Effects of chlorpyrifos toxicity on brain, pseudobranchial neurosecretory system and swimming performance of a catfish, Heteropneustes fossilis.

In the present study, it was aimed to evaluate the adverse effects of CPF on the histopathology of the optic tectum and cerebellum, pseudobranchial neurosecretory system (PNS), biochemical assays of brain tissue, and locomotory behavior in catfish, Heteropneustes fossilis. The fishes were exposed to an environmentally relevant concentration of 0.09 and 0.192 mg/L of CPF for 7, 15, and 30 d. The CPF toxicity induced degenerative changes with significantly decreased cell size, number, and nucleo-cytoplasmic (N/C) ratio of the PNS; and altered neuro-architectural pattern of optic tectum with degenerative changes in mononuclear and granular cells and necrotic variation in granular and Purkinje cells of the cerebellum. The Acetylcholinesterase (AChE) and Catalase (CAT) activity in the CPF-exposed brain was significantly decreased, whereas Superoxide dismutase (SOD) and Malondialdehyde (MDA) level was significantly increased in comparison with control. In CPF-exposed fishes, the respiratory movements and locomotory behavioral pattern like swimming speed, total distance traveled, time mobile, absolute turn angle, head: distance traveled, maximum speed were significantly decreased, whereas time immobile and time freezing episodes were significantly increased as compared to control fishes. The present study concludes that environmentally relevant concentration of CPF may induce histopathological, biochemical, physiological, and behavioral disturbances in a non-target organism, H. fossilis.

Acute toxic effects of chlorpyrifos on pseudobranchial neurosecretory system, brain regions and locomotory behavior of an air-breathing catfish, Heteropneustes fossilis (Bloch 1794).

In the late twentieth century, tremendous use of second-class organophosphate insecticides especially chlorpyrifos (CPF) resulting into heavy accumulation in different non-targeted aquatic species including fishes leads to apparent structural and biochemical changes in different organs and related abnormal behavioral responses. The present study has been undertaken as a pioneer attempt to assess the toxic effects of CPF on histopathological changes in pseudobranchial neurosecretory cells (PNSCs) of a neuroendocrine system of gill region, optic tectum (OT) and cerebellum, biochemical changes (acetylcholinesterase (AChE) activity and antioxidant markers) in the brain and associated locomotory behavioral alterations in air-breathing catfish, Heteropneustes fossilis. The fishes were exposed to CPF concentration of 1.92 mg/l for four days and their locomotor activities were recorded by ANY-MAZE software (Stoelting, Kiel, WI), an automated behavior tracking device. The acute exposure of CPF induced pathological changes in PNSCs, subtle changes in granular cells of the cerebellum and neuroarchitectural pattern of different layers of OT as compared to control. In the CPF exposed brain, AChE activity was significantly decreased while antioxidant enzymatic activity such as SOD activity was increased but CAT activity was substantially decreased. The CPF exposed fishes displayed significantly reduced locomotory activities with symptoms of motionless, loss of equilibrium and erratic movements. This study concludes that acute exposure to CPF for short duration may induce dys-regulation of neurosecretory activity of PNSCs, altered biochemical activity of brain and reduced locomotory/swimming performances in fishes.

Paraneuronal pseudobranchial neurosecretory system in tank goby Glossogobius giuris with special reference to novel neurohaemal contact complex.

Various putative oxygen chemosensory cells are reported to be present throughout the vertebrate body performing pivotal roles in respiration by initiating responses during acute hypoxia. Since air-breathing fishes often are exposed to the oxygen-deficient milieu, in such conditions various chemosensory cells operate in an orchestrated fashion. The Pseudobranchial neurosecretory system (PSNS) a newly discovered system, is one of these. It has been placed in the category of "Diffuse NE systems (DNES)". It is found in all the catfish species and in some other non-catfish group of teleosts. In catfishes, it is present in close association with the carotid labyrinth- a chemosensory structure, known in fish and amphibians. The presence of this system in Glossogobius giuris, in association with the pseudobranch, a structure considered to be precursor of carotid labyrinth, is a significant finding. In an attempt to study the structure and organization of the pseudobranchial neurosecretory system in a non-catfish species of teleost, the present investigation was undertaken on a goby G. giuris. The histological observations, using a neurosecretion-specific stain, revealed the presence of this system in G. giuris. The findings are discussed in the light of the association of PSNS with pseudobranch and the type of "neurohaemal contact complex" formed between this neurosecretory system and the elements of the circulatory system.

Expression of Acetylcholine- and G protein coupled Muscarinic receptor in the Neuroepithelial cells (NECs) of the obligated air-breathing fish, Arapaima gigas (Arapaimatidae: Teleostei).

The air-breathing specialization has evolved idependently in vertebrates, as many different organs can perfom gas exchange. The largest obligate air-breathing fish from South America Arapaima gigas breathe air using its gas bladder, and its dependence on air breathing increases during its growth. During its development, gill morphology shows a dramatic change, remodeling with a gradual reduction of gill lamellae during the transition from water breathing to air breathing . It has been suggested that in this species the gills remain the main site of O2 and CO2 sensing. Consistent with this, we demonstrate for the first time the occurrence of the neuroepithelial cells (NECs) in the glottis, and in the gill filament epithelia and their distal halves. These cells contain a broader spectrum of neurotransmitters (5-HT, acetylcholine, nNOS), G-protein subunits and the muscarininic receptors that are coupled to G proteins (G-protein coupled receptors). We report also for the first time the presence of G alpha proteins coupled with muscarinic receptors on the NECs, that are thought as receptors that initiate the cardiorespiratory reflexes in aquatic vertebrates. Based on the specific orientation in the epithelia and their closest vicinity to efferent vasculatures, the gill and glottal NECs of A. gigas could be regarded as potential O2 and CO2 sensing receptors. However, future studies are needed to ascertain the neurophysiological characterization of these cells.

The paraneuronal gill neuroendocrine system in ocellated puffer fish Leiodon cutcutia.

Pseudobranchial neurosecretory system (PSNS) is the third Neuroendocrine (NE) system found in the gill region of fishes in close association with pseudobranch/carotid labyrinth/carotid gland and can suitably be placed under the category of "Diffused NE system (DNES)." The cells belonging to this system fall under the category of "Paraneurons," a concept proposed by Fujita and coworkers. It is found uniformly in all the catfish species and some other noncatfish group of teleosts as Atheriniformes, Channiformes, Perciformes, and Clupeiformes. The fishes, in which the PSNS is present, belong to different breathing habits. Most of these have the capacity to tolerate low O2 conditions. Leiodon cutcutia although not an air-breathing fish, is known to retain air in its stomach for varied periods when threatened. In an attempt to verify the veracity of this system in a fish of another peculiar breathing habit, ocellated puffer fish L. cutcutia (order Tetradontiformes) was investigated. The histological observations undertaken on L. cutcutia revealed the presence of a well-developed extrabranchial NE system. The findings are discussed in the light of the association of PSNS with chemosensory system and its evolution in fishes, especially in the view of the transition from aquatic to terrestrial life.

Localization of neurotransmitters, peptides and nNOS in the pseudobranchial neurosecretory cell system and associated carotid labyrinth of the catfish, Clarias batrachus.

The carotid labyrinth is an enigmatic endocrine structure of unknown chemosensory function lying in the gill region of the catfishes. The carotid body is found at the carotid bifurcation of amphibians and all mammalian vertebrates on the evolutionary tree. It is a vascular expansion comprised of a cluster of glomus cells with associated (afferent and efferent) innervations. In the catfish species studied (Clarias batrachus) a neurosecretory cell system consisting of pseudobranchial neurosecretory cells connect the carotid labyrinth or large vessels (both the efferent branchial artery and dorsal aorta), and is likely akin to the glomus cells, but comparing these structures in widely divergent vertebrate species, the conclusion is that the structural components are more elaborate than those of terrestrial vertebrates. However, these cells reveal both an endocrine phenotype (such as the association with capillaries and large vessels) and the presence of regulatory substances such as neurotransmitters and neuropeptides producing good evidence for high levels of conservation of these substances that are present in the glomus cells of mammalian vertebrates. VIP-immunopositive neuronal cell bodies are detected in the periphery of the carotid labyrinth. They are presumptive local neurons that differ from pseudobranchial neurosecretory cells, the latter failing to express VIP in their soma.

Acetylcholinesterase: a potential biochemical indicator for biomonitoring of fertilizer industry effluent toxicity in freshwater teleost, Channa striatus.

Monitoring of acetylcholinesterase (EC: 3.1.1.7, AChE) activity has been widely used in aquatic and terrestrial systems as an indicator of pollutant exposure. The reports regarding impact of fertilizer industry effluent on the level of AChE activity are very scanty. In this paper, an attempt has been made to investigate the in vitro impact of fertilizer industry effluent upon the levels of AChE activity and protein content in different tissues of non-target aquatic fish, Channa striatus (Bloch). The fish when exposed to three sublethal concentrations (3.5, 4.7, and 7.0%; v/v) of fertilizer industry effluent for short (96 h) and long (15 days) durations registered sharp reduction in the levels of AChE activity (15-75%) and protein (10-71%) in different fish organs. The highest effluent concentration treatment for short or long duration, the fish brain and gills registered significant (P < 0.001) inhibition (64-75%) in the activity of AChE whereas other organs such as muscles, liver, and heart exhibited slightly lower inhibition (40-59%) in enzyme activity. However, kidney of C. striatus was the only organ where very less effect (14-18%) of the effluent was observed on the activity of AChE when the fish were exposed to all the three concentrations of the effluent for both treatment durations. This effluent also induced alterations in the level of protein in different fish organs; in kidney the effect was pronounced only at higher concentrations at both treatment durations. The most affected organs were muscle and gills where in 60-71% reduction in the protein content was recorded due to highest effluent concentration treatment at short or long durations. The results of present study indicated that the fertilizer industry effluents might significantly influence the neurotransmission system and protein turnover in the non-target organisms after exposure even at very low concentrations. Further, the data suggested that the fish AChE could be used as a potential biochemical marker for fertilizer industry effluent pollution in aquatic systems.

Fertilizer industry effluent induced biochemical changes in fresh water teleost, Channa striatus (Bloch).

The industrial activities pose threat to the life of aquatic organisms in many ways. This research communication presents an account of the impact of fertilizer industry effluent upon the levels of protein and the activity of lactate dehydrogenase (EC 1.1.1.28, LDH), a terminal key enzyme in glycolytic pathway, in different organs of a fresh water teleost fish, Channa striatus (Bloch). The fish exposed to different sublethal concentrations of fertilizer industry effluent (3.5, 4.7 and 7.0% v/v) equivalent to 1/20th, 1/15th and 1/10th of LC(50) value (70% v/v) for varying treatment periods (96 h and 15 days) exhibited decrease in the level of protein (8-76%) in different organs of the effluent treated fish. At highest effluent concentration (7% v/v) treatment for short (96 h) or long (15 days) duration, the liver of the fish registered significant (p < 0.001) decrease (62-76%) in protein content as compared to control, whereas other organs of the fish showed only 38-52% decrease in the level of protein. The industrial effluent also caused marked reduction in the activity of LDH in different fish tissues when compared to the control. The treatment of fish with 7% effluent concentration for 96 h caused 78% decrease (p < 0.001) in the LDH activity in fish muscle whereas after 15 days the effect was maximum in fish brain as it exhibited 86% decrease (p < 0.001) in LDH activity as compared to control. The effect of effluent on the activity of LDH and protein content in different body tissues of the fish was dependent on concentration and duration of exposure. The significant reductions in the activity of LDH and level of protein in fish tissues due to treatment with the fertilizer industry effluent indicated the possibility of impairments in energy metabolism and protein turnover, respectively, in C. striatus.