ACTIVATION OF HEXOSE MONOPHOSPHATE PATHWAY IN BRAIN BY ELECTRICAL STIMULATION IN VITRO

Abstract— The incubation of cerebral cortical slices for 15 min in Krebs-Ringer-tris (pH 7.6) solution at 37°C with [1-¹⁴C]glucose or [6-¹⁴C]glucose as substrates yielded a C-1:C-6 ¹⁴CO₂ ratio of 1.21, whereas this ratio increased to 3.01 after the application of electrical stimulation (ES). Tissue levels of 6-phosphoglu-conate (6PG) and glucose 6-phosphate (G6P), intermediary metabolites of hexose monophosphate (HMP) pathway, were 7 and 180 nmol/g tissue following 15 min incubation, and increased by 33 and 45 per cent respectively following the application of ES. Activities of 6-phosphogluconate dehydrogenase (6PGDH, 6-phospho- d -gluconate: NADP⁺ 2-oxidoreductase, EC 1.1.1.44) and glucose-6-phosphate dehydrogenase (G6PDH, d -glucose-6-phosphate: NADP⁺ 1-oxidoreductase, EC 1.1.1.49), important enzymes in regulating the activity of HMP pathway, in cerebral cortical slices were 689 and 907 pmol/mg protein/min and were increased by 66 and 25 per cent respectively by the application of ES. Synaptosomal G6PDH and 6PGDH activities were maximally activated by the addition of 40 m m -Na⁺ to the reaction mixture, whereas no activation by Na⁺ was observed in microsomal G6PDH and 6PGDH. Amobarbital inhibited more strongly the Embden–Meyerhof (EM) pathway than the HMP pathway, while imipramine had a stronger inhibitory effect on HMP pathway than on EM pathway in the electrically stimulated cerebral tissues.
The present results indicate that the HMP shunt pathway in the cerebral cortex is activated by the application of ES in vitro , possibly at synaptic regions and may play an important metabolic and functional role in the brain.     

MALFORMATIONS OF THE CENTRAL NERVOUS SYSTEM INDUCED BY NEUROTROPIC DRUGS IN MOUSE EMBRYOS

Out of a sample of fifteen neurotropic drugs consisting of seven antidepressants and anti-psychotics, two antianxiety drugs, one anticonvulsant, three opiates and two synthetic analgesics, twelve were found to be teratogenic for mouse embryos, causing malformations of the central nervous system. After single injections of the teratogenic dose administered at the very beginning of the ninth day of gestation, four days later, i.e. in 13-day-old embryos, the induced defects appeared to make up a recurring syndrome of malformations which consists of several abnormalities present in various frequencies either individually or in combination in the same embryos. These malformations are: exencephaly, craniorachischisis, cervical and thoraco-lumbar myeloschisis, hydrocephalic dilatation of the fourth brain ventricle, Z-shaped kinking of the spinal cord and lumbar hydromyelia. In addition, after administration of some of the drugs, branchyury or anury with or without lumbar myeloaplasia were recorded.
In general the results reported here seem to suggest that because of their possible affinity neurotropic drugs are potentially teratogenic for the embryonic central nervous system if applied at the time of the neural tube closure although it is known that there are drugs in this group which do not cause any malformations of the central nervous system and that many non-neurotropic agents do cause such malformations. Secondly, the results seem to suggest also that the position of the malformations along the cerebro-spinal axis may be depending to some extent on the pharmacological properties of the drugs tested. These conjectures are treated here as entirely provisional pending further investigations.     

MYELIN IN THE CENTRAL NERVOUS SYSTEM AS OBSERVED IN EXPERIMENTALLY INDUCED EDEMA IN THE RAT

The compact arrangement of cells in the normal white matter of the brain makes an analysis of cellular architecture difficult. To overcome this difficulty, cerebral edema was induced in rats by means of the unilateral intracerebral implantation of silver nitrate. Within 48 hr, the brains were fixed by perfusion with glutaraldehyde followed by immersion in Dalton's chrome-osmium. Sections of the callosal radiations were studied in the electron microscope. The untreated hemisphere appeared entirely unaltered, whereas in the edematous hemisphere the edema fluid separated individual cell processes and small groups of them. The myelin sheaths and their relationships to the axons appeared essentially unaltered. In this material, analysis of cellular architecture was relatively easy, and the widely held theory of spiral wrapping could be confirmed. In addition, several other aspects of the myelin and myelin-forming cell relationships became apparent in the edematous tissue. Most of these were later confirmed by extensive and careful study of the nonedematous tissue. These included the presence of occasional isolated cytoplasmic areas in myelin and the presence of two complete sheaths around a single axon. Other observations, such as the appearance of mitochondria and dense bodies within the outer loop and the separation of myelin lamellae, are apparently limited to the edematous tissue.     

PHOSPHOLIPIDS IN THE NERVOUS SYSTEM OF MOLLUSCS

Abstract The phospholipid composition of nervous ganglia of the bivalve Unio crassa , the gastropod Helix pomatia and the cephalopods Octopus sp. and Ommastrephes sloanei pacificus have been investigated.
The ganglia of cephalopods contain considerably more phospholipids than do gastropod and bivalve ganglia. Especially rich in phospholipids are the optic ganglion of the squid Ommastrephes and the cerebral ganglion of Octopus , where their content is of the same order as in the brain of teleosts and amphibia.
In the ganglia of the lower molluscs, the bivalve and the gastropod, no sphingomyelin nor X-phospholipid could be detected.
No sphingomyelin nor X-phospholipid were found in the optic ganglion of Octopus , whereas in its cerebral ganglion sphingomyelin but no X-phospholipid was present.
In both the optic and the cerebral ganglia of the squid Ommastrephes both sphingomyelin and X-phospholipid were found.     

华支睾吸虫神经系统的乙酰胆碱酯酶定位

应用乙酰胆碱酯酶显示的华支睾吸虫神经构造十分清晰,呈左右对称排列。它由中枢神经节、神经连合、纵行神经干、神经联系以及双极和多极神经细胞所组成。中枢神经节位于咽下方的两侧,由粗大的神经连合相连。从中枢神经节向前伸出咽、前背、前腹、前侧4对神经干;向后伸出后背、后腹、后侧3对神经干。以后腹神经干为最粗大,并从其伸出分支分布于腹吸盘、消化道、卵黄腺和生殖器官。后3对纵行神经干又由许多横向神经联系将其互相连接构成神经网。体内广泛分布双极和多极神经细胞,前者较小,数目众多,而后者略大,数目较少。     

SYNAPSES IN THE CENTRAL NERVOUS SYSTEM

A number of different synapses have been described in the medulla, cerebellar cortex, and cerebral cortex of the rat. All of these possess the same fundamental fine structure as follows: 1. Close apposition of the limiting membranes of presynaptic and postsynaptic cells without any protoplasmic continuity across the synapse. The two apposed membranes are separated by a cleft about 200 A wide, and display localized regions of thickening and increased density. 2. The presynaptic expansion of the axon, the end-foot or bouton terminal, contains a collection of mitochondria and clusters of small vesicles about 200 to 650 A in diameter. Although the significance of these structures in the physiology of the synapse is still unknown, two suggestions are made: that the mitochondria, by means of the relation between their enzymatic activity and ion transport, participate in the electrical phenomena about the synapse; and that the small synaptic vesicles provide the morphological representation of the prejunctional, subcellular units of neurohumoral discharge at the synapse demanded by physiological evidence.     

ERGOTHIONEINE IN THE CENTRAL NERVOUS SYSTEM

Abstract— Further investigations have been made into ergothioneine in the brains of several mammalian species, and the distribution of ergothioneine in the brain of the ox is described. It has not been possible to confirm many of the findings of earlier workers and the results do not appear to support their conclusion that ergothioneine is identical with the cerebellar factor.     

SOME ASPECTS OF THE STRUCTURE OF THE NERVOUS SYSTEM IN THE ANEMONE CALLIACTIS

In the light of existing work on tbe behavioral physiology ofthis anemone, the structure of parts of the neuroimiscular systemhas been examined in detail. In the sphincter region, the morphologicalbasis for rapid through-conduction and motor innervation isa network of bipolar nerve cells, which is connected to thesimilar retractor nerve-nets of mesenteries. Sphincter musclefibers are arranged at the periphery of tubes, which form ameshwork within the mesogloea. Bipolar nerve cells appear torun in these tubes. Neurites also reach the sphincter from theendodermal nerve-net by penetrating the mesogloea directly.The nerve-net over the circular muscle is richer than in otherparts of the column, but shows similar features. It includessmall multipolar cells of unknown function. Coordination between different parts of the anemone is discussedin terms of possible pathways for the transmission of excitation.For example, bundles of retractor and parietobasilar musclefibers continue from both surfaces of mesenteries into the mesogloeaof the pedal disk, suggesting a possible route for neuritespassing to or from the ectoderm. If confirmed, the existenceof this route could throw light on a number of sequences ofbehavior.     

THE DISTRIBUTION OF MUSCARINIC RECEPTOR SITES IN THE NERVOUS SYSTEM OF THE DOG

Abstract— The concentration of muscarinic receptors has been measured in 22 areas of the dog nervous system by measuring the atropine-sensitive uptake of tritium-labelled propylbenzilylcholine mustard. The highest concentration of receptor was found in the caudate nucleus, intermediate concentrations were found in five areas of cerebral cortex, the other basal ganglia and the superior colliculus. Significant concentrations were found in the corpus callosum and subcortical white matter, and are believed to be on axons derived from cholinoceptive neurons. The results are discussed in relation to other evidence concerning cholinergic transmission in the nervous system.     

THE VALUE OF THE PULMONATE CENTRAL NERVOUS SYSTEM IN PHYLOGENETIC HYPOTHESIS

Study of the pattern of fusion of the ganglia of the visceralchain of pulmonates provides invaluable information for determiningthe direction of evolution at a local level in particular lineages.Information derived from the study of the procerebrum aloneis unlikely to be adequate to construct a phylogeny of the Pulmonata. (Received 25 May 1977;