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R Klausner

Publications and source records attributed to R Klausner.

13 recordsLinked to original sources
PubMed2003

Public health. Grand Challenges in Global Health.

This week an international panel announces a list of 14 Grand Challenges in Global Health, and scientists throughout the world will be invited to submit grant proposals to pursue them with funds provided by the Bill and Melinda Gates Foundation. We describe the characteristics of these challenges and the process by which they were formulated and selected after receiving over 1000 responses to a "call for ideas" from the scientific community.

Animals↗
PubMed1998

Improved detection of germline mutations in the von Hippel-Lindau disease tumor suppressor gene.

von Hippel-Lindau disease (VHL) is an inherited neoplastic disorder characterized by the development of tumors in the eyes, brain, spinal cord, inner ear, adrenal gland, pancreas, kidney, and epididymis. The VHL tumor suppressor gene was identified in 1993. Initial studies reported the detection of germline mutations in the VHL gene in 39-75% of VHL families. We used tests that detect different types of mutations to improve the frequency of detection of germline mutations in VHL families. The methods included quantitative Southern blotting to detect deletions of the entire VHL gene, Southern blotting to detect gene rearrangements, fluorescence in situ hybridization (FISH) to confirm deletions, and complete sequencing of the gene. Here we report that we have detected germline mutations in the VHL gene in 100% (93/93) of VHL families tested. In addition, we describe 13 novel intragenic VHL germline mutations. With the methodology described in this article, it is now possible to identify germline mutations in virtually all families with VHL.

Blotting, Southern↗
PubMed1997

Regulation of iron metabolism in eukaryotes.

Iron metabolism is regulated in cells to ensure that iron supplies are adequate and nontoxic. The expression of iron metabolism is regulated primarily by posttranscriptional mechanisms. Ferritin, eALAS, SDHb of Drosophila, and mammalian mitochondrial aconitase are translationally regulated. The TfR is regulated at the level of mRNA stability. Iron regulatory proteins are regulated either by assembly or by disassembly of an iron-sulfur cluster (IRP1) or by rapid degradation in the presence of iron (IRP2). The list of targets for IRP-mediated regulation is growing longer, and a range of possibilities for versatile regulation exists, as each IRP can bind to unique targets that differ from the consensus IRE. The reactivity of iron with oxygen and the creation of toxic by-products may be the evolutionary stimulus that produced this system of tight posttranscriptional gene regulation.

Aconitate Hydratase↗
PubMed1986

Regulation of intracellular iron distribution in K562 human erythroleukemia cells.

Following a pulse with 59Fe-transferrin, K562 erythroleukemia cells incorporate a significant amount of 59Fe into ferritin. Conditions or manipulations which alter the supply of iron to cells result in changes in the rate of ferritin biosynthesis with consequent variations in the size of the ferritin pool. Overnight exposure to iron donors such as diferric transferrin or hemin increases the ferritin level 2-4- or 6-8-fold above that of the control, respectively. Treatment with the anti-human transferrin receptor antibody, OKT9 (which reduces the iron uptake by decreasing the number of transferrin receptors) lowers the ferritin level by approximately 70-80% with respect to the control. The fraction of total cell-associated 59Fe (given as a pulse via transferrin) that becomes ferritin bound is proportional to the actual ferritin level and is independent of the instantaneous amount of iron taken up. This has allowed us to establish a curve that correlates different levels of intracellular ferritin with corresponding percentages of incoming iron delivered to ferritin. Iron released from transferrin appears to distribute to ferritin according to a partition function; the entering load going into ferritin is set for a given ferritin level over a wide range of actual amounts of iron delivered.

Biological Transport↗
PubMed1985

Effects of alterations in cellular iron on biosynthesis of the transferrin receptor in K562 cells.

Treatment of K562 cells, a human erythroleukemia cell line, with desferrioxamine raised the levels of the receptor for transferrin (Tf) two- to threefold over that of the control cells. The levels of receptor were reduced by at least 50 and 35% of that of the control in cells treated with diferric Tf and ferric ammonium citrate, respectively. These changes were of total cellular receptors with no alteration in the proportion of receptors found on the cell surface. The half-lives of the receptor were identical in cells treated with desferrioxamine, diferric Tf, or ferric ammonium citrate. Cells metabolically labeled with [35S]methionine showed a 2.5-fold increase in the rate of receptor synthesis when treated with desferrioxamine and a 35 and 65% decrease when treated with ferric ammonium citrate and diferric Tf, respectively. In vitro translations of polyadenylated mRNA isolated from cells incubated with desferrioxamine showed a 2.5-fold increase in translatable mRNA for the receptor, whereas treatment of cells with ferric ammonium citrate and diferric Tf resulted in a 25 and 50% reduction, respectively, in translatable mRNA for this receptor.

Cell Line↗
PubMed1983

Role of microtubules in the distribution of the Golgi apparatus: effect of taxol and microinjected anti-alpha-tubulin antibodies.

Immunofluorescence microscopy reveals that both microtubule organizing center (MTOC) and Golgi apparatus are contained in the same perinuclear area of A549 cells in interphase. The cells display long microtubules stretching radially from the MTOC to the plasma membrane. Treatment of cells with taxol results in polymerization of microtubules without relation to the MTOC and formation of microtubule bundles predominantly localized in the cell periphery. After incubation with taxol, the Golgi apparatus is fragmented and is conspicuously present in areas of the cytoplasm enriched in microtubules. Incubation of cells with Colcemid results in complete depolymerization of microtubules and fragmentation of the Golgi into elements randomly distributed throughout the cytoplasm. Cells treated with taxol before being incubated with Colcemid contain large numbers of Golgi-derived elements in close association with Colcemid-resistant microtubules. Microtubule depolymerization by vinblastine also is followed by fragmentation of the Golgi apparatus. These Golgi-derived elements show no association with the atypical polymers of tubulin induced by vinblastine. The codistribution of Golgi-derived elements with taxol-induced microtubule bundles can be reversed by microinjection of a monoclonal (YL 1/2) antibody reacting specifically with the tyrosylated form of alpha-tubulin.

Alkaloids↗
PubMed1982

Inhibition of cap formation on lymphocytes by free fatty acids is not mediated by a depletion of ATP.

We have previously reported that cis-unsaturated free fatty acids, e.g. linoleic acid, introduced as free fatty acids into lymphocyte membranes inhibited surface immunoglobulin capping. Trans-unsaturated and saturated free fatty acids had no effect. These results were interpreted as being due to perturbation of specific membrane lipid domains. Corps, A. N., Pozzan, T., Hesketh, T. R., and Metcalfe, J. C. (1980) J. Biol. Chem. 255, 10566-10568) in a recent paper argued, however, that linoleic acid causes depletion of ATP, as measured by the luciferin/luciferase assay, and respiratory uncoupling. We now present data showing that under the same conditions as the capping inhibition, there is neither ATP depletion, as found using a hexokinase/glucose-6-phosphate dehydrogenase assay, nor respiratory uncoupling. Linoleic acid produces artifacts in ATP measurements made using the luciferin/luciferase assay which leads to an erroneous conclusion regarding the ATP dependence of the capping inhibition.

Adenosine Triphosphate↗