Effect of contralateral cane use on hip moment impulse in the frontal plane during the stance phase

BackgroundRecent reports have shown that the daily cumulative moment in the frontal plane (i.e., product of hip moment impulse in the frontal plane during the stance phase and mean steps per day) is a risk factor for hip osteoarthritis. This study aimed to clarify the effect of contralateral cane use on hip moment impulse in the frontal plane of the stance limb.MethodsThis study included 15 healthy subjects who walked under four experimental conditions: (1) without a cane and (2–4) contralateral cane use with 10%, 15%, and 20% body weight support (BWS), respectively. To maintain the same walking speed in all conditions, the cadence was set to 80 steps/min, and the step length was fixed. The hip moment impulses in the frontal plane (i.e., area under the hip ab-adduction moment waveform) and peak hip adduction moments in all conditions were calculated.ResultsContralateral cane use significantly decreased the hip moment impulse in the frontal plane and peak hip adduction moment compared to non-cane use. Moreover, the hip moment impulse in the frontal plane and peak hip adduction moment decreased significantly with increased cane BWS. There were no significant differences in walking speed, cadence, and step length between the four conditions.ConclusionContralateral cane use decreases the hip moment impulse in the frontal plane and peak hip adduction moment in the stance limb. These findings may help clarify how to delay the progression of hip osteoarthritis.     

脉冲振荡技术在儿童支气管舒张试验中的应用

目的：探讨脉冲振荡方法(IOS)在儿童支气管舒张试验中的应用及其与常规肺量计法结果的相关关系。方法：发作期的哮喘患儿同时应用两种方法做吸入支气管扩张剂前后肺功能测定，以FEV1改善≥15％判断为阳性，应用统计学处理对两种方法各指标作相关性分析。结果：IOS各指标舒张后改善明显，△Zrs、△R5与金标准△FEV1密切相关，经多元回归得出方程△FEV1=-1．527△Zrs 0．883△R5。结论：IOS法可以作为不能配合用力呼气动作的儿童行支气管舒张试验。     

5-HT1A receptor agonists: recent developments and controversial issues

During the last decade, serotonin (5-HT)_1A receptors have been a major target for neurobiological research and drug development. 5-HT_1A receptors have been cloned and a variety of selective agonists, such as the aminotetraline 8-OH-DPAT and the pyrimidinylpiperazine ipsapirone, have become available. Demonstrations of apparent intrinsic activity of these ligands at 5-HT_1A receptors, however, depend highly on the particular assay system. This may be due to the possible existence of receptor subtypes and to assay (or brain region)-dependent differences in receptor reserve and the nature of receptor-effector coupling. Nevertheless, the apparent intrinsic activity of 8-OH-DPAT seems to be higher (although possibly not yet maximal) than that of the pyrimidinylpiperazines. In the brain, 5-HT_1A receptors are located presynaptically as somatodendritic receptors on 5-HT neurons and postsynaptically in particular limbic and cortical regions. Although it is generally accepted that presynaptic 5-HT_1A receptors control 5-HT neuronal activity, recent evidence suggests an additional role of postsynaptic 5-HT_1A receptors in cortex as part of a negative feedback loop. Anxiolytic and antidepressive properties of selective 5-HT_1A receptor agonists have now been confirmed by clinical studies. Although it is well established that the latter properties depend on theagonistic activity of these compounds, theoptimal level of intrinsic activity is still a matter of debate and may be dependent on the clinical indication. Such compounds may also have antiaggressive effects, and possibly anticraving effects (manifested by their alcohol intake-reducing effects in dependent animals), but the specificity of these so-called anti-impulsivity effects is still controversial and not yet tested clinically. Anticataleptic, antiemetic and neuroprotective properties have been demonstrated in different species. Behavioral studies on the mechanisms underlying the anxiolytic and antidepressive effects have examined the relative contribution of pre-and postsynaptic 5-HT_1A receptors by means of local cerebral application and lesion techniques. Most evidence points towards a critical involvement of presynaptic receptors in the anxiolytic effects of 5-HT_1A receptor agonists (although a possible contribution of postsynaptic receptors cannot be excluded). With regard to the antidepressive properties, a case can be made for the reverse; i.e., a strong involvement of postsynaptic receptors and a questionable contribution of presynaptic receptors. However, as the therapeutic effects of those 5-HT_1A receptor (partial) agonists which have been tested clinically require repeated administration, attention has been directed increasingly towards chronic studies. These studies have shown that a number of electrophysiological, biochemical, behavioral and endocrinological 5-HT_1A receptor-related events adapt differentially to repeated or sustained administration. Thus, several hypotheses accounting for the delayed onset of action have been advanced. Among these, time-dependent downregulation /desensitization of eitherpre- orpostsynaptic 5-HT_1A receptors, or cortical 5-HT₂ receptors have received much attention. However, these hypotheses have their weaknesses, and it is argued thatfunctional sensitization of particular postsynaptic 5-HT_1A receptor-mediated events remains a valuable alternate hypothesis. Basic research on the role of 5-HT_1A receptors in psychopathology and in the therapeutic effects of clinically effective therapeutics, as well as on the mechanism of action of 5-HT_1A receptor ligands, will enable rational design of ligands with particular profiles of intrinsic activity at different 5-HT_1A receptor populations, and may contribute to a more efficient treatment of a multiplicity of brain disorders.     

Impulse patterns of Ia afferents and Ia-activated DSCT neurons during sinusoidal muscle stretch in cats

Summary The cat gastrocnemius muscles of one hind leg were stretched sinusoidally with amplitudes between 10 m and 2.5 mm and frequencies between 1 and 30 Hz. The stretch response of deefferented muscle spindle afferents and of Ia-activated cells within Clarke's column were investigated by means of extra-cellular recordings of action potentials. The responses to 20–50 cycles were displayed in impulse patterns (raster diagrams) of the responding action potentials. The impulse patterns of Ia afferents exhibited a high degree of phase-locking (regularity) on the stretch cycle of amplitudes of about 50 m at 3 Hz and all higher amplitudes or frequencies. At comparable stretch parameters the regularity in Ia afferents was 4–6 times larger than in Ia-activated DSCT neurons. The regularity in the DSCT patterns increased with an increase in stretch frequency. The impulse patterns of DSCT cells exhibited a high negative correlation between successive interspike intervals (–0.4 to –0.6) at low stretch frequencies (<3 Hz), which decreased with an increase in stretch frequency.     

Compact and accurate linear and nonlinear autoregressive moving average model parameter estimation using Laguerre functions

A linear and nonlinear autoregressive moving average (ARMA) identification algorithm is developed for modeling time series data. The algorithm uses Laguerre expansion of kernals (LEK) to estimate Volterra-Wiener kernals. However, instead of estimating linear and nonlinear system dynamics via moving average models, as is the case for the Volterra-Wiener analysis, we propose an ARMA model-based approach. The proposed algorithm is essentially the same as LEK, but this algorithm is extended to include past values of the ouput as well. Thus, all of the advantages associated with using the Laguerre function remain with our algorithm; but, by extending the algorithm to the linear and nonlinear ARMA model, a significant reduction in the number of Laguerre functions can be made, compared with the Volterra-Wiener approach. This translates into a more compact system representation and makes the physiological interpretation of higher order kernels easier. Furthermore, simulation results show better performance of the proposed approach in estimating the system dynamics than LEK in certain cases, and it remains effective in the presence of significant additive measurement noise.     

Origin of impulse initiation in the slowly adapting stretch receptor of the crayfish

Summary Characteristic for the crayfish stretch receptor is a gradual decrease in axon diameter up to a stretch of axon about 350 m away from the soma-axon border. In response to depolarizing currents applied at different positions along the axon this stretch of axon can be localized as the most excitable membrane region. When depolarizing current steps of 10–25 nA intensity are injected into the soma the first impulse is always triggered in the soma (due to sudden rise in the membrane potential) while the second impulse originates at the axon region of highest escitability. As the intensity of the stimulus is increased the site of impulse initiation along the axon shifts nearer to the receptor soma. At a stimulus intensity of 50 nA the second impulse is suppressed and only the membrane potential at the axon hillock increases slightly. An analysis of the conductances for sodium and potassium ions as well as of the leakage current suggests that the molecular basis for the observed variations in excitability resides in a gradual decrease of the sodium conductance between the cell soma and the small-diameter region of the axon. However, the resting potential in this most excitable axon region is only some 3 mV more positive as compared to the receptor soma. A mathematical formulation is presented for the encoder mechanism in a soma-axon region with varying diameter. Using a slightly modified form of the Hodgkin-Huxley equations the experimentally observed changes in membrane potential and in the time course of the ionic currents can be adequately described by applying a nonlinear cable equation to the inhomogeneous axon.     

Pseudorandom testing technique for the characterization of local hemodynamic control

Summary In order to investigate the low frequency properties of renal and femoral hemodynamic variables, pseudorandom testing techniques were used. The arterial flow of each bed, in separate experiments, was modulated by a low amplitude signal based on a pseudorandom binary sequence (PRBS) generated by digital computer.The cross-correlation functions between input flow and arterial pressure, venous pressure, and venous flow exhibit damped oscillations in all cases. These responses are parameterized in terms of a damping ratio () and an undamped natural frequency _n for a second order model. The parameters of the model are dependent upon the state of the bed as defined by mean arterial and venous pressures, mean flow through the bed, resistance, and oxygen consumption.The results of this study offer further insight into the dynamic low frequency autoregulation phenomenon for the renal and femoral beds of the dog.Supported by NIH Grant HE 11747.     

Model identification and estimation of organ-function parameters using radioactive tracers and the impulse-response function

Examination of the input-output events in functioning organs by the use of the impulse-response function (IRF) for a radioactive tracer is gaining more and more ground in nuclear medicine. This study summarizes the development of deconvolution analysis, laying special stress on the model-free approach. System linearity and time invariance are discussed, and means of eliminating noise in IRFs originating from the input and organ-time-activity curves are outlined. Typical IRFs are illustrated by flow diagrams, time-domain curves, and their representation by Laplace transforms. The cases of nondiffusible and diffusible tracers as well as parenchymally extracted and transported substances are discussed. Methods for the derivation of models and for the calculation of physiologically important parameters from theIRFs are suggested.At present, a guest scientist at the Institute for Medicine, Nuclear Research Center Jülich, Jülich, Federal Republic of Germany     

Preventive effect of magnesium supplement on noise-induced hearing loss in the guinea pig

The effect of magnesium (Mg) on noise-induced hearing loss was investigated in two groups of adult pigmented guinea pigs maintained either on optimal or suboptimal (physiologically high or low) Mg produced by different diets. The total Mg concentrations of the perilymph (PL), cerebrospinal fluid, blood plasma and red blood cells were measured by atomic absorption spectrometry and were found to differ significantly between the two groups (P < 0.01). One ear of each animal was exposed to either a single shooting impulse at a peak pressure level of 187 dB or two impulse noise series at a rate of 1/s and peak pressure levels of 150 dB (1,000 impulses) and 167 dB (2,280 impulses), respectively. Temporary (TTS) and permanent (PTS) hearing threshold shifts in anesthetized animals were measured 2 h and 1 week after the noise exposure, using auditory brain stem response (ABR) audiometry at a frequency range from 3.75 to 30 kHz. Exposure to the single noise impulse resulted in a mean TTS that was significantly lower in the high Mg group than that in the low Mg group (P < 0.05), although no substantial PTS was observed in either group. In the animals exposed to 150 dB noise, the TTS showed a tendency towards an Mg-related reduction at the higher frequencies. A small difference in PTS was found between the low Mg and high Mg groups, but was not significant. Exposure to the 167-dB noise series caused a considerable TTS, which was significantly lower in the high Mg group at 7.5 and 15 kHz than in the low Mg group (P < 0.05). The mean PTS showed a significant difference between the two Mg groups over the whole frequency range (P < 0.05) and was found to correlate negatively with the total Mg concentrations of both PL and plasma (P < 0.05). Moreover, the high Mg group showed a faster recovery from the hearing threshold shift than the low Mg group. The present findings show that preventive oral Mg supplements can significantly reduce the rate of acoustic trauma caused by high-level impulse noise exposure in the guinea pig. Received: 23 March 1999 / Accepted: 15 April 1999     

Relationships of plasma tryptophan availability to course of illness and clinical features of alcoholism: a preliminary study

Rationale: Serotonergic (5-HT) mechanisms may be involved in impulse control (including anti-social behavior) across psychiatric syndromes. Age of onset may differentiate alcoholics on psychopathological characteristics associated with impulse control, especially mood disturbance, hostility, and a broad range of antisocial behaviors. Thus, there may be a predictable relationship between markers of 5-HT function and age of onset-related characteristics. Objective: We tested the hypothesis that there would be a predictable relationship between the ratio of plasma tryptophan to large neutral amino acids (i.e. TRYP/LNAA ratio), a marker of 5-HT function, age of onset and related psychopathological characteristics associated with impulse control. Methods: Fifty-eight male and female DSM-IV diagnosed alcoholics attending an outpatient treatment center completing a comprehensive psychopathological assessment, and from whom blood samples were obtained. Results: Plasma TRYP/LNAA ratio was positively correlated with symptoms of dysphoria, and negatively associated with harm avoidance on Cloninger’s Temperament and Character Inventory. Low tryptophan availability was associated with antisocial-type personality characteristics. Interestingly, the few (nine) subjects who had both early onset alcoholism and antisocial personality disorder had a higher plasma tryptophan but similar TRYP/LNAA ratio to the others. Conclusions: These data suggest that a low plasma TRYP/LNAA ratio is associated with susceptibility to anxiety, antisocial-type personality characteristics, and an early age of onset for alcoholism. In contrast, a high plasma TRYP/LNAA ratio is associated with a later onset of alcoholism and dysphoria. Received: 26 May 1998/Final version: 24 November 1998