Oxygen reactivity of p-hydroxybenzoate hydroxylase containing 1-deaza-FAD

The flavin prosthetic group (FAD) of p-hydroxybenzoate hydroxylase (EC 1.14.13.2) was replaced by 1-deaza-FAD (carbon substituted for nitrogen at position 1). An improved method for production of apoenzyme by precipitation with acidic ammonium sulfate was developed. The modified enzyme, in the presence of p-hydroxybenzoate, catalyzed the oxidation of NADPH by oxygen, yielding NADP+ and H2O2, but the ability to hydroxylate p-hydroxybenzoate and other substrates was lost. An analysis of the mechanism of NADPH-oxidase catalysis showed a close analogy between the reaction pathways for native and modified enzymes. In the presence of p-hydroxybenzoate, the rate of NADPH consumption catalyzed by the 1-deaza-FAD form was about 11% that of the native enzyme. Both formed a stabilized flavin-C (4a)-OOH intermediate upon reaction of reduced enzyme with oxygen, but the 1-deaza-FAD enzyme could not utilize this peroxide to hydroxylate substrates, and the peroxide decomposed to oxidized enzyme and H2O2.     

The effect of trans-[Rh(4-ethylpyridine)4Cl2]Cl x 2H2O on nucleic acid and protein syntheses in Escherichia coli

The effect of the transition metal compound trans-[Rh(4-ethylpyridine)4Cl2]Cl x 2H2O on the syntheses of DNA, RNA, and protein has been investigated for an auxotrophic bacterial strain, Escherichia coli JS-1, incapable of thymidine, uridine, and histidine syntheses. At low concentration (7.4 x 10(-6) M), this rhodium complex interferes with normal cell division and induces the formation of filaments comparable to those observed in the presence of the cis-(NH3)2PtClx antitumour agents. Once the suppressed growth rate of the filamenting cells has been taken into account, the rhodium compound is found not to alter macromolecular synthesis. Again this is consistent with similar observations made for the platinum compounds.     

Internally elongated rodent α-crystallin A chain: Resulting from incomplete RNA splicing?

αA^Ins, an elongated α-crystallin A chain previously observed in rat, was present beside the normal αA chain in mouse, gerbil and hamster, which places its origin at least 30 million years ago. Like in rat the sequences of golden hamster αA^Ins and αA were found to be identical, apart from the internal insertion of 22 residues in αA^Ins. The hamster chains only differed from the rat chains by a single substitution in the inserted sequence of αA^Ins. The origin of αA^Ins, by insertion of 22 residues in an otherwise unchanged αA chain, and its rigid evolutionary conservation are most easily explained by assuming the incomplete removal of a putative intervening sequence from the precursor mRNA of αA, leaving an intracistronic insert of 66 nucleotides in part of the eventually translated mRNA.     

Displacements of Simulium damnosum and strategy of control against onchocerciasis.

Regular aerial treatment of 14 000 km of watercourses has achieved and maintained, over an area of 700 000 km2 of West African savannah, a very high degree of control of the larvae of Simulium damnosum sensu stricto and S. sirbanum, the vectors of onchocerciasis in this area. However, particular and relatively restricted parts of this area, mainly in northern Ivory Coast and neighbouring parts of Upper Volta, experience regular and prolonged reinvasions by parous female vectors, which have already taken bloodmeals (and many of them carrying the parasites) and arrive from unknown sources probably hundreds of kilometres away, from directions probably between southwest and north. This reinvasion, now experienced in three successive years, represents the outstanding scientific, epidemiological and logistic problem still facing the WHO Onchocerciasis Control Programme. An outline is presented of the multidisciplinary investigations being undertaken to find a solution.     

Hypotonic hemolysis of human red blood cells: a two-phase process

Summary Previous use of hemolysis time measurement to determine permeability coefficients for the red blood cell membrane rested on the assumption that cells swelling in a hypotonic medium hemolyzed immediately on reaching critical volume. By preswelling red cells to various volumes prior to immersion in hemolytic solutions we extrapolate to the hemolysis time of red cells immersed at critical volume and thereby find a significant period of time during which the cells apparently remain in a spherical form prior to release of hemoglobin. Revised estimates of permeability coefficients follow from including this spherical (nonswelling) phase. In addition, the appreciation of a characteristic time period during which the membrane is under tension provides new opportunity to study physical and chemical properties of the membrane.Presented in part at the 1974 joint meeting of the Biophysical Society and the American Society of Biological Chemists.     

Identification of specificityH-2.7 as an erythrocyte antigen: Control by an independent locus,H-2G,between theS andD regions

SpecificityH-2.7 is expressed predominantly on erythrocytes and controlled by a gene that maps within theH-2 gene complex at a locus, designated asH-2G, which apparently lies between regionsS andD. Three phenotypes have been observed with respect to this antigen: a) positive by direct test and absorption (haplotypesH-2 ^f ,H-2 ^j ,H-2 ^p ,H-2 ^s ); b) positive only by absorption (H-2 ^k ); and c) negative (H-2 ^b ,H-2 ^d ,H-2 ^q ). New crossover positions have been established for severalH-2 recombinants based on classifications for theH-2G locus.     

Pancreatic islet cytology of ictaluridae (Teleostei)

Summary The endocrine pancreas of the bullhead catfish, Ictalurus nebulosus, and the channel catfish, I. punctatas was studied by light and electron microscopy. In addition to the usual A, B and D cells, a fourth endocrine cell type was consistently observed in the electron microscope. All endocrine cell types were innervated. The vesicles of most of the nerve endings were ultrastructurally different from typical adrenergic and cholinergic vesicles, strongly suggesting the possibility of a third autonomic neurotransmitter serving as a regulator of catfish islet secretion.Supported in part by PHS grant AM 11407 awarded to Dr. Bryce Munger.     

The mushroom ribosome-inactivating protein lyophyllin exerts deleterious effects on mouse embryonic development in vitro

Earlier investigations disclose that some plant ribosome-inactivating proteins (RIPs) adversely affect mouse embryonic development. In the present study, a mushroom RIP, namely lyophyllin from Lyophyllum shimeji, was isolated, partially sequenced, and its translation inhibitory activity determined. Its teratogenicity was studied by using a technique entailing microinjection and postimplantation whole-embryo culture. It was found that embryonic abnormalities during the period of organogenesis from E8.5 to E9.5 were induced by lyophyllin at a concentration as low as 50 μg/ml, and when the lyophyllin concentration was raised, the number of abnormal embryos increased, the final somite number decreased, and the abnormalities increased in severity. The affected embryonic structures included the cranial neural tube, forelimb buds, branchial arches, and body axis, while optic and otic placodes were more resistant. Lyophyllin at a concentration higher than 500 μg/ml also induced forebrain blisters within the cranial mesenchyme. When the abnormal embryos were examined histologically, an increase of cell death was found to be associated with abnormal structures, indicating that cell death may be one of the underlying causes of teratogenicity of the mushroom RIP. This constitutes the first report on the teratogenicity of a mushroom RIP.