The mercapturic acid pathway metabolites of a glutathione conjugate of aflatoxin B1

A glutathione conjugate of aflatoxin B1 (AFB1) which has previously been identified as 8,9-dihydro-8-(S-glutathionyl)-9-hydroxy aflatoxin B1 (AFB1-GSH) (E.J. Moss, D.J. Judah, M. Przybylski and G.E. Neal, Biochem. J., 210 (1983) 227-233) has been degraded in vitro to all of the intermediates of the mercapturic acid pathway (MAP) and the chromatographic and spectral characteristics of each of these compounds investigated. The cysteinylglycyl conjugate (AFB1-Cys.Gly) was prepared by incubating the AFB1-GSH conjugate with a rat hepatoma cell line rich in gamma-glutamyl-transpeptidase (GGT). Incubations of the AFB1-Cys.Gly conjugate with dipeptidase produced a metabolite, which was purified and characterized by 1H-NMR spectroscopy as 8,9-dihydro-8-(S-cysteinyl)-9-hydroxy aflatoxin B1 (AFB1-Cys). The N-acetyl derivative of the AFB1-Cys conjugate resulted from the incubation of the AFB1-GSH conjugate in vitro with isolated rat kidney cells. Mass spectral data were consistent with the compound being 8,9-dihydro-8-(S-cysteinyl-(N-acetyl))-9-hydroxy aflatoxin B1 (AFB1-Nac.Cys). A chromatographically identical compound was obtained by the chemical acetylation of AFB1-Cys.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Biosynthesis of serum albumin in rat liver. Isolation and probable structure of ''proalbumin'' from rat liver.

1. Two methods are described for the preparation of 'proalbumin' in good yields from rat liver. 2. One of the methods does not depend on the use of specific antisera. 3. The product from both methods is identical as judged by electrophoresis on polyacrylamide gel, isoelectric focusing on pH gradients, ion-exchange chromatography and quantitative immunoelectrophoresis. The protein also appears to be radiochemically pure by these criteria. 4. The protein is free from serum albumin as judged by isoelectric focusing and co-chromatography on ion-exchange columns. It is judged to be free from other proteins by these same criteria and by specific precipitation with antibody. 5. It is converted into serum albumin by limited tryptic hydrolysis. The albumin so produced has the same N-terminal (glutamic acid) and C-terminal (alanine) amino acids as reported for rat serum albumin. 6. A hexapeptide is liberated from the N-terminal end of 'proalbumin' simultaneously. It contains three arginine, one phenylalanine, one valine and one glycine residues.     

Evidence for the coupling of biosynthesis and secretion of serum albumin in the rat. The effect of colchicine on albumin production

1. By using isotopic-dilution techniques it was found that colchicine causes a slight increase in the proalbumin content of liver, from 0.63+/-0.06 to 0.83+/-0.10mg/g of liver, but has no effect on albumin content (0.50+/-0.05mg/g of liver). All the proalbumin and 67% of the albumin is found in vesicles from which they are liberated by detergents. 2. Colchicine inhibits secretion of albumin, decreases the rate of conversion of proalbumin into albumin and decreases the rate of incorporation of l-[1-(14)C]leucine into proalbumin. 3. Balance studies in vivo show that all the (14)C appearing in serum albumin can be accounted for by the flow of (14)C through the proalbumin, in the presence or absence of colchicine. 4. When cycloheximide is given to the rats, 2min after [(14)C]leucine, further synthesis of protein stops. The label in proalbumin disappears and the proalbumin content of the liver falls, so as to account for the albumin appearing in the plasma. This occurs both in the presence and in the absence of colchicine. By contrast, there is little change in liver albumin. Studies with isolated perfused livers are in agreement with the above. Lumicolchicine has no effect on any of these systems at doses at which colchicine exerts its action. 5. These results suggest that biosynthesis and conversion of proalbumin into albumin, and secretion of serum albumin are controlled at each step.     

Age-Specific Mortality During the 1918 Influenza Pandemic: Unravelling the Mystery of High Young Adult Mortality

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.

“The war is over – and I must go” Egon Schiele, 1890–1918.

     

The placenta theory and the origin of infantile hemangioma

The pathogenesis of infantile hemangioma is unknown. In recent years, much of the focus has been placed at identifying the cell type(s) responsible for tumor initiation. New discoveries in infantile hemangioma suggest an involvement of progenitor cells in the pathogenesis of this vascular tumor. Both embryonic and extra-embryonic tissues have been postulated as potential sources for these progenitor cells. This review focuses on the placental theory, which proposes that a fetal placental progenitor is the cell type of origin for infantile hemangioma. Special emphasis will be placed on placental vasculogenesis and the presence and transit of placental progenitor cells during gestation.     

The cover of living and dead corals from airborne remote sensing

Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m² pixels and 6 spectral bands with 0.25-m² pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral resolution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead Porites (total colony mortality within 6 months), old dead (>6 months) Porites, Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562–580 nm. However, partially dead and recently dead Porites colonies could not be distinguished from an airborne platform. Spectral differences among substrata are then exploited to predict the cover of reef substrata in ten 25-m² plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01-m² grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m² quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of Porites spp.). At the scale of the reef (all ten 25-m² quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living Porites, recently dead Porites and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods required 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Remote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m² of reef, which represents 3,700 plots of 25 m² each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m² and 0.25-m² image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6–1.8 times greater in 0.25-m² pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, providing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey).     

Fundamental concepts of the angiogenic process

The process of angiogenesis encompasses the growth and regression of capillary blood vessels. Angiogenesis is finely regulated at the molecular and genetic levels, not unlike other physiologic processes such as coagulation, glucose metabolism, and blood pressure. During the development of the field of angiogenesis research over the past three decades, fundamental concepts have been introduced along the way in an attempt where possible, to unify new data from a variety of different laboratories. I have assembled here the major concepts which underlie the angiogenic process as we currently understand it. Many of these are now taken for granted, but this was not always the case, and I have tried to show how they were developed. My goal is to provide a conceptual framework for those basic scientists or clinicians who may enter this rapidly expanding field. Each concept discussed here is accompanied by a few key references as a guide to the pertinent literature.