Diverse populations of intrinsic cholinergic interneurons in the mouse olfactory bulb.

Cholinergic activities affect olfactory bulb (OB) information processing and associated learning and memory. However, the presence of intrinsic cholinergic interneurons in the OB remains controversial. As a result, morphological and functional properties of these cells are largely undetermined. We characterized cholinergic interneurons using transgenic mice that selectively mark choline acetyltransferase (ChAT)-expressing cells and immunolabeling. We found a significant number of intrinsic cholinergic interneurons in the OB. These interneurons reside primarily in the glomerular layer (GL) and external plexiform layer (EPL) and exhibit diverse distribution patterns of nerve processes, indicating functional heterogeneity. Further, we found these neurons express ChAT and vesicular acetylcholine transporter (VAChT), but do not immunoreact to glutamatergic, GABAergic or dopaminergic markers and are distinct from calretinin-expressing interneurons. Interestingly, the cholinergic population partially overlaps with the calbindin D28K-expressing interneuron population, revealing the neurotransmitter identity of this sub-population. Additionally, we quantitatively determined the density of VAChT labeled cholinergic nerve fibers in various layers of the OB, as well as the intensity of VAChT immunoreactivity within the GL, suggesting primary sites of cholinergic actions. Taken together, our results provide clear evidence showing the presence of a significant number of cholinergic interneurons and that these morphologically and distributionally diverse interneurons make up complex local cholinergic networks in the OB. Thus, our results suggest that olfactory information processing is modulated by dual cholinergic systems of local interneuron networks and centrifugal projections.

Tetrapod-like hypothalamo-hypophysial portal system in the teleost Megalops cyprinoides (Broussonet).

A tetrapod-like hypothalamo-hypophysial portal system and a persistent bucco-hypophysial canal are present in Megalops cyprinoides. The complicated loops of the primary capillary plexus are seen on the ventral side of the infundibular floor and contact the perikarya of the nucleus lateralis tuberis and the preoptico-hypothalamo-neurohypophysial-neurosecretory tract. Although the pars intermedia receives part of its vascular supply from the pars distalis, the caudal hypophysial artery directly vascularizes the neurointermedia interface and forms the plexus intermedialis. The bucco-hypophysial canal is short and narrow in the fry and fingerlings but becomes long and tortuous as the fish grows. Megapopidae seem to be closer to the polypteriformids than to the teleosts. The possession of the pituitary portal system in megalopids may be a connecting link between the polypteriformids and other advanced teleosts.

Cythion-induced histophysiological changes in thyroid and thyrotrophs of the teleost fish, Channa punctatus (Bloch).

The chronic effects of continuous exposure for 6 months, from January to June, to safe (2.0 ppm) and sublethal (4.0 ppm) concentrations of a commonly used organophosphorus pesticide, cythion, on the histophysiology of the thyroid and thyrotrophs in Channa punctatus are described in this investigation. The pharyngeal thyroid of fish of both treated groups exhibited hypertrophy and hyperplasia of the follicular epithelium and reduction of colloid content. Apart from this, in the fish exposed to 4.0 ppm, some of the follicles were exhausted and transformed into degenerated cystic masses. The presence of free blood cells at these sites suggests rupture of blood vessels and possible phagocytosis. These histopathological changes could be correlated with a significant and dose-dependent reduction of thyroidal radioiodine uptake and conversion ratio (serum protein-bound iodine:total serum iodine) values. After cythion exposure, the thyrotrophs in the pituitary were activated. These results suggest that the thyroid dysfunction caused by cythion may be responsible for the stimulation of the thyrotrophs which in turn stimulated the thyroid follicles through the pituitary-thyroid axis in this species.

Cadmium chloride-induced changes in hypothalamic 5-hydroxytryptamine, noradrenaline and dopamine levels in the Indian palm squirrel, Funambulus pennanti (Wroughton).

A single intraperitoneal injection of cadmium chloride (CdCl2, 0.32 mg/kg body weight) was administered to 15 adult female palm squirrels (Funambulus pennanti (Wroughton] and the hypothalamic 5-hydroxytryptamine (5-HT), noradrenaline (NA) and dopamine (DA) levels were quantified on the 1st, 7th and 40th day. 5-HT levels significantly decreased on the 1st and 40th day but showed an increase on the 7th day. Similarly, NA levels significantly decreased after 1, 7 and 40 days of treatment, and DA levels decreased on the 1st and 7th day but insignificantly increased on the 40th day. This suggests that CdCl2 interferes in the functioning of the hypothalamo-hypophyseal axis by impairing the hypothalamic 5-HT, NA and DA levels, which may in turn affect the physiology of the peripheral endocrine glands.

Histopathological changes in liver and thyroid of the teleost fish, Channa punctatus (Bloch), in response to ammonium sulfate fertilizer treatment.

In Channa punctatus exposed to safe (100 ppm) and sublethal (500 ppm) concentrations of the commonly used fertilizer ammonium sulfate for 6 months, from January to June, hepatocytes revealed initial hypertrophy followed by exhaustion as evidenced by degranulation, nuclear pyknosis, and focal necrosis. Thyroid follicles exhibited various degrees of hypertrophy, hyperplasia, hyperemia, and reduction in colloid content. Both in the liver and in the thyroid, changes were more pronounced in the 500-ppm-treated fish. These results suggest that this fertilizer, which is washed into the water system in small quantities, may cause dose-dependent dysfunction of liver and thyroid.

Lead nitrate induced changes in the thyroid physiology of the catfish Clarias batrachus (L).

Chronic exposure of Clarias batrachus to sublethal dose of 5 ppm lead nitrate for a period of 150 days impaired thyroid function. Histological observations revealed hypertrophy, increased cell height, vacuolation, and reduction of colloid. The thyrotrophs of the pituitary also exhibited hypertrophy. But radioiodine (131I) uptake was significantly lowered. Fish exposed to 5, 10, and 25 ppm of lead nitrate for 7 days also exhibited significant reduction in 131I uptake which was dose dependent. These findings suggest that lead nitrate impairs thyroid function involving the hypothalamohypophysiothyroid axis.

Histopathological and biochemical changes in the liver of a teleost fish, Channa punctatus (Bloch) induced by a mercurial fungicide.

The chronic toxic effects of a prolonged exposure of 6 months, from January to June, to a 'safe dose' (0.20 mg litre(-1)) of a commercial organomercurial fungicide, Emisan (methoxy ethyl mercuric chloride: MeEHgCl), on the histophysiology of liver in adults and young (yearlings) of Channa punctatus, are described in this investigation. In both of the experimental groups, liver histology exhibited various abnormalities, including hyperplasia, nuclear pyknosis, fatty necrosis, and degeneration of hepatocytes leading to tumour and syncytium formation, which are indicative of carcinogenesis. Apart from this, blood vessel congestion and oedema were also observed in young treated fish. In the livers of both exposed groups, corresponding with this cellular damage, a marked reduction in hepatosomatic index, levels of total protein and lipid, and an elevation in cholesterol and acid and alkaline phosphatase contents were recorded. However, these alterations were more pronounced in young than in adult fish. These Emisan-induced, histopathological and biochemical changes are suggestive of severe hepatic dysfunction, which may result in the impairment of the physio-metabolic process, in this species.

Effects of long-term exposure to cythion on the reproduction of the teleost fish, Channa punctatus (Bloch).

The chronic toxic effects of an organophosphorus pesticide on some aspects of the physiology of reproduction in a teleost fish, Channa punctatus, are described in this investigation. Fish exposed to 2.0 mg litre(-1) of commercial cythion continuously for 6 months, from January (resting phase) to June (spawning phase), exhibited a significant inhibition of gonadal development and gonadosomatic index. These changes were correlated with less active, and a reduced number of, pituitary gonadotrophs, and biochemical changes in the gonads and liver. The immature oocytes of the experimental fish exhibited cytoplasmic proteinaceous 'inclusion bodies', which ultimately led to their degeneration. The results suggest that cythion may act directly on the gonads and/or through the pituitary-gonadal axis, in this species.

Effect of antiandrogens on the hypothalamic gamma-aminobutyric acid (GABA) and glutamate contents of the Indian palm squirrel (Funambulus pennanti, Wroughton).

Intramuscular administration of 20 mg/kg flutamide (Flut) or 50 mg/kg of cyproterone acetate (CPA) daily for a period of three weeks significantly elevated the hypothalamic GABA content. CPA is found to decrease the hypothalamic glutamate level while Flut elevated it. Both, Flut and CPA reduced the hypothalamic weight.

Inclusion bodies: formation and degeneration of the oocytes in the fish Channa punctatus (Bloch) in response to ammonium sulfate treatment.

In the adult Channa punctatus exposed to 500 ppm of the commonly used fertilizer ammonium sulfate for 6 months from January to June, ovarian growth was retarded significantly. The inhibition of the ovarian growth is reflected on the gonadosomatic index which was significantly reduced as compared with control. Apart from this, in treated fish, several stage-I oocytes exhibited proteinaceous extra- and intranuclear "inclusion bodies" which are apparently due to cumulative toxic effect of ammonium sulfate. These oocytes ultimately degenerate.

Effect of a mercurial fungicide on the gonadal development of the teleostean fish Channa punctatus (Bloch).

Channa punctatus exposed to a "safe" concentration of 0.20 ppm of a commercial mercurial fungicide, Emisan (MeEHgCl), for 6 months, from January to June, exhibited significant inhibition of gonadal development as evidenced by their histology and reduced gonadosomatic index. Degenerative changes were also evident. Correlative histological changes were also noted in the pituitary gonadotrophs which were reduced in the exposed fish. Several stage I oocytes exhibited proteinaceous extra and intranuclear "inclusion bodies," and intranuclear "ring-like bodies" associated with the ultimate degeneration of the oocytes. These observations suggest that MeEHgCl inhibits gonadal development through the hypothalamic-pituitary-gonadal axis in this species.

Lead nitrate induced changes in the brain constituents of the freshwater fish Clarias batrachus (L).

Exposure of C batrachus to 5 ppm lead nitrate for 150 days resulted in the significant elevation of brain histamine and serotonin content, but Gamma aminobutyric acid level showed a decrease. Lead significantly reduced the brain monoamine oxidase and acetylcholinesterase activity. In addition, lead significantly lowered the brain lipid, cholesterol, protein and ascorbic acid contents. These findings suggest that lead significantly impairs the brain neurotransmitter function.

The pineal gland of the Indian palm squirrel, Funambulus pennanti (Wroughton).

In the adult palm squirrel, F. pennanti the pineal is a club shaped, elongated structure with a connective tissue capsule. It consists of various types of pinealocytes, glial cells, neurons, nerve fibres, blood vessels and connective tissue. Two types of pinealocytes could be identified by light microscopy. They are large rounded with centrally placed nucleus, and small rounded pinealocytes. They have medium sized processes stainable with Alcian blue, periodic acid Schiff and Nissl methods. The pinealocytes are not stainable with bromophenol blue. However, they are moderately stainable with PAS, Sudan black and Baker's acid hematin. Neurons are seen either singly or in groups with axonal processes. Cystic cavities often lined by cells are a normal feature of adult squirrel pineal, and the lining cells are both pinealocytes and glial cells. Often neuronal endings are seen terminating on these lining cells. PAS positive globules were also seen inside the cysts. In some squirrel pineals, fibrous cysts with an inner core of cells are also seen. Occasionally groups of lymphocytes were also encountered in the pineal. In the fetal pineal, the cells are both larger and smaller ones and arranged in a cortex and medulla pattern and no cystic cavities are seen. The third ventricle enters the base of the pineal as pineal recess.