Are combined orthopaedic and rheumatology clinics worth while?

The practice of holding combined orthopaedic and rheumatology clinics is widespread, but no attempt has been made to assess their usefulness. In a one year prospective study patients were randomised either to a combined clinic with a rheumatologist and an orthopaedic surgeon or to a clinic with an orthopaedic surgeon alone. The details of the patients'' disease, the interview, the surgeons'' and rheumatologists'' responses, and the patients'' opinions were recorded on questionnaires. Interviews were appreciably longer in the combined clinic, and more referrals for surgery were made. The rheumatologist correctly predicted the need for surgery in 95% of cases, and his presence in the clinic was considered desirable by the surgeon, principally when the referral letter was inadequate. It is concluded that most patients with rheumatic diseases can be seen more efficiently in routine orthopaedic clinics provided a good quality letter of referral is sent.     

The presence of pericytes and transitional cells in the vasculature of the human dental pulp: an ultrastructural study

The aim of this study was to determine the ultrastructural characteristics of the microvasculature of healthy human dental pulp, with particular reference to pericytes. Pulp tissue was taken from healthy impacted third molars following extraction. Eight teeth were obtained from 17- to 25-year-old patients and pulp tissue was processed for examination using standard techniques for transmission electron microscopy. The pulp was rich in capillaries composed of endothelial and peri-endothelial cells in a 4 : 1 ratio. Endothelial cells contained typical and abundant Weibel–Palade bodies. Three types of peri-endothelial cells were identified: pericytes, transitional cells and fibroblasts. Pericytes were embedded within the capillary basement membrane. Transitional cells were partly surrounded by basement membrane, but separated from the endothelium by collagen fibrils; fibroblasts were outside, but adjacent to the basement membrane and closely associated with collagen fibrils. Pericytes and transitional cells, but not peri-endothelial fibroblasts, contained low numbers of dense bodies similar to the endothelial Weibel–Palade bodies. Our observations are consistent with the hypothesis that, during normal tissue turnover, some pericytes may originate from endothelium and migrate away from the vessel wall to undergo transition to a fibroblastic phenotype.     

Longitudinal studies on human schistosomiasis

A major difficulty in understanding the epidemiology of human schistosomiasis has been to distinguish between acquired immunity and reduced exposure as possible reasons for an observed decline, in older individuals, of levels of superinfection or of reinfection after chemotherapy. A series of studies of Schistosoma mansoni infections in Kenya has been undertaken to approach this problem, by investigation of intensities of reinfection after treatment of individuals whose levels of contact with contaminated water is subsequently observed. Intensities of reinfection are highest among younger children, thereafter declining sharply. This decline can be attributed only in part to age-related changes in the duration and nature of exposure; there is also evidence for the development of an acquired resistance to reinfection that is dependent both on age and on previous experience of infection, and that may be immunologically mediated. Evidence has been obtained that the slow development of this acquired immunity with age may be associated with the early development and subsequent slow decline of inappropriate immune responses that 'block' the effect of potentially protective responses. Implications of these findings for immunological intervention through vaccination are discussed.     

High-Resolution Crystal Structures of Drosophila melanogaster Angiotensin-Converting Enzyme in Complex with Novel Inhibitors and Antihypertensive Drugs

Angiotensin I-converting enzyme (ACE), one of the central components of the renin-angiotensin system, is a key therapeutic target for the treatment of hypertension and cardiovascular disorders. Human somatic ACE (sACE) has two homologous domains (N and C). The N- and C-domain catalytic sites have different activities toward various substrates. Moreover, some of the undesirable side effects of the currently available and widely used ACE inhibitors may arise from their targeting both domains leading to defects in other pathways. In addition, structural studies have shown that although both these domains have much in common at the inhibitor binding site, there are significant differences and these are greater at the peptide binding sites than regions distal to the active site. As a model system, we have used an ACE homologue from Drosophila melanogaster (AnCE, a single domain protein with ACE activity) to study ACE inhibitor binding. In an extensive study, we present high-resolution structures for native AnCE and in complex with six known antihypertensive drugs, a novel C-domain sACE specific inhibitor, lisW-S, and two sACE domain-specific phosphinic peptidyl inhibitors, RXPA380 and RXP407 (i.e., nine structures). These structures show detailed binding features of the inhibitors and highlight subtle changes in the orientation of side chains at different binding pockets in the active site in comparison with the active site of N- and C-domains of sACE. This study provides information about the structure-activity relationships that could be utilized for designing new inhibitors with improved domain selectivity for sACE.     

Quantifying the impact of soil compaction on root system architecture in tomato (Solanum lycopersicum) by X-ray micro-computed tomography

Background and Aims

We sought to explore the interactions between roots and soil without disturbance and in four dimensions (i.e. 3-D plus time) using X-ray micro-computed tomography.

Methods

The roots of tomato Solanum lycopersicum ‘Ailsa Craig’ plants were visualized in undisturbed soil columns for 10 consecutive days to measure the effect of soil compaction on selected root traits including elongation rate. Treatments included bulk density (1·2 vs. 1·6 g cm⁻³) and soil type (loamy sand vs. clay loam).

Key Results

Plants grown at the higher soil bulk density exploited smaller soil volumes (P < 0·05) and exhibited reductions in root surface area (P < 0·001), total root volume (P < 0·001) and total root length (P < 0·05), but had a greater mean root diameter (P < 0·05) than at low soil bulk density. Swelling of the root tip area was observed in compacted soil (P < 0·05) and the tortuosity of the root path was also greater (P < 0·01). Root elongation rates varied greatly during the 10-d observation period (P < 0·001), increasing to a maximum at day 2 before decreasing to a minimum at day 4. The emergence of lateral roots occurred later in plants grown in compacted soil (P < 0·01). Novel rooting characteristics (convex hull volume, centroid and maximum width), measured by image analysis, were successfully employed to discriminate treatment effects. The root systems of plants grown in compacted soil had smaller convex hull volumes (P < 0·05), a higher centre of mass (P < 0·05) and a smaller maximum width than roots grown in uncompacted soil.

Conclusions

Soil compaction adversely affects root system architecture, influencing resource capture by limiting the volume of soil explored. Lateral roots formed later in plants grown in compacted soil and total root length and surface area were reduced. Root diameter was increased and swelling of the root tip occurred in compacted soil.     

Probing the basis of domain-dependent inhibition using novel ketone inhibitors of Angiotensin-converting enzyme

Human angiotensin-converting enzyme (ACE) has two homologous domains, the N and C domains, with differing substrate preferences. X-ray crystal structures of the C and N domains complexed with various inhibitors have allowed identification of active site residues that might be important for the molecular basis of this selectivity. However, it is unclear to what extent the different residues contribute to substrate domain selectivity. Here, cocrystal structures of human testis ACE, equivalent to the C domain, have been determined with two novel C domain-selective ketomethylene inhibitors, (5 S)-5-[( N-benzoyl)amino]-4-oxo-6-phenylhexanoyl- l-tryptophan (kAW) and (5 S)-5-[( N-benzoyl)amino]-4-oxo-6-phenylhexanoyl- l-phenylalanine (kAF). The ketone groups of both inhibitors bind to the zinc ion as a hydrated geminal diolate, demonstrating the ability of the active site to catalyze the formation of the transition state. Moreover, active site residues involved in inhibitor binding have been mutated to their N domain counterparts, and the effect of the mutations on inhibitor binding has been determined. The C domain selectivity of these inhibitors was found to result from interactions between bulky hydrophobic side chain moieties and C domain-specific residues F391, V518, E376, and V380 (numbering of testis ACE). Mutation of these residues decreased the affinity for the inhibitors 4-20-fold. T282, V379, E403, D453, and S516 did not contribute individually to C domain-selective inhibitor binding. Further domain-selective inhibitor design should focus on increasing both the affinity and selectivity of the side chain moieties.     

A review of the use of primates in studying human schistosomiasis

Rodents, useful models for studies of human schistosomiasis not ethically possible in man, are not satisfactory in every respect. Primates, in many ways better models than rodents, though too expensive for general use, remain invaluable for testing the relevance of rodent findings to man. Higher primates such as chimpanzees are ideal models but, as endangered species, should only be used for critical studies for which lower, nonhuman primates are unsuitable.     

Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion

The silkmoth chorion has provided a stimulating model for the study of evolution and developmental regulation of gene families. Previous attempts at inferring relationships among chorion sequences have been based on pairwise comparisons of overall similarity, a potentially problematic approach. To remedy this, we identified the alignable regions of low sequence variability and then analyzed this restricted database by parsimony and neighbor-joining methods. At the deepest level, the chorion sequence tree is split into two branches, called "alpha" and "beta." Within each branch, early- and late-expressing genes each constitute monophyletic groups, while the situation with middle-expressing genes remains uncertain. The HcB gene family appears to be the most basal beta-branch group, but this conclusion is qualified because the effect of gene conversion on branching order is unknown. Previous studies by Eickbush and colleagues have strongly suggested that ErA, HcA, and HcB families undergo gene conversion within a gene family, whereas the ErB family does not. The occurrence of conversion correlates with a particular tree structure; namely, branch lengths are much greater at the base of the family than at higher internodes and terminal branches. These observations raise the possibility that chorion gene families are defined by gene conversion events (reticulate evolution) rather than by descent with modification (synapomorphy).