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Biomedical subjects

S K Chopra

Publications and source records attributed to S K Chopra.

At least 19 recordsLinked to original sources
PubMed2000

NMR imaging investigations of drug delivery devices using a flow-through USP dissolution apparatus.

A system for performing NMR imaging experiments on drug delivery devices within a flow-through dissolution apparatus, USP Apparatus 4, has been developed. The system was used to image the physical changes that occur in solid dosage forms during dissolution in the flow-through apparatus. Simultaneous cumulative drug release measurements were also made. The NMR images obtained under these conditions and the drug release data provide a better understanding of the processes involved in the release of drugs from drug delivery systems based on diffusion, dissolution and osmosis mechanisms.

Drug Delivery Systems↗
PubMed2000

Ultrasound biomicroscopy in the diagnosis and management of pars planitis caused by caterpillar hairs.

PURPOSE: To report the use of ultrasound biomicroscopy in the detection of caterpillar hairs in the pars plana in a patient with unilateral pars planitis. METHOD: Ultrasound biomicroscopic imaging of the anterior segment of the eye. RESULTS: Ultrasound biomicroscopy located a hair in the posterior chamber at the first visit and five more in the pars plana 1 month later. This finding was confirmed intraoperatively. CONCLUSION: Ultrasound biomicroscopy is useful in the diagnosis and management of unilateral pars planitis of uncertain cause.

Animals↗
PubMed2000

Estimation of trace amounts of benzene in solvent-extracted vegetable oils and oil seed cakes.

A new method is presented for the qualitative and quantitative estimation of trace amounts (up to 0.15 ppm) of benzene in crude as well as refined vegetable oils obtained by extraction with food grade hexane (FGH), and in the oil seed cakes left after extraction. The method involves the selection of two solvents; cyclohexanol, for thinning of viscous vegetable oil, and heptane, for azeotroping out trace benzene as a concentrate from the resulting mixture. Benzene is then estimated in the resulting azeotrope either by UV spectroscopy or by GC-MS subject to availability and cost effectiveness of the latter. Repeatability and reproducibility of the method is within 1-3% error. This method is suitable for estimating benzene in vegetable oils and oil seed cakes.

Animal Feed↗
PubMed1998

Use of NMR imaging in the optimization of a compression-coated regulated release system.

Nuclear magnetic resonance (NMR) imaging is routinely used to detect the protons of mobile water molecules within samples. In this investigation, this non-destructive, non-invasive technique was used to determine the cause for faster than predicted drug release from a dissolution-based regulated-release tablet. The NMR images of tablets, from two different formulations, taken at various intervals of time while immersed in static USP dissolution medium showed that the tablet with faster than predicted drug release had a porous coating. The porous coat exposed more of the core surface area to the dissolution medium than desired and this caused an increase in the rate of dissolution of the core. The data presented in this paper demonstrate the usefulness of NMR imaging in solid dosage form development.

Cellulose↗
PubMed1994

A review of childhood admission with perforating ocular injuries in a hospital in north-west India.

A retrospective study of perforating ocular injuries in children below the age of fifteen years was conducted. Eighty patients (eighty-nine eyes) were included in this study. Male children were more susceptible to ocular injury as compared to females (p = < 0.01). Children of the school-going age were the most affected (73.8%). Majority of the injuries occurred in the sports field (p = < 0.01). Playing with bow and arrow, and gillidanda* accounted for majority of the sport injuries (47.2%). Sixty-eight percent of the perforated eyes had no light perception at the end of treatment. Health education on the preventive aspects of ocular injuries in schools as well as through mass media should reduce the incidence of visual loss due to ocular injuries.

Adolescent↗
PubMed1990

Intraocular pressure profile during general anesthesia.

The effect of some anesthetic drugs on intraocular pressure (IOP) was studied in 120 normal healthy patients undergoing non-ophthalmic surgical procedures. IOP rose significantly following the injection of succinylcholine (SCh) alone, or when such injection had been preceded by a pretreatment with a "self-taming" dose of SCh or d-tubocurarine (d-Tc). Though the rise in IOP after diazepam pretreatment was significant, the magnitude was lower than that observed in the groups pretreated with the other two agents. Halothane brought the IOP down faster and lower than ether. SCh is unsafe for intubation for the administration of general anesthesia in cases involving penetrating ocular injuries. It can, however, be used safely for routine ophthalmic surgery, providing that 8 minutes are allowed to elapse between injection and corneal or scleral incision. Halothane is preferred to ether, since the former lowers IOP faster and in a greater amount than the latter.

Anesthesia, General↗
PubMed1987

Occurrence and characterization of lympho-agglutinins in Indian plants.

Lympho-agglutinins have been detected and characterized in 31 plant species. Out of these, 14 agglutinated only the neuraminidase-treated cells. The lectin-rich genera included Crotalaria and Erythrina (Fabaceae), Amaranthus (Amaranthaceae), Artocarpus (Moraceae) and Clerodendron (Verbenaceae). The new lectins varied in their potency and biological action spectra. The 3 Artocarpus species were found to be exceptionally potent and specific for melibiose, an alpha-D-galactoside. Among the most effective sugar inhibitors for other lectins were N-acetyl-galactosamine, lactose, galactose and asialofetuin/fetuin.

Animals↗
PubMed1985

Tack behavior of coating solutions III.

The effect of finely divided solids on the tackiness of coating solutions was determined using a parallel-plate technique. Results demonstrated that the tackiness of coating solutions containing relatively low concentration of polymers augments with the increase in concentration and diminishes with the increasing particle size of finely divided solids. In contrast, the tackiness of coating solutions containing high concentrations of polymers is suppressed upon increasing the concentration and decreasing the size of finely divided solids.

Chemistry, Pharmaceutical↗
PubMed1984

Tack behavior of coating solutions II.

The tackiness of coating solutions containing high concentrations of polymers was determined using a parallel plate technique. Kinematics of the film-splitting process was also investigated using a high-speed movie camera. The results showed that the impulse required to split a liquid film of highly concentrated polymer solution (semisolid), in contrast to a dilute solution is related not to viscosity, but to the internal structures of the system. Evidence has been found that the materials that are considered to be tacky in practice, display "delayed elastic effects" and require far larger impulses than nontacky materials.

Chemical Phenomena↗
PubMed1982

Tack behavior of coating solutions I.

The tackiness of various tablet coating solutions was determined using a parallel plate technique with a tensile testing machine in conjunction with an oscilloscope where the separation force was displayed as a function of time. Measurements were made at various rates of separation on liquid films of constant thickness. Results showed that the force required to split a liquid film increases with an increase in rate of separation, and that tackiness increases with an increase in viscosity. The relation between tack and viscosity was not linear, and a modified Stefan equation was proposed.

Chemistry, Pharmaceutical↗
PubMed1982

Effect of intravenous cimetidine on mucociliary transport in anesthetized dogs.

Previous studies have shown that aerosolized histamine increases tracheal mucociliary transport velocity, whereas topically administered H1-antihistamines depress mucociliary function. Using a radiolabelled tracer method in anesthetized dogs, we determined tracheal transport velocity (TTV) before and 30 and 60 min after intravenous administration of 150 mg of cimetidine, an H2-antihistamine. In 12 experiments, 30 and 60 min after cimetidine, mean TTV increased significantly (mean changes 5.1 +/- 1.8 and 5.7 +/- 2.6 mm/min, respectively, P less than or equal to 0.05), whereas in seven control experiments in which cimetidine was not given, mean TTV did not change over 1 h (mean change 1.1 +/- 2.5 mm/min; P greater than 0.05). However, the increase in TTV after cimetidine was not significantly different from the spontaneous change in the control animals (P greater than 0.1). These results suggest that cimetidine, unlike H1-antihistamines, does not depress and may possibly improve mucociliary transport function.

Aerosols↗
PubMed1982

Effect of iodide on mucociliary transport in anesthetized dogs.

Using a recently described tracer method, we determined tracheal transport velocity (TTV) before and after intravenous administration of 10 ml of 0.1% sodium iodide (NaI) in anesthetized dogs. In nine experiments in hydrated dogs TTV did not change significantly after NaI therapy (mean change -1.3 mm/min +/- 1.8 SEM; P greater than 0.10). In 10 experiments in dehydrated dogs TTV increased significantly after NaI therapy (mean change 6.1 mm/min +/- 2.1; P less than 0.02). In 13 control experiments in dehydrated dogs not given NaI, TTV did not change significantly (mean change 1.4 mm/min +/- 1.1; P greater than 0.2). The increase in TTV in the dehydrated dogs treated with NaI was significantly greater than the change in TTV in the dehydrated dogs not given NaI (P less than 0.025). Previous studies have shown a dehydration-induced depression of TTV which was reversed by rehydration. These findings suggest that iodides improve mucociliary transport function in the dehydrated state but not the hydrated state and that this improvement is comparable to that following rehydration.

Anesthesia, Intravenous↗
PubMed1981

Abnormalities of pulmonary vascular dynamics and inflammation in early progressive systemic sclerosis.

Abnormalities of pulmonary function were studied in 10 patients with progressive systemic sclerosis (PSS) and 3 control subjects. All underwent 81M krypton lung scanning and total body gallium scanning. Immune complexes were measured by Raji cell radioimmunoassay and polyethylene glycol (PEG) assay. Perfusion scans were abnormal in 7 of 9 patients, and 5 of 9 showed a decrease in pulmonary perfusion after cold challenge. Increased gallium uptake was noted in the lungs of 6 of 9 patients. Krypton scans were normal in the control group. Elevated immune complexes were noted in 8 of 10 patients by the Raji assay and in 5 of 10 with the PEG assay. Efforts to separate patients with PSS into subgroups may lead to a better understanding of and advances in therapy for PSS.

Adult↗
PubMed1980

Sites of airway dilatation in asthma following inhaled versus subcutaneous terbutaline. Comparison of physiologic tests with radionuclide lung images.

In 12 asthmatic subjects with mild to severe airways obstruction, we compared the relative magnitude and sites of airway dilatation of a beta-adrenergic stimulant administered by different routes. Specific airway conductance (SGaw), peak expiratory flow, the sum of the absolute volume of isoflow and residual volume as a percentage of total lung capacity (capacity of isoflow) and the ratio of maximal expiratory flow at 50 per cent of vital capacity breathing 80 per cent helium-20 per cent oxygen to that breathing air (ratio Vmax50) were determined before and after the administration of aerosolized terbutaline (0.5 mg), subcutaneous terbutaline (0.5 mg) or placebo. Increases in SGaw and peak expiratory flow of greater than or equal to 25 per cent were considered to indicate significant dilatation of central airways; increases in ratio Vmax50 of greater than or equal to 0.10 and decreases in capacity of isoflow of greater than or equal to 10 per cent were assumed to reflect dilatation of peripheral airways. In addition, radioaerosol and radioxenon lung imaging was performed to determine the relationship between changes in lung imaging patterns and changes in physiologic indices in response to bronchodilator therapy. Placebo caused little change in lung function or lung imaging. After inhaled terbutaline, SGaw and peak expiratory flow increased greater than or equal to 25 per cent in seven subjects, ratio Vmax50 increased greater than or equal to 0.10 in only three subjects, capacity of isoflow decreased greater than or equal to 10 per cent in only one subject, radioaerosol images showed less central deposition in nine subjects and radioxenon images showed improved distribution and/or washout of xenon in five subjects. After the administration of subcutaneous terbutaline, SGaw and peak expiratory flow increased greater than or equal to 25 per cent in 10 subjects, ratio Vmax50 increased greater than or equal to 0.10 in 10 subjects, capacity of isoflow decreased greater than or equal to 10 per cent in 11 subjects, and radioaerosol and xenon images showed improvement in 11 and eight subjects, respectively. These findings are consistent with the action of inhaled terbutaline mainly on large airways and of subcutaneous terbutaline on both large and small airways. Although reduced central radioaerosol deposition correlated well with physiologic evidence of large airway dilatation, improvement in xenon distribution and washout could be attributed to dilatation of either large and/or small airways.

Aerosols↗
PubMed1979

Diagnostic value of fiberoptic bronchoscopy in lung cancer presenting as mediastinal mass(es).

The diagnostic yields of prebonchoscopy sputum specimens and fiberoptic bronchoscopy (including brushings, washings, and/or biopsies) were determined in 35 patients who presented primarily with middle or anterior mediastinal and/or paratracheal mass(es) on chest radiographs. The diagnosis was confirmed on histopathology of tissue obtained by needle biopsy, mediastinoscopy, thoracotomy, and/or autopsy. Thirty-one of the patients were found to have primary bronchogenic carcinomas. At bronchoscopy, extrinsic compression of trachea and/or bronchi was visualized in 23 (Group I) and the tracheobronchial tree appeared normal in 12 (Group II). Prebronchoscopy sputa gave a positive yield in only three of the 35 (8%) patients; the yield was similar in both groups of patients. One or more of the bronchoscopic modalities were diagnostic in 69% of Group I patients but were not helpful in Group II patients. The diagnostic yield of brushings, washings, and biopsies in Group I patients was 52%, 61%, and 37%, respectively. The addition of biopsies to washings and/or brushings did not significantly alter the yield. Washings and brushings are recommended as useful, non-invasive procedures in diagnosing middle mediastinal masses with extrinsic compression. Sputum cytology gives a very low yield.

Bronchoscopy↗