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1.
The cytochromes c are a useful model for the study of the pathways and mechanisms of assembly of the cofactor-containing components of energy transducing membranes. Genetic analyses have identified proteins that are required for the assembly of c-type cytochromes in mitochondria, bacteria and chloroplasts. The components of the pathway operating in fungal and animal mitochondria, i.e. the cytochrome (cyt) c and c1 heme lyases in the intermembrane space, were identified over a decade ago through the study of cytochrome deficiencies in Neurospora crassa and Saccharomyces cerevisiae. More recently, a large number of membrane or membrane-associated components were identified in various alpha- and gamma-proteobacteria as c-type cytochrome assembly factors; they comprise an assembly pathway that is evolutionarily and mechanistically distinct from that in fungal and animal mitochondria. The components function not only in the lyase reaction but also in the delivery and maintenance of the substrates in a state that is suitable for reaction in the bacterial periplasm. Yet a third pathway is required for cytochrome maturation in chloroplasts. Genetic analyses of Chlamydomonas reinhardtii ccs mutants, which are pleiotropically deficient in both the membrane-anchored cytochrome f and the soluble cytochrome c6, revealed a minimum of six loci, plastid ccsA and nuclear CCS1 through CCS5, that are required for the conversion of the chloroplast apocytochromes to their respective holo forms. Sequence analysis of the cloned ccsA and Ccs1 genes indicates that the predicted protein products are integral membrane proteins with homologues in cyanobacteria, some gram-positive bacteria (Bacillus subtilis, Mycobacterium spp.), beta-proteobacteria (Neisseria spp.) and an epsilon-proteobacterium (Helicobacter pylori). CcsA and Ccs1 require each other for accumulation in vivo and are therefore proposed to function in a complex, possibly with the products of some of the other CCS loci. A tryptophan-rich motif, which has been proposed to represent a heme binding site in bacterial cytochrome biogenesis proteins (CcmC and CcmF), is functionally important in plastid CcsA. As is the case for CcmC and CcmF, the tryptophan-rich sequence is predicted to occur in a loop on the p-side of the membrane, where the heme attachment reaction occurs. Conserved histidine residues in the CcsA and Ccs1 may serve as ligands to the heme iron. A multiple alignment of the tryptophan-rich regions of the CcsA-, CcmC- and CcmF-like sequences in the genome databases indicates that they represent three different families.  相似文献   

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The prevalence of rheumatoid arthritis (RA) is about 0.5-1%. The disease course is variable, but RA causes substantial morbidity and mortality. The effect of conventional therapy for RA, i.e. nonsteroidal antiinflammatory drugs (NSAID), glucocorticosteroids and Slow Acting Anti-Rheumatic Drugs (SAARD) including methotrexate, gold salts, anti-malarials, d-penicillamine and salazopyrine, is often suboptimal. Since the aim of treatment is a complete remission, combination therapy, i.e. treatment with two or more SAARDs, may be feasible since an additive/synergistic effect may be obtained. In this paper the literature about the effectiveness and toxicity of combination therapy is reviewed. Only a few randomized, clinically controlled trials have been published. None of them have documented that gold salts, d-penicillamine and azathioprine in combination with other SAARDs are better than monotherapy. However, recent trials have indicated that methotrexate in combination with salazopyrine and hydroxychloroquine or in combination with cyclosporine may cause a better therapeutic effect than methotrexate alone, without additional toxicity. Long term studies of the effect of combination therapy are not yet available.  相似文献   

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A study of 6 series of concentrated and purified -- by ultracentrifugation -- dry cultural rabies vaccine inactivated with ultra-voilet rays demonstrated that in case of a 31--316 increase of concentration immunogenicity of the preparation rose 3--13-fold. Purification of the vaccine took place with its concentration. Additional purification of the concentrated vaccine on aluminium oxide led to a partial loss of the viral protein and to reduction of immunogenicity.  相似文献   

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Recent data indicate that rheumatoid arthritis is more often systemic, progressive, and disabling than benign, and that it reduces life expectancy. The new evidence argues for a dramatic alteration in pharmacologic management. If several months of rest, exercise, and anti-inflammatory therapy are ineffectual, aggressive treatment with disease-modifying antirheumatic and immunosuppressive agents may be in order.  相似文献   

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Songbirds have emerged as extremely important animals for investigating sex steroid hormone effects on the central nervous system. The masculinizing effects of exogenous estrogen on the neural circuits controlling song in female zebra finches are well documented. There is evidence that estrogens are necessary for the full activation of singing behavior in several species. These kinds of studies have led us and others to investigate the mechanisms whereby estrogens are made available to the brains of songbirds during development and adulthood. In this article, I review results of some of these studies examining the estrogen synthetic enzyme aromatase and its expression and activity in brain and in other tissues of songbirds. I will discuss some results and thoughts we have about the interactions of aromatase with the two remaining androgen-metabolizing enzymes in the avian brain, 5alpha-reductase, the enzyme that converts T into the active androgen 5alpha-dihydrotestosterone (DHT); and 5beta-reductase, the enzyme that converts T into the inactive 5beta-DHT. Finally, I will consider some ideas raised by these studies concerning potential sources of the androgen substrate for brain aromatization as well as some possible new functions that aromatase might be playing in the songbird telencephalon.  相似文献   

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OBJECTIVE: To document a cumulative experience with removal of the Telectronics 330-801 Accufix atrial lead after it was withdrawn from the market. DESIGN: We reviewed our results with 96 attempted lead extraction procedures through Dec. 1, 1995. MATERIAL AND METHODS: All patients underwent preoperative assessment, including fluoroscopic screening of the lead. Patients had blood typing and screening done before the extraction procedure, and extractions were performed with cardiac surgical intervention available. Pacing dependence was assessed to determine the need for temporary pacing. RESULTS: The mean patient age was 65.7 +/- 1.6 years and the mean duration of lead implantation was 31.0 +/- 1.4 months. Of the 96 lead extractions attempted, 94 were successful. Of the 96 cases, the retention wires were normal in 29, fractured without protrusion in 34, and fractured with protrusion in 33. Fifty-three leads were removed with use of simple traction only, and seven leads were removed by using a locking stylet and telescoping sheaths. The Cook workstation was used in the removal of 32 leads through the femoral vein; in 1 of these 32 patients, the retention wire was removed before lead extraction. The retention wire was removed but the lead was left intact in one patient. One lead was removed during an opertive maze procedure. Associated complications were minimal. CONCLUSION: Although lead extraction is a potentially fatal procedure, the Telectronics 330-801 Accufix atrial lead can be extracted safely with minimal morbidity when performed by experienced personnel.  相似文献   

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Design of highly selective biological substances made use of three basic components of a complex pathogenetic model of RA: the presence of antigen-presenting cells, genetic defects and autoimmune aggression. Efforts now are directed to development of monoclonal antibodies (MAB) to receptors of T-cells, B lymphocytes, MAB to CD 18 and CD54, cytokines, search for natural inhibitors of cytokines, introduction of cytokines. Many of such preparations including recombinant interferons proved clinically promising.  相似文献   

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To analyze the possible adverse effects of low dose methotrexate (MTX) therapy, 276 patients with rheumatoid arthritis (RA) were examined retrospectively. One hundred and seven patients (39%) experienced 113 adverse events : 57 showed liver dysfunction, 24 gastrointestinal complaints, 13 cutaneous symptoms, 6 respiratory symptoms, and 6 malignancies. Interestingly, 3 patients developed a dry cough without infiltration nor interstitial shadow on chest X-ray. The cough was rapidly resolved by discontinuation of MTX, but it recurred in 1 patient when MTX was re-administered. This finding might suggest a close association between MTX administration and the occurrence of dry cough. Of the 6 patients with malignancies diagnosed during MTX therapy, 2 showed malignant lymphoma, 2 lung cancer, 1 breast cancer and 1 colon cancer. MTX might have an oncogenic potential in RA because the coincidence rate, especially with respect to lymphoma, was significantly higher than estimated in a normal population.  相似文献   

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OBJECTIVE: To determine the efficacy of sodium fluoride (40 mg/day) in preventing rheumatoid arthritis (RA) induced bone loss, which may lead to osteoporosis. METHODS: We conducted an 18 month, randomized, double blind, placebo controlled trial in 38 patients with RA. The primary outcome measure was the difference in the percentage change between groups in lumbar spine bone mineral density (BMD) from baseline values after 18 months of therapy. The secondary outcome measures were the differences in the percentage change between groups in femoral neck, Ward's triangle, trochanter, and total body BMD from baseline after 18 months of therapy. RESULTS: There was a significant percentage difference (SD) between groups of 6.2% (7.3%) (p = 0.0005) in lumbar spine BMD after 18 months of treatment in favor of the fluoride group. The fluoride group experienced a 5.2% (8.4%) (p = 0.0125) increase, whereas the placebo group showed a 1.0% (4.8%) (p = 0.8015) decrease in lumbar spine BMD after treatment. No significant differences were found for the femoral neck, Ward's triangle, trochanter, and total body BMD in terms of the percentage changes from baseline within each treatment group or in the differences in the degree of change between groups after therapy. Lumbar spine BMD increased in about 80% of patients treated with fluoride (responders) compared to 44% of patients treated with placebo. CONCLUSION: The results showed that fluoride therapy was well tolerated and increased vertebral bone mass in patients with RA.  相似文献   

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Minocycline is arguably the most interesting new drug for rheumatoid arthritis since the development of methotrexate. Tetracycline compounds have long been used by rheumatologists who were considered mavericks by their peers, and recent controlled studies have demonstrated their antirheumatic activity. The reason that minocycline works is unclear, and their niche in the treatment of rheumatoid arthritis remains to be established. Nonetheless, it is clear that some patients with rheumatoid arthritis respond favorably to this form of treatment.  相似文献   

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The aim of this systematic review was to determine the effectiveness of dynamic exercise therapy in improving joint mobility, muscle strength, aerobic capacity and daily functioning in patients with rheumatoid arthritis (RA). In addition, possible unwanted effects such as an increase in pain, disease activity and radiological progression were studied. A computer-aided search of the MEDLINE, Embase and SCISEARCH databases was performed to identify controlled trials on the effect of exercise therapy. Randomized trials were selected on the effect of dynamic exercise therapy in RA patients with an exercise programme fulfilling the following criteria: (a) intensity level such that heart rates exceeded 60% of maximal heart rate during at least 20 min; (b) exercise frequency > or = 2 a week; and (c) duration of intervention > or = 6 weeks. Two blinded reviewers independently selected eligible studies, rated the methodological quality and extracted data. Six out of 30 identified controlled trials met the inclusion criteria. Four of the six included studies fulfilled > or = 7/10 methodological criteria. Because of heterogeneity in outcome measures, data could not be pooled. The results suggest that dynamic exercise therapy is effective in increasing aerobic capacity and muscle strength. No detrimental effects on disease activity and pain were observed. The effects of dynamic exercise therapy on functional ability and radiological progression are unclear. It is concluded that dynamic exercise therapy has a positive effect on physical capacity. Research on the long-term effect of dynamic exercise therapy on radiological progression and functional ability is needed.  相似文献   

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Two trials were carried out to compare the nutritional values of two Zambian indigenous plant protein sources--soy bean cake (SBC) and sunflower meal (SFM) in the diets of broilers and growing pigs. In trial 1, 120 one week old chickens (Abbor acre strain) were used. There were no differences (P > 0.05) between chickens on SBC and SFM in voluntary feed intake. Average daily gain of SBC chickens differed (P < 0.05) from those of SFM. The protein source had an effect (P < 0.05) on N retained [g/day]. Carcasses dry matter and crude protein were higher (P < 0.05) in SBC chickens, but ash, ether extract, Ca and P were the same as SFM. In trial 2, 12 Large white x Landrace growing barrows 1-2 months old were used. In this trial, SBC diet was consumed more than SFM. Pigs on SBC and SFM gained 0.526 and 0.284 g/head/day, respectively (P < 0.05). Nutrient digestibility was higher (P < 0.05) in SBC diet. Trial 1, demonstrated that SBC and SFM could be used for broilers without adverse effect on growth rate and body conformation. However, for growing pigs SBC is a better protein source than SFM in the tropical environment of Zambia. Finally, results obtained seem to suggest that SBC and SFM can be used as plant protein sources, but SFM is not an ideal plant protein source for growing pigs.  相似文献   

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