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Biomedical subjects

R Chitra

Publications and source records attributed to R Chitra.

15 recordsLinked to original sources
PubMed2006

Conformation and structure of bis(glycyl-L-aspartic acid) oxalate 0.4-hydrate.

The title bis(glycyl-L-aspartic acid) oxalate complex {systematic name: bis[2-(2-ammonioacetamido)butanedioic acid] oxalate 0.4-hydrate}, 2C6H11N2O5+.C2O4(2-).4H2O, crystallizes in a triclinic space group with the planar peptide unit in a trans conformation. The asymmetric unit consists of two glycyl-L-aspartic acid molecules with positively charged amino groups and neutral carboxyl groups, and an oxalate dianion. The twist around the C-Calpha bond indicates that both the peptide molecules adopt extended conformations, while the twist around the N-Calpha bond shows that one has a folded and the other a semi-extended state. The present complex can be described as an inclusion compound with the dipeptide molecule as the host and the oxalate anion as the guest. The usual head-to-tail sequence of aggregation is not observed in this complex, as is also the case with the glycyl-L-aspartic acid dihydrate molecule. The study of aggregation and interaction patterns in binary systems is the first step towards understanding more complex phenomena. This further leads to results that are of general interest in bimolecular aggregation.

Crystallography, X-Ray↗
PubMed2006

Host-guest interaction in a thiourea-dimethyl oxalate (2/1) complex at 300 and 100 K.

The title complex, 2CH4N2S.C4H6O4, is a host-guest system. The asymmetric unit consists of one complete thiourea molecule and one-half of a dimethyl oxalate molecule lying on an inversion centre. The host thiourea molecules are connected to form zigzag chains by N-H...S hydrogen bonds. The guest dimethyl oxalate molecules provide O-atom acceptors for N-H...O hydrogen bonds, thus interconnecting the chains of thiourea molecules to form completely connected sheets. The reduction in temperature from 300 to 100 K leaves the structure unchanged and still isostructural with that previously determined for the analogous thiourea-diethyl oxalate (2/1) complex. It does, however, induce closer packing of the molecules, general shrinkage of the unit cell and shortening of the hydrogen bonds, these last two to the extent of 1-2%.

Journal Article↗
PubMed2006

Bis(glycinium) oxalate: evidence of strong hydrogen bonding.

In the title 2:1 salt, 2C2H6NO2+.C2O4(2-), the glycine molecule is in the cationic form with a positively charged amino group and an uncharged carboxylic acid group. The doubly charged oxalate anion lies across a crystallographic inversion centre. One of the reasons why the 1:1 glycinium oxalate salt has a higher melting point than the title compound may be the difference in their hydrogen-bonding patterns. A database search for salts formed between amino acids or substituted amino acids and oxalic acid revealed that, in most of the structures, the conformation about the O=C-OH bond is synplanar. D-Tryptophan oxalate is the only example where the OH group of a semi-oxalate adopts an antiplanar conformation. The 2:1 stoichiometry seen in the present salt is observed only in the salts of DL-serine, DL-aspartic acid and betaine with oxalic acid.

Crystallography, X-Ray↗
PubMed2000

Effect of long range coulomb interactions on the mott transition

We reconsider the Mott transition problem in the presence of long range Coulomb interactions. Using an extended dynamical mean field theory (DMFT) that sums an important class of diagrams absent in ordinary DMFT, we show that in the presence of Coulomb interactions, the zero temperature Mott transition is, as envisioned by Mott, discontinuous in two and three dimensions.

Journal Article↗
PubMed2000

A comparative trial of zolmitriptan and sumatriptan for the acute oral treatment of migraine.

OBJECTIVE: This randomized, double-blind, parallel group multicenter study compared response rates and tolerability of zolmitriptan with sumatriptan in the acute treatment of migraine. METHODS: A sample consisting of 1445 outpatients with an established diagnosis of migraine was randomized to zolmitriptan, 2.5 mg or 5 mg, or sumatriptan, 25 mg or 50 mg. Patients took 1 tablet for moderate/severe migraine and a second identical tablet, if necessary, for recurrent headache of moderate/severe intensity 4 to 24 hours after the initial dose. Up to six attacks were treated during a 6-month period. The primary outcome measure was headache response 2 hours after the initial dose. Secondary end points included 1-hour and 4-hour headache response and pain relief over 24 hours. RESULTS: A headache response at 2 hours was noted in 67.1% of patients taking zolmitriptan, 2.5 mg, and 64.8% of those taking zolmitriptan, 5 mg, versus 59.6% of patients taking sumatriptan, 25 mg, and 63.8% of those taking sumatriptan, 50 mg. At 2 and 4 hours, the differences between zolmitriptan, 2.5 mg, and sumatriptan, 25 mg, were statistically significant (odds ratio=1.49 and 1.67, respectively; both P<.001). Statistically significant differences between zolmitriptan, 2.5 mg, and sumatriptan, 50 mg, were seen at 2 and 4 hours post dose (odds ratio=1.21 and 1.23, respectively; both P<.05). At 1 hour post dose, the headache response rate for zolmitriptan, 2. 5 mg, was numerically higher than response rates for sumatriptan, 25 mg and 50mg (odds ratio=1.16, odds ratio=1.06, though they failed to reach statistical significance; P=.061, P=.461 respectively). Differences between zolmitriptan, 5 mg, and sumatriptan, 25 mg, were statistically significant at 1, 2, and 4 hours (odds ratio=1.43, 1. 46, and 1.78, respectively; all P<.001) and at 1 and 4 hours versus sumatriptan, 50 mg (odds ratio=1.28, P=.002; odds ratio=1.29, P=.012, respectively). Although not statistically significant at 2 hours, more patients responded to zolmitriptan, 5 mg, than to sumatriptan, 50 mg (odds ratio=1.16, P=.064). Patients receiving zolmitriptan, 2. 5 mg or 5 mg, achieved more pain relief over 24 hours than patients receiving sumatriptan, 25 mg (odds ratio=1.47, and 1.54 respectively, both P<.001) or sumatriptan, 50 mg (odds ratio=1.17, P=.021; odds ratio=1.22, P=.005, respectively). All treatments were well tolerated. CONCLUSIONS: Zolmitriptan, 2.5 mg and 5 mg, was at least as effective as sumatriptan, 25 mg or 50 mg, for all parameters studied. Zolmitriptan, 2.5 mg, was significantly more effective than sumatriptan, 50 mg, in terms of headache response at 2 and 4 hours. Patients taking zolmitriptan were significantly more likely to have pain relief over 24 hours than those taking sumatriptan.

Acute Disease↗
PubMed1998

A meta-analysis of the effects of venlafaxine on anxiety associated with depression.

Venlafaxine is the first member of a novel class of antidepressants that inhibits the reuptake of both serotonin and norepinephrine. Clinical trials of venlafaxine have demonstrated its efficacy and safety in the treatment of patients diagnosed with major depression. Because patients who have depression also often have anxiety, recent investigations have focused on determining whether venlafaxine can relieve symptoms of anxiety in depressed patients. We performed a pooled analysis of six short-term trials of venlafaxine, retrospectively measuring anxiety in anxious depressed patients using the Hamilton Rating Scale for Depression (HAM-D), Anxiety/Somatization factor and Anxiety Psychic item scores. Three studies were placebo-controlled, and three were placebo- and active-drug-controlled; active controls were imipramine in two trials and trazodone in the third trial. Patients were categorized as having anxiety accompanying depression if baseline HAM-D Anxiety Psychic item scores were 2 or greater. Anxious depressed patients treated with venlafaxine showed greater improvement than those treated with placebo beginning at week 3, according to the HAM-D Anxiety/Somatization factor score, and beginning at week 1, according to the Anxiety Psychic item score. Both effects were maintained at week 6 of treatment (and at week 12 in the one study of longer duration). Finally, treatment with venlafaxine resulted in a highly significant (p < or = 0.001) improvement in depression scores in patients who were anxious at baseline, compared with placebo-treated patients. The results of this analysis demonstrate that venlafaxine is more effective than placebo in reducing symptoms of anxiety in depressed patients and suggest that venlafaxine may afford a monotherapy option for treating patients who have a comorbid diagnosis of depression with anxiety.

Adult↗
PubMed1997

A benefit-risk analysis of once-daily venlafaxine extended release (XR) and venlafaxine immediate release (IR) in outpatients with major depression.

The traditional analysis of clinical trial data for antidepressants separately evaluates the results of efficacy and tolerability. The present analysis simultaneously evaluated these outcome criteria in a double-blind, placebo-controlled study of outpatients with major depression. Patients received either once-daily extended release (XR) venlafaxine or immediate release (IR) venlafaxine. Individual patient data on efficacy and treatment-emergent study events (TESE) for venlafaxine XR and venlafaxine IR were grouped into five categories. Efficacy was defined as a final on-therapy Clinical Global Impressions improvement score of 1 (very much improved) or 2 (much improved). A TESE was defined as any new adverse event or any adverse event that existed at baseline and increased in severity during treatment. Benefit/risk was evaluated using a linear measure and a ratio measure for dizziness, Insomnia, nausea, nervousness, somnolence, and a composite of anticholinergic events. This analysis demonstrated a superior benefit/risk ratio for the once-daily venlafaxine XR compared with venlafaxine IR, and a statistically significant benefit-to-risk ratio of at least 2:1 for venlafaxine XR over venlafaxine IR was demonstrated for nausea and dizziness. This approach to the statistical analysis of clinical trial data represents an advancement in addressing treatment outcome by incorporating clinically relevant measures of both efficacy and safety.

Antidepressive Agents, Second-Generation↗
PubMed1995

Effectiveness of venlafaxine treatment in a broad spectrum of depressed patients: a meta-analysis.

The effectiveness of the novel antidepressant venlafaxine was assessed in various subpopulations of depressed patients. Data from six comparable placebo-controlled, double-blind studies were pooled and analyzed (venlafaxine, n = 930; placebo, n = 500). Outcome variables were the Hamilton Rating Scale for Depression total score, Montgomery-Asberg Depression Rating Scale total score, and Clinical Global Impressions severity scores. Venlafaxine had notable antidepressant results in depressed patients regardless of age (although no age differences were apparent, too few patients over age 65 had been enrolled in the six studies to permit definitive conclusions), gender, presence of melancholia, and severity or duration of depression. Our analysis indicates that venlafaxine treatment is effective in a broad range of depressed patients.

Adult↗
PubMed1994

Destructive operations still have a place in developing countries.

OBJECTIVES: To determine the place of destructive operations in developing countries in patients arriving late in labor with a dead fetus and advanced infection, and to compare them with LSCS for patients with similar indications. METHODS: A total of 56 cases of destructive operations were carried out on patients with obstructed labor and intrauterine fetal death (IUFD) from the labor wards of Smt. S.K. Hospital from January 1985 to December 1991. These were compared with 27 cases of LSCS done for similar indications during the years 1989 to 1990. RESULTS: Patients treated with destructive operations had no maternal deaths, had very few complications and required a short hospital stay. Patients treated by LSCS, however, had one maternal death and complications such as post-partum hemorrhage, incidence of blood transfusion, post-operative shock, post-operative pyrexia and duration of hospital stay were more frequent. CONCLUSIONS: It is felt that in some properly selected cases presenting late with obstructed labor, IUFD and intrauterine sepsis, destructive operations should be performed as first choice. Thus, destructive operations still have a limited place in developing countries and are safer than LSCS for these patients.

Adult↗