A 31P-NMR study of tissue respiration in working dog muscle during reduced O2 delivery conditions.

To investigate the role of tissue oxygenation as one of the control factors regulating tissue respiration, 31P-nuclear magnetic resonance spectroscopy (31P-NMR) was used to estimate muscle metabolites in isolated working muscle during varied tissue oxygenation conditions. O2 delivery (muscle blood flow x arterial O2 content) was varied to isolated in situ working dog gastrocnemius (n = 6) by decreases in arterial PO2 (hypoxemia; H) and by decreases in muscle blood flow (ischemia; I). O2 uptake (VO2) was measured at rest and during work at two or three stimulation intensities (isometric twitch contractions at 3, 5, and occasionally 7 Hz) during three separate conditions: normal O2 delivery (C) and reduced O2 delivery during H and I, with blood flow controlled by pump perfusion. Biochemical metabolites were measured during the last 2 min of each 3-min work period by use of 31P-NMR, and arterial and venous blood samples were drawn and muscle blood flow measured during the last 30 s of each work period. Muscle [ATP] did not fall below resting values at any work intensity, even during O2-limited highly fatiguing work, and was never different among the three conditions. Muscle O2 delivery and VO2 were significantly less (P < 0.05) at the highest work intensities for both I and H than for C but were not different between H and I. As VO2 increased with stimulation intensity, a larger change in any of the proposed regulators of tissue respiration (ADP, P(i), ATP/ADP.P(i), and phosphocreatine) was required during H and I than during C to elicit a given VO2, but requirements were similar for H and I.(ABSTRACT TRUNCATED AT 250 WORDS)     

Total CA activity in isolated perfused guinea pig lung by 18O-exchange method

The rate of exchange of 18O between alveolar CO2 and lung water was measured in isolated perfused guinea pig lungs to quantify carbonic anhydrase (CA) activity. The average lung CA activity, with a reaction velocity constant of 5.32 +/- 2.2 s-1, is sufficient to accelerate CO2 reactions in lung water by two orders of magnitude over the uncatalyzed rate at 22 degrees C and a PCO2 of 40 Torr. Three sulfonamide inhibitors of CA with different human erythrocyte membrane permeabilities were used to determine the availability of the enzyme to the perfusate. Ethoxzolamide, the most permeable at 0.1 microM (100 times its inhibition constant, of Ki) inhibited 85% of enzyme activity after exposure of the lung for 3 min and 94% of enzyme activity after 30 min, whereas 1.25 microM (320 times its Ki) acetazolamide (1/165 as permeable) only inhibited CA 28% at 3 min and 75% at 30 min. Benzolamide (less than 1/1,000 as permeable) at 4 microM (1,000 times its Ki) inhibited only approximately 17% of control CA activity by 5 min and 48% by 30 min after the start of perfusion. These data indicate the CA available to pulmonary capillary plasma is approximately 10% of the total lung CA activity, in agreement with published measurements on the homogenized lung.     

Time-resolved spectroscopy of hemoglobin and myoglobin in resting and ischemic muscle

Difficulties of quantitation of hemoglobin/myoglobin absorption changes in muscle have led to the development of a new approach using short pulses of light. This method uses input light pulses sufficiently short so that the time course of travel of light through the brain can be precisely measured. The time of arrival of light at the detector gives the optical path length, given the velocity of light in tissues. The intensity profile of photon migration in tissues permits determination of the path length that the exiting photons have traveled and the concentration change of the pigments. A cavity-dumped liquid dye laser illuminates the tissue with 130-ps pulses detected as 600-ps duration at a half height at 3.0-cm distance from the input point. The decay of intensity from the 50% point onward to 0.1% follows a logarithmic function of slope mu which is attributed to the total absorption coefficient of the tissue. Increments of mu due to deoxyhemoglobin absorption at 760 and 630 nm are used to calculate the concentration change. This permits the calculation of the path length for continuous light measurements of 2 cm for a particular geometry. Variation of the wavelength of the laser affords determination of a spectrum of changes in the tissue.     

Discrepancy between cardiorespiratory system and skeletal muscle in elite cyclists after hypoxic training

BACKGROUND: The purpose of this study was to determine the effects of hypoxic training on the cardiorespiratory system and skeletal muscle among well-trained endurance athletes in a randomized cross-over design. METHODS: Eight junior national level competitive cyclists were separated into two groups; Group A trained under normoxic condition (21% O2) for 2 hours/day, 3 days/week for 3 weeks while Group B used the same training protocol under hypoxic condition (15% O2). After 3 weeks of each initial training condition, five weeks of self-training under usual field conditions intervened before the training condition was switched from NT to HT in Group A, from HT to NT in Group B. The subjects were tested at sea level before and after each training period. O2 uptake (O2), blood samples, and muscle deoxygenation were measured during bicycle exercise test. RESULTS AND DISCUSSION: No changes in maximal workload, arterial O2 content, O2 at lactate threshold and O2max were observed before or after each training period. In contrast, deoxygenation change during submaximal exercise in the vastus lateralis was significantly higher at HT than NT (p < 0.01). In addition, half time of oxygenation recovery was significantly faster after HT (13.2 PlusMinus; 2.6 sec) than NT (18.8 PlusMinus; 2.7 sec) (p < 0.001). CONCLUSIONS: Three weeks of HT may not give an additional performance benefit at sea level for elite competitive cyclists, even though HT may induce some physiological adaptations on muscle tissue level.     

Quantitation of time- and frequency-resolved optical spectra for the determination of tissue oxygenation.

The recent development of near-infrared time- and frequency-resolved tissue spectroscopy techniques to probe tissue oxygenation and tissue oxygenation kinetics has led to the need for further quantitation of spectroscopic signals. In this paper, we briefly review the theory of light transport in strongly scattering media as monitored in the time and frequency domains, and use this theory to develop algorithms for quantitation of hemoglobin saturation from the photon decay rate (delta log R/delta t) obtained using time-resolved spectroscopy, and from the phase-shift (theta) obtained from frequency-resolved, phase-modulated spectroscopy. To test the relationship of these optical parameters, we studied the behavior of delta log R/delta t and theta as a function of oxygenation in model systems which mimicked the optical properties of tissue. Our results show that deoxygenation at varying hemoglobin concentrations can be monitored with the change in the photon decay kinetics, delta delta log R/delta t in the time-resolved measurements, and with the change in phase-shift, delta theta, in the frequency-resolved technique. Optical spectra of the adult human brain obtained with these two techniques show similar characteristics identified from the model systems.     

Progesterone receptor in human endometrium of leiomyoma uteri

This study was designed to examine whether 8S protein as progesterone receptor exists in the human endometrium which has been primed with estrogen. The kinetic study showed that 8S-progesterone binding was specific with Kd of 2.0 X 10(-9) M. 5S-progesterone binding was inhibited competitively by cortisol. The study of ligand specificity also showed that progesterone and its related steroids had much stronger affinity for 8S component than for 5S component. Therefore, 5S protein may be CBG. Progesterone-8S protein binding was easily dissociated during the 5-20% sucrose gradient centrifugation, but such a protein from which progesterone had been dissociated could be sedimented at 8S region. Glycerol could stabilize progesterone-8S protein binding. These results indicate the existence of 8S protein as a progesterone receptor under the low salt medium in the estrogen primed human endometrium.     

A novel method to measure regional muscle blood flow continuously using NIRS kinetics information

Background

This article introduces a novel method to continuously monitor regional muscle blood flow by using Near Infrared Spectroscopy (NIRS). We demonstrate the feasibility of the new method in two ways: (1) by applying this new method of determining blood flow to experimental NIRS data during exercise and ischemia; and, (2) by simulating muscle oxygenation and blood flow values using these newly developed equations during recovery from exercise and ischemia.

Methods

Deoxy (Hb) and oxyhemoglobin (HbO₂), located in the blood ofthe skeletal muscle, carry two internal relationships between blood flow and oxygen consumption. One is a mass transfer principle and the other describes a relationship between oxygen consumption and Hb kinetics in a two-compartment model. To monitor blood flow continuously, we transfer these two relationships into two equations and calculate the blood flow with the differential information of HbO₂ and Hb. In addition, these equations are used to simulate the relationship between blood flow and reoxygenation kinetics after cuff ischemia and a light exercise. Nine healthy subjects volunteered for the cuff ischemia, light arm exercise and arm exercise with cuff ischemia for the experimental study.

Results

Analysis of experimental data of both cuff ischemia and light exercise using the new equations show greater blood flow (four to six times more than resting values) during recovery, agreeing with previous findings. Further, the simulation and experimental studies of cuff ischemia and light exercise agree with each other.

Conclusion

We demonstrate the accuracy of this new method by showing that the blood flow obtained from the method agrees with previous data as well as with simulated data. We conclude that this novel continuous blood flow monitoring method can provide blood flow information non-invasively with NIRS.

     

Effects of long-term treatment with 17 β-estradiol and medroxyprogesterone acetate on water maze performance in middle aged female rats

Although previous research has indicated that hormone replacement therapy benefits memory in menopausal women, several recent studies have shown either detrimental or no effects of treatment. These inconsistencies emphasize the need to evaluate the role of ovarian hormones in protecting against age-related cognitive decline in an animal model. The present study investigated the effects of long-term hormone treatment during aging on the Morris water maze. Female Long Evans hooded rats were ovariectomized at middle age (12-13 months) and were immediately placed in one of five groups: no replacement, chronic 17 β-estradiol only, chronic 17 β-estradiol and progesterone, chronic 17 β-estradiol and medroxyprogesterone acetate (MPA), or cyclic 17 β-estradiol only. 17 β-estradiol was administered in the drinking water in either a chronic or cyclic (3 out of 4 days) fashion. Progesterone and MPA were administered via subcutaneous pellets. Following 6 months of hormone treatment, animals were tested on the Morris water maze. Animals performed four trials a day for 4 days and after the final day of testing a subset of animals completed a probe trial. Across 4 days of testing, rats receiving 17 β-estradiol in combination with MPA performed significantly worse than all other groups receiving hormone replacement. In addition on the last day of testing, chronic 17 β-estradiol administration was more beneficial than cyclic administration and no replacement. Thus compared to other hormone-treated groups, long-term 17 β-estradiol treatment in combination with MPA results in impaired performance on the spatial Morris water maze.     

Evaluation of physiological responses during recovery following three resistance exercise programs

The present study was conducted to examine (a) whether there is an association between maximal oxygen uptake (Vo(2)max) and reduction in postexercise heart rate (HR) and blood lactate concentrations ([La]) following resistance exercise and (b) how intensity and Volume of resistance exercise affect postexercise Vo(2). Eleven regularly weight-trained males (20.8 +/- 1.3 years; 96.2 +/- 14.4 kg, 182.4 +/- 7.3 cm) underwent 4 sets of squat exercise on 3 separate occasions that differed in both exercise intensity and volume. During each testing session, subjects performed either 15 repetitions.set(-1) at 60% of 1 repetition maximum (1RM) (L), 10 repetitions.set(-1) at 75% of 1RM (M), or 4 repetitions.set(-1) at 90% of 1RM (H). During each exercise, Vo(2) and HR were measured before (PRE), immediately post (IP), and at 10 (10P), 20 (20P) 30 (30P), and 40 (40P) minutes postexercise. The [La] was measured at PRE, IP, 20P, and 40P. Decrease in HR (DeltaHR) was determined by subtracting HR at 10P from that at IP, whereas decrease in [La] (Delta[La]) was computed by subtracting [La] at 20P from that at IP. A significant correlation (p < 0.05) was found between Vo(2)max and DeltaHR in all exercise conditions. A significant correlation (p < 0.05) was also found between Vo(2)max and Delta[La] in L and M but not in H. The Vo(2) was higher (p < 0.05) during M than H at IP and 10P, while no difference was seen between L and M and between L and H. These results indicate that those with greater aerobic capacity tend to have a greater reduction in HR and [La] during recovery from resistance exercise. In addition, an exercise routine performed at low to moderate intensity coupled with a moderate to high exercise volume is most effective in maximizing caloric expenditure following resistance exercise.     

The detection of cytochrome oxidase heme iron and copper absorption in the blood-perfused and blood-free brain in normoxia and hypoxia.

The resolution of cytochrome and hemoglobin changes in in vivo rat and cat brains has required studies over wide wavelength ranges (580-1100 nm) with a novel spectroscopic technique using blood-free and blood-perfused brains. Tissue oxygen was varied from physiological levels to 0 and hematocrits were varied from normal to less than 1%. The experimental results were subjected to a multicomponent analysis using the Beer-Lambert law. At normal hematocrits, the oxygen saturation of hemoglobin in the brain was found to be 30-50% in rats and cats, indicating that the optical method responded primarily to the saturation of the venous ends of the capillary beds. With low hematocrits, both brains showed the absorption band of reduced cytochrome c, the iron component of cytochrome aa3, plus the absorption band of the oxidized copper component. In cat brains, the background absorption changed at all wavelengths. Thus, no isosbestic points were observed in the spectra. In rat brains, however, they were readily observed. The "overtones" of water absorption in the NIR region were found to be significant in the difference spectra of the cat brain, but not in the rat brain. Parallel absorbance changes in the heme and copper components of cytochrome aa3 were obtained in rat and cat brains during the normoxic-hypoxic transition. The ratio of the iron absorbance at 605 nm to the copper absorbance at 830 nm is much smaller in both brains than the in vitro value due to the shorter path length of photon migration at the shorter wavelengths.(ABSTRACT TRUNCATED AT 250 WORDS)