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Biomedical subjects

I Tkác

Publications and source records attributed to I Tkác.

At least 19 recordsLinked to original sources
PubMed1999

Cardiovascular risk factors as predictors of mortality in type II diabetic patients.

BACKGROUND: Mortality among diabetic patients is high and attempts have been made to find clinical markers which would help to identify patients at risk. MAIN PURPOSE: The purpose of this study was to assess whether cardiovascular risk factors like previous myocardial infarction, left ventricular dysfunction, hypertension, renal insufficiency, and 24-hour mean or minimum heart rate, significantly contribute to the mortality in this group of patients. METHODS: 45 male patients with type II diabetes mellitus were studied by ambulatory electrocardiography to obtain the information about the 24-hour mean and minimum heart rates; records from baseline hospitalization were reviewed for clinical variables. After 55 months mortality data were retrieved. Cox's proportional hazards regression model was used to study the effect of clinical variables on mortality in multivariate analysis. RESULTS: All-cause mortality was 38%. The groups of survivors and nonsurvivors differed significantly in terms of age, the presence of left ventricular dysfunction and renal insufficiency. No significant difference in 24-hour mean or minimum heart rate was registered. In the Cox's model, the presence of left ventricular dysfunction, renal insufficiency and age significantly and independently predicted mortality. CONCLUSION: The present study, showed that left ventricular dysfunction and renal insufficiency were related to the all-cause mortality of type II diabetic patients independently of age, after 55 months of follow-up. Prognostic significance of 24-hour mean or minimum heart rate has not been proven.

Adult↗
PubMed1998

New approach for quantitation of short echo time in vivo 1H MR spectra of brain using AMARES.

Short echo time in vivo STEAM 1H MR spectra (4.7 T, TE = 16 ms) of normal rat brain were fitted in the time domain using a VARPRO-like algorithm called AMARES which allows an inclusion of a large amount of prior knowledge. The prior knowledge was derived from phantom spectra of pure metabolite solutions measured under the same experimental conditions as the in vivo spectra. The prior knowledge for the in vivo spectra was constructed as follows: for each VARPRO-fitted phantom spectrum one peak (the most prominent one in the in vivo spectrum) was chosen and left unconstrained in the AMARES fitting while all the other peaks in the metabolite spectrum (i.e. their corresponding parameters--amplitudes, damping factors, frequencies and phases) were fixed to the parameter values of the unconstrained peak via amplitude and damping ratios and frequency and phase shifts. Including N-acetyl-aspartate, glutamate, total creatine, cholines, glucose and myo-inositol into the fits provided results which were in agreement with published data. An inclusion of glutamine into the set of fitted metabolites was also investigated.

Algorithms↗
PubMed1998

Motion artifacts reduction in DWI using navigator echoes: a robust and simple correction scheme.

NMR signal phase variation caused by macroscopic motion of an object during application of the diffusion gradient is a well-known effect in diffusion-weighted imaging (DWI) using the standard pulsed gradient spin-echo sequence (PGSE). This phase error causes severe ghost artifacts in the output image when phase encoding techniques, such as two dimensional Fourier transform (2DFT) imaging, are used. One possible way to eliminate the motion effects is the navigator echo technique. The method is based on estimating the phase error from the navigator echo and using it for the correction of the image echo. The phase errors (zero and first order) for the phase correction of the image echo are usually evaluated from the navigator echo after Fourier transform (FT) in the readout direction, correcting for both translation and rotation. We present here a simple algorithm which enables evaluation and correction in the time domain of phase errors induced by motion. This approach has the advantage of improved correction of motional artifacts and minimized sensitivity to noise and inaccurate setting up of the experiment.

Algorithms↗
PubMed1998

Important contribution of lipoprotein particle number to plasma triglyceride concentration in type 2 diabetes.

The aim of the present study was to determine the contributions of particle size versus number to differences in plasma triglyceride-rich lipoprotein concentrations in patients with type 2 diabetes. Fasting plasma was obtained from 174 consecutive eligible men and women with type 2 diabetes (with or without insulin treatment, mean age 57.0 + 6.3 years) who were undergoing coronary angiography. The triglyceride-rich (Sf 12-400) lipoproteins (TRL) were subfractionated into the Sf 12-60 and Sf 60-400 subfractions. Particle numbers, estimated by measuring apolipoprotein B by electroimmunoassay, in each of these lipoprotein fractions were related to enzymatically determined triglyceride levels in the triglyceride-rich lipoproteins. Approximately 87% of the triglyceride-rich lipoprotein particles were in the Sf 12-60 fraction and 13% in the Sf 60-400 fraction. Multiple linear regression indicated that 69% (i.e. r2=0.69) of the variance in the triglyceride levels could by explained by differences in TRL particle number and 17% (i. e. r2=0.17) by the differences in particle triglyceride content. These observations are similar in each gender and in those with or without insulin treatment. In conclusion, in type 2 diabetes, the vast majority of triglyceride-rich lipoproteins are smaller particles which are in the Sf 12-60 fraction. Differences in particle number, rather than triglyceride content, account for approximately 70% of the differences in triglyceride levels observed between individuals. Previous demonstrations, in those without diabetes, of an association between small triglyceride-rich lipoproteins with coronary artery disease suggest the importance of these findings to the increased atherosclerosis in diabetes.

Adult↗
PubMed1998

Absolute metabolite quantification by in vivo NMR spectroscopy: II. A multicentre trial of protocols for in vivo localised proton studies of human brain.

We have performed a multicentre trial to assess the performance of three techniques for absolute quantification of cerebral metabolites using in vivo proton nuclear magnetic resonance (NMR). The techniques included were 1) an internal water standard method, 2) an external standard method based on phantom replacement, and 3) a more sophisticated method incorporating elements of both the internal and external standard approaches, together with compartmental analysis of brain water. Only the internal water standard technique could be readily implemented at all participating sites and gave acceptable precision and interlaboratory reproducibility. This method was insensitive to many of the experimental factors affecting the performance of the alternative techniques, including effects related to loading, standing waves and B1 inhomogeneities; and practical issues of phantom positioning, user expertise and examination duration. However, the internal water standard method assumes a value for the concentration of NMR-visible water within the spectroscopic volume of interest. In general, it is necessary to modify this assumed concentration on the basis of the grey matter, white matter and cerebrospinal fluid (CSF) content of the volume, and the NMR-visible water content of the grey and white matter fractions. Combining data from 11 sites, the concentrations of the principal NMR-visible metabolites in the brains of healthy subjects (age range 20-35 years) determined using the internal water standard method were (mean+/-SD): [NAA]=10.0+/-3.4 mM (n=53), [tCho]=1.9+/-1.0 mM (n=51), [Cr + PCr]=6.5+/-3.7 mM (n=51). Evidence of system instability and other sources of error at some participating sites reinforces the need for rigorous quality assurance in quantitative spectroscopy.

Adult↗
PubMed1998

[Infections of the diabetic foot--etiopathogenesis and possible preventive strategies].

The St. Vincent declaration defined the aim to achieve within the next five years a 50% reduction of the number of amputations on account of diabetic gangrene. This can be achieved by systematic application of preventive and therapeutic provisions in practice. The authors mention the most important pathogenetic factors leading to the development of lesions of the lower extremities in diabetics as well as the most frequent microorganisms participating in their infection. They remind also of the most important preventive measures to be taken by patients and physicians.

Bacterial Infections↗
PubMed1998

Serum creatinine level is an independent risk factor for the angiographic severity of internal carotid artery stenosis in subjects who have previously had transient ischaemic attacks.

BACKGROUND: Serum creatinine level has been reported to be related to the incidence of strokes. OBJECTIVE: To examine the relationship between serum creatinine level and the severity of extracranial carotid artery atherosclerosis. DESIGN AND METHODS: This is a secondary analysis of data from 88 patients (59 men and 29 women) who had previously had transient ischaemic attacks or minor strokes and had been included in intervention trials of symptomatic carotid disease. Narrowing of internal carotid artery was estimated by angiography. Both internal carotid arteries were measured and the severity was expressed as the sum of percentage stenoses on both sides. The risk profiles of patients with moderate and severe internal carotid artery stenosis were compared. RESULTS: The sex-adjusted mean serum creatinine concentration in those with severe carotid disease was significantly higher than that in those with moderate disease (106.3 +/- 3.3 versus 91.3 +/- 3.7 mumol/l, P = 0.003), but still within the normal range. The risk of having severe disease was compared with risk of having moderate disease for people ranked by their serum creatinine levels. Univariate logistic regression showed that the odds ratio (OR) for having severe involvement of internal carotid artery was greater for patients in mid-tertile of creatinine values than it was for those in the lowest tertile (OR 6.3, 95% confidence interval 2.0-20.4, P = 0.002). The creatinine levels of patients in these two tertiles were within the normal range. The OR was no greater for patients in the highest tertile of creatinine values, which were slightly elevated above the normal range. These OR did not change after adjustment for age, sex, hypertension or systolic blood pressure, diabetes, smoking and lipid levels. CONCLUSION: Results of this study demonstrate for the first time that serum creatinine level, even within the range of upper normal or mildly elevated levels, is related to the angiographic severity of internal carotid artery disease in patients who have previously had transient ischaemic attacks and that this relationship is independent of classic cardiovascular risk factors.

Aged↗
PubMed1998

Application of NMR spectroscopy in biochemical studies of tumor cells sensitive and resistant to anticancer drugs.

Drug resistance is a prominent problem of cancer therapy. Differences in quantity and quality of many metabolites in normal and malignant cells and their changes after treatment by anticancer drugs can be detected by nuclear magnetic resonance (NMR) both in vivo and in vitro. The results of in vivo and in vitro 1H, 13C, 19F and 31P NMR spectroscopy and their correlation with the degree of resistance to anticancer drugs are discussed. Monitoring of treatment and development of drug resistance by this non-invasive method could be useful not only in cancer research related to drug resistance but also in clinical medical oncology.

Amino Acids↗
PubMed1997

The severity of coronary atherosclerosis in type 2 diabetes mellitus is related to the number of circulating triglyceride-rich lipoprotein particles.

The presence or absence of coronary artery disease (CAD) in diabetic patients has been related to the level of circulating plasma lipoproteins. This study examines whether there is a relationship between the actual severity of CAD and the plasma concentration of major classes of plasma lipoproteins (HDL, LDL, triglyceride-rich lipoproteins (TRL), and their Sf 12 to 60 and Sf 60 to 400 subfractions), particularly the numbers of lipoprotein particles, in men and women with type 2 diabetes. 174 diabetic patients (136 men, 38 women) who underwent angiography were studied. Nine specific coronary segments were scored. The population was divided into tertiles according to the angiographic severity of their coronary disease: mild CAD: coronary score 1 to 10; moderate CAD: coronary score 11 to 13; or severe CAD: coronary score 14 to 22. The main findings were that the numbers of particles (as reflected by the apoB levels) of the TRL were greater in those with moderate and severe disease than in those with mild disease (P = .001). There was a significant correlation between the coronary score and the apoB in TRL (P = .006). There were parallel but nonsignificant changes in triglyceride levels. ApoA-I was lower in patients with moderate and severe disease (P = .01). These differences were more striking in women than they were in men. There were no differences in plasma, LDL, or HDL cholesterol or in LDL apoB or Lp(a). Multiple linear regression analysis, when adjusted for sex, age, and BMI, showed that three lipid variables (TRL apoB, LDL cholesterol, and plasma apoA-I) significantly and independently predicted the coronary score. This study demonstrates that in type 2 diabetes, the severity of angiographically evaluated CAD is positively related to the numbers of TRL particles in the plasma. This relationship is stronger in women than in men, and it is independent of HDL and LDL.

Adult↗
PubMed1997

Fibrinogen and albuminuria are related to the presence and severity of peripheral arterial disease in women with type 2 diabetes mellitus.

The relationship between the ultrasonographically determined presence and severity of peripheral arterial disease (PAD) and cardiovascular risk factors was studied in 30 post-menopausal, nonsmoking women with type 2 diabetes mellitus. PAD was established on the basis of decreased ankle/arm index (AAI) of < 0.9 in 15 patients. The control group included 15 type 2 diabetic women with AAI > 1.0. There were no differences with respect to diabetes control and systolic blood pressure between the patients with PAD and controls. The patients with PAD had significantly higher mean fibrinogen concentrations (4.75 +/- 0.35 vs 3.53 +/- 0.36 g/L, P < 0.01) and urinary albumin excretion (UAE) values (893 +/- 501 vs 57 +/- 24 mg/day, P < 0.05) than the subjects in the control group. There was no significant difference between the study groups with respect to any lipid variables. Significant partial correlations adjusted for age were observed between AAI (which expressed the severity of PAD) and log UAE (r = -0.55, P < 0.01), creatinine (r = -0.48, P < 0.01) and fibrinogen (r = -0.45, P < 0.01). In the multiple stepwise regression analysis with AAI as a dependent variable, only fibrinogen (P = 0.033) and log UAE (P = 0.029) were included into the best model. In conclusion, in nonsmoking women with type 2 diabetes mellitus, fibrinogen and albuminuria were the only risk factors associated with both the presence and severity of peripheral arterial disease.

Aged↗
PubMed1995

[Neurohumoral activity in liver cirrhosis].

The authors assessed in 40 patients with cirrhosis of the liver and in 33 controls the plasma renin activity (PRA), aldosterone (PA), the atrial natriuretic factor (ANF) and the digoxin like activity (DLA) in plasma under basal conditions. In patients with cirrhosis of the liver they found significantly lower levels of PRA, PA and DLA, as compared with the control group, the ANF levels were not significantly altered. In the group with cirrhosis the highest neuroendocrine activity was recorded, in particular of PRA and PA in decompensated cirrhotics receiving diuretic treatment. Therefore it is useful to combine diuretics with preparations or measures which reduce the activity of the renin-angiotensin-aldosterone system and/or promote the activity of natriuretic substances. The authors found a negative correlation between PRA and SNa, PRA and UNaV, while ANF did not correlate with natriuresis. The main determinant of Na excretion in decompensated cirrhosis is the activity of the renin-angiotensin-aldosterone system. DLA plasma levels also correlated inversely with SNa values and Na excretion and thus also reflect the severity of fluid retention.

Adult↗
PubMed1994

[The present status of treatment of unstable angina pectoris].

UAP is a frequent manifestation of ischaemic heart disease; it is intermediary between stable angina and myocardial infarction and sudden death resp. The hospitalization mortality is 5%, approximately 15% of the patients with UAP develop myocardial infarction. The aim of UAP treatment is: 1. prevention of ischaemic episodes, 2. prevention of infarction and 3. control or elimination of risk factors, to improve the long-term prognosis in these patients. As antianginal drugs in UAP as a routine calcium antagonists, beta-blockers and nitrates are used. A very important part in the treatment of UAP is played by antithrombotic and thrombolytic treatment as in this disease rupture or fissure of plaques and subsequent thrombus formation is important. Non-occlusive thrombi are present in 80% in UAP, while in infarctions they are present in 21%. Rupture of an atherosclerotic plaque leads to thrombocyte activation, release of tissue thromboplastin and activation of the coagulation system aspirin inhibits platelet function and thus reduces thromboxane A2 formation. Heparin affects the coagulation process in UAP, reduces the number of anginal attacks and protects from the development of infarction. Treatment of UAP with streptokinase and rt-PA has no great advantages, when compared with heparin. Surgical treatment of UAP has somewhat better results than conservative treatment. Coronary angioplasty is an ideal solution in UAP when one or two arteries are damaged.

Angina, Unstable↗
PubMed1994

[Factors affecting serum lipid levels in patients with type 2 diabetes mellitus].

Serum lipid concentrations were assessed in 147 type 2 diabetics. The patients were divided into different sub-groups in order to follow up different factors which could have an impact on serum lipids. The mean total cholesterol concentrations were significantly higher in diabetic women as compared with men. The authors did not reveal significant differences in lipid concentrations between obese and non-obese diabetics. Hypertensive diabetics had higher mean total cholesterol levels and LDL-cholesterol levels, as compared with diabetic patients without hypertension. Patients using oral antidiabetics had significantly higher mean triglyceride levels and lower HDL-cholesterol levels, as compared with insulin-treated diabetics. In a multiple stepwise regression analysis correlated triglycerides with three independent variables: total cholesterol, diastolic blood pressure and inversely with HDL-cholesterol. On the other hand, total cholesterol correlated significantly with triglycerides, HDL-cholesterol and proteinuria/day. To sum up, it may be stated, that the results of the present investigation are consistent with Reaven's concept of the syndrome X, however the cholesterol concentration is affected also by the proteinuria.

Cholesterol↗
PubMed1994

[Changes in lipoprotein metabolism in patients with diabetes mellitus and the effect on lipid profile in diabetics].

Diabetic patients have a 2 to 4 times higher risk of development of atherosclerosis than non-diabetic subjects. One of the risk factors of atherosclerosis is an impaired lipid and lipoprotein metabolism which is influenced by the type of diabetes, the degree of its metabolic compensation, character of treatment and other concurrently present metabolic abnormalities. In metabolically balanced type 1 diabetes the levels of commonly assessed lipoproteins do not differ from those in non-diabetic subjects, the HDL-cholesterol level can be even higher. The lipid profile of type 2 diabetics is not very homogeneous, however, usually elevated levels of VLDL-triglycerides and of apoprotein B and a reduced HDL-cholesterol level are found. At present there are no unequivocal views on the role of the lipoprotein (a) ratio in the increased risk of atherosclerosis in diabetics as investigations devoted to the lipoprotein (a) level and its relation to macrovascular complications in diabetes did not give unequivocal results. The scope of dyslipidemia in diabetics with nephropathy is in addition to the effect of the basic disease influenced also by the extent of renal damage. The lipid disorder, on the other hand, leads to deterioration of albuminuria and progression of the renal disease.

Arteriosclerosis↗
PubMed1993

Type IV renal tubular acidosis associated with Alport's syndrome.

A case of hereditary nephritis with mild reduction of renal function associated with renal tubular acidosis type IV is described. The patient was admitted with life-threatening hyperkalaemia. To our knowledge, type IV renal tubular acidosis has not been reported previously in association with Alport's syndrome in an adult patient.

Acidosis, Renal Tubular↗
PubMed1993

[Neuroendocrine changes in chronic heart failure].

Chronic heart failure is a complex clinical syndrome characterized by many neuroendocrine manifestations by which the organism responds to the reduced cardiac output--the reduced minute volume. In order to ensure the blood flow to vitally important organs in several regions of the circulation vasoconstriction occurs. The plasma noradrenaline (NA) level rises and this correlates with the stage of chronic heart failure. In chronic heart failure the renin production in the kidney and vascular wall rises and thus also the angiotensin II (AG II) formation is increased. AG II is an affective direct arterial constrictor which facilitates NA release from terminal nerve endings and stimulates aldosterone secretion. AG II conditions also myocardial hypertrophy. Arginine vasopressin (AVP) is usually also elevated in chronic heart failure. In vasoconstriction associated with chronic heart failure participates also endothelin, an effective vasoconstrictor substance which modulates the renin-angiotensin-aldosterone system and has also an antinatriuretic effect. As a compensating response to the increased formation of vasoconstrictor substance during chronic heart failure endogenous vasodilatating and natriuretic substances are formed. Another vasodilatating factor is the atrial natriuretic factor (ANF) which is secreted by atrial myocytes as a result of atrial distension, hypernatremia or tachycardia. ANF inhibits renin, aldosterone and AVP formation. The ANF level correlates closely with the grade of chronic heart failure. With advancing heart failure also down regulation of receptors for ANF occurs. Dopamine, a natural precursor of NA, is also a vasodilatating substance and is secreted during stimulation of the sympathetic nerve. In chronic heart failure the formation of vasoconstrictor substances predominates above vasodilating ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart Failure↗