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Biomedical subjects

C Dietz

Publications and source records attributed to C Dietz.

15 recordsLinked to original sources
PubMed2006

Miniaturised selective pressurised liquid extraction of polychlorinated biphenyls from foodstuffs.

The feasibility of miniaturised pressurised liquid extraction (PLE) with in-cell purification and subsequent gas chromatography with micro-electron capture detection (GC-micro-ECD) for the determination of prioritary and toxic polychlorinated biphenyls (PCBs) in a variety of foodstuffs (fat contents in the range 22-49%, w/w, on a freeze-dried basis) has been investigated. After optimisation of the several experimental parameters affecting the efficiency of the selective PLE process, the developed method provided quantitative recoveries of the endogenous PCBs studied and complete fat elimination in a single step using n-hexane as extraction solvent. A total solvent volume of 3.5 mL was used for the two consecutive 7 min static PLEs of 100-mg samples. Detection limits using GC-micro-ECD were below 0.2 ng/g freeze dried sample for all 22 PCBs investigated in real-life foodstuffs, and the repeatability of the complete PLE plus GC-micro-ECD method as calculated for the analysis of the endogenous PCBs in general was better than 14%. Comparison of the miniaturised PLE method developed with either conventional Soxhlet extraction or matrix solid phase dispersion with subsequent (off-line) clean-up for the analysis of non-spiked samples showed that the efficiency of PLE was similar to or better (recoveries in the range 83-133%, as calculated for the endogenous analytes) than for the other two extraction methods assayed.

Analytic Sample Preparation Methods↗
PubMed2006

Identification of nanoscale dissipation processes by dynamic atomic force microscopy.

Identification of energy-dissipation processes at the nanoscale is demonstrated by using amplitude-modulation atomic force microscopy. The variation of the energy dissipated on a surface by a vibrating tip as a function of its oscillation amplitude has a shape that singles out the dissipative process occurring at the surface. The method is illustrated by calculating the energy-dissipation curves for surface energy hysteresis, long-range interfacial interactions and viscoelasticity. The method remains valid with independency of the amount of dissipated energy per cycle, from 0.1 to 50 eV. The agreement obtained between theory and experiments performed on silicon and polystyrene validates the method.

Journal Article↗
PubMed2006

Accelerated extraction for determination of polycyclic aromatic hydrocarbons in marine biota.

A rapid and simple method is proposed for determination of polycyclic aromatic hydrocarbons (PAH) in complex matrices such as marine biota. The method uses sonication, by means of an ultrasonic probe, as a new tool for assisted extraction, coupled with reversed-phase liquid chromatography (RP-LC) with fluorescence detection (FL) for determination of 16 US EPA priority PAH. Separation and detection of the 16 PAH were complete in 45 min by RP-LC with a C18 column and acetonitrile-water gradient elution. Multivariate optimisation of the variables affecting extraction (ultrasound radiation amplitude, sonication time, and temperature of the water-bath in which the extraction cell was placed) was conducted. The accuracy of the method was determined by analysis of a certified reference material and comparison of the results obtained with those from another method (microwave-assisted extraction and GC-MS). The new technique avoids the main problems encountered in the determination of PAH in complex matrices such as marine biota, and no clean-up step is necessary. The method was applied to determination of PAH in estuarine biota samples from the Urdaibai estuary (Biscay, Spain).

Animals↗
PubMed2006

Evaluation of uridine metabolism in human and animal spermatozoa.

The objective of this study was to elucidate the role of uridine for spermatozoa, since this pyrimidine nucleoside was found in millimolar concentration in human seminal plasma. Here, the degradative activity of uridine-phosphorylase [EC 2.4.2.3] and the salvage activity of uridine kinase [EC 2.7.1.48] were detected in human spermatozoa. HPLC analysis depicted the uptake of exogeneous 14C-labelled adenine, but not of uridine and of hypoxanthine, into nucleotide pools of boar spermatozoa. On addition of uridine, the computer-assisted semen analysis (CASA) of human cells revealed a reduction of the percentage of motile spermatozoa in contrast to an elevation of some velocity parameters. It is concluded that exogeneous uridine could function as suppressor for early capacitation and as a substrate for phosphorolysis, if ribose is needed, rather than to satisfy a demand for intracellular pyrimidine nucleotides.

Adenine↗
PubMed2005

[Reoperation for primary hyperparathyroidism].

While the initial treatment for primary hyperparathyroidism (pHPT), if managed by an experienced surgeon, is almost always successful, reoperations are challenging. Patients are at high risk for complications and the rates of success are plainly below those of primary cervical explorations. In this paper the reasons for failure during initial procedures are reviewed, as are the most important localization procedures and the prerequisites with regard to technical infrastructure as well as personnel, when planning repeat operations for a missed parathyroid adenoma. Provided that a standardized diagnostic and surgical approach is used, the surgeon is experienced, and up-to-date technical equipment is available, permanent normocalcemia following reoperations in pHPT is more frequently achieved than it used to be. The best option to avoid reoperations and associated complications is a successful initial intervention by an experienced surgeon. However, reoperations should always be performed by an experienced surgeon.

Adenoma↗
PubMed2002

Detection and location of the enzymes of de novo pyrimidine biosynthesis in mammalian spermatozoa.

Enzymes of the pathway for de novo biosynthesis of pyrimidine nucleotides have been reported in spermatozoa from fruitfly and mammals. The aim of the present study was to test the hypothesis that the enzymes for biosynthesis of uridine monophosphate (UMP) are concentrated near the mitochondria, which are segregated in the mid-piece of spermatozoa. Baby hamster kidney fibroblasts were compared with spermatozoa from rams, boars, bulls and men. Antibodies raised against synthetic peptides from sequences of the multienzyme polypeptides containing glutamine-dependent carbamyl phosphate synthetase, aspartate transcarbamylase and dihydroorotase (CAD) and UMP synthase, which catalyse reactions 1-3 and 5-6, respectively, were used, together with an affinity-purified antibody raised against dihydroorotate dehydrogenase (DHODH), the mitochondrial enzyme for step 4. Western blot analysis, immunofluorescent microscopy and immunoelectron microscopy confirmed that CAD and UMP synthase are found in the cytoplasm around and outside the mitochondria; DHODH is found exclusively inside the mitochondria. CAD was also located in the nucleus, where it has been reported in the nuclear matrix, and in the cytoplasm, apparently associated with the cytoskeleton. It is possible that CAD in the cytoplasm has a role unconnected with pyrimidine biosynthesis.

Animals↗
PubMed2001

Pediatric otolaryngologists' knowledge and understanding of genetic testing for deafness.

OBJECTIVE: To assess the level of a cohort of pediatric otolaryngologists' knowledge and understanding of genetics and genetic testing for deafness and hard of hearing (D/HOH). METHODS: A questionnaire was designed to assess the level of knowledge and understanding of the genetic basis and genetic testing for deafness among a cohort of pediatric otolaryngologists. Three hundred questionnaires were made available to attendees of the 14th (1999) Annual Meeting of the American Society of Pediatric Otolaryngology, Palm Desert, Calif. A series of questions asked to gauge the respondent's level of knowledge of genetics and hearing impairment addressed estimating recurrence risks for deaf and normal-hearing parents and the likelihood of detecting a mutation in connexin 26 in specific clinical scenarios. RESULTS: A total of 28 questionnaires were completed and returned. All respondents reported that they regularly saw patients for D/HOH. Almost half commonly refer these patients for genetic testing and counseling. Seventeen (71%) of 24 otolaryngologists stated they offered genetic testing in all situations, while 6 offered counseling only at parental request or to address recurrence risk issues. One otolaryngologist offered genetic testing if there was a deaf sibling. Twelve (67%) of 18 offered pretest counseling, which was most frequently provided by a genetic counselor. Although 3 (19%) of 16 otolaryngologists provided the counseling themselves, 2 (13%) reported that they and a genetic counselor provided the counseling. While 24 (89%) of the 27 correctly stated that nonsyndromic D/HOH is usually autosomal recessive, recurrence risks were incorrectly estimated in several examples. CONCLUSIONS: While the surveyed pediatric otolaryngologists have a good knowledge of genetics and genetic testing for D/HOH, recurrence risks were often inaccurate. Since D/HOH testing is clinically available, it is imperative that physicians are educated about genetics and genetic testing and are able to communicate this to their patients and their patients' families.

Child↗
PubMed2000

The capillary cold trap as a suitable instrument for mercury speciation by volatilization, cryogenic trapping, and gas chromatography coupled with atomic absorption spectrometry.

An innovative accessory for speciation analysis has been developed. The system is based on the combination of cryogenic trapping and gas chromatographic separation, carried out within the same capillary. The instrument, hyphenating derivatization, gas-phase extraction, preconcentration, and analyte separation, is semiautomated, and all operational parameters are adjustable via an in-house-developed control unit, which regulates the selected parameters throughout the analysis process. Species detection was carried out by atomic absorption spectrometry. The detection limits achieved were 33, 39, and 71 ng L(-1) for dimethylmercury, methylmercury, and inorganic mercury, respectively. A complete chromatogram could be obtained within three minutes, resulting in the duration of one whole analysis cycle of about 15 min. The proposed method was applied to mercury speciation in freeze-dried tuna fish powder after microwave-assisted extraction, finding that mercury is present at 80% as methylmercury and about 20% as inorganic mercury, in this kind of biological material.

Animals↗
PubMed2000

Immunocytochemical detection of mitochondrial dihydroorotate dehydrogenase in human spermatozoa.

In mammalian cells the requirement for pyrimidines is met by uridine phosphate (UMP) de novo synthesis and, to a greater or lesser extent, by salvage of free nucleosides. The fourth enzyme of the de novo synthesis, the mitochondrially bound dihydroorotate dehydrogenase (DHODH) was the focus of the present study. Rabbit anti-DHODH IgG, which was generated using an immunization protocol with truncated recombinant human DHODH protein and purified by an immunosorbent method, was used for immunocytochemical detection and localization of this enzyme in ejaculated human spermatozoa. The presence of DHODH protein was demonstrated by Western blotting of solubilized membrane fractions with peroxidase conjugated anti-rabbit IgG in combination with chemiluminescence detection. Indirect immunofluorescence microscopy, using Cy3-conjugated anti-rabbit IgG, revealed specific binding in the midpiece of spermatozoa. As these cells no longer have a demand for de novo biosynthesis of pyrimidines, we hypothesize that the pathway could serve a specialized function in nitrogen or zinc metabolism during the process of spermiogenesis and/or epididymal maturation.

Animals↗
PubMed2000

[Intraoperative cholangiography in laparoscopic cholecystectomy for acute cholecystitis].

In our prospective study we wanted to prove whether the safety of laparoscopic treatment of acute cholecystitis could be improved by intraoperative cholangiography. From July 1993 to June 1998 210 patients with acute cholecystitis underwent a laparoscopic cholecystectomy. In 23 cases (10.9%) a conversion was necessary. 189 patients underwent a laparoscopic cholangiography. In 2 cases (1.1%) an incision of the common bile duct was detected which had been mistaken for the cystic duct. So the cutting of the common bile duct could be prevented. In 12 patients (6.3%) unknown common bile duct stones were found. The complication rate was 9.5% without any mortality or major injury of the common bile duct.

Acute Disease↗
PubMed1994

A new type of Ca(2+)-dependent, Mg(2+)-stimulated ATPase of rat liver plasma membrane.

Incubation of a glycoprotein fraction obtained from rat liver plasma membrane which has been previously well characterized using [gamma-32P]ATP results in the phosphorylation of a 230-kDa glycoprotein (pgp230). It is composed of a 120-kDa subunit (pgp120) and a 110-kDa subunit (pgp110) linked by interchain disulfide bonds. Peptide maps of pgp120 and pgp110 suggest extensive similarity in their polypeptide chains. Glycan analysis reveals between four and six hybrid-type oligosaccharide chains for both phosphoproteins. Immunoblotting using monoclonal antibodies and endoglycosidase digestion exclude an identity of pgp120 or pgp110 with the hepatocyte plasma membrane glycoproteins dipeptidylpeptidase IV or the taurocholate transport protein, which co-purify and co-migrate in SDS/PAGE. Protein phosphorylation is Ca(2+)-dependent (K0.5(Ca2+) = 0.35 microM, in the absence of Mg2+). In the presence of Mg2+, the glycoprotein undergoes rapid cycles of phosphorylation and dephosphorylation, resulting in ATPase activity. Analysis of phosphorylated amino acids identifies phosphothreonine as the major one. Photoaffinity labeling with 8-azido-[alpha-32P]ATP demonstrates the presence of one or more ATP binding site(s). Preincubation of pgp230 with various purine or pyrimidine nucleotides (ATP, UTP, TTP, ADP, GDP, AMP, CMP) or known P2-purinoceptor agonists or antagonists (adenosine 5'-[alpha,beta-methylene]triphosphate, 2-methyl-thio-adenosine 5'-triphosphate, suramin) inhibits its phosphorylation by [gamma-32P]ATP. The biological function of pgp230 is unknown at present. Several findings of the present study are compatible with the idea that pgp230 may be involved in a P2-purinoceptor function of the hepatocyte. Following this concept, a mechanism is discussed where a cytosolically exposed high-affinity Ca(2+)-binding site of pgp230 would allow for receptor feedback control, via phosphorylation and dephosphorylation, by sensing changes in cytosolic Ca2+ concentration.

Adenosine Triphosphate↗
PubMed1994

Immuno-gold electron microscopical detection of heat shock protein 60 (hsp60) in mitochondria of rat hepatocytes and myocardiocytes.

We characterize the specificity of a polyclonal antibody against heat shock protein 60 (hsp60) and present an application for ultrastructural localization studies of this protein. The antibody was obtained from an IgG fraction (AB 121) originally raised against the calcium binding protein calsequestrin by immunoabsorption on isolated rat liver hsp60. As shown by partial N-terminal amino acid sequence analysis of immunoprecipitated proteins AB 121 contained reactivities against hsp60, calsequestrin and the glycoprotein fetuin. In rat heart AB 121 recognized calsequestrin and hsp60. In human and rat liver the only reacting protein was hsp60. In rat erythrocytes the antibody bound to 61 kDa and 58 kDa isoforms of fetuin. According to published data no amino acid sequence homologies nor common motifs are found between calsequestrin, hsp60 and fetuin. As the first application the anti-hsp60 antibody was used for immuno-gold electron microscopical localization of hsp60: in myocardiocytes and hepatocytes of the rat strong labelling was obtained exclusively in mitochondria. No extramitochondrial structures were labelled. The specificity of the antibody and its ability to be visualized by immuno-gold electron microscopy offers the possibility to study the expression of this protein in the liver and in other organs. Possible clinical applications of these studies are discussed, since hsp60 could be a target antigen of autoantibodies in diseases such as autoimmune hepatitis, primary sclerosing cholangitis or primary biliary cirrhosis.

Amino Acid Sequence↗
PubMed1991

[Postoperative analgesia following spondylodesis using a peridural catheter placed during surgery. Results of a pilot study].

For the treatment of postoperative (p.o.) pain following vertebral surgery, systemic analgesics are frequently used in high doses with a variety of side effects. It was the aim of this study to investigate p.o. epidural catheter analgesia in 20 patients following surgical correction of scoliosis using the Cotrel and Dubousset technique. METHODS. The patients received balanced general anesthesia with fentanyl and isoflurane. At the end of the operation, before closing the fascia, an epidural catheter was placed by the orthopedic surgeon. After extubation and following evaluation of the motor function of all extremities. 6-10 ml bupivacaine 0.25% was injected into the epidural catheter followed by continuous administration of 0.25% bupivacaine 4-8 ml/h. Analgesic level and hemodynamic parameters were monitored. Pain was measured by the visual analogue scale. If analgesia was not sufficient, the patients received tramadol or piritramide intravenously. RESULTS. In 11 of 20 patients epidural analgesia was rated adequate; 5 needed additional systemic analgesics, and in 4 effective analgesia was not achieved with either epidural analgesia or systemic opioids. No complications were observed. DISCUSSION. The pilot study documented that epidural analgesia using an intraoperatively placed epidural catheter can be used for p.o. pain relief after vertebral surgery using the Cotrel and Dubousset technique. Additional studies will compare the method described to other pain-relieving procedures.

Adolescent↗