模型溶液的分子动力学模拟及扩散系数计算

通过对模型溶液的分子动力学模拟，确定了这些溶液的径向分布函数，自扩散系数Ｄ１、Ｄ２和互扩散系数Ｄ１２。结果表明，用Ｅｉｎｓｔｅｉｎ法和Ｇｒｅｅｎ－Ｋｕｂｏ法得到的扩散系数在数值上是一致的；溶液互扩散系数Ｄ１２与自扩散系数Ｄ１和Ｄ２满足关系式Ｄ１２＝ｘ１Ｄ１＋ｘ２Ｄ２。     

Blood flow velocity waveform in the common carotid artery and its analysis in elderly subjects

We investigated common carotid artery blood flow in 99 elderly nursing home residents using an ultrasonic quantitative blood flow measurement system. Systolic velocity and end-diastolic velocity were obtained from the waveform and classified, using the end-diastolic/systolic volume as Type A which is normal flow (>20% bilaterally), Type B which is unilateral decreased flow (<20% unilaterally), Type C which is bilateral decreased flow (<20% bilaterally), Type D which is Type C plus a saw tooth pattern and Type E which is no diastolic pattern, i.e. a value of 0 unilaterally or bilaterally. Five per cent of subjects showed Type A of blood flow velocity waveform (normal flow pattern) and about 40% showed Type E (no diastolic pattern). The subjects were divided into three groups according to blood flow velocity waveform. Groups 1, 2 and 3 showed Types A or B, C or D, and E, respectively. The total blood flow volume and mean blood flow velocity of Group 1 were significantly higher than those of Groups 2 and 3 in both the supine and sitting positions. Although both total blood flow volume and mean blood flow velocity of Group 1 decreased significantly in postural change, those of Groups 2 and 3 did not change. These results suggest that total blood flow volume and mean blood flow velocity decrease in proportion to changes in the blood flow velocity waveform.     

A new measuring design for autonomic dysfunction of skin in neuropathies: hyperthermal laser-Doppler flowmetry

Twenty patients suffering from diabetic neuropathy, 20 patients suffering from alcoholic neuropathy and 20 healthy volunteers within the same age range were studied for the stimulability of microcirculation with a new measuring design. A laser method (laser-Doppler flowmetry) was used to evaluate the increase of the microvascular blood flow of the skin during the hyperthermal phase. It evaluated the degree of increase of microcirculatory blood flow as well as the time from the beginning of hyperthermy to the onset of change in perfusion (the hyperthermal perfusion latency). This was significantly prolonged in both neuropathy groups; the increase of the microvascular blood flow in the diabetic neuropathies was significantly lower than found in alcoholic neuropathies and in healthy volunteers.     

左室内血流播散速度的测量方法及其生理意义

目的 :比较 M-型彩色多普勒测量的舒张早期左室内血流传播速度 (velocity of propagation,Vp)的两种方法 ,探讨 Vp的生理意义。方法 :2 0例受试者 (包括正常人和患者 ) ,每例受试者分别用 Garcia和 Takatsuji两种方法测量 Vp值。结果 :两种定义 Vp的方法的测值具有显著性差异 (P<0 .0 5 )。结论 :本文认为在临床上应采用Garcia的方法测量 Vp,因为该方法不依赖于单个像素点的选择 ,且在不同病例间具有一致性。     

灵芝多糖口服液对小鼠微循环及耐缺氧能力的研究

目的　探讨灵芝多糖对小鼠微循环及耐缺氧的影响。方法　小鼠 4 8只 ,随机分为 :⑴生理盐水对照组⑵⑶分别为口服液 15 0mg·kg- 1 组、30 0mg·kg- 1 组 ,各组灌胃一次 d ,连续 10天 ,观察对小鼠耳廓、脑膜血流速度、血流量及耐缺氧的作用。结果　 15 0mg·kg- 1 组、30 0mg·kg- 1 组均能加速小鼠耳廓、脑膜血流速度、增加血流量 ,并能增加呼吸次数及延长存活时间 ,与对照组比较有显著性差异 (P<0 0 5 ;P<0 0 1)。结论　口服液具有改善微循环、增加耐缺氧的能力。     

Higher sensitivity of CA1 synapses to aglycemia in streptozotocin-diabetic rats is age-dependent

We studied conduction velocity in peripheral nerves and the block of synaptic transmission produced by lack of glucose in hippocampal slices from 4- and 12-month-old streptozotocin-induced diabetic rats and their age-matched controls. In sural nerves of young and old diabetic rats, the conduction velocity was reduced by 30–35%. In slices from young diabetics, CA1 synaptic transmission was more sensitive to aglycemia than in control slices. However, all slices from older rats showed comparable increases in CA1 synaptic sensitivity to aglycemia. We conclude that the cerebral adaptation to diabetic hyperglycemia apparent in the hippocampus of young rats is masked in older rats by an age-dependent increase in sensitivity to lack of glucose.     

Cholesterol lowering therapy inhibits the low-flow mediated vasoconstriction of the brachial artery in hypercholesterolaemic subjects

1 We tested whether lipid lowering treatment with HMG CoA reductase inhibitor modified the flow mediated large artery reactivity in primary pure hypercholesterolaemia.
2 Abnormalities in arterial reactivity have been described in the presence of high blood cholesterol, in particular an enhanced constriction of the brachial artery in response to acute induction of a low flow state.
3 Using pulsed-Doppler, we measured brachial artery diameter and flow velocity at rest and their changes induced by wrist occlusion before and after 3 months of double-blind treatment by pravastatin (40  mg orally) in 13 subjects and placebo in 15 others.
4 The significant decrease ( P <0.01) in diameter induced by wrist occlusion before (0.34±0.08  mm) placebo and pravastatin (0.39±0.10  mm) persisted after placebo (0.26±0.07  mm) but was abolished after pravastatin (0.07±0.05  mm). The absolute change in diameter induced by wrist occlusion was lower after than before pravastatin ( P <0.01) and lower after pravastin than after placebo ( P <0.05). Diameter during wrist occlusion was higher after pravastatin than after placebo (4.35±0.16 vs 3.89±0.09  mm); P <0.01).
5 These findings indicate that the lipid changes induced by pravastatin and/or some unknown but direct mechanism of the drug itself inhibit low-flow-mediated vasoconstriction associated with hypercholesterolaemia. Such effects may have important implications for the treatment of vasospasm often seen in the presence of high blood cholesterol.     

Renal artery velocity mapping with MR imaging

An MR phase imaging sequence with a very short echo time was used to assess blood velocity and flow at the renal artery bifurcation. Cardiac-gated MR imaging data were obtained in six healthy subjects in sagittal planes adjacent to the abdominal aorta and transverse planes above and below the renal artery bifurcation. Average renal artery flow rate was 23.8 ±9 mL/sec. A strong individual variability was found for the velocity profiles in the abdominal aorta during end-systolic regurgitation. Flow rate was also determined in three patients with reduced renal artery blood flow. Two patients received therapy with percutaneous transluminal angioplasty. The successful outcome was documented with MR imaging. A reliable assessment of renal artery flow with MR phase imaging is feasible. Measurement of the velocity profiles yields valuable insights in the complicated flow regime at the renal artery bifurcation.     

壳聚糖对药液絮凝作用的研究

以壳聚糖为絮凝剂，研究了它对丹参水提液的絮凝情况。比较了絮凝剂加入量不同和分子量不同时，絮凝物的沉降速率，从而考察了它们对絮凝效果的影响以及所得产品的质量。     

Shortening velocity is different in longitudinal · and circular muscle layers of the rabbit urethra

The aim of the study was to investigate whether the functional difference between circular and longitudinal muscles in the female rabbit urethra is reflected in their shortening properties and lactate dehydrogenase (LDH) activity. For mechanical experiments the preparations were chemically skinned to avoid influence of membrane-related mechanisms and to enable maximal activation. Force–velocity relations and the maximal shortening velocity (v_max) were determined using the isotonic quick-release method. The v_max was three times higher in longitudinal muscle. LDH isoform pattern was determined on agarose gels. The M-subunit, favourable for lactate formation, constituted 70% of the total in both types of muscle. There was no difference in the LDH isoform pattern despite the marked difference in v_max. We conclude that the difference in v_max reflects differences in the contractile machinery itself. These mechanical characteristics are advantageous for the role of the circular as a tonic muscle contracting during bladder filling, and the longitudinal as a phasic muscle active in opening up the urethra during micturition. Received: 9 December 1997 / Accepted: 2 June 1998