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Biomedical subjects

C E Hulstaert

Publications and source records attributed to C E Hulstaert.

At least 37 records · Page 2Linked to original sources
PubMed1985

Regeneration of the arterial wall in microporous, compliant, biodegradable vascular grafts after implantation into the rat abdominal aorta. Ultrastructural observations.

The ultrastructure of a new type of vascular graft, prepared from a mixture of polyurethane (95 weight %) and poly-L-lactic acid (5 weight %), was examined six weeks after implantation into the abdominal aorta of rats. These microporous, compliant, biodegradable, vascular grafts function as temporary scaffolds for the regeneration of the arterial wall. Smooth muscle cells, covering the grafts, regenerated a neo-media underneath an almost completely regenerated endothelial layer (neo-intima). These smooth muscle cells varied in morphology from normal smooth muscle cells to myofibroblasts. They were surrounded by elastic laminae and collagen fibers. Macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries were present in the disintegrating graft lattices. The epithelioid cells and multinucleated giant cells engulfed polymer particles of the disintegrating grafts. The regeneration of the endothelial and smooth muscle cells is similar to the natural response of arterial tissue upon injury. The presence of macrophages, epithelioid cells, multinucleated giant cells, fibroblasts and capillaries in the graft lattices resembles the natural response of tissue against foreign body implants. Both of these responses result in the formation of a neo-artery that possesses sufficient strength, compliance and thromboresistance to function as a small caliber arterial substitute.

Animals↗
PubMed1985

Prevention of penetration hindrance in cerium-based glucose-6-phosphatase cytochemistry by freezing tissue in melting nitrogen.

The demonstration of the ultrastructural localization of glucose-6-phosphatase in rat liver is hampered by penetration problems of the medium as appears from ultrathin cross-sections of vibratome sections. Besides the plasma membrane, also the cytoplasm forms a serious barrier for the penetration of the medium constituents. Prolonged preincubation for as long as 48 h at 4 degrees C in the complete incubation medium could not prevent the penetration hindrance. However, when employing 30 micron vibratome sections from tissue blocks that were frozen in melting nitrogen, the penetration hindrance was prevented.

Animals↗
PubMed1985

Changes of relaxation times T1 and T2 in rat tissues after biopsy and fixation.

NMR spectroscopical measurements of relaxation times were conducted on muscle, intestine, fatty tissue and cerebral cortex and white matter of the rat at various time intervals following removal of the tissue. It appeared that most tissues can be stored at 4 degrees C up to 24 hours without noticeable effects on NMR relaxation parameters. Exceptions are the T2 of muscle and the T1 and T2 of intestine, which tended to change in the first hour after biopsy. Relaxation parameters change considerably after fixation of the tissues. Therefore the effects of fixation have to be taken into account when carrying out NMR measurements on fixed tissues.

Adipose Tissue↗
PubMed1984

Genesis of unusual vesicles in rat periportal hepatocytes after administration of N-hydroxy-2-acetylaminofluorene.

Administration of N-hydroxy-2-acetylaminofluorene (90 mumol/kg, iv) to rats results in damage to periportal hepatocytes. The most prominent ultrastructural changes are the appearance of numerous unusual vesicles of about 200 nm diameter and the proliferation of the endoplasmic reticulum to form fingerprint-like structures. In order to characterize these vesicles and to investigate their possible origin, their enzymatic activity was studied by ultrastructural enzyme histochemistry. The vesicles as well as the fingerprint-like structures exhibited glucose-6-phosphatase activity. Continuities between the vesicles and the membranes of both the RER and the SER were frequently seen. The vesicles lacked ATPase, 5'nucleotidase and catalase activity. From these results we conclude that the vesicles may be an unusual proliferation of the endoplasmic reticulum.

2-Acetylaminofluorene↗
PubMed1984

Interaction of liposomes with Kupffer cells in vitro.

We investigated the interaction of liposomes with rat Kupffer cells in monolayer maintenance culture. The liposomes (large unilamellar vesicles, LUV) were composed of 14C-labelled phosphatidylcholine, cholesterol and phosphatidylserine (molar ratio 4:5:1) and contained either 3H-labelled inulin or 125I-labelled bovine serum albumin as a non-degradable or a degradable aqueous space marker, respectively. After 2-3 days in culture the cells exhibited optimal uptake capacity. The uptake process showed saturation kinetics, maximal uptake values amounting to 2 nmol of total liposomal lipid/h/10(6) cells. This is equivalent to 1500 vesicles per cell. The presence of fetal calf serum (FCS) during incubation increased uptake nearly two-fold, whereas freshly isolated rat serum had no effect. The binding of the liposomes to the cells caused partial release of liposomal contents (about 15-20%) both at 4 degrees C and at 37 degrees C. In the presence of metabolic inhibitors the uptake at 37 degrees C was reduced to about 20% of the control values. Inulin and lipid label became cell-associated at similar rates and extents, whereas the association of albumin label gradually decreased after attaining a maximum at relatively low values. When, after 1 h incubation, the liposomes were removed continued incubation for another 2 h in absence of liposomes led to an approx. 30% release of cell-associated lipid label into the medium in water-soluble form. Under identical conditions as much as 90% of the cell-associated albumin label was released in acid-soluble form. Contrarily, the inulin label remained firmly cell-associated under these conditions. From these results we conclude that Kupffer cells in monolayer culture take up liposomes primarily by way of an adsorptive endocytic mechanism. This conclusion was confirmed by morphological observations on cells incubated with liposomes containing fluorescein isothiocyanate (FITC) dextran or horseradish peroxidase as markers for fluorescence microscopy and electron microscopy, respectively.

Adsorption↗
PubMed1983

Cytochemical demonstration of phosphatases in the rat liver by a cerium-based method in combination with osmium tetroxide and potassium ferrocyanide postfixation.

Acid phosphatase, alkaline phosphatase, glucose-6-phosphatase, Mg-activated adenosine triphosphatase and 5'nucleotidase were demonstrated in the rat liver using a cerium-based method. This method can be applied routinely and yields better results than the lead-based method. The tissue was postfixed in osmium tetroxide and potassium ferrocyanide which considerably enhances the membrane contrast in comparison with solely osmium tetroxide postfixation. This facilitates the precise localization of the reaction product.

Acid Phosphatase↗
PubMed1983

Effects of liposome dose and the presence of lymphosarcoma cells on blood clearance and tissue distribution of large unilamellar liposomes in mice.

Large unilamellar liposomes (50 to 500 mumol of lipid per kg) were injected i.v. or i.p. into normal and lymphosarcoma-bearing mice. The percentage of the dose remaining in the blood and that accumulated in liver, spleen, and various other organs was measured 4 hr after injection. The results indicate that liposomes cause a dose-dependent saturation of the hepatic and splenic clearance capacities. One day after injection of 10(6) lymphosarcoma cells, the capacity of the tumor-bearing mice to eliminate liposomes from the blood (in a 4-hr period) was inhibited 30 to 50%. This could be ascribed to a decreased activity of the reticuloendothelial system caused by the tumor cells, as was indicated by the simultaneous inhibition of carbon clearance. Six days after injection of the lymphosarcoma cells, the elimination of liposomes from the blood in tumor-bearing mice was restored to the value in normal mice. The possible involvement of tumor cells in the uptake of liposomes by the liver was investigated morphologically after i.v. injection of peroxidase-containing liposomes into lymphosarcoma-bearing mice. Liposome-entrapped peroxidase activity was never observed in the tumor cells. The results presented here indicate that the lymphosarcoma cells do not directly participate in the hepatic accumulation of liposomes, although their mere presence may have significant indirect effects on the elimination of liposomes from the blood and on their tissue distribution.

Animals↗
PubMed1981

Nutritional myopathy in ducklings: a growth rate-dependent symptom of "tissue peroxidosis' due to a net nutritional shortage of vitamin E plus selenium in skeletal muscle.

Although low dietary vitamin E is an absolute prerequisite for the occurrence of nutritional myopathy in ducklings, it was found that the myopathy can be prevented if the vitamin E depletion does not start before 2 weeks of age and if the dietary selenium content is not too low (greater than 74 ppb). Under these circumstances growth remained normal and the animals stayed alive during the experimental period of 14 weeks, despite low levels of vitamin E in serum, liver, and muscle. The weekly growth rate of the nondeficient duckling, as derived from the growth curve, is extremely high during the first 2 weeks of age with a distinct peak during the 2nd week followed by a steep fall during the 3rd week. In vitamin E-deficient ducklings tissue vitamin E dilution curves were calculated by mathematic transformation of the growth curve. Th results suggest that a critical net nutritional shortage of vitamin E plus selenium in skeletal muscle causes myopathy in ducklings. It is proposed that nutritional myopathy should be considered as a symptom of "tissue peroxidosis' and not as a symptom of vitamin E deficiency per se.

Age Factors↗
PubMed1981

Plasma membrane specialization and intracellular polarity of freshly isolated rat hepatocytes.

It was investigated whether rat hepatocytes maintain their plasma membrane specialization (sinusoidal, lateral and bile canalicular sites) and their intracellular polarity (peribiliary region, rich in lysosomes and poor in mitochondria) after isolation. The morphology of the hepatocytes and the cytochemical localization of marker enzymes for the bile canalicular membrane (alkaline phosphatase, adenosine triphosphatase and 5' nucleotidase), for the lysosomes (acid phosphatase) and for the mitochondria (beta-hydroxybutyrate dehydrogenase and succinate dehydrogenase) were studied in situ and directly after isolation using both light and electron microscopy. The morphology of the cells and the cytochemical activity of acid phosphatase, succinate dehydrogenase and beta-hydroxybutyrate dehydrogenase showed that in isolated cells, as in situ, the lysosomes were concentrated in bands, devoid of mitochondria. Unlike in situ the reaction product of alkaline phosphatase, adenosine triphosphatase and 5'nucleotidase was evenly distributed along the entire plasma membrane of the isolated cells. Morphologically, no tight or gap junctions or desmosomes could be detected in the isolated cells, while the plasma membrane appeared to be homogeneously covered with uniform microvilli. In conclusion it can be stated that during isolation the hepatocytes loose their distinct plasma membrane specialization, but maintain their peribiliary region rich in lysosomes and poor in mitochondria.

Animals↗
PubMed1979

Quantitative analysis of morphological changes in skeletal muscle of the rat after hormone administration.

Thyroxine and cortisone acetate administration of rats of 4--7 days of age is not only accompanied by the induction of the muscle-specific enzyme, creatine kinase, but the hormones also induce morphological changes in the gastrocnemius during this period. Administration of thyroxine to these rats causes a splitting of myofibrils as shown by stereological measurements on electron micrographs. This splitting of myofibrils was not observed upon cortisone acetate administration and when both hormones were given simultaneously. It is suggested that cortisone acetate counteracts the effect of thyroxine. Both thyroxine and cortisone acetate increase the volume percentage taken by the mitochondria at 7 days of age. The effect of the simultaneous injection of both hormones is equal to the sum of the separate effects of these hormones. These changes in volume percentage of the mitochondria were compared with changes in a mitochondrial marker enzyme, i.e. citrate synthase. The difference between the morphological measurements and citrate synthase activity is due to a change in the specific activity of citrate synthase in the mitochondria.

Animals↗
PubMed1977

A patient with severe neurologic symptoms and acetoacetyl-CoA thiolase deficiency.

A detailed kinetic characterization of the cytosolic acetoacetyl-CoA thiolase in liver, subcutaneous adipose tissue, and cultured fibroblasts of a patient with severe neurologic symptoms showed this enzyme to be much more sensitive to inhibition by CoA than that enzyme of normal human liver. The activity of the cytosolic acetoacetyl-CoA of this patient (14.0 mu mol-min-1-g (w/w) was in the lower range of normal (48.7 +/- 20.4 mu mol-min-1 g (w/w), n=6), but the ratio of the mitochondrial thiolase over the cytosoli thiolase was significantly increased (14.9 versus 4.54 +/- 2.92, n =6). The increased inhibition of the cytosolic acetoacetyl-CoA thiolase by CoA shows up as a 2-fold increase of the apparent Km for acetoacetyl-CoA at physiologic concentrations of CoA (64 micrometer for the enzyme of the patient verus 35 micrometer for the normal enzymes), resulting in a decreased utilization of the substrate. Aberrant kinetic behaviour of the mitochondrial thiolases of the patient has also been observed, but this has not been analysed further. Morphologic studies of the liver showed greatly increased deposition of glycogen and the occurrence of lipofuschin-like granules.

Acetyl-CoA C-Acetyltransferase↗
PubMed1976

Selenium in in vitamin-E-deficient diets and the occurrence of myopathy as a symptom of vitamin E deficiency.

The occurrence of myopathy in vitamin-E-deficient ducklings, which is used for the determination of the degree of vitamin E deficiency, is depending on the selenium content of the diet. The selenium content of a semi-synthetic diet and its constituents was determined by neutron activation analysis, which showed to be an adequately sensitive and precise method of analysis for selenium. The casein compound was the main source of the selenium in the diet. Myopathy occurred with diets containing about 50 ppb Se; diets containing about 100 ppb Se failed to induce any signs of myopathy.

Animal Feed↗
PubMed1975

Cellular membranes and membrane-bound enzymes in vitamin E deficiency. A histochemical, cytochemical, biochemical, and morphologic study of the liver of the Pekin duckling.

The objective of this investigation was to find out whether vitamin E deficiency, apart from influencing the lipid component of cellular membranes, also influences the protein component. For that purpose a number of membrane-bound enzymes in the liver of the Pekin duckling were histochemically, cytochemically, and biochemically examined. Furthermore, cells, cellular membranes, and protein particles in membranes were morphometrically investigated. Histochemically five membrane-bound enzymes appeared to be stimulated in vitamin E deficiency: 5'-nucleotidase, glucose-6-phosphatase, isocitrate dehydrogenase (NADP), tetrazolium reductase (NADH), and tetrazolium reductase (NADPH). 5'-Nucleotidase and glucose-6-phosphatase were also investigated cytochemically and biochemically. The cytochemical localization of these enzymes was identical in control and vitamin E-deficient ducklings. Biochemically, a stimulation of these two enzymes also could be demonstrated. The increase per milligram of DNA appeared to be largest whereas the increase per milligram of protein, per milligram of phospholipid, and per milligram of RNA was only half of the increase per milligram of DNA. This can be explained by the 30 per cent increase of the cell volume in vitamin E deficiency leading to an increase of protein, phospholipid, and RNA per cell. The thickness of membranes and the diameter of protein particles in membranes were measured in liver parenchymal cells. In vitamin E deficiency the thickness of the outer mitochondrial membrane and the diameter of protein particles in this membrane were smaller whereas the thickness of the endoplasmic reticular membrane was larger. The increase of the activities of mitochondrial and microsomal enzymes and the decrease of the thickness of the outer mitochondrial membrane and of its protein particles are interpreted to be the result of the influence of free radicals on membranes with electron transport functions. The increase of 5'-nucleotidase activity in the plasma membrane is likely to have a different cause; it may be related to the transport of nucleotides across this membrane.

Animals↗