Ion channel block in rat diaphragm by the venom of the digger wasp Philanthus triangulum

In the rat phrenic nerve-diaphragm preparation the twitch tension and tetanic contractions, already reduced by d-tubocurarine, succinylchloride or neostigmine, are further reduced by the venom of the digger wasp Philanthus triangulum F. The venom reduces the temperature- and voltage-sensitivity of the acetylcholine-receptor-activated ion channels, at the motor end-plate, and shortens the decay time of the miniature end-plate currents, analogous to a block described for the purified toxin, delta-PTX, on insect glutamate-activated channels. Preliminary results show that delta-PTX has an effect similar to that of the total venom on the decay phase of miniature end-plate currents.     

Effects of monocarboxylates and external pH on some parameters of insect muscle fibres

The resting membrane potential and the conductance of flight muscle fibres of the butterfly Pieris brassicae were measured by means of two intracellular electrodes. The intracellular potassium, chloride, and hydrogen ion concentrations were estimated by measuring the concentrations in diluted muscle homogenates. Chloride in the bath was replaced in part by monocarboxylates and the pH was subsequently lowered. Replacement of chloride by propionate caused decrease in the internal chloride concentration, a marked hyperpolarization and a small increase in conductance. Lowering the pH in the propionate saline caused an additional decrease in the internal chloride concentration, an increase in the internal hydrogen ion concentration, a marked depolarization and a concurrent decrease in conductance. This was followed by an irreversible increase in conductance. With glycolate the effects on the membrane parameters were small and with pyruvate no effect was observed.     

Smooth muscle contracting compounds in the venom of Megascolia flavifrons (Hym: Scoliidae) with notes on the stinging behaviour

1. The wasp Megascolia flavifrons stings larvae of the stag beetle Oryctes nasicornis on the ventral side of all segments, except the last three, which do not contain nerve ganglia. 2. Experiments indicate a central rather than a peripheral action of the venom. 3. From pharmacological analysis it is concluded that the venom does not contain cholinergic or serotonergic activity, but contains histamine- and bradykinin-like substances. 4. The presence of histamine was confirmed by a radioenzymatic method.     

Improved reduced representation bisulfite sequencing for epigenomic profiling of clinical samples

Background

DNA methylation plays crucial roles in epigenetic gene regulation in normal development and disease pathogenesis. Efficient and accurate quantification of DNA methylation at single base resolution can greatly advance the knowledge of disease mechanisms and be used to identify potential biomarkers. We developed an improved pipeline based on reduced representation bisulfite sequencing (RRBS) for cost-effective genome-wide quantification of DNA methylation at single base resolution. A selection of two restriction enzymes (Taq^αI and MspI) enables a more unbiased coverage of genomic regions of different CpG densities. We further developed a highly automated software package to analyze bisulfite sequencing results from the Solexa GAIIx system.

Results

With two sequencing lanes, we were able to quantify ~1.8 million individual CpG sites at a minimum sequencing depth of 10. Overall, about 76.7% of CpG islands, 54.9% of CpG island shores and 52.2% of core promoters in the human genome were covered with at least 3 CpG sites per region.

Conclusions

With this new pipeline, it is now possible to perform whole-genome DNA methylation analysis at single base resolution for a large number of samples for understanding how DNA methylation and its changes are involved in development, differentiation, and disease pathogenesis.     

Transgenic expression of stromal cell-derived factor-1/CXC chemokine ligand 12 enhances myeloid progenitor cell survival/antiapoptosis in vitro in response to growth factor withdrawal and enhances myelopoiesis in vivo

Hemopoiesis is regulated in part by survival/apoptosis of hemopoietic stem/progenitor cells. Exogenously added stromal cell-derived factor-1 ((SDF-1)/CXC chemokine ligand (CXCL)12) enhances survival/antiapoptosis of myeloid progenitor cells in vitro. To further evaluate SDF-1/CXCL12 effects on progenitor cell survival, transgenic mice endogenously expressing SDF-1/CXCL12 under a Rous sarcoma virus promoter were produced. Myeloid progenitors (CFU-granulocyte-macrophage, burst-forming unit-erythroid, CFU-granulocyte-erythrocyte-megakaryocyte-monocyte) from transgenic mice were studied for in vitro survival in the context of delayed addition of growth factors. SDF-1-expressing transgenic myeloid progenitors were enhanced in survival and antiapoptosis compared with their wild-type littermate counterparts. Survival-enhancing effects were due to release of low levels of SDF-1/CXCL12 and mediated through CXCR4 and G(alpha)i proteins as determined by ELISA, an antagonist to CXCR4, Abs to CXCR4 and SDF-1, and pertussis toxin. Transgenic effects of low SDF-1/CXCR4 may be due to synergy of SDF-1/CXCL12 with other cytokines; low SDF-1/CXCL12 synergizes with low concentrations of other cytokines to enhance survival of normal mouse myeloid progenitors. Consistent with in vitro results, progenitors from SDF-1/CXCL12 transgenic mice displayed enhanced marrow and splenic myelopoiesis: greatly increased progenitor cell cycling and significant increases in progenitor cell numbers. These results substantiate survival effects of SDF-1/CXCL12, now extended to progenitors engineered to endogenously produce low levels of this cytokine, and demonstrate activity in vivo for SDF-1/CXCL12 in addition to cell trafficking.     

Exploratory Movement Generates Higher-Order Information That Is Sufficient for Accurate Perception of Scaled Egocentric Distance

Body movement influences the structure of multiple forms of ambient energy, including optics and gravito-inertial force. Some researchers have argued that egocentric distance is derived from inferential integration of visual and non-visual stimulation. We suggest that accurate information about egocentric distance exists in perceptual stimulation as higher-order patterns that extend across optics and inertia. We formalize a pattern that specifies the egocentric distance of a stationary object across higher-order relations between optics and inertia. This higher-order parameter is created by self-generated movement of the perceiver in inertial space relative to the illuminated environment. For this reason, we placed minimal restrictions on the exploratory movements of our participants. We asked whether humans can detect and use the information available in this higher-order pattern. Participants judged whether a virtual object was within reach. We manipulated relations between body movement and the ambient structure of optics and inertia. Judgments were precise and accurate when the higher-order optical-inertial parameter was available. When only optic flow was available, judgments were poor. Our results reveal that participants perceived egocentric distance from the higher-order, optical-inertial consequences of their own exploratory activity. Analysis of participants’ movement trajectories revealed that self-selected movements were complex, and tended to optimize availability of the optical-inertial pattern that specifies egocentric distance. We argue that accurate information about egocentric distance exists in higher-order patterns of ambient energy, that self-generated movement can generate these higher-order patterns, and that these patterns can be detected and used to support perception of egocentric distance that is precise and accurate.