Biomedical subjects

S A Gerber

Publications and source records attributed to S A Gerber.

6 recordsLinked to original sources

PubMed2003

Mechanism of IL-12 mediated alterations in tumour blood vessel morphology: analysis using whole-tissue mounts.

New blood vessel formation within tumours is a critical feature for tumour growth. A major limitation in understanding this complex process has been the inability to visualise and analyse vessel formation. Here, we report on the development of a whole-tissue mount technique that allows visualisation of vessel structure. Mice expressing green fluorescent protein (GFP) made it possible to easily see GFP(+) vessels within non-GFP-expressing B16 melanoma tumours. The small fragments of tumour used in this technique were also effectively stained with fluorescent probe-conjugated antibodies, allowing characterisation of the vessels based on surface marker phenotype. The vessels within tumour tissue were much more irregular and tortuous compared to those within surrounding normal muscle. B16 tumours stably transfected with the genes for IL-12 were used to assess the effects of this cytokine on tumour growth and vessel formation. The IL-12-expressing tumours grew more slowly and had much smaller blood vessels than the large, webbed vessels characteristic of the parental tumours, effects that were dependent on interferon gamma (IFN-gamma). Vessels in the parental tumours were found to express VEGFR-3, the receptor for VEGF-C and VEGF-D. Expression of this receptor by the endothelial cells of the blood vessels was lost in the cytokine expressing tumours, thus suggesting a mechanism for the antiangiogenic effects of IL-12. The combination of the whole mount technique and the GFP transgenic mice provides a powerful method for visualising tumour vasculature and characterising the effects of agents such as cytokines.

Animals↗

PubMed2001

Dual inhibition of sister chromatid separation at metaphase.

Separation of sister chromatids in anaphase is mediated by separase, an endopeptidase that cleaves the chromosomal cohesin SCC1. Separase is inhibited by securin, which is degraded at the metaphase-anaphase transition. Using Xenopus egg extracts, we demonstrate that high CDC2 activity inhibits anaphase but not securin degradation. We show that separase is kept inactive under these conditions by a mechanism independent of binding to securin. Mutation of a single phosphorylation site on separase relieves the inhibition and rescues chromatid separation in extracts with high CDC2 activity. Using quantitative mass spectrometry, we show that, in intact cells, there is complete phosphorylation of this site in metaphase and significant dephosphorylation in anaphase. We propose that separase activation at the metaphase-anaphase transition requires the removal of both securin and an inhibitory phosphate.

Anaphase↗

PubMed2001

Direct profiling of multiple enzyme activities in human cell lysates by affinity chromatography/electrospray ionization mass spectrometry: application to clinical enzymology.

We describe a new method for enzyme analysis using affinity capture followed by electrospray ionization mass spectrometry (ACESIMS) for the quantitative determination of the initial velocities of four heparin-modifying enzymes. These enzymes, when defective in affected children, lead to the lysosomal storage disease known as Sanfilippo syndrome. The method relies on substrates and internal standards conjugated to the molecular handle biotin via a heavy isotope-encodable, mass-adjustable linker. Reaction velocities of the Sanfilippo enzymes in a crude lysate prepared from as little as 2500 human skin fibroblasts can be determined. In addition, the ACESIMS method is widely applicable to the simultaneous analysis of multiple enzymes in a complex biological sample by a single analytical technique and will thus serve as a useful tool in basic and clinical biomedical research.

Cells, Cultured↗

PubMed1999

Quantitative analysis of complex protein mixtures using isotope-coded affinity tags.

We describe an approach for the accurate quantification and concurrent sequence identification of the individual proteins within complex mixtures. The method is based on a class of new chemical reagents termed isotope-coded affinity tags (ICATs) and tandem mass spectrometry. Using this strategy, we compared protein expression in the yeast Saccharomyces cerevisiae, using either ethanol or galactose as a carbon source. The measured differences in protein expression correlated with known yeast metabolic function under glucose-repressed conditions. The method is redundant if multiple cysteinyl residues are present, and the relative quantification is highly accurate because it is based on stable isotope dilution techniques. The ICAT approach should provide a widely applicable means to compare quantitatively global protein expression in cells and tissues.

Affinity Labels↗

PubMed1979

AET-treated platelets: their usefulness for platelet antibody detection and an examination of their altered sensitivity to immune lysis.

2-Aminoethylisothiouronium bromide (AET) increases the sensitivity of blood cells to complement-mediated immune lysis. We compared the sensitivities of untreated or AET-treated platelets to immune lysis induced by different types of platelet antibody in the 51Cr platelet lysis test. AET platelets were 8-16 times more sensitive to autoantibody and alloantibody, but 8-16 times less sensitive to drug-dependent antibody. AET-platelets bound similar amounts of alloantibody but less drug-dependent antibody, and they lysed at higher complement dilutions than did untreated platelets. AET-platelets detected 10 of 25 autoantibodies, 9 of 9 alloantibodies, and 5 of 8 drug-dependent antibodies. Untreated platelets detected 1 of 25, 6 of 9, and 7 of 8 of these respective platelet antibodies. The use of AET-platelets in the 51Cr platelet lysis test increases its sensitivity for detecting non-drug-dependent platelet antibodies. AET-platelets resemble paroxysmal nocturnal hemoglobinuria (PNH) platelets in their enhanced sensitivity to complement-mediated lysis. They differ from PNH platelets in their insensitivity to immune lysis induced by drug-dependent antibodies and, in this respect, are similar to Bernard-Soulier syndrome platelets.

Autoantibodies↗

PubMedDate not supplied

Design and synthesis of substrate and internal standard conjugates for profiling enzyme activity in the Sanfilippo syndrome by affinity chromatography/electrospray ionization mass spectrometry.

We describe the design and synthesis of substrate and internal standard conjugates for application in profiling enzyme activity of the enzymes alpha-D-2-deoxy-2-N-sulfonamido-glucosamine sulfamidase, alpha-D-2-deoxy-2-N-acetyl-glucosamine hydrolase, acetyl-coenzymeA:alpha-D-2-deoxy-2-amino-glucosamine transferase, and alpha-D-2-deoxy-2-N-acetyl-glucosamine-6-sulfate sulfatase. Deficiency of any one of these enzymes results in a single clinical phenotype known as Sanfilippo syndrome. Such substrates have been proven effective in the confirmation of enzyme deficiency by a combination of affinity chromatography (AC) and electrospray ionization mass spectrometry (ESIMS), which forms the foundation for a new analytical technology (ACESIMS) of general interest and application to clinical and biomedical research.

Acetylgalactosamine↗