A study of variance in measurements of tank-treading frequency in populations of normal human red cells

The statistical variance in rheoscopic measurements of tank-treading frequency ( TTF ) of normal human red cells has been investigated and the sources of this variance analyzed. Experiments were designed to expose the influence of donor, the stability of a donor's cells over a 2-month period, storage time from venipuncture to testing, cell age, applied shear rate and variations in the rheoscope gap due to trial-to-trial manipulation. The results show that the TTF varies linearly with applied shear rate within the range 20 to 180 s-1 and is strongly dependent on cell age. The slope of the TTF characteristic is not significantly different in cells taken from different, but hematologically normal adults nor does it change significantly over time in a particular donor. TTF measurements may be useful in distinguishing rheologically abnormal cell populations which differ from normal cells by at least 10%.     

The level of CRABP-I expression influences the amounts and types of all-trans-retinoic acid metabolites in F9 teratocarcinoma stem cells.

The CRABP-I and CRABP-II proteins are high affinity cytoplasmic retinoic acid-binding proteins. In undifferentiated F9 teratocarcinoma stem cells, only the CRABP-I protein is expressed at detectable levels. We have previously shown that overexpression of the CRABP-I protein in stably transfected F9 stem cell lines results in a lower sensitivity to a given external concentration of retinoic acid relative to that of untransfected F9 cells; in contrast, reduced CRABP-I expression in CRABP-I cDNA anti-sense transfected lines is associated with increased sensitivity of these lines to retinoic acid. These three types of cell lines were cultured in the presence of 50 nM [3H]retinoic acid, and the metabolism of retinoic acid was followed over the next 24 h. The results demonstrate that CRABP-I has the ability to alter both the levels and types of RA metabolites produced in the cytoplasm of differentiating embryonic stem cells. Moreover, the level of CRABP-I determines the rate of RA metabolism to 4-oxo-RA such that the higher the CRABP-I level, the faster the metabolism of [3H]retinoic acid. This is the first reported connection between the level of CRABP-I expression and intracellular RA metabolism.     

Isolation and physical characterization of three essential conidiation genes from Aspergillus nidulans.

We cloned and characterized three genes from Aspergillus nidulans, designated brlA, abaA, and wetA, whose activities are required to complete different stages of conidiophore development. Inactivation of these genes causes major abnormalities in conidiophore morphology and prevents expression of many unrelated, developmentally regulated genes, without affecting the expression of nonregulated genes. The three genes code for poly(A)+ RNAs that begin to accumulate at different times during conidiation. The brlA- and abaA-encoded RNAs accumulate specifically in cells of the conidiophore. The wetA-encoded RNA accumulates in mature conidia. Inactivation of the brlA gene prevents expression of the abaA and wetA genes, whereas inactivation of the abaA gene prevents expression of the wetA gene. Our results confirm genetic predictions as to the temporal and spatial patterns of expression of these genes and demonstrate that these patterns are specified at the level of RNA accumulation.     

Arsenic and selenium in human hair

The selenium (Se) content of the diet and/or selenium supplements might have an ameliorating effect on arsenic (As) toxicity as recently shown by Wang et al. (1), Yang et al. (2), and as reviewed by Spallholz et al. (3). The underlying principles of the ameliorating effect is the complexation of Se with As forming the seleno-bis (S-glutathionyl) arsinium ion (4) excreted in bile and the complexation of Se with As in tissues forming nontoxic insoluble selenides (5,6). Addition protection afforded by Se supplementation from arsenicosis could be the elevation of glutathione peroxidase activity reducing the oxidative stress induced by As (7,8). The present study assessed the status of Se and As in hair by neutron activation analysis (NAA). Human hair samples were collected from the United States, Canada, The People's Republic of China (PRC), Bangladesh, and Nepal, the latter two countries now engaged in a struggle to find relief from human arsenicosis resulting from extensive domestic groundwater contamination by As. No statistically significant differences were observed in the samples between the Se and As content of hair from, Lubbock, Texas (USA) or Winnipeg, Canada. The concentration of As in all hair samples analyzed correlated (r=0.960, p<0.001) with the amount of As in the drinking water. Selenium levels in hair were highest from Nepal. The results demonstrate the viability of hair as a noninvasive biomonitor in assessing aspects of dietary Se and environmental As exposure. The hair data confirmed the known low intake of Se in the Keshan disease area of the PRC, the very high accumulation in hair of As from subjects consuming contaminated ground waters, and an adequate Se status in subjects from North America consuming municipal water of low As content. The high As content of hair from people in Bangladesh is the result of a high As consumption from contaminated water compounded by a less than desirable intake of Se (9). From Nepal, the As content of hair corresponded to the known low and high intake of As from contaminated groundwater. The very high Se content found in all hair samples from Nepal might be the result of the use of henna.     

Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.     

Bioavailability of selenium from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine, and sodium selenite assessed in selenium-deficient rats

The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine (SeMet), and sodium selenite was assessed in Se-deficient Fischer-344 rats. Se as veal, chicken, beef, pork, lamb, flounder, tuna, SeMet, and sodium selenite was added to torula yeast (TY) basal diets to comprise Se-inadequate (0.05 mg Se/kg) diets. Se as sodium selenite was added to a TY basal diet to comprise a Se-adequate (0.10 mg Se/kg), Se-control diet. The experimental diets were fed to weanling Fischer-344 rats that had been subjected to dietary Se depletion for 6 wk. After 9 wk of the dietary Se repletion, relative activity of liver glutathione peroxidase (GSHPx) from the different dietary groups compared with control rats (100%) was: flounder 106%, tuna 101%, pork 86%, sodium selenite 81%, SeMet 80%, beef 80%, chicken 77%, veal 77%, and lamb 58%. Se from flounder was the most efficient at restoring Se concentrations in the liver and skeletal muscle. Se from sodium selenite, SeMet, beef, veal, chicken, pork, lamb, and tuna was not dietarily sufficient to restore liver and muscle Se after 9 wk of recovery following a 6-wk period of Se depletion.     

The influence of broad scale climatic phenomena on long term trends in Atlantic salmon population size: an example from the River Foyle, Ireland

The effect of marine climatic conditions in the North Atlantic on the abundance of returning migrant Atlantic salmon Salmo salar in the River Foyle, Ireland was examined. Catches of Atlantic salmon from commercial netting stations significantly predicted a measure of population size independent of catches over a 48 year period, thus commercial net catches were used as a measure of relative population size over a longer period in this study. The North Atlantic Oscillation index in winter (wNAOI) provides a generalized measure of climate variation for the northern hemisphere and between 1875 and 2001, the wNAOI was a highly significant predictor of the 5 year running mean of catches of migrant Atlantic salmon returning to the River Foyle. When the index was <0·151, the wNAOI correlated significantly and negatively with Atlantic salmon catches, with 70% of the variance in population size explained by variation in conditions in the marine environment between 1875 and 2001. When the wNAOI was >0·151, however, this relationship uncoupled. The probability of catches exceeding the long‐term median was 2·34 times lower in years where the wNAOI was above the 0·151 breakpoint than for years when it was <0·151. The wNAOI exceeded the 0·151 threshold on 8 out of the 10 years prior to 2001. Models of climate change indicated that the NAOI is likely to increase significantly with time. If these models are correct, this study would lead to the conclusion that a decoupling of these broad scale climate effects on Atlantic salmon population size will become the norm. Data presented here suggests two consequences of this. Firstly that the value of the NAOI as a predictive tool for forecasting adult Atlantic salmon population size will be limited and secondly that the median population size will become lower in the future.