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P Das

Publications and source records attributed to P Das.

At least 163 records · Page 9Linked to original sources
PubMed1992

R-ELISA: repeated use of antigen-coated plates for ELISA and its application for testing of antibodies to HIV and other pathogens.

In this paper we report on the evaluation of several procedures that allow for the repeated use of an antigen-coated, enzyme-linked immunosorbent assay (ELISA) plate for enzyme immunoassay (EIA). We have shown that antigen-coated ELISA plates that were incubated once with an aqueous solution containing 8 M urea, 2% sodium dodecyl sulfate and 2% mercaptoethanol, after an EIA, can be reused again for EIA without loss of antigenic capacity. Thus, in this procedure, after an EIA, the ELISA plates were washed once with the above solution and then in a buffer containing 20 mM Tris-HCl, pH 7.5, 0.1% Tween 20 and 500 mM NaCl. This washing protocol was shown to remove the primary antibody, enzyme-conjugated secondary antibody and substrate without removing the antigen from the ELISA plate microwells. Thus, an antigen-coated ELISA plate previously used for an assay could be reused. We tested this repeat ELISA (R-ELISA) procedure on high antigen-binding ELISA plates coated with two different plant virus proteins, a synthetic peptide, the p25/24 gag and the gp120 proteins of the human immuno-deficiency virus, or the staphylococcus enterotoxin protein. In each case tested, the procedure allowed for the repeated use of the same antigen-coated plates for EIA of the respective antibodies. This procedure should prove to be particularly valuable for mass screening of samples tested for HIV and other disease-causing agents.

Amino Acid Sequence↗
PubMed1991

Mammalian sex chromosomes. III. Activity of pseudoautosomal steroid sulfatase enzyme during spermatogenesis in Mus musculus.

Parallel to the inactivation of the X chromosome in somatic cells of female, the male X in mammals is rendered inactive during spermatogenesis. Pseudoautosomal genes, those present on the X-Y meiotically pairable region of male, escape inactivation in female soma. It is suggested, but not demonstrated, that they may also be refractory to the inactivation signal in male germ cells. We have assayed activity of the enzyme steroid sulfatase, product of a pseudoautosomal gene, in testicular cells of the mouse and shown its presence in premeiotic, meiotic (pachytene), and postmeiotic (spermatid) cell types. It appears that, as in females, pseudoautosomal genes may escape inactivation in male germ cells also.

Animals↗
PubMed1991

Identification of heterogeneity in human isolates of Giardia lamblia by isoenzyme studies.

Electrophoretic mobility patterns of six enzymes, viz. alkaline phosphatase E.C. 3.1.3.1., acid phosphatase E.C. 3.1.3.2., malic enzyme E.C. 1.1.1.40., phosphoglucomutase E.C. 2.7.5.1., isocitrate dehydrogenase E.C. 1.1.1.42., glucose-6-phosphate dehydrogenase E.C. 1.1.1.49 of two axenically cultured human Giardia lamblia isolated from India (PD-1 and PD-2) and one strain from Portland, Oregon, USA (P-1) were compared using polyacrylamide gel electrophoresis (PAGE). Based on the difference in the mobility patterns of the enzymes phosphoglucomutase, isocitrate dehydrogenase and malic enzyme, the PD-1 and PD-2 isolates appeared to be quite different from P-1. In the present study, the isocitrate dehydrogenase and alkaline phosphatase enzymes were used for the first time for differentiation of Giardia isolates. In the case of PD-1, two alkaline phosphatase bands could be seen whereas only one band was observed in PD-2 and P-1. Thus, the three strains could be grouped into three different zymodemes. These findings reveal the significant heterogeneity in G. lamblia isolates both from widely separated areas and within a single region. Heterogeneity among G. lamblia strains may explain the variable clinical manifestations, host response and treatment efficacy characteristic of human giardiasis.

Acid Phosphatase↗
PubMed1991

Epidemiology of campylobacteriosis in a cohort of rural population near Calcutta.

Over a 2-year period, 25 families comprising of 181 individuals of all ages were longitudinally observed for the excretion of Campylobacter species. Faecal samples were taken from all persons with diarrhoea. Specimens were also taken from apparently healthy individuals and from domestic animals living within the confines of the study families at monthly intervals. The overall diarrhoea attack rate was 19 episodes per 100 person-years with peak incidence in the 1- to 4-year-old age group (76/100 person-years). Eight (11.5%) of the total episodes were campylobacter-associated and the overall rate of campylobacter positive diarrhoeal episodes were 2.2 per 100 person-years. Of the 1002 stool samples from healthy individuals 32 (3.2/100 samples) were positive for campylobacter. The organism was most frequently isolated from children under 1 year of age both during diarrhoeal episodes (11.5 per 100 person-years) and non-diarrhoeal (11.1 per 100 samples). Multiple infections in a family were rare. In 19.4% of the occasions one or more animals were campylobacter positive. However, only in 7.7% of these occasions was a human infection recorded within 1 month after the animal was found to be positive. The study showed that the epidemiology of campylobacteriosis in this community was distinct compared to that observed in developed countries.

Adolescent↗
PubMed1991

A temporal study of the expression of the capsid, cytoplasmic inclusion and nuclear inclusion proteins of tobacco etch potyvirus in infected plants.

Young leaves of tobacco, systemically infected by tobacco etch potyvirus (TEV), were examined for the presence and distribution of four virus encoded proteins [capsid, cytoplasmic inclusion (CI) and two nuclear inclusion (NI) proteins] at various time periods after inoculation of expanded leaves of the plants. The analyses were carried out by ELISA and by immunogold electron microscopy of thin sections of the leaves. All four proteins were detected simultaneously in the systemic leaves for the first time on the fifth day after inoculation of the expanded leaves. All four proteins increased in concentration until the seventh day and then showed no further increase with the exception of the capsid protein which continued to accumulate. The CI protein was first detected in association with the plasmalemma/cell wall and was subsequently found mostly in the form of pinwheels in the cytoplasm. The two NI proteins were found at all times after infection within the nucleus, although small concentrations were detected in the cytoplasm. These experiments suggest that both the NIa and NIb proteins are transported into the nucleus immediately after synthesis. At the earliest time periods after infection, high concentrations of these proteins (NIa and NIb) were found in their non-inclusion form in the nucleolus. At 14 days after infection, both proteins were found only as inclusions in the nucleus. The capsid protein was found at all stages of infection only in the cytoplasm.

Capsid↗
PubMed1991

Metacyclogenesis of Leishmania spp: species-specific in vitro transformation, complement resistance, and cell surface carbohydrate and protein profiles.

Metacyclic (stationary) and logarithmic (log) forms of promastigotes of Leishmania donovani and Leishmania major were characterized in several ways. The highly active metacyclic forms were larger with more protein and less carbohydrate. The flagellum increased in length 2.4 times in L. major as compared to 1.8 times in L. donovani. Resistance to complement-mediated lysis by normal human serum of in vitro grown Leishmania promastigotes was related to the species, the growth phase in culture, and also the temperature. Metacyclic forms of both species had a much increased resistance to killing by normal serum at different temperatures. Differences in membrane-exposed carbohydrates were detected by fluorescein-conjugated lectins. Peanut agglutinin and Ulex agglutinin I differentiated log and stationary phase promastigotes of L. major. Higher amounts of acid phosphatase were demonstrated in the metacyclic phase. Differences in polypeptides were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Two polypeptides of approximately 51 and 114 kDa were found exclusively in metacyclic promastigotes of both species, whereas 38- and 23-kDa polypeptides were lost or reduced during transformation from log to metacyclic phase promastigotes of L. donovani. In addition, a 75-kDa polypeptide was expressed only in metacyclic promastigotes of L. major.

Acid Phosphatase↗
PubMed1990

Characterization of peptidyl-nucleoside antifungal antibiotics from fermentation broth.

Characterization of sinefungin related antifungal antibiotics from fermentation broth was accomplished by coupling photodiode array (PDA) detection to high performance liquid chromatography (HPLC). From the combined HPLC-PDA evaluation of broth filtrate, we detected five sinefungin related components. Fast atom bombardment (FAB) mass spectroscopic evaluations, mass-analysed ion kinetic energy spectra (MIKES) and collision activated (CA) MIKES of these components confirmed their respective identities. Our findings from the combination of HPLC photodiode array acquisition and FAB-mass spectrometry suggest we have detected the presence of a previously unreported sinefungin analogue.

Adenosine↗
PubMed1990

Potato virus Y helper component protein is associated with amorphous inclusions.

The distribution of the helper component (HC) protein of potato virus Y in tissues and cells of infected plants was studied by immunoblotting and immunogold labelling techniques. This HC protein was found in leaf blade and vein tissue but not in the petiole of leaves. In infected cells, the protein was localized in rod-shaped cytoplasmic inclusions known as amorphous inclusions.

Antibodies, Viral↗
PubMed1990

Sphere-linked immunodiagnostic assay (SLIDA): an electron microscopic method for detecting specific antibodies.

We have developed a sensitive method, sphere-linked immunodiagnostic assay, using specific antigens covalently bonded to microspheres for the detection of antibodies in serum. In this method, specific antigens, such as the capsid proteins of tobacco mosaic virus and tobacco etch virus, were independently, covalently bonded to plastic micropheres of 0.5 microns or 0.9 microns in diameter. The antigen-linked spheres were then exposed to normal serum or serum containing specific antibody, followed by treatment with gold-labeled secondary antibodies. The binding of the gold-labeled secondary antibodies to the specific primary antibodies on the spheres acted as an indication of the presence of the specific primary antibodies. The spheres were then examined and photographed by transmission electron microscopy. The number of gold particles bound to the spheres was counted manually using the photographs. The gold labeling was found to be specific and sensitive, enabling detection of antibodies present in highly diluted antisera. The efficiency and sensitivity of the technique for detection of antibodies were compared with those of the enzyme-linked immunosorbent assay and found to be highly sensitive. The technique was also used for testing for the presence of antibodies to herpes simplex virus as well as antibodies to Staphylococcus enterotoxin using microspheres coated with the respective antigens. We believe that this technique could be applied clinically when needed for detection of antibodies to other viruses, such as the Human Immunodeficiency Virus.

Antibodies↗
PubMed1990

Regulation of stability and synthesis of EGF-receptor mRNAs encoding for intact and truncated receptor forms.

The EGF-receptor is a proto-oncogene encoded membrane protein related to the v-erb-B oncogene product of avian erythroblastosis virus. Here we have studied the expression and stability characteristics of two forms of receptor mRNA--a 5.6 kb form that encodes for the intact transmembrane 170 kDa receptor and a 3' deleted 2.6 kb form that encodes for a 100 kDa secreted EGF-receptor. In previous studies we showed that EGF increased the synthesis of its own receptor in human cytotrophoblasts and A431 cells. Now we show that EGF stimulates the transcription of the receptor gene and blocks the degradation of transcripts, and thus elevates the level of receptor mRNA in these cells. To test the role of prior protein synthesis in these phenomena, we examined the effect of cycloheximide, and found that this reagent, either alone or in combination with EGF, leads to an increase in the level of EGF-receptor mRNA. Increases were seen in both size classes of receptor mRNA. Further analysis showed that cycloheximide enhances both synthesis and stability of receptor mRNA. While the intrinsic stability of the 3'-truncated 2.6 kb mRNA is approximately 2-fold higher than that of the 5.6 kb species, it is enhanced by more than 10-fold in the presence of cycloheximide and EGF acting in a synergistic manner. The extent of stabilization was less for the larger mRNA form. The results suggest the involvement of ligand as well as labile proteins in the control of synthesis and stability of EGF-receptor mRNA, and imply the involvement of 3' located structural features in the control of receptor mRNA stability.

Blotting, Northern↗
PubMed1989

Evaluation of the carcinogenicity of different preparations of areca nut in mice.

Areca nut has been used as a masticatory since antiquity and it is estimated that more than 10% of the world population chews it in a variety of forms. We have evaluated the carcinogenicity of different preparations of areca nut: ripe-unprocessed-sundried nut (R-UP-SD), ripe-processed-sundried nut (R-P-SD), unripe-processed-sundried nut (UR-P-SD), ripe-unprocessed-sundried-water-soaked nut (R-UP-SD-WS) and ripe-unprocessed-undried-water-soaked nut (R-UP-UD-WS) in mice following diet-feeding or oral feeding for 12 months. Only unprocessed areca nuts (R-UP-SD, R-UP-SD-WS and R-UP-UD-WS), at high doses, displayed a very weak carcinogenicity.

Administration, Oral↗
PubMed1989

Bean mild mosaic virus: genome and its translation products.

Viral RNA from purified preparations of bean mild mosaic virus (BMMV) was resolved into two RNAs of mol. wt 1.5 X 10(6) daltons (R1) and 0.76 X 10(6) daltons (R2). Complementary DNA hybridizations, infectivity tests, and in-vitro translation studies established that R2 is a subgenomic RNA derived from R1. In-vitro translation studies showed that the genomic RNA (R1) coded for two major proteins of mol. wt. 40.5 kD and 25.7 kD. Of these, the 40.5 kD protein was shown to be the capsid protein that is translated in vitro from both the R1 and R2 RNAs. Time-course studies on the appearance of in-vitro translation products showed that the 25.7 kD product is the earliest product made when the genomic R1 RNA is translated. This is not one of the products of R2 RNA. Several of the characteristics of BMMV described in this paper show similarities with turnip crinkle virus (TCV) and carnation mottle virus (CarMV).

Blotting, Northern↗
PubMed1988

Modulatory influences of exogenous estrogen on MCA-induced carcinogenesis in the uterine cervix of mouse.

Placement of cotton-thread impregnated with beeswax containing methylcholanthrene (approx. 600 micrograms) inside the canal of uterine cervix of virgin adult mice results in the emergence of precancerous and cancerous lesions in the cervical epithelium. Employing this experimental cervical carcinogenesis model system, the present study evaluates the modulatory influence of exogenous 17 beta-estradiol on the incidences of precancerous and cancerous lesions in the cervical epithelium. When 17 beta-estradiol was administered weekly at the dose levels of 0.01 microgram, 0.1 microgram, 5 micrograms and 50 micrograms for 16 weeks following carcinogen-thread insertion, the cervical carcinoma incidences, as compared to that in positive control mice (76.1%), were 66.6%, 61.5%, 55.5% and 42.1%, respectively. The decline in the incidence of carcinomas at 50 micrograms/week dose level was significant (P less than 0.05). Hyperplastic and dysplastic changes did not show any definite correlation with the various treatments.

Animals↗
PubMed1988

Invariant structure in locomotion.

Biological systems are hypothesized to control behavior with reference to invariants, because this would allow the variable but robust accomplishment of tasks observed in biological behaviors. Invariants for legged locomotion are specified. Combined with observed properties of locomotion, they lead to predictions of forms of control for legged locomotion.

Animals↗
PubMed1988

Observations on the interpretation of amoebic serology in endemic areas.

Antibody to Entamoeba histolytica antigen was evaluated in cases of proven and suspected intestinal amoebiasis as well as in extra-intestinal cases from an endemic area. Screening methods included the gel diffusion precipitation test (GD), counter immunoelectrophoresis (CIE) and the indirect haemagglutination test (IHA). Control populations consisting of asymptomatic cyst passers, non-amoebic individuals, patients with giardiasis and cases of enteric fever were also screened using the above tests. All (100%) cases of amoebic liver abscess and 75-80% of hepatic amoebiasis without overt abscess formation could be detected by serology, with good correlation between the tests used. However, the interpretation of serology in cases of proven and suspected intestinal amoebiasis posed two main problems. The presence of low antibody levels even in proven cases and the persistence of antibodies due to past infection was found to reduce the diagnostic efficiency of serology for acute intestinal amoebiasis. There was no statistical difference between intestinal cases and controls when comparing either percentage of cases detected or titre of antibody obtained. The results of this study indicate that serology for acute intestinal amoebiasis can be unreliable; however, it is of undoubted value as an adjunct to clinical diagnosis in cases of hepatic amoebiasis.

Animals↗