Pili in Gram-negative and Gram-positive bacteria — structure, assembly and their role in disease

Many bacterial species possess long filamentous structures known as pili or fimbriae extending from their surfaces. Despite the diversity in pilus structure and biogenesis, pili in Gram-negative bacteria are typically formed by non-covalent homopolymerization of major pilus subunit proteins (pilins), which generates the pilus shaft. Additional pilins may be added to the fiber and often function as host cell adhesins. Some pili are also involved in biofilm formation, phage transduction, DNA uptake and a special form of bacterial cell movement, known as ‘twitching motility’ In contrast, the more recently discovered pili in Gram-positive bacteria are formed by covalent polymerization of pilin subunits in a process that requires a dedicated sortase enzyme. Minor pilins are added to the fiber and play a major role in host cell colonization. This review gives an overview of the structure, assembly and function of the best-characterized pili of both Gram-negative and Gram-positive bacteria. Received 08 August 2008; received after revision 24 September 2008; accepted 01 October 2008     

AMP deaminase, 5′-nucleotidase and adenosine deaminase in rat myocardial tissue in myocardial infarction and hypothermia

Summary AMP deaminase, 5-nucleotidase and adenosine deaminase have been estimated in skeletal muscle and myocardial tissue in normal rats and in rats subjected to experimental myocardial infarction or hypothermia. A difference in the enzyme distribution was found between the right and left ventricles in the normal rat. A decrease in the activity of 5-nucleotidase and an increase in the activity of adenosine deaminase were observed in infarcted myocardial tissue. The activity of all 3 enzymes was found to be depressed in the myocardium in rats subjected to hypothermia. These results are discussed in relation to adenosine production and its beneficial effects.     

Vital Instability: Life and Free Will in Physics and Physiology, 1860–1880

During the period 1860–1880, a number of physicists and mathematicians, including Maxwell, Stewart, Cournot and Boussinesq, used theories formulated in terms of physics to argue that the mind, the soul or a vital principle could have an impact on the body. This paper shows that what was primarily at stake for these authors was a concern about the irreducibility of life and the mind to physics, and that their theories can be regarded primarily as reactions to the law of conservation of energy, which was used among others by Helmholtz and Du Bois-Reymond as an argument against the possibility of vital and mental causes in physiology. In light of this development, Maxwell, Stewart, Cournot and Boussinesq showed that it was still possible to argue for the irreducibility of life and the mind to physics, through an appeal to instability or indeterminism in physics: if the body is an unstable or physically indeterministic system, an immaterial principle can act through triggering or directing motions in the body, without violating the laws of physics.     

Navigational enterprises in Europe and its empires, 1730–1850

Scientific chemical production on a commercial scale was evident in Britain in the early nineteenth century. One of the first palaeotechnic chemical industries was the manufacture of synthetic alkali. By 1823 a well-defined pattern of soda production had emerged. An understanding of this initial distribution is important as those areas associated with the early growth of the synthetic alkali industry showed a remarkable continuity of inorganic chemical production for the remainder of the century. The paper attempts to consider those factors which contributed to this selective regional response, and in doing so, a number of interesting factors of location are revealed.     

Properties of γ-glutamyltranspeptidase,and glutathione levels in rat mammary gland

Summary -Glutamyltranspeptidase activity and glutathione levels were studied in rat mammary gland during the lactogenic cycle; both increased during mid-lactation. The enzyme's specific activity with several amino acids showed that glutamine and methionine were the best substrates. Maleate decreased the transpeptidation reaction and increased the hydrolytic activity. These results suggest that -glutamyltranspeptidase from the mammary gland is similar to the enzyme described in other tissues in relation to these properties and the physiological role proposed in amino acids transport.     

Conceiving processes in atmospheric models—General equations,subscale parameterizations,and ‘superparameterizations’

The scientific understanding of atmospheric processes has been rooted in the mechanical and physical view of nature ever since dynamic meteorology gained ground in the late 19th century. Conceiving the atmosphere as a giant ‘air mass circulation engine’ entails applying hydro- and thermodynamical theory to the subject in order to describe the atmosphere’s behaviour on small scales. But when it comes to forecasting, it turns out that this view is far too complex to be computed. The limitation of analytical methods precludes an exact solution, forcing scientists to make use of numerical simulation. However, simulation introduces two prerequisites to meteorology: First, the partitioning of the theoretical view into two parts—the large-scale behaviour of the atmosphere, and the effects of smaller-scale processes on this large-scale behaviour, so-called parametrizations; and second, the dependency on computational power in order to achieve a higher resolution. The history of today’s atmospheric circulation modelling can be reconstructed as the attempt to improve the handling of these basic constraints. It can be further seen as the old schism between theory and application under new circumstances, which triggers a new discussion about the question of how processes may be conceived in atmospheric modelling.     

The platypus in Edinburgh: Robert Jameson,Robert Knox and the place of the Ornithorhynchus in nature, 1821–24

The duck-billed platypus, or Ornithorhynchus, was the subject of an intense debate among natural historians in the late eighteenth and early nineteenth centuries. Its paradoxical mixture of mammalian, avian and reptilian characteristics made it something of a taxonomic conundrum. In the early 1820s Robert Jameson (1774–1854), the professor of natural history at the University of Edinburgh and the curator of the University's natural history museum, was able to acquire three valuable specimens of this species. He passed one of these on to the anatomist Robert Knox (1791–1862), who dissected the animal and presented his results in a series of papers to the Wernerian Natural History Society, which later published them in its Memoirs. This paper takes Jameson's platypus as a case study on how natural history specimens were used to create and contest knowledge of the natural world in the early nineteenth century, at a time when interpretations of the relationships between animal taxa were in a state of flux. It shows how Jameson used his possession of this interesting specimen to provide a valuable opportunity for his protégé Knox while also helping to consolidate his own position as a key figure in early nineteenth-century natural history.     

β-Adrenoceptor blocking drugs,heart rate and genetic hypertension development in rats

Summary In spontaneously hypertensive rats (SHRs) chronically treated during their growth with -adrenoceptor blocking drugs, no correlation was found between the reduction in heart rate and the prevention of genetic hypertension development.This work was supported by a grant from the Scientific Council of the Faculté de Médecine Paris-Sud (1978/754).     

Animal experiments, vital forces and courtrooms: Mateu Orfila, François Magendie and the study of poisons in nineteenth-century France

The paper follows the lives of Mateu Orfila and Fran?ois Magendie in early nineteenth-century Paris, focusing on their common interest in poisons. The first part deals with the striking similarities of their early careers: their medical training, their popular private lectures, and their first publications. The next section explores their experimental work on poisons by analyzing their views on physical and vital forces in living organisms and their ideas about the significance of animal experiments in medicine. The last part describes their contrasting research on the absorption of poisons and the divergences in their approaches, methods, aims, standards of proof, and intended audiences. The analysis highlights the connections between nineteenth-century courtrooms and experimental laboratories, and shows how forensic practice not only prompted animal experimentation but also provided a substantial body of information and new research methods for dealing with major theoretical issues like the absorption of poisons.     

The in vivo expression of the globin genes of theβ cistron in γ-,δ-, andδβ-thalassemia heterozygotes

There is considerable evidence suggesting that the switch from to and chain production after birth is due, in part, to silencing of the genes by stage-specific factors which bind to their promoters and to the competition from the adult ( and ) genes for a common enhancer element located in the locus control region. As a consequence one can expect that the increased Hb F production in adults with hereditary persistence of fetal hemoglobin or -thalassemia is directed mainly by -globin genes in cis to the deletion(s) responsible for these conditions. Here we review data on heterozygotes with -, -, or -thalassemia, who also had an^AT mutation, in cis or in trans, which was used as a marker of gene expression. The results show that a deletion affecting adult genes favors the expression of genes in cis, while the deletion of a single gene does not affect the expression of the gene in cis but leads to a faster switch postnatally.     

The presence of β-phenylethylamine,p-tyramine,m-tyramine and tryptamine in ganglia and foot muscle of the garden snail (Helix aspersa)

Summary The concentrations of -phenylethylamine,p-tyramine,m-tyramine,m-octopamine and tryptamine in the ganglia or foot muscle ofHelix aspersa range from <0.6 to 11 ng/g.p-Octopamine levels are higher in ganglia (327 ng/g) than in foot muscle (4.1 ng/g). Dopamine and 5-hydroxytryptamine range from 840 to 2710 ng/g while their acid metabolites, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid and 5-hydroxyindoleacetic acid range from <20 to 130 ng/g.Acknowledgments. We thank Dr A.A. Boulton for helpful discus sion, Dr D.A. Durden for supervising the mass spectrometric analyses, Dr B.A. Davis for the synthesis of the deuterated standards, G.H. Wheatley, E.P. Zarycki and M. Mizuno for expert technical assistance, and Saskatchewan Health and the MRC of Canada for providing financial support.     

Aryl and aniline hydroxylases in rat nuclear membranes after pretreatment with pregnenolone 16α-carbonitrile,phenobarbital and methylcholanthrene

Résumé L'aryl hydrocarbure hydroxylase nucléaire répond seulement au méthylcholanthrène tandis que le phénobarbital et la prégnénolone 16-carbonitril ne l'affectent pas. Les trois substances n'induisent pas l'aniline hydroxylase nucléaire. Cependant elles sont des puissants inducteurs de l'aryl et l'aniline hydroxylase microsomiale.

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We thank Dr.H. Gelboin for the 3-hydroxybenzo(a)pyrene, Dr.J. Babcock for pregnenolone 16-carbonitrile, and Dr.M. Bornens for his helpful discussions.     

The effects of 9α-halohydrocortisones and of aldosterone on survival,growth and sodium-potassium excretion in adrenalectomized rats

Zusammenfassung Die Wirkungen von Aldosteron und 9-Halogenhydrocortison-azetaten auf das Überleben und Wachstum adrenalektomierter Ratten wurden studiert. Im Na/K-Ausscheidungstest zeigten sich 9-Chlor-hydrocortison-azetat bzw. 9-Fluor-hydrocortison-azetat 35-bzw. 10mal wirksamer als DCA und wiesen 1/3 bzw. 1/10 der Wirksamkeit von Aldosteron auf.     

5′-Nucleotidase activity in liver homogenates of rats treated with CCl4, colchicine,cycloheximide, emetine,ethanol, ethionine and 5-fluorotryptophan

Summary 5-Nucleotidase activity, an enzyme marker of the plasma membranes, increases in female rat liver homogenates following ethionine administration, while homogenates from males show no changes. Treatment with CCl₄, colchicine, cycloheximide, emetine, ethanol and 5-fluorotryptophan does not significantly modify the 5-nucleotidase activity of liver homogenates of either female or male rats.