Production of Vero cytotoxin by strains of Escherichia coli as related to the availability of iron

Abstract Vero cytotoxin (VT) producing strains of Escherichia coli (VTEC), including isolates from cases of haemolytic uraemic syndrome and infantile diarrhoea, were used to determine the effect of iron availability on the production of intra- and extracellular VT, with particular interest in elevating toxin production by low-level toxin producing VTEC. Culturing bacteria under iron restriction resulted in growth retardation and a decrease in the production of VT. For the routine detection of both high- and low-level VT-producing E. coli , there was no advantage to be gained by growing bacteria under iron restriction or using disrupted bacterial cell preparations; on the contrary, testing culture supernatants from bacteria grown in iron-replete media for approximately 14 h proved to be the most sensitive and accurate method for detecting VT and the resultant identification of VTEC.     

Restriction analysis of lambda EMBL3 background recombinants: occurrence of lambda phages carrying a head to tail oriented left arm DNA sequence

Summary Eight representative recombinant background clones of λEMBL3 were analysed usingKpnI,BamHI,SalI,EcoRI andHindIII digestion. We found that λEMBL3 carries its own left arm in theBamHI cloning site. In this way, recombinant molecules were found to be generated which can grow onEscherichia coli strain NM539. In all cases analysed, the left arm DNA was inserted in a head to tail orientation. Seven clones carried a restoredBamHI site at thecos site-BamHI site connection. In the region where the inserted left arm and the right arm were ligated,BamHI cloning produces a large palindromic sequence consisting of two polylinkers. ThisBamHI site was incompletely cleaved in all cases analysed. We assume that a part of the λ DNA molecule in this region shows a cruciform structure prohibiting recognition or cleavage of this site by restriction endonucleaseBamHI.     

Evolutionary steps of ecophysiological adaptation and diversification of ruminants: a comparative view of their digestive system

Summary A review is made of the ruminant digestive system in its morphophysiological variations and adaptations relating to foraging behaviour, digestive physiology, to interactions between plants and ruminants and to geographic and climatic diversity of ruminants' ecological niches. Evidence is provided for evolutionary trends from an extreme selectivity mainly for plant cell contents and dependence upon a fractionated fore- and hindgut fermentation, to an unselective intake of bulk roughage subjected to an efficient plant cell wall fermentation, mainly in the forestomachs. The review is based on detailed comparative morphological studies of all portions of the digestive system of 65 ruminant species from four continents. Their results are related to physiological evidence and to the classification of all extant ruminants into a flexible system of three overlapping morphophysiological feeding types: concentrate selectors (40%), grass and roughage eaters (25%) and intermediate, opportunistic, mixed feeders (35%). Several examples are discussed how ruminants of different feeding types are gaining ecological advantage and it is concluded that ruminants have achieved high levels of digestive efficiency at each evolutionary stage, (including well-documented seasonal adaptations of the digestive system) and that ruminant evolution is still going on. Deductions made from the few domesticated ruminant species may have, in the past, biased scientific evaluation of the free-ranging species' ecology. The main threat to a continuous ruminant evolution and diversity appears to be man's neglect for essential ecological interactions between wild ruminants and their specific habitats, which he alters or destroys.Abbreviations bw body weight - CS concentrate selector - DFC distal fermentation chamber (distended caecocolon) - GR grass and roughage eater - IM intermediate (mixed) feeder - PFC proximal fermentation chamber (ruminoreticulum/forestomachs) - RR Ruminoreticulum - SCFA Short-chain fatty acis (acetic, butyric, propionic acid set free by rumen bacteriae) - SE Surface enlargement (of absorptive mucosa) Supported by German Research Community grant DFG Ho 273/6Dedicated to Professor Dr. Dr. h.c. Dietrich Starck on the occasion of his 80th birthday     

Cyclic AMP,fructose-2,6-bisphosphate and catabolite inactivation of enzymes in the hydrocarbon-assimilating yeast Candida maltosa

The inactivation of fructose-1,6-bisphosphatase, isocitrate lyase and cytoplasmic malate dehydrogenase in Candida maltosa was found to occur after the addition of glucose to starved cells. The concentration of cyclic AMP and fructose-2,6-bisphosphate increased drastically within 30 s when glucose was added to the intact cells of this yeast. From these results it was concluded that catabolite inactivation, with participation of cyclic AMP and fructose-2,6-bisphosphate, is an important control mechanism of the gluconeogenetic sequence in the n-alkane-assimilating yeast Candida maltosa, as described for Saccharomyces cerevisiae.     

Nucleotide and deduced amino acid sequence of the hydrophobic surfactant protein SP-C from rat: expression in alveolar type II cells and homology with SP-C from other species

Pulmonary surfactant lowers surface tension in the lung. Its deficiency leads to the severe physiologic abnormalities seen in the respiratory distress syndrome. The hydrophobic surfactant proteins, SP-B and SP-C, appear to be especially important in the surface-spreading characteristics of pulmonary surfactant. We report the nucleotide sequence of cDNA clones for rat SP-C and compare the deduced amino acid sequence for SP-C from several species. A highly conserved domain exists within the confines of mature human SP-C. An Eisenberg plot of this region predicts a membrane-associated helix. We also demonstrate by Northern analysis the tissue-specific expression of SP-C. A comparison of signal strength between total lung RNA and RNA derived from isolated type II cells supports the idea that most SP-C messenger RNA in total lung can be accounted for by that present in alveolar type II cells.     

Characterization of a mutant of the yeast Candida maltosa defective in catabolite inactivation of gluconeogenetic enzymes

A spontaneous mutant of the yeast Candida maltosa SBUG 700 was isolated showing pseudohyphal marphology under all growth conditions tested. The C. maltosa PHM mutant takes up glucose with the kinetics of C. maltosa SBUG 700 and starved cells contain the same cyclic AMP concentration. Addition of glucose to the PHM mutant does not result in an increase of the intracellular cyclic AMP level and in catabolite inactivation of fructose-1,6-bisphosphatase, malate dehydrogenase and phosphoenolpyruvate carboxykinase. However, addition of 2,4-dinitrophenol is followed by a rapid, transient increase of the cyclic AMP level in the mutant cells, but not by catabolite inactivation. These results show that a common mechanism might be responsible for catabolite inactivation and glucose-induced cAMP signaling or that glucose-induced cAMP signaling is required for catabolite inactivation in C. maltosa.     

Rapid quantitative analysis of a gibberellin-sterol inhibitor using high-performance liquid chromatographic cartridge columns

A rapid, sensitive, and economical chemical analysis of the triazole, gibberellin-inhibitor, paclobutrazol (PP333, [(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4 triazol-1-yl) pentan-3-ol]) was sought, featuring high-performance liquid chromatography (HPLC) as the final quantitation step. Three C₁₈-reverse phase columns (conventional, 250×4.6 mm; cartridge type, 125×4.6 mm; and minicolumn, 33×4.6 mm) were evaluated for their performance in HPLC separation and quantitation of PP333 applied to soil and plant foliage. The 125-mm Whatman Partisil 5 ODS-3 cartridge column was superior to the standard 250-mm DuPont Zorbax ODS unit, and provided enhanced resolution and reduced solvent consumption, analysis time, and cost. A Perkin-Elmer Pecosphere 3×3C-C₁₈ cartridge system was also superior to the 125-mm column with respect to these parameters. Although this minicolumn necessitated an additional purification step prior to HPLC analysis, its exceptionally fast analysis time and recovery period coupled with a high degree of sensitivity rendered it the most superior unit. This HPLC technology provided an efficient means of assaying for PP333 in large-scale experiments dealing with the chemical's absorption, translocation, and physiological response.     

Ultrastructural localization of WGA,RCA I,LFA and SBA binding sites in the seven-day-old mouse embryo

Summary Transglutaminases are Ca²⁺-dependent intra-and extracellular enzymes catalyzing the cross-linking between proteins and/or polyamines, thereby eliciting divergent physiological effects such as fibrin clot stabilization or hair follicle cross-linking. A secretory transglutaminase (EC 2.3.2.13) was isolated from the coagulating gland of the rat. The protein is highly glycosylated. A fraction purified to homogeneity was used as an antigen to raise polyclonal antibodies in rabbits. These antibodies were used to identify the secretion sites of the protein within the male accessory sex glands as well as to study the immunological relationships of the respective antigen within different organs of different species. In the rat, the coagulating gland and likewise the dorsal prostate gave a positive immunoreaction. In the guinea pig, a closely related protein was detected in the anterior prostate. No cross-reactivity was found with membrane-bound transglutaminase from liver, erythrocytes or blood clotting factor XIIIa. The intraluminal secretion of the aforementioned glands was only weakly stained. No secretory granules were observed in the glandular epithelium but instead bleb-like structures reminiscent of apocrine secretion. A slight background stain of the epithelium remained even in castrated animals where secretion is largely suppressed. The background stain is attributed to a tissue-type, membrane-bound, non-secretory transglutaminase that is not androgen dependent, but instead synthesized only after androgen deprivation.