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Biomedical subjects

M Castagneto

Publications and source records attributed to M Castagneto.

At least 91 records · Page 5Linked to original sources
PubMed1994

Immunomicroscopical localization of human preformed natural antibodies against pig tissues in xenogeneic transplantation.

The targets of preformed natural antibodies need to be identified whenever the use of pig organs is considered for human transplantation. In this study we used extracorporeal perfusion of pig organs with human blood, immunocytological techniques and immuno-electron microscopy to identify the targets and the nature of human preformed natural antibodies against pig antigens. The antibodies were found to be mainly of the IgG and IgM type and directed not only against endothelial cells, but also against mesenchymal and epithelial structures. To reproduce an in vivo situation, a Bio-pump was used to xenoperfuse pig kidneys and livers with human fresh oxygenated blood at 37 degrees C, drawn from polycythaemic patients. Biopsies showed a deposition of human IgG and IgM on tubuli and glomeruli of pig kidneys and on endothelial cells of pig livers. Preperfusion of pig liver with human blood for 45 minutes before perfusion of kidneys significantly reduced the deposition of the natural antibodies.

Animals↗
PubMed1994

PC-based differential model fitting as a support for clinical research.

A PC-based minimisation software written in C-language is described, which solves numerically both simple non-linear regression problems and problems expressed as systems of (unsolved) initial-value ordinary or partial differential equations. The software uses second-order iterated Runge-Kutta algorithm to approximate numerically the solution curves. It uses a quasi-Newton algorithm to minimize either sums of squares (weighted or unweighted) or NONMEM loss functions. Inverse Hessian approximation to the parameter dispersion and Monte Carlo generation of artificial samples are offered to test the robustness of the parameter values obtained. A real test problem is described, involving the hydrolysation of plasma Medium Chain Triglycerides to Free Fatty Acids and the uptake of these from plasma. Two competing models were evaluated, one involving linear terms for each transfer and one involving carrier-mediated, rate-limited hydrolysis and tissue absorption steps. The simpler linear model was found to be more robust and eventually used to describe the experimental data.

Algorithms↗
PubMed1994

Glucose-induced thermogenesis in postobese women who have undergone biliopancreatic diversion.

We evaluated the metabolic response to a standard (75-g) oral-glucose-tolerance test (OGTT) in eight post-obese women (PO) who underwent biliopancreatic diversion and in eight healthy control women (C). All subjects had been weight-stable for > or = 2 y. Blood samples for glucose, insulin, C-peptide, and nonesterified free fatty acids were taken at baseline and during 180 min after the glucose load. Plasma glucose and insulin concentrations at baseline and during the OGTT were similar in the two groups, suggesting the absence of an insulin-resistant state in the PO. Continuous indirect calorimetry was performed throughout the test. Glucose-induced thermogenesis (GIT) was higher in PO than in C (8.6 +/- 2.6 vs 4.3 +/- 1.9%; P < 0.01). These data indicate that GIT and insulin-glucose metabolism are not impaired in postobese patients when a near ideal body weight is reached and maintained after weight loss; this suggests that thermogenic deficiencies and hyperinsulinemia-insulin resistance are alterations secondary to obesity.

Adult↗
PubMed1994

Pulmonary gas exchange during orthotopic liver transplantation.

The aim of this study was to evaluate the efficiency of pulmonary gas exchange during the course of liver transplantation. We studied 25 adult cirrhotic patients undergoing transplantation, performed with venovenous bypass. A significant increase in PaO2, and a significant decrease in physiological shunt and alveolar-arterial partial pressure difference were observed just before the start of venovenous bypass. These changes were probably caused by modifications in respiratory mechanics, such as an increase in functional residual capacity. There were no other respiratory changes during the anhepatic and post-anhepatic phases.

Adolescent↗
PubMed1994

Normalization of Insulin Sensitivity in the Obese Patient after Stable Weight Reduction with Biliopancreatic Diversion.

Insulin resistance is a common feature in obese patients. To evaluate the modifications in insulin sensitivity after a bariatric operation such as Bilio-pancreatic diversion (BPD), three groups of subjects (14 normal controls (N); seven ex-obese patients (X) with at least 2 years at weight-stable conditions after BPD surgery; and eight morbidly obese patients (0)) were studied with intravenous (IVGTT) and oral (OGTT) glucose tolerance tests. The ratio of the area under the curve (AUC) for glucose over that of insulin was used as a measure of insulin sensitivity. All the following tests were conducted as Bonferroni-corrected pairwise t-tests, in case overall ANOVA was significant. No significant difference was found between N and X subjects, while obese patients showed a reduced AUCg/AUCI ratio with respect to the normal controls (O vs N: 0.01164 +/- 0.00039 vs 0.02392 +/- 0.0039, p < 0.05). IVGTT, AUCS: significant differences were found in each case: N vs X: 0.0591 +/- 0.0075 vs 0.1402 +/- 0.0399, p < 0.05; N vs 0:0.0591 +/- 0.0075 vs 0.0223 +/- 0.0031, p < 0.01; X vs 0:0.1402 +/- 0.0399 vs 0.0223 +/- 0.0031, p < 0.05. IVGTT-derived data were also analyzed using the minimal model of glucose kinetics; with this method, glucose effectiveness was significantly different between normal subject and obese subjects (0.0248 +/- 0.00288 Vs 0.00906 +/- 0.00135 per min, p < 0.001). The insulin sensitivity index was not significantly different between normal and ex-obese subjects, while both of these groups were significantly different from obese patients (N vs 0: 12.04 x 10&sup5; +/- 2.61 x 10&sup5; vs 3.29 x 10&sup5; +/- 0.61 x 10&sup5;, p < 0.066; X vs 0: 16.42 x 10&sup5; +/- 4.23 x 10&sup5; vs 3.29 x 10(1)+/- 0.61 x 10&sup5; per min per pM, p < 0.02). In conclusion, the present study indicates that, after a body weight reduction operation capable of almost re-establishing ideal body weight like BPD, obese individuals with a family history of obesity show a normalization of insulin response to glucose load.

Journal Article↗
PubMed1994

Reference values for respiratory rate in the first 3 years of life.

BACKGROUND: Raised respiratory rate is a useful sign to diagnose lower respiratory infections in childhood. However, the normal range for respiratory rate has not been defined in a proper, large sample. OBJECTIVE: To assess the respiratory rate in a large number of infants and young children in order to construct percentile curves by age; to determine the repeatability to the assessment using a stethoscope and compare it with observation. METHODS: Respiratory rate was recorded for 1 minute with a stethoscope in 618 infants and children, aged 15 days to 3 years old, without respiratory infections or any other severe disease when awake and calm and when asleep. In 50 subjects we compared respiratory rate taken 30 to 60 minutes apart to assess repeatability, and in 50 others we compared simultaneous counts obtained by stethoscope versus observation. RESULTS: Repeatability was good as the standard deviation of differences was 2.5 breaths/minute in awake and 1.7 breaths/minute in asleep children. Respiratory rate obtained with a stethoscope was systematically higher than that obtained by observation (mean difference 2.6 breaths/minute in awake and 1.8 breaths/minute in asleep children; P = .015 and P < .001, respectively). A decrease in respiratory rate with age was seen for both states, and it was faster in the first few months of life when also a greater dispersion of values was observed. A second degree polynomial curve accurately fitted the data. Reference percentile values were developed from these data. CONCLUSIONS: The repeatability of respiratory rate measured with a stethoscope was good. Percentile curves would be particularly helpful in the first months of life when the decline in respiratory rate is very rapid and prevents to use cut off values for defining "normality."

Aging↗
PubMed1994

[The choice of substrates in total parenteral nutrition].

This review contains a full outline on the choice of substrates in total parenteral nutrition (NPT). The basic properties of "conventional" substrates (glucose, long chain triglyceride-containing fat, common amino acid mixtures) are used to outline the general principles for NPT support in normal conditions and in stress (surgical and nonsurgical trauma, sepsis). Without taking into account factors which are not strictly metabolic (vascular access, local availability of products, costs), particular attention is then paid to "non-conventional" substrates and substrate mixtures, including some under study, with specific reference to properties and features which may motivate their choice.

Amino Acids↗
PubMed1993

Enzymatic determinations in acute rejection after liver transplantation: preliminary report on necrosis index.

The catalytic activities of some mitochondrial and cytoplasmic enzymes were measured in plasma from 19 patients after orthotopic liver transplantation, in order to detect and monitor the evolution of hepatocellular damage and to predict liver rejection. The enzymatic activities determined were: mitochondrial isoenzyme of aspartate aminotransferase, glutamate dehydrogenase, alanine aminotransferase, aspartate aminotransferase, gamma-glutamyltranspeptidase and alkaline phosphatase. The results of all enzymatic activities were normalized by expressing them as multiples of the upper limit of the relevant reference range and then the necrosis index (NI) has been calculated. The proposed NI consists of percent ratio of the normalized mitochondrial enzymatic activities over the sum of cytoplasmic and mitochondrial normalized activities. We observed that NI values higher than 30% correctly identified all but two acute rejection events which were documented by liver biopsies showing a diagnostic sensitivity of 90%, specificity of 78% and a predictive value of 90%.

Adult↗
PubMed1993

A rapid GLC method for the direct analysis of plasma medium chain fatty acids.

A new, rapid, gas-liquid-chromatographic (GLC) method for the direct determination of plasma medium-chain fatty acids (MCFA) (from C8 to C12) which does not require derivatization procedures is described. Analysis of underivatized MCFA by GLC showed a detection limit ranging from 0.50 to 0.217 microgram depending on chain length: the longer the chain, the higher the detection limit. Compared with the HPLC and GLC methods currently described in the literature, this GLC procedure appears to be easy, adequately sensitive, accurate and well reproducible for those MCFA, like n-octanoic and n-decanoic acids, present in plasma after p.o. or i.v. MCT administration and it requires a short time (about 30 min) for complete processing.

Adult↗
PubMed1993

Hydra: a C-language environment for real-time DOS multitasking at the bedside.

Patient monitoring at the bedside is an inherently parallel job, best handled by multiple individual tasks running concurrently. Cost and diffusion considerations strongly favor the use of PC's at the bedside, but their most widespread operating system, DOS, is not built for multitasking. Hence, a software platform in C language has been prepared, allowing the intermediate programmer to easily write independent modules which will then run simultaneously without conflicts. Such a platform aims at allowing effortless sharing of data among concurrently running processes, while providing strong insulation between tasks, enough to allow multiple copies of any one task to run simultaneously unknown to each other. A cooperative, memory sharing multitasking paradigm has been chosen, which offers fine granularity of timeslicing and low execution overhead at the price of some loss in generality of design. Speed, data exchange capability and number of stackable windows are greater than with commercial packages like Windows or LabWindows. Dynamical reprioritization of tasks is built in, allowing the computerized monitor to focus its attention and resources on urgent tasks.

Algorithms↗
PubMed1993

Calculation of venoarterial CO2 concentration difference.

Quantitative relationships in CO2 transport and exchange processes were combined for use as the basic components of an original mathematical model for the calculation of venoarterial blood CO2 concentration difference (v-aDCO2). This is calculated as the sum of the increment in CO2 concentration (CCO2) related to the increase in CO2 tension (delta P) from arterial to venous value at constant O2 saturation (delta CCO2/delta P) and of the increment in CO2 concentration related to the decrease in O2 saturation (delta S) from arterial to venous value at constant CO2 tension (delta CCO2/delta S). The newly developed relationships correlated well with the experimental data from which they were derived (r2 = 0.94-0.99). The results provided by the model compared remarkably well with the results of previously published measurements (r2 = 0.96-0.99). This new model allows one to overcome some of the limitations implicit in previously available methods and provides a useful tool for the assessment and monitoring of hemodynamic, metabolic, and O2-CO2 exchange patterns in whole body and regional vascular beds.

Arteries↗