Deficiencies of total collagen, type III collagen, and elastin have been proposed to explain aneurysm formation. Infrarenal aortas were collected from 19 patients (age 70 +/- 7 years) undergoing operative repair of abdominal aortic aneurysms (diameter 7 +/- 2 cm) and from 13 autopsies (age 63 +/- 17 years) of patients without aneurysm disease (controls). Wall thickness and collagen and elastin concentration were determined in full-thickness aorta. Collagen types I and III were measured after digestion with cyanogen bromide, which solubilized nearly 90% of total collagen for typing. Cyanogen bromide peptides were separated by sequential carboxymethylcellulose and agarose chromatography and quantified by peak area measurement with computerized image analysis. Histologic examination revealed prominent inflammatory cell infiltration and deficient, fragmented elastin in the aneurysms. Aortic wall thickness was similar in aneurysms and in control specimens. In the aneurysms, collagen was increased (37% +/- 16% vs 24% +/- 5%; p less than 0.05) and elastin was decreased (1% +/- 1% vs 12% +/- 7%; p less than 0.001), expressed as a percentage of delipidized, decalcified dry weight. Collagen type I accounted for 74% +/- 4% of aneurysm and 73% +/- 4% of control collagen solubilized for typing, and collagen type III accounted for 26% +/- 4% of aneurysm and 27% +/- 4% of control collagen solubilized for typing. Neither patients with a family history of aneurysms nor those without a history of aneurysms had collagen type III deficiency. Atherosclerotic abdominal aortic aneurysms are associated with an inflammatory process and may result from elastin degradation and not a deficiency of type III collagen.

Antibodies to collagen types I, II, and IV were measured in patients with otosclerosis and patients with Meniere's disease. Levels of antibodies to type II collagen were significantly higher in these patients than in control subjects, while no differences were found among levels of antibodies to collagen type I or type IV. These observations suggest a possible role for type II collagen autoimmunity in the etiology of otosclerosis and Meniere's disease.

Although elastin depletion is thought to be an etiologic factor in abdominal aortic aneurysm, little is known about its transcription and posttranslational modification in normal and diseased human aorta. Our objectives were to quantify total elastin and elastin cross-links (desmosine/isodesmosine [DID]) and to determine if elastin mRNA was detectable in the disease-prone infrarenal aorta from patients with abdominal aortic aneurysm and a comparative group with no aneurysmal diseases. After preliminary extraction and thermolysin digestion, content of DID and the elastin tetrapeptide, valine-alanine-proline-glycine (VAPG), were determined by high-performance liquid chromatography. Tissue mRNA was studied by Northern blot analysis. Mean values (+/- SE) were compared by Student's t test. The proportion of insoluble elastin was markedly decreased in abdominal aortic aneurysm tissue (1.3% +/- 0.04% vs 12% +/- -2.8%; p less than 0.001). There was no difference in the small percentage of elastin solubilized during extraction in abdominal aortic aneurysm (5.3% +/- 1%) and no aneurysmal disease (6.0% +/- 1.2%; p = 0.71) tissues. The DID concentration of insoluble elastin was not different for abdominal aortic aneurysm and no aneurysmal disease tissue (0.18% +/- 0.07 vs 0.18 +/- 0.05 nm DID/nm VAPG; p = 0.97). On the basis of VAPG content, only 26% +/- 4% of the sodium hydroxide insoluble residue from abdominal aortic aneurysm was elastin; the predominate protein(s) was high in polar amino acids. Elastin mRNA was detectable in all tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

Studies of mineralization of embryonic spicules and of the sea urchin genome have identified several putative mineralization-related proteins. These predicted proteins have not been isolated or confirmed in mature mineralized tissues. Mature Lytechinus variegatus teeth were demineralized with 0.6 n HCl after prior removal of non-mineralized constituents with 4.0 m guanidinium HCl. The HCl-extracted proteins were fractionated on ceramic hydroxyapatite and separated into bound and unbound pools. Gel electrophoresis compared the protein distributions. The differentially present bands were purified and digested with trypsin, and the tryptic peptides were separated by high pressure liquid chromatography. NH2-terminal sequences were determined by Edman degradation and compared with the genomic sequence bank data. Two of the putative mineralization-related proteins were found. Their complete amino acid sequences were cloned from our L. variegatus cDNA library. Apatite-binding UTMP16 was found to be present in two isoforms; both isoforms had a signal sequence, a Ser-Asp-rich extracellular matrix domain, and a transmembrane and cytosolic insertion sequence. UTMP19, although rich in Glu and Thr did not bind to apatite. It had neither signal peptide nor transmembrane domain but did have typical nuclear localization and nuclear exit signal sequences. Both proteins were phosphorylated and good substrates for phosphatase. Immunolocalization studies with anti-UTMP16 show it to concentrate at the syncytial membranes in contact with the mineral. On the basis of our TOF-SIMS analyses of magnesium ion and Asp mapping of the mineral phase composition, we speculate that UTMP16 may be important in establishing the high magnesium columns that fuse the calcite plates together to enhance the mechanical strength of the mineralized tooth.

No abstract

Echinoderm teeth are continuously growing calcite-mineralized tissues of complex structure. Two features are of special interest: (1) cell division takes place in a restricted aboral domain, the plumula, and the cells immediately merge into multinucleated syncytial layers; (2) the major part of the heavily mineralized tooth elongates and moves towards the adoral incisal tip continuously as the syncytial cells actively expand the syncytium and intermembrane mineral phase. As the first step to understanding the nature of the mineralization processes, we have isolated the proteins of the plumula and of the mature mineralized portions of the tooth, and begun their characterization. Peptide sequences were used to screen a plumula cDNA library by polymerase chain reaction. One primer set yielded a prominent amplified product which was cloned, and sequenced. Comparison with the nucleotide and protein data banks revealed the protein to be Mortalin, a member of the hsp-70 family, with >75% of its sequences identical to that of human mortalin. Immunocytochemical localization of mortalin within the plumula, using Anti-human Grp75, showed staining of the odontoblast cytosol and matrix at the point where syncytial formation was occurring. The cytosol of the syncytial layers was weakly stained. The nuclei within the syncytia were stained at their periphery. In the mature part of the tooth, the perinuclear staining of the nuclei was more prominent. We conclude that mortalin is involved in syncytium formation and maintenance. The urchin mortalin has a distinctive aspartic acid and serine-rich C-terminal domain that may link it to the mineralization process.

No abstract