Biomedical subjects

N Das

Publications and source records attributed to N Das.

At least 55 records · Page 3Linked to original sources

PubMed1999

Effect of angiotensin II on liposome uptake by the rat brain in vivo.

Studies have been performed to assess the possibility of using small unilamellar liposomes as therapeutic carriers to the brain of hypertensive rats. Rats were made temporal hypertensive by the infusion of angiotensin II (AII; 15 micrograms in 1 ml) through their right common carotid artery. Another control group was infused with physiological saline. Free 125iodine-BSA (125I-BSA) and 125I-BSA encapsulated liposomes (average diameter approximately equal to 100 nm) were injected in the tail vein 2 min after the infusion of AII or saline. Plasma radioactivity was monitored at different times up to 15 min when the cerebral uptake of 125I-BSA was determined. While a little variation in plasma clearance pattern of liposomes in hypertensive and control group was noticed, the uptake by cerebral tissues was markedly higher in hypertensive group. Analysis of pharmacokinetic parameters in relation to cerebral uptake indicated AII induced a short term opening of the blood-brain barrier (BBB) resulting in an increased cerebral uptake. Positively charged liposomes was found to be most effective in hypertensive state.

Angiotensin II↗

PubMed1998

Report of a hitherto unreported sequence present and expressed in a cancer cell line.

During the amplification of a 202 base pair (bp) fragment around the 61st codon of the N-ras gene, an extra band of about 150 bp in length was observed when genomic DNA from a human epidermoid carcinoma cell line was used as template. This fragment was cloned and sequenced. However, this sequence was not found in the databank. RT-PCR experiments indicated that the sequence is expressed in the cells about 8 h after serum induction. The relevant RNA hybridized to one strand of the sequence but not to the other.

Base Sequence↗

PubMed1998

Problem based learning as a curricular strategy for medical undergraduates: a tutor's experience.

This article focuses on the experiences and role of a tutor while conducting a problem based learning (PBL) exercise to facilitate the learning of biochemistry and molecular biology. A case presentation of sickle cell anemia was used to frame a module. The objective of this experimental exercise was to assess the suitability and effectiveness of problem based learning in the first year of undergraduate medical course and to practice self-assessment by tutors in this new role of a facilitator of learning through small group discussion. A tutor during such a learning session encouraged the students to apply their reasoning to analyze the problem and to develop self-directed learning skills in acquiring the knowledge appropriate to their perceived needs to work on a problem. The tutors ensured that they apply this knowledge in their work with other similar problems that they would encounter later in life.

Anemia, Sickle Cell↗

PubMed1998

Immobilization of urease from pigeonpea (Cajanus cajan L.) in polyacrylamide gels and calcium alginate beads.

Urease from pigeonpea was entrapped in polyacrylamide gel with 50% immobilization at 10% total monomer (containing 5% cross-linker) with high mechanical stability of the gel. Approximately 0.61 mg of protein could be loaded per 5 ml of gel. The immobilized enzyme had a t1/2 of approx. 200 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 degrees C. The gel strips were used 4-5 times for urea assay over a period of 6 h with less than 2% loss of activity. Approximately 50% immobilization of urease in calcium alginate was observed at 3% alginate with 0.12 mg protein/ml alginate. The resultant enzyme beads showed a t1/2 of approx. 75 days when stored in 0.1 M Tris/acetate buffer, pH 6.5, at 4 degrees C. The beads were used 4-5 times for urea assay over a period of 6 h with about 40% loss of activity. In both cases, the enzyme activity was directly proportional to the amount of immobilized enzyme. There was practically no leaching of the entrapped enzyme over a period of 48 h from either of the polymers. Both the immobilized enzyme preparations were used to analyse the blood urea of some clinical samples from the University hospital. The results obtained compared favourably with those obtained by the usual method employed in the clinical pathology laboratory.

Acrylic Resins↗

PubMed1998

Histidine decarboxylase gene in the mouse uterus is regulated by progesterone and correlates with uterine differentiation for blastocyst implantation.

Cell-cell interactions between the blastocyst trophectoderm and uterine luminal epithelium are essential to the process of implantation. The factors that participate in these interactions or their mechanism of actions are poorly understood. Histamine has long been suspected as one of the factors that is involved in implantation. Histamine is formed from L-histidine by histidine decarboxylase (HDC). We examined the expression and regulation of HDC gene in the mouse uterus during early pregnancy and under steroid hormonal stimulation. Northern blot hybridization detected a 2.6-kb transcript of HDC messenger RNA (mRNA) in uterine poly(A)+ RNA samples. Maximum uterine accumulation of HDC mRNA occurred on days 3 and 4 of pregnancy, followed by marked declines on later days (days 5-8). In ovariectomized mice, uterine mRNA levels were up-regulated by an injection of progesterone (P4) by 6 h, and the levels were maintained through 24 h. In contrast, an injection of estradiol-17beta neither stimulated nor antagonized P4-induced HDC mRNA accumulation. P4-induced up-regulation was considerably abrogated by pretreatment with RU-486, a P4 receptor antagonist, suggesting involvement of P4 receptor. In situ hybridization detected HDC mRNA specifically in uterine epithelial cells but not in other cell types. Again, high epithelial accumulation occurred on day 4 of pregnancy. With the progression of implantation (days 5-8), HDC mRNA levels declined in the luminal epithelium surrounding the implanting blastocysts, as compared with that away from the blastocysts. Immunoreactive histamine and HDC were colocalized with HDC mRNA. Western blotting detected a 54-kDa protein in epithelial cell extracts, which also exhibited HDC activity. Expression of HDC in epithelial cells, preceding implantation on day 4, at lower levels after initiation of implantation on day 5, and its regulation by P4 suggest that this gene plays an important role in implantation.

Animals↗

PubMed1998

Biochemical and histopathological changes in respiratory system of rats following exposure to diesel exhaust.

Effect of exposure to diesel exhaust (DE) for different durations was evaluated using histopathological and biochemical parameters in respiratory system of the rats. Animals were exposed to 1 part DE diluted with 5 parts of clean air in a simulation chamber for 15 min/day for 1, 7, 14 and 21 days. After completion of various exposures, biochemical parameters including elastase inhibitory capacity (EIC) and protein content of the bronchial airway lavage (BAL) and histopathological changes along with lung/body weight ratio were assessed. The elastase inhibitory capacity (an index of the protection against destruction of elastin, a lung connective tissue) was maximum at 1 week indicating thereby that the body renders protection against injury by increasing EIC levels in the initial phase. However, protein content in the BALF increased after 1 week and reached maximum at 2 weeks. Histopathological changes followed similar time course of pattern with accumulation of macrophages and protein exudation. Prolonged exposure up to 3 weeks, however was accompanied by chronic inflammatory changes and thickening of alveolar septa and blood vessels. Changes in lung/body weight ratio and suspended particulate matter (SPM) deposited on filters (simulation chamber) correlated well with EIC, protein content in BALF and histopathological changes. The biochemical findings accompanied with chronic structural changes in the lungs of rats following exposure to DE could be relevant to the clinical observation of increased incidence of chronic lung diseases after continued DE exposure.

Air Pollutants↗

PubMed1997

Expression of betacellulin and epiregulin genes in the mouse uterus temporally by the blastocyst solely at the site of its apposition is coincident with the "window" of implantation.

In the mouse, the process of implantation is initiated by the attachment reaction between the blastocyst trophectoderm and uterine luminal epithelium that occurs at 2200-2300 h on day 4 (day 1 = vaginal plug) of pregnancy. Several members of the EGF family are considered important in embryo-uterine interactions during implantation. This investigation demonstrates that the expression of two additions to the family, betacellulin and epiregulin, are exquisitely restricted to the mouse uterine luminal epithelium and underlying stroma adjacent to the implanting blastocyst. These genes are not expressed during progesterone-maintained delayed implantation, but are rapidly switched on in the uterus surrounding the implanting blastocyst following termination of the delay by estrogen. These results provide evidence that expression of betacellulin and epiregulin in the uterus requires the presence of an active blastocyst and suggest an involvement of these growth factors in the process of implantation.

Animals↗

PubMed1997

Modulation of cerebral calcium homeostasis in rats by angiotensin II in vivo.

The uptake of 45Ca2+ by different regions of the brain was determined in anaesthetised rat after infusing angiotensin II (AII; 14 micrograms in 1 ml) through the carotid artery. The control animals (C) were infused with physiological saline. 45Ca2+ was injected in the tail vein 2 min after the infusion of AII or saline. Plasma radioactivity was monitored until euthanasia at different times post injection when the cerebral uptake of 45Ca2+ was determined. While the plasma turnover of 45Ca2+ was similar in AII and C animals, the uptake was markedly higher in AII vs. C at the different brain sites at all times. Kinetic analysis suggested that AII induced a short term increase in Ca2+ transport across the blood-brain barrier and also in the cellular uptake. The effect of AII was receptor mediated being abolished by saralasin, an AII antagonist, and appeared to be at least in part independent of its pressor effect.

Angiotensin II↗

PubMed1997

Uterine preparation for implantation in the mouse is associated with coordinate expression of estrogen-responsive finger protein and estrogen receptor.

Estrogen-responsive finger protein (Efp) is a member of the RING finger-containing proteins. It is a putative transcription regulator that is speculated to amplify estrogen actions in the target organs. The present study examined the temporal and cell-type specific expression of Efp mRNA in the periimplantation mouse uterus (days 1-8) by Northern and in situ hybridization. Consistent with previous observation, a 6.0-kb transcript was detected in uterine RNA samples. The steady-state levels of Efp mRNA in whole uterine RNAs exhibited modest fluctuations during the periimplantation period. However, results of in situ hybridization showed cell-specific distribution of Efp mRNA in the periimplantation uterus in a temporal manner. On days 1-2 of pregnancy, distinct autoradiographic signals for Efp mRNA were detected in uterine luminal and glandular epithelia. However, on days 3 and 4, the accumulation of Efp mRNA occurred in stromal cells, in addition to its presence in the epithelium. After initiation of implantation on day 5, signal intensity was higher in stromal cells immediately surrounding the implantation chamber. However, on days 6-8, Efp mRNA was localized throughout the deciduum. To determine whether ovarian steroids influence the uterine expression of this gene, cell-specific localization of Efp mRNA was examined in the adult ovariectomized mouse uterus at 12 hr and 24 hr after an injection of estradiol-17 beta (E2) or progesterone (P4). An injection of E2 caused a modest increase in Efp mRNA levels in the luminal and glandular epithelia, while stromal cell accumulation occurred after an injection of P4. These results suggest that Efp is involved in P4/E2-mediated uterine cellular proliferation and/or differentiation. Since previous studies showed that Efp is colocalized with estrogen receptor (ER) in target cells, we also examined the cell-specific nuclear localization of ER in the periimplantation mouse uterus by immunohistochemistry. On days 1-2 of pregnancy, nuclear staining was distinct in the luminal epithelium and glandular epithelium. In contrast, nuclear staining was noted in stromal cells on days 3-4. However, glandular epithelium showed distinct staining during this period. On day 5, stromal cells surrounding the lumen at the mesometrial site were ER-positive. On days 6-8, the intensity of nuclear staining was very low, and limited to the cells adjacent to the luminal epithelium. The coordinate expression of Efp and ER in specific uterine cells during the preimplantation period (days 1-4) was consistent with the absolute requirement for estrogen in the preparation of the uterus for implantation. Since the amount of estrogen required for the preparation of the uterus is minuscule as compared to that of P4, these results suggest that the coexpression of Efp with ER is involved in amplifying the estrogen effects required for uterine cell proliferation and/or differentiation during implantation. In contrast, discoordinate expression of Efp and ER during the postimplantation period (days 5-8) suggests primary dependence of the decidualization process on P4, but not estrogen.

Animals↗

PubMed1997

Cerebral calcium fluxes and calcium homeostasis in the rat: a minimal model.

Disturbance of calcium homeostasis and unregulated increase in intracellular calcium have been implicated in cell damage and cell death in the central nervous system in particular. To determine the specific pathway(s) of cerebral Ca transport of importance in a pathophysiological situation, we have measured long term Ca flux in brain in vivo in rat, and developed a kinetic model incorporating physiologically relevant pathways of cerebral Ca transport. 45Ca was injected into a tail vein in conscious rats. Plasma 45Ca was monitored up to 4 days post-injection and 45Ca uptake determined in samples of cerebrospinal fluid (CSF) and at several sites of brain at euthanasia. Uptake of the tracer by tissues peaked after 1 h, isotopic equilibration taking longer. The uptake at hippocampus was the highest. Computer simulation of the kinetics of the plasma, CSF and tissue data was performed using a compartmental model, which included two subcompartments (intra- and extra-cellular) and two pathways from plasma to the brain: directly across the blood-brain barrier and via CSF, which included a delay. The analysis based on this model enabled estimation of the fractional rates of transport of Ca to cerebral and noncerebral tissues across all the barriers of the model.

Animals↗

PubMed1997

Importance of laccase in vegetative growth of pleurotus Florida.

Mycelial culture of Pleurotus florida produced highest extracellular laccase in optimum growth medium. At least two laccases (L(inf1) and L(inf2)) were shown to be present in the culture filtrate. Low-laccase-yielding mutants with impaired L(inf2) activity had poor mycelial growth and could not form fruit body, whereas the revertants from the same mutants were similar to the parent in mycelial growth and fruit body formation.

Journal Article↗

PubMed1997

Cadmium induced nephrotoxicity in rats.

Onset of hypertension and nephropathy after 1,2, and 4 weeks of exposure to cadmium chloride (1 mg/kg, ip) was studied in rats by measuring changes in blood pressure and renal function (urinary output, electrolytes, serum creatinine, inulin clearance and Na+K+ ATPase). Significant decrease in body weight and rise in blood pressure were observed as early as one week of exposure while microalbuminuria was detected in 50% of the animals after 2 weeks. Na+K+ ATPase, a renal tubular enzyme, was depressed after 1 week with maximum lowering occurring after 4 weeks. There were no detectable changes in fluid intake, urine output, electrolytes, inulin clearance and serum creatinine even after 4 weeks. It is concluded that hypertension and tubular lesion set in earlier than glomerulopathy as indicated by microalbuminuria and the latter could be the consequence of rise in blood pressure.

Animals↗

PubMed1997

Involvement of renin-angiotensin system in hypertensive effect of cadmium in rats.

Role of renin-angiotensin system in hypertension induced by cadmium chloride (CdCl2) in rats has been investigated. Intravenous administration of CdCl (1 mg/kg) produced a biphasic response i.e. a transient fall followed by a marked and consistent rise in blood pressure. The peak hypertensive effect was accompanied by raised PRA levels. Pretreatment with captopril (1 mg/kg, i.v.) losartan (1 mg/kg, i.v.) or captopril + losartan attenuated the pressor response to Cd by 62%, 42% and 100% respectively in separate groups. Central administration of Cd (10 micrograms/rat, i.c.v.) showed a biphasic response similar to that observed after i.v. route. However, it was not accompanied by raised PRA levels. Prior treatment with losartan (10 micrograms/rat, i.c.v.) completely abolished the pressor response to Cd (i.c.v.) whereas it was not affected significantly by captopril (10 micrograms/rat, i.c.v.). On the other hand, centrally administered losartan only partially reduced the pressor response to i.v. Cd. The results are discussed in light of a differential involvement of central vs peripheral renin-angiotensin system in the hypertensive effect of Cd.

Animals↗

PubMed1996

The effect of age on calcium dynamics in rat brain in vivo.

Different biochemical changes accompany development and ageing. However, the time frame for a particular biochemical change may be different than that for another. In the ageing brain, neurological deficits related to ageing have been suggested to be due to a breakdown of calcium (Ca++) homeostasis, and an increase in intracellular Ca+2. To understand the dynamics of calcium in CNS in relation to normal ageing, we have determined 45Ca++ uptake by the different regions of brain in young (3 months) and aged (15 months) rats after a single i.v. injection of 90 microCi/kg 45Ca++. In the a-ed group, the initial plasma contents of the tracer were higher than in the young rats (3 months). The mean values of uptake (as fraction of injected dose/g x 10(5)) of 45Ca at different sites were higher in the 15-month-old animals than in the young rats (viz. cortex: 50 vs. 26; hippocampus: 90 vs. 46 and putamen: 54 vs. 30 at 120 min). Computer simulation of the uptake data indicated that the values of most of the fractional transport rates were similar or lower in the aged compared to the controls. However, the steady state ratio of intra/extracellular Ca++ was higher in the 15-month-old animals, suggestive of intracellular accumulation of Ca++.

Aging↗

PubMed1995

Molecular cloning and sequence analysis of a seed-expressed acyl carrier protein (ACP) gene from Brassica campestris (Agrani).

We describe here the nucleotide sequence of the Brassica campestris ACPSF1 gene which encodes a seed-expressed acyl carrier protein (ACP). The 3600 bp sequence consists of 1740 bp upstream of the translation start codon, 828 bp spanning the coding region which is interrupted by three introns and 1032 bp downstream of the stop codon. Using a ACPSF1 gene-specific probe, transcripts could be detected in developing seeds, but not in leaves. The gene is now the only known member that represents group I seed-expressed ACP multigene family of Brassica species. The 5' flanking sequence of the ACPSF1 gene was examined for putative transcriptional regulatory elements. A sequence alignment of the 5' flanking regions of the available seed-expressed ACP genes of Brassica species showed some conserved regions which might have some common regulatory significance.

Acyl Carrier Protein↗

PubMed1995

Physical and motor fitness in twins.

Thirty pairs of monozygotic (MZ) and 20 pairs of dizygotic (DZ) twins, of both sexes, were studied to estimate the role of genetic and environmental factors determining fitness measurements comprising vital capacity (VC), vertical jump, flexibility, agility, and PFI score. Intra-pair variances for VC, vertical jump, and heart rate were significantly smaller (p < 0.05-0.01) in MZ than in DZ twins, where values for flexibility, agility, and PFI were insignificant. Intra-pair correlations for VC, vertical jump, and heart rate were higher (p < 0.01) in MZ than in DZ twins where the opposite was found in the case of flexibility and agility. The correlation value for PFI was higher in both MZ and DZ twins. Following adjustment for physical characteristics including age, weight, and height, none of the results of all the residual fitness measurements were similar to the unadjusted values. Both unadjusted and residual variables with smaller intra-pair variances showed higher heritability estimates. These results suggest that VC, vertical jump, and heart rate are influenced more by genetic factors than environmental factors where the inverse is true of flexibility, agility, and PFI. Thus, the genetic and environmental influence of all the fitness measurements, except VC, more or less depend upon physical characteristics in this study.

Adolescent↗

PubMed1995

Glycoside-bearing liposomal delivery systems against macrophage-associated disorders involving Mycobacterium leprae and Mycobacterium tuberculosis.

Asiaticoside, a plant glycoside with rhamnose as end sugar and having microbicidal properties was tested against Mycobacterium leprae and Mycobacterium tuberculosis both in vivo and in vitro. As rhamnose is reported to have no tissue specificity, corchorusin D having glucose as end sugar was used for targeting with an equimolar proportion of asiaticoside in liposomal form for testing the drug value. Results showed that liposomal asiaticoside had better microbicidal property against M. leprae and M. tuberculosis when compared to that of free asiaticoside whereas liposomes containing asiaticoside and corchorusin D were found to be equally or more active in comparison to liposomal asiaticoside alone. It is inferred that appropriate glycosides, if used in liposomal form (incorporated or covalently grafted) have enhanced drug efficacy and such glycoside bearing liposomes as targeted delivery systems could be used for chemotherapeutic control of several other diseases.

Animals↗

PubMed1993

Physical and motor fitness level of Indian school-going boys.

A cross-sectional study of physical and motor fitness measurements was undertaken on 629 healthy Indian (Bengalee) school-going boys of 9-18 years. The study brought to light gradual increase in physical and motor fitness measurements with the advancement of age except physical fitness score. Major increments were recorded between 13 and 15 years of age. All the fitness test scores showed significant positive correlations with age, height and weight but Dash, Shuttle Run and PFI showed significantly negative relationship. Indian boys of the present study were superior in Sit and Reach and inferior in Vertical Jump to the Belgian boys of comparable ages. These boys showed higher values in Vertical Jump than American boys after the age of 13. Dash and Shuttle Run test scores of Indian boys fall between 15th to 25th and 30th to 45th percentiles of American Standard respectively. Besides, American boys are superior in Grip Strength to Indian boys. Percentile values of physical and motor fitness test scores of Indian (Bengalee) boys are, therefore, useful for determining their present fitness status and potentiality in that particular community for specific sports activity.

Adolescent↗