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At least 451 records · Page 25Linked to original sources
PubMed2000

A new impedance cardiograph device for the non-invasive evaluation of cardiac output at rest and during exercise: comparison with the "direct" Fick method.

The objectives of this study were to evaluate the reliability and accuracy of a new impedance cardiograph device, the Physio Flow, at rest and during a steady-state dynamic leg exercise (work intensity ranging from 10 to 50 W) performed in the supine position. We compared cardiac output determined simultaneously by two methods, the Physio Flow (QcPF) and the direct Fick (QcFick) methods. Forty patients referred for right cardiac catheterisation, 14 with sleep apnoea syndrome and 26 with chronic obstructive pulmonary disease, took part in this study. The subjects' oxygen consumption values ranged from 0.14 to 1.19 l x min(-1). The mean difference between the two methods (QcFick - QcPF) was 0.04 l x min(-1) at rest and 0.29 l x min(-1) during exercise. The limits of agreement, defined as mean difference +/- 2SD, were -1.34, +1.41 l x min(-1)] at rest and -2.34, +2.92 l x min(-1) during exercise. The difference between the two methods exceeded 20% in only 2.5% of the cases at rest, and 9.3% of the cases during exercise. Thoracic hyperinflation did not alter QcPF. We conclude that the Physio Flow provides a clinically acceptable and non-invasive evaluation of cardiac output under these conditions. This new impedance cardiograph device deserves further study using other populations and situations.

Aged↗
PubMed2000

Short-term cardiovascular responses to rapid whole-body tilting during exercise.

Our objective was to characterize the responses of heart rate (HR) and arterial blood pressure (BP) to changes in posture during concomitant dynamic leg exercise. Ten men performed dynamic leg exercise at 50, 100, and 150 W and were rapidly and repeatedly tilted between supine (0 degrees ) and upright (80 degrees ) positions at 2-min intervals. Continuous recordings of BP and HR were made, and changes in central blood volume were estimated from transthoracic impedance. Short-lasting increases in BP were observed immediately upon tilting from the upright to the supine position (down-tilt), averaging +18 mmHg (50 W) to +31 mmHg (150 W), and there were equally short-lasting decreases in BP, ranging from -26 to -38 mmHg upon tilting from supine to upright (up-tilt). These components occurred for all pressure parameters (systolic, mean, diastolic, and pulse pressures). We propose that these transients reflect mainly tilt-induced changes in total peripheral resistance resulting from decreases and increases of the efficiency of the venous muscle pump. After 3-4 s (down-tilt) and 7-11 s (up-tilt) there were large HR transients in a direction opposite to the pressure transients. These HR transients were larger during the down-tilt (-15 to -26 beats. min(-1)) than during the up-tilt (+13 to +17 beats. min(-1)), and increased in amplitude with work intensity during the down-tilt. The tilt-induced HR fluctuations could be modelled as a basically linear function of an arterial baroreflex input from a site half-way between the heart and the carotid sinus, and with varying contributions of fast vagal and slow sympathetic HR responses resulting in attenuated tachycardic responses to hypotensive stimuli during exercise.

Adult↗
PubMed2006

MHSPY: a children's health initiative for maintaining at-risk youth in the community.

The Massachusetts Mental Health Services Program for Youth (MHSPY) is a home-based clinical intervention that seeks to maintain youth with severe functional impairment in the community via delivery of integrated primary care, mental health, substance abuse, and social services. Using blended public agency funding, traditional and nontraditional services are provided within a private, not-for-profit, managed care organization. Individualized, comprehensive care plans are developed by an MHSPY care manager, who works intensively with the family and the Care Planning Team to identify needs and resources. Data on clinical functioning are collected at baseline and every six months during the program. Service utilization and cost are measured on a quarterly basis. Family, youth, and agency satisfaction ratings are collected at disenrollment. Aggregate analyses based on four years of data show that MHSPY participants have improved clinical functioning, including significant reduction in risk to self and others. They also experience reduced service utilization and cost and high rates of family satisfaction.

Adolescent↗
PubMed1983

Exercise in pregnancy. II. Fetal responses.

Healthy pregnant women underwent a mild exercise study to evaluate the effects of this amount of work on their fetuses. The results indicated that there were no direct correlations between exercise and fetal body or breathing movements at this particular work intensity (2.33 m). We found a relationship between the maternal sympathetic activity as reflected in epinephrine levels and the degree of fetal activity.

Adult↗
PubMedDate not supplied

Equine thyroid function tests: a preliminary investigation.

A similar and significant (P less than 0.001) increase in plasma thyroxine (T4) concentration was seen in seven clinically normal thoroughbred horses 2 h after the intravenous administration of either 2.5 iu or 5 iu of thyroid stimulating hormone (TSH) with a peak response around 4 h after administration. The intravenous administration of 0.2, 0.5 or 1 mg thyrotrophin releasing hormone (TRH) resulted in a significant (P less than 0.01) increase in T4 concentration in three groups of animals; six thoroughbreds in full work, five thoroughbreds at rest and four ponies at rest. The peak response was recorded at 3 or 4 h after administration. A significant difference between the groups in the degree of response to TRH was only found between the thoroughbreds in work and those at rest with 1 mg TRH (P less than 0.05). When two additional ponies were investigated in a similar way, a reduced response to TRH was observed: a pregnant mare had a similar response to 5 iu TSH as the thoroughbreds; the other pony also showed a lowered response to TSH. In a group of 2- or 3-year-old thoroughbreds in training no difference in the T4 response 4 h after intravenous administration of 0.5 mg TRH could be determined, according to the month, age, sex or work intensity. Although resting T4 concentrations did not differ significantly between animals believed to be suffering from the equine rhabdomyolysis syndrome (ERS) and those suffering from a variety of other conditions, some ERS sufferers may have a lowered response to TRH.

Animals↗
PubMed1993

To test or not to test, that is the question.

This paper describes a system that is used in Maastricht, the Netherlands, to provide general practitioners with feedback about the adequateness of their test requesting behaviour. The system has proven to be effective. Since the screening of test requests and additional patient data is work-intensive a project was started in the framework of the AIM programme OPENLABS to design a computer-based feedback system. In this system the general practitioner sends test requests to the laboratory decision support system by means of electronic data interchange (EDI). The authors were involved in the development of the EDI messages, which are now accepted standards in the Netherlands. The requests are stored in a database that is part of the laboratory decision support system. The other part of the decision support system, an expert system, obtains the request data (including patient data) from the database, screens the requests for adequateness and provides feedback when necessary.

Clinical Laboratory Information Systems↗
PubMed1983

Hemodynamic significance of metabolic turn-over rate.

Method in establishing mammalian hemodynamic similarity criteria via the classical allometric approach was examined. Metabolic rate (MR) per unit body weight (w), termed the metabolic turn-over rate (MTR), was found to be linearly related to mammalian resting heart rate (fh). The external ventricular work (EW) per unit body weight was found to be constant among mammalian species. The ratio of (EW/w)/(MTR/fh) is dimensionless, and is about 1/70. This latter qualifies as a new similarity principle. It states that the external ventricular work intensity during each cardiac cycle is directly proportional to the metabolic turn-over rate.

Animals↗
PubMed1986

Free radicals: a potential pathogenic mechanism in inherited muscular dystrophy.

Despite years of intensive work, the biochemical defect responsible for the pathogenesis of inherited muscular dystrophy has not been identified either in humans or animal models. This review examines evidence in support of the hypothesis that free radicals may be responsible for muscle degeneration in this disorder. A variety of cellular abnormalities noted in dystrophic muscles can be accounted for by free radical mediated damage. In addition, chemical by-products associated with free radical damage are found in dystrophic muscle tissue from humans and animals with this disease. Various enzymatic antioxidant systems can be enhanced as a normal cellular response to oxidative stress, and such changes are seen both in dystrophic muscle cells and certain other tissues of dystrophic animals. An increased level of free radical damage would follow from either: enhanced production of free radical species, or a deficient component of the cellular antioxidant system, such as vitamin E. The free radical hypothesis of muscular dystrophy can account for data supporting several alternative theories of the pathogenesis of this disease, as well as other observations which have not previously been explained.

Calcium↗
PubMed1987

Increased removal rate of exogenous triglycerides after prolonged exercise in man: time course and effect of exercise duration.

Ten healthy young men exercised for 1.5 and 3 hours, respectively, 4 to 6 weeks apart at the same work intensity, corresponding to 77% of the individual maximal heart rate. In the fasting state 1 mL of 10% Intralipid/kg body weight was injected IV, the fractional removal rate was calculated (k2-value), and fasting lipid and apolipoprotein C-I, C-II, and CIII concentrations were determined one day before, immediately before, immediately after, and one day after the exercise: measurements were also made two and three days after the three-hour session. An increase of the k2-value was found only the day after the three-hour exercise (+66%, P less than .01), while after the 1.5-hour exercise the k2-value was not changed. One and two days after the three-hour exercise the fasting serum triglyceride concentration was significantly decreased by 33% and 16%, respectively. Serum triglyceride concentration was decreased also the day after the shorter session (-17%, P less than .05). Decreases in serum cholesterol concentrations were significant after both exercise bouts, but the significance disappeared if corrections for the changes in calculated plasma volume were made. Serum level of C apolipoproteins was decreased one day after the three-hour exercise, while it was not changed after the shorter exercise. This study shows that prolonged exercise produces an increase in the removal rate of Intralipid triglycerides from the bloodstream, that this change is related to the duration of exercise, and that some time is required following the exercise, before it is manifest.

Adult↗
PubMed1990

Impaired plasma catecholamine response to submaximal treadmill exercise in obese women.

After an overnight fast, blood samples were obtained from seven obese women (50% +/- 3% body fat) and from seven control women (25% +/- 1% body fat) before, during, and after 10 minutes of treadmill exercise at 70% of each individual's maximal oxygen uptake (VO2max). During exercise, peak plasma epinephrine (E), norepinephrine (NE), and glucagon concentrations in the control group significantly exceeded corresponding peak values in the obese group by 1.4-fold to twofold, whereas lactate responses did not differ. After 5 minutes of rest, peak plasma glucose, free fatty acid (FFA), and growth hormone (GH) concentrations in the control group also were significantly higher than in the obese women, but the plasma cortisol responses were comparable. Although plasma insulin concentrations decreased during exercise and rose to maximum values at 5-minute recovery in all individuals, levels were more than 3.5-fold higher in the obese group throughout the study. We conclude that the combination of heightened plasma insulin and diminished catecholamine and other counterregulatory hormone responses may account for subnormal plasma substrate increments that distinguish obese from non-obese women during exercise at comparable work intensities.

3-Hydroxybutyric Acid↗
PubMed1985

Effects of hypoxia on catecholamine and cardiorespiratory responses in exercising dogs.

The sympathoadrenal contribution to cardiorespiratory response elicited by hypoxia and/or exercise was assessed in the dog. The increased plasma norepinephrine (NE) and dopamine (DA) levels which follow hypoxia (fraction of inspired O2 equals 0.12) while epinephrine (E) remained unchanged ruled out the possibility of a primacy of the adrenal medulla in the response to hypoxia. In contrast to the lack of effect of hypoxic exposure, the adrenal medulla was substantially stimulated during exercise. The exercise-induced sympathoadrenal response remained unchanged during hypoxia as compared to normoxia when expressed as function of relative work intensity. Nevertheless at a given oxygen uptake, all plasma catecholamines were increased by hypoxia. These modifications in hormonal milieu failed, however, to alter the cardiac responses to exercise but were associated with a change in breathing pattern.

Animals↗
PubMed1987

Regional distribution of brain blood flow during maximal exertion in splenectomized ponies.

It has been reported in exercising ponies that O2 supply to all regions of the brain increased primarily due to a large increment in CaO2 and it was implied that this may reflect a generalized increase in brain metabolism during strenuous exercise. Splenectomy ameliorates the rise in CaO2 observed with exercise in ponies. Thus, the objective of the present study was to examine changes in regional brain blood flow and O2 supply of splenectomized ponies with sub-maximal and maximal exercise and to compare these data with previous observations in normal ponies. It was reasoned that in the absence of a marked rise in CaO2, the brain blood flow of splenectomized ponies would have to increase markedly if brain metabolism also increased with severe exercise. Regional brain blood flow was studied using 15 micron diameter radionuclide labeled microspheres injected into the left atrium during rest (control) and sub-maximal as well as maximal exertion on a treadmill. It was observed that despite marked arterial hypocapnia and acute systemic hypertension which developed during exercise, blood flow as well as O2 supply in the cerebral cortex, caudate nuclei, cerebral white matter, cerebellar white matter, thalamus-hypothalamus, mid-brain, pons and medulla were not different from control values. In the cerebrellar cortex, however, blood flow and O2 supply increased with both work intensities. Thus, it was concluded that in exercising ponies, metabolic O2 requirement increased in the cerebellar cortex but was most likely not different from control (rest) in other regions of the brain.

Animals↗
PubMed1985

Zinc and copper concentrations in the hair of workers from zinc based industries in India.

Some trace elements have been identified as potential hazards following long term exposure, and recently there has been intense work on different elemental exposure studies. Hair being the most convenient biopsy material has enabled the study of these elements in the human body and periodic sampling provides rates for their uptake. The present study has been done to compare the concentration of zinc and copper in human hair of the workers from the zinc based industry at Udaipur. The study shows that the concentration of zinc is higher in smelter workers than in the population of Udaipur city; the value of zinc in the mine workers is close to that of Udaipur city subjects. However, the correlation between the two elements is significant at p less than 0.01 for zinc mine workers.

Adult↗
PubMedDate not supplied

Interaction between exercising humans and growing plants in a Closed Ecological Life Support System.

The purpose of this study was to quantify the gas exchange between plants growing in a Closed Environmental Life Support System (CELSS) and the metabolism of human subjects undergoing various levels of physical exercise, and subsequently determine the buffer characteristics in relation to the carbon exchange established for plants in this closed loop life support system. Two men (ages 42 and 45 yr) exercised on a cycle ergometer at three different work intensities, each on a separate day. The CELSS, a 113 m3 chamber, was sized to meet the needs of one human. The plants, consisting of 20 m2 of potato, provided oxygen to the human during an artificially lighted photosynthesis phase and the human provided CO2 to the plants. The average rates of exchange for the subjects were 0.88, 1.69, and 2.47 liters O2/min and 0.77, 1.47, and 2.21 liters CO2/min at approximately 25%, 50%, and 75% of their maximal aerobic capacity, respectively. The photosynthetic rate for the CELSS was 0.95 liters/min. A balance between human CO2 production and plant utilization was noted at approximately the 50% VO2max level. The oxygen balance and changes were not within detectable limits of the CELSS instrumentation for the durations of these exercise exposures. If a CELSS environment is the methodology selected for long term spaceflight, it will be important to select plants that efficiently grow at the available light and nutrient levels while balancing the needs for the human crew at their levels of physical activity.

Adult↗
PubMed1993

Liver cytoprotection by prostaglandins.

During the last decade intensive work on the relationships between the liver and the arachidonic acid cascade has greatly expanded our knowledge of this area of research. The liver has emerged as the major organ participating in the degradation and elimination of arachidonate products of systemic origin. The synthesis in the liver of arachidonate products derived from the cyclooxygenase, lipoxygenase and cytochrome P450 system pathways has been demonstrated. The participation of leukotriene B4 and cysteinyl-leukotrienes as mediators of liver damage and the possible therapeutic usefulness of prostaglandins (PGs) in acute liver injury has attracted the interest of clinicians. This article reviews the essential features regarding the role of arachidonate metabolites in liver disease and specially focuses on the cytoprotective effects on the liver displayed by PGE2, PGE1, PGI2 and synthetic PG analogs in experimental models of liver damage induced by ischemia-reperfusion injury, carbon tetrachloride, bacterial lipopolysaccharide and viral hepatitis and on the possible mechanisms underlying liver cytoprotection in these experimental models. The therapeutic usefulness of PGs in clinical practice is critically analyzed on the basis of available evidence in patients with fulminant hepatic failure and primary graft nonfunction following liver transplantation.

Animals↗
PubMed1995

Coeliac disease research and clinical practice: maintaining momentum into the twenty-first century.

Recent research shows that each word in the definition of coeliac disease, permanent gluten sensitive enteropathy, must now be reviewed, revised or reinterpreted. Permanent--but there are now well-documented cases of acquired disease, and perhaps also partial recovery of gut gluten tolerance. Enteropathy--gluten sensitivity is expressed in a spectrum, with a mild form seen as normal architecture with high count of intraepithelial lymphocytes. Gluten--the provoking agent--Investigators are intensively working to identify the precise toxic sequence, and to establish how this will link in with new genetic information. Mechanism of sensitivity? or hypersensitivity?--Critical to this is new knowledge on the modulation and regulation of immunity to intestinal antigens, including gliadin. A hypothesis is presented, as to the pathogenesis of gluten-sensitive enteropathy, which combines concepts of oral tolerance and of the regulation of expression of delayed type hypersensitivity reactions in the gut mucosa.

Celiac Disease↗
PubMed1992

Inositol lipids in cellular signalling mechanisms.

At the opening of the 1980s, two camps vigorously contested whether receptor-stimulated inositol lipid hydrolysis was a transmembrane signalling reaction that brought about an elevation of cytosolic [Ca2+] or simply a frequent, but unexplained, response of many stimulated cells to a stimulated elevation of cytosolic [Ca2+]. Since 1984, this discussion has been replaced by intensive work that is well on the way to providing a detailed description of the complex set of signalling pathways initiated by phosphatidylinositol 4,5-bisphosphate hydrolysis to form the second messengers inositol 1,4,5-trisphosphate and 1,2-diacylglycerol. In addition, it has been realized that cells closely regulate their levels both of a novel family of 3-phosphorylated inositol lipids and of a large number of water-soluble inositol polyphosphates; the definition of the functions of these molecules will be a job for the 1990s.

Animals↗
PubMed2006

Thermodynamics of membrane domains.

The concept of lipid rafts and the intense work toward their characterization in biological membranes has spurred a renewed interest in the understanding of domain formation, particularly in the case of cholesterol-containing membranes. The thermodynamic principles underlying formation of domains, rafts, or cholesterol/phospholipid complexes are reviewed here, along with recent work in model and biological membranes. A major motivation for this review was to present those concepts in a way appropriate for the broad readership that has been drawn to the field. Evidence from a number of different techniques points to the conclusion that lipid-lipid interactions are generally weak; therefore, in most cases, massive phase separations are not to be expected in membranes. On the contrary, small, dynamic lipid domains, possibly stabilized by proteins are the most likely outcome. The results on mixed lipid bilayers are used to discuss recent experiments in biological membranes. The clear indication is that proteins partition preferentially into fluid, disordered lipid domains, which is contrary to their localization in ordered, cholesterol/sphingomyelin rafts inferred from detergent extraction experiments on cell membranes. Globally, the evidence appears most consistent with a membrane model in which the majority of the lipid is in a liquid-ordered phase, with dispersed, small, liquid-disordered domains, where most proteins reside. Co-clustering of proteins and their concentration in some membrane areas may occur because of similar preferences for a particular domain but also because of simultaneous exclusion from other lipid phases. Specialized structures, such as caveolae, which contain high concentrations of cholesterol and caveolin are not necessarily similar to bulk liquid-ordered phase.

Lipid Bilayers↗