Ecological change, group territoriality, and population dynamics in Serengeti lions

Territorial behavior is expected to buffer populations against short-term environmental perturbations, but we have found that group living in African lions causes a complex response to long-term ecological change. Despite numerous gradual changes in prey availability and vegetative cover, regional populations of Serengeti lions remained stable for 10- to 20-year periods and only shifted to new equilibria in sudden leaps. Although gradually improving environmental conditions provided sufficient resources to permit the subdivision of preexisting territories, regional lion populations did not expand until short-term conditions supplied enough prey to generate large cohorts of surviving young. The results of a simulation model show that the observed pattern of "saltatory equilibria" results from the lions' grouping behavior.     

Complex I binding by a virally encoded RNA regulates mitochondria-induced cell death

Human cytomegalovirus infection perturbs multiple cellular processes that could promote the release of proapoptotic stimuli. Consequently, it encodes mechanisms to prevent cell death during infection. Using rotenone, a potent inhibitor of the mitochondrial enzyme complex I (reduced nicotinamide adenine dinucleotide-ubiquinone oxido-reductase), we found that human cytomegalovirus infection protected cells from rotenone-induced apoptosis, a protection mediated by a 2.7-kilobase virally encoded RNA (beta2.7). During infection, beta2.7 RNA interacted with complex I and prevented the relocalization of the essential subunit genes associated with retinoid/interferon-induced mortality-19, in response to apoptotic stimuli. This interaction, which is important for stabilizing the mitochondrial membrane potential, resulted in continued adenosine triphosphate production, which is critical for the successful completion of the virus' life cycle. Complex I targeting by a viral RNA represents a refined strategy to modulate the metabolic viability of the infected host cell.     

Prolonged immunosuppression and tumor induction by a chemical carcinogen injected at birth

The injection of 60 micrograms of 9,10-dimethyl-1,2-benzanthracene into newborn mice gave rise to a very high incidence of malignant thymomas. The tumor incidence was directly related to the dose of the carcinogen. The neonatal injection of the carcinogen also resulted in a depression in the immune response when the animals were challenged with an antigert as early as 4 weeks or as late as 11 weeks after administration of the carcinogen.     

The serological incidence of Hypoderma bovis in cattle in England and Wales in spring 1989

Sera from 152,434 cattle held on 6175 farms in England and Wales were tested for the presence of antibodies to Hypoderma bovis during the 10 weeks starting on February 6, 1989. Thirty-nine positive animals (25.6 animals/100,000 tested) were identified on 21 of the farms (0.34 per cent). In comparison, the survey in 1988 examined 74,502 cattle on 3087 farms and found 29 positive animals (38.9/100,000 tested) on 18 farms (0.58 per cent).     

Deaths due to goitre in new-born lambs prevented by iodized poppy-seed oil

Abstract

Extract

In a previous publication (Sinclair and Andrews, 1958 Sinclair, D. P. 1958. N.Z. vet. J., 6: 87–87. [Taylor &; Francis Online] , [Google Scholar]) the writers discussed methods of preventing goitre in lambs from ewes fed brassica crops. In particular, it was found that two oral doses of an inorganic iodine compound, one given. about two months and the other about one month before lambing, largely prevented signs of the disease. Death rates associated with severe outbreaks were markedly reduced. Later, Myers and Ross (1959 Myers, Ballinda J. and Ross, D.A. 1959. N.Z. J. agric. Res., 2: 552–552. [Taylor &; Francis Online] , [Google Scholar]) reported that injections of “Neo-Hydriol” (May and Baker) an iodized poppy-seed oil preparation of specific gravity 1·375 and containing 40 per cent, (weight/weight) of bound iodine, had a significant effect on the thyroid glands of ewes as measured by decreased cell height and increased iodine content. The main aims of the work reported here were to determine the effects of single injections of Neo-Hydriol given to ewes grazed during the last two months of pregnancy on thousand-headed kale (Brassica oleracea var. acephala), on gestation periods, lamb lamb birth weights, lamb thyroid glands, and the high death rate accompanying severe goitre in new-born lambs.