Cell metabolism pathways involved in the pathophysiological changes of diabetic peripheral neuropathy

Diabetic peripheral neuropathy is a common complication of diabetes mellitus.Elucidating the pathophysiological metabolic mechanism impels the generation of ideal therapies.However,existing limited treatments for diabetic peripheral neuropathy expose the urgent need for cell metabolism research.Given the lack of comprehensive understanding of energy metabolism changes and related signaling pathways in diabetic peripheral neuropathy,it is essential to explore energy changes and metabolic changes in diabetic peripheral neuropathy to develop suitable treatment methods.This review summarizes the pathophysiological mechanism of diabetic peripheral neuropathy from the perspective of cellular metabolism and the specific interventions for different metabolic pathways to develop effective treatment methods.Various metabolic mechanisms(e.g.,polyol,hexosamine,protein kinase C pathway)are associated with diabetic peripheral neuropathy,and researchers are looking for more effective treatments through these pathways.

Performances of Clustering Methods Considering Data Transformation and Sample Size: An Evaluation with Fisheries Survey Data

Clustering is a group of unsupervised statistical techniques commonly used in many disciplines. Considering their applications to fish abundance data, many technical details need to be considered to ensure reasonable interpretation. However, the reliability and stability of the clustering methods have rarely been studied in the contexts of fisheries. This study presents an intensive evaluation of three common clustering methods, including hierarchical clustering(HC), K-means(KM), and expectation-maximization(EM) methods, based on fish community surveys in the coastal waters of Shandong, China. We evaluated the performances of these three methods considering different numbers of clusters, data size, and data transformation approaches, focusing on the consistency validation using the index of average proportion of non-overlap(APN). The results indicate that the three methods tend to be inconsistent in the optimal number of clusters. EM showed relatively better performances to avoid unbalanced classification, whereas HC and KM provided more stable clustering results. Data transformation including scaling, square-root, and log-transformation had substantial influences on the clustering results, especially for KM. Moreover, transformation also influenced clustering stability, wherein scaling tended to provide a stable solution at the same number of clusters. The APN values indicated improved stability with increasing data size, and the effect leveled off over 70 samples in general and most quickly in EM. We conclude that the best clustering method can be chosen depending on the aim of the study and the number of clusters. In general, KM is relatively robust in our tests. We also provide recommendations for future application of clustering analyses. This study is helpful to ensure the credibility of the application and interpretation of clustering methods.

Training Mode of Aquaculture Professionals in Local Applied Marine Colleges and Universities

In the training of aquaculture professionals,there are problems such as unreasonable structure of teachers,unclear understanding of aquaculture by parents and students,poor practical ability of students,lack of grass-roots aquaculture talents,and imperfect multi-party cooperation training mechanism.In view of the above situation,the training mode of applied talents in aquaculture needs to be reformed and innovated.In this paper,some measures to establish the training mode of aquaculture professionals were proposed,including strengthening students’correct understanding of the major,improving the curriculum system for cultivating applied talents,establishing a training model for practical teaching,improving the practical ability of teachers,increasing the provision of high-quality educational resources,and adopting school-enterprise cooperation,so as to cultivate high-quality and high-tech aquatic talents under the training mechanism of applied talents.

The key factors on the composition of phytoplankton functional groups in different watersheds in the Huanghe River

To understand the distribution of phytoplankton functional groups(PFGs)and key factors on their compositions in different watersheds of the Huanghe(Yellow)River basin,25 river sites and 25 lake-reservoirs sites were selected.The contents of nephelometric turbidity(NTU),total nitrogen(TN),and total phosphorus(TP)were significantly higher in rivers than that in lakes or reservoirs,whereas the pH and CODMn(chemical oxygen demand or potassium permanganate index)were lower.Results show that,27 PFGs,namely,assemblages A,B,C,D,E,F,G,H,J,K,LM,Lo,M,MP,N,P,S1,S2,T,TC,W1,W2,X1,X2,X3,XPh,and Y,were identified.Additionally,ANOSIM correlation analysis demonstrated significant differences in PFG composition between the riverine and lake-reservoir sections in the Huanghe River basin.In the riverine watersheds,the group MP was dominant,while assemblages B and J were prevalent in lakes and reservoirs.The Mantel correlation tests and RDA analysis showed that environmental variables,such as NTU,water temperature(WT),conductivity(Cond),and TP,were key driving factors of shaping the dominant PFGs of the study area.Using the Venn diagram based on variation partitioning analysis,PFGs were mainly influenced by WT and TP in lake-reservoir sites,while in the river sites were affected mainly by geo-climatic variables.This study helps understanding the PFGs in river ecosystems,and unraveling the key driving factors in different watersheds,which shall be important for the protection and management of entire Huanghe River basin.

A Transcriptome Analysis of Neural Tissue of Litopenaeus vannamei After Acute Exposure to Alexandrium pacificum

Alexandrium pacificum(A.pacificum)is a typical paralytic shellfish poisonous dinoflagellate.Harmful algal blooms(HABs)caused by this species can bring serious environmental problems and economic losses to the aquaculture industry.In this study,transcriptome sequencing and analyses were performed on the neural tissue of Litopenaeus vannamei(L.vannamei)after acute exposure to A.pacificum disrupted solution for 72 h,and differentially expressed genes(DEGs)were identified.The results showed that,compared with the control samples,300 DEGs were identified in the experimental group,of which 194 were up-regulated,and 106 down-regulated.The gene ontology(GO)functional enrichment analysis showed that DEGs were significantly enriched in the cortical cytoskeleton organization,troponin complex,amylo-alpha-1,6-glucosidase and thymidine phosphorylase.Kyoto encyclopedia of genes and genomes(KEGG)enrichment analysis found that DEGs were mainly enriched in the oxidative phosphorylation process,intercellular tight junctions and mitophagy.The results showed that the proteoglycans,signaling pathways,and various metabolic processes that regulate cell proliferation,differentiation,and apoptosis all played an essential role in the response of L.vannamei to A.pacificum toxins.

Identification,Characterization,and Probiotic Potentials of Lactobacillus pentosus SF-1

In recent years probiotics have been considered as a potential substitution of antibiotics to control pathogens and treat infectious diseases in aquaculture.In the present study a strain of Lactobacillus pentosus,named as L.pentosus SF-1,was isolated from waters in aquaculture.The species identification of this strain was conducted by 16S rRNA sequence,and the physiological and biochemical characteristics of this strain were assessed.Furthermore,the virulence,antibiotic sensitivity,cell surface characteristics and acid/base-resistance of L.pentosus SF-1 were determined to evaluate the probiotic potentials of this strain.Specifically,L.pentosus SF-1 is sensitive to most common antibiotics,and no hemolysin was generated from it,indicating the safety of this strain to hosts.In addition,L.pentosus SF-1 was able to tolerate the artificial gastric juice at pH 3 for 4 h and the artificial intestinal fluid at pH 6.8 or 8.0 for 6 h.Moreover,the analysis of self-aggregation and the adhesion of L.pentosus SF-1 to organic solvents suggested a high potential of L.pentosus SF-1 to inhabit the hosts,which was confirmed by testing the colonization of L.pentosus SF-1 in germ-free zebrafish.Interestingly,L.pentosus SF-1 displayed a high bactericidal activity against several bacterial pathogens.Consistently,the incubation of L.pentosus SF-1 significantly promoted the expression of antimicrobial components in zebrafish,contributing to the protection of the fish from E.tarda infection in vivo.Taken together,the probiotic strain L.pentosus SF-1 could be applied as anti-infection reagent in aquaculture.

Anti-infective immune functions of type Ⅳ interferon in grass carp(Ctenopharyngodon idella):A novel antibacterial and antiviral interferon in lower vertebrates

Type Ⅳ interferon(IFN-υ)is a recently discovered cytokine crucial for host defense against viral infections.However,the role and mechanisms of IFN-υin bacterial infections remain unexplored.This study investigated the antibacterial and antiviral functions and mechanisms of grass carp(Ctenopharyngodon idella)IFN-υ(CiIFN-υ)both in vivo and in vitro.The CiIFN-υgene was first identified and characterized in grass carp.Subsequently,the immune expression of CiIFN-υsignificantly increased following bacterial challenge,indicating its response to bacterial infections.The eukaryotic recombinant expression plasmid of CiIFN-υwas then constructed and transfected into fathead minnow(FHM)cells.Supernatants were collected and incubated with four bacterial strains,followed by plate spreading and colony counting.Results indicated that CiIFN-υexhibited more potent antibacterial activity against gram-negative bacteria compared to gram-positive bacteria and aggregated gram-negative bacteria but not gram-positive bacteria.In vivo experiments further confirmed the antibacterial function,showing high survival rates,low tissue edema and damage,reduced tissue bacterial load,and elevated proinflammatory response at the early stages of bacterial infection.In addition,the antiviral function of CiIFN-υwas confirmed through in vitro and in vivo experiments,including crystal violet staining,survival rates,tissue viral burden,and reverse transcription-quantitative real-time polymerase chain reaction(RT-qPCR).This study highlights the antibacterial function and preliminary mechanism of IFN-υ,demonstrating that IFN-υpossesses dual functions against bacterial and viral infections.

Stock appraisal for Atlantic tripletail(Lobotes surinamensis;Bloch,1790)in the Bay of Bengal,Bangladesh

The Atlantic tripletail(Lobotes surinamensis)is a high revenue-generating fish species predominantly caught by mechanized artisanal fishers community and the most available member of its family in Bangladesh.This is a ground work of fish stock assessment study in the Bay of Bengal region to explore the life history parameters and associated biomass of this species,using three length-based approaches of TropFishR,the length-based Bayesian biomass estimation(LBB),and Froese’s length based indicators(LBIs).An almost homogenous body growth pattern(b=3.07;R^(2)=0.98)was observed in the length-weight relationship of tripletail.The life history parameters for tripletail,as determined by the von Bertalanffy Growth Function(VBGF)model,were L_(∞)=113.36 cm and k=0.51/a.The length converted catch curve(LCCC)yielded an estimation of the total mortality(Z=1.77/a),with the natural mortality estimated at(M=0.53/a)and the fishing mortality estimated at(F=1.24/a).But,the ratio of mortality(F/M=0.15)by LBB captured the non-fully exploited status of biomass(B/B_(MSY)=2.1).LBI analysis indicated that the tripletail fishery’s spawning stock biomass is greater than the target and limit reference points,indicating a healthy state of biomass.

Investigating the molecular mechanisms of oocyte maturation and ovulation in Nile tilapia:A focus on the steroidogenic enzyme Cyp17a2

Previous research has highlighted the significant role of progestins and glucocorticoids in fish oocyte maturation and ovulation.To clarify the molecular mechanisms underlying these processes,comprehensive investigations were conducted using a cyp17a2 mutant Nile tilapia(Oreochromis niloticus) model.Analysis revealed pronounced Cyp17a2 expression in ovarian somatic cells of the tilapia.Female cyp17a2-deficient mutants exhibited markedly reduced levels of 17,20β-dihydroxy-4-pregnen-3-one(DHP) and cortisol/cortisone,leading to delayed meiotic initiation and impaired oocyte maturation and spawning.Notably,supplementation with human chorionic gonadotrophin(hCG),DHP,and cortisol effectively induced germinal vesicle breakdown(GVBD) and facilitated oocyte release with follicular cell layers in cyp17a2^(-/-)females.Additionally,cyp17a2-/-and rescued cyp17a2-/-females showed elevated transcription of steroidogenic enzymes involved in 17β-estradiol(E2)production compared to spawning wild-type females.Moreover,the reduction in Akt phosphorylation observed in cyp17a2-deficient females and upon inhibitor treatment impaired hCG-induced oocyte maturation.Conversely,activation of the phosphoinositide 3-kinase/protein kinase B(PI3K-Akt) signaling pathway partially rescued the oocyte maturation impairment caused by cyp17a2mutation.Overall,these findings provide functional evidence supporting the critical role of Cyp17a2 in DHP and cortisol biosynthesis,which,in turn,facilitates oocyte maturation and ovulation through activation of the PI3K-Akt signaling pathway in fish.

Characterization of Nutrients,Heavy Metals,Petroleum and Their Impact on Phytoplankton in Laizhou Bay:Implications for Environmental Management and Monitoring

The Laizhou Bay(LB)represents a substantial ecological area that is vulnerable to human activities and confronts diverse environmental challenges.This study provides a comprehensive characterization of nutrients,petroleum,heavy metals,and phytoplankton community structure across seven distinct areas in LB.The results indicate relatively high concentrations of NO_(2)-N,SiO_(4)-Si,and NO_(3)-N in the Southwest Laizhou Bay(SWLB)and Huanghe River Estuary(HRE).In contrast,the East Laizhou bay(ELB)and the North of Huanghe River Estuary(NHRE)exhibit the highest concentrations of heavy metals(As,Cr and Hg).The areas with high phytoplankton density and community diversity are mainly located in the SWLB.After adjusting for basic environmental factors,phytoplankton density and Margalef richness index D are significantly associated with nutrients(NO_(3)-N,NO_(2)-N,NH_(4)-N,SiO_(4)-Si),and heavy metal(Cr)concentrations.We highlight that,in addition to Xiaoqinghe River,nutrients brought by the Mihe River in the SWLB and heavy metal(Cr)pollution in the ELB resulting from industrial and mining activities along the coast significantly influence phytoplankton growth and community structure.Therefore,it is recommended that more monitoring and management efforts be focused on these regions in the future.

Temporal variations of food web in a marine bay ecosystem based on LIM-MCMC model

Climate change has led to significant fluctuations in marine ecosystems,including alterations in the structure and function of food webs and ecosystem status.Coastal ecosystems are critical to the functioning of the earth’s lifesupporting systems.However,temporal variations in most of these ecosystems have remained unclear so far.In this study,we employed a linear inverse model with Markov Chain Monte Carlo(LIM-MCMC)combined with ecological network analysis to reveal the temporal variations of the food web in Haizhou Bay of China.Food webs were constructed based on diet composition data in this ecosystem during the year of 2011 and 2018.Results indicated that there were obvious temporal variations in the composition of food webs in autumn of 2011 and 2018.The number of prey and predators for most species in food web decreased in 2018 compared with 2011,especially for Trichiurus lepturus,zooplankton,Amblychaeturichthys hexanema,and Loligo sp.Ecological network analysis showed that the complexity of food web structure could be reflected by comprehensive analysis of compartmentalized indicators.Haizhou Bay ecosystem was more mature and stable in 2011,while the ecosystem’s self-sustainability and recovery from disturbances were accelerated from 2011 to 2018.These findings contribute to our understanding of the dynamics of marine ecosystems and highlight the importance of comprehensive analysis of marine food webs.This work provides a framework for assessing and comparing temporal variations in marine ecosystems,which provides essential information and scientific guidance for the Ecosystem-based Fisheries Management.

Impacts of Aggregation Methods and Trophospecies Number on the Structure and Function of Marine Food Webs

Aggregation of species with similar ecological properties is one of the effective methods to simplify food web researches.However,species aggregation will affect not only the complexity of modeling process but also the accuracy of models’outputs.Selection of aggregation methods and the number of trophospecies are the keys to study the simplification of food web.In this study,three aggregation methods,including taxonomic aggregation(TA),structural equivalence aggregation(SEA),and self-organizing maps(SOM),were analyzed and compared with the linear inverse model–Markov Chain Monte Carlo(LIM-MCMC)model.Impacts of aggregation methods and trophospecies number on food webs were evaluated based on the robustness and unitless of ecological net-work indices.Results showed that aggregation method of SEA performed better than the other two methods in estimating food web structure and function indices.The effects of aggregation methods were driven by the differences in species aggregation principles,which will alter food web structure and function through the redistribution of energy flow.According to the results of mean absolute percentage error(MAPE)which can be applied to evaluate the accuracy of the model,we found that MAPE in food web indices will increase with the reducing trophospecies number,and MAPE in food web function indices were smaller and more stable than those in food web structure indices.Therefore,trade-off between simplifying food webs and reflecting the status of ecosystem should be con-sidered in food web studies.These findings highlight the importance of aggregation methods and trophospecies number in the analy-sis of food web simplification.This study provided a framework to explore the extent to which food web models are affected by dif-ferent species aggregation,and will provide scientific basis for the construction of food webs.

Effects of nutrient limitations on the sinking velocity of Thalassiosira weissflogii

The sinking of diatoms is critic al to the formation of oceanic biological pumps and coastal hypoxic zones.However,little is known about the effects of different nutrient restrictions on diatom sinking.In this study,we measured the sinking velocity(SV) of Thalassiosira weissflogii using a new phytoplankton video observation instrument and analyzed major biochemical components under varying nutrient conditions.Our results showed that the SV of T.weissflogii under different nutrient limitation conditions varied substantially.The highest SV of(1.77±0.02) m/d was obtained under nitrate limitation,signific antly surpassing that under phosphate limitation at(0.98±0.13) m/d.As the nutrient limitation was released,the SV steadily decreased to(0.32±0.03) m/d and(0.15±0.05) m/d,respectively.Notably;under conditions with limited nitrate and phosphate concentrations,the SV values of T.weissflogii significantly positively correlated with the lipid content(P <0.001),with R^(2) values of 0.86 and 0.69,respectively.The change of the phytoplankton SV was primarily related to the intracellular compo sition,which is controlled by nutrient conditions but did not significantly correlate with transparent extracellular polymer and biosilica contents.The results of this study help to understand the regulation of the vertical sinking process of diatoms by nutrient restriction and provide new insights into phytoplankton dynamics and their relationship with the marine nutrient structure.

foxl2l is a germ cell-intrinsic gatekeeper of oogenesis in zebrafish

Zebrafish serve as a valuable model organism for studying germ cell biology and reproductive processes.The AB strain of zebrafish is proposed to exhibit a polygenic sex determination system,where most males initially develop juvenile ovaries before committing to male fate.In species with chromosomal sex determination,gonadal somatic cells are recognized as key determinants of germ cell fate.Notably,the loss of germ cells in zebrafish leads to masculinization,implying that germ cells harbor an intrinsic feminization signal.However,the specific signal triggering oogenesis in zebrafish remains unclear.In the present study,we identified foxl2l as an oocyte progenitor-specific gene essential for initiating oogenesis in germ cells.Results showed that foxl2l-knockout zebrafish bypassed the juvenile ovary stage and exclusively developed into fertile males.Further analysis revealed that loss of foxl2l hindered the initiation of oocyte-specific meiosis and prevented entry into oogenesis,leading to premature spermatogenesis during early gonadal development.Furthermore,while mutation of the pro-male gene dmrt1 led to fertile female differentiation,simultaneous disruption of foxl2l in dmrt1 mutants completely blocked oogenesis,with a large proportion of germ cells arrested as germline stem cells,highlighting the crucial role of foxl2l in oogenesis.Overall,this study highlights the unique function of foxl2l as a germ cell-intrinsic gatekeeper of oogenesis in zebrafish.

Combining genome-wide association study and transcriptome analysis to identify molecular markers and genetic basis of population-asynchronous ovarian development in Coilia nasus

Coilia nasus,a migratory fish species found in the middle and lower reaches of the Yangtze River and along offshore areas of China,possesses considerable aquacultural and economic potential.However,the species faces challenges due to significant variation in the gonadal development rate among females,resulting in inconsistent ovarian maturation times at the population level,an extended reproductive period,and limitations on fish growth rate due to ovarian prematurity.In the present study,we combined genome-wide association study(GWAS)and comparative transcriptome analysis to investigate the potential single nucleotide polymorphisms(SNPs)and candidate genes associated with population-asynchronous ovarian development in C.nasus.Genotyping of the female population based on whole-genome resequencing yielded 2120695 high-quality SNPs,39 of which were suggestively associated with ovarian development.Of note,a significant SNP peak on LG21 containing 30 suggestively associated SNPs was identified,with cpne5a determined as the causal gene of the peak.Therefore,single-marker and haplotype association analyses were performed on cpne5a,revealing four genetic markers(P<0.05)and seven haplotypes(r2>0.9)significantly associated with the phenotype.Comparative transcriptome analysis of precociously and normally maturing individuals screened out 29 and 426 overlapping differentially expressed genes in the brain and ovary,respectively,between individuals of different body sizes.Integrating the GWAS and transcriptome analysis results,this study identified genes and pathways related to hypothalamic-pituitary-gonadal axis hormone secretion,extracellular matrix,angiogenesis,and gap junctions involved in population-asynchronous ovarian development.The insights gained from this study provide a basis for a deeper understanding of the molecular mechanisms underlying ovarian development in fish and may facilitate the genetic breeding of C.nasus strains exhibiting population-synchronous ovarian development in the future.

High-quality Development Path of Graduate Education in Aquaculture Discipline:A Case Study of Guangdong Ocean University

Aquaculture is a discipline system that focuses on exploring the growth,development,reproduction,aquaculture,and resources of aquatic animals and plants,and their complex relationships.Under the tide of the"high-quality development"strategy,the aquaculture discipline is also facing new opportunities and challenges for transformation,upgrading,and deepening development.Therefore,exploring and practicing an effective path for the high-quality development of graduate education in aquaculture is not only the key to promoting the transformation of graduate education in aquaculture from scale expansion to quality improvement,but also has immeasurable value for implementing the strategy on developing a quality workforce and the strategy of scientific and technological powerhouse.The high-quality development of graduate education in aquaculture can be promoted from the following aspects:optimizing and improving the construction of the graduate education system,focusing on enhancing the quality of high-level talent cultivation,strengthening the overall strength of the graduate supervisor team,actively promoting the adjustment and upgrading of the disciplinary and professional structure,strengthening the construction of resource platforms and deepening the implementation of collaborative education mechanisms,and continuously expanding and deepening the new pattern of international exchange and cooperation.Through the comprehensive promotion of the above paths,the aim is to fully build a model for the improvement and governance of graduate education quality.

Qualitative Analysis of Solutions of a Nonlinear Biomechanical Model

The behavior of objects in motion is described by the equations of motion, which are basic concepts in mathematical physics. These equations are useful in explaining how forces and torques cause body components to move around a joint when applied to joint movement, especially in biomechanics. In the orthopedic industries, biomechanics is widely used to develop orthopaedic implants for a range of body joints, dental parts, external fixations, exoskeletons, and other medical uses. In this case, the motion of a phenomenon is described using a nonlinear differential model. One of the most effective approaches for describing the qualitative behavior of a dynamical system is the introduction of Lyapunov methods. Stability analysis and boundedness of solutions of a nonlinear differential equation model, particularly in the context of knee joint movement, entails analyzing how minor perturbations (like changes in force, position, or velocity) influence the behavior of the joint and remain within a finite range over time, respectively. The goal is to determine whether the system returns to a steady state (stable) or becomes unstable when subjected to these small changes. The effect of viscous damping, external input, and angular motions at different times in seconds are all controlled to govern the shank knee movement surrounding the knee joint. Numerical simulations with Matlab and Mathematica are drawn to demonstrate the effectiveness of the shank knee motion around the knee joint.

Immunocytochemical identification and localization of APUD cells in the gut of seven stomachless teleost fishes

AIM To study the cell types,localization,distribution density and morphology of APUDcells in the intestinal mucosa of stomachlessteleost fishes.METHOD By using the peroxidase-antiperoxidase complex(PAP)immunocytochemical staining technique theidentification,localization and morphology ofimmunoreactive(IR)endocrine cells seattered inthe intestinal mucosa of grass carp(Cyenopharyngodon idellus),black carp(Mylopharyngodon piceus)and common carp(Cyprinus carpio)were investigated with 20kinds of antisera prepared against mammalianpeptide hormones of APUD cells,and likewise byusing avidin-biotin-peroxidase complex(ABC)method those of silver carp(Hypophthalmichthys molitrix),bighead(Aristichthys nobilis),silver crucian carp(Carassius gibelio)and bluntnose black bream(Megalobrama amblyocephala)were alsostudied with 5 different antisera.Thereplacement of the first antiserum by phosphatebuffered saline(PBS)was employed as a control.IR endocrine cells were counted with asquare-mesh ocular micrometer from 10 fieldsselected randomly in every section of each partof the intestine specimen.The average numberof IR endocrine cells per mm2 was counted toquantify their distribution density.RESULT Gastrin(GAS)-,Gastric inhibitorypeptide(GIP)-,glucagon(GLU)-,glucagon-likeimmunoreactants(GLI)-,bovine pancreaticpolypeptide(BPP)-,leucine-enkephalin(ENK)-and substance P(SP)-IR endocrine cells werefound in the gut of grass carp,black carp andcommon carp,and somatostatin(SOM)-IRendocrine cells were only seen in common carp.GAS-,GIP-and GLU-IR endocrine cells werefound in the intestinal mucosa of silver carp,bighead,silver crucian carp and bluntnose blackbream.Most of IR endocrine cells had the higherdistribution density in the foregut and midgut,and were longer in shape.They had a long apicalcytoplasmic process extended to the gut lumenand a basal process extended to adjacent cellsor basement membrane and touched with it.Sometimes,the basal cytoplasmic processformed an enlarged synapse-like structure in thecontiguous part with basement membrane.Thisphenomenon provided new morphologicalevidence for neuroendocrine and paracrinesecretory function of these enteroendocrinecells.CONCLUTION At least 8 kinds of IR endocrinecells were found in the gut of stomachlessteleost species for the first time in China.TheseIR endocrine cells scattering in the gut mucosabelong to the APUD system.Among them,thehormones secreted by SP-,ENK-,SOM-and GLU-IR endocrine cells belong to the peptides of dualdistribution in the brain and gut.This providednew evidence for the concept of brain-gutpeptide.According to the cell types,distribution density,morphologicalcharacteristics and variety in shape of APUDcells in the gut of stomachless teleost fishes,itis deemed that the digestive tract of fishes isalso an endocrine organ of great importance andcomplexity.

Identification,localization and morphology of APUD cells in gastroenteropancreatic system of stomach-containing teleosts

AIM To identify the type localization andmorphology of APUD endocrine cells in thegastroenteropancreatic(GEP)system ofstomach-containing teleosts,and study APUDendocrine system in the stomach,intestine andpancreas of fish species.METHODS Two kinds of immunocytochemical(ICC)techniques of the streptavidin biotin-peroxidase complex(SABC)and streptavidin-peroxidase(S-P)method were used.Theidentification,localization and morphology ofAPUD endocrine cells scattered in the mucosa ofdigestive tract,intermuscular nerve plexus andglandular body of northern snakehead(Channaargus),ricefield eel(Monopterus albus),yellow catfish(Pelteobagrus fulvidraco),mandarinfish(Siniperca chuatsi),largemouthbass(Micropterus salmoides),orientalsheatfish(Silurus asotus),freshwater pomfret(Colossoma brachypomum)and nile tilapia(Tilapia nilotica)were investigated with 8 kindsof antisera.RESULTS The positive reaction of 5-hydroxytryptamine(5-HT)immunoreactiveendocrine(IRE)cells was found in the digestive tract and glandular body of 8 fish species indifferent degree.Only a few gastrin(GAS)-IREcells were seen in C.argus,M.albus and P.fulvidraco.Glucagon(GLU)-IRE cells were notfound in the digestive tract and glandular bodybut existed in pancreatic island of most fishspecies.The positive reaction of growthhormone(GH)-IRE cells was found only inpancreatic island of S.Chuatsi and S.Asotus,no positive reaction in the other 6 fish species.Somatostatin(SOM)-,calcitonin(CAL)-,neurofilament(NF)-and insulin(INS)-IRE cellsin the stomach,intestine and pancreas of 8 kindsof fish were different in distribution and types.The distribution of all 8 APUD cells was the mostin gastrointestinal epithelium mucosa and then indigestive glands.The positive reaction of SOM-and 5-HT-IRE cells was found in intermuscularnerve plexus of intestine of P.fulvidraco andS.chuatsi.Only GH-IRE cells were denselyscattered in the pancreatic islands of S.chuatsiand S.asotus,and odd distribution in thepancreas of S.asotus,SOM-IRE cells weredistributed in the pancreatic islands of S.asotus,C.Brachypomum and T.nilotica.There were INS-IRE cells in the pancreaticislands of S.chuatsi and S.asolus.Eightkinds of APUD cells had longer cell body andcytoplasmic process when they were located inthe gastrointestinal epithelium,and had shortercell body and cytoplasmic process in the gastricgland,and irregular shape in the esophagus andpancreatic island.CONCLUSION Eight kinds of IRE cells were identified in the GEP system of stomach-containing teleosts. These endocrine cells were scattered in gastrointestinal mucosa, intermuscular nerve plexus, gland body, pancreatic gland and islands under APUD system. CAL- and GH-IRE cells in the pancreatic islands of fishes showed functional diversity for these two hormones. Their morphological feature provides evidence of endocrine-paracrine and endocrine-exocrine acting mode. This research can morphologically prove that the GEP endocrine system of fish ( the lowest vertebrate) is almost the same as of mammal and human.

Growth and Mortality of Small Yellow Croaker(Larimichthys polyactis) Inhabiting Haizhou Bay of China

Length frequency data of small yellow croaker （Larimichthys polyactis） were acquired from the survey vessel in May, July, September and December, 2011 in Haizhou Bay of China. In this study, 921 fish individuals were analyzed for the estimation of growth and mortality parameters. Between length and weight, the power coefficient b was 2.7321, 2.9703, 3.0418 and 2.7252 for the 4 surveying months, respectively. The estimated von Bertalanffy growth function parameters were 230mm （L∞） and 0.26yr-1 （K） as were calculated with ELEFAN method equipped in FiSAT computer package. With length-converted catch curve analysis, the total mortality rate （Z） and its 95% confidence interval were 2.16 （1.69-2.64） yr-1, 0.59 （0.15-1.04） yr-1, 1.16 （0.80-1.52） yrl and 0.96 （0.70-1.23） yr1 for the 4 surveying months, respectively, with the pooled data the value was 1.15 （0.81-1.48） yr1. The natural mor- tality rate （M） was 0.516 yr 1 as was calculated with Pauly＇s equation （the annual average sea water temperature was 11 ℃）. Therefore, fish mortality rate was 0.634 yrz. The yield-per-recruit analysis indicated that when tc was 1, Fmax, was 0.7 and F01 was 0.55. Cur- rently, the age at first capture is about 1 year and Fcurrent was 0.634. Therefore, Fcurrent was larger than F0.1 and less than Fmax. This indicates that current fish mortality is at a dangerously high level. With Gulland method, the biological reference point for fishery （Fopt） was estimated as 0.516 yr1, lower than current fish mortality. Accordingly, reducing catch in the region was strongly recom- mended.