Sylvaticin: a new cytotoxic and insecticidal acetogenin from Rollinia sylvatica (Annonaceae)

Sylvaticin (I), a new tetrahydroxy annonaceous acetogenin with nonadjacent tetrahydrofuran rings, has been isolated from the dried fruits of Rollinia sylvatica St. Hil. (Annonaceae). This compound is extremely cytotoxic to human tumor cells and shows promising insect control properties.     

Defining the resistance to oxygen transfer in tissue hypoxia

Studies of O2 supply in freshly isolated adult mammalian cells provide new insight into the factors that limit mitochondrial oxygenation in vivo. Of particular importance, mitochondria are present at high densities and often in apparent clusters, both of which contribute to local O2 gradients under hypoxic conditions. Current evidence indicates that the mitochondrial distribution is a component of the differentiated phenotype of adult mammalian cells and that specific motors and anchoring mechanisms are present to allow redistribution in response to developmental, physiological and pathological challenges. To compare the importance of resistance to O2 transfer under different conditions and at different sites along the supply path in vivo, a simple mathematical expression of relative resistance to O2 supply is introduced. Under various pathophysiological conditions, this resistance increases in specific regions of the pulmonary, circulatory or cellular supply path and results in O2 deficiency in the mitochondria. Regardless of cause, the relative resistance increases dramatically in the vicinity of mitochondrial clusters during hypoxia.     

Dopamine-induced relaxation in human pulmonary arteries

Dose-dependent relaxations were induced by dopamine in human pulmonary arteries that had been contracted with prostaglandin F2 alpha without alpha-adrenergic blocking agents. The dopamine-induced relaxation was inhibited by haloperidol and fluphenazine, but not by domperidone, suggesting that this relaxation was mediated via DA1 receptors.     

D-Amino acids in mouse tissues are not of microbial origin

Summary Neutral free D-amino acid contents in the serum, kidney, liver, brain, small intestine and urine in germ-free mice and those in specific pathogen-free mice were compared. No significant difference was found. This strongly suggests that the free D-amino acids which were shown to be present in mice in our previous work^{1, 2} did not originate from the enteric microbial flora.     

The effect of sulfhydryl compounds on the catalytic activity of Cu, Zn-superoxide dismutase purified from rat liver

Sulfhydryl compounds such as reduced glutathione, cysteine and 2-mercaptopropionylglycine, a hepato-protective agent, activated Cu, Zn-superoxide dismutase purified from rat liver at low concentrations (below 10 microM). Furthermore we found evidence indicating that this activation is achieved by reducing Cu2+ present in the catalytic site of the dismutase, and thereby promoting the dismutation of superoxide anions.     

Inhibition of interleukin-1 beta release from cultured human peripheral blood mononuclear cells by prednisolone

Prednisolone, a water-soluble glucocorticoid hormone, suppressed the secretion of interleukin-1 beta from human peripheral blood mononuclear cells in culture. The prednisolone-induced suppression of the monokine release was dose-related and the half maximal response was observed at 0.1 nM.     

Bicuculline and picrotoxin block gamma-aminobutyric acid-gated Cl- conductance by different mechanisms

Using isolated, internally perfused bullfrog dorsal root ganglion cells we have studied the dose-response curves for gamma-aminobutyric acid (GABA) in the presence of internally or externally applied GABA antagonists. With external application of antagonists the inhibition of the GABA current by bicuculline was competitive and that by picrotoxin was noncompetitive. Picrotoxin but not bicuculline blocked when internally perfused.     

Acute toxicity of folic acid in mice

Summary The toxicity of folic acid (PGA) was studied in different inbred strains of mice. LD₅₀ values of PGA by the i.p. route showed a unique toxicity pattern. In some strains, convulsions, ataxia and weakness were observed. Histopathological study in strains S/RVCri, BDF₁, DBA/2 and DBA/2fNCri showed acute renal tubular necrosis.Acknowledgment. The authors thank Ms N. Hasgekar for her technical assistance