Biomedical subjects

R Bose

Publications and source records attributed to R Bose.

At least 55 records · Page 3Linked to original sources

PubMed1992

ATPase-inhibitor proteins of brown-adipose-tissue mitochondria from warm- and cold-acclimated rats.

1. A group of male Sprague-Dawley rats (5-6 weeks old) was cold-acclimated at 4 degrees C for 4 weeks. Warm-acclimated controls remained at 24 degrees C. Total protein content of brown adipose tissue (BAT) increased more than 3-fold and total uncoupling protein (UCP) content increased more than 6-fold upon cold-acclimation. The concentration of UCP in isolated BAT mitochondria almost doubled. 2. Specific ATPase activity of the non-thermogenic BAT mitochondria (from warm-acclimated controls) was low and increased about 6-fold on addition of 1 microM-Ca2+, which raised free Ca2+ levels (measured by Fura-2) in the incubation media from 1.32 +/- 0.28 microM (mean +/- S.E.M.) to 2.29 +/- 0.39 microM [at which the Ca(2+)-binding ATPase-inhibitor protein (CaBI) is inactivated]. Correspondingly, the specific ATP synthetase activity of the non-thermogenic BAT mitochondria was high and was decreased by 74% by addition of 1 microM-Ca2+. 3. In contrast, specific ATPase activity of thermogenic BAT mitochondria (from cold-acclimated rats) was 5 times that of the control group, and addition of Ca2+ had only a small stimulatory response. Correspondingly, the specific ATP synthetase activity of the thermogenic BAT mitochondria was low, and the decrease by Ca2+ was small, albeit significant. 4. Extracts of BAT mitochondria from both groups of animals contained significant amounts of the ATPase-inhibitor protein of Pullman and Monroy (PMI) as well as of CaBI, as shown by gel electrophoresis. Kinetic studies of inhibition of mitochondrial ATPase activity showed that PMI activity was unaltered in extracts from the thermogenic BAT mitochondria, whereas CaBI activity was slightly but significantly increased. 5. The presence of active ATPase-inhibitor proteins in BAT mitochondria was shown for the first time. We conclude that uncoupling of oxidative phosphorylation occurs in thermogenic BAT mitochondria, even in the presence of the ATPase-inhibitor proteins.

Adenosine Triphosphatases↗

PubMed1992

The Na+/Ca2+ exchanger regulates cytolysin/perforin-induced increases in intracellular Ca2+ and susceptibility to cytolysis.

The Ca2+ dependency of NK cell-mediated and cytolysin-mediated cytolysis may be related to increases in target cell intracellular Ca2+. In a previous study we hypothesized that the Na+/Ca2+ exchanger can act as a counter-lytic mechanism by regulating the damaging increases in intracellular free calcium ([Ca2+]i) produced by cytolysin. We found that conditions said to inhibit Ca2+ extrusion by Na+/Ca2+ exchange, namely low extracellular Na+ or the presence of certain amiloride analogs which block Na+/Ca2+ exchange, enhanced the cytolysin-mediated cytolysis of YAC-1 lymphoma cells. In the present work we have confirmed the above hypothesis by measuring the [Ca2+]i of fura-2- or aequorin-labeled YAC-1 cells treated with cytolysin and low Na+ medium or amiloride analogs. YAC-1 cells appear to have a Na+/Ca2+ exchange system: low Na+ medium caused gradual increases in [Ca2+]i, and this effect was reversed in Na(+)-replete medium. Cytolysin purified from NK cell granules caused rapid dose-dependent increases in [Ca2+]i, and low Na+ medium enhanced these cytolysin-mediated increases. The Na+/Ca2+ exchange system appeared to be more active in cytolysin-challenged cells: amiloride analogs, which inhibit Na+/Ca2+ exchange in other systems, acted synergistically with cytolysin to cause large increases in [Ca2+]i, but had little effect, if any, on their own. 5-(N-4-Chlorobenzyl)-2',4'-dimethylbenzamil, the amiloride analog which has the greatest specificity for the Na+/Ca2+ exchanger and which previously was found to be the most potent enhancer of cytolysin-mediated cytolysis, was the most potent enhancer of cytolysin-mediated increases in [Ca2+]i. The above results suggest that Na+/Ca2+ exchange may be one of the target cell mechanisms of resistance to cytolysin and NK cell-mediated cytolysis.

Amiloride↗

PubMed1992

Modulation of melphalan uptake in murine L5178Y lymphoblasts in vitro by changes in ionic environment.

The alkylating agent melphalan is actively transported in mammalian cells by two amino acid transport carriers: the sodium-dependent carrier with substrate preference for alanine-serine-cysteine (system ASC), and a sodium-independent carrier with preference for leucine (system L). The effect of altering the ionic environment of murine L5178Y lymphoblasts was investigated in order to determine not only the direct effects of hydrogen and calcium ions on these transport systems, but also the indirect effects of agents or modulators known to alter intracellular calcium. Melphalan transport followed a bell-shaped distribution curve over a pH range from 3 to 9 with a pH optimum of 4.3 and 4.6 for transport by systems ASC and L, respectively. Those agents that could cause a decrease in cytosolic calcium such as the calcium channel blockers verapamil, diltiazem and nitrendipine, the calcium chelator (ethyleneglycol-bis-(beta-aminoethylether) N,N,N',N'-tetraacetic acid (EGTA) and reduction of pH were found to augment melphalan uptake, whereas conditions that would elevate intracellular calcium such as the calcium ionophore A23187, the calcium channel agonist (-) Bay K 8644, elevation of extracellular calcium and the calcium pump inhibitor trifluoperazine were all found to decrease melphalan uptake. These findings suggest that modification of ionic environment directly or indirectly by agents known to alter intracellular calcium can modulate melphalan uptake.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMed1992

Pyridine and other coal tar constituents as inhibitors of potato polyphenol oxidase: a non-animal model for neurochemical studies.

Potato polyphenol oxidase activity was strongly and noncompetitively inhibited by the "Perov mixture" of coal tar components and by pyridine alone, while phenol competitively inhibited the enzyme. These two inhibitors are structural components of the parkinsonogenic neurotoxin N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). By extension, dopamine and neuromelanin synthesis in the brain may be influenced by the inhibitory effects of such compounds upon the copper-dependent steps of tyrosine metabolism. The non-animal model used in this study may represent an alternative to the use of animal tissues in neurodegenerative disease research.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1992

Parenteral domoic acid impairs spatial learning in mice.

The present study is the first to examine the effect of a single intraperitoneal injection of the neuroexcitotoxin domoic acid on learning in mice. Compared to saline controls, animals exposed to domoic acid (2.0 mg/kg) showed significant impairment on the acquisition of the place task in the Morris water maze. Observation of swim paths taken by mice searching for the underwater platform revealed a failure on the part of the domoic acid-exposed mice to select the appropriate problem solving strategies. The results, along with neuroanatomic work done here and elsewhere, suggest that impairment of acquisition and retention of this spatial navigation task by domoic acid, involves a neuropathology that includes not only the hippocampus, but other limbic, and possibly extralimbic brain regions.

Animals↗

PubMed1992

Effects of excitotoxins on free radical indices in mouse brain.

Excitotoxins and free radicals individually have been implicated in several neurological disorders including those associated with aging. We observed that systemically administered domoic acid enhanced mouse brain superoxide dismutase activity with either an associated decrease or no change in mouse brain lipid peroxidation. These findings reflect a state of adequately compensated oxidative stress induced by excitotoxins. In homogenates containing disrupted cells from various regions of mouse brain, however, kainic acid produced a 2 to 5-fold increase in lipid peroxidation. This suggests that excitotoxins cause lipid peroxidation possibly by acting at intracellular loci which become more accessible following disruption of cells in vitro and by extrapolation, possibly in vivo due to cellular permeability changes during the edematous stage of ischemic and other related neuropathological conditions.

Animals↗

PubMed1992

Embryo associated immunosuppressor factor(s) secreted by preembryo and serum estradiol levels are predictive of pregnancy outcome: effect of gonadotropin releasing hormone agonist (GnRHa) treatment of patients undergoing in vitro fertilization and embryo transfer (IVF-ET).

The aim of the present study was to determine whether (i) the secretion of embryo associated immunosuppressor factor (EASF) by preimplantation embryo and serum estradiol (E2) play a cooperative role in pregnancy outcome and (ii) whether this association was affected by gonadotropin releasing hormone agonist (GnRHa) pretreatment of IVF-patients for ovarian stimulation. EASF activity was measured using concanavalin A-induced lymphocyte proliferation assay in 251 IVF-culture media obtained from 59 patients undergoing IVF-ET. EASF activity in embryo growth media, cycle day 3 serum E2 level and peak E2 levels were correlated with pregnancy outcome. Results indicate that in GnRHa non-treated patients (i) the immunosuppressive activity of embryo growth media significantly (p less than 0.05) differed between the patients with varying concentration of day 3 serum E2, (ii) the presence of immunosuppressive activity in the embryo growth media was associated with success of pregnancy in patients with day 3 serum E2 level of 21-40 pg/ml (p less than 0.005) and in patients with peak E2 level in serum of less than = 1500 pg/ml (p less than 0.05). No association in immunosuppressive activity, serum E2 level and successful pregnancy was seen in GnRHa treated patients. This preliminary study suggests that the concentration of serum hormones and factors that are altered due to GnRHa pretreatment of IVF-patients may affect the cooperative role played by EASF, E2 and other factors in the success of pregnancy.

Blastocyst↗

PubMed1991

Temperature-dependence of LDL binding and activation of human platelets.

The effect of low density lipoprotein (LDL) on intracellular free calcium ion concentration ([Ca2+]i), taken as an index of the degree of platelet activation, was investigated in normal volunteers. At 37 degrees C LDL, in a dose of 20 micrograms of protein/ml, increased [Ca2+]i in all subjects tested (basal 57 +/- 11 to 113 +/- 19 nM). In contrast, when measurements were performed at 20 degrees C, no effect on [Ca2+]i was seen following LDL. Thrombin (0.2 U/ml) increased [Ca2+]i to 455 +/- 98 nM. When platelets had been exposed to LDL before thrombin stimulation, this increase was less pronounced (to 301 +/- 43 nM). Our finding of a temperature dependence of LDL induced increase in platelet [Ca2+]i supports the concept of a platelet-LDL receptor mediated mechanism. Furthermore, the lower thrombin response following LDL exposure suggests a LDL-thrombin interaction, possibly at the thrombin receptor level and/or calcium recruitment from the same stores.

Adult↗

PubMed1991

Global elevation of brain superoxide dismutase activity following forebrain ischemia in rat.

Regional superoxide dismutase (SOD) activity and lipid peroxidation (as reflected by thiobarbituric acid-reactive substances (TBARS)) have been measured at increasing post-ischemic time intervals following a (10 min) forebrain ischemic insult in rat. All brain regions showed significant progressive increases in SOD activity with increasing post-ischemic time intervals. Lipid peroxidation also was significantly increased in frontal and parietal/occipital regions at 1 and 24 h post-ischemia, although this was several orders of magnitude less than the increase in SOD activity. By 7 days post-ischemia lipid peroxidation had returned to control values for all regions. These data are consistent with the hypothesis that cerebral ischemia is accompanied by glial activation with an associated increase in SOD activity. Global increases in SOD activity may protect the brain from free radicals, thereby preventing large increases in lipid peroxidation.

Animals↗

PubMed1991

The genes for a mouse hematopoietic differentiation marker called the heat-stable antigen.

We have isolated a murine cDNA by virtue of its expression in pre-B cell lines but not in plasmacytomas. In mouse, mRNA is detected by Northern blot analysis exclusively in hematopoietic tissues with the exception of brain. When expressed in bacteria, the encoded protein is specifically recognized by several antibodies against the murine hematopoietic differentiation marker called heat-stable antigen (HSA). In contrast to previous speculations, these results suggest that the antigenic determinant recognized by anti-HSA antibodies is proteinaceous. The cDNA sequence is essentially identical to a mouse HSA cDNA recently published (Kay et al., J. Immunol. 1990. 145: 1952). Three HSA genes were isolated, one of which corresponds to the isolated cDNA. The other two appear to be intronless retroposons which, despite numerous sequence changes, maintain an open reading frame. One of these intronless genes could code for an alternative form of HSA with a transmembrane domain and a cytoplasmic tail not encoded by the intron-containing gene. This gene could be expressed, based on sequence comparisons of the three genes. However, using polymerase chain reaction amplification of first strand cDNA from various cell lines and adult mouse tissues, we could detect expression only of the intron-containing gene.

Animals↗

PubMed1991

Properties of human pre- and post-implantation embryo-associated immunosuppressor factor(s).

Embryo-associated immunosuppressor factor (EASF), a factor detected by its suppressive property on the concanavalin A (ConA) stimulated lymphocyte proliferation assay, was purified from human embryo growth media of in vitro fertilized ova (pre-implantation source) and from pregnancy sera (post-implantation source) as 3 fractions, CM-1, CM-3 and CM-6, the immunosuppressive properties of which were studied. The results show that, (i) the 3 fractions of EASF from both sources suppressed ConA- and pokeweed mitogen (PWM)-induced lymphocyte proliferation, suggesting that they have suppressive effects on both T and B cells; (ii) all 3 EASFs were suppressive when added at the early phase of ConA-supplemented cultures; (iii) CM-1 of both sources were suppressive when added to PWM-supplemented cultures between 24 and 48 h; and (iv) CM-6 of both sources showed an irreversible immunosuppressive effect on PWM-induced lymphocyte proliferation, demonstrating that some similarities exist in the immunosuppressive property of EASF from the 2 sources. On the other hand, (i) CM-6 of pre- and post-implantation EASF were immunosuppressive when added to the PWM-supplemented cultures at 24-48 h and 0-16 h, respectively; and (ii) the CM-6 fraction of pregnancy sera, but not the CM-6 fraction of embryo growth media, possessed an irreversible immunosuppressive effect on ConA-supplemented cultures. This active process by which EASF affects T cell and B cell functions directly may be one of several responses by which the maternal immune response against the fetus is prevented.

B-Lymphocytes↗

PubMed1991

The partially purified pre-implantation suppressor factor may be one of several factors to play a role in successful pregnancy.

Embryo-associated immunosuppressor factor (EASF) is detected by its suppressive properties in the concanavalin A (ConA)-induced lymphocyte proliferation assay. EASF was partially purified from human embryo growth media of in vitro fertilized ova (pre-implantation EASF) as three fractions. The aim of the present study was to determine whether the EASF isolated from human embryo growth media is similar to the EASF secreted by the pre-embryo, which has been shown to be associated with successful pregnancy. EASF activity was measured in the purified pre-implantation EASF fractions and in a total of 24 individual embryo growth media obtained from 10 patients undergoing in vitro fertilization and embryo transfer, where 6 patients achieved successful pregnancy and 4 did not. The results show that: (i) all three EASF fractions and the individual embryo growth media from patients who became pregnant were suppressive when added to the early phase of ConA-supplemented cultures; this was not seen with the embryo growth media from patients who failed to become pregnant, suggesting that the purified pre-implantation EASF may be one of several factors responsible for successful pregnancy; and (ii) some embryo growth media, irrespective of the pregnancy outcome of the patient, showed an irreversible immunosuppressive effect on ConA-induced lymphocyte proliferation, whereas none of the purified EASF fractions did; this could be due to the loss of activity during purification.

Blastocyst↗

PubMed1991

Circumventricular organ origin of domoic acid-induced neuropathology and toxicology.

The neuroexcitotoxin, domoic acid, was responsible for an episode of mussel poisoning in Eastern Canada in 1987. Severe neurologic impairment and some deaths occurred. We have characterized the nature of domoate-induced neuropathology in the mouse brain. Domoic acid was administered intraperitoneally at doses of 2, 3 or 7 mg/kg to Swiss-Webster mice. Brains were examined at 0.5, 1, 24, 48 or 72 h postinjection for evidence of damage. Significant pathologic changes occurred only after the largest dose of domoic acid. Damage was confined to circumventricular organs lacking a blood-brain barrier and their environs, including the organon vasculosum of the lamina terminalis, subfornical organ, mediobasal hypothalamus and area postrema. The neural damage induced by domoic acid was evident at as early as 30 min after injection and increased by 60 min postinjection. The loci of domoic acid-induced neuropathological changes accounts for several central and peripheral effects and toxicities observed following systemic domoate treatment, these included gastroduodenal lesions, hypodipsia, analgesia, and blood pressure fluctuations.

Animals↗

PubMed1991

Increased calcium influx in caudal artery of rats made hypertensive with pyridoxine deficiency.

Moderate pyridoxine deficiency in rats has been shown to induce hypertension, which can be corrected by pyridoxine supplementation. In this study, calcium handling by isolated caudal arteries from pyridoxine-deficient and age-matched control rats was evaluated. We found 45Ca influx into the intracellular compartment to be significantly elevated in deficient rats. This increased influx could be attenuated with nifedipine, a calcium channel blocker, in a dose-dependent manner, suggesting alterations in the calcium channels that would make them leaky. The pyridoxine-deficient arterial segments maintained a higher resting tone; removal of extracellular calcium by EGTA or entry blockade by nifedipine decreased the tone significantly in the deficient arteries, compared with little or no effect in controls.

Animals↗

PubMed1991

Intracellular pH measurement with fluorescent dye in canine basilar arteries.

The intracellular pH (pHi) of basilar artery rings was determined with 2',7'-bis-(carboxyethyl)-5,(6)-carboxyfluorescein (BCECF) by measuring the ratio of emitted (540 nm) fluorescence intensities (FI) at excitation wavelengths of 500 and 440 nm. There was a dye loss from the rings in 90 min (39.3 +/- 3.6%, p less than 0.001). We found that the ratio of fluorescence intensities does not adequately correct for dye loss; hence, we derived a method to correct for dye loss during pHi determinations. Calibration curves of the ratio versus pHi were constructed for the artery rings. The slope and intercept of the calibration curves depended on FI440. Linear regression lines for the slope and intercept versus FI440 were: [formula; see text] In solutions with different pH and different concentrations of free BCECF, the slope of the ratio versus pH of the solution was steeper at high concentrations of BCECF. Thus, pHi was calculated from a calibration curve in which the slope and intercept were determined from FI440 with the above formula. The corrected pHi was 7.37 +/- 0.05 (n = 25) at pHo 7.4 and 37 degrees C.

Amiloride↗

PubMed1991

Calcium channels in smooth muscle.

The molecular and biophysical characterization of Ca2+ channels in smooth muscle has lagged behind that in cardiac and skeletal muscles. This is caused by the difficulties in isolating viable cells and applying electrophysiological techniques to smooth muscle cells. The heterogeneity of smooth muscle cells from different organs also adds to the complexity. In spite of these problems there has been an increasing number of reports on Ca2+ channels in smooth muscle. This review provides an overview of this area. As in skeletal muscles, L (long-acting) and T (transient) voltage-dependent Ca2+ channels are found in smooth muscle; the former is better characterized. L channel is regulated by voltage, Ca2+, cyclic nucleotides, and protein kinase C. Ca2+ also influxes through receptor-operated channels that are voltage insensitive. The receptor-operated and T channels are insensitive to dihydropyridine. Clinically, Ca2+ blockers are extensively used for diseases of the cardiovascular system, with more limited use in the gastrointestinal tract. Further understanding of the properties of Ca2+ channels could lead to development of selective Ca2+ channel blockers for the gastrointestinal tract.

Calcium Channel Blockers↗

PubMed1990

Characterization of alpha 2-adrenoceptors in the rat: proximal tubule, renal membrane and whole kidney studies.

In the present study, alpha 2-adrenoceptors have been characterized in rat renal proximal tubules which were isolated by a Percoll gradient technique. Competitive binding curves with [3H]rauwolscine (0.5 nM) and alpha 2-adrenoceptor agonists and antagonists were consistent with an alpha 2B-adrenoceptor subtype. However, the rank order of potency (Ki) for clonidine and UK 14,304 was reversed from that reported for other tissues (clonidine, 48 nM greater than UK 14,304, 330 nM). This rank order was confirmed in a crude renal membrane preparation consisting of whole kidney as well as separated medullary and cortical segments. An intrarenal infusion of clonidine at 11 nmol/kg per min resulted in a greater diuresis and natriuresis than an equimolar dose of UK 14,304 suggesting that clonidine also had a greater affinity in the collecting tubules. Further displacement studies in proximal tubules with [3H]rauwolscine and calcium channel blockers demonstrated that verapamil was the most potent (Ki, 2.3 microM), followed by diltiazem (48% displacement at 100 microM) and then nifedipine (no displacement at 100 microM). These studies indicated that alpha 2-adrenoceptor in the rat proximal tubule may be of the alpha 2B-adrenoceptor subtype. Further studies will be required to determine whether the reverse rank order of potency of clonidine and UK 14,304 is consistent with an alpha 2-adrenoceptor subtype which is different from that found in other tissue.

Animals↗

PubMed1990

Immunosuppressive activity in human embryo growth media is associated with successful pregnancy: effect of gonadotropin releasing hormone agonist (GnRHa) treatment of patients undergoing in vitro fertilization and embryo transfer (IVF-ET).

The aim of the present study was to determine whether the secretion of embryo-associated immunosuppressor factor (EASF) by preimplantation embryo correlates with pregnancy outcome and whether this relationship is influenced by pretreatment of gonadotropin releasing hormone agonist (GnRHa) in patients undergoing in vitro fertilization and embryo transfer (IVF-ET). EASF activity was measured using concanavalin A-induced human lymphocyte proliferation assay in 256 embryo growth media obtained from 61 patients undergoing IVF-ET. EASF activity was then correlated with GnRHa treatment and pregnancy outcome in these IVF patients. Results indicate that (i) the presence of immunosuppressive activity in human embryo growth media is associated with success of pregnancy in GnRHa nontreated patients and (ii) serum factors present in GnRHa-treated patients may affect the EASF secretion by preembryos in vitro.

Blastocyst↗