Do hypothalamo-cerebellar fibres terminate in all layers of the cerebellar cortex?

Summary The terminal distribution of hypothalamo-cerebellar fibres has been studied with anterograde transport of the wheat germ agglutinin-horseradish peroxidase complex in the cat and rat. The hypothalamo-cerebellar fibres appear to enter all three layers of the cerebellar cortex. Anterogradely labelled branching axons were found in the ranular layer and near the Purkinje cell perikarya. In addition, anterogradely filled hypothalamo-cerebellar axons could be traced into the molecular layer, where they ramified. The branches ran parallel to the long axis of the folia, resembling parallel fibres.Our findings give evidence that the hypothalamo-cerebellar fibres are neither mossy fibres nor climbing fibres, but represent a third type of cerebellar cortical afferents. Fibres of this third category are tentatively called multilayered fibres. It appears from the literature that some other cerebellar afferent projections show the same general pattern of cortical terminal distribution.     

Morphological changes in the cerebellar cortex of aging Macaca nemestrina

The cerebellar cortices in 4, 10 and 20 year old Macaca nemestrina have been examined for the number of Purkinje (P) and granule cells and the deposition of lipofuscin in P cells in relation to aging. Lipofuscin distribution significantly increased with age in the P cells in these animals. The number of P cells was significantly reduced, while there were no changes in the number of granule cells. It appears from this and other studies that the Purkinje cells are more prone to aging changes than the granule cells of the cerebellum both in lipofuscin formation and cell loss. Although the precise functional significance of these changes in P cells is not clear, their vulnerability may be related to changes in motor function in old age.     

Performance of a motor task after cerebellar cortical lesions in rats

Rats with lesions of the cerebellar cortex of the hemispheres, the lobus medius of the vermis and the caudal vermis were tested on a difficult motor task. Hemisphere lesions produced no significant deficits but lesions of the medial and caudal vermis did. No evidence of recovery was seen in the latter two groups.     

The role of the cortical parts of the cerebellar hemispheres in discrimination learning of cats

Summary Eighteen cats were used as subjects in a study which investigated the effects of bilateral cortical cerebellar hemispheric ablations upon light-dark discrimination learning. From the operated control group (8 animals), 5 were tested two weeks and 3 three weeks postoperatively. From the experimental group (10 animals) 4 were tested two weeks and 6 three weeks postoperatively. The discrimination task consisted of an instrumentally conditioned bar-pressing response. The results showed that almost during the entire 23-day learning period, the experimental cats performed more poorly on the discrimination task than their controls. It is hypothesized that the difference between the two groups of animals derives from the disturbance (caused by the ablation) of the connections between the cerebellum and other structures involved in the habituation process.Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

NGF treatment promotes development of basal forebrain tissue grafts in the anterior chamber of the eye

Summary The effects of nerve growth factor (NGF) on developing central cholinergic neurons were studied using intraocular grafts of rat fetal (E17) basal forebrain tissue. Prior to grafting, grafts were incubated in NGF or saline. Transplants were allowed to mature for six weeks, receiving weekly intraocular injections of NGF or saline. Measurements of NGF levels in oculo after one single injection showed that NGF slowly decreases in the anterior chamber fluid, and after one week, low but significant levels were still present in the eye. Following pretreatment with diisopropylfluorophosphate (DFP), the cholinergic neurons in the grafts were analyzed using three morphological markers: antibodies to cholineacetyltransferase (ChAT), antibodies to acetylcholinesterase (AChE Ab) and acetylcholinesterase histochemistry (AChE). The transplants grew well and became vascularized within the first week. The growth of the NGF-treated basal forebrain grafts was significantly enhanced as compared to the growth of the saline-treated grafts evaluated with repeated stereomicroscopical observations directly through the cornea of the etheranaesthetized hosts. The NGF-treated grafts contained almost twice as many cholinergic neurons seen with all the cholinergic markers used, as the salinetreated grafts. However, there was no difference in cholinergic cell density between the two groups. The morphology and size of an individual cholinergic neuron was similar in the two groups. The fiber density as evaluated with AChE-immunohistochemistry did not change after NGF-treatment. The DFP-treatment did not seem to affect the AChE-immunoreactivity since an extensive fiber network was found, whereas almost no fibers were seen using conventional AChE histochemistry. We have demonstrated that in oculo transplantation of basal forebrain is a useful model for examining in vivo effects of NGF on central cholinergic function. The marked volume increase of NGF-treated grafts and the unchanged density of cholinergic cells and terminals suggests, that NGF increases the survival of not only developing cholinergic neurons, but possibly other non-cholinergic neurons and non-neuronal cells as well. These results support the notion that NGF acts as a neurotrophic factor on cholinergic and possibly non-cholinergic cells in the central nervous system     

The cerebellar corticonuclear projection from lobule Vb/c of the cat anterior lobe: a combined electrophysiological and autoradiographic study

Summary The present study examines the projection to the cerebellar nuclei of Purkinje cells in particular sagittal zones within the intermediate region of the cerebellar cortex. The boundaries between the zones were delimited electrophysiologically on the basis of their climbing fibre input so that a small volume (10–120 nl) of ³H-leucine could be injected into the centre of a chosen zone. The subsequent uptake and orthograde transport of labelled material by the Purkinje cells was studied autoradiographically. It was found that the smallest injections resulted in injection sites restricted to a single cortical zone and extremely reproducible results could be obtained using such a combined electrophysiological/autoradiographic technique. Larger injections sometimes spread to a neighbouring zone but the resultant terminal labelling within the deep nuclei was invariably consistent with the results obtained from smaller injections. The c₁ and c₃ olivocerebellar zones, which are known to receive climbing fibre input transmitted from the ipsilateral forelimb via a dorsal funiculus spino-olivo-cerebellar pathway (DF-SOCP), were found to project to partially overlapping regions within nucleus interpositus anterior (NIA). No projection to nucleus interpositus posterior (NIP) was demonstrated for either zone. No distinction could be seen between the terminal fields for the medial and lateral halves of the c₁ zone which are, however, known to receive their climbing fibre input from quite separate regions within the inferior olive. The c₂ zone, which was delimited on the basis of its climbing fibre input which is transmitted from both forelimbs via a lateral funiculus SOCP, was found to project exclusively to interpositus posterior. The hemispheral d₁ zone was found to project to the transitional region where interpositus anterior and the dentate nucleus adjoin.     

Immune privilege in the anterior chamber of the eye

Since the 19th century, it has been recognized that the anterior chamber of the eye permits the prolonged, and sometimes permanent, survival of foreign tissue and tumor grafts. It was initially believed that the absence of patent lymphatics draining the interior of the eye prevented antigens from reaching regional lymphoid tissues. However, sequestration of intraocular antigens alone cannot account for ocular immune privilege, and a clear picture is now emerging that a constellation of anatomical, physiological, and dynamic immunoregulatory factors contribute to ocular immune privilege. Ocular fluids contain a potpourri of immunosuppressive and immunoregulatory factors that suppress T-cell proliferation and secretion of proinflammatory cytokines. The interior of the eye is decorated with Fas ligand (CD95L), which induces apoptosis of infiltrating inflammatory cells. Antigens introduced into the eye induce a unique immune deviation in which TH1 responses, namely delayed-type hypersensitivity (DTH), are actively suppressed. Thus, ocular immune privilege is sustained by factors that suppress immune cell proliferation and purge immune cells that enter the eye and by a dynamic immunoregulatory process that suppresses antigen-specific DTH. Suppression of certain inflammatory responses is an important adaptation for preventing immune-mediated injury to ocular tissues that have little or no capacity to regenerate. Thus, immune privilege is a crucial adaptation for preserving vision.     

Neuronal responses to eye muscle stretch in cerebellar lobule VI of the cat

Summary Extraocular proprioceptive input to cerebellar vermis, lobule VI, was investigated in cats under N₂O analgesia by recording neuronal responses to eye muscle stretch. Both optic tracts were transected and the periorbital skin and conjunctiva were locally anaesthetized. Eye rotation within the physiological range was achieved by applying a pull of predetermined length and tension to each of the eight musculi recti at their insertion to the globe. Within lobule VI, only small patches of cortex receive stretch receptor afferents. The information made available by these afferents corresponds to a change of eye position. Minimal responses were dependent upon angular deflections of a few degrees. Maximal response amplitudes were obtained within the physiological range of angular deflections and angular velocities for the units tested. Most cells responded to stretch of more than one muscle. Three types of convergence were found: (1) neurons responding according to a certain direction of a conjugated movement of both eyes, (2) neurons responding to movements in either direction of one plane, (3) more complicated response patterns.     

The neurological mutation staggerer is expressed in embryonic cerebellar transplants matured in the anterior eye chamber of normal mice

Horseradish peroxidase (HRP)-filled neurons and their processes were consistently detected in the ventral portion of the dog hypothalamus after intraocular injection of HRP. The number of HRP-filled neurons decreased in parallel with the extent of the resection of the optic nerve. HRP-filled neurons were never detected in specimens with a complete resection of the optic nerve. These findings strongly indicate that these HRP-filled neurons in the ventral hypothalamus are the source of centrifugal fibers to the retina.     

Fluid flow in the anterior chamber of a human eye

A simple model is presented to analyse fluid flow in the anteriorchamber of a human eye. It is shown that under normal conditionssuch flow inevitably occurs. The flow, whose reduced Reynoldsnumber is small, is viscosity dominated and is driven by buoyancyeffects which are present because of the temperature differencebetween the front and back of the anterior chamber. In casesof severe eye trauma or as a result of certain diseases andmedical conditions, particulate matter may be introduced intothe anterior chamber. The motion and distribution of such particlesis analysed and it is shown that the model is capable of predictingwell-established and observed features that may be present ina traumatized eye such as hyphemas, keratic precipitates, hypopyonsand Krukenberg spindles.     

Responses of Purkinje cells in the cerebellar anterior vermis to off-vertical axis rotation

Responses of 67 Purkinje cells (P-cells) and 44 unidentified neurons (U-cells) located in the cerebellar anterior vermis were recorded in decerebrate cats during off-vertical axis rotation (OVAR). This stimulus consisted of a slow constant velocity (9.4°/s) rotation in the clockwise (CW) and counterclockwise (CCW) directions around an axis inclined by 5° with respect to the vertical. OVAR imposes on the animal head a 5° tilt, whose direction changes continuously over the horizontal plane, thus eliciting a selective stimulation of macular receptors. A total of 27/67 P-cells (40%) and 24/44 U-cells (55%) responded to both CW and CCW rotations. For these bidirectional units, the direction of maximum sensitivity to tilt (S_max) could be identified. S_max directions were distributed over the whole horizontal plane of stimulation. Among bidirectional neurons, 48% of the P-cells and 33% of the U-cells displayed an equal amplitude of modulation during CW and CCW rotations, indicating a cosinetuned behaviour. In these instances, the temporal phase of the unit response to a given direction of tilt remained constant, while the sensitivity was maximal along the S_max direction and declined with the cosine of the angle between S_max and the tilt direction. The remaining bidirectional units displayed unequal amplitudes of modulation during CW and CCW rotations. For these neurons, a nonzero sensitivity along the null direction was expected and the response phase varied as a function of stimulus direction. Finally, 31% and 23% of P-cells and U-cells, respectively, responded during OVAR in one direction only (unidirectional units). This behaviour predicts equal sensitivities along any tilt direction in the horizontal plane and a response phase that changes linearly with the stimulus direction. The possibility that the tested neurons formed a population which coded the direction of head tilt in space was also investigated. The data from the whole population of cells were analysed using a modified version of vectorial analysis. This model assumes that for a particular tilt each cell makes vectorial contributions; the vectorial sum of these contributions represent the outcome of the population code and points in the direction of head tilt in space. Thus, a dynamic head tilt along four representative directions was simulated. For each of the four directions, 12 population vectors were calculated at regular time intervals so as to cover an entire cycle of head tilt. The results indicate that for each selected time in the cycle the direction of the population vector closely corresponded to that of the head tilt, while its amplitude was related to the amount of head tilt. These data were particularly obtained for the P-cells. In view of their efferent connections, the cerebellar anterior vermis may provide a framework for the spatial organization of vestibulospinal reflexes induced by stimulation of otolith receptors.     

保留前纵韧带的椎体间植骨术的稳定性实验研究

目的：为评价保留前纵韧带的椎体间支撑植骨治疗脊柱爆裂骨折提供的生物力学稳定能力。方法：用传感器及电测技术，采用新鲜人体胸腰段脊柱标本。结果：除旋转外，轴压、前屈、后伸、侧弯四种运动方式皆能提供满意的稳定性。结论：实验提示，该方法能明显增加损伤脊柱的力学稳定性，有利于提高脊柱的融合率，是一种治疗脊柱骨折较为理想的植骨方法     

An HRP and autoradiographic study of cerebellar corticonuclear-nucleocortical reciprocity in the monkey

Summary Combined injections of ³H-leucine and HRP were made into the monkey cerebellar cortex in order to identify any reciprocal connections between the corticonuclear and the nucleocortical pathways. These combined intraaxonal labeling experiments have demonstrated a considerable overlap of orthogradely labeled Purkinje cell axons and terminals with retrogradely labeled HRP-positive neurons in the ventrolateral region of the dentate nucleus following combined injections into the lateral hemisphere, and in the dorsal area of the dentate following combined injections into medial cortical areas of the anterior lobe. There were also areas within the deep cerebellar nuclei where orthogradely labeled corticonuclear terminals did not overlap with retrogradely labeled nucleocortical neurons.     

Scanning electron microscope study of the rabbit anterior chamber angle

The three-dimensional fine structure and the collagenous framework of the anterior chamber angle (chamber angle) of albino rabbits, which does not posses a Schlemms canal, were examined, with or without NaOH maceration, by scanning electron microscopy. The chamber angle is ill defined because the deep ciliary cleft appears parceled by iris pillars. The collagenous framework of the pectinate ligaments and iris pillars arising from the iris root join to the collagen bundles of the trabecular sheet, and the surface of the ciliary cleft is covered by an endothelial cell layer that screens the trabecular meshwork. Round openings are apparent in the recesses of the ciliary cleft, with junctions between more superficial or deeper trabecular sheets resulting in direct communication between adjacent trabecular spaces. Openings of the angular aqueous plexus/sinus in place of Schlemms canal were seen on the inner surface of the corneosclera after removing the trabecular meshwork. The framework of the trabecular sheet is basically formed of circumferentially arranged flat collagen bundles and reticularly diverged narrow collagen bundles extending from them. There is no shift between collagen bundles of the trabecular meshwork and the corneosclera, suggesting a frail connection between the two tissues.     

Spread of synaptic activity along parallel fibres in cat cerebellar anterior lobe

Summary 1. Mossy fibre evoked activity in the cerebellar cortex elicited by peripheral electrical stimulation was studied in chloralose anesthetized cats. The distribution of intracortical field potentials in the C3 and D zones was mapped in order to determine if there is a spread of synaptic activity outside the mossy fibre termination area. This area was identified by the presence of short latency synaptic field potentials in the granular layer. 2. Molecular layer field potentials were recorded up to 1.5 mm outside the mossy fibre termination area. The latencies of these potentials increased with increasing distance from the mossy fibre termination area, corresponding to a conduction velocity of about 0.4 m/s. 3. Recordings from Purkinje cells, within and outside the mossy fibre termination area, revealed an increase of simple spike activity at latencies corresponding to those of the field potentials in the same location. 4. From the spatial and temporal characteristics of the evoked activity, it is concluded that a mossy fibre input results in spread of synaptic activity along the parallel fibres. 5. The findings are discussed in relation to the recently discovered microzonal organization of the C3 zone. It is proposed that the organization of this zone offers a possibility for the control of muscle synergies, each synergy being represented by a mossy fibre input and the specific set of microzones activated by this input via the parallel fibres.