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Beryllium has multiple industrial applications, but its manufacture is associated with a serious occupational risk of developing chronic inflammation in the lungs known as berylliosis, or chronic beryllium disease. Although the Be2+-induced abnormal immune responses have recently been linked to a specific MHC-II allele, the nature of long-lasting granulomas is not fully understood. Here we show that Be2+binds with a micromolar affinity to phosphatidylserine (PS), the major surface marker of apoptotic cells. Isothermal titration calorimetry indicates that, like that of Ca2+, binding of Be2+to PS liposomes is largely entropically driven, likely by massive desolvation. Be2+exerts a compacting effect on PS monolayers, suggesting cross-linking through coordination by both phosphates and carboxyls in multiple configurations, which were visualized in molecular dynamics simulations. Electrostatic modification of PS membranes by Be2+includes complete neutralization of surface charges at ∼30 μM, accompanied by an increase in the boundary dipole potential. The data suggest that Be2+can displace Ca2+from the surface of PS, and being coordinated in a tight shell of four oxygens, it can mask headgroups from Ca2+-mediated recognition by PS receptors. Indeed, 48 μM Be2+added to IC-21 cultured macrophages specifically suppresses binding and engulfment of PS-coated silica beads or aged erythrocytes. We propose that Be2+adsorption at the surface of apoptotic cells may potentially prevent normal phagocytosis, thus causing accumulation of secondary necrotic foci and the resulting chronic inflammation.

Nebulette physically links desmin to sarcomeric actin in hearts. An intact desmin network is required for nebulette to function as major actin-binding protein in sarcomeres. This study provides biochemical evidence that the desmin–nebulette complex is involved in filament-forming desminopathy.

While biological membrane fusion is classically defined as the leak-free merger of membranes and contents, leakage is a finding in both experimental and theoretical studies. The fusion stages, if any, that allow membrane permeation are uncharted. In this study we monitored membrane ionic permeability at early stages of fusion mediated by the fusogenic protein influenzahemagglutinin (HA). HAb2 cells, expressing HA on their plasma membrane, fused with human red blood cells, cultured liver cells PLC/PRF/5, or planar phospholipid bilayer membranes. With a probability that depended upon the target membrane, an increase of the electrical conductance of the fusing membranes (leakage) by up to several nS was generally detected. This leakage was recorded at the initial stages of fusion, when fusion pores formed. This leakage usually accompanied the “flickering” stage of the early fusion pore development. As the pore widened, the leakage reduced; concomitantly, the lipid exchange between the fusing membranes accelerated. We conclude that during fusion pore formation, HA locally and temporarily increases the permeability of fusing membranes. Subsequent rearrangement in the fusion complex leads to the resealing of the leaky membranes and enlargement of the pore.

Abstract: Pain threshold sensitivity determination and recording of somatosensory evoked potentials in response to electrical skin stimulation were used to study the dynamics of pain sensitivity in medical students in mid-semester before blood donor and examination procedures and in the post-procedure period during performance of an editing test. Increases in pain sensitivity thresholds were seen in all subjects during the examination period and on performance of the editing test. Differences in changes in evoked potential amplitudes were found, depending on the individual-typological characteristics of the nervous system and the quality of motivationally determined states. Subjects with different individual-typological characteristics had different subjective pain sensation dynamics in test conditions.

The topology of the tight junction is probed by introducing dipicrylamine (dpa-), a lipid-soluble anion, into the membranes of hepatocyte pairs in culture. Once partitioned into the membrane, dpa- ions are free to move in the hydrophobic core of the membrane, where their mobile charges greatly increase membrane capacitance. If tight junctions are lines of membrane fusion, dpa- will cross the tight junction without traversing a polar headgroup layer. Furthermore, the electric potential across the tight junction will be equal to the difference in membrane potentials of the two cells. dpa- can therefore be expected to move electrophoretically from cell membrane to cell membrane across the junction in response to an intercellular voltage difference. Experiments performed under double whole-cell clamp show that this transfer occurs as follows: First, dpa- causes an intercellular current unrelated to gap junctions to flow in response to an intercellular voltage difference. Second, this electrophoretic removal or addition of dpa- from a cell's membrane through the tight junction must reduce or increase its dpa- content and thus its capacitance. Experiments confirm this prediction: We detect rapid, symmetric, and reversible changes in membrane capacitance in response to changes in the membrane potential of the neighboring cell. Finally, we find that hepatocyte membranes contain a negatively charged endogenous molecule that contain a negatively charged endogenous molecule that can move from cell to cell like dpa- under the influence of an intercellular potential difference. We conclude that membrane fusion occurs at tight junctions and that this hydrophobic intercellular pathway can play a role in intercellular communication.

HeLa cells seem not to be junctionally coupled when probed with techniques such as Lucifer yellow spreading and/or ionic coupling measured with three inserted microelectrodes. When investigated with double whole-cell patch-clamp measurements, HeLa cells in monolayer cultures were electrically coupled in 39% of the cases with very low transjunctional conductances (average one to five open channels). These gapjunction channels had a single-channel conductance ?= 26±6 pS and were voltage-gated with an equivalent gating charge z=3.1±1.5 for a voltage of half-maximal inactivation Uo=49±10 mV. The voltage-dependent component represents only 31±8% of the total junctional conductance. The voltage-insensitive conductance is characterized by a residual open probability po(8)=0.34±0.12, which corresponds to a ratio Gmin/Gmax=0.50±0.12. Dissociation of monolayer cells into cell pairs yielded about 58% coupled cell pairs with no notably altered single-channel properties.

In 2004, we collected 211 specimens of European field mice (genus Apodemus; subgenus Sylvaemus) from 16 localities in northern, western, central, and southern Ukraine, including the Crimean Peninsula. We used cytochrome-b mitochondrial DNA sequence data to investigate species diversity, distributional patterns, and taxonomy of Apodemus in Ukraine. Sequence data proved useful for species-level discrimination, because the 11 species examined were defined by low levels of intraspecific variation (mean range, 0.00–3.35%) and by high levels of interspecific variation (mean range, 5.37–18.9%). We identified the 211 specimens to 1 of 4 species: A. flavicollis (n = 121), A. sylvaticus (n = 34), A. uralensis (n = 16), and A. witherbyi (n = 40). Although all 4 species are known from Ukraine, this study provides new information about the ranges and population identity for these species in southeastern Europe. For example, our analyses substantiate the marked genetic structure reported for A. sylvaticus and document the presence of northern and southern continental lineages of this species in Ukraine that are hypothesized to have been isolated from each other in glacial refugia approximately 1.5 million years ago (>5% genetic divergence). Banks of the Dneiper River in northern Ukraine represent an area of secondary contact for the 2 lineages. Additionally, although application of A. witherbyi as a species-level name is debatable, examination of our genetic and morphological data supports its validity and priority over junior synonyms A. hermonensis and A. iconicus.

Specimens may pose a risk to personnel handling them such as the radioactive fauna collected from contaminated areas in Chornobyl. To minimize radiation exposure and to evaluate an inexpensive molecular tool in identifying species of shrew, we analyzed DNA sequences from the cytochrome-b gene. Specimens were visually identified as Sorex araneus, S. minutus, and Neomys fodiens, and morphological variants were noted that could represent additional species. Cytochrome-b sequences indicated the apparent variants represented intraspecific polymorphisms. This approach substantially reduced exposure to radioactivity present in the archived material. Excluding salaries and cost of equipment, the analytical cost per specimen was US$9.00. The benefit and accuracy in identifying specimens this way is justified based on the reduction of risk these samples may pose.