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Biomedical subjects

M Bhattacharya

Publications and source records attributed to M Bhattacharya.

At least 19 recordsLinked to original sources
PubMed2006

Detecting level crossings without looking at the spectrum.

In many physical systems it is important to be aware of the crossings and avoided crossings which occur when eigenvalues of a physical observable are varied using an external parameter. We have discovered a powerful algebraic method of finding such crossings via a mapping to the problem of locating the roots of a polynomial in that parameter. We demonstrate our method on atoms and molecules in a magnetic field, where it has implications in the search for Feshbach resonances. In the atomic case our method allows us to point out a new class of invariants of the Breit-Rabi Hamiltonian of magnetic resonance. In the case of molecules, it enables us to find curve crossings with practically no knowledge of the corresponding Born-Oppenheimer potentials.

Journal Article↗
PubMed2006

Analysis of a missense variant of the human N-formyl peptide receptor that is associated with agonist-independent beta-arrestin association and indices of inflammation.

Formyl-Met-Leu-Phe (fMLP) is a potent chemoattractant molecule released from both bacteria and damaged mitochondria that activates fMLP receptors (FPR) leading to neutrophil chemotaxis, degranulation and superoxide production. A common missense single nucleotide polymorphism in the human FPR1 gene at nucleotide c.32C>T results in the amino-acid substitution, p.I11T, in the FPR1 extracellular amino-terminus. The minor (c.32T) allele frequencies were 0.25, 0.27, 0.25, 0.15 and 0.14 in healthy Caucasian, African, East Indian, Chinese and Native Canadian individuals, respectively. In subjects homozygous for the p.T11 allele, we find elevated serum concentrations of C-reactive protein, increased absolute counts of blood leukocytes and neutrophils, and erythrocyte sedimentation rates. When expressed in HEK 293 and RBL-2H3 cells a substantial proportion of FPR1 p.I11T variant is retained intracellularly and agonist-independent internalization of the FPR1 p.I11T variant, but not the wild-type FPR1, is constitutively associated with beta-arrestin2-GFP in vesicles. Moreover, basal N-acetyl-D-glucosaminidase release is increased in primary neutrophils isolated from subjects either heterozygous or homozygous for the FPR1 p.T11 allele. Taken together, the data suggest an increased receptor activity and phenotypic expression of increased inflammatory indices in subjects with the p.T11 allele.

Arrestins↗
PubMed2005

Entanglement of a photon and a collective atomic excitation.

We describe a new experimental approach to probabilistic atom-photon (signal) entanglement. Two qubit states are encoded as orthogonal collective spin excitations of an unpolarized atomic ensemble. After a programmable delay, the atomic excitation is converted into a photon (idler). Polarization states of both the signal and the idler are recorded and are found to be in violation of the Bell inequality. Atomic coherence times exceeding several microseconds are achieved by switching off all the trapping fields--including the quadrupole magnetic field of the magneto-optical trap--and zeroing out the residual ambient magnetic field.

Journal Article↗
PubMed2005

Glass transition in ultrathin polymer films: a thermal expansion study.

The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T(g)) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T(g) was found to be very small. The existence of reversible negative and positive thermal expansion below and above T(g) increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T(g) variation as a function of depth expected from sliding motion could explain the results.

Journal Article↗
PubMed2005

Clinicohematologic spectrum in patients with lupus anticoagulant.

A retrospective analysis of clinicohematologic parameters of 25 patients with lupus anticoagulant was carried out. The hematologic tests included dilute Russel viper venom test (dRVVT), kaolin clotting time (KCT), activated partial thromboplastin time, and prothrombin time. The diagnosis of lupus anticoagulants was based on the presence of prolonged KCT/dRVVT, its absence of correction with normal plasma and correction by phospholipids. Specific factor assays and platelet aggregation studies were performed wherever required. Ten patients (40%) had thrombosis, which was venous in 5 (50%) and arterial in 4 (40%). One patient (10%) had both arterial and venous thrombosis and presented with catastrophic antiphospholipid syndrome. Eighteen female patients conceived. Four (22%) of these had recurrent first trimester abortion. Five (20%) patients had bleeding manifestations. One (4%) of these had hypoprothrombinemia and was diagnosed to have hypoprothrombinemia lupus anticoagulant syndrome. However in two of these patients, no cause of bleeding could be identified other than the presence of lupus anticoagulants. It is concluded that patients with lupus anticoagulant have a varied spectrum of hemostatic disorders. Bleeding may sometimes occur in these patients due to associated thrombocytopenia or associated factor inhibitors. Rarely, it may occur due to presence of lupus anticoagulants alone.

Adolescent↗
PubMed2005

Clinico-hematologic profile of factor XIII-deficient patients.

A retrospective analysis of clinico-hematologic parameters of 18 factor XIII-deficient patients was carried out. The hematologic tests included activated partial thromboplastin time (APTT), prothrombin time (PT), and clot solubility. Laboratory diagnosis of FXIII deficiency was made where bleeding time, PT, APTT, and thrombin time were normal and the clot solubility test result with 5M urea was positive. Factor XIII level with family screening was performed using commercially available kits. History of prolonged bleeding from the umbilical stump was present in four (22.2%) patients. The most common site of bleeding was the skin (11 of 18 patients). Three patients were given prophylaxis (FFP in two, factor XIII in one). A high prevalence of recurrent abortion in female patients with FXIII deficiency (two of the three patients in this study) was observed.

Abortion, Habitual↗
PubMed2004

Small GTP-binding protein-coupled receptors.

Heterotrimeric GPCRs (G-protein-coupled receptors) form the largest group of integral membrane receptor proteins and mediate diverse physiological processes. In addition to signalling via heterotrimeric G-proteins, GPCRs can also signal by interacting with various small G-proteins to regulate downstream effector pathways. The small G-protein superfamily is structurally classified into at least five families: the Ras, Rho/Rac/cdc42, Rab, Sar1/Arf and Ran families. They are monomeric G-proteins with molecular masses over the range 20-30 kDa, which function as molecular switches to control many eukaryotic cell functions. Several studies have provided evidence of crosstalk between GPCRs and small G-proteins. It is well documented that GPCR signalling through heterotrimeric G-proteins can lead to the activation of Ras and Rho GTPases. In addition, RhoA, Rabs, ARFs and ARF GEFs (guanine nucleotide-exchange factors) can associate directly with GPCRs, and GPCRs may also function as GEFs for small GTPases. In this review, we summarize the recent progress made in understanding the interaction between GPCRs and small GTPases, focusing on understanding how the association of small G-proteins with GPCRs and GPCR-regulatory proteins may influence GPCR signalling and intracellular trafficking.

Animals↗
PubMed2004

Clinical, haematological and histomorphological profile of adult myelodysplastic syndrome. Study of 96 cases in a single institute.

Myelodysplastic syndromes (MDS) are clonal haematopoietic stem cell disorders characterised by ineffective and dyspoietic haematopoiesis. The natural history of these disorders is variable and ranges from a chronic to a rapid course towards leukaemic progression. Certain shortcomings have been encountered in the French-American-British (FAB) classification over the years, and therefore there is a need for an alternative method of classification. In 1999, the WHO published a revised classification of MDS. In the present study, we have analysed the clinical, haematological and histomorphological features in 96 cases of primary MDS seen in the department of haematology at the All India Institute of Medical Sciences (AIIMS) over a 6-yr period (1996-2001). Both FAB and WHO classifications have been incorporated and the Bournemouth scoring system applied in each case at presentation. The Bournemouth scoring system, in the absence of a cytogenetic study, offers a good prognostication and long-term survival estimate.

Adolescent↗
PubMed2003

Forbidden transitions in a magneto-optical trap.

We report the first observation of a nondipole transition in an ultracold atomic vapor. We excite the 3P-4P electric quadrupole (E2) transition in 23Na confined in a magneto-optical trap, and we demonstrate its application to high-resolution spectroscopy by making the first measurement of the hyperfine structure of the 4P(1/2) level and extracting the magnetic dipole constant A=30.6+/-0.1 MHz. We use cw optical-optical double resonance accompanied by photoionization to probe the transition.

Journal Article↗
PubMed2002

Reversible negative thermal expansion of polymer films.

A basic understanding of the properties of thin polymer films is of fundamental importance for developing applications in nanotechnology. Results of energy and angle dispersive x-ray reflectivity measurements on polymer thin films as a function of temperature exhibit reversible negative thermal expansion below the glass transition temperature T(g). Above T(g), the thickness expansion becomes almost equal to the expected bulk volume expansion. These results could be explained on the basis of evolution of disorder with temperature at the interfaces, chain entanglement and associated entropy changes.

Journal Article↗
PubMed2002

Human fetal adrenal transplant: a possible role in relieving intractable pain in advanced rheumatoid arthritis.

BACKGROUND: The art of transplant surgery has gone a long way in establishing itself as an important discipline in medicine with the support of molecular biology, immunology, biochemistry, etc., as the ultimate treatment for the restoration of function of a failing organ. With the progressive increase in the life expectancy of human beings, there is an increasing discrepancy in the demand and supply of organ grafts. A less efficient alternative could be synthetic or mechanical grafts. Nucleated cell therapy, that is, cellular transplant, is a promising new area of study with its proven efficacy in neuro-degenerative disorders, hematopoietic disorders, diabetes and trauma-induced tissue loss, to name a few. Human fetal cell/tissue with its intrinsic hypo-antigenic advantage (up to 20 weeks of study), could be an interesting area of cellular/tissue transplant. Our research group has earlier reported on the safe use of umbilical cord whole blood and the successful transplant of a human fetal lung, heart, pancreas, liver, thymus, in an artificially prepared vascular subcutaneous axillary fold in which there was no feature of hyper-acute, acute or chronic rejection of the graft in HLA- and sex-randomized adult recipients, without concomitant immunosuppressives or radiation of the host to potentiate the survival of the fetal graft (within 20 weeks of gestation) within the lowest observation period of one month. The present study was aimed at examining the role of developing fetal adrenal transplants for patients with rheumatoid arthritis and severe pain due to involvement of inflammatory and neuropathic components. MATERIALS AND METHOD: Ten cases were enrolled in the present study after thorough informed consent and approval by the ethical committee of the institute. The age of the patients varied from 50 to 76 years and the group was comprised of three males and seven females. The age of the adrenal grafts varied from 16 to 20 weeks and these were collected from mothers admitted for hysterotomy and ligation. These long-standing rheumatoid patients (suffering for five to 15 years), presented with at least four of the seven 1987 revised criteria of the American College of Rheumatology for diagnosis of rheumatoid arthritis. A 2.5 cm long and 2 cm deep tissue space was dissected and prepared in each transplant recipient at the axilla using diathermy and knife after infiltrating the site with one percent lignocaine solution. The tissue collected from the consenting mother undergoing hysterotomy and ligation was inserted into this site, and the site was closed with 00 atraumatic vicryl. All necessary pre- and postoperative surgical precautions were taken to prevent infections. Sequential total count and differential count of leucocytes were undertaken to analyze the impact of the transplant on the host. After one month, a part of the transplanted fetal tissue was recovered for histological staining to examine whether there was any graft versus host reaction. RESULTS AND ANALYSIS: All ten patients tolerated the transplant procedure well. There was no fever, intractable pain or any other specific serious side-effect which could justify the removal of the transplant before one month. There was no discharge from the incision site and the healing of the scar was by and large normal. There was no unusual leucocytosis, lymphocytosis and the retrieved graft tissue did not suggest transplant rejection. However, there was definite pain relief, reduction in swelling and improvement of mobility of varying degree in a majority of the patients which was perceivable from the 15th day onwards. There was also a sense of well being (in 80%) and a gain in weight of three pounds or more (in 70%) among the fetal transplant recipients. DISCUSSION AND CONCLUSION: To understand the underlying mechanism, in case of pregnancy immunotolerance, we are of the opinion that emphasis should be placed on the role of non-specific and non-cytopathic blocking antibodies produced during pregnancy. The hypo-antigenicity of the developing human fetal system may possibly contribute to the production of this blocking antibody during pregnancy, and thus may play a role in the lack of recognition by the host's HLA system. This behaviour of the developing human fetal tissue provides some advantages over adult tissue for fetal cell/tissue transplantation purposes. The relief of pain, inflammation and restoration of mobility may be due to the effect of the transplanted adrenal graft, with the medullary component contributing to endorphin-like substance liberation and the cortical component contributing to glucocorticoid synthesis.

Adrenal Glands↗
PubMed2002

Can human fetal cortical brain tissue transplant (up to 20 weeks) sustain its metabolic and oxygen requirements in a heterotopic site outside the brain? A study of 12 volunteers with Parkinson's disease.

BACKGROUND: Neural and stem cell transplantation is emerging as a potential treatment for neurodegenerative diseases from Parkinson's to Huntington's disease. Stereotactic placement of dopaminergic neurons in the caudate-putamen (striatum), is being attempted in centers of excellence and has proved to be beneficial. Basic research using cell transplantation indicates that structural development mechanisms seen in immature brains, i.e., fetal brains, can also function in the adult brain. The adult brain consumes 15% of the resting cardiac output for its metabolic needs. While most human tissues can sustain an anaerobic assault for a few minutes up to 30 minutes, a sudden total lack of oxygen supply to the brain cells in an adult will render the person unconscious within five to ten seconds. Our team has been working on the problem of human fetal tissue response to antigenic assault for the last two decades. In the present series, 12 patients with prolonged histories of Parkinsonism, who were not responding to anti-Parkinsonian drugs, and could not afford costly stereotactic surgery or deep brain stimulation and other modalities of recent Parkinson's disease treatment, were enrolled in the study. MATERIALS AND METHOD: After obtaining proper informed consents from the patients or their guardians and from the multidisciplinary ethical committee, the patients, varying in age from 45 to 75 years and suffering for many years with Parkinsonism, were enrolled in the heterotopic brain tissue transplant programme. We followed standard antiseptic, aseptic and premedication protocols, after selecting a proposed site of transplantation of the brain in the axillary fold of the skin, under local infiltration anaesthesia. In an adjacent OR, a fetus was collected from a consenting patient undergoing hysterotomy and ligation (before 20 weeks), under general anaesthesia. Within a minute of hysterotomy, the fetal brain tissue was dissected, and under the guidance of the operative microscope, 1 g of fetal cortical brain tissue was dissected and weighed in an electronic machine. The tissue was collected from around 1 cm of the frontal opercula of the developing human fetal brain and grafted in the already dissected and prepared subcutaneous site in the axilla and the skin was closed. Hematological parameters (Hgb; total count, Tc; differential count, Dc; erythocyte sedimentation rate, ESR) were estimated sequentially up to one month. A small portion of the transplanted tissue was retrieved after one to two months, and a serial histological study was done along with a clinical assessment of the disease condition as per the specifications of the Unified Parkinson's Disease Rating Scale. The results were matched with the pre-transplant ratings of the individual cases. Presenting dyskinesia was also rated (0-4), on the basis of objective criteria assessment like walking, putting on a coat, lifting a cup to drink, etc. RESULTS AND ANALYSIS: Initially 30 patients suffering from advanced Parkinson's disease (PD) were approached after getting the necessary clearance from the institutional multidisciplinary ethical committee; however, we have been able to arrange transplantation in only 12 cases so far. These patients were evaluated at the pre- and one month post-transplant period by the Unified Parkinson's Disease Rating Scale (0-108) and the minimum score was 40 in the motor portion of the unified scale at the pre-transplant state. Evaluation of the patients after one month revealed mild improvement of the pre-transplant scoring (up to 33.3%) in 41.6% of the cases, and moderate improvement (up to 66.6%) in another 41.6% of the cases. While 16.8% of the cases did not show any improvement from the basal score, i.e., the pre-transplant score, there was a definite sense of well being and rise in weight (2-4 pounds) noted in each case and there was also a reduction of the L-Dopa dosage in 75% of the cases. There was also a 58.3% improvement in the bradykinesia scoring from the pre-transplant level. What is intriguing is the survival, growth and proliferation of the grafted fetal brain tissue in the HLA- and sex-randomized adult axilla without any immunosuppressive support. Not a single histological study of the fetal brain tissues after removal from the axilla showed any signs of graft vs. host or inflammatory reaction (Figures 1-9) but there were features of growth of the transplanted cortical brain tissue along with its different components like neurogenesis, gliogenesis, early neovascularisation and angiogenesis, etc. There was also no systemic leucocytosis or lymphocytosis. DISCUSSION AND CONCLUSION: Histological evidence at the transplanted tissue site suggests that fetal cortical brain tissue can sustain life in sex-randomized, HLA-randomized adult hosts, without the support of immuno-suppressive drugs and the tacit support of the blood-CSF and blood-brain barrier and other specific requirements of adult brain cells in the skull. Whether the clinical improvement in PD is transient or long lasting is presently under investigation along with basic questions like, is it due to transplanted fetal dopaminergic or non-dopaminergic neurons or is it the growth factors and the cytokine mediated hitherto unknown reactions causing the clinical improvement.

Aged↗
PubMed2001

Spatial-temporal patterning of metabotropic glutamate receptor-mediated inositol 1,4,5-triphosphate, calcium, and protein kinase C oscillations: protein kinase C-dependent receptor phosphorylation is not required.

The metabotropic glutamate receptors (mGluR), mGluR1a and mGluR5a, are G protein-coupled receptors that couple via G(q) to the hydrolysis of phosphoinositides, the release of Ca(2+) from intracellular stores, and the activation of protein kinase C (PKC). We show here that mGluR1/5 activation results in oscillatory G protein coupling to phospholipase C thereby stimulating oscillations in both inositol 1,4,5-triphosphate formation and intracellular Ca(2+) concentrations. The mGluR1/5-stimulated Ca(2+) oscillations are translated into the synchronized repetitive redistribution of PKCbetaII between the cytosol and plasma membrane. The frequency at which mGluR1a and mGluR5a subtypes stimulate inositol 1,4,5-triphosphate, Ca(2+), and PKCbetaII oscillations is regulated by the charge of a single amino acid residue localized within their G protein-coupling domains. However, oscillatory mGluR signaling does not involve the repetitive feedback phosphorylation and desensitization of mGluR activity, since mutation of the putative PKC consensus sites within the first and second intracellular loops as well as the carboxyl-terminal tail does not prevent mGluR1a-stimulated PKCbetaII oscillations. Furthermore, oscillations in Ca(2+) continued in the presence of PKC inhibitors, which blocked PKCbetaII redistribution from the plasma membrane back into the cytosol. We conclude that oscillatory mGluR signaling represents an intrinsic receptor/G protein coupling property that does not involve PKC feedback phosphorylation.

Calcium↗
PubMed2001

Protection of translation initiation factor eIF2 phosphorylation correlates with eIF2-associated glycoprotein p67 levels and requires the lysine-rich domain I of p67.

The rate of protein synthesis in mammals is largely regulated by phosphorylation of the alpha-subunit of eukaryotic initiation factor 2 (eIF2) that is modulated by the cellular glycoprotein, p67, due to its protection of eIF2alpha phosphorylation (POEP) activity. At the N-terminus of p67, there are three unique domains, and at the C-terminus there is a conserved amino acid sequence. To analyze the importance of these domains, C-terminal deletion mutants of rat p67 were expressed constitutively in KRC-7 cells. In these cells, the phosphorylation level of the alpha-subunit of eIF2 was determined, and it was found that expression of the 1-97 amino acid segment of rat p67 increases POEP activity in vivo, and induces the endogenous levels of p67. These cells also show increased growth rate, and efficient translation of chloramphenicol acetyltransferase and beta-galactosidase reporter genes. At the N-terminus of p67, there are two unique domains: a lysine-rich domain I with the sequence (36)KKKRRKKKK(44), and an acidic residue-rich domain with the sequence (77)EEKEKDDDDEDGDGD(91). Substitution of lysine-rich domain I with (36)NMKSGNKTQ(44) in rat recombinant p67 resulted in the inhibition of its POEP activity, and substitution of the acidic residue-rich domain with (77)QNIQKALEPEAGDGA(91), resulted in no inhibition of POEP activity in KRC-7 cells. Taken together, our data suggest that protection of translation initiation factor eIF2 phosphorylation correlates with eIF2-associated glycoprotein p67 levels and requires the lysine-rich domain I of p67.

Amino Acid Sequence↗
PubMed2001

Characterization of PGE2 receptors in fetal and newborn ductus arteriosus in the pig.

We compared the total density and the relative expression of EP receptor (EP) subtypes in ductus arteriosus (DA) of the newborn with that of the fetal piglet. Saturation binding experiments showed 3-fold less PGE2 receptors in the newborn than in the fetus because of loss of EP3 and EP4 receptors thus explaining, at least partly, the reduced responsiveness to PGE2 of the newborn DA. Displacement experiments showed that the relative proportions of EP2, EP3, and EP4 were similar in the fetal DA but only EP2 was detected in the DA of the newborn pig. Hence, PGE2 effects in the newborn DA seem to be exclusively mediated by EP2 receptors both in vitro and in vivo. These findings may help to propose more specific therapies for regulation of DA's tone in certain newborns for whom conventional therapy is contraindicated.

Animals↗
PubMed2001

Agonist-stimulated and tonic internalization of metabotropic glutamate receptor 1a in human embryonic kidney 293 cells: agonist-stimulated endocytosis is beta-arrestin1 isoform-specific.

Metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors (GPCRs) that contribute to the regulation of integrative brain functions such as cognition, motor control, and neural development. Metabotropic glutamate receptors are members of a unique class of GPCRs (class III) that include the calcium sensing and gamma-aminobutyric acid type B receptors. Although mGluRs bear little sequence homology to well-characterized members of the GPCR superfamily, both second messenger-dependent protein kinases and G protein-coupled receptor kinases (GRKs) contribute to mGluR desensitization. Therefore, in the present study, we examined whether beta-arrestins, regulators of GPCR desensitization and endocytosis, are required for mGluR1a desensitization and internalization in human embryonic kidney (HEK) 293 cells. Unlike what has been reported for other GPCRs, we find that in response to agonist stimulation, mGluR1a internalization is selectively mediated by beta-arrestin1 in HEK 293 cells. However, even though beta-arrestin1 binds directly to the carboxyl-terminal tail of mGluR1a and redistributes with mGluR1a to endosomes, neither beta-arrestin1 nor beta-arrestin2 seems to contribute to mGluR1a desensitization in HEK 293 cells. We also observed extensive tonic mGluR1a internalization via clathrin-coated vesicles in the absence of agonist. The tonic internalization of mGluR1a is insensitive to antagonist treatment, dominant-negative mutants of GRK2, beta-arrestin1, and dynamin as well as treatments that disrupt caveolae, but is blocked by hypertonic sucrose and concanavalin A treatment. Internalized mGluR1a is colocalized with clathrin, transferrin receptor, beta2-adrenergic receptor, and Rab5 GTPase in endocytic vesicles. Therefore, although mGluR1a internalizes with beta-arrestin in response to agonist, the agonist-independent internalization of mGluR1a involves the beta-arrestin-independent targeting of mGluR1a to clathrin-coated vesicles.

Arrestins↗
PubMed2001

Prostanoid receptors: ontogeny and implications in vascular physiology.

Prostanoids exert significant effects on circulatory beds. They play a role in the response of the vasculature to adjustments in perfusion pressure and oxygen and carbon dioxide tension, and they mediate the actions of numerous factors. The role of prostanoids in governing circulation of the perinate is suggested to surpass that in the adult. Prostanoids are abundantly generated in the perinate. They have been implicated in autoregulation of blood flow as studied in brain and eyes. Prostaglandins are also dominant regulators of ductus arteriosus tone. The effects of these autacoids are mediated through specific G protein-coupled receptors. In addition to the pharmacological characterization of the prostanoid receptors, important advances in understanding the biology of these receptors have been made in the last decade. Their cloning and the development of animals with disrupted genes of these receptors have been very informative. The involvement of prostanoid receptors in the developing subject, especially on brain and ocular vasculature and on ductus arteriosus, has also begun to be investigated; the expression of these receptors changes with development. Some but not all of the ontogenic changes in these receptors are attributed to homologous regulation. Interestingly, in the process of elucidating their effects, functional perinuclear prostaglandin E2 receptors have been uncovered. This article reviews prostanoid receptors and addresses implications on the developing subject with attention to vascular physiology.

Animals↗