Virulence and aggressiveness of single-zoospore isolates of Phytophthora fragariae

A system for scoring the virulence of isolates of Phytophthora fragariae based on a scale of root rot from 0 ( no symptoms ) to 5 (76-100% roots roiled) on a series of strawberry cultivars is described. Thirty-two single-zoospore isolates from one field site were compared by subjecting their root rot scores to cluster analysis and this grouped them into two major clusters equivalent to physiologic races B66–3 and B66-11, Different sub-clusters of isolates of race B66-11 produced different degrees of rotting on the same hosts. Apart from differences in virulence between the sub-clusters there was some evidence for differences in aggressiveness between isolates within sub-clusters.
Increasing inoculum concentration by over 300-fold increased rotting by c . 25% but did not alter the rankings of different isolate/host combinations. Repeated passage of isolates through cultivars of differing susceptibilities did not affect their pathogenicity.     

Drug residues in food animals. III. Plasma and tissue kinetics of potassium penicillin G in young cross-bred swine

Twenty-two young cross-bred swine were treated either intravenously or orally with potassium penicillin G. The pharmacokinetics of penicillin G were determined in plasma and tissues. The plasma half-life of penicillin G in swine was found to be 19.45±1.69 min, and the distribution and elimination kinetics were found to fit a classical two-compartment model. The volume of distribution was found to be 0.53±0.12 1/kg, and the body clearance was found to be 19.06±5.06 ml/min/kg which exceeded the effective renal plasma flow of 16.50±2.73 ml/min/kg, suggesting that the drug was eliminated both by tubular excretion and glomerular filtration. The elimination rate constants (Beta) for the major organs were as follows: muscle, 0.00343 min^-1; lung, 0.0310 min^-1; fat, 0.0394 min^-1; and kidney, 0.0213 min^-1, which compared favorably with the elimination rate constant found in plasma (0.0320 min^-1). These values were found to be significantly similar at the level of P < 0.005 in muscle, spleen and fat, and at a level of P < 0.025 in lung tissue. The data indicates that blood plasma would be a satisfactory body fluid for estimating this drug in tissue.     

Bacterial Isolates From Plaque and From Blood During and After Routine Dental Procedures in Dogs

Objective — This study evaluates the association between dental procedures and bacteremia in dogs, including a comparison of bacteria isolated from plaque and blood, severity of the bacteremia versus the severity of dental disease, and the longevity of bacteremia.
Study Design — Bacteria cultured from the blood over time were compared with those isolated from the plaque and crevicular fluid and in relation to severity of dental disease.
Animals or Sample Population — Twenty adult greyhounds.
Methods — Blood samples were collected for culture before induction of general anesthesia, immediately after intubation, 20 minutes after initiation of the dental procedure, and at 10-minute intervals until 10 minutes after the dental procedure was completed. Samples of plaque were taken for microbiological culture.
Results — Sixty to ninety percent of the bacterial genera isolated from the plaque were present in the blood. Dogs classified according to severity of dental disease showed no difference in the total number of different species or number of different Gram-negative, Gram-positive, or anaerobic bacteria isolated from plaque or blood (P <.05). Bacteremia was present in all of the dogs studied, within 40 minutes from the initiation of the dental procedure, regardless of the severity of oral disease.
Conclusions — Gram-negative, Gram-positive, and anaerobic bacteria are present in blood during dental procedures; the bacteremia can persist beyond the dental procedure, and is not associated with the severity of dental disease.
Clinical Relevance — The nature and extent of bacteremia occuring during routine dental procedures is important in understanding a potential risk to dogs.     

Surgical Repair of Mid‐body Proximal Sesamoid Bone Fractures in 25 Horses

Objective— To describe the characteristics of unilateral mid‐body proximal sesamoid bone (PSB) fractures, to determine factors associated with the outcome of horses after surgical repair, and to describe a technique for arthroscopically assisted screw fixation in lag fashion. Study Design— Retrospective case series. Animals— Horses (n=25) with unilateral mid‐body PSB fracture. Methods— Medical records (1996–2006), radiographs, and arthroscopic videos of horses with surgically repaired unilateral mid‐body PSB fractures were reviewed. Retrieved data included signalment, affected limb and PSB, fracture characteristics, and surgical technique. Outcome was established by radiographic assessment of healing and race records; categorical data were analyzed using Fisher's Exact test. Results— Medial forelimb PSBs were most commonly affected (80%). Surgical technique and degree of reduction were significantly associated with outcome; 44% of horses with screw repair and none of the horses with wire fixation raced (P=.047). Factors that may have influenced this outcome were differences in fracture reduction (improved reduction in 22% wire repairs and 88% screw repairs, P=.002) and use of external coaptation (22% wire repair and 88% lag screw repair, P=.002). None of the horses with unimproved reduction raced after surgery. Conclusions— Only 28% of horses with mid‐body PSB fractures raced after surgery. Compared with wire fixation, screw fixation in lag fashion resulted in good reduction and is seemingly a superior repair technique. Clinical Relevance— For mid‐body PSB fractures, arthroscopically assisted screw fixation in lag fashion and external coaptation for anesthesia recovery and initial support provides the best likelihood of return to athletic use.     

Changes in the long‐term distribution of zooplankton in the Humboldt Current Ecosystem off Peru, 1961–2005, and its relationship to regime shifts and environmental factors

We used a dataset assembled by the Peruvian Marine Research Institute (IMARPE) from 1961 to 2005, to examine the influence of seasonal, environmental (temperature and salinity), temporal (day–night and year) and location (north‐south and on‐off shelf) variables on the distribution and biovolume of zooplankton. Classification and regression trees (CART) showed that the zooplankton distribution can be divided into four time regimes: prior to 1974.5, 1974.5–1989.5, 1989.5–1997.5 and 1997.5–2005. These periods differ in overall biovolume but, more importantly, in having different spatial distributions of variables. Offshore‐onshore, seasonal, diel and north‐south patterns are all apparent in the temporal changes observed in zooplankton distribution. In the early period zooplankton biovolume was high throughout the Peruvian Humboldt Current Ecosystem, with enhanced biovolume in all seasons but winter. After 1974.5, biovolume was considerably lower. There was an increased difference between the shelf (lower biovolume) and offshore (higher biovolume), with a significant day–night effect offshore, due to diel migration and possibly diel catchability changes. After 1989.5, seasonal effects were more marked and biovolume appeared to be higher in the winter in the northern region. In other seasons, during the daytime, biovolume was highest farther offshore (greater than 65 km offshore of the 200‐m isobath) and, during the night, higher after 1997.5 than before. We relate these changes in distribution and biovolume to changes in large‐scale current patterns in different regimes and to the possible effect of the fishery in removing nutrients from the system.     

EFFECT OF CULTIVATION ON THE NUMBERS OF VIABLE WEED SEEDS IN SOIL

Summary. In a 6-year experiment with a naturally occurring population of viable weed seeds, the numbers in the top 9 in. of soil decreased exponentially from year to year in the absence of further seeding. The rates of loss were equivalent to 22% per year in undisturbed soil, 30% per year on plots dug twice a year (March and September) and 36% per year on those dug four times a year (March, June, September, December). Seed numbers of individual species also decreased exponentially, although not all at the same rates.
On the dug plots, the numbers of seedlings that emerged each year decreased exponentially once the regimes had become established. The proportions of the viable seeds which gave rise to seedlings in the course of a year were 7 % on plots dug twice and 9 % on those dug four times a year; although there was some variation, these proportions remained much the same from year to year. On undisturbed soil the number of seedlings that emerged declined rapidly, and in the 4th year represented no more than 03% of the viable seeds still present in the top 9 in. of soil.     

Note on the Estimation of Viable Weed Seeds in Soil Samples

Techniques for estimating populations of viable weed seeds in soil can be grouped into those which involve sieving, flotation and subsequent viability determination, and those which rely on direct assessment of the seedlings arising from the soil samples (Kropáč, 1966). This germination technique, although undoubtedly useful, may be less efficient than extraction methods (Jensen, 1969) and has the disadvantage that the samples must be kept for a long period to ensure that germination of a high proportion of the seeds takes place. Experiments were made to examine some of the factors which might affect seed germination in soil samples placed in shallow dishes, and the results are summarized in this note.     

Drug residues in food animals II. Plasma and tissue kinetics of oxytetracycline in young cross-bred swine

Tissue distribution and elimination kinetics of oxytetracycline in sixteen organs and body fluids were determined in young pigs following intravenous and oral administration. Seventeen non-fasted pigs, 8–10 weeks of age, weight range 16.4–34.5 kg were dosed intravenously at a dose rate of 11 mg/kg bodyweight. An additional seventeen weaning pigs, 12–14 weeks of age, weight range 27.2–36.3 kg were dosed orally at a dose rate of 48–65 mg/kg bodyweight. Oxytetracycline was rapidly distributed (half-life, 6.71 ± 1.13 min) in swine. The mean volume of distribution was 1.26 ± 0.18 l/kg and overall body clearance was 3.82 ± 0.59 ml/kg/min. The elimination half-life of oxytetracycline in pigs was 3.87 ± 0.62 h, which is shorter than has been observed in other domestic animal species. Oxytetracycline became rapidly and efficiently involved in enterohepatic cycling, with as much as 70% of a total intravenous dose being available for reabsorption from the gastrointestinal tract within 1 h after administration. This high degree of enterohepatic recycling prolonged the half-life, and the large amount of drug that entered the enteric tract contributed to the high volumes of distribution and high k ₁₂/ k ₂₁ ratios. The excellent tissue penetration of this drug further contributed to the high volume of distribution and high k ₁₂/ k ₂₁ ratios obtained. Relationships between plasma and tissue depletion for several major edible organs were found to be statistically significant. Blood plasma is proposed as a body fluid for monitoring oxytetracycline tissue residues.     

COMPARISON OF THE CERAMIC PLATE AND THE PRESSURE MEMBRANE TO DETERMINE THE 15 BAR WATER CONTENT OF SOILS

Volumetric water contents of 17 mineral and 3 peat soils were measured at 15 bar pressure using the ceramic plate and the pressure membrane apparatus. There was no overall significant difference between the results from the two types of apparatus and both ranked the soils in essentially the same order. Although soils of high clay or organic matter content retained up to 13.5% more water on the ceramic plate than on the pressure membrane, available water capacity (AWC) of a clay soil would be decreased by only 1–2%, and that of a peat soil by 3–4%. Due to its greater reliability, the ceramic plate is an acceptable alternative to the pressure membrane when used to determine the 15 bar water content.     

Effects of seasonal variations in meteorology and oceanography on the Brazilian sardine fishery

Seasonal variations in meteorological and oceanographic processes in the South Brazil Bight were studied to assess their influence on the Brazilian sardine Sardinella brasiliensis fishery. According to its environmental characteristics, the South Brazil Bight was divided into three sectors. The northern and southern sectors were similar during the spring and summer, showing areas of coastal upwelling and low rainfall rates. The middle sector was characterized by the presence of low-salinity coastal waters in the inner shelf and by high rainfall. During autumn and winter, the middle and southern sectors were similar, both being under the influence of sub-Antarctic waters. Multiple regression analyses showed significant correlation between environmental data and catches, although at a lower level in the northern sector ( r ² = 0.57). In the middle and southern sectors, environmental data were highly correlated with the catches ( r ² = 0.90 and 0.84). The sardine landings in the middle sector are principally affected by meteorological parameters, and in the south by oceanographic ones. In the middle sector, an inverse correlation between landings and rainfall is shown, while in the south, landings are positively correlated with salinity and sea temperature. The conclusion is that the seasonal landings of the Brazilian sardine within the South Brazil Bight are influenced by the distribution of less saline waters, the coastal waters and sub-Antarctic waters.