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Biomedical subjects

M Gabriel

Publications and source records attributed to M Gabriel.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1983

Examination of operation specimens from patients with spinal tuberculosis for tubercle bacilli.

Operation specimens from 52 Hong Kong patients considered to have tuberculosis of the spine were sent at -78 degrees C to London where they were cultured on two Löwenstein-Jensen medium slopes, a slope of 7H11 medium made selective with antibiotics and in two bottles of selective liquid Kirchner medium. Cultures of M tuberculosis, usually with only scanty colonies, were obtained from 37 of the patients. Pus and caseous matter yielded more positive cultures and more numerous colonies than other specimens, but eight of the 37 patients yielded positive cultures only from tissues lining abscess walls or from bone or intervertebral disc specimens. Cultures in Kirchner medium were never contaminated and twice as many were positive as cultures on the slopes; nine patients had cultures positive only on Kirchner medium. It is recommended that (i) a variety of operation specimens, always including pus or caseous material in volumes of at least 1 ml, should be sent for bacteriology; (ii) specimens should be cultured in selective Kirchner medium, with or without Löwenstein-Jensen slopes; (iii) cultures should be incubated for a minimum of 8-9 wk.

Culture Media↗
PubMed1983

Plasma levels of catecholamine metabolites in the newborn period.

Plasma levels of homovanillic acid (HVA) and vanillylmandelic acid (VMA) were measured mass fragmentographically in 37 healthy preterm infants and 62 healthy infants born at term during the postnatal period. HVA and VMA levels increased after birth and declined steadily afterwards. Infants with various clinical problems showed marked elevations of HVA and VMA during episodes of clinical deterioration. The results indicate a readily functioning sympathoadrenal system in newborns.

Adrenal Glands↗
PubMed1982

Binding of adducts of NAD(P) and enolizable ketones to NAD(P)-dependent dehydrogenases.

Carbonyl compounds such as alpha-ketoglutarate, pyruvate, oxaloacetate, butyraldehyde, acetaldehyde or acetone react with NAD or NADP to give adducts. Binding studies of adducts to dehydrogenases are performed by means of ultraviolet differential spectroscopy, circular dichroism and spectrofluorimetry. The dehydrogenases show a high degree of binding specificity toward the adducts which contain their specific oxidized substrate and their specific coenzyme. The high selectivity of the dehydrogenases for adducts is evidenced by binding studies of NAD(P)-pyruvate and NAD(P)-alpha-ketoglutarate adducts on glutamate dehydrogenase at pH 7.6 and 8.9. Evidence is presented showing that adducts bind to the active site of the enzymes.

Alcohol Dehydrogenase↗
PubMed1982

A comparison of spontaneous and CSF added CFU-MG colony formation in healthy, sick and hypotrophic pre-term infants.

Myelopoietic progenitor cells (CFU-MG) have been studied from peripheral blood of healthy, sick, and hypotrophic pre-term infants. Methylcellulose cultures were prepared simultaneously with and without exogenous colony stimulating factor. It was found that large numbers of circulating CFU-M are present at birth in healthy infants, smaller numbers in sick infants, and very few in hypotrophic infants. Exogenous CSF increases the number of colonies in cultures of healthy infants at birth. A limiting factor in spontaneous colony formation is the production of CSF by the cells in culture. This is particularly evident in sick infants. During the postnatal course similar levels of circulating CFUc, higher than in adult blood, are found in all three groups of pre-term infants.

Colony-Stimulating Factors↗
PubMed1982

Cingulate cortical and anterior thalamic neuronal correlates of the overtraining reversal effect in rabbits.

Multiple-unit activity of the cingulate cortex and the anteroventral (AV) nucleus of the thalamus in rabbits was recorded during reversal training, following differential conditioning of a locomotory (wheel rotation) avoidance response. The CS+ and CS- were pure tones (1 or 8 kHz) and the UCS was a footshock delivered through the grid floor of the wheel. One group of the rabbits received original training to a criterion followed immediately by reversal training. A second group received training to criterion followed by additional training sessions (overtraining), prior to reversal training. The results indicated that the overtraining reversal effect (ORE) occurred. That is, the overtrained subjects acquired the reverse discrimination in significantly fewer sessions than the non-overtrained subjects. The overall (non-discriminative) neuronal reactivity in all cingulate cortical laminae was reduced by overtraining, whereas the overall reactivity of the AV thalamus was enhanced. In addition, the non-overtrained subjects manifested a discriminative neuronal response appropriate to the original task (i.e. a greater response to the CS- than to the CS+ for reversal training), throughout the precriterial sessions of reversal training. This persistent 'original habit effect' occurred only at brief latencies (20-30 msec) after CS onset, and only in the deep cortical laminae (V-VI). The neuronal activity of the superficial laminae (I-IV) in non-overtrained subjects underwent a transition, in parallel with the behavior, from a discriminative response appropriate to the original task to one appropriate to the reversal task. No significant training-related changes were seen at any cortical depth in the overtrained subjects. Presentation of non-contingent footshocks during two sessions of reversal training following criterion re-enhanced the overall reactivity and the brief-latency discriminative neuronal response appropriate to the original task, which had undergone decline during reversal training, in the deep cortical laminae of the non-overtrained subjects. The enhanced overall reactivity and the discriminative activity in the superficial laminae of non-overtrained subjects had not declined during reversal training and were not altered by the non-contingent footshocks. The implications of these data are discussed in regard to the neural causation of the ORE.

Animals↗
PubMed1982

Parallel and serial processes of the prefrontal and cingulate cortical systems during behavioral learning.

Multiple unit activity of the prefrontal cortex (PFC) and the mediodorsal (MD) nucleus of the thalamus was recorded during differential conditioning of a locomotory (wheel-rotation) avoidance response. The positive and negative conditional stimuli (CS+ and CS-) were pure tones (l kHz and 8 kHz), and the unconditional stimulus was a footshock (1.5-2.0 mA) delivered through the grid floor of the wheel apparatus. A principal objective was to compare the development during training of CS-related neuronal activity in the PFC and MD nucleus, to that obtained in past studies of the adjacent limbic mesocorticothalamic system (the cingulate cortex and the anteroventral (AV) thalamic nucleus). The results indicated that these systems perform associative processing of task-related stimuli in parallel: as in the cingulate cortex, discriminative neuronal discharges (greater discharges to the CS+ than to the CS-) developed in the PFC in the earliest training stage, before incipient discriminative behavior, and as in the AV nucleus, discriminative discharges in the MD nucleus developed in a later training stage. Nevertheless the possibilities of serial processing and intercausality in these systems was suggested by the finding that discriminative activity in the PFC and MD nucleus developed at briefer latencies and earlier in the course of trials than in the cingulate cortex and the AV nucleus.

Animals↗
PubMed1982

Studies of covalent adducts of NAD(P) and enolizable ketones as specific glutamate dehydrogenase inhibitors.

Structural analogues of the reduced coenzymes, NADH or NADPH, of dehydrogenases are prepared by addition of carbonyl compounds including: pyruvate, alpha ketoglutarate, oxaloacetate, butyraldehyde, acetaldehyde and acetone, to the oxidized coenzymes NAD(P). Some of the adducts obtained are specific inhibitors of the glutamate dehydrogenase. The specificity is related to the carbonyl compound used. The high selectivity of the dehydrogenases for adducts is evidenced by inhibition studies of NAD(P)-pyruvate and NAD(P)-alpha ketoglutarate adducts on both activities of glutamate dehydrogenase. The inhibitions are competitive with the reduced coenzymes and the oxidized substrates: adducts could be considered as structures closely related to the ternary complexes of the dehydrogenase.

Animals↗
PubMed1981

Circulating myelopoietic stem cells (CFUc): high levels in healthy pre-term infants and reduced levels in sick pre-term infants.

In healthy and diseased pre-term infants at birth, levels of circulating CFUc are 2,586 +/- 3,063 (s. d.) and 269 +/- 292 (s.d.) per 5 X 10(5) lymphoid cells, as compared to data from the literature of 5 CFUc per 5 X 10(5) mononuclear cells from the blood of adults [8]. Hypotrophic infants have the lowest concentration of CFUc in the blood, namely 78 +/- 105 (s.d.). In formerly sick infants recovering from their perinatal illness, blood CFUc levels increase to approach those from healthy infants of the same age. Our results provide evidence that blood CFUc levels in pre-term infants reflect the strong myelopoietic activity of fetal bone marrow and suggest a correlation to the clinical status of the infant.

Female↗