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Biomedical subjects

J A Foster

Publications and source records attributed to J A Foster.

At least 109 records · Page 6Linked to original sources
PubMed1988

Multiple chick tropoelastin mRNAs.

Several overlapping chick tropoelastin cDNAs were isolated from a lambda gt11 cDNA library constructed from whole 10 day chick embryo total RNA. Comparison of the nucleotide sequence of the 2.3 kb tropoelastin cDNA to the sequences published by Bressan et al. (1) and Tokimitsu et al. (2) revealed the presence of two inserts (72 and 30 base pairs) in the cDNA derived from embryonic tissue. Northern blot analysis of 14 day embryonic aortae RNA with tropoelastin cDNA clones showed hybridization to a 3.5 kb mRNA. However, S1 nuclease protection experiments performed on RNA extracted from the same tissue showed that at least two if not more tropoelastin mRNAs exist and that the proportion of each varies in the ages examined. These results provide an origin and substantiate the differential expression of the multiple tropoelastin polypeptides found in developing chick aortic tissue.

Amino Acid Sequence↗
PubMed1988

Synthesis of soluble and insoluble elastins in cultures of chick aortic cells.

Aortic cells were isolated from 9- and 12-day embryonic chick aortas and cultured for varying periods after first passage. Cells obtained from 9-day tissue remained indefinitely as monolayers and possessed a relatively low rate of tropoelastin synthesis. Cells obtained from 12-day tissue remained monolayers for 4 to 8 days, after which time portions of the culture contracted into matrix containing chemically definable insoluble elastin and forming desmosine cross-links. The rate of tropoelastin synthesis was significantly higher in the 12-day derived cells suggesting that these cells had been committed to elastogenesis in vivo and retained this commitment in vitro. A chick tropoelastin cDNA was obtained and partially characterized from a lambda gt11 expression cDNA library. Using the tropoelastin cDNA probe, measurement of the steady-state level of tropoelastin revealed that the increased rate of tropoelastin synthesis in the 12-day cells was accompanied by a significant increase in the level of tropoelastin mRNA steady-state levels. The aortic cell cultures present an important model system for extending studies of chick aortic elastogenesis. The aortic cell cultures synthesize tropoelastin at a rate 10% less than the corresponding organ culture. Significantly, the production of tropoelastin is productive in formation of insoluble, chemically definable elastin. The definition of insoluble includes both amino acid composition and desmosine formation.

Amino Acids↗
PubMed1987

Evidence for the existence of three chick lung tropoelastins.

Three tropoelastin polypeptides are identified among the cell-free translation products of chick embryo lung mRNAs and organ cultures extracts. The tropoelastins are distinguished by one and two dimensional gel electrophoretic systems and are all immunoreactive with monospecific chick tropoelastin antiserum. The ratio of the three tropoelastins does not vary significantly between 10 and 16 days of lung embryogenesis. The third tropoelastin (c) is found to co-migrate with tropoelastin b on SDS-polyacrylamide gel electrophoresis but is visible after cyanogen bromide cleavage of reticulocyte lysate proteins. Immunoprecipitates from lung organ culture also contain tropoelastins a, b and c.

Animals↗
PubMed1987

Pulmonary fibroblasts: a model system for studying elastin synthesis.

Pulmonary interstitial fibroblasts were isolated from 4-day neonatal rat lung and cultured for varying periods of time after first passage. The ability of the cells to synthesize both soluble and insoluble elastin was examined by biochemical, immunological, and ultrastructural techniques. The cells synthesize a tropoelastin of 75,000 daltons which is cross-linked in the extracellular matrix to form sufficient amounts of insoluble elastin to be characterized directly by amino acid analysis. Although the cells produce a soluble form of elastin immediately after confluency and the deposition in the matrix begins shortly thereafter, the actual chemical definition of alkali-resistant elastin does not occur until 4 weeks after confluency. The apparent molecular weight of tropoelastin synthesized by the cells agrees with the molecular size of tropoelastin found in organ culture of neonatal lungs. The pulmonary fibroblast cultures provide an important model system for examining the regulation and response of elastin synthesis in lung interstitium.

Animals↗
PubMed1986

Tropoelastin synthesis in fetal bovine tissues.

Tropoelastin was examined in bovine lung, aortic and ligament tissues using both organ culture and cell-free translation systems. The bovine tissues synthesized two tropoelastin polypeptides of approximately 70,000 and 68,000 daltons. Two polypeptides were also seen amongst the translation products directed by mRNAs isolated from each of the individual tissues. Both proteins were shown to be tropoelastins directly by immunoprecipitation with specific antibody and limited NH2-terminal sequence analyses and indirectly by two-dimensional gel electrophoresis. The finding of two forms of tropoelastin is similar to that previously reported in chick tissues although the apparent molecular weights of the tropoelastins differ between the two species. Another interesting observation is that the proportion of the two tropoelastins differs amongst the three fetal tissues examined. This situation is similar to the differences seen in the ratio of tropoelastin a and be between embryonic chick lung and aortic tissues.

Animals↗
PubMed1984

Isolation of tropoelastin a from lathyritic chick aortae.

Tropoelastin a was isolated from lathyritic chick aortae by using severe denaturing conditions for the initial extraction. The amino acid composition of this new species of tropoelastin is elastin-like in its high proportion of proline, glycine, alanine and valine. However, it differs from authentic tropoelastin b in containing a higher percentage of polar amino acids and cysteine residues. In addition, the amount of proline hydroxylation is 3 times higher than that found in chick tropoelastin b.

Amino Acids↗
PubMed1983

Monoclonal antibodies as probes for differentiating tropoelastin a and b.

BALB/C mice were immunized with a mixture of aortic tropoelastin a and b. To ensure the presence of tropoelastin a, the lathyritic chick aortic tissue was first extracted with denaturing and reducing agents. After dialysis, the standard procedure for tropoelastin purification was followed. Following immunization, the lymphocytes were fused with a myeloma cell line. Resulting hybridomas were cloned and tested for reactivity towards tropoelastin a and b. The majority of monoclonal antibodies exhibited crossreactivity between the two tropoelastins. Two of the clones were further characterized because of their ability to differentiate both tropoelastin a and b. As demonstrated by immunoprecipitation and Western blot analyses, one clone reacted preferentially with tropoelastin b and the other with tropoelastin a and b. Significantly, these results demonstrate that tropoelastin a and b can be differentiated by immunological techniques.

Animals↗
PubMed1981

Primary structure of the signal peptide of tropoelastin b.

Elastin is a major protein of compliant connective tissue and is characterized by an amino acid composition abundant in nonpolar residues. The soluble precursor to elastin tropoelastin, is extractable in organic solvents and possesses an extensive clustering of nonpolar amino acid residues in the immediate NH2-terminal region (Foster, J. A., Shapiro, R., Voynow, P., Crombie, G., Faris, B., and Franzblau, C. (1975) Biochemistry 14, 857-864). It was, therefore, of special interest to determine whether tropoelastin requires a hydrophobic signal peptide for vectorial transport of the nascent polypeptide. The possibility that the initial tropoelastin translation product possesses a short signal peptide was examined in a cell-free translation system. Total RNA, isolated from aortae of 1-day-old chicks, was translated in an mRNA-dependent reticulocyte lysate translation assay. The translation products were then immunoprecipitated and subjected to automated radiosequencing. Comparison of the NH2-terminal sequence of tropoelastin b synthesized in the cell-free system versus that synthesized in organ culture demonstrated the presence of a signal peptide 24 amino acid residues in length. The signal peptide sequence is as follows: Met-Arg-Gln-Ala-Ala-Ala-Pro-Leu-Leu-Pro-Gly-Val-Leu-Leu-Leu-Phe-Ser-Ile-Leu-Pro -Ala-Ser-Gln-Gln. The preponderance of hydrophobic amino acid residues as well as the polar residues adjacent to the initiator methionine and the carboxyl termini found in the signal peptide is similar to that reported for other secreted proteins.

Amino Acid Sequence↗
PubMed1981

Naloxone suppresses food/water consumption in the deprived cat.

Intraperitoneal administration of the opiate antagonist, naloxone hydrochloride, resulted in decreased food and water consumption in drug-naive cats. In a cross-over Latin Square design, food consumed by six cats in a one hour period following 23 hours of deprivation, was decreased significantly below control (p less than 0.05) in linear relation to increasing dose (1 mg/kg and 10 mg/kg) of naloxone. Non-linear and time/order effects were not significant. Water consumption was decreased below control in a linear relation to increasing dose (1 and 10 mg/kg) for 5 of 6 cats at the 0.05 significance level. Non-linear and time/order effects on water consumption were not statistically significant for the same 5 cats. These results, and behavioral signs (i.e., vomiting, persistant vocalization, heavy salivation, mydriasis, moderate catatonia, and hissing) occasionally exhibited by four of the six cats in a 1-hr period following injection of the high dose, suggest a malaise-effect of naloxone.

Animals↗
PubMed1981

Optimal conditions for cell-free synthesis of elastin.

Optimal conditions for the translation of elastin mRNA1 in a mRNA-dependent rabbit reticulocyte lysate were determined. Using total RNA isolated from embryonic chick aortae as the source of exogenous RNA, the concentrations of various components present in the translation assay were varied and the effect on elastin synthesis quantitated by immunoprecipitation. Components examined included: magnesium acetate, potassium chloride, spermidine, creatine phosphate, ATP, and GTP. In addition, it was found that heating of the RNA prior to translation significantly enhanced total protein synthesis, elastin synthesis, and the synthesis of proteins possessing molecular weights of greater than 80,000.

Cell-Free System↗
PubMed1981

The biosynthesis of tropoelastin in chick and pig tissues.

The cell-free translation of elastin mRNA's from different tissues as well as different animal sources was investigated. In all cases elastin mRNA's coding for both tropoelastin a and b were found. Of special significance was the finding that the ratio of the two tropoelastins varied between lung and aortic tissues and this observation was consistent for two animal species.

Animals↗