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Biomedical subjects

M Visentin

Publications and source records attributed to M Visentin.

At least 37 records · Page 2Linked to original sources
PubMed1998

The interface of bone microstructure and an innovative coating: an X-ray diffraction study.

The in vivo compatibility and degradation aspects of an innovative coating to be sprayed onto titanium implants were investigated. The surface of fluorinated apatite (fHA), consisting of fluorhydroxyapatite plasma sprayed in a vacuum atmosphere, was treated with carbonate to improve its biological compatibility. fHA coating was compared with titanium implants coated (a) with hydroxyapatite (HA) by the traditional plasma spraying, and (b) with titanium oxide (TiOx). Screw-shaped implants were inserted in the cortical bone of sheep tibiae. X-ray diffraction (XRD) analysis of bone tissue and coatings was carried out at 2, 4, 12 and 36 weeks after surgery. The crystallographic habit of the implant-facing bone, as well as the structural stability of the coating, were evaluated. For each time period and type of ceramic bone apatite lattice at the interface, no significantly different reference apatite lattice and no foreign peak were recorded. Two weeks after implantation, the bone at the interface was strongly unmineralized in all samples; after 4 weeks, poorly mineralized bone microareas decreased. At 12 weeks, the newly formed bone tissue at the interface with both the new coating and HA coating was shown to be fully mineralized; this crystallographic habit was retained at 36 weeks, when particle release from the tested material was lower compared to the controls. The XRD pattern of bone apatite surrounding the coating particles was unmodified. The innovative coating did not alter the mineralization process at the interface. It improved implant osteointegration, mainly due to a limited release of particles. Consequently, clinical performance of external fixation treatment could be improved by modifying the chemical composition of the implant surface.

Animals↗
PubMed1997

High-performance liquid chromatography assay of N,N-dimethyl-p-toluidine released from bone cements: evidence for toxicity.

Five commercially available bone cements were analysed by high-performance liquid chromatography for detecting the residual content of an accelerator, the amine N,N-dimethyl-p-toluidine (DMPT), after curing. It was found that the concentration of DMPT in aqueous extracts decreases with time, being almost absent 7 days after curing. Differences were noticed among the cements; residual DMPT is higher in cements prepared with higher content of the amine. It is verified that DMPT's toxic effect on cell cultures is dose-related; a delay in the cell replication cycle is induced in vitro. Damage is reversible, thus justifying the low bone cement toxicity that is clinically ascertained.

Bone Cements↗
PubMed1997

Biomechanical, scanning electron microscopy, and microhardness analyses of the bone-pin interface in hydroxyapatite coated versus uncoated pins.

OBJECTIVE: To evaluate the bone-pin interface in hydroxyapatite coated versus uncoated pins. DESIGN: Eighty-four bicylindrical stainless steel external fixation pins were implanted in a test group of 14 sheep. One-half of the pins were coated with hydroxyapatite and the rest remained uncoated. INTERVENTION: Six coated pins were implanted in the left tibia of seven sheep, and six uncoated pins were implanted in the left tibia of the other seven sheep. In all sheep, the right tibia was left intact. During pin implantation, the final insertion torque was measured, and a linear external fixator was mounted on the pins. Then the medial tibial mid-diaphysis was exposed and a 5-mm resection osteotomy was performed. The sheep were killed six weeks after surgery. MAIN OUTCOME MEASURES: The extraction torque was measured on four pins removed from each sheep. Radiographic pin tract rarefaction was measured on all the pins. Two pins from each sheep were used for histologic, scanning electron microscopy (SEM), and microhardness analysis. Histomorphometric analysis was carried out on the SEM specimens at x 36 magnification. RESULTS: Radiographic pin tract rarefaction was significantly lower in the hydroxyapatite coated pins than in the uncoated pins (P < 0.001). Group average insertion torque was 960 +/- 959 N/mm in the hydroxyapatite coated pins, and 709 +/- 585 N/mm in the uncoated pins (p = not significant). Group average extraction torque was 1485 +/- 1308 N/mm and 298 +/- 373 N/mm, respectively (p = 0.0001). Histomorphometric analysis showed that the group average bone-pin contact was 50.7 +/- 16.9% in the hydroxyapatite coated pins and 27.6 +/- 7.1% in the uncoated pins (p < 0.01). Microhardness analysis showed that bone tissue close to the pins was softer than bone tissue far from them. CONCLUSION: Hydroxyapatite coating is an effective method of refining the bone-pin interface and may improve the clinical results of the external fixation technique.

Animals↗
PubMed1997

The influence of dietary nucleotides on erythrocyte membrane fatty acids and plasma lipids in preterm infants.

OBJECTIVE: The objective of this study was to evaluate whether a regular formula for premature infants supplemented with nucleotides has any influence on plasma lipids and erythrocyte membrane fatty acids. METHODS: Preterm infants fed either human milk supplemented with human milk protein (HM, n = 14), nucleotide-supplemented preterm formula (NF, n = 13), or a regular preterm formula (F, n = 13) were included in the study. The NF was supplemented with 18.2 mg cytidine monophosphate/l (CMP), 7.0 mg uridine monophosphate/l (UMP), 6.4 mg adenosine monophosphate/l (AMP), 3.0 mg inosine monophosphate/l (IMP) and 3.0 mg guanosine monophosphate/l (GMP). RESULTS: There were significantly higher concentrations of triglycerides (TG) in infants fed NF compared to those fed F (191.42 +/- 79.58 vs 108.21 +/- 43.73, p < 0.001, mean +/- SD lipid concentrations, mg/100 ml plasma). Infants fed F had significantly lower concentrations of total cholesterol (94.34 +/- 11.71 vs 115.69 +/- 39.29, p < 0.01) and TG in plasma (108.21 +/- 43.73 vs 172.27 +/- 68.19, p < 0.001, mean +/- SD lipid concentrations, mg/100 ml plasma) when compared to HM-fed infants. There were no significant differences in any of the erythrocyte membrane fatty acids and total long-chain polyunsaturated fatty acids (LC-PUFA) between NF and F during the study period (6 weeks). Furthermore, total LC-PUFA and docosahexaenoic acid (DHA) concentrations in red blood cell were not significantly different when infants fed NF were compared to those fed HM. In contrast, however, infants fed F had significantly lower concentrations of total n-3 LC-PUFA (p < 0.01) and DHA (p < 0.01) than those found in HM-fed infants. CONCLUSIONS: These results do not suggest an effect of nucleotides on the red blood cell LC-PUFA profile in preterm infants. However, the nucleotides may increase the concentrations of triglycerides in plasma.

Cholesterol↗
PubMed1996

Peripheral benzodiazepine receptor ligands in rat liver mitochondria: effect on 27-hydroxylation of cholesterol.

The effect of peripheral benzodiazepine receptor ligands: PK11195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)isoquinoline-3-carboxamid e), Ro 5-4864 (4-chlorodiazepam), hemin, N-methyl protoporphyrin IX and protoporphyrin IX on liver mitochondrial 27-hydroxylation of cholesterol was studied by adding them together with [4-14C]cholesterol. N-Methyl protoporphyrin IX, PK11195 and protoporphyrin IX stimulated mitochondrial 27-hydroxylation of [4-14C] cholesterol in vitro, the first two being the most potent (2-3-fold increase). Ro 5-4864 and hemin were not active. 27-Hydroxylation of [4-14C]cholesterol was reduced to below control levels (respectively 40 and 56% decrease compared to control, P < 0.01) when PK11195, N-methyl protoporphyrin IX or protoporphyrin IX were allowed to equilibrate in vitro with mitochondria for 20 min at 37 degrees C. Hepatic protoporphyria was induced using 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) (100 mg/kg, i.p.) to study the effect of in vivo accumulation of large amounts of dicarboxylic porphyrins, i.e. endogenous peripheral benzodiazepine receptor ligands, on cholesterol 27-hydroxylation. DDC treatment caused an increase in total porphyrin content in liver homogenate (10-fold) and mitochondria (2-fold). Mitochondrial 27-hydroxylation of [4-14C]cholesterol was depressed after treatment (60% decrease, P < 0.01). We suggest that peripheral benzodiazepine receptor ligands act on liver mitochondrial 27-hydroxylation of cholesterol by a mechanism coupled to these receptors and that the time of exposure of peripheral benzodiazepine receptors to ligands is a major factor. The modulation of 27-hydroxycholesterol production may have a physiological role in liver and possibly in other tissues.

Animals↗
PubMed1996

Improvement of the bone-pin interface with hydroxyapatite coating: an in vivo long-term experimental study.

The present study was designed to comparatively evaluate the bone-pin interface in a long-term unloaded experimental study in two groups of pins, uncoated and coated with hydroxyapatite. Forty pins made of stainless steel were used. Half of the pins were plasma-sprayed with hydroxyapatite, and the other half remained uncoated. Four adult sheep were selected. Each sheep tibia was implanted with five pins. Two sheep were euthanized 4 months after surgery and the remaining two 12 months after surgery. Extraction torque was higher in the hydroxyapatite-coated pins compared with the uncoated ones at both 4 (p < or = 0.0005) and 12 months (p < or = 0.0005) after implantation. The histological patterns observed in the sheep euthanized 4 and 12 months after implantation were very similar. An extensive bony coverage of the hydroxyapatite-coated pins without any coating resorption and delamination from the metallic substrate was observed. Fibrous tissue encapsulation was found in the uncoated pins. These results demonstrate that the hydroxyapatite coating significantly improved the bone-pin interface. A similar improvement of bone-pin interface rigidity in many clinical situations is likewise possible.

Animals↗
PubMed1995

Quantitative cytochemistry of human leukocyte elastase compared with plasma elastase and acute phase proteins in inflammatory diseases.

Plasma levels of human leukocyte elastase, a serine proteinase stored in the azurophilic granules of polymorphonuclear granulocytes, increase in the early stages of several inflammatory diseases. We studied the intracellular enzyme activity by cytochemical quantitative image analysis and the amount of elastase released in plasma by an automatic immunoactivation immunoassay method in 66 patients with inflammatory diseases and in a control group. The patients were divided into two groups with infective disease (severe and moderate) and one group with non-infective inflammation. Intracellular activity and plasmatic levels of elastase were also compared with other inflammatory markers, i.e. erythrocyte sedimentation rate, C-reactive protein, alpha 1-antitrypsin, haptoglobin, alpha 1-acid glycoprotein and fibrinogen. Our studies suggest that plasma and leukocyte elastase are correlated both with etiology and with the severity of the inflammation.

Acute-Phase Proteins↗
PubMed1995

Microhardness of bone at the interface with ceramic-coated metal implants.

We evaluated bone microhardness at the interface with hydroxyapatite-coated stainless-steel pins used in an external fracture fixation system. Pins were transversally inserted into the diaphyses of sheep tibiae and were loaded in for 6 weeks. Uncoated pins were implanted as controls. Microhardness analysis, based on the measure of the resistance of the bone to the penetration of a small diamond pyramid, yielded an accurate and reproducible measure of the mineralization degree and of the orientation of collagen fibers. Bone tissue close to the pin is less hard than bone tissue far from it. Moreover, the presence of hydroxyapatite coating on the pins did not significantly affect bone hardness; actually, the mean hardness at the interface with the pins was 56.9 Vickers degrees, whereas at the interface with the uncoated pins it was 62.2. It can be concluded that, 6 weeks postsurgery, the bone growing into the threadings of a loaded screwed implant reached maturity at a degree lower than that of the host bone in both uncoated and coated implants.

Animals↗
PubMed1995

A quantitative method to measure alkaline phosphatase activities in individual leukocytes by image analysis.

Leucocyte alkaline phosphatase (L-ALP) is well known as leukemia marker, but recent results suggest its usefulness for the diagnosis of several diseases. The aim of this study was to develop a quantitative method to measure alkaline phosphatase activities in individual leukocytes by image analysis. We studied the reaction rate of L-ALP in human polymorphonuclear leucocytes by a microscope attached to a TV camera and a computerized image analyzer. The optical density (OD) measured was standardized by grey filters with known absorbance. We measured IOD for individual cells after a set incubation time by end-point measurements. Studies of kinetic parameters of L-ALP were performed by single-point measurements in the linear phase of the reaction and at increasing substrate concentrations. Cellular IOD increased proportionally with incubation time up to 10 min. The mean KM(mM) and Vmax(delta IOD/min) values were 0.70 +/- 0.11 and 1.76 +/- 0.2 (mean +/- SE, n = 5) respectively. Our findings are comparable to previous results using a polyvynil alcohol method in microphotometry analysis. The image analysis of cellular L-ALP activity appears a valuable tool for quantitative studies.

Alkaline Phosphatase↗
PubMed1995

Reye's and Reye-like syndromes, drug-related diseases? (causative agents, etiology, pathogenesis, and therapeutic approaches).

In the literature the separation between RS and RLS is confusing and makes it difficult to plan an appropriate preventive action or to develop new therapeutic approaches. We suggest that the generalized damage and encephalopathy seen in both RS and RLS may be due to a wide variety of causative agents that contribute to a common derangement, principally involving mitochondrial oxidative pathway. Fasting status and infections increase the catabolism and the subsequent flux of metabolites from peripheral tissues to the liver (FA and amino acids); cytokines (TNF, IL-1, and IL-6), in particular, mediate this effect during infection and experimental endotoxemia. Some drugs and other toxic compounds induce functional and morphological liver mitochondrial derangement. Oxidative metabolism is impaired, with subsequent stimulation of alternative pathways of oxidation, following production of unusual toxic acyl CoAs and dicarboxylic acids. Toxic compounds accumulate in the liver, deranging its functions and causing energy depletion, and are also released in the circulation from which they reach other tissues, including the brain. Neurons and astrocytes in the brain may be affected differently: Neurons suffer from the lack of energy and the effect of toxic compounds arriving from the bloodstream, and astrocytes may be directly affected by the beta-oxidation derangement. Very important may be genetic predisposition, which, by making the patient more sensitive to a particular causative agent, may facilitate the onset of RS and RLS. The therapeutic approach is, presently, mainly symptomatic, directed as it is to counteracting each alteration shown, depending by the clinical gravity. Other pharmacological approaches are only studied experimentally, like carnitine supplementation and PGE2 administration, or theoretically envisaged, like monoclonal antibody therapy directed at LPS or at pro-inflammatory cytokines or treatment with interferon-alpha.

Child↗
PubMed1995

Reye syndrome model in rats: protection against liver abnormalities by L-carnitine and acetyl-L-carnitine.

The effects of L-carnitine (LCn) and acetyl-L-carnitine (AcLCn) were assessed on the liver alterations observed in Kilpatrick's model of Reye syndrome in rats; fasted rats were given lipopolysaccharide (LPS), 0.2 mg/kg i.p., 12 hr before they were sacrificed, plus acetylsalicylic acid (ASA), 50 mg/kg i.p., 11 hr before sacrifice; LCn or AcLCn were given twice, 500 mg/kg orally, 12 and 2 hr before sacrifice. LPS+ASA-treated rats showed a dramatic decrease of hepatic ketone bodies and acetyl-CoA and an increase of isobutyryl-CoA, isovaleryl-CoA and succinyl-CoA. Electron microscopy of LPS+ASA-treated rat liver showed a slight but significant alteration in mitochondrial inner structure. Because impairment of mitochondrial function in RS is associated with swelling, we investigated whether the microviscosity of mitochondrial lipids and the cholesterol-phospholipid ratio (CHOL/PL), were involved in the RS model used. Mitochondria from LPS+ASA-treated rats showed a decrease in lipid microviscosity, in CHOL/PL ratio and in CHOL/PL ratio of both inner and outer membrane fractions; these alterations suggested a general increase in membrane fluidity. LCn and AcLCn reversed the morphological alterations in mitochondria after LPS+ASA, observed by electron microscopy, the decrease in KB and the toxic increase in short-chain acyl-CoAs; AcLCn only reversed the decrease in acetyl-CoA. LCn and AcLCn prevented mitochondrial lipid alterations mainly in the inner membrane fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcarnitine↗
PubMed1994

Contribution to the study of the tributaries and the termination of the external jugular vein.

The dissection of 100 external jugular veins in 50 cadavers was the object of this anatomic study. A certain number of notions concerning the afferent veins, the mode of termination and the valvular system of this vessel were defined. 1) Afferent veins. Along its pathway toward the deep venous system, the external jugular vein successively received: the transverse cervical vein in 88 cases (88%), usually opposite the intersection of the external jugular vein with the dorsal border of the sterno- cleidomastoid muscle; the suprascapular vein in 47 cases (47%); the anterior jugular vein in 46 cases (46%); the cervical vein or anastomosis with the latter in 13 cases (13%). 2) Mode of termination. Forty-three subjects presented a symmetric mechanism. 100 anastomoses can be classed into three types: in 60 cases (60%), the external jugular vein flowed into the jugulo-subclavian venous confluence; in 36 cases (36%), in to the subclavian vein at a distance from its junction with the internal jugular vein; in 4 cases (4%) in to the trunk of the internal jugular vein. 3) Study of the valves. There were studied in 25 subjects (50 external jugular veins). The valves were found in the ostial and paraostial position in 49 out of 50 veins.

Humans↗
PubMed1992

[Gracilis muscle in man].

This study is based upon the dissection of 84 gracilis muscles in 42 cadavers. It allowed to emphasize the following features: 1-The proximal insertion of the muscle is a strong tendinous lamina arising from the anterior aspect of the pubis and from the ischio-pubic branch; the distal insertion to the tibia is common to both the gracilis and the semi-tendinous muscles. 2-The distal tendon of the gracilis is tightly connected to the posterior branch of the internal saphenous nerve which crosses the muscle behind the medial femoral condyle. 3-The arterial supply (52 dissections) appears to be very rich, consisting in various pedicles entering the muscle by is lateral side. The main neurovascular bundle is issued from the profound vessels of the thigh, coming either from the adductors artery (73%), either from the medial circumflex artery (19.2%), either from both networks (7.7%). The site of penetration of the vessels in the muscle is remarkably constant. The remaining pedicles (2 to 4, one of which is quite constant at the musculotendinous junction) arise from the muscular branches of the femoral artery. 4-There is a good correlation between the measured length of the muscle and the distance between the superior aspect of the pubic arch and the medial epicondyle. A 0.37 corrective factor applied to this latter distance allows to determine the exact sit of penetration of the main neurovascular bundle in the muscle.

Arteries↗
PubMed1991

Pyloric obstruction with complicated pancreatic heterotopia.

A case of pyloric obstruction associated with pancreatic heterotopia is described in an 18-day old child. The association of several pathologic processes like acute pancreatitis and abscess formation in the heterotopic mass and the long-term follow-up are the main points of interest in this report.

Choristoma↗
PubMed1990

[Non-palpable testes. Apropos of 161 cases].

A series of 161 boys with 178 impalpable testes is reviewed. Extended inguinal exploration was the main form of investigation and treatment. Hormone injections and studies were performed in bilateral cases. Sonography was unhelpful. Laparoscopy was not used. Impalpables testes account for 7% of all boys with an anomaly of testicular descent and 8.5% of operated boys. One hundred and twenty six testes were found, 58 in the abdomen, 68 in the inguinal canal. Thirty one nodular vestige were found and all 25 with histopathology were spermatic duct residue. In 21 boys no trace of testes or spermatic duct remnant were found. Ninety five testes were successfully brought to the scrotum with one (85) or two (10) stage procedure. Anomalies of the upper urinary tract in 13 of 21 cases without testes or spermatic duct remnant were very rare. In bilateral cases it looks better to search a testes whatever the biological responses to gonadotropin stimulation.

Abdomen↗
PubMed1990

[Management of a biliary cyst disclosed prenatally. Apropos of 2 cases].

Two cases of prenatal detection of congenital biliary cysts are reported. Prenatal and postnatal ultrasonography demonstrate a solitary sonolucent cystic lesion. The differential diagnosis in fetus and infant includes any abdominal cystic lesions: ovarian cyst, duplication cyst, cystic lymphangioma, choledochal cyst and other congenital cysts of the liver. In opposite to the difficulty of diagnosis, the choice for treatment is easy: surgery is the only way to allow histologic diagnosis and to avoid any relapse or complications.

Choledochal Cyst↗
PubMed1990

[Techniques of celiac plexus block and clinical results].

Coeliac plexus neurolesion techniques for pain due to upper abdominal cancer (pancreas cancer above all), have changed during the years. In this paper we report the results of coeliac plexus alcohol neurolysis for cancer of pancreas and of other abdominal organs achieved with the different techniques. It appears that precrural techniques provide very favorable results but they require the use of CT scan. Retrocrural techniques, while giving good results, can be performed under fluoroscopic control.

Autonomic Nerve Block↗