Determinants of density- and frequency-dependent fitness in competing plant pathogens     

Newton MR  Kinkel LL  Leonard KJ 《Phytopathology》1998,88(1):45-51

ABSTRACT Using mathematical models, we investigated how infection and sporulation characteristics of competing plant pathogens determine the density and frequency dependence of relative fitness. Two models, one for the infection stage and one for the sporulation stage of a pathogen's life cycle, describe reproductive output of pathogen strains in mixture as a function of the strains' population densities. Model parameters include infection and sporulation efficiencies, carrying capacities on leaves for sporulating lesions and spore production, and coefficients of interstrain competitive effects in both life cycle stages. Although the models were originally developed for rust fungi, they are generally applicable to any organism with distinct colonization (e.g., infection) and propagative (e.g., sporulation) life cycle stages. In this work, paired hypothetical strains were assigned equal baseline parameter values. Parameters were then altered one at a time for one or both strains, and relative fitness was calculated over a range of densities and strain frequencies. Except for infection efficiency, the fitness benefit conferred by an advantage in a single parameter was always density dependent. Relative fitness was frequency dependent whenever inter- and intrastrain competitive effects were not equal. These results suggest that the fitness of pathogens in nature is rarely fixed, but, rather, may typically be highly dependent on the densities and frequencies of all coexisting strains in a habitat.  相似文献   

Oviductal Fluid Proteins Associated with the Bovine Zona Pellucida and the Effect on In Vitro Sperm–Egg Binding,Fertilization and Embryo Development     

RF Gonçalves  AL Staros  GJ Killian 《Reproduction in domestic animals》2008,43(6):720-729

Studies have demonstrated that oviductal fluid (ODF) proteins associate with eggs of numerous species including the bovine. In this study, the association of three ODF proteins, the bovine oestrus‐associated protein, osteopontin (OPN), lipocalin‐type prostaglandin D synthase (L‐PGDS), with the bovine zona pellucida (ZP) was demonstrated by immunohistochemistry and western blot. The biological function of ODF derived egg‐associated OPN and L‐PGDS in sperm binding, fertilization and embryonic development was also explored. In vitro matured bovine oocytes were pre‐incubated with ODF collected by cannula from cows in oestrus, or ODF with antibodies to OPN, L‐PGDS and bovine serum albumin (BSA). Following incubation, oocytes were inseminated with 1 × 10⁵ frozen‐thawed spermatozoa, and they were evaluated for sperm binding, fertilization and embryonic development in vitro. Pre‐treatment of ODF with antibodies to all of proteins reduced sperm binding to the ZP and fertilization in vitro. Cleavage rates were not significantly different among incubations, but rates of embryo development were significantly decreased. We conclude that antibodies to OPN, L‐PGDS and BSA react with oocytes incubated with ODF and inhibit sperm binding, fertilization and embryonic development in vitro, suggesting a potential role of these proteins in these events.  相似文献   

Cardiovascular effects of desflurane following acute hemorrhage in dogs     

Paulo S.P. Santos  DVM  MS    James N.B.M. Andrade  DVM  MS    ré L. Selmi  DVM  MS    Jorge L.O. Costa  DVM  MS    Rafael R. Faleiros  DVM  MS    Newton Nunes  DVM  MS  PhD 《Journal of Veterinary Emergency and Critical Care》2003,13(1):7-12

Objective: To determine the cardiovascular effects of desflurane in dogs following acute hemorrhage. Design: Experimental study. Animals: Eight mix breed dogs. Interventions: Hemorrhage was induced by withdrawal of blood until mean arterial pressure (MAP) dropped to 60 mmHg in conscious dogs. Blood pressure was maintained at 60 mmHg for 1 hour by further removal or replacement of blood. Desflurane was delivered by facemask until endotracheal intubation could be performed and a desflurane expiratory end‐tidal concentration of 10.5 V% was maintained. Measurements and main results: Systolic, diastolic, and mean arterial blood pressure (SAP, DAP and MAP), central venous pressure (CVP), cardiac output (CO), stroke volume (SV), cardiac index (CI), systemic vascular resistance (SVR), heart rate (HR), respiratory rate (RR), partial pressure of carbon dioxide in arterial blood (PaCO₂), and arterial pH were recorded before and 60 minutes after hemorrhage, and 5, 15, 30, 45 and 60 minutes after intubation. Sixty minutes after hemorrhage, SAP, DAP, MAP, CVP, CO, CI, SV, PaCO₂, and arterial pH decreased, and HR and RR increased when compared with baselines values. Immediately after intubation, MAP and arterial pH decreased, and PaCO₂ increased. Fifteen minutes after intubation SAP, DAP, MAP, arterial pH, and SVR decreased. At 30 and 45 minutes, MAP and DAP remained decreased and PaCO₂ increased, compared with values measured after hemorrhage. Arterial pH increased after 30 minutes of desflurane administration compared with values measured 5 minutes after intubation. Conclusions: Desflurane induced significant changes in blood pressure and arterial pH when administered to dogs following acute hemorrhage.  相似文献   

Transmission of visceral leishmaniasis through blood transfusions from infected English foxhounds to anemic dogs.     

S D Owens  D A Oakley  K Marryott  W Hatchett  R Walton  T J Nolan  A Newton  F Steurer  P Schantz  U Giger 《Journal of the American Veterinary Medical Association》2001,219(8):1076-1083

OBJECTIVE: To conduct serologic surveillance for Leishmania spp in English foxhounds from a kennel, as well as recipients of blood from these dogs, and determine whether L infantum organisms could be transmitted via blood transfusion. DESIGN: Serologic prevalence survey. ANIMALS: 120 English foxhounds and 51 dogs of various breeds receiving blood from these donors. PROCEDURE: Foxhound blood donors, foxhound nondonors, and nonfoxhound blood recipient dogs were evaluated serologically for Leishmania spp by indirect fluorescent antibody testing. Dogs that received packed RBC (PRBC) transfusions from foxhound donors from mid-1996 through mid-2000 were identified. Furthermore, dogs were serologically evaluated if they had received fresh frozen plasma (FFP) transfusions in 1999 and 2000 from seropositive foxhound blood donors. RESULTS: Thirty percent of the English Foxhounds were seropositive for Leishmania spp (titer > or = 1:16), although the degree of seropositivity varied considerably during the period. Furthermore, 57 foxhounds had been used as donors from 1996 to 2000, and 342 units of PRBC had been transfused to at least 227 patients. All 25 dogs screened that received PRBC from seronegative foxhound donors tested negative, whereas 3 of 7 dogs that received PRBC from seropositive donors tested positive. All 9 dogs that received FFP from seropositive foxhound donors remained seronegative. CONCLUSIONS AND CLINICAL RELEVANCE: To our knowledge, this report documents the first transmission of Leishmania spp by blood transfusion. The use of foxhounds as blood donors may not be advisable in North America.  相似文献   

Vascular hamartoma in the tongue of a horse     

Brandon L. Brunson DVM  Jennifer Taintor DVM  Joseph Newton DVM  PhD  John Schumacher DVM  Undine Christman DVM  MS   《Journal of Equine Veterinary Science》2006,26(6):275-277

Hamartoma is defined as a benign tumor-like nodule composed of an overgrowth of mature cells and tissues that normally occur in the affected part but with disorganization. Vascular hamartomas are defined as disorganized and excessive proliferations of vascular tissue. Most vascular hamartomas are present at birth or during early infancy and are considered developmental lesions rather than true neoplasms. Vascular hamartomas are rarely described in horses, and reports have been limited to the dorsal carpal region, the ovary, and the face. In this report, we describe a vascular hamartoma arising from the tongue of a 2-year-old Quarter Horse.  相似文献   

RELATIONSHIPS BETWEEN DIETARY SODIUM AND POTASSIUM, LEVEL OF MEAT AND BONE MEAL AND INFECTIOUS BRONCHITIS INC CHICKENS     

R. J. W. Gartner  B.Sc.  L. G. Newton  B.V.Sc. H. W. Burton  H.D.A. 《Australian veterinary journal》1966,42(10):357-363

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Out-of-season breeding in sheep     

J E Betts  J E Newton  H L Denehy 《The Veterinary record》1969,84(14):358-359

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A review of 116 diaphragmatic hernias in dogs and cats   总被引：1，自引：0，他引：1  

G P Wilson  C D Newton  J K Burt 《Journal of the American Veterinary Medical Association》1971,159(9):1142-1145

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Effect of motor cortex ablation on conditioned learning in sheep     

C D Newton  T F Fletcher 《American journal of veterinary research》1969,30(10):1765-1772

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ESOPHAGEAL DISEASES     

Dr.  Newton B. Tennille 《Veterinary radiology & ultrasound》1962,3(1):30-31

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