Quantifying arbitrary magnetic susceptibility distributions with MR.

Magnetic susceptibility, as a physical property of materials, plays important roles in many physical, chemical, engineering, and medical applications. Its quantification becomes of significant interest when MRI becomes a commonly used technique in biomedical applications. A general method is presented here for quantifying arbitrary magnetic susceptibility distributions in a localized region on the basis of first principles of magnetic induction field distributions in space. A proof of the concept was demonstrated by computer simulations. The study establishes the methodological basis for quantitative magnetic susceptibility imaging with MR.     

A Note on the Asymptotic Properties of Affected-sib-pair Linkage Tests

This article concerns the asymptotic properties of linkage tests for affected‐sib‐pair data under the null hypothesis of no linkage. We consider a popular single‐locus analysis model where the unknown parameters are the disease allele frequency, the three penetrances for the three genotypes at the disease locus, and the recombination fraction between the marker locus and the disease locus. These parameters are completely confounded under the null hypothesis of no linkage. We show that 1) If the total variance of the trait (i.e., the additive variance plus the dominance variance) is “separated” from 0, then the likelihood ratio statistic has an asymptotic 0.5χ²₀+ 0.5χ²₁ distribution; 2) If the prevalence of the trait is “separated” from 0 and the recombination fraction is fixed at 0, then the likelihood ratio statistic has an asymptotic distribution which is a mixture of χ²₀, χ²₁ and χ²₂ . The implications of these results are discussed.     

Effect of Temperature on the Longitudinal Variability of Quantitative Ultrasound Variables

It is unclear whether longitudinal change in phantom measurements bears any relation to the long-term in vivo instrument performance of quantitative ultrasound devices. Longitudinal quantitative ultrasound phantom data were obtained by measuring the manufacturer-provided phantom at ambient temperature and two different sets of Leeds phantoms at either ambient temperature or following a phantom temperature-control protocol. Measurements were performed using the Achilles Plus bone densitometer. Changes in longitudinal phantom data were compared to in vivo quantitative ultrasound data obtained from seven healthy, young volunteers. A cosinor model with linear trend and Hotelling's T2-test were used to quantify seasonal rhythms and long-term drift in quantitative ultrasound variables. Temperature effects and marked seasonal rhythms on quantitative ultrasound phantom measurements were evident but were far less apparent in vivo. Longitudinal precision of quantitative ultrasound variables was poorer for the manufacturer-provided phantom than for phantoms that were subjected to a temperature-control protocol or for healthy volunteers. This study has shown that longitudinal precision and longitudinal change differs between in vivo and phantom data. Longitudinal quantitative ultrasound measurements for monitoring change in skeletal status cannot, as yet, be properly controlled.     

Danish version of the Oswestry disability index for patients with low back pain. Part 2: Sensitivity, specificity and clinically significant improvement in two low back pain populations

In studies evaluating the efficacy of clinical interventions, it is of paramount importance that the functional outcome measures are responsive to clinically relevant change. Knowledge thereof is in fact essential for the choice of instrument in clinical trials and for clinical decision-making. This article endeavours to investigate the sensitivity, specificity and clinically significant improvement (responsiveness) of the Danish version of the Oswestry disability index (ODI) in two back pain populations. Two hundred and thirty three patients with low back pain (LBP) and/or leg pain completed a questionnaire booklet at baseline and 8 weeks follow-up. Half of the patients were seen in the primary (PrS) and half in the secondary sectors (SeS) of the Danish Health Care System. The booklet contained the Danish version of the ODI, along with the Roland Morris Questionnaire, the LBP Rating Scale, the SF36 (physical function and bodily pain scales) and a global pain rating. At follow-up, a 7-point transition question (TQ) of patient perceived change and a numeric rating scale relating to the importance of the change were included. Responsiveness was operationalised using three strategies: change scores, standardised response means (SRM) and receiver operating characteristic (ROC) analyses. All methods revealed acceptable responsiveness of the ODI in the two patient populations which was comparable to the external instruments. SRM of the ODI change scores at 2 months follow-up was 1.0 for PrS patients and 0.3 for SeS (raw and percentage). A minimum clinically important change (MCID) from baseline score was established at 9 points (71%) for PrS patients and 8 points (27%) for SeS patients using ROC analyses. This was dependable on the baseline entry score with the MCID increasing with 5 points for every 10 points increase in the baseline score. We conclude that the Danish version of the ODI has comparable responsiveness to other commonly used functional status measures and is appropriate for use in low back pain patients receiving conservative care in both the primary and secondary sector.     

钛接圈在不同烘烤温度下对镍铬合金浇注质量的影响

目的：研究钛接圈在不同烘烤温度下浇注镍铬合金的质量关系。方法：选择临床骨融合种植义齿二期手术后典型病例石膏模型，在基桩上固定纯钛接圈，常规制作桥架蜡型，使桥架接圈周围嵌体蜡厚度为１ｍｍ，常规内、外包埋，放置２４ｈ后，分４组不同温度烘烤，ａ组烘烤升温至６００℃，ｂ组升温至６５０℃，ｃ组升温至７００℃，ｄ组升温至８００℃。每组试件１０个，共４０个试件。用远红外温度测试仪控制合金浇注温度为１３０６℃，自然冷却后，电镜观察。结果：钛接圈烘烤温度６００℃、８００℃时镍铬合金支架断口出现二次断裂及气孔机会多，当６５０℃、７００℃时二次断裂出现机会少。结论：在常规牙科操作中，钛接圈烘烤温度为６５０℃、７００℃时，浇注镍铬合金较好。     

Central tumour necrosis factor-α mediates the early gastrointestinal motor disturbances induced by lipopolysaccharide in sheep

Cytokines are involved in fever and other symptoms of the acute phase response induced by endotoxins. The aim of this work was to study the involvement of central tumour necrosis factor-alpha (TNF-alpha) in the changes induced by lipopolysaccharide (LPS) on gastrointestinal (GI) motility in sheep. Body temperature and myoelectric activity of the antrum, duodenum and jejunum was recorded continuously. Intravenous (i.v.) administration of LPS (0.1 micro g kg-1)-induced hyperthermia, decreased gastrointestinal myoelectric activity and increased the frequency of the migrating motor complex (MMC). These effects started 40-50 min after LPS and lasted for 6-7 h. TNF-alpha (50 and 100 ng kg-1) mimicked these effects when injected intracerebroventricularly (i.c.v.) but not i.v. Pretreatment with soluble recombinant TNF receptor (TNFR:Fc, 10 micro g kg-1, i.c.v.) abolished the TNF-induced actions and reduced those evoked by LPS. Furthermore, the effects induced by either LPS or TNF were suppressed by prior i.c.v. injection of indomethacin (100 micro g kg-1). In contrast, the i.v. injections of TNFR:Fc or indomethacin were ineffective. Our data suggest that LPS disturbs GI motility in sheep through a central pathway that involves TNF-alpha and prostaglandins sequentially.     

The routine assessment of sperm motility at room temperature and 37°C

The World Health Organization (WHO) laboratory manual (1992) states that assessment of sperm motility can be performed at either 37^OC or room temperature (20–24^OC). The motility of spermatozoa in 44 semen samples (22 fresh samples and 22 frozen-thawed samples) was assessed at both of these temperatures and a significant difference in the motility profiles was noted, specifically an increase at 37^OC in the percentage (expressed here as median and ranges) of spermatozoa with excellent progressive motility and an overall increase in the percentage with total progressive motility. With fresh samples the excellent progressive motility increased from 41 (19–53) to 54 (30–66) and the overall motility from 58.5 (39–74) to 65.0 (40–79). With the frozen—thawed samples the excellent motility increased from 14 (1–33) to 25 (6–45) and the overall motility from 30.5 (14–51) to 33.0 (16–52). As the WHO laboratory manual was published. 'In response to a growing need for the standardisation of procedures for the examination of human spermatozoa' it is proposed that only one temperature for routine analysis should be used, namely 37^OC, which may have more physiological relevance and eliminate effects of fluctuations in ambient laboratory temperature.     

Convection warmers — not just hot air

We sought to determine whether the forced air convection warmers (nine Bair Huggers, Augustine Medical, and one Warm Touch, Mallinkrodt Medical) used in our operating theatres could be a source of microbial pathogens. Agar plates were placed directly in the air stream of the warmers. Four of these grew potentially pathogenic organisms. When the warmers were set to blow through perforated blankets, no growth occurred. Three of the warmers were swabbed and sites of colonisation were found in their hoses. After fixing a microbial filter to the end of the hose, organisms were no longer detectable. We conclude that these warming devices are a potential source of nosocomial infection. They should only be used in conjunction with perforated blankets, should have their microbial filters changed regularly and their hoses sterilised. The inclusion of a microbial filter into the nozzle of the hose could be incorporated into the design of the warmer.     

The effect of cooling on toe systolic pressures in subjects with and without Raynaud's syndrome in the lower extremities

Summary. The effect of changes in local and body temperature on the toe systolic pressures was studied in 20 subjects with and 30 without Raynaud's syndrome in the toes. The pressures were significantly lower in the group with Raynaud's syndrome under all experimental conditions (P < 0·01). The pressures were significantly lower during body cooling than during body warming in both groups (P < 0·01). The mean decrease with body cooling was 58 mmHg in the group with Raynaud's syndrome and 24 mmHg in the control subjects (P < 0·01). During body cooling pressures fell to less than 30 mmHg in 70% of subjects with Raynaud's syndrome and in 3% of the controls. Local cooling from 30 to 10°C during body cooling resulted in a significant mean decrease in pressure of over 40 mmHg in both groups (P < 0·01) and the pressure fell below 30 mmHg in over 90% of the group with and in 26% of those without Raynaud's attacks. The results indicate the importance of body cooling and local temperature in the mechanism of vasospasm in the toes. They are also relevant to the diagnosis of Raynaud's syndrome in the lower limbs and have implications for the testing of patients with arteriosclerotic occlusion since erroneously low pressure values could be obtained in tests when the feet are cold.     

Simultaneous genetic analysis of longitudinal means and covariance structure in the simplex model using twin data

A longitudinal model based on the simplex model is presented to analyze simultaneously means and covariance structure using univariate longitudinal twin data. The objective of the model is to decompose the mean trend into components which can be attributed to those genetic and environmental factors which give rise to phenotypic individual differences and a component of unknown constitution which does not involve individual differences. Illustrations are given using simulated data and repeatedly measured weight obtained in a sample of 82 female twin pairs on six occasions.