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Biomedical subjects

H J Merker

Publications and source records attributed to H J Merker.

At least 145 records · Page 8Linked to original sources
PubMed1981

[Prevention of cleft palate in animal experiments. Clinical inferences (author's transl)].

The almost 100% successes with drug prophylaxis of cheilognathopalatoschisis in humans described by some authors are dubious, not only because of the dose level, but particularly because of the fact that the data do not result from controlled studies. In order to clarify the efficacy of cleft prophylaxis, we undertook animal experiments. To produce clefts, NMRI mice were treated with dexamethasone on day 13 of pregnancy. Another group also received a deproteinized hemoderivative in addition from day 11 to day 18 and two other groups were used as controls. It was found on autopsy shortly before birth that the incidence of clefts was significantly lower in the animals treated with additional hemoderivative.

Animals↗
PubMed1981

Embryotoxic effects of magnesium deficiency and stress on rats and mice.

Pregnant rats an mice received a magnesium (Mg)-deficient diet with different Mg contents from 40 t 360 ppm. The control received 2,000 ppm. At the end of gestation, the Mg concentration in the maternal serum was found to have decreased by up to 0.3 mmole/liter, depending on the Mg content of the food. Mg-dose-dependent embryotoxic effects (resorptions, retardation, disturbed bone development, and skeletal malformations) were observed only below a threshold value of 0.7 mmole/liter of the maternal serum Mg concentration. Noise stress in rats, in addition to a mild Mg deficiency (360 ppm Mg), which by itself had no effects, increased the rate of resorptions only.

Animals↗
PubMed1981

The morphology of basement membrane formation.

A transplantable, basement-membrane (BM)-producing murine tumor was investigated using immunofluorescence and electron microscopy. Collagen type IV, fibronectin, laminin, and a BM proteoglycan (BM-1) could be discriminated in the intercellular substance (ICS). The occurrence of these substances and the electron microscopic findings speak for a comparability of the ICS of the tumor with the BM of normal tissues. Hence, a model has become available to study the morphology of BM-formation. The BM-producing cells are characterized by numerous, often enlarged cavities of the rough endoplasmic reticulum (RER) and a large Golgi complex. The BM-material is released into the ICS via prosecretion and electron-dense secretion granules. The morphology of the extracellular BM-material depends upon the fixation technique. After addition of tannic acid, typical BM-lamellae are formed, which in most cases show a granular structure. This is due to shrinkage and attachment of glycoproteins to the collagen skeleton. After ruthenium red or after glutaraldehyde fixation, the extracellular matrix consists of homogeneously distributed filamentous material with only few granular structures. This situation corresponds to the small amount of acid proteoglycans in the BM. The present findings facilitate the evaluation of BM-formation in other cell types.

Animals↗
PubMed1980

An improved method for the preparation of human fetal and adult hepatocytes.

A method to prepare isolated hepatocytes from the small amounts of liver or liver fragments obtained from the human fetus following therapeutic abortion in early pregnancy is described. The hepatocytes have been characterized by electron microscopy and by their ability to dealkylate the benzodiazepine drug prazepam. The preparation of hepatocytes from a liver sample obtained from a kidney transplant donor is described and discussed.

Cytological Techniques↗
PubMed1980

Behaviour of epiphyseal mouse chondrocyte populations in monolayer culture. Morphological and immunohistochemical studies.

Growth and dedifferentiation of a heterogeneous mouse chondrocyte population, prepared from epiphyses of mouse embryos (day 17 of gestation), were studied in primary monolayer culture. At different times of culture, light and electron microscopic investigations were carried out and the change of collagen types was shown by immunofluorescence microscopy. During the first four days in culture, chondrocytes express their typical phenotype. Round or polygonal cells are embedded in a metachromatically staining matrix and produce type II collagen. After four to eight days in vitro most of the chondrocytes lose their matrix capsule and alter to fibroblast-like cells. Simultaneously, a switch of collagen synthesis to type III and type I collagen occurs, whereas the type II collagen synthesis is stopped. Altered cells and transitional stages have intracellular glycogen like typical chondrocytes, but show phagocytosis and indications of cell migration like fibroblasts. It is proposed that these cells, originating from a subpopulation of epiphyseal cartilage, are able to differentiate and dedifferentiate in vitro.

Animals↗
PubMed1980

The influence of lanthanons on morphology and function of rat exocrine pancreas in vivo.

The intravenously administered light lanthanon praseodymium selectively destroys the Golgi complex of rat exocrine pancreas. This effect impairs the normal secretion of proteolytic enzymes which manifests in a reduced output of amylase and trypsin from rat pancreas and a decrease of the basal level of amylase in serum after pilocarpine stimulation.

Amylases↗
PubMed1979

[Organ preservation by heavy water (D2O). Morphological and biochemical studies on heart and liver (author's transl)].

The tissue H2O of rabbit heart and rat liver was partially exchanged in situ with D2O. In rat liver, the loss of ATP, resulting from normothermic ischemia, was decreased after perfusion with D2O. The maximal protective effect was found when the proportion of D2O in the water of the liver tissue was 0.20. In both organs the protective effect of D2O could be correlated with a marked decrease in severe ischemic damage of cellular organelles, in particular mitochondria. D2O also increased the protective action of Mg-ions in the heart.

Adenosine Triphosphate↗
PubMed1979

[Electron microscopic study of the effect of colchicine on limb bud cartilage in organ culture (mouse embryos)].

Limb buds of 11-day-old mouse embryos were cultured. On day 5, 0.1 mM colchicine was added for 3, 6, 12 or 24 h in vitro. 3 or 6 h after application of colchicine, electron-dense granula appear to an increasing extent. These granula can be interpreted as collagen-containing secretion granula and as an indication of a secretion inhibition. The peripheral localization of the granula groups speaks for an effect on the actual discharge of the secretion after having passed the Golgi apparatus. Additional effects of colchicine are fragmentation of the Golgi apparatus and an increased occurrence of bundles of fine filaments. Since only few microtubuli occur in the periphery of the chondroblasts and recent studies indicate an influence of colchicine not only on the microtubule system, a site of action at the functional unity 'cell membrane-microfilaments' is discussed. 12 or 24 h after colchicine application, the contents of the congested secretion granula change. The occurrence of cross-striated structures indicates an activity of procollagen peptidase in the granula in the case of secretion inhibition. In addition, cytolysosomes (autophagic vacuoles) develop. The occurrence of polymorphism of the granula contents under these conditions is attributed to an effect of lysosomal enzymes.

Animals↗
PubMed1978

Collagen metabolism in granulating wounds of rat skin.

Collagen metabolism in granulating wounds of rat skin was studied with biochemical, isotopic and electron microscopical methods. Deposition of collagen in rat skin wounds was not only the result of an increase in collagen synthesis but it was also caused by a decrease in collagen degradation. Our investigations showed significant differences in the collagen turnover at different times of wound healing. Decreased collagen catabolism at the early stages of wound healing contributed decisively to collagen accumulation in the wound area. At later stages, during wound contraction and remodelling of the scar, the rate of collagen degradation rose. The above-mentioned results are discussed in the context of general criteria of scar formation.

Animals↗
PubMed1978

Formation of an atypical collagen and cartilage pattern in limb bud cultures by highly sulfated GAG.

Addition of 1 mg/ml or higher doses of the highly sulfated pentosanpolysulfoester SP54 or the mucopolysaccharidepolysulfoester Arteparon to limb bud cultures from 11-day-old mouse embryos caused a marked reduction in the growth of the distal parts of the cartilage anlagen. The most striking effect, however, was the change in the collagen structure of the cartilaginous intercellular substance. After more than 0.05 mg/ml SP54 or Arteparon no collagen filaments were seen but collagen aggregates with an altered cross-striation occurred. They were produced by an antiparallel arrangement of collagen molecules caused by the highly sulfated substances. By immunofluorescence microscopy it was shown that SP54 and Arteparon did not influence the distribution of the collagen types but only affected the aggregation of collagen type II. From the morphological point of view the production of endogenous PG seemed to be uneffected by SP54 and Arteparon. The effect of SP54 and Arteparon was reversible. After removal of these substances characteristic collagen filaments re-formed. The collagen aggregates were decomposed extracellularly or phagocytosed by chondroblasts and decomposed intracellularly.

Animals↗
PubMed1978

Investigation of the effect of hydroxyurea on the cell cycle and the development of necrosis in the embryonic CNS of mice.

On day 10 of gestation pregnant mice (strain NMRI) were given an intravenous injection of 500 mg/kg Hydroxyurea (HU). Simultaneously either 5 muCi/g or 10 muCi/g 3H-thymidine (3H-Tdr; specific activity 5Ci/mmol) was administered to the animals. At various times after treatment embryos and electron microscopy. Two hours after administration of HU condensations of the chromatin structure could be detected electron microscopically in some cells. Thirty minutes later the nucleolus became smaller and denser, the cytoplasm shrank, and the cell organelles moved closer together. Three hours after application of the drug break-down of the involved cells set in. As in the autoradiograms about 98% of the counted necroses were labelled, and since labelled thymidine is almost exclusively incorporated during the S-phase, it can be stated the HU influences only metabolic processes which take place during the S-phase. From the morphological findings it can be concluded that in the case of the S-phase-specific metabolic pathway, which is influenced by HU, we are primarily dealing with DNA synthesis.

Animals↗
PubMed1978

Effect of 4-methylumbelliferyl-beta-D-xylopyranoside on the morphology of embryonic cartilage in limb bud cultures.

Limb buds of 11-day-old mouse embryos were cultured for six days in the presence of 0.1, 0.5 or 2 mg/kg 4-methylumbelliferyl-beta-D-xylopyranoside. A dose-dependent decrease in chondrogenesis could be observed in preparations stained with methylene blue and cleared. A reduction or even disappearance (after 2 mg/kg) of intercellular spaces and a change in shape and size of chondroblasts was striking in the light microscopical picture. The electron microscopical findings reveal a decrease in the number, size, and electron-density of the ruthenium-red-positive proteoglycan granules as well as an alteration in the collagen morphology. Up to 1,000 A thick fibrils occur which partly show a so-called continuous cross-striation. In addition, bundles of thin (50-100 A) collagen filaments without cross-striation occur. The number, distribution and packing density of the cell organelles in the chondroblasts are very variable. The vacuoles of the Golgi apparatus are dilated. These effects may be attributed to the xyloside-induced alterations of proteoglycans.

Cartilage↗
PubMed1978

Thiouracil-induced myocardial fibrosis.

Rabbits were fed with thiouracil for 8 months. Subsequently their hearts were examined electron microscopically as well as biochemically for collagen and hexosamine content. Chronic treatment with thiouracil induced an increase in interstitial connective tissue collagen and hexosamine without visible necrosis. As seen by electron microscopy, the increase in collagen content might have been caused by stimulation of the fibrocytes. Furthermore, the heart muscle cells showed deep indentations and bulges of the cell membrane and an enlargement of the T-system.

Animals↗
PubMed1978

[Electrolyte and collagen content of rat heart in chronic Mg-deficiency and stress (author's transl)].

In chronic Mg-deficiency, there is a decrease in the content of Mg and K+ in the heart muscle. The contents of Ca, Na+ and hydroxyproline increase. There is also an increased urinary excretion of adrenaline and especially noradrenaline. With simultaneous noise stress, these changes are even greater. The magnitude of the changes increases with the degree of Mg-deficiency. The changes in the contents of Na+, K+, Ca, Mg and hydroxyproline correlate with the excretion of noradrenaline. The increase in the collagen content can be verified by electron microscopy, and it is due to a stimulation of the fibrocytes.

Calcium↗