Transcobalamin II-mediated uptake of vitamin B12 by rat liver cells

Vitamin B12 plays a unique role in mammalian metabolism not only because, as a coenzyme, it is involved in two completely different and unrelated biochemical pathways, - the synthesis of nucleic acid precursors and the catabolism of some fatty acids -, but even more because it gives an excellent example how different groups of living organisms work together and depend on each other for the supply of vital nutrients. Vitamin B12 is almost exclusively found in animal products. However, it is not synthesized by the animals themselves but, they are able in one or the other way to absorb vitamin B12 which is produced bv microorganisms. For instance in ruminants the bacteria in the rumen are the source of the vitamin, which is taken up by the gut, distributed over the tissues and which is subsequently consumed by man with the meat or with the milk. However, the quantity of vitamin B12 , which is available in the food. is so low, that it would be lost if not an elaborate system of carrier proteins and cellular receotor mechanisms selectively collected it from the food and delivered it to the tissues. Intrinsic factor, produced and secreted by the qastric mucosa, binds the vitamin, which enters the body with the food, and hands it over to the ileal mucosa cells, which carry specific receptors for this protein. When the vitamin enters the blood, the plasma transport proteins, the transcobalamins, take it up immediately and deliver it to the tissues

A new representation of acid-base disturbances

The acid-base status of intensive care patients is monitored on the basis of three quantities. The graphical representation which may be of help for the monitoring task is therefore cumbersome. The classical Siggaard-Andersen acid-base chart is such a representation, but it is only suited for evaluating one acid-base status at a time and not for representing acid-base paths. A new representation, obtained after a principal components transformation is presented. It is shown that the representation is characteristic for the laboratory instrument used. Its most attractive feature is that it is distortionless with respect to the three-dimensional configuration

Effect of nitrous oxide on folate coenzyme distribution and de novo synthesis of thymidylate in human bone marrow cells

Abstract The effect of nitrous oxide on intracellular folate metabolism of the human bone marrow was studied in vitro. Bone marrow cells, obtained from healthy volunteers, were incubated with 5 × 10−8m-[3H]5-formyltetrahydrofolate (5-formylTHF) for 18 hr to label intracellular folate pools. Subsequently the cells were exposed to nitrous oxide for up to 10 hr, and the intracellular folate coenzyme levels were quantitated by HPLC. The dU suppression test was carried out on part of the bone marrow samples in order to measure folate-dependent synthesis of the DNA precursor thymidylate (dTMP). After 5 hr exposure to nitrous oxide the de novo dTMP synthesis of the bone marrow cells was significantly decreased (P < 0.05), and this reduced synthesis persisted at 10 hr. After both 5 and 10 hr of exposure to nitrous oxide the amount of 10-formylTHF was reduced (P < 0.05) while that of 5-methylTHF was increased (P < 0.05). At 10 hr the level of THF was also decreased (P < 0.05). This study shows that nitrous oxide exposure of human bone marrow cells causes a redistribution of the various folate coenzymes which supports the idea of ‘functional cobalamin deficiency’. Moreover it seems probable that following prolonged exposure to nitrous oxide, not only folate-dependent dTMP synthesis but also de novo purine synthesis is reduced

Significance of various parameters derived from biological variability of lipoprotein(a), homocysteine, cysteine, and total antioxidant status

Analytical and biological components of variability and various derived indices have been determined for lipoprotein(a) [Lp(a)], homocysteine (Hcy), cysteine (Cys), and total antioxidant status (TAOS) in ostensibly healthy adult Caucasians and in stable outpatients with an increased serum Lp(a). In healthy Caucasians, average intraindividual biological CVs (CVb) were 20.0% for Lp(a), 9.4% for Hcy, 5.9% for Cys, and 2.8% for TAOS, CVbs being similar in men and women. In the outpatient group, CVbs were comparable for Hcy, Cys, and TAOS, but significantly lower for Lp(a) (7.5% vs 20.0%; P <0.0001). Moreover, a significant inverse relation between both biological and analytical CVs (CVa) and serum Lp(a) concentrations was demonstrated. We conclude that average CVa and CVb values, and hence average derived indices, are adequate for Hcy, Cys, and TAOS, whereas individual values should be used for Lp(a)

Relation between cytokines and routine laboratory data in children with septic shock and purpura

Objective To establish the relation between routine laboratory data (lactate, fibrinogen, CRP) and cytokines (TNF,IL-1 and-6) and to estimate their prognostic value in pediatric patients with severe infectious purpura on admission. Design Prospective study. Setting Pediatric intensive care unit (PICU). Patients 17 children aged 5–172 months (median 46) were hospitalized in our PICU in 1989–90 with severe infectious purpura.Neisseria meningitidis was isolated in 15 children andHaemophilus influenzae in two. The patients were divided into 3 groups: non-shock, shock and severe shock leading to death. Shock was defined by standard criteria. Measurements Arterial blood was sampled for lactate, CRP, fibrinogen, TNF, and IL-1 and-6 on admission. The PRISM (pediatric risk of morality)-score was recorded. Methods Statistical analysis was performed with the Student'st-test using the logarithmic values of the cytokine concentration, and Spearman correlation analysis. Results According to the shock criteria, 9 patients were in shock of whom 4 did not survive. Significant differences existed between the 3 groups concerning lactate, TNF, and IL-6. Fibrinogen, CRP, IL-1, and PRISM-score discriminated only between survivors and non-survivors. A highly significant correlation existed between cytokines, the PRISM-score and lactate (TNF:r=0.69, IL-1:r=0.56, IL-6:r=0.65, PRISM:r=0.65). A significant inverse correlation existed between cytokines and CRP (TNF:r=−0.55, IL-1:r=−0.64, and IL-6:r=−0.56), and IL-6 and fibrinogen (r=−0.65). Conclusion These results show a significant correlation between cytokines and lactate, and lactate, TNF and IL-6 are closely associated with the severity of septic shock with purpura in children

Anti-leukemic potential of methyl-cobalamin inactivation by nitrous oxide

Myelo‐cytotoxicity of extended nitrous oxide (N2O) inhalation was described almost forty years ago and then incidentally applied already with temporary success for suppressing leukemia. In 1948 the accompanying megaloblastic maturation arrest was explained by inactivation of the methylcobalamin coenzyme and subsequent folate deficiency. We studied the anti‐leukemic effect of N2O on a transplantable acute leukemia in B(rown) N(orway) rats. Progression of this B,N,M(yelocytic)L(eukemia) was measured as spleen and liver weights, and leukemic blood cell counts. The deoxyuridine (dU)‐suppression test provided in vitro indication of the functional folate activity of leukemic cells. Breathing of N2O‐oxygen considerably reduced but did not eradicate, BNML‐proliferation. Addition of anti‐metabolites, interfering with some enzyme in the folate metabolism beyond the methylcobalamin co‐enzyme dependent methionine synthase step, acted at least synergistically. The anti‐leukemic effect of cycloleucine, which reduces S‐adenosyl‐methionine synthesis by inactivation of methionine adenosyltransferase, was moderate but became much stronger with N2O inhalation. Methotrexate, a potent anti‐leukemic agent by inhibiting tetrahydrofolate (THF) generation through inactivation of di‐HF reductase, became highly anti‐BNML, even in low dosage when combined with or preceded by N2O. 5‐Fluorouracil, which inhibits methylene‐THF dependent thymidilate synthase, itself was surprisingly anti‐BNML, but also became much more potent with previous or concomittant N2O exposure. Preliminary dU‐suppression test results with human acute leukemia cells, exposed to N2O and/or folate antagonists in vitro, correlated well with the in vivo BNML‐experiments. Combining the anticobalamin activity of N2O with an anti‐folate therefore seems to be a promising chemotherapeutic approach. Copyrigh

Portable blood gas and electrolyte analyzer evaluated in a multiinstitutional study

A recently introduced blood gas/electrolyte analyzer (SenDx 100((R)), renamed ABL70) intended for point-of-care, near-patient, or stat laboratory use was evaluated simultaneously in four different institutions and compared with three different laboratory bench analyzers with respect to imprecision, inaccuracy (assessed by tonometry), and patient-sample analyses. The analyzer is equipped with a sensor cassette and a reagent cartridge for 50, 100, or 200 analyses and 100 or more traditional quality-control measurements. One analysis requires 170 microL of whole blood and takes <90 s. Statistically, the instrument performed somewhat better (lower CVs) for PO2 and potassium and somewhat worse for pH, PCO2, and ionized calcium than the respective comparison analyzers. However, the overall performance (in terms of CV and accuracy) was satisfactory in terms of clinical (e.g., CLIA '88) goals in all institutions. The mean difference and the CV of that difference in some 400 patient-sample comparisons were as follows: 0.010 (+/- 0.002%) for pH, -0.65 mmHg (+/- 4%) for PCO2, -0.49 mmHg (+/- 6%) for Po2, 0.44 mmol/L (+/- 1.2%) for sodium, -0.013 mmol/L (+/- 2.9%) for potassium, -0.016 mmol/L (+/- 2.6%) for ionized calcium, and -0.016 L/L (+/- 7. 1%) for the hematocrit. Its acceptable analytical performance and ease of operation make the SenDx 100 suitable for the analysis of blood gases and electrolytes

CYP3A5 variant allele frequencies in Dutch Caucasians

BACKGROUND: Enzymes of the cytochrome P450 3A (CYP3A) family are responsible for the metabolism of >50% of currently prescribed drugs. CYP3A5 is expressed in a limited number of individuals. The absence of CYP3A5 expression in approximately 70% of Caucasians was recently correlated to a genetic polymorphism (CYP3A5*3). Because CYP3A5 may represent up to 50% of total CYP3A protein in individuals polymorphically expressing CYP3A5, it may have a major role in variation of CYP3A-mediated drug metabolism. Using sequencing, have been identified (Hustert et al. Pharmacogenetics 2001;11:773-9; Kuehl et al. Nat Genet 2001;27:383-91) variant alleles *2 through *7 for CYP3A5. Detection of CYP3A5 variant alleles, and knowledge about their allelic frequency in specific ethnic groups, is important to establish the clinical relevance of screening for these polymorphisms to optimize pharmacotherapy. METHODS: In a group of 500 healthy Dutch Caucasian blood donors, we determined the allelic frequency of the CYP3A5*2, *3, *4, *5, *6, and *7 alleles by use of newly developed PCR-restriction fragment length polymorphism assays. RESULTS: The frequency of the defective CYP3A5*3 allele in the Dutch Caucasian population was 91%, followed by the CYP3A5*2 (1%) and CYP3A5*6 (0.1%) alleles. The CYP3A5*4, *5, and *7 alleles were not detected. CONCLUSIONS: On the basis of its allelic frequency, screening for the CYP3A5*3 allele in the Caucasian population is extremely relevant. In addition, screening for the CYP3A5*2 allele may be taken into consideration in individuals heterozygous for the CYP3A5*3 allele. The CYP3A5*4, *5, *6, and *7 alleles have low allelic frequencies that do not support initial screening