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Biomedical subjects

G R Jansen

Publications and source records attributed to G R Jansen.

At least 55 records · Page 3Linked to original sources
PubMed1975

Comparison of Type A and nutrient standard menus for school lunch. II. Management aspects.

An extensive study compared school lunches planned to meet a specific nutrient standard (NSM) with those planned according to the Type A pattern. Average daily participation, food and labor costs, accuracy of the menus, and differences in the four-week menus between the two methods are reported. Twenty-nine menu planners representing a variety of living environments quickly learned the NSM method and enthusiastically planned and served the Type A and NSM test menus to fifth and tenth grade students. Type A data were collected in the fall and NSM data in the spring of the 1972-73 academic year. Changing from Type A to NSM menu planning resulted in no significant change in lunch participation or food and labor costs. Work functions also did not vary significantly when the menu planning method was changed. Menu planners of varying education and experience successfully planned accurate NSM menus and endorsed the method as an exciting and viable alternative to the Type A pattern. Sixty per cent preferred NSM due to its nutrient assurance, flexibility, and potential for nutrition education.

Adolescent↗
PubMed1975

Comparison of Type A and nutrient standard menus for school lunch. III. Nutritive content of menus and acceptability.

The caclulated nutritional value of school lunches for fifth and tenth grade students planned according to the Type A pattern and a nutrient standard (NSM) WEre compared on the basis of meals as planned, served, and eaten. On an "as eaten" basis, menus planned by both methods were low in calories, iron, and thiamin. Although the differences were small, the NSM menus were consistently higher in nutrients, including calories, iron, and thiamin, and lower in percentage of calories coming from fat. The number of schools where the lunches, on the average, furnished less than 60 per cent of the standard for calories, iron, and thiamin was significantly less for NSM than for Type A. Animportant reason for the higher level of nutrients in NSM menus was that a higher ratio of food planned was actually served. In addition, in the case of iron, a higher nutrient: calorie ratio was observed. Food ratings, as determined in the classroom before the meal, correlated positively with food consumption as determined by plate waste analyses. Milk beverages had the highest ratings and consumption, followed by starches, baked goods, sandwiches, and entrées. Salads and vegetables were rated low and consumed least.

Adolescent↗
PubMed1968

Studies on lipogenesis in vivo. Lipogenesis during extended periods of re-feeding after starvation.

1. Lipogenesis was studied in mice re-fed for up to 21 days after starvation. At appropriate times [U-(14)]glucose was given by stomach tube and incorporation of (14)C into various lipid fractions measured. 2. In mice starved for 48hr. and then re-fed for 4 days with a diet containing 1% of corn oil, incorporation of (14)C from [U-(14)C]glucose into liver fatty acids and cholesterol was respectively threefold and eightfold higher than in controls fed ad libitum. The percentages by weight of fatty acids and cholesterol in the liver also increased and reached peaks after 7 days. Both the radioactivity and weights of the fractions returned to control values after 10-14 days' re-feeding. These changes could be diminished by re-feeding the mice with a diet containing 20% of corn oil. Incorporation of (14)C from [U-(14)C]glucose into extrahepatic fatty acids (excluding those of the epididymal fat pads) was not elevated during re-feeding with a diet containing either 1% or 20% of corn oil. However, incorporation of (14)C from [U-(14)C]glucose into the fatty acids of the epididymal fat pads was increased in mice re-fed with either diet, as compared with non-starved controls. 3. Lipogenesis was also studied in mice alternately fed and starved. Mice given a diet containing 1% of corn oil for 6hr./day for 4 weeks lost weight initially and never attained the weight or carcass fat content of controls fed ad libitum. Incorporation of (14)C from dietary [U-(14)C]-glucose into the fatty acids of the epididymal fat pads was elevated threefold in the mice allowed limited access to food, although the incorporation into the remainder of the extrahepatic fatty acids was not different from that found for controls. Mice given a diet containing 20% of corn oil for 6hr./day adapted to the limited feeding regimen quicker and in 4 weeks did attain the weight and carcass fat content of controls. Incorporation of (14)C from [U-(14)C]glucose into the fatty acids of the epididymal fat pads and the remainder of the extrahepatic fatty acids was respectively fivefold and threefold higher than in controls fed ad libitum. 4. The elevation in liver lipogenesis during re-feeding was greatest on a diet containing 1% of corn oil, whereas in extrahepatic tissues the increase in lipogenesis was greater when the mice were re-fed or were allowed limited access to a diet containing 20% of corn oil. These results suggest that the causes of the increased rate of incorporation of (14)C from [U-(14)C]glucose into fatty acids during re-feeding may be different in liver from that in extrahepatic tissues.

Animals↗
PubMed1967

Studies on lipogenesis in vivo: Comparison of cholesterol and fatty acid synthesis in rats and mice.

1. The importance of fatty acid synthesis as a pathway for the disposal of ingested glucose has been evaluated in rats and mice given a purified diet high in glucose and low in fat. [U-(14)C]Glucose was either added to the diet and fed for 24hr. or given by stomach tube as a 250mg. (mice) or 1000mg. (rats) meal. The two methods of isotope administration gave similar results. 2. Under the conditions employed fatty acid synthesis appeared to be a more important pathway for glucose disposal in mice than in rats. In mice 15.3% of ingested [U-(14)C]glucose was converted into fatty acid and in rats the corresponding value was 8.6%. In contrast, the conversion of [U-(14)C]glucose into cholesterol, as a percentage of dose, was twice as high in rats as in mice. 3. The effect of 20% of corn oil in the diet on the conversion of dietary [U-(14)C]glucose into fat was also investigated. Mice given diets containing 1% or 20% of corn oil converted 14.6% or 7.0% respectively of dietary [U-(14)C]glucose into fatty acid over a 24hr. period. There was no effect of fat on the incorporation of the isotope into cholesterol. 4. In mice given diets containing 1% or 20% of corn oil approx. 10% and 2% respectively of newly synthesized fatty acids were found in the liver. Hepatic fatty acid synthesis appears to be more sensitive to dietary fat than is extrahepatic synthesis.

Journal Article↗
PubMed1967

Studies on lipogenesis in vivo: Fatty acid and cholesterol synthesis in hyperglycaemic-obese mice.

1. Lipogenesis has been studied in intact genetically obese mice by measuring the incorporation of a single oral dose of 250mg. of [U-(14)C]glucose into fatty acid and cholesterol in the liver and extrahepatic tissues. Studies were also carried out with [U-(14)C]glucose added to the diet and fed for 24hr. With either method of isotope administration, the conversion of [U-(14)C]glucose into fatty acid was greatly elevated in the livers of the obese mice. In contrast, conversion of the single dose of [(14)C]glucose into fatty acid in extrahepatic tissues of obese mice was only half that occurring in the non-obese litter mates. When [(14)C]glucose was given in the diet for 24hr. the total accumulation of labelled fatty acid in extrahepatic tissues of obese mice was slightly less than in the non-obese. Uptake of labelled glucose and conversion into fatty acid in adipose tissue of the obese mice decreased with age. 2. Conversion of the single dose of [(14)C]glucose into liver cholesterol was comparable in obese and non-obese mice fed on a purified low-fat diet. However, obese mice given this diet for 12 weeks accumulated 1.54% of cholesterol in the liver compared with 0.29% in the non-obese litter mates. This accumulation apparently resulted from a decrease in removal of cholesterol from the liver, rather than an increased synthesis. 3. Conversion of the single dose of [(14)C]glucose into extrahepatic fatty acid was decreased by 18hr. starvation proportionally as much in obese as in non-obese mice. The decrease in liver fatty acid synthesis caused by starvation also was considerable in obese mice, although somewhat less marked than in the non-obese. 4. The metabolic derangements in the liver could be more fundamental to the development of the obesity than the changes seen in extrahepatic tissues.

Journal Article↗
PubMed1966

Studies on lipogenesis in vivo. Effect of dietary fat or starvation on conversion of [14]glucose into fat ad turnover of newly synthsized fat.

1. Lipogenesis was studied in vivo by giving mice 250mg. meals of [U-(14)C]glucose and measuring the disposition and incorporation of label. About 48% of the (14)C dose was eliminated as (14)CO(2) in the first 2hr. At 60min. after administration, 1.0, 1.9 and 11.9% of the dose was recovered as liver glycogen, liver fatty acid and carcass fatty acid respectively. Of the [(14)C]glucose converted into fat in the epididymal pads about 90% was present as glyceride fatty acid and 10% as glyceride glycerol. 2. Hepatic synthesis of fatty acid was depressed by dietary fat to a much greater extent than was synthesis outside the liver. Both feeding with fat and starvation decreased the proportion of the label taken up by adipose tissue present as fat (triglyceride) and increased the proportion of triglyceride label present as glyceride glycerol. These results are consistent with the hypothesis that the primary action of both these conditions in decreasing fat synthesis is to inhibit synthesis of fatty acids. 3. Turnover of body fat labelled in vivo from [U-(14)C]glucose was estimated from the decline in radioactivity measured over the first 24hr. of the experiment. The half-life of liver and extrahepatic fatty acids (excluding epididymal fat) was 16hr. and 3 days respectively. In contrast, no measurable decrease in radioactivity of the fatty acids of epididymal fat was observed for 7 days after administration of the [U-(14)C]glucose.

Adipose Tissue↗
PubMed1966

Stdies on lipogenesis in vivo. Effects of starvation andre-feeding, and studies on cholesterol synthesis.

1. Studies in vivo have been carried out on hepatic and extrahepatic cholesterol synthesis and also on the effects of starvation and re-feeding on both cholesterol and fatty acid synthesis. 2. In rats and mice fed on a stock diet, extrahepatic tissues accounted for about 4 times as much newly synthesized cholesterol as did the liver. The liver appeared to be somewhat more important in the rat than the mouse. Feeding with cholesterol greatly decreased and cholestyramine greatly increased hepatic cholesterol synthesis without much effect on extrahepatic synthesis. 3. Mice starved for up to 7hr. did not lose any of the ability to convert a [U-(14)C]glucose meal into fat, whereas 18hr. of starvation resulted in an 80% loss of fatty acid synthesis in liver and carcass, an 80% loss in liver cholesterol synthesis and a 65% decrease in carcass cholesterol synthesis; 18hr. of food deprivation also decreased the proportion of counts in epididymal fat pads present as fat and increased the proportion present as glyceride glycerol. 4. Re-feeding for up to 7hr. restored fatty acid synthesis from a [U-(14)C]glucose meal to about 50% of the values for non-starved mice but had no effect on hepatic cholesterol synthesis. The altered distribution of counts in the epididymal fat pads caused by starvation was restored to normal after feeding for 1hr.

Acetates↗
PubMed1966

Studies in lipogenesis in vivo: Fatty acid and cholesterol synthesis during starvation and re-feeding.

1. Lipogenesis in vivo has been studied in mice given a 250mg. meal of [U-(14)C]glucose (2.5muc) or given an intraperitoneal injection of 25mug. of [U-(14)C]glucose (2.0muc). 2. The ability to convert a [U-(14)C]glucose meal into fatty acid was not significantly depressed by 6-7hr. of starvation. In contrast, incorporation of (14)C into fatty acid in the liver after the intraperitoneal dose of [(14)C]glucose was depressed by 80% and by more than 90% by 1 and 2hr. of starvation respectively. Carcass fatty acid synthesis from the [U-(14)C]glucose meal was not depressed by 12hr. of starvation, whereas from the tracer dose of [U-(14)C]glucose the depression in incorporation was 80% after 6hr. of starvation. 3. Re-feeding for 3 days, after 3 days' starvation, raised fatty acid synthesis and cholesterol synthesis in the liver fivefold and tenfold respectively above the levels in non-starved control mice. These increases were associated with an increased amount of both fatty acid and cholesterol in the liver. 4. After 18hr. of starvation incorporation of a [U-(14)C]glucose meal into carcass and liver glycogen were both increased threefold.

Journal Article↗