Conduction block in vasculitic neuropathy

Vasculitis involving peripheral nerves usually presents as an acute asymmetrical axonal neuropathy. We report a 67-year-old man with a symmetrical subacute neuropathy in which nerve conduction studies showed prominent conduction block, a finding indicative of demyelination. Sural nerve biopsy showed a vasculitic neuropathy with invasion of blood vessel walls by inflammatory cells and a mixture of nerve fiber loss and demyelination. The demyelination in this case was presumably a consequence of subinfarctive nerve ischemia.     

Ex vivo gene therapy prevents chronic graft vascular disease in cardiac allografts

There continues to be considerable effort towards the construction of compound libraries targeted for the inhibition of protease enzymes. New tag-encoding methods for library deconvolution have been applied to this problem and there has been particular interest in novel solid-phase linkers for the introduction of key pharmacophore groups required for protease inhibition. Recent reports have tended to focus on nonpeptidic libraries, and, notably, structure-based design methods are now being applied to direct library design.     

The absence of p27Kip1, an inhibitor of G1 cyclin-dependent kinases, uncouples differentiation and growth arrest during the granulosa->luteal transition

The involvement of cyclin-dependent kinase inhibitors in differentiation remains unclear: are the roles of cyclin-dependent kinase inhibitors restricted to cell cycle arrest; or also required for completion of the differentiation program; or both? Here, we report that differentiation of luteal cells can be uncoupled from growth arrest in p27-deficient mice. In these mice, female-specific infertility correlates with a failure of embryos to implant at embryonic day 4.5. We show by ovarian transplant and hormone reconstitution experiments that failure to regulate luteal cell estradiol is one physiological mechanism for infertility in these mice. This failure is not due to a failure of p27-deficient granulosa cells to differentiate after hormonal stimulation; P450scc, a marker for luteal progesterone biosynthesis, is expressed and granulosa cell-specific cyclin D2 expression is reduced. However, unlike their wild-type counterparts, p27-deficient luteal cells continue to proliferate for up to 3.5 days after hormonal stimulation. By day 5.5, however, these cells withdraw from the cell cycle, suggesting that p27 plays a role in the early events regulating withdrawal of cells from the cell cycle. We have further shown that in the absence of this timely withdrawal, estradiol regulation is perturbed, explaining in part how fertility is compromised at the level of implantation. These data support the interpretation of our previous observations on oligodendrocyte differentiation about a role for p27 in establishing the nonproliferative state, which in some cases (oligodendrocytes) is required for differentiation, whereas in other cases it is required for the proper functioning of a differentiated cell (luteal cell).     

Ethnic variation of twinning rates in Malawi

To examine the usefulness of magnetic resonance imaging (MRI) in the preoperative determination of cancerous invasion, we examined 39 patients with advanced colorectal cancer with 0.5T MRI. We employed short inversion time inversion recovery (STIR) sequences, in addition to ordinary spin echo sequences for T1- and T2-weighted images. Preoperatively, the estimated depth of tumor invasion was classified into three grades according to MRI findings, and confirmed on the basis of surgical and histopathologic results. The depth of tumor invasion estimated preoperatively using STIR sequences corresponded well with the surgical and histopathologic results in 85% of the cases. In contrast, assessments based on T1-weighted images corresponded well in only 62% of the cases and T2-weighted images corresponded well in only 64%.     

Structure, subunit topology, and actin-binding activity of the Arp2/3 complex from Acanthamoeba

The Arp2/3 complex, first isolated from Acanthamoeba castellani by affinity chromatography on profilin, consists of seven polypeptides; two actin-related proteins, Arp2 and Arp3; and five apparently novel proteins, p40, p35, p19, p18, and p14 (Machesky et al., 1994). The complex is homogeneous by hydrodynamic criteria with a Stokes' radius of 5.3 nm by gel filtration, sedimentation coefficient of 8.7 S, and molecular mass of 197 kD by analytical ultracentrifugation. The stoichiometry of the subunits is 1:1:1:1:1:1:1, indicating the purified complex contains one copy each of seven polypeptides. In electron micrographs, the complex has a bilobed or horseshoe shape with outer dimensions of approximately 13 x 10 nm, and mathematical models of such a shape and size are consistent with the measured hydrodynamic properties. Chemical cross-linking with a battery of cross-linkers of different spacer arm lengths and chemical reactivities identify the following nearest neighbors within the complex: Arp2 and p40; Arp2 and p35; Arp3 and p35; Arp3 and either p18 or p19; and p19 and p14. By fluorescent antibody staining with anti-p40 and -p35, the complex is concentrated in the cortex of the ameba, especially in linear structures, possibly actin filament bundles, that lie perpendicular to the leading edge. Purified Arp2/3 complex binds actin filaments with a Kd of 2.3 microM and a stoichiometry of approximately one complex molecule per actin monomer. In electron micrographs of negatively stained samples, Arp2/3 complex decorates the sides of actin filaments. EDC/NHS cross-links actin to Arp3, p35, and a low molecular weight subunit, p19, p18, or p14. We propose structural and topological models for the Arp2/3 complex and suggest that affinity for actin filaments accounts for the localization of complex subunits to actin-rich regions of Acanthamoeba.     

Radiographic sizing for meniscal transplantation

Allograft or synthetic meniscal replacement has the potential to delay the arthritic sequelae of the meniscectomized knee. Meniscal implants must, however, be side and size specific. A cadaveric study was performed in which medial and lateral menisci were painted with a radiopaque tantalum powder-cyanoacrylic mixture. Radiographs of this preparation demonstrated reproducible relationships between each meniscus and established bony landmarks. When corrected for magnification, meniscal size could be derived from plain films. Meniscal width equaled the distance (coronal) from the peak of the tibial eminence to the periphery of the tibial metaphysis on anteroposterior films. Meniscal length was measured from lateral radiographs. Medial meniscal length was 80%, and lateral meniscal length was 70% of the measured sagittal length of the tibial plateau. Measurement error averaged 7.8% by these parameters.     

A study of the influence of fibre/resin adhesion on the mechanical behaviour of ultra-high-modulus polyethylene fibre composites

The interlaminar shear strength of unidirectional ultra-high-modulus polyethylene composites was measured as a means of accessing the level of fibre/epoxy resin adhesion for a number of different reinforcing yarns, produced by melt and gel-spinning. The fibres were shown to possess poor adhesive properties due partly to inadequate wetting associated with the inert polyolefine surface and also because of a weak boundary layer, formed by the segregation of low molecular weight impurities to the surface during fibre formation. The interlaminar shear strength was significantly increased by pretreating the reinforcement with an oxygen plasma. This improved wetting by producing oxygen-containing groups on the fibre surface and removed the weak boundary layer by the formation of a cross-linked skin. For a fixed fibre volume fraction, the interlaminar shear strength was found to be inversely proportional to the filament diameter. The other mechanical properties were shown to be largely independent of fibre/resin adhesion, with plasma treatment having little or no effect.     

Book reviews

Landscape and Power in Vienna

Robert Rotenberg

Baltimore and London, The John Hopkins University Press, 1995, ISBN 0-8018-4961-6, 416 pp, £33.00, ($39.95), hb

The Avebury Cycle

Michael Dames

London, Thames & Hudson Ltd, 2nd edition (revised), ISBN 0-500-27886-5, 240 pp, 201 illus., £10.95 ($16.95), pb

Landscapes of Settlement: prehistory to the present

Brian K. Roberts

London and New York, Routledge, 1996, ISBN 0-415-11968-5, x +181 pp, £47.50 hb, £16.99 pb

The Body Language of Trees: a handbook of failure analysis

Claus Mattheck & Helge Breloer (translator: Robert Strouts)

London, HMSO, 1996, ISBN 0 11 753067 0, 239 pp, £17.50     

Classifying tissue and structure in echocardiograms

The authors present a system to automatically classify structures and tissues in echocardiogram images. The approach uses a multiple-feature, hierarchical, fuzzy, neural network fusion solution to the problem. The technique appears to work well. The technique is general and can be applied to a variety of image processing problems not only in the medicine but other areas as well. The processing presented here is computationally expensive; every pixel is processed independently. However, there are several ways to improve performance. The most obvious is to take advantage of the parallelism. In addition, every pixel need not be processed. If only large cardiac structures, such as the left ventricle, need be classified, then processing of the compressed image through the binary nets is sufficient. Neighboring class information may be used as well. Finally, the authors have not accounted for time in the processing. There is a high degree of redundancy in the successive frames of video images. It is anticipated that including temporal information will increase both statistical and computational performance. Temporal information will also force smoothing of the images over time and give better classification performance to even those areas that do not move