Histological and immunocytochemical localization of serotonin-like immunoreactivity in the brain and optic ganglia of the Indian white shrimp, Fenneropenaeus indicus.

Serotonin is one of the important neurotransmitter and neuromodulator so far studied in crustacean models. With its secretory sites well-studied in higher crustaceans, its function in controlling the release of metabolic hormones from their storage and release sites has been well proved. The present study attempts to localize serotonin-like immunoreactivity in Fenneropenaeus indicus, a commercially important shrimp species and a natural inhabitant of the Indian oceans. Histological studies were employed to visualize the different types of neurosecretory cells and their regions of occurrence in brain and optic ganglia on the basis of their size, shape, and tinctorial properties. Immunocytochemical studies were performed in the brain and optic ganglia with specific antisera against serotonin in combination with peroxidase anti-peroxidase to map the serotonin-like immunoreactive cells. Variations in the immunoreactivity were observed on comparing the cells of brain and optic ganglia. Medulla terminalis region had intense serotonin immunoreactivity suggesting it to be the primary source of the neurotransmitter.

Ultrastructure of cyst shell and underlying membranes of three strains of the brine shrimp Artemia (Branchiopoda: Anostraca) from South India.

The cyst of Artemia has shell and membranous coverings over the embryo. The membranous coverings have special adaptive features to allow the physical changes accompanying repeated hydration and dehydration cycles that might occur and adversely influence postembryonic development. Whole and slices of cryptobiotic cysts were processed for electron microscopy to study the internal details and to compare the morphological architecture of three Artemia strains of South India. Surface topography of scanning electron microscopic (SEM) studies revealed distinct button shaped structures on the cyst of Puthalam strain. Transmission electron microscopic (TEM) studies of the cysts displayed the conventional pattern of anostracan crustaceans with outer cortex and alveolar layer, cuticular membranes, and the cytoplasmic inclusions namely nucleus, yolk droplets, lipoid bodies, and mitochondria. The prominent wavy outer cortex layer of Puthalam cysts corroborates the results of SEM studies.

Carotenoprotein complexes in entomostracan crustaceans (Streptocephalus dichotomus and Moina micrura).

The carotenoprotein complexes of a freshwater fairy shrimp (Streptocephalus dichotomus) and a daphnid (Moina micrura) were characterised and compared. Based on thin layer chromatography and mass spectral analysis, a variety of cartenoprotein complexes such as astaxanthin, canthaxanthin, antheraxanthin, lutein, beta-cryptoxanthin and violaxanthin were found. Both crustaceans had astaxanthin and canthaxanthin as predominant prosthetic groups. Amino acid analysis of the complexes further revealed high levels of asparagine, glutamine and glycine in both species. Our study highlights the presence of naturally available carotenoid species in both crustaceans and their possible inter-conversion in anostracans.

In vitro effect of some anthelmintics on lactate dehydrogenase activity of Cotylophoron cotylophorum (Digenea: paramphistomidae).

Effects of praziquantel (PZQ), levamisole (LEV), mebendazole (MBZ), fenbendazole (FBZ) and albendazole (ABZ) on the lactate dehydrogenase (LDH) activity of Cotylophoron cotylophorum were studied in vitro. Maximum levels of inhibition of LDH catalysing both oxidation and reduction reactions were observed in PZQ- and LEV-treated worms. Similarly, benzimidazoles - MBZ, FBZ and ABZ - have also significantly inhibited the activity of LDH catalysing the oxidation of lactate; whereas the activity of LDH catalysing the reduction of pyruvate was accelerated. This affects the mitochondrial energy generating process which ultimately proves fatal to the parasite. Therefore, the mode of action of benzimidazoles is primarily on the activation of LDH catalysing the conversion of pyruvate to lactate.

In vitro studies on the effects of some anthelmintics on Cotylophoron cotylophorum (Digenea, Paramphistomidae): a structural analysis.

The effects of the anthelmintics praziquantel (PZQ), levamisole (LEV), mebendazole (MBZ), fenbendazole (FBZ) and albendazole (ABZ), on the morphology and the histology of a digenetic trematode, Cotylophoron cotylophorum, were studied. Scanning electron micrographs of the drug-treated worms revealed that PZQ was the most effective drug inducing surface damages to a great extent. The parasite exposed to PZQ for 6 h, showed smaller blebs on the oral sucker region as well as on the sensory papillae. These blebs enlarged in size after 24 h and ruptured after 30 h of exposure. The worms treated with LEV showed a few smaller blebs on the ventrolateral margin. In MBZ- and FBZ-treated worms the blebs appeared between the oral and genital sucker after 6 h of incubation. The changes were not apparent in the ABZ-treated worms.

Identification and partial purification of phosphatidylcholine phospholipase C from the cryptobiotic cysts of the fairy shrimp, Streptocephalus dichotomus.

The occurrence of phosphatidyl choline specific phospholipase C (PC-PLC)(EC 3.1.4.3) which liberates diacylglycerol (DAG), an important second messenger molecule, has been reported for the first time from the cryptobiotic cysts of the fairy shrimp, Streptocephalus dichotomus. Since the cysts undergo a revival of metabolism and resumption of development upon hydration, the possible role of the enzyme, in these processes was investigated. The results revealed enzyme's presence and an increase in its activity with the advancement of cyst development. Further partial purification of the enzyme using a lipoprotein linked- Sepharose CL-4B column (an affinity chromatographic principle) was attempted. The purification of 19.3 fold with a yield of 80% was attained.

Variations in the activity of some metabolic enzymes during development of Artemia parthenogenetica (Crustacea: Anostraca).

Metabolic activity of the cysts as well as other developmental stages of Artemia parthenogenetica was determined by studying various key metabolic enzymes such as lactate dehydrogenase (LDH) and malate dehydrogenase (MDH). The electrophoretic studies on LDH show the existence of a single fraction uniformly in all the developmental stages of A. parthenogenetica. Electrophoretic patterns of MDH during the same stages show variations in isozymic fractions as development proceeds towards adults. Enzyme assay during lactate oxidation and pyruvate reduction of LDH as well as malate oxidation and oxaloacetate reduction of MDH in different developmental stages reveals that the anaerobic metabolism is more prevalent than the aerobic type. Further quantification of these enzymes shows that their activities are low and stable in the encysted gastrulae, and increase rapidly when the embryo emerges. One of the kinetic properties such as pH has impact on the general behavior of the enzymes throughout the developmental stages.