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Biomedical subjects

G Sartori

Publications and source records attributed to G Sartori.

At least 19 recordsLinked to original sources
PubMed2005

Semantic relevance best predicts normal and abnormal name retrieval.

The relevance of a semantic feature measures its contribution to the "core" meaning of a concept. In a naming-to-description task, we investigated the predictive power of relevance in comparison with frequency, familiarity, typicality, and Age-of-Acquisition. In a group of Alzheimer patients with semantic disorder, relevance turned out to be the best predictor of name retrieval accuracy in a naming-to-description task. The same pattern of results was observed in normal controls. Relations between semantic relevance and the parameters of the concepts are discussed in order to highlight the mechanism of concept activation in a naming-to-description task.

Age Factors↗
PubMed2005

The value of c-kit mutational analysis in a cytokeratin positive gastrointestinal stromal tumour.

The expression of cytokeratins in gastrointestinal stromal tumours (GISTs) is rare and may lead to diagnostic confusion when it occurs. This report describes a metastatic GIST that stained strongly for cytokeratins, CD117, and CD34 in a patient who was previously diagnosed with gastric epithelioid angiosarcoma. A review of both tumours showed the same histological and immunohistochemical profiles, and c-kit molecular analysis revealed an insertional mutation at codon 558 of exon 11 in both tumours. Thus, pathologists should be aware that GISTs can occasionally express cytokeratins, and that c-kit mutational investigations may have a key diagnostic role and may prevent diagnostic mistakes that could have important clinical implications.

Adult↗
PubMed2002

Computationally inexpensive methods for intra-cardiac atrial bipolar electrogram compression.

AIM: This paper reports studies of mathematical algorithms for intra-cardiac atrial bipolar electrogram compression suitable with implementation on implantable devices. PATIENTS AND METHODS: Bipolar intra-cardiac electrograms (IEGMs) of high right atrium were obtained from 20 patients who underwent electrophysiological studies for arrhythmias. Four thousand seven hundred and eighty-two seconds of IEGM were collected and divided into three rhythm groups: sinus rhythm (SR), atrial fibrillation (AF) and atrial flutter (AFL). Since mathematical algorithms suitable for use with implantable devices demand low computational cost, we employed piecemeal linear approximation methods (ZOP--Zero Order Prediction and SAPA--Scan Along Polygonal Approximation), and beat detection method (Peak) both or which need small numbers of operations to perform electrogram compression. Compression ratio (CR) and percent root mean square difference (PRD) were used to compare the three methods, with statistical analyses performed using paired t-test. RESULTS AND CONCLUSION: The best performance was obtained using the Peak method which reaches an average CR of 10.6 in the case of SR group, 2.8 for AF, and 3.6 for AFL groups, respectively, while PRD lies below 2% for SR and AFL groups and 6% for the AF group. Results show that, for bipolar electrograms, the Peak method reaches statistically significant better performance (P<0.001) in all cases except for Peak vs SAPA applied to AF (P=0.2). The number of operations necessary to compress the data indicate that time consumption can be reduced to be suitable for real time compression in implantable devices. The Peak method, which was assumed to receive the instant of occurrence of each recognized beat, from the hardware of the device, requires fewer operations than ZOP and SAPA. Increasing the length of electrograms recorded in pacemakers will enhance the amount of information provided by the implantable device, allowing more detailed characterization of the intra-cardiac activity and leading to new perspectives in arrhythmia diagnosis and therapy.

Adult↗
PubMed2001

Large-scale phenotypic analysis reveals identical contributions to cell functions of known and unknown yeast genes.

Sequencing of the yeast genome has shown that about one-third of the yeast ORFs code for unknown proteins. Many other have similarity to known genes, but still the cellular functions of the gene products are unknown. The aim of the B1 Consortium of the EUROFAN project was to perform a qualitative phenotypic analysis on yeast strains deleted for functionally orphan genes. To this end we set up a simple approach to detect growth defects of a relatively large number of strains in the presence of osmolytes, ethanol, high temperature, inhibitory compounds or drugs affecting protein biosynthesis, phosphorylation level or nucleic acids biosynthesis. We have now developed this procedure to a semi-quantitative level, we have included new inhibitors, such as hygromycin B, benomyl, metals and additional drugs interfering with synthesis of nucleic acids, and we have performed phenotypic analysis on the deleted strains of 564 genes poorly characterized in respect to their cellular functions. About 30% of the deleted strains showed at least one phenotype: many of them were pleiotropic. For many gene deletions, the linkage between the deletion marker and the observed phenotype(s) was studied by tetrad analysis and their co-segregation was demonstrated. Co-segregation was found in about two-thirds of the analysed strains showing phenotype(s).

Gene Deletion↗
PubMed2000

Inactivation of six genes from chromosomes VII and XIV of Saccharomyces cerevisiae and basic phenotypic analysis of the mutant strains.

Within the frame of the EUROFAN project, aimed at the functional analysis of the novel ORFs revealed by the systematic sequencing of the Saccharomyces cerevisiae genome, we have inactivated six ORFs encoding putative proteins with unknown function in the two S. cerevisiae strains FY1679 and W303-1B. Five ORFs are located on chromosome VII (YGR250c, YGR251w, YGR260w, YGR262c, YGR263c) and one on chromosome XIV (YNL234w). The genes have been inactivated in the FY1679 strain by a strategy that makes use of deletion cassettes containing the kanMX4 module, which confers resistance to geneticin to yeast cells, and short flanking regions homologous to the target locus (SFH). Tetrad dissection of heterozygous mutants and basic phenotypic analysis of the spores revealed that ORF YGR251w is an essential gene, while the disruption of YGR262c causes a severe slow-growth phenotype. Deletion of the remaining ORFs did not give rise to a detectable phenotype in the mutant strains. For each ORF we have cloned, in the pUG7 plasmid, a replacement cassette that possesses long flanking regions homologous to the target locus (LFH) and, in the pRS416 plasmid, the cognate wild-type gene. The LFH replacement cassettes were used to inactivate the respective genes in the W303-1B strain. This work has been performed in the framework of the B0 Consortium of the EUROFAN I project.

Anti-Bacterial Agents↗
PubMed2000

How to avoid the fallacies of cognitive subtraction in brain imaging.

Functional neuroanatomy of cognitive processes is generally derived by subtraction of a control task from an experimental task. We show that this method is logically untenable and propose to replace it with an adaptation of the specific-effect method and of the additive-factor method. The basic flaw that undermines the subtractive method is the comparison between different tasks. We argue that the specific-effect method should be used when investigating activations produced by different levels of a qualitative variable, whereas the additive-factor method should be used for quantitative variables. The use of these methods allows one to distinguish between parallel and serial stages of processing and between local and distributed processing.

Brain↗
PubMed2000

Automatic atrial tachyarrhythmia detection from intracardiac electrograms.

BACKGROUND: Automatic atrial tachyarrhythmia recognition is crucial in order to allow a correct switching-mode function of dual-chamber pacemakers and to avoid inappropriate shocks of ventricular implantable cardioverter-defibrillators. In this paper we considered three algorithms suitable for implantable devices. The first was based on the atrial cycle length; the others analyze different morphologic characteristics of atrial signals. METHODS: Intracardiac bipolar electrogram recordings were obtained from the high right atrium during electrophysiological study. Twenty patients were considered, some of them presenting with different types of cardiac rhythm at different intervals of the study. Cardiac rhythms were divided into three groups: sinus rhythm consisting of 2,196 s obtained from 12 subjects, atrial fibrillation consisting of 771 s obtained from 7 subjects, and atrial flutter consisting of 1,793 s obtained from 7 subjects. The automatic detection was performed on each electrogram segment lasting 1 or 4 s. Atrial segments were separated into two subgroups: the first for the training of the algorithm and the second for testing and validation of results. We considered two types of statistical analysis: comparison between pairs of rhythm (paired classification), and classification among the three different groups (direct classification). RESULTS: The combination of the cycle length algorithm with a morphological method achieved the best performance for both statistical analyses. Paired classification resulted in the following: atrial fibrillation vs sinus rhythm was detected with no error; atrial flutter vs sinus rhythm with a total accuracy of 99.3% (sensitivity 99.4%, specificity 99.2%); atrial fibrillation vs atrial flutter with a total accuracy of 99.1% (sensitivity 98.5%, specificity 99.4%). The total accuracy achieved for the direct classification was 98.6% (average sensitivity 98.5%, specificity 98.8%). CONCLUSIONS: Our results support the association of algorithms for future enhancement of atrial tachyarrhythmia detection in dual-chamber devices, thanks to the limited computational effort.

Algorithms↗
PubMed1999

Characterization of a new hemoprotein in the yeast Saccharomyces cerevisiae.

The Saccharomyces cerevisiae gene YNL234w encodes a 426-amino acid-long protein that shares significant similarities with the globin family. Compared with known globins from unicellular organisms, the Ynl234wp polypeptide is characterized by an unusual structure. In this protein, a central putative heme-binding domain of about 140 amino acids is flanked by two sequences of about 160 and 120 amino acids, respectively, which share no similarity with known polypeptides. Northern analysis indicates that YNL234w transcription is very low in cells grown under normal aerobic conditions but is induced by oxygen-limited growth conditions and by other stress conditions such as glucose repression, heat shock, osmotic stress, and nitrogen starvation. However, the deletion of the gene had no detectable effect on yeast growth. The Ynl234wp polypeptide has been expressed in Escherichia coli, and the hemoprotein nature of the recombinant protein was demonstrated by heme staining after SDS/polyacrylamide gel electrophoresis and spectroscopic analysis. Our data indicate that purified recombinant Ynl234wp possesses a noncovalently bound heme molecule that is predominantly found in a low spin form.

Amino Acid Sequence↗
PubMed1999

How to bring orphan genes into functional families.

In the framework of the B1 Consortium of the EUROFAN-1 project, we set up a series of simple phenotypic tests that can be performed on a large number of strains at a time. This methodological approach was intended to help assign functions of putative genes coding for unknown proteins to several specific aspects of cell biology. The tests were chosen to study phenotypes which should be affected by numerous genes. In this report, we examined the sensitivity/resistance or the adaptation of the cell to physical or chemical stresses (thermotolerance, osmotolerance and ethanol sensitivity), the effects of the alteration of the level of protein phosphorylation (sensitivity or resistance to compounds affecting the activity of protein kinases or phosphatases) and the effects of compounds interfering with synthesis of nucleic acids or proteins. Deletions in 66 genes of unknown function have been tested in 21 different conditions. In many deletant strains, phenotypes were observed and, for the most promising candidates, tetrad analysis was performed in order to verify co-segregation of the deletion marker with the phenotype.

Adaptation, Physiological↗
PubMed1998

Evolution of mitochondrial DNA in yeast: gene order and structural organization of the mitochondrial genome of Saccharomyces uvarum.

We have determined the size, the restriction map and the gene order of the mitochondrial genome of the yeast Saccharomyces uvarum. Sequence analysis of the mitochondrial COXII gene confirmed the position of this yeast in the Saccharomyces cerevisiae-like group, near Saccharomyces cerevisiae and Saccharomyces douglasii. Most mitochondrial genes have been positioned on this approximately 57-kb long genome and three regions containing putative replication origins have been identified. The gene order of S. uvarum suggests that the mitochondrial genome of the S.cerevisiae-like yeasts could have evolved from an ancestral molecule, similar to that of S. uvarum, through specific genome rearrangements.

Cytosine↗
PubMed1998

Deficits in the control of the attentional focus in chronic schizophrenics.

The ability to control the size of the attentional focus and thus to modulate processing efficiency was investigated using simple reaction times in central vision in 17 chronic schizophrenic patients and 17 normal control subjects. The size of the attentional focus was manipulated by varying the size of a central box (i.e., a pre-cue), where the imperative stimulus appeared. In accordance with previous studies, in normal controls reaction time increased with box size. In contrast, in schizophrenic patients reaction time did not depend on box size. That is, schizophrenic patients did not show the inverse relation between size of the box and speed of processing, which is observed in normal controls. These results suggest that a deficit in controlling the size of the attentional focus is a basic impairment in chronic schizophrenia. It was also found that schizophrenics are more susceptible than controls to paracontrast.

Adult↗
PubMed1997

Analysis of an 11.6 kb region from the right arm of chromosome VII of Saccharomyces cerevisiae between the RAD2 and the MES1 genes reveals the presence of three new genes.

Sequence analysis of an 11,628 bp DNA segment from the right arm of Saccharomyces cerevisiae chromosome VII revealed the presence of the 5' end of the RAD2 gene, the MES1 gene and six open reading frames (ORFs) each longer than 300 bp. Four of these ORFs are expressed genes, as indicated by transcript analysis. One of them, YGR261c, which specifies a putative beta-adaptine, corresponds to gene YKS5, which has recently been identified as a suppressor of loss of casein kinase 1 function. The remaining three ORFs are new genes; of these, YGR260w encodes a protein showing similarity to the S. cerevisiae allantoate permease and YGR262c specifies a putative protein kinase.

Blotting, Northern↗
PubMed1997

Performance characteristics of chronic schizophrenia on attention tests sensitive to unilateral brain damage.

The aims of this study were to investigate the lateralization hypothesis of schizophrenia, comparing chronic schizophrenics with unilateral brain-damaged subjects and normal controls, using attentional tests sensitive to the unilateral brain damage. Three attentional tests with different modes of stimuli, two vigilance tasks that require the self-paced or nonself-paced responses of subjects and one divided attention task, were administered to 28 chronic schizophrenics, 26 right and 24 left unilateral brain-damaged subjects, and 20 normal controls. The results indicated that schizophrenics performed a possible right-hemisphere damages pattern and also a left pattern in part, with failure of all tasks to show either pattern related to a number of differences between the three tasks. Furthermore, the attention deficits of schizophrenics are less than those of brain-damaged subjects but are clearly abnormal compared with the normal controls.

Attention↗
PubMed1996

Progressive visual agnosia with posterior cortical atrophy.

A patient of posterior cortical atrophy characterized by early signs of progressive visual agnosia documented by repeated neuropsychological tests, is reported. SPECT and MRI findings showed left unilateral parieto-occipital involvement in the earlier stage. A PET study executed eight months later showed bilateral parieto-occipital hypometabolism, but predominantly in the left hemisphere. This suggests that the degeneration may have developed asymmetrically, progressing from left unilateral to bilateral.

Agnosia↗
PubMed1996

Semantic memory impairment in Alzheimer's disease.

The present study investigated semantic memory and the presence of category-specific impairments in patients with dementia of the Alzheimer's type (DAT). Patients in advanced stages of Parkinson's disease (PD) and matched control subjects served as comparison groups. Semantic memory was assessed by a range of verbal and visual tasks and by direct and indirect memory tests. The DAT patients showed severe deficits on all semantic knowledge tasks. Performance was poorer on animate relative to inanimate items, on naming with and without cues, and on semantic knowledge probes, indicating a category-specific knowledge loss on these tasks. Indirect memory tests yielded significantly better preservation of knowledge compared to the traditional semantic memory tasks. Analyses of the nature of the semantic breakdown in DAT suggested combined storage and access deficits and a disturbance of the structural description and phonological output systems.

Aged↗
PubMed1996

Startle reflex and emotion modulation impairment after a right amygdala lesion.

In the present study, startle responses during resting states as well as during the presentation of a set of emotive slides were recorded from a 32-year-old male patient with a rare localized lesion of the right amygdala. The startle reflex is a response modulated by affective states: it has been reliably used in the literature to measure the aversiveness of emotive stimuli. The animal literature has shown that the circuit of this reflex is directly influenced by amygdala projections. The startle responses of the patient were compared with those of eight age-matched normal subjects. The patient's startle amplitudes showed an overall impaired response and an inhibited reflex contralateral to the lesion. In addition, he failed to show the typical startle potentiation induced by an aversive emotive background. The data confirm, in the human, previous results from the literature in other species on amygdala involvement in startle and emotional responses. Furthermore, the observation of the importance of the right amygdala in the modulation of emotion is consistent with the hypothesis of right hemisphere specialization for aversive emotions. The results are discussed in the context of the literature on human amygdala lesions.

Adult↗