Widespread formation of intracellular calcium carbonates by the bloom-forming cyanobacterium Microcystis

The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments.     

Antituberculous drug resistance in Manitoba from 1980 to 1989.

OBJECTIVES: To estimate the magnitude of antituberculous drug resistance and identify the risk factors for its development in tuberculosis patients in Manitoba over a 10-year period. As well, to examine the clinical course of the patients whose initial or subsequent isolates of Mycobacterium tuberculosis were resistant to one or more drugs. DESIGN: Comparison of drug-resistant and non-drug-resistant cases of tuberculosis. SETTING: Manitoba. PATIENTS: All people with tuberculosis reported to the Central Tuberculosis Registry of Manitoba between Jan. 1, 1980, and Dec. 31, 1989. MAIN OUTCOME MEASURES: Of 1478 cases of active tuberculosis 1086 were culture positive, and drug susceptibility testing was performed in these cases. The clinical course, including outcome of treatment, of all drug-resistant cases was described. RESULTS: Of 1086 culture-positive cases of tuberculosis 77 (7.1%) were drug resistant. Odds ratios suggested that the risk of drug resistance was significantly higher among the immigrants than among the other Canadians. Compared with the other Canadians the risk of drug resistance was 9.9 times greater among the immigrants in whom tuberculosis developed within the first year after arrival in Canada and 5.4 times greater among the immigrants in whom it developed 2 to 5 years after arrival in Canada. Of the 71 patients with drug-resistant disease whose type of resistance was known 62% had never taken antituberculous drugs before and 38% had. Most (91%) of the 77 cases of drug-resistant disease were resistant to first-line drugs, especially isoniazid and streptomycin. Thirty-two (42%) of the 77 cases were resistant to two or more first-line drugs. Of patients with drug-resistant disease a subgroup of 10 had disease that became resistant to several drugs over the 10-year period. The outcome of treatment in these individuals was poor, and they presented a particular public health problem. CONCLUSION: Resistance to one or more first-line antituberculous drugs continues to complicate the treatment of tuberculosis and may facilitate the spread of the disease.     

Effect of larval population density on the adult morphology of two species of Lepidoptera, Plusia gamma L. and Pieris brassicae L.

The morphological effects of population density in locusts in the production of phases is now well established and in recent years somewhat parallel effects have been observed in the larvae of Lepidoptera. Unlike locusts Lepidoptera pass through a quiescent pupal period but nevertheless the adult may be affected. In both P. gamma and P. brassicae adults from crowded larval cultures were smaller in both size and weight although the effect was counteracted to some extent by approaching pupal diapause in P. brassicae. The effect was similar in many cases to that produced by an increase in temperature except that it disturbed the relationships between the lengths of the wing and hind femur with the live weight. The ratio of these lengths (equivalent to E/F ratio in locusts) was significantly increased but was not a satisfactory index of larval population density. No effects were observed in the wing pattern and colouration in either species.

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Zusammenfassung Die Einwirkung der larvalen Populationsdichte auf die Morphologie der jungen Falter wurde bei Plusia gamma und Pieris brassicae durch Vergleich frischgeschlüpfter Falter aus Einzel- und aus Massenzuchten bestimmt.Bei P. gamma wogen Puppen aus Massenkulturen etwas weniger und verloren während des Puppenstadiums mehr an Gewicht. Die entstehenden Falter waren gewichtsmäßig deutlich leichter und hatten etwas kürzere Flügel. Größe und Gewicht der Männchen waren größer als die der Weibchen, und da die Massenzucht die meßbaren Größen bei den Weibchen stärker beeinflußt, verstärkte sie den Unterschied zwischen den Geschlechtern. Jahreszeitliche Unterschiede wurden beobachtet, wobei Gewicht und Größen in der warmen Jahreszeit geringer waren, doch blieb der jahreszeitliche Einfluß geringer als der durch Übervölkerung hervorgerufene.Bei P. brassicae hatte die Massenzucht eine ähnliche Wirkung auf die Puppen- und Erwachsenengewichte und auch auf die Maße, außer daß der Flügel kürzer und schmaler war. Die Unterschiede zwischen den Geschlechtern wurden durch die Massenaufzucht nicht verschärft. Lebendgewicht und Femurlänge waren beim Männchen größer, währen das Weibchen größere Flügel hatte. Bei Herannahen der Diapause wurde die Wirkung der Massenkultur auf Puppen- und Imaginalgewicht kompensiert, aber die Wirkungen auf die Erwachsenenmaße blieben noch erhalten, wenn auch in geringerem Ausmaß als sie bei nichtdiapausierenden Generationen zu beobachten waren. In der wärmeren Jahreszeit wurden Variationen erzielt, die in etwa den durch Übervölkerung bewirkten ähnlich waren, außer daß die Flügel abweichende Form aufwiesen und daß Übervölkerung bei den Männchen die Wirkung stark reduzierte.In Einzelkulturen beider Arten wurden positive, aber nicht stark signifikante Korrelationen in der Beziehung von Costa- und Hinterschenkellänge mit dem Lebendgewicht gefunden. Diese Beziehungen wurden durch Massenkultur gestört.In beiden Arten wurde das Costa-Schenkel-Verhältnis durch Massenkultur signifikant vergrößert (cf. E/F-Rate bei Heuschrecken), ergab aber keinen befriedigenden Index für die larvale Populationsdichte.In der Flügelzeichnung und Färbung beider Arten wurden durch larvale Massenkultur keine Wirkungen beobachtet.

     

NMR and CD studies of triple-helical peptides.

Triple-helix formation of the peptide (Pro-Hyp-Gly)10 was monitored by nmr and CD spectroscopy. The two-dimensional nmr spectra indicated that the Gly C alpha H and Pro C delta H proton resonances shift upfield in going from the nonhelical to helical form, while hydroxy-proline resonances are unchanged. The integrated areas of the helical and nonhelical resonances could be monitored in the one-dimensional nmr spectrum, and indicate that in the (Pro-Hyp-Gly)10 about 90% of the residues are in a defined triple-helical conformation. The introduction of a glycine to alanine substitution or the deletion of a single hydroxyproline residue in the stable triple-helical peptide (Pro-Hyp-Gly)10 still allows trimers to be formed, but the trimers show a substantial loss of triple helix and decreased thermal stability compared with (Pro-Hyp-Gly)10. Two computer models were generated for the Gly----Ala peptide, one with the Ala side chains packed inside the helix and the other with the region containing the alanines forming a beta-bend that loops out from the helix. The nmr data is more consistent with the latter model.     

COMPARATIVE ONTOGENY OF A WILD CUCURBIT AND ITS DERIVED CULTIVAR

Most previous studies of evolutionary modification of form in plants have focused primarily on individual organs or flowers. Few have investigated the role of evolutionary changes in timing or position at the level of whole plant ontogeny. This study compares ontogenies of the primary shoots of two subspecies of Cucurbita argyrosperma, one a cultivar and the other its wild progenitor. Differences in flowering times between these subspecies suggested that the cultivar may have evolved from the wild subspecies via heterochronic processes leading to paedomorphosis. Analyses showed that both subspecies are similar in vegetative architecture and rates of leaf production. Earlier flowering in the cultivar, both in terms of position and absolute time, appears to have arisen through progenesis. Initial observations of leaf blade morphology led to the hypothesis that paedomorphosis and gigantism also may have been involved in the evolution of leaf blade shape in the cultivar: all leaves of the cultivar are larger and visually similar in shape to early leaves of the wild subspecies. However, quantitative analysis revealed that leaves of the cultivar are neither geometrically, nor solely allometrically larger versions of early leaves of the progenitor. Leaf shape in the cultivar exhibits novel features as well as effects of allometry shared with the progenitor, hence a simple hypothesis of paedomorphic evolution of leaf shape is not supported.     

Reliability and stability of mothers' reports about their pregnancies with twins.

The objective of this study was to determine if mothers' retrospective reports about events in their pregnancies with twins are reliable and stable. Six hundred and twenty-four mothers completed psychiatric interviews about their twins. These interviews also contained questions about the mothers' pregnancies, the perinatal period, and the child's early development. The mothers reported first on one twin and then on the other with interviews spaced from 3 days to 2 weeks apart. Thus mothers reported on the same pregnancy twice. Of these mothers, 47 were re-interviewed 6 to 18 months later by raters blind to the results of the initial interview. The twin design allowed us to compare the short-term reliability of the 624 mothers' reports of the same pregnancy. The re-interview of the 47 mothers enabled us to compare the stability of reports over a longer time period. Agreement between the reports was measured with the kappa statistic. Kappas were good to excellent for the short-term reports of pregnancy for each twin for the 624 mothers. Kappas were equally high for the 47 mothers that were re-interviewed 6 to 18 months later. Mothers show good reliability and stability of reporting about events during pregnancy.     

Solid-phase synthesis of triple-helical collagen-model peptides

Summary The triple-helical conformation of collagen has been proposed to be important for mediation of cellular activities, such as adhesion and activation, extracellular matrix assembly, and enzyme function. We have developed synthetic protocols that allow for the study of biological activities of specific collagen sequences in triple-helical conformation. These methods primarily involve solid-phase assembly and covalent linkage of three peptide chains. The resultant triple-helical peptides have sufficient thermal stabilities to permit structural and biological characterization under physiological conditions. The present article critically reviews the various approaches for constructing synthetic triple-helices.This paper is based on a presentation given at the Symposium on Peptide Structure and Design as part of the 31st Annual ACS Western Regional Meeting held in San Diego, CA, USA, October 18–21, 1995.     

Cloning of an Aeromonas hydrophila type IV pilus biogenesis gene cluster: complementation of pilus assembly functions and characterization of a type IV leader peptidase/N-methyltransferase required for extracellular protein secretion

Aeromonas hydrophila secretes several extracellular proteins that are associated with virulence including an enterotoxin, a protease, and the hole-forming toxin, aerolysin. These degradative enzymes and toxins are exported by a conserved pathway found in many Gram-negative bacteria. In Pseudomonas aeruginosa this export pathway and type IV pilus biogenesis are dependent on the product of the pilD gene. PilD is a bifunctional enzyme that processes components of the extracellular secretory pathway as well as a type IV prepilin. An A. hydrophila genomic library was transferred into a P. aeruginosa pilD mutant that is defective for type IV pilus biogenesis. The A. hydrophila pilD homologue, tapD , was identified by its ability to complement the pilD mutation in P. aeruginosa . Transconjugants containing tapD were sensitive to the type IV pilus-specific phage, PO4. Sequence data revealed that tapD is part of a cluster of genes ( tapABCD ) that are homologous to P. aeruginosa type IV pilus biogenesis genes ( pilABCD ). We showed that TapB and TapC are functionally homologous to P. aeruginosa PilB and PilC, the first such functional complementation of pilus assembly demonstrated between bacteria that express type IV pili. In vitro studies revealed that TapD has both endopeptidase and N -methyltransferase activities using P. aeruginosa prepilin as substrate. Furthermore, we show that tapD is required for extracellular secretion of aerolysin and protease, indicating that tapD may play an important role in the virulence of A. hydrophila     

成人革兰阴性杆菌肺炎23例临床分析

本文以临床体征,胸片和连续二次以上细菌培养阳性为诊断标准,报告革兰阴性杆菌肺炎２３例,并就其临床表现,并发症及预后进行分析,提出８种情况应考虑革兰阴性杆菌肺炎,对临床诊断和治疗有指导意义．     

HMG-GoA reductase and terpenoid phytoalexins: Molecular specialization within a complex pathway

Terpenoid phytoalexins and other defense compounds play an important role in disease resistance in a variety of plant families but have been most widely studied in solanaceous species. The rate-limiting step in terpenoid phytoalexin production is mediated by 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), which catalyzes mevalonic acid synthesis. HMGRs are involved in the biosynthesis of a broad array of terpenoid compounds, and distinct isoforms of HMGR may be critical in directing the flux of pathway intermediates into specific end products. Plant HMGRs are encoded by a small gene family, and genomic or cDNA sequences encoding HMGR have been isolated from several plant species. In tomato, four genes encode HMGR; these genes are differentially activated during development and stress responses. One gene, hmg 2 , is activated in response to wounding and a variety of pathogenic agents suggesting a role in sesquiterpene phytoalexin biosynthesis. In contrast, expression patterns of tomato hmg l suggest a role in sterol biosynthesis and cell growth. Other plant species show an analogous separation of specific HMGR isoforms involved in growth and/or housekeeping function and inducible isoforms associated with biosynthesis of phytoalexins or other specialized "natural products". We are applying a variety of cell and molecular techniques to address whether subcellular localization and/or differential expression of these isoforms are key factors in determining end product accumulation during development and defense.