Effects of estrogen on daylong circulating calcium, phosphorus, 1,25-dihydroxyvitamin D, and parathyroid hormone in postmenopausal women.

We studied the effects of estrogen on daylong circulating levels of calcium, inorganic phosphorus, parathyroid hormone (PTH), and 1,25-(OH)2D3 (calcitriol) in a group of 10 postmenopausal women (68.5 +/- 1.4 years, mean +/- SEM). The study was conducted under strict dietary control, with mean calcium and phosphorus intakes of 845 and 970 mg. After treatment with conjugated equine estrogens, 1.25 mg/day, for 1 month, significant decreases in fasting (0800 h) serum levels were observed for calcium (9.09 +/- 0.08 versus 9.46 +/- 0.10 mg/dl, p less than 0.01) and phosphorus (3.38 +/- 0.10 versus 3.73 +/- 0.08 mg/dl, p less than 0.01). On the 0800 h fasting specimen, midmolecule PTH concentrations were higher (44.0 +/- 7.9 versus 34 +/- 8.2 pg/ml, p less than 0.05), but intact PTH was unchanged (28.6 +/- 2.7 versus 29.1 +/- 1.7 pg/ml) and a rise in circulating calcitriol (39.8 +/- 4.3 versus 31.6 +/- 2.1 pg/ml) was marginally significant (p = 0.07). When data represented multiple samples averaged over 7 and 15 h, significant estrogen-related reductions in serum calcium and phosphorus concentrations were observed. In addition, estrogen was associated with a significant rise in the daylong (15 h) level of calcitriol (39.4 +/- 4 versus 30.5 +/- 2.4 pg/ml, p less than 0.01). Daylong mid- and intact PTH concentrations were unchanged on estrogen compared to baseline values. No significant correlations were observed between changes in fasting calcitriol level and changes in fasting concentrations of calcium, phosphorus, or PTH. Further, the rise in daylong calcitriol concentration did not correlate significantly with changes in fasting or integrated values of calcium or PTH.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of aluminum hydroxide on the parathyroid-vitamin D axis of postmenopausal women.

In previous studies we proposed that estrogen increases circulating calcitriol in postmenopausal women by reducing plasma phosphorus concentrations. For this model to be plausible, a reduction in plasma phosphorus must be itself be sufficient to increase circulating calcitriol in elderly women. To assess this question we studied the effects of Al(OH)3 on daylong circulating levels of phosphorus, calcium, PTH, and calcitriol in 14 postmenopausal women. Subjects were studied on two 7-day periods of dietary control, in which calculated intakes for phosphorus, calcium, and sodium were 950, 800, and 3000 mg/day, respectively. During one randomly assigned period, subjects were given Al(OH)3 with each meal. Al(OH)3 significantly lowered daylong plasma phosphorus concentrations by 17% (0.95 +/- 0.02 mmol/L vs. 1.15 +/- 0.02, P less than 0.0005) (2.94 +/- 0.06 mg/dL vs. 3.57 +/- 0.07), and this was associated with a 38% rise in circulating calcitriol from 61.8 +/- 10.3 pmol/L to 85.2 +/- 10.1 pmol/L (25.7 +/- 4.3 pg/ml to 35.5 +/- 4.2 pg/ml) (P less than 0.0001). The rise in calcitriol correlated significantly with the reduction in phosphorus (r = 0.51, P = 0.03). Al(OH)3 did not significantly alter average daily circulating total calcium (2.32 +/- 0.008 vs. 2.32 +/- 0.005 mmol/L) (9.31 +/- 0.03 vs. 9.29 +/- 0.02 mg/dL), ionized calcium (1.19 +/- 0.003 vs. 1.19 +/- .004 mmol/L), or intact PTH (24.6 +/- 0.6 vs. 24.2 +/- 0.8 ng/L). Moreover, neither the renal phosphorus reabsorption maximum (TmP/GFR), baseline excretion of cAMP, nor the phosphaturic, cAMP, or calcitriol responses to infused hPTH(1-34) were altered by Al(OH)3. We conclude that Al(OH)3 treatment of older women lowers plasma phosphorus concentrations by restricting intestinal phosphorus absorption, and that older women retain the capacity to increase calcitriol levels in response to phosphorus restriction.

Purchasing infant shoes: attitudes of parents, pediatricians, and store managers.

Questionnaires designed to collect data about the purchase of shoes for normal infants were completed by 104 parents in a university ambulatory unit, 127 practicing pediatricians, and 36 shoe store managers. Infants received their first pair of walking shoes at an average age of 8.1 months (range: 4 to 12 months) and at an average cost of $14.56 (range: $2 to $43). Most of these shoes had laces (95%), high tops (87%), hard soles (74%), and special arch supports (50%). Of the 104 children, 73 had shoes before they were walking (average cost: $13.21) and 35 wore walking shoes before they were even standing (average cost: $12.68). Parents obtained much more information about shoes from friends and relatives than from physicians. Those parents who obtained most of their information from salespersons spent the most for shoes. The average cost of shoes recommended by store managers was $18.74. Although 77% of pediatricians felt that inexpensive canvas sneakers are adequate, only 28% of the salespersons and 37% of the parents believed that wearing sneakers is healthy.

Relationship of chronic endurance exercise to the somatotropic and sex hormone status of older men.

To investigate putative abrogating effects of habitual endurance exercise on age-related changes in endocrine function and body composition, we compared insulin-like growth factor-I (IGF-I), sex hormonal status and body composition in 15 Masters runners and 15 minimally exercising men (MEM) aged 60-70 years. A higher maximal oxygen uptake (VO2 max.) in the runners (41.4+/-1.6 compared with 27.3+/-1.4 ml/kg/min, P=0.0001; mean+/-S.E.M.) reflected our group allocations. Analysis of body composition and bone mineral density (BMD) by dual energy X-ray absorptiometry showed no group differences in lean tissue mass or in regional or whole body BMD, but MEM were heavier, reflecting greater adiposity. Of nine muscle groups tested, only quadriceps strength differed significantly, being greater in runners (60.3+/-2.8 compared with 51.1+/-2.3 kg, P=0.02). Total IGF-I (129+/-10 compared with 124+/-11 ng/ml, P=0.72) and IGF-binding protein-3 (2854+/-94 compared with 2623+/-128ng/ml, P=0.16), were similarly depressed compared with young adult norms in both groups. There was no relationship between total or bioavailable IGF-I and any body composition, BMD or muscle strength variable. In the runners, concentrations of total testosterone (19.1+/-0.8 compared with 15.0+/-0.9 nmol/l, P=0.002) and sex hormone binding globulin (SHBG) (124.4+/-21.6 compared with 67.7+/-11.6 nmol/l, P=0.03) were significantly greater, but the free androgen index was significantly lower (20.7+/-2.7 compared with 31.4+/-4.1, P=0.04). Directly measured free testosterone, however, was similar between the runners and MEM (47.9+/-1.8 compared with 47.1+/-2.0 nmol/l P=0.80). Therefore the group differences in total testosterone and free androgen index were due to their different SHBG concentrations. Although estrone concentration was higher in MEM (85.1+/-5.2 compared with 108+/-6.7 pmol/l, P=0.03), estradiol concentration was similar between groups (73.0+/-6.3 compared with 81.8+/-8.0 pmol/l, P=0.18), indicating that estrogens were not responsible for the increased SHBG in runners. These results indicate that even high levels of regular endurance exercise do not prevent the decline in the somatotropic axis that occurs with aging. Furthermore, the somatic effects of exercise in older men (reduced adiposity and increased regional muscle strength) occurred independently of somatotropic or androgen status. Although habitual exercise does not influence free testosterone concentrations in older men, it appears to enhance the age-associated increase in SHBG synthesis.

Rumen fermentation and liveweight gain in beef cattle treated with monensin and grazing lush forage.

OBJECTIVE: To determine the prevalence of subacute rumen acidosis (SARA) in beef cattle grazing lush pasture and the effect of monensin on reducing SARA and improving animal performance. DESIGN: Commercial Angus and Murray Grey steers received a monensin slow-release capsule (n = 19) or remained untreated (n = 19). Cattle grazed an oats crop or tetraploid ryegrass pasture for a total of 91 days. Rumen fluid pH, volatile fatty acids (VFA) and lactic acid concentrations and body weight data were collected prior to treatment and again 28, 56 and 91 days after treatment. Changes in measures over time were analysed using mixed model repeated measures analysis. Differences in average daily gain between treatment groups were determined. RESULTS: The prevalence of SARA was low during the study, with only one animal satisfying criteria for SARA at one time point. Cattle treated with monensin capsules were 11.9 kg heavier at the completion of the study compared with untreated controls (414.5 ± 3.88 kg vs 402.6 ± 4.03 kg, P = 0.04). Rumen VFA and L- and D-lactate levels did not differ between cattle treated with monensin and untreated cattle. However, the ratio of propionate to acetate plus two times butyrate was higher (P < 0.001) when cattle were treated with monensin. CONCLUSIONS: Subacute rumen acidosis was not consistently detected under the conditions of the study. The higher body weight of cattle treated with monensin may have been due to improved energy utilisation of the pasture, indicated by increased propionate proportions in the rumen, rather than prevention of SARA.

The use of 13C nuclear magnetic resonance of aromatic amino acid residues to determine the midpoint oxidation-reduction potential of each iron-sulfur cluster of Clostridium acidi-urici and Clostridium pasteurianum ferredoxins.

13C NMR of the aromatic residues of Clostridium acidi-urici [Phe2]ferredoxin (a chemically modified ferredoxin in which a phenylalanyl residue replaces a tyrosyl residue) and Clostridium pasteurianum ferredoxin permits one to distinguish and probe each iron-sulfur (Fe7S7) cluster neighboring the aromatic residues within each protein. This is because the ring carbon resonance shifts of the phenylalanyl and tyrosyl residues can be distinguished. The 13C NMR results suggest that the midpoint oxidation-reduction potentials of the two Fe4S4 clusters in C. pasteurianum and C. acidi-urici ferredoxin differ by 10 plus or minus 5 mv and smaller than mv, respectively. 13C NMR of an equilibrium mixture of methyl viologen-reduced C. acidi-urici and C. pasteurianum ferredoxin shows that the protein midpoint oxidation-reduction potential of C. acidi-urici ferredoxin is 47 plus or minus 10 mv lower than that of C. pasteurianum ferredoxin. We attribute the differences in cluster and protein midpoint oxidation-reduction potentials to differences in protein structure.

Direct assignment of the cysteinyl, the slowly exchangeable, and the aromatic ring 1H nuclear magnetic resonances in clostridial-type ferredoxins.

We have directly assigned the 1H NMR corresponding to the cysteinyl protons, the slowly exchangeable protons, and the aromatic ring protons in the 1H NMR spectrum of Clostridium acidi-urici ferredoxin by isotopic labeling and 13C NMR decoupling techniques. We also show that the resonance pattern in the 8- to 20-ppm (from 2,2-dimethyl-2-sialapentanesulfonic acid) region of the 1H NMR spectra of oxidized Clostridium acidi-urici, Clostridium pasteurianum, Clostridium perfringens, and Peptococcus aerogenes ferredoxins are very similar, and we assign the resonances in this region by analogy with the spectrum of C. acidi-urici ferredoxin. The 1H NMR spectra of the beta protons of the cysteinyl residues of these ferredoxins differ, however, from the 1H NMR spectra of equivalent beta protons of the methylene carbon atoms bonded via a sulfur atom to [4Fe-4S] clusters in synthetic inorganic analogues. In the spectra of the synthetic compounds, the beta protons appear as a single resonance shifted 10 ppm from its unbonded reference position. In the spectra of oxidized clostridial ferredoxins, the cysteinyl beta protons appear as a series of at least eight resolved resonances with shifts that range from 6 to 14 ppm, relative to the free amino acid resonance position. This difference in the spectra of the protein and the synthetic compounds probably results from the fact that the equivalent beta protons of the synthetic compounds are not constrained and are free to rotate and thus assume the same average orientation with respect to the [4Fe-4S] cluster. The shift pattern in the 9- to 14-ppm region is identical in three different clostridial ferredoxins. This suggests that the molecular environments of the corresponding cysteinyl residues are identical. Significant differences in the resonance positions occur, however, in the 14- to 18-ppm region, suggesting that the physical environments of these cysteinyl residues differ. This may reflect differences in the orientation of the corresponding cysteinyl residues relative to the [4Fe-4S] clusters or differences in charge density at the cysteinyl beta protons or both. The slowly exchangeable protons were identified by comparing the 1H NMR spectra of ferredoxins reconstituted in H2O and 2H2O. The remaining resonances in the 8- to 20-ppm region were assigned to each of the 2 tyrosyl residues in C. acidi-urici ferredoxin. This was done by comparing the 1H NMR spectra of C. acidi-urici [(3',5'-2H2)Tyr]ferredoxin and C. acidi-urici [PHE2]ferredoxin with that of C. acidi-urici native ferredoxin.

Assignment of the cysteinyl 13C nuclear magnetic resonances and comparison of other aliphatic amino acid resonances of Clostridium acidi-urici, Clostridium pasteurianum, and Peptococcus aerogenes ferredoxins.

13C NMR spectra of Clostridium acidi-urici, Clostridium pasteurianum, and Peptococcus aerogenes ferredoxins show that some 13C resonances of the aliphatic amino acid residues are shifted significantly from their corresponding resonance positions in the spectra of model polypeptides or apoferredoxin. Thirteen 13C resonances are shifted into the 80- to 120-ppm (from CS2) region, and have been assigned to the cysteinyl alpha and beta carbon atoms. The remaining shifted resonances in the 120- to 190-ppm region are tentatively assigned to amino acid residues that may be close to [4Fe-4S] clusters of the oxidized and reduced ferredoxins. The similarity in the shift pattern of the corresponding 13C resonances of the cysteinyl alpha and beta carbon atoms in the three ferredoxins studied suggests that the three-dimensional amino acid environments of the corresponding [4Fe-4S] clusters in each protein are similar.

The possible role of aromatic residues of Clostridium acidi-urici ferredoxin in electron transport.

The (13)C-resonances of the 2',6'-ring carbon atoms of both tyrosyl residues of Clostridium acidi-urici ferredoxin are shifted downfield in the oxidized and reduced protein relative to these resonance positions in free tyrosine. These results show that both tyrosyl residues in the oxidized and reduced protein are in magnetically equivalent environments, and suggest that both tyrosyl residues are close to the two iron-sulfur clusters in the reduced and oxidized proteins and that each cluster is equally accessible to one reducing electron.