University of Saskatchewan

About: University of Saskatchewan is a education organization based out in Saskatoon, Saskatchewan, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 25021 authors who have published 52579 publications receiving 1483049 citations. The organization is also known as: USask.

Effects of acetic acid and lactic acid on the growth of Saccharomyces cerevisiae in a minimal medium.

Abstract: Specific growth rates (μ) of two strains of Saccharomyces cerevisiae decreased exponentially (R 2>0.9) as the concentrations of acetic acid or lactic acid were increased in minimal media at 30°C. Moreover, the length of the lag phase of each growth curve (h) increased exponentially as increasing concentrations of acetic or lactic acid were added to the media. The minimum inhibitory concentration (MIC) of acetic acid for yeast growth was 0.6% w/v (100 mM) and that of lactic acid was 2.5% w/v (278 mM) for both strains of yeast. However, acetic acid at concentrations as low as 0.05–0.1% w/v and lactic acid at concentrations of 0.2–0.8% w/v begin to stress the yeasts as seen by reduced growth rates and decreased rates of glucose consumption and ethanol production as the concentration of acetic or lactic acid in the media was raised. In the presence of increasing acetic acid, all the glucose in the medium was eventually consumed even though the rates of consumption differed. However, this was not observed in the presence of increasing lactic acid where glucose consumption was extremely protracted even at a concentration of 0.6% w/v (66 mM). A response surface central composite design was used to evaluate the interaction between acetic and lactic acids on the specific growth rate of both yeast strains at 30C. The data were analysed using the General Linear Models (GLM) procedure. From the analysis, the interaction between acetic acid and lactic acid was statistically significant (P≤0.001), i.e., the inhibitory effect of the two acids present together in a medium is highly synergistic. Journal of Industrial Microbiology & Biotechnology (2001) 26, 171–177.

International variation in rates of uptake of preventive options in BRCA1 and BRCA2 mutation carriers.

Abstract: Several options for cancer prevention are available for women with a BRCA1 or BRCA2 mutation, including prophylactic surgery, chemoprevention and screening. The authors report on preventive practices in women with mutations from 9 countries and examine differences in uptake according to country. Women with a BRCA1 or BRCA2 mutation were contacted after receiving their genetic test result and were questioned regarding their preventive practices. Information was recorded on prophylactic mastectomy, prophylactic oophorectomy, use of tamoxifen and screening (MRI and mammography). Two thousand six hundred seventy-seven women with a BRCA1 or BRCA2 mutation from 9 countries were included. The follow-up questionnaire was completed a mean of 3.9 years (range 1.5-10.3 years) after genetic testing. One thousand five hundred thirty-one women (57.2%) had a bilateral prophylactic oophorectomy. Of the 1,383 women without breast cancer, 248 (18.0%) had had a prophylactic bilateral mastectomy. Among those who did not have a prophylactic mastectomy, only 76 women (5.5%) took tamoxifen and 40 women (2.9%) took raloxifene for breast cancer prevention. Approximately one-half of the women at risk for breast cancer had taken no preventive option, relying solely on screening. There were large differences in the uptake of the different preventive options by country of residence. Prophylactic oophorectomy is now generally accepted by women and their physicians as a cancer preventive measure. However, only the minority of women with a BRCA1 or BRCA2 mutation opt for prophylactic mastectomy or take tamoxifen for the prevention of hereditary breast cancer. Approximately one-half of women at risk for breast cancer rely on screening alone.

Sources of Metals and Fluids in Orogenic Gold Deposits: Insights from the Otago and Alpine Schists, New Zealand

Abstract: The Otago and Alpine schists of the South Island of New Zealand form a young ( A large suite of samples representative of the lithologic and metamorphic variation in the Otago and Alpine schists was collected and analyzed for a comprehensive suite of elements. The aim was to identify any rock type or metamorphic setting that may be depleted in the suite of ore-forming elements (Au, Ag, As, Sb, Hg, Mo, and W) relative to unmetamorphosed protoliths, perhaps representing the source for the enrichments observed in the Otago ore deposits. Gold, Ag, As, Sb, Hg, Mo, and W were found to have significantly lower concentrations in higher grade metamorphic rocks compared to unmetamorphosed protolith samples. These were the only elements in a suite of 12 major and 50 trace elements to show systematic depletions with metamorphic grade. Investigation of the trace element chemistry of sulfide minerals indicates that the whole-rock depletions are caused by the disappearance between greenschist and amphibolite facies conditions of pyrite, galena, sphalerite, and cobaltite, the major host phases for the ore-forming elements. More than 95 percent of upper greenschist and amphibolite facies samples are significantly depleted in the ore-forming elements. Such regional-scale depletions require pervasive, grain-boundary fluid flow throughout these rocks. The leaching is most likely to have been caused by metamorphic fluid produced by dehydration reactions at the greenschist-amphibolite boundary. The suite of elements depleted in mid- to high-grade Otago and Alpine schists is almost identical to those enriched in the orogenic gold deposits in Otago. Furthermore, the vertical zonation in depletions is similar to the vertical zonation in enrichments that occurs in the Otago deposits. Mass-balance calculations suggest that 2 metric tons (t) Au and 24,000 t As was leached from 1 km3 of amphibolite facies rock and that the Macraes deposit could have been formed by leaching of a 5- × 5- × 5-km cube of amphibolite facies rock. We propose that the orogenic gold deposits in Otago, such as Macraes, were formed directly from metal-rich metamorphic fluid produced during prograde metamorphism at depth. The contribution of other fluid and metal sources in the formation of these deposits, such as magmatic fluids, cannot be ruled out, but there is no direct evidence to support their involvement. Infiltration of meteoric water, such as occurs currently in the Southern Alps of New Zealand may have contributed to the formation of the late-stage deposits that formed at shallow level during uplift of the Otago schists.

Norepinephrine triggers release of glial ATP to increase postsynaptic efficacy.

Abstract: Glial cells actively participate in synaptic transmission. They clear molecules from the synaptic cleft, receive signals from neurons and, in turn, release molecules that can modulate signaling between neuronal elements. Whether glial-derived transmitters can contribute to enduring changes in postsynaptic efficacy, however, remains to be established. In rat hypothalamic paraventricular nucleus, we demonstrate an increase in the amplitude of miniature excitatory postsynaptic currents in response to norepinephrine that requires the release of ATP from glial cells. The increase in quantal efficacy, which likely results from an insertion of AMPA receptors, is secondary to the activation of P2X7 receptors, an increase in postsynaptic calcium and the activation of phosphatidylinositol 3-kinase. The gliotransmitter ATP, therefore, contributes directly to the regulation of postsynaptic efficacy at glutamatergic synapses in the CNS.