Radical mechanism of aminopyrine oxidation by cumene hydroperoxide catalyzed by purified liver microsomal cytochrome P-450

Under identical experimental conditions, purified preparations of rabbit liver microsomal cytochrome P-450 and beef heart metmyoglobin were equally effective at stimulating the oxidation of aminopyrine to a free radical species by cumene hydroperoxide. Mannitol had no effect on radical levels produced with either hemeprotein-hydroperoxide system; however, specific ligands of the two hemeproteins, substrates of cytochrome P-450, and phospholipid affected the two systems quite differently. Only the metmyo-globindependent oxidation of aminopyrine was significantly inhibited by fluoride and cyanide. Metyrapone, a specific ligand of cytochrome P-450, and benzphetamine, which was N-demethylated by cumene hydroperoxide only in the presence of cytochrome P-450, inhibited only the cytochrome P-450-stimulated oxidation of aminopyrine. Moreover, only with the solubilized liver hemeprotein was aminopyrine radical generation markedly stimulated by phospholipid. Similar properties of aminopyrine N-demethylation and radical formation by the cytochrome P-450-cumene hydroperoxide system have strongly implicated the radical as a requisite intermediate in product formation. Micromolar concentrations of metyrapone caused parallel inhibition, by at least 50%, of both radical generation and formaldehyde production. These results support a radical pathway of N-demethylation proposed for other hemeprotein-hydroperoxide systems (B. W. Griffin and P. L. Ting, 1978, Biochemistry, 17, 2206–2211), in which the substrate undergoes two successive one-electron abstractions, followed by hydrolysis of the iminium cation intermediate. Thus, for this class of substrates, the experimental data are consistent with the oxygen atom of the product arising from H₂O and not directly from the hydroperoxide, which has been previously proposed as a general mechanism for cytochrome P-450 peroxidatic activities.     

Effects of DCPA,EPTC, and Chlorpropham on Pathogenicity of Meloidogyne hapla to Alfalfa

Treatments wilh the herbicides chlorpropham (isopropyl m-chlorocarbinilate), DCPA (dimethyl tetrachloroterephthalate), and El''TC (S-ethyl dipropylthiocarbamate), alone or in combination with Meloidogyne hapla Chilwood, significantly reduced the growth of both nemalode-resistant ''Nev Syn XX'' atttt susceptible ''Ranger" alfalfa (Medicago saliva L.) seedlings. M. hapla infection of both alfalfas was reduced by all herbicides because of fewer available infective courts in the treated plants. EPTC, however, reduced resistance to M. hapla, as indicated by increased galling of ''Nev Syn XX'' plants.     

Requirement for the C-terminal region of middle T-antigen in cellular transformation by polyoma virus

Deletions of polyoma virus DNA around the region that codes for the C-terminus of the viral middle T-antigen were created using a transforming fragment (BamH I/EcoR I) of viral DNA cloned in the plasmid vector pAT153. These species were recloned and assayed for their ability to transform Rat-1 cells in culture. Our results showed that whereas the DNA sequence between the presumed translational termination codon for the viral middle T-antigen and the single viral EcoR I site could be removed with no apparent effect on transformation, the removal of the termination codon itself or any amino acid coding sequences of this protein caused a drastic decrease in the transforming ability of the DNA. Transfection of Rat-1 cells with plasmids that contained viral DNA with deletions which corresponded to the last fourteen or more amino acids of the middle T-antigen never gave rise to cellular transformation.     

Role of gonadal hormones in development of the sexual phenotypes

Summary Male and female embryos develop in an identical fashion during the initial portion of gestation. If the indifferent gonad differentiates into an ovary (or if no gonad is present), a female phenotype is formed. Male phenotypic differentiation, however, requires the presence of an endocrinologically active testis. Two secretion of the fetal testis, Müllerian inhibiting substance and testosterone, are responsible for male development. Studies of single gene mutations that interfere with androgen action indicate that testosterone itself is responsible for virilization of the Wolffian duct system into the epididymis, vas deferens, and seminal vesicle, whereas the testosterone metabolite dihydrotestosterone induces development of the prostate and male external genitalia. Thus, impairment of dihydrotestosterone formation results in a characteristic phenotype consisting of predominantly female external genitalia but normally virilized Wolffian ducts. The molecular mechanisms by which testosterone and dihydrotestosterone act during fetal development appear to involve the same high affinity receptor, a protein that transports both testosterone and dihydrotestosterone to the nucleus of target cells. When this receptor is either absent, deficient, or structurally abnormal, the actions of both testosterone and dihydrotestosterone are impaired, and the resulting developmental anomalies involve both internal and external genital structures.The original work described in this review was supported by grant AM 03892 from the National Institutes of Health     

Reproductive studies of Brahman cattle II. Luteinizing hormone patterns in ovariectomized Brahman and Hereford cows before and after injection of gonadotropin releasing hormone

Six Brahman and six Hereford long-term ovariectomized cows were bled via tail vessel at 15 minute intervals for a period of 4 hours. Serum was collected and analyzed via radioimmunoassay (RIA) for luteinizing hormone (LH) to determine if ovariectomized Brahman and Hereford cows have pulsatile LH patterns and if breed of animal influenced LH patterns. Brahman and Hereford ovariectomized cattle did have pulsatile LH patterns. Although the trend was for higher LH levels in Hereford than Brahman cows there were no significant differences in mean serum LH levels, number or magnitude of LH peaks or serum LH pulse height.Six Brahman and five Hereford long-term ovariectomized cows were injected (IM) with a single dose of 500μg of gonadotropin releasing hormone (GnRH). Animals were bled via tail vessel at 15 minute intervals for a period of 6 hours. Serum was assayed for LH via RIA to determine if ovariectomized Brahman and Hereford cows differ in GnRH induced LH response. All animals showed increased serum LH in response to GnRH injection within the first 15 minute collection interval. There were no significant differences in duration of response between ovariectomized Brahman or Hereford cows. Ovariectomized Brahman cows had significantly lower (P<.005) Lh values per period than ovariectomized Hereford cows. It was therefore concluded that ovariectomized Brahman cows were significantly less responsive to GnRH induced LH release than were ovariectomized Hereford cows, although duration and shape of the response curves were not different.     

Orientation of Euglena gracilis by electromagnetic fields: theory and experiment.

Computer data derived from theoretical treatments of the orientation of ellipsoidal particles in alternating fields is compared with experimental data from microscopic studies on Euglena gracilis, and elongated free-living flagellate. Computed data based upon a theoretical treatment by SAITO, SCHWAN and SCHWARZ showed good agreement with experimental results, predicting the relationship between cellular orientation, the frequency of the impressed field, and the conductivity of the suspending medium.