摘要:

Abstract—The purification of small amounts of 2′,3′‐cyclic nucleotide 3′‐phosphohydrolase from bovine white matter by ion‐exchange techniques (Drummondet al., 1978) has been used to provide antigen for the production of specific rabbit antibodies to this enzyme. Specific antibody has been purified from immune serum by affinity chromatography on a column of Sepharose to which the enzyme has been attached, and the purified antibody has been coupled to cyanogen bromide‐activated Sepharose. Affinity chromatography on the immunoadsorbent effectively purifies 2′,3′‐cyclic nucleotide 3 ‐phosphohydrolase in one step from an extract of an acetone powder made from bovine white matter. This modified purification procedure has reduced the time required for purification and increased the yield of the enzyme to 57%. In SDS‐gel electrophoresis in phosphate buffer the enzyme migrates as an aggregate of about 98,000MW. When the buffer is Tris‐glycine, the apparent MW is about 44,000 and under specific conditions two proteins of only slightly different mobilities can be discerned. Within experimental error the amino acid compositions of the proteins in the two bands are indistinguishable. Peptide patterns obtained by polyacrylamide gel electrophoresis following proteolytic digestion withStraphylococcus aureusV8 protease or papain show extensive structural homology between the two proteins, but detectab

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05257.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The ability of cholinergic agonists to block the specific interaction of α‐bungarotoxin (α‐Bgt) with membrane‐bound sites derived from rat brain is enhanced when membranes are preincubated with agonist. Thus, pretreatment of α‐Bgt receptors with agonist (but not antagonist) causes transformation of sites to a high‐affinity form toward agonist. This change in receptor state occurs with a half‐time on the order of minutes, and is fully reversible on dilution of agonist. The results are consistent with the identity of α‐Bgt binding sites as true central nicotinic acetylcholine receptors. Furthermore, this agonist‐induced alteration in receptor state may represent an in vitro correlate of physiological desensitization. As determined from the effects of agonist on toxin binding isotherms, and on the rate of toxin binding to specific sites, agonist inhibition of toxin binding to the high‐affinity state is non‐competitive. This result suggests that there may exist discrete toxin‐binding and agonist‐binding sit

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05258.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The effects of selective inactivation of propionylcholinesterase (PrChE) by tetramonoisopropylpyrophosphortetramide (iso‐OMPA) on the steady state and regenerating levels of acetylcholinesterase (AChE) were investigated on the superior cervical ganglion (SCG) of the rat. Over the dosage range of 1.5‐40.0 μmol iso‐OMPA/kg intraperitoneally, which produced nearly total inactivation of ganglionic PrChE and 0‐35% inactivation of AChE, there was no subsequent increase in AChE activity above the control level. Single or repeated injections of iso‐OMPA at total doses of 5.0‐40.0 μmol/kg intraperitoneally caused no reduction in the rate of regeneration of ganglionic AChE during the 24 h following its inactivation by sarin, 2.0 μmol/kg intravenously. Both sets of findings differ from those obtained previously in a similar study of ganglionic AChE and butyrylcholinesterase (BuChE) in the cat. Possible reasons for this distinct species differen

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05259.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Muscarinic cholinergic agonists increase cyclic GMP levels in a number of neural tissues. Since the rat hippocampus receives a cholinergic innervation from the septum, we decided to test whether cyclic GMP levels of the rat hippocampus are increased by bethanechol, a muscarinic cholinergic agonist. Incubation of rat hippocampi with varying concentrations of bethanechol showed that the increase in cyclic GMP levels is concentration‐dependent, 500 pwbethanechol producing a maximum increase of 490% over control values. The bethanechol‐evoked increases were blocked by the muscarinic antagonist atropine, and were calcium‐dependent. It is concluded that at least some of the cells projecting to the rat hippocampus form muscarinic cholinergic synapses which act via a cyclic GMP‐dependent

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05260.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Two NADPH‐linked aldehyde reductases (alcohol:NADP+oxidoreductase, EC 1.1.1.2) capable of reducing succinic semialdehyde to the anaesthetic Chydroxybutyrate have been purified from human brain to electrophoretic homogeneity. The first of these enzymes, which is typical of its category, is not specific for succinic semialdehyde and can reduce some aromatic aldehydes at a high rate. It is a monomer of molecular weight about 45,000 and is strongly inhibited by various hypnotics and anticonvulsants. The second enzyme is, in contrast, fairly specific for succinic semialdehyde. It is a dimer of molecular weight about 90,000 and is not inhibited by the hypnotics and anticonvulsants which inhibit the first enzyme. It is thus different from previously described aldehyde reductases from human br

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05261.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Morphine has been observed to have only a minor effect on the prostaglandin E1(PGE1) stimulated adenylate cyclase or the basal cyclase activity in the neuroblastoma N18TG2 calls. However, this ineffectiveness of the opiates was not due to the absence of opiate receptor in this cell line. Contrary to previous observations, neuroblastoma N18TG2 cells possessed a high affinity, stereospecific opiate receptor. When [3H]dihydromorphine and [3H]naloxone binding were determined, a single component receptor with Kdiss= 25‐31 nmand with a capacity of 165 fmol/mg protein could be observed. This receptor has similar properties to those observed in the brain homogenates. The naloxone specific binding was dependent on the pH of the incubation medium and maximal binding occurred at pH 7.6. The agonist binding was inhibited by the alkali metal cations and divalent cations, while the antagonist binding was not affected by the cations significantly. There was no observable reversal of the Na+inhibitory effect on agonist binding by the addition of Mn2+to the incubation mixtures. Opiate binding to the neuroblastoma N18TG2 cells could be attenuated by pretreating the cells withN‐ethylmaleimide or proteolytic enzymes. Of the lipases tested, only phospholipase A2has an inhibitory effect on the naloxone binding. Fractionation of the cell homogenates with differential centrifugation and purification of the membrane fractions by sucrose gradients suggested the localization of the receptor at the plasma membranes. Thus, the receptor in the neuroblastoma N18TG2 cells closely resembles those observed in the brain homog

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05262.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The high affinity choline uptake system present in T‐sacs prepared fromTorpedo californicaelectric organ was shown to be insensitive to external Ca2+and to be absolutely dependent on external NaCl, with optimal uptake at approx 200 mM‐NaCl. Both Na+and Cl−separately stimulate uptake. Uptake also exhibited an optimum at approx 10mM‐external K+. Uptake was completely inhibited at 4°C. Approximately 50% of newly accumulated [3H]choline was released by depolarization of T‐sacs regardless of the time or method of de

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05263.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Changes in the activities of several specific enzymes were measured in the cerebellum during development. Early transient increases were found in both ornithine decarboxylase andS‐adenosylmethionine decarboxylase, enzymes involved in the initial steps of polyamine synthesis. Different patterns of changes were found in neurotransmitter synthesizing enzymes. Tyrosine hydroxylase activity achieved adult levels very early, by 3 days after birth, and remained at this level. Glutamic acid decarboxylase activity, while very low at early stages, increased rapidly before birth and then after a lag period of 10 days started to increase rapidly, directly related to the general growth of cerebellar weight and protein content. Choline acetyltransferase activity started to increase rapidly, reaching a peak of about 100% of adult levels at 3‐7 days after birth; the activity then gradually declined and at 20 days, after reaching a low of about 55% of adult values, gradually started to increase, reaching adult levels later than 40 days after birth. The development of protein carboxymethylase activity was similar to that of glutamic acid decarboxylase, directly related to the general growth of the cerebellum. Several interpretations of the results are disc

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05264.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—The amount of α‐melanocyte‐stimulating hormone (α‐MSH) in the entire hypothalamus as well as the amount of α‐MSH in free granule and synaptosome fractions of hypothalamic homogenates was investigated throughout the lifespan of female rats (1‐24 months). A 900gsupernatant fluid was prepared from hypothalami following homogenization in an iso‐osmotic sucrose solution, and free granules and synaptosomes containing α‐MSH were fractionated by means of continuous sucrose density gradient centrifugation. α‐MSH was quantified by radioimmunoassay. The total amount of α‐MSH in the hypothalamus, as well as the amount in free granules and synaptosomes prepared from hypothalami increased progressively from the 1st to the 5th month of life, and this increase was more pronounced in the free granules than in the synaptosomes. On the other hand, the amount of α‐MSH in the hypothalamus and the amount present in free granules and synaptosomes prepared from 5‐24‐month‐old animals decreased with age, and this decrease appeared to proceed at similar rates in both subcellular compartments. Based on these results, it is suggested that ageing of α‐MSH neurons in the hypothalamus is accompanied by a degeneration of the axons and/or an alteration in the biosynthetic and

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05265.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY

摘要:

Abstract—Changes in morphology and in transformations of [U‐14C]glucose and [1‐14C]acetate into amino acids of the brain cortex were followed on the Sth, 10th and 21st days after production of mechanical lesions and compared with control tissue. In the experimental tissue, proliferation of astroglia and reduction of the number of neurons had taken place. On the 10th day, accumulation of mitochondria and of some gliofilaments in the cytoplasm of astroglia was observed. On the 21st day, the gliofilaments occupied a substantial portion of the astroglial cytoplasm and the mitochondria were reduced in number and compressed to the cell membrane. Incorporation of14C from acetate into amino acids was substantially increased on the 10th day (up to 240% with respect to controls) and normalized again on the 21st day. Incorporation of [14C]glucose into amino acids decreased somewhat during the experimental period. It has been proposed that the proliferation of astrocytes and their ultrastructural changes may account for the increased transformation of [14C]acetate into amino acids, in particular into glutamine which is formed from the small glutamate

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1979.tb05266.x

出版商:Blackwell Publishing Ltd    

年代:1979

数据来源: WILEY