Glucose and amino acid metabolism in chick telencephalon slices: Changes with incubation conditions and animals' development

Glucose and amino acid metabolism in 1- and 30-day-old chick telencephalon slices was studied in two incubation media in the presence or in the absence of a continuous oxygenation. Medium 1 has a composition and a tonicity similar to cerebrospinal fluid, medium 2 is hypertonic and does not contain any K⁺ ions. The incorporation of glucose carbon into amino acids and the distribution of radioactivity between the different amino acids are close to the ones observed in the chick brain in vivo only when the slices are incubated in medium 1, with oxygen at 30 days and without oxygen for the 1-day-old chick. It also appears that if oxygenation is necessary for incubation of mature brain tissue in vitro, the absence of the medium oxygenation is more suitable for the study of glucose metabolism in 1-day-old chick brain slices.     

The nucleotide sequences of barley cytoplasmic glutamate transfer RNAs and structural features essential for formation of δ-aminolevulinic acid

In chloroplasts and a number of prokaryotes, -aminolevulinic acid (ALA), the universal precursor of porphyrins, is synthesized by a multistep enzymatic pathway with glutamyl-tRNA^Glu as an intermediate. The ALA synthesizing system from barley chloroplasts is highly specific in its tRNA requirement for chloroplast tRNA^Glu; a number of other Glu-tRNAs are inactive in ALA formation although they can be glutamylated by chloroplast aminoacyl-tRNA synthetases. In order to obtain more information about the structural features defining the ability of a tRNA to be recognized by the ALA synthesizing enzymes, we purified and sequenced two cytoplasmic tRNA^Glu species from barley embryos which are inactive in ALA synthesis. By using glutamylated tRNAs as a substrate for the overall reaction, we showed that Glu-tRNA reductase is the enzyme responsible for tRNA discrimination.     

Respiration and soluble sugar metabolism in sugar pine embryos

Embroys excised from dormant seeds of sugar pine ( Pinus lambertiana Dougl.) incubated at 25°C (non-dormancy-breaking) or stratified at 5°C (dormancy-breaking) were analyzed to determine temperature effects on the relative activities of respiration and fermentative metabolism, the levels of soluble sugers and the activities of the hydrolytic enzymes, invertase and sucrose synthase, as related to the release of dormancy and germinatio. At 25°C, despite a sharp drop in embryo oxygen uptake after 48 h, a simultaneous decline in acetaldehyde and ethanol concentrations indicated that there was not a shift to fermentative metabolism. The concentrations of soluble sugars showed no treatment effects. Embryo invertase (EC 3.2.1.26) activity changed only slightly at either temperature, while stratification was accompanied by a 4-fold increase in sucrose synthase (EC 2.4.1.13) activity (cleavage direction). Upon transfer of stratified seeds to 25°C, embryo sucrose synthase activity rapidly increased almost 10-fold, with the increase beginning prior to germination, while mvertase activity increased 20-fold, concomitant with germination.     

Somatostatin as a mediator of the effect of neurotensin on pentagastrin-stimulated acid secretion in rats

Neurotensin and somatostatin have both been shown to inhibit gastric acid secretion, but no interaction between these peptides has been demonstrated. To determine whether somatostatin might be a mediator of neurotensin's effect on pentagastrin-stimulated gastric acid secretion, we performed the following three experiments. First, we collected 0.2-ml samples of portal venous blood as frequently as every 5 min, and we confirmed a significant release of somatostatin-like immunoreactivity into portal venous blood during neurotensin-induced inhibition of acid secretion. This release of somatostatin-like immunoreactivity and inhibition of acid secretion were only seen in pentobarbital-anesthetized rats, but no sustained release of somatostatin-like immunoreactivity or inhibition of acid secretion occurred in urethane-anesthetized animals. In the second experiment, we analyzed portal plasma by high pressure liquid chromatography, and found that portal somatostatin-like immunoreactivity in blood collected during neurotensin infusion was composed of a single peak corresponding to somatostatin-14. In the third experiment, we found that infusion of antibody to somatostatin prevented neurotensin from inhibiting pentagastrin-stimulated acid secretion. Taken together, these data show that somatostatin, possibly from the stomach itself, is a necessary mediator of neurotensin's inhibitory effect in pentobarbital-anesthetized rats.     

Extraction and measurement of myocardial nucleotides, nucleosides, and purine bases by high-performance liquid chromatography

Nucleotides, nucleosides, and purine bases were extracted from human endomyocardial biopsies, freeze-clamped rat hearts, and porcine coronary sinus plasma. Perchloric acid extracts were neutralized with Freon-trioctylamine and analyzed at 250 nm by reverse-phase ion-pairing high-performance liquid chromatography. To achieve the sensitivity necessary for analyzing small (1-3 mg wet wt) tissue samples, a small-bore, 2.1-mm-internal-diameter, C18, 5-micron reverse-phase column and a flow rate of 0.2 ml/min were used. All of the myocardial nucleotides and AMP degradation products were resolved in a total separation time of 27 min with 30 mM KH2PO4, 7.5 mM tetrabutylammonium phosphate buffers, and binary pH and acetonitrile gradients.     

Regional Amino Acid Concentration in the Brains of Rats Exposed to High Pressures

Regional amino acid concentrations were measured in rat brain fixed by microwave irradiation at three levels of elevated atmospheric pressure corresponding to different phases of the high-pressure neurological syndrome [20 atmospheres absolute (ATA), no clinical signs; 60 ATA, tremor; 85 ATA, severe tremor and myoclonic jerks]. No changes in amino acid content occurred at 20 or 60 ATA. At 85 ATA glutamine content increased in hippocampus, striatum, cerebellum, and substantia nigra, and gamma-aminobutyric acid content increased in hippocampus. It is suggested that enhanced glutamate release in various subcortical structures contributes to the myoclonic activity observed at 85 ATA.     

A quantitative analysis of C3 binding to O-antigen capsule, lipopolysaccharide, and outer membrane protein of E. coli 0111B4

The binding of serum C3 to the O-antigen capsule (OAg Cap), lipopolysaccharide (LPS), and outer membrane proteins (OMP) of Escherichia coli 0111B4 was examined. Bacteria were intrinsically labeled with [3H] or [14C]galactose (*gal) in the OAg Cap and LPS moieties or with [14C]leucine (*leu) to label proteins. Organisms were then incubated in serum containing differentially labeled C3, the above fractions were separated, and the proportion of each binding to a column containing anti-C3 was measured. The OAg Cap fraction bound 72 to 82% of the C3, which bound to E. coli 0111B4 during incubation in absorbed 10% pooled normal human serum (10% PNHS) or absorbed 40% C8-deficient serum (C8D). This distribution did not change when the organism was presensitized with immune IgG before serum incubation. A total of 2.93% +/- 0.48 of OAg Cap and 0.52% +/- 0.16 of LPS *gal bound specifically to Sepharose-containing antibodies to C3 (A:C3-Seph) after incubation in 10% PNHS; these values increased to 10.1% +/- 4.5 and 1.8% +/- 0.3, respectively, when C3 deposition was increased fourfold by incubation in 40% C8D. When encapsulated E. coli 0111B4 was incubated in 10% PNHS containing biotinylated C3, specific attachment of OAg Cap *gal to avidin-Sepharose was demonstrated in 1% sodium dodecyl sulfate (SDS), and complete release of bound *gal but not C3 occurred with 1 M NH2OH. When a mutant of E. coli 0111B4 lacking OAg Cap was incubated in 40% C8D, the outer membrane (OM) bound 85% of C3. Five percent of OM *gal from the unencapsulated organism bound to A:C3-Seph in 0.05% SDS, indicating that the fraction of LPS molecules with bound C3 increased threefold in the absence of OAg Cap. OAg Cap does not contain protein, and no net specific binding of *leu from OAg Cap fractions to A:C3 was detectable; 2.4 to 3.6% of OM *leu bound to A:C3-Seph. Immunoprecipitation of 82.9% of OAg Cap *gal with antisera that were directed to E. coli 0111B4 was associated with co-precipitation of 69.5% of C3 in the capsular fraction. Therefore, the majority of C3 bound to E. coli 0111B4 was covalently attached to OAg Cap and LPS. As corroboration of experiments with whole bacteria, purified OAg Cap and purified LPS consumed C3 when incubated in serum in the fluid phase. These results are the first to evaluate the acceptor site for C3 deposition on a Gram-negative organism incubated in serum, and show that LPS, OAg Cap, and OMP are all major acceptor sites for C3 in nonimmune serum.