Phosphorus Inputs to Lake Simcoe from 1990 to 2003: Declines in Tributary Loads and Observations on Lake Water Quality

Total phosphorus (TP) inputs to Lake Simcoe have led to hypolimnetic dissolved oxygen (DO) depletion and loss of cold water fish habitat. Since 1990, efforts have been made to reduce the total TP input to the lake below a defined target of 75 t/year, which was predicted to lead to reductions in spring TP concentration and improvements in end-of-summer hypolimnetic DO concentrations. The total TP load to the lake during the most recent period of record (1998/99-2003/04) ranged from 53 to 76 t/yr and averaged 67 t/yr, compared to an average of 114 t/yr estimated between 1990/91 and 1997/98 (range 85-157 t/yr). Reductions in TP loads from the catchment via tributary discharge (∼26 t) accounted for the majority of the decrease in total load between the two time periods. Total P concentrations decreased significantly in four out of six long-term monitored tributaries; however, concentrations in all six tributaries remain above the level recommended to avoid nuisance plant growth (30 μg/L). Although TP loads to the lake are currently below the target 75 t/yr, excessive growths of filamentous algae and macrophytes continue to be a problem in the nearshore zone. End-of-summer minimum hypolimnetic DO concentrations (average 4.3 mg/L, 1998/99-2003/04) remain substantially below the level (7 mg/L) that is considered protective of lake trout. Efforts to reduce TP loads to the lake therefore need to continue.     

Effects of a single dose of N-Acetyl-5-methoxytryptamine (Melatonin) and resistance exercise on the growth hormone/IGF-1 axis in young males and females

Melatonin and resistance exercise alone have been shown to increase the levels of growth hormone (GH). The purpose of this study was to determine the effects of ingestion of a single dose of melatonin and heavy resistance exercise on serum GH, somatostatin (SST), and other hormones of the GH/insulin-like growth factor 1 (IGF-1) axis. Physically active males (n = 30) and females (n = 30) were randomly assigned to ingest either a melatonin supplement at 0.5 mg or 5.0 mg, or 1.0 mg of dextrose placebo. After a baseline blood sample, participants ingested the supplement and underwent blood sampling every 15 min for 60 min, at which point they underwent a single bout of resistance exercise with the leg press for 7 sets of 7 reps at 85% 1-RM. After exercise, participants provided additional blood samples every 15 min for a total of 120 min. Serum free GH, SST, IGF-1, IGFBP-1, and IGFBP-3 were determined with ELISA. Data were evaluated as the peak pre- and post-exercise values subtracted from baseline and the delta values analyzed with separate three-way ANOVA (p < 0.05). In males, when compared to placebo, 5.0 mg melatonin caused GH to increase (p = 0.017) and SST to decrease prior to exercise (p = 0.031), whereas both 0.5 and 5.0 mg melatonin were greater than placebo after exercise (p = 0.045) and less than placebo for SST. No significant differences occurred for IGF-1; however, males were shown to have higher levels of IGFBP-1 independent of supplementation (p = 0.004). The 5.0 mg melatonin dose resulted in higher IGFBP-3 in males (p = 0.017). In conclusion, for males 5.0 mg melatonin appears to increase serum GH while concomitantly lowering SST levels; however, when combined with resistance exercise both melatonin doses positively impacts GH levels in a manner not entirely dependent on SST.     

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.     

Chemorheology of thermosetting resins. I. The chemorheology and curing kinetics of unsaturated polyester resin

The rheological properties and curing kinetics of a general-purpose polyester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone-and-plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). It was found that, as cure progresses, the steady shear viscosity increases very rapidly with cure time at all shear rates investigated, and normal forces show negative values at low shear rates and positive values at high shear rates. The observed negative normal forces are believed to result from material shrinkage during cure, and positive normal forces from the deformation of large molecules, formed by crosslinking reactions during cure. Note that, in a cone-and-plate rheometer, the shrinkage force acts in the direction opposite to that of normal forces. It is, therefore, concluded that extreme caution is needed in the interpretation of normal force measurements with thermosetting resins, subjected to steady shearing flow. Dynamic measurements seem to offer some insight on the onset of gel formation. More specifically, we have found that, when the unsaturated polyester resin was cured at a fast rate, the time at which a maximum in the loss modulus G” occurs coincides reasonably well with the time t_η∞ at which the steady shear viscosity η approaches infinity. However, at a slow rate of cure, the time at which tan δ equals unity agrees fairly well with t_η∞. DSC measurement has permitted us to determine the degree of cure as a function of cure time and the kinetic parameters in an empirical expression for the curing kinetics advanced by Kamal and co-workers. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various values of isothermal curing temperature.     

Antioxidant activity and antimicrobial properties of phenolic extracts from acerola (Malpighia emarginata DC) fruit

The antioxidant activity and antimicrobial property of phenolic extracts from acerola (Malpighia emarginata DC) fruit were assessed. The contribution of ascorbic acid and phenolic compounds in the total antioxidant capacity of the extracts was also evaluated. The extracts showed high total phenolic values and possessed high antioxidant activity as expressed by 2,2′‐diphenylpicrylhydrazyl (DPPH) and oxygen radical absorbance capacity assays (ORAC). The ascorbic acid content ranged from 405 to 1744 mg/100 g of fruit on a fresh weight basis. The antioxidant capacity of the phenolic fractions was in the following order: anthocyanins<phenolic acids<flavonoids. The phenolic fractions contributed 7.1–36.5% of the antioxidant activity expressed by ORAC, whereas the contribution of ascorbic accounted for 18–39% of the total activity. Selected extracts from the flavonoids fraction showed some activity against Staphylococcus aureus.     

Chemorheology of thermosetting resins. IV. The chemorheology and curing kinetics of vinyl ester resin

The rheological properties and curing kinetics of a vinyl ester resin have been determined during isothermal cure. Both steady and oscillatory shearing flow properties were determined using a cone-and-plate rheometer, and the curing kinetics were determined using a differential scanning calorimeter (DSC). Also determined were the rheological properties and curing kinetics of the resin when it had been thickened using magnesium oxide (MgO), in the presence of calcium carbonate (CaCO₃) as filler and polyvinyl acetate (PVAc) as low-profile additive. The steady shearing flow behavior observed with the vinyl ester resin was found to be very similar to that observed with a general-purpose polyester resin, reported in Paper I of this series [C. D. Han and K. W. Lem, J. Appl. Polym. Sci., 28 , 3155 (1983)]. However, a significant difference in the oscillatory shearing flow behavior was found between the two resins. We have concluded that dynamic measurement is much more sensitive to variations in resin chemistry than steady shearing flow measurement. DSC measurement has permitted us to determine the degree of cure as a function of cure time. By combining the rheological and DSC measurements, we have constructed plots describing how the viscosity increases with the degree of cure, at various isothermal curing temperatures.     

Fate and effects of Camembert cheese micro-organisms in the human colonic microbiota of healthy volunteers after regular Camembert consumption

The objective of this study was to determine i) if Camembert cheese micro-organisms could be detected in fecal samples after regular consumption by human subjects and ii) the consequence of this consumption on global metabolic activities of the host colonic microbiota. An open human protocol was designed where 12 healthy volunteers were included: a 2-week period of fermented products exclusion followed by a 4-weeks Camembert ingestion period where 2x40 g/day of Camembert cheese was consumed. Stools were collected from the volunteers before consumption, twice during the ingestion period (2nd and 4th week) and once after a wash out period of 2 weeks. During the consumption of Camembert cheese, high levels of Lactococcus lactis and Leuconostoc mesenteroides were measured in fecal samples using real-time quantitative PCR, reaching median values of 8.2 and 7.5 Log(10) genome equivalents/g of stool. For Ln. mesenteroides, persistence was observed 15 days after the end of Camembert consumption. The survival of Geotrichum candidum was also assessed and the fecal concentration reached a median level of 7.1 Log(10) CFU/g in stools. Except a decreasing trend of the nitrate reductase activity, no significant modification was shown in the metabolic activities during this study.     

Chemorheology of thermosetting resins. II. Effect of particulates on the chemorheology and curing kinetics of unsaturated polyester resin

The effect of particulates on both the rheological properties during cure and the curing kinetics of unsaturated resin has been investigated. For the investigation, a general-purpose unsaturated polyester resin was used, with calcium carbonate and clay as inorganic particulates and high-density polyethylene powder as organic particulates. It has been found that, as the particulate content increases, the resin/particulate mixture gives rise to shear-thinning behavior and the rate of cure increases. It has also been found that the CaCO₃ particles helped control shrinkage during cure when the material was subjected to steady shear deformation and that the gel time tη∞ is shorter for mixtures of resin and particulates than for the neat resin alone. Differential scanning calorimetry (DSC) is found useful for determining the curing kinetics of resin/particulate mixtures. We have combined rheological and DSC measurements to obtain a correlation between viscosity and the degree of cure during isothermal curing operations.