Regulatory factor linked to late-onset diabetes?
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Animals↗
Biomedical subjects
S Dutta
Publications and source records attributed to S Dutta.
Serotypes and antimicrobial susceptibility patterns of Shigella species isolated from children in Calcutta, India.
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Anti-Bacterial Agents↗
Liposomal tacrolimus and intestinal drug concentration.
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Animals↗
Formulation-dependent brain and lung distribution kinetics of propofol in rats.
BACKGROUND: Propofol when administered by brief infusion in a lipid-free formulation has a slower onset, prolonged offset and greater potency compared with an emulsion formulation. To understand these findings the authors examined propofol brain and lung distribution kinetics in rats. METHODS: Rats were infused with equieffective doses of propofol in emulsion (n = 21) or lipid-free formulation (n = 21). Animals were sacrificed at various times to harvest brain and lung. Arterial blood was sampled repeatedly from each animal until sacrifice. Deconvolution and moment analysis were used to calculate the half-life for propofol brain turnover (BT) and brain:plasma partition coefficient (Kp). Lung concentration-time profiles were compared for the two formulations. RESULTS: Peak propofol plasma concentrations for the lipid-free formulation were 50% of that observed for emulsion formulation, whereas peak lung concentrations for lipid-free formulation were 300-fold higher than emulsion formulation. Brain Kp calculated from tissue disposition curve and ratio of brain:plasma area under the curves were 8.8 and 13, and 7.2 and 9.1 for emulsion and lipid-free formulations, respectively. BT were 2.4 and 2.5 min for emulsion and lipid-free formulations, respectively. CONCLUSIONS: Significant pulmonary sequestration and slow release of propofol into arterial circulation when administered in lipid-free vehicle accounts for the lower peak arterial concentration and sluggish arterial kinetics relative to that observed with the emulsion formulation. Higher Kp for the lipid-free formulation could explain the higher potency associated with this formulation. BT were independent of formulation and correlated with values reported for effect-site equilibration half-time consistent with a distribution mechanism for pharmacologic hysteresis.
Anesthetics, Intravenous↗
Formulation-dependent pharmacokinetics and pharmacodynamics of propofol in rats.
Propofol, a highly lipophilic anaesthetic, is commercially formulated as a lipid emulsion (diprivan) for intravenous use. This formulation is characterized by rapid onset and offset of effect after rapid intravenous administration and an effect-site equilibration half-life (t1/2kE0) of 1.7 min in rats. Paradoxically these characteristics are usually associated with relatively water-soluble anaesthetics. To test the influence of the formulation on propofol pharmacokinetics, effect-site equilibration kinetics and pharmacodynamics we performed a pharmacokinetic-pharmacodynamic study of propofol in chronically instrumented rats after administration in a lipid-free formulation. In this report we present the results of this study and compare these results with previous data obtained with rats receiving propofol in the emulsion formulation. Compared with the emulsion formulation the distribution volumes (VdC and VdSS) were significantly higher but the t1/2kE0 (2.0 min) was similar for the lipid-free formulation. The concentration-effect relationship was biphasic. Propofol effect-site concentrations required to achieve 50% activation, peak activation, 50% inhibition of peak activation effect and maximum inhibition were significantly lower, indicating a higher apparent steady-state potency for the lipid-free formulation compared with the emulsion formulation. The evanescent characteristics of propofol's effect-time-course disappeared when the anaesthetic was administered in the lipid-free formulation. These results suggest that the nature of the formulation can profoundly influence the clinical characteristics of intravenously administered drugs by modifying the pharmacokinetics or pharmacodynamics or both.
Anesthetics, Intravenous↗
Multiple unfolded states of UDP-galactose 4-epimerase from yeast Kluyveromyces fragilis. Involvement of proline cis-trans isomerization in reactivation.
UDP-galactose 4-epimerase from yeast Kluyveromyces fragilis is a dimeric molecule of 75 kDa per subunit with one molecule of cofactor NAD per dimer. It undergoes unfolding and complete dissociation in presence of 8 M urea at pH 7.0 by 10 min. It can be functionally reconstituted almost quantitatively in 2 h by dilution with 20 mM sodium phosphate buffer, pH 7 containing 1 mM extraneous NAD under a second order kinetics [Bhattacharyya, D. (1993) Biochemistry 32, 9726-9734]. Denaturation between 10-60 min inversely affects both the rate and maximum recovery of activity upon refolding. Aggregation of this protein has not been observed under these conditions. The time dependent reaction at the unfolded state is independent of pH between 5.4-10.4 but strongly dependent on temperature of denaturation between 0-20 degrees C. Unfolding at 0 degrees C divides the protein largely into two populations-34% of fast folding species following an apparent first order kinetics and 59% of slow folding species following a second order kinetics of reactivation. A very fast folding species of low abundance 3.5-7.5% depending on temperature of denaturation has been identified, which gets active status within the dead time of mixing. Interaction with the active site directed fluorescence probe 1-anilino 8-naphthalene sulfonic acid (1-ANS) and estimation of bound NAD suggest that the catalytic region of this enzyme is not formed in the long term denatured samples. The whole process of reactivation is catalysed by peptidyl prolyl cis-trans isomerase and thus suggests that one or more proline residues stereochemically control the rate limiting step of reactivation.
Anilino Naphthalenesulfonates↗
The cloning and overexpression of a cruciform binding protein from Ustilago maydis.
The structural gene HMP1 encoding a cruciform DNA binding protein from Ustilago maydis has been cloned. Gene isolation was enabled by a polymerase chain reaction procedure using primers designed from amino acid sequence obtained from the purified protein. DNA sequence determination has revealed that the gene encodes a protein containing 98 amino acids with a calculated molecular weight of 10151. Comparison of the cDNA and genomic sequences indicated the presence of a single intron in the 5' coding region of the gene. The gene was over-expressed as a translational fusion with a hexahistidine leader sequence enabling affinity purification of the protein on an immobilized metal matrix. Protein isolated after over-expression exhibited cruciform binding activity, conforming earlier purified native protein results. Sequence analysis indicated that no HMG box was present and very little homology to other known cruciform binding proteins was found. It is plausible that HMP1 represents a novel class of proteins that recognize such secondary structures.
Amino Acid Sequence↗
Reversible folding of UDP-galactose 4-epimerase from Escherichia coli.
UDP-galactose 4-epimerase from Escherichia coli is a homodimer of 39-kDa subunits having 1 or 2 molecules of NAD bound non-covalently/dimer. The enzyme can be dissociated and denatured by 8 M urea at pH 7.0 to a state having only 15% of residual secondary structure. Dilution of the denaturant by 20 mM potassium phosphate, pH 8.5, leads to functional reconstitution of the enzyme. No addition of extraneous NAD is required for reactivation, indicating a strong affinity of the cofactor for refolded molecule. The reactivation follows a second-order kinetics (k = 1.2 +/- 0.07 X 10(3) M(-1) s(-1) at 25 degrees C) with an energy of activation of 23.79 +/- 0.33 kJ/mol. The native, denatured and renatured states of the enzyme were characterized by far-ultraviolet CD spectra for secondary structure: protein fluorescence, interaction with extrinsic fluorescence probe ANS (1-anilino 8-naphthalene sulfonic acid) and ultraviolet absorption spectra for tertiary structure and size-exclusion HPLC, gel-filtration chromatography and light-scattering for quaternary structure. The folding process could be broadly divided into two distinct steps: (a) regain of secondary structure and dimerization were fast and were complete within 2 min and 9 min, respectively, and (b) regain of catalytic activity was slow and was complete by 45 min. No active holoenzyme could be identified. It appears that generation of the NAD-binding site and subsequent assembly of NAD is the rate-limiting step expressing catalytic activity.
Binding Sites↗
Effect of Maharishi AK-4 on H2O2-induced oxidative stress in isolated rat hearts.
Oxidative damage to crucial biomolecules due to excess generation of reactive oxygen species has been implicated as a major cause of organ damage and hence compounds capable of negating such damage have potential benefits. Using hydrogen peroxide (H2O2) as a model pro-oxidant to induce oxidative stress, we have examined the ability of natural food supplement Maharishi Amrit Kalash (MAK-4) to decrease oxidative damage in potassium-arrested isolated rat hearts. The protocol was that hearts isolated from male Sprague-Dawley rats were retrograde-perfused with Krebs-Henseleit (K-H) solution for 30 min for equilibration. After this period, the hearts were subjected to cardioplegia with high potassium (26-30 mM), followed by reperfusion with K-H solution in the presence or absence of 200 microM H2O2. As expected, H2O2 treatment following cardioplegia induced a high degree of oxidative stress as assessed by release of lactate dehydrogenase (LDH, a marker of plasma membrane damage) and total glutathione (GSH + GSSG). H2O2 also impaired the ability of heart to regain developed tension during the testing period. However, addition of MAK-4 in the perfusate containing H2O2 decreased oxidative stress in terms of release of LDH and glutathione. In parallel with these biochemical studies, in a few experiments the cardiac function was assessed by measuring developed contractile tension. These preliminary studies also showed that in the presence of MAK-4 the H2O2-treated hearts were able to regain better developed tension. Further in vitro studies to examine the possible mechanisms of MAK-4 action reveal that this formulation contains H2O2 binding activity which resulted in the decreased availability of H2O2 itself. Our studies hence reveal that the ayurvedic food supplement MAK-4 may have potential benefits in reducing oxidative stress.
Animals↗
Concentration-EEG effect relationship of propofol in rats.
Propofol is a unique highly lipid-soluble anesthetic that is formulated in a fat emulsion (Diprivan) for intravenous (i.v.) use. It has the desirable properties of rapid onset and offset of effect following rapid i.v. administration and minimal accumulation on long-term administration. Based on physicochemical properties and preliminary brain solubility data, propofol should have an extended effect-site turnover and a resulting prolonged effect. However, a preliminary study in humans has reported a rapid blood-brain equilibration half-time (T1/2 kE0) of only 2.9 min. We used a chronically instrumented rat model to examine the unique disposition and electroencephalographic (EEG) pharmacodynamics of propofol. Although the pharmacokinetics were variable, there was low interindividual variability in the concentration-EEG effect relationship. The duration of EEG sleep was 26 (+/- 44% CV) min following 11-15 mg/kg doses of propofol. The T1/2 kE0 was 1.7 (+/- 32%) min. Apparent effect-site concentrations of 0.5-1 microg/mL were required to maintain sleep in rats. Like other general anesthetics, the concentration-EEG effect relationship of propofol is biphasic. At a propofol concentration of 0.6 (+/- 35%) microg/mL, the number of EEG waves/s was maximal at 175% of baseline awake state. Further increases in the concentration of propofol depressed EEG activity until complete suppression occurred at 7 (+/- 22%) microg/mL.
Anesthetics, Intravenous↗
Parameter estimability of biphasic response models.
Pharmacodynamics of general anesthetic agents generally exhibit biphasic concentration-effect relationships (i.e., an activation phase at low concentrations and inhibition at higher concentrations). These relationships are usually characterized with biphasic models constructed from various combinations and modifications of the nonlinear sigmoid E(MAX) model. We tested and quantified the parameter estimability of the simplest additive biphasic pharmacodynamic models by a Monte Carlo method. The estimated model parameters were used to calculate descriptors of the concentration-effect data. Parameters and descriptors were compared with their true values. When the IC50/EC50 ratio was low (<10), E(MAX), EC50, and IC50 were poorly estimated (high coefficient of variation and pronounced bias). However, the fit to the data was excellent, and the data descriptors calculated from the estimated model parameters demonstrated high precision and accuracy. Baseline effect (E0) was estimated with good precision and accuracy. As the IC50/EC50 ratio was increased, the estimability of model parameters and data descriptors improved, with the data descriptors continuing to be more estimable than model parameters. Thus, model parameters become estimable when there is sufficient separation between EC50 and IC50 to produce a plateauing of peak effect (activation), which can be observed directly from the data signature. Data descriptors are not subject to this limitation and thus may serve as better metrics for summarizing concentration-effect relationships.
Anesthetics↗
Propofol pharmacokinetics and pharmacodynamics assessed from a cremophor EL formulation.
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Anesthetics, Intravenous↗
Emulsion formulation reduces propofol's dose requirements and enhances safety.
BACKGROUND: Propofol, a highly lipophilic anesthetic, is formulated in a lipid emulsion for intravenous use. Propofol has brisk onset and offset of effect after rapid administration and retains rapid offset characteristics after long-term administration. The authors tried to determine whether the emulsion vehicle is requisite for propofol's evanescent effect-time profile. METHODS: The time course of sedation and electroencephalographic (EEG) effect after propofol administration was measured in three studies in rats instrumented. In study 1, propofol was infused in either emulsion or lipid-free vehicle (n = 12), in a repeated measures cross-over design. In study 2, propofol in lipid-free vehicle was infused with or without simultaneous infusion of drug-free lipid emulsion (n = 6) in a repeated measures cross-over design. In study 3, propofol was infused in either emulsion (n = 5) or lipid-free vehicle (n = 5) to EEG burst suppression. RESULTS: In study 1, relative to the emulsion formulation, propofol administered at equivalent doses in lipid-free vehicle resulted in a longer time to effect onset (1.4 +/- 0.2 vs. 0.5 +/- 0.1 min, EEG) and a trend for delayed anesthetic recovery (26.8 +/- 9.4 vs. 17 +/- 3.5 min, EEG; 26.1 +/- 8.8 vs. 16.8 +/- 3.3 min, sleep). In study 2, coadministration of drug-free emulsion with propofol did not alter the time course of effect. In study 3, more than twice the dose of propofol was required to achieve EEG burst suppression with the lipid-free formulation. Two animals died after administration of propofol to EEG burst suppression with the lipid-free formulation; no deaths occurred in the emulsion group. CONCLUSION: The incorporation of propofol in emulsion reduces dose requirements and produces rapid onset and recovery of anesthetic effect.
Anesthetics, Intravenous↗
Double-blind, randomized clinical trial for safety and efficacy of norfloxacin for shigellosis in children.
In a randomized, double-blind clinical trial, the efficacy and safety of norfloxacin were compared with nalidixic acid in the treatment of shigellosis in children. Out of 59 cases, Shigella spp. were isolated from 8 cases in the nalidixic acid group and 14 cases in the norfloxacin group. The norfloxacin group had significantly less duration of diarrhoea and presence of blood in stool as compared to the nalidixic acid group. No joint problem was encountered in this study at up to 4 months follow-up. Norfloxacin is safe and effective and showed no cartilage toxicity on short-term follow-up.
Anti-Infective Agents↗
Isolation of Escherichia coli to detect faecal contamination of infants and their mothers in West Bengal.
The present study was undertaken to gain insight into the sources of faecal contamination of infants in rural Bengal. It was carried out in three villages near Calcutta, India, from June 1993 to August 1995 among 148 infants and their mothers. Escherichia coli was used as an indicator of faecal pollution. A total of 725 samples, including hand rinsings of children and mothers, feeding utensils and leftover food were examined. The total isolation rate of faecal E. coli was 30%. The isolation rates from hands of children and mothers were 17% and 40% respectively. The germs from 30% of utensils and 59% of leftover food and drinks were recovered further. The study highlights the precarious hygiene in rural Bengal.
Adult↗
Composition of lipids from the glands of the external ear canal of the adult chicken.
Six classes of neutral lipids, i.e. triacylglycerol (TG), free fatty acids (FFA), monoester waxes (MW), free- and esterified sterols (FST and SE), and squalene (SQ) were identified by thin layer chromatography of the lipid materials extracted separately from the secretion as well as from the isolated whole glands present in the skin of the floor of the external ear canal of the domestic fowl. Secretory lipids contained considerable proportions of MW fractions (17.03%), TG (22.23%), and SQ (14.66%), while TG was the major component (41.10%) in the lipids from the isolated glands. Polar lipids, which comprised about 16-20% of total glandular lipids, were shown to be composed primarily of sphingomyelin.
Animals↗
Phase I/II trial of combined 131I anti-CEA monoclonal antibody and hyperthermia in patients with advanced colorectal adenocarcinoma.
BACKGROUND: This pilot project was undertaken to evaluate the toxicity of and tumor response to combined 131I anti-carcinoembryonic antigen monoclonal antibody (131I anti-CEA RMoAb) and hyperthermia in patients with metastatic colorectal adenocarcinoma. METHODS: Nine patients who had colorectal carcinoma with liver metastases were enrolled in this study. Intact 131I anti-CEA RMoAb was used (the specific antibody was IMMU-4, provided by Immunomedics, Inc., Morris Plains, NJ). During the diagnostic phase, dosimetry revealed that the tumor site received a higher radiation dose than the surrounding normal tissues in only six patients. These six, who were treated with radioimmunotherapy and hyperthermia, were the basis of this study. The first three patients were treated with 30 mCi/m2 of 131I anti-CEA RMoAb, and the next three received 60 mCi/m2. Pharmacokinetic clearance data were reported for all nine patients. RESULTS: Thermometry data revealed an average T90 of 40.3 (+/- 1.4 degrees C) and T50 of 41.1 (+/- 1.2 degrees C). The average thermal dose equivalent at 42.5 degrees C was 34.5 (+/- 21.5) minutes. The average Tmin, Tmax, and Tmeam were 40 (+/- 1.2 degrees C), 42.4 (+/- 0.7 degrees C), and 41.1 (+/- 1.1 degrees C), respectively. The pharmacokinetic clearance data of antibody showed monoexponential plasma clearances in all patients except one, in whom a biexponential plasma clearance was observed. In general, similar plasma and whole-body clearances as well as similar urinary excretions were observed when diagnostic and therapeutic phases for each patient were compared. Two of the six patients showed a marked improvement in their symptoms; five patients showed a drop in carcinoembryonic antigen levels. A follow-up computed tomography scan one month after treatment showed no change in tumor volume in five patients; one patient showed a partial response. Three patients developed toxicity, two developed moderate thrombocytopenia (39,000 and 58,000), and the other patient developed hematoma resulting from the insertion of a catheter for thermometry. CONCLUSIONS: It is feasible to combine hyperthermia and radiolabeled monoclonal antibodies, and the combination was well tolerated by these patients. The interaction between hyperthermia and low dose rate radioimmunotherapy is complex. Further studies are necessary to explore the use of this combined modality in the management of maligancies.
Adult↗
Inhibition of gastric mucosal regeneration by tyrphostin: evaluation of the role of epidermal growth factor receptor tyrosine kinase.
Although induction of mucosal cell proliferation is a crucial event in gastric mucosal regeneration after injury, intracellular regulatory processes have not been fully elucidated. We hypothesize that tyrosine kinases (Tyr-k)--specifically the enzyme associated with epidermal growth factor receptor (EGF-R)--play an important role in mucosal regeneration. Utilizing tyrphostin--a Tyr-k inhibitor with a greater specificity for EGF-R Tyr-k than for other Tyr-ks--we have examined the role of EGF-R Tyr-k in gastric mucosal regeneration after injury. Gastric mucosal injury in 3-to 4-month-old rats was induced by orogastric administration of 2 mol/L NaCl, whereas the control animals received an equivalent volume of water. The animals were killed 24 hours later. During this 24-hour experimental period (reparative phase), one of the groups was also injected (IP) with tyrphostin-51 (0.65 mg/kg in 30% dimethyl sulfoxide), whereas the control group received the vehicle. In the absence of tyrphostin, the gastric mucosa showed signs of extensive regeneration, whereas in its presence the degree of regeneration was greatly attenuated. These changes were accompanied by parallel alterations in the number of proliferating cell nuclear antigen-immunoreactive cells and the Tyr-k activity of EGF-R. In water-fed control animals, tyrphostin also caused a significant 30% reduction in proliferating cell nuclear antigen-immunoreactive cells. In these animals, the Tyr-k activity of EGF-R was also decreased by 30%. At 24 hours after injury, EGF-R mRNA levels were increased 36-fold over the water-fed controls, and this increase was not significantly affected by tyrphostin. Our current data suggest that activation of EGF-R is an important event in mucosal regeneration.
Animals↗