Adenovirus early gene products may control viral mRNA accumulation and translation in vivo

The mechanisms controlling early adenovirus gene expression in vivo have been studied using inhibitors of protein synthesis. When inhibitors were added shortly before or at the onset of infection, viral mRNA from all early regions was transcribed, spliced and accumulated over a 7 hr period. After longer pretreatment, accumulation of several early mRNAs were suppressed. Addition of inhibitors 1 hr after infection enhanced the accumulation of viral mRNA in the cytoplasm. Translation of early mRNA selected on adenovirus DNA in a cell-free system reflected the amount of viral mRNA present. A viral coded product may therefore control accumulation of viral mRNA.A different pattern emerged when inhibitors of protein synthesis were removed at 5 hr postinfection and cells were pulse-labeled in vivo. If inhibitors were introduced at or before infection, early viral proteins were synthesized only after a lag of 1–3 hr. However, if treatment was introduced 1 hr post-infection, reversion of the protein synthesis block was instantaneous. It appears that protein synthesis inhibitors reveal an in vivo translational block for viral mRNA. This block could be overcome by preinfection with a related virus. Furthermore, no block was observed in a virus-transformed human embryonic kidney cell line (293) which expresses early region 1 of the viral genome. Viral gene product(s) encoded in early region 1 may control translation of early adenovirus messenger RNA in vivo.     

Structure of Cu2(indomethacin)4 and the reaction with superoxide in aprotic systems

The copper complex of indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate), a common anti-inflammatory drug, was prepared and characterized. Crystal structure determination revealed the dimeric form of the 1:2 complex, namely Cu₂(indomethacin)₄ · L₂, in the unit cell. Suprisingly, the copper-copper distance (263 pm) was very close to metallic copper (256 pm). The two coordination sites in the copper-copper axis can be readily replaced by superoxide. An intriguing similarity to Cu₂(acetate)₄ was seen.Due to the lipophilic nature of the indomethacin ligand, this copper complex reacted with superoxide in aprotic solvents. The superoxide dismutating activity was successfully demonstrated in Me₂SO/water and acetonitrile/water mixtures using the nitro-blue tetrazolium assay and pulse radiolysis. The second-order rate constant of 6 · 10⁹ M^?1 · s^?1 in strictly aqueous systems dropped only slightly to 1.1 · 10⁹ M^?1 · s^?1 when aprotic solvents were used. This is the fastest rate constant ever observed for a copper-dependent dismutation of superoxide. The KO₂-induced lipid peroxidation in both erythrocytes and liver microsomes was suppressed by 70% in the presence of 1 · 10^?10 mol · ml^?1 of Cu₂(indomethacin)₄. The inhibitory action dropped to 25% when Cu₂Zn₂superoxide dismutase was employed. The formation of copper · indomethacin in rat serum after administration of indomethacin was shown in vitro and in vivo.     

Biological rhythms in birds — development, insights and perspectives

The aim of this review is to show that probably the internal clock of precocial birds is imprinted in the prenatal period by exogenous factors (zeitgeber). The activity of organ functions occurs early during embryonic development, before this function is ultimately necessary to ensure the survival of the embryo. Prenatal activation of some functional systems may have a training effect on the postnatal efficiency.The development of physiological control systems is influenced by endogenous and exogenous factors during the late prenatal and early postnatal period: epigenetic adaptation processes play an important role in the development of animals; they have acquired characteristics which are innated but not genetically fixed. As a rule, the actual value during the determination period has a very strong influence on the set-point of the system. This will be explained using the example of thermoregulation.It is shown in detail that it seems to be possible to imprint the prenatal development of circadian rhythms by periodic changes of the light-dark cycle but not by rhythmic influence of acoustic signals.Altogether, there are more questions open than solved concerning the perinatal genesis of circadian rhythms in birds. Topics are given for the future research.     

The relationship between turgor pressure and titratable acidity in mesophyll cells of intact leaves of a Crassulacean-acid-metabolism plant,Kalanchoe daigremontiana Hamet et Perr

Day/night changes in turgor pressure (P) and titratable acidity content were investigated in the (Crassulacean-acid-metabolism (CAM) plant Kalanchoe daigremontiana. Measurements of P were made on individual mesophyll cells of intact attached leaves using the pressure-probe technique. Under conditions of high relative humidity, when transpiration rates were minimal, changes in P correlated well with changes in the level of titratable acidity. During the standard 12 h light/12 h dark cycle, maximum turgor pressure (0.15 MPa) occurred at the end of the dark period when the level of titratable acidity was highest (about 300 eq H⁺·g^-1 fresh weight). A close relationship between P and titratable acidity was also seen in leaves exposed to perturbations of the standard light/dark cycle. (The dark period was either prolonged, or else only CO₂-free air was supplied in this period). In plants deprived of irrigation for five weeks, diurnal changes in titratable acidity of the leaves were reduced (H=160 eq H⁺·g^-1 fresh weight) and P increased from essentially zero at the end of the light period to 0.02 MPa at the end of the dark period. Following more severe water stress (experiments were made on leaves which had been detached for five weeks), P was zero throughout day and night, yet small diurnal changes in titratable acidity were still measured. These findings are discussed in relation to a hypothesis by Lüttge et al. 1975 (Plant Physiol. 56,613-616) for the role of P in the regulation of acidification/de-acidification cycles of plants exhibiting CAM.Abbreviations CAM crassulacean acid metabolism - FW fresh weight - P turgor pressure