Fluidodynamic evaluation of arteriovenous fistulae for hemodialysis.

Arteriovenous fistulae (AVF) are commonly used in dialysis treatment of uremic patients. However, many AVF create problems and have to be re-examined. Problems arise in the cannulation site and must be treated with antibiotics, and stenosis, both in the arterial and in the venous side of the AVF. In the worst case, the AVF must be replaced for treatment to continue. However, this can only be repeated once before the AVF site is no longer viable. This increases the discomfort, the morbidity and the mortality of the dialysis patient. Several kinds of AVF were studied to determine whether flow disturbances give rise to these complications. Many studies have already demonstrated the importance of hemodynamic factors in vascular disease pathogenesis. These factors include: the pulsatility of flow, the elasticity of the vessel, the non-Newtonian blood, flow behavior and, very importantly for AVF, the vessel geometry. In model studies, intimal changes have been observed in bends and bifurcations, regions of vessel construction and vessel stenosis. In these regions, blood flow changes abruptly and this contributes to arterial disease. We prepared several one-to-one, true-to-scale elastic silicon rubber models of different AVF. The AVF models were based on angiographic studies of chronic dialysis patients and on AVF from the arms of cadavers. The models had a similar compliance to that of the human blood vessel. Flow was visualized using photoelasticity apparatus and a birefringent blood-like fluid. This method is suitable to analyze the spatial configuration of flow profiles, to differentiate laminar flow from disturbed flow, and to visualize flow separation, vortex formation and secondary flow. It was found that AVF create disturbances that are not found under normal physiological flow conditions. The X-formed AVF was very unsatisfactory, creating significant flow disturbances. The AVF had high velocity fluctuations. These could lead, for example, to aneurysm formation. A better configuration would be an end-to-end AVF. However, this formation creates other complications. For example, there is not enough blood to the hand and parts of the hand lose feeling. The recommended AVF would be an end-to-side anastomosis. In this case, attention is needed for placement geometry, to minimize additional flow disturbances. Several models as well as patient angiographic studies are discussed.

Computerized detection of clustered microcalcifications: a modular approach with non-linear filters.

The ideal computerized mammogram processing system still needs to be developed. In order to achieve maximum flexibility we suggest a modular scheme, dividing the processing sequence into functionally autonomous modules. This paper provides a general scheme for detection and/or automated recognition of microcalcifications. Some modules that perform ROI selection are introduced, using special non-linear filters designed for microcalcification detection. A first type of filter selects pixels with specific statistical local features, as compared to the local mean. Among these, only pixels satisfying particular constraints on the local standard deviation are kept. Another type of filter then checks the local mean values of gradient components, so that sharp variations, unrelated to small close objects, can be eliminated. The scheme thus applies different non-linear filters in combination, making precise identification of clustered microcalcifications possible. This modular approach seems greatly to simplify system maintenance and consistency, as well as affording a comparison of different processing techniques and parameters.

Air pollution and daily mortality in Rome, Italy.

OBJECTIVES: To assess the relation between several daily indicators of air pollution (particulates and gases) and daily mortality in the metropolitan area of Rome and in the central part of the city. METHODS: Time series analysis. The associations between daily concentrations of pollutants (particles, SO2, NO2, CO, O3) recorded by five fixed monitors and daily total mortality in the period from January 1992 to June 1995 were evaluated. The analysis included examination of the pollution effect on mortality by place of residence within the metropolitan area, by season, age, place of death (in and out a hospital), and cause of death (cardiovascular and respiratory disease). The Poisson model included loses smooth functions of the day of study, mean temperature, mean humidity, and indicator variables for day of the week and holidays. RESULTS: The mean daily number of deaths was 56.9 (44.8 among people > or = 65 years old). A mean of 36.3 deaths occurred in the city centre; 37.3 deaths a day were recorded in a hospital. Total mortality was significantly associated with a 10 micrograms/m3 increase in particles (0.4%) on that day (log 0), and with a 10 micrograms/m3 increase in NO2 at lag 1 (0.3%) and lag 2 (0.4%) (1 and 2 days before, respectively). The effect of particles (lag 0) and of NO2 (lag 2) on total mortality was higher among those living in the city centre (0.7% and 0.5%, respectively). The risk estimates were higher in the warmer season (1.0% and 1.1%, respectively), whereas no difference was found for those dying in or out of the hospital. The effect of particles was robust to a sensitivity analysis and to the inclusion of NO2 in the regression model. CONCLUSIONS: Increase in particulates and NO2, generated by the same mobile combustion sources, is associated with a short term increase in mortality in Rome. The effect is more evident among residents in the city centre, where the levels of exposure to pollutants recorded by fixed monitors are probably more reliable indicators of personal exposure.

Mechanical effects of heart pulse propagation on a vessel-graft suture line stress.

The effects of vessel joint where the both sides have different wall properties on the heart pulse propagation are investigated. Such a local disturbance can influence post-transplantation pathology and evolution of the organ inconsistency. Using a mathematical model, developed in a previous article, we perform analytical analysis and present some qualitative and quantitative estimations. The effects of jointed vessels with different thicknesses and radii on the local concentration of the pressure, radial wall displacement, bending moment and shear force are analyzed in detail. In particular, it is obtained that the bending and shear stresses at a joint sharply and strongly increase in comparison with the uniform vessel ones.

Serum levels of tumour necrosis factor alpha and other cytokines do not correlate with weight loss and anorexia in cancer patients.

Cancer anorexia-cachexia syndrome (CACS), which is characterized by progressive weight loss (WL) and anorexia (A), is present in 50% of advanced cancer patients and in 80% of terminally ill cancer patients. One of the most controversial aspects of CACS is its oetiopathogenesis; experimental studies have identified certain cytokines [Tumour necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1), interleukin 6 (IL-6), and gamma interferon (gamma-IFN)] as possible co-factors in the onset of the syndrome. The aim of our study was to investigate the correlation between serum levels of circulating cytokines and severity of CACS. The following series of parameters was identified in 61 patients with advanced and terminal cancer: stage of disease; Karnofsky performance status (KPS) and clinical symptoms; biohumoral, anthropometric and immunological situation; level of circulating cytokines. All these parameters were evaluated for a possible link with WL/A. Our data do not show any significant correlation between circulating cytokines and WL/A. A direct correlation was identified between WL/A and nausea (P = 0.03 and P < 0.001, respectively) whereas inverse correlations were observed for both factors as regards arm circumference (P < 0.001 for both), wrist circumference (P < 0.001 for both), KPS (P < 0.001 and P = 0.003, respectively) and creatinine (P = 0.005 and P = 0.03, respectively). Other biochemical factors, such as haemoglobin, haematocrit, glycaemia, prealbumin, sodium and chlorine were also correlated with at least one of two clinical parameters in question. Unexpected results were seen in the increases in CD20 and CD4 and in the CD4/CD8 ratio. Serum levels of these cytokines do not, therefore, appear to be critical in the onset of CACS. On the contrary, our findings confirmed the clinico-laboratory picture that is characteristic of CACS. If we consider the possibility that CACS is provoked by an aspecific response of the host's defence mechanisms against prolonged neoplastic attack, the increase in CD4 (helper lymphocytes) could be linked to the persistent response.

Multicentre evaluation of the Bayer DAX system.

The analytical performance of the DAX, a high-throughput random access analyser, was studied according to ECCLS guidelines (ECCLS Document Vol. 3, No. 2, Beuth Verlag, Berlin, 1986) in a multicentre evaluation involving four laboratories. The trial took about 4 months. Determinations of 12 analytes produced more than 60,000 data. The imprecision study on 3 control sera for all analytes gave a within-run CV (median of 4 laboratories) which never exceeded 3% and was below 2% in 94% of the results. The median between-day CV was less than 3% in 92% of the results, with a highest value of 5.0%. No significant drift was detected during the 5-hour work period. No relevant sample- and cuvette-related carry-over was found. The manufacturer's claims concerning linearity were fulfilled or exceeded. The recovery of the assigned values for the control sera (median of 4 laboratories) ranged from 94 to 106%. In the method comparison on patients' samples, deviations were statistically significant in some cases, due to differences either in the methods used or in the calibration of the systems used for comparison; the regression lines, as inspected visually, and the coefficients of correlation were, however, generally acceptable. Imprecision and inaccuracy were within the acceptability limits as recommended by the Société Française de Biologie Clinique (SFBC) (Biochim. Clin. 12 (1988) 284-327) and the Deutsche Gesellschaft für Klinische Chemie (DGKC) (Dt. Arztebl. 85 (11) (1988) A697-A712). The limits of acceptance, proposed more recently by Fraser et al. (Eur. J. Clin. Chem. Clin. Biochem. 30 (1992) 311-317), were met in thirty-three of thirty-six cases. The alpha-amylase assay was significantly affected by bilirubin and haemolysis; interferences for the remaining analytes were predictable and well-known from the literature. The rate of sample throughput was found to be in agreement with that claimed by the manufacturer. The software did not present problems and was readily accepted by the operators. The practicability of the instrument was rated very good. Since the DAX is the primary chemistry analyzer in all four participating laboratories, the present experiments were necessarily intermixed with a large routine workload. Therefore, the system performance was assessed under definitely "usual" conditions. Because of its high productivity and reliability, the DAX is highly suitable for routine use in medium to large sized hospitals.

A physical model for the cardiovascular and the respiratory systems.

We propose a two degrees of freedom oscillating system to simulate the working of both respiratory and cardiovascular apparatus and to investigate the physico-mathematical characteristics of a possible decoupling between the physiological systems. We suppose a double mathematical pendulum with forced and damped oscillations, with the first frequency equal to four times the second one; not only, does the system not give resonance or beatings, but it also simulates with reasonable approximation the ratio between natural relative frequencies. The two Langragian equations, that have form: (formula; see text) cannot be solved in an analytical way, even if we suppose an approximation for little oscillations. Now we are studying another two d-o-f mechanical system, with only one suspension point; we are also studying both the electrical equivalent circuits.

A stochastic process approach to the development of atheroma.

This study aims at formulating a dynamic model of particle sedimentation as applied to lipoprotein deposition during atheroma progression. The basic assumption is that all particles are identical and that the number of sedimented particles is relatively great. It is hypothised that sedimentation of a given particle is random; according to the theory of stochastic processes, the probability of a certain number of particles to sediment or deposit changes with time. The stochastic approach may explain some aspects of atherosclerosis development, i.e. its progression or regression.

Postmenarchal evolution of endocrine pattern and ovarian aspects in adolescents with menstrual irregularities.

Ninety-five adolescents with menstrual irregularities persisting since menarche were studied and the data analyzed in relation to gynecologic age. In each year, in the premenstrual phase, luteinizing hormone (LH), testosterone (T), and androstenedione (delta 4A) values were higher than those of adults. Estrone (E1), estradiol (E2), 17-hydroxyprogesterone (17-OHP), progesterone (P), and dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) gradually increased up to adult values correlating with gynecologic age. By ultrasound, nearly half the ovaries were multicystic and ovarian volume was greater than that of adults in each gynecologic year. When the data were classified as ovulatory or anovulatory, ovulation appeared to be a dynamic process characterized by ovaries similar to those of adults and by increasing hormonal levels correlated to gynecologic age. By contrast, in anovulatory cycles, mean T, delta 4A, and LH values were stable in each year and constantly higher than in ovulatory cycles and adult controls. These findings suggest that, despite persistent irregular cycles, some adolescents normalize all endocrine and ovarian parameters toward maturity, while subjects with persistent irregular anovulatory cycles maintain marked hyperandrogenism, increasingly high LH values, and enlarged multicystic ovaries.

CEA levels in gastric juice in precancerous conditions and cancer.

First described in 1965 as a specific antigen for cancer of the colon, CEA is now considered to be an antigen associated with many types of malignant neoplasia, although the CEA-Test's role in clinical routine has yet to be clearly defined. In the present study CEA levels in gastric juice were measured in subjects with gastric carcinoma (n = 25) and with benign gastric lesions (n = 171). CEA was significantly (p less than 0.05) higher in patients with gastric carcinoma (GC) than in subjects with benign gastric lesions, other than chronic atrophic gastritis (CAG) associated with intestinal metaplasia (IM). In this latter condition CEA levels were similar to those in patients with GC. These results suggest that the assay of CEA in gastric juice could be included in the diagnostic program for gastric cancer and its precursors with the aim of assessing its utility as risk indicator in the management of precancerous conditions and lesion.

Lead levels in whole blood of an adult population group from Rome.

Pb-blood levels of 801 adult non-occupationally exposed subjects from Rome are reported. The investigation was carried out according to EEC Directive No. 77/312 with acceptable quality control of analytical data. A mean Pb-blood level of 173 micrograms/l (198 micrograms/l for males and 150 micrograms/l for females) was found; good correlations were found between Pb-blood levels and age, sex and smoking habits but no correlation was found in relation to drinking habits, residence and other variables which were examined. In the present survey all the three EEC reference levels were observed.

Carotid wall as an isotropic mechanical system.

The morphological organization of the structural components in the dog carotid wall is investigated by X-ray diffraction and microscopic analysis. Histological analysis confirms an anisotropic morphology of smooth muscle cells and elastic fibers in the tissue. Collagen fibers, as revealed by X-ray diffraction technique, are organized in an isotropic network in the unstretched carotid media. Collagen fibers stretch without a preferential direction of orientation when a carotid segment is deformed in the physiological range under intraluminal pressure. A mathematical model which takes into account the isotropic distribution of the collagen fibers is developed. The validity of this model has been tested by computing several mechanical parameters using Anliker's data on the axial and radial oscillation obtained for carotids of living dogs. In spite of the anisotropic morphology of the main constituents of the carotid media layer, from a mechanical point of view the tissue can be considered as an isotropic material for the random distribution of the collagen fibers which represent the component of higher tensile strength.

Total mercury levels in whole blood, hair and fingernails for a population group from Rome and its surroundings.

Whole blood, hair and fingernails of 80 representative subjects from the Province of Rome were analysed for total mercury. The mean value for whole blood was 0.020 mg/kg, for hair 0.51 mg/kg and for nails 1.08 mg/kg. Correlations were found (except for hair) between mercury levels and the number of fish meals, mercury amalgam dental fillings and residence (urban or rural) of the subjects examined. The levels found in hair appear to be influenced by external and individual pollution factors and thus unsuitable for any direct determination of the distribution in other organs of the human body.