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Biomedical subjects

J Petit

Publications and source records attributed to J Petit.

At least 253 records · Page 14Linked to original sources
PubMed1984

[Outcome of infants operated on for aortic coarctation before 3 months of age].

Between January 1966 and June 1982, 177 infants less than 3 months of age underwent surgical cure of coarctation of the aorta. Seventy-one percent had associated cardiac lesions not including a patent ductus arteriosus. With the cure of the coarctation either by resection anastomosis or angioplasty, 45% underwent associated surgical procedure, mainly pulmonary artery banding. Early mortality was 26% for the last 4 years of the study. Early deaths, significantly correlated with the severity of the preoperative heart failure and the importance of pulmonary hypertension, were not correlated with an associated heart disease. Of the 95 survivors operated on before December 31, 1981 and with a long follow-up, 18 died later on. Late deaths are related with associated cardiac malformations. Thirty-nine (41%) of the survivors had recurrent coarctation. This was correlated with the year of surgery and not with the surgical technique. In cases with coarctation of the aorta surgical cure should not be withheld before age 3 months, when there is heart failure, with or without associated cardiac malformations. The mortality, even in isolated coarctation (6%), the occurrence of sudden deaths after good surgical repair, the frequency of recoarctations lead to suggest that in infants under 3 months of age, careful supervision and conservative medical treatment should be considered, if the coarctation is isolated and well tolerated.

Aortic Coarctation↗
PubMed1984

[Assay of plasma xanthine and hypoxanthine by coupled gas chromatography-mass spectrometry and sampling problems].

The differential assay of xanthine and hypoxanthine in plasma, serum and erythrocytes was performed using a combination of GC and MS with chemical ionisation. The influence of sampling conditions was studied, in particular the latency period between the collection of the blood and the separation of the plasma and the cells, the nature of the anticoagulant used and the method of storage of the samples. Firstly, this study confirms that EDTA is the most appropriate anticoagulant. It also showed that an immediate deproteinisation is necessary after separation of the plasma and the cells, in order to prevent any "in vitro" modification of the oxypurines, in particular erythrocyte hypoxanthine.

Anticoagulants↗
PubMed1983

Action of dantrolene sodium on single motor units of cat muscle in vivo.

Dantrolene sodium, a skeletal muscle relaxant, was investigated for its action on single motor units of the peroneus tertius muscle in cats anaesthetized with pentobarbitone sodium. Motor axons were isolated in ventral root filaments and their muscle units were identified as either fast-fatiguable (FF), fast-resistant (FR), fast-intermediate (FI) or slow-resistant (S). Dantrolene sodium (2 mg/kg) was administered intravenously in a solution of 1,2-propanediol. Effects were observed on the twitches, unfused tetanic contractions and maximal tetanic tensions of 78 motor units in 5 experiments. Contractile tension was depressed whereas muscle action potentials appeared unaffected. Maximal tetani were less depressed than unfused tetani and twitches. The reduction of tension was more pronounced for fast (FF, FR and FI) than for slow units. After drug injection, the mean tensions developed at the end of a 3 s period of stimulation at 40/s were: 13.1%, 10.6% and 12.7% of pre-drug control for FF, FR and FI units, respectively, and 67.1% for S units. Upon prolonged stimulation at 40/s fast units depressed by Dantrolene sodium were able to potentiate back to their initial pre-drug tension.

Action Potentials↗
PubMed1983

Patterns of fusimotor innervation by gamma-efferents in cat peroneus tertius.

The pattern of gamma-efferent innervation of the muscle spindle was investigated in the peroneus tertius muscle of the cat. A number of spindle group Ia afferents were isolated and monitored during tetanic stimulation of isolated gamma-axons. The sample was dominated by efferents producing a static fusimotor effect on the afferent. An individual static axon normally projected to less than five but at times as many as seven muscle spindles. Each spindle normally received innervation from three to five static gamma-efferents but occasionally up to eight. The number of spindles innervated by a static gamma-axon was directly related to the efferent axonal conduction velocity. For each experiment, a probability distribution of the number of fusimotor effects was constructed from all available connections between the muscle spindles and static gamma-efferents considered in matrices of four afferents and four efferents. This distribution was then compared to a random binomial distribution. In each of the ten experiments, statistically significant differences (p less than 0.01) were noted between the experimental and random distributions. In order to interpret such deviations from the random distributions, similar analyses were performed on various combinations of afferents and efferents in simulated sets displaying grouping of effects. It was concluded that the observed differences between experimental and random distributions may be produced by a grouping of fusimotor innervation limited to a small set of spindles.

Afferent Pathways↗
PubMed1983

After-effects of repetitive stimulation at low frequency on fast-contracting motor units of cat muscle.

Twitch and tetanic contractions of single motor units of the cat peroneus tertius muscle were examined after application of a test allowing their identification as either fast fatigable (f.f.) or fast fatigue-resistant (f.r.) or fast intermediate (f.i.) or slow units as established by Burke, Levine, Tsairis & Zajac (1973). The test was found to leave two kinds of after-effects in f.f., f.r. and f.i. units whereas it did not affect slow units. The first after-effect was an early and brief potentiation of twitch tension occurring in all f.r. and f.i. units and in most f.f. units. The second after-effect, termed 'delayed fatigue', was a prolonged depression of tension output, that developed slowly following the early potentiation in all f.f. and f.i. units and more than half of the f.r. units. One hour after the test, unfused tetanic contractions elicited by 20-40/sec stimulation were deeply depressed in motor units that had been left without stimulation since the end of the test. Recovery took place in 3-5 hr. Motor units affected by delayed fatigue could nevertheless be made to develop nearly normal tension by gradual build-up upon prolonged stimulation at 30-40/sec. Maximal tetanic contractions elicited by 200/sec stimulation were much less depressed during delayed fatigue than unfused tetanic contractions. These observations suggest that contractile mechanism were not impaired by delayed fatigue. Since absence of change in muscle action potential indicated that excitation of muscle fibres was not affected either, delayed fatigue might be due to a temporary failure of excitation-contraction coupling.

Action Potentials↗
PubMed1982

[Treatment of urinary tract infections by dibekacin].

In this cooperative trial, 181 patients with various urinary tract infections were treated by dibekacin, a new hemi-synthetic aminoglycoside. Clinical and bacteriological results confirm the efficacy of dibekacin in this indication. Local and systemic tolerance, and thus renal and cochleo-vestibular, were very satisfactory.

Dibekacin↗
PubMed1982

Histochemical evidence for the existence of skeletofusimotor (beta) innervation in the primate.

A total of ten alpha motor axons which innervated the peroneus brevis muscle were isolated in two cynomolgus monkeys. In each experiment, the isolated alpha axons were stimulated collectively to deplete glycogen from their muscle units. The muscle was then frozen quickly , cut serially, and stained for glycogen. Of the 52 muscle spindles that were examined, zones of glycogen depletion were found in the intrafusal fibres of 32 spindles. The glycogen-depleted motor units included both fast-twitch and slow-twitch types. Depleted zones were observed in all three types of intrafusal muscle fibres. It was concluded that skeletofusimotor (beta) efferents were among the stimulated motor axons. This finding constitutes the first anatomical evidence for the existence of beta innervation in the primate.

Animals↗
PubMed1982

Distribution of physiological types of motor units in the cat peroneus tertius muscle.

Motor units of the cat peroneus tertius muscle were systematically analyzed using the criteria established by Burke et al. (1973). On the basis of their speed of contraction and resistance to fatigue, 121 (97%) of 125 motor units examined in ten adult cats could be classified as belonging to one of four types: fast-fatigable (FF), fast-resistant (FR), fast-intermediate (FI), and slow-resistant (S). Peroneus tertius was found to contain 30% FF motor units, 9% FI units, 39% FR units, and 22% S units. Contraction times of fast motor units (FF, FR, and FI) ranged from 15 to 27 ms and those of S units from 26 to 42 ms. The mean tetanic tensions were 37 g for FF units, 29 g for FI units, 7.5 g for FR units, and 1.1 g for S units. Fast motor units displayed considerable post-tetanic potentiation of twitch tension. Under similar conditions of stimulation, FF units appeared able to potentiate more and faster than FR units.

Animals↗
PubMed1982

A quantitative study of skeletofusimotor innervation in the cat peroneus tertius muscle.

1. Physiological tests were used to identify skeletofusimotor or beta axons to the cat peroneus tertius muscle in order to assess the proportion of beta axons in the motor supply to this muscle. 2. Static beta axons (beta S) were identified by: (a) observation of a delay between the complete block of extrafusal contraction and the failure of spindle activation upon prolonged stimulation, (b) increase of spindle excitation with stimulation frequencies above that eliciting maximal extrafusal contraction, (c) observation of 'unfused' frequencygram of spindle primary afferent discharge during stimulation of the axon at frequencies above that eliciting complete fusion of extrafusal contraction and (d) static action exerted on the response of the spindle afferent to ramp stretch. 3. Dynamic beta axons (beta D) were identified by the persistence of spindle activation after selective block of extrafusal neuromuscular junctions and by their dynamic action on spindle primary endings. 4. The actions of 116 motor axons (conduction velocity 56-104 m/sec) on ninety-five spindle afferents (fifty-seven from primary and thirty-eight from secondary endings) were examined in ten experiments. Thirty-six beta axons (31% of the total sample) were identified: twenty-four beta S (conduction velocity 69-104 m/sec) and twelve beta D (conduction velocity 56-91 m/sec). 5. Twenty (35%) primary endings were activated by a beta S and sixteen (28%) by a beta D axon. Nineteen (45%) secondary endings were activated by a beta S and five (13%) by a beta D axon. Convergence of beta D and beta S axons on the same spindle occurred in 10% of instances. beta-innervated spindles were also supplied by gamma axons. 6. Most of the beta S motor units were of the fast-fatigue resistant (FR) type, with a few units of the fast-fatigable (FF) type, and nearly all the beta D motor units were of the slow (S) type.

Action Potentials↗