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Biomedical subjects

S Samanta

Publications and source records attributed to S Samanta.

At least 19 recordsLinked to original sources
PubMed2007

Interannual consistency in canopy stomatal conductance control of leaf water potential across seven tree species.

We investigated interannual variability of canopy transpiration per unit ground area (E (C)) and per unit leaf area (E (L)) across seven tree species in northern Wisconsin over two years. These species have previously been shown to be sufficient to upscale stand-level transpiration to the landscape level during one growing season. Our objective was to test whether a simple plant hydraulic model could capture interannual variation in transpiration. Three species, wetland balsam fir (Abies balsamea (L.) Mill), basswood (Tilia Americana L.) and speckled alder (Alnus rugosa (DuRoi) Spreng), had no change in E (C) or E (L) between 2000 and 2001. Red pine (Pinus resinosa Ait) had a 57 and 19% increase in E (C) and E (L), respectively, and sugar maple (Acer saccharum Marsh) had an 83 and 41% increase in E (C) and E (L), respectively, from 2000 to 2001. Quaking aspen (Populus tremuloides Michx) had a 50 and 21% decrease in E (C) and E (L), respectively, from 2000 to 2001 in response to complete defoliation by forest tent caterpillar (Malascoma distria Hüber) and subsequent lower total leaf area index of the reflushed foliage. White cedar (Thuja occidentalis L.) had a 20% decrease in both E (C) and E (L) caused by lowered surface water in wetlands in 2001 because of lower precipitation and wetland flow management. Upland A. balsamea increased E (L) and E (C) by 55 and 53%, respectively, as a result of release from light competition of the defoliated, overstory P. tremuloides. We hypothesized that regardless of different drivers of interannual variability in E (C) and E (L), minimum leaf water potential would be regulated at the same value. Minimum midday water potentials were consistent over the two years within each of the seven species despite large changes in transpiration between years. This regulation was independently verified by the exponential saturation between daily E (C) and vapor pressure deficit (D) and the tradeoff between a reference canopy stomatal conductance (G (S)) and the sensitivity of G (S) to D, indicating that trees with high G (S) must decrease G (S) in response to atmospheric drought faster than trees with low G (S). Our results show that models of forest canopy transpiration can be simplified by incorporating G (S) regulation of minimum leaf water potential for isohydric species.

Plant Leaves↗
PubMed2006

OCA1 in different ethnic groups of india is primarily due to founder mutations in the tyrosinase gene.

Oculocutaneous albinism (OCA) is a heterogeneous group of autosomal recessive disorders characterized by an abnormally low amount of melanin in the eyes, skin and hair, and associated with common developmental abnormalities of the eye. Defects in the tyrosinase gene (TYR) cause a common type of OCA, known as oculocutaneous albinism type 1 (OCA1). The molecular basis of OCA has been studied extensively in different population groups, but very little information is available on Indian patients. Our investigation covering thirteen ethnic groups of India, some representing >20 million people, revealed that among 25 OCA families 12 were affected with OCA1, and that these cases were primarily due to founder mutations in TYR. We detected nine mutations and eight SNPs in TYR, of which six mutations (five point mutations & one gross deletion) were novel. In contrast to most reports describing compound heterozygotes, the presence of homozygotes in 10 out of the 12 pedigrees underscores the lack of intermixing between these ethnic groups in India. Haplotype analysis suggested a few founder chromosomes causing the disease in the majority of the patients. Direct detection of the mutations prevalent in specific ethnic groups could be used for carrier detection and genetic counselling.

Albinism, Oculocutaneous↗
PubMed2005

Heavy metals in water of the rivers Hooghly and Haldi at Haldia and their impact on fish.

The paper deals with the measurement of five heavy metals viz., Cd, Cu, Mn, Pb and Zn in water of the rivers Hooghly and Haldi at Haldia during June 1999 to October 2002. The industrial effluent out fall (OF) at Patikhali, Haldia was also taken as sampling site along with above out fall (AOF) and below out fall (BOF) sites. Most of the metals exhibited their least concentration at the sampling site above the Haldia industrial area of river Hooghly. The average concentrations of the studied metals were Cd 2-14, Cu 5-19, Mn 8-88, Pb 17-41 and Zn 22-37 microg l(-1). Comparison of the data with the Criterion Continuous Concentration (CCC) of USA revealed that Cd, Cu and Pb were the pollutants present at alarming level to disturb the aquatic life process in the zone. The effect was found to reflect on the tissue level aberrations in the residential fishes. The other two metals viz., Mn and Zn were probably less harmful to the aquatic ecosystem. In India, necessity is felt to develop the CCC values, which will be more appropriate for protection of aquatic environment than comparing with drinking water standards.

Animals↗
PubMed2005

Evaluation of fluorenhymustine as a rationally designed novel anticancer agent.

AIM: To develop a rationally designed new nitrogen mustard namely Fluorenhymustine (compound 2), where N,N'-bis(2chloro-ethyl)amino group, the established anticancer functionality, is attached to the 2-ethyl fluorenone hydantoin moiety. MATERIALS AND METHODS: Starting from fluorenone hydantoin, a 3-step synthetic procedure was followed to obtain the title compound. 4-(4-Nitrobenzyl)pyridine was used to assess its chemical alkylating activity. Murine tumors (Ehrlich ascites carcinoma (EAC) and Sarcoma-180 (S-180)) were used to assess its in vivo activity. Its cytotoxicity was determined in vitro in MCF-7 human breast tumor cell line, toxicity - in vivo in normal and EAC bearing mice. 3H-Thymidine and 3H-Uridine were employed to study its inhibitory effect on DNA and RNA synthesis respectively in S-180 tumor cells in vitro. RESULTS: Alkylating activity of fluorenmustine exceeded that of N-di(2-chloroethyl)amine used as a standard alkylating compound. It has displayed an excellent and reproducible antitumor activity in vivo against EAC and S-180 comparable to that of 5-fluorouracil judging by the increase in median survival times of treated animals. It also significantly increased the life span of mice bearing advanced tumors for 6 days before the drug challenge. However in vitro screening in MCF-7 did not reveal any significant cytotoxicity. The compound did not adversely affect hematopoiesis at its optimum dose. Drug-induced hepatotoxicity and nephrotoxicity were also not detected. It inhibited the synthesis of DNA and RNA in S-180 tumor cells at 8 microM concentration. CONCLUSION: Results indicated promising chemotherapeutic potential of Fluorenhymustine.

Animals↗
PubMed2004

The value of Bilicheck as a screening tool for neonatal jaundice in term and near-term babies.

AIMS: To determine the accuracy of Bilicheck in assessing serum bilirubin. To evaluate the effectiveness of Bilicheck as a screening device in a population of jaundiced term and near-term babies. METHODS: Prospective evaluation of paired Bilicheck measurements and serum bilirubin in 300 babies. RESULTS: There was a strong correlation between Bilicheck and serum bilirubin. The mean difference between Bilicheck and serum bilirubin was -10.7 micromol/l, but the 95% limits of agreement were wide at -80 micromol/l to +60 micromol/l. Bilicheck identified significant jaundice (serum bilirubin above 250 micromol/l) with a sensitivity (95% confidence interval) of 91% (88% to 94%) and specificity of 66% (60% to 71%). The area under the receiver operator characteristic curve was 0.85. There were five false negatives, all of whom had a serum bilirubin below 300 micromol/l. If Bilicheck had been used as a screening device, there would have been a 55% decrease in blood samples taken in these babies. CONCLUSION: Bilicheck cannot be used to measure serum bilirubin in term and near-term babies with jaundice, but is an effective screening method, which can be used to safely reduce the number of blood tests in these babies.

Bilirubin↗
PubMed2003

Evaluation of naphthalmustine, a nitrogen mustard derivative of naphthalimide as a rationally-designed anticancer agent.

Naphthalmustine, 2-[2-[bis-(2-chloroethyl)amino]ethyl]-1H-benz[de]isoquinoline-1,3-dione (Compound 1) has been synthesized as a rationally designed new anticancer agent from N-(2-bromoethyl)naphthalimide. Its chemical alkylating activity exceeded that of nor-HN2 used as standard compound for comparison. Its antitumour efficacy was assessed in vivo in two murine ascites tumours namely Sarcoma-180 (S-180) and Ehrlich ascites carcinoma (EAC) by measuring the increase in median survival times (MST) of drug treated (T) over untreated control (C) mice. The clinical drug cyclophosphamide and the experimental compound mitonafide were used as positive controls for comparison. Compound 1 has displayed substantial and reproducible antitumoural activity in these tumours since very high remission times of treated animals were observed. Significant increase in the life span of mice bearing highly advanced tumour for 10 days before the drug challenge was also noted after its treatment. Its LD50 value was 200 mg/Kg by single i.p. injection. Its toxicity was also assessed in vivo in normal and in S-180 bearing mice by measuring drug-induced changes in hematological parameters, femoral bone marrow and splenic cellularity sequentially on days 9, 15 and 21 following drug treatment at the optimum dose of 12 mg/kg from day 1 to 7. The results indicated that the compound did not adversely affect hematopoiesis. Drug-induced hepatotoxicity and nephrotoxicity were also evaluated on those days but no such toxicities were detected. Naphthalmustine inhibits the synthesis of DNA and RNA in S-180 tumour cells. It was further screened in vitro in 4 different human tumour cell lines but no significant activity was observed in those lines.

Animals↗
PubMed2002

Safe transition from open to laparoscopic fundoplication by an established consultant--the importance of repeated audit.

BACKGROUND: Serious complications of laparoscopic fundoplication (LF) have been reported by surgeons new to LF. We investigated whether the reported benefits of LF could be realised by an established consultant, new to LF, without compromising safety, control of reflux or dysphagia rates obtained after open surgery. PATIENTS AND METHODS: Outcome of 65 consecutive open fundoplications was audited. After training in LF, this audit was compared with an identical prospective audit of 65 patients undergoing LF. RESULTS: No significant differences occurred between the two groups in relief of reflux. LF resulted in: (i) shorter postoperative stay (median 2 days versus 7 days, P < 0.001); (ii) earlier return to work (median 4 weeks versus 9 weeks, P < 0.001); (iii) shorter duration of postoperative dysphagia (median 4 weeks versus 9 weeks, P = 0.01); and (iv) less intra/postoperative complications (7.7% versus 32.3%, P < 0.001). CONCLUSIONS: LF can be introduced safely by established consultants provided that adequacy of training is confirmed by repeated audit.

Adult↗
PubMed2002

Evaluation of naphthal-NU, a 2-chloroethylnitrosourea derivative of naphthalimide, as a mixed-function anticancer agent.

Naphthal-NU, 2-[2-[3-(2-chloroethyl)-3-nitrosoureido]ethyl]-1H-benz[de]isoquinoline-1,3-dione (Compound 1) has been synthesized as a rationally designed new mixed-function anticancer agent from 1,8-naphthalic anhydride. Its chemical alkylating activity compared with CCNU as standard compound indicated that it possesses greater alkylating activity than the latter. Its antitumour efficacy was assessed in vivo in two murine ascites tumours namely Sarcoma-180 (S-180) and Ehrlich ascites carcinoma (EAC) by measuring the increase in median survival times (MST) of drug treated (T) over untreated control (C) mice. Three clinical drugs namely CCNU (lomustine), endoxan (cyclophosphamide) and 5-fluorouracil (5-FU) were used as positive controls for comparison. Compound 1 has displayed excellent and reproducible antitumoural activity having curative effects in these tumours comparable with CCNU and 5-FU. It has also significantly increased the life span of mice bearing highly advanced tumour for 10 days before the drug challenge. Its toxicity was also assessed in vivo in normal and in S-180 bearing mice by measuring drug-induced changes in hematological parameters, femoral bone marrow and splenic cellularity sequentially on days 9, 15 and 21 following drug treatment at the optimum dose of 50 mg/kg from day 1 to 7. The results indicated that the compound did not adversely affect hematopoiesis. Drug-induced hepatotoxicity and nephrotoxicity were also evaluated at its optimum dose on those days but no such toxicities were detected. It was further screened in vitro in 6 different human tumour cell lines but no significant activity was observed in those lines.

Animals↗
PubMed2001

Borrelia burgdorferi-induced inflammation facilitates spirochete adaptation and variable major protein-like sequence locus recombination.

Spirochete adaptation in vivo is associated with preferential Borrelia burgdorferi gene expression. In this paper, we show that the administration of B. burgdorferi-immune sera to IFN-gammaR-deficient mice that have been infected with B. burgdorferi N40 for 4 days causes spirochete clearance. In contrast, immune sera-mediated clearance of B. burgdorferi N40 is not apparent in immunocompetent mice, suggesting a role for IFN-gamma-mediated responses in B. burgdorferi N40 host adaptation. B. burgdorferi-immune sera also induces clearance of B. burgdorferi N40 that have been passaged in vitro 75 times (B. burgdorferi N40-75), a derivative of B. burgdorferi N40 that does not rapidly adapt in vivo in immunocompetent mice. B. burgdorferi N40-75 produce lower levels of IFN-gamma and IL-12 in mice than does B. burgdorferi N40, and the administration of these cytokines to B. burgdorferi N40-75-infected mice results in an increased spirochetal burden, further indicating that IFN-gamma-mediated events promote B. burgdorferi survival. Differential immunoscreening and RT-PCR demonstrate that IFN-gamma-mediated signals facilitate spirochete recombination at the variable major protein like sequence locus, a site for early antigenic variation in vivo, and that recombination rates by B. burgdorferi N40 are lower in IFN-gammaR-deficient mice than in control animals. These results suggest that the murine immune response can promote the in vivo adaptation of B. burgdorferi.

Adaptation, Physiological↗
PubMed2001

Dissociation of infectivity and pathogenicity in Borrelia burgdorferi.

Clonal Borrelia burgdorferi N40 (cN40) passaged 75 times in vitro (N40-75) infects mice but does not cause disease. N40-75 passaged 45 times further in vitro (N40-120) was no longer infectious and lacked genes encoded on linear plasmids 38 and 28-1, among other differences. These data suggest that B. burgdorferi cN40, N40-75, and N40-120 have distinct phenotypes that can be used to dissect the genetic elements responsible for pathogenicity and infectivity.

Animals↗
PubMed2001

Escherichia coli heat stable enterotoxin receptors & guanylyl cyclase activity in the intestinal brush border membrane of hamsters & guinea pigs.

BACKGROUND & OBJECTIVES: Although Escherichia coli heat stable enterotoxin (STa) causes diarrhoea in laboratory animals, no studies were done to find out the species specific variation of distribution of the STa receptors in laboratory animals. The present investigation evaluates the density of STa receptors and the guanylyl cyclase (GC) activity in the small intestinal epithelial cells of hamsters and guinea pigs. METHODS: Brush border membrane (BBM) was prepared from the small intestines of hamsters and guinea pigs. Receptor binding assay, GC assay and autoradiography were performed to determine the density of STa receptors, the GC activity and molecular weights of the STa binding proteins respectively. RESULTS: The receptor densities, per mg BBM protein at equilibrium, were found to be 4.1 x 10(9) and 1.5 x 10(12) in hamsters and guinea pigs respectively. The GC activity was found to be lower in STa treated hamster BBM compared to that of guinea pig. Scatchard analysis of the stoichiometric data showed a linear plot, and STa bound with association constants of 0.31 x 10(12) M-1 and 1.04 x 10(12) M-1 in hamsters and guinea pigs respectively. Autoradiographic analysis of the SDS-PAGE, revealed that 125I-STa bound apparently to a 45 kDa membrane protein in hamster and a 115 kDa membrane protein in guinea pig. INTERPRETATION & CONCLUSIONS: It appears that a lower density of STa receptor exists in hamsters compared to that in guinea pigs. STa binds with a single population of STa receptors in each species with different ligand binding affinities. Also, the molecular weights of the STa binding proteins differ in these species. Moreover, the GC activity was found to be lower in hamsters than in guinea pigs.

Animals↗
PubMed2001

Distribution of tannic acid degrading microorganisms in the soil and comparative study of tannase from two fungal strains.

A quantitative survey on microbial population including tannase producing organisms have been made from different soil samples. Most of the samples harbour negligible number of tannase producers in comparison to total microbial flora. Among the tannase producers, fungal members are more frequent than bacteria. Tannase production and tannic acid degradation have been studied in two newly isolated potent fungal strains. Both the strains produce maximum tannase at their stationary phases of growth. Enzymes produced by both the strains remain active within pH 3.5-6.0 and temperature 30-60 degrees C.

Aspergillus↗
PubMed2000

Evaluation of dimethylaminosulfonates of alkane diols as a novel group of anticancer agents.

A series of title compounds has been synthesized and evaluated by the cytotoxicity assays conducted in vitro in seven human tumor cell lines, initially in MT-4 and H-9, followed by U-937, PM-1, MCF-7, Hep-3B, and K-562. These compounds were simultaneously compared with the existing clinical drug, busulfan and also with an experimental drug, hepsulfam. IC(50) values of these agents in T-cell lymphoma and leukemic cell lines indicate that two of these agents hexsulfamyl and octsulfamyl (compounds 3 and 4) were significantly more potent than busulfan and were comparable in antileukemic activity with hepsulfam. In order to determine the effect of these agents on normal proliferating cells, the toxicity of 3 and 4 was also determined in vitro against human peripheral blood mononuclear cells (PBMC) and against murine bone marrow progenitor cells. PBMC assay data indicate that these agents were generally less toxic than hepsulfam. The results of the colony forming unit-erythroid (CFU-E) and granulocyte-macrophage colony forming unit (CFU-GM) assays, however, indicate that these agents were more toxic than hepsulfam to erythroid progenitor cells than to granulocyte-macrophage progenitors. The toxicity of octsulfamyl was further assessed in vivo in normal Swiss mice by measuring drug-induced changes in hematological parameters, femoral bone marrow cellularity and splenic cellularity as well as hepatotoxicity and nephrotoxicity on day 7 and 14 following drug treatment at the dose of 1.0 mg/kg body weight from days 1 to 5. The results indicate that the compound did not adversely affect hematopoiesis. Marginal bone marrow suppression was observed on day 7, which gradually tends to reach normalcy on day 14. The other parameters were within normal limit.

Alkanes↗
PubMed2000

Borrelia burgdorferi gene expression in vivo and spirochete pathogenicity.

Borrelia burgdorferi spirochetes that do not cause arthritis or carditis were developed and used to investigate Lyme disease pathogenesis. A clonal isolate of B. burgdorferi N40 (cN40), which induces disease in C3H/HeN (C3H) mice, was repeatedly passaged in vitro to generate nonpathogenic spirochetes. The passage 75 isolate (N40-75) was infectious for C3H mice but did not cause arthritis or carditis, and spirochetes were at low levels or absent in the joints or hearts, respectively. N40-75 could, however, cause disease in severe combined immunodeficient (SCID) mice, suggesting that the response in immunocompetent mice prevented effective spirochete dissemination and the subsequent development of arthritis and carditis. Administration of immune sera at 4 days after spirochete challenge aborted N40-75, but not cN40, infection in SCID mice. A B. burgdorferi genomic expression library was differentially probed with sera from cN40- and N40-75-infected mice, to identify genes that may not be effectively expressed by N40-75 in vivo. N40-75 was defective in the up-regulation of several genes that are preferentially expressed during mammalian infection, including dbpAB, bba64, and genes that map to the cp32 family of plasmids. These data suggest that adaptation and gene expression may be required for B. burgdorferi to effectively colonize the host, evade humoral responses, and cause disease.

Animals↗
PubMed1999

Selective anti-inflammatory action of interleukin-11 in murine Lyme disease: arthritis decreases while carditis persists.

The role of interleukin (IL)-11, a cytokine with potent anti-inflammatory properties, in murine Lyme disease was investigated. Borrelia burgdorferi-infected mice treated with IL-11 developed less arthritis than did control animals. In contrast, IL-11 blocking antibodies increased Lyme arthritis. Murine Lyme carditis was not affected by either IL-11 or IL-11 antibodies. Administration of IL-11 was associated with increased production of mRNA for IL-12 and inducible nitric oxide synthase but not interferon-gamma or IL-4 in B. burgdorferi-infected mice, suggesting a predominant effect of IL-11 on the innate immune response. These data show that IL-11 selectively reduced joint but not cardiac inflammation caused by B. burgdorferi in mice.

Animals↗
PubMed1998

Hydrogen peroxide enhances signal-responsive arachidonic acid release from neurons: role of mitogen-activated protein kinase.

Hydrogen peroxide (H2O2) is a potent stimulator of signal-responsive phospholipase A2 (PLA2) in vascular smooth muscle and cultured endothelial cells. We investigated whether H2O2 plays a similar regulatory role in neurons. H2O2 did not stimulate a release of arachidonic acid from cultured neurons when applied alone but strongly enhanced the liberation of arachidonic acid evoked by maximally effective concentrations of either glutamate, the glutamate receptor agonist N-methyl-D-aspartate (NMDA), the muscarinic receptor agonist carbachol, the Na+-channel opener veratridine, or the Ca2+-ionophore ionomycin. The potentiating effects of H2O2 were strongly inhibited in the presence of the PLA2 inhibitor mepacrine, suggesting that the site of action was within the signal responsive arachidonic acid cascade. The enhancing effect of H2O2 was not reversed by protein kinase C inhibitors (chelerythrine chloride or GF 109203X) nor was it mimicked by phorbol ester treatment. H2O2 alone strongly enhanced the levels of immunodetectable activated mitogen-activated protein kinase (activated MAP kinases ERK1 and ERK2) in a Ca2+-dependent manner and this effect was additive with increases in the levels of activated MAP kinase evoked by glutamate. The enhanced release of arachidonic acid, however, was not clearly reversed by the MAP kinase kinase (MEK) inhibitor PD 98059, although this treatment effectively abolished H2O2 activation of MAP kinase. Thus, MAP kinase activation and Ca2+-dependent arachidonic acid release are regulated by oxidative stress in cultured striatal neurons.

Animals↗