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Biomedical subjects

A Zittermann

Publications and source records attributed to A Zittermann.

28 records · Page 2Linked to original sources
PubMed1999

Calcium metabolism in microgravity.

Unloading of weight bearing bones as induced by microgravity or immobilization has significant impacts on the calcium and bone metabolism and is the most likely cause for space osteoporosis. During a 4.5 to 6 month stay in space most of the astronauts develop a reduction in bone mineral density in spine, femoral neck, trochanter, and pelvis of 1%-1.6% measured by Dual Energy X-ray Absorption (DEXA). Dependent on the mission length and the individual turnover rates of the astronauts it can even reach individual losses of up to 14% in the femoral neck. Osteoporosis itself is defined as the deterioration of bone tissue leading to enhanced bone fragility and to a consequent increase in fracture risk. Thinking of long-term missions to Mars or interplanetary missions for years, space osteoporosis is one of the major concerns for manned spaceflight. However, decrease in bone density can be initiated differently. It either can be caused by increases in bone formation and bone resorption resulting in a net bone loss, as obtained in fast looser postmenopausal osteoporosis. On the other hand decrease in bone formation and increase in bone resorption also leads to bone losses as obtained in slow looser postmenopausal osteoporosis or in Anorexia Nervosa patients. Biomarkers of bone turnover measured during several missions indicated that the pattern of space osteoporosis is very similar to the pattern of Anorexia Nervosa patients or slow looser postmenopausal osteoporosis. However, beside unloading, other risk factors for space osteoporosis exist such as stress, nutrition, fluid shifts, dehydration and bone perfusion. Especially nutritional factors may contribute considerably to the development of osteoporosis. From earthbound studies it is known that calcium supplementation in women and men can prevent bone loss of 1% bone per year. Based on these results we studied the calcium intake during several European missions and performed an experiment during the German MIR 97 mission where we investigated the effects of high calcium intake (>1000 mg/d) and vitamin D supplementation (650 IU/d) on the calcium and bone metabolism during 21 days in microgravity. In the MIR 97 mission high calcium intake and vitamin D supplementation led to high ionized calcium levels and a marked decrease in calcitriol levels together with decreased bone formation and increased bone resorption markers. Our conclusion from the MIR 97 mission is that an adequate calcium intake and vitamin D supplementation during space missions is mandatory but, in contrast to terrestrial conditions, does not efficiently counteract the development of space osteoporosis.

Bone and Bones↗
PubMed1999

Wheat bran supplementation does not affect biochemical markers of bone turnover in young adult women with recommended calcium intake.

We investigated the effect of wheat bran on biochemical indicators of Ca and bone metabolism in nineteen healthy women, aged 25.5 (SE 0.9) years. Subjects received six wheat bran biscuits or six white flour biscuits per day for a period of 4 weeks (crossover). Wheat bran consumption increased fibre intake from 17.7 (SE 1.3) to 29.6 (SE 1.3) g/d (7 d food record) and enhanced P intake from 1225 (SE 59) mg/d to 1663 (SE 65) mg/d; P < 0.001. Mean daily Ca intake during wheat bran consumption (1110 (SE 82) mg/d) significantly (P = 0.008) exceeded Ca ingestion during the white flour period (955 (SE 67) mg/d). Wheat bran increased the number of defecations per week from 7.9 (SE 0.8) to 12.2 (SE 1.4) (P = 0.0018). Urinary Ca excretion over 24 h significantly (P = 0.021) decreased from 473 (SE 53) mumol/mmol creatinine (control period) to 339 (SE 37) mumol/mmol creatinine (wheat bran period). Serum 25-hydroxyvitamin D, 2 h fasting urinary Ca/creatinine excretions and 24 h urinary P excretion remained constant. No differences in serum levels of carboxy-terminal propeptide of type I procollagen (biomarker of bone formation) or in 2 h fasting urinary hydroxyproline/creatinine excretions (biomarker of bone resorption) were observed at the end of the two cycles of dietary supplementation. We conclude that a high fibre intake of approximately 30 g/d has no significant adverse effects on bone turnover in subjects with Ca intakes above 1000 mg/d and that the reduction in 24 h urinary Ca excretion is most probably the result of an adaptation process, induced by a decrease in net absorbed Ca.

Adult↗
PubMed1998

Biological dosimetry to determine the UV radiation climate inside the MIR station and its role in vitamin D biosynthesis.

The vitamin D synthesis in the human skin, is absolutely dependent on UVB radiation. Natural UVB from sunlight is normally absent in the closed environment of a space station like MIR. Therefore it was necessary to investigate the UV radiation climate inside the station resulting from different lamps as well as from occasional solar irradiation behind a UV-transparent quartz window. Biofilms, biologically weighting and integrating UV dosimeters successfully applied on Earth (e.g. in Antarctica) and in space (D-2, Biopan I) were used to determine the biological effectiveness of the UV radiation climate at different locations in the space station. Biofilms were also used to determine the personal UV dose of an individual cosmonaut. These UV data were correlated with the concentration of vitamin D in the cosmonaut's blood and the dietary vitamin D intake. The results showed that the UV radiation climate inside the Mir station is not sufficient for an adequate supply of vitamin D, which should therefore be secured either by vitamin D supplemental and/or by the regular exposure to special UV lamps like those in sun-beds. The use of natural solar UV radiation through the quartz window for 'sunbathing' is dangerous and should be avoided even for short exposure periods.

25-Hydroxyvitamin D 2↗
PubMed1998

Seasonal variations in vitamin D status and calcium absorption do not influence bone turnover in young women.

OBJECTIVE: To evaluate the effect of seasonal variations in UV B-exposure on calcium absorption and bone turnover in young women with the overall goal to assess the potential benefit of a vitamin D supplementation during wintertime. DESIGN: Cross-sectional study. SETTING: Area of Bonn, Germany (51 degrees N). SUBJECTS: Thirty-eight women (24.5+/-0.5 y) studied in winter and 38 females of the same age (24.7+/-0.4 y) studied in summer. RESULTS: As estimated by a 4 d food record, both groups had similar dietary calcium and phosphorus intakes (> 1200 mg/d, respectively) covering actual recommendations. Significant reductions in serum concentrations of 25-hydroxyvitamin D (25OHD) and calcitriol, fractional calcium absorption (Fc220, measured by means of a stable strontium test), 24h urinary calcium and 24h urinary phosphorus excretion were observed during wintertime. 25OHD but not calcitriol was correlated with Fc220 values and with 24h urinary phosphorus excretion. Moreover, Fc220 was related to 24 h urinary calcium excretion. Fasting 2 h-urinary deoxypyridinoline concentrations (biomarker of bone resorption) and serum levels of carboxyterminal propeptide of type I procollagen (biomarker of bone formation) showed no differences between summer and winter. CONCLUSIONS: Our data indicate a decrease in intestinal calcium and phosphorus absorption during wintertime, most likely because of a reduction in serum 25OHD levels. Since bone turnover was not affected by the seasonal differences in mineral metabolism, there is no objective for young women with high calcium intake to supplement vitamin D during wintertime.

Adult↗
PubMed1998

The effect of a specific strength-development exercise on bone mineral density in perimenopausal and postmenopausal women.

The objective of this study was to assess the effect of physical activity on bone density at the distal radius in healthy perimenopausal (23) and postmenopausal (60) women. The 83 women, aged 40-62 years, were randomized into two groups. The women participated in an exercise program of 40 minutes of jogging and 20 minutes of gymnastics three times a week for 1 year (group 1, n = 46) or 6 months (group 2, n = 37), respectively. Subjects in group 2 served as controls during the first 6 months. They were introduced to exercise classes after the first 6 months of the study and wore wrist weights (0.8 kg on each arm) during the gymnastics session. None of the women were on hormone replacement therapy (HRT). Results show a decrease in bone mineral density (BMD) during the first 6 months of the study in group 1 (2%, p < 0.01) and group 2, although this was not significant for the latter group (1.2%, n.s., p = 0.045). There was no significant change in osteocalcin serum concentration, fasting urinary calcium excretion, and calcium serum concentration during the first half of the study. After an additional 6 months, it was possible to stop BMD loss in both groups. Osteocalcin serum concentration significantly increased, and calcium serum concentration significantly decreased in groups 1 and 2. Fasting urinary calcium excretion decreased in both groups, although this was significant only in group 2 during the 1-year study. In conclusion, it proved possible to prevent BMD loss at the distal radius by our exercise program in perimenopausal and postmenopausal women. The effects of exercise may be general as well as localized. According to our results, additional localized benefits from a specific strength-development exercise may be seen.

Adult↗
PubMed1998

Effects of elevated carbon dioxide environment on calcium metabolism in humans.

BACKGROUND: Chronic respiratory acidosis induced by an elevated carbon dioxide (CO2) environment should provoke hypercalciuria with related total body and subsequent bone calcium losses. We examined this hypothesis in four healthy male volunteers, who were exposed during a 25-d period to an 0.7% CO2 environment within a deep diving isolation chamber. Three months later the same subjects were reexamined during a second campaign being exposed to a 1.2% CO2 atmosphere. METHODS: The subjects received a constant calcium intake (1.4 g.d-1) and vitamin D supplement (1000 IU.d-1) during both campaigns. Calcium balance (oral calcium intake minus urinary and fecal calcium output) was evaluated. Serum calcium concentrations and biomarkers of bone metabolism were measured, in order to evaluate bone turnover. Additionally, the response to an acute oral calcium load was examined as a sensitive measure of changes in calcium metabolism. RESULTS: Both, urinary calcium excretion (from 245 +/- 38 to 199 +/- 31 mg.d-1; mean +/- SE, 0.7% and 1.2%, respectively) and fecal calcium losses (from 1229 +/- 128 to 996 +/- 62 mg.d-1) were significantly reduced in the higher (1.2%) CO2 atmosphere. Although more calcium was retained in the body during the 1.2% than during the 0.7% CO2 campaign, serum calcium concentrations and biomarkers of bone formation were significantly lower in the higher CO2 campaign. Furthermore, bone resorption was slightly increased in the 1.2% experiment. CONCLUSION: Elevated CO2 atmosphere may dose-dependently preserve body calcium without a parallel improvement of bone substance.

Acidosis, Respiratory↗
PubMed1995

[Determination of intestinal strontium absorption--assessment and validation of routinely manageable test procedures].

Intestinal strontium absorption has been discussed recently as an indirect measure for calcium uptake. Prerequisite for the clinical use of an oral strontium test is the availability of a reliable procedure including controlled strontium supply, sample pretreatment and analysis as well as the assessment of normal values. In the present study, a group of young females (n = 33; 24.0 +/- 2.7 y; BMI 21.5 +/- 1.9) received an oral dose of 2.27 mmol strontium in a standardized breakfast that contained 0.625 mmol calcium. Before and 220 min after the bolus serum strontium concentrations were determined by means of atomic absorption spectrophotometry (coefficient of variation: within day 4.8%, n = 10; day-to-day 9.5%, n = 8). The error of the method was 2.7%. Calculation of the fractional strontium absorption rate considered the respective distribution volume (extracellular fluid; either estimated using body weight or determined by means of bioimpedance analysis [BIA]). Average absorption rates were 13.3 +/- 3.1% and, considering BIA measurement 13.6 +/- 2.6%, respectively. Smoking, exercise and, use of oral contraceptives showed no effects. Our oral strontium test is characterized by excellent reliability, easy handling and low costs and, thus, is suitable for routine use.

Administration, Oral↗
PubMed1991

[Nutrition and primary osteoporosis].

Osteoporosis is a bone disease of great sociomedical and economic importance. Postmenopausal women are primarily affected. Pathogenesis is of multifactorial origin. In Western countries, reduced physical activity and an inadequate nutritional calcium supply are important aspects besides decreased postmenopausal oestrogen secretion. Food statistics confirm that in the Federal Republic of Germany calcium intake is below the DGE recommendation in almost all age groups, especially in women. Calcium may play a role in prevention of osteoporosis. The paper reports on individual measures to enhance calcium intake. Furthermore, the influence of the postmenopausal status on calcium metabolism and calcium requirement is demonstrated. Finally, the importance of other nutritional aspects for the manifestation of osteoporosis is discussed.

Calcium, Dietary↗
PubMed1989

[The contribution of nutrition to the pathogenesis of osteoporosis].

Osteoporosis primarily affects women and is a bone disease of great social, medical and economic importance. The pathogenesis is thought to be of multifactorial origin. The current work discusses nutritional aspects relative to osteoporosis. In this aspect, calcium supply seems to have the largest preventional importance. In contrast, food statistics and individual food records show that calcium intake of females is below the DGE's recommendation of 800 mg/daily. Furthermore, in view of skeletal integrity, calcium intake should be increased up to 1,500 mg/daily after menopause, because of endocrinological changes in calcium metabolism. Therefore, calcium intake on the whole is usually found to not be sufficient. The importance of further nutritional aspects for manifestation of osteoporosis are discussed. In some cases, influences on skeletal integrity are quite evident, whereas the literature has only infrequently drawn conclusions about the pathogenesis of osteoporosis.

Calcium↗