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PubMed2003

Occurrence of electromyographic and ventilatory thresholds in professional road cyclists.

The temporal relationship between the electromyographic (EMG) and ventilatory thresholds was investigated during incremental exercise performed by eight professional road cyclists. The exercise, performed on a cycloergometer, started at 100 W with successive increments of 26 Wx min(-1) until exhaustion. Gas exchange and the root mean square value of EMG (RMS) from eight lower limb muscles were examined throughout the exercise period. Professional cyclists achieved a maximal oxygen consumption, i.e. VO(2max), of 5.4 (0.5) l x min(-1) [74.6 (2.5) ml x min(-1) x kg(-1), range: 67.8-82.4 ml x min(-1) x kg(-1)] and a maximum power ( W(max)) of 475 (30) W (range: 438-516 W). Our results showed at least the occurrence of a first EMG threshold (EMG(Th1)) in 50% (gastrocnemius lateralis) of the subjects and a second EMG threshold (EMG(Th2)) in 63% (gastrocnemius medialis). EMG(Th1) occurred significantly before the first ventilatory threshold (VT(1)), i.e. at 52 (2)% and 62 (9)% of W(max), respectively. Inversely, no significant difference was observed between the occurrence of EMG(Th2) and the second ventilatory threshold (VT(2)), i.e. at 86 (1)% and 89 (7)% of W(max), respectively. These results suggest that the use of EMG may be a useful non-invasive method for detecting the second ventilatory threshold in most of the muscles involved in cycling exercise.

Adult↗
PubMed1989

Three models of free radical-induced cell injury.

Three models of free radical-induced cell injury are presented in this review. Each model is described by the mechanism of action of few prototype toxic molecules. Carbon tetrachloride and monobromotrichloromethane were selected as model molecules for alkylating agents that do not induce GSH depletion. Bromobenzene and allyl alcohol were selected as prototypes of GSH depleting agents. Paraquat and menadione were presented as prototypes of redox cycling compounds. All these groups of toxins are converted, during their intracellular metabolism, to active species which can be radical species or electrophilic intermediates. In most cases the activation is catalyzed by the microsomal mixed function oxidase system, while in other cases (e.g. allyl alcohol) cytosolic enzymes are responsible for the activation. Radical species can bind covalently to cellular macromolecules and can promote lipid peroxidation in cellular membranes. Of course both phenomena produce cell damage as in the case of CCl4 or BrCCl3 intoxication. However, the covalent binding is likely to produce damage at the molecular site where it occurs; lipid peroxidation, on the other hand, besides causing loss of membrane structure, also gives rise to toxic products such as 4-hydroxyalkenals and other aldehydes which in principle can move from the site of origin and produce effects at distant sites. Electrophilic intermediates readily reacts with cellular nucleophiles, primarily with GSH. The result is a severe GSH depletion as in the case of bromobenzene or allyl alcohol intoxication. When the depletion reaches some threshold values lipid peroxidation develops abruptly and in an extensive way. This event is accompanied by cellular death. The reason for which lipid peroxidation develops in a cell severely depleted of GSH remains to be clarified. Probably the loss of the defense systems against a constitutive oxidative stress is not compatible with cellular life. Some free radicals generated by one-electron reduction can react with oxygen to give superoxide anions which can be converted to other more dangerous reactive oxygen species. This is the case of paraquat and menadione. Damage to cellular macromolecules is due to the direct action of these oxygen radicals and, at least in the menadione-induced cytotoxicity, lipid peroxidation is not involved. All these initial events affect the protein sulfhydryl groups in the membranes. Since some protein thiols are essential components of the molecular arrangement responsible for the Ca2+ transport across cellular membranes, loss of such thiols can affect the calcium sequestration activity of subcellular compartments, that is the capacity of mitochondria and microsomes to regulate the cytosolic calcium level.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkylating Agents↗
PubMed1979

Toxicological studies of shale oils, some of their components, and commercial products.

Estonian shale oil contains about 25--30% phenols, and their action determines the toxicity of shale oils. The clinical symptoms of intoxication are rather similar, regardless of route of administration. Due to neurotropic action, the coordination of movements is impaired, and clonic and tetanic convulsions, paresis and paralysis of extremities, and narcosis are observed. In subacute and chronic toxicity tests, dysfunction of the central nervous system was found. In long-term (4--6 month) experiments, changes in liver and kidney function were found. Shale oil has gonadotropic activity and causes changes in the sexual cycle as well as diminution of the number of primordial folicles in the ovaries or a decrease in the quantity of normal spermatogonia in testicular germinal epithelium. Shale oils produce local irritation of skin and mucous membranes. Shale oil can induce sensitization of the organism after repeated administration. The results of acute intoxication tests have proved that volatile and nonvolatile phenol fractions, isomeric dimethylphenols, and 5-methylresorcinol, must be characterized as moderately toxic substances; the LD50 ranges from 501 to 1500 mg/kg. The clinical symptoms of acute toxication are similar for all studied phenols (restlessness, unsteadiness, clonic tremor, paresis and paralysis of extremities, and death). In spite of the moderate toxicity of phenols in acute experiments, repeated administration of small doses can cause different changes in the nervous system and internal organs of experimental animals. For all the phenols studied, the maximum allowable concentration in water was limited by their effect on the organoleptic properties of water. The nonactive dose for warm-blooded animals is from 100 to 3000 times the threshold limit value of phenols on the basis of their organoleptic properties. The effect of commercial products of oil shale industry is generally determined by the toxicity of the main components: water-soluble oil shale phenols.

Animals↗
PubMed1997

The relationship between electromyography and work intensity revisited: a brief review with references to lacticacidosis and hyperammonia.

The aim of this investigation was to re-evaluate the relationship between electromyography and work intensity during incremental work in light of highly discrepant literature. Trained male subjects participated in the study (n = 14). Each subject completed a VO2max test on a cycle ergometer. Tests started at a power output of 60 Watts with a 30 Watt.4 min-1 work increment. Each test was terminated at exhaustion. Blood was collected at the end of each work intensity for lactate and ammonia analysis. EMG were recorded from the vastus lateralis, rectus femoris and vastus medialis using pre-amplified surface electrodes. EMG were collected at each intensity over a period of 60 cycle revolutions. EMG signals were analyzed using integration and EMG spectral analysis. Gas exchange variables were recorded on-line for each test (15 second interval). Ammonia and lactate threshold points were surpassed at the same absolute work intensity (200 Watts) which was equivalent to 64-69% VO2max. When a linear model was applied to the iEMG data, coefficients of determination achieved were greater than those obtained when an exponential model was used for the vastus lateralis and medialis. Gradients of regression lines fitted to iEMG data at pre- and post-lactate/ammonia threshold work intensities were not different. Alternatively, the iEMG-work intensity relationship for the rectus femoris muscle tended to be curvilinear. Significant increases in iEMG were observed at post-lactate/ammonia threshold work intensities for the rectus femoris reflecting increases in fatigue and type II motor unit recruitment at these intensities. In general, median frequency of the EMG power spectrum function were unchanged during incremental work, although highly individualistic results were observed between some subjects and muscles. Grouped median frequency values were insensitive to changes in recruitment, metabolite accumulation and fatigue associated with the increases in work intensity. Consequently, the usefulness of EMG spectral analysis during incremental work was questioned.

Acidosis, Lactic↗
PubMed1986

Membrane potentials and sodium channels: hypotheses for growth regulation and cancer formation based on changes in sodium channels and gap junctions.

Based on several convergent lines of investigation, we make two hypotheses which are sufficient to explain many phenomena of growth regulation in both normal and cancer cells. 1. The first hypothesis is that there is a boundary or threshold of resting cell membrane potential that separates normal resting cells from normal proliferating cells and cancer cells. The basis for this in existing literature values of membrane potentials in resting and proliferating cells is established. A discussion of how these differences in potential can be explained focuses on changes in sodium permeability and internal sodium concentration. Of many sodium transfer mechanisms, the sodium channel is emphasized and how increased intracellular transfer may stimulate DNA synthesis. The effects of changing cell junctions, in particular gap junctions, on membrane potentials is also discussed, as well as the indications of altered junctions in tumor cells. The linking factor of the effects of growth factors on both cell junctions and sodium permeability leads to the second hypothesis. 2. Since growth initiation and inhibition involve sodium channels and gap junctions, several phenomena can be explained by postulating that they are one and the same entity. The basis for this hypothesis in existing descriptions of functional and structural similarities is outlined. The possible interchange of these elements in the cell cycle lead to several corollaries consequent to the conservation of their total number. The formation of gap junctions would consume sodium channels, decrease sodium permeability and stop DNA synthesis. Conversely, growth factors may competitively bind to channel-connexon elements, cleave gap junctions, liberate sodium channels to increase sodium permeability, and trigger DNA synthesis. Alterations in the structure of gap junction-channel elements in tumor cells would be sufficient to explain some carcinogenesis.

Cell Cycle↗
PubMed2006

Effects of exercise and training in hypoxia on antioxidant/pro-oxidant balance.

OBJECTIVE: The aim was to investigate the effects of acute exercise under hypoxic condition and the repetition of such exercise in a 'living low-training high' training on the antioxidant/prooxidant balance. DESIGN: Randomized, repeated measures design. SETTING: Faculté de Médecine, Clermont-Ferrand, France. SUBJECTS: Fourteen runners were randomly divided into two groups. A 6-week endurance training protocol integrated two running sessions per week at the second ventilatory threshold into the usual training. INTERVENTION: A 6-week endurance training protocol integrated two running sessions per week at the second ventilatory threshold into the usual training. The first hypoxic group (HG, n=8) carried out these sessions under hypoxia (3000 m simulated altitude) and the second normoxic group (NG, n=6) in normoxia. In control period, the runners were submitted to two incremental cycling tests performed in normoxia and under hypoxia (simulated altitude of 3000 m). Plasma levels of advanced oxidation protein products (AOPP), malondialdehydes (MDA) and lipid oxidizability, ferric-reducing antioxidant power (FRAP), lipid-soluble antioxidants (alpha-tocopherol and beta-carotene) normalized for triacyglycerols and cholesterol were measured before and after the two incremental tests and at rest before and after training. RESULTS: No significant changes of MDA and AOPP level were observed after normoxic exercise, whereas hypoxic exercise induced a 56% rise of MDA and a 44% rise of AOPP. Plasma level of MDA and arterial oxygen hemoglobin desaturations after the acute both exercises were highly correlated (r=0.73). alpha-Tocopherol normalized for cholesterol and triacyglycerols increased only after hypoxic exercise (10-12%, P<0.01). After training, FRAP resting values (-21%, P<0.05) and alpha-tocopherol/triacyglycerols ratio (-24%, P<0.05) were diminished for HG, whereas NG values remained unchanged. CONCLUSIONS: Intense exercise and hypoxia exposure may have a cumulative effect on oxidative stress. As a consequence, the repetition of such exercise characterizing the 'living low-training high' model has weakened the antioxidant capacities of the athletes. SPONSORSHIP: International Olympic Committee and the Direction Régionale de la Jeunesse et des Sports de la Région Auvergne.

Adult↗
PubMed2005

Effect of exercise-induced dehydration on lactate parameters during incremental exercise.

Cyclists often use heart rate limits or power output zones, obtained from lactate parameters during incremental exercise testing, to control training intensity. However, the relationship between heart rate or power output, and blood lactate can be changed by several factors including dehydration. Therefore, in the current study we investigated the impact of exercise-induced dehydration on lactate parameters during graded exercise. Nine triathletes completed two test sessions in random order, with a 1-week interval. Each session consisted of 2 graded cycling tests to exhaustion (pretest, posttest), interspersed by a 2-h endurance exercise bout. In one session the cyclists received adequate fluid replacement (EH, 1350 ml . h (-1)) whilst in the other session dehydration was not prevented (DH, 225 ml . h (-1)). Subjects received equal amounts of carbohydrates (150 g) during either condition. The 4-mmol lactate threshold (OBLA) and the d (max) lactate threshold (TH-Dm) were calculated from the power : lactate curves. Weight loss was 0.5 +/- 0.3 kg in EH versus 2.5 +/- 0.2 kg in DH (p < 0.05). Heart rate (HR) at TH-Dm remained unchanged in all test occasions. Conversely, HR at OBLA increased by approximately 10 beats . min (-1) from the pretest to the posttest (p < 0.05), in both EH and DH. Compared to the pretest, in the posttest power output at TH-Dm was reduced (minus approximately 12 %, p < 0.05) in DH, but not in EH. Gross mechanical efficiency at TH-Dm was 20.7 +/- 1 % in the pretest in EH and was not different from the pretest value in DH (21.4 +/- 0.7 %, n.s.). Gross efficiency decreased in the posttest in DH (18.4 +/- 0.6 %, p < 0.05), but not in EH (20.2 +/- 0.8 %, n.s.). It is concluded that heart rate rather than power output should be used to monitor training load in cyclists exercising in environmental conditions predisposing to dehydration. Furthermore, in the latter condition, adequate rehydration is essential to preserve optimal mechanical efficiency.

Adult↗
PubMed2000

Cyproterone acetate reduced antler growth in surgically castrated fallow deer.

We studied the role of androgens in antler growth. In particular, we investigated whether the onset of antler regrowth is triggered by a short-term pulse of testosterone and if low levels of androgens are required for antler growth. The study was conducted on 12 surgically castrated fallow deer bucks (Dama dama) aged approximately 27 months. Six animals (CA group) were given the antiandrogen, cyproterone acetate (CA, 1000 mg/treatment); the others were given vehicle solution only (control). Before each CA treatment, blood was sampled and analysed for testosterone, androstenedione, IGF-1, cortisol, FSH, and LH. CA treatment and blood sampling were performed 2 days before castration, on the day of castration and afterwards at 2-day intervals until day 22. Subsequently, CA treatment and blood sampling continued at weekly intervals until day 270. All animals cast their antlers, followed by antler regrowth in all control bucks, but in only four of the six CA-treated castrates. Plasma testosterone concentrations were low in all animals (between 0.01 and 0.20 ng/ml), but were significantly (P<0001) greater in the controls. In both groups, a temporary increase in testosterone values was recorded around the time of antler regrowth, the peak being significantly (P<0.01) higher in the controls. Androstenedione showed a similar pattern as testosterone. Plasma IGF-1 concentrations increased sharply during the antler growth spurt and did not differ significantly between the two groups throughout the study period. Cortisol concentrations were greater in controls than in the CA group. However, no link with the antler cycle was apparent. FSH and LH concentrations were higher in the controls for most of the study. Antlers produced by the control bucks were significantly larger than those in the CA group (P<0.03). For antler length, testosterone, androstenedione and IGF-1, areas under the curve (AUC) were calculated over the period of antler growth. For the pooled deer (n=12) significant correlations existed between AUCs of antler length and testosterone, but not for antler length and IGF-1. Also, a trend for a positive correlation between AUCs of antler length and androstenedione was noted. It is concluded that a plasma androgen concentration at least above a minimal threshold level is a necessary prerequisite for normal antler regrowth in fallow deer, and that this androgen effect is not mediated via circulating IGF-1. The biological role of low levels of androgens may be to sensitize antler cells to the stimulating effect of IGF.

Androgen Antagonists↗
PubMed2002

Reduction of fat accumulation and lipid disorders by individualized light aerobic training in human immunodeficiency virus infected patients with lipodystrophy and/or dyslipidemia.

BACKGROUND: The management of abdominal fat accumulation and metabolic disorders in HIV1-infected patients, by an aerobic training program, is considered. METHODS: Seventeen lipodystrophic and 2 dyslipidemic (without body modification) adults were studied before and after 4 months of training. The training load was individualized on a ventilatory threshold basis, determined during a maximal exercise test on cycle ergometer. Total (TAT), Visceral (VAT) and Subcutaneous Adipose Tissue (SAT) were assessed by CT-scan. Total (TC) and High Density Lipoprotein (HDL-C) Cholesterol, Triglycerides (TG), lactate (La), insulin and glucose were measured after a 12-hour-overnight fast. LDL, TC/HDL, TG/HDL, HOMA-insulin resistance index and coronary heart disease (CHD) relative risk (RR(CHD)) were calculated. RESULTS: Besides a significant improvement of aerobic fitness, trained patients exhibited a reduction in TAT (-12.8%, p < 0.001), specially at the visceral level (- 12%, p < 0.01) and in TC, TG and La (- 23%, - 43% and - 19% respectively, p < 0.01). HDL-C was increased (+ 6%, p < 0.01). All these effects were above changes that could be expected by a possible regression to the mean artefact. Both TC/HDL and TG/HDL were reduced (p < 0.01) and the estimated RR(CHD) decreased by approximately 13% (p < 0.01). No significant training effect was observed on the 9 available HOMAs. Significant correlations were found between changes in blood lipid values and baseline measures (r range - 0.55 to - 0.79, p < 0.05), indicating a larger improvement when baseline lipid parameters were higher. CONCLUSION: Aerobic training reduced visceral fat, lipid disorders, basal blood lactate and CHD markers in HIV patients. Training effects were particularly important for patients with marked dyslipidemia.

Adipose Tissue↗
PubMed2002

Maximal oxygen uptake and lactate metabolism are normal in chronic fatigue syndrome.

PURPOSE: Previous studies in chronic fatigue syndrome (CFS) have reported reductions in maximal oxygen uptake (VO(2max)), yet often the testing procedures have not followed accepted guidelines, and gender data have been pooled. The present study was undertaken to reevaluate exercise capacity in CFS patients by using "gold standard" maximal exercise testing methodology and stratifying results on a gender basis. METHODS: Sixteen male and 17 female CFS patients and their gender-, age-, and mass-matched sedentary controls performed incremental exercise to volitional exhaustion on a stationary cycle ergometer while selected cardiorespiratory and metabolic variables were measured. RESULTS: VO(2max) in male CFS patients was not different from control values (CFS: 40.5 +/- 6.7; controls: 43.3 +/- 8.6; mL x kg(-1) x min(-1)) and was 96.3 +/- 17.9% of the age-predicted value, indicating no functional aerobic impairment (3.7 +/- 17.9%). In female CFS patients, VO(2max) was lower than control values (CFS: 30.0 +/- 4.7; controls: 34.2 +/- 5.6; mL x kg(-1) x min(-1), P = 0.002), but controls were higher than the age-predicted value (112.6 +/- 15.4%, P = 0.008) whereas the CFS patients were 101.2 +/- 20.4%, indicating no functional aerobic impairment (-1.2 +/- 20.4%). Maximal heart rate (HR(max)) in male CFS patients was lower than their matched controls (CFS: 184 +/- 10; controls: 192 +/- 12; beats x min(-1); P = 0.016) but was 99.1 +/- 5.5% of their age-predicted value. In female CFS patients, HR(max) was not different from controls (CFS: 183 +/- 11; controls: 186 +/- 10; beats x min(-1)) and was 98.9 +/- 5.1% of the age-predicted value. The VO(2) at the lactate threshold (LT) in each gender group, whether expressed in mL x kg(-1) x min(-1) or as a percentage of VO(2max), was not different between CFS patients and controls. CONCLUSIONS: In contrast to most previous reports, the present study found that VO(2max), HR(max), and the LT in CFS patients of both genders were not different from the values expected in healthy sedentary individuals of a similar age.

Adult↗
PubMed1997

[Evaluation of the validity of spiroergometric parameters in the differentiation of circulatory and ventilatory physical limitation].

BACKGROUND: One of the indications postulated for cardiopulmonary exercise testing (CPX) is the distinction between ventilatory and cardiocirculatory reasons of an exercise limitation. Though data such as anaerobic threshold, breathing- and heart-rate-reserve, difference of arterial and alveolar oxygen pressure, ratio of ventilation to O2 and CO2 output and aerobic capacity are commonly considered in CPX interpretation, exact choice of parameters and cut-off-points is not definitely clear. The aim of our study therefore was to scrutinize the validity of these parameters and the recommended cut-off-points. A second goal was to evaluate the reliability of a standardized CPX interpretation as postulated by Wassermann and Palange. PATIENTS AND METHODS: We examined 19 patients with congestive or ischemic cardiomyopathy, 24 subjects with chronic obstructive or interstitial lung disease (n = 11 resp. n = 13). The control group consisted of 15 healthy people. During incremental cycle exercise we measured the ventilatory frequency, the peak O2 uptake and the oxygen pulse as well as the above mentioned parameters. Data were interpreted according to Wassermann and Palange in order to confirm the diagnosis of a cardiocirculatory or ventilatory conditioned exercise limitation. Additionally we determined the cut-off-points with the highest diagnostic value for our patient groups. RESULTS: According to Palange only 7% of the diagnosis could be confirmed, 55% were correctly ascertained by data interpretation according to Wassermann. Breathing reserve (45% of maximum voluntary ventilation) proved to be the only parameter with satisfying selectivity (sensitivity = 75%; specificity = 95%). Diagnostic value of all other recorded data was worse by far. CONCLUSIONS: Our study shows that standardized interpretation of CPX data does not lead to the correct diagnosis in a satisfying percentage. In any case results have to be confirmed by conventional tests such as ECG or spirometry, so that the additional diagnostic value of CPX in patients with an exercise limitation of unknown origin has to be seen very critically. Except breathing reserve from our point of view there is still no valid parameter or cut-off-point to distinct cardiocirculatory from ventilatory exercise limitation that can be recommended.

Adult↗
PubMed2005

Continuous energy variation during the seizure cycle: towards an on-line accumulated energy.

OBJECTIVE: Increases in accumulated energy on intracranial EEG are associated with oncoming seizures in retrospective studies, supporting the idea that seizures are generated over time. Published seizure prediction methods require comparison to 'baseline' data, sleep staging, and selecting seizures that are not clustered closely in time. In this study, we attempt to remove these constraints by using a continuously adapting energy threshold, and to identify stereotyped energy variations through the seizure cycle (inter-, pre-, post- and ictal periods). METHODS: Accumulated energy was approximated by using moving averages of signal energy, computed for window lengths of 1 and 20 min, and an adaptive decision threshold. Predictions occurred when energy within the shorter running window exceeded the decision threshold. RESULTS: Predictions for time horizons of less than 3h did not achieve statistical significance in the data sets analyzed that had an average inter-seizure interval ranging from 2.9 to 8.6h. 51.6% of seizures across all patients exhibited stereotyped pre-ictal energy bursting and quiet periods. CONCLUSIONS: Accumulating energy alone is not sufficient for predicting seizures using a 20 min running baseline for comparison. Stereotyped energy patterns through the seizure cycle may provide clues to mechanisms underlying seizure generation. SIGNIFICANCE: Energy-based seizure prediction will require fusion of multiple complimentary features and perhaps longer running averages to compensate for post-ictal and sleep-induced energy changes.

Algorithms↗
PubMed1992

Blood ammonia and lactate concentrations during endurance exercise of differing intensities.

The purpose of this study was to examine the changes of blood ammonia concentration ([NH3]b) during endurance exercise of differing intensities on the cycle ergometer and to compare [NH3]b to the changes observed in the simultaneously monitored blood lactate acid concentrations ([la-]b) measurements. A group of 16 endurance-trained athletes participated in the first part of the study and performed exercise of 30 min duration in a randomized order at intensities of 85%, 95%, 100% and 105% of their individual anaerobic threshold (Th(an,ind); E85-E105) which had been determined beforehand by a cycle exercise test with stepwise increments in intensity. In the second part, 18 average endurance-trained sports students underwent exhausting intensive endurance exercise (IEE) with an intensity of 95% of Th(an,ind). An extensive endurance exercise (EEE) of the same duration at 85% of the Th(an,ind) was carried out 2 days later. The [NH3]b increased constantly with increasingly duration of all exercise. However, [la-]b only increased during exercise with intensities above the Th(an,ind) (E105). The increase of [NH3]b was higher with higher exercise intensities. At IEE, [NH3]b was significantly higher from the 30th min than at EEE, whereas [la-]b increased from the 5th min. In conclusion, [la-]b responded more sensitively to the intensity of exercise than [NH3]b, but it is conceivable that in the future measurements of [NH3]b could be used to advise on the duration of endurance training. At present, however, the lack of experience and lack of appropriate values still hinders the systematic use of [NH3]b measurements in the physiological monitoring of sports training.

Adult↗
PubMed1999

Resetting of the carotid arterial baroreflex during dynamic exercise in humans.

Recent investigations have demonstrated that at the onset of low-to-moderate-intensity leg cycling exercise (L) the carotid baroreflex (CBR) was classically reset in direct relation to the intensity of exercise. On the basis of these data, we proposed that the CBR would also be classically reset at the onset of moderate- to maximal-intensity L exercise. Therefore, CBR stimulus-response relationships were compared in seven male volunteers by using the neck pressure-neck suction technique during dynamic exercise that ranged in intensity from 50 to 100% of maximal oxygen uptake (VO(2 max)). L exercise alone was performed at 50 and 75% VO(2 max), and L exercise combined with arm (A) exercise (L + A) was performed at 75 and 100% VO(2 max). O(2) consumption and heart rate (HR) increased in direct relation with the increases in exercise intensity. The threshold and saturation pressures of the carotid-cardiac reflex at 100% VO(2 max) were >75% VO(2 max), which were in turn >50% VO(2 max) (P < 0.05), without a change in the maximal reflex gain (G(max)). In addition, the HR response value at threshold and saturation at 75% VO(2 max) was >50% VO(2 max) (P < 0.05) and 100% VO(2 max) was >75% VO(2 max) (P < 0.07). Similar changes were observed for the carotid-vasomotor reflex. In addition, as exercise intensity increased, the operating point (the prestimulus blood pressure) of the CBR was significantly relocated further from the centering point (G(max)) of the stimulus-response curve and was at threshold during 100% VO(2 max). These findings identify the continuous classic rightward and upward resetting of the CBR, without a change in G(max), during increases in dynamic exercise intensity to maximal effort.

Adult↗
PubMed1995

Diaphragmatic breathing reduces efficiency of breathing in patients with chronic obstructive pulmonary disease.

The effects of diaphragmatic breathing learning on chest wall motion, mechanical efficiency of the respiratory muscles, breathing pattern, and dyspnea sensation were studied in seven patients with severe chronic obstructive pulmonary disease (COPD) (FEV1 34 +/- 7% of the predicted value) during loaded and unloaded breathing. Chest wall motion was studied focusing on amplitude and phase relation of rib cage and abdominal motion. Mechanical efficiency was defined as the ratio of added external power output and added oxygen consumption during inspiratory threshold loading (40% maximal inspiratory pressure [Plmax]). After 2 wk run-in, all subjects participated in a diaphragmatic breathing program for 3 wk. Variables obtained during diaphragmatic breathing were compared with those obtained during natural breathing. During diaphragmatic breathing the ratio of rib cage to abdominal motion decreased significantly during unloaded (0.86 versus 0.37; p < 0.01) as well as during loaded breathing (0.97 versus 0.50; p < 0.01). Chest wall motion became more asynchronous during diaphragmatic breathing in the unloaded conditions (mean phase difference for natural breathing 3.5 versus 10.4% for diaphragmatic breathing; p < 0.02) and loaded conditions (mean phase difference for natural breathing 6 versus 11.4% for diaphragmatic breathing; p < 0.02). Surprisingly, mechanical efficiency decreased significantly during diaphragmatic breathing (2.57 +/- 0.76%) in comparison with natural breathing (3.35 +/- 1.48%; p < 0.01). Tidal volume, respiratory frequency, and duty cycle did not change significantly during diaphragmatic breathing. Dyspnea sensation tended to increase during diaphragmatic breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1982

Cytotoxic and cell kinetic effects of 3,4,5-trihydroxybenzohydroxamic acid (VF 122) in hepatoma 3924A cells.

3, 4, 5-Trihydroxybenzohydroxamic acid (VF 122), an inhibitor of ribonucleotide reductase, killed rat hepatoma 3924A cells in tissue cultured after 7 days of incubation. A concentration of 15 microM caused 50% inhibition of colony-forming ability (IC50). Under the same conditions, hydroxyurea, also an inhibitor of ribonucleotide reductase, had an IC50 of 52 microM. Treatment for 1 hr with VF 122 of exponentially growing culture resulted in a biphasic exponential dose-response curve (Do = 0.5 mM, IC50 = 0.75 mM, and Do = 1.8 mM, IP = 0.8 mM). In plateau-phase cells, a threshold exponential curve was obtained (Do = 2.2 mM, Dq = 1.7 mM, and IC50 = 2.7 mM). Exponentially growing hepatoma 3924A cells were more sensitive to VF 122 than were plateau-phase cultures. In contrast, hydroxyurea killed only exponentially growing 3924A hepatoma cells, exhibiting an exponential plateau dose-response curve without achieving achieving an IC50 value at concentrations from 1 to 200 mM. In synchronized cultures, VF 122 (1 MM for 1 hr) was toxic for cells in mid and late G1 phase, in early and mid S phase, and, to a lesser degree, in G2 phase, Hydroxyurea (10 mM for 1 hr) killed cells only in S phase. Proliferating and resting hepatoma 3924A cells recovered from sublethal and potentially lethal damage induced by VF 122.

Animals↗
PubMed1999

Maximal accumulated oxygen deficit must be calculated using 10-min time periods.

PURPOSE: The accumulated O2, calculated by an extrapolation procedure from measurements of the O2 uptake at moderate powers, has been suggested as a measure of the anaerobic energy release during high intensity exercise. While some suggest that repeated 10-min bouts are required to establish the relationships in question, other use bouts of shorter durations. The purpose of this study was to examine how different exercise durations influence the calculated accumulated O2 deficit. METHODS: Eight endurance trained male cyclists with the following characteristics (Mean +/- SE): age, 25 +/- 3 yr; weight, 69.9 +/- 1.7 kg: height, 178.2 +/- 1.0 cm; and VO2max 57.5 +/- 2.4 mL x kg(-1) x min(-1) volunteered for participation in this study. The O2 uptake was measured at 2-4, 4-6, 6-8, and 8-10 min of exercise at ten different constant powers. These O2 uptakes were used to establish four relationships between the power and O2 demand for each subject. On a separate day the subjects cycled at a power of 336 +/- 42 W (corresponding to about 110% of the maximal O2 uptake) for 296 +/- 43 s to exhaustion while the O2 uptake was measured continuously. For each subject the accumulated O2 deficit was determined from the different relationships. RESULTS: The accumulated O2 deficit determined from the relationships from the 2 to 4-min exercises in the pretests were significantly less than the value calculated from the relationships obtained after the 8-10 min of exercise at constant power, the values being 39.6 +/- 11.6 mL O2 eq x kg(-1) and 53.4 +/- 14.6 mL O2 eq x kg(-1), respectively. CONCLUSIONS: This study suggests that reducing the exercise duration used in the pretests to establish the relationships between power and O2 demand from 10 min may lead to a too low accumulated O2 deficit.

Adult↗
PubMed2005

Redefining the relationship between sperm deoxyribonucleic acid fragmentation as measured by the sperm chromatin structure assay and outcomes of assisted reproductive techniques.

OBJECTIVE: To test the hypothesis that couples with sperm chromatin structure assay (SCSA) DNA fragmentation index (DFI) values >27% would not achieve pregnancy with assisted reproductive techniques (ART) and to investigate how DFI and high DNA stainability (HDS), as measured by the SCSA, affect fertilization, cleavage, implantation, and pregnancy rates in IVF cycles. DESIGN: Prospective clinical study. SETTING: Academic human reproduction laboratory. PATIENT(S): One hundred couples undergoing IVF with conventional insemination or intracytoplasmic sperm injection. INTERVENTION(S): Testing with SCSA was performed by SCSA Diagnostics (Brookings, South Dakota) on a semen aliquot taken from ejaculate used for ART. MAIN OUTCOME MEASURE(S): Relating total DFI and HDS to conventional semen parameters and cycle-specific outcomes after ART. RESULT(S): Nine of nineteen couples achieved clinical pregnancy when DFI was > or =27%, and 2 of 22 couples achieved clinical pregnancy when DFI was < or =9%. One of nine couples achieved clinical pregnancy with HDS >17%. The DFI was negatively correlated with sperm density (r = -0.23, P<.03) and motility (r = -0.55, P<.00), and HDS was negatively correlated with sperm density (r = -0.37, P<.00). CONCLUSION(S): Sperm chromatin structure assay failed to identify elevated DFI thresholds for negative pregnancy outcome after ART. Patients with low DFI (< or =9%) were least likely to become pregnant, which is also contradictory to SCSA marketing, which states that DFIs of < or =15% have excellent fertility potential. Patients with HDS > or =17% had low pregnancy rates, indicating decreased fertility potential, which deserves further investigation. Larger studies are necessary to confirm that low DFI is associated with decreased fertility and, if proved, might redefine the use of the SCSA in evaluating infertility.

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