Availability of linuron to plants in different soils

Total uptake of linuron by wheat seedlings in nutrient solutions was close to that expected from the product of the amounts of water transpired by the plants and the concentrations of herbicide in solution. Uptake from 19 different soils was less than the amount supplied by mass-flow when the concentrations of linuron in the soil solution were estimated from slurry adsorption measurements. Using a pressure-membrane technique, it was shown that the actual soil solution concentrations of linuron were less than those estimated, and following rewetting of pressure-membrane samples, the rate of redistribution of linuron between the adsorbed and solution phases was slow. The results suggest that under the conditions of the uptake experiments, the systems were not in equilibrium, and show that the rates of adsorption and desorption of linuron may be important in determining its availability to plants.     

The metabolism of DDT in vivo by the Japanese quail (Coturnix coturnix japonica)

Male and female Japanese quail (Coturnix coturnix japonica) were given intraperitoneal injections of [¹⁴C]DDT in ethanol at a rate of 13.4 mg/kg body wt. Fifty-six days later the tissues and droppings were analysed for total ¹⁴C and metabolites. The rate of loss of ¹⁴C in droppings was very similar in males and females. The maximal rate was reached on the third day, and 65–66% of the injected dose was voided by the fifty-sixth day. Ninety-three to ninety-four percent of the ¹⁴C in droppings and 83–90% of the ¹⁴C in tissues were extracted by solvents. Combined extracts from males and females were used for determination of DDT and its metabolites. Expressing all results as percentages of injected dose, the following were isolated from droppings: DDA (24%), DDT (3%), DDD (5.1%), DDE (11%), and uncharacterised polar metabolites (17%). Twenty-five percent of the dose was retained in the tissues and this was largely accounted for as DDT (10.4%) and DDE (10.5%). Of the total metabolites found 31% was DDE (almost equally divided between tissues and droppings) and 35% was DDA (almost entirely in droppings). Since DDD was not found in significant quantities in tissues, the substantial quantities in droppings were probably produced from DDT by the action of microorganisms.     

Fascicular nerve biopsy in the dog

A nerve fascicular biopsy technique that preserves the functional integrity of the parent nerve is reported in the dog. Fascicular biopsies from ulnar and peroneal nerves did not produce clinical sensory or motor deficits. Electrodiagnostic testing for the modalities of latency, duration, amplitude, and conduction velocities were not markedly altered after fascicular biopsies. Morphometric analysis of muscle fiber types, delineated by histochemic techniques, revealed no statistical (P greater than 0.05) difference between muscles from biopsied or control limbs. Fascicular biopsies resulted in small neuromas in all dogs.     

Persistence of 2,4,5-T in a heavy clay soil

The persistence of the herbicide 2,4,5-T was studied at different controlled temperatures and moisture levels in Regina heavy clay. Degradation approximated to first-order kinetics and the half-life varied from about 4 days at 35°C and 34% soil moisture to about 60 days at 10°C and 20% soil moisture. The laboratory data were used in conjunction with the appropriate measurements of surface soil temperature and moisture content in the field to simulate the degradation pattern for the herbicide in five separate micro-plot experiments. Satisfactory agreement with the observed patterns of loss was obtained in two of the experiments but in the other three, the model over-estimated rates of loss. It is suggested that the reason for this was the difficulty of obtaining a correct measure of soil moisture content to use in the simulation program.     

Neutrophil mediated and IgA dependent antibacterial immunity against enteropathogenic Escherichia coli in the porcine intestinal mucosa

The role of polymorphonuclear neutrophils (PMN) in the antibacterial immunity against enteropathogenic Escherichia coli (EEC) 0:149 in the porcine intestine was studied using intestinal Thiry-Vella loop (T-V loop) as a model. Intraluminal immunizations of T-V loops resulted in elevated levels of immunoglobulin A (IgA) anti-EEC 0:149 antibody in the loop secretions, an infiltration of PMN in the lumen of the loops and an increase in the concentrations of lactoferrin (LF), lysozyme (LY), cationic proteins (CP), and a specific bactericidal response in the immunized loops. PMN were observed by electron microscopy (EM) to be actively phagocytic in the lumen of the immune loops. EM observations of loop fluids as well as the abrogating effect of iron on the in vivo bactericidal response strongly suggest that the pMN played an important role in the bactericidal response in the loops against EEC. In addition to phagocytosis by PMN and subsequent intracellular killing, disintegration of PMN in the lumen of the loops and extracellular killing of EEC by the antibacterial products of PMN such as LF, LY and CP, with and/or without synergistic effect of IgA antibodies, also contribute to the bactericidal response of the immunized loops.     

Spatial and temporal clustering of Salmonella serotypes isolated from adult diarrheic dairy cattle in California.

Electronic records from the California Animal Health and Food Safety Laboratory System between January 1, 1991, and June 30, 1998, were reviewed, and data on 593 Salmonella serotypes isolated from feces or intestinal contents of adult dairy cattle with diarrhea were analyzed to determine spatial and temporal clustering. A statistically significant clustering in space was detected with 10 (Typhimurium, Montevideo, Muenster, Anatum, Give, Menhaden, Kentucky, Agona, Derby, and Newport) of the 13 serotypes examined. Significant temporal clustering was also detected with 10 serotypes (Typhimurium, Montevideo, Muenster, Anatum, Give, Newbrunswick, Menhaden, Kentucky, Derby, and Newport). Six serotypes (Anatum, Menhaden, Montevideo, Muenster, Newbrunswick, and Newport) were significantly spatially and temporally clustered. A difference in temporal and spatial distribution patterns of some serotypes associated with diarrhea in adult dairy in California was found. Knowledge of the specific type of clustering, if present, should improve our understanding of the transmission and control of salmonellosis in the field.     

Gross Morphometry of the Bovine Placentome during Gestation

Forty-seven pregnant uteri were collected from an abattoir at eight chronological stages of gestation. Assessments were made of placentome number, weight, length shape and ratio of foetal to maternal tissue by weight. The study showed that there was a great variation in number, size, weight and shape of placentomes. There was no significant change in the total number of placentomes during gestation. Both mean weight and length increased significantly during gestation, but there was a significant change in the relationship between the two as gestation progressed. There was no correlation between the number of placentomes and the mean weight or length of the placentomes. The development of the placenta in the non-pregnant horn was significantly different from that of the pregnant horn, with fewer, smaller, lighter placentomes. However, there was no evidence that placentome development in the non-pregnant horn was affected by placentome development in the pregnant horn. The proportion of the placentome that was maternal tissue increased during gestation, but there was no significant effect of placentome number, or individual placentome weight or length on this proportion. Two placentome shapes were identified, but no effect on foeto-maternal proportion or relationship between shape and total placentome number or weight was identified.