Mapping nucleotides in the 126-kDa protein gene that control the differential symptoms induced by two strains of tobacco mosaic virus

The differential symptom determinants of the Holmes' masked (M) and U1 strains of tobacco mosaic virus previously were mapped to the 5'-coterminal open reading frame (ORF) encoding the 126-kDa protein and the N-terminal two-thirds of the 183-kDa protein. Both proteins influence viral RNA accumulation, but the function of, and impact on, symptom formation by large domains within the 126-kDa gene, which are not conserved with sequences in analogous ORFs from other related viruses, are unknown. In the current study, cDNA clones representing each strain (i.e., MIC-TMV and U1-TMV) were mutated in these nonconserved domains to further define the nucleotides responsible for mosaic symptom induction on Nicotiana tabacum. Progeny virus of a mutant containing only eight nucleotide substitutions from the MIC-TMV sequence to the U1-TMV sequence within the 126-kDa protein ORF of MIC-TMV induced U1-TMV-like symptoms. Single or multiple substitutions among these eight nucleotides further defined residues critical for symptom modulation. Complementary substitutions in the MIC-TMV and U1-TMV sequences did not always yield progeny virus that induced complementary visual symptoms. Progeny of some mutants contained second-site spontaneous mutations at specific positions shown to influence symptom phenotype. For a subset of the stable site-directed mutants, there was no correlation between severity of systemic symptoms and chlorotic lesion size or virus accumulation in these chlorotic lesions on inoculated leaves.

Effects of ambulation on foot oxygen tension in limbs with peripheral atherosclerosis

As walking a few steps increases the arteriovenous pressure difference for blood flow through the feet, we studied the effect of a brief period of walking on transcutaneous oxygen tension (tcPO2). Foot tcPO2 was measured using Clarke type electrodes before, during and after a brief period of repetitive walking on the treadmill in 15 patients with various degrees of arterial obstruction. TcPO2 was significantly higher during walking, than while standing on the treadmill, in limbs with severe disease manifested by toe systolic pressure <30 mmHg (mean change 0.7 kPa or 5 mmHg, P=0.001). Also, supine tcPO2 was significantly higher following periods of walking than before in limbs with toe pressure both below and above 30 mmHg (mean change 1.5 kPa or 11 mmHg, P<0.001). The results indicate that a brief period of walking increases skin oxygenation. Regimens of such exercise may promote healing in some limbs with arterial disease.

Enhanced cytochemical detection of viral proteins and RNAs using double-sided labeling and light microscopy

We have developed a double-sided labeling technique for detecting viral proteins or RNAs in plastic-embedded leaf tissue by immunocytochemistry or in situ hybridization, respectively, and light microscopy. The signal from the target was enhanced by double-sided labeling when compared with single-sided labeling because sections were submerged in labeling solutions with both sides accessible to antibodies or complementary RNAs. The additional label was visible during microscopic analysis. Background signal was decreased since the tissue was probed and washed under conditions where folds and creases in the tissue were minimized. This technique uses the same equipment and chemicals as for single-sided labeling, and thus adjustments for reagent expenditures are not necessary. The procedure should be applicable to animal and plant tissue.

Linkage analyses in British pedigrees suggest a single locus for Darier disease and narrow the location to the interval between D12S105 and D12S129

Darier disease is a dominantly inherited skin disorder in which there appears to be abnormal adhesion between keratinocytes. We and others have shown that the disease in some British pedigrees is closely linked to markers mapping to 12q23-q24.1. In the present study we have defined crossovers that enable us to narrow the location of the disease gene to the interval between the D12S105 and the D12S129 markers. This interval may be expected to be on the order of about 4 cM on the basis of linkage data obtained using the primary CEPH reference families. Our data provide further evidence for locus homogeneity: each of four large British pedigrees, two of which have previously been subjected to preliminary characterization, shows statistically significant evidence for linkage to markers mapping to 12q23-q24.1.

A mutation in the neurofibromatosis type 2 tumor-suppressor gene, giving rise to widely different clinical phenotypes in two unrelated individuals

We have sought mutations in the recently identified neurofibromatosis type 2 (NF2) tumor-suppressor gene in a large panel of NF2 patients, using PCR-based SSCP and heteroduplex analysis, followed by cloning and sequencing of appropriate PCR products. Two unrelated NF2 patients were found to have identical nonsense mutations caused by a C-to-T transition in a CpG dinucleotide that is a potential mutational hot spot in the NF2 tumor-suppressor gene. Unexpectedly, the two individuals had widely different clinical phenotypes, representing the severe Wishart and mild Gardner clinical subtypes. Analysis of DNA samples from different tissues of the mildly affected patient suggests that he is a somatic mosaic for the mutation.

Germline mutations in the neurofibromatosis type 2 tumour suppressor gene

The recent identification of the NF2 tumour suppressor gene has enabled large scale screening for pathological mutations in the gene. We have sought germline mutations in the NF2 gene by SSCP and heteroduplex analysis of cDNA and genomic DNA samples followed by cloning and sequencing of mutant alleles. In the present report we describe 11 putative pathological mutations, including five nonsense mutations, three short insertions or deletions causing frameshifts and three missense mutations. Most stop mutations and frameshift mutations were found in individuals expressing a severe phenotype while one of the three missense mutations was associated with a mild phenotype. Four unrelated NF2 patients of the 93 tested were found to have identical nonsense mutations caused by a C to T transition (C169) in a CpG dinucleotide, which is a potential mutational hotspot in the NF2 tumour suppressor gene.

Outcome criteria in patients with peripheral arterial disease

To adequately evaluate patients with chronic occlusive arterial disease several factors will need to be taken into account and documented. These include associated diseases such as diabetes mellitus. When surgical or endovascular therapy is applied, analysis of outcome must include the symptomatic status of the patient, the anatomic evidence of patency of the procedure and of the proximal and distal disease, the hemodynamic result, limb preservation, and mortality. All of these factors will provide a better global picture of the disease and information on how it can be best treated.

A new locus for autosomal dominant retinitis pigmentosa on chromosome 7p

Autosomal dominant retinitis pigmentosa (adRP) is known to result from mutations in two different retinal genes--rhodopsin and peripherin--while a third locus has been implicated by linkage data. However, families have been reported in which all three known loci have been excluded. We report linkage of adRP in one such family to two microsatellite markers on chromosome 7p. D7S435 has previously been localized to 7p13-15.1; D7S460, previously only localized to chromosome 7, maps to within 2 cM of D7S435 with a lod score of 12.15. Two point linkage analysis between these markers and adRP gave lod scores of 5.65 (theta = 0) and 4.19 (theta = 0.046) for D7S460 and D7S435, respectively. Multipoint analysis gave a maximum lod score of 8.22. These data strongly suggest a new adRP locus on chromosome 7p.

Elective foot surgery in limbs with arterial disease

Surgical correction of foot deformities is generally indicated to relieve the disability. The presence or suspicion of arterial disease may lead to the reluctance to operate because of the concern that healing might not occur, however. Twenty-three patients were referred for vascular assessment before elective foot surgery. There was little or no evidence of arterial disease in 15 limbs. In eight limbs there was unequivocal evidence of complete obstruction in the main limb artery. Contrary to what might be expected, healing after surgery occurred without difficulties in the limbs with arterial obstruction. The arterial disease as assessed by laboratory methods was not severe. The results indicate that elective foot surgery can be safely undertaken in some limbs. Simple laboratory methods for assessment of arterial circulation include measurements of distal blood pressure, skin temperature, transcutaneous oxygen tension, and assessment of digital pulsatility. A useful approach for estimating the chances of healing after elective surgery in limbs with arterial obstruction is formulated on the basis of the clinical and laboratory assessment.

Tissue penetration of clindamycin in diabetic foot infections

Serum and tissue samples were obtained during surgery from four diabetics with neuropathy who underwent debridement or amputation for foot infections while receiving clindamycin 600 or 900 mg iv. Clindamycin concentrations were assayed by radioimmunoassay. Clindamycin was detected in all serum and tissue samples (range: 0.04-2.8 mg/kg in tissues and 1.1-11.1 mg/L in serum). In nine of the eleven tissue samples the clindamycin concentration exceeded the MICs reported for many pathogens commonly involved in such infections. In only a single instance was the ratio of tissue to serum concentration < 0.13.

Ankle and toe systolic pressures comparison of value and limitations in arterial occlusive disease

Ankle and toe systolic pressures represent the most convenient and useful measurements in the assessment of limbs with arterial occlusive disease. Each is a sensitive index of the presence and severity of the arterial obstruction and they both correlate with angiographic findings and with the severity of the symptoms. The measurements can be used to follow individual patients, to study the natural history of the disease, to assess prognosis and plan management, and to evaluate long-term results of surgical and transcutaneous interventions. However, because of the limitations of the ankle pressures related to the rigidity of the arterial walls of the tibial vessels and the more distal site of the measurement in the toes, measurements of pressure in the toes should be included in the evaluation of arterial disease in all patients with diabetes, and in all limbs with severe ischemia.

Exclusion of chromosome 6 and 8 locations in nonrhodopsin autosomal dominant retinitis pigmentosa families: further locus heterogeneity in adRP

Genetic studies have revealed that 25 to 30% of autosomal dominant retinitis pigmentosa (adRP) families have mutations in the rhodopsin gene, while the remainder do not. More recently linkage data and mutation detection have demonstrated two further loci implicated in adRP, at an as yet unidentified gene on chromosome 8p and at the human gene homologue of the mouse Rds (Retinal Degeneration Slow) gene on chromosome 6p. We have previously reported exclusion of adRP from the rhodopsin locus on 3q in two large adRP families. We now report exclusion data for both families, on chromosomes 6 and 8, demonstrating that the adRP phenotype results from mutations in at least four locations.