切尾拟鲿的个体生殖力

于2013年4～5月在长江上游岷江河口区域采集63尾性腺发育至Ⅳ期的切尾拟鲿(Pseudobagrus truncatus)雌性个体,所有样本均测量其体长(L)、体重(M)、净体重(W)和性腺重(Wa)等生物学指标。取耳石鉴定年龄,测量卵径,用重量法计数个体绝对生殖力(F),并对体长相对生殖力(FL)、体重相对生殖力(FW)进行计算,用5种数学模型及多元逐步回归方程拟合个体生殖力与生物学指标的关系。结果显示,调查样本由2+～5+龄组成,个体绝对生殖力(F)为566～6758粒,平均为3056粒;体长相对生殖力(FL)68～469粒/cm,平均为234粒/cm;体重相对生殖力(FW)为45～349粒/g,平均为145粒/g。个体绝对生殖力(F)和体长相对生殖力(FL)与体长(L)、体重(M)和成熟系数(GSI)均呈幂函数相关;而体重相对生殖力(FW)仅与成熟系数(GSI)呈幂函数相关,和其他形态指标的相关性不显著。多元逐步回归分析结果表明,长江上游切尾拟鲿个体绝对生殖力(F)与体重(M)和成熟系数(GSI)密切相关,相关式为:F=16370.714+3284.028 GSI+58.361M(n=63,R2=0.973,P0.01);体长相对生殖力(FL)与体重(M)、净体重(W)和成熟系数(GSI)密切相关,相关式为:FL=251.749+18.961 M+684.273 W+3 268.421 GSI(n=63,R2=0.852,P0.01);而体重相对生殖力(FW)仅与成熟系数(GSI)相关:FW=138.590+837.641 GSI(n=63,R2=0.539,P0.01)。依据卵径频数分布结果推测,切尾拟鲿属于一次性产卵鱼类。     

Major biogeographic barriers in eastern Australia have shaped the population structure of widely distributed Eucalyptus moluccana and its putative subspecies

We have investigated the impact of recognized biogeographic barriers on genetic differentiation of grey box (Eucalyptus moluccana), a common and widespread tree species of the family Myrtaceae in eastern Australian woodlands, and its previously proposed four subspecies moluccana, pedicellata, queenslandica, and crassifolia. A range of phylogeographic analyses were conducted to examine the population genetic differentiation and subspecies genetic structure in E. moluccana in relation to biogeographic barriers. Slow evolving markers uncovering long term processes (chloroplast DNA) were used to generate a haplotype network and infer phylogeographic barriers. Additionally, fast evolving, hypervariable markers (microsatellites) were used to estimate demographic processes and genetic structure among five geographic regions (29 populations) across the entire distribution of E. moluccana. Morphological features of seedlings, such as leaf and stem traits, were assessed to evaluate population clusters and test differentiation of the putative subspecies. Haplotype network analysis revealed twenty chloroplast haplotypes with a main haplotype in a central position shared by individuals belonging to the regions containing the four putative subspecies. Microsatellite analysis detected the genetic structure between Queensland (QLD) and New South Wales (NSW) populations, consistent with the McPherson Range barrier, an east‐west spur of the Great Dividing Range. The substructure was detected within QLD and NSW in line with other barriers in eastern Australia. The morphological analyses supported differentiation between QLD and NSW populations, with no difference within QLD, yet some differentiation within NSW populations. Our molecular and morphological analyses provide evidence that several geographic barriers in eastern Australia, including the Burdekin Gap and the McPherson Range have contributed to the genetic structure of E. moluccana. Genetic differentiation among E. moluccana populations supports the recognition of some but not all the four previously proposed subspecies, with crassifolia being the most differentiated.     

Target cell contact suppresses neurite outgrowth from soma–soma paired Lymnaea neurons

Neurite extension from developing and/or regenerating neurons is terminated on contact with their specific synaptic partner cells. However, a direct relationship between the effects of target cell contact on neurite outgrowth suppression and synapse formation has not yet been demonstrated. To determine whether physical/synaptic contacts affect neurite extension from cultured cells, we utilized soma–soma synapses between the identified Lymnaea neurons. A presynaptic cell (right pedal dorsal 1, RPeD1) was paired either with its postsynaptic partner cells (visceral dorsal 4, VD4, and Visceral dorsal 2, VD2) or with a non‐target cell (visceral dorsal 1, VD1), and the interactions between their neurite outgrowth patterns and synapse formation were examined. Specifically, when cultured in brain conditioned medium (CM, contains growth‐promoting factors), RPeD1, VD4, and VD2 exhibited robust neurite outgrowth within 12–24 h of their isolation. Synapses, similar to those seen in vivo, developed between the neurites of these cells. RPeD1 did not, however, synapse with its non–target cell VD1, despite extensive neuritic overlap between the cells. When placed in a soma–soma configuration (somata juxtaposed against each other), appropriate synapses developed between the somata of RPeD1 and VD4 (inhibitory) and between RPeD1 and VD2 (excitatory). Interestingly, pairing RPeD1 with either of its synaptic partner (VD4 or VD2) resulted in a complete suppression of neurite outgrowth from both pre‐ and postsynaptic neurons, even though the cells were cultured in CM. A single cell in the same dish, however, extended elaborate neurites. Similarly, a postsynaptic cell (VD4) contact suppressed the rate of neurite extension from a previously sprouted RPeD1. This suppression of the presynaptic growth cone motility was also target cell contact specific. The neurite suppression from soma–soma paired cells was transient, and neuronal sprouting began after a delay of 48–72 h. In contrast, when paired with VD1, both RPeD1 and this non‐target cell exhibited robust neurite outgrowth. We demonstrate that this neurite suppression from soma–soma paired cells was target cell contact/synapse specific and Ca²⁺ dependent. Specifically, soma–soma pairing in CM containing either lower external Ca²⁺ concentration (50% of its control level) or Cd²⁺ resulted in robust neurite outgrowth from both cells; however, the incidence of synapse formation between the paired cells was significantly reduced. Taken together, our data show that contact (physical and/or synaptic) between synaptic partners strongly influence neurite outgrowth patterns of both pre‐ and postsynaptic neurons in a time‐dependent and cell‐specific manner. Moreover, our data also suggest that neurite outgrowth and synapse formation are differentially regulated by external Ca²⁺ concentration. © 2000 John Wiley & Sons, Inc. J Neurobiol 42: 357–369, 2000     

Effects of captivity and testosterone on the volumes of four brain regions in the dark‐eyed junco (Junco hyemalis)

This study investigates the effects of captivity and testosterone treatment on the volumes of brain regions involved in processing visual and spatial information in adult dark‐eyed juncos (Junco hyemalis). We treated captive and free‐living male juncos with either testosterone‐filled or empty implants. Captive juncos had a smaller hippocampal formation (HF) (both in absolute volume and relative to telencephalon) than free‐living birds, regardless of hormone treatment. Testosterone‐treated males (both captive and free‐living) had a smaller telencephalon and nucleus rotundus, but not a smaller HF or ectostriatum, than controls. We found that free‐living testosterone‐treated males had larger home ranges than free‐living controls in agreement with earlier experiments, but we found no corresponding difference in HF volume. We discuss the implications of the effect of captivity on HF volume for past and future laboratory experiments. © 2000 John Wiley & Sons, Inc. J Neurobiol 43: 244–253, 2000     

Preparation of fluorescence quenched libraries containing interchain disulphide bonds for studies of protein disulphide isomerases

Protein disulphide isomerase is an enzyme that catalyses disulphide redox reactions in proteins. In this paper, fluorogenic and interchain disulphide bond containing peptide libraries and suitable substrates, useful in the study of protein disulphide isomerase, are described. In order to establish the chemistry required for the generation of a split-synthesis library, two substrates containing an interchain disulphide bond, a fluoroescent probe and a quencher were synthesized. The library consists of a Cys residue flanked by randomized amino acid residues at both sides and the fluoroescent Abz group at the amino terminal. All the 20 natural amino acids except Cys were employed. The library was linked to PEGA‒beads via methionine so that the peptides could be selectively removed from the resin by cleavage with CNBr. A disulphide bridge was formed between the bead‒linked library and a peptide containing the quenching chromophore (Tyr(NO₂)) and Cys(pNpys) activated for reaction with a second thiol. The formation and cleavage of the interchain disulphide bonds in the library were monitored under a fluoroescence microscope. Substrates to investigate the properties of protein disulphide isomerase in solution were also synthesized. © 1998 European Peptide Society and John Wiley & Sons, Ltd.     

Reactions of adult and immature squirrel monkeys to intergroup exposure

Initial encounters between unfamiliar animals raise the practical problem of controlling aggression and provide the opportunity to examine changes in social structure that may occur as groups merge. Social interactions and spatial grouping patterns were examined in newly formed squirrel monkey groups, in which a subgroup of familiar adults was introduced to a subgroup of familiar immature squirrel monkeys. Yearlings (10–11 months) and subadults (20–50 months) generally remained spatially distinct from adults, and intergroup interactions often consisted of adult-initiated antagonism. Adults exhibited sexual segregation in their spatial grouping patterns and interactions, whereas yearlings and subadults generally showed sexual integration. These data suggest that there is considerable adult resistance to integration of unfamiliar immatures into established adult social groups. Zoo Biol 17:519–524, 1998. © 1998 Wiley-Liss, Inc.     

Age-related changes in bone formation,osteoblastic cell proliferation,and differentiation during postnatal osteogenesis in human calvaria

We have determined the age-related changes in the growth characteristics and expression of the osteoblast phenotype in human calvaria osteoblastic cells in relation with histologic indices of bone formation during postnatal calvaria osteogenesis. Histomorphometric analysis of normal calvaria samples obtained from 36 children, aged 3 to 18 months, showed an age-related decrease in the extent of bone surface covered with osteoblasts and newly synthesized collagen, demonstrating a progressive decline in bone formation during postnatal calvaria osteogenesis. Immunohistochemical analysis showed expression of type I collagen, bone sialoprotein, and osteonectin in the matrix and osteoblasts, with no apparent age-related change during postnatal calvaria osteogenesis. Cells isolated from human calvaria displayed characteristics of the osteoblast phenotype including alkaline phosphatase (ALP) activity, osteocalcin (OC) production, expression of bone matrix proteins, and responsiveness to calciotropic hormones. The growth of human calvaria osteoblastic cells was high at 3 months of age and decreased with age, as assessed by (³H)-thymidine incorporation into DNA. Thus, the age-related decrease in bone formation is associated with a decline in osteoblastic cell proliferation during human calvaria osteogenesis. In contrast, ALP activity and OC production increased with age in basal conditions and in response to 1,25(OH)₂, vitamin D₃, suggesting a reciprocal relationship between cell growth and expression of phenotypic markers during human postnatal osteogenesis. Finally, we found that human calvaria osteoblastic cells isolated from young individuals with high bone formation activity in vivo and high growth potential in vitro had the ability to form calcified nodular bone-like structures in vitro in the presence of ascorbic acid and β-glycerophosphate, providing a new model to study human osteogenesis in vitro. J. Cell. Biochem. 64:128–139. © 1997 Wiley-Liss, Inc.     

Preliminary crystallographic characterization of ricin agglutinin

The quaternary structure of ricin agglutinin (RCA) has been determined by x-ray crystallography. The refined structure of ricin proved to be a successful search model using the molecular replacement method of phase determination. RCA forms an elongated molecule of dimensions 120 Å × 60 Å × 40 Å with two A chains at the center and a B chain at each end. The A chains are covalently associated via a disulfide bridge between Cys 156 of both chains. Additional contacts at residues 114–115 stabilize the dimer interface. The covalent association of RCA A chains was confirmed by gel filtration under reducing and nonreducing conditions. Proteins 28:586–589, 1997. © 1997 Wiley-Liss, Inc.