Biomedical subjects

R Tessadri

Publications and source records attributed to R Tessadri.

5 recordsLinked to original sources

PubMed2000

Quantification of lanthanides in rocks using succinic acid-derivatized sorbents for on-line SPE-RP-ion-pair HPLC

The use of new poly(norbornene-block-7-oxanorborn-2ene-5,6-dicarboxylic acid)-coated silica-based sorbents as well as of beaded polymers based on poly(norborn-2-ene-5,6-dicarboxylic acid-co-1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphthalene) for the on-line preconcentration of lanthanides from rock digests and their subsequent RP-ion-pair HPLC separation is described. Block co-polymers of norborn-2-ene and 7-oxanorborn-2-ene-5,6-dicarboxylate used for coating were prepared by ring-opening metathesis polymerization (ROMP) and poly(norborn-2-ene-5,6-dicarboxylic acid-co-1,4,4a,5,8,-8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphthalene)-based polymer beads were prepared by ring-opening metathesis precipitation polymerization. Both types of sorbents exhibit an extraordinarily good pH stability, are hydrophilic and therefore easily wetable by water alone, and show high extraction efficiencies for lanthanides within a pH of 3.5-5.5. The rare earth element (REE) content in the investigated rocks varied over 3 orders of magnitude (0.19-108 microg/g). REE concentrations prior to enrichment were typically in the range of 1-25 ng/mL; the total amount of each REE sorbed onto the precolumn was in the range of 8-270 ng. Extraction selectivities of the sorbent may be enhanced by adding 5-sulfosalicylic acid as a masking agent for iron and aluminum as well as methanol as an inhibitor for the precipitation of o-silicic acid. Gradient elution of the lanthanides from the precolumn and their subsequent separation on a RP-C18 column was achieved using hydroxyisobutyric acid (HIBA) and sodium octanesulfonate. Depending on the actual concentration of the lanthanides in the digests and in order to suppress interfering cations, UV detection was carried out with two different postderivatization reagents, 4-(2-pyridylazo)resorcinol (PAR) and arsenazo III. The high selectivity in enrichment as well as the complementary use of post-derivatization reagents allows the fast, quantitative, and highly reproducible quantification of REEs present in rocks by complete removal or suppression of all other interfering components. Thus, recoveries were found to be within a range of 97-103% for most REEs with relative standard deviations of 2-5%.

Journal Article↗

PubMed1996

Intraperitoneal cholelithiasis after laparoscopic cholecystectomy--behavior of 'lost' concrements and their role in abscess formation.

UNLABELLED: In two experimental studies we sought preliminary information about the behavior of concrements lost in the peritoneal cavity during laparoscopic cholecystectomy. MATERIALS AND METHODS: In study 1, human gallstones were analyzed using X-ray diffraction, classified in three groups and examined with an ultramicroscope; then they were implanted in the peritoneal cavity of rats. After 8 weeks or 6 months, the animals were sacrificed and the concrements analyzed again as before. The tissues surrounding the calculi were also examined histologically. In study 2, human gallstones were examined with regard to bacterial contamination on the surface or in the middle of the calculi. The cholesterol content was analyzed, and the stones were divided into three groups and implantated in the rats as in the first study. After 8 weeks, the animals were sacrificed and areas with identifiable tissue reactions were examined histologically and microbiologically. RESULTS: The concrements lost their crystalline formation without any relation to their former cholesterol content, as shown by X-ray diffraction as well as ultramicroscopy. Mineralogically, these changes are a certain sign of structural dissolution. Cholesterol stones only caused abscess formations in association with gram-negative bowel germs. Sterile pigment concrements often led to a mesenchymal reaction such as granulomas. Contaminated pigment stones also resulted in extensive abscess formations.

Abscess↗

PubMed1987

[Analysis of a dacrolith ].

Dacryoliths are uncommon and there are only a few reports in the literature. In a patient with recurrent stenosis of the lacrimal drainage system a lacrimal stone (dacryolith) was removed from the lacrimal sac during dacryocystorhinostomy. A histological and immunohistochemical examination was performed and keratin antibodies could be detected. In a chemical analysis calcium, sulfur and some phosphorus were determined as major constituents.

Adult↗

PubMed1987

Trace element investigations in kidney stone patients.

31 different trace elements were analyzed in 24 kidney stones using the atomic absorption method. Where a significant trace element content in the concrements was detected, blood, urine and hair from the stone patients were investigated with respect to their trace element concentrations. In calcium stones mainly Fe, Pb, Sr and Zn and in organic stones As, Fe and Zn were found. No correlation could be found between the trace element content in stones, blood and urine. The hair of a woman with high As content in her stone contained a normal As concentration.

Female↗

PubMed1983

Combined analysis of kidney stones by X-ray diffraction and electron microprobe.

Oxalate, apatite, struvite, uric acid and cystine stones were routinely analysed by X-ray diffraction. A second analysis was performed by electron microprobe. The substances not detected by X-ray diffraction were apatite and struvite in oxalate and cystine stones. Oxalate was not found in uric acid stones because of insufficient routine sample preparation, but could be detected in a second X-ray analysis. Conclusions concerning the exact stone composition can only be reached after X-ray diffraction has been completed in conjunction with a second procedure, such as electron microprobe analysis. For clinical routine use X-ray diffraction is sufficient if adequate sample preparation is performed. The electron microprobe analysis provides further information about mixed phase formations (single or multiple layers, diffuse distributions etc.) and about inclusions in a phase, which have some clinical consequences.

Crystallization↗