Serum gamma glutamyl transpeptidase activity in cattle with induced fascioliasis

Six-month-old calves were inoculated with 200 metacercariae of Fasciola hepatica over a 72 day period. Their aspartic transaminase, alkaline phosphatase, arginase and gamma glutamyl transpeptidase (GGT) values were measured at two-week intervals. Infections with a final fluke count of 19 to 87 flukes did not result in an increase of serum alkaline phosphatase or arginase compared with those in control calves. Serum aspartic transaminase values were increased significantly (P less than 0.025) above those of controls but were not increased over reference values. Seemingly, measurement of these enzymes would not be useful in assessing the degree of fluke infestation. In contrast, serum values of GGT increased 56 days after preliminary inoculation and remained high for at least 83 days after infection. The initial rise coincided with the penetration of bile ducts by migrating flukes. This relationship may be useful in further studies of fluke-induced biliary damage.     

Plasma concentrations of oxytetracycline in swine after administration of the drug intramuscularly and orally in feed

Four pigs were used in a 2 X 2 crossover study to determine plasma oxytetracycline (OTC) concentration and OTC pharmacokinetic variables after IM administration of 2 OTC preparations--long acting OTC and a 100-mg of OTC/ml solution (OTC-LA and OTC-100, respectively)--at a dosage of 20 mg/kg of body weight. In a second study, 3 additional pigs were given ad libitum access to feed containing pure OTC (0.55 g/kg of feed). The mean (+/- SD) peak plasma OTC concentration after OTC-LA administration was 6.0 +/- 2.2 micrograms/ml at 30 minutes; the mean peak plasma OTC concentration after OTC-100 administration was 6.7 +/- 3.4 micrograms/ml at 90 minutes. Mean plasma OTC concentration after oral OTC administration in feed peaked at 0.4 micrograms/ml 48 hours after access to OTC-medicated feed and decreased to 0.25 micrograms/ml by the end of that study. Mean plasma OTC concentration was maintained at greater than 0.5 micrograms/ml for less than 48 hours after OTC-LA administration and for less than 36 hours after OTC-100 administration. Mean plasma OTC concentration decreased to less than 0.2 micrograms/ml by 72 hours after IM administration of either product. Calculation of area under the plasma OTC concentration-time curve (AUC) did not reveal significant difference between the 2 OTC formulations. There also was not significant difference (between OTC-LA and OTC-100) in the value of the disappearance rate constant after administration of either OTC formulation. The data did not indicate significant pharmacologic advantage of OTC-LA, compared with OTC-100, when either formulation was administered IM at a dosage of 20 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)     

A survey of the diagnosis and treatment of canine exocrine pancreatic insufficiency

A questionnaire was sent to veterinary surgeons who had diagnosed exocrine pancreatic insufficiency (EPI) by assay of low serum concentration of trypsin-like immunoreactivity in 302 dogs. Two-thirds of cases were German shepherd dogs, in which EPI was found equally in males and females. The disease was also diagnosed in 33 other breeds, most commonly in crossbreeds, spaniels, small terriers and collies, and was more common in females. Detailed replies on 160 cases were returned; 79 dogs were alive and 41 dead, with the remainder lost to long term follow-up. The major reasons for death were euthanasia because of the cost, the prognosis, and failure to respond to treatment. An adequate response to treatment was obtained in 92 per cent of dogs. Uncoated preparations of pancreatic enzyme replacement were found to be more successful, and the use of dietary manipulation and antibiotics were frequently reported to be useful adjunctive therapies.     

Immobilized long-lived free radicals at the host–pathogen interface in sycamore (Acer pseudoplatanusL.)

High concentrations (up to 2.4 m ) of long-lived, immobilized, organic free radicals were observed in column boundary layer (CBL) reaction zones at the boundary between fungal lesions and healthy, functional sapwood (xylem) in sycamore (Acer pseudoplatanusL.). These free radicals, with measured half-lives of up to 142 days at ambient temperature, were associated with the green polymeric material characteristically deposited in CBL reaction zones in this species, and may represent a novel category of chemical defence in plants. Such free radicals could contribute to the durable protection required in the bulky secondary tissues of living trees by acting as free radical scavengers, quenching the free radical chain reactions involved in the biodegradation of lignocellulose, thus protecting cell walls from decay and conferring a barrier function on the altered tissue. Reaction zone tissues were more resistant to decay and fungal colonization than normalA. pseudoplatanussapwood.     

Effects of thuringiensin on European red mite (Acarina: Tetranychidae) mortality,oviposition rate and feeding

Effects of two formulations of thuringiensin (ABG-6162A and ABG-6266) on mortality, oviposition rate, and feeding of European red mite, Panonychus ulmi (Koch) were evaluated. Mite toxicities of the formulations were not significantly different. Immature instars were significantly more susceptible than adults. Low mortality of all instars was recorded after 3 d, indicating slow activity. The relationship between log (concentration + 1) of ABG-6162A and ABG-6266 and P. ulmi oviposition rate was best described by fourth-order polynomial equations, suggesting that thuringiensin both inhibits and stimulates P. ulmi oviposition. ABG-6162A affected oviposition at lower concentrations than ABG-6266. A quadratic relationship was observed between log (concentration + 1) of thuringiensin and P. ulmi adult female feeding. ABG-6162A reduced feeding more than ABG-6266 at concentrations ? 1 mg liter^?1. Toxicity to immatures and the sublethal effects described suggest that thuringiensin may control field populations of P. ulmi despite low initial mortality.     

The Effect of Temperature on Variation in Transmission of a BYDV PAV-like isolate by Clones of Rhopalosiphum Padi and Sitobion Avenae

The efficiencies of seven clones of Rhopalosiphum padi and five clones of Sitobion avenae (originating from Greece and the United Kingdom) as vectors of barley yellow dwarf virus (PAV-like isolate) were evaluated at 5, 10 and 15°C. When inoculation took place at 5 or 10°C, clones of R. padi differed in their ability to transmit. At 15°C there were no differences in the vectoring ability of different clones. For S. avenae, there were no interclonal differences in the transmission efficiency at any of the temperatures. The epidemiological consequences of differences in virus transmission at different temperatures are discussed.     

Using allele-specific oligonucleotide probes to characterize benzimidazole resistance in Rhynchosporium secalis

Benzimidazole fungicides are important mixture components in strategies to combat fungicide resistance in Rhynchosporium secalis Davis. To monitor the performance of these strategies, a rapid, accurate assay has been developed to detect point mutations in the β-tubulin gene which confers resistance of benzimidazoles. The β-tubulin gene of a benzimidazole-resistant strain of R. secalis has been cloned and sequenced. Except for the difference in the position of one of its six introns, this gene showed a strong homology with other β-tubulin genes from filamentous fungi. Resistance was related to a point mutation in codon 198 which caused a glutamic acid to glycine change in resistant field strains, but glutamic acid to lysine in a laboratory mutant. A DNA fragment surrounding codon 198 was amplified directly from diseased lesions using a ‘nested’ set of PCR primers. Combining PCR amplificiation of a target DNA sequence with hybridization of Allele-Specific Oligonucleotide probes (ASO_s, 15-mers) allowed accurate detection of benzimidazole resistance. Only two probes, one sensitive and one resistant, were sufficient to monitor current field populations. Detection was achieved using either ³²P-labelled probe, or non-radioactively using a biotin-labelled probe coupled to streptavidin/alkaline phosphatase. This rapid method using ASOS can detect benzimidazole resistance within 48 h compared with 6–8 weeks by conventional assay procedures.     

Irrigation management methods for reducing water use of cowpea (Vigna unguiculata [L.] Walp.) and lima bean (Phaseolus lunatus L.) while maintaining seed yield at maximum levels

Summary In a previous study conducted at the University of California at Riverside, it was shown that water use of cowpea could be reduced while maintaining seed yields by withholding irrigation during the vegetative stage in a rain-free environment, and then irrigating when estimates based on potential evapotranspiration, indicated 40% depletion of available moisture in 90-cm depth of soil. The general applicability of this efficient irrigation management method was tested by experiments conducted at the West Side Field Station in the San Joaquin Valley of California with six irrigation treatments, three different row spacings (single rows on 76- and 102-cm beds, and double rows on a 102-cm bed), a semi-erect cultivar of cowpea (Vigna unguiculata [L.] Walp.), and a prostrate cultivar of lima bean (Phaseolus lunatus L.).Withholding irrigation during the vegetative stage following pre-irrigation substantially reduced dry matter at anthesis (–17% to –38%) and water use (–101 mm) of cowpea, but did not influence seed yield or shoot dry matter at harvest for either cowpea or lima bean. Increasing the irrigation interval until 75% nominal depletion of available water in 90-cm depth of soil reduced water use (–139 cm), but did not affect seed yield of cowpea. Lima bean, however, showed a significant decrease in shoot dry matter production (–17%) and in seed production (–18%) at the longest irrigation interval involving 75% nominal depletion. The different row spacings used in this experiment did not affect shoot dry matter or seed production of the semi-erect cowpea. However, shoot dry matter and seed yield were significantly greater for the prostrate lima bean grown with double rows on a 102-cm bed. Seed yield was 46% and 18% greater than with single rows on 76-cm and 102-cm beds, respectively. Generally, variations in seed yields of lima bean were positively correlated with variations in shoot dry matter production.Nominal depletion of available soil water provided a practical method for scheduling irrigations, but the results with cowpea indicated that the critical level, which resulted in the greatest reductions in water use while maintaining maximum seed yield varied from 40% (at Riverside) to 75% (at West Side Field Station). Additional methods are needed to fine-tune irrigation which is based mainly on nominal depletion of available water. Generally, pressure chamber estimates of leaf water potential exhibited too little variation among plants subjected to different irrigation treatments for it to be useful for fine-tuning irrigation schedules for either cowpea or lima bean. However, differences in temperature between canopy and air, when expressed as a function of either vapor pressure deficit or canopy temperature, and related to percent reduction in yield, appeared to have sufficient resolution to provide a practical method for fine-tuning irrigation schedules for cowpea during flowering and pod-filling, but not lima bean. Normalizing temperature differences with vapor pressure deficit was more effective, but normalizing with canopy temperatures is more convenient because it does not require a measurement of air humidity.     

The effect of monsoonal atmospheric moisture on lightning fire ignitions in southwestern North America

The seasonal arrival of increased atmospheric moisture associated with the North American monsoon in southwestern North America greatly affects the lightning fire regime. Dramatically increased lightning strikes from monsoon-related thunderstorm activity in July and August are counterbalanced by decreased ignition probability and fire spread due to increased atmospheric moisture and precipitation. Using 16 years of lightning flash, relative humidity, and precipitation data from a 34,800 km² study area with high lightning fire activity in Arizona and New Mexico, we quantified the effect of a single measure of atmospheric moisture, daily minimum relative humidity (DMRH), on observed lightning fire data. The probability that a lightning flash would ignite an observed fire was highly correlated with DMRH in the form of a power law, ranging from 0.023 on days with lowest humidity to <0.0001 on high humidity days. The number of observed lightning fires/day was highly correlated with DMRH in the form of a log–normal distribution peaking at 4.09 fires/day at 22.1% DMRH. Area burned/day was also correlated with DMRH with a log–normal distribution peaking at 53.7 ha/day at 16.5% DMRH. Despite strong relationships based on long-term aggregated data, large uncertainties at shorter time scales prevented using DMRH alone for daily or yearly fire prediction. Estimates of observed fire ignitions derived from existing models of ignition probability and survival based on fuel moisture closely approximated our real world data. Our results suggest that a model based on relative humidity provides a useful framework for understanding the lightning fire regime in this region.     

Effects of experimental acidification on macroinvertebrate drift diversity in a mountain stream

A small stream (Norris Brook) within the Hubbard Brook Experimental Forest was acidified to determine what effect elevated H⁺ stress may have on the ecology of a mountain stream. The experiment was designed to simulate a pH level (4.0) that can occur during initial snowmelt (acute period) and during longer term (chronic period) acidification. Daily macroinvertebrate drift samples were collected from treatment and reference areas of Norris Brook. Drift diversity at the generic level was calculated using Brillouin's formula and partitioned hierarchically following macroinvertebrate classifications based on taxonomy (orders) and feeding strategies (functional groups or guilds). The rate of movement of individuals and genera was significantly greater for those organisms leaving the acid-stressed area during the first five days than for those entering, whereas no difference between the rate of macroinvertebrates entering or leaving the acid-stressed area was apparent for either numbers or genera over the remaining 25-day study period. For the acute period (first five days), the increased macroinvertebrate drift leaving the acidified area was significantly more diverse at the levels of aquatic insect orders and functional groups but less diverse at the generic level than the drift entering. For the chronic period (25-day period) no significant differences were detected in either major taxa, functional group (with the exception of collectors), or generic diversity between the drift entering and leaving the treatment reach. Mayflies and probably chironomids leaving the acid-stressed area during the acute period were generically more diverse than those entering, whereas stoneflies drifting out of the acidified reach were generically less diverse than those drifting in. The overall change in the normal pattern of spatial and temporal variation in drift rate and diversity provides quantitative evidence that H⁺ stress significantly altered the structure and function of the macrobenthic community.