Assessment of image quality of a standard and two dose-reducing protocols in paediatric pelvic CT

Background: Concerns exist regarding the effect of radiation dose from paediatric pelvic CT scans and the potential later risk of radiation-induced neoplasm and teratogenic outcomes in these patients. Objective: To assess the diagnostic quality of CT images of the paediatric pelvis using either reduced mAs or increased pitch compared with standard settings. Materials and methods: A prospective study of pelvic CT scans of 105 paediatric patients was performed using one of three protocols: (1) 31 at a standard protocol of 200 mA with rotation time of 0.75 s at 120 kVp and a pitch factor approximating 1.4; (2) 31 at increased pitch factor approaching 2 and 200 mA; and (3) 43 at a reduced setting of 100 mA and a pitch factor of 1.4. All other settings remained the same in all three groups. Image quality was assessed by radiologists blinded to the protocol used in each scan. Results: No significant difference was found between the quality of images acquired at standard settings and those acquired at half the standard mAs. The use of increased pitch factor resulted in a higher proportion of poor images. Conclusions: Images acquired at 120 kVp using 75 mAs are equivalent in diagnostic quality to those acquired at 150 mAs. Reduced settings can provide useful imaging of the paediatric pelvis and should be considered as a standard protocol in these situations.

Blockade of vascular smooth muscle cell proliferation and intimal thickening after balloon injury by the sulfated oligosaccharide PI-88: Phosphomannopentaose sulfate directly binds FGF-2, blocks cellular signaling, and inhibits proliferation

Percutaneous transluminal coronary angioplasty is a frequently used interventional technique to reopen arteries that have narrowed because of atherosclerosis. Restenosis, or renarrowing of the artery shortly after angioplasty, is a major limitation to the success of the procedure and is due mainly to smooth muscle cell accumulation in the artery wall at the site of balloon injury. In the present study, we demonstrate that the antiangiogenic sulfated oligosaccharide, PI-88, inhibits primary vascular smooth muscle cell proliferation and reduces intimal thickening 14 days after balloon angioplasty of rat and rabbit arteries. PI-88 reduced heparan sulfate content in the injured artery wall and prevented change in smooth muscle phenotype. However, the mechanism of PI-88 inhibition was not merely confined to the antiheparanase activity of this compound. PI-88 blocked extracellular signal-regulated kinase-1/2 (ERK1/2) activity within minutes of smooth muscle cell injury. It facilitated FGF-2 release from uninjured smooth muscle cells in vitro, and super-released FGF-2 after injury while inhibiting ERK1/2 activation. PI-88 inhibited the decrease in levels of FGF-2 protein in the rat artery wall within 8 minutes of injury. PI-88 also blocked injury-inducible ERK phosphorylation, without altering the clotting time in these animals. Optical biosensor studies revealed that PI-88 potently inhibited (K-i 10.3 nmol/L) the interaction of FGF-2 with heparan sulfate. These findings show for the first time the capacity of this sulfated oligosaccharide to directly bind FGF-2, block cellular signaling and proliferation in vitro, and inhibit injury-induced smooth muscle cell hyperplasia in two animal models. As such, this study demonstrates a new role for PI-88 as an inhibitor of intimal thickening after balloon angioplasty. The full text of this article is available online at http://www.circresaha.org.

pH dependence of the progression in NMR T-2 relaxation times in post-mortem muscle

Continuous NMR T-2 relaxation measurements were carried out on seven rabbit longissimus muscle samples in the period from 25 min to 28 h post-mortem at 200 MHz for H-1. To display differences in post-mortern pH progress and extent of changes in water characteristics during conversion of muscle to meat, three of the seven animals were pre-slaughter injected with adrenaline (0.5 mg/kg live weight 4 h before sacrifice) to differentiate muscle glycogen stores at the time of slaughter. Distributed analysis of T-2 data displayed clear differences in the characteristics of the various transverse relaxation components dependent on progress in pH, as did the water-holding capacity of samples 24 h postmortem. This reveals a pronounced effect of the progressive change in pH on the subsequent development in physical/chemical states of water during the conversion of muscle to meat. Finally, the relaxation characteristics are discussed in relation to supposed post-mortem processes of protein denaturation.

Impact of undergraduate and postgraduate rural training, and medical school entry criteria on rural practice among Australian general practitioners: national study of 2414 doctors

Objective To determine the association between rural undergraduate training, rural postgraduate training and medical school entry criteria favouring rural students, on likelihood of working in rural Australian general practice. Methods National case - control study of 2414 rural and urban general practitioners (GPs) sampled from the Health Insurance Commission database. Participants completed a questionnaire providing information on demographics, current practice location and rural undergraduate and postgraduate experience. Results Rural GPs were more likely to report having had any rural undergraduate training [ odds ratio ( OR) 1.61, 95% confidence interval (CI) 1.32 - 1.95] than were urban GPs. Rural GPs were much more likely to report having had rural postgraduate training ( OR 3.14, 95% CI 2.57 - 3.83). As the duration of rural postgraduate training increased so did the likelihood of working as a rural GP: those reporting that more than half their postgraduate training was rural were most likely to be rural GPs ( OR 10.52, 95% CI 5.39 - 20.51). South Australians whose final high school year was rural were more likely to be rural GPs ( OR 3.18, 95% CI 0.99 - 10.22). Conclusions Undergraduate rural training, postgraduate training and medical school entry criteria favouring rural students, all are associated with an increased likelihood of being a rural GP. Longer rural postgraduate training is more strongly associated with rural practice. These findings argue for continuation of rural undergraduate training opportunities and rural entry schemes, and an expansion in postgraduate training opportunities for GPs.

The force-velocity relationship of the human soleus muscle during submaximal voluntary lengthening actions

In experiments on isolated animal muscle, the force produced during active lengthening contractions can be up to twice the isometric force, whereas in human experiments lengthening force shows only modest, if any, increase in force. The presence of synergist and antagonist muscle activation associated with human experiments in situ may partly account for the difference between animal and human studies. Therefore, this study aimed to quantify the force-velocity relationship of the human soleus muscle and assess the likelihood that co-activation of antagonist muscles was responsible for the inhibition of torque during submaximal voluntary plantar flexor efforts. Seven subjects performed submaximal voluntary lengthening, shortening(at angular, velocities of +5, -5, +15, -15 and +30, and -30degrees s(-1)) and isometric plantar flexor efforts against an ankle torque motor. Angle-specific (90degrees) measures of plantar flexor torque plus surface and intramuscular electromyography from soleus, medial gastrocnemius and tibialis anterior were made. The level of activation (30% of maximal voluntary isometric effort) was maintained by providing direct visual feedback of the soleus electromyogram to the subject. In an attempt to isolate the contribution of soleus to the resultant plantar flexion torque, activation of the synergist and antagonist muscles were minimised by: (1) flexing the knee of the test limb, thereby minimising the activation of gastrocnemius, and (2) applying an anaesthetic block to the common peroneal nerve to eliminate activation of the primary antagonist muscle, tibialis anterior and the synergist muscles, peroneus longus and peroneus brevis. Plantar flexion torque decreased significantly (P<0.05) after blocking the common peroneal nerve which was likely due to abolishing activation of the peroneal muscles which are synergists for plantar flexion. When normalised to the corresponding isometric value, the force-velocity relationship between pre- and post-block conditions was not different. In both conditions, plantar flexion torques during shortening actions were significantly less than the isometric torque and decreased at faster velocities. During lengthening actions, however, plantar flexion torques were not significantly different from isometric regardless of angular velocity. It was concluded that the apparent inhibition of lengthening torques during voluntary activation is not due to co-activation of antagonist muscles. Results are presented as mean (SEM).

Osmotic properties of the sealed tubular system of toad and rat skeletal muscle

A method was developed that allows conversion of changes in maximum Ca2+-dependent fluorescence of a fixed amount of fluo-3 into volume changes of the fluo-3-containing solution. This method was then applied to investigate by confocal microscopy the osmotic properties of the sealed tubular (t-) system of toad and rat mechanically skinned fibers in which a certain amount Of fluo-3 was trapped. When the osmolality of the myoplasmic environment was altered by simple dilution or addition of sucrose within the range 190-638 mosmol kg(-1), the sealed t-system of toad fibers behaved almost like an ideal osmometer, changing its volume inverse proportionally to osmolality However, increasing the osmolality above 638 to 2,550 mosmol kg(-1) caused hardly any change in t-system volume. In myoplasmic solutions made hypotonic to 128 mosmol kg(-1), a loss of Ca2+ from the sealed t-system of toad fibers Occurred, presumably through either stretch-activated cationic channels or store-operated Ca2+ channels. In contrast to the behavior of the t-system in toad fibers, the volume of the sealed t-system of rat fibers changed little (by

Recruitment of single human low-threshold motor units with increasing loads at different muscle lengths

We investigated the recruitment behaviour of low threshold motor units in flexor digitorum superficialis by altering two biomechanical constraints: the load against which the muscle worked and the initial muscle length. The load was increased using isotonic (low load), loaded dynamic (intermediate load) and isometric (high load) contractions in two studies. The initial muscle position reflected resting muscle length in series A, and a longer length with digit III fully extended in series B. Intramuscular EMG was recorded from 48 single motor units in 10 experiments on five healthy subjects, 21 units in series A and,27 in series B, while subjects performed ramp up, hold and ramp down contractions. Increasing the load on the muscle decreased the force, displacement and firing rate of single motor units at recruitment at shorter muscle lengths (P < 0.001, dependent t-test). At longer muscle lengths this recruitment pattern was observed between loaded dynamic and isotonic contractions, but not between isometric and loaded dynamic contractions. Thus, the recruitment properties of single motor units in human flexor digitorum superficialis are sensitive to changes in both imposed external loads and the initial length of the muscle. (C) 2003 Elsevier Ltd. All rights reserved.

The neurosurgical training curriculum in Australia and New Zealand is changing. Why?

The Neurosurgical Advanced Training curriculum of the Royal Australasian College of Surgeons (RACS) is currently undergoing change. Given the high standard of neurosurgery in Australia and New Zealand, it may be questioned why such change is necessary. However, the curriculum has not kept pace with developments in professional practice, educational practice or educational theory, particularly in the assessment of medical competence and performance. The curriculum must also adapt to the changing training environment, particularly the effects of reduced working hours, reducing caseloads due to shorter inpatient hospital stays and restricted access to public hospital beds and operating theatres, and the effects of subspecialisation. A formal review of the curriculum is timely. (c) 2004 Elsevier Ltd. All rights reserved.

Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain

Study Design. A clinical study was conducted on 39 patients with acute, first-episode, unilateral low back pain and unilateral, segmental inhibition of the multifidus muscle. Patients were allocated randomly to a control or treatment group. Objectives. To document the natural course of lumbar multifidus recovery and to evaluate the effectiveness of specific, localized, exercise therapy on muscle recovery. Summary of Background Data. Acute low back pain usually resolves spontaneously, but the recurrence rate is high. Inhibition of multifidus occurs with acute, first-episode, low back pain, and pathologic changes in this muscle have been linked with poor outcome and recurrence of symptoms. Methods. Patients in group 1 received medical treatment only. Patients in group 2 received medical treatment and specific, localized, exercise therapy. Outcome measures for both groups included 4 weekly assessments of pain, disability, range of motion, and size of the multifidus cross-sectional area. Independent examiners were blinded to group allocation. Patients were reassessed at a 10-week follow-up examination. Results. Multifidus muscle recovery was not spontaneous on remission of painful symptoms in patients in group 1. Muscle recovery was more rapid and more complete in patients in group 2 who received exercise therapy (P = 0.0001). Other outcome measurements were similar for the two groups at the 4-week examination. Although they resumed normal levels of activity, patients in group 1 still had decreased multifidus muscle size at the 10-week follow-up examination. Conclusions. Multifidus muscle recovery is not spontaneous on remission of painful symptoms. Lack of localized, muscle support may be one reason for the high recurrence rate of low back pain following the initial episode.

A comparison of computer-based methods for the determination of onset of muscle contraction using electromyography

Little consensus exists in the literature regarding methods for determination of the onset of electromyographic (EMG) activity. The aim of this study was to compare the relative accuracy of a range of computer-based techniques with respect to EMG onset determined visually by an experienced examiner. Twenty-seven methods were compared which varied in terms of EMG processing (low pass filtering at 10, 50 and 500 Hz), threshold value (1, 2 and 3 SD beyond mean of baseline activity) and the number of samples for which the mean must exceed the defined threshold (20, 50 and 100 ms). Three hundred randomly selected trials of a postural task were evaluated using each technique. The visual determination of EMG onset was found to be highly repeatable between days. Linear regression equations were calculated for the values selected by each computer method which indicated that the onset values selected by the majority of the parameter combinations deviated significantly from the visually derived onset values. Several methods accurately selected the time of onset of EMG activity and are recommended for future use. Copyright (C) 1996 Elsevier Science Ireland Ltd.

Elevated plasma membrane and sarcoplasmic reticulum Ca2+ pump mRNA levels in cultured aortic smooth muscle cells from spontaneously hypertensive rats

We have observed previously that Ca2+ pump-mediated Ca2+ efflux is elevated in cultured aortic smooth muscle cells from spontaneously hypertensive rats compared to those from Wistar-Kyoto rat controls. The objective of this work was to determine if these strains differ in mRNA levels for the PMCA1 isoform of the plasma membrane Ca2+-ATPase and the SERCA2 isoform of the sarcoplasmic reticulum Ca2+-ATPase. mRNA levels were compared in cultured aortic smooth muscle cells from 10-week-old male rats. PMCA1 and SERCA2 mRNA levels were elevated in SHR compared to WKY. Angiotensin II increased the level of PMCA1 and SERCA2 mRNA in both strains. These studies provide further evidence for alterered Ca2+ homeostasis in hypertension at the level of Ca2+ transporting ATPases in the spontaneously hypertensive rat model. These data are also consistent with the hypothesis that the expression of these two Ca2+ pumps may be linked. (C) 1997 Academic Press

Muscle-specific regulation of tropomyosin gene expression and myofibrillogenesis differs among muscle systems examined at metamorphosis of the gastropod Haliotis rufescens

The spatial and temporal association of muscle-specific tropomyosin gene expression, and myofibril assembly and degradation during metamorphosis is analyzed in the gastropod mollusc. Haliotis rufescens. Metamorphosis of tile planktonic larva to the benthic juvenile includes rearrangement and atrophy of specific larval muscles, and biogenesis of the new juvenile muscle system. The major muscle of the larva - the larval retractor muscle - reorganizes at metamorphosis, with two suites of cells having different fates. The ventral cells degenerate, while the dorsal cells become part of the developing juvenile mantle musculature. Prior to these changes in myofibrillar structure, tropomyosin mRNA prevalence declines until undetectable in the ventral cells, while increasing markedly in the dorsal cells. In the foot muscle and right shell muscle, tropomyosin mRNA levels remain relatively stable, even trough myofibril content increases. In a population of median mesoderm cells destined to form de novo the major muscle of the juvenile and adult (the columellar muscle), tropomyosin expression is initiated at 45 h after induction of metamorphosis. Myofibrillar filamentous actin is not detected in these cells until about 7 days later. Given that patterns of tropomyosin mRNA accumulation in relation to myofibril assembly and disassembly differ significantly among the four major muscle systems examined, we suggest that different regulatory mechanisms, probably operating at both transcriptional and post-transcriptional levels, control the biogenesis and atrophy of different larval and postlarval muscles at metamorphosis.