A theory of charge separation,ion, electron and proton transport in photosynthetic membranes based on asymmetry of surface charges

We present a model for the light-induced charge separation, proton and ion transport across photosynthetic membranes based on an assumption of the transmembrane surface charge asymmetry. In dark equilibrium, this asymmetry gives rise to an internal membrane electric field whose direction is perpendicular to the membrane surfaces. The role of the field in the light-induced charge separation is similar to the function of the built-in electric field across a solid-state p-n junction. Light-generated free charge carriers in the membrane flow according to its direction and upon recombination on the surface give rise to an electrochemical potential difference for electrons across the membrane. The associated coupled electron-proton transport, and ion diffusion can be viewed as a response of the system to the light-induced redox and electric potential changes.     

Gel formation with leucocytes and heparin

Heparin in concentrations of 5–225 units/ml caused suspensions of thymus lymphocytes, spleen or bone marrow cells to gel. The extent of gel formation was related to concentration of heparin and of cells. The reaction was observed only with intact cells and was temperature-dependent. It did not require Ca⁺⁺, was not inhibited with EDTA, adenosine, prostaglandin synthetase inhibitors, or phosphodiesterase inhibitors and, in this respect, differed from platelet aggregation induced by heparin. Since heparin is released along with histamine from mast cells during injury and certain forms of allergic reaction, a possible role for heparin in promoting accumulation of white cells in the extravascular space is suggested.     

Natural hazards and building history: Roof structures of Segovia cathedral (Spain) reveal its history through tree-ring research

Combined dendrochronological and archival research revealed the history of construction and subsequent repairs to the roof structures of Segovia Cathedral, the last gothic cathedral built in Spain. Although this iconic building has been extensively documented by different scholars, the completion date of the 16th century original sacristy was uncertain. Furthermore, disaster struck the building on two occasions, in the 17th and 18th centuries. First, on September 1614, lightning hit the bell tower and fire spread through the roof of the nave. Then, on 1 November 1755, the Lisbon earthquake shook the cathedral building. However, the extent of the damage caused by these events was unknown.Our combined research revealed that the trees used to make the tie-beams of the sacristy were cut in the late summer/winter months of 1676/77, one century later than the completion date, suggesting that this part of the original sacristy was renewed when a new one was built together with the offices in an annexed building. Furthermore, absolute dates obtained for the nave indicate that the trees used to build the current roof structure were cut in the autumn/winter of 1614/15, which implies that the 16th century original roof must have burned down entirely due to the lightning fire. A historical document registering the purchase of the wood to repair this structure in 1614 confirms this information. Finally, the damage caused by the Lisbon earthquake must have compromised the structural integrity of the roof, as the support timbers used to reinforce it belong to small trees cut in the spring or summer of that same year 1755. Archival research revealed that the roofs were inspected a few weeks after the earthquake, and that repairs were carried out in 1756. This suggests that the wood to prop up the structure was most likely purchased shortly after the inspection (probably in a nearby saw mill where cheap wood from trees cut in the summer of 1755 was available), and before the repairs took place.     

Inhibition of the mixed lymphocyte culture by peritoneal exudate cells.

Inhibition of mixed lymphocyte cultures (MLC) by macrophages and by supernatants of short term cultured macrophages was assessed by incorporation of ³H-thymidine (TdRH3) and also by blast cell counts and by determination of cellmediated lympholysis. Peritoneal exudate cells (PEC) induced by thioglycollate, at concentrations >10%, inhibited all three parameters of MLC. Lower concentrations of PEC, and supernatants from cultured PEC, inhibited TdRH3 incorporation, but had no significant effect on blast cell counts or on generation of cytotoxic effector cells. Inhibition by the supernatants could be reversed by dialysis or by use of low specific activity TdRH3. These data indicate that macrophages can inhibit proliferative responses in MLC, but that this must be carefully distinguished from selective inhibition of TdRH3 incorporation.     

A facile tritium release assay for mammalian L-dihydroorotate dehydrogenase

Proteinase B activity in crude yeast extract is difficult to detect, unless the firmly bound peptide inhibitor is previously inactivated. Methods currently used to accomplish this inactivation suffer from serious limitations, particularly when applied to crude extracts obtained from yeast grown in complete media. These limitations are discussed on the basis of the kinetics of activation. A novel procedure to unmask proteinase B activity, based on pepsin treatment of crude extracts, is described. Specific activity of proteinase B, determined after pepsin A treatment, is always two to three times higher than that obtained by other methods. The method proposed is simple, reliable, and can be applied to crude extracts stored at ?20°C for up to 1 week, repeatedly giving the same specific activity for proteinase B.     

Synthesis of a tetrasaccharide donor corresponding to the O-specific polysaccharide of Shigella dysenteriae type 1

O-(2,4-Di-O-chloroacetyl-α-l-rhamnopyranosyl)-(1 → 2)-O-(3,4,6-tri-O-benzoyl-α-d-galactopyranosyl)-(1 → 3)-O-(2-acetamido-4,6-di-O-acetyl-2-deoxy-α-d-glycopyranosyl)-(1 → 3)-2,4-di-O-benzoyl-α-l-rhamnopyranosyl trichloroacetimidate (1) was synthesized in a stepwise manner, using the following monosaccharide units: 2-(trimethylsilyl)ethyl 2,4-di-O-benzoyl-α-l-rhamnopyranoside, 2-azido-4,6-O-benzylidene-3-O-chloroacetyl-2-deoxy-β-d-glycopyranosyl chloride, methyl 3,4,6-tri-O-benzoyl-2-O-(4-methoxybenzyl)-1-thio-β-d-galactopyranoside, and 2,4-di-O-benzoyl-3-O-chloroacetyl-α-l-rhamnopyranosyl chloride. Compound 1 corresponds to a complete tetrasaccharide repeating unit of the O-specific polysaccharide of the lipopolysaccharide of Shigella dysenteriae type 1.     

Protecting buildings against feral pigeons

Feral pigeons (Columba livia, Gmelin 1789) cause different problems for building owners when using structures for daytime perching, sleeping, and breeding. Problems include fouling of building facades and pavements, transmission of allergens and pathogenic microorganisms, and infestations with ectoparasites emanating from breeding sites. Owners are primarily interested in keeping away unwanted pigeons from their property. Pest control companies offer different deterrent systems, of widely varying efficacy, for proofing buildings against feral pigeons. A better solution is avoiding attractive structures during building design or subsequent alterations of existing structures used by feral pigeons. With our study, we elaborate the relevant structural data to help to maintain a building free of pigeons. We performed experiments with free ranging feral pigeons in a feral pigeon loft in the City of Basel, Switzerland. The maximum outlet width a pigeon is not able to pass through is 4 cm; the respective outlet height is 5 cm and a pigeon-safe square opening is not larger than 6 × 6 cm. The maximum ledge width a pigeon is not able to sit on is 4 cm. The pigeon-safe angle of inclination for smooth construction materials (tinplate, glass, plastics) is 25°, for medium rough materials (wood, plane concrete) 35°, and for rough materials (sandstone, rough concrete) at least 50°. Additionally, we studied the behavioral strategies used by feral pigeons to surmount our experimental constructional restrictions, ledge width, and ledge inclinations. Our data provide the essential data to prevent feral pigeons from using building structures.     

The suppression of experimental allergic encephalomyelitis in Lewis rats by treatment with myelin basic protein-cell conjugates

Pretreatment of Lewis rats with guinea pig (GP) myelin basic protein (MBP) coupled to syngeneic spleen leukocytes (SL) suppressed the subsequent induction of experimental allegic encephalomyelitis (EAE) with GP-MBP in Freund's complete adjuvant. The degree of suppression correlated positively with the amount of antigen coupled to the SL. GP-MBP coupled to syngeneic red blood cells (RBC) also resulted in suppression of EAE and the extent of the suppression was related to the dose of cells. These regimens of pretreatment also resulted in a decrease in the in vitro lymphocyte proliferative response to GP-MBP and in the extent of perivascular cuffing in the spinal cord. No decrease in the anti-MBP antibody response was detected in rats pretreated with either GP-MBP-SL or GP-MBP-RBC conjugates. Transfer of lymph node cells from rats pretreated with GP-MBP-RBC resulted in a decrease in disease severity in recipients. It is concluded that prior administration of MBP-cell conjugates is an effective way of suppressing the symptoms of EAE.