Lymphocyte proliferation and cytotoxic assays using flat-bed scintillation counting.

Lymphocyte 51Cr release and [3H]thymidine uptake assays were evaluated with respect to measurement of sample radioactivity using the flat-bed scintillation counter. 51Cr lysates were spotted onto a glass fibre filter sheet while [3H]thymidine-labelled cells were filtered onto a similar sheet using a cell harvester. The 96 samples were rapidly processed for counting, without removal of individual sample areas. Either form of preparation showed good linearity of count rate with the quantity of material on the filter. Reproducibility was good; the coefficient of variation for 96 samples being within 5%. The low background and high efficiency of this counter results in increased assay sensitivity and allows considerable economies in materials to be made. A commercial version of the counter has six counting heads permitting a high rate of sample throughput.

Enoxaparin: in the prevention of venous thromboembolism in medical patients.

Enoxaparin (enoxaparin sodium) is a low-molecular-weight heparin that binds to and increases the activity of antithrombin III. The resulting complex inhibits prothrombinase-mediated thrombin generation and direct thrombin generation by binding to factor Xa and thrombin factor IIa. Enoxaparin, used as prophylaxis in medically ill patients at increased risk for thromboembolism, has shown significantly increased efficacy compared with placebo in reducing the incidence of deep vein thrombosis and pulmonary embolism. Indeed, 291 patients receiving subcutaneous enoxaparin 40 mg/day had a frequency of venous thromboembolism of 5.5% during 14 days of treatment, whereas 14.9% of the 288 placebo recipients experienced thromboemboli (p < 0.001). There was no reduction in the incidence of thromboembolism in the 287 recipients of enoxaparin 20 mg/day (15%). In other studies, prophylactic treatment for 7 days with subcutaneous enoxaparin 40 mg/day was at least as effective as unfractionated heparin in reducing the frequency of venous thromboembolism in 959 nonsurgical patients at increased risk for deep vein thrombosis and pulmonary embolism (total incidence = 0.2 and 1.4%, respectively). Moreover, enoxaparin recipients experienced fewer adverse events than did heparin recipients. The most frequent adverse events reported in medically ill and surgical patients receiving enoxaparin 40 mg/day were hemorrhage (17.4 vs 14.3% for placebo), hematoma at injection site, anemia, fever, peripheral edema, nausea, ecchymosis and edema (unspecified site).

Physiological and pharmacological aspects of 24,25-dihydroxycholecalciferol in man.

The present study describes the response to small oral doses (1--10 microgram/day) of 24,25-DHCC in man. Contrary to expectation, 24,25-DHCC was as potent as 1,25-DHCC in increasing intestinal absorption of calcium both in normal persons and in patients with a variety of disorders of calcium metabolism. Despite this increase in intestinal absorption, plasma and urine calcium did not increase after 24,25-DHCC as they did after 1,25-DHCC. Metabolic balance studies showed calcium balances to increase by 1.6 to 11.5 mmoles/day in 5 of the 6 patients studied. 24,25-DHCC increased intestinal absorption of calcium equally well in anephric patients, suggesting that conversion of 24,25-DHCC to 1,24,25-trihydroxycholecalciferol by the kidney cannot be the sole mechanism by which 24,25-DHCC expresses biological activity, even though in vitamin D deficient rats nephrectomy does abolish the ability of large doses of 24,25-DHCC to increase calcium absorption. It is concluded that 24,25-DHCC may be a calcium-regulating hormone in man. In view of the effects demonstrated here and its relatively high concentration in plasma and slow turnover rate, 24,25-DHCC has the properties that might be ideal for a long-acting stimulator of bone mineralisation. Further work is needed to explain why 24,25-DHCC has effects in man which are not readily seen in other species.

Factors influencing the early plasma disappearance rate and liver uptake of thyroxine.

The early disappearance from plasma (T 1/2) of i.v. administered thyroxine (T4) labelled with 131I was studied in order to find a simple biochemical parameter with which it could be correlated in health and disease. The radioactivity of the liver was also measured by surface counting to determine the time for the peak liver count rate. The T 1/2 for the 131I-T4 showed a correlation of borderline significance with T4 in plasma but a good correlation was found with T4-binding globulin (TBG) in plasma and an even better with the T3-test. The T3-test showed a significant correlation with TBG but when the T4-binding capacity of prealbumin (TBPA) was taken into account the correlation was even better indicating that the result of the T3-test was not only dependent on the TBG concentration in plasma but also on the TBPA. The T 1/2 correlated best with the time for the liver peak count rate. The study supports the hypothesis that in the early distribution phase of T4, the free binding sites extracellularly and the available intracellular binding locations compete for T4 until a state of equilibrium is reached.

Absorption of therapeutic preparations of iron measured with a whole body counter.

The Oxford Whole Body Counter was used to measure absorption from various therapeutic preparations of iron in five groups of subjects. Succinic acid enhanced absorption of iron when added to a solution of ferrous fumarate, but not when given with tablets of ferrous fumarate or ferrous sulphate. Ferrous fumarate plus ascorbic acid was absorbed better than ferrous fumarate alone but no better than ferrous sulphate. The addition of ascorbic acid and succinic acid to tablets of ferrous sulphate did not enhance absorption significantly.

Absorption of inorganic and haemoglobin iron in coeliac disease.

Absorption from a 5 mg dose of iron as Fe++ or haemoglobin iron was studied using a Total Body Counter in control subjects and patients with coeliac disease. In both groups the majority of subjects were iron deficient. Thirteen control subjects, 13 patients with untreated coeliac disease and 14 on treatment with gluten-free diet had both absorption tests. Absorption of Fe++ iron was reduced in untreated coeliac disease. This was particularly significant in iron deficient patients. Absorption was improved on treatment with gluten-free diet; In contrast, the absorption of haemoglobin iron was not affected in coeliac disease, indicating that absorption of iron in this form is not dependent on the integrity of the mucosa of the proximal small bowel.

The role of chronic blood loss in the pathogenesis of postgastrectomy iron-deficiency anaemia.

The role of chronic blood loss in the pathogenesis of postgastrectomy iron-deficiency anaemia was assessed by measurements of blood loss over periods of up to three months, using a whole-body counter and (59)Fe. Eleven patients were investigated and eight of these were selected because of a history of iron-deficiency anaemia. Six were shown to be losing blood abnormally, five at a rate of over 150 ml per month. None of the three patients without a history of anaemia lost more than 60 ml per month. At gastroscopy contact bleeding from the mucosa of the gastric remnant was observed in four of the six patients losing blood. The results indicate that in some patients chronic blood loss plays an important role in the pathogenesis of postgastrectomy iron-deficiency anaemia.

Treatment of menorrhagia with tranexamic acid. A double-blind trial.

In a double-blind trial tranexamic acid (Cyclokapron) 1 g. four times a day for the first four days of menstruation, significantly decreased menstrual blood loss in women with menorrhagia for which no organic cause had been found. No difference in side-effects was noted between the active and placebo treatment.

The thyroid in ulcreative colitis and Crohn's disease. III. The daily fractional turnover of thyroxine.

The daily fractional turnover of thyroxine (T4) labelled with 131 I has been determined in 11 patients with ulcerative colitis (uC) of Crohn's disease and 8 controls. The daily fractional turnover of 131I-T4 was significantly increased in the patient group. The daily total disposal of T4 iodine was not significantly different although it was excessive in 3 of the 11 patients. The amount of T4 in plasma did not differ significantly between the patients and the controls. It is concluded that the T4 metabolism is disturbed in UC and Crohn's disease and that excessive losses of T4 iodine can be a cause of iodine depletion in some patients with longstanding and severe disease.

A new design for a liquid scintillation counter for micro samples using a flat-bed geometry.

A new design for a liquid scintillation counter based on a flat-bed geometry is described. Micro-samples are dried or filtered onto transfer membranes or glass fibre filters in a 6 X 16 matrix, compatible with 96-well micro-titration plate filtration assays of labelled cells. A prototype counter without lead shielding had low background countrates (2-3 cpm for 3H) giving a figure of merit of 1325 (and 1292 for 14C). Only 5-15 ml of scintillant/96 samples are required and thus the volume of radioactive waste is low.