1,720,976 research outputs found
The energetics of cycling on Earth, Moon and Mars
No full textFrom 1885, technological improvements, such as the use of special metal alloys and the application of aerodynamics principles, have transformed the bicycle from a human powered heavy transport system to an efficient, often expensive, object used to move not only in our crowded cities, but also in leisure activities and in sports. In this paper, the concepts of mechanical work and efficiency of cycling together with the corresponding metabolic expenditure are discussed. The effects of altitude and aerodynamic improvements on sports performances are also analysed. A section is dedicated to the analysis of the maximal cycling performances. Finally, since during the next decades the return of Man on the Moon and, why not, a mission to Mars can be realistically hypothesised, a section is dedicated to cycling-based facilities, such as man powered short radius centrifuges, to be used to prevent cardiovascular and skeletal muscle deconditioning otherwise occurring during long-term exposure to microgravit
Parturition in two pregnant women with Addison's disease: changes of plasma corticotropin releasing factor levels
No full textObjectives Addison's disease is characterized by a primary adrenocortical insufficiency associated with a derangement of the hypothalamus-pituitary-adrenal axis. Before identification of cortisone supplementation therapy, only a few cases of pregnancy in Addison's patients were described. Indeed human pregnancy is characterized by a physiological state of hypercortisolemia. Corticotropin releasing factor (CRF) is a hypothalamic peptide which regulates the pituitary-adrenal cortex axis, and which is also produced during pregnancy by the human placenta, fetal membranes and decidua. In healthy women, a progressive increase of plasma CRF levels throughout gestation occurs, reaching the highest values at term and during labor, so that a placental source has been suggested.
Patients and methods The present study aimed to examine the modification of maternal CRF plasma levels at term and at parturition in two women with Addison's disease. In one patient, the disease was associated with an autoimmune hypothyroidism. Both patients had a normal pregnancy, spontaneous labor, vaginal delivery and a regular postpartum period. Plasma CRF levels were measured during the third trimester of pregnancy (at 32, 36, 40 weeks) in Case 1, while in Case 2 blood samples were drawn at the end of gestation, during labor, at delivery and from the umbilical cord. A group of normal pregnant women (n = 5) was used as a control group.
Results Plasma CRF levels during pregnancy did not differ between the Addison's patients and the healthy controls, showing a progressive increase in both groups during the last weeks of gestation. During labor and at delivery, a further significant increase of CRF plasma levels was observed in Case 2
24-Hour ambulatory blood pressure monitoring in smoker and non smoker post-menopuasal women treated with ERT
No full textPathological monolateral Doppler velocimetry of the uterin artery and materno fetal outcome
No full textBlood growth hormone-binding protein levels in premenopausal and postmenopausal women: roles of body weight and estrogen levels
No full textABSTRACT
A substantial proportion of GH circulates bound to high affinity
GH-binding protein (GHBP), which corresponds to the extracellular
domain of the GH receptor. Current evidence indicates that nutritional
status has an important role in regulating plasma GHBP levels
in humans. In the present study the relationship among plasma
GHBP levels, body composition [by bioelectrical impedance analysis
(BIA) and dual energy x-ray absorptiometry (DEXA)] and serum estradiol
(E2) was evaluated in premenopausal (n 5 92) and postmenopausal
(n 5 118) healthy women with different body weight [three
groups according to body mass index (BMI): normal, 18.5–24.99; overweight,
25–29.99; obese, 30–39.99 kg/m2]. Plasma GHBP levels were
measured by high pressure liquid chromatography gel filtration. GH
and insulin-like growth factor I levels were determined by immunoradiometric
assay and RIA, respectively.
GHBP levels were significantly higher in premenopausal women
with BMI above 25 kg/m2 (overweight, 3.789 6 0.306 nmol/L; obese,
4.37260.431 nmol/L) than those observed in postmenopausal women
(overweight, 1.425 6 0.09 nmol/L; obese, 1.506 6 0.177 nmol/L). No
significant differences were found between normal weight premenopausal
(1.741 6 0.104 nmol/L) and postmenopausal (1.524 6 0.202
nmol/L) women. In premenopausal women GHBP levels correlated
positively with BMI (r 5 0.675; P , 0.001), fat mass (FM; r 5 0.782;
P , 0.001; by BIA; r 5 0.776; P , 0.001; by DEXA), truncal fat (TF;
r 5 0.682; P , 0.001), waist to hip circumference ratio (WHR; r 5
0.551; P , 0.001), and E2 (r 5 0.298; P , 0.05), whereas no significant
correlation was found in postmenopausal women between GHBP levels
and BMI, FM, TF, WHR, or E2. In normal weight pre- and postmenopausal
women GHBP levels did not change between the ages of
20 and 69 yr. No statistically significant correlation was found between
GHBP and age for all groups studied. Moreover, in two distinct
subgroups of pre- and postmenopausal women, aged 40–49 yr, the
direct relationship between GHBP levels and all indexes of adiposity
were only observed in premenopausal women [BMI: r 5 0.836; P ,
0.001; FM: r 5 0.745 (BIA) and r 5 0.832 (DEXA); P , 0.001; TF: r 5
0.782; P , 0.001; WHR: r 5 0.551; P , 0.05], but not in postmenopausal
women.
In conclusion, the present data indicate a strong direct correlation
between GHBP and body fat in premenopausal, but not in postmenopausal
women, whereas they failed to detect a relationship between
GHBP and age. Therefore, these results suggest that endogenous
estrogen status may be an important determinant of the changes in
GHBP levels in women with different body weights
Blood GH-binding protein levels in premenopausal and postmenopausal women: role of body weight and estrogen levels
No full textA substantial proportion of GH circulates bound to high affinity GH-binding protein (GHBP), which corresponds to the extracellular domain of the GH receptor. Current evidence indicates that nutritional status has an important role in regulating plasma GHBP levels in humans. In the present study the relationship among plasma GHBP levels, body composition [by bioelectrical impedance analysis (BIA) and dual energy x-ray absorptiometry (DEXA)] and serum estradiol (E2) was evaluated in premenopausal (n = 92) and postmenopausal (n = 118) healthy women with different body weight [three groups according to body mass index (BMI): normal, 18.5-24.99; overweight, 25-29.99; obese, 30-39.99 kg/m2]. Plasma GHBP levels were measured by high pressure liquid chromatography gel filtration. GH and insulin-like growth factor I levels were determined by immunoradiometric assay and RIA, respectively. GHBP levels were significantly higher in premenopausal women with BMI above 25 kg/m2 (overweight, 3.789 ± 0...
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