Accumulation of very long chain fatty acids in X-linked and neonatal forms of adrenoleukodystrophy (ALD) appears to be a consequence of deficient peroxisomal oxidation of very long chain fatty acids. Peroxisomes were readily identified in liver biopsies taken from a patient having the X-linked disorder. However, in liver biopsies from a patient having neonatal-onset ALD, hepatocellular peroxisomes were greatly reduced in size and number, and sedimentable catalase was markedly diminished. The presence of increased concentrations of serum pipecolic acid and the bile acid intermediate, trihydroxycoprostanic acid, in the neonatal ALD patient are associated with a generalized diminution of peroxisomal activities that was not observed in the patient with X-linked ALD.
Culture conditions can modify the composition of the extracellular matrix of cultured calf aorta smooth muscle cells. In the absence of ascorbate the major components of the matrix are microfibrillar proteins ; deposition of collagen occurs upon ascorbate supplementation and, with increased time of exposure of cells to ascorbate, collagen becomes the dominant protein of the extracellular matrix (>80%) . Collagen accumulation follows a sigmoidal time-course, suggesting that it is a cooperative phenomenon . Covalent crosslinks are not required for collagen accumulation in the matrix . Microfibrillar proteins and increased amounts of proteoglycans and fibronectin accumulate concurrently with collagen but elastin deposition was not observed either with or without ascorbate feeding. Addition of ascorbate leads to a general stimulation of incorporation of [' 4C]proline into cellular protein and to changes in cell growth parameters and morphology: cell-doubling time decreases from 62 to 47 h and plating efficiency increases approximately fourfold . We conclude that the composition of the extracellular matrix assembled by cultured cells is subject to experimental manipulation and that changes in endogenously deposited matrix may have significant effects on cellular functions.The role of the substrata in cell attachment, proliferation, and differentiation has recently received much attention (14, 18) . Artificial collagen substrates and those of more complex composition approximating the extracellular matrix of the cell in vivo are being widely used in studies of growth and differentiation of a number of diploid cell types . For example, improved survival and maintenance of differentiated function were observed when rat hepatocytes were cultured on "biomatrix" or collagen gels than when cultured on plastic (26), and growth factors were not required when bovine vascular smooth muscle cells were maintained on the extracefular matrix assembled by corneal endothelial cells (13). Liotta et al. reported that collagen was required for cell attachment, spreading, and proliferation, and that artificial collagen substrates could substitute for the endogenously deposited collagen (22). These observations support the idea that the substrate, either provided to the cell and/or the extracellular matrix that the cell elaborates, is crucially important in determining cell behavior and diferentiatioe fate. The role of the endogenously produced extracellular matrix of cultured cells in regulating cellular properties such as growth and metabolism has received little attention . Recent studies on rat heart smooth muscle cells showed that the matrix composition can be altered by ascorbic acid; in the absence of ascorbate, elastin was the major component whereas in its presence glycoprotein and collagen were deposited (9, 30) . However, in this system, ascorbate had a variable effect on cell growth.In a previous study, we presented evidence that the major components of the extracellular matrix of the calfaorta smooth muscle cells cul...
SUMMARY Vascular disease in diabetics could arise in part from altered vessel wall catebolism. Specific activities of hydrolases in aortic smooth muscle cells from rats with streptozotocin-induced diabetes were measured. Enzymes included: neutral a-glucosidase, a-mannosidase, and lysosomal /V-acetyl /3-glucosaminidase, /3-galactosidase, cathepsin C, acid a-glucosidase, and acid cholesteryl esterase. After 4 , 8 , and 11 weeks of diabetes, activities of all enzymes studied were decreased significantly in diabetic vessels, decreases ranging from 15% for cathepsin C to 62% for amannosidase. After 3 weeks of diabetes, insulin treatment for 1 week restored enzyme levels to normal. After 7 weeks of diabetes, 1 week of insulin treatment did not restore enzyme levels fully to normal (acid cholesteryl esterase was unchanged); 4 weeks of insulin did. Acid phosphatase and JV-acetyl /3-glucosaminidase activities were reduced markedly in histochemical studies of diabetic aortas at all time periods and were restored by insulin treatment. AUoxan-induced diabetes gave results similar to those with streptozotocin. Significant decreases of aortic hydrolase activities, including those of lysosomes, occur in experimental diabetes mellitus and could contribute to accumulation of substrates in vascular smooth muscle cells.
Microfibrils are the insoluble, 10-to 12-nm components of the extracellular matrix that are involved in elastogenesis. Microfibrils are the predominant insoluble extracellular protein in such cultures, which do not deposit collagen or elastin. These studies demonstrate that microfibrils are tu-Literature Cited
Primary fixation in an osmium-potassium ferrocyanide (K4Fe(CN)6) mixture combines selective fixation, staining, and extraction of various cellular components; membranes, glycogen, glycoproteins, and elastin are preserved and stained. An intranuclear reticular structure that is composed of 3-6 nm fibers and permeates the entire nucleus, except for the nuclear pores, is demonstrated by electron microscopic examination of tissues prepared in an osmium-potassium ferrocyanide fixative. Condensations of the reticulum parallel the distribution of heterochromatin in interphase nuclei. This preparative procedure also reveals a network of trabeculae that are associated with the cisternae of rough endoplasmic reticulum and connect the parallel cisternae in hepatocytes, plasmacytes, neurons, and pancreatic ancinar cells. The intercisternal trabeculae are associated with both free and bound ribosomes.
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