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Short Life Span (short + life_span)
Selected AbstractsFc,RIIB deficiency with Fas mutation is sufficient for the development of systemic autoimmune diseaseEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2003Kaori Yajima Abstract MRL.Faslpr/lpr mice, a model for systemic lupus erythematosus (SLE) and arthritis in humans, have a Fas mutation that results in spontaneous development of systemic autoimmune diseases and a short life span. Half of them die by 5,6,months of age due to massive progression of systemic autoimmune diseases, such as lupus nephritis. However, C57BL/6 (B6).Faslpr/lpr strain does not develop such disorders within the normal life span, indicating that suppressor gene(s) in B6 mice may control the onset and exacerbation of disease. Here, we show that the gene for a unique inhibitory Fc receptor for IgG (Fc,RIIB) is a critical SLE suppressor. Fc,RIIB-deficient B6.Faslpr/lpr (B6.IIB,/,Faslpr/lpr) mice developed systemic autoimmune diseases, including anti-DNA and anti-type,II collagen autoantibodies and cryoglobulin production, immune complex glomerulonephritis and arthritis. They were short-lived, due to enhanced autoantibody production by B cells culminating in fatal lupus nephritis. Thus, Fc,RIIB deletion with Fas mutation is sufficient for the development of systemic autoimmunity in B6 mice. The inhibitory signaling cascade via Fc,RIIB may be critical for suppressing SLE in humans. [source] Yield, growth and mortality rate of the Thai river sprat, Clupeichthys aesarnensis, in Sirinthorn Reservoir, ThailandFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2003T. Jutagate Abstract The Thai river sprat, Clupeichthys aesarnensis Wongratana, is a clupeid with a short life span, and supports artisanal fisheries in a number of reservoirs in the Mekong Basin. The growth parameters, mortality rates and the status of the Thai river sprat in Sirinthorn Reservoir (28 800 ha), NE Thailand (15°N; 105°E), are presented. The fishery is based on lured lift-nets, operated 7,14 days in the new moon period, September to April each year. It was shown that the von Bertalanffy growth function (VBGF) model was Lt (mm) = 78.43[1 , exp{,0.211[t , (,0.7996)]}] and its growth conformed to an isometric pattern. Natural mortality rate (month,1) was 0.13 month,1. Total mortality rates ranged from 0.69 to 1.53 month,1 depending on the weather and the fishing season. Recruitment was continuous throughout the year but peaked in June and July. The yield per recruit model indicated that the exploitation rate of this fishery is probably too high. [source] What limits insect fecundity?FUNCTIONAL ECOLOGY, Issue 3 2008Body size-, oviposition in a butterfly, temperature-dependent egg maturation Summary 1Large female insects usually have high potential fecundity. Therefore selection should favour an increase in body size given that these females get opportunities to realize their potential advantage by maturing and laying more eggs. However, ectotherm physiology is strongly temperature-dependent, and activities are carried out sufficiently only within certain temperature ranges. Thus it remains unclear if the fecundity advantage of a large size is fully realized in natural environments, where thermal conditions are limiting. 2Insect fecundity might be limited by temperature at two levels; first eggs need to mature, and then the female needs time for strategic ovipositing of the egg. Since a female cannot foresee the number of oviposition opportunities that she will encounter on a given day, the optimal rate of egg maturation will be governed by trade-offs associated with egg- and time-limited oviposition. As females of different sizes will have different amounts of body reserves, size-dependent allocation trade-offs between the mother's condition and her egg production might be expected. 3In the temperate butterfly Pararge aegeria, the time and temperature dependence of oviposition and egg maturation, and the interrelatedness of these two processes were investigated in a series of laboratory experiments, allowing a decoupling of the time budgets for the respective processes. 4The results show that realized fecundity of this species can be limited by both the temperature dependence of egg maturation and oviposition under certain thermal regimes. Furthermore, rates of oviposition and egg maturation seemed to have regulatory effects upon each other. Early reproductive output was correlated with short life span, indicating a cost of reproduction. Finally, large females matured more eggs than small females when deprived of oviposition opportunities. Thus, the optimal allocation of resources to egg production seems dependent on female size. 5This study highlights the complexity of processes underlying rates of egg maturation and oviposition in ectotherms under natural conditions. We further discuss the importance of temperature variation for egg- vs. time-limited fecundity and the consequences for the evolution of female body size in insects. [source] Consequences of elevated temperatures on life-history traits of an introduced fish, pumpkinseed Lepomis gibbosusJOURNAL OF FISH BIOLOGY, Issue 2 2006S. Dembski Life-history reactions of a pumpkinseed Lepomis gibbosus population in north-eastern France exposed to heated waters were studied. The study was conducted from 2001 to 2003 in an artificial reservoir, adjacent to a nuclear power plant, in which water temperatures are cool in winter (8·2,12·4° C) and rise early in spring (April: 14·7° C) nearly 5° C and 3° C over the temperature of its tributary, respectively. Fast growth among young-of-the-year, precocious maturity and short life span were observed, in contrast to related studies. The short life span appeared to be the price paid for early maturity in breeding fish, which suffered high mortality rates just after their first reproduction. [source] Establishment and characterization of immortalized human gingival keratinocyte cell linesJOURNAL OF PERIODONTAL RESEARCH, Issue 6 2008S. Gröger Background and Objective:, Primary human keratinocytes are used to analyze the properties of the oral epithelium and the early stages of oral bacterial infections. In vitro, these cells are characterized by their short life span and restricted availability. Approaches for culturing these cells will end after approximately 6,10 passages as a result of entry into apoptosis. For this reason, it is important to generate cell lines suitable for obtaining an unlimited source of cells. Therefore, the aim of the present study was to generate gingival keratinocyte cell lines and to compare their in vitro behaviour with those of primary human gingival keratinocytes. Material and Methods:, Primary human gingival keratinocytes were immortalized with a combination of the human papilloma virus onkoproteins E6 and E7. The pattern of the cytokeratins, involucrin and filaggrin was investigated by intracellular staining using flow cytometry. This method allows quantitative analysis of the expression of a variety of intracellular or extracellular markers. Results:, The immortalized cell lines showed many morphological similarities, expressing a cytokeratin pattern that is comparable with that of primary gingival keratinocytes. Furthermore, they developed transepithelial electrical resistance, which is a marker for the generation of tight junctions. These results indicate that the cells might be able to act as an epithelial barrier, reflecting the reaction of primary human cells. Conclusion:, The establishment of a continuous line of human gingival epithelial cells with functional characteristics of the epithelial barrier provides a valuable in vitro model for using to study the early steps of gingival/periodontal infections. [source] GEOGRAPHICAL VARIATION OF THE PARASITE, PHYLLOBOTHRIUM DELPHINI (CESTODA), IN BALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE NORTHERN NORTH PACIFIC, BERING SEA, AND SEA OF OKHOTSKMARINE MAMMAL SCIENCE, Issue 2 2001William A. Walker Abstract Prevalence of the larval cestode, Phyllobothrium delphini, was estimated from 2,445 Dall's porpoise, Phocoenoides dalli, from the incidental take of the Japanese high seas salmon drift-net fishery in the northwestern North Pacific Ocean, Bering Sea, and a local hand harpoon fishery in the southern Sea of Okhotsk. Prevalence of P. delphini was 22.7% in the northwestern North Pacific Ocean and 1.4% in the Bering Sea. This parasite was not found in the southern Sea of Okhotsk. Geographical differences in the prevalence of P. delphini may be due, at least in part, to regional differences in abundance of elasmobranchs known to feed on marine mammals and suspected as hosts of the parasite. Estimated intensity of infection of individual porpoises by P. delphini was low (estimated mean intensity of 3.5 plerocercoids per animal). This is a low intensity of infection compared to other species of small cetaceans studied and may be due to both differences in regional abundance of elasmobranchs and the comparatively short life span of P. dalli. [source] A NEW TEREBRATULID BRACHIOPOD SPECIES FROM THE SIEGENIAN OF THE DRA VALLEY, MOROCCO, AND ITS STRATIGRAPHIC, PALAEOGEOGRAPHIC AND PHYLOGENETIC SIGNIFICANCEPALAEONTOLOGY, Issue 4 2008MENA SCHEMM-GREGORY Abstract:, A new terebratulid brachiopod species, Rhenorensselaeria jansenii, has been identified in the Merzâ-Akhsaï Formation of the Dra Valley, Morocco, and the Grauwacke de Montguyon of the Amorican Massif, France. It is compared with the other known species of Rhenorensselaeria from Europe, Rh. strigiceps and Rh. demerathia, as well as with Rh. macgerriglei from North America, from which it differs in being larger and having coarser costae. Its possible life habit in clusters and its fossil community are compared with those of Rh. strigiceps from the Rheinisches Schiefergebirge (,Rhenish Slate Mountains'), Germany, which it most resembles. A new phylogeny of the subfamily Rhenorensselaerinae is constructed. The close phylogenetic relationship between Rh. jansenii and Rh. strigiceps confirms close palaeobiogeographical relationships between North Africa, France and the Rheinisches Schiefergebirge as well as a wider relationship between Central Europe and Gaspé, eastern Canada, during the Early Devonian. Taxa of Rhenorensselaeria are mainly restricted to the Middle and Upper Siegenian, although rare individuals have been found in the Lower Emsian of Central Europe and North America. Because of their abundance in the Dra Valley and Rheinisches Schiefergebirge and their short life span, rhenorensselaerid taxa can be regarded as important stratigraphical markers of Middle,Late Siegenian and Early Emsian sediments in North Africa and Central Europe. [source] | ||||||||||||||||