Retracing migration pattern in reproductive and non-reproductive female kutum Rutilus frisii,in south Caspian Sea,using otolith microchemistry

Because trace elements of otoliths are considered a natural marker capable of recognizing the chemical composition of ambient water and fish migration history, these elements could be potentially used to analyse the movement of reproductive (R) and non-reproductive (NR) mature-sized fish. Supposedly, it is not essential for NR individuals to migrate to rivers for spawning because they do not have developed gonads. To investigate the potential differences in migration history between female R and NR kutum, Rutilus frisii, in the southwest waters of the Caspian Sea, the ratios of Sr, Ba, Mg, Na, K and P to Ca in otoliths (from the core to the edge) were examined using laser ablation–inductively coupled plasma–mass spectrometry. In NR fish, a significant increase in Sr:Ca ratio in the otoliths' growth rings, likely due to greater seawater residency, and an increase in Ba:Ca ratio in the last two rings were observed. Increased Ba:Ca ratio could be due to the movement of NR mature-sized fish to the coastal zones for foraging. Seasonal physiological factors such as gonad maturation and spawning activity are more likely to be involved in differences in the other elemental ratios (Mg, Na, K and P). These results suggest that microchemical analyses of growth rings of otolith can be used as a valuable tool for better understanding the movement pattern of different types of adult fish, which could be completed with data from other methods like tagging.     

A comparison of osmoregulatory responses in plasma and tissues of rainbow trout (Oncorhynchus mykiss) following acute salinity challenges

Euryhaline teleosts regulate their internal osmotic and ionic status across a wide range of external salinities. Studies often rely on measurements on plasma when osmoregulatory status is perturbed, whereas tissue measurements are used for small fish with limited blood volume. However, a direct comparison is lacking for plasma and various tissues. In the present study the relationships between plasma, white muscle and carcass were examined for a range of osmoregulatory variables in rainbow trout (Oncorhynchus mykiss) following challenge with an acute (24 h) transfer from freshwater to a hyper-osmotic salinity of either 25 or 35. Significant increases in plasma osmolality, [Na+], [Cl?], [Ca2+], and [Mg2+] were observed when salinity was increased, but plasma [K+] was unaffected. The water content of both tissues showed reciprocal changes to plasma osmolality. The carcass content of all ions measured showed a significant increase at the highest ambient salinity. In white muscle, Na+, K+ and Mg2+ showed significant increases with external salinity, but Cl? and Ca2+ were unaffected. Measurements from both tissues can provide reliable surrogates for most of the plasma osmoregulatory variables except Cl? and Ca2+ when using white muscle tissue. In the case of internal regulation of K+ both tissues provide sensitive and quantitatively similar indicators of environmental salinity disturbance, whereas plasma does not.     

瓦氏雅罗鱼生殖洄游过程中离子调节相关生理变化研究

为了解达里湖瓦氏雅罗鱼(Leuciscus waleckii)生殖洄游过程中血清离子调节相关生理变化, 对比了达里湖和贡格尔河瓦氏雅罗鱼血清离子(Na+、K+、Cl?、Ca2+和Mg2+)水平, 鳃、肠和肾组织Na+/K+-ATPase和鳃Ca2+/Mg2+-ATPase活性、血清催乳素(PRL)、生长激素(GH)和类胰岛素生长因子-1(IGF-1)水平及鳃组织结构差异; 并利用实验生态学方法, 研究达里湖中瓦氏雅罗鱼转入贡格尔河水24h后上述生理参数的响应。研究结果显示, 与达里湖未洄游的瓦氏雅罗鱼相比, 洄游到贡格尔河后其血清Na+含量显著降低(P<0.05), Cl?含量显著升高(P<0.05), 肾脏和肠组织中Na+/K+-ATPase活性显著升高(P<0.05), 而鳃组织中Na+/K+-ATPase活性无显著变化; 血清K+、Ca2+、Mg2+水平和GH、IGF-1、PRL含量无显著变化。将达里湖瓦氏雅罗鱼转入河水中24h后, 其血清Cl?含量显著升高(P<0.05)、K+含量显著降低(P<0.05), 且在鳃、肠和肾组织中Na+/K+-ATPase及鳃Ca2+/Mg2+-ATPase活性均显著升高(P<0.05), 血清PRL和IGF-1水平显著升高(P<0.05); 比较湖中和河中瓦氏雅罗鱼鳃组织形态结构, 显示湖中瓦氏雅罗鱼鳃基底膜分布着大量黏液细胞, 洄游到河水中后黏液细胞数量明显减少, 鳃基底膜上氯细胞体积增大而数量未见明显变化。本研究结果表明: 瓦氏雅罗鱼从达里湖洄游到贡格尔河后通过提高血清PRL和IGF-1水平, 进而介导鳃、肠和肾组织中Na+/K+-ATPase活性增加, 从而维持鱼体较高或稳定的血清离子水平。     

Unusual physiology of scale-less carp,Gymnocypris przewalskii,in Lake Qinghai: a high altitude alkaline saline lake

The scale-less carp (Gymnocypris przewalskii) inhabits Lake Qinghai located on the Qinghai-Tibet plateau (elevation, 3200 m) in western China. The lake waters are alkaline (pH 9.4, titratable alkalinity=30 mmol l(-1)), Mg(2+)-rich (18.7 mmol l(-1)), Ca(2+)-poor (0.30 mmol l(-1)) and saline (9 per thousand ). These fish make annual spawning migrations into freshwater rivers. We investigated the physiology of nitrogen excretion and ionoregulation of fish from the lake and river. Fish from both waters were ammonotelic, although ammonia-N excretion rates were lower in lake fish (175 vs. 344 micromol kg(-1) h(-1), P<0.05) resulting in unusually high levels of ammonia in blood plasma (2.23 vs. 0.32 mmol l(-1)), bile, liver, muscle and brain. Exposure to 0.4 mmol l(-1) total ammonia in lake water ([NH(3)]=0.16 mmol l(-1)) killed fish within 8 h. River fish survived exposure to 1.0 mmol l(-1) total ammonia in river water at pH 8.0 ([NH(3)]=0.023 mmol l(-1)) for 24 h suggesting high ammonia tolerance in lake fish. High glutamate dehydrogenase and glutamine synthetase activities in tissues probably allow the fish to alleviate ammonia toxicity by amino acid accumulation. Neither lake nor river fish relied on urea excretion to remove excess N. Urea-N excretion rates were below 20 micromol kg(-1) h(-1) for both groups, and levels of urea in plasma and tissues were moderate. When exposed to elevated ammonia, urea-N excretion increased slightly (approximately 50 micromol kg(-1) h(-1)) and liver and muscle urea levels increased in the river fish. Plasma ion levels were within the range typical of cyprinids, but river fish had significantly higher plasma [Na(+)] and [Cl(-)] and lower [K(+)] than fish from the lake. During 48-h lake-to-river water transfer, plasma Na(+) and Cl(-) levels rose significantly. Significantly higher Na(+)/K(+)-ATPase activity in the gills of river fish may be related to the higher plasma ion levels. Plasma [Mg(2+)] and [Ca(2+)] were tightly regulated despite the great differences in the lake and river water levels.     

Cation distributions across the larval and pupal midgut of the lepidopteran, Hyalophora cecropia, in vivo.

1. The levels of potassium, sodium, magnesium and calcium in leaves, midgut contents, midgut tissue, and blood were analysed in seven developmental stages between feeding, fourth-instar larvae and new pupae of the Cecropia silkworm. 2. Three dramatic changes in cation levels were found: the K level in the contents drops from 284 /+- 51 mEquiv./1 tissue water in the fifth-instar larva to 51 +/- 6 mEquiv./1 in the new pupa; the Mg level in the midgut tissue increases from 28 +/- 3 mEquiv./1 at the time of gut evacuation to 1093 +/- 104 mEquiv./1 in the new pupa; and the Ca level in the contents drops temporarily from 56 +/- 12 mEquiv./1 in the feeding fourth instar larva to 17 +/- 5 mEquiv./1 in the new fifth instar larva. The Na level was nerve higher than 2.8 +/- 0.5 mEquiv./1. 3. The relative levels of the four cations were different for each tissue studied, but each tissue maintained the same relative levels during the developmental stages studied. The sequences are: leaf, Ca greater than K GREATEr than Mg greater than Na; midgut contents, K greater than Ca greater than Mg greater than Na; midgut tissue, K GREATEr than Mg greater than Ca greater than Na; and blood, Mg greater than K greater than Ca greater than Na. 4. There were three large concentration gradients across the midgut; the K level in the midgut contents is approximately 10 times the level in blood; the Mg level in contents is one-half to one-sixth the level in blood; and the Ca level in contents is 3-4 times the level in blood. The K gradient and the Ca gradient are opposed and the Mg gradient is favoured by the electrical gradient across the larval midgut, the contents being 100 mV positive with respect to the blood. The K gradient and the electrical gradient are not present across the pupal midgut while the Mg gradient and the Ca gradient persist. 5. The K gradient is presumably maintained by the midgut K pump, the Mg gradient is aided by the midgut Mg pump, and the Ca gradient suggests that the midgut may possess a Ca pump.     

Physiological effects of dietary cadmium acclimation and waterborne cadmium challenge in rainbow trout: respiratory, ionoregulatory, and stress parameters

A suite of respiratory, acid-base, ionoregulatory, hematological, and stress parameters were examined in adult rainbow trout (Oncorhynchus mykiss) after chronic exposure to a sublethal level of dietary Cd (500 mg/kg diet) for 45 days and during a subsequent challenge to waterborne Cd (10 microg/L) for 72 h. Blood sampling via an indwelling arterial catheter revealed that dietary Cd had no major effects on blood gases, acid-base balance, and plasma ions (Ca(2+), Mg(2+), K(+), Na(+), and Cl(-)) in trout. The most notable effects were an increase in hematocrit (49%) and hemoglobin (74%), and a decrease in the plasma total ammonia (43%) and glucose (49%) of the dietary Cd-exposed fish relative to the nonexposed controls. Dietary Cd resulted in a 26-fold increase of plasma Cd level over 45 days (approximately 24 ng/mL). The fish exposed to dietary Cd showed acclimation with increased protection against the effects of waterborne Cd on arterial blood P(aCO2) and pH, plasma ions, and stress indices. After waterborne Cd challenge, nonacclimated fish, but not Cd-acclimated fish, exhibited respiratory acidosis. Plasma Ca(2+) levels declined from the prechallenge level, but the effect was more pronounced in nonacclimated fish (44%) than in Cd-acclimated fish (14%) by 72 h. Plasma K(+) was elevated only in the nonacclimated fish. Similarly, waterborne Cd caused an elevation of all four traditional stress parameters (plasma total ammonia, cortisol, glucose, and lactate) only in the nonacclimated fish. Thus, chronic exposure to dietary Cd protects rainbow trout against physiological stress caused by waterborne Cd and both dietary and waterborne Cd should be considered in determining the extent of Cd toxicity to fish.     

Effects of adrenalectomy and of adrenal hormones on the tissue distribution of 14 elements in the rat

The effects of adrenalectomy (ADY) and of replacement therapy using a mineralocorticoid, deoxycorticosterone (DOC) and a glucocorticoid, dexamethasone (DEX) on the tissue distribution of elements in the rat, were studied under semichronic conditions. The elements, Na, K, Ca, Mg, Fe, S, P, Rb, Sr, Mn, Cu, and Zn were determined in whole blood, plasma, brain liver, kidney, heart, skeletal muscle, spleen, thymus, and bone. Additionally Mo was determined in kidney and liver and Ba in bone. ADY modified concentrations of all elements tested. Small changes were observed for K, Mg, Ca, S, and P, whereas much larger changes were noted for Na, Rb, and Sr. Cu, Zn, and Fe were mainly modified in liver and kidney, organs involved in storage and/or elimination. The consequences of ADY were corrected fairly well by DEX for Mg, Mn, Ca, Cu, and Mo; by DOC for Na and K, and by the two corticoids for Zn, Fe, Sr, and Rb. This study revealed that corticoids, mainly glucocorticoids, play an important role in the plasma and tissue balance of elements. It is suggested that these results may have a pathological and clinical significance.     

Epizootic cutaneous papillomatosis, cortisol and male ornamentation during and after breeding in the roach Rutilus rutilus

The prevalence of epidermal papillomatosis in roach is known to peak during the spawning period and to be higher in males than in females. The high occurrence of papillomatosis in polluted waters suggests that stress may contribute to the outbreak of the disease. However, little is known about breeding-induced stress in fish and its relationship with diseases. In this study, plasma cortisol concentration, hematocrit and the relative size of the spleen were determined in healthy and diseased male and female roach Rutilus rutilus during and shortly after spawning in a wild population. In addition, the sexual ornamentation (breeding tubercles on the lateral sides and on the frontal) of male roach during spawning was examined. Plasma cortisol concentration was higher during than after the spawning period, and higher in males than in females during spawning, indicating a spawning-induced stress and higher spawning stress among males. There was no correlation between cortisol concentration and the intensity of papillomatosis (number of scales under papilloma tumors) among the diseased fish. However, the significant interaction sex x disease status revealed by ANCOVA suggested that diseased males could be more prone to increased cortisol levels than diseased females or healthy males. Hematocrit values (ratio of the volume of red blood cells to total volume of blood) but not condition factor were lowered in papilloma-diseased fish after spawning. The relative size of the spleen was greater in males than in females. The number of frontal breeding tubercles correlated negatively with the intensity of papillomatosis. Experimental studies are needed to investigate the association of papillomatosis with stress and cortisol.     

Cationic distribution in vessels, heart, skeletal muscle, and blood of normotensive (NWR) and spontaneously hypertensive rats (SHR)

Electrolytic analysis carried out with the atomic absorption spectrophotometer permitted to compare the cationic (Ca2+, Mg2+, Zn2+, K+ and Na+) tissue content of spontaneously hypertensive male rats (SHR) and normotensive male Wistar rats (NWR). In all SHR-tissues, Zn2+ is augmented, but mainly in the atria (left atrium), inferior vena cava, left ventricle, and skeletal muscle. The inferior cava vein and the right atrium have a similar, accentuated high bivalent (Ca2+, Mg2+, and Zn2+) cation content; Ca2+ and Mg2+ is present in a minor content in the right ventricle and type II "pale" skeletal muscle while only Mg2+ was also reduced in the left atrium, aorta, and the whole blood. A higher K+ concentration is seen in the right atrium, aorta, and type I "red" skeletal muscle. In the aortic wall and the whole blood a higher Na+- tissue content is found, confirming earlier observations. There is a discret water retention in the tissues from the left ventricle and skeletal muscle, simultaneously with a small depletion in the whole blood. We have concluded, that there is a specific cationic profile in SHR structural and functional different cardiovascular tissues, including skeletal muscle. The cationic tissue distribution is related to underlying genetic and adaptative factors and may be involved into specific drug effects.     

Reproductive and growth strategies of the red roach, Rutilus arcasii (Steindachner, 1866), in two contrasting tributaries of the River Duero, Spain

The life-histories of red roach were assessed in the R. Moros and the R. Ucero, two contrasting tributaries of the R. Duero. Growth occurred from April to October and Ucero red roach were larger than those in the Moros from their second year onwards. Condition increased with gonad development and abruptly decreased after spawning in both populations. The condition of Ucero fish recovered during the summer, but that of the Moros fish remained low. The same year classes (1980 and 1982) dominated both populations. River Moros red roach spawned in a 4-week period between the end of April and early June, while the spawning season of Ucero red roach lasted until August. The length to fecundity relationship was similar for both populations, and fecundity and ovum size increased with fish length. The life-history traits of these red roach populations are discussed in relation to current life-history theories.     

Distribution of 14 elements in various rat tissues following hypophysectomy,thyroparathyroidectomy, adrenalectomy,and castration

The tissue distribution of 14 elements was simulatneously determined in rats 28 d after hypophysectomy (HPY), thyroparathyroidectomy (TPTY), adrenalectomy (ADY), and castration (CTN). The elements Na, K, Ca, Mg, Fe, S, P, Rb, Sr, Mn, Cu, and Zn were investigated in whole blood, plasma, brain, liver, kidney, heart, skeletal muscle, and bone. Additionally Mo was determined in kidney and liver. The following results were obtained: 1) With regard to hormone deficiency: HPY induced the most noticeable, variations on all the elements tested owing probably to the direct and indirect effects of adenohypophyseal hormones. ADY led to the expected modification of Na and K but also to a Sr accumulation and a Rb depletion. TPTY induced a sharp decrease in plasma and tissues Ca, an increase in plasma P, but did not disturb the two elements in bone. An increase of Rb in many tissues and of Fe in heart, kidney, and liver were also observed. CTN had little consequences except in bone whose Cu and Fe contents were increased: 2) With regard to element variations: K, Mg, and S underwent little change. Discriminations were revealed between elements such as K and Rb, Ca and Sr, Ca and Mg, and Cu and Zn. The changes of Rb and Sr were consistent with regulatory mechanisms. The accumulation of Fe and Cu in tissues such as liver after HPY, TPTY, and ADY, suggest that the hormonal deficiencies could worsen the hemochromatosis with Wilson's disease; 3), With regard to plasma and tissues: No correlation appeared in element levels between plasma and other tissues. Brain was the least affected and liver, kidney and bone the most.     

Effects of thyroparathyroidectomy and of thyroxin and calcitonin on the tissue distribution of twelve elements in the rat

The effects of thyroparathyroidectomy (TPTY) and of replacement therapy using thyroxin (T4) and calcitonin (CT) on the tissue distribution of elements were studied in the rat under semichronic conditions. The elements Na, K, Ca, Mg, Fe, S, P, Rb, Sr, Mn, Cu, and Zn were determined in whole blood, plasma, brain, liver, heart, kidney, skeletal muscle, and bone. TPTY modified concentrations of all elements tested but only small changes were observed for K, Mg, S, and P. The mineral bone composition was slightly modified, 28 d after TPTY, whereas plasma was the most altered. The consequences of TPTY were corrected fairly well by T4 for Na, Cu, Zn, Fe, and S, and by CT for K, P, Rb but with less efficiency for Ca. This study revealed that hormones of the thyroid gland, mainly T4, play an important role in the plasma and tissue balance of elements. It is suggested that T4 participates in tissue fixation of Cu, Zn, and Fe and that CT influences phosphoremia and cellular Ca binding.     

Competitive inhibition and selectivity enhancement by Ca in the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, Hf) by carrot (Daucus carota cv. U.S. harumakigosun)

We investigated the uptake of inorganic elements (Be, Na, Mg, K, Ca, Sc, Mn, Co, Zn, Se, Rb, Sr, Y, Zr, Ce, Pm, Gd, and Hf) and the effect of Ca on their uptake in carrots (Daucus carota cv. U.S. harumakigosun) by the radioactive multitracer technique. The experimental results suggested that Na, Mg, K, and Rb competed for the functional groups outside the cells in roots with Ca but not for the transporter-binding sites on the plasma membrrane of the root cortex cells. In contrast, Y, Ce, Pm, and Gd competed with Ca for the transporters on the plasma membrane. The selectivity, which was defined as the value obtained by dividing the concentration ratio of an elemental pair, K/Na, Rb/Na, Be/Sr, and Mg/Sr, in the presence of 0.2 and 2 ppm Ca by that of the corresponding elemental pair in the absence of Ca in the solution was estimated. The selectivity of K and Rb in roots was increased in the presence of Ca. The selectivity of Be in roots was not affected, whereas the selectivity of Mg was increased by Ca. These observations suggest that the presence of Ca in the uptake solution enhances the selectivity in the uptake of metabolically important elements against unwanted elements.     

Changes in tissue free amino acid contents, branchial Na+/K+ -ATPase activity and bimodal breathing pattern in the freshwater climbing perch, Anabas testudineus (Bloch), during seawater acclimation

This study aimed to examine effects of short- or long-term acclimation to brackish water or seawater on the climbing perch, Anabas testudineus, which is an aquatic air-breathing teleost living typically in freshwater. A. testudineus exhibits hypoosmotic and hypoinoic osmoregulation; the plasma osmolality, [Na+] and [Cl-] of fish acclimated to seawater were consistently lower than those of the external medium. However, during short-term (1 day) exposure to brackish water (15 per thousand) or seawater (30 per thousand), these three parameters increased significantly. There were also significant increases in tissue ammonia and urea contents, contents of certain free amino acids (FAAs) in the muscle, and rates of ammonia and urea excretion in the experimental fish. The accumulated FAAs might have a transient role in cell volume regulation. In addition, these results indicate that increases in protein degradation and amino acid catabolism had occurred, possibly providing energy for the osmoregulatory acclimation of the gills in fish exposed to salinity stress. Indeed, there was a significant increase in the branchial Na+/K+ -ATPase activity in fish exposed to seawater for a prolonged period (7 days), and the plasma osmolality, [Na+] and [Cl-] and the tissue FAA contents of these fish returned to control levels. More importantly, there was a significant increase in the dependence on water-breathing in fish acclimated to seawater for 7 days. This suggests for the first time that A. testudineus could alter its bimodal breathing pattern to facilitate the functioning of branchial Na+/K+ -ATPase for osmoregulatory purposes.     

The cause of extreme year class variation in a population of roach, Rutilus rutilus L., from a eutrophic lake in southern England

Investigations into the biology of the roach population at Slapton Ley, Devon, U.K. were carried out between October 1982 and December 1984 and data collected from the lake since 1977 have been re-analysed to assist interpretation. The roach population has been characterized in recent years by extreme year class variation and a tendency for year classes to alternate in strength. The survival of the roach was very poor, and the spawning population therefore consisted largely of 2-and some 3-year-old fish. Consequently, the size of the spawning stock was small and dependent on the strengths of the year classes that it contained. Recruitment to many year classes was probably limited by the size of the spawning stock. The occurrence of a poor year class in the population would therefore set up an autonomous cycle of poor recruitment to alternate year classes in a manner similar to many tropical marine fisheries. Observation of other British roach populations showed that a short life-span may be associated with conditions that promote very rapid growth rates. The growth rate of individual roach at Slapton was found to be one of the fastest in Britain, and this was apparently due to the very high productivity of Slapton Ley together with the persistence of the roach population at very low densities.     

Homing precision of roach Rutilus rutilus in Lake Arungen,Norway

Synopsis The present study tests the precision of repeat homing of roach, Rutilus rutilus, to two tributaries of a small Norwegian Lake, Årungen. A sample of 19 959 spawners was tagged or marked in the spawning area. After spawning the roach intermingled with other spawning demes in the lake. The year after marking, 2515 (12.6%) roach were recaptured during spawning in the five tributaries, 340 (13.5) of these were strayers. This straying is considerably larger than found in comparable autumn spawning species, but approximately the same as reported for other spring spawning species. The recapture rate was lower for females than for males, probably due to increased female mortality induced by the tagging manipulation.     

Adenosine triphosphatases during maturation of cultured human skeletal muscle cells and in adult human muscle.

Na+/K(+)-ATPase, Mg(2+)-ATPase and sarcoplasmic reticulum (SR) Ca(2+)-ATPase are examined in cultured human skeletal muscle cells of different maturation grade and in human skeletal muscle. Na+/K(+)-ATPase is investigated by measuring ouabain binding and the activities of Na+/K(+)-ATPase and K(+)-dependent 3-O-methylfluorescein phosphatase (3-O-MFPase). SR Ca(2+)-ATPase is examined by ELISA, Ca(2+)-dependent phosphorylation and its activities on ATP and 3-O-methylfluorescein phosphate. Na+/K(+)-ATPase and SR Ca(2+)-ATPase are localized by immunocytochemistry. The activities of Na+/K(+)-ATPase and SR Ca(2+)-ATPase show a good correlation with the other assayed parameters of these ion pumps. All ATPase parameters investigated increase with the maturation grade of the cultured muscle cells. The number of ouabain-binding sites and the activities of Na+/K(+)-ATPase and K(+)-dependent 3-O-MFPase are significantly higher in cultured muscle cells than in muscle. The Mg(2+)-ATPase activity, the content of SR Ca(2+)-ATPase and the activities of SR Ca(2+)-ATPase and Ca(2+)-dependent 3-O-MFPase remain significantly lower in cultured cells than in muscle. The ouabain-binding constant and the molecular activities of Na+/K(+)-ATPase and SR Ca(2+)-ATPase are equal in muscle and cultured cells. During ageing of human muscle the activity as well as the concentration of SR Ca(2+)-ATPase decrease. Thus the changes of the activities of the ATPases are caused by variations of the number of their molecules. Na+/K(+)-ATPase is localized in the periphery of fast- and slow-twitch muscle fibers and at the sarcomeric I-band. SR Ca(2+)-ATPase is predominantly confined to the I-band, whereas fast-twitch fibers are much more immunoreactive than slow-twitch fibers. The presence of cross-striation for Na+/K(+)-ATPase and SR Ca(2+)-ATPase in highly matured cultured muscle cells indicate the development and subcellular organization of a transverse tubular system and SR, respectively, which resembles the in vivo situation.     

Spatio-temporal variation in the elemental compositions of otoliths of southern bluefin tuna Thunnus maccoyii in the Indian Ocean and its ecological implication

The elements Na, Mg, Mn, Ca, Sr and Ba in otoliths of southern bluefin tuna Thunnus maccoyii , collected from their feeding ground in the central Indian Ocean and spawning ground between southern Java and north-western Australia were measured by laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and compared among sampling locations and developmental stages. The Na, Mg and Mn to Ca concentration ratios were significantly higher at the larval stage than at the adult stage, and the ratio reached a peak at the first inflection point of the otolith, mean ± s.d. 43·3 ± 4·9 days after hatching and decreased sharply to a low level thereafter. The temporal change of the elements:Ca ratios in the first inflection point corresponded to the life stage transition from larva to juvenile, indicating that the uptake rate of elements from ambient waters was significantly influenced by the ontogenetic change in the fish. The elemental composition at the otolith edge differed significantly in sub-adults on the feeding grounds and adults on the spawning grounds. Thus, the otolith elemental composition can be used as a biological tracer to study the time of the ontogenetic shift and to reconstruct the past migratory environmental history of T. maccoyii . In addition, the elemental composition of the otolith core of the adult was similar between feeding and spawning grounds, indicating that the fish in the Indian Ocean had the same larval origin, which is consistent with the single spawning population hypothesis.     

The effect of ouabain on the guinea pig ileum longitudinal smooth muscle: 2. Intracellular levels of Ca, Na, K, and Mg during the ouabain response and the dependence of the response on extracellular Ca.

Isotonic Tris-HCl containing 10 mM LaCl3 at 4 degrees C effectively removed extracellular ions in 30 min while preventing loss of intracellular ions. Intracellular Ca and Na increased during the contraction in the presence of 10 mM ouabain and then decreased during relaxation. Intracellular Na increased again during the latter part of the relaxation phase when K loss became apparent. Mg levels remained essentially constant. Ouabain responses were rapidly lost in Ca-free medium indicating that they were dependent on extracellular Ca. A 5.5-fold increase in the normal levels of extracellular K did not reduce the contraction to a submaximal dose of ouabain. A full phasic response to high K (60 mM) was observed after a 10-min exposure of the tissue to ouabain, at which time the ouabain response had returned to basal tension. The contraction to ouabain appears to be dissociated from inhibition of the Na,K-ATPase at the K site. The changes in intracellular ions indicated that ouabain contracted the muscle by increasing the plasma membrane permeability to Ca and Na and later decreased the K and Na concentration gradients, probably by inhibition of the Na,K-ATPase.     

Extracellular calcium is required for the maintenance of plasma membrane integrity in nucleated cells

In contrast to rat and human erythrocytes, nucleated erythrocytes from two fish species (Cyprinus carpio and Salmo trutta) underwent almost complete haemolysis in 20 min of EDTA addition. Using Ca2+/Mg2+ EGTA-citrate buffer, we observed that half-maximal haemolysis of fish erythrocytes occurs at [Ca2+]o approximately 10 microM independently of extracellular Mg2+ concentration. Attenuation of [Ca2+]o with EGTA also decreased stability of the plasma membrane of vascular smooth muscle cells (VSMC) and HeLa cells, indicated by a three- to five-fold elevation of lactate dehydrogenase release and passive permeability of plasma membrane for Na+. In VSMC, EGTA lowered [Ca2+]i by approximately 20%. This effect was absent in VSMC-loaded with the intracellular Ca2+ chelator BAPTA. In contrast to EGTA, BAPTA did not affect haemoglobin release from fish erythrocytes and passive permeability for Na+ in VSMC. Viewed collectively, our data show that in nucleated cells, extracellular Ca2+ plays a crucial role in the maintenance of plasma membrane integrity.