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Biomedical subjects

R Nicoletti

Publications and source records attributed to R Nicoletti.

At least 37 records · Page 2Linked to original sources
PubMed1997

Antiviral activity of natural and semisynthetic polysaccharides on the early steps of rubella virus infection.

The natural and semisynthetic carbohydrates scleroglucan, locust bean gum, tamarind gum (glyloid) and its three sulphate derivatives (GP4311, GP4327 and GP4324), glycogen and its two sulphate derivatives (GP4427 and GP4435), alginic acid and dextran sulphate, were investigated for their inhibitory effect on rubella virus (RV) infection of Vero cells. The neutral polymer scleroglucan and two highly negatively charged compounds, glyloid sulphate 4324 and dextran sulphate, had the highest inhibitory effect on RV antigen synthesis. The antiviral properties of active molecules appears to be dependent on the shape of the macromolecule and/or on the electric charge, while saccharide units play a minor role. The results indicated that polysaccharides blocked a step in virus replication subsequent to virus attachment, such as internalization and/or uncoating. Confirmation that the inhibitory activity of the compounds was directed at the early steps of RV multiplication, was that none of the polysaccharides had any effect on infection initiated by transfection of cells with RVRNA.

Animals↗
PubMed1996

Parathyroid scintigraphy: comparison of technetium-99m methoxyisobutylisonitrile and technetium-99m tetrofosmin studies.

We report the preliminary results of a prospective study demonstrating tetrofosmin uptake in surgically and histologically proven parathyroid adenomas. In ten patients with primary chronic hyperparathyroidism, parathyroid imaging was performed using (1) technetium-99m methoxyisobutylisonitrile (MIBI) and (2) 99mTc-1, 2-bis(bis(2-ethoxyethyl)phosphino)ethane (tetrofosmin) within a time interval of 3-5 days. Both tracers correctly identified the parathyroid adenomas by focal prolonged tracer retention. On visual inspection image contrast was generally higher with MIBI than with tetrofosmin in all the patients studied. Tetrofosmin showed a slower elimination from the parathyroid adenomas than MIBI in six of the ten cases. Our preliminary results show that tetrofosmin, like MIBI, as a feasible, sensitive tracer for parathyroid scintigraphy. For routine use, the rapid kit preparation without heating and the lower radiation dose to the patient make tetrofosmin an alternative tracer for parathyroid scintigraphy. Further evaluation is needed to determine which of the two tracers is the more sensitive for the detection of parathyroid adenomas, and which tracer properties better reflect the degree of endocrine activity.

Adenoma↗
PubMed1996

Antiviral effect of a polysaccharide from Sclerotium glucanicum towards herpes simplex virus type 1 infection.

Among different neutral polysaccharides from natural sources, scleroglucan from Sclerotium glucanicum significantly inhibits the replication of herpes simplex virus type 1 on Vero cells. Scleroglucan belongs to a class of exopolymers, expressed by members of genus Sclerotium and consists of a linear beta-1,3-linked glucopyranose with side chains of single glucopyranose residues linked through beta-1,6 glycosidic bonds. The effective antiviral concentration of this polysaccharide is far from the cytotoxicity threshold and consequently this natural product possesses a good selectivity index. Results obtained in experiments carried out in order to clarify the mechanism of action of this carbohydrate indicate that the block of infection occurs during the very early phases of the viral mutliplication cycle since the highest inhibitory effect took place when it was added during the attachment step. The antiviral effect of scleroglucan seems to be related to its binding with membrane glycoproteins of HSV-1 particles which impedes the complex interactions of the virus with the cell plasma membrane.

Animals↗
PubMed1996

Semi-quantitative scintigraphic follow-up studies of cerebral arteriovenous malformations after radiosurgical treatment.

An evaluation of semi-quantitative 99Tcm-red blood cell scintigraphy (RBCS) was undertaken in patients with cerebral arteriovenous malformations (AVM) during follow-up after radiosurgical treatment. Twenty-seven patients were studied with an initial dynamic imaging sequence of 32 frames each lasting 2 s, planar images in four projections beginning 15 min post-injection and single photon emission tomography immediately following the planar imaging. A 2 ml cubital vein blood sample was imaged to obtain an extracorporeal equivalent of the intravascular activity. The counts within the AVM on a planar image were divided by the counts obtained from the image of the blood sample (corrected for the same acquisition time and radioactive decay). This value yielded the 'volume index' (VI), which was proportional to the volume of the AVM. The VI obtained from the first RBCS served as the initial reference value and was set at 100%. The VIs obtained from the follow-up investigations of the same patient in the same projection were expressed as the percentage of the initial VI. We found RBCS identified the AVM in all patients. The VIs obtained from the follow-up studies demonstrated a decrease in blood volume at different time intervals after radiosurgical treatment. RBCS provides a sensitive, relatively non-invasive, semi-quantitative method for measuring the relative volume and follow-up of the degree of obliteration of AVMs after radiosurgical treatment.

Cerebral Arteries↗
PubMed1996

Dynamic and static scintigraphic evaluation of cerebral arteriovenous malformations to evaluate radiosurgical treatment.

The radiobiologic changes induced by cobalt-60 gamma irradiation in cerebral arteriovenous malformations (AVMs) is a torpid process. Complete obliteration may take 1 or 2 years or even longer. Neuroradiological modalities like magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) do not provide sufficient information to comprehend this process. Digital subtraction angiography represents an invasive method and is therefore most often performed when complete obliteration is expected. The purpose of this study was to investigate the value of blood pool scintigraphy and functional imaging, such as single photon emission computed tomography (SPECT), to gain more knowledge about the volumetric changes of AVMs treated by radiosurgery. Twenty consecutive candidates for Gamma Knife treatment were selected for comparative MRI/ MRA and scintigraphic studies. All lesions ranging from 0.6 to 18.6 cm3 could be identified on blood pool and SPECT images. Seven patients had repetitive examinations at 3-month intervals to compare the relative volumetric change of the lesion. In 5 cases, a marked decrease in blood pooling was noticed after 3 months, and in 2 patients no significant change was evident. In contrast, MRI/MRA scans done at the same time did not similarly indicate progressive obliteration changes. This preliminary result indicates that scintigraphic evaluation using the blood pool technique is a very sensitive method to describe the relative volumetric change of radiosurgically treated AVMs.

Adolescent↗
PubMed1995

Inhibition of herpes simplex virus infection by negatively charged and neutral carbohydrate polymers.

Different natural and semisynthetic polysaccharides were evaluated for their inhibitory effect on in vitro replication of herpes simplex virus (HSV) types 1 and 2. Some neutral and negatively charged carbohydrates were able to inhibit viral infection by interfering mainly with the adsorption process showing a dose-dependent relationship. Their effect was shown within the concentration range of 200-0.8 micrograms/ml, and the inhibiting compounds were in order of action: dextran sulfate = scleroglucan = lambda carrageenan > glyloid sulfate 4324 > locust beam gum towards HSV-1 and dextran sulfate = glyloid sulfate 4324 = lambda carrageenan > scleroglucan > glycogen sulfate 4435 towards HSV-2. The data obtained indicate that the antiviral activity of polysaccharides was not only related to their electric charge. Other characteristics of the molecules such as the polymeric backbone, the carbohydrate moieties and the degree of polymerization could play a role in influencing their antiviral properties.

Animals↗
PubMed1995

SPET quality control: a comprehensive test procedure for evaluating the rotation system parameters COR-offset, y-shift and detector tilt.

This paper describes a method for SPET quality control that facilitates the determination of COR-offset, parallel y-shift and detector tilt by means of a single, comprehensive test using a special phantom consisting of three point sources. The evaluation of the method was performed by a series of measurements utilizing manually adjusted detector tilts and a simulation of y-shift by moving the phantom. The results show that y-shift and detector tilt are measured with reasonable accuracy, and that y-shift caused by variations in detector tilt can be differentiated from y-shift caused by other factors.

Evaluation Studies as Topic↗
PubMed1995

[A new concept in imaging pelvic recurrence of curatively operated rectal carcinoma--image fusion of nuclear magnetic resonance tomography and anti-CEA immunoscintigraphy (SPECT): technique and clinical example].

We present a new technique of image fusion (IF) of magnetic resonance imaging (MRT) and anti-CEA-immunoscintigraphy (Behring 431/26) and single photon emission computed tomography (SPECT). We performed SPECT and MRT within 8 hours on the same day. Glucagon intravenously was used to reduce artefacts due to intestinal motility. Before image fusion we analysed the SPECT and MRT images independently of each other. The MRT and SPECT were connected by a local area network (LAN) to a Gateway computer, which is also used as a picture archive. There a program automatically starts, translates the MRT data from the ACR/NEMA format to the Elscint one and these data are sent for image fusion to the nuclear medicine computer Elscint SP1. By means of a clinical example we present anatomic concordant superimposition and explain the findings and the clinical value of our technique. This system and technique are equally applicable to other digital imaging investigations. By IF, on the basis of the certain evidence of the tracer depot of a pathological lesion diagnosed by MRT and the reliability of the anatomical assignment of a focal lesion diagnosed by SPECT, early detection of local recurrence after surgical treatment of rectal cancer, the correct localisation of recurrent disease and its distinction from non-malignant tissue becomes possible. This enables planning of further therapeutical strategies.

Adenocarcinoma↗
PubMed1994

Left-right asymmetry of callosal transfer in normal human subjects.

Interhemispheric transfer (IT) of visuomotor information can be assessed by measuring the crossed-uncrossed difference (CUD) in the Poffenberger paradigm [14]. We report a series of experiments aimed at casting light on two aspects of IT: the importance of motor response variables and the nature of the left-right asymmetries found in a recent meta-analysis of studies using the Poffenberger paradigm [10]. In Experiments 1 and 2 we found no effect of varying the finger used for response while there was a larger CUD when using the left hand in comparison to the right hand. In Experiment 3, which employed visual stimuli different from the two preceding experiments, CUD asymmetries were related to hemifields rather than to hands with a CUD larger for the right than for the left visual hemifield. These findings suggests that both motor and visual variables are important for CUD asymmetries to occur and are in keeping with a horse race model according to which overall speed of IT is determined by whichever signal (visual or pre-motor) is more rapid in crossing from one side to the other. As to the issue of lateral asymmetries in the CUD, the results of Expt. 3 have also shown that asymmetries arise only in tasks requiring an IT and therefore cannot depend upon additive hemispheric effects.

Adult↗
PubMed1994

Analysis of a bioactive synthetic analogue of tuftsin by tandem mass spectrometry: anomalous fast atom bombardment activated processes.

Fast atom bombardment (FAB) tandem mass spectrometry has been used to analyse the biologically potent, partially modified retro-inverso (PMRI) synthetic isomer of tuftsin: this compound represents the active peptide of the fraction of gamma-globulin (leukokinin) which binds specifically to blood neutrophilic leukocytes and monocytes. Protonated molecules and fragment ions were collisionally dissociated at low energies in a triple-quadrupole mass spectrometer to yield a complete picture of the reactions that occur in the condensed and in the gas phase. The study shows that, when retro-inversion is within the N-terminal amino acid, charge localization at the basic sites (possibly at the N-terminus) induces a marked decomposition of the molecule, the loss of ammonia being the most favourable fragmentation process. Also, artifacts are formed in the liquid phase via bimolecular reactions promoted by the high-energy beam. The findings indicate that despite the fact that PMRI isomers of this type are stable against exo-peptidases and also stable under acidic conditions, they appear to be labile under conditions where the energy deposition, due to FAB is necessarily high.

Amino Acid Sequence↗
PubMed1994

Attention shifts produce spatial stimulus codes.

In the Simon task the spatial position of the stimulus, though task irrelevant, influences speed of response. We (Umiltà & Nicoletti, 1992) proposed that the orienting of attention to the imperative stimulus produces a Stroop-like interference. This paper reports the results of three experiments that provide empirical support for two predictions of this hypothesis. One is that the stimulus spatial code is formed with relation to the position to which attention is directed. The other prediction is that the Simon effect is obtained on condition that attention can orient to the stimulus.

Adult↗
PubMed1993

Scintigraphy and sonography in reflux nephropathy: a comparison.

The evaluation of reflux nephropathy (RNP) is a major task in the following up of children with vesicoureteral reflux (VUR). Adequate monitoring of RNP development depends on the frequent use of sonographical and scintigraphical examinations. In order to evaluate the accuracy of sonography in monitoring RNP 63 patients suffering from VUR (mean age: 8.8 years, range: newborn to 18 years, male:female = 19:44) were examined prospectively. We calculated renal size sonographically and compared our data to static and dynamic renographic findings. Our results showed a good correlation between relative DMSA uptake and sonographically estimated relative renal size (r = 0.95, P < 0.001), whereas not unexpectedly the correlation between relative kidney function and sonographically estimated renal size was poor (r = 0.83, P < 0.01). We therefore believe, that in monitoring children with VUR, sonography can offer accurate information on questions about renal size and renal parenchymal structure as well as pelvic distention. With very small kidneys as well as with kidneys showing severe dilatation and above all for evaluating renal function, scintigraphy proved to be the better method.

Adolescent↗
PubMed1992

Spatial representations of words and nonwords.

The first two experiments investigated whether the representations of words, besides being unitary, are also spatial in nature. Subjects were required to search for target letters in either five-letter words or five-letter nonwords. They were instructed to press the right-side key for one target and the left-side key for the other target. The center item of the letter string was always at fixation. Targets appeared one at a time, located at the second (left side) or the fourth (right side) position within the letter string. The results showed that: a) responses to targets within words were faster than responses to targets within nonwords (the word-superiority effect); b) responses to compatible stimulus-response pairings were faster than responses to incompatible stimulus-response pairings (the spatial compatibility, or, more precisely, the Simon effect); and c) in Experiment 2, left-side targets were responded to faster than right-side targets within nonwords (the left-right scanning effect). It was concluded that representations of both words and nonwords are spatial in nature. Experiment 3 was aimed at testing whether the spatial layout of the representations of words is always along the left-right horizontal dimension, regardless of the topographic transformation of the stimulus. The same words and nonwords used in the previous experiments were shown vertically and the subjects were required to make left-right discriminative responses to upper and lower target letters. The results showed the word-superiority effect but no spatial compatibility effects. It was concluded that the representation of a vertically presented word is vertically arranged.

Adult↗
PubMed1992

[Intestinal transit studied with radiopaque markers in patients with multiple sclerosis].

The patients affected with multiple sclerosis (MS) often complain of constipation. This symptom is little tolerated by the patient; its etiology is still unknown. MS patients often have their movements impaired by disease progress, so that they have to sit down for a long time, or else they exhibit severe problems walking or moving. MS patients also present low intraabdominal pressure during voluntary contraction of abdominal wall muscles. In these patients, the authors suggest to study intestinal transit time by means of radiopaque markers. To this purpose, the radiological follow-up contributes to the setting of colorectal MS dysfunctions by daily controls of the progress of per os radiopaque markers, focusing on colonic transit time and temporary deposit areas. The results show high incidence of anorectal constipation. Thus, the examination can be considered a useful tool in the study of MS dysfunctions and an effective alternative to anorectal manometry.

Colon↗
PubMed1991

New evidence for the perceptual precedence of global information.

Two experiments are reported investigating the order in which global and local information of visual forms is processed. Subjects were presented with compound stimuli and were asked to identify the local level, always consisting of small letters. At the global level, the stimuli could be either large letters, consistent or inconsistent with the local level, or meaningless patterns derived from the large letters by modifying the spatial relations among segments. Results showed that inconsistent stimuli were responded to more slowly than both consistent stimuli and meaningless patterns, which did not differ from each other. This was true both when letters and patterns were presented intermixed, as in experiment 1 or separately, as in experiment 2. The pattern obtained accords well with predictions derived from the perceptual precedence hypothesis which states that global information becomes available at a faster rate than local information. No support for the alternative, post-perceptual, hypothesis was found.

Attention↗
PubMed1991

Is interhemispheric transfer of visuomotor information asymmetric? Evidence from a meta-analysis.

Using a meta-analytic procedure we have analysed 16 studies employing a simple unimanual reaction time (RT) paradigm and lateralized visual stimuli to provide an estimate of interhemispheric transfer time in normal right-handed subjects. We found a significant overall RT advantage of the left visual field over the right and of the right hand over the left. These asymmetries can be explained by a superiority of the right hemisphere for the detection of simple visual stimuli and by a corresponding superiority of the left hemisphere for the execution of the manual response, respectively. Alternatively, they may be interpreted as related to an asymmetry of interhemispheric transmission of visuomotor information, with transfer from the right hemisphere (side of stimulus entry) to the left (side of response generation) faster than in the reverse direction. Although a direct test of these hypotheses is still lacking, we think that the evidence available is more in keeping with the latter possibility.

Arousal↗
PubMed1991

[Recommendations for carrying out nuclear medicine kidney function tests with a gamma camera and computer].

Standardization of nuclear medicine renal studies is required in order to permit the comparison of study results of a patient obtained at different laboratories. Furthermore, standardization is a prerequisite for quality control of the analysis part of the procedure. The guidelines presented here are based on a survey carried out amongst nuclear medicine laboratories in Austria and have been edited and harmonized in a workshop organized by the Austrian Nuclear Medicine Society. The guidelines include detailed descriptions of the requirements of instrumentation, of the methods of acquisition, dosage and radiation dose of the commonly used radiopharmaceuticals and all aspects of the analysis of digital renograms. A comprehensive section deals with the determination of renal clearance from the renogram, further sections cover the usage and recommended methods of captopril renography for the diagnosis of unilateral renal artery stenosis and of the frusemide renogram for the diagnosis of nephropathy and uropathy.

Austria↗