An in vitro study of the reduction in wear of metal-on-metal hip prostheses using surface-engineered femoral heads

Although the wear of existing metal-on-metal (MOM) hip prostheses (1 mm3/10(6) cycles) is much lower than the more widely used polyethylene-on-metal bearings, there are concerns about the toxicity of metal wear particles and elevated metal ion levels, both locally and systemically, in the human body. The aim of this study was to investigate the possibility of reducing the volume of wear, the concentration of metal debris and the level of metal ion release through using surface-engineered femoral heads. Three thick (8-12 microm) coatings (TiN, CrN and CrCN) and one thin (2 microm) coating (diamond-like carbon, DLC), were evaluated on the femoral heads when articulating against high carbon content cobalt-chromium alloy acetabular inserts (HC CoCrMo) and compared with a clinically used MOM cobalt-chromium alloy bearing couple using a physiological anatomical hip joint simulator (Leeds Mark II). This study showed that CrN, CrCN and DLC coatings produced substantially lower wear volumes for both the coated femoral heads and the HC CoCrMo inserts. The TiN coating itself had little wear, but it caused relatively high wear of the HC CoCrMo inserts compared with the other coatings. The majority of the wear debris for all half-coated couples comprised small, 30 nm or less, CoCrMo metal particles. The Co, Cr and Mo ion concentrations released from the bearing couples of CrN-, CrCN- and DLC-coated heads articulating against HC CoCrMo inserts were at least 7 times lower than those released from the clinical MOM prostheses. These surface-engineered femoral heads articulating on HC CoCrMo acetabular inserts produced significantly lower wear volumes and rates, and hence lower volumetric concentrations of wear particles, compared with the clinical MOM prosthesis. The substantially lower ion concentration released by these surface-engineered components provides important evidence to support the clinical application of this technology.

A comparison of physiological responses and rating of perceived exertion in two modes of aerobic exercise in men and women over 50 years of age

OBJECTIVES

To compare the physiological responses and ratings of perceived exertion to aerobic dance and walking sessions completed at a self selected pace.

METHODS

Six women and six men with a sample mean (SD) age of 68 (7) years completed aerobic dance and walking sessions in random order. A treadmill test was performed by each subject from which peak oxygen uptake (.VO(2)) and maximum heart rates (HRmax) were determined. During the aerobic dance and walking sessions, heart rate and .VO(2) were measured continuously throughout. Rate of perceived exertion (RPE) was measured every three minutes throughout the session.

RESULTS

The sample means (SD) for %peak .VO(2) were 67 (17)% for the aerobic dance sessions and 52 (10)% for the walking sessions, and the %HRmax sample means (SD) were 74 (12)% for the aerobic dance sessions and 60(8)% for walking sessions. The sample mean (SD) RPE for the aerobic dance sessions was 11(2), and for the walking sessions it was 10(2).

CONCLUSIONS

%peak .VO(2), %HRmax, and RPE were significantly higher for aerobic dance than for walking. However, both the aerobic dance and walking sessions were of adequate intensity to improve aerobic fitness in most subjects. Further investigation into the relation between RPE and %peak .VO(2) in a field setting over representative exercise time periods would be useful.

Charcot neuroarthropathy in diabetes mellitus

Charcot neuroarthropathy has been recognised for over 130 years and yet it remains a major cause of morbidity for patients with diabetes mellitus and a continuing challenge for physicians. It is rare but it seems to be increasing in prevalence and this provides hope that with larger studies it will soon be possible to clarify the natural history and optimal treatment regimens. The underlying cause is thought to be trauma in a neuropathic foot that leads to a complex series of pathological processes culminating in bone and joint destruction and subsequent deformity. The acute reaction is often misdiagnosed and many patients present late with established deformity. Even when the diagnosis is considered at an early stage there are no definitive criteria or tests to confirm charcot neuroarthropathy and a high index of suspicion is necessary in any diabetic patient with a swollen warm foot in the presence of somatic or autonomic neuropathy. Treatment has traditionally involved the use of various methods to avoid weight bearing but recent work has begun to suggest that bisphosphonates might be able to arrest the acute process. In the long term, treatment involves a multidisciplinary approach aimed at providing appropriate footwear to reduce plantar pressures and avoid foot ulceration; in some circumstances this involves surgical correction of deformities before adequate footwear can be supplied. Further studies of the emerging treatments for Charcot neuroarthropathy are needed to provide long-term outcome data on morbidity and deformity.

[The effects of quinine on active motile responses and fine structure of isolated outer hair cells from the Guinea pig cochlea]

BACKGROUND

Large doses of quinine (as well as of salicylate) are known to produce reversible hearing loss and tinnitus. Cochlear outer hair cells seem to be the common site for the ototoxic effect of both drugs.

METHODS

Isolated outer hair cells from the guinea pig cochlea were exposed to ototoxic doses of quinine hydrochloride (0.05-1.5 mmol/l). The cells were examined using tight-seal whole-cell recording techniques and transmission electron microscopy.

RESULTS

Quinine exposure led to a hyperpolarization followed by a depolarization of the hair cells' membrane potential. It also caused a diminution of evoked rapid motile responses that was more apparent in response to hyperpolarizing than to depolarizing pulses. These effects were largely dose dependent and reversible. Ototoxic doses of quinine were not found to induce changes in turgor, shape or fine structure of outer hair cells such as those reported with ototoxic doses of salicylates in vitro.

CONCLUSIONS

The present in vitro findings show that quinine (as well as salicylate) directly and reversibly affects cochlear outer hair cells. They also indicate that the underlying mechanisms of quinine ototoxicity are considerably different to that of salicylate although both substances clinically lead to identical symptoms.

Incidence of Trypanosoma cruzi infection in two Guatemalan communities

The prevalence of human infection by Trypanosoma cruzi was assessed using an enzyme-linked immunosorbent assay (ELISA) in a serological survey in 1998 of 2 rural communities (SMH and PS) in Guatemala. In SMH (Department of Zacapa), where Rhodnius prolixus was the principal vector, the seroprevalence amongst 373 people tested was 38.8%. In PS (Department of Santa Rosa), where the main vector was Triatoma dimidiata, 8.9% of the 428 people tested were seropositive. The overall prevalence of seropositivity was higher in females than in males in both SMH (40% vs 36%) and PS (11.9% vs 4.9%), although this difference was significant only in PS. Historical seroconversion rates, estimated retrospectively by fitting a transmission model to the age-prevalence curves, were 3.8% per year in SMH and 0.5% per year in PS. There was some indication of a recent reduction in incidence in both villages. In PS, but not in SMH, both the observed prevalence and the estimated incidence rates were significantly higher in females than in males.

Expression patterns of cell wall-modifying enzymes during grape berry development

During ripening of grape (Vitis vinifera L.) berries, softening occurs concomitantly with the second growth phase of the fruit and involves significant changes in the properties of cell wall polysaccharides. Here, the activities of enzymes that might participate in cell wall modification have been monitored throughout berry development. Alpha-galactosidase (EC 3.2.1.22), beta-galactosidase (EC 3.2.1.23) and pectin methylesterase (EC 3.1.1.11) activities were present, but no polygalacturonase (EC 3.2.1.15), cellulase (EC 3.2.1.4), xyloglucanase (xyloglucan-specific cellulase EC 3.2.1.4) or galactanase (EC 3.2.1.89) could be detected. The accumulation of mRNAs encoding wall-modifying enzymes was examined by northern hybridization analysis. Transcripts for beta-galactosidase, pectin methylesterase, polygalacturonase, pectate lyase (EC 4.2.2.2) and xyloglucan endotransglycosylase (EC 2.4.1.207) were present during ripening, although polygalacturonase activity had not been detected in berry extracts. Cellulases could not be detected in ripening berries, either at the enzyme or mRNA levels. The increase in beta-galactosidase activity and mRNA is consistent with the observed decrease in type-I arabinogalactan content of the walls during ripening, and the detection of polygalacturonase and pectate lyase mRNAs might explain the increased solubility of galacturonan in walls of ripening grapes. Thus, the modification of cell wall polysaccharides during softening of grape berries is a complex process involving subtle changes to different components of the wall, and in many cases only small amounts of enzyme activity are required to effect these changes.

Clinical governance and operations management methodologies

The clinical governance mechanism, introduced since 1998 in the UK National Health Service (NHS), aims to deliver high quality care with efficient, effective and cost-effective patient services. Scally and Donaldson recognised that new approaches are needed, and operations management techniques comprise potentially powerful methodologies in understanding the process of care, which can be applied both within and across professional boundaries. This paper summarises four studies in hospital Trusts which took approaches to improving process that were different from and less structured than business process re-engineering (BPR). The problems were then amenable to change at a relatively low cost and short timescale, producing significant improvement to patient care. This less structured approach to operations management avoided incurring overhead costs of large scale and costly change such as new information technology (IT) systems. The most successful changes were brought about by formal tools to control quantity, content and timing of changes.

Use of Doppler ultrasound in leg ulcer assessment

Adequate patient assessment is the most important element of chronic wound management, and the use of holistic techniques enables practitioners to make informed clinical judgements. Doppler ultrasound is integral to the holistic assessment of leg ulcers. This article reviews the procedure for measuring ankle/brachial pressure indices using Doppler ultrasound and outlines various diagnostic tests that employ the Doppler principle.

A comparison of the anthropometric, strength, endurance and flexibility characteristics of female elite and recreational climbers and non-climbers

There is limited information on the anthropometry, strength, endurance and flexibility of female rock climbers. The aim of this study was to compare these characteristics in three groups of females: Group 1 comprised 10 elite climbers aged 31.3 +/- 5.0 years (mean +/- s) who had led to a standard of 'hard very severe'; Group 2 consisted of 10 recreational climbers aged 24.1 +/- 4.0 years who had led to a standard of 'severe'; and Group 3 comprised 10 physically active individuals aged 28.5 +/- 5.0 years who had not previously rock-climbed. The tests included finger strength (grip strength, finger strength measured on climbing-specific apparatus), flexibility, bent arm hang and pull-ups. Regression procedures (analysis of covariance) were used to examine the influence of body mass, leg length, height and age. For finger strength, the elite climbers recorded significantly higher values (P < 0.05) than the recreational climbers and non-climbers (four fingers, right hand: elite 321 +/- 18 N, recreational 251 +/- 14 N, non-climbers 256 +/- 15 N; four fingers, left hand: elite 307 +/- 14 N, recreational 248 +/- 12 N, non-climbers 243 +/- 11 N). For grip strength of the right hand, the elite climbers recorded significantly higher values than the recreational climbers only (elite 338 +/- 12 N, recreational 289 +/- 10 N, non-climbers 307 +/- 11 N). The results suggest that elite climbers have greater finger strength than recreational climbers and non-climbers.

Distribution of members of the PSD-95 family of MAGUK proteins at the synaptic region of inner and outer hair cells of the guinea pig cochlea

PDZ-domain containing proteins of the MAGUK (membrane-associated guanylate kinase) family target, anchor, and cluster receptors and channels to subcellular sites. Among the MAGUK proteins, the members of the PSD-95 family (MAGUKs: PSD-95, PSD-93, SAP-97, and SAP-102) target and anchor glutamate receptors to the synaptic terminals. Associations of glutamate receptors with MAGUKs have been described in the brain but not in the cochlea. In this study, RT-PCR, immunofluorescence microscopy, and immunoelectron microscopy were used to investigate the presence and distribution of MAGUK proteins in the organ of Corti. The presence of the mRNA for PSD-95, PSD-93, SAP-97, and SAP-102 in the organ of Corti was confirmed by RT-PCR. Immunocytochemistry using a "pan-MAGUK" antibody, which recognizes all four MAGUK proteins, and selective antibodies against these proteins revealed that all four MAGUKs are present within the base of inner hair cells while all except SAP-97 are found within the base of the outer hair cells. In addition, PSD-93 and PSD-95 are found in postsynaptic afferent terminals on inner hair cells, while postsynaptic afferent terminals on outer hair cells have PSD-93.

The crystal structure of human phosphoglucose isomerase at 1.6 Å resolution: implications for catalytic mechanism, cytokine activity and haemolytic anaemia

Phosphoglucose isomerase (PGI) is a multifunctional protein, which, inside the cell, functions as a housekeeping enzyme of glycolysis and gluconeogenesis and, outside the cell, exerts wholly unrelated cytokine properties. We have determined the structure of human PGI to a resolution of 1.6 A using X-ray crystallography. The structure is highly similar to other PGIs, especially the architecture of the active site. Fortuitous binding of a sulphate molecule from the crystallisation solution has facilitated an accurate description of the substrate phosphate-binding site. Comparison with both native and inhibitor-bound rabbit PGI structures shows that two loops move closer to the active site upon binding inhibitor. Interestingly, the human structure most closely resembles the inhibitor-bound structure, suggesting that binding of the phosphate moiety of the substrate may trigger this conformational change. We suggest a new mechanism for catalysis that uses Glu357 as the base catalyst for the isomerase reaction rather than His388 as proposed previously. The human PGI structure has also provided a detailed framework with which to map mutations associated with non-spherocytic haemolytic anaemia.

Glutoxylon Chowdhury (Anacardiaceae): the first record of fossil wood from Bangladesh

This paper documents the first record of silicified fossil wood from a previously undescribed wood-rich horizon in the Sitakund Anticline, Eastern Bangladesh. The outcrop is composed of cross-stratified, fine-medium grained sandstones with bidirectional cross stratification indicative of a tidal environment, deposited ca. 5-5.2 million years before present (Miocene/Pliocene). The wood is characterised by large solitary vessels with alternate intervascular pits, banded parenchyma, uniseriate rays, and multiseriate rays with one radial canal per ray. This character combination closely resembles the wood of extant Gluta L. of the Anacardiaceae. This specimen has been assigned to the organ genus Glutoxylon Chowdhury erected for fossil woods with anatomical similarity to Gluta (including Melanorrhoea Wall.). The excellent preservation of this mature wood specimen illustrates the potential for using fossil wood from the Sitakund locality for palaeoecological studies in terms of biodiversity and adaptational response to climate change. Moreover such investigations of fossil woods from Bangladesh will compliment studies undertaken on fossil plants in other parts of Central and Southeastern Asia which will further the understanding of plant migration routes between India and Southeast Asia during the Tertiary.

Emergency response to raccoon rabies introduction into Ontario

During 15 July to 4 October, 1999, rabies control programs were implemented with the objective being to contain the first three confirmed cases of raccoon rabies in Canada. The strategy, called point infection control (PIC) involved the use of three tactics: population reduction (PR), trap-vaccinate-release (TVR) and oral rabies vaccination with baits (ORV), to control the spread of raccoon rabies. A total of 1,202 raccoons (Procyon lotor) and 337 skunks (Mephitis mephitis) were captured and euthanized using 24,719 trap-nights in the three PR zones around the location of the three rabies cases, near Brockville, Ontario. That represented an 83% to 91% reduction in the raccoon populations in an approximate 225 km2 area around the three rabies cases. Raccoon density in the PR zones declined from 5.1-7.1/km2 to 0.6-1.1/km2 following control. All tested specimens were negative for rabies by the fluorescent antibody test (FAT). In addition, 1,759 raccoons and 377 skunks were intramuscularly vaccinated against rabies and released using 27,956 trap-nights in an approximate 485 km2 TVR zone implemented outside of the PR zones. A total of 856 cats from both PR and TVR areas were also captured, vaccinated and released. Cost for the three PIC operations was $363,000.00 Cdn or about $500.00 Cdn/km2. To further contain the outbreak, about 81,300 baits containing Raboral V-RG oral rabies vaccine were aerially distributed on 8 and 27 September 1999, to create an 8 to 15 km wide buffer zone (1,200 km2 area) of vaccinated raccoons immediately beyond the PR and TVR zones. This was the first time that V-RG was used in Canada to orally vaccinate free ranging raccoons against rabies. Baiting costs were $241,000.00 Cdn or about $200.00 Cdn/km2 including post baiting assessment costs. As of 31 August, 2000, thirty-five additional cases (38 in total) of raccoon rabies have occurred in the control and vaccination zones. This number is far below the level of rabies prevalence in USA jurisdictions where raccoon rabies was epizootic. In the future, PIC methodologies will continue to be used in Ontario to contain isolated cases of raccoon rabies.

Value of ST elevation in lead III greater than lead II in inferior wall acute myocardial infarction for predicting in-hospital mortality and diagnosing right ventricular infarction

ST elevation in lead III > II has a higher sensitivity than lead V4R in diagnosing right ventricular myocardial infarction. Lead III > II is also predictive of in-hospital mortality.

Crystal structure of a deacylation-defective mutant of penicillin-binding protein 5 at 2.3-A resolution

Penicillin-binding protein 5 (PBP 5) of Escherichia coli functions as a d-alanine carboxypeptidase, cleaving the C-terminal d-alanine residue from cell wall peptides. Like all PBPs, PBP 5 forms a covalent acyl-enzyme complex with beta-lactam antibiotics; however, PBP 5 is distinguished by its high rate of deacylation of the acyl-enzyme complex (t(12) approximately 9 min). A Gly-105 --> Asp mutation in PBP 5 markedly impairs this beta-lactamase activity (deacylation), with only minor effects on acylation, and promotes accumulation of a covalent complex with peptide substrates. To gain further insight into the catalytic mechanism of PBP 5, we determined the three-dimensional structure of the G105D mutant form of soluble PBP 5 (termed sPBP 5') at 2.3 A resolution. The structure is composed of two domains, a penicillin binding domain with a striking similarity to Class A beta-lactamases (TEM-1-like) and a domain of unknown function. In addition, the penicillin-binding domain contains an active site loop spatially equivalent to the Omega loop of beta-lactamases. In beta-lactamases, the Omega loop contains two amino acids involved in catalyzing deacylation. This similarity may explain the high beta-lactamase activity of wild-type PBP 5. Because of the low rate of deacylation of the G105D mutant, visualization of peptide substrates bound to the active site may be possible.