N-Monomethyl-arginine and nicotinamide prevent streptozotocin-induced double strand DNA break formation in pancreatic rat islets

The impact of short term in vitro exposure to the diabetogenic drug streptozotocin on pancreatic islet glucose metabolism, insulin secretion, DNA fragmentation and cell viability, was studied. Streptozotocin impaired cell viability as well as insulin secretion and the oxidation of glucose. These effects were partially counteracted by inhibition of the inducible form of nitric oxide synthase with N-monomethyl-arginine and by scavenging oxygen free radicals with nicotinamide. Isolated islets underwent double strand DNA fragmentation after 24 h in culture. The degree of DNA breakdown was strongly enhanced by exposure of the islet DNA was obtained with N-monomethyl-arginine and nicotinamide. These data suggest that the generation of reactive oxygen and nitrogen species is involved in the deleterious action of streptozotocin on pancreatic islet tissue. A role for oxygen radicals generated during streptozotocin-induced islet cell damage as possible mediators of the expression of the inducible form of nitric oxide synthase and the scavenging action of nicotinamide on these radicals, is then proposed.     

Modification of diuresis in the rat by chlorpropamide,glibenclamide and tolbutamide

Zusammenfassung Es wurden die Wirkungen von Chlorpropamid, Glibenclamid und Tolbutamid auf die Nieren wasserbelasteter normaler und diabetischer Ratten untersucht.     

On the genesis of the soil mantle of the region of Manaus,Central Amazonia,Brazil

Summary The dynamics of the forest to the north of Manaus is tightly linked to that of the soil. The latosol that covers the plateau, which supports a dense forest, consists from top to bottom of: (a) a brown, clayey organic horizon (0.3 m), (b) a yellow horizon, very rich in clay but permeable (from 0.3 to 4 m), (c) a nodular horizon rich in Al and Fe oxides (from 4 to 9 m), and (d) a horizon which still preserves the sedimentary structures of the parent sandstone, where quartz is intensely dissolved and kaolinite crystallizes in pores. In perfectly flat areas, the clay of the organic horizon is destroyed by acidocomplexolysis, and the dissolved Al is transported vertically by the drainage water. A part of this Al is used to make the gibbsite nodules of horizon (c), and the rest is used to make kaolinite in horizon (d). Because aluminum is thus conserved within any vertical prism, the rate of destruction of horizon (a) is equivalent to the rate of advance of the kaolinization zone into the sediment: the latosol is said to be in equilibrium, the surface remains perfectly flat as it slowly sinks, the quantity of kaolinite increases with time, and the silica released by quartz dissolution in the whole profile is exported by drainage water to the water table. In contrast, near drainage axes, however small initially, the drainage becomes inclined toward the axis. Part of the Al released by acidocomplexolysis of horizon (a) is now exported to rivers, and Al is no longer conserved within any given prism. The rate of advance of the kaolinization zone (d) into the sediment now becomes less than the rate of destruction of horizon (a) and the surface sinks faster than that of the surrounding plateau. After this differential podzolization has gone on long enough, it creates a network of geochemical valleys characterized by convex slopes and bounded by sandy soils (campinas). The vegetation becomes sparser and sparser. At the end, only some bushes and lichens survive on the white sand.Acknowledgments. The authors are indebted to Dr E. Merino (Dept. of Geology, Indiana University) for helpful criticisms and suggestions. This research was carried out in I.N.P.A. (Instituto Nacional de Pesquisas da Amazonia) and was financially supported by the CNPq-CNRS/ORSTOM conv.     

The tortoise caterpillar: carnivory and armoured larval morphology of the metalmark butterfly Pachythone xanthe (Lepidoptera: Riodinidae)

ABSTRACT

The natural history and morphology of the later instars and pupa of the metalmark butterfly Pachythone xanthe H. Bates are described and illustrated for the first time. The caterpillars are myrmecophilous and carnivorous, feeding on scale insects (Hemiptera: Coccoidea) tended by Azteca cf. chartifex Forel (Formicidae: Dolichoderinae) ants and appear to be physically shielded from potential ant attacks by a carapace-like body that protects the head and appendages. In addition, the larvae present several types of specialised setae and ant-organs such as perforated cupola organs, glandular openings and functional tentacle nectary organs that may be related to appeasement of aggressive ant behaviour. Our results reveal the first detailed life cycle data for the Pachythonina subtribe and record a new independent origin of carnivory in Riodinidae.     

Forensic Science: Current State and Perspective by a Group of Early Career Researchers

Forensic science and its influence on policing and the criminal justice system have increased since the beginning of the twentieth century. While the philosophies of the forensic science pioneers remain the pillar of modern practice, rapid advances in technology and the underpinning sciences have seen an explosion in the number of disciplines and tools. Consequently, the way in which we exploit and interpret the remnant of criminal activity are adapting to this changing environment. In order to best exploit the trace, an interdisciplinary approach to both research and investigation is required. In this paper, nine postdoctoral research fellows from a multidisciplinary team discuss their vision for the future of forensic science at the crime scene, in the laboratory and beyond. This paper does not pretend to be exhaustive of all fields of forensic science, but describes a portion of the postdoctoral fellows’ interests and skills.     

Intensions, belief and science: Kuhn’s early philosophical outlook (1940-1945)

Between 1940 and 1945, while still a student of theoretical physics and without any contact with the history of science, Thomas S. Kuhn developed a general outline of a theory of the role of belief in science. This theory was well rooted in the philosophical tradition of Emerson Hall, Harvard, and particularly in H. M. Sheffer’s and C. I. Lewis’s logico-philosophical works—Kuhn was, actually, a graduate student of the former in 1945. In this paper I reconstruct the development of that general outline after Kuhn’s first years at Harvard. I examine his works on moral and aesthetic issues—where he displayed an already ‘anti-Whig’ stance concerning historiography—as well as his first ‘Humean’ approach to science and realism, where his earliest concern with belief is evident. Then I scrutinise his graduate work to show how his first account of the role of belief was developed. The main aim of this paper is to show that the history of science illustrated for Kuhn the epistemic role and effects of belief he had already been theorising about since around 1941.