Olaf Mickelsen

Androgen secretion and spermatogenesis in rats following semistarvation.

Summary Male Sprague-Dawley rats were allowed to feed freely until 10 weeks of age and then were restricted to 50% of the ad libitum food intake of controls for 8 or 23 weeks. Serum testosterone, determined by gas-liquid chromatography, decreased during the first 8 weeks of food restriction to 31% of that in full-fed controls, but then rebounded to control levels following another 15 weeks of semistarvation. Similarly, weights and secretory activities of accessory reproductive organs declined during the first 8 weeks and increased during the last 15 weeks of food restriction. When allowed to refeed for 3 weeks following 20 weeks of semistarvation, serum testosterone rose to 3.0 ng/ml, twice the 1.5 ng/ml in fully fed controls and three times the 1.2 ng/ml for chronically semistarved rats at the same age. The complete absence of food from previously full-fed rats for 6 days lowered testosterone levels to undetectable quantities. Absolute weights of testes and epididymides and their concentration of sperm (per gram of tissue) were affected less than androgens during a 50% reduction in feed intake as well as during the subsequent ad libitum refeeding period.

Blood pressure of rats as affected by diet and concentration of NaCl in drinking water.

Summary In the first experiment, weanling rats were fed a grain ration or one of three semipurified diets high in fat, sucrose, or cornstarch. Rats in each dietary group were divided into two subgroups, one of which drank distilled deionized water whereas the other group drank 2% NaCl solution. Blood pressure and sodium intake were individually measured for each rat at weekly intervals for a 10-week period. Rats receiving the salt solution had higher mean blood pressures (127-178 mmHg) than rats offered distilled water (108-127 mmHg). When drinking solutions were the same, more severe rises in blood pressure occurred in rats fed the semipurified diets than in those rats fed grain. In a second experiment, rats were fed one of the four diets used in the first experiment; however, they received a 1% NaCl drinking solution for 9 weeks followed by a 1.5% NaCl solution for an additional 9 weeks. At Week 18, pressures among these groups of rats ranged from 136-140 mmHg, regardless of diet.

The influence of high-fat diets on estrous cycles, sperm production and fertility of rats.

Summary The estrous cycle lengths of rats fed high-fat diets ad libitum or restricted, a grain diet or a low-fat diet were determined in two long-term studies. In the first experiment, with a 40% fat diet, the rats had prolonged estrous cycles beginning at 37–40 weeks of age caused primarily by a prolongation of diestrus. During the early stages of feeding the high-fat diet did not prolong the estrous cycles. In the second experiment, the diet contained 60% fat and the prolongation of diestrus occurred at 23–27 weeks of age. In male rats, however, high fat diets from weanling to 11 weeks of age did not affect fertility or sperm production.

Vitamin C in tomatoes: Comparison of tomatoes developed for mechanical or hand harvesting

Variety does affect the ascorbic acid content of tomatoes. However, the tomatoes currently being developed for mechanical harvesting have as high ascorbic acid concentrations as those developed for more conventional harvesting. Tomatoes of the same variety, grown in different areas may have vitamin C concentrations which deviate as much as 17 percent from the average value for that variety. Although the vitamin C concentration of some varieties of tomatoes developed for mechanical and manual harvesting were highest when the plants were grown in one area of the country, this was not true for other varieties. The environmental factors which have been shown to influence the vitamin C content of conventional tomatoes have a comparable effect on the tomatoes developed for mechanical harvesting.

Utilization of 14C-labeled E. coli by the Rat Cecum and After Force-feeding

Summary Radioactive E. coli produced by means of adding glucose-U-14C into the culture medium was placed into the cecum of six adult male rats. The rats were then placed in metabolic chambers for the collection of respiratory CO2. At the end of 4 hr, almost 5% of the dose appeared as CO2 indicating that the E. coli were digested in and absorbed from the cecum. Further evidence that this occurred came from the finding that 30.5% of the dose appeared in the carcass of the rats killed at the end of the metabolic CO2 collection period. About 70% of the dose remained in the cecum and large intestine at this time which is the portion not absorbed. Another six comparable rats were gavaged with the radioactive E. coli. Carcass and fecal analyses and measurements of activities in the gastrointestinal contents indicate that 24 hr after gavage, the rat retained 43.5% of the gavaged dose. They did not digest 7.3% (fecal activity) plus 4.2% (remaining in the gastrointestinal tract) for a total of 11.5%. Thus, the digestion coefficient for E. coli is 88.5% and net utilization is 83.8% since 4.7% of the gavaged dose appeared in the urine in 24 hr. Fractionation of carcass samples revealed that the rat utilized the products obtained from the digestion or degradation of the radioactive E. coli force-fed or placed in the cecum for the formation of lipids, protein and other carbon-containing materials.

Carcinogenicity of Long-Term Feeding of Cycad Husk to Rats

Summary Guamanians eat the fleshy husk of the seeds of the cycad, Cycas circinalis, which is indigenous to Guam. The fresh husk is eaten to relieve thirst. The dried husk is eaten as candy. The kernel of this seed is soaked in water, sun dried, and ground for preparation as an ingredient in foods. This processed kernel was not toxic or carcinogenic in contrast to unprocessed kernels. Since the husk is consumed without cooking or processing other than drying, and since the husk is reported to be eaten primarily by children, it is imperative to evaluate the safety of this food. The acute toxic effects have already been studied whereas the carcinogenic properties of the husk have not. For this reason rats were fed diets containing 0.5-2.0% of the dry husk for prolonged periods. Malignant tumors were found in the liver and kidney of experimental animals. Metastatic tumors were found in the pancreas, spleen, and lung.

Effect of diet and stress on the thiamin and pyramin excretion of normal young men maintained on controlled intakes of thiamin

Abstract Thiamin excretion of young men adapts rapidly (t 1/2 = 1 day) to increases or decreases in thiamin intake, but is independent of the amount of carbohydrate (38–80% of energy), protein (75–200g), riboflavin (2.5–3.5 mg), water (2-fold range), and energy (in range 3200–4700 kcal/day) present in the diet. The thiamin RDA should be expressed in terms of mg/day rather than in terms of mg of thiamin per 1000 kcal of total energy or carbohydrate energy in the diet. Most stresses had little or no effect on thiamin excretion. Pyramin excretion was strongly influenced by dietary pyrimidines.

Oral contraceptive steroids: effects on various nutrient balances and body composition in adult female rats.

Summary Norethynodrel and mestranol fed to 11-week-old female rats on a physiological level reduced food consumption and body weight gain. The withdrawal of the oral steroids for 42 days did not accelerate the growth rates of the treated rats when they had been previously fed the steroids for 28 or 180 days. Treatment with steroids for a short or long period did not affect digestibility of protein, fat, sodium, or potassium. However, retention of dietary nitrogen was higher for control rats than for treated rats after 22 days of steroid treatment (p <0.05). At this time the treated rats retained significantly more dietary sodium than the control rats (p <0.05). After feeding the oral steroids for 178 days, the treated rats retained more dietary nitrogen than did the control rats (p <0.01). No statistically significant effect on sodium retention was observed at this time. Thus, the effects caused by the oral steroids on the retention of this mineral as well as nitrogen was temporary in nature. The oral steroids did not significantly alter the retention of dietary potassium whether the treatment was for short or long time. Concomitant with the increased retention of sodium measured after 22 days of treatment was an increased proportion of water in the carcasses of treated rats compared to the control rats. Again, this effect disappeared after 178 days of treatment or after refeeding of control diet subsequent to 22 or 180 days of treatment. Furthermore, there was no difference in body moisture concentration when it was expressed as a percentage of lean body masses.

Dental caries: Possible sugar substitutes for sucrose†

This study investigated the use of sucrose, fructose, glucose, high fructose corn syrup (HFCS)§, and equal weights of fructose and glucose in cakes containing fat and prepared by the solution method of mixing. Cakes prepared with glucose scored lowest in all sensory attributes. According to objective measurements of product quality, cakes made with monosaccharides were smaller, more easily broken and more moist than the cakes made with sucrose. When compared to other cakes, those which contained fructose were darkest in color as indicated by Hunter Color Difference Meter L or lightness values. As measured by aL or greeness values, fructose cakes were also the most green. These color differences suggest that increased browning reactions occurred during baking in cakes prepared from fructose. The composite methods used for evaluation of cakes prepared with sucrose, fructose, high fructose corn syrup, and fructose/glucose were sufficiently high so that these products were all considered acceptable whereas ca...

Effect of obesity in the rat on renal transport of organic acids and bases.

Summary The effect of obesity on accumulation of PAH by rat renal cortical slices was determined using an in vitro slice technique. Accumulation of PAH was significantly depressed in animals made obese by feeding a high-fat diet. Accumulation of PAH decreased with increasing age, body weight and kidney weight independent of diet. Organic base accumulation was determined to demonstrate the specificity of the effect of the high-fat diet and obesity on organic acid transport. Accumulation of the base NMN was not different in renal tissue from grain-fed and high-fat-fed animals. There was no correlation between NMN accumulation and body weight. In high-fat-fed animals NMN accumulation by renal cortical slices decreased with increased age and kidney weight. Age and kidney weight in the grain-fed animals was not related to NMN accumulation. The data suggest that obesity and/or the constituents of the high-fat diet have a depressant effect upon the kidney. Since NMN accumulation was not influenced it is concluded that the effect is not a generalized depression of renal function but selective depression of organic anion transport.