Expression cloning of human EGF receptor complementary DNA: gene amplification and three related messenger RNA products in A431 cells

In order to further define the mechanisms by which polypeptide growth factors regulate gene transcription and cellular growth, expression cloning techniques were used to select human epidermal growth factor (EGF) receptor complementary DNA clones. The EGF 3' coding domain shows striking homology to the transforming gene product of avian erythroblastosis virus (v-erbB). Over-expression of EGF receptors in A431 cell lines correlates with increased EGF receptor mRNA levels and amplification (up to 110 times) of the apparently singular EGF receptor gene. There appear to be three cytoplasmic polyadenylated RNA products of EGF receptor gene expression in A431 cells, one of which contains only 5' (EGF binding domain) sequences and is postulated to encode the secreted EGF receptor-related protein.

Cytokinins of the Developing Mango Fruit : Isolation, Identification, and Changes in Levels during Maturation

The cytokinin activity has been isolated and identified from extracts of immature mango (Mangifera indica L.) seeds. The structures of zeatin, zeatin riboside, and N(6)-(Delta(2)-isopentenyl)adenine riboside were confirmed on the basis of their chromatographic behavior and mass spectra of trimethylsilyl derivatives. Both trans and cis isomers of zeatin and zeatin riboside were also identified by the retention times of high performance liquid chromatography. In addition, an unidentified compound appeared to be a cytokinin glucoside.The concentration of cytokinins in the panicle and pulp of mango reached a maximum 5 to 10 days after full bloom and decreased rapidly thereafter. The cytokinin level in the seed remained high until the 28th day after full bloom. The quantity of cytokinins in pulp per fruit increased from the 10th day after full bloom, the maximum being attained around the 50th day after full bloom. Similarly, the amount of cytokinins per seed increased from the 10th day after full bloom, reaching a peak on the 40th day and decreasing gradually thereafter.A high percentage of fruit set in mango was persistently maintained by supplying 6-benzylaminopurine (1.5 x 10(3) micromolar) onto the panicle at the anthesis stage and by supplying gibberellic acid (7.2 x 10(2) micromolar) and naphthalene acetamide (3.1 x 10 micromolar) at the young fruit stage.

Inactivation of liver alcohol dehydrogenases and inhibition of ethanol metabolism by ambivalent active-site-directed reagents

Active-site-directed reagents, of the general structure omega-(BrCH2CONH)RCOY, where R = alkyl, aryl, or aralkyl, and Y = OH or NH2, inactivated horse, mouse, rat, and human liver alcohol dehydrogenases at widely different rates, reflecting differences in reagent specificity and in the structures of the enzymes. Treatment of mice and rats with either of two optimally specific reagents, p-(XCH2CONH)C6H4(CH2)3CONH2, where X = Br (7) or CH3SO3 (10), partially (20 to 40%) inactivated alcohol dehydrogenase in liver, inhibited ethanol metabolism, and prolonged the impairment of coordination produced by ethanol in these animals. Although the dose of 7 used (0.13 mmol/kg) approximated the LD50, 10 was effective at a dose of 0.48 mmol/kg that was not acutely toxic.

Kinetics and control of alcohol oxidation in rats

The rates of oxidation of ethanol and isopropanol by purified rat liver alcohol dehydrogenase were determined in vitro and compared to the rates of metabolism in vivo in order to estimate the extent to which alcohol dehydrogenase activity limits ethanol metabolism. The metabolism of isopropanol and isopropanol-d7 (CD3CDOHCD3) was examined by measuring blood alcohol and acetone levels at various times and apparently proceeds by an irreversible, enzyme-catalyzed pathway: isopropanol leads to acetone leads to an unidentified metabolite. The kinetic constants for the metabolism were computed from simultaneous fits to the appropriate differential equations using a nonlinear least-squares program. The relative rates of oxidation of the alcohols, ethanol:isopropanol:isopropanol-d7, at 25 mM were 9.6 : 2.3 : 1.0 in vitro and 4.1 : 2.4 : 1.0 in vivo. Since the ratio of rates for isopropanol is about the same in vitro and in vivo, it appears that alcohol dehydrogenase activity is the predominant rate-limiting factor in isopropanol metabolism. The relatively slower rate of ethanol oxidation in vivo as compared to in vitro suggests that liver alcohol dehydrogenase is partially (about 40%) limiting for ethanol metabolism.

In vivo evaluation of ambivalent active-site-directed inactivators of liver alcohol dehydrogenase

In order to decrease the rate of ethanol metabolism for the treatment of acute and chronic alcoholism it would be useful to inhibit liver alcohol dehydrogenase in vivo. Based on a knowledge of the three-dimensional structure of the horse enzyme, we designed active-site-directed inactivators [p-(XCH2CONH)C6H4(CH2)3COHN2] which bind to the enzyme-NAD or enzyme-NADH complex and alkylate methionine residue 306. In vitro, these reagents inactivated mouse, rat, horse and human liver alcohol dehydrogenases faster in the presence than in the absence of NAD or NADH, but with slightly different specificity. Mice and rats pretreated with the reagents eliminated ethanol in blood more slowly than those not treated, and the specific activity of alcohol dehydrogenase in liver homogenates of treated animals was decreased. It appears that the design of active-site-directed reagents is feasible, but these reagents must be improved so that they are more efficacious in vivo.

Binding of mono- and bis-N-substituted benzoquinolinium halides to butyrylcholinesterase: fluorescence measurements

The dissociation constants (Kdiss) of mono-and bis-N-substituted benzoquinolinium salts from butyrylcholinesterase were determined by the disappearance of the fluorescence of the free ligand. The Kdiss value determined by this method agreed closely with the dissociation constants (KI,s) of the free enzyme obtained by steady-state kinetic studies. The results indicate that the N-substituted benzoquinolinium salts with a strong binding ability to butyrylcholinesterase also are potent inhibitors of the esterolytic properties of the enzyme. Enzyme binding is favored by the coplanar structure and does not require a high concentration of charge on the onium function. The shape of the hydrophobic structures markedly influences binding.

Tissue analysis of plasticizer in dogs

Acute renal failure was produced in animals and analytical procedures for DEHP estimation in urine and tissues of dogs developed. The presence of DEHP in urine samples of control and sham operated dogs indicated that significant excretion of this plasticizer by kidney occurred. Delay in elevation of DEHP serum levels in nephrectomized dogs and similar concentrations of DEHP in 72 hr and 96 hr serum samples in all 3 groups indicate possible metabolism and/or uptake of DEHP by tissues. DEHP levels in brain, heart, and lung tissues of nephrectomized dogs were higher than those in control and sham operated dogs; however, the highest concentration of DEHP was found in lung regardless of grouping. Gas chromatographic spectra of kidney and liver homogenates showed several extraneous peaks with shorter retention times than DEHP, probably representing metabolites of DEHP. Identification and quantitation of DEHP metabolites in tissues are presently under way in our laboratory.

Potent reversible anticholinesterase agents. Bis- and mono-N-substituted benzoquinolinium halides

A number of bis- and mono-N-substituted benzoquinolinium salts and their analogues were prepared and evaluated as inhibitors of acetylcholinesterase (AcChE) and butyrylcholinesterase (BuChE). These compounds were also used to help identify some of the morphologic characteristics of the surface at or near the active sites of the cholinesterases. The shape, size, configuration, and conformation of the onium moieties of the quaternary ammonium compounds were found to be the important factors in their anticholinesterase activity. A high concentration of the positive charge of the quaternary ammonium compound is not a critical factor for the cholinesterase inhibitory activity. The order of decreasing potency of cholinesterase inhibition of the benzoquinolinium compounds was found to be acridinium greater than phenanthridinium greater than 5,6-benzoquinolinium greater than 7,8-benzoquinolinium. The inhibitory activity of the monobenzoquinolinium halides against cholinesterases is influenced by the N-substituent. A bis-quaternary ammonium compound with a flexible bridge that links the two nitrogen atoms was found to be more potent in inhibiting AcChE and less potent in inhibiting BuChE than a bis-quaternary ammonium compound with a rigid bridge. The acridinium and phenanthridinium derivatives of the benzoquinolinium compounds are very potent reversible inhibitors against both AcChE and BuChE.