Principles for the safety evaluation of flavouring substances

This paper reviews efforts by various organizations to develop principles and procedures for the safety evaluation of flavouring substances. Critical factors considered in safety evaluation of these substances include their level of human intake, ease of metabolism to innocuous end-products and the margin of safety between no-observed-effect levels in animal studies and human intakes. These factors form the basis for the principles and criteria laid out in this paper.     

Molecular events including p53 and k-ras alterations in the in vitro progression of a human colorectal adenoma cell line to an adenocarcinoma

The aim of the current study was to identify genetic abnormalities in human colorectal adenoma and carcinoma derived cell lines, and to determine whether the genetic changes which occur in vitro are relevant to the in vivo situation. Loss of 1p(33-35) region was shown to be the most common chromosome 1 abnormality and loss of heterozygosity (LOH) of the DCC gene and/or adjacent sequences was detected in all adenoma derived cells as well as the carcinoma cell lines. The level of p53 protein was also investigated as increased cellular p53 protein had previously been associated with mutation of the p53 gene. A further aim was to investigate genetic changes in our in vitro model of tumour progression, where the adenoma derived PC/AA cell line has previously been converted in vitro to two distinct tumorigenic phenotypes, producing either an adenocarcinoma or a mucinous carcinoma in athymic nude mice. Progression to the adenocarcinoma phenotype was shown to involve a specific chromosome 1 rearrangement, loss of both normal copies of chromosome 18 (although DCC gene sequences were retained), loss of the remaining wild type allele of k-ras resulting in homozygosity for the k-ras codon 12 mutation and increased cellular p53 protein as detected by SDS-PAGE Western blotting. The increase in p53 protein was shown not to be due to the acquisition of a mutation in the p53 gene. Interestingly, progression of the adenoma derived PC/AA cell line to the mucinous malignant phenotype did not involve any of these molecular rearrangements, suggesting that different genetically distinct pathways are involved in colorectal carcinogenesis. These studies show that the genetic changes in our in vitro model of human colorectal tumour progression are similar to those observed in in vivo studies.     

The lymph nodes of the porta hepatis

The area under the liver was dissected in 27 human autopsy specimens to search for lymph nodes in the fissures. Nodes were present in all instances. They were in the transverse fissure, posterior to the portal vein, posterior to pars transversus of the left portal vein and associated with the left hepatic artery. The size varied from 2 millimeters to 2 centimeters. Each node was histologically confirmed. Nodes were infrequent and small on the right. Nodes were not found between the portal vein, hepatic artery and bile ducts in the fissures. Nodes were found outside the fissures in the fascia between the bile duct and hepatic artery. Occlusion of the portal vein and hepatic artery could be expected before occlusion of the bile duct. Node enlargement in the transverse fissure is anticipated as a rare cause of jaundice.     

Activation of NMDA and non-NMDA receptors in the caudal ventrolateral medulla dilates the airways

Calpain is a ubiquitous calcium-dependent cysteine protease, whose cytoskeletal protein substrates suggest that it may be important in neuronal differentiation. Lead (Pb2+) is known to substitute for Ca2+ in a variety of intracellular processes, and interferes with the development of hippocampal neurons in vitro. We found that free Pb2+ at 1 nM does not activate calpain in the absence of Ca2+. Pb2+ inhibited the activity of calpain; the degree of calpain inhibition was dependent on an interaction between concentrations of both Ca2+ and Pb2+. In the presence of 1 microM free Ca2+, 10 pM free Pb2+ reduced calpain activity, but in the presence of 100 microM free Ca2+, 1 nM free Pb2+ failed to inhibit calpain. This provides evidence that Pb2+ competes for the Ca2+ binding sites on calpain. In the presence of 40 microM free Ca2+, 1 nM free Pb2+ significantly reduces Vmax without altering Km, suggesting that Pb2+ acts as a noncompetitive inhibitor of calpain. Inhibition of calpain is one mechanism by which Pb2+ may interfere with neuronal development.     

Culture supernatant of Shiga toxin-producing Escherichia coli strains provoke fluid accumulation in rabbit ileal loops

In the present study, in order to get a better insight into the mechanism of action of cyclophosphamide (CY) in rheumatoid arthritis (RA), we monitored the changes in lymphocytes' expression of leukocyte function associated antigen 1 (LFA-1). A group of 28 patients with refractory severe RA were treated with CY and methylprednisolone (MO) intravenously. Using flow cytometry we evaluated the changes in LFA-1 molecule expression on peripheral lymphocytes. In the analyzed group of patients the proportion of LFA-1 "dim" cells was reduced. After the treatment the ratio was partly normalized. Twelve months after cessation of the therapy high proportion of LFA-1 "dim" was observed only among CY/MP treated patients. The changes were related to clinical improvement. Based on the obtained data, it seems, that the treatment affecting the expression of LFA-1 may slow down lymphocyte migration and by that limit chronic inflammation within the synovium.