Preliminary studies on a lectin on the surface of adipocytes

A lectin-like component on the surface of porcine adipocytes was identified, chiefly by means of the cell adhesion and hemagglutination assays. This component, named porcine adipocyte lectin (PAL), was isolated with Triton X-100 solubilization followed by affinity chromatography. By SDS-polyacrylamide gel electrophoresis, two hands of PAL stained with Coomassie blue were revealed with the apparent molecular weights of 112,000 and 89,000. Moreover, the glycoprotein nature of PAL, was demonstrated by periodic-Schiff reagent staining. PAL was able to recognize maltose, mannose and mannan and glycoproteins with analogous sugar structure in the presence of Ca. By the finding that adipocytes in suspension could be aggregated by adding PAL, the hypothesis was advanced that PAL may be involved in the recognition and adhesion of adipocytes in vivo.

Effects of positive end expiratory pressure and counterpressurization on circulating prostaglandins in the dog

The effects of the application of positive end expiratory pressure (PEEP) ventilation, with and without body counterpressure (CP), on circulating prostaglandin-like substances (PGL) were studied in chloralose anesthetized dogs. The normal respiratory movements were paralysed with succinylcholine chloride. Arterial levels of PGL were continuously bioassayed using Vane's blood superfusion method. PEEPs of 10 and 20 mm Hg elicited PEEP-related increases in functional residual capacity and circulating PGL levels and decreases in blood pressure, left ventricular dP/dt, and heart rate. The PGL appeared to be PGE or prostacyclin in character. When PEEP and CP were simultaneously applied, the increments or decrements of indices described above were reduced. It is concluded that increases in the levels of circulating PGL are attributable, at least in part, to hyperexpansion of the lungs during PEEP and that some of the cardiovascular deterioration observed during and after PEEP may be the result of the vasodilating and cardiodepressing effects of PGL.

Antagonistic action of alpha- and beta-agonists on the bullfrog atrium

Action of alpha- and beta-agonists on the membrane potential, current and tension components on the bullfrog atrial muscle were studied by means of the single or double sucrose-gap technique. Isoproterenol (10(-9)-10(-5) M) as well as adrenaline (10(-7)-10(-4) M) produced a dose-dependent positive inotropic effect, while methoxamine (10(-8)-10(-4) M) and phenylephrine (10(-8)-10(-3) M) with propranolol (10(-6) M) elicited a negative inotropic effect. The positive inotropic effect was accompanied by slight hyperpolarization and marked increase of over-shoot and plateau level of action potential, and the negative inotropic effect, by opposite changes. Under voltage clamp, isoproterenol and adrenaline produced enhancement of slow inward current (Is), delayed outward current (Ix) and Is-dependent phasic tension, while Is-independent tonic tension was inhibited. Contrarily, methoxamine and phenylephrine depressed these currents and elicited beta-antagonistic inotropic actions, especially when isoproterenol was present. Specific feature of alpha-agonist action in the presence of isoproterenol was an inward shift of the semi-steady I-V relationship. It is thus suggested that, in the bullfrog atrium, alpha-agonists produce a strong beta-receptor blocking action and an inward shift of the background current. A possible relationship between the latter effect and inhibition of the Na-K pump is also suggested.

SV40 T-antigen expression in skin fibroblasts from clinically normal individuals and from ten cases of Fanconi anemia

Previous studies of the expression of SV40 genetic information by skin fibroblasts included limited numbers of cell donors and failed to adequately consider possible effects of age, sex, and ethnic origin on assay results. A population of 76 healthy subjects were selected for study following determination of personal and family disease history and karyological analysis. Skin fibroblasts from these individuals were tested for expression of SV40 T-antigen by indirect immunofluorescent assay. The data were normally distributed and showed no significant differences between the age, sex, or ethnic groups tested. The occurrence of rare karyological anomalies in this control population had no effect on T-antigen expression. Fibroblasts from 10 Fanconi anemia patients demonstrated significantly elevated expression of T antigen compared to the well-defined control population, based on simple statistical criteria. T-antigen expression was elevated in two young patients prior to the onset of anemia and did not appear to correlate with the incidence or severity of other specific symptoms. Thus, elevated T-antigen expression in Fanconi anemia fibroblasts reflects an actual defect at the cellular level, rather than clinical, age, sex or ethnic factors not previously considered.

On the size of the DNA in the mammalian chromosome. Structural subunits

Alkaline degradation of mammalian DNA indicates that the molecule exists in the chromosome as an array of structural subunits. The size of the subunit of single-stranded DNA is circa 5 x 10(8) daltons, and it is of sufficient length to contain a number of synthetic units, replicons. The upper size limit of the multicomponent structure is in excess of 10(10) daltons. Mammalian cells of three different origins have been shown to contain the same basic structural DNA components and these components exist throughout the cell cycle. The nature of the links between the subunits is not known.