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Biomedical subjects

M Giacomini

Publications and source records attributed to M Giacomini.

At least 55 records · Page 3Linked to original sources
PubMed1997

Application of neural networks to the follow-up of AIDS patients.

The present work aims to obtain groups of patients with similar profiles of p24 antigen concentration and of CD4+ cell counts. These two markers were chosen because their evaluation represents a significant step in the clinical follow up of HIV-1 infected subjects. The classifications were obtained by a Kohonen neural net trained in three ways: with p24 antigen profiles only, with CD4+ cell count profiles only and with both sets of profiles. The results show that the clustering fashion of the two parameters closely resembles the clustering fashion of CD4+ only rather than the one of p24Ag, both with reference to cluster formation and with reference to distance among clusters.

Acquired Immunodeficiency Syndrome↗
PubMed1997

An integrated model of sleep regulation.

We present a new model of sleep regulation which integrates the two process model and the limit cycle reciprocal interaction model. In the two process model the interaction of a homeostatic process (S signal) and of a circadian process determines the timing of sleep and waking. In the limit cycle model, the NREM-REM sleep cycle is generated by the reciprocal interaction of two coupled cell population. The present model integrates the two considered models introducing the trigger REM-NREM generated by the REM-ON signal and activated when REM-ON overcomes the S signal.

Cerebral Cortex↗
PubMed1996

Regional cerebral blood flow (rCBF) in migraine during the interictal period: different rCBF patterns in patients with and without aura.

The aim of this study was to evaluate the rCBF (133Xe clearance method) in migrainous patients free from attack. Fifty patients suffering from migraine without aura (group M) and 20 suffering from migraine with aura (group MA) (age range 20-50 years) were submitted to 32 channel rCBF mapping during the interictal period. The rCBF data of patients were compared with those obtained from 60 healthy control subjects (group C) and 21 patients suffering from tension-type headache (group TH). The mean (average of all channels) rCBF values were: group M = 70.5 +/- 13.7 ml/100g/min; group MA = 56.6 +/- 11.4 ml/100g/min; group C = 62.3 +/- 8.3 ml/100g/min; group TH = 62.1 +/- 8.4 ml/100g/min (F = 11.93; p < 0.001). As expected, patients belonging to group TH had a normal rCBF. The mean rCBF of group M was significantly higher than that of groups C and TH, while in group MA it was significantly lower than in groups C and TH. Group M showed a diffuse hyperemia, while group MA showed rCBF values significantly lower than normal in posterior regions, according to aura. Our results suggest that: (a) the rCBF pattern in migrainous patients is different from that in both controls and TH patients, even during the interictal period; (b) patients suffering from migraine with and without aura are two distinct subpopulations with opposite rCBF deviations.

Adult↗
PubMed1996

New ultrathin-walled endotracheal tube with a novel laryngeal seal design. Long-term evaluation in sheep.

BACKGROUND: A new endotracheal tube (ETT) was fabricated and tested in sheep. It had no tracheal cuff; airway seal was achieved at the level of the glottis through a no-pressure seal made of "gills"; the laryngeal portion was oval-shaped; and the wall thickness was reduced to 0.2 mm. METHODS: Sheep were tracheally intubated either with a standard tube or with the new tube, and their lungs were mechanically ventilated for 1 or 3 days. Air leak was recorded at different peak inspiratory pressures (PIPs). Liquid seepage into the trachea was assessed using an indicator dye. Tracheolaryngeal lesions were scored grossly and histologically. RESULTS: There was no air leak up to 40 cmH2O of PIP, in either group, in short- and long-term studies. Methylene blue leaked across the cuff in two sheep with standard ETTs. No dye leaked across the gills with the new ETTs. In the new ETT group, the trachea appeared better preserved, grossly and histologically, than in the standard ETT group at both 1 and 3 days (P < 0.05). At day 1, the larynx and vocal cords appeared grossly less injured in the new ETT group (P < 0.05), whereas there was no difference at day 3. Histology did not show significant difference on vocal cords, epiglottis, and larynx between the two groups at any time. CONCLUSIONS: The novel, no-pressure seal design of the new ETT is highly effective in preventing air leak and aspiration. It causes no significant tracheal injury.

Animals↗
PubMed1996

Automated systems for identification of heterotrophic marine bacteria on the basis of their Fatty Acid composition.

The fatty acid methyl ester composition of a total of 71 marine strains representing the genera Alteromonas, Deleya, Oceanospirillum, and Vibrio was determined by gas-liquid chromatographic analysis. Over 70 different fatty acids were found. The predominant fatty acids were 16:0, 16:1 cis 9, summed-in-feature (SIF) 4 (15:0 iso 2OH and/or 16:1 trans 9) and SIF 7 (18:1 cis 11, 18:1 trans 9, and/or 18:1 trans 6) for all the strains considered, but minor quantitative variations could be used to distinguish the different genera. In addition to a conventional statistical processing method to analyze the data and draw comparison between species and genera, an approach involving neutral network-based elaboration is applied. The statistical analysis and dendrogram representation gave a comparison of the species considered, while the neural network computation provided a more accurate assignment of species to their genera. Moreover, by using neural networks, it was possible to conclude that only 22 fatty acids were important for the identification of the marine genera considered. A database of Alteromonas, Deleya, Oceanospirillum, and Vibrio fatty acid methyl ester profiles was generated and is now routinely used to identify fresh marine isolates.

Journal Article↗
PubMed1996

An object programming based environment for protein secondary structure prediction.

The most frequently used methods for protein secondary structure prediction are empirical statistical methods and rule based methods. A consensus system based on object-oriented programming is presented, which integrates the two approaches with the aim of improving the prediction quality. This system uses an object-oriented knowledge representation based on the concepts of conformation, residue and protein, where the conformation class is the basis, the residue class derives from it and the protein class derives from the residue class. The system has been tested with satisfactory results on several proteins of the Brookhaven Protein Data Bank. Its results have been compared with the results of the most widely used prediction methods, and they show a higher prediction capability and greater stability. Moreover, the system itself provides an index of the reliability of its current prediction. This system can also be regarded as a basis structure for programs of this kind.

Amino Acid Sequence↗
PubMed1995

Risk adjusting community rated health plan premiums: a survey of risk assessment literature and policy applications.

This paper surveys recent health care reform debates and empirical evidence regarding the potential role for risk adjusters in addressing the problem of competitive risk segmentation under capitated financing. We discuss features of health plan markets affecting risk selection, methodological considerations in measuring it, and alternative approaches to financial correction for risk differentials. The appropriate approach to assessing risk differences between health plans depends upon the nature of market risk selection allowed under a given reform scenario. Because per capita costs depend on a health plan's population risk, efficiency, and quality of service, risk adjustment will most strongly promote efficiency in environments with commensurately strong incentives for quality care.

Actuarial Analysis↗
PubMed1995

Alterations of lung and chest wall mechanics in patients with acute lung injury: effects of positive end-expiratory pressure.

In 16 mechanically ventilated patients with acute lung injury (ALI) (eight patients with moderate ALI [moderate group], eight patients with severe ALI [adult respiratory distress syndrome, ARDS group]) and in eight normal anesthetized-paralyzed subjects (control group), we partitioned the total respiratory system mechanics into the lung (L) and chest wall (w) mechanics using the esophageal balloon technique together with the airway occlusion technique during constant flow inflation. We measured lung elastance (Est,L), chest wall elastance (Est,w), and total lung (Rmax, L) and chest wall (Rmax,w) resistance. Rmax,L includes airway (Rmin,L) and "additional" lung resistance (DR,L). DR,L represents the "additional" component due to the viscoelastic phenomena of the lung tissues and time-constant inequalities (pendelluft). Measurements were repeated at 0, 5, and 10 cm H2O of positive end-expiratory pressure (PEEP) in the control group and at 0, 5, 10, and 15 cm H2O PEEP in patients with ALI. The end-expiratory lung volume (EELV) was measured at each level of PEEP. Specific total lung (sRmax,L), airway (sRmin,L), and "additional" lung (sDR,L) resistances were obtained as Rmax,L x EELV, Rmin,L x EELV, and DR,L x EELV, respectively. At PEEP 0 cm H2O, we found that both Est,L (23.7 +/- 5.5 and 13.8 +/- 3.3 versus 9.3 +/- 1.7 cm H2O/L; p < 0.01) and Est,w (13.2 +/- 5.4 and 9.9 +/- 2.1 versus 5.6 +/- 2.3 cm H2O/L; p < 0.01) were markedly increased in patients with ARDS and moderate ALI compared with control subjects, with a significant (p < 0.01) effect of the severity of the disease on Est,L (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1994

A qualitative process theory based model of the HIV-1 virus-cell interaction.

We present a qualitative model of the interaction between the HIV-1 virus and the human cell, based on qualitative process theory. This model takes into account a previous qualitative model of the cell growth. The model presented here can be regarded as a first step for setting up a comprehensive model of the HIV-1 virus-cell interaction in which the possible points where a drug can attack the virus are evident. The first simulation trials indicate that the presented model reproduces (even though in a simplified way) the features of the real behaviour that have been considered in the modelling phase. Although our simulation is limited in the knowledge it expresses, it still gives a stimulating opportunity for the evaluation of the criteria chosen as discriminant in the interaction between virus and cell.

Antiviral Agents↗
PubMed1994

Qualitative reasoning for AIDS treatment.

We present a qualitative model of the interaction between HIV-1 virus and human cell, based on qualitative process theory. This model can be regarded as a first step for setting up a comprehensive model of the HIV 1 infection treatment in which the possible points where a drug can attack the virus are evidentiated. The first simulation trials indicate that the model reproduces the major features of the real behavior of the virus inside and outside the human cell.

Acquired Immunodeficiency Syndrome↗
PubMed1993

A qualitative model of the dynamics of blood glucose and its hormonal control.

A qualitative model of the short term glucose regulation system is presented. The model is based on the qualitative process theory, based on the concept of physical process defined by the property of causing changes in objects over time. The model has been successfully validated on inputs of several tests. It is intended to employ this model within a comprehensive system encompassing qualitative and quantitative aspects of modelling, building an environment useful for new treatment planning and for education.

Blood Glucose↗
PubMed1993

Interpretation of gascromatographic data via artificial neural networks for the classification of marine bacteria.

We propose a new method for classification of marine bacteria. This method uses gaschromatograms, which contain information of fatty acid percentage contents of the fresh isolate. For the interpretation of these gaschromatograms we use a surpervisioned artificial neural network. We present a preliminary study on this matter, whose first results show good convergence and classification features.

Algorithms↗
PubMed1991

A qualitative approach to cell growth modeling and simulation for cancer chemotherapy.

A qualitative model of cell growth, based on qualitative process theory, is presented. The model can be used to analyze the effects of the interaction of antiproliferative drugs on cells when the effects of each specific drug are known, mainly when designing multi-drug protocols for optimal cancer treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Changes in the hypothalamo-corticotrope axis after bilateral adrenalectomy: evidence for a median eminence site of glucocorticoid action.

Bilateral adrenalectomy (ADX) leads to increased ACTH synthesis and secretion. It is thought that endogenous glucocorticoids exert a feedback mechanism at both pituitary and brain levels. The present study has been performed in order to determine the effect of ADX on the release of hypothalamic neuropeptides with corticotropin-releasing activity (CRA) and if there exists a median eminence site of glucocorticoid action to regulate hypothalamic-pituitary-adrenal (HPA) function. Adrenalectomized and sham-operated male rats were killed at different periods after surgery (2, 5, 7 and 14 days) and trunk blood was collected for ACTH and corticosterone (B) concentrations measurement. Brain (median eminence, ME; and medial basal hypothalamus, MBH) and pituitary (anterior lobe, AP; and neurointermediate lobe, NIL) tissues were dissected in order to evaluate either peptide content or in vitro hormone release. The results indicate that ADX blunted plasma B levels and increased AP ACTH content and secretion in a time-related fashion up to the 14th day. ADX significantly decreased both CRF and CRA contents in the ME at all periods studied; ME arginine-vasopressin (AVP) increased 7 and 14 days after ADX. MBH CRF decreased after ADX, but returned to sham value 2 weeks later; similarly, MBH AVP decreased at all periods after ADX. Removal of endogenous glucocorticoids did not vary neither oxytocin (OXY) content in the ME and MBH nor AVP and OXY contents in the NIL. In our superfusion experiments, we found that ADX increased basal AVP release and did not change spontaneous CRF secretion from ME terminals. Dexamethasone (Dxm, 10 nM) diminished AVP but not CRF output by ME tissues from adrenalectomized rats. A direct relationship was found between ME CRF and 28 mM KCl (hK+)-induced CRF release by MEs from adrenalectomized rats. ME fragments from adrenalectomized rats were hyperresponsive to kH+ stimulation of AVP release. Dxm (10 nM) decreased the hK(+)-evoked CRF and AVP release by MEs from adrenalectomized rats. ADX and dexamethasone treatment did not influence basal and hK(+)-elicited ME OXY release. Additionally, a rapid glucocorticoid inhibitory effect on ACTH secretion by isolated AP cells from both sham and adrenalectomized rats was found, and an in vitro corticotrope hyporesponse to 0.63 nM CRF and 9.25 nM AVP stimulation during several days after ADX.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenalectomy↗
PubMed1991

[Problems in emergency visceral reconstruction in colorectal pathology].

A diagnostic-therapeutic protocol for colorectal haemorrhage is suggested. The Authors underline the need to remove inflammatory foci when a perforation of the colon occurs; furthermore, in the acute obstruction due to colorectal carcinoma a resection followed, when possible, by an immediate anastomosis is recommended.

Acute Disease↗