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R Huot

Publications and source records attributed to R Huot.

10 recordsLinked to original sources
PubMed1997

Stability of motor-unit force thresholds in the decerebrate cat.

To further test the hypothesis that some fixed property of motoneurons determines their recruitment order, we quantified the variation in force threshold (FT) for motoneurons recruited in muscle stretch reflexes in the decerebrate cat. Motor axons supplying the medial gastrocnemius (MG) muscle were penetrated with micropipettes and physiological properties of the motoneuron and its muscle fibers, i.e., the motor unit, were measured. FT, defined as the amount of MG force produced when the isolated motor unit was recruited, was measured from 20 to 93 consecutive stretch trials for 29 motor units. Trials were selected for limited variation in base force and rate of rise of force, which have been shown to covary with FT, and in peak stretch force, which gives some index of motor-pool excitability. Under these restricted conditions, large variation in FT would have been inconsistent with the hypothesis. Analysis of the variation in FT employed the coefficient of variation (CV), because of the tendency for FT variance and mean to increase together. We found that CV was distributed with a median value of 10% and with only 2 of 29 units exceeding 36%. Some of this variation was associated with measurement error and with intertrial fluctuations in base, peak, and the rate of change of muscle force. CV was not significantly correlated with motor-unit axonal conduction velocity, contraction time, or force. In three cases FT was measured simultaneously from two motor units in the same stretch trials. Changes in recruitment order were rarely observed (5 of 121 stretch trials), even when FT ranges for units in a pair overlapped. We suggest that the large variation in recruitment threshold observed in some earlier studies resulted not from wide variation in the recruitment ranking of motoneurons within one muscle, but rather from variation in the relative activity of different pools of motoneurons. Our findings are consistent with the hypothesis that recruitment order is determined by some fixed property of alpha-motoneurons and/or by some unvarying combination of presynaptic inputs that fluctuate in parallel.

Animals↗
PubMed1993

Influence of packaging and processing conditions on the decontamination of laboratory biomedical waste by steam sterilization.

The conditions for optimal steam decontamination of polypropylene bags half loaded with laboratory biomedical waste were studied (276 bags were processed). Controls were single-closed bags without water added or incisions made in the top, standing freely in an autoclave set at 121 degrees C. The average time required to reach 121 degrees C at the load center was 46 min for controls. A significant increase in this time occurred following addition of water to bags without incisions (60 min), with double bagging (60 min), or when using vertical containers (82 min). A significant decrease occurred when bags were slashed (37 min) or processed at 123 degrees C (32 min) or 132 degrees C (19 min). Horizontal containers or addition of water to slashed bags had no significant effect.

Journal Article↗
PubMed1982

The estimation of hepatic blood flow with indocyanine green: comparison between the continuous infusion and single injection methods.

We compared the estimation of hepatic blood flow obtained using a continuous infusion of indocyanine green with that obtained after a single intravenous injection of indocyanine green in 35 patients with liver disease. There was no significant difference in the values of hepatic blood flow measured by these two methods, and there was a close correlation between the continuous infusion and single injection methods (r = 0.926, p less than 0.001). In a second group of nine patients with cirrhosis, we evaluated the effect of sampling from the right versus left hepatic vein on hepatic blood flow estimation. There was no significant difference between the two estimates and a good correlation was found (r = 0.878, p less than 0.001). Since values of hepatic blood flow measured after a single indocyanine green injection are similar to those measured using the more classical continuous infusion method, the single injection method may be preferable since it requires only 15 min to be performed.

Blood Flow Velocity↗
PubMed1976

[Effort electrocardiogram in woman].

On the basis of 150 results on patients who underwent an ECG at submaximal exercise, selective coronary arteriography and cine-arteriography, this study has established that: -- certain elecerographic criteria of coronary insufficiency which have a high predictive value in males (a "near ischeamic" appearance, an J depression at or above 4 mm) are not applicable to the female; -- where an ECG tracing which is abnormal at rest becomes normal on exercise, then in both males and females there is a healthy coronary tree; -- the incidence of false-positives is 22.9%, which is 4 times that found in males; -- propranolol (60 mg orally) returns these pseudo-ischaemic changes in the resting and exercise ECG to normal and affords a simple method of identifying the false positives.

Adult↗
PubMed1975

Effect of changes in arterial oxygen content on circulation and physical performance.

To evaluate the effect of different levels of arterial oxygen content on hemodynamic parameters during exercise nine subjects performed submaximal bicycle or treadmill exercise and maximal treadmill exercise under three different experimental conditions: 1) breathing room air (control); 2) breathing 50% oxygen (hyperoxia); 3) after rebreathing a carbon monoxide gas mixture (hypoxia). Maximal oxygen consumption (Vo2 max) was significantly higher in hyperoxia (4.99 1/min) and significantly lower in hypoxia (3.80 1/min) than in the control experiment (4.43 1/min). Physical performance changes in parallel with Vo2 max. Maximal cardiac output (Qmax) was similar in hyperoxia as in control but was significantly lower in hypoxia mainly due to a decreased stroke volume. A correlation was found between Vo2 max and transported oxygen, i.e., Cao2 times Amax, thus suggesting that central circulation is an important limiting factor for human maximal aerobic power. During submaximal work HR was decreased in hyperoxia and increased in hypoxia. Corresponding Q values were unchanged except for a reduction during high submaximal exercise in hyperoxia.

Adult↗
PubMed1975

[Correlations between the sub-maximal exercise electrocardiogram and selective coronarography: a critical study of positive criteria].

A critical study of the electrical criteria for coronary insufficiency was undertaken on the basis of a group of 150 patients who underwent a selective coronary arteriography and a submaximal effort electrocardiogram and free of any functional coronary insufficiency. The three following notions became apparent: -- a downward displacement of the J point is greater than or equal to 4 mm has a very high predicitive value (90%) for coronary insufficiency, whatever the slope of the following ST segment; -- anslowly ascending, rigid ST segment with a slope included between 0.1 and 1 mV/sec. has a value equivalent to that of the classical criterion: horizontal or descending slope of the ST segment greater or equal than 1 mm; -- the ischaemic index put formard by McHenry (J is less than or equal 1 - J + ST is greater than or equal 0) is not specific enough to be of practical value.

Coronary Angiography↗