Biomedical subjects
R Tilvis
Publications and source records attributed to R Tilvis.
Comparison of different components in the fractional conversion of mevalonate to cholesterol with cholesterol synthesis and serum methyl sterols.
Serum squalene and methyl sterols (cholesterol precursors), and the fractional conversion of mevalonate to cholesterol (FCM) were determined after an i.v. injection of a labelled mevalonate-labelled cholesterol mixture in fifteen studies in eleven subjects with varying cholesterol synthesis rates (sterol balance values), including three cases with ileal dysfunction. FCM was divided in two components, FCM I and FCM II, hypothesised to represent rapidly and slowly mixing components of newly formed cholesterol, respectively. Cholesterol synthesis ranged from 1.42 to 8.75 mmol day-1 and FCM from 0.352 to 0.857. The synthesis rate was correlated with FCM, with FCM II, weakly or not at all with FCM I, highly significantly with serum methyl sterols and insignificantly with serum squalene. However, within the fairly narrow normal synthesis limits (less than 3.3 mmol day-1) the synthesis rate was not correlated significantly with FCM. Despite a marked range of obesity and a highly significant correlation between the synthesis and body weight only FCM II was correlated with body weight in subjects without ileal dysfunction. The findings suggest that FCM, and its components FCM I and FCM II reflect weakly the total cholesterol synthesis rate, and the rapidly and slowly mixing portions of newly formed cholesterol, respectively.
Squalene, methyl sterol, and cholesterol levels in human organs. Postmortem analysis of their distributions.
The postmortem tissue distribution of cholesterol precursors, squalene, and methyl sterols was quantitated in ten human subjects by the use of gas-liquid chromatography. Five methyl sterol subfractions were found, with each organ having a pattern of its own. The mean esterification percentage of the methyl sterol mixture tended to correlate with the methyl sterol concentration and was higher than that of cholesterol in each tissue; the ester percentage was lowest for a diunsaturated dimethyl sterol and highest for a monounsaturated dimethyl sterol. The squalene levels were very high in adipose tissues, while methyl sterols concentrated in organs that produce little cholesterol. The levels in cholesterolgenic tissues were not very high. Squalene level was not correlated with methyl sterol or cholesterol levels in any organs, while methyl sterol and cholesterol levels were highly significantly correlated in the gallbladder wall.
Effects of weight reduction on squalene, methyl sterols and cholesterol and on their synthesis in human adipose tissue.
Quantitation of cholesterol and its precursors from human adipose tissue biopsies revealed very high squalene and moderately high methyl sterol concentrations. The squalene and cholesterol values were correlated with each other. Weight reduction in obese subjects following a jejuno-ileal bypass resulted in a significant but transient increase in adipose tissue cholesterol. The squalene concentration was also increased postoperatively, the maximum being reached about 6 months later than that of cholesterol as if the mobilization of squalene from shrunken adipocytes had been slow. Weight reduction with a 2--14 day total fast significantly reduced the adipocyte size but had no consistent effect on adipose tissue squalene, methyl sterol and cholesterol concentrations or on their adipocyte contents. Incubation of adipose tissue with labelled acetate and mevalonate revealed that the bulk of the labels in non-saponifiable lipids stayed in the large intermediate pools of methyl sterols and squalene in particular, fairly little being found in the cholesterol fraction itself. The total fast inhibited the incorporation of both 14C-acetate and 3H-mevalonate to squalene, methyl sterols and cholesterol, suggesting that cholesterol synthesis was inhibited before and after the mevalonate step.
Effect of probucol on cholesterol synthesis, plasma lipoproteins and the activities of lipoprotein and hepatic lipase in the rat.
The postheparin plasma lipoprotein lipase (LPL) activity and plasma HDL and LDL cholesterol concentrations, decreases significantly during probucol treatment of the rat. The reduction of the LPL activity obviously took place in adipose tissue. The activity of hepatic lipase and the in vitro synthesis of cholesterol in the liver or isolated jejunal villous cells were unaffected by the probucol treatment. Plasma triglyceride and VLDL cholesterol concentrations remained similar in the control and probucol groups despite the difference in the LPL activity, whereas the esterified VLDL cholesterol level was significantly reduced in the probucol group. The results suggest that the HDL lowering action of probucol is contributed by the reduced LPL activity probably via impaired VLDL metabolism.
Cardiovascular diseases, health status, brain imaging findings and neuropsychological functioning in neurologically healthy elderly individuals.
The aim of our study was to evaluate the relationship between health-related factors, brain imaging findings and cognitive functioning. We examined 113 neurologically healthy subjects from 55 to 85 years of age. Health-related variables included a clinical health evaluation, cardiovascular diseases, and other systemic diseases. The presence of white matter changes and cerebral and peripheral atrophy were obtained with magnetic resonance imaging. Neuropsychological tests measuring verbal memory, visual memory, intellectual and language functions, visuoconstructional functions, flexibility, and speed and attention were administered. Results showed that overall health status was not related to cognition. Subjects, who had both arterial hypertension and white matter changes had difficulties in flexibility. Cardiac failure and white matter changes were related to impairment in visuoconstructional functions, flexibility and attention. Significant speed and attention deficits were observed in subjects with cardiac failure and central atrophy. In conclusion, this study verifies the relationship between hypertension, white matter changes and cognitive functions. We found also specific patterns in relation with cardiac failure, brain imaging findings and cognitive functioning, the most vulnerable domains were visuoconstructional functions, flexibility and attention.
Oral health in the elderly with non-insulin-dependent diabetes mellitus.
The purpose of this study was to examine salivary flow rates and selected oral health parameters in 12 patients (aged 76-86 years) with non-insulin-dependent diabetes mellitus (NIDDM) and also in 20 subjects (aged 76-86 years) with NIDDM and cardiovascular diseases (CVD) and to compare them with 32 healthy controls matched for age and gender. Unstimulated salivary flow rates were lower in both groups of NIDDM patients than in the controls, although the differences were not statistically significant. Subjective oral dryness and other oral and non-oral symptoms were more frequently reported by the patients with NIDDM + CVD; however, the differences were usually non-significant. Root-surface caries was more frequently detected in the subjects with NIDDM only, although the difference among groups was not statistically significant. Periodontal treatment need, according to CPITN values, was more frequent in the subjects with NIDDM only, compared with controls or those with NIDDM + CVD, although the differences were again not statistically significant. There were no statistically significant differences in the oral health parameters of the subjects with NIDDM or NIDDM + CVD compared with those of their age- and sex-matched healthy controls.
Liver blood flow. metabolic heat production and body temperature before, during and after phenobarbitone administration.
Using an improved apparatus based on Grayson's principle of internal calorimetry, conductivity as a measurement of liver blood flow and metabolic heat production in the liver as a measurement of liver tissue metabolism were recorded in the conscious rat before, during and after phenobarbitone administration. In addition, rectal body temperature was measured under the same experimental conditions using an electronic thermometer. Liver blood flow increased by a mean of about 100% above control values in rats treated with phenobarbitone 30 mg/kg daily for 4 days. In contrast, changes in metabolic heat production showed no clear tendency and remained more or less constant. However, body temperature rose significantly during phenobarbitone administration up to 38.9% C and this temperature changes showed the same time course as liver blood flow and parameters of microsomal enzyme activity. Therefore it is suggested that metabolic heat production is not a very important factor in influencing the increase in liver blood flow following enzyme induction. On the other hand the increase in body temperature observed in the present study might be an important factor in influencing the increase in blood flow to the liver.