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Biomedical subjects

H F Baker

Publications and source records attributed to H F Baker.

At least 91 records · Page 5Linked to original sources
PubMed1987

Effects of arecoline and pilocarpine on learning ability in marmosets pretreated with hemicholinium-3.

Common marmosets (Callithrix jacchus) were trained to perform serial reversal position discrimination tasks in a Wisconsin General Test Apparatus. Intraventricular injection of hemicholinium-3 4 h before testing resulted in a profound impairment of position discrimination learning which could be overcome by the intramuscular administration of low doses of the muscarinic agonists, arecoline or pilocarpine.

Animals↗
PubMed1986

Learning impairment following lesion of the basal nucleus of Meynert in the marmoset: modification by cholinergic drugs.

Five common marmosets (Callithrix jacchus) received unilateral ibotenic acid lesions of the basal nucleus of Meynert (nBM). Seven days later, choline acetyltransferase activity was significantly reduced by 50% in the frontal and temporal neocortex, 40% in the amygdala, and approximately 30% in the motor, parietal and occipital cortex in the ipsilateral hemisphere. Four marmosets receiving equivalent bilateral ibotenic acid lesions were severely impaired on new visual object discrimination learning and on relearning an object discrimination learnt prior to surgery when compared with operated controls. New learning in lesioned animals was substantially improved by i.m. administration of the cholinergic agonist arecoline. Lesioned animals' learning ability improved with time but these animals were then differentially sensitive to the disruptive effect of scopolamine on discrimination learning. These results show that lesions of the nBM which destroy the rising cholinergic pathways impair learning ability but that this ability can be substantially restored by administration of a cholinergic agonist.

Acetylcholine↗
PubMed1986

Transmissible and non-transmissible neurodegenerative disease: similarities in age of onset and genetics in relation to aetiology.

In only a few cases is transmissible dementia known to have been acquired by infection from a source outside the individual; the remaining cases can be classified as sporadic, loosely familial, or autosomal dominant. Each group has a characteristic mean age of onset. A range of neurodegenerative diseases (including Alzheimer-type dementia and amyotrophic lateral sclerosis) can also be classified in this way, with similar characteristic mean ages of onset. The emergence of these diseases in later middle age, and the interdependence of age of onset and the type of familial occurrence suggest that these pathological processes are related to those genetic mechanisms which determine senescence. It is argued that the majority of cases of transmissible dementia arise, not from infection, but from the expression of endogenous virogene sequences as part of the aging processes.

Adult↗
PubMed1985

Experimental transmission of an autosomal dominant spongiform encephalopathy: does the infectious agent originate in the human genome?

Marmosets inoculated intracerebrally with brain tissue from a woman with Gerstmann-Straussler syndrome (an autosomal dominant dementia associated with spongiform change and amyloid deposition) developed an encephalopathy indistinguishable from that seen in marmosets inoculated with brain tissue from a typical case of Creutzfeldt-Jakob disease. As in Huntington's disease, in the pedigree of the patient with Gerstmann-Straussler syndrome women who subsequently developed the illness had increased fecundity. The pathogen in human transmissible dementia may arise from a sequence (which itself sometimes confers a selective advantage) located within the human genome.

Aged↗
PubMed1985

Effects of ibotenic acid lesions of the basal forebrain on serial reversal learning in marmosets.

Five common marmosets (Callithrix jacchus) received unilateral ibotenic acid lesions of the basal forebrain. Seven days post-operatively, choline acetyltransferase activity was reduced by 60% in frontal cortex and 40% in temporal cortex in the ipsilateral side compared with the contralateral side. Four animals receiving bilateral lesions of the same area were impaired on the first post-operative task of serial reversal learning when compared with four animals receiving bilateral saline injections. Although their performance improved with time, the lesioned animals were subequently impaired following administration of a low dose of scopolamine which did not affect the control group. These results show that lesions within the basal forebrain can affect cholinergic function in the cortex and impair learning ability.

Animals↗
PubMed1984

Cholinergic learning deficits in the marmoset produced by scopolamine and ICV hemicholinium.

Common marmosets (Callithrix jacchus) were trained to perform daily position discrimination learning tasks in a Wisconsin General Test Apparatus. Acetylcholine receptor blockade with scopolamine was found to impair position learning. Testing on the day after scopolamine treatment suggested that a task learnt under scopolamine was not encoded into long term memory. Acetylcholine depletion achieved by the intraventricular injection of hemicholinium 4 h before testing resulted in a profound impairment of position discrimination learning. It is suggested that central acetylcholine depletion in primates may provide a useful model of senile dementia.

Animals↗
PubMed1984

An involvement of acetylcholine in object discrimination learning and memory in the marmoset.

Five marmosets (Callithrix jacchus) were tested, using a Wisconsin General Test Apparatus, on a series of junk object visual discrimination tasks, including new learning, 24-hr reversal and 24-hr retention. The effects of administering the cholinergic receptor blocking agent, scopolamine either just before or immediately after the new learning task, or just before the 24-hr reversal and retention tasks, were assessed. Results suggest that scopolamine impairs new learning and impairs the encoding of new information in long term memory. Some evidence of a mild retrieval deficit under scopolamine was also seen, while state-dependent effects were not apparent.

Acetylcholine↗
PubMed1983

Further consideration of the learning impairment after aceperone in the marmoset: effects of the drug on shape and colour discrimination and on an alternation task.

Ten marmosets (Callithrix jacchus) learned to discriminate between pairs of small grey objects differing only in shape or small plain plaques differing only in colour, in a Wisconsin General Test Apparatus. Each day, each animal was presented with three consecutive visual discrimination problems in the order shape-colour-shape or colour-shape-colour. After aceperone, an alpha-noradrenergic antagonist, animals were impaired at learning the first but not the subsequent tasks of each trio. These results suggest that the previously observed impairment [10] on the first of a pair of object discrimination tasks after aceperone is a consequence of disruption of a mechanism common to both shape and colour discrimination learning. The fact that there is no impairment on task 2 in a dimension differing from task 1 suggests that the deficit is not one of attending to, or switching attention to, the appropriate visual dimension. Three further marmosets were trained to perform an alternation task and tested under aceperone. No impairment in performance was seen, suggesting that a variety of cognitive skills other than stimulus-reward association were intact. We conclude that the impairment following aceperone is a dysfunction of processes involved in association formation, but that it is one which is manifest only when the animal is faced with a type of task which has not recently been performed and that it can be overcome with persistence even the animal encounters novel stimuli.

Animals↗
PubMed1983

An investigation of the effects of intracerebral injection in the marmoset of cytopathic cerebrospinal fluid from patients with schizophrenia or neurological disease.

In experiments designed to investigate transmission, cerebrospinal fluid (CSF) from patients with schizophrenia and neurological disease (huntington's chorea and multiple sclerosis) which had been found to induce cytopathic effects in human embryonic fibroblast cell culture was injected intracerebrally into mice, hamsters and marmosets (small New World primates). No evidence was obtained of transmission to mice or hamsters. A total of 15 marmosets (Callithrix jacchus) was injected intracerebrally with CSF [8 with samples from 4 patients with schizophrenia. 3 with samples from patients with neurological disease (2 with Huntington's chorea and 1 with multiple sclerosis) and 4 with samples from 3 patients without neurological or psychiatric disease] and was observed over a period of 2 1/2 years. Analysis of variance on data obtained from behavioral observations averaged over 6-month periods revealed that animals injected with CSF from patients with schizophrenia and neurological disease became progressively more inactive when compared with animals injected with CSF from control patients. The change detected by behavioural observation was confirmed as a difference 2 and 2 1/2 years after injection by automated activity monitoring. There was an incidence of reproductive anomalies (including two occipital encephalocoeles) in the females in the experimental group, but the numbers are too small to draw firm conclusions from this observation. Many reported differences in biological samples from schizophrenic patients and normal controls have subsequently been found to be due to factors unrelated to the disease state. This may prove to be the case with the changes observed in this experiment. Nevertheless, the fact that marmosets injected with CSF from patients suffering from neuropsychiatric disease, including schizophrenia, subsequently differed in their behaviour from those injected with control CSF warrants further investigation.

Animals↗
PubMed1983

Respiratory disease associated with parainfluenza Type I (Sendai) virus in a colony of marmosets (Callithrix jacchus).

An outbreak of acute respiratory disease was observed in a colony of marmosets (Callithrix jacchus). Parainfluenza Type I (Sendai) virus was isolated from the lungs and from throat swabs of 2 animals which showed clinical signs of disease. A rising titre of serum neutralizing antibody to the virus isolated was detected in several affected animals. Approximately 50% of the colony showed clinical signs of disease, and 3 animals died. The duration of illness ranged from 3 to 16 days.

Age Factors↗