电子对生物分子DNA损伤可能性的分析

目的研究电子在人体组织等效材料中形成的“簇点”能量分布情况，以及簇点的产生对生物效应发生的意义。方法针对电子与人体组织等效介质作用的物理机理，利用蒙特卡罗(MC)方法，按一个个相互作用事件(电离、激发、弹性散射、Auger电子发射)方式真实模拟电子在介质中的径迹，通过对这些事件进行统计分析，得到相关结论。结果电子在穿过介质过程中，主要以簇点(大于30％)形式沉积能量，并且80％以上的簇点中的能量沉积在50eV以上；簇点的密集程度与电子能量、簇点直径密切相关，簇点中能量沉积也取决于辐射类型和能量。结论簇点中的能量沉积是诱发组织细胞核内DNA分子各种损伤的最主要因素。     

Effects of glucagon-like peptide 1 (7–36 amide) on whole-body protein metabolism in healthy man

The incretin glucagon-like peptide 1 (GLP-1) shows glucose-dependent insulinotropic activity and may exert anabolic effects. Whole-body protein metabolism was assessed by measuring [1-¹³C]-leucine kinetics in 13 healthy volunteers during hyperglycaemic clamping with or without pancreatic clamping (somatostatin infusion) in order to differentiate between insulin-mediated and direct GLP-1 effects. During intact pancreatic secretion leucine flux and leucine oxidation rate as parameters of whole-body protein breakdown decreased markedly after 180 min of synthetic GLP-1 infusion (GLP-1 vs. placebo: P  < 0.003). Indirect calorimetry showed an increase in energy expenditure and CO₂ production during GLP-1 administration ( P  < 0.0005). Plasma insulin increased after 3 h of GLP-1 infusion to 1486 ± 145 pmol L⁻¹ vs. 185 ± 12 pmol L⁻¹ for saline ( P  < 0.0001). When plasma insulin levels were kept constant (GLP-1 vs. saline, NS) during pancreatic clamping, GLP-1 effects on both protein metabolism and energy expenditure were abolished. Thus, GLP-1 infusion in man exerts protein anticatabolic and thermic effects, which are mediated by GLP-1-induced stimulation of insulin secretion.     

周围剂量当量仪的研制

周围剂量当量仪研制是根据国际辐射单位和测量委员会（ＩＣＲＵ）３９号报告推荐的周围剂量当量而设计的一种数字化智能型辐射防护仪。方法采用能量补偿对探测器进行能响校正。结果补偿结果使得探测器在４７～２３０ｋｅＶ与ＩＳＯ推荐的Ｈ＊（１０）／Ｋａ值误差在５％以内。本文重点描述了周围剂量当量仪探测器部分的工艺结构和剂量学性能以及电子学测量部分的主要功能。结论通过实际应用我们初步获得的结论是由于该仪器可直接测量周围剂量当量，稳定性好且具有自动取平均值特点，它可做为实验室校准用测量仪器，又由于该仪器体积小，电池供电，读数面板又有背光功能，它也可以做为现场仪器用于辐射防护实践的现场测量     

四逆汤煎煮过程中乌头类生物碱的溶出和水解平衡

目的 研究四逆汤中乌头类生物碱的溶出平衡和水解平衡。方法 利用电喷雾质谱分析，比较了制附子、四逆汤、四逆汤药渣和含有3种双酯型生物碱的混合对照品体系中的乌头碱类二萜生物碱。结果 在煎煮过程中双酯型生物碱溶解并发生水解反应，而脂类生物碱则难溶于水。乌头碱、中乌头碱、次乌头碱水溶性相近，但是次乌头碱在水中的热稳定性更高，C19二萜骨架上C3取代基(—OH或—H)的变化影响生物碱的稳定性。结论四逆汤中的乌头碱类生物碱的种类及含量由其溶解性和化学稳定性共同决定。     

Plasma atrial natriuretic peptide (ANP) concentration and fluid balance during rapid intravenous saline infusions in camels

Human muscle samples were obtained with the percutaneous biopsy technique. The samples were membrane-hyperpermeabilized (skinned) using a chemical or freeze-drying technique. Short single fibre segments were dissected from the sample, transferred to an experimental chamber, connected to a force transducer and manipulator, and exposed to temperature-controlled solutions. The force generating-capacity, the sensitivity of the contractile apparatus to calcium and the caffeine threshold for calcium release from the sarcoplasmic reticulum could be studied in the short muscle fibre segments obtained from man with the percutaneous muscle biopsy technique. The average length of the fibre segments between the connectors was 0.44±0.21 mm. Thus, detailed studies of the contractile machinery can be made on human skinned muscle fibres with only minimal discomfort to the patient or subject during biopsy, which should be useful in studies of neuromuscular disease, muscle plasticity or in applied physiology.     

A critical period for functional vestibular development in zebrafish.

We have determined a critical period for vestibular development in zebrafish by using a bioreactor designed by NASA to simulate microgravity for cells in culture. A critical period is defined as the briefest period of time during development when stimulus deprivation results in long lasting or permanent sensory deficits. Zebrafish eggs were collected within 3 hours of being laid and fertilized. In experiment 1, eggs were placed in the bioreactor at 3, 24, 30, 36, 48, or 72 hours postfertilization (hPF) and maintained in the bioreactor until 96 hPF. In experiment 2, eggs were placed in the bioreactor immediately after they were collected and maintained in the bioreactor until 24, 36, 48, 60, 66, 72, or 96 hPF. Beginning at 96 hPF, all larvae had their vestibulo-ocular reflexes (VOR) evaluated once each day for 5 days. Only larvae that hatched from eggs that were placed in the bioreactor before 30 hPF in experiment 1 or removed from the bioreactor later than 66 hPF in experiment 2 had VOR deficits that persisted for at least 5 days. These data suggest a critical period for vestibular development in the zebrafish that begins before 30 hPF and ends after 66 hPF. To confirm this, zebrafish eggs were placed in the bioreactor at 24 hPF and removed at 72 hPF. VORs were evaluated in these larvae once each day for 5 days beginning at 96 hPF. These larvae had VOR deficits that persisted for at least 5 days. In addition, larvae that had been maintained in the bioreactor from 24 to 66 hPF or from 30 to 72 hPF, had only temporary VOR deficits. In a final experiment, zebrafish eggs were placed in the bioreactor at 3 hPF and removed at 96 hPF but the bioreactor was turned off from 24 hPF to 72 hPF. These larvae had normal VORs when they were removed from the bioreactor at 96 hPF. Taken as a whole, these data support the idea that there is a critical period for functional maturation of the zebrafish vestibular system. The developmental period identified includes the timeframe during which the vestibular primary afferent neurons are born, innervate their central and peripheral targets, and remodel their central projections.     

Quantitative evidence of peripheral conversion of angiotensin within the human leg: effects of local angiotensin-I administration and angiotensin-converting enzyme inhibition on regional blood flow and angiotensin-II balance across the leg

Summary The renin-angiotensin system relevantly contributes to the maintenance of systemic vascular tone and there is experimental evidence that large amounts of angiotensin-converting enzyme (ACE) are present in peripheral vascular tissues, including resistance vessels. To determine and quantify peripheral vascular conversion of angiotensin-I (ANG-I) to angiotensin-II (ANG-II) across the human leg, the response of regional blood flow to local regional intra-arterial infusion of ANG-I and changes in associated ANG-I1 balance were evaluated during ANG-I infusion and following additional ACE inhibition. Ten sodium-loaded healthy men were enrolled in the study. Following cannulation of both femoral arteries and the right femoral vein, leg blood flow was determined (indocyanine-green dye-dilution method) at baseline conditions and during constant intra-arterial infusion of haemodynamically ineffective doses of ANG-I as well as following concomitant intra-arterial administration of low doses of the non-sulfhydril ACE inhibitor cilazapril. From the transfemoral arterio-venous differences in ANG-II plasma concentrations and the corresponding regional blood (plasma) flow, the ANG-II balance across the leg was calculated. Systemic blood pressure did not change throughout the trial, indicating that no major systemic effects were present during ANG-I infusion or concomitant ACE inhibition. Moreover, arterial ANG-II plasma concentrations were not significantly changed by ANG-I infusion. Leg blood flow decreased to below baseline values following ANG-I infusion, increasing again then in a dose-dependent manner during concomitant cilazapril administration. The calculated baseline ANG-II balance across the leg revealed a net extraction in 6 out of 10 subjects and a net ANG-II formation in 4. Following ANG-I, a shift towards net ANG-II formation or decrease in extraction was seen in 8 subjects, while 2 had no change in ANG-II balance.During concomitant ACE inhibition, ANG-II balance was again shifted towards net extraction or reduced formation. Our results confirm that, in man, considerable regional arterio-venous differences in ANG-II plasma concentrations are present, resulting in either net transfemoral extraction or net formation of the peptide. It is suggested that systemic vascular conversion of circulating ANG-I might contribute to the maintenance of peripheral vasuclar tone in man. Send offprint requests to S. Gasic at the above address     

山东农村儿童膳食中人体锌吸收率的测定

目的:测定山东农村儿童代表性膳食中锌(Zn)的人体吸收率。方法:模拟山东农村典型膳食模式,采用富集的天然低丰度稳定性同位素67Zn标记ZnCl2,使用热电离质谱法(TIMS)检测膳食和粪便中总锌含量与67Zn/68Zn比值,计算锌的真吸收率;使用原子吸收分光光度计穴AAS雪测定膳食与粪便的总锌,计算锌的表观吸收率。同时测定影响锌吸收的因子膳食脂肪、蛋白、植酸、纤维素和维生素C(Vc)的含量,计算日平均摄入量,将其结果与我国儿童每日推荐膳食营养素摄入量(RNIs)进行比较。结果:锌的真吸收率为(12.94±3.32)%,锌的表观吸收率为(22.37±1.59)%,两者差异有统计学意义(P<0.05)。锌的平均日摄入量为11.16mg,占RNI的111.6%,高于推荐量。蛋白质和Vc的日摄入量分别为31.2g与13.3mg,占RNIs的56.73%和29.60%,低于推荐量。脂肪、植酸和膳食纤维的日摄入量较高。结论:在蛋白质和Vc的日摄入量较低,脂肪、植酸和膳食纤维的日摄入量较高的条件下,锌的真吸收率较低。     

Phobic postural vertigo: a first follow-up

Seventy-eight patients with phobic postural vertigo (PPV) and 17 patients with psychogenic disorder of stance and gait (PSG) were asked to evaluate their condition 6 months to 5.5 years after their original referral and short-term psychotherapy. Two results seem most important: (1) PPV had a favourable course with a 72% improvement rate (22% of patients becoming symptom free), whereas the majority of patients with PSG (52%) remained unchanged; (2) the majority of patients with PPV experienced complete remission or considerable improvement even if their condition had lasted between 1 and 20 years prior to diagnosis. Complete remission of PSG was observed only if the disorder had been present less than 4 months; there was no improvement if it had lasted longer than 2 years. PPV can be defined as a distinct clinical entity with a relatively benign course. It can be reliably diagnosed on the basis of typical features.