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PubMed1991

Magnesium prophylaxis of menstrual migraine: effects on intracellular magnesium.

The effects of oral Magnesium (Mg) pyrrolidone carboxylic acid were evaluated in 20 patients affected by menstrual migraine, in a double-blind, placebo controlled study. After a two cycles run-in period, the treatment (360 mg/day of Mg or placebo) started on the 15th day of the cycle and continued till the next menses, for two months. Oral Mg was then supplemented in an open design for the next two months. At the 2nd month, the Pain Total Index was decreased by both Placebo and Mg, with patients receiving active drug showing the lowest values (P less than 0.03). The number of days with headache was reduced only in the patients on active drug. Mg treatment also improved premenstrual complaints, as demonstrated by the significant reduction of Menstrual Distress Questionnaire (MDQ) scores. The reduction of PTI and MDQ scores was observed also at the 4th month of treatment, when Mg was supplemented in all the patients. Intracellular Mg++ levels in patients with menstrual migraine were reduced compared to controls. During oral Mg treatment, the Mg++ content of Lymphocytes (LC) and Polymorphonucleated cells (PMN) significantly increased, while no changes in plasma or Red Blood Cells were found. An inverse correlation between PTI and Mg++ content in PMN was demonstrated. These data point to magnesium supplementation as a further means for menstrual migraine prophylaxis, and support the possibility that a lower migraine threshold could be related to magnesium deficiency.

Administration, Oral↗
PubMed2004

Proliferation markers predictive of the pathological response and disease outcome of patients with breast carcinomas treated by anthracycline-based preoperative chemotherapy.

The cell proliferation rate has been correlated to the response of breast carcinomas to preoperative chemotherapy (CT) and to disease outcome. However, this parameter is not yet used to select which tumours should be treated with preoperative CT. Furthermore, there is no consensus in the method used to evaluate cell proliferation. In poor prognosis breast carcinomas (PPBCs) treated by intensive preoperative CT, we compared the predictive value of S phase fraction (SPF), mitotic index (MI) and Ki67. We also evaluated the prognostic significance of the variation of the MI after CT. A series of 55 T2-T4N0N1M0 breast carcinomas were treated with 4 cycles of cyclophosphamide, 5-fluorouracil (5-FU) and doxorubicin. SPF was determined by flow cytometry on pre-therapeutic needle aspiration products. MI and Ki67 were evaluated on pre-therapeutic biopsy samples and on the tumours after CT. Fifteen patients (27%) had a pathological complete response (pCR), whereas 40 (73%) had residual disease. All three proliferative markers were found to have predictive value, but this value was higher for MI than for SPF (P = 0.04) and Ki67 (P = 0.03): the rate of pCR was 50% in cases with MI > 17/3.3 mm2, but was only 7% in cases with MI under this threshold (P = 0.0003). A significant decrease of MI (mean 10.97) was observed after CT (P = 0.001). Furthermore, we observed that even for patients with residual tumour, the variation of MI after CT was a prognostic parameter and overall survival. The sequential analysis of MI in breast cancers treated by preoperative CT thus provides a surrogate for predicting long-term outcome.

Adult↗
PubMed1997

Antiphospholipid antibodies and pregnancy rates and outcome in in vitro fertilization patients.

OBJECTIVE: To determine the relationship between antiphospholipid antibodies and pregnancy rates (PRs) and outcome among IVF patients. DESIGN: Prospective collection of all serum samples with assays for immunoglobulin G (IgG), IgA, and IgM antibodies for anticardiolipin, antiphosphatidyl serine, antiphosphatidyl ethanolamine, antiphosphatidyl choline, antiphosphatidyl inositol, antiphosphatidyl glycerol, and antiphosphatidic acid being done following completion of all treatment cycles. SETTING: A tertiary care teaching hospital. PATIENT(S): Seven hundred ninety-three patients attempting to conceive through IVF. MAIN OUTCOME MEASURE(S): Pregnancy rates (PRs) and pregnancy loss rates relative to each of the various antiphospholipid antibodies that were measured. RESULT(S): There were 528 pregnancies for an overall PR of 66%. Pregnancy rates were equal among patients with positive and negative antiphospholipid antibodies for each of the 21 measured antibodies. Use of receiver operator characteristic curves and logistic regression further confirmed that there was no relationship between PRs or outcome based on antiphospholipid antibodies for any definable threshold value. CONCLUSION(S): Elevated antiphospholipid antibody levels are not associated with any change in PRs or pregnancy loss rates in patients attempting to conceive through IVF.

Adult↗
PubMed1998

Dyspnea ratings for prescription of cross-modal exercise in patients with COPD.

STUDY OBJECTIVE: To investigate the ability of patients with COPD to reproduce an exercise intensity accurately on the treadmill using dyspnea ratings obtained during incremental exercise on the cycle ergometer (cross-modal exercise prescription). DESIGN: Five visits over an 8-week period. PATIENTS: Thirteen symptomatic patients with stable COPD. Age was 67+/-6 years (mean+/-SD). FEV1 was 1.15+/-0.22 L (45+/-7% predicted). INTERVENTIONS: At each visit, patients performed spirometry and exercise. Visit 1 was a practice incremental exercise test on the cycle ergometer. At visit 2 (1 week later), patients estimated the intensity of dyspnea using the 0 to 10 category-ratio scale during an incremental exercise test on the cycle ergometer (cycle estimation trial). Visit 3, 5 weeks later, was a practice session on the treadmill. At visit 4, 1 week later, patients were instructed to produce specific intensities of dyspnea (ie, dyspnea targets) at 50% and at anaerobic threshold (AT) or 80% of peak oxygen consumption (VO2) as calculated from results at visit 2 (treadmill production trial). Visit 5, 1 week later, was the treadmill estimation trial. MEASUREMENTS AND RESULTS: Lung function was stable at all visits. Dyspnea ratings were 1.9+/-0.9 at 50% of VO2 and 5.6+/-1.5 at AT/80% of peak VO2 (17.5+/-3.3 mL/kg/min). The VO2 at the treadmill production trial (761+/-185 mL/min) was significantly higher than at the cycle estimation trial (612+/-159 mL/min) at the low dyspnea target (p < 0.0002; upward bias, 26+/-16%). In contrast, there was no significant difference in VO2 values (929+/-176 mL/min vs 948+/-259 mL/min) at the high dyspnea target (p > 0.5; 0+/-11% bias). CONCLUSIONS: Patients with COPD can use dyspnea ratings from an incremental cycle ergometry test to regulate exercise on the treadmill without systematic bias at an intensity of 80% of peak VO2, but exceed the desired VO2 when using the dyspnea rating at an intensity of 50% of peak VO2.

Aged↗
PubMed2005

On the potential role of the corticospinal tract in the control and progressive adaptation of the soleus h-reflex during backward walking.

When untrained subjects walk backward on a treadmill, an unexpectedly large amplitude soleus H-reflex occurs in the midswing phase of backward walking. We hypothesized that activity in the corticospinal tract (CST) during midswing depolarizes the soleus alpha-motoneurons subliminally and thus brings them closer to threshold. To test this hypothesis, transcranial magnetic stimulation (TMS) was applied to the leg area of the motor cortex (MCx) during backward walking. Motor-evoked potentials (MEPs) were recorded from the soleus and tibialis anterior (TA) muscles in untrained subjects at different phases of the backward walking cycle. We reasoned that if soleus MEPs could be elicited in midswing, while the soleus is inactive, this would be strong evidence for increased postsynaptic excitability of the alpha-motoneurons. In the event, we found that in untrained subjects, despite the presence of an unexpectedly large H-reflex in midswing, no soleus MEPs were observed at that time. The soleus MEPs were in phase with the soleus electromyographic (EMG) activity during backward walking. Soleus MEPs increased more rapidly as a function of the EMG activity during voluntary activity than during backward walking. Furthermore, a conditioning stimulus to the motor cortex facilitated the soleus H-reflex at rest and during voluntary plantarflexion but not in the midswing phase of backward walking. With daily training at walking backward, the time at which the H-reflex began to increase was progressively delayed until it coincided with the onset of soleus EMG activity, and its amplitude was considerably reduced compared with its value on the first experimental day. By contrast, no changes were observed in the timing or amplitude of soleus MEPs with training. Taken together, these observations make it unlikely that the motor cortex via the CST is involved in control of the H-reflex during the backward step cycle of untrained subjects nor in its progressive adaptation with training. Our observations raise the possibility that the large amplitude of H-reflex in untrained subjects and its adaptation with training are mainly due to control of presynaptic inhibition of Ia-afferents by other descending tracts.

Adaptation, Physiological↗
PubMed1998

Catabolite repression mutants of Saccharomyces cerevisiae show altered fermentative metabolism as well as cell cycle behavior in glucose-limited chemostat cultures.

In glucose-limited continuous cultures, a Crabtree positive yeast such as Saccharomyces cerevisiae displays respiratory metabolism at low dilution rates (D) and respiro-fermentative metabolism at high D. We have studied the onset of ethanol production and cell cycle behavior in glucose-limited chemostat cultures of the wild type S. cerevisiae strain CEN.PK122 (WT) and isogenic mutants, snf1 (cat1) and snf4 (cat3) defective in proteins involved in catabolite derepression and the mutant in glucose repression mig1 (cat4). The triggering of fermentative metabolism was dependent upon catabolite repression properties of yeast and was coincident with a significant decrease of G1 length. WT cells of the strain CEN.PK122 displayed respiratory metabolism up to a D of 0.2 h-1 and exhibited longer G1 lengths than the snf1 and snf4 mutants that started fermenting after a D of 0.1 and 0.15 h-1, respectively. The catabolite derepression mutant snf4 showed a significant decrease in the duration of G1 with respect to the WT. An increase of 300% to 400% in the expression of CDC28 (CDC28-lacZ) with a noticeable shortening in G1 to values lower than approximately 150 min, was detected in the transformed wild type CEN.SC13-9B in glucose-limited chemostat cultures. The expression of CDC28-lacZ was analyzed in the wild type and isogenic mutant strains growing at maximal rate on glucose or in the presence of ethanol or glycerol. Two- to three-fold lower expression of the CDC28-lacZ fusion gene was detected in the snf1 or snf4 disruptants with respect to the WT and mig1 strains in the presence of all carbon sources. This effect was further shown to be growth rate-dependent exhibiting apparently, a threshold effect in the expression of the fusion gene with respect to the length of G1, similar to that shown in chemostat cultures. At the onset of fermentation, the control of the glycolytic flux was highly distributed between the uptake, hexokinase, and phosphofructokinase steps. Particularly interesting was the fact that the snf1 mutant exhibited the lowest fluxes of ethanol production, the highest of respiration and correspondingly, the branch to the tricarboxylic acid cycle was significantly rate-controling of glycolysis.

Biotechnology↗
PubMed1997

Lactate distribution in the blood during progressive exercise.

The purpose of this study was to examine the effect of increment durations of 1-min and 4-min during progressive incremental exercise tests on: 1) the distribution of lactate between plasma and red blood cells (RBCs), and 2) lactate threshold (LT) detection via three conventional methods using whole blood lactate concentration ([La]) or plasma [La]. Eight males (age, 22.5 +/- 0.6 yr: height, 170.6 +/- 2.3 cm, weight, 76.0 +/- 3.1 kg, and VO2peak, 42.8 +/- 2.0 mL.kg-1.min-1) performed two progressive load tests to volitional fatigue on a cycle ergometer. Work rate was increased 30 W at 1-min or 4-min intervals. All data were normalized to individual LT work rates. For both protocols, whole blood [La], plasma [La], RBC [La], and [La] gradient increased significantly (P < 0.05) after exercise intensity exceeded LT. However, the RBC:plasma [La] ratio remained at the resting value throughout the progressive exercise tests. The increase in [La] gradient after LT, with no change in the RBC:plasma lactate ratio, suggests that given an incremental work rate increase of 30 W, 1 min is adequate for equilibration of lactate between the plasma and RBCs. Also, under the conditions of this investigation, neither blood fraction analyzed nor exercise protocol had any effect on estimations of LT (in terms of VO2) by the Visual and Log-Log methods. However, LT determined by a fixed [La] of 2 mM may underestimate LT when plasma samples are used.

Adult↗
PubMed2004

Exercise testing in pulmonary arterial hypertension and in chronic heart failure.

Exercise capacity is reduced in pulmonary arterial hypertension and in chronic left heart failure, but it is not known whether the cardiopulmonary exercise testing profile is different in the two conditions at the same severity of functional limitation. Nineteen patients with pulmonary arterial hypertension and 19 with chronic heart failure underwent a 6-min walk test and symptom-limited maximal incremental cycle ergometry. The patients with pulmonary arterial hypertension and chronic heart failure did not differ in New York Heart Association Functional Class (mean +/- SEM 2.8 +/- 0.1 versus 2.8 +/- 0.2), 6-min walking distance (395 +/- 30 versus 419 +/- 20 m), peak work-rate, oxygen consumption, ventilation and cardiac frequency. However, patients with pulmonary arterial hypertension exhibited higher dyspnoea scores (5.8 +/- 0.6 versus 3.8 +/- 0.5) higher ventilatory equivalents for carbon dioxide (58 +/- 3 versus 44 +/- 3 at the anaerobic threshold) and lower peak oxygen pulse (5.9 +/- 0.4 versus 8.7 +/- 0.5 mL x beat(-1), or 53 +/- 4 versus 64 +/- 4% of the predicted value). It is concluded that the cardiopulmonary exercise testing profile in pulmonary arterial hypertension differs from that in chronic heart failure by showing more dyspnoea at comparable work-rates, related to greater reductions in ventilatory efficiency and stroke volume.

Adult↗
PubMed1996

Prediction of blood lactate accumulation from excess CO2 output during constant exercise.

To determine the predictability of blood lactate accumulation from excess CO2 output derived from bicarbonate buffering of lactic acid during constant exercise, eight normal active volunteers were studied during three stages of constant exercise on a cycle ergometer. Three work rates consisted of 100% (stage I), 120% (stage II) and 150% (stage III) of each subject's anaerobic threshold (AT), each of which was lasted for 4 min. Excess CO2 output (Ex CO2, ml) at each stage of constant exercise was estimated form the integral of difference between total VCO2 and aerobic VCO2 (from regression line for VCO2 and VO2 at exercise intensities below the AT obtained in incremental exercise test). Ex CO2 per body mass (Ex CO2-mass-1) was increased progressively with blood lactate (La) accumulation from rest to each stage of constant exercise. Mean values (+/-SD) in the measured La accumulation (delta La,measured) and predicted La accumulation (delta La,predicted) at three stages of constant exercise were 1.82 +/- 0.83 vs 3.19 +/- 1.70 for stage 1, 5.58 +/- 3.47 vs 7.09 +/- 3.28 for stage II and 12.19 +/- 2.36 vs 12.74 +/- 1.83 mmol.l-1 for stage III, respectively. There was a significant difference between delta La,measured and delta La,predicted at stage I (p < 0.05), but no significant differences between these two variables at stage II and III. The averaged difference from delta La,predicted to delta La,measured at stage III (0.55 mmol.l-1) showed a tendency to be smaller than stage I (1.38 mmol.l-1) and II (1.50 mmol.l-1). On the other hand, delta La,predicted was found to correlate very closely with delta La,measured (r = 0.954, P < 0.001, n = 20). The results of this study suggest that the changes of La accumulation could be predicted from excess CO2 output generated in constant exercises above the AT.

Adolescent↗
PubMed2006

Atypical progesterone profiles and fertility in Swedish dairy cows.

The incidence of normal and atypical progesterone profiles in Swedish dairy cows was studied. Data were collected from an experimental herd over 15 yr, and included 1,049 postpartum periods from 183 Swedish Holstein and 326 Swedish Red and White dairy cows. Milk progesterone samples were taken twice weekly until initiation of cyclical ovarian activity and less frequently thereafter. Progesterone profiles were 1) normal profile: first rise in milk progesterone above the threshold value before d 56 postpartum, followed by regular cyclical ovarian activity (70.4%); 2) delayed onset of cyclical ovarian activity: low milk progesterone the first 56 d postpartum (15.6%); 3) cessation of cyclical ovarian activity: ovarian activity resumed within 56 d postpartum, but ceased for a period of 14 d or more (6.6%); and 4) prolonged luteal phase: ovarian activity resumed within 56 d postpartum, but milk progesterone remained elevated in the nonpregnant cow for a period of 20 d or more (7.3%). Swedish Holsteins had 1.5 times higher risk of atypical profile than Swedish Red and Whites. Risk of atypical profiles was 0.5 and 0.7 times lower for older cows compared with first-parity cows; 2.3 times higher for cows in tie-stalls compared with those in loose housing; 2.6 times higher for cows calving during winter compared with summer; 0.5 times lower for cows in earlier (1994-1999) calving-year groups compared with the most recent (2000-2002); 2.5 times higher for cows with planned extended calving interval compared with conventional calving interval; and 2.2 times higher for an atypical profile in previous lactation compared with a normal profile. Cows with atypical profiles had a 15-d increase in interval from calving to first artificial insemination and an 18-d increase in interval from calving to conception. Progesterone samples taken within the first 60 d postpartum were used to calculate the percentage of samples above the threshold value of luteal activity. This measure had a significantly different mean in profiles and can be used to separate delayed onset of cyclical ovarian activity profiles and prolonged luteal phase profiles from normal. Thereby, it may be a more effective tool than measurements based only on the onset of ovarian cyclical activity in genetic evaluation of early postpartum fertility in dairy cows.

Aging↗
PubMed1999

Response to inspiratory resistive loading during sleep in normal children and children with obstructive apnea.

The response to inspiratory resistance loading (IRL) of the upper airway during sleep in children is not known. We, therefore, evaluated the arousal responses to IRL during sleep in children with the obstructive sleep apnea syndrome (OSAS) compared with controls. Children with OSAS aroused at a higher load than did controls (23 +/- 8 vs. 15 +/- 7 cmH(2)O. l(-1). s; P < 0.05). Patients with OSAS had higher arousal thresholds during rapid eye movement (REM) vs. non-REM sleep (P < 0.001), whereas normal subjects had lower arousal thresholds during REM (P < 0.005). Ventilatory responses to IRL were evaluated in the controls. There was a marked decrease in tidal volume both immediately (56 +/- 17% of baseline at an IRL of 15 cmH(2)O. l(-1). min; P < 0.001) and after 3 min of IRL (67 +/- 23%, P < 0.005). The duty cycle increased. We conclude that children with OSAS have impaired arousal responses to IRL. Despite compensatory changes in respiratory timing, normal children have a decrease in minute ventilation in response to IRL during sleep. However, arousal occurs before gas-exchange abnormalities.

Airway Resistance↗
PubMed2000

A novel approach to maintain planned dose chemotherapy on time: a decision-making tool to improve patient care.

Studies of primary prophylaxis of febrile neutropenia with recombinant granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim), administered to all patients starting with the initial course of chemotherapy, have demonstrated an economic advantage over a wide range of settings. In these analyses, the threshold risk for febrile neutropenia at which a cost saving is realised is inversely related to the direct medical costs of hospitalisation. Clinical practice guidelines for the use of filgrastim have been developed based on these observations. Recent studies incorporating indirect institutional costs have demonstrated that cost savings can be achieved at substantially lower febrile neutropenia risk thresholds than previously estimated. Despite the demonstrated efficacy of filgrastim in primary prophylaxis, its value may be further enhanced through the appropriate selection of patients for such therapy and a better understanding of the importance of sustaining dose intensity in specific malignancies. Clinical prediction models capable of identifying individuals at high risk for neutropenic complications yield further reductions in febrile neutropenia risk thresholds and treatment costs in patients receiving cancer chemotherapy. Prediction models can also be used to evaluate the cost-effectiveness or cost-efficiency of filgrastim use. Such a model has recently been developed and validated and is described here which incorporates both baseline clinical characteristics as well as the results of the first cycle of chemotherapy in patients with early-stage breast cancer. A cost-effectiveness ratio of US$ 34297 (Euro 32002)dagger per year of life saved (YLS) was calculated based on dose-response assumptions derived from a previously reported adjuvant breast cancer trial studying the impact of dose reduction on disease-free survival. This figure is comparable with accepted cost-effectiveness ratios for other interventions, e.g. US$ 45000/LYS (Euro 41989) for renal dialysis for patients with end-stage renal disease. The cost-effectiveness of filgrastim was evident over a wide range of clinical and cost assumptions. Clinical prediction models permit rational and cost-effective selection of patients for filgrastim support. Current guidelines should be re-evaluated in light of new information available on both the total cost of febrile neutropenia, as well as the cost-effectiveness of these agents in specific clinical situations.

Antineoplastic Agents↗
PubMed2000

Exercise intensity during competition time trials in professional road cycling.

PURPOSE: To estimate, upon competition heart rate (HR), exercise intensity during time trials (TT) in professional road cycling. METHODS: Eighteen world-class cyclists completed an incremental laboratory cycling test to assess maximal power output (Wmax), maximal HR (HRmax), onset of blood lactate accumulation (OBLA), lactate threshold (LT), and a HR-power output relationship. An OBLA(ZONE) (HR(OBLA) +/- 3 beats x min(-1)) and a LT(ZONE) (HR(LT) +/- 3 beats x min(-1)) were described. HR was monitored during 12 prologue (<10 km, PTT), 18 short (<40 km, STT), 19 long (>40 km, LTT), eight uphill (UTT), and seven team (TTT) time trials. A HR-power output relationship was computed to estimate each cyclist's power output during TT racing from competition HR. Competition training impulse (TRIMP) values were estimated from HR and race duration. RESULTS: %HRmax were 89+/-3%, 85+/-5%, 80+/-5%, 78+/-3%, and 82+/-2% in PTT, STT, LTT, UTT, and TTT, respectively. The amount of TRIMP were, respectively, 21+/-3, 77+/-23, 122+/-27, 129+/-14, and 146+/-6. Competition HR values relative to HR(OBLA) and HR(LT) were, respectively, 100+/-3%, 114+/-8% in PTT, 95+/-7%, 108+/-9% in STT, 89+/-5%, 103+/-8% in LTT, 87+/-2%, 101+/-5% in UTT, and 91+/-4%, 105+/-11% in TTT. CONCLUSIONS: %HRmax, TRIMP and time distribution around HR(OBLA) and HR(LT) reflected the physiological demands of different TT categories. HR(OBLA) and HR(LT) were accurate intensity markers in events lasting, respectively, < or =30 (PTT and STT) and > or =30 min (LTT, UTT, TTT).

Adult↗
PubMed1988

Osmoregulation of thirst and vasopressin during normal menstrual cycle.

Changes in osmoregulation during normal menstrual cycle were examined in 15 healthy women. In 10 women, studied repetitively during two consecutive menstrual cycles, basal plasma osmolality, sodium, and urea decreased by 4 mosmol/kg, 2 meq/l, and 0.5 mM, respectively (all P less than 0.02) from the follicular to luteal phase. Plasma vasopressin, protein, hematocrit, mean arterial pressure, and body weight did not change. In five other women, diluting capacity and osmotic control of thirst and vasopressin release were assessed in follicular, ovulatory, and luteal phases. Responses of thirst and/or plasma vasopressin, urine osmolality, osmolal and free water clearance to water loading, and infusion of hypertonic saline were normal and similar in the three phases. However, the plasma osmolality at which plasma vasopressin and urine osmolality were maximally suppressed as well as calculated osmotic thresholds for thirst and vasopressin release were lower by 5 mosmol/kg in the luteal than in the follicular phase. This lowering of osmotic thresholds for thirst and vasopressin release, which occurs in the luteal phase, is qualitatively similar to that observed in pregnancy and should be taken into account when studying water balance and regulation of vasopressin secretion in healthy cycling women.

Adult↗
PubMed1999

Oxygen uptake kinetics of older humans are slowed with age but are unaffected by hyperoxia.

Cross-sectional studies have compared the oxygen uptake (VO2) kinetics during the on-transient of moderate intensity exercise in older and younger adults. The slower values in the older adults may have been due to an age-related reduction in the capacity for O2 transport or alternatively a reduced intramuscular oxidative capacity. We studied: (1) the effects of ageing on VO2 kinetics in older adults on two occasions 9 years apart, and (2) the effect of hyperoxia on VO2 kinetics at the second test time. After a 9 year period, follow-up testing was undertaken on seven older adults (78 +/- 5 years, mean +/- S.D.). They each performed six repeats of 6 min bouts of constant-load cycle exercise from loadless cycling to 80% of their ventilatory threshold. They breathed one of two gas mixtures (euoxia: inspired O2 fraction, FI,O2, 0.21; hyperoxia: FI,O2, 0.70) on different trials determined on a random basis. Breath-by-breath VO2 data were time aligned and ensemble averaged. VO2 kinetics, modelled with a single exponential from phase 2 onset (+20 s) to steady state and described by the exponential time constant (tau) were compared with data collected from the same adults 9 years earlier. One-way repeated measures analysis of variance revealed that tau was slowed significantly with age (from 30 +/- 8 to 46 +/- 10 s), but was unaffected by hyperoxia (43 +/- 15 s). We concluded that: (1) in older adults studied longitudinally over a 9 year period, the on-transient VO2 kinetics are slowed, in agreement with, but to a greater extent, than from cross-sectional data; and (2) the phase 2 time constant (tau) for these older adults was not accelerated by hyperoxic breathing. Thus the expected hyperoxia-induced increase in the capacity for O2 transport was not associated with faster on-transient VO2 kinetics suggesting either that O2 transport may not limit VO2 kinetics during the 8th decade, or that O2 transport was not improved with hyperoxia.

Aged↗
PubMedDate not supplied

[Bicycle ergometry exercise tests: a comparison between 3 protocols with an increasing load].

A group of 26 male long-distance runners performed 3 cycle ergometer tests of progressively increasing intensity up to exhaustion. The tests were performed on 3 different days. The workload increased as follows: 30 Watts every 3 min (test I), 10 Watts every min (test II), and 30 Watts every min (test III). Ventilatory and gas exchange measurements were averaged every 30 sec during each test. The heart rate (HR) was monitored continuously by ECG. In each test the anaerobic threshold (AT) was determined using ventilatory and gas exchange indices (VE, VCO2, VE/VO2). The work load on exhaustion and power at AT were the same comparing test I with test II, but these values were significantly higher in the 30 Watts/1 minute test. Conversely, maximal oxygen uptake (VO2 max) and the VO2 observed at anaerobic threshold were comparable in the 3 protocols. The slopes of VO2, VCO2, VE and HR against the work load (Watts) were identical in test I and II, but were slower in test III. However, no differences in the ventilatory and heart rate patterns versus oxygen uptake were observed comparing the three exercise tests. These results suggest a good comparability between the 30 Watts/3 min test and the 10 Watt/1 min protocol. Furthermore, for workloads below AT, a steady state was attained at the 3rd minute of each phase during test I, while oxygen uptake and other cardio-respiratory variables were underestimated during the protocol in which phases of 30 Watts were maintained only for 1 minute.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Impaired visual contrast sensitivity in epileptic patients treated with carbamazepine.

Critical flicker fusion frequencies and visual contrast sensitivity were determined in 27 adult epileptic patients receiving carbamazepine monotherapy and in 24 healthy, drug-free control subjects. Flicker fusion thresholds were the same in patients and control subjects, whereas the contrast sensitivity was significantly reduced in the patient group at all spatial frequencies. There was a significant negative correlation between the plasma concentration of carbamazepine and the contrast sensitivity at 11.4 and 22.8 cycles per degree, indicating that the reduced contrast sensitivity was due to the drug therapy.

Adolescent↗
PubMed2005

When can herbivores slow or reverse the spread of an invading plant? A test case from Mount St. Helens.

Here we study the spatial dynamics of a coinvading consumer-resource pair. We present a theoretical treatment with extensive empirical data from a long-studied field system in which native herbivorous insects attack a population of lupine plants recolonizing a primary successional landscape created by the 1980 volcanic eruption of Mount St. Helens. Using detailed data on the life history and interaction strengths of the lupine and one of its herbivores, we develop a system of integrodifference equations to study plant-herbivore invasion dynamics. Our analyses yield several new insights into the spatial dynamics of coinvasions. In particular, we demonstrate that aspects of plant population growth and the intensity of herbivory under low-density conditions can determine whether the plant population spreads across a landscape or is prevented from doing so by the herbivore. In addition, we characterize the existence of threshold levels of spatial extent and/or temporal advantage for the plant that together define critical values of "invasion momentum," beyond which herbivores are unable to reverse a plant invasion. We conclude by discussing the implications of our findings for successional dynamics and the use of biological control agents to limit the spread of pest species.

Animal Feed↗