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Biomedical subjects

A Visconti

Publications and source records attributed to A Visconti.

At least 73 records · Page 4Linked to original sources
PubMed1985

Identification of iso-TC-1 as a new T-2 toxin metabolite in cow urine.

The structure of a new metabolite T-2 toxin (iso-TC-1) has been established as 3,15-diacetoxy-4-hydroxy-8(3-methyl-3'-hydroxy-butyryloxy)-12, 13-epoxytrichothec-9-ene. The compound is an isomer of TC-1 (a recently isolated T-2 derivative) in which the hydroxy and acetoxy groups at the C-3 and C-4 positions, respectively, are reversed. Direct probe analysis by electron impact (EI) of the underivatized iso-TC-1, as well as EI, positive chemical ionization (CI) in methane, and positive CI in ammonia of its trimethylsilylether or trifluoroacetate provided evidence to support the structure assignment of the new metabolite. The mass spectra of iso-TC-1 were compared with those of TC-1, T-2 toxin and iso-T-2 toxin (the isomer of T-2 toxin having reversed substituents at C-3 and C-4) with regard to molecular weight and fragments involving the substituents at C-3, C-4, C-8 and C-15. Although the two isomers, TC-1 and iso-TC-1, were not easily resolved by thin layer chromatography (TLC), a very good separation of their trimethylsilyl and trifluoroacetate derivatives was obtained by capillary gas chromatography. Acetylation of TC-1 or iso-TC-1 gave the same product. Iso-TC-1 is one of the main products of T-2 metabolism in the cow (more abundant than TC-1) and is found in the urine.

Acetylation↗
PubMed1985

Occurrence of zearalenols (diastereomeric mixture) in corn stalk rot and their production by associated fusarium species.

Zearalenol was extracted from Fusarium-infected stems of corn from southern Italy. The toxin, which appeared as a single compound in various thin-layer chromatography systems, was resolved by high-pressure liquid chromatography into two components. A gas chromatography-mass spectrometry examination of a purified fraction confirmed the natural occurrence of zearalenol as a diastereomeric mixture and led to the identification of alpha (56 ng/g) and beta (27 ng/g) isomers. Among nine Fusarium species found associated with stalk rot in corn, only Fusarium culmorum (F. roseum ;Culmorum') and F. equiseti (F. roseum ;Gibbosum') produced zearalenol and always produced it in a diastereomeric mixture of alpha and beta isomers.

Journal Article↗
PubMed1985

Identification of various T-2 toxin metabolites in chicken excreta and tissues.

Gas chromatography-mass spectrometry was used to identify various T-2 toxin metabolites in chicken excreta and organs 18 h after intraperitoneal injection of the toxin. No trichothecenes were detected in the heart and kidneys, and only trace amounts were detected in the lungs. Most of the T-2 metabolites were found in the excreta, although considerable amounts were also found in the liver. In addition to the previously identified T-2 metabolites in chicken excreta (HT-2 toxin, 15 acetoxy T-2 tetraol, and T-2 tetraol), we found 3'-hydroxy HT-2 toxin (the major metabolite in excreta and organs), 3'-hydroxy T-2 toxin, 4-acetoxy T-2 tetraol, and trace amounts of 8-acetoxy T-2 tetraol, 3-acetoxy-3'hydroxy HT-2 toxin, and T-2 triol. Unmetabolized T-2 toxin and an unidentified isomer of T-2 tetraol monoacetate were also detected in the excreta. Most of the metabolites in the chicken are similar to those encountered in cultures of fungal species producing T-2 toxin. A comparison with T-2 toxin metabolism in the cow is also reported.

Animals↗
PubMed1985

Colonization and infection of mothers and neonates with group B streptococci in three Italian hospitals.

In the absence of previous published studies from Italy on the epidemiology of group B streptococci we investigated 1516 mothers at delivery and 1294 neonates in three hospitals. Of mothers in labour, 7.5% were colonized with group B streptococci and 4.9% of their babies. Of the neonates born to a positive mother 45.1% were colonized, whilst only 2.2% of babies born to a negative mother were colonized. For the mothers, the vagina was colonized more often (7.3% of all women) than the cervix (6.0%), the urethral meatus (3.9%) or the rectum (2.9%). For the neonates, the rates of colonization of the throat, external auditory canal, and the umbilicus were 3.2%, 3.0% and 2.6%, respectively. The distributions of the serotypes were similar to that reported from other parts of Europe and the USA and vertical transmission of group B streptococci was demonstrated in most of the mothers and their neonates. Of 30 mother-neonate pairs, 25% of mothers carried group B streptococci intermittently and 58% had persistent carriage until the 90th day postpartum, the rectum being the commonest positive site. Of 20 infants that were positive at birth, only six were still positive on the 15th day and none by the 90th day of life. Of 1294 infants, four (0.3%) developed early-onset sepsis with group B streptococci and one died. The overall incidence of clinical infection amongst colonized infants was 6.2%.

Female↗
PubMed1984

Production of trichothecenes and zearalenone by Fusarium species isolated from wheat.

Fusaria isolates from wheat were tested for ability to produce trichothecenes and zearalenone. Four isolates of F. culmorum out of 13 produced vomitoxin (DON) and 3 Ac-DON, one produced diacetoxysirpenol and 12 zearalenone. Particularly high yield of zearalenone was observed in cultures of sever pathogenic isolates. Higher temperature (20 degrees C) during first week of incubation favoured yield of zearalenone. About 50% of zearalenone was produced by surface mycelium.

Food Microbiology↗
PubMed1984

Retinoic acid enhances the growth of only one subpopulation of granulomonocyte precursors.

The effect of various concentrations of retinoic acid on the growth of committed granulomonopoietic precursors (CFU-GM) was studied on semisolid agar cultures. Retinoic acid increased the growth of day 14 CFU-GM but had no significant effect on day 7 CFU-GM. Since the latter are believed to represent the progeny of day 14 CFU-GM it is suggested that the effect of retinoic acid is confined to the early stages of granulomonocytic differentiation.

Bone Marrow Cells↗
PubMed1982

Evaluation of the MS-2 automated antimicrobial susceptibility testing system: report of a European collaborative study.

The MS-2 is an instrument for rapid automated testing of antimicrobial susceptibility. Its performance was evaluated by comparison with disc diffusion and MIC tests in a collaborative study in four European laboratories. Tests on independently isolated organisms showed the MS-2 to be in essential agreement with conventional methods in 94.8% of tests. A further series of 170 well-defined pathogens for which a reference antibiogram was available were tested by MS-2 and the manual methods in all of the participating laboratories. MS-2 results were in full accord in 90% of tests and in essential agreement in 94%. MS-2 results compared at least as well with the reference values as did either of the manual methods. Initial problems of false susceptibility results with erythromycin and penicillin were resolved by (1) the addition of small amounts of erythromycin which acted as an inducer and (2) by the use of a low content penicillin disc. MS-2 was found to be reliable and needed no attention following loading of the test cuvette cartridges. A print-out of the results was available 2-5 h after inception of the test.

Anti-Bacterial Agents↗
PubMed1979

[Quantitative evaluation methods of the chemoantibiotic associations (author's transl)].

In the introductory part a new classification of joint drug actions is submitted, according which three fundamental types are distincted, named respectively interference, cooperation and true interaction. In its turn, interaction is subdivided in three classes (uni-effectual, bis-ineffectual, bis-effectual) in the last of which is placed the most relevant of the interactions, that is synergism, subclassified, at its turn, as additive, super and infra-additive. The second part is devoted to the classification of the bacteriological techniques hitherto proposed in order to evaluate in vitro and in vivo the antibacterial interaction of chemoantibiotics. The third part is devoted to the classification and critical analysis of biometrical techniques hitherto applied to above quoted bacteriological techniques in order to obtain a quantitative evaluation of interaction. Criticism versus isobolic model is pointed out. In the final part a new procedure, named isoeffectual, is proposed. According to such a procedure a close grid of single and joint concentrations of a couple of chemoantibiotics, broad enough in order to cover the whole of the effects to be explored, is tested in vitro adopting the one-center agar diffusion test or a liquid medium. The experimental data so obtained are related in a planar diagram to the log of the sum obtained by adding to the concentrations of the first the concentrations of the second agent, converted into equi-effectual concentrations of the first. By this way a series of curvilinear regressions is obtained, which may be all explained by a mathematical formula according which the data may be submitted to statistical analysis and elaborated in order to draw the parameters able to define quantitatively the interaction. The model so applied is discussed as a general model for joint drug action.

Anti-Bacterial Agents↗
PubMed1978

The assessment of interaction between drugs by the Autobac 1 system.

A study has been undertaken on the applicability of the Autobac 1 system to the checker board method to determine the interaction of combined drugs on bacterial populations. Preliminary results are reported which show that the Autobac makes easier, accurate, flexible and rapid such a method. In order to improve the significance and facilitate technical operations and data processing of this test additional equipment and device are suggested.

Cephacetrile↗