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Biomedical subjects

M Fields

Publications and source records attributed to M Fields.

At least 19 recordsLinked to original sources
PubMed2004

Patterns of cardiovascular reactivity in disease diagnosis.

BACKGROUND: Aberrations of cardiovascular reactivity (CVR), an expression of autonomic function, occur in a number of clinical conditions, but lack specificity for a particular disorder. Recently, a CVR pattern particular to chronic fatigue syndrome was observed. AIM: To assess whether specific CVR patterns can be described for other clinical conditions. METHODS: Six groups of patients, matched for age and gender, were evaluated with a shortened head-up tilt test: patients with chronic fatigue syndrome (CFS) (n = 20), non-CFS fatigue (F) (n = 15), neurally-mediated syncope (SY) (n = 21), familial Mediterranean fever (FMF) (n = 17), psoriatic arthritis (PSOR) (n = 19) and healthy subjects (H) (n = 20). A 10-min supine phase was followed by recording 600 cardiac cycles on tilt (5-10 min). Beat-to-beat heart rate (HR) and pulse transit time (PTT) were measured. Results were analysed using conventional statistics, recurrence plot analysis and fractal analysis. RESULTS: Multivariate analysis evaluated independent predictors of the CVR in each patient group vs. all other groups. Based on these predictors, equations were determined for a linear discriminant score (DS) for each group. The best sensitivities and specificities of the DS, consistent with disease-related phenotypes of CVR, were noted in the following groups: CFS, 90.0% and 60%; SY, 93.3% and 62.5%; FMF, 90.1% and 75.4%, respectively. DISCUSSION: Pathological disturbances may alter cardiovascular reactivity. Our data support the existence of disease-related CVR phenotypes, with implications for pathogenesis and differential diagnosis.

Adult↗
PubMed2003

Assessment of cardiovascular reactivity by fractal and recurrence quantification analysis of heart rate and pulse transit time.

Methods used for the assessment of cardiovascular reactivity are flawed by nonlinear dynamics of the cardiovascular responses to stimuli. In an attempt to address this issue, we utilized a short postural challenge, recorded beat-to-beat heart rate (HR) and pulse transit time (PTT), assessed the data by fractal and recurrence quantification analysis, and processed the obtained variables by multivariate statistics. A 10-min supine phase of the head-up tilt test was followed by recording 600 cardiac cycles on tilt, that is, 5-10 min. Three groups of patients were studied, each including 20 subjects matched for age and gender--healthy subjects, patients with essential hypertension (HT), and patients with chronic fatigue syndrome (CFS). The latter group was studied on account of the well-known dysautonomia of CFS patients, which served as contrast against the cardiovascular reactivity of the healthy population. A total of 52 variables of the HR and PTT were determined in each subject. The multivariate model identified the best predictors for the assessment of reactivity of healthy subjects vs CFS. Based on these predictors, the "Fractal & Recurrence Analysis-based Score" (FRAS) was calculated: FRAS=76.2+0.04*HR-supine-DET -12.9*HR-tilt-R/L -0.31*HR-tilt-s.d. -19.27*PTT-tilt-R/L -9.42*PTT-tilt-WAVE. The median values and IQR of FRAS in the groups were: healthy=-1.85 (IQR 1.89), hypertensives=+0.52 (IQR 5.78), and CFS=-24.2 (5.34) (HT vs healthy subjects: P=0.0036; HT vs CFS: P<0.0001). Since the FRAS differed significantly between the three groups, it appears likely that the FRAS may recognize phenotypes of cardiovascular reactivity.

Adult↗
PubMed2003

The head-up tilt test with haemodynamic instability score in diagnosing chronic fatigue syndrome.

BACKGROUND: Studying patients with chronic fatigue syndrome (CFS), we have developed a method that uses a head-up tilt test (HUTT) to estimate BP and HR instability during tilt, expressed as a 'haemodynamic instability score' (HIS). AIM: To assess HIS sensitivity and specificity in the diagnosis of CFS. DESIGN: Prospective controlled study. METHODS: Patients with CFS (n=40), non-CFS chronic fatigue (n=73), fibromyalgia (n=41), neurally mediated syncope (n=58), generalized anxiety disorder (n=28), familial Mediterranean fever (n=50), arterial hypertension (n=28), and healthy subjects (n=59) were evaluated with a standardized head-up tilt test (HUTT). The HIS was calculated from blood pressure (BP) and heart rate (HR) changes during the HUTT. RESULTS: The tilt was prematurely terminated in 22% of CFS patients when postural symptoms occurred and the HIS could not be calculated. In the remainder, the median(IQR) HIS values were: CFS +2.14(4.67), non-CFS fatigue -3.98(5.35), fibromyalgia -2.81(2.62), syncope -3.7(4.36), generalized anxiety disorder -0.21(6.05), healthy controls -2.66(3.14), FMF -5.09(6.41), hypertensives -5.35(2.74) (p<0.0001 vs. CFS in all groups, except for anxiety disorder, p=NS). The sensitivity for CFS at HIS >-0.98 cut-off was 90.3% and the overall specificity was 84.5%. DISCUSSION: There is a particular dysautonomia in CFS that differs from dysautonomia in other disorders, characterized by HIS >-0.98. The HIS can reinforce the clinician's diagnosis by providing objective criteria for the assessment of CFS, which until now, could only be subjectively inferred.

Adult↗
PubMed2001

Aspirin reduces blood cholesterol in copper-deficient rats: a potential antioxidant agent?

The purpose of this study was to examine whether the hypocholesterolemic effect of aspirin is to due to its antioxidant properties. Oxidative stress was induced in rats by feeding them a copper-deficient diet. Copper deficiency reduced the activity of the enzyme superoxide dismutase (SOD) and lowered liver copper concentration but elevated liver iron. The combination of reduced SOD activity, high liver iron, and low liver copper resulted in an oxidative stress assessed by increased liver lipid peroxidation compared with copper-adequate controls. In addition, copper-deficient rats exhibited elevation of blood cholesterol. The administration of aspirin lowered both liver lipid peroxidation and blood cholesterol. It is suggested that the hypocholesterolemic properties of aspirin could be due to its ability to reduce oxidative stress.

Animals↗
PubMed2001

Guiding across the generations: rediscovering nursing's promise.

This report describes the parallels between guiding and nursing. The principles of guiding, safety, discovery, integrity, and intention are reviewed and tied to specific skills. Nursing guides integrate these principles and skills to show the way to people for whom they care. The safety that guiding provides serves multiple generations and their unique needs.

Adult↗
PubMed2000

Intestinal beta-carotene 15,15'-dioxygenase activity is markedly enhanced in copper-deficient rats fed on high-iron diets and fructose.

The purpose of the present work was to examine effects of the Cu-Fe interaction on intestinal beta-carotene 15,15'-dioxygenase activity when a wide range of dietary Fe (deficiency to excess) was used in relation to Cu status of rats. The effect of dietary carbohydrates was also examined since they play a role in the Cu-Fe interaction in vivo. Weanling male Sprague-Dawley rats (n 72) were divided into twelve dietary groups, which were fed on either low-, normal-, or high-Fe levels (0.9, 9.0, and 90.0 mmol Fe/kg diet respectively) combined with Cu-adequate or -deficient levels (0.94 and 0.09 mmol Cu/kg diet respectively) and with starch or fructose in the diets. The data showed that both Fe concentration and beta-carotene 15,15'-dioxygenase activity in small intestinal mucosa were enhanced with increasing dietary Fe and with Cu deficiency v. Cu adequacy. Dietary fructose did not aggravate the Fe-enhancement, related to Cu deficiency, in the small intestine; however, fructose increased the intestinal dioxygenase activity in rats fed on normal- or high-Fe diets when compared with starch controls. Thus, the highest intestinal dioxygenase activity associated with the lowest hepatic retinol (total) concentration was found in rats fed on the Cu-deficient, high-Fe, fructose-based diet. Finally, a positive linear relationship was found between the dioxygenase activity and Fe concentration in intestinal mucosa. In conclusion, the data indicate that beta-carotene 15,15'-dioxygenase activity requires Fe as cofactor in vivo and the enzyme is modulated by the three dietary components: Cu, Fe, and fructose.

Analysis of Variance↗
PubMed1999

Cholesterol-lowering nature of unsaturated fat in rats may be due to its inability to increase hepatic iron.

The present investigation was conducted to determine whether the cholesterol-raising properties of saturated fat and cholesterol-lowering properties of unsaturated fat are associated with levels of hepatic iron. The magnitude of hepatic iron retention was manipulated by feeding rats diets that were either copper-deficient or -adequate, iron-adequate or -supplemented, and contained either beef tallow or corn oil. Weanling male Sprague-Dawley rats were randomly divided into eight dietary groups according to the type of dietary fat (beef tallow or corn oil) and level of dietary copper (0.74 or 6.9 microg Cu/g diet) or iron (44.4 or 86.7 microg Fe/g diet). Beef tallow and copper deficiency alone increased hepatic iron levels, which in turn were associated with increased plasma cholesterol. When the three dietary factors were combined, ie, iron, beef tallow, and copper deficiency, they induced the highest magnitude of hepatic iron retention, which in turn was associated with the highest concentration of plasma cholesterol. In contrast, when hepatic iron retention was not increased, such as by feeding a diet containing corn oil or by consumption of a copper-adequate diet, plasma cholesterol was not elevated. Based on these data, it is suggested that nutrients that have the ability to increase hepatic iron have the potential to increase plasma cholesterol.

Animals↗
PubMed1999

Dietary fructose but not starch is responsible for hyperlipidemia associated with copper deficiency in rats: effect of high-fat diet.

OBJECTIVE: To test the hypothesis that copper deficiency in rats may be hyperlipidemic only when the diets consumed contain nutrients which contribute to blood lipids such as fructose and high fat. METHODS: Weanling male Sprague Dawley rats were fed diets which contained either starch or fructose as their sole carbohydrate source. The diets were either inadequate (0.6 microg Cu/g) or adequate (6.0 microg Cu/g) in copper and contained either high (300 g/kg) or low (60 g/kg) fat. At the end of the 4th week the rats were killed. Livers were analyzed for copper content. Plasma was analyzed for cholesterol and triglyceride concentrations. RESULTS: High-fat diet did not increase blood lipids in rats fed a copper-deficient diet containing starch. In contrast, the combination of high-fat diet with fructose increased blood triglycerides and fructose with copper deficiency resulted in a significant increases in blood cholesterol. CONCLUSIONS: Hyperlipidemia of copper deficiency in rats is dependent on synergistic effects between dietary fructose and copper deficiency and fructose and amount of dietary fat. Hyperlipidemia does not develop if starch is the main source of dietary carbohydrate in a copper-deficient diet even if a high-fat diet is fed.

Analysis of Variance↗
PubMed1999

Beta-carotene 15,15'-dioxygenase activity is responsive to copper and iron concentrations in rat small intestine.

OBJECTIVE: Previous in vitro studies have suggested that beta-carotene 15,15'-dioxygenase is an iron-dependent enzyme. However, in vivo, it is difficult to alter iron tissue concentration by varying dietary iron because of homeostatic control. On the other hand, an interaction between iron and copper has been shown, i.e., copper-deficiency results in an increase of iron in rat liver. Therefore, we hypothesized that intestinal iron concentration could be increased by copper-deficiency. Our objective was to examine the effects of iron as affected by dietary copper on beta-carotene 15,15'-dioxygenase activity in the small intestine. METHODS: Weanling male Sprague-Dawley rats (40 to 45g) were divided into four dietary groups: two copper-adequate groups (6.0 microg Cu/g diet) and two copper-deficient groups (0.6 microg Cu/g) combined with either normal iron (44 microg Fe/g) or high iron (87 microg Fe/g). Iron and copper concentrations were determined by atomic absorption spectrophotometry and the dioxygenase activity by reverse phase HPLC. RESULTS: Intestinal copper concentration was significantly reduced (40%) by the consumption of the copper-deficient diets, but intestinal iron was not changed by doubling dietary iron in rats fed either copper-adequate or copper-deficient diets. However, as hypothesized, the two copper-deficient groups exhibited higher intestinal iron concentration (> or =137%, p<0.001) than the copper-adequate controls. In addition, intestinal beta-carotene 15,15'-dioxygenase activity was increased by 27% and 106%, respectively, for copper-deficient rats fed either normal or high iron diets, compared to the respective copper-adequate controls (p<0.01). The dioxygenase activity was not significantly affected by dietary iron in either copper-adequate or copper-deficient groups. Finally, the enzyme activity was positively correlated (r=0.67, p<0.0001) with iron concentration and negatively correlated (r=-0.49, p<0.01) with copper concentration in small intestine. CONCLUSIONS: Intestinal beta-carotene 15,15'-dioxygenase may be an iron-dependent enzyme sensitive to copper status in vivo.

Analysis of Variance↗
PubMed1999

Level of dietary iron, not type of dietary fat, is hyperlipidemic in copper-deficient rats.

OBJECTIVE: This study was conducted to determine whether high dietary iron will negate the protective effect of unsaturated fat against hyperlipidemia. METHODS: Forty-eight weanling, male Sprague Dawley rats were randomly assigned to eight dietary groups differing in the levels of copper and iron and type of dietary fat (saturated or unsaturated). The diets were either deficient (0.6 microg Cu/g) or adequate (6.8 microg Cu/g) copper and either adequate (53 microg Fe/g) or high (506 microg Fe/g) iron. All diets contained starch as the sole source of dietary carbohydrate. RESULTS: Regardless of the type of dietary fat, three copper-deficient rats fed the high levels of dietary iron died prematurely due to ruptured hearts. Surviving rats belonging to the copper deficiency and high-dietary iron regimen developed severe anemia, enlarged hearts and livers, and exhibited the highest levels of liver iron. These rats also developed hypercholesterolemia. Triglycerides were elevated by the consumption of high iron diets. CONCLUSION: Data show that levels of dietary iron, not the type of dietary fat, are potential inducers of hypertriglyceridemia. Data also show that the combination of high iron intake and dietary copper deficiency is responsible for elevating blood cholesterol.

Analysis of Variance↗
PubMed1999

Expression and regulation of relaxin-like factor gene transcripts in the bovine ovary: differentiation-dependent expression in theca cell cultures.

The relaxin-like factor (RLF) was recently discovered as a new member of the insulin-insulin-like growth factor-relaxin family of growth factors and hormones predominantly in the Leydig cells of the testis. In cattle, in contrast to other species, the RLF gene is also expressed to a high level in the ovary, where its expression pattern in the corpus luteum of the late cycle and pregnancy is similar to that of relaxin in the pig. The RLF gene was also transcribed to a high level in the theca cells of estrogen-rich, large antral follicles. Long-term primary cultures of bovine theca cells showed that expression was insulin dependent. After an initial decline in specific mRNA concentrations, there was a switch to a transcript with a longer poly(A) tail at about Day 6 of culture, which continued to increase to very high levels by Day 15 of culture. Addition of fetal calf serum to cultures caused a rapid and irreversible down-regulation of the RLF gene. Also, LH caused a decline in specific gene expression in long-term primary theca cell cultures. As in the Leydig cells of the testis, the pattern of RLF gene expression appears to reflect the differentiation state of the ovarian theca-luteal cell lineage, and should prove useful for mapping the fate of these cells under differing stimulation regimes.

Androstenedione↗
PubMed1998

Effect of hepatic iron on hypercholesterolemia and hypertriacylglycerolemia in copper-deficient fructose-fed rats.

The purpose of this investigation was to establish whether plasma cholesterol and triacylglycerol(s) in copper deficiency can be increased or decreased by hepatic iron levels. Weanling male Sprague-Dawley rats were randomly divided into six dietary groups based on levels of dietary copper and iron. They were fed from weaning their respective diets for 6 wk. Forty percent of the copper-deficient rats fed a 15.7 mumol Fe/g diet died; 22% of those fed a diet containing 8.6 mumol Fe/g died; and there were no deaths in the 3.4 mumol Fe/g diet group. Rats belonging to the group fed the high-iron diet also exhibited the highest levels of liver iron, liver glutathione, and plasma cholesterol and triacylglycerol(s) compared with those fed either the adequate or low levels of dietary iron. There was a direct correlation (r = 0.82 and 0.77, respectively) between levels of cholesterol and triacylglycerol(s) in plasma and hepatic iron concentrations. These results provide strong evidence that points to a major involvement of iron in the lipemia of copper deficiency. These data may be important to those individuals who consume large quantities of fortified iron foods and supplement with iron but whose intake of copper is suboptimal.

Animals↗
PubMed1998

Nutritional factors adversely influencing the glucose/insulin system.

For the majority of people, particularly if they do not smoke, the food they eat is the largest controllable factor determining their long-term health. The disproportionate consumption of foods high in fat, especially high in saturated fat, and high in simple sugars at the expense of foods high in complex carbohydrate and unsaturated fat has the potential of inducing abnormal metabolic processes in a normal healthy individual and to promote chronic degenerative diseases. Some of the effects of individual macronutrients such as fat, refined sugars and alcohol in promoting abnormalities in glucose/insulin system are presented. These nutrients were chosen because they also have the ability to alter oxidative state of the individual, which in turn could affect the glucose/insulin system. This review focuses on the role of dietary nutrient interactions in influencing the glucose/insulin system through the generation of reactive oxygen species. The importance of dietary macronutrient interaction with micronutrients such as copper and iron and the potential it has in affecting the glucose/insulin system is addressed.

Alcohol Drinking↗
PubMed1997

Hepatic iron overload may contribute to hypertriglyceridemia and hypercholesterolemia in copper-deficient rats.

The present study was conducted in order to determine whether hepatic iron retention in rats fed a copper-deficient diet containing fructose is associated with hypertriglyceridemia and hypercholesterolemia, and whether a reduction of iron intake will prevent elevation of blood triglycerides and cholesterol. Rats were fed from weaning either a copper-deficient (0.6 microgram Cu/g) or copper-adequate (6.0 micrograms Cu/g) diet for 4 weeks. Half the rats consumed either an adequate level of iron (50 micrograms Fe/g) or a low level (17 micrograms Fe/g). Reduction of iron intake reduced blood levels of both triglycerides and cholesterol in rats fed a copper-deficient diet containing fructose. In addition, hepatic lipid peroxidation was also decreased. The combination of high iron, low copper, and fructose may be responsible for increased levels of risk-factor metabolites associated with heart disease.

Animals↗
PubMed1997

Benfluorex, a hypotriglyceridemic drug, reduces lipid peroxidation and alleviates adverse metabolic complications of copper deficiency.

The pathologies associated with copper deficiency in rats fed fructose may be induced, in part, by hypertriglyceridemia and lipid peroxidation. Reducing triacylglycerol levels in plasma may result in lowering lipid peroxidation, which in turn could ameliorate metabolic effects resulting from the combination of fructose feeding and copper deficiency. Benfluorex, a hypolipidemic factor able to reduce hypertriglyceridemia, was administered to weanling male rats fed either copper-deficient (0.6 microgram Cu/g) or adequate (6.0 micrograms Cu/g) diets containing fructose as the sole dietary carbohydrate. In copper-deficient rats, benfluorex (50 micrograms.kg-1.d-1) reduced plasma triacylglycerols from 45 to 31 mg/dL, reduced lipid peroxidation by approximately 50%, and prevented the enlargements of heart and liver size and the atrophy of the pancreas, and ameliorated anemia. It is suggested that lipid peroxidation associated with hypertriglyceridemia may be responsible for the pathologies induced by the combination of fructose consumption and copper deficiency.

Amylases↗
PubMed1997

Impaired endocrine and exocrine pancreatic functions in copper-deficient rats: the effect of gender.

OBJECTIVE: To examine the effect of gender on endocrine and exocrine pancreatic function in female and male rats fed from weaning a copper-deficient diet. METHODS: Weanling male and female rats were fed a copper-deficient or adequate diet for 4 weeks. Rats were sacrificed after an overnight fast. Livers and pancreata were removed, weighed and the concentrations of copper and iron were determined. In addition, insulin was measured in pancreatic tissue and plasma. Lipase and amylase activities were measured in pancreas. Lipid peroxidation was assessed in liver. RESULTS: Copper deficiency in the male resulted in a profound reduced glandular mass of the pancreas. The pancreas continued low activities of lipase and amylase but excessive levels of insulin. Iron retention in the pancreas of the copper-deficient male rat was greater than in the female counterpart. Effects of copper deficiency in female rats on pancreas mass and endocrine pancreas were of lesser magnitude compared with males. Plasma insulin in the female rat was much higher than in the male rat. Hepatic lipid peroxidation was increased by copper deficiency in the male rat but was unaffected in the female. CONCLUSIONS: Data show that pancreatic atrophy is more pronounced in males compared with females, and the endocrine pancreas of the male is more susceptible to dietary copper deprivation than the female rat. The greater degree of pancreatic atrophy and associated abnormalities in males compared with females may be related to the greater retention of pancreatic iron and subsequent peroxidative damage.

Amylases↗