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Biomedical subjects

L M Reid

Publications and source records attributed to L M Reid.

At least 55 records · Page 3Linked to original sources
PubMed1991

The role of the kidney in lung growth and maturation in the setting of obstructive uropathy and oligohydramnios.

The contribution of the kidneys to lung development, which includes growth and maturation, is uncertain but it appears to be complex. Obstructive uropathy with oligohydramnios produces pulmonary hypoplasia characterized by small lungs (decreased lung volume/body weight) and retarded maturation (reduced total airspace). Lung growth and maturation were studied in a model of early gestation obstructive uropathy to understand better their relationship and their prenatal regulation. Of 26 fetal sheep studied at near term (135 days of gestation) 9 had bladder obstruction created at 60 days of gestation, 11 had bladder obstruction at 60 days with in utero decompression at 95 days, and 6 served as controls and shams. Amniotic fluid volume was measured, kidneys were prepared and evaluated histologically, lungs were inflation-fixed and volumes were measured, and airspace volume percentage was measured morphometrically. Experimental and serendipitous variations in the condition of the kidneys and amniotic fluid at delivery permitted an analysis of the contribution of the kidneys and the amniotic fluid to lung growth and maturation. Impairment of growth and maturation was dissociated in certain animals, and this dissociation was referable to the histological status of the kidneys and the presence or absence of amniotic fluid at delivery. Growth was normal when amniotic fluid was present or likely to have been present in late gestation, even with structurally damaged kidneys. With severe renal damage amniotic fluid was not restored even with in utero decompression and it resulted in severely impaired lung growth. Maturation was normal only in the presence of amniotic fluid and intact kidneys. The dissociation of lung growth and structural maturity suggests their independent regulation. The data suggest that the kidneys are important in early lung growth, while the presence of amniotic fluid contributes to growth later in gestation. Lung maturity requires both factors, suggesting a primary kidney contribution with the amniotic fluid acting in a permissive or supportive role.

Amniotic Fluid↗
PubMed1991

Effect of in utero vesicostomy on pulmonary hypoplasia in the fetal lamb with bladder outlet obstruction and oligohydramnios: a morphometric analysis.

A model of early gestation bladder outlet obstruction and oligohydramnios in the fetal lamb is characterized by small, immature lungs (pulmonary hypoplasia). The current study examines how in utero relief of urinary tract obstruction produced early in gestation modifies pulmonary hypoplasia. Bladder obstruction was created at 60 days gestation in fetal sheep (term = 140 days); 11 fetuses then underwent in utero decompression at 95 to 100 days; six were left obstructed. Five normal fetuses served as controls and two underwent sham obstruction and vesicostomy. All were delivered and sacrificed near term (135 days), the right lung was inflation-fixed and its volume determined. Relative volumes of alveoli, alveolar ducts, and tissue, alveolar surface area, and alveolar numerical density were estimated morphometrically. Kidneys were examined histologically. In all animals persistent bladder obstruction produced oligohydramnios. Bladder obstruction to term produced pulmonary hypoplasia with a mean right lung volume-to-body weight ratio (LV:BW) of 14.3 cc./kg. (normal = 36.4, p less than 0.001). Structural immaturity was evidenced by an airspace fraction of only 57% (normal = 68%, p less than 0.05). Kidneys in these animals were not dysplastic; there was hydronephrosis or evidence of spontaneous urinary decompression. In eight of the 11 animals, decompression improved the LV:BW ratio to 28.4 cc./kg. (vs. obstructed, p less than 0.001; vs normal, p less than 0.05) and normalized maturity. All had increased amniotic fluid at delivery; kidneys in 7/8 animals were normal, and the other had moderate hydronephrosis. One of the 11 animals had normal kidneys, oligohydramnios, immature lungs, but with normal volume. Oligohydramnios was present in the other two of 11 fetuses despite successful decompression and they had markedly dysmorphic kidneys and profoundly hypoplastic and immature lungs (LV:BW 5.1 cc./kg.). Even after 35 days (25% gestation) of obstruction, in utero urinary tract decompression permits better lung growth and maturation than in persistently obstructed animals. The degree of renal damage from obstruction appears to be a critical determinant in the correction of pulmonary hypoplasia.

Animals↗
PubMed1991

Heparin and hormonal regulation of mRNA synthesis and abundance of autocrine growth factors: relevance to clonal growth of tumors.

Highly sulfated, heparinlike species of heparan sulfate proteoglycans, with heparinlike glycosaminoglycan chains, are extracellular matrix components that are plasma membrane bound in growth-arrested liver cells. Heparins were found to inhibit the growth and lower the clonal growth efficiency of HepG2, a minimally deviant, human hepatoma cell line. Heparan sulfates, closely related glycosaminoglycans present in the extracellular matrix around growing liver cells, had no effect on the growth rate or clonal growth efficiency of HepG2 cells. Neither heparins nor heparan sulfates had any effect on the growth rate or clonal growth efficiency of two poorly differentiated, highly metastatic hepatoma cell lines, SK-Hep-1 and PLC/PRF/5. Heparin's inhibition of growth of HepG2 cells correlated with changes in the mRNA synthesis and abundance of insulinlike growth factor II (IGF II) and transforming growth factor beta (TGF beta). HepG2 cells expressed high basal levels of mRNAs encoding IGF II and TGF beta that were inducible, through transcriptional and posttranscriptional mechanisms, to higher levels by specific heparin-hormone combinations. For both IGF II and TGF beta, the regulation was multifactorial. Transcriptionally, IGF II was regulated by the additive effects of insulin, glucagon, and growth hormone in combination with heparin; TGF beta was regulated primarily by the synergistic effects of insulin and growth hormone in combination with heparin. Posttranscriptionally, the mRNA abundance of the IGF II 4.5- and 3.7-kb transcripts was affected by insulin. Heparin induction of all IGF II transcripts was also dependent on triiodotyronine and prolactin, but it is unknown whether their induction by heparin was via transcriptional or posttranscriptional mechanisms. Heparin-insulin combinations regulated TGF beta posttranscriptionally. The poorly differentiated hepatoma cell lines PLC/PRF/5 and SK-Hep-1 either did not express or constitutively expressed low basal levels of IGF I, IGF II, and TGF beta, whose mRNA synthesis and abundance showed no response to any heparin-hormone combination. We discuss the data as evidence that matrix chemistry is a variable determining the expression of autocrine growth factor genes and the biological responses to them.

Blotting, Northern↗
PubMed1991

Recent advances in the study of pulmonary hypertension.

The endothelial cell for the intima, the smooth muscle cell for the media, and the vascular fibroblast for the adventitia are responsible for the development of the wall of an artery or vein. The structural changes in these components seen in pulmonary hypertension of diverse etiologies are discussed.

Animals↗
PubMed1990

Dexamethasone-mediated regulation of 3-methylcholanthrene-induced cytochrome P-450d mRNA accumulation in primary rat hepatocyte cultures.

We have previously demonstrated that cytochrome P-450c and P-450d mRNAs can be induced by 3-methylcholanthrene (MCA) in primary cultures of rat hepatocytes grown in serum-free hormonally defined medium (HDM) plus minimal salts (Silver, G., and Krauter, K. S. (1988) J. Biol. Chem. 263; 11802-11807). Such cultures were used to investigate the role of the individual hormonal components present in the medium in the hydrocarbon-mediated induction process. Replacing HDM with minimal salts plus 10% fetal bovine serum (FBS) resulted in a 4-fold reduction in the accumulation of P-450d mRNA in response to MCA. In contrast, no effect was seen on induced levels of P-450c mRNA. Mixing experiments, in which primary cultures of hepatocytes were grown in medium containing HDM plus 10% FBS, indicated that there was no negative acting component present in FBS, but rather there was a positive acting component present in the mixture of hormones in HDM which permitted P-450d induction by MCA. Testing the effects of singly deleting each of the 10 components in HDM on MCA-induced P-450d expression demonstrated that dexamethasone was the only factor which affected the induction of P-450d. Deletion of this component from HDM resulted in a 4-fold decrease in the maximum MCA induced expression of P-450d mRNA. Moreover, supplementation of minimal salts plus 10% FBS with dexamethasone restored full P-450d inducibility by MCA. Deletion of the other components from HDM had no effects on P-450d mRNA accumulation. Although substratum clearly contributed to the quality of primary hepatocyte cultures, we were unable to demonstrate any role of the substratum on MCA induction of P-450d. In vitro nuclear run-on experiments revealed that dexamethasone had little effect on the rate of transcription of the P-450d genes. Therefore, the effect of dexamethasone on induction must be at the posttranscriptional level.

Animals↗
PubMed1990

Stem cell biology, hormone/matrix synergies and liver differentiation.

Extracellular matrix, in conjunction with hormones and growth factors, plays a profound role in regulating gene expression in liver and in all tissues. The availability of matrix components for liver cells in culture is having a major impact on our ability to study every aspect of gene expression. Its significance has been particularly profound in permitting cultures with partial restoration of transcription rates of tissue-specific mRNAs. However, the matrix reagents available to date are not so potent as the forms known to be present uniquely in the liver. Thus, there is a great need to purify and characterize these tissue-specific matrix components (e.g. heparin-PG) to enable the eventual production of them for general use by investigators. The use of matrix reagents and the eventual use of cultures of liver stem cells will begin a new era in the understanding of liver differentiation.

Animals↗
PubMed1990

Negative and positive cis-acting elements control the expression of murine alpha 1-protease inhibitor genes.

The alpha 1-protease inhibitor (alpha 1-PI) proteins of mice are encoded by a group of genes whose members are expressed coordinately in a liver-abundant pattern and are regulated primarily at the transcriptional level. To better understand the developmental and tissue-specific regulation of this gene family, one member that is analogous to the human alpha 1-antitrypsin gene was chosen for study. Deletional analysis of the upstream regulatory region of this gene was performed, spanning from -10 kilobases to -80 base pairs relative to the transcriptional start site. Two functional positive cis-acting elements within the 522 bases immediately upstream of the start site for transcription were shown to modulate the level of expression from this promoter when introduced into human or mouse hepatoma cells, and a third region acted as a negative regulatory element in that its deletion resulted in a two- to sixfold increase of expression of a transfected minigene construct. Sequence comparison between the regulatory domains of two mouse alpha 1-PI genes and the human alpha 1-antitrypsin gene showed that the mouse gene contains a novel positive cis-acting element which is absent in human gene and that a specific eight-base-pair difference between species results in a strong positive cis-acting element in the human gene acting as a negative element in the mouse gene. An enhancer located approximately 3,000 base pairs upstream of the major start site for transcription was also identified. This element is position and orientation independent. Several different DNA-protein binding assays were used to demonstrate that each DNA segment with functional significance in transfection assays interacts specifically with proteins found in adult mouse liver nuclei. The major positive-acting element appeared to be specifically recognized by nuclear proteins found only in tissues that express alpha 1-PI, while the negative element binding proteins were ubiquitous. Thus, the distal regulatory domain including bases -3500 to -133 of this murine alpha 1-PI gene family member is more complex than was previously demonstrated. It is composed of a set of at least three additional functional cis-acting regulatory elements besides those which have been mapped by others and has a far upstream enhancer.

Amino Acid Sequence↗
PubMed1990

Recovery of an epitope recognized by a novel monoclonal antibody from airway lavage during experimental induction of chronic bronchitis.

Prolonged exposure of dogs to high concentrations of SO2 gas results in a syndrome with many of the characteristics of human chronic bronchitis, including cough and chronic mucous hypersecretion as well as airway obstruction. We developed and used a novel monoclonal antibody, GB-4B, raised against epithelial glycoprotein isolated from human hypersecretory mucus to probe airway lavage samples from dogs before and during prolonged exposure to SO2 gas. There were relatively low mean titers of the epitope recognized by GB-4B in airway lavage fluid as evidenced by enzyme-linked immunosorbent assay before exposure to SO2 gas. After 25 to 50 wk of SO2 exposure, the dogs showed a significant increase in pulmonary resistance and there was a significant increase in the titer of the epitope in the airway lavage fluid. Using the same antibody immunohistochemical analysis of airway tissues from SO2-exposed dogs revealed patchy staining of the mucous glands and airway secretory cells and dense staining along the airway surface; airway tissue from control dogs and one SO2-exposed dog whose lavage fluid did not contain the epitope showed little or no staining. These data demonstrate that similar mucin epitopes appear in airway lavage fluid under hypersecretory conditions in both animals and humans. The epitope may have utility as a marker of chronic mucous hypersecretion.

Animals↗
PubMed1990

Role of lung biopsy in patients undergoing a modified Fontan procedure.

Fifty-six patients undergoing a modified Fontan procedure from 1977 to 1985 had lung tissue available from the perioperative period (n = 51) or recent palliative procedure (n = 5) (37 biopsy, 12 autopsy, 7 biopsy and autopsy). Twenty-six patients had tricuspid atresia, and 30 had other causes of functional univentricular heart. Pulmonary arterial structure was classified by both the Heath-Edwards and morphometric scales. Biopsy and autopsy grades were identical except for a minor difference in Heath-Edwards scale in one case. Elevated preoperative mean pulmonary artery pressure (greater than 15 mm Hg) was associated with medial hypertrophy (p = 0.04), although six patients with normal pulmonary artery pressure had medial hypertrophy and six patients with mean pulmonary artery pressure greater than 15 mm Hg did not have medial hypertrophy. Medial hypertrophy was a possible risk factor in patients with univentricular heart: Patients with medial hypertrophy had a ninefold greater risk of death (p = 0.08). Controlling for confounding variables did not alter this result (0.06 less than or equal to p less than or equal to 0.10). Medial hypertrophy was not a risk factor for death in patients with tricuspid atresia: Four had this feature and each survived. Four patients with tricuspid atresia died and none had medial hypertrophy. A mean transpulmonary pressure gradient was measured on the first postoperative day in 45 patients. In patients with medial hypertrophy there was a trend toward a higher gradient (p = 0.13). All patients with medial hypertrophy who had this measurement (n = 9) had a transpulmonary pressure gradient of 7 mm Hg or greater, whereas this was true in only 18 of 36 without medial hypertrophy (p = 0.007). On the basis of an evaluation of medial hypertrophy, we conclude that biopsy does not aid in selection of patients with tricuspid atresia for a Fontan procedure; its role in patients with univentricular heart is uncertain.

Adolescent↗
PubMed1989

Clonal growth of tumors on tissue-specific biomatrices and correlation with organ site specificity of metastases.

We have found that neoplastic transformation alters the ability of cells to grow on substrata of tissue extracts, "biomatrices", enriched in extracellular matrix. Tumor cells were able to survive and grow at lower densities and on more types of biomatrices than normal cells. When plated at high densities (greater than 10(5) cells/60 mm dish), tumor cells attached with equal efficiency and grew at similar rates and to equivalent saturation densities on biomatrices derived from all tissues. However, at low (10(2)-10(4)/60-mm dish) seeding densities, the tumor cells grew only on certain types of biomatrix. For the various hepatoma and mammary carcinoma cell lines tested, the tissue specificity in clonal growth on biomatrices correlated with their organ site specificity for metastasis in vivo in immunosuppressed, athymic nude mice. Analysis of the effects of purified matrix components (adhesion proteins, collagens, glycosaminoglycans) indicated that only the glycosaminoglycans influenced density-dependent survival and growth of tumor cells with effects that differed with respect to the cell's metastatic potential. The results indicate that the ability of tumor cells to colonize specific tissues represents, in part, regulation of low density survival and growth by extracellular matrix and are suggestive that one of the matrix components responsible may be proteoglycans or their glycosaminoglycan chains.

Animals↗
PubMed1989

Regulation of beta-adrenergic receptor expression in rat liver.

To begin defining the factors regulating neurotransmitter receptor expression, we examined beta-adrenergic receptors in rat liver in vivo and in primary liver cultures under defined hormonal conditions. beta-receptors described a remarkable developmental profile in vivo, increasing fivefold between embryonic days 16 and 20, and decreasing tenfold by early adulthood. The developmental decrease reflected reduced receptor number without a change in receptor properties. The ontogenetic decrease appeared to be specific for beta-receptors; alpha-receptors developed in a hyperbolic fashion, reaching high plateau values by the third postnatal week. Adult rat liver cells plated into culture re-expressed high beta-receptor levels, exhibiting a 4-8-fold increase. A similar pattern of expression of the beta-receptors, having similar pharmacological properties, was observed in primary liver cultures maintained in serum-free medium, in a serum-supplemented medium or in several variations of a serum-free, hormonally defined medium designed for primary liver cultures. Thus, the degree of expression of the beta-receptors was not found affected by various hormones, by serum, or by any medium condition. By contrast, the degree of expression of the beta-receptors was markedly sensitive to cell density. High expression of the beta-receptors was observed at low cell densities (1-3 x 10(6) cells/150 mm dish), and low expression or no expression was observed in confluent cultures (10-20 x 10(6) cells/150 mm dish). Our experiments suggest that beta-receptor expression does not follow an immutable program, but may be regulated by density-dependent cell-cell interactions.

Age Factors↗
PubMed1989

Gene expression in implanted rat hepatocytes following retroviral-mediated gene transfer.

An hepatocyte transplantation-gene transfer protocol has been developed whereby liver cells containing an expressing NeoR gene can be successfully implanted in vivo. Adult primary cultures of rat hepatocytes, after infection with the retroviral vector N2, were grown on a floating solid support (coated with purified collagen IV) in a serum-free hormonally defined medium designed for hepatocytes that also contained G418. Under these conditions, normal adult hepatocytes expressing the NeoR gene could be grown to high density. The solid supports holding the gene-engineered hepatocytes were then implanted into adult rats into subcutaneous and intraperitoneal sites. After one to two weeks, the supports were removed and shown to still contain the gene-engineered hepatocytes expressing the NeoR gene. These results suggest that cells from solid organs, such as the liver, are potential targets for gene transfer and expression studies in vivo.

Animals↗
PubMed1989

Successful repair of an atrial septal defect associated with right to left shunting.

An atrial septal defect was successfully repaired in a young woman despite the presence of pulmonary hypertension and right to left shunting. Before repair both isoprenaline infusion and 100% inspired oxygen produced significant falls in pulmonary artery pressure and pulmonary vascular resistance. A lung biopsy specimen at operation indicated a considerable decrease in the concentration of parenchymal pulmonary arteries and an absence of intimal fibrosis or medial hypertrophy. Pulmonary artery banding performed in infancy, as part of the management of a ventricular septal defect, may have contributed to the underdevelopment of the pulmonary vascular tree. The reduced number of pulmonary arteries is a possible explanation for the pulmonary hypertension.

Adult↗
PubMed1989

Effects of dimethylthiourea on chronic hypoxia-induced pulmonary arterial remodelling and ventricular hypertrophy in rats.

Ischemia, followed by reperfusion and restoration of oxygen to tissues, generates hydrogen peroxide which in turn generates injurious free radicals, particularly hydroxyl. Chronic hypoxia may also result in liberation of free radicals. In rats, chronic hypoxia causes pulmonary hypertension, associated with structural remodelling of pulmonary arteries, polycythemia, and vasoconstriction. We studied in rats the effects of dimethylthiourea (DMTU), a hydroxyl and hydrogen peroxide scavenger, on acute hypoxic vasoconstriction, and on the arterial structure and development of polycythemia after chronic hypoxia (FIO2 0.10 for 10 days, daily DMTU). DMTU did not affect acute vasoconstriction nor polycythemia. It significantly reduced muscularization of alveolar wall and alveolar duct arteries, medial thickening of alveolar wall and preacinar arteries, and right ventricular hypertrophy, suggesting reduction of pulmonary hypertension. However, DMTU caused marked growth retardation in both control and hypoxic rats, an effect not previously described. In other rats a similar degree of growth retardation due to reduced food intake failed to prevent the effects of hypoxia, suggesting that DMTU's effect is not through this mechanism. The results of this study support but do not confirm the hypothesis that free radicals may have a role in the pathogenesis of the arterial structural changes in the microcirculation contributing to chronic hypoxic pulmonary hypertension. However, in view of DMTU's effects on growth, definitive testing of the hypothesis will not be possible until other, less toxic, chronic hydroxyl scavengers become available.

Animals↗
PubMed1989

Macromolecular and lipid constituents of bronchial epithelial mucus.

The physical and chemical properties of bronchial epithelial mucus depend on its special mix of macromolecules and lipid constituents: these are different in the normal airway under baseline conditions from one stimulated acutely, and show major modification in disease. Since the last conference, density gradient ultracentrifugation has been extended to the study of normal bronchial mucus in addition to that of sputum from patients with chronic bronchitis, cystic fibrosis and asthma, and has revealed striking differences between the chemical profiles of normal and hypersecretory mucus. Normal mucus represented individual bronchial aspirates, obtained at fiberoptic bronchoscopy from healthy human volunteers (non-smokers), aspirates from normal dogs (before SO2 exposure in a canine model of SO2 induced bronchitis) and secretions released in vitro by human bronchial and canine tracheal explants. Mucus 'in transition' included aspirates from otherwise healthy smokers and from dogs early in irritation. Hypersecretory mucus included, besides those mentioned above, aspirates from dogs that had developed bronchitis and the excessive mucus produced by some patients with acute quadriplegia. Lipids. In normal mucus, human (unpooled) and canine, neutral lipids are the predominant species, with lesser amount of phospholipids: no glycolipids are detected. The first qualitative change on irritation, even before macromolecular yield increases, is appearance of glycolipids. In hypersecretory mucus, human (including quadriplegics) or canine, glycolipids are detected in appreciable amounts and often are the predominant species: they include complex forms such as sialic acid containing gangliosides. Organ and cell culture studies establish that these lipids are produced by airway epithelial cells. These lipids are important to gel formation. Glycoconjugates. A major recent advance is the recognition that normal mucus does not contain typical epithelial glycoprotein. Its glycoconjugate is of higher density with sugars typical of both glycoprotein (GP) and proteoglycan (PG) and with an amino acid profile more akin to PG (glycine greater than serine greater than threonine). In transition to hypersecretion, a 'mixed molecule' changes its sugar mix to produce a density typical of GP. In hypersecretion, the epithelial GP develops a typical buoyant density and amino acid profile (threonine greater than serine greater than glycine). Organ culture of bronchial explants, and more recently cell culture, establish that the PGs are major products of airway secretory cells. The normal airway is capable of producing glycoprotein on cholinergic stimulation. The range of glycoconjugates present in the secretion support the wide range of granule and cell features identified in vivo. Monoclonal antibody raised to a pure preparation of bronchial epithelial glycoprotein reacts with mucous cells in the surface epithelium and also in the submucosal gland in both human and canine airways.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Characterization of airway mucus from a fatal case of status asthmaticus.

We used density gradient methods to analyze mucus recovered from the airways of a patient who died from status asthmaticus. At postmortem the mucus that plugged the length of the bronchial tree could only be removed by cutting with forceps. It was dispersed in cesium bromide (CsBr) and examined in the analytical ultracentrifuge. Surprisingly, no macromolecular component was seen in the buoyant density region typical of mucus glycoprotein (at 1.5 g/ml). The gelatinous material migrated to the region of lowest density, typical of lipids, and thin-layer chromatography indicated that besides neutral lipids, a variety of phospho- and glycolipids (including gangliosides) were present. The residue left after the lipid extraction contained all sugar components of mucus glycoprotein, and alkaline borohydride cleaved oligosaccharides three to 12 sugars long, indicating that the sugars were O-glycosidically linked as in mucus glycoproteins. Prior desulfation of the residue increased the number of oligosaccharides released by borohydride; analysis showed the presence in these of components (glucose, methylmannuronate) not present in epithelial glycoprotein. A trace component of high buoyant density was also present: Glucose was the predominant component in this, but glycoprotein sugars were also present. The above results suggest that in status asthmaticus plugging of the airways with mucus can occur even in the absence of typical epithelial glycoprotein and that lipids play a crucial role in such plugging.

Adolescent↗