Biomedical subjects

K G Pradeep

Publications and source records attributed to K G Pradeep.

6 recordsLinked to original sources

PubMed1998

Starvation induced hypothyroidism involves perturbations in thyroid superoxide-SOD system in pigeons.

This study investigated the influence of starvation over seven days on avian thyroidal superoxide radical levels and superoxide dismutase activity profiles in the Indian rock pigeon Columba livia intermeida, in relation with iodine metabolism. The serum thyroid hormone profile was assayed to correlate the thyroidal redox status with the circulating thyroid hormone levels. The spin-trapping results suggest a role for thyroidal superoxide anion (O2.-) in causing a hypothyroid state in pigeons during long term energy withdrawal. Pigeons starved for 1 day generated superoxide and iodide free radicals in their thyroids, with a significant decrease in SOD activity. Regain of SOD activity in 2nd- and 3rd-day starved birds is marked by complete scavenging of radicals in the thyroid, suggesting the significance of SOD in thyroid glands as a potential antioxidant sink against reactive oxygen species, O2.- Resurgence of O2.- radicals with a parallel decrease in SOD activity in the thyroid gland on 5th- and 7th-day of starvation provides evidence of disruption of homeostasis between pro-oxidant and antioxidant states, leading to oxidative stress in avian thyroid during long-term calorie crisis. Following starvation both thyroid hormones thyroxine (T4) and triiodothyronine (T3) decreased, putting pigeons in a hypothyroid state. We argue that oxidative inactivation of thyroid peroxidase and other thyroid proteins by radical attack during starvation invoked oxidative stress, which could be one of the factors responsible for the hypothyroid state in pigeons.

Animals↗

PubMed1994

Photochemical reaction sequences of blue light activated flavins: sensory transduction through free radical messengers.

Flavin photochemistry involves the production of transient flavin free radicals which in turn sensitize molecular oxygen to generate superoxide. The blue light induced photochemical chain reaction of flavins may be blocked at two different levels by photoresponse inhibitors. A protein-bound/lipid-bound flavin located on the biomembrane may take part in the blue-light mediated sensory transduction by 'releasing' a 'free radical messenger' equivalent into the cell interior.

Flavins↗

PubMed1993

Survival in hanging.

Although hanging is a popular means for suicides in India, the attempt frequently does not result in death. Of 12 cases of hanging, only one of which was accidental, seen at our institution during 1985-90, all but two victims survived. We present data indicating that hanging victims can be resuscitated even after prolonged periods of suspension and unconsciousness, and we discuss some of the reasons why asphyxiation by hanging may be delayed when there is no damage to the spinal cord.

Adult↗

PubMed1991

Over-expression of superoxide dismutase and lack of surface-thiols in spermatozoa: inherent defects in oligospermia.

The infertility associated with oligospermia had been suspected to be a direct consequence of the impairment in fertilizing ability of the spermatozoa rather than the presence of low sperm number per se. This study defines some of these impairments, which include an over expression of superoxide dismutase, poor superoxide anion radical generation capacity and a lack of sperm-surface thiols in oligospermia. The abnormal biochemical make-up of spermatozoa could explain their low fertilizing ability in case of oligospermia.

Cell Membrane↗

PubMed1990

Superoxide dismutase as a regulatory switch in mammalian testicular steroidogenesis.

The delta 4-pathway of testosterone biosynthesis in leydig cells, widely believed to proceed through pregnenolone--greater than pregnenedione--greater than progesterone route catalyzed by 5 delta-3 beta-hydroxysteroid dehydrogenase and delta 5-delta 4-isomerase respectively is shown to pass through an alternate pathway mediated by superoxide dismutase and peroxidase. A built-in regulatory switch is incorporated in this route, with the superoxide dismutase inducible upon LH-stimulation of the leydig cells.

Animals↗

PubMed1988

Changes in the levels of superoxide anion radical and superoxide dismutase during the estrous cycle of Rattus norvegicus and induction of superoxide dismutase in rat ovary by lutropin.

Superoxide dismutase, which has been shown to be present in a number of tissues, exhibits cyclic changes during the reproductive cycle of rats. An inverse correlation is seen between the levels of superoxide dismutase and superoxide radical. In immature, pseudopregnant rats, primed with human Chorionic Gonadotropin, lutropin seemed to induce ovarian superoxide dismutase, which could be blocked significantly by the introduction of anti-LH serum. These results point out the specific induction of superoxide dismutase by lutropin. It is reasonable to postulate that during luteal functioning, luteinizing hormone induces superoxide dismutase which in turn seems to play a central role generating hydrogen peroxide from superoxide anion radicals. Hydrogen peroxide, thus formed, drives the peroxidase-ascorbate system, responsible for production of progesterone.

Animals↗