Interrelationships between Vitamin B12 and folic acid in myelomatosis: cobalamin coenzyme and tetrahydrofolic acid function

Cobalamin forms and analogues in plasma and myeloid cells during chronic myelogenous leukaemia related to clinical condition

Plasma and buffy coat specimens of CML patients with untreated disease, in chronic and accelerated phase, and in overt blastic crises were analysed for the cobalamin patterns using non-polar extraction, thin-layer chromatography and bioautography. Splenic tissue specimens from four splenectomized patients in accelerated phase were analysed similarly. Cellular extracts were separated into two compartments by adsorption to haptocorrin antibodies. Plasma concentrations of all cobalamin forms were increased in CML. The proportion of methylcobalamin was significantly lower than in a reference population, and a low plasma proportion of methylcobalamin was associated with a poor prognosis. Buffy coat cells and splenic tissue had a higher proportion of 5'-deoxyadenosylcobalamin and a lower proportion of methylcobalamin than plasma; still, there was relatively more methylcobalamin than in normal tissue. The haptocorrin-bound compartment differed from the non-haptocorrin compartment in untreated or chronic phase patients by binding less methylcobalamin. An estimate of cobalamin analogues in plasma was achieved by comparing two different isotope dilution assays employing a cobalamin-specific binder, intrinsic factor, and a nonspecific binder, hog non-intrinsic factor. Values for total cobalamin and analogues were increased to the same degree in CML plasma.

Inter-relationships between single carbon units' metabolism and resting energy expenditure in weight-losing patients with small cell lung cancer. Effects of methionine supply and chemotherapy

The one-carbon unit metabolism was investigated in 8 weight-losing patients with small cell carcinoma of the lung (SCLC). At diagnosis, 6 of the 8 patients had elevated formiminoglutamic acid (FIGLU) excretion after a histidine load, suggesting a lack of one-carbon units. In accordance, a significant decrease of FIGLU excretion was observed in the patients after oral administration of DL-methionine for 4 days. The elevated FIGLU excretion was positively correlated to weight loss prior to diagnosis and negatively correlated to serum albumin at time of diagnosis. After 3 months of combination chemotherapy, FIGLU excretion was reduced in all patients except 1, who had progressive disease. Despite the elevated FIGLU excretions, all patients had normal blood folate levels. The resting energy expenditure (REE) was recorded in 7 patients, and a significant, positive correlation was observed between pretreatment FIGLU excretion and REE, although the REE measured in this group of patients was within the normal range. These data demonstrate an increased demand of "active" one-carbon units in energy consumption in a group of weight-losing cancer patients. The one-carbon unit deficit was reconditioned by oral administration of the one-carbon unit donor DL-methionine.

A specific radioimmunoassay for 5'-deoxyadenosyl cobalamin in serum

A specific radioimmunoassay for 5'-deoxyadenosyl cobalamin (ado-Cbl) has been developed using an antiserum raised to this cobalamin (Cbl). At a 1:100 or greater dilution the antiserum did not bind radiolabelled methyl-, hydroxo-, sulphito- or cyano-Cbl and these Cbl analogues did not compete in the radioimmunoassay even at 100-fold higher concentration. The serum concentration (range and mean +/- SD) of ado-Cbl in 30 normal subjects was 47-134 and 81 +/- 16 pg/ml. The corresponding values for total Cbl in these sera were 189-610 and 355 +/- 144 pg/ml, and the computed values for methyl-Cbl were 142-476 and 274 +/- 127 pg/ml. The coefficient of variation was substantially greater for methyl-Cbl than for ado-Cbl (46% v. 21%, respectively). The ado-Cbl concentration was in the normal range (75-95 pg/ml) in five healthy subjects with a low normal concentration (189-217 pg/ml) of total Cbl. In two subjects with low total Cbl (118 and 170 pg/ml) and without any clinical evidence of Cbl deficiency, ado-Cbl was normal (63 and 95 pg/ml, respectively). Thus, in this group, low methyl-Cbl accounted for the lower total Cbl. The concentration (mean +/- SD) of serum ado-Cbl and methyl-Cbl in six patients with low total Cbl (57 +/- 25 pg/ml) and clinical evidence for Cbl deficiency was 35 +/- 12 pg/ml and 22 +/- 22 pg/ml, respectively. This difference from the normal mean for each cofactor was highly significant (P less than 0.001). The decrease in the concentration of methyl-Cbl in Cbl deficiency was relatively greater than the decrease in ado-Cbl (92% v. 57%, respectively) which raised the relative concentration of ado-Cbl in Cbl deficiency to 61% of the total Cbl. Although a low serum methyl-Cbl is a sensitive indicator of Cbl deficiency, it may not be as specific as a decrease in serum ado-Cbl. Factor(s) other than tissue stores of Cbl may lower serum methyl-Cbl below the 95% confidence limit in the absence of clinical Cbl deficiency.

Renal plasma clearance: a valuable marker in myelomatosis

Forty-two consecutive patients with untreated myelomatosis (MM) formed the basis of settling the validity of measuring the renal plasma clearance (RPC), either indirectly using the serum creatinine or directly using the glomerular filtration rate (GFR) when studying anaemia, calcium metabolism, proteins in serum and urine, and prognosis. Patients without light chain excretion in the urine had a higher GFR (P less than 0.01) than patients with light chain excretion. The haemoglobin concentration (Hb) was strongly correlated (P less than 0.001) to both, serum creatinine and GFR. Patients with normal serum concentrations of the physiological immunoglobulins had higher Hb (P less than 0.01) than patients with reduced serum immunoglobulins. Patients with serum calcium greater than 3.00 mmol/1 had additional reduced GFR compared with the other myeloma patients. The serum parathyroid hormone was decreased (P less than 0.01) and inversely correlated to the GFR. Patients with increased serum creatinine, reduced GFR or with osteolytic bone lesions had a decreased survival rate. The study shows that the major factor in prediction of Hb and prognosis in patients with MM is the RPC expressed either as the serum creatinine or the GFR. In addition, the significant correlations between the GFR and the other variables in MM assessed the RPC to be a useful and valuable marker in studies of anaemia, protein and calcium metabolism and prognosis in MM.

Interference by methylcobalamin analogues with synthesis of cobalamin coenzymes in human lymphocytes in vitro

1. 72 h uptake of cyano[57Co]cobalamin and formation of 57Co-labelled methylcobalamin, adenosylcobalamin and hydroxocobalamin has been estimated with and without the addition of methylcobalamin analogues in phytohaemagglutinin-stimulated lymphocytes from healthy human subjects. 2. Difluorochloromethylcobalamin reduced cell uptake of cyanocobalamin and caused a disproportionate reduction in synthesis of adenosylcobalamin. 3. Methylcobalamin-palladium trichloride reduced cell uptake of cyanobalamin more effectively than did difluorochloromethylcobalamin and reduced the formation of methylcobalamin, adenosylcobalamin and hydroxocobalamin in proportion. 4. The results suggest that in addition to inhibiting uptake of cyanocobalamin, one or both compounds may have interfered directly with the mechanism of synthesis of the cobalamin coenzymes.

Bone marrow studies in myelomatosis

The percentage of fat-cell areas in bone marrow particles from 22 patients with untreated myelomatosis was estimated. In only 1 patient was the mean fat cell area below 25% of the bone marrow area measured. A negative correlation was found between the area of fat cells and plasma cells, indicating a displacement of the fat cell area by the plasma cells. 28% of the patients had empty bone marrow deposits of iron. However, based on a normal iron saturation of S-transferrin and a normal sideroblast count in the bone marrow, the supply of iron to the erythropoiesis was considered sufficient. All patients but one had normoblastic bone marrows. Using a deoxyuridine suppression test in 10 patients, no biochemical defect could be demonstrated. To judge from the correlation coefficient a minor degree (9-14%) of the variation in Hb values could be predicted from the cellularity in the bone marrow while a major degree (70%) could be predicted from the renal glomerular filtration rate. The results do not support a displacement of blood-forming elements, iron deficiency, vitamin B12 or folic acid deficiency to be of general significance in the pathogenesis of anaemia, but agrees with a causal relationship between anaemia and renal failure.