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Biomedical subjects

S Bose

Publications and source records attributed to S Bose.

At least 19 recordsLinked to original sources
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

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↗
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

Recovery from pre-operative sedation with clonidine--brain stem auditory evoked response.

In a randomised double-blind study, 34 elderly patients (ASA grades 1-2) underwent elective intra-ocular surgery. Patients were allocated randomly to two groups to receive oral clonidine 300 micrograms or oral diazepam 10 mg 2 h before surgery. Facial block and retrobulbar block were given at 2 h after premedication. Anaesthetic recovery was assessed using a clinical recovery score (at 0, 30, 60 and 120 min after arrival in the recovery room) and brain stem auditory evoked potential responses (BAER) (immediately after operation and at 120 min after operation). In both the groups the clinical recovery scores decreased significantly at 30 and 60 min following recovery (p < 0.01). At 120 min this score returned to the pre-operative value in the clonidine group, but in the diazepam group there was a significant difference between the 2h value and pre-operative value (p < 0.05). In the clonidine group there was no significant rise in the interpeak latencies and absolute peak latencies of brain stem auditory evoked responses recorded immediately after operation and 120 min after operation. In the diazepam group, there was a significant rise in the interpeak latencies immediately after operation and 120 min after operation and a rise in absolute peak latencies (p < 0.05) immediately after operation. In the clonidine group there was a reduction (p < 0.05) in amplitude of wave V at immediately after operation. We conclude that clonidine 300 micrograms orally before surgery does not delay recovery.

Aged↗
PubMed1994

Correlation of metal distribution, reduced glutathione and metallothionein levels in liver and kidney of rat.

Effect of group IIB metals on the endogenous status of metallothionein (MT) and reduced glutathione (GSH) was studied in two vital detoxifying organs namely, liver and kidney of rat. The metals were administered at non lethal levels (1/10 LD50) which were found to cause no death. Zinc showed accumulation in both liver and kidney, cadmium preferentially in the liver while mercury in the kidney. Hepatic MT content was increased by 18-fold, 15-fold and 2-fold by cadmium, zinc and mercury respectively while renal MT was increased maximally by zinc. Among the metals, mercury caused highest depletion of hepatic GSH level (51%). The renal GSH showed differential response to the metal treatment, the level increasing slightly by cadmium and depleting significantly by zinc and mercury. A positive correlation was found between group IIB metal accumulation and the manifestation of toxic response.

Animals↗
PubMed1994

Induction of metallothionein in rat liver by cadmium chloride: probable mechanism of action.

The mechanism of action of cadmium in the inductive pathway of metallothionein (MT) synthesis was studied in the rat. Cadmium significantly elevated the MT level by 872% which was antagonised by coadministration of either verapamil (343.5%) or ionophore (570%). The Ca-dependent biomolecules such as cyclic AMP or calmodulin remained depressed in all treatment regimens except calmodulin in the ionophore treated rat. Total Ca2+ showed no increase in its profile except in the ionophore treatments either alone or with CdCl2. The Na+ profile is, however, significantly elevated in all cases except the ionophore treated rat. The present study clearly indicates that (a) Ca2+ has no first messenger role in the schematic events leading to MT synthesis and (b) Na+ may be regarded as a possible candidate in the molecular events of Cd-induced MT synthesis.

Animals↗
PubMed1994

Psychologic adjustment of human immunodeficiency virus-infected school-age children.

We investigated the psychosocial adjustment of school-aged, human immunodeficiency virus-positive children and factors associated with level of adjustment. Participants were primarily transfusion-infected children living in middle-class families. We administered measures of depression, anxiety, and self-concept to children, and measures of behavior problems, social functioning, personality characteristics, and life events to parents. An index of disease stage was also collected. Children reported experiencing low levels of depressive and anxious affect and generally felt positively about themselves. By contrast, parents saw their children as more anxious and less socially active than respective standardization samples. A greater than expected proportion of these children, as reported by their parents, scored in the maladaptive range on measures of social functioning, anxiety, and conduct problems. Experience of adversive life events and progression of the disease were associated with more behavioral and social problems. Findings are discussed in terms of their generalizability and implications for future research.

Adaptation, Psychological↗
PubMed1994

Effect of variable low doses of aspirin on platelet functions.

The effect of chronic administration of variable low doses of Aspirin was studied on platelet adhesiveness, platelet count, bleeding time and clotting time to find out as to how low the dose of aspirin needs to be in order to have an effective antiplatelet effect in patients who require such therapy. A statistically significant reduction in the platelet adhesiveness was observed in all the groups, but the best effect was exhibited by 50 mgm of aspirin dose. Bleeding time was also increased in all the groups but statistically significant difference was observed with 50, 75 and 100 mgm doses. There was no change in platelet count and clotting time.

Adolescent↗
PubMed1993

Distribution kinetics of inorganic mercury in the subcellular fractions of fish liver.

The present study tries to find out the kinetics of distribution of mercury in the different subcellular fractions of the liver in a freshwater perch Anabas testudineus over a period of 48 h after a single i.m. injection of [203Hg]mercuric nitrate at a dose of 4 mg/kg body weight. The fish were killed at 15 min, 2 h, 6 h and 48 h post injection. In addition the interaction of this metal with different biomolecules, viz., protein, DNA and RNA, was also investigated. Cytosol was found to be the major site of mercury accumulation. Moderate amounts of accumulation occurred in the nuclear, mitochondrial and microsomal fractions, although varying with time, while the lysosomal fraction did not reveal any spectacular retention of mercury. A significant increase in the protein content of nuclear, mitochondrial, lysosomal and cytosolic fractions was also noticed at different time periods of mercury injection. In the nuclear, microsomal and cytosolic proteins, mercury binding increased more significantly over time than the mitochondrial and lysosomal proteins. A biphasic binding pattern of mercury was seen in nuclear and mitochondrial DNA and mitochondrial and cytosolic RNA.

Animals↗
PubMed1993

Time dependent distribution of [203Hg] mercuric nitrate in the subcellular fractions of rat and fish liver.

Cytotoxicity of inorganic mercury to the liver of two species, Anabas testudineus and Sprague Dawley male rat was evaluated. Distribution kinetics of this metal in the different hepatic subcellular fractions were followed for 48 h after a single injection of [203Hg] mercuric nitrate at a dose of 4mg/kg b.w. Interaction of this metal with protein, DNA and RNA was also studied. In rat, nuclear and lysosomal fractions showed a significant increase in the protein content, while in fish, the amount of protein increased in all fractions except microsome. Comparatively more mercury was bound to protein in fish during the later phase of treatment. Retention of mercury in nuclear DNA of rat gradually declined from 15 min to 48 h of treatment, while, mitochondrial DNA binding to mercury increased from 15 min to 2 h of post injection and then declined in the later phase of the experiment. Such a biphasic binding pattern of mercury was shown by both the nuclear and mitochondrial DNA of the fish. The nuclear RNA of rat and mitochondrial and cytosolic RNA of both test species also showed a biphasic pattern of mercury binding, however, with a higher rate of binding in fish at the later phase of the experiment. The present study thus highlights that (a) mercury follows a definite distribution pattern in the subcellular fractions of the liver in both animal species, (b) cytosol is the major site of mercury accumulation.

Animals↗