Karen C. Scott

Supplemental Vitamin C Appears to Slow Racing Greyhounds

During strenuous exercise, markers of oxidation increase and antioxidant capacity decreases. Antioxidants such as vitamin C may combat this oxidation stress. The benefits of vitamin C to greyhounds undertaking intense sprint exercise has not been investigated. The objective of this experiment was to determine whether a large dose (1 g or 57 mmol) of ascorbic acid influences performance and oxidative stress in greyhounds. Five adult female, trained racing greyhounds were assigned to receive each of three treatments for 4 wk per treatment: 1) no supplemental ascorbate; 2) 1 g oral ascorbate daily, administered after racing; 3) 1 g oral ascorbate daily, administered 1 h before racing. Dogs raced 500 m twice weekly. At the end of each treatment period, blood was collected before and 5 min, 60 min and 24 h after racing. Plasma ascorbate, alpha-tocopherol, thiobarbituric acid-reducing substances (TBARS) and Trolox equivalent antioxidant capacity (TEAC) concentrations were measured and adjusted to compensate for hemoconcentration after racing. TBARS, TEAC and alpha-tocopherol concentrations were unaffected by supplemental vitamin C. Plasma ascorbic acid concentrations 60 min after racing were higher in dogs that received vitamin C before racing than in dogs that either received no vitamin C or received vitamin C after racing. The dogs ran, on average, 0.2 s slower when supplemented with 1 g of vitamin C, equivalent to a lead of 3 m at the finish of a 500-m race. Supplementation with vitamin C, therefore, appeared to slow racing greyhounds.

Nutrient and metal analyses of Chinese herbal products marketed for veterinary use.

Many Chinese herbs and herbal mixtures are fed to domestic animals for their reputed medicinal properties. These herbs could contribute to the intake of essential nutrients and toxic metals, but their composition is mostly unknown. The purpose of this study was to measure major nutrient (crude protein, crude fat, carbohydrate, fibre) and mineral (Ca, P, Mg, K, Na, Fe, Zn, Cu, Mn, Mo, S, Al, Cd, Ni, Pb) concentrations in samples of fourteen combination formulas labelled for veterinary use and commonly administered to horses and dogs. Three single herbs, Bupleurum chinense, Curcuma zedoaria and Astragalus membranaceus, each obtained from several sources, and Yunnan Baiyao, a proprietary hemostatic mixture, were also analysed. Proximate analyses and some mineral concentrations differed (p < 0.05) among single herbs, and high concentrations of several minerals were detected in some herbal combinations. Those containing the highest concentrations [g/kg dry matter (DM)] of calcium (92.4), iron (2.6) and manganese (0.28) could provide >38%, 142% and 96%, respectively, of recommended allowances in adult dogs, and >13%, 122% and 2%, respectively, of maintenance requirements in horses, at the maximum labelled dose assuming complete availability. Concentrations of cadmium, nickel and lead were below published oral tolerance levels. Aluminium concentrations (median 380, maximum 920 mg/kg DM) were higher than has been previously reported in Chinese herbs. These nutrient analyses suggest that herbal combinations marketed to veterinarians, when fed at the maximal labelled dose, are unlikely to produce clinically relevant changes in the dietary intake of essential nutrients. However, small amounts of non-essential contaminant minerals are present in some formulas, and further research is necessary to understand the significance of this finding.

The fate of [3H]folic acid in folate-adequate rats

To assess more fully the metabolic fate and in vivo kinetics of dietary folate, we conducted an in depth study that followed the metabolism and excretion of radiolabeled folate from a single administration, through its many forms in the organs and tissues of folate-adequate rats. Twenty-two rats were equilibrated with an amino acid diet containing 1 mg folic acid/kg diet, then given 185 kBq [3H]folic acid intragastrically. The isotopic label was followed through the tissues and in urine and feces for 32 days, every 8 hours for the first 48 hours. Individual folates, as their monoglutamyl forms, were separated and measured by high performance liquid chromatography (HPLC), and the peaks counted for 3H. Liver and kidney folates exhibited labeling (∼0.8 kBq/g for each) by 8 hours post-dose. These organs exhibited a peak of [3H]folate at 40 hours post-dose, then slowly lost label from 48 hours to 32 days, with the exception of a rise in renal radioactivity at 16 days. Heart and spleen exhibited low levels of labeling at 8 hours, a peak at 32 hours, then a gradual loss of label. Testes and muscle (hind leg) showed very low levels of labeling throughout the study. Whole blood showed labeling almost entirely associated with 5-methyl-tetrahydrofolate (THF). Urinary excretion of intact folate occurred mainly as 5-methyl-THF, although excretion of products of folate catabolism exceeded urinary excretion of intact folates. Much of the labeled dose (35%) was excreted into the urine as catabolites and intact folates by 32 days post-dose, whereas 15% of the label was lost through the feces by 32 days post-dose. Unexpected differences were observed among the specific radioactivity values among tissues (liver < kidney << testes, spleen, whole blood < heart << muscle). These may indicate different rates of clearance of labeled folates from these tissues or else the presence of kinetically slow pools comprising a significant portion of total folate in certain tissues (especially liver and kidney). The results of this study will be used to develop a compartmental model to simulate folate metabolism in folate-adequate rats.

Proximate Nutrient Analyses of Four Species of Submerged Aquatic Vegetation Consumed by Florida Manatee (Trichechus manatus latirostris) Compared to Romaine Lettuce (Lactuca sativa var. longifolia)

Abstract Free-ranging Florida manatees (Trichechus manatus latirostris) consume a variety of sea grasses and algae. This study compared the dry matter (DM) content, proximate nutrients (crude protein [CP], ether-extracted crude fat [EE], nonfiber carbohydrate [NFC], and ash), and the calculated digestible energy (DE) of sea grasses (Thalassia testudinum, Halodule wrightii, and Syringodium filiforme) collected in spring, summer, and winter, and an alga (Chara sp.) with those of romaine lettuce (Lactuca sativa var. longifolia). Neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and lignin (L) measured after ash-extraction were also compared. Results of statistical tests (α  =  0.01) revealed DM content was higher in aquatic vegetation than in lettuce (P  =  0.0001), but NDF and ADF were up to threefold greater, EE (P  =  0.00001) and CP (P  =  0.00001) were 2–9 times less, and NFC (P  =  0.0001) was 2–6 times lower in sea grass than in lettuce, on a DM basis. Chara was lower in NDF, ADF, L, EE, CP, and NFC relative to lettuce on a DM basis. Ash content (DM basis) was higher (P  =  0.0001), and DE was 2–6 times lower in aquatic vegetation than in lettuce. Sea grass rhizomes had lower L and higher ash contents (DM basis) than sea grass leaves. Based on the nutrient analyses, romaine lettuce and sea grasses are not equivalent forages, which suggests that the current diet of captive Florida manatees should be reassessed.

Chapter 4 - Modeling of Folate Metabolism1

This chapter discusses the modeling of folate metabolism. Developing and improving the model of folate metabolism includes the multiple routes of excretion of folic acid and its catabolites (pABG, apABG, pterins), and the interconversion of the various forms of folate must also be considered, including polyglutamylation within tissues. The models provide a base to study the effects of altered folate nutriture and the influence of other factors such as pregnancy, and aging on folate metabolism. Factors that affect folate metabolism include dietary folate level, nutritional status of vitamins B6, B12, and riboflavin, zinc status, alcoholism, and physical states such as pregnancy and lactation. Folate catabolism occurs by oxidative cleavage of tetrahydrofolates by free radicals and various oxidants (primarily in liver and other tissues), and represents a major irretrievable loss from the body. Stable-isotopic labeling methods permit the evaluation of micronutrient kinetics with the high specificity of isotopic procedures, but with no radiation exposure to the subjects.

Evaluation of the secretory response to endogenous and exogenous prostaglandins in mucosa from the proximal and distal portions of the colon of dogs

OBJECTIVE To compare secretory responses to prostaglandin (PG) E(2) in mucosa obtained from the proximal and distal portions of the colon of dogs. SAMPLE Colonic mucosa from cadavers of 18 clinically normal adult dogs. PROCEDURES Short-circuit current (I(SC)) and maximum change in I(SC) (ΔI(sc)) in response to administration of 1μM PGE(2) were measured across mucosa obtained from the proximal and distal portions of the colon. Responses were evaluated in mucosa (n = 6 dogs) incubated in Ussing chambers with or without 1 mM amiloride or without chloride in the Ringers bathing solution. Responses were also evaluated in mucosa (n = 9 dogs) incubated with or without pretreatment with 1 μM indomethacin, with or without amiloride in the subsequent bathing solution. Histologic changes in mucosa from 3 dogs were assessed over time. RESULTS I(SC) and ΔI(SC) were significantly reduced when chloride was removed from, but not when amiloride was added to, the bathing solution and were significantly reduced after pretreatment with indomethacin. The ΔI(SC) was significantly greater in mucosa from the distal portion of the colon than in the proximal portion of the colon. Histologic changes after incubation for 3 hours were minimal. CONCLUSIONS AND CLINICAL RELEVANCE I(SC) and ΔI(SC) resulted from electrogenic chloride secretion. Chloride secretion was reduced when release of PGs was prevented by indomethacin and was induced by administration of PGE(2). Chloride secretion in response to PGE(2) was greater in mucosa from the distal portion of the colon than in mucosa from the proximal portion of the colon.