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Biomedical subjects

A Mari

Publications and source records attributed to A Mari.

At least 91 records · Page 5Linked to original sources
PubMed1993

Circulatory models of intact-body kinetics and their relationship with compartmental and non-compartmental analysis.

Circulatory models for interpreting the kinetics of substances in vivo explain the kinetics of the intact body with the concepts of organ kinetics. In this paper, it is first shown that classical organ kinetic analysis is incomplete for metabolized substances, and an appropriate extension is developed. It is then discussed how the concepts of the extended organ kinetic analysis apply to circulatory models. At an organ level, it is shown that two impulse responses are necessary to characterize the organ, one relating influx and outflux, and one relating influx and uptake. The consideration of the inlet-uptake path is of fundamental importance for a correct calculation of the organ volume. It is demonstrated that the total volume is the sum of two components, the first related to the inlet-outlet path, the second to the inlet-uptake path. The first term is computable without assumptions, while the second is model-dependent. Analogous results hold at a total-body level. The relationships between circulatory models and compartmental and non-compartmental analysis are also precisely established. The significance of the non-compartmental estimate of the distribution volume is clarified. The usual strategy of compartmental modeling by which losses are placed in peripheral compartments according to a correspondence between tissues and compartments is shown to be misleading. An example concerning glucose kinetics is given. In conclusion, this paper shows that many of the dominating paradigms of organ and total-body kinetic analysis must be revised.

Humans↗
PubMed1993

Interrelations between electrical and biochemical processes in ischemic porcine livers at low temperature.

Recently it has been shown that during liver ischemia at 25 degrees C the presence of glycogen, by supporting glycolytic supply, not only retards ATP decay but also leads to a corresponding delay of the rise of the electrical impedance of the ischemic organ. A sudden rise of impedance during ischemia is supposed to indicate the closure of gap junctions. Although similar effects on energy state do exist at low temperature, the impact of glycogen on the electrical impedance under storage conditions has still to be evaluated. Therefore, in a model with protected porcine livers, we examined the intraischemic effects of a preischemic glucose and potassium feeding on impedance changes, lactate production and ATP-content at a storing temperature of 5 degrees C. Impedance was measured both in the low frequency alpha- and the higher frequency beta-dispersion range. In addition, the same parameters were determined in a group of unprotected livers. In this group all animals had received glucose and potassium orally prior to ischemia. Whereas in case of preischemic glucose feeding the rise of impedance in the range of the beta-dispersion (e.g. 5kHz) roughly coincided with the exhaustion of ATP, the corresponding impedance changes in the protected group without a glucose premedication only occurred when glycolysis had already stopped and ATP had reached basal values for some hours. In contrast, in the alpha-dispersion range the impedance changes in the latter group just began at the time when ATP became exhausted and lactate production ceased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1992

[Reconstruction of the mandible using a vascularized graft from the iliac bone].

Twelve vascularized iliac crest free-tissue transfers were used for oromandibular reconstruction, 2 as osteocutaneous and 10 as osseous flaps. Two patients had preoperative radiotherapy. Nine of the 12 reconstruction were carried out primarily, following radical surgery for oral cancer. One graft was lost by venous thrombosis. Evidence of bone union was noted in 11 patients, and no pseudoarthrosis was observed. The main advantage of this method is the availability of a large bloc of living composite tissue and both the functional and cosmetic results should be improved in patients undergoing resection of the anterior part of the mandible.

Bone Transplantation↗
PubMed1992

The radial forearm flap in intraoral reconstruction after a pull-through operation.

Free fasciocutaneous forearm flaps, based on the radial artery, were used to replace the tissue defect caused by pull-through operations for cancer of the floor of the mouth in 11 patients. There was no total or partial flap failure. The greatest advantage of the method is that restriction of the tongue movement is less when compared with the results of other methods. The thin forearm flaps are adaptable and pliable. The newly developed lower alveolar crest and the sublingual sulcus make prosthetic rehabilitation possible.

Adult↗
PubMed1992

Estimation of the rate of appearance in the non-steady state with a two-compartment model.

A simple tracer-based method for calculating the rate of appearance of endogenous substances in the non-steady state, free from the inconsistencies of Steele's equation, is still lacking. This paper presents a method based on a two-compartment model by which the rate of appearance can be calculated with only a modest increase in complexity over Steele's approach. An equation is developed where the rate of appearance is expressed as a sum of three terms: a steady-state term, a term for the first compartment, and a term for the second compartment. The formula employs three parameters and makes the relationship between rate of appearance and specific activity changes explicit. An equation is also provided for estimating the error of the method in each individual run. The algorithm can be implemented with a spreadsheet on a personal computer. Simulated and experimental data obtained by the hyperinsulinemic euglycemic glucose clamp technique were used as a test. The accuracy with which the time course of glucose production could be reconstructed was clearly better than that using Steele's equation. Marked negative values for endogenous glucose output were calculated with Steele's equation but not with the new method. The characteristics of generality, simplicity, and accuracy and the availability of an error estimate make this new method suitable for routine application to non-steady-state tracer analysis.

Algorithms↗
PubMed1991

[Use of an osteo-musculo-cutaneous flap from the trapezius muscle for the immediate restoration of a mandibular defect following surgery for cancer of the oral cavity].

The authors state their experiences using trapezius osteomusculocutaneous flaps in 22 clinical patients for primary reconstruction of mandibular defects. The additional investigative study examines the anatomy of 100 osteomusculocutaneous flaps in 50 fresh cadavers. 78 percent of the major vascular pedicle arose form the thyreocervical trunk. The advantages of this method are as follows: 1. This flap provides a well-vascularized bone graft; 2. The operation comparing to other bone grafting methods is simple; 3. After radical neck dissection the trapeziu muscle protects the carotid artery; 4. The vascularized bone graft can be used after irradiation; 5 Good functional and esthetic results can be obtained.

Adult↗
PubMed1991

Influence of tissue acidification and halothane anesthesia on hepatic electrical and biochemical properties during ischemia.

In order to further corroborate the recent findings on liver ischemia after perfusion with solutions containing an additive of heptanol, that the intraischemic loss of cell-to-cell communication in protected livers can be detected by electrical impedance measurement (1), we tried to induce uncoupling in porcine liver by tissue acidification applying acidified protective solutions. Moreover, the effects of preischemic inhaling of high concentrations of the decoupling anesthetic halothane were examined in unprotected ischemic livers (2-5). Electrical impedance, biochemical analyses, and pH measurements were applied in parallel. In addition, typical time courses of impedance parameters of unprotected liver and skeletal muscle were compared, because the latter is devoid of gap junctions. In spite of overlapping side-effects of the respective uncoupling measure, the results suggest that the loss of cell-to-cell communication in the liver is associated with measureable effects on the electrical impedance.

Acid-Base Equilibrium↗
PubMed1990

Heptanol effects on protected livers.

Heptanol, an agent known for inducing closure of gap junctions in a variety of organs, was used to evaluate the influence of uncoupling on the electrical impedance of livers during ischemia. Heptanol was added to a modified HTK solution or to Belzer's UW-CSS solution. Livers of swine were then perfused for 8 min with either one of the solutions containing heptanol or a solution devoid of this additive. During the following ischemia the phase angle of impedance at 5 kHz, pH and different biochemical parameters were determined. Heptanol fundamentally changed the time course of impedance and made the otherwise characteristic fast increase of the phase angle of impedance disappear. Already early during ischemia the phase angle was raised in a dose-dependent manner up to even highest values at the beginning of the whole observation period in case of a fully developed effect. Heptanol also stimulated anaerobic energy turnover. The results suggest that, besides unspecific effects, heptanol induces uncoupling which is detectable by electrical impedance measurement.

Alcohols↗
PubMed1989

T cell responses to a Parietaria judaica pollen extract: comparison between Parietaria-sensitive patients, other atopics and healthy controls.

We investigated the in vitro proliferation of peripheral blood mononuclear cells (PBMC) from Parietaria-allergic subjects, atopic patients with other sensitizations and healthy controls to Parietaria judaica pollen extracts. PBMC from almost all 44 subjects, divided into five groups (Parietaria-, grass-, Parietaria and grass-, Dermatophagoides-sensitive patients and normal individuals) were able to proliferate in response to the extract without statistically significant differences between groups. Mean values of the stimulation indexes for the five groups were respectively: 10.73, 3.18, 5.50, 10,56, 9.28. The results of separation experiments showed that the responding cells were T lymphocytes. Mitogenic effect of the Parietaria pollen extract was excluded by the absence of proliferative PBMC response from cord blood of seven newborns. These results indicate that Parietaria-sensitive, other atopics and normal individuals have Parietaria-specific T cells able to proliferate in vitro to Parietaria allergens.

Cell Separation↗
PubMed1989

[The condition of the permanent teeth of students 15 to 17 years of age in secondary schools in Csongrád County].

The teeth of altogether 1253 students studying in 38 secondary educational establishments of the County of Csongrád have been examined. The number of the examined amounts in case of the 15 years old to 13.51% and in case of the 17 years old to 8.8% of the total number of youth of similar age living in the County. The caries frequency is 98.95% at the age of 15 years, and 98.78% at the age of 17 years. The DMF-T index is 10.35 for the 15 years old, and 10.93 for the 17 years old. With respect to the DMF-T indices found with people of the same year in Szeged in 1961 the present data are higher by 39.11% (15 years old) and by 29.66% (17 years old), respectively.

Adolescent↗
PubMed1988

Identification and description of low-molecular weight chemicals inducing hypersensitivity in man.

The purpose of this study is to compose a list of allergenic chemicals. Each chemical is described in a monograph. The objective of such a monograph program is to collect from the international scientific literature available relevant experimental, chemical, and epidemiological data on chemicals to which humans are known to be exposed and sensitized. A list of 721 chemicals, with related synonyms and trade names, that induce allergic responses and hypersensitivities was prepared. The chemicals were selected on the basis of evidence of human exposure and sensitization. Each monograph contains several data considered relevant to the evaluation of the sensitizing hazards of chemical substances. The data are divided in three sections: chemical identity, sensitizing power, and occurrence. All the data contained in the monographs along with the references and the synonyms are stored in a database application computer program. Preliminary results of 308 of 721 monographs analyzed are reported.

Allergens↗