PubMed Health⌕ Search

Biomedical subjects

S Basak

Publications and source records attributed to S Basak.

17 recordsLinked to original sources
PubMed1992

Infectious entry pathway for canine parvovirus.

We have investigated whether canine parvovirus (CPV) infection involves a low pH-dependent entry pathway. The effects of two lysosomotropic bases, NH4Cl and chloroquine, on CPV entry were studied by immunofluorescence and ultrastructural and biochemical methods. In the presence of these reagents, input virions appear to accumulate in large vacuoles. Ultrastructural studies indicated that uptake of virions takes place predominantly in small uncoated vesicles that appear to fuse with larger vesicles. In the presence of NH4Cl, virions accumulate in the latter structures and their uncoating appears to be prevented. Viral DNA as well as antigen synthesis were found to be significantly inhibited in the presence of these reagents. In addition, inhibition of viral DNA and antigen synthesis appeared to be most extensive when NH4Cl was present from 30 min preinfection, whereas no significant inhibition was observed when the cells were treated after 2 hr postinfection. Thus, the results indicate that CPV requires exposure to low pH in an endosomal compartment to initiate a productive infection.

Ammonium Chloride↗
PubMed1992

Expression of SV40 receptors on apical surfaces of polarized epithelial cells.

We have investigated the interaction of SV40 virions with polarized monkey kidney epithelial cells. Virions were tagged with biotin to facilitate their detection and were found to retain full infectivity. When polarized Vero C1008 cells were incubated with biotinylated virions followed by a strepavidin-rhodamine conjugate, distinct cell populations were identified which expressed very different levels of SV40 receptors. The parental Vero C1008 cells yielded three types of cell clones which exhibited low, moderate, or predominantly high levels of SV40 binding. Virus-binding assays to each of these clones as well as to parental Vero C1008 cells indicated that the level of SV40 receptor expression is cell-cycle-dependent. The cellular receptors for influenza A virus (WSN strain) were also found to be distributed heterogeneously on polarized epithelial cells. In contrast, in several types of nonpolarized cells, SV40 receptors were found to be uniformly distributed over the monolayer. SV40 binding was not found to correlate with HLA expression on Vero C1008 cells or other cell types. Also in contrast to SV40 receptor expression, which is restricted to the apical domain, HLA was found to be distributed on both apical and basolateral domains of Vero C1008 cells.

Animals↗
PubMed1992

Morphogenesis of human immunodeficiency virus type 1.

Human immunodeficiency virus (HIV) has been implicated as the etiologic agent of acquired immunodeficiency syndrome and is a member of the sub-family Lentivirinae within the family Retroviridae. HIV type 1 (HIV-1) contains three major genes, gag, pol and env, which code for (1) core proteins, (2) a protease, reverse transcriptase and integrase, and (3) envelope glycoproteins, respectively. The core proteins p17, p24 and p15 are derived from gag precursor, p55, by endoproteolytic cleavage. The two nucleic-acid-binding proteins p7 and p9 are synthesized from p15 by proteolytic cleavage. These two structural proteins are apparently needed for the ribonucleoprotein-core formation. The envelope glycoproteins gp120 and gp41 (gp120-gp41 complex) are also generated by cleavage env precursors, gp160. The assembly of HIV-1 particles, like other retroviruses, appears to involve the association of the env precursor gp160 with the gag proteins. There are several factors which influence the assembly and budding process of HIV-1. In this article, we describe important events in HIV-1 morphogenesis and factors which influence this aspect of the HIV-1 life cycle.

HIV-1↗
PubMed1992

Bacteriology of wound infection: evaluation by surface swab and quantitative full thickness wound biopsy culture.

A total of 171 cases of wounds of various aetiology were examined and screened bacteriologically for evidence of infection by surface swab culture and quantitative full thickness wound biopsy culture techniques. Staphylococcus pyogenes was the most frequently isolated (39.9%) single organism. Other organisms being Escherichia coli (26.1%), Pseudomonas aeruginosa (15.4%), klebsiella species (5.8%), Streptococcus pyogenes (4.9%), proteus species (4.8%) and coliform organism (3.1%). Collectively the Gram-negative organisms were the majority among the isolated organisms. As indicator of wound infection, surface swab culture was found to be reliable in 72% cases when correlated with wound biopsy culture. The latter technique was found to be more consistently valuable (in 95% cases) both for regular assessment of the wounds as well as to judge the response to treatment.

Bacterial Infections↗
PubMed1992

Aetiological studies on hospital inpatients with secretory diarrhoea in Calcutta.

Twenty-five cases of all age groups with secretory diarrhoea admitted to the Infectious Diseases Hospital, Calcutta were studied. Bacterial enteropathogens were detected by bacteriological examination of the faeces, in each and every case. The main pathogens detected were Escherichia coli and Vibrio cholerae. V cholerae was more commonly associated with severe illness except in the very young, while Esch coli was equally associated with moderate and severe illness. Multiple isolates were more commonly associated with severe illness and single isolates were more common in illness of moderate severity.

Adolescent↗
PubMed1990

Host cell-dependent lateral mobility of viral glycoproteins.

The lateral mobility of viral envelope proteins on the plasma membranes of infected cells is an important factor in both virus assembly and pathogenesis. The envelope glycoproteins of measles and human parainfluenza virus are mobile on the surfaces of infected HeLa cells and undergo lateral redistribution in the presence of specific antibody, forming unipolar caps. In contrast, no such redistribution was observed with influenza virus hemagglutinin (HA) or vesicular stomatitis virus (VSV) G glycoproteins on infected HeLa cell surfaces. However, the HA and G glycoproteins were both found to be mobile in the plasma membrane of CV-1 cells, or human or murine peritoneal macrophages. These results indicate that host cell-dependent as well as virus-specific factors are involved in determining viral glycoprotein mobility. No significant differences in the patterns of synthesis of influenza or VSV viral proteins were found in the various cell types examined. The HA and G proteins, when expressed from vaccinia virus recombinants, were each found to be immobile in HeLa cells and mobile in CV-1 cells, thus indicating that the host cell-dependent differences in mobility are an intrinsic property of each viral glycoprotein molecule and not the result of interaction with other viral components. It is suggested that the association of viral glycoproteins with either the cytoskeleton or membrane-associated cellular proteins may be related to the observed differences in lateral mobility.

Animals↗
PubMed1989

Nucleotide sequence analysis of the capsid genes and the right-hand terminal palindrome of porcine parvovirus, strain NADL-2.

The genome of the porcine parvovirus, strain NADL-2, has been cloned and the sequence of map units 28 to 100, which is 3670 bp in length and contains the capsid coding regions and the right-hand terminal palindrome, has been determined. The sequence shows extensive homology with other parvoviruses such as MVM, H-1, CPV, and FPV in the capsid coding region. Given the information available from these sequences, the regulatory and capsid coding regions for PPV have been proposed and the amino acid sequences of capsid proteins compared. The right end, which has a 188-nucleotide-long imperfect palindromic sequence, has an organization similar to that of other parvoviruses and the homologies in this region with other parvoviruses correspond to the homologies observed in the rest of the respective genomes.

Amino Acid Sequence↗
PubMed1989

Polarized entry of canine parvovirus in an epithelial cell line.

The binding and uptake of canine parvovirus (CPV) in polarized epithelial cells were investigated by growing the cells on a permeable support and inoculating with the virus either from the apical or basolateral surface. Binding of radiolabeled CPV occurred preferentially on the basolateral surface. In contrast, when a similar experiment was carried out on nonpolarized A72 cells, virus binding occurred regardless of the direction of virus input. Binding appeared to be specific for CPV and could not be competitively inhibited by either bovine or porcine parvovirus. Analysis of the binding data revealed a high-affinity receptor (10(5) per cell) for CPV on the basolateral surfaces of MDCK cells (Kd, 29 pM). In indirect immunofluorescence studies, virus entered only from the basolateral surfaces of MDCK cells. These results provide evidence for a functional CPV-specific receptor that is expressed only on the basolateral surfaces of polarized epithelial cells, a result that has interesting consequences for viral pathogenesis.

Animals↗
PubMed1988

Preliminary X-ray crystallographic analysis of canine parvovirus crystals.

The first diffraction pattern of a crystalline single-stranded DNA virus has been obtained. Canine parvovirus was crystallized in a monoclinic P21 unit cell with a = 264.4 A, b = 350.3 A, c = 267.8 A and beta = 90.86 degrees (1 A = 0.1 nm). The diffraction pattern extends to at least 2.8 A resolution. Packing of the particles suggests that they have a diameter around 257 A, in excellent agreement with the reported molecular weight of 5.5 x 10(6).

Animals↗
PubMed1988

Kinetics of domain formation by sickle hemoglobin polymers.

We have monitored the growth of domains of sickle hemoglobin polymers by using temporally and spatially resolved light scattering and birefringence measured pseudosimultaneously on a 50-microns square area. Polymerization was induced and indefinitely maintained by photolysis of the carbonmonoxy derivative using an argon ion laser. Intensity of scattering and birefringence (measured as intensity transmitted through crossed polarizers) were measured using a silicon-intensified target vidicon interfaced to a computer. Polymer concentration, as inferred by light scattering, grew with primarily circular symmetry, with approximately 20% of the signal initially in a twofold symmetric pattern. In time the circular symmetry increased. A distinct decrease in the scattering signal developed which spread outward from the center of the domain. Birefringence lagged the scattering and initially grew in a twofold pattern, with the formation of a characteristic Maltese cross only appearing much later, and well after the scattering signal had peaked. Radial profiles of the domain scattering and birefringence were both approximately gaussian. We successfully modeled the decrease in scattering by fitting the profiles to a large gaussian from which a second smaller gaussian was subtracted. This second gaussian had the width of the birefringence gaussian. The width of the birefringence gaussian grew linearly in time, while the width of the scattering gaussian showed a notable acceleration. We conclude that domains form primarily as disordered arrays which align at later times. We explain the above observations, including the shape of the birefringence progress curves, as the result of an alignment transition which is solely due to a redistribution of monomers from short to long, and from entangled to radial, polymers. We present a theoretical justification for this process in an appendix. In a separate paper (Zhou, H. X., and F. A. Ferrone, manuscript submitted for publication) we show that the gaussian shapes and acceleration of the width naturally arise from a generalization of the double nucleation mechanism for sickle hemoglobin gelation (Ferrone, F. A., J. Hofrichter, H. Sunshine, and W. A. Eaton 1980. Biophys. J. 32:361-377; Ferrone, F. A., J. Hofrichter, and W. A. Eaton. 1985. J. Mol. Biol. 183:611-631).

Birefringence↗
PubMed1987

Polymer domains, gelation models and sickle cell crises.

The multistranded fibers formed by deoxygenated sickle hemoglobin form well ordered spherulitic arrays called domains. Employing laser photolysis of the carboxy derivative to initiate polymerization and domain formation, we have monitored the evolution of the spatial character of domains by light scattering and birefringence. Spatial growth is analyzed by observing a 62.5 microns square area of the sample and storing the image as 2500 discrete elements. Domain formation appears to consist of two phases. In the early phase even symmetric domains are not radially isotropic. Although the domain expands during this period, the internal polymer density as inferred by the light scattering intensity also increases. In the second phase, the domain becomes structurally symmetric and spatially homogeneous, and changes in the scattered intensity including pronounced overshoots occur uniformly across the monitored region. In this phase, the birefringence increases as the scattering decreases, with the same apparent rate.

Birefringence↗
PubMed1985

Sialic acid is incorporated into influenza hemagglutinin glycoproteins in the absence of viral neuraminidase.

We have analyzed the pronase-derived glycopeptides of the hemagglutinin glycoproteins expressed from SV40 vectors carrying cloned cDNA copies of the HA gene and of HA isolated from influenza virions (A/Jap/305/57). The glycopeptides derived from he HA glycoprotein obtained from cloned genes were heterogeneous, ranging in size from 3800 to 2800 daltons. Upon treatment with neuraminidase, sialic acid was released from the glycopeptides and their size was reduced to 2900-2400 daltons. However, under the same conditions, no sialic acid was detected in the virion HA. The presence of sialic acid was confirmed by monosaccharide analysis of the HA glycoprotein derived from products of cloned genes. These results support the idea that during replication of influenza virus, the viral neuraminidase cleaves sialic acid from the HA glycoprotein in infected cells.

Glycopeptides↗
PubMed1985

Conformational kinetics of triligated hemoglobin.

We have used the method of modulated excitation (Ferrone, F.A., and J.J. Hopfield, 1976, Proc. Natl. Acad. Sci. USA. 73:4497-4501), with an improved apparatus and a revised analytical procedure, to measure the rate of conformational change between the oxy (R) and deoxy (T) conformations of triligated carboxy-hemoglobin A at pH 6.5 and 7.0. We have found the rates to be kRT = 1.2 X 10(3) s-1 and kTR = 3.5 X 10(3) s-1 for pH 6.5, while for pH 7.0, kRT = 1.0 X 10(3) s-1, and kTR = 3.0 X 10(3) s-1. The value for L3, the equilibrium constant between conformations, was virtually unchanged between pH 6.5 and 7.0. While the rates measured here differ from those obtained in the original use of this method, these new rates are fully consistent with the original data when analyzed by the revised procedures presented here. When taken with other kinetic and equilibrium data, our measurements suggest that the transition state between structures is dominated by the behavior of the T quaternary structure. Finally, a spectral feature near the HbCO Soret peak has been observed that we ascribe to an allosteric perturbation of the spectra of the liganded hemes.

Carboxyhemoglobin↗
PubMed1979

Glycopeptides of murine leukemia viruses. I. Comparison of two ecotropic viruses.

The glycopeptides obtained by pronase digestion of two ecotropic strains of murine leukemia virus (MuLV) were compared by gel filtration. Four different glycopeptide size classes, designated G(1), G(2), G(3), and G(4), with molecular weights of approximately 5,100, 2,900, 2,200, and 1,500, respectively, were shown to be associated with Rauscher MuLV virions grown in JLS-V9 cells. Various sugar precursors, including glucosamine, galactose, fucose, and mannose were incorporated into G(1) and G(2), suggesting that these are complex (type I) glycopeptides. The two smaller glycopeptide size classes, G(3) and G(4), were shown to be mannoserich (type II) glycopeptides. G(4) was more sensitive to digestion with endo-beta-N-acetylglucosaminidase H than G(3), suggesting that the core of G(3) may contain fewer mannose residues. Glycopeptides of the same size class as G(1) and G(2) were associated with both Rauscher MuLV and AKR-MuLV grown in III6A (mouse embryo) cells. Previous studies have shown that gp52, a proteolytic cleavage product of gp70, possessed primarily G(1) glycopeptides and that gp52 was more highly sulfated than gp70. We observed that G(1) is approximately twofold more highly sulfated than G(2), explaining the observed difference in sulfation of gp52. The unusually large size of G(1) suggested that infection with MuLV may alter the host cell glycosylation pattern. To test this possibility, glycopeptides from Sindbis virions grown in uninfected and Rauscher MuLV-infected JLS-V9 cells were compared, and no differences were observed. G(1) was not detected in Sindbis virions, indicating that acquisition of G(1) depends on properties of the virus-coded polypeptide backbone of the gp70 molecule.

AKR murine leukemia virus↗