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Biomedical subjects

S Guha

Publications and source records attributed to S Guha.

At least 37 records · Page 2Linked to original sources
PubMed2001

Multiple antibiotic changes during the first 72 hours of hospitalization.

BACKGROUND: Increasing concern about inappropriate antibiotic use prompted us to examine whether our patients were receiving frequent and perhaps unwarranted changes of antibiotic therapy. METHODS: We evaluated antibiotic prescribing by the physicians in the Emergency Department and by those on the inpatient medical service during the first 72 hours of hospitalization in 119 patients admitted with suspected serious infections to an acute care, university-affiliated, municipal teaching hospital. The appropriateness of antibiotic prescriptions was assessed independently and retrospectively by 2 infectious disease specialists (each based at a different hospital) using a 4-grade scale (from 1 = wrong choice to 4 = appropriate). Of their evaluations of the 427 antibiotic regimens given to the 119 patients during 4 defined intervals during their first 72 hours of hospitalization, 90% agreed with each other within 1 grade. Their evaluations were then compared with the selections that had been made at each interval by the prescribing physicians. RESULTS: Successive prescribing physicians changed the antibiotic regimens in 77% of cases during the first 24 hours and in 56% during the next 48, often without apparent clinical or microbiologic indications. By 72 hours, the 119 patients had received a mean of 3.1 +/- 1.3 (+/-SD) different antibiotics, and 40 received between 4 and 7. Only 7% of the patients had no change in the regimen prescribed originally. CONCLUSIONS: Many patients had multiple changes of antibiotics, often unnecessarily, resulting in exposure to too many agents.

Anti-Bacterial Agents↗
PubMed2001

Study on early intervention with ACE inhibitor in myocardical infarction and short term outcome.

The present study was carried out on 100 patients with acute myocardial infarction (AMI) being treated with angiotensin converting enzyme (ACE) inhibitor and another 80 patients with conventional treatment but without ACE inhibitor during the period from May 1, 1995 to August 7, 1996 in Medical College, Calcutta. Clinical and other laboratory investigations including echocardiographic parameters were noted and recorded meticulously within 24-48 hours after AMI and repeated at 4th week. The present study based on non-invasive methods other than haemodynamic methods has shown that the echocardiographic assessment of left ventricular functional parameters after 4 weeks of ACE inhibitor therapy (n = 100) were better in treated group in comparison to control group without ACE inhibitor (n = 80) and the difference was statistically significant at 99% level of confidence. Overall mortality was 4% in ACE inhibitor group and 8.75% in the control group. This short term study with early intervention with ACE inhibitor within 48 hours of AMI has shown statistically significant evidence of beneficial effect of ACE inhibitor in improving the ventricular functional parameters and also reducing short term mortality from cardiac cause within 4 weeks compared to the group not receiving ACE inhibitors.

Adult↗
PubMed2000

Geometry-dependent electronic properties of highly fluorescent conjugated molecules

We present a combined experimental/theoretical study of the electronic properties of conjugated para-phenylene type molecules under high pressure up to 80 kbar. Pressure is used as a tool to vary the molecular geometry and intermolecular interaction. The influence of the latter two on singlet and triplet excitons as well as polarons is monitored via optical spectroscopy. We have performed band structure calculations for the planar poly(para-phenylene) and calculated the dielectric function. By varying the intermolecular distances and the length of the polymer repeat unit the observed pressure effects can be explained.

Journal Article↗
PubMed2000

Metallic nonsuperconducting phase and D-wave superconductivity in Zn-substituted La1.85Sr0.15CuO4

Measurements of the resistivity, magnetoresistance, and penetration depth were made on films of La1.85Sr0.15CuO4, with up to 12 at. % of Zn substituted for the Cu. The results show that the quadratic temperature dependence of the inverse square of the penetration depth, indicative of d-wave superconductivity, is not affected by doping. The suppression of superconductivity leads to a metallic nonsuperconducting phase, as expected for a pairing mechanism related to spin fluctuations. The metal-insulator transition occurs in the vicinity of k(F)l approximately 1, and appears to be disorder driven, with the carrier concentration unaffected by doping.

Journal Article↗
PubMed1999

Multisubstrate biodegradation kinetics of naphthalene, phenanthrene, and pyrene mixtures.

Biodegradation kinetics of naphthalene, phenanthrene and pyrene were studied in sole-substrate systems, and in binary and ternary mixtures to examine substrate interactions. The experiments were conducted in aerobic batch aqueous systems inoculated with a mixed culture that had been isolated from soils contaminated with polycyclic aromatic hydrocarbons (PAHs). Monod kinetic parameters and yield coefficients for the individual compounds were estimated from substrate depletion and CO(2) evolution rate data in sole-substrate experiments. In all three binary mixture experiments, biodegradation kinetics were comparable to the sole-substrate kinetics. In the ternary mixture, biodegradation of naphthalene was inhibited and the biodegradation rates of phenanthrene and pyrene were enhanced. A multisubstrate form of the Monod kinetic model was found to adequately predict substrate interactions in the binary and ternary mixtures using only the parameters derived from sole-substrate experiments. Numerical simulations of biomass growth kinetics explain the observed range of behaviors in PAH mixtures. In general, the biodegradation rates of the more degradable and abundant compounds are reduced due to competitive inhibition, but enhanced biodegradation of the more recalcitrant PAHs occurs due to simultaneous biomass growth on multiple substrates. In PAH-contaminated environments, substrate interactions may be very large due to additive effects from the large number of compounds present.

Biodegradation, Environmental↗
PubMed1999

Bradycardia, reversible panconduction defect and syncope following self-medication with a homeopathic medicine.

Alkaloid extracts from the plant Aconitum species have been used in various forms of herbal remedies predominantly as anti-inflammatory and analgesic agents. Many of these alkaloids are extremely potent cardiotoxins and documented cases of various arrhythmias with fatal outcomes have been reported. We report a case of self-medication with 'tincture of aconite' resulting in severe bradycardia, reversible panconduction defect evidenced by sinus inactivity, atrioventricular dissociation with idiojunctional rhythm and left bundle branch block pattern resulting in hypotension and syncope. Complete reversal of ECG findings with marked improvement in symptoms was noted within a few hours. Herbal medicines containing aconite alkaloids may result in severe cardiotoxicity, and strict regulatory measures are warranted to curb unsupervised use for therapeutic purposes.

Aconitum↗
PubMed1999

A comparative study of balloon mitral valvuloplasty and closed mitral commissurotomy in patients with rheumatic mitral stenosis.

Rheumatic mitral stenosis is frequently encountered in our country. It affects younger population and is a major cause of morbidity Mitral valvotomy is the definitive therapy for this disease and can be achieved by closed mitral commissurotomy (CMC), open mitral commissurotomy (OMC) or by percutaneous transluminal mitral valvuloplasty (PTMV). Compared to CMC, PTMV is less invasive but more expensive at this moment. With the reduction of cost, PTMV may become the procedure of choice for the treatment of rheumatic mitral stenosis in future.

Adolescent↗
PubMed1998

Chaperone-like activity of tubulin.

Tubulin, a ubiquitous protein of eukaryotic cytoskeleton, is a building block unit of microtubule. Although several cellular processes are known to be mediated through the tubulin-microtubule system, the participation of tubulin or microtubule in protein folding pathway has not yet been reported. Here we show that goat brain tubulin has some functions and features similar to many known molecular chaperones. Substoichiometric amounts of tubulin can suppress the non-thermal and thermal aggregation of a number of unrelated proteins such as insulin, equine liver alcohol dehydrogenase, and soluble eye lens proteins containing beta- and gamma-crystallins. This chaperone-like activity of tubulin becomes more pronounced as temperature increases. Aging of tubulin solution at 37 degreesC also enhances its chaperone-like activity. Tubulin loses its chaperone-like activity upon removal of its flexible hydrophilic C-terminal tail. These results suggest that both electrostatic and hydrophobic interactions are important in substrate binding by tubulin and that the negatively charged C-terminal tails play a crucial role for its chaperone-like activity.

Alcohol Dehydrogenase↗
PubMed1998

Increased expression of a hemimethylated oriC binding protein, SeqA, in an aphA mutant.

In Escherichia coli, the origin of DNA replication, oriC, becomes transiently hemimethylated at the GATC sequences immediately after initiation of replication and this hemimethylated state is prolonged because of its sequestration by a fraction of outer membrane. This sequestration is dependent on a hemimethylated oriC binding protein such as SeqA. We previously isolated a clone of phage lambda gt11 called hobH, producing a LacZ fusion protein which recognizes hemimethylated oriC DNA. Very recently, Thaller et al. (FEMS Microbiol. Lett. 146 (1997) 191-198) found that the same DNA segment encodes a non-specific acid phosphatase, and named the gene aphA. We show here that the interruption of the aphA reading frame by kanamycin resistance gene insertion, abolishes acid phosphatase (NAP) activity. Interestingly, in the membrane of the null mutant, the amount of SeqA protein is about six times higher than that in the parental strain, suggesting the existence of a regulatory mechanism between SeqA and NAP expression.

Acid Phosphatase↗
PubMed1998

Rate of gastric emptying is a determinant of postprandial hypotension in non-insulin-dependent diabetes mellitus.

1. Postprandial hypotension is now recognized as an important clinical problem, particularly in the elderly and in patients with autonomic dysfunction. The mechanisms responsible are poorly understood; however, impaired regulation of splanchnic blood flow and the release of gastrointestinal hormones appear to be important. The effect of gastric emptying on the magnitude of the postprandial fall in blood pressure has not been evaluated. 2. The aim of this study was to determine whether there is a relationship between changes in blood pressure and the rate of gastric emptying after ingestion of 75 g of glucose in patients with non-insulin-dependent diabetes mellitus (NIDDM) and both young and older normal subjects. Sixteen patients with recently diagnosed NIDDM, median age 57 (39-79) years, 10 'young' subjects with a median age of 23 (19-26) years and nine 'older' subjects, median age 48 (40-68) years, were measured simultaneously for gastric emptying of 75 g of glucose in 350 ml of water blood pressure and blood glucose concentrations, commencing at approximately 10.00 hours after an overnight fast. Measurements of blood pressure were made in the sitting position immediately before glucose ingestion and at 15 min intervals up to 180 min. 3. Gastric emptying of glucose was not significantly different between the three groups [50% emptying time (T50): 95 +/- 7.3 min in patients with NIDDM compared with 120 +/- 13.2 min in the 'young' group and 97 +/- 8.1 min in the 'older' group]. There was a significant fall in mean blood pressure after the glucose load in the patients with NIDDM (P < 0.0001) and the 'older' normal subjects (P < 0.05), but not the 'young' normal subjects. Postprandial hypotension (fall in systolic blood pressure > or = 20 mmHg) was evident in seven (44%) patients with NIDDM and three (33%) 'older' normal subjects. The area under the change in mean blood pressure curve was related significantly to the gastric emptying T50 (r = 0.67, P < 0.005) in the patients with NIDDM, but not in either control group. 4. In conclusion, in patients with recently diagnosed NIDDM the fall in blood pressure after an oral glucose load is (i) greater than in both young and older normal subjects and (ii) related to the rate of gastric emptying.

Adult↗
PubMed1997

Refolding of urea-denatured tubulin: recovery of nativelike structure and colchicine binding activity from partly unfolded states.

Tubulin unfolding in urea proceeds via the formation of a partially unfolded intermediate state, stable in 2 M urea, that unfolds further in higher urea concentrations. The intermediate state had spectroscopic properties reminiscent of a molten globule and negligible colchicine binding activity. Refolding of totally unfolded tubulin in 8 M urea yielded an intermediatelike state characterized by partial burial of tryptophans and partial recovery of secondary and tertiary structures, although colchicine-binding activity of the protein was not regained. Further folding of this intermediatelike state, toward the native conformation, with respect to both structural and functional parameters did not occur. However, a significant percentage of colchicine binding activity and nativelike tertiary structure was recovered when refolding was initiated from partially denatured protein samples, viz., from <1.2 M urea. Thus, although high concentration of urea induced loss of structure and activity was irreversible, the conformational changes induced in restricted regions of tubulin by lower concentrations of urea, which are probably crucial for its various functional properties, could be reversed.

2-Naphthylamine↗
PubMed1997

Differential interactions of the Mg2+ complexes of chromomycin A3 and mithramycin with poly(dG-dC) x poly(dC-dG) and poly(dG) x poly(dC).

The interaction of the two anticancer antibiotics, chromomycin A3 and mithramycin, with the polynucleotides poly(dG-dC) x poly(dC-dG), representative of B-DNA, and poly(dG) x poly(dC), representative of A-DNA, in the presence of Mg2+ is studied by spectroscopic techniques such as absorbance, fluorescence, and dircular dichroism (CD). The studies were done with both drug x Mg2+ complexes, I and II, having 1:1 and 2:1 stoichiometries with respect to drug and Mg2+, respectively [Aich, P., Sen, R., & Dasgupta, D. (1992) Biochemistry 31, 2988-2997]. The objective of the present work is 2-fold. First, an attempt is made to understand the structural basis of the ligand-DNA interaction, particularly the role of DNA backbone conformation with its groove size and the accessibility of the 2-amino group in the minor groove of guanosine. Second, the role of the antibiotic saccharide moieties in the association with DNA was studied. For this purpose, the spectroscopic characterization of the binding was done followed by the evaluation of binding parameters and associated thermodynamics. Analysis of the observed thermodynamics for the ligand-DNA interactions in terms of the different structures of the polynucleotides was done. The salient results are as follows. Complex I does not discriminate significantly among the A- and B-forms of DNA when it binds to them in an entropy-driven process. On the other hand, complex II for both drugs recognizes B- and A-forms of DNA in different ways. This observation implies that the sequence specificity shown by this complex is a sequel to the difference in the parameters such as groove size and accessibility of the guanosine amino group. Another important finding is that binding with the same polynucleotide is not comparable for the complex II of the two drugs. It emphasizes the involvement of the sugar moieties, when the drug x Mg2+ complex binds to DNA. The presence of an acetoxy group in the sugars of chromomycin A3 imparts some distinctive specific features of the association of the chromomycin dimer x Mg2+ complex with DNA. Finally, the results are compared with those available from NMR studies of different drug-oligonucleotide complexes under conditions where complex II is the ligand.

Chromomycin A3↗
PubMed1997

Blood glucose concentration influences postprandial fullness in IDDM.

OBJECTIVE: Upper gastrointestinal (GI) symptoms and delayed gastric emptying both occur frequently in patients with long-standing IDDM, but the relationship between them is relatively weak. Recent studies in normal subjects have indicated that blood glucose concentration may increase the perception of sensations arising from the upper GI tract. The purpose of this study was to examine the relationships among postprandial fullness, the rate of gastric emptying, and blood glucose concentration in IDDM patients. RESEARCH DESIGN AND METHODS: We studied measurements of gastric emptying, blood glucose concentrations, cardiovascular autonomic nerve function, upper GI symptoms, and postprandial hunger and fullness in 40 IDDM patients (16 men, 24 women). ages 19-63 years. Gastric emptying of solids and liquids was measured scintigraphically, upper GI symptoms were measured by questionnaire immediately before ingestion of the test meal, and fullness and hunger were measured by visual analog scales every 15 min. Blood glucose concentrations were measured at -5, 30, 60, 90, and 120 min. RESULTS: Solid gastric emptying was delayed in 58% of the patients, and both solid and liquid gastric emptying were slower (P < 0.05) in women than in men. The score for upper GI symptoms was not significantly related to gastric emptying. In contrast, postprandial fullness, but not hunger, was related to the amount of solid (r = 0.36, P < 0.05) but not liquid in the stomach. Both before (r = 0.39, P < 0.05) and after (r = 0.47, P < 0.01) the meal, fullness was related to blood glucose concentration. Postprandial fullness was also related to autonomic nerve dysfunction (r = 0.39, P < 0.05). Multiple regression analysis confirmed that blood glucose concentration, the rate of solid gastric emptying, and autonomic nerve dysfunction were independent determinants of postprandial fullness, together accounting for 47% of the variance. CONCLUSIONS: These observations demonstrated that, in IDDM, postprandial fullness is influenced by blood glucose concentration, the rate of solid gastric emptying, and autonomic nerve function.

Adult↗
PubMed1996

Tubulin conformation and dynamics: a red edge excitation shift study.

The fluorescence emission maximum of a polar fluorophore in viscous medium often shows a dependence on excitation wavelength, a phenomenon which is named red edge excitation shift (REES). We have found that the fluorescence spectra of the tubulin tryptophans exhibit a REES of about 7 nm. Also, their steady state fluorescence polarization and mean lifetimes show a dependence on both excitation and emission wavelengths. These results indicate that the average tryptophan environment in tubulin is motionally restricted. Although the tryptophan(s) responsible for the observed REES effect could not be localized, it could be concluded from energy transfer experiments with the tubulin-colchicine complex that the tryptophan(s) participating in energy transfer with bound colchicine probably does not contribute to the REES. A REES of 7 nm was also observed in the case of colchicine complexed with tubulin. However, such a REES was not seen in similar studies with the B-ring analogs of colchicine, viz. 2-methoxy-5-(2',3',4'-trimethoxyphenyl)tropone (called AC because it lacks the B ring of colchicine) and deacetamidocolchicine (which lacks the acetamido substituent at the C-7 position of the B ring). There may be two possible reasons to explain these data. (1) Structural differences between colchicine and its analogs may give rise to differences in their excited state dipole moments which will directly affect the extent of REES, and (2) The B-ring substituent, hanging outside the colchicine binding site on the beta-subunit of the tubulin dimer, probably makes contact with the alpha-subunit of tubulin and imparts a rigidity to that region of the protein, which facilitates the REES.

Animals↗