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961.
Four hundred and eight quantitative grab samples collected during the winter and spring of 1977 from the New England Continental Shelf (Georges Bank) yielded 333 species of polychaetes. Polychaetes comprised 53.8% of the number of all infaunal species, 53% of the density, and 60.5% of the wet weight biomass for all soft-bodied organisms, at least for the winter. Mean number of species and mean density was significantly higher in the spring than in the winter. Mean values of number of species, H', SDN, density, and biomass were associated with various environmental factors. Based on numerical classification (normal and inverse) five polychaete site groups were identified. To a great extent these site groups were molded by major physical, geologic and biologic processes which influence the productivity of this ecologically and economically important area.  相似文献   
962.
Exo-galactanase/beta-galactosidase (EC 3.2.1.23) activity is thought to be responsible for the loss of galactosyl residues from the cell walls of ripening tomatoes. Transgenic tomato plants (Lycopersicon esculentum Mill cv. Ailsa Craig) with reduced exo-galactanase/beta-galactosidase mRNA were generated to test this hypothesis and to investigate the role of the enzyme in fruit softening. A previously identified tomato beta-galactosidase cDNA clone, TBG1, was used in the experiments. Heterologous expression of the clone in yeast demonstrated that TBG1 could release galactosyl residues from tomato cell wall galactans. Transgenic plants showed a reduction in TBG1 mRNA to 10% of normal levels in the ripening fruits. However, despite the reduction in message, total beta-galactosidase and exo-galactanase activities were unaffected. Furthermore, there was no apparent effect on levels of cell wall galactosyl residues when compared with the control. It was concluded that during the ripening of tomato fruits a family of beta-galactosidases capable of degrading cell wall galactans are active and down-regulation of TBG1 message to 10% was insufficient to alter the degree of galactan degradation.  相似文献   
963.
964.
Egg size is a critical life-history trait because it can profoundlyinfluence offspring fitness and the number of offspring thatcan be produced. Recently, interest has grown in how egg sizeinfluences fertilization rate and in turn how sperm availabilitymight influence the evolution of egg size among broadcast-spawningmarine invertebrates. In this article I review the empiricalevidence on the ways in which egg size and egg accessory structuresinfluence fertilization and theoretical models of the ways spermavailability might influence the evolution of egg size. Evidencesuggests that egg size does influence the collision frequencywith sperm, and models suggest that sperm availability can influenceselection on egg size. Sperm availability appears to be oneof the several factors that influence optimal egg size in broadcast-spawningmarine invertebrates.  相似文献   
965.
Surveillance of animal diseases provides information essential for the protection of animal health and ultimately public health. The voluntary pig health schemes, implemented in the United Kingdom, are integrated systems which capture information on different macroscopic disease conditions detected in slaughtered pigs. Many of these conditions have been associated with a reduction in performance traits and consequent increases in production costs. The schemes are the Wholesome Pigs Scotland in Scotland, the BPEX Pig Health Scheme in England and Wales and the Pig Regen Ltd. health and welfare checks done in Northern Ireland. This report set out to compare the prevalence of four respiratory conditions (enzootic pneumonia-like lesions, pleurisy, pleuropneumonia lesions and abscesses in the lung) assessed by these three Pig Health Schemes. The seasonal variations and year trends associated with the conditions in each scheme are presented. The paper also highlights the differences in prevalence for each condition across these schemes and areas where further research is needed. A general increase in the prevalence of enzootic pneumonia like lesions was observed in Scotland, England and Wales since 2009, while a general decrease was observed in Northern Ireland over the years of the scheme. Pleurisy prevalence has increased since 2010 in all three schemes, whilst pleuropneumonia has been decreasing. Prevalence of abscesses in the lung has decreased in England, Wales and Northern Ireland but has increased in Scotland. This analysis highlights the value of surveillance schemes based on abattoir pathology monitoring of four respiratory lesions. The outputs at scheme level have significant value as indicators of endemic and emerging disease, and for producers and herd veterinarians in planning and evaluating herd health control programs when comparing individual farm results with national averages.  相似文献   
966.
967.
The binding of biologically active [125I]thyrotropin to purified plasma membranes prepared from bovine thyroid glands was studied. At 4°C, specific binding reached a maximum after 2 h of incubation and a plateau was maintained for up to 20 h. Degradation of [125I]thyrotropin was undetectable after 2 h of incubation and was only 10% of the total after 20 h.At pH 6.0, at which binding was maximal, a single class of binding sites, having a dissociation constant of approx. 25 nM, was evident. Dissociation studies revealed first order kinetics with a half-time of 2–3 min. At pH 7.5, binding curves were complex, suggesting two orders of binding sites with dissociation constants of approx. 200 nM and 80 pM. Further, at this pH, dissociation of the thyrotropin from its receptor was also complex, suggesting the presence of two first order reactions, one with a half-time similar to that seen at pH 6.0 and another with a half-time of 4 h. At both pH 6.0 and 7.5, insulin, glucagon, growth hormone, and prolactin were without effect on [125I]thyrotropin binding.Similar high affinity and low affinity binding sites were seen with porcine thyroid membranes, but only low affinity sites were seen with either rat liver membranes or human cultured lymphocytes.  相似文献   
968.
Cardiac ischemia associated with acute coronary syndrome and myocardial infarction is a leading cause of mortality and morbidity in the world. A rapid detection of the ischemic events is critically important for achieving timely diagnosis, treatment and improving the patient''s survival and functional recovery. This minireview provides an overview on the current biomarker research for detection of acute cardiac ischemia. We primarily focus on inosine and hypoxanthine, two by-products of ATP catabolism. Based on our published findings of elevated plasma concentrations of inosine/hypoxanthine in animal laboratory and clinical settings, since 2006 we have originally proposed that these two purine molecules can be used as rapid and sensitive biomarkers for acute cardiac ischemia at its very early onset (within 15 min), hours prior to the release of heart tissue necrosis biomarkers such as cardiac troponins. We further developed a chemiluminescence technology, one of the most affordable and sensitive analytical techniques, and we were able to reproducibly quantify and differentiate total hypoxanthine concentrations in the plasma samples from healthy individuals versus patients suffering from ischemic heart disease. Additional rigorous clinical studies are needed to validate the plasma inosine/hypoxanthine concentrations, in conjunction with other current cardiac biomarkers, for a better revelation of their diagnostic potentials for early detection of acute cardiac ischemia.  相似文献   
969.
The spicate inflorescence of Saururus cernuus L. (Saururaceae) results from the activity of an inflorescence apical meristem which produces 200–300 primordia in acropetal succession. The inflorescence apex arises by conversion of the terminal vegetative apex. During transition the apical meristem increases greatly in height and width and changes its cellular configuration from one of tunica-corpus to one of mantle (with two tunica layers) and core. Primordia are initiated by periclinal divisions in the subsurface layer. These are “common” primordia, each of which subsequently divides to produce a floral apex above and a bract primordium below. The bract later elongates so that the flower appears borne on the bract. All common primordia are formed by the time the inflorescence is about 4.4 mm long; the apical meristem ceases activity at this stage. As cessation approaches, cell divisions become rare in the apical meristem, and height and width of the meristem above the primordia diminish, as primordia continue to be initiated on the flanks. Cell differentiation proceeds acropetally into the apical meristem and reaches the summital tunica layers last of all. Solitary bracts are initiated just before apical cessation, but no imperfect or ebracteate flowers are produced in Saururus. The final event of meristem activity is hair formation by individual cells of the tunica at the summit, a feature not previously reported for apical meristems.  相似文献   
970.
Mitochondrial DNA variation was surveyed in nine populations of the pigtail macaque (Macaca nemestrina), covering all three recognized subspecies in Southeast Asia. To do this, a 2,300 base pair fragment spanning the mitochondrial NAD 3 and NAD 4 genes and flanking tRNA subunits leucine and glycine was targeted for amplification and digested with a battery of 16 restriction endonucleases. Out of a total of 107 individuals, 32 unique haplotypes could be distinguished. Parsimony and neighbor-joining analyses grouped the haplotypes into five strongly supported assemblages representing China/Thailand, Malaysia, Sumatra, Borneo, and Siberut. These results indicate that the mainland and island mtDNA haplotypes are strictly and uniquely limited to the geographic ranges of the recognized morphological subspecies. Cladistic and neighbor-joining analyses indicate that inferred phylogenies of mtDNA haplotypes are congruent with subspecies designations. Furthermore, in support of morphological studies, results indicate that the Mentawai macaque is most likely not a distinct species but a subspecies of M. nemestrina. Am J Phys Anthropol 104:35–45, 1997. © 1997 Wiley-Liss, Inc.  相似文献   
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