The resurgence of TB and its implications for radiology

Tuberculosis is re-emerging as a major health threat. Between 1985 and 1990, the number of TB cases reported in the United States increased by more than 15%. In addition, multidrug-resistant strains of Mycobacterium tuberculosis have begun to proliferate. Multidrug-resistant tuberculosis is extremely difficult to treat and is associated with high mortality rates. Tuberculosis poses tremendous risk to certain populations, including HIV-positive or otherwise immunocompromised patients, the homeless and individuals in correctional facilities or nursing homes. Also, tuberculosis is the sixth most common occupationally acquired infection among laboratory workers. This article traces the etiology of tuberculosis and outlines diagnostic techniques and treatment modalities. It also discusses the role of radiologic technologists in screening patients with suspected tuberculosis.

Cigarette smoking increases the risk of rheumatoid arthritis. Results from a nationwide study of disease-discordant twins

OBJECTIVE

To test the hypothesis that cigarette smoking is associated with susceptibility to rheumatoid arthritis (RA) by comparing smoking history between twins with RA and their unaffected co-twins.

METHODS

Interview questionnaires on smoking history were administered to 79 identical (monozygotic [MZ]) and 71 same-sex nonidentical (dizygotic, [DZ]) twin pairs who were discordant for RA, recruited from the Arthritis and Rheumatism Council Twin Study. Results were expressed as odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

Although most twin pairs were concordant for smoking history, there was a strong association between ever smoking and RA in the MZ pairs (OR 12.0, 95% CI 1.78-513), with a similar trend observed in the DZ pairs (OR 2.5, 95% CI 0.92-7.87).

CONCLUSION

The discordance in cigarette smoking history for individuals who are at presumed identical genetic risk for RA supports other data suggesting the role of smoking in disease susceptibility.

Perturbations in the surface structure of A22 Iraq foot-and-mouth disease virus accompanying coupled changes in host cell specificity and antigenicity

BACKGROUND

Foot-and-mouth disease virus (FMDV) is an extremely infectious and antigenically diverse picornavirus of cloven-hoofed animals. Strains of the A22 subtype have been reported to change antigenically when adapted to different growth conditions. To investigate the structural basis of this phenomenon we have determined the structures of two variants of an A22 virus.

RESULTS

The structures of monolayer- and suspension-cell-adapted A22 FMDV have been determined by X-ray crystallography. Picornaviruses comprise four capsid proteins, VP1-4. The major antigenic loop of the capsid protein VP1 is flexible in both variants of the A22 subtype but its overall disposition is distinct from that observed in other FMDV serotypes (O and C). A detailed structural comparison between A22 FMDV and a type O virus suggests that different conformations in a portion of the major antigenic loop of VP1 (the GH loop, which is also central to receptor attachment) result in distinct folds of the adjacent VP3 GH loop. Also, a single mutation (Glu82-->Gly) on the surface of VP2 in the suspension-cell-adapted virus appears to perturb the structure of the VP1 GH loop.

CONCLUSION

The GH loop of VP1 is flexible in three serotypes of FMDV, suggesting that flexibility is important in both antigenic variability and structural communication with other regions of the virus capsid. Our results illustrate two instances of the propagation of structural perturbations across the virion surface: the change in the VP3 GH loop caused by the VP1 GH loop and the Glu82-->Gly change in VP2 which we believe perturbs the GH loop of VP1. In the latter case, the amplification of the sequence changes leads to differences, between the monolayer- and suspension-cell-adapted viruses, in host-cell interactions and antigenicity.

Electrostatic Protein-Protein Interactions: Comparison of Point-Dipole and Finite-Length Dipole Potentials of Mean Force

Based on summation of Coulombic interactions, a model is developed for finite-length dipole potentials of mean force in a salt-free dielectric continuum. Point-dipole and finite-length dipole potentials of mean force are compared for protein-protein interactions using parameters for bovine alpha-chymotrypsin. The two approximations made in the commonly used analytical point-dipole potentials of mean force are not valid at distances near contact. Relative to the finite-length dipole model, the high-temperature approximation overpredicts, and the point-dipole approximation underpredicts charge-dipole and dipole-dipole attractions.

Hospital input price indexes in Australia: are they worth the effort?

This paper summarises aspects of the design and use of hospital input price indexes, and describes four indexes produced in Australia in the last decade. It argues that there would be some benefit in establishing a routine national index, if it were designed to be low-cost. However, care should be taken to avoid excessive reliance on the results in the resource allocation and funding context. Input prices contribute relatively little in hospitals' expenditure changes. It is also necessary to monitor and manage changes in the volumes of inputs, and this is likely to be a more rewarding task.

Mg- and Ca-actin filaments appear virtually identical in steady-state as determined by dynamic light scattering

Dynamic light scattering measurements show that although Mg-actin polymerizes more rapidly than Ca-actin (actin at 0.04-0.4 mg/ml polymerized with 0.1 M KCl +/- 2 mM MgCl2 or CaCl2, at room temperature or at 10 degrees C), steady-state filaments exhibit nearly identical intensity autocorrelation functions and similar mean scattered intensities. The dynamic data are used to measure the persistence length of the filaments which is found to be 4.2 microns independent of the bound cation and of the actin concentration.

An experimental test of "the mozart effect": does listening to his music improve spatial ability?

This experiment was designed as a test of the 1993 findings of Rauscher, Shaw, and Ky who reported a positive effect of listening to classical music on spatial reasoning. Present results do not demonstrate the "Mozart effect." In our study, 114 students were pretested on items from the Raven's Progressive Matrices--Advanced Form, then instructed to listen to either 8 min. of Mozart's music, relaxation instructions, or silence. Then subjects were posttested on an equivalent set of Raven's items. The subjects were also asked to provide information about their musical background and preferences. All instructions and treatments were audiotaped and played to individual subjects through earphones in the university language laboratory, ensuring standardization of procedures. Subjects in all 3 treatment groups showed a practice effect, but this improvement in Raven's scores was not dependent on the type of treatment received. There were no differences in Raven's scores among groups before or after treatment so our results do not confirm the prior ones. There was no evidence that the brief music had a different effect on subsequent problem solving according to listeners' musical background and training.

A comparison of gene organization in the zwf region of the genomes of the cyanobacteria Synechococcus sp. PCC 7942 and Anabaena sp. PCC 7120

The region of the genome encoding the glucose-6-phosphate dehydrogenase gene zwf was analysed in a unicellular cyanobacterium, Synechococcus sp. PCC 7942, and a filamentous, heterocystous cyanobacterium, Anabaena sp. PCC 7120. Comparison of cyanobacterial zwf sequences revealed the presence of two absolutely conserved cysteine residues which may be implicated in the light/dark control of enzyme activity. The presence in both strains of a gene fbp, encoding fructose-1,6-bisphosphatase, upstream from zwf strongly suggests that the oxidative pentose phosphate pathway in these organisms may function to completely oxidize glucose 6-phosphate to CO2. The amino acid sequence of fructose-1,6-bisphosphatase does not support the idea of its light activation by a thiol/disulfide exchange mechanism. In the case of Anabaena sp. PCC 7120, the tal gene, encoding transaldolase, lies between zwf and fbp.

Structure and immunogenicity of experimental foot-and-mouth disease and poliomyelitis vaccines

The physico-chemical properties and immunogenicity of experimental vaccines against foot-and-mouth disease (FMD) and poliomyelitis, prepared by treatment of the viruses with N-acetylethyleneimine (AEI), formaldehyde or neutral red, have been studied. None of these reagents affects the rate of sedimentation of the particles or their reaction with antibody against the major immunogenic sites. FMD vaccines prepared by inactivation with AEI or neutral red, behaved like the untreated virus, in that they were disrupted on lowering the pH below 7. The RNA of the AEI-inactivated virus was degraded into slowly sedimenting molecules. Unlike AEI-inactivated virus, from which all the RNA could be extracted with phenol-SDS, the recovery from the neutral red inactivated virus was variable and was sometimes as low as 40%; this RNA gave a heterogenous profile in sucrose gradients. The capsid proteins in the AEI preparation migrated in SDS-PAGE to the same positions as those of untreated virus, but in the neutral red preparation there was evidence of cross-linking. In contrast, the formaldehyde-inactivated vaccine was stable below pH 7 and the RNA could not be released by extraction with phenol-SDS at pH 5, because the capsid proteins had become cross-linked and/or linked to the RNA. As with foot-and-mouth disease virus (FMDV), poliovirus which had been inactivated with formaldehyde did not release its RNA on extraction with phenol-SDS and the capsid proteins were also cross-linked. Surprisingly, although AEI cleaved the viral RNA slowly in situ, the virus was no longer infectious after 6 h. Neutral red did not reduce the infectivity of the virus. All of the preparations gave similar levels of neutralizing antibody after a single inoculation. The high levels obtained with the formaldehyde-inactivated vaccines have implications for the processing of fixed particles by the antigen-presenting cells.

Structural comparison of two strains of foot-and-mouth disease virus subtype O1 and a laboratory antigenic variant, G67

BACKGROUND

Foot-and-mouth disease viruses (FMDVs) are members of the picornavirus family and cause an economically important disease of cloven-hoofed animals. To understand the structural basis of antigenic variation in FMDV, we have determined the structures of two viruses closely related to strain O1BFS whose structure is known.

RESULTS

The two new structure are, like O1BFS, both serotype O viruses. The first, O1 Kaüfbeuren (O1K), is a field isolate dating from an outbreak of FMD in Europe in the 1960s. The second, called G67, is a quadruple mutant of O1K, generated in the laboratory, that bears point mutations conferring resistance to neutralizing by monoclonal antibodies, specific for each of the four major antigenic sites defined previously. The availability of the three related virus structures permits a detailed analysis of the way amino acid substitutions influence antigenicity. Structural changes are seen to be limited, in general, to the substituted side chain. For example, the GH loop of VP1, a highly antigenic and mobile protuberance which becomes ordered only under reducing conditions, was essentially indistinguishable in the three viruses despite the accumulation of up to four changes within its 15-residue sequence. At one of the other antigenic sites, however, changes between the two field strains did perturb both side-chain and main-chain structures in the vicinity.

CONCLUSIONS

The conservation of conformation of the GH loop of VP1 adds to the evidence implicating an integrin as the cellular receptor for FMDV, since this loop contains a conserved RGD (Arg-Gly-Asp) sequence structurally similar to the same tripeptide in some other integrin-binding proteins. Structural changes required for the virus to escape neutralization by monoclonal antibodies are generally small. The more extensive type of structural change exhibited by the field isolates probably reflects differing selective pressures operating in vivo and in vitro.

Thalamic contributions to attention and consciousness

A tacit assumption since the 19th Century has been that the neocortex serves as the "seat of consciousness." An unexpected challenge to that assumption arose in 1949 with the discovery that high-frequency EEG activation associated with an alert state requires the intactness of the brainstem reticular formation. This discovery became the impetus for nearly three decades of research on what came to be known as the reticular activating system. By the 1970s, however, methodological and philosophical controversies led to the general abandonment of subcortical theories of attention and consciousness, with a return to an almost exclusive focus upon the cortex. With recent advances in the neurosciences the focus is shifting once more, this time to the unique contributions of cortical, thalamic, and brainstem structures in mediating selective attention and perceptual awareness. This paper offers a nontechnical review of the history of these developments up to contemporary interest in the putative role of oscillatory EEG patterns in the integration of perceptual features of experience. It puts forward the thesis that a key to understanding attention and consciousness is an appreciation of the contributions of the thalamus to these cognitive processes.

Characterization of a zwf mutant of Synechococcus sp. strain PCC 7942

A mutant of the cyanobacterium Synechococcus sp. strain PCC 7942 carrying a disrupted gene encoding glucose-6-phosphate dehydrogenase (zwf) produced no detectable glucose-6-phosphate dehydrogenase as assessed by enzyme assay and Western blot (immunoblot) analysis. This mutant exhibited significantly impaired dark viability.

Sarcoidosis in systemic sclerosis: report of 7 cases

OBJECTIVE

To describe the clinical, radiologic, and pathologic features of coexistent systemic sclerosis (SSc) and sarcoidosis, 2 conditions of unknown cause associated with altered cellular immune response.

METHODS

We reviewed clinical information, results from laboratory and radiologic studies, and lung or lymph node biopsy samples of 7 patients with concurrent SSc and sarcoidosis evaluated at 2 academic referral centers between 1989 and 1993.

RESULTS

Each patient fulfilled American College of Rheumatology criteria for the classification of SSc. SSc and sarcoidosis developed simultaneously in 4 patients, whereas in 3 others sarcoidosis was diagnosed more than 6 years after the onset of SSc. The onset of sarcoidosis was characterized by fever, weight loss, or increasing respiratory symptoms. Each patient had radiographic evidence of intrathoracic lymphadenopathy and/or interstitial lung disease. Examination of lung or lymph node biopsies demonstrated noncaseating granulomas. Treatment with corticosteroids was associated with improved lung function.

CONCLUSION

Since sarcoidosis coexists with SSc more frequently than previously suggested, it should be considered in patients with SSc presenting with new pulmonary symptoms. Recognizing sarcoidosis in patients with SSc is important, since these patients may benefit from corticosteroid therapy.

Hydroxyl radical generation by coal mine dust: possible implication to coal workers' pneumoconiosis (CWP)

Occupational exposure to coal mine dust causes coal workers' pneumoconiosis (CWP) and other pulmonary diseases by mechanisms that remain unclear. Because the hydroxyl radicals (.OH) may play an important role in the pathogenesis of CWP, we studied the potential role of bituminous coal mine dust samples for catalyzing the generation of .OH from hydrogen peroxide (H2O2). These coal mine dusts evaluated represented two geographic areas with diversity in CWP prevalence. Electron spin resonance (ESR), with the aid of spin trapping techniques, was used to measure the .OH radical generation. Bituminous coal mine dusts representing the Pittsburgh seam in the eastern United States and Blind Canyon seam in the mid-western United States were used together with a standard coal dust obtained from the National Institute of Standards and Technology, Gaithersburg, MD. All the coal mine dust samples generated varying levels of .OH radicals from H2O2 in the presence of a .OH spin trap 5,5-dimethyl-l-pyrroline-N-oxide (DMPO). .OH radical generation by the coal from H2O2 was effectively inhibited by deferoxamine and catalase, but only partially inhibited by superoxide dismutase. Metal chelators DETAPAC and EDTA enhanced the radical generation. These results indicated that the Fenton reaction is predominantly involved in the generation of .OH radicals from H2O2. The .OH-generating potential of all the coal dusts showed a positive correlation with the surface iron content of coal mine dusts. In addition, the potential to induce lipid peroxidation by the coal samples exhibited a good correlation with the available surface iron. Based on the results presented here, we propose that higher concentrations of surface iron in coal mine dust may be involved in the generation of increased levels of .OH radicals and may play an important role in the development of CWP in different coal mining areas.

Effects of chemotherapy on ultrastructure of oesophageal squamous cell carcinoma

Seven oesophageal squamous carcinomas, treated with pre-operative chemotherapy (mitomycin-C, ifosfamide and cisplatin-MIC), with a course finishing 21 days prior to resection, were examined by electronmicroscopy. In one treated case detailed light microscopy failed to reveal any tumour. Five of the remaining six tumours showed cytotoxic damage in that apoptosis and unusual necrotic changes were observed in almost all the neoplastic cells. These features were not seen in untreated cases. In four additional cases, who received one pulse of MIC followed by biopsy or resection within 3-6 days, apoptotic changes were very pronounced and extensive and most neoplastic cells presented unusual degeneration with characteristic derangement of the cytoskeleton, destruction of organelles and accumulation of glycogen. The ultrastructural appearance of 18 untreated resected oesophageal squamous carcinomas was studied for comparison with the treated tumours. The study has demonstrated ultrastructural changes resulting from chemotherapy. Results suggest that the regimen is more effective against squamous carcinomas than against adenocarcinomas of the oesophagus, as judged by comparison with the results of a previous study.

Genetic and environmental factors in scleroderma

Recent epidemiologic research on scleroderma has been directed toward both genetic and environmental factors. The nature of any genetic contribution is unknown, although the major histocompatibility complex region is important in determining antibody response. Environmentally, an occupational basis in a small proportion of cases seems likely. There is no evidence to support the hypothesis that silicone gel breast implants are an important risk factor in the development of scleroderma.

Structure of an effector-induced inactivated state of ribulose 1,5-bisphosphate carboxylase/oxygenase: the binary complex between enzyme and xylulose 1,5-bisphosphate

BACKGROUND

Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) catalyzes the addition of CO2 to ribulose 1,5-bisphosphate in all photosynthetic organisms. During catalysis, the bisphosphate is depleted by reactions other than carboxylation and some of the products are potent inhibitors of rubisco. We have used one of these, xylulose 1,5-bisphosphate as an analogue of the natural substrate and co-crystallized it with the enzyme.

RESULTS

We have solved the crystal structure of Synechococcus rubisco with bound xylulose 1,5-bisphosphate to 2.3 A and compared it with the previously solved 2'-carboxylarabinitol 1,5-bisphosphate (2CABP) enzyme quaternary complex. Unlike 2CABP, xylulose 1,5-bisphosphate forms a binary complex with no activating CO2 or essential metal present. Five flexible elements that restrict access to the active site in the 2CABP complex also close off the active site in the xylulose 1,5-bisphosphate complex, stabilized by interactions with the hydrated form of the analogue.

CONCLUSIONS

Xylulose 1,5-bisphosphate induces closure of critical loops of the protein without essential cofactors resident at the active site. In the case of rubisco in one species, catalysis is completely inhibited.

Intracapillary glomerular metastases in a nephrectomy specimen removed for ipsilateral renal cell carcinoma

A case of intraglomerular metastases observed in a nephrectomy specimen removed for primary renal cell carcinoma is reported. The intraglomerular metastases arose by dissemination of malignant cells into the systemic circulation via invasion of the renal veins. Intraglomerular metastases are therefore an indicator of malignant dissemination which in turn should be associated with a poor prognosis. It is recommended that in nephrectomies undertaken for primary renal cell carcinoma at least one random block of renal cortex should be examined to confirm or exclude intraglomerular metastases.

Repeat dilation of Palmaz stents in pulmonary arteries: study of safety and effectiveness in a growing animal model

PURPOSE

This study assessed the technical feasibility and safety of repeat dilation of Palmaz stents in growing pulmonary arteries.

MATERIALS AND METHODS

Palmaz stents (1.2 cm long) were placed percutaneously into the pulmonary arteries of 20 newborn lambs. After 4 months, pulmonary arteriography was performed. Where vessel growth in excess of stent diameter had created a stenosis (> 15%), stents were dilated again percutaneously. Six months later, pulmonary arteriography was performed, before the animal was killed and histologic examination performed.

RESULTS

Twenty-four pulmonary artery stent placements were attempted; 23 were successful. One stent placement was unsuccessful owing to stent displacement from the balloon. Acute complications included branch pulmonary artery occlusion (n = 3) and stent displacement from the delivery balloon (n = 2). At 4 months, the desired degree of stenosis (> 15%) was achieved in 11 animals. The average stenosis was 35% (standard deviation, 16%; range, 17%-66%). The mean predilation stent diameter was 6 mm +/- 1.1 (range, 4-8 mm), and the final diameter of 8 mm +/- 1.4 (range, 6-10 mm), represented a 35% mean increase (P < .001). Complications included stent (n = 1) and branch vessel (n = 1) thrombosis. At 6-month follow-up, all stents were patent. Areas of previously noted branch thrombosis were fully recanalized in all cases. At histologic inspection, only a thin layer of neointima was found on the stents.

CONCLUSION

Repeat dilation of Palmaz stents may be safely performed in growing pulmonary arteries in an animal model. Neointimal hyperplasia is minimal in pulmonary artery stents.