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Biomedical subjects

I Jacobs

Publications and source records attributed to I Jacobs.

At least 127 records · Page 7Linked to original sources
PubMed1988

Acute altitude exposure and altered acid-base states. I. Effects on the exercise ventilation and blood lactate responses.

This study examined the influence of acute altitude (AL) exposure alone or in combination with metabolic acid-base manipulations on the exercise ventilatory and blood lactate responses. Four subjects performed a 4 min, 30 W incremental test to exhaustion at ground level (GL) and a 4 min, 20 W incremental test during three acute exposures to a simulated altitude of 4200 m; (i) normal (NAL), (ii) following 0.2 g.kg-1 ingestion of sodium bicarbonate (BAL), and (iii) following 0.5 g.day-1 ingestion of acetazolamide for 2 days prior to exposure (AAL). VE.VO2-1 increased progressively throughout the incremental tests at AL and the minimum value was not related to a change in the blood lactate response. In contrast, the VE.VCO2-1 decreased initially to reach a minimum value at the same power output for each altitude trial and was related to a lactate threshold defined by a log-log transformation (r = 0.78). This transformation of the blood lactate data was not influenced by the altered acid-base states. The relative exercise intensity corresponding to both a delta lactate of 1 mM and an absolute lactate of 4 mM was significantly increased during the AAL (79.9 +/- 12.9 and 93.9 +/- 13.7% VO2max, respectively) compared with NAL (59.1 +/- 5.5 and 78.0 +/- 5.8% VO2max, respectively). These data suggest that strong relationships exist between the ventilatory and blood lactate response during AL exposure and altered acid-base states. Further, it is concluded that, unless the acid-base status is known, the use of an absolute or delta lactate value to compare submaximal exercise should be interpreted with caution.

Acetazolamide↗
PubMed1988

Acute altitude exposure and altered acid-base states. II. Effects on exercise performance and muscle and blood lactate.

This study examined the influence of the respiratory alkalosis of acute altitude (AL) exposure alone or in combination with metabolic acid-base manipulations on exercise performance and muscle and blood lactate accumulation. Four subjects exercised for 10 min at 50% and 75% and to exhaustion at 90% of ground level (GL) VO2max, and at the same relative exercise intensities during three exposures to a simulated altitude of 4200 m; (i) normal (NAL), (ii) following 0.2 g.kg-1 ingestion of sodium bicarbonate (BAL), and (iii) following 0.5 g.day-1 ingestion of acetazolamide for 2 days prior to exposure (AAL). Muscle and blood lactate values were similar throughout exercise for GL and NAL. Although muscle lactates were similar among AL conditions blood lactate was reduced for AAL and increased following exhaustive exercise for BAL compared with NAL. Time to exhaustion at 90% VO2max was increased for NAL (10.4 +/- 1.6 min) compared with GL (7.1 +/- 0.2 min). Performance time was decreased for AAL (6.3 +/- 2.8 min) compared with NAL and BAL (12.4 +/- 4.2 min). These data suggest that the induced respiratory alkalosis of acute AL exposure may enhance exercise performance at high relative intensities. In contrast, the ingestion of acetazolamide before AL exposure would have detrimental effects on performance. The mechanism responsible for these changes may relate to the possible influence of altered extracellular acid-base states on intracellular hydrogen ion accumulation and lactate release.

Acid-Base Equilibrium↗
PubMed1988

Comparison of isokinetic and isoinertial lifting tests as predictors of maximal lifting capacity.

This study compared the relationship between isokinetic lifting test (ILT) performance and a maximal operational lifting test (OLT) with that between an isoinertial progressive lifting test (PLT) and OLT. Fifty subjects performed the ILT, PLT and OLT after familiarization trials. OLT was defined as the weight of the heaviest crate that could be lifted to 1.34 m with a progressive, incremental test. ILT performance was the force generated during a single maximal simulated lift on an isokinetic dynamometer. PLT performance was the maximal weight lifted to 1.52 m with a progressive, incremental protocol on a weight stack. OLT was highly correlated with ILT (r = 0.96) and PLT (r = 0.97); the standard error was similar for both linear regression equations. The results demonstrate that a single maximal voluntary lift on an isokinetic dynamometer is as good a predictor of OLT as in the PLT presently used in military recruit centers.

Female↗
PubMed1988

Two fetal antigens (FA-1 and FA-2) and endometrial proteins (PP12 and PP14) isolated from amniotic fluid; preliminary observations in fetal and maternal tissues.

Rabbit antihuman antibodies were derived by the injection of fractions of second trimester amniotic fluid known to contain proteins of endometrial/decidual origin. Using standard separation and absorption procedures, two antibody preparations were generated which demonstrated specificities against two and three proteins, respectively, in line immunoelectrophoresis and crossed immunoelectrophoresis. Analysis against proteins of fetal, maternal, endometrial and placental origin revealed that the bispecific antiserum reacted only with placental protein 14 (PP14; also known as progestagen-dependent endometrial protein, PEP) and one other hitherto undescribed antigen referred to as Fetal Antigen 1 (FA-1) molecular mass 60 kDa; electrophoretic mobility: slow; alpha 1-alpha 2; fast, albumin. The trispecific antiserum demonstrated specifities against placental protein 12 (PP12), alpha-fetoprotein (AFP) and another previously undescribed antigen referred to as Fetal Antigen 2 (FA-2) molecular mass 35 and 140 kDa; electrophoretic mobility: albumin. Following purification, monospecific antisera against each of these proteins (with the exception of AFP) were derived in new rabbits. Maternal and fetal blood, amniotic fluid and aqueous extracts from endometrial/decidual and placental tissues were analysed in rocket immunoelectrophoresis using these antisera to examine the distribution in these tissues. The analyses demonstrated a pattern of distribution typical for proteins of endometrial/decidual origin in these compartments in the case of PP12 and PP14, but suggested that the primary source of origin of FA-1 and FA-2 may be the fetus.

Amniotic Fluid↗
PubMed1988

Muscle glycogen utilization during shivering thermogenesis in humans.

The purpose of the present study was to clarify the importance of skeletal muscle glycogen as a fuel for shivering thermogenesis in humans during cold-water immersion. Fourteen seminude subjects were immersed to the shoulders in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Biopsies from the vastus lateralis muscle and venous blood samples were obtained before and immediately after the immersion. Metabolic rate increased during the immersion to 3.5 +/- 0.3 (SE) times resting values, whereas Tre decreased by 0.9 degrees C to approximately 35.8 degrees C at the end of the immersion. Intramuscular glycogen concentration in the vastus lateralis decreased from 410 +/- 15 to 332 +/- 18 mmol glucose/kg dry muscle, with each subject showing a decrease (P less than 0.001). Plasma volume decreased (P less than 0.001) markedly during the immersion (-24 +/- 1%). After correcting for this decrease, blood lactate and plasma glycerol levels increased by 60 (P less than 0.05) and 38% (P less than 0.01), respectively, whereas plasma glucose levels were reduced by 20% after the immersion (P less than 0.001). The mean expiratory exchange ratio showed a biphasic pattern, increasing initially during the first 30 min of the immersion from 0.80 +/- 0.06 to 0.85 +/- 0.05 (P less than 0.01) and decreasing thereafter toward basal values. The results demonstrate clearly that intramuscular glycogen reserves are used as a metabolic substrate to fuel intensive thermogenic shivering activity of human skeletal muscle.

Adult↗
PubMed1988

Screening for ovarian cancer.

Whilst the majority of patients with ovarian cancer present with advanced stage disease and have a poor prognosis, the outlook for women with stage I disease is relatively good. An effective screening test for early stage ovarian cancer may therefore result in a significant improvement in ovarian cancer statistics. Extremely high specificity is an essential requirement of any potential screening test in view of the need for surgical investigation of women with a positive test result. No single test has yet demonstrated sufficient specificity when used alone to screen apparently healthy postmenopausal women. A multimodal approach incorporating serum CA-125 measurement, pelvic examination and real time ultrasonography has achieved high levels of specificity. The sensitivity of this screening programme for early stage ovarian cancer is currently under investigation.

Biomarkers, Tumor↗
PubMed1987

Potential nephrotoxic effects of exposure to silver.

A cross sectional study was conducted on workers engaged in manufacturing precious metal powder. Of the 27 workers, 96% had raised urine silver concentrations (range 0.5-52.0 micrograms/l, mean 11.3 micrograms/l) and 92% had raised blood silver concentrations (range 0.05-6.2 micrograms/100 ml, mean 1.0 microgram/100 ml). Nineteen per cent also had raised urine cadmium concentrations (range 1.9-76.0 micrograms/l, mean 11.8 micrograms/l). Most workers had symptoms of respiratory irritation and nose bleeds were reported in eight (30%) of the 27 workers. Deposition of silver in the cornea of the eye was detected in five of eight (63%) of the long term workers. Although not statistically significant, corneal deposition was associated with complaints of decreased night vision. The urinary enzyme N-acetyl-B-D glucosaminidase (NAG) was significantly raised in four individuals and was correlated with blood silver concentrations and age. In addition, the group's average NAG concentration was significantly higher than that found in a control population. No association between age and urinary NAG was found in the control group. Estimated creatinine clearance was also significantly lower in the group exposed to silver than in the control group. Kidney function appears to have been adversely affected by exposures at work but because of the exposure to cadmium the role of silver in causing the decrement in kidney function could not be definitely determined.

Acetylglucosaminidase↗
PubMed1987

Sprint training effects on muscle myoglobin, enzymes, fiber types, and blood lactate.

The purpose of this study was to determine if changes in intra-muscular myoglobin concentration accompany histochemical and enzymatic adaptations to supra-maximal exercise training. Subjects were assigned to either a training group (N = 11), who trained 2 to 3 times weekly for 6 wk, or a control group (N = 6). Training progressed from two 15-s and two 30-s "all-out" sprints on a cycle ergometer during week 1 to six 15-s and six 30-s bouts per session during week 6. The Wingate test was performed before and after the 6 wk, but performance variables were not changed in either group. In the training group, peak lactate after the Wingate test was significantly higher after training. No significant changes in enzyme activities, myoglobin concentration, or fiber-type frequency were observed in the control group. In contrast, in the training group, the percent fast twitch oxidative fibers increased, myoglobin decreased, and both citrate synthase and phosphofructokinase activities increased (P less than 0.05). The results suggest that muscle myoglobin concentration is not increased by 6 wk of supra-maximal exercise training and that such training induces cellular adaptations without accompanying performance changes. Alternatively, the Wingate test is not a sensitive test of adaptations to the training.

Adult↗
PubMed1987

Prophylactic oophorectomy.

There are no generally accepted criteria for the removal or conservation of the apparently normal ovary during surgery for other conditions. In this article the benefits and disadvantages of prophylactic oophorectomy are reviewed and a schema for clinical practice is suggested.

Female↗
PubMed1987

Effects of hydraulic resistance circuit training on physical fitness components of potential relevance to +Gz tolerance.

Recent studies carried out in the United States and Sweden have demonstrated that strength training can improve +Gz acceleration tolerance. Based on these findings, the Canadian Forces have introduced a training program for aircrew of high performance aircraft. This report describes the changes in physical fitness components considered relevant to +Gz tolerance after 12 weeks of training with this program. Prior to beginning training, 45 military personnel were tested, but only 20 completed a minimum of 24 training sessions. The following variables were measured in these 20 subjects before and after training: maximal strength of several large muscle groups during isokinetic contractions, maximal aerobic power and an endurance fitness index, maximal anaerobic power, anthropometric characteristics, and maximal expiratory pressure generated during exhalation. Training involved hydraulic resistance circuit training 2-4 times/week. The circuit consisted of 3 consecutive sets at each of 8 stations using Hydra-Gym equipment. The exercise:rest ratio was 20:40 s for the initial 4 training weeks and was then changed to 30:50. After training the changes in anthropometric measurements suggested that lean body mass was increased. Small, but significant, increases were also measured in muscle strength during bench press, biceps curls, squats, knee extension, and knee flexion. Neither maximal anaerobic power (i.e. muscular endurance) nor maximal expiratory pressure were changed after the training. Indices of endurance fitness were also increased in the present study. The relatively small increases in strength are probably due to the design of the exercise:rest ratio which resulted in improved strength and aerobic fitness.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Electro-mechanical response times and rate of force development in males and females.

Muscle force development is influenced by both central (pre-motor end plate) and peripheral (post-motor end plate) components. Conflicting results are available concerning gender-related differences in the central component. This study compared males and females with regard to the following electro-mechanical response variables: total reaction time, pre-motor time, electro-mechanical delay, and the rate of force development during a maximal voluntary isometric contraction (MVC) of the elbow flexors. Forty-six males and 40 females performed MVCs against a bar attached to a force transducer. Subjects were instructed to attempt to flex the elbow with maximal force as rapidly as possible after perceiving a visual stimulus. Surface electromyographic activity was recorded from the biceps brachii and was sampled simultaneously with the force transducer data at 2 kHz and stored digitally. For data analyses the subjects were separated into four groups based on the force generated during the MVC: weak females, weak males, strong females, and strong males. Neither total reaction time nor pre-motor time was significantly different across groups. The electro-mechanical delay for both male groups was significantly shorter than for both female groups. Electro-mechanical delay was weakly, but significantly, correlated with rate of force development and maximum force. During a single MVC the times required to attain 25, 50, 75, and 100% MVC were similar in all groups. The results suggest that at least part of the gender difference in maximum strength may be due to differences in electro-mechanical response times.

Adult↗
PubMed1985

Levobunolol vs timolol for open-angle glaucoma and ocular hypertension.

A group of 162 patients with chronic open-angle glaucoma or ocular hypertension were treated twice daily for up to 15 months with one of the following topical ophthalmic solutions: 0.5% levobunolol, 1% levobunolol, or 0.5% timolol. Overall mean reductions in intraocular pressure were 8 mm Hg for patients receiving 0.5% levobunolol or timolol and 8.2 mm Hg for patients receiving 1% levobunolol. There were no significant differences between levobunolol and timolol in mean reductions in intraocular pressure, percent of patients with adequately controlled intraocular pressure, or life-table estimates of the probability of successful treatment.

Clinical Trials as Topic↗
PubMed1985

The effects of inspiratory resistive training on respiratory muscle function in patients with muscular dystrophy.

The effects of inspiratory resistive training on respiratory muscle function was evaluated in 11 patients with Duchenne, limb-girdle, and facio-scapulo-humeral (FSH) type muscular dystrophy. Muscle training consisted of breathing against an inspiratory resistance for two 15-minute sessions each day while at home. Following 6 weeks of training, there were significant increases in the maximum resistance that could be tolerated for at least 5 minutes (P < 0.01) and also in the maximum duration that ventilations equal to 30%, 50%, 70%, and 90% of the maximum voluntary ventilation could be sustained (P < 0.05). In six patients who trained for an additional 6-week period, respiratory muscle endurance increased even further. The degree of improvement in respiratory muscle endurance was positively correlated with baseline vital capacity (r = 0.84, P < 0.05) and maximal inspiratory pressure (r = 0.76, P < 0.05). Spirometry, functional residual capacity, and maximal inspiratory and expiratory pressures were not affected by training. We conclude that inspiratory resistive training improves respiratory muscle endurance in muscular dystrophy patients. Improvement in respiratory muscle function may serve to delay the onset of respiratory complications in patients with muscular dystrophy.

Adolescent↗
PubMed1985

Muscle glycogen depletion during exercise at 9 degrees C and 21 degrees C.

This study compared glycogen depletion in active skeletal muscle after light and moderate exercise in both cold and comfortable ambient conditions. Twelve male subjects (Ss) were divided into two groups equally matched for the submaximal exercise intensity corresponding to a blood lactate concentration of 4 mM (W4) during cycle exercise. On two separate days Ss rested for 30 min at ambient temperatures of either 9 degrees C or 21 degrees C, with the order of temperature exposure being counter-balanced among Ss. Following rest a tissue specimen was obtained from the m. vastus lateralis with the needle biopsy technique. Six Ss then exercised on a cycle ergometer for 30 min at 30% W4 (range = 50 - 65 W) while the remaining group exercised at 60% W4 (range = 85 - 120 W). Another biopsy was taken immediately after exercise and both samples were assayed for glycogen content. Identical procedures were repeated for the second environmental exposure. No significant glycogen depletion was observed in the Ss exercising at 30% W4 in 21 degrees C, but a 23% decrease (p = 0.04) was observed when the same exercise was performed at 9 degrees C. A 22% decrease (p = 0.002) in glycogen occurred in the 60% W4 group at 21 degrees C, which was not significantly different from that observed during the same exercise at 9 degrees C. The results suggest that muscle substrate utilization is increased during light exercise in a cold environment as compared to similar exercise at a comfortable temperature, probably due to shivering thermogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Blood lactate vs. exhaustive exercise to evaluate aerobic fitness.

This study compared the predictive power of a lactate-related index determined during submaximal cycle exercise to that of an exhaustive cycle ergometer test for evaluating the endurance exercise capacity of soldiers. The subjects (n = 48 males) performed a continuous exercise test to voluntary exhaustion on the cycle ergometer. Power output (PO) increased by 50 W steps each fourth min, with determinations of heart rate (HR), RPE and blood lactate concentrations (HLa) just prior to each PO increase. The PO at a 4 mmol L(-1) HLa concentration (WOBLA) was interpolated; based on the time to exhaustion the maximal PO that could be maintained for 6 min (Wmax6) was calculated from previously documented formulae. Subjects were timed during a 3000 m cross-country run. Both the cycle test and the run were performed again 3 months later, as was an additional 3000 m run with full military equipment weighing about 21 kg. All 3000 m times were significantly correlated (p less than 0.05) with both Wmax6 and WOBLA; similar predictive power was demonstrated for both Wmax6 and WOBLA, suggesting that accuracy in evaluation would not be sacrificed by substituting the submaximal for the exhaustive exercise test. HR and RPE-related indices showed markedly lower predictive power. The results extend the previously documented relationship between HLa during treadmill ergometry and running performance to include the use of cycle ergometry for the evaluation of running performance. The results also proved applicable to running performance while load carrying.

Adult↗