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Biomedical subjects

L J Martinez

Publications and source records attributed to L J Martinez.

10 recordsLinked to original sources
PubMed1998

The effects of custom tray material on the accuracy of master casts.

PURPOSE: The accuracy of master cast reproduction by a polyvinylsiloxane impression material using two visible-light-curing resin and an autopolymerizing polymethyl methacrylate resin custom tray materials was investigated. MATERIALS AND METHODS: Custom trays were fabricated from a master cast that had three index points marked on both the inner and outer vestibules. Impressions were made of the master cast using Extrude and then poured in Die Keen Green stone. The distances between the reproduced index points were measured to +/- 0.01 mm with a traveling microscope and the algebraic norms calculated for each tray material. RESULTS: No differences (p > .05) were found in the dimensions of the inner index points, while the separations of the outer index points indicated that there were differences in the accuracy of reproduction (p < .01) by the three tray materials. The index points reproduced on the casts, compared with the master cast, were closer together for the Triad Blue trays than for the TruTray and Ontray impression trays. CONCLUSIONS: All three tray materials produced acceptable casts, but the greatest accuracy was achieved with TruTray, followed by Ontray. Triad Blue produced casts that were slightly smaller than the master. In practice, the small measured differences in cast dimensions may not have clinical significance.

Analysis of Variance↗
PubMed1998

Influence of solvent polarity and proticity on the photochemical properties of norfloxacin.

The fluoroquinolone antibacterial norfloxacin (NF) is a moderate photosensitizer of singlet molecular oxygen (1O2). We have studied photosensitization by NF as a function of medium polarity and proticity in solvent mixtures. We have used 1,4-dioxane and propylene carbonate mixtures to keep proticity constant while modulating polarity, and water/D2O and ethylene carbonate mixtures to alter proticity without large changes in polarity. The absorption spectrum of NF was little affected by solvent changes, as compared to the fluorescence spectrum that exhibited as much as a 50 nm blue-shift, e.g. 1,4-dioxane versus D2O. The quantum yield of NF fluorescence saturated at an almost 10 times higher value (approximately 0.14) when proticity was increased by added water, up to 0.2 mol fraction, to ethylene carbonate. Less pronounced, the increasing polarity in 1,4-dioxane/propylene carbonate mixtures affected the fluorescence yield much less. Norfloxacin produces 1O2 and is able to quench 1O2. The rate constant for 1O2 quenching is 4.5 x 10(7) M-1 s-1 in propylene carbonate but decreases ca four times in D2O. The quantum yield of 1O2 photogeneration was also up to five times higher in solvents that were both protic and polar than vice versa. Our data show that NF is more photochemically active in an environment that is both protic and polar. This suggests the involvement of polar excited state(s) and possible proton/hydrogen transfer during photoexcitation. Similar processes may initiate the phototoxic response reported in some patients treated with the fluoroquinolone drugs. The phototoxicity of NF and other fluoroquinolone antibiotics may strongly depend on their localization in hydrophilic or hydrophobic cell/tissue regions.

Animals↗
PubMed1997

Safe biotechnology. 8. Transport of infectious and biological materials. Working Party "Safety in Biotechnology" of the European Federation of Biotechnology.

The transport of infectious and biological material is regulated by a number of international organizations. This mini-review has been compiled to increase awareness within the scientific community of problems caused by differences in terminology (such as infectious materials/substances, biological products, diagnostic specimens, genetically modified microorganisms) and certain technical aspects of the main international guidelines, and to assist policy makers in the creation of harmonized guidelines. A list of relevant Internet resources has been compiled.

Animals↗
PubMed1997

Photogeneration of fluoride by the fluoroquinolone antimicrobial agents lomefloxacin and fleroxacin.

The photolysis (> 320 nm) of the fluoroquinolone antibacterial agents lomefloxacin and fleroxacin results in the loss of their F3 atoms as fluoride. The quantum yield for lomefloxacin was 0.98 at pH 7.4. The mechanism probably involves aryl-F heterolysis from the S1 state with the concomitant generation of a carbene at C-8. In contrast, the monofluorinated fluoroquinolones norfloxacin and ciprofloxacin do not generate fluoride upon irradiation. Carbenes are highly reactive species that undergo addition, insertion and abstraction reactions and can cause DNA cleavage. These findings may explain why lomefloxacin and fleroxacin are more photomutagenic and photocarcinogenic than fluoroquinolones in which C-8 is either unsubstituted or bears a substituent other than fluorine.

Anti-Infective Agents↗
PubMed1996

Photosensitization by norfloxacin is a function of pH.

Norfloxacin is a fluoroquinolone (FQ) antibiotic that has been reported to cause cutaneous photosensitivity in animals and occasionally in humans. We have studied the fluorescence and singlet oxygen (1O2)-generating properties of norfloxacin. Upon UV excitation the drug fluoresces in water, and the relative intensities of two major fluorescence bands at ca 420 and 450 nm are affected by pH. The overall quantum yield of fluorescence (phi F) is also strongly pH dependent: phi F is low in 0.2 N HCl solution (0.2), increasing steeply to 0.12 at pH 4, then gradually decreasing to 0.01 at pH 10. The changes in phi F are accompanied by changes in fluorescence lifetime from 0.6 ns at pH 1 to 1.8 ns at pH 4. Norfloxacin exhibits phosphorescence in low temperature glasses. The formation of a triplet state at room temperature is also suggested by 1O2 phosphorescence in aerobic D2O. This phosphorescence is "self-quenched" by norfloxacin itself with an efficiency that is pH dependent: kq is 7.9 x 10(6) M-1 s-1 at pD 4, decreases to 1.9 x 10(6) M-1 s-1 at pD 7.5 but then increases about 20-fold in alkaline D2O solutions. This quenching causes the observed 1O2 production by norfloxacin (0.1 mM) to show a maximum at around pH 8-9. However, after correction for self-quenching, the quantum yield of 1O2 production (phi 50)y measured by using perinaphthenone as a standard, yielded the following values: phi s0 is about 0.07 in 0.2 N DCI solution, 0.08 at pH 7.5 and then increases smoothly to approximately 0.2 in 0.1 M NaOD solution. The relatively high, unquenched 1O2 production at physiological pH 7.4 (phi s0 approximately 0.08) suggests that 1O2 reactions may play an important role in the cutaneous phototoxicity of norfloxacin and other FQ antibiotics.

Animals↗
PubMed1994

Gliosarcoma. Case report with immunohistochemical study.

A typical case of gliosarcoma in a 74 year-old woman is reported. The exact origin of sarcomatous areas of this tumor has been a matter of debate. Our immunohistochemical findings, using a panel of antibodies (GFAP), vimentin, keratins, F-VIII related antigen, muscle specific actin, KP-1 and HMB-45), support its undifferentiated nature. The literature concerning this topic is reviewed and briefly discussed.

Aged↗
PubMed1990

Identification and cloning of nodulation genes and host specificity determinants of the broad host-range Rhizobium leguminosarum biovar phaseoli strain CIAT899.

Rhizobium leguminosarum biovar phaseoli type II strain CIAT899 nodulates a wide range of hosts: Phaseolus vulgaris (beans), Leucaena esculenta (leucaena) and Macroptilium atropurpureum (siratro). A nodulation region from the symbiotic plasmid has been isolated and characterized. This region, which is contained in the overlapping cosmid clones pCV38 and pCV117, is able to induce nodules in beans, leucaena and siratro roots when introduced in strains cured for the symbiotic plasmid, pSym. In addition, this cloned region extends the host range of Rhizobium meliloti and R. leguminosarum biovar (bv.) trifolii wild-type strains to nodulate beans. Analysis of constructed subclones indicates that a 6.4kb HindIII fragment contains the essential genes required for nodule induction on all three hosts. Rhizobium leguminosarum bv. phaseoli type I strain CE3 nodulates only beans. However, CE3 transconjugants harbouring plasmid pCV3802 (which hybridized to a nodD heterologous probe), were capable of eliciting nodules on leucaena and siratro roots. Our results suggest that the CIAT899 DNA region hybridizing with the R. meliloti nodD detector is involved in the extension of host specificity to promote nodule formation in P. vulgaris, L. esculenta and M. atropurpureum.

Cloning, Molecular↗
PubMed1979

Trans-sphenoidal removal of a Rathke's cleft cyst.

Symptomatic Rathke's cleft cysts are uncommon. We present a case with suprasellar extension manifested by hypopituitarism and visual disturbances. The treatment was trans-sphenoidal evacuation and partial removal of the capsule. We suggest that the trans-sphenoidal approach to these lesions is usually adequate and that radical removal of the capsule is not necessary.

Confusion↗