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Biomedical subjects

R Fiocchi

Publications and source records attributed to R Fiocchi.

At least 73 records · Page 4Linked to original sources
PubMedDate not supplied

Heart rate variability in the human transplanted heart: nonlinear dynamics and QT vs RR-QT alterations during exercise suggest a return of neurocardiac regulation in long-term recovery.

RATIONALE: Functional reinnervation of the transplanted human heart by the autonomic nervous system has not been demonstrated. A lack of autonomic control of the transplanted allograft is reflected by an increased resting heart rate, a sluggish heart rate response to dynamical exercise and a reduced heart rate variability. Recent evidence suggests that a measure of deterministic chaos in the heartbeat interval series (point correlation dimension, PD2i) is superior to the conventional power spectrum or other stochastic measures in detecting changes in the mechanism underlying heartbeat generation. METHODS: The PD2i is based on the presumption that the variability is determined and patterned, whereas the stochastic measures all assume that the variability is around a stationary mean and is noise. The PD2i reconstructs the degrees of freedom (number of independent variables) in the system that generates the time series examined, and does this irrespective of whether the system is stochastic or deterministic and is stationary in time. RESULTS: PD2i was determined for heartbeat intervals (RR, ECG digitized at 1200 Hz; supine posture) of 23 heart transplant recipients (HTR: 9 adults, 14 children; 0.04-7.7 years after transplantation) and 21 healthy control subjects (CTL; 13 adults, 8 children). The PD2i (+/-SD) averaged 5.4 +/- 0.7 for the CTL adults and 5.4 +/- 0.6 for the CTL children. Mean PD2i was reduced after transplantation to 1.1 +/- 0.1 in 6 HTRs recorded within 1 year after surgery; in one HTR recorded 2 weeks after surgery the mean PD2i was 3.7. Between 1 to 2 years PD2i was found increased in 2 of 3 subjects and between 2 to 8 years it was increased in 13 of 13, but not to control levels. In normal hearts the QT subinterval of each heartbeat cycle is associated with inotropy and the RR-QT remainder with chronotropy (i.e., the dyastolic interval during which RR is primarily regulated). To examine more closely the residual and returning heartbeat dynamics of the HTR subjects, these subinterval series were examined during mild exercise (40 to 90 Watts) and its recovery. In recent HTRs, resting QT and RR-QT were moderately reduced and modulated by exercise and recovery, but with an approximate 100 beat latency. In long-term (7-8 years) HTR subjects there was a rapid and larger response to exercise/recovery, but compared to normal the range was smaller and the complexity of the subinterval trajectories in time was simpler. CONCLUSIONS: Recurrence of low-dimensional deterministic dynamics after transplantation suggests recovery of neurocardiac control attributable to 1) reorganization of the viable intrinsic cardiac nervous system, 2) reinnervation by the extrinsic autonomic nervous system, or 3) both.

Adult↗
PubMedDate not supplied

Morphine inhibits gastrointestinal transit in the rat primarily by impairing propulsive activity of the small intestine.

The effect of a single dose of morphine on small intestinal transit was studied in fasted rats by feeding a charcoal test meal either by stomach tube to normal animals or through a duodenal cannula to chronically implanted rats. The percentage of small intestine traversed by charcoal in 5 min was reduced by morphine (0.7 mg/kg s.c.) given 5 min before the meal to a similar extent in normal and implanted rats. In contrast administration of atropine (0.8 mg/kg s.c.) 30 min before the meal reduced charcoal transit only in normal rats fed the test meal by stomach tube. Inhibition of gastrointestinal transit in the rat by systemically administered morphine is mainly due to impaired small intestinal propulsion and does not depend to any significant extent on a direct action on the stomach delaying gastric emptying.

Animals↗
PubMedDate not supplied

Inhibition of gastrointestinal transit by morphine and FK 33-824 in the rat and comparative narcotic antagonist properties of naloxone and its N-methyl quaternary analog.

Morphine and the enkephalin-like peptide FK 33-824 given i.p. to rats potently inhibit gastrointestinal transit of a charcoal test meal, the doses inhibiting transit by 50% being respectively about 10 and 1 microgram/kg. These intestinal effects are opiate-specific, locally elicited and presumably involve the same action site since they are reversed by the "peripherally selective" narcotic antagonist N-methyl naloxone with apparent pA2 values of 7.34 and 7.10 respectively against morphine and FK 33-824. The calculated pA2 value for naloxone/morphine with the same in vivo test procedure (8.83) and the relative ability of naloxone and N-methyl naloxone to prevent 3H-etorphine binding to rat brain membranes (IC50 43 and 541 nM), indicate different potency ratios between the two narcotic antagonists in the in vitro binding cell-free system (about 1:10) and in vivo (about 1:30), but the latter ratio agrees with published findings in the isolated guinea pig ileum.

Animals↗
PubMedDate not supplied

Alpha-adrenoceptor blockade by tibalosine: hemodynamic and humoral effects at rest and during exercise, and effect of opioid receptor antagonism.

In a randomized double-blind protocol, 12 healthy male volunteers were studied twice at rest and during exercise after pretreatment for 1 week with placebo or 150 mg daily of the new alpha 1-adrenoceptor antagonist tibalosine. Six subjects received, on both experimental days, an intravenous infusion of saline and the other six received the opioid receptor antagonist naloxone. Combined measurements taken during rest and exercise showed tibalosine, on average, to decrease mean intraarterial pressure by 4.7 mm Hg and heart rate by 3.5 beats/min. Urinary volume and sodium excretion were transiently reduced by tibalosine as compared with placebo. Opioid antagonism by naloxone stimulated the pituitary-adrenal axis, but had no effect on the influence of tibalosine, as shown by hemodynamic, respiratory, and most humoral measurements. However, on interruption of exercise, opioid antagonism counteracted the inhibition of the plasma renin-angiotensin system by tibalosine, probably through the naloxone-induced increase in epinephrine release. In conclusion tibalosine reduced blood pressure at rest and during exercise independently of opioidergic mechanisms. This hypotensive action may be accompanied by sodium and fluid retention.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Antihypertensive action and serotonin-induced platelet aggregation during long-term ketanserin treatment in hypertensive patients.

Ketanserin (3 X 40 mg daily) was administered during 6 weeks in 14 patients with mild to moderate essential hypertension using a double-blind, placebo-controlled, crossover design. Ketanserin decreased (p less than 0.01) the recumbent blood pressure from 159/104 to 153/97 mm Hg and the recumbent heart rate from 75 to 72 beats/min. Platelet aggregation induced by 5-hydroxytryptamine (5-HT), whether or not amplified by threshold doses of collagen, was not inhibited; however, it was reduced in 10 normal volunteers after a single oral dose of 40 mg ketanserin. The results suggest that long-term treatment with ketanserin reduces blood pressure; whereas 5-HT receptor inhibition could not be demonstrated when assessed by platelet aggregation.

Adult↗
PubMedDate not supplied

[Certain aspects of the relationship between the patient with a heart transplant and the donor's family].

The anonimity of cardiac transplant donors and recipients is protected by law but very often media and the press disclose information that are supposed to be strictly confidential. Aim of the survey was to explore how many cardiac transplant recipients are aware of the identity of the donors, if they had any kind of contact with the family of the donor and their overall opinion on the law that protects anonymity. All the patients who underwent a cardiac transplant in the Bergamo Hospital from 1985 to 1991 were mailed a questionnaire. 152 of 154 questionnaires were returned (two patients had died). Only a minority of subjects 44 (29%) contacted the family of the donor and 36 (86.3%) were still in touch. 50% of the subjects knew the name of the donor; 67% of patients would disclose the information of the identity of the donor only if specifically requested by both parties. The results of the survey stress the importance of the issue of the cardiac transplant patients information, both for the patient and the staff.

Heart Transplantation↗