Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The activity of the blood-brain neutral amino acid transport system is increased in rats infused with ammonium salts or rendered hyperammonemic by a portacaval anastomosis. This effect may be due to a direct action of ammonia or to some metabolic consequence of high ammonia levels, such as increased brain glutamine synthesis. To test these possibilities we evaluated the kinetic parameters of blood-brain transport of leucine and phenylalanine in control rats, in rats after continuous 24 h infusion of ammonium salts (NH4+= 2.5 mmol. kg−1 h−1), and in rats treated with methionine sulfoximine, an inhibitor of glutamine synthetase, before infusion of ammonium salts. In ammonia-infused rats without methionine sulfoximine treatment, the KD and Vmax of phenylalanine transport were increased, respectively, about 170% and 80% compared to controls, whereas the Km and Vmax of leucine transport were increased, respectively, about 100% and 200%. Electron microscopy demonstrated marked swelling of astrocytic processes around brain capillaries of ammonia-infused rats; however, capillary permeability to horseradish peroxidase apparently was not increased by ammonia infusion. Administration of methionine sulfoximine before ammonia infusion inhibited glutamine synthesis and prevented the changes in transport of leucine and phenylalanine, but apparently did not reverse the perivascular swelling. These results suggest that the ammonia-induced increase in the activity of transport of large neutral amino acids across the blood-brain barrier requires glutamine synthesis in brain, and is not a direct effect of ammonia.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Portal-systemic shunting and hyperammonemia lead to an accumulation of the large neutral amino acids in brain and apparently alter transport of neutral amino acids across the blood-brain barrier. It has been proposed that portal-systemic shunting leads to a high brain concentration of glutamine, a product of cerebral ammonia detoxification, and thereby affects the transport of other neutral amino acids across the blood-brain barrier. To test this hypothesis, rats with a portacaval shunt were treated with l-methionine-dl-sulfoximine (MSO), an inhibitor of glutamine synthesis. Treatment with MSO resulted in lower concentrations of the neutral amino acids in brain of portacaval-shunted rats and a higher brain ammonia concentration, compared with untreated shunted rats. These results suggest that the accumulation of neutral amino acids in brain after portacaval shunt depends on the increased synthesis of glutamine in brain.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract l-Dopa therapy has been suggested as effective in the reversal of hepatic coma both in humans and in animals. Beneficial effects have been reported also in chronic hepatic encephalopathy. There are many possible mechanisms through whichl-dopa could ameliorate this pathological state. The present study was carried out to clarify whether thel-dopa effect could be mediated through an improvement of the brain neutral amino acid patterns, since it competes for the same transport carrier at the blood-brain barrier. A first group of rats was orally administeredl-dopa (10 mg/100 g body weight daily) for 1 month following portocaval anastomosis. A second group was intraperitoneally injected (1.5 mg/100 g body weight daily) for 1 week, a month after portocaval shunt. Amino acid levels were determined in plasma and in four cerebral regions. No beneficial effects were observed clinically (in general condition, body weight, or hypertonic posture) in rats receivingl-dopa compared to controls. The large increase of tyrosine, phenylalanine, tryptophan, histidine, and glutamine that occurs in the cerebral tissue after portocaval shunt was also not affected byl-dopa administrations. In conclusion, in this experimental condition we had no clinical improvement in shunted animals receivingl-dopa. Moreover, this compound did not seem to influence the pathological increase of aromatic amino acids in the brain, which is considered to play an important role in hepatic encephalopathy.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-904X
    Keywords: cyclosporine ; pharmacokinetics ; rats ; portacaval shunt
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1432-2323
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Les perforations digestives représentent souvent une complication fatale de l'immunosuppression. Chez 325 transplantés rénaux traités par la cyclosporin A (CsA), 4 (1.2%) ont présenté une perforation digestive; 1 cas de perforation d'ulcère gastrique, 3 cas de perforation de diverticule colique. Les 4 malades furent opérés avec succès. Trois d'entre eux ont gardé une fonction rénale normale. Par comparaison avec l'Azathioprine la CsA ne paraît pas affecter considérablement la réponse immunitaire à l'infection bactérienne et de ce fait elle présente un avantage considérable pour traiter les complications gastro-intestinales sérieuses.
    Abstract: Resumen Las complicaciones gastrointestinales no son raras en pacientes con transplante renal bajo inmunosupresión con azatioprina-prednisona, especialmente las perforaciones de úlcera péptica o de enfermedad diverticular del colon, las cuales frecuentemente vienen a significar una complicación letal de la inmunosupresión. El manejo de estas complicaciones que ponen en peligro la vida del paciente, comprende descontinuar la inmunosupresión con abandono del injerto. Sinembargo el nuevo agente inmunosupresor, la ciclosporina (CsA), un endecapéptido fungal de novedosa estructura química, exhibe una acción inmunosupresiva más específica sobre las células T que la azatioprina, dejando casi intacta la respuesta de células B a la infección bacteriana. Estos factures deben hacer que las perforaciones gastrointestinales en pacientes bajo CsA sean eventos menos desastrosos. De 325 pacientes receptores de transplante renal tratados con CsA, 4 (1.2%) desarrollaron perfora ción: 1 por úlcera gástrica y 3 por divertículos colónicos. Todos fueron sometidos a tratamiento quirúrgico y todos sobrevivieron sin complicaciones. Tres mantuvieron su aloinjerto funcionando bien. En comparación con la azatioprina, la CsA no parece afectar mayormente la respuesta inmune a las infecciones bacterianas, lo cual representa una ventaja de significación en el manejo de complicaciones gastrointestinales serias.
    Notes: Abstract Gastrointestinal perforations frequently represent a lethal complication of immunosuppression. Of 325 renal transplant recipients treated with cyclosporin (CsA), 4 patients (1.2%) developed gastrointestinal perforation: 1 from gastric ulcer and 3 from colonic diverticula. All patients underwent operative treatment and all survived without complications. Three patients maintained a well-functioning allograft. In comparison to azathioprine, CsA does not seem to greatly affect the immune response to bacterial infections, thus representing a considerable advantage in the management of serious gastrointestinal complications.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...