Development of oxidative metabolism in the non-innervated optic lobe of the chick

Early removal of the optic cup of the chick embryo prevents innervation of the contralateral optic lobe. This reduces the rate of development od citrate synthetase. The posthatch increase of the level of this enzyme related to oxidative metabolism is not impaired by denervation of the chick optic lobe.

Light-evoked changes in chick optic lobe GABA system

In young chicks the effects of 3 min stroboscope stimulation on GABA and free glutamic acid content and on GAD and GABA-T activity in optic lobes were studied. A significant depletion in GABA and glutamic acid levels was found to occur. In addition a sustained increase in GABA-T and GAD activity was observed. In conclusion present experiments are in favour of an inhibitory role played by GABA in chick optic tectum during stroboscope stimulation.

Utilization in vivo of glucose carbon in the optic lobes and the cerebellum of the chick during postnatal growth

1. The incorporation of glucose carbon in vivo into amino acids was studied in the chick optic lobes and cerebellum during postnatal growth after subcutaneous injection of [U-14C]glucose. 2. The rapid incorporation of glucose carbon into free amino acids appears between the 1st and the 2nd day of postnatal growth in the optic lobes and between the 1st and the 4th day after hatching in the cerebellum. 3. The period during which the properties of mature brain metabolism are obtained is characterized in both structures during the first 48 hr of postnatal growth by changes in the specific radioactivity of some amino acids such as aspartate and alpha-alanine, and also by transient increases of glucose and glutamine concentrations. 4. The gamma-aminobutyrate content in the optic lobes is very high; the cerebellum on the contrary is characterized by its low gamma-aminobutyrate concentration linked to a very fast metabolism of this amino acid.

Ligand responses of alpha-bungarotoxin binding sites from skeletal muscle and optic lobe of the chick

Binding properties of detergent-solubilized receptors for alpha-bungarotoxin from skeletal muscle of the 13th day chick embryo and from optic lobe of the hatching chick were compared. It was found that both types of receptor are nicotinic, although they differ in their affinities for individual ligands and in the rank order of ligands. In contrast to the muscle receptor, the neuronal receptor binds the toxin in a reversible fashion (KD = 2.1 X 10(-10) M at 23 degrees C). Small ligands inhibit brain equilibrium procedures. Toxin and ligands compete for a single type of noninteracting site, and the ratio of toxin binding sites to ligand-binding sites is unity. The inhibitory potency of ligands parallels their ability, at higher concentrations, to accelerate receptor . toxin by interaction with the same site on the receptor derived from the optic lobe.

Progesterone metabolism in the pineal, brain stem, thalamus and corpus callosum of the female rat

Specific brain regions, namely, thalamus, tectum, tegmentum, cerebellum, medulla and pineal, from five proestrous rats were incubated for 30 min with [3H]progesterone. After reverse isotopic dilution analysis, the following metabolites were identified in all incubations by purification to constant specific activity, derivative formation and/or gas liquid chromatography trapping: [3H]5alpha-pregnane-3, 20-dione (10-20% of the starting substrate except pineal -- 0.7%), [3H]3alpha-hydroxy-5alpha-pregnan-20-one (1.6-3.8% except for pineal -- 0.5%) and [3H]20alpha-hydroxy-4-pregnen-3-one (0.05-0.11%). Preliminary results from the corpus collosum incubation indicated the presence of the same metabolites. Although some apparent constant specific activities were obtained for 20alpha-hydroxy-5alpha-pregnan-3-one and 5beta-pregnane-3, 20-dione, the low levels of 3H associated with these steroids did not permit a definitive identification. The results indicate the presence of at least delta1-steroid 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase and 20alpha-hydroxysteroid dehydrogenase activities with progesterone as substrate in the brain regions examined.

Putative neurotransmitters of the avian visual pathway

The ability of homogenates of the chick optic lobe to accumulate a series of possible neurotransmitters has been studied. High affinity uptake of several possible neurotransmitters was examined in optic lobes of 21-day-old embryos that had a single eye removed on the third day of incubation and in 23-day-old chicks that had an eye removed at hatch. Embryonic enucleation resulted in severe reduction of development of the ability of the contralateral optic lobe to take up tritiated GABA, dopamine, choline, serotonin and glutamate from solutions around 10(-8)M. Unilateral eye removal of new-hatched chicks caused failure of the denervated optic lobe to grow, but only the uptake capacity for glutamate was significantly recuced. This deficit was apparent as early as 4 days after enucleation. The transport of other compounds was unimpaired. The uptake of glutamate by homogenates of the optic tract was 43% of that or the optic lobe. This was a much greater fraction than the corresponding value for other postulated neurotransmitters. These data suggest that glutamate may be the primary neurotransmitter of the fibers of the optic tract originating in the retinal ganglion cells.

[Effect of chlorpromazine on the incorporation of sialic acid into gangliosides and glycoproteins of the chicken brain (author's transl)]

Three-days-old White Leghorn chickens were used to study the effect of i.p.-injected chlorpromazine (CP, 2.5 or 5 mg/animal) on the incorporation of N-(3H)-acetylmannosamine into glycoprotein- and ganglioside-bound sialic acid and 14C-histidine into the proteins of the cerebrum, the optic lobes, and the cerebellum after incorporation periods of 1-24 h. All experiments were performed under constant temperature conditions. 1. The incorporation of 14C-histidine into the proteins of the optic lobes was not influenced by CP. 2. Within 24 h in the optic lobes neither the concentration of particle-bound sialic acid (mug sialic acid/mg protein) nor the content of radioactive-labeled sialic acid precursor was affected by the drug. 3. The rate of incorporation of labeled sialic acid into glycoproteins and gangliosides, however, was up to 6 h after the injection of the precursor much lower in the CP-treated animals than in controls. This may indicate, that the turnover of sialo-compounds was diminished by CP. 4. The inhibition was the most intensive in the cerebrum (up to 80%), lower in the optic lobes (up to 70%), and only small in the cerebellum (up to 20%), but was always the same for glycoproteins and gangliosides. The different inhibition rates in the different structures may indicate a correlation between the pharmacologic, sedative effects of the drug and the diminished turnover of sialo compounds.

Regional serotonin levels in brain: a comparison of depressive suicides and alcoholic suicides with controls

The levels of 5-hydroxytryptamine have been measured in 33 areas of the human brain and these levels compared in depressed suicides, in alcoholic suicides, and in controls. The values obtained for control brains ranged from 5.3 mumole 5-HT/kg wet weight in substantia nigra to 0.4 mumole 5-HT/kg wet weight in frontal gray. No significant differences were found among diagnostic groups in any of the areas studied.

Incorporation of sialic acid into gangliosides and glycoproteins of the optic pathway following an intraocular injection of [N-3H]acetylmannosamine in the chicken

Following an intraocular (i.o.) injection of [N-3H]acetylmannosamine, low molecular soluble radioactive label is distributed rapidly along the optic pathway. At the same time glycoproteins and gangliosides were found radioactively labelled in the distal parts of the optic pathway. Negligible amounts of radioactivity were incorporated into the same structures via the blood. The present data confirm, that glycoproteins are transferred in the retinal ganglion cells by a rapid axonal transport mechanism towards the nerve endings. Unlike glycoproteins labelled gangliosides accumulated in the optic nerves up to 4 days after the precursor injection. Simultaneously radioactive material, soluble in TCA/PTA, disappeared from the optic nerves. The specific radioactivities (disint./min/mug NeuNAc) of the single ganglioside fractions of the optic lobes, which contain the nerve endings of the retinal ganglion cells, differed considerably. Especially one fraction, moving on TLC plates identically to 'GD1a', was up to 20 times higher labelled than the other gangliosides. After an intracerebral injection of the same precursor, radioactivity was incorporated into the ganglioside fractions of the optic lobes to the same extent.

Axoplasmic transport of a brain-specific soluble protein

The rate and extent of axoplasmic transport of the brain-specific soluble protein (14-3-2 protein) has been investigated in the avian visual system. 1-day-old chicks were injected monocularly with tritiated proline, Incorporation of the isotope into the 14-3-2 protein synthesized within the retina of the injected eye, as well as the appearance of the labeled protein in the optic lobes was determined at 6 h and 6 days. These time periods were chosen to distinguish between the rapid and slow phases of axophlasmic flowmfollowing preparation of high-speed supernatant fractions, dialysis, chromatography on Sephadex G-150 and immunoprecipitation with specific antiserum, identification of the labeled 14-3-2 protein was carried out by sodium dodecylsulfate-polyacrylamide gel analysis of the radioactive immunoprecipitates; 6 days after isotope administration, approxo% of the 14-3-2 protein synthesized in the chick retina had been transported to the contralateral optic lobe. By contrast, at 6 h no labeled 14-3-2 protein was detectablemthus, transport of this neuronal protein appears to be relatively slow process with little or no rapid component.

Distribution, metabolism and biological activity of deoxycorticosterone in the central nervous system

Intravenously injected [1,2-3H]deoxycorticosterone (DOC) readily enters all parts of the central nervous system. In intact and eviscerated rats the highest concentration of radioactive label was recovered from areas corresponding to the reticular formation from the brain stem. In addrenalectomized animals, in addition to high brain stem concentration, there was also a marked increase in the uptake of radioactivity in the septum, hippocampus and pituitary. Data from the eviscerated rat point to a uniform distribution of [1,2-3H]DOC in neural tissues and suggest that the higher levels of radioactivity found in the brain stem may be due to a DOC metabolite with the chromatographic characteristics of allo-tetrahydro-DOC, an anaesthetic-type steroid. A decrease in the amplitude of evoked sciatic potentials in brain stem sites but not in the thalamic relay nucleus was observed in 52% of the cases studied, following the i.v. injection of 100-150 mug DOC.