Precise extracellular marking in the auditory nerve with high impedance micropipettes

A procedure is described which permitted for the first time accurate marking of the recording sites of primary auditory nerve fibers, peripheral to their entrance into the brainstem. The technique, which involves a modification of the fast green FCF dye marking procedure, does not interfere with the recording quality of the high-impedance micropipettes, requires no special histology, permits routine production od 5-15 micron diameter marks at extracellular recording sites, and employs a dye known to be noncytotoxic.     

Contralateral influence on recruitment of curarized muscle fibres during maximal voluntary extension of the legs

The force of maximal voluntary contraction (MVC) was compared during extension of one leg alone and during simultaneous extension of both legs. In 6 subjects MVC of two leg extension was 75 + 3.6 (S.E.) % of the sum of the single one leg MVC. This may indicate a reduced muscle fibre involvement during two leg extension as compared with one leg extension. We investigated the possibility that either red (type I) or white (type II) muscle fibre recruitment was restricted during two leg extension. The neuromuscular transmission in the two types of fibres was partially blocked with d-tubocurarine (dtc) or decamethonium (C₁₀) for either type 1 or II, respectively. In 5 subjects receiving dtc the ratio between the reduced two leg and one leg extension forces (75 ± 2.3%) did not change. During administration of C₁₀, however, this ratio decreased by 16 ± 3.1 %. Partial blocking with dtc caused a two component curve during tension development with a first maximum at 0.22 s, and another maximum at 1.03 s of a 3 s attempt to reach MVC. During partial blocking with C₁₀ the first maximum disappeared indicating human fast twitch fibres to be blocked by C₁₀. Thus, partial blocking with C₁₀ results in muscle contractions where a relatively large amount of type I muscle fibres are contributing to the force developed. The experiment suggests that type I fibre recruitment is restricted during severe static exercise in normal muscles. Furthermore, it demonstrates that fibre recruitment can vary in the same muscle function performed with one leg or two legs.     

Rate of tension development in isometric contractions of a human hand muscle

The amplitude and rate of tension development during both electrical stimulation and voluntary activation of a human hand muscle were compared. The contractile responses from the first dorsal interosseous muscle of 14 normal human subjects were studied to provide the experimental data. At different forces less than 400g, under conditions of both electrical stimulation and voluntary contraction, force was directly proportional to speed of contraction. This linear relationship between the speed and force of contraction, as the proportion of active motor units varied, implies that these two parameters are similarly related in motor units of various sizes. In fast voluntary contractions, the rate of rise of tension at any given force level was greater than that observed in response to repetitive stimuli delivered to the motor nerve. Even at 200 and 500 impulses per second at maximal intensity, the speed of tension development was less than that found in fast voluntary contractions. The importance of asynchronous impulses and optimum discharge sequencing in generating a faster speed of tension development in fast voluntary contractions is underscored by these findings.     

A clinical procedure for the simultaneous recording of fast and slow EOG oscillations

A new method is described for the simultaneous registration of the slow and fast oscillations of the corneo-fundal potential. The means and standard errors of the parameters are given, and the relation of these parameters with the sex, age and iris pigmentation is discussed.     

Effects of serial lateral hypothalamic destruction on feeding behavior, body weight, and neocortical and hippocampal EEG activity

A comparison was made of effects of simultaneous vs. serial lateral hypothalamic lesions on (i) feeding behavior, (ii) body weight, (iii) hippocampal rhythmical slow activity, (iv) neocortical low voltage fast activity, and (v) atropine-resistant patterns of neocortical and hippocampal EEG in rats. Serial lesions separated by 30 days produced no significant sparing of function on the first three variables but produced significant sparing on the last two. The results suggest the effects may be related to anatomic and/or pharmacologic differences in the way neural systems subserving the different functions are organized.     

应用微量末梢全血检测华支睾吸虫病抗体研究

应用微量末梢全血快速ＥＬＩＳＡ法检测江门地区６３例居民标本中特异性华支睾吸虫抗体。与静脉血清、末梢血清检测结果对照，总符合率分别为９３．６５％和８７．３０％．其抗体阳性检出率与上述两法比较差异无显著性。以静脉血清检测为参照，末梢全血法的阳性和阴性预测值分别为９０．０％和９５．３５％。末梢全血快速ＥＬＩＳＡ用血量少，取血方便、易于接受，在华支睾吸虫病诊断尤其是现场普查中有较高的实用价值。     

豚鼠心室肌细胞Ikr快速失活过程的直接测定及意义

目的：直接测定豚鼠心室肌细胞Ｉｋｒ的失活过程。方法：在全细胞电压钳制下采用间期很短（３０ｍｓ）的双刺激法进行观察。结果：Ｉｋｒ的失活过程时程短（〈２０ｍｓ），速度快（从－２０ｍＶ到＋８０ｍＶ），呈电压依赖性。结论：Ｉｋｒ的内向整流作用是由其失活过程所致。双刺激法直接测定技术能更好地模拟心律失常过程，对心律失常的发生机理及抗心律失常药物作用的研究有重要价值。     

SPLICE: Sub-second diffusion-sensitive MR imaging using a modified fast spin-echo acquisition mode

Recent human studies for measuring of the apparent diffusion coefficient in tissue by magnetic resonance imaging have been conducted by time-consuming standard spin-echo acquisition sequences and phase correction with navigator echoes. Diffusion-weighted echo-planar sequences have been shown to be rapid alternatives for brain imaging. Both methods show inherent disadvantages in applications on thoracic or abdominal sites. A new approach combining single-shot diffusion-weighted imaging with a modified fast spin-echo acquisition mode is reported here. The modification is necessary, because normal fast spin-echo acquisition requires a particular phase relation between the magnetization and the refocusing pulses. Unfortunately, this phase relation is not provided after diffusion sensitive preparation. Therefore, the split echo acquisition mode was developed and is shown to be insensitive to the phase of the magnetization. The advantages of both fast spin-echo acquisition and diffusion weighting can be combined in the SPLICE sequence (split aqcuisition of fast spin-echo signals for diffusion imaging). The applicability of the new technique is shown by series of sub-second diffusion-weighted images from different parts of the body.     

Motor unit function in skeletal muscle autografts of rats

Standard and nerve-intact grafts of the extensor digitorum longus (EDL) muscles of rats do not fully recover control values for maximum tetanic tension (P_o). We compared the physiologic properties of motor units from standard and nerve-intact EDL grafts of rats with those of control EDL muscles. Standard grafts were completely removed and replaced in their original site. For nerve-intact grafts all physical connections were severed except for the nerve. Isometric contractile properties of whole muscles and single motor units were measured in situ 75 and 50 days after surgery for standard and nerve-intact grafts, respectively. Motor units from both types of grafts showed a mean and distribution for time-to-peak twitch tension (TPT) not different from control motor units. The absolute P_o of nerve-intact grafts showed a greater recovery than the standard grafts, but was still significantly lower than the control value. The average decrease in the P_o of motor units from nerve-intact grafts of 16% was not different from the decrease in the P_o of the total EDL graft which suggests no loss of motor units in nerve-intact grafts. In standard grafts, the 57% decrease in P_o for the whole muscle was attributable to a 20% decrease in the average tension development per motor unit and a 45% decrease in the number of motor units. These differences suggest a more complete reinnervation of the nerve-intact grafts than standard grafts.