Ureogenesis in a freshwater teleost: an unusual sub-cellular localization of ornithine-urea cycle enzymes in the freshwater air-breathing teleost Heteropneustes fossilis.

Sub-cellular localization of different ornithine-urea cycle enzymes was studied in the liver and kidney of a freshwater air-breathing teleost. Carbamyl phosphate synthetase, ornithine transcarbamylase, and arginase were found to be localized inside the mitochondria, and argininosuccinate synthetase and argininosuccinate lyase were found in the soluble fraction. Mitochondrial localization of arginase, a feature known in marine elasmobranchs and toadfishes, indicates the evolutionary position of H. fossilis to be different from that of present day freshwater teleosts.     

Food intake,conversion and swimming activity in the air-breathing catfish Heteropneustes fossilis

Summary Reared in tubular aquaria containing 20, 40 and 60 cm depth 0f water, Heteropneustes fossilis (20 g; 17 cm body length), an air-breathing catfish, swam 40, 80 and 120 cm/surfacing to exchange atmospheric air. With decreasing Po₂, the starving groups reduced the surfacing, whereas, the decrease in the Po₂ beyond 70 mm Hg induced the feeding groups to surface more frequently. Feeding groups exposed to 20 and 40 cm depth surfaced 353 and 423 times, travelling distances of 141 and 338 m/day, at the energy cost of 8.5 and 9.7 mg dry fish substance/g live fish/day, respectively. The corresponding starving groups surfaced only 163 times/ day and swam 65 and 130 m/day at the expense of 1.2 and 1.6 mg/g/day. Feeding and starving groups reduced the number of surfacing, when the distance they have to swim exceeded 0.8 m/day and increased the proportion of O₂ taken up branchially; the starving and feeding groups exposed to 60 cm depth surfaced only 70 and 271 times, swimming 84 and 325 m/day, at the energy cost of 2.9 and 17.6 mg/g/day. Feeding and conversion rates steadily increased from 16.9 mg dry liver/g live fish/day and 6.7 mg dry fish substance/g live fish/day in those exposed to the shallowest aquarium to 27.4 mg/g/day and 7.0 mg/g/day in those exposed t0 the maximum depth, respectively; conversion efficiency was 44% in the former and 28% in the latter; hence culturing H. fossilis in the shallow waters is profitable.     

Purification and immunological characterization of catfish (Heteropneustes fossilis) metallothionein

Catfish hepatic metallothionein was purified to homogeneity by Sephadex G-75 gel filtration, DEAE-Sephadex A-25 column chromatography and preparative polyacrylamide gel electrophoresis. Induction by cadmium and zinc, characteristic UV spectrum, cadmium binding property and its low MW established that it was a metallothionein. Antibody was raised in rabbit against catfish metallothionein. Catfish antimetallothionein cross-reacted with other fish metallothioneins but not with chicken or rodent metallothionein. Catfish metallothionein is more electronegative as compared to mouse, rat, chicken or hamster metallothionein. Catfish MT appeared to aggregate readily on storage and to be less electronegative.     

Purification and immunological characterization of catfish (Heteropneustes fossilis) metallothionein

Summary Catfish hepatic metallothionein was purified to homogeneity by Sephadex G-75 gel filtration, DEAF-Sephadex A-25 column chromatography and preparative polyacrylamide gel electrophoresis. Induction by cadmium and zinc, characteristic UV spectrum, cadmium binding property and its low MW established that it was a metallothionein. Antibody was raised in rabbit against catfish metallothionein. Catfish antimetallothionein cross-reacted with other fish metallothioneins but not with chicken or rodent metallothionein. Catfish metallothionein is more electronegative as compared to mouse, rat, chicken or hamster metallothionein. Catfish MT appeared to aggregate readily on storage and to be less electronegative.Abbreviations MT Metallothionein - PBS Phosphate Buffered Saline - SDS Sodium Dodecyl Sulfat - PAGE Polyacrylamide Gel Electrophoresis Part of the work was reported in Proceedings of 54th Annual General Meeting of the Society of Biological Chemists, India, 1985.     

Sublethal malathion induced changes in the ovary of an air-breathing fish,Heteropneustes fossilis: a histological study

This paper describes effects of a sublethal (1.2 mg 1^–1) organophosphate, malathion, on the ovary of an air breathing catfish, Heteropneustes fossilis. The study focuses on microscopic changes that occur on ovigerous lamellae, oocytes at different stages of development and the nucleus of the immature oocyte. Also, change in estrogen levels in blood serum is investigated. Clumping of cytoplasm appears after 24 h of exposure to malathion. Clumping intensified after 48 h. Degeneration in the follicular cells was also observed. After 72 h exposure the number of nucleoli increased, nuclear materials shrunk, oocytes became adhered. With 96 h of exposure, nuclear materials of all the oocytes shrunk to a smaller clump. The oocytes fused together, and follicular epithelium became loose and ruptured. A few atretic oocytes were visible. Radioimmunoassay of the estrogen level in blood serum after 72 h of exposure of malathion showed a reduction in the level. This study showed that the histopathological condition of the gonad is reflected in malfunctioning of the endocrine system and hormonal disbalance.     

Surface ultrastructure of the olfactory rosette of an air-breathing catfish,Heteropneustes fossilis (Bloch)

The surface architecture of the olfactory rosette ofHeteropneustes fossilis (Bloch) has been studied by scanning electron microscopy. The olfactory rosette is an oval structure composed of a number of lamellae arranged pinnately on a median raphe. The raphe is invested with epithelial cells and pits which represent goblet cell openings. On the basis of cellular characteristics and their distribution the lateral surface of each olfactory lamella is identified as sensory, ciliated non-sensory and non-ciliated non-sensory epithelium. The sensory epithelium is provided with receptor and supporting cells. The ciliated non-sensory epithelium is covered with dense cilia obscuring the presence of other cell types. The non-ciliated non-sensory epithelium is with many polygonal areas containing cells.     

Seasonal variation of ammonia-quotient in an Indian air-breathing freshwater teleost, Channa punctatus

The ammonia-quotient, calculated from the data on the levels of ammonia excreted and oxygen consumed from the water, is a potent tool for understanding the utilization of macromolecules as metabolic fuel. The fish, Channa punctatus, utilizes more protein in the summer and spawning months for getting its metabolic energy but in the winter and post-spawning months it also utilizes other substrates like lipid and carbohydrate for its metabolic energy.     

Vascular organization of the head and respiratory organs of the air-breathing catfish,Heteropneustes fossilis

Light and scanning electron microscopy of vascular replicas from the facultative air-breathing fish Heteropneustes fossilis show modifications in the macrocirculation of the respiratory organs and systemic circulation, whereas, gill microcirculation is similar to that found in typical water-breathing fish. Three and sometimes four ventral aortae arise directly from the bulbus. The most ventral vessel supplies the first pair of arches. Dorsal to this another aorta supplies the second gill arches, and a third, dorsal to, and larger than the other two, supplies the third and fourth arches and the air sacs. Occasionally a small vessel that may be the remnant of a primitive aortic arch arises from the first ventral aorta and proceeds directly to the mandibular region without perfusing gill tissue. The air sac is perfused by a large-diameter extension of the afferent branchial artery of the fourth gill arch and its circulation is in parallel with the gill arches. Blood drains from the air sac into the fourth arch epibranchial artery. A number of arteries also provide direct communication between the efferent air sac artery and the dorsal aorta. All four gill arches are well developed and contain respiratory (lamellar) and nonrespiratory (interlamellar and nutrient) networks common to gills of water-breathing fish. Air sac lamellae are reduced in size. The outer 30% of the air sac lamellar sinusoids are organized into thoroughfare channels; the remaining vasculature, normally embedded in the air sac parenchyma, is discontinuous. A gill-type interlamellar vasculature is lacking in the air sac circulation. Despite the elaborate development of the ventral aortae, there is little other anatomical evidence to suggest that gill and air sac outflow are separated and that dorsal aortic oxygen tensions are maintained when the gills are in a hypoxic environment. Physiological adjustments to hypoxic water conditions probably include temporal regulation of gill and air sac perfusion to be effective, if indeed they are so.     

Diurnal and Infradian Rhythms in Lipid Parameters of Indian Catfish, Heteropneustes fossilis

Twentyfour-hour variation in ( 14 C) acetate incorporation in the liver lipid, and lipid concentrations in the liver and muscle tissues were studied during different phases of the annual reproductive cycle in the female freshwater catfish, H. fossilis . A 24-h rhythm in hepatic lipogenic activity was validated. Lipid concentration in liver and muscle also varied in a rhythmic fashion (t = 24 h). The mesor and amplitude of these rhythms appeared to be modulated by the phase of the annual gonadal cycle of H. fossilis . All three lipid parameters, in addition, exhibited low frequency rhythms with a t = 6 months or 3 months. The results indicate that the time of the day and month of the year for sampling in any experiment involving examination of lipid metabolism are of critical importance.     

Thermal tolerance and preference of the Indian catfish Heteropneustes fossilis

Synopsis The catfish Heteropneustes fossilis tolerates a wide range of temperatures. The minimal (7.9°C) and maximal (39.8°C) lethal temperature values obtained during summer are higher than the minimal (4°C) and maximal (37.7°C) lethal temperature values obtained during winter; gradual heating or cooling versus abrupt exposure to various temperatures did not produce significant differences. Catfish acclimated to temperatures of 28° (summer) or 16°C (winter) finally selected temperatures ranging from 31.3° to 32° C, when placed in a temperature gradient of 15° to 35° C. Catfish avoid temperatures below 25° C regardless of seasonal acclimatization.     

Diurnal and Infradian Rhythms in Lipid Parameters of Indian Catfish,Heteropneustes fossilis

Twentyfour-hour variation in (14 C) acetate incorporation in the liver lipid, and lipid concentrations in the liver and muscle tissues were studied during different phases of the annual reproductive cycle in the female freshwater catfish, H. fossilis. A 24-h rhythm in hepatic lipogenic activity was validated. Lipid concentration in liver and muscle also varied in a rhythmic fashion (t = 24 h). The mesor and amplitude of these rhythms appeared to be modulated by the phase of the annual gonadal cycle of H. fossilis. All three lipid parameters, in addition, exhibited low frequency rhythms with a t = 6 months or 3 months. The results indicate that the time of the day and month of the year for sampling in any experiment involving examination of lipid metabolism are of critical importance.     

Induction of hepatic mitochondrial alpha-glycerophosphate dehydrogenase by L-triiodothyronine in Singi fish (Heteropneustes fossilis Bloch)

A single injection of L-triiodothyronine (T3) in different doses (0.25, 0.5, 5, 20 and 50 micrograms/g) increased the hepatic mitochondrial cytochrome-linked alpha-glycerophosphate dehydrogenase (alpha-GPD) activity and mitochondrial protein content of Singi fish, as observed on the 3rd day. A non-linear dose-response relationship with respect to enzyme activity was observed with different doses of T3. A low dose of 0.1 micrograms of T3 per g failed to cause any change in alpha-GPD activity and mitochondrial protein content of the liver. The enhancement of alpha-GPD activity over the control level with a low and a high dose of T3, viz., 0.5 and 5 micrograms/g, was followed from the 1st to the 7th day, when it was found that enzyme activity reached the maximum level on the 3rd day and then gradually declined to the control value on the 7th day. The percentage increase in enzyme activity with 5 micrograms/g was higher than that with 0.5 microgram/g from the 2nd to 5th day. Compared to the control, these two doses of T3 caused an increase in alpha-GPD activity from the 1st to the 6th day. Cycloheximide inhibited the T3-induced increase in alpha-GPD activity, mitochondrial and total protein content of liver. Immersion of Singi fishes in thiourea-containing (1 mg/ml) medium for 30 days showed a fall in hepatic alpha-GPD activity in comparison to the euthyroid control. A single injection of T3 (0.5 microgram/g) to the hypothyroid fish recovered alpha-GPD activity to more than the euthyroid control level. An increase in mitochondrial protein content in the T3-injected hypothyroid fish has been observed. DNA content of the fish liver remained unchanged in every experimental condition. The results thus showed the significant responsiveness of the fish liver to thyroid hormone.     

Demonstration of hepatic cytosolic malic enzyme activity as a thyroid hormone sensitive physiologic parameter in a teleost, Heteropneustes fossilis bloch

Single injections of various doses (0.1, 0.25, 0.5, 5 and 20 micrograms/g) of T3 significantly increased the cytosolic malic enzyme activity (delta OD/min/mg cytosolic protein) in liver of Singi fish Heteropneustes fossilis Bloch, in a dose-dependent nature, maximum up to 5 micrograms/g dose on the 3rd day in comparison to the control. There was no difference in the enzyme activity between 5 and 20 micrograms/g of T3 doses. When the enzyme activity was expressed per mg DNA, the dose-dependent increase in the malic enzyme activity was observed upto 0.5 microgram/g of T3, whereas a fall in the enzyme activity was noticed with 5 and 20 micrograms/g of T3 doses. Lowering the dose of T3 to 0.05 microgram/g was without any effect on the malic enzyme activity (delta OD/min/mg cytosolic protein or DNA). Hepatic cytosolic protein content showed a biphasic nature of variation, significant increase with single injections of 0.05, 0.1, 0.25 and 0.5 microgram/g and a fall with 5 and 20 micrograms/g of T3 doses in comparison to the untreated control. Cycloheximide treatments of the Singi fishes counteracted both the T3-induced rise in the hepatic cytosolic malic enzyme activity (delta OD/min/mg cytosolic protein or DNA) and the hepatic cytosolic protein contents. Thiourea-treated hypothyroid fishes showed significantly decreased level of malic enzyme activity (delta OD/min/mg cytosolic protein or DNA) and cytosolic protein content in liver. A single injection of T3 at 0.25 microgram/g to the thiourea-treated fishes not only recovered but also increased the enzyme activity and cytosolic protein content above the untreated control values.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of temperature on ovarian recrudescence in the Indian catfish, Heteropneustes fossilis

Over a 60-day experiment during the preparatory phase of the reproductive cycle, ovarian weights increased with rise in temperature in Heteropneustes fossilis and oocyte diameters suggested an optimum temperature of 22° C for Stage II oocyte formation. The oocytes did not reach Stage II at 10° C. Atresia of Stage III oocytes occurred following 60 days of exposure at 30°C.     

Respiratory surface areas of an air-breathing siluroid fish Saccobranchus (Heteropneustes) fossilis in relation to body size

The surface area of the gills, air sacs and skin have been measured in specimens of different body size and their relationship to body weight fits the equation: area= aW^b . The slopes ( b ) of the double logarithmic plots are 0.746 (gills), 0.662 (air sacs) and 0.684 (skin). The gills are poorly developed and their average weight specific area is less than figures obtained for sluggish marine fishes. The skin has an area about 70% of the total respiratory surfaces (gills+air sac+skin). Nevertheless the greater thickness of the skin leads to a smaller diffusing capacity of the tissue barrier ( D_t ) as compared with the gills and air sac. The air sac area for each ml of air that it contains is about 10.5 cm² which is much lower than figures obtained for lungs of other air-breathing fish and for tetrapods.     

Electron microscopic studies of the corpuscles of Stannius of an airbreathing teleost (Heteropneustes fossilis)

The ultrastructure of the corpuscles of Stannius (CS) ofHeteropneustes fossilis reveals a homogenous cellular composition characterized by only one cell type, with large secretory granules and abundant ribosomal endoplasmic reticulum. These cells are comparable to the type 1 cell described in the CS of other teleosts; type 2 cells, whose presence is ubiquitous in the CS of freshwater species are absent inH. fossilis. Our data on the CS ofH. fossilis demonstrate that not all freshwater species possess type 2 cells in their CS and these are not essential for life in freshwater.     

Studies on blood components of an air-breathing siluroid fish, Heteropneustes fossilis (Bloch) in relation to body weight.

Different haematological parameters have been studied in relation to the body weight of Heteropneustes fossil (Bloch). The erythrocytes and leucocytes number and haemoglobin concentration increases from lower to higher weight groups. The heart weight also increases along with other blood components. With the unit increase in the body weight of this fish, the heart weight, erythrocytes, leucocytes and haemoglobin increase by a fractional power of 0.85700, 0.13480, 0.13215 and 0.22876, respectively. This shows that haemoglobin increases at a higher rate than erythrocyte number. The coefficient of correlation between body weight and erythrocyte (r = 0.70015), leucocytes (r = 0.95861), haemoglobin (r = 0.96615) and heart weight (0.97577) indicate high degree of correlation. The erythrocytes and leucocytes count and haemoglobin concentration per gram body weight is higher in younger fishes and decrease as the animal grows in size. The haematocrit values and mean corpucsular volumes decrease from lower to higher weight groups, whereas mean corpuscular haemoglobin concentration increases with body weight. The erythrocyte cell surface has a decreasing trend from lower to higher weight group. Due to difference in the rate of decrease of greatest and least diameter of erythrocytes, the elliptical shape of R.B.C. which is common in younger animals, becomes circular in higher weight group. The non-granulocytes increase constantly while the percentage of granulocytes decreases from lower to higher weight groups. The lymphocytes constitute the main bulk of all the leucocytes. The total lymphocytes also increase with the body weight. Spindle cells and monocytes are relatively less in numbers. The percentage of eosinophils, basophils and neutrophils also decrease from lower to higher weight groups.     

Oxygen uptake through gills and skin in relation to body weight of an air-breathing siluroid fish, Saccobranchus (=Heteropneustes) fossilis

Oxygen uptake through gills and skin has been measured in juvenile and adult Saccobranchus fossilis and its relationship represented by the equation Vo₂= aW^b. When air-breathing is allowed the O₂ uptake via the gills and skin together increases by powers of 1 -084, 0–986 and 1–328 in juvenile, adult and juvenile+adult respectively. When air-breathing is prevented the slope (b) for O₂ uptake via the gills appear to be less in juveniles (0–765) than in adults (0–784) and juveniles+adults together (0–814). Under the same experimental condition, the slope for O₂ uptake via the gills+skin is also less in juveniles (0–478) than in adults (0–799) and juveniles+adults (0–755). Further decrease in the exponent value is found for the oxygen uptake of skin in relation to body weight under surfacing-prevented conditions ( b = 0–542). Different exponent values for juvenile and adult fishes may be due to their different growth pattern and physiology.