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Biomedical subjects

G R Jansen

Publications and source records attributed to G R Jansen.

At least 19 recordsLinked to original sources
PubMed2000

A comparison of extrahepatic lipogenesis from a small glucose meal in obob and gold thioglucose obese mice fed low- or high-fat diets with or without the addition of Delta22-5beta-taurocholenic acid.

Extrahepatic fatty acid synthesis from a 250 mg meal of [U-(14)C]-glucose was measured in epidymal fat pads and the remaining carcass of hyperglycemic obese (obob), gold thioglucose obese, and nonobese controls under conditions of maximum and minimum lipogenesis. Also assessed was the effect of Delta(22)-5beta-taurocholenic acid, previously shown to inhibit hepatic fatty acid synthesis. Both types of obese and nonobese mice were fed for 6 weeks glucose-based diets containing either 1% corn oil or 40% lard with or without the addition of 0.05% taurocholenic acid. In mice fed 1% corn oil, incorporation of labeled glucose into carcass fatty acids was 25% greater in nonobese than obese mice of either type of obesity. On this diet incorporation of labeled glucose into epididymal fatty acids was reduced 83% in hyperglycemic obese mice compared with nonobese littermates. The corresponding reduction in lipogenesis in gold thioglucose obese mice was only 23% compared with nonobese controls. Feeding 40% lard reduced incorporation of labeled glucose into epididymal and carcass fatty acid 67 to 95% compared with mice fed 1% corn oil in both types of obese and nonobese mice whether or not taurocholenic acid had been fed. Both types of obesity or feeding 40% lard reduced lipogenesis in fat pads to a greater extent than glucose uptake by the pads with the reductions additive. Feeding taurocholenic acid reduced pad weight 30% across strain and obesity status, increased uptake of labeled glucose into epididymal fat pads and increased the percentage of the labeled glucose in the pad recovered as fatty acid in both types of obese and nonobese mice when the diet was 1% corn oil. Similarities and differences between the two obesity models are discussed.

Journal Article↗
PubMed1999

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.

Journal Article↗
PubMed1998

Stress fractures in female army recruits: implications of bone density, calcium intake, and exercise.

OBJECTIVE: To identify characteristics and factors associated with increased risk for stress fractures in military women. DESIGN: Case-control study to retrospectively examine physical activity, prior calcium intake, and bone density as predictors of stress fractures. SETTING: A military training installation which incorporates physical training for women. SUBJECTS: Forty-nine female soldiers with confirmed stress fractures (cases) and 78 female soldiers with no orthopedic injuries (controls), aged 18 to 33 years. MEASURES: Retrospective self-reports of habitual exercise, sports participation, and food intake; current height, weight, and body mass index (BMI); demographic variables (age, ethnicity, menstrual patterns, smoking habits); and bone density on radiologically defined stress fractures. RESULTS: Cases and controls were similar in height, weight, and BMI. Measurements of bone density (g/cm2) at the trochanter (cases, 0.77+/-0.09; controls, 0.77+/-0.08); femoral neck (cases, 0.94+/-0.10; controls, 0.94+/-0.09); Ward's triangle (cases, 0.91+/-0.11; controls, 0.93+/-0.11); lumbar spine (cases, 1.21+/-0.12; controls, 1.24+/-0.10); and radius shaft (cases, 0.67+/-0.09; controls, 0.68+/-0.05) were not different between groups. Calcium intake was not different between groups (cases, 1154+/-751 mg/day; controls, 944+/-513 mg/day) and did not correlate with bone density (r=0.01 to -0.06 at four sites). Sports participation positively correlated with bone density in the hip (r=0.49). Leisure activity energy expenditure (kcal/day) tended toward association with lower stress fracture risk as expenditure level increased (p=0.06). CONCLUSION: Stress fracture in female Army recruits was not correlated with bone density or calcium intake during adolescence, although a weak relationship to prior physical activity was observed.

Adolescent↗
PubMed1991

Effect of dietary protein and environmental factors on lactation performance in rats.

The effects of dietary protein and environmental conditions on lactation performance in rats were evaluated. Female rats were fed from conception until day 9 of lactation diets containing 21% wheat protein (21W), 21% casein + methionine (21CM) or 11% casein + methionine (11CM). At parturition, dams were kept in their normal environment (20 degrees C) or were exposed to crowded conditions or an elevated ambient temperature (30 degrees C). Feeding poor-quality protein (21W) or a lower amount of high-quality protein (11CM) reduced day 8 pup weights and average daily gains (ADG). Pup ADG's nursed by crowded dams fed either 11CM or 21CM were greater than those of pups nursed by noncrowded dams. Pup ADG's were reduced by heat exposure in dams fed 21CM but not in pups raised by dams fed diets reduced either in protein quality (21W) or protein quantity (11CM). Thus lactation performance was not further reduced by heat exposure in dams fed poor-quality wheat protein in spite of reduced food consumption and increasing lactation weight loss in these dams. The study indicates that lactating rats have considerable ability to raise their litters under potentially adverse conditions.

Animals↗
PubMed1991

Protein quality and quantity influence free amino acid levels in the brain and serum of rats during lactation.

Diets containing 11 or 21% protein supplied by wheat, wheat + lysine + threonine or casein + methionine were fed to pregnant rats from conception until d 4 or 8 of lactation. Dams then were decapitated, serum was collected and brains and left inguinal-abdominal mammary glands were quickly excised and weighed. Serum and brains were frozen in liquid nitrogen and stored at -70 degrees C. Free amino acids in either serum or brain were not significantly different on d 8 as compared with d 4 of lactation. Increasing dietary protein quality or quantity increased concentrations of most essential amino acids in serum and brain. Changes in the concentrations of nonessential amino acids in serum or brain associated with increases in protein quality or quantity were variable. For all 16 amino acids measured, brain free amino acids were highly correlated with serum levels. In this experiment, pup growth varied from 0.3 g/d for the offspring of dams fed 11% wheat to 1.4 g/d for the offspring of dams fed 21% wheat + lysine + threonine. Concentrations of lysine and threonine in the brain were more than twice as high under the latter as compared with the former condition, but differences in all other amino acids among the dietary groups were small, ranging from -20% for glycine to +21% for leucine and isoleucine.

Amino Acids↗
PubMed1990

Educating patients with diabetes: comparison of nutrient-based and exchange group methods.

This study compared the effectiveness of a nutrient-based (diet guide) approach with that of a food-group (exchange lists) approach to menu planning for persons with noninsulin-dependent diabetes. Each method was presented to four groups in three-session workshops emphasizing meal planning to reduce risk of heart disease. The diet guide method evaluated menus specifically for calories, source of calories, cholesterol, fiber, sodium, and key vitamins and minerals. Of 105 subjects recruited, 97 completed the workshops and 83 the 6-month follow-up. Subjects responded positively to the diet guide method, finding it as easy to use as the exchange lists method. Menu planning and evaluation initially took longer using the diet guide than the exchange group method (25 vs. 16 minutes per day), but subjects indicated that time was well spent. Also, with practice, the time required to use the diet guide method decreased to 17 minutes per day. Both diet-education programs improved attitude and knowledge regarding diabetes, diet, and nutrition, with retention of knowledge gained for up to 6 months. Increases in applied nutrition knowledge scores were significantly greater, however, for diet guide than for exchange lists subjects both 3 months (24% vs. 15% increase) and 6 months postworkshop (15% vs. 8% increase). We conclude that the diet guide method can effectively serve as an alternative menu-planning system to exchange lists for patients with noninsulin-dependent diabetes who have at least a high school education.

Adult↗
PubMed1987

A comparison of nutrient-based and exchange-group methods of diet instruction for patients with noninsulin-dependent diabetes.

This study compared effectiveness of nutrient-based (Diet Guide) vs food-group (Exchange Lists) methods of diabetic diet evaluation in improving dietary compliance, glycemic control, and biochemical indicators of heart disease risk. Eighty-three persons with noninsulin-dependent diabetes were taught one of two diet-planning methods in a 3-session workshop. Both methods led to reductions in energy intake and percent of calories from fat and saturated fatty acids in 6 mo postworkshop. Reductions in fat intake were greater and more long lasting for persons using Diet Guide than using Exchange Lists method of diet planning. Despite dietary changes, neither diet-planning method led to significant decreases in weight or skinfold thickness. Few differences were seen in clinical measurements pre- and 6 mo postworkshop. Total and LDL cholesterol values were lower than preworkshop values for men in both groups. Suggestions are given for improving effectiveness of both diet-planning methods.

Adult↗
PubMed1987

Wheat gluten during pregnancy and lactation: effects on mammary gland development and pup viability.

Diets containing 13% protein supplied by wheat gluten (WG), wheat gluten + lysine + threonine (WGLT), or casein + methionine (CM) were fed to pregnant rats from conception through day 15 of lactation. A crossover design was used with combinations of WG, WGLT, and CM during pregnancy and lactation. Out of six dams fed WG during both pregnancy and lactation and nursing a total of 48 pups on day 1 of lactation, only two pups were still alive on day 15 of lactation. In contrast, CM dams still were nursing 47 pups at this time. Differences in the weight and composition of mammary tissue were directionally similar to and consistent with pup viability. The data obtained confirm the importance of protein quality in the lactation diet and also demonstrate that deficits in mammary gland development occurring during pregnancy may not necessarily be overcome by a nutritionally adequate diet consumed during lactation.

Animals↗
PubMed1986

Dietary protein quality, protein quantity and food intake: effects on lactation and on protein synthesis and tissue composition in mammary tissue and liver in rats.

Rate of protein synthesis in mammary tissue and liver as well as pup weight and milk yield were measured at d 15 of lactation in rats fed throughout gestation and lactation diets that varied in protein quality (wheat, wheat supplemented with lysine and threonine or casein supplemented with methionine), protein quantity [11 or 21% (wt/wt)] and feeding level (ad libitum or pair-fed to 100 or 85% of the consumption of dams fed wheat ad libitum). Improvement in dietary protein quality or quantity at the ad libitum feeding level produced large increases in mammary protein synthesis and pup weight; pair-feeding at 100 or 85% of the ad libitum wheat consumption level reduced or eliminated these increases. Increases in protein synthesis and pup weight associated with protein quality improvement were of similar magnitude to those associated with nearly doubling protein content of maternal diets. The responses of liver protein synthesis to dietary manipulation were qualitatively similar to those seen in mammary tissue. These data demonstrate that maternal dietary protein quality, protein quantity and feeding level all affect mammary protein synthesis and pup weight, and that, considered across all diets, changes in mammary protein synthesis are highly correlated with changes in pup weight and protein nutritional value.

Animals↗
PubMed1986

Free amino acid levels during lactation in rats: effects of protein quality and protein quantity.

Free amino acid levels were determined in serum, mammary gland, liver and muscle during lactation in rats fed diets varying in protein. Using a 3 X 2 factorial design, after conception female rats were fed purified diets varying in protein quality (wheat, wheat + lysine + threonine or casein + methionine) and in protein level (11.6% vs. 22.3%). On d 15 of lactation dams were decapitated; blood was collected, and the serum was quickly frozen. Samples of mammary gland, liver and calf muscle were also removed and quickly frozen. After deproteinization, free amino acids were determined on an LKB 4400 Amino Acid Analyzer. As the protein nutritional value of the diet increased, milk yield increased threefold and the level of free lysine in the mammary gland increased six- to eightfold. With protein quality or quantity improvement, the level of free methionine increased two- to threefold, and no consistent changes were seen in the levels of free threonine, aromatic and branched chain amino acids in mammary glands. Free lysine concentrations in mammary gland, liver and muscle were highly correlated with free lysine in serum (r2 = 0.94, 0.96, 0.93, respectively). Under the conditions of this experiment, a direct relationship between dietary lysine, free lysine in the mammary gland and milk secretion was observed.

Amino Acids↗
PubMed1986

Effect of dietary protein and energy on protein synthesis during lactation in rats.

A series of experiments was carried out in which effects of dietary protein and energy on protein synthesis during lactation were evaluated. Purified diets were fed to female rats from conception until d 15 of lactation. Protein supplied by wheat gluten, gluten + lysine + threonine or casein + methionine was fed at 20 or 25% in the diet. Protein synthesis in mammary gland and liver was measured with a large dose of L-[4-3H]phenylalanine. As lactation proceeded, protein absolute synthesis rates (ASRs) in casein-fed dams increased from 1056 to 2246 mg/d in mammary gland but remained unchanged in liver. In contrast, ASRs in wheat gluten-fed dams remained unchanged in both tissues. Feeding a protein-free diet or starving dams for 3 d reduced ASR in mammary gland 59 and 72%, respectively, when measured on d 15 of lactation. The corresponding reductions in liver ASR were 41 and 46%. A 20% restriction of dietary energy at a constant protein intake reduced protein synthesis in mammary glands 34, 55 and 28% in dams fed gluten, gluten + lysine + threonine or casein, respectively. In summary, protein synthesis during lactation was reduced less in liver than in mammary gland in response to dietary restriction of protein or energy.

Animals↗
PubMed1985

The effect of dietary protein quality and feeding level on milk secretion and mammary protein synthesis in the rat.

Protein synthesis was studied in mammary tissue of rats fed diets deficient in protein quality and/or restricted in food intake throughout gestation and lactation. Diets containing 25% wheat gluten (WG), wheat gluten plus lysine and threonine (WGLT), or casein (C) were pair-fed from conception until day 15 of lactation at 100% or 85% of WG ad libitum consumption (PF100 and PF85, respectively). A seventh group was fed C ad libitum. Rates of protein synthesis were measured in vivo at day 15 of lactation from incorporation of [3-3H]phenylalanine. At both PF100 and PF85, fractional and absolute rates of mammary gland protein synthesis were two- to three-fold higher in rats fed C than in those fed WG. Pup weights showed similar treatment effects. Both mammary protein synthesis rates and pup weights were significantly higher in rats fed C at PF85 than rats fed WG ad libitum. Food restriction from PF100 to PF85 depressed pup weights and mammary protein synthesis rates in rats fed WGLT, but had no effect in rats fed WG. These results demonstrate that when food intake is restricted, improvement of protein quality of the maternal diet increases milk output in the rat in association with increased rates of mammary protein synthesis.

Animals↗
PubMed1984

Protein synthesis in rat tissues during lactation. No effect of diethyl ether anaesthesia.

Rates of protein synthesis were measured in mammary gland, liver, intestinal mucosa and muscle of lactating rats by using a flooding dose of [3H]phenylalanine that was injected into diethyl ether-anaesthetized dams via a lateral vein or into undisturbed dams via a jugular cannula. Ether anaesthesia did not alter rates of protein synthesis significantly in any tissue.

Anesthesia, Inhalation↗
PubMed1984

A method for isolation of undegraded free and membrane-bound ribosomes from rat lactating mammary gland.

Mammary gland polysomes are difficult to isolate from the lactating rat using methods developed for other species and tissues, most likely due to high calcium-stimulated ribonuclease activity in that tissue. A new method, utilizing ethyleneglycol-bis-(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) to bind calcium, yields highly aggregated polysomes from lactating rat mammary gland. Fresh mammary tissue is pulverized under liquid nitrogen. Free and membrane-bound polysomes are isolated by differential centrifugation in solutions containing 100 mM KCl, 100 mM MgCl2, 75 mM EGTA, 500 micrograms/ml heparin and 50 mM Tris buffer, pH 8.2 at 5 degrees C. Bound polysomes are released from the endoplasmic reticulum using Triton X-100 and deoxycholate. Polysome profiles are obtained on linear sucrose gradients and scanned at 254 nm. The method gives quantitative recovery of homogenate total RNA. To demonstrate that the method can be used to study nutritional effects on mammary gland polysome aggregation, lactating rats were fasted 22-66 h and then refed a stock diet for 71-95 h. Refeeding increased the percentage of polysomes (trimers or larger) in the bound fraction from 84 +/- 1 to 93 +/- 1% (P less than 0.001) and in the free fraction from 42 +/- 2 to 55 +/- 3% (P less than 0.001).

Animals↗
PubMed1984

Protein synthesis during lactation: no circadian variation in mammary gland and liver of rats fed diets varying in protein quality and level of intake.

Circadian changes in protein synthesis were studied in lactating rats fed diets varying in protein quality and feeding level. At parturition, rats previously fed a stock diet were assigned to semipurified diets supplying 23% protein. Two groups were fed wheat gluten (WG) or casein (C) ad libitum; a third group was pair-fed casein to consumption of the WG group (C-PF). At four different times on day 15 of lactation, protein synthesis was measured in vivo in mammary gland, liver and calf muscle with a large dose of L-[4-3H]phenylalanine. Pup weights at day 15 for dams fed WG, C and C-PF were 19.3 +/- 0.3, 33.9 +/- 0.5 and 27.2 +/- 0.5 g, respectively. No significant circadian variation in fractional synthesis rate (FSR) was observed in either mammary gland or liver. Higher variability in muscle FSRs precludes conclusions in regard to this tissue. However, protein quality and level of feeding both affected FSR. For rats fed WG, C and C-PF, FSRs were, respectively: 77 +/- 4, 116 +/- 6 and 64 +/- 3%/day in mammary gland; 67 +/- 4, 78 +/- 5 and 74 +/- 4%/day in liver; and 3.4 +/- 0.5, 6.7 +/- 1.0 and 4.0 +/- 0.8%/day in muscle. Absolute synthesis rates were, respectively: 584 +/- 60, 1743 +/- 148 and 663 +/- 58 mg/day in mammary gland; and 469 +/- 46, 970 +/- 72 and 702 +/- 62 mg/day in liver. The results confirm that dietary protein quality and feeding level affect protein synthesis rates in lactating rats and demonstrate that there is no circadian variation in protein synthesis in mammary gland and liver of lactating rats.

Animals↗