Biomedical subjects

J D Funkhouser

Publications and source records attributed to J D Funkhouser.

27 records · Page 2Linked to original sources

PubMed1983

Additional effects of monovalent cations on the lysine-sensitive aspartokinase of E. coli B.

The apparent specificity of activation of lysine-sensitive aspartokinase (E.C.2.7.2.4) from E. coli by monovalent cations differs depending on the assay used and on the Mg2+ concentration. Activity is nearly absolutely dependent on and is highly specific for a monovalent cation in the aspartate semialdehyde dehydrogenase coupled assay or the adenosine triphosphate-adenosine diphosphate exchange assay. Little specificity for monovalent cations is observed using the aspartyl hydroxamate assay. Activation and specificity are also altered by Mg2+ concentrations at a constant 5 mM nucleotide concentration. At a low (1.25 or 1.6 mM)Mg2+ concentration, monovalent cation activation and specificity are nearly absolute. Less dependence on monovalent cations and less specificity are observed at a higher Mg2+ concentration (6 mM). Li+ inhibits aspartokinase competitively with respect to either K+ or NH4+. Monovalent cations are also thermoprotective and differential thermal inactivation experiments at 56 degrees C reveal that NH4+ and K+, either of which will produce maximum catalytic activity, interact differently with aspartokinase. K+ interacts with positive cooperativity, whereas NH4+ does not. K+, NH4+, and Na+ are about equally effective in enhancing the dissociation of the aspartokinase-aspartylphosphate complex. Li+ is less effective.

Animals↗

PubMed1981

Acylation of 1-palmitoyl-lysophosphatidylglycerol in a alveolar type II cells from rat lung.

1. Alveolar type II cells from adult rat lung have the enzymic capability to acylate 1-palmitoyl-lysophosphatidyl-glycerol, using palmitoyl-CoA to form dipalmitoylphosphatidylglycerol. 2. On a protein basis the acylation of 1-palmitoyl-lysophosphatidylglycerol is at least 2-fold more active in sonicated type II cells than in whole lung homogenates. 3. Both type II cells and whole lung homogenates show higher activity towards palmitoyl-CoA than towards oleoyl-CoA for acylation of 1-palmitoyl-lysophosphatidylglycerol. 4. Both in type II cells and in whole lung homogenates the rates of acylation of 1-palmitoyl-lysophosphatidylglycerol and 1-palmitoyl-lysophosphatidylcholine with palmitate are of the same order of magnitude, while the rate of acylation of 1-palmitoyl-lysophosphatidylethanolamine is much lower.

Acyl Coenzyme A↗

PubMed1980

Fetal lung disaturated phosphatidylcholine. Ostensible increase following exposure to dexamethasone.

Fetal rat lung removed at 15 days gestation and placed in organ culture incorporates choline into phosphatidylcholine. Addition of 10(-9) M dexamethasone resulted in increased rates of choline incorporation per micrograms protein after both 6 and 12 days culture. This concentration of dexamethasone did not increase tissue phosphatidylcholine or disaturated phosphatidylcholine. Thus, at a culture time when dexamethasone had a significant effect on choline incorporation, there was no change in either the total phospholipid or disaturated phosphatidylcholine content of the lung tissue. The transplacental administration of dexamethasone decreased fetal lung DNA and phospholipid content. At the mid-range dosage tested (400 micrograms), dexamethasone depressed DNA (51%) appreciably more than total phosphatidylcholine (28%) and disaturated phosphatidylcholine (33%). These results show that the hormone does not increase the total amount of surfactant per lung. The increased disaturated phosphatidylcholine per mg DNA results in an ostensible beneficial effect of dexamethasone on surfactant and may reflect an increased proportion of Type II cells in fetal lung both in vitro and in vivo following hormone exposure. Disaturated phosphatidylcholine per Type II alveolar cell is no doubt increased but the trade-off is fewer total cells in the lung.

Animals↗

PubMed1978

Differentiation of the pulmonary surfactant system. Disaturated phosphatidylcholine accumulation in fetal rat lung in vivo and in vitro.

Fetal rat lung was placed in organ culture at 15 days gestation (22 days total gestation period), before biochemical and morphological development of the pulmonary surfactant system. At the fifth day of culture numerous Type II cells containing lamellar bodies were present as determined by electron micrography. Phospholipid accumulation in the cultures increased abruptly beginning at 6 days in culture. The phospholipid which accumulated between the sixth and twelfth culture days was composed of 21--27% disaturated phosphatidylcholines. Both the percent of disaturated phosphatidylcholines in the phospholipid fraction and the qualitative pattern of accumulation as a function of time were similar to observations for fetal rat lung developing in vivo. The data presented provide evidence for development of the pulmonary surfactant system in organ culture in vitro.

Animals↗

PubMed1978