摘要:

Abstract:Taurine, cysteinesulfinic acid decarboxylase (CSAD), glutamate, γ‐aminobutyric acid (GABA), and glutamic acid decarboxylase (GAD) were measured in subcellular fractions prepared from occipital lobe of fetal and neonatal rhesus monkeys. In addition, the distribution of [35S]taurine in subcellular fractions was determined after administration to the fetus via the mother, to the neonate via administration to the mother prior to birth, and directly to the neonate at various times after birth. CSAD, glutamate, GABA, and GAD all were found to be low or unmeasurable in early fetal life and to increase during late fetal and early neonatal life to reach values found in the mother. Taurine was present in large amounts in early fetal life and decreased slowly during neonatal life, arriving at amounts found in the mother not until after 150 days of age. Significant amounts of taurine, CSAD, GABA, and GAD were associated with nerve ending components with some indication that the proportion of brain taurine found in these organelles increases during development. All subcellular pools of taurine were rapidly labeled by exogenously administered [35S]taurine. The subcellular distribution of all the components measured was compatible with the neurotransmitter or putative neuro‐transmitter functions of glutamate, GABA, and taurine. The large amount of these three amino acids exceeds that required for such function. The excess of glutamate and GABA may be used as a source of energy. The function of the excess of taurine is still not clear, although circumstantial evidence favors an important role in the development and maturation of the

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12550.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Recent immunocytochemical studies indicated that the myelin‐associated glycoprotein (MAG) is localized in the periaxonal region of central nervous system (CNS) and peripheral nervous system (PNS) myelin sheaths but previous biochemical studies had not demonstrated the presence of MAG in peripheral nerve. The glycoproteins in rat sciatic nerves were heavily labeled by injection of [3H]fucose in order to re‐examine whether MAG could be detected chemically in peripheral nerve. Myelin and a myelin‐related fraction, WI, were isolated from the nerves. Labeled glycoproteins in the PNS fractions were extracted by the lithium diiodosalicylate (LIS)‐phenol procedure, and the extracts were treated with antiserum prepared to CNS MAG in a double antibody precipitation. This resulted in the immune precipitation of a single [3H]fucose‐labeled glycoprotein with electrophoretic mobility very similar to that of [14C]fucose‐labeled MAG from rat brain. A sensitive peptide mapping procedure involving iodination with Bolton‐Hunter reagent and autoradiography was used to compare the peptide maps generated by limited proteolysis from this PNS component and CNS MAG. The peptide maps produced by three distinct proteases were virtually identical for the two glycoproteins, showing that the PNS glycoprotein is MAG. The MAG in the PNS myelin and Wl fractions was also demonstrated by Coomassie blue and periodic acid‐Schiff staining of gels on which the whole US‐phenol extracts were electrophoresed, and densitometric scanning of the gels indicated that both fractions contained substantially less MAG than purified rat brain myelin. The presence of MAG in the periaxonal region of both peripheral and central myelin sheaths is consistent with a similar involvement of this glycoprotein in axon‐sheath cell interactions

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12551.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:On polyornithine (PORN) substrata dissociated 8‐day chick embryo ciliary ganglionic neurons will survive if the culture medium is supplemented with Ciliary Neuronotrophic Factor. However, neuritic growth will not occur unless the substratum is derivatized with a PORN‐bindable Neurite Promoting Factor (PNPF). In this preliminary study we report that soluble PNPF can be (1) assayed by a convenientin vitrosystem; (2) obtained in relatively large amounts from serum‐free media conditioned over RN22 Schwannoma cultures; (3) concentrated by using Amicon XM100 ultrafiltration; and (4) separated from nearly all of the non‐active protein by using ion‐exchange chromatography. The partially purified PNPF can be concentrated using XM100 and is heat‐ and protease‐sensitive. In the course of these fractionation studies we observed in some cases a concentration‐dependent interference with the expression of PNPF activity in the bioassay; we propose graphical methods to permit the simultaneous determination of PNPF and the extent of such interference. Different treatments that affected the interference property did not always affect PNPF activity in a reciprocal manner, leaving open the possibility that the interference with PNPF activity results from reversible alteration of the PNPF molecule, or that there exists a separate in

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12552.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:The choroid plexus is intimately involved in the production and regulation of the cerebrospinal fluid. Populations of surface membranes from this epithelial tissue were separated by density gradient centrifugation by use of modified colloidal silica (Percoll). A fraction of heavy microsomes (P3) containing plasma membranes was prepared by differential centrifugation. Membranes in fraction P3were mixed with a given concentration of Percoll and density gradients generated during centrifugation. When fraction P3was mixed with 20% (v/v) Percoll and centrifuged at 20,000 r.p.m. for 1 h in a 50.2 Ti fixed‐angle rotor, membranes containing alkaline phosphatase (AP) were found at a density of 1.037 g/cm3while those containing NaK ATPase were found at 1.047 g/cm3. With more shallow density gradients using 12% and 14% Percoll, a broad shoulder of AP activity became manifest at densities greater than 1.060 g/cm3suggesting multiple populations of membranes containing AP. Membranes containing AP could also be separated from membranes containing γ‐glutamyl transpeptidase (γ‐GTP); this separation was most pronounced in 12% Percoll. The activity of γ‐GTP could not be separated from activity of NaK ATPase. Total protein was distributed broadly throughout the gradients. Studies have been undertaken to compare the behavior of choroidal membranes in Percoll gradients with that of renal membranes because the biochemical anatomy of the kidney has been extensively studied. In contrast to choroidal membranes, renal membranes with NaK ATPase activity were found to have densities lower than those membranes with AP. Thus, the distribution of membrane‐bound enzymes from kidney in a Percoll gradient was exactly the opposite of that observed for these same enzymes from choroid plexus. In addition, unlike the γ‐GTP activity of choroid plexus, γ‐GTP from kidney could be separated from the activities of both alkaline phosphatase and NaK ATPase. These marked differences in membrane populations between choroid plexus and kidney as defined by Percoll density gradient centrifugation analyses are presumably reflective of differences in the functions of the two

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12553.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Pumiliotoxins (PTX) A, B, and 251D, members of a new class of indolizidine alkaloids isolated from the skin of poison frogs of the family Dendrobatidae, inhibit Ca2+‐ATPase activity in sarcoplasmic reticulum vesicles from frog and rat hind‐limb muscles. PTX‐B and PTX‐A appear to be relatively specific inhibitors of Ca2+‐ATPase; PTX‐A is much less potent than PTX‐B. PTX‐251D is a potent inhibitor of Ca2+‐ATPase, and was also found to inhibit Na+, K+, and Mg2+‐ATPases in rat brain synaptosomes. Caffeine and verapamil, two drugs known to affect calcium translocation, are very weak inhibitors of the Ca2+‐ATPase. The K, values for inhibition of the Ca2+‐ATPase of rat and frog sarcoplasmic reticulum by PTX‐B were comparable and ranged between 22 and 36 μM. Inhibition of calcium‐dependent ATPase in sarcoplasmic reticulum by pumiliotoxin‐B is noncompetitive with calcium and is not readily reversible. Based on structure‐activity profiles, it is concluded that inhibition of Ca2+‐ATPase by the indolizidine alkaloids is responsible for the alkaloidelicited prolo

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12554.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Abstract:Dihydroxyphenylalanine/5‐hydroxytryptophan (DOPA/5‐HTP) decarboxylase activity varied widely in different parts of the CNS, being highest in the neostriatum and lowest in the frontal cortex. The addition of 2.5 μm‐pyridoxal 5′‐phosphate (PLP), the coenzyme, increased enzyme activity in brainstem and liver, while higher concentrations led to a decrease in activity. In brainstem, the addition of 1000 μmPLP shows activity similar to that obtained without exogenous PLP. The effects of different monoamine oxidase (MAO) inhibitors on decarboxylase activity were demonstrated. Iproniazid phosphate and harmaline significantly decreased the decarboxylation in liver and brainstem, while pargyline inhibited only liver decarboxylation. Some decarboxylase inhibitors such as RO4–4602 and α‐methyl DOPA, as well as piribedil, a dopaminergic receptors agonist, were addedin vitroto measure their action on decarboxylase with or without exogenous PLP or with double concentrations of substrate (5‐HTP). Piribedil (5000 μm) affected the enzymic reaction and triggered a higher inhibition in liver. Inhibition in brainstem needed less RO4–4602 (50 μm) than in liver (300 μm). Addition of PLP did not reverse this inhibition, while doubling the concentration of 5‐HTP nullified the inhibitory effect in liver only. Inhibition induced by α‐methyl DOPA (5 μm) was easily reversed by doubling the concentration of substrate. However, the presence of exogenous PLP restored the enzymic activity in liver only. We conclude from this work thus that the enzyme can decarboxylate its substrate without exogenous PLP, that MAO inhibitors might inhibit decarboxylase activity, and that decarboxylase inhibitors react differently when brain and liver are used as enzymic source. PLP seems to act as a protective agent on the active site of the enzyme in the brainstem and preferentially wi

ISSN:0022-3042    

DOI:10.1111/j.1471-4159.1982.tb12555.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY