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1.
Arch Biochem Biophys ; 463(1): 128-32, 2007 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-17442257

RESUMO

Total gastrectomy (TG) causes cobalamin (Cbl) deficiency followed by increases in tumor necrosis factor (TNF)-alpha levels in the spinal cord (SC) of the rat. In order to understand how Cbl deficiency may influence cell Cbl transport, we have measured by immunoblotting protein levels of the receptor for the Cbl-transcobalamin (TC) complex (TC-R) in both animal and cell models. TC-R protein levels were elevated in the total membranes of duodenal mucosa, kidneys, liver, and SC of rats made Cbl-deficient (Cbl-D) by means of TG or feeding with a Cbl-D diet. Postoperative Cbl-replacement treatment normalized the TC-R protein levels in each of the tested organs, regardless of whether this treatment was given during the first two post-TG or during the third and fourth post-TG mo. In Caco-2 cells, progressively increasing TNF-alpha concentrations supplemented to culture medium induced an up-regulation of TC-R protein levels. We provide the first evidence of the regulation of a Cbl-specific receptor by the vitamin itself in some rat organs.


Assuntos
Receptores de Superfície Celular/fisiologia , Vitamina B 12/fisiologia , Animais , Células CACO-2 , Duodeno/fisiologia , Gastrectomia , Humanos , Mucosa Intestinal/fisiologia , Fígado/fisiologia , Masculino , Ratos , Ratos Sprague-Dawley , Medula Espinal/fisiologia , Deficiência de Vitamina B 12/fisiopatologia
2.
Glia ; 45(4): 406-11, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-14966871

RESUMO

In the present study, we hypothesized that cobalamin (Cbl) deficiency might affect astrocytes and oligodendrocytes of rat spinal cord (SC) differently. Radiolabeled Cbl ([Cyano-14C]cyano-Cbl) was used to investigate whether the in vitro uptake of Cbl is different in primary cultures of oligodendrocytes and astrocytes. In culture medium supplemented with serum that naturally contains Cbl, the time course of labeled Cbl uptake by neonatal oligodendrocytes had two peaks, at 8 h and 24 h. No uptake was observed when the same cells were cultured in a serum-free medium and consequently in the absence of Cbl. Oligodendrocytes isolated from adult rat SC showed no uptake under any of the tested conditions. Astrocytes isolated from adult Cbl-deficient and newborn rat SC, both cultured in a medium supplemented with serum, showed peak Cbl uptake at 8 h and 12 h, respectively, whereas those isolated from the SC of an adult normal rat cultured under the same conditions showed no uptake throughout the experimental period. Astrocytes isolated from normal, Cbl-deficient adult rats and newborns cultured in a serum-free medium not containing Cbl, showed a similar trend of Cbl uptake with a peak at 24 h. Oligodendrocytes isolated from Cbl-deficient rats showed no uptake when cultured in medium with or without serum. This study provides evidence for a difference in the uptake of labeled Cbl between rat SC astrocytes and oligodendrocytes in relation to (1) age of the donor SC, (2) Cbl status of the donor SC, and (3) Cbl deficiency in the incubation medium that facilitates Cbl uptake in neonatal and adult astrocytes.


Assuntos
Astrócitos/metabolismo , Oligodendroglia/metabolismo , Medula Espinal/metabolismo , Vitamina B 12/metabolismo , Animais , Animais Recém-Nascidos , Astrócitos/citologia , Células Cultivadas , Oligodendroglia/citologia , Ratos , Ratos Sprague-Dawley , Medula Espinal/citologia , Vitamina B 12/genética , Deficiência de Vitamina B 12/metabolismo
3.
FASEB J ; 16(13): 1820-2, 2002 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12354698

RESUMO

We have demonstrated previously that chronic vitamin B12 [cobalamin (Cbl)] deficiency preferentially affects glial cells in the rat central nervous system (CNS) and severely affects peripheral glial cells independently of and concomitantly with the central neuropathy. In this study, we determined the mRNA levels for myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) in different CNS areas of rats made Cbl-deficient by total gastrectomy, as well as the mRNA levels for glycoprotein Po and peripheral myelin protein (PMP)22 in the sciatic nerve. GFAP-mRNA levels were significantly decreased in the spinal cord (SC) and hypothalamus, but not in the cortex, hippocampus, or striatum of totally gastrectomized (TGX) rats. No differences in GFAP protein levels were found in the SC and hypothalamus of the TGX rats treated or not with Cbl. MBP-mRNA levels were significantly decreased only in the hypothalamus, and the levels of mRNA for both glial markers returned to normal with Cbl replacement therapy. The levels of mRNA for the various myelin proteins in the sciatic nerve were not modified by Cbl deficiency. These results demonstrate that: a) the neurotrophic action of Cbl in rat CNS occurs in a zonal manner; and b) Cbl deficiency does not affect myelin synthesis (with the sole exception of the hypothalamus).


Assuntos
Proteína Glial Fibrilar Ácida/genética , RNA Mensageiro/metabolismo , Medula Espinal/metabolismo , Deficiência de Vitamina B 12/fisiopatologia , Animais , Sistema Nervoso Central/metabolismo , Gastrectomia , Expressão Gênica , Hipotálamo/metabolismo , Proteína Básica da Mielina/genética , Bainha de Mielina/metabolismo , Sistema Nervoso Periférico/metabolismo , RNA Mensageiro/genética , Ratos , Nervo Isquiático/metabolismo
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