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Biomedical subjects

S Mukherjee

Publications and source records attributed to S Mukherjee.

At least 19 recordsLinked to original sources
PubMed2003

Excited state complex formation between methyl glyoxal and some aromatic bio-molecules: a fluorescence quenching study.

Fluorescence quenching of some important aromatic bio-molecules (ABM) such as 3-aminophthalhydrazide (luminol), tryptophan (Try), phenylalanine and tyrosine (Tyr) by methyl glyoxal (MG) has been studied employing different spectroscopic techniques. The interaction of MG with ABM in the excited state has been analysed using Stern-Volmer (S-V) mechanism. In the case of MG-luminol system time correlated single photon counting (TCSPC) technique has also been applied to explain the S-V mechanism. The bimolecular rate constants obtained are found to be higher than the rate constant for diffusion controlled process. A plausible explanation of the quenching mechanism has been discussed on the basis of hydrogen bonding, charge transfer and energy transfer interaction between the colliding species.

Amino Acids↗
PubMed2002

Excited state proton transfer reaction of two new intramolecularly hydrogen bonded Schiff bases at room temperature and 77K.

Two new orthohydroxy Schiff bases, 7-phenylsalicylidene benzylamine (PSBA) and 7-ethylsalicylideneaniline (ESA) have been synthesized. The excited state intramolecular proton transfer (ESIPT) and the structure of PSBA and ESA in its crystalline form and in the solvents n-hexane, n-heptane and 1,4-dioxane have been investigated by means of absorption, emission and nanosecond spectroscopy at room temperature and 77K. One ground state species has been detected both in neutral and basic solutions of both PSBA and ESA: the cis-enol form with an intramolecular hydrogen bond. The ESIPT and formation of keto tautomer are evidenced by a large Stokes shifted emission (approximately 12000 cm(-1)) at room temperature only in the case of ESA. On the other hand the keto tautomer is the predominant species at 77K in a solid matrix and as a solid sample at room temperature both in the case of ESA and PSBA. In the case of both ESA and PSBA the more intense, higher energy emission is due to the species which has not undergone ESIPT and attributed mainly due to cis-enol form. The trans-enol form is also observed by changing the excitation wavelength. Both the compounds are found to undergo a structural change to a zwitterionic and intermolecular hydrogen bonded form in the presence of a strong base like triethylamine. From the nanosecond measurements and quantum yield of fluorescence we have estimated the decay rates of proton transfer reaction in the case of PSBA. Our theoretical calculation at the AM1 level of approximation shows that the ground singlet state has a rather large activation barrier both in the case of PSBA and ESA. The barrier height is much lower on the corresponding excited singlet surface only in the case of ESA. The process is predicted to be endothermic in the ground state and exotherrmic in the excited singlet state.

Benzylamines↗
PubMed2002

Communicating about pupils in mainstream school with special health needs: the NHS perspective.

AIM: To add to previous research carried out with young people, parents and teachers, by investigating health staff's perspectives on the difficulties, and possibilities for, achieving good communication with school staff with regard to children in mainstream school with a chronic illness or physical disability. RESEARCH DESIGN AND METHODS: A qualitative research study was carried out in one NHS Trust. Twenty semi-structured interviews were carried out with a purposive sample of health staff to cover the spectrum of professionals who have responsibility for meeting the needs of children with a chronic illness or physical disability in mainstream schools (paediatricians, school doctors, school nurses, specialist nurses, health visitors, GPs, speech and language therapists, paediatric occupational therapists, paediatric physiotherapists, clinical psychologists and psychiatrists). RESULTS: The extent to which health professionals communicated with school staff, and the way in which they went about it, varied widely. Communication was facilitated by joint meetings, shared documentation, and local policy development. Sources of difficulty in communication between health and education staff were: the parent as a conduit of information; the practical difficulties of arranging meetings; and lack of knowledge about other professionals' roles. The ethos of the school with regard to health matters, and the flow of information within health services, also had an impact on the communication process. Participants' recommendations focused on two key issues: clarification of the roles of health and education staff with regard to this group of pupils; and how information should flow from health to school staff. DISCUSSION: Many of the findings parallel the previous research with teachers, indicating agreement between professionals from different agencies about aspects of the communication process which are problematic and require attention. The findings suggest that improving communication requires both joint work between health and education staff, and improvements to practice within each agency.

Child↗
PubMed2002

STD treatment for men in rural and urban Zimbabwe: choice of practitioner, perceptions of access and quality of care.

STD treatment choices and perceptions of treatment services (access, quality of care) by Zimbabwean men are examined in 2 settings: Mbare, a district within the capital city Harare, and Gutu, a rural town. Data collection included a survey of 457 men 18 years of age or older (from a stratified systematic sample), focus groups and key informant interviews. Of 220 cases of self-reported genital symptoms, 81.4% were treated by allopathic practitioners, 9% by traditional/faith healers, 8.6% by the subject, a friend or another person; 1.4% were not treated. Traditional/faith healers were consulted primarily for symptoms involving pain or discomfort rather than ulcers or exudation. Disrespect by the health care provider and consultations that were not private were cited as problems by a small minority of subjects. Significantly more respondents in Mbare than in Gutu had been prevented from obtaining the STD treatment they desired at some point in their life because of cost of treatment (chi(2)=5.23, P=0.02). Given the current deteriorating economic situation in Zimbabwe, cost of treatment may become an even more important impediment in the future.

Adult↗
PubMed2002

Left sided cervical and thoracic malignant extra-adrenal pheochromocytoma.

Extra-adrenal Pheochromocytomas are rare entities. High index of suspicion among diastolic hypertensives followed by screening test for 24-hour urinary catecholamine level helps in diagnosis. 123I MIBG scintigraphy is specific for tumour localisation and surgical debulking of tumour or 131I MIBG therapy are alternative modes of treatment.

3-Iodobenzylguanidine↗
PubMed2001

Multiclass cancer diagnosis using tumor gene expression signatures.

The optimal treatment of patients with cancer depends on establishing accurate diagnoses by using a complex combination of clinical and histopathological data. In some instances, this task is difficult or impossible because of atypical clinical presentation or histopathology. To determine whether the diagnosis of multiple common adult malignancies could be achieved purely by molecular classification, we subjected 218 tumor samples, spanning 14 common tumor types, and 90 normal tissue samples to oligonucleotide microarray gene expression analysis. The expression levels of 16,063 genes and expressed sequence tags were used to evaluate the accuracy of a multiclass classifier based on a support vector machine algorithm. Overall classification accuracy was 78%, far exceeding the accuracy of random classification (9%). Poorly differentiated cancers resulted in low-confidence predictions and could not be accurately classified according to their tissue of origin, indicating that they are molecularly distinct entities with dramatically different gene expression patterns compared with their well differentiated counterparts. Taken together, these results demonstrate the feasibility of accurate, multiclass molecular cancer classification and suggest a strategy for future clinical implementation of molecular cancer diagnostics.

Biomarkers, Tumor↗
PubMed2001

The white morphotype of Mycobacterium avium-intracellulare is common in infected humans and virulent in infection models.

Isolates of Mycobacterium avium-intracellulare (MAI) form multiple colony types named red-opaque, white-opaque, red-transparent (RT), and white-transparent (WT). The newly discovered WT morphotype is multidrug resistant relative to other variants in vitro. To determine whether the WT morphotype occurs in humans, 32 MAI-positive clinical samples from 2 sites were plated directly onto indicator agar without prior passage in vitro. WT was the predominant morphotype in 26 (81%) of these samples and was absent in only 2 samples. WT variants grew better than isogenic RT variants in mouse and human macrophage models of infection, and RT clones that passed through such systems underwent rapid shifts to the WT morphotype. The RT morphotype was heterogeneous with regard to infectivity. In summary, the white morphotype was common in humans and was favored in disease models. It may play an important role in the establishment and persistence of MAI infection.

Animals↗
PubMed2001

Cholesterol depletion induces large scale domain segregation in living cell membranes.

Local inhomogeneities in lipid composition play a crucial role in regulation of signal transduction and membrane traffic. Nevertheless, most evidence for microdomains in cells remains indirect, and the nature of membrane inhomogeneities has been difficult to characterize. We used lipid analogs and lipid-anchored proteins with varying fluidity preferences to examine the effect of modulating cellular cholesterol on domain formation. We show that lowering cholesterol levels induces formation of visible micrometer-scale domains in the plasma membrane of several mammalian cell types with complementary distributions of fluorescent lipid analogs with preferences for fluid or ordered domains. A uniform distribution is restored by cholesterol repletion. Unexpectedly, cholesterol depletion does not visibly alter the distribution of a crosslinked or uncrosslinked glycosylphosphatidylinositol-anchored protein (the folate receptor). We also examined the effect of varying cholesterol content on the cold Triton X-100 solubility of several membrane constituents. Although a cholesterol analog, dehydroergosterol, and a glycosylphosphatidylinositol-anchored protein are largely retained after extraction, a lipid analog with saturated 16-carbon acyl chains is largely removed when the cellular cholesterol level is lowered. This result indicates that after cholesterol depletion molecules in the more ordered domains can be extracted differentially by cold nonionic detergents.

Animals↗
PubMed2001

Membrane immunoglobulins are stabilized by interchain disulfide bonds occurring within the extracellular membrane-proximal domain.

Membrane-bound immunoglobulins have, in addition to the transmembrane and cytoplasmic portions, an extracellular membrane-proximal domain (EMPD), absent in the secretory forms. EMPDs of immunoglobulin isotypes alpha, gamma, and epsilon contain cysteines whose role has so far not been elucidated. Using a genetic strategy, we investigated the ability of these cysteines to form disulfide bridges. Shortened versions of human membrane immunoglobulins, depleted of cysteines known to form intermolecular disulfide bonds, were constructed and expressed on the surface of a B-cell line. The resulting membrane proteins contain a single chain fragment of variable regions (scFv) linked to the dimerizing domain from the immunoglobulin heavy chains (CH3 for alpha and gamma or CH4 for epsilon isotypes), followed by the corresponding EMPD and the transmembrane and cytoplasmic domains. The two functional membrane versions of the epsilon chain, containing the short and long EMPD, were analyzed. Our results show that the single cysteine within alpha1L and gamma1 EMPD and the short version of epsilon EMPD form an interchain disulfide bond. Conversely, the cysteine resident in the epsilon transmembrane domain remains unreacted. epsilon-long EMPD contains four cysteines; two are involved in interchain bonds while the remaining two are likely forming an intrachain bridge. Expression of a full-length membrane epsilon heavy chain mutant, in which Cys(121) and Cys(209) within domain CH2 (involved in interchain bridges) were mutated to alanines, confirmed that, within the complete IgE, EMPD cysteines form interchain disulfide bonds. In conclusion, we unveil evidence for additional covalent stabilization of membrane-bound immunoglobulins.

Amino Acid Sequence↗
PubMed2001

Novel lipase-catalysed enantioselective deacetylation of (+/-)-5-acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine.

(+/-)-5-Acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine has been synthesised by a highly diastereoselective [3+2] cycloaddition reaction between alpha-(4-fluorophenyl)-N-phenylnitrone and vinyl acetate in good yield. Candida rugosa lipase catalyses the deacetylation of this (+/-)-5-acetoxyisoxazolidine in a highly enantioselective fashion in diisopropyl ether containing n-butanol affording (-)-5-acetoxy-3-(4-fluorophenyl)-2-phenylisoxazolidine in 43% yield and >99% ee.

Acetylation↗
PubMed2001

Development and characterization of cholinephosphotransferase antibody.

In the present study, we generated antibodies in rabbits against two synthetic peptides, one based on peptide sequence from yeast CPT cDNA (position 86 to 98 of the amino acid sequence) and the other from our guinea pig CPT cDNA (it corresponds to amino acid positions 119 to 130 according to yeast CPT gene). The antibody titers were measured by both dot blot analysis and ELISA using Keyhole limpets hemocyanin coupled CPT peptides. The CPT antibody recognized a single band by Western blot analysis of proteins from guinea pig liver mitochondria and microsomes. The molecular weight of the protein recognized by Western blot analysis is close to the predicted molecular weight (46 kDa) of yeast CPT. Further analysis revealed that the antibody inhibited CPT activity in both subcellular fractions in a dose dependent manner, thus confirming the specificity of the antibody against both subcellular CPT.

Animals↗
PubMed2001

Activation of the luteinizing hormone/choriogonadotropin hormone receptor promotes ADP ribosylation factor 6 activation in porcine ovarian follicular membranes.

Previously we demonstrated in a cell-free ovarian follicular plasma membrane model that agonist-dependent desensitization of the luteinizing hormone/choriogonadotropin receptor (LH/CG R) is GTP-dependent, mimicked by the addition of ADP-ribosylation factor (ARF) nucleotide binding site opener, which acts as a guanine nucleotide exchange factor for ARFs 1 and 6, and selectively inhibited by synthetic N-terminal ARF6 peptides. We therefore sought direct evidence that activation of the LH/CG R promotes activation of ARF1 and/or ARF6. Using a classic ARF activation assay, the cholera toxin-catalyzed ADP-ribosylation of G alpha(s), results show that LH/CG R activation stimulates an ARF protein by a brefeldin A-independent mechanism. Synthetic N-terminal inhibitory ARF6 but not ARF1 peptide blocks LH/CG R-stimulated ARF activity. LH/CG R activation also promotes the binding of a photoaffinity GTP analog to a protein that migrates on one- and two-dimensional polyacrylamide gel electrophoresis with ARF6. These results suggest that ARF6 is the predominant ARF activated by the LH/CG R. To activate ARF6, the LH/CG R does not appear to signal through the C-terminal regions of G alpha(i) or G alpha(q) or through the second or third intracellular loops or the N terminus of the cytoplasmic tail of the LH/CG R. Although exogenous recombinant ARNO promotes only a small increase in ARF6 activation in the presence of activated LH/CG R, hCG-stimulated ARF6 activation is reduced to basal levels by catalytically inactive ARF nucleotide binding-site opener. These results provide direct evidence that LH/CG R activation leads to the activation of membrane-delimited ARF6.

ADP-Ribosylation Factor 6↗
PubMed2001

Tumor progression despite efficient tumor antigen cross-presentation and effective "arming" of tumor antigen-specific CTL.

To determine whether APC function or "arming" of CTL for lytic function are the points at which Ags from a nonimmunogenic tumor fail to induce an effective immune response, we established a murine tumor model that expressed intracellular OVA and selected a clone (cOVA-9) that remained susceptible to lysis by specific CD8(+) T cells throughout tumor growth. Viable cOVA-9 tumor cells grew in normal mice at a rate similar to the parental tumor, and vaccination with irradiated cOVA-9 cells did not induce protection against itself or the parental line, confirming its nonimmunogenic status. In vivo evaluation during tumor growth demonstrated persisting tumor Ag cross-presentation accompanied by the generation of potent, specific CTL which were detectable when tumors were barely palpable. Despite the presence of highly active CTL in the tumor-draining lymph nodes, there was no apparent lysis of tumor-associated APC. These data show that tumor-draining APC are not dysfunctional with regard to two crucial processes, in vivo tumor Ag cross-presentation and specific CTL arming, and that failure to prevent tumor growth is not in the induction phase, but in the effector phase and occurs within the tumor itself before the tumor matrix is established.

Animals↗
PubMed2001

Regulation of cholinephosphotransferase by thyroid hormone.

We have demonstrated earlier that thyroid hormone (T3) regulates the activity of cholinephosphotransferase (CPT) in guinea pig lung. This effect of T3 is not organ specific because we found T3 also regulates CPT activity in the guinea pig liver. Northern blot analysis using two oligonucleotide probes, one synthesized on the basis of the yeast CPT gene sequence and another on the basis of partial cDNA clone from guinea pig CPT clone, revealed that T3 stimulates the expression of new CPT mRNA. Studies with transcriptional and translational inhibitors indicated that T3 enhanced the translation of the CPT mRNA as well as translocation of preformed CPT enzyme protein from cytosol to mitochondria. Furthermore, it strengthens our previous finding that yeast CPT and guinea pig CPT have high homology in their sequence as both the oligonucleotide probes gave the similar type of Northern blot in the present study.

Animals↗
PubMed2001

Sequential immunization of macaques with two differentially attenuated vaccines induced long-term virus-specific immune responses and conferred protection against AIDS caused by heterologous simian human immunodeficiency Virus (SHIV(89.6)P).

Four rhesus macaques were sequentially immunized with live vaccines DeltavpuDeltanefSHIV-4 (vaccine-I) and Deltavpu SHIV(PPC) (vaccine-II). The vaccine viruses did not replicate productively in the peripheral blood mononuclear cells (PBMCs) of the vaccinated animals. All four animals developed binding antibodies against both the vaccine-I and -II envelope glycoproteins but neutralizing antibodies only against vaccine-I. They developed vaccine virus-specific CTLs that also recognized homologous as well as heterologous pathogenic SHIVs. Thirty weeks after the last immunization, the vaccinated animals and three unvaccinated control animals were challenged iv with a highly virulent heterologous SHIV(89.6)P. As expected, the three unvaccinated control animals developed large numbers of infectious PBMCs, high plasma viremia, and precipitous loss of CD4(+) T cells. Two controls did not develop any immune response and succumbed to AIDS in about 6 months. The third control animal developed neutralizing antibodies and had a more chronic disease course, but eventually succumbed to AIDS-related complications 81 weeks after inoculation. The four vaccinated animals became infected with challenge virus as indicated by the presence of challenge virus-specific DNA in the PBMCs and RNA in plasma. However, virus in these animals replicated approximately 200- to 60,000-fold less efficiently than in control animals and eventually, plasma viral RNA became undetectable in three of the four vaccinates. The animals maintained normal CD4(+) T-cell levels throughout the observation period of 85 weeks after a transient drop at Week 3 postchallenge. They also maintained CTL responses throughout the observation period. These studies thus showed that the graded immunization schedule resulted in a safe and highly effective long-lasting immune response that was associated with protection against AIDS by highly pathogenic heterologous SHIV(89.6)P.

AIDS Vaccines↗