Physiology of fish endocrine pancreas

From the very beginning of physiological studies on the endocine pancreas, fish have been used as experimental subjects. Fish insulin was one of the first vertebrate insulins isolated and one of the first insulins whose primary and then tertiary structures were reported. Before a second pancreatic hormone, glucagon, was characterized, a physiologically active ‘impurity’, similar to that in mammalian insulin preparations, was found in fish insulins. Fish have become the most widely used model for studies of biosynthesis and processing of the pancreatic hormones. It seems inconceivable, therefore, that until the recent past cod and tuna insulins have been the only purified piscine islet hormones available for physiological experiments. The situation has changed remarkably during the last decade. In this review the contemporary status of physiological studies on the fish pancreas is outlined with an emphasis on the following topics: 1) contents of pancreatic peptides in plasma and in islet tissue; 2) actions of piscine pancreatic hormones in fish; 3) specific metabolic consequences of an acute insufficiency of pancreatic peptides; 4) functional interrelations among pancreatic peptides which differ from those of mammals. The pitfalls, lacunae and the perspectives of contemporary physiological studies on fish endocrine pancreas are outlined.     

6 种胃肠激素样内分泌细胞在细鳞鲑消化道的定位

采用免疫细胞化学ABC方法,选择5-羟色胺(5-hydroxytryptamine,5-HT)、生长抑素(somatostatin,SS)、胰多肽(pancreatic polypeptide,PP)、胃泌素(gastrin,GAS)和P物质(substance P,SP)6种特异性哺乳类胃肠激素抗血清,对不同年龄段(1龄、2龄和3龄)细鳞鲑(Brachymystax lenok)的消化道内分泌细胞进行了免疫细胞化学定位研究.结果表明,仅在食管、胃贲门、胃体和胃幽门检出有5-HT、SS和PP阳性细胞的分布(除1龄鱼食道),且这3种内分泌细胞均大量定位于胃部;在前肠、中肠、后肠和直肠中均未检测到这3种内分泌细胞的阳性反应.在3个年龄段的细鳞鲑胃肠各部位均未检测到GAS、GLU和SP阳性细胞.细鳞鲑的5-HT、SS和PP与其他有胃鱼类的内分泌细胞一样,可分为2种类型,即开放型和闭合型,这类细胞主要通过腔分泌和旁分泌两种方式释放激素.5-HT、SS和PP这3种细胞在1龄幼鱼消化道内就已经发育成熟,其对胃肠道活动的调节作用已经与成鱼没有差别,细胞的分布密度随着细鳞鲑的年龄增长不断增加.本研究揭示了不同生长阶段细鳞鲑消化道中这6种胃肠激素内分泌细胞的发育特征,并阐明了这些胃肠激素细胞在细鳞鲑幼鱼消化道的分布、形态以及生理作用.     

鱼类消化道内分泌细胞概述及研究方法

消化道内分泌细胞能产生多种具有调节胃肠功能的胃肠激素。该类激素除了能促进胃肠对营养物质的消化与吸收外,还能控制摄食行为、调控消化道运动以及细胞营养作用,甚至能够影响其他一些内分泌腺的活动。了解肠道内分泌细胞的基本概况有助于深入地研究鱼类的消化生理,组织化学、免疫细胞化学和电子显微镜等技术是研究消化道内分泌细胞鉴别、定位...     

鱼类消化道内分泌细胞概述及研究方法

消化道内分泌细胞能产生多种具有调节胃肠功能的胃肠激素。该类激素除了能促进胃肠对营养物质的消化与吸收外,还能控制摄食行为、调控消化道运动以及细胞营养作用,甚至能够影响其他一些内分泌腺的活动。了解肠道内分泌细胞的基本概况有助于深入地研究鱼类的消化生理,组织化学、免疫细胞化学和电子显微镜等技术是研究消化道内分泌细胞鉴别、定位以及形态学的重要方法,利用这些技术能够揭示鱼类消化道内分泌细胞的生物功能及作用机理,对研究鱼类摄食、消化和吸收等生理机制有重要意义。因此,本文综述了近年来国内外鱼类消化道内分泌细胞的研究进展及主要研究手段,旨在为鱼类消化生理学、内分泌学和营养学提供参考资料。     

Effects of lamprey gonadotropin-releasing hormone and analogs on steroidogenesis and spermiation in male sea lampreys

The biological activities of lamprey GnRH and analogs were determined in the adult male lamprey,Petromyzon marinus. Two successive injections of lamprey GnRH at 0.005, 0.065 or 0.163 μg/g body weight or [D-Ala⁶,Pro⁹-NHEt] mammal GnRH at 0.05 μg/g stimulated plasma estradiol and progesterone levels in adult male lampreys undergoing final maturation. In these experiments, a lamprey GnRH putative antagonist, [D-Phe^2,6,Pro³] lamprey GnRH, at 0.075, 0.150 or 0.3 μg/g stimulated plasma estradiol but not progesterone levels. Four successive injections of lamprey GnRH at 0.05 or 0.1 μg/g stimulated plasma progesterone and spermiation. [D-Phe^2,6,Pro³] lamprey GnRH at 0.05 or 0.1 μg/g depressed plasma progesterone levels and inhibited spermiation. In contrast, lamprey GnRH analog, [D-Ala⁶,Pro⁹-OH free carboxylic acid] lamprey GnRH, at 0.05 or 0.1 μg/g stimulated plasma progesterone levels and inhibited spermiation. In summary, lamprey GnRH is biologically active in stimulating the pituitary-gonadal axis in adult male lampreys as determined by steroidogenesis and spermiation.     

Differences in the total lipid and lipid class composition of larvae and metamorphosing sea lampreys, Petromyzon marinus

This study compared the alterations in total lipid and lipid class composition of kidney, liver, and intestine from sea lamprey, Petromyzon marinus, during their nontrophic metamorphosis with these parameters in unmetamorphosed larvae. Total lipid in kidney and liver initially was higher by 104 and 66%, respectively, in the earliest metamorphic stage (3) examined compared to larvae and then decreased by 73 and 37%, respectively, from stage 3 to stage 7. Total lipid in intestine, on the other hand, was 53% lower at stage 3 compared to larvae and then significantly increased by 260% from stage 3 to stage 7. Large amounts of triacylglycerol (TG) in kidney and liver implicate these organs as lipid depots; much of the change in total lipid content of kidney and liver could be explained by alterations in TG, although significant variations in other lipid classes (e.g., phospholipid, cholesterol) also were noted. These results suggest that lamprey metamorphosis may proceed in two metabolic phases in a tissue-specific manner and that lipid depletion results from specific catabolism of stored TG reserves.     

牙鲆消化道组织学观察及内分泌细胞分布

牙鲆(Paralichthys olivaceus)体质量约0.5 kg,活体取材,通过免疫组织化学染色和H.E染色,在光学显微镜下观察牙鲆消化道组织结构。结果表明,牙鲆消化道和高等脊椎动物类似,分为口咽腔、食道、胃、胃盲囊和肠。肠也可分为前肠、中肠和后肠,三者之间没有明显的界限。胃和前肠是消化吸收主要的部位,胃盲囊和前肠结构和功能非常类似。Serotonnin细胞和P Substance细胞在牙鲆胃前部的黏膜中零星分布,在胃体中较多见,平均每104μm2胃体黏膜上皮约各有2.2和2.0个阳性细胞。而Gastrin细胞分布在胃盲囊和前肠中,平均每104μm2黏膜上皮分别有0.98个和0.71个阳性细胞。可见,牙鲆和哺乳动物消化道一样都分布有肽能神经元。这些结果将为神经内分泌系统的研究提供资料。     

Influence of enteric helminths on the distribution of intestinal endocrine cells belonging to the diffuse endocrine system in brown trout,Salmo trutta L

The presence of intestinal helminths in the alimentary canal of brown trout, Salmo trutta L., can alter the number of cells that synthesize modulatory peptides. A total of 167 brown trout were collected from tributaries of the River Brenta (northern Italy), of which 119 (71.3%) specimens were infected with enteric helminths, 28 with the acanthocephalan Pomphorhynchus laevis Müller, 1776 with intensity of infection ranging from 1 to 162 (18.57 +/- 30.79) worms per host and 67 fish with the cestode Cyathocephalus truncatus Pallas, 1781. Intensity of infection with C. truncatus ranged from 1 to 85 (6.87 +/- 12.59) per fish. In 24 fish there were concurrent infections of both species of helminths. The caecal and middle regions of the intestine were the most heavily parasitized. Immunohistochemical tests showed a decrease in endocrine cells (ECs) of the diffuse endocrine system (DES) positive to gastrin, cholecystokinin-8, bombesin and secretin antisera in the intestine of the infected trout. The number of ECs immunoreactive to anti-glucagon serum did not show differences in the digestive tract of uninfected brown trout and in conspecifics parasitized with P. laevis. The density of cells containing glucagon-like material was low in the fish parasitized with C. truncatus. The results suggest that endoparasitic helminths induce alterations in the DES of infected S. trutta.     

中华鳖胃肠胰内分泌细胞的鉴定与定位

应用过氧化物酶标记的链霉亲和素（Streptavidin-peroxidase简称S－P法）免疫组织化学技术，用抗胰高血糖素、胃泌素、生长抑素、5－羟色胺抗体对中华鳖（Trionyx simensis）的胃、肠、胰内分泌细胞进行研究，结果表明：5－HT细胞在消化道各段均有分布，以小肠密度最高，胃、大肠、直肠其次，食管最少。Som细胞在胃底部、幽门部和小肠各段密度较高，胃贲门部、大肠和直肠密度较低。Gas细胞分布于胃体部、幽门部和小肠各段；胃贲门部、大肠和直肠未检出Gas细胞。Glu细胞在消化道各段均未检出，在胰腺中均鉴别出Glu细胞和Som细胞。     

南方鲇胰腺组织结构及胰腺泡的超微结构

南方鲇 (Silurusmeridionalis)具有独立而发达的胰腺 ,为致密型。光镜观察可见 ,胰腺外被覆明显的被膜 ,厚度 5～ 2 2 μm ,发达的结缔组织纤维伸入胰腺内部 ,将腺体分隔成明显的小叶 ;胰腺组织包括外分泌部和内分泌部 ,其外分泌部是 1种管泡状腺 ,包括胰腺泡和排泄管 ;其内分泌部即胰岛 ,细胞中有甲细胞、乙细胞和丁细胞 ,核径分别为 4 .2、5 .0和 5 .3μm ,胞质颗粒分别呈红色、桔黄色和淡蓝色。超微结构观察到 ,胰腺细胞呈锥形 ,细胞中具有大而明显的核仁 ,分布着异常发达的粗面内质网、线粒体和核糖体 ,有丰富的酶原颗粒 ,胰腺细胞排列紧密 ,细胞间界限明显 ,连接复合体、泡心细胞和成纤维细胞非常清晰     

Effect of pancreas disease caused by SAV 2 on protein and fat digestion in Atlantic salmon

Salmonid alphavirus (SAV) causes pancreas disease (PD) in farmed Atlantic salmon (Salmo salar L.), and exocrine pancreas tissue is a primary target of the virus. Digestive enzymes secreted by the exocrine pancreas break down macromolecules in feed into smaller molecules that can be absorbed. The effect of SAV infection on digestion has been poorly studied. In this study, longitudinal observations of PD outbreaks caused by SAV subtype 2 (SAV2) in Atlantic salmon at two commercial sea sites were performed. The development of PD was assessed by measurement of SAV2 RNA load and evaluation of histopathological lesions typical of PD. Reduced digestion of both protein and fat co‐varied with the severity of PD lesions and viral load. Also, the study found that during a PD outbreak, the pen population comprise several subpopulations, with different likelihoods of being sampled. The body length of sampled fish deviated from the expected increase or steady state over time, and the infection status in sampled fish deviated from the expected course of infection in the population. Both conditions indicate that disease status of the individual fish influenced the likelihood of being sampled, which may cause sampling bias in population studies.     

日本鳗鲡胃肠胰内分泌细胞的鉴别与定位

应用过氧化物酶标记的链霉亲和素(streptavidin-peroxidase简称S-P法)免疫组织化学技术,用抗5-羟色胺、生长抑素、胃泌素、β-内啡肽、胰高血糖素抗体对日本鳗鲡的胃肠胰内分泌细胞进行研究。结果表明：日本鳗鲡胃肠道各段均存在5-HT和Som免疫活性内分泌细胞。Gas细胞分布于胃体部、幽门部和前肠、中肠;胃贲门部和后肠未检出Gas细胞。β-内啡肽、Glu细胞在胃肠道各段均未检出。在胰腺中均鉴别出Glu细胞和Som细胞。     

长鳍篮子鱼消化道内分泌细胞的免疫组织化学鉴别和定位

应用4种兔抗胃肠激素抗体和SABC免疫组织化学方法,对长鳍篮子鱼(Siganus canaliculatus)消化道中的内分泌细胞进行鉴别和定位。结果表明:5-羟色胺(5-HT)细胞在消化道各段均有分布,食道和胃中分布数量多,在幽门盲囊和肠道分布数量少;生长抑素(Som)细胞集中位于食道和胃部,数量多,幽门盲囊和肠道中未检出;神经肽Y(NPY)细胞在肠道有少量分布,其余各段均未检出;胃泌素(Gas)细胞在幽门盲囊和肠道有少量分布,食道和胃中均未检出。4种内分泌细胞的数量分布和形态特征存在一定的差异,并对其可能的生理作用进行了讨论。     

哲罗鱼肝脏和胰脏发生和发育的组织学研究

采用形态观察与连续组织切片技术,观察和研究了哲罗鱼（Hucho tai men）肝脏和胰脏在胚胎期（水温7～8℃）和胚后期（水温3～14℃）的发育。结果表明,与大多数硬骨鱼类不同,哲罗鱼的肝脏是在破膜前就开始发生、发育,而胰脏是在破膜后出现,以后逐渐发育完善。受精18 d肝原基细胞出现,破膜8 d,胰细胞出现,破膜8 d肝后部开始贮存脂质,破膜18 d后肝前部开始积累脂质,肝脏发育与卵黄囊有密切的关系。肝脏和胰脏为相互分开的独立器官,具有丰富的肝、胰管。     

哲罗鱼肝脏和胰脏发生和发育的组织学研究

采用形态观察与连续组织切片技术,观察和研究了哲罗鱼（Hucho tai men）肝脏和胰脏在胚胎期（水温7～8℃）和胚后期（水温3～14℃）的发育。结果表明,与大多数硬骨鱼类不同,哲罗鱼的肝脏是在破膜前就开始发生、发育,而胰脏是在破膜后出现,以后逐渐发育完善。受精18 d肝原基细胞出现,破膜8 d,胰细胞出现,破膜8 ...     

Effects of water velocity,turbulence and obstacle length on the swimming capabilities of adult Pacific lamprey

The swimming capabilities of adult Pacific lamprey, Entosphenus tridentatus Gairdner, were tested in an experimental vertical‐slot fishway in response to three different fishway features: water velocity (1.2, 1.8 and 2.4 m s^?1), the length of the vertical slot (0.33, 0.66, 1.00 m) and during the presence/absence of a turbulence‐intensifying structure that increased turbulence for each respective treatment. Passage success was lowest (52.7%) and attachment rates were highest (92.9%) during the most difficult passage conditions (high velocity, high turbulence, long slot length). Passage success was >83% for all other treatment combinations. Although passage of the vertical‐slot weir was not associated with fish body size, Pacific lamprey with larger dorsal distances (distance between the two dorsal fins) were more likely to pass the vertical‐slot weir. Increased attachment rates and longer attachment times during strenuous passage conditions suggest that endurance capacity may be an important factor limiting the passage of Pacific lamprey at fishway obstacles.     

Distribution, growth and transformation timing of larval Geotria australis in New Zealand

Lamprey, Geotria australis, are widely distributed in New Zealand and are common in streams and rivers of the west coast of both islands, the southern tip of the North Island, the Banks Peninsula and the southern coast of the South Island. In fresh water, lamprey are found in association with all substrate types but are most commonly (> 50% of the sample sites) found in association with finer gravels. There is insufficient evidence to determine any change in historically abundant adult spawning migrations. Spawning, back calculated from larval growth rates, probably occurs late November-December, and emergence at 9.63 mm occurs in January. We estimate that, on average, ammocoetes grow 0.068 mm/day throughout the year, and metamorphose and emigrate to sea between January-May, 3.5 years after spawning at 101 mm (SD = 6.7).     

Instream size segregation and density of Geotria australis ammocoetes in two New Zealand streams

Geotria australis occurred almost to the upstream limit of detectable discharge in two New Zealand streams. The length, and consequently age, of larvae differed over the course of the stream and smallest animals - presumed to be age 0 - predominated upstream. Metamorphosing larvae (mean length 99.5 mm) typically occurred in downstream reaches, where flows were higher and substrate was coarser. We estimated that annual larval survival was 47% for age 0 to 1 and 77% for age 1 to 2. Differences in the relation between length and weight occurred both between years within a stream and between streams; thus, we assume growth is generally variable. The density of ammocoetes in New Zealand streams ranged from 0 to 104 m^?2 and was significantly related to substrate type and depth in a multiple linear regression model. Because of the predictable nature of lamprey distribution and abundance, we believe it should be possible to estimate the absolute abundance of ammocoetes in a catchment with only a limited assessment of substrate properties.