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Biomedical subjects

S Bhattacharya

Publications and source records attributed to S Bhattacharya.

At least 595 records · Page 33Linked to original sources
PubMedDate not supplied

Composition and stress analysis in Si structures using micro-raman spectroscopy.

Strained silicon (Si) technology enables improvements in complementary metal oxide semiconductor (CMOS) performance and functionality via replacement of the bulk, cubic-crystal Si substrate with an Si substrate that contains a tetragonally distorted, biaxially strained Si thin film at the surface. Here we use Raman spectroscopy to allow us to characterise growth processes of strained si, and to characterise the resulting level of strain/stress in the si and the effect it has on the underlying layer of graded SiGe.

Journal Article↗
PubMedDate not supplied

Outbreak of neonatal septicemia with multidrug resistant Klebsiella pneumoniae.

A nosocomial outbreak of neonatal septicemia due to K. pneumoniae occurred in nursery during June-July, 1991. Klebsiella pneumoniae (Klebocin type 314) was recovered from blood of 33 (70.2%) of 47 neonates with septicemia. Multiple drug resistance was observed in all the cases. The same strain of K. pneumoniae was recovered from the neonates and environment of nursery and labour room as well. The outbreak was attributable to environmental dissemination.

Cross Infection↗
PubMedDate not supplied

Detection of tyrosinase mRNA by reverse transcription-polymerase chain reaction in melanoma sentinel nodes.

BACKGROUND: Sentinel lymph node (SLN) biopsy is an alternative to elective dissection or observation for management of lymph node basins in patients with cutaneous melanomas. The detection of tyrosinase mRNA in melanoma SLN specimens by reverse transcription-polymerase chain reaction (RT-PCR) has been reported to be a more sensitive method to detect subclinical metastases, compared with histological analysis. The aims of this study were to (1) define the yield of RT-PCR in assessing SLNs, compared with histological analysis, (2) identify the incidence of false-positive results in SLNs, and (3) report the rate of actin PCR negativity (i.e., samples with degraded RNA) in SLNs. METHODS: Twenty-eight patients with 1.2-9.6-mm cutaneous melanomas underwent SLN biopsy (between October 1996 and March 1997). One half of each SLN was analyzed by nested RT-PCR for tyrosinase mRNA. The other half of the SLN was examined by routine microscopy. Twenty-one lymph nodes from patients without melanoma were evaluated as controls. RESULTS: Two of the 28 patients with melanoma were excluded because of RNA degradation, as indicated by actin negativity. Six of the remaining 26 patients exhibited melanoma metastases in routine histological examinations. All histologically positive lymph nodes were RT-PCR-positive. Thirteen of the 20 (65%) histologically negative cases were RT-PCR-positive. Of 21 control lymph nodes, 3 were actin-negative and were not assessable for tyrosinase mRNA. Two of the remaining 18 (11%) negative-control nodes were RT-PCR-positive. CONCLUSIONS: Among patients undergoing SLN biopsy, tyrosinase mRNA was detectable in 73% of SLNs from patients at risk for regional nodal metastases, including all of those with histologically positive SLNs. There is a definable false-positive rate for tyrosinase mRNA detection in the lymph nodes of patients who do not have melanoma. Actin verification of RNA integrity is necessary to ensure the accuracy of this test in detecting tyrosinase mRNA. Ongoing follow-up monitoring will define the prognostic value of this assay.

Adolescent↗
PubMedDate not supplied

Peripheral blood mononuclear cells of patients with Indian visceral leishmaniasis suppress natural killer cell activity in vitro.

Peripheral blood mononuclear cells (PBMC) of patients with Indian visceral leishmaniasis (VL) suppressed the natural killer cell (NK) activity of normal human PBMC in vitro in a dose-dependent manner. Adherent monocytes, but not the non-adherent lymphocytes of VL patients suppressed NK activity through soluble mediators. The level of suppression seen in different patients was variable.

Cell Adhesion↗
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Role of the central metal ion and ligand charge in the DNA binding and modification by metallosalen complexes.

Several metal complexes of three different functionalized salen derivatives have been synthesized. The salens differ in terms of the electrostatic character and the location of the charges. The interactions of such complexes with DNA were first investigated in detail by UV-vis absorption titrimetry. It appears that the DNA binding by most of these compounds is primarily due to a combination of electrostatic and other modes of interactions. The melting temperatures of DNA in the presence of various metal complexes were higher than that of the pure DNA. The presence of additional charge on the central metal ion core in the complex, however, alters the nature of binding. Bis-cationic salen complexes containing central Ni(II) or Mn(III) were found to induce DNA strand scission, especially in the presence of co-oxidant as revealed by plasmid DNA cleavage assay and also on the basis of the autoradiogram obtained from their respective high-resolution sequencing gels. Modest base selectivity was observed in the DNA cleavage reactions. Comparisons of the linearized and supercoiled forms of DNA in the metal complex-mediated cleavage reactions reveal that the supercoiled forms are more susceptible to DNA scission. Under suitable conditions, the DNA cleavage reactions can be induced either by preformed metal complexes or by in situ complexation of the ligand in the presence of the appropriate metal ion. Also revealed was the fact that the analogous complexes containing Cu(II) or Cr(III) did not effect any DNA strand scission under comparable conditions. Salens with pendant negative charges on either side of the precursor salicylaldehyde or ethylenediamine fragments did not bind with DNA. Similarly, metallosalen complexes with net anionic character also failed to induce any DNA modification activities.

Autoradiography↗
PubMedDate not supplied

Effect of chronic low dose of methotrexate on cellular proliferation during spermatogenesis in rats.

This study was conducted to evaluate cellular proliferation of germinal and non-germinal elements of seminiferous tubules following continuous Day 1 to Day 17 exposure of methotrexate (12.5 microgram) in male rats. There was significant decrease in the diameter of seminiferous tubules (P < 0.10) followed by increase of interstitial space (P < 0.01). The size of various stages of primary, secondary spermatocytes, and spermatids was altered significantly compared to controls. Vacuolization/decondensation of "chromatin-mass" in spermatocytes changed from rounded to oval. The size of the Sertoli and Leydig cells were reduced significantly. Basement membrane at some places seems to be disrupted and thin in experimental testis. Methotrexate induced cytotoxicity on the proliferation of cellular contents of seminiferous tubules elucidating the mechanism of dose-dependent drug induced testicular damage during spermatogenesis.

Animals↗
PubMedDate not supplied

Tattooing and hepatitis B infection.

To determine the prevalence of HBV carrier status in tattooed persons, 200 healthy, tattooed volunteers and 200 non-tattooed volunteers to match the first group for age, sex and ethnic group were screened. Prevalence of HBsAg in tattooed and non-tattooed volunteers was 19.5 and 9% respectively, which was a statistically significant difference (P less than 0.01). There was no difference in the prevalence in various age groups, ethnic groups, or sex, between the two groups.

Adult↗
PubMedDate not supplied

Circular DNA of Entamoeba histolytica encodes ribosomal RNA.

The presence of repeated DNA sequences encoding RNA in Entamoeba histolytica has been reported. In the present study we demonstrate by agarose gel electrophoresis. DNase digestion and electron microscopic analysis that these genes are located on extrachromosomal circular DNA molecules with an approximate size of 26 kb. Detection of replication intermediates suggests the episomal nature of these molecules. Amplified, extrachromosomal rRNA genes appear to be a common feature among the lower eukaryotes, occurring more commonly as linear molecules and less commonly as circles. Entamoeba histolytica is 1 of the few organisms studied in which rRNA genes are located predominantly on extrachromosomal circles.

Animals↗
PubMedDate not supplied

Lipophosphoglycan is present in distinctly different form in different Entamoeba histolytica strains and absent in Entamoeba moshkovskii and Entamoeba invadens.

Lipophosphoglycan has recently been demonstrated on the cell surface of Entamoeba histolytica strain HM-1:IMSS. A monoclonal antibody against this molecule had failed to react with some other strains of E. histolytica, including the strain Rahman. To determine if a structurally distinct lipophosphoglycan existed in Rahman, [3H]galactose-labeled glycoconjugates were electrophoresed through sodium dodecyl sulfate polyacrylamide gel electrophoresis. The electrophoretic pattern in Rahman was very different compared to that obtained with strains HM-1:IMSS and 200:NIH. A number of experiments including sensitivity to mild acid, nitrous acid and phosphoinositol-specific phospholipase C suggest that the Rahman glycoconjugate is indeed a lipophosphoglycan-like molecule but distinctly different from that of HM-1:IMSS. Mild acid-treated glycoconjugates from Rahman and HM-1:IMSS revealed the presence of neutral trisaccharides and monosaccharides in Rahman but not in HM-1:IMSS. Human immune sera from amoebiasis patients and a polyclonal antibody against HM-1:IMSS lipophosphoglycan both recognized Rahman glycoconjugate. Thus, while lipophosphoglycan molecules from the two strains share common epitopes, they are clearly distinct from each other. Molecules bearing resemblance to lipophosphoglycan could not be detected in other Entamoeba species, namely Entamoeba invadens and Entamoeba moshkovskii.

Animals↗
PubMedDate not supplied

Molecular changes in Entamoeba histolytica in response to bacteria.

Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme-linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.

Animals↗
PubMedDate not supplied

Ribosomal DNA fragments enhance the stability of transfected DNA in Entamoeba histolytica.

Genetic manipulation of Entamoeba histolytica is limited by the inability to express foreign genes at high levels. We tested whether sequences from the E. histolytica rDNA episome, present in 200 copies per cell, could act to stabilize the episomal transfection vector pTCV1. Ligation of the rDNA transcription unit, or sequences downstream of the rDNA transcription unit, increased pTCV1 copy number and stability and conferred additional zones of DNA replication. Sequences upstream of the rDNA transcription unit dramatically destabilized pTCV1. These experiments give additional insights into the mechanism of DNA replication and provide for E. histolytica a set of transfection vectors with unique properties.

Animals↗
PubMedDate not supplied

Synthesis and thermoelectric power of nitrogen-doped carbon nanotubes.

We have previously shown that high-purity multiwalled carbon nanotubes (pristine MWNTs) can be prepared from a mixture of xylene-ferrocene (99 at% C:1 at% Fe) inside a quartz tube reactor operating at approximately 700 degrees C. In a similar process, approximately 3 g of melamine (C3H6N6) was introduced during the growth of MWNTs to prepare nitrogen-doped nanotubes. The structural and electronic properties of nitrogen-doped MWNTs were determined by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), and thermopower measurements. The individual nitrogen-doped nanotube exhibits a bamboo-like structure and comprises 6-16 tube walls, as evidenced by HRTEM studies. The EELS measurements yielded an average nitrogen content of approximately 5 at% in the doped tubes. The thermoelectric power data of nitrogen-doped MWNTs remained negative even after exposure to oxygen for an extended period of time, suggesting that nitrogen doping of MWNTs renders them n-type, consistent with scanning tunneling spectroscopic studies on similar nanotubes.

Crystallization↗