Kousik Pramanick

Steroid-induced oocyte maturation in Indian shad Tenualosa ilisha (Hamilton, 1822) is dependent on phosphatidylinositol 3 kinase but not MAP kinase activation

Fully grown fish and amphibian oocytes exposed to a maturation-inducing steroid (MIS) activates multiple signal transduction pathways, leading to formation and activation of maturation-promoting factor (MPF) and induction of germinal vesicle breakdown (GVBD). The present study was to investigate if phosphatidylinositol 3 kinase (PI3 kinase) and mitogen-activated protein kinase (MAP kinase) activation are required for naturally occurring MIS, 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P)-induced cdc2 activation and oocyte maturation (OM) in Tenualosa ilisha. We observed that 17,20β-P-induced OM was significantly inhibited by PI3 kinase inhibitors Wortmannin and LY29400. 17,20 β-P was shown to activate PI3 kinase maximally at 90 min and cdc2 kinase at 16 h of treatment. Relative involvement of PI3 kinase, MAP kinase and cdc2 kinase in 17,20β-P-induced OM was examined. MAP kinase was rapidly phosphorylated and activated (60-120 min) after MIS treatment and this response preceded the activation of cdc2 kinase by several hours. A selective inhibitor of MAP kinase (MEK), PD98059, sufficiently blocked the phosphorylation and activation of MAP kinase. Inhibition of MAP kinase activity using PD98059 however, had no effect on MIS-induced cdc2 kinase activation and GVBD. These results demonstrate that activation of the PI3 kinase is required for 17,20β-P-induced cdc2 kinase activation and OM in T. ilisha. MAP kinase although was activated in response to 17,20β-P and PI3 kinase activation, it is not necessary for cdc2 activation and OM in this species.

Changes in plasma steroid levels during oocyte development in Indian shad, Tenualosa ilisha (Hamilton, 1822): role of gonadotropins on in vitro steroid production and development of oocyte maturational competence.

Circanual variations in plasma testosterone (T), 17-estradiol (E2), and 17,20-dihydroxy-4-pregnen-3-one (17,20-P) levels and ovarian steroid synthetic potential of Tenualosa ilisha of river Hooghly, West Bengal, India were examined. This fish exhibited bi-annual spawning; one during April-May and another during August-September. Coinciding with the GSI values, present study recorded a decline in plasma T and E2 levels from October, reaching their lowest values in January followed by a rapid rise in March when the ovary contained mostly vitellogenic follicles and remained high up to April (postvitellogenic stage). Plasma 17,20β-P level was detected in March and reached peak value in April during oocyte maturation. After spawning, all the steroid levels declined to reach lowest values in June. From June onwards, T and E2 levels again increased for the next cycle and peaked at the end of vitellogenesis. Plasma 17,20β-P was reappeared in August and reached maximum in September during oocyte maturation and spawning. Of the two gonadotropins tested, in vitro production of both T and E2 by the vitellogenic and postvitellogenic follicles was regulated by FSH and LH respectively. Production of 17,20-P by the post-vitellogenic follicles was regulated by LH only. Acquisition of in vitro oocyte maturational competence (OMC) was developed by the addition of HCG in culture medium. Treatment of a 3β-HSD inhibitor blocked LH-induced steroid production, but not development of OMC. Both Cycloheximide and actinomycin D inhibited LH-induced development of OMC, indicating the requirement of de novo protein synthesis for this process.

Estrogen-regulated expression of P450arom genes in the brain and ovaries of adult female Indian climbing perch, Anabas testudineus

Cytochrome P450arom (CYP19), a product of cyp19a1 gene, catalyzes the conversion of androgens to estrogens and is essential for regulation of reproductive function in vertebrates. In the present study, we isolated partial cDNA encoding the ovarian (cyp19a1a) and brain (cyp19a1b) P450arom genes from adult female perch, Anabas testudineus and investigated their regulation by estrogen in vivo. Results demonstrated that cyp19a1a and cyp19a1b predominate in ovary and brain respectively, with quantity of both attuned to reproductive cycle. To elucidate estrogen-regulated expression of cyp19a1b in brain and cyp19a1a in ovary, dose- and time-dependent studies were conducted with estrogen in vitellogenic-stage fish in the presence or absence of specific aromatase inhibitor fadrozole. Results demonstrated that treatment of fish with 17β-estradiol (E2; 1.0 μM)) for 6 days caused significant upregulation of cyp19a1b transcripts, aromatase B protein, and aromatase activity in brain in a dose- and time-dependent manner. Ovarian cyp19a1a mRNA, aromatase protein, and aromatase activity, however, was less responsive to E2 than brain. Treatment of fish with an aromatase inhibitor fadrozole for 6 days attenuated both brain and ovarian cyp19a1 mRNAs expression and stimulatory effects of E2 was also significantly reduced. These results indicate that expression of cyp19a1b in brain and cyp19a1a in ovary of adult female A. testudineus was closely associated to plasma E2 levels and seasonal reproductive cycle. Results further show apparent differential regulation of cyp19a1a and cyp19a1b expression by E2/fadrozole manipulation.

Molecular mechanism of mercury-induced reproductive impairments in banded gourami, Trichogaster fasciata

Mercury is one of the key pollutants responsible for the degradation of natural aquatic ecosystems. Among the different forms of mercury that exist in the environment, mercuric chloride (HgCl2) is the dominant pollutant for freshwater environments as it is used as an ingredient in antiseptics, disinfectants and preservatives, insecticides, batteries and in metallurgical and photographic operations. Pollutant may exert their action on organisms or populations by affecting their normal endocrine function as well as reproduction. Thus, the present study tried to understand the effect of mercuric chloride (HgCl2) on reproductive function and to decipher the molecular mechanism of Hg-induced reproductive impairments of female Trichogaster fasciata. Both in vivo and in vitro experiments were performed by using ecologically relevant doses of HgCl2 and the resulting effects on follicular development, steroidogenic potentiality, aromatase activity, aromatase gene expression and steroidogenic factor-1 (SF-1) expression pattern were analysed. In vivo exposure to HgCl2 caused reproductive impairments as shown by the inhibitory role of HgCl2 on follicular development, steroid biosynthesis and SF-1 activity. In vitro experiments revealed that aromatase activity, steroidogenesis, aromatase and SF-1 expression were blocked by HgCl2. The results obtained from this study contribute to understand the molecular mechanism of HgCl2-induced reproductive impairment of T. fasciata.

The role of some extra-gonadal hormones on the circannual ovarian cycle of the flat head grey mullet, Mugil cephalus L.

The role of extra-gonadal hormones on the induction of circadian ovarian cycle of the grey mullet Mugil cephalus L. was investigated. The findings revealed that thyroid hormones (T3 and T4) showed their peak with lowest thyroid stimulating hormone level in pre-spawning, with another peak in April during post-spawning phase. Serum cortisol, epinephrine and norepinephrine concentrations were highest in spawning phase. Insulin level was the highest followed by the lowest blood glucose level in the spawning phase. But, pineal N-acetyl serotonin (NAS) and melatonin (MEL) levels were least with the highest level of serotonin in spawning phase. The findings suggest that (a) T3 and T4 are involved probably to trigger oocyte growth and vitellogenesis. (b) Whereas, cortisol, epinephrine, norepinephrine and insulin synergistically help to induce final maturation in the spawning phase. (c) Pineal hormonal profiles (NAS and MEL) were reversely altered to those of spawning, indicating negative role of these hormones especially on oocyte growth, vitellogenesis and oocyte maturation in the mullet. Thus, all the extra-gonadal hormones, except pineal, have a role in regulation of circannual ovarian cycle in the flat head grey mullet.

A national \'safe and just operating space\' for all in India: Past, Present and Future

With 1.3 billion populaces on the commencement of the 21st century, India is currently impending towards upholding a subtle equilibrium between persisting social development and well-being without depleting existing biophysical resources at the national level or surpassing global average per capita obtainability. In this paper, we have structured a top-down per capita framework to explore national ‘safe and just operating space’ (NSJOS) to apprehend not only past fluctuations that bring about the present conditions but also the plausible future consequences, with India as a case study. Coalescing 27 indicators, all pertaining to Sustainable Development Goals (except – SDG 17), accompanied by their corresponding environmental boundaries or preferred social thresholds, present study probes into both biophysical (for environmental stress) and social development (for social deficit) attributes of India. This analysis shows India has already crossed three of seven dimensions of biophysical boundaries (freshwater, nitrogen and phosphorus use). Also, at the existing rate, India is going to cross the remainder of the boundaries within 2045-2050 (climate change, arable land use, ecological and material footprint). Of 20 indicators used for social development, only five have already or will meet corresponding desired thresholds of United Nations Sustainable Development Goals 2015. Using tendencies of past variations, the results indicate that if lowest per capita consumption can be attained and uphold, even with projected population growth, total consumption of four biophysical resources (climate change, nitrogen use, ecological and material footprint) can be slashed from today’s level in 2050. Adaptations in national policy are indispensable if India wants to accomplish sufficiency in biophysical resources whilst bestowing social equity in access and exploitation of those resources towards the continuance of social developments in forthcoming times.

A comparative study of \'safe and just operating space\' for the south and south-east Asian countries

The world is presently maintaining a delicate balance of continuing well-being and social development for the people through consumption of biophysical resources of nature without topping global average per capita availability. In this paper, we have framed a per capita top-down framework to survey national‘safe and just operating space’ (NSJOS) for the countries of south and southeast Asia to understand past variations and as a consequence, the present scenario. Amalgamating 27 indicators, all regarding Sustainable Development Goals (except – SDG 17), in consort with their respective environmental boundaries or desirable social development thresholds, this study explores into both biophysical (for ecological stress) and social development (for social deprivation) attributes of 19 countries of south and southeast Asia. This analysis shows, only 2 have remained either unchanged (political voice) or declining (social equity) among the 12 dimensions of social development in countries of this region. The remaining 10 dimensions of social development showing positive progress and will meet corresponding desired thresholds of United Nations Sustainable Development Goals 2015. All the 7 indicators showing tendencies of overconsumption of biophysical resources, that might be leading to exceeding per capita global average planetary boundaries in forthcoming future. However, ecological boundaries have remained protected to a decent degree so far for these countries. The challenge would be to maintain and increase the pace of social development and bringing it in equal strata of a global standard in future without depleting drivers of these, i.e. biophysical resources. National policy adaptations are crucial if these countries of south and southeast Asia desire to bring about adequacy in biophysical resources reserve whilst granting social equity in access and exploitation of these resources for the people towards the persistant social development in impending decades.

Analysing progress of SDG 6 in India: Past, Present, and Future

Human endeavors to meet social and economic water needs at national scale might cause negative environmental manifestations and water stress from local to global scale. So, appropriation of Sustainable Development Goals requires a comprehensive monitoring and knowledge base of the water resource availability, utilization and access. Hence, scientific research progression has a significant role to facilitate the implementation of sustainable development goals through assessment and policy implementation from global to local scales. India holds a key position among developing economies with a complex interconnected web of a fast-growing population, coupled with biophysical stress, social deprivation and economic inequality related to water and sanitation. This study addresses some of these challenges related to monitoring and implementation of the targets of the United Nations Sustainable Development Goal 6 in India. Acknowledging the contribution of society and economy in sustainability paradigm, here we have chosen 28 indicators (clustered into eleven dimensions) under two major groups, concerning biophysical and social development aspects of water and sanitation. We have shown declining level of per capita biophysical water resource and slow to rapidly developing social indicators related to Sustainable Development Goal 6 in India. From past trends, we have calculated probable scenario of biophysical consumption of India up to 2050, which shows at least 1.3 times increase. This cumulative assessment framework contributes a tool to prioritize water resource appropriation, management response and policy implementations to national level sustainability of water and sanitation in India. We also advocate the necessity of restraining threats both at source and consumption process levels in order to ensure national water security for both human and biodiversity, keeping in mind the societal and economic development scenario.

Description of a new species of genus Trachischium with a redescription of Trachischium fuscum (Serpentes: Colubridae: Natricinae)

We describe a new species, Trachischium sushantai sp. nov., from Jammu, India. The new species can be distinguished from its congeners by a combination of the following characters: -a single nasal, a singleprefrontal, a single post-ocular, 13 rows of dorsal scales at mid-body, 152 ventrals, 23 pairs of subcaudals and those on anterior half of tail as long as wide and regular hexagon or rhomboid shaped, uniformly dark brown dorsum and brown subcaudals, edged incream or yellow posteriorly. The new species closely resembles T. fuscum. We also provide a redescription of T. fuscum and comments on its subjective synonyms.

Seasonal ovarian development in relation to the gonadotropins, steroids, aromatase and steroidogenic factor 1 (SF-1) in the banded gourami, Trichogaster fasciata

The endocrine regulation of gonadal development and annual variation of key sex steroids is the basic knowledge to understand the reproductive cycle of teleost fish. Present study was aimed to investigate the levels of gonadotropins in relation to the follicular development and plasma steroids during the reproductive cycle of female Trichogaster fasciata. Female fish were sampled and ovarian development is described histologically throughout the year in relation to the seasonal variations of gonadosomatic index (GSI); follicle stimulating hormone (FSH) and luteinizing hormone (LH); three key steroids for folliculogenesis and maturation i.e. testosterone (T), 17β-estradiol (E2) and 17α20βdihydroxy4pregnen3one (17,20β-P). Relatively higher level of FSH was observed till the ovary reaches in late vitellogenic stage confirms that FSH regulates the early folliculogenesis of the ovary, whereas LH peak was observed in the postvitellogenic stage, which indicates that maturation and ovulation were controlled by LH. Seasonal steroid profiles show that both T and E2 reach its maximum level prior to the 17,20β-P which attain its peak value in the month of August. Thus, single peak values of LH and 17,20β-P coinciding with GSI peak, clearly indicates that T. fasciata breeds only once in a year. Furthermore, to elucidate the molecular basis of the reproductive cycle, this study analyzes the other key factors of ovarian function such as cyp19a1a gene expression, aromatase activity and SF-1 localization throughout the year. cyp19a1a gene expression and the aromatase activity were highest in vitellogenic stages indicate that relatively higher E2 production in this stage is regulated by FSH. Immunohistochemical localizations of aromatase and SF-1 in the cellular layer of oocytes demonstrated that aromatase is FSH-dependent and SF-1 could be regulated by both FSH and LH as relatively higher amount of aromatase was localized in the vitellogenic stage oocytes than the postvitellogenic and post germinal vesicle breakdown (post-GVBD) stages; whereas, high amount of SF-1 was observed in vitellogenic, postvitellogenic and post-GVBD stages. These data regarding the reproductive endocrinology of T. fasciata may be useful to understand the interaction between gonadotropins, steroids, aromatase and SF-1 in teleost fishes and may contribute to restoration of the ecologically important fish through artificial reproduction.