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Biomedical subjects

E Jensen

Publications and source records attributed to E Jensen.

At least 91 records · Page 5Linked to original sources
PubMed1988

Insulin stimulates the uptake of chylomicron remnants in cultured rat hepatocytes.

The effects of insulin (10-1000 microU ml-1) on chylomicron remnant uptake and degradation were studied in hepatocyte monolayer cultures. Both uptake and degradation were stimulated by insulin. The degree of stimulation was influenced by cell density, being most pronounced in sparse cultures. The uptake was stimulated in a dose-dependent fashion and was noticed already at a physiological insulin level (100 microU ml-1). At this insulin concentration uptake was stimulated by approximately 50% (range 26-84%). As suggested by the increase in Vmax for the remnant uptake, the number of lipoprotein receptors on the hepatocytes was increased by 100 microU ml-1 of insulin. Apolipoprotein-E-free low density lipoproteins (LDL) competed much less efficiently for the uptake of radioactive remnants than did unlabelled remnant particles. About half of the stimulatory effect of insulin on the remnant uptake could, however, be abolished by adding an excess of LDL, indicating that at least part of the stimulation by insulin was due to increased activity of the LDL receptor. This study thus shows that physiological insulin levels increase chylomicron remnant uptake in hepatocyte monolayer cultures. It is assumed that the effect of insulin is to increase the number of lipoprotein receptors at the cell surface, and at least part of the stimulation is due to an increase in LDL receptor activity.

Animals↗
PubMed1988

Measurement of acceleration: a new method of monitoring neuromuscular function.

A new method for monitoring neuromuscular function based on measurement of acceleration is presented. The rationale behind the method is Newton's second law, stating that the acceleration is directly proportional to the force. For measurement of acceleration, a piezo-electric ceramic wafer was used. When this piezo electrode was fixed to the thumb, an electrical signal proportional to the acceleration was produced whenever the thumb moved in response to nerve stimulation. The electrical signal was registered and analysed in a Myograph 2000 neuromuscular transmission monitor. In 35 patients anaesthetized with halothane, train-of-four ratios measured with the accelerometer (ACT-TOF) were compared with simultaneous mechanical train-of-four ratios (FDT-TOF). Control ACT-TOF ratios were significantly higher than control FDT-TOF ratios: 116 +/- 12 and 98 +/- 4 (mean +/- s.d.), respectively. In five patients not given any relaxant during the anaesthetic procedure (20-60 min), both responses were remarkably constant. In 30 patients given vecuronium, a close linear relationship was found during recovery between ACT-TOF and FDT-TOF ratios. It is concluded that the method fulfils the basic requirements for a simple and reliable clinical monitoring tool.

Acceleration↗
PubMed1988

The Accelograph: a new neuromuscular transmission monitor.

A new neuromuscular transmission monitor based on measurement of acceleration is presented. The monitor consists of an acceleration transducer, i.e. a piezo-electric ceramic wafer with an electrode on each side, and a stimulation and computing unit. The transducer can be fastened to the thumb, and when the finger is moved in response to nerve stimulation a voltage difference develops between the two electrodes. The voltage is then measured and registered in the computing unit. The acceleration transducer does not require preload, but merely that the muscle on which the measurement is being made can move freely. The accelograph is therefore easy to set up and operate. In daily clinical practice it has proved possible, using this new apparatus, to achieve reliable evaluation of the degree of non-depolarizing neuromuscular blockade in less than 2 min.

Acceleration↗
PubMed1988

Lipoprotein-deficient serum stimulates the uptake of chylomicron remnants in cultured rat hepatocytes.

Rat hepatocyte monolayers were cultured in the presence of 1-10% lipoprotein-deficient foetal calf serum. This increased the uptake and degradation of chylomicron remnant cholesteryl ester significantly. The increase occurred at all cell densities, i.e. also with less dense cultures where the basal rate of uptake per mg protein was highest. This indicates that tissue culture medium content of lipoprotein cholesterol can regulate the uptake of chylomicron remnants in hepatocytes, analogous to the regulation of the LDL receptor in extrahepatic cell.

Animals↗
PubMed1987

Cell-density-dependent uptake of chylomicron remnants in rat hepatocyte monolayers. Effects of compactin and mevalonic acid.

In rat hepatocytes cultured in lipoprotein-deficient serum, the uptake and degradation of chylomicron remnant cholesteryl ester per mg cell protein varies inversely with cell density. Compactin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme-A reductase, stimulates the uptake at all cell densities. Mevalonic acid, on the other hand, can suppress a significant part of the remnant uptake. Chylomicron remnant uptake in hepatocyte cultures can thus be influenced by factors known to regulate the apolipoprotein-BE receptor activity.

Animals↗
PubMed1987

Absorption and lymphatic transport of exogenous and endogenous arachidonic and linoleic acid in the rat.

[3H]Arachidonic (20:4) and [14C]linoleic acid (18:2) were fed to thoracic duct-cannulated rats in test meals of either tracers alone, cream, Intralipid, pure arachidonic acid, or pure linoleic acid. Less [3H]20:4 than [14C]18:2 was recovered in chyle during the first 5 h. After cream feeding, the proportion of radioactivity found in phospholipids was high and increased during the first 3 h. After the meal (3-5 h) 61 +/- 6% of the 3H and 57 +/- 10% of the 14C was in phosphatidylcholine, and 11 +/- 3% of the 3H and 3.0 +/- 4% of the 14C was in phosphatidylethanolamine. Changing the fat vehicle to Intralipid or pure 18:2 decreased the proportion of label in the phospholipids and increased the 3H and 14C radioactivity in the triacylglycerol fraction, the distribution of 14C being influenced more than that of 3H. After feeding the tracers in 200 microliters of pure 20:4, greater than 90% of both isotopes was in triacylglycerol. During fasting, triacylglycerol transported 56% (0.7 mumol/h), phosphatidylcholine transported 34% (0.4 mumol/h), and phosphatidylethanolamine transported 10% (0.1 mumol/h) of the 20:4 mass. After cream or Intralipid feeding, the output of 20:4-containing phosphatidylcholine and phosphatidylethanolamine increased 2.1- to 2.8-fold, whereas the transport of 20:4 with triacylglycerol remained constant. Phospholipids thus became the predominant transport form for 20:4. After feeding 200 microliters of 20:4, the intestine produced, however, 20:4-rich triacylglycerols that transported 89% of the chyle 20:4.

Animals↗
PubMed1986

Microcalorimetric investigation of metabolism in rat hepatocytes cultured on microplates and in cell suspensions.

In the present work, heat production rate in rat hepatocytes has been measured by use of thermopile heat conduction calorimeters. Both hepatocytes cultured in monolayers on microplates and hepatocytes in suspensions were used for microcalorimetric measurements. The highest heat production rate was found in newly cultured cells; thereafter, a gradual decrease was noted. After 1 day of culture, metabolic activity had reached a steady state that lasted about 4 days. A cell-density dependence of heat production was found, both in cell suspensions and in cultured hepatocytes on microplates. Higher cell concentration in the calorimeter ampoule was accompanied by decreasing heat production per cell. The heat output recorded for hepatocytes cultured on microplates (25 X 10(3) cells) was found to be 0.327 +/- 0.13 nW per cell after 24-48 h. Addition of sodium azide and sodium fluoride to tissue culture medium reduced heat production rate in cultured hepatocytes by 60 and 20%, respectively. Recording of heat production with the present calorimetric technique is relatively simple and fast, and offers the possibility to perform measurements in small samples of cultured hepatocytes on microplates, thus allowing long-term as well as repeated measurements on the same cell population.

Animals↗
PubMed1986

Cloning of the human oestrogen receptor cDNA.

Poly A+ RNA isolated from the human breast cancer cell line MCF-7 was fractionated by sucrose gradient centrifugation and those fractions enriched in oestrogen receptor (ER) mRNA were used to prepare randomly primed cDNA libraries in the lambda gt11 vectors. Clones corresponding to the ER were isolated from both libraries after screening with either ER monoclonal antibodies (lambda gt11) or synthetic oligonucleotide probes designed from two peptide sequences of purified ER (lambda gt10). Five cDNA clones were isolated by antibody screening and five after screening with synthetic oligonucleotides. The two largest ER cDNA clones, lambda OR3 (1.3 kbase) and lambda OR8 (2.1 kbase), isolated using antibodies and oligonucleotides, respectively, were able to enrich selectively for ER mRNA by hybrid-selection. Furthermore, lambda OR8 contains DNA sequences which cross-hybridize with each of the other ER cDNA clones. These results demonstrate that the clones isolated correspond to the ER mRNA sequence. Using lambda OR8 as a hybridization probe revealed a single poly A+ RNA band of approx. 6.2 kbase in the ER containing human breast cancer cell lines MCF-7 and T47D. In contrast, no hybridization was seen in the human ER-cell line HeLa. The same probe hybridizes to a chicken gene which is expressed in oviduct tissue as a 7.5 kbase poly A+ RNA.

Animals↗
PubMed1986

Thyroid hormones stimulate the release of hepatic lipase from cultured rat hepatocytes.

We have investigated the effects of triiodothyronine (T3) and thyroxine (T4) on the heparin-stimulated release of hepatic lipase (HL) activity from cultured rat hepatocytes. Addition of T4 (1-10 nmol/l) to the culture medium for 24 h stimulated HL release from cells derived from normal and hypothyroid rats, whereas T3 (0.1-10 nmol/l) was active (at the highest concentration) only in hepatocytes from hypothyroid animals. The effects of T4 could largely be abolished by 5-iodo-2-thiouracil (0.1 mmol/l), an inhibitor of T4-5'-deiodinase. This indicates that the effects of T4 treatment are exerted by T3, formed by deiodination in the hepatocytes.

Animals↗