Malignant transformation of ovarian epithelium.
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Animals↗
Biomedical subjects
I Jacobs
Publications and source records attributed to I Jacobs.
Adaptations to training at the individual anaerobic threshold.
The individual anaerobic threshold (Th(an)) is the highest metabolic rate at which blood lactate concentrations can be maintained at a steady-state during prolonged exercise. The purpose of this study was to test the hypothesis that training at the Th(an) would cause a greater change in indicators of training adaptation than would training "around" the Th(an). Three groups of subjects were evaluated before, and again after 4 and 8 weeks of training: a control group, a group which trained continuously for 30 min at the Th(an) intensity (SS), and a group (NSS) which divided the 30 min of training into 7.5-min blocks at intensities which alternated between being below the Th(an) [Th(an) -30% of the difference between Th(an) and maximal oxygen consumption (VO2max)] and above the Th(an) (Th(an) +30% of the difference between Th(an) and VO2max). The VO2max increased significantly from 4.06 to 4.27 l.min-1 in SS and from 3.89 to 4.06 l.min-1 in NSS. The power output (W) at Th(an) increased from 70.5 to 79.8% VO2max in SS and from 71.1 to 80.7% VO2max in NSS. The magnitude of change in VO2max, W at Th(an), % VO2max at Th(an) and in exercise time to exhaustion at the pretraining Th(an) was similar in both trained groups. Vastus lateralis citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities increased to the same extent in both trained groups. While all of these training-induced adaptations were statistically significant (P < 0.05), there were no significant changes in any of these variables for the control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
Adaptation, Physiological↗
Energy metabolism during cold exposure.
Recent advances on the influence of cold exposure on energy metabolism in animals and humans are summarized. Although the cold-induced enhancements in carbohydrate metabolism have been the focus of numerous studies, it was only recently that pieces of evidence from animal studies have suggested that cold exposure exerts an insulin-like effect on peripheral tissue glucose uptake, which appears to proceed primarily via insulin-independent pathways. Interestingly, this phenomenon was observed in insulin-sensitive tissues of warm- a well as cold-adapted rats. Whereas previous human studies have concentrated on the cold-induced changes in basal levels of hormones and metabolic substrates, recent work from our laboratory has demonstrated that exposure to cold at rest shifts substrate utilization from mainly lipids at thermal neutrality to carbohydrates, representing the main fuel for shivering thermogenesis. Further investigation has revealed that the marked increment in carbohydrate oxidation in cold-exposed humans is derived from a greater utilization of both circulating glucose and intramuscular glycogen. With respect to lipid metabolism, recent studies have shown that the cold-induced increase in lipid oxidation in man is fuelled primarily by the fatty acids released from white adipose tissue triglycerides (TG) and possibly intramuscular TG, not plasma TG. One practical application of this work on energy metabolism in the cold resides in the pharmacological approach to improve cold tolerance, where pharmacological agents that alter energy metabolism and substrate utilization could be used to enhance cold thermogenesis and produce warmer body temperatures.
Animals↗
Relative intensity of muscular contraction during shivering.
The intensity of cold-induced shivering, quantified by surface electromyography (EMG) and then expressed as a function of the maximal myoelectrical activity (integrated EMG) obtained during a maximum voluntary contraction (MVC), was examined in this study in individuals classified by body fat. In addition, the relationship between shivering and metabolic rate (MR) and the relative contribution of various muscle groups to total heat production were studied. Ten seminude male volunteers, 5 LEAN (less than 11% body fat) and 5 NORM (greater than 15% body fat) were exposed to 10 degrees C air for 2 h. EMG of six muscle groups (pectoralis major, rectus abdominis, rectus femoris, gastrocnemius, biceps brachii, and brachioradialis) was measured and compared with the EMG of each muscle's MVC. A whole body index of shivering, determined from the mass-weighted intensity of shivering of each muscle group, was correlated with MR. After the initial few minutes of exposure, only the pectoralis major, rectus femoris, and biceps brachii continued to increase their intensity of shivering. Shivering intensity was higher in the central muscles, ranging from 5 to 16% of MVC compared with that in the peripheral muscles, which ranged from 1 to 4% of MVC. Shivering intensities were similar in the peripheral muscles for the LEAN and NORM groups, whereas differences occurred in the trunk muscles for the pectoralis major and rectus abdominis. The whole body index of shivering correlated significantly with each individual's increase in MR (r = 0.63-0.97).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Blood lactate response to the Canadian Aerobic Fitness Test (CAFT).
This study evaluated the blood lactate (LA) response to stepping exercise, specifically the Canadian Aerobic Fitness Test (CAFT). It also compared the correlation between either LA or heart rate (HR) at a given stage of the CAFT and directly measured maximal aerobic power (VO2max). A total of 137 male Canadian Forces (CF) personnel between the ages of 18 and 53 years participated in this study. The LA concentration after each stage of the CAFT was measured in all subjects from blood sampled from the fingertip. Seventy-eight of these subjects also had their VO2max measured directly during a maximal treadmill run. The results showed that increasing stages of the CAFT were associated with exponentially increasing LA. At Stage 5, LA concentration ranged from 1.0 to 7.0, with a mean of 2.6 mmol.L-1, while HR ranged from 72 to 192 with a mean of 132 beats. When the LA and HR measures at Stage 5 of the CAFT were compared for their ability to predict VO2max, the correlation between lactate and VO2max was -0.71 (p less than .001); between HR and VO2max it was -0.36 (p less than .01). These results suggest that LA is a better predictor of VO2max than HR.
Adolescent↗
Velocity specificity of training in bodybuilders.
This study investigated the effects of many years of bodybuilding on muscular strength and endurance. Eight bodybuilders (BB), 4 males and 4 females, and 8 controls (C), 4 males and 4 females, performed a muscle fatigue test (MFT) consisting of 25 maximal leg extensions at angular velocities of 180 and 300 degrees/s. The results for strength showed that at both the slow and fast contraction speeds, BB were significantly stronger than C and males were significantly stronger than females. For muscular endurance the results showed that at the slow contraction speed the torques and torque decline were greater in the BB than in the C, and greater in the males than the females. At the faster contraction speed, torque decline was similar in all groups while torques for the BB and male-C were similar and significantly greater than the torques for the female-C. The ratio of torques (fast/slow) for both strength and muscular endurance showed a main effect due to training status which supported the velocity specificity hypothesis. However, when the relative torques over the 25 contractions at both speeds were looked at, no velocity specificity occurred for muscular endurance. The data suggest a definite velocity specificity for the strength factor in BB whereas the same conclusion is not as clear for the muscular endurance factor.
Adaptation, Physiological↗
Blood lactate response to the Canadian Aerobic Fitness Test in females.
This study evaluated the blood lactate concentration ([LA-]) response to the Canadian Aerobic Fitness Test (CAFT) in female subjects and compared the strength of prediction of VO2max determined by [LA-] and heart rate (HR). The sample was composed of 98 Canadian Forces females between the ages of 18 and 45 years. The [LA-] after each stage of the step-test was measured in all subjects by sampling blood from the fingertip. VO2max was measured directly during a maximal treadmill run in 66 of these subjects. The results showed that increasing stages of the step-test were associated with increasing [LA-]. The correlation between [LA-] after Stage 5 of the step-test and the directly determined VO2max was r = -0.72 and did not differ significantly from the correlation between HR and VO2max (r = -0.66). The relationship between [LA-] and VO2max for these females was similar to the one established earlier for males; however, the correlation between HR and VO2max for females was different from that observed in males. The present data for the females suggest that [LA-] and HR after Stage 5 of the CAFT predict VO2max equally well for females under age 40.
Adult↗
Effect of simulated air combat maneuvering on muscle glycogen and lactate.
Muscle glycogen and muscle and blood lactate were evaluated before and after a +4.0/7.0 Gz simulated air combat maneuvering (SACM) protocol in the human centrifuge. The subjects were eight healthy males, ages 25-43 years. Muscle glycogen and lactate were determined from biopsies of m. vastus lateralis in six subjects and whole blood lactate was analyzed in finger-tip blood samples from eight subjects. G-tolerance time was 256 +/- 33 s (Mean +/- S.E.M.). The decrease in glycogen concentration averaged 81 +/- 36 mmol.kg-1 dry wt (p = 0.07). The rate of glycogen utilization was low, averaging 0.4 +/- 0.1 mmol.kg-1.s-1. Muscle lactate increased significantly from 28 +/- 2 mmol.kg-1 dry wt pre-SACM to 51 +/- 4 mmol.kg-1 post-SACM. Post-SACM blood lactate was 4.2 +/- 0.3 mmol.L-1. Neither final blood nor muscle lactate values nor the difference between pre- and post-SACM muscle lactate concentrations were related to G-tolerance time. It was concluded that glycogen availability in m. vastus lateralis is not a limiting factor during exposure to headward acceleration of this type and duration. The lactate values, while high, cannot fully explain the muscular fatigue occurring during centrifuge exposures of the type used here. Therefore, the suggestion by others that anaerobic energy metabolism in skeletal muscles is the crucial factor limiting the ability to resist fatigue during exposure SACM is not supported and is likely an oversimplification of a much more complex problem.
Adult↗
Muscle glycogen utilization and the expression of relative exercise intensity.
Previous research has shown that the rate of muscle glycogen utilization is related to exercise intensity expressed relative to maximal aerobic power (%VO2max). The purpose of this study was to compare the relationship between glycogen utilization and %VO2max to that between glycogen utilization and intensity expressed relative to the onset of blood lactate accumulation (%OBLA) during cycle exercise. It was hypothesized that the rate of glycogen utilization would be related more closely to intensity expressed as %OBLA than to intensity expressed as %VO2max. Nineteen subjects (15 males and 4 females) performed two separate tests to determine VO2max and OBLA during continuous incremental exercise. On a third occasion biopsies were taken from the m. vastus lateralis before and after 30 min of exercise at randomly assigned intensities ranging from 50-80% VO2max, corresponding to 67-117% OBLA. There was a large inter-subject variation in aerobic fitness with VO2max ranging from 34 to 66 mL.kg-1.min-1 and OBLA ranging from 64-84% VO2max. Absolute VO2max and the VO2 at OBLA were correlated strongly (r = 0.90). The change in glycogen concentration during the 30-min exercise bout ranged from an increase of 58 to a depletion of 200 mmol glucose units.kg-1 dry muscle weight. Neither absolute nor relative glycogen utilization was significantly related to the exercise intensity expressed as either %VO2max or %OBLA. Stepwise multiple regression was used to identify variables which could account for the variation in glycogen depletion.(ABSTRACT TRUNCATED AT 250 WORDS)
Female↗
Incremental test protocol, recovery mode and the individual anaerobic threshold.
The individual anaerobic threshold (IAT) is defined as the highest metabolic rate at which blood lactate (LA) concentrations are maintained at a steady-state during prolonged exercise. The purpose of this study was to compare the effects of active and passive recovery on the determination of IAT following both a submaximal or maximal incremental exercise test. Seven males (VO2max = 57.6 +/- 5.8 ml.kg-1.min -1) did two submaximal, incremental cycle exercise tests (30 W and 4 min per step) and two maximal incremental tests. Blood was sampled repeatedly during exercise and for 12 min during the subsequent recovery period, which was passive for one submaximal and one maximal test and active (approximately 35% VO2max) during the other tests. An IAT metabolic rate and power output were calculated for the submax-passive (IATsp, LA = 1.85 +/- 0.42 mmol.l-1), max-passive (IATmp, LA = 3.41 +/- 1.14 mmol.l-1), submax-active (IATsa, LA = 2.13 +/- 0.45 mmol.l-1) and max-active (IATma, LA = 3.44 +/- 0.73 mmol.l-1) protocols. At weekly intervals, the subjects exercised for 30 min at one of the four IAT metabolic rates. Active recovery did not affect the calculation of IAT, but following the maximal incremental tests, IAT occurred at a higher (p less than 0.05) power output, absolute VO2 and %VO2max (71% VO2max) compared with the IAT determined with the submaximal incremental tests (61% VO2max).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Shivering onset, metabolic response, and convective heat transfer during cold air exposure.
The onset and intensity of shivering of various muscles during cold air exposure are quantified and related to increases in metabolic rate and convective heat loss. Thirteen male subjects resting in a supine position and wearing only shorts were exposed to 10 degrees C air (42% relative humidity and less than 0.4 m/s airflow) for 2 h. Measurements included surface electromyogram recordings at six muscle sites representing the trunk and limb regions of one side of the body, temperatures and heat fluxes at the same contralateral sites, and metabolic rate. The subjects were grouped according to lean (LEAN, n = 6) and average body fat (NORM, n = 7) content. While the rectal temperatures fluctuated slightly but not significantly during exposure, the skin temperature decreased greatly, more at the limb sites than at the trunk sites. Muscles of the trunk region began to shiver sooner and at a higher intensity than those of the limbs. The intensity of shivering and its increase over time of exposure were consistent with the increase in the convective heat transfer coefficient calculated from skin temperatures and heat fluxes. Both the onset of shivering and the magnitude of the increase in metabolic rate due to shivering were higher for the LEAN group than for the NORM group. A regression analysis indicates that, for a given decrease in mean skin temperature, the increase in metabolic rate due to shivering is attenuated by the square root of percent body fat. Thus the LEAN group shivered at higher intensity, resulting in higher increases in metabolic heat production and convective heat loss during cold air exposure than did the NORM group.
Adipose Tissue↗
Effects of muscle glycogen and plasma FFA availability on human metabolic responses in cold water.
The purpose of this study was to investigate whether simultaneous alterations in the availability of plasma free fatty acids and muscle glycogen would impair the maintenance of thermal balance during cold water immersion in humans. Eight seminude subjects were immersed on two occasions in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Each immersion followed 2.5 days of a specific dietary and exercise regimen designed to elicit low (LOW) or high glycogen levels (HIGH) in large skeletal muscle groups. Nicotinic acid (1.6 mg/kg) was administered for 2 h before and during immersion to inhibit white adipose tissue lipolysis. Biopsies from the vastus lateralis showed that the glycogen concentration before the immersion was significantly lower in LOW than in HIGH (223 +/- 19 vs. 473 +/- 24 mmol glucose units/kg dry muscle). However, the mean rates of glycogen utilization were not significantly different between trials (LOW 0.62 +/- 0.14 vs. HIGH 0.88 +/- 0.15 mmol glucose units.kg-1.min-1). Nicotinic acid dramatically reduced plasma free fatty acid levels in both trials, averaging 127 +/- 21 mumol/l immediately before the immersion. Cold water immersion did not significantly alter those levels. Plasma glucose levels were significantly reduced after cold water immersion to a similar extent in both trials (18 +/- 4%). Mean respiratory exchange ratio at rest and during immersion was greater in HIGH than LOW, whereas there were no intertrial differences in O2 uptake. The calculated average metabolic heat production during immersion tended to be lower (P = 0.054) in LOW than in HIGH (15.3 +/- 1.9 vs. 17.5 +/- 1.9 kJ/min).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Neurovascular complications of cocaine abuse.
A 3-year prospective study of 31,081 admissions to an inner-city, emergency trauma hospital revealed 33 patients less than or equal to 45 years of age who had a total of 35 acute neurovascular events (infarction or hemorrhage) related to cocaine abuse (3% of the total 979 cocaine-related admissions). Fifty-four percent of the events were ischemic, and 46% were hemorrhagic. Six patients died. The majority (63%) of ischemic events were hemispheric and subcortical in distribution. Eleven of 13 angiograms were abnormal (five aneurysms and two arteriovenous malformations were identified). No case of "vasculitis" was seen. Seventy percent of the patients exclusively abused crack cocaine, and 94% of the neurovascular events were related to its use. No first-time cocaine users were identified. During the last year of the study, 29% of the 558 cocaine-related admissions were psychiatric admissions, and most (58%) were for treatment of depressive illness (34 patients were admitted for attempted suicide).
Adult↗
The effect of hypoxia on performance during 30 s or 45 s of supramaximal exercise.
The purpose of this study was to evaluate the effect of hypoxia (10.8 +/- 0.6% oxygen) on performance of 30 s and 45 s of supramaximal dynamic exercise. Twelve males were randomly allocated to perform either a 30 s or 45 s Wingate test (WT) on two occasions (hypoxia and room air) with a minimum of 1 week between tests. After a 5-min warm-up at 120 W subjects breathed the appropriate gas mixture from a wet spirometer during a 5-min rest period. Resting blood oxygen saturation was monitored with an ear oximeter and averaged 97.8 +/- 1.5% and 83.2 +/- 1.9% for the air (normoxic) and hypoxic conditions, respectively, immediately prior to the WT. Following all WT trials, subjects breathed room air for a 10-min passive recovery period. Muscle biopsies from the vastus lateralis were taken prior to and immediately following WT. Arterialized blood samples, for lactate and blood gases, were taken before and after both the warm-up and the performance of WT, and throughout the recovery period. Open-circuit spirometry was used to calculate the total oxygen consumption (VO2), carbon dioxide production and expired ventilation during WT. Hypoxia did not impair the performance of the 30-s or 45-s WT. VO2 was reduced during the 45-s hypoxic WT (1.71 +/- 0.21 l) compared with the normoxic trial (2.16 +/- 0.26 l), but there was no change during the 30-s test (1.22 +/- 0.11 vs 1.04 +/- 0.17 l for the normoxic and hypoxic conditions, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Influence of cold exposure on plasma triglyceride clearance in humans.
Recent human studies have shown that cold exposure increases lipid oxidation, even when the oxidation of circulating free fatty acid (FFA) is markedly reduced by the ingestion of nicotinic acid, thus seriously questioning the importance of FFA for lipid oxidation in the cold-exposed humans. It was therefore hypothesized that similarly to prolonged exercise, fatty acids from plasma triglycerides (TG) are important energy substrates for oxidation during prolonged cold exposure in man. The goal of this study was to determine the influence of cold exposure on an index of plasma TG utilization, the intravenous fat tolerance test (IVFTT). To evaluate the possibility of a delayed increase in fat tolerance, a second cold exposure and an IVFTT were also performed 24 hours after the first cold exposure. Seven healthy males (fasting, seminude) were subjected to an IVFTT (1 mL/kg 10% Intralipid) on three occasions while resting for 160 minutes: (1) at 29 degrees C, (2) in the cold (10 degrees C, 1 m/s wind), and (3) at 10 degrees C 24 hours after the first cold test. One week separated the warm test from the cold tests. Cold exposure reduced mean body temperature by 3.4 +/- 0.1 degree C and increased energy expenditure 2.5 times in comparison to warm values (P less than .01). It also increased fat oxidation by 70% (P less than .05) and plasma glycerol levels (P less than .05), but did not alter fat tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Skeletal muscle fiber type, fiber size, and capillary supply in elite soccer players.
This study determined the fiber type composition, the fiber size, and the capillary characteristics of the vastus lateralis muscle in 11 young, elite, male soccer players and 8 sedentary male, age-matched controls. There were no significant differences (P less than 0.05) in the fiber type percentages and fiber diameter between the soccer players and controls; however, all fiber types tended to be larger in the soccer players. The soccer players possessed a greater capillary supply; this was characterized by a significantly greater mean number of capillaries surrounding each fiber (5.7 +/- 0.9 vs. 4.9 +/- 0.4), a significantly larger capillary density (282.7 +/- 42.0 vs. 220.8 +/- 38.1), and a significantly higher capillary to fiber ratio (2.2 +/- 0.6 vs 1.7 +/- 0.1). The results indicate that soccer may be an appropriate stimulus for simultaneous adaptation to endurance and high intensity exercise.
Adult↗
A risk of malignancy index incorporating CA 125, ultrasound and menopausal status for the accurate preoperative diagnosis of ovarian cancer.
Age, ultrasound score, menopausal status, a clinical impression score and serum CA 125 level were assessed to see how they could best distinguish between patients with benign (n = 101) and malignant (n = 42) pelvic masses. Each criteria used alone provided statistically significant discrimination. The most useful individual criteria were a serum CA 125 level of 30 U/ml (sensitivity 81%, specificity 75%) and an ultrasound score of 2 (sensitivity 71%, specificity 83%). Three criteria could be combined in a risk of malignancy index (RMI) which is simply calculated using the product of the serum CA 125 level (U/ml), the ultrasound scan result (expressed as a score of 0, 1 or 3) and the menopausal status (1 if premenopausal and 3 if postmenopausal). This index was statistically virtually as effective a discriminant between cancer and benign lesions as more formal methods. Using an RMI cut-off level of 200, the sensitivity was 85% and the specificity was 97%. Patients with an RMI score of greater than 200 had, on average, 42 times the background risk of cancer and those with a lower value 0.15 times the background risk.
Adult↗
Increase in the proportion of fast-twitch muscle fibres by sprint training in males.
Fifteen male physical education students were studied. The subjects trained for 4-6 weeks, 2-3 days per week, on a mechanically braked bicycle ergometer. A training session consisted of repeated 30-s 'all-out' sprints on a Wingate bicycle ergometer, on which the brake band of the flywheel was loaded with 75 g kg-1 body wt, with rest periods of 15-20 min between consecutive sprints. Thigh muscle biopsies were taken before and after the training period and were analysed for fibre types using a myofibrillar ATPase stain. The proportion of type I fibres decreased from 57 to 48% (P less than 0.05) and type IIA fibres increased from 32 to 38% (P less than 0.05). This study indicates that it is possible to achieve a fibre type transformation with high-intensity training. The effect of two-legged 'sprint' training on muscle fibre type composition may be related to a changed pattern of muscle fibre activation (e.g. an increased stimulation frequency). A change in fibre activation frequency may induce an increased synthesis of type II fibre myosin (fast myosin). Hormonal influences such as enhanced adrenergic stimulation of the muscle fibres cannot be excluded as a contributing factor, however.
Adenosine Triphosphatases↗