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Biomedical subjects

J Bert

Publications and source records attributed to J Bert.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1983

Cerebral glucose utilization: local changes after microinoculation of scrapie agent in hamster.

The effects of scrapie agent on local cerebral energy metabolism were studied by the [14C]2-deoxyglucose (2-DG) autoradiographic method of Sokoloff et al. after stereomicroinoculation (0.5 microliter, 10(-2) of scrapie suspension) in hamster left striatum. From a group of 20 hamsters inoculated, 2 animals were killed every 10 days from the 30th day after inoculation to the terminal stage of the disease. Experiments were carried out according to the qualitative 2-DG procedure and cerebral autoradiographs of inoculated animals were compared to those of 3 controls. The results show changes of local cerebral glucose utilization in some discrete brain regions, ipsilateral to the side of inoculation, and their sequential spreading to other cerebral structures with a definite order: left anterior thalamus, left posterior thalamus, then medial geniculate body (ipsilateral, then controlateral), and finally some brainstem nuclei (inferior colliculus, superior olivary nucleus); the inoculated striatum is affected very late, after clinical signs. Metabolic changes which first occur ipsilaterally to the side of inoculation precede the clinical symptoms, while their contralateral spreading is concomitant with the clinical signs. The data demonstrate a rostral--caudal sequence of the cerebral metabolic changes, ipsilateral to the side of inoculation, which may reflect in part the slow spread of agent in the central nervous system from the inoculation site.

Animals↗
PubMed1982

Changes in the nigrostriatal system following microinjection of an unconventional agent.

The effect of apomorphine, a direct dopamine receptor agonist, was studied in golden hamsters after unilateral injection of scrapie agent (strain 263K) into the nigrostriatal system. Twenty-five received an injection into the left striatum and 24 into the left substantia nigra. Varying volumes (5, 1 and 0.5 microliterss) and dilutions of the homogenate (10(-2), 10(-3), 10(-4)) were used. The duration of the incubation period (delay of appearance of clinical signs of the disease) was dependent on the dose of the agent used: it varied within a range of 72 +/- 5 days (5 microliter 10(-4) and 123 +/- 8 days (0.5 microliter 10(-4)). Apomorphine-induced circling behavior appeared after an average of 84 +/- 15 days post-injection and this delay was closely related to the dose of agent. The direction of the rotation dependent on the site of injection: most of the animals circled towards the inoculated side after striatal injection and away from it after inoculation in the substantia nigra. In the group of animals inoculated in the substantia nigra with 0.5 X 10(-4) microliters, 6 presented the clinical phase of the disease and showed circling behavior but no clinical signs when they were killed 200 days post-injection. However, neuropathological studies revealed characteristic foci of vacuolation in the brain stem. Apomorphine-induced circling behavior can only be contained by replication of scrapie agent into the nigrostriatal neurons and the subsequent imbalance between the two sides which it reveals. Circling behavior and clinical signs of the disease can be temporally dissociated: low doses of agent slightly extended the circling behavior latency, whereas the incubation period was considerably increased. Circling behavior and neuropathological lesions in nigrostriatal system were not closely related.

Animals↗
PubMed1981

Apomorphine-induced circling behaviour in hamsters following unilateral injection of scrapie gent in the striatum.

Twenty golden hamsters received a microinjection of scrapie agent into the left striatum. At different times after inoculation animals were injected intraperitoneally with apomorphine, a direct dopamine receptor agonist. Two types of effects developed simultaneously, starting at about 80 days after infection. First, apomorphine induced a rotational behaviour which showed a progressive destruction of the striatal neurones at the site of injection. This suggest a local spread of scrapie agent by cell to cell transfer in the striatum. Secondly, the clinical signs of scrapie developed, indicating a more widespread distribution of agent throughout the brain.

Animals↗
PubMed1981

Anatomical study of experimental kuru in the Rhesus monkey.

The authors report the morphology and topography of CNS lesions in experimental kuru (third passage) in the rhesus monkey. The main lesions encountered are spongiosis of the neuropile with neuronal vacuolization, moderate astrocytic gliosis, and slight neuronal depopulation. In all cases, lesions predominated in the grey matter of the cerebral hemispheres (cortex, neostriatum). Lesions were minimal in cerebellum and brain stem. The authors compare their results with these observed species of Primates (chimpanzee, spider monkey, marmoset, squirrel monkey).

Animals↗
PubMed1980

Experimental kuru in the rhesus monkey. A clinical study.

Serial neurologic examinations of six rhesus monkeys inoculated with a strain of kuru revealed complex clinical signs falling into two distinct syndromes. Experimental kuru in the rhesus monkey is different from the disease in man and to a lesser extent in the chimpanzee. Two factors are proposed to account for these observations: modification of the strain, and specific host characteristics.

Animals↗
PubMed1980

[Night sleep study in acute and chronic psychosis (author's transl)].

A group of 22 psychotics (19 schizophrenics) was recorded in acute and/or chronic phase by series of 3 consecutive nights. Our main purposes were to study correlations between subgroups and sleep patterns and to follow the clinical evolution of these patients in looking at the quantitative and/or qualitative modifications of the various sleep states. Schizoaffective psychotics showed a lack of the "first night effect". The patients recorded in acute and in remission phases differ from unmedicated normal subjects: the former had less deep sleep and more "intermediate phases": the later presented an increase, sometimes very high, of REM total duration. Finally, within each subgroup, the analysis of individuals pointed out, for some of them, an evolution opposite to the general tendency.

Adult↗
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↗