Biomedical subjects
Publications and source records attributed to P G Kumar.
Dyshormonogenesis is an uncommon cause of congenital hypothyroidism. The most common abnormality is absent or insufficient thyroid peroxidase enzyme. Perchlorate discharge test can be used to diagnose thyroid peroxidase deficiency. We report three siblings with hypothyroidism due to thyroid dyshormonogenesis. Early institution of therapy in these patients can prevent mental retardation and other features of hypothyroidism.
The autoimmune regulator (AIRE) protein is a putative transcription regulator with two plant homeodomain-type zinc fingers, a putative DNA-binding domain (SAND), and four nuclear receptor binding LXXLL motifs. We have shown here that in vitro, recombinant AIRE can form homodimers and homotetramers that were also detected in thymic protein extracts. Recombinant AIRE also oligomerizes spontaneously upon phosphorylation by cAMP dependent protein kinase A or protein kinase C. Similarly, thymic AIRE protein is phosphorylated at the tyrosine and serine/threonine residues. AIRE dimers and tetramers, but not the monomers, can bind to G-doublets with the ATTGGTTA motif and the TTATTA-box. Competition assays revealed that sequences with one TTATTA motif and two tandem repeats of ATTGGTTA had the highest binding affinity. These findings demonstrate that AIRE is an important DNA binding molecule involved in immune regulation.
In this study, we examined the effect of 17 beta-estradiol and selected antiestrogens on uterine NADPH-oxidase activity, superoxide dismutase (SOD) activity, hydride (H.-), dienyl radical and O2 -radical generation, and membrane fluidity. NADPH oxidase activity was positively modulated in estradiol-treated animals and negatively regulated in animals that received injections of AF-45, RU-39411, tamoxifen, or ICI-182780. The SOD activity was markedly reduced in estradiol-treated animals when compared with the control animals. A positive modulation of SOD activity was observed upon treatment with AF45, RU39411, tamoxifen, and ICI 182780, though the potency varied among the individual test compounds. We observed detectable H(.-)-radical generation as evidenced from MNP H.- adduct formation in the uterine cell preparations from untreated control animals. Estradiol produced a tremendous augmentation in the superoxide radical profiles in uterine cell preparations compared to the control levels. All the other compounds that were tested significantly lowered the superoxide levels in the test set-up. AF-45, RU-39411, tamoxifen, and ICI-182780 induced varying orders of suppression of H(.-)-radical generation in the test subjects. There was a significant enhancement in membrane fluidity, hydride radical levels, and dienyl radical generation in the estradiol-treated group. All the antiestrogens did not exhibit a similar action on these parameters. RU-39411 exhibited antiestrogen-like activity in modulating hydride levels and membrane fluidity, whereas it stimulated dienyl radical generation. Thus our tests showed that the selected antiestrogens failed to show estrogen-like activity in these assays. It appears that estradiol exerts feedback control over pro- and antioxidant pathways and that markers of oxidative status could be used as a measure to evaluate the antiestrogenic activity of estradiol agonists/antagonists.
A single, low-dose administration of a potent antiprogesterone such as mifepristone (RU486) in the early luteal phase results in inhibition of blastocyst implantation in primates. The aim of the present study was to examine the status of leukaemia inhibitory factor (LIF), transforming growth factor beta (TGF beta) and vascular endothelial growth factor (VEGF) in day 6 gestational endometrium of rhesus monkeys with or without exposure to a single dose (2 mg/kg body weight, s.c.) of mifepristone on day 2 after ovulation. Densitometric analyses of immunoblots of endometrial spent media revealed an increase (P < 0.01) in TGF beta pan (TGF beta 1, 2, 3 and 5) and a decrease (P < 0.01) in VEGF secretion from RU486-exposed endometrial samples compared with control samples. Secretory profiles for LIF, TGF beta 1 and TGF beta 1 LAP (latency associated peptide) remained unchanged in the two treatment groups. Morphometric analyses of immunohistochemical staining showed altered cell-specific distribution. TGF beta 1 (P < 0.01) and TGF beta pan (P < 0.02) were higher, while VEGF declined (P < 0.05) in endometrial glands of RU486-exposed endometria compared with control tissue samples. Stromal cell staining patterns for all experimental cytokines studied remained unchanged. In blood vessels, VEGF was found to be low (P < 0.05), while LIF (P < 0.05) and TGF beta 1 (P < 0.01) were higher in mifepristone-exposed endometrial samples compared with control tissue samples. Increased TGF beta secretion together with elevated levels of TGF beta in glandular epithelia and in blood vessels with no apparent change in stromal levels of TGF beta or in levels of TGF beta LAP in any endometrial compartment in the two treatment groups suggest an altered paracrine involvement of this cytokine and an enhanced activation of latent TGF beta in endometrium following mifepristone treatment. Higher levels of TGF beta in gland cells may result in dysregulated growth control and degenerative morphology. Also, higher levels of LIF and TGF beta together with lower levels of VEGF in the vascular compartment in mifepristone-exposed endometrium suggest that endometrial vascular physiology is a target of this anti-progestin during the peri-implantation stage. It is thus plausible that LIF, TGF beta and VEGF in the glandular and vascular compartments of implantation stage endometrium play important roles in rendering the endometrium receptive, and that early luteal phase treatment with an anti-progestin such as mifepristone affects the involvement of these cytokines resulting in endometrial contraception.
It is generally believed that progesterone is essential for inducing the changes in oviduct and uterus necessary for embryo viability and implantation in a number of mammalian species. The aim of this study was, in the rhesus monkey, to examine in conception cycles with and without early luteal phase antiprogestin (mifepristone; RU 486) treatment: (i) the growth status of preimplantation embryos and (ii) the implantation ability of the preimplantation embryo after transfer to a synchronous-cycle surrogate recipient. A total of 43 proven fertile rhesus monkeys were randomly placed in the control (group 1, n = 18) and mifepristone (group 2, n = 25) groups. All monkeys cohabited with proven fertile male monkeys on cycle days 8-16 and were injected with vehicle alone [benzyl benzoate:olive oil, 1:4 (v/v), s.c.] for group 1 and with mifepristone (2 mg/kg body weight s.c.) for group 2, on day 2 after the presumed day of ovulation. A total of 12 preimplantation embryos [premorula (n = 1), morula (n = 2), zona-encased (n = 7) and zona-free (n = 1) blastocysts and degenerate embryos (n = 1)] were recovered from 17 ovulatory, mated cycles in group 1 on day 6 after ovulation. In group 2, of the 23 ovulated cycles, 12 preimplantation embryos [premorula (n = 2), morula (n = 7), zona-encased blastocyst (n = 1), and degenerate embryos (n = 2)] were retrieved. Despite no significant difference in the recovery rate between the two groups, early luteal phase RU 486 exposure induced delay (P < 0.01) in preimplantation embryo growth, primarily at the morula-blastocyst transition stage. Nine of the embryos from group 1 and seven of the embryos from group 2 recovered on day 6 were transferred to naturally synchronized, non-mated and untreated surrogate recipients. In group 1, five embryos implanted (55%) and, of these, three (60%) gave rise to live infants through natural delivery; implantation was assessed from extension of the cycle (i.e. no menstrual bleeding) and rise in concentrations of oestradiol and progesterone from day 10 of conception; rectal palpation was performed on cycle day 50 to confirm clinical pregnancy. In group 2, however, there was not a single case of establishment of pregnancy following transfer of embryos retrieved from mifepristone-exposed monkeys. Thus, preimplantation embryos recovered from RU 486-exposed monkeys failed to establish evolutive implantation and pregnancy, while significant (P < 0.02) success was observed in transfers of embryos from the control group. We postulate that progesterone-mediated actions are involved in mediating the growth and viability of preimplantation-stage embryos in the rhesus monkey.
There is a growing awareness of a need for developing novel methods of contraceptive technology which should not only be effective in providing protection against conception but also take into consideration the reproductive health issues confronting men and women. This paper considers the process of embryo implantation as one such potential target. The hormonal basis of embryo implantation in primates has been discussed to indicate that progesterone, and not estrogen, from ovarian source is the primary determinant of embryo-endometrial maturation and their synchronization for implantation. Thus, low dose administration of the anti-progesterone, mifepristone, during early luteal phase has been shown to be an effective anti-implantation approach to for fertility control. Furthermore, the dissociation of endometrial-hormonal synchrony at the time of blastocyst implantation following the post-ovulatory mifepristone administration has been shown to be the physiological basis of its anti-implantation effect with undisturbed circulatory hormone profiles and ovarian functions. Further studies are required to appreciate the full potential and to mollify the limitations of this approach.
Use and efficacy of hyperbaric oxygen therapy (HOT) in liver disease has not been established. A prospective control study of HOT in liver diseases was undertaken. Sixty cases were selected for this study (30 with HOT and 30 with conventional therapy only). Almost equal number of Hepatitis B virus surface antigen (HbsAg) positive cases were included in both groups. All patients were male. Only cases with serum bilirubin over 10 mg/dl were included in this study. It was found that study cases recovered faster, gained appetite and had an earlier sense of well-being. There was faster disappearance of pruritus, earlier achievement of normal liver function, HbsAg negativity and overall shorter duration of hospital stay and convalescence. Short term adverse effects were unremarkable.
The hydrogen peroxide-dependent and peroxidase-mediated iodination of tyrosine, a pivotal step in the thyroxine biosynthesis in thyroid glands of mammals, has always been thought to be dependent on a glucose-glucose oxidase system to meet its demand for hydrogen peroxide. This report documents a novel and probably kinetically faster hydrogen peroxide-generating system operating in the thyroid gland cells involving the superoxide dismutase and superoxide anion radical. In the female cycling mice, the superoxide radical and superoxide dismutase activity are shown to be at persistently high levels, quite likely acting as a potent hydrogen peroxide synthesizer in the mammalian thyroid gland. The significance of this discovery in relation to the thyroid physiology is discussed.
Mammalian spermatozoa, which like other living cells are susceptible to oxygen toxicity, generate increasing quantities of superoxide radical as epididymal maturation proceeds. This is associated with a concomitant reduction in the activity of superoxide dismutase. A possible involvement of superoxide radicals in bringing about some of the reported oxidative changes occurring during epididymal maturation of mammalian spermatozoa is discussed. It is suggested that superoxide radical may be involved in regulating membrane changes accompanying sperm maturation.
Even though the aminopeptidase and amylase are the major liquefying factors in the liquefaction process of the ejaculated semen-coagulum, the exact nature of "switching on" phenomena has not been elucidated yet. Monitoring the rate of production of the asborbyl radical, an indirect method for oxyradical-stress measurement, this prima facie study reports the involvement of oxygen radical in the liquefaction process of coagulated semen.
Sperm is highly sensitive to superoxide radical surge in the granuloma interior. To investigate possibility of a superoxide radical bomb, the role of an oxyradical on the spermatozoon was studied in vitro using potassium superoxide, a potent superoxide radical producer. Results confirm that the superoxide radical has a unique site-specific scissoring power.
The postcoitus phagocytic engulfment of spermatozoa following disintegration of a sperm cell has not been well understood until now. By monitoring the free radical status of the vagina in accordance with the various stages of the estrous cycle and the sperm-cutting power of vaginal flushing, a positive correlation has been detected that favors the superoxide theory of the sperm-cutting technique in vivo. This finding is also consistent with the previous experience of free radical bombing of spermatozoa in spermatic granuloma.
The nongenomic action of progesterone (P) on capacitated sperm in mediating acrosomal exocytosis operates through transmembrane signal transduction involving increased intracellular calcium ions and modulation of protein kinases and phospholipid metabolism through a second messenger pathway. Conflicting views exist regarding the nature of the nongenomic receptor of P. It is thought to be a cell-surface receptor having the properties of a calcium channel, chloride channel, bicarbonate/chloride exchanger, and gamma aminobutyric acid type A (GABA(A)). In this study, we tried to understand the role of bicarbonate and/or P in inducing membrane perturbations in capacitated and acrosome-reacting spermatozoa. We also attempted to characterize the membrane responses in P-stimulated and bicuculline-poisoned sperm. The presence of a high level of bicarbonate in the medium favored high rotational mobility of lipids and proteins in capacitated sperm. However, the capacitated sperm exhibited low lipid ordering and unaltered protein ordering in response to the high bicarbonate concentration. P and bicuculline appeared to bind to the same or similar binding sites, probably a GABA(A) receptor, eliciting similar motional perturbations in sperm membranes. It appears that both P and bicuculline can induce receptor aggregation and lipid ordering in sperm membranes, which alter the capability of sperm to bind zona pellucida, and that the P action on sperm takes effect through a bicarbonate-dependent signal transduction mechanism.