Biomedical subjects

M Gabriel

Publications and source records attributed to M Gabriel.

At least 91 records · Page 5Linked to original sources

PubMed1987

Hippocampal control of cingulate cortical and anterior thalamic information processing during learning in rabbits.

Past studies of the neural determinants of discriminative avoidance conditioning in rabbits have fostered a theoretical model that describes the interactive functioning of the cingulate cortex (Brodmann's Areas 24 and 29), the anterior ventral and medial dorsal thalamic nuclei (AVN and MDN) and the hippocampus. Here we test hypotheses of the model concerning the influence of the hippocampus on cortical and thalamic information processing. The rabbits learned to perform locomotory conditioned responses (CRs) in an activity wheel in response to an acoustic (pure tone) positive conditional stimulus (CS+). A shock unconditional stimulus (US) was given 5 s after CS+ onset, but locomotion during the CS+ - US interval prevented the US. The rabbits also learned to ignore a second tone (a negative conditional stimulus, CS-) of different auditory frequency than the CS+, that did not predict the US. Multi-unit activity and intracranial macropotentials were recorded in the cingulate cortex and the AVN during acquisition, overtraining, extinction, reacquisition and reversal training. Data were obtained in intact rabbits and in rabbits with bilateral lesions of the subicular complex, the origin of projections of the hippocampal formation to the cingulate cortex and AVN. In addition, the activity in the AVN was recorded in a separate group of rabbits with posterior cingulate cortical (Area 29) lesions. Subicular and Area 29 lesions were associated with an enhancement of the training-induced CS+ elicited neuronal response in the AVN. The frequency of CRs was enhanced in animals with subicular lesions. CS elicited unit responses in the cingulate cortices were attenuated in rabbits with subicular lesions. Both of the lesions were associated with significantly increased amplitudes of the CS elicited average cortical and thalamic macropotentials. These results suggested the following conclusions: subiculocortical afferents provide an enabling influence that is essential for CS elicited excitation in the cingulate cortex; the cingulate cortical excitatory response in intact animals exerts a limiting influence on the activity in the AVN; the enhanced AVN neuronal response in rabbits with lesions is due to the absence of the limiting influence and it contributes to the increased CR frequency in those animals. It is hypothesized that the hippocampus via subiculocortical projections, governs the flow of CR-inducing thalamocortical excitatory volleys. This governance determines the timing of CR output. The results of hippocampal processing of contextual information acting through the subiculocortical projection determines the moment most appropriate for the CR.

Acoustic Stimulation↗

PubMed1987

Melioidosis: a serological survey in a tuberculosis sanatorium in Hong Kong.

A serological survey of 275 Chinese patients with underlying pulmonary diseases in a tuberculosis sanatorium in Hong Kong showed that 39 (14%) had haemagglutinating antibody (HA) against Pseudomonas pseudomallei in a titre of 1: 80 or above. Only 9 of these 39 patients had travelled to endemic areas, suggesting that at least 30 patients (11%) had been exposed to Ps. pseudomallei locally. Females are affected as often as males, and the seropositive rate is the same whether patients are immunosuppressed or not. Because subclinical melioidosis is prevalent and HA may persist for a long time, even at a high titre, after infection, determination of HA alone cannot differentiate between active melioidosis and its masquerade--active tuberculosis.

Adolescent↗

PubMed1987

Unexpected findings amongst the skin test responses to mycobacteria of BCG vaccinated Kuwaiti school children.

A multiple skin test survey was carried out in Kuwait on 1200 school children aged 8-11 years, and on 1228 children aged 12-16 years. With only 15 exceptions, all these children had received vaccination with Japanese BCG just before they started school, 5 years and 9 years earlier respectively. Tuberculin positivity was almost 90% in both groups, with a mean response size of 8.7 mm. This was associated with remarkably high responsiveness to many of the other mycobacterial species investigated. Since this high reactivity was also to Mycobacterium ulcerans, a species most unlikely to be present in Kuwait, it is proposed that this might be due to responsiveness to group ii antigen which is present in all slow growing species. Only M. flavescens and M. rhodesiae amongst the fast growing species, were absent as sensitising organisms. After correction for the supposed reactivity to group ii antigen, M. avium B, M. gordonae, M. ulcerans and M. xenopi amongst the slow growing species, also appeared to be absent from the Kuwait environment. The species most commonly encountered were M. leprae, M. chitae, M. neoaurum, M. diernhoferi, and M. vaccae in this order. This was a remarkable finding for a country assumed to be poor in contact with environmental species, and known to have a very low prevalence of leprosy. As previously reported from Iran, but not confirmed in other places, there was a 95% correlation between responsiveness to Leprosin A and Vaccin. Amongst the slow growing species M. avium A, M. intracellulare, and M. kansasii appear to be frequent sensitising agents, in common with many other places.

Adolescent↗

PubMed1986

Anterior thalamic discriminative neuronal responses enhanced during learning in rabbits with subicular and cingulate cortical lesions.

The neuronal discharge that develops in the anterior ventral thalamic nucleus (AVN) in response to a task-relevant stimulus during learning is enhanced in rabbits with damage in the cingulate and subicular (hippocampal) cortical areas that project to this nucleus. These results indicate that the corticothalamic projections limit the anterior thalamic response but they do not appear to contribute causally to its development. Thus, the discriminative neuronal response is owed to interactions that occur wholly within the subcortical domain of the AVN. The production of this neural code for significant stimuli may be the principal function of the AVN. The enhanced thalamic discharges may be a neural cause of behavioral hyperactivity in animals and amnesia in humans with hippocampal damage.

Action Potentials↗

PubMed1986

Neuropathologic and morphometric studies in hereditary motor and sensory neuropathy type II with neurofilament accumulation.

Histological, electron microscopic and morphometric data on sural nerve, muscle, and skin biopsies of three patients affected by autosomal dominant hereditary motor and sensory neuropathy type II with neurofilament accumulation, whose neurological, cardiological and electrophysiological data have been provided in a previous paper disclosed focally enlarged myelinated axons, due to aggregation of neurofilaments in sural nerves of all 3 biopsied patients, as well as densely packed clusters of filaments in occasional non-myelinated axons without axonal enlargement, in several fibroblasts and endothelial cells in muscle and particularly in skin. This accumulation of filaments was less pronounced in our patients' tissues than in autosomal-recessive GAN. No ultrastructural differences concerning the accumulated filaments appear to exist between the affected cells of our patients and GAN. Taken together, these findings best fit a hereditary motor and sensory neuropathy type II with focal accumulation of intra-axonal neurofilaments.

Axons↗

PubMed1986

Effect of age on homovanillic and 4-hydroxy-3-methoxymandelic acid levels in plasma.

The plasma levels of homovanillic and 4-hydroxy-3-methoxymandelic acids have been determined in 524 normal subjects ranging from birth to 49 years of age using a mass fragmentographic method. The mean concentration of homovanillic acid in plasma declines exponentially from the age of 1 day (X = 2342.0 nmol/l, 426.6 ng/ml) to adulthood (X = 60 nmol/l, 10.9 ng/ml). 4-Hydroxy-3-methoxymandelic acid behaves in a similar although not so extreme manner (392 nmol/l, 77.6 ng/ml-50 nmol/l, 10 ng/ml).

Adolescent↗

PubMed1986

Spinal tuberculosis presenting with abdominal symptoms--a report of two cases.

We present two unusual cases of tuberculosis of the spine presenting with abdominal symptoms; both patients underwent exploratory laparotomy before the true nature of the diagnosis became known. The diagnosis of spinal tuberculosis was evident on the pre-operative abdominal radiographs but this was overlooked.

Adult↗

PubMed1986

Brain stem reticular formation neuronal correlates of stimulus significance and behavior during discriminative avoidance conditioning in rabbits.

Multiple-unit activity in the reticular formation of the midbrain and pons was recorded in rabbits during discriminative conditioning of locomotor (wheel-running) avoidance behavior. The conditional stimuli (CS+ and CS-) were pure tones of different auditory frequency, and the unconditional stimulus (US) was a constant-current footshock (1.5-2.5 mA) delivered through the grid floor of the wheel. The pontine, but not the midbrain, sites manifested development during behavioral acquisition, of brief-latency (10-40-ms) discriminative neuronal discharges (i.e., greater discharges to the CS+ than to the CS-). The greatest magnitude of the discriminative discharges in the rostral pontine loci occurred in the first conditioning session. The discriminative response in the caudal loci developed more slowly, and it persisted to the criterial stage of training. Both rostral and caudal pontine loci, during the interval from CS onset to US onset, manifested a progressive build-up of neuronal firing in anticipation of the behavioral response. The occurrence in the rostral and caudal pontine areas, respectively, of early- and late-developing discriminative discharges is analogous to effects observed in past studies in the limbic mesocortical and thalamic systems. These findings provide a basis for establishing the possible functional relatedness or independence of these analogous effects.

Animals↗

PubMed1986

[Angelman syndrome].

An eight-year-old boy with Angelman-(Happy Puppet-)Syndrome is described. Nearly all typical symptoms of the syndrome, especially severe psychomotoric retardation with spontaneous outbursts of laughing and protrusions of the tongue, athetoid movements, typical electroencephalogram and microcephaly, could be found in our patient. The incidence of the Angelman-syndrome may be underestimated.

Abnormalities, Multiple↗

PubMed1986

Choledochal cyst type I: successful endoscopic balloon dilatation of the distal common bile duct and sphincter of Oddi: a case report.

A 12-year-old boy with a choledochal cyst type I is reported with clinical features of abdominal pain, postprandial vomiting, weight loss and fatigue since 3 months. Diagnosis was made by ultrasound and confirmed by computer-assisted tomography (CAT) and endoscopic retrograde cholangiography (ERC). Instead of the usual surgical treatment balloon dilatation of the sphincter of Oddi and the distal common bile duct was performed by endoscopic means. The patient was relieved from his complaints, gained weight and felt healthy again. Sonographic and endoscopic reexamination had proven that the diameter of the common bile duct had diminished from 3,0 to 2,6 cm. Endoscopic balloon dilatation of choledochal cysts type I may be a valuable alternative to surgical treatment.

Ampulla of Vater↗

PubMed1986

Cryptic miliary tuberculosis.

Fifteen patients with cryptic miliary tuberculosis seen over a six-year period in a large teaching hospital were reviewed. This form of tuberculosis tended to be difficult to diagnose and was most common in older people and those with underlying diseases such as malignancy or blood dyscrasias. Bacteriological investigation was of the little help in diagnosis while bone marrow and liver biopsies were more useful. The diagnosis was made during life in only seven (47 per cent) of the 15 cases, and the overall mortality was 80 per cent. Tuberculosis should be considered in all cases of pyrexia of unknown origin, and investigations performed to establish or exclude the diagnosis. A prompt and adequate therapeutic trial with antituberculous treatment even in the absence of definite evidence of tuberculosis can be life-saving.

Adolescent↗

PubMed1985

Hereditary motor sensory neuropathy type II with neurofilament accumulation: new finding or new disorder?

Peroneal muscular atrophy is now known to be heterogeneous and to be due to various underlying genetic mechanisms. Exploring this heterogeneity further, we report on a German kinship with the clinical, genetic, and nerve conduction features of hereditary motor and sensory neuropathy type II (HMSN type II) but whose sural nerves on biopsy were found to show infrequent axonal swellings with neurofilament accumulations not previously described. The dominant inheritance and absence of kinky hair set this disorder apart from giant axonal neuropathy. There was no history of toxic exposure to industrial chemicals. We conclude that the disorder either is a new type of HMSN or is HMSN type II with previously unencountered neurofilament accumulations. Neurofilament accumulation indicates that the axon could be a site for primary derangement and may implicate an abnormality of slow axonal flow. In addition, some of the patients exhibited features suggestive of a cardiomyopathy.

Adolescent↗

PubMed1985

Generalised glucosephosphate isomerase (GPI) deficiency causing haemolytic anaemia, neuromuscular symptoms and impairment of granulocytic function: a new syndrome due to a new stable GPI variant with diminished specific activity (GPI Homburg).

A new glucosephosphate isomerase (GPI) variant is described which is characterised by very low specific activity in erythrocytes, granulocytes and muscle tissue, nearly normal stability, normal kinetic properties and a decreased electrophoretic mobility. The propositus suffers from a complex syndrome involving erythrocytes (congenital haemolytic anaemia), granulocytes (decreased production of superoxide anion and reduced bactericidal activity in vitro) and the neuromuscular system (myopathy, mental retardation). It is suggested that the clinical syndrome results from generalised GPI deficiency due to a decreased specific activity of the variant enzyme, which cannot be compensated by an increase of de-novo synthesis of GPI protein even in cells exhibiting active protein synthesis such as granulocytes and muscle cells.

Adolescent↗

PubMed1984

Mitochondrial myopathy with lactic acidosis and deficient activity of muscle succinate cytochrome-c-oxidoreductase.

A male infant had severe muscular hypotonia from birth. Recurrent vomiting with dehydration and severe metabolic acidosis complicated the course. Elevated lactate (up to 12.3 mmol/l; n less than 2), pyruvate (0.4 mmol/l; n less than 0.05) and alanine levels were found in serum with an abnormal lactate/pyruvate ratio (greater than 30; n less than 15). In urine the concentrations of lactate, pyruvate, alanine and of several intermediates of the citric acid cycle were increased. In muscle, numerous disseminated "ragged red fibres" were found by light microscopy; muscle fibres were found to contain subsarcolemmal aggregates of mitochondria, lipid droplets and glycogen by electromicroscopical methods. Moreover, mitochondria with a typical circular arrangement of cristae were noticed. In liver homogenates normal activities of pyruvate carboxylase and pyruvate dehydrogenase complex were found; in liver mitochondria also succinate-cytochrome-c-oxidoreductase activity was normal. However, in muscle no succinate-cytochrome-c-oxidoreductase activity was detectable. The patient became increasingly lethargic and died because of sepsis at 5 months of age.

Acidosis↗

PubMed1983

Multiple-unit activity of the prefrontal cortex and mediodorsal thalamic nucleus during acquisition of discriminative avoidance behavior in rabbits.

Multiple-unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) thalamic nucleus was recorded during discriminative conditioning of a locomotory avoidance response in rabbits. A major objective was to compare the results with those previously obtained from the posterior limbic (cingulate) cortex, and the anteroventral (AV) thalamic nucleus. The results indicated the development, with training, of discriminative neuronal activity, i.e., greater neuronal discharges to presentation of the positive conditional stimulus (CS+, a tone paired with a footshock unconditional stimulus), relative to the negative conditional stimulus (CS-, a tone not paired with the footshock). The rostral-sulcal subfield of the PFC developed the discriminative activity during the first session of conditioning, prior to the acquisition of discriminative behavioral responding. This effect persisted throughout training to the asymptote of behavioral acquisition. The medial subdivision of the MD nucleus, with which the rostral-sulcal PFC is interconnected, did not develop discriminative effects. The caudal (supragenual) subfield of the PFC also developed discriminative activity in the first session of training but the effect declined progressively in the remaining acquisition sessions. The lateral subdivision of the MD nucleus, with which the caudal PFC is interconnected, manifested robust discriminative activity in the late acquisition sessions, concomitant with acquisition of significant behavioral discrimination. Thus, as in the cingulate cortical AV nuclear system, a corticothalamic sequential progression of discriminative activity occurred in the PFC-MD nuclear system during behavioral acquisition. However, the effect was confined to one subsystem: the caudal subfield of the PFC and the lateral subdivision of the MD nucleus. Also, discriminative activity developed more rapidly in the PFC than in the cingulate cortex, and it developed more rapidly in the MD nucleus than in the AV nucleus. Implications are considered concerning the contributions to learning and memory processes, of the PFC-MD thalamic system.

Animals↗

PubMed1983

Multiple-unit activity of the prefrontal cortex and mediodorsal thalamic nucleus during reversal learning of discriminative avoidance behavior in rabbits.

Multiple-unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) thalamic nucleus was recorded during reversal training following differential conditioning of a locomotory (wheel rotation) avoidance response in rabbits. The positive and negative conditional stimuli (CS+ and CS-) were pure tones and the unconditional stimulus (UCS) was footshock. A major objective was to compare the activity in the PFC and MD nucleus with that in the neighboring cingulate cortical and anteroventral (AV) thalamic system, studied previously. During the first session of reversal training the rostral-sulcal subfield of the PFC manifested significant discriminative activity appropriate to the original habit, i.e., a greater discharge to the original CS+ than to the original CS-. The difference between the CS+ and CS- elicited discharges diminished as reversal learning progressed, but discriminative activity appropriate to the reversal problem did not develop. The medial subdivision of the MD nucleus which is interconnected reciprocally with the rostral-sulcal PFC subfield did not manifest discriminative activity during reversal training (nor had it done so during original learning). The caudal subfield of the PFC (which had shown rapidly developing acquisition of the discriminative discharges followed by diminution of the discriminative discharges during original training) manifested an original discriminative effect in the initial session of reversal training followed by the reverse discriminative discharge in the criterial session. The lateral subdivision of the MD nucleus which is interconnected reciprocally with the caudal PFC subfield, also manifested the original discriminative effect in the initial session of reversal training, followed by the reverse discriminative effect during the subsequent (precriterial and criterial) sessions. Thus, as in the AV nucleus, the lateral MD subdivision showed earlier and more robust development of discriminative activity appropriate to the reversal problem, than its cortical counterpart. The present results also suggested that cerebral cortical areas such as the caudal PFC, which transfer discriminative activity to their respective thalamic nuclei during discriminative acquisition, are subsequently more likely to manifest the reverse discriminative activity, than are cortical areas such as the rostral-sulcal subfields of the PFC, which do not transfer their discriminative activity.

Animals↗

PubMed1983

The structure of the abortive nicotinamide adenine dinucleotide-pyruvate-lactate dehydrogenase complex as determined by circular dichroism.

Both ternary complexes consisting of lactate dehydrogenase-NAD+ and pyruvate or alpha ketobutyrate were compared, by means of circular dichroism spectra, with the corresponding binary complexes formed between lactate dehydrogenase and both NAD-pyruvate and NAD-alpha ketobutyrate adducts. Strong differences were observed. They disappeared when the ternary complexes were dissociated by addition of urea. This behaviour is explained by assuming the existence, in the abortive ternary complexes of a NAD+ activated transient form having a partial carbonium ion at position 4. Such a structure may account for the abortive and for the evolutive ternary complexes of the dehydrogenases as well as for the chemical synthesis mechanism of adducts.

Animals↗

PubMed1983

Anterior thalamic lesions and neuronal activity in the cingulate and retrosplenial cortices during discriminative avoidance behavior in rabbits.

Bilateral electrolytic lesions of the anteroventral (AV) nucleus of the thalamus given after training impaired retention performance (extinction and reacquisition) of rabbits in a differential avoidance conditioning task. In addition, the lesions abolished the excitatory, discriminative multiple-unit discharges that had developed in the cingulate and retrosplenial cortices to the auditory conditional stimuli (CSs) during the course of behavioral acquisition, prior to the induction of the lesions. The excitatory discharges were supplanted in the subjects with lesions by CS-elicited reduction of neuronal firing to levels below the prestimulus baseline. Lesions given before training did not disrupt behavioral acquisition, but they did eliminate the excitatory tone-elicited neuronal discharges that normally occur in the cortex before and during training. The CS-elicited reduction of neuronal firing did not occur at the beginning of training in the subjects given lesions before training, but it developed during the course of training. The lesions did not eliminate the excitatory and discriminative neuronal activity of the prefrontal cortex. These results demonstrate that excitatory and discriminative neuronal discharges in the cingulate and retrosplenial cortices are critically dependent on the connections of these areas with the anterior thalamic nuclei. Also the lesion-induced disruption of performance during extinction and reacquisition but not during original learning confirms a prediction from past electrophysiological studies, that the AV thalamic nucleus is involved in the mediation of the maintenance and retention of the conditioned avoidance behavior, but not in its original acquisition.

Animals↗