Erythromelalgic, thrombotic and hemorrhagic manifestations in 50 cases of thrombocythemia

Fifty consecutive patients with thrombocythemia (35 men and 15 women) were diagnosed as primary thrombocythemia (PT) in 30 and thrombocythemia associated with polycythemia vera (PV) in 20. The symptoms were platelet-mediated erythromelalgia in 16 PT and 15 PV, coronary artery disease in 3 PT and 2 PV, atypical cerebral ischemic attacks in 8 PT and 3 PV, paradoxical thrombosis and bleeding in 3 PT and 2 PV and hemorrhages alone in 6 PT and 2 PV patients. Erythromelalgia was localized in the forefoot sole and toes in 28, the fingertips in 9, the handpalm in 2. Untreated erythromelalgia progressed to acrocyanosis or peripheral ischemia with necrosis in a toe or fingertip in 14 cases. Painful red, warm and indurated erythromelalgic hot spots in the skin of the upper legs were misdiagnosed as superficial thrombophelebitis in 5 PT and 2 PV patients. Erythromelalgia in thrombocythemia already occurred at slightly increased platelet counts above 400 x 10(9)/l. The curative effect of aspirin on erythromelalgia in thrombocythemia was consistently accompanied by a significant increase of platelet counts. Erythromelalgia and bleeding paradoxically occurred in 5 patients at platelet counts between 1000 and 2000 x 10(9)/l. In this situation aspirin prevents erythromelalgic and microcirculatory circulation disturbances, but further increases the risk of serious bleeding complications. Presenting hemorrhagic manifestations in thrombocythemia were observed at platelet counts in excess of 1000 x 10(9)/l in 9 PT and 4 PV patients as severe epistaxis in 5, atypical ecchymoses in 3, gastrointestinal bleeding in 2 and secondary bleeding in 3. The concept of platelet-mediated erythromelalgia, thrombosis and hemorrhages in thrombocythemia is discussed.

Phenotyping and genotyping of coagulation factor V Leiden

The currently used activated Protein C resistance test demonstrated to be of limited diagnostic value for the detection of the mutant Factor V Leiden. Moreover, this assay is not useful for patients under anticoagulant therapy. A modification of the APC resistance test, applying Factor V deficient plasma is described which demonstrates a specificity and sensitivity of 1.0. The superiority of the modified APC resistance test over the existing APC resistance test was verified by genotyping. For that purpose, the Amplification Refractory Mutation System (ARMS) was applied to the detection of the G to A mutation at position 1691 in the gene encoding coagulation Factor V. The mutation at that position could be easily detected by using each of two allele-specific oligonucleotide primers concomitantly with one common primer in two separate polymerase chain reactions, thereby amplifying a fragment of 186 base-pairs of the Factor V gene.

Design and representation of multivariate patient-based reference regions for arterial pH, PCO2 and base excess values

OBJECTIVES

To determine and compare the shape and location of three data sets of arterial pH, PCO2, and BE values from intensive care patients in a new acid-base chart for the purpose of deriving multivariate reference regions.

DESIGN AND METHODS

The new chart is constructed by applying a statistical technique called principal component analysis (PCA). Three different data sets, each comprised of 1500 arterial pH, PCO2, and BE values, were subjected to PCA. The 3 data sets were collected in a respiratory intensive care unit (ICU) of a University Hospital, in a general ICU of a District Hospital, and in a neonatal ICU of a Children's Hospital.

RESULTS

The outlines of the resulting charts are similar for all 3 data sets, but the representations of the three distributions in the new chart are highly dissimilar, both in shape and in location.

CONCLUSIONS

PCA can be used to derive a patient-based reference region for arterial pH, PCO2, and BE values. Furthermore, the new chart may be useful for the graphical monitoring of acid-base data because distances between consecutive observations are faithfully represented.

Diagnostic analysis of total protein, albumin, white cell count and differential in ascitic fluid

Accurate and precise procedures are described for the measurement of total protein, albumin, white cell count and differential in ascitic fluid. The total protein method (biuret) on the serum chemistry analyser, Bayer-Technicon Chem-1, was calibrated against the biuret reference method in the measuring range from 1-100 g/l, covering serum as well as ascitic fluid values. The albumin method (bromcresol green) on the Chem-1 was calibrated for the measurement range from 1-50 g/l against the new human plasma protein international reference preparations and compared to the nephelometric method on the Beckman Array, which was also calibrated against these reference preparations. A good correlation was obtained for total protein between the Chem-1 (y) and the biuret reference method (x) in 58 ascitic fluids (y = 1.02x -0.3; r = 1.00). A good correlation between the Chem-1 (y) and the Array (x) was also obtained for albumin (r = 0.99). The bromcresol green method, however, which is not fully specific, resulted in significantly higher results (y = 1.32x - 1.3). The immunochemical procedure is considered the more accurate and therefore the bromcresol green method is not suitable for the determination of albumin in ascitic fluids. The white cell count in ascitic fluid can be measured reliably by most haematology analysers if the sample is fresh and homogeneous, but the differential is flagged as a result of differing morphology. Handmade smears from ascitic fluid, however, show uneven distribution of cells and disturbed morphology.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet consumption in thrombocythemia complicated by erythromelalgia: reversal by aspirin

The involvement of platelets in the pathogenesis of erythromelalgia, a frequent and characteristic microvascular thrombotic manifestation in patients with primary thrombocythemia and polycythemia rubra vera, was investigated by measuring the survival and turnover of 51Cr labeled autologous platelets in 10 patients with thrombocythemia complicated by erythromelalgia, in 10 asymptomatic thrombocythemia patients and in 6 subjects with reactive thrombocytosis. The mean platelet survival time of the erythromelalgia patients was 4.2 +/- 0.2 days, which is significantly decreased as compared with asymptomatic thrombocythemia patients (6.6 +/- 0.3 days, p < 0.001) and patients with reactive thrombocytosis (8.0 +/- 0.4 days, p < 0.001). The mean platelet survival time of asymptomatic thrombocythemia patients was significantly decreased (p < 0.01) as compared with reactive thrombocytosis patients. Treatment of erythromelalgia with aspirin increased the mean platelet survival time from 4.0 +/- 0.3 days to 6.9 +/- 0.4 days (p < 0.001) and was associated with an elevation of the platelet count of 216 +/- 30 x 10(9) platelets per liter (p < 0.001). Coumadin failed to improve platelet survival or symptoms caused by erythromelalgia. The increased platelet consumption in erythromelalgia is attributed to the formation of platelet thrombi in the arterial microvasculature. This conclusion is supported by the ability of aspirin to interrupt platelet consumption and clinical features of erythromelalgia.

A computer program for the multivariate and graphical monitoring of acid-base data in an intensive care unit

Monitoring the arterial acid-base status of ICU patients is done by measuring and calculating the acid-base variables pH, the partial pressure of carbon-dioxide (PCO2) and the bicarbonate-ion concentration ([HCO-3]). Univariate normal reference ranges exist for these values. However, it is well known that an exact linear relationship exists between pH, the logarithm of PCO2 and the logarithm of [HCO-3] values. We developed a computer program for the multivariate evaluation and graphical monitoring of these values in an intensive care setting that takes this intrinsic two-dimensionality into account. A composite index is introduced for the monitoring of all three laboratory values. Moreover, using this index, a multivariate statistical reference region based on an unselected population of ICU patients was derived.

Effects of prenatal exposure to betamethasone and indomethacin on the glomerular filtration rate in the preterm infant

The effects of gestational age (GA), body weight, and prenatal exposure to betamethasone and indomethacin on the glomerular filtration rate (GFR) on d 3 of life in preterm infants were studied. GFR measurements were performed in 147 preterm infants with a GA between 23.4 and 37.0 wk by means of the continuous inulin infusion technique. Mean GFR values increased significantly with GA (r = 0.60, p < 0.001) and with body weight (r = 0.44, p < 0.001). Multivariate analysis indicated that GA was the most important determinant for this increase. Prenatal exposure to indomethacin resulted in significantly lower GFR values (-0.15 +/- 0.03 mL/min, p < 0.001) at d 3 after birth. Prenatal administration of betamethasone and indomethacin significantly (p < 0.001) increased the GFR in comparison with exposure to indomethacin alone to levels not different than those seen in patients who were not prenatally exposed to betamethasone or indomethacin. GFR measurements were repeated in 40 preterm infants on d 10 after birth. During this 7-d period, a significant increase in GFR values (0.17 +/- 0.03 mL/min, p < 0.001) was detected. This postnatal increase in GFR values was independent of GA and was not influenced by prenatal exposure to betamethasone or indomethacin. We conclude that prenatal exposure to betamethasone or indomethacin exerts significant effects on the renal function of preterm infants in the first days of life.

Quantitative urinalysis with a common predilution on a DuPont Dimension

Urine was quantitatively analysed for sodium, potassium, creatinine, calcium, urea, uric acid, inorganic phosphate and magnesium in one manual central predilution. The analysis was implemented on a DuPont Dimension and the results were compared with those obtained with our analysers currently in use. Based on modified serum methods and their assessed linearities, the 8 urine constituents were analysed with high accuracy and reproducibility in a 6-fold diluted urine with DuPont reagents. The Dimension method correlated well with flame photometry for sodium and potassium; with the EPOS analyser for creatinine, calcium, uric acid, urea and inorganic phosphate; with atomic absorption spectroscopy for magnesium. All between-run coefficients of variation were smaller than 5%, except for the analysis of sodium in the lower part of the measurement range. However, a dilution ratio of 6 is an acceptable compromise when these 8 constituents are determined collectively from a common predilution, thereby covering the complete measurement ranges for these analytes in urine specimens. An additional dilution step is necessary for only a few urine samples (fewer than 1% of samples for calcium and urea and fewer than than 2% for inorganic phosphate). The combined analysis of these 8 constituents can be carried out only on untreated urine samples. Currently recommended pretreatments, such as acidification for calcium and inorganic phosphate analysis, and uric acid analysis under alkaline conditions, can be avoided.

The effects of human growth hormone (GH) administration in GH-deficient adults: a 20-day metabolic ward study

The early effects of human GH administration in GH-deficient (GHD) adults on protein, electrolyte homeostasis, and body composition were investigated in a metabolic ward study. Four patients were studied. In addition to a constant caloric and nitrogen (N)-sufficient diet, the patients received GH for 15 days in dosages of 12.5-25 micrograms/kg.day, with a maximum of 1.48 mg (4 IU)/day. GH replacement therapy was well tolerated by all patients. There was a slowly increasing effect on IGF-I levels, which reached a maximum after 8-12 days. The lowered IGFBP-3 levels normalized quicker, reaching maximum circulating concentrations 3 days after the start of GH treatment. Insulin concentrations maximally increased after 5 days, after which they leveled off. Insulin-like growth factor-binding protein-1 levels were maximally suppressed after 2 days of treatment. N balance became positive in all patients (mean, +2.8 +/- 0.2 g/day). Maximal N retention occurred after 2-5 days of GH administration, after which adaptation occurred. This degree of N retention represents a formation of 20 g muscle/day, which would mean an increase of 3.6 kg muscle over a period of 6 months of GH replacement therapy. A rapidly occurring positive sodium balance was observed within 24-72 h. Maximal sodium retention amounted to 61 mmol/day. It slowly decreased spontaneously over the subsequent 12 days. In parallel, rapid changes in bioelectrical impedance analysis (BIA) were observed. There was a close parallel between the net cumulative sodium retention and the decrease in BIA in these patients during the first 15 days of GH therapy. This suggests that the calculation of body composition compartments on the basis of BIA measurements during the initial phase of GH replacement does not represent actual changes in fat mass. This was substantiated with measurements of body composition using dual energy x-ray absorptiometry. In conclusion, measurements of early metabolic changes in GHD adults during the first 15 days after the start of GH replacement indicate that IGF-I values reach maximal levels only after 8-12 days, that the measurements of changes in IGFBP-1 and IGFBP-3 levels probably do not contribute to a determination of the optimal GH replacement dose, that maximal N-retaining effects occur within 2-5 days, after which adaptation occurs, that massive sodium retention occurs during this period, which spontaneously levels off, and that cumulative sodium retention closely correlates during this period with changes in BIA.(ABSTRACT TRUNCATED AT 400 WORDS)

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.

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 and Haemophilus 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's t-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.

Evaluation of the Cholestech L.D.X. desktop analyser for cholesterol, HDL-cholesterol, and triacylglycerols in heparinized venous blood

The analytical performance of the Cholestech L.D.X. lipid analyzer for total and HDL-cholesterol and triacylglycerols in heparinized venous blood was evaluated, using two Cholestech L.D.X. analysers and two reagent cassette lots. Within-day and day-to-day precision were checked with commercial quality control sera. Within-day coefficients of variation (CVs) were 2.0 to 4.7% for total cholesterol, 3.4 to 5.5% for HDL-cholesterol, and 2.1 to 4.8% for triacylglycerols. Between-day CVs were < or = 6.0% for triacylglycerols, and < or = 7.0% for HDL-cholesterol. A method comparison study, according to the NCCLS EP9-P guidelines, was performed for all three analytes. Cholestech whole blood values (y) were compared with serum values (x) generated by a standardized enzymatic method for cholesterol, and by current state-of-the-art methodology for HDL-cholesterol and triacylglycerols. Correlation coefficients were all > 0.98. Mean slopes and intercepts for the Passing & Bablok regression equations of total and HDL-cholesterol were not significantly different from one and zero, respectively. Overall, the Cholestech means differed by < 1.8% for total cholesterol, and < 5% for HDL-cholesterol versus the comparison method means. For total cholesterol the National Cholesterol Education Program (NCEP) requirements for accuracy and precision of < or = 3% were met. For triacylglycerols, significant negative intercepts ranging from -0.26 to -0.33 mmol/l were observed, with slopes significantly greater than one.

Somatostatin-receptor scintigraphy in primary breast cancer

Somatostatin-receptor (SS-R) scintigraphy successfully shows primary cancers and distant metastases in most patients with carcinoids, islet cells tumours, and paragangliomas. Previous in-vitro studies indicated that somatostatin receptors are present in human breast cancers. We report positive scintigraphy with [111In-DTPA-D-Phe1]-octreotide in 39 of 52 primary breast cancers (75%). Parallel in-vitro autoradiography with [125I-Tyr3]-octreotide of 30 of these showed a corresponding somatostatin-receptor status in 28. Significantly more invasive ductal cancers could be shown than invasive lobular carcinomas (85% vs 56%; p < 0.05). Also the number of T2 cancers which were shown was higher than T1 (86% vs 61%; p < 0.05). Imaging of the axillae showed non-palpable cancer-containing lymph nodes in 4 of 13 patients with subsequently histologically-proven metastases. In the follow-up after a mean of 2.5 yr, SS-R scintigraphy in 28 of the 37 patients with an originally SS-R-positive cancer, was positive in the 2 patients with clinically-recognised metastases, as well as in 6 of the remaining 26 patients who were symptom-free. Raised carcinoembryonic antigen (CEA) and CA 15-3 values were observed in only 2 and 1, respectively, of these patients. Most primary breast cancers can be shown by SS-R scintigraphy, especially invasive ductal cancers. This technique may be of value in selecting patients for clinical trials with somatostatin analogues or other medical treatments. Furthermore, SS-R scintigraphy is more sensitive than measurements of the usual serum cancer markers for detecting recurrences of SS-R-positive breast cancer.

Automated enzymatic methods for creatinine measurement with special attention to bilirubin interference

Four enzymatic methods for creatinine measurement were evaluated on a DuPont Dimension automatic analyzer. Biomed Creatinine-Duo-UV (BIO) and Raichem Creatinine Reagent Enzymatic (RAI) start creatinine breakdown with creatinine iminohydrolase (EC 3.5.4.21) resulting in the formation of NH4+. The Boehringer Mannheim Creatinine PAP (BM1) and SopaChem Creatinine (SOP) start the breakdown of creatinine with creatininase (EC 3.5.2.10) which yields creatine. In order to reduce bilirubin interference, the BM1 method was modified to contain K4Fe(CN)6. This substance was added with reagent 1 (BM2) or with reagent 2 (BM3). All the enzymatic creatinine methods tested displayed good linearity for concentrations up to at least 1000 mumol/l. The BIO, BM3, RAI and SOP methods showed good stability of test outcome for the tested period of a week. The outcome of the BM1 and BM2 method increased continually with time. Only the results of the RAI method were diminished by the presence of lipids. The BM1, BM2, BM3 and SOP methods showed no interference with haemoglobin, whereas this increased the outcome of the BIO method and slightly decreased the results of the RAI method. Using spiked human albumin solutions it was found that the BIO, BM2, BM3 and RAI methods displayed good resistance to interference by bilirubin or ditauro-bilirubin. The outcome of the BM1 and SOP method was strongly decreased by both bilirubin and ditauro-bilirubin. When creatinine was measured in a panel of sera originating from 100 patients with bilirubin concentrations higher than 50 mumol/l, the obtained results were in close agreement with those found for the spiked human albumin solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation and sequence analysis of variant forms of human transcobalamin II

Two cDNA clones (1.9 kb and 1.5 kb, respectively) encoding full length human TC II have been isolated from a human endothelial cell cDNA library and sequenced. The differences between the two clones are the length of the 5' end and the 3' end non-coding regions and the codon at position 198 and 219. Both the clones differ from the recently isolated (human endothelial cell) cDNA for TC II (Platica, O., Janecko, R., Quadros, E.V., Regee, A., Romain, R. and Rothenberg, S.P. (1991) J. Biol. Chem. 266, 7860-7863) in codon 259 and 376 and in their calculated pI values. In vitro transcription followed by translation in a reticulocyte lysate system and SDS-PAGE revealed that the isolated cDNA clones encode a protein of 43 kDa. Upon treatment with canine pancreatic microsomes, the molecular mass of the in vitro translated product was reduced to 41.5 kDa, indicating the presence of an approximately 1.5 kDa signal peptide. This translation product was immunoprecipitated with rabbit anti-serum to human TC II and was able to bind to Cbl-Sepharose beads. The amino acid sequence alignment of TC II with that of other Cbl binding proteins (rat intrinsic factor, human transcobalamin I and porcine haptocorrin) revealed only 33% overall homology. However, there were four regions of greater than 80% homology and two regions of about 60% homology. These regions encompass the majority of the hydrophobic areas of the Cbl-binders. Based on these studies, we suggest that structural basis for the expression of different polymorphic forms of TC II may be due to single point mutations and that TC II, like other mammalian Cbl-binders, have evolved from a common ancestral gene. Furthermore, the Cbl-binding functional domain most probably resides in a hydrophobic pocket which is formed by all or some of the six regions of high homology.

Comparison of two preterm formulas with or without addition of medium-chain triglycerides (MCTs). II: Effects on mineral balance

Medium-chain triglycerides (MCTs) are included in the fat blend of several preterm formulas because of their complete absorption and rapid oxidation. The effects of two different fat blend compositions on calcium (Ca), phosphorus (P), and magnesium (Mg) balances and plasma levels and on plasma levels of parathyroid hormone (PTH), alkaline phosphatase (AP), and 1,25-dihydroxyvitamin D [1,25-(OH)2D] were investigated in 28 healthy very-low-birth weight infants at 4 weeks of age. A preterm formula with a traditional corn oil/MCT blend containing 38% MCTs (MCT group) was compared to a new fat blend, designed to resemble human milk more, containing 6% MCTs (LCT group). There was a higher absorption of Ca in the MCT group (73% vs. 60%. p less than 0.005), and an equal absorption of P (both 92%). The excretion of Ca correlated with the excretion of fat (p less than 0.00005). The LCT group showed a higher median PTH level (MCT: 2.1 pmol/L, LCT: 4.7 pmol/L, p less than 0.01) and a higher urinary P excretion (p less than 0.001). Mg absorption was also lower with LCT, but retention of Mg exceeded intrauterine values in both groups. Mineral plasma levels were in the normal range in both groups. AP was not different between groups and in the upper part of the reference range, whereas 1,25-(OH)2D levels were above the normal range and also not different between groups. We conclude that with the LCT formula, Ca absorption is slightly lower than with the MCT formula, whereas P absorption is unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional aspects of small-bowel transplantation in rats

Although clinical small-bowel transplantation is still severely hindered by rejection of the graft, prolonged graft survival can be achieved by using cyclosporin A in several experimental models of small-bowel transplantation. In an immunologically quiescent phase after transplantation, the important question arises whether a small-bowel allograft has enough functional capacity to maintain a normal nutritional status. We investigated the functional capacity of orthotopic small-bowel transplants and evaluated the ability of the total small-bowel transplant to absorb orally given cyclosporin in the early postoperative period and the effect of this oral cyclosporin treatment on allograft survival as compared with intramuscular administration. Between 3 and 7 months postoperatively, recipients of syngeneic and allogeneic total small-bowel transplants and syngeneic jejunal segmental grafts had significantly decreased serum triglyceride levels. Total serum protein and albumin concentrations, serum cholesterol values, fecal fat excretion, and percentage of split fatty acids were normal. One year after transplantation the weight in the groups transplanted with a total small-bowel graft was not different from age-matched untreated controls. Animals grafted with a segmental graft, however, showed a significantly impaired growth and had not reached a normal weight 1 year after transplantation. Growth was also significantly impaired after near-total small-bowel resection. These animals had to be killed because of their poor condition. Cyclosporin absorption after small-bowel transplantation equalled that in normal controls. Graft survival after intramuscular treatment, however, was significantly better than after oral treatment.

Elevated serum transcobalamin levels in anaemia of rheumatoid arthritis: correlation with disease activity but not with serum tumour necrosis factor alpha and interleukin 6

Transcobalamin (TCII) and haptocorrins (TCI and III), tumour necrosis factor alpha (TNF), interleukin-6 (IL6) and parameters of disease activity were assessed in 20 rheumatoid arthritis (RA) patients without anaemia and 19 subjects with anaemia of chronic disease (ACD) in order to determine if there was a possible correlation between these parameters. TCII, TNF and IL6 correlated positively with RA disease activity parameters, whereas their serum levels were higher in the ACD patients. TC levels were not correlated with cytokine levels. Vitamin B12 serum levels were lower in ACD. We conclude that in RA, elevated serum TCII levels are possibly mediated by increased RA disease activity, but probably not by actions of TNF or IL6. Increased TCII levels found in ACD may be explained by the higher degree of RA activity in these patients, and could also be viewed as a compensatory reaction to anaemia or reduced vitamin B12 levels. However, these preliminary findings require further confirmation.

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

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 x 10(-8)m-[(3)H]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.

Monitoring cobalamin inactivation during nitrous oxide anesthesia by determination of homocysteine and folate in plasma and urine

The effects of nitrous oxide-induced cobalamin inactivation on homocysteine and folate metabolism have been investigated. Plasma levels of cobalamin, folate, homocysteine, and methionine were determined in 40 patients before and after operation under nitrous oxide anesthesia (range of exposure time, 70 to 720 minutes). Twelve patients anesthetized with total intravenous anesthesia served as control subjects (range of exposure time, 115 to 600 minutes). Postoperative plasma levels of folate and homocysteine increased (p less than 0.001) up to 220% and 310%, respectively, in nitrous oxide-exposed patients, whereas plasma levels of methionine decreased (p less than 0.025). Response occurred after 75 minutes of nitrous oxide exposure. The percentage increase of plasma folate and homocysteine correlated significantly with exposure time (p less than 0.025 and p less than 0.0001, respectively). In eight patients receiving nitrous oxide anesthesia plasma homocysteine levels had not returned to preoperative levels within 1 week (p less than 0.01). Urinary excretion of folate and homocysteine increased during and after nitrous oxide exposure (p less than 0.01 and p less than 0.002, respectively) and correlated with exposure time (p less than 0.01 and p less than 0.005, respectively). It can be concluded that disturbance of homocysteine and folate metabolism by nitrous oxide develops with little delay and return to normal levels requires several days. Elevation of plasma homocysteine levels may therefore be used for monitoring nitrous oxide-induced cobalamin inactivation.

Interleukin-6 and interleukin-1 enhancement of GM-CSF-dependent proliferation of haematopoietic progenitor cells in myelodysplastic syndromes

Interleukin-1 (Il-1) and Interleukin-6 (Il-6) have been reported to enhance the growth factor dependent colony formation of normal primitive haematopoietic progenitor cells as well as of leukaemic blast-cell progenitors. We investigated the effects of Il-1 beta and Il-6 in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) on the in vitro colony formation of myeloid progenitors from 23 patients with a myelodysplastic syndrome (MDS). Neither Il-1 beta nor Il-6 were found to have colony stimulating activity on their own. In normal bone marrow cultures, either stimulated with optimal or suboptimal doses of GM-CSF, no enhancing or antagonistic effect of Il-6 or Il-1 beta was detected. In a majority of the MDS cases, however, an enhancing effect of Il-6 and Il-1 beta in combination with GM-CSF was observed (20/23 and 10/21 cases respectively). In three cases of the Il-6 and GM-CSF combination an antagonistic effect was observed as well as in four cases of the Il-1 beta and GM-CSF combination. A delayed addition of Il-6 to the cultures did not result in an abrogation of the effect, indicating that Il-6 is not required immediately at the initiation of the culture. These results indicate that costimulation with Il-6 or Il-1 beta is able to augment the GM-CSF activity on MDS myeloid progenitor cells.

Effect of nitrous oxide and methotrexate on folate coenzyme pools of blast cells from leukemia patients

The effects of methotrexate (inhibiting dihydrofolate reductase) and nitrous oxide (inactivating methionine synthase) on intracellular folate coenzyme levels of leukemic cells were studied. Blast cells from 10 cases of acute myeloid leukemia (AML) and 5 cases of acute lymphoid leukemia (ALL) were incubated with 5 x 10(-8) M [3H] 5-formyltetrahydrofolate (5-formylTHF) for 18 h to label intracellular folate pools, which were subsequently quantitated by high performance liquid chromatography (HPLC). In AML, 5-methylTHF made up 53% of the total folate pool followed by 10-formylTHF (26%), 5-formylTHF (10%), THF (9%) and DHF (1%). Cells from ALL differed from AML (p less than 0.05) with respect to 10-formylTHF (17%) and DHF (10%). Exposure to nitrous oxide (8 h) caused an equal decrease of 10-formylTHF and 5-formylTHF in both AML (30%) and ALL (45%), whereas 5-methylTHF increased (130%). Methotrexate (4 h, 10(-6) M) caused an accumulation of DHF and a decrease of 5-methylTHF in both AML (32%) and ALL (12%). A specific reduction of the 10-formylTHF (50%) and 5-formylTHF (25%) pools was noticed in ALL. Exposure to nitrous oxide prior to methotrexate treatment aggravated the reduction of 10-formylTHF and 5-formylTHF presumably by impaired replenishment from the 5-methylTHF pool. In conclusion, this study demonstrates a significant difference in folate coenzyme distribution between cells from AML and ALL. Moreover it is shown that nitrous oxide and methotrexate treatment of leukemic cells cause an accumulation of 5-methylTHF and DHF respectively at the expense of other folate forms. The presence of substantial amounts of DHF in cells from ALL together with the specific reduction of 10-formylTHF (necessary for purine synthesis) during MTX treatment may in part explain the efficacy of methotrexate in the treatment of ALL.

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 concomitant 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.