Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus     

M.-H. Chang  H.-C. Lin  P.P. Hwang 《Fish physiology and biochemistry》1997,16(6):459-470

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.  相似文献   

Tolerance of striped trumpeter Latris lineata embryos to ozonated seawater     

Stephen C. Battaglene  David T. Morehead 《Aquaculture International》2006,14(5):421-429

The tolerance of striped trumpeter, Latris lineata (Bloch and Schneider 1801) embryos to ozonated seawater was examined as a possible means of disinfection. The effect of a range of ozone doses and exposures (CT = concentration × exposure time) was tested at different stages of embryonic development. Three-day-old embryos two-thirds developed around the yolk were exposed for 0.5, 1 or 5 min to ozone concentrations of 0.5, 1, 2 and 5 mg O₃ l⁻¹ in a fully orthogonal factorial design. For each treatment there were four replicate 250 ml containers that each received 100 ± 15 embryos. There was no significant difference in hatching success between control-treated embryos or embryos ozonated at 0.5 or 1 mg O₃ l⁻¹ for 0.5, 1 or 5 min (P < 0.05). However, hatching success was significantly reduced when embryos were treated with 2 or 5 mg O₃ l⁻¹ for 5 min or 5 mg l⁻¹ O₃ for 1 min (P < 0.05). The tolerance of embryos to 0, 0.5 or 2 mg O₃ l⁻¹ for 1 min at different stages of development (Day 0, 1, 2, 3 or 4), was then examined. An ozone concentration of 0.5 mg l⁻¹ had no effect on hatching success at any stage of development, but a concentration of 2 mg l⁻¹ significantly reduced hatching success on all days except Day 3. A safe and tested hatchery practise is to disinfect striped trumpeter embryos with 1 mg O₃ l⁻¹ for 1 min on Day 3 post-fertilisation when the embryo is two-thirds developed around the yolk.  相似文献   

Intracellular mediation of GnRH action on GTH release in tilapia     

Berta Levavi-Sivan  Zvi Yaron 《Fish physiology and biochemistry》1993,11(1-6):51-59

The objective of the present study was to confirm previous results on the mediation of GnRH signal in tilapia by providing evidence from experiments in cultured pituitary cells and from perifusion experiments using a GnRH-antagonist. After 4 days in culture under identical conditions, cells taken from pituitaries of fish maintained at 26°C were more sensitive to GnRHa ([D-Ala⁶, Pro⁹-NEt]-LHRH) than those taken from fish maintained at 19°C. Cells from female pituitaries were more responsive than those from males. taGTH release in culture was augmented by Ca²⁺ ionophore (A23187; 1–100 μM) or ionomycin (0.02–10 μM). The response of perifused pituitary to GnRH was reduced by nimodipine (1–10 μM) indicating that Ca²⁺ influx via voltage-sensitive Ca²⁺ channels is involved in the stimulation of GTH release. Activation of protein kinase C by OAG (1-oleyl-2-acetyl glycerol; 0.16–160 μM) or TPA (1-O-tetra-decanoyl phorbol-13-acetate; 1.25–125 nM) resulted in a dose-dependent stimulation of taGTH release from cultured cells. Arachidonic acid (0.33–330 μM) also augmented the release of taGTH from the culture. Four sequential pulses of sGnRH (100 nM) at 2h intervals resulted in surges of taGTH release from perifused pituitary fragments; the surges were similar in magnitude with no signs of desensitization. Sequential stimulation with graded doses of sGnRH (0.1 nM to 1 μM) in the presence of GnRH-antagonist ([Pro^2,6, Trp³]-GnRH) resulted in an attenuation of taGTH release. However, the GnRH-antagonist did not alter the pattern of forskolin-stimulated GTH release, indicating that forskolin stimulation is exerted at the level of the adenohypophyseal cells. It is concluded that, as in other vertebrates, the transduction of GnRH stimulation of GTH release involves Ca²⁺ influx through voltage-sensitive Ca²⁺ channels, mobilization of the ion from intracellular sources, arachidonic acid and activation of PKC. Adenylate cyclase-cAMP system us also involved in the mediation but its relationship with other transduction cascades requires further investigations.  相似文献   

Effect of environmental calcium levels on calcium uptake in tilapia larvae Oreochromis mossambicus     

Pr. Pung-Pung Hwang  Yu-Chi Tung  Min-Hwang Chang 《Fish physiology and biochemistry》1996,15(5):363-370

Effects of environmental calcium concentrations on the survival, growth, body calcium content and calcium uptake kinetics in developing tilapia (Oreochromis mossambicus) larvae were studied. Fertilized eggs were incubated in high- and low-calcium artificial freshwater (0.88–0.96 mmol l^–1 vs. 0.02–0.03 mmol l^–1 CaCl₂ or CaSO₄) until 3 days after hatching. Tilapia larvae showed similar hatching rates and wet weights in either high- or low-calcium medium, indicating neither the development nor the growth in tilapia larvae was affected by the environmental calcium levels. The body calcium content in low-calcium groups was about 90–95% that of high-calcium groups, No matter what calcium source was used (CaCl₂ or CaSO₄), acclimation to low calcium medium caused a stimulation of calcium uptake (measured in 0.2 mmol l^–1 calcium),i.e., 1.2–1.3 fold higher than that of high calcium groups. This enhanced calcium uptake capacity was characterized by a 50% decrease in K_m and a 25% increase in J_max. Effect of different calcium salts on calcium influx was significant only in low calcium level,i.e., calcium influx in low-CaCl₂ group higher than that in low-CaSO₄ group. These results suggest that tilapia larvae are able to modulate their calcium uptake mechanism to maintain normal body calcium content and growth in environments with different levels of calcium.  相似文献   

An increase in the concentration of hepatic iron during the metamorphosis of the lamprey Geotria australis is accompanied by increased superoxide dismutase activity     

L. R. Harris  M. H. Cake  D. J. Macey  I. C. Potter 《Fish physiology and biochemistry》1990,8(6):451-457

The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight⁻¹ in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg⁻¹ in stages 5–7 and to 8.8 μg.mg⁻¹ in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg⁻¹. Superoxide dismutase activity fell sharply from 0.39 μg.mg⁻¹ in large ammocoetes to between 0.07 μg.mg⁻¹ in stage 1 and 0.15 μg.mg⁻¹ in stage 6, before rising significantly to 0.26 μg.mg⁻¹ in stage 7 and 0.35 μg.mg⁻¹ in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.  相似文献   

Sodium dependent ion transporters in trout gills     

G. Flik  T. Kaneko  A.M. Greco  J. Li  J.C. Fenwick 《Fish physiology and biochemistry》1997,17(1-6):385-396

Biochemical procedures developed to isolate plasma membranes from the branchial epithelium of rainbow trout (Oncorhynchus mykiss) yield membrane fractions that are specifically enriched in the plasma membrane marker enzyme Na⁺/K⁺-ATPase. As the bulk of the branchial Na⁺/K⁺-ATPase is assumed to be confined to the mitochondria-rich chloride cells, such membrane preparations must contain the essence of the enzymatic machinery of the chloride cells. Basal Na⁺ activity in branchial (chloride) cells is around 10 millimolar and, accordingly, we find a K_m for Na⁺ of the Na⁺/K⁺-ATPase of 13 millimolar, indicating that the enzyme may be regulated by changes in cytosolic sodium. The Na⁺-gradient across the serosal plasma membrane created by this pump provides energy for 3Na⁺/Ca²⁺-exchange and bumetanide-sensitive Na⁺/K⁺/2Cl^--cotransport. Here we further postulate the presence of a Na⁺/Cl^--cotransporter, indicated by thiazide-sensitive, bumetanide-insensitive transport of Na⁺ and Cl^-; this cotransporter activity awaits the characterization of its kinetics. The Na⁺/Ca²⁺-exchanger has kinetic characteristics compatible with a regulatory role of cytosolic Na⁺ in the activity of this carrier. Both Na⁺/Ca²⁺-exchange and Ca²⁺-ATPase activity may contribute to transport of Ca²⁺, the former having lower affinity for calcium but a higher capacity than the latter carrier. The Na⁺/K⁺/2Cl^--cotransporter has kinetics that favor a regulatory role for plasma K⁺ in the activity of this carrier. Seawater adaptation leads to increased activity of cotransporter molecules in the plasma membrane fractions (the activity increases relative to that of the Na⁺/K⁺-ATPase) and this may reflect a function in Cl^--extrusion performed by the chloride cells in a seawater environment. A function for the cotransporter in the gills of freshwater fish may be the regulation of cell volume.  相似文献   

Effects of Na/K and Mg/Ca ratios in saline groundwaters on Na-K-ATPase activity, survival and growth of Marsupenaeus japonicus postlarvae     

Lu-Qing Pan  Zhi-Hua Luan  Cai-Xia Jin 《Aquaculture (Amsterdam, Netherlands)》2006,261(4):1396-1402

The effects of the Na⁺/K⁺ and Mg²⁺/Ca²⁺ ratios in saline groundwaters on Na⁺-K⁺-ATPase activity, survival and growth of Marsupenaeus japonicus postlarvae were investigated. The results indicate that the Na⁺-K⁺-ATPase activity, survival rate and weight gain of postlarvae were significantly affected by the Na⁺/K⁺ and Mg²⁺/Ca²⁺ ratios (P < 0.05). The Na⁺-K⁺-ATPase activity of postlarvae, in every treatment, changed corresponding to Na⁺/K⁺ and Mg²⁺/Ca²⁺ ratios, and came to a stable level after 24 h. There was a negative relation between Na⁺-K⁺-ATPase activity and Na⁺/K⁺ ratio, while there was a positive relation between Na⁺-K⁺-ATPase activity and Mg²⁺/Ca²⁺ ratio. Compared with seawater (the Na⁺/K⁺ and Mg²⁺/Ca²⁺ ratios are 27.8 and 4.64 respectively), the Na⁺-K⁺-ATPase activity of the Na⁺/K⁺ ratio 30 treatment showed no significant difference, while the Mg²⁺/Ca²⁺ ratio 4.5 treatment showed distinct difference. The survival rates and weight gain of postlarvae increased markedly when the suitable amount of K⁺ and Ca²⁺ was added to test water, and arrived at their maximum in the Na⁺/K⁺ ratio 20-30 or Mg²⁺/Ca²⁺ ratio 4.5 treatment, having no significant difference compared with normal seawater. Therefore, considering the Na⁺/K⁺, Mg²⁺/Ca²⁺ ratios and the absolute concentration of Mg²⁺, Ca²⁺ in the experimental saline groundwaters applied to Marsupenaeus japonicus farming, it should be modulated to around 30, 4.5 and 1312 mg/l, 291 mg/l, respectively.  相似文献   

Osmoregulation in juvenile Chinese sturgeon (<Emphasis Type="Italic">Acipenser sinensis</Emphasis> Gray) during brackish water adaptation     

Xugang He  Ping Zhuang  Longzhen Zhang  Congxin Xie 《Fish physiology and biochemistry》2009,35(2):223-230

The osmoregulation capabilities of 7-month-old juvenile Chinese sturgeon (Acipenser sinensis Gray) (128.8 ± 15 g) transferred directly from fresh water (0‰, 46 mOsmol kg⁻¹) to brackish water (10‰, 273 mOsmol kg⁻¹) were studied over a 20-day period. Changes in serum osmolarity, chloride (Cl⁻), sodium (Na⁺), potassium (K⁺) and calcium (Ca²⁺) ion concentrations, as well as gill and spiral valve Na⁺,K⁺-ATPase activities were measured at 3, 12, 24, 72, 216 and 480 h after transfer to BW. The serum osmolarity and ion concentrations (Na⁺, Cl⁻ and Ca²⁺) increased immediately after the transference to BW, reaching maximum at 24 h and returned to a new steady state at 216 h, while the FW control group maintained basal levels which showed lower (P < 0.05) than the BW group. Gill Na⁺,K⁺-ATPase activity of BW group exhibited an abrupt decrease in the first 3 h after transfer, but began to increase at 3 h, reaching a peak value at 24 h, and returned to a new steady state at 216 h. The differences between gill Na⁺,K⁺-ATPase activity of BW and FW fish were significant (P < 0.05) after 12 h. In contrast, Na⁺,K⁺-ATPase activity of the spiral valve showed transient increase after transference from FW to BW, and then decreased rapidly at 3 h, reaching the lowest at 24 h after transference. At 216 h after exposure to BW, Na⁺,K⁺-ATPase activities of the spiral valve increased slowly to the levels of FW control. The results of our study indicate the existence of hyposmoregulatory adaptive mechanisms in 7-month-old juvenile Chinese sturgeon which enable this fish to acclimate itself successfully to brackish water.  相似文献   

Some proteolytic properties of hatching liquid in the sea trout,Salmo trutta m. trutta L.     

Zofia Luberda  Jerzy Strzezek  Miroslaw Luczynski 《Fish physiology and biochemistry》1993,12(1):75-80

Proteolytic activity of sea trout hatching liquid was examined towards casein and azocazein as a function of pH and temperature. The optimum pH for caseinolytic and azocaseinolytic activities were 9.4, and 9.0, respectively. At alkaline pH the enzyme was activated by low concentrations of Zn²⁺ ions (10⁻⁵ M). Maximum proteolytic activity of the hatching liquid was observed at 25°C. Temperatures exceeding 30°C caused a rapid reduction in enzyme activity. Proteolytic activity observed at 10°C was approximately 50% of that observed at 25°C. In general, a pseudo-Arrhenius plot indicated a Q₁₀ of 1.6 between 6 and 25°C.  相似文献   

Treatment Method Affects Color,Chemical, and Mineral Composition of Seabream (Sparus aurata) Fish Bone Powder from by-Products of Fish Fillet     

Nazlı Savlak  Özlem Çağındı  Gizem Erk  Birsen Öktem  Ergün Köse 《Journal Of Aquatic Food Product Technology》2020,29(6):592-602

ABSTRACT

Seabream fish bone powder was produced using different chemical methods and tap water. The effect of different chemical procedures (sodium hydroxide (NaOH); NaOH + citric acid; NaOH + sodium hypochlorite (NaOCl); NaOH + ethanol (EtOH); and NaOH + hydrogen chloride (HCl)) and tap water on proximate composition, yield, mineral composition, color, and sensorial odor was investigated. Despite its high bone powder yield (59.39%), tap water treatment was not an efficient method due to low calcium (Ca²⁺, 232.13 g/kg) and phosphorus (P, 111.63 g/kg) concentration and heavy fish odor. Sensorial odor analysis of seabream fish bone powder showed that tap water received the lowest scores (1.71/5), while chemically treated samples received sensorial odor scores higher than 4.00, with an average of 4.61, indicating that they had a very slight odor. The best fish bone powder yield was obtained using NaOH treatment (21.46%), where Ca²⁺ (276.73 g/kg) and P (147.23 g/kg) content was also high. The utilization of chemicals in combination with NaOH did not increase the sensorial odor score of seabream fish powders but resulted in a decrease in powder yield. Moreover, the mineral composition of all chemical processing techniques was comparable. Processing by-products of seabream fillet production with 8% NaOH will contribute to daily Ca²⁺ and P intake of individuals.  相似文献   

Mechanisms of action of pituitary adenylate cyclase-activating polypeptide (PACAP) on growth hormone release from dispersed goldfish pituitary cells     

Noel R. Wirachowsky  Patrick Kwong  Warren K. Yunker  James D. Johnson  John P. Chang 《Fish physiology and biochemistry》2000,23(3):201-214

The mechanisms of pituitary adenylate cyclase activating polypeptide (PACAP) action on goldfish growth hormone (GH) release were investigated by examining GH release responses from dispersed goldfish pituitary cells to a synthetic mammalian (m)PACAP₃₈ peptide. It was established that GH release stimulated by 2-h exposure to mPACAP₃₈ was concentration-dependent, attenuated by the PACAP receptor antagonist mPACAP_6–38, and subject to neuroendocrine modulation by somatostatin. Maximal mPACAP₃₈-stimulated GH release was not additive to the responses elicited by either the adenylate cyclase activator forskolin or the cyclic (c)AMP analog 8-bromo-cAMP. The GH responses to mPACAP₃₈, forskolin and 8-bromo-cAMP, either alone or in combination, were abolished by H89, a protein kinase A (PKA) inhibitor. SQ22536, an adenylate cyclase inhibitor, attenuated forskolin- and mPACAP₃₈-stimulated GH release. In contrast, mPACAP₃₈-stimulated GH release were additive to the responses to two protein kinase C (PKC) activators and unaffected by two PKC inhibitors. These results suggest that the stimulatory action of PACAP on GH secretion is mediated through a cAMP- / PKA-dependent mechanism, whereas the involvement of PKC appears unlikely. The ability of mPACAP₃₈ to further enhance maximal GnRH (PKC)-dependent GH release, but not dopamine D1 agonist (PKA)-dependent GH secretion, is consistent with this hypothesis. A possible involvement of Ca²⁺ in PACAP action is also suggested. Two inhibitors of voltage-sensitive Ca²⁺ channel reduced the GH responses to mPACAP₃₈ in static incubation; conversely, mPACAP₃₈ increased intracellular [Ca²⁺] in identified, single goldfish somatotropes.  相似文献   

The effect of feeding on oxygen consumption and ammonia excretion of juvenile tench Tinca tinca (L.) reared in a water recirculating system     

ZdzisŁaw Zakęś  Krystyna Demska-Zakęś  PrzemysŁaw Jarocki  Konrad Stawecki 《Aquaculture International》2006,14(1-2):127-140

The effect of feeding frequency (one, three, and continuous feeding), feed ration (0.2, 0.5, 0.8% of total fish biomass), and feeding per se on the oxygen consumption (OC, mg O₂ kg⁻¹ h⁻¹) and ammonia excretion (AE, mg TAN kg⁻¹ h⁻¹) of juvenile tench (body weight 15–19 g) and variations in these parameters in daily cycles were examined. Fish metabolism was studied in a recirculating system (rearing tanks of 0.2 m³, water temperature 23 °C). It was found that oxygen consumption and ammonia excretion depended significantly on feed ration. An increase of feed ration from 0.2 to 0.8% of fish biomass caused an increase of OC and AE from 126.80 mg O₂ kg⁻¹ h⁻¹ and 1.95 mg TAN kg⁻¹ h⁻¹ to 187.35 mg O₂ kg⁻¹ h⁻¹ and 8.80 mg TAN kg⁻¹ h⁻¹ (p<0.05). There was no dependence between feeding frequency and the mean rate of oxygen consumption. However, the relationship between feeding frequency and ammonia excretion by juvenile tench was statistically significant (p<0.05). Feeding frequency significantly affected daily fluctuations of AE and OC. It was found that diurnal variations in metabolic rates were strictly related to tench feeding, and the daily variations of AE were significantly higher than OC.  相似文献   

pH值和Ca^2＋浓度对日本沼虾生长和能量收支的影响   总被引：18，自引：1，他引：18  

董双林  堵甫山  赖伟 《水产学报》1994,18(2):118-123

本文报道了不同ｐＨ值（６．５、７．５和８．５）和不同Ｃａ＾２＋浓度（３８．８、６１．１和７８．８ｐｐｍ）对日本沼是生长和能量收支的影响，实验结果表明，ｐＨ值对该虾的生长有一定的影响，Ｃａ＾２＋和ｐＨ值在影响其生长的过程中可能有一定的交互作用，ｐＨ值和Ｃａ＾２＋对该虾生长的影响主要是通过影响其能量摄入量实现的，本实验条件下，该虾摄入的能量平均有１５．８％用于生长，１．８％作为粪便排出体外，其余用于呼  相似文献   

Potassium flux in juvenile striped bass (Morone saxatilis): influence of external concentrations of sodium chloride and calcium     

John M. Grizzle  Keith A. Cummins 《Fish physiology and biochemistry》1996,15(2):181-186

Whole-body influx and efflux of K⁺ were determined for 25-day-old striped bass,Morone saxatilis, in conditions that simulated harvesting fish from ponds. During the first 5h in fresh water with combined high NaCl (80 mM) and low Ca²⁺ (0.12 mM) concentrations, a combination that is acutely lethal to this age of striped bass, K⁺ influx for fish in 0.07 mM K⁺ was 21±1.7 (SEM) compared to 3.4±0.33 nmol g^–1 h^–1 for fish in water with low Na⁺ (0.25 mM) or high Ca²⁺ (2.5 mM) concentrations. Influx of K⁺ was inhibited during the first few hours after fish were placed in flux chambers. Potassium efflux as percentage of⁴²K lost per hour was two-fold higher from fish in the high Na-low Ca treatment compared to fish in low concentrations of Na⁺ or high concentrations of Ca²⁺. Potassium efflux was probably much greater than influx, but exact values for efflux could not be calculated from the data available. Survival of fish in water with high Na-low Ca was not increased by addition of KCl to the water, indicating that the net loss of K⁺ was probably not the cause of death.  相似文献   

虾夷扇贝闭壳肌和外套膜肌原纤维蛋白的特性分析   总被引：4，自引：2，他引：2  

吴忠  刘俊荣  田元勇 《水产学报》2015,39(11):1640-1649

为探索采捕后活品虾夷扇贝品质变化与其肌肉蛋白质生理特性变化间的关联,本研究以虾夷扇贝2个可食部肌肉为研究对象,以肌原纤维蛋白ATPase活性为指标(Ca²⁺-ATPase,Mg²⁺-ATPase),对扇贝肌原纤维蛋白(Mf)的稳定性进行了系统探索。首先,分别提取闭壳肌肌原纤维(A-Mf)和外套膜肌原纤维(M-Mf);然后,考察了不同因素(离子强度I、pH、温度)对Mf的ATPase活性的影响规律;对A-Mf及M-Mf的稳定性进行了探索;进一步比较了闭壳肌和外套膜肌原纤维蛋白ATPase的失活特性。研究结果表明:(1)虾夷扇贝闭壳肌与外套膜的Mf的理化性质相似,A-Mf与M-Mf的pI均在5.0附近,粘度分析发现A-Mf热稳定性高于M-Mf。(2)ATPase活性变化规律的结果发现,与脊椎动物中的鱼类一样,作为无脊椎动物的扇贝,与Mg²⁺-ATPase相比,Ca²⁺-ATPase更能准确地反映Mf的稳定性。(3)闭壳肌和外套膜二者的Mf的Ca²⁺-ATPase呈现出共同特性,在pH为中性时活性最高;A-Mf与M-Mf的差异性则表现为前者的Ca²⁺-ATPase在较低离子强度(I=0.2)下活性最高,后者则在较高离子强度(I=0.5)下活性最高;离子强度对A-Mf的热稳定性影响不明显,而M-Mf的热稳定性明显受到离子强度的影响,其在较低离子强度下表现出更好的稳定性。(4)Ca²⁺-ATPase失活速率的研究发现,无论是闭壳肌还是外套膜,其稳定性与离子强度I和温度均呈现显著正相关(R²=0.8181、0.8436和R²=0.9887、0.9557);二者在pH 7.0左右的稳定性最好,偏离中性会促使Ca²⁺-ATPase失活,与碱性条件相比,酸性对蛋白质稳定性的破坏更加明显。  相似文献   

The tilapia prolactin cell: A model for stimulus-secretion coupling     

E. Gordon Grau  Lisa M. H. Helms 《Fish physiology and biochemistry》1989,7(1-6):11-19

The tilapia prolactin (PRL) cell responds rapidly (10–20 min) to small physiological changes in medium osmotic pressure (OP), releasing increasing quantities of hormone as medium OP is reduced. This release is rapidly (≤ 10 min) inhibited by somatostatin (SRIF). There is now extensive evidence that tilapia PRL cell function is regulated through the second messengers Ca⁺⁺ and cAMP. Our studies have shown that PRL release is augmented by treatments that lead to increased levels of intracellular Ca⁺⁺ or cAMP. On the other hand, PRL release is blocked when tissues are incubated in Ca⁺⁺-depleted medium or upon the addition of Co⁺⁺, an inhibitor of Ca⁺⁺-mediated processes. The use of⁴⁵Ca⁺⁺ to characterize the movement of Ca⁺⁺ into PRL cells has provided evidence that an increase in the influx of extracellular Ca⁺⁺ may participate in PRL release upon exposure to hyposmotic medium. Our studies have also shown that SRIF suppresses the increase in⁴⁵Ca⁺⁺ accumulation that is brought about when OP is reduced. We have also examined the effects of OP and SRIF on cAMP levels. The reduction of medium OP did not alter cAMP metabolism during 20 min of incubation. By contrast, cAMP accumulation in the presence of IBMX was enhanced at 1 hr of incubation in reduced OP. Thus, an increase in cAMP turnover may play a role in maintaining PRL release under sustained stimulation. SRIF reduced the accumulation of cAMP during 10 min of incubation with IBMX and also reduced the forskolin-stimulated increase in cAMP. Thus, SRIF may suppress adenylate cyclase activity. Finally, our studies have revealed that the forskolin-stimulated increase in cAMP levels is not dependent upon medium Ca⁺⁺. The presence of Ca⁺⁺ in the medium is required, however, for PRL release even when the cAMP messenger system has been activated. Moreover, cAMP accumulation was augmented when intracellular Ca⁺⁺ was increased. This raises the possibility that reduced OP may stimulate an increase in cAMP turnover indirectly through its action(s) on cytosolic Ca⁺⁺.  相似文献   

Insemination, fertilization and gamete management in tench, Tinca tinca (L.)     

OTOMAR LINHART  MAREK RODINA  MARTIN KOCOUR  DAVID GELA 《Aquaculture International》2006,14(1-2):61-73

Various procedures for artificial insemination in tench, Tinca tinca (L.) were re-examined with evaluation of fecundity of males and females among different tench strains. The objectives of this study were to enhance fertilization and hatching rates through optimization of the activation solution, the insemination process, the activation of gametes, and the elimination of eggs stickiness. Sperm for all experiments was collected directly into immobilization solution of modified Kurokura solution containing 180 mM of NaCl and stored at 2 °C for 2.5–5 h prior to the experiment. When dechlorinated tap water was used for activation a gamete ratio of 1150 spermatozoa per egg showed the best significant fertilisation and hatching rates. Optimal ratio between eggs (weight in g) and activation solution (in cm³) was 1:1. Different concentrations of activation solutions such as NaCl from 0 to 68 mM (0–136 mOsmol kg⁻¹) without buffer statistically decreased fertilization and hatching rates. The activation solution containing 17 mM of NaCl, 10 mM Tris–HCl, pH 8 and 9 significantly increased fertilization and hatching rates compared to dechlorinated tap water of pH 7 or activation solution containing 17 mM of NaCl, 10 mM Tris–HCl, pH 6 and 7. Adhesiveness of the eggs was successfully removed by incubation in Alcalase and activity: 3.16 Anson units per cm³.  相似文献   

Influence of ionic composition on acid-base regulation in rainbow trout (Oncorhynchus mykiss) exposed to environmental hypercapnia     

B. K. Larsen  F. B. Jensen 《Fish physiology and biochemistry》1997,16(2):157-170

The influence of ambient calcium, bicarbonate and chloride levels on acid-base regulation was investigated in rainbow trout acclimated and exposed to hypercapnia in five different water types. In soft water (low [Ca⁺⁺] and [HCO₃ ⁻]), compensation of the respiratory acidosis was slow and incomplete within 72h. High ambient [HCO₃ ⁻] clearly improved extracellular HCO₃ ⁻ accumulation, and pH recovery was accomplished within 24h. This may result from stimulation of branchial HCO₃ ⁻ (influx)/Cl⁻ (outflux) exchange. Elevation of ambient [Cl⁻] had a small, positive effect on pH compensation. High ambient [Ca⁺⁺] improved the degree of pH compensation. Plasma [HCO₃ ⁻] and [Cl⁻] showed an inverse 1:1 relationship in all acclimation groups, revealing an ubiquitous chloride-mediated acid-base regulation. Ventilation activity was increased by hypercapnia and only returned to control values in hard water (high [HCO₃ ⁻]and [Ca⁺⁺]). During progressive hypercapnia (up to 3% CO₂), hard water acclimated fish obtained significantly higher plasma [HC0₃ ⁻] (51.2 mM) than fish acclimated to low [Ca⁺⁺]/high [HCO₃ ⁻] (44.7 mM). This suggests an additive effect of ambient Ca⁺⁺ on plasma HCO₃ ⁻ accumulation. At levels of CO₂ above 1%, some mortality was induced in low [Ca⁺⁺]/high [HCO₃ ⁻] water. Dying fish could be distinguished from surviving fish by an excessive Cl⁻loss and increasing extracellular anion gap.  相似文献   

Enhanced hypoosmoregulatory response to growth hormone after cortisol treatment in immature rainbow trout,Salmo gairdneri     

Steffen S. Madsen 《Fish physiology and biochemistry》1990,8(4):271-279

The growth-independent effect of ovine growth hormone (oGH) and oGH + cortisol treatment on seawater (SW) adaptation in immature rainbow trout, Salmo gairdneri was investigated. Fish were injected every second day with saline, 2.0 μg oGH/g or 2.0 μg oGH + 8.0 μg cortisol/g for a maximum of 8 injections in freshwater (FW). Subgroups were transferred to 28‰ SW after 4 or 8 injections, and changes in plasma Na⁺ and Cl⁻, muscle water content and gill Na⁺/K⁺-ATPase activity were measured. In both of the hormone-treated groups retained in FW, gill Na⁺/K⁺-ATPase activity and interlamellar chloride cell density increased. The effects were most pronounced in the oGH + cortisol group after 2 weeks of treatment. After transfer to SW most of the control fish died due to the osmotic stress, whereas in the hormone-treated groups, mortality was low and there was a positive correlation between pretransfer gill Na⁺/K⁺-ATPase and the ability to maintain ionic-osmotic homeostasis after SW transfer. After two weeks of oGH + cortisol treatment, gill Na⁺/K⁺-ATPase activity was maximal. In contrast, after SW transfer, Na⁺/K⁺-ATPase activity increased further in the oGH-treated group. This group regulated ionic-osmotic parameters less effectively than the oGH + cortisol-treated group. The data indicate that GH and cortisol are important hormones in the regulation of hypoosmoregulatory mechanisms in S. gairdneri.  相似文献   

Catechol-O-methyltransferase in the brain of the male African catfish,Clarias gariepinus; distribution and significance for the metabolism of catecholestrogens and dopamine     

R. J. M. Timmers  J. G. D. Lambert 《Fish physiology and biochemistry》1989,7(1-6):201-210

Catechol-O-methyltransferase, involved in the methylation of catechol substrates, was localized in the brain of the male African catfish,Clarias gariepinus, by means of a radiometric assay using [Methyl-³H]S-adenosylmethionine as methyldonor and catecholestrone as substrate. Fore- and midbrain were divided into eighteen, 500 μm thick, transverse sections. With a hollow needle (diameter 1 mm), specific areas of the brain were punched out and assayed. The catechol-O-methyltransferase activity was calculated from the amount of radioactive methoxyestrone formed from catecholestrone and expressed in pmol.mg⁻¹ tissue.h⁻¹. The enzyme could be demonstrated throughout the brain. Although the enzyme activity did not differ very much between the various brain regions (max. 15.4; min. 7.5 pmol), there were some areas in the brain with a more than average activity,i.e., the lateral telencephalon (10.3 pmol), the nucleus preopticus (13.1 pmol), nucleus lateralis tuberis (11.0 pmol) and nucleus recessus posterioris (12.0 pmol) of the diencephalon, the tectum opticum (15.4 pmol) and torus semicircularis (13.6 pmol) of the mesencephalon, and the caudal cerebellum of the metencephalon (10.8 pmol). The lowest activity was detected in the caudal metencephalon (7.5 pmol). The presence of the enzyme catechol-O-methyltransferase in the brain of the African catfish and the observation that both catecholestrogens and dopamine can be methylated by this enzyme suggest that catecholestrogens can influence the methylation (inactivation) of dopamine. Incubations of forebrain homogenates with dopamine and catecholestrone or catecholestradiol confirmed that both catecholestrogens can inhibit the methylation of dopamine. Lineweaver-burk plots with various concentrations of the catecholestrogens indicated that the inhibition is competitive. Dixon plots from the inhibition studies gave inhibition constants of 1.4 and 0.6 μM for catecholestrone and catecholestradiol, respectively, indicating that catecholestradiol is a two times stronger inhibitor than catecholestrone. The significance of the inhibition of the methylation of dopamine by the catecholestrogens in the brain is discussed in the light of the negative feedback of gonadal steroids on the central regulation of reproductive processes.  相似文献