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Rapid Growth Phase (rapid + growth_phase)
Selected AbstractsPhenotypical variation in a toxic strain of the phytoplankter, Cylindrospermopsis raciborskii (nostocales, cyanophyceae) during batch cultureENVIRONMENTAL TOXICOLOGY, Issue 6 2001Peter R. Hawkins Abstract A nonaxenic strain of Cylindrospermopsis raciborskii Woloszynska (AWT 205) was grown in batch culture, with and without nitrate as the primary N source. Rapid log-phase growth with nitrate was 1.0 doubling/day versus 0.3 doubling/day without nitrate. Cylindrospermopsin (CYN) production was measured by HPLC. The rate of intracellular CYN production matched cell division rate for both the diazotrophies at cell densities less than 107 cell/ml. At cell density >107 cell/ml, additional resource limitation in batch culture slowed log-phase growth to 0.04 division/day and cell division and CYN production decoupled. Intracellular CYN concentration increased at a rate of 0.08 doubling/day, twice the cell division rate. Extracellular CYN as a proportion of the total CYN increased from 20% during the rapid growth phase, to 50% during the slow growth phase. The total CYN yield from cultures grown out to stationary phase (55 days) exceeded 2 mg CYN/l. C. raciborskii cells in log-phase growth, exposed to 1 ppm copper (as copper sulphate), lysed within 24 hours. After copper treatment, all CYN was in the filterable fraction. These findings imply that in naturally occurring blooms of C. raciborskii, the movement of intracellular CYN into solution will be the greatest during stationary phase, when intracellular concentrations are highest and cell lysis is more frequent. The application of algicides that promote cell lysis will exacerbate this effect. © 2001 John Wiley & Sons, Inc. Environ Toxicol 16: 460,467, 2001 [source] Insulin-like growth factor I in growing thoroughbredsJOURNAL OF ANIMAL PHYSIOLOGY AND NUTRITION, Issue 9-10 2007W. B. Staniar Summary The objective of this longitudinal study was to characterize growth and plasma insulin-like growth factor I (IGF-I) concentrations in pasture-raised thoroughbreds fed two sources of dietary energy. Mares and foals were randomly assigned to either a sugar and starch (SS) or fat and fibre (FF)-rich feed, and plasma IGF-I and growth were measured once a month from 1 to 16 months of age. These dependent variables were also compared with day length and ambient temperature. There was an association between plasma IGF-I concentration and average daily gain (ADG) (r = 0.32, p < 0.001). There were also clear seasonal patterns in both ADG and plasma IGF-I, with high values in June and May, and a low value in March. Plasma IGF-I and ADG were positively associated with day length and temperature. Plasma IGF-I was never higher (p > 0.10) in the FF group when compared with the SS group, and was higher in the SS group during a rapid growth phase in the spring of year 2 (p < 0.10). The results establish an association between ADG and IGF-I in the horse and indicate that environment and age may influence this relationship. In addition, plasma IGF-I is influenced by dietary energy source at particular times of year. This link has important implications in designing feeding management strategies that are aimed at addressing skeletal development. [source] The galactokinase of Hypocrea jecorina is essential for cellulase induction by lactose but dispensable for growth on d -galactoseMOLECULAR MICROBIOLOGY, Issue 4 2004Bernhard Seiboth Summary Lactose is the only soluble carbon source which can be used economically for the production of cellulases or heterologous proteins under cellulase expression signals by Hypocrea jecorina (=Trichoderma reesei). Towards an understanding of lactose metabolism and its role in cellulase formation, we have cloned and characterized the gal1 (galactokinase) gene of H. jecorina, which catalyses the first step in d -galactose catabolism. It exhibits a calculated Mr of 57 kDa, and shows moderate identity (about 40%) to its putative homologues of Saccharomyces cerevisiae and Kluyveromyces lactis. Gal1 is a member of the GHMP family, shows conservation of a Gly/Ser rich region involved in ATP binding and of amino acids (Arg 51, Glu 57, Asp 60, Asp 214, Tyr 270) responsible for galactose binding. A single transcript was formed constitutively during the rapid growth phase on all carbon sources investigated and accumulated to about twice this level during growth on d -galactose, l -arabinose and their corresponding polyols. Deletion of gal1 reduces growth on d -galactose but does only slightly affect growth on lactose. This is the result of the operation of a second pathway for d -galactose catabolism, which involves galactitol as an intermediate, and whose transient concentration is strongly enhanced in the delta- gal1 strain. In this pathway, galactitol is catabolised by the lad1 -encoded l -arabinitol-4-dehydrogenase, because a gal1/lad1 double delta-mutant failed to grow on d -galactose. In the delta- gal1 strain, induction of the Leloir pathway gene gal7 (encoding galactose-1-phosphate uridylyltransferase) by d -galactose, but not by l -arabinose, is impaired. Induction of cellulase gene expression by lactose is also impaired in a gal1 deleted strain, whereas their induction by sophorose (the putative cellulose-derived inducer) was shown to be normal, thus demonstrating that galactokinase is a key enzyme for cellulase induction during growth on lactose, and that induction by lactose and sophorose involves different mechanisms. [source] Folinic acid protects against suppression of growth by Methotrexate in miceBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 4 2001M. Perwaiz Iqbal Abstract The objective of this study was to investigate whether folinic acid supplementation would protect young mice against suppression of growth by methotrexate (MTX). Four equal groups of Balb/c young male mice (5 animals in each group; mean±SD body weight 9.64±0.85 g, in their rapid growth phase) were subjected to the following drug treatment: One group was given MTX (3.5 mg/kg body weight) intraperitoneally on every 2nd day, another received folinic acid (7.0 mg/kg body weight) intraperitoneally every 2nd day. The third group was given both of these drugs (MTX on every 2nd day and folinic acid 8 h post-MTX injection). The fourth group was injected with physiological saline every other day to serve as a control group. Total body weight, food and water consumption by animals in each group were monitored every second day for a period of 3 weeks. After this period mice were sacrificed and liver, spleen and kidneys were excised, weighed and analyzed for MTX and dihydrofolate reductase activity. A small segment of the proximal part of small intestine and small pieces of liver and kidney were also removed to study morphological changes. Compared to the groups, which received folinic acid alone, folinic acid plus MTX or physiological saline, mean increase in body weight (6.8±0.8 g) of mice over a period of 3 weeks was minimal in the group receiving MTX alone (one-way ANOVA p=0.0001). The mean weights of liver and kidney in this group receiving MTX alone were also found to be significantly less than the mean weights of these organs in the 3 groups (p<0.001). The negative effect on growth of animals appears not only due to malabsorption but inhibition of pathway of de novo DNA synthesis may also be involved. This is supported by loss of villous pattern in small intestine of mice treated with MTX alone and increased accumulation of free MTX and decreased dihydrofolate reductase in the liver of the group receiving MTX alone as compared with the group receiving MTX plus folinic acid. The data indicate that the administration of folinic acid protects mice against suppression of growth by MTX. On the basis of these observations it can be deduced that patients suffering from juvenile rheumatoid arthritis or acute lymphoblastic leukaemia receiving MTX over a long period of time might be at a risk of experiencing short-term suppression of growth, however they could benefit from supplementation with folinic acid. Copyright © 2001 John Wiley & Sons, Ltd. [source] | ||||||||||