Alterations of Blood Brain Barrier Function in Hyperammonemia: An Overview

Ammonia is a neurotoxin involved in the pathogenesis of neurological conditions associated with hyperammonemia, including hepatic encephalopathy, a condition associated with acute—(ALF) or chronic liver failure. This article reviews evidence that apart from directly affecting the metabolism and function of the central nervous system cells, ammonia influences the passage of different molecules across the blood brain barrier (BBB). A brief description is provided of the tight junctions, which couple adjacent cerebral capillary endothelial cells to each other to form the barrier. Ammonia modulates the transcellular passage of low-to medium-size molecules, by affecting their carriers located at the BBB. Ammonia induces interrelated aberrations of the transport of the large neutral amino acids and aromatic amino acids (AAA), whose influx is augmented by exchange with glutamine produced in the course of ammonia detoxification, and maybe also modulated by the extracellularly acting gamma-glutamyl moiety transferring enzyme, gamma-glutamyl-transpeptidase. Impaired AAA transport affects neurotransmission by altering intracerebral synthesis of catecholamines (serotonin and dopamine), and producing “false neurotransmitters” (octopamine and phenylethylamine). Ammonia also modulates BBB transport of the cationic amino acids: the nitric oxide precursor, arginine, and ornithine, which is an ammonia trap, and affects the transport of energy metabolites glucose and creatine. Moreover, ammonia acting either directly or in synergy with liver injury-derived inflammatory cytokines also evokes subtle increases of the transcellular passage of molecules of different size (BBB “leakage”), which appears to be responsible for the vasogenic component of cerebral edema associated with ALF

Large scale production and purification of human retrovirus-like particles related to the mouse mammary tumor virus.

Human retrovirus-like particles related to mouse mammary tumor virus (MMTV) are secreted in a steroid-dependent manner by the breast cancer cell line T47D. We report the successful large scale production and purification of these particles from culture supernatants of T47D cells and describe the experimental conditions established for this purpose. Thus, mg amounts of particles were produced by large scale culturing of T47D cells in an autoharvesting roller bottle system and purified by differential centrifugation and continuous flow ultracentrifugation on density gradients with a 50% recovery and a 350-fold enrichment

Endogenous retroviral elements in human DNA.

Endogenous retroviruses and retroviral elements represent a substantial component of vertebrate genomes. They are inherited as stable Mendelian genes and may be activated spontaneously or by physical or chemical agents. In the human genome various retroviral elements have been detected by their relationship with mammalian endogenous and exogenous retroviruses. The structure of these elements resembles either full-length or truncated proviruses. The biological function of human retrovirus-related sequences is still unknown, but like other transposable elements, they may have contributed in shaping the eukaryotic genome. Furthermore, they exhibit a number of features giving them a potential for involvement in carcinogenesis. Expression of endogenous retroviral elements has been detected in various human tissues and cell lines and in some cases appears to be associated with human neoplasias

Herstellung retrovirusspezifischer monoklonaler Antikoerper fuer die Frueherkennung und Diagnosesicherung bei Brustkrebs Abschlussbericht

SIGLETIB: FR 4359+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman