PubMed Health⌕ Search

Biomedical subjects

A Bhattacharyya

Publications and source records attributed to A Bhattacharyya.

At least 19 recordsLinked to original sources
PubMed2001

A small protein-protein interaction domain common to KlcB and global regulators KorA and TrbA of promiscuous IncP plasmids.

The kor regulon of broad host-range, incompatibility group P (IncP) plasmids uses the KorA, KorB, and KorC repressors to regulate expression of genes for replication, conjugation, segregation, and host range. One operon, kilC, encodes the KorC repressor and two genes of unknown function (klcA and klcB). The predicted sequences of the 51.1 kDa KlcB protein, the 11.3 kDa KorA repressor, and another small (13.5 kDa) regulatory protein, TrbA, show a highly related 35 amino acid residue segment (V-L-P domain). We found that induction of the klcB gene is toxic to Escherichia coli host cells harboring an IncP plasmid. We confirmed a model in which the V-L-P domain of KlcB interacts directly with the V-L-P domain of KorA to derepress KorA-regulated operons, thereby allowing expression of toxic genes. First, a lacZ reporter fused to the kleA promoter, which is regulated by KorA and KorC, revealed that klcB induction specifically releases KorA-repression but has no effect on KorC repression. Second, induced expression of the V-L-P domains from KorA or KlcB is sufficient to release KorA-repression at the kleA promoter. Third, purified GST-KlcB fusion protein interacts specifically with His-tagged KorA. Fourth, fusion of the V-L-P domains of KorA and TrbA and full-length KlcB polypeptide to the DNA-binding domain of bacteriophage lambda repressor leads to the formation of functional, dimeric repressors, and mutations that alter conserved residues of the V-L-P domain adversely affect dimerization. Fifth, crosslinking experiments demonstrated that the V-L-P domain of KorA is able to dimerize in solution and form heterodimers in mixtures with full-length KorA polypeptide. These findings show that the V-L-P domain is a protein-protein interaction module that is likely to be responsible for dimerization of KorA and TrbA, and important for KlcB dimerization. We speculate on the possible significance of KlcB-KorA heterodimers in IncP plasmid maintenance.

Amino Acid Sequence↗
PubMed2001

Lipoarabinomannan from Mycobacterium tuberculosis promotes macrophage survival by phosphorylating Bad through a phosphatidylinositol 3-kinase/Akt pathway.

Efforts in prevention and control of tuberculosis suffer from the lack of detailed knowledge of the mechanisms used by pathogenic mycobacteria for survival within host cell macrophages. The exploitation of host cell signaling pathways to the benefit of the pathogen is a phenomenon that deserves to be looked into in detail. We have tested the hypothesis that lipoarabinomannan (LAM) from the virulent species of Mycobacterium tuberculosis possesses the ability to modulate signaling pathways linked to cell survival. The Bcl-2 family member Bad is a proapoptotic protein. Phosphorylation of Bad promotes cell survival in many cell types. We demonstrate that man-LAM stimulates Bad phosphorylation in a phosphatidylinositol 3-kinase (PI-3K)-dependent pathway in THP-1 cells. Man-LAM activated PI-3K. LAM-stimulated phosphorylation of Bad was abrogated in cells transfected with a dominant-negative mutant of PI-3K (Delta p85), indicating that activation of PI-3K is sufficient to trigger phosphorylation of Bad by LAM. Since phosphorylation of Bad occurred at serine 136, the target of the serine/threonine kinase Akt, the effect of LAM on Akt kinase activity was tested. Man-LAM could activate Akt as evidenced from phosphorylation of Akt at Thr(308) and by the phosphorylation of the exogenous substrate histone 2B. Akt activation was abrogated in cells transfected with Deltap85. The phosphorylation of Bad by man-LAM was abrogated in cells transfected with a kinase-dead mutant of Akt. These results establish that LAM-mediated Bad phosphorylation occurs in a PI-3K/Akt-dependent manner. It is therefore the first demonstration of the ability of a mycobacterial virulence factor to up-regulate a signaling pathway involved in cell survival. This is likely to be one of a number of virulence-associated mechanisms by which bacilli control host cell apoptosis.

Carrier Proteins↗
PubMed2001

Toxico-kinetics, recovery, and metabolism of napropamide in goats following a single high-dose oral administration.

Toxicokinetic behavior, recovery and metabolism of napropamide (a pre-emergent herbicide) and its effect on Cytochrome P(450) of liver microsomal pellet were studied following a single high-dose oral administration of 2.5 g kg(-1) and continuous (7 days) oral administration of 500 mg kg(-1) in black Bengal goat. Napropamide was detected in blood at 15 min and the maximum quantity was recovered at 3 h after administration. The absorption rate constant (Ka) value was low indicating poor absorption from the gastrointestinal tract. High elimination half-life (t(1/2) beta) and low body clearance (Cl(B)) values coupled with higher transfer of compound from tissue to central compartment (K(21)) suggest that napropamide persisted in the blood for a long time, i.e., after 72 h of oral administration. The recovery percentage of napropamide, including metabolites, from goats varied from 75.94 to 80.08 and excretion of the parent compound through feces varied from 18.86 to 21.59%, indicating that a major portion of the orally administered napropamide was absorbed from the gastrointestinal tract of goat. Napropamide significantly increased the Cytochrome P(450) content of liver microsomal pellet. The recovery of metabolites from feces, urine, and tissues ranged from 4.2--6.2, 40.81--49.42, and 2.7--11.6%, respectively, during a 4--7 day period. The material balance of napropamide (including metabolites) following a single high-dose oral administration at 2.5 g kg(-1) during 4--7 days after dosing was found to be in the range of 75--80%.

Absorption↗
PubMed2001

Insulin lispro and regular insulin in pregnancy.

We assessed the safety of insulin lispro in gestational, type 1 and type 2 diabetes mellitus, analysing 635 pregnancies over a period of 7 years. We also evaluated patient satisfaction, sending an internationally-accepted anonymous diabetes treatment satisfaction questionnaire to 22 patients (three type 1, 19 gestational diabetes) who received regular and lispro insulin in successive pregnancies. The success rate of pregnancies in women with gestational diabetes managed with diet alone (n=325) was 99.3%. All 213 pregnancies in women with gestational diabetes requiring insulin were successful. There was no difference in maternal or fetal outcomes whether patients used regular insulin (n=138) or insulin lispro (n=75), but pre-delivery HbA1c was lower with insulin lispro (p<0.05). Pregnancy loss in patients with pre-gestational diabetes (89 pregnancies in type 1 and eight in type 2 diabetes) was 18.6% for insulin and 3.7% for insulin lispro (p=0.10). The incidences of congenital anomalies with regular insulin were 7.9% and 15.8% in gestational and pre-gestational diabetes, respectively; the figures for insulin lispro were 6.6% (p=0.79) and 3.8% ( p=0.16), respectively. Nineteen of the 22 surveyed patients completed the questionnaire. Satisfaction was higher with insulin lispro (26.3+/-2.3 vs. 18+/-8.9, p=0.0005). We found no increase in adverse outcome using lispro insulin in diabetic pregnancies, in either gestational or pre-gestational diabetes. Patient satisfaction favoured insulin lispro. Several patients with type 1 diabetes who used regular insulin during pregnancy, chose lispro after delivery, but all who used lispro in pregnancy preferred to continue.

Adolescent↗
PubMed2001

Renal blood flow changes induced with endothelin-1 and fenoldopam mesylate at quantitative Doppler US: initial results in a canine study.

PURPOSE: To evaluate quantitative Doppler ultrasonography (US) for assessing renal blood flow changes induced with endothelin-1 (ET-1) and fenoldopam mesylate in conscious dogs. MATERIALS AND METHODS: A blood flow probe was surgically implanted around the renal artery in eight adult dogs. Color and power Doppler US images were acquired in conscious restrained dogs during intravenous infusion of ET-1 and fenoldopam mesylate. Simultaneous with imaging, blood flow through the renal artery was measured with the implanted probe. The color level of the images within the region representing the kidney was analyzed to derive flow indices. These indices were compared with direct-flow measurements. RESULTS: The flow indices, color-weighted flow area (CWFA), and percentage of area of color, derived from color and power Doppler US images, correlated linearly with direct flow. The mean color level of color and power Doppler US images correlated weakly with direct flow. Pre- versus postinfusion CWFA decreased with all ET-1 infusions (P < or =.032). Infusion of fenoldopam mesylate increased CWFA in all cases (P < or =.032). CONCLUSION: Quantitative Doppler US enabled successful measurement of the flow changes induced with ET-1 and fenoldopam mesylate. Quantitative Doppler US is potentially useful as a noninvasive surrogate endpoint in evaluating the action of various therapeutic agents.

Animals↗
PubMed2001

Acute adrenocortical crisis: three different presentations.

The adrenal cortex normally produces three principal steroid hormones: the glucocorticoid cortisol, the mineralocorticoid aldosterone, and a small quantity of sex steroids. In primary adrenocortical insufficiency, there is a deficiency of both cortisol and aldosterone with characteristic clinical and laboratory findings. In contrast, with a pituitary disorder there is isolated hypocortisolism, because its production is dependent on pituitary adrenocorticotropic hormone (ACTH), whereas aldosterone production is controlled by extracellular fluid volume, renin and serum potassium. Acute adrenocortical crisis is an absolute medical emergency and its presentation is not always typical. We describe three recent cases of acute adrenocortical crisis in our hospital who presented in three different ways in three different wards.

Acute Disease↗
PubMed2000

Dynamics of compact denatured states of glutaminyl-tRNA synthetase probed by bis-ANS binding kinetics.

Bis-ANS binds to native glutaminyl-tRNA synthetase (GlnRS) with a fast and a slow phase. The rate constant of the slow phase is independent of bis-ANS concentration suggesting a slow conformational change in the pathway of bis-ANS binding. Aging of GlnRS causes a large decrease of the slow phase amplitude with concomitant increase of the fast phase amplitude. Several other large, multi-domain proteins show similar patterns upon aging. The near UV-CD spectra of the native and the aged GlnRS remain similar. Significant changes in far UV-CD, acrylamide quenching and sulfhydryl reactivity, are seen upon aging, suggesting disruptions in native interactions. Refolding of GlnRS from the urea-denatured state rapidly produces a state that is very similar to the equilibrium molten globule state. Bis-ANS binds to the molten globule state with kinetics similar to that of the aged state and unlike that of the native state. This suggests that the slow binding phase of bis-ANS, seen in native proteins, originate from relatively high energy barriers between the native and the more open states. Thus bis-ANS can be used as a powerful probe for large amplitude, low-frequency motions of proteins.

Amino Acyl-tRNA Synthetases↗
PubMed2000

The breast cancer susceptibility gene BRCA1 is required for subnuclear assembly of Rad51 and survival following treatment with the DNA cross-linking agent cisplatin.

Mutations in breast cancer tumor susceptibility genes, BRCA1 and BRCA2, predispose women to early onset breast cancer and other malignancies. The Brca genes are involved in multiple cellular processes in response to DNA damage including checkpoint activation, gene transcription, and DNA repair. Biochemical interaction with the recombinational repair protein Rad51 (Scully, R., Chen, J., Ochs, R. L., Keegan, K., Hoekstra, M., Feunteun, J., and Livingston, D. M. (1997) Cell 90, 425-435), as well as genetic evidence (Moynahan, M. E., Chiu, J. W., Koller, B. H., and Jasin, M. (1999) Mol. Cell 4, 511-518 and Snouwaert, J. N., Gowen, L. C., Latour, A. M., Mohn, A. R., Xiao, A., DiBiase, L., and Koller, B. H. (1999) Oncogene 18, 7900-7907), demonstrates that Brca1 is involved in recombinational repair of DNA double strand breaks. Using isogenic Brca1(+/+) and brca1(-/-) mouse embryonic stem (ES) cell lines, we investigated the role of Brca1 in the cellular response to two different categories of DNA damage: x-ray induced damage and cross-linking damage caused by the chemotherapeutic agent, cisplatinum. Immunoflourescence studies with normal and brca1(-/-) mutant mouse ES cell lines indicate that Brca1 promotes assembly of subnuclear Rad51 foci following both types of DNA damage. These foci are likely to be oligomeric complexes of Rad51 engaged in repair of DNA lesions or in processes that allow cells to tolerate such lesions during DNA replication. Clonogenic assays show that brca1(-/-) mutants are 5-fold more sensitive to cisplatinum compared with wild-type cells. Our studies suggest that Brca1 contributes to damage repair and/or tolerance by promoting assembly of Rad51. This function appears to be shared with Brca2.

Animals↗
PubMed2000

Cell surface Trk receptors mediate NGF-induced survival while internalized receptors regulate NGF-induced differentiation.

Internalization and transport of a ligand-receptor complex are required to initiate cell body responses to target-derived neurotrophin. However, it is not known whether internalized receptors and cell surface receptors initiate the same signaling pathways and biological responses. Here we use a temperature-sensitive mutant of dynamin (G273D) to control the subcellular localization of activated NGF receptors (Trks). We show that dynamin function is required for ligand-dependent endocytosis of Trk receptors. In PC12 cells, nerve growth factor (NGF) stimulation promotes both survival and neuronal differentiation. These distinct biological responses to NGF are controlled by receptors signaling from different locations within the cell. Neuronal differentiation is promoted by catalytically active Trks within endosomes in the cell interior. In contrast, survival responses are initiated by activated receptors at the cell surface where they orchestrate prolonged activation of the kinase Akt. Thus, interactions between Trk receptor tyrosine kinases and intracellular signaling molecules are dictated both by phosphotyrosine motifs within the receptors and by the intracellular location of phosphorylated receptors.

Amino Acid Sequence↗
PubMed2000

Meniscal ossification in spontaneous osteoarthritis in the guinea-pig.

OBJECTIVE: The purpose of this study was to evaluate the ossification state of the meniscus in the guinea-pig stifle joint using micro-computerized tomography. DESIGN: Hind limbs from six (N=12) and 24 (N=11) month-old male Hartley guinea-pigs were removed and the joints were imaged using high resolution micro-computerized tomography. The ossified volume of the medial and lateral menisci from both groups of animals was quantified. RESULTS: Ossification of both the medial and lateral menisci of the both the 6- and 24-month-old animals was observed. In both age groups, the ossified region of the medial meniscus was significantly larger than the lateral meniscus. In addition, there is a significant increase in ossified volume of the medial meniscus between 6 and 24 months of age. CONCLUSIONS: There is a significant amount of ossification of the menisci in the male Hartley guinea-pig, with the medial compartment showing more bone than the lateral. In addition, as the animals age, there is an increase in ossification within the medial compartment. Bone remodeling and cartilage degeneration is evident in the medial compartment within these animals as they age. It is possible that the increased ossification of the medial meniscus could alter the joint biomechanics and, in part, stimulate this medial compartment joint destruction.

Aging↗
PubMed2000

Long-term follow-up of intestinal metaplasia of the gastric cardia.

OBJECTIVE: Recent studies have found a relatively high prevalence of gastric cardia intestinal metaplasia in individuals presenting for elective upper endoscopy. It has been hypothesized that this lesion may be a precursor of gastric cardia cancer. Our objective was to identify the incidence of dysplasia in patients with gastric cardia intestinal metaplasia. METHODS: Twenty-eight patients who had previously been identified with cardia intestinal metaplasia had follow-up examinations performed. None of the patients had dysplasia at the time of diagnosis. All had an examination at 1 yr, and 20 patients had an examination at 3 yr after diagnosis. During follow-up examinations all patients underwent vital staining with methylene blue to help identify areas of intestinal metaplasia in the cardia. Two to four biopsies were taken from blue-stained mucosa. Histological specimens were stained using a combination of hematoxylin and eosin with Alcian blue at pH 2.5. RESULTS: There were 27 men and one woman with a mean age of 69.8 yr (range, 48-83 yr). The mean length of follow-up was 2.5 yr (range, 12-46 months). Only one patient was diagnosed with dysplasia (low-grade) during the study, for an incidence of 1.4% per yr. CONCLUSIONS: The prevalence (0%) and incidence (1.4%/yr) of dysplasia in cardia intestinal metaplasia are low. Although further studies are needed, screening and surveillance for gastric cardia intestinal metaplasia is unlikely to be clinically useful for the prevention of gastric cardia cancer.

Aged↗
PubMed2000

Screening for genetic haemochromatosis in blood samples with raised alanine aminotransferase.

BACKGROUND: In the UK approximately 1 in 140 people are homozygous for the C282Y mutation of the HFE gene and are at risk from iron overload caused by genetic haemochromatosis (GH). Early detection can prevent organ damage secondary to iron deposition and increase life expectancy. AIM: To screen for GH in all blood samples sent to the laboratory for routine liver function tests in which raised serum alanine aminotransferase (ALT) activity was detected. METHODS: ALT was measured in sera sent to the laboratory for routine liver function tests. In those samples found to have raised activity, transferrin saturation and ferritin were measured followed by genetic testing when transferrin saturation was increased. RESULTS: Of the 35 069 serum samples assayed for routine liver function tests, 1490 (4.2%) had raised ALT levels (>50 u/l). Transferrin saturation and serum ferritin concentrations were measured in these patient samples, and in 56 transferrin saturation was >60%. Further blood samples were requested from these patients for genetic testing: 33 samples were obtained. There were nine patients homozygous for the C282Y mutation of the HFE gene and three compound heterozygotes (heterozygous for both C282Y and H63D mutations). CONCLUSIONS: The association of raised ALT activity and transferrin saturation of >60% could provide a simple, cost effective method for detecting individuals with clinical haemochromatosis. Although many patients with GH may have been missed, this study suggests that the clinical penetrance of the disorder may be much lower than is generally supposed and that genetic screening will identify many people who may never develop clinical haemochromatosis.

Adult↗