PHOSPHOCHOLINE DIGLYCERIDE TRANSFERASE ACTIVITY DURING DEVELOPMENT OF THE CHICKEN BRAIN

Abstract— The activity of chicken brain phosphocholine diglyceride transferase was followed during pre- and postnatal development. The specific activity of this enzyme increases from the 10th day of embryonic life, reaches a maximum at hatching and decreases thereafter. Total brain activity increases in parallel with the increase of brain lecithins. The apparent K _m of the enzyme for CDP choline is 1.5 × 10^-4 m before the 10th day of embryonic life, 2.5 × 10^-5 m between the 13th day of the embryo and the 10th day after hatching, and finally 1.3 × 10^-4 m after the 38th day of postnatal life. These data suggest the existence of isoenzymes, one of which appears at the beginning of myelination.     

ENZYMES OF PHOSPHOINOSITIDE METABOLISM DURING RAT BRAIN DEVELOPMENT

—The activities of four enzymes concerned with inositol lipid metabolism have been determined in homogenates of rat brains of different ages. The enzymes are CDP-diglyceride inositol phosphatidate transferase, phosphatidylinositol kinase, diphosphoinositide kinase and triphosphoinositide phosphomonoesterase. The activities of all the enzymes increased with age. Phosphatidylinositol kinase activity rose most sharply well before myelination, reaching a maximum at about 6 days of age. Diphosphoinositide kinase and triphosphoinositide phosphomonoesterase activities increased most rapidly during myelination. The increase in CDP-diglyceride inositol phosphatidate transferase showed no definite association with any period of development. It is concluded that triphosphoinositide metabolism is associated with myelin or a closely related structure.     

NUCLEAR RIBONUCLEASE ACTIVITIES OF RAT BRAIN DURING POSTNATAL DEVELOPMENT

Abstract— The activities of alkaline and acidic RNAses were determined in soluble and insoluble fractions from nuclei of brain hemispheres of rats, aged from 1 day to adult. The activities increased rapidly and reached a maximum, at 30 days, of about 10 times (alkaline RNAsel or 5 times (acidic RNAse) that seen at day 1.     

RNA POLYMERASE ACTIVITY IN VARIOUS CLASSES OF NUCLEI FROM DIFFERENT REGIONS OF RAT BRAIN DURING POSTNATAL DEVELOPMENT

—The changes in the wet weight and the numbers of cell nuclei recovered from the cerebral hemispheres, the cerebellum and the brain stem of rats from the period of 5–30 days after birth have been determined. In parallel a study has been made of the RNA polymerase activity, both in the unfractionated nuclei from these regions and in the nuclei separated by zonal centrifugation. In general there is a considerable decline in activity during this period, which occurs in all class of nuclei although not to the same extent. The most dense nuclei from the cerebellum retain relatively high activity at 20 days after birth, possibly due to the contribution of the microneuronal nuclei.     

LOCALIZATION OF THE THY-1 ANTIGEN IN THE CEREBELLAR CORTEX OF RAT BRAIN BY IMMUNOFLUORESCENCE DURING POSTNATAL DEVELOPMENT

Abstract— At birth in the rat brain the Thy-1 antigen was present at 10% of the adult level and increased rapidly to reach near adult levels after 3 weeks. Localization studies by immunofluorescence on sections of rat cerebellar cortex during this period showed that at day 5 there was weak fluorescence associated mainly with the molecular layer and some fibre-like structures in the centre of the folium; no fluorescence was found around the cells of external granular layer. From 5 to 16 days there was a rapid increase in Thy-1 immunofluorescence with noticeably higher levels associated with the white matter than the molecular layer. However, by 21 days the reverse was found' with lower levels in white matter than in the molecular layer with a similar distribution to that observed previously in adult rat cerebellum. Small rings and patches of fluorescence were observed in the molecular and granular layers. The results indicated that Thy-1 was present on axons, mature neurons and their processes. In addition, Thy-1 immunofluorescence was found in the pia-arachnoid until around day 16.     

METABOLISM OF HIGHLY BASIC PROTEINS OF RAT BRAIN DURING POSTNATAL DEVELOPMENT

Abstract— (1) The encephalitogenic basic protein obtained from adult rat brain by treatment with 0·03 N-HCl was demonstrable in the brain on the 10th day after birth. It showed a marked increase in quantity during the phase of active myelination.
(2) The proteins extracted under similar conditions from 5-day old rat brain contained several highly basic proteins other than the encephalitogenic basic protein. These basic proteins, which were electrophoretically similar to highly basic proteins extracted similarly from adult rat liver, are histones.
(3) For metabolic studies the entire group of highly basic proteins in the acid extract was obtained after one-step adsorption of other proteins on DEAE-cellulose equilibrated at pH 9·8
(4) After injection of [¹⁴C]lysine the fractions containing highly basic proteins, water soluble non-basic proteins and other tissue proteins of the brain showed higher relative specific radioactivities during the period 1–10 days after birth than during later stages of postnatal development. The fraction containing proteolipid protein, another myelin protein, showed a low relative specific radioactivity throughout the whole period of postnatal development. The relative specific radioactivity of proteolipid protein was somewhat higher in young than in adult rat brain.     

ACTIVITY OF CYCLIC AMP-DEPENDENT MICROSOMAL PROTEIN KINASE AND PHOSPHORYLATION OF RIBOSOMAL PROTEIN IN RAT BRAIN DURING POSTNATAL DEVELOPMENT

Abstract— Microsomes from rat brain exhibited protein kinase activity which was stimulated by cyclic AMP when assayed in the presence of exogenous protein substrate, such as thymus histone. In the absence of exogenous substrate some phosphorylation of microsomal protein occurred, but no stimulation by cyclic AMP could be discerned, probably because of limitations of substrate. The maximal activity of microsomal protein kinase observed in the presence of saturating concentrations of histone and the optimal concentration (5 μ m ) of cyclic AMP remained essentially unchanged from birth to early adulthood, but the magnitude of the stimulation by cyclic AMP was significantly higher at birth than at 30 days of age. Brain ribosomal proteins could be phosphorylated by the cyclic AMP-dependent brain protein kinase. Their total capacity for acceptance of phosphate by means of this phosphorylation reaction remained unchanged throughout the postnatal development of the brain. Our results are consistent with the possibility that phosphorylation of ribosomal protein mediated by cyclic AMP-dependent protein kinase may play a a role in the postnatal regulation of cerebral protein synthesis, as a result of the changes in the levels of cyclic AMP known to occur in brain during postnatal maturation.     

REGIONAL CHANGES IN RAT BRAIN CHOLINE ACETYLTRANSFERASE AND ACETYLCHOLINESTERASE ACTIVITY RESULTING FROM UNDERNUTRITION IMPOSED DURING DIFFERENT PERIODS OF DEVELOPMENT1

Abstract— The severity of mental changes in malnourished children is related to both the period of development when the malnutrition occurs and the amount of environmental stimulation. In the present study the effect of imposing protein undernutrition during the period of gestation or postweaning period, and protein-energy undernutrition during the suckling period on cholinergic enzyme activity was investigated in the rat. Six different dietary treatments were given and the activity of ChAc, ChE, and AChE determined in the forebrain, brainstem, and cerebellum of male rats on day 49. Undernutrition imposed during gestation, suckling or postweaning all resulted in changes in cholinergic enzyme activity. The direction and degree of change of enzyme activity depended on the period when undernutrition was imposed as well as the brain region. In the forebrain ChE and AChE activities were altered, in the brainstem, ChAc, ChE and AChE activities were altered, and in the cerebellum ChAc activity was altered. The effect on the activity of the individual cholinergic enzymes was complex and was not the same in the different regions of the brain or even for the same brain region exposed to undernutrition during different periods of development. These results along with earlier work indicate that cholinergic enzyme activity in brain of undernourished rats can be altered by both the period of development when undernutrition is imposed and the amount of environmental stimulation.     

MANIFESTATION OF METABOLIC COMPARTMENTATION DURING THE MATURATION OF THE RAT BRAIN

—(1) The fate of [U-¹⁴C]leucine was studied in rat brain in vivo from birth to five weeks of age. The major route of leucine metabolism at all ages was conversion into protein. The rate of protein synthesis was low in the newborn; it reached a peak at about 15 days and slowed down moderately later. Incorporation into brain lipids was relatively low under the experimental conditions (less than 2 per cent of the total tissue ¹⁴C). (2) The conversion of leucine-carbon into amino acids associated with the tricarboxylic acid cycle was low in the first 9 days after birth (less than 4 per cent of the acid-soluble ¹⁴C at 10 min after injection) and increased rapidly until 15 days when the level characteristic of the adult was approached (about 20 per cent of the acid-soluble ¹⁴C). The results indicated that the oxidation of acetyl-CoA derived from leucine reached the adult level at an earlier age than that derived from glucose. (3) The glutamine/glutamate specific radioactivity ratio was 0·3 in the brain of newborn animals and increased progressively; it was 1·3 and 2·4 at 15 and 35 days of age respectively. The specific radioactivity of aspartate and of GABA relative to that of glutamate was less than 1 throughout the experimental period. (4) The factors involved in the development of metabolic compartmentation in brain were analysed. It is proposed that although the experimental results show that a 'small’compartment becomes functionally manifested with maturation the primary cause is the development of the‘large’metabolic compartment. (5) Morphological correlates of the metabolic compartments in brain tissue are suggested and it is concluded that the manifestation of metabolic compartmentation is related to maturational changes in glia-neuronal relations rather than to developmental processes affecting the individual components only.     

MEMBRANE PROTEINS OF RAT BRAIN: COMPOSITIONAL CHANGES DURING POSTNATAL DEVELOPMENT

Abstract— Membrane fractions from forebrain of rat were isolated at ages ranging from 5 to 93 days. Among these fractions were total membranes, three fractions isolated by density gradient centrifugation, and three subfractions which consisted of purified myelin and of two supernatant fractions. All membrane fractions showed an increase in protein content during the first postnatal month; however, only the myelin fraction and one of its supernatant fractions showed a prolonged accumulation. Myelin protein increased continually from 0.17 mg/g brain at 15 days to 8.3 mg/g brain at 93 days.
All fractions were analysed for protein composition by sodium dodecyl sulphate polyacrylamide gel electrophoresis. Characteristic changes in protein composition were noted during postnatal development, most of which were pronounced up to the age of 20 days. Among others was a decrease in histones as compared to other proteins, with a concomitant shift in preponderance from the slow- to the fast-migrating histone band. In parallel, other proteins of high molecular weight became more prominent. No myelin could be isolated at 5 and 10 days. The deposition of myelin proteins was parallelled by the appearance of the Wolfgram protein which points to a close correlation of the Wolfgram protein to the process of myelination.     

ACETYL-COENZYME A: 1,4-DIAMINOBUTANE N-ACETYLTRANSFERASE: ACTIVITY IN RAT BRAIN DURING DEVELOPMENT, IN EXPERIMENTAL BRAIN TUMOURS AND IN BRAINS OF FISH OF DIFFERENT METABOLIC ACTIVITY

—Acetyl-CoA: 1,4-diaminobutane N-acetyltransferase catalyses the first step of putrescine catabolism in mammalian brain. It may be important in putrescine degradation of other tissues as well. Its specific activity is higher in homogenates of immature than of mature rat brains. A steady decline of putrescine acetylase activity is observed from birth until approx adult levels are reached at day 30. Microsomes and purified nuclei from brains of 2-day-old rats show considerably higher putrescine acetylase activities than the corresponding subcellular organelles from adult brains. Increased putrescine acetylase activities were found in nitroso-ethylurea-induced gliomas, together with a dramatic increase of putrescine concentration. High tissue concentrations of putrescine are, however, not necessarily correlated with enhanced putrescine acetylase activities. In trout brains a linear increase of acetyl-CoA: 1,4-diaminobutane N-acetyltransferase activity was observed together with a decrease of putrescine concentration after adaptation of the animals to increased water temperature.     

GLYCOPROTEIN CHANGES DURING THE DEVELOPMENT OF HUMAN BRAIN

Brain glycoprotein sugars were studied during human brain development. Marked changes were found in the sugar content of glycopeptides derived from soluble and insoluble glycoproteins, showing a general decrease in the soluble and an increase in the insoluble fraction. The data indicate that changes in glycan moiety and/or in glycoprotein population occur during development. The existence of a‘critical period’in glycoprotein development which coincides with the formation of axonal and synaptic membranes sprouting has been established (Dobbing , 1971).     

THE POSTNATAL DEVELOPMENT OF CATECHOL-O-METHYL TRANSFERASE IN THE RAT BRAIN

Abstract— The postnatal development of three enzymes in the rat forebrain was studied. When expressed per tissue weight the catechol- O -methyl transferase (COMT) increased 2-fold from birth to adult age, the lactate dehydrogenase (LDH) 4-fold and the monoamine oxidase (MAO) 12-fold. Expressed per mg protein the increase in the enzyme activities in the subcellular fractions which contained the main part of the different enzymes was still 2–4-fold for COMT and LDH while for MAO it was 4-fold.
There was a relative increase in the COMT activity in the P₂ fraction (synaptosomes and mitochondria). This increase was identical with a corresponding increase in LDH activity and protein and was probably due to growth of nerve terminals. The COMT in the cytoplasm of the synaptosomes showed the same increase relative to the proteins as did the 'free' cytoplasmic enzyme.
The conclusion is drawn that the enzymes in the rat brain show a certain degree of development during brain growth. An additional increase of some enzymes is due to the development of specialized structures such as mitochondria and nerve terminals with synapses. COMT is not related to any such specialized structure.     

CHOLINE ACETYLTRANSFERASE ACTIVITY OF HUMAN BRAIN TISSUE DURING DEVELOPMENT AND AT MATURITY

Abstract— (1) On analysis of human brain tissue to determine its choline acetyltransferase (ChAc) content the recovery of enzyme from many regions is very poor when the tissue is acetone-dried and then extracted in the standard manner; for this reason the method is unsuitable when quantitative recoveries are required; it is preferable to prepare sucrose homogenates and activate these with ether before incubation.
(2) From measurements made on homogenates of one adult brain the highest concentration of ChAc was found in the putamen and the lowest in the corpus callosum. The caudate nucleus also had a high activity. As in other mammals, the concentration of enzyme in the cerebellum was found to be low. Analogous results were obtained on a nine-year-old brain but the level of ChAc activity was generally higher than in the older brain.
(3) During foetal development up to thirty-two weeks, ChAc is higher in the cerebellum than in the caudate, the thalamus, corpora quadrigemina, medulla and spinal cord. In all regions the concentration and total amount of enzyme rise fairly steadily up to this time; between 24 and 32 weeks, however, its concentration in the cerebellum and corpora quadrigemina falls slightly although the total increases considerably.
(4) Comparison of the results with the data of other authors indicates general agreement between the distribution of the enzyme in the human brain and its distribution in other mammals, especially the rhesus monkey. The corpus callosum may be an exception since in man it contains little ChAc while in lower mammals it seems to have relatively high concentrations of both ACh and ChAc.
(5) In comparing the values for ChAc reported here with the values for AChE reported by others, three tissues, the globus pallidus, substantia nigra and cerebellum are found to be exceptional in that relative to their concentration in the caudate the activity of ChAc is only about one-tenth that of AChE.     

SYNTHESIS OF GANGLIOSIDES DURING DEVELOPMENT AND ITS RELATION TO THE QUANTITATIVE CHANGES OF SUBCELLULAR PARTICLES OF RAT BRAIN

Abstract— Different subcellular fractions prepared from developing rat cerebrum were quantified by determinations of dried weights and protein contents. It was found that there is an increase of 2–2·5 times in the weights of synaptosomes and mitochondria/g of tissue during the first 20 days of extrauterine life.
A period of fast synthesis of gangliosides, with a similar pattern of increase for the different subcellular particles, was found during the first 15 days of life by study of the incorporation of injected d -[1-¹⁴C]glucosamine in rats at different stages of development. Attempts to find out if gangliosides from a certain fraction are precursors of those of other fractions indicated that in all fractions the gangliosides increase independently of the other fractions. It is concluded that the enzymic systems of synthesis of these glycolipids are present in vivo in all the fractions considered.     

大鼠发育过程中肝、肺r-GT酶活性和定位

用生物化学和组织化学方法研究正常发育中大鼠肝、肺r-GT活性和定位。结果表明:肝r-GT活性自胚龄17天开始升高,21天达高峰,出生第一天明显降低,第六天降至接近成年低水平。在胚胎期肝r-GT主要位于肝细胞内,出生后则主要位于胆小管。该结果提示胚胎期肝r-GT主要参与肝细胞膜上氨基酸的转运。出生后可能主要参与解毒功能,大鼠肺r-GT活性随发育逐步升高,主要分布于肺支气管上皮细胞。提示肺r-GT可能参与解毒功能。