Integument and sensory nerve differentiation ofDrosophila leg and wing imaginal discs in vitro

Summary An ultrastructural analysis is presented of the cuticular and neural structures formed by the prothoracic leg and wing imaginal discs of maleDrosophila melanogaster larvae during culture in vitro with 0.2 g/ml of -ecdysone. A pupal cuticle, and subsequently an imaginal cuticle with a well-defined epicuticle and a laminated endocuticle is formed. The ultrastructure of the epidermis and of cuticular structures such as bristles, trichomes, apodemes, and tracheoles is very similar to that found in situ. Dendrites and nerve cell bodies are formed in vitro, and sensory axons form nerve bundles similar to those of normal appendages in situ, despite their isolation from the central nervous system. It is concluded that at the ultrastructural level, differentiation in vitro closely parallels the normal course of development.     

Arachidonic acid metabolism in rat basophilic leukemia (RBL-1) cells

Rat basophilic leukemia (RBL-1) cells metabolized arachidonic acid through more than one enzymatic pathway. The major cyclooxygenase product was prostaglandin (PG) D₂ as established by chromatographic and chemical behavior and the effect on platelet aggregation. PGD₂ formation from exogenous arachidonic acid was inhibited by indomethacin, 1 μg/ml. RBL-1 incubated with exogenous arachidonic acid also formed SRS-A the synthesis of which was not inhibited by indomethacin. However, the SRS-A activity was blocked by the specific receptor antagonist FPL 55712. [¹⁴C]arachidonic acid was effectively incorporated into the phospholipids of RBL-1 cells. Challenge of such prelabelled cells or unlabelled cells with A 23187 caused release of PGD₂, SRS-A and another presently unidentified product. However, with A 23187 as a stimulus, the RBL-1 cyclo-oxygenase could not be blocked by low concentrations of indomethacin. This work further substantiates our earlier findings that SRS-A formed from arachidontic acid is not a cyclooxegenase product.     

Ultrastructure of the Somatic and Buccal Cortex of the Tetrahymenine Hymenostome Glaucoma chattoni

SYNOPSIS The membranes, epiplasm, and fiber systems are described in the somatic cortex of Glaucoma chattoni strain HZ-1. Kinetodesmal fibers, postciliary and transverse microtubular ribbons, basal microtubules, transverse fibers and transverse accessory material are associated with kinetosomes. Longitudinal microtubular ribbons and mitochondria occur interkinetally. In the buccal cortex, the membranes, epiplasm and fibers of the 3 membranelles, the paroral kinety, the ribbed wall, and the cytostome are described. Comparisons between G. chattoni and other ciliates reveal ultrastructural differences of possible systematic significance. In the somatic cortex of this and other tetrahymenines. Iongitudinal microtubular ribbons and basal microtubules occur concurrently. In the buccal cortex, alveoli are absent in tetrahymenine membranelles. A table is presented of the fiber systems associated with single somatic kinetosomes of various ciliates whose cortical ultrastructure has been studied to date.     

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.     

Studies on the synthesis of CDP-diacylglycerol: Stimulation by GTP and inhibition by ATP and fluoride

The rat liver microsomal enzyme CTP: phosphatidate cytidylyltransferase (EC 2.7.7.41) which catalyzes the formation of CDP-diacylglycerol has been found to be markedly stimulated by GTP. The requirement for GTP is absolute, the novel GTP analogues such as guanosine 5′-[β,γ-methylene]-triphosphate, guanosine 5′-[α,β-methylene]-triphosphate, guanosine 5′-[β,γ-imido]-triphosphate and guanosine 3′-diphosphate 5′-diphosphate are without significant effect. Maximal stimulation occurs at 1 mM GTP. ATP at a concentration of 5 mM totally inhibits the formation of CDP-diacylglycerol even in the presence of optimal GTP concentration. Analogues of ATP such as adenosine 5′-[α,β-methylene]-triphosphate, adenosine 5′-[β,γ-methylene]-triphosphate and adenosine 5′-[β,γ-imido]-triphosphate are without effect on the reaction. The addition of fluoride (8 mM) likewise abolishes the stimulatory effect of GTP.     

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.