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Biomedical subjects

I S Russell

Publications and source records attributed to I S Russell.

At least 37 records · Page 2Linked to original sources
PubMed1986

Effects of unilateral frontal eye-field lesions on eye-head coordination in monkey.

We studied the effects of unilateral frontal eye-field (FEF) lesions on eye-head coordination in monkeys that were trained to perform a visual search task. Eye and head movements were recorded with the scleral search coil technique using phase angle detection in a homogeneous electromagnetic field. In the visual search task all three animals showed a neglect for stimuli presented in the field contralateral to the lesion. In two animals the neglect disappeared within 2-3 wk. One animal had a lasting deficit. We found that FEF lesions that are restricted to area 8 cause only temporary deficits in eye and head movements. Up to a week after the lesion the animals had a strong preference to direct gaze and head to the side ipsilateral to the lesion. Animals tracked objects in contralateral space with combined eye and head movements, but failed to do this with the eyes alone. It was found that within a few days after the lesion, eye and head movements in the direction of the target were initiated, but they were inadequate and had long latencies. Within 1 wk latencies had regained preoperative values. Parallel with the recovery on the behavioral task, head movements became more prominent than before the lesion. Four weeks after the lesion, peak velocity of the head movement had increased by a factor of two, whereas the duration showed a twofold decrease compared with head movements before the lesion. No effects were seen on the duration and peak velocity of gaze. After the recovery on the behavioral task had stabilized, a relative neglect in the hemifield contralateral to the lesion could still be demonstrated by simultaneously presenting two stimuli in the left and right visual hemifields. The neglect is not due to a sensory deficit, but to a disorder of programming. The recovery from unilateral neglect after a FEF lesion is the result of a different orienting behavior, in which head movements become more important. It is concluded that the FEF plays an important role in the organization and coordination of eye and head movements and that lesions of this area result in subtle but permanent changes in eye-head coordination.

Animals↗
PubMed1985

Breast screening.

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Australia↗
PubMed1985

Visuomotor strategies in pattern discrimination learning in rats.

Normal rats were trained on a series of visual tilt discriminations ordered from simple to difficult to measure their angular difference thresholds. The stereotyped visuomotor running pattern which the animal made was recorded for all angular differences binocularly and whilst the animal was monocularly patched. The results show that the running pattern does not reflect visual guidance strategies and can produce a visual field bias for the field ipsilateral to the preferred approach side.

Animals↗
PubMed1985

Frequency of benign and malignant breast lesions in 207 consecutive autopsies in Australian women.

A histopathological study was undertaken on breast tissue dissected during the course of 207 consecutive forensic post-mortems on women over the age of 15 years in order to define the frequency and types of lesions found in Australian women. At least 10 blocks were obtained from each breast and a total of 4,738 blocks were examined. A particularly high frequency of atypical hyperplasia (12.6%), carcinoma in situ (13.0%), focal secretory change (24.1%) and perilobular haemangiomas (11.2%) was found. The radial scar, considered by some to be a precursor of infiltrating ductal carcinoma was found in 7.7% of the women.

Adolescent↗
PubMed1984

Effect on immunologic and other indices of adjuvant cytotoxic chemotherapy including melphalan in breast cancer.

Thirty patients with histologically proven node-positive early breast cancer (Stage II) were treated by total mastectomy and axillary clearance and adjuvant chemotherapy regimens including melphalan for 1 year. These patients were studied sequentially, at 3-month intervals, for up to 2 years to assess effects of cytotoxic drugs on immune function, and to determine whether any changes in immune function were related to recurrence. All indices were in the normal range before chemotherapy. The most marked and long-lasting effects of chemotherapy were on numbers of circulating T-cells and B-cells. Mean counts +/- one standard error (X 10(6)/ml) for T-cells before and 12 months after stopping chemotherapy were 1.537 +/- 0.118 and 0.874 +/- 0.120 (P less than 0.01), and for B-cells 0.345 +/- 0.060 and 0.207 +/- 0.030 (P less than 0.01). Functional indices of T-cell and B-cell competence were less compromised than values for cell counts and, in contrast, recovery occurred either during or within 3 months of stopping chemotherapy. This held for both T-cell function measured by delayed-type hypersensitivity (DTH) responsiveness to five recall antigens and mitogenic responsiveness to phytohemagglutinin, and for B-cell function measured by titration of blood group isohemagglutinins. After 4 years the 30 subjects were divided into groups according to whether there was recurrence of cancer (14) or no recurrence (16); the only index predictive of recurrence was depression of DTH to recall antigens. Thus it was found that cytotoxic chemotherapy with melphalan appears to cause long-lasting depression of cell counts but only short-lasting depression of functional indices of immunocompetence, and that levels of immunologic indices during chemotherapy are mostly nonpredictive of recurrence of cancer. The results prompt some caution in the use of adjuvant chemotherapy, at least with melphalan.

Adult↗
PubMed1984

Trace conditioning of the nictitating membrane response in decorticate rabbits.

Rabbits with substantial neocortical lesions were given trace conditioning of the nictitating membrane response over a range of interstimulus intervals (ISIs). Unlike hippocampal lesioned animals, which show deficits in such conditioning, the decorticates were not impaired and they gave greater numbers of conditioned responses at longer ISIs than did sham-operated controls. These results suggest that a neocortical-entorhinal input to the hippocampus may not be crucial for trace conditioning.

Animals↗
PubMed1984

The effect of devascularization of the visual cortex on visual function in the rabbit.

The role of the visual cortex in brightness and pattern vision was re-examined in the rabbit. Animals were trained on both a brightness and a horizontal-vertical striation discrimination. Bilateral removal of the dura mater overlying the entire visual cortex produced no impairments in either brightness or pattern vision. When the visual cortex was devascularized by removal of the pia mater bilaterally, total loss of pattern vision was found with no impairment of brightness discrimination ability. The significance of the finding that the effects of slowly developing degenerative lesions are the same as those of surgical ablation was discussed.

Animals↗
PubMed1983

Visual discrimination learning under conditions of interocular conflict in hooded and albino rats.

Hooded and albino rats were trained on a paradigm of interocular conflict, in which the animals were trained on a discrimination of vertically inverted triangles with one eye, and on the reversed discrimination with the other eye on alternate days. Albino rats acquired the conflicting tasks as quickly as a single monocularly trained task. Hooded rats required considerably longer training on the conflicting discriminations. The role of some non-visual behavioral strategies in the performance of the conflicting tasks was explored, and possible mechanisms are discussed with reference to the different size of the ipsilateral optic projection in hooded and albino rats.

Animals↗
PubMed1983

Retention of conditioned inhibition of the nictitating membrane response in decorticate rabbits.

Rabbits were trained on a Pavlovian conditioned inhibition (CI) task using light as the reinforced conditional stimulus (CS) and the same light compounded with a tone as the non-reinforced CS. The conditional response was the nictitating membrane response (NMR). The subjects then received an extensive neocortical lesion or a sham operation. After 9 weeks postoperative recovery, the animals were retrained on the CI task. Sham operated control animals showed immediate and high levels of CI retention but the decorticates showed a profound initial loss, showing that there is a cortical influence in CI. Reacquisition of CI by the decorticates was rapid and showed considerable savings over de novo acquisition. This supports our earlier finding that the neocortex is not essential for the acquisition of CI.

Animals↗
PubMed1983

Angular acuity in normal and commissure-sectioned rabbits.

Both normal and commissure-sectioned rabbits were examined over a variety of visual discrimination tasks. The visual displays were projected at various distances within the frontal visual field of the rabbit. The learning of either a black-white or a vertical-horizontal problem was found to be normal in commissure-cut animals. Furthermore, no deficit in angular acuity was observed. However, when they were tested with the patterns displayed at 25 cm distance, large impairments were found in the commissure-sectioned animals.

Animals↗
PubMed1982

Some observations on the problem of recovery of function following brain damage.

Functional restitution following brain damage can occur either because of a return of the original function or because of compensatory changes involving functional substitution. In any study of post-traumatic recovery it is important to use an experimental model which can discriminate between these separate mechanisms. Recovery from unilateral frontal eye-field damage was used as a model in both monkeys and rats. In particular, the role of the intact hemisphere in the recovery process was examined. Section of the corpus callosum was found to restore the original visual neglect both in monkey and in rat; indicating that that recovery was due to adaptation mechanisms in the intact hemisphere. Pseudo-recovery that was seen on occasion in monkeys was not a return of the original control processes, but was an improvement due to the adoption of new behavioural strategies.

Agnosia↗
PubMed1981

The role of the corpus callosum and some subcortical commissures in interocular transfer in the hooded rat.

The effect of sectioning the corpus callosum on interocular transfer of a brightness and a horizontal/vertical discrimination was examined in hooded rats. Lesions of the posterior portion of the callosum usually led to moderate transfer deficits, but considerable individual variation was found. Lesions involving only the anterior part of the callosum had little effect on transfer. This suggests a functional localisation in the corpus callosum of the rat similar to that seen in higher mammals. Section of the posterior and tectal commissures and the thalamic massa intermedia in addition to the callosum had no greater effect on transfer thatn callosal section alone. It is therefore unlikely that these structures play a crucial role in interocular transfer in the rat.

Animals↗
PubMed1981

Delayed recovery of peripheral blood cell numbers after adjuvant cytotoxic chemotherapy for stage II breast cancer.

A study was made on the recovery of the bone marrow after adjuvant chemotherapy given to 30 post-mastectomy patients with stage II breast cancer treated with either melphalan or melphalan and methotrexate at 6-weekly intervals for 1 year. Counts of peripheral blood cells were made serially during treatment and then for a further 2 years after stopping chemotherapy. Mean counts for all cell types fell during chemotherapy and recovery was long-delayed. Thus 24 months after chemotherapy, mean counts for total leucocytes and platelets were significantly lower than mean pretreatment counts and counts for a normal female population, and the count for neutrophils was significantly lower than the count before treatment; after 24 months mean counts for lymphocytes were not significantly depressed. Melphalan was assumed to be the agent responsible. Slow haematological recovery after cessation of adjuvant chemotherapy with one particular regimen points to the need for including long-term post-chemotherapy observation of the bone marrow in the assessment of adjuvant chemotherapy programmes.

Antineoplastic Agents↗
PubMed1981

The effects of unilateral frontal eye field lesions in the monkey: visual-motor guidance and avoidance behaviour.

Macaque monkeys were tested on a visual-motor guidance task and observations of avoidance behaviour were made following unilateral frontal eye field lesions. Visual-motor guidance was assessed by speed and accuracy of reaching to press recessed, illuminated buttons arrayed in a 90 degree arc in front of the monkey. Unilateral frontal eye field lesions produced a marked neglect of stimulus lights contralateral to the side of the lesions, as shown in greatly increased errors and response latencies. Responses to the most peripheral of the ipsilateral stimulus lights were also affected, although not to the same degree. Partial to complete recovery occurred, usually within a month. A unilateral lesion of the principal sulcus did not cause symptoms of neglect in the visual-motor guidance task. Section of the cerebral commissures partially restored the visual-motor guidance deficit in the frontal eye field-lesioned monkeys, with recovery again occurring. Commissurotomy and the unilateral frontal eye field lesion performed in a single-stage operation produced an initially more severe neglect than the two-stage operation, but recovery was no less rapid. The unilateral frontal eye field lesions resulted in a severe neglect of contralateral threat objects when the monkeys were threatened from both sides (avoidance-avoidance tests). Avoidance was normal when the threat was presented to one side. Commissurotomy fully restored the avoidance-avoidance deficit and made it permanent. These and other recent findings suggest that the contralateral visual field defect and the other symptoms resulting from frontal eye field lesions represent an impairment in directing and sustaining attention in regions of the visual field arising from disruption of a corticothalamotectal sensorimotor integration system.

Animals↗
PubMed1980

Interocular transfer of two visual discriminations in hooded and albino rats.

Interocular transfer of a brightness and a pattern discrimination was compared in hooded and albino rats. Equally high levels of transfer were found in the two strains, and there was no difference in transfer between the two discriminations. The results indicate that interocular transfer in the rat does not necessarily depend on the uncrossed optic fibres, and that the commissures of the rat's brain are capable of efficient transfer.

Animals↗