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21.
22.
The present study elucidates the relationship between deep-hole MR cells (Lee et al. 1996) and salinity adaptation in tilapia (Oreochromis mossambicus). Freshwater tilapia were transferred to salt water of various salinities, i.e., 5 (hypotonic), 10 (isotonic), 20 (hypertonic), and 30 (hypertonic), for 2 weeks. The density of MR cells, protein content, activity, and localization of the sodium pump were examined. There was no significant difference in serum osmolarity and Na+, K+, Cl– levels in fish of the various treatment groups. The amounts of protein and activity of Na,K-ATPase were elevated in fish from SW with the highest salinity. MR cells observed by scanning electron microscope revealed small pits (0.5–1.0 m in diameter) in groups from hypotonic and isotonic water and large crypts (2.4–3.8 m in diameter) in fish from hypertonic water. Moreover, the density of these deep-hole MR cells increased significantly in fish adapted to hypertonic SW. Larger and more numerous deep-hole MR cells of euryhaline tilapia may account for higher protein amounts and activities of Na,K-ATPase, probably to meet the physiological demand of euryhaline teleosts engaged in hyporegulation. 相似文献
23.
The surface binding characteristics and permeability properties of the endothelium of secondary lamellae from the gills of
several species of marine teleosts were investigated by introducing cationized ferritin and native ferritin into the microcirculation
under normal environmental conditions. Neither type of ferritin bound to the luminal surface of the gill endothelium. No transcellular
movement of cationized ferritin was detected, either via transendothelial channels or individual vesicles, nor was passage of cationized ferritin through the tight intercellular
junctions of the endothelium observed. Anionic binding sites in the endothelial basement membranes could not be identified.
Binding and transport of ferritin were unaffected by normal changes in environmental temperatures over the range of -2 to
+ 15°C. These findings suggest that the endothelial cell surface of the gills from these fishes is a primary barrier to the
extracapillary movement of blood borne constituents. 相似文献
24.
James O Harris Mark D Powell Michael G Attard & Luke DeHayr 《Aquaculture Research》2005,36(8):776-784
Infections of gill amoebae that manifest as amoebic gill disease (AGD) occur in Atlantic salmon in Tasmania. The treatment of choice is freshwater bathing; however, the effectiveness of this treatment has declined over time. In this experiment, cage trials of chloramine‐T (Cl‐T) to treat AGD in Atlantic salmon were conducted over 3 months, and involved an initial bath in either freshwater or seawater with Cl‐T, followed by a second bath 6 weeks later. Amoeba densities were reduced to 50–80% of original values for both treatments. Neoparamoeba sp. density was not affected by bathing, and was not significantly different over the course of the experiment. Lesion prevalence was higher for Cl‐T‐treated fish than for freshwater‐treated fish, with overall prevalence levels of 14.30±1.00% and 8.03±0.57% respectively. This was also seen for gross gill scores. In the fortnight after each of the two baths, Cl‐T‐treated fish had significantly higher lesion levels, although this difference was then resolved by 4 weeks post bathing. The use of Cl‐T in seawater is at least as effective as freshwater at reducing amoebae density, and may be a more practical alternative when freshwater is in short supply. 相似文献
25.
The drinking rate of cod larvae 1–7 days post hatching was measured from the uptake of3H-labelled dextran (MW = 70000) admixed in the incubation seawater (34 ppt 5°C). The drinking rate increased gradually from 0.15% to 0.59% of the larval body weight on day 1 and day 7 respectively. This increase in drinking rate correlated with an observed decrease in the volume of the yolk sac and its water store. Autoradiographs showed the labelled dextran to be confined to the intestine. Electron micrographs showed an open mouth communicating with the oesophagus and the intestine in cod larvae at the time of hatching. Chloride cells were present on the opercular folds but not on the vestigial, developing gills. The data indicate that the water acquisition mechanism of larval cod is similar to that of adult marine fish. 相似文献
26.
Pieter M. Verbost Gert Flik James C. Fenwick Anna-Maria Greco Peter K. T. Pang Sjoerd E. Wendelaar Bonga 《Fish physiology and biochemistry》1993,11(1-6):205-215
The branchial Ca2+ uptake by teleost fish is under inhibitory control by the hormone stanniocalcin (STC) which is generated by the corpuscles
of Stannius (CS). Removal of the CS in North American eel, Anguilla rostrata LeSueur, induced a rapid rise in blood calcium levels. Branchial Ca2+ influx following the extirpation of the CS (stanniectomy, STX) increased during the first four days and stayed elevated thereafter
(in agreement with previous studies). The transepithelial potential (TEP) across the gills did not change after STX and this
means that the electrochemical gradient for Ca2+ is less favourable for passive influx of Ca2+ in STX eel. Therefore, the Ca2+ influx in STX eels is a transcellular flux, with Ca2+ crossing the apical and basolateral membrane barrier. The kinetics of ATP-driven Ca2+-transport across basolateral plasma membranes from eel gills did not change after STX. Thus, the increased Ca2+-influx after STX is not correlated with changes in ATP-dependent Ca2+-extrusion across the basolateral membrane, suggesting a regulation at the apical membrane. Moreover, STC did not affect ATP-driven
Ca2+-transport in isolated basolateral membranes (in vitro). STC (0.1 nM) reduced cAMP levels in dispersed eel gill cells. It had no significant effect on the IP3 levels in these cells. We postulate that STC controls the permeability to Ca2+ of the apical membranes of the Ca2+ transporting cells of fish gills by controlling second messenger operated Ca2+ channels in the apical membrane.
Résumé L'entrée de calcium au niveau des branchies est sous le controle inhibiteur de la stanniocalcine (STC) qui est synthétisée au niveau des corpuscules de Stannius (CS). L'ablation des CS chez l'anguille d'Amérique du Nord, Anguilla rostrata LeSueur, induit une augmentation rapide des niveaux de calcium dans le sang. Le flux entrant branchial de calcium consécutif à l'ablation des CS (stanniectomie, STX) augmente pendant les 4 premiers jours et reste élevé au-delà (en accord avec des études antérieures). Le potentiel transépithélial (TEP) à travers les branchies ne change pas après STX, ceci indiquant que le gradient électrochimique du Ca2+ est moins favorable pour le flux entrant passif du Ca2+ chez l'anguille STX. En conséquence, le flux entrant de Ca2+ chez l'anguille STX est un flux transcellulaire, avec le Ca2+ traversant la barrière membranaire apicale et basolatérale. La cinétique du transport de Ca2+ conduit par l'ATP à travers les membranes plasmatiques basolatérales de branches d'anguille n'est pas modifiée après STX. Ainsi, l'augmentation du flux entrant de Ca2+ après STX n'est pas corrlée avec des modifications de l'excrétion de Ca2+ conduit par l'ATP à travers la membrane basolatérale, suggérant donc une régulation au niveau de la membrane apicale. De plus, la STC ne modifie pas le transport de Ca2+ conduit par l'ATP dans des membranes basolatérales isolées (in vitro). La STC (0.1 nM) réduit les niveaux d'AMPc dans des cellules dispersées de branchies d'anguille. Cette hormone n'a pas d'effet significatif sur les niveaux d'IP3 dans ces cellules. Nous suggérons que la STC régule la perméabilité au Ca2+ des membranes apicales des cellules branchiales transporteuses de Ca2+ en controlant un second messager agissant sur les canaux calciques de la membrane apicale.相似文献
27.
The cardiovascular effects of the kallikrein-kinin system (KKS) have not been completely characterized in lower vertebrates. In the present study, a specific, irreversible kallikrein inhibitor, Phe-Phe-Arg-chloromethyl ketone (PPACMK) was used to examine: 1. the role of the KKS in blood pressure regulation in vivo; 2. the nature of the pressor substance formed by the action of kallikrein on trout plasma in vivo and in vitro; and 3. the presence of kallikrein in trout gills and kidney. Dorsal aortic cannulated rainbow trout were used for in vivo blood pressure assays and two colorimetric serine-protease assays were used to examine tissue kallikrein activity. PPACMK alone had no effect on blood pressure in vivo. Pretreatment of porcine kallikrein with PPACMK inhibited the enzyme's pressor effect in trout by 80% and significantly attenuated the synthesis of vasopressor substance(s) from heat-treated trout plasma in vitro. Approximately 30% of gill serine protease activity was inhibited by pretreatment with PPACMK; no PPACMK-sensitive kallikrein activity was observed in the kidney. Salt water adaptation did not affect kallikrein-specific activity in the gill. These results show that the salmonid KKS does not appear to be involved in the regulation of systemic blood pressure. Further, the formation of pressor substances from trout plasma in vivo and in vitro is due to kallikrein activity and the peptides generated are similar. A kallikrein, similar to the mammalian enzyme, is found in trout gills, suggesting that the salmonid KKS may be a local mediator of gill function. 相似文献
28.
《African Zoology》2013,48(2):342-347
Diurnal birds generally sleep during the hours of darkness. Most male southern African sunbirds have pectoral tufts, although the function of these is not always understood. We examined nocturnal tuft display in male malachite sunbirds (Nectarinia famosa) and found that they display their pectoral tufts almost continuously throughout the night, whilst asleep. We suggest the possible function of this behaviour and suggest that these tufts might be a deterrent to predators, as they look like ‘eyes’ in the dark. A review of the use and occurrence of pectoral tufts in southern African sunbird species is also discussed. We suggest the ‘anti-predator’ hypothesis be investigated further. 相似文献
29.
Candidatus Actinochlamydia pangasiae sp. nov. (Chlamydiales,Actinochlamydiaceae), a bacterium associated with epitheliocystis in Pangasianodon hypophthalmus 下载免费PDF全文
N Sood D K Verma M K Yadav Ravindra A K Dev T R Swaminathan N K Sood 《Journal of fish diseases》2018,41(2):281-290
Chlamydial infections are recognised as causative agent of epitheliocystis, reported from over 90 fish species. In the present study, the farmed striped catfish Pangasianodon hypophthalmus (14–15 cm, 70–90 g) with a history of cumulative mortality of about 23% during June and July 2015, were brought to the laboratory. The histopathological examination of gills from the affected fish revealed presence of granular basophilic intracellular inclusions, mostly at the base of the interlamellar region and in gill filaments. A concurrent infection with Trichodina spp., Ichthyobodo spp. and Dactylogyrus spp. was observed in the gills. The presence of chlamydial DNA in the gills of affected fish was confirmed by amplification and sequencing of 16S rRNA gene. BLAST‐n analysis of these amplicons revealed maximum similarity (96%) with Candidatus Actinochlamydia clariae. On the basis of phylogenetic analysis, it was inferred that the epitheliocystis agents from striped catfish were novel and belonged to the taxon Ca. Actinochlamydia. It is proposed that epitheliocystis agents from striped catfish will be named as Ca. Actinochlamydia pangasiae. The 16S rRNA gene amplicons from novel chlamydiae were labelled and linked to inclusions by in situ hybridisation. This is the first report of epitheliocystis from India in a new fish host P. hypophthalmus. 相似文献
30.
Ève B. Dussault Richard C. Playle D. George Dixon R. Scott McKinley 《Fish physiology and biochemistry》2001,25(4):347-357
Doppler flow probes were fitted around the ventral aorta of rainbow trout, which were exposed to combinations of pH and aluminum (pH 5.1–6.2, Al 0–80 g l–1) for 60 h. Fish accumulated Al at the gill and exhibited decreased blood Na+, Cl–, and Ca2+ concentrations, and increased K+, hematocrit, hemoglobin, glucose, and lactate, indicating increasing ionoregulatory disturbance with increasing Al concentration. Fish exposed to ambient water (6.2) or low-pH (5.3) water without Al exhibited slight reductions in heart rates, as well as increased stroke volume, resulting in little variation in cardiac output. In the presence of Al (20 to 40 g l–1) at low pH (5.1–5.3), fish increased their heart rate slightly and generally maintained their stroke volume, resulting in increased cardiac output in the first two days of exposure. At the highest Al concentration (80 g l–1, pH 5.1), tachycardia was observed, concomitant with a decrease in stroke volume. The ionoregulatory imbalance and resulting increased blood viscosity explain these increases in heart rate rather than stroke volume in fish exposed to high concentrations of Al. 相似文献