Arun K. Ray

The biology of triploid fish

This review deals with major areas of triploidy research in fish. It includes not only methods for induction and detection of triploidy but also the impact of triploidy on morphology, anatomy, growth, haematology, energetics, behaviour, endocrinology and gonads in various species of fish, studied so far. The future prospects of research on triploid fish are discussed inviting researchers with diverse areas of interest in fish biology.

Targeting RET to induce medullary thyroid cancer cell apoptosis: an antagonistic interplay between PI3K/Akt and p38MAPK/caspase-8 pathways.

Mutations in REarranged during Transfection (RET) receptor tyrosine, followed by the oncogenic activation of RET kinase is responsible for the development of medullary thyroid carcinoma (MTC) that responds poorly to conventional chemotherapy. Targeting RET, therefore, might be useful in tailoring surveillance of MTC patients. Here we showed that theaflavins, the bioactive components of black tea, successfully induced apoptosis in human MTC cell line, TT, by inversely modulating two molecular pathways: (i) stalling PI3K/Akt/Bad pathway that resulted in mitochondrial transmembrane potential (MTP) loss, cytochrome-c release and activation of the executioner caspases-9 and -3, and (ii) upholding p38MAPK/caspase-8/caspase-3 pathway via inhibition of Ras/Raf/ERK. Over-expression of either constitutively active myristoylated-Akt-cDNA (Myr-Akt-cDNA) or dominant-negative-caspase-8-cDNA (Dn-caspase-8-cDNA) partially blocked theaflavin-induced apoptosis, while co-transfection of Myr-Akt-cDNA and Dn-caspase-8-cDNA completely eradicated the effect of theaflavins thereby negating the possibility of existence of other pathways. A search for the upstream signaling revealed that theaflavin-induced disruption of lipid raft caused interference in anchorage of RET in lipid raft that in turn stalled phosphorylation of Ras and PI3Kinase. In such anti-survival cellular micro-environment, pro-apoptotic signals were triggered to culminate into programmed death of MTC cell. These findings not only unveil a hitherto unexplained mechanism underlying theaflavin-induced MTC death, but also validate RET as a promising and potential target for MTC therapy.

Effect of thyroxine and analogs on protein and nucleic acid contents of liver and muscle of Lata fish (Ophicephalus punctatus)

Injection of thyroxine (T4) induced a change, biphasic in nature, in the amounts of protein and RNA in liver and muscle of Lata fish (Ophicephalus punctatus). The lower doses of T4 (0.5 μg/g, three injections; or 1 μg/g, single injection) increased and the higher doses (2 or 4 μg/g, single injection) decreased the amounts of protein and RNA in liver and muscle on the fourth or fifth day after injection. The enhanced or reduced levels of liver protein and RNA with 1 or 4 μg of T4/g, respectively, continued up to the 12th day after injection. The muscle protein and RNA levels at 1 or 2 μg of T4/g were not different from the control values on the 12th day, whereas the reduced level of only muscle protein (not RNA) with 4 μg of T4/g remained unchanged up to the 12th day. A single injection of tetraiodothyroacetic acid (TETRAC, 1, 2, or 4 μg/g) increased the protein and RNA contents of liver and muscle in Lata fish. The increased levels of these substances continued up to the 12th day after injection, except in muscle at a dose of 1 μg/g. Triiodothyroacetic acid (TRIAC, 2 or 4 μg/g, single injection) also enhanced the amounts of protein and RNA in liver and muscle. This enhanced level of these cellular substances was also observed on the 12th day at a dose of only 4 μg of TRIAC/g. DNA contents of both liver and muscle remained unaltered at all doses of T4, TETRAC, and TRIAC used.

Rise of intrasynaptosomal Ca2+ level and activation of nitric oxide synthase in adult rat cerebral cortex pretreated with 3-5-3'-L-triiodothyronine.

Accumulation of free, ionized calcium (Ca2+) and stimulation of nitric oxide synthase (NOS) activity in depolarization-induced synaptosomes prepared from adult rat cerebral cortex have been demonstrated after addition of various doses (0.1–1,000 nM) of 3,5,3′-L-triiodothyronine (T3). The effects of T3 doses on those parameters are found to occur in a dose-dependent manner. The T3 (100 nM)-induced optimum rise in intrasynaptosomal Ca2+ level [Ca2+]i seems to be an early event occurring within 5 s; whereas, the maximum stimulation of NOS activity is observed during 10 to 30 s of T3 (100 nM) administration, indicating a delayed effect. T3 has no such effects on those parameters in synaptosomes at nondepolarized condition. Although the rise in [Ca2+]i and stimulation of NOS activity after application of T3 seem to be sequential events, the present data indicate a definite role of T3 in nongenomic signal generation and transfer in mature rat cerebral cortex.

Effect of estrogen and testosterone on the protein and nucleic acid contents of liver, muscle, and gonad and plasma protein content of male and female (vitellogenic and nonvitellogenic) Singi fish, Heteropneustes fossilis bloch

Daily injections of estradiol dipropionate (0.5, 1, 2, and 4 μg/g, for 7 consecutive days) increased the hepatosomatic index, protein and RNA contents of liver, and protein content of plasma of male and female (vitellogenic and nonvitellogenic) Singi fish (Heteropneustes fossilis). The gonadosomatic index and protein and RNA contents of gonad (ovary or testes) and muscle remained unchanged in these male and female fish under such treatments. Testosterone propionate injections (0.5, 1, 2, and 4 μg/g, for 7 consecutive days) failed to cause any of these changes in male or female fish, except in the case of nonvitellogenic females where the muscle protein content increased after injections of 2 and 4 μg of testosterone per gram. The DNA content of liver, muscle, and ovary or testes was not affected by any of these hormones.

Effect of thyroid hormones and analogues on ammonia and urea excretion in Lata fish (Ophicephalus punctatus)

The influence of single intraperitoneal injection of thyroxine (T4), triiodothyronine (T3), tetraiodothyroacetic acid (TETRAC), and triiodothyroacetic acid (TRIAC) were studied on the nitrogen excretion (urea-N and NH3N) of Lata fish acclimatized at 25 or 30°. The actions of T4 and the iodinated analogs, studied at these temperatures on nitrogen excretion of these animals, appear to be temperature-specific. The NH3N as well as urea-N excretion of normal Lata fish was also found to be directly proportional to the environmental temperature (10 to 30°). Thyroxine (T4) injection at lower doses (0.5 or 1 μg/g) caused anabolic effect with respect to NH3N and urea-N excretions at 25°. With higher doses of T4 (2 μg/g or 4 μg/g) at 25° C, the results on nitrogen excretion were not significantly different from the control. At 30°, T4 (1, 2, or 4 μg/g) increased NH3N and urea-N excretion. Triiodothyronine (T3) with higher doses (2 or 4 μg/g) was effective in causing increased NH3N excretion at 25°. The responses of T3 with a dose of 4 μg/g with respect to nitrogen excretion was about at the same level as found with 10 μg/g of T4/g of body wt at this temperature. Tetraiodothyroacetic acid, or TETRAC, (1, 2, or 4 μg/g) enhanced NH3N excretion, but not urea-N excretion, at 25°. Triiodothyroacetic acid (TRIAC) even with 4 μg/g was ineffective in this respect, at 25°. Both TETRAC and TRIAC with 1, 2, or 4 μg/g at 30° significantly increased NH3N excretion. Compared to the controls, urea excretion remained unchanged with 1 μg of TRIAC/g at 30°. This nitrogen excretion (urea-N) was enhanced with higher doses of this analog (2 and 4 μg/g) at 30°. TETRAC with all doses used (1, 2, or 4 μg/g) increased urea-N excretion at this temperature. The results shown that TETRAC was more potent than TRIAC.

Specific binding of L-triiodothyronine modulates Na + -K + - ATPase activity in adult rat cerebrocortical synaptosomes

INTERACTIONS of L-triiodothyronine (T3) in adult rat cerebrocortical synaptosomes were studied in vitro. Scatchard plot analysis revealed two sets of T3 binding sites. The degree of saturation of T3 binding sites (putative receptor) correlated well with the dose-dependent inhibition of Na+-K+-ATPase activity in synaptosomes. The relative binding affinities and relative inhibition of enzyme activities for different TH analogues were L-T3 > T3-amine > TRIAC = L-T4 > r-T3 > T2 and L-T3 > T3-amine > TRIAC > L-T4 > r-T3 > T2, respectively. The present study demonstrates the nature of inhibition of synaptosomal Na+-K+-ATPase activity may be as a function of T3 occupancy of synaptosomal receptor sites in adult mammalian brain.

Estrogen stimulated lipogenic activity in the ovary of the freshwater prawn, Macrobrachium Rosenbergü

Summary Three consecutive-day injections with different doses (0.1, 0.25, 0.5, 1.0, 2.0 and 4.0 μg/g) of estradiol-17β (E2) produced statistically significant increases in the cytosolic NADP-linked malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in the ovary of the freshwater prawn (Macrobrachium rosenbergii) on the 4th day of treatment over the control values, depending upon the doses administered. Dose-dependent increases in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities were observed between 0.1–0.25, 0.25–0.5, and 0.5–1.0 μg/g doses. A similar magnitude of response was found at 1.0, 2.0 and 4.0 μg/g dose in both the cases of malate dehydrogenase and glucose-6-phosphate dehydrogenase activities. A lower dose of 0.5 μg/g was ineffective in eliciting any response to either enzyme. Ergosterol (2.0 μg/g) did not evoke any change in the malate dehydrogenase and glucose-6-phosphate dehydrogenase activities in comparison to the control values. Simultaneous inje...

Induction of CYP1A by carbofuran in primary culture of fish hepatocytes.

Carbofuran is a nematicide used in agricultural fields throughout the world. Indiscriminate use of this pesticide poses severe detrimental effects on our ecosystem. We have shown that it induces the CYP1A (cytochrome P4501A) monooxygenase enzyme system in cultured hepatocytes from Indian catfish, Heteropneustes fossilis (Bloch). We have quantified this induction by measuring the activity of the enzyme 7‐ethoxyresorufin‐O‐deethylase (EROD), synthesized from CYP1A1 gene. The induction followed a dose‐dependent relationship with carbofuran. The dose‐dependent curve of EROD using carbofuran was very much similar with β‐napthoflavone, which is a known inducer of CYP1A1. Coexposure of these compounds to the culture media showed a synergistic effect on the enzyme activity. A blocker of aromatic hydrocarbon receptor, α‐napthoflavone, blocked carbofuran‐induced EROD activity in a dose‐dependent manner. All these findings suggest that metabolism of carbofuran might be mediated by the CYP1A monooxygenase system through binding of the aromatic hydrocarbon receptor. We have also studied the superinduction phenomenon, which is a typical characteristic of the CYP1A gene in our system.

Estradiol-17β in Bombyx mori: possible significance and its effect on silk production

Although estrogen is well known as a vertebrate sex steroid, its presence in insects, including Bombyx mori, raises questions about its precise role in the physiology of insects. It was reported earlier that estradiol-17beta (E(2)) exerts a specific effect on silk-gland function in B. mori and that it may act in a nuclear-mediated way. To evaluate further the effect of E(2) on cocoon characters, larval growth and development, 1µg/g of E(2) was applied topically to the first and second day of fifth instar larvae. This resulted in a significant enhancement of cocoon characters, such as cocoon shell weight, silk filament length per cocoon, denier per filament and reelability of the cocoons, without any adverse effect on fecundity and hatchability. In the present study, E(2) levels in the haemolymph were quantified on different days of the fifth instar larvae and age-dependent changes in the endogenous E(2) titre have been demonstrated. These age-dependent variations in E(2) content coincide with physiological events occurring during the fifth instar. Such observations exclude the possibility of a dietary origin for E(2), as a sudden and sharp rise of the E(2) level in the haemolymph was observed on the 10th day of the fifth instar, preceded by a small increase on the ninth day after an eight-day feeding period. The increased level of estradiol in the haemolymph of larvae treated topically with E(2) indicates effective penetration of this hormone through the larval cuticle. Moreover, similar patterns of alteration of E(2) levels on different days of the fifth instar in both control and treated groups suggests the existence of some internal metabolic pathway in the silkworm body to regulate the hormone titre. Thus, the present investigation offers a system for investigating the unique function of E(2) in B. mori and offers potential for improvement of silk production.