Anaerobic Oxidation of Acetylene by Estuarine Sediments and Enrichment Cultures

Acetylene disappeared from the gas phase of anaerobically incubated estuarine sediment slurries, and loss was accompanied by increased levels of carbon dioxide. Acetylene loss was inhibited by chloramphenicol, air, and autoclaving. Addition of ¹⁴C₂H₂ to slurries resulted in the formation of ¹⁴CO₂ and the transient appearance of ¹⁴C-soluble intermediates, of which acetate was a major component. Acetylene oxidation stimulated sulfate reduction; however, sulfate reduction was not required for the loss of C₂H₂ to occur. Enrichment cultures were obtained which grew anaerobically at the expense of C₂H₂.     

Targeted point mutation that creates a unique Eco RI site within the signal codons of the beta-lactamase gene without altering enzyme secretion or processing

A method has been developed for constructing site-specific mutations by using a strongly selectable marker on which to "piggy-back" a desired mutation that may be phenotypically silent. Using this approach, a new unique Eco RI restriction site has been generated at the beginning of the signal codons of the beta-lactamase gene of the plasmid pBR322. The consequential alteration of the second amino acid of the signal from Ser to Arg has no effect on either the transport or the processing of the beta-lactamase.     

The preparation of bile acid amides and oxazolines, II, the synthesis of the amides and oxazolines of ursodeoxycholic acid, deoxycholic acid, hyodeoxycholic acid and cholic acid

Bile acid amides and oxazolines were synthesized by a sequence of steps involving the reaction of the free bile acid with formic acid to yield the formyloxy derivative, preparation of the formyloxy acid chloride, condensation of the acid chloride with 2-amino-2-methyl-1-propanol to give the amide and, finally, cyclization of the amide with thionyl chloride to give the oxazoline. The oxazolines were characterized by physical constants, thin layer and gas-liquid chromatography and identified by elemental analysis and gas-liquid chromatography-mass spectrometry. Some of the bile acid oxazoline derivatives alter the activity of bacterial 7-dehydroxylases $\text{in vitro}$, and inhibit the growth of certain anaerobic bacteria in pure culture.     

Stereochemical aspects of forcing special substrate hydrazides to behave either as electrophiles or as nucleophiles during catalysis by crude papain

Restriction of hydrazides of N-blocked amino acids mainly to electrophilic action, in acylating crude papain, has been achieved by means of a large amount of aniline, with formation of insoluble anilides of N-acylamino acids. Similarly, nucleophilic behavior, on the part of a hydrazide, has been promoted by introducing a large proportion of an N-acylamino acid to produce an insoluble N¹,N²-diacylhydrazine. Achiral, chiral and racemic hydrazides and their corresponding N-acylamino acids were utilized in the study. Among the more informative combinations of reactants were Z-dl-alanine hydrazide with aniline and then with Z-glycine. A stereospecific response in the former situation produced Z-l-alanine anilide. In the latter case, a stereoselective interaction produced Z-Gly-NHNH-lAla-Z more rapidly than Z-Gly-NHNH-d-Ala-Z. The final incubation period yielded an optically pure D product. Differences in stereochemical control have been delineated in terms of different spatial aspects for interactions at the S and S′ subsites of sulfhydryl proteolytic enzymes. A racemic reactant encountered firm stereospecificity as an electrophile at the S subsite but only modest stereoselectivity as a nucleophile at the S′ subsite. The ready availability of crude papain allows an effective procedure for the synthesis of substantial quantities of diacylhydrazines.     

Evaluation of a new modified pediatric bubble oxygenator

A comparison was made of the S-070 Pediatric Bubble Oxygenator, which was unreliable above flow rates of approximately 1.5 L/min, with a modified S-070A, which proved to be extremely efficient to flow rates of 2.5 L/min.     

Genetic variability of the tumorous-head maternal effect in Drosophila melanogaster

Summary The tumorous-head maternal effect in Drosophila melanogaster is produced by a recessive gene (tuh-1) in chromosome 1. Polymorphism exists at this locus. This maternal effect, which is part of the normal variation found in this species, is detected with the aid of a mutant gene. In the presence of the maternal effect, a semi-dominant mutant gene (tuh-3) causes homoeotic changes in the eye-antennal imaginal discs. The phenotype in the adult is known as the tumorous-head abnormality. The mutant gene, which is located in the right arm of chromosome 3, is characterized by reduced penetrance. Using the penetrance of the mutant gene as the criterion, the results of these experiments show that the level of the maternal effect activity is influenced remarkably by modifiers present in wild type strains. The assay is to mate females homozygous for tuh-1 with males homozygous for tuh-3 and to determine the percent of the offspring showing the tumorous head abnormality. Using this procedure, it was observed that parental females with various combinations of chromosomes 1 and 3 from Lausanne and Stephenville wild type strains show great variability in the level of maternal effect activity. Modifiers in chromosome 1 and 3 from the Stephenville strain increase the level of the maternal effect activity. The level is reduced if these chromosomes are replaced by those from the Lausanne strain. A major locus in chromosome 3 is in the same region occupied by clusters of functionally related genes with regulating action. These results demonstrate that the penetrance of a mutant gene, which acts during embryogenesis, is influenced by modifiers which act during oogenesis.This investigation was supported by Public Health Service Research Grant GM 18664 to Arizona State University from the National Institute of General Medical Sciences     

Immunocytochemical localization of GABAergic neurones at the electron microscopical level

Summary Antibodies prepared to purified brain glutamic acid decarboxylase (GAD), the synthesizing enzyme for the neurotrasmitter, -aminobutyric, acid (GABA), have been utilized with an unlabelled antibody method to localize GABAergic neurones in both light and electron microscopic preparations. A modification of Sternberger's peroxidase-antiperoxidase (PAP) complex is used to localize the site of anti-GAD binding, and the PAP complex is visualized with diaminobenzidine and H₂O₂. The reaction product is visible in both the light and electron microscopes. The ability to localize and identify labelled profiles in the electron microscope provides more functional information than light microscopical preparations. For example, the GAD-positive reaction product occurs mostly in association with synaptic vesicles within axon terminats, and this localization indicates the importance of GAD for the packaging and storage of GABA. The somata and dendrites of neurones giving rise to these terminals are visualized in colchicine-injected material. The GABAergic neurones form axo-somatic, axo-dendritic, axo-axonal and dendro-dendritic synapses in various regions of the rat central nervous system. Pretreatments of animals with anterograde degeneration have shown the significance of some of the GABAergic terminals that form axo-axonal synapses in the spinal cord.An many brain regions, such as the cerebral cortex, hippocampus and olfactory bulb, virtually all of the GABAergic synapses are derived from local circuit neurones. In other regions such as the cerebellum and neostriatum, the GABAergic terminals are derived from both local circuit neurones and the local axon collaterals of projection neurones that have their somata within these regions. A third type of configuration of GABAergic terminals occurs in the globus pallidus and substantia nigra where these terminals are derived from distant brain regions, axon collaterals of projection neurones and from local circuit neurones. Together, these results indicate the complex organization of the GABAergic system of the brain that has been vividly revealed with electron in croscopical immunocytochemistry.     

Simulation of grana stacking in a model membrane system. Mediation by a purified light-harvesting pigment-protein complex from chloroplasts

An isolated light-harvesting pigment-protein complex contains polypeptides which bind chlorophyll a and b. The individual complexes can be purified from detergent-solubilized membranes. The isolated light-harvesting complex, when dialyzed to remove detergents, was examined by freeze-fracture electron microscopy. The material consisted of planar sheets of 80-Å subunits which interacted via an edge-to-edge contact. Addition of cations caused the planar light-harvesting complex sheets to become tightly appressed in multilamellar stacks, with distinct subunits still visible within each lamellar sheet. A transition of particle organization from random to crystalline occurred in parallel with the cation-induced lamellar association. Treatment of the dialyzed light-harvesting complex subunits with low levels of the proteolytic enzyme trypsin removed a 2000 molecular weight segment of the major polypeptide of the light-harvesting complex and blocked all subsequent cation-induced changes in structural organization of the isolated light-harvesting complex lamellar sheets.To gain further evidence for mechanisms of cation effects upon the organization of the light-harvesting complex in native membranes, the light-harvesting complex was incorporated into uncharged (phosphatidylcholine) lipid vesicles. The protein complexes spanned the lipid bilayer and were arranged in either a random pattern or in hexagonal crystalline lattices. Addition of either monovalent or divalent cations to ‘low-salt’ (20 mM monovalent cation) vesicles containing light-harvesting complex caused extensive regions of membrane appression to appear. It is concluded that this cation-induced membrane appression is mediated by surface-exposed segments of the light-harvesting complex since (a) phosphatidylcholine vesicles themselves did not undergo cation-induced aggregation, and (b) mild trypsin digestion of the surface-exposed regions of the light-harvesting complex blocked cation-induced lamellar appression. The particles in the appressed vesicle membranes tended to form long, linear arrays of particles, with occasional mixed quasi-crystalline arrays with an angular displacement near 72°. Surface-mediated interactions among light-harvesting complex subunits of different membranes are, therefore, related to changes in structural organization and interaction of the particles within the lipid phase of the membrane.Numerous previous studies have implicated the involvement of the light-harvesting complex in mediating grana stocking in intact chloroplast membranes. The data presented herein provide a simulation of the membrane appression phenomena using a single class of chloroplast-derived membrane subunits. The data demonstrate that specific surface-localized regions of the light-harvesting complex are involved in membrane-membrane interactions.