Synthesis and degradation of proteins during wheat endosperm development

Synthesis of proteins rich in lysine declines progressively with endosperm development and these proteins appear to be degraded preferentially at later stages. The proteolytic enzymes in extracts of endosperms at a late stage of development release considerably more lysine radioactivity from labelled endosperm proteins as compared with the enzymes in endosperms at an early stage.     

An interactive nonrandom-mating two-sex model whose intrinsic growth rate lies between one-sex rates.

In a recent paper, the author has presented an interactive two-sex model and applied it to the U.S. population, 1940–1971. While the model has removed many inconsistencies in the one-sex models for males and females, it has two major limitations. First, the model assumes random mating of men and women within their reproductive ages. Second, it gives an intrinsic growth rate that is not necessarily intermediate between the male and the female intrinsic growth rates, as obtained from the one-sex models. A new two-sex model is provided in this paper that removes both these limitations. The new model is applied to the U.S. population for the years 1940–1974.     

Response of poly(adenylic acid) polymerase in rat liver nuclei and mitochondria to stravation and re-feeding with amino acids.

Poly(adenylic acid) polymerase was extracted from liver nuclei and mitochondria of rats either fed ad libitum, starved overnight or starved and then re-fed with a complete amino acid mixture for 1-3 h. The enzymes were partially purified and assayed by using exogenous primers. Starvation resulted in an 80% decrease in the total activity of the purified nuclear enzyme, and the mitochondrial enzyme activity diminished to almost zero after overnight starvation. Measurements of the protein content of whole nuclei or mitochondria and of the enzyme extracts from these organelles indicated that the decrease in enzyme activity on starvation was not caused by incomplete extraction of the enzyme from the starved animals. Re-feeding the animals with the complete amino acid mixture increased the total activity of poly(A) polymerase from the nuclei and mitochondria by 1.9-fold and 63-fold respectively. Under these conditions, the total protein content of the nuclei and mitochondria increased by only 13 and 32% respectively. These data indicate that poly(A) polymerase is one of the cellular proteins specifically regulated by amino acid supply.     

A procedure for decreasing the level of 2,3-bisphosphoglycerate in red cells in vitro

The physiological adaptation to anemia and other hypoxic states includes an increase in the level of 2,3-bisphosphoglycerate (2,3-DPG) in the red cell. We suggest that the high level of 2,3-DPG may have adverse effects in vivo. It has been found that red cells incubated with glycolate lose 2,3-DPG at a rapid rate relative to controls. ATP is stable. Net 2,3-DPG synthesis is observed after the glycolate is removed from the cells suggesting that they are not harmed. The effect appears to be specific for glycolate since lactate, glyoxylate, glycerate, acetate, and citrate were without effect. This procedure could be used to assess the effects of decreasing the 2,3-DPG level to normal in the erythrocytes of sickle cell and other anemias.     

Social network diagram.

A diagram that shows at a glance the social network and support of patients was found useful in a follow-up study of patients with strokes. We believe that the diagram would prove valuable in medical case records and should be an essential part of medical-social reports, particularly for patients at risk of losing their independence.     

Primary hyperlipoproteinemia in childhood and adolescence: identification and treatment of persons at risk for premature atherosclerosis.

Determination of serum cholesterol values in three populations of children and adolescents, totalling 4013 subjects aged 1 month to 20 years, revealed 16 cases of primary hyperbetalipoproteinemia (overall frequency, 1:251) and led to the detection of the disorder in 12 asymptomatic siblings. The upper limit of normal for serum cholesterol concentration was approximately 200 mg/dl at all ages studied. Dietary treatment was instituted in patients whose serum cholesterol value exceeded this limit and in whom a primary lipid defect was confirmed; the serum cholesterol value decreased in all patients who adhered to the diet. However, since the potential hazards and long-term results of dietary treatment, with or without drug therapy, in growing children are not known, such treatment should be reserved for affected children with a family history of premature atherosclerosis, and follow-up is essential.     

Oxalacetate decarboxylase activity in muscle is due to pyruvate kinase.

The enzyme from cod fish muscle that catalyzes the irreversible decarboxylation of oxalacetate and is homogeneous by several criteria contains very significant pyruvate kinase activity. For every unit of decarboxylase activity (0.90 unit/mg) there are 235 units of pyruvate kinase activity (212 units/mg). The inability to separate the two activities by a variety of physical techniques indicates that both are due to a single enzyme protein. Improtantly, the two activities appear to take place at the same or overlapping sites on the enzyme. Phosphoenolpyruvate and 4-ethyloxalacetate are strong linear competitive inhibitors of the decarboxylase activity with respect to oxalacetate having dissociation constants of 3.2 and 10.2 muM, respectively, while 4-ethyloxalacetate is a linear competitive inhibitor of the pyruvate kinase activity with respect to phosphoenolpyruvate, Ki - 13.5 muM. In addition, both activities exhibit sigmoidal kinetics for substrates. The differential influence of effectors on substrate cooperativity for the two reactions indicates that the decarboxylase reaction may be an important tool for studying allosteric mechanisms in this enzyme.     

Appearance of lymphocyte surface markers and functional responses in neonatal and young rabbit spleens

We examined spleen cells from newborn to 1-month-old rabbits for easily detectable surface immunoglobulin, complement receptors, and for in vitro proliferative responsiveness to anti-immunoglobulin antisera and several mitogens. From birth through the first month of life about 15% of the cells from rabbit spleens had easily detectable surface immunoglobulin while about 45% had C3 receptors. In adults as many as 77% of the spleen cells had easily detectable surface Ig but the proportion with C3 receptors remained about 45%. The proliferative response to anti-allotype antisera was present at birth, and was at adult levels by 1 month of age. The proliferative response to pokeweed mitogen was low when cells were obtained during the first week of life but was comparable in magnitude to the response of adult cells by 2 weeks of age. In vitro responsiveness to concanavalin A was present at low levels at birth and increased sharply during the first week. We did not observe significant stimulation of spleen cells from neonatal to 4-week-old rabbits by lipopolysaccharide from Salmonella typhosa. Our data suggest that lymphocyte surface markers and functional responses appear asynchronously in spleen cells of developing rabbits.     

The distribution and anisotropy of the stiffness of cancellous bone in the human patella

The distribution and anisotropy of the stiffness of cancellous bone in the human patella was studied by compression testing of small cubes cut from autopsy speciments. The observed variations bear a definite relationship to the internal architecture which can be accounted for by a simple sheet-and-strut model. The observed stiffness can be calculated with reasonable accuracy for loads approximately parallel to the sheets, with the proposed model. The spatial distribution of the stiffness was plotted and a close relationship to mechanical function is suggested.