Inhibition of cathepsin L-induced degradation of epidermal growth factor receptors by c-Ha-ras gene products

The inhibitory activities of c-Ha-ras gene products (p21s) toward several cysteine proteinases have been investigated. The activity of cathepsin L was inhibited by p21s most effectively while those of cathepsin B and papain were slightly inhibited by p21s. p21s did not show any inhibitory activity toward cathepsin H. In order to connect the protease-inhibitor activity of p21s with cell growth, the degradation of epidermal growth factor receptors (EGF-receptors) was investigated. EGF-receptors were preferentially cleaved by cathepsin L but not by cathepsin B or H. The cleavage of EGF-receptors by cathepsin L was inhibited by p21s dose-dependently. These results raise the possibility that p21s can suppress the degradation of growth-related proteins such as EGF-receptors and thereby affect cell growth.     

Different immunolocalizations of cathepsins B, H, and L in the liver

Different localizations of cathepsin B, H, and L in normal rat liver were revealed immunohistochemically with anticathepsin Fab'-horseradish peroxidase conjugates. Staining of cathepsin B was strong in the periportal sinusoids, possibly in Kupffer cells; and weaker in panlobular hepatocytes. Staining of cathepsin H was strong in panlobular hepatocytes, especially in the periphery of the cytoplasm, possibly representing the peribiliary dense bodies; and weaker in periportal sinusoidal cells, possibly Kupffer cells. Staining of cathepsin L was strongest in centrilobular hepatocytes and weaker in periportal sinusoidal cells, possibly Kupffer cells. These findings, revealed for the first time in the present study, show that the histologic and intracellular localizations of the three cathepsins are different, suggesting that they have different roles in degradation of exogenous and endogenous proteins.     

Physiological Effects of a and {alpha} Sexual Agglutination Substances on Mating Reaction in the Yeast Saccharomyces cerevisiae

The sex-specific glycoprotein agglutination substance, responsiblefor sexual agglutination, solubilized from the surface of haploidcells of a or a mating type by the autoclave method had thefollowing effects on mating reaction in Saccharomyces cerevisiae.Sexual agglutination was inhibited by the agglutination substanceof the opposite mating type in living cells as well as in heat-killedcells. Formation of zygotes was completely inhibited, when botha and a cells were treated with the agglutination substanceof the opposite mating type. The a and a agglutination substanceswere inactivated by cells of the opposite mating type, withthe degree of inactivation being greater for the former. Theenzyme responsible for the inactivation of a agglutination substanceseems to be carboxypeptidase Y. ¹ This paper is dedicated to the late Professor J. Ashida, KyotoUniversity. ² Present address: Department of Plant Pathology, Universityof California, Davis, CA. 95616, U.S.A. (Received November 1, 1982; Accepted January 19, 1983)     

Sexual hormones in yeast

Summary Hormone-like substances were isolated from culture media of haploid strains of Saccharomyces cerevisiae. The one excreted by cells of mating type a made cells of the type expand; the other, excreted by type cells, made cells of the a type expand. Tentatively we call the former a hormone and the latter hormone. The cell-expanding action of the a hormone was inhibited by actinomycin D, chloramphenicol and cycloheximide. The a hormone was shown to be heat-stable and dialyzable. Both hormones could be extracted with methylene chloride. The abilities of cells to produce these hormones and to respond to them are under control by the mating-type genes.     

Nucleic Acid Metabolism Involved in Auxin-induced Elongation of Yeast Cells

The following results were obtained using a variant yeast strain, N55, which can respond to the cell-elongating action of auxin. Base analogs of nucleic acids (2-thiouracil, 8-azaguanine, and 5-fluorouracil) inhibited the auxin-induced elongation of yeast cells only when they were added to the preculture prior to auxin treatment. The inhibitory effect of 2-thiouracil and 5-fluorouracil was reversed by uracil and that of 8-azaguanine by guanine. Actino-mycin D inhibited the auxin-induced elongation when given to the culture containing auxin, but not when given to the preculture. The similarity in these respects between yeast and tissues of higher plants is discussed.     

Light-Induced Changes in Cytosolic pH in Leaf Cells of Egeria densa: Measurements with pH-Sensitive Microelectrodes

Light-induced changes of cytosolic pH (pH_c) and the plasmalemmapotential (E_m) in dark-adapted leaf cells of the aquatic plant,Egeria densa were measured simultaneously with double-barreledpH-sensitive microelectrodes. Upon illumination, pH_c increasedtransiently and then decreased to a level that was lower thanthe original value, while the plasmalemma was greatly hyperpolarizedafter an initial small depolarization. DCMU inhibited the light-inducedchanges in both pH_c and E_m. DCMU acted without directly inhibitingthe electrogenic proton pump in the plasmalemma since a decreasein pH_c caused by treatment with butyrate (H⁺-loading) hyperpolarizedthe plasmalemma in DCMU-pretreated cells. N.N-Dicyclohexylcarbodiimide(DCCD) also inhibited the light-induced changes in both pH_cand E_m. This result may be explained by direct inhibition ofthe proton pump in the plasmalemma by DCCD since the decreasein pH_c caused by butyrate did not induce membrane hyperpolarizationin DCCD-treated leaf cells. Fusicoccin induced membrane hyperpolarizationand slight acidification of the cytosol. DCCD inhibited thefusicoccin-induced changes in both pH_c and E_m. The mechanismof the light-induced changes in pH_c is discussed in relationto activities of the proton pump in the plasmalemma and photosynthesis. (Received January 10, 1994; Accepted June 9, 1994)     

Rapid shifting of foraging pattern by Yakushima macaques ( Macaca fuscata yakui ) in response to heavy fruiting of Myrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.     

Rapid shifting of foraging pattern by Yakushima macaques (Macaca fuscata yakui) in response to heavy fruiting ofMyrica rubra

We describe short-term changes in foraging behavior by wild Yakushima macaques (Macaca fuscata yakui),which inhabit a warm-temperate broad—leaved forest on Yakushima Island (30°N, 131°E), Japan. Rapid changes of dietary composition, activity budget, and range use by the monkeys occurred from May to June, apparently associated with changes in the availability of the fruit of Myrica rubraBefore the fruit ripened, monkeys spent less time moving and more time feeding on many species of leaves, which accounted for 40% of feeding time. However, when M. rubrabegan to ripen, they fed intensively on the fruit, which accounted for three-fourths of feeding time,though the activity budget remained unaffected As fiuit of M. rubradecreased,the monkeys fed more on the fruit of other species and on insects, and spent more time moving at higher speeds. There marked shifts in foraging pattern occurred within only two months. In terms of moving cost and dietary quality,Yakushima macaques shifted their foraging pattern according to the availability of M. rubrafrom a “low-cost, low-yield” strategy to a “low-cost, high-yield” strategy, and then to a more costly strategy. The ability to make such rapid shifts in foraging pattern may allow the macaques to effectively use the highly variable food supply within their small range.