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PubMed2001

On the relationship between fractal geometry of space and time in which a system of interacting cells exists and dynamics of gene expression.

We report that both space and time, in which a system of interacting cells exists, possess fractal structure. Each single cell of the system can restore the hierarchical organization and dynamic features of the entire tumor. There is a relationship between dynamics of gene expression and connectivity (i.e., interconnectedness which denotes the existence of complex, dynamic relationships in a population of cells leading to the emergence of global features in the system that would never appear in a single cell existing out of the system). Fractal structure emerges owing to non-bijectivity of dynamic cellular network of genes and their regulatory elements. It disappears during tumor progression. This latter state is characterized by damped dynamics of gene expression, loss of connectivity, loss of collectivity (i.e., capability of the interconnected cells to interact in a common mode), and metastatic phenotype. Fractal structure of both space and time is necessary for a cellular system to self-organize. Our findings indicate that results of molecular studies on gene expression should be interpreted in terms of space-time geometry of the cellular system. In particular, the dynamics of gene expression in cancer cells existing in a malignant tumor is not identical with the dynamics of gene expression in the same cells cultured in the monolayer system.

Animals↗
PubMed2001

[Comparison of 133Xe gas dynamic SPECT and thin-section CT in patients with pulmonary emphysema].

PURPOSE: We assessed 133Xe gas dynamic single photon emission computed tomography (SPECT) by comparing washout axial images with thin-section CT (TSCT) in patients with pulmonary emphysema. METHODS: Twenty-three patients were studied. All patients were diagnosed as having pulmonary emphysema on the basis of TSCT. We compared TSCT of upper, middle and lower lung fields with 133Xe gas dynamic SPECT axial images at the corresponding levels during the 3 to 4 minutes of washout phase. If the degree of 133Xe gas retention or TSCT finding of ventral and dorsal parts was not the same, the images were divided into two parts. RESULTS: A total of 174 lesions in 23 cases were examined, but 3 lesions having no retention of 133Xe gas at equilibrium phase were excluded. The results showed that: there were 37 lesions (21.6%) with equivalent severity on both images; there were 42 lesions (24.5%) with more severity on 133Xe gas dynamic SPECT than on TSCT; and there were 92 lesions (53.8%) with more severity on TSCT than on 133Xe gas dynamic SPECT. The severity on 133Xe gas dynamic SPECT and TSCT was not always compatible. One of the reasons for the variable 133Xe gas retention even when the lesion had the same severity on TSCT, may be bronchial stricture which cannot be seen on TSCT. CONCLUSION: By comparison of axial images of 133Xe gas dynamic SPECT with CT images, we could recognize the areas of 133Xe gas retention in detail. Results suggest that 133Xe gas dynamic SPECT can be useful to identify ventilation impairment in pulmonary emphysema.

Aged↗
PubMed2002

Recovery from spinal cord injury achieved by 3 months of coordination dynamic therapy.

Coordination dynamic therapy was applied to 18 patients (average age 31 years) after a spinal cord injury between C4/5 and L4/5; the therapy was administered on average 5 years after the injury for a minimum of 3 months. All complete spinal cord lesions became incomplete, i.e. motor functions improved below the lesion level, including trunk stability and arm, hand and leg functions. The organization of the CNS, quantified by the coordination dynamics between arm and leg movements, improved by 42% for forward and by 49% for backward moving when exercising on a special coordination dynamic therapy device. The improvements of the coordination dynamics were 53%, 32% and 48% for lesions in the cervical, thoracic, and lumbar range, respectively. The plasticity for spinal cord lesions was thus higher when the intumescence was lesioned. Since the coordination dynamics did not change substantially prior to coordination dynamic therapy, did further improve with continued therapy, and worsened when the therapy was terminated, it is concluded that the improvement of CNS functioning above and below the spinal cord lesion level was due to the therapy. Since in stroke and traumatic brain lesion the CNS functioning further improved if the therapy was continued over longer time periods beyond 3 months, it is suggested that spinal cord lesions can partly be cured if coordination dynamic therapy is administered for 1 to 2 years.

Adolescent↗
PubMed2003

[Filtration capability of the bio-dynamic membrane].

The filter modules made of common mesh material were submerged in to a bioreactor to form a dynamic-membrane bioreactor. This paper studied the filtration capability of the dynamic bio-membrane forming on 100-micron Dacron mesh material. The outstanding solid-liquid separation capability of the dynamic bio-membrane was mainly contributed to the gel-layer attaching on the mesh material. The dynamic bio-membrane could checked 30%-60% TOC of various molecule weights ranging < 3000 to > 10(5), whereas its separation accuracy was not high enough to intercept all the organics of molecules weights larger than 10(5). The tap water filtration resistance of the dynamic bio-membrane sheet with gel-layer attaching on was about 1.9 x 10(9) m-1, which almost equaled to that of the untapped sheet. The resistance caused by cake-layer contributed about 70% to the total filtration resistance of the dynamic bio-membrane on working. The untapped dynamic bio-membrane sheet showed an initial resistance to tap water permeation, but the one with gel-layer attaching on had little initial resistance. The reason might be that the gel-layer eliminated the hydrophobicity of the mesh material.

Bioreactors↗
PubMed2003

Low-load coordination dynamics in athletes, physiotherapists, gymnasts, musicians and patients with spinal cord injury, after stroke, traumatic brain lesion and with cerebral palsy.

Low-load coordination dynamics were measured in athletes, physiotherapists, gymnasts, musicians and patients after stroke, traumatic brain injury and spinal cord lesion during exercise on a special coordination dynamic therapy device to quantify differences in central nervous system (CNS) organization between healthy subjects and patients with CNS injury. In healthy humans coordination dynamics (arrhythmicity of turning) varied between 5.2 and 6.0 for forward and between 6.9 and 10.7 1/s for backward turning. The frequency of turning varied between 1.24 (athletes) and 1.49 Hz (musicians) for forward and between 1.11 and 1.25 Hz for backward turning. Apart from the poor rhythmicity of backward turning among physiotherapists, gymnasts and musicians, inter-group differences were small in comparison to intra-group variation. In patients with spinal cord lesion the coordination dynamics value was 8.3 for forward and 11.0 for backward turning. The frequencies for forward and backward turning were 1.20 and 1.20 Hz respectively. The values for coordination dynamics and frequency of turning thus did only slightly differ from those measured for healthy subjects. The patients after stroke, traumatic brain injury and cerebral palsy had much higher coordination dynamic values (20.4, 22.9 and 30 1/s respectively) and lower forward (0.85, 0.93, and 0.52 Hz) and backward turning frequencies (0.98, 1.06, 0.42 Hz), suggesting strongly pathologic CNS organization. Low-load coordination dynamics (20N) are thus useful to measure progress in CNS organization due to therapy in patients with CNS injury.

Adult↗
PubMed2004

Determinants of dynamic hyperinflation in a bench model.

BACKGROUND: Previous in vivo data suggest that high airway resistance (R(aw)) promotes dynamic hyperinflation, especially when coupled to high minute ventilation (V(E)). However, no studies have systematically examined the relative effects of various mechanical parameters on dynamic hyperinflation. METHODS: Intrinsic positive end-expiratory pressure (PEEPi) was measured with a ventilator-lung model, over a range and various permutations of R(aw), V(E), respiratory system compliance (C(RS)), and duty cycles/flow regimes. RESULTS: Substantial dynamic hyperinflation (PEEPi > 5 cm H(2)O occurred at various V(E), even when R(aw) was low (4 cm H(2)O/L/s) or just above normal (18 cm H(2)O/L/s). A V(E) > or = 15 L/min was associated with increasing PEEPi in this model, across a broad range of mechanical permutations. PEEPi was significantly higher in all models during descending ramp flow than during constant flow, at equivalent peak flows (wherein duty cycle during descending ramp flow was twice that of constant flow). PEEPi was equivalent when duty cycles (and all other mechanical parameters) were equal. PEEPi was significantly greater, irrespective of duty cycle, R(aw), and C(RS), when delivered with lower tidal volume (0.6 L vs 1.0 L). The change in peak airway pressure associated with development of dynamic hyperinflation was consistently greater than the observed PEEPi. Higher V(E), resistance, compliance, and duty cycles were all independently associated with dynamic hyperinflation. CONCLUSIONS: In this bench model, dynamic hyperinflation occurred with high V(E), even at low R(aw). Since moderate R(aw) and V(E) frequently occur in vivo, even without obstructive lung disease, occult dynamic hyperinflation is likely to occur commonly. PEEPi was greater with high frequency and small tidal volume (0.6 L) than with equal V(E) of lower frequency and larger tidal volume (1.0 L).

Equipment Design↗
PubMed2004

[Measurement of glomerular filtration rate with renal dynamic imaging: comparison with two-sample method].

OBJECTIVE: To compare the estimation of glomerular filtration rate (GFR) by renal dynamic imaging with that estimated by two-sample method and evaluate the reliability of measurement of GFR by renal dynamic imaging. METHODS: The study was performed in 54 patients (33 males and 21 females; aged 15 to 82 years) with primary or secondary chronic nephrosis. The patients were intravenously bolus injected with 185 MBq /1mL of (99)Tc(m)-DTPA 20 min after drinking 300 mL of water. Renal dynamic imaging was performed and the image was processed according to standard procedure (Gates' method) to obtain GFR. 3 mL of blood was withdrawn 2 h and 4 h postinjection, respectively, and radioactivity of 1mL plasma was measured. GFR was calculated by the formula of two-sample method. The correlation of GFRs measured by renal dynamic imaging and by two-sample method was analyzed using regression analysis. The correlations of GFRs determined by the two methods with urea and creatinine were also measured. RESULTS: The GFR measured by renal dynamic imaging was slightly lower than that measured by two-sample method. Excellent correlation was obtained by two methods with r= 0.881 5 and P<0.01. The linear regression equation was GFR (renal dynamic imaging method)=0.661 4GFR (two-sample method) +21.89. The related lines of GFRs measured by the two methods with urea or creatinine were similar, which indicated the two methods were similar in identifying the changes in renal function. GFRs measured by the two methods showed good agreement for most of patients except three patients who were too thin or too fat. CONCLUSION: Generally, GFR obtained by renal dynamic imaging is reliable for identifying the changes in renal function and correlated well with GFR obtained by two-sample method. But great error may be obtained with specific individuals, such as too thin or too fat subjects.

Adolescent↗
PubMedDate not supplied

Three-dimensional dynamic MR digital subtraction angiography using sensitivity encoding for the evaluation of intracranial arteriovenous malformations: a preliminary study.

BACKGROUND AND PURPOSE: Our aim was to develop 3D dynamic MR digital subtraction angiography with high temporal resolution without sacrificing spatial resolution by using sensitivity encoding for the evaluation of cerebral arteriovenous malformations. METHODS: Nineteen patients with 19 angiographically proven arteriovenous malformations (16 supratentorial and 3 infratentorial) were assessed by conventional catheter angiography and 3D dynamic MR digital subtraction angiography. A 3D contrast-enhanced gradient-echo sequence with sensitivity encoding based on a parallel imaging technique was performed and acquired 20 dynamic images, repeated 18 times every 1.7 seconds. Three-dimensional dynamic MR digital subtraction angiograms were analyzed independently by two radiologists in a blinded fashion with regard to arteriovenous malformation nidus and venous drainage. Conventional catheter angiography was used as reference. RESULTS: All MR imaging examinations were assessable. Interobserver agreement was excellent for the detection of nidus and for the evaluation of nidus size (kappa = 1 and 0.875, respectively) but moderate for the visualization of the venous drainage (kappa = 0.56). All nidi detected on conventional catheter angiography were clearly depicted on 3D dynamic MR digital subtraction angiography. The evaluation of the size of the nidus by both techniques was similar. On 3D dynamic MR angiograms, veins were correctly analyzed in 17 of 19 arteriovenous malformations. CONCLUSION: Our preliminary study demonstrates that 3D dynamic MR digital subtraction angiography using sensitivity encoding with a high spatial resolution is appropriate for the assessment of arteriovenous malformations.

Adult↗
PubMed2005

[Research advance on lake ecosystem dynamic models].

Starting with the role of system analysis in lake ecosystem research, this paper summarized the tentative procedures and softwares for studying the dynamics of lake ecosystem. There are several main stages in modeling the dynamics of lake ecosystem, namely, problems identification, mathematical formulation, computation, validation, sensitive analysis, calibration, and verification. In the modeling, selecting temporal and spatial scales is essential but complex. Since 1960s, a rapid progress has been made in modeling the dynamics of lake ecosystem, being developed from simple zero-dimension models to complex ecological-aquatic-hydrodynamic ones, among which, exergy was applied popularly as an objective function in modeling. In this paper, LakeWeb and LEEDS (Lake Eutrophication, Effect, Dose, and Sensitivity model) were analyzed as examples. In China, the development of lake ecosystem dynamic models could be traced back to 1980s, and most of them were focused on Lake Dianch, Lake Taihu, Lake Chaohu and Lake Donghu. Some softwares such as CE-QUAL-ICM, WASP, AQUATOX, PAMOLARE and CAEDYM were developed to simulate lake ecosystem dynamics, among which, CE-QUAL-ICM is more suitable for long and narrow water bodies. WASP consists of three parts, i. e., DYNHYD, EUTRO, and TOXI. AQUATOX is an ecological risk model, and the parameters are mainly calibrated in U. S. A, which has limited its further application in China. The software ECOPATH for simulating the energy flows in lakes was also described in this paper. There are still many shortages in the lake ecosystem dynamic models, e. g., the lack of sufficient monitoring data for validation, insufficient consideration of uncertainties and the role of bacteria, and inconsistent relationship with watershed changes. The uncertainties are mainly from the intrinsic uncertainties in aquatic ecosystem, in modeling, in parameters selection, and also in forecast and application. Setting up long-term monitoring and data sharing mechanism, using interpolation to make data more densely, introducing objective functions, dealing with uncertainties, and constructing watershed-lake ecosystem dynamic model could be the available ways for overcoming the shortages.

China↗
PubMed2005

Advantages of terminating Zippy Estimation by Sequential Testing (ZEST) with dynamic criteria for white-on-white perimetry.

PURPOSE: A number of automated perimeters use the Zippy Estimation by Sequential Testing (ZEST) algorithm, which is an adaptive Bayesian method, for determining sensitivity measures. There are two popular rules for deciding when to terminate Bayesian procedures: (1) after a fixed number of presentations; or (2) when the probability density function (pdf) over all thresholds modified by the procedure becomes sufficiently narrow (a dynamic termination criterion). It has recently been argued that fixed termination criteria perform equally as well as dynamic criteria when applied in a fashion typical of laboratory-based visual psychophysics. Perimetry, however, has specific requirements; the tests must be very short, there is a wide range of possible sensitivities, and erroneous responses from the patient must be tolerated. This study used computer simulation to compare fixed and dynamic termination criteria for the ZEST algorithm using conditions typical of white-on-white perimetry. METHODS: Eight ZEST procedures were compared using the following termination criteria: fixed termination after 4, 5, 6, 7, and 8 presentations; dynamic termination when the standard deviation of the pdf was 1 dB, 1.5 dB, and 2 dB. Four patient error models were used: ideal, typical false-positive, typical false-negative, and unreliable patients. We also ran a version of ZEST that set the likelihood function exactly equal to the patient's frequency of seeing curve. RESULTS: The mean absolute error and standard deviation of error in threshold measurement was higher for the fixed termination criteria than for dynamic termination criteria of the same average number of presentations. CONCLUSIONS: The results of our simulations indicate that dynamic procedures have some distinct benefits over fixed termination procedures when a minimum of presentations are required and response errors are made as in a white-on-white perimetric setting. Dynamic termination criteria are at least partially successful in expending more presentations when required to enhance test precision.

Algorithms↗
PubMed2006

[Value of dynamic enhanced magnetic resonance in diagnosis of pancreatic carcinoma and endocrine tumors].

OBJECTIVE: To explore the value of dynamic enhanced magnetic resonance (MR) in diagnosis of pancreatic carcinoma and endocrine tumors. METHODS: Twenty-two patients with pancreatic carcinoma and 9 patients with pancreatic endocrine tumors underwent routine MR scanning and dynamic contrast enhanced MR examination before they underwent operation. RESULTS: No tumor image was seen in 4 of the 22 patients with pancreatic carcinoma by routine MR scanning. Fat-saturated T(1)-weighted imaging (FS-T(1) WI) showed that 11 of them were hyposignal, 6 slightly hyposignal, and 1 isosignal; and fat-saturated T(2)-weighted imaging (FS-T(2) WI) showed that 5 were hypersignal, 7 slightly hypersignal, 5 isosignal, 1 slightly hyposignal, and 13 with heterogeneous signals. After dynamic MR imaging no tumor was enhanced in the arterial phase (AP); and all the tumors were obviously enhanced during the pancreatic phase (PP) and portal venous phase (PVP), 5 of which showed isosignal intensity, 10 slightly hyposignal intensity, and 3 hyposignal intensity. Four of the 5 cases with small pancreatic carcinoma were demonstrated as isosignal and one was slightly hyposignal. During the delayed enhancement phase (DEP) the signal intensity of the tumors became slightly weaker. No tumor image was seen in 14 of the 9 patients with pancreatic endocrine tumors by routine MR scanning. FS-T(1) WI showed that 5 of them were hyposignal, and 3 slightly hyposignal; and FS-T(2) WI showed that 2 were hypersignal, 4 slightly hyposignal, and 2 isosignal. After dynamic MR imaging 2 cases were moderately enhanced and 6 cases mildly enhanced during AP, and all pancreatic endocrine tumors were obviously enhanced during PP and PVP, with isosignal intensity in 2 cases, slightly hyposignal intensity in 1 case, and slightly hypersignal intensity in 5 cases. Peritumor thin-walled enhancement was seen in 6 cases. CONCLUSION: Dynamic enhanced MR has a certain value in the diagnosis of pancreatic carcinoma and endocrine tumors. Pancreatic carcinoma shows various enhanced forms by dynamic enhanced magnetic resonance, the degree of the greatest enhanced form not surpassing that of normal pancreatic tissue. Pancreatic endocrine carcinoma shows obvious enhanced forms by dynamic enhanced magnetic resonance, the degree of the greatest enhanced form surpassing that of normal pancreatic tissue. Peritumor thin-walled enhancement is a characteristic feature of pancreatic endocrine carcinoma.

Adult↗
PubMedDate not supplied

[Connection of the tangents of the regression slope of the heart rate graph with linear and nonlinear dynamics in stationary short-time series].

The connection of the regression slope of heart rate graph (b1) with linear and nonlinear dynamics in stationary short-time series (256 points) was studied. A new index for the estimation of nonlinear dynamics in stationary short-time series was used, which is based on the correlation dimension. The results of the study indicated that the dynamics of heart rate in stationary short-time series can be represented as the sum of linear (periodic) and nonlinear (stochastic) processes. A relation of b1 with both linear and nonlinear dynamics of heart rate was found. The formulas for the calculation of absolute and relative (to the amplitude of periodic fluctuations) noise levels in heart rate dynamics were derived. A comparative analysis of nonlinear dynamics of heart rate in stationary short-time series for different functional states of humans was performed. The increase in the relative noise level in heart rate dynamics with increasing breathing frequency is related not only to a decrease in control breathing amplitude but also to an increase in the noise amplitude. The decrease in the absolute noise level for nervous excitation, fatigue, and mental stress were found. The predominance of nonlinear (stochastic) processes over linear (periodic) processes in the relaxed state was established.

Heart↗
PubMed1991

Hidden skills: a dynamic systems analysis of treadmill stepping during the first year.

When prelocomotor infants are supported on a motorized treadmill, they perform well-coordinated, alternating stepping movements that are kinematically similar to upright bipedal locomotion. This behavior appeared to be a component of independent walking that could not be recognized without the facilitating context of the treadmill. To understand the ontogenetic origins of treadmill stepping and its relation to later locomotion, we conducted a longitudinal study using an experimental strategy explicitly derived from dynamic systems theory. Dynamic systems theory postulates that new forms in behavior emerge from the cooperative interactions of multiple components within a task context. This approach focuses on the transitions, often nonlinear, where one preferred mode of behavior is replaced by a new form. Specific predictions about these transitions help uncover the processes by which development proceeds. Chapters II, III, and IV introduce dynamic principles of pattern formation and their application to development. In our application of these principles, we tested nine normal infants twice each month beginning from month 1 in a task where the treadmill speed was gradually scaled up and in an additional condition where each leg was driven by the treadmill at a different speed. Kinematic variables were derived from computerized movement analysis equipment and videotaped records. We also collected a number of anthropometric measurements, Bayley motor scores, and a behavioral mood scale for each month. Several infants stepped on the treadmill in their first month, but in all infants performance showed a rapidly rising slope from month 3 to month 6. Infants also showed corresponding improvement in adjustments to speed and relative coordination between the legs. In dynamic terminology, we found evidence that alternating stepping on the treadmill became an increasingly stable attractor during the middle months of the first year. Dynamic predictions that transitions would be characterized by increased variability and sensitivity to perturbation were borne out. Identifying the transitions enabled us to suggest a control parameter or variable moving the system into the stable response to the treadmill. This appeared to be the waning of flexor dominance in the legs during posture and movement that allowed the leg to be stretched back on the treadmill and so elicited the bilaterally alternating response. Further studies are needed to test this hypothesis. This dynamic analysis confirmed earlier suggestions that skill in general, and locomotion in particular, develops from the confluence of many participating elements and showed how emergent forms may result from changes in nonspecific components. A dynamic approach may be useful for understanding ontogenetic processes in other domains as well.

Exercise Test↗
PubMed1989

[A dynamic fitness test and a new method to measure the thickness of film using the digital subtraction system of X-ray photographic density].

It is impossible to show the dynamic fitness conditions of a denture base using White Silicone or other fitness test materials. In the present paper, materials and the measuring method for the dynamic fitness test were investigated. In order to choose the suitable materials for the dynamic fitness test, various kinds of ready made materials, such as wax or dynamic impression materials, were examined by load test and investigated the change on standing of flow character. EXPERIMENTAL WAX was made for dynamic fitness test, and was examined by load test and clinical test. EXPERIMENTAL WAX consists of DISCLOSING WAX (KERR), as a basic material, and the contrast medium. Extending the system of the conventional measuring method for White Silicone, DIGITAL SUBTRACTION SYSTEM (DSS) was developed as a new method of quantitative analysis for the thickness of wax film. In this system, thickness of wax film is measured from the X-ray photographic density and it's digital subtraction management. Accuracy of this system was also investigated. The summary of results is shown below. 1. It became evident that ready made materials had no useful characters for the dynamic fitness test. 2. EXPERIMENTAL WAX showed similar load effects with White Silicone when the load was 5 or 10kg. 3. Dynamic fitness and the mobility of the denture base during function were able to be shown by EXPERIMENTAL WAX, but it's operation was more complicated than White Silicone. 4. DIGITAL SUBTRACTION SYSTEM (DSS), a new method of quantitative analysis for the thickness of wax film, was developed. 5. Resolving power and measuring range of DSS were effected by quantity of subtraction. 6. DSS is not only useful to measure the thickness of EXPERIMENTAL WAX, but also has wide applications.

Dental Stress Analysis↗
PubMed1987

[Left ventricular function assessment using a floating catheter in dynamic and isometric (handgrip) stress in normal and heart infarct patients].

UNLABELLED: Left ventricular function was examined in a control group of 8 healthy men (average age 26 +/- 6.2 years) and was compared to 40 post-MI patients (average age 50 +/- 8.2 years, 39 men, one woman). It was measured using the floating-catheter technique under isometric exercise (50% of maximal voluntary contraction using both hands) and also under dynamic exercise (progressive supine bicycle-ergometry). In the control group, there was a significant increase in heart rate, arterial blood-pressure and the average PCP from rest to isometric exercises. PCP was noted to stay within its normal range (less than 20 mm Hg) under both modes of exercise. There was no significant difference comparing the effects of dynamic and isometric exercise (isometric: PCP 13.3 +/- 3.3 mm Hg; dynamic: PCP 11.8 +/- 3.6 mm Hg). In Group I (20 post-MI-patients showing ischemia during exercise-ECG) PCP stayed normal under isometric exercise (PCP 18.8 +/- 10.2 mm Hg). Under dynamic exercise, their PCP increased up to a pathological level (PCP 24.9 +/- 10.1 mm Hg, p less than 0.01). In Group II (20 post-MI-patients with lacking proof of ischemia during exercise-ECG) there was no significant difference between the increase in PCP under isometric vs dynamic exercise (isometric: PCP 18.7 +/- 13.4 mm Hg; dynamic: PCP 18.5 +/- 10.0 mm Hg). CONCLUSION: The results lead to the conclusion that isometric exercise alone (50% of maximal voluntary contraction using both hands, handgrip) can replace dynamic exercise in the diagnosis of LV malfunction in post-MI patients who do not show ischemia during exercise-ECG.

Adult↗
PubMed1985

The physiologic sequelae of chronic dynamic exercise.

The physiologic results of acute dynamic exercise include complex neurologic, hormonal, pulmonary, and cardiovascular adjustments that provide an integrated response perfectly matching oxygen supply with oxygen demands. Long-term repeated bouts of dynamic exercise of sufficient intensity and duration yield predictable changes in anatomy and physiology. These changes affect active skeletal muscle and the heart. Changes in skeletal muscle include an increased capillary blood volume, increased mitochondrial density, increased oxidative pathway enzymes, and more efficient regulation of blood flow. These adaptations result in an increased oxidative capacity and more favorable fuel utilization. Oxygen extraction increases, accounting for up to 50 per cent of the increased maximal oxygen consumption, and endurance improves. Following chronic dynamic exercise the heart beats slower and has a larger stroke volume at rest and throughout a broad range of work intensities. The maximal cardiac output increases substantially, accounting for up to 50 per cent of the increased maximal oxygen consumption. The metabolic and biochemical changes found in skeletal muscle are not found in cardiac muscle. Changes found in isolated cardiac muscle do not always correlate with heart performance. The separation of central and peripheral factors in assessing heart performance is difficult because preload and afterload are major determinants of heart function and are altered by chronic dynamic exercise. Ischemia is a major stimulus for the development of coronary collateral vessel development in animals. Because dynamic exercise does not induce ischemia in normal humans, collateral vessel development may only occur in those with coronary heart disease. However, there is no convincing evidence that chronic dynamic exercise results in physiologically important coronary collateral vasculature in patients with angina. Improved work capacity is predictable following chronic dynamic exercise in patients with coronary heart disease. Although the rate pressure product that produces angina does not change following training, heart rates are lower at matched absolute workloads and the maximal consumption of oxygen increases. Changes in heart function are largely secondary to peripheral changes in these patients.

Animals↗
PubMed1994

[Mutuality as the central dimension of family dynamics].

Mutuality is the central dimension of family dynamics. This study of family dynamics in Finland forms part of an international comparative family dynamics project. The aim of the study was to describe the family dynamics of childbearing and childrearing families using the six dimensions of Barnhill's model of Healthy Family Systems. In addition to this changes in family dynamics after the childbirth were studied. In this article results of the dimension of mutuality are reported. The sample consisted of families expecting (n = 118) and rearing (n = 94) their first or second child in Finland. The data were collected by questionnaires, using the Family Dynamics Questionnaire and Family Dynamics Measure of 62 Likert-type items developed in U.S. (Lasky et al 1985). In generally childbearing and childrearing families were healthy and well-functioning. However, unmarried couples, fathers and families expecting and rearing their second child seemed to be vulnerable and therefore they need more support in adapting to the normal stages of development.

Adult↗
PubMed1993

Subaortic stenosis revisited: the importance of the dynamic pressure gradient.

Brachfeld and Gorlin's revised concept of subaortic stenosis derived from their recognition that the large magnitudes of the pressure gradients were incompatible with the relatively mild anatomic lesions found at surgery in 3 of their patients, and the rapidity of their arterial pulse upstroke. They proposed that a gradient caused by a superimposed systolic stenosis was responsible for the large pressure gradients and the overestimation of the severity of the discrete subaortic stenosis (DSAS). A fourth patient had no anatomic cause for the pressure gradient, and findings compatible with hypertrophic cardiomyopathy (HCM). All 4 patients had septal hypertrophy which they felt was instrumental in the brisk pulse contour and dynamic gradients across the outflow tract. In the ensuing decades, imaging techniques have been developed which permit detailed studies of ventricular ejection patterns in dynamic gradients associated with HCM and DSAS. These studies have been interpreted variously. The prevailing view is that there is a dynamic obstruction that increases progressively in severity during systole, as proposed by Brachfeld and Gorlin. An opposing view is that dynamic gradients can occur in the absence of any hindrance to ejection, and that these gradients instead result from rapid and complete emptying of the ventricle. Regardless of their cause, dynamic gradients are often superimposed upon gradients caused by DSAS and valvar aortic stenosis, leading to exaggerated estimates of severity. These dynamic gradients are uncovered when the anatomic cause of stenosis is removed, and seemingly increase the postoperative morbidity. A greater understanding of the significance of dynamic gradients and the mechanism(s) responsible for them should lead to more rational management of DSAS and HCM in the future.

Aortic Valve Stenosis↗