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Biomedical subjects

R Nicoletti

Publications and source records attributed to R Nicoletti.

At least 73 records · Page 4Linked to original sources
PubMed1986

Peptide sequencing by using a combination of partial acid hydrolysis and fast-atom-bombardment mass spectrometry.

To overcome the limit of the intensity of ions carrying sequence information in structural determinations of peptides by fast-atom-bombardment m.s., we have developed a method that consists in taking spectra of the peptide acid hydrolysates at different hydrolysis times. Peaks correspond to the oligomers arising from the peptide partial hydrolysis. The sequence can then be identified from the structurally overlapping fragments.

Amino Acid Sequence↗
PubMed1985

[Measurement of inner ear circulation using radioactive indicators].

To clarify the possibility of measuring the inner ear blood flow by radionuclide imaging, we used a skull phantom and a scintillation camera and found that a concentration difference of at least 100: 1 between the inner ear and the background is needed for external detection. Similar concentration differences can be found in aminoglycosid antibiotics because of their special pharmacokinetic characteristics. We believe, therefore, that with an appropriate radioactive indicator, such as labelled aminoglycoside or labelled (99mTc, 123J)-inulin, it would be possible to measure the inner ear blood flow in a non-invasive and selective way.

Ear, Inner↗
PubMed1984

Right hemisphere interference during negative affect: a reaction time study.

Two experiments are described in which simple reaction times (RTs) to lateralized visual stimuli were measured in normal subjects during negative affect and during recollection of everyday life scenes. In both experiments the mental activity produced a remarkable increase of RTs with respect to a control situation without interfering activity. During production of the negative affect there was a selective lengthening of RTs mediated by the right hemisphere. The role of the right hemisphere in producing emotions is discussed.

Adult↗
PubMed1983

[Spatial compatibility and position of the effectors].

Mean reaction times obtained with crossed hands (right had on the left and left hand on the right) are slower than reaction times obtained with uncrossed hands (right hand on the right and left hand on the left). These results have been explained as a compatibility effect between the responding hand and its spatial position. The goal of the present experiment was to establish whether the position of the hand is encoded by the subjects relative to their body (absolute position) or relative to the other hand (relative position). The subjects performed a discrimination task on two visual stimuli. Stimuli and hands were either on the same side of the body (both on the left or both on the right) or had different absolute position. In all conditions the subjects responded with crossed and uncrossed hands. The results support the hypothesis that relative position is encoded.

Functional Laterality↗
PubMed1983

[Simon effect and relative position of the stimuli].

The so-called Simon effect can be determined (a) by a natural tendency to respond towards the source of stimulation, or (b) by a comparison between the encoding of the position of the stimulus and the encoding of the position of the effectors producing the response. Twelve subjects performed a manual choice between two visual stimuli in the same visual hemifield. The results of the experiment supported hypothesis (b).

Humans↗
PubMed1983

Effect of calcium antagonists on cardiac performance in patients with dilatative cardiomyopathy evaluated by noninvasive methods.

We present 14 patients with dilatative cardiomyopathy, proven by hemodynamic and angiographic assessment who received in a single-blind, randomized study, equipotent doses of the three calcium blockers: verapamil (0.1 mg/kg i.v., followed by an infusion of 0.01 mg/kg/min), nifedipin (20 mg sublingually), or diltiazem (0.2 mg/kg i.v., followed by infusion of 0.02 mg/kg/min). Before and after treatment in 8 patients systolic time intervals were recorded with an AVL-Myocard-Check (Q-S2, pre-ejection period, left ventricular ejection time, and pre-ejection period/left ventricular ejection time) and end-systolic and end-diastolic diameter, fractional shortening, and circumferential fiber shortening velocity were measured by M-mode echocardiography. In another 6 patients radionuclide ventriculography was performed before and after each treatment (ejection fraction, cardiac index). PEP/LVET increased slightly after verapamil (+ 15%) and decreased after nifedipin (-5%) and diltiazem (-3%), the changes being not significant. Fractional shortening and circumferential fiber shortening velocity however, decreased after verapamil (-5%, resp. -15%) and increased after nifedipin (+ 14%, resp. + 25%) and after diltiazem (+ 23%, resp. + 16%). In the radionuclide studies ejection fraction increased after verapamil (+ 9%), nifedipin (+ 14%), and diltiazem (+ 13%), while cardiac index remained unchanged with verapamil and nifedipin and increased with diltiazem (+ 14%). In conclusion there are no significant changes in myocardial performance with the calcium blockers verapamil, nifedipin, and diltiazem. However, under verapamil there is a tendency to deterioration of myocardial performance, while it was slightly improved after nifedipin and diltiazem. Calcium antagonists may be used safely, therefore, also in patients with impaired myocardial performance.

Adult↗
PubMed1982

Osteoscintimetry--a method of semiquantitative evaluation of skeletal scintigrams by use of profiles and a macro function for computer processing.

A computer macro-program was developed for standardized, semiquantitative measurement of radiotracer uptake. The method uses profiles of selectable length, width, and inclination according to the anatomical structures of the pathological and the corresponding healthy region. The ratio of the two curves is calculated automatically and shown as an 'uptake curve'. The essential use of osteoscintimetry is in the follow-up examination if small changes of regional uptake have to be identified. The profile-technique rather than the ROI-technique was selected, because the main benefit of the profile-technique is that the results of follow-up examinations are comparable to previous examinations with a standard deviation of +/-5%.

Adolescent↗
PubMed1982

Spatial compatibility effects on the same side of the body midline.

Stimulus-response compatibility effects have been hypothesized to result (a) from a subject's innate tendency to respond in the direction of the source of stimulation, (b) from a correspondence between the spatial codes associated with the effector and the stimulus, or (c) from an attentional bias favoring the effector located in the same hemispace as the command signal. Two experiments were conducted to test these three hypotheses. In Experiment 1 the subjects were requested to make unimanual discriminative key-pressing responses to two light stimuli, both appearing to either the right or left of the fixation point. In one condition the two hands were in anatomical position (uncrossed); in the other they were crossed. The procedure of Experiment 2 was similar to that of Experiment 1 with the exception that both hands, always in an uncrossed position, were placed on the same side of the body midline (on the right or left). The results showed that the compatibility effect depends on a correspondence between the spatial codes associated with the location of the effector and the location of the command stimulus.

Adult↗
PubMed1982

[A computer macro-programme for osteoscintimetry and activity profile in Perthe's disease (author's transl)].

A computer macro-programme has been developed which permits quantitative scintigraphy by means of an activity profile. The slope and width of the profile are variable; a view at right angles to the epiphyseal plate of the femoral head is able to determine activity in the plate and in the epiphysis. Measurements of the abnormal and normal hip produce uptake rates. These indicate to what extent the abnormal femoral head and epiphyseal plate differ from the normal side, with respect to their uptake. The method and results are discussed.

Child↗
PubMed1981

Evaluation of blood toxicity in chronic uremia by an improved chromatographic method.

Biogel P2 gel chromatography of ultrafiltrate from chronic uremic patients leads to better resolution of the compounds present than so far reported in the literature. Reproducibility is good. Toxicity, evaluated by cell cultures, was detected in only one chromatographic fraction. Further purification of this fraction with HPLC on a RP18 column revealed two toxic fractions, to the better defined of which a polyol structure was ascribed.

Animals↗
PubMed1980

[Spatial stimulus-response compatibility: presentation of stimuli within one visual hemifield].

Choice reaction times of two lateralized unstructured visual stimuli located within the same (right or left) visual hemifield were studied in subjects with hands crossed and uncrossed. The subjects were instructed to respond with their right or left hand depending on the position of the stimulus. In one experimental condition they have to use their right hand for responding to the right light and their left hand for responding to the left light. In another experimental condition the reverse arrangement was used. The two light stimuli were presented, one at a time and 3 degrees apart, in both visual fields. Thus, the analyzed factors were: hand position (crossed or uncrossed), responding hand (right or left), field of presentation (right or left), and relative position of the light stimulus (right or left). The main finding of the present study was that spatial compatibility effects were present even when both stimuli were presented within the same visual field. That means that the factor determining which hand is faster in responding is the relative position of the two stimuli and of the two hands and not the position of the stimuli with reference to the vertical meridian.

Functional Laterality↗