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Biomedical subjects

H Jansen

Publications and source records attributed to H Jansen.

At least 163 records · Page 9Linked to original sources
PubMed1983

Separation of rat plasma HDL subfractions by density gradient centrifugation and the effect of incubation on these fractions.

The conditions for the separation of rat high density lipoproteins (HDL) in a single ultracentrifuge run are described. By this method six serum samples can be processed simultaneously. HDL is separated into two main fractions, one with apolipoprotein E and the other with apolipoprotein A-I as the major protein component. The apolipoprotein E-rich HDL contains a relatively high amount of phospholipid and unesterified cholesterol and therefore resembles HDL-1 or apolipoprotein E HDL as isolated by other methods. The other HDL fraction resembles HDL-2. The two HDL fractions appeared to be heterogeneous with respect to apolipoprotein composition. The HDL-1 consisted of particles with and without a low percentage of apolipoprotein A-I. The HDL-2 consisted of particles with a variable amount of apolipoprotein E and A-IV. During incubation of rat serum for 5 h at 37 degrees C in the presence of dithiobis(2-nitrobenzoic acid) (DTNB) a small shift of the HDL-2 peak to lower densities occurred. Incubation of the serum without DTNB led to a loss of cholesterol from the 'light' HDL-1 fractions and an increase in cholesterol ester in fractions at densities intermediate between those of HDL-1 and HDL-2 and in fractions at the densest part of the gradient.

Animals↗
PubMed1983

Regulation of liver lipase. I. Evidence for several regulatory sites, studied in corticotrophin-treated rats.

The activity of liver lipase, an enzyme that can be released from the liver by heparin, varies under several hormonal conditions. The site(s) at which regulation of the enzyme activity may occur was investigated in vitro. As a model, rats were used which had been treated with a corticotrophin analogue, to induce hypercortisolism, a condition in which liver lipase activity is lowered. Lipases isolated from heparin-containing perfusates of livers from ACTH or control rats were identical with respect to heat stability and specific activity as determined by immunotitration and binding to isolated non-parenchymal liver cells, indicating that the enzyme structure was not affected by the treatment. The secretion of liver lipase by isolated parenchymal liver cells was studied. During incubation of parenchymal cells derived from ACTH rats, less enzyme activity was found to be secreted when compared with hepatocytes isolated from control rats (ACTH rats, 2.30 +/- 0.2 mU/10(6) cells; control rats, 3.3 +/- 0.3 mU/10(6) cells). Liver lipase partially purified from control rats could be bound specifically to saturation by non-parenchymal cells, isolated from ACTH or control rats. Non-parenchymal cells from ACTH rats bound less lipase activity (29 mU/mg cell protein) than cells from control rats (50 mU/mg cell protein). This reduction in binding capacity seems to be due to a diminished number of binding sites, since the affinity based on Scatchard analysis and half-maximal binding was not different. These results suggest that the lowered liver lipase activity found during hypercortisolism may be due to an impaired synthesis and/or secretion of the enzyme by the parenchymal cells and to a reduced binding capacity of the non-parenchymal cells for liver lipase.

Adrenocorticotropic Hormone↗
PubMed1983

The effect of corticotrophin on liver-type lipase activity in adrenals, liver and high-density lipoprotein subfractions in the rat.

Hypercortisolism was induced in rats by the administration of a corticotrophin analogue (Synacthen depot). The effect of this treatment during different periods was studied in normally fed and overnight-fasted rats. The activity of liver-type lipases, i.e., of lipases similar to the heparin-releasable lipase of rat liver (liver lipase), was determined in the adrenal gland and in the liver. Short-term (16 h) treatment had no effect on the lipase activity in the adrenal gland. During prolonged treatment, however, the lipase activity rose to 600-700% of control values in 10 days and from then on remained constant. The effect was similar in fed and overnight-fasted rats. The lipase activity in the liver decreased upon Synacthen administration. In the fed rats a decrease of 25% of the initial value was found after 16 h, 40% after 3 days and 50% after 20 days of treatment. In overnight-fasted rats the lowering of the lipase activity was less marked than in fasted controls. Serum lipid levels and high-density lipoprotein (HDL) subclass concentrations were also measured. The cholesterol concentration in the lipoproteins with a density greater than 1.050 g/ml (HDL) was elevated in rats treated for 3-20 days. If the rats were treated for longer than 10 days, overnight fasting led to a normalization of the HDL-cholesterol levels. After separation of the HDL into two subfractions, a relatively 'light' apolipoprotein E-rich fraction and a more 'heavy' apolipoprotein A-I-rich fraction, in fed and fasted animals treated with Synacthen for 3 days both HDL subfractions were elevated. After 10 days treatment only the apolipoprotein A-I-rich HDL fraction was still enhanced in both fed and fasted rats.

Adrenal Glands↗
PubMed1983

Liver lipase and high-density lipoprotein. Lipoprotein changes after incubation of human serum with rat liver lipase.

Human sera were incubated with rat liver lipase after inactivation of lecithin:cholesterol acyltransferase, and the changes in serum lipoprotein composition were measured. In the presence of liver lipase serum triacylglycerol and phosphatidylcholine were hydrolyzed. The main changes in the concentrations of these lipids were found in the high-density lipoprotein fraction. Subfractionation of high-density lipoprotein by rate-zonal ultracentrifugation showed a prominent decrease in all constituents of high-density lipoprotein2, a smaller decrease in the 'light' high-density lipoprotein3 and an increase in the 'heavy' high-density lipoprotein3. These data support a concept in which liver lipase is involved in high-density lipoprotein2 phospholipid and triacylglycerol catabolism and suggest that as a result of this action high-density lipoprotein2 is converted into high-density lipoprotein3.

Animals↗
PubMed1983

[Spinal and cerebral somatosensory evoked potentials in single and double stimulation of the tibial nerve].

In 33 normal subjects aged between 15 and 60 years, the cortical somatosensory evoked potentials (SEP) recorded above the mastoid process, HWK2, LWK1, and the nerve action potential above the poplitea were examined following single stimulation of the tibial nerve at the medial malleolus. There is a correlation between size and N1, P1 latencies of the cortical SEP, but no relationship was found between age and N1, P1 latencies. The spinal conduction velocity determined as the difference between HWK2 and LWK1 did not show any correlation with age. The double stimuli examination showed a rise in the N1, P1 latencies within the relative refractory period on shortening of the interstimulus time. The cerebral relative and absolute refractory times were higher than those of the median nerve.

Adolescent↗
PubMed1983

Post-heparin lipases, lipids and related hormones in men undergoing coronary arteriography to assess atherosclerosis.

Post-heparin lipase activities were measured in normolipemic men with complaints suggestive of symptomatic coronary artery disease. A study group, who showed diffuse atherosclerotic narrowing of the coronary vessels, assessed by a quantitative computer-assisted analysis method, had a lowered hepatic lipase in comparison with a group with normal angiograms. Lipoprotein lipase was lower in the study group but well within the normal range and not statistically different. Some related hormones (cortisol, estradiol, testosterone and glucagon) were different in the two groups while others (insulin, human growth hormone, prolactin, thyroid hormones) were not. The results are discussed in view of the proposed role of hepatic lipase in the uptake of HDL-cholesterol by the liver.

Adult↗
PubMed1983

Formate concentrations in plasma from patients poisoned with methanol.

Formate and methanol were quantified in blood samples from 11 untreated methanol-poisoned subjects. The range for whole blood methanol concentrations was 0-137 mmol/l and for plasma formate concentrations 0.4-17.1 mmol/l. Simultaneously determined acid-base status and serum electrolyte concentrations allowed assessment of the relative importance of formate accumulation for the acidosis. The plasma formate concentration was highly correlated to both the calculated anion gap (r = 0.833), the bicarbonate concentration (r = 0.852) and the negative base excess (r = 0.865). The accumulation of formate fully accounted for the increase in the anion gap and the fall in plasma bicarbonate, whereas the negative base excess values were about 22% higher than the plasma formate concentration. We conclude that formate accumulation is the main or only reason for acidosis in the early, uncomplicated stages of methanol poisoning. Lactate may appear at more advanced stages.

Acid-Base Imbalance↗
PubMed1983

Diurnal changes in serum triglycerides as related to changes in lipolytic enzymes, (apo) lipoproteins and hormones in normal subjects on a carbohydrate-rich diet.

Normal subjects in steady state on a carbohydrate-rich diet (three equivalent meals a day at 9.00, 13.00 and 17.00 h), show a wave-like serum triglyceride (TG) pattern with a peak at 14.00 h. Post-heparin lipoprotein lipase (LPL) activity increased from a mean value of 49 mU/ml +/- 13 (SD) in the fasting state to 127 mU/ml +/- 18 in the fed state (P less than 0.005). This was due to an increase in adipose tissue LPL activity which, at 16.30 and 21.30 h, was significantly higher than basal levels (128.3 +/- 81.5 and 87.7 +/- 23.2 v. 43.3 +/- 9.3 mU/g, P less than 0.05 and P less than 0.01, respectively). Skeletal muscle LPL activity was low (5.8 mU/g +/- 2.3, mean +/- SD) and showed no diurnal change. The observed changes in TG-hydrolysing capacity in the course of the day might explain the TG-pattern. High density lipoprotein (HDL) subfractions HDL2 and HDL3 were separated by density gradient ultracentrifugation and had mean hydrated densities of 1.088 and 1.135 g/ml, respectively. While HDL2 showed no diurnal change, HDL3-cholesterol and-phospholipid significantly increased during the day (P less than 0.005 and P less than 0.001 respectively), reaching their highest levels in the evening. Since te rise in HDL3-lipids follows the fall in serum TG, this provides further indication that the metabolism of these fractions in mutually related.

Adipose Tissue↗
PubMed1983

Different causes for hypertriglyceridemia in male and female patients with chronic renal failure?

The changes in plasma postheparin lipolytic activities that occur in patients with chronic renal insufficiency were found to be sex dependent. Male patients showed decreased hepatic lipase activity, while female patients exhibited decreased lipoprotein lipase activity. These findings offer 1) an explanation for the hitherto confusing data on postheparin lipolytic activities in chronic renal failure reported in the literature, and 2) a further argument for a role of hepatic lipase activity in the regulation of the breakdown of plasma triglycerides.

Female↗
PubMed1982

Dual localization of lipoprotein lipase in rat heart. Its relationship to chylomicron degradation.

Rat hearts were perfused retrogradely using a modified technique that allows the separate collection of coronary (Qrv) and interstitial (Qi) effluents. Evidence is presented that Qrv contains products from the coronary vasculature and that Qi contains products arising from cardiac myocytes. Heparin perfusion of rat hearts led to a release of lipolytic activity in Qrv and Qi which was characterized as lipoprotein lipase (LPL). The relative amounts of LPL released in Qrv and Qi were dependent on the feeding condition of the rat. A high LPL activity was recovered from Qrv of fasted rats, and Qi was high in LPL during feeding. On perfusion of hearts with [3H]cholesterol-labeled chylomicrons, the tissue uptake of cholesterol was highest in the fasted state, whereas release of radioactivity in Qi was predominant in the fed state. This radioactivity in Qi appeared to be associated with chylomicron degradation products (remnants and surface fragments). Our experiments indicate that cholesterol uptake during chylomicron breakdown is inhibited in the fed state, and the relationship between myocyte LPL activity and interstitial formation of chylomicron degradation products suggests a role for the myocyte LPL in lipoprotein metabolism.

Animals↗
PubMed1982

Studies on methanol poisoning.

Eleven patients concomitantly poisoned with methanol are described. Their whole blood methanol concentration ranged from 137.2 mmol/l (4.39 g/l) to 7.4 mmol/l (0.24 g/l). The clinical course in most patients was mild, which was attributed to the concomitant and subsequent ethanol ingestion and rapid transport to dialysing units. One patient suffered permanent visual impairment of one eye while the others recovered completely. Symptoms of poisoning were most clearly correlated to the degree of metabolic acidosis. All patients were hemodialysed. In two patients the average dialysator clearance of methanol was 157 and 176 ml/min at blood flows of 200 and 215 ml/min, respectively. In the same patients the average dialysator clearance of ethanol was 149 and 164 ml/min. Assuming a volume of distribution of methanol of 0.7 l/kg, the dialysator represented about 89 and 95%, respectively, of the total body clearance of methanol during ethanol therapy. Ethanol in concentrations even lower than usually recommended may be useful as the only treatment of patients with blood methanol concentrations up to 15 mmol/l (0.5 g/l), provided there is no acidosis or visual impairment.

Adolescent↗
PubMed1981

Stabilization of liver lipase in vitro by heparin or by binding to non-parenchymal liver cells.

The effect of heparin on the secretion of acylglycerol hydrolase activity by isolated parenchymal liver cells was studied. In the presence of heparin, the lipase activity, secreted in 3 h, was almost doubled. Heparin did not influence the activity of the enzyme, but affected the stability of the enzyme. In the absence of heparin, the triacylglycerol hydrolase activity declined to 50% of the initial value during 1 h incubation at 37 degrees C. The addition of heparin prevented this loss of activity almost completely. The optimal stabilization of enzyme activity was reached at 15 U heparin/ml NaCl (1 M) and protamine sulphate (120 microgram/ml) abolished this effect of heparin. Instead of heparin, liver lipase activity could also be stabilized by binding to non-parenchymal liver cells. The results are discussed in connection with the binding of the enzyme in vivo.

Animals↗
PubMed1981

Heparin-releasable lipase activity of rat adrenals, ovaries and testes.

The presence of NaCl-resistant, neutral triacylglycerol hydrolase (lipase) activity in rat adrenal gland, ovary and testis was studied. Both adrenals and ovaries but not testes were found to contain such a lipase. The activity of the enzyme in the adrenal gland was lowered during cortisol treatment and hypothyroidism. An elevated adrenal lipase activity was found during hyperthyroidism. Pseudo-pregnant and lactating rats had higher ovarian lipase activities than cyclic rats. Ovarian lipase activity in lactating rats was positively correlated with the serum concentrations of progesterone and of 20 alpha-hydroxyprogesterone and negatively correlated with the high-density-lipoprotein non-esterified cholesterol concentration. The lipase activity of adrenals and of ovaries was largely releasable from these organs by heparin and could be inhibited by an antibody against heparin-releasable liver lipase. This indicated that the lipase is extracellularly located and is similar to 'liver' lipase. A possible role of this lipase in adrenals and ovaries is discussed.

Adrenal Glands↗