摘要:

AbstractFree amino acids have been studied in the brains offastedmice (18 h) injected intraperitoneally with a 3 mmol/kg dose of imidazole‐4‐acetic acid (IMA). Groups of mice were killed by cervical dislocation and their brains were removed before injection or at 5, 15, 30, 60, 90 and 120 min after injection and treated immediately with perchloric acid. Amino acid analyses were performed on the perchlorate extracts. Of the 16 amino acids evaluated quantitatively, only glutamic acid and glutamine showed progressive changes during the period of observation, the glutamic acid falling and glutamine levels rising. Serine and threonine levels were increased significantly above the control values from 30 min after the injection to the end of the experiment. Rectal temperatures (measured with a thermistor probe) after injection of IMA showed a progressive reduction from the control levels throughout the period of observation. An essentially linear correlation was noted between the decreases in body temperature and the differences between the glutamic acid and glutamine values for the first 90 min post‐injection. Our data suggest that IMA affects mechanisms of temperature regulation, possibly in the hypothalamus, and that, among other processes, the activities of glutaminase and of serine and threonine dehydratases in brain might be reduced when brain temperatures

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05111.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractSmall amounts of nerve growth factor (NGF) were present in the superior cervical ganglion and the iris of the rat. The observations that NGF content in each of the tissues was depleted during organ culture and that more NGF appeared in the media than was originally present in the tissues indicated that synthesis or activation of NGF had occurred in organ culture. Antibody to NGF or the depletion of endogenous NGF retarded growth of new sympathetic axons into irides in organ culture. Exogenously added NGF appeared to enhance the initiation of axonal sprouting and the rate of the ramification of nerve fibres.

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05112.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe composition and metabolism of the proteins of the cerebral pallium of the rabbit during the final one‐third of the gestational period were measured. During this period, the brain increased in size almost 10‐fold and the migration of neuroblasts to form the cerebral cortex became complete. Concurrent with the marked structural changes, the solubility characteristics and electrophoretic distribution of various brain proteins showed little change. However, at the time of birth and in the adult, significant differences in gel electrophoresis patterns were apparent. The rate of synthesis of protein in brain slices from the fetus of 20 days gestation was 3‐fold higher per mg of tissue than in the neonate and about 30‐fold higher than in the adult. Activities of acidic and neutral proteases per unit weight were virtually the same and nearly constant throughout the late fetal period. However, during this stage, while rapid growth persists, the total protein synthetic activity of the pallium predominated over the total proteolytic activity, whereas sometime after birth the ratios of these activities reversed consequent to a shutdown of the synthetic

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05113.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe chronological order of changes in rat peripheral nerve proteins during Wallerian degeneration has been investigated by microdensitometric and electrophoretic techniques. Both methods revealed an early loss of myelin proteins. The histochemical microdensitometric study showed a very substantial early loss of stainable protein basic groups and a somewhat slower progressive loss of the major protein component of peripheral nerve myelin (the J band). The electrophoretic study showed an early loss of both the J band protein and the slower‐moving basic protein band. The histochemical study also suggested that some cerebroside may be lost in the early stage of Wallerian degeneration. It is concluded that degradation of myelin proteins is an initial event in the process of myelin breakdow

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05114.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractCatechol‐O‐methyl transferase (COMT) activities determined in different regions of rat brain showed small variations. Highest activities were found in the hypothalamus and corpora quadrigemina, and lowest activities in the hippocampus and corpus striatum. The regional distribution of COMT was thus at variance with the distribution of DOPA decar‐ boxylase in this study and with the distribution of catecholamines and tyrosine hydroxylase reported in the literature. Determinations of the subcellular distribution of COMT in rat forebrain showed that 50 per cent of the activity was recovered in the high speed supernatant fluid and about 33 per cent in the crude mitochondrial fraction. Further separation of the latter by discontinuous sucrose gradients showed that the particulate COMT was found in the synaptosomal fraction in an occluded form. Full enzyme activity was only obtained after treatment with a detergent or after resuspension in water. After hypo‐osmotic rupture of the crude mitochondrial fraction, COMT was recovered in the cytoplasmic fraction. The subcellular distribution of COMT was very similar to the ones of lactate dehydrogenase and DOPA decarboxylase.The proportions of soluble COMT obtained from homogenates of various regions of the brain differed from that of choline acetyl transferase and DOPA decarboxylase but were similar to that of lactate dehydrogenase. In conclusion, COMT is a cytoplasmic enzyme almost evenly distributed in the CNS. Its distribution does not resemble the distributions of the catecholamines or of the enzymes participating in the synthesis of catecho

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05115.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe kinetics of the incorporation into protein of [3H]phenylalanine, [3H]tyrosine and [3H]tryptophan were studied with homogenates prepared from whole brain of 1‐, 7‐, 21‐ and 60‐day‐old rats. The maximal velocities (Vmax)of incorporation of phenylalanine and tyrosine decreased and the apparent Michaelis‐constants (Km) for all three amino acids increased with increasing age of the rats. Tyrosine had the smallest and tryptophan the largestKmvalues in all age groups. Phenylalanine competitively inhibited the incorporation of tyrosine, but tyrosine inhibited non‐competitively the incorporation of phenylalanine. Tryptophan inhibited competitively the incorporation of phenylalanine, but at least partially non‐competitively the incorporation of tyrosine. Phenylalanine and tyrosine did not significantly affect the incorporation of tryptophan in homogenates from 60‐day‐old rats. In 1‐day‐old rats only a very large excess of phenylalanine or tyrosine inhibited detectably. TheKifor phenylalanine in the incorporation of tyrosine was significantly smaller in 1‐ than in 60‐day‐old rats. In every case the inhibition presumably occurred at a single rate‐limiting step in the complicated process of incorporat

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05116.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe pattern of the methylation of RNA was investigated in organ cultures of the sciatic nerve of the chicken. Nerve tissue from 14‐day embryos, 17‐day embryos and 3‐day‐ old chicks was incubated with [methyl‐3H]methionine or with [2‐14C]uridine and [methyl‐3H]methionine simultaneously for various periods of time. Subsequently, RNA was extracted from the tissues and the purified preparations were fractionated by polyacrylamide gel electrophoresis. The electrophoretic patterns of the rapidly labelled RNA changed during the three developmental stages. The incorporation of both uridine and the methyl groups from methionine was highest in the‘heavy’RNA species of the 14‐day embryonic nerve during the 0.5 and 1.0 h incubation periods. In contrast, in the nerves of 3‐day‐old chicks during a 0.5 h pulse with both precursors, methylation was almost entirely limited to the transfer RNA species. Furthermore, the incorporation of uridine in the nerves from 3‐day‐old animals revealed the presence of a heterogeneous population of rapidlylabelled, unmethylated species of RNA, most of which migrated between the smaller ribosomal RNA and transfer RNA components of the bulk RNA. The pattern of uridine incorporation and the methylation of the rapidly‐labelled RNA of the 17‐day embryonic nerve represented a transitional state between that of the 14‐day embryos and that of the 3‐day‐old chicks. The 17‐day embryonic stage of development corresponded to the phase of the onset of rapid deposition of myelin lipids in the sciatic nerve. Pulse‐chase experiments on the embryonic nerves indicated that a number of methylated precursors of ribosomal RNA and labile, heterogeneou

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05117.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA new protein component has been demonstrated in myelin isolated from rat whole brain and from white matter dissected from bovine, dog and rabbit brain. It is also present in rabbit optic nerve. It does not appear to be present in other subcellular fractions of rat brain. It has a molecular weight of 20,540 ± 490(S.D.), as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. A rapid procedure for the isolation of myelin is also described

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05118.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractThe metabolism ofN‐acetyl‐l‐aspartic acid (NAA) was studied in rat brain. [Aspartyl‐U‐14C]NAA was metabolized predominantly by deacylation. Studies of NAA biosynthesis froml‐[U‐14C]aspartic acid have confirmed previous reports that NAA turns over slowly in rat brain. However, intracerebrally‐injectedN‐acetyl‐l‐[U‐14C]asparticacid was rapidly metabolized. Exogenous NAA appears to be taken up rapidly into a small, metabolically‐active pool. This pool serves as substrate for a tricarboxylic acid cycle associated with the production of glutamate for the biosynthesis of glutamine. The bulk of the NAA content in brain appears to be relative

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05119.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY

摘要:

AbstractA subconvulsant dose of sodium fluoroacetate inhibited the metabolic utilization of intracerebrally‐administeredN‐acetyl‐l‐[U‐14C]asparticacid and the labelling of glutamine from this precursor in mouse brain, but not the labelling of glutamate or aspartate. A convulsant dose also inhibited the utilization ofl‐[U‐14C]aspartic acid. When intraperitoneal injection of a convulsant dose of sodium fluoroacetate was followed by intracerebral injection ofN‐acetyl‐l‐[U‐14C]asparticacid, the levels ofN‐acetylaspartate, aspartate and glutamate in brain were lowered, while the glutamine content was increased. The specific radioactivity of glutamine relative to that of glutamate was much lower when these compounds were labelled froml‐[U‐14C]aspartic acid than whenN‐acetyl‐l‐[U‐14C]aspartic acid was used as the precursor. Intracerebral injection of tracer amounts ofl‐[U‐14C]aspartic acid reduced the content ofN‐acetylaspartate in brain and raised the glutamine content. Sodium fluoroacetate had no additional effect on the relative specific radioactivity of glutamine or the content ofN‐acetylaspartate, aspartate, glutamate or glutamine whenl‐[U‐14C]aspartic acid was the precursor. We consider the results to be consistent with a selective inhibition both by sodium fluoroacetate and by exogenous aspartic acid of the tricarboxylic acid cycle in brain associated with the biosynthesis of glutamine. We suggest that the activity of this pathway may regulate t

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1972.tb05120.x

出版商:Blackwell Publishing Ltd    

年代:1972

数据来源: WILEY