Changes induced in the ultrastructure of the cytoplasmic and intracytoplasmic membranes of several Gram-positive bacteria by variations in OsO 4 fixation

Several Gram-positivebacteria, belonging to different genera, fixed by the complete Ryter-Kellenberger procedure exhibited asymmetric membranes and prominent, tubular or vesicular, intracytoplasmic membrane systems (mesosomes). When the prefixation step was omitted mesosomes were not generally observed in three of the four bacteria studied. Fixation under conditions of Ca²⁺ deficiency resulted in symmetric membranes and lamellar mesosomes. From the data available it is difficult to conclude which, if any, of these different patterns of membrane ultrastructure is real.     

The prevalence, stability and significance of developmental language delay in preschool children

A sample of 937 children in Dunedin, New Zealand, was assessed at ages three and five years in order to estimate the nature, prevalence, stability and significance of developmental language delays in three-year-olds. Assessments included language development, intelligence, and fine and gross motor-co-ordination. Detailed results are given which described three types of language delay at age three: delayed verbal comprehension only, delayed verbal expression only, and delayed development in both aspects of language. Follow-up testing at age five indicated that the specific language delays were not highly stable, whereas delays in both aspects were highly stable. A large proportion of the latter children gained very low scores on the measures at age five, and they accounted for 84 per cent of all children with very low intelligence. The implications of the results for a screening programme to identify three-year-old children at high risk of later developmental delays are considered.     

Competition between sodium reabsorption and gluconeogenesis in kidneys of steroid-treated rats

Kidneys of rats treated with methylprednisolone show altered substrate requirements for sodium reabsorption when perfused in vitro. Such kidneys synthesize glucose from lactate at twice the rate of control. Optimum sodium reabsorption is not seen with glucose, which is normally the preferred substrate. Sodium reabsorption is restored toward normal by the combination of glucose and butyrate, by pyruvate, or by 3-mercaptopicolinate. All of these results point to a metabolic adaptation in the kidney; butyrate may improve sodium reabsorption by sparing glucose, pyruvate is a gluconeogenic precursor and an effective fuel of respiration, and 3-mercaptopicolinate is an inhibitor of gluconeogenesis. In kidneys from rats treated with methylprednisolone there is an increased requirement for metabolic energy because of the increased rate of gluconeogenesis. It is suggested that the availability of energy from glucose oxidation is limited in part by the diversion of pyruvate back to glucose. Under these special circumstances, gluconeogenesis competes with sodium reabsorption in the intact kidney.     

The tensile properties of mixtures of cohesive powders

The theory of tensile stress proposed by Cheng has been extended to deal with binary and three-component mixtures of powders by means of an equation which relates the tensile strength to the particle size parameters and the composition of the mixtures and also to the interparticle force. The interparticle force is expressed in terms of a “strength” parameter ε₀ and a range parameter to by applying the law of corresponding states.By means of ε₀, the tensile strength of the mixtures can be compared relative to the strength of an arbitrarily chosen (single) material.The modified equation has been used in combination with the law of corresponding states to predict the tensile strengths of binary and three-component mixtures with an accuracy of about ± 20%.