A single nucleotide change in the 5' noncoding region of Sindbis virus confers neurovirulence in rats

Two pairs of Sindbis virus (SV) variants that differ in their neuroinvasive and neurovirulent traits in mice have been isolated. Recently, we mapped the genetic determinants responsible for neuroinvasiveness in weanling mice. Here, we extend this study to newborn and adult rats and to rat neuronal cultures. Remarkably, certain aspects of the pathogenesis of these strains in rats were found to be quite distinct from the mouse model. Suckling rats were susceptible to all four isolates, and replication in the brain was observed after both intraperitoneal and intracranial (i.c.) inoculation. None of the isolates was neuroinvasive in adult rats, although all replicated after i.c. inoculation. For the isolate pair that was highly neurovirulent in mice, SVN and SVNI, only SVNI caused death after i.c. inoculation of adult rats. Similarly, only SVNI was cytotoxic for primary cultures of mature neurons. The genetic determinants responsible for the pathogenic properties of SVNI were mapped to the E2 glycoprotein and the 5' noncoding region (5'NCR). Substitution of two amino acids in SVN E2 with the corresponding residues of SVNI (Met-190 and Lys-260) led to paralysis in 3- and 5-week-old rats. More dramatically, a single substitution in the 5'NCR of SVN (G at position 8) transformed the virus into a lethal pathogen for 3-week-old rats like SVNI. In 5-week-old rats, however, this recombinant was attenuated relative to SVNI by 2 orders of magnitude. Combination of the E2 and 5'NCR determinants resulted in a recombinant with virulence properties indistinguishable from those of SVNI. These data indicate that the 5'NCR and E2 play an instrumental role in determining the age-dependent pathogenic properties of SV in rats.     

Phytohormones and light regulation of the growth habit in peanuts (Arachis hypogaea L.)

Diageotropic side branches in runner type peanuts assume anorthotropic position when grown in the dark but return to aplagiotropic postition when transferred back to light. The effectof light on the trailing habit of lateral branches depends onthe quality and intensity of the light taking place under blue+farred light, but not under blue alone. Light intensity below 28Kergs.cm^–2.sec^–1 changed the growth of the runner'slaterals from trailing to erect. Inhibitors of both GA and auxinactivity were higher in the laterals of runners than in thoseof the erects. Along with the change in the trailing habit bylow light intensity, a decrease in inhibitor level was observed.Gibberellin-like activity was smaller in both extracts and diffusatesof the growing tip of lateral branches than in the main axis.An inhibitor found only in lateral branches of runner type plantscould be detected in erect plants in the presence of auxin.The predominant factor controlling differences in the growthhabit of side branches of the erect and runner types is thepresence of an inhibitor; while, within each type, levels ofgibberellin seem to account for the different growth habit ofthe axis and laterals. (Received January 23, 1973; )     

Foliar uptake and translocation of rubidium in bean plants as affected by root absorbed growth regulators

Summary The absorption and subsequent transport of foliar applied Rb⁸⁶ labeled Rb Cl (10 mM) was studied on bean plants (Phaseolus vulgaris, L. cv. Black Seeded Blue Lake) exposed to physiologically tolerable levels of certain plant growth substances in the solution culture root media. Gibberellin A₃ (10^-5 M) increased Rb uptake but did not affect total translocation from the treated leaf. Translocation was directed to the upper vegetative parts and markedly reduced to the roots. Foliar influx of Rb and transport to the roots were greatly enhanced by 1-naphthaleneacetic acid (10^-6 M) but mobilization of Rb into the leaves and upper stem was reduced. 2-Chloroethyltrimethylammonium chloride (10^-3 M) and N,N-dimethylaminosuccinamic acid (3×10^-4 M) decreased the mobility of Rb to the upper stem, increased it to the roots, and had no effect on initial uptake. Rb absorption was depressed by 2,4-dichlorobenzyltributylphosphonium chloride (10^-5 M) with no effect on subsequent translocation. Both uptake and mobility were strikingly inhibited by N⁶-benzyladenine (10^-6 M).These results suggest that absorption and the subsequent transport of foliar absorbed Rb are independent processes and that the distribution or mobilization of Rb in the various plant organs was not always a function of the chemically modified growth rate of the corresponding organ.Report No. COO-888-50 in cooperation with the Division of Biology and Medicine of the United States Atomic Energy Commission, Contract No. AT (11-1)-888. Journal Article No. 3643 of the Michigan Agricultural Experiment Station.     

Dual effect of light on flowering and sprouting of rose shoots

Shade, caused by a dense leaf canopy in the light conditions of a normal greenhouse, reduced sprouting of the third axillary bud (from the top) on decapitated rose branches ( Rosa hybrida cv. Marimba) in comparison to less shaded buds on branches protruding above the canopy and sparsely spaced. Flowering of the third young shoot on shaded branches bearing 3 lateral shoots was totally inhibited. Mixed fluorescent and incandescent light in a growth chamber reduced sprouting of the third bud on decapitated rose branches in comparison to decapitated branches on rose plants held in fluorescent light of similar photon flux density. This was attributed to the higher R:FR ratio in fluorescent vs mixed light that reached the third bud, and in exposed vs shaded branches. Flowering of the third shoot was promoted by several factors: high photon flux density, 0.5 m M gibberellic acid (GA) or 0.2 m M benzyladenine (BA). BA was the most effective treatment. Treatments promoting flowering of the third shoot did not reduce growth or flowering of the upper shoots. However, spraying the uppermost shoot with BA suppressed the growth of the shoots below. It is concluded that light affects flowering in two ways. The effect on bud sprouting is related mainly to R:FR ratios, while the effect on flower development is related mainly to photon flux density. Cytokinins may substitute for the light effect on flower development.     

Correlative changes in sucrose uptake, ATPase activity and membrane fluidity in carnation petals during senescence

Apparent sucrose uptake. ATPase activity and membrane fluidity changes were studied during the development and senescence of carnation flowers ( Dianthus caryophyllus L., cv. Cerise Royallette). Typical changes associated with senescence of a cut flower, such as respiration, ethylene production and fresh weight, were measured. Concomitant with a rise in respiration and ethylene production and a decline in fresh weight, a sharp decrease in apparent sucrose uptake was observed. Sucrose uptake was pH dependent (pH optimum, 5.5) and influenced by membrane integrity. Apparently, the activity of ATPase is related to sucrose uptake, because similar changes occurred during flower development. In addition, the activity of ATPase was well correlated with membrane fluidity.
It is suggested that sucrose uptake is controlled by ATPase activity, which in turn is modulated by membrane lipid fluidity. The decline in membrane fluidity associated with senescence leads to a corresponding reduction in ATPase activity and sucrose uptake. Further evidence supporting this view comes from experiments in which senescence was enhanced by 1-aminocyclopropane-l-carboxylic acid. It shortened the time to decline in fresh weight, rise in respiration and ethylene production. In parallel, reduction in membrane fluidity, ATPase activity and sucrose uptake were observed.     

Sonic hedgehog promotes proliferation and differentiation of adult muscle cells: Involvement of MAPK/ERK and PI3K/Akt pathways

Sonic hedgehog (Shh) has been reported to act as a mitogen and survival factor for muscle satellite cells. However, its role in their differentiation remains ambiguous. Here, we provide evidence that Shh promotes the proliferation and differentiation of primary cultures of chicken adult myoblasts (also termed satellite cells) and mouse myogenic C2 cells. These effects are reversed by cyclopamine, a specific chemical inhibitor of the Shh pathway. In addition, we show that Shh and its downstream molecules are expressed in adult myoblast cultures and localize adjacent to Pax7 in muscle sections. These gene expressions are regulated during postnatal muscle growth in chicks. Most importantly, we report that Shh induces MAPK/ERK and phosphoinositide 3-kinase (PI3K)-dependent Akt phosphorylation and that activation of both signaling pathways is essential for Shh's signaling in muscle cells. However, the effect of Shh on Akt phosphorylation is more robust than that on MAPK/ERK, and data suggest that Shh influences these pathways in a manner similar to IGF-I. By exploiting specific chemical inhibitors of the MAPK/ERK and PI3K/Akt signaling pathways, UO126 and Ly294002, respectively, we demonstrate that Shh-induced Akt phosphorylation, but not that of MAPK/ERK, is required for its promotive effects on muscle cell proliferation and differentiation. Taken together, we suggest that Shh acts in an autocrinic manner in adult myoblasts, and provide first evidence of a role for PI3K/Akt in Shh signaling during myoblast differentiation.