Nicotinamide, a SIRT1 inhibitor, inhibits differentiation and facilitates expansion of hematopoietic progenitor cells with enhanced bone marrow homing and engraftment

Strategies that increase homing to the bone marrow and engraftment efficacy of ex?vivo expended CD34(+) cells are expected to enhance their clinical utility. Here we report that nicotinamide (NAM), a form of vitamin B-3, delayed differentiation and increased engraftment efficacy of cord blood-derived human CD34(+) cells cultured with cytokines. In the presence of NAM, the fraction of CD34(+)CD38(-) cells increased and the fraction of differentiated cells (CD14(+), CD11b(+), and CD11c(+)) decreased. CD34(+) cells cultured with NAM displayed increased migration toward stromal cell derived factor-1 and homed to the bone marrow with higher efficacy, thus contributing to their increased engraftment efficacy, which was maintained in competitive transplants with noncultured competitor cells. NAM is a known potent inhibitor of several classes of ribosylase enzymes that require NAD for their activity, as well as sirtuin (SIRT1), class III NAD(+)-dependent-histone-deacetylase. We demonstrated that EX-527, a specific inhibitor of SIRT1 catalytic activity, inhibited differentiation of CD34(+) cells similar to NAM, while specific inhibitors of NAD-ribosylase enzymes did not?inhibit differentiation, suggesting that the NAM effect is SIRT1-specific. Our findings suggest?a critical function of SIRT1 in the regulation of hematopoietic stem cell activity and imply the?clinical utility of NAM for ex?vivo expansion of functional CD34(+) cells.     

Graves' disease presenting with severe cholestasis

BACKGROUND: Hyperthyroidism has been associated with liver function abnormalities; however, cholestasis as the presenting feature of adolescent Graves' disease has not been previously reported. PATIENT SUMMARY: The patient was a 17-year-old girl who presented with severe cholestasis and was found to have Graves' disease. She also had a positive hepatitis A immunoglobulin M antibody but her clinical course, the liver histopathology, and her mildly elevated transaminases indicated that the acute hepatitis A infection was not dominant at the time of presentation with severe cholestasis. Other causes of cholestasis, including congestive heart failure, autoimmune hepatitis, and viral infection, were excluded. Treatment with methimazole resolved the hyperthyroidism, and the cholestasis improved, as well. CONCLUSION: Severe cholestasis is a rare presenting feature of Graves' disease. With careful monitoring, methimazole can be used to treat the hyperthyroidism in the setting of cholestasis.     

The history of cryosurgery in Canada: A tale of two cities

Although not commonly available in Canada, cryosurgery (cryoablation) for prostate cancer has been practiced in many countries. The field of cryoablation has evolved significantly over the past 30 years. Two prostate cryoablation programs were started in Canada in the early 1990s, in London, ON and Calgary, AB, focusing, respectively, on salvage therapy following radiation failure and primary local treatment. This article chronicles the development of the two programs and outlines the scientific and clinical contributions by investigators at the two centers.     

Electron paramagnetic resonance studies of photosynthetic electron transport: Photoreduction of ferredoxin and membrane-bound iron-sulfur centers

Electron paramagnetic resonance spectrometry was used to investigate, at physiological temperatures, light-induced electron transport from membrane-bound iron-sulfur components (bound ferredoxin) to soluble ferredoxin and NADP(+) in membrane fragments (from the blue-green alga, Nostoc muscorum) that had high rates of electron transport from water to NADP(+) and from an artificial electron donor, reduced dichlorophenolindophenol (DCIPH(2)) to NADP(+). Illumination at 20 degrees resulted in the photoreduction of membrane-bound iron-sulfur centers A and B. Photoreduction by water gave electron paramagnetic resonance signals of both centers A and B; photoreduction by DCIPH(2) was found to generate a strong electron paramagnetic signal of only center B.When water was the reductant, the addition and photoreduction of soluble ferredoxin generated additional signals characteristics of soluble ferredoxin without causing a decrease in the amplitude of the signals due to centers A and B. The further addition of NADP(+) (and its photoreduction) greatly diminished signals due to the bound iron-sulfur centers and to soluble ferredoxin. An outflow of electrons from center B to soluble ferredoxin and NADP(+) was particularly pronounced when DCIPH(2) was the reductant. These observations provide the first evidence for a light-induced electron transport between membrane-bound iron-sulfur centers and ferredoxin-NADP(+). The relationship of these observations to current concepts of photosynthetic electron transport is discussed.     

Anti-influenza response achieved by immunization with a synthetic conjugate.

The peptide corresponding to sequence 91--108 of the hemagglutinin of type A H3N2 influenza virus has been synthesized by the solid-phase peptide synthesis method and covalently attached to several macromolecular carriers. The conjugate with tetanus toxoid was used for immunization of rabbits and mice. The immunoglobulin fraction of the rabbit antiserum showed the presence and antipeptide antibodies by both agar gel diffusion and radioimmunoassay. In the latter assay, the antibodies showed marked crossreactivity with the intact virus of the A/Texas/77 strain. The antibodies were also capable of inhibiting the hemagglutination of chicken erythrocytes by the virus; the highest hemagglutination inhibition titer (1:32) was achieved with a serum-resistant strain of A/Texas/77. When the in vitro virus plaque formation assay was used with monolayers of Madin--Darby canine kidney (MDCK) cells, the number of plaques was reduced on interaction with the immunoglobulin fraction of the antiserum, which was effective up to a dilution of 1:32. Preliminary results indicate that C3H/DiSn mice immunized with the peptide--tetanus toxoid conjugate are partially protected against a further challenge with A/Texas mouse-adapted influenza virus. The results are thus indicative of the efficacy of the synthetic material in eliciting anti-influenza immune response.