Elevation of a threonine phospholipid in polyoma virus transformed hamster embryo fibroblasts.

Analysis of the lipids of normal hamster embryo fibroblasts and polyoma virus transformed fibroblasts shows a decrease in phosphatidylcholine and phosphatidylethanolamine and a marked increase in a threonine phospholipid after transformation. Transformed cells also react differently with fluorodinitrobenzene and trinitrobenzenesulfonate. phosphatidylethanolamine of transformed cells reacts to a greater extent with both probes. Phosphatidylserine and the threonine phospholipid of both cells do not react with trinitrobenzenesulfonate. The threonine phospholipid is provisionally identified as phosphatidylthreonine.     

Proline excretion in Escherichia coli: A comparison of an argD + strain and a proline-excreting argD − derivative

In an attempt to deduce the physiological basis of proline excretion in argD ^– strains of Escherichia coli K12, several properties of an argD ⁺ (nonexcreting) and an argD ^– (excreting) derivative were compared. No difference was found in the transport or in the utilization of either proline or its immediate precursor, ¹-pyrroline-5-carboxylate (PCA). Furthermore, no differences were found in the physical or kinetic properties of partially purified preparations of the enzyme mediating the final step in proline biosynthesis, PCA reductase. The specific activity of PCA reductase was, however, consistently higher in crude extracts prepared from the argD ^– mutant.This work was supported by grants from the National Institutes of Allergy and Infectious Diseases (Public Health Service No. AI-10862) and The University of Connecticut Research Foundation (to C. M. B.). J. J. R. was supported by an NDEA Predoctoral Fellowship.     

Biochemical genetics of Chinese hamster cell mutants with deviant purine metabolism. VI. Enzymatic studies of two mutants unable to convert inosinic acid to adenylic acid

Ade^–H and ade^–I are two auxotrophic mutants of Chinese hamster ovary (CHO-K1) cells which specifically require adenine as the purine source to grow. The enzymatic defects of these mutants were examined in cell-free extracts. It was found that ade^–H did not have any detectable adenylosuccinate synthetase activity and ade^–I was defective in the adenylosuccinate lyase enzyme. The relevance of adenine-requiring mutants to the study of the regulation of purine metabolism in mammalian cells is discussed.This work was supported by research grants from the National Institute of Aging (AG00029) and the National Foundation, March of Dimes (1-423), and by a contract from the Center for Toxicological Research, Food and Drug Administration (72-213). David Patterson is a recipient of a Research Career Development Award from the National Institute of Arthritis, Metabolic and Digestive Diseases (AM00044).Contribution (No. 218) from the Eleanor Roosevelt Institute for Cancer Research.     

Prolactin increases the density of striatal dopamine receptors in normal and hypophysectomized male rats

Administration of prolactin to adult male rats, by s.c. injection, significantly increases the density of the striatal dopamine (DA) receptors, without altering the apparent affinity of the receptors for [³H]spiroperidol. Larger doses of prolactin are required to increase the density of the striatal DA receptors in hypophysectomized rates compared to normal rats. These results suggest that prolactin might be the common mediator of the increase in striatal DA receptor density produced by either estrogen or haloperidol administration. Monitoring and/or altering prolactin levels might be informative in neurologic or psychiatric disorders involving striatal DA neurotransmission.     

The structures of garcinones a,b and c: Three new xanthones from Garcinia mangostana

Three new tetraoxygenated xanthones (garcinones A, B and C), each disubstituted with C₅-units, have been isolated from the chloroform extract of the fruit-hulls of Garcinia mangostana. Their structures were established by a combination of spectral interpretation and chemical correlation.     

Germacrane and eudesmane derivatives from Calea reticulata

Calea reticulata afforded in addition to known compounds two new sesquiterpenes. These were germacrane and eudesmane derivatives, identified as germacra-4(15),5,10(14)-trien-1-one and 6-epi-β-verbesinol coumarate, respectively.     

Response of excised embryos of rice (Oryza sativa L.) to X-rays

Summary The response of rice (Oryza sativa L.) embryos to X-rays (M₁ to M₃) was studied. By means of irradiating excised embryos, both chlorophyll and macromutation were successfully induced in three genotypes of rice. However, differential responses in terms of mutation frequency, mutation spectrum and optimal levels of X-rays required for induction of mutation (chlorophyll as well as morphological) were found to exist between cultivars. In Satika and Ashkhata, LD₅₀ values and maximum induced seed sterility are concomitant to optimum level of radiation required for triggering chlorophyll mutation. However, optimum dose for induction of macromutation in Satika and Kerangserang is independent of either LD₅₀ and/or induced seed sterility.Chances of obtaining both dominant and locus specific recessive mutations in the immediate X-ray treated generation (M₁) are large. This indicates the very high degree of effectiveness of the excised embryo irradiation technique with rice.     

Lysosomal proliferation in rachitic avian intestinal absorptive cells following 1,25-Dihydroxycholecalciferol

Lysosomes in chick intestinal absorptive cells from rachitic (vitamin D-deficient) and vitamin D-replete animals were studied utilizing transmission electron microscopic histochemistry and ultrastructural morphometry. Absorptive cells from rachitic animals, serum calcium = 7.3±0.3 mg%, contained an average of 4.0±0.3 supranuclear lysosomes. In rachitic chicks sacrificed 9 hr post-injection of 1,25-dihydroxycholecalciferol, the active metabolite of vitamin D, the values for both serum calcium, 9.8 ± 0.2 mg%, and the number of apical absorptive cell lysosomes, 12.9±0.6, were increased over non-injected or vehicle-only injected animals. Lysosomes in vitamin D-replete absorptive cells were characterized by their intense staining with pyroantimonate, indicative of their high calcium content. The same organelles also produced a positive reaction for acid phosphatase. Rachitic lysosomes, also acid phosphatase positive, were only lightly stained with pyroantimonate. The lysosomal proliferation apparently induced by 1,25-dihydroxycholecalciferol may be a further indication that these organelles play a role in intestinal calcium transport and/or intracellular calcium homeostasis within the absorptive cell.     

Ethylene-promoted formation of aerenchyma in seedling roots of Zea mays L. under aerated and non-aerated conditions

The role of ethylene in the formation of lysigenous cortical cavities (aerenchyma) in seedling roots of Zea mays L. cv. Capella, has been studied under aerated and non-aerated conditions. Passing roots from air to aerated water or from an aerated nutrient solution to a non-aerated solution, promoted cavity formation and was accompanied by an increase of the endogenous ethylene concentration. When the endogenous ethylene concentration of roots in aerated nutrient solutions, which otherwise would not produce much cavities, was enhanced by applying ethylene gas (0.1 and 1.0 μl 1^-1 in air) or the ethylene precursor 1-aminocyclopropane-1-car-boxylic acid, cavity formation was promoted. When, on the contrary, the endogenous ethylene concentration of the roots was reduced by adding the inhibitors of ethylene biosynthesis, cobalt ions and aminooxyacetic acid, or when the ethylene action was prevented by silver ions, cavity formation was prevented. It is concluded that endogenous ethylene controls the induction of cavity formation in the roots.