Suppressing effect of tannic acid on the frequencies of mutagen-induced sister-chromatid exchanges in mammalian cells

The effects of tannic acid (m-galloyl gallic acid) and 7 of its analogues on the frequencies of sister-chromatid exchanges (SCEs) were investigated in cultured Chinese hamster cells. SCEs induced by UV-light or mitomycin C (MMC) were suppressed by post-treatment with tannic acid and 5 of its analogues. These effects were independent of the extension of the cell cycle. The compounds which showed an SCE-suppressing effect have a common structure of 3 neighboring hydroxy or methoxy groups substituted on the phenyl group in benzoic acid or ester. These decreasing effects of tannic acid were observed in the G1 phase but not in the S or G2 phase of the cell cycle and a greater decline of the frequencies of UV-induced SCEs during liquid holding was seen in the presence of tannic acid. However, cells irradiated with X-rays were not influenced by tannic acid. In cells from a xeroderma pigmentosum (XP) patient, a Fanconi's anemia (FA) patient, and a normal human embryo, MMC-induced SCEs were also decreased by post-treatment with tannic acid. Tannic acid reduced the SCE frequencies in UV-irradiated FA and normal human cells but not in UV-irradiated XP cells. Our results suggest that tannic acid modifies DNA-excision repair and that the decrease in the amount of unrepaired DNA damage might cause the reduction of induced SCEs.     

Glucagon and insulin responses to alpha-adrenergic subtype receptor blockade in sheep

1. Five sheep were used to investigate the influences of alpha-adrenergic subtype receptor blockade on the secretion of both glucagon and insulin. 2. The glucagon secretion was stimulated through an alpha 2-adrenergic subtype mechanism. 3. The secretion of insulin was inhibited by an alpha 2-adrenergic subtype mechanism in conscious sheep.     

Stimulation of Locomotion of Peripheral Blood Monocytes by Human Plasma Fibronectin

The motility of human peripheral blood granulocytes and monocytes in response to human plasma fibronectin was quantified by an in vitro assay using blind-well chemotaxis chambers. Purified fibronectin under nondenaturing conditions produced increased migration of granulocytes only at concentrations higher than 100 nm, and induced increased chemotactic and random locomotion of monocytes at concentrations higher than 0.1 nm. The monocyte migration-inducing activity of fibronectin was concentration dependent, and was strongly inhibited by low concentrations of colchicine (100 nm–100 μm). These findings suggest the possibility that plasma fibronectin serves as a chemotactic stimulus for monocytes in vivo and attracts these cells to sites of microscopic tissue injury where plasma fibronectin is deposited.     

Intracellular localization and size of glycogen particles in glycogen synthesized under histochemical conditions.

During the investigation of the histochemical synthesis of glycogen particles from glucose 1-phosphate by the phosphorylase-branching glycosyltransferase system in various tissue cells, it was observed that focal synthesis localized in a certain area of the cytoplasm occurred in some cells. This differed from the usual synthesis in which particles of similar size were synthesized within the cytoplasm. Otherwise, cytoplasmic particles of various size were also synthesized in other cells under the same histochemical condition. The possible significance of the presence of these patterns in glycogen synthesis is discussed.     

Demonstration of lysosomal and extralysosomal sites for acid phosphatase in mouse kidney tubule cells with p-nitrophenylphosphate lead-salt technique.

Dual localization of acid phosphatase in lysosomal and extralysosomal sites of the tubule epithelial cells of normal mouse kidney was observed at the light and electron microscope level using a modified Gomori lead-salt method with p-nitrophenylphosphate (pNPP) as substrate. Based on previous biochemical and cytochemical findings, we developed optimal conditions for the enzyme activity in extralysosomal sites. The conditions used for the light microscopic level consisted of 1.5 mM PNPP, 2.0 MM Pb(NO3)2 and 0.05 M acetate buffer (pH 5.8). Those for the electron microscopic study required 3.0 mM PNPP, 3.6 MM Pb(NO3)2 and 0.1 M acetate buffer (pH 5.8). This modified lead-salt technique was highly specific and provided a suitable method for the demonstration of nonlysosomal as well as lysosomal sites of acid phosphatase activity in the tubule epithelial cells of normal mouse kidney. As expected, the enzyme activity appeared in the lysosomes, but the prominent reaction in the brush border, the rough endoplasmic reticulum and basal infolding plasma membranes was not anticipated. We were able to demonstrate in situ organelle precursors of microsomal acid phosphatase such as endoplasmic reticulum, plasma membrane and basal infolding membranes showing the same substrate preference, which had been observed previously in biochemical studies in our laboratory. Since the possible participation of alkaline phosphatases, K+-pNPPase or Na+-K+-adenosine triphosphatase was ruled out by use of appropriate inhibitors, the enzyme-reactive sites can be interpreted as reflecting nonspecific acid phosphatase.     

Restoration of radiation-induced G1-depression in transformed fibroblasts treated with dextran sulfate

3T6 and 3T3 cells were cultured with dextran sulfate and irradiated with a dose of 1 000 R of ⁶⁰Co gamma-rays. The rate of progress of cells from G1 to S phase was estimated by radioautograms using ³H-thymidine as a tracer. When cultured in normal medium, 3T3 cells showed a rate of progress from G1 to S phase which was retarded by gamma-ray radiation, whereas 3T6 cells were unaffected. Dextran sulfate alone did not prolong the cell cycle time during logarithmic growth in either cell line, but reduced markedly the saturation density of 3T6 cells. Radiation-induced G1-suppression was observed in 3T6 cells which were cultured in the presence of dextran sulfate for at least 2 days. Replacement of normal media by media containing dextran sulfate at the confluent stage led to the onset of DNA synthesis (and subsequently cell division) in 3T6 cells. Gamma-ray irradiation before the change of media delayed the onset of DNA synthesis.     

Polysome formation induced by light in Pinus thunbergii seed embryos

Ribosome patterns in embryos of light-requiring pine seeds duringprolonged dark imbibition and after red light irradiation werestudied. Ribosomes isolated from dry embryos were essentiallyhomogeneous monomer particles. During a dark imbibition periodas long as 42 days, no appreciable changes in ribosomal patternswere observed. However, a decrease in monomer ribosomes anddistinct polysome formation were detected within 24 hr aftera brief red light had been given at any point in the dark imbibitionperiod. (Received May 11, 1974; )