Inherited retinal degeneration: exceptional genetic and clinical heterogeneity

The function of the retina is to detect light and to send appropriate signals to the brain in response. Inherited diseases that cause the retina to degenerate, leading to either partial or total blindness, affect approximately 1 in 3000 people. Rapid progress is being made in identifying the genetic causes of common, inherited retinal diseases, such as retinitis pigmentosa and macular degeneration, as well as some of the rare forms of retinal disease. Linkage studies of large families and candidate-gene screening of known retinal genes have already identified 59 independent genetic loci that can cause retinal degeneration. The astounding genetic and clinical heterogeneity that is being revealed is a 'nightmare' for those interested in molecular diagnostics but, at the same time, provides great insight into functional aspects of the normal retina.     

Equilibrium binding studies of non-claret disjunctional protein (Ncd) reveal cooperative interactions between the motor domains

Non-claret disjunctional protein (Ncd) is a minus end-directed microtubule motor required for normal spindle assembly and integrity during Drosophila oogenesis. We have pursued equilibrium binding experiments to examine the affinity of Ncd for microtubules in the presence of the ATP nonhydrolyzable analog 5'-adenylyl-beta, gamma-imidodiphosphate (AMP-PNP), ADP, or ADP + Pi using both dimeric (MC1) and monomeric (MC6) Ncd constructs expressed in Escherichia coli. Both MC1 and MC6 sediment with microtubules in the absence of added nucleotide as well as in the presence of either ADP or AMP-PNP. Yet, in the presence of ADP + Pi, there is a decrease in the affinity of both MC1 and MC6 for microtubules. The data for dimeric MC1 show that release of the dimer to the supernatant is sigmoidal with the apparent Kd(Pi) for the two phosphate sites at 23.3 and 1.9 mM, respectively. The results indicate that binding at the first phosphate site enhances binding at the second site, thus cooperatively stimulating release. Stopped-flow kinetics indicate that MgATP promotes dissociation of the Mt.MC1 complex at 14 s-1, yet AMP-PNP has no effect on the Mt.MC1 complex. These results are consistent with a model for the ATPase cycle in which ATP hydrolysis occurs on the microtubule followed by detachment as the Ncd.ADP.Pi intermediate.     

Current concepts and controversies in IgA nephropathy

A randomized, open trial involving 260 Tanzanian children, aged 1-5 years, with acute Plasmodium falciparum malaria was conducted to evaluate the efficacy of the combination antimalarial CGP 56697 (artemether and benflumetol), and to compare it with chloroquine, the standard drug used for malaria treatment in the Kilombero area. Children who had received rescue medication within the first 48 h or had a negative slide at the same time were excluded. Seven-day parasitological cure rates were 94% (95% CI 88-97.5) for CGP 56697 and 35.4% (95% CI 25.9-45.8) for chloroquine. Using the same definition, the 14-day parasitological cure rates were 86.4% (95% CI 78.5-92.2) for CGP 56697 and 10.3% (95% CI 5.1-18.1) for chloroquine. Gametocytes were more effectively suppressed by CGP 56697 than by chloroquine. There were no major adverse events with either drug. CGP 56697 is highly efficacious against P. falciparum in this area of Tanzania. The study contributes to the discussion on treatment strategies, particularly whether chloroquine may still fulfil its role as first-line drug in an area of high malaria transmission and very high levels of chloroquine resistance.     

Effect of butylated hydroxyanisole on catalase activity and malondialdehyde content in aging Zaprionus paravittiger (diptera)

Catalase activity and malondialdehyde (MDA) content were measured in whole body and mitochondrial homogenates of the banana fruit fly, Zaprionus paravittiger, fed on control and butylated hydroxyanisole (BHA, 10 mM) mixed diets. Catalase activity increased during the reproductive period and decreased thereafter with age. However, the MDA content increased with advancing age in both sexes. In general, females exhibited higher catalase activity and lower MDA content as compared to their male counterparts. BHA feeding increased catalase activity significantly during all age intervals in both sexes. Mitochondrial fractions had lower catalase activity and lower MDA content than whole body homogenates. However, the pattern of changes was similar in both homogenates with age as well as on antioxidant feeding. These results suggest that BHA strengthens the defense mechanism of the insects by increasing catalase activity and reducing MDA content which may be responsible for increased longevity of insects.     

Passive avoidance training and recall are associated with increased glutamate levels in the intermediate medial hyperstriatum ventrale of the day-old chick

In the young chick, the intermediate medial hyperstriatum ventrale is involved in learning paradigms, including imprinting and passive avoidance learning. Biochemical changes in the intermediate medial hyperstriatum ventrale following learning include an up-regulation of amino-acid transmitter levels and receptor activity. To follow the changes of extracellular amino acid levels during passive avoidance training, we used an in vivo microdialysis technique. Probes were implanted in chicks before training the animals, either on a methylanthranylate- or water-coated bead. One hour later, recall was tested in both groups by presenting a similar bead. An increase of extracellular glutamate levels accompanied training and testing in both groups; during training, glutamate release was higher in methylanthranylate-trained than in water-trained chicks. When compared with the methylanthranylate-trained chicks during testing, the water-trained chicks showed enhanced extra-cellular glutamate levels. No other amino acid examined showed significant changes. After testing, the chicks were anesthetized and release-stimulated with an infusion of 50 mM potassium. Extracellular glutamate and taurine levels were significantly increased in both methylanthranylate- and water-trained chicks. The presentation of methylanthranylate as an olfactory stimulus significantly enhanced glutamate levels, especially in methylanthranylate-trained chicks. The results suggest that such changes in extracellular glutamate levels in the intermediate medial hyperstriatum ventrale accompany pecking at either the water- or the methylanthranylate-bead. The taste of the aversant may be responsible for the greater increases found in methylanthranylate-trained birds.     

Two high-affinity monoclonal IgG2a antibodies with differing thermodynamic stability demonstrate distinct antigen-induced changes in protein A-binding affinity

Injection of anti-AChR antibodies in passive transfer experimental autoimmune myasthenia gravis (EAMG) results in increased degradation of acetylcholine receptor (AChR) and increased synthesis of AChR alpha-subunit mRNA. Passive transfer of anti-Main Immunogenic Region (MIR) mAb 35 in aged rats does not induce clinical signs of disease nor AChR loss. The expression of the AChR subunit genes was analyzed in susceptible and resistant rats. In aged EAMG resistant rats, no increase in the amount of AChR alpha-subunit mRNA was measured. In vivo AChR degradation experiments did not show any increase in AChR degradation rates in aged resistant rats, in contrast to young susceptible rats. Taken together, these data demonstrate that resistance of the AChR protein to antibody-mediated degradation is the primary mechanism that accounts for the resistance to passive transfer EAMG in aged rats.