PubMed Health⌕ Search

Biomedical subjects

A K Mathur

Publications and source records attributed to A K Mathur.

At least 19 recordsLinked to original sources
PubMed2001

In vitro plantlet regeneration in Panax sikkimensis.

A three-step procedure for complete plantlet regeneration via somatic embryogenesis has been developed in Panax sikkimensis. Somatic embryos (SE) were induced in root callus upon lowering the level of 2,4-D from 1.0 mg/l to 0.25 mg/l in the callusing medium. Maturation of SE occurred on a half-strength MS medium with 0.5 mg/l each of BAP and GA3. An exposure for 15 days of cotyledonary and heart-shaped SE to 1.0 mg/l IBA in liquid shake 1/2 MS medium significantly improved the rate of embryo-to-plantlet conversion and plantlet quality. The procedure has now allowed the retention of high regeneration potential of the root callus for over three years.

Organ Culture Techniques↗
PubMed1999

Effect of linear alkylbenzene sulphonate on topical absorption of chromium and nickel.

The effect of the topical applications of linear alkylbenzene sulphonate (LAS), or chromium (Cr) + nickel (Ni), or the combination of LAS + Cr + Ni for 30 d were investigated. Increased activities of aspartate amino transferase, alanine amino transferase, acid phosphatase and gamma glutamyl transpeptidase and decreased activity of superoxide dismutase occurred. Increased lipid peroxidation and decreased glutathione were observed. Accumulation of Cr and Ni increased in tissues. Biochemical alterations and metal accumulations were more marked in the Cr + Ni + LAS group.

Alkanesulfonates↗
PubMed1997

Comparative calibration without a gold standard.

Comparative calibration is the broad statistical methodology used to assess the calibration of a set of p instruments, each designed to measure the same characteristic, on a common group of individuals. Different from the usual calibration problem, the true underlying quantity measured is unobservable. Many authors have shown that this problem, in general, does not have a unique solution. Most commonly used assumptions to obtain a unique solution are (i) one instrument is the gold standard (that is, unbiased) and (ii) the measurement errors of the p instruments are independent. Such constraints, however, may not be valid for many clinical applications, for example, the universal standardization project for dual X-ray absorptiometry (DXA) scanners. In this paper, we propose a new approach to resolve the comparative calibration problem when a gold standard is unavailable. Instead of the usual assumptions, we use external information in addition to data from the p instruments, to solve the problem. We address statistical estimation, hypothesis testing and missing data problems. We apply the new method specifically to the universal standardization project data where a group of individuals have been measured for bone mineral density (BMD) by three DXA scanners. We compare the results of the new method to currently used methods and show that they have better statistical properties.

Absorptiometry, Photon↗
PubMed1997

Comparison of immunomodulation by cyclosporin A and azathioprine on pancreatic xenograft survival.

Prolonged survival of pancreatic xenografts in the muscles of diabetic rabbits under the immunomodulation of cyclosporin A and azathioprine was achieved. The mean graft survival time (as assessed by euglycemic status and histopathological findings) in Group A (azathioprine treated) was 36 days, in Group B (cyclosporin A treated) it was 69 days, and the difference was significant (p < 0.001). Adequate immunosuppression helps the pancreatic xenograft to normalize the blood glucose level (BGL) by prolonging its survival time. Our study demonstrates that xenotransplanted islet cells in a natural environment (pancreatic tissue in the form of thin slices) survive and function adequately in immunosuppressed recipients, and addition of cyclosporin A significantly prolongs survival of the xenograft. This discordant xenotransplantation model may be useful for future xenotransplantation studies.

Adjuvants, Immunologic↗
PubMed1996

Dual X-ray absorptiometry quality control: comparison of visual examination and process-control charts.

Dual X-ray absorptiometry (DXA) is widely used to monitor treatment efficacy in reducing the rate of bone mineral loss. In order to assure the validity of these measurements, instrument quality control of the DXA scanners becomes very important. This paper compares five quality control procedures (visual inspection, Shewhart chart with sensitizing rules, Shewhart chart with sensitizing rules and a filter for clinically insignificant mean changes, moving average chart and standard deviation, and cumulative sum chart [CUSUM]) in their ability to identify scanner malfunction by means of (1) an analysis of five longitudinal phantom data sets that had been collected during a clinical trial and (2) an analysis of simulated data sets. The visual inspection method is relatively subjective and depends on the operator's experience and attention. The regular Shewhart chart with sensitizing rules has a high false alarm rate. The Shewhart chart with sensitizing rules and an additional filter for clinically insignificant mean changes has the lowest false alarm rate but a relatively low sensitivity. The CUSUM method has good sensitivity and a low false alarm rate. In addition, this method provides an estimate of the date a change in the DXA scanner performance might have occurred. The method combining a moving average chart and a moving standard deviation chart came closest to the performance of the CUSUM method. Comparing the advantages and disadvantages of all methods, we propose the use of the CUSUM method as a quality control procedure for monitoring DXA scanner performance. For clinical trials use of the more intuitive Shewhart charts may be acceptable at the individual sites provided their scanner performance is followed up by CUSUM analysis at a central quality assurance center.

Absorptiometry, Photon↗
PubMed1994

Histological appearance of the synovium in early rheumatoid arthritis.

This report reviews and discusses studies on the synovial fluid and biopsy specimens of synovial membrane obtained during the first 6 weeks of synovitis that evolved into rheumatoid arthritis (RA). Five previously unreported cases are described. Early changes in the microvasculature and synovial lining seem to antedate the classical chronic inflammation of established RA. Further characterization in the joint tissues in very early RA offers opportunities for identification of exogenous triggers and may allow more appropriate targeting of early therapy to potentially reversible aspects of pathogenesis.

Adult↗
PubMed1994

Pancreatic xenograft survival in diabetic rabbits.

Prolonged survival of pancreatic xenografts in the muscles of diabetic rabbits was achieved. The mean graft survival time (assessed by euglycemic status) in nonimmunosuppressed (Group A) was 10 days and in immunosuppressed (Group B) was 36 days (P < 0.05). Adequate immunosuppression helps pancreatic xenograft to normalize blood glucose level (BGL) by prolonging survival time. Our study demonstrates that xenotransplantation of islet cells in their natural environment (pancreatic tissue in four of thin slices) survive and function adequately in immunosuppressed recipients. This discordant Xenotransplantation model may be useful for future xenotransplantation studies.

Animals↗
PubMed1994

Dermal toxicity of nickel and chromium in guinea pigs.

Liver and kidney enzyme activities and blood glucose and hemoglobin increased after 15 or 30 d of dermal exposure to nickel and chromium. Concentration of nickel and chromium increased in tissues. The changes were related to the duration of exposure.

Administration, Cutaneous↗
PubMed1993

Epidemiology of facial clefts in the central province of Saudi Arabia.

A pilot study collecting data both retrospectively and prospectively covering a span of 4 years (January 1989 to December 1992) was carried out at King Fahd Specialist Hospital, Al-Gassim, Saudi Arabia. The aim was to study the epidemiology of facial clefts in the exclusively Saudi population. A total of 137 cases were studied. This study gives the highest reported incidence of clefts (2.19 per 1000 live births) with some distinct differences in the pattern of clefts as compared to other documented studies.

Abnormalities, Multiple↗
PubMed1993

Effect of calcium channel blockers on serum levels of thyroid hormones.

One month oral therapy with calcium channel blockers caused significant (P < 0.001) decrease in serum levels of triiodothyronine and thyroxine and significant increase in serum levels of thyroid stimulating hormone in rabbits. Most probable mechanism of action was block in the synthesis and/or release of thyroid hormones.

Animals↗
PubMed1993

Insulin resistance and insulin secretion are determinants of oral glucose tolerance in normal individuals.

Plasma glucose values after oral glucose challenge vary widely in nondiabetic subjects. We have now evaluated the role of insulin resistance in determining the plasma glucose response to oral glucose in 74 volunteer subjects with normal glucose tolerance. In these subjects, we determined the plasma glucose and insulin responses over a 3-h period to a 75-g oral glucose challenge, and the steady-state plasma glucose concentration during a continuous infusion of somatostatin, glucose, and insulin (a quantitative measure of insulin resistance). The plasma glucose response was defined as the incremental increase in plasma glucose concentration above the fasting value for 3 h after the oral glucose challenge. Multiple regression analysis was used to define the relationship between the dependent variable (plasma glucose response) and various predictors of this response. These analyses indicated that both the steady-state plasma glucose and the incremental insulin response during the first 30 min after the glucose load were significant predictors of the plasma glucose response. In those individuals in whom insulin action was impaired and the 30-min plasma insulin response was decreased, plasma glucose values reached higher levels. When standardized regression coefficients were determined, the incremental glucose response was directly correlated with steady-state plasma glucose (r = 0.700, P < 0.001) and inversely with the insulin response during the first 30 min (r = 0.268, P = 0.023). Furthermore, the correlation between steady-state plasma glucose and glucose response was significantly greater (P < 0.005) than that between the glucose response and 30-min insulin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Renal toxicity of nickel, sodium lauryl sulphate and their combination after dermal application in guinea pigs.

The guinea pigs were dermally exposed to nickel (Ni), sodium lauryl sulphate (SLS) and in their combination for 7 and 14 days. The exposure to Ni and SLS produced changes in enzymes and lipid peroxidation in kidney. The exposure to Ni or SLS depicted slight changes while combined exposure to Ni plus SLS exhibited more degenerative changes in kidney. The result of the study suggests that industrial workers and/or populations exposed simultaneously to Ni and SLS produces more damage to kidney.

Administration, Cutaneous↗