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Biomedical subjects

M J Keenan

Publications and source records attributed to M J Keenan.

At least 19 recordsLinked to original sources
PubMed2000

Swimming eliminates the weight gain and abdominal fat associated with ovariectomy in the retired breeder rat despite high-fat diet selection.

The effects of swim-training on choice of dietary fat, carbohydrate or protein, weight gain, energy intake, and energy efficiency were examined in ovariectomized and sham-operated retired breeder rats. After a 3 week training period of increased duration, rats swam for 75 min per session (5 days per week) for 4 weeks. Ovariectomized rats gained more weight than sham rats, while swimming reduced weight gain and abdominal fat. As a percentage of total intake, macronutrient choices (weight and energy) were similar for all groups, ovariectomized animals consumed more food and more energy, compared with sham animals. All rats freely chose the majority of their food (g) as carbohydrate and the majority of energy (kJ) as fat. Results indicate that a moderate intensity training program of swimming prevented the weight gain following ovariectomy in older rats despite their excessive caloric intake of fat.

Adipose Tissue↗
PubMed1998

Substrate oxidation and energy expenditure in athletes and nonathletes consuming isoenergetic high- and low-fat diets.

Changes in substrate oxidation with isoenergetic high-carbohydrate (HC) and high-fat (HF) diets in male nonathletic subjects, aerobically trained athletes, and weight-trained athletes were examined in a crossover study. A whole-room respiration chamber was used to measure 24-h energy expenditure (EE) and substrate oxidation with control, HC, or HF diets for 7 d. The nonathletic group had higher 24-h EE (P < 0.05), exercise EE (P < 0.03), and resting metabolic rate (P < 0.04) than did the aerobically trained athletes when these measurements were corrected for lean body mass. Fat oxidation was significantly correlated with lean body mass and diet. However, athletic status had no effect on substrate oxidation. Carbohydrate oxidation across groups increased acutely by 23% after 24 h of the HC diet (P < 0.0001). Carbohydrate balance increased significantly over time with the HC diet (P < 0.002) and decreased acutely after return to the control diet (P < 0.0001). With the HF diet, carbohydrate balance increased and was significantly different from balance with the control diet by day 7 (P < 0.03). Fat balance decreased significantly with both the HF (P < 0.04) and HC (P = 0.0075) diets by day 7. Carbohydrate oxidation correlated with carbohydrate intake with both the control (r = 0.61, P < 0.01) and HC diets (r = 0.59, P < 0.02), but not the HF diet. Fat oxidation was not correlated with fat intake. In conclusion, substrate oxidation in a respiration chamber is significantly affected by diet, but not by prior athletic training.

Basal Metabolism↗
PubMed1997

Comparison of bone density measurement techniques: DXA and Archimedes' principle.

The standard method for determination of density (g/cm3) of bones from small animals has been the application of Archimedes' principle. A recent development has been software for the determination of "density" (g/cm2) of small animal bones with dual-energy X-ray absorptiometry (DXA). We compared Archimedes' principle and DXA (Hologic QDR-2000) in the measurement of the densities of whole and hollowed femurs of 5- to 6-month-old retired female breeder rats. In an attempt to ensure detectable treatment differences, rats were used from a low-vitamin D Holtzman and a supplemental-vitamin D Sprague-Dawley colony. Whole femur densities were higher for supplemental-vitamin D colony rats than for low vitamin D rats using both techniques (Archimedes' principle, p < 0.002; DXA, p < 0.005), and the densities from the two techniques were highly correlated (r = 0.82, p < 0.0001). Actual density values were higher for Archimedes' principle than for DXA. Other variables such as femur ash weight and calcium content were also highly correlated to densities with both techniques. Hollowed femur density values were higher than whole femur values with Archimedes' principle but lower with DXA. Colony effects for hollowed femur densities were diminished with Archimedes' principle (p < 0.03) and eliminated with DXA (p < 0.53). Investigation of whole bones is more biologically relevant, and both techniques were effective in detecting differences between whole femurs from low-vitamin D and supplemental-vitamin D colony rats.

Absorptiometry, Photon↗
PubMed1995

Maternal consumption of a low vitamin D diet retards metabolic and contractile development in the neonatal rat heart.

During the fetal and suckling periods of mammalian development, the mother serves as the sole nutritional source for the offspring. As such, the quality of the maternal diet effects growth and development of the offspring during these periods. This study sought to determine if a maternal vitamin D deficiency altered the well characterized development of the neonatal heart. Weaned rat pups (21-day-old) were obtained from mothers who had consumed either a vitamin D-supplemented diet (3000 IU of vitamin D/kg) or a low vitamin D diet (< 200 IU of vitamin D/kg) prior to becoming pregnant and throughout pregnancy and suckling. These pups were sacrificed, hearts excised, and the hearts biochemically analysed for metabolic and contractile protein properties. The pups of dams fed the low vitamin D diet were slightly hypocalcemic relative to those on the supplemented diet (2.28 v 2.41 mumol/l, P < 0.05), had significantly lower body weights (43 v 55 g), heart weights (143 v 174 mg), citrate synthase activity (106 v 147 mumol g-1 min-1), and 3-hydroxyacyl CoA dehydrogenase activity (59 v 91 mumol g-1 min-1). Hexokinase activity (1.98 v 2.02 mumol g-1 min-1), and the distribution of cardiac myosin among its three isoforms (> 85% V1), were unaffected by this dietary deficiency, however myofibrillar protein content was approximately 15% lower in the experimental hearts. These data demonstrate that maternal consumption of a low vitamin D diet results in a general but significant slowing of neonatal cardiac development.

Animals↗
PubMed1994

Effects of dietary boron in rats fed a vitamin D-deficient diet.

Although boron has long been known to be a required nutrient for plants, it was not until recently that there was any suggestion of a nutritional requirement for animals and humans. Addition of boron to the diet of vitamin D-deficient chicks indicated that boron may play a role in animal nutrition. Studies with rats have demonstrated that supplemental dietary boron has most marked effects when the diet is deficient in known nutrients. We observed higher apparent-balance values of calcium, magnesium, and phosphorus for rats fed a vitamin D-deprived diet with dietary supplemental boron (2.72 ppm), than for rats fed the same diet without added boron (0.16 ppm). The treatment group with dietary supplemental boron demonstrated a high degree of variability in response to boron. We hypothesize that relatively large and variable vitamin D stores in weanling rats from a colony supplemented with 3000 IU vitamin D/kg diet accounted for the observed variable response. A recent, unpublished study using weanling rats from a low-vitamin D colony appears to support this hypothesis.

Animals↗
PubMed1992

Carotid artery resection for head and neck cancer.

Occasionally, the head and neck surgeon encounters a patient whose malignancy involves the carotid artery. In these patients, curative or palliative surgery may require excision of the common or the internal carotid artery. However, the high complication and death rates dissuade many surgeons from undertaking carotid artery resection. This study reviews the outcomes in 20 patients treated between 1979 and 1985 at the Department of Otolaryngology-Head and Neck Surgery, The University of Iowa Hospitals and Clinics, with resection of the carotid artery for head and neck cancer. The carotid artery was electively resected in 16 patients, while 4 patients underwent emergent carotid artery ligation. In the group of patients studied the stroke rate was 25%, the death rate 20%, and the combined stroke and death rate 30%. Of the patients who survived the procedure, all but 1 died of complications caused by tumor recurrence. These results are discussed, and compared with results from other studies.

Adult↗
PubMed1992

Interactions of vitamin D with sodium zeolite A in rats from low and adequate vitamin D colonies.

Weanling rats (21 days old) from either a low vitamin D colony or an adequate vitamin D colony fed either a vitamin D adequate or a vitamin D deprived AIN-76A purified diet were used as a model to investigate interactions of vitamin D status with dietary sodium zeolite A (100 mg/kg body wt/day). Rats with adequate or replete vitamin D status had greater overall body weight gain, dry tibia weights and femur densities and ash weights than rats fed a vitamin D deprived diet. Addition of sodium zeolite A to the diets did not have an effect on plasma calcium, body weight gain or on femur density, ash and percent ash. Dietary sodium zeolite A increased total tibia fat in rats fed the vitamin D adequate diet and decreased total tibia fat in rats fed the vitamin D deprived diet. This effect of sodium zeolite A appeared to be beneficial to bone status in the groups fed adequate vitamin D, since these treatment groups had higher, although not significant, dry tibia weights with and without fat.

Aluminum Silicates↗
PubMed1991

Effect of boron on vitamin D deficient rats.

The effects of different levels of dietary boron were determined in vitamin D deficient rats. Vitamin D deficient diets containing either 0.158 ppm or 2.72 ppm of boron were fed to rats for 11 w, and calcium, magnesium, and phosphorus apparent absorption and balance were measured in the twelfth week. Higher apparent absorption and balance values for calcium and phosphorus were observed in the rats with higher dietary boron, but very few differences were seen in body wt, organ wt, and bone parameters. Balance measurements represented the present status of the rats after 12 w on the diets, but other measurements represented an accumulation over the lifetime of the rat, including a suckling period with ample vitamin D and boron. The data demonstrated that when rats are vitamin D deficient, as indicated by hypocalcemia, the level of boron in the diet affects mineral balance.

Animals↗
PubMed1991

The uptake and metabolism of 25-hydroxyvitamin D3 and vitamin D binding protein by cultured porcine kidney cells (LLC-PK1).

1. Uptake of 3H-25OHD3, 3H-25OHD3-DBP, 125I-holo-DBP and 125I-apo-DBP by LLC-PK1 cells was linearly related to the concentration of each in the culture media. The presence of DBP in the medium significantly reduced the amount of 3H-25OHD3 taken up by cells. 2. Free 25OHD3 and 25OHD3 bound to DBP were both metabolized by the cells to 24,25(OH)2D3 and an unidentified product of apparent lower polarity than 25OHD3. 3. A significant amount of DBP taken up by the LLC-PK1 cells was metabolized to a TCA-soluble form. 4. Uptake of DBP was similar to horseradish peroxidase, but higher than inulin, indicative of a non-specific endocytic mechanism with an adsorptive component. 5. It is suggested that both free circulating 25OHD3 and that derived from lysosomal degradation of 25OHD3-DBP are available for hydroxylation by the kidney.

Animals↗
PubMed1991

Recovery of rats from vitamin D-deficient mothers.

Two separate studies were conducted using weanling rats from either an unsupplemented, low vitamin D colony or a supplemented, adequate vitamin D colony. Severe hypocalcemia, slower increases in body weight gain, and lower apparent calcium, magnesium, and phosphorus balance values occurred in the rats from the low vitamin D colony fed a purified AIN-76A, vitamin D-devoid diet compared to rats from the vitamin D-adequate colony fed the same diet. Apparent calcium, magnesium, and phosphorus balance values, as well as most other measurements, in rats from the low vitamin D colony fed a purified AIN-76a, vitamin D-adequate diet were greater than or equal to those of rats never subjected to low vitamin D. This was suggestive of overcompensation in recovery from low maternal vitamin D. However, rats from the low vitamin D colony fed an unrefined (chow), vitamin D-adequate diet had lower apparent balance and bone values compared with rats from the vitamin D-supplemented colony fed the same diet. Presumably high levels of calcium, magnesium, and phosphorous in the unrefined diet prevented any overcompensation during recovery, as occurred with purified diets, from the earlier vitamin D deficiency. Overall, results indicated weanling rats from a low vitamin D colony had low vitamin D stores and were marginally vitamin D-deficient. In addition, recovery from the marginal deficiency had occurred to a large extent after feeding a purified, vitamin D-adequate diet. The results suggest the use of low vitamin D colony rats as a model for human, marginal vitamin D deficiency.

Animals↗
PubMed1985

Chromatofocusing in the purification and separation of apo- and holo-(vitamin D-binding protein).

Chromatofocusing was used to purify the vitamin D-binding protein (DBP) from pig plasma in a procedure that consisted of an initial DEAE-cellulose chromatography followed by DEAE-Sephadex chromatography, with final purification by chromatofocusing. The protein was purified 184-fold over its concentration in plasma. When the plasma was labelled with a tracer concentration of [3H]calcidiol, it was apparent that holo- and apo-DBP did not co-chromatograph on chromatofocusing. The separation of these two forms of DBP on chromatofocusing was verified by using purified apo-DBP mixed with either a tracer or a saturating concentration of calcidiol. This separation was consistent with differences observed in their isoelectric points. The ability to separate apo and holo forms of DBP should permit the study of their specific interactions with other binding proteins and help determine the physiological relevance of these interactions.

25-Hydroxyvitamin D 2↗