V. de Leonardis

Comparison of immuno- and HPLC-assays for the measurement of urinary collagen cross-links.

Pyridinoline (Pyr) and deoxypyridinoline (D-Pyr) are two cross-links of collagen molecules, that are present in the extracellular matrix and released during its degradation. Pyr is present in bone and cartilage, but not in significant amounts in other connective tissues and D-Pyr appears to be specific for bone tissue. Therefore, the urinary excretion of Pyr and D-Pyr might be a sensitive marker of bone matrix degradation. For the determination of urinary Pyr and D-Pyr two methods are available: a chromatographic method (HPLC) by which it is possible to measure separately Pyr and D-Pyr, and a new immunoassay which measures total free and low molecular weight pyridinoline released in the urine. We compared the results obtained by HPLC analysis of 205 urinary samples from normal subjects and patients affected by various bone disorders with those obtained by the immunoassay. The overall correlation coefficient between the results obtained by the two methods was 0.34. When calculated in a range of pyridinoline concentrations from 0 to 30, 30 to 60, and over 60 pmol/μmol creatinine the correlation coefficient was respectively − 0.094, 0.38, and 0.12. The two methods yielded variable profiles in the detection of circadian rhythms and these differences did not segregate with normal or pathological conditions. We conclude that the immunoassay proposed for the determination of urinary collagen cross-links is not immediately applicable to clinical use. The improvement of the antibody specificity will probably contribute to replace the HPLC method with the immunoassay.

Response of Some Haemocoagulatory and Haemorheological Variables to Maximal Exercise in Sedentary and Active Subjects

The purpose of this study was to evaluate how physical conditioning is associated with haemostatic and rheological responses to strenuous exercise. A total of 25 males, divided into two groups differing in exercise fitness (14 sedentary and 11 active), underwent exercise testing on a bicycle ergometer with an initial 25 W workload increasing by the same amount every 3 min. The following variables were evaluated before and after the test: platelet count and aggregability, plasma fibrinogen, fibrinolytic degradation products, viscometry and micro-haematocrit. Significant differences in baseline values between the two groups were found only for blood viscosity. Irrespective of the group, significantly increased values were demonstrated for all the variables, except platelet aggregability and fibrinogen levels, in response to strenuous exercise. It is concluded that the possible protective effect of exercise against cardiovascular disease does not seem to be related to changes in the haemorheological and haemostatic measures evaluated.

Urinary excretion of pyridinoline and deoxypyridinoline: Circadian rhythm in healthy premenopausal women

Abstract Urinary cross‐linking amino acids (pyridinoline and deoxypyridinoline) are used as biochemical markers of bone resorption. Therefore, the study of their diurnal behavior might provide information on whether circadian variability could be observed in bone remodelling. We showed a significant circadian rhythm of both urinary pyridinoline and deoxypyridinoline in healthy premenopausal females with higher concentrations at 05.35 and 0457, respectively. The reported observations suggest an increased rate of bone resorption during the night in subjects living on a usual day‐night schedule. Moreover, these findings focus the attention on the importance of the sampling time for the comparison of data from different studies and from patients with different pathological conditions.

Effect of aging on heart rate: a chronobiological study

Abstract A group of 39 males divided into three groups according to age and with no clinical or instrumental signs of cardiovascular disease was studied by continuous 24‐h electrocardiogram recording. All the subjects were under the same sleep‐wakefulness cycle and meals schedule. Single cosinor analysis demonstrated significant circadian rhythms in heart rate for all the subjects. Multiple regression analysis revealed the existence of a significant inverse relationship between age and mesor and amplitude of the rhythm. Analysis of variance and extended Tukey test demonstrated significantly different mesors and amplitudes among the three different groups of ages. We conclude that aging is characterized by a progressive decrease in mesor and amplitude of the circadian rhythm in heart rate.