PCR-based detection of blood parasites in cattle and adult Rhipicephalus appendiculatus ticks

To ascertain the infection rate for tick-borne pathogens in Zambia, an epidemiological survey of Theileria parva, Babesia bigemina and Anaplasma marginale in traditionally managed Sanga cattle was conducted using PCR. Of the 71 native Zambian cattle, 28 (39.4%) were positive for T. parva, 16 (22.5%) for B. bigemina and 34 (47.9%) for A. marginale. The mixed infection rate in cattle was 8.5% (6/71), 16.9% (12/71), 7.0% (5/71) and 2.8% (2/71) for T. parva/B. bigemina, T. parva/A. marginale, B. bigemina/A. marginale and T. parva/B. bigemina/A. marginale, respectively.To predict the risk for transmission of tick-borne pathogens from ticks to cattle, a total of 74 Rhipicephalus appendiculatus ticks were collected from a location where cattle had been found positive for T. parva. Of the ticks collected, 10 (13.5%) were found to be PCR-positive for T. parva. The results suggest that the infection rate for tick-borne pathogens was relatively high in Sanga cattle and that adult R. appendiculatus ticks were highly infected with T. parva.     

Bacillus thuringiensis insecticides in crop protection — reality and prospects

Bacillus thuringiensis (Bt) has been the leading biopesticide against lepidopterous pests since 1959. In the 1990 s the following developments contributed to increased rational uses of Bt: (1) natural and recombinant Bt products were developed to broaden the insect host range in pest management programs; (2) new formulations based on conventional or genetically engineered encapsulation of the toxins and/or feeding stimulants to increase ingestion and, in turn, the efficacy of the microbe; (3) screening of the interactions of Bt with insect herbivores and plant allelochemicals or natural enemies of the pests, to aid the formulation of biological control strategies; and (4) knowledge and management of insect resistance to Bt. The prospects for Bt insecticides will be described and discussed.     

Irrigation influences on growth, yield, and water use of persimmon trees

A 3-year irrigation trial provided basic information on the response of persimmon (Diospyros kaki cv. Triumph) water use and development to irrigation levels. Constant experimental factors applied to recommended “baseline” crop factors resulted in ratios of irrigation (I) to FAO56 reference crop evapotranspiration (ET₀) ranging from 0.35 to 1.14. Vegetative and reproductive growth, sap flow, stem water potential (SWP), and local climate were monitored. An overall increase in yield and vegetative growth in response to irrigation was found, which suggests a potential yield increase for higher irrigation levels (40 tons/ha for annual irrigation of 1,000 mm). At high irrigation, the yield response curve levelled off and the marginal contribution of additional water declined. The up to threefold increase in number of fruits with irrigation, with no influence on natural abscission, suggests that differences in fruit quantities stem from response to irrigation at the earlier growth stages. Mean fruit size and fruit quality, as indicated by the ratio of rejected fruit, increased with irrigation up to I/ET₀ of ~0.8. Relative yield increased linearly with relative transpiration. However, post-harvest quality was not influenced. SWP, sap flow, and non-transpirable water fractions indicated that the seasonal irrigation tables were not well tuned. Initial adjustments were made during the final season of the experiment and a new table was developed based on our results. The new table should be a basis for further trials.     

Tumor immunity in vitro: destruction of a mouse ascites tumor through a cycling pathway

Lymphocytes in peritoneal exudate from BALB/(c) mice immunized against ascites leukemia EL4 are uniquely efficient at destroying (51)chromiumlabeled EL4 cells in vitro. The lytic process depends upon the number of lymphocyte-tumor cell interactions. Efector lymphocytes are not inactivated as a result of lethal contact but can interact repeatedly with tumor cells.     

The effects of photoperiod and water exchange rate on growth and survival of gilthead sea bream (Sparus aurata, Linnaeus; Sparidae) from hatching to metamorphosis in mass rearing systems

The effects of photoperiod and water exchange rate on the larvae of gilthead sea bream, Sparus aurata, from hatching to metamorphosis, 60–70 days later, were tested. Survival, growth rate and condition factor were determined with photoperiods of 12 and 24 h, and water exchange rates of 0 and 25%/day.Continuous light supported the highest mean survival (3.25%), with a maximum of 7.8% from hatching to metamorphosis. Growth rate in dry weight was best under continuous light in a water system with no exchange, up to 20 days post-hatching. Highest growth rates of larvae 40–60 days old were obtained in tanks with 25% of their water exchanged daily, along with a 12-h photoperiod. Condition factor was directly correlated with larval age. For the first 30 days after hatching, condition factor was affected by photoperiod and was highest for larvae exposed to continuous light.