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Biomedical subjects

R Rajagopalan

Publications and source records attributed to R Rajagopalan.

At least 55 records · Page 3Linked to original sources
PubMed1997

Monte Carlo Simulations for Micellar Encapsulation

The solubilization of solutes in surfactant aggregates (micelles) is studied using lattice-based Monte Carlo simulations. Various properties such as the size and shape of the micelles, the critical micelle concentration, the locus of solubilization, and the partition coefficient of the solute are obtained, and the implications of the results for the thermodynamics of solubilization are examined. The presence of contaminants in the solution affects micellar properties by promoting micellization and stabilizing micelles. The ratio of head group size to tail group size for the surfactant is found to greatly affect both micellar properties and contaminant solubilization. The partitioning of the solute is found to be independent of surfactant concentration, but increases with solute concentration. The results show that contaminant partitioning is controlled primarily by enthalpic contributions.

Journal Article↗
PubMed1997

Development and validation of a quality of life instrument for cutaneous diseases.

BACKGROUND: The Dermatology-Specific Quality of Life (DSQL) instrument is a new tool to quantify the effects of skin disease on physical discomfort and symptoms, psychologic well-being, social functioning, self-care activities, performance at work or school, and self-perceptions. OBJECTIVE: Our purpose was to describe the reliability and validity of the DSQL in two disease cohorts comprising patients with contact dermatitis and acne vulgaris. METHODS: Reliability was assessed from the internal consistency of the items, and correlations were made between DSQL scores from a 3- to 7-day retest. Validity was assessed from correlations of DSQL scales with global ratings of bothersome symptoms and perceived severity and by discrimination of clinically defined severity groups. RESULTS: The DSQL scales had high internal consistency (0.70 to > 0.90) and test-retest reliability (r = 0.81 to 0.89), and were moderately to highly correlated with patient global ratings of symptom distress (r = 0.25 to 0.67) and overall disease severity (r = 0.19 to 0.54). Patients rated with severe contact dermatitis or acne scarring had higher DSQL scores than those with less severe skin disease. Factor analyses found separate dimensions of physical, emotional, and social functioning involvement from skin disease. CONCLUSION: The DSQL provides valid and reliable assessments of quality of life impacts associated with acne and contact dermatitis.

Acne Vulgaris↗
PubMed1997

HL 752: a potent and long-acting antispasmodic agent.

Ester analogues of methyl-2-(4-(2-piperidinoethoxy)benzoyl)-benzoate hydrochloride (pitofenone) (2) were prepared with an aim to find a more potent and metabolically stable antispasmodic compound. The compounds were evaluated for their in vitro and in vivo antispasmodic activity, and stability to in vitro enzymatic hydrolysis. Of the compounds synthesised, HL 752 (21) showed the most potent and long-lasting antispasmodic activity and was selected as the candidate for clinical development.

Animals↗
PubMed1997

The profile of a patient with contact dermatitis and a suspicion of contact allergy (history, physical characteristics, and dermatology-specific quality of life).

According to the National Center for Health Statistics Survey, a large proportion of patients with contact dermatitis, atopic dermatitis, or eczema visit nondermatologists, and only approximately 40% visit dermatologists. Therefore, the prompt, proper diagnosis of the cause and prescription of precise treatment can be delayed. We wanted to create a clear understanding of the nuances of the allergic contact dermatitis and its effect on the economics and life quality of the patients for not only the dermatologists but also the primary care physicians. In an observational multicenter study planned for a span of 1 year with approximately 570 patients suspected of allergic contact dermatitis, data were collected at enrollment on their history, physical characteristics, and quality of life and were analyzed using routine statistical procedures. The "quality of life" data on these patients, most of whom have a history of long-standing disease, show a high correlation between the clinical factors such as symptom activity and frequency of episodes and the subscales of quality of life. These patients had a lesser score on mental and vital subscales (SF-36) than US population norms, showing a moderate impact of the disease on their mental health and vitality. There is an urgent need for a simpler and quicker method that could lead to an earlier and more precise diagnosis so the causal substance can be identified and avoided and the disease treated in a timely and cost-effective manner.

Dermatitis, Allergic Contact↗
PubMed1997

Clobetasol propionate emollient 0.05 percent: hypothalamic-pituitary-adrenal-axis safety and four-week clinical efficacy results in plaque-type psoriasis.

Two clinical trials were conducted to evaluate the safety and antipsoriatic efficacy of a new 0.05 percent emollient formulation of clobetasol propionate (CP). In a crossover study of hypothalamic-pituitary-adrenal (HPA)-axis effects in 12 patients with psoriasis or eczema, 1.5 gm of CP emollient, applied to lesions twice daily for seven consecutive days, resulted in fewer patients with serum cortisol concentrations < 10 micrograms/100 mL than CP cream 0.05 percent (1vs 4); such concentrations were seen in two other patients during both treatment phases. A double-blind, randomized, parallel-group clinical trial in patients with moderate to severe plaque-type psoriasis showed that four weeks' treatment with CP emollient 0.43 to 0.5 gm twice daily (n = 35) was significantly more effective than emollient vehicle (n = 39) in reducing total signs/symptoms and scaling by Day 4, erythema and skin thickening by Day 8, and pruritus by Day 15. CP emollient was rated superior to vehicle by Day 4 in physician's gross assessment ratings and by Day 15 in patient's self-assessment ratings. In all assessments, CP emollient continued to be superior to vehicle during the remainder of the treatment period and two-week posttreatment period. No significant differences were observed in tolerability or serum cortisol effects during the course of the study.

Adult↗
PubMed1997

Impact of patch testing on dermatology-specific quality of life in patients with allergic contact dermatitis.

BACKGROUND: A dermatology-specific quality-of-life instrument has been created and validated for its sensitivity, reproducibility, content, and construct validity. This instrument was used in an observational prospective study that evaluated the cost-effectiveness of patch testing in patients with contact dermatitis and suspicion of allergic component. OBJECTIVE: This multicenter, prospective, observational study was designed to study the various direct and indirect costs associated with diagnosis and treatment of suspected allergic contact dermatitis and the benefits of diagnosis with and without patch testing. The costs and benefits of various methods of diagnosis are evaluated to determine if patch testing is more cost-effective as a diagnostic method. One of the outcomes evaluated was the quality of life of the participants in the study and the impact of patch testing on this cohort. METHODS: A total of 567 subjects were enrolled to obtain evaluable data from at least 500 subjects from ten study centers; the investigators were chosen so as to obtain a mix of stratified degrees of usage of patch testing. Data were collected on demographics, physical characteristics, history of disease, visits to physicians, and, to evaluate costs, the use of resources such as drugs, nondrug substances, and services; other outcome data collected were on physician evaluation of improvement, confirmation of diagnosis, physician opinion of the disease management, and patient evaluation of dermatology-specific quality of life (DSQL), and pertinent economic factors. Only 6-month and 12-month follow-up visits were mandatorily scheduled according to the protocol; however, participants and providers were free to arrange additional visits as deemed necessary for health care. RESULTS: This report focuses on the evaluations at the 6-month follow-up. There are completely evaluable data on pharmacoeconomics and DSQL for 431 patients. About 43% were patch tested, and the rest were diagnosed using the information from history and physical examinations. There was significantly better improvement in each of the DSQL domains in patch tested subjects compared with non-patch-tested subjects. In addition, patients treated in "low" use clinics had lower quality of life at 6-month follow-up than those treated in "high" use clinics. CONCLUSION: Patch testing helps to diagnose the etiology of contact dermatitis early and treat the disease before it becomes chronic, thus reducing resources used and improving patient quality of life considerably.

Case-Control Studies↗
PubMed1996

A retrospective evaluation of patch testing in patients diagnosed with allergic contact dermatitis.

One reason given by clinicians for not using patch testing in patients with dermatitis is that it may not improve the treatment outcome. The main objectives of this retrospective study were to determine the frequency of use of patch testing as an aid to the diagnosis of allergic contact dermatitis (ACD), to determine the ACD-related costs before and after diagnosis of the disease, and to determine the benefit of the diagnosis of ACD, with or without patch testing, to the patient's treatment outcome. This study will also provide definite direction for a prospective outcome study. Medical records of 270 patients with ACD were utilized retrospectively to study the benefit of patch testing. Patch testing was performed on 56 percent of these patients. Patch testing was found to bring about a larger decrease in the disease severity index and percentage disease activity from prediagnosis to postdiagnosis than diagnosis without patch testing. In the group of patients with a prediagnosis disease duration of two months to one year, the postdiagnosis duration was considerably less for those patch tested and treated than those that were treated without patch testing. Patch testing was found to be the most cost-effective in patients with a disease duration of two months to one year.

Adult↗
PubMed1995

Lack of effect of tacrine administration on the anticoagulant activity of warfarin.

The effect of tacrine administration on prothrombin time was studied in 13 patients receiving prolonged warfarin therapy. After a 3-week baseline period and 5 days of placebo administration, patients received 20 mg tacrine four times daily for 5 days. Prothrombin times were determined during baseline, daily before the morning doses of placebo and tacrine, and 14 days after the last tacrine dose (closeout). Mean (+/- SD) prothrombin times were 16.2 +/- 2.8 seconds at baseline, 15.1 +/- 2.6 seconds during the placebo phase, 15.8 +/- 3.6 seconds during the tacrine phase, and 15.3 +/- 3.6 seconds at closeout, indicating that tacrine has no effect on the anticoagulant activity of warfarin. Alteration of warfarin dosage should not be required in patients receiving concurrent tacrine therapy.

Aged↗
PubMed1995

Preparation, physico-chemical characterization, and relaxometry studies of various gadolinium(III)-DTPA-bis(amide) derivatives as potential magnetic resonance contrast agents.

Macroscopic protonation constants were measured for a series of DTPA mono- and bis-amide ligands using potentiometric titrations. Proton NMR pH titrations yielded protonation populations of the various nitrogen and oxygen basic sites of the ligands for the different protonation stages. Amide formation decreased the basicity of the backbone nitrogens of the ligands and the thermodynamic stability of the corresponding Gd3+ chelates. Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths were measured for the Gd3+ chelates. Some of these exhibited an elevated high field relaxivity relative to Gd(DTPA)2-, in response to their high molecular weight. As opposed to Gd(DTPA)2-, at 5 degrees C the chemical exchange process of the single inner-sphere water molecule of the bis-amide complexes becomes so slow that it governs the paramagnetic relaxation process, causing the observed NMRD profiles to be close to those expected for the outer-sphere contribution. The chelates containing long alkyl side chains, such as Gd(DTPA-HPA2), showed increased relaxivity values in the presence of human serum albumin (HSA), indicative of noncovalent interaction with the protein. These chelates could be useful as nonionic hepatobiliary contrast agents.

Contrast Media↗
PubMed1995

Extramammary Paget's disease: a report of three cases and review of the literature.

Extramammary Paget's disease (FMPD) is a rare skin disease with a tendency to recur even in the face of adequate excision. It was first suggested by Weiner in 1937 to be a carcinoma of the apocrine sweat gland with intraepithelial excision. Thus, most cases of EMPD occur in the perianal, perigenital and axilla regions where sweat glands abound, with scrotal EMPD being the commonest. EMPD can occur in both benign or malignant form and is often confused with chronic dermatitis. Diagnosis can only be confirmed by an excision biopsy. The long-term survival in patients without an underlying carcinoma is good. However, EMPD associated with an underlying adnexal carcinoma tends to be more aggressive and the prognosis is poor in such cases. EMPD is also associated with other malignancies such as prostatic, rectal, cervical, breast, bladder and skin carcinomas. Incidences of up to 40% have been reported. Thus, patients with EMPD should be thoroughly screened for associated primary growths. The treatment of EMPD is essentially by surgical excision with clear margins. The options available for a clear margin include intraoperative frozen section,Moh's surgery and paraffin section with delayed re-excision. In this report, we present three cases of EMPD with markedly different outcomes and a review of the literature.

Aged↗
PubMed1994

"Wired" enzyme electrodes for amperometric determination of glucose or lactate in the presence of interfering substances.

Glucose oxidase (GOX) or lactate oxidase (LOX) were immobilized in an osmium-based three-dimensional redox hydrogel that electrically connected the enzyme's redox centers to electrodes. The enzyme "wiring" hydrogel was formed by cross-linking poly(1-vinylimidazole) (PVI) complexed with Os-(4,4'-dimethylbpy)2Cl (termed PVI15-dmeOs) with poly(ethylene glycol) diglycidyl ether (peg). Glucose and lactate sensors exhibited typical limiting current densities of 250 and 500 microA/cm2, respectively. When the electrodes were poised at 200 mV (SCE), the currents resulting from electrooxidation of ascorbate, urate, acetaminophen, and L-cysteine were negligible. When a Nafion film was employed, the linear range was extended from 6 to 30 mM glucose and from 4 to 7 mM lactate. The redox potential of the gel-forming polymer was 95 mV (SCE). Glucose and lactate measurements performed in bovine calf serum correlated well with a substrate calibration in phosphate buffer.

Animals↗
PubMed1994

Characterisation and purification of ribulose-bisphosphate carboxylase from heterotrophically grown halophilic archaebacterium, Haloferax mediterranei.

The CO2-fixing enzyme of Calvin cycle ribulose-1,5-bisphosphate-carboxylase/oxygenase has been isolated from a halophilic bacterium, Haloferax mediterranei grown heterotrophically. A homogeneous preparation was obtained from sonicated extract of the cells by three steps, resulting in a specific activity of 52 nmol.min-1.mg protein-1. The physicochemical and catalytic properties of the enzyme were studied. The halobacterial ribulose-bisphosphate carboxylase is an oligomer of 54-kDa and 14-kDa subunits as detected by SDS/PAGE. By sucrose-density-gradient centrifugation, the molecular mass of the enzyme was estimated as approximately 500 kDa indicating a hexadecameric nature. No evidence for an additional form of the enzyme devoid of small subunits was obtained. The enzyme required Mg2+ for activity, KCl for activity and stability, and an optimal pH of 7.8. In contrast to many halophilic proteins, ribulose-bisphosphate carboxylase from H. mediterranei is not an acidic protein. From the comparison of amino acid composition of halobacterial enzyme with its counterparts from a few eukaryotic and eubacterial sources, the S delta Q values showed that these proteins share some compositional similarities.

Amino Acids↗
PubMed1994

Diuretic effects, pharmacokinetics, and safety of a new centrally acting kappa-opioid agonist (CI-977) in humans.

The diuretic effects, pharmacokinetics, and safety of CI-977, a new centrally acting selective kappa-opioid agonist, were determined in 16 healthy subjects. Subjects received single intramuscular doses of CI-977 (5, 15, or 25 micrograms) or placebo 1 week apart according to a randomized, double-blind, placebo-controlled, four-period, crossover design. Serial blood and urine specimens were collected after each dose. Significant dose-related decreases in negative free water clearance and urine osmolality and increases in urine volume were observed after administration of 15- and 25-micrograms doses of CI-977. CI-977 had no effect on urine electrolyte excretion or serum antidiuretic hormone. Absorption of CI-977 was rapid with individual tmax values ranging from 0.17 to 1.5 hours. Cmax and AUC(0-infinity) increased proportionally with dose. Individual elimination half-life values ranged from 0.6 to 3.3 hours and were independent of dose. Changes in free water clearance were related to CI-977 Cmax (r2 = 0.29, P = 0.0001) and AUC(0-4 hr) (r2 = 0.32, P = 0.0001) values. The most frequently reported adverse events after CI-977 administration were dizziness, fatigue, paresthesia, headache, vasodilatation (facial flushing), emotional lability, high feeling, and abnormal thinking. The frequency and intensity of adverse events increased with increasing CI-977 dose. In conclusion, CI-977 Cmax and AUC(0-infinity) increased in proportion to dose over the range of 5 to 25 micrograms; decreases in negative free water clearance were related to CI-977 dose and Cmax and AUC(0-4 hr) values; and the frequency and intensity of adverse events increased with increasing CI-977 dose.

Adult↗
PubMed1993

Glucose electrodes based on cross-linked [Os(bpy)2Cl]+/2+ complexed poly(1-vinylimidazole) films.

Enzyme electrodes based on a redox hydrogel formed upon complexing water-soluble poly(1-vinylimidazole) (PVI) with [Os(bpy)2Cl]+ and cross-linked with water-soluble poly(ethylene glycol) diglycidyl ether (molecular weight 400, peg 400) are described. The properties of the electrodes depended on their polymers' osmium content, the extent of cross-linking, the pH, and the ionic strength in which they were used. The redox hydrogels' electron diffusion coefficients (De) increased with osmium content of their polymers. The De values were 1.5 x 10(-8), 1.3 x 10(-8), and 4.3 x 10(-9) cm2/s for PVI3-Os, PVI5-Os, and PVI10-Os, respectively, the subscripts indicating the number of monomer units per osmium redox center. De decreased with increasing ionic strength and increased upon protonation of the polymer. In glucose electrodes, made by incorporating into their films glucose oxidase (GOX) through covalent bonding in the cross-linking step, glucose was electrooxidized at > 150 mV (SCE). The characteristics of these electrodes depended on the GOX concentration, film thickness, O2 concentration, pH, NaCl concentration, and electrode potential. The steady-state glucose electrooxidation currents were independent of the polymers' osmium content in the studied (3-10 monomer units per osmium center) range. Electrodes containing 39% GOX reached steady-state glucose electrooxidation current densities of 400 microA/cm2 and, when made with thick gel films, were selective for glucose in the presence of physiological concentrations of ascorbate and acetaminophen.

2,2'-Dipyridyl↗
PubMed1993

Cardiotonic activity of the water soluble forskolin derivative 8,13-epoxy-6 beta-(piperidinoacetoxy)- 1 alpha, 7 beta, 9 alpha-trihydroxy-labd- 14en-11-one.

8,13-Epoxy-6 beta-(piperidinoacetoxy)-1 alpha,7 beta, 9 alpha-trihydroxy-labd -14en-11-one (HL 706, CAS 114376-11-3) is a water soluble derivative of forskolin with positive inotropic and vasodilating properties. In both in vitro and in vivo preparations, it exhibited significant positive inotropic activity with concomitant increase in heart rate and decrease in mean blood pressure. Though its potency is lower than that of forskolin, its duration of action is more prolonged. In conscious dog experiments, HL 706, administered orally, also showed a dose related increase in LV dP/dtmax. A significant reversal of cardiac failure was attained in anaesthetised dogs subjected to propranolol induced cardiac insufficiency. HL 706, like forskolin increased cAMP by virtue of its adenylate cyclase stimulant activity. Through increase in cAMP it also exhibited non-specific smooth muscle relaxant activity in isolated vascular and ileal preparations. Its therapeutic ratio is quite favourable.

Adenosine Diphosphate↗