Reciprocal effect of Waardenburg syndrome mutations on DNA binding by the Pax-3 paired domain and homeodomain

The Pax-3 protein contains two DNA-binding domains, a paired domain and a homeodomain. Mutations in Pax-3 cause Waardenburg syndrome (WS) in humans and the mouse Splotch (Sp) phenotype. In the Sp-delayed mouse, a mutation in the Pax-3 paired domain (G9R) abrogates the DNA-binding activity of both the paired domain and the homeodomain, suggesting that they may functionally interact. To investigate this possibility further, we have analyzed the DNA-binding properties of additional point mutants in the Pax-3 paired domain and homeodomain that occur in WS patients (F12L, N14H, G15S, P17L, R23L, G48A, S51F and G66D in the paired domain, V47F and R53G in the homeodomain), the Pax-1 un mutation (G15A) and a substitution associated with Peters' anomaly in the PAX-6 gene (R23G). Within the paired domain, seven of 10 mutations were found to abrogate DNA-binding by the paired domain. Remarkably, these seven mutations also affected DNA binding by the homeodomain, causing either a complete loss (P17L and G66D), a reduction (R23G, R23L, G15S and G15A) or an increase in DNA-binding activity (N14H). In addition, the effect of paired domain mutations occurred at the level of monomer formation by the homeodomain, while the dimerization potential of this domain seemed unaffected in mutants where it could be analyzed. Furthermore, while both homeodomain mutations were found to abolish DNA binding by this domain, the R53G mutation also abrogated DNA binding by the paired domain. The important observation that independent mutations in either domain can affect DNA binding by the other in the intact Pax- 3 protein strongly suggests that the two domains are not functionally independent but bind DNA through cooperative interactions. Modeling the deleterlous mutations on the three-dimensional structure of the paired domain of Drosophila Prd shows that these mutations cluster at the DNA interface, thus suggesting that a series of DNA contacts are essential for DNA binding by both the paired domain and the homeodomain of Pax-3.      

MR technology: effect of even-echo rephasing on calculated T2 values and T2 images

In multiple spin-echo image sequences of blood flow, the "even-echo" phenomenon produces an absolute increase in signal magnitude from first- to second-echo images of normal vessels harboring slow flow. Distinguishing this from the apparent relatively high signal intensity seen on second-echo images in pathologic foci of stationary tissue is important to the diagnostician. Selected case material containing two tissue types was reviewed retrospectively: tissues known to harbor slow flow, such as normal veins and venous sinuses and vascular malformations, and tissues that have long transverse (T2) relaxation times and appear as intense structures on second-echo images, such as neoplasms, infarcts, and regions of demyelination. Calculations of T2 parameters were made by computer for defined regions of interest. T2 images were also generated. Visual inspection of the acquired images did not reliably distinguish increased intensity due to even-echo rephasing from the relative changes between adjacent tissues seen on second-echo images. More definitive differentiation of the even-echo phenomenon was provided by calculated values of T2 and computer-synthesized T2 images representing acquired intensity data of two-echo sequences. The synthesized images were especially useful when stationary tissue with lengthened T2 values was adjacent to or in proximity to vessels or vascular lesions. A five spin-echo image sequence was valuable for separating slow flow from stationary tissue by a technique of synthesizing T2-difference images using three consecutive echoes.     

Multiple cerebral metastases: detectability with Gd-DTPA-enhanced MR imaging

Sixteen patients with suspected cerebral metastases were studied with magnetic resonance (MR) imaging before and after the intravenous administration of 0.1 mmol/kg of gadolinium diethylenetriaminepenta-acetic acid. The images were interpreted blindly by two neuroradiologists; all clinical, radiologic (computed tomographic and MR imaging), and pathologic data were reviewed to arrive at a final "best diagnosis," which was then compared with the prior blinded interpretations. Of seven patients found to have multiple metastases, six (86%) had at least one tumor nodule depicted by postinfusion MR imaging that was missed by one or both observers on review of preinfusion images alone. Lesions missed on preinfusion studies were usually small nodules hidden by or not detected next to regions of high-signal edema thought to be related to the adjacent tumor nodule. The authors believe that contrast enhancement improves detection of metastatic foci with MR imaging and that the findings indicate broader implications for the detection of multiple lesions from other causes.     

Multiple sclerosis and childhood infections

Migration from an area where MS is common to an area where it is rare (and vice versa) affects the risk of MS, provided migration occurs in childhood. A childhood infection might explain this effect. Therefore, the age pattern of infectious diseases in different regions was examined. A higher proportion of children showed positive titers to many viral diseases early in life in areas where MS is rare compared with those where MS is common. Also, mortality rates from a variety of infectious diseases correlated negatively with the MS mortality. Thus, infection early in life may "protect" against MS, and conversely, later infection, when the immune system has partially matured, may increase risk. MS may be an age-dependent, host-immune response to childhood infection.     

Creutzfeldt-Jakob disease

There has been significant advance in our understanding of CJD and similar spongiform encephalopathies in recent years. The range in clinical expression of the disease is better appreciated, and the existence of "atypical" cases of CJD is increasingly recognized. New ideas about the possible modes of natural transmission have been derived from case-control studies in different parts of the world.     

细胞因子激活骨髓免疫细胞的实验研究

目的：通过对骨髓单个核细胞在体外与不同细胞因子培养,了解不同细胞因子对骨髓淋巴细胞的激活能力和对骨髓干祖细胞的损伤情况。方法：将IL-1、IL-2、γ-IFN、CD3单抗进行不同组合后,在体外与骨髓单个核细胞分成对照组、IL-2组、CD3-AK、CIK组进行培养。培养过程中观察细胞形态和数量的变化,并在培养后检测免疫活性细胞的细胞毒性和造血干细胞的保存情况。结果：培养过程中对照组细胞数量减少;IL-2组细胞数量变化不明显;CD3-AK组、CIK组细胞数量显著增多,并出现较多的集聚成簇的淋巴样细胞,培养后其细胞毒性明显强于对照组及IL-2组,但细胞数量增加和细胞毒性无明性差异,培养后各组造血干细胞保存情况约16%～87%。结论：IL-2、CD3单抗在体外与骨髓单个核细胞培养后,即能激活免疫细胞增殖,又能保留足够的造血干细胞。     

胰弹力蛋白酶I和核糖核酸酶检测的临床价值

目的　探讨人胰弹力蛋白酶Ⅰ (Humanpancreaticelastase 1 ,HPE1 )放射免疫测定 (Radioimmunoassay ,RIA)和核糖核酸酶(Ribonuclease ,RNase)活性检测的临床价值。方法　参照Satake等建立的改良HPE1RIA和Thomas等的改良酸溶性产物法检测 82例正常成年人和 2 2 2例各类患者血清并分析结果。结果　 82例健康成人HPE1值为 2 3.8( 3.4ng L) ,RNase活性为 5 7.0 3( 1 2 .1 6 μ ml) ;急性胰腺炎和胰腺癌HPE1 值明显高于其他疾病 (P <0 .0 1 )。联合检测HPE1 、RNase活性可提高胰腺癌的检出率 ( 92 .47% )。结论　HPE1 RIA对急性胰腺炎有诊断价值 ,联合检测HPE1 、RNase活性检测对胰腺癌诊断有一定的临床价值     

口服莫沙必利治疗功能性消化不良的随机对照试验

目的　观察新型促胃肠动力药莫沙必利 (胃 5 HT4受体促进剂 )对功能性消化不良 (FD)的随机对照试验。方法　FD患者 42例 ,随机分为试验组 (2 1例 ,服枸橼酸莫沙必利片 )和对照组 (2 1例 ,服吗叮啉片 )。采用GCP标准 ,双盲法观察 ,在实验开始前、服药第 1 4、2 8天记录症状变化及副作用发生情况。随机抽取部分患者于实验开始前和结束时做99MTc胃排空试验。结果　莫沙必利对FD症状的疗效与吗叮啉组相当 (P >0 .0 5 )。99MTc胃排空测定发现莫沙必利组治疗后的半排时间 (45 .0 5± 1 2 .2 1 )min缩短 ,1 2 0min残留率 (2 9.73%± 8.5 1 % )减少 (P <0 .0 5 ) ,两组病例未发现毒副反应。结论　莫沙必利对于FD疗效良好 ,对胃排空延迟有良好疗效 ,安全度高。     

关于建立非隶属关系附属医院的实践与思考

本文从医学人才培养的高度,论述高校与附属医院建立非隶属关系的附属医院的过程、体会和思考,指出目前存在的问题和解决途径.对进一步深化临床教育教学改革具有重要意义.