Preferential Absorption of Potassium by Leaf Tissue of the Mangrove, Avicennia Marina: An Aspect of Halophytic Competence in Coping with Salt

One aspect of the salt tolerance of the mangrove, Avicennia marina, was investigated: the preferential absorption of potassium by leaf tissue in the presence of high concentrations of salt (sodium chloride). The rate of absorption of potassium, over the concentration range 0�02 to 1�5 mM, follows the Michaelis-Menten relation, approaching the theoretical maximum, V max, at 1� 5 mM. The apparent Michaelis constant is 0�20 mM. At higher concentrations, up to 50 mM potassium, the rate of potassium absorption reaches values several times higher than the theoretical maximum calculated on the basis of the relation applying over the low range of concentrations, indicating the operation of a second mechanism of absorption. At both low (1 mM) and high (10 mM) concentrations of potassium, its absorption was little affected by sodium chloride concentrations up to 200 mM. At 10 mM potassium, sodium chloride at concentrations up to and including 500 mM (more than its concentration in sea.water) failed to interfere with the absorption of potassium.

Planing for precancerous skin. A ten-year evaluation

A 10-year follow-up of 10 patients with precancerous cutaneous alterations that could be expected to recur (actinic keratoses, radiodermatitis, leukoplakia) revealed that dermabrasion gave excellent results in four cases and at least some benefit in four others. While planing is not a panacea for the premalignant skin, this study suggests that it is of prophylactic value in the control of this condition in a reasonable proportion of cases.

Characteristics of a 17-Ketosteroid Reaction

An improved method for the determination of 17-ketosteroids is described, which involves an increase in sensitivity by the simple expedient of upsetting the equilibrium of the reaction in removing the products of reaction by precipitating the chromophore formed. This precipitation system appears to achieve about 1.6 times the color sensitivity for the same reaction carried out as a solution process. An alternative extraction step for color purification is described. Spectrums, variabilities in reagent parameters, and statistical evaluations are discussed.

PRESENT STATUS OF DERMABRASION

The use of dermabrasion for cosmetic purposes is becoming less popular due to limitations inherent in the method despite the fact that it is still the best method available for the minimizing of acne scarring. Planing for precancerous skin is increasing in demand because of definite benefits to be gained from its use. While the method has not attained universal acceptance for the latter purpose, 80 per cent of dermatologists who have tried this approach, and who answered a questionnaire, rate the benefits obtained as excellent or good. Only 3.5 per cent considered the results as poor. In a five-year period between two questionnaires, there was in general a trend away from enthusiasm for this modality, but esteem for it as a way of dealing with precancerous skin held up better than opinion of its use for cosmetic purposes.

New Cholesterol Reagent

A study was carried out on a new cholesterol reagent which was reported to be a saturated solution of ferrous sulfate in glacial acetic acid. This solution was shown to be unstable and it is suggested that the reactive state of the metal involved is that of the more stable trivalent ferric iron.