Specific stimulation of ribosomal RNA synthesis in E. coli by a protein factor

Summary Ribosomal RNA synthesis in a purified system is stimulated by a crude protein fraction prepared from E. coli. The positive effector which is not associated with RNA polymerase, nor is the sigma factor, increases the initiation frequency on a rRNA operon. The additional rRNA synthesis is inhibited by ppGpp to the same extent as the basal one.The evidence presented points to the existence of a positive control element for rRNA synthesis, which activity depends upon the physiological state of the cell.     

Synthesis of malvidin and petunidin in pigmented tissue cultures ofPetunia hybrida

Summary In petunia cells culturedin vitro anthocyanin synthesis is usually repressed resulting in white/ yellow cells. However, we observed that in petunia strain AK-5000 purple cells appeared at a frequency of about 5 × 10^–5. Analysis of the pigments showed that these cells contained the same anthocyanidins (petunidin and malvidin) as found in corollas of the parental plants. This suggests an induction of anthocyanin synthesis in these cells. In white/yellow cells, from which these pigmented cells originated, we could not observe any of the known precursors of these pigments.     

NEUROCHEMICAL PROPERTIES OF ADRENERGIC NERVES REGENERATED AFTER 6-HYDROXYDOPAMINE

Abstract— The uptake-storage properties and synthesis of noradrenaline, and fluorescence morphology of adrenergic nerves which have been allowed to regenerate for 4 weeks after a chemical sympathectomy produced by 6-hydroxydopamine have been investigated in mouse iris and atrium. The regenerated nerve terminals displayed a lower formaldehyde-induced fluorescence intensity whereas the non-terminal axons exhibited a stronger fluorescence intensity and a more beaded appearance compared with mature nerves. The endogenous noradrenaline concentration after 6-hydroxydopamine was 30% in iris and 45% in atrium compared to control values. Recovery of [³H]noradrenaline uptake was found to be more rapid than that of endogenous noradrenaline concentration after the 6-hydroxydopamine treatment. [³H]Noradrenaline uptake in regenerating and adult mature nerves both obeyed Michaelis-Menten kinetics having identical K_m values. There was a close correlation between [³H]noradrenaline uptake and nerve density of adrenergic nerves regenerated after 6-hydroxydopamine. These results show that [³H]noradrenaline uptake is a better index for the number of regenerated nerve terminals than is the endogenous noradrenaline concentration. The retention of [³H]noradrenaline taken up and accumulated in vitro was about the same in regenerated and mature nerves, although a slight tendency to less effective retention was observed in the regenerated nerves. Subcellular distribution studies showed that relatively less [³H]noradrenaline was recovered in the microsomal fraction after 6-hydroxydopamine treatment. The formation of ¹⁴C-labelled catecholamines from [¹⁴C]DOPA was higher in regenerating nerves than indicated by the endogenous noradrenaline concentration but lower than that indicated by the [³H]noradrenaline. It is concluded that the regenerating nerves contain less endogenous noradrenaline than adult mature nerves and that the uptake mechanism develops promptly, whereas the development of the storage mechanism lags behind.     

The "two-state folder" MerP forms partially unfolded structures that show temperature dependent hydrogen exchange

We have analysed the folding energy landscape of the 72 amino acid protein MerP by monitoring native state hydrogen exchange as a function of temperature in the range of 7-55 degrees C. The temperature dependence of the hydrogen exchange has allowed us to determine DeltaG, DeltaH and DeltaC(p) values for the conformational processes that permit hydrogen exchange. When studied with the traditional probes, fluorescence and CD, MerP appears to behave as a typical two-state protein, but the results from the hydrogen exchange analysis reveal a much more complex energy landscape. Analysis at the individual amino acid level show that exchange is allowed from an ensemble of partially unfolded structures (i.e. intermediates) in which the stabilities at the amino acid level form a broad distribution throughout the protein. The formation of partially unfolded structures might contribute to the unusually slow folding of MerP.     

Behavioural comparison of human-animal (dog) and human-robot (AIBO) interactions

The behavioural analysis of human-robot interactions can help in developing socially interactive robots. The current study analyzes human-robot interaction with Theme software and the corresponding pattern detection algorithm. The method is based on the analysis of the temporal structure of the interactions by detecting T-patterns in the behaviour. We have compared humans' (children and adults) play behaviour interacting either with an AIBO or a living dog puppy. The analysis based on measuring latencies and frequencies of behavioural units suggested limited differences, e.g. the latency of humans touching the dog/AIBO was similar. In addition other differences could be accounted for by the limited abilities of the robot to interact with objects. Although the number of interactive T-patterns did not significantly differ among the groups but the partner's type (whether humans were playing with dog or AIBO) had a significant effect on the structure of the patterns. Both children and adults terminated T-patterns more frequently when playing with AIBO than when playing with the dog puppy, which suggest that the robot has a limited ability to engage in temporally structured behavioural interactions with humans. As other human studies suggest that the temporal complexity of the interaction is good measure of the partner's attitude, we suggest that more attention should be paid in the future to the robots' ability to engage in cooperative interaction with humans.     

Spatial and temporal density dependence regulates the condition of central Baltic Sea clupeids: compelling evidence using an extensive international acoustic survey

For the first time an international acoustic survey dataset covering three decades was used to investigate the factors shaping the spatial and temporal patterns in the condition of sprat and herring in the Baltic Proper. Generalized additive models showed that the spatial and temporal fluctuations in sprat density have been the main drivers of the spatio-temporal changes of both sprat and herring condition, evidencing intra- and inter-specific density dependence mediated by the size and distribution of the sprat population. Salinity was also an important predictor of herring condition, whereas temperature explained only a minor part of sprat model deviance. Herring density was an additional albeit weak significant predictor for herring condition, evidencing also intra-specific density dependence within the herring population. For both species, condition was high and similar in all areas of the Baltic Proper until the early 1990s, coincident with low sprat densities. Afterwards, a drop in condition occurred and a clear south–north pattern emerged. The drop in condition after the early 1990s was stronger in the northern areas, where sprat population increased the most. We suggest that the increase in sprat density in the northern areas, and the consequent spatial differentiation in clupeid condition, have been triggered by the almost total disappearance of the predator cod from the northern Baltic Proper. This study provides a step forward in understanding clupeid condition in the Baltic Sea, presenting evidence that density-dependent mechanisms also operate at the spatial scale within stock units. This stresses the importance of spatio-temporal considerations in the management of exploited fish.     

Laboratory studies on Australian isolates of Metarhizium anisopliae as a biopesticide for the cattle tick Boophilus microplus

Thirty-one isolates of Metarhizium anisopliae were bioassayed against the cattle tick (Boophilus microplus). More than half of the isolates showed a high degree of virulence to ticks. Radial growth curves for growth between 20 degrees C and 40 degrees C were obtained for all isolates. This information together with information on virulence will be important for the selection of isolates suitable to kill ticks on the surface of cattle. A biopesticide for cattle ticks must kill ticks rapidly at temperatures within the upper end of most isolates' growth curves. It was also found that the time taken to achieve 100% tick mortality in vitro using a virulent isolate could be halved by applying conidia in a 10% oil emulsion. Scanning electron microscopy and light microscopy were used to investigate and compare the germination and penetration of conidia formulated in aqueous and oil formulations. It was found that conidia in both formulations were able to germinate and produce appressoria on the surface of ticks in less than 11h. Marked weakness within 26h, followed by extensive hyphal growth on the cuticle characterised the invasion of ticks by M. anisopliae.     

Developmental plasticity of central noradrenaline neurons after neonatal damage--changes in transmitter functions.

The effects of neonatal 6-hydroxydopamine (6-OH-DA) treatment (systemic administration) on noradrenaline (NA) metabolism, turn over, and receptor characteristics have been investigated in rat brain in the adult stage. This treatment is known to preferentially affect the locus coeruleus (LC) NA system leading to a marked NA denervation in the central cortex and hyperinnervation of NA nerve terminals in the pons and medulla oblongata without influencing the LC perikarya. The main NA metabolite, 3-methoxy-4-hydroxy-phenylglycol (MOPEG) was reduced by about 70% in the cerebral cortex after 6-OH-DA treatment at birth while the endogenous NA was almost completely depleted (-92%). The MOPEG levels were not significantly changed in the pons medulla after 6-OH-DA treatment in contrast to the 60% increase of the endogenous NA concentration. The relative reduction of NA in the cerebral cortex of 6-OH-DA treated rats increased in the cerebral cortex following administration of the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine (H44/68) compared to the control, while the H44/68 induced depletion of NA was reduced in the pons medulla after 6-OH-DA. The steady-state level of endogenous NA and the effect of H44/68 were unchanged in the LC perikarya after 6-OH-DA treatment. These results indicate that the NA turn over in remaining NA nerve terminals in the cerebral cortex is increased after 6-OH-DA, while decreased in the pons-medulla, possible related to changes in the activation of presynaptic alpha-adrenoreceptors in both regions. NA-induced formation of cAMP in vitro was found to be markedly increased in the cerebral cortex after 6-OH-DA, whereas no consistent change was observed in the pons medulla. Measurements of alpha- and beta-receptor binding in vitro using radioligand techniques showed an increase of binding sites (20%--50%) for both receptors in the neocortex aster 6-OH-DA, whereas no changes were observed in the pons medulla. The 6-OH-DA induced changes in NA turnover, cAMP generating systems, and receptor density may all represent compensatory processes following the altered development of the NA neurons induced by 6-OH-DA.     

Solution structure and characterization of the DNA-binding activity of the B3BP-Smr domain

The MutS1 protein recognizes unpaired bases and initiates mismatch repair, which are essential for high-fidelity DNA replication. The homologous MutS2 protein does not contribute to mismatch repair, but suppresses homologous recombination. MutS2 lacks the damage-recognition domain of MutS1, but contains an additional C-terminal extension: the small MutS-related (Smr) domain. This domain, which is present in both prokaryotes and eukaryotes, has previously been reported to bind to DNA and to possess nicking endonuclease activity. We determine here the solution structure of the functionally active Smr domain of the Bcl3-binding protein (also known as Nedd4-binding protein 2), a protein with unknown function that lacks other domains present in MutS proteins. The Smr domain adopts a two-layer α-β sandwich fold, which has a structural similarity to the C-terminal domain of IF3, the R3H domain, and the N-terminal domain of DNase I. The most conserved residues are located in three loops that form a contiguous, exposed, and positively charged surface with distinct sequence identity for prokaryotic and eukaryotic Smr domains. NMR titration experiments and DNA binding studies using Bcl3-binding protein-Smr domain mutants suggested that these most conserved loop regions participate in DNA binding to single-stranded/double-stranded DNA junctions. Based on the observed DNA-binding-induced multimerization, the structural similarity with both subdomains of DNase I, and the experimentally identified DNA-binding surface, we propose a model for DNA recognition by the Smr domain.