Six elite, male, cross-country runners were assessed on a motorized treadmill for aerobic endurance capacity using blood lactate (HLa) recovery ability ($\Delta$La) in three square-wave endurance exercise tests (SWEET) with repeat intervals below (S1), at (S2), and above (S3) threshold (OBLA). Each SWEET was composed of 6 possible repeat intervals (OVERs) followed by active rest intervals (UNDERs) of the same distance where $\Delta$La = (HLa) $\sb{\rm OVER}$- (HLa) $\sb{\rm UNDER}$. S1 and S2 interval (HLa) values where stable whereas S3 interval (HLa) values drifted upwards over the 6 repeats. Interval HR values were rising slightly over the SWEET durations. Interval VO$\sb2$s were similar in value over the SWEET durations. $\Delta$La (mM) values were significantly increased (p 0.05) from 0.66 $\pm$ 0.06 for $\Delta$La$\sb{\rm S1}$, to 1.31 $\pm$ 0.45 for $\Delta$La$\sb{\rm S2}$, to a nearly significant increase (p = 0.06 for N = 6) to 1.58 $\pm$ 0.79 for $\Delta$La$\sb{\rm S3}$, $\Delta$La$\sb{\rm S1}$ and $\Delta$La$\sb{\rm S2}$ were 40% and 80% of $\Delta$La$\sb{\rm S3}$ values. Post hoc analysis revealed the source of statistical significance as all SWEET repeats except 1 and 6. Within SWEET repeat $\Delta$Las were not significantly different. Lactate recovery ability increases were attributed to either the increased utilization of La as a fuel during periods of increased metabolic rate or the augmented flow of La down concentration gradients from lactate producing space to lactate usage and storage space. Implications for runners were that excursions at or above threshold levels were compensated for by increased $\Delta$La, but that the number of repeat intervals possible during racing and or training may vary for individuals and should be considered.

In order to assess glucose dynamics and the pathways (direct and gluconeogenic) by which muscle and liver glycogen is synthesized during and following prolonged submaximal exercise, twelve-hour-fasted catheterized rats were infused intravenously with ($\sp3$H-6) -glucose (or ($\sp3$H-3) -glucose) and either (i) NaH$\sp $CO$\sb3,$ (ii) ($\sp $C-U) -lactate or (iii) ($\sp $C-1) -glucose (three gluconeogenic tracers) throughout two-hour basal, four-hour swim (or rest) and three-hour postexercise recovery periods. During recovery, rats were infused with either saline, lactic acid or glucose. Arterial blood samples were taken throughout the protocols. Liver and three muscles (soleus, white and red gastrocnemii) were excised and assessed for total and radiolabelled glycogen content. The results indicate that: (1) While plasma glucose concentrations are maintained during the prolonged swim owing to matched doubling of both glucose production (R$\sb{\rm a}$) and clearance (MCR), glucose increases during the recovery period as the fall in R$\sb{\rm a}$ lags behind that of MCR and the rate of gluconeogenesis remains elevated. (2) Despite increases in direct glycogenesis during prolonged swimming, glycogen is significantly depleted in white and red gastrocnemii. Glyconeogenesis contributes at least 20-25% to glycogen repletion during fasted recovery. The source of this gluconeogenic substrate appears to be lactate which is formed locally in the muscles (as traced by recycled $\sp $C-glucose). Although not required to elicit muscle gluconeogenic activity, high lactate levels enhance glyconeogenesis, especially in the postexercise period. (3) There is a high turnover of soleus glycogen at rest. The soleus does not respond to prolonged swimming but rather to the availability of substrate (glucose) to synthesize its glycogen almost entirely via the direct route. (4) Glyconeogenesis is the primary pathway of hepatic glycogen synthesis. While glucose infusion is the most potent stimulus of glycogenesis, the combined effects of lactate and exercise appear synergistic in the formation of liver glycogen.

The purpose of this study was to compare the heart rate (HR) and blood lactate (BLa) responses of elite male and female cross-country skiers. The testing consisted of a progressive incremental test on a sport-specific ski treadmill (ST) on Day 1 followed by dryland field tests using 2 training techniques, running with cross-country ski poles (RP) and freestyle rollerskiing (FR), on Days 2 and 3. The dryland field tests consisted of discontinuous bouts of exercise using 3 selected exercise intensities called Zone 1, Zone 2 and Zone 3. The Zones were intended to elicit steady-state responses corresponding to the dryland training intensities of the cross-country skiers. The immediate post-exercise HRs and the one minute post-exercise BLas from the 3 Zones and the 2 training techniques were compared with the HRs and BLas on the ST. The results suggest that there were no significant physiological differences between the dryland training techniques across the three Zones but that there were significant physiological differences when the laboratory responses were compared with the field responses. (Abstract shortened by UMI.)

Mononuclear phagocytes are one of the targets for HIV-1 infection. We wished to study the HIV receptor, CD4, on fresh blood monocytes, as well as a group of cell adhesion molecules (CD11/CD18) on cultured monocytes. The objectives were: (1) to determine the frequency and antigenic density of surface CD4 on blood monocytes, (2) to establish the effect of HIV infection on CD4 density on T cells and monocytes and (3) to determine the effect of growth factors on the expression of CD11/CD18 molecules on cultured monocytes. We found that all monocytes are CD4+ in normal donors and HIV infected patients. The relative concentration of monocytes was not affected in HIV infected patients in contrast to the decline in T cells. In HIV+ patients, the CD4 density on monocytes is increased (p 0.05) but is decreased on T cells (p 0.05). The lower CD4 antigenic density in T cells correlated with the decreased frequency of CD4+ T cells (p 0.03). (Abstract shortened by UMI.)

The purpose of this study was to determine the influence of muscle mass and exercise intensity on blood pressure response to isometric contraction. Twenty male subjects (mean age = 27 yrs) performed one-arm handgrip (HG), one-leg extension (LE) and combined one-arm handgrip plus one-leg extension (COMB) in a random order of exercise for one minute at 30% and 40% of maximal voluntary contraction (MVC). Blood pressure responses were significantly higher (p $$ HG and COMB $>$ LE at both 30% and 40% MVC. However, for each mode of static exercise the hemodynamic responses at 40% MVC were significantly higher than the hemodynamic responses at 30% MVC. There were no significant differences in blood pressure responses between HG and LE within each intensity, except for systolic blood pressure which was significantly greater at 40% MVC than at 30% MVC. Heart rate response increased progressively with increasing size of muscle mass, (COMB $>$ LE $>$ HG) at both intensities. Results indicate that the blood pressure response to static exercise can be attributed in part to the size of the muscle mass being recruited (i.e. COMB) within the same intensity of MVC, and in part to the relative intensity at which the muscle is being contracted. (Abstract shortened by UMI.)

Le but de cette recherche etait de verifier si une intensite d'exercice equivalente a 70% du MVO2 des sujets stimulerait l'axe hypothalamique-pituitaire-corticosurrenal. Il s'agissait aussi de determiner si le niveau d'entrai nement des sujets influencerait cette reponse et enfin d'etablir la relation entre la corticotrophine et le cortisol. Pour ce faire, 12 sujets entrai nes et 9 sujets non-entrai nes se sont exerces sur un tapis roulant a 70% de leur MVO2 pendant 20 minutes. Des prelevements sanguins ont ete effectues avant l'exercice, immediatement apres, 30 et 60 minutes apres celui-ci. Les resultats ne demontrent aucune difference significative entre les groupes. Toutefois, l'ACTH augmenta de 97% apres l'exercice pour descendre sous les valeurs de repos 60 minutes apres celui-ci (p 0.05). Aucune augmentation significative concomittante (12%) dans les niveaux de cortisol n'a ete observee. Toutefois, la tendance indique que l'ACTH et le cortisol se sont accrus dans des proportions superieures chez les sujets non-entrai nes et que l'augmentation du taux catabolique chez le groupe entrai ne serait responsable de l'absence de cortisol dans le plasma. Enfin, des correlations positives ont ete etablies entre l'ACTH et le cortisol a tous les niveaux pour le groupe non-entrai ne mais seulement avant l'exercice pour le groupe entrai ne (p 0.05).

The purpose of this investigation was to identify the intensity of recovery exercise, relevant to endurance event performance, that would result in the most rapid times for half decrease in blood lactate concentration, following 2 minutes of cycling at maximal rates. Three recovery exercise intensities were investigated: (a) 7% of the maximal rate of oxygen consumption (VO$\sb2$) (LT $-$7%), (b) lactate threshold VO$\sb2$ ( LT), and (c) 7% of VO$\sb2$max above lactate threshold VO$\sb2$ (LT +7%). Seven well-trained male cyclists (mean VO$\sb2$max 4.6 $\pm$ 0.49 L $\times$ min$\sp{-1}$ participated as subjects in the investigation. Each subject completed seven separate cycling tests: (a) one combined lactate threshold-VO$\sb2$max test, (b) three constant work rate tests, and (c) three tests of recovery following supra-lactate threshold exercise (surge-recovery tests). The absolute values of blood lactate concentration were significantly different across the three recovery intensities (p .01). At the end of the 20 minute recovery period the mean blood lactate concentrations were 1.57, 2.49, and 4.17 mmol $\times$ L$\sp{-1}$ for the LT $-$7%, LT%, and LT +7% recovery intensities, respectively. Times for half decrease in blood lactate concentration were calculated. There were no significant differences in these half decrease times between the three recovery intensities (p .01). (Abstract shortened by UMI.)

The aim of this dissertation was to provide a thorough description of the coronary microvasculature at different phases of cardiac contraction, during normal postnatal growth, and pathologically accelerated growth due to pressure and volume overloading. The histochemical technique used to visualize capillaries was novel in that it served to distinguish arteriolar and venular capillary regions by colour. Arteriolar capillary (AC) regions stained blue in colour, positive for the presence of Alkaline Phosphatase in the endothelium. Venular capillary (VC) regions stained red in colour, positive for the presence of Dipeptidyl Peptidase IV. The morphometric methods used to assess capillary geometry from cross and longitudinal tissue sections were classified according to AC and VC regions. From tissue cross sections, capillaries were represented as a bivariate (CV, blue; VC, red) point pattern in the tissue plane. Our software program for capillary domains served to divide the plane into polygonal regions of tissue, each polygon enclosing one capillary. The area subtended by each polygon, the capillary domain, was closer to the enclosed capillary than any other. From individual domain areas, the equivalent radius of the Krogh cylinder with the same area was calculated. As the distribution of these radii is log-normal, the variability was best characterized by the logarithmic standard deviation (SDlog). In this manner, SDlog, the heterogeneity of capillary spacing was determined. From longitudinal sections, scale drawings of capillary sets, which consisted of all the capillary pathways that could be clearly followed from the same terminal arteriole to collecting venule served as the basic unit of study. From these capillary sets, we have defined and measured several morphometric parameters, appropriate as indicators of geometrical conditions for oxygen supply. Among these parameters are the minimal capillary length, the shortest contiguous pathway from arteriole to venule; mean capillary length, the average length of all possible capillary paths from arteriole to venule; and capillary segment length, the distance between two successive capillary branch points. To illustrate the effect of changes in capillary geometry on myocardial oxygenation, we have chosen as an illustration, the results obtained from pressure overloaded hearts. (Abstract shortened by UMI.)

No description available.

Reproductive technologies could be markedly improved by the development of methods to evaluate oocyte and/or embryo quality in a non-invasive, quantitative manner. Previous work from this lab has shown that human embryos secrete factors that inhibit progesterone and estradiol production by granulosa cells. To determine if the presence of the progesterone-inhibitory factor (PIF) and estradiol-regulatory factor in human embryo-conditioned (HEC) media correlates with the health and developmental capacity of the embryos, an interspecies bioassay was established. Oocyte-cumulus complexes were isolated from superovulated mouse ovaries, the oocytes were microsurgically removed and the oocytectomized complexes were cultured in (HEC) media for 48 hours in the presence of FSH and testosterone. Steroid accumulation in the media was determined by radioimmunoassay. Despite the potential limitations of very small volumes of HEC media to evaluate, and the need to freeze this media at the source, the bioassay was able to detect PIF activity in HEC media, but no success was achieved measuring estradiol-regulatory factor. Most embryos produced PIF activity, but the degree of inhibition did not correlate with the ability of the oocytes to be fertilized nor with embryo morphology or their ability to cleave and develop after transfer. The role of the oocyte-specific protein, growth differentiation factor-9 (GDF-9), in cumulus expansion and steroidogenesis was also investigated to determine its potential as a marker for oocyte and embryo quality. Results with (HEC) media demonstrated that the secretion of PIF by human embryos could be measured by this bioassay and that human PIF could inhibit murine granulosa cell steroidogenesis; however, PIF activity did not correlate with human embryo quality or developmental competence. GDF-9 was shown to enable cumulus expansion and inhibit progesterone and stimulate estradiol production by murine cumulus granulosa cells.