Heterogeneous mass distribution of the rubble-pile asteroid (101955) Bennu

The gravity field of a small body provides insight into its internal mass distribution. We used two approaches to measure the gravity field of the rubble-pile asteroid (101955) Bennu: (i) tracking and modeling the spacecraft in orbit about the asteroid and (ii) tracking and modeling pebble-sized particles naturally ejected from Bennu's surface into sustained orbits. These approaches yield statistically consistent results up to degree and order 3, with the particle-based field being statistically significant up to degree and order 9. Comparisons with a constant-density shape model show that Bennu has a heterogeneous mass distribution. These deviations can be modeled with lower densities at Bennu's equatorial bulge and center. The lower-density equator is consistent with recent migration and redistribution of material. The lower-density center is consistent with a past period of rapid rotation, either from a previous Yarkovsky-O'Keefe-Radzievskii-Paddack cycle or arising during Bennu's accretion following the disruption of its parent body.

The dynamic geophysical environment of (101955) Bennu based on OSIRIS-REx measurements

The top-shape morphology of asteroid (101955) Bennu is commonly found among fast-spinning asteroids and binary asteroid primaries, and might have contributed significantly to binary asteroid formation. Yet a detailed geophysical analysis of this morphology for a fast-spinning asteroid has not been possible prior to the Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission. Combining the measured Bennu mass and shape obtained during the Preliminary Survey phase of OSIRIS-REx, we find a significant transition in Bennu's surface slopes within its rotational Roche lobe, defined as the region where material is energetically trapped to the surface. As the intersection of the rotational Roche lobe with Bennu's surface has been most recently migrating towards its equator (given Bennu's increasing spin rate), we infer that Bennu's surface slopes have been changing across its surface within the last million years. We also find evidence for substantial density heterogeneity within this body, suggesting that its interior has a distribution of voids and boulders. The presence of such heterogeneity and Bennu's top-shape is consistent with spin-induced failure at some point in its past, although the manner of its failure cannot be determined yet. Future measurements by the OSIRIS-REx spacecraft will give additional insights and may resolve questions regarding the formation and evolution of Bennu's top-shape morphology and its link to the formation of binary asteroids.

Novel case-control observational method for assessing effectiveness of red-light cameras

Conventional methods for estimating the effect of an intervention suffer from selection bias, where the units that receive the treatment have different characteristics from those in the control group. This paper proposes a novel method that provides a specific criterion for selecting the control group. The method, called propensity score matching (PSM), was applied to the evaluation of red-light cameras (RLC) and its performance was compared with conventional cross-sectional and empirical Bayes methods. The application was performed using field data from the City of Ottawa involving 30 RLC intersections and 89 non-camera intersections observed for a period of 15 years. All three methods yielded fairly consistent results, indicating an increase in property damage collisions and a decrease in injury and fatal collisions. Given the strong theoretical basis of the PSM method and its ability to produce a more stable and reliable estimator, the method is recommended as a viable alternative to the conventional methods.

Automated ECG diagnostic P-wave analysis using wavelets

P-wave characteristics in the human ECG are an important source of information in the diagnosis of atrial conduction pathology. However, diagnosis by visual inspection is a difficult task since the P-wave is relatively small and noise masking is often present. This paper introduces novel wavelet characteristics derived from the continuous wavelet transform (CWT) which are shown to be potentially effective discriminators in an automated diagnostic process. Characteristics of the 12-lead ECG P-wave were derived using CWT and statistical methods. A normal control group and an abnormal (atrial conduction pathology) group were compared. The wavelet characteristics captured frequency, magnitude and variance components of the P-wave. The best individual characteristics (i.e. ones that significantly discriminated the groups) were entered into a linear discriminant analysis (LDA) for four different models: two-lead ECG, three-lead ECG, a derived three-lead ECG and a factor analysis solution consisting of wavelet characteristic loadings on the factors. A comparison was also made between wavelet characteristics derived form individual P-waves verses wavelet characteristics derived from a signal-averaged P-wave for each participant. These wavelet models were also compared to standard cardiological measures of duration, terminal force and duration divided by the PR segment. Results for the individual P-wave approach generally outperformed the standard cardiological measures and the signal-averaged P-wave approach. The best wavelet model on the basis of both classification performance and simplicity was the two-lead model that uses leads II and V1. It was concluded that the wavelet approach of automating classification is worth pursuing with larger samples to validate and extend the present study.

Internet based ECG medical information system

Physiological monitoring of humans for medical applications is well established and ready to be adapted to the Internet. This paper describes the implementation of a Medical Information System (MIS-ECG system) incorporating an Internet based ECG acquisition device. Traditionally clinical monitoring of ECG is largely a labour intensive process with data being typically stored on paper. Until recently, ECG monitoring applications have also been constrained somewhat by the size of the equipment required. Today's technology enables large and fixed hospital monitoring systems to be replaced by small portable devices. With an increasing emphasis on health management a truly integrated information system for the acquisition, analysis, patient particulars and archiving is now a realistic possibility. This paper describes recent Internet and technological advances and presents the design and testing of the MIS-ECG system that utilises those advances.

Breast papilloma: mammogram, ultrasound and MRI appearances

Breast papilloma are difficult to diagnose by triple assessment. Their symptoms, clinical signs and radiological appearances are differing widely. In this paper, we report the symptoms and clinical signs of 35 patients with proven breast papilloma and consider the relative merits of mammography, ultrasound scans and magnetic resonance imaging in their assessment.

Clinical and histopathological correlation of nasal polyps: are there any surprises?

Nasal polypectomy is a common operation. There is debate about whether all nasal polyps removed at operation should be sent for histopathological examination. To investigate this, a prospective study was performed to check the correlation of clinical and histopathological examination. Three hundred and forty-four nasal polypectomy specimens during the period from September 1997 to September 1999 were sent for histopathological diagnosis, with the clinical diagnosis documented on the pathology form. The clinical diagnosis was then correlated with the histological diagnosis. Three hundred and twenty-eight specimens were diagnosed as inflammatory polyps and 16 as tumours, of which seven were malignant. There was a good correlation between the clinical and histological findings in 340 cases. There was disagreement between the forms and reports in four cases. When the notes were consulted, three cases had forms that were incorrectly filled in. There was only one unsuspected case of inverted papilloma in a polyp specimen, which looked like a benign inflammatory polyp. This study indicates there is a 99.7% correlation between clinical and histopathological diagnosis.

Assessment of iron status in cystic fibrosis patients

We investigated the use of soluble transferrin receptor (sTfR), together with more traditional measurements such as iron, transferrin and ferritin, to assess iron status in 70 adult cystic fibrosis patients. sTfR concentration was measured using particle-enhanced immunonephelometry. We found that 69% of subjects as determined by transferrin saturation had iron deficiency, but only 29% as determined by sTfR and 11% as determined by ferritin. We found a significant correlation between C-reactive protein (CRP) and both ferritin (r = 0.38, P = 0.0001) and transferrin saturation (r = -0.54, P < 0.0001). In addition, because the CRP concentration was elevated in 64% of subjects, we feel that the transferrin saturation was overestimating, and the ferritin underestimating, iron deficiency in these patients. The sTfR concentration, on the other hand, is unaffected by the acute-phase response and was therefore thought to be the most useful test for detecting iron deficiency in this group of patients.

Limbic encephalitis and antibodies to Ma2: a paraneoplastic presentation of breast cancer

A patient with atypical medullary breast cancer is described who presented with symptoms of limbic encephalitis. The patient's serum and CSF contained antibodies that reacted with the nervous system and the tumour. These antibodies recognised Ma2, a neuronal protein related to paraneoplastic limbic and brainstem encephalitis in men with testicular tumours. This report highlights the importance of testing for paraneoplastic antineuronal antibodies in cases of unexplained limbic encephalitis and suggests screening for breast cancer in women with antibodies predominantly directed to Ma2.

Cardiology questions for the MRCP (UK) examination

Images

Structural requirements for initiation of translation by internal ribosome entry within genome-length hepatitis C virus RNA

Cap-independent translation of hepatitis C virus (HCV) RNA is mediated by an internal ribosomal entry segment (IRES) located within the 5' nontranslated RNA (5'NTR), but previous studies provide conflicting views of the viral sequences which are required for translation initiation. These discrepancies could have resulted from the inclusion of less than full-length 5'NTR in constructs studied for translation or destabilization of RNA secondary structure due to fusion of the 5'NTR to heterologous reporter sequences. In an effort to resolve this confusion, we constructed a series of mutations within the 5'NTR of a nearly full-length 9.5-kb HCV cDNA clone and examined the impact of these mutations on HCV translation in vitro in rabbit reticulocyte lysates and in transfected Huh-T7 cells. The inclusion of the entire open reading frame in HCV transcripts did not lead to an increase in IRES-directed translation of the capsid and E1 proteins, suggesting that the nonstructural proteins of HCV do not include a translational transactivator. However, in reticulocyte lysates programmed with full-length transcripts, there were multiple aberrent translation initiation sites resembling those identified in some picornaviruses. The deletion of nucleotides (nt) 28-69 of the 5'NTR (stem-loop IIa) sharply reduced capsid translation both in vitro and in vivo. A small deletion mutation involving nt 328-334, immediately upstream of the initiator AUG at nt 342, also resulted in a nearly complete inhibition of translation, as did the deletion of multiple intervening structural elements. An in-frame 12-nt insertion placed within the capsid-coding region 9 nt downstream of the initiator AUG strongly inhibited translation both in vitro and in vivo, while multiple silent mutations within the first 42 nt of the open reading frame also reduced translation in reticulocyte lysates. Thus, domains II and III of the 5'NTR are both essential to activity of the IRES, while conservation of sequence downstream of the initiator AUG is required for optimal IRES-directed translation.

Chimeric hepatitis B virus core particles as probes for studying peptide-integrin interactions

An RGD-containing epitope from the foot-and-mouth disease virus (FMDV) VP1 protein was inserted into the e1 loop of the hepatitis B virus core (HBc) protein. This chimeric protein was expressed at high levels in Escherichia coli and spontaneously assembled into virus-like particles which could be readily purified. These fusion particles elicited high levels of both enzyme-linked immunosorbent assay- and FMDV-neutralizing antibodies in guinea pigs. The chimeric particles bound specifically to cultured eukaryotic cells. Mutant particles carrying the tripeptide sequence RGE in place of RGD and the use of a competitive peptide, GRGDS, confirmed the critical involvement of the RGD sequence in this binding. The chimeric particles also bound to purified integrins, and inhibition by chain-specific anti-integrin monoclonal antibodies implicated alpha 5 beta 1 as a candidate cell receptor for both the chimeric particle and FMDV. Some serotypes of FMDV bound to beta 1 integrins in solid- phase assays, and the chimeric particles competed with FMDV for binding to susceptible eukaryotic cells. Thus, HBc particles may provide a simple, general system for exploring the interactions of specific peptide sequences with cellular receptors.

A rapid anion exchange high-performance liquid chromatography method for the measurement of HbA2 in whole blood

We developed a binary gradient high-performance liquid chromatography (HPLC) method for measuring HbA2 in whole blood samples using a Pharmacia Mono Q column (1 mL) and measurement at 415 nm. The assay requires a simple lysis and centrifugation step before injection onto the column. We found good agreement of results between the HPLC method and the Helena column chromatography method. The within batch precision was 2-6% and between batch precision was 4-6%. We found that using 30 mM Tris buffers (pH 7-8) with a sodium chloride gradient resulted in short analysis times and good chromatographic separation of HbA2, HbS and HbA. We conclude that this is a robust assay for the diagnosis of beta-thalassaemia.

The solution conformational features of two highly homologous antigenic peptides of foot-and-mouth disease virus serotype A, variant A and USA, correlate with their serological properties

The solution structure of a peptide corresponding to the VP1 region 141-160 of foot-and-mouth disease virus (FMDV) serotype A variant USA has been studied by NMR and computer calculations and compared with the results from a study on a highly homologous peptide deriving from serotype A, variant A. The two peptides differ in their serological behavior and contain the immunodominant epitope of the virus which partly overlaps with its receptor binding region. Distance constraints, derived both from 2D and 3D homonuclear NMR and 2D-heteronuclear NMR experiments, were combined with DG calculations to yield 50 structures. After refinement through EM and restrained molecular dynamics simulations the selected structures shared several general features. In particular the 151-158 region was a helix in all cases while a large loop similar to that found in peptide A but comprising less residues and stabilized by an H-bond between the side chains of D147 and S150 was found in the majority of structures. A further loop, common to all structures, was identified around the RGD sequence (145-147). This was different from that found in the corresponding region of peptide A as were the conformations of the individual residues within the RGDX sequence. The different structural features shown by the two peptides were rationalized in terms of the S148 (peptide A) to F148 (peptide USA) mutation. The second mutation, that at position 153 (L in A, P in USA) did not appear to affect the structure of the peptide significantly although the different dimensions of the loop in the central region and the type of H-bond stabilizing it could be potentially ascribed to this second mutation. All criteria used pointed to different structural features for the two peptides consistent with their serological behaviour.

The solution structure of the immunodominant and cell receptor binding regions of foot-and-mouth disease virus serotype A, variant A

Abstract: The solution structure of a 20 amino acid long peptide corresponding to the region 141-160 of the envelope protein Vp1 from foot-and-mouth disease virus (FMDV) serotype A, variant A, has been determined by a combination of NMR experiments and computer calculations. The peptide contains both the immunodominant epitope as well as the sequence (RGD) used by the virus to bind the cell receptor in the initial stages of infection. These two sites have been shown to partially overlap. One hundred and thirty-five NMR distance constraints were used to obtain a set of 11 structures by distance geometry, minimization and molecular dynamics simulations. These structures were divided into two homogeneous families based upon backbone superimposition. The first and most populated family was characterized by a backbone RMS of 1.5 +/- 0.4 A, the second by a backbone RMS of 0.8 +/- 0.2 A. The two families had similar structural features and differed mainly in the backbone angles of G149. In the larger of the two families these angles favoured the formation of a loop comprising residues 147 to 152 and stabilized by a H-bond between NH of D147 and the CO of A152. In the second family, where this bond was absent, the peptide adopted in this region the shape of an irregular helix. The C-terminal half of the peptide (152-159) was similar in both families and largely helical. Similar structural features were also found within the VRGDS sequence (144-148) which was assigned to a beta-turn type IV. The features of the two families of structures were found to be different from those of the recently published X-ray structure of the antigenic loop of a chemically modified form of FMDV. Proposals accounting for these differences are provided which take into account the dual activity of the 141-160 sequence (i.e. antibody binding and cell invasion through receptor binding).

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.

Putative dimeric organization of nuclear receptor hormone-binding domains, deduced from hydrophobic cluster analysis

2D hydrophobic cluster analysis (HCA) protein sequence processing, efficient at low levels of sequence identity, leads to a coherent scheme for the structural organization of the hormone-binding domains (HBDs) of nuclear receptors. The typical serine protease inhibitor (serpin) fold, previously proposed, is confirmed as a likely framework for the hormone-binding domain and leads to a logical dimerization. Furthermore, homo- or hetero-dimerization creates sites where hormone could likely be bound, itself being an active component of the dimerization. This model fulfils many of the biochemical and biological data.

Crystal structure of a human rhinovirus neutralizing antibody complexed with a peptide derived from viral capsid protein VP2

The three-dimensional structure of the complex between the Fab fragment of an anti-human rhinovirus neutralizing antibody (8F5) and a cross-reactive synthetic peptide from the viral capsid protein VP2 has been determined at 2.5 A resolution by crystallographic methods. The refinement is presently at an R factor of 0.18 and the antigen-binding site and viral peptide are well defined. The peptide antigen adopts a compact fold by two tight turns and interacts through hydrogen bonds, some with ionic character, and van der Waals contacts with antibody residues from the six hypervariable loops as well as several framework amino acids. The conformation adopted by the peptide is closely related to the corresponding region of the viral protein VP2 on the surface of human rhinovirus 1A whose three-dimensional structure is known. Implications for the cross-reactivity between peptides and the viral capsid are discussed. The peptide-antibody interactions, together with the analysis of mutant viruses that escape neutralization by 8F5 suggest two different mechanisms for viral escape. The comparison between the complexed and uncomplexed antibody structures shows important conformational rearrangements, especially in the hypervariable loops of the heavy chain. Thus, it constitutes a clear example of the 'induced fit' molecular recognition mechanism.

Val-237 for Ala substitution in the TEM-2 beta-lactamase dramatically alters the catalytic efficiencies towards carbenicillin and ticarcillin

The mutant 554 of TEM-2 beta-lactamase was selected for a decrease in the resistance to carbenicillin of an Escherichia coli K12 carrier. The amino acid sequence of the mutant beta-lactamase was determined by manual Edman degradation analysis of proteolytic peptides. A single substitution Val for Ala was localized at position 237. The mutant exhibited only 2% of the catalytic efficiency of the wild-type enzyme towards carbenicillin and ticarcillin, whereas it retained 30-60% of the hydrolytic activity towards other penicillin and cephalosporin substrates. Carfecillin, the phenyl ester of the side-chain carboxyl group of carbenicillin, was hydrolysed as a good substrate. This suggests that the behaviour of the mutant enzyme towards carbenicillin may result from ionic rather than steric constraints. A molecular model of the Val-237 TEM-2 mutant suggests possible electrostatic interaction between Glu-171 and the carboxylic group of the side chain of carbenicillin.

The structure of an immunodominant loop on foot and mouth disease virus, serotype O1, determined under reducing conditions

Residues 136-159 of VPI of foot and mouth disease virus (FMDV) comprise the G-H loop of the protein and form a prominent feature on the surface of virus particles. This sequence contains an immunodominant neutralizing epitope, which can be mimicked with synthetic peptides, and includes an Arg, Gly, Asp motif which has been implicated in the binding of the virus to cellular receptors. Crystallographic analysis of native virus particles failed to resolve the structure of this region due to its disordered state. However, reduction of a disulphide bond between cysteine residues 134 of VP1 and 130 of VP2 caused the G-H loop to collapse onto the surface of the virus particle and allowed its conformation to be determined.

Stimulation of specific immune responses to simian immunodeficiency virus using chimeric hepatitis B core antigen particles

Subunit approaches to vaccines against viral diseases have resulted in the development of a number of methods for presentation of defined epitopes to the immune system. We have exploited a highly immunogenic presentation system based on hepatitis B core antigen (HBcAg) particles to produce a number of candidate vaccines against simian immunodeficiency virus (SIV). Recombinant particles have been produced in bacteria which carry multiple copies of defined or predicted neutralizing epitopes of SIV at a number of different sites within the particle. In parallel, a number of synthetic peptide-based SIV vaccines have been produced based on homology to reported neutralizing epitopes in human immunodeficiency virus. Although potent immune responses were elicited against both particulate and peptide forms of the antigen, neutralizing antibodies were not induced as judged by available assays.

Correlations between the conformations elucidated by CD spectroscopy and the antigenic properties of four peptides of the foot-and-mouth disease virus

The conformational features of four related antigenic peptides (A, B, C and USA) from the foot-and-mouth disease virus (FMDV) (VP1; 141-160 of serotype A, subtype 12), assessed by CD, were found to correlate with the serological properties of these peptides. The CD spectra of the four peptides, obtained under cryogenic and solvent titration conditions, were consistent with three conformational components (a left-handed extended helix, an alpha-helix and a 3(10) helix) for peptides A and C and four components (a beta-turn of type II, an alpha-helix, a gamma-turn and a 3(10) helix) for peptides B and USA. The amino acid substitutions at positions 148 and 153, which distinguish the peptides, are therefore responsible for both their conformational and antigenic differences.

Structural and serological evidence for a novel mechanism of antigenic variation in foot-and-mouth disease virus

Changes resulting in altered antigenic properties of viruses nearly always occur on their surface and have been attributed to the substitution of residues directly involved in binding antibody. To investigate the mechanism of antigenic variation in foot-and-mouth disease virus (FMDV), variants that escape neutralization by a monoclonal antibody have been compared crystallographically and serologically with parental virus. FMDVs form one of the four genera of the Picornaviridae. The unenveloped icosahedral shell comprises 60 copies each of four structural proteins VP1-4. Representatives from each of the genera have similar overall structure, but differences in the external features. For example, human rhinovirus has a pronounced 'canyon' that is proposed to contain the cell attachment site, whereas elements of the attachment site for FMDV, which involves the G-H loop (residues 134-160) and C-terminus (200-213) of VP1, are exposed on the surface. Moreover, this G-H loop, which is a major antigenic site of FMDV, forms a prominent, highly accessible protrusion, a feature not seen in other picornaviruses. It is this loop that is perturbed in the variant viruses that we have studied. The amino acid mutations characterizing the variants are not at positions directly involved in antibody binding, but result in far-reaching perturbations of the surface structure of the virus. Thus, this virus seems to use a novel escape mechanism whereby an induced conformational change in a major antigenic loop destroys the integrity of the epitope.

Auranofin-induced suppression of autoimmune antibody production and inflammation in genetically autoimmune-prone mice

The gold compound auranofin and lobenzarit (CCA) were compared in regard to effects on development of an autoimmune-like disease in MRL/1 mice, which normally develop elevated levels of serum anti-DNA antibodies and rheumatoid factor as well as joint lesions similar to those seen in patients with rheumatoid arthritis. MRL/1 mice, which are genetically prone to development of autoimmune disease, were given auranofin or lobenzarit by gavage for 15 weeks, starting at 6 weeks of age. Mice were examined periodically for immunological abnormalities as well as histologic changes in articular joints. The auranofin-treated mice showed marked diminution in development of anti-DNA antibodies and serum rheumatoid factor as compared to control animals. Although higher than in the auranofin-treated animals, CCA-treated mice also had lower levels of serum autoantibodies than those seen in the control animals. Examination of limb joints for histopathologic changes indicated that the auranofin-treated animals developed only the slightest evidence of lesions as compared to control animals. CCA-treated mice also had a lessening of lesion development compared to control animals, but lesions were more developed than in auranofin-treated mice. This study indicates that auranofin is more effective than CCA in diminishing development of autoimmunity in MRL/1 mice.

The structure of foot-and-mouth disease virus: implications for its physical and biological properties

The structure of foot-and-mouth disease virus has been solved at a resolution of 2.9 A by X-ray diffraction techniques. The overall structural organisation of the particle is similar to that seen in other picornaviruses but there are several unique features. Many of these help to explain its characteristic physical and biological properties. In particular the canyon or pit found at the surface of other picornaviruses is lacking, which has important implications for cell attachment and the process of infection. Also there are 60 large disordered protrusions at the surface corresponding to the major antigenic site. This disorder is of particular interest in relation to the striking ability of linear synthetic peptides to induce protective immunity against foot-and-mouth disease.

The three-dimensional structure of foot-and-mouth disease virus at 2.9 A resolution

The structure of foot-and-mouth disease virus has been determined at close to atomic resolution by X-ray diffraction without experimental phase information. The virus shows similarities with other picornaviruses but also several unique features. The canyon or pit found in other picornaviruses is absent; this has important implications for cell attachment. The most immunogenic portion of the capsid, which acts as a potent peptide vaccine, forms a disordered protrusion on the virus surface.

Pericardial obliteration by angiosarcoma

Primary cardiac angiosarcoma caused pericardial obliteration and death from tamponade in a 66 year old man.

Malignant melanotic schwannoma of the bronchus

A case of malignant melanotic schwannoma arising in the right upper lobe bronchus of a 27 year old man is presented. Tumours of this type most commonly occur in spinal nerve roots and are generally considered to be benign. The behaviour of those originating elsewhere is less predictable. As far as we are aware this is the first reported case affecting the respiratory tract.

Crystallization and preliminary X-ray diffraction analysis of foot-and-mouth disease virus

Foot-and-mouth disease virus has been crystallized with the objectives of (1) determining the composition and conformation of the major immunogenic site(s) and (2) comparing its structure with those of the related polio, rhino and Mengo viruses, representing the other three genera of the picornaviruses. Most of the work has been done with virus strain O1BFS 1860, which crystallized as small rhombic dodecahedra of maximum dimension 0.3 mm. Virus recovered from crystals was infectious, and was indistinguishable from native virus both in protein composition and buoyant density. The stability of the crystals in the X-ray beam was comparable with that of other picornavirus crystals and they diffracted to a resolution of better than 2.3 A. Initial analysis of the X-ray diffraction data shows the virus to be positioned on a point of 23 symmetry in a close-packed array so that examples of all the icosahedral symmetry elements, except the 5-fold axes, are expressed crystallographically. The cell dimensions are a = b = c = 345 A, alpha = beta = gamma = 90 degrees, with a space group of I23. The diameter of the virus particle is 300 A. Despite the small size of the crystals, diffraction data have been collected to a reasonable resolution using a synchrotron source. Phasing of the diffraction data will be attempted using the methods of molecular replacement.

Familial exudative vitreoretinopathy associated with familial thrombocytopathy

Two families with familial exudative vitreoretinopathy were studied in which platelet aggregation defects were found in all the affected members. The major defect observed was absent platelet aggregation with arachidonic acid. In addition platelet aggregation with collagen and adrenaline was reduced in one severely affected member. The implication of the platelet aggregation defect in the pathogenesis of this retinal vascular disorder is discussed.