Elevated interleukin-12 in progressive multiple sclerosis correlates with disease activity and is normalized by pulse cyclophosphamide therapy

The technique of pulse radiolysis has been used to investigate the possibility of intramolecular charge transfer in the dipeptide histidyltyrosine, following one-electron oxidation of one of its amino acid residues. The radical anion, Br2.- was found to react with the dipeptide at pH 6.0 with a bimolecular rate constant of 2.3+/-0.2 x 10(7) dm3 mol(-1)s(-1) suggesting that it reacts very selectively with the histidine moiety. Spectral observations at, or close to the end of this reaction show only the presence of a tyrosinyl free radical (TyrO.), however, indicating that fast (>10(6) s(-1) intramolecular charge transfer has taken place between histidine radicals (His+.) and tyrosine (TyrOH). This finding was supported by the direct observation of the rate of formation of TyrO. in experiments with the free amino acids, histidine and tyrosine, under conditions where Br2.- reacted selectively with histidine. The bimolecular rate constant for the reaction between His+. and TyrOH was found to be 2.4+/-0.5 x 10(6) dm3 mol(-1)s(-1). Taken together, the results of the study indicate that His+. is a relatively strong oxidising agent where (E (His+./His) > 770 mV at pH 6.0.     

Screening for the aneuploid fetus

Advances in ultrasound technology have dramatically improved the detection of fetal defects. Although only an invasive test can provide a diagnosis, the incorporation of sonography into current biochemically based screening programs should significantly improve the detection of a host of other physically based fetal abnormalities. This article provides an overview and discussion of the prenatal sonographic features that may suggest the presence of a significant chromosomal abnormality.     

Specific antiviral activity demonstrated by TGTP, a member of a new family of interferon-induced GTPases

The GTPase superfamily includes a diversity of molecules whose functions are regulated through the binding and hydrolysis of GTP. This superfamily can be segregated into families of functionally related molecules that typically share amino acid sequence similarity within and around the nucleotide-binding domains. A new family of putative GTPases, including IRG-47, LRG-47, IGTP, and TGTP/Mg21, has recently emerged that share significant sequence identity (25-40%). Expression of these molecules has been shown to be selectively induced by IFN-gamma and in some cases by IFN-alpha beta or bacterial LPS. This induction pattern implicates these putative GTPases as part of the innate defense of cells to infection, but their role in such defense has not yet been defined. We have previously described the cloning of TGTP and now confirm its intrinsic activity as a GTPase. We found that TGTP is strongly induced by endogenous IFN-alpha beta produced in response to standard lipofection of plasmid DNA or polyinosinic polycytidylic acid. The ability of endogenously produced IFN-alpha beta to efficiently induce expression of TGTP under these conditions suggested that TGTP might participate in defense against viral infection. This proposal was borne out when TGTP-transfected L cells displayed relative resistance to plaque formation by vesicular stomatitis virus but not herpes simplex virus. This observation places TGTP among a small family of innate antiviral agents and has implications for the functions of other members of this family of GTPases.     

On infinite queueing tandems

We study the flow of jobs on an infinite series of first-come-first-served queues. Jobs are placed in the buffer of the first queue and allowed to flow through the infinite tandem of queues. The service times of each job on consecutive queues form a stationary and ergodic sequence. We are interested in characterizing the flow of jobs asymptotically, after they have passed through a large number of queues.It is shown that the job flow reaches asymptotically a stationary state, which can be characterized in terms of the average service times of the jobs. They eventually form clusters, such that every two consecutive jobs belonging to the same cluster collide infinitely often, while jobs belonging to different clusters eventually cease to interact.     

Metabolic activation and carcinogen-DNA adduct detection in human larynx

Putative carcinogen-DNA adducts in human larynx tissues (n = 25) from smoker and non/ex-smoker patients were examined by 32P-postlabeling and compared with the metabolic activation capacity of larynx microsomes and cytosols from the same tissues. Hydrophobic DNA adducts were evident only in smokers, and chromatographic profiles of the adducts were similar using either the butanol extraction or nuclease P1 enhancement method, which suggested that the adducts may be derived from polycyclic aromatic hydrocarbons but not aromatic amines. Immunoblots of larynx microsomes using anti-cytochrome P450 1A1/1A2, 2C, 3A4, 2E1, and 2A6 antibodies showed intensities ranging from 1-10% of that typically observed with human liver microsomes. Enzymatic assays of larynx microsomes showed appreciable activity for benzo(a)pyrene hydroxylation (P450 1A1 and 2C) but not for 4-aminobiphenyl N-oxidation (P450 1A2), which indicated that the observed immunoreactivity was for P450 1A1; this represents the highest level of this P450 yet detected in human extrahepatic tissues. Accordingly, total DNA adduct levels in the larynx correlated strongly with levels of P450 2C, 1A1, and 3A4 but not with P450 2E1 or 2A6. Larynx cytosols also showed appreciable aromatic amine N-acetyl-transferase activity for p-aminobenzoic acid (NAT-1) but not for sulfamethazine (NAT-2); however, NAT-1 activity was not correlated with total DNA adducts, which is again consistent with the lack of aromatic amine-DNA adducts detected by 32P-postlabeling. Thus, these results suggest that the DNA adducts detected in human larynx are largely derived from metabolic activation of polycyclic aromatic hydrocarbons in cigarette smoke by P450 2C, 3A4, and/or 1A1.     

The Pichia pastoris PAS4 gene encodes a ubiquitin-conjugating enzyme required for peroxisome assembly

We report here the cloning and initial characterization of PAS4, a gene required for peroxisome assembly in the yeast Pichia pastoris. The PAS4 gene encodes a 24-kDa protein (Pas4p) that is located on the cytoplasmic surface of peroxisomes and is induced during peroxisome proliferation. Analysis of the Pas4p sequence revealed a high degree of similarity to ubiquitin-conjugating enzymes, particularly in the region surrounding the putative active-site cysteine residue with which ubiquitin forms a thioester bond. As expected for a ubiquitin-conjugating enzyme, substitution of alanine or serine for the conserved active-site cysteine residue abolished PAS4 function. In addition, a small amount of a 32 kDa form of Pas4p (the predicted size of a Pas4p-ubiquitin conjugate) was detected both in vivo and in vitro. This species was eliminated by reducing agents and was not detected in the cysteine to alanine substitution mutant, suggesting that it is a Pas4p-ubiquitin conjugate. Using a yeast strain that overexpresses a Myc-ubiquitin fusion protein, we demonstrate directly that this conjugate contains ubiquitin. We conclude from these observations that PAS4 is a member of the ubiquitin-conjugating enzyme gene family and that one or more ubiquitination reactions are required for peroxisome assembly.     

Post-translational processing of the insulin-like growth factor-2 precursor. Analysis of O-glycosylation and endoproteolysis

Insulin-like growth factor-2 (IGF-2) is expressed in most embryonic tissues and is required for normal development during gestation. After birth IGF-2 expression is extinguished in most tissues, but the gene is often reactivated during tumorigenesis. Tumors secrete high molecular weight forms of IGF-2 that result from aberrant post-translational processing of pro-IGF-2. As a first step toward understanding how high molecular weight IGF-2 peptides might contribute to tumor progression, we have characterized the biosynthesis of IGF-2 in a human embryonic cell line. We have found that pro-IGF-2 can initially form two disulfide isomers that undergo rearrangement to a single conformation in vivo. The addition of N-acetylgalactosamine to Ser71, Thr72, Thr75, and Thr139 likely occurs in the cis- Golgi apparatus. Sialic acid addition begins in the trans- Golgi apparatus, but IGF-2 peptides must reach the trans-Golgi network for oligosaccharide maturation to be completed. Endoproteolysis occurs concomitant to or slightly after oligosaccharide maturation. Cleavage was observed only at Arg104, resulting in the secretion of IGF-2-(1-104) and free E-peptide. Proteolysis required basic residues in the P1 (Arg104) and P4 (Arg101) positions, was completely blocked by a furin inhibitor, and was enhanced by coexpression with furin, PACE4, PC6A, PC6B, and LPC. These data suggest that members of the subtilisin-related proprotein convertase family mediate processing of pro-IGF-2 at Arg104. We did not detect the IGF-2 peptides that are most abundant in normal serum, mature IGF-2, and IGF-2-(1-87), in this expression system, which indicates that novel endoproteases are responsible for generating these products.     

Allelotype analysis of oesophageal adenocarcinoma: loss of heterozygosity occurs at multiple sites

Deletions of tumour-suppressor genes can be detected by loss of heterozygosity (LOH) studies, which were performed on 23 cases of adenocarcinoma of the oesophagus, using 120 microsatellite primers covering all non-acrocentric autosomal chromosome arms. The chromosomal arms most frequently demonstrating LOH were 3p (64% of tumours), 5q (45%), 9p (52%), 11p (61%), 13q (50%), 17p (96%), 17q (55%) and 18q (70%). LOH on 3p, 9p, 13q, 17p and 18q occurred mainly within the loci of the VHL, CDKN2, Rb, TP53 and DCC tumour-suppressor genes respectively. LOH on 5q occurred at the sites of the MSH3 mismatch repair gene and the APC tumour-suppressor gene. 11p15.5 and 17q25-qter represented areas of greatest LOH on chromosomes 11p and 17q, and are putative sites of novel tumour-suppressor genes. LOH on 9p was significantly associated with LOH on 5q, and tumours demonstrating LOH at both the CDKN2 (9p21) and MSH3 (5q11-q12) genes had a significantly higher fractional allele loss than those retaining heterozygosity at these sites. Six of nine carcinomas displaying microsatellite alterations also demonstrated LOH at CDKN2, which may be associated with widespread genomic instability. Overall, there are nine sites of LOH associated with oesophageal adenocarcinoma.     

Lovastatin disrupts early events in insulin signaling: a potential mechanism of lovastatin's anti-mitogenic activity

The mechanism by which lovastatin lowers cholesterol levels is well characterized but little is known about its anti-mitogenic and anti-tumorigenic mechanism. Here we demonstrate that lovastatin disrupts early events in the mitogenic signaling pathways of insulin. Insulin treatment (200 mM) of quiescent HIR rat-1 fibroblasts results in an 8-fold stimulation of phosphatidylinositol-3-kinase (PI-3-K) activity. Overnight pretreatment of cells with lovastatin (20 microM) inhibits insulin stimulation of PI-3-K activity by 75%. Immunoprecipitation and immunoblotting experiments using antibodies against the regulatory subunit of PI-3-K (p85), phosphotyrosine, and insulin receptor alpha and beta subunits demonstrate that lovastatin inhibits the association of p85 with tyrosine phosphorylated insulin receptor substrate-1 and the beta subunit of the insulin receptor. Furthermore, lovastatin dramatically reduces (70-100%) the level of tyrosine phosphorylated insulin receptor beta subunit following insulin stimulation. These results clearly demonstrate that lovastatin disrupts early events of insulin mitogenic signaling by reducing the levels of tyrosine phosphorylated beta subunit and suggest that this disruption is a potential mechanism for the anti-mitogenic effect of lovastatin.