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Biomedical subjects

A Ghosh

Publications and source records attributed to A Ghosh.

At least 109 records · Page 6Linked to original sources
PubMed2000

Characterization of large plasmids encoding resistance to toxic heavy metals in Salmonella abortus equi.

Salmonella abortus equi vaccine strains were found to be resistant to high levels of toxic heavy metals--arsenic, chromium, cadmium, and mercury. The two strains 157 and 158 were resistant to ampicillin also. Curing of these strains resulted in loss of one or more resistance marker indicating plasmid borne resistance. Plasmid profile of strain 157 showed presence of three plasmids of 85, 54, and 0.1 Kb, whereas 158 strain showed presence of 85 Kb and 2 Kb plasmids. Plasmids were isolated from strain 157 and introduced into E. coli DH5alpha with a transformation efficiency of 2 x 10(3) transformants/microg DNA. Interestingly the transformants were resistant to antibiotics, heavy metals (As, Cr, Cd, Hg) and was also able to utilize citrate, a trait specific to Salmonella species. We report and establish for the first time the transferable large plasmids encoding resistance to various heavy metals, antibiotics and biochemical nature of S. abortus equi.

Ampicillin Resistance↗
PubMed2000

Universal conductance fluctuations in three dimensional metallic single crystals of Si

In this paper we report the measurement of conductance fluctuations in 3D crystals of Si made metallic by heavy doping. ( L/L(straight phi) approximately 10(3), where L(straight phi) is the phase coherence length.) Temperature and magnetic field dependence of noise strongly indicate the universal conductance fluctuations as a predominant source of the observed magnitude of noise. Conductance fluctuations within a single phase coherent region of L(3)(straight phi) were found to be saturated at <(deltaG(straight phi))(2)> approximately (e(2)/h)(2). An accurate knowledge of the level of disorder enables us to calculate the change in conductance deltaG1 due to movement of a single scatterer as <(deltaG1)(2)> approximately (e(2)/h)(2), which is approximately 2 orders of magnitude higher than its theoretically expected value in 3D systems.

Journal Article↗
PubMed2000

Semaphorin 3A is a chemoattractant for cortical apical dendrites.

The apical dendrites of pyramidal neurons integrate inputs from various cortical layers and are central to information processing. Here we show that the growth of apical dendrites towards the pial surface is regulated by a diffusible chemoattractant present at high levels near the marginal zone. A major component of this signal is semaphorin 3A (Sema3A), which was previously characterized as a chemorepellant for cortical axons. Soluble guanylate cyclase is asymmetrically localized to the developing apical dendrite, and is required for the chemoattractive effect of Sema3A. Thus the asymmetric localization of soluble guanylate cyclase confers distinct Sema3A responses to axons and dendrites. These observations reveal a mechanism by which a single chemotropic signal can pattern both axons and dendrites during development.

Animals↗
PubMed2000

Scaling of the conductivity spectra in ionic glasses: dependence on the structure

A scaling approach in the conductivity formalism is applied to lithium tellurite glasses of different compositions. We observe that the hopping frequency can be used as the scaling frequency in the absence of well-defined dielectric loss peaks, and a universality of the scaling of the conductivity can be obtained for compositions with a similar structure. Further, the reasons behind the inapplicability of the scaling approach reported recently are elucidated in terms of structure of the glasses.

Journal Article↗
PubMed2000

Cell growth regulatory and antiviral effects of the P69 isozyme of 2-5 (A) synthetase.

Among the many interferon-induced proteins that carry out multiple cellular functions of interferons is the family of enzymes called 2'-5' oligoadenylate synthetases. We examined the anticellular and antiviral activities of a specific member of that family, the P69 isozyme. P69 was expressed in human cells by transfection and shown to be localized primarily in the endoplasmic reticulum. For further studies, permanent cell lines expressing different levels of P69 or an enzymatically inactive mutant were isolated. Constitutive P69 expression caused inhibition of replication of encephalomyocarditis virus but not of vesicular stomatitis virus, Sendai virus, or reovirus. Increasing levels of P69 expression also caused increasing perturbations in cell growth properties. There was increasing accumulations of the P69-expressing cells in the G1 phase of the cell cycle; cell-doubling time was increased by P69 expression; and there were many multinucleated cells in the P69-expressing line, indicating a defect in cytokinesis.

2',5'-Oligoadenylate Synthetase↗
PubMed2000

Valence tautomerism and macrocycle ruffling in nickel(III) porphyrins.

Nonlocal density functional calculations with full geometry optimization have been carried out on the low-lying electronic states of oxidized nickel porphyrins. For [NiIII(P)(Py)2]+, the ground state corresponds to a t2g6(z2)1 configuration and the t2g6(x2-y2)1 configuration is 0.43 eV higher in energy. In contrast, the ground state of [NiIII(P)(CN)2]- corresponds to a t2g6(x2-y2)1 configuration, the t2g6(z2)1 configuration being 0.96 eV higher in energy. The results are consistent with EPR spectroscopic results on the TPP analogs of these complexes. For [Ni(P)(Py)2]+, the a2u- and a1u-type Ni(II) porphyrin cation radical states are higher in energy by 0.63 and 1.23 eV, respectively, relative to the t2g6(z2)1 Ni(III) ground state. The Ni-N(Porphyrin) distance is significantly shorter in [NiIII(P)(Py)2]+ (196 pm) than in [NiIII(P)(CN)2]- (206 pm), which is consistent with the ruffled and planar macrocycle conformations, respectively, in the two complexes.

Electron Spin Resonance Spectroscopy↗
PubMed2000

Development of a simple sperm cryopreservation model using a chemically defined medium and goat cauda epididymal spermatozoa.

This investigation was carried out to develop a simple sperm cryopreservation model using a chemically defined synthetic medium (modified Ringer's solution) and mature goat cauda epididymal sperm as the model system. Rates of cooling, freezing, and maximum freezing temperature were manipulated with the help of a computer-controlled programmable biofreezer. Highly motile goat cauda sperm dispersed in a modified Ringer's solution was subjected to the freezing protocol: cooling 0.25 degrees C min(-1) to 5 degrees C, 5 degrees C min (-1) to -20 degrees C, 20 degrees C min(-1) to -100 degrees C, prior to plunging into liquid nitrogen. In the absence of any cryoprotective agent, all of the spermatozoa lost their motility. Addition of glycerol (0.22 to 0.87 M) caused a dose-dependent increase of sperm motility recovery. The highest recovery of forward and total motility was (32 and 35%, respectively) at 0.87 M. Further increase of the glycerol concentration caused a marked decrease in motility. Changes in the cooling rate particularly before and during freezing had a notable effect on the sperm motility recovery. There was no or low recovery (0-18%) of sperm motility when the cells were transferred directly to liquid nitrogen from the initial two cooling stages. The data demonstrate the importance of all of the cooling stages in the cryopreservation of the cells. Like glycerol, dimethyl sulfoxide (Me(2)SO) and ethylene glycol also showed a dose-dependent increase in motility recovery as well as a biphasic curve of cryoprotection. At optimal concentrations, dimethyl sulfoxide (1.00 M) and ethylene glycol (1.29 M) were effective in recovering sperm motility to the extent of 20 and 13%, respectively. Thus these reagents have markedly lower cryoprotection potential than glycerol.

Animals↗
PubMed2000

Cervical cancer outcomes analysis: impact of age, race, and comorbid illness on hospitalizations for invasive carcinoma of the cervix.

OBJECTIVE: The aim of this study was to evaluate the association of age, race, and comorbid illness with procedures and complications in hospitalized patients with invasive carcinoma of the cervix in a statewide population-based database over a 3-year period. METHODS: Hospitalizations were classified into homogeneous subgroups based on a diagnosis of invasive cervical cancer. Cancer-related complications and comorbid diseases were evaluated. chi(2) and t tests determined differences in means or proportions. Linear regression techniques were applied to build models for hospitalization charges and lengths of stay (LOS). RESULTS: There were 1009 admissions. The mean age was 49.5, with a median age of 46 (21-100, SD 15.4). Of the total, 606/1009 (60%) were white, 354/1009 (35%) were African-American (AA), and 5% were "other" races. AAs were more likely to have Medicaid or be uninsured (44% vs 23%, P = 0. 001) and were more likely to be admitted for an emergency (unadjusted odds ratio (OR) = 1.6; 1.2-2.2), to have a comorbid illness (P = 0.001), to be admitted for a cancer-related complication (P = 0.036), to be admitted for a transfusion (P = 0. 01), and to be admitted for radiation therapy rather than surgery (P = 0.001). The following were associated with LOS and higher hospital costs: emergency admissions for complications of cancer, comorbid illness, and older age. CONCLUSIONS: Racial differences exist in patterns of admission, type of therapy, and severity of illness; however, there were no differences in charges or LOS for similar procedures. The large percentage of African-Americans uninsured or insured by government-supported programs indicates the potential impact of public policy on the care of these patients. Socioeconomic status rather than phenotypic appearance may be a more important determinant of outcome.

Adult↗
PubMed2000

The journey of the malaria parasite in the mosquito: hopes for the new century.

In this review, Anil Ghosh, Marten Edwards and Marcelo Jacobs-Lorena follow the journey of the Plasmodium parasite in the mosquito vector. At each developmental step, they highlight some of the major unanswered questions currently challenging cell and molecular biologists. A more thorough understanding of Plasmodium-mosquito interactions might lead to the development of mosquitoes unable to support parasite development.

Animals↗
PubMed2000

Domestic burns prevention and first aid awareness in and around Jamshedpur, India: strategies and impact.

This article highlights the strategy for awareness creation regarding burns prevention and first aid and its impact in and around the steel-producing city of Jamshedpur, India. This is a joint venture of the Burns Centre and the Medico Social Welfare Unit of the Tata Main Hospital, Jamshedpur in collaboration with the Social Service Division of Tata Steel and city schools. The first phase of 5 years has been devoted to general awareness building in the population through two main programmes, namely "Community Awareness Programmes" for the target group of ladies and teenage girls and "School Education Programmes" for the target group of school children of Standard 8 in the steel-producing city. These programmes include audio-visual presentations as well as face to face interactions regarding structure and arrangements in the kitchen, floor level cooking, clothing while cooking, careful use of electrical appliances, pressure stoves, etc. The discussions also include suicidal and homicidal burns prevention strategies. Various competitions for the target group provide feedback on programmes. The growing awareness about burns prevention among school children and community members, and steady increase in the number of patients who use water as first aid, speak about the success of the strategies.

Accidents, Home↗
PubMed2000

Vanillin as an antioxidant in rat liver mitochondria: inhibition of protein oxidation and lipid peroxidation induced by photosensitization.

Using rat liver mitochondria, as model systems, we have examined the ability of the natural compound and the food-flavoring agent, vanillin to protect membranes against oxidative damage induced by photosensitization at concentrations normally used in food preparations. Vanillin, at a concentration of 2.5 mmol/L, has afforded significant protection against protein oxidation and lipid peroxidation in hepatic mitochondria induced by photosensitization with methylene blue plus light. The effect observed was both time- and concentration-dependent. The inhibitory effect is similar to ascorbic acid and the singlet oxygen quencher, diazabicyclo[2.2.2]octane (DABCO) but less effective than sodium azide and glutathione. Examination of possible mechanisms responsible for the observed protection, showed that vanillin has a significant ability to quench singlet oxygen (1O2), a reactive species responsible for damage induced during photosensitization by Type II mechanism. Hence, this flavoring compound, due to its antioxidant ability, may have potential to prevent oxidative damage to membranes in mammalian tissues and thereby the ensuing diseased states.

Animals↗
PubMed2000

Nuclear Notch1 signaling and the regulation of dendritic development.

To understand the function of Notch in the mammalian brain, we examined Notch1 signaling and its cellular consequences in developing cortical neurons. We found that the cytoplasmic domain of endogenous Notch1 translocated to the nucleus during neuronal differentiation. Notch1 cytoplasmic-domain constructs transfected into cortical neurons were present in multiple phosphorylated forms, localized to the nucleus and could induce CBF1-mediated transactivation. Molecular perturbation experiments suggested that Notch1 signaling in cortical neurons promoted dendritic branching and inhibited dendritic growth. These observations show that Notch1 signaling to the nucleus exerts an important regulatory influence on the specification of dendritic morphology in neurons.

Animals↗
PubMed2000

Horse-related injuries in pediatric patients.

PURPOSE: The aim of this study was to describe the characteristics, nature, severity and outcome of injuries from horse-related trauma in pediatric patients, aged of 19 years or younger. METHODS: Retrospective analysis was conducted of 315 patients recorded in the National Pediatric Trauma Registry from February 1995 to August 1999. RESULTS: A total of 62% of the 315 patients were girls. The median age of injury was 10 years. Sixty-five percent of the patients were injured while mounted on a horse, and the most common mechanism of injury was falling off the horse. The most frequent reason for hospital admission was skeletal fractures followed by head injuries. The head, neck, and face area was the most commonly injured anatomic site, followed by the upper extremity, the abdomen, and then the lower extremity. The median length of stay in the hospital was 2 days. Forty percent of the patients needed treatment in the intensive care unit with a median length of stay of 2 days. Thirty-nine percent of patients underwent surgical procedures. The Injury Severity Score ranged from moderate to critical in 31.5% of the children. There were 8 deaths, 2.5% of the injured children. The most common cause of mortality was head injuries. Of the 307 survivors, 3% were discharged to a rehabilitation center, and 2% of the children had 1 or more functional impairments lasting longer than 7 months after discharge. CONCLUSIONS: Horse-related trauma is frequent in children and can cause severe injuries resulting in death and long-term disability. Awareness of the nature of injuries is important to avoid underestimation of their severity.

Abdominal Injuries↗
PubMed2000

Euglycemic and hypolipidemic activity of PAT5A: a unique thiazolidinedione with weak peroxisome proliferator activated receptor gamma activity.

The euglycemic and hypolipidemic activities of PAT5A, a novel pyridine analog of thiazolidinedione, have been evaluated in different animal models. Administration of PAT5A to db/db mice resulted in dose-dependent decreases in plasma glucose, triglyceride, and insulin levels, and an improved glucose tolerance. The glucose-lowering activity of PAT5A was better than that of troglitazone and comparable to that of rosiglitazone. In addition, PAT5A showed better lipid-lowering activity than troglitazone or rosiglitazone. A similar profile was seen in ob/ob mice. In high-fat-fed Sprague Dawley rats, PAT5A treatment reduced plasma triglyceride and total cholesterol levels. An in vitro peroxisome proliferator activated receptor gamma (PPARgamma) transactivation assay in HEK-293 cells showed poor transactivation for PAT5A compared with rosiglitazone. PAT5A did not show any PPARalpha- or PPARdelta-activating properties. Ex vivo study in db/db mice treated with PAT5A showed decreased activity of liver glucose 6-phosphatase, a key enzyme in gluconeogenesis. A 28-day probe toxicity study in Wistar rats did not show any treatment-related alterations in hematologic and biochemical parameters, nor any macroscopic and microscopic changes in the vital organs, whereas rosiglitazone treatment increased liver and heart weights. Our results indicate that PAT5A is a potent insulin sensitizer and hypolipidemic compound with a weak PPARgamma activation potential. Both in vivo and in vitro results suggest that PAT5A improves glucose kinetics and lipid levels through mechanisms not related to PPAR activation.

Animals↗
PubMed2000

Homology model of a novel xylanase: molecular basis for high-thermostability and alkaline stability.

Xylanases form enzymes of considerable interest to a variety of biotechnological industries. Their industrial usage is especially attractive since they can replace some of the environmental pollutants, and are economically viable. Those with higher thermostability and optimal activity at alkaline pH are of particular importance to the paper and pulp industry due to the demands of conditions under which the enzymatic reactions are carried out. We have earlier isolated a xylanase from Bacillus sp. NG-27, which is active both at high temperature as well as at alkaline pH. In order to find out factors responsible for the adaptation of this enzyme to the extreme conditions, three dimensional structure of NG-27 xylanase has now been obtained by homology modelling. The tertiary structure shows TIM barrel fold consisting of 8 parallel beta-strands surrounded by alpha-helices. The active site is located at the carboxy terminal end of the TIM barrel. Factors which contribute to the thermostability of the enzyme are increased number of salt bridges. The salt bridges occur remarkably on one face of alpha-helices, with oppositely charged residues occupying i, i+4, i+7 positions. A solvent shielded salt bridge interaction is also observed, which is absent in the mesophilic homologous xylanases. Solvent shielding may enhance electrostatic interaction through lowering of the dielectric, and contribute to increased stability of the enzyme.

Amino Acid Sequence↗
PubMed2000

Tricritical behavior in deterministic aperiodic ising systems

We use a mixed-spin model, with aperiodic ferromagnetic exchange interactions and crystalline fields, to investigate the effects of deterministic geometric fluctuations on first-order transitions and tricritical phenomena. The interactions and the crystal-field parameters are distributed according to some two-letter substitution rules. From a Migdal-Kadanoff real-space renormalization-group calculation, which turns out to be exact on a suitable hierarchical lattice, we show that the effects of aperiodicity are qualitatively similar for tricritical and simple critical behavior. In particular, the fixed point associated with tricritical behavior becomes fully unstable beyond a certain threshold dimension (which depends on the aperiodicity), and is replaced by a two-cycle that controls a weakened and temperature-depressed tricritical singularity.

Journal Article↗
PubMed2000

Ten years' experience of antenatal mean corpuscular volume screening and prenatal diagnosis for thalassaemias in Hong Kong.

OBJECTIVE: To determine the prevalence of thalassaemia carriers in Hong Kong. SUBJECTS AND METHODS: From 1988 to 1997, 25,834 (53.7%) of 48,089 mothers were screened for thalassaemias by mean corpuscular volume (MCV) at the first antenatal visit. RESULTS: In the screened population of 25,834, 2229 (8.6%) had MCV < or = 75 fl. Of these, 1121 (4.3%) were alpha-thal, 715 (2.8%) were beta-thal, 23 (0.1%) were alpha beta-thal, 57 (0.2%) were other haemoglobin variants, and 281 (1.1%) had either iron deficiency or uncertain causes. Out of 200 pregnancies at risk for homozygous alpha-thal-1 and 32 at risk for beta-thal major, 27 homozygous alpha-thal-1 and 7 beta-thal major were identified, compared favourably with the expected figures of 23 and 9. CONCLUSION: Antenatal screening for thalassaemias by MCV is simple, effective and reliable. Universal screening has a different impact as bone marrow or cord blood stem cell transplant provides cure for beta-thal major. At risk couples have, as an alternative to termination of pregnancy, the option of early detection and treatment for their affected newborns or fetuses.

China↗