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Biomedical subjects

M K Das

Publications and source records attributed to M K Das.

At least 91 records · Page 5Linked to original sources
PubMed1988

Oral application of insulin encapsulated liposomes.

125Iodine labelled insulin encapsulated liposomes were introduced orally to rats. After different intervals of feeding, blood from the portal vein and heart was collected. The plasma was passed through a Sepharose 2B column to establish the presence of liposomes or intact hormone. Liposomal and hormonal fractions from the column loaded with plasma from the portal vain contained radioactivity. It was found that approx. 60% of the loaded radioactivity was associated with the liposomes whereas 20% of the loaded count was found with the hormonal fractions. It is noted that undegraded protein is not detected in portal plasma from rats fed with free insulin. When plasma from the heart of rats fed with liposomal insulin was passed through Sepharose 2B column, neither liposomes nor insulin was detected.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Suppression of liver uptake of orally fed liposomes by injection (i.p.) of dextran sulfate 500.

125Iodine labelled human immunoglobulin-G encapsulated liposomes were administered orally to rats. Distribution of radioactivity was checked in various tissues and in portal blood. The effect of dextran sulfate (DS 500,000 m. wt., liver blockade agent) injection (i.p.) on the liver uptake of liposomes and on the amount of liposomes appearing in the portal blood from the gastrointestinal tract have been studied. An increased amount of radioactivity was observed in the portal blood and the amount of radioactivity in the liver decreased appreciably after injection of dextran sulfate. In both the cases the action of dextran sulfate started 2 hours after injection and reached maximum at 12 hour, falling slightly at 24 hour.

Administration, Oral↗
PubMed1987

A study of the antigen, antibody and immunecomplex levels in Wuchereria bancrofti filariasis with reference to clinical status.

Circulating antigens, antibodies to somatic and sheath components of microfilariae (mf) and immune complexes were determined in parallel in different categories of Wuchereia bancrofti infection using, respectively, reverse indirect haemagglutination (RIHA), indirect haemagglutination (IHA), indirect immunofluorescent (IFA) and polyethylene glycol (PEG) precipitation assays. Rabbit hyperimmune anti-W. bancrofti mf serum and mf homogenates were used as reagents. Appreciable levels of antigens and antibodies were detected in all categories; endemic normals, asymptomatic carriers, acute and chronic filarial cases. For example, even amongst endemic normals, i.e. those with neither clinical nor parasitological evidence of infection, 66%, 71% and 74% had mf antigens, anti-mf antibodies and anti-sheath antibodies, respectively. Notably, only a small proportion (9.4%) of microfilaraemic individuals had detectable level of anti-sheath antibodies. The relationship of these parameters with the spectrum of filariasis is discussed.

Adolescent↗
PubMed1986

Membrane channel forming polypeptides. Molecular conformation and mitochondrial uncoupling activity of antiamoebin, an alpha-aminoisobutyric acid containing peptide.

The conformations of the 16-residue fungal peptide antiamoebin I (Ac-Phe-Aib-Aib-Aib-D-Iva-Gly-Leu-Aib-Aib-Hyp-Gln-D-Iva-Hyp-Aib-Pro-P hol) have been investigated in dimethyl sulfoxide solution by one- and two-dimensional NMR techniques. A substantial number of resonances in the 270-MHz 1H NMR spectrum have been assigned. Intramolecularly hydrogen-bonded (solvent inaccessible) NH groups have been identified by determining solvent and temperature dependence of NH chemical shifts and rates of hydrogen-deuterium exchange. Ten backbone NH groups are inaccessible to solvent, while three NH groups assigned to the Phe(1), Aib(2), and Aib(8) residues are exposed to solvent. Interresidue nuclear Overhauser effects are consistent with psi values of approximately 120 +/- 30 degrees for Phe(1) and Leu(7). The NMR results, together with the stereochemical constraints imposed by the presence of alpha-aminoisobutyryl, isovalyl, prolyl, and 4-hydroxyprolyl residues, favor a highly ordered structure. Two backbone conformations consistent with the data are considered. Antiamoebin is shown to be an effective uncoupler of oxidative phosphorylation in rat liver mitochondria, providing evidence for its membrane-modifying activity.

Aminoisobutyric Acids↗
PubMed1985

Effects of membrane channel-forming polypeptides on mitochondrial oxidative phosphorylation. A comparison of alamethicin, gramicidin A, melittin and tetraacetyl melittin.

Transmembrane channel-forming polypeptides can function as uncouplers of mitochondrial oxidative phosphorylation. The observed effects are dependent on the phosphate ion (Pi) concentration in the medium. At low Pi (2.5 mM) the order of uncoupling efficiencies is gramicidin A much greater than alamethicin greater than tetraacetyl melittin greater than melittin. The remarkably high activity of gramicidin A suggests insertion of preformed channel dimers into the membrane. It is also suggested that lipid phase association of peptides is necessary in the other cases. At Pi = 100 mM inhibitory effects are observed for alamethicin and tetraacetyl melittin. Less pronounced inhibition is seen for melittin, while no such effect is noted for gramicidin A. The site of inhibition is shown to be complex IV, and the differences in the behavior of the peptides are rationalized in terms of channel structures.

Alamethicin↗
PubMed1984

Characterization of anti-N-acetyl-D-glucosamine antibodies elicited through haptenated liposomes.

Antiserum was raised in rabbits against p-aminophenyl 2-acetamido-2-deoxy-beta-D-glucoside covalently coupled to phosphatidylaminoethanol-containing lecithin liposomes. The affinity-purified antibodies were found to be IgM. The properties of the antibodies were studied by ligand inhibition of quantitative precipitation, fluorescence titration with 2-acetamido-2-deoxy-D-glucose, and complement lysis of haptenated liposomes.

Acetylglucosamine↗
PubMed1984

Binding of anti-galactosyl antibodies to galactosylated liposomes.

The binding characteristics of rabbit anti-galactosyl antibodies elicited through galactosylated liposomes were studied. The association constants (13 X 10(5) M-1 and 21 X 10(5) M-1 of Fabmu and Fab fragments with the galactosylated liposomes were determined by measuring the binding of radioiodinated antibodies. The effect of free ligand (methyl-beta-D-galactopyranoside) and the ligand coupled to the liposomal surface (galactosylated liposomes) on the structure of antibodies was investigated using circular dichroism (CD) measurements. Changes were observed in both the secondary and tertiary structure of antibodies upon binding to galactosylated liposomes. In contrast, the free ligand induced alterations only in the near-UV region of the CD spectra, indicating a change in tertiary structure only.

Animals↗
PubMed1984

Preparation of anti-polysaccharide antiserum using liposomes as immunological adjuvant.

Bovine serum albumin (BSA) was coupled to dextran by controlled periodate oxidation followed by sodium borohydride reduction. The conjugate was entrapped in negatively charged, multilamellar phosphatidylcholine (lecithin) liposomes in which the polysaccharide remained surface-exposed, at least partially. Liposome-entrapped conjugate elicited in rabbits an appreciable anti-dextran response when compared with the sera raised in saline or in Freund's adjuvant. The anti-dextran antibodies belonged to both the IgM and IgG classes. The precipitin reaction of dextran with the antiserum raised in liposomes was determined.

Adjuvants, Immunologic↗
PubMed1984

Immunogenicity of galactosylated liposomes.

The kinetics of the immune response to galactosylated liposomes in saline was studied in rabbits. The antibody level in the secondary immunization was found to be higher compared to that in the primary response. The antibodies were purified on an immunoadsorbent column of galactosylated bovine serum albumin. Anti-galactosyl antibodies belonged to both IgM and IgG classes, the former being the major fraction. Both failed to agglutinate normal or neuraminidase treated human or rabbit erythrocytes but they agglutinated trypsinized cells.

ABO Blood-Group System↗