Arachidonic acid metabolic pathway of the rabbit placenta

Placenta microsomes prepared from animals late in gestation (29 days) efficiently metabolize arachidonic acid into PGE2, PGF2 alpha, PGD2, TxA2 and little or no prostacyclin. In contrast to the late gestation placenta, the early (17 day) placental microsomes synthesize primarily PGE2. The cytosolic (100,000 X g supernatant) fraction from early or late gestation placentae converted arachidonic acid, with a calcium dependent enzyme, into non-polar metabolites whose synthesis was inhibited by ETYA but not indomethacin. These metabolites were purified by HPLC and GC-MS analysis indicated the presence of 12-hydroxy-, 15-hydroxy-, and 11-hydroxy-eicosatetraenoic acid. The mitochondrial (8,000 X g pellet) produced PGE2; PGF2 alpha; 12-, 11-, 15-HETE; the C-17 fragment HHT; and the unusual cyclooxygenase metabolite 15-keto-PGE2. These biologically active metabolites may play a vital role in the reproductive function of the placenta.     

Role of supernatant protein factor and anionic phospholipid in squalene uptake and conversion by microsomes

Supernatant protein factor (SPF), a cytosolic protein (Mr = 47,000) stimulates microsomal squalene epoxidase activity 4- to 10-fold in the presence of anionic phospholipid such as phosphatidylglycerol (PG) (Saat, Y., and Bloch, K. (1976) J. Biol. Chem. 251, 5155-5160). This effect has been ascribed to substrate translocation from inactive to active pools within the membrane of the endoplasmic reticulum (Friedlander, E. J., Caras, I. W., Lin, L. F. H., and Bloch, K. (1980) J. Biol. Chem. 255, 8042-8045). Here we show that SPF and PG also stimulate squalene uptake per se by microsomes as well as stimulate squalene epoxidase. Microsomes preloaded with substrate in the presence of SPF and PG show full epoxidase activity. They do not require further addition of these factors during enzyme assay. Addition of SPF and PG to assay mixtures containing microsomes preloaded with substrate in the presence of SPF and PG did not further increase epoxidase activity. We also show that PG tightly binds to microsomes. This binding of PG is essential for the response of microsomal epoxidase to SPF. Solubilized microsomal enzymes have been reconstituted and show high epoxidase activity. In this system, SPF and PG do not stimulate the conversion of squalene into products.     

A chromatin core particle obtained by selective cleavage of histones by clostripain.

Rat liver chromatin core particles digested with clostripain yield a structurally well-defined nucleoprotein particle with an octameric core made up of fragmented histone species (designated H'2A, H'2B, H'3 and H'4, respectively) after selective loss of a sequence segment located in the N-terminal region of each core histone. Sequential Edman degradation and carboxypeptidase digestion unambiguously establish that histones H2A, H2B, H3 and H4 are selectively cleaved at the carboxyl side of Arg 11, Lys 20, Arg 26 and Arg 19 respectively and that the C-terminal sequences remain unaffected. Despite the loss of the highly basic N-terminal regions, including approximately 17% of the total amino acids, the characteristic structural organization of the nucleosome core particle appears to be fully retained in the proteolyzed core particle, as judged by physicochemical and biochemical evidence. Binding of spermidine to native and proteolyzed core particles shows that DNA accessibility differs markedly in both structures. As expected the proteolyzed particle, which has lost all the in vivo acetylation sites, is not enzymatically acetylated, in contrast to the native particle. However, proteolyzed histones act as substrates of the acetyltransferase in the absence of DNA, as a consequence of the occurrence of potential acetylation sites in the core histones thus rendered accessible. The possible role of the histone N-terminal regions on chromatin structure and function is discussed in the light of the present observations with the new core particle obtained by clostripain proteolysis.     

Buspirone: A potential atypical neuroleptic

Buspirone produces a dose-dependent but short-lived elevation in striatal dopamine (DA) metabolites in the rat. $\text{In}$$\text{vitro}$, buspirone possesses an affinity similar to sulpiride for DA receptors (3H-spiperone). A moderate affinity for α₁ receptors was also observed while buspirone was inactive at α₂, β, muscarinic and serotonin₂ receptors. This pharmacological profile as well as previous behavioral data indicate that buspirone may be a potential “atypical” neuroleptic.     

A STUDY OF GLUCO-CORTICOSTEROID-INDUCED PYKNOSIS IN THE THYMUS AND LYMPH NODE OF THE ADRENALECTOMIZED RAT

Pyknotic nuclei, observed in the thymus of steroid-treated rats, are dense, homogeneous, intensely basophilic and Feulgen positive. Under the electron microscope, the image is that of a complete segregation of the chromatin from the nuclear sap producing a margin or crescent of condensed chromatin. Approximately 30% of all small thymocytes appeared to undergo this type of degeneration within 3–4 hr after administration of the synthetic corticosteroid, dexamethasone. At this time, pyknotic thymocytes were observed in clusters, probably as a result of the activity of dense reticular cells and macrophages. Topographical and experimental data suggest the existence of a select population of steroid-sensitive thymic cells. Furthermore, on the basis of thymidine-³H incorporation studies, it appears that the steroid-sensitive population of thymocytes does not correspond to "aged" cells. In addition, many plasma cells became pyknotic after the same steroid treatment, indicating an unexpected similarity between their nuclei and those of lymphocytes. Finally, steroid failed to induce pyknosis of thymocytes in a variety of in vitro experiments, suggesting that the in vivo effect of steroid is of an indirect nature. The results are discussed in terms of (a) the nature of the nuclear changes characterizing pyknosis, (b) the hypothetical mechanism whereby steroids trigger such changes, and (c) the population of cells susceptible to steroid-induced pyknosis.     

Culture Medium for Enterobacteria

A new minimal medium for enterobacteria has been developed. It supports growth of Escherichia coli and Salmonella typhimurium at rates comparable to those of any of the traditional media that have high phosphate concentrations, but each of the macronutrients (phosphate, sulfate, and nitrogen) is present at a sufficiently low level to permit isotopic labeling. Buffering capacity is provided by an organic dipolar ion, morpholinopropane sulfonate, which has a desirable pK (7.2) and no apparent inhibitory effect on growth. The medium has been developed with the objectives of (i) providing reproducibility of chemical composition, (ii) meeting the experimentally determined nutritional needs of the cell, (iii) avoiding an unnecessary excess of the major ionic species, (iv) facilitating the adjustment of the levels of individual ionic species, both for isotopic labeling and for nutritional studies, (v) supplying a complete array of micronutrients, (vi) setting a particular ion as the crop-limiting factor when the carbon and energy source is in excess, and (vii) providing maximal convenience in the manufacture and storage of the medium.