重金属离子Cd2+对泥蚶鳃及肝脏细胞显微和超微结构的影响

研究了镉(Cd)的各个不同暴毒浓度(5,15,45,90μg/L)对泥蚶鳃和肝脏组织显微结构的影响,及高浓度暴毒情况下对泥蚶鳃和肝脏组织超微结构的影响。实验处理时间为96 h。结果发现,随着暴毒浓度的升高,鳃丝内腔隙肿胀,内有血细胞堆积,最后鳃丝出现断裂融合,其上的呼吸上皮细胞脱落,超微结构发现鳃上皮细胞中出现黑色嗜锇性物质,且次级溶酶体和线粒体数量都增加,最后细胞内出现空泡现象;Cd对肝脏显微结构的影响不大,仅出现了黄色沉积物,超微结构表明,肝细胞内亦出现了嗜锇性物质,次级溶酶体亦大量增加,这些现象与鳃丝内出现的情况一致,且肝细胞核还出现变形皱缩,甚至产生空泡,细胞出现了不可逆的损伤。最为敏感的线粒体和内质网没有出现损伤现象,研究推测可能是由于机体内Cd诱导产生的抗氧化活性酶作用的结果。     

三角帆蚌怀卵期外侧瓣鳃结构初步研究

对怀卵期三角帆蚌的外侧瓣鳃分别从水平、横、纵等三个方向作组织切片,利用光镜观察其组织形态结构。结果显示,在怀卵期外侧瓣鳃增至(2 876.77±123.58)μm,两鳃小瓣之间被鳃间隔分成许多鳃小腔,其宽度为(474.06±32.01)μm(纵切),(410.74±70.69)μm(水平切)。瓣间隔的厚度为(244.92±17.23)μm(纵切),(288.80±35.16)μm(水平切)。从横切面观察,瓣间隔又由横向隔板组成瓣间隔孔,隔板宽度为(309.2±50.56)μm,两隔板间的孔宽度为(365.22±37.74)μm。鳃小腔通过瓣间隔孔而互相连通,从而形成鳃腔育儿囊。同时还观察到:在胚胎发育初期,受精卵被粘液状物质包裹,随着孵化的进行包裹物逐渐消失。     

雌性三角帆蚌外鳃组织形态周年变化及低氧胁迫对外鳃组织形态和酶活性影响

雌性三角帆蚌的外鳃不仅是呼吸器官,而且在繁育时期行使胚胎发育的育儿囊功能,繁育期鳃腔充满早期胚胎,呼吸效率降低。通过石蜡切片观察雌性三角帆蚌外鳃组织形态周年变化,并探究低氧环境对雌性三角帆蚌外鳃组织形态及酶活性的影响。结果表明,雌性三角帆蚌外鳃鳃瓣1月份最薄,至5月份增至最厚,较1月份显著增厚173.86%,随后鳃瓣逐渐变薄,其鳃小腔宽度随鳃瓣厚度增厚也显著增大,至6月增至最宽较1月份显著增宽171.22%,随后鳃小腔逐渐变窄;且3~6月在雌性三角帆蚌外鳃发育为育儿囊,其中发现大量早期胚胎。在低氧环境下,乳酸脱氢酶（LDH）活性在1~5天逐渐升高,第5天达到最大值,较对照组显著提升131.1%,5~9天缓慢下降;超氧化物歧化酶（SOD）活性在1~7天逐渐下降,在第7天达到最小值,较对照组显著降低40.53%,7~9天缓慢上升;过氧化氢酶（CAT）活性在1~7天逐渐上升,7~9天无明显变化,第7天活性最高,较对照组显著提升91.34%,琥珀酸脱氢酶（SDH）活性在1~9天呈下降趋势,最低值出现在第9天,较最对照组显著降低68.9%;低氧胁迫5天后,外鳃侧纤毛较对照组增宽了79.58%,外鳃小水管较对照组增宽了248.73%。本研究分别为怀卵期雌性三角帆蚌外鳃组织结构变化和低溶氧对雌性三角帆蚌外鳃组织结构和酶活性的影响提供了基础资料,为提升三角帆蚌繁育技术提供了理论依据。     

三角帆蚌胚胎在外鳃育儿囊内形态变化初步研究

对三角帆蚌胚胎在其外鳃育儿囊内的形态变化进行了显微观察。结果表明：在水温20℃-23℃时，受精卵发育为膜内钩介幼虫需11d；受精卵吸水后，卵膜膨胀，在整个发育过程中，其大小无显著变化，但膜内胚胎生长明显；整个发育期分为受精卵、卵裂期、原肠期、膜内钩介幼虫期，经过这4个时期，胚胎最大长度增长了82．8％，生长速度在后期快于前期，并且以原肠期和膜内勾介幼虫期增长速度最快。胚胎发育的不同时期与外鳃特征具相关性。     

Efficacy and toxicity of oxidative disinfectants for the removal of gill amoebae from the gills of amoebic gill disease affected Atlantic salmon (Salmo salar L.) in freshwater

Amoebic gill disease (AGD) of Atlantic salmon is treated commercially by bathing affected fish in freshwater. Recently, the efficacy of freshwater bathing has been questioned, and the aim of this study was to examine the potential for improving bathing efficacy using additives to the freshwater bath. AGD‐affected Atlantic salmon were bathed in 350 L tanks containing oxygenated freshwater to which chlorine dioxide (0–50 mg L^?1), chloramine‐T (0–50 mg L^?1) or hydrogen peroxide (0–100 μL L^?1) was added. Before and following a 3‐h exposure to the freshwater and chemical additive, the gills were removed from a sub‐sample of fish and the number of live amoebae on the gills were counted and smears made for confirmation of the presence of Neoparamoeba pemaquidensis, the causative agent of AGD. Following a further 3‐h exposure, a sub‐sample of fish was bled from the caudal vein and the gills were removed for histological examination. Chlorine dioxide and chloramine‐T at 25–50 and 10–50 mg L^?1, respectively, reduced the number of amoebae on the gills by approximately 50% compared with pre‐exposure numbers. The results from hydrogen peroxide treatment were equivocal and the toxicity of hydrogen peroxide was high. The toxicity of chlorine dioxide varied with freshwater hardness and/or suspended solid load, whereas chloramine‐T toxicity was low, with mortalities attributable only to elevated temperatures at the highest concentration tested. In conclusion, chlorine dioxide and chloramine‐T show promise as potential freshwater additives for the improved removal of N. pemaquidensis and possibly, other amoebae from the gills of commercially farmed Atlantic salmon.     

New methods for the primary culture of gill epithelia from freshwater rainbow trout

Gill epithelia from freshwater rainbow trout can be grown in primary culture in Leibovitz's L-15 medium, by seeding freshly isolated gill cells on two successive days, from two different fish, directly onto permeable filter supports (DSI technique). This preparation allows the measurement of transepithelial resistance (TER) and exposure of the apical surface to freshwater, as in vivo. New culture methods were developed and evaluated, using TER as an indicator of epithelial integrity, in an effort to improve the utility of the preparation for proteomic and toxicological research. TER was not related to cell density or protein content in DSI epithelia. To eliminate bovine proteins, the 5% foetal bovine serum (FBS) normally required for epithelial development was replaced with trout plasma. While previously frozen trout plasma proved toxic, freshly collected heparinized plasma, provided by chronically cannulated adult trout, was not. The use of 5% fresh trout plasma supported a TER development curve identical to that with 5% FBS, a useful advance for proteomic research because foreign (bovine) proteins are eliminated. However, 10% plasma reduced TER development, and 100% plasma abolished it. The inhibitory effect on TER of high plasma levels was seen only early in epithelial development, and was exerted from the apical side, likely an effect on tight junction formation. Mature plasma-supplemented preparations mounted a TER rise in response to apical freshwater exposure comparable to that of FBS-supplemented epithelia. Yolk-sac fry extract was inhibitory to TER development, even in the presence of 5% FBS. Transfer of mature epithelia from 18 °C to 4 °C maintained stable TER and extended the useable lifespan by at least ten days, thereby facilitating storage of preparations for toxicity testing. A new method of growing epithelia, involving only a single seeding of cells from a single fish, directly onto filter inserts (SDSI technique), provided mature epithelia with much lower TER, a smaller TER response to apical freshwater, and lower cell density and protein content than DSI epithelia. These SDSI epithelia offer the advantage of multiple preparations grown directly from unique individuals for in vitro toxicity testing. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dependence on body size of respiratory function in Hoplias malabaricus (Teleostei,Erythrinidae) during graded hypoxia

Oxygen uptake and ventilatory responses to environmental hypoxia were assessed for two groups of Hoplias malabaricus of nearly tenfold different body weights (mean weights, group I = 39 g; group II = 365 g). The main purpose of the study was to evaluate the relationships between body weight and the critical O₂ tension (P_CO₂) for maintenance of normal resting O₂ uptake. The smaller specimens had a threefold larger weight-specific O₂ uptake compared to that of the larger specimens. Moreover, smaller size coincided with a higher P_CO₂, i.e., a more limited range for maintenance of O₂ uptake during hypoxia. Likewise, at any inspired PO₂ the weight-specific gill ventilation was largest for group I. This was most pronounced during severe hypoxia where both tidal volume and respiratory frequency increased markedly. In addition, the oxygen cost of breathing tended to be highest in the smaller individuals. The results open questions as to correlations between development, weight-dependent O₂ demands, and tolerance to hypoxia on an intraspecific level.     

多氯联苯对剑尾鱼Na^＋／K^＋—ATPase活性的影响

采用毒性实验的方法，定量地研究了多氯联苯暴露对剑尾鱼肝脏、卵巢及鳃组织中Na^ ／K^ —ATPase活性的影响。结果表明：不同组织其Na^ ／K —ATPase活性的高低存在明显差异。多氯联苯对剑尾鱼肝脏及卵巢的Na^ ／K^ —ATPase活性有抑制作用但不显著；对鳃的Na^ ／K^ —ATPase活性则显示有显著的抑制作用，并随暴露浓度和时间的增加而提高。3种组织中鳃Na^ ／K^ —ATPase对多氯联苯显得更为敏感。     

苏氏Mang鲶鳃超微结构观察

对苏氏Mang鲶鳃结构进行扫描和透射电镜观察。Mang鲶鳃丝末端膨大呈杓状结构，每一鳃丝两侧具有许多呈褶状的鳃小片，相邻两鳃丝上的鳃小片紧密镶嵌排列。鳃弓和鳃耙表面分布众多味蕾。鳃丝呼吸面上皮细胞薄，高度血管化，形成呼吸面隆起，非呼吸面由微脊细胞彼此相连，间缝具分泌细胞开口。鳃小片由单层或数层外上皮细胞和由基膜相隔的柱状细胞及其围在血管腔的凸缘构成，氯细胞多分布在鳃小片基部，并有开口通外，还探讨了Mang鲶鳃丝和鳃小片特殊的结构与功能。