Biomedical subjects
S Subramanian
Publications and source records attributed to S Subramanian.
Development of alginate-based slow release formulation of Bacillus sphaericus for controlling Culex quinquefasciatus.
Seven types of formulations were prepared as granules using the larvicidal factor of Bacillus sphaericus and different concentrations of calcium alginate which was used as matrix to immobilize and entrap the active ingredient (ai). All formulations were tested in disused wells against Culex quinquefasciatus at the rate of 15 kg ai per hectare. Among the seven types tested, the type 2 which contained 5% calcium alginate as immobilizing agent, exhibited the maximum larvicidal activity. Persistent control in breeding was noticed for 8 weeks with this formulation type.
Quantitative analysis of transient gene expression in mammalian cells using the green fluorescent protein.
The green fluorescent protein (Gfp) has been used as a reporter, along with flow cytometric analysis, to follow the dynamics of gene expression in transiently transfected mammalian cells. Gene transfer conditions for lipofection were optimized. The highest fraction of transfectants were obtained when lipid-DNA complexes were formed with 6 microliters lipid and 1 microgram DNA for chinese hamster ovary (CHO) cells and with 9 microliters lipid and 2 micrograms DNA for NIH/3T3 cells. Chinese hamster ovary cells were monitored for Gfp expression and growth for 6 days following transfection. An initial decrease in viability for 36 h was observed after which cell growth followed exponential kinetics with increasing viability. Intracellular accumulation of recombinant protein peaked at 24 h post-transfection and then decreased with first order kinetics at a rate comparable to the specific growth rate. It appears that dilution by growth accounts for the decrease of Gfp in the biomass. Immunofluorescent staining of Gfp and subsequent flow cytometric analysis of transfected cells revealed a linear correlation between the green fluorescence and immunofluorescence. This indicates that green fluorescence is a quantitative measure of intracellular Gfp in single cells in spite of the dynamics of post-translational modifications involved in the conversion of expressed protein into its fluorescent form. A structured model has been formulated to describe the observed kinetics of gene expression and fluorophore formation. The model accurately predicts experimental trends and suggests that the fraction of non-fluorescent Gfp is significant only during the initial period of gene expression.
Hormonal modulation of riboflavin carrier protein secretion by immature rat Sertoli cells in culture.
We report here that a protein species with biochemical and immunological similarity with chicken egg riboflavin carrier protein (RCP) is synthesized and secreted by immature rat Sertoli cells in culture. When quantitated by a specific heterologous radioimmunoassay, optimal concentrations of FSH (25 ng/ml) brought about 3-fold stimulation of RCP secretion. FSH, in the presence of testosterone (10(-6) M) brought about 6-fold stimulation of secretion of RCP over the control cultures which were maintained in the absence of these two factors. The aromatase inhibitor (1,4,6-androstatrien-3,17-dione) curtailed 85% of the enhanced secretion of RCP, suggesting that the hormonal stimulation is mediated through in situ synthesized estrogen and this could be confirmed with exogenous estradiol-17 beta which brought about 3-fold enhancement of secretion of RCP at a concentration of 10(-6) M. When tamoxifen (10 microM) was added along with FSH and testosterone, there was 75% decrease in the enhanced secretion of RCP. Addition of this anti-estrogen together with exogenous estradiol resulted in 55% decrease in elevated levels of RCP. Cholera toxin (1 microgram/ml) and 8-bromo-cyclic AMP (0.5 mM) mimicked the action of FSH on the secretion of RCP thus suggesting that FSH stimulation of RCP production may be mediated through cyclic AMP. These findings suggest that estrogen mediates RCP induction in hormonally stimulated Sertoli cells presumably to function as the carrier of riboflavin to the developing germ cells through blood-testis barrier in rodents.
AgNORs and their relationship to cell size, histological grade, lymph node involvement, metastases, and survival pattern in carcinoma of the breast: a study from south India.
An AgNOR count using the Smith and Crocker [Histopathology 12:113-125, 1988] method of staining was performed on 200 cases of carcinoma of the breast. A count of coarse AgNORs per nucleus was made on 50 random cells and the mean of their number per nucleus calculated. The relationship of a single variable "AgNOR count" to other variables such as cell size, histological grade, number of positive ipsilateral axillary lymph nodes, and presence of metastasis in regions other than the ipsilateral axillary lymph nodes was found using a univariate method of analysis. Also, the effect of different independent variables, e.g., number of AgNORs, cell size, histological grade, number of positive axillary lymph nodes, and metastasis on a single variable, i.e., 4-year period of survival, was also assessed by a univariate method of statistical analysis. It was found that the AgNOR count was significantly related to the cell size, histological grade, and presence of metastasis. Large cells, grade III tumors, and neoplasms with evidence of metastasis showed larger numbers of AgNORs in their nuclei. It was observed that the number of AgNORs significantly affected the 4-year survival of patients. The higher the AgNOR counts, the poorer were the chances of surviving for 4 years. The other factors that influenced survival in the present study were the number of positive axillary lymph nodes and metastasis to sites other than axillary lymph nodes.
Natural history, trend of prevalence and spectrum of manifestations of Bancroftian filarial disease in Pondicherry (South India).
The study examines the changes in the disease parameters of lymphatic filariasis over a period of time based on three surveys during 1957, 1986 and 1992 in Pondicherry, South India. The overall prevalence of filarial disease in the three surveys was 4.7, 6.7 and 9.9% respectively. It was significantly higher in males (1957:5.3%; 1986:13.7%; 1992:18.8%) when compared to females (1957:3.8%; 1986:2.3%; 1992:2.7%) in all the three surveys (P <0.05). The overall prevalence of acute adenolymphangitis declined from 1.0 in 1957 to 0.2 in 1986 and 0.04% in 1992. While the prevalence of hydrocele showed an increasing trend from 2.7 in 1957 to 11.9 in 1986 and 17.3% in 1992, the prevalence of lymphoedema (1.9 in 1957; 1.9 in 1986 and 1.8% in 1992) was stable over the same period. The prevalence of disease was relatively higher in all age groups of both male and female population in 1992 when compared either to 1957 or 1986. Similarly a monotonic increase in the prevalence of hydrocele was observed in all age groups in 1992 when compared to previous surveys. The implications of the changes in prevalence of the chronic manifestations when compared to the changes in the acute manifestations over a period of 35 years are discussed.
Spontaneous resolution of antenatally diagnosed adrenal masses.
Four infants had adrenal masses detected prenatally, through ultrasonography, between 18 and 30 weeks' gestation. Two were predominantly cystic, and two were solid. The sizes ranged from 0.8 to 1.5 cm. There were no associated prenatal maternal complications or stress factors. The urine vanillylmandelic acid levels at birth were normal in three infants. Two infants had a documented decrease in mass size at birth (compared with the last intrauterine study). All masses had a progressive decrease in size after birth, and ultrasound results were normal at 6 to 12 weeks of age. All four patients are well, with normal study results, at 2 to 5 years of age.
Past exposure and the dynamics of lymphatic filariasis infection in young children.
This study utilizes parallel, longitudinal entomological and parasitological data collected during a 5-year vector control programme in Pondicherry, South India, to quantify Wuchereria bancrofti transmission from the vector to the human population. A simple mathematical model, derived from the standard catalytic model, is used to examine the hypothesis that current infection prevalence in young children is a dynamical function of their cumulative past exposure to infective bites. Maximum likelihood fits of the model to the observed data indicate a constant child infection rate with age, above a threshold representing the pre-patent period, or equivalently, the cumulative biting intensity required to produce patent infections. Extrapolation of the model allows the crude estimation of the equilibrium microfilaria age-prevalence curve due to control. The results suggest that vector control alone may have little impact on the overall age-prevalence of infection even when sustained for long periods. These observations are discussed in terms of the likely impact of density dependent mechanisms, such as acquired immunity, on model predictions.
Antigenic similarities among biotin-binding proteins.
Using polyclonal antisera to avidin, streptavidin, and biotin binding protein-II (BBP-II), the extents of immunological cross-reactivities shared by this family of biotin-binders were investigated. In Western blot analysis, varying degrees of cross-reactivities among these proteins depending on the antisera used was observed. Using liquid phase radioimmunoassay, evidence for the existence of common antigenic determinants shared by all the biotin-binders was deduced. Antibodies directed against such epitopes inhibited the binding of [3H]biotin to as well as displace the bound ligand from all the three high affinity biotin-binders in a dose dependent manner.
Active immunization of rats with chicken egg thiamin carrier protein results in early embryonic loss at periimplantation stages.
Active immunization with chicken egg white thiamin carrier protein (TCP) was performed to assess the functional importance of the vitamin carrier during gestation in rats. Towards this, fertile female rats were immunized with heterologous TCP and when the circulatory titres of anti-TCP IgG were high, these animals were mated with fertile male rats. Progression of pregnancy was monitored by measuring circulatory progesterone levels. A sudden fall in the steroid hormonal levels around day 8 post coitus was observed. Histological examination of the uterine tissue sections on day 7 revealed that active immunization with TCP affected the blastocyst viability resulting in unsuccessful implantation and hence pregnancy termination.
Establishment of the functional importance of thiamin carrier protein in pregnant rats by using monoclonal antibodies.
Monoclonal antibodies (mAbs) to chicken thiamin carrier protein (TCP) have been produced by hybridoma technology to identify the crucial epitopes involved in bioneutralization of the vitamin carrier. The monoclonality of these mAbs (A4C4, F3H6, H8H3, C8C1 and G7H10) was sought to be confirmed by sub-class isotyping; they all belong to IgG1, k type. The epitopes recognized by all the five mAbs are conserved in TCP from the chicken to the rat as assessed by liquid phase RIA and immunoprecipitation of 125I-labelled proteins from pregnant rat serum. Among these mAbs. passive immunization of pregnant rats with the mAb C8C1 only on three consecutive days (day 10, 11 and 12) resulted in embryonic resorption. These results demonstrate the importance of epitopic structure specified by the mAb C8C1 on TCP during pregnancy in rats.
Hormonal modulation of secretion of immunoreactive riboflavin carrier protein by adult rat Leydig cells in vitro.
Adult rat Leydig cells in culture synthesize and secrete riboflavin carrier protein (RCP) as demonstrated by [35S]-methionine incorporation into newly synthesized proteins followed by immunoprecipitation as well as specific radioimmunoassay. LH stimulates the secretion of RCP 4-fold which could be inhibited upto 75% by an aromatase inhibitor. 8-bromo-cyclic AMP and cholera toxin could mimic the LH stimulated secretion of the carrier protein. The extent of stimulation of RCP secretion brought about by exogenous estradiol-17 beta is comparable to that of LH. The antiestrogen tamoxifen, when added along with either LH or estrogen, inhibited the stimulated levels significantly. These results show that the estrogen-inducible riboflavin carrier is secreted by Leydig cells under positive regulation of LH.
Near atomic scale studies of electronic structure at grain boundaries in Ni3Al.
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Magnetic anisotropies in body-centered-cubic cobalt films.
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Oxidation state of mercury in HgBa2(Ca0.86Sr0.14)2Cu3O8+ delta studied by x-ray photoelectron spectroscopy.
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High-performance liquid chromatographic determination of 4,4'-dihydroxybenzophenone-2,4-dinitrophenylhydrazone in plasma.
An analytical method has been developed for the determination of 4,4'-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (I, trade name A-007) in plasma. Plasma samples are primed with the internal standard, 2,2'-dihydroxybenzophenone-2,4-dinitrophenylhydrazone (II), deproteinized with acetonitrile, centrifuged and filtered prior to assay. The components are then separated on a reversed-phase column with retention times of 4.4 and 6.0 min for I and II, respectively. Ultraviolet detection at 365 nm was employed and little interference with the analyte or the internal standard was noted from other plasma components. This method has been applied to the plasma of rats and monkeys doses for pharmacokinetic and toxicity studies.
Frequency distribution of Wuchereria bancrofti infection in the vector host in relation to human host: evidence for density dependence.
This paper uses detailed entomological data from Pondicherry to compare the microfilaria distribution in vector with that of human and also to examine the evidence for the operation of density dependence on parasite transmission. Analysis showed that the distribution in vector is similar to that in human. The expected distribution derived from the fit of a zero-truncated negative binomial to the human data, closely reflected the observed microfilaria distribution in the vector. This implies that a relatively large proportion of observed microfilaria negatives in the vector population may be true zeros, as observed in human, arising from the biting on true negatives (as yet uninfected, with unmated female worms or immune) in humans, rather than attributable to the blood sampling process. Further it was found that both the prevalence of infection and the degree of parasite aggregation in the vector population falls significantly with parasite stage, implying the operation of density dependence, perhaps via parasite-induced vector mortality.
Single cell analysis demonstrating somatic mosaicism involving 11p in a patient with paternal isodisomy and Beckwith-Wiedemann syndrome.
Partial isodisomy of 11p has been observed in some patients with Beckwith-Wiedemann syndrome. In this study, we demonstrate somatic mosaicism directly through PCR and single cell analysis on blood lymphocytes from a patient with Beckwith-Wiedemann syndrome. Whole genome amplification was performed on single cells and the resultant product was subjected to locus specific microsatellite marker analysis using PCR. Two populations of cells were detected, a population of cells with normal biparental inheritance for chromosome 11 and a population of cells with partial paternal isodisomy of 11p between markers D11S922 (11p15.5) and D11S904 (11p14-p13). These results are consistent with somatic recombination resulting in mosaicism for paternal isodisomy. The use of single cell PCR is ideal for studying the distribution of mosaicism within and between tissues and has been used in this study to identify a cell line with uniparental disomy in a patient with Beckwith-Wiedemann syndrome.