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Reproduction in teleost is controlled by brain-hypophyseal-gonadal axis as like in tetrapoda. In this system GnRH secreted from hypothalamus binds to GnRH receptors in pituitary and induces secretion of gonadotropin hormones. These hormones induce gonadal maturation and spawning in fish. The study of this system is important for developing induce breeding methodology as well as understanding the physiology of fish. Zebrafish (Danio rario) is an important model organism for research for both human and fish. It is also an interesting animal as it is having multiple isoforms of GnRH and its receptors. Sequence information, tissue distribution and signalling responses of all the four receptors (zfGnRH-R) is available and predicted some sort of sub-functionalization. The present study was designed to analyse physic-chemical properties, secondary structure, tertiary structure and membrane orientation properties of four zfGnRH-Rs using various bioinformatics tools. All four receptors showed variation in sequence length and their molecular weights. All contain Leu as most abundant amino acid. They all are positively charged, hydrophobic and basic proteins. They are composed of mainly α-helix and random coils. They all have 7 TM helices as a like other GPCRs. Random coils are dominant between these TM helices. Some of the loops present between the TM helices showed variation in the length and have tendency to form α-helix and β-sheet. C-terminal helix remains perpendicular to 7th TM helix. All the four receptors require around 31 Å thick lipidmembrane and have negative membrane transfer energy. They remain slightly tilted in the membrane. [ABSTRACT FROM AUTHOR]

Columnaris disease, caused by Flavobacterium columnare, is a common bacterial disease, affecting cultured and wild freshwater fish species around the globe. This bacterium has different virulence factors and prolyl oligopeptidase (POP) is among one of them. Currently, there are no effective vaccine for controlling the F. columnare infection. Thus, the production of appropriate vaccines against this pathogen is an important goal to avoid columnaris. Considering the role of POP antigens in virulence and satisfactory immunogenicity, they can be used as promising vaccine candidates against F. columnare. In the present study, in-silico approach was used to analyze various aspects of the POP protein, including physico-chemical characteristics, the potential epitopes of B-cell, the secondary and tertiary structure, the subcellular localization and the transmembrane domain using several bioinformatics tools to design a proper vaccine against F. columnare. The results revealed that POP protein contained 649 amino acid. The secondary structure of the POP protein comprises 20.34% alphahelix (Hh), 44.53% random coil (Cc) and 25.89% extended strand. Moreover, several potential B-cell epitopes were identified for POP.Based on the results of Ramachandran plot, 83.5% of the amino acid residues were located in the favoured, 0.6% in allowed regions. The QMEAN score obtained for our structure was -3.66, which is less than -4.0, which indicate the model has an acceptable quality. Our findings suggested that structural and functional predictions applied to POP protein using in-silico tools can reduce the failure risk of the laboratory research studies. Further studies are needed on the development of effective vaccines in vivo using POP alone or in combination with other antigenic peptide in the future. [ABSTRACT FROM AUTHOR]

In fish reproduction is largely controlled hypothalamus-pituitary-gonadal axis like other vertebrates. Reproductive behaviour of fish differs from mammal as environment plays a significant role here. GnRH secreted from hypothalamus of the brain sits at the apex of the axis and controls secretion of gonadotropins from pituitary and thus overall gonadal maturation and reproduction. Fish including Danio rerio (zebra fish) has multiple isoforms of GnRH and its receptors expressed in different areas of brain and pituitary. GnRH is used extensively for induce maturation of fishes for captive breeding. The data regarding three dimensional structure and ligand interaction is not available for fish. This type of data will not only help in understanding the physiology but also lead to designing of more potent inducing agents. In this study 3D structure of chicken GnRH(cGnRhii) and zebrafish GnRH receptor isoform 1 (zfGnRH-R1) was generated using computational modelling approach. Data-driven docking was performed to understand protein ligand interaction. zfGnRH-R1 is a G-protein coupled receptor with 7 transmembrane (7-TM) helices. Loops of variable lengths having tendency to form secondary structures were predicted between the helices towards both exoplasmic and endoplasmic side. C-terminal helix remains perpendicular to 7th TM. cGnRH-ii fits in the cavity lined by 7 TMs and interacts strongly with polar and nonpolar interactions. Predicted binding affinity (∆G) and dissociation constant [Kd (M)]were -8.0 kcal mol-11.4×10-6, respectively. [ABSTRACT FROM AUTHOR]

Background/Aims: The growth promoting effect of lysine and betaine as well as the expression of candidate genes reflecting their efficacy, such as ghrelin, leptin, Growth Hormone Secretagogue Receptor (GHS-R), Insulin like Growth Factor (IGF- 1) and Growth Hormone Releasing Hormone (GHRH) was examined in Labeo rohita fingerlings. Methods: One hundred eighty healthy juveniles from a homologous population were randomly distributed to 15 rectangular tanks of 150 litres capacity. The experiment was carried out for 60 days with five treatment groups consisting T1 (0.25% Betaine), T2 (0.5% Betaine), T3 (0.75% Lysine) and T4 (1.5% Lysine) and control group.  At the end of trial, the growth parameters such as weight gain, SGR, PER were estimated from the weight of the triplicate groups. The digestive, metabolic and antioxidant enzymes were analysed using spectrophotometric methods. The intestine, brain and liver were sampled from the treatments and expression of different genes ghrelin, leptin, GHSR, IGF-1 and GHRH was also performed by realtime PCR. Results: A significant (P<0.05) increase in weight gain, SGR, PER and lowest FCR was found in T4 group which was significantly (p < 0.05) different from other experimental groups. The highest mRNA expression levels of expression were found in T4 group which was similar to that of ghrelin gene mRNA of T2 group. The significantly (p<0.05) highest GHSR, GHRH and IGF-1 gene expression levels were found in T4 treatment group compared to other groups. Conclusion: The present study reveals that the lysine and betaine stimulate growth and expression of ghrelin GHRH, GHS-R and IGF-1 genes. The increase of IGF-I mRNA expression with lysine and betaine supplementation revealed that these compounds act as growth modulators. However, lysine was found to be a more potent modulator of growth compared to betaine. [ABSTRACT FROM AUTHOR]

Biofloc technology degrades waste into useful resources exploiting microbes and can be used in zero‐water exchange systems. To study the effect of different biofloc systems on haematological and metabolic response of Labeo rohita fingerlings, a 60‐days experiment was conducted using four long lasting carbon sources. Seven hundred and fifty fingerlings having mean weight of 4.80 ± 0.12 g were randomly distributed into 15 tanks (n = 50 per tank). Five experimental groups were set in triplicate; T1 (Tapioca), T2 (Wheat), T3 (Corn) T4 (Sugar bagasse) and control (clear water). In‐situ biofloc was developed in 300 L fibre‐reinforced plastic (FRP) tanks and a C/N ratio of 15 was maintained. Water quality variables indicated ammonia immobilization by heterotrophic bacteria, as the dominant mechanism for the removal of toxic‐nitrogenous compounds in the biofloc systems. Results exhibited significantly higher floc volume (53.33 ± 7.88 ml/L), haemoglobin content (6.61 ± 0.03 g/dl) and total leucocyte count (109.66 ± 0.06 thousand cells/mm3) in tapioca biofloc system. Furthermore, the digestive and anti‐oxidative enzymes activities were also significantly higher in tapioca biofloc system. The lactate dehydrogenase and malate dehydrogenase enzyme assays showed a decreased level in tapioca biofloc system as compared with other biofloc systems and control group. Our observations indicate that tapioca biofloc system could improve the water quality, haematological and anti‐stress responses of L. rohita fingerlings in biofloc systems and thus can effectively replace other carbohydrate sources for the biofloc system. [ABSTRACT FROM AUTHOR]

Immune competence and prevalence of disease are highly influenced by seasonal differences in humans and other vertebrates including fishes. Keeping this in mind this study was conducted to evaluate the seasonal influences in the normal immune response in rohu (Labeo rohita Ham.).The innate immunity parameters were assessed by measuring the plasma lysozyme activity and respiratory burst of head kidney macrophages in each month, in a 12-month trial period (July 2019 to June 2020) along with measuring serum albumin and globulin ratio in rohu. It was observed that lysozyme activity was highest in summer and lowest in winter and could be considered as seasonal. The respiratory burst activity of head kidney macrophages and serum albumin and globulin ratio was less influenced by seasonal variation. [ABSTRACT FROM AUTHOR]