The peptidoglycan crosslinking enzyme system in Streptomyces strains R61, K15 and rimosus

The DD-carboxypeptidase-transpeptidase enzyme system in Streptomyces strain K15 consists of: (1) a membrane-bound transpeptidase capable of performing low DD-carboxypeptidase activity; and (2) a set of DD-carboxypeptidases: (a) membrane-bound, (b) lysozyme-releasable and (c) exocellular, having low transpeptidase activities in aqueous media and at low acceptor concentrations. The DD-carboxypeptidases are related to each other and may belong to the same pathway leading to enzyme excretion. A similar enzyme system occurs in Streptomyces strain R61 except that the membrane-bound DD-carboxypeptidase activity is low when compared with the membrane-bound transpeptidase activity. In Streptomyces rimosus the enzyme system consists almost exclusively of the membrane-bound transpeptidase and the levels of membrane-bound, lysozyme-releasable and exocellular DD-carboxypeptidases are very low.     

Produits neutres et alcaloides de Myrtopsis macrocarpa,M. myrtoidea,M. novae-caledoniae et M. sellingii

Stems and leaves of Myrtopsis macrocarpa, M. myrtoidea, M. novae-caledoniae and M. sellingii yielded terpenes, sterols, coumarins, alkaloids (furoquinolines and quinolones) and amides. A new quinolone (8-methoxy flindersine) occurs in Myrtopsis macrocarpa, a new amide (N-benzoyltryptamine) in M. myrtoidea, two new coumarins (myrsellin and myrsellinol) and a new dihydrofuroquinoline (myrtopsine) in M. sellingii. Structures of the new compounds are proposed from chemical and spectroscopic evidence.     

Mitochondrial DNA evolution in lagomorphs: Origin of systematic heteroplasmy and organization of diversity in European rabbits

Summary A characterization was conducted on mitochondrial DNA (mtDNA) molecules extracted separately from 107 European rabbits (Oryctolagus cuniculus) both wild and domestic, 13 European hares (Lepus capensis), and 1 eastern cottontail (Sylvilagus floridanus). Experimentally this study took into account restriction site polymorphism, overall length variation of the noncoding region, and numbers of repeated sequences. Nucleotide divergences indicate that the mtDNAs from the three species derived from a common ancestor some 6–8 million years (Myr) ago. Every animal appeared heteroplasmic for a set of molecules with various lengths of the noncoding region and variable numbers of repeated sequences that contribute to them. This systematic heteroplasmy, most probably generated by a rate of localized mtDNA rearrangements high enough to counterbalance the cellular segregation of rearranged molecules, is a shared derived character of leporids.The geographic distribution of mtDNA polymorphism among wild rabbit populations over the western European basin shows that two molecular lineages are represented, one in southern Spain, the second over northern Spain, France, and Tunisia. These two lineages derived from a common ancestor some 2 Myr ago. Their present geographical distribution may be correlated to the separation of rabbits into two stocks at the time of Mindel glaciation.Finally the distribution of mtDNA diversity exhibits a mosaic pattern both at inter- and intrapopulation levels.     

Metal exchanges in the fauna-sediment system. The case of Nereis diversicolor and Scrobicularia plana in the Bou Regreg estuary (Morocco)

This study identifies the types and quantities of metals retained by Nereis diversicolor and Scrobicularia plana in a predominantly arid estuary environment.Certain abiotic parameters and a number of physiological processes linked to metabolic and reproductive functions play a decisive role in the seasonal influence of metal levels on the tissues of these organisms.Given the deposivoric diet of the organisms, the sedimentary bed would appear to be the principal source of metal accumulation.The following classification illustrates the bioaccumulation of metals: 209-1The possibility that these metals may be carried into the estuary by sewage water from the cities of Rabat and Sále should certainly not be ignored.     

Predictive value of the ear-crease sign in coronary artery disease.

The value of the ear-crease sign in predicting the presence of coronary artery disease was studied in 340 consecutive patients who underwent coronary arteriography. In this selected population, 75.6% of whom had coronary artery disease, the sensitivity of the sign was 59.5%, the specificity 81.9% and the positive predictive value 91.1%. The sign was associated with increasing age but was also independently associated with obstructive coronary artery disease. No significant correlation was found between the sign and the presence of risk factors or other signs of such disease, except for corneal arcus. In symptomatic patients the sign suggested the presence of more extensive coronary artery disease. In an asymptomatic population with a low prevalence of coronary artery disease it appears to be of limited value in predicting obstructive coronary artery disease. However, it may identify a subset of patients prone to early ageing and to the early development of coronary artery disease, whose prognosis might be improved by early preventive measures.     

Regulation of amino acid transport in growing cells of Streptomyces hydrogenans

The uptake of various amino acids into Streptomyces hydrogenans grown in chemostatically and turbidostatically controlled steady state cultures has been investigated. A close correlation between transport capacity and the growth rates of the cells was found. As shown by kinetic analysis, the increased transport is due to elevated maximum uptake rates, the apparent Michaelis constants remaining unchanged. Analysis of the unidirectional fluxes of cycloleucine revealed that not only the influx is raised as the growth rate is increased but also the efflux. Hence, the conclusion is drawn that the growth-rate dependent modulation of transport capacity is, at least, partially due to the variation of the concentration of active transport components. Since the cells were grown in the absence of external amino acids the results suggest that amino acid transport into S. hydrogenans is under the control of endogenous effectors.List of Abbreviations AIB 2-aminoisobutyric acid - Cycloleucine 1-aminocyclopentane-1-carboxylic acid     

Cycloheximide resistance in Chinese hamster cells. II. Induction of Chm resistance in Chinese hamster cells by N-nitrosomethylurea.

Mutant Chinese hamster ovarian (CHO) cells with a resistance to 7-10(-7) and 8-10(-7) M cycloheximide (CHM) were induced at mutation rates of 1.9-5.2-10(-3) and 1.6-1.8-10(-3) respectively after treatment with N-nitrosomethylurea (NMU) at 100 mug/ml. The induced mutation rates differed by two orders of magnitude from the spontaneous rate of mutation to CHM resistance.