Search PubMed⌕ Search

Biomedical subjects

F Orrego

Publications and source records attributed to F Orrego.

53 records · Page 3Linked to original sources
PubMed1976

Effects of anisomycin on brain protein synthesis and passive avoidance learning in newborn chicks.

The effects of anisomycin (ANM) on newborn chicks have been studied with respect to brain protein synthesis, growth, EEG, toxicity, and several passive avoidance learning tasks. It was found that intracerebral ANM (80 nmol) gave a maximum inhibition of brain protein synthesis of 30%, while a combination of subcutaneous (10 mumol; 53 mg/kg) plus intracerebral (80 nmol; 21 mug) ANM inhibited by 91% in the first 2 hr and by 75% in the subsequent 2 hr period. Cycloheximide (CXM) also in combined injections at the same doses as ANM, inhibited by 97% in the 4 hr that followed injection. However, all the CXM-injected chicks were dead by 18 hr, while the lethality of ANM did not differ from that of saline. ANM also did not affect EEG measured at 1, 3, 5, or 24 hr following the subcutaneous plus intracerebral injections, nor did ANM affect body or brain growth curves or brain protein accretion. In the learning experiments, animals were initially trained to peck at water-coated metal spheres (type A learning) or at water imbibed birdseed (types B and C learning) in less than 1 sec, and were exposed to the same lures treated with the aversant methylanthranilate (MeA) one day later on one occasion (types A and B learning) or exposed twice (type C learning) and tested for learning retention one day later. Learning criterion was set as failure to peck at the lure during the first 20 sec of presentation. If ANM was injected 1 hr prior to MeA exposure, large and highly significant memory deficits were found during the retention test, as compared with saline injected controls. No effect of ANM was seen, however, if it was injected one day after learning, indicating that it did not interfere with retrieval mechanisms. ANM also decreased the external manifestations of fear or displeasure that chicks express during retention testing. Such manifestations have a high correlation with pecking suppression (r = 0.88, P less than 0.001).

Amino Acids↗
PubMed1976

Electrically induced release of labelled taurine, alpha- and beta-alanine, glycine, glutamate and other amino acids from rat neocortical slices in vitro.

The electrically induced release of labelled alpha-aminoisobutyrate, L-alpha-alanine, beta-alanine, glycine, histidine, serine, glutamate, aspartate and taurine, from superfused thin slices of the rat neocortex, held on quick-transfer electrodes was studied. In no instance did the release of these substances resemble that of (3H)-labelled noradrenaline, acetylcholine or 5-hydroxytryptamine, which can be released by 0.5-3 V stimuli and whose release shows an absolute dependency on calcium ions. Small amounts of alpha-aminoisobutyrate, beta-alanine, serine, glutamate and aspartate were released with 4 V stimuli, but the release was statistically significant for the first two substances only. Following incubation with (3H)-histidine, substantial labelling of homocarnosine was found, but no electrically induced release of this dipeptide could be detected. With (14C)-taurine, however, small but significant release was found with sinewave stimuli of 1.5 V or higher. Such release was significantly increased in the absence of calcium ions. Biphasic pulses of frequencies ranging between 10 and 100 Hz. (1 V, 3 ms duration) did not evoke the release of (14C)-taurine, although this type of stimulation readily induced the release of (3H)-noradrenaline studied simultaneously. Differences in threshold, calcium dependency and shape of the taurine efflux peak, relative to that seen with (3H)-noradrenaline and other transmitters, suggest that taurine release occurs by mechanisms unrelated to those that mediate transmitter secretion. The release of all the above amino acids can readily be elicited, however, if stimuli that are too intense, prolonged or damaging are utilized. The occurrence of these artifacts in the present and in previous work is discussed.

Alanine↗
PubMed1975

Interaction of glycine with brain-cortex membrane fragments: kinetics, ionic requirements and amino acid specificity.

The binding of [14]glycine to rat brain-cortex membrane fragments, incubated in artificial cerebrospinal fluid, was studied in vitro by means of a nitrocellulose filter assay. The membranes were obtained from the large granule fraction (P2) of a brain-cortex homogenate, which was osmotically shocked and the larger membrane fractions isolated by centrifugation. Initial binding velocity lasts for about 2 min and equilibrium is reached in 10 min. The binding reaction is reversible, and [14C]glycine can de displaced by an excess of [12C]glycine or by dilution. Binding is strongly dependent on temperature and on sodium ions. The latter activate the binding process in a cooperative manner. Two binding components may be discerned: one with high affinity for glycine (Km = 40 +/- 8 muM) and one with lower affinity. Lowering the sodium concentration to 60 mM increases the Km of the high-affinity component to 59 muM, with no change in Vmax. The bound product is, after incubating the membranes at 37 degrees C for 10 min, 85% glycine. A large fraction of it may released by hypo-osmotic media.

Amino Acids↗
PubMedDate not supplied

[Molecular mechanism of noradrenaline transport by rat auricles in vitro].

The transport of tritium-labelled noradrenaline (3H-NA) into bisected rat auricular appendages in vitro, has been studied, using 14C-inulin as an extracellular space tracer, thus allowing a precise measurement of the 3H-NA transported into the cells. The NA transport time course is relatively fast, and initial rates lasted 5 min. in 150 mM sodium, 3 min. in 26 mM sodium, and about 1 min. in 50 mM potassium. Intracellular accumulation of 3H-NA by synaptic vesicles, was found not to be important in the first minute of transport. In the presence of 150 mM sodium a transport Km for NA of 0.59 +/- 0.06 muM (mean +/- S.E.M.) and a maximal velocity (Vmax.) of 2.44 +/- 0.43 pmol/mg. protein/min. were estimated. When sodium was lowered to 26 mM, the Km increased to 2.26 +/- 0.7 muM (P less than 0.001), while Vmax. showed no change. With 0 mM sodium (choline substitution) active NA transport is completely suppressed, and only a diffusional component can be discerned. No binding of NA to beta adrenergic receptors was found, and a small but highly significant binding to the non-specific catechol receptors could be detected.

Animals↗