Role of arterial baroreceptors in mediating cardiovascular response to exercise.

The role played by the major arterial baroreceptor reflexes in the cardiovascular response to exercise was examined by comparing the responses of untethered conscious dogs instrumented for the measurement of aortic pressure and cardiac output with those of dogs with total arterial barorecptor denervation (TABD). Moderately severe levels of exercise (12 mph) in intact dogs increased cardiac output from 111 +/- 17 ml/kg per min, increased heart rate from 101 +/- 5 to 265 +/- 8 beats/min, and reduced total peripheral resistance from 0.039 +/- 0.003 to 0.015 +/- 0.002 mmHg/ml per min. Dogs with TABD responded in a very similar fashion; exercise increased cardiac output from 119 +/- 8 to 356 /+- 23 ml/kg per min, increased heart rate from 122 +/- 7 to 256 +/- 5 beats/min, and decreased total peripheral resistance from 0.042 +/- 0.005 to +/- 0.015 +/- 0.001 mmHg/ml per min. The reflex heart rate responses to intravenous bolus doses of methoxamine were also examined in intact animals, both at rest and during exercise. Methoxamine caused striking bradycardia at rest, but little bradycardia during exercise. These results suggest that the arterial baroreceptor reflex is normally turned off during severe exercise and thus does not modify significantly the cardiovascular response to exercise.     

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.     

Tear of the distal biceps branchii tendon: A new method of ultrasound evaluation

Tear of the distal biceps brachii tendon is an uncommon injury. Ultrasound evaluation of the distal tendon using an anterior approach is often difficult because of technical factors. We describe a new method of ultrasound evaluation of the distal biceps tendon insertion. This involves a posterior approach with the forearm pronated. With pronation of the forearm, the radial tuberosity faces posteriorly, bringing the distal biceps tendon insertion into view. A surgically proven case of distal biceps tendon tear is presented to illustrate our technique.     

培养创新型临床医学人才的思考

文章从创新及创新型人才的概念入手，通过调研指出，目前临床医学人才培养存在的主要问题，提出在新时期要转变教育教学观念、强化创新意识教育、增强创新思维训练、着力创新人格塑造，以培养创新型临床医学人才。     

YD383、YD439对JAK-STAT6信号传导通路作用的特异性研究

目的:探讨化合物YD383和YD439对STAT6信号传导通路的作用是否具有特异性.方法:通过瞬时转染的方法将分别依赖于STAT1和STAT6活性的带有荧光素酶报告基因的质粒转染至HeLa细胞株,两种细胞株在各自相应的细胞因子(IFN-γ或IL-4)刺激下激活JAK-STAT1或JAK-STAT6信号传导通路.通过测定荧光素酶的活性来评价细胞株在化合物存在的情况下报告基因的表达.结果:YD383和YD439均能降低相应细胞因子刺激引起的报告基因的表达,并且具有剂量依赖性.随着化合物剂量的增加,报告基因的表达降低(P＜0.05).但化合物引起的两种转染细胞报告基因表达降低的差异比较无统计学意义(P＞0.05).结论:两种化合物对JAK-STAT1和JAK-STAT6信号传导通路均有抑制作用,对JAK-STAT6通路的抑制不具有特异性.