The mouse bioassay for the detection of estrogenic activity in rodent diets: III. Stimulation of uterine weight by dextrose, sucrose and corn starch

We have shown previously that mice fed the American Institute of Nutrition (AIN-76A) purified diet experience a significant increase in uterine:body weight (U:BW) ratios when compared to the U:BW ratios of mice fed a closed formula natural ingredient diet (Certified Rodent Chow #5002) for 7 days. The AIN-76A purified diet contains 5% corn oil and 65% carbohydrates with 50% of the carbohydrates coming from sucrose or dextrose and 15% from corn starch. The objective of this study was to determine whether the fat and carbohydrate content contributed to the unexpected uterine growth promoting activity observed in mice fed the AIN-76A diet. Estrogen bioassays were performed using CD-1 mice weaned at 15 days of age and assigned randomly to the negative control diet (Certified Rodent Chow #5002) or to the positive control diet (#5002) containing 4 or 6 ppb DES for comparison or to the test diets. The test diets were prepared by adding sucrose, dextrose, corn starch, corn oil or soybean oil to the #5002 negative control diet at 10% w/w concentration. Uterine:BW ratios were determined at 7 days post-feeding. The uterine weights and the U:BW ratios of mice fed the test diets containing dextrose, corn starch, or corn oil, were increased significantly (P less than 0.05) over those of mice fed the negative control diet. The uterine weights and U:BW ratios of mice fed the test diets containing sucrose or soybean oil also were increased over those of mice fed the negative control diet. These increases in uterine weights and U:BW ratios were similar to the increases in uterine weights and U:BW ratios of mice fed the positive control diet containing 4 ppb DES. It was concluded that the fats and carbohydrates caused preferential increases in uterine weights and in U:BW ratios and may account for the estrogen-like uterine growth promoting activity observed in mice fed the AIN-76A purified diet.     

The effect of transient food stress on female mate preference in the stalk-eyed fly Cyrtodiopsis dalmanni.

The effect of transient nutritional stress (sucrose culture medium) on female mate preference was investigated in the stalk-eyed fly Cyrtodiopsis dalmanni. Two experimental treatments were run in parallel. In the first, female preference was initially tested on corn (standard medium) and subsequently on sucrose (novel medium). In the second, female preference was tested in the reverse order: sucrose then corn. Females fed on corn had stronger preferences for large-eyespan males than females fed on sucrose. Female age, experience or the order of exposure to culture media had no effects on the strength of preference. An additional experiment demonstrated that the sucrose diet reduced the number of developing and mature eggs. We discuss the adaptive significance of changes in female preference due to transient nutritional stress, and the effect of changes in female preference on the strength of sexual selection.     

Comparative effects of non-gelatinized corn and rice starches on the life-span of ICR mice

We compared the effects of non-gelatinized rice and corn starches on the life-span of ICR mice. Six groups of male ICR mice consisting of 30 animals each were maintained on purified experimental diets containing either corn or rice starch and different amounts of soybean oil (6, 12 or 24%) throughout their life-time. Plots of the survival rates of the mice indicate that rice compared to corn starch conferred a longer life-span to ICR mice, although a significant difference due to the starch type was only observed in the mice fed on the 24% fat diet (p=0.012). A divergent effect of rice and corn starches on the survival rate was apparent when observations were combined with respect to the starch type regardless of the dietary fat level (p=0.005). In addition, two-way ANOVA data indicate that the mean survival time was longer for the mice given rice starch (593-645 days) than for those fed corn starch (538-580 days) (p=0.011). However, no significant difference in these parameters due to dietary fat levels was observed. The results of our study indicate that starch type is one of the determinants of longevity in mice.     

Lack of Toxicity of Helminthosporium maydis-Invaded Corn and Culture Filtrates to Chicks and Mice

Six isolates of Helminthosporium maydis, obtained from southern leaf blight-damaged corn, were grown separately on autoclaved corn and fed to chicks and mice to evaluate their toxigenicity. Two-, three-, and four-week-old culture filtrates from three pathogenic isolates grown separately on modified Fries medium were also evaluated for toxigenicity. None of the invaded corn samples or culture filtrates affected the weights of chicks or mice when compared to controls. Postmortem examinations did not reveal significant gross lesions. H. maydis was not toxigenic under our experimental conditions.     

Initiation of hyperinsulinemia and hyperleptinemia is diet dependent in C57BL/6 mice.

C57BL/6 female mice were fed high fat diets containing different types of carbohydrate (sucrose or corn starch) and contents of cholesterol (0.03 % or 1 %) to identify early metabolic changes leading to increases in leptin levels and eventual insulin resistance. Under identical dietary fat conditions, type of carbohydrate and cholesterol content contributed to the timing of leptin increases. Mice fed a high-fat, high-sucrose diet showed early (4 weeks) and robust increases in circulating insulin and leptin levels (2-fold and 5-fold, respectively). In contrast, mice fed this diet with added cholesterol or with sucrose substituted by corn starch led to marked delays (8-10 weeks) in the elevations of insulin and leptin, although body weight gains were nearly identical among test diet groups. Thus, sucrose in combination with saturated fat played a specific role in initiating early metabolic changes associated with elevated leptin and insulin levels. Because leptin levels were most reflective of changes in insulin, our data support a role for insulin in determining plasma leptin levels in mice.     

Toxicity to Rats of Corn Invaded by Chaetomium globosum

Of 53 isolates of Chaetomium globosum Kunze isolated from corn, manufactured feed, and fiberboard, grown on autoclaved corn, and fed to rats, 25 were lethal within 4 to 6 days. Thirty-six single ascospore cultures of one isolate were uniformly lethal when similarly grown and fed to rats. Incubation of the fungus on corn for 6 to 8 weeks resulted in greater toxicity than shorter incubation times. Premortem symptoms indicated damage to the central nervous system of the affected animals, and postmortem lesions included hemoglobinuria, hemorrhagic enteritis, and subdural hemorrhaging. Corn invaded by C. globosum and toxic to rats had no detectable effects on swine when fed as their sole ration for 6 weeks, and appeared to be consumed with relish. The toxic substance was best obtained by defatting the fungus-invaded corn with petroleum ether (bp, 60 to 70 C), extraction with acetone, and further purification by elution from a silica gel column with acetone and 5% acetone in chloroform.     

The control of lipogenesis by dietary linoleic acid and its influence on the deposition of fat.

The replacement of dietary starch by sucrose results in an increase in hepatic lipogenesis in the rat. When corn oil (4% by weight or 9% of the energy content of the diet) was included with the sucrose (20% by weight, 20% of the energy content) the lipogenic effect of the sucrose was completely suppressed. In contrast, when beef tallow replaced the corn oil, the induced activity caused by the sucrose was reduced by only approximately 20%. No significant differences were observed between males and females. These diets containing sucrose supplemented with either 4% (w/w) corn oil or 4% (w/w) beef tallow, were then used to ascertain whether or not the effects on hepatic lipogenesis were reflected in changes in the amount of fat deposited during growth from 4--24 weeks of age. It was shown that the percentage body fat was only statistically different (P less than 0.05) when animals fed sucrose-supplemented diets were compared with animals fed diets supplemented with sucrose and beef tallow. However, there were no significant differences in total carcass weight of these rats. The results are discussed in terms of the relative contribution of liver and adipose tissue to total lipogenesis and the factors which control the lipogenic activity in the two tissues.     

Macrocyclic trichothecenes produced by Stachybotrys isolated from Egypt and Eastern Europe

Twenty seven isolates of Stachybotrys chartarum, S. albipes, S. kampalensis and S. microspora from Egypt and Eastern Europe were tested for production of macrocyclic trichothecenes. Twenty of the 27 isolates, grown on rice seeds, were toxic to brine shrimp larvae. Based on TLC and HPLC analyses, 5 macrocyclic trichothecenes (verrucarin J, roridin E, satratoxins F, G & H) as well as trichoverrols were identified. When grown in liquid culture on rice extract medium, only 3 isolates were toxic and produced verrucarin J, roridin E and satratoxins G & H. Extracts from mycelial mats were more toxic than culture filterates of two isolates grown on rice extract and both contained the same macrocyclic trichothecenes (285.5 mg/4 L), in addition to trichoverrols A & B (31 mg/4 L) found in mycelial mats only. When grown on 3% sucrose Czapek's medium supplemented with peptone and yeast extract (still cultures), all isolates were non-toxic to brine shrimp and no trichothecenes could be detected in the extracts.     

Nutritional Value of Lipids in Hydrogenomonas eutropha as Measured in the Rat

Hydrogenomonas eutropha is known to accumulate lipid, comprised largely of polymerized beta-hydroxybutyric acid, when maintained in nitrogen-deficient medium. This lipid was very poorly absorbed by mice from bacteria-containing diets, even though nitrogen absorption was adequate. The monomer, free beta-hydroxybutyric acid, was well absorbed from purified diet. Rats fed the monomer or butyric acid ate less food and grew more slowly than rats fed corn oil.     

Optimization of culture variables for improving glucoamylase production by alginate-entrapped Thermomucor indicae-seudaticae using statistical methods

Alginate-entrapped sporangiospores of Thermomucor indicae-seudaticae were used for the production of glucoamylase. The critical variables that affected glucoamylase production were identified by Plackett-Burman design (sucrose, yeast-extract, K(2)HPO(4) and asparagine) and further optimized by using a four factor central composite design (CCD) of response surface methodology (RSM). Immobilized sporangiospores secreted 41% and 60% higher glucoamylase titers in shake flasks and airlift fermenter, respectively, when the variables were used at their optimum levels (sucrose 3.0%, yeast-extract 0.2%, K(2)HPO(4) 0.1% and asparagine 0.35%). Glucoamylase production (26.3 U ml(-1)) in the optimized medium was in good agreement with the values predicted by the quadratic model (26.7 U ml(-1)), thereby confirming its validity. The enzyme production was sustainable in flasks of higher volume and also airlift fermenter, and attained a peak within 32 h in the fermenter as compared to that of 48 h in shake flasks.     

Stearolyl-CoA desaturase: a control enzyme in hepatic lipogenesis.

1. Hepatocytes were isolated by perfusion of the liver with collagenase/salt solutions and incubated in culture after attachment to plastic culture dishes for periods up to 48 h. 2. The cells, when incubated in serum-free culture medium in the presence of insulin, showed enhanced stearolyl-CoA desaturase activity which was not observed when 50 muM cycloheximide was included. When insulin was omitted from the medium, the cells lost 80% of their original desaturase activity. 3. Cells isolated from animals fed 20% (w/w) sucrose for two weeks prior to sacrifice, showed high levels of fatty acid synthesis, stearolyl-CoA desaturase activity and triacylglycerol synthesis when compared with cells isolated from animals fed a corn oil supplemental diet. 4. The observations are discussed in terms of the influence of stearoyl-CoA desaturase activity on hepatic lipogenesis.     

Identification of T-2 Toxin in Moldy Corn Associated with a Lethal Toxicosis in Dairy Cattle

Over a 5-month period during the winter of 1970-71, 20% of the lactating Holstein cows in a Wisconsin dairy herd died after prolonged ingestion of a diet containing 60% moldy corn infested with Fusarium tricinctum (2 x 10(5) propagules per g of moldy corn). Ethyl acetate extracts of the ground dried corn induced severe dermal reactions when applied to the skin of shaved 60-g albino rats and killed four of five 100-g rats that were force fed 1 ml in 2 ml of pure corn oil. T-2 toxin (3-hydroxy-4, 15-diacetoxy-8-[3-methylbutyryloxy]-12, 13-epoxy-Delta(9)-trichothecene) at concentrations of 2 mg per kg of dry corn was identified in purified extracts of the moldy corn by means of gas-liquid chromatography and mass spectrometry. This concentration of T-2 toxin in the moldy feed and the nature of the toxic effects observed strongly suggest a major causal relationship.     

Comparative hormonal profile of two newly developed obese congenic rat strains

1. The effect of feeding diets containing either 54% sucrose or cooked corn starch for 12 weeks on levels of fasting plasma insulin, corticosterone, growth hormone and glucagon were compared in two newly developed genetically obese rat strains--the normoglycemic LA/N-cp and the diabetic SHR/N-cp. 2. In corpulent rats of either strain, levels of plasma insulin and corticosterone were greater when compared to the lean littermates. Corpulent LA/N-cp rats had lower levels of plasma glucagon and higher levels of plasma growth hormone than did lean LA/N-cp rats. 3. SHR/N-cp rats fed sucrose had greater levels of corticosterone and glucagon than did SHR/N-cp rats fed starch.     

Evidence of peroxisomes and peroxisomal enzyme activities in the oleaginous yeast Apiotrichum curvatum

The presence of peroxisomes and peroxisomal enzyme activities were investigated in the oleaginous yeast Apiotrichum curvatum ATCC 20509 (formerly Candida curvata D.) Catalase, a marker enzyme for peroxisomes, was measured in cell-free extracts prepared by sonication. The nature of the carbon and nitrogen sources in the growth medium greatly affected catalase activity. Cells grown on corn oil had high specific activity of catalase, but those grown on glucose, sucrose, or maltose had low specific activity. High specific activity of catalase was measured in cultures grown on media that supported poor growth (with soluble starch as carbon source or with methylamine, urea, or asparagine as nitrogen source). Peroxisomes from cells grown on corn oil were separated from other subcellular fractions in a discontinuous sucrose gradient. Major peaks of activity of fatty acid beta-oxidation and of two key enzymes in the glyoxylate cycle were found in fractions containing peroxisomes, but not in fractions corresponding to the mitochondria. Peroxisomal beta-oxidation showed equivalent activity with palmitoyl CoA or n-octanoyl CoA as substrate. Mitochondria did not seem to contain NAD-linked glutamate dehydrogenase. Peroxisomes with a homogeneous matrix and core surrounded by a single-layer membrane were observed with an electron microscope in cells grown on corn oil, but not in those grown on glucose. Staining with 3,3'-diaminobenzidine revealed that catalase activity was located in peroxisomes. Peroxisomes in this oleaginous yeast play important roles in lipid metabolism.     

Effect of delta22-5beta-taurocholenic acid on hepatic cholesterol and fatty acid in gold thioglucose obese mice fed low- or high-fat diets

We previously demonstrated that hyperglycemic-obese (obob) mice fed a 1% corn oil diet accumulated 10 times as much hepatic cholesterol as did their non-obese (+/?) littermates fed this diet because of difficulty in removal of cholesterol from the liver rather than from increased synthesis. Furthermore, feeding the bile acid analog Delta(22)-5beta-taurocholenic acid completely prevented the accumulation of hepatic cholesterol in obob mice fed the 1% corn oil diet. The hypothesis to be tested in the current study is that these aspects of cholesterol metabolism in the obob mouse do not occur in the hyperinsulinemic and insulin-resistant gold thioglucose obese mouse. Gold thioglucose obese (gtgo) and non-obese (ngtgo) mice were fed diets containing either 1% corn oil or 40% lard each with or without added taurocholenic acid for 6 weeks and then given a 250 mg meal of [U-(14)C]-glucose with incorporation of label into hepatic cholesterol and fatty acid measured 2 hours later. Consistent with earlier results in the obob model, incorporation of labeled glucose was significantly increased in obese compared with non-obese mice fed 1% corn oil and significantly reduced either by feeding 40% lard or by adding taurocholenic acid to the diet. In addition, taurocholenic acid greatly increased incorporation of labeled glucose into hepatic cholesterol in obese or non-obese mice fed either diet. In contrast to obob mice, the percentage of fat in the liver of gtgo mice was increased only 50% compared with ngtgo mice. The comparable increase in obob mice was 480%. Hepatic cholesterol did not increase significantly in the liver of gtgo mice fed 1% corn oil when compared with the ngtgo controls. The comparable increase in obob mice fed 1% corn oil was 350%. Also in marked contrast to obob mice, feeding taurocholenic acid increased hepatic cholesterol compared with non-obese controls fed either diet. The results are discussed in the light of the presence of circulating leptin in gtgo but not in obob mice.     

甘蔗、玉米气味对亚洲玉米螟成虫产卵和幼虫取食的影响

【目的】农作物间套作对害虫的影响很大程度上取决于害虫的行为反应,通过研究玉米/甘蔗套作系统中植物气味对亚洲玉米螟Ostrinia furnacalis(Guenee)行为的影响,将为利用化学生态手段防治套作田中的害虫提供依据。【方法】通过昆虫触角电位实验、成虫产卵和幼虫取食实验,测定了甘蔗、玉米植株及二氯甲烷漂洗物对亚洲玉米螟成虫产卵、幼虫取食的影响。【结果】亚洲玉米螟成虫在甘蔗植株上的落卵量(卵粒数、卵块数)与玉米植株差异不显著,取食甘蔗植株的幼虫数量显著低于玉米植株。亚洲玉米螟对甘蔗、玉米叶片漂洗物均可产生EAG反应,且在同一浓度下的反应值之间无显著差异。成虫产卵量(卵粒数、卵块数)在0.1 gE/mL浓度的甘蔗和玉米漂洗物间差异不显著;幼虫对经甘蔗叶片漂洗物处理过的饲料的相对取食率均低于65.00%,显著低于玉米漂洗物处理的饲料。【结论】甘蔗和玉米气味对亚洲玉米螟产卵的影响没有差异,但甘蔗气味会导致初孵幼虫表现出很强的逃逸行为。     

Plasma lipoprotein cholesterol and triglycerides and lipoprotein lipase activity in epididymal white adipose tissue of rats fed high sucrose or high corn oil diets

The present study was undertaken to compare plasma lipoprotein lipid composition, as well as white adipose tissue lipoprotein lipase activity, in rats fed purified diets high in either sucrose or corn oil. The experimental diets (65% of calories as sucrose or corn oil, 15% as the opposite nutrient, and 20% as casein) were given ad libitum for 4 weeks. An additional group was fed a nonpurified diet as a reference diet. Both sucrose and oil diets were spontaneously consumed in isocaloric amounts by the animals. Despite energy intakes that were 35% lower than that of the reference group, the sucrose and oil groups exhibited final body weights that were only 6 and 9% lower, respectively, than that of the reference group, and accumulated more fat in the epididymal depots. Postprandial as well as fasting total cholesterol levels were similar in the sucrose and oil groups, while the high-density lipoprotein to total cholesterol ratio was highest in the animals fed corn oil. In both the fasted and fed states, plasma total triglyceride levels were 73% higher in the sucrose group than in the corn oil group. The largest triglyceride differences due to diet were observed in the chylomicron + very-low-density lipoprotein fraction. The oil-fed rats accumulated large amounts of triglycerides in their livers. Postprandial lipoprotein lipase activity in epididymal adipose tissue was almost twice as high in the sucrose group as in the oil group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Economical glucoamylase production by alginate-immobilized Thermomucor indicae-seudaticae in cane molasses medium

AIMS: The present investigation is aimed at assessing the suitability of cane molasses as a cheaper carbon and energy source for glucoamylase production using alginate-immobilized Thermomucor indicae-seudaticae. METHODS AND RESULTS: The culture variables for glucoamylase production were optimized by 'one-variable-at-a-time' strategy and response surface methodology (RSM). A high glucoamylase titre was attained when 40 alginate beads (c. 5x10(6) immobilized spores) were used to inoculate 50 ml of cane molasses (8%) medium in 250-ml Erlenmeyer flasks. Response surface optimization of fermentation parameters (cane molasses 7%, inoculum level 44 alginate beads per 50 ml of medium and ammonium nitrate 0.25%) resulted in 1.8-fold higher glucoamylase production (27 U ml(-1)) than that in the unoptimized medium (15 U ml(-1)). Enzyme production was also sustainable in 22 l of laboratory air-lift bioreactor. CONCLUSIONS: Cane molasses served as an excellent carbon and energy source for the economical production of glucoamylase, which was almost comparable with that in sucrose yeast-extract broth. The statistical model developed using RSM allowed determination of optimum levels of the variables for improving glucoamylase production. SIGNIFICANCE AND IMPACT OF THE STUDY: The cost of glucoamylase produced in cane molasses supplemented with ammonium nitrate was considerably lower (euro1.43 per million U) than in synthetic medium containing sucrose and yeast-extract (euro35.66 per million U). The reduction in fermentation time in air-lift bioreactor with sustainable glucoamylase titres suggested the feasibility of scale up of the process.     

Zinc‐Induced Hyperleptinemia Relates to the Amelioration of Sucrose‐Induced Obesity with Zinc Repletion

Objective: Dietary zinc repletion can ameliorate sucrose‐induced obesity. A positive correlation between zinc and leptin has been recently noted, and both are known as important mediators in appetite control. In this study, we examined whether the reported amelioration of sucrose‐induced obesity by zinc repletion was consequent on the changes in circulating leptin levels. Research Methods and Procedures: Mice with obesity that was induced by giving a 32% sucrose solution in addition to a semipurified diet were divided into two groups based on whether they had 20 mg/liter zinc supplementation in their drinking water. Results: As expected, the mice with sucrose‐induced obesity had hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hyperleptinemia, and hypozincemia when compared with the mice given the diet alone. Body weight gain, body fat content, and food and sucrose intake tended to decrease but not with statistical significance in sucrose‐fed obese mice with zinc supplementation. Nevertheless, some serum variables (glucose, insulin, triglycerides, and zinc) in sucrose‐fed obese mice with zinc treatment were approximate to those values of the mice given the diet alone. Moreover, sucrose‐fed obese mice with zinc supplementation had the highest serum values of leptin. Discussion: This study indicates that the amelioration of sucrose‐induced obesity by zinc repletion may be partly attributable to the hyperleptinemia induced by the mineral.     

Potentiation effect of corn extract on the production of eremofortin C, EC oxidase, and PR toxin by Penicillium roqueforti.

Eremofortin C (EC) and PR toxin are secondary metabolites of Penicillium roqueforti. Their structures are similar and differ only by an alcohol and an aldehyde group at the C-12 position. EC has been demonstrated to be the precursor of PR toxin, and EC is transformed to PR toxin by EC oxidase. These two compounds and EC oxidase are secreted by P. roqueforti in the culture medium, which is usually composed of 15% sucrose and 2% yeast extract. Recently, we discovered that the addition of corn extract to this medium increased the production of EC and PR toxin and the activity of EC oxidase in a coordinative manner. In a time-course study, we found that the peak yield of EC and PR toxin and the maximum activity of EC oxidase in the culture medium containing 7.5% sucrose, 1% yeast extract, and 20% corn extract were increased 6.2, 4.6, and 4.7-fold, respectively, as compared with those obtained in the medium without corn extract. Moreover, corn extract increased the production of EC and PR toxin and the activity of EC oxidase by P. roqueforti in a dose-dependent manner. On the other hand, when the concentrations of sucrose and yeast extract were increased while fixing the ratio of corn extract, we found that the levels of EC and PR toxin and the enzyme activity were decreased concomitantly. We thus conclude that corn extract can enhance the production of EC, PR toxin and EC oxidase by P. roqueforti when grown in a minimal medium and that the potentiation effect of corn extract is suppressed when the fungi are grown in a rich medium.