Effects of vasoactive intestinal peptide on glycogenolysis in cultured liver cells.

When isolated rat liver cells were incubated in the presence of vasoactive intestinal peptide at the concentrations ranging from 0.2 microgram to 2 micrograms per ml, glycogenolysis was maximally stimulated within 15 min. However, somatostatin inhibited the liver glycogenolysis. The combined addition to the incubation medium showed that insulin and somatostatin inhibited the stimulated glycogenolysis induced by vasoactive intestinal peptide, while vasoactive intestinal peptide plus secretin showed no additive effect on glycogenolysis, as compared with single the addition of vasoactive intestinal peptide. On the other hand, the additon of glucagon to vasoactive intestinal peptide showed additive effects on glycogenolysis. These results suggest that the receptor site for vasoactive intestinal peptide may be distinguishable from that for glucagon. Extracellular calcium ions were demonstrated to play an important role in the modulation of vasoactive intestinal peptide-induced glycogenolysis. The evidence presented in this paper indicates that glucose metabolism may be partly regulated by the direct action of vasoactive intestinal peptide on hepatocytes, which is referred to as an enterohepatic axis and that the axis is inhibited by insulin and somatostatin.     

Variation in cannibalistic polyphenism between populations in the salamander Hynobius retardatus

Organisms sometimes change their phenotype to maximize fitness according to local environments. If the frequency of the broad-headed "cannibal" morph in the larvae of the salamander Hynobius retardatus has been evolutionarily maintained at a certain level within a population as a result of local adaptation, variations in its frequency should be found among different populations with environmental variation. We investigated whether variations in the frequency of the broad-headed morph were present in 2 different populations, Nopporo (a low-density population) and Erimo (a high-density population), by raising larvae from the respective populations under the same experimental conditions. The occurrence rate of the broad-headed "cannibal" morph was significantly different between the 2 populations when examined with different experimental larval densities. These results suggest that the reaction norm with respect to the frequency of the broad-headed morph is different between the Nopporo and Erimo populations. Because the local populations are assumed to be selected for under different environments, the different reaction norm might have evolved in response to different selection pressures.     

The crystal structure of N(1)-[2-(2-amino-ethylamino)-ethyl]-ethane-1,2-diamine (polyamines) binding to the minor groove of d(CGCGCG)(2), hexamer at room temperature

A novel experimental technique, based on atomic force microscopy (AFM), is proposed to visualize the lateral organization of membrane systems in the nanometer range. The technique involves the use of a ligand-receptor pair, biotin-avidin, which introduces a height variation on a solid-supported lipid bilayer membrane. This leads to a height amplification of the lateral membrane organization that is large enough to be clearly imaged by scanning AFM. The power of the technique is demonstrated for a binary dipalmitoylphosphocholine-diarachidoylphosphocholine lipid mixture which is shown to exhibit a distinct lateral lipid domain formation. The new and simple ligand-receptor-based AFM approach opens up new ways to investigate lipid membrane microstructure in the nanometer range as well as the lateral distribution of ligand-lipid and receptor-protein complexes in supported membrane systems.     

Human DNA replication-related element binding factor (hDREF) self-association via hATC domain is necessary for its nuclear accumulation and DNA binding

We previously demonstrated that hDREF, a human homologue of Drosophila DNA replication-related element binding factor (dDREF), is a DNA-binding protein predominantly distributed with granular structures in the nucleus. Here, glutathione S-transferase pulldown and chemical cross-linking assays showed that the carboxyl-terminal hATC domain of hDREF, highly conserved among hAT transposase family members, possesses self-association activity. Immunoprecipitation analyses demonstrated that hDREF self-associates in vivo, dependent on hATC domain. Moreover, analyses using a series of hDREF mutants carrying amino acid substitutions in the hATC domain revealed that conserved hydrophobic amino acids are essential for self-association. Immunofluorescence studies further showed that all hDREF mutants lacking self-association activity failed to accumulate in the nucleus. Self-association-defective hDREF mutants also lost association with endogenous importin beta1. Moreover, electrophoretic gel-mobility shift assays revealed that the mutations completely abolished the DNA binding activity of hDREF. These results suggest that self-association of hDREF via the hATC domain is necessary for its nuclear accumulation and DNA binding. We also found that ZBED4/KIAA0637, another member of the human hAT family, also self-associates, again dependent on the hATC domain, with deletion resulting in loss of efficient nuclear accumulation. Thus, hATC domains of human hAT family members appear to have conserved functions in self-association that are required for nuclear accumulation.     

Characterization of the catalytic domains of <Emphasis Type="Italic">Trichoderma reesei</Emphasis> endoglucanase I,II, and III,expressed in <Emphasis Type="Italic">Escherichia coli</Emphasis>

The genes encoding the catalytic domains (CD) of the three endoglucanases (EG I; Cel7B, EG II; Cel5A, and EG III; Cel12A) from Trichoderma reesei QM9414 were expressed in Escherichia coli strains Rosetta-gami B (DE3) pLacI or Origami B (DE3) pLacI and were found to produce functional intracellular proteins. Protein production by the three endoglucanase transformants was evaluated as a function of growth temperature. Maximal productivity of EG I-CD at 15°C, EG II-CD at 20°C and EG III at 37°C resulted in yields of 6.9, 72, and 50 mg/l, respectively. The endoglucanases were purified using a simple purification method based on removing E. coli proteins by isoelectric point precipitation. Specific activity toward carboxymethyl cellulose was found to be 65, 49, and 15 U/mg for EG I-CD, EG II-CD, and EG III, respectively. EG II-CD was able to cleave 1,3–1,4-β-d-glucan and soluble cellulose derivatives. EG III was found to be active against cellulose, 1,3–1,4-β-d-glucan and xyloglucan, while EG I-CD was active against cellulose, 1,3–1,4-β-d-glucan, xyloglucan, xylan, and mannan.     

When should signals of submission be given?-A game theory model

During contests, losing animals often show signals communicating submission. From an evolutionary viewpoint, however, it is not so obvious why the losing individual gives such a signal instead of running away and why the winning individual accepts the signal instead of inflicting more severe damage. We investigated factors influencing the evolution of signals of submission using a numerical ESS model. The present analysis reveals that there is much space for the evolution of signals of submission, even when the winner of an escalated contest gets some extra benefit. In most cases, signals of submission are given by animals which are slightly or moderately weaker than the opponent. Signals of submission are expected to occur frequently (1) when the value of contested resource does not differ greatly from the cost of injury, (2) when the extra benefit of winning an escalated contest is small, (3) when the opportunity for safe retreat by the losing animal is small, and (4) when the estimation of the difference in the resource holding potential (RHP) between the combatants is accurate but not perfect.