Serodiagnosis of Streptococcus pneumoniae infection in guinea pigs by an enzyme-linked immunosorbent assay

Guineapig antibodies to Streptococcus pneumoniae (SPN) serotype 19F were detected by an enzyme-linked immunosorbent assay using a simple procedure. In experimentally infected hosts, antibody was detectable as early as 2 to 3 weeks after infection, and high titres were maintained for a long period. Antibodies higher than 1:64 were regarded as specific. In a field study, high antibody titres were shown in SPN enzootic colonies in contrast to negative or low antibody titres in a majority of the animals from non-enzootic and SPF colonies.     

The effects of monensin on membrane lipids of cultured human skin fibroblasts

We have investigated the effects of monensin, a monovalent cationophore, on the metabolism of neutral lipids, fatty acids, ceramide and phospholipids in cultured human skin fibroblasts. Treatment with 1 microM monensin for 18 h reduced the cellular cholesterol ester content to less than one-third of untreated cells, and incorporation of [3H]acetate into cholesterol ester was also reduced, to less than one-fifth. Concomitantly, a greater conversion of [3H]acetate into free cholesterol occurred. There was a moderate increase in free fatty acids, but no change in triacylglycerol content, although the content of the latter appeared to increase in the presence of fetal calf serum in the culture medium. Phosphatidylcholine decreased in content and phosphatidylserine increased among the phosphatides, but ceramide remained unchanged after monensin treatment. These findings suggest that monensin influences the metabolic interrelationships of structural lipids in fibroblasts.     

Changes in plasma fibronectin levels in thyroid diseases

The plasma levels of fibronectin (Fn) have been measured in normal subjects and in patients with thyroid diseases. The mean plasma Fn levels in 62 normal adults was 32.0 +/- 6.0 mg/dl, whereas it was elevated to 62.6 +/- 16.1 mg/dl (mean +/- SD) in 25 patients with hyperthyroidism and decreased to 19.2 +/- 8.0 mg/dl in 9 patients with hypothyroidism. The 9 patients with simple goiter have normal values of 29.1 +/- 8.0 mg/dl. With the administration of anti-thyroid drugs, plasma Fn levels normalized, with a time lag, in parallel with normalization of the thyroid function. Positive correlation was obtained between Fn levels and serum levels of triiodothyronine (T3) and thyroxine (T4). The present findings indicate that measurement of plasma Fn both in the basal state and during treatment provides evidence of altered Fn metabolism in thyroid diseases and serves to follow up the effect of treatment.     

Molecular species of platelet-activating factor generated by human neutrophils challenged with ionophore A23187

Two species of platelet-activating factor (PAF), 1-hexadecyl- and 1-octadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16 = 0 AGEPC and C18 = 0 AGEPC) were detected in ionophore A23187-stimulated human neutrophils. The amount of AGEPC in 1 x 10(7) neutrophil cells was 80 +/- 26 pmol (mean +/- standard error) with a range of 14 to 223 pmol (n = 8), and it consisted of 80% of the C16 = 0 species and 20% of the C18 = 0 species. Most of the AGEPC derived from ionophore-treated neutrophils remained cell associated rather than being secreted into the medium, even when the medium contained ample albumin protein, which can trap AGEPC. These results were obtained by a technique of gas chromatography-mass spectrometry coupled with selected ion monitoring.     

Production of platelet-activating factor by washed rabbit platelets

Production of platelet-activating factor by washed rabbit platelets under stimulation with the ionophore A23187 was investigated utilizing two groups of platelet preparations. The first platelet preparation contained 0.03 +/- 0.02% contaminating white cells, while the second preparation contained 0.48 +/- 0.27% white cells. The latter preparation produced platelet-activating factor, mainly 1-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 8.3 +/- 6.3 pmol (mean +/- standard deviation) with a range of 2.6 to 21.4 pmol (n = 9), followed by small quantities of 1-octadecenyl- and 1-octadecyl-2-acetyl-sn-glycero-3-phosphocholine. In contrast, there was no production of 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine by the former platelet preparation having 0.03% leukocytes. These quantitative analyses were carried out by the selected ion monitoring technique and it was concluded that it is necessary to consider the presence of contaminating white cells in studies on the production of platelet-activating factor by platelets.     

Differences in redox and kinetic properties between NAD-dependent and O2-dependent types of rat liver xanthine dehydrogenase

Reductive titrations of a NAD-dependent type (type-D) and an O2-dependent type (type-O) of rat liver xanthine dehydrogenase showed that only the type-D enzyme formed a pronounced stable FAD semiquinone (FADH*). The FAD semiquinone was less stabilized in the presence of NAD. The Vmax value for xanthine-NAD activity of type-D enzyme was close to that for xanthine-O2 activity of type-O enzyme, while the Vmax value for xanthine-O2 activity of type-D enzyme was about one-fourth of that of type-O enzyme. The Km value for O2 of type-D enzyme was about five times as large as that of type-O enzyme. The absorbance spectrum of type-D enzyme during turnover with xanthine and O2 as substrates showed a considerable amount of FADH* formation, but that with xanthine and NAD as substrates showed only a negligible one. Low xanthine-O2 activity of type-D enzyme, as compared with that of type-O enzyme, seems to be explained by the conformational change occurring in conversion from type-O to type-D enzyme, which results in different reactivity of FAD to molecular oxygen and a higher fraction of FADH* during turnover. The binding of NAD may possibly increase the fraction of FADH2, resulting in a Vmax value of xanthine-NAD activity almost as high as that of xanthine-O2 activity of type-O enzyme.