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Biomedical subjects

C Letizia

Publications and source records attributed to C Letizia.

At least 127 records · Page 7Linked to original sources
PubMed1987

The gerontological decline of the renin-aldosterone system: a chronobiological approach extended to essential hypertension.

The circadian (about 24-hr) oscillating function of the renin-angiotensin-aldosterone system (RAAS) was investigated as a function of age in clinically healthy participants and in essential hypertensive patients. A peculiar age-related decline in the RAAS circadian mesor (rhythm-adjusted mean) and amplitude (variability from mesor) was found in the essential hypertensive patients. This finding suggests a nonphysiologic evolution in the tonic (24-hr mean level) as well as phasic (oscillating amplitude) circadian activity of the RAAS with increasing age. A relative hyperreninemic aldosteronism characterized the aged essential hypertensive patients.

Adolescent↗
PubMed1987

Discrimination and spectral resolution of ultradian and circadian periodicities for 24-hour blood pressure patterns on sodium manipulation in normotensive humans.

The effects of a severe (10-20 mEq/24-h) but short-term (7-days) restriction in dietary sodium on 24-h blood pressure (BP) patterns were investigated in 20 normotensive volunteers (10 men, 10 women; 20-25 years old) by means of non-invasive automatic sphygmomanometric monitoring (recordings at 1-h interval) at home, with subjects in bedrest. Statistical methods used include bivariate Gaussian distribution analysis for systolic and diastolic BP bivariate discriminant analysis, periodic regression analysis with a 24-h period (cosinor method) and spectral analysis of time series. Casual BP measurements were unable to detect the tensinogenic effects, while the bivariate Gaussian analysis documented a total rearrangement in the pattern distribution to show discriminated values of BP after sodium restriction. A significant decrease (p less than 0.01) in the 24-h mean level (mesor) for systolic BP was observed. An increase in the extent of fluctuation (amplitude) for the circadian components was documented by the spectral analysis, mainly in diastolic BP patterns. Such a phenomenon of 'amplitude magnification' was not accompanied by a change in the repartition of the ultradian and circadian harmonic components. The extensive changes in the time structure support the hypothesis of an interaction of sodium regimen with the centrally-located oscillators which physiologically organize the circadian rhythmicity of BP.

Adult↗
PubMed1987

Effects of a mild and prolonged restriction in sodium or food intake on the circadian rhythm of aldosterone and related variables.

The effect of a mild reduction in dietary sodium intake (-30 mEq/24 hr) and body weight (-2 kg/2 months) on circadian rhythms of urinary aldosterone (UA), sodium (UNa), potassium (UK), creatinine (UC) and volume (UV) have been investigated in nine clinically healthy subjects. The mild reduction in dietary sodium is associated with: (1) a decrease in the 24-hr excretion rate of UNa, UK and UV, and an increased mesor of UA and UC; (2) a lowered extent of the circadian variation for UNa, UK, UV and a greater amplitude for UA and UC (3) a later crest in the temporal phase for UK, UA, UC, an earlier phasic wave for UNa. The mild reduction in calorie intake resulting in a body weight loss is associated with a more pronounced decrease in the 24-hr excretion rate of UNa and UK, and in the extent of circadian fluctuation for UNa. Peculiar events are: (1) the decreased 24-hr excretion rate for UA, and the increased mesor for UV; (2) the extent variability increased for UV, decreased for UC. Such effect may have a practical resonance for heuristic physiology since the role of dietary sodium and food intake has been better clarified. Dietary sodium and food can be regarded as 'chronomodulatory agents' for the adrenal cortex since their adrenotropic influence is extended to the tonic as well as phasic secretion of aldosterone.

Adult↗
PubMed1987

Internal desynchronization between circadian rhythms of plasma aldosterone and erythrocyte membrane-bound Na/K-ATPase.

Normal-renin essential mesor hypertensives are characterized by a consistent increase in erythrocyte membrane-bound Na/K-ATPase activity. Low-renin essential hypertensives exhibit, in contrast, a lower activity in Na/K-ATPase of cell membranes. This study documents a third disorder characterized by a temporal shift in the rhythmic activity of the erythrocyte membrane-bound Na/K-ATPase in normal-renin hypertensives. The disorder causes the synchronism with the aldosterone circadian rhythm to be invariably lost. The uncoupling phenomenon could be invoked to explain the inversion in the day-night sodium excretion rate found in essential hypertensives. In addition, it suggests that the circadian rhythm in Na/K-ATPase is under the control of cycling factors other than aldosterone.

Adolescent↗
PubMed1987

Occurrence of a circadian rhythmicity for blood pressure in patients with circulatory shock.

Ten patients hemodynamically in shock were monitored for blood pressure along the 24-hr span while under antishock therapy. Time-qualified data were analyzed by means of the cosinor procedure. The fit of a 24-hr cosine function was able to reject the null hypothesis of amplitude = O in the majority of patients under intensive care. The blood pressure circadian rhythm was found to be independent of whether the patient was responsive or refractory to therapy. This phenomenon demonstrates that the maintenance of a blood pressure circadian rhythm is a characteristic intrinsic to hemodynamic shock even if blood pressure falls to very low values along the time scale.

Adult↗
PubMed1987

Postural effects on the circadian rhythm of blood pressure and heart rate in young and elderly subjects.

This investigation compares the effects of changes in activity-rest patterns on the 24-hr rhythms of blood pressure and heart rate in elderly and young subjects. Blood pressure and heart rate were monitored by means of noninvasive, automatic, quasiportable recording equipment. The subjects either rested both diurnally and nocturnally or were active diurnally and rested nocturnally. Time-qualified data were analyzed for circadian rhythmicity by means of the cosinor procedure. In both activity-rest patterns, elderly subjects showed a dissociation between circadian rhythms of blood pressure and heart rate due to a peculiar shift of acrophases. Because of the particular timing of the acrophase, elderly subjects differed from young individuals in the overall adaptation of the blood pressure and heart rate 24-hr patterns to upright posture and physical activity. Of particular interest is the reduced amplitude in the circadian rhythm of blood pressure, which might contribute to the compromised orthostatic tolerance of older people.

Adolescent↗
PubMed1986

[Disorders of renin secretion in arterial hypertension].

The present work is devoted to investigate the meaning of disorders in renin secretion in primary and secondary hypertension and report the results of bayesan analysis applied to a group of 125 hypertensives who underwent selective renal angiography and polydistrictual renal vein samplings for the determination of plasma renin activity for diagnostic and therapeutic purposes. Data obtained from statistical analysis allow specifications on the prevalence of disorders, rates of false positives and false negatives, predictive value, diagnostic value, sensitivity and specificity. The weighted data are useful to validate the reliability of the renin renal vein measurements which are used in clinical practice for identifying the potentially surgically curable forms of arterial hypertension.

Adolescent↗
PubMed1985

May a lymphocytic infiltration have a pathogenic role in an aldosterone-producing adrenal tumor?

A 38-year-old woman is described to have a primary hyperaldosteronism due to an aldosteronoma with foci of lymphocytic infiltration. The finding suggests: a concomitant lymphoid adrenalitis; or, an immunological attack to neoplastic cells. The hypothesis is that there may be a relationship in the association. The lymphocytic infiltrates could have a pathogenic role in the development of the aldosterone-producing adrenocortical neoplasm by interrupting some inhibitory mechanism(s) of the cells that secrete aldosterone.

Adrenal Cortex Neoplasms↗
PubMed1985

Temporal correlation of some endocrine circadian rhythms in elderly subjects.

The aim of this chronobiological study was to investigate temporal correlations in the circadian patterns of 6 hormones, namely somatotrophic hormone (STH), prolactin (PRL), cortisol (F), aldosterone (ALD), insulin (IRI) and C-peptide (CP), assayed in systemic blood serum drawn at 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00 h from an antecubital vein in 19 young subjects (aged 20-29 yr, comprising 10 males and 9 females; and 20 elderly subjects (aged 70-81 yr, comprising 10 males and 10 females). All subjects were sampled on a normal dietary sodium intake (120-140 mEq/24h) while following a social routine of diurnal activity (07:00-23:00) and nocturnal rest (23:00-07:00). Time-qualified data were analyzed by lead-lag correlation and by cosinor analysis. According to the lead-lag correlation findings, it would appear that the correlation which exists between several time-qualified series in young subjects is no longer present in elderly subjects. The circadian rhythms which were found to have lost their temporal correlations with advancing age were those between STH and IRI, STH and ALD, PRL and IRI, PRL and CP, and ALD and CP. It should be noted that the correlation between hormonal rhythms breaks down mainly on account of a peculiar age-related change in the magnitude of the circadian fluctuation. This chronological decline in amplitude led to the conclusion that the senescence of endocrine rhythmic functions is a biological phenomenon characterized by altered circadian variability.

Adult↗
PubMed1985

Circadian rhythms of plasma renin activity and aldosterone: changes related to age, sex, recumbency and sodium restriction. Chronobiologic specification for reference values.

Plasma renin activity (PRA) and aldosterone (PA) levels are characterized by a circadian rhythmicity (CR). The present study revealed that this rhythmicity is influenced by several factors including posture, sodium intake and age. Time-qualified PRA and PA reference intervals can reduce the incidence of false positives and false negatives in a diagnostic work-up. The circadian rhythmicity of PRA and PA have been quantified in relation to posture, sodium intake and age. The cosinor procedure has been applied to quantify the properties of the circadian rhythmicity under these conditions. Chronograms and circadian parameters can be used to optimize the use of PRA and PA measurements in clinical practice. The chronobiological specification of reference values for PRA and PA is of valuable importance since the assessment of PRA and PA circadian rhythmicity has a diagnostic interest for a certain type of clinical disorder. It should be noted that several studies have described circannual variations for renin and aldosterone. The next step in the optimation of laboratory time-qualified reference values is the assessment of changes induced by the deterministic factors on a circannual domain.

Adult↗
PubMed1985

Study of the diurnal variation of human lymphocyte subsets.

The diurnal variation of peripheral white cells and in particular of different lymphocyte subsets has been investigated in 11 normal subjects. Monoclonal antibodies (Mab) phenotyping total T lymphocytes (UCHT1), cytotoxic/suppressor (UCHT4), helper T cells (Leu 3a), B lymphocytes (231) and K/NK cells (H25) have been used. In addition to the traditional parametric statistics, the chronobiological approach of cosinor was adopted in order to inferentially obtain the waveform covering the 24-hr period. Cosinor analysis validated the existence of a significant rhythm for leucocytes (p = 0.04, lymphocytes (p = 0.03), and Leu 3a positive cells (p = 0.04). The best fitting period was equal to 28 hr. No circadian rhythm was documented for lymphocyte subsets positive for Mab UCHT4, 231, H25, by testing the variability with a frequency ranging from 1 cycle every 12hr to 1 cycle every 28 hr. By the non-inferential analysis of temporal curves, a significant peak of Leu 3a positive cells at 20.00 hr (p less than 0.001) was observed. The acrophase has been recorded by cosinor analysis at 20.36 hr. We conclude that the circadian variability of Leu 3a positive cell profile must be taken into account when the helper/suppressor ratio is calculated. The time-dependence of this lymphocyte subpopulation suggests that when therapy with corticosteroids is considered in autoimmunity, it should be planned by keeping the peak of Leu 3a positive cells as a marker time.

Adult↗
PubMed1984

[Clinical significance of anomalies of renin secretion in arterial hypertension].

Aim of the present investigation is to define the clinical meaning of disorders in renin secretion in the field of vascular hypertensive diseases. In view of this scope, we report the results of a retrospective study on the levels of plasma renin activity assayed in renal veins, aorta and peripheral vein of 124 hypertensive, angiographically studied for a diagnostic work-up. The behavior of renal vein renin has been related to epidemiologic, clinical and etiopathogenetic factors. Results indicate that disorders in renin secretion occur in every type of arterial hypertension. However, some disorders are prevalent in a determined type of hypertensive disease. The incidence of disorders in renin secretion is different in relation to sex, age and duration of hypertension. Hypersecretion is prevalent in men and young hypertensives, while hyposecretion of renin is more frequent in the oldest hypertensive patients. Vascular damage is prevalent in men and young hypertensives, while hyposecretion of renin is more frequent in the oldest hypertensive patients. Vascular damage is prevalent in renin hyposecretive hypertensives. Hypersecretion and lateralization in renin release can be mainly encountered in the renovascular type of hypertension and, less frequently, in unilateral nephroparenchymal hypertension. However, totally lateralized hypersecretion can be detected even in essential hypertensive patients suggesting the possibility of false positives for the diagnosis of renovascular hypertension.

Adult↗