Clinical research: a novel approach to the analysis of repeated measures

In current clinical research, repeated measures in a single subject are common. The problem with repeated measures is that they are closer to one another than unrepeated measures. If this is not taken into account, then data analysis will lose power. In the past decade, user-friendly statistical software programs such as SAS and SPSS have enabled the application of mixed models as an alternative to the classical general linear model for repeated measures with, sometimes, better sensitivity. The objective was to assess whether in studies with repeated measures, designed to test between-subject differences, the mixed model performs better than does the general linear model. In a parallel group study of cholesterol-reducing treatments with 5 evaluations per patient, the mixed model performed much better than did the general linear model with P values of 0.0001 and 0.048, respectively. In a crossover study of 3 treatments for sleeplessness, the mixed model and general linear model performed similarly well with P values of 0.005 and 0.010. Mixed models do, indeed, seem to produce better sensitivity of testing, when there are small within-subject differences and large between-subject differences and when the main objective of your research is to demonstrate between- rather than within-subject differences. The novel mixed model may be more complex. Yet, with modern user-friendly statistical software, its use is straightforward, and its software commands are no more complex than they are with standard methods. We hope that this article will encourage clinical researchers to make use of its benefits more often.     

Broadband proton decoupling for in vivo brain spectroscopy in humans.

A new decoupling sequence, PBAR, is described for broadband heteronuclear decoupling in vivo in humans at 1.5T. The sequence uses non-adiabatic, frequency- and amplitude-modulated inversion pulses designed to minimize decoupling sidebands at low applied gammaB(2) RF field levels and to cover only the narrow range of resonance offsets encountered in practice. The offset dependence of the decoupling efficiency of PBAR is demonstrated and compared to the conventional WALTZ-4 sequence. At the same average power levels, PBAR had slightly reduced bandwidth but significantly less intense decoupling sidebands. Applications of PBAR are shown in vivo in the human brain both for (31)P and natural abundance (13)C spectroscopy using volume decoupling coils. The PBAR sequence allows whole brain [(1)H]-[13]C decoupling to be performed at 1.5T with a standard head coil within FDA guidelines for RF power deposition. Magn Reson Med 45:226-232, 2001.     

Hexose monophosphate shunt activity in erythrocytes related to cell age

Erythrocytes were separated by age using a combination of density centrifugation and counterflow centrifugation and tested for basal activity of the hexose monophosphate shunt (HMP-shunt) as well as the methylene blue-stimulated maximal capacity by measuring CO2 production. No significant differences were found in basal HMP-shunt activity, but the maximal methylene blue-stimulated activity of old erythrocytes reached only half of the activity of the total cell population. The maximal HMP-shunt activity showed a significant correlation with hexokinase activity, but not with glucose-6-phosphate dehydrogenase activity in all but the youngest cells. The sensitivity to oxidative stress was tested by measuring the kinetics of pyruvate kinase isolated from erythrocytes incubated in presence and absence of methylene blue. Pyruvate kinase kinetics were affected more in the old cell population than in the total cell population: the K0.5 for phosphoenol-pyruvate increased four times in the unseparated cells and eight times in old cells.     

A relapse of paratyphoid fever after treatment with ciprofloxacin in a child with congenital biliary atresia

This report describes a relapse of Salmonella paratyphi B infection in a child with biliary atresia, following 2 weeks of treatment with ciprofloxacin. The recrudescence was complicated by the development of osteomyelitis and was treated with chloramphenicol, trimethoprim, ceftriaxone and ampicillin in succession.     

雌二醇对动情间期切除卵巢母羊黄体生成素分泌脉冲的抑制作用

动情间期母羊切除卵巢并皮下植入持续释放的E_2后,平均LH基础分泌水平和LH脉冲幅高比对照组显著减低,LH脉冲频率无明显改变。LH的平均基础分泌水平和脉?中幅高显著相关。表明植入E_2对垂体LH分泌的抑制作用主要是抑制LH对GnRH的反应,作用部位在垂体,不在下丘脑。LH基础分泌水平的下降,亦可能是E_2的抑制作用所致。     

The Asp84Glu variant of the melanocortin 1 receptor (MC1R) is associated with melanoma

Melanocyte stimulating hormone (MSH) plays an important role in determining the cutaneous response to ultraviolet radiation and may also influence melanoma progression. We have previously shown that variants of the melanocortin receptor present on melanocytes, MC1R, are associated with sun sensitivity and red hair in a UK population and therefore now consider the gene as a candidate for melanoma susceptibility. We have compared the frequency of known MC1R variants in the second and seventh transmembrane domains in 43 melanoma cases and 44 controls. MC1R variants were more common in cases than controls (chi 2 = 6.75, 1 d.f.; P = 0.0094) with a relative risk to carriers of variant alleles compared with normal homozygotes of 3.91 (95% c.l.: 1.48-10.35), and a population risk attributable to carriers of 34.6% (95% c.i. 10.7-52.1%). The Asp84Glu variant was only present in melanoma cases and appears to be of particular significance. The contribution of variant MC1R alleles was largely independent of skin type. Variants of the MC1R gene are likely to be causally associated with the development of melanoma.      

Radiotherapy planning: direct tumor location on simulation and port films using CT. Part I. Principles

Although there have been great advances in cancer diagnosis in recent years, it remains difficult to transfer tumor location information from cross-sectional computed tomographic (CT) scans or magnetic resonance images to the simulation and verification films used in planning radiotherapy. A newly developed system uses radioopaque markers attached to the patient as reference points. These markers are identified on both CT scans and simulation films and their locations entered into the treatment planning computer. The tumor and any desired normal structures are then outlined manually on each CT section. Transparent overlays produced by the computer show the position of the reference markers and tumor outlines for any combination of gantry angles and source-film distance. Because the overlays are scaled to the simulation films, the reference points enable precise alignment of overlay and film. The tumor outline thus appears on the simulation or verification films exactly as it is "seen" by the therapy beam, making field verification straightforward and accurate, even on oblique films.