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Biomedical subjects

R J Mason

Publications and source records attributed to R J Mason.

At least 181 records · Page 10Linked to original sources
PubMed1985

Pulmonary alveolar type II epithelial cells and adult respiratory distress syndrome.

During the past ten years, functions of alveolar type II cells have been well characterized with isolated cells in vitro. Some of the functions were well known from studies in vivo, but others such as transepithelial sodium transport were unsuspected. A better understanding of this important pulmonary cell type improves our knowledge of the pathophysiology of adult respiratory distress syndrome and may in time lead to new therapeutic strategies.

Biological Transport↗
PubMed1984

Synthesis of saturated phosphatidylcholine and phosphatidylglycerol by freshly isolated rat alveolar type II cells.

Saturated phosphatidylcholine and phosphatidylglycerol are important components of pulmonary surface active material, but the relative contributions of different pathways for the synthesis of these two classes of phospholipids by alveolar type II cells are not established. We purified freshly isolated rat type II cells by centrifugal elutriation and incubated them with [1-14C]palmitate as the sole exogenous fatty acid in one series of experiments or with [9,10-3H]palmitate, mixed fatty acids (16:0, 18:1 and 18:2), and [U-14C]glucose in another series of experiments. Type II cells readily incorporated [1-14C]palmitate into saturated phosphatidic acid (55-59% of total phosphatidic acid), saturated diacylglycerol (82-87% of total diacylglycerol), saturated phosphatidylcholine (69-76% of total phosphatidylcholine), and saturated phosphatidylglycerol (55-59% of total phosphatidylglycerol). Saturated phosphatidic acid, diacylglycerol and phosphatidylglycerol were nearly equally labeled in the sn-1 and sn-2 positions, whereas saturated phosphatidylcholine was preferentially labeled in the sn-2 position. With [9,10-3H]palmitate and [U-14C]glucose, the labeling patterns of phosphatidic acid, diacylglycerol and phosphatidylglycerol were similar to each other but different from that of phosphatidylcholine. The glucose label was found predominantly in the unsaturated phosphatidylcholines at early times (3-10 min) and in the saturated phosphatidylcholines at later times (30-90 min). Similarly, the 3H/14C ratio was very high in saturated phosphatidylcholine and always above that in saturated diacylglycerol. We conclude that freshly isolated type II cells synthesize saturated phosphatidic acid, diacylglycerol, phosphatidylcholine and phosphatidylglycerol and that under our in vitro conditions the deacylation-reacylation pathway is important for the synthesis of saturated phosphatidylcholine but is less important for the synthesis of saturated phosphatidylglycerol. By the assumptions stated in the text during the pulse chase experiment de novo synthesis of saturated phosphatidylcholine from saturated diacylglycerol accounted for 25% of the total synthesis of saturated phosphatidylcholine.

Animals↗
PubMed1984

Electrical currents flow out of domes formed by cultured epithelial cells.

Domes are localized areas of fluid accumulation between a cultured epithelial cell monolayer and the impermeable substratum on which the cells are cultured in vitro. Dome formation has been documented in a variety of epithelial cell lines that retain their transepithelial transport properties in vitro. However, it is not known whether domes are predominantly areas of specific active transport, or, alternatively, are predominantly areas of relative weak attachment to the culture surface. In the present study we adapted a vibrating microelectrode, which can detect small currents flowing in extracellular fluid, to determine if current was flowing into or out of domes and thereby to determine if domes were specialized areas of active transport. We used alveolar type II cells as the main epithelial cell type because they readily form domes in vitro and because they transport sodium from the apical to the basal surface. We found that electrical current flowed out of domes. The direction of the current was independent of the size of a dome, of the age of an individual dome, and of the number of days in primary culture for alveolar epithelial cells. This current was inhibited by amiloride and ouabain and was dependent on sodium in the medium. We made similar observations (outward current from domes which is blocked by amiloride and by sodium substitution) with domes formed by the Madin-Darby canine kidney cell line. The data support the hypothesis that sodium is transported across the entire monolayer and leaks back mainly through the domes. We conclude that domes in epithelial monolayers are not predominantly special sites of active transport but are more likely simply areas of weak attachment to the substratum.

Animals↗
PubMed1984

Noncytotoxic antibodies to paternal antigens in maternal sera and placental eluates.

Noncytotoxic antibodies were detected in sera from 6 of 7 primigravid women during the first trimester of pregnancy. Such antibodies directed to antigens expressed on paternal B lymphocytes were detectable within the first 4-5 weeks of gestation. Antibody activity toward paternal B lymphocytes was also detected in 6 of 10 placental eluates, and in 3 of 10 predelivery and 2 of 10 postdelivery maternal serum samples. When B lymphocytes from umbilical cord blood were used as target cells, antibodies were detected in 5 of 7 placental eluates, and in 3 of 7 predelivery and 2 of 7 postdelivery serum samples. These antibodies also reacted with selected members of a normal B lymphocyte panel. The concept of an immunological enhancing mechanism in normal pregnancy is supported by these data.

B-Lymphocytes↗
PubMed1984

Insulin binding and effects on glucose and transepithelial transport by alveolar type II cells.

The present experiments were designed to investigate the presence of insulin receptors on isolated adult rat alveolar type II epithelial cells and to study the effect of insulin on glucose transport and ion transport in alveolar type II cell monolayers. Alveolar type II cells in primary culture possess high affinity insulin binding sites, which share biochemical and immunologic similarities with insulin receptors previously identified on other cell types. Competition curves demonstrated half-maximal inhibition of 125I-porcine insulin binding at an unlabeled insulin concentration of 4 ng/ml. Scatchard plots of the binding data were concave upward, as has been reported for insulin binding to other cell types, and were used to calculate that alveolar type II cells contained 17,000 insulin receptor sites per cell. Glucose transport was determined by measurement of initial rates of 2-deoxy-D-glucose uptake. Insulin-stimulated 2-deoxy-D-glucose transport [67.8 +/- 15.7% (mean +/- SE), n = 5, P less than 0.01] with a half-maximally effective insulin concentration of 1.2 +/- 0.6 ng/ml, which is in the physiological range of rat serum insulin concentrations. Insulin effects on the electrical properties of the alveolar type II cell monolayers maintained on collagen-coated Millipore filters were tested in Ussing-type chambers. Insulin increased the potential difference (PD) by 44 +/- 10% (n = 5, P less than 0.01) and short-circuit current (Isc) by 50 +/- 13% (n = 5, P less than 0.01) when it was added to the basolateral side but produced little effect when it was added to the apical side.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Non-cytotoxic alloantibodies defined by the EA rosette inhibition assay.

Sera from both transfused individuals and pregnant women mediated inhibition of Fc-rosette formation. Both normal blood B lymphocytes and chronic lymphocytic leukemia cells were used as targets. Inhibition was not related to the presence or absence of lymphocytotoxic antibodies. When tested against a panel of B lymphocytes these sera displayed selective reactivity in keeping with the recognition of allospecific determinants. No association between the target antigen(s) and classically defined MHC-coded structures was evident. Heteroantibodies to both class I and class II MHC structures as well as beta 2-microglobulin also mediated FcR blockade. However, unlike the alloantisera tested, these antibodies displayed no restriction in their reactivity toward individual target cells.

Antibodies, Heterophile↗
PubMed1984

Isolation and culture of human alveolar type II epithelial cells. Characterization of their phospholipid secretion.

Alveolar type II epithelial cells have been isolated previously from rodents but not from humans. The aims of this study were to isolate and culture alveolar type II cells from human lungs, and to study their phospholipid secretion. Lung tissue was obtained from 13 patients after lobectomy or pneumonectomy. Type II cells were isolated by a modification of our method for isolating rat type II cells with porcine pancreatic elastase and discontinuous metrizamide density gradients. Cells were purified further by differential adherence and they were then cultured on an extracellular matrix prepared from bovine corneal endothelial cells. We obtained 1.3 to 4.8 X 10(6) cells per gram of tissue with cell viability on the day of isolation of 96 +/- 1% (mean +/- SE, n = 10). Type II cell purity, assessed by Papanicolaou stain on Day 1 in culture, was 84 +/- 4% (mean +/- SE) in 9 of the 13 experiments. In the remaining 4 experiments, the purity was less than 50%. Electron microscopy showed well-preserved ultrastructure. The cells, radiolabeled with 32Pi, secreted the phospholipids characteristic of pulmonary surfactant, primarily phosphatidylcholine (68%) and phosphatidylglycerol (12%). Phospholipid secretion was stimulated by tetradecanoyl phorbol acetate (4.5 times baseline) and by the beta adrenergic agonist terbutaline (2.0 times baseline), but not by the cholinergic agonist carbamylcholine chloride. In summary, human alveolar type II epithelial cells can be isolated from resected lung and maintained in culture, and they secrete the phospholipids characteristic of pulmonary surface active material.

Cells↗
PubMed1983

Phospholipid-transfer activities in cytosols from lung, isolated alveolar type II cells and alveolar type II cell-derived adenomas.

We have examined phospholipid-transfer activities in cytosols from rat and mouse whole lung, isolated rat alveolar type II cells and alveolar type II cell-derived mouse pulmonary adenomas. We report an enrichment in phosphatidylcholine and phosphatidylglycerol (but not phosphatidylinositol) protein-catalysed transfer in the type II cell and adenoma cytosols compared with the whole-lung cytosols. The activities from these cytosols were resolved using column chromatofocusing, which clearly demonstrated the presence of a phosphatidylcholine-specific transfer protein in each of the four tissues. In addition, two proteins (rat) or three proteins (mouse) catalysing both phosphatidylcholine and phosphatidylglycerol transfer were resolved from whole lung, whereas in both the rat isolated alveolar type II cells and the mouse type II cell-derived adenomas one of these less specific proteins is not present.

Adenoma↗
PubMed1983

The fetus as an allograft: evidence for protective antibodies to HLA-linked paternal antigens.

Non-cytotoxic antibodies to paternal B lymphocytes were detected in sera from 11 of 11 multiparous women and from 11 of 16 normal primigravidae during the first trimester of pregnancy. These antibodies were not, however, detected in sera from 9 of 10 women of comparable gestation at the time of spontaneous abortion. By means of a rosette inhibition assay, the difference in antibody activity between the primigravidae (mean 37.9 +/- 19%, median 36.5%) and the women subject to spontaneous abortion (mean 7.3 +/- 11.6%, median 0%) was statistically significant. This antibody activity was not directed to the known HLA specificities (HLA--A, B, C, or DR), but linkage to the HLA gene complex was suggested by family studies. These results provide evidence for an HLA-linked antigen system not defined by conventional tissue-typing techniques. Fetomaternal disparity at this antigenic site may be important for successful pregnancy.

Abortion, Habitual↗
PubMed1983

Identification of subpopulations of T lymphocytes and Ia positive B lymphocytes using a rosette assay based upon the biotin-avidin interaction.

Bovine erythrocytes were coated with avidin using a chromic chloride coupling technique and used successfully in an indirect rosette assay to identify and quantitate: (a) T-lymphocyte helper and suppressor subpopulations, and (b) Ia positive B-lymphocyte populations. Using mouse monoclonal antibodies to the T-lymphocyte markers OKT3, OKT4, and OKT8 it was shown that the proportion of OKT4 and OKT8 positive cells were respectively 60.9 and 39.2% of the total OKT-3 positive T lymphocytes. In a similar way, using a monoclonal anti-human Ia antibody, the percentage Ia positive cells in B-lymphocyte enriched preparations was shown to vary between 18 and 55% for normal peripheral blood and 31 and 58% for chronic lymphocytic leukaemia derived peripheral blood.

Animals↗
PubMed1983

Cholera toxin stimulates secretion of saturated phosphatidylcholine and increases cellular cyclic AMP in isolated rat alveolar type II cells.

We compared the time course of saturated phosphatidylcholine secretion and cellular cyclic AMP concentrations in isolated rat alveolar type II cells following stimulation by cholera toxin, terbutaline, and 12-0-tetradecanoyl-13-phorbol acetate. Secretion of saturated phosphatidylcholine was stimulated by cholera toxin at concentrations from 1.2 X 10(-11) M to 5.0 X 10(-7) M. In time course experiments there was no significant stimulation with cholera toxin before 1 hr; all subsequent points between 90 and 180 min were significantly different from controls. Secretion stimulated by 10 microM terbutaline was similar in magnitude to stimulation by 1.2 X 10(-9) M cholera toxin; stimulation following either of these agonists was higher than control secretion and lower than secretion stimulated by 10 nM 12-0-tetradecanoyl-13-phorbol acetate. Terbutaline caused an early rise in cellular cyclic AMP that peaked within 5 min and then returned to basal level by 60 min. In contrast, cholera toxin did not increase cellular cAMP levels until 60 min after addition, but then produced a sustained increase in cyclic AMP levels for up to 3 hr. In conclusion, we have presented evidence that more than one mechanism exists by which secretion can be stimulated in type II cells. It is likely that both terbutaline and cholera toxin act by stimulating cellular cyclic AMP and that 12-0-tetradecanoyl-13-phorbol acetate acts by a mechanism different from terbutaline or cholera toxin.

Animals↗
PubMed1983

Pretransplant antibodies and renal allograft survival.

Fc receptor blocking antibodies directed against autologous lymphocytes were present in pretransplant sera from only one of a group of 24 cadaver donor renal transplant recipients. Such antibodies were present in recipient sera against B lymphocytes from the donor in 11/24, against normal B lymphocytes in 12/24 and against leukaemic B lymphocytes in 15/24 cases. There was a significant correlation between EA inhibiting antibodies directed against donor (p less than 0.01), normal (p less than 0.05) and leukaemic B lymphocytes (p less than 0.001) and improved one year allograft survival. No autolymphocytotoxic antibodies were detected. Fc receptor blocking antibodies detected by the Erythrocyte Antibody Inhibition assay may thus have a beneficial effect on graft outcome but do not appear to be autoantibodies.

Antilymphocyte Serum↗
PubMed1983

B lymphocyte antibodies associated with successful renal transplantation and successful pregnancy.

This study shows that non-cytotoxic Fc receptor blocking antibodies occurred more frequently in pre-transplant sera when the recipient had been transfused over five units of blood. Moreover 7/12 previously untransfused patients developed Fc receptor blocking antibodies during an elective blood transfusion regime. Erythrocyte antibody-rosette-inhibiting antibodies were also found at significantly higher values in the sera of women during the first trimester of a normal first pregnancy than in women studied at the time of spontaneous abortion. Family studies showed that this activity was linked to the HLA gene complex. These results indicate that EA inhibiting antibodies directed against MHC linked antigens are associated with specific abrogation of the immune response.

Abortion, Habitual↗
PubMed1982

Secretion of surfactant by primary cultures of alveolar type II cells isolated from rats.

Pulmonary surfactant conventionally is prepared from material obtained by endobronchial lavage. Although it has been assumed that the components of surfactant are secreted by alveolar type II cells, direct proof of this assumption has not been available. Furthermore, it is possible that the final material obtained by lavage has been modified after secretion or altered during the isolation procedure. It has been shown previously that type II cells, after 1 day in primary culture, secrete saturated phosphatidylcholine, one of the lipid components of surfactant. Because saturated phosphatidylcholine is not unique to surfactant and because type II cells in culture lose differentiated characteristics over the first several days in culture, it has not previously been established how closely the secretory products of cultures of type II cells resemble surfactant as obtained by endobronchial lavage. We therefore studied the morphologic, physical and chemical characteristics of the material that type II cells secrete under basal conditions and after stimulation with terbutaline or 12-O-tetradecanoyl-13-phorbol acetate. The secreted material resembled surfactant obtained by lavage; it was similar morphologically to the lamellar material and tubular myelin seen in the fluid-filled alveoli of fetal rats, it lowered surface tension to 5 mN per meter, and it contained the 72000 dalton apolipoprotein of surfactant (as measured by the 'rocket' immunoelectrophoresis technique). When cells were incubated for 22 h with [1-(14)C]acetate, the distribution of radioactivity in the secreted material was very similar to the phospholipid composition of rat surfactant. We conclude that the material secreted by alveolar type II cells after 1 day in primary culture is similar to surfactant obtained by endobronchial lavage.

Animals↗
PubMed1982

Possible mechanism of action of transfusion effect in renal transplantation.

The mechanism by which blood transfusions given before renal transplantation improves allograft survival was studied in 31 transplant recipients. The presence of non-cytotoxic, Fc receptor blocking antibodies to donor and leukaemic B lymphocytes in pre-transplant sera correlated with both improved graft survival (p less than 0.03 and less than 0.1, respectively) and the number of blood transfusions given (p less than 0.05 and less than 0.03, respectively). Moreover, 6 out of 10 previously untransfused prospective transplant recipients developed these potentially protective antibodies during a course of elective blood transfusions. These results indicate that such non-cytotoxic, Fc receptor blocking antibodies in pretransplant recipient sera (a) are associated with improved allograft survival, (b) correlate with the number of blood transfusions given, and (c) can develop in response to blood transfusion.

B-Lymphocytes↗