A one-generation reproductive toxicity study of the mycotoxin ochratoxin A in Fischer rats

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium molds. Grain-based foods account for most human dietary exposures to OTA. OTA is a teratogen, but its reproductive and developmental effects are poorly understood. A one-generation reproductive toxicity study was conducted with groups of 16 male and 16 female Fischer rats exposed to 0, 0.026, 0.064, 0.16, 0.4 or 1.0 mg OTA/kg in diet. Dams exposed to 1.0 mg OTA/kg diet had statistically significant F1 pup losses between implantation and postnatal day (PND 4). Delays in preputial separation (PPS) and vaginal opening (VO) were indicative of delayed puberty in F1 rats. Mild renal lesions in nursing pups indicated that exposure prior to weaning impacted the kidneys. The developing kidney was more susceptible to OTA than the adult kidney. Significant increases in multi-oocyte follicles (MOFs) and proportional changes in resting and growing follicles were observed in F1 female ovaries. Plasma testosterone was reduced in F0 males, and there were negative effects on sperm quality in F0 and F1 male rats. The results confirm that continuous dietary exposure to OTA causes post-implantation fetotoxicity in dams, and renal and reproductive toxicity in their male and female offspring.

Modeling acclimation of photosynthesis to temperature in evergreen conifer forests

• In this study, we used a canopy photosynthesis model which describes changes in photosynthetic capacity with slow temperature-dependent acclimations. • A flux-partitioning algorithm was applied to fit the photosynthesis model to net ecosystem exchange data for 12 evergreen coniferous forests from northern temperate and boreal regions. • The model accounted for much of the variation in photosynthetic production, with modeling efficiencies (mean > 67%) similar to those of more complex models. The parameter describing the rate of acclimation was larger at the northern sites, leading to a slower acclimation of photosynthesis to temperature. The response of the rates of photosynthesis to air temperature in spring was delayed up to several days at the coldest sites. Overall photosynthesis acclimation processes were slower at colder, northern locations than at warmer, more southern, and more maritime sites. • Consequently, slow changes in photosynthetic capacity were essential to explaining variations of photosynthesis for colder boreal forests (i.e. where acclimation of photosynthesis to temperature was slower), whereas the importance of these processes was minor in warmer conifer evergreen forests.

Simulated management effects on ammonia emissions from field applied manure

A need exists to improve the utilization of manure nutrients by minimizing NH(3) emissions from land application of manure. Management strategies to reduce NH(3) emissions are available; however, few have been validated under Canadian conditions. A well tested and accurate simulation model, however, can help overcome this challenge by determining appropriate management strategies for a given set of field conditions. The Volt'Air simulation model was utilized to estimate NH(3) volatilization from manure spreading for various manure spreading considerations under a range of atmospheric conditions typically encountered in eastern Canada. Considerations included: (i) soil liming, (ii) time of day of manure spreading, (iii) rainfall (timing and amount) and (iv) manure incorporation (timing, depth and manure coverage). Results demonstrated that liming to increase soil pH, increased NH(3) emissions by 3.3 kg ha(-1) for each increment of 0.1 pH (up to a 1.5 total increase), over no liming at 34.6 kg ha(-1). For each hour delay in manure spreading past 0800 h, NH(3) losses were reduced by 1.5 kg ha(-1). Rainfall (10mm) at least 20 h after manure application reduced losses, with increased reductions at higher rainfall amounts. Incorporation soon (1h) after application was best for NH(3) mitigation. Increasing the depth of incorporation by 5c m reduced NH(3) emissions by 4.4 kg ha(-1); also increasing manure coverage by incorporation reduced losses by 2 kg ha(-1) for each 10% increase in coverage, compared to surface application at 34.6 kg ha(-1). This investigation using Volt'Air yielded valuable information about simulating manure management strategies and the magnitude of their effects on NH(3) emissions.

Co-injection strategies to modify radiation sensitivity and tumor initiation in transgenic Zebrafish

The zebrafish has emerged as a powerful genetic model of cancer, but has been limited by the use of stable transgenic approaches to induce disease. Here, a co-injection strategy is described that capitalizes on both the numbers of embryos that can be microinjected and the ability of transgenes to segregate together and exert synergistic effects in forming tumors. Using this mosaic transgenic approach, gene pathways involved in tumor initiation and radiation sensitivity have been identified.

Medium- versus long-chain triglycerides for 27 days increases fat oxidation and energy expenditure without resulting in changes in body composition in overweight women

OBJECTIVE

To determine the effects of long-term consumption of medium chain (MCT) versus long chain triglycerides (LCT) on energy expenditure (EE), substrate oxidation and body composition.

HYPOTHESIS

MCT consumption will not result in greater EE, substrate oxidation, and body weight loss compared with LCT consumption.

RESEARCH METHODS AND PROCEDURES

Seventeen healthy obese women participated in this randomized, crossover inpatient trial. Meals were prepared and consumed on site for two periods of 27 days. Diets containing 40% of energy as fat, with treatment fat comprising 75% of the total fat, were designed to supply each subject with their individual weight-maintaining energy needs. The MCT diet contained 67% of treatment fat as MCT oil (49% octanoate, 50% decanoate) whereas the LCT diet contained exclusively beef tallow as treatment fat. Body composition was assessed by magnetic resonance imaging (MRI) on day 1 and 28 of each phase while energy expenditure was measured on day 2 and 27.

RESULTS

Changes in total and subcutaneous adipose tissue volumes following consumption of MCT and LCT were not different (-0.61+/-0.38 l vs -0.54+/-0.48 l and -0.58+/-0.35 l vs -0.48+/-0.40 l, respectively). Average EE and fat oxidation were greater (P<0.05) during MCT than LCT consumption (0.95+/-0.019 vs 0.90+/-0.024 kcal/min, respectively, for EE and 0.080+/-0.0026 vs 0.075+/-0.0022 g/min, respectively for fat oxidation).

DISCUSSION

These results show that long-term consumption of MCT enhances EE and fat oxidation in obese women, when compared to LCT consumption. The difference in body composition change between MCT and LCT consumption, although not statistically different, was consistent with differences predicted by the shifts in EE. It can be concluded that substitution of MCT for LCT in a targeted energy balance diet may prevent long-term weight gain via increased EE.

Specialized membrane domains for water transport in glial cells: high-resolution immunogold cytochemistry of aquaporin-4 in rat brain

Membrane water transport is critically involved in brain volume homeostasis and in the pathogenesis of brain edema. The cDNA encoding aquaporin-4 (AQP4) water channel protein was recently isolated from rat brain. We used immunocytochemistry and high-resolution immunogold electron microscopy to identify the cells and membrane domains that mediate water flux through AQP4. The AQP4 protein is abundant in glial cells bordering the subarachnoidal space, ventricles, and blood vessels. AQP4 is also abundant in osmosensory areas, including the supraoptic nucleus and subfornical organ. Immunogold analysis demonstrated that AQP4 is restricted to glial membranes and to subpopulations of ependymal cells. AQP4 is particularly strongly expressed in glial membranes that are in direct contact with capillaries and pia. The highly polarized AQP4 expression indicates that these cells are equipped with specific membrane domains that are specialized for water transport, thereby mediating the flow of water between glial cells and the cavities filled with CSF and the intravascular space.

An investigation of the mechanisms of action of 5-hydroxytryptamine in the suppression of ethanol intake

The effect of blockage of 5-hydroxytryptamine and norepinephrine uptake on voluntary ethanol consumption in rats was investigated. It was demonstrated that attenuation of ethanol intake occurred only as a result of treatment with specific 5-hydroxytryptamine uptake inhibitors. These results suggested that increasing the availability of central 5-hydroxytryptamine may in some way interfere with the positive reinforcing properties of ethanol. The second phase was designed to determine whether the attenuation of ethanol intake following blockade of 5-hydroxytryptamine uptake may be due to increased post-synaptic activity. Ethanol-preferring animals were pretreated with methergoline, a post-synaptic receptor blocker, followed by treatment with zimelidine, a 5-hydroxytryptamine uptake inhibitor. The results indicate that treatment with methergoline did not alter the zimelidine-induced attenuation of ethanol intake. Based on these results it is suggested that blockade of 5-hydroxytryptamine uptake produces an attenuation of ethanol intake but not as a result of increased post-synaptic activity.

Reduction of voluntary morphine consumption following treatment with zimelidine

Male Wistar rats were presented with an everyday free choice between water and a morphine-sucrose solution. Following a 5-day baseline period animals were injected with either zimelidine (10 or 20 mg/kg, i.p.), a neuronal serotonin uptake inhibitor, or Ringer's solution (2 ml/kg, i.p.) for 5 consecutive days. Treatment with zimelidine was shown to significantly attenuate morphine drinking suggesting that an increased availability of serotonin may interfere with the positive reinforcing properties of morphine. The results are also discussed in terms of a possible interaction with brain norepinephrine. The possibility that the reinforcing effects of both morphine and ethanol are subserved by common mechanisms is suggested.

Cholera-like diarrhea in Canada. Report of a case associated with enterotoxigenic Escherichia coli and a toxin-producing Aeromonas hydrophila

A 67-year-old Indian patient was admitted with an acute cholera-like illness. Toxigenic Escherichia coli producing both heat-stable and heat-labile enterotoxins grew from cultures of feces. In addition, an Aeromonas hydrophila producing a cytotoxic toxin was also isolated from this patient's feces. The unusual severity of this patient's illness may have resulted from coinfection with these two toxigenic organisms, although any role of the toxin produced by a hydrophila is speculative.