Biomedical subjects

R Tarquini

Publications and source records attributed to R Tarquini.

39 records · Page 3Linked to original sources

PubMedDate not supplied

Chronome assessment of circulating melatonin in humans.

BACKGROUND: Melatonin (MEL) production occurs mainly during the dark span. A prominent circadian variation is demonstrated in both blood and urine in humans. MATERIALS AND METHODS: The circadian, circannual, age and gender patterns of MEL were concomitantly investigated in 40 men and 132 women, each providing blood samples every 4 hours for 24 hours for conventional and cosinor analysis. RESULTS: Circulating MEL is circadian periodic (P < 0.001), peaking at night. The MESOR (rhythm-adjusted mean) is higher in women than in men. The circadian amplitude decreases with age. Both are modulated by a circannual variation, the MESOR peaking in winter (P < 0.001) and the circadian amplitude in summer (P < 0.05). CONCLUSIONS: Samples, unqualified as to gender, age and/or season, incompletely characterize the circadian MEL patterns. This chronome approach detects changes that may escape detection otherwise, checking whether a value is too high or too low, and also whether "swinging" occurs to the right extent.

Adult↗

PubMedDate not supplied

Age-related changes of neuro-endocrine-immune interactions in healthy humans.

Numerous interactions exist among the nervous, endocrine and immune systems, mediated by neurotransmitters, hormones and cytokines. The function of these systems shows patterns of circadian rhythmicity and a number of age-related changes in the 24-hour hormonal and nonhormonal rhythms have been found in older human beings. The aim of this study was to evaluate the presence of altered integration among the nervous, endocrine and immune systems in older adults. Cortisol, melatonin, thyrotropin-releasing hormone (TRH), thyroid-stimulatinghormone (TSH), free thyroxine (FT4), growth hormone (GH), insulin-like growth factor I (IGF-I) and interleukin 2 (IL-2) serum levels were measured and lymphocyte subpopulation analyses were performed on blood samples collected every four hours for 24 hours from seven healthy young subjects aged 36-58 years (mean age +/- s.e. 45.28 +/- 3.31) and from seven healthy old subjects aged 65-78 years (mean age +/- s.e. 68.57 +/- 1.91). There was a statistically significant difference between the groups in the observed values of CD20 (total B cells, higher in the young subjects, t = 2.48, P = 0.028) and CD25 (activated T cells with expression of the alpha chain of IL-2 receptor, higher in elderly subjects, t = -2.23, P = 0.045); DR+ T cells were also higher in elderly subjects, T=34.0, P=0.01). There was no statistically significant difference in the observed values of CD2(total T lymphocytes), CD4 (helper/inducer T cells), CD8 (suppressor/cytotoxic T cells), CD4/CD8 ratio, CD16 (natural killer cells), HLA-DR (B cells and activated T cells), TcR delta 1 (epitope of the constant domain of delta chain of T-cell receptor 1), cortisol, melatonin, TRH, TSH, FT4" GH, IGF-I, IL-2. In the group of younger subjects a clear circadian rhythm was validated for the time-qualified changes of all the factors studied, with the exception of CD16, FT4 and IL-2. In the group of elderly subjects a clear circadian rhythm was validated for the nyctohemeral changes of CD2 (with a phase delay of three hours), CD8, CD4/CD8 ratio, CD16, CD25 (in opposite phase), cortisol (with a phase delay of one hour), melatonin, TSH (with a phase delay of one hour) and GH (with a phase advance of one hour). The results of the current study show that aging is associated with enhanced responsiveness of the T cell compartment and alterations in temporal architecture of neuro-endocrine-immune system.

Adult↗

PubMedDate not supplied

[Melatonin and seasonal depression].

Melatonin (MEL) hypothesis in seasonal affective disorders (SAD) is supported by: a) historical hint; b) circadian and seasonal MEL periodicity with evidence that the SAD is related to photoperiod; c) relationship between incidence and severity of SAD and latitude; d) the response to bright artificial light (ineffective in depression) which mimics summer time; e) MEL administration can induce some symptoms of the SAD; f) several antidepressant drugs increase MEL plasma levels. Several of these findings are disproved: the light acts independently from the MEL, some antidepressant agents act without modifying MEL levels; a consistent alteration in MEL secretion within SAD has not been convincingly demonstrated. Relationship between incidence and severity of SAD and latitude suggests a new potential implication of MEL in SAD. The daytime melatonin values reflect changes along the scale of a year in sunshine. Accordingly, the about-yearly periodicity, much larger in amplitude than the half-yearly component, yields ratios smaller than unity. By contrast during darkness an about-half-yearly component is more prominent. As the aurora zone is approached, the intensity of magnetic disturbances increases. Thus, the intensity of these two variables shows inverse relationships with latitude and geomagnetic field decreases plasma levels of MEL and inhibits MEL function.

Circadian Rhythm↗