Direct evidence for the link between monoaminergic descending pathways and motor activity:: II. A study with microdialysis probes implanted in the ventral horn of the spinal cord

In order to define precisely the relation between descending monoaminergic systems and the motor system, we measured in the ventral horn of spinal cord of adult rats the variations of extracellular concentrations of 5-HT, 5-HIAA, DA and MHPG. Measurements were performed during rest, endurance running on a treadmill, and a post-exercise period, with microdialysis probes implanted permanently for 45 days. We found a slight decrease in both 5-HT and 5-HIAA during locomotion with a more marked decrease during the post-exercise period compared to the mean of rest values. In contrast, the concentration of DA and MHPG increased slightly during the exercise and decreased thereafter. These results, when compared with those of a previous study, which measured monoamines in the spinal cord white matter [C. Gerin, D. Bécquet, A. Privat, Direct evidence for the link between monoaminergic descending pathways and motor activity: I. A study with microdialysis probes implanted in the ventral funiculus of the spinal cord, Brain Res. 704 (1995) 191–201], highlight the complex regulation of the release of monoamines that occurs in the ventral horn.     

心绞痛患者血小板功能改变及丹参对其影响

本实验观察了心绞痛患者血小板环核苷酸水平,血浆TXB_2、6酮PGF_(10)深度、血小板内外5—HT含量及血小板聚集性的变化以及丹参治疗前后各指标的改变。结果表明,心绞痛患者血小板聚集性血浆5—HT和血浆TXB_2水平明显增高,而血小板内5—HT、血浆6—酮—PGF_(10)水平则明显低于对照组。丹参能增加血小板内cAMP水平,降低血浆5—HT水平,对血小板聚集性有抑制作用。     

Functional mri of human brain activation combining high spatial and temporal resolution by a cine flash technique

Functional mapping of human brain activation has been accomplished at high spatial and temporal resolution (voxel size 4.9 μl, temporal increment 100 ms). The approach was based on oxygenation-sensitive long-echo time FLASH MRI sequences synchronized to multiply repeated cycles of visual stimulation in a CINE acquisition mode. This high temporal resolution revealed that stimulus-related signal intensity changes in human visual cortex display an initial latency followed by increases extending over several seconds. Furthermore, the temporal characteristics of the complete CINE MRI signal time course depended on the absolute and relative durations of activation and control periods and, for example, caused an apparent absence of a poststimulation “undershoot” phenomenon. Complementing hyperoxygenation due to rapid hemodynamic adjustments, these results suggest signal intensity modulation by enhanced oxygen consumption and concomitant deoxygenation during prolonged and/or repetitive stimulation.     

Pineal response after pyridoxine test in children

Summary To characterize the pineal response to pyridoxine, plasma melatonin was measured in one hundred and twenty children 3 hours after vitamin B₆ administration. The children, aged between 1.5 and 8 years, were divided in four groups as follows: a) control day group, grouping 27 children sampled at 9:00 and at 12:00; b) control night group, grouping 29 children sampled at 21:00 and at 24:00; c) pyridoxine day group, grouping 30 children sampled at 9:00, then intravenously (i.v.) injected with 3mg/kg of pyridoxine, and sampled at 12:00; and d) pyridoxine night group, grouping 34 children sampled at 21:00, i.v. injected with 3mg/kg of pyridoxine, and sampled at 24:00. Melatonin concentration was measured by radioimmuno assay. The data obtained showed a significant increase in melatonin levels after pyridoxine administration in the pyridoxine night group (39.87 ± 8.02pg/ml basal vs 88.45 ± 9.21 pg/ml after pyridoxine, p < 0.001). The other groups did not showed significant differences in melatonin concentrations. Statistical analysis shows that the administration of pyridoxine during the nocturnal hours represents a stimulating factor to increase the pineal production of melatonin in children.     

Pattern electroretinogram can be more than the sum of local luminance responses

It is generally accepted that the pattern electroretinogram for very large spatial elements is the result of local luminance stimulation. Responses due to the luminance differences between elements may be assumed to be relatively unimportant because in the case of large elements only few retinal units are stimulated by gradients. With decreasing pattern element size one wonders to what extent the electroretinogram continues to be based on the local luminance stimulation. We investigated this question using 8 Hz checkerboard reversal and compared the pattern recordings with the recordings resulting from the same stimulus field modulated homogeneously (focal electroretinogram). A 100% modulated checkerboard at retinal level may be considerably less modulated because of imperfect optics of the eye. So the pattern electroretinogram should be compared with homogeneous field stimulation of correspondingly lower modulation depth. On the basis of the optical transfer properties of the eye we compared by subtracting the proper focal electroretinogram from the pattern electroretinogram. The difference response was virtually zero for check sizes larger than 120. For checks from 60 down the difference response was of the same order of magnitude as the adjusted focal recording. This difference response for eyes with normal optics is largest around 30; its wave form was found to be rather invariant with check size.     

Haemodynamic effects of atropine during halothane or isoflurane anaesthesia in infants and small children

In this study, two-dimensional and pulsed Doppler echocardiography were used to measure cardiovascular changes before and after IV atropine in 31 infants and small children during halothane (n = 15) or isoflurane (n = 16) anaesthesia. Prior to induction of anaesthesia heart rate (HR), mean blood pressure (MBP), and two0dimensional echocardiographic dimensions of the left ventricle and pulmonary artery bloodflow velocity were measured by pulsed Doppler echocardiography. Cardiovascular measurements were repeated while anaesthesia was maintained at 1.5 MAC halothane (n = 15) or isoflurane (n = 16). Atropine 0.02 mg·kg⁻¹ IV was then administered and two minutes later, a third set of cardiovascular data was obtained. Heart rate decreased during halothane anaesthesia but did not change significantly during isoflurane anaesthesia. Mean blood pressure, cardiac output (CO) and stroke volume (SV) decreased similarly during 1.5 MAC halothane or isoflurane anaesthesia. Ejection fraction (EF) decreased and left ventricular end-diastolic volume (LVEDV) increased significantly in bothgroups, but decreases in EF (32 ± 5 percentvs18 ± 5 per cent) and increases in LVEDV (18 ± 7 per cent vs7 ± 5 per cent) were significantly greater during halothane than during isoflurane anaesthesia. Following atropine, HR increased more in the patients maintained with halothane (31 ± 6 per cent), than during isoflurane anaesthesia (18 ± 5 per cent). Atropine increased CO in both groups of patients, but SV and EF remained unchanged. When compared with awake values, HR increased similarly and significantly (18 ± 4 per cent) following atropine in both groups, and CO returned to control levels. Halothane decreased EF and increased LVEDV more than isoflurane at 1.5 MAC end— expired anaesthetic levels. Atropine did not diminish the myocardial depression produced by halothane or isoflurane. The increase in CO following atropine during halothane and isoflurane anaesthesia in infants and small children is the result of increases in HR alone. Nous avons utilisé un appareil à échocardiographie bi-dimensionnelle couplé à un Doppler pulsé chez des bébés et de jeunes enfants pour évaluer l’impact hémodynamique de l’halothane (n = 15) et de l’isoflurane (n = 16) et la modification possible de ces effets par l’atropine. Nous avons mesure la frequence cardiaque (FC), la pression artérielle moyenne (PAM), la dimension de la cavité ventriculaire gauche (par écho bi-dimensionnelle) et la vélocité du flot sanguin pulmonaire (par Doppler) et ce, en trois occasions soit avant l’induction, après l’instauration de 1.5 MAC d’halothane ou d’isoflurane et finalement, deux minutes après l’injection IV de 0.02 mg·kg⁻¹ d’atropine. On ne nota une baisse de la frequence cardiaque qu’avec l’halothane tandis que la PAM, le débit cardiaque (DC) et le volume d’éjection (VE) diminuaient autant avec l’un ou l’autre anesthésique. La diminution de la fraction d’éjection (FE) et l’augmentation du volume télédiastolique du ventricule gauche (VTDVG) significatives pour les deux groupes, étaienl plus marqué avec l’halothane qu’avec l’isoflurane: FE 32 ± 5 pour cent vs18 ±5 pour cent; VTDVG 18 ± 7 pour cent vs 7 ± 5 pour cent. Avec l’atropine, la FC monta plus dans le groupe halothane (31 ± 6 pour cent) que dans le groupe isoflurane (18 ± 5 pour cent), le DC augmentant dans les deux groupes, alors que le VE et la FE demeuraient inchangés. Comparée aux mesures pré-induction, l’atropine amenait une hausse significative de la FC, semblable dans les deux groupes (18 ± 4 pour cent) et restaurait le DC. Donc, chez les bebes et les jeunes enfants, a 1.5 MAC, l’halothane diminue la FE et augmente le VTDVG plus que ne le fait l’isoflurane. L’atropine ne modifie pas la depression myocardique et elle ne restaure le DC que par une hausse de la FC.

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Supported by PHS Grant No. 8507300 from the College of Medicine, University of Iowa Hospital, Iowa City, IA.     

筑起抗击"非典"的心理长城

目的 探讨心理疗法对防治SARS的作用,方法 本文综合国内外心理疗法研究成果,提出了应对非典的心理处方：“接纳恐惧,顺其自然;平衡思维,端正认识;积极暗示,增强信心;切已体察,心理常态”;结果 从原理上解释其发生作用的机制,明确心理处方的实际操作,提出具体的步骤和要点,并对日常生活中的不妥做法进行了剖析。结论 采用心理疗法可增强抗击“非典”的信心及提高免疫功能。     

Advection and Diffusion of Substances in Biological Tissues With Complex Vascular Networks

For highly diffusive solutes the kinetics of blood–tissue exchange is only poorly represented by a model consisting of sets of independent parallel capillary–tissue units. We constructed a more realistic multicapillary network model conforming statistically to morphometric data. Flows through the tortuous paths in the network were calculated based on constant resistance per unit length throughout the network and the resulting advective intracapillary velocity field was used as a framework for describing the extravascular diffusion of a substance for which there is no barrier or permeability limitation. Simulated impulse responses from the system, analogous to tracer water outflow dilution curves, showed flow-limited behavior over a range of flows from about 2 to 5 ml min^–1 g^–1, as is observed for water in the heart in vivo. The present model serves as a reference standard against which to evaluate computationally simpler, less physically realistic models. The simulated outflow curves from the network model, like experimental water curves, were matched to outflow curves from the commonly used axially distributed models only by setting the capillary wall permeability–surface area (PS) to a value so artifactually low that it is incompatible with the experimental observations that transport is flow limited. However, simple axially distributed models with appropriately high PSs will fit water outflow dilution curves if axial diffusion coefficients are set at high enough values to account for enhanced dispersion due to the complex geometry of the capillary network. Without incorporating this enhanced dispersion, when applied to experimental curves over a range of flows, the simpler models give a false inference that there is recruitment of capillary surface area with increasing flow. Thus distributed models must account for diffusional as well as permeation processes to provide physiologically appropriate parameter estimates. © 2000 Biomedical Engineering Society. PAC00: 8719-j, 8710+e     

改变在体兔左心室后负荷对其电生理参数的影响

目的：探讨改变在体兔左心室后负荷对室性心律失常发生情况及左心室电生理参数的影响。方法：改变左心室后负荷，观察室性心律失常发生情况，并测定左心室舒张阈值（ＶＤＴ），相对不应期（ＲＲＰ），有效不应期（ＥＲＰ）及其不应期离散和心室纤颤阈（ＶＦＴ）。结果：逐级增加左心室后负荷（ＡＢ级）可使左室空间ＲＲＰ，ＥＲＰ离散增加（Ｂ级，Ｐ＜００５），ＶＦＴ降低（Ｂ级，Ｐ＜００１）；各实验动物均出现室性心律失常（Ｂ级）；而逐级减小左室后负荷（ＣＤ级），心室电生理参数无变化（Ｐ＞００５），各实验动物亦无室性心律失常发生。结论：增加左心室后负荷诱发室性心律失常，与左室空间不应期离散增加有关。