Needlestick injuries amongst medical students in Birmingham, UK.
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England↗
Biomedical subjects
P Venkatesan
Publications and source records attributed to P Venkatesan.
Inhibition of radiation-induced lipid peroxidation by tetrahydrocurcumin: possible mechanisms by pulse radiolysis.
The antioxidant property of tetrahydrocurcumin (THC), a reduced derivative of curcumin, was examined by its ability to inhibit radiation-induced lipid peroxidation in rat liver microsomes and compared with curcumin. The lipid peroxidation caused by irradiation of N2O-purged and aerated buffered aqueous solutions was found to be inhibited by THC in a dose- and concentration-dependent manner. In order to understand the actual reaction mechanisms involved in the inhibition process, pulse radiolysis investigation of THC with radiolytically produced radicals like hydroxyl, model peroxyl radicals, and azide radicals were done and the transients were detected by kinetic spectrophotometry. The reaction of THC with hydroxyl and azide radicals gave rise to transient absorption in the region 200-400 nm with two peaks at 310 nm and 390 nm. From the spectral properties and kinetics of these radicals, a suitable mechanism is discussed to explain the antioxidant actions of THC.
Animals↗
Modulation of acetylcholine release from parasympathetic nerves innervating guinea-pig and human trachea by endomorphin-1 and -2.
Endomorphin-1 and -2 (mu-opioid receptor agonists) produced a concentration-dependent and naloxone-sensitive inhibition of cholinergic contractile responses in guinea-pig trachea (at 10 microM, 46.1 +/- 8.0% and 33.8 +/- 8.6%, respectively). Endomorphin-1 and -2 also inhibited electrically-evoked acetylcholine release from cholinergic nerves innervating guinea-pig (at 0.1 microM, 41.8 +/- 10.9%; at 1 microM 60.1 +/- 6.3%, respectively) and human trachea (at 10 microM, 76.2 +/- 18.1%, and 77.7 +/- 14.3%, respectively). Naloxone prevented the inhibition by endomorphin-1 and -2 in both guinea-pig and human trachea, suggesting that these peptides can inhibit cholinergic, parasympathetic neurotransmission to the airways via the activation of classical opioid receptors.
Acetylcholine↗
The treatment of Legionnaires' disease.
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4-Quinolones↗
Bioavailability of rifampicin, isoniazid and pyrazinamide in a triple drug formulation: comparison of plasma and urine kinetics.
SETTING: The present study assesses bioavailability indices for rifampicin, isoniazid and pyrazinamide when administered to healthy volunteers separately or in a fixed triple-drug formulation, Rifater 125 SCT. OBJECTIVE: To compare the pharmacokinetics of rifampicin, isoniazid and pyrazinamide based on their blood concentrations up to 12 hours with the proportions of the doses of the drugs and their metabolites excreted in urine up to 12 hours, and to assess the bioavailability indices for the free and fixed triple drug formulations. DESIGN: An open cross-over study was conducted in 18 healthy volunteers with normal hepatic and renal functions to whom the drug combinations were administered in free and fixed dose formulations a week apart, to the same subject. RESULTS: Concentrations of the three drugs/metabolites were assessed in blood and urine. The results indicated the absence of negative pharmacokinetic interactions between the drugs when administered in both the free and the new fixed triple drug formulation. CONCLUSION: Human bioavailability studies provide direct straightforward information, particularly when studying compounds such as rifampicin and other major anti-tuberculosis drugs. The results of the present study indicate that the pharmacokinetic properties of rifampicin, isoniazid and pyrazinamide as assessed after individual and combined administration do not change when combined in a single pharmaceutical preparation. The bioavailability indices calculated based on plasma concentrations and urinary levels for all three drugs compared well.
Adult↗
Socio-economic impact of tuberculosis on patients and family in India.
OBJECTIVE: To quantify the socio-economic impact of tuberculosis on patients and their families from the costs incurred by patients in rural and urban areas. DESIGN: An interview schedule prepared from 17 focus group discussions was used to collect socio-economic demographic characteristics, employment, income particulars, expenditure on illness and effects on children from newly detected sputum-positive pulmonary tuberculosis patients. The direct and indirect costs included money spent on diagnosis, drugs, investigations, travel and loss of wages. Total costs were projected for the entire 6 months of treatment. RESULTS: The study population consisted of 304 patients (government health care 202, non governmental organisation 77, private practitioner 25), 120 of whom were females. Mean direct cost was Rs.2052/-, indirect Rs.3934/-, and total cost was Rs.5986/- ($171 US). The mean number of work days lost was 83 and mean debts totalled Rs.2079/-. Both rural and urban female patients faced rejection by their families (15%). Eleven per cent of schoolchildren discontinued their studies; an additional 8% took up employment to support their family. CONCLUSIONS: The total costs, and particularly indirect costs due to TB, were relatively high. The average period of loss of wages was 3 months. Care giving activities of female patients decreased significantly, and a fifth of schoolchildren discontinued their studies.
Absenteeism↗
The substrate-binding site in the lactose permease of Escherichia coli.
Site-directed N-ethylmaleimide labeling was studied with Glu-126 and/or Arg-144 mutants in lactose permease containing a single, native Cys residue at position 148 in the substrate-binding site. Replacement of either Glu-126 or Arg-144 with Ala markedly decreases Cys-148 reactivity, whereas interchanging the residues, double-Ala replacement, or replacement of Arg-144 with Lys or His does not alter reactivity, indicating that Glu-126 and Arg-144 are charge-paired. Importantly, although alkylation of Cys-148 is blocked by ligand in wild-type permease, no protection whatsoever is observed with any of the Glu-126 or Arg-144 mutants. Site-directed fluorescence with 2-(4-maleimidoanilino)-naphthalene-6-sulfonic acid (MIANS) in mutant Val-331 --> Cys was also studied. In marked contrast to Val-331 --> Cys permease, ligand does not alter MIANS reactivity in mutant Glu-126 --> Ala/Val-331 --> Cys, Arg-144 --> Ala/Val-331 --> Cys, or Arg-144 --> Lys/Val-331 --> Cys and does not cause either quenching or a shift in the emission maximum of the MIANS-labeled mutants. However, mutation Glu-126 --> Ala or Arg-144 --> Ala and, to a lesser extent, Arg-144 --> Lys cause a red-shift in the emission spectrum and render the fluorophore more accessible to I-. The results demonstrate that Glu-126 and Arg-144 are irreplaceable for substrate binding and suggest a model for the substrate-binding site in the permease. In addition, the findings are consistent with the notion that alterations in the substrate translocation pathway at the interface between helices IV and V are transmitted conformationally to the H+ translocation pathway at the interface between helices IX and X.
Anilino Naphthalenesulfonates↗
Sulfhydryl oxidation of mutants with cysteine in place of acidic residues in the lactose permease.
To examine further the role of charge-pair interactions in the structure and function of lactose permease, Asp237 (helix VII), Asp240 (helix VII), Glu126 (cytoplasmic loop IV/V), Glu269 (helix VIII), and Glu325 (helix X) were replaced individually with Cys in a functional mutant devoid of Cys residues. Each mutant was then oxidized with H2O2 in order to generate a sulfinic and/or sulfonic acid at these positions. Due to the isosteric relationship between aspartate and sulfinate, in particular, and the lower pKa of the sulfinic and sulfonic acid side chains, oxidized derivatives of Cys are useful probes for examining the role of carboxylates. Asp237-->Cys or Asp240-->Cys permease is inactive, as shown previously, but H2O2 oxidation restores activity to an extent similar to that observed when a negative charge is reintroduced by other means. Glu126-->Cys, Glu269-->Cys, or Glu325-->Cys permease is inactive, but oxidation does not restore active lactose transport. The data are consistent with previous observations indicating that Asp237 and Asp240 are not critical for active lactose transport, while Glu126, Glu269, and Glu325 are irreplaceable. Although Glu269-->Cys permease does not transport lactose, the oxidized mutant exhibits significant transport of beta,D-galactosylpyranosyl 1-thio-beta,D-galactopyranoside, a property observed with Glu269-->Asp permease. The observation supports the idea that an acidic residue at position 269 is important for substrate recognition. Finally, oxidized Glu325-->Cys permease catalyzes equilibrium exchange with an apparent pKa of about 6.5, more than a pH unit lower than that observed with Glu325-->Asp permease, thereby providing strong confirmatory evidence that a negative charge at position 325 determines the rate of translocation of the ternary complex between the permease, substrate, and H+.
Amino Acid Substitution↗
Key developments in infection.
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Anti-Bacterial Agents↗
Bioluminescence assay of adenosine triphosphate in drug susceptibility testing of Mycobacterium tuberculosis.
Twenty three clinical isolates M. tuberculosis and the reference strain, M. tuberculosis H37Rv were tested for their susceptibility to trifluoperazine (TFP) by the standard broth dilution method and the bioluminescence assay. The results showed that in 15 of the 23 isolates, the minimal inhibitory concentration (MIC) was identical in both the methods and in the remaining 8 isolates the difference in the MIC values between the methods, was less than two fold and was not significant. The findings suggest that the measurement of adenosine triphosphate (ATP) by bioluminescence assay can be employed as an alternative method for the rapid screening of clinical isolates for their susceptibility to anti-mycobacterial agents.
Adenosine Triphosphate↗
Treating diarrhoea. More evidence is needed that widespread use of quinolones will benefit patients.
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Adolescent↗
Design of compounds that increase the absorption of polar molecules.
Hydrophilic drugs are often poorly absorbed when administered orally. There has been considerable interest in the possibility of using absorption enhancers to promote absorption of polar molecules across membrane surfaces. The bile acids are one of the most widely investigated classes of absorption enhancers, but there is disagreement about what features of bile acid enhancers are responsible for their efficacy. We have designed a class of glycosylated bile acid derivatives to evaluate how increasing the hydrophilicity of the steroid nucleus affects the ability to transport polar molecules across membranes. Some of the glycosylated molecules are significantly more effective than taurocholate in promoting the intestinal absorption of a range of drugs, showing that hydrophobicity is not a critical parameter in transport efficacy, as previously suggested. Furthermore, the most effective glycosylated compound is also far less damaging to membranes than the best bile acid absorption promoters, presumably because it is more hydrophilic. The results reported here show that it is possible to decouple absorption-promoting activity from membrane damage, a finding that should spark interest in the design of new compounds to facilitate the delivery of polar drugs.
Animals↗
Binding of ligand or monoclonal antibody 4B1 induces discrete structural changes in the lactose permease of Escherichia coli.
By using Cys-scanning mutagenesis with site-directed sulfhydryl modification in situ [Frillingos, S., & Kaback, H. R. (1996) Biochemistry 35, 3950-3956], conformational changes induced by binding of ligand or monoclonal antibody (mAb) 4B1 in the lactose permease of Escherichia coli were studied. Out of 31 single-Cys replacement mutants in helices I, V, VII, VIII, X, or XI, 4B1 binding alters the reactivity of Val238-->Cys (helix VII), Val331-->Cys (helix X), or single-Cys355 (helix XI) permease with N-ethylmaleimide (NEM) in right-side-out membrane vesicles. In addition, site-directed fluorescence spectroscopy shows that mAb 4B1 binding causes position 331 (helix X) in the permease to experience a more hydrophobic environment. In contrast, ligand binding elicits more widespread changes, as evidenced by enhancement of the NEM reactivity of Ala244-->Cys, Thr248-->Cys (helix VII), Thr265-->Cys (helix VIII), Val315-->Cys (helix X), Gln359-->Cys, or Met362-->Cys (helix XI) permease, none of which are altered by 4B1 binding. Furthermore, no effect of 4B1 is observed on the reactivity of Cys148 (helix V), Val264-->Cys, Gly268-->Cys, or Asn272-->Cys (helix VIII), positions which probably make direct contact with substrate. With respect to the N-terminal half of the permease, 4B1 binding causes a small increase in the reactivity of mutants Pro28-->Cys or Pro31-->Cys (helix I), while ligand binding causes much greater increases in reactivity. The findings indicate that 4B1 binding induces a structural change in the permease that is much less widespread than that induced by ligand binding.
Antibodies, Monoclonal↗
Activation of large conductance potassium channels inhibits the afferent and efferent function of airway sensory nerves in the guinea pig.
Sensory nerves play an important role in airway disease by mediating central reflexes such as cough, and local axon reflexes resulting in the peripheral release of neuropeptides. We have tested whether the benzimidazolone compound, NS1619, an opener of large conductance calcium-activated potassium (BK Ca) channels, inhibits the activity of sensory fibers, and central and local airway reflexes in guinea pig airways. In in vitro single fiber recording experiments, NS1619 applied to identified receptive fields in the trachea inhibited the firing of A(delta)-fibers evoked by hypertonic saline and distilled water, and bradykinin-evoked firing of C-fibers. Electrically evoked nonadrenergic noncholinergic contractions of isolated bronchi mediated by the release of neurokinin A (NKA) from C-fibers, but not those elicited by exogenous NKA, were inhibited by NS1619. These effects of NS1619 were prevented by iberiotoxin, a selective blocker of BK Ca channels. In conscious guinea pigs, cough evoked by aerosolized citric acid was also inhibited by NS1619. These data show that BK Ca channel activation inhibits sensory nerve activity, resulting in a reduction of both afferent and efferent function. BK Ca channel openers may therefore be of potential benefit in reducing neurogenic inflammation and central reflexes seen during inflammatory conditions of the airways, and may represent a new class of antitussive drug.
Afferent Pathways↗
Conservative management of osteomyelitis in the feet of diabetic patients.
Experience of conservative management of osteomyelitis in a specialized, multidisciplinary, diabetic foot clinic was reviewed. The records of all patients attending the clinic over a 10-year period were examined retrospectively, and 22 patients with overt osteomyelitis were identified. Median age was 66 (31-87) years. In 12 cases the bone infection was a complication of a pre-existing ulcer; the most prevalent organism cultured from swabs was Staphylococcus aureus. The main site of infection was the first toe. The total duration of antibiotic treatment was 12 weeks (median, range 5-72), and clindamycin was the most commonly used oral agent. Four patients did not respond to initial conservative therapy and proceeded to amputation, while 1 patient responded clinically but had a recurrence of osteomyelitis at the same site 6 years later. In the remaining 17 patients resolution of osteomyelitis was achieved with conservative management over a median period of follow-up of 27 (range 5-73) months. The success of conservative therapy with prolonged courses of oral antibiotics challenges conventional advice that excision of infected bone is essential in the management of osteomyelitis affecting the foot in diabetes.
Administration, Oral↗
A comparison of mucosal inflammatory responses to Giardia muris in resistant B10 and susceptible BALB/c mice.
In the first three weeks of primary Giardia muris infections B10 mice clear infection more rapidly than BALB/c mice. There is evidence that interferon-gamma contributes to the relative resistance of B10 mice. The nature of the functional contribution of interferon-gamma is unclear and does not relate to the secretory or serum antibody response. Mucosal inflammatory events in these strains have been studied. Apart from a small rise in both strains of goblet cell and mucosal mast cell numbers, associated with release of mast cell protease-1 in serum, no inflammatory infiltrate was observed at the time trophozoites were cleared from the intestinal lumen. Inhibition of mast cell products (5-hydroxytryptamine and histamine) by cyproheptadine enhanced the intensity of infection in both strains. The relative resistance of B10 mice could not be explained in terms of the mucosal inflammatory response.
Animals↗
Protection by taurine against adriamycin-induced proteinuria and hyperlipidemia in rats.
Taurine was used in the present study to evaluate its beneficial effects against proteinuria and hyperlipidemia associated with nephrotic syndrome. Rats made nephrotic with adriamycin had a high excretion of protein, albumin, and N-acetyl-beta-D-glucosaminidase compared with nonnephrotic rats. Nephrotic rats manifested hyperlipidemia with significant elevation in all major lipoprotein fractions. Treatment with taurine significantly suppressed adriamycin-induced proteinuria, albuminuria, and urinary excretion of N-acetyl-beta-D-glucosaminidase. Treatment of rats wit taurine for 7 days before adriamycin, and daily thereafter, significantly lowered plasma cholesterol, triglycerides, phospholipids, lipid peroxides, and malondialdehyde associated with lipoprotein fractions. Similarly, total lipids, cholesterol, triglycerides, lipid peroxides, hydroperoxides, and hydroxyl radicals in the liver and kidneys of taurine-treated adriamycin rats were decreased significantly compared with adriamycin alone. Lecithin cholesterol acyl transferase activity and free fatty acid levels in plasma, lipoprotein lipase activity, glutathione, total thiol, and ascorbic acid in the liver and the kidneys of taurine-treated adriamycin groups were significantly elevated compared with adriamycin alone. These results suggest that taurine might be applicable as a protective agent for proteinuria and hyperlipidemia associated with nephrotic syndrome.
Acetylglucosaminidase↗