Biomedical subjects

M Post

Publications and source records attributed to M Post.

At least 109 records · Page 6Linked to original sources

PubMed1994

Ontogeny and regulation of platelet-derived growth factor gene expression in distal fetal rat lung epithelial cells.

Using flow cytometry, thymidine uptake into DNA, and expression of two growth-related genes, histone 3 and c-myc, we found an increase in the proportion of distal lung epithelial cells in the G0/G1 phase of the cell cycle with advancing gestation. Since our previous studies had demonstrated that platelet-derived growth factor (PDGF) is essential for the progression of these cells from the G0/G1 to the S phase of cell cycle, we investigated the gene and protein expression of PDGF-related genes (PDGF-A, PDGF-B, alpha-receptor, and beta-receptor) in distal fetal lung epithelial cells. The cells transcribed all the PDGF-related genes and translated the PDGF-A and PDGF-B mRNAs into protein, as demonstrated by immunocytochemistry and immunoprecipitation. To explore an autocrine role for PDGF in distal fetal lung epithelial cells, intervention studies using PDGF-A and -B chain-specific antisense oligodeoxynucleotides (ODN) were carried out. Antisense PDGF-B ODN, but not antisense PDGF-A ODN, significantly reduced the DNA synthesis of these cells. The inhibitory effect of antisense PDGF-B ODN on DNA synthesis was reversed by the addition of exogenous PDGF-BB, which supports an autocrine role in the DNA synthesis of these cells. We also examined the expression of PDGF genes in distal fetal lung epithelial cells during late gestation. PDGF-A chain and beta-receptor gene expressions declined with advancing gestation, whereas expression of message for PDGF-B chain and alpha-receptor increased. The increases in message for PDGF-B chain and alpha-receptor with advancing gestation were due to a greater rate of transcription, whereas the developmental decrease of PDGF-A chain and beta-receptor mRNAs was caused by a decrease in RNA stability. Taken together with the ODN data, these results suggest that the G0/G1 cell cycle arrest of distal lung epithelial cells during late fetal gestation is due to a decrease in PDGF beta-receptor expression by the cells.

Animals↗

PubMed1994

A novel member of the transmembrane serine/threonine kinase receptor family is specifically expressed in the gonads and in mesenchymal cells adjacent to the müllerian duct.

The activin and TGF-beta type II receptors are members of a separate subfamily of transmembrane receptors with intrinsic protein kinase activity, which also includes the recently cloned TGF-beta type I receptor. We have isolated and characterized a cDNA clone (C14) encoding a new member of this subfamily. The domain structure of the C14-encoded protein corresponds with the structure of the other known transmembrane serine/threonine kinase receptors. It also contains the two inserts in the kinase domain that are characteristic for this subfamily. Using in situ hybridization, C14 mRNA was detected in the mesenchymal cells located adjacent to the müllerian ducts of males and females at day 15 (E15) of embryonic development. Marked C14 mRNA expression was also detected in the female gonads. In female E16 embryos, the C14 mRNA expression pattern remained similar to that in E15 embryos. However, in male E16 embryos C14 mRNA was detected in a circular area that includes the degenerating müllerian duct. The expression of C14 mRNA was also studied using RNase protection assays. At E15 and E16, C14 mRNA is expressed in the female as well as in the male urogenital ridge. However, at E19, a high C14 mRNA level in the female urogenital ridge contrasts with a lack of C14 mRNA in the male urogenital ridge. This correlates with the almost complete degeneration of the müllerian ducts in male embryos at E19. C14 mRNA expression was also detected in embryonic testes at E15, E16 and E19 using RNase protection assays, but at much lower levels than those found in the developing ovaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Activin Receptors↗

PubMed1994

Antisense oligodeoxynucleotides targeting PDGF-B mRNA inhibit cell proliferation during embryonic rat lung development.

There is increasing evidence to suggest that platelet-derived growth factor (PDGF) or PDGF-like molecules play a role in fetal lung morphogenesis. Our previous studies demonstrated the presence of PDGF-AA and PDGF-BB homodimers in embryonic and fetal rat lung. To explore further the role for PDGF-BB in embryonic lung development, we conducted intervention studies using PDGF-B chain-specific antisense oligodeoxynucleotides in a simple embryonic rat lung explant system. Unmodified antisense PDGF-B oligodeoxynucleotides inhibited, in a concentration-dependent manner, DNA synthesis of embryonic lung. A maximal inhibition of 50% was observed. The inhibitory effect of antisense PDGF-B oligodeoxynucleotides on DNA synthesis was reversed by the addition of exogenous PDGF-BB but not PDGF-AA. Antisense treatment decreased PDGF-BB but not PDGF-AA protein content, as assessed by immunoblot analyses. Incubation of lung explants with PDGF-BB neutralizing antibodies also resulted in an inhibition of DNA synthesis. Morphometric analyses of antisense-treated cultures showed a significant reduction in lung size when compared to control cultures. The epithelial component of the embryonic lungs was specifically reduced, both in mass and DNA labelling index, by antisense treatment. The number of terminal buds of the lung explants was not significantly affected by antisense PDGF-B treatment. Scrambled PDGF-B oligodeoxynucleotides had no effect. These data suggest that PDGF-BB is involved in regulating growth, but not the degree of branching, of embryonic rat lung.

Animals↗

PubMed1994

Induction of the heat shock response reduces mortality rate and organ damage in a sepsis-induced acute lung injury model.

OBJECTIVE: To test the hypothesis that induction of heat shock proteins before the onset of sepsis could prevent or reduce organ injury and death in a rat model of intra-abdominal sepsis and sepsis-induced acute lung injury produced by cecal ligation and perforation. DESIGN: Prospective, blind, randomized, controlled trial. SETTING: University research laboratory. SUBJECTS: One-hundred forty-two adult Sprague-Dawley rats (weight range 200 to 300 g). INTERVENTIONS: Production of intra-abdominal sepsis and exposure to heat stress. Animals were randomly divided into four groups: heated and septic, heated and sham-septic, unheated and septic, and unheated and sham-septic. MEASUREMENTS AND MAIN RESULTS: We evaluated the mortality rate and pathologic changes in lung, heart, and liver at 18 hrs after cecal perforation, at 24 hrs after removal of the cecum, and at 7 days after perforation. Heated animals exhibited a maximum increase in heat shock protein of 72 kilodalton molecular weight protein concentrations in the lungs and heart 6 to 24 hrs after the hyperthermic stress. By 18 hrs after perforation, 25% of the septic, unheated animals had died whereas none of the septic heated animals had died (p < .005). Septic, heated animals showed a marked decrease in 7-day mortality rate (21%) compared with septic unheated animals (69%) (p < .01). Furthermore, septic heated animals showed less histologic evidence of lung and liver damage than septic unheated animals. CONCLUSIONS: These data suggest that thermal pretreatment, associated with the synthesis of heat shock proteins, reduces organ damage and enhances animal survival in experimental sepsis-induced acute lung injury. Although the mechanisms by which heat shock proteins exert a protective effect are not well understood, these data raise interesting questions regarding the importance of fever in the protection of the whole organism during bacterial infection.

Animals↗

PubMed1993

Ontogeny of platelet-derived growth factor receptor in fetal rat lung.

There is increasing evidence that platelet-derived growth factor (PDGF) or PDGF-like molecules play a role in fetal lung morphogenesis. Our previous studies demonstrated the presence of PDGF-AA and PDGF-BB homodimers in fetal rat lung. To study further the target cells of PDGF in lung development, immunolocalization studies of PDGF receptors (PDGFR) were conducted on embryonic and fetal rat lung from day 13 to day 21 of gestation (term = 22 days) using two polyclonal PDGFR antibodies, one of which one recognizes both alpha and beta receptors (PDGFR-alpha/beta), while the other is specific for the beta receptor (PDGFR-beta). A similar immunostaining pattern for both antibodies was noted. Immunoreactivity to PDGFR was evident in both epithelial and mesenchymal cells of the embryonic lung bud as early as 13 days gestation. The number of PDGFR immunoreactive cells increased with advancing gestation. Intense immunoreactivity was noted in both epithelial cells and interstitial cells during the saccular stage of lung development. The immunoreactivity to PDGFR was localized to the apical/luminal side of bronchial and distal airway epithelial cells. PDGFR-immunopositive bronchial and vascular smooth muscle cells were detected only during the canalicular and saccular stages of lung development. Immunopositive endothelial cells lining the internal vascular plexuses were observed from days 14-16 of gestation. No PDGFR was detected in endothelial cells of large pulmonary vessels. We conclude that PDGFR are present in airway epithelial cells, interstitial cells, and bronchial and vascular smooth muscle cells and that gestation-dependent up- and down-regulation of PDGFR may play a role in developmental regulation of PDGF bioactivity during lung morphogenesis.

Animals↗

PubMed1993

Epitope-specific enhancement of antigen presentation by invariant chain.

The MHC class II-associated invariant chain (Ii) is involved in the intracellular sorting of class II molecules to the endocytic pathway where peptides from processed exogenous antigens are bound, and thereby Ii is thought to enhance antigen presentation. Here we demonstrate that presentation of only one out of five epitopes of a given antigen is augmented by Ii. We have compared the presentation of five different epitopes derived from hen egg white lysozyme (HEL) to Ak-restricted T hybridomas by rat-2 fibroblasts transfected with A alpha k and A beta k (RKK) and RKK cells supertransfected with the mouse invariant chain (RKKI). Only the presentation of the HEL epitope 46-61 was enhanced whereas the presentation of the HEL epitopes 25-43, 34-45, 112-124, and 116-129 was unchanged or even slightly diminished in RKKI cells. The presentation of the epitopes 25-43 and 34-45 was virtually insensitive to the lysosomotropic reagent chloroquine. Brefeldin A (BFA), which inhibits protein egress from the endoplasmic reticulum, blocked the presentation of all epitopes tested in RKKI cells. In contrast, in Ii-negative RKK cells only the presentation of the epitope HEL(46-61) was inhibited by BFA and the presentation of the epitopes 25-43 and 34-45 was only slightly impaired. These findings suggest that Ii may target class II molecules to selected endosomal subcompartments involved in the processing of different peptides derived from an endocytosed antigen. As a result, the enhancement of the class II-restricted presentation in Ii expressing cells appears to be epitope specific rather than antigen specific.

Animals↗

PubMed1993

Glucocorticoid prevention of neonatal hypoxic-ischemic damage: role of hyperglycemia and antioxidant enzymes.

Recently, we observed that pre-treatment of neonatal rats with dexamethasone prevents brain damage associated with cerebral hypoxia-ischemia (unilateral carotid occlusion + 3 h hypoxia). Presently, we investigate whether hyperglycemia or an induction of endogenous free radical scavengers explains dexamethasone's neuroprotective effect. Pathological damage was examined in rats maintained hyperglycemic during hypoxia-ischemia by the repeated administration of 10% glucose (10 ml/kg, i.p.) at 0, 1, 2 and 3 h of hypoxia (n = 14) and this damage was compared to that in control (n = 15) or dexamethasone (0.1 mg/kg, i.p., n = 15) treated animals. Despite similar elevations in blood glucose at the end of hypoxia, glucose treated animals had greater damage than dexamethasone treated animals and both of these groups had less damage than controls (volumes of damage of approx. 30.9 +/- 10, 3.4 +/- 2.3 and 60.4 +/- 7.1% of the hemisphere, respectively; P < 0.0001). Anti-oxidant enzyme activities were measured within brains of animals treated with dexamethasone or vehicle (n = 44). Activities of the enzymes catalase, glutathione peroxidase and CuZn- or Mn-superoxide dismutase were similar in both treatment groups, with or without exposure to hypoxia-ischemia. Thus, an induction of antioxidant enzymes does not explain dexamethasone's effects whereas the relative hyperglycemia associated with glucocorticoid treatment may contribute partially. Neither account fully for dexamethasone's protective effect suggesting an additional glucocorticoid mediated mechanism must be involved.

Animals↗

PubMed1993

Regulation of phosphatidylcholine synthesis in fetal type II cells by CTP:phosphocholine cytidylyltransferase.

Phosphatidylcholine synthesis increases in fetal rat type II cells during late gestation, as demonstrated by an increased incorporation of radiolabeled palmitate, glycerol, acetate, and choline into phosphatidylcholine. However, the percentage of phosphatidylcholine present in the saturated form remains essentially constant. The developmental profile of the enzymes of the CDP-choline pathway suggests that CTP:choline-phosphate cytidylyltransferase catalyses a rate regulatory step in de novo phosphatidylcholine synthesis by fetal type II cells. When cytidylyltransferase activity is assayed in different subcellular fractions, the greatest increase, as a function of development, is found in microsomes. This developmental increase is accompanied by a shift in subcellular distribution of cytidylyltransferase activity from cytosol to microsomes in fetal type II cells during late gestation. This shift is evident even when cytidylyltransferase activity is assayed in the presence of 0.5 mM phosphatidylcholine/oleic acid (1/1 molar ratio) vesicles. We speculate that either a subcellular translocation of CTP:phosphocholine cytidylyltransferase from cytosol to microsomes or an increase in cytidylyltransferase gene expression are responsible for the developmental increase of de novo phosphatidylcholine synthesis by fetal type II cells.

Animals↗

PubMed1993

Assessment of postpreservation rat lung function using a new model for extended venous reperfusion.

Understanding the physiological significance of biochemical events after lung preservation in rats has been hampered by the lack of a suitable model for physiological assessment. We have developed an ex vivo paracorporeal rat lung perfusion model that permits hemodynamic and gas exchange evaluation of lung function. After anesthesia and heparinization, the heart-lung block was removed and the left lung was reperfused for 1 h at a constant flow of 4 ml/min with homologous venous blood drained from the inferior vena cava of the paracorporeal (host) rat. The lung effluent was returned at the same flow rate to the host distal aorta. The model was validated by the assessment of lung function after room temperature ischemia. Animals were allocated into three groups (n = 6) according to the ischemic interval (group 1, 20 min; group 2, 3 h; group 3, 4 h). In groups 1 and 2, PO2, PCO2, mean airway pressure, and pulmonary arterial pressure were within the normal ranges and stable throughout the experiment. In contrast, lungs in group 3 demonstrated higher pulmonary arterial pressure and lower blood effluent PO2 than were found in either group 1 or 2. A significant weight gain during reperfusion was observed only in group 3 (4.23 +/- 0.9 g; P < 0.002). For each lung, the final blood effluent PO2 correlated with the weight gain (R2 = 0.81; P < 0.0001). Our results indicate that this model can be used reliably to detect lung dysfunction after ischemic injury.

Air Pressure↗

PubMed1993

Dexamethasone prevents cerebral infarction without affecting cerebral blood flow in neonatal rats.

BACKGROUND AND PURPOSE: We recently demonstrated that pretreatment with the synthetic glucocorticoid dexamethasone prevents hypoxic-ischemic brain damage in neonatal rats. Presently, we examine whether this protective effect of dexamethasone is due to an improvement in local cerebral blood flow. METHODS: Neonatal rats were treated with either vehicle or 0.1 mg/kg i.p. dexamethasone 24 hours before hypoxia-ischemia (right carotid artery occlusion +3 hours of 8% O2). Cerebral blood flow was measured with [14C]iodoantipyrine autoradiography after either 2 (n = 17) or 3 (n = 15) hours of hypoxia-ischemia. Additional animals (n = 20) were perfusion-fixed 3 days after hypoxia-ischemia. The area of cerebral pathological changes was measured from hematoxylin and eosin-stained coronal sections taken at three different levels. RESULTS: Pathological outcome differed between groups. In vehicle-treated rats, sections from anterior, mid, and posterior portions of the cerebrum all had extensive infarction or cellular necrosis ipsilateral to the occlusion (mean areas of damage were 62.6 +/- 10%, 70.2 +/- 9%, and 54.2 +/- 8%, respectively). However, in dexamethasone-treated animals, brain damage in sections at corresponding levels was minimal (0%, 1.6 +/- 2%, and 1.5 +/- 1%, respectively; p < 0.0002). In contrast to the pathological results, cerebral blood flow was equivalent in the dexamethasone- and vehicle-treated groups. After either 2 or 3 hours of hypoxia, cerebral blood flow was reduced 60-80% ipsilateral to the carotid artery occlusion in animals treated with either vehicle or dexamethasone. CONCLUSIONS: Despite ischemic levels of cerebral blood flow, pretreatment with dexamethasone prevents cerebral damage in neonatal rats. Instead of improving local cerebral perfusion, dexamethasone presumably acts via peripheral or central glucocorticoid receptors to produce some alteration in the brain that decreases its susceptibility to hypoxia-ischemia.

Animals↗

PubMed1993

Induction of heat stress proteins is associated with decreased mortality in an animal model of acute lung injury.

This study examined the hypothesis that transient, whole-body hyperthermia would reduce lung damage and/or mortality in a previously described animal model of acute lung injury. Normal, adult Sprague-Dawley rats were randomly assigned either to a heated (n = 40) or to a sham-heated (n = 49) group. Heated animals were warmed to 41 to 42 degrees C 18 h before intratracheal instillation of phospholipase A2. Forty-eight hours after phospholipase A2 exposure, the two groups were compared in a blinded fashion for mortality rate, PaO2, AaPO2, lung wet/dry weight ratio, alveolar inflammatory cell number, and lung histopathology. Heated, injured animals exhibited a reduced mortality rate and less lung damage than did unheated animals: mortality (zero versus 27%, p < 0.001); AaPO2 (22 +/- 3 versus 36 +/- 15 mm Hg, p < 0.002); lung lavage cell counts (5.3 +/- 3 versus 16.9 +/- 7 x 10(6)/ml, p < 0.05); lung wet/dry weight ratio (4.1 +/- 0.6 versus 5.1 +/- 0.7, p < 0.025); parenchymal lung injury fraction (0.10 versus 0.51, p < 0.001). Transcription and translation of heat shock proteins (HSP70) were examined by Northern and Western analysis. Pulmonary tissue HSP70 mRNA was elevated 1 h after heating. HSP72 protein levels were increased over baseline levels between 12 and 72 h after whole-body hyperthermia, but they were unchanged in sham-heated animals. These data indicate that thermal pretreatment associated with the induction of HSP72 protein synthesis, attenuates tissue damage and mortality in experimental lung injury.

Animals↗

PubMed1993

Fetal lung epithelial cells express receptors for platelet-derived growth factor.

There is increasing evidence to suggest that platelet-derived growth factor (PDGF) or PDGF-like molecules play a role in fetal lung morphogenesis. Our previous studies demonstrated that fetal lung epithelial cells respond mitogenically to exogenous PDGF, while fetal lung fibroblasts respond with increased glycosaminoglycan synthesis. To further study the target cells of PDGF in fetal rat lung, we investigated the presence and nature of PDGF receptors in fetal lung cells. Functional PDGF receptors were expressed on normal epithelial cells of fetal rat lung. All three isoforms of PDGF (AA, AB, and BB) were mitogenic for quiescent epithelial cells. Northern blot and protein analysis demonstrated the presence of PDGF alpha-receptor and PDGF beta-receptor. All isoforms of PDGF enhanced tyrosine kinase activity and stimulated receptor autophosphorylation. In contrast, fetal lung fibroblasts expressed only the PDGF beta-receptor. PDGF-AB and PDGF-BB, but not PDGF-AA, stimulated tyrosine kinase activity. No PDGF isoform was mitogenic for quiescent fibroblasts. However, PDGF-BB stimulated fibroblast proliferation on a collagen type I substratum in the presence of transferrin. Binding experiments with [125I]PDGF-AA and [125I]-PDGF-BB to epithelial cells and fibroblasts confirmed these observations.

Animals↗

PubMed1993

Congenital anteroinferior instability treated by Bankart repair.

A subset of patients with symptomatic anteroinferior instability of the shoulder has been recognized. All patients had a history of minimal trauma that was not related to their symptoms. There were 29 men and four women, averaging 29 years of age. Forty-five percent of the patients had failed treatment for associated impingement syndrome. Eleven patients had 17 operations on the shoulder that failed to relieve pain. Preoperative duration of symptoms ranged from four to 130 months (average, 28 months). No Hill-Sachs lesions were present. After a Bankart stabilization, wherein 11 of 33 shoulders had labral tears, pain relief was achieved in 27 of 33 patients. Three additional patients had pain relief after a second-stage acromioplasty. Thus, three of 15 patients with associated impingement syndrome required a second-stage acromioplasty (20%). In summary, 30 of 33 patients had pain relief. There were three failures. Two of the three patients had multidirectional instability. One of these was lost to follow-up evaluation. Another, repaired by a capsular shift, has no further dislocations. One patient required a revision Bankart repair after he sustained a traumatic tear of the capsule ten days after his initial operation; there was no recurrence. The Bankart operation is a worthwhile procedure for congenital unidirectional anteroinferior instability with or without impingement syndrome. It should be done first rather than initially treating the associated impingement.

Adolescent↗

PubMed1992

Temporal and spatial differences in glycosaminoglycan synthesis by fetal lung fibroblasts.

In studies of the ontogeny of fibroblast-epithelial interactions during late fetal lung rat lung development, we have identified two subpopulations of fibroblasts which differed in their ability to promote epithelial cell proliferation or differentiation. As glycosaminoglycans (GAGs) have been implicated in the regulation of these processes we have tested whether the two fibroblast populations synthesize different GAGs and whether the GAG pattern changes with development. Fibroblasts incorporate more [3H]glucosamine and Na2 35SO4 into GAGs than epithelial cells. Both cell types deposited a significant amount of newly synthesized GAGs in the cell-matrix layer. GAGs were lost faster from the cell-matrix layer of fibroblasts (t1/2 = 12 h) than from that of epithelial cells (t1/2 = 48 h). Total GAG synthesis by fibroblasts did not change with advancing gestation, but synthesis of sulfated GAGs by epithelial cells declined with advancing gestation. Independent of gestational age epithelial cells synthesized predominantly heparan sulfate. Depending on their proximity to the epithelium, fibroblasts differed in their production of GAGs. Fibroblasts in close proximity to the epithelium mainly produced and secreted hyaluronan. More distant fibroblasts, from the pseudoglandular stage of lung development synthesized primarily heparan sulfate and chondroitin sulfate. This same population of fibroblasts from the canalicular stage of lung development, produced more hyaluronan. As the shift to hyaluronan occurs with the thinning of the alveolar septal wall, this finding suggests that developmentally regulated GAG production by fibroblasts may facilitate epithelial-fibroblast interaction, thus influencing fetal lung growth and differentiation.

Animals↗

PubMed1992

Platelet-derived growth factor and growth-related genes in rat lung. II. Effect of exposure to 85% O2.

The expression of platelet-derived growth factor (PDGF), its receptor, and related genes was studied in the lung tissue of rats exposed to air or 85% O2. PDGF-B chain mRNA was increased by 6 days and PDGF B-type receptor mRNA was increased by 4 and 6 days of exposure to 85% O2. Despite a continued increase of cell division, both PDGF-B chain and B-type receptor mRNAs had returned to control values by 14 days of exposure to 85% O2. PDGF-A chain mRNA was unaffected by exposure to 85% O2. Nuclear runoff transcription analysis confirmed increased transcription of PDGF-B chain mRNA, whereas Western blot analysis of lung homogenates suggested consequent increased translation of PDGF-B chain mRNA to PDGF-BB at 7 days of exposure to 85% O2. Combined immunocytochemistry and autoradiography localized PDGF-BB to the major site of cell division, the pulmonary interstitium. We speculate that the early pulmonary fibroblast hyperplasia observed following exposure to 85% O2 is mediated by increased PDGF-B chain gene expression and may also be mediated by changes in PDGF B-type receptor gene expression.

Animals↗

PubMed1992

Stimulation of fetal rat lung cell proliferation in vitro by mechanical stretch.

On the basis of in vivo animal studies and on experiments of nature, it has been suggested that fetal breathing movements are essential for normal lung growth in utero. To study this hypothesis in vitro, we examined the effect of mechanical stretch on proliferation of fetal rat lung cells maintained in organotypic culture to provide a three-dimensional matrix. Initial studies demonstrated that stretch-mediated effects on cell division and DNA synthesis in such cultures were influenced by cell inoculation density, fetal calf serum concentration, and by the amplitude, frequency, periodicity, and duration of the applied stretch. After a 48-h exposure to an intermittent stretch pattern (5% elongation, 60 stretches/min for 15 min of each hour), cell number increased 10% (P less than 0.05), cell doubling time was reduced from 71 to 55 h (P less than 0.05), [3H]thymidine incorporation into DNA increased 61% (P less than 0.01), and the [3H]thymidine-labeling index increased 2.8-fold (P less than 0.001) compared with nonstretched controls. This effect did not appear to be mediated by prostaglandins or leukotrienes because the prostaglandin synthase inhibitors ibuprofen (2.5-50 microM) or BW 755C (5 microM), leukotriene biosynthesis inhibitors BW 755C (5 microM) or MK-886 (0.3 microM), and leukotriene D4 receptor antagonist MK-571 (0.3 microM) did not block stretch-mediated effects. We conclude that mechanical forces act directly to stimulate fetal rat lung cell growth and that these results are compatible with a significant role for fetal breathing in normal fetal lung growth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Differential effect of platelet-derived growth factor on glycosaminoglycan synthesis by fetal rat lung cells.

Lung morphogenesis is in part regulated by extracellular matrix (ECM), and cytokines may indirectly control lung development via modulation of ECM. In the present study, we investigated the effect of different platelet-derived growth factor (PDGF) isoforms AA, AB, and BB on the synthesis of glycosaminoglycans (GAG) by fetal rat lung cells. Independent of gestational age, PDGF-BB, but not PDGF-AA or -AB, stimulated GAG synthesis of fetal lung fibroblasts. In contrast, GAG synthesis by epithelial cells was not affected by any of the PDGF molecules. The stimulatory effect of PDGF-BB on fibroblast GAG biosynthesis was dose (> 10 ng/ml) and time (> 8 h) dependent. The relative proportion of the individual GAG molecules was not altered by PDGF-BB exposure. Blockage of tyrosine kinase activity with staurosporine did abolish the effect of PDGF-BB on fibroblast GAG formation. Actinomycin D and cycloheximide did not abrogate the PDGF-BB effect, suggesting that no new RNA or protein synthesis is required. The proteoglycan synthesis blocker, beta-D-xyloside, also did not inhibit the PDGF-BB action on fibroblast GAG synthesis. These data suggest that the effect of PDGF on GAG synthesis is cell type and isoform specific and is most likely a direct effect on the GAG chain elongation enzymes.

Alkaloids↗

PubMed1992

Platelet-derived growth factors and growth-related genes in rat lung. III. Immunolocalization during fetal development.

To further study the role of platelet-derived growth factor (PDGF) in fetal lung development, the distribution of the PDGF homodimers PDGF-AA and PDGF-BB was examined by immunohistochemistry in embryonic and fetal rat lung from d 12 to 22 of gestation (term = 22 d). PDGF-AA and PDGF-BB were localized to airway epithelial cells as early as d 12 of gestation, 2 d before their appearance in mesenchymal cells. Both PDGF homodimer immunoreactivities increased until the late pseudoglandular stage of lung development, followed by fluctuations in reactivity during the canalicular stage. Only weak immunoreactivity to either PDGF homodimer was evident during the saccular stage of lung development. Immunodetection by Western blotting revealed that PDGF-AA and PDGF-BB homodimer protein concentrations were high during the embryonic and pseudoglandular stage of lung development and decreased with advancing gestation. We conclude that the presence of PDGF in both developing airway epithelial cells and mesenchymal cells, as well as gestation-dependent changes of PDGF homodimers, is compatible with a role for this growth factor during fetal lung development.

Animals↗