PubMed1995

Neuro-ophthalmologic presentations of functional visual disorders.

Functional or nonorganic visual loss is a common problem that requires an active diagnosis. A complete neuro-ophthalmologic examination of the afferent and efferent visual system is essential to eliminate the possibility of organic causes of visual loss. With a sound knowledge of the anatomic, physiologic, and optical basis of the tests used to evaluate the visual pathway, the physician can detect the inconsistencies in visual performance that secure the diagnosis. The majority of patients will resolve their symptoms with time and reassurance.

Adult↗
PubMed1995

Biomonitoring of anticholinesterase pesticides in the soil: usefulness of soil Collembola.

The impact of Methyl parathion and Carbaryl was evaluated on an ecologically important soil Collembola, Cyphoderus sp. Enzyme characteristics demonstrate substrate optimum at 1 10(-2) mol/L temperature optimum at 30 degrees C with a pH requirement of 8.0. In vivo inhibition of whole body AChE reveals higher degree of inhibition by LD50 dose of Methyl parathion as compared to that of Carbaryl where maximum inhibition was noticed at the agricultural dose.

Acetylcholinesterase↗
PubMed1994

Membrane-mediated control of the bacteriorhodopsin photocycle.

The ability of actinic light to modify the proportion of fast and slow forms of the M intermediate (i.e., Mf and M(s)) in the bacteriorhodopsin (BR) photocycle is lost by exposure of the purple membrane (PM) to 0.05% Triton for 1-2 min. The decay path of Mf through the O intermediate is also lost, and new, much slower kinetic forms of M appear. In this brief exposure, the trimer structure for BR, as measured by circular dichroism (CD) exciton coupling and sedimentability, is unaffected. The optical properties of the treated PM are affected within seconds of exposure to the detergent as indicated by an increase in transmittance and a blue shift in the wavelength of maximum absorbance for the ground state. Different concentrations of Triton cause reproducibly different changes in the kinetics of the system. These observations support the view that the BR trimer-membrane interaction is important in controlling the BR photocycle.

Bacteriorhodopsins↗
PubMed1994

Peptidyl prolyl cis-trans-isomerase activity associated with the lumen of the endoplasmic reticulum.

Peptidyl prolyl cis-trans-isomerase (PPI) activity was detected in microsomal fractions from bovine and rat liver. Extensive washing, proteinase and sonication treatments indicated that although some of this activity was due to adsorbed cytosolic enzymes, there was also an active but latent microsomal PPI activity. Density-gradient subfractionation indicated that activity was associated with vesicles derived from both the rough and the smooth endoplasmic reticulum (ER), suggesting that the activity was located within the ER lumen. The luminal PPI activity was inhibited by cyclosporin A and was active towards an unfolded protein substrate as well as towards the standard peptide substrate.

Amino Acid Isomerases↗
PubMed1994

The characterization of a cyclophilin-type peptidyl prolyl cis-trans-isomerase from the endoplasmic-reticulum lumen.

A luminally located peptidyl prolyl cis-trans-isomerase (PPI) has been purified from bovine liver microsomes. It has a molecular mass of 20.6 kDa, and N-terminal sequencing demonstrates strong sequence similarity to the sequences of the cyclophilin B family. The enzyme catalyses the isomerization of the standard proline-containing peptide N-succinyl-Ala-Ala-Pro-Phe p-nitroanilide, as well as the refolding of RNAase T1. Kinetic properties, substrate-specificity data and inhibition by cyclosporin A indicate that it is a cyclophilin-type PPI, consistent with the amino-acid-sequence results.

Amino Acid Isomerases↗
PubMed1994

Influence of excitation energy on the bacteriorhodopsin photocycle.

Kinetic curves for the bacteriorhodopsin (BR) photocycle were obtained both at 570 and at 412 nm at a series of increasing levels of intensity of the exciting laser. Singular value decomposition (SVD) of these curves showed two transitions in the kinetic profiles that occurred at specific levels of actinic light. This means that the photocycle was influenced by photon density in two ways. In a separate application of SVD, time-resolved optical spectra were analyzed at each of many levels of exciting laser intensities. The studies showed that the transition at the low level of laser intensity was due principally to an increase in the amount of BR that was turning over. The transition at the higher level of laser intensity showed a fundamental change in kinetics of the photocycle. At low intensity levels, the fast form of M (Mf) predominated, whereas at high levels the slow form of M (Ms) predominated. A distinction was found between Mf and Ms, in that the former decayed directly to the O intermediate whereas the latter decayed directly to BR.

Bacteriorhodopsins↗
PubMed1994

Modulation of ochratoxin-produced genotoxicity in mice by vitamin C.

Ochratoxin A (OA), when administered orally daily for 45 days to albino Swiss mice, Mus musculus, at a level equivalent to the human dietary concentration of 1 microgram/kg body weight/day, increased the production of abnormalities in both mitotic and meiotic chromosomes as well as in the gross morphology of the sperm head. The sperm count per unit volume of caput epididymal suspension also decreased. Vitamin C at a concentration equivalent to the human therapeutic dose (10 mg/kg body weight/day), when administered orally concurrently with OA, significantly minimized the incidence of these abnormalities. The protective effect of vitamin C was most marked in mitotic chromosomes followed by that in meiotic chromosomes and sperm head morphology; the improvement in sperm count was least marked. The possible mechanism of this effect is discussed.

Administration, Oral↗
PubMed1994

Abnormal endocervical cells. Really abnormal? Really endocervical?

With the increasing incidence of endocervical adenocarcinoma, cytopathologists must distinguish between benign dysplastic and malignant endocervical cells. For this reason, the authors began a retrospective review of 44 cytology specimens initially interpreted as "abnormal endocervical cells of uncertain significance" and of 10 endocervical carcinomas. Cytologic specimens were categorized according to tissue into three groups: reactive cells (9), abnormalities associated with squamous intraepithelial lesions (17 low grade, 18 high grade), and adenocarcinoma (10). Reactive cells were monolayered, with demarcated cytoplasm and bland nuclei. Abnormal cells from squamous intraepithelial lesions showed crowding and irregular nuclei with smudgy or granular chromatin. Cells from adenocarcinoma showed multilayering and nuclei with clumped chromatin and occasional mitoses. On reexamination, numerous cells were found to be of metaplastic rather than endocervical origin. Surprisingly, the presence of abnormal metaplastic or endocervical cells sometimes was the only indicator of associated squamous intraepithelial lesion.

Adenocarcinoma↗