白内障晶状体上皮细胞及晶状体纤维超微结构的观察

应用胎儿晶状体发育的超微结构为形态学依据,观察老年性、外伤性、先天性白内障晶状体的超微结构.结果:老年性白内障晶状体上皮多数细胞膜破裂,作者首先发现其原因是相邻细胞顶部的紧密连结缺失,房水侵入所致.胞质中线粒体空泡化,内质网扩张、脱粒.晶状体纤维膨胀、崩溃.细胞之间的各种连结消失.外伤性白内障除具有白内障特点外,胞质中出现大量溶酶体、残体.1例先天性白内障,上皮细胞发育尚好,晶体纤维不发育.     

Inheritance of ocular dominance

Evidence for an inherited component in the determination of the preferred eye in sighting dominance is presented that replicates the earlier findings by Merrell (1957). Significantly more left-sighting-preferent individuals were found in the progeny of R×L and L×L matings than in the R×R matings.The preparation of this study was supported by National Institute of Mental Health Grant MH-21989.     

The hippocampus and neurotransplantation

The present article is a review of our own results from histological and electron microscopic studies of hippocampal neurotransplants with different levels of integration with recipient brains. A model providing complete isolation from the brain was obtained using transplants developing in the anterior chamber of the eye. The growth, development, and cytological composition of transplanted tissue was found to depend on factors such as the age of the donor embryo tissue, the genetic compatibility between the donor and recipient, and the level of integration with the brain. Ultrastructural analysis of intraocular and intracortical transplants showed that overall, nerve and glial cells have the characteristics of highly differentiated, mature elements; the numerical density and structures of synaptic contacts were similar to those in normal conditions. However, transplanted tissues contained morphological features providing evidence of continuing growth of several nerve processes and increases in non-synaptic and transport-metabolic intercellular interactions. The ultrastructural deviations observed here are regarded as the manifestations of compensatory-adaptive changes during the development of tissues in conditions deficient in natural afferent synaptic influences. It is also demonstrated that the axons of transplanted neurons lacking adequate cellular targets can establish functional synaptic contacts with neuronal elements in the recipient brain which are not their normal targets.Translated from Zhurnal Vysshei Nervnoi Deyatelnosti, Vol. 54, No. 2, pp. 149–162, March–April, 2004.     

Corticospinal excitability during laughter: implications for cataplexy and the comparison with REM sleep atonia

Cataplexy is usually seen as rapid eye movement (REM) sleep atonia occurring at an inopportune moment. REM sleep atonia is the result of postsynaptic inhibition, i.e. inhibition of alpha motor neurones. Although this may explain the suppression of H-reflexes during REM sleep, cataplexy and laughter, it is not the only explanation. Presynaptic inhibition, in which afferent impulses are prevented from reaching motor neurones, is an alternative. Testing H-reflexes and magnetic-evoked potentials (MEPs) helps to tell them apart: in postsynaptic inhibition MEPs and H-reflexes change in tandem, while H-reflexes may decrease independent of MEPs with other inhibition modes. We studied motor inhibition during laughter, the strongest trigger for cataplexy. H-reflexes were evoked every 2 s in the soleus muscle in 10 healthy subjects watching comical video fragments. MEPs were evoked when H-reflexes decreased during laughter, and, as a control, when subjects did not laugh. Pairs of MEPs and the immediately preceding H-reflexes were studied. Compared with the control condition, laughter caused mean MEP area to increase by 60% (P=0.006) and mean H-reflex amplitude to decrease by 33% (P=0.008). This pattern proves that postsynaptic inhibition cannot have been the sole influence. The findings do not prove which mechanisms are involved; one possibility is that the decrease in H-reflex amplitude was the result of presynaptic inhibition, and that cortical and/or spinal facilitation accounted for increased MEPs. Regardless, the pattern differs fundamentally from the reported mechanism of REM sleep atonia. Existing scanty data on cataplexy suggest a pattern of H-reflexes and MEPs similar to that during laughter, but this needs further study.     

Eye movement disorders after frontal eye field lesions in humans

Eye movements were recorded electro-oculographically in three patients with a small ischemic lesion affecting the left frontal eye field (FEF) and in 12 control subjects. Reflexive visually guided saccades (gap and overlap tasks), antisaccades, predictive saccades, memory-guided saccades, smooth pursuit and optokinetic nystagmus (OKN) were studied in the three patients. Staircase saccades and double step saccades were also studied in one of the three patients. For both leftward and rightward saccades, latency in the overlap task (but not in the gap task) and that of correct antisaccades and of memory-guided saccades was significantly increased, compared with the results of controls. There was a significant decrease in the amplitude gain of all rightward saccades programmed using retinotopic coordinates (gap and overlap tasks, predictive and memory-guided saccades), whereas the amplitude gain of corresponding leftward saccades was preserved. Such an asymmetry between leftward and rightward saccades was significant. In the staircase paradigm as well as for the first saccade in the double step paradigm (with the use of retinotopic coordinates in both cases), the amplitude gain of rightward saccades was also significantly lower than that of leftward saccades. Moreover, in the double step paradigm, the amplitude gain of the first rightward saccade was significantly lower than that of the second rightward saccade (programmed using extraretinal signals), which was preserved. The percentage of errors in the antisaccade task did not differ significantly from that of normal subjects. In the predictive saccade paradigm, the percentage of predictive rightward saccades was significantly decreased. The left smooth pursuit gain for all tested velocities, the right smooth pursuit gain for higher velocities, and the left OKN gain were significantly decreased. The results show, for the first time in humans, that the FEF plays an important role in (1) the disengagement from central fixation, (2) the control of contralateral saccades programmed using retinotopic coordinates, (3) saccade prediction and (4) the control of smooth pursuit and OKN, mainly ipsilaterally. In contrast, the left FEF did not appear to be crucial for the control of the only type of saccades programmed using extraretinal signals studied here.     

Seasonal allergic conjunctivitis is accompanied by increased mast cell numbers in the absence of leucocyte infiltration

Background Seasonal allergic conjunctivitis (SAC) is the most common allergic disease to affect the eye. occurring alone or in association with allergic rhinitis. Infiltration with mast cells and eosinophils is characteristic of the chronic forms of allergic conjunctivitis such as vernal and atopic keratoconjunctivitis. and these cell types also contribute significantly to allergic inflammation in the skin. Indirect evidence for a similar pattern of cellular events in SAC comes from studies which demonstrate raised eosinophil and neutrophil numbers in conjunctival scrapings and elevated levels of mast cell tryptase in tears following allergen challenge. Objective To directly characterize the inflammatory cell infiltrate in SAC and to determine its clinical relevance. Methods We employed specific immunohistochemical staining to count masi cells, eosinophiis and neutrophiis in the conjunctival epithelium and lamina propria of eight atopic patients with SAC in, and 12 SAC patients out of the hay fever season. Sixteen patients with no history of ocular allergy were used as control subjects. Results Mast cells were absent from normal epithelium. During the pollen season median mast cell numbers in the lamina propria were found to be increased by 6I'J(in patients with SAC compared with normals (P= 0.012). Eosinophils were found in the lamina propria in less than half of the symptomatic patients with SAC and in only three patients were eosinophils present in the epithelium. The neutrophil numbers in the lamina propria of patients with SAC tended to be higher than normals but these changes did not reach statistical significance. Conclusion Conclusion These data based on the direct assessment of conjunctival tissue provide evidence that symptoms occur in SAC in the absence of detectable recruitment of eosinophils or neutrophils. This suggests that this disorder is related to mast cell-mediated changes.     

Development of oculomotor functioning in preadolescence, adolescence, and adulthood

We examined developmental differences in smooth pursuit eye tracking proficiency in a large sample of preadolescent, adolescent, and adult males. Smooth pursuit was quantified using general measures of oculomotor functioning and by examining the frequency and dynamic characteristics of specific saccadic events. Examination of age effects using general measures indicated that, by late adolescence, the smooth pursuit system reached adult levels of functioning. No significant differences were found between the adolescent and adult groups on most global measures. However, both groups had better eye tracking than the preadolescent group, suggesting that during preadolescence the oculomotor system is still developing and is not yet capable of optimal performance. Examination of the frequency and dynamic characteristics of the saccadic events yielded additional information regarding the nature of the smooth pursuit eye tracking differences of the three age groups.     

Smooth eye movements evoked by electrical stimulation of the cat's superior colliculus

Head-fixed gaze shifts were evoked by electrical stimulation of the deeper layers of the cat superior colliculus (SC). After a short latency, saccades were triggered with kinematics similar to those of visually guided saccades. When electrical stimulation was maintained for more than 150–200 ms, postsaccadic smooth eye movements (SEMs) were observed. These movements were characterized by a period of approximately constant velocity following the evoked saccade. Depending on electrode position, a single saccade followed by a slow displacement or a staircase of saccades interspersed by SEMs were evoked. Mean velocity decreased with increasing deviation of the eye in the orbit in the direction of the movement. In the situation where a single evoked saccade was followed by a smooth movement, the duration of the latter depended on the duration of the stimulation train. In the situation where evoked saccades converged towards a restricted region of the visual field (goal-directed or craniocentric saccades), the SEMs were directed towards the centre of this region and their mean velocity decreased as the eye approached the goal. The direction of induced SEMs depended on the site of stimulation, as is the case for saccadic eye movements, and was not modified by stimulation parameters (place code). On the other hand, mean velocity of the movements depended on the site of stimulation and on the frequency and intensity of the current (rate code), as reported for saccades in the cat. The kinematics of these postsaccadic SEMs are similar to the kinematics of slow, postsaccadic correction observed during visually triggered gaze shifts of the alert cat. These results support the hypothesis that the SC is not exclusively implicated in the control of fast refixation of gaze but also in controlling postsaccadic conjugate slow eye movements in the cat.