Seasonal variation in food allergy to apple

The aim of the study was to investigate the possibility of a seasonal variation in reactivity to apples in 27 birch pollen allergic patients. Before and during the birch pollen season 1998, the patients were subjected to double-blind, placebo-controlled food challenges (DBPCFCs) with grated fresh Golden Delicious apple followed by an open food challenge with whole fresh apple. The clinical reactions elicited during the challenges were evaluated both by the patients and the investigators. Moreover, the skin reactivity and the in vitro reactivity to apple were evaluated by skin prick test (SPT), leukocyte histamine release (HR), measurement of specific IgE, and immunoblotting experiments. The sensitivity of the DBPCFC, when compared with the result of the open challenge, was 0.74 (14/19) before the season and 0.80 (16/20) during the season. None of the patients reacted to the blinded challenge without a subsequent reaction to the open challenge. One placebo reaction was registered both before and in season, but not in the same patient. The patient scores of the first positive challenges, and the maximal scores of each combined blinded and open challenge session, were significantly increased during the pollen season (P<0.05). The scores of the open challenge were significantly higher than the scores of the DBPCFC both before the season and during the in-season challenges (P<0.05). Specific IgE against Golden Delicious increased during season (P<0.05), while neither SPT, HR, nor immunoblotting experiments could confirm an increase in reactivity. In conclusion, the results of the oral challenge tests indicated an increase in clinical reactivity to apples during the birch pollen season in birch pollen allergic individuals.     

α-MSH Stimulates Glucose Uptake in Mouse Muscle and Phosphorylates Rab-GTPase-Activating Protein TBC1D1 Independently of AMPK

The melanocortin system includes five G-protein coupled receptors (family A) defined as MC1R-MC5R, which are stimulated by endogenous agonists derived from proopiomelanocortin (POMC). The melanocortin system has been intensely studied for its central actions in body weight and energy expenditure regulation, which are mainly mediated by MC4R. The pituitary gland is the source of various POMC-derived hormones released to the circulation, which raises the possibility that there may be actions of the melanocortins on peripheral energy homeostasis. In this study, we examined the molecular signaling pathway involved in α-MSH-stimulated glucose uptake in differentiated L6 myotubes and mouse muscle explants. In order to examine the involvement of AMPK, we investigate α-MSH stimulation in both wild type and AMPK deficient mice. We found that α-MSH significantly induces phosphorylation of TBC1 domain (TBC1D) family member 1 (S237 and T596), which is independent of upstream PKA and AMPK. We find no evidence to support that α-MSH-stimulated glucose uptake involves TBC1D4 phosphorylation (T642 and S704) or GLUT4 translocation.     

Inhibitory effect of ammonium chloride and chloroquine on the entry of the toxic lectin modeccin into HeLa cells

Ammonium chloride and chloroquine protected a variety of cell lines against diphtheria toxin and the toxic lectin modeccin. Experiments where the ability of antibody to neutralize the toxin was measured indicate that in the presence of ammonium chloride and chloroquine, modeccin remains at the cell surface and that the two compounds inhibit the uptake of modeccin into the cytoplasm. A cell line tolerating increased concentrations of modeccin was not protected against modeccin by ammonium chloride or chloroquine, whereas the compounds did protect these cells against diphtheria toxin.     

Formation and activity of covalent conjugates of poliovirus and ligands binding to cell surface structures

Disulfide-linked conjugates of poliovirus with streptavidin or concanavalin A were formed and the binding of the conjugates to mouse L cells that lack natural poliovirus receptors was studied. The conjugate with streptavidin was specifically bound to biotinylated L cells, but not to unmodified L cells. The conjugate with conA was bound to L cells in the absence of, but not in the presence of alpha-methyl mannoside. Incubation of L cells with bound conjugates did not produce virus, although the conjugates were highly infectious in HeLa cells, containing natural poliovirus receptors. This suggests that the artificially bound virus was unable to penetrate the L cells and start replication. The possibility that binding of the virus to the natural receptor is required for efficient infection is discussed.     

Bicarbonate/chloride antiport in Vero cells: I. Evidence for both sodium-linked and sodium-independent exchange

The effect of bicarbonate on the ability of cells to regulate the internal pH after acid and alkali loads was studied. In the presence of Na+, the normalization of the internal pH after acid loads occurred more rapidly in the presence than in the absence of bicarbonate. DIDS (4,4'-diisothiocyano-2,2'-stilbene-disulfonic acid) strongly inhibited the pH increase, whereas amiloride inhibited it to a lesser extent. The Na+-linked, bicarbonate-dependent pHi increase after an acid load was strongly reduced in cells depleted of Cl-. When cells were transferred to gluconate or mannitol balanced buffers containing bicarbonate, there was a rapid alkalinization of the cytosol, apparently due to influx of bicarbonate induced by chloride efflux. When the internal pH was below 7.0, the pH increase was much more rapid in the presence than in the absence of Na+, whereas at higher internal pH, there was no measurable effect of Na+. The ability of the cells to reduce the internal pH after an alkali load was increased in the presence of bicarbonate. The data indicate that both Na+-linked and Na+-independent bicarbonate/chloride exchange occur in Vero cells.     

Attack of Didymella bryoniae on Roots of Cucumber

Didymella bryoniae is very common in cucumber crops grown in Danish glasshouses and is able to attack all aerial parts of the plant. In October 1984 an attack of D. bryoniae on cucumber roots was observed for the first time. Some of the roots were dark because of pseudothecia containing asci. This fact may have importance for the spread and survival of the disease and for its control.     

Resolution of d,l-menthol by interesterification with triacetin using the free and immobilized lipase of Candida cylindracea

Summary Interesterification in isooctane with triacetin as an acyl donor was found to be a new and effective method of racemic resolution of d,l-menthol, when using the free and immobilized lipase of Candida cylindracea. No water was produced by this highly stereoselective type of reaction in contrast to ester synthesis with acetic acid as an acyl donor. Even with diacetin no possible back reaction occurred and the enzyme was easily separated from the reaction solution as opposed to ester hydrolysis in aqueous systems. Inhibition of interesterification was caused by increasing concentrations of the acyl donor triacetin by more than 10 mmol·l^-1 on the one hand, and especially by diacetin on the other hand. The reaction product menthyl acetate had no influence. By adding water the interesterification activity of the lipase was reduced significantly. An alteration of the acyl donor triacetin to longerchained triglycerides caused changes in higher specific activities but poor enantioselectivities of the products, as in the case of ester synthesis starting from longer-chained organic acids.Dedicated to Prof. Dr. Fritz Wagner on the occasion of his 60th birthday     

Permeabilization of the plasma membrane by deletion mutants of diphtheria toxin.

Diphtheria toxin B-fragment binds to cell-surface receptors and facilitates translocation of the enzymatically active A-fragment to the cytosol. In this process the B-fragment inserts into the plasma membrane and induces formation of cation-selective channels. We examined the ability of a number of diphtheria toxin-derived molecules translated in vitro to permeabilize cells. Two proteins consisting of the whole B-fragment and small parts of the A-fragment, and one protein comprising most of the B-fragment alone, were more efficient than full-length toxin in permeabilizing the plasma membrane to monovalent cations. Two shorter B-fragment-derived proteins, with 3 and 10 kd N-terminal deletions, permeabilized the cells to sulfate and sucrose in addition to monovalent cations. The relationship between channel formation and toxin translocation is discussed.     

Membrane interactions of diphtheria toxin analyzed using in vitro synthesized mutants.

We have developed a system to study the interactions of diphtheria toxin with the cell surface using non-toxic mutant proteins synthesized in vitro. Proteins obtained by N-terminal deletions containing the whole B fragment bound strongly to cells. Deletions extending into the B fragment did not yield an autonomous binding domain. Loss of only the N-terminal 3 kd of the B fragment significantly impaired the ability to recognize the receptor. This, together with previous reports that the C-terminal end of the B fragment is required for binding, suggests that both ends of the B fragment are necessary for receptor recognition. Receptor bound diphtheria toxin undergoes a conformational change at pH less than 5.3 that results in translocation of the A fragment to the cytosol and the appearance of a B fragment-derived 25 kd polypeptide (P25) resistant to externally applied protease. Only the B fragment was required for generation of P25. N-terminal deletions of 130 amino acids or more resulted in proteins that gave rise to P25 at higher pH than full length toxin. Furthermore, a second protease-inaccessible polypeptide of 18 kd (P18) was observed.