Search PubMed⌕ Search

Biomedical subjects

L Dominguez

Publications and source records attributed to L Dominguez.

At least 55 records · Page 3Linked to original sources
PubMed1990

A morphological study of primordial germ cells at pregastrular stages in the chick embryo.

The spatial distribution, germ layer location, number and appearance of primordial germ cells (PGCs) are studied. Blastoderms from stage X (Eyal-Giladi and Kochav, 1976) to stage 2 (Hamburger and Hamilton, 1951) were serially sectioned and distribution patterns of PGCs were reconstructed. The presence of PGCs in clusters was noted at all stages examined. PGCs were found in relation to the epiblast, the primary hypoblast and in the blastocoel, during the whole period under examination. These observations show that PGCs can be directly studied at blastula stages. The results are consistent with observations on an early segregation of chick germ line that begins as early as stage X.

Animals↗
PubMed1990

Revision of the validity of CAMP tests for Listeria identification. Proposal of an alternative method for the determination of haemolytic activity by Listeria strains.

The validity of CAMP tests with Staphylococcus aureus and Rhodococcus (Corynebacterium) equi as defined for Listeria identification was revised. This characterization method appeared to be unreliable for two reasons: first, a positive CAMP test with R. equi is not specific for Listeria ivanovii as Listeria monocytogenes (and Listeria seeligeri) give also a clear positive reaction; second, doubtful reactions could be observed with S. aureus when assaying haemolytic and non-haemolytic Listeria strains (possibility of false negative and false positive results; subjectivity of the interpretation). The use of a Microplate technique previously described instead of CAMP tests is proposed for the reliable demonstration of the haemolytic character of Listeria in the routine identification of these organisms.

Bacterial Typing Techniques↗
PubMed1989

Structure of an ether dimer of deoxydihydroqinghaosu, a potential metabolite of the antimalarial arteether.

C30H49O7, Mr = 518.69, triclinic, P1, a = 9.013 (2), b = 10.520 (2), c = 15.187 (3) A, alpha = 93.3 (2), beta = 93.73 (1), gamma = 95.88 (2) degrees, V = 1426.2 (5) A3, Z = 2, Dx = 1.21 Mg m-3, lambda(Cu K alpha) = 1.54178 A, mu = 0.65 mm-1, F(000) = 564, T = 295 K, final R = 0.043, wR = 0.042 for 3842 observed reflections. The dimer is formed such that the deoxyarteether moieties are cis to one another. Attempts to determine the absolute configuration of the molecule were inconclusive so the conformation corresponding to that found for qinghaosu was used for the refinement. Both halves of the dimer have the same chirality with five of the seven asymmetric carbons having an S conformation and two (C5 and C6) having an R conformation.

Antimalarials↗
PubMed1989

Preliminary evidence that different domains are involved in cytolytic activity and receptor (cholesterol) binding in listeriolysin O, the Listeria monocytogenes thiol-activated toxin.

The inactive truncated 52 Kilodaltons (kDa) Listeriolysin O (LLO) produced by a transposon Tn1545-induced Listeria monocytogenes non-hemolytic/avirulent mutant previously described (Gaillard et al. (1986) Infect. Immun. 52, 50-55), that lacks a 48 aminoacid fragment at the C-terminal end including the single cysteine residue essential for activity (Mengaud et al. (1988) Infect. Immun. 56, 766-772), bound to the SH-cytolysin membrane receptor cholesterol, as did the active 60 kDa toxin. These results indicate that the missing fragment is a functionally important region needed in the 60 kDa LLO to cause membrane-disruption but not to bind to cholesterol, which strongly suggests that in LLO (and presumably in the other SH-cytolysins, in accordance with their structural and functional homologies) different domains are involved in cytolytic activity and cholesterol binding. The cysteine residue contained in the missing fragment, therefore, would not be essential for cholesterol binding, as is currently thought, rather it seems to be essential specifically for cell lysis.

Bacterial Toxins↗
PubMed1989

Purification and characterization of two Listeria ivanovii cytolysins, a sphingomyelinase C and a thiol-activated toxin (ivanolysin O).

The strong bizonal hemolysis on blood agar and the positive CAMP reaction with Rhodococcus equi denotes the production of two different cytolytic factors by Listeria ivanovii. One was characterized as a thiol-activated (SH) cytolysin of 61 kilodaltons and was termed ivanolysin O (ILO) since data suggested that it is different from listeriolysin O, the SH-cytolysin produced by Listeria monocytogenes. The other is a 27-kilodalton hemolytic sphingomyelinase C that was found to be the cytolytic factor responsible for the halo of incomplete hemolysis synergistically enhanced by R. equi exosubstances. When thiol-disulfide exchange affinity chromatography and gel filtration were applied to the purification of ILO from concentrated L. ivanovii culture supernatants, the copurification of the two cytolysins was observed. This phenomenon seems to be due to the formation of intermolecular disulfide bonds between ILO and the sphingomyelinase, since the latter was found to contain free SH groups, not essential for the activity. These SH groups could react with the single cysteine residue characteristically present in the SH-cytolysins, forming a dimeric cytolytic complex. The purification of ILO was achieved by a further gel filtration with a reducing agent (dithiothreitol) in the eluent. A method for the purification of the sphingomyelinase based on selective sequestration of ILO from the L. ivanovii concentrated culture supernatant by the SH cytolysin target molecule cholesterol and thiol-disulfide affinity chromatography is described.

Bacterial Toxins↗
PubMed1989

Direct isolation (without enrichment) of Listeria monocytogenes in milk.

In the present work we have developed a direct method (without enrichment) for the isolation of listeriae in milk, using the combinated action of SDS (sodium dodecyl sulphate), centrifugation and selective media. It is possible to identify even 0.5 listeriae/ml amongst 7.2 x 10(7) c.f.u. contaminants/ml.

Animals↗
PubMed1989

Serological diagnosis of listeriosis in man, sheep and rabbit by immunoperoxidase technique.

Due to the already demonstrated specificity and usefulness of Listeria intracellular antigen in paraffin-embedded tissues for the direct diagnosis, we have used an indirect immunoperoxidase technique for the serological diagnosis of listeriosis in man, sheep and rabbit. This technique has been compared with other immunoperoxidase techniques (PAP) using the same antigen, and with other serlogical techniques--ELISA and microplate agglutination test--using two kinds of Listeria antigens, live formalinized and heat at 100 degrees C for one hour whole cells.

Agglutination Tests↗
PubMed1988

Assessment of different selective agar media for enumeration and isolation of Listeria from dairy products.

Different selective agar media were compared for the recovery and isolation of five species of Listeria from raw milk and cheese. The selective media examined were Beerens medium, MacBride medium and that described by Dominguez et al. (1984) with 6 mg/l acriflavine, listeria selective agar medium (LSAM), and LSAM with 12 mg/l acriflavine (LSAM X 2A); a non-selective yeast glucose Lemco agar was included for comparison. When the difference between listeria and the natural microflora of raw milk and cheese was 10(2) cfu/ml, listeria could be isolated by direct plating on all media tested. When it was lower than 10(3)-10(4) cfu/ml, listeria were isolated by direct plating only on LSAM and LSAM X 2A. When the difference was greater than 10(4) cfu/ml, a previous enrichment was necessary to isolate them. LSAM and LSAM X 2A media performed better than the other media tested for isolating listeria by direct plating and improved their isolation from dairy products. This superior performance was evaluated by the ability of these media to support colony formation of different species of Listeria tested, the easy recognition of these colonies from those formed by other microorganisms and by their capacity to inhibit the natural microflora of these foods.

Agar↗