Specific 3H radioimmunoassay with a monoclonal antibody for monitoring cyclosporine in blood.

A specific radioimmunoassay involving a mouse monoclonal antibody to cyclosporine has been developed for monitoring the parent drug in blood. Pretreatment with methanol removes cyclosporine from the erythrocytes. The limit of detection is about 12 micrograms/L, sample volume is 50 microL of blood, and within- and between-assay CVs are less than 7%. Assay results correlated well with those obtained by "high-performance" liquid chromatography (HPLC) for liver (n = 42), for heart (n = 64), for bone-marrow (n = 36), and for kidney (n = 140). For blood specimens obtained from patients treated with cyclosporine postoperatively for as long as 65 months, the mean RIA/HPLC ratio in all with transplant indications was close to 1. Therefore, the specific radioimmunoassay apparently can be used instead of HPLC to measure the parent drug in blood.

Spontaneous, in vitro, malignant transformation of a basophil/mast cell line.

It has recently become possible to grow basophil/mast cells in vitro for extended periods of time. Normally, these cultures remain fully dependent upon the presence of an adequate supply of growth factor(s) and the cells express several basophil/mast cell differentiated traits. We report here a case of spontaneous, in vitro, malignant transformation of such a basophil/mast cell line. The transformed cells no longer require the addition of growth factor(s) for continuous proliferation in vitro, and they have become highly tumorigenic in vivo. In contrast, when compared to their untransformed counterparts, they display the same set of differentiated traits, characteristic of immature basophil/mast cells. Thus, the data support the hypothesis that cell transformation results from a decreased sensitivity of precursor cells toward normal growth regulators but does not affect significantly the expression of differentiated functions.

Changes in the tissue concentration of folate and vitamin B(12) during maturation and ageing.

Age-dependent changes in folate and vitamin B(12) metabolism of mice have been investigated. The concentration of folate in liver plasma and blood showed a postnatal increase to a maximum at approx. 25 weeks. Total folate concentrations then remained constant whereas free folate decreased slowly up to week 98. Conversely both total and free folate of the brain were reduced extensively during the first 10 weeks of life after which time total folate concentration stabilised whilst that of free folate continued to decline slowly. The concentration of vitamin B(12) in brain, liver and plasma showed an initial rapid increase. The vitamin continued to accumulate more slowly in the brain and liver from weeks 10 to 98. The concentration of vitamin B(12) in the plasma appeared to achieve equilibrium after a period of accumulation lasting 25 weeks. These results suggest that during maturation the characteristics of folate metabolism of the brain are distinct from those of peripheral tissues, and that folate, unlike vitamin B(12) metabolism, undergoes continuing change with advancing age.

Circadian rhythms of folate and vitamin B(12) concentration in relation to convulsive thresholds of mice.

Circadian rhythms of folate and vitamin B(12) concentrations in the liver, brain and blood of Swiss mice have been determined. The relation of the changes in vitamin concentration to circadian rhythms in locomotor activity, drinking activity and convulsive thresholds (maximal electroshock seizure threshold) have been determined also. Both free folic acid (FFA) and total folic acid (TFA) of liver and blood showed minimum values at 21.00-24.00 h and maximum values at 06.00-09.00 h. Liver TFA declined at a steady rate from the peak value at 09.00 h whereas liver FFA and plasma folate maintained constant values from 09.00-18.00 h then declined rapidly. Brain folate (TFA and FFA) showed no rhythm. The concentrations of vitamin B(12) in plasma, liver and brain showed only minor fluctuations. Locomotor and drinking activities showed very similar rhythms with a sustained period of high activity between 12.00-21.00 h followed by a much shorter second period of high activity (23.00-03.00 h). Convulsive threshold declined during the first period of increased locomotor and drinking activities reaching a minimum value at 21.00 h thus just preceding the nadir in folate concentrations in liver and blood.