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Biomedical subjects

F Benedetti

Publications and source records attributed to F Benedetti.

At least 19 recordsLinked to original sources
PubMed1992

The development of the somatosensory representation in the superior colliculus of visually deprived mice.

Mice were enucleated bilaterally at birth in order to investigate whether early visual deprivation had any influence on the development of the somatosensory representation in the superior colliculus (SC). Single unit recordings were performed during the 2nd, 3rd, 5th and 8th postnatal week in both normal and enucleated mice. It was found that, in visually deprived mice, there was a dramatic increase of the SC somatosensory units starting from the 3rd postnatal week, as occurs in normal mice. During the 5th and 8th postnatal week, this increase was larger than in normal mice, mainly due to the invasion of the somatosensory input into the superficial layers. In visually deprived mice, both the orientation of the somatosensory map and the magnification of some body parts, such as the upper vibrissae, did not show any difference with respect to normal mice. These results indicate the involvement of both vision-dependent and independent mechanisms in the formation of the SC somatosensory representation. In fact, whereas the segregation of the somatosensory afferents in the deep layers depended on the presence of visual input, the postnatal emergence and the topographic arrangement of the somatosensory map resulted to be independent of vision.

Animals↗
PubMed1992

[The clinical implications of the use of an amino acid mixture without tryptophan in liver cirrhosis].

The ingestion of an amino acid mixture lacking tryptophan causes a rapid fall of plasma tryptophan in healthy subjects. This is because amino acids elicit protein synthesis and endogenous tryptophan is incorporated into new proteins. If protein synthesis is the mechanism through which tryptophan-free solution decrease blood tryptophan, it may be interesting to study tryptophan levels after a tryptophan-free mixture in subjects with impaired protein synthesis. In the present paper we show that in 27 cirrhotics the administration of a tryptophan-free solution caused a fall of total plasma tryptophan that began significantly later than in 14 control subjects, the delay being significantly proportional to the severity of the disease. The difference between control and cirrhotic subjects was due to the bound fraction of plasma tryptophan. The diagnostic and clinical usefulness of our findings are discussed.

Amino Acids↗
PubMed1991

The postnatal emergence of a functional somatosensory representation in the superior colliculus of the mouse.

The somatosensory map of the superior colliculus was studied in the mouse during the 2nd and 3rd postnatal weeks, with particular attention to the representation of the vibrissae. The presence of an organized somatosensory projection was not electrophysiologically demonstrable until the beginning of the 3rd postnatal week, in coincidence with the opening of the eyes. Recordings performed during the 2nd postnatal week showed that the collicular units responding to tactile stimuli were rare and functionally immature. Starting from the beginning of the 3rd postnatal week, there was a dramatic increase of the number of somatosensory units and the appearance of an ordered topography, together with the maturation of the neuronal electrical properties. All the features of the adult collicular somatosensory map were found in the 3rd postnatal week, including the magnification of the vibrissae occupying the central portion of the visual field. The functional maturation of the collicular somatosensory map of the mouse is therefore a postnatal event which starts during the 3rd postnatal week, just after the opening of the eyes.

Aging↗
PubMed1991

Decrease in plasma tryptophan after a tryptophan-free amino acid solution. A comparison between cirrhotic and control subjects.

In healthy subjects the administration of an amino acid mixture devoid of tryptophan causes a marked decrease of plasma tryptophan. This is because amino acid mixtures induce protein synthesis and tryptophan in blood is incorporated into newly synthesized proteins. We hypothesized that a tryptophan-free mixture could differently affect plasma tryptophan levels in subjects with an impaired protein synthesis such as chronic liver patients. We studied tryptophan levels after a tryptophan-free amino acid solution in controls and cirrhotics fasting 12 hours. Plasma total tryptophan fell to 91% of the initial level 60 minutes after the administration of the diet, to 71% after 120, and to 50% after 210' in controls. In cirrhotics the solution caused a decrease of plasma tryptophan that began significantly later than in controls, the delay being proportional to the severity of the disease. Cirrhotics were subdivided into two groups in accordance to the Pugh modification of the Child-Turcotte criteria. Total plasma tryptophan was 100% of base line levels after 60', 88% after 120', and 65% after 210' in less severe clinical condition; total plasma tryptophan was 102% of base line levels after 60', 98% after 120', and 75% after 210' in more severe clinical condition.

Adult↗
PubMed1991

Perceptual learning following a long-lasting tactile reversal.

Crossing 2 adjacent fingers produces a distorted perception when 2 tactile stimuli are touched to the crossed fingertips. This is because a given pair of fingers has a functional range of action within which spatial perception is correct (uncrossed fingers) and beyond which perceived location of tactile stimuli is wrong (crossed fingers). The present study tested the possibility that this range of action could be modified following a long-lasting crossing. Therefore, the functional range of action of the 2nd and 3rd fingers was tested every month in 6 volunteers who maintained the finger crossing for as long as 6 months. The results show that after a variable period of time the range of action was enlarged such that spatial perception was correct with crossed fingers as well. The perceptual organization of the human hand therefore depends on experience and is not rigidly determined on a genetic basis.

Adult↗
PubMed1991

Reorganization of tactile perception following the simulated amputation of one finger.

The tactile counterpart of diplopia has recently been described: tactile diplopia or diplesthesia. The human fingers show a rather precise organization of the cutaneous areas eliciting diplesthesia. In particular, these areas are very extensive between nonadjacent fingers (second and fourth, second and fifth, and third and fifth), suggesting that the illusory doubling depends on the lack of reciprocal interaction between cutaneous zones during manipulation. In the present study, four subjects agreed to explore and manipulate objects only through nonadjacent fingers for a period of up to six months. The amputation of the third finger was simulated by excluding it from active exploration by means of a bandage. After six months, the diplesthetic areas of the nonadjacent fingers decreased in size or completely disappeared. It is suggested that this reorganization of tactile perception is due to the increase in temporal correlation of the sensory inputs between nonadjacent fingers.

Amputation, Surgical↗
PubMed1990

Goal directed motor behavior and its adaptation following reversed tactile perception in man.

When two adjacent fingers are crossed over each other and two tactile stimuli are touched to the two crossed fingertips, the two stimuli are perceived to be inverted in space. This phenomenon of tactile reversal was used in the present work to study the sensorimotor transformation occurring in goal directed motor behavior. When the subjects had to perform a movement toward a tactile stimulus (target) in tactile reversal conditions, the stimulus directed movements were performed wrongly, that is, away from the target. However, not all the subjects perceived a complete inversion of the stimuli; in this case, the target stimulus was perceived to be on the same side as its actual position, although with an error. In these conditions, the stimulus directed movements were performed correctly, that is, toward the target. These results show that the illusory spatial perception of the stimuli controls motor behavior on the basis of the amount of the perceptual error. Within the first hour of training, several compensatory responses occurred so as to produce correct motor performance. Despite this motor learning, reversed tactile perception remained reversed. Therefore, what subjects learned was the execution of the movements opposite to those necessary for reaching the target stimulus, without any change in perception. In the context of theories concerning the relationship between motor learning and perceptual adaptation, the present study shows that, with this experimental paradigm, motor learning during the first hour was mainly cognitive and did not have short-term effects upon perceptual processes.

Adaptation, Psychological↗
PubMed1990

Mediastinal large-B-cell lymphoma with sclerosis: a clinical study of 21 patients.

We report the clinical findings of 21 consecutive patients affected by mediastinal large B-cell lymphoma with sclerosis. This type of lymphoma is a recently described histopathologic entity characterized on clinical grounds by distinctive features, which, according to our series, can be summarized as follows: young age (median, 30 years; range, 15 to 42 years), prevalence of females over males (15 v six), rare occurrence of superficial lymph node enlargement (three of 21 patients), and involvement of unusual extranodal sites (kidney six, adrenal cortex two patients). The clinical course appears to be closely related to treatment. In fact, complete remission (CR) was not obtained in the six patients submitted to conventional cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) or CHOP plus bleomycin (CHOP-Bleo) regimens until 1985, as opposed to 13 CRs reached in the 15 patients subsequently treated with more aggressive regimens after 1985 (methotrexate with leucovorin, doxorubicin, cyclophosphamide, vincristine, prednisone, and bleomycin [MACOP-B], 12 patients; methotrexate, bleomycin, doxorubicin, cyclophosphamide, vincristine, and dexamethasone [M-BACOD], two patients; and vincristine, cyclophosphamide, fluorouracil, cytarabine, doxorubicin, methotrexate, and prednisone [F-MACHOP], one patient; plus involved-field radiotherapy, 10 patients). Among the 13 patients who achieved a CR, only one relapse was observed at 10 months. The median overall survival of complete responders after an observation period of 11 to 69 months has not yet been reached, and the event-free survival curve indicates that 90% of patients who achieve CR may be potentially cured.

Adolescent↗
PubMed1990

[Venous replacement surgery: history, update and perspectives].

The impulse given to vascular surgery by new technologies has facilitated the use of the bypass technique in a number of arterial pathologies with better and better results over time. At the moment, however, we haven't a "sure prosthesis" in venous surgery. Our intention has been to examine the most significant developments, studying all the available material dating from the beginnings of the art up to the present. After a careful examination of the venous pathophysiology as well as the most valid surgical approaches, we tried to evaluate on laboratory animals the results of experimental graft replacement of the inferior vena cava. In this study we analysed prostheses in PTFE, biological prostheses, spiral composite vein grafts, arterial autologous grafts. For the experimental study we used 55 rabbits (New Zealand and Fiandra). Results have been rather successful with respect to biological prostheses (62.5% patency) and PTFE (66.6%). As for spiral composite vein graft prosthesis patency over time was very low (16.6%); this was affected by the different venous graft (heterologous graft) and caval wall thicknesses. Arterial autologous graft was carried out only once because rabbit experimented on did not stand up to surgical stress.

Animals↗
PubMed1989

Bone marrow transplantation monitoring by DNA analysis.

Variable Number of Tandem Repeats (VNTR) DNA polymorphisms analysis was used in bone marrow transplantation (BMT) follow up. Three Acute Myeloid Leukemia (AML) transplants were investigated with YNH 24/MspI and with EFD 64.2/Rsa or HinfI highly polymorphic VNTRs. Absence of mosaicism and complete engraftment of donor cells was observed in two cases, while mixed hematopoietic chimerism was present in a case in which T cell depleted marrow was transplanted. VNTR systems represent accurate and sensitive individual specific markers for monitoring the clinical course of patients undergoing BMT, and for detecting the biological origin of relapses.

Bone Marrow Transplantation↗
PubMed1988

Localization of tactile stimuli and body parts in space: two dissociated perceptual experiences revealed by a lack of constancy in the presence of position sense and motor activity.

Two motor acts were analyzed at the level of tongue and fingers. These motor acts generated illusions. When subjects voluntarily rotated the tongue by 90 degrees, the perceived orientation of a tactile stimulus applied to the tongue did not covary with the perceived orientation of the tongue itself. Analogously, when subjects voluntarily crossed two adjacent fingers, the perceived position of two tactile stimuli applied to the fingers did not covary with the perceived position of the fingers themselves. Although tongue and fingers were positioned accurately in space, a lack of perceptual constancy occurred for tactile stimuli applied to these body parts. Therefore, whereas position sense was preserved, correct localization of objects was lost. The occurrence of this perceptual dissociation suggests that spatial localization of tactile stimuli may be independent both of knowledge of body part location and motor activity.

Attention↗
PubMed1987

Immunologic abnormalities in angioimmunoblastic lymphadenopathy.

In this study we describe the results of phenotypic, serologic, and functional analyses performed in nine patients with angioimmunoblastic lymphadenopathy (AILD). The study investigates the nature of the T-cell defects which seem to represent a consistent feature in this disease. The study, based on the analysis of T-cell subsets with monoclonal antibodies and on functional in vitro tests, showed the following main abnormalities: reduction of the absolute number of circulating T-cells; inversion of the CD4/CD8 ratio, both in the peripheral blood and in the involved lymph nodes; high percentages of activated T-cells (CD8+/HLA-DR+); defective T-cell response in vitro to the PHA mitogen; and minimal helper and enhanced in vitro suppressor functions. Some of these immunologic dysfunctions are also observed in acquired immune deficiency syndrome (AIDS) which has in common with AILD several clinical features. However, no evidence of HTLV-III infection could be demonstrated in our patients with AILD.

Acquired Immunodeficiency Syndrome↗
PubMed1987

High serum levels of soluble interleukin 2 receptor in patients with B chronic lymphocytic leukemia.

By using an enzyme-linked immunosorbent assay, the presence of the soluble form of the interleukin-2 receptor (sIL-2R) was evaluated in the peripheral blood of 54 patients with B cell chronic lymphocytic leukemia (B-CLL). Serum levels of sIL-2R were correlated with clinical features, relevant hematologic and immunological data, and in some cases, with in vitro functional studies. In 51 patients (94.4%), the levels of sIL-2R were increased as compared with normal age-matched controls (1,781 U/mL +/- 231 v 276 U/mL +/- 26, respectively; P less than .001). Although this increase was observed in all stages of the disease and independently of several hematologic and immunologic parameters, a trend toward lower levels of sIL-2R was documented in patients with a less-invasive disease. When the values were correlated with the functional status of the residual T cell population, it was found that patients with the lowest levels of sIL-2R showed the best mitogenic response and helper capacity. It is suggested that in B-CLL patients the high levels of serum sIL-2R, capable of binding to its ligand, may block the T cell-produced IL-2, thus contributing toward a defective physiological action by this lymphokine. In turn, this defective availability of IL-2 may play a part in the abnormal immunoregulation that is implicated in the hypogammaglobulinemia, susceptibility to infections, and incidence of second neoplasias often observed in this disease.

Aged↗