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Results for “physiologic variables”

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At least 163 records · Page 9Linked to original sources
PubMed1980

Physiologic variability and fetal electrocortical activity.

The relationship between fetal electrocortical activity and multiple fetal parameters was examined in chronically instrumented fetal lambs. Consistent small but significant changes in fetal heart rate, mean arterial pressure, umbilical blood flow, and the cerebral uptake of glucose relative to oxygen were observed as fetal electrocortical activity cyclically shifted between high-voltage slow activity and low-voltage fast activity. Cardiovascular parameters were higher and the cerebral uptake of glucose relative to oxygen was lower during high-voltage slow activity than during low-voltage fast activity. The implication of these observations is discussed.

Animals↗
PubMed1985

Pyruvate inhibition of pyruvate dehydrogenase kinase is a physiological variable.

Pyruvate inhibited pyruvate dehydrogenase kinase activity in mitochondria from adipose tissue, heart, brain and kidney of fed rats. Starvation for 24 h led to increased kinase activity in mitochondria from adipose tissue and heart but not from brain or kidney and to reduction of pyruvate inhibition of the enzyme from adipose tissue, heart and brain. Insulin injection into starved animals rapidly restored pyruvate inhibition without alteration of kinase activity in adipose tissue and heart mitochondria. Induction of streptozotocin diabetes resulted in loss of pyruvate inhibition of the kinase in heart mitochondria at 48 h but not at 24 h whereas a significant increase of kinase activity was seen at 24 h. It is concluded that the mechanisms which control fluctuations of pyruvate sensitivity of the kinase are different from the mechanisms which control fluctuations of the uninhibited kinase activity.

Adipose Tissue↗
PubMed1989

Physiological variables affecting collagen lattice contraction by human dermal fibroblasts.

Normal human dermal fibroblasts cultured in collagen lattices can compact that matrix by the process known as lattice contraction. That process is a model of the pathological one of scar contracture or wound contraction and is affected by several factors. Lattice contraction is promoted by the addition of adequate amounts of fetal bovine serum to the medium (maximum contraction with 10% serum). The process requires energy, of which glucose and pyruvate have been shown to be adequate sources. When glucose is used as the substrate, the major pathway of energy generation appears to be anaerobic metabolism. When pyruvate is the only substrate, aerobic metabolism may be crucial. The synthesis of DNA is not required for lattice contraction, while protein synthesis is, although the identities of the specific proteins are unknown. Impairment of calcium ion transport inhibits lattice contraction, and the specific inhibition of calmodulin-calcium interactions by W-7 blocks contraction. W-7 at a concentration of 6 x 10(-6) M blocks lattice contraction completely, while it has no effect at any lower concentration. Impairing dynamic microtubule activity impairs contraction. Disrupting microfilaments by cytochalasin B completely blocks lattice contraction. Microfilament function and calcium-calmodulin may be linked by a mechanism involving myosin-ATPase. The process of cell-mediated lattice contraction requires the production of energy, protein synthesis, and a functional cytoskeleton.

Calcium↗
PubMed2006

Influence of lifetime food restriction on physiological variables in Labrador retriever dogs.

Effects of lifetime food restriction on erythrocytes and numerous clinical chemistry, thyroid, parathyroid, and acid-base variables are reported from a paired-feeding study of 25% diet restriction in dogs. The 48 dogs were paired by gender and weaning weight within litter, and 1 dog in each pair was fed 25% less than its pair mate, from age 8 weeks until death. Erythrocyte and serum biochemistry profiles were evaluated by annual sampling intervals and longitudinally. Erythrocyte variables were slightly higher among control-fed dogs, a possible reflection of the need to support both higher body fat mass and lean mass that uses energy less efficiently. Among serum biochemistry variables, glucose and triglyceride were lower among diet-restricted dogs, while creatinine was slightly higher in the absence of renal disease or failure, over the life spans of the dogs. Glucose outcomes reflect improved glucose tolerance that has been demonstrated with diet restriction protocols in several species, while triglyceride data may reflect the difference in total body fat cells between feeding groups. Creatinine outcomes may reflect lean mass responses to diet restriction or more efficient function of the intracellular proteasome. Serum triiodothyronine levels were lower among diet-restricted dogs. Other clinical chemistry and thyroid variables, parathyroid variables, and acid-base variables were not strongly influenced by diet restriction but revealed age-related effects.

Aging↗
PubMed1999

Scanning laser ophthalmoscopy-based evaluation of epipapillary velocities: method and physiologic variability.

PURPOSE: Scanning laser ophthalmoscopy is capable of producing high-resolution fluorescein angiograms. Measurements of capillary blood velocities in the fovea are well established. In this study, we used an identical technique to measure particle velocities in the superficial layers of the optic nerve head. We compared these data with simultaneous velocity measurements in the retinal and macular vasculature. METHODS: Fluorescein angiograms were performed in 30 subjects (12 men, 18 women; mean age, 26 years; standard deviation [SD], 3 years). Off-line, the velocities of hypofluorescent particles through the microvasculature of epipapillary and macular vessels were measured by image-processing techniques. We also assessed the arteriovenous passage (AVP) time of the fluorescein dye front. RESULTS: Epipapillary blood velocities ranged from 2.7 to 6.5 mm/sec (mean, 4.0 mm/sec; SD, 0.99 mm/sec) and differed significantly from macular capillary blood velocities (MCBVs), which ranged from 1.67 to 3.31 mm/sec (mean, 2.53 mm/sec; SD, 0.34 mm/sec). The AVP time in all subjects was 1.74 +/- 0.5 sec (mean +/- SD) and correlated with the MCBV (P < 0.05, r = -0.46). Epipapillary blood velocities showed no correlation with either AVP time or MCBV. CONCLUSIONS: The scanning laser methodology, adapted to objectively assess velocities in the epipapillary vasculature, shows that these measurements are neither correlated with velocities in the perifoveal network, nor inversely correlated with overall retinal transit time. Epipapillary blood velocities were found to be substantially higher than those measured in macular capillaries. This result might be explained by the different anatomy of epipapillary vessels compared with macular capillaries.

Adult↗
PubMedDate not supplied

Echocardiography in serial evaluation of left ventricular systolic and diastolic function: importance of image acquisition, quantitation, and physiologic variability in clinical and investigational applications.

Quantitative echocardiography is frequently used for serial evaluation of left ventricular performance. This prospective study was designed to determine the extent to which the acts of image acquisition and quantitation, and the subjects themselves, affect total variability in two-dimensional and Doppler echocardiographic indexes of left ventricular morphology and performance. Therefore, two technicians and two readers acquired and analyzed 60 echocardiograms from 15 normal subjects, each of whom was studied four times (twice on each of two visits). Analysis of variance based on generalizability theory was used to estimate the magnitude of these variability sources by calculating standard deviations (SD) and used to estimate their contribution to total variability. Of the two-dimensional echocardiographic indexes tested, ejection fraction varied least (SD, 6.6%) and left ventricular mass varied most (SD, 35.3 gm). Of the Doppler indexes, normalized early diastolic filling velocity integral varied least (SD, 8.4%) and deceleration time varied most (SD, 48.6 msec). Technical (image acquisition and quantitation) variability contributed most (and subject variability least) to total variability of stroke volume (68%) and deceleration time (67%). Technical variability contributed least (and subject variability most) to variability of ejection fraction (43%) and diastolic filling time (25%). The acts of image acquisition and quantitation varied more between than within technicians and readers. Peak atrial filling velocity and the ratio of peak early to atrial filling velocity significantly differed between technicians. Left ventricular ejection fraction, left ventricular mass, peak atrial filling velocity, early filling integral, and deceleration of early filling differed significantly between readers. Therefore the acts of image acquisition and quantitation, and subject variability itself, all contribute to total variability in echocardiographic indexes. Changes seen on clinical studies should be interpreted as abnormal only when exceeding the total variability originating from these sources. Generalizability theory allows one to tailor strategies to reduce variability. These strategies include increasing the number of observations, readers, and technicians for any given "baseline" study and using the same readers and technicians for sequential follow-up studies.

Adult↗
PubMed2004

Effect of recovery modality on 4-hour repeated treadmill running performance and changes in physiological variables.

The purpose of this study was to compare the effectiveness of three different recovery modalities--active (ACT), passive (PAS) and contrast temperature water immersion (CTW)--on the performance of repeated treadmill running, lactate concentration and pH. Fourteen males performed two pairs of treadmill runs to exhaustion at 120% and 90% of peak running speed (PRS) over a 4-hour period. ACT, PAS or CTW was performed for 15-min after the first pair of treadmill runs. ACT consisted of running at 40% PRS, PAS consisted of standing stationary and CTW consisted of alternating between 60-s cold (10 degrees C) and 120-s hot (42 degrees C) water immersion. Run times were converted to time to cover set distance using critical power. Type of recovery modality did not have a significant effect on change in time to cover 400 m (Mean +/- SD; ACT 2.7 +/- 3.6 s, PAS 2.9 +/- 4.2 s, CTW 4.2 +/- 6.9 s), 1000 m (ACT 2.2 +/- 4.0 s, PAS 4.8 +/- 8.6 s, CTW 2.1 +/- 7.2 s) or 5000 m (ACT 1.4 +/- 29.0 s, PAS 16.7 +/- 58.5 s, CTW 11.7 +/- 33.0 s). Post exercise blood lactate concentration was lower in ACT and CTW compared with PAS. Participants reported an increased perception of recovery in the CTW compared with ACT and PAS. Blood pH was not significantly influenced by recovery modality. Data suggest both ACT and CTW reduce lactate accumulation after high intensity running, but high intensity treadmill running performance is returned to baseline 4-hours after the initial exercise bout regardless of the recovery strategy employed.

Adult↗
PubMed2000

Relationship between perceived readiness to run and physiological variables during repeated 2000 m bouts in middle-distance runners.

The aim of this study was to investigate how heart rate (HR) and blood lactate (LA) concentrations are associated with perceived readiness ratings (PRR) to begin a new run during recovery after four different intensity steady-state 2000 m runs in college-level male middle-distance runners (n=15). A typical 4x2000 m run test with stepwise increasing speed was used on the indoor track (150 m lap). A new PRR scale was administered at each minute of recovery. The scale ranges from 1 to 5 points (from "not at all ready to begin" to "completely ready to begin"). Blood LA concentrations were measured immediately after runs and in the 3rd min of recovery after the first and second runs. In case of the third and fourth runs, blood LA was measured immediately after the runs and in the 3rd and 6th min of recovery. HR was recorded at the end of every minute of recovery. Highly significant inverse relationships were revealed between PRR, blood LA concentrations and HR during recovery (r>0.9 as a rule). After the third and the fourth 2000 m runs, where intensity was higher than LA threshold, PRR increased during 6 min up to 4.8+/-0.4 and 4.5+/-0.6, respectively, while HR fell below 120 beats x min(-1). However, blood LA concentration remained high. The reliability of the new PRR scale (tested on four runners), during recovery was very high (r=0.98). These results suggest that the PRR scale can be used by runners to determine the optimal duration of resting intervals between runs.

Adult↗
PubMed1999

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 1. Changes in blood gases as a function of ambient temperature.

1. Male broilers of 5 genetic stocks (A, B, C, D, E) selected in different ways for fast growth and low food conversion ratio (FCR) and differing in ascites sensitivity were subjected to 2 different ambient temperature step down regimens: high temperature (HT: 33 to 20 degrees C over 33 d) and low temperature (LT: 30 to 15 degrees C over 17 d). 2. Ascites incidence was recorded daily. Food intake and body weight gain were measured weekly and FCR was calculated. Heat production (Hp) was calculated using the comparative slaughter method. At 28 d venous samples were taken for blood gas analysis and haematocrit and relative heart, lung and liver weights were recorded. 3. Populations A and C showed the highest growth rates combined with a low FCR and a higher ascites incidence. A low FCR in these stocks was attributable to low values for Hp. These stocks also had low PO2 and high pCO2 in venous blood at low ambient temperature compared with other stocks. Stock B, which exhibited the slowest growth rate and the highest FCR, was not susceptible to ascites and showed higher Hp and PO2 and pCO2 at low ambient temperature. Populations D and E were intermediate for almost all variables. Heart and lung weights were both increased at LT, while liver weight did not differ between temperature regimes. 4. Our results show that a high haematocrit is not necessarily linked with an increased susceptibility to ascites.

Animals↗
PubMed1999

Performance and physiological variables in broiler chicken lines differing in susceptibility to the ascites syndrome: 2. Effect of ambient temperature on partial efficiencies of protein and fat retention and plasma hormone concentrations.

1. Male broilers of 5 genetic stocks (A, B, C, D and E), selected in different ways for fast growth and low food conversion rate (FCR) and differing in sensitivity to ascites, were subjected to 2 different ambient temperature (Ta) step-down programmes: normal (HT) and low (LT) Ta. 2. Ascites incidence was followed daily. Growth and food intake were measured weekly. Heat production (Hp), oxygen consumption (Oxc) and energy- metabolism parameters were calculated according to the comparative slaughter method. At week 4 blood samples were taken for the analysis of plasma T4, T3, growth hormone (GH) and insulin-like growth factor-I (IGF-1) concentrations. 3. Within-line changes of GH and IGF-1 point to the relative independence of both hormone concentrations. 4. Partial protein efficiency was higher in lines with lower GH, especially at LT. 5. The increase in plasma T3 concentration at LT was accompanied by a decrease in relative fat deposition from the increased energy expenditure. 6. The combination of fast growth and low FCR, linked to a low plasma T4 concentration at LT is indicative of a thyroid insufficiency which is related to an increased occurrence of ascites in these lines.

Adipose Tissue↗