Physicochemical Characterization of a Neonatal Calf Diarrhea Virus

Physicochemical characteristics of two isolates of a neonatal calf diarrhea virus were investigated. Neither isolate was sensitive to ether or chloroform, both were stable at pH 3.0, were relatively heat resistant, but were thermolabile when heated to 50°C for one hour in the presence of 1.0 M MgCl₂. Multiplication of virus was not inhibited by concentrations of 5-iodo-2'-deoxyuridine (IDUR) up to 500 µg/ml, which indicated that the nucleic acid was ribonucleic acid (RNA). Also, multiplication was not inhibited by concentrations of actinomycin D (AD) up to 0.5 µg/ml. Thermal denaturation studies demonstrated that the nucleic acid had a high melting temperature.

Resistance to lipid solvents, stability at an acid pH, relatively high thermostability, type of nucleic acid, plus previous reports from this laboratory on general morphology and cytopathogenicity suggest that the virus may belong to the diplornavirus (reovirus) group. However, thermolability in the presence of 1.0 M MgCl₂ is not consistent with characteristics of this group.

     

Long-term effect of timber harvesting in the Bartica Triangle, Central Guyana

In one of the longest time series available, we present a comparison between forest inventories of 1924, 1964 and 1999 of an 800 km² forest-harvesting area in Central Guyana. Harvesting mainly targeted one species Chlorocardium rodiei (Greenheart), of which the population declined by 63% over the 75 years of harvesting. The decline of the population was not only detectable in the harvested size classes (>30 cm) but also among the smaller size classes. In 1999, however, Greenheart still ranked third in abundance. There was little change in the overall species composition, proportion of disperser groups or proportion of functional groups in the tree community. There were also no detectable changes in tree diversity. The conservation value of these unique forests can still be considered high. Thus, while the long-term sustainability of Greenheart harvesting is low, other ecological criteria of sustainability are met. Short-term recovery of Greenheart is not to be expected due to low population growth and small numbers of seed trees. Strategic choices will have to be made with regard to harvesting the remaining Greenheart stands—three scenarios are discussed.     

Descriptive summary of an outbreak of porcine post-weaning multisystemic wasting syndrome (PMWS ) in New Zealand

CASE HISTORY: Investigations were conducted to determine the cause of an acute, multi-farm outbreak of porcine respiratory disease that included diarrhoea and subsequent loss of body condition in affected pigs. A definition for post-weaning multisystemic wasting syndrome (PMWS) including both clinical and pathological features, previously developed for the pig industry in New Zealand, was applied to the current outbreak. In addition to self-reporting by owners of affected farms, local veterinarians, disease and epidemiology consultants, and animal health officials from the Ministry of Agriculture and Forestry (MAF) were involved in conducting farm visits and submission of diagnostic specimens. CLINICAL FINDINGS AND DIAGNOSIS: Pathogens known to be endemic in the pig industry in New Zealand as well as likely exotic diseases were excluded as causative agents of the outbreak. Clinical signs including dyspnoea, diarrhoea, and rapid loss of body condition were consistent with the New Zealand case definition for PMWS. Interstitial pneumonia, pulmonary oedema, generalised lymph-node enlargement, and presence of porcine circovirus type 2 (PCV2) inclusion bodies were consistently identified in affected pigs. Classical swine fever virus (CSFv), Porcine reproductive and respiratory syndrome virus (PRRSv), and Influenza virus were ruled out, using molecular and traditional virological techniques. Spread of the disease between farms was hypothesised to be facilitated by locally migrating flocks of black-backed seagulls. The original source of the disease incursion was not identified. DIAGNOSIS: Based on the consistent presence of circovirus-associated lesions in lymphoid tissues in combination with generalised enlargement of lymph nodes, histiocytic interstitial pneumonia, clinical wasting, and poor response to antibiotic therapy, a diagnosis of PMWS was made. CLINICAL RELEVANCE: PMWS should be considered in the differential diagnoses of sudden onset of respiratory dyspnoea, diarrhoea, and rapid loss of body condition in young pigs in New Zealand pig herds.     

Use of fluorescence-activated flow cytometry to determine membrane lipid peroxidation during hypothermic liquid storage and freeze-thawing of viable boar sperm loaded with 4, 4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid

Part of the reduction in boar sperm motility and fertility associated with hypothermic liquid storage and cryopreservation may be due to membrane lipid peroxidation. Lipid peroxidation was monitored by the shift from red to green fluorescence emission of the lipophilic probe 4, 4-difluoro-5-(4-phenyl-1,3-butadienyl)-4-bora-3a,4a-diaza-s-indacene-3-undecanoic acid, C(11)BODIPY(581/591) (BODIPY), as measured by fluorescence-activated flow cytometry in live sperm (negative for propidium iodide). Experiments were conducted with Percoll-washed sperm to determine the specificity of BODIPY oxidation in the presence of different reactive oxygen species generators and metal chelators. Compared with no FeSO(4) and Na ascorbate, the combination of FeSO(4) and Na ascorbate (FeAc) increased (P < 0.01) the percentage of sperm containing oxidized BODIPY from 70% and increased (P < 0.05) BOD-IPY fluorescence intensity/cell by 5- to 10-fold after a 30-min incubation. Motility was depressed (P < 0.05) after exposure to FeAc, but viability was not affected. Of the reactive oxygen species generators tested, BODIPY oxidation was specific for FeAc, because menadione and H(2)O(2) had little or no effect. The oxidization of hydroethidine to ethidium was specific for menadione and H(2)O(2); FeAc had no effect. The presence of the metal chelators EDTA or deferoxamine mesylate at 3 and 9 muM inhibited FeAc-induced BODIPY oxidation and maintained motility. Experiments were conducted to determine the effect of liquid storage at 17 degrees C for 1 and 5 d and the effect of freeze-thawing on basal and FeAc-induced BODIPY oxidation. Basal BODIPY oxidation (no FeAc) was low in liquid stored and thawed viable sperm (1.3 and 3.4%, respectively). Although the incidence of basal or spontaneous membrane lipid peroxidation was low during liquid storage and after freeze-thawing, viable boar sperm were susceptible to FeAc-induced lipid peroxidation.     

The role of sand lances (Ammodytes sp.) in the Northwest Atlantic Ecosystem: A synthesis of current knowledge with implications for conservation and management

The American sand lance (Ammodytes americanus, Ammodytidae) and the Northern sand lance (A. dubius, Ammodytidae) are small forage fishes that play an important functional role in the Northwest Atlantic Ocean (NWA). The NWA is a highly dynamic ecosystem currently facing increased risks from climate change, fishing and energy development. We need a better understanding of the biology, population dynamics and ecosystem role of Ammodytes to inform relevant management, climate adaptation and conservation efforts. To meet this need, we synthesized available data on the (a) life history, behaviour and distribution; (b) trophic ecology; (c) threats and vulnerabilities; and (d) ecosystem services role of Ammodytes in the NWA. Overall, 72 regional predators including 45 species of fishes, two squids, 16 seabirds and nine marine mammals were found to consume Ammodytes. Priority research needs identified during this effort include basic information on the patterns and drivers in abundance and distribution of Ammodytes, improved assessments of reproductive biology schedules and investigations of regional sensitivity and resilience to climate change, fishing and habitat disturbance. Food web studies are also needed to evaluate trophic linkages and to assess the consequences of inconsistent zooplankton prey and predator fields on energy flow within the NWA ecosystem. Synthesis results represent the first comprehensive assessment of Ammodytes in the NWA and are intended to inform new research and support regional ecosystem‐based management approaches.     

Plankton associations and related factors in a hypereutrophic lake

Cluster analysis was used to group samples collected from ten stations in Moses Lake, Washington, according to the similarity of their contained algal species. During the period 1968 to 1970, nine recurring distinct sample groups, or algal populations, were identified. Of the nine, three were most distinct; they consistently recurred at the same stations, and were dominated by diatom, green, and blue-green algae, respectively. Of the six species of blue-greens that characterized that population, the recreationally nuisance forms,Aphanizomenon flos-aquae andMicrocystis aeruginosa, were dominant. The blue-green population was the most widespread in the lake and occurred in waters that were warmest and contained the lowest concentrations of inorganic nutrients: N, P, and C. Green algae dominated in waters that received treated sewage effluent and contained relatively high concentrations of nutrients. As the nutrient content declined when proceeding away from that area, blue-green algae became dominant. Temporal variation in biomass (chlorophyll content) of the blue-green population was inversely related to phosphate content, but not to the other nutrients. These results support the hypothesis that nuisance blue-green algae dominate in shallow eutrophic lakes during warm summer months when ambient nutrient content is low because, under these conditions, they apparently out-compete other forms for nutrients. In shallow unstable eutrophic lakes like Moses Lake, the nutrient supply rate from sediments may be considered great although ambient concentrations are low which allow the dominating blue-green population to reach a large biomass, e. g., maximums as high as 300 µg l^?1 chlorophyll were observed. Because correlation analysis andin situ bioassays showed that biomass of blue-green algae was most closely related to inorganic phosphate even at times when nitrate was very low and invariable, we suggest that phosphorus availability is most critical to biomass formation. Control of ambient phosphorus content, therefore, would be most apt to result in a reduction in maximum biomass of the blue-greens. Phosphorus control would be unlikely to alter algal dominance in this shallow lake, however, since blue-greens seem to be generally favored over other populations by reduction in nutrient concentration during warm weather.