放牧对内蒙古草原群落和土壤种子库的影响及两者关系的研究

选取内蒙古草原三种主要草原类型（草甸草原、典型草原和荒漠草原）代表性群落羊草杂类草群落、羊草群落和大针茅群落、小针茅群落，应用样线法沿水分梯度研究放牧对内蒙古草原不同植物群落功能群组成、多样性、生产力以及多样性与生产力关系的影响和放牧对土壤种子库组成、大小以及多样性的影响，在此基础上，研究土壤种子库与地上植被间的关系。主要结论如下： 1 放牧对植物群落的影响 荒漠草原的放牧演替规律为小针茅群落→猪毛菜 + 小针茅群落→猪毛菜群落;典型草原为羊草或大针茅群落→糙隐子草 + 大针茅群落或克氏针茅群落→星毛委陵菜 + 糙隐子草群落;草甸草原为羊草杂类草群落→羊草 + 贝加尔针茅群落，这是不同物种对牧压的不同适应结果造成的。 放牧使4种草原群落生活型功能群组分间发生强烈的生态替代作用，但不同的群落生态替代模式不同：放牧使小针茅群落多年生丛生禾草作用减弱，一二年生草本作用增强;羊草群落和大针茅群落多年生丛生禾草、多年生根茎禾草作用减弱，多年生杂类草作用增强;羊草杂类草群落多年生根茎禾草作用减弱，多年生丛生禾草作用增强。放牧使非旱生和C3植物作用减弱，而旱生、C4植物作用增强。 放牧对4种群落物种和功能群多样性的影响随不同的群落而表现不同：物种丰富度、物种多样性、生活型多样性 和水分生态类型多样性除羊草杂类草群落外随放牧强度的加大而降低，但适度放牧增加了羊草杂类草群落的上述多样性指标。 群落地上现存量一般随放牧强度的增大而下降，但小针茅群落反之，主要与一年生植物猪毛菜的生物量迅速增加有关。除羊草群落外，0~10 cm 地下生物量随放牧强度的变化不显著;除大针茅群落外，放牧显著降低0~30 cm 地下生物量。 放牧影响下内蒙古草原植物群落生物量随水分生态类型多样性的升高而升高，其回归方程为：Y = 809 + 774x （R2=0.84, P<0.001），其中Y代表群落地上现存量和地下生物量之和，x代表群落水分生态类型多样性。 2 放牧对土壤种子库的影响 小针茅群落、大针茅群落、羊草群落和羊草杂类草群落土壤种子库组成中均以多年生杂类草为主，分别占各自群落种子库总物种数的40%、52%、54%和67%。 生活型功能群种子库密度除羊草杂类草群落外，均以一二年生草本占优势。中度放牧升高了除小针茅群落外多年生禾草种子库密度;放牧增大了小针茅群落和羊草杂类草群落一二年生草本种子库密度;除羊草杂类草群落外，放牧对多年生杂类草种子库密度影响不大;总种子库组成中，灌木半灌木和小半灌木种子库密度不大，不随取样时间和牧压而变化。 中度放牧种子库总密度最大，小针茅群落在重度放牧最大，主要是由于猪毛菜种子库密度在重度放牧突增所致。总体上，内蒙古草原4种群落在不同取样时间不同牧压下种子库总密度波动在20.8~3819.2粒/m2。 土壤种子库物种丰富度最大值一般出现在10月份，除羊草杂类草群落外，不放牧群落较放牧群落为高，中度放牧使羊草杂类草群落土壤种子库物种丰富度增加。中度放牧增加了小针茅群落、大针茅群落7月份和羊草杂类草群落各取样时间土壤种子库物种多样性。 3 地上植被与土壤种子库的关系 土壤种子库的优势种在特定时间特定放牧强度下与地上现有植被优势种一致，但一致率仅为三次取样时间不同放牧强度下总体的23.3%。 地上植被与土壤种子库物种组成相似性指数受不同取样时间的影响，一般的10月取样最大。不同放牧强度对二者间的相似性亦有影响，中度放牧提高了小针茅群落、羊草杂类草群落各取样时间和大针茅群落、羊草群落4月份的相似性指数。隔年二次萌发法提高了二者间的相似性水平。总体上相似性指数变动在0.1~0.75之间。 地上植被现存量、总密度与各取样时间土壤种子库总密度之间不存在显著的相关性。 4 对于估计土壤种子库密度、物种组成和确定种子库与地上植被间的关系，隔年二次萌发法对于弥补直接萌发法本身所具有的不足不失为一种有益的尝试。

紫茎泽兰种群补充特征

外来种紫茎泽兰 (Eupatorium adenophorum Spreng.) 对我国西南地区生态系统的危害已长达50~60年之久，我国于20世纪70年代开展紫茎泽兰的研究，但目前仍然没有能力将其限制在一个可控范围之内，随着我国对生物多样性重要性认识的加深，对于紫茎泽兰的研究也越来越深入。本文以四川攀枝花受入侵生态系统为例，通过对该地区植被、土壤种子库以及当地紫茎泽兰无性繁殖和种子萌发特征开展研究，分析受入侵生态系统的特征，结合紫茎泽兰种群补充特征，揭示紫茎泽兰入侵机制，探索管理受害生态系统的方法。 所选实验点为紫茎泽兰危害严重的地带，群落中紫茎泽兰为优势种，伴生种灌木18种，草本植物65种，草本层以紫茎泽兰最为昌盛，种群构成为1～4年生植株与其荫庇下大量的实生幼苗，Drude多度极大，频度达100%。紫茎泽兰与灌木重要值之间极显著负相关 (P<0.01) ，与其他草本重要值之间极显著负相关 (P<0.01) ，灌木与其他草本重要值间的相关性不显著 (P>0.05) 。说明紫茎泽兰的生长与灌木或草本间存在微妙的此消彼长的关联，充分显示了紫茎泽兰与当地物种间的竞争事实。 紫茎泽兰种子雨前的种子库为所研究地区绝大部分物种的长久性土壤种子库，本地区种子库的组成物种共有13种，包括灌木和草本。紫茎泽兰占整个种子库储量的61.3%，在长久种子库中占有明显的优势;种子库与植被间相似度为0.31，虽然种子库中物种均为植被的组成成分，但是植被中绝大多数物种种子未检测出，种子库中出现的物种与该物种本身的生理生态特性密切相关。种子雨是种子库的来源，紫茎泽兰种子雨前表层种子储量只占种子雨后的7.4%，中下层储量占33.8%，共占41.2%，即每年仅58.8%的种子在当年雨季萌发，剩余的在土壤中保持休眠状态。依 目前的研究结果，本地植被仅靠自然恢复的可能性不大。 紫茎泽兰种子最适发芽温度为25℃;储藏1.5 a后的种子萌发率有所下降，25℃下萌发率由77%下降为66%;紫茎泽兰种子有良好的休眠机制，对生境的干扰可以促进紫茎泽兰长久土壤种子库的形成，为紫茎泽兰种群补充奠定了基础。稀疏的植被有利于紫茎泽兰种子萌发及幼苗建植，对原生植被的破坏则促进了紫茎泽兰实生苗的补充。因而保护原始生境、减少对原生态系统的破坏，是减少和抑制紫茎泽兰种群补充的有效途径。 紫茎泽兰 (克隆) 离体无性繁殖的部位为根颈部分，其他离体部分没有无性繁殖能力或很弱;灌丛和路域生境下的离体部分在给予相同培养条件下，克隆繁殖效益有差别，灌丛生境萌芽较早，而主茎和叶生长速度较慢。拔除干扰对于紫茎泽兰萌生新枝具有刺激作用，对紫茎泽兰植株上部的割取类似于给它提供更新复壮的机会，因此在紫茎泽兰防治过程中一定要注意将其拔除干净，以防后患。

Population genetic structure of Rutilus frisii kutum in Caspian Sea using biometry and microsatellite molecular technique

In order to carry out Biometric studies, 75 samples were caught from 3 locations ( Tajan river, Sefidrud and Shirud) using Salic and the length (±1 mm) and weights (± 5 gr) of samples were determined. Using One-way ANOVA by SPPSS software, there wasn’t significant difference between locations in length and fecondity (P ≥0.01(, but there was significant difference between Shirud and tajan samples with sefidrud in weight ) P≤0.01(. In order to carry out genetic variation studies, 210 fish were caught from 3 different regions of the Iranian coastline (Khoshkrud, Tonekabon, Gorganrud) and 1 region in Azerbaijan (Waters of the Caspian Sea close to Kura River mouth) during 2008-2009 . Genomic DNA was extracted of fin using the phenol-chloroform. The quantity and quality of DNA from samples were assessed by spectrophptometer and 1% agarose gel electro-phoresis. PCR was carried out using 15 paired microsatellite primers. PCR products were separated on 8% polyacrylamide gels that were stained using silver nitrate. Molecular weight calculate using UVTech software. The recorded microsatellite genotypes were used as input data for the GENALEX software version 6 package in order to calculate allele and genotype frequencies, observed (Ho) and (He) expected heterozygosities and to test for deviations from Hardy-Weinberg equilibrium. Genetic distance between two populations was estimated from Nei standard genetic distance and genetic similarity index (Nei, 1972). Genetic differentiation between populations was also evaluated by the calculation of pairwise estimates of Fst and Rst values. From 15 SSR markers were used in this investigation, 9 of them were polymorph. Average of expected and observed heterozygosity was 0.54 and 0.49 respectively. Significant deviations from Hardy-Weinberg expectations were observed in all of location except Anzali lagoon- autumn in AF277576 and EF144125, Khoshkrud in EF144125 and Gorganrud and Kura in AF277576. Using Fst and Rst there was significant difference between locations ) P≤0.01(. According to Fst , the highest population differentiation (Fst= 0.217) was between Gorganrud and Khoshkrud that have the lowest Nm and the lowest (Fst= 0.086) was between Gorganrud and Tonekabon that have the highest Nm. Using Rst the highest population differentiation (Rst= 0.271) was between Tonekabon and spring Anzali lagoon and the lowest (Rst= 0.026) was between Tonekabon and Autumn Anzali 159 lagoon. Also the difference between Spring Anzali lagoon and Autumn Anzali lagoon was noticeable (Fst=0.15). AMOVA analysis with consideration of 2 sampling regions (Iran and Azerbaijan) and 7 sampling locations (Iran: Khoshkrud, Tonekabon, Gorganrud, Spring Anzali lagoon and Autumn Anzali lagoon ; Azerbaijan: the Kura mouth) revealed that almost all of the variance in data namely 83% )P≤0.01( was within locations, Genetic variances among locations was 14% )P≤0.01( and among regions was 3% )P≤0.01(. The genetic distance was the highest (0.646) between Gorganrud and Autumn Anzali lagoon populations, whereas the lowest distance (0.237) was between Gorganrud and Tonekabon River. Result obtained from the present study show that at least 2 different population of Rutilus frissi kutum are found in the Caspian sea,which are including the kura river population and the southern Caspian sea samples and it appears that there is more than one population in southern Caspian sea that should be attantioned in artifical reproduction Center and stoke rebilding.

Bayesian correlated clustering to integrate multiple datasets.

MOTIVATION: The integration of multiple datasets remains a key challenge in systems biology and genomic medicine. Modern high-throughput technologies generate a broad array of different data types, providing distinct-but often complementary-information. We present a Bayesian method for the unsupervised integrative modelling of multiple datasets, which we refer to as MDI (Multiple Dataset Integration). MDI can integrate information from a wide range of different datasets and data types simultaneously (including the ability to model time series data explicitly using Gaussian processes). Each dataset is modelled using a Dirichlet-multinomial allocation (DMA) mixture model, with dependencies between these models captured through parameters that describe the agreement among the datasets. RESULTS: Using a set of six artificially constructed time series datasets, we show that MDI is able to integrate a significant number of datasets simultaneously, and that it successfully captures the underlying structural similarity between the datasets. We also analyse a variety of real Saccharomyces cerevisiae datasets. In the two-dataset case, we show that MDI's performance is comparable with the present state-of-the-art. We then move beyond the capabilities of current approaches and integrate gene expression, chromatin immunoprecipitation-chip and protein-protein interaction data, to identify a set of protein complexes for which genes are co-regulated during the cell cycle. Comparisons to other unsupervised data integration techniques-as well as to non-integrative approaches-demonstrate that MDI is competitive, while also providing information that would be difficult or impossible to extract using other methods.

Apoptosis induction on human hepatoma cells Hep G2 of decabrominated diphenyl ether (PBDE-209)

Polybrominated diphenyl ethers (PBDEs) are an important class of halogenated organic brominated flame retardants. Because of their presence in abiotic and biotic environments widely and their structural similarity to polychlorinated biphenyls (PCBs), concern has been raised on their possible adverse health effects to humans. This study was designed to determine the anti-proliferative, apoptotic properties of decabrominated diphenyl ether (PBDE-209), using a human hepatoma Hep G2 line as a model system. Hep G2 cells were cultured in the presence of PBDE-209 at various concentrations (1.0-100.0 mu mol/L) for 72 h and the percentage of cell viability was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The results showed that PBDE-209 inhibited the cells viability in time and concentration-dependent characteristics at concentrations (10.0-100.0 mu mol/L). We found that anti-proliferative effect of PBDE-209 was associated with apoptosis on Hep G2 cells by determinations of morphological changes, cell cycle and apoptosis. Mechanism study showed that PBDE-209 could increase the generation of intracellular reactive oxygen species (ROS) concentration-dependently. Antioxidant N-acetylcyteine partially inhibited the increase of ROS. The mechanism for its hepatoma-inhibitory effects was the induction of cellular apoptosis through ROS generation. In addition, activity of lactate dehydrogenase (LDH) release increased when the cells incubated with PBDE-209 at various concentrations and times. These results suggested that PBDE-209 had the toxicity activity of anti-proliferation and induction of apoptosis in tumor cells in vitro. (c) 2007 Elsevier Ireland Ltd. All rights reserved.

Development of the microbial communities in Lake Donghu in relation to water quality

There is increasing recognition that protozoa is very useful in monitoring and evaluating water ecological healthy and quality. In order to study the relationship between structure and function of protozoan communities and water qualities, six sampling stations were set on Lake Donghu, a hypereutrophic subtropical Chinese lake. Microbial communities and protists sampling from the six stations was conducted by PFU (Polyurethane foam unit) method. Species number (S), diversity index (DI), percentage of phytomastigophra, community pollution value (CPV), community similarity and heterophy index (HI) were mensurated. The measured indicators of water quality included total phosphorus (TP), dissolved oxygen (DO), Chemical oxygen demand (COD), NH4 (+), NO2 (-) and NO3-. Every month water samples from stations I, II, III, IV were chemically analyzed for a whole year, Among the chemically analyzed stations, station I was the most heavily polluted, station II was the next, stations III and IV had similar pollution degrees. The variable tendencies of COD, TP, NH3, NO2-, NO3-, and DO during the year was approximately coincident among the six stations. Analysis from the community parameters showed that the pollution of station 0 was much more serious than others, and station V was the most slight. Of the community parameters, CPV and HI were sensitive in reflecting the variables of the water quality. Community similarity index was also sensitive in dividing water qualities and the water quality status of different stations could be correctly classified by the cluster analysis. DI could reflect the tendency of water quality gradient, species number and percentage of Phytomastigophora was not obvious in indicating the water quality gradient.

Visible Volume: a Robust Measure for Protein Structure Characterization

We propose a new characterization of protein structure based on the natural tetrahedral geometry of the β carbon and a new geometric measure of structural similarity, called visible volume. In our model, the side-chains are replaced by an ideal tetrahedron, the orientation of which is fixed with respect to the backbone and corresponds to the preferred rotamer directions. Visible volume is a measure of the non-occluded empty space surrounding each residue position after the side-chains have been removed. It is a robust, parameter-free, locally-computed quantity that accounts for many of the spatial constraints that are of relevance to the corresponding position in the native structure. When computing visible volume, we ignore the nature of both the residue observed at each site and the ones surrounding it. We focus instead on the space that, together, these residues could occupy. By doing so, we are able to quantify a new kind of invariance beyond the apparent variations in protein families, namely, the conservation of the physical space available at structurally equivalent positions for side-chain packing. Corresponding positions in native structures are likely to be of interest in protein structure prediction, protein design, and homology modeling. Visible volume is related to the degree of exposure of a residue position and to the actual rotamers in native proteins. In this article, we discuss the properties of this new measure, namely, its robustness with respect to both crystallographic uncertainties and naturally occurring variations in atomic coordinates, and the remarkable fact that it is essentially independent of the choice of the parameters used in calculating it. We also show how visible volume can be used to align protein structures, to identify structurally equivalent positions that are conserved in a family of proteins, and to single out positions in a protein that are likely to be of biological interest. These properties qualify visible volume as a powerful tool in a variety of applications, from the detailed analysis of protein structure to homology modeling, protein structural alignment, and the definition of better scoring functions for threading purposes.

Bradykinins and their precursor Cdnas from the skin of the Fire-Bellied Toad (Bombina orientalis)

Bradykinin and (Thr6)-bradykinin have been identified in the defensive skin secretion of the fire-bellied toad, Bombina orientalis. The homologous cDNAs for both peptides were cloned from a skin library using a 3'- and 5'-RACE strategy. Kininogen-1 (BOK-1) contained an open-reading frame of 167 amino acid residues encoding four repeats of bradykinin, and kininogen-2 (BOK-2) contained an open-reading frame of 161 amino acid residues encoding two repeats of (Thr6)-bradykinin. Alignment of both precursor nucleotide and amino acid sequences revealed a high degree of structural similarity. These amphibian skin kininogens/preprobradykinins are not biologically analogous to mammalian kininogens.

Kasstasin: A novel potent vasoconstrictor peptide from the skin secretion of the African red-legged running frog, Kassina maculata

Amphibian skin secretions are established sources of bioactive peptides. Here we describe the isolation, structural and pharmacological characterisation of a novel vasoconstrictor peptide from the skin secretion of the African hyperoliid frog, Kassina maculata, which exhibits no structural similarity to any known class of amphibian skin peptide. The peptide consists of 21 amino acid residues, FIKELLPHLSGIIDSVANAIK, and is C-terminally amidated. The provisional structure was obtained by MS/MS fragmentation using an Orbitrap mass spectrometer and L/I ambiguities were resolved following molecular cloning of biosynthetic precursor-encoding cDNA. A synthetic replicate of the peptide was found to possess weak antimicrobial and haemolytic activities but was exceptionally effective in constricting the smooth muscle of rat tail artery (EC50 of 25pM). In reflection of its exceptional potency in constricting rat arterial smooth muscle, the peptide was named kasstasin, a derivation of Kassina and “stasis” (stoppage of flow). These data illustrate the continuing potential of amphibian skin secretions to provide novel natural peptide templates for biological evaluation.

A comparative analysis of multidimensional features of objects resembling sets of graphs

In the present paper, we introduce a notion of a style representing abstract, complex objects having characteristics that can be represented as structured objects. Furthermore, we provide some mathematical properties of such styles. As a main result, we present a novel approach to perform a meaningful comparative analysis of such styles by defining and using graph-theoretic measures. We compare two styles by comparing the underlying feature sets representing sets of graph structurally. To determine the structural similarity between the underlying graphs, we use graph similarity measures that are computationally efficient. More precisely, in order to compare styles, we map each feature set to a so-called median graph and compare the resulting median graphs. As an application, we perform an experimental study to compare special styles representing sets of undirected graphs and present numerical results thereof. (C) 2007 Elsevier Inc. All rights reserved.

Comparing large graphs efficiently by margins of feature vectors

Measuring the structural similarity of graphs is a challenging and outstanding problem. Most of the classical approaches of the so-called exact graph matching methods are based on graph or subgraph isomorphic relations of the underlying graphs. In contrast to these methods in this paper we introduce a novel approach to measure the structural similarity of directed and undirected graphs that is mainly based on margins of feature vectors representing graphs. We introduce novel graph similarity and dissimilarity measures, provide some properties and analyze their algorithmic complexity. We find that the computational complexity of our measures is polynomial in the graph size and, hence, significantly better than classical methods from, e.g. exact graph matching which are NP-complete. Numerically, we provide some examples of our measure and compare the results with the well-known graph edit distance. (c) 2006 Elsevier Inc. All rights reserved.

Functional peptidomics of amphibian skin secretion: A novel Kunitz-type chymotrypsin inhibitor from the African hyperoliid frog, Kassina senegalensis

Amphibian skin secretions are, for the most part, complex peptidomes. While many peptide components have been biologically- and structurally-characterised into discrete "families", some of which are analogues of endogenous vertebrate regulatory peptides, a substantial number are of unique structure and unknown function. Among the components of these secretory peptidomes is an array of protease inhibitors. Inhibitors of trypsin are of widespread occurrence in different taxa and are representative of many established structural classes, including Kunitz, Kazal and Bowman-Birk. However, few protease inhibitors with activity against other specific proteases have been described from this source. Here we report for the first time, the isolation and structural characterisation of an inhibitor of chymotrypsin of Kunitz-type from the skin secretion of the African hyperoliid frog, Kassina senegalensis. To this end, we employed a functional peptidomic approach. This scheme involves fractionation of the peptidome, functional end-point screening, structural characterisation of resultant actives followed by molecular cloning of biosynthetic precursor-encoding cDNA(s). The novel mature and active polypeptide identified consisted of 62 amino acid residues (average molecular mass 6776.24 Da), of which 6 were positionally-conserved cysteines. The P(1) position within the active site was occupied by a phenylalanyl residue. Bioinformatic analysis of the sequence using BLAST, revealed a structural similarity to Kunitz-type chymotrypsin inhibitors from other organisms, ranging from silkworms to snakes.

A novel Kazal-type trypsin inhibitor from the skin secretion of the Central American red-eyed leaf frog, Agalychnis callidryas.

The chemical complexity of the defensive skin secretion of the red-eyed leaf frog, (Agalychnis callidryas), has not been elucidated in detail. During a systematic study of the skin secretion peptidomes of phyllomedusine frogs, we discovered a novel Kazal-type protein with potent trypsin inhibitory activity (Ki = 1.9 nM) that displays the highest degree of structural similarity with Kazal proteins from bony fishes. The protein was located in reverse-phase HPLC fractions following a screen of such for trypsin inhibition and subsequent partial Edman degradation of the peak active fraction derived the sequence: ATKPR-QYIVL-PRILRPV-GT. The molecular mass of the major component in this fraction was established by MALDI-TOF MS as 5893.09 Da. This partial sequence (assuming blank cycles to be Cys residues) was used to design a degenerate primer pool that was employed successfully in RACE-PCR to clone homologous precursor-encoding cDNA that encoded a mature Kazal protein of 52 amino acid residues with a computed molecular mass of 5892.82 Da. The protein was named A. callidryas Kazal trypsin inhibitor (ACKTI). BLAST analysis revealed that ACKTI contained a canonical Kazal motif (C-x(7)-C-x(6)-Y-x(3)-C-x(2,3)-C). This novel amphibian skin Kazal trypsin inhibitor adds to the spectrum of trypsin inhibitors of Kunitz- and Bowman Birk-type reported from this amphibian source.

ISOLATION, LOCALIZATION, AND CARDIOVASCULAR ACTIVITY OF TACHYKININS FROM THE STOMACH OF THE BOWFIN AMIA-CALVA

The bowfin is an extant representative of an ancient group of ray-finned fish with evolutionary connections to modern teleosts. A peptide with substance P-like immunoreactivity was isolated from an extract of bowfin stomach and its primary structure was established as Ser-Lys-Ser-His-Gln-Phe-Tyr-Gly-Leu-Met-NH2. This amino acid sequence resembles mammalian substance P only in the COOH-terminal region of the peptide. A second tachykinin with neurokinin A-like immunoreactivity isolated from the extract comprises 23 amino acid residues and shows limited structural similarity to mammalian neuropeptide-gamma. A randomly distributed population of cells in the gastric glands of the bowfin were immunostained with an antiserum raised against substance P, but no immunopositive structures were identified in the surface epithelium, lamina propria, or the nerve plexuses of the submucosa. Bolus injections of synthetic bowfin substance P (0.1-10 nmol/kg) into the bulbus arteriosus of unanesthetized bowfin resulted in a significant and dose-dependent rise in vascular resistance and arterial blood pressure (P < 0.01) and a fall in cardiac output (P < 0.05) without change in heart rate. After 5-10 min, arterial pressure and vascular resistance returned to preinjection levels, but cardiac output significantly (P < 0.05) increased over baseline values. The response to the peptide was unaffected by pretreatment of the animals with phentolamine. The study has shown that the stomach of the bowfin synthesizes tachykinins with novel structural features that display cardiovascular activity in this species.

A PEPTIDE FROM THE CAUDAL NEUROSECRETORY-SYSTEM OF THE DOGFISH SCYLIORHINUS-CANICULA THAT IS STRUCTURALLY RELATED TO UROTENSIN-I

Using reversed-phase HPLC in combination with a radioimmunoassay for ovine corticotropin-releasing hormone (CRH), a peptide with CRH-like immunoreactivity was isolated in pure form from an extract of the caudal spinal cord region of the spotted dogfish, Scyliorhinus canicula. The primary structure of the peptide was established as Pro-Ala-Glu-Thr-Pro-Asn-Ser-Leu-Asp-Leu(10)-Thr-Phe-His-Leu-Leu-Arg-Glu-Met-Ile-Glu(20)-Ile-Ala-Lys-His-Glu-Asn-Gln-Gln-Met-Gln(30)-Ala-Asp-Ser-Asn-Arg-Arg-Ile-Met-Asp-Thr(40)-Ile . NH2. This amino acid sequence shows moderate structural similarity to Catostomus urotensin I (51%) and to human CRH (56%). The data provide, therefore, chemical evidence to support the conclusions of earlier immunohistochemical studies that the diffuse caudal neurosecretory system of elasmobranchs produces a peptide that is immunochemically related to teleost urotensin I peptides. However, the primary structure of urotensin I has been poorly conserved during evolution. (C) 1995 Academic Press, Inc.