Uncatalyzed assembly of spherical particles from SV40 VP1 pentamers and linear dsDNA incorporates both low and high cooperativity elements

The capsid of SV40 virion is comprised of 72 pentamers of the major capsid protein, VP1. We examined the synergism between pentamer-pentamer interaction and pentamer-DNA interaction using a minimal system of purified VP1 and a linear dsDNA 600-mer, comparing electrophoresis with electron microscopy and size exclusion chromatography. At low VP1/DNA ratios, large tubes were observed that apparently did not survive native agarose gel electrophoresis. As the VP1 concentration increased, electrophoretic migration was slower and tubes were replaced by 200 Å diameter particles and excess free pentamer. At high VP1/DNA ratios, a progressively larger fraction of particles was similar to 450 Å diameter virions. VP1 association with DNA is very strong compared to the concentrations in these experiments yet, paradoxically, stable complexes appear only at high ratios of VP1 to DNA. These data suggest a DNA saturation-dependent nucleation event based on non-specific pentamer-DNA interaction that controls assembly and the ultimate capsid geometry.     

Sudden unilateral hearing loss with simultaneous ipsilateral posterior semicircular canal benign paroxysmal positional vertigo: a variant of vestibulo-cochlear neurolabyrinthitis?

We describe 4 patients who all simultaneously developed a sudden total or partial unilateral sensorineural hearing loss and an unusual acute peripheral vestibulopathy in the same ear characterized by posterior semicircular canal benign paroxysmal positional vertigo with intact lateral semicircular canal function. Two patients also had ipsilateral loss of otolith function. The vertigo resolved in all 4 patients after particle-repositioning maneuvers. The findings of audiometry and vestibular tests indicated that the lesion responsible for this syndrome was probably located within the labyrinth itself rather than within the vestibulocochlear nerve and that it was more likely a viral vestibulocochlear neurolabyrinthitis than a labyrinthine infarction.     

A rapid quantitative D-dimer assay at admission correlates with the severity of community acquired pneumonia.

Previous research has shown a link between infectious inflammatory processes and hemostatic abnormalities. No data exist, however, on whether coagulation markers correlate with the severity of community-acquired pneumonia (CAP) at admission. We conducted a prospective, observational study in an Emergency Medicine Department of a primary care hospital. Sixty-eight patients admitted with CAP were included. Blood samples were collected at admission and assayed for D-dimer levels. D-dimers were correlated with the Pneumonia Patient Outcome Research Team (PORT) score and Acute Physiology and Chronic Health Evaluation II score on admission, with length of hospital stay, number of organ failures, time to defervescence and hospital mortality. D-dimer levels were positively correlated with the Acute Physiology and Chronic Health Evaluation II score (r = 0.44, P = 0.0002), the PORT score (r = 0.36, P = 0.002) and the length of hospital stay (r = 0.24, P = 0.046). Mean D-dimer levels of patients for whom hospitalization is recommended, according to PORT guidelines, were significantly higher than D-dimer levels of patients for whom hospitalization is not recommended (1.47 +/- 1.05 microg/ml and 0.71 +/- 0.79 microg/ml respectively; P = 0.006). The correlation between D-dimer levels and time to defervescence, development of organ system failure and outcome was not statistically significant. We conclude that D-dimer levels at admission may predict the severity of CAP.     

Determinants of ELISA D-dimer sensitivity for unstable angina pectoris as defined by coronary catheterization

Unstable angina pectoris is associated with elevated D-dimer levels. However, the operating characteristics (sensitivity, specificity, positive and negative predictive value) of the D-dimer assay for the diagnosis of coronary artery disease (CAD) are unknown. Using a prospective, observational design, we collected blood from 54 patients with unstable angina pectoris at admission and assayed for ELISA D-dimer levels. The sensitivity, specificity, and negative and positive prediction values for angiographically determined coronary artery disease were calculated at multiple discriminate levels. All patients underwent coronary catheterization. A statistically significant correlation was noted between ELISA D-dimer levels and age, male sex, hypertension, use of beta-blocker, fibrinogen levels and catheterization findings. No correlation was noted between ELISA D-dimer levels and degree of the coronary artery disease. Best results were provided at a discriminate level of 270 ng/ml, with sensitivity 70%, negative predictive value 72%, and overall accuracy 67%. All discriminate levels, however, provided values too low for diagnosis. In conclusion, ELISA D-dimer assay is a non-sensitive, non-specific test for coronary artery disease as defined by coronary catheterization. However, the assay adds information regarding the severity of disease in patients presenting with acute coronary syndrome.     

Prevalence,causes, and characterization of factor XI inhibitors in patients with inherited factor XI deficiency

Factor XI deficiency, an injury-related bleeding disorder, is rare worldwide but common in Jews in whom 2 mutations, Glu117Stop (type II) and Phe283Leu (type III), prevail. Mean factor XI activities in homozygotes for Glu117Stop and for Phe283Leu are 1 and 10 U/dL, respectively. Inhibitors to factor XI in patients with severe factor XI deficiency have been reported in a small number of instances. This study was undertaken to determine the prevalence of acquired inhibitors against factor XI in patients with severe factor XI deficiency, discern whether these inhibitors are related to specific mutations, and characterize their activity. Clinical information was obtained from unrelated patients with severe factor XI deficiency, and blood was analyzed for factor XI activity, inhibitor to factor XI, and causative mutations. Immunoglobulin G purified from patients with an inhibitory activity was tested for binding to factor XI, effects on activation of factor XI by factor XIIa and thrombin, and activation of factor IX by exogenous factor XIa. Of 118 Israeli patients, 7 had an inhibitor; all belonged to a subgroup of 21 homozygotes for Glu117Stop who had a history of plasma replacement therapy. Three additional patients with inhibitors from the United Kingdom and the United States also had this genotype and were exposed to plasma. The inhibitors affected factor XI activation by thrombin or factor XIIa, and activation of factor IX by factor XIa. The results imply that patients with a very low factor XI level are susceptible to development of an inhibitor following plasma replacement.     

Severe thalassaemia intermedia caused by interaction of homozygosity for α-globin gene triplication with heterozygosity for β thalassaemia

Summary A 3-year-old child was evaluated for β-thalassaemia intermedia. Molecular characterization including β-globin gene sequence analysis revealed heterozygosity for a single β-thalassaemia mutation, IVSI nt1 (GA). In addition the patient was found to be homozygous for α-globin gene triplication (ααα^anti3,7/ααα^anti3,7). The propositus has a significantly more severe phenotype than has been previously reported with this combination of genetic defects. In contrast, four individuals heterozygous for both triplicated α and for β-thalassaemia had a phenotype of thalassaemia minor, and a fifth had very mild thalassaemia intermedia.