Femoral neck stress fractures in military personnel--a case series

Femoral neck stress fractures (FNSF) are uncommon, representing 5% of all stress fractures. In military personnel, FNSF represents one of the more severe complications of training, which can result in medical discharge. Clinical examination findings are often non-specific and plain radiography may be inconclusive--leading to missed or late diagnosis of FNSF This paper highlights the significance of FNSFs in military personnel and alerts physicians to the potential diagnosis. We identified all military recruits, aged 17 to 26, who attended the Infantry Training Centre (Catterick, U.K.), over a four-year period from the 1st July 2002 to 30th June 2006, who had suffered a FNSF. The medical records, plain radiographs, bone scans and MRIs of the recruits were retrospectively reviewed. Of 250 stress fractures 20 were of the femoral neck; representing 8% of all stress fractures and an overall FNSF rate of 12 in 10,000 military recruits. FNSFs were most prevalent amongst Parachute Regiment recruits (1 in 250, p < 0.05). Onset of symptoms was most commonly between weeks 13-16 of training. The majority (17/20, 85%) of FNSFs were undisplaced, these were all treated conservatively. Three FNSFs were displaced on presentation and were treated surgically. Overall, the medical discharge rate was 40% (8/20). FNSFs are uncommon and the diagnosis remains a challenge to clinicians and requires a high index of suspicion in these young athletic individuals. In such individuals early referral for MRI is recommended, to aid prompt diagnosis and treatment and to prevent more serious sequelae.

Secondary prevention of osteoporosis: Calcium, Vitamin D and bisphosphonate prescribing following distal radial fracture

Over 200,000 osteoporotic fractures occur in the UK annually. Patients with fragility fractures are at highest risk of further fracture, though preventative treatment has been shown to reduce subsequent fracture incidence. We reviewed the pre- and post-fracture medication (via the PCTs and in-patient discharge letters) of all patients over 55 years who suffered a distal radial fracture between April 2003 and November 2004. Complete data was available for 175 patients (170 female): 95 were in-patients, 80 out-patients. Following distal radial fracture, calcium and Vitamin D was prescribed for 39 patients (22%), bisphosphonates to 16 patients (9%) and only 15 patients (8.5%) were referred for DEXA scanning. Higher rates of prescribing were seen in hospital, with over half of all in-patients started on fracture prevention treatment; however, less than a half of these patients continued to receive this medication in primary care. We believe, the results demonstrate a lack of health promotion opportunities to prevent future fracture, which is a common finding across healthcare systems nationally. Although there is clear focus and impetus for developing falls prevention services nationwide, this enthusiasm has not been translated across to bone health, despite the potential savings in terms of morbidity, mortality and healthcare costs. Important deficiencies in local services have been identified, particularly with respect to communication between secondary and primary care. This study has added weight to secure funding for a fracture liaison nurse in our institution; we suggest others follow suit and employ similarly dedicated personnel to ensure assessment and treatment for the prevention of further fractures.

Musculoskeletal tuberculosis in Bradford - a 6-year review

INTRODUCTION

Tuberculosis (TB) remains the most common cause of death from infectious disease world-wide. In the UK, the incidence of TB has risen by 25% over the last 10 years; extrapulmonary diagnosis remains challenging and can be delayed. This study evaluates the epidemiology of musculoskeletal tuberculosis in a large multi-ethnic UK city.

PATIENTS AND METHODS

A review of prospectively recorded data of incidence, anatomical site, ethnic distribution, treatment and drug resistance of musculoskeletal tuberculosis over a 6-year period was performed.

RESULTS

From January 1999 to December 2004, there were 729 TB notifications; 61 cases (8.4%) had musculoskeletal involvement. Of the patients, 74% were immigrants from the Indian subcontinent; nearly 50% had spinal involvement; 24 patients underwent surgical intervention; 29 were subjected to either diagnostic or therapeutic radiological intervention; and resolution of symptoms was achieved in 59 out of 61 cases.

CONCLUSIONS

This study highlights the high proportion of musculoskeletal TB in immigrant patients in an area with a relatively large at-risk population, but will also serve to alert physicians, in areas with smaller at-risk populations, of the possibility of musculoskeletal TB.

Gradual alteration of mitochondrial structure and function by beta-amyloids: importance of membrane viscosity changes, energy deprivation, reactive oxygen species production, and cytochrome c release

Intracellular amyloid beta-peptide (A beta) accumulation is considered to be a key pathogenic factor in sporadic Alzheimer's disease (AD), but the mechanisms by which it triggers neuronal dysfunction remain unclear. We hypothesized that gradual mitochondrial dysfunction could play a central role in both initiation and progression of sporadic AD. Thus, we analyzed changes in mitochondrial structure and function following direct exposure to increasing concentrations of A beta(1--42) and A beta(25--35) in order to look more closely at the relationships between mitochondrial membrane viscosity, ATP synthesis, ROS production, and cytochrome c release. Our results show the accumulation of monomeric A beta within rat brain and muscle mitochondria. Subsequently, we observed four different and additive modes of action of A beta, which were concentration dependent: (i) an increase in mitochondrial membrane viscosity with a concomitant decrease in ATP/O, (ii) respiratory chain complexes inhibition, (iii) a potentialization of ROS production, and (iv) cytochrome c release.

Dynamics and orientation of amphipathic peptides in solution and bound to membranes: a steady-state and time-resolved fluorescence study of staphylococcal delta-toxin and its synthetic analogues

The environment of both the hydrophilic and hydrophobic sides of alpha-helical delta-toxin are probed by tryptophanyl (Trp) fluorescence, when self-association occurs in solution and on binding to membranes. The fluorescence parameters of staphylococcal delta-toxin (Trp15 on the polar side of the amphipathic helix) and synthetic analogues with single Trp at position 5 or 16 (on the apolar side) were studied. The time-resolved fluorescence decays of the peptides in solution show that the local environment of their single Trp is always heterogeneous. Although the self-association degree increases with concentration, as shown by fluorescence anisotropy decays, the lifetimes (and their statistical weight) of Trp16 do not change, contrary to what is observed for Trp15. The first step of self-association is then driven by hydrophobic interactions between apolar sides of alpha-helices, whilst further oligomerization involves their polar side (Trp15) via electrostatic interactions. This is supported by dissociation induced by salt. For all self-associated peptides, the polarity of the Trp microenvironment was not significantly modified upon binding to phospholipid vesicles, as indicated by the small shifts of the fluorescence emission spectra and lifetime values. However, the relative populations of the lifetime classes vary with bound-peptide density similar to the rates of their global motions in bilayers or smaller particles. Quenching experiments by water or lipid-soluble compounds show changes of the orientation of membrane-inserted peptides, from probably dimers lying flat at the interface at low peptide density, to oligomers spanning the membrane and inducing membrane fragmentation at high peptide density.

Mechanism of factor IXa inhibition by antithrombin in the presence of unfractionated and low molecular weight heparins and fucoidan

Heparin exerts its anticoagulant activity by catalysing the inhibition of coagulation proteases by antithrombin (AT). Its main target is thrombin but it also catalyses the inhibition of the other serine-proteases of the coagulation cascade, such as factor IXa (fIXa). The aim of this study was to compare the catalysis of inhibition of blood fIXa by antithrombin in the presence of several sulfated polysaccharides with anticoagulant activity, i.e. heparin, three widely used in therapeutics low molecular weight heparins (LMWH) and fucoidan. Plots of the second-order rate constants of the fIXa-antithrombin reaction vs. the concentration of added heparin and LMWH are bell-shaped and fit the kinetic model established for thrombin-antithrombin reaction by Jordan R., Beeler D., Rosenberg R. (1979) J. Biol. Chem., 254, 2902-2913. In the ascending branch, the catalyst (C) binds quickly to the inhibitor (I) to form a catalyst-inhibitor (CI) complex which is more reactive towards the enzyme (E) than the free inhibitor, leading to the formation of an inactive enzyme-inhibitor complex (EI) and the release of free catalyst, in a rate-limiting second step. After a maximum corresponding to an optimal catalyst concentration, the decrease in the reaction rate was in keeping with the formation of a catalyst-enzyme (CE) complex, whose inactivation by the CI complex was slower than that of the free enzyme. Maximum second-order rate constants for the inhibition of fIXa by AT were 105, 6.8, 12.24 and 22 microM-1 min-1 with heparin, Enoxaparin, Fraxiparin and Fragmin, respectively, leading to 3500-, 225-, 405- and 728-fold increases in the inhibition rate in the absence of polysaccharide, respectively. Fucoidan yielded 23-fold increase in the fIXa-antithrombin interaction rate. The kinetic profiles obtained with this polysaccharide exhibited ascending branch which correlated well with the kinetic model based on the formation of binary complexes (CI or CE). Fucoidan was covalently conjugated with a fluorescent probe (DTAF) and used in conjunction with fluorescence anisotropy to follow its binding to antithrombin, heparin cofactor II (HCII), thrombin and fIXa. The binding of fucoidan to these proteins occurred with low affinities when compared to heparin and LMWH. Fucoidan had higher affinity for the inhibitor HCII compared to antithrombin and enzymes. These data suggest that binding of heparins and fucoidan to the inhibitor (CI) is required for the polysaccharide-dependent enhancement in the rate of neutralization of the enzyme by the inhibitor.

Pathology of idiopathic megarectum and megacolon

BACKGROUND

The aetiology and pathology of both idiopathic megarectum and idiopathic megacolon are unknown. In particular, it is unknown whether there are abnormalities involving enteric nerves or smooth muscle.

METHODS

Resected tissue was examined from 24 patients who underwent surgery for idiopathic megarectum, from six patients who had tissue resected for idiopathic megacolon, and 17 control patients who had surgery for non-obstructing large bowel cancer. Qualitative and quantitative histological examination was performed after staining with haematoxylin and eosin, periodic acid Schiff (PAS), Martius scarlet blue (MSB), and phosphotungstic acid haematoxylin (PTAH). Neural and glial tissue were examined after immuno-staining with S100 and PGP9.5.

RESULTS

Compared with controls, patients with idiopathic megarectum had significant thickening of their muscularis mucosae (median 78 v 33 microns, p < 0.005), circular muscle (1000 v 633 microns, p < 0.005), and longitudinal muscle (1083 v 303 microns, p < 0.005), despite rectal dilatation. This thickening was relatively greater in the longitudinal than in the circular muscle. Fibrosis of the longitudinal muscle was seen, using MSB staining, in 58%, of circular muscle in 38%, and of muscularis mucosae in 29% of patients. The relation between muscle thickening and fibrosis was variable. The density of neural tissue in the longitudinal muscle seemed to be reduced in patients with idiopathic megarectum. There was no thickening of enteric muscle or alteration in the density of innervation in patients with idiopathic megacolon.

CONCLUSION

There is notable thickening of the enteric smooth muscle in patients with idiopathic megarectum, but the architecture of the enteric innervation seems to be intact. Functional abnormalities of the latter remain a possible cause of the smooth muscle hypertrophy.

The haemodynamic effects of rocuronium and vecuronium are different under balanced anaesthesia

BACKGROUND

Rocuronium has been reported to have minimal haemodynamic effects. However, this conclusion has been drawn primarily from investigations conducted under narcotic-based anaesthesia. This study was designed to evaluate the cardiovascular effects of rocuronium under isoflurane/N2O/fentanyl anaesthesia and to compare rocuronium's haemodynamic effects to those of vecuronium and pancuronium.

METHODS

Anaesthesia was induced with fentanyl 2 micrograms/kg, thiopentone 4 mg/kg, and suxamethonium 0.5 mg/kg in 75 ASA I or II patients. After tracheal intubation, anaesthesia was maintained with isoflurane 0.5% and N2O 50% in oxygen. Five min after intubation (baseline), patients randomly received either vecuronium 100 micrograms/kg, rocuronium 600 micrograms/kg, rocuronium 900 micrograms/kg, rocuronium 1200 micrograms/kg, or pancuronium 140 micrograms/kg. One min after administration of muscle relaxant, mean arterial pressure (MAP) and heart rate (HR) were recorded and were subsequently measured at 1-min intervals for the next 4 min.

RESULTS

HR decreased significantly (P < 0.05) at all times compared to baseline in patients receiving vecuronium. HR significantly (P < 0.05) increased in those receiving rocuronium 1200 micrograms/kg or pancuronium. Patients who received vecuronium had a significant (P < 0.05) decrease in MAP at all times compared to baseline. Comparing results between groups, patients who received rocuronium or pancuronium had significantly (P < 0.05) higher MAP compared to those administered vecuronium.

CONCLUSION

The haemodynamic effects of rocuronium and vecuronium are different under balanced anaesthesia. Rocuronium may attenuate the fall in MAP that often occurs under balanced anaesthesia without surgical stimulation.

The safety and tolerability of sumatriptan: an overview

Safety information was pooled from 4,859 patients, mainly treated in controlled clinical trials with a dispersible tablet of sumatriptan or by a subcutaneous injection, and from 1,164 patients who received placebo by these routes. Safety monitoring involved collection of all adverse events, regardless of their relationship to treatment, and included routine laboratory screening tests and some special investigations. Individuals experienced several groups of symptoms that might be considered to be features of migraine itself or of the post-migraine period or due to treatment. The commonest complaints were an unpleasant taste or pain on injection. After oral sumatriptan (100-300 mg), some events (nausea, malaise) were characteristic of migraine and others (fatigue, sedation, weakness) were characteristic of the recovery period. With subcutaneous sumatriptan (4-8 mg) similar events were observed, but certain distinctive symptoms variously described as heaviness, pressure sensation, tingling, feelings of heat or warmth, were more common and affected various parts of the body. Their early onset and transient nature suggests some pharmacological mechanism, as yet not identified. Despite the mixed picture of symptoms recorded after treatment, they were not serious, they were transient and they were accepted by patients. Close patient monitoring allowed detailed evaluation of any possible cardiovascular side-effects as seen with other anti-migraine agents, particularly ergotamine. The evidence is reassuring but, since experience in patients with symptomatic ischaemic heart disease is limited, it is recommended that they should initially be treated with sumatriptan under medical supervision for their first two or three attacks.(ABSTRACT TRUNCATED AT 250 WORDS)

The amphiphilic alpha-helix concept. Consequences on the structure of staphylococcal delta-toxin in solution and bound to lipids

Staphylococcal delta-toxin, a synthetic analogue and a fragment were studied in order to determine their structure in solution and bound in lipids. In solution, a self-association process is observed. Analytical ultracentrifuge and quasi-elastic light-scattering experiments suggest an isodesmic aggregation in the high concentration domain above 2 microM up to very large asymmetrical species. Decreasing concentrations below 2 microM of delta-toxin and the analogue allows dissociation, probably into monomers. The self-associated species are essentially alpha-helical (70%) with buried and highly immobilized Trp either at position 15 for natural delta-toxin or 16 for the analogue. At the lowest concentration studied, the alpha-helix content severely decreases down to 35% while Trp fluorescence shows that these residues are exposed to buffer. The fragment 11-26 is always monomeric and structureless. From all the data, a structural model of aggregated species is proposed with stacked antiparallel amphipathic rods. When bound to lipids, whatever their initial structure in solution, 26-residue long peptides mainly adopt an alpha-helix conformation (80%) while fragment 11-26 exhibits about 50% alpha-helix. The lipid-peptide interactions were quantitatively analysed. For fragment 11-26, a single-step mechanism fits the spectroscopic changes and defines a single monomeric bound structure. On the other hand, for the 26-residue-long analogue, multiple-step processes must occur. The data were analysed with a partition of tetramers into lipids followed by a partial dissociation. Finally, the affinity of fragment 11-26 severely decreases from micelles to fluid and gel-state bilayers. The partition coefficient of the delta-toxin analogue is higher than those of other more apolar peptides, such as melittin and alamethicin, correlating with Eisenberg's hydrophobic moments. It is therefore proposed that delta-toxin probably lies parallel to the surface, only penetrating weakly in lipids, depending on their packing.

Different states of self-association of melittin in phospholipid bilayers. A resonance energy transfer approach

Melittin is known to self-associate as tetramers in solutions of high ionic strength. Here, an N-bromosuccinimide oxidized-Trp19 melittin is prepared. This derivative can act as an acceptor of the fluorescence of native melittin and is used in order to observe a possible self-association of melittin in phospholipid bilayers. Resonance energy transfer was shown to occur in solutions of high ionic strength, showing that oxidized melittin can associate with native melittin. In phospholipid bilayers, no association is detected in the absence of NaCl. In its presence, an equilibrium between monomeric melittin and oligomeric species is observed. These species are not dimers, but any other degree of association may account for our experimental results. Significant differences in characteristic transfer efficiency reveal differences in the structure of these oligomers according to the length or state of phospholipids (fluid or at the transition temperature). These bound complexes are also different from the soluble hetero-oligomer. Some models of bound complexes are proposed which may explain the leakage and the further disruption of vesicles or cells induced by melittin.

Adverse reactions to acetylcysteine and effects of overdose

Since the introduction in 1979 of intravenous acetylcysteine (Parvolex) as an antidote for overdosage of paracetamol the National Poisons Information Service and the manufacturer have been notified of 38 adverse reactions that were anaphylactoid in nature and 19 accidental overdoses. The most common feature of the anaphylactoid reaction to normal dosage was rash; other features reported included angioedema, hypotension, and bronchospasm; all the patients recovered. The features associated with an overdose of acetylcysteine were similar but more severe; two patients died, but the extent to which the overdose of acetylcysteine may have been implicated was not clear in either case.

Redefining death. Are we any closer to a consensus?

As medical and technologic advances blur the once-distinct lines between life and death, legal scholars and physicians struggle to maintain a consistent and ethical definition of death. Pressures created by the possibility of organ donation and the problem of terminally ill patients or those in chronic vegetative states further complicate the question.

Effect of the state of association of melittin and phospholipids on their reciprocal binding

In solutions of increasing ionic strength, the molecular weight of melittin varies from 2840 (monomeric melittin) to 11200. This polymerization, concomitant with an important change in conformation (Talbot, J.C., Dufourcq, J., De Bony, J., Faucon, J.F. and Lussan, C. (1979) FEBS Lett. 102, 191-193), is accompanied by a significant alteration in the partial specific volume of the molecule. The binding of melittin to phospholipids (phosphatidylserine, lysolecithin, dihexanoyl-, dioctanoyl- and lysolauroylphosphatidylcholine) depends on the state of association of the toxin and on the critical micelle concentration of lipids. No interaction is observed between monomeric melittin and free lipids, whereas tetrameric melittin can bind free lipids to form mixed micelles. At phospholipid concentrations above the critical micelle concentration, melittin in any state of self-association can bind lipids. The mixed micelles formed at saturation appear to be independent of the initial state of association of melittin.

Melittin-phospholipid interactions: binding of the mono- and tetrameric form of this peptide, and perturbations of the thermotropic properties of bilayers

The binding of melittin to phospholipid bilayers and micelles depends on its quaternary structure and on the state of association of lipids. Monomeric melittin only binds to lipids above their cmc, whereas tetrameric melittin exhibits a biphasic binding; the interaction with monomeric lipids being possible without dissociation of the tetramer. In lipid excess, the bound state observed by fluorescence, polarization and ORD are always very similar. We propose the following model: the presence of a lipidic interface is necessary for the binding of monomeric melittin, while the tetramer may interact with lipid monomers without any dissociation: it might increase in size by addition of lipid molecules to form a micelle-like particle. The perturbations induced by melittin on the thermotropic behaviour of charged phospholipids are detected by calorimetry (DSC) and fluorescence polarization of DPH. For the first group of lipids, constituted of mono or divalent C14 and of divalent C16 lipids, the transitions are progressively abolished in the presence of melittin, without any shift of the temperature. For a second group of lipids, essentially constituted of monovalent C16 lipids, a cooperative transition is always observed. Moreover, at lipid to protein molar ratios higher than 8, there are two distinct well-defined transitions, at the same temperature as for pure lipid and 10 degrees C to 15 degrees C lower. All these results are interpreted by a phase separation occurring between quasi-pure lipid regions and the lipid-melittin complex. These last ones either could, or not, give rise to a phase transition, according to the cohesion of the initial bilayer. In the case of binary mixtures, there would be a phase separation between enriched phosphatidylcholine regions and negative lipid-melittin complexes.

Physicochemical evidence for the existence of two pyridoxal 5'-phosphate binding sites on glutamate dehydrogenase and characterization of their functional role

Kinetic studies of pyridoxal 5'-phosphate binding to glutamate dehydrogenase (EC 1.4.1.3) has provided evidence for two specific binding sites, chemically identified as Lys 126 and Lys 333. Use of protecting ligands permitted the selective modification of only one of these lysines, and showed that (1) Lys 333 modification results in depolymerisation of the enzyme into active hexamers; (2) Lys 126-modified enzyme was 92% inactivated. The residual activity was desensitized to GTP. The inactivation process was cooperative, maximum inactivation occurring as soon as half of the Lys 126 were modified.

Left ventricular dyskinesia in infarction and angina

In 29 patients, the site and extent of coronary artery obstruction were related to the position and area of abnormally contracting segments of the left ventricle, both in patients with a history of angina without myocardial infarction (group I) and in patients with prior documented myocardial infarction (group II). The degree of coronary artery obstructive disease was estimated in the standard manner and also by a coronary artery index which considered not only the degree of obstruction but also the total length of the obstructed segment. A kinetic or dyskinetic segments were present in 22 of the 29 patients. An abnormally contracting segment was present in 12 or 18 patients without prior myocardial infarction in comparison with 10 of the 11 patients with prior infarction. Complete obstruction of a coronary vessel and resultant dyskinesia were more frequent in the right coronary artery than in either the left anterior descending or the circumflex artery. There was a significant correlation between total per cent of vessel obstruction and degree of ventricular asynergy in both groups; consideration of length of obstructed segment did not improve this correlation.