Beiträge zur geographischen Pathologie von Suriname

Zusammenfassung Bei einer Reihe von S?ugetieren in Suriname fanden sich in der Milz bei der Untersuchung von Tupfpr?paraten intracellul?r und gelegentlich auch extracellul?r gelagerte Gebilde, die von Histoplasma nicht zu unterscheiden waren. In einer Reihe von F?llen liessen sich die Parasiten auf weisse M?use verimpfen und bei diesen gleichfalls in der Milz zurückfinden. Mitt.:W. A. Collier, A. E. Wolff undA. E. G. Zaal, Documenta Med. Geogr. et Trop.4, 92, 1952; 2. Mitt.:W. A. Collier undW. E. F. Winckel, Z. f. Hyg. [im Druck; 3. Mitt.:C. F. A. Bruyning, Documenta Med. Geogr. et Trop.4, 171, 1952; 4. Mitt.:W. A. Collier undD. A. de la Parra, Documenta Med. Geogr. et Trop. im Druck; 5. Mitt.:W. E. F. Winckel, W. A. Collier undA. E. G. Treurniet, Documenta Med. Geogr. et Trop. im Druck.     

THE ACCELERATION OF SAPONIN HEMOLYSIS BY PROFLAVINE

Proflavine is a very powerful accelerator of saponin hemolysis of rabbit, human, and dog erythrocytes. Lysolecithin hemolysis, on the other hand, is inhibited. Dog erythrocytes in the presence of proflavine undergo marked changes in shape, finally becoming rods of about 13 µ in length. Rabbit and human erythrocytes are not altered in form under these conditions.     

Appendix: A model of plaque formation

Equations describing plaque formation in soft agar have been based on certain simplifying assumptions, for which data are presented. The derived equations permit one to calculate (i) average plaque size as a function of the initial density of indicator cells (D_o), (ii) the number of cells lysed per plaque as a function of D_o, and (iii) the cumulative number of cells lysed at various stages of plaque development. The calculated values agree well with those determined experimentally.     

The use of barium salts of protected deoxyribonucleoside-3'' p-chlorophenyl phosphates for construction of oligonucleotides by the phosphotriester method: high-yield synthesis of dinucleotide blocks.

A new experimental approach to the synthesis of polydeoxyribonucleotides via the phosphotriester method involves construction of oligonucleotide blocks by direct use of the easily prepared barium salts of O5',N-protected deoxyribonucleoside-3' p-chlorophenyl phosphates as the key monomers in condensation reactions. The procedure has been demonstrated by the rapid synthesis in high yield and purity of all sixteen fuly protected dinucleotides (Formula: see text) (where dN' = dT, dbzC, dbzA, or dibG; (Formula: see text) This set of molecules constitutes a "syllabary" for the preparation of defined sequence oligonucleotides.     

The Diphtheria Toxin Channel-forming T Domain Translocates Its Own NH2-Terminal Region Across Planar Bilayers

The T domain of diphtheria toxin, which extends from residue 202 to 378, causes the translocation of the catalytic A fragment (residues 1–201) across endosomal membranes and also forms ion-conducting channels in planar phospholipid bilayers. The carboxy terminal 57-amino acid segment (322–378) in the T domain is all that is required to form these channels, but its ability to do so is greatly augmented by the portion of the T domain upstream from this. In this work, we show that in association with channel formation by the T domain, its NH₂ terminus, as well as some or all of the adjacent hydrophilic 63 amino acid segment, cross the lipid bilayer. The phenomenon that enabled us to demonstrate that the NH₂-terminal region of the T domain was translocated across the membrane was the rapid closure of channels at cis negative voltages when the T domain contained a histidine tag at its NH₂ terminus. The inhibition of this effect by trans nickel, and by trans streptavidin when the histidine tag sequence was biotinylated, clearly established that the histidine tag was present on the trans side of the membrane. Furthermore, the inhibition of rapid channel closure by trans trypsin, combined with mutagenesis to localize the trypsin site, indicated that some portion of the 63 amino acid NH₂-terminal segment of the T domain was also translocated to the trans side of the membrane. If the NH₂ terminus was forced to remain on the cis side, by streptavidin binding to the biotinylated histidine tag sequence, channel formation was severely disrupted. Thus, normal channel formation by the T domain requires that its NH₂ terminus be translocated across the membrane from the cis to the trans side, even though the NH₂ terminus is >100 residues removed from the channel-forming part of the molecule.     

Expression of functional RANK on mature rat and human osteoclasts

The present study was aimed at investigating effects of hypochlorite (HOCl) modification of high density lipoproteins subclass 3 (HDL3) on their ability for cellular cholesterol removal from permanent J774 macrophages. Our findings indicate that HOCl (added as reagent or generated enzymatically by the myeloperoxidase/H2O2/Cl- system) damages apolipoprotein A-I, the major protein component of HDL3. Fatty acid analysis of native and HOCl-modified HDL3 revealed that unsaturated fatty acids in both major lipid subclasses (phospholipids and cholesteryl esters) are targets for HOCl attack. HOCl modification resulted in impaired HDL3-mediated cholesterol efflux from J774 cells, regardless of whether reagent or enzymatically generated HOCl was used to modify the lipoprotein. Decreased cholesterol efflux was also observed after HOCl modification of reconstituted HDL particles. Impairment of cholesterol efflux from macrophages was noticed at low and physiologically occurring HOCl concentrations.     

Companion planting – do aromatic plants disrupt host‐plant finding by the cabbage root fly and the onion fly more effectively than non‐aromatic plants?

Brassica and Allium host‐plants were each surrounded by four non‐host plants to determine how background plants affected host‐plant finding by the cabbage root fly (Delia radicum L.) and the onion fly [Delia antiqua (Meig.)] (Diptera: Anthomyiidae), respectively. The 24 non‐host plants tested in field‐cage experiments included garden ‘bedding’ plants, weeds, aromatic plants, companion plants, and one vegetable plant. Of the 20 non‐host plants that disrupted host‐plant finding by the cabbage root fly, fewest eggs (18% of check total) were laid on host plants surrounded by the weed Chenopodium album L., and most (64% of check total) on those surrounded by the weed Fumaria officinalis L. Of the 15 plants that disrupted host‐plant finding in the preliminary tests involving the onion fly, the most disruptive (8% of check total) was a green‐leaved variant of the bedding plant Pelargonium × hortorum L.H. Bail and the least disruptive (57% of check total) was the aromatic plant Mentha piperita × citrata (Ehrh.) Briq. Plant cultivars of Dahlia variabilis (Willd.) Desf. and Pelargonium×hortorum, selected for their reddish foliage, were less disruptive than comparable cultivars with green foliage. The only surrounding plants that did not disrupt oviposition by the cabbage root fly were the low‐growing scrambling plant Sallopia convolvulus L., the grey‐foliage plant Cineraria maritima L., and two plants, Lobularia maritima (L.) Desv. and Lobelia erinus L. which, from their profuse covering of small flowers, appeared to be white and blue, respectively. The leaf on which the fly landed had a considerable effect on subsequent behaviour. Flies that landed on a host plant searched the leaf surface in an excited manner, whereas those that landed on a non‐host plant remained more or less motionless. Before taking off again, the flies stayed 2–5 times as long on the leaf of a non‐host plant as on the leaf of a host plant. Host‐plant finding was affected by the size (weight, leaf area, height) of the surrounding non‐host plants. ‘Companion plants’ and aromatic plants were no more disruptive to either species of fly than the other plants tested. Disruption by all plants resulted from their green leaves, and not from their odours and/or tastes.     

The effect of aluminum exposure on root respiration in an aluminum-sensitive and an aluminum-tolerant cultivar of Triticum aestivum

The effects of aluminum (Al) exposure on intact root respiration of an Al-sensitive (Scout-66) and an Al-tolerant (Atlas-66) cultivar of Triticum aestivum were investigated. Exposure to a wide range of Al concentrations (0–900 μmol) for 4 days stimulated respiration along the energy-conserving cytochrome pathway in both cultivars and increased the ratio of maintenance respiration to growth respiration. The maximum rate of Scout-66 root respiration occurred after exposure to 100–200 μmol Al. Atlas-66 root respiration peaked after exposure to 300–400 μmol Al. Similarly, calculations of theoretical adenosine 5'-triphosphate (ATP) production indicated that maximum daily rate of ATP production also increased upon exposure to Al in both cultivars, with peak ATP production occurring during peak respiration. Maximum root respiration rates in both cultivars were related to the Al concentration that inhibited root growth. Temporal exposure to 200 μmol Al quickly stopped root growth and stimulated cytochrome pathway respiration in Scout-66 after 4 days. Atlas-66 root growth and respiration were unaffected by 200 μmol Al. These results suggest that Al exposure imposes a demand for additional metabolic energy. A model describing Al effects on root respiration is presented     

pH-dependent permeabilization of the plasma membrane of mammalian cells by anthrax protective antigen

Protective antigen (PA) of anthrax toxin forms ion-conductive channels in planar lipid bilayers and liposomes under acidic pH conditions. We show here that PA has a similar permeabilizing action on the plasma membranes of CHO-K1 and three other mammalian cell lines (J774A.1, RAW264.7 and Vero). Changes in membrane permeability were evaluated by measuring the efflux of the K⁺ analogue, ⁸⁶Rb⁺, from prelabelled cells, and the influx of ²²Na⁺. The permeabilizing activity of PA was limited to a proteolytically activated form (PA_N) and was dependent on acidic pH for membrane insertion (optimal at pH 5.0), but not for sustained ion flux. The flux was reduced in the presence of several known channel blockers: tetrabutyl-, tetrapentyl-, and tetrahexylammonium bromides. PA_N facilitated the membrane translocation of anthrax edema factor under the same conditions that induced changes in membrane permeability to ions. These results indicate that PA_N permeabilizes cellular membranes under conditions that are believed to prevail in the endosomal compartment of toxin-sensitive cells; and they provide a basis for more detailed studies of the relationship between channel formation and translocation of toxin effector moieties in vivo.