Divergence in cuticular hydrocarbons between parapatric subspecies of the meadow grasshopper, Chorthippus parallelus (Orthoptera, Acrididae)

Two subspecies of the grasshopper Chorthippus parallelus (Orthoptera; Acrididae) meet and form a hybrid zone in the Pyrenees. Here we investigate whether the subspecies differ in the blend of cuticular hydrocarbons. Such differences may function as chemical signals, being detected via contact chemoreception and used during mate choice as in other insects. Gas chromatography shows that the subspecies have diverged in the composition of their cuticular hydrocarbons. This difference between subspecies exists over and above variation in cuticular hydrocarbons among individual populations. The majority of the difference can be attributed to the relative amounts of a small group of compounds present in the cuticle. The possible consequences of this chemical divergence for mating encounters between the subspecies are discussed.     

Control of Embryoid Development in Tissue Cultures of Celery

Scanning electron microscope photographs of the embryoids showedglobular embryoids attached to the surface of aggregates inliquid medium and also some free floating. The surface structureof the unattached embryoids was very irregular, but, with thechange to polarized growth in the heart and torpedo forms, thesurface of the embryoid became smoother. The stage of developmentof the embryoids could be controlled by modifying the compositionof the medium to the extent that the majority of the embryoidsin the culture were either globular or torpedo forms. One ofthe most effective compounds in controlling development was2,4–dichlorophenoxy acetic acid (2,4–D). At high2,4–D concentrations, embryogenesis in the callus wasrestricted to the globular stage and after two subcultures itwas totally repressed, while after ten subcultures the potentialfor embryogenesis was lost and could not be regained even aftersubculture on a normal medium. On the normal agar medium thecallus always continued to show embryogenesis, but when it wastransferred to liquid medium of the same composition, embryoidswere produced in the first subculture but the potential haddeclined by the third subculture, when only roots were produced,and after ten subcultures cell growth and all differentiationwas totally it hibited. However, in the first subculture inliquid medium, embryogenesis was sequential with the whole cultureprogressing from globular to torpedo forms. This was particularlyeffective when the callus inoculum had been maintained on ahigh 2,4–D concentration for the two subcultures priorto inoculation of the liquid medium. By making use of this sequentialchange in embryoid development, a large number of embryoidscould be obtained at any particular stage. Apium graveolens, celery, tissue culture, embryoids, 2,4–D     

Physiological Considerations of Lipid Storage and Utilization

Normally, rats and mice eat chow-type rations. When fed sucha ration, body fat usually ranges between 11 and 18%. If a semi-purifieddiet high in fat is fed instead of the chow-type ration, somestrains of rats and mice respond by accumulating abnormal amountsof weight and fat. Their bodies now contain as much as 40% fatand fat depots are enlarged. Rats which respond to a high fatdiet with excessive weight and fat gain consume more kilocaloriesin the same time interval and are more efficient in energy utilizationthan rats of the same strain which consume a grain diet. Forthese rats, if medium-chain triglycerides are substituted forthe long-chain triglycerides in the high fat diet, there isa depression in food intake, accretion of body weight and fatas well as energy utilization. Blood makes up 3.5 to 5.1% of the fat organ weight. The lowervalue represents the quantity present in adipose tissue of obeserats while the higher value is for "normal-weight" rats. Thetriglyceride content of perirenal and epididymal fat depotsis around 90%. On the other hand, the triglyceride content ofinguinal fat tissue ranges from 56 to 80% and is affected bystrain, age and diet. If diets are high in fat, the proportionaldistribution of fatty acids in the adipose tissue reflects theproportional distribution in dietary fat, except when medium-chaintriglycerides are fed.     

Chilling to zero degrees disrupts pollen formation but not meiotic microtubule arrays in Triticum aestivum L.

Throughout the wheat‐growing regions of Australia, chilling temperatures below 2 °C occur periodically on consecutive nights during the period of floral development in spring wheat (Triticum aestivum L.). In this study, wheat plants showed significant reductions in fertility when exposed to prolonged chilling temperatures in controlled environment experiments. Among the cultivars tested, the Australian cultivars Kite and Hartog had among the lowest levels of seed set due to chilling and their responses were investigated further. The developmental stage at exposure, the chilling temperature and length of exposure all influenced the level of sterility. The early period of booting, and specifically the +4 cm auricle distance class, was the most sensitive and corresponded to meiosis within the anthers. The response of microtubules to chilling during meiosis in Hartog was monitored, but there was little difference between chilled and control plants. Other abnormalities, such as plasmolysis and cytomixis increased in frequency, were associated with death of developing pollen cells, and could contribute to loss of fertility. The potential for an above‐zero chilling sensitivity in Australian spring wheat varieties could have implications for exploring the tolerance of wheat flower development to chilling and freezing conditions in the field.     

Impact of predation by domestic cats Felis catus in an urban area

• 1 As companion animals, domestic cats Felis catus can attain very high densities, and have the potential to exert detrimental effects on prey species. Yet, there is a paucity of information on the impact of cat predation in urban areas, where most cats are likely to be present.
• 2 We quantified the minimum number of animals killed annually by cats in a 4.2-km² area of Bristol, UK, by asking owners to record prey animals returned home by their pets. The potential impact of cat predation on prey species was estimated by comparing the number of animals killed with published estimates of prey density and annual productivity.
• 3 Predator density was 229 cats/km².
• 4 Five mammal, 10 bird and one amphibian prey species were recorded. Mean predation rate was 21 prey/cat/annum. The most commonly recorded prey species was the wood mouse Apodemus sylvaticus.
• 5 Predation on birds was greatest in spring and summer, and probably reflected the killing of juvenile individuals. For three prey species (house sparrow Passer domesticus, dunnock Prunella modularis, robin Erithacus rubecula), estimated predation rates were high relative to annual productivity, such that predation by cats may have created a dispersal sink for juveniles from more productive neighbouring areas. The impact of cats on these species therefore warrants further investigation.

     

The Development of Tomato Root System in Relation to the Carbohydrate Status of the Whole Plant

The decrease in growth rate of the root system or complete cessationof its growth in developed, fruit-bearing tomato plants areknown phenomena. It has been suggested that a limited supplyof carbohydrates to this organ, due to its relative weaknessin competition with the flowers and developing fruitlets isthe main cause for these disorders. This theory was tested inthe present study with plants grown in an aerohydroponic systemup to the appearance of 12–13 trusses per plant, 172 dafter transplanting. The changes in the contents of carbohydratesin the various organs during this period were monitored. Theconcentrations of soluble sugars and starch in the leaves increasedwith the increase in truss number. The upper stem was foundto contain more carbohydrates than the lower stem, while nosignificant changes in the concentration of these compoundscould be detected in the roots throughout the experiment. Nevertheless,120–130 d after transplanting, the roots of the plants,bearing five to six trusses and two to three inflorescences,ceased growing and remained at the same or a slightly reducedsize for another 40–50 d. Calculations show that at thestage of five to six trusses, 38 g total soluble sugars and35 g starch were stored in the vegetative organs. Therefore,it seems unlikely that carbon deficiency caused by the competitionwith the reproductive organs (mainly developing fruits), affectedthe root growth. Instead, it is suggested that some other factoris responsible. Lycopersicon esculentumMill; carbohydrates; root growth rate; sink-source relationship; soluble sugars; starch     

MODULATION OF OSTEOGENIC DIFFERENTIATION IN HUMAN SKELETAL CELLS IN VITRO BY 5-AZACYTIDINE

Cellular differentiation is controlled by a variety of factors including gene methylation, which represses particular genes as cell fate is determined. The incorporation of 5-azacytidine (5azaC) into DNA in vitro prevents methylation and thus can alter cellular differentiation pathways. Human bone marrow fibroblasts and MG63 cells treated with 5azaC were used as models of osteogenic progenitors and of a more mature osteoblast phenotype, respectively. The capacity for differentiation of these cells following treatment with glucocorticoids was investigated. 5azaC treatment led to significant expression of the osteoblastic marker alkaline phosphatase in MG63 osteosarcoma cells, which was further augmented by glucocorticoids; however, in human marrow fibroblasts alkaline phosphatase activity was only observed in glucocorticoid-treated cultures. MG63 cells represent a phenotype late in the osteogenic lineage in which demethylation is sufficient to induce alkaline phosphatase activity. Marrow fibroblasts are at an earlier stage of differentiation and require stimulation with glucocorticoids. In contrast, the expression of osteocalcin, an osteoblastic marker, was unaffected by 5azaC treatment, suggesting that regulation of expression of the osteocalcin gene does not involve methylation. These models provide novel approaches to the study of the control of differentiation in the marrow fibroblastic system.