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A Chandra

Publications and source records attributed to A Chandra.

At least 19 recordsLinked to original sources
PubMed2001

Structural and kinetic modifications of aldose reductase by S-nitrosothiols.

Modification of aldose reductase (AR) by the nitrosothiols S-nitroso-N-acetyl penicillamine (SNAP) and N-(beta-glucopyranosyl)-N(2)-acetyl-S-nitrosopenicillamide (glyco-SNAP) resulted in a 3-7-fold increase in its k(cat) and a 25-40-fold increase in its K(m) for glyceraldehyde. In comparison with the native protein, the modified enzyme was less sensitive to inhibition by sorbinil and was not activated by SO(2-)(4) anions. The active-site residue, Cys-298, was identified as the main site of modification, because the site-directed mutant in which Cys-298 was replaced by serine was insensitive to glyco-SNAP. The extent of modification was not affected by P(i) or O(2), indicating that it was not due to spontaneous release of nitric oxide (NO) by the nitrosothiols. Electrospray ionization MS revealed that the modification reaction proceeds via the formation of an N-hydroxysulphenamide-like adduct between glyco-SNAP and AR. In time, the adduct dissociates into either nitrosated AR (AR-NO) or a mixed disulphide between AR and glyco-N-acetylpenicillamine (AR-S-S-X). Removal of the mixed-disulphide form of the protein by lectin-column chromatography enriched the preparation in the high-K(m)-high-k(cat) form of the enzyme, suggesting that the kinetic changes are due to the formation of AR-NO, and that the AR-S-S-X form of the enzyme is catalytically inactive. Modification of AR by the non-thiol NO donor diethylamine NONOate (DEANO) increased enzyme activity and resulted in the formation of AR-NO. However, no adducts between AR and DEANO were formed. These results show that nitrosothiols cause multiple structural and functional changes in AR. Our observations also suggest the general possibility that transnitrosation reactions can generate both nitrosated and thiolated products, leading to non-unique changes in protein structure and function.

Aldehyde Reductase↗
PubMed2001

Cdc13 both positively and negatively regulates telomere replication.

Cdc13 is a single-strand telomeric DNA-binding protein that positively regulates yeast telomere replication by recruiting telomerase to chromosome termini through a site on Cdc13 that is eliminated by the cdc13-2 mutation. Here we show that Cdc13 has a separate role in negative regulation of telomere replication, based on analysis of a new mutation, cdc13-5. Loss of this second regulatory activity results in extensive elongation of the G strand of the telomere by telomerase, accompanied by a reduced ability to coordinate synthesis of the C strand. Both the cdc13-5 mutation and DNA polymerase alpha mutations (which also exhibit elongated telomeres) are suppressed by increased expression of the Cdc13-interacting protein Stn1, indicating that Stn1 coordinates action of the lagging strand replication complex with the regulatory activity of CDC13. However, the association between Cdc13 and Stn1 is abolished by cdc13-2, the same mutation that eliminates the interaction between Cdc13 and telomerase. We propose that Cdc13 participates in two regulatory steps-first positive, then negative-as a result of successive binding of telomerase and the negative regulator Stn1 to overlapping sites on Cdc13. Thus, Cdc13 coordinates synthesis of both strands of the telomere by first recruiting telomerase and subsequently limiting G-strand synthesis by telomerase in response to C-strand replication.

Chromatin↗
PubMed2001

[Diagnostic value of a clinical test for exclusion of fractures after acute ankle sprains. A prospective study for evaluating the "Ottowa Ankle Rules" in Germany].

Previous studies have shown that clinical criteria can be used for determining the need for radiographs after spraining injuries of an ankle. Following the criteria of the "Ottawa Ankle Rules" (OAR) fractures could be ruled out with a sensitivity of 100% and a specificity of 50% while reducing radiographs by 28%. The aim of this study was to assess the "OAR" when applied in a German emergency department. Patients older than 18, who presented with blunt ankle trauma were examined by clinicians, then radiographs were ordered in all and the "OAR" were retrospectively applied. In 397 treated injuries 79 fractures were diagnosed and 5 patients had radiologically suspected fractures. Following to the "OAR" 58 were unnecessarly X-rayed and 5 fractures would not have been discovered, all of which were minor. Sensitivity using the "OAR" was 94% and specificity 17%. We found that 15% less radiographs can be ordered applying the "OAR". The "OAR" have the ability to rule out significant fractures at the ankle and midfoot.

Adult↗
PubMed2001

Stress testing for risk stratification of patients with low to moderate probability of acute cardiac ischemia.

In summary, this article focused on the use of stress testing to risk-stratify patients at the conclusion of their emergency evaluation for ACI. As discussed, those patients in the probably not ACI category require additional risk stratification prior to discharge. It should be kept in mind that patients in this category are heterogeneous, containing subgroups at both higher and lower risk of ACI and cardiac events. The patients with lower pretest probability for ACI may only need exercise testing in the ED. Patients with higher pretest probability should undergo myocardial perfusion or echocardiographic stress testing to maximize diagnostic and prognostic information. Prognostic information is the key to provocative testing in the ED. Prognostic information is the component that will help emergency physicians identify the patients who may be discharged home safely without having to worry about a 6% annual cardiac death rate and a 10% overall death rate over the next 30 months. Stress testing provides this key prognostic data, and it can be obtained in short-stay chest pain observation units in a safe, timely, and cost-effective fashion.

Acute Disease↗
PubMed2001

Separation, identification, quantification, and method validation of anthocyanins in botanical supplement raw materials by HPLC and HPLC-MS.

A method has been established and validated for identification and quantification of individual, as well as total, anthocyanins by HPLC and LC/ES-MS in botanical raw materials used in the herbal supplement industry. The anthocyanins were separated and identified on the basis of their respective M(+) (cation) using LC/ES-MS. Separated anthocyanins were individually calculated against one commercially available anthocyanin external standard (cyanidin-3-glucoside chloride) and expressed as its equivalents. Amounts of each anthocyanin calculated as external standard equivalent were then multiplied by a molecular-weight correction factor to afford their specific quantities. Experimental procedures and use of a molecular-weight correction factors are substantiated and validated using Balaton tart cherry and elderberry as templates. Cyanidin-3-glucoside chloride has been widely used in the botanical industry to calculate total anthocyanins. In our studies on tart cherry and elderberry, its use as external standard followed by use of molecular-weight correction factors should provide relatively accurate results for total anthocyanins, because of the presence of cyanidin as their major anthocyanidin backbone. The method proposed here is simple and has a direct sample preparation procedure without any solid-phase extraction. It enables selection and use of commercially available anthocyanins as external standards for quantification of specific anthocyanins in the sample matrix irrespective of their commercial availability as analytical standards. It can be used as a template and applied for similar quantification in several anthocyanin-containing raw materials for routine quality control procedures, thus providing consistency in analytical testing of botanical raw materials used for manufacturing efficacious and true-to-the-label nutritional supplements.

Anthocyanins↗
PubMed2001

Identification of causal relationships among traits related to drought resistance in Stylosanthes scabra using QTL analysis.

Previous studies have shown that a negative relationship exists between transpiration efficiency (TE) and carbon isotope discrimination (Delta) and between TE and specific leaf area (SLA) in Stylosanthes scabra. A glasshouse experiment was conducted to confirm these relationships in an F(2) population and to study the causal nature of these relationships through quantitative trait loci (QTL) analysis. One hundred and twenty F(2) genotypes from a cross between two genotypes within S. scabra were used. Three replications for each genotype were maintained through vegetative propagation. Water stress was imposed by maintaining plants at 40% of field capacity for about 45 d. To facilitate QTL analysis, a genetic linkage map consisting of 151 RAPD markers was developed. Results from this study show that Delta was significantly and negatively correlated with TE and biomass production. Similarly, SLA showed significant negative correlation with TE and biomass production. Most of the QTL for TE and Delta were present on linkage groups 5 and 11. Similarly, QTL for SLA, transpiration and biomass productivity traits were clustered on linkage groups 13 and 24. One unlinked marker was also associated with these traits. There were several markers coincident between different traits. At all the coincident QTL, the direction of QTL effects was consistent with phenotypic data. At the coincident markers between TE and Delta, high alleles of TE were associated with low alleles of Delta. Similarly, low alleles of SLA were associated with high alleles of biomass productivity traits and transpiration. At the coincident markers between trans-4-hydroxy-N:-methyl proline (MHP) and relative water content (RWC), low alleles of MHP were associated with high alleles of RWC. This study suggests the causal nature of the relationship between TE and Delta. Phenotypic data and QTL data show that SLA was more closely associated with biomass production than with TE. This study also shows that a cause-effect relationship may exist between SLA and biomass production.

Alleles↗
PubMed2001

Early beneficial effect of preservation of papillo-annular continuity in mitral valve replacement on left ventricular function.

BACKGROUND AND AIM OF THE STUDY: Impairment of left ventricular (LV) function after mitral valve replacement (MVR) has been the most important factor to determine morbidity and mortality. With this in mind, LV performance in the postoperative period was assessed with and without preservation of papillo-annular continuity in MVR. METHODS: Between March 1994 and August 1998, a total of 383 valve prostheses (202 MVR, 65 AVR, 58 MVR+AVR) were implanted in 325 patients, 177 of whom underwent MVR with Starr Edwards ball cage prostheses (the study group). Of these 177 patients, 105 had MVR with preservation of the posterior mitral leaflet (group I), and 72 had conventional MVR (group II). Predominant lesions were mitral stenosis in 81, mitral regurgitation in 42, and mixed mitral lesion (MS/MR) in 54. Concomitant tricuspid valve annuloplasty was performed in 13, and atrial septal defect repair in five. Sixteen patients underwent MVR for mitral restenosis. In-vivo performance of the prostheses and LV function was evaluated by M-mode and Doppler echocardiography. RESULTS: At 3-6 months clinical improvement was seen in NYHA class, with reduction in cardiothoracic ratio among patients with preserved papillo-annular continuity, irrespective of lesion type. Significant reductions (p <0.05) were seen in left atrial dimensions (54.10 +/- 8.79 preop. versus 44.64 +/- 8.54 postop.; p <0.05), left ventricular end-diastolic dimensions (LVEDD) (50.84 +/- 10.42 preop. versus 41.21 +/- 7.16 postop.; p <0.05) and end-systolic dimensions (LVESD) (34.76 +/- 7.94 preop. versus 28.81 +/- 5.79 postop.; p <0.05) in patients who had their posterior mitral leaflet preserved with significant improvement in ejection fraction (60.31 +/- 8.22 versus 64.47 +/- 7.93; p <0.05). Further analysis of data in group I patients showed significant reductions in left atrial dimensions, LVESD and peak gradient, along with improved ejection fraction compared with conventional (group II) patients. CONCLUSION: Deterioration in LV function in patients undergoing conventional MVR indicates chordal resection as a putative mechanism. This study supports the concept that maintenance of continuity between the mitral annulus and papillary muscles has a beneficial effect on postoperative LV function, and is particularly important in patients with mitral stenosis with depressed preoperative LV systolic function.

Adult↗
PubMed2000

Effects of ion atmosphere on hydrogen-bond dynamics in aqueous electrolyte solutions

We have performed a series of molecular dynamics simulations of aqueous NaCl and KCl solutions at different concentrations to investigate the effects of ion atmosphere on the dynamics of water-water hydrogen bonds at room temperature. The average number of hydrogen bonds per water molecule decreases with increase of ion concentration. The dynamics of hydrogen-bond breaking is found to accelerate somewhat and that of hydrogen-bond structural relaxation, which occurs at a longer time scale, is found to slow down with increasing ion concentration for both NaCl and KCl solutions.

Journal Article↗
PubMed2000

Structure of a mixed dipolar liquid near a metal surface: A combined approach of weighted density and perturbative approximations

We study the interfacial structure of a mixed dipolar liquid in contact with a metal surface by using a combined approach of the weighted density and the perturbative approximations. Both the molecular size and the dipole moment of various species can be unequal. The metal surface is treated by using the jellium model. Explicit numerical results are obtained for the interfacial structure of a binary dipolar liquid in contact with a metal surface of varying electron density. The theoretical predictions are compared with the results of Monte Carlo simulations and a good agreement is found for the inhomogeneous density, mole fraction, and polarization profiles of both the species in the interfacial region.

Journal Article↗
PubMed1999

Detection of distinct patterns of anti-tat antibodies in HIV-infected individuals with or without Kaposi's sarcoma.

Patterns of antibody response to recombinant transactivator protein (HIV-1 tat) in serum samples from HIV-1-negative persons (n = 60), HIV-1-infected asymptomatic persons (n = 20), HIV-1-infected people with Kaposi's sarcoma (n = 25) and of people with Kaposi's sarcoma without HIV-1 infection have been analyzed. None of the healthy people had anti-tat IgG in their serum. All asymptomatic patients with HIV-1 infection were anti-tat IgG-positive. Epitope mapping revealed that these sera have anti-tat IgG to all the functional domains of tat protein. Four of the 25 HIV-1-infected patients with Kaposi's sarcoma were anti-tat IgG-positive; however, epitope analysis revealed that IgG to functional domains of tat protein, in particular to TAR-binding site, were absent. All patients with Kaposi's sarcoma without HIV-1 infection were anti-tat IgG-negative. Presence or absence of anti-tat IgG, and prevalence of different antibody profiles in different groups of patients suggest the pathophysiologic role of tat protein. Thus, a passive immunization with anti-tat IgG could be a useful strategy to influence the pathophysiologic state of the disease.

AIDS-Related Opportunistic Infections↗
PubMed1999

Amino acid substitution in alpha-helix 7 of Cry1Ac delta-endotoxin of Bacillus thuringiensis leads to enhanced toxicity to Helicoverpa armigera Hubner.

Insecticidal proteins or delta-endotoxins of Bacillus thuringiensis are highly toxic to a wide range of agronomically important pests. The toxins are formed of three structural domains. The N-terminal domain is a bundle of eight alpha-helices and is implicated in pore formation in insect midgut epithelial membranes. All the delta-endotoxins share a common hydrophobic motif of eight amino acids in alpha-helix 7. A similar motif is also present in fragment B of diphtheria toxin (DT). Site-directed mutagenesis of Cry1Ac delta-endotoxin of B. thuringiensis was carried out to substitute its hydrophobic motif with that of DT fragment B. The mutant toxin was shown to be more toxic to the larvae of Helicoverpa armigera (cotton bollworm) than the wild-type toxin. Voltage clamp analysis with planar lipid bilayers revealed that the mutant toxin opens larger ion channels and induces higher levels of conductance than the wild-type toxin.

Amino Acid Substitution↗
PubMed1999

Adoption, adoption seeking, and relinquishment for adoption in the United States.

OBJECTIVES: This report presents national data on adoption and adoption-related behaviors among ever-married women 18-44 years of age in the United States, according to selected characteristics of the women. Trends are shown in the prevalence of adoption and relinquishment of children for adoption. For 1995, the report shows demand for adoption and women's preferences for characteristics of the child. METHODS: Data are based on nationally representative samples of women 15-44 years of age from the 1973, 1982, 1988, and 1995 National Surveys of Family Growth (NSFG). RESULTS: The percent of ever-married women 18-44 years of age who have ever adopted a child declined from 2.1 percent in 1973 to 1.3 percent in 1995. Of the 9.9 million women who had ever considered adoption, 16 percent had taken steps toward adoption, and 31 percent of these had actually adopted a child. Older women, nulliparous women, women with fecundity impairment, and women who have used infertility services were more likely to have considered adoption, to have taken concrete steps toward adoption, and to have actually adopted a child. In response to the questions about preferred characteristics of an adopted child, women expressed strong preferences with respect to age, sex, race, and disability level of the child, but were willing to accept children with the less-desired traits. Between 1989 and 1995, about 1 percent of babies born to never-married women were relinquished for adoption, down from 9 percent among such babies born before 1979. CONCLUSIONS: Federally supported adoption data collection sources corroborate the decline in adoption shown by the NSFG over the past 25 years. Demand for adoption in the United States varies, depending on whether demand is conceptualized liberally as "ever having considered adoption" or more narrowly, as "currently taking concrete steps toward adoption." The narrow definition was fulfilled by 232,000 ever-married women in 1995.

Adolescent↗
PubMed1999

Intercellular traffic of human immunodeficiency virus type 1 transactivator protein defined by monoclonal antibodies.

Monoclonal antibodies (mAbs) directed against the amino-terminal region (N-terminal sequence 2-19) of transactivator protein (tat) of HIV-1 have been shown to inhibit intercellular transactivation mediated by the extracellular tat protein. The intracellular transactivation was not significantly affected by anti-tat mAbs. The specificity of anti-tat mAbs in abolishing the transactivating potential of extracellular tat is documented by studies with mAbs to HIV-1 reverse transcriptase, or to a human mammary cancer protein. None of these antibodies showed any inhibitory effect on intercellular transactivation. Specific interaction of anti-tat IgG with tat protein expressed in Jurkat cells is further supported by experiments on immunoblotting. Extracellular tat is responsible for signals which induce a variety of biological responses in HIV-infected cells, as well as in uninfected cells. The fact that anti-tat mAbs can abolish the intercellular traffic of tat protein offers a unique strategy in the development of vaccines against AIDS.

Animals↗
PubMed1999

Health insurance coverage of the unemployed: COBRA and the potential effects of Kassebaum-Kennedy.

We use the April 1993 Current Population Survey to examine the health insurance coverage decisions of the unemployed and to simulate the potential effects of the new Kassebaum-Kennedy legislation. After controlling for demographic characteristics, COBRA eligibility raises the probability of health insurance coverage by 0.095, while eligibility for spouse employer insurance increases the likelihood of coverage by 0.318, and eligibility for both increases the likelihood of coverage by 0.341. In our simulations, we find that had Kassebaum-Kennedy been in effect in April 1993, 9.0 percent of the unemployed would be eligible to take up coverage, and the coverage rate of the unemployed would have been increased by 0.85 percent to 1.5 percent from 41.6 percent. Our estimates of the effect of Kassebaum-Kennedy on health insurance coverage are much lower than those reported by the Government Accounting Office prior to the passage of the legislation.

Eligibility Determination↗