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Biomedical subjects

J C Howe

Publications and source records attributed to J C Howe.

16 recordsLinked to original sources
PubMed1997

Breath-hydrogen production and amylose content of the diet.

Recommendations to increase dietary intakes of starch and fiber in the United States may result in increased intake of resistant starch. High-amylose starch appears to resist digestion in vitro. To investigate the in vivo effect of high-amylose starch, diets containing 70% amylose or amylopectin cornstarches were fed for 14 wk each in a crossover design to 24 men [10 control, 14 hyperinsulinemic (HI)]. Fasting breath samples and periodic postingestion samples were analyzed for hydrogen during weeks 12 (nibbling tolerance test) and 14 (acute tolerance test) of each phase. Overall breath hydrogen was significantly higher after the amylose tolerance tests (nibbling, P < 0.0005; and acute, P < 0.0006). Control subjects, regardless of body mass index (BMI; in kg/m2), appeared to adapt to the high-amylose starch diet. Fasting breath hydrogen was significantly higher at week 12 but not at week 14 in HI subjects with a low BMI (< 25) consuming amylose than in other subjects. Breath hydrogen of the HI subjects with a moderate (between 25 and 27.8) or high (> 27.8) BMI increased from week 12 to week 14. The HI subjects with a high BMI averaged lower breath-hydrogen expiration than other HI subjects. After 3 d of excess energy intake, breath hydrogen after amylose was still significantly greater than after amylopectin (P < 0.019); fasting breath hydrogen of the control subjects after amylose more closely resembled that of the HI subjects. HI subjects with a high BMI may be more efficient at digesting all starch, therefore decreasing the amount available for colonic digestion. This may be a factor contributing to their greater body weight.

Adult↗
PubMed1997

Effects of crating and transport on stress and meat quality characteristics in broilers.

Experiments were conducted to determine 1) whether different crating durations influence stress responses and meat quality in broilers, and 2) whether holding crated broilers after transport influences corticosterone (CORT) levels and meat quality. In a preliminary experiment, male broilers (n = 50) were held in crates (10 birds per crate) for either 0, 1, 2, 3, or 4 h prior to processing. Crating duration did not affect plasma CORT level, cooking loss, shear value of breast or thigh muscles, or carcass skin discolorations. Crating duration also did not affect the color (L*, a*, b*, chroma, and hue angle) of breast meat, but did change the color of thigh meat, with samples from the 3 h crating group having the highest hue values (P < 0.01). Corticosterone concentrations and hue values of thigh samples were positively correlated (P < 0.05, r = 0.244). In Experiment 1, broilers (n = 36) were crated for either 1 or 3 h, with 9 birds per crate. Crating time did not influence plasma CORT, epinephrine, or norepinephrine concentrations, initial pH, color, or texture of breast and thigh meat samples. In Experiment 2, broilers were crated (nine birds per crate) early in the morning and transported 3 h to the processing facility by truck. Nine crates of birds were held in a dark quiet place for 4 h prior to processing (H) and the remaining nine crates were processed immediately (NH). Corticosterone levels were significantly lower (P < 0.01) in the H group than in the NH group. Initial pH of thigh meat of the H group was also significantly lower (P < 0.01), although breast meat pH was not affected by treatment. Holding had no effect on shear values, color (breast and thigh), or total heme concentration (thigh). There was a significant correlation (P < 0.01, r = 0.302) between CORT levels and hue values of thigh meat. These results suggest that higher preslaughter stress levels in broilers could influence the color of thigh meat, although overall meat quality was not affected under the conditions of this study.

Analysis of Variance↗
PubMed1996

Resistant starch as energy.

OBJECTIVE: This study was designed to compare the metabolizable energy of two starch sources, standard cornstarch and high amylose cornstarch. METHODS: Diets containing 70% amylose (AM) or 70% amylopectin (AP) cornstarches were fed to 10 control and 14 hyperinsulinemic men for 14 weeks. During the last 4 weeks of each period, subjects were fed a controlled diet containing 34% of total energy from fat, 15% from protein and 51% from carbohydrate (55% of carbohydrate provided AM or AP). Duplicate food and all urine and feces were collected during the second week of the controlled diets for energy, nitrogen, fiber and starch determinations. Metabolizable energy (ME) was calculated as [energy intake minus (fecal plus urinary energy excretion)]. RESULTS: Total fiber uncorrected for resistant starch was 35.2 g and 48.8 g in the AP and AM diets, respectively. The AM diet contained an average of 29.7 g resistant starch (16% of total starch) while the AP diet averaged 0.8 g (less than 0.01%). ME was not significantly different between the AM and AP diets nor between the control and hyperinsulinemic subjects. Fecal energy and nitrogen was significantly higher after the AM compared to AP diet. Based on energy intake and fecal excretion from all subjects, the partial digestible energy value for the resistant starch averaged 11.7 kJ/g resistant starch which was 67.3% of the energy of standard cornstarch. Control and hyperinsulinemic subjects differed in their ability to digest resistant starch, averaging 81.8% and 53.2, respectively. The hyperinsulinemic, but not control, subjects had significantly higher breath hydrogen expirations (LS means, p > 0.05) in the fasting, 1-5 hours and 7 hour collections after consuming the AM when compared to the AP tolerance meal. CONCLUSIONS: The type of starch consumed in the diet did not statistically affect metabolizable energy. Based on ME and breath hydrogen expiration, amylose and the resistant starch from amylose appears to be utilized as an energy source. Resistant starch averaged 2.8 kcal/g for all 24 subjects but only 2.2 kcal/g in the hyperinsulinemic subjects.

Adult↗
PubMed1996

Dietary starch composition and level of energy intake alter nutrient oxidation in "carbohydrate-sensitive" men.

The effect of dietary starch type on components of 24-h energy expenditure (total, sleep, exercise) were examined in 13 hyperinsulinemic and nine control men, aged 28-58 y. Subjects consumed products containing 70% amylopectin or 70% amylose cornstarch for two 14-wk periods in a crossover design. A 10-wk period of starch replacement in the subjects' self-selected diets was followed by a 4-wk controlled feeding period at 100% maintenance energy intake; diets during the last 4 d of the controlled feeding period provided excess energy, i.e., 125% of maintenance energy. Data for insulin, glucose, 24-h energy expenditure and its components, respiratory quotient and nutrient oxidation were analyzed by ANOVA for mixed models. Although insulin and glucose responses to a starch tolerance test remained greater for hyperinsulinemic than for control subjects, both were reduced with high amylose consumption (P < 0.04). No component of energy expenditure was significantly affected by dietary starch or subject type. However, excess energy intake did increase metabolic energy expenditure (P < 0.0001). Protein oxidation increased with excess energy intake when subjects consumed the high amylopectin starch but did not increase in response to excess energy consumption when the high amylose diet was consumed, suggesting increased protein retention. The magnitude of the response in carbohydrate and fat oxidation was blunted in hyperinsulinemic subjects consuming excess levels of the amylose diet. This may be due to an improvement in overall insulin response or to a change in available substrates for oxidation resulting from microbial fermentation.

Adult↗
PubMed1995

Effect of long-term consumption of amylose vs amylopectin starch on metabolic variables in human subjects.

Long-term consumption of high-amylose starch on insulin and glucose response was investigated in 24 men: 10 control and 14 hyperinsulinemic (HI) subjects. Subjects consumed products made with standard (70% amylopectin, 30% amylose) or high-amylose (70% amylose, 30% amylopectin) cornstarch for two 14-wk periods in a crossover pattern. Starch products replaced usual starches in the self-selected diet for 10 wk followed by 4 wk of a controlled diet. After a starch-tolerance test with bread made from the starch consumed during that period, the insulin response curve area was significantly lower in all subjects after amylose consumption (P < 0.002). Glucose responses in HI and control subjects were similar and did not vary with the type of starch. Fasting triglyceride concentrations were significantly lower in subjects who consumed the high-amylose compared with the standard-starch diet throughout the study. Chronic consumption of high-amylose foods normalized the insulin response of hyperinsulinemic subjects and showed a potential benefit for diabetic subjects.

Adult↗
PubMed1995

Contribution of fiber and resistant starch to metabolizable energy.

Recommendations made to increase complex carbohydrate and fiber intake in the United States may result in energy loss from increased fecal losses of starch, protein, and fat. The type of fiber or starch and the amount consumed affect digestion of the carbohydrate and interactions with other nutrients. On average, 8.4 kJ (2 kcal) digestible energy/g is available from up to 70 g poorly digested carbohydrate/d. Undigested fiber and starch are important substrates for colon bacteria and are fermented to short-chain fatty acids, hydrogen, and methane. Hydrogen and methane excreted through the lungs have been used as indicators of colonic fermentation. Fermentation appears to contribute significant digestible energy when > 20 g poorly digested carbohydrate/d is consumed.

Dietary Fiber↗
PubMed1993

Measurement of body composition of live rats by electromagnetic conductance.

Measurement of body composition in vivo is important in many nutritional studies. One method for estimating body composition is total body electrical conductance (TOBEC). The TOBEC methodology is based on measuring changes of an electromagnetic field that are proportional to lean body mass (LBM). Sprague-Dawley rats (n = 117) ranging in age from 49 to 105 days were measured by TOBEC, and the TOBEC results were compared with direct carcass chemical analyses. The rats ranged in weight from 155 to 500 g. Mean LBM was 92.4% of total body weight (b.wt.), and mean body fat was 7.4% of total b.wt. Mean hydration of LBM was 71.7% and decreased (r = -0.59, p < 0.0001) with age. Using the manufacturer's supplied equation, TOBEC measurement underestimated actual LBM by 12% (p < 0.0001). As a consequence of this error, a new prediction equation was generated using half of the data set, and this equation was cross-validated with the other half of the data set. The mean LBM calculated from the new prediction equation was not different from chemically determined LBM, but the estimated percent body fat of some rats was negative. Thus, TOBEC may be useful in predicting mean LBM of a population, but this indirect method may lack the sensitivity to provide accurate estimates of body composition of an individual.

Adipose Tissue↗
PubMed1990

Postprandial response of calcium metabolism in postmenopausal women to meals varying in protein level/source.

The postprandial response of calcium metabolism to single meals varying in protein source and level was determined in eight postmenopausal women, age 51 to 65 years. Following an overnight fast, subjects consumed a liquid meal containing either 15 g or 45 g of protein from beef (B), cottage cheese (C), or soy isolate (S; 45 g only); one meal provided 0 g protein (basal). Blood was collected before the meal and at 30, 60, 120, and 180 minutes post-meal. Urine was collected every 30 minutes post-meal. Urinary Ca excretion significantly increased following 45-g protein meals when compared with basal meals, but not when compared with 15 g protein meals. Although glomerular filtration rate (GFR) was unaffected by diet, percent renal tubular Ca reabsorption was significantly reduced following C45 or S45 meals. No consistent changes in serum levels of parathyroid hormone (PTH) and calcitonin (Ct) were observed in response to diet. Serum phosphorus levels were significantly reduced following high-protein meals when compared with no-protein meals. Insulin response varied with protein level and source (C45 greater than S45 greater than C15 greater than B45 greater than B15 greater than basal). Significant associations found between insulin and calcium metabolism indicate a possible role of insulin in the mechanism of protein-induced calciuria.

Absorption↗
PubMed1988

Bone status of senescent male rats: chemical, morphometric, and mechanical analysis.

The bone status of male rats 6, 12, and 24 months of age (n = 10) was examined. Femur calcium (Ca), phosphorus (P), and osteocalcin contents; serum chemistry; and mechanical properties of the bone were measured and correlated. Diaphyseal Ca, P, and osteocalcin contents were not different in animals 6 and 12 months of age but decreased significantly at 24 months: -7.4% for Ca, -4.2% for P, and -24% for osteocalcin compared to 12 months. Femurs from 24-month-old (senescent) rats were characterized by a scalloped appearance of the midfemoral endosteal surface and by cortical porosities. These age-associated changes coincided with nearly two-fold increases in serum immunoreactive parathyroid hormone (PTH) and osteocalcin. Serum Ca did not change with age, whereas serum P decreased (-14.8%) from 6 to 24 months. Maximum breaking force required to fracture femurs at midshaft did not change with age. Hence, the strength of the femur as an intact organ was not compromised with age despite the loss of diaphyseal Ca and P in the senescent animal. However, ultimate stress, a parameter that normalizes for differences in bone geometry and size, decreased 35% in femurs from 12- compared with 24-month-old animals. These mechanical results might be explained by the morphometric finding that, in contrast to the small but progressive age-associated increases in femur weight and length, the cortical and medullary areas increased at least two-fold. Therefore, the strength of the intact femur was maintained by architectural compensations, even though normalized tissue strength decreased with age. These findings suggest that bone status was compromised in the aged male rat.

Aging↗
PubMed1988

Bone mineral content in the senescent rat femur: an assessment using single photon absorptiometry.

The single photon absorptiometry technique was evaluated for measuring bone mineral content (BMC) of the excised femurs of the rat, and the system was used to examine the changes in cortical and trabecular bone from young adult (6 mo), mature adult (12 mo), and senescent (24 mo) male and female animals. BMC of the femur midshaft, representing cortical bone, apparently increased progressively with advancing age. The width of the femur at the scan site also increased with age. Normalizing the midshaft BMC by width partially compensated for the age-associated increase. However, when bone mineral values were normalized by the cortical area at the scan site, to take into account the geometric differences in the femurs of different aged animals, maximum bone densities were found in the mature adult and these values decreased slightly in the femurs from senescent rats. In contrast, the BMC of the femur distal metaphysis, representing trabecular bone, decreased markedly in the aged rat. The loss of trabecular bone was also evident from morphological examination of the distal metaphysis. These findings indicated that bone mineral loss with age was site specific in the rat femur. These studies provided additional evidence that the rat might serve as a useful animal model for specific experiments related to the pathogenesis of age-associated osteopenia.

Aging↗
PubMed1988

Bone status of senescent female rats: chemical, morphometric, and biomechanical analyses.

The bone status of female rats, 6, 12, and 24 months of age was examined. Femur Ca, Pi, and osteocalcin contents, as well as biomechanical properties, were measured and correlated to physical indices and serum chemistry. Diaphyseal Ca, Pi, and osteocalcin did not change significantly with increasing age. Serum Ca and Pi concentrations were not altered in the aged rat. Immunoreactive parathyroid hormone (PTH) levels increased significantly with age, when analyzed by linear regression. Serum osteocalcin decreased progressively from 6 to 12 months (-21%) and from 12 to 24 months (-23%). Maximum breaking force required to fracture femurs at midshaft did not change with senescence. Hence, the strength of the femurs as an intact organ was not compromised in aging. However, ultimate stress, a parameter that normalizes for differences in bone geometry and size, decreased 14% from 12 to 24 months. Changes in other biomechanical parameters, including yield and ultimate deformation, strain, and modulus of elasticity, were relatively small, but statistically significant, or were negligible. Morphometric measurements indicated a progressive age-related increase in second moment of area and cortical area. Medullary area did not change with age. Therefore, strength of the intact femur was maintained by architectural compensations, although normalized tissue strength decreased in senescence. The bone status and Ca/Pi homeostasis of the female rat were compared to similar findings, reported previously, for the male animal. The results suggest that bone status and mineral metabolism were compromised in the aged female rat, but the magnitude of change was less than that found for the senescent male rat.

Aging↗
PubMed1985

Amobarbital interactions with 25-hydroxycholecalciferol: effects on the extraction, quantification, and competitive protein binding in vitro.

Amobarbital has been found to coelute with 25-hydroxycholecalciferol (25OHD3) on a normal phase high performance liquid chromatographic system and cause subsequent interference in the UV detection and plasma transport competitive protein binding assay for this vitamin D metabolite. Concentrations of 25OHD3 were overestimated by 95% in the presence of 0.4 mg amobarbital in the competitive protein binding assay; as little as 0.1 mg amobarbital caused a 22% overestimation in the concentration of 25OHD3 in the assay. Separation of 25OHD3 from amobarbital on a reverse phase high performance liquid chromatographic system allowed for proper quantification without interference. Because of the similarity of chemical structures, other barbital-based compounds may cause similar interactions with 25OHD3 or other vitamin D metabolites as well.

Amobarbital↗
PubMed1983

Dietary protein and phosphorus: effect on calcium and phosphorus metabolism in bone, blood and muscle of the rat.

Four- or 12-week-old rats were fed diets containing either 25 or 45% casein and either 0.35 or 0.8% phosphorus (P) for 7 weeks. Calcium (Ca) level of each diet was 0.9%. In the young, fast-growing rat (expt 1), plasma P was increased (P less than 0.01) when 0.8%, rather than 0.35%, P was fed. In the more mature rats (expt 2), increased dietary P depressed Ca in plasma but elevated P; high protein intake elevated whole-blood Ca, but depressed plasma P. Dietary treatment had little effect on muscle of mature rats, but wet weight and total P content of muscle were higher in young rats fed 0.8%, rather than 0.35%, P. Femur dry weight and P concentration were greater when 0.8%, rather than 0.35%, P was fed to young rats; dietary P did not affect any other parameter of bone (expt 1, 2). Excessive protein intake elevated femur P concentration in young rats, but depressed length and strength of femurs in mature rats. Some parameters of bone, blood and muscle can be influenced by dietary levels of protein and P. The response, however, is dependent on the physical maturity of the rat when dietary treatment begins.

Animals↗
PubMed1981

Effect of dietary protein and phosphorus levels on calcium and phosphorus metabolism of the young, fast growing rat.

Utilizing a 2 X 2 factorial design, male weanling rats were fed diets containing either 25% or 45% casein with 0.35% or 0.8% phosphorus (P). Dietary calcium (Ca) was set at 0.9% for each diet. During the 7 weeks of this experiment, food intakes and body weights were measured weekly; urine and fecal samples were collected daily. Regardless of dietary P level, increasing dietary protein resulted in significantly decreased fecal Ca output accompanied by an increase in the Ca content of urine. Increasing dietary P resulted in significantly increased fecal Ca content, decreased absolute and percent Ca absorption, and decreased urinary Ca output. Increased fecal and urinary P excretion were obtained when dietary P levels were increased. Increasing dietary protein at the 0.35% P level slightly increased the values for absolute and percent Ca and P absorption. However, when 0.8% P was fed, increasing the protein level of the diet decreased these Ca (weeks 1-5) and P absorption values. Ca and P balances were positive at all times.

Absorption↗