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Biomedical subjects

H J Merker

Publications and source records attributed to H J Merker.

At least 163 records · Page 9Linked to original sources
PubMed1977

Effects of cytosine arabinoside, 6-aminonicotinamide, and 6-mercaptopurine riboside on ectoderm and mesoderm of mouse limb buds.

The effects of cytosine arabinoside, 6-aminonicotinamide, and 6-mercaptopurine riboside on the incorporation of [14C] glucose moieties and [32P] phosphate into acid-soluble material and lipids, RNA, DNA, and protein were measured in the dissected mesoderm and ectoderm of mouse limb buds at the 42-45 (day 11) somite stage. Due to the different proliferative capacities of the two tissues the incorporation of the precursors into mesodermal cells was considerably higher the than into ectodermal ones. Cytosine arabinoside inhibited the incorporation of the precursor moieties only into DNA, but very early after its application. This effect was more obvious in mesoderm than ectoderm. 6-Aminonicotinamide interfered only with glucose metabolism, whereas the incorporation of phosphate was not affected. 14C radioactivity in the various cell components was similarly reduced in mesoderm and ectoderm. 6-mercaptopurine riboside caused an increased incorporation of precursor material in all fractions studied in the mesoderm as well as in the ectoderm during the first 12 hours. This was succeeded by a dramatic decrease of incorporated 14C and 32P radioactivity. Differences of response in the tissues could not be detected with this drug. It is suggested that the malformations of the extrmities caused by these antimetabolites may be predominantly attributed to changes in the cell function rather than to gross effects on cell metabolism.

6-Aminonicotinamide↗
PubMed1977

Effects of cyclophosphamide treatment before implantation on the development of rat embryos after implantation.

After treatment of pregnant rats 24 h before implantation with a single injection of cyclophosphamide (20--80 mg/kg), a dose-dependent increase in resorption was observed at term but no malformed fetuses could be found. The lowest cyclophosphamide dose that caused 100% resoprtion was 60 mg/kg. Somite number and wet weight indicated retardation of about 24 h during organogenesis. Determination of the time of implantation revealed that the developmental retardation in treated embryos was not due to delayed implantation. At implantation, 24 h after cyclophosphamide treatment, a significant and dose-dependent decrease of the cell number of blastocysts was found. Embryo transplantation experiments showed that early cyclophosphamide treatment interfered with the subsequent development of both the embryo and the mother. The decidual reaction seemed to be more affected by the treatment than the embryos. Most teratologists hold that mouse embryos after treatment in the preimplantation period either die before implantation or survive to term without being malformed. The present study, however, proves that the reaction of drugs at this early stage of pregnancy is more complex than is generally assumed.

Animals↗
PubMed1976

[Contribution to the problem of Arthrogryposis multiplex (author's transl)].

A case of Arthrogryposis multiplex appearing after birth and of no characteristical course is described. It is shown that in respect to existing works for diagnosis of Arthrogryposis multiplex the insufficiency of the hitherto existing valid diagnostic criterions is obvious. This especially because the pathogenesis of Arthrogryposis multiplex is unknown. Trying to look for the condition of the connective tissue of our patient, it was found that the collagen of skin shows a young matter of polymerisation and a nearly correlating electron microscopical picture.

Adult↗
PubMed1976

Isolation of the basal and lateral plasma membranes of rat kidney tubule cells.

A method was developed to isolate renal basolateral membranes from cortical kidney tubule cells of single rats. The isolated membrane fraction was characterized by the measurement of marker enzyme activities and by electron microscopy. 1. After centrifugation of crude plasma membranes on a discontinuous sucrose density gradient the basolateral membranes accumulated at a sucrose density of p= 1.14-1.15 g/ml. The yield was 147 mug membrane protein/g kidney wet weight. Protein recovery was 0.1%. 2. (Na+ + K+)-ATPase was enriched 22-fold from the homogenate. The recovery was 2.6%. The (Na+ + K+)/Mg2+-ATPase ratio was 4.1. 3. The contamination by brush borders was small. Alkaline phosphatase was 1.6-fold enriched and 0.2% was recovered. Aminopeptidase was 1-fold enriched with a recovery of 0.1%. The contamination by mitochondria, lysosomes and endoplasmic reticulum was negligible. 4. In electron micrographs the basolateral membranes showed a typical triple layered profile and were characterized by the presence of junctional complexes, gap junctions or tight junctions.

Adenosine Triphosphatases↗
PubMed1976

Distribution of alkaline phosphatase in the microcirculatory pathways of the coronary system.

By histochemistry alkaline-phosphatase-activity in the microcirculatory pathways of the coronary vascular system were investigated. In the capillary network paralleling the myocardial fibers enzyme activity was found positive whereas in the large sinusoidal, endothelial vessels, linking transmurally neighbouring capillaries, there was no alkaline phosphatase activity. In both endothelial cell types, in capillaries and in sinusoids, a transendothelial vesicular thorotrast transport could be shown. It is supposed that the sinusoidal vessels preponderantly have to cope with intercapillary shear stress. Their nutritial function is believed to be of less importance. At least the lack of alkaline phosphatase activity should indicate that there is no selective transendothelial transport in the wall of these sinusoids.

Alkaline Phosphatase↗
PubMed1976

[Electron microscopy picture of oxyphenisatin-induced liver damage].

Ultrastructural investigations of liver biopsies are performed in 20 cases after phenolisatin reexposition and corresponding reactions of the laboratory findings. Alterations of the nucleus (segregation of nucleolus, condensation of chromatin) and of the rough endoplasmatic reticulum ("disarrangement", fragmentation and loss of ribosomes) were evident in all cases. In contrast, changes of the mitochondria (swelling) in various extent could only be observed in some cases. Besides that, frequently lipid includings and occasionally includings like lysosomal residual bodies are to be seen. Thus, as a hypothesis we suggest the nucleus resp. nucleolus to be one site of aggression of phenolisatin containing drugs. Findings already described by light microscopy such as reactions of the v. KUPFER cells and proliferations of the ductuli as well as cell proliferations in the portal fields are documentated by electronmicroscopy, too.

Cell Nucleus↗
PubMed1976

[Electron microscopic study of guinea pig tracheal epithelium after administration of NAB 365 (author's transl)].

After application of 4-amino-alpha-[(tert.-butylamino)methyl]-3,5-dichlorobenzyl alcohol hydrochloride (clenbuterol, NAB 365) the following changes in the secretory cells of the tracheal epithelium of the guinea pig can be visualised by electron microscope: 1. increase of membrane-bordered structures which might be regarded as primary lysosomes, 2. a faster and more pronounced loosening of secretion granula. These findings suggest a selective site of action of the substance at the lysosomal system. It is stimulated, loosens the secretion intensively already within the cell, and possibly develops some activity even in the lumen. These conceptions can serve as an explanation of the clinically and experimentally demonstrated secretolytic effect.

Animals↗
PubMed1976

[Increase of connective tissue in rat hearts under exposure to noise and with magnesium deficiency (author's transl)].

Only a small amount of noise caused, combined with a nutritional Mg deficiency, a significant increase of collagen in the myocard of rats. While Mg deficiency or noise each for its own had no effect, the combination of both had a noxious effect. The results of these experiments give a hint to a correlation between collagen-increase in the myocard and an increase of urinal Catecholamine during the same time.

Animals↗
PubMed1975

Cytotoxic effects of 6-mercaptopurine on the limb-bud blastemal cells of rat embryos.

On day 12 of pregnancy Wistar rats were each given a single ip injection of 5, 8, 16, 25, or 50 mg/kg 6-mercaptopurine. The embryos were removed 1, 2, 3, 5, 6, 10, 24, 48, or 72 h after injection or on day 20 and studied by light and electron microscopy. After 25 or 50 mg/kg all embryos showed no mineralization in the lower extremities. By electron microscopy condensation, shrinking, and fragmentation of cells in the limb bud blastema could be seen after 5 h. The fragments were phagocytosed and broken down by neighboring cells or remained in the extracellular space. After 25 or 50 mg/kg the damage was so extensive that the number of undamaged cells and of cells transforming into phagocytes was not sufficient to remove the debris or to compensate for the defect by mitotic activity. Epithelial cells, nerves, and blood vessels, show no morphological signs of damage. The "critical period" was the time cartilage just starts developing, i.e., when the blastema begins to differentiate.

Animals↗
PubMed1975

The effect of D-penicillamine of the skeletal development of rat foetuses.

Rats received 20, 50 or 100 mg/animal D-penicillamine i.p. twice daily on days 15, 16, 17, 18, and 19 of gestation, i.e. a total dose of 200, 500 resp. 1000 mg/animal. At all dosages the number of fetal resorptions did not increase significantly. Weight of the 20 day old embryos as well as length of the long bones in the extremities in the 100 mg-group showed a significant decrease. Numerous skeletal alterations could be observed in the 1000 mg-group such as absence, deformations or incomplete mineralisation of bones. Light microscopic examinations revealed an inhibition of the ossification as well as a decrease of number and size of the trabecula and of the thickness of the perichondrial bone sheath. A swelling of the collagenous fibrils can be demonstrated with the electron microscope. The first apatite crystals aggregate in collagen-free areas. The fusion of these aggregates to homogenously mineralized trabecula is inhibitied. In contrast to bones from untreated embryos, mineralized areas show varying content of collagen and apatide crystals. A regular spatial relationship between apatite crystals and collagenous fibrils does not develop. These findings show that even after the so-called "critical period" malformations can be pproduced by substances which disturb synthesis and maturation of the mesenchymal intercellular substance.

Abnormalities, Drug-Induced↗
PubMed1975

[On a special form of extremity malformation in rats following administration of 6-mercaptopurine on day 12 of gestation (author's transl)].

After i.p. application of 16 or 25 mg/kg, resp., 6-mercaptopurine on day 12 of gestation, numerous bone aplasias in the extremities can be demonstrated using the alizarine-red clearing method or X-ray techniques. In a few cases, however, histological examination reveals the presence of an unmineralized cartilagenous skeletal piece. The cause of this malformation is presumably the damaging of precursor cells of the osteoblasts responsible for the desmal and enchondral esteogenesis during the blastema stage. Therefore, it is to be distinguished between the true and the cartilagenous aplasias.

Abnormalities, Drug-Induced↗