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M E Holtrop

Publications and source records attributed to M E Holtrop.

26 records · Page 2Linked to original sources
PubMed1971

Microanalysis of individual mitochondrial granules with diameters less than 1000 angstroms.

A scanning electron microscope was converted to an electron microprobe with high spatial resolution by the addition of a transmitted electron detector and a solid-state x-ray detector. Spectra obtained from mitochondrial granules of chondrocytes in situ confirm the suspected presence of calcium and phosphorus. Contamination during analysis can lead to false indications of silicon in living tissue.

Animals↗
PubMedDate not supplied

The ultrastructure of bone.

The ultrastructure of the three specialized bone cells are described in relation to their function. Osteoblasts are the bone forming cells with an abundance of RER and a large Golgi area. Osteoblasts and osteocytes form an integrated cell system connected with each other by cell processes filled with actin-like filaments and joined by specialized cell junctions, probably gap junctions. Osteoclasts resorb bone. Characteristics are multiple nuclei, and abundance of mitochondria, a sparcity of RER and clusters of ribosomes. Lysosomes and vesicles contain hydrolytic enzymes. The resorbing area consists of a ruffled border completely encircled by a clear zone.

Bone and Bones↗
PubMedDate not supplied

The ultrastructure of the osteoclast and its functional implications.

Recent findings on the ultrastructure of the osteoclast indicate that special attention should be given to the ruffled border, clear zone, and the vacuoles and vesicles of the cell and their significance for the mechanism of breakdown of bone matrix. The ruffled border is seen as an extensive area of cell surface where secretion of enzymes as well as uptake of matrix components takes place. The clear zone encircles the ruffled border completely and thus forms an integral part of the resorbing apparatus. Vacuoles and vesicles are thought to secret enzymes as well as take up extracellular material and possible digest or transport these products in the cell. The changes that occur in the ultrastructure of the osteoclast after exposure to parathyroid hormone and calcitonin indicate an important role of the ostioclast in bone metabolism. The cell can increase its activity very rapidly in response to parathyroid hormone, and decrease its activity in response to calcitonin.

Bone and Bones↗