Biomedical subjects

S Kar

Publications and source records attributed to S Kar.

At least 19 recordsLinked to original sources

PubMed1996

Integration of the DNA of a novel filamentous bacteriophage VSK from Vibrio cholerae 0139 into the host chromosomal DNA.

An unusual filamentous bacteriophage, VSK, containing single-stranded, circular DNA as its genome was isolated from Vibrio cholerae 0139 strains P07 and B04. Unlike other single-stranded DNA phages, VSK can integrate its genome into the chromosome of the host and enter into a lysogenic state. The double-stranded replicative form (RF) of the single-stranded phage DNA was isolated. A restriction map of the VSK RF DNA was constructed using HaeII, AvaII, ClaI and XbaI. By Southern blot analysis of the chromosomal DNA of the lysogen using labeled phage DNA as probe, the attachment site (attP) on the viral genome was also identified.

Bacteriophages↗

PubMed1996

Distribution and levels of insulin-like growth factor (IGF-I and IGF-II) and insulin receptor binding sites in the spinal cords of amyotrophic lateral sclerosis (ALS) patients.

The structurally related peptides, insulin and insulin-like growth factors (IGF-I and IGF-II), have neurotrophic properties and potentially could be of therapeutic value in human neurodegenerative disorders. In this study, we compared the anatomical distribution of [125I]IGF-I, [125I]IGF-II and [125I]insulin binding sites in thoracic spinal cords from patients who died of amyotrophic lateral sclerosis (ALS) and normal controls. For these three ligands, the greatest amounts of specific binding were located in the deeper layers of the dorsal horn > intermediate zone > lamina X > ventral horn > superficial layers of the dorsal horn > white matter of the spinal cord. Highly significant (P < 0.001) increases in the density of [125I]IGF-I and [125I]IGF-II binding were apparent in various laminae of the cord of ALS patients with increased binding being particularly evident in the ventral horn and the intermediate zone. Significant (P < 0.05) increases were also seen in lamina X and in the dorsal horn. In contrast, no significant differences in [125I]insulin binding were observed between ALS and control spinal cords. Taken together, these data reveal significant increases in both [125I]IGF-I and [125I]IGF-II binding levels in the spinal cords of ALS patients albeit to different extents. These findings may be of relevance for future therapeutic strategies aimed at slowing the progression of this chronic neurodegenerative disease, as recently suggested by the beneficial therapeutic effects of an IGF-I treatment in ALS patients.

Aged↗

PubMed1996

Measurement of phenols on a loop-supported liquid film by micellar electrokinetic chromatography and direct UV detection.

This paper describes a direct measurement of phenolic substances in the gas phase at levels relevant to occupational health by micellar electrokinetic chromatography (MEKC) using direct ultraviolet detection. A small circular loop (2 mm O.D.) is formed with 100 mm Pt-wire at the sampling end of a fused-silica capillary. The capillary tip of the sampling end is present at the center of the loop and in the same plane. A thin film of 0.50 mM NaOH is formed on the loop by immersion and withdrawal. The film is in fluid communication with the capillary and acts as an absorber for gaseous phenols. Gas sampling is performed by transferring the film-bearing loop into a chamber through which air is aspirated for a preset time at a preselected flow-rate (typically 1 min at 100 cm3/min). A part of the film content is then introduced into the capillary by gravity injection and then MEKC is performed. A total of twelve chloro- and nitrophenols were selected for this study. Under the above sampling conditions, limits of detection (LODs) for various phenols range from high-single-digit to low-double-digit ppbv levels. The effect of several critical parameters, such as the composition of the liquid film and the MEKC running electrolyte, sampling period and film evaporation on the collection efficiency, separation efficiency and calibration behaviour are described.

Adsorption↗

PubMed1996

A calcitonin gene-related peptide receptor antagonist prevents the development of tolerance to spinal morphine analgesia.

Tolerance to morphine analgesia is believed to result from a neuronal adaptation produced by continuous drug administration, although the precise mechanisms involved have yet to be established. Recently, we reported selective alterations in rat spinal calcitonin gene-related peptide (CGRP) markers in morphine-tolerant animals. In fact, increases in CGRP-like immunostaining and decrements in specific [125]hCGRP binding in the superficial laminae of the dorsal horn were correlated with the development of tolerance to the spinal antinociceptive action of morphine. Other spinally located peptides such as substance P, galanin, and neuropeptide Y were unaffected. Thus, the major goal of the present study was to investigate whether the development of tolerance to spinally infused morphine could be modulated by the blockade of dorsal horn CGRP receptors using the potent CGRP antagonist hCGRP(8-37). Indeed, cotreatments with hCGRP(8-37) prevented, in a dose-dependent manner, the development of tolerance to morphine-induced analgesia in both the rat tail-flick/tail-immersion and paw-pressure tests. Moreover, alterations in spinal CGRP markers seen in morphine-tolerant animals were not observed after a coadministration of morphine and hCGRP(8-37). These results demonstrate the existence of specific interaction between CGRP and the development of tolerance to the spinal antinociceptive effects of morphine. They also suggest that CGRP receptor antagonists could become useful adjuncts in the treatment of pain and tolerance to the antinociceptive effects of morphine.

Analgesics, Opioid↗

PubMed1996

Beta-amyloid-related peptides inhibit potassium-evoked acetylcholine release from rat hippocampal slices.

The 4 kDa beta-amyloid (A beta) protein, a major component of cerebral and cerebrovascular plaques in Alzheimer's disease (AD), is derived from the proteolytic cleavage of a larger, membrane-bound precursor, the A beta precursor protein (APP). Until recently, it was assumed that an aberrant AD-specific proteolysis generated A beta peptides, which subsequently could initiate and/or contribute to the pathological cascade leading to plaque formation and losses of selected neuronal populations, including basal forebrain cholinergic neurons that provide major inputs to the hippocampus and neocortex. However, the recent detection of soluble A beta fragments in the plasma and CSF of normal individuals, as well as in the conditioned media of cultured brain cells, suggests a role for A beta-related peptides in normal brain functions. Taking into consideration the reported toxic properties of A beta and the preferential vulnerability of basal forebrain cholinergic neurons in AD, we investigated the possible effects of A beta-related peptides on the release of endogenous acetylcholine (ACh) from rat brain slices. A beta 1-28, in a concentration-dependent manner (10(-12)-10(-8) M), potently inhibited K(+)-evoked ACh release from hippocampal slices. The inhibition of ACh release was fully reversible and was observed using other A beta-related peptides such as A beta 1-42, A beta 1-40, and A beta 25-35, but not with the scrambled, reverse, or all D-isomer A beta-peptide sequences, indicating that the effect of A beta on ACh release is mediated via a stereoselective mechanism. Tetrodotoxin (10 microM) failed to alter the effect of A beta 1-28 on ACh release, which suggests the lack of involvement of voltage-dependent Na+ channels. Except for the hippocampal formation, the inhibitory effect of A beta on K(+)-evoked ACh release also was observed in the frontal cortex but not in the striatum. Taken together, our results demonstrate that APP-derived A beta-related peptides can regulate the release of ACh potently by acting on cholinergic terminals. Additionally, the evidence that selected cholinergic neuronal populations are sensitive to A beta suggests a potential mechanistic link between the deposition of A beta and the preferential vulnerability of certain cholinergic projections in AD.

Acetylcholine↗

PubMed1996

Comitogenic effects of vasoactive intestinal polypeptide on rat hepatocytes.

The primary mitogens such as epidermal growth factor and transforming growth factor-alpha are known to stimulate DNA synthesis in primary cultures of adult rat hepatocytes. Vasoactive intestinal polypeptide (VIP) was found to amplify DNA synthesis induced by the primary mitogens and thus acted as a comitogen. The comitogenic effect of VIP was specific for the culture medium, suggesting that minor components in the medium were required for hepatocytes to fully respond to VIP. Glutamic acid is probably one of these minor components, although other components present in the nutrient-rich medium were also necessary for the full comitogenic effect. Other comitogens such as insulin, vasopressin, and angiotensin II interacted additively with low concentrations of VIP. The comitogenic effect of VIP was also found in hepatocytes cultured from regenerating rat liver after a partial hepatectomy. In the regenerating hepatocyte cultures, VIP can act as a mitogen even in the absence of the primary mitogen EGF. VIP mRNA was found in several organs including brain, intestine, and liver, and its expression was slightly induced in liver 24 h after a partial hepatectomy. These results suggest that VIP can act as a hepatic comitogen and may play a role in liver cell proliferation.

Animals↗

PubMed1996

Infarct size reduction with coronary venous retroinfusion of diltiazem in the acute occlusion/reperfusion porcine heart model.

Calcium channel blockers are commonly used for the treatment of ischemic heart disease, but their effects on myocardial infarct size (IS) after reperfusion are not well known. Enflurane-anesthetized open-chest pigs subjected to 60-min left anterior descending coronary artery (LAD) occlusion followed by 3-h reperfusion were referred to one of the four experimental groups. Beginning 10 min before the onset of reperfusion, pigs in group A received diltiazem (7.5 micrograms/kg/min) retrogradely infused into the coronary vein for 30 min. In group B, the same amount of diltiazem was infused into the right atrium. A corresponding volume of saline was infused into the coronary vein in group C or into the right atrium in group D. IS expressed as a percentage of the myocardium at risk was significantly smaller (p < 0.01) in group A (33 +/- 14%; mean +/- SD) than in groups B (58 +/- 11%), C (58 +/- 11%), and D(63 +/- 10%). After reperfusion, functional recovery of the ischemic myocardium, determined by ultrasound crystals, was significantly more improved (p < 0.05) in group A as compared with other groups. The ischemic and nonischemic regional myocardial blood flow (RMBF), determined by radioactive microspheres, did not differ between four groups. Coronary venous retroinfusion of diltiazem had a myocardial protective effect in the porcine experimental model of acute coronary occlusion/reperfusion, whereas intravenous drug administration was not effective. The protective effect could not be attributed to washout of toxic metabolites from the ischemic area or to improved microcirculation. It was probably related to a pronounced accumulation of the calcium-channel blocker diltiazem in the ischemic myocardium achieved by the coronary venous route of delivery.

Animals↗

PubMed1996

Protective role of anion channel blocker in lipid peroxidation caused by H2O2 in microsomes of bovine pulmonary arterial smooth muscle tissue.

The role of hydroxyl radical (OH.) in H2O2-mediated stimulation of lipid peroxidation in microsomes of bovine pulmonary arterial smooth muscle tissue and the protective effects of DIDS, the anion channel blocker have been studied. Treatment of microsomes with H2O2 (1 mM) stimulate iron release, OH. production and lipid peroxidation. Pretreatment with DFO (an iron chelator) or DMTU (a hydroxyl radical scavenger) prevents OH. production and thereby reduces lipid peroxidation without any appreciable reduction of iron release. Simultaneous treatment of either DFO or DMTU with H2O2 significantly reduces lipid peroxidation and prevents OH. production without any significant reduction of iron release. However, addition of DFO or DMTU 2 min after treatment of the microsome with H2O2 does not produce any significant reduction of lipid peroxidation, OH production and iron release. Pretreatment of microsomes with DIDS markedly reduces the stimulation of lipid peroxidation without appreciably altering the increase in OH. production and iron release caused by H2O2.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1995

Growth inhibition of hepatoma cells induced by vitamin K and its analogs.

Congeners of vitamin K are known to inhibit cell growth, although the precise mechanisms of growth inhibition are not well understood. To investigate the mechanisms involved, we synthesized several vitamin K analogs and examined their growth inhibitory activities for a human hepatoma cell line (Hep3B). The analogs included 2-methyl-1,4-naphthoquinone and trimethyl-benzoquinone, with and without aliphatic side chains at position 3. The side chains were all-carbon, thioethers, or O-ethers. Growth inhibition was potent in the compounds with short chains. The presence of a sulfur (thioether) or oxygen atom (O-ether) at the site of attachment of the side chain to the ring potentiated the activity. Apoptotic cell death was induced by the potent growth inhibitory compounds at low concentrations (20-60 microM), whereas necrotic cell death followed treatment with the same compounds at high concentrations. Expression of c-myc, which is thought to be associated with apoptosis, was increased by most of the compounds tested. Both reduced glutathione and cysteine almost completely abrogated the growth inhibitory effects of the thioether analogs as well as of vitamin K3. The effect of glutathione was less prominent for the all-carbon and O-ether analogs, and cysteine had no effect on these analogs. Catalase and deferoxamine mesylate had no significant effect on the thioether analogs, although they showed partial antagonistic effects on the growth inhibition of vitamin K3 and the all-carbon and O-ether analogs. Other non-thiol antioxidants tested had no effect on any of the analogs. Our results indicated that vitamin K-related quinoid compounds cause growth inhibition and both apoptotic and necrotic cell death and that the effects may be mediated by interaction at position 3 of their quinoid nuclei with cellular thiols.

Amino Acid Sequence↗

PubMed1995

Endothelin-1 expression by human hepatocellular carcinoma.

Plasma levels of endothelin-1 (ET-1) are markedly higher in patients with hepatocellular carcinoma (HCC) than in normal controls. In order to further investigate this, we evaluated ET-1 immunoreactivity and mRNA expression in human HCC tissue. 70% (14/20) of the tumor tissues immunostained positively with ET-1 antibody and a significant association was observed between immunostaining in cells lining the tumor feeding vessels and tumor vascularity as determined by hepatic angiography. Moreover, the neoplastic hepatocytes in the tumors also stained positively with ET-1 antibody. All of the HCC tissue samples which immunostained for ET-1 also expressed ET-1 mRNA, indicating that ET-1 is actively synthesized by the tumors.

Amino Acid Isomerases↗

PubMed1995

Characterization of phage phi O139, a Vibrio cholerae O139 temperate bacteriophage with cohesive DNA termini.

A temperate bacteriophage isolated from Vibrio cholerae O139, the new epidemic strain of cholera, was found to have a polyhedral head 65 nm in diameter and a rigid contractile tail 120 nm in length. The phage chromosome was a double-stranded DNA of 35 kb, with unique cohesive ends and had a G + C content of 58.8%. A restriction map of the phage DNA was constructed using the restriction endonucleases AvaI and BstEII. The phage, whose presence could be detected in nine out of 13 V. cholerae O139 isolates tested, was found to have identical chromosomal integration sites in all the strains. The phage attachment site (attP) was found to be located very close to one end of the genome.

Bacteriophages↗

PubMed1995

Differential display and cloning of messenger RNAs from the late phase of rat liver regeneration.

Liver regeneration allows for recovery from hepatic injuries and regeneration after partial hepatectomy has been extensively used as a model system to study mitogenesis. Many genes have been identified that are induced in the early growing phase of liver regeneration but only a few genes have been identified that are induced in the later stages of regeneration before growth arrest. We used the newly discovered differential display method to identify several genes that were found to be induced at this later stage. Two of them were analyzed further. DNA sequencing of one of them revealed perfect homology to ribosomal protein S24. The sequence of the other gene did not have extensive homology to any sequence in the databases. These results may suggest a role of these two genes in the growth arrest phase of liver regeneration.

Aniline Compounds↗

PubMed1995

Neuropeptide receptors in developing and adult rat spinal cord: an in vitro quantitative autoradiography study of calcitonin gene-related peptide, neurokinins, mu-opioid, galanin, somatostatin, neurotensin and vasoactive intestinal polypeptide receptors.

A number of neuroactive peptides including calcitonin gene-related peptide (CGRP), substance P, neurokinin B, opioids, somatostatin (SRIF), galanin, neurotensin and vasoactive intestinal polypeptide (VIP) have been localized in adult rat spinal cord and are considered to participate either directly and/or indirectly in the processing of sensory, motor and autonomic functions. Most of these peptides appear early during development, leading to the suggestion that peptides, in addition to their neurotransmitter/neuromodulator roles, may possibly be involved in the normal growth and maturation of the spinal cord. To provide an anatomical substrate for a better understanding of the possible roles of peptides in the ontogenic development of the cord, we investigated the topographical profile as well as variation in densities of [125I]hCGRP alpha, [125I]substance P/neurokinin-1 (NK-1), [125I]eledoisin/neurokinin-3 (NK-3), [125I]FK 33-824 ([D-Ala2, Me-Phe4, Met(O)ol5]enkephalin)/mu-opioid, [125I]galanin, [125I]T0D8-SRIF14 (an analog of somatostatin); [125I]neurotensin and [125I]VIP binding sites in postnatal and adult rat spinal cord using in vitro quantitative receptor autoradiography. Receptor binding sites recognized by each radioligand are found to be distributed widely during early stages of postnatal development and then to undergo selective modification to attain their adult profile of distribution during the third week of postnatal development. The apparent density of various receptor sites, however, are differently regulated depending on the lamina and the stage of development studied. For example, the density of mu-opioid binding sites, following a peak at postnatal day 4 (P4), declines gradually in almost all regions of the spinal cord with the increasing age of the animal. [125I]substance P/NK-1 binding sites, on the other hand, show very little variation until P14 and then subsequently decrease as the development proceeds. In the adult rat, most of these peptide receptor binding sites are localized in relatively high amounts in the superficial laminae of the dorsal horn. To varying extents, moderate to low density of various peptide receptor binding sites are also found to be present in the ventral horn, intermediolateral cell column and around the central canal. Taken together, these results suggest that each receptor-ligand system is regulated differently during development and may each uniquely be involved in cellular growth, differentiation and in maturation of the normal neural circuits of the spinal cord. Furthermore, the selective localization of various receptor binding sites in adult rat spinal cord over a wide variety of functionally distinct regions reinforces the neurotransmitter/modulator roles of these peptides in sensory, motor and autonomic functions associated with the spinal cord.

Aging↗

PubMed1995

Differentially expressed genes in TGF-beta 1 sensitive and resistant human hepatoma cells.

The pathway of growth inhibitory cellular signal transduction by transforming growth factor beta 1 is largely unknown. Although several cellular proteins have been shown to be involved in the pathway, others remain to be identified. To search for other involved proteins, differentially expressed genes were examined in two human hepatoma cell lines that were respectively sensitive and resistant to growth inhibition by TGF-beta 1. Two such genes (SB31 and SB16) were characterized and found to be 100% homologous to leucine-rich alpha 2-glycoprotein and the ribosomal protein S25, respectively. SB31 was coordinately expressed with the TGF-beta I type II receptor, implicating a possible interaction. Expression of both genes in different cell lines can be broadly correlated with the sensitivity of the cell lines to growth inhibition by TGF-beta 1. SB16 expression is strongly suppressed in rat liver regeneration after partial hepatectomy, suggesting that it may have a role in liver growth.

Animals↗

PubMed1995

Identification of a human hepatocellular carcinoma-associated tumor suppressor gene by differential display polymerase chain reaction.

Differential gene expression between the normal human liver and a cell line derived from human hepatocellular carcinoma (HCC) was studied using the differential display polymerase chain reaction technique. One gene (mitochondria proteolipid like gene, MPL), whose expression was found to be repressed in the HCC cell line compared to normal liver, was cloned and sequenced. Amino acid sequence translated from the nucleotide sequence had a 73% homology with the carboxyl terminus of a mitochondria proteolipid (MPLP) isolated from beef heart. Northern blot analysis showed that the expression of the 3 kb MPL transcript was undetectable in 20 of 45 (44%) of human hepatocellular carcinomas, whereas only 1 of 14 (17%) of cirrhotic livers without HCC had undetectable expression when compared to normal livers. Hence MPL may be a candidate tumor suppressor gene for human HCC. This decrease in MPL expression was not due to gross alteration of its genomic DNA.

Amino Acid Sequence↗

PubMed1995

Quantitative autoradiographic localization of [125I-Tyr8]bradykinin receptor binding sites in the rat spinal cord: effects of neonatal capsaicin, noradrenergic deafferentation, dorsal rhizotomy and peripheral axotomy.

In vitro receptor autoradiography was used to localize, quantify and characterize [125I-Tyr8]bradykinin binding sites in all major spinal cord segments of normal rats and animals subjected to various chemical treatments and surgical lesions. [125I-Tyr8]bradykinin specific binding sites were predominantly located to superficial laminae of the rat dorsal horn, with the substantia gelatinosa showing the highest density of labelling (values ranging from 3.1 fmol/mg tissue in cervical to 4.5 fmol/mg tissue in lumbar segments). A moderate density (1.8-3.0 fmol/mg tissue) of specific binding was observed in lamina III, whereas in other areas, i.e. laminae I and IV-X, lower amounts of labelling were detected. Within the superficial laminae of the dorsal horn, [125I-Tyr8]bradykinin binding was largely distributed over the neurophil with some perikarya showing concentrations of labelling. In contrast, the ventral horn showed a rather homogeneous distribution of [125I-Tyr8]bradykinin binding over the neuropil, with silver grain alignments surrounding motoneuron perikaryas and proximal processes. Bradykinin, [Tyr8]bradykinin and B2 receptor antagonists (D-Arg[Hyp3,Thi5,D-Tic7,Oic8]bradykinin (Hoe 140), D-Arg[Tyr3,D-Phe7,Leu8]bradykinin, D-Arg[Hyp3, Leu8]bradykinin, D-Arg[Hyp2, Thi5,8,-Phe7]bradykinin D-Arg[Hyp3, D-Phe7, Leu8]bradykinin, Tyr0, D-Arg[Hyp3, D-Phe7, Leu8]bradykinin inhibited [125I-Tyr8]-bradykinin binding with very high subnanomolar affinities, while the B1 receptor agonist (Tyr0,des-Arg10-kallidin) and antagonist ([Leu8]-des-Arg9-bradykinin) did not significantly affect [125I-Tyr8]bradykinin binding at up to micromolar concentrations. Two weeks after unilateral lumbar dorsal rhizotomy (L1-L6) or peripheral lesions of the sciatic nerve, significant decreases ( +/- 50%) in [125I-Tyr8]bradykinin binding sites were found in ipsilateral laminae I-III of lumbar spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Biotype traits and antibiotic susceptibility of Vibrio cholerae serogroup O1 before, during and after the emergence of the O139 serogroup.

Sixty-nine strains of Vibrio cholerae O1 isolated at different times were analysed to investigate if there were any differences among the O1 strains isolated before, during and after the advent of the O139 serogroup. Of the 69 O1 strains examined, 68 belonged to the Ogawa serotype while one belonged to the Inaba serotype. With the exception of one strain all other strains of V. cholerae O1 belonged to the eltor biotype. A single O1 strain isolated before the emergence of the O139 serogroup could not be classified as either eltor or classical biotype because it was resistant to both classical and eltor specific bacteriophages. Marked variations in the susceptibility to antibiotics of V. cholerae O1 isolated during the different periods were observed. In addition, strains of V. cholerae isolated after the epidemic of serogroup O139 in Calcutta showed an expanding R-type with resistance to a variety of drugs as compared to the O1 strains isolated before the advent of the O139 serogroup. From this study, it is clear that there is a substantial mobility in genetic elements of V. cholerae O1 which necessitates a continuous monitoring to keep abreast of the changing traits of the etiologic agent of cholera.

Agglutination Tests↗

PubMed1995

Ethnic minorities, health care systems, and behavior.

This article presents an overview of research on health care use and provider behavior, on doctor-patient relationships, adherence to medical regimens, self-care, practices and avoidance health care behaviors, and attitudes of 4 ethnoracial groups: African Americans, American Indians, Asian Americans, and Latinos. Although issues within the groups varied, common themes between the groups emerged. It became apparent, after discussion, that whatever the issues and health problems, these can be resolved most effectively when addressed within the social contexts of each ethnoracial group.

Black or African American↗