Epitope mapping of four monoclonal antibodies recognizing the hexose core domain of Salmonella lipopolysaccharide.

Four murine monoclonal antibodies reactive with distinctive regions of the hexose core domain of Salmonella lipopolysaccharide (LPS) were generated and their epitope specificities were delineated. MAST 56 (IgG1) and MAST 50 (IgG3) antibodies elicited by immunizations with Salmonella typhimurium Rb1 and Rb2 mutants, reacted selectively in enzyme immunoassay with the LPS from rough mutants. In contrast, MATy 1 (IgM) and MATy 2 (IgG2b) antibodies raised by an attenuated Salmonella typhi 620 Ty strain were reactive with LPS from both smooth and rough Salmonellae. Immunoblotting analysis showed that MATy 1 distinguished only the bottom bands (naked LPS core) among the heterogeneous LPS populations, whereas MATy 2 gave a ladder pattern (reactive with both naked and O-chain-substituted LPS cores). Differential binding specificities of MATy 1 and MATy 2 antibodies to the naked and capped LPS cores were further analyzed utilizing S. typhimurium polysaccharide fractions with different O-chain:core ratios which were obtained after separation by Sephacryl S-200 chromatography. Steric effects on the antibody reactivity by the bulky O-polysaccharide chain were detected. The use of chemically defined native and synthetic saccharides as inhibitors, in combination with the conformation of the Salmonella core oligosaccharide, permitted the definition of antigenic determinants carried in the core domain recognized by each antibody: (i) the branches I and VIII are essential for MATy 1 recognition, (ii) the backbone III-IV-V for MATy 2, (iii) the backbone II-III-IV-V for MAST 56, and (iv) the backbone plus the branch III-IV-V-VIII for MAST 50. (formula; see text)     

Temperature influence on life table statistics of the chicken miteDermanyssus gallinae (Acari: Dermanyssidae)

An age-specific life table for the chicken miteDermanyssus gallinae (DeGeer, 1778) was based on various observations carried out at 25°C. The generation time was calculated to be 16.8 days; the intrinsic rate of natural increase was 0.12 per day, and the net reproductive rate was 7.2. A nonlinear function was found satisfactory to describe the developmental rate of the different immature lifestages at temperatures below 40°C. The stage-specific survival of the immature life-stages was generally high between 10 and 37°C, but decreased quickly outside this temperature range. Most of the eggs were laid during the first three weeks of the adult life. The proportion of surviving females rapidly decreases after moulting to the adult stage. At a temperature of 30°C, the highest number of eggs (3 eggs per day) was laid.     

Promotive effect of abscisic acid in flowering ofChenopodium rubrum as the result of decreasing apical dominance

Abscisic acid (ABA) was applied in a concentration of 1. 10^?3 M and 1. 10^?4 M to the quantitative SD plantChenopodium rubrum under various light regimes. ABA did not influence flowering in plants under continuous illumination, enhanced flowering in plants subjected to long days and inhibited it in plants induced by short days. It was concluded that ABA can not substitute for inductive treatment but its action may be additive to initial stages of reproductive morphogenesis (enhanced growth rate and branching of the apical meristem) as evoked by long days.     

Infloreszenz- und Blütenentwicklung bei der KugeldistelEchinops exaltatus (Asteraceae)

InEchinops the flowers are surrounded by several scales and initiated in an acropetal and spiral succession on a cone-like inflorescence axis (Figs. 1–6). The floral organs originate in the following sequence: petals—stamens—carpels—pappus. The petals arise from a meristematic rim and therefore are already interconnected when they arise as primordia. This sympetalous zone remains rather inconspicuous for a long period, but eventually, the elongated corolla tube is formed through intercalary growth in a ring zone. Thereby, the stamens are moved upwards and form ledges on the corolla tube (Fig. 34). In the inferior ovary the usual zones of the typical angiospermous gynoecium can be distinguished, namely a synascidiate, symplicate and hemisymplicate zone. The ovule is borne on carpellary tissue.

     

Effect of collagenase on mechanical activity and fine structure of an intestinal smooth muscle

Summary The effect of the enzyme collagenase (40–200 units · ml^-1) on the spontaneous mechanical activity in vitro and on the fine structure of the taenia coli of the guinea-pig was investigated. Initially, the spontaneous activity of the taenia was enhanced both in the isometric and isotonic recordings; after several minutes the muscles became slack or elongated to up to twice their resting lengths. The structural changes were dramatic but a number of muscle cells remained apparently unaltered even with the highest concentration and the longest incubation time (120 minutes). The large variety of structural changes were tentatively grouped into two separate sequences. One sequence involved swelling of the muscle cell, dispersion of the filaments and breaking up of the cell membrane: the thick myofilaments increased considerably in size and became heterogeneous in size and shape, but were still recognizable after disruption of the cell membrane. The other disruptive sequence involved separation of the superficial part of the muscle cell, which became electron-lucent, from the core of the cell where filaments were very densely packed. Few or no changes were observed in non-muscle cells.Supported by grants from the Medical Research Council and the Central Research Fund of the University of LondonFinancial support from the F.W.G.O. (Grant n 20.487) is gratefully acknowledged     

The Oscillopolarographic Behaviour of Deoxyribonucleic Acids Isolated from Bacillus Subtilis and Bacillus brevis

Summary The behaviour of DNA from several strains ofB. subtilis andB. brevis on the dropping mercury electrode in a medium of ammonium formate was studied. Native DNA yields in this medium on the oscillogram dE/dt againstE an anodic indentation for which the residues of deoxyguanylic acid are responsible.B. subtilis DNA produces a substantially smaller indentation thanB. brevis DNA does. It was found that the difference is not conditioned by impurities in the DNA samples, nor by the presence of denatured DNA. The difference in the depth of the indentation produced byB. subtilis andB. brevis DNAs almost disappears after denaturation of these DNAs or in an ammonium formate medium of higher concentration. The assumption was advanced that the different oscillopolarographic behaviour of DNAs obtained fromB. subtilis andB. brevis is connected with the different primary structure of these DNAs.     

Characterization of the mitochondrial Na+-H+ exchange. The effect of amiloride analogues

The kinetic properties and inhibitor sensitivity of the Na+-H+ exchange activity present in the inner membrane of rat heart and liver mitochondria were studied. (1) Na+-induced H+ efflux from mitochondria followed Michaelis-Menten kinetics. In heart mitochondria, the Km for Na+ was 24 +/- 4 mM and the Vmax was 4.5 +/- 1.4 nmol H+/mg protein per s (n = 6). Basically similar values were obtained in liver mitochondria (Km = 31 +/- 2 mM, Vmax = 5.3 +/- 0.2 nmol H+/mg protein per s, n = 4). (2) Li+ proved to be a substrate (Km = 5.9 mM, Vmax = 2.3 nmol H+/mg protein per s) and a potent competitive inhibitor with respect to Na+ (Ki approximately 0.7 mM). (3) External H+ inhibited the mitochondrial Na+-H+ exchange competitively. (4) Two benzamil derivatives of amiloride, 5-(N-4-chlorobenzyl)-N-(2',4'-dimethyl)benzamil and 3',5'-bis(trifluoromethyl)benzamil were effective inhibitors of the mitochondrial Na+-H+ exchange (50% inhibition was attained by approx. 60 microM in the presence of 15 mM Na+). (5) Three 5-amino analogues of amiloride, which are very strong Na+-H+ exchange blockers on the plasma membrane, exerted only weak inhibitory activity on the mitochondrial Na+-H+ exchange. (6) The results indicate that the mitochondrial and the plasma membrane antiporters represent distinct molecular entities.     

Transmembrane adaptor protein WBP1L regulates CXCR4 signalling and murine haematopoiesis

WW domain binding protein 1‐like (WBP1L), also known as outcome predictor of acute leukaemia 1 (OPAL1), is a transmembrane adaptor protein, expression of which correlates with ETV6‐RUNX1 (t(12;21)(p13;q22)) translocation and favourable prognosis in childhood leukaemia. It has a broad expression pattern in haematopoietic and in non‐haematopoietic cells. However, its physiological function has been unknown. Here, we show that WBP1L negatively regulates signalling through a critical chemokine receptor CXCR4 in multiple leucocyte subsets and cell lines. We also show that WBP1L interacts with NEDD4‐family ubiquitin ligases and regulates CXCR4 ubiquitination and expression. Moreover, analysis of Wbp1l‐deficient mice revealed alterations in B cell development and enhanced efficiency of bone marrow cell transplantation. Collectively, our data show that WBP1L is a novel regulator of CXCR4 signalling and haematopoiesis.