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Biomedical subjects

A Avolio

Publications and source records attributed to A Avolio.

At least 19 recordsLinked to original sources
PubMed2007

In vitro and in vivo tissue repair with laser-activated chitosan adhesive.

BACKGROUND AND OBJECTIVES: Sutures are currently the gold standard for wound closure but they are still unable to seal tissue and may induce scarring or inflammation. Biocompatible glues, based on polysaccharides such as chitosan, are a possible alternative to conventional wound closure. In this study, the adhesion of laser-activated chitosan films is investigated in vitro and in vivo. In particular we examine the effect of varying the laser power, as well as adding a natural cross-linker (genipin) to the adhesive composition. STUDY DESIGN/MATERIALS AND METHODS: Flexible and insoluble strips of chitosan films (surface area approximately 34 mm(2), thickness approximately 20 microm) were bonded to sheep intestine using several laser powers (0, 80, 120, and 160 mW) at 808-nm wavelength. The strength of repaired tissue was tested by a calibrated tensiometer to select the best power. A natural cross-linker (genipin) was also added to the film and the tissue repair strength compared with the strength of plain films. The adhesive was also bonded in vivo to the sciatic nerve of rats and the thermal damage induced by the laser assessed 4 days post-operatively. RESULTS: Chitosan adhesives successfully repaired intestine tissue, attaining a maximum repair strength of 14.7+/-4.3 kPa (n = 30) at the laser power of 120 mW. The chitosan-genipin films achieved lower repair strength (9.1+/-2.9 kPa). The laser caused partial demyelination of axons at the site of operation, but the myelinated axons retained a normal morphology proximally and distally. CONCLUSIONS: The chitosan adhesive effectively bonded to tissue causing only localized thermal damage in vivo, when the appropriate laser parameters were selected.

Animals↗
PubMed2006

Antibiotic prophylaxis in surgery: an observational prospective study conducted in a large teaching hospital in Naples.

This was a 9-month observational prospective study conducted in two steps to evaluate surgical prophylaxis procedures used by surgeons in several departments of the Second University of Naples (SUN). In step 1 (4 months), we collected and analyzed data on surgical interventions and antibiotic prophylaxis. Surgeons were informed of the analysis outcome and were given an antibiotic prophylaxis protocol based on international guidelines. In step 2 (5 months), we collected data on surgical interventions and antibiotic prophylaxis, and compared them with step 1 data. The analysis of 354 forms (step 1) showed that third-generation cephalosporins were the preferred prophylactic antibiotics. The analysis of 369 forms (step 2) showed that ceftriaxone and ampicillin were the most frequently used antibiotics. Surgeons did not comply with guidelines for antibiotic prophylaxis as regards type of antibiotic and treatment duration but implementation of antibiotic prophylaxis protocols resulted in more appropriate and better timing of antibiotic prophylaxis.

Anti-Bacterial Agents↗
PubMed2005

Chitosan adhesive for laser tissue repair: in vitro characterization.

BACKGROUND AND OBJECTIVES: Laser tissue repair usually relies on hemoderivate protein solders, based on serum albumin. These solders have intrinsic limitations that impair their widespread use, such as limited tensile strength of repaired tissue, poor solder solubility, and brittleness prior to laser denaturation. Furthermore, the required activation temperature of albumin solders (between 65 and 70 degrees C) can induce significant thermal damage to tissue. In this study, we report on the design of a new polysaccharide adhesive for tissue repair that overcomes some of the shortcomings of traditional solders. STUDY DESIGN/MATERIALS AND METHODS: Flexible and insoluble strips of chitosan adhesive (elastic modulus approximately 6.8 Mpa, surface area approximately 34 mm2, thickness approximately 20 microm) were bonded onto rectangular sections of sheep intestine using a diode laser (continuous mode, 120 +/- 10 mW, lambda = 808 nm) through a multimode optical fiber with an irradiance of approximately 15 W/cm2. The adhesive was based on chitosan and also included indocyanin green dye (IG). The temperature between tissue and adhesive was measured using a small thermocouple (diameter approximately 0.25 mm) during laser irradiation. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were cultured in extracted media from chitosan adhesive to assess cytotoxicity via cell growth inhibition in a 48 hours period. RESULTS: Chitosan adhesive successfully repaired intestine tissue, achieving a tensile strength of 14.7 +/- 4.7 kPa (mean +/- SD, n = 30) at a temperature of 60-65 degrees C. Media extracted from chitosan adhesive showed negligible toxicity to fibroblast cells under the culture conditions examined here. CONCLUSION: A novel chitosan-based adhesive has been developed, which is insoluble, flexible, and adheres firmly to tissue upon infrared laser activation.

Animals↗
PubMed2005

Interferon-induced depression: prevalence and management.

BACKGROUND: Interferon-induced depression ranges from 0 to 50%. Interferon schedule and a history of psychiatric illnesses are not enough to predict who will develop symptoms and who will not. AIMS: To assess the prevalence of depression during interferon therapy; to test whether Minnesota Multiphasic Personality Inventory is useful in clinical practice for the early identification of patients at risk of depression; whether and how the depression can be cured. PATIENTS: One hundred and eighty-five patients treated with interferon and ribavirin for chronic hepatitis C. METHODS: Before therapy, all patients underwent a Minnesota Multiphasic Personality Inventory and a clinical examination, specifically for the identification of depressive symptoms. RESULTS: Thirty-one patients developed a psychiatric disorder, 11 of them requiring treatment with anti-depressant drugs. Among the 18 patients with Minnesota Multiphasic Personality Inventory positive tests, 16 developed a psychiatric disorder, 8 of them a severe disorder (sensitivity of 0.58; 0.73 for severe disorders). Among the 154 who did not develop psychiatric side effects, 152 had a negative Minnesota Multiphasic Personality Inventory (specificity: 0.99). Severe psychiatric disorders were successfully treated with anti-depressant drugs. CONCLUSIONS: Psychiatric side effects are easy to see during interferon therapy. A psychiatric evaluation should be considered on all patients before treatment. If depression develops, it should be treated aggressively, and selective serotonin re-uptake inhibitors are the anti-depressants of choice.

Adult↗
PubMed2004

Albumin-genipin solder for laser tissue repair.

BACKGROUND: Laser tissue soldering (LTS) is an alternative technique to suturing for tissue repair that avoids foreign body reaction and provides immediate sealing of the wound. One of the major drawbacks of LTS, however, is the weak tensile strength of the solder welds when compared to sutures. In this study, a crosslinking agent of low cytotoxicity was investigated for its ability to enhance the bond strength of albumin solders with sheep intestine. STUDY DESIGN/MATERIALS AND METHODS: Solder strips were welded onto rectangular sections of sheep small intestine using a diode laser. The laser delivered in continuous mode a power of 170 +/- 10 mW at lambda = 808 nm, through a multimode optical fiber (core size = 200 microm) to achieve a dose of 10.8 +/- 0.5 J/mg. The solder thickness and surface area were kept constant throughout the experiment (thickness = 0.15 +/- 0.01 mm, area = 12 +/- 1.2 mm2). The solder was composed of 62% bovine serum albumin (BSA), 0.38% genipin, 0.25% indocyanin green dye (IG), and water. Tissue welding was also performed with a BSA solder without genipin, as a control group. The repaired tissue was tested for tensile strength by a calibrated tensiometer. Murine fibroblasts were also cultured in extracted media from heat-denatured genipin solder to assess cell growth inhibition in a 48 hours period. RESULTS: The tensile strength of the genipin solder was doubled that of the BSA solder (0.21 +/- 0.04 N and 0.11 +/- 0.04 N, respectively; P = 10(-15) unpaired t-test, N = 30). Media extracted from crosslinked genipin solder showed negligible toxicity to fibroblast cells under the culture conditions examined here. CONCLUSION: Addition of a chemical crosslinking agent, such as genipin, significantly increased the tensile strength of adhesive-tissue bonds. A proposed mechanism for this enhanced bond strength is the synergistic action of mechanical adhesion with chemical crosslinking by genipin.

Adhesives↗
PubMed2004

Equipotential earthing study: equipotential wiring is unnecessary.

This study was undertaken to determine the ongoing need for Equipotential (EP) earthing as required in AS/NZS 3003, section 4.4.2. A total of 2279 earth points were tested in four clinical institutions in Body Protected areas (as defined in AS/NZS 3003). Each earth point was tested for potentials existing in the earthing in order to assess whether any potentials exceeded the 100 mV requirement of AS/NZS 3003 for EP earthing. The voltage measured was 1.21 mV +/- 3.59 mV, (mean +/- standard deviation (SD)), with a of 99 % confidence interval between 1.0 mV and 1.4 mV. This study suggests that the requirements for EP earthing in section 4.4.2 of AS/NZS 3003 are unnecessary. It is further suggested that Standards Australia review these requirements with the view of withdrawing them from the Standard.

Humans↗
PubMed2004

Estimation of pressure pulse amplification between aorta and brachial artery using stepwise multiple regression models.

The pressure pulse is amplified between the aorta and peripheral sites. This study compares two methods to estimate pressure pulse amplification (PPA) between the aorta and the brachial artery. Method 1: PPA was determined from a multi-parameter linear regression of subject parameters (gender, age, height, weight, heart rate (HR), brachial systolic pressure (BSP), diastolic pressure (BDP), mean pressure (MP)). Method 2: PPA was calculated from central aortic pressure waveforms (CW) estimated from the same subject parameters. The sample population (1421 male, 992 female) was selected from a database where aortic pressure was estimated by mathematical transformation of a peripheral (radial) pulse calibrated to sphygmomanometric BSP and BDP. The two methods were consistent in showing HR and MP as the most important parameters to estimate PPA. Correlation coefficients (R2) of 0.48 (method 1) and 0.44 (method 2) were obtained using height, weight, HR, BSP, BDP and age. Inclusion of MP increased R2 to 0.77 (method 1) and 0.71 (method 2). This study shows that databases containing peripheral and central aortic pressure waveforms can be used to construct multiple regression models for PPA estimation. These models could be applied to studies of similar subject groups where peripheral waveforms may not be available.

Adult↗
PubMed2001

Peripheral "oscillatory" compliance is associated with aortic augmentation index.

The augmentation index (AIx) and "oscillatory" compliance (C(2)) are wave contour analysis parameters for the central aorta (P(ao)) and radial artery pressure wave (P(rad)), respectively. Both are sensitive to cardiovascular risk factors such as aging, hypertension, and diabetes and have been proposed as prognostic markers for cardiovascular disease. In this work, we studied the relation between both. We first calculated P(rad) corresponding to a typical aortic A-type (AIx >0.15) and C-type wave (AIx <0), taken from the literature, by using a generalized aorta-radial pressure transfer function. P(rad) corresponding to C-type waves yielded the highest C(2) value. We further used simultaneously measured aortic and radial artery pressure in 45 human subjects age 34 to 84 years (63+/-12 [SD]) at baseline and after administration of nitroglycerin to calculate AIx(meas) and C(2), respectively. Transfer function was used to calculate reconstructed aortic pressure and AIx(rec). AIx(rec) underestimates AIx(meas) by 0.03+/-0.16, but both values correlate well (r=0.64; P<0.001). C(2) and AIx were inversely correlated (r=-0.36; P<0.001 for AIx(meas); r=-0.30; P<0.01 for AIx(rec)). Both AIx(meas) (0.06+/-0.17 versus 0.20+/-0.21; P<0.01) and AIx(rec) (0.04+/-0.12 versus 0.16+/-0.16; P<0.001) were lower after nitroglycerin, whereas C(2) increased only nonsignificantly (0.080+/-0.036 versus 0.071+/-0.042). C(2) is related to AIx and reflects, at least in part, hemodynamic changes affecting central aortic pressure. Nevertheless, given the model assumptions and computational steps associated with calculating C(2), AIx could be a more appropriate parameter to use in the clinical setting because it is determined directly from the pressure wave contour.

Adult↗
PubMed1998

Quantification of alterations in structure and function of elastin in the arterial media.

The structure of medial elastin determines arterial function and affects wall mechanical properties. The aim of this study was to (1) characterize the structure of elastin in terms of textural features, (2) relate structural parameters to total number of cardiac cycles (TC), and (3) determine the contribution of medial elastin to lumen mechanical stress. Images of pressure-fixed aortic sections stained for elastin were obtained from specimens collected postmortem from 35 animals of different species with a wide range of age, heart rate, and TC and divided into 2 groups: TClow=3.69+/-0.38x10(8) (n=17) and TChigh=15.8+/-2.38x10(8) (n=18) (P<0.001). A directional fractal curve was generated for each image, and image texture was characterized by directional fractal curve parameters. Elastin volume fraction and interlamellar distance were obtained by image analysis. Wall stress distribution was determined from a finite element model of the arterial wall with multiple layers simulating elastin lamellae. DFC amplitude was related to elastin volume fraction. Increased TC (TClow versus TChigh) was associated with lower directional fractal curve amplitude (0.23+/-0.02 versus 0.14+/-0.02; P<0.001), reduced elastin volume fraction (36.5+2.6% versus 25.7+2.1%; P<0.01), and increased interlamellar distance (8.5+/-0.5 versus 11.5+/-1.0 microm; P<0.05). Loss of medial elastic function increased pressure-dependent maximal circumferential stress. Structural alterations of medial elastin, quantified by fractal parameters, are associated with cumulative effects of repeated pulsations due to the combined contribution of age and heart rate. Loss of medial functional elasticity increases luminal wall stress, increasing the possibility of endothelial damage and predisposition to atherosclerosis.

Age Factors↗
PubMed1996

[Effects of PGE1 (alprostadil alpha-cyclodestrin) in a case of probable paraneoplastic thrombocytopenic purpura].

The authors report the case of a severely vasculopathic patient with pulmonary mediastinal tumour who presented, probably on a paraneoplastic basis, the onset of severe thrombocytopenic purpura persisting for several months. The syndrome was not classifiable in any of the forms known to the authors and was completely resolved by treatment with PGE1 (alprostadil-alpha-cyclodextrine (Prostavasin, Schwarz Pharma).

Aged↗
PubMed1995

Genetic and environmental factors in the function and structure of the arterial wall.

In large arteries the structure of the arterial wall determines pulsatile hemodynamics of pressure and flow. Mechanical wall stiffness, wall thickness, and elastin and collagen content vary along the arterial tree. The contribution of genetic and environmental factors to such structural properties is not yet known, but some data are available on possible functional correlates. In hypertensive rats diastolic and pulse pressure have been shown to be linked to two different genes on separate chromosomes. Although a genetic component contributes to intimal calcification, medial hypertrophy is not associated with genetic factors. A study of French West Indies families showed a preferential genetic determinant for pulse pressure in contrast to systolic or diastolic pressure. Environmental and geographic factors are associated with markedly different prevalences of hypertension and age-related increases in arterial stiffening in urban and rural communities in China. Salt consumption has also been implicated in modifications of pulse wave velocity. Recent data on structural parameters of the aortic trunk in oriental (Chinese) and occidental (American and Australian) subjects have shown that the ascending aorta in oriental subjects is of a relatively large diameter and thinner media. This suggests that in this population a relatively higher primary pressure pulse would be generated because of increased stiffness of the proximal aorta. This suggests that factors other than arterial pressure are responsible for structural differences in the aortic wall and that oriental populations may have a predisposition to increased arterial pressure based on structural factors that affect the interaction between ventricular ejection and arterial load.

Adolescent↗
PubMed1994

Acetabular osteolysis in total hip arthroplasty: prevention and treatment.

Osteolysis can occur around loose, as well as well fixed, cemented or cementless acetabular components in total hip arthroplasty. Histologic studies of tissues biopsied from osteolytic regions suggest an adverse foreign body response to polyethylene and other particulate debris from prosthetic materials. Phagocytosis of these particles by macrophages and giant cells stimulate the production of proteolytic enzymes and inflammatory mediators, all leading to tissue destruction. The importance of polyethylene wear debris is now fully appreciated, and it is clear that this is the major contributor to particulate debris. The authors strongly recommend the avoidance of 32 mm femoral heads, thin acetabular component liners, titanium heads, and acetabular screws when absolutely necessary. We strongly advise 26 mm to 28 mm femoral heads, polyethylene thickness of at least 8 mm, precise liner shell contact, rigid fixation of the acetabular metal shell, intimate bone-acetabular shell contact, and circumferential porous coating of femoral components to decrease the amount of and migration potential of polyethylene debris (Table). Based on our current knowledge, these measures will minimize the problem of acetabular osteolysis.

Acetabulum↗
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↗
PubMed1992

Ageing and wave reflection.

AIM: To determine the effects of wave reflection on the increase in arterial pressure that occurs with age and its association with concomitant changes in both the magnitude and contour of the arterial pressure pulse. RESULTS OF DATA SURVEY: While age-related changes in mean pressure are similar in central and peripheral arteries, changes in pulse pressure and pulse waveform features are different. Because of the specific architectural, geometrical and elastic properties of the arterial vasculature, wave reflection plays an important role in determining peak pressure, the value usually specified as systolic pressure. While the late systolic increase usually determines peak systolic pressure in the central aorta, it is not necessarily related to the peak pressure in the periphery. Peak pressure depends on the timing and intensity of wave reflection, which is a function of the state of the peripheral microvasculature and the elastic properties of the large conduit arteries. Ageing causes changes in both the terminal and central vasculature, so that the intensity of the wave reflection and the transmission properties of arteries affect the arterial pulse to different degrees. Therefore, age-related changes that are observed in the central pressure pulse are different from those observed in the pulse when measured in a limb. Thus the contribution of wave reflection to the determination of peak arterial pressure is not the same at all locations. CONCLUSIONS: These findings have profound implications for therapeutic strategies aimed at altering systolic pressure and for a proper assessment of the alteration in cardiac load that occurs with age or with antihypertensive therapy, when measurements are taken in a limb.

Adult↗