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Ishwar Singh

Publications and source records attributed to Ishwar Singh.

27 records · Page 2Linked to original sources
PubMed2003

Effect of 24-epibrassinolide on pollen viability during heat-stress in tomato.

Tomato pollen when treated with 24-epibrassinolide (EBR), it was observed that in vitro pollen germination was more tolerant to high temperature. A significantly higher in vitro pollen germination, enhanced tube growth and low pollen bursting were observed in presence of EBR at 35 degrees C. Since a preconditioning treatment of tomato plant was not required for these effects, it is concluded that EBR treatment increased basic thermotolerance of germinating pollen. This study provided the first evidence for EBR induced thermotolerance in germinating pollen.

Adaptation, Physiological↗
PubMed2002

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part 9: comparison of acetoxy 4-methylcoumarins and other polyphenolic acetates reveal the specificity to acetoxy drug: protein transacetylase for pyran carbonyl group in proximity to the oxygen heteroatom.

The evidences for the possible enzymatic transfer of acetyl groups (catalyzed by a transacetylase localized in microsomes) from an acetylated compound (acetoxy-4-methylcoumarins) to enzyme proteins leading to profound modulation of their catalytic activities was cited in our earlier publications in this series. The investigations on the specificity for transacetylase (TA) with respect to the number and positions of acetoxy groups on the benzenoid ring of coumarin molecule revealed that acetoxy groups in proximity to the oxygen heteroatom (at C-7 and C-8 positions) demonstrate a high degree of specificity to TA. These studies were extended to the action of TA on acetates of other polyphenols, such as flavonoids and catechin with a view to establish the importance of pyran carbonyl group for the catalytic activity. The absolute requirement of the carbonyl group in the pyran ring of the substrate for TA to function was established by the observation that TA activity was hardly discernible when catechin pentacetate and 7-acetoxy-3,4-dihydro-2,2-dimethylbenzopyran (both lacking pyran ring carbonyl group) were used as the substrates. Further, the TA activity with flavonoid acetates was remarkably lower than that with acetoxycoumarins, thus suggesting the specificity for pyran carbonyl group in proximity to the oxygen heteroatom. The biochemical properties of flavonoid acetates, such as irreversible activation of NADPH cytochrome C reductase and microsome-catalyzed aflatoxin B(1) binding to DNA in vitro were found to be in tune with their specificity to TA.

Acetates↗
PubMed2002

Xanthones as inhibitors of microsomal lipid peroxidation and TNF-alpha induced ICAM-1 expression on human umbilical vein endothelial cells (HUVECs).

Xanthones bearing different functionalities, namely 1-hydroxyxanthone (1), 3-hydroxyxanthone (2), 1,4-dihydroxyxanthone (3), 2,6-dihydroxyxanthone (4), 1,2-diacetoxyxanthone (5), 2,6-diacetoxyxanthone (6), 3-methoxyxanthone (7), 1,3,7-trimethoxyxanthone (8) and 1,5-dihydroxy-6-methoxyxanthone (9) were synthesised and examined for their effect on nicotinamide adenine dinucleotide phosphate (NADPH)-catalysed liver microsomal lipid peroxidation and on tumour necrosis factor-alpha (TNF-alpha) induced expression of intercellular adhesion moledule-1 (ICAM-1) on endothelial cells, with a view to establish structure-activity relationship. Hydroxy- and acetoxyxanthones showed potent inhibitory effects on NADPH-catalysed lipid peroxidation and TNF-alpha induced expression of ICAM-1 on endothelial cells.

Animals↗
PubMed2002

Serum selenium levels in patients with head and neck cancer.

OBJECTIVE: The objective of this research was to estimate serum selenium levels in patients with head and neck cancer and to correlate them with tumour burden, as well as to study the effect of radiotherapy on serum selenium levels to determine its prognostic significance. DESIGN: This prospective study was carried out by selection of head and neck cancer patients using periodic random numbers. SETTING: This was a hospital-based study. METHODS: Estimation of serum selenium was done using the Atomic Absorption Spectrophotometer (Model AAS 4129; Electronic Corporation of India Ltd., Hydrabad, India) with a hydride generator after digestion of the serum sample. MAIN OUTCOME MEASURES: Patients were followed for 1 year postradiotherapy for any change in serum selenium level and its correlation with the outcome of the treatment. RESULTS: All 30 patients had serum selenium levels significantly lower as compared with controls, and these levels decreased further as tumour burden increased. Levels came within normal range after 1 year of radiotherapy in 10 patients who were cured but in the remaining patients who had residual disease, levels remained persistently low. CONCLUSIONS: The serum selenium level may serve as a useful marker in head and neck cancer.

Adult↗
PubMed2002

Nasopharyngeal angiofibroma.

OBJECTIVE: To study the clinical profile of nasopharyngeal angiofibromas, various surgical approaches, and the outcome of surgery. DESIGN: The retrospective study was carried out in 110 consecutive cases of nasopharyngeal angiofibroma over a period of 25 years. SETTING: A hospital-based study. METHODS: In 65 patients, a transpalatal approach was used, and in 38 patients, a lateral rhinotomy approach was used. The tumour was removed by external ethmoidectomy in 2 cases and in by transnasal approach in 3 cases. A modification of the transpalatal approach was also designed. MAIN OUTCOME MEASURES: Patients were regularly followed up for any recurrence for 2 to 5 years. RESULTS: Of 118 operated cases, in 33 patients, recurrence was observed. Four cases had to be operated three times and one case four times. All of the recurrences were observed within 2 years. CONCLUSIONS: Angiofibroma, a disease of adolescent males, arises from either the lateral wall or the roof of the nasopharynx. Patients usually present at the late stage of the disease. Surgery is the treatment of choice. No single approach is applicable to all cases. However, most of the tumours are excisable by a lateral rhinotomy approach, with less chance of recurrence. The modified transpalatal approach provides excellent exposure. Recurrence occurs within 2 years.

Adolescent↗
PubMedDate not supplied

Fatal pyothorax: a rare complication of retropharyngeal abscess.

Fatal pyothorax following a massive acute retropharyngeal abscess in an adult is reported. Acute non-tuberculous retropharyngeal abscess usually develops following a penetrating injury due to a foreign body or endoscopy. Microbial isolates are mixed and consists of aerobic and anaerobic organisms. It may lead on to mediastinitis since there is a potential communication between the two spaces. Immediate cervical, pleural and mediastinal surgical drainage along with appropriate antibiotics can be life saving.

Adult↗