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PubMed2004

Evaluation of fitness level by the oxygen uptake efficiency slope after a short-term intermittent endurance training.

Several indicators are used as indices of cardiorespiratory reserve. Among them, oxygen uptake (VO(2)) at peak and ventilatory threshold (VAT) levels are the most common used. In the present study, endurance training was used to evaluate and compare the usefulness of a new index, the Oxygen Uptake Efficiency Slope (OUES) as an alternative to the previous ones. Fifteen physical education student women participated in the study (8 as a trained group [T: age (mean +/- SD) 21.9 +/- 3.3 y, height 165.1 +/- 5.5 cm, weight 60.4 +/- 3.3 kg] and 7 as a control group [C: age 21.7 +/- 1.9 y, height 165.4 +/- 7.2 cm, weight 59.6 +/- 8.6 kg]). Before and after 6 weeks of the Square-Wave Endurance Exercise Test (SWEET) training program or daily activities, they performed an incremental test (30 W/3 min) on a cycle ergometer to determined VO(2), power output and parameters associated with breathing efficiency (the respiratory equivalents, and the ventilatory dead space to tidal volume ratio [Vd/Vt]) at peak- and VAT-levels. The slope of the relationship between ventilation and carbon dioxide production was also calculated. OUES, derived from the logarithmic relationship between VO(2) and minute ventilation (V(E)), was determined at 75 % (OUES75), 90 % (OUES90) and 100 % (OUES100) of exercise duration. After endurance training in T, VO(2) and power output were significantly improved at peak- and VAT-levels while all breathing efficiency indices remained unchanged. No changes were observed in C after 6 weeks. Despite significant correlation between OUES values and VO(2) at peak- and VAT-levels, OUES75, OUES90 and OUES100 did not significantly change after endurance training. While VO(2) and power output at peak- and VAT-levels increased in all T, training-induced changes in OUES appeared more variable. We concluded that OUES was not sufficiently sensitive to highlight improvement of cardiorespiratory reserve after endurance training whereas VO(2) at peak and VAT levels did.

Adult↗
PubMed2005

Individual consistency of dairy cows' activity in their home pen.

The aim of this research was to investigate the long-term individual consistency of dairy cow activity in the home pen. Activity in a loose-housing barn was examined in 35 Holstein-Friesian dairy cows using an automatic monitoring system. Different amounts of activity could be distinguished by dynamic thresholds. Subsequently, the following categories of activities were calculated as mean daily values: number of high activity counts (NHA), number of low activity bouts (NLB), and mean duration of low activity bouts (DLB). Category NHA reflects locomotor behavior, and NLB and DLB reflect resting behavior. Recordings were repeated 4 times during a period of 2 lactations for 10 d each (total observation time: 40 d). Effects of parity, week of lactation, and environmental conditions (light intensity and ambient temperature) on activity were also assessed. Our results reveal a high degree of consistency in individual cow activity throughout 2 lactations. Repeatability (REP), calculated using covariance parameters, was high for all traits, although the REP of NHA (REP = 0.62) was higher than the REP of NLB (0.40) or DLB (0.49). Parity, week of lactation, and environmental conditions had no significant effects on activity. In conclusion, our results indicate that activity of dairy cows in their home pen was highly consistent over time, and thus, could be considered as individual traits.

Activity Cycles↗
PubMedDate not supplied

Visual electrophysiological effect of a GABA transaminase blocker.

Vigabatrin is an antiepileptic drug for the treatment of partial seizures. The anticonvulsant effect is achieved by irreversible inhibition of the enzyme GABA-transaminase which catalyses the inactivation of GABA. Vigabatrin has been associated with visual field loss and electrophysiological abnormalities. The purpose of the study was to determine any alterations in normal volunteers of the visual field and the visual electrophysiology resulting from a short exposure to vigabatrin. A three-way, double-blind study of placebo, carbamazepine and vigabatrin was undertaken at baseline and on days two, four and nine. Seven subjects completed all three cycles and 14 subjects (six females and eight males; mean age 27.3 years SD 6.7) completed at least one cycle. Static threshold automated perimetry comprised Humphrey Visual Field Analyzer Programs 30-2 and 30/60-2. Electro-oculography and electroretinograms were performed with undilated pupils using the Medelec Ganzfeld stimulator GS2000. The visual field was unaffected by placebo, carbamazepine or vigabatrin. The group mean amplitudes and latencies for the scotopic ERG, 30 Hz flicker ERG and the oscillatory potentials remained unchanged for any cycle. The group mean photopic ERG b-wave latency increased from baseline (p<0.05); no significant change occurred with carbamazepine or placebo. The group mean Arden Index for vigabatrin decreased from baseline to day 9 (p<0.01); no significant differences were present for carbamazepine or placebo. Vigabatrin has a rapid effect on both the photopic ERG and the EOG; however, the changes merely reflect alterations in retinal GABA levels secondary to concomitant blocking of GABA transaminase by existing vigabatrin therapy.

4-Aminobutyrate Transaminase↗
PubMed1985

Fertilization potential and electrical properties of the Xenopus laevis egg.

The membrane potential of Xenopus eggs was monitored continuously from prior to fertilization until early cleavage. A rapid decay of the initial potential of -33.1 +/- 8.1 (SD) mV (N = 14) upon impalement to a value of -19.3 +/- 4.2 (SD) mV (N = 68) suggested that insertion of the first electrode caused depolarization. Outward and inward rectification were observed when the resting potential was made more positive than about 5 mV or more negative than about -30 mV. Eggs were not activated by this level of current injection. Fertilization and activation evoked a membrane depolarization which was influenced by the external Cl- concentration, the nature of the halide species, and 4,4-diisothiocyanostilbene-2,2-disulfonic acid. Smaller transient depolarizations were associated with the initial stages of the fertilization potential but not with activation. Only when the fertilization potential was significantly diminished, as in high external Cl- or in the presence of Br- or I- solutions did polyspermy ensue. The input resistance of the unfertilized egg was 13.2 +/- 9.8 M omega (N = 26) and decreased about 200-fold at the peak of the fertilization potential to 0.077 +/- 0.020 M omega (N = 9). Ninety minutes after the onset of the fertilization potential and about 6 min after the start of furrow formation the membrane began a series of cleavage cycle-associated hyperpolarizations. These were unaffected by either the external Cl- concentration or other halide species. Reduction in amplitude of the fertilization potential had no apparent effect upon the normal elevation of the fertilization envelope or upon cleavage and later development. The fast electrical block to polyspermy appears to have a lower threshold in Xenopus compared with other species and is also effective at negative membrane potentials.

Animals↗
PubMed1999

Steroid hormones affect limbic afterdischarge thresholds and kindling rates in adult female rats.

UNLABELLED: Catamenial epileptics show particular vulnerability to seizures during menstruation and at the time of ovulation, when circulating estradiol (E(2))/progesterone (P(4)) ratios are high. The present study tested the hypothesis that alterations in neuronal excitability induced by E(2) and P(4) affect thresholds and the development of secondary generalization in kindled rats. METHODS: The effects of endogenous hormones secreted during the estrous cycle, and of exogenous exposure to E(2) and P(4) after ovariectomy (OVX), with and without adrenalectomy (ADX), were tested. Kindling electrodes were implanted in the basolateral amygdala or dorsal hippocampus in adult female rats. The anticonvulsive effects of P(4) on amygdala kindled seizures were also determined in intact subjects. RESULTS: In intact females, afterdischarge thresholds (ADTs) in the amygdala were significantly lower (306+/-48 microA; peak to peak) at mid-day proestrus, just prior to ovulation, when serum E(2) is elevated. ADTs were more than twofold higher (808+/-95 microA) during metestrus, coincident with peak ovarian P(4) secretion. In OVX females, amygdala thresholds were lowest with E(2) replacement and highest with P(4) replacement. Hippocampal ADT was unaffected by hormone replacement after OVX. The rates of both amygdala and hippocampal kindling were significantly accelerated by E(2) and slowed by P(4). E(2) replacement significantly increased serum corticosterone (CORT) levels. In ADX rats, CORT replacement increased kindling rates, synergizing with the effects of E(2). In fully kindled animals, P(4) administration suppressed motor seizures in approximately 60% of cases. CONCLUSIONS: E(2) lowers amygdala ADTs and facilitates kindling. This effect may involve both direct E(2) effects and indirect effects mediated via increased levels of circulating corticosterone. P(4) raises amygdala ADTs, slows kindling development and suppresses fully kindled seizures. Hence, P(4) may have potential therapeutic value for women with catamenial epilepsy.

Amygdala↗
PubMed1982

[Atrial refractoriness and its dispersion in different physiopathologic conditions].

Previous studies have demonstrated a prolonged and non-uniform atrial refractoriness in patients with both sinus node dysfunction and supraventricular tachyarrhythmias. However, they have not been able to define separately the influence on atrial electrophysiologic properties of isolated "bradycardia", of sinus node dysfunction and of supraventricular tachyarrhythmias. Therefore we have measured the effective and functional refractory periods at three different sites of the right atrium (high, middle and low lateral wall) in 16 normal subjects (N), in 9 patients with chronic asymptomatic sinus bradycardia (AB), in 9 patients with sinus node dysfunction but without evidence of supraventricular tachyarrhythmias (SSS) and in 10 patients with paroxismal atrial fibrillation (PAF). The study was performed both in sinus rhythm and during atrial pacing (120 beats/min) utilizing twice threshold stimuli. Dispersion of atrial refractoriness (D) was determined from the range of refractory periods measured at the three different atrial sites as the longest minus the shortest refractory period. Refractoriness at the high site of the lateral wall (parasinusal zone), mean values of the refractory periods obtained at the three atrial sites, and dispersion were compared among the three groups. Refractoriness at the two rates (sinus rhythm and 120 beats/min) was also compared. During sinus rhythm SSS, AB and PAF showed a significantly higher refractoriness than N, while only SSS and PAF showed increased D. Atrial pacing reduced refractoriness but not D in all groups. At the same driven frequency refractoriness of SSS and AB, and D of SSS and PAF were still significantly higher than those of N. Finally, it is noteworthy that during paced rhythm, single values of mean refractoriness of SSS did not correspond with those of N. In conclusion, our data suggest that: 1) sinus node dysfunction and supraventricular tachyarrhythmias exert an independent influence on atrial electrophysiologic properties; 2) the presence of a less homogeneous recovery of atrial excitability should be considered as a possible concause in the genesis of atrial fibrillation; 3) chronic isolated sinus bradycardia seems to be characterized by a longer atrial refractoriness and not by an increased D; 4) contrary to results obtained in animal subjects, there does not seem to be a relation between D and cycle length in man.

Adult↗
PubMedDate not supplied

Effects of peripheral nerve implants on the regeneration of partially and fully innervated urodele forelimbs.

This study addresses the cellular mechanism of the nerve requirement for regeneration of the urodele forelimb. Others have suggested that only the Schwann cell lineage of the blastema requires nerves for regeneration and that upon limb denervation, Schwann cells arrest in the cell cycle and produce a factor that inhibits the cycling of the remaining blastema cells. Our objective was to test this Schwann cell inhibitor model. First, pieces of peripheral nerve were implanted into partially denervated (one third of the nerve supply cut) axolotl forelimbs in an attempt to provide sufficient additional Schwann cells to increase the threshold nerve requirement above that provided by the remaining nerves. These limbs showed delayed regeneration in 68% of the cases and mild deformities, as seen by Victoria Blue staining, in 10% of the cases, as compared with control, partially denervated contralateral limbs that received grafts of muscle or frozen/thawed nerve. Second, when pieces of peripheral nerve were implanted into fully innervated newt limbs, blastema formation was limited, and regeneration was delayed in 80% of experimental cases when compared with control, contralateral newt limbs with muscle or frozen/thawed nerve implants. The results support the inhibition model and further link the need for nerves in regeneration to a possible specific requirement by Schwann cells.

Amputation, Surgical↗
PubMed1997

[Mechanisms facilitating oxygen delivery during exercise in patients with chronic heart failure].

The aim of the study was to estimate the relative importance of the Bohr effect and redistribution of blood from the non-exercising tissues on the arterial-venous oxygen content differences across the exercising extremities and the central circulation in patients with chronic heart failure; the relationship among femoral vein, systemic and pulmonary artery oxygen partial pressure and hemoglobin saturation was determined. It has been reported that the maximal reduction in femoral vein pO2 precedes peak oxygen consumption and lactic acidosis threshold in patients with chronic heart failure and normal subjects during exercise. The increase in oxygen consumption at work rates above lactic acidosis threshold, therefore, must be accounted for by increase in blood flow in the exercising muscles and right-ward shift on the oxyhemoglobin dissociation curve. Since the total cardiac output increase is blunted in patients with chronic heart failure, diversion of blood flow from non-exercising to exercising tissues may account for some of the increase in muscle blood flow. Ten patients with chronic heart failure performed a progressively increasing leg cycle ergometer exercise test up to maximal effort while measuring ventilation and gas concentration for computation of oxygen uptake and carbon dioxide production, breath-by-breath. Blood samples were obtained, simultaneously, from systemic and pulmonary arteries and femoral vein at rest and every minute during exercise to peak oxygen consumption. At comparable levels of exercise, femoral vein pO2, hemoglobin saturation and oxygen content were lower than in the pulmonary artery. PCO2 and lactate concentration increased steeply in femoral vein and pulmonary artery blood above lactic acidosis threshold (due to lactic acid build-up and buffering), but more steeply in femoral vein blood. These increases allowed femoral vein oxyhemoglobin to dissociate without a further decrease in femoral vein pO2 (Bohr effect). The lowest femoral vein pO2 (16.6 +/- 3.9 mmHg) was measured at 66 +/- 22% of peak VO2 and before the lowest oxyhemoglobin saturation was reached. Artero-venous oxygen content difference was higher in the femoral vein than in the pulmonary artery; this difference became progressively smaller as oxygen consumption increased. "Ideal" oxygen consumption for a given cardiac output (oxygen consumption expected if all body tissues had maximized oxygen extraction) was always higher than the measured oxygen consumption; however the difference between the two was lost at peak exercise. This difference positively correlated with peak oxygen consumption and cardiac output increments at submaximal but not at maximal exercise. In conclusion, femoral vein pO2 reached its lowest value at a level of exercise at or below the lactic acidosis threshold. Further extraction of oxygen above the lactic acidosis threshold was accounted for by a right shift of the oxyhemoglobin dissociation curve. The positive correlation between increments of cardiac output vs "ideal" and measured oxygen consumption suggests a redistribution of blood flow from non-exercising to exercising regions of the body. Furthermore the positive correlation between exercise capacity and the difference between "ideal" and measured oxygen consumption suggests that patients with the poorer function have the greater capability to optimize blood flow redistribution during exercise.

Aged↗
PubMedDate not supplied

Leg tourniquets modify the on-kinetics of oxygen uptake during cycle exercise.

PURPOSE: Obstructive cardiovascular disease decelerates the on-kinetics of the body's oxygen uptake rate (VO2), either by reducing the O2 delivery or by degrading the exercise capacity of skeletal muscle. This study sought to determine whether obstructed blood flow decelerates the on-kinetics of VO2 by reducing O2 delivery. METHODS: Breath-by-breath measurements of VO2 were studied in eight healthy youth (age, 16.5 +/- 0.6 years) during two-legged square-wave exercise on the cycle ergometer. The square protocol was 5 minutes of unloaded exercise followed by an immediate increase to 5 minutes of loaded exercise at 78 +/- 5 W. In the experimental trials, thigh cuffs were inflated 30 seconds before the onset of loaded exercise. Control trials replicated the square-wave exercise with deflated thigh cuffs. RESULTS: The on-kinetics of VO2 were biphasic in the control trial and triphasic in the experimental trial. Experimental VO2 was significantly higher than control values in the final 90 seconds of exercise (P<.05). CONCLUSIONS: The difference between experimental and control VO2 was attributable to inflated thigh cuffs. At no time was experimental VO2 significantly lower than control VO2. The clinical implication of the results is that skeletal myopathy, not reduced blood flow, is essential for decelerating the VO2 on-kinetics of patients with obstructive vascular disease. The warranted conclusion is that square-wave exercise with inflated thigh cuffs stimulates a third phase of VO2 on-kinetics.

Adolescent↗
PubMed2000

Role of BCL-2 and cell cycle regulatory proteins for corticosensitivity assessment in childhood acute lymphoblastic leukaemia.

Results of treatment in childhood acute lymphoblastic leukaemia (ALL) remain unsatisfactory because relapses occur even after high-dose chemotherapy. Corticosensitivity is used in numerous therapeutic trials as a prognostic factor for treatment choice. The aim of this study was to evaluate the role of cell cycle regulatory protein expression before and during the first 48 h of corticotherapy for predicting corticosensitivity. Fifty-two children presenting with ALL were studied at diagnosis and during the first 48 h of treatment for cell proliferation and apoptosis level by measurement of DNA content, and for expression of several cell proliferation regulatory proteins by means of Western blot. Glucocorticoids induced a significant decrease in the percentage of cells in S-phase and in CDK1, CDK4 and CDK6 expression and an increase in the percentage of cells in subG1 peak. Two criteria for corticosensitivity were used: (i) the number of blast cells after 7 d of treatment with a threshold at 1 x 109/l (usual criterion), (ii) the J8/J1 blast cell ratio, which is independent from initial leucocytosis. Bcl-2 expression at diagnosis was the best predictive variable for the usual corticosensitivity criterion in B- and T-cell ALL. For the second criterion, in B-cell ALL, p21waf1 expression at diagnosis was the sole (albeit poorly) predictive variable, whereas bcl-2 remained of high interest in T-cell ALL. Interestingly, these proteins, bcl-2 and p21waf1, are associated with prolonged cell lifespan and their increased expression is often linked to poor response to cytotoxic drugs. Such preliminary results call for subsequent studies on large independent sets of T-cell and B-cell lineage ALL in order to confirm the J8/J1 blast cell ratio value as well as the role of bcl-2 and p21waf1 expression in predicting corticosensitivity.

Adolescent↗
PubMed1995

Isokinetic cycle ergometer--application in sports medicine.

Paper deals with application of fully computerized isokinetic cycle ergometer with on-line registration of effective crank force in sports medicine, namely in functional diagnostic and rehabilitation. The system allows to carry out the time and position course analyses of effective pedal force and power produced at various revolution rates. Maximal or mean values of force and power produced by action of right and left leg may be used for the estimation of strength as well as for detection and quantitative assessment of lateral functional deficit for example due to injury. Short term bouts on isokinetic cycle ergometer may be applied as an effective means for the improvement of strength of lower extremities in patients as well as in competitive cyclists. The estimation of individual fluctuation of effective force (i.e. differences between maxima at horizontal and minima at vertical crank position) may be used for the evaluation of pedalling technique. Short term all-out efforts at various cadences allow to register not only peak and mean force and power at particular revolution rates, but also to estimate an optimal individual revolution rate, i.e. those allowing to produce highest power output. Such information can be employed for diagnostic assessment of anaerobic capabilities, namely in cyclists. Isokinetic cycling with self-controlled effort may be also used as a comfortable aerobic exercise. It may be concluded that isokinetic cycle ergometer represents a valuable diagnostic as well as therapeutic tool, which may be utilized in several areas of sports medicine.

Adult↗
PubMed1995

Bursting and oscillating neurons of the cat basolateral amygdaloid complex in vivo: electrophysiological properties and morphological features.

1. To characterize the physiological properties of lateral and basolateral (BL) amygdaloid neurons, intracellular recordings were performed in barbiturate-anesthetized cats. Morphological identification of recorded cells was achieved by intracellular injection of neurobiotin. Two types of physiologically identified projection neurons were distinguished in the BL and lateral nuclei. 2. The first type of neurons prevailed in the BL nucleus (80% of BL cells). Their resting membrane potential (Vm) averaged -66 +/- 4.9 (SE) mV. They generated stereotyped spike doublets or bursts in response to threshold depolarizing pulses. In most cells, depolarizing pulses of higher amplitude elicited spike bursts or doublets at a shorter latency followed by a nonadapting train of single spikes whose frequency rose with the amplitude of the current pulses. However, 15% of BL bursting neurons generated repetitive spike bursts or doublets in response to prolonged depolarizing current pulses. The response of BL bursting neurons to hyperpolarizing current pulses revealed the presence of slow inward rectification in the form of a depolarizing sag, thus suggesting the presence of a hyperpolarization-activated current. 3. The second type of neurons prevailed in the lateral nucleus. Their resting Vm was quite polarized (-74 +/- 2.85 mV) and they generated slow Vm oscillations (2-10 Hz) upon steady depolarization beyond congruent to -62 mV. The frequency of the oscillation increased with the amount of depolarizing current. In the majority of cells, analysis of voltage responses to subthreshold current pulses revealed the presence of voltage- and time-dependent rectification in the depolarizing direction. Current pulses that brought the Vm to -65 mV and beyond elicited a voltage response that reached an early peak and then decayed. Increasing the amplitude of the pulse decreased the latency of the early peak until it triggered an action potential. Current-voltage plots demonstrated inward rectification in the depolarizing direction. At the break of hyperpolarizing current pulses applied at depolarized levels, the Vm overshot prepulse values and generated one or more oscillatory cycles. 4. An important proportion of bursting and oscillating neurons (45.8% and 29%, respectively) were physiologically identified as projection neurons by antidromic invasion from the basal forebrain, entorhinal cortex, or perirhinal cortex. The conduction velocity of bursting and oscillating neurons estimated from the latency of antidromic spikes was low (< or = 2.5 m/s). 5. Most bursting and oscillating neurons of the BL nucleus were spiny cells with a pyramidal morphology. Four to eight dendritic trunks emerged from the apex, base, and sides of their triangular soma.(ABSTRACT TRUNCATED AT 400 WORDS)

Amygdala↗
PubMed2003

Pattern of energy expenditure during simulated competition.

PURPOSE: To determine how athletes spontaneously use their energetic reserves when the only instruction was to finish in minimal time, and whether experience from repeated performance changes the strategy of recreational athletes. METHODS: Recreational road cyclists/speed skaters (N = 9) completed three laboratory time trials of 1500 m on a windload braked cycle. The pattern of energy use was calculated from total work and from the work attributable to aerobic metabolism, which allowed computation of anaerobic energy use. Regional level speed skaters (N = 8) also performed a single 1500-m time trial with the same protocol and measurements. RESULTS: The serial trials were completed in (mean +/- SD) 133.8 +/- 6.6, 133.9 +/- 5.8, 133.8 +/- 5.5 s (P > 0.05 among trials); and in 125.7 +/- 10.9 s in the skaters (P < 0.05 vs cyclists). The [OV0312]O(2peak) during the terminal 200 m was similar within trials (3.23 +/- 0.44, 3.34 +/- 0.44, 3.30 +/- 0.51 (P > 0.05)) versus 3.91 +/- 0.68 L.min-1 in the skaters (P < 0.05 vs cyclists). In all events, the initial power output and anaerobic energy use was high and decayed to a more or less constant value ( approximately 25% of peak) over the remainder of the event. Contrary to predictions based on an assumed "all out" starting strategy, the subjects reserved some of their ability to perform anaerobic work for a terminal acceleration. The total work accomplished was not different between trials (43.53, 43.78, and 47.48 kJ in the recreational athletes, or between the cyclists and skaters (47.79 kJ). The work attributable to anaerobic sources was not different between the rides (20.67, 20.53, and 21.12 kJ in the recreational athletes). In the skaters, the work attributable to anaerobic sources was significantly larger versus the cyclists (24.67 kJ). CONCLUSION: Energy expenditure during high-intensity cycling seems: 1) to be expended in a manner that allows the athlete to preserve an anaerobic energetic contribution throughout an event, 2) does not appear to have a large learning effect in already well trained cyclists, and 3) anaerobic energy expenditure may be the performance discriminating factor among groups of athletes.

Adult↗
PubMed1999

Cardiovascular effects of a single slow release lanreotide injection in patients with acromegaly and left ventricular hypertrophy.

In our study we assessed the effects of a single i.m. injection of slow-release Lanreotide (30 mg) (SR-L), a new long-acting somatostain analog, on circulating GH levels, baseline cardiac function (M-mode, 2D guided, doppler-echocardiographic study) and cardiopulmonary response to exercise (cycloergometric test, performed using a computer drived, electrically braked cycle ergometer), tested at baseline, after 7 and 14 days from the injection in 10 acromegalic patients (5 M, 5 F, mean age 57.7 +/- 3.1 yrs, body mass index (BMI) 27 +/- 0.8 kg/m2, blood pressure 141 +/- 6.5/82 +/- 3 mmHg). SR-L administration decreased GH levels in acromegalic patients (mean +/- SEM) from 16.1 +/- 6.9 to 10.8 +/- 5.1 micrograms/L (p = 0.045) after 7 days and to 11.9 +/- 5 micrograms/L (p = 0.078) after 14 days from the injection. Moreover, we observed a significant (p < 0.05) decrease in systolic blood pressure and heart rate at the 7th (135 +/- 6.1 vs 141 +/- 6.5 mmHg, and 68 +/- 2.1 vs 74 +/- 2.1 bpm) and 14th (137 +/- 6.2 vs 141 +/- 6.5 mmHg, and 72 +/- 2 vs 74 +/- 2.1 bpm) day of the study with respect to the baseline values. After SR-L administration we also found an increase in ejection fraction (69 +/- 2 vs 63 +/- 2.3% at 7th day, p = 0.006; 65 +/- 2.3 vs 63 +/- 2.3% at the 14th day, p = 0.027) and shortening fraction (40.8 +/- 1.8 vs 36.6 +/- 1.9% at 7th day, p = 0.005; 38.7 +/- 1.8 vs 36.6 +/- 1.9% at the 14th day, p = 0.045). The positive acute cardiac response to SR-L injection was also demonstrated by the increase in A/E velocity ratios at 7th (1.14 +/- 0.1 vs 0.98 +/- 0.07, p = 0.016) and 14th (1.04 +/- 0.08 vs 0.98 +/- 0.07, p = 0.008) day of the study. After SR-L injection, exercise capacity and VO2 at anaerobic threshold were also increased with respect to the baseline test: 61.1 +/- 8.2 vs 38.9 +/- 6.8 watts (p = 0.002) and 1012.4 +/- 71.5 vs 915.3 +/- 77.8 mL/min (p = 0.033) after 7 days, and 61.4 +/- 7.2 vs 38.9 +/- 6.8 watts (p = 0.002) and 1010.1 +/- 62.5 vs 915.3 +/- 77.8 mL/min (p = 0.010) after 14 days from the injection. In conclusion, these results suggest that in acromegalic patients: (1) SR-L causes a rapid improvement in baseline cardiac function and in cardiopulmonary performance during exercise in acromegaly; (2) the endocrine (decrease in GH levels) and echocardiographic responses to SR-L are maximal after 7 days from the injection, whereas the effect of SR-L on the exercise performance are longer lasting.

Acromegaly↗
PubMed2004

A refined technique for determining the respiratory gas exchange responses to anaerobic metabolism during progressive exercise - repeatability in a group of healthy men.

The respiratory gas exchange and ventilation during an incremental cycle exercise test were analysed in a group of 19 healthy, moderately fit men. Different computer algorithms were used to estimate the VO2 values where: (i) the rate of VCO(2) increase just exceeds the rate of VO(2) increase (DX, derivative crossing), (ii) VCO(2)/VO(2) = 1.00 (PX, point of crossing) and (iii) ventilation (VE) increases disproportionately in relation to VCO(2) (PQ, point of VCO(2) equivalent rise). The DX and PQ measurements were analysed using a new approach employing polynomial regression and the value of PX was determined following low-pass filtration of raw data. The repeatability of the measurements was evaluated with a 5-6 week interval between the tests. The correlations between tests were 0.75 at DX, 0.85 at PX and 0.62 at PQ. The mean differences between the repeated tests were not statistically significant. The repeatability of VO2, in absolute values expressed as +/-2 SD of the differences between the tests, had values of 5.0, 6.1 and 9.5 ml min(-1) kg(-1) for DX, PX and PQ, respectively. The mean value of VO(2) for each measurement point expressed as a percentage of VO(2 max) was 54% at DX, 68% at PX and 70% at PQ. The most common sequence of the measured values was DX < PX < PQ, but the sequence DX < PQ < PX was also observed. It is concluded that the gas exchange responses to developing anaerobic metabolism during progressive exercise can be characterized by a series of thresholds. However, the considerable variation in absolute values in the two testing occasions requires further attention.

Adult↗
PubMed1995

Anaerobic capacity assessment in male and female children with all-out isokinetic cycling exercise.

Anaerobic capacity was assessed by calculating the maximal accumulated oxygen deficit (AOD) in 7 male and 6 female children (aged 10.8 and 10.7 years, respectively) who exercised "all-out" to fatigue on a CYBEX TM (Met, 100) isokinetic cycle ergometer. Each child performed a series of submaximal steady state oxygen uptake tests and a peak oxygen uptake test. Data from submaximal and peak oxygen uptake tests were used to predict the oxygen demand for each child as they worked under "all-out" isokinetic cycling to volitional fatigue. The AOD was calculated as the difference between the predicted oxygen demand and the actual oxygen uptake for the duration of the test. In order to examine the repeatability of the testing the children performed two "all-out" tests on an isokinetic cycle ergometer. The absolute (I) and relative (ml kg1) AOD values for the males were not significantly different between trials (1.34 + or - .13 and 1.41 + or - 16 litres, and 35.6 + or - 3.7 and 37.7 + or - 4.7 ml-kg1, for trials one and two, respectively) (Mean +SEM). Similarly there were no significant differences in the AOD values for the female children between trials (1.40 + or -.13 and 1.37 + or -.16 litres and 35.6 + or - 3.8 and 34.6 + or - 3.6 for ml-kg1, for trials one and two, respectively). Over the two tests the respective peak and mean power results revealed no significant differences between the sexes (307.4 and 192.4 W for males and 274.3 and 192.6 W for females). Intraclass correlation coefficients (R) for the AOD results in litres and ml-kg in the tests were higher in the males (.96 and .95) than the females (.86 and .89), respectively. It was concluded that the isokinetic testing produced AOD results which were repeatable in this group of children, showed no sex differences and were comparable to those from children who had been tested using a constant power to exhaustion protocol.

Anaerobic Threshold↗
PubMed2006

Axonal function and activity-dependent excitability changes in myotonic dystrophy.

To investigate peripheral nerve function and its potential contribution to symptoms of weakness in myotonic dystrophy type 1 (MD), nerve excitability was assessed in 12 MD patients. Compound muscle action potentials (CMAPs) were recorded at rest from abductor pollicis brevis (APB) following stimulation of the median nerve. Stimulus-response behavior, threshold electrotonus, a current-threshold relationship, and recovery cycles were successfully recorded in each patient. Compared with controls, there was significant reduction in CMAP amplitude in MD patients. This was accompanied by reduction in depolarizing threshold electrotonus and an increase in refractoriness and in the duration of the relative refractory period. To determine whether alteration in axonal resting membrane potential was a factor underlying these changes, axonal excitability was assessed following maximal contraction of APB for 60 seconds. Following contraction, there was reduction in CMAP amplitude for a submaximal stimulus (by 51.5+/-11.8%) and an increase in super-excitability (of 22.2+/-12.0%), consistent with activity-dependent hyperpolarization, with a greater increase in threshold for MD patients compared to controls (MD group, 22.3+/-5.1%; controls, 11.7+/-2.1%; P<0.04) and prolonged recovery to baseline. The present study has established that greater activity-dependent changes in excitability may be induced in MD patients by maximal voluntary contraction when compared to controls. The excitability changes and prolonged recovery of threshold following contraction are likely to contribute to symptoms of fatigue and weakness in MD patients.

Action Potentials↗
PubMed2001

Acute versus chronic sodium bicarbonate ingestion and anaerobic work and power output.

BACKGROUND: The aim of this study was to compare and contrast the effects of acute versus chronic sodium bicarbonate ingestion. METHODS PARTICIPANTS: Eight male, (mean+/-SE): age, 20.8+/-0.4 yrs; height, 179.6+/-0.6 cm; body mass, 79.4+/-0.85 kg, Sigma7skf, 48.6+/-4.8 mm, VO2max=55.9+/-0.8 ml x kg(-1) x min(-1)) volunteer subjects, ingested NaHCO3 in either a dose of 0.5 g x kg(-1) body mass acutely or the same dose daily over a period of six days in order to determine whether there were any differences in performance of 90 sec maximal cycling ergometry. INTERVENTION: After subjects undertook an initial control (C) test session, all were then randomly assigned to one of two groups, acute or chronic NaHCO3 ingestion. Subjects in the acute ingestion (AI) group completed their supplemented test on day one, and then on the following day. Chronic ingestion (CI) subjects completed the test after one day of chronic ingestion as well as following six days of bicarbonate ingestion. Following ten days rest, subjects repeated the protocol in the opposite group. MEASURES: Blood samples were taken pre- and postingestion, daily, and pre- and postexercise and were analysed for, pH, Base excess (BE), HCO3-, PO2, PCO2, Na+, K+, Cl-, and lactate. RESULTS: Both the chronic (CI) and acute ingestion (AI) groups were significantly different to the control (C) value (p<0.001 and p<0.05, respectively). CONCLUSIONS: We would suggest using chronic ingestion as a means to improve high intensity work rather than the acute ingestion of sodium bicarbonate. The ingestion of sodium bicarbonate, over a period of six days, significantly improved work output two days after bicarbonate ingestion ceased.

Acid-Base Equilibrium↗