摘要:

Abstract—In growing rat brain, the specific activity of DNA at 12 h after the subcutaneous injection of [3H]thymidine underwent a sharp rise during the first 6 days of life, dropping just as precipitously by 15 days, thereafter continuing to decrease with increasing age.When [3H]thymidine was given to 6‐day‐old rats, a considerable amount was taken up immediately into the brain. Thymidine taken up into the acid‐soluble fraction was readily phosphorylated to its nucleotides, thymidine mono‐, di‐, and triphosphate (TMP, TDP and TTP) within only 30 min following injection. The highest specific activity was found in TTP. The incorporation of of [3H]thymidine into DNA took place over a longer period of time afte

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02237.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Nuclear RNA from neurones, astrocytes and other glial cells was pulse‐labelledin vivowith [3H]uridine and analysed by sucrose density‐gradient centrifugation after various periods of incorporation. Thirty min after the injection of the isotope, rapidly‐labelled RNA appeared in all three cell types, a heterogeneous fraction sedimenting above 30S, the others at 25 and 12S. The transformation rate of the two latter components was equally rapid in all three types of nuclei studied. These components are assumed to be of messenger nature. The heavy fractions underwent transformations which in other cells have been described to lead to rRNA formation. The temporal pattern as well as the sequence of changes were similar in nuclei from neurones and astrocytes, the only difference being that a 35S intermediate was found in the former and a 32S in the latter. In non‐astrocytic glial nuclei, synthesis and transformation of the 45S component were delayed as compared to the other cell types and the processing of this component may involve both a 32S and a 35S intermediate. Moreover, the radioactivity incorporated in all the nuclear RNA species was always lower in th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02238.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Tritium‐labelled RNA precursors were injected at 30 min intervals into the fourth ventricle of rats or rabbits. After 4 h the nuclei from neurones, astrocytes, and other glial cells were isolated and RNA extracted. Investigations were performed in order to establish optimum conditions for RNA extraction from this particular material.The sedimentation patterns obtained in sucrose gradients were similar to those of nuclear RNA from other mammalian tissues and showed the presence of RNA species with high specific activities in the region of the gradient between 10S and 16S and above 28S. All three types of nuclei contained a 45S and a 38S RNA. Moreover, a 32S component could be identified in astrocytic nuclei, a 35S fraction in neuronal nuclei, and both a 32S and 35S RNA in nuclei from glial cells. The nuclei from the various cell types also differ with respect to the rate of incorporation of the label into the nuclear RNA, being four times higher in astrocytic and neuronal nuclei than in those derived from the other glial ce

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02239.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—The properties and subcellular localization of type I (nitrophenyl) and type II (nitrocatechol) arylsulphatases were investigated in brain tissue of the rat, and optimal assay conditions were established. Sulphate, phosphate and sulphite ions inhibited the nitrocatechol sulphatases; nitrophenyl sulphatase was inhibited only by sulphite. The presence of latent enzyme activity was demonstrated for the nitrocatechol sulphatases, beta‐glucuronidase, and beta‐glycerophosphatase in rat and mouse brain homogenates. These hydrolases were highly sensitive to mechanical and osmotic damage; and Triton X‐100 was very effective in releasing their latent (bound) activities, a finding suggestive of a lysosomal localization. Activity of nitrophenyl sulphatase was unaffected by osmotic changes or Triton X‐100, characteristics suggesting a membranous association for this enzyme. Total activity of nitrophenyl sulphatase was approximately twice as great in canine gray matter as in canine white matter; the converse obtained for beta‐glucuronidase activity. Values for total enzymic activity of the nitrocatechol sulphatases in canine white and gray matter were similar.Fractionation of homogenates from rat brain by differential centrifugations and separation of crude mitochondrial fractions by sucrose density gradient centrifugations revealed the following: (1) most of the nitrocatechol sulphatase activity (93 per cent) and all of the nitrophenyl sulphatase activity were sedimentable; (2) crude mitochondrial fractions exhibited the highest relative specific activity (RSA = 1·38) for the nitrocatechol sulphatases, whereas microsomal fractions displayed the highest RSA for nitrophenyl sulphatase (1·89); (3) the lightest fraction (A + B) and the densest fraction (E) from the sucrose density gradient contained most of the activity for both the type I and type II arylsulphatases, whereas the RSA of cytochrome oxidase was greatest in the intermediate density regions (fractions C and D); (4) the highest RSA for beta‐glucuronidase and beta‐glycerophosphatase occurred in gradient fraction C; (5) appreciable activity of beta‐glycerophosphatase was found in a nerve ending fraction (M3).It is suggested that the hydrolases in heterogeneous tissue like brain might be associated with lysosomal particles of differing enzyme compositions and varying populations, and that the data on distribution lend credence to the concept of bimodal and possible trimodal particle affinity for the hydrolas

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02240.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Levorphanol (10‐3M) reversibly blocked conduction in the giant axon of the squid and axons from the walking legs of spider crab and lobster. Similar concentrations of levallorphan and dextrorphan blocked conduction in the squid giant axon. Under the same experimental condition morphine caused an approximately 40 per cent decrease in spike height. Levorphanol did not affect the resting potential or resistance of the squid axon. Spermidine, spermine and dinitrophenol had little or no direct effect on the action potential nor did they alter the potency of levorphanol. Concentrations of levorphanol as low as 5 × 10‐5M blocked repetitive or spontaneous activity in the squid axon induced by decreasing the divalent cations in the medium. After exposure to tritiated levorphanol, the axoplasm and envelope of the squid axon accumulated up to 500 per cent of the concentration of tritium found in the external medium, dependent on time of exposure, and other variables. At pH 6 the levels of penetration were 33‐50% of those found at pH 8, which correlates with our observation that levorphanol is about 33 % as potent in blocking the action potential at pH 6. The penetrability of levorphanol was not affected by spermidine, dinitrophenol or cottonmouth moccasin venom. Levorphanol did not alter the penetration of [C14]acetylcholine nor did it render the squid axon sensitive to it. The block of axonal conduction by compounds of the morphine series is discussed both as to possible mechanisms and sign

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02241.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Cell nuclei were isolated from four regions of the brains of ovariectomized female rats 2 hr after the injection of [3H]oestradiol. By light microscopy, the nuclear pellets contained highly purified nuclei of neuronal and glial cells with little cytoplasmic contamination. Tritium was concentrated in cell nuclei from the preoptic‐hypothalamic area, to a lesser extent in nuclei from the amygdaloid region and hippocampus, and least of all in cerebral cortical nuclei. In comparison with whole homogenates (= 1‐0), the nuclear concentrations of radioactivity were 12·9, 4·7, 1·9 and 0·8, respectively. Approximately 40 per cent of the radioactivity in homogenates of the preoptic‐hypothalamic area was present in cell nuclei, and upon TLC more than 85 per cent of the radioactive material in the nuclei exhibited theRFof oestradiol‐17β.Pretreatment of ovariectomized females with 1 mg of unlabelled oestradiol 30 min before the injection of labelled hormone abolished the nuclear uptake of [3H]oestradiol in all four regions of the brain. A concurrent injection of 10 μg of unlabelled oestradiol‐17β significantly reduced nuclear uptake, while a similar injection of testosterone or oestradiol‐17α had no significant effect. One mg of oestradiol‐17α, but not testosterone, did reduce nuclear uptake.The retention of [3H]oestradiol by the preoptic‐hypothalamic area decreased exponentially in the tissue from 30 min to 4 h after an intraperitoneal injection; however, nuclear binding reached a peak at 1‐2 h and still showed high retention at 4 h. These results, together with observations in other laboratories of morphological changes induced by oestrogens, establish that certain regions of the brain arebona fidetargets

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02242.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—The proteolytic activity of brain homogenates obtained from 1‐, 5‐, 14‐, 60‐, 150‐, and 300‐day‐old rats was assayed with urea‐denatured haemoglobin and casein, endogenous tissue proteins, Nα‐benzoyl‐dl‐arginine 2‐naphtylamide (BANA), Nα‐benzoyl‐dl‐arginine methyl ester (BAME), Nα‐toluenep‐sulphonyl‐dl‐arginine methyl ester (TAME), Nα‐benzoyl‐dl‐phenylalanine 2‐naphthyl ester (BPANE), and Nα‐acetyl‐dl‐tyrosine ethyl ester (ATEE) as substrates.Several peaks of activity were detected with all these substrates in different pH ranges. Activity was highest with protein substrates at pH 3·0‐4·0, with smaller peaks of activity at pH 5·5‐6·5 and 8·0‐9·0. At pH 3·0 the activity with trypsin substrates, viz. BANA, BAME and TAME, was also relatively high, but much less with chymotrypsin substrates, ATEE or BPANE. With BAME, TAME, BPANE and ATEE the hydrolysis rate was highest at neutral or slightly alkaline pH. During postnatal development the hydrolysis of protein substrates increased three‐fold at pH 3·0 and about two‐fold at pH 6·5 and 8·5. The rate of hydrolysis of BANA, BAME and TAME generally increased during the first 2 postnatal weeks and thereafter decreased, whereas no marked increase in the rate of hydrolysis of BPANE and ATEE occurred until the age of about 2 weeks. The results were less consistent with synthetic substrates than with protein substrates, indicating the existence of non‐uniform alterations during development in the activity of th

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02243.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Incorporation of [14C]fucose or [14C]glucosamine into the glycoproteins of developing mouse brain was studied using polyacrylamide gel electrophoresis. Between 1 and 10 days after birth two fractions of soluble glycoproteins were extensively labelled, but by 15 days after birth incorporation into these fractions was no longer prominent. These glycoproteins have apparent molecular weights in the range of 150,000‐250,000, as estimated by the electrophoretic procedure. The more rapidly migrating fraction has a half‐life of about 1 week whereas the other is far more s

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02244.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Some properties of glutamate decarboxylase (GAD) were studied in the brain of the carp (Carassius auratus), the pigeon (Columbia livia) and the mouse (Mus musculus). The optimum pH for GAD in the three species was 6·3‐6·5. In the three species studied, GAD activity of brain homogenates in water was higher than that of homogenates in buffer. The supernatant from homogenates in Triton‐X‐100 gave an enzyme preparation which showed greater activation by pyridoxal phosphate than those obtained from complete water or buffer homogenates or from the supernatant of Water homogenates.In the absence of pyridoxal phosphate, the activity of carp GAD was considerably lower than that of mouse or pigeon GAD. The addition of pyridoxal phosphate resulted in a much greater activation of carp GAD than that of pigeon or mouse GAD. Pyridoxal phosphate content was also measured in brains of the species studied. The difference between coenzyme levels in carp and mouse was very small in comparison to the difference in GAD activity in the absence of exogenous coenzyme. The pyridoxal phosphate content of pigeon brain was higher than that of the other tw

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02245.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY

摘要:

Abstract—Nerve bundles from the walking legs of the lobster have been homogenized in either isosmotic or hyperosmotic sucrose solutions and subjected to differential and discontinuous density gradient centrifugation. The resulting subcellular fractions were analysed for their concentrations of acetylcholine (ACh), choline acetyltransferase (ChAc) and cholinesterase (ChE). Enzymic characteristics were used for a biochemical identification of the subfractions. Regardless of the osmotic conditions, ACh was always found in the free form; there was no evidence of any‘bound’ester. After ultracentrifugation of homogenates in the hyperosmotic medium a pellet floating atop was formed; it consisted of membrane fragments and contained more than 30 per cent of the choline‐esterhydrolysing enzymes, with a 3 to 4‐fold increased specific activity. ChAc was found to be increasingly soluble if the ionic concentration was raised to that of the haemolymph body fluid of the lobster. Thus, all the components of the ACh system were present in substantial amounts but the question of their physiological function rem

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1970.tb02246.x

出版商:Blackwell Publishing Ltd    

年代:1970

数据来源: WILEY