Monocular enucleation prevents retinal ganglion-cell loss following neonatal visual cortex damage in cats

Studies were conducted to assess the utility of free solution capillary electrophoresis (CE) for monitoring the effects of selected excipients on the thermal denaturation of a model protein (Ribonuclease A, RNase A) at low pH. Thermal denaturation/unfolding experiments were conducted via temperature-controlled CE using a run buffer of 20 mM citric acid in the pH range of 2.3-3.1, with a marker peptide incorporated to correct for temperature-induced changes in endoosmotic flow. The effects of selected excipients on the thermal unfolding of RNase A were then evaluated by adding either sorbitol, sucrose, polyethylene glycol 400 (PEG 400) or 2-methyl-2,4-pentanediol (MPD) to the electrophoretic run buffer (pH 2.3). Confirmatory denaturation experiments were conducted under the same solution conditions using circular dichroism (CD) spectropolarimetry. Using temperature-controlled CE, an increase in solution pH from 2.3 to 2.7 and 3.1 resulted in an increase in transition temperatures of RNase A by approximately 8 and 13 degrees C, respectively. Similar shifts in transition temperatures were observed when thermal denaturation transitions were monitored by far-UV CD. Sorbitol (0.55-1.1 M) and sucrose (0.55 M) each shifted the denaturation transition temperatures of RNase A to higher values, whereas PEG 400 and MPD had minimal effect on the unfolding transition midpoint at the concentrations evaluated (0.55 M for each). The observed changes in the transition temperatures for RNase A as a function of pH and selected excipients were similar when measured by either CE or far-UV CD. These results support the utility of CE for monitoring the effects of neutral excipients on the thermal denaturation of a model protein under selected conditions. The widespread utility of the technique may be limited by the narrow temperature range of most commercial CE instruments and the need to use extreme pH conditions to monitor the complete denaturation transition.     

Marginal and extramarginal cortical lesions and visual discrimination by cats.

75 mongrel cats learned a shape discrimination with 0, 1, or 2 irrelevant cues. They were then subjected to either sham operations, ablation of the marginal and splenial gyri, or lesions in the extramarginal (EM) cortex. The 32 EM cats comprised 4 groups, 3 with small (EM1), intermediate (EM2), large (EM3) decortications, and a 4th group with both EM lesions and heavy degeneration in the lateral geniculate nucleus (LGN). Ss with marginal or extensive extramarginal lesions were severely impaired in shape and size discrimination. Results show the following: (a) The errors made by marginal gyrus cases increased sharply as a function of the number of irrelevant cues present in shape discrimination training; no other group, including Group EM3, was affected by this variable. (b) Ss with extramarginal ablations and strong LGN degeneration were no more severely impaired than were Ss with comparable extramarginal damage and little or no LGN degeneration. While the nature of the 2 kinds of deficits remains unclear, they seem parallel to those following posterior cortical lesions in monkeys. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Amphetamine-induced recovery of visual cliff performance after bilateral visual cortex ablation in cats: Measurements of depth perception thresholds.

After bilateral visual cortex ablation, cats exhibit a loss of depth perception as measured on a visual cliff, which recovers following administration of d-amphetamine. In this Study, 3 amphetamine-treated cats with visual cortex ablations showed a rapid and enduring recovery, with 2 of these animals obtaining levels of performance seen only with binocular vision, suggesting a restoration of binocular depth perception. Cats with asymmetrical lesions showed only a transient improvement during amphetamine treatment, and some animals not displaying autonomic signs of amphetamine intoxication did not improve. Saline-treated cats showed no signs of improvement, and the effect of amphetamine was blocked by the catecholaminergic antagonist haloperidol. These results indicate that amphetamine can induce an enduring recovery from a behavioral deficit after brain injury, which if left untreated would not spontaneously recover. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Striate cortical contribution to the transcorneal electrically evoked response of the visual system

Analyses of current-source-density (CSD) and multiple unit activity (MUA) in area 17 of the cat were performed to determine the sources of the cortical transcorneal electrically evoked response. Cortical field potential, CSD and MUA profiles were obtained with multi-electrodes. CSD findings include: current sinks (inward cell membrane current) within 20 ms latency, in layers 4 and 6 of the striate cortex; current sinks corresponding to N3 (negative component of the EER; latency, 35 ms) in layer 4 and lower layer 3 with current sources (outward cell membrane current) for N3 in the supragranular layers; current sinks with latency over 40 ms in the supragranular layers. In the layers 4 and 6, simultaneous MUA was seen. When the stimulus frequency was increased or with dual stimulation, the N3 current sinks were decreased. This indicates that N1 (latency, 9 ms) and N2 (latency, 20 ms) reflect near-field potentials in layers 4 and 6, generated by geniculocortical afferents, and that N3 is a post- and polysynaptic component. It is also suggested that dipoles composed of cell bodies and the apical dendrites of pyramidal cells of layer 3, generated by satellite cells in layer 4, play a major role in generating N3.     

The effect of superior colliculus lesions upon the visual fields of cats with cortical ablations

The visual fields of 18 cats were measured before and after various lesions. Preoperatively, all cats had identical fields. With both eyes open, they saw from 90 degrees left to 90 degrees right; with one eye, from 90 degrees ipsilateral to 45 degrees contralateral. Thus the field for nasal retina extends from 90 degrees ipsilateral through to the midline; for temporal retina, from the midline through to 45 degrees contralateral. In summary, postoperative testing led to two major conclusions. (1) Large occipito-temporal cortical lesions produce a stable field blindness, but the blindness is alleviated by a transection of the commissure of the superior colliculus (or a unilateral collicular ablation). This transection yields the same result whether it occurs in an operation before, during, or after the cortical lesion. These data confirm and extend the Sprague effect. (2) Cats made dependent upon retinotectal pathways due to cortical ablations responded much better to stimulation of nasal retina than to stimulation of temporal retina. This presumably is related to the preponderance of nasal retina as a source of the retinotectal pathway. Since even smaller cortical lesions limited to areas 17, 18, and 19 produce this nasal/temporal retinal difference, it is concluded that integrity of the geniculocortical pathways is necessary for good temporal retinal vision as determined by these methods.     

Extent of recovery of function after early sensory deprivation in the rat.

Compared the performances of 400 90- and 150-day-old light-reared and dark-reared Long-Evans rats on rigorous tests of depth and form discriminative abilities in 2 experiments. Significant differences due to rearing and age were found. Exposure to a normal light environment for 60 days was found to partially alter the effects of an early 90-day period of visual deprivation in the case of depth discrimination but to have little impact in the case of form discrimination. It is theorized that the initial deficits in the performance of the dark-reared rats and the extent of recovery of function after exposure to a normal environment are related to the kind of perceptual ability being measured and to the sensitivity of the test. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unilateral cortical lesions and paw preferences in cats.

Conducted 3 experiments to examine the effects of unilateral cortical lesions on the paw preferences of a total of 30 laboratory-reared mongrel and 3 Siamese 6-146 mo. old cats. Results show that paw preferences were reversed by ablations of the sensorimotor cortex contralateral to the preferred paw. These shifts in manual preferences remained constant throughout several mo. of postoperative testing. Ss with lesions in sensorimotor cortex, tested only after the acute effects of the cortical lesion subsided, showed a permanent reversal in their responses on object-displacement tasks, but not on simpler retrieval tasks. Extensive ablations of the posterior cortex, alone or in combination with section of the corpus callosum, had no significant effect upon paw preferences when the sensorimotor cortex was spared. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Norepinephrine and brain damage: Alpha noradrenergic pharmacology alters functional recovery after cortical trauma.

Evaluated the effects of drugs affecting noradrenergic (NE) synaptic transmission in 2 experiments. The effects of chronic haloperidol (HAL) treatment begun early or late after brain injury were assessed by measuring recovery from a transient hemiplegia produced by a traumatic contusion in sensorimotor cortex (SMC) of 179 rats. Using the same model, the effects of a single administration of drugs with selective action at NE receptors were evaluated early or late after injury. Drugs with antagonistic effects at alpha?-NE receptors (HAL, prazosin) administered early after SMC contusion seemed to retard locomotor recovery. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biological and psychosocial factors in recovery from brain damage in humans.

Explores biological and psychosocial factors relevant to recovery of function following brain damage, with emphasis on neurorehabilitation programs. Possible mechanisms of brain plasticity that are related to synaptic reorganization include neurotransmitters and other neuroactive substances, memory, volume transmission, and receptor plasticity. Discussion of psychosocial factors beyond the early phases of rehabilitation focuses on environmental considerations, support systems, and cognitive appraisal. Future directions for neurorehabilitation are offered. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distortions in the gradient of stimulus generalization related to cortical brain damage and schizophrenia.

Measurement of the gradient of stimulus generalization (GSG) of 60 schizophrenics (S group), 60 medical control patients (C group), and 60 patients with cortical brain damage (O group), by means of an apparatus consisting of a panel of 11 lamps placed in an arc around the subject, showed: "(1) The GSG for both the C and S groups is considerably more elevated than that of the control group (O group). (2) The differences between the S and C groups, while in the main in the predicted direction, are not conclusive. (3) Damage to the cortex of the dominant hemisphere results in considerably more diminution of the elevation of the GSG than damage to the cortex of the non-dominant hemisphere. (4) The number of EST's received by patients in the S group was found to vary inversely with the degree of SG responsivity; but in view of the limitations of the data, no conclusions were drawn." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of activation and sensory stimuli in recovery from lateral hypothalamic damage in the cat.

Analyzed the early stages of recovery from lateral hypothalamic lesions in 30 adult cats. In addition to aphagia and adipsia, neurological examination revealed deficits suggestive of deficient endogenous arousal, including somnolence, catalepsy, akinesia, and sensory neglect. Manipulations (tail pinch and injection of amphetamine) that counteracted these deficits also restored feeding. During recovery from aphagia, feeding gradually became activated by sensory stimuli (sight, feel, and smell) associated with food. These data suggest that activation is an important component in the control of normal feeding. (3? p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of heparin on recovery from ischemic brain injuries in cats

Since ischemic anoxia in experimental animals has been reported to produce areas of cerebral postocclusive nonperfusion, the authors studied the effect of heparin on recovery from tourniquet-produced cerebrovascular injury in 41 barbiturate-anesthetized, ventilated cats (PaCO2 30 +/- 2.5 torr). Twenty-four control animals were subjected to 2-to-12-minute ischemic injuries without further treatment. Seven experimental animals were given heparin (1000 u/kg) 1 minute before 4-to-7-minute ischemic injuries, while 10 animals received heparin (1000 u/kg) immediately after 4-to-7-minute injuries. All animals were monitored with continuous arterial and intracranial pressure (ICP) recordings, EEG, and evoked cortical responses. Ischemia and evoked-response recovery times were linearly related in all groups (r = 0.998 control, r = 0.936 heparin preinjury, r = 0.951 heparin postinjury). Regression-line slope comparison indicated shorter evoked response and EEG recovery times in the heparin-treated groups than in the control group. Heparin administration did not effect elevations of ICP seen 6 and 12 hours postinjury in control versus experimental groups. In cats with injuries lasting 5 minutes or more, all control animals were decerebrate and apneic, while 5/12 heparin-treated animals had lesser neurologic deficits.     

Light deprivation accelerates recovery from frontal cortical neglect: Relation to locomotion and striatal fos expression.

Rats given unilateral medial agranular (AGm) cortex ablations show neglect for contralateral multimodal stimuli, symptoms that are reversed by 48 hr of light deprivation. To address processes that contribute to this restorative effect, both the rats' locomotion and basal ganglia c-fos expression were studied. AGm-lesioned rats showed less activity in continuous darkness than in normal (12 hr light/12 hr dark) cycles, and the reduced locomotion correlated with the extent of their subsequent behavioral recovery. The AGm ablation reduced the numbers of amphetamine-stimulated Fos-immunoreactive nuclei in the ipsilateral dorsolateral striatum, where the AGm innervation is normally densest. Light deprivation also reduced Fos in this striatal region and attenuated the lesion-induced hemispheric Fos asymmetry. A restored balance of activity between the 2 hemispheres, especially the basal ganglia, appears central to the action of light deprivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Long-term effects of sectioning the olivocochlear bundle in neonatal cats

The olivocochlear bundle (OCB) was cut in neonatal cats to evaluate its role in the development of normal cochlear function. Approximately 1 year after deefferentation, acute auditory nerve fiber (ANF) recordings were made from lesioned animals, lesion shams, and normal controls. The degree of deefferentation was quantified via light microscopic evaluation of the density of OCB fascicles in the tunnel of Corti, and selected cases were analyzed via electron microscopy. In the most successful cases, the deefferentation was virtually complete. ANFs from successfully lesioned animals exhibited significant pathophysiology compared with normals and with other animals in which the surgery failed to interrupt the OCB. Thresholds at the characteristic frequency (CF), the frequency at which ANFs are most sensitive, were elevated across the CF range, with maximal effects for CFs in the 10 kHz region. Frequency threshold or tuning curves displayed reduction of tip-to-tail ratios (the difference between CF and low-frequency "tail" thresholds) and decreased sharpness of tuning. These pathological changes are generally associated with outer hair cell (OHC) damage. However, light microscopic histological analysis showed minimal hair cell loss and no significant differences between normal and deefferented groups. Spontaneous discharge rates (SRs) were lower than normal; however, those fibers with the highest SRs remained more sensitive than those with lower SRs. Findings suggest that the interaction between OC efferents and OHCs early in development may be critical for full expression of active mechanical processes.     

Nature of visual recovery following posterior neodecortication in the hooded rat.

Subsequent to bilateral, single-stage posterior neodecortication, 32 male hooded rats were either retrained on a preoperatively-learned brightness discrimination, or trained on the reversal of the preoperatively-learned discrimination. Postoperative relearning was significantly retarded when the discrimination involved a reversal of the original discrimination. Results suggest that the preoperatively-established brightness habit is not exclusively localized in the neocortex and that postoperative recovery of the discrimination does not involve relearning a new and independent memory engram. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of the differences in human evoked cortical potentials to visual stimuli

Saccharomyces cerevisiae nuclei possess a polyphosphatase activity which is insensitive to a number of inhibitors of ATPase and pyrophosphatase (PPase) activities of the same organelle. Heparin, an effective inhibitor of the nuclear polyphosphatase activity, does not alter either the ATPase and PPase activity. The nuclear polyphosphatase activity is optimal at pH 7.5. Bivalent metal cations stimulate this activity in the following order: Co2+ > Mg2+ > Zn2+ > Mn2+. However, the magnitude of the stimulating effect is much lower than that for the polyphosphatase activities from other organelles of the same yeast. The polyphosphatase activity is nearly the same for polyphosphates ranging from [symbol: see text] = 9 to [symbol: see text] = 208, but is 1.5 times higher for tripolyphosphate. The K(m) values for the hydrolysis of polyphosphates with chain lengths [symbol: see text] = 3, 15 and 208 are 100, 5 and 4.1 microM, respectively. The polyphosphatase activity differs in some properties from that of the cell envelope, cytosol and vacuoles of the same S. cerevisiae strain.     

Deficits in visual learning produced by posterior temporal lesions in cats.

Eight cats with lesions in the posterior temporal (PT) cortex, 7 cats with lesions in the basolateral amygdala (BLA), and 8 intact controls were observed on 8 tests of visual discrimination learning and spontaneous responses to salient visual stimuli. The effects of the 2 lesions were somewhat dissociable. The PT lesions were accompanied by a severe deficit in pattern discrimination learning but no loss in visual tracking or orientation to the silhouette of a threatening cat. The BLA lesions produced a milder and less consistent loss in pattern discrimination but serious defects in tracking and response to the cat silhouette. Both operated groups performed well on the visual cliff. The deficit from PT lesions appeared independent of damage to the geniculocortical system. The parallel of symptoms from PT lesions in cats and inferotemporal lesions in monkeys is discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)