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Biomedical subjects

P Christen

Publications and source records attributed to P Christen.

At least 19 recordsLinked to original sources
PubMed2005

The effects of cranberry juice consumption on antioxidant status and biomarkers relating to heart disease and cancer in healthy human volunteers.

BACKGROUND: Consumption of fruit and vegetables is associated with a decreased risk of heart disease and cancer. This has been ascribed in part to antioxidants in these foods inactivating reactive oxygen species involved in initiation or progression of these diseases. Non-nutritive anthocyanins are present in significant amounts in the human diet. However, it is unclear whether they have health benefits in humans. AIM: To determine whether daily consumption of anthocyanin-rich cranberry juice could alter plasma antioxidant activity and biomarkers of oxidative stress. METHODS: 20 healthy female volunteers aged 18-40 y were recruited. Subjects consumed 750 ml/day of either cranberry juice or a placebo drink for 2 weeks. Fasted blood and urine samples were obtained over 4 weeks. The total phenol, anthocyanin and catechin content of the supplements and plasma were measured. Anthocyanin glycosides were identified by tandem mass spectrometry (MS-MS). Vitamin C, homocysteine (tHcy) and reduced glutathione (GSH) were measured by HPLC. Total antioxidant ability was determined using electron spin resonance (ESR) spectrometry and by the FRAP assay. Plasma total cholesterol, high density lipoprotein (HDL), and low density lipoprotein (LDL) cholesterol and triglycerides (TG) were measured. Glutathione peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD) activities were measured in erythrocytes. Urine was collected for analysis of malondialdehyde (MDA) by HPLC and 8-oxo-deoxyguanosine (8-oxo-dG) by ELISA. Endogenous and induced DNA damage were measured by single cell gel electrophoresis (SCGE) in lymphocytes. RESULTS: Vitamin C, total phenol, anthocyanin and catechin concentrations and FRAP and ESR values were significantly higher in the cranberry juice compared with the placebo. Cyanidin and peonidin glycosides comprised the major anthocyanin metabolites [peonidin galactoside (29.2%) > cyanidin arabinoside (26.1%) > cyanidin galactoside (21.7%) > peonidin arabinoside (17.5%) > peonidin glucoside (4.1%) > cyanidin glucoside (1.4 %)]. Plasma vitamin C increased significantly (P<0.01) in volunteers consuming cranberry juice. No anthocyanins (plasma) or catechins (plasma or urine) were detectable and plasma total phenols, tHcy,TC,TG,HDL and LDL were unchanged. The antioxidant potential of the plasma, GSH-Px, CAT and SOD activities, and MDA were similar for both groups. Supplementation with cranberry juice did not affect 8-oxo-deoxyguanosine in urine or endogenous or H(2)O(2)-induced DNA damage in lymphocytes. CONCLUSIONS: Cranberry juice consumption did not alter blood or cellular antioxidant status or several biomarkers of lipid status pertinent to heart disease. Similarly, cranberry juice had no effect on basal or induced oxidative DNA damage. These results show the importance of distinguishing between the in vitro and in vivo antioxidant activities of dietary anthocyanins in relation to human health.

Adolescent↗
PubMed2004

[Preserving vision in the elderly: a survey to start a quality development program in general practice].

The study examined the rate of patients, who do not follow recommendations for routine screening, do not visit physicians for eye-symptoms and when suffering from diabetes or glaucoma do not adhere to follow-up. To what extent can primary care physicians impact on these deficits of ophthalmologic care? 4918 consecutive, > or = 40 old patients of 107 primary care physicians of 9 networks participated. Of these patients 15% had never, 43% not within the last 3 years, consulted an ophthalmologist. 16% were diabetics, 7% had glaucoma and 46% had observed subjective eye symptoms. A quarter of these patients turn to their primary care physician, when having eye problems. Primary care physicians do not frequently suggest routine ophthalmologic controls nor do they use diagnostic tools like the Amsler-grid or the Swinging-Flash-Light Test.

Adult↗
PubMed2003

Cardiac arrest in an infant with congenital adrenal hyperplasia.

We report a 3-month-old boy who suffered an out-of-hospital cardiac arrest. During resuscitation, the medical team was informed that he was receiving hydrocortisone treatment. The possibility of adrenal insufficiency with hyperkalemic cardiac arrest prompted the administration of calcium, which resulted in the return of spontaneous circulation. The infant's diagnosis of congenital adrenal hyperplasia was not spontaneously mentioned by the parents. This case illustrates the importance of obtaining adequate parental information and considering hyperkalemia as a possible cause of cardiac arrest.

Adrenal Hyperplasia, Congenital↗
PubMed2002

Biofiltration of volatile ethanol using sugar cane bagasse inoculated with Candida utilis.

Candida utilis (C. utilis) growing on sugar cane bagasse complemented with a mineral salt solution was studied for gaseous ethanol removal in a biofilter. Ethanol loads from 93.7 to 511.9 g/h m(3) were used, by varying both inlet ethanol concentration (9.72 to 52.4 g/m(3)) and air flow rate (1.59 x 10(-3) to 2.86 x 10(-3) m(3)/h). At a loading rate of 93.7 g/h m(3), a steady-state was maintained for 300 h. Ethanol removal was complete, and 76.3% of the carbon consumed was found in carbon dioxide. At an higher aeration rate (ethanol load=153.8 g/h m(3)), the biofilter displayed an average removal efficiency (RE) of 70%, and an elimination capacity (EC) of 107.7 g/h m(3). Only 64.4% of the carbon consumed was used for CO(2) production. Acetaldehyde and ethyl acetate in the outlet gas attained 7.86 and 20.4% in terms of carbon balance, respectively. In both cases, the transient phase was less than one day. At a high inlet ethanol concentration (52.4 g/m(3)), no steady-state was observed and the process stopped during the third day. In the three cases, final biomass was poor, ranging from 10.5 to 14.8 mg/g dm. Final pH 4.0-4.6, indicated that acidifying non-volatile metabolites, such as acetate, accumulated in the reactor.

Agriculture↗
PubMed2002

Effect of mineral salts addition on the behaviour of an ethanol biofilter.

Ethanol biofiltration was studied in a 0.1651 packed bed reactor filled with sugar cane bagasse complemented with mineral medium and inoculated with Candida utilis. The main objective was to improve the elimination capacity of the system by adding salts to the solid medium. The biofilter was operated for one month, varying both the inlet ethanol concentration (7.6-16.5 g m(-3) and the airflow rate (1.61-2.50 x 10(-3) m3 h(-1)). Removal efficiency (RE) of 100% was attained at ethanol loads ranging from 74.2 to 250 g h(-1) m(-3). When the RE decreased, acetaldehyde and ethyl acetate appeared in the outlet stream; adding mineral salts restored a 100% RE. Both ammonium sulfate and ammonia were assimilated by the yeast (conversion yield of nitrogen from the N-source to biomass of 75%), but only ammonia restored the pH of the medium to a value adequate for efficient biofiltration (7.7). Fifty seven percent of the carbon from ethanol was converted into CO2, and 8.7% into biomass. Final yeast population was 7 x 10(9) cells g(-1) dry matter, corresponding to 56 mg protein g(-1) dry matter, which offers potential to also use the protein enriched bagasse as feed.

Biodegradation, Environmental↗
PubMed2001

Non-aqueous capillary electrophoresis with diode array and electrospray mass spectrometric detection for the analysis of selected steroidal alkaloids in plant extracts.

Nonaqueous capillary electrophoresis coupled to UV detection is described for the separation and determination of steroidal alkaloids. After optimization of electrophoretic parameters, including the electrolyte nature and the organic solvent composition, a reliable separation of solasodine and solanidine was achieved in a methanol-acetonitrile (20:80, v/v) mixture containing 25 mM ammonium acetate and 1 M acetic acid. For quantitative purposes, a fused-silica capillary with a bubble cell was used and detection was performed at low wavelength (195 nm). Method performances, including migration time and peak area reproducibility, linearity, sensitivity and accuracy, were also evaluated. The method was applied to determine solasodine in Solanum elaeagnifolium berries and Solanum sodomaeum leaves and seeds. To further improve sensitivity in the analysis of solasodine-related compounds, solanidine, demissidine and tomatidine, the developed method was interfaced with electrospray ionization mass spectrometry. In the case of solasodine, the detection limit was estimated at 3 microg/ml for NACE-UV and at 0.05 microg/ml for NACE-MS, in the selected ion-monitoring mode.

Electrophoresis, Capillary↗
PubMed2001

Mutations in the interdomain linker region of DnaK abolish the chaperone action of the DnaK/DnaJ/GrpE system.

Hsp70s assist the folding of proteins in an ATP-dependent manner. DnaK, the Hsp70 of Escherichia coli, acts in concert with its co-chaperones DnaJ and GrpE. Amino acid substitutions (D388R and L391S/L392G) in the linker region between the ATPase and substrate-binding domain did not affect the functional domain coupling and oligomerization of DnaK. The intrinsic ATPase activity was enhanced up to 10-fold. However, the ATPase activity of DnaK L391S/L392G, if stimulated by DnaJ plus protein substrate, was five times lower than that of wild-type DnaK and DnaK D388R. This defect correlated with the complete loss of chaperone action in luciferase refolding. Apparently, the conserved leucine residues in the linker mediate the synergistic effects of DnaJ and protein substrate on ATPase activity, a function which might be essential for chaperone action.

Adenosine Triphosphatases↗
PubMed2001

From cofactor to enzymes. The molecular evolution of pyridoxal-5'-phosphate-dependent enzymes.

The pyridoxal-5'-phosphate (vitamin B(6))-dependent enzymes that act on amino acid substrates have multiple evolutionary origins. Thus, the common mechanistic features of B(6) enzymes are not accidental historical traits but reflect evolutionary or chemical necessities. The B(6) enzymes belong to four independent evolutionary lineages of paralogous proteins, of which the alpha family (with aspartate aminotransferase as the prototype enzyme) is by far the largest and most diverse. The considerably smaller beta family (tryptophan synthase beta as the prototype enzyme) is structurally and functionally more homogenous. Both the D-alanine aminotransferase family and the alanine racemase family consist of only a few enzymes. The primordial pyridoxal-5'-phosphate-dependent protein catalysts apparently first diverged into reaction-specific protoenzymes, which then diverged further by specializing for substrate specificity. Aminotransferases as well as amino acid decarboxylases are found in two different evolutionary lineages, providing examples of convergent enzyme evolution. The functional specialization of most B(6) enzymes seems to have already occurred in the universal ancestor cell before the divergence of eukaryotes, archebacteria, and eubacteria 1500 million years ago. Pyridoxal-5'-phosphate must have emerged very early in biological evolution; conceivably, metal ions and organic cofactors were the first biological catalysts. To simulate particular steps of molecular evolution, both the substrate and reaction specificity of existent B(6) enzymes were changed by substitution of active-site residues, and monoclonal pyridoxal-5'-phosphate-dependent catalytic antibodies were produced with selection criteria that might have been operative in the evolution of protein-assisted pyridoxal catalysis.

Amino Acid Isomerases↗
PubMed2001

5',6'-dehydroguiachrysine and 5',6'-dehydroguiaflavine, two curarizing quaternary indole alkaloids from the stem bark of Strychnos guianensis.

Two new quaternary indole alkaloids 5',6'-dehydroguiachrysine (1) and 5',6'-dehydroguiaflavine (2) were isolated from Strychnos guianensis stem bark. Their structures were determined by analysis of spectral data. Their inhibitory effects on neuromuscular transmission are also reported and compared to that of other quaternary alkaloids.

Alkaloids↗
PubMed2001

Calystegine distribution in some solanaceous species.

The distribution of eight calystegines (A(3), A(5), B(1), B(2), B(3), B(4), C(1) and N(1)) and their content was investigated by gas chromatography coupled to mass spectrometry (GC-MS) in Datura metel, Atropa belladonna, Hyoscyamus albus, Mandragora autumnalis, Solanum sodomaeum, Withania somnifera, Withania frutescens and Brunfelsia nitida. The most frequently encountered calystegines were A(3), B(1), B(2) and B(3), while distribution of N(1) and C(1) was more limited. In all the investigated samples, calystegines A(5) and B(4) were never detected. This report focuses for the first time on calystegines in Withania and Brunfelsia genera and in Mandragora autumnalis and Solanum sodomaeum species.

Alkaloids↗
PubMed2001

Similar haemodynamic, respiratory and metabolic changes with the use of sevoflurane or halothane in children breathing spontaneously via a laryngeal mask airway.

BACKGROUND: In preschool children, short-lasting surgical procedures are often performed under combined inhalational and regional anaesthesia with the child breathing spontaneously via a laryngeal mask airway (LMA). Despite widespread use, only limited data are available on haemodynamic, respiratory and metabolic effects of sevoflurane and halothane during LMA anaesthesia. METHODS: In an open-label, randomised, controlled study, 49 children (aged 3-8 years) were allocated to receive either sevoflurane or halothane in 60% nitrous oxide. After insertion of the LMA, end-tidal concentrations of sevoflurane or halothane were maintained at 1 MAC with the child ventilating spontaneously throughout the entire procedure. Analgesia was provided by caudal block. Haemodynamic and respiratory parameters were recorded, and capillary blood-gas samples were obtained repeatedly. RESULTS: Changes in heart rate (HR) and systolic blood pressure were similar in both groups during all observed periods, apart from a significantly higher increase in HR during inhalational induction with sevoflurane (P<0.05). Regression slope analysis during anaesthesia revealed a decrease of the respiratory rate of 5 breaths h-1 (P<0.001) and an increase of end-tidal PCO2 and capillary PCO2 of about 0.25 kPa h-1 (P<0.001), with no significant difference between the two groups. Base excess, calculated in capillary blood gas samples, did not change over time (P>0.5) in either group. CONCLUSIONS: The use of approximately 1 MAC sevoflurane or halothane in 60% N2O in children breathing spontaneously via LMA resulted in comparable haemodynamic, respiratory and metabolic changes, and clinically relevant deteriorations did not occur during the 65-min study period.

Anesthesia, Inhalation↗
PubMed2001

New trends in extraction, identification and quantification of artemisinin and its derivatives.

Artemisinin, a sesquiterpene lactone endoperoxide, and a number of its precursors, metabolites and semisynthetic derivatives have shown to possess antimalarial properties. Several methods have been reported for the measurement of artemisinin and its main derivatives in plant material and biological fluids. However, most of them are either not sufficiently sensitive and do not offer reliable results, or are difficult to apply in routine analyses. Therefore, new methods for the determination of these compounds, such as supercritical fluid extraction and chromatography, pressurized solvent extraction, microwave-assisted extraction, high-performance liquid chromatography coupled to mass spectrometry or evaporative light scattering detection, will be presented. Applications to plant material, pharmaceutical formulations and biological fluids will also be reviewed.

Antimalarials↗
PubMed2000

Reversible thermal transition in GrpE, the nucleotide exchange factor of the DnaK heat-shock system.

DnaK, a Hsp70 acting in concert with its co-chaperones DnaJ and GrpE, is essential for Escherichia coli to survive environmental stress, including exposure to elevated temperatures. Here we explored the influence of temperature on the structure of the individual components and the functional properties of the chaperone system. GrpE undergoes extensive but fully reversible conformational changes in the physiologically relevant temperature range (transition midpoint at approximately 48 degrees C), as observed with both circular dichroism measurements and differential scanning calorimetry, whereas no thermal transitions occur in DnaK and DnaJ between 15 degrees C and 48 degrees C. The conformational changes in GrpE appear to be important in controlling the interconversion of T-state DnaK (ATP-liganded, low affinity for polypeptide substrates) and R-state DnaK (ADP-liganded, high affinity for polypeptide substrates). The rate of the T --> R conversion of DnaK due to DnaJ-triggered ATP hydrolysis follows an Arrhenius temperature dependence. In contrast, the rate of the R --> T conversion due to GrpE-catalyzed ADP/ATP exchange increases progressively less with increasing temperature and even decreases at temperatures above approximately 40 degrees C, indicating a temperature-dependent reversible inactivation of GrpE. At heat-shock temperatures, the reversible structural changes of GrpE thus shift DnaK toward its high-affinity R state.

Adenosine Triphosphate↗
PubMed2000

Empirical calculation of the relative free energies of peptide binding to the molecular chaperone DnaK.

We describe a methodology to calculate the relative free energies of protein-peptide complex formation. The interaction energy was decomposed into nonpolar, electrostatic and entropic contributions. A free energy-surface area relationship served to calculate the nonpolar free energy term. The electrostatic free energy was calculated with the finite difference Poisson-Boltzmann method and the entropic contribution was estimated from the loss in the conformational entropy of the peptide side chains. We applied this methodology to a series of DnaK*peptide complexes. On the basis of the single known crystal structure of the peptide-binding domain of DnaK with a bound heptapeptide, we modeled ten other DnaK*heptapeptide complexes with experimentally measured K(d) values from 0.06 microM to 11 microM, using molecular dynamics to refine the structures of the complexes. Molecular dynamic trajectories, after equilibration, were used for calculating the energies with greater accuracy. The calculated relative binding free energies were compared with the experimentally determined free energies. Linear scaling of the calculated terms was applied to fit them to the experimental values. The calculated binding free energies were between -7.1 kcal/mol and - 9.4 kcal/mol with a correlation coefficient of 0.86. The calculated nonpolar contributions are mainly due to the central hydrophobic binding pocket of DnaK for three amino acid residues. Negative electrostatic fields generated by the protein increase the binding affinity for basic residues flanking the hydrophobic core of the peptide ligand. Analysis of the individual energy contributions indicated that the nonpolar contributions are predominant compared to the other energy terms even for peptides with low affinity and that inclusion of the change in conformational entropy of the peptide side chains does not improve the discriminative power of the calculation. The method seems to be useful for predicting relative binding energies of peptide ligands of DnaK and might be applicable to other protein-peptide systems, particularly if only the structure of one protein-ligand complex is available.

Binding Sites↗
PubMed2000

Optimization of the production of aroma compounds by Kluyveromyces marxianus in solid-state fermentation using factorial design and response surface methodology.

Studies were carried out for the production of aroma compounds in solid-state fermentation using factorial design and response surface methodology (RSM) experiments. Five agro-industrial residues were evaluated as substrate for cultivating a strain of Kluyveromyces marxianus. The results proved the feasibility of using cassava bagasse and giant palm bran (Opuntia ficus indica) as substrates to produce fruity aroma compounds by the yeast culture. In order to test the influence of the process parameters on the culture to produce volatile compounds, two statistical experimental designs were performed. The parameters studied were initial substrate pH, addition of glucose, cultivation temperature, initial substrate moisture and inoculum size. Using a 2(5) factorial design, addition of glucose and initial pH of the substrate was found statistically significant for aroma compounds production on palm bran. Although this experimental design showed that addition of glucose did not have a significant role with cassava bagasse, 2(2) factorial design revealed that glucose addition was significant at higher concentrations. Head-space analysis of the culture by gas chromatography showed the production of nine and eleven compounds from palm bran and cassava bagasse, respectively, which included alcohols, esters and aldehyde. In both the cases, two compounds remained unidentified and ethyl acetate, ethanol and acetaldehyde were the major compounds produced. Esters produced were responsible for the fruity aroma in both the cases. With palm bran, ethanol was the compound produced in highest concentration, and with cassava bagasse (both supplemented with 10% glucose), ethyl acetate was produced at highest concentration, accumulating 418 and 1395µmoll(-1) head-spaceg(-1) substrate in 72h, respectively.

Journal Article↗
PubMed2000

Experimental design in supercritical fluid extraction of cocaine from coca leaves.

An optimisation procedure for the supercritical fluid extraction (SFE) of cocaine from the leaves of Erythroxylum coca var. coca was investigated by means of experimental design. After preliminary experiments where the SFE rate-controlling mechanism was determined, a central composite design was applied to evaluate interactions between selected SFE factors such as pressure, temperature, nature and percentage of the polar modifier, as well as to optimise these factors. Predicted and experimental contents of cocaine were compared and robustness of the extraction method estimated by drawing response surfaces. The analysis of cocaine in crude extracts was carried out by capillary GC equipped with a flame ionisation detector (GC-FID), as well as by capillary GC coupled with a mass spectrometer (GC-MS) for peak identification.

Cacao↗
PubMed2000

Comparison of folding rates of homologous prokaryotic and eukaryotic proteins.

The rate of polypeptide chain elongation is up to one order of magnitude faster in prokaryotic cells than in eukaryotes. Here we report that the rates of in vitro refolding of orthologous prokaryotic and eukaryotic proteins correlate with their differential rates of biosynthesis. The mitochondrial and cytosolic aspartate aminotransferases of chicken and aspartate aminotransferase of Escherichia coli show pairwise sequence identities of 41-48% and nearly identical three-dimensional structures. Nevertheless, the prokaryotic enzyme refolded 6 times faster (at 25 degrees C) than the eukaryotic isoenzymes after denaturation in 6 m guanidine hydrochloride. Prokaryotic malate dehydrogenase and lactate dehydrogenase also renatured faster than their orthologous eukaryotic counterparts, suggesting that evolutionary pressure has adapted the rate of folding to the rate of elongation of polypeptide chains.

Aspartate Aminotransferases↗