Biomedical subjects

M Amati

Publications and source records attributed to M Amati.

11 recordsLinked to original sources

PubMed2000

In vitro cleavage by asbestos fibers of the fifth component of human complement through free-radical generation and kallikrein activation.

Chrysotile and crocidolite fibers incubated in normal human plasma (NHP) generated from the C5 component of complement C5a-type fragments that stimulated polymorphonuclear leukocyte (PMN) chemotaxis. Absorption of NHP with antiserum against C5a totally abolished neutrophil chemotactic activity. Asbestos fibers also produced C5a small peptides in the presence of ethylene glycol bis(beta-aminoethyl ether) N,N,N'N'-tetraacetic acid (EGTA) but not ethylene diamine tetraacetic acid (EDTA). Activation of C5 was significantly inhibited when asbestos fibers were pretreated with iron chelators such as sodium dithionite (DTN), deferoxamine (DFX), or ascorbate (AA). Concentration-related inhibition of C5 activation was also observed when asbestos fibers were added concurrently to plasma in the presence of DFX, 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl scavenger, or aprotinin (APR), a specific protease inhibitor. Further, chrysotile and crocidolite significantly increased plasma kallikrein activity. Data demonstrate that asbestos-induced C5 activation plays a role in inflammatory reactions characteristic of asbestosis through mechanisms involving iron ions, hydroxyl radicals, and oxidized C5-ike fragments. The ferrous ions present at the asbestos fiber surface trigger this activation and catalyze, via Fenton reaction, the production of hydroxyl radicals, which in turn convert native C5 to an oxidized C5-like form. This product is then cleaved by kallikrein, activated by the same asbestos fibers, yielding an oxidized C5a with the same functional properties as C5a.

Adult↗

PubMed2000

Ropivacaine-clonidine combination for caudal blockade in children.

BACKGROUND: Adding clonidine to weak ropivacaine solutions (<0.2%) could potentially enhance analgesia as well as further reduce the risk for unwanted motor blockade. The aim of the present study was to compare the postoperative pain-relieving quality of a ropivacaine 0.1%-clonidine mixture to that of plain ropivacaine 0.2% following caudal administration in children. METHODS: In a prospective, observer-blinded fashion, 40 ASA 1 paediatric patients undergoing subumbilical surgery were randomly allocated to receive a caudal injection of either plain ropivacaine 0.2% (1 ml/kg) (R0.2) or a mixture of ropivacaine 0.1% with clonidine 2 microg/kg (1 ml/kg) (R0.1C). Objective pain scale score and need for supplemental analgesia were used to evaluate analgesia during the first 24 h postoperatively. Residual postoperative sedation was also assessed. RESULTS: A significantly higher number of patients in the R0.1C group (18/20) could be managed without supplemental analgesia during the first 24 h postoperatively compared to the R0.2 group (11/20) (P=0.034). Both the degree and the duration of postoperative sedation was similar in both groups. No signs of postoperative motor blockade were observed. CONCLUSIONS: The combination of clonidine (2 microg/kg) and ropivacaine 0.1% is associated with an improved quality of postoperative analgesia compared to plain 0.2% ropivacaine. The improved analgesic quality of the clonidine-ropivacaine mixture is achieved without causing any significant degree of postoperative sedation.

Adjuvants, Anesthesia↗

PubMed1999

Role of iron in asbestos-body-induced oxidant radical generation.

Asbestos bodies (AB) were harvested from human lung tissue digests and isolated from uncoated asbestos fibers. Samples containing 1000 AB were added to a reactive solution to investigate the ability of AB to oxidize deoxy-D-ribose and generate reactive oxygen species (ROS) in the presence of ascorbate and hydrogen peroxide as determined by formation of thiobarbituric acid (TBA)-reactive products. Three types of asbestos fibers were tested for comparison, since they are known to be able to produce ROS. The absorbance values measured with 1000 AB were significantly higher than those observed with 1000 fibers of the three types of asbestos. Since in our reaction system the only source of transition metals was the iron-rich AB, data suggest iron derived from the ferritin coating of AB was involved in oxidant generation. Addition of iron to AB enhanced TBA-reactive product formation, while chelation of Fe with deferoxamine reduced this reaction. Hydroxyl radical scavengers 1,3-dimethyl-2-thiourea (DMTU) and mannitol (MN) also effectively blocked TBA-reactive product generation. Data indicate the importance of Fe in AB-induced oxidant damage. With the addition of polymorphonuclear leukocytes (PMN) to AB, incubation in the reactive solution gave very high amounts of TBA-reactive products, but using a reactive solution devoid of ascorbate, very low amounts of TBA-reactive products were generated. In the latter condition, the superoxide of cell membranes probably reduced and removed iron from AB-coating ferritin, but less effectively than ascorbate. Further after the possible reoxidation of Fe2+, Fe3+ could be coordinated by lactoferrin. Since such availability of reductant is never approached in living systems, the iron in the AB coating is unlikely to function as a catalyst of Fenton-type reactions in vivo.

Asbestos↗

PubMed1998

Wollastonite fibers in vitro generate reactive oxygen species able to lyse erythrocytes and activate the complement alternate pathway.

Wollastonite fibers were tested in vitro for their ability to produce reactive oxygen species (ROS) with two different systems: a cell-free reactive mixture containing deoxyribose and a polymorphonuclear leukocyte suspension. After adding the fibers, we measured the thiobarbituric acid-reactive substances produced by deoxyribose degradation and luminol-enhanced chemiluminescence, respectively. Compared with asbestos, wollastonite fibers produced higher ROS levels both in the PMN suspensions and in the cell-free reactive mixtures. A large amount of these ROS were not hydroxyl radicals. Indeed we obtained remarkable differences in ROS generation between unground and ground wollastonite fibers and negative results with fibers modified with ferric chloride and dithionite. In addition, ROS generation was partially inhibited (by 46-54%) in the reactions performed in the presence of 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl radical scavenger. Wollastonite fibers were also analyzed for their ability to lyse erythrocytes and activate complement. Hemolytic potency was about twice that of chrysotile and half that of crocidolite. The levels of complement activation (via the alternate pathway) were about four-fifths of those measured in zymosan-activated plasma (a typical stimulus used to activate the alternate pathway), equal to those obtained with crocidolite, and two-thirds of those found with chrysotile. The addition of DMTU markedly reduced both these activities. Since asbestos fiber toxicity is mainly due to hydroxyl radical generation, our results indicate that wollastonite fibers are probably less toxic than asbestos fibers.

Adult↗

PubMed1998

Decrease in peripheral blood polymorphonuclear leukocyte chemotactic index in endometriosis: role of prostaglandin E2 release.

OBJECTIVE: To investigate the effect of disease on peripheral blood polymorphonuclear leukocyte chemotactic index and natural killer cell cytotoxicity and to provide additional information concerning the cell-mediated immune function in endometriosis. METHODS: Chemotactic index of peripheral blood polymorphonuclear leukocytes, natural killer cell activity, and plasma estradiol (E2) and plasma prostaglandin (PG) E2 levels were evaluated in 46 women who underwent laparoscopy or laparotomy for pelvic pain, infertility, and/or benign adnexal masses. RESULTS: The 20 women (43%) with endometriosis showed a decrease in peripheral blood polymorphonuclear leukocyte chemotactic index, related to advanced disease stage (P < .001). A significant inverse correlation was observed between plasma PGE2 levels and chemotactic index in stage III and IV endometriosis (r = -.73, P = .004). Similarly, natural cytotoxicity was decreased significantly with respect to the stage of endometriosis (P = .004) and related inversely to plasma PGE2 levels (r = -.74, P = .003). A direct relationship was observed between PGE2 and plasma E2 levels (r = .59, P = .006). CONCLUSION: Advanced endometriosis is associated with decreased peripheral blood polymorphonuclear leukocyte chemotactic index and natural killer cytotoxicity, which may be related to plasma PGE2 and E2 levels.

Adult↗

PubMed1995

In vitro biological effects of clay minerals advised as substitutes for asbestos.

We studied one sample of commercial sepiolite and two samples of commercial vermiculite--clay minerals proposed as replacements for asbestos--and tested in vitro their abilities to activate complement, to lyse erythrocytes, and to elicit the production of reactive oxygen species (ROS) with human polymorphonuclear leukocytes (PMN) or bovine alveolar macrophages (AM); their behavior was compared with that of asbestos fibers obtained from the Union International Contra Cancer (UICC) as reference standards, as well as with kaolinite and illite, main members of the clay mineral family. Since in short-term in vitro tests the biological activity of mineral particles seems especially related to the active sites on their surface, we first measured the specific surface area of each mineral. Sepiolite was unreactive in two of the three tests we used (complement activation and ROS production) and able to lyse a minimal percentage of red blood cells. Vermiculite was shown to be incapable of activating complement, to have a moderate hemolytic activity and a high ability to elicite ROS production, although lower than that of chrysotile. Sepiolite, therefore, might be of more interest than vermiculite, given the low level of biological effects detected during the tests used to compare both clay minerals with asbestos fibres. The ROS production does not seem to require phagocytosis. A high ROS production was observed with kaolinite: this result casts doubt on the ability of pathogenic mineral dusts in vitro to induce a greater release of ROS than nonpathogenic mineral dusts.

Acridines↗

PubMed1987

[Epidemiology of trichinosis in Italy: correlation between the wild cycle and man].

In Italy trichinellosis is a zoonosis caused by Trichinella nelsoni, with an exclusively sylvatic cycle involving wild and synanthropic animals (fox, wolf, stray dog, wild boar, foraging pig). The recent increase and diffusion of wild boar population in all Italy, have caused two human epidemic foci of trichinellosis involving about 100 persons in the years 1985-1986. The custom of eating fox meat have caused other human infections. The results of serological examinations of wild boar population showed the role played by this animal in the epidemiology of the disease. The examination of rodent population has pointed out the infection in these mammals (rat, porcupine). The epidemiological implications of wild cycle on man are reported.

Animals↗

PubMed1987

[Genetic differentiation of the Trichinella genus with isoenzymatic analysis].

Twenty-six Trichinella isolates have been examined by the isoenzyme typing of ten enzyme systems (LDH, ME, 6PGDH, G6PDH, GOT, AK, PGM, ACON, MPI, GPI). Four different zymodemes were obtained. All the examined isolates have shown an electrophoretic behaviour like one or other of four reference strains. The isolates from Italy and Yugoslavia have an electrophoretic mobility like T. nelsoni reference strain. The isolates from France, Holland, Great Britain, Poland and USA have an electrophoretic mobility like T. spiralis reference strain. For T. nativa and T. pseudospiralis we have tested only the reference strains. These results support the validity of the taxonomy of Trichinella genus in four good species.

Animals↗

PubMedDate not supplied

[Importance of the specific surface area in the study of the biological effects of dusts of industrial use].

We have studied a sample of commercial sepiolite and two samples of commercial vermiculite which are advised to replace asbestos, and we have in vitro tested their abilities to activate the complement and to lyse erythrocytes. Their behaviours has been compared with those of asbestos fibres given by Union Internationale Contre le Cancer (UICC) as reference standards. We have first measured the specific surface area and the weight of each mineral. Sepiolite has been inactive in complement activation and little able to lysis red blood cells on the base of surface area; on the base of the weight it has been unreactive in complement activations but very reactive in red blood cells lysis. We believe that in the in vitro assays to evaluate the biological effects of the substitutes of asbestos it is very important to considerate as the weight and as the specific surface are of each clay mineral.

Aluminum Silicates↗

PubMedDate not supplied

[Acrylonitrile and chemotaxis: in vitro experiments].

We have verified that chemotaxis of isolated human polymorphonuclear leukocytes (PMN) was a target of in vitro toxicant effect of acrylonitrile (ACN). This toxicant induced a significant dose dependent decreasing of chemotaxis with 50% inhibition (IC50) occurring at 15 mM. We assume that PMN from workers exposed to ACN reacts vivo in a similar way to PMN exposed in vitro to ACN. We propose therefore to use chemotaxis assay as a biomarker of early biological effect of ACN in workers, since for their monitoring there are so far only internal dose indicators but no suitable effect indicators.

Acrylonitrile↗

PubMedDate not supplied

[Reactive oxygen species produced by the addition of sepiolite and vermiculite (expanded or not) to suspensions of human polymorphonuclear phagocytes and bovine alveolar macrophages].

We have studied a sample of commercial sepiolite and two samples of commercial vermiculite, which are clay minerals advised to replace asbestos. We have in vitro tested their abilities to produce reacting oxygen species (ROS) after they have been added to suspension of human polymorphonuclear leukocytes and bovine alveolar macrophages. The behaviour of sepiolite and vermiculite have been compared with those of asbestos fibres given by Unione Internationale contre le Cancer (UICC) and with kaolin and illite. Sepiolite was not able to induce ROS production, while vermiculite was able to induce a relevant ROS generation, even if the values were always lower than that obtained from chrysotile. Kaolin was able to generate a high ROS production.

Adult↗