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Biomedical subjects

A Puri

Publications and source records attributed to A Puri.

At least 19 recordsLinked to original sources
PubMed2000

The structure of human beta-defensin-2 shows evidence of higher order oligomerization.

Defensins are small cationic peptides that are crucial components of innate immunity, serving as both antimicrobial agents and chemoattractant molecules. The specific mechanism of antimicrobial activity involves permeabilization of bacterial membranes. It has been postulated that individual monomers oligomerize to form a pore through anionic membranes, although the evidence is only indirect. Here, we report two high resolution x-ray structures of human beta-defensin-2 (hBD2). The phases were experimentally determined by the multiwavelength anomalous diffraction method, utilizing a novel, rapid method of derivatization with halide ions. Although the shape and charge distribution of the monomer are similar to those of other defensins, an additional alpha-helical region makes this protein topologically distinct from the mammalian alpha- and beta-defensin structures reported previously. hBD2 forms dimers topologically distinct from that of human neutrophil peptide-3. The quaternary octameric arrangement of hBD2 is conserved in two crystal forms. These structures provide the first detailed description of dimerization of beta-defensins, and we postulate that the mode of dimerization of hBD2 is representative of other beta-defensins. The structural and electrostatic properties of the hBD2 octamer support an electrostatic charge-based mechanism of membrane permeabilization by beta-defensins, rather than a mechanism based on formation of bilayer-spanning pores.

Amino Acid Sequence↗
PubMed2000

Immunomodulatory activity of hexapeptides related to proline rich peptide from colostrum.

Twelve analogues of an immunomodulatory hexapeptide YVPGFP (I) derived from Proline rich peptide (from colostrum) have been synthesized with modifications at positions 2, 4 and 6. In MLR assay one of the analogues exhibited approx 50% inhibition at 0.1 microg/mL concentration in contrast to prednisolone and I which caused around 70 and 20% suppression respectively, at the same concentration.

Adjuvants, Immunologic↗
PubMed2000

Varying effects of temperature, Ca(2+) and cytochalasin on fusion activity mediated by human immunodeficiency virus type 1 and type 2 glycoproteins.

We examined fusion mediated by the human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) envelope glycoproteins under various experimental conditions. Incubation of HeLa cells expressing HIV-2(ROD) and HIV-2(SBL/ISY) envelope glycoproteins with HeLa-CD4 target cells resulted in fusion at temperatures >/=25 degrees C whereas fusion with cells expressing HIV-1(Lai) occurred only at >/=31 degrees C. HIV-2 envelope glycoprotein-mediated fusion proceeded in the absence of Ca(2+) in the culture medium, whereas HIV-1 fusion required Ca(2+) ions for fusion. In contrast to HIV-2 envelope glycoprotein fusion, incubations in the presence of the 0.5 microM cytochalasin B completely inhibited HIV-1 envelope glycoprotein-mediated fusion. Our results suggest that in contrast to HIV-2, HIV-1 fusion is dependent on dynamic processes in the target membrane.

Actins↗
PubMed2000

Influenza virus upregulates CXCR4 expression in CD4+ cells.

We examined the effect of prior influenza virus infection on the susceptibility of CD4+ cells to HIV-1 infection. Influenza virus infection of HeLa-CD4 cells resulted in a marked increase in susceptibility to infection by CXCR4-dependent but not CCR5-dependent HIV isolates. Influenza virus infection resulted in an increase in the steady state level of CXCR4 transcripts and an increase in cell surface CXCR4 expression. Our observations suggest that infectious agents such as influenza may contribute to HIV disease progression by modulating coreceptor availability.

CD4-Positive T-Lymphocytes↗
PubMed2000

Dietary restraint and self-reported meal sizes: diary studies with differentially informed consent.

Psychometric methods were used to explore the reliability and criterion validity of self-reported food intake in studies of dietary restraint. In Study 1 the reliabilities over days of daily aggregate intakes and of intakes at meals at particular times of day were assessed in 7 day food diaries by 27 low-BMI females. The sizes of particular meals correlated poorly with each other and with the total of all other meals; daily aggregate intakes also had poor reliability (Cronbach's alpha). Individuals meal sizes were consistent from day to day, with high inter-correlations between meal sizes, high correlations between meals at particular times and the sum of the remainder and high reliabilities. Aggregate intake had moderate criterion validity. Of individual meals, only breakfast achieved criterion validity, but there was a significant cubic component in its relationship with restraint. In Study 2, young male and female participants with various BMIs, completed a food diary on a single day. Again, aggregate daily intake had low reliability. Total intake and breakfast both had criterion validity, dietary restraint correlating negatively with total intake and breakfast size in the whole sample and in females, but there were significant quadratic components in the relationships. In contrast, restraint correlated positively with lunch size in the whole sample and in males. The combination of low reliability of individual meals as estimates of total intake, and the low criterion validity of all meals except breakfast, suggests that it may be inappropriate to study dietary restraint using aggregate self-reported intake measures.

Adult↗
PubMed2000

Immunostimulant activity of dry fruits and plant materials used in indian traditional medical system for mothers after child birth and invalids.

Products of certain plants given to mothers after child birth or to invalids were studied for immunostimulant activity using the macrophage migration index (MMI) as a parameter of macrophage activation and cell-mediated immunity and haemagglutinating antibody (HA) titres and plaque-forming cell (PFC) counts as parameters of humoral immunity. Feeding of Prunus amygdalus (Almond(1)) and Buchanania lanzan (Chirronji(1)) significantly stimulated both CMI and humoral immunity in BALB/c mice as evidenced by the enhancement of MMI, HA titres, and PFC counts. Euryale ferox (Tel makhana(1)), Phoenix dactylifera (Chhohara(1)) and Zingiber officinale (Sonth(1)), however, stimulated humoral immunity to a greater extent than CMI. The observation provides scientific basis for feeding the products of above plants to mothers after child birth and to invalids with a relatively poor immune status.

Adjuvants, Immunologic↗
PubMed2000

P-glycoprotein-overexpressing multidrug-resistant cells are resistant to infection by enveloped viruses that enter via the plasma membrane.

The multidrug resistance gene product P-glycoprotein confers drug resistance to tumor cells by acting as a transporter that blocks the entry into the cell of a great variety of drugs and hydrophobic peptides. In this study we find that in drug-resistant cells, the insertion of the influenza virus fusion protein (hemagglutinin-2) into the plasma membrane is blocked and that the fusion of the viral envelope with the plasma membrane of these cells is impaired. Multidrug-resistant cells display significant resistance to infection by envelope viruses that invade cells by fusion with the plasma membrane, but not to infection by pH-dependent viruses that penetrate cells by fusion with endocytic vesicles. These observations suggest that multidrug resistance phenomena may protect cells from infection by a large group of disease-causing viruses that includes human immunodeficiency virus, herpes simplex virus, and some cancer-inducing retroviruses.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Glycosphingolipids promote entry of a broad range of human immunodeficiency virus type 1 isolates into cell lines expressing CD4, CXCR4, and/or CCR5.

Treatment of human osteosarcoma cells, expressing CD4 and various chemokine receptors, with the glucosylceramide synthase inhibitor 1-phenyl-2-hexadecanoylamino-3-morpholino-1-propanol (PPMP), blocked target membrane glycosphingolipid (GSL) biosynthesis and reduced the susceptibility of cells to infection and fusion mediated by envelope glycoproteins from a variety of human immunodeficiency virus type 1 (HIV-1) isolates that utilize CXCR4 and/or CCR5. PPMP treatment of the cell lines did not significantly change the cell surface expression of CD4, CXCR4, and/or CCR5, nor did it alter the chemokine receptor association with CD4. PPMP-treated cells exhibited no changes in chemokine-induced Ca(2+) mobilization and chemotaxis. However, massive envelope glycoprotein conformational changes triggered by CD4 and the appropriate chemokine receptor on the target membrane were inhibited when the target cells were treated with PPMP. Addition of various purified GSLs to PPMP-treated target cells showed that for all isolates tested, globotriaosylceramide (Gb3) was the most potent GSL in restoring the fusion susceptibility of target cells with cells expressing HIV-1 envelope glycoproteins; addition of the monosialoganglioside GM3 yielded a slight enhancement of fusion susceptibility. Our data are consistent with the notion that a limited number of specific GSL species serve as crucial elements in organizing gp120-gp41, CD4, and an appropriate chemokine receptor into a membrane fusion complex.

3T3 Cells↗
PubMed1999

Role of glycosphingolipids in HIV-1 entry: requirement of globotriosylceramide (Gb3) in CD4/CXCR4-dependent fusion.

We have recently shown that addition of human erythrocyte glycosphingolipids (GSL) to non-human CD4+ or GSL-depleted human CD4+ cells rendered those cells susceptible to gp120-gp41-mediated cell fusion (Puri et al., BBRC, 1998). One GSL fraction (Fraction 3) isolated from human erythrocyte GSL mixture exhibited the highest recovery of fusion following incorporation into CD4+ non-human and GSL-depleted HeLa-CD4 cells (HeLa-CD4/GSL-). Structural analysis of Fraction 3 showed that this GSL had identical head group as the known GSL, Gal(alpha1-->4)Gal(beta1-->4)Glc-Ceramide (Gb3) (Puri et al., PNAS, 1998). Here we report that presence of Gb3 in CD4+/CXCR4+ cells but not CD4+/CXCR4 cells allows fusion with HIV-1Lai-envelope glycoprotein expressing cells (TF228). Therefore, Gb3 functions in conjunction with HIV-1 co-receptor, CXCR4 to promote fusion. We propose that Gb3 functions by recruiting CD4 and/or CXCR4 at the fusion site through structurally specific interactions.

CD4 Antigens↗
PubMed1999

Family studies and human leukocyte antigen class II typing in Indian probands with seizures in association with single small enhancing computed tomography lesions.

PURPOSE: To define the clinical features of the syndrome of seizures associated with single, small, enhancing computed tomography (CT) lesions (SSELs) in 235 Indian probands and seizure types among their family members. Human leukocyte antigen (HLA) class II genomic typing in randomly selected 41 probands was done to identify the role of hereditary factors in this syndrome. METHODS: The seizure types among 235 probands, their clinical outcome, and seizures in their family members were studied. Family data were collected on relatives of 212 additional probands with neurologic diseases other than epilepsy. HLA class II antigens were studied by using polymerase chain reaction (PCR) amplified DNA and sequence-specific oligonucleotide probe (PCR-SSOP) hybridization. RESULTS: The seizures in 86% were partial with or without generalization; 77% had fewer than five seizures before the first CT scan. Evanescent focal neurologic deficits after seizures were noted in 40%. Most patients (97%) were treated with a single antiepileptic drug (AED). Significant resolution of the CT scan lesion was noted within 6 months in 125 (53%) of 235 cases. Two thirds of patients had no seizures while taking a single AED, and an additional 18% had no seizures even after their AEDs were discontinued. Epilepsy among relatives of Indian probands having seizures in association with SSELs was more common as compared with relatives of probands with other neurologic diseases. A family history of seizures was noted in 21% probands, the ratio of affected first- to second-degree relatives was 4.3:1, and 60% of affected sibs had syndromic concordance with probands. There was a positive association of HLA-DRB1*13 (Pc = 0.036) with this syndrome. CONCLUSIONS: The syndrome of seizures in association with SSELs seems to be a benign localization-related epileptic syndrome. Our results of HLA studies point to an inherited susceptibility to an infective agent, which in most cases is of cysticercal etiology.

Adult↗
PubMed1998

The neutral glycosphingolipid globotriaosylceramide promotes fusion mediated by a CD4-dependent CXCR4-utilizing HIV type 1 envelope glycoprotein.

Previously, we showed that the addition of human erythrocyte glycosphingolipids (GSLs) to nonhuman CD4(+) or GSL-depleted human CD4(+) cells rendered those cells susceptible to HIV-1 envelope glycoprotein-mediated cell fusion. Individual components in the GSL mixture were isolated by fractionation on a silica-gel column and incorporated into the membranes of CD4(+) cells. GSL-supplemented target cells were then examined for their ability to fuse with TF228 cells expressing HIV-1LAI envelope glycoprotein. We found that one GSL fraction, fraction 3, exhibited the highest recovery of fusion after incorporation into CD4(+) nonhuman and GSL-depleted HeLa-CD4 cells and that fraction 3 contained a single GSL fraction. Fraction 3 was characterized by MS, NMR spectroscopy, enzymatic analysis, and immunostaining with an antiglobotriaosylceramide (Gb3) antibody and was found to be Gal(alpha1-->4)Gal(beta1-->4)Glc-Cer (Gb3). The addition of fraction 3 or Gb3 to GSL-depleted HeLa-CD4 cells recovered fusion, but the addition of galactosylceramide, glucosylceramide, the monosialoganglioside, GM3, lactosylceramide, globoside, the disialoganglioside, GD3, or alpha-galactosidase A-digested fraction 3 had no effect. Our findings show that the neutral GSL, Gb3, is required for CD4/CXCR4-dependent HIV-1 fusion.

Acetylation↗
PubMed1998

Immunosuppressant activity in human beta-casein fragment analogs.

Human beta-casein fragment (54-59) having the amino acid sequence Val-Glu-Pro-Ile-Pro-Tyr, has been shown potent immunostimulant activity. Several analogs of this hexapeptide have been synthesized with modification in the N-terminal region and tested for their immunomodulatory activity. Interestingly, two hexapeptides have shown significant immunosuppressant activity.

Amino Acid Sequence↗
PubMed1998

Human erythrocyte glycolipids promote HIV-1 envelope glycoprotein-mediated fusion of CD4+ cells.

We examined the role of target membrane glycolipids in CD4-mediated HIV-1 fusion by altering the glycolipid levels in CD4+ cells. CD4+ human cells exhibited 50% reduction in extent of fusion with gp120-gp41 expressing cells (TF228) when grown in the presence of a glycolipid synthesis inhibitor PPMP. We added erythrocyte glycolipids (GL) to fusion-incompetent CD4+ non-human cells by influenza-hemagglutinin-mediated fusion between GL-containing liposomes and target cells. Human erythrocyte GL (HuGL)-modified CD4+ non-human cells became susceptible to fusion with TF228 cells. Transfer of bovine erythrocyte glycolipids (BoGL) to CD4+ non-human cells under similar conditions did not complement HIV-1 fusion. Furthermore, addition of HuGL, but not BoGL, to PPMP-inhibited cells rescued fusion to the original levels. Our observations demonstrate that human erythrocyte glycolipids promote CD4-mediated HIV-1 fusion and certain glycolipid(s) from human erythrocytes may serve as alternative and/or additional cofactors in HIV-1 entry.

Animals↗
PubMed1998

The metabotropic glutamate receptors of the vestibular organs.

This research sought to test the presence and function of metabotropic excitatory amino acid receptors (mGluR) in the frog semicircular canal (SCC). The mGluR agonist +/- 1-aminocyclopentane-trans-1,3-dicarboxylate (ACPD) produced an increase in afferent firing rates of the ampullar nerve of the intact posterior canal. This increase was not due to a stimulation of cholinergic efferent terminals or the acetylcholine (ACh) receptor, since atropine, in concentrations which blocked the response to exogenous acetylcholine, did not affect the response to ACPD. Likewise, ACPD effects were not due to stimulation of postsynaptic NMDA receptors, since the NMDA antagonist D(-)-2-amino-5-phosphonopentanoate (AP-5) did not affect the response to ACPD, reinforcing the reported selectivity of ACPD for mGluRs. When the SCC was superfused with artificial perilymph known to inhibit hair cell transmitter release (i.e. low Ca-high Mg), ACPD failed to increase afferent firing. This suggests that the receptor activated by ACPD is located on the hair cell. Pharmacological evidence suggested that the mGluRs involved in afferent facilitation belong to Group I (i.e. subtypes 1 and 5). In fact, the Group III agonist AP-4 had no effect, and the ACPD facilitatory effect was blocked by the Group I mGluR antagonists (S)-4-carboxyphenylglycine (CPG) and (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA). Additional pharmacological evidence supported the presence of Group I mGluRs. Interestingly, the mGluR antagonists, AIDA and 4CPG, by themselves did not affect the resting firing rates of ampullar afferents. This may suggest that the mGluRs are not involved in resting activity but perhaps only in evoked activity (as suggested in Guth et al. (1991) Hear. Res. 56, 69-78). In addition, the mRNA for the mGluR1 has been detected in hair cells of both SCC, utricle, and saccule. In summary, the evidence points to an mGluR localized to the hair cell (i.e. an autoreceptor) which may be activated to produce a positive feedback augmentation of evoked but not resting transmitter release and thus affect afferent activity.

Afferent Pathways↗
PubMed1998

Epilepsies among twins born in families of Indian probands with epilepsy.

Twins have a high frequency of adverse perinatal events and have been reported to have an increased risk of seizures. Contrary to popular belief, a recent study reported that twins do not have an increased risk of seizures. We studied the relationship of twinning and epilepsy in India. The frequency of twinning in families of probands with epilepsy was compared with the frequency of twinning among hospital births in the same region of India. We also compared consecutively ascertained probands with epilepsy for their twin status and the occurrence of epilepsies in their twin and non-twin relatives. The frequency of twin births in families of 524 probands with epilepsy was comparable to the twin births among consecutive deliveries over a 3-year period in another government hospital in the same catchment area (1:99 vs. 1:75). Every 1 in 58 of probands with epilepsy was a twin while a twin was born in these families every 1 in 71 live births. The frequency of epilepsy in non-proband twin relatives was 1.5% compared with 2% among non-proband, non-twin relatives. This data suggests that twin birth is not a major risk factor for seizures even in families of Indian probands with epilepsy. Family data such as ours can be used to study the contribution by genetic factors in the pathogenesis of complex genetic diseases such as human epilepsies.

Adult↗
PubMed1998

Juvenile myoclonic epilepsy: disease expression among Indian families.

OBJECTIVES: Juvenile myoclonic epilepsy (JME) is a common, age related, idiopathic generalized epileptic syndrome. We aimed to define the expression of JME in Indian probands and study the occurrence of seizures/epileptic syndromes in their family members. METHODS: We studied 225 JME probands with a uniform protocol. recording the type and frequency of seizures, precipitating factors, EEG data, and family history. Detailed family pedigrees were drawn to include all the 1st- and 2nd-degree relatives of probands. The seizures/epileptic syndromes in relatives examined were classified in a uniform way. RESULTS: The clinical and EEG characteristics of 225 JME probands from India were similar to those reported in probands from different ethnic backgrounds. The incidence of febrile convulsions in probands with JME was similar to that of the general population but was much lower (0.2%) among their relatives. A positive family history of seizures among 1st- or 2nd-degree relatives was noted in 79 of 225 (35%) probands. The risk of relatives being affected as well as their risk of expressing a type of idiopathic generalized epilepsy (IGE) varied as a function of the degree of relation with the probands. CONCLUSIONS: The clinical expression of JME among probands from India is fairly similar to that reported in probands of different ethnic backgrounds. The risk of relatives being affected as well as their risk of expressing a type of IGE (including JME) varies as a function of the degree of relation with the probands. The reduced occurrence of febrile convulsions among the relatives of JME probands probably represents an ascertainment bias. A much larger database of this type should be helpful in understanding the interactions of different genes that are believed to be responsible for some of the inherited human epileptic syndromes like JME and other IGEs.

Adolescent↗
PubMed1997

Conformational changes and fusion activity of vesicular stomatitis virus glycoprotein: [125I]iodonaphthyl azide photolabeling studies in biological membranes.

The interaction of VSV glycoprotein (VSV G) with biological membranes was studied by photosensitized labeling. The method is based on photosensitized activation by the fluorescent lipid analog 3,3'-dioctadecyloxacarbocyanine (DiO) of a hydrophobic probe, [125I]iodonaphthyl azide (125INA), that rapidly partitions into the membrane bilayer of virus and cells. 125INA labeling of proteins and lipids can be confined to the site of chromophore localization by photosensitized labeling. Photoactivation using visible light of target membrane labeled with DiO and 125INA, to which unlabeled virions are bound, results in exclusive labeling of envelope glycoproteins inserted into the target membrane [Pak et al. (1994) J. Biol. Chem. 269, 14614]. In this study, we labeled lipid symmetric erythrocyte ghosts with 125INA and DiO. Photosensitized activation of VSV prebound to labeled ghosts with visible light resulted in VSV G labeling under fusogenic conditions. Photoactivation of 125INA by UV light, which is nonspecific, produced labeled VSV G at both acidic and neutral pH. Photosensitized labeling of VSV G by DiO-125INA-ghosts was also observed at pH 5.5, 4 degrees C, in the absence of mixing between viral and cellular lipids, suggesting insertion of the ectodomain of VSV G. Soluble VSV G lacking the transmembrane domain inserted into DiO-125INA-ghosts under the same conditions as intact VSV G. DiO inserted into intact VSV appeared to be a suitable fluorophore for continuous kinetic measurements of membrane fusion by fluorescence dequenching. Our photosensitized labeling results establish biochemical correlates for the three states of VSV G, which we had proposed based on kinetic data [Clague et al., Biochemistry 29, 1303]. In addition, we found that VSV G insertion into the target membrane is reversible, suggesting a "velcro"-like attachment of the fusogenic domain with the target membrane.

Affinity Labels↗