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Biomedical subjects

P Oliva

Publications and source records attributed to P Oliva.

At least 19 recordsLinked to original sources
PubMed2006

A completely automated CAD system for mass detection in a large mammographic database.

Mass localization plays a crucial role in computer-aided detection (CAD) systems for the classification of suspicious regions in mammograms. In this article we present a completely automated classification system for the detection of masses in digitized mammographic images. The tool system we discuss consists in three processing levels: (a) Image segmentation for the localization of regions of interest (ROIs). This step relies on an iterative dynamical threshold algorithm able to select iso-intensity closed contours around gray level maxima of the mammogram. (b) ROI characterization by means of textural features computed from the gray tone spatial dependence matrix (GTSDM), containing second-order spatial statistics information on the pixel gray level intensity. As the images under study were recorded in different centers and with different machine settings, eight GTSDM features were selected so as to be invariant under monotonic transformation. In this way, the images do not need to be normalized, as the adopted features depend on the texture only, rather than on the gray tone levels, too. (c) ROI classification by means of a neural network, with supervision provided by the radiologist's diagnosis. The CAD system was evaluated on a large database of 3369 mammographic images [2307 negative, 1062 pathological (or positive), containing at least one confirmed mass, as diagnosed by an expert radiologist]. To assess the performance of the system, receiver operating characteristic (ROC) and free-response ROC analysis were employed. The area under the ROC curve was found to be Az = 0.783 +/- 0.008 for the ROI-based classification. When evaluating the accuracy of the CAD against the radiologist-drawn boundaries, 4.23 false positives per image are found at 80% of mass sensitivity.

Algorithms↗
PubMed2006

Comparison of two portable solid state detectors with an improved collimation and alignment device for mammographic x-ray spectroscopy.

We describe a portable system for mammographic x-ray spectroscopy, based on a 2 X 2 X 1 mm3 cadmium telluride (CdTe) solid state detector, that is greatly improved over a similar system based on a 3 X 3 X 2 mm3 cadmium zinc telluride (CZT) solid state detector evaluated in an earlier work. The CdTe system utilized new pinhole collimators and an alignment device that facilitated measurement of mammographic x-ray spectra. Mammographic x-ray spectra acquired by each system were comparable. Half value layer measurements obtained using an ion chamber agreed closely with those derived from the x-ray spectra measured by either detector. The faster electronics and other features of the CdTe detector allowed its use with a larger pinhole collimator than could be used with the CZT detector. Additionally, the improved pinhole collimator and alignment features of the apparatus permitted much more rapid setup for acquisition of x-ray spectra than was possible on the system described in the earlier work. These improvements in detector technology, collimation and ease of alignment, as well as low cost, make this apparatus attractive as a tool for both laboratory research and advanced mammography quality control.

Calibration↗
PubMed2005

GPCALMA: a Grid-based tool for mammographic screening.

OBJECTIVES: The next generation of high energy physics (HEP) experiments requires a GRID approach to a distributed computing system: the key concept is the Virtual ORGANISATION (VO), a group of distributed users with a common goal and the will to share their resources. METHODS: A similar approach, applied to a group of hospitals that joined the GPCALMA project (Grid Platform for Computer Assisted Library for MAmmography), will allow common screening programs for early diagnosis of breast and, in the future, lung cancer. The application code makes use of neural networks for the image analysis and is useful in improving the radiologists' diagnostic performance. GRID services allow remote image analysis and interactive online diagnosis, with a potential for a relevant reduction of the delays presently associated with screening programs. RESULTS AND CONCLUSIONS: A prototype of the system, based on AliEn GRID Services [1], is already available, with a central server running common services [2] and several clients connecting to it. Mammograms can be acquired in any location; the related information required to select and access them at any time is stored in a common service called Data Catalogue, which can be queried by any client. Thanks to the PROOF facility [3], the result of a query can be used as input for analysis algorithms, which are executed on the nodes where the input images are stored,. The selected approach avoids data transfers for all the images with a negative diagnosis and allows an almost real time diagnosis for the set of images with high cancer probability.

Algorithms↗
PubMed2004

Direct analysis of molybdenum target generated x-ray spectra with a portable device.

In routine applications, information about the photon flux of x-ray tubes is obtained from exposure measurements and cataloged spectra. This approach relies mainly on the assumption that the real spectrum is correctly approximated by the cataloged one, once the main characteristics of the tube such as voltage, target material, anode angle, and filters are taken account of. In practice, all this information is not always available. Moreover, x-ray tubes with the same characteristics may have different spectra. We describe an apparatus that should be useful for quality control in hospitals and for characterizing new radiographic systems. The apparatus analyzes the spectrum generated by an x-ray mammographic unit. It is based on a commercial CZT produced by AMPTEK Inc. and a set of tungsten collimator disks. The electronics of the CZT are modified so as to obtain a faster response. The signal is digitized using an analog to digital converter with a sampling frequency of up to 20 MHz. The whole signal produced by the x-ray tube is acquired and analyzed off-line in order to accurately recognize pile-up events and reconstruct the emitted spectrum. The energy resolution has been determined using a calibrated x-ray source. Spectra were validated by comparison of the HVL measured using an ionization chamber.

Algorithms↗
PubMed2001

Interaction between metabotropic and NMDA glutamate receptors in the periaqueductal grey pain modulatory system.

The formalin test was used to investigate the interactive role of periaqueductal grey (PAG) N-methyl-D-aspartate (NMDA) and metabotropic glutamate (mGlu) receptors in the modulation of persistent noxious stimulation in mice. Intra-PAG microinjections of 1 or 3 nmol NMDA, a selective agonist at NMDA-subtype receptors, decreased the nociceptive response (-94+/-5% with 3 nmol) during the latter phase of the test. This effect was antagonized by MK-801, a selective antagonist at NMDA receptors. No change in the early nociceptive phase was observed after NMDA injection. Pretreatment either with 2-methyl-6-phenylethynylpyridine (MPEP, 25 nmol/mouse), a selective antagonist at mGlu5 receptors, or with (2S)-alpha-ethylglutamic acid [(2S)-alpha-EGlu, 30 nmol/mouse], a selective antagonist at group-II mGluRs, prevented the NMDA-induced antinociceptive effect during the late hyperalgesic phase. Pretreatment with (R,S)-alpha-methylserine-O-phosphate [(R,S)-alpha-MSOP, 70 nmol/mouse], a selective antagonist at group-III mGlu receptors, had no effect on the NMDA-induced antinociception. None of the antagonists changed the formalin-induced nociceptive behaviour per se with the dosages used in combination with NMDA. MPEP at 50 nmol/mouse, however, potentiated the early nociceptive phase whilst 100 nmol/mouse attenuated the late phase. Similarly, at the higher dose of 140 nmol/mouse, (R,S)-alpha-MSOP decreased the late hyperalgesic phase. These results provide additional evidence that NMDA and mGlu receptors participate in modulating the hyperalgesia induced by peripheral noxious stimulation. In particular, mGlu receptors may modulate the NMDA receptors in the PAG since their physiological stimulation seems to be required for the NMDA-induced effect. This suggests that, together with ionotropic glutamate receptors, mGlu receptors also play a role in modulating a type of spinal cord neuroplasticity (i.e. wind-up) that has been proposed to mediate hyperalgesia.

Animals↗
PubMed2001

Metabotropic and NMDA glutamate receptors participate in the cannabinoid-induced antinociception.

The purpose of this study was to evaluate the possible contribution of metabotropic glutamate receptors (mGluRs) to cannabinoid-induced antinociception in the periaqueductal grey (PAG) matter of rats. Intra-PAG microinjection of WIN 55,212-2, a cannabinoid receptor agonist, increased the latency of the nociceptive reaction (NR) in a dose-dependent fashion in the plantar test. This effect was prevented by pretreatment with SR141716A, a selective antagonist of CB1 receptors. When injected alone, SR141716A produced, with the highest dosage used, a significant reduction in the latency of the NR. CPCCOEt, a selective mGlu1 receptor antagonist, was unable to prevent the analgesia produced by WIN 55,212-2. On the contrary, MPEP, a selective mGlu5 receptor antagonist, completely antagonized the effect of WIN 55,212-2. However, the analgesia induced by CHPG, a selective mGlu5 receptor agonist, was blocked by MPEP but not by SR141716A. When injected alone, CPCOOEt produced no effect, whereas MPEP produced, with the highest dosage used, a significant reduction in the latency of the NR. These data emphasize that mGlu5 receptors, but not mGluR1, may modulate nociception in the PAG. Similarly, a pretreatment with either 2-(S)-alpha-EGlu or (RS)-alpha-MSOP, selective antagonists for group II and III mGluRs, respectively, prevented the WIN 55,212-2-induced analgesia. When the higher dosage of (RS)-alpha-MSOP was used a decrease in the latency of the NR was observed. This was not the case for 2-(S)-alpha-EGlu. Pretreatment with DL-AP5, a selective antagonist of N-methyl-D-aspartate (NMDA) receptors, blocked the effect of WIN 55,212-2, and by increasing the dosage strongly reduced per se the latency of the NR. This study suggests that endogenous glutamate could tonically modulate nociception through mGlu and NMDA receptors in the PAG matter. In particular, the physiological stimulation of these receptors seems to be required for the cannabinoid-induced analgesia in this midbrain area.

Analgesics↗
PubMed2001

Dietary intake of calcium, magnesium and phosphorus in an elderly population using duplicate diet sampling vs food composition tables.

The aim of this study was to estimate the dietary intake of calcium, magnesium and phosphorus in the elderly institutionalised population using duplicate diet sampling and to establish any related difference with the results obtained using food composition tables. The study was carried out on a sample group of 112 subjects in Granada (Spain). 1-week food duplicate samples offered by the elderly were studied. Calcium and magnesium were determined by AAS and phosphorus was determined by spectrophotometry. Anova showed significant differences (p<0.05) in all the minerals analyzed. These results suggest that the use of food composition tables is not suitable to evaluate the calcium, magnesium and phosphorus in nutritional trials. Moreover, the results show clearly that it is essential to consider these differences to establish the adequate intakes of calcium, magnesium and phosphorus for the elderly population in relation to the mineral bone status.

Aged↗
PubMed2000

Neurochemical changes after morphine, dizocilpine or riluzole in the ventral posterolateral thalamic nuclei of rats with hyperalgesia.

A number of studies suggest the involvement of glutamate in central hyperalgesia through NMDA receptors in animal models of inflammation. Most studies analyze glutamate effects at the spinal cord level. In this work, the effects of morphine, dizocilpine and riluzole on the hyperalgesia induced by carrageenan administration in the rat paw model were investigated. The effects of morphine and riluzole on the release of glutamate and aspartate and on the concentrations of citrulline and arginine in dialysates of the ventral posterolateral nucleus of the thalamus were also examined. All three drugs decreased hyperalgesia when administered prior to carrageenan injection. Morphine decreased the glutamate concentration in dialysates of the ventral posterolateral nucleus but did not affect the concentrations of the other amino acids. The effect of morphine was observed in the absence of painful stimulation and when pressure applied to the rat paw induced a nociceptive reaction. Riluzole decreased the concentrations of glutamate and aspartate and those of citrulline and arginine in the presence or absence of painful stimulation. These experiments suggest that morphine and riluzole attenuate the hyperalgesia induced by injection of carrageenan in the rat hind paw, at least partly, by decreasing glutamate release in the ventral posterolateral thalamic nucleus.

Analysis of Variance↗
PubMed2000

Periaqueductal gray matter metabotropic glutamate receptors modulate formalin-induced nociception.

The role played by periaqueductal gray (PAG) matter metabotropic glutamate receptors (mGluRs) in the modulation of persistent noxious stimulation was investigated in mice. The formalin test was used as a model of persistent pain. Intra-PAG microinjections of (S)-3, 5-DHPG (25 and 50 nmol/mouse) and L-CCG-I (30 and 60 nmol/mouse), agonists of group I and group II mGluRs, respectively, decreased the nociceptive response (-92+/-6% and -89+/-8%, respectively) during the late phase. No change of the early nociceptive phase was observed after (S)-3,5-DHPG or L-CCG-I treatments. These effects were antagonized by a pretreatment with CPCCOEt (40 nmol/mouse) and (2S)-alpha-EGlu (30 nmol/mouse). CPCCOEt is a selective antagonist of group I mGlu receptors, while (2S)-alpha-EGlu is an antagonist of group II. Intra-PAG microinjections of L-SOP (60 and 120 nmol/mouse), a selective agonist of group III mGluRs, induced an increase of the nociceptive response (+95+/-7%) during the late hyperalgesic phase. (R,S)-alpha-M-SOP (70 nmol/mouse), a selective antagonist of group III mGluRs, completely antagonized the L-SOP-induced effect. These results show that PAG mGluRs participate in modulating the late hyperalgesic behaviours induced by formalin. It seems, therefore, possible that group I and group II mGluRs positively modulate PAG antinociceptive descending pathway following a persistent noxious stimulation, while group III mGluRs modulate it negatively.

Animals↗
PubMed1999

Periaqueductal gray matter glutamate and GABA decrease following subcutaneous formalin injection in rat.

Glutamate and GABA are important nociception modulating transmitters in specific brain regions, i.e. the spinal cord, the thalamic nuclei and the periaqueductal gray (PAG). However, quantitative and topographical changes in glutamate and GABA release in these brain regions during peripheral inflammation episodes have not been characterized in awake animals. To address this issue, an in vivo microdialysis study was carried out in freely moving rats in order to analyze PAG extracellular glutamate and GABA concentrations following unilateral formalin injection into the dorsal skin of the right hind-paw. Both glutamate and GABA release decreased after the injection of formalin during phase I and phase II of hyperalgesia. Because naloxone prevented the decrease of GABA and glutamate release induced by formalin, this study shows that, in vivo, a nociceptive stimulation may activate opioidergic fibres into the PAG. The increased release of endogenous opioids may, in turn, inhibit the activity of the GABAergic neurons (i.e. opioid disinhibition). Formalin injection also decreased extracellular glutamate concentration. However, we found that intra-PAG perfusion with tetrodotoxin only decreased GABA, but not glutamate dialysate values. Although it should be reasonable to speculate that opioids also inhibit glutamate fibres, further investigation is needed to clarify whether or not the dialysate glutamate we measured reflects change in the metabolism or neurotransmitter pool of this amino acid.

Analysis of Variance↗
PubMed1998

Role of vasopressin on excitatory amino acids mediated pressor responses in the periaqueductal gray area.

In order to evaluate the role played by vasopressin on pressor responses elicited by stimulation of the periaqueductal gray (PAG) area by excitatory amino acids we carried out in vivo studies in genetically vasopressin deficient rats (Brattleboro). Microinjections of 1-glutamic acid (glutamate, 0.6 to 60 nmol/rat) or N-methyl-d-aspartic acid (NMDA, 0.07 to 7 nmol/rat) into the PAG area of freely moving Brattleboro rats induced increases of arterial blood pressure values significantly lower than those obtained in Long Evans rats (control) (glutamate in Brattleboro rats: from +2+/-1 mmHg to 16+/-3 mmHg; glutamate in Long Evans rats: from +16+/-2 mmHg to +36+/-4 mmHg; NMDA in Brattleboro rats: from +5+/-2 mmHg to +34 +/-8 mmHg; NMDA in Long Evans rats: from +18+/-7 mmHg to 80+/-9 mmHg; n=5). Similarly, in anaesthetized Brattleboro rats (urethane 1.2 g/kg i.p.) pressor responses to NMDA microinjections (0.7 nmol/rat) into the PAG area were significantly lower than in Long Evans rats (controls) (+15+/-3 mmHg vs +24+/-4 mmHg). In Long Evans rats NMDA injection also reversed blood pressure decrease induced by ganglionic blocker, hexamethonium and/or losartan (3 mg/kg i.v.), an AT1 receptor antagonist. In Brattleboro rats, NMDA injection did not reverse blood pressure decreases induced by hexamethonium (5 mg/kg i.v.). Moreover, hexamethonium induced blood pressure decrease was not reversed by acetylcholine injection (137 nmol/rat) into the PAG area of anaesthetized Long Evans rats, but if injected before hexamethonium, acetylcholine was able to increase blood pressure (+25+/-3 mmHg). Our results document: i) the importance of the PAG area in the control of cardiovascular system; ii) the involvement of excitatory amino acids in the neural control of vasopressin release; iii) the close relationship between glutamate and vasopressin in the central blood pressure regulation.

Acetylcholine↗
PubMed1998

Questionable validity of 'dissociative amnesia' in trauma victims. Evidence from prospective studies.

BACKGROUND: We reviewed evidence from prospective studies to test whether individuals can develop amnesia for traumatic experiences, a process variously termed 'repression', 'dissociative amnesia' or 'psychogenic amnesia'. METHOD: Using specified criteria, we selected and analysed studies which prospectively assessed memory in victims of documented traumatic experiences. RESULTS: In studies in which people were asked directly about a past traumatic experience, they consistently reported memories. Non-reporting occurred only in studies where subjects were not asked directly about the experience. This latter design leaves open the well-documented possibility that subjects simply did not disclose events that they actually remembered. Some prospective studies were also limited by incomplete documentation of trauma and failure to rule out other more ordinary causes of amnesia. CONCLUSIONS: Prospective data as yet fail to demonstrate that individuals can develop dissociative amnesia for traumatic events.

Adult↗
PubMed1997

Ion Adsorption and Agglomeration Mechanism in Si3N4/H2O(l) Dispersions Compatible with Thermodynamical Stability

Adsorption isotherms from aqueous liquid phase of H+ and/or OH- ions onto Si3N4 solid surface agglomerates have been derived through titration measurements (Beruto et al., J. Chem. Soc., Faraday Trans. 91(2), 323 (1995)). The isotherms exhibit S-shape and can be fitted with Freundlich as well as with Langmuir type isotherms. In order to explain the agglomeration process based on the decrease of total solid-liquid interfacial energy, a model (ISD) has been developed. The agreement between numerical data derived by this model and the experimental data is quite good. Isotherm equation and agglomeration law should obey also the dispersion thermodynamic stability criterion. This condition yields an extra equation to select the pair of functions, thus providing a criterion to choose between the several equations that fit adsorption and agglomeration data fairly well. The solution of the problem mentioned above, from the mathematical point of view, is based on the Dini implicit function theorem (Mezzasalma and Oliva, Appl. Math. Lett., submitted). The results indicate that Van der Waals adsorption isotherm coupled with the ISD model are compatible with the thermodynamic stability of the aqueous Si3N4 dispersions.

Journal Article↗
PubMed1997

Very long-term users of marijuana in the United States: a pilot study.

The authors recruited a sample of 37 Americans, aged 30-74, who had smoked marijuana on at least 5,000 separate occasions. These subjects were found to span a wide range of ethnic groups, educational backgrounds, occupations, and annual income; they did not display any obvious features which distinguished them from the population as a whole. They typically began smoking in the 1960s or early 1970s, and then continued to smoke heavily into middle adulthood because they felt that marijuana relieved unpleasant feeling states such as anxiety or depression. To our knowledge, individuals of this type have not previously been examined; further studies of older, long-term American marijuana users are needed.

Adult↗
PubMed1995

Fat-free mass index in users and nonusers of anabolic-androgenic steroids.

We calculated fat-free mass index (FFMI) in a sample of 157 male athletes, comprising 83 users of anabolic-androgenic steroids and 74 nonusers. FFMI is defined by the formula (fat-free body mass in kg) x (height in meters)-2. We then added a slight correction of 6.3 x (1.80 m - height) to normalize these values to the height of a 1.8-m man. The normalized FFMI values of athletes who had not used steroids extended up to a well-defined limit of 25.0. Similarly, a sample of 20 Mr. America winners from the presteroid era (1939-1959), for whom we estimated the normalized FFMI, had a mean FFMI of 25.4. By contrast, the FFMI of many of the steroid users in our sample easily exceeded 25.0, and that of some even exceeded 30. Thus, although these findings must be regarded as preliminary, it appears that FFMI may represent a useful initial measure to screen for possible steroid abuse, especially in athletic, medical, or forensic situations in which individuals may attempt to deny such behavior.

Adipose Tissue↗