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Biomedical subjects

M Post

Publications and source records attributed to M Post.

At least 181 records · Page 10Linked to original sources
PubMed1984

Insulin acts on the fibroblast to inhibit glucocorticoid stimulation of lung maturation.

The effects of insulin and cortisol on saturated phosphatidylcholine synthesis are examined in fetal type II cell cultures and in mixed cell cultures containing type II cells and fibroblasts. In 19-day fetal rat lung type II cell cultures, 100 nM cortisol and 2 nM insulin have no significant effect. Fibroblast-pneumonocyte factor results in enhanced saturated phosphatidylcholine synthesis by fetal type II cells. The significant stimulatory effect of cortisol in mixed-cell cultures is abolished in the presence of insulin or of monoclonal antibodies to fibroblast-pneumonocyte factor. Incubation of type II cells with conditioned media from fibroblasts exposed to cortisol results in increased saturated phosphatidylcholine synthesis. This process is not stimulated when type II cells are incubated with conditioned media from fibroblasts exposed to insulin and cortisol (or to insulin alone). These observations demonstrate that insulin inhibits cortisol induction of lung maturation and suggest that this antagonism results from an inhibitory effect of insulin on the elaboration of fibroblast-pneumonocyte factor by fetal lung fibroblasts.

Animals↗
PubMed1984

Alveolar type II cells isolated from fetal rat lung organotypic cultures synthesize and secrete surfactant-associated phospholipids and respond to fibroblast-pneumonocyte factor.

Alveolar type II cells that were isolated from organotypic cultures of fetal rat lung and maintained in primary monolayer culture were analyzed. Morphologically the cells retained many characteristics of type II cells in vivo. Biochemical analysis revealed that the cells contained and synthesized phosphatidylcholine with a high degree of saturation. Furthermore, the cells released saturated phosphatidylcholine and responded to adrenergic stimulation with increased release. The type II cells retained their ability to proliferate and responded to fibroblast-pneumonocyte factor. These data indicate that primary cultures of fetal type II cells will be useful to elucidate mechanisms modulating type II cell proliferation, surfactant synthesis, and surfactant secretion.

Animals↗
PubMed1983

Mechanisms involved in the synthesis of disaturated phosphatidylcholine by alveolar type II cells isolated from adult rat lung.

1. Alveolar type II cells isolated from adult rat lung incorporated radioactively labelled palmitate predominantly into the 2-position of disaturated phosphatidylcholine. In disaturated diacylglycerol, however, the radioactivity was almost equally distributed between the 1- and 2-positions. 2. Exposure of isolated type II cells to the phospholipase A2 inhibitors 4-bromophenacylbromide or quinacrine dihydrochloride led to a decreased synthesis of total phosphatidylcholines from various labelled precursors. Interestingly, it also led to an increased degree of unsaturation of the phosphatidylcholines synthesized by the cells. 3. Incubation of type II cell sonicates with radioactively labelled CDPcholine resulted in the formation of labelled phosphatidylcholine; 56% of this phosphatidylcholine appeared to be disaturated. In similar experiments with homogenates from whole lung, 20% of the synthesized phosphatidylcholine was disaturated. 4. These results suggest that both direct synthesis de novo and remodeling of 1-saturated-2-unsaturated phosphatidylcholines contribute to the biosynthesis of disaturated phosphatidylcholine in isolated alveolar type II cells.

Acetophenones↗
PubMed1983

The lipoprotein profile and phospholipase activity of subretinal fluid.

We have studied the lipoprotein profile of subretinal fluid by crossed immunoelectrophoresis using an antiserum against apolipoprotein A-I. If the detachment had occurred recently, we found that the subretinal fluid contained only the alpha 1-lipoprotein of serum. However, if the detachment was of longer duration an increasing amount of an electrophoretically slower-moving lipoprotein was also present in the subretinal fluid. We present evidence that subretinal fluid contains an enzyme, phospholipase A, which can form the slower-moving component from alpha 1-lipoprotein. Since the retina has a high phospholipid content, permanent damage may be caused to its structure by the action of this hydrolysing enzyme.

Apolipoprotein A-I↗
PubMed1983

Constrained total shoulder arthroplasty. Long-term follow-up observations.

Constrained total shoulder arthroplasty is a salvage procedure for patients with disabling pain and a nonfunctioning rotator cuff mechanism. Considering the advanced pathologic process and severe symptoms of these patients, the results of pain relief are gratifying. Many of the patients have weak or absent deltoid muscles, and active overhead motion is not possible. A method of attaching the metal glenoid to the scapula has been designed to reduce the risk of loosening. However, constrained total shoulder arthroplasty does produce considerable stress on bony attachments. Careful patient selection and an excellent, carefully supervised postoperative rehabilitation program are mandatory for success. Before considering a constrained total joint arthroplasty, the surgeon should carefully assess the patient's needs and consider other less extensive shoulder reconstructions.

Adult↗
PubMed1983

Rotator cuff tear. Diagnosis and treatment.

Early surgical repair of rotator cuff tears with a partial anterior acromionectomy is recommended as a means of minimizing a progression of symptoms and findings. It was more important to achieve adequate tension in the cuff tissues than to obtain a water-tight closure. Even patients with old complete tears may obtain good results from reconstruction of the rotator cuff. However, merely closing a rotator cuff tear will not permit a good functional result if the ability of the muscles to contract adequately is lost forever. This group of patients rarely achieves full restoration of muscle strength in their operated shoulders, primarily due to muscle atrophy. In shoulders previously operated on, functional results were not as good as in those cases operated on for the first time. Avoidance of interposed soft tissue grafts and restoration of a direct continuity of viable rotator cuff tissue to its bony insertion are recommended whenever possible, to achieve the optimum functional result. In those patients with arthritis of the glenohumeral joint or permanent long-standing nonfunctional rotator cuff muscle, the results of reconstruction were poor. A carefully supervised postoperative rehabilitation program is essential for optimum results.

Acromion↗
PubMed1982

Tissue distribution and subcellular localization of phosphatidylcholine transfer protein in rats as determined by radioimmunoassay.

A radioimmunoassay for the phosphatidylcholine-transfer protein from rat liver was used to measure levels of PC-transfer protein in rat tissues. The assay as described before (Teerlink, T., Poorthuis, B.J.H.M., Van der Krift, T.P. and Wirtz, K.W.A., Biochim. Biophys. Acta 665 (1981) 74-80) was modified in order to measure PC-transfer protein in tissue homogenates and subcellular membrane fractions. To this end both a detergent (Triton X-100) and a proteolytic enzyme inhibitor (aprotinin) were added to the assay medium. The radioimmunoassay measured levels of PC-transfer protein in the range of 5-50 ng and was specific for PC-transfer protein from rat tissues. Subcellular distribution studies showed that in 10% (w/v) homogenates of liver approximately 60% of the PC-transfer protein was present in the 105000 X g supernatant fraction, the remainder being evenly distributed over the particulate fractions. PC-transfer protein associated with the particulate fractions was almost completely removed by a single washing step, suggesting a dynamic equilibrium between membrane-bound and soluble PC-transfer protein. Both 105000 X g supernatants and homogenates of various rat tissues were assayed. The highest levels of PC-transfer protein were measured in liver and intestinal mucosa. Lower values were found in kidney, spleen and lung, whereas heart and brain contained hardly any PC-transfer protein. PC-transfer protein levels in regenerating rat liver did not differ significantly from levels in normal liver. In fetal lung a change in PC-transfer protein content during development was observed, with a clear maximum 2 days before term, suggesting an involvement of PC-transfer protein in the secretion of lung surfactant.

Aging↗
PubMed1982

The rate-limiting step in the biosynthesis of phosphatidylcholine by alveolar type II cells from adult rat lung.

1. The rate-limiting reaction in the biosynthesis of surfactant phosphatidylcholine by type II cells isolated from adult rat lung was examined. 2. Studies on the uptake of [Me-14C]choline and its incorporation into its metabolites over a 5 h period indicated that in these cells the cholinephosphate pool was much larger than both the choline and CDPcholine pool. This is consistent with the idea that the rate-limiting reaction is that catalyzed by cholinephosphate cytidylyltransferase. 3. Evidence that cholinephosphate cytidylyltransferase is the slowest of the three enzymes incorporating choline into phosphatidylcholine was also obtained from pulse-chase experiments. [Me-14C]Choline taken up by the cells was rapidly converted into cholinephosphate during the pulse period. As the radioactivity disappeared from cholinephosphate during the chase period, the label was incorporated immediately into phosphatidylcholine, without much change in the labelling of CDPcholine. This indicates that the cholinephosphotransferase is at least as fast as the cholinephosphate cytidylyltransferase. 4. Inclusion of palmitate in the chase medium accelerated the conversion of labelled cholinephosphate into phosphatidylcholine and decreased the radioactivity associated with CDPcholine. This indicates that under these conditions the cholinephosphate cytidylyltransferase reaction cannot keep up with increased utilization of the CDPcholine in the terminal step of the CDPcholine pathway.

Animals↗
PubMed1982

Lamellar bodies isolated from adult human lung tissue.

Lamellar bodies, the intracellular storage form of pulmonary surfactant, were isolated from adult human lung tissue. As shown by electron microscopy, the isolated human lamellar bodies resembled the lamellar bodies isolated from experimental animals. Chemical analysis revealed that the lamellar bodies consisted largely of lipids, particularly phospholipids (85%). The major phospholipid was phosphatidylcholine, which accounted for 71% of the total phospholipids. Phosphatidylglycerol and phosphatidylethanolamine were 10 and 8%, respectively, of the lamellar body phospholipid. Phosphatidylserine, phosphatidylinositol, lysophosphatidylcholine, and sphingomyelin were minor components. Cholesterol was found to represent 60% of the neutral lipids or 9% of the total lipids. Phosphatidylcholine contained largely saturated fatty acids, of which palmitic acid was the most abundant. Disaturated phosphatidylcholines comprised 67% of the total phosphatidylcholines. Phosphatidylglycerol and phosphatidylethanolamine contained considerably less saturated fatty acids. Only 24% of phosphatidylglycerol was disaturated. The chemical composition of adult human lamellar bodies was very similar to that of lamellar bodies derived from experimental animals. The similarities in morphology and chemical composition of lamellar bodies suggest that surfactant metabolism in human lung may be similar to that of other mammals.

Aged↗
PubMed1981

beta-Adrenergic stimulation of the release of ACTH- and LPH-related peptides from the pars intermedia of the rat pituitary gland.

The intermediate lobe of the rat pituitary gland produces a series of peptides related to ACTH and LPH. The spontaneous and isoproterenol-stimulated release of such peptides was studied during in vitro superfusion of rat neurointermediate lobes with Krebs-Ringer medium. Products released into the superfusion medium were quantified by direct measurement or after chromatography on Sephadex G-50. ACTH bioactivity was determined by use of adrenal cortical cell suspension assay. In addition, NH2-terminal ACTH, CO2H-terminal ACTH, alpha-MSH and beta-endorphin radioimmunoassays were used. The results show that 1. neurointermediate lobes of rats secret spontaneously various ACTH- and LPH-related peptides in amounts proportional to the amounts in which these peptides are found in extracts of the neurointermediate lobe; 2. the beta-adrenergic agonist, isoproterenol, stimulated the spontaneous release of various peptides, including alpha-MSH, ACTH, CLIP, glycosylated CLIP, and beta-endorphin-like peptides; 3. isoproterenol induced a dose-dependent (10(-9)-10(-7) M), parallel increase in the release of alpha-MSH and ACTH following similar time courses and showing identical EC50 values (about 10(-8)M). Although the spontaneous release of alpha-MSH and ACTH from rat neurointermediate lobes is not strictly coupled under the conditions used in this study, isoproterenol seems to affect the spontaneous release of these peptides to the same relative extent.

Adrenergic beta-Agonists↗
PubMed1980

Phospholipid-transfer activity in type II cells isolated from adult rat lung.

The soluble fraction from adult rat lung type II cells stimulated the transfer of various phospholipids between either liposomes or rat lung microsomes and rat lung mitochondria. Compared to whole lung, type II cells are highly enriched in transfer activity suggesting that phospholipid-transfer proteins play a role in the transport of surfactant phospholipids. Sephadex chromatography of pH 5.1 supernatant from type II cells yielded only one fraction catalysing the transfer of phosphatidylcholine, phosphatidylglycerol and phosphatidylethanolamine, while chromatography of pH 5.1 supernatant from whole lung yielded in addition a specific phosphatidylcholine-transfer and a specific phosphatidylglycerol-transfer protein.

Animals↗
PubMed1980

Phospholipid transfer proteins in rat lung. Identification of a protein specific for phosphatidylglycerol.

From the soluble fraction of a rat lung homogenate, two proteins were partially purified which catalyzed the transfer of phosphatidylglycerol between liposomes and rat lung mitochondria. One protein was specific for phosphatidylglycerol, the other also catalyzed the transfer of phosphatidylcholine and phosphatidylethanolamine. The soluble fraction from rat liver also contained the nonspecific, but not the specific phosphatidylglycerol-transfer protein. It is suggested that the specific phosphatidylglycerol-transfer protein, as well as the phosphatidylcholine-transfer protein, which is also present in rat lung, contribute in the lung to the biogenesis of lamellar bodies, the organelles where surfactant phosphatidylcholine and phosphatidylglycerol are stored prior to secretion onto the alveolar surface.

Animals↗
PubMed1980

Effects of cortisol and thyroxine on phosphatidylcholine and phosphatidylglycerol synthesis by adult rat lung alveolar type II cells in primary culture.

1. The effect of cortisol and thyroxine on the formation of phosphatidylcholines and phosphatidylglycerols was studied in adult rat lung type II cells in primary culture. 2. Addition of cortisol enhanced the incorporation of [Me-14C]choline, [1-14C]acetate, [1-14C]palmitate, D-[U-14C]glucose, and [1(3)-3H]glycerol into total and disaturated phosphatidylcholines. 3. Cortisol also stimulated the formation of phosphatidylglycerols from labelled acetate, palmitate, glucose, and glycerol, but did not affect the formation of phosphatidylethanolamines. 4. Thyroxine alone did not significantly affect the formation of total and disaturated phosphatidylcholines nor that of phosphatidylglycerols or phosphatidylethanolamines. 5. Exposure of the cells to a combination of cortisol and thyroxine caused increases in the rates of synthesis of total and disaturated phosphatidylcholines from labelled choline, palmitate, and glycerol and in that of phosphatidyl-glycerols from labelled glycerol. These increases were about the same as those brought about by cortisol alone. In contrast to cortisol alone, the combination of cortisol and thyroxine did not significantly affect the entry of labelled acetate and glucose into phosphatidylcholines and phosphatidylglycerols. 6. The present results suggest that direct effects of glucocorticosteroids on the alveolar type II cell may play a role in the regulation of the synthesis of surfactant lipids in the adult lung.

Animals↗
PubMed1980

The perfused isolated lung as a possible model for the study of lipid synthesis by type II cells in their natural environment.

The incorporation of radioactively labeled palmitate and acetate into total and disaturated phosphatidylcholines was studied in the perfused whole lung, in surfactant secreted during perfusion, and in isolated alveolar type II cells. Exogenously added palmitate was found to be incorporated preferentially into the 2-position of total and disaturated phosphatidylcholines in all cases. Acetate, when supplied at a high concentration, was incorporated preferentially into the 2-position in all cases. However, acetate supplied at a low concentration was incorporated preferentially into the 2-position in type II cells and in surfactant, but preferentially into the 1-position in the whole lung. The dissimilarity in incorporation of acetate between isolated type II cells and perfused whole lung and the similarity in this respect between isolated type II cells and surfactant indicate that the perfused isolated lung may only be a good model for studying the synthesis of surfactant components by the type II cells in their natural environment if the products of processes in type II cells are separated from products of other cells after the perfusion. Both in surfactant and in lavaged lung tissue, labeled palmitate and acetate incorporated mainly into the 2-position of phosphatidylglycerol. This indicates that remodeling reactions are involved in the synthesis of dipalmitoylphosphatidylglycerol.

Acetates↗