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A K Dasmahapatra

Publications and source records attributed to A K Dasmahapatra.

9 recordsLinked to original sources
PubMed1992

Alterations of ion-dependent ATPase activities in the brain of Singi fish, Heteropneustes fossilis (Bloch), by triiodothyronine.

The activities of Na+K(+)- and Mg(2+)-ATPases in mitochondrial, microsomal, and cytosolic fractions of Singi fish (Heteropneustes fossilis Bloch) brain were investigated after injections of various doses (0.012, 0.025, 0.05, and 0.10 micrograms/g) of triiodothyronine (T3) for 3 consecutive days. Both ATPases were found in the mitochondrial and microsomal fractions. The cytosolic fraction showed only Mg(2+)-ATPase activity. Mitochondrial Na+K(+)-ATPase activity increased to almost the same level in fish treated with 0.025, 0.05, or 0.10 micrograms of T3/g, while the T3 dose of 0.012 micrograms/g was ineffective in this respect. Microsomal Na+K(+)-ATPase activity increased to about the same level with all of the doses of T3 used. No detectable amount of Na+K(+)-ATPase was found in the brain cytosolic fraction. Mitochondrial Mg(2+)-ATPase activity was enhanced with 0.025, 0.05, and 0.10 micrograms of T3/g. The last dose, however, produced a higher increase in activity than the other two doses. Surprisingly, microsomal and cytosolic Mg(2+)-ATPase activity was not increased by T3 treatment. Although T3 concentrations rose sharply after each T3 injection, the serum T3 level in T3-injected fish was not different from that in the control as observed on the fourth day. The T3-induced rise of Na+K(+)- and Mg(2+)-ATPase activities was inhibited by cycloheximide treatment. Immersion of Singi fishes in thiourea significantly reduced brain Na+K(+)-ATPase activity in microsomal and mitochondrial fractions but decreased Mg(2+)-ATPase activity only in the mitochondrial fraction. Three consecutive daily injections of T3 (0.10 micrograms/g) into the thiourea-treated fishes increased their ATPase activities even beyond the control level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Isolation, stabilization, and molecular weight estimation of thyroid hormone receptors of tadpole and chick embryo erythrocytes.

Typical procedures for the isolation of triiodothyronine (T3) receptors from mammalian nuclei involve extraction of nuclei with buffers containing divalent cations and 0.40M KCl. However, when applied to tadpole erythrocyte (RBC) nuclei, this method gave low yields of relatively unstable T3 receptors. The use of EDTA (10 mM) and 0.4M KCl in a sucrose-Tris buffer resulted in the extraction of 90% of the specifically bound [125I]-T3 from RBC nuclei. It was also found that 5 mM thiol reagent (DTT, GSH, or beta-mercaptoethanol) was required for maximal stability of the receptor. Fractionation of labeled RBC nuclear extracts on a Sephadex G-100 column yielded only one peak of specific T3 binding activity. The T3 receptor peak eluted at the same position as bovine serum albumin (BSA), with an estimated mol wt of 68 kDa. Specific T3 binding activity was destroyed by protease digestion but not by DNAse or RNAse. Scatchard analysis of the fractions from the receptor peak supported the existence of one class of T3 binding sites, with an estimated Kd (about 7 pM) comparable to the Kd reported for the intact RBC. Using the same methods, T3 receptors from the nuclei of chick embryo RBCs were also isolated, again with a Kd (7 pM) similar to that for the intact RBC. The chick receptor also eluted from the Sephadex G-100 column at the same position as BSA. The estimated mol wt of the T3 receptors from both sources is comparable to those reported for T3 receptors from other sources. The results show that T3 receptors derived from both tadpole and chick RBC nuclei could be isolated in a soluble and stable form with no apparent change in Kd.

Animals↗
PubMed1991

Demonstration of putative thyroid hormone receptor in the brain nuclei of Singi fish, Heteropneustes fossilis (Bloch).

A single injection of [125I]triiodothyronine (T3) with or without stable T3 in Singi fish, Heteropneustes fossilis (Bloch), showed that the fish brain has saturable binding sites and that the specific uptake is 60-70% higher than the nonspecific uptake. The distribution kinetics of [125I]T3 in the serum, whole brain, and brain nuclei after a single injection of the labeled hormone showed that the removal of [125I]T3 from the serum was very rapid with the t1/2 of about 3.3 hr and the incorporation of the hormone into the brain and brain nuclei were very slow and achieve a maximal value after 4-6 hr of postinjection. The binding of [125I]T3 to the isolated brain nuclei of Singi fish was further studied in vitro. Binding was linearly increased with the increasing concentration of the DNA (nuclei). The binding achieved equilibrium between 15 and 20 min at 27 degrees and was stable at least for 1 hr. The binding was reversible in the presence of excess unlabeled T3. Scatchard analysis showed only a single class of binding sites. The mean dissociation constant (Kd) is 2.15 +/- 0.45 x 10(-10) M and maximum binding capacity (MBC) is 0.044 +/- 0.024 pmol/mg DNA. The relative binding affinities of thyroid hormone analogs for T3 sites were as follows: TRIAC greater than T3 greater than TETRAC greater than T4 greater than reverse T3 greater than T2. These findings were similar to those for other animals. Therefore, the nuclear binding sites in Singi fish brain, as demonstrated, may be regarded as thyroid hormone receptors.

Animals↗
PubMed1990

In vitro demonstration of putative nuclear 3,5,3'-triiodothyronine receptors in isolated liver nuclei of Singi fish, Heteropneustes fossilis (Bloch).

Putative thyroid hormone (TH) receptors have been demonstrated in the isolated liver nuclei of Singi fish, Heteropneustes fossilis (Bloch), and their binding characteristics have been examined. Nuclear T3 saturation analyses were carried out in vitro at 27 degrees C in a sucrose-Tris-HCl buffer (pH 7.5) containing calcium (2 mM), magnesium (3 mM) and 2-mercaptoethanol (5 mM). After incubation the bound and free hormones were separated by centrifugation and the nuclei were treated with Triton X-100 (final concentration 0.25%) to reduce the non-specific binding. The binding was saturable and reached equilibrium by 20 minutes of incubation and was also stable for 2 hours. The binding was reversible and the rate of dissociation was more or less equal to the rate of association. The binding was linearly increased with the increased concentrations of the DNA (nuclei). Scatchard analyses of the equilibrium binding data revealed that only one class of binding sites for T3 did exist in the hepatic nuclei of Singi fish. The affinity of these sites or the mean dissociation constant (Kd = 0.20 +/- 0.07 x 10(-10) M) and the mean maximum binding capacity (MBC = 0.17 +/- 0.04 pmol/mg DNA) were in reasonable agreement with the values reported for other teleost fishes.

Animals↗
PubMed1990

Effect of lead, zinc, mercury, and copper with and without estrogen on serum vitellogenin level in Magur fish (Clarias batrachus L.).

Injection(s) of lead, zinc, and mercuric acetate decreased the serum vitellogenin content in Magur fish, while cupric acetate failed to cause any change in the vitellogenin level. Estrogen injections on 7th, 8th and 9th d increased the serum vitellogenin level in normal and copper salt treated fish, but were totally ineffective in altering the reduced vitellogenin content in lead, zinc, and mercury salts treated fish. Vitellogenin level almost restored to normal level at 6 week in lead, zinc, and mercury treated fish, and estrogen injections on 37th, 38th, and 39th d enhanced the serum vitellogenin content in all groups.

Animals↗
PubMed1989

Effect of 17 beta-estradiol on different parts of central nervous system of female Singi fish (Heteropneustes fossilis Bloch) in relation to reproductive stages.

Effects of different doses of 17 beta-estradiol (1, 2 and 4 micrograms/g, 3 consecutive days injections) on the protein, RNA and DNA contents of cerebrum (CB), cerebellum (CE), midbrain (MB), medulla oblongata (MO) and spinal cord (SC) of female non-vitellogenic (NV) and vitellogenic (V) Singi fish (Heteropneustes fossilis Bloch) were investigated. The amounts of these macromolecules in all these substructures of the central nervous system were enhanced on the 4th and/or 7th day in NV fish by estradiol depending on the dose. The higher dose(s) caused more marked effect. The dose of 1 microgram/g was ineffective in case of protein and mostly in case of DNA. There was no enhancement of protein content with any dose of estradiol on the 4th day in CE, MB, MO and SC, but in CB 4 micrograms of estradiol/g increased the protein content on this day. However, the increase was marked on the 7th day in all substructures. The enhancement of RNA content was elicited earlier (4th day) even with lower dose of 1 microgram/g in NV fish in most of the substructures, except MO. With exception of this substructure again, the DNA content of any part did not increase with the hormone on the 4th day with 1 microgram of estrogen/g. The changes in protein and nucleic acid contents of the different substructures of central nervous system in V fish with 17 beta-estradiol were mostly opposite to those in NV fish. Depending on the dose and time, protein and RNA contents of these parts decreased with estradiol in V fish. No change in DNA content, however, was found, except MO where this cellular constituent was surprisingly enhanced on the 4th and 7th day with all doses of estradiol used. The spinal cord of V fish did not show any change in RNA and DNA contents with the hormone. Thus a reproductive stage-specificity of estrogen action in fish brain is documented.

Animals↗
PubMed1988

A comparative study of copper ion induced lysis of vertebrate red blood cells.

1. Erythrocytes from different vertebrate classes were tested for susceptibility towards copper ion-induced lysis under identical copper ion concentration and per cent cell volumes. 2. The susceptibility towards lysis was found to be correlated with the rate of copper ion entry into the erythrocytes. 3. GSH levels decline in red blood cells at a rate proportional to the rate of copper ion entry. 4. Hemolysis does not seem to be causally related to the level of GSH in the erythrocytes.

Animals↗
PubMed1987

Decrease in triiodothyronine binding sites in chick embryo erythrocytes during early development.

Specific thyroid hormone (TH) binding sites have been detected in nuclei of erythrocytes obtained from developing chick embryos. The binding characteristics and relative affinities for TH analogs were those expected of TH receptors. Nuclear triiodothyronine (T3) saturation analysis was carried out in vitro by incubating intact erythrocytes in M199 medium with 3-200 pM [125I]T3 for 1 hr at 37 degrees C or 20-24 hr at 21 degrees C. Nuclei were obtained by centrifugation after lysing the erythrocytes in a stabilizing buffer containing 0.3% saponin, followed by addition of Triton X-100 (final concentration 0.2%) to minimize the nonspecific binding. Scatchard analysis of equilibrium binding data suggested that the nuclei possess a single class of binding sites. The binding is reversible and the rate of dissociation is temperature dependent. T3 and T4 appear to bind to the same sites, but the affinity of T3 was 16 times greater. Among TH analogs tested, Triac had the highest affinity followed by L-T3, D-T3, Tetrac, L-T4, D-T4, T2, and rT3. Serial studies performed on different days of chick embryogenesis demonstrated a rapid and significant decrease of the erythrocyte nuclear T3 receptor. On Day 5, the number of T3 binding sites was maximal at 1600 +/- 100 per nucleus. The number declined steadily until, by Day 20, it had reached about 60 +/- 10 sites/nucleus. RBC from adult and baby chickens had less than 1% as many binding sites as those from Day 5 embryos. There was no significant change in the affinity of the sites (Kd approximately equal to 20 pM at 37 degrees C). The reason for the loss of T3 binding sites during embryogenesis is not known. Since the plasma level of the TH increases during embryogenesis, this may reflect down regulation. Another possibility is that the change in erythrocyte population which occurs during this period involves production of erythrocytes which contain fewer T3 binding sites.

Animals↗