Pleistocene extinction of genyornis newtoni: human impact on australian megafauna     

GH Miller  JW Magee  BJ Johnson  ML Fogel  NA Spooner  MT McCulloch  LK Ayliffe 《Science (New York, N.Y.)》1999,283(5399):205-208

More than 85 percent of Australian terrestrial genera with a body mass exceeding 44 kilograms became extinct in the Late Pleistocene. Although most were marsupials, the list includes the large, flightless mihirung Genyornis newtoni. More than 700 dates onGenyornis eggshells from three different climate regions document the continuous presence of Genyornis from more than 100,000 years ago until their sudden disappearance 50,000 years ago, about the same time that humans arrived in Australia. Simultaneous extinction of Genyornis at all sites during an interval of modest climate change implies that human impact, not climate, was responsible.  相似文献   

Intrahepatic biliary coccidiosis in a dog     

T P Lipscomb  J P Dubey  J M Pletcher  N H Altman 《Veterinary pathology》1989,26(4):343-345

  相似文献   

Spontaneous malignant hemangioendothelioma in two rabbits     

J M Pletcher  J C Murphy 《Veterinary pathology》1984,21(5):542-544

  相似文献   

Seasonality of Reproduction in Mammals: Intimate Regulatory Mechanisms and Practical Implications     

P Chemineau  D Guillaume  M Migaud  JC Thiéry  MT Pellicer-Rubio  B Malpaux 《Reproduction in domestic animals》2008,43(S2):40-47

Farm mammals generally express seasonal variations in their production traits, thus inducing changing availability of fresh derived animal products (meat, milk and cheese) or performances (horses). This is due to a more or less marked seasonal birth distribution in sheep and goats, in horses but not cattle. Birth peak occurs at the end of winter-early spring, the most favourable period for the progeny to survive. Most species show seasonal variations in their ovulation frequency (presence or absence of ovulation), spermatogenic activity (from moderate decrease to complete absence of sperm production), gamete quality (variations in fertilization rates and embryo survival), and also sexual behaviour. The intimate mechanism involved is a complex combination of endogenous circannual rhythm driven and synchronized by light and melatonin. Profound and long-term neuroendocrine changes involving different neuromediator systems were described to play a role in these processes. In most species artificial photoperiodic treatments consisting of extra-light during natural short days (in sheep and goats and mares) or melatonin during long days (in sheep and goats) are extensively used to either adjust the breeding season to animal producer needs and/or to completely overcome seasonal variations of sperm production in artificial insemination centres. Pure light treatments (without melatonin), especially when applied in open barns, could be considered as non-invasive ones which fully respect animal welfare. Genetic selection could be one of the future ways to decrease seasonality in sheep and goats.  相似文献   

Natriuretic peptide system regulation in granulosa cells during follicle deviation and ovulation in cattle          下载免费PDF全文

JG Ferst  JE Nóbrega Jr  PRA Rosa  MT Rovani  GF Ilha  RC Bohrer  R Ferreira  BG Gasperin  V Bordignon  PBD Gonçalves 《Reproduction in domestic animals》2018,53(3):710-717

Natriuretic peptides (NPs) are known to regulate reproductive events in polyovulatory species, but their function and regulation in monovulatory species remain to be fully characterized. Using a well‐established in vivo model, we found that bovine granulosa cells from follicles near the deviation stage express mRNA for the three NP receptors (NPR1, NPR2 and NPR3), but not for NP precursors (NPPA, NPPB and NPPC). The abundance of NPR3 mRNA was higher in dominant compared to subordinate follicles at the expected time of follicular deviation. After deviation, mRNA for all NP receptors was significantly more abundant in the dominant follicle. Intrafollicular inhibition of oestrogen receptors downregulated NPR1 mRNA in dominant follicles. In granulosa cells from preovulatory follicles, NPPC mRNA increased at 3 and 6 h after systemic GnRH treatment, but decreased at 12 and 24 h to similar levels observed in samples collected at 0 h. After GnRH treatment, NPR1 mRNA was upregulated at 24 h, NPR3 mRNA gradually decreased after 3 h, while NPR2 mRNA was not regulated. The mRNA expression of the enzyme FURIN increased at 24 h after GnRH treatment. These findings revealed that the expression of mRNA encoding important components of the NP system is regulated in bovine granulosa cells during follicular deviation and in response to GnRH treatment, which suggests a role of NP system in the modulation of these processes in monovulatory species.  相似文献   

Demodectic mange in threatened southern sea otters (Enhydra lutris nereis)     

Nadia Javeed  Janet Foley  Arturo Oliver-Guimera  Verena K. Affolter  Michael K. Keel  Angelina Reed  Risa Pesapane  Pádraig J. Duignan  Michael Murray  MT Tinker  Melissa A. Miller 《Veterinary dermatology》2021,32(3):211-e55

  相似文献   

Local anesthetics: significance of hydrogen bonding in mechanism of action     

Sax M  Pletcher J 《Science (New York, N.Y.)》1969,166(3912):1546-1548

The action of local anesthetics is considered in terms of their ability to function as the donor in a hydrogen bond. The formation of a hydrogen-bonded complex between the drug and an acceptor group on the neural membrane is suggested as a feature in the action of local anesthetics.  相似文献   

Regulation of Drosophila life span by olfaction and food-derived odors     

Libert S  Zwiener J  Chu X  Vanvoorhies W  Roman G  Pletcher SD 《Science (New York, N.Y.)》2007,315(5815):1133-1137

Smell is an ancient sensory system present in organisms from bacteria to humans. In the nematode Caenorhabditis elegans, gustatory and olfactory neurons regulate aging and longevity. Using the fruit fly, Drosophila melanogaster, we showed that exposure to nutrient-derived odorants can modulate life span and partially reverse the longevity-extending effects of dietary restriction. Furthermore, mutation of odorant receptor Or83b resulted in severe olfactory defects, altered adult metabolism, enhanced stress resistance, and extended life span. Our findings indicate that olfaction affects adult physiology and aging in Drosophila, possibly through the perceived availability of nutritional resources, and that olfactory regulation of life span is evolutionarily conserved.  相似文献   

Regulation of longevity and stress resistance by Sch9 in yeast     

Fabrizio P  Pozza F  Pletcher SD  Gendron CM  Longo VD 《Science (New York, N.Y.)》2001,292(5515):288-290

  相似文献   

Demography of dietary restriction and death in Drosophila     

Mair W  Goymer P  Pletcher SD  Partridge L 《Science (New York, N.Y.)》2003,301(5640):1731-1733

Dietary restriction (DR) increases life-span in organisms from yeast to mammals, presumably by slowing the accumulation of aging-related damage. Here we show that in Drosophila, DR extends life-span entirely by reducing the short-term risk of death. Two days after the application of DR at any age for the first time, previously fully fed flies are no more likely to die than flies of the same age that have been subjected to long-term DR. DR of mammals may also reduce short-term risk of death, and hence DR instigated at any age could generate a full reversal of mortality.  相似文献