De novo purine synthesis in skeletal muscle

Myoblast and primary muscle cultures from rat were found to contain the complete pathway of de novo purine nucleotide synthesis. Quantitative assessment of the pathway in skeletal muscle in mice in vivo, revealed a more intensive purine production in muscle than in liver. Skeletal muscle is thus a major site of de novo purine production in the mammalian body.     

Species of Dickinsonia Sprigg from the Ediacaran of South Australia

An iconic member of the Ediacara Biota, Dickinsonia Sprigg is one of few such taxa with multiple species. Here we use Gaussian finite mixture models to assess the validity of species distinctions for this genus. Our results indicate that the five described species of Dickinsonia from the Ediacara Member, South Australia are better classified as two based on multiple approaches. Two different methods for dimension reduction both provide strong support for two groups, with overlapping but distinct mixture models. The variable selection method produces the most biologically realistic clusters, indicating that the two species can be primarily differentiated based on the greater relative size of the anterior most unit of Dickinsonia costata Sprigg compared with Dickinsonia tenuis Glaessner & Wade. Despite differences in aspect ratio and number of modules, both species regulated growth to maintain overall shape. The greater likelihood of preservation of a midline and an irregular outer margin in D. tenuis highlights differential structural integrity and flexibility. Co-occurrence in the Ediacara Member indicates that both species occupied the same environments and temporal distribution. Smaller maximum and average size for D. costata, combined with higher abundance, may suggest a comparatively shorter lifespan and increased rates of reproduction.     

Condensation-inhibition by 33258-Hoechst of centromeric heterochromatin in prematurely condensed mouse chromosomes

The phenomenon of premature chromosome condensation has been applied to study the kinetics of condensation-inhibition exerted by the fluorochrome 33258-Hoechst (33258-H) on the centromeric heterochromatic regions of mouse chromosomes. Asynchronous mouse A-9 cells in culture were fused with mitotic HeLa cells in the presence of 33258-H. Pronounced condensation-inhibition of the c-heterochromatin was observed in prematurely condensed early G2, S and late G1 chromosomes in the 33258-H-treated cells. It is concluded that the c-heterochromatic regions begin to condense quite early in G2, decondense again late in G1 and remain decondensed in the S phase.     

Evidence for X-linkage of phosphoribosylpyrophosphate synthetase in man. Studies with cultured fibroblasts from a gouty family with mutant feedback-resistant enzyme.

Skin fibroblast cultures were utilized to study the mode of inheritance of a mutant feedback-resistant phosphoribosylpyrophosphate synthetase in a gouty family with purine overproduction. Selective conditions were applied to allow the survival in culture of mutant cells only. Whereas in the male gouty propositus the cell culture was homogenous for the mutant enzyme, in the cell culture from his nongouty mother two cell populations were demonstrated, one normal and the other mutant. The mosaicism in the mother is compatible with X-linkage of the enzyme. From this finding, together with the clinical and biochemical data available, it is concluded that in this family the enzyme mutation is transmitted in a X-linked recessive pattern.     

Cardiomyocytes cultured in serum-free medium: Growth and creatine kinase activity

Primary cultures of newborn rat heart cells were grown for up to 3 weeks in serum-free medium supplemented by insulin, hydrocortisone, transferrin and fetuin. The cells resumed spontaneous beating at 20 h post plating. Mean rates of beating on the second and third day were 79.5 and 94 beats per min, respectively. Cell proliferation occurred during the first 3 days of culture with maximal rates of DNA and protein synthesis on the second day. The highest values of creatine kinase activity were observed on days 2–5 and the three cytoplasmic isozymes, MM, MB and BB, were present in the cultures in proportions similar to those of the newborn heart, indicating stability of the differentiated state of the cells. The relative amount of each isozyme remained unchanged throughout the experiments, MM constituted 70–90% of enzyme activity, MB contributed up to 30% and BB did not exceed 15% of activity. The very low proportion of BB and the lack of increase in this isozyme with age of culture support our earlier morphological observations that non-myocytes do not overgrow the culture.     

Rubella Syndrome—Cardiovascular Manifestations and Surgical Therapy in Infants

Of nine patients under five months of age with cardiovascular manifestations of the rubella syndrome, six had patent ductus arteriosus. Three of these six also had pulmonary artery stenosis. One infant had bilateral isolated pulmonary artery stenosis. The significant clinical findings leading to the diagnosis of pulmonary artery stenosis were axillary murmurs in the presence of right ventricular hypertrophy. Demonstration of a gradient across the stenosis at the time of catheterization, together with cineangiography, established the diagnosis. In two cases ventricular septal defect was the only cardiac anomaly.Six babies under five months of age had interruption of a patent ductus arteriosus because of uncontrollable congestive heart failure or failure to thrive. Although growth failure was not necessarily due to heart disease, all were developing satisfactorily following operation.Diagnosis and therapy of the cardiac complications of the rubella syndrome is possible in the first few months of life. Early recognition of cardiac defects in the young infant with the rubella syndrome permits aggressive medical management and in selected instances surgical therapy.