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Biomedical subjects

P Bornstein

Publications and source records attributed to P Bornstein.

At least 163 records · Page 9Linked to original sources
PubMed1978

A new variety of spondyloepiphyseal dysplasia characterized by punctate corneal dystrophy and abnormal dermal collagen fibrils.

Several individuals from one family are described with a unique form of spondyloepiphyseal dysplasia. Characteristic features include short-trunked short stature, punctate corneal dystrophy and marked disorganization of dermal collagen fibrils when examined by transmission electron microscopy. Inheritance is compatible with either dominance and a variable expression or X-linkage. Although the basic defect has not been determined, the tissue distribution is consistent with a defect in a non-collagenous component that affects collagen fibril formation or stability.

Adult↗
PubMed1978

Amniotic fluid fibronectin. Characterization and synthesis by cells in culture.

A glycoprotein immunologically related to plasma cold-insoluble globulin (CIG) and fetal skin fibroblast fibronectin has been purified from second-trimester human amniotic fluid. This protein (amniotic fluid fibronectin) migrated more slowly than CIG on sodium dodecyl sulfate gel electrophoresis and showed greater polydispersity which could result, at least in part, from heterogeneity in glycosylation. Cloned human amniotic fluid epithelioid and fibroblastic cells synthesized and secreted a protein with similar properties into the culture medium. Fibronectin was shown to be associated with the pericellular and extracellular matrix of cultured amniotic fluid cells by immunofluorescence, lactoperoxidase-catalyzed iodination, and labeling with ferritin-conjugated antibodies. The kinetics of secretion of the protein were consistent with its role as a matrix protein. We anticipate that amniotic fluid fibronectin will prove to be the same protein which elsewhere in the body is incorporated into connective tissues and basement membranes. Amniotic fluid could, therefore, serve as a convenient source of in vivo synthesized fibronectin for biological and structural studies.

Amniotic Fluid↗
PubMed1978

Regulation of growth and gene activity in euploid hybrids between human neonatal fibroblasts and epithelioid amniotic fluid cells.

Pure populations of proliferating synkaryons were obtained from polyethylene glycol-mediated crosses between diploid human foreskin fibroblasts and epithelioid amniotic fluid cells. These hybrids proved to be chromosomally stable tetraploids. They continuously produced heteropolymeric G6PD and showed strictly additive patterns of silver staining of both parental sets of nucleolar organizing chromosomes. Collagenous proteins characteristic of the fibroblast parent were synthesized, while fibronectin production appeared to be directed by the epithelioid portion of the genome. Even though these heterotypic hybrids proliferated at a reduced rate and achieved fewer population doublings relative to homotypic (fibroblast X fibroblast) crosses, they survived passage by trypsinization better than pure populations of epithelioid cells. These observations suggest a concerted action of both parental genomes with respect to proteins responsible for "household" functions, but complementation and possibly modulation of gene action with respect to "luxury" protein synthesis and cell growth.

Amniotic Fluid↗
PubMed1977

Intermediates in the conversion of procollagen to collagen. Evidence for stepwise limited proteolysis of the COOH-terminal peptide extensions.

Intermediates in the conversion of procollagen to collagen were isolated from radioactively labeled chick cranial bones by ion-exchange chromatography. Cleavage of these proteins with vertebrate collagenase revealed that each of the several forms of these intermediates lacked NH2-terminal but retained COOH-terminal extensions. The chain composition of each intermediate was resolved by two-dimensional slab gel electrophoresis. The intermediates differed from each other in having sustained cleavages in zero, one or two pcalpha chains. The relative proportions of intermediates with different intact pcalpha chains, observed in conversion of procollagen, have enabled us to construct a detailed model of the stepwise limited proteolysis of procollagen.

Amino Acids↗
PubMed1977

Synthesis of types I and III procollagen and collagen by monkey aortic smooth muscle cells in vitro.

Analysis of pepsin-resistant proteins produced in culture by monkey aortic smooth muscle cells (SMC) indicates the synthesis of types I and III collagen. As determined by carboxymethylcellulose chromatography and disc gel electrophoresis, SMC cultures synthesize more type III collagen than monkey skin fibroblast cultures; aortic adventitial cell cultures (a mixture of SMC and fibroblasts) synthesize an intermediate amount of type III collagen. Both types I and III procollagens can also be isolated from the culture medium of SMC and skin fibroblasts. The procollagens were separated by diethylaminoethylcellulose (DEAE-cellulose) chromatography in identified by electrophoresis and after cleavage with pepsin and cyanogen bromide. Quantitation of the procollagen by DEAE-cellulose chromatography suggests that 68% of the SMC procollagens and less than 10% of the skin fibroblast procollagens are type III. On the other hand, estimation of the proportions of collagen types secreted by cells, employing pepsin digestion of cell culture medium at 15 degrees C, leads to an underestimation of the amount of type III collagen relative to type I. SMC and fibroblasts may differ in their ability to convert type I procollagen to collagen ad indicated by the observation that skin fibroblast culture medium contains both pN and pC collagen intermediates after 24 h, while cultures of SMC essentially lack the pC collagen intermediates.

Animals↗
PubMed1977

Impaired conversion of procollagen to collagen by fibroblasts and bone treated with tunicamycin, an inhibitor of protein glycosylation.

Tunicamycin, an inhibitor of lipid carrier-dependent protein glycosylation, was used in studies of procollagen synthesis, secretion, and proteolytic modification by chick cranial bones in organ culture and by chick tendon fibroblasts in tissue culture. Tunicamycin inhibited the incorporation of D-[2-3H]mannose into procollagen by greater than 90% whereas general protein synthesis and collagen synthesis were decreased by only 10 to 20%. The procollagen synthesized in the presence of tunicamycin was secreted normally and its immunological characteristics, as detected by an antiserum to the intact protein, were unchanged. However, tunicamycin caused an accumulation of biosynthetic intermediates containing disulfide-bonded COOH-terminal extensions in both cell and bone culture. Cleavage of NH2-terminal extensions was not detectably impaired. These findings provide additional support for the involvement of more than one enzyme in the limited proteolytic conversion of procollagen to collagen.

Amino Acids↗
PubMed1977

Cell surface-associated structural proteins in connective tissue cells.

Collagen and/or procollagen was demonstrated on the surface of monolayers of fibroblasts from normal rat kidney by indirect immunofluorescence with affinity-purified antibodies to collagen. The protein was arrayed in a reticular fashion on the cell surface and, in cells attached to a substratum, was severely restricted in its ability to undergo antibody-induced translational movement in the plane of the membrane. A similar pattern was observed for fibronectin (LETS protein, fibroblast surface antigen). These macromolecules were lost when fibroblasts were dissociated and examined in suspension cultures and were not regained until after the cells were replated. On the basis of the morphological findings, and in view of the likelihood of an interaction between fibronectin and collagen, we propose that these that these proteins form a meshwork on the cell surface. This external protein meshwork may mediate a number of important cellular functions, including attachment to a substratum and other interactions with the extracellular matrix.

Cell Line↗
PubMed1977

Changes in surface properties of normal and transformed cells caused by tunicamycin, an inhibitor of protein glycosylation.

Normal and virally transformed mouse (3T3) and human (WI-38) cells were treated with tunicamycin, an inhibitor of lipid-carrier-dependent glycosylation of proteins. Incubation of cells with tunicamycin (1 microgram/ml) caused detachment and death of simian virus 40- and polyoma-transformed cells within 24 hr; these effects were not seen with nontransformed cell lines. However, the proliferation of 3T3 cells was inhibited by tunicamycin and, after a few days, a distinct change from an epithelioid to an abnormally elongated shape was observed. Both inhibition of growth and the morphological changes were reversible. A marked decrease in concanavalin A agglutinability was observed in virally transformed cells treated with tunicamycin (0.5 microgram/ml), but agglutination by wheat germ agglutinin or soybean agglutinin was unaffected. Analysis of biosynthetically labeled proteins showed that a high-molecular-weight protein, presumed to be related to fibronectin, is markedly reduced in the medium of cells cultured in the presence of tunicamycin. These results suggest that tunicamycin interferes with the insertion or function of one or more cell-surface glycoproteins. Such cell-surface changes could affect a number of cellular properties, including attachment, cell shape, and agglutinability by some lectins.

Agglutination Tests↗
PubMed1976

A presumptive subunit of elastic fiber microfibrils secreted by arterial smooth-muscle cells in culture.

Monkey smooth cells, maintained for five weeks in confluent cultures, accumulated a substantial extracellular matrix. Elastic fibers possessing the characteristic amorphous elastin component and 11 nm diameter microfibrils could be isolated from this matrix by extraction with 5 M guanidine. Further extraction under reducing conditions selectively removed the microfibrillar component. Gel electrophoresis of this extract in the presence of sodium dodecylsulfate revealed a single protein band with an apparent molecular weight of 270000. The amino acid composition of this presumptive subunit of the microfibrillar protein was rich in acidic and hydrophilic amino acids and distinctly different from that of collagen or elastin. When smooth muscle cell cultures were incubated with labeled cystine, the predominant labeled protein in the culture medium also had a molecular weight of 270000. This labeled protein comigrated with a major protein band and could be partially purified by DEAE-cellulose ion-exchange chromatography and gel filtration on agarose. It shared manu of the properites of the presumptive microfibrillar protein.

Amino Acids↗
PubMed1976

Evidence contrary to the protein error hypothesis for in vitro senescence.

A strain of diploid fibroblasts, obtained from the skin of a male infant, was cultured in vitro and cells were tested throughout their lifespan for the appearance of altered glucose-6-phosphate dehydrogenase (G-6-PD) detected either by thermostability studies or by immunotitration. No significant difference was found in the proportion of thermolabile enzyme in 31 young cultures (4.8 +/- 1%, S.E.), in comparison with that in 19 old cultures (4.9 +/- 1%, S.E.). Old cultures had ceased active cell division (49-60 doublings); DNA replication, measured by [3H]thymidine uptake over a period of 24 hours, was limited to less than 5% of these cells. Young cells (5-22 doublings) had a [3H]thymidine labeling index of 75-85%. Titration of G-6-PD activity in extracts of young and old cells with neutralizing antibody directes specifically against G-6-PD failed to detect an increment of enzymatically defective G-6-PD in old cells. The thermostability studies were capable of detecting altered G-6-PD in skin fibroblasts from a female heterozygous for a thermolabile mutant of G-6-PD, and in fibroblasts treated with a proline analogue, azetidine carboxylic acid. The immunotitration technique was also capable of detecting catalytically altered G-6-PD from the thermolabile mutant and G-6-PD inactivated with N-ethylameimide. These findings argue against a protein error catastrophe as the cause of in vitro clonal senescence.

Adult↗
PubMed1975

Intermediates in the limited proteolytic conversion of procollagen to collagen.

The conversion of chick bone procollagen to collagen proceeds in a stepwise fashion to produce a limited number of intermediates. Initial proteolytic cleavages remove NH2-terminal nonhelical extensions and yield an intermediate which remains disulfide-bonded via COOH-terminal extensions. Subsequent stepwise scission of one or two chains of the triple-stranded molecule in its COOH-terminal domain produces intermediates which can only be distinguished after dissociation of the noncovalently bonded alpha chains. A final cleavage in this region produces the collagen molecule and a disulfide-bonded triple-stranded fragment which represents the COOH-terminal domain. In all likelihood the endopeptidases which effect cleavage in the NH2- and COOH-terminal regions differ. More than two enzymes may be required for conversion of procollagen to collagen if the nonhelical domains are not released in an en bloc fashion.

Animals↗
PubMed1975

The order of cyanogen-bromide peptides and location of carbohydrate in the alpha2 chain of guinea-pig skin collagen.

The alpha2 chain of guinea pig skin collagen contains two additional methionyl residues in comparison with the alpha2 chain of other vertebrate species. The order of the three CNBr peptides unique to the alpha2 chain was established on the basis of the homology of their primary structures to sequences of previously ordered regions in the alpha1 and alpha2 chains of other colagens. The two larger peptides, 4A + 4B, were found to correspond to the region homologous to alpha2-CB4 of other species, while the smaller peptide, 3A, was homologous to the NH2-terminal portion of alpha2-CB3. Thus, the order of the peptides in the alpha2 chain of this collagen is 1-O-4A-4B-2-3A-3B-5. Periodate oxidation and alkaline or acid hydrolysis of the CNBr fragments showed that all of the hydroxlysine-linked carbohydrate in the alpha2 chain was present in alpha2-CB4B. Carbohydrate analyses were most consistent with the existence of single monosaccharide and disaccharide units in this region.

Amino Acid Sequence↗
PubMed1975

Characterization of procollagen-derived peptides unique to the precursor molecule.

A disulfide-bonded fragment with a molecular weight of about 100,000 was identified in the medium of cultured chick cranial bone and its derivation from procollagen was established by immunological criteria. The molecular weight of the fragment was reduced to 33,000 after cleavage of disulfide bonds, indicating a triple-stranded structure. The amino acid composition of the fragment lacked hydroxyproline and hydroxylysine and differed markedly from that of collagen in other respects. A similar but somewhat larger fragment was isolated after bacterial collagenase digestion of chick bone procollagen purified by chromatography on DEAE-cellulose. The characterization and comparison of these fragments further define the nature of the additional regions in procollagen and, when combined with information derived from studies of acid-extracted and dermatosparactic procollagens, support a mechanism for the conversion of procollagen to collagen which involves more than one proteolytic step.

Amino Acids↗
PubMed1975

The metabolic requirements for transcellular movement and secretion of collagen.

Cultures of chick tendon fibroblasts were capable of normal ATP production and protein synthetic activity even though the normally high rate of glycolysis was markedly reduced by substitution of pyruvate for glucose. Iodoacetate and 2-deoxyglucose reduced ATP levels and protein synthesis even in the presence of pyruvate. Under these conditions, both inhibitors were shown to have effects on the energy metabolism of cells which were apparently unrelated to an inhibition of glycolysis. Selective inhibition of either glycolysis, by incubation in glucose-free medium, or of oxidative phosphorylation, by incubation with an uncoupler, was shown to have little effect on cellular ATP levels or intracellular transport and secretion of collagen. However, inhibition of both glycolysis and oxidative phosphorylation resulted in decreased cellular ATP levels and an inhibition of collagen secretion. This effect was not due to a requirement for continued protein synthesis, since inhibition of protein synthesis with cycloheximide or puromycin had little effect on collagen secretion. The ATP requirement for intracellular transport and secretion is discussed in relation to the secretory pathway for collagen.

Adenosine Triphosphate↗