The effect of establishing native woodland on habitat selection and ranging of moorland mountain hares (Lepus timidus), a flexible forager

Mountain hares Lepus timidus L. typify species that occupy a broad geographic range and have flexible foraging and nutritional strategies. Such species may show a range of responses to habitat modification. This study aimed to provide a basis for prediction of the impact of mountain hares on woodland establishment, and of woodland establishment on mountain hare distribution. The selection of and the extent of incorporation of new woodland into the home range of mountain hares was investigated in an area where Scots pine Pinus sylvestris L. woodland was establishing within their usual habitat in Britain, upland heather moorland. Seasonal home, day and night-range sizes of radio-tracked mountain hares were determined using the multinuclear probability polygon technique and analysed using residual maximum likelihood (REML). Habitat selection was analysed using compositional analysis. Three main habitat types were available to hares: heather moorland with trees, heather moorland and grassland-mire. Mean home-range size of mountain hares in summer was 10.3 ha and in winter 9.6 ha. There were no significant seasonal or sex differences in home-range size. Females selected grassland-mire habitat in summer and showed no strong selection for any habitat in winter. Males selected heather moorland in both summer and winter. Heather moorland with trees was not selected preferentially by mountain hares of either sex in summer or winter. The absence of selection for areas of newly establishing-Scots pine woodland suggests that any browsing damage to trees by hares is most likely to be a function of the local abundance of mountain hares, rather than a result of active preference of hares for the modified habitat.     

Genotypic and developmental regulation of transient expression of a reporter gene in soybean zygotic cotyledons

Processes involved in transformation of regenerable soybean (Glycine max (L.) Merrill) immature zygotic cotyledons were studied by assaying the transient expression of the -glucuronidase gene driven by the 35S promoter and terminated at the 3 end by the soybean 7S storage protein gene. The plasmid containing the chimeric gene was delivered to the cotyledons via particle bombardment 900 PSI. Zygotic cotyledons from six soybean varieties were tested for transient expression of the -glucuronidase gene. The level of reporter gene expression differed between genotypes. The genotypes could be classified as high, fair or poor expressors. Cotyledons from different genotypes were then bombarded at 650, 900 or 1100 PSI. GUS expression varied among genotypes independently of the pressure of bombardment. Finally, the ability of cotyledons to express the reporter gene depended on the developmental stage of the seed from which it was excised with the younger stage being the least responsive. However, genotypic specific expression remained after controlling for developmental stage of the cotyledons.Abbreviations ANOVA analysis of variance - GUS -glucuronidase - PSI pounds per square inch - TEUs transient expression units - MSO3 MS media with 3% sucrose     

Conditions which affect initiation of animal cell division by trypsin and thrombin

It has been well documented that trypsin or thrombin initiate proliferation of quiescent secondary chick embryo cells. However, there has been less certainty about the ability of these proteases to initiate division of quiescent mammalian cells. Accordingly, we studied the conditions under which quiescent chick embryo (CE), mouse embryo (ME), and human diploid foreskin (HF) cells respond to trypsin or thrombin Extended culture of these cell strains in serum-free medium increased the initiation of cell division by both proteases. Under these conditions, CE cell number was increased 90% over controls by trypsin and 70% by thrombin. In contrast, quiescent ME and HF cells both responded better to thrombin than trypsin, giving maximal increases, respectively, of 70 and 40% over controls with thrombin and 22 and 14% with trypsin. Calf serum inhibited the initiation of these cell strains, particularly the ME cells, by both trypsin and thrombin. This inhibition of initiation could be attributed to decreased proteolytic activity in the case of trypsin, but not thrombin In contrast to the cell strains tested, quiescent cultures of the 3T3 cell line showed no detectable increase in cell number with trypsin or thrombin in the absence of serum, and only a slight increase in cell number with thrombin in the presence of serum. However, in the presence of plasma, 3T3 cell number increased up to 20% with thrombin Initiation of cell division by proteases has been reported and confirmed mostly for early passage cell strains rather than cell lines. Our experiments with CE cells indicate that this is possibly the result of a rapid decline in protease responsiveness upon serial subculture. With these cells we found a decline in response first to trypsin, then thrombin, and finally serum Throughout these studies, we compared the ability of trypsin and thrombin to initiate cell division under various conditions. We found several differences between the two proteases, indicating that they initiate cell division by somewhat different mechanisms.     

Effect of triarimol on sterol and fatty acid composition of three species of Chlorella

The concentration of triarimol giving ca 50% inhibition of growth was different for each of 3 species of Chlorella [C. emersonii, 1 mg/l. (1.5 × 10^?6 M), C. ellipsoidea 10 mg/l. (3 × 10^?5 M), C. sorokiniana, 2 mg/l. (6 × 10^?6 M)]. The total lipid of 3 species of Chlorella grown in a culture medium containing triarimol were analysed for chlorophyll, fatty acids and sterol composition. Growth rates were studied in the presence of different concentrations of triarimol. The growth rates of the 3 species were differentially inhibited by triarimol. The growth of Chlorella sorokiniana was 50% inhibited by 2 mg/l. triarimol but 20 mg/l. did not produce a cessation of growth. The greatest inhibition of growth rates and chlorophyll content was observed in Chlorella emersonii. The quantity of unsaturated fatty acids was increased by triarimol treatment in all 3 species of Chlorella. Triarimol strongly inhibited 14α-demethylation in Chlorella emersonii, and C. ellipsoidea and less in C. sorokiniana, resulting in accumulation of 14α-methyl sterols. Triarimol also inhibited the second alkylation of the side chain in C. ellipsoidea and C. emersonii. The introduction of the 22-double bond was inhibited in all 3 species of Chlorella studied. Although some differences were apparent, the effect of triarimol was quite similar to that of triparanol and AY-9944 in these 3 species of Chlorella.     

Sterols and fatty acids of some non-photosynthetic angiosperms

Sterols and fatty acids were extracted and identified from three parasitic angiosperms, Cuscuta campestris, Monotropa uniflora and M. hypopitys. Each plant contained the typical 16 and 18-carbon fatty acids of angiosperms, but the partially-photosynthetic Cuscuta contained much larger quantities of linolenic acid than the non-green Monotropa species which had smaller amounts of linolenic acid characteristic of non-photosynthetic tissue. Sterol quantity was three times higher in Cuscuta than in the Monotropa species. Sitosterol was the major sterol in all species with smaller amounts of campesterol and cholesterol.     

Effect of Corynebacterium parvum on the immune response in guinea pigs. II. Passive transfer of enhanced anamnestic response and delayed hypersensitivity observed after treatment with Corynebacterium parvum]

After intradermal immunization with a mixture of Corynebacterium parvum (C. parvum) and ovalbumin guinea pigs show a markedly increased anamnestic response to an intradermal booster of ovalbumin as compared to controls treated with ovalbumin only. At the same time a reaction of delayed type hypersensitivity is observed in the treated animals, but not in controls. The enhanced anamnestic response as well as the posivitive skin reaction were transferred to strain 2 histocompatible guinea pigs by peripheral blood leukocytes as well as by peritoneal exudate cells. Passive transfer was not obtained after prior irradiation of donor animals.     

The dependency of nuclear division on volume in the dimorphic yeast Candida albicans

When stationary phase cells of the dimorphic yeast Candida albicans are induced to synchronously form mycelia, over 90% of the cells undergo nuclear division. However, when stationary phase cells are induced to synchronously form buds, less than half undergo nuclear division even though all form buds. The majority of cells which do not undergo nuclear division form buds with volumes below a threshold value and the majority of cells which do undergo nuclear division form buds with volumes above this threshold value. In this report, we have investigated the possibilities that cells which form small buds do not attain a particular mass threshold. Cell cultures were examined for DNA replication, dry weight, and protein content during synchronous bud and during synchronous mycelium formation. Evidence is presented which indicates that the lack of nuclear division in over half of a budding population is due to low daughter cell volumes or to low surface areas, and not to their failure to attain a mass threshold or to replicate their DNA. The dependency of nuclear division on daughter cell volume is discussed.     

Reproductive biology of the German cockroach,Blattella germanica: Juvenile hormone as a pleiotropic master regulator

Juvenile hormone (JH) exerts major pleiotropic effects on cockroach development and reproduction. The production of JH by the corpora allata (CA) in the adult female German cockroach, Blattella germanica, is dependent upon and modulated by both internal and environmental stimuli. Mating, intake of high-quality food, social interactions, and the presence of vitellogenic ovaries facilitate JH synthesis. Conversely, starvation, deficient diets, enforced virginity, isolation, and a pre- or post-vitellogenic ovary cause the CA to produce less JH. Sensory stimulation of the genital vestibulum by the ootheca also inhibits the CA via signals that ascend the ventral nerve cord. All these stimulatory and inhibitory signals are integrated by the brain, and a preponderance of favorable signals results in a graded lifting of brain inhibition, permitting the synthesis and release of JH. The effects of inhibitory signals on JH biosynthesis can be lifted experimentally by severing nervous connections between the brain and the CA. Such an operation accelerates activation of the CA. Besides controlling gonadal maturation in females, JH concurrently regulates the production of sexual signals, including both attractant- and courtship-eliciting pheromones, and the behavioral expression of calling (pheromone release) and sexual receptivity. Although JH is required for the expression of copulatory readiness in female B. germanica, it appears that signals associated with copulation (spermatophore, sperm, accessory secretions) can inhibit this behavioral state even when titers of JH are permissive for receptivity. These observations suggest that JH might regulate sexual receptivity in females indirectly through other directives. In males, JH accelerates not only the onset of sexual readiness but also synthesis of accessory reproductive products. Lastly, we present a novel cockroach control strategy that is based on the intimate association between food intake and rising JH titers in B. germanica females. JH analogs cause abortion of fertile oothecae in gravid females. In turn, rising JH titers and vitellogenic oocytes induce feeding in females. With strategic placement of insecticidal baits and JH analogs, gravid females, which normally feed little and are difficult to control, can thus be effectively targeted for elimination. Arch. Insect Biochem. Physiol. 35:405–426, 1997. © 1997 Wiley-Liss, Inc.