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Biomedical subjects

M Gabriel

Publications and source records attributed to M Gabriel.

At least 127 records · Page 7Linked to original sources
PubMed1981

Sleep-wake pattern in preterm infants under two different care schedules during four-day polygraphic recording.

The sleep-wake pattern of healthy preterm infants under two different schedules of routine procedures was studied by 4-day polygraphic-recording. Group-I experienced the usual routine care conditions, Group-II remained less disturbed by means of time-coordination of the procedures. Group-II-infants were less awake, showed a higher percentage of active sleep and the undisturbed phases of active and quiet sleep were longer than in Group-I-infants. Routine procedures left Group-II-infants more often in an unchanged state than Group-I-infants, the latter exhibiting an arousal reaction more frequently. The unknown effect of sleep disturbances in preterm-infants demands a reduction and coordination of routine procedures as far as possible.

Arousal↗
PubMed1980

Interaction of laminae of the cingulate cortex with the anteroventral thalamus during behavioral learning.

Neurons in deep laminae of the rabbit cingulate cortex develop discriminative activity at an early stage of behavioral discrimination learning, whereas neurons in the anteroventral nucleus of thalamus and neurons in the superficial cortical laminae develop such activity in a late stage of behavioral learning. It is hypothesized that early-forming discriminative neuronal activity, relayed to anteroventral neurons via the corticothalamic pathway, contributes to the construction of changes underlying the late-forming neuronal discrimination in the anteroventral nucleus. The resultant late discriminative activity in the anteroventral nucleus is then relayed via the thalamocortical pathway back to the superficial cortical laminae, promoting disengagement of cortex from further task-processing.

Animals↗
PubMed1980

Sleep induced PO2-changes in preterm infants.

In seven healthy preterm infants the transcutaneous PO2 was measured during different sleep states. The tcPO2 is lower during active sleep than during quiet sleep and shows a higher variability in active sleep. The incidence of apneic spells, which occur predominantly during active sleep, was not found to be correlated to tcPO2 levels.

Apnea↗
PubMed1980

Ultrastructure of spores of Rhizopus nigricans after repeated freezing and thawing shocks.

Disintegration of nuclear envelopes is the only ultrastructural change detectable by freeze-etching in dormant spores of the mould Rhizopus nigricans, both dry and swollen, subjected to repeated freezing and thawing. The increase of the number of freeze-inactivated spores corresponds well with the increase of the number of damaged nuclei. This fact led us to formulate a hypothesis that the structure of the nucleus is the primary target of the freezing or thawing damage. As other biomembranes are not damaged it may be assumed that the disintegration of the nuclear membrane is probably secondary. No changes in ultrastructure of metabolically activated spores could be detected, in spite of the fact that the spores lost their germinative ability. Thus, the mechanism of the freeze injury may be different in dormant and growing spores.

Cytoplasm↗
PubMed1980

Early and late acquisition of discriminative neuronal activity during differential conditioning in rabbits: specificity within the laminae of cingulate cortex and the anteroventral thalamus.

Multiple-unit activity of the cingulate cortex and the anteroventral (AV) nucleus of the thalamus was recorded during discriminative conditioning of an avoidance response (locomotion) in rabbits. The results indicated a greater unit response in cingulate cortex to the positive conditional stimulus (CS+; a tone paired with a footshock unconditional stimulus [UCS]) relative to the negative conditional stimulus (CS-; a tone randomly interspersed with the positive stimuli but never paired with the UCS). The majority of neuronal records obtained from the deep laminae (V and VI) of cingulate cortex manifested first neuronal discrimination in the session of first exposure to conditioning. However, the majority of neuronal records of the superficial laminae (I-IV) showed first discrimination at a late stage of training, during the session in which the criterion of behavioral discrimination was met. The late developing discriminative activity of the superficial laminae was coincident with the late developing discriminative activity of the AV thalamus. Once acquired, neuronal discrimination in cortex persisted throughout 600 msec after CS onset, and during six sessions of training (overtraining) beyond criterion. Analysis of individual neuronal records suggested that the persistence during overtraining resulted from replacement of early fading neuronal discriminations by late neuronal discriminations.

Animals↗
PubMed1980

Cingulate cortical and anterior thalamic neuronal correlates of reversal learning in rabbits.

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 positive and negative conditional stimuli (CS+ and CS-) were pure tones (1 kHz and 8 kHz), and the unconditional stimulus was footshock (1.5 mA). During the first session, activity appropriate to the original task (i.e., a greater neuronal response to the CS- than to the CS+) occurred in the deep cortical laminae (V and VI), but the superficial laminae (I-IV) manifested the original discrimination in certain records and the reverse discrimination in others. All discriminative effects diminished during subsequent sessions except the short-latency (25-msec) deep laminar original discrimination, which persisted throughout reversal training. Activity of the AV nucleus underwent gradual transition, in parallel with the behavior, from the original to the reverse discrimination. Arousal-producing footshocks given after behavioral reversal educed the original and reverse discriminations in the deep and superficial laminae, respectively. These data are interpreted to indicate the role of cingulate cortex and anterior thalamus for encoding the associative significance of the conditional stimuli.

Animals↗
PubMed1980

Antibody response following prolonged hyposensitization with Dermatophagoides pteronyssinus extract.

An antigen-binding radioimmunoassay was used to measure IgG, IgA and IgE antibody (ab) to Dermatophagoides pteronyssinus in sera from patients who had been hyposensitized with either aqueous D. pteronyssinus extract or placebo. An allergen, F4P1, was obtained from D. pteronyssinus culture and 125I-labelled for use in the assay. The radioallergosorbent test was also used to measure IgE ab to D. pteronyssinus and IgE ab to Dermatophagoides farinae. The radioimmunoassay results showed a selective rise in IgG ab in sera from D. pteronyssinus-treated (DP) patients. An increase of greater than twofold in IgG ab in post-treatment sera was found in 27 of 29 DP patients compared to 1 of 29 placebo-treated ('placebo') patients (p less than 0.001). The mean rise in IgG ab in DP patients was sixfold, and the maximum rise was 50-fold. There was little change in the levels of IgA ab or IgE ab in either DP or 'placebo' patients during treatment. The DP patients showed significant clinical improvement compared with the 'placebo' patients (p less than 0.01). However, no correlation was found between post-treatment IgG ab and post-treatment symptom scores, or between the changes in IgG ab and the changes in symptom scores during treatment. The time course of the antigen-binding assay was investigated using very low concentrations of F4P1. The results showed that antigen-binding was slow, even in the presence of an excess of IgG ab. The role of IgG ab in hyposensitization is discussed.

Animals↗
PubMed1980

[Cot death, contributing factors and practical implications (author's transl)].

A review is given on the current knowledge regarding the sudden infant death syndrome. Facts of epidemiology, morphological and physiological results recently reported are discussed for the question of SIDS-etiology, where developmental defects in cardiorespiratory control might play an important role. Practical implications are presented for future research as well as for current handling of infants at risk.

Age Factors↗
PubMed1978

Sleep and aminophylline treatment of apnea in preterm infants.

The influence of short-term aminophylline treatment on sleep behaviour was studied in six preterms infants with recurrent apnea. The incidence of apnea, respiratory pauses, and bradycardias which were closely related to the phases of active sleep, decreased during aminophylline treatment. However, the amount of active sleep remained unaffected. The mode of action of aminophylline is discussed in view of the previously proposed neurophysiological concept of apnea of prematurity.

Aminophylline↗
PubMed1978

Viability of spores after repeated freezing and thawing shocks.

Survival of spores of the fungus Rhizopus nigricans after repeated freezing and thawing was investigated. The cooling rate was 10(4) degrees C/min. Dry spores were fully inactive after 32 repeated shocks. About one-half of spores were killed after 8 repetitions. The water content did not change the resistance, swollen spores reacted to shocks much like dry ones. The sensitivity of spores to freezing-thawing shocks increased considerably when the spores changed from the dormant to the active state. Already after a 30 min cultivation of spores in the nutrient medium two freezing and thawings were sufficient for inactivation of 60% spores. After a 90 min cultivation one freezing and one thawing were sufficient to inactivate practically all spores.

Culture Media↗
PubMed1978

[Progressive External Ophthalmoplegia (authors transl)].

The case of a 16-year-old boy with progressive external ophthalmoplegia ("Ophthalmoplegia plus") is reported. Clinical symptoms consisted of complete external ophthalmoplegia, ptosis, short stature, atrophy and weakness of skeletal muscles, and elevated csf protein. Abnormal mitochondria were found by electron microscopy in scattered atrophic fibres of the muscle biopsy. The syndrome and it's relevance for paediatric differential diagnosis is discussed.

Adolescent↗
PubMed1977

Effects of unpaired footshock on rabbit limbic and auditory neuronal responses to tone stimuli.

Multiple unit activity was recorded from the anterior cingulate cortical area (AC), anteroventral nucleus of the thalamus (AV), and medial geniculate nucleus (MGN) in rabbits during presentations of pure tone stimuli. In one experimental session (S) the tones were presented with unpaired footshock, and in a different session (NS) tones alone, without footshock, were presented. The order of the sessions was counterbalanced, and they were separated by 24 hr. The response of AC neurons to the tones was greater in the S treatment, relative to NS, and the S-related enhancement carried over to the NS session when the latter followed S. The response of AV neurons was also greater in the S treatment, relative to NS, but the enhancement did not carry over to NS. The response of MGN neurons showed different relationships to the experimental variables in different animals. This suggested that the effect of the treatments depended on the specific recording site in MGN.

Acoustic Stimulation↗
PubMed1977

Unit activity in cingulate cortex and anteroventral thalamus of the rabbit during differential conditioning and reversal.

Multiple-unit activity was recorded from the rabbit anterior cingulate cortical area (AC) and from the anteroventral nucleus of the thalamus (AV) during differential avoidance conditioning and reversal. The positive and negative conditioned stimuli were tones of different frequency, and the unconditioned stimulus (UCS) was shock delivered through the grid floor of a rotating-wheel conditioning apparatus. Conditioning was preceded by pretraining with tones and noncontingent presentations of the shock UCS. The results showed associative (differential) neuronal activity in both AC and AV during differential conditioning. The effect in AC occurred in the intermediate and final sessions of conditioning. A very large differential effect appropriate to original conditioning occurred in AC in the first two sessions of reversal training. The differential effect in AV occurred in the final session of conditioning when the behavioral response was well learned. There was no clear neuronal reversal in AC or AV.

Acoustic Stimulation↗
PubMed1977

Rapid eye movement sleep, apnea, and cardiac slowing influenced by phenobarbital administration in the neonate.

Polygraphic recordings were performed in seven preterm infants who had been given phenobarbital (phenobarbitone) to evaluate its effect on neonatal sleep behavior and on the incidence of neurogenic apnea and/or bradycardia. The amount of active sleep, as well as the incidence of apnea and/or cardiac slowing occurring predominantly in active sleep, were decreased at therapeutic serum levels of phenobarbital. With declining serum drug levels, active sleep showed a rebound effect; at the same time, apnea and/or cardiac slowing relapsed. Thus, our previously proposed neurophysiologic concept that neonatal apnea is facilitated by active sleep-inhibitory brain mechanisms seems to be confirmed.

Apnea↗