Discovery and functional interrogation of SARS-CoV-2 RNA-host protein interactions

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Structure and thermotropic phase behaviour of detergent-resistant membrane raft fractions isolated from human and ruminant erythrocytes

Detergent-resistant membrane raft fractions have been prepared from human, goat, and sheep erythrocyte ghosts using Triton X-100. The structure and thermotropic phase behaviour of the fractions have been examined by freeze-fracture electron microscopy and synchrotron X-ray diffraction methods. The raft fractions are found to consist of vesicles and multilamellar structures indicating considerable rearrangement of the original ghost membrane. Few membrane-associated particles typical of freeze-fracture replicas of intact erythrocyte membranes are observed in the fracture planes. Synchrotron X-ray diffraction studies during heating and cooling scans showed that multilamellar structures formed by stacks of raft membranes from all three species have d-spacings of about 6.5 nm. These structures can be distinguished from peaks corresponding to d-spacings of about 5.5 nm, which were assigned to scattering from single bilayer vesicles on the basis of the temperature dependence of their d-spacings compared with the multilamellar arrangements. The spacings obtained from multilamellar stacks and vesicular suspensions of raft membranes were, on average, more than 0.5 nm greater than corresponding arrangements of erythrocyte ghost membranes from which they were derived. The trypsinization of human erythrocyte ghosts results in a small decrease in lamellar d-spacing, but rafts prepared from trypsinized ghosts exhibit an additional lamellar repeat 0.4 nm less than a lamellar repeat coinciding with rafts prepared from untreated ghosts. The trypsinization of sheep erythrocyte ghosts results in the phase separation of two lamellar repeat structures (d = 6.00; 5.77 nm), but rafts from trypsinized ghosts produce a diffraction band almost identical to rafts from untreated ghosts. An examination of the structure and thermotropic phase behaviour of the dispersions of total polar lipid extracts of sheep detergent-resistant membrane preparations showed that a reversible phase separation of an inverted hexagonal structure from coexisting lamellar phase takes place upon heating above about 30 °C. Non-lamellar phases are not observed in erythrocytes or detergent-resistant membrane preparations heated up to 55 °C, suggesting that the lamellar arrangement is imposed on these membrane lipids by interaction with non-lipid components of rafts and/or that the topology of lipids in the erythrocyte membrane survives detergent treatment.     

Neutrophil inhibition with L-selectin-directed MAb improves or worsens survival dependent on the route but not severity of infection in a rat sepsis model.

Both route and severity of infection may influence immunomodulator agents in sepsis. We studied the effect of each variable on HRL-3, an L-selectin-directed MAb that inhibits neutrophil function, in a rat sepsis model. Animals (n = 800) were randomized to be treated with either HRL-3 or placebo and to receive Escherichia coli either intravenously (IV) or intrabronchially (IB) in doses producing low or high mortality rates. Animals received antibiotics and were observed for 168 h. Route but not dose of E. coli altered the effects HRL-3 on mortality rate (mean hazards ratio +/- SE). With IV E. coli, compared with control, HRL-3 was beneficial and reduced the hazards ratio both early (0 to 6 h; -0.75 +/- 0.23) and late (6 to 168 h; -0.72 +/- 0.36) (P = 0.001 and 0.04, respectively, over all E. coli doses). In contrast, with IB E. coli HRL-3 reduced the hazards ratio early (-1.1 +/- 0.36) but worsened it late (0.87 +/- 0.23) (P = 0.002 for both effects over all E. coli doses) in patterns significantly different from IV E. coli (P < 0.0001). Compared with control, although HRL-3 did not alter lung neutrophil numbers or injury score at 6 or 168 h with IV E. coli (P = ns for all), it reduced both early and increased them late with IB E. coli (P 相似文献   

EMG median frequency changes in the neck–shoulder stabilizers of symptomatic office workers when challenged by different physical stressors

The problem of work-related neck and upper limb disorders among computer users has been reported extensively in the literature, and commonly cited risk factors include static posture, speed and force of keyboard operation. The present study examined changes in median frequency (MF) of the neck–shoulder muscles in symptomatic and asymptomatic office workers when they were exposed to these three physical stressors.

A quasi-experimental Case–Control design was used to examine MF changes in two groups of female office workers when they were subjected to controlled doses of computer work involving prolonged static posture, increased typing speed and increased typing force. The MF of four major neck–shoulder muscles were examined bilaterally and compared between groups.

The MF changes over time-at-task did not clearly illustrate any muscle fatigue mechanism. However, Case Group consistently showed trends for higher MF than the Control Group, and this pattern was observed in response to all three physical stressors. The consistent group differences in MF suggest different muscle recruitment strategies between symptomatic and asymptomatic office workers. These results implied that symptomatic individuals had altered motor control, which may have important implications in understanding the etiology of work-related musculoskeletal disorders.     

Microencapsulation of nanoparticulate complexes of DNA with cationic lipids and polymers in pectin beads for targeted gene delivery

Nanoparticulate complexes of plasmid DNA (pDNA) with cationic liposomes/polymer, of approx 200 nm diameter, were encapsulated with a high degree of efficiency within calcium pectinate gel beads. Electron microscopy showed the DNA nanocomplexes to be evenly distributed throughout the gel matrix. Controlled release of pDNA-lipid nanocomplexes was achieved by the action of pectinase enzymes, whereas release of naked and polymer-complexed DNA was found to be more greatly influenced by the swelling behavior of the polysaccharide matrices in buffer alone. Physical degradation of pDNA within pectin beads was found to be accelerated during bead drying, most probably as a result of shear forces generated within the gel matrices by the evaporation of water. Plasmid complexation with cationic liposomes provided a greater degree of protection for the DNA during bead drying than complexation with cationic polymer, and was shown to successfully transfect cultured cells after release from the beads, via the action of pectinase. Observations concerning the physical stability of nanocomplexed pDNA, and its encapsulation within and release from pectin gel beads, are discussed with reference to the electrostatic interactions existing between the various components.     

Effect of pH on Na induced Ca deficiency

Although it is well known that high Na concentrations induce Ca deficiency in acidic conditions, the effect of high pH on this competitive mechanism is not so well understood. The effect of Ca activity ratio (CAR) and pH on the Ca uptake of mungbeans (Vigna radiata (L.) Wilczek cv. Emerald) and Rhodes grass (Chloris gayana cv. Pioneer) in Na dominated solution cultures and in soil was investigated. Changes in pH in the alkaline range were shown not to affect the critical CAR of 0.024 (corresponding to 90% relative root length) for mungbeans grown in solution culture. Results from soil grown mungbeans confirmed those from solution culture, with a critical CAR of 0.025. A critical CAR of 0.034 was also established for soil grown Rhodes grass. The similarity of critical values established for mungbeans and Rhodes grass in solution culture and soil justifies the use of both solution culture and soil solution measurement as techniques for studying plant growth and limitations across plant species.     

Shifts in native ungulate communities on a former cattle ranch in Tanzania

When an area is brought under protection, current animal populations and their habitat preferences need to be assessed to predict population trends and future habitat availability. Using data from walking transects, we estimated the size of native ungulate populations on an abandoned cattle ranch in a coastal savannah in Tanzania, now included in the new Saadani National Park. Data were analysed with distance sampling and conventional strip transect techniques and were compared with results of previous wildlife counts. Few individuals of mainly browsing species were present in former cattle grazing areas exhibiting high bush‐encroachment while a ten times higher biomass of browsers and grazers was found in the cattle‐unmodified savannah. Population sizes of some species increased twofold between 1991 and 2001 within the entire area but neither population size nor species richness increased in the abandoned rangeland during our 3‐year study period from 2001 to 2003. We conclude that the former ranch has potential for future recolonization by wild ungulates. Resettlement will take place gradually with ‘pioneer‐species’ facilitating the entry of more demanding species. Habitat restoration through wildlife can be observed and quantified on Mkwaja Ranch which will be of importance for future management of native ungulates reclaiming abandoned rangeland.