Autoxidation of ubiquinol-6 is independent of superoxide dismutase

Ubiquinone (Q) is an essential, lipid soluble, redox component of the mitochondrial respiratory chain. Much evidence suggests that ubiquinol (QH2) functions as an effective antioxidant in a number of membrane and biological systems by preventing peroxidative damage to lipids. It has been proposed that superoxide dismutase (SOD) may protect QH2 form autoxidation by acting either directly as a superoxide-semiquinone oxidoreductase or indirectly by scavenging superoxide. In this study, such an interaction between QH2 and SOD was tested by monitoring the fluorescence of cis-parinaric acid (cPN) incorporated phosphatidylcholine (PC) liposomes. Q6H2 was found to prevent both fluorescence decay and generation of lipid peroxides (LOOH) when peroxidation was initiated by the lipid-soluble azo initiator DAMP, dimethyl 2,2'-azobis (2-methylpropionate), while Q6 or SOD alone had no inhibitory effect. Addition of either SOD or catalase to Q6H2-containing liposomes had little effect on the rate of peroxidation even when incubated in 100% O2. Hence, the autoxidation of QH2 is a competing reaction that reduces the effectiveness of QH2 as an antioxidant and was not slowed by either SOD or catalase. The in vivo interaction of SOD and QH2 was also tested by employing yeast mutant strains harboring deletions in either CuZnSOD and/or MnSOD. The sod mutant yeast strains contained the same percent Q6H2 per cell as wild-type cells. These results indicate that the autoxidation of QH2 is independent of SOD.     

Interactions between the two surface proteins of rotavirus may alter the receptor-binding specificity of the virus

The infection of target cells by most animal rotavirus strains requires the presence of sialic acids (SAs) on the cell surface. We recently isolated variants from simian rotavirus RRV whose infectivity is no longer dependent on SAs and showed that the mutant phenotype segregates with the gene coding for VP4, one of the two surface proteins of rotaviruses (the other one being VP7). The nucleotide sequence of the VP4 gene of four independently isolated variants showed three amino acid changes, at positions 37 (Leu to Pro), 187 (Lys to Arg), and 267 (Tyr to Cys), in all mutant VP4 proteins compared with RRV VP4. The characterization of revertant viruses from two independent mutants showed that the arginine residue at position 187 changed back to lysine, indicating that this amino acid is involved in the determination of the mutant phenotype. Surprisingly, sequence analysis of reassortant virus DS1XRRV, which depends on SAs to infect the cell, showed that its VP4 gene is identical to the VP4 gene of the variants. Since the only difference between DS1XRRV and the RRV variants is the parental origin of the VP7 gene (human rotavirus DS1 in the reassortant), these findings suggest that the receptor-binding specificity of rotaviruses, via VP4, may be influenced by the associated VP7 protein.     

The OKT3 Antibody Response Study: a multicentre study of human anti-mouse antibody (HAMA) production following OKT3 use in solid organ transplantation

Human anti-murine antibody titres following patient exposure to the monoclonal antibody Orthoclone OKT3 (muromonab-CD3) are determined by laboratories using diverse analytical methods which are not standardized and whose concordance is not established. A multicentre study group therefore compared testing for IgG anti-OKT3 antibody among seven laboratories. A set of 270 sera was obtained from 30 heart, 30 kidney and 30 liver transplant recipients with no previous exposure to OKT3 who were receiving OKT3 for induction immunosuppression. Sera were collected from each patient prior to and at 24 +/- 2 days and 31 +/- 2 days following initial OKT3 exposure. Identical aliquots of all 270 sera were tested for IgG anti-OKT3 antibody by each laboratory. In addition, the limit of detection of each laboratory's method was estimated by titration of an affinity-purified IgG anti-OKT3 reference material of known concentration. Anti-OKT3 antibody formation differed greatly among the three organ groups. Cardiac patients demonstrated the least sensitization and almost exclusively lower titres, while kidney recipients had more frequent and higher titre antibody formation. Liver recipients yielded the highest sensitization rate and the most frequent high titre sera. Importantly, the seven laboratories differed widely in the number of pretreatment sera reported as positive (ranging from 0% to 41% among laboratories), the number of post-OKT3 sera reported as positive (17-63%), the number of post-OKT3 samples with titre > or = 1000 (2-31%), and the number of patients sensitized 19-69%). Concordance among laboratories was highly variable, with interlaboratory agreement ranging from 38% to 83% on the sample titres assigned to 180 post-OKT3 sera. Many of the discordant results were consistent with differences in the limit of detection of the analytical methods, which ranged from 0.19 microgram/ml to > or = 15 micrograms/ml, a nearly 100-fold difference among laboratories. This study demonstrated the presence of both good concordance and significant discordance among laboratories in determining human anti-mouse antibody titres, and demonstrated that common titre categories (100, 1000, 10,000) were not equivalent among laboratories. The level of concordance among methods should be considered when comparing anti-OKT3 antibody results from different centres and their correlation with clinical events. Universal comparative testing, patterned after proficiency testing programmes, is needed to assess differences among laboratories and to bring uniformity and a sound interpretative basis to this field of testing.     

Evaluation of different methods of catching anopheline mosquitoes in western Venezuela

During a longitudinal study of vector biology and malaria transmission in western Venezuela, adult mosquitoes were collected by different methods and their efficiency was compared with human landing catches. CDC light traps, a double-net, a calf-baited trap and collection of resting mosquitoes on vegetation were tested. These methods did not prove to be effective substitutes for human landing catches.     

Molecular cloning and nucleotide sequencing of a novel aminoglycoside 6'-N-acetyltransferase gene from an R-plasmid of Salmonella typhimurium S24 isolated in Taiwan

A conjugative aminoglycoside resistance plasmid pST2 has been isolated from Escherichia coli K-12 14R525, which was mated with a clinical isolate of Salmonella typhimurium S24. A novel resistance gene of aminoglycoside 6'-N-acetyltransferase[AAC(6')] was cloned from plasmid pST2 on a 1,393 kilobase (kb) of SphI-SalI fragment into vector pACYC184 and pUC18. This novel AAC(6') gene in plasmid pST2 acetylated kanamycin, amikacin, dibekacin, tobramycin, gentamicin, netilmicin, and sisomicin. The complete nucleotide sequence of the novel AAC(6') gene and its neighboring sequences were also determined. Minicell experiments detected only one protein of 24.7 kilodaltons (kDa) translated from an open reading frame of the 618 base pairs (bp) gene.     

Cell cultures and nephrolithiasis

Large bone flaps for free transfer can be successfully and safely harvested based on the deep branch of the superior gluteal artery. The anatomy is consistent, the vessels are large, and the complications of this technique are minimal.     

The prevalence of preferential nasal breathing in adults

The prevalence of preferential nasal breathing was studied in an awake adult population. One hundred and ninety-four people consented to gentle manual compression of the nostrils. They were advised to 'breathe in and out', but no further information regarding breathing was given to avoid influencing the patient. One hundred and eighty patients (92.8%) commenced immediate regular relaxed breathing. Fourteen patients (7.2%) had difficulty with oral breathing which ranged from irregular mouth breathing associated with distress to no spontaneous respiration. The prevalence of preferential nasal breathing was strongly associated with increasing age (chi 2 for trend, P = 0.007). In addition, a weakly significant association was demonstrated between a history of asthma and this phenomenon (P = 0.047). These findings suggest a tendency for the elderly person to revert to the infant pattern of obligate nasal breathing. Physicians should be aware of this possibility in the elderly patient, especially prior to any procedure which may induce nasal obstruction.     

Neurotoxic effects of sodium nitroprusside in rat hippocampal slices

The effect of a permanent transection on myelin gene expression in a regenerating sciatic nerve and in an adult sciatic nerve was compared to establish the degree of axonal control exerted upon Schwann cells in each population. First, the adult sciatic nerve was crushed, and the distal segment allowed to regenerate. At 12 days post-crush, the sciatic nerve was transected distal to the site of crush to disrupt the Schwann cell-axonal contacts that had reformed. Messenger RNA (mRNA) levels coding for five myelin proteins were assayed in the distal segment of the crush-transected nerve after 9 days and were compared to corresponding levels in the distal segments of sciatic nerves at 21 days post-crush and 21 days post-transection using Northern blot and slot-blot analysis. Levels of mRNAs found in the distal segment of the transected and crush-transected nerve suggested that Schwann cells in the regenerating nerve and in the mature adult nerve are equally responsive to axonal influences. The crush-transected model allowed the genes that were studied to be classified according to their response to Schwann cell-axonal contact. The levels of mRNAs were 1) down-regulated to basal levels (P0 and MBP mRNAs), 2) down-regulated to undetectable levels (myelin-associated glycoprotein mRNAs), 3) upregulated (mRNAs encoding 2'3'-cyclic nucleotide phosphodiesterase and beta-actin), or 4) not stringently controlled by the removal of Schwann cell-axonal contact (proteolipid protein mRNAs). This novel experimental model has thus provided evidence that the expression of some of the important myelin genes during peripheral nerve regeneration is dependent on continuous signals from the ingrowing axons.