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Biomedical subjects

R G Crystal

Publications and source records attributed to R G Crystal.

At least 343 records · Page 19Linked to original sources
PubMed1986

Expression of the alpha-1-antitrypsin gene in mononuclear phagocytes of normal and alpha-1-antitrypsin-deficient individuals.

To evaluate the contribution of mononuclear phagocytes, and particularly alveolar macrophages, to alpha-1-antitrypsin (alpha 1AT) production in normal and alpha 1AT-deficient individuals, Northern analysis with a human alpha 1AT complementary DNA was used to demonstrate that alpha 1AT messenger RNA (mRNA) can be detected in liver, blood monocytes, and alveolar macrophages. Quantification of alpha 1AT mRNA expression demonstrated that: (a) type PiMM monocytes and alveolar macrophages expressed, respectively, 200-fold and 70-fold less alpha 1AT mRNA per cell than the liver; (b) the level of expression of the alpha 1AT gene was increased during the in vitro maturation of blood monocytes; and (c) blood monocyte and alveolar macrophage levels of expression of the alpha 1AT gene were the same in PiMM and PiZZ individuals. However, the amount of newly synthesized alpha 1AT secreted by ZZ alveolar macrophages was 10 times lower than that secreted by MM alveolar macrophages. Thus, mononuclear phagocytes of PiZZ individuals express a secretory defect in alpha 1AT in a fashion similar to hepatocytes. Not only do mononuclear phagocytes provide a readily accessible cell to evaluate the regulation of alpha 1AT gene expression, but these cells may contribute to the levels of alpha 1AT present in the lower respiratory tract in the normal and ZZ states.

Adult↗
PubMed1986

Spontaneous release of interleukin 2 by lung T lymphocytes in active pulmonary sarcoidosis is primarily from the Leu3+DR+ T cell subset.

The inflammation within the lower respiratory tract of individuals with pulmonary sarcoidosis is dominated by large numbers of helper T lymphocytes that proliferate and spontaneously release interleukin 2 (IL-2). To identify the lymphocyte subpopulation that releases IL-2 in this disorder, lung lymphocytes recovered by bronchoalveolar lavage were characterized using the monoclonal antibodies Leu4 (T lymphocyte), Leu3 (helper/inducer), Leu2 (suppressor/cytotoxic), and anti-HLA-DR, and separated by panning and flow cytometry. The majority of the IL-2 spontaneously released by T cells in the sarcoid lung was contributed by the Leu3+ cell population (Leu3+65 +/- 23 IL-2 units released/10(6) cells per 24 h; Leu2+ 9 +/- 8, P less than 0.04). Further characterization of the lung Leu3+ T cells in sarcoid demonstrated that 30 +/- 3% were expressing HLA-DR molecules on their surface compared with 6 +/- 1% in normals (P less than 0.01). Importantly, the subpopulation of Leu3+ lung T lymphocytes expressing a high intensity of HLA-DR molecules on their surface was responsible for the majority of the release of IL-2 in the sarcoid lung (Leu3+ high-intensity DR 42 +/- 17 U/10(6) cells per 24 h, Leu3+ low-intensity DR 8 +/- 1 U/10(6) cells per 24 h; P less than 0.01). Thus, the spontaneous release of IL-2 in the lung of sarcoid patients appears to be localized to a subset of Leu3+ high-intensity DR ("activated" lung helper/inducer) T lymphocytes. Because the sarcoid lung is characterized by markedly increased numbers of these cells, it is likely that this compartmentalized T cell population plays a major role in sustaining the exaggerated localized immune processes of this disorder.

Adult↗
PubMed1986

Spontaneous expression of the c-sis gene and release of a platelet-derived growth factorlike molecule by human alveolar macrophages.

Alveolar macrophages from normal individuals and patients with interstitial lung diseases spontaneously expressed a 4.2-kilobase mRNA complementary to the c-sis gene, a proto-oncogene coding for one of the chains of platelet-derived growth factor (PDGF). Concomitantly, these cells released a mediator with the properties of PDGF, including: chemotactic factor for smooth muscle cells whose activity was resistant to heat and acid, but sensitive to reduction; mitogenic (competence) activity for fibroblasts; ability to compete with PDGF for its receptor; and precipitated by an anti-PDGF antibody. While blood monocytes did not contain c-sis mRNA transcripts, monocytes matured in vitro expressed c-sis, consistent with the concept that expression of c-sis occurs during the differentiation of monocytes into alveolar macrophages. Together with the known actions of PDGF, these observations suggest that the c-sis proto-oncogene and its PDGF product are part of the armamentarium available to the alveolar macrophages for normal lung defense and participation in lung inflammation.

Chemotaxis↗
PubMed1986

Bronchoalveolar lavage. The report of an international conference.

The application of the method of bronchoalveolar lavage to an increasing array of pulmonary diseases was evident, and the use of sophisticated technology to study cells and measure minute amounts of protein and other components in bronchoalveolar lavage fluid indicated that more meaningful information may be gained about diseased airways and alveolar spaces than suspected. That new techniques are being developed to make assays more sensitive and specific was evident. The popularity of this research approach was underscored by the interest and participation of colleagues in the United States and especially in Europe (notably France, England, Italy, and West Germany) and in Japan. This meeting was an opportune time to reflect on what bronchoalveolar lavage analysis has contributed to date and to focus attention on new applications that will be forthcoming and will improve our understanding of immunopathogenic mechanisms in an expanding number of pulmonary diseases.

Asthma↗
PubMed1986

Intraluminal fibrosis in interstitial lung disorders.

The histopathologic and ultrastructural features of intraluminal organizing and fibrotic changes were studied in open lung biopsies and autopsy specimens from 373 patients with interstitial lung disorders, including hypersensitivity pneumonitis (n = 44), idiopathic pulmonary fibrosis (n = 92), collagen-vascular diseases (n = 20), chronic eosinophilic pneumonia (n = 10), pulmonary histiocytosis X (n-90), pulmonary sarcoidosis (n = 62), pneumoconioses (n = 25), Legionnaire's disease (n = 5), drug- and toxin-induced pneumonitis (n = 4), radiation-induced pneumonitis (n = 2), lymphangioleiomyomatosis (n = 11), and chronic organizing pneumonia of unknown cause (n = 8). Three patterns of intraluminal organization and fibrosis were recognized: 1) intraluminal buds, which partially filled the alveoli, alveolar ducts and/or distal bronchioles; 2) obliterative changes, in which loose connective tissue masses obliterated the lumens of alveoli, alveolar ducts or distal bronchioles, and 3) mural incorporation of previously intraluminal connective tissue masses, which fused with alveolar, alveolar ductal, or bronchiolar structures and frequently became reepithelialized. All three patterns had common morphologic features, suggesting that, regardless of their severity, they resulted from a common pathogenetic mechanism, ie, the migration of activated connective tissue cells, through defects in the epithelial lining and its basement membrane, from the interstitial into the intraluminal compartment. Intraluminal buds were observed most frequently in hypersensitivity pneumonitis, chronic eosinophilic pneumonia, and organizing pneumonia of unknown cause. Mural incorporation and, to a lesser extent, obliterative changes were observed in most interstitial disorders and were very prominent in idiopathic pulmonary fibrosis. Mural incorporation and obliterative changes play an important role in pulmonary remodeling, especially when several adjacent alveoli and/or other air spaces are involved. Under these circumstances, intraluminal organization can mediate the fusion of adjacent alveolar structures by intraluminal connective tissue.

Alveolitis, Extrinsic Allergic↗
PubMed1985

Evaluation of recombinant DNA-directed E.coli produced alpha 1-antitrypsin as an anti-neutrophil elastase for potential use as replacement therapy of alpha 1-antitrypsin deficiency.

alpha 1-antitrypsin (alpha 1AT) deficiency is an inherited disorder almost always associated with the development of panacinar emphysema in the fourth to fifth decades. One source of alpha 1AT for chronic replacement therapy of such individuals is that produced by E.coli directed by a cDNA coding for the human alpha 1AT molecule. Using TG1(E.coli), an alpha 1AT molecule produced by E.coli transformed with the plasmid-expressing vector pTG922, the present study shows that recombinant DNA-directed E.coli-produced alpha 1AT is as an effective inhibitor of neutrophil elastase as alpha 1AT purified from plasma. Importantly, TG1(E.coli) inhibited human neutrophil elastase with an association rate constant of 1.3 +/- 0.4X10(7) M-1 sec-1, similar to that of normal plasma alpha 1AT (1.1 +/- 0.1, p greater than 0.2). Furthermore, when TG1(E.coli) was added to alpha 1AT-deficient plasma obtained from homozygous alpha 1AT type Z individuals, the TG1(E.coli) remained functional and augmented the anti-neutrophil elastase activity of the serum proportional to the amount of TG1(E.coli) added. These observations suggest that if sufficient amounts of recombinant DNA methodology-produced alpha 1AT molecules could be safely delivered to the alveolar structures of alpha 1AT-deficient individuals, they would function to protect the alveolar walls from elastolytic attack.

DNA↗
PubMed1985

Experimental polymyxin B-induced interstitial lung disease characterized by an accumulation of cytotoxic eosinophils in the alveolar structures.

A variety of lung disorders are associated with the accumulation of eosinophils in the alveolar structures. To help understand the role of eosinophils in these disorders, an animal model of eosinophilic lung disease was developed. Administration of an aerosol of polymyxin B to guinea pigs (3 times per wk for 4 wk) produced diffuse interstitial lung disease with alveolar wall thickening and an alveolitis characterized by marked increases in eosinophils and alveolar macrophages. Bronchoalveolar lavage confirmed the presence of significantly increased numbers of eosinophils and alveolar macrophages in polymyxin-B-treated animals compared with those in control animals. Using density gradient centrifugation, approximately 10(7) eosinophils could be purified from the lungs of a single polymyxin-B-treated animal. Importantly, eosinophils purified from the lungs from polymyxin B-treated animals exhibited significant spontaneous cellular cytotoxicity for human fetal lung fibroblasts. In contrast, neither eosinophils from control animals nor alveolar macrophages from either group of animals were cytotoxic. These findings demonstrate that eosinophils possess effector processes capable of injuring the lung parenchyma and suggest that eosinophils can contribute to the pathogenesis of the interstitial lung disease.

Aerosols↗
PubMed1985

Motheaten mice--an animal model with an inherited form of interstitial lung disease.

The motheaten gene represents a single recessive mutation that occurs in mice and is associated with systemic immune abnormalities. Although they have abnormalities in several organs, homozygote animals (me/me) die by 8 wk of age from a diffuse, noninfectious lung disease. To evaluate this genetically determined model of interstitial lung disease, the lungs of these animals were studied by light and transmission electron microscopy and by bronchoalveolar lavage. Two control groups of mice were evaluated: (1) littermate normal mice, including mice without the motheaten gene (+/+) and mice heterozygous (me/+) the motheaten gene, and (2) nonlittermate normal mice (+/+). While the lungs of both control groups were normal morphologically, the lung disease in the homozygous motheaten mice progressed through 3 stages: (1) focal intra-alveolar hemorrhage with accumulations of alveolar macrophages and neutrophils in the lower respiratory tract; (2) persistent alveolitis and hemorrhage, and reparative processes including frequent mitoses of fibroblasts and type II alveolar epithelial cells; and (3) consolidation of the alveolar structures by massive accumulation of macrophages and marked derangement and fibrosis of the alveolar walls. Consistent with the morphologic findings, evaluation of mid-stage lung disease by lavage demonstrated that the alveolitis was characterized by a marked expansion of the total number of effector cells, an accumulation of neutrophils, and a marked expansion of the total numbers of T-lymphocytes and B-lymphocytes. Thus, the motheaten mouse can be regarded as a genetically determined model of interstitial lung disease characterized by alveolar hemorrhage, derangement of parenchymal cells, fibrosis, and an alveolitis with distinctive features.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Evidence for chronic inflammation as a component of the interstitial lung disease associated with progressive systemic sclerosis.

Progressive systemic sclerosis (PSS) is a generalized disorder characterized by fibrosis of many organs including the lung parenchyma. Unlike most other interstitial disorders, traditional concepts of the interstitial lung disease associated with PSS have held it to be a "pure" fibrotic disorder without a significant inflammatory component. To directly evaluate whether an active alveolitis is associated with this disorder, patients with chronic interstitial lung disease and PSS were studied by open lung biopsy, gallium-67 scanning, and bronchoalveolar lavage. Histologic evaluation of the biopsies demonstrated that the interstitial fibrosis of PSS is clearly associated with the presence of macrophages, lymphocytes, and polymorphonuclear leukocytes, both in the interstitium and on the alveolar epithelial surface. Gallium-67 scans were positive in 77% of the patients, showing diffuse, primarily lower zone uptake, suggestive of active inflammation. Consistent with the histologic findings, bronchoalveolar lavage studies demonstrated a mild increase in the proportions of neutrophils and eosinophils with occasional increased numbers of lymphocytes. Importantly, alveolar macrophages from patients with PSS showed increased release of fibronectin and alveolar-macrophage-derived growth factor, mediators that together stimulate lung fibroblasts to proliferate, thus suggesting at least one mechanism modulating the lung fibrosis of these patients. Thus, evidence from several different points of view together demonstrates that the interstitial lung disease associated with PSS is associated with chronic inflammation in the local milieu, leading to the hypothesis that the inflammation plays some role in the derangements to the alveolar structures that characterize this disorder.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Enhanced alveolar macrophage-mediated antigen-induced T-lymphocyte proliferation in sarcoidosis.

Expansion of T-lymphocyte numbers is a characteristic feature of the alveolitis of pulmonary sarcoidosis. One mechanism that may influence the numbers of T-lymphocytes in the lung is the process of antigen presentation in which alveolar macrophages, in the presence of antigen, induce T-lymphocytes to replicate. To evaluate this process in sarcoidosis, alveolar macrophages were obtained by bronchoalveolar lavage, pulsed with tetanus toxoid, and co-cultured with purified autologous T cells. Strikingly, antigen-pulsed alveolar macrophages from sarcoid patients induced more than a twofold increase in autologous T-lymphocyte proliferation compared with the response seen using cells from normal or patients with idiopathic pulmonary fibrosis (P less than 0.001), all comparisons). In contrast, when monocytes were used as the antigen presenting cell, no significant differences were observed in T cell proliferation induced by antigen among the three groups. The enhanced T-lymphocyte proliferation induced by sarcoid alveolar macrophages was not dependent on the compartment from which the T cells were derived, and was independent of the specific antigen used. One possible explanation for augmented antigen presentation seen in sarcoid is that an increased percentage of sarcoid alveolar macrophages express HLA-DR or HLA-DS surface antigens. However, most normal and sarcoid alveolar macrophages express HLA-DR and HLA-DS surface antigens, and the percentage of macrophages expressing these antigens was not significantly different in the two groups. Thus, while the mechanisms of the enhanced antigen presentation in the sarcoid lung are unknown, the process of antigen-driven, alveolar macrophage-modulated lung T cell proliferation may explain, at least in part, the expansion of lung T-lymphocyte numbers that characterizes this disease.

Adolescent↗
PubMed1985

Gamma interferon is spontaneously released by alveolar macrophages and lung T lymphocytes in patients with pulmonary sarcoidosis.

Gamma interferon (IFN gamma) is a potent immune mediator that plays a central role in enhancing cellular immune processes. This study demonstrates that while lung mononuclear cells from normal individuals spontaneously release little or no interferon (less than 10 U/10(6) cells per 24 h), those from patients with pulmonary sarcoidosis spontaneously release considerable amounts (65 +/- 20 U/10(6) cells per 24 h, P less than 0.02 compared to normals). Furthermore, cells from patients with active disease release far more interferon than those from patients with inactive disease (101 +/- 36 compared to 24 +/- 8 U/10(6) cells per 24 h, P less than 0.02). Characterization of this interferon using acid sensitivity, specific antibody inhibition, and target cell specificity criteria demonstrated that it was almost entirely IFN gamma. This spontaneous release of IFN gamma appeared to be compartmentalized to the lung of these patients in that their blood mononuclear cells spontaneously released little or no IFN gamma (P less than 0.02, compared to sarcoidosis lung mononuclear cells) and no IFN gamma was detected in their serum. Both lung T lymphocytes and alveolar macrophages contributed to the spontaneous release of IFN gamma by lung mononuclear cells from sarcoid patients; purified preparations of T lymphocytes and alveolar macrophages from these patients spontaneously released similar amounts of IFN gamma (56 +/- 21 and 32 +/- 11 U/10(6) cells per 24 h, respectively, P greater than 0.3). At least one role for IFN gamma in the pathogenesis of sarcoidosis appeared to be related to activation of alveolar macrophages, as alveolar macrophages recovered from patients with active disease spontaneously killed [3H]uridine-labeled tumor cell targets (17.7 +/- 4.5% cytotoxicity compared with 2.8 +/- 0.9% in normals, P less than 0.02) and purified IFN gamma enhanced the ability of alveolar macrophages from sarcoidosis patients with inactive disease to kill similar targets (P less than 0.001, compared to alveolar macrophages cultured in medium alone). Treatment of sarcoid patients with corticosteroids, a therapy known to suppress the activity of the disease, caused a marked reduction in the level of spontaneous IFN gamma release by lung mononuclear cells compared with untreated patients (P less than 0.02), which suggests that the effectiveness of corticosteroid therapy in controlling active pulmonary sarcoidosis may, at least in part, be due to suppression of IFN gamma release.

Adrenal Cortex Hormones↗
PubMed1985

Oxidants, antioxidants and the pathogenesis of emphysema.

Emphysema is a chronic pulmonary disorder characterized by a permanent enlargement of the air spaces distal to the terminal bronchioles consequent to destruction of the alveolar walls, including the epithelial and endothelial cells and the connective tissue matrix. There is increasing evidence that an imbalance of oxidants and antioxidants in the lower respiratory tract contributes to this process. Oxidants such as O2-., H2O2, OH, OCl- are generated in the lower respiratory tract as a result of normal biochemical processes, activation of inflammatory cells and inhaled toxic gases. Under normal circumstances, the parenchymal cells are protected by intracellular antioxidants and membrane radical scavengers. In addition, the fluid lining the epithelial surface contains a catalase-like antioxidant that protects the epithelial cells from oxidants. If the oxidant burden overcomes these defenses, the parenchymal cells may be injured, the connective tissue matrix may be partially degraded, the antiprotease screen that protects the lower respiratory tract from attack by neutrophil elastase may be rendered impotent. The alveolar wall then becomes highly vulnerable to elastolytic attack, with a complete destruction of the interstitial connective tissue matrix. In this regard, it is reasonable to hypothesize that reestablishment of the oxidant-antioxidant balance in favor of the antioxidants would be useful as a therapeutic strategy to suppress the emphysematous process.

Antioxidants↗
PubMed1985

Patterns of pulmonary structural remodeling after experimental paraquat toxicity. The morphogenesis of intraalveolar fibrosis.

For a study of the evolution of interstitial and intraalveolar fibrosis, ultrastructural and immunohistochemical observations were made of the lungs of 16 cynomolgous monkeys given 1 or 2 injections of 10 mg/kg of paraquat and sacrificed 2 days to 8 weeks later. At 2-3 days, alveolar epithelial cells were denuded in many areas, and fibronectin was conspicuous in alveolar spaces. At 1 week, fibroblasts and inflammatory cells were migrating through gaps in the denuded epithelial basement membranes; Type II cells were regenerating in some areas. At 3-4 weeks, alveoli developing intraalveolar fibrosis contained many myofibroblasts, collagen fibrils, and small elastic fibers; fibrotic alveolar walls were lined by metaplastic squamous cells and bronchiolar epithelial cells. Spiraling collagen fibrils were found in interstitium but not in alveolar spaces, which suggests that they were formed from breakdown of collagen. Newly formed intraalveolar collagen was mainly Type I. At 8 weeks, intraalveolar fibrosis had led to extensive remodeling, with new glandlike alveoli lined by Type II cells; alveoli without intraalveolar fibrosis had more normal architecture. Thus, intraalveolar fibrosis in paraquattreated lung is mediated by intraalveolar migration of interstitial cells, through gaps in the epithelial basement membranes, after epithelial injury. This is followed by connective tissue synthesis on the luminal side of the epithelial basement membrane, by differentiation of interstitial cells into myofibroblasts and smooth-muscle cells, by incorporation of areas of intraalveolar fibrosis into the interstitium, and by coalescence of alveolar walls. Intraalveolar fibrosis is more important than interstitial fibrosis in the structural remodeling that occurs in paraquattreated lung, because it results in obliteration of alveoli, coalescence of alveolar walls, and loss of functional alveolar-capillary units.

Animals↗
PubMed1985

Characterization of mononuclear phagocyte subpopulations in the human lung by using monoclonal antibodies: changes in alveolar macrophage phenotype associated with pulmonary sarcoidosis.

Current concepts of pulmonary sarcoidosis suggest that the alveolar macrophage plays a central role in the pathogenesis of the disease. To help define the population of alveolar macrophages in sarcoidosis, we compared the surface phenotype of alveolar macrophages from patients with sarcoidosis and from normal individuals by using monoclonal antibodies (63D3, OKM1, M phi P-9, M phi S-1, 61D3, and M phi S-39) that detect surface antigens on cells of monocyte/macrophage lineage. Although almost all blood monocytes expressed surface antigens detected by each of these antibodies, only a minority of normal alveolar macrophages expressed the same surface antigens (p less than 0.05, each comparison). However, in sarcoidosis, the percentage of alveolar macrophages expressing these surface antigens was increased (p less than 0.05, each comparison with normal alveolar macrophages). Several findings supported the conclusion that the increased expression of these monocyte-lineage surface antigens on sarcoid alveolar macrophages resulted from increased recruitment of monocytes to the lung in sarcoidosis and not from abnormal "activation" of alveolar macrophages. First, alveolar macrophages expressing these antigens had an immature morphology. Second, in vitro cultivation of blood monocytes and alveolar macrophages in the presence of immune and inflammatory mediators, including mediators known to be present in the lung in sarcoidosis, did not prevent the loss of expression of monocyte-lineage surface antigens from monocytes or induce reexpression of monocyte-lineage surface antigens on alveolar macrophages. Third, the expression of monocyte-lineage surface antigens was only increased on sarcoid macrophages from patients whose lower respiratory tract contained an increased number of T lymphocytes, cells known to release monocyte chemotactic factor in sarcoidosis. Consistent with the knowledge that corticosteroids usually suppress the alveolitis of active sarcoidosis, when the expression of alveolar macrophage surface antigens was evaluated before and during therapy, the percentage of alveolar macrophages expressing monocyte-lineage surface antigens returned to normal after 1 to 3 mo of therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1984

Sheep elastin genes. Isolation and preliminary characterization of a 9.9-kilobase genomic clone.

A sheep genomic library containing sheep DNA in the bacteriophage vector Charon 4A was screened for elastin-gene sequences with partially purified, 32P-labelled elastin mRNA (mRNAE). A recombinant containing a 9.9-kb (kilobase) insert was selected from several positive clones by secondary and tertiary screening for further characterization. Positive identification of this elastin clone, designated SE1, was made with radiolabelled mRNAE by hydridization-selected translation and Southern blotting of restriction-enzyme fragments of SE1 DNA. Hybridization of either mRNAE or elastin complementary DNA to restriction fragments of SE1 showed that most of these fragments of SE1 contained elastin-coding sequences. Orientation of the insert was established by preferential hybridization of a short complementary elastin DNA to restriction fragments adjacent to the right arm of Charon 4A. Reciprocal hybridizations of nick-translated SE1 and sheep genomic DNA on Southern blots showed that two restriction fragments of SE1 contained sequence elements which were repeated at high frequency in a restriction-endonuclease-EcoR1 digest of total sheep genomic DNA. In the accompanying paper [Davidson, Shibahara, Boyd, Mason, Tolstoshev & Crystal (1984) Biochem. J. 220, 653-663], it is shown that a subcloned fragment of this elastin gene quantitatively and specifically hybridized to mRNAE sequences in sheep tissue RNA. Electron microscopy of SE1-mRNAE hybrids indicated the presence of at least seven large R-loops. Measurements of these structures indicated that SE1 is likely to contain less than 2 kb of coding sequence and more than 8 kb of intervening sequence, with an average exon size of 120 base-pairs. Thus the elastin gene is distributed over an extended region of the sheep genome and contains numerous intervening and coding sequences.

Animals↗
PubMed1984

Elastin mRNA levels during foetal development of sheep nuchal ligament and lung. Hybridization to complementary and cloned DNA.

Elastin mRNA levels were quantified in sheep nuchal ligament and lung during the latter half of foetal development with elastin-specific cDNA (complementary DNA) probes using both hybridization in solution (saturation analysis) and hybridization on a fixed support (Northern analysis). For the solution-hybridization studies, cDNA prepared from nuchal-ligament mRNA was enriched to 65% for elastin sequences by hybridizing it to its template at a R0t (mol X s X litre-1) value that included only the abundant class of mRNA sequences. Hybridization of this probe to RNA extracted from nuchal ligament between 70 and 138 days after conception demonstrated elastin sequences increased about 10-fold (from 0.047 to 0.438% of total RNA). In contrast, lung elastin mRNA levels increased only 3-fold (from 0.009 to 0.022% of total RNA) during the same period. Over this development period these values correspond to increases in the average number of elastin mRNA molecules from 950 to 20 000 molecules/ligament cell and from 130 to 330 molecules/lung cell. For Northern analysis, elastin mRNA was purified from near-term-sheep nuchal ligament on sucrose density gradients. Analysis of the translation products of this elastin mRNA showed that relative elastin precursor synthesis was at least 80% of total [3H]valine incorporation. The Mr of this elastin mRNA, determined by methylmercury-agarose-gel electrophoresis, was approx. 1.25 X 10(6). Northern hybridization of nuchal ligament and lung RNA to a [32P]cDNA probe, transcribed from this sucrose-gradient-purified elastin mRNA, confirmed the developmental changes in elastin mRNA levels detected by solution-hybridization techniques. The specificity of this method was confirmed by using a cloned elastin gene fragment. These studies demonstrate that elastin mRNA levels in organs such as nuchal ligament and lung increase with foetal development, but that there are significant differences in the average cellular elastin mRNA content of these two organs.

Animals↗