Presence of Conjugated 5-Hydroxytryptamine in In Vivo Superfusates of Rat Spinal Cord

The presence of an acid-hydrolyzable conjugate of 5-hydroxytryptamine, presumably 5-hydroxytryptamine-O-sulfate, was demonstrated in in vivo superfusates of rat spinal cord by HPLC with electrochemical detection. In untreated rats, the concentration of the 5-hydroxytryptamine conjugate measured during the basal efflux of 5-hydroxytryptamine did not differ from that measured during the release of 5-hydroxytryptamine evoked by DL-p-chloroamphetamine. Pretreatment of the rats with clorgyline, an inhibitor of the enzyme monoamine oxidase (EC 1.4.3.4), or with probenecid did not alter the concentrations of conjugated 5-hydroxytryptamine measured during the basal efflux of 5-hydroxytryptamine, but did elevate the concentrations of conjugate measured during the evoked release of 5-hydroxytryptamine.     

Notizen über endopolyploide Kerne im Bereich der Samenanlage von Angiospermen

Zusammenfassung Es bestätigt sich die Beobachtung, daß gerade in der Samenanlage nicht nur sehr häufig hohe Polyploidiegrade erreicht werden, sondern daß sich die Struktur in diesen Kernen zumeist sehr wesentlich von der in den diploiden unterscheidet.In den hochendopolyploiden Kernen des mikropylaren und des chalazalen Endospermhaustoriums vonLoasa papaverifolia findet sich eine den pflanzlichen Riesenchromosomen ähnliche Struktur, wobei die Endochromosomen wohl im heterochromatischen Abschnitt, aber nicht — oder nur über einen außerordentlich kurzen Teil — im euchromatischen zusammenhalten.In den entsprechenden Kernen vonPlantago psyllium sind die Endochromosomen stets als mehr oder weniger gewundene Fäden erkennbar, die entweder im Kernraum annähernd gleichmäßig verteilt sind, oder aber selten radiär gebaute Gruppen in der Anzahl 3n bilden; die SAT-Endochromosomen sind stets zu drei radiär gebauten Gruppen vereinigt. Außerdem erfährt die Kernstruktur eine weitere Abwandlung durch die unterschiedliche Dicke der Endochromosomen.Von den 25 Pflanzen, deren Antipodenkerne untersucht wurden, besitzen 17 hochendopolyploide Kerne; bei 11 zeigen sie Ausbildung bemerkenswerter Strukturen, wie Riesenchromosomen, Bündel, lichtmikroskopisch deutliche Spiralen oder lockere Areale, wobei manche nur einen bestimmten Strukturtypus ausbilden, andere dagegen mehrere.In den Kernen des Suspensorhaustoriums vonGagea lutea weisen die als zarte Fäden erkennbaren Endochromosomen in den niedrigen Polyploidiestufen eine leichte Gruppierung auf, während sie sich in den hochendopolyploiden Kernen zu Riesenchromosomen zusammenschließen.     

Über die Histologie der Intumeszenzen und die Cytologie zweierIpomoea-Arten

Zusammenfassung Ipomoea Batatas undIpomoea purpurea besitzen Chromozentrenkerne; bei ersterer entspricht die Chromozentrenzahl mit durchschnittlich 83 ungefähr der Chromosomenzahl (2n=90), bei letzterer ist sie mit durchschnittlich 60 Chromzentren doppelt so groß (2n=30). In den Dauergeweben der Wurzel bzw. der Knolle sowie in der Achse beider Arten finden sich keine Anzeichen von Endopolyploidie; die Gewebe bleiben also diploid. — Die Entwicklung der Intumeszenzen, die ebenfalls diploid bleiben, geht entweder von den Nebenzellen oder ihnen benachbarten Zellen der Epidermis, oder von der subepidermalen Zellschicht aus; im letztgenannten Fall finden sich die ersten Teilungen dann stets unterhalb einer Spaltöffnung. Die Intumeszenzen sind feste, aus der Epidermis und der ersten Mesophyllschicht hervorgegangene Wucherungen, die bei der Batate eine Länge von ungefähr 1,5 mm erreichen, beiIpomoea purpurea var. morning glory sogar 2 mm lang werden. — Der Endodermis ergrünter Achsen vonIpomoea Batatas fehlt einCasparyscher Streifen, bei im Dunkeln getriebenen Sprossen hingegen wird ein solcher ausgebildet.     

Expression of the pro-apoptotic gene gadd153/chop is elevated in liver with aging and sensitizes cells to oxidant injury

Aging is generally accompanied by reduced tolerance to oxidative stress and altered responsiveness to proliferative signals. We have shown that hepatocytes derived from aged rats (24-26 months) exhibit greater sensitivity to H(2)O(2) treatment and reduced proliferation following epidermal growth factor (EGF) treatment than cells of young adult rats (5-6 months). Here we examined the effects of aging and calorie restriction (CR) on expression of the oxidative stress-inducible and pro-apoptotic gene gadd153 (chop) in these hepatocytes, and we investigated its influence on sensitivity to oxidants. We show that aging was associated with elevated expression of gadd153, both basally and in response to H(2)O(2) treatment. CR, which attenuates age-associated declines in stress tolerance, prevented the age-related increase in gadd153 expression. EGF treatment also resulted in gadd153 induction in old cells. This effect was absent in young cells and in old cells of CR rats. gadd153 induction by EGF was reactive oxygen species-dependent and correlated with heightened sensitivity to subsequent H(2)O(2) treatment, suggesting that elevated Gadd153 contributes to the greater sensitivity of EGF-pretreated old cells to oxidative stress. Additional support for this hypothesis was provided by experiments with Rat1 fibroblasts in which conditional expression of Gadd153 conferred increased sensitivity to H(2)O(2). We propose a model whereby the diminished ability of old hepatocytes to overcome an EGF-triggered reactive oxygen species load leads to induction of the proapoptotic gene gadd153, which, in turn, sensitizes the cells to oxidant injury. Our findings point to gadd153 expression levels as an important factor in liver aging.     

Caveolin-induced activation of the phosphatidylinositol 3-kinase/Akt pathway increases arsenite cytotoxicity

The inhibitory effect of caveolin on the cellular response to growth factor stimulation is well established. Given the significant overlap in signaling pathways involved in regulating cell proliferation and stress responsiveness, we hypothesized that caveolin would also affect a cell's ability to respond to environmental stress. Here we investigated the ability of caveolin-1 to modulate the cellular response to sodium arsenite and thereby alter survival of the human cell lines 293 and HeLa. Cells stably transfected with caveolin-1 were found to be much more sensitive to the toxic effects of sodium arsenite than either untransfected parental cells or parental cells transfected with an empty vector. Unexpectedly, the caveolin-overexpressing cells also exhibited a significant activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, which additional studies suggested was likely due to decreased neutral sphingomyelinase activity and ceramide synthesis. In contrast to its extensively documented antiapoptotic influence, the elevated activity of Akt appears to be important in sensitizing caveolin-expressing cells to arsenite-induced toxicity, as both pretreatment of cells with the PI3K inhibitor wortmannin and overexpression of a dominant-negative Akt mutant markedly improved the survival of arsenite-treated cells. This death-promoting influence of the PI3K/Akt pathway in caveolin-overexpressing cells appeared not to be unique to sodium arsenite, as wortmannin pretreatment also resulted in increased survival in the presence of H(2)O(2). In summary, our results indicate that caveolin-induced upregulation of the PI3K/Akt signaling pathway, which appears to be a death signal in the presence of arsenite and H(2)O(2), sensitizes cells to environmental stress.     

The Drug Diazaborine Blocks Ribosome Biogenesis by Inhibiting the AAA-ATPase Drg1

The drug diazaborine is the only known inhibitor of ribosome biogenesis and specifically blocks large subunit formation in eukaryotic cells. However, the target of this drug and the mechanism of inhibition were unknown. Here we identify the AAA-ATPase Drg1 as a target of diazaborine. Inhibitor binding into the second AAA domain of Drg1 requires ATP loading and results in inhibition of ATP hydrolysis in this site. As a consequence the physiological activity of Drg1, i.e. the release of Rlp24 from pre-60S particles, is blocked, and further progression of cytoplasmic preribosome maturation is prevented. Our results identify the first target of an inhibitor of ribosome biogenesis and provide the mechanism of inhibition of a key step in large ribosomal subunit formation.     

Ultrastructure of the y-organs of Cancer antennarius in normal and de-eyestalked crabs

The paired Y-organs of crustaceans control the molting process. In males of C. antennarius, these glands are opalescent, lobulated, epithelioid structures embedded in brown fatty tissue. Cells in the periphery extend processes to the connective tissue capsule, an arrangement that suggests increased surface area for metabolic exchange. The processes contain mitochondria and are tipped distally with electron dense material. The cytoplasm, scarce relative to nuclear volume, contains vesicles, polymorphic mitochondria with tubular cristae, and numerous free ribosomes, but little in way of smooth or rough endoplasmic reticulum or Golgi complexes. Progressing from intermolt to the premolt stage, mitochondria, as well as vesicles, and electron-dense particles in peripheral processes increase somewhat in number. Also, heterochromatin masses concentrate adjacent to the nuclear envelope. Eyestalk removal, which induces premolt stages in some species, did not produce consistent change in Y-organ substructure in C. antennarius. Although evidence is accumulating that Y-organs secrete a steroid molting hormone during late intermolt-premolt, the substructure of the glands exhibits neither (a) striking changes with the molt cycle, nor (b) all the characteristics typical of vertebrate steroid hormone synthesizing glands. Nevertheless, the structural features, respectively, are consistent with biochemical evidence that Y-organs (a) rapidly take up and convert sterol precursor and secrete a product without its accumulation or change in total sterol pool size, and (b) apparently cannot synthesize the sterol precursor. Y-organ cytology closely resembles that of some vertebrate steroid hormone secreting glands in which this synthetic capacity is minimal.     

The Use of Carbon and Carmine Particles in Cell Fusion Experiments to Distinguish Hybrids from Parental Cells

The phagocytosis of inert particles, a long-known in vivo phenomenon among cells of the reticuloendothelial system, has more recently been found to be a widespread capability of cells in vitro (Gropp 1963) and can be utilized as a marking system when colored particles are employed. Carbon particles (black) were used by Stoker (1964) as cellular markers and later carmine particles (red) were used as markers in cell transformation studies (Stoker 1967; Rabinowitz and Sachs 1968).