Interactions of lipid micelles with blood proteins

Interaction of lipid micelles (LM), containing cholesterol and hydroxycholesterol, with human serum lipoproteins was investigated. It was shown that cholesterol-containing LM interact with low density lipoproteins (LDL). Selectivity of LM-LDL interaction depended on the cholesterol content of micelles and almost did not depend on the composition of LM core. Up to 90% of LDL were bound with cholesterol-saturated LM. By means of gel chromatography it was shown that interaction of cholesterol- and 7-hydroxycholesterol-containing micelles with serum led to the partial fusion of LDL with LM and LDL-LM complex formation, as well as to the cholesterol and 7-hydroxycholesterol transfer from micelles to LDL. The obtained results indicate that cholesterol-containing LM can be used for the delivery of oxidized cholesterol to cells involving LDL and receptor-dependent pathway of their capture by peripheral cells.     

Thermohaemolysis of human erythrocytes in sucrose containing isotonic media

1. 1.|The thermohaemolysis of human erythrocytes in NaCl/sucrose isotonic media can be best accounted for in terms of the colloid-osmotic theory of haemolysis.

2. 2.|The thermohaemolysis in NaCl saline was preceded by leakage of K⁺ and cell swelling. If the inner oncotic osmoactivity was balanced with external sucrose the cells progressively shrinked losing K⁺, but the haemolysis was strongly reduced.

3. 3.|Time dependence of the shrinking of cells and one-step resealed ghosts suspended in isotonic 60 mOsm NaCl/sucrose media was studied between 50 and 58°C.

4. 4.|After a lag period for cells only, this shrinking proceeded with apparently constant rate for cells and ghosts.

5. 5.|The rate constant of shrinking for cells and ghosts obeys the Arrhenius relation, giving the value of 250 ± 15 kJ/mol for the activation energy of shrinking in both cases. This is also the case for the activation energy of the membrane ion permeability constant.

6. 6.|These results are consistent with the thermal inactivation of membrane associated protein(s) acting as a trigger for the ion permeability barrier disturbance.

7. 7.|The mid-point temperature for these membrane events was about 61°C.

Organization of human replicon: Singles or zipping couples?

According to a general paradigm, proper DNA duplication from each replication origin is ensured by two protein complexes termed replisomes. In prokaryotes and in budding yeast Saccharomyces cerevisiae, these two replisomes seem to be associated with one another until DNA replication initiated from the origin has finished. This arrangement results in the formation of the loop of newly synthesized DNA. However, arrangement of replisomes in other eukaryotic organisms including vertebrate cells is largely unknown. Here, we used in vivo labeling of DNA segments in combination with the electron microscopy tomography to describe the organization of replisomes in human HeLa cells. The experiments were devised in order to distinguish between a model of independent replisomes and a model of replisome couples. The comparative analysis of short segments of replicons labeled in pulse-chase experiments of various length shows that replisomes in HeLa cells are organized into the couples during DNA replication. Moreover, our data enabled to suggest a new model of the organization of replicated DNA. According to this model, replisome couples produce loop with the associated arms in the form of four tightly associated 30 nm fibers.     

Basal forebrain cholinergic system in the dementias: Vulnerability,resilience, and resistance

The basal forebrain cholinergic neurons (BFCN) provide the primary source of cholinergic innervation of the human cerebral cortex. They are involved in the cognitive processes of learning, memory, and attention. These neurons are differentially vulnerable in various neuropathologic entities that cause dementia. This review summarizes the relevance to BFCN of neuropathologic markers associated with dementias, including the plaques and tangles of Alzheimer's disease (AD), the Lewy bodies of diffuse Lewy body disease, the tauopathy of frontotemporal lobar degeneration (FTLD-TAU) and the TDP-43 proteinopathy of FTLD-TDP. Each of these proteinopathies has a different relationship to BFCN and their corticofugal axons. Available evidence points to early and substantial degeneration of the BFCN in AD and diffuse Lewy body disease. In AD, the major neurodegenerative correlate is accumulation of phosphotau in neurofibrillary tangles. However, these neurons are less vulnerable to the tauopathy of FTLD. An intriguing finding is that the intracellular tau of AD causes destruction of the BFCN, whereas that of FTLD does not. This observation has profound implications for exploring the impact of different species of tauopathy on neuronal survival. The proteinopathy of FTLD-TDP shows virtually no abnormal inclusions within the BFCN. Thus, the BFCN are highly vulnerable to the neurodegenerative effects of tauopathy in AD, resilient to the neurodegenerative effect of tauopathy in FTLD and apparently resistant to the emergence of proteinopathy in FTLD-TDP and perhaps also in Pick's disease. Investigations are beginning to shed light on the potential mechanisms of this differential vulnerability and their implications for therapeutic intervention.

     

Antiviral activity of acyclic nucleoside phosphonates PMEA, (S)-HPMPC, PMEDAP and ribavirin against Cauliflower mosaic virus in Brassica pekinensis

Antiviral effects of acyclic nucleoside phosphonates PMEA, (S)-HPMPC, PMEDAP, and ribavirin on double-stranded DNA Cauliflower mosaic virus (CaMV) were evaluated in Brassica pekinensis plants grown in vitro on liquid medium. A double-antibody sandwich ELISA was used for relative quantification of viral protein and PCR for detection of CaMV nucleic acid in plants. Ribavirin and PMEA had no significant antiviral effect. (S)-HPMPC at concentration 50?mg?l^?1 and PMEDAP at concentrations 50 and 12.5?mg?l^?1 significantly (P?<?0.05) reduced CaMV concentration in plants within 42?C63?days to levels detectable neither by ELISA nor by PCR. A phytotoxicity experiment resulted in progressive yellowing of leaves and dwarfing in plants cultured 42?days on media with concentrations 12.5, 25 and 50?mg?l^?1 of (S)-HPMPC and PMEDAP. Reduction in fresh and dry weights of plants was significant (P?<?0.05) already at 12.5?mg?l^?1 with both compounds.     

Effects of Endolithic Parasitism on Invasive and Indigenous Mussels in a Variable Physical Environment

Biotic stress may operate in concert with physical environmental conditions to limit or facilitate invasion processes while altering competitive interactions between invaders and native species. Here, we examine how endolithic parasitism of an invasive and an indigenous mussel species acts in synergy with abiotic conditions of the habitat. Our results show that the invasive Mytilus galloprovincialis is more infested than the native Perna perna and this difference is probably due to the greater thickness of the protective outer-layer of the shell of the indigenous species. Higher abrasion due to waves on the open coast could account for dissimilarities in degree of infestation between bays and the more wave-exposed open coast. Also micro-scale variations of light affected the level of endolithic parasitism, which was more intense at non-shaded sites. The higher levels of endolithic parasitism in Mytilus mirrored greater mortality rates attributed to parasitism in this species. Condition index, attachment strength and shell strength of both species were negatively affected by the parasites suggesting an energy trade-off between the need to repair the damaged shell and the other physiological parameters. We suggest that, because it has a lower attachment strength and a thinner shell, the invasiveness of M. galloprovincialis will be limited at sun and wave exposed locations where endolithic activity, shell scouring and risk of dislodgement are high. These results underline the crucial role of physical environment in regulating biotic stress, and how these physical-biological interactions may explain site-to-site variability of competitive balances between invasive and indigenous species.     

Comparative study of chromosomal nonhistone proteins pp23 in cells from different types of tissue]

A specific immunoserum against nonhistone chromosomal protein pp23 from rat kidney was produced. A similar protein was obtained in cells of different tissue specificity (in the liver cells of rats submitted to a single effect of hepatocarcinogens, in rat hepatomas G-27, HTC, Zajdela, in cultivated non-tumor myogenic L6 cells and in kidney cells of newborn rats) by means of immunofluorescent method on using this immunoserum. In all cases a specific fluorescence of the nucleus and nuclear membrane was observed.