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Biomedical subjects

T C Kumar

Publications and source records attributed to T C Kumar.

At least 19 recordsLinked to original sources
PubMed2000

Differential formation of octadecadienoic acid and octadecatrienoic acid products in control and injured/infected potato tubers.

Lipoxygenases in plants have been implicated in the activation of defense responses against injury/infection. Pathogen-derived polyunsaturated fatty acids, such as arachidonic acid, eicosapentaenoic acid and their metabolites have been shown to elicit defense responses against pathogen infection in plants. However, not much is known about the role of host-derived fatty acids and their metabolites in plant defense responses. In this study, isolation and characterisation of endogenous lipoxygenase metabolites formed in potato tubers in response to injury/infection was undertaken. While 9-hydroperoxyoctadecadienoic acid (9-HPODE), derived from octadecdienoic acid (linoleic acid) is the major lipoxygenase product formed in control potato tubers, 9-hydroperoxyoctadecatrienoic acid (9-HPOTrE), derived from octadecatrienoic acid (alpha-linolenic acid) is the major lipoxygenase product formed in potato tubers in response to injury or infection with Rhizoctonia bataticola. As a result, the relative ratio of 9-HPODE to 9-HPOTrE showed a shift from 4:1 in control to 1:2 and 1:4.5 in injured and infected potato tubers respectively. From this study, it is proposed that lipoxygenase metabolites of octadecadienoic acid may be involved in physiological responses under control conditions, while octadecatrienoic acid metabolites are mediating the defense responses. This forms the first report on the differential formation of endogenous lipoxygenase products in potato tubers under control and stress conditions.

Chromatography, High Pressure Liquid↗
PubMed2000

Purification and characterization of rat testicular glutathione S-transferases: role in the synthesis of eicosanoids.

AIM: Purification of glutathione S-transferases (GSTs) from rat testis; separation and identification of various subunits and their role in eicosanoid biosynthesis. METHODS: Purification of rat testicular GSTs by affinity chromatography, employing S-hexylglutathione-linked epoxy-activated Sepharose 6B column and separation of individual subunits by reverse phase-high pressure liquid chromatography (RP-HPLC). Characterization of affinity purified GSTs by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis. The role of testicular GSTs in eicosanoid biosynthesis was determine by incubating GSTs with 5, 6-Leukotriene A4Me (LTA4Me) and prostaglandin H2(PGH2) and analyzing the products formed on HPLC/TLC. RESULTS: The present study reveals that majority of rat testicular GSTs are of Yb size (60%) with molecular weight of 27 kDa. The most predominant subunits, however, are GST Yn2(27%), followed by GST Yc(24%) and GST Yn1(20%). These testicular GSTs showed very high Leukotriene C4 (LTC4) synthase activity with 5, 6-Leukotriene A4Me (LTA4Me) as the substrate and prostaglandin D (PGD) synthase activity with prostaglandin H2(PGH2) as the substrate. CONCLUSION: Majority of rat testicular GSTs are Yb sized and are involved in the synthesis of eicosanoids like LTC4 and PGD2.

Androgens↗
PubMed1998

Pulmonary lipid peroxidation and antioxidant defenses during exhaustive physical exercise: the role of vitamin E and selenium.

Physical exercise is known to induce oxidative stress leading to the generation of free radicals. This increased generation of free radicals might lead to lipid peroxidation and tissue damage, more so under deficient/impaired antioxidant states. In the present study, we report the role of vitamin E and selenium (Se) during exercise-induced oxidative stress in the pulmonary tissue. Vitamin E and/or Se deficiency in female albino rats resulted in generation of free radicals as revealed by electron spin resonance (ESR) spectra in the lung tissue, indicating the onset of oxidative stress. When these animals were subjected to a single bout of exhaustive exercise, there was an additional increase in the generation of oxy-free radicals, which might lead to tissue damage. However, no such signals were recorded in the lung tissue of vitamin E- and Se-supplemented animals, when subjected to a similar exercise program, suggesting that protection is offered by vitamin E and Se in combating oxidative stress.

Animals↗
PubMed1997

Enhanced production of LTB4 and free radicals in rat lung by exhaustive physical exercise.

Leukotrienes formed by the action of 5-lipoxygenase on arachidonic acid are a group of endogenous compounds active in hypersensitivity reactions and inflammation. In this report the formation of LTB4 from LTA4 was measured by incubating lung microsomes from normal and exercised rats to determine whether LTB4 may have a role in the mediation of exercise-induced oxidant stress. Exhaustive exercise in the form of swimming results in the enhanced production of LTB4 in lung microsomes. Further, free radicals measured by ESR spectroscopy were also significantly increased in lung tissue from exercised rats. These results suggest a role for LTB4 in the mediation of lung tissue damage during exercise-induced oxidative stress.

Animals↗
PubMed1995

Induction of Ya1 subunit of rat hepatic glutathione S-transferases by exercise-induced oxidative stress.

Adult female rats subjected to exercise training in the form of swimming daily (for 20 min initially with gradual increase up to 90 min within a week) for 130 days showed a significant elevation of liver glutathione S-transferase (GST) activity when compared to controls. Electrophoresis and Western blot analysis of cytosolic as well as affinity-purified hepatic glutathione S-transferases revealed the induction of Ya-sized subunit in exercise-trained animals. Reverse-phase HPLC analysis of affinity-purified GSTs further revealed that Ya-sized subunits in control animals consisted of predominantly Ya2, whereas the trained animals displayed a dramatic 4.3-fold increase in Ya1. The GSTs of exercise-trained animals showed increased peroxidase activity when compared to corresponding controls, which is consistent with the changes in sub-unit composition. This could be a response to the physiological oxidative stress induced by physical exercise.

Animals↗
PubMed1994

The value and use of different contraceptive methods.

Reductions in the rates of maternal and child mortality as well as in demographic growth are directly linked to contraceptive usage. The development and availability of safer, improved contraceptives which are convenient to use could be expected to be used by a larger group of individuals and thus make an impact on reproductive health as well as on population growth rates. Such arguments have been used to support contraceptive research. This article deals with some of the developments that have occurred as a consequence of such efforts.

Contraception↗
PubMed1992

Volume of semen as a parameter of its quality.

A total of 1655 semen samples obtained from men who underwent initial semen analysis before enrolling for IVF-ET programme were analysed. The semen samples were categorized arbitrarily on the basis of volume as high (> 4.5 ml), normal (1.5-4.5 ml) and low (< 1.5 ml). The semen parameters studied vis-a-vis volume of the sample were viscosity, osmolality, motility, sperm count and morphology. The different volume groups were also compared to the overall quality of the sample. The study showed that high and low volume semen were associated with high incidence of spermatozoa exhibiting subfertile characteristics. Normal volume per se did not indicate the quality of the sample, however high and low volumes were indicators of semen of subfertile quality. There was an inverse correlation between osmolality and volume of semen sample. Thus the parameter 'volume' gives a rough estimate of the quality of the sample.

Humans↗
PubMed1992

Incidence of abnormalities in sperm morphology as an indicator of its fertilizing potential.

A retrospective analysis was carried out to assess the correlation of sperm morphology with the occurrence of fertilization in vitro of human oocytes. Seventy women who were subjected to in vitro fertilization procedure were taken up for this study. The cytological smears of semen were evaluated for the morphological characteristics of spermatozoa. Instances where in vitro fertilization did not occur (group II) had significantly (P less than 0.001) higher morphological abnormalities (head defects) when compared with those where fertilization occurred in vitro (group I). The results indicate that evaluation of sperm morphology with special reference to head abnormalities has diagnostic potential in human in vitro fertilization.

Adult↗
PubMed1991

Effects of intranasal administration of norethisterone on folliculogenesis, cervical mucus, vaginal cytology, endometrial morphology and reproductive-endocrine profile in women.

The effects of intranasal administration of norethisterone (NET) on menstrual cycle length, folliculogenesis, serum levels of estradiol, FSH, LH and progesterone, vaginal cytology, cervical mucus and endometrial morphology were studied in 8 volunteers (age 28 to 39 years, weighing between 46 and 54 kg). The study period comprised 4 consecutive menstrual cycles. In the first cycle (pretreatment cycle), only the vehicle (alcohol, propylene glycol, water; 3:3:4) was sprayed intranasally (100 microliters in each nostril), using a metered nebulizer, once daily from day 3 to the last day of menstrual cycle. In the next two cycles (treatment cycles), NET (300 micrograms/day) was administered once daily, starting from day one of menstrual cycle, between 9 and 10 a.m. The fourth cycle was a post-treatment cycle in which the volunteers were monitored for recovery. Blood samples (about 5 ml each) were collected once daily from day 8 to 24 and thereafter on alternate days until the last day of cycle during all the 4 cycles. Levels of estradiol, FSH, LH and progesterone were measured in the serum samples by radioimmunoassay methods. Cervical mucus samples and vaginal smears were collected once daily starting from day 7 or 8 of each cycle until the mucus was very scanty. Serial pelvic ultrasonography was performed starting from day 7 or 8 until the growing follicle disappeared or throughout the cycle in case a growing follicular cyst was observed. Endometrial aspirates were collected once around day 22 in each cycle and processed for routine histological examination.

Administration, Intranasal↗
PubMed1991

Comparison of four different ovarian stimulation protocols in an in vitro fertilisation & embryo transfer programme.

Four different ovarian stimulation protocols were evaluated in an in vitro fertilisation and embryo transfer programme in 208 women (228 treatment cycles). In the rigid protocol (RP), 100 mg of clomiphene citrate (CC) was given from day 3 to day 7 of the menstrual cycle and 300 IU of human menopausal gonadotropin (hMG) was given from day 5 of the menstrual cycle. In the individualised protocol (IP) the same drugs and doses were used as in RP, but the day of initiation of CC depended on the length of the individual's menstrual cycle and hMG was administered from the last day of CC. In the programmed protocol (PP), ovarian function was suppressed with oral contraceptive pills (ethinyl estradiol 30 micrograms and norethisterone 1 mg) started on day 5 of the menstrual cycle for 45 to 70 days. Considering the last day of pill intake as day 0, CC was given for 5 days from day 5 and hMG (300 IU) from day 7. In the alternate day protocol (ADP), 100 mg of CC was administered from day 2 to day 6 and hMG (300 IU) was given on alternate days from day 2 to day 8 or day 10 of the cycle. In all the women, hCG (5000 IU) was administered when the diameter of at least 2 follicles was greater than or equal to 16 mm and estradiol levels were 300 pg/ml/dominant follicle. Patients not showing such a response were not treated further. The cardinal events of IVF-ET such as number of good responders, incidence of oocytes harvested, fertilised and embryos transferred per cycle were compared and it was concluded that the pregnancy rates were highest in women treated by the PP.

Adult↗