Hyperbaric hyperoxia reversibly inhibits erythrocyte phospholipid fatty acid turnover

The present study is one component of a comprehensive investigation of oxygen tolerance of tissues and organs in normal human subjects. The focus of this study was the acylation of membrane phospholipid in situ by erythrocytes. Activation of exogenous [9,10-3H]oleic acid to acyl thioester and transesterification of the acyl thioester into phospholipid by intact human erythrocytes incubated in vitro decreased 30% after exposure of 10 human subjects to hyperbaric hyperoxia (100% O2, 3 ATA, 3.5 h). Partial recovery of activity could be detected when additional cells were obtained from these subjects and assayed in vitro 24 h after cessation of exposure. No significant change in membrane phospholipid fatty acid composition was detected under these conditions. The reduced glutathione content of intact erythrocytes increased by 15% after hyperbaric hyperoxia and remained elevated 24 h after exposure. In isolated membranes prepared from the same cells activation of [9,10-3H]oleic acid to acyl thioester and its transesterification into phospholipid did not change after hyperoxia. Since the ability of intact cells to replace oxidized fatty acids in membrane phospholipids via deacylation and reacylation in situ may be necessary for the maintenance of membrane integrity during exposure to oxidative stress, the decrease in [9,10-3H]oleic acid incorporation by human erythrocytes detected in vitro after hyperbaric hyperoxia in vivo may reflect an early event in the pathogenesis of oxygen-induced cellular injury and may be a useful index for assessment of the tolerance of tissues to hyperoxia.     

Ionized and wobble base-pairing for bromouracil-guanine in equilibrium under physiological conditions. A nuclear magnetic resonance study on an oligonucleotide containing a bromouracil-guanine base-pair as a function of pH

A one and two-dimensional nuclear magnetic resonance study of a non-selfcomplementary oligonucleotide containing a central 5-bromouracil-guanine pair is reported. For these two bases three types of hydrogen bonding schemes could exist; wobble, rare tautomer and ionized. The two-dimensional spectra of non-exchangeable protons together with one-dimensional spectra recorded in water show that at pH 7.0 the predominant species is a right-handed B-form DNA in which the brU.G pair has wobble geometry. On raising the pH we observe a transition monitored by proton chemical shift changes for the brU.G and adjacent base-pairs. The mid-point of the transition was observed at pH 8.6. Spectra recorded at pH 9.8 show that the helix remains intact with B form conformation. It is shown that this high pH form has an ionized brU.G base-pair now in Watson-Crick geometry. Thus under physiological conditions an equilibrium exists between wobble and ionized structures.     

Experimental avian PMV-2 infection in a domesticated wild host: daily behavior and effect on activity levels

Paramyxovirus type 2 (PMV-2) isolated from wild birds is often considered non-pathogenic, but nothing is known about its effects on overall behavior and fitness of free-flying birds. Domestically bred, African cut-throat finches (Amadina fasciata), a species from which PMV-2 has been isolated in the wild, were inoculated with a Central American field strain of PMV-2. Patterns of behavior were examined before and after viral challenge to quantify inapparent, sublethal effects of the disease. Infected birds demonstrated a significant decrease in activity (P = 0.01) followed by an apparent recovery period. Antibody titers confirmed infection in inoculated birds and indicated that sentinel birds did not become infected.     

Respiratory physiology and energy conservation efficiency of Campylobacter jejuni

A study of the electron transport chain of the human intestinal pathogen Campylobacter jejuni revealed a rich complement of b- and c-type cytochromes. Two c-type cytochromes were partially purified: one, possibly an oxidase, bound carbon monoxide whereas the other, of high potential was unreactive with carbon monoxide. Respiratory activities determined with membrane vesicles were 50- to 100-fold higher with formate and hydrogen than with succinate, lactate, malate, or NADH as substrates. Evidence for three terminal respiratory components was obtained from respiratory kinetic studies employing cyanide, and the following Ki values for cyanide were determined from Dixon plots: ascorbate + reduced N,N,N', N'-tetramethyl-p-phenylenediamine, K1 + 3.5 muM; malate, K1 = 55 muM; and hydrogen, K1 = 4.5 muM. Two oxidases (K1 = 90 muM, 4.5 mM) participated in the oxidation of succinate, lactate, and formate. Except with formate, 37 muM HQNO inhibited respiration by approximately 50%. Carbon monoxide had little inhibitory effect on respiration except under low oxygen tension (less than 10% air saturation). The stoichiometry of respiratory-driven proton translocation (H+/O) determined with whole cells was approximately 2 for all substrates examined except hydrogen (H+/) = 3.7) and formate (H+/O = 2.5). The higher stoichiometries observed with hydrogen and formate are consistent with their respective dehydrogenase being located on the periplasmic face of the cytoplasmic membrane. The results of this study suggest that the oxidation of hydrogen and formate probably serves as the major sources of energy for growth.     

The amino acid sequence of elephant (Elephas maximus) myoglobin and the phylogeny of Proboscidea

The complete amino acid sequence of skeletal myoglobin from the Asian elephant (Elephas maximus) is reported. The functional significance of variations seen when this sequence is compared with that of sperm whale myoglobin is explored in the light of the crystallographic model available for the latter molecule. The phylogenetic implications of the elephant myoglobin amino acid sequence are evaluated by using the maximum parsimony technique. A similar analysis is also presented which incorporates all of the proteins sequenced from the elephant. These results are discussed with respect to current views on proboscidean phylogeny.     

Glucocorticoid induction of tyrosine hydroxylase in a continous cell line of rat pheochromocytoma.

We have established a continous cell line (G1) in which the tyrosine hydroxylase specific activity is increased as much as 50-100-fold in response to dexamethasone. This response is specific for the glucocorticoid class of steroid hormones; it is elicited by dexamethasone, corticosterone, and triamcinolone, but not by estradiol, testosterone, progesterone, or deoxycorticosterone acetate. The increase in tyrosine hydroxylase specific activity is likely to be due to the increased synthesis of new enzyme protein rather than an activation of existing protein molecules, inasmuch as this increase is completely blocked by cycloheximide.