Influence of Three Factors on the Growth and Nutrition of Grapevine Microcuttings

Grapevine microcuttings grown in vitro were subjected to differentculture conditions within the framework of a factorial experiment.Threefactors were studied: genotype, sucrose content of the mediumand physical conditions of culture. There were three valuesor three different cases for each controlled factor, leadingto a total of 27 experimental batches and 15 induced variableswere measured. These concerned growth of plants, uptake of carbohydratesfrom the medium and uptake of essential minerals. Analysis ofthe results revealed the overall action of each of the threecontrolled factors. These actions were significant in most cases.At 21°C, genotype and culture conditions influenced length,fresh and dry weight of the plants and the amounts of carbohydratesand nitrate taken up; however, the relative dry matter contentof plants remained normal. In contrast, when the greater partof the culture was carried out at 12°C (long-term cultureconditions) the percentage dry weight increased considerably. Key words: Vitis, in vitro, nutrition     

Theories of Life-History Evolution

In order to assess current scientific understanding of life-historyevolution, the alternative fundamental theories are formulatedin a refutable form and compared with the available empiricalevidence. The hypothesis that life-history does not evolve isrejected on the grounds that life-history can be readily modifiedby artifical selection. The hypothesis that life-history evolvesaccording to mechanisms other than natural selection actingon genetic variation is shown to have no sound experimentalbasis. The hypothesis that life-history evolution depends primarilyon group selection is undermined by the absence of the predictedgroup adaptations. The hypothesis that life-history is a unitarycharacter which evolves in the same fashion as fitness is rejectedbecause of the disparity between life-history genetics and basictheory concerning the evolution of fitness. The hypothesis thatlife-history is composed of a set of autonomous characters whichare subject to mutation accumulation at later ages is refutedby the lack of any detectable increase in genetic variabilitywith age and the evidence for the interdependence of life-historycharacters. It is concluded that the hypothesis of antagonisticinteractions between life-history characters, generalized totake genetic variability into account, is the most satisfactorytheory of life-history evolution available.     

Synthesis of Carcinoembryonic Antigen <Emphasis Type="Italic">in vitro</Emphasis>

NORMAL and neoplastic mammalian cells cultivated in vitro retain a number of functions that characterize their cellular origin, even after extensive passage¹. It therefore seems reasonable to expect that cell products such as tumour-associated antigens could, if present from the outset, be retained in a demonstrable state when the tumour cells are cultivated outside the original host organism. The discovery by Gold and Freedman² of an antigenic substance specific for entodermally-derived cancers of the digestive system, carcinoembryonic antigen (CEA), provides a suitable candidate for studying one such property related to a particular type of human cancer. It has been proposed, however, that tumour-specific antigens such as CEA are not indigenous to the tumours, but are glycoproteins produced elsewhere in the body and coating the tumour cells secondarily³. If this were the case, then human colonic cancer cells in long-term propagation in vitro should not synthesize this material. We now present evidence to the contrary.     

BRAIN CARBONIC ANHYDRASE: ACTIVITY IN ISOLATED MYELIN AND THE EFFECT OF HEXACHLOROPHENE

Abstract— Animals receiving hexachlorophene (HCP) in their diet develop cerebral edema with vacuolation of the myelin sheath. When carbonic anhydrase activities were measured in homogenates of brains from HCP-fed and control rats, the HCP-fed rats showed small decreases in the enzyme activity, but these changes were not statistically significant. HCP did inhibit the enzyme in vitro but at higher concentrations (10⁻⁵-10⁻⁴ m ) than have been reported for HCP levels in brains of experimental animals. Carbonic anhydrase activity was present in myelin preparations obtained by gradient centrifugation and osmotic shock or by subcellular fractionation. When the latter procedure was used, myelin carbonic anhydrase had a specific activity which was higher than that of the mitochondrial fraction. The myelin enzyme was inhibited by 10⁻⁹10⁻⁸ m -acetazolamide and, like the homogenates and the commercial enzyme, was inhibited by HCP. The mechanism for HCP toxicity remains unknown, but this study does suggest that carbonic anhydrase is an intrinsic component of the myelin sheath.     

THE INFLUENCE OF TASTANTS ON ORAL IRRITATION BY CAPSAICIN

Single-point intensity scaling and time-intensity methods were used to record oral irritation from solutions of 2 ppm capsaicin, capsaicin with added sucrose (0.04M), NaCl (0.3M), citric acid (0.01M) or xanthan gum (0.2%). Only sucrose depressed mouth-burn, both in magnitude and duration. The viscosity imparted by xanthan retarded perception of mouth-burn but did not effect its duration. While single-point scaling averaged perceived intensity across time, time-intensity provided much more information by displaying perception from onset to decay. Eaters and non-eaters of chili peppers did not differ in their perception of mouth-burn.