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Biomedical subjects

J Bert

Publications and source records attributed to J Bert.

At least 19 recordsLinked to original sources
PubMed1992

Estimation of total body fluid shifts between plasma and interstitium in man during extracorporeal circulation.

Fluid transport between plasma and interstitium during extracorporeal circulation was studied in seven patients undergoing aortocoronary bypass grafting. The absolute shifts in plasma volume during hypothermia were determined as the difference between input and loss of fluid and the changes in blood volume. The change in haemoglobin concentration due to acute haemodilution when starting extracorporeal circulation was used to calculate the absolute blood and plasma volume. The Starling equation for exchange across the capillary wall was used to describe fluid shifts. The total fluid filtered during the 60- to 90-min period of extracorporeal circulation averaged 34.1 +/- 11.1 (s.d.) ml/min. The total body filtration coefficient from the Starling relationship averaged 0.046 +/- 0.012 ml/kg.mmHg.min (0.354 +/- 0.092 ml/kg.kPa.min). Haemodilution, reducing colloid osmotic pressure in plasma (COPP) by approximately 10 mmHg (1.3 kPa) will result in a loss of plasma fluid of around 2 1 per hour. When corrected for lower fluid viscosity due to hypothermia during extracorporeal circulation, CFC would be about 40% higher, and a filtered volume of nearly 3 1 in a normothermic 70-kg person would be expected. Crystalloid haemodilution for shorter periods of time does not produce excessive oedema and thus may be well tolerated.

Aged↗
PubMed1991

A method for estimating the Young's modulus of complete tracheal cartilage rings.

Cartilage is primarily responsible for maintaining the stability of the large airways; yet very little is known about the mechanical properties of airway cartilage. This work establishes a technique whereby average values for the equilibrium modulus of excised tracheal cartilage rings can be obtained. An apparatus was designed to apply preset deformations to a tracheal segment and to monitor the deforming force. Segments of four human tracheae obtained postmortem and containing three rings were mounted in the apparatus after being stripped of posterior membrane. The load-deformation behavior was analyzed with a model on the basis of thin curved beam theory. Agreement between predicted deformed shapes and those observed was good in three of the four cases and in the case of a short length of longitudinally split rubber tube. The technique is suitable for comparing mechanical properties of cartilage before and after an intervention.

Biomechanical Phenomena↗
PubMed1990

[Circadian analysis of sleep, rectal temperature and immunological and endocrinological variables in sleeping sickness: preliminary study].

A multidisciplinary study was conducted in 8 patients with neurological Human African Trypanosomiasis. The sleep-wake cycle followed an ultradian pattern which was more pronounced in patients with more severe symptoms. The EEG trace was consistently interrupted by numerous cyclic activation patterns with K complexes, rapid low amplitude elements and slow high voltage elements. Circadian rhythmicity was also disturbed in other physiological (rectal temperature), immunological (interleukins) or hormonal (cortisol, prolactin) variables, the disturbance being greater in severely hit patients.

Adolescent↗
PubMed1986

Alveolar flooding: a computer simulation.

A validated computer simulation of pulmonary microvascular exchange (J.L. Bert and K.L. Pinder, Microvasc. Res., 27 (1984) 51-70) has been extended to include exchange with the air space (alveoli). Equations which hypothetically describe characteristics associated with this additional compartment and the exchange of both fluid and plasma proteins between the lung tissue and the alveolar space are presented. These are incorporated into the simulation which has been used to predict the behavior of the pulmonary microvascular exchange system including alveolar flooding. The predicted trends associated with alveolar flooding are reasonable. However, due to the lack of specific experimental or clinical findings, the simulation remains essentially unvalidated. The effect on alveolar flooding and interstitial edema of the parameters associated with the additional relationships is presented and discussed. Primarily, results for perturbations in circulatory pressure are presented. Additionally, changes in permeability characteristics are shown and discussed.

Blood Proteins↗
PubMed1986

Effect of intravenous papain on tracheal pressure-volume curves in rabbits.

To investigate the effects of airway cartilage softening on tracheal mechanics, pressure-volume (PV) curves of excised tracheas were studied in 12 rabbits treated with 100 mg/kg iv papain, whereas 14 control animals received no pretreatment. The animals were killed 24 h after the injection and the excised specimens studied 24 h later. Treated tracheas exhibited decreased ability to withstand negative transmural pressures, reflected in increased collapse compliance: 6.2 +/- 2.1 vs. 2.0 +/- 0.5% peak volume (Vmax)/cmH2O means +/- SD, P less than 0.001, (Vmax = extrapolated maximal tracheal volume), increased kc (exponential constant that reflects the shape of collapse limb of the PV curve): 0.244 +/- 0.077 vs. 0.065 +/- 0.015 (P less than 0.001). The distension limb of the PV curve greater than 2.5 cmH2O transmural pressure (Ptm) was no different. Compliance between 0 and 2.5 cmH2O Ptm was increased in papain-treated rabbits: 4.97 +/- 1.73 vs. 2.30 +/- 0.31% Vmax/cmH2O (P less than 0.001). Tracheal volume, and therefore mean diameter, was decreased at 0 Ptm: 2.7 +/- 0.26 vs. 3.2 +/- 0.27 mm (P less than 0.001). We conclude that airway cartilage softening increases the compliance of the trachea at pressures less than 2.5 cmH2O Ptm.

Animals↗
PubMed1985

Changes in tyrosine hydroxylase, glutamic acid decarboxylase and choline acetyltransferase after local microinoculation of scrapie agent into the nigrostriatal system of the golden hamster.

A microinjection of a homogenate of scrapie agent-infected brain (strain 263 K) into the nigrostriatal system in the golden hamster is followed by the progressive development of the disease which terminates by the death of animals around the 4th month postinoculation. These intracerebral inoculations induce more rapid changes in neuronal activity which can be revealed by the assessment of the specific synthesizing enzymes of neurotransmitter systems. The microinoculation of a homogenate of an infected brain unilaterally into the substantia nigra (SN) provokes a decrease in tyrosine hydroxylase (TH), the synthesizing enzyme for dopamine in the dopaminergic neurones, in the striatum ipsilateral to the injected SN. This biochemical response, specifically induced by the active pathogen, is detectable as soon as the 5th day postinoculation and is detectable towards the 80th day. A return of TH levels to control values is detected after this period. At the end of the incubation period and towards the death of the animals, TH is not different from control TH measured from intact animals. The decrease in TH is concomitant with an increase in striatal glutamic acid decarboxylase (GAD), the synthesizing enzyme for gamma-aminobutyric acid (GABA), measured 20 days postinoculation with no change in choline acetyltransferase (ChAT), the synthesizing enzyme for acetylcholine. Studies of the biochemical responses associated locally to the scrapie agent inoculation have been performed at the striatal level. The intrastriatal administration of the infective agent induces 20 days postinoculation an increase in GAD with no change in TH and ChAT. Ninety days postinoculation, a decrease in GAD was detected associated with an increase in TH with no change in ChAT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Early changes in tyrosine hydroxylase and glutamate decarboxylase activity in the golden hamster striatum after intracerebral inoculation of the nigrostriatal system with scrapie agent (strain 263 K).

Unilateral inoculation of hamster substantia nigra (SN) with scrapie agent led to an early decrease in tyrosine hydroxylase (TH) activity in the corresponding striatum, which was detectable by the 5th day. This decrease was accompanied by an increase in glutamate decarboxylase (GAD) observed on the 20th day. Local phenomena related to administration of the agent were investigated by intrastriatal inoculation followed by local measurement of TH, GAD and choline acetyltransferase (ChAT) activities. A rise in GAD activity was observed 20 days later. The decrease in TH activity which occurred 5 days after inoculation of the substantia nigra with scrapie agent constitutes an extremely early indication in hamsters of the slow pathological processes at work: at clinical and behavioural levels, these can be detected at best only 80 days after the intracerebral inoculation.

Animals↗
PubMed1978

Experimental kuru in the rhesus monkey: a study of EEG modifications in the waking state and during sleep.

EEG patterns recorded in the waking state and during sleep were studied in 6 rhesus monkeys inoculated with a strain of Kuru previously passaged in rhesus monkey (ENAGE strain, rhesus L6 56). The onset of the disease was confirmed by the appearance of various clinical signs in 4 monkeys 15 months after inoculation. At the 16th month, the first EEG modifications appeared during sleep, which became lighter. The waking EEG was abnormal during the mature phase of the disease; it was characterized by slow anomalies and scattered spikes. The sleep EEG still presented 3 stages of Slow Wave Sleep which, however, were totally unlike the physiological stages. REM sleep rapidly disappeared, as did the cyclic organization pattern. Irritative phenomena became very significant and, in particular, very frequent 'tonic seizures' were observed. Experimental Kuru thus appears, in the rhesus monkey, as an epileptogenic encephalopathy, which is differentiated from both the human disease and the experimental disease in the chimpanzee.

Animals↗
PubMed1978

Appearance of EEG changes reminiscent of a secondary generalized epilepsy in a rhesus monkey inoculated with a strain of kuru.

In a group of rhesus monkeys (Macaca mulatta) inoculated intracerebrally and intravenously with a strain (Enage strain rhesus L6 56) of kuru already passaged in rhesus monkeys, 1 monkey presented the typical EEG pattern of epileptogenic encephalopathy reminiscent of the Lennox-Gastaut syndrome. This observation provides no direct evidence for the viral origin of epilepsies of this type. It does, however, show that it is possible to induce an epileptogenic encephalopathy by an unconventional infectious agent.

Animals↗
PubMed1977

[Effect of chlorimipramine on the so-called ponto-geniculo-occipitalactivity (PGO) in a primate, Papio hamadryas (author's transl)].

Three hamadryas adult baboons (female) received 24 daily injections of Chlorimipramine (1.7 mg/kg). The effects on sleep were nearly identical with the effects observed in man. PGO activity, recorded in the lateral geniculate nucleus, was much disturbed. The total number of PGO fell downward from the first recording. The number of PGO/min during paradoxial sleep was even more decreased. This fact suggests a selective influence of CL I on the mechanisms of PGO activity. Is the particular effect of importance to the treatment of depression symptoms?

Animals↗
PubMed1977

[Alterations of sleep caused by acute and chronic adminstration of lithium].

The sleep of 2 groups of subjects receiving lithium was studied. Ten normal controls after 17 days of lithium had a significant decrease of Paradoxical Sleep duration, with an increase of PS latency. A second group of 10 manic-depressive patients had received lithium for 22 +/- 6 months when they were recorded. They had a greater amount of slow wave sleep than the control group before lithium but the difference of PS duration was only related to a first night effect. Therefore sleep changes induced by lithium are different according to the duration of lithium administration. In any case they are less important than those induced by most of the anti-depressants.

Adult↗
PubMed1977

Nonhuman primates: laboratory animals of choice for neurophysiologic studies of sleep.

A systematic study was made of several nonhuman primates to learn more about their relative usefulness for studies of sleep. Species studied included the Guinea baboon (Papio papio), Kenya or yellow baboon (P cynocephalus), olive baboon (P anubis), sacred baboon (P hamadryas), vervet monkey (Cercopithecus aethiops), rhesus monkey (Macaca mulatta), bonnet monkey (M radiata), crab-eating monkey (M fascicularis), patas monkey (Erythrocebus patas), chimpanzee (Pan troglodytes), mongoose lemur (Lemur mongoz), black lemur (Lemur macaco fulvus), and bushbaby (Galago senegalensis). Comparisons were made of electroencephalographic activity, states of vigilance, and responses to sleep-waking drugs. The results showed that there were major similarities among the genera studied as well as individual intrageneric and intraspecies differences. It was concluded that the chimpanzee, olive baboon, and rhesus monkey were the best species for comparative studies, and that the rhesus monkey was the best single model because of its well defined sleep organization and ease of handling and housing.

5-Hydroxytryptophan↗
PubMed1976

[The neuroendocrinology of sleep].

It is now well established that some pituitary hormones have a pattern of secretion closely linked to the sleep-waking cycle. These data open a new approach to the problem of sleep disturbances and suppose a completely new evaluation of their meaning.

Adrenocorticotropic Hormone↗
PubMed1975

The sleep of the baboon, Papio papio, under natural conditions and in the laboratory.

The sleep pattern of sixteen baboons (Papio papio) was studied under two very different conditions: (1) in a laboratory at Marseilles, the monkey being immobilized in a restraining chair in a soundproof cubicle; (2) in an African reserve, the monkey being housed in a large cage placed in its natural environment. Some very marked differences emerged. Sleep in the laboratory was longer (by 24 min) and richer in stage 3 and paradoxical sleep. In Africa, however, the sleep showed much more stage 1, was more fragmented and stages 2 and 3 and paradoxical sleep episodes were of shorter duration. Records made in Africa indicate that sleep is independent of slight environmental changes (day length, brightness of the moon, variations in temperature, calls of predators). But the comparison of the two series of results reveals the reorganization which occurs when the monkey is exposed to such different conditions. This adaptation to the environment affects, unequally, the various slow sleep stages and paradoxical sleep. In fact, the major modifications occur in stages 1 and 3 of slow sleep and in paradoxical sleep, while stage 2 appears to constitute the stable, unmodifiable nucleus of sleep.

Animals↗