How to encourage non-donors to be more willing to donate blood? Testing of binding communication based interventions.

OBJECTIVES: Our study aims to test the effectiveness of binding communication based interventions (vs classical persuasive communication based ones) inciting non-donors to act in favour of blood donation. BACKGROUND: The implementation of effective communication interventions represents a major public health issue. Nevertheless, persuasive media campaigns appear to have little effect on behaviours. Even though non-donors hold a positive attitude towards blood donation, they are not inclined to donate. As an alternative to producing behavioural changes, many recent studies have shown the superiority of binding communication over persuasive communication. METHODS: All participants, non-donors, were randomly assigned to one of four experimental conditions of a 2 (type of communication: persuasive vs binding) × 2 (source credibility: low vs high) factorial design. Then, they were asked to report their intention to donate blood, and their intention to distribute leaflets regarding blood donation. RESULTS: Binding communication is a more effective strategy for increasing intention towards blood donation compared with persuasive communication, especially when combined with high credibility source. DISCUSSION: Accordingly this study calls for more consideration of knowledge of social psychology to design effective communication interventions and increase the number of donations.

Iotrol, iodixanol, and 2-deoxy-D-glucose effects on neural tissue CO2 production.

In vivo and in vitro experiments have demonstrated that the myelographic agent metrizamide decreases neural tissue glucose metabolism whereas iohexol and iopamidol do not. This study compares the changes in slices of rat hippocampus CO2 production caused by the nonionic dimers iotrol and iodixanol with the effects of metrizamide and 2-deoxy-D-glucose. After 6-hr incubations, 70-mmol/l concentrations of iotrol and iodixanol increased CO2 production by 11 +/- 20% and 31 +/- 35%, respectively, as compared with the artificial CSF control medium. Metrizamide at 70 mmol/l and 2-deoxy-D-glucose at 35 mmol/l decreased CO2 production by 32 +/- 13% and 96 +/- 1%, respectively. The increases in CO2 production with iotrol and iodixanol appear to indicate that these molecules have some effect on cell metabolism. The mechanism for the increase in CO2 production could involve an effect on the glucose metabolic pathway or could be indirect via a mechanism that increases cell energy utilization. These in vitro effects have not been verified with in vivo experiments.

Effects of contrast media on neural tissue glucose uptake in vitro.

The authors previously showed that metrizamide causes an inhibition in CO2 production in rat neural tissue. The purposes of this work were to test if this inhibition was the result of a competitive inhibition of metrizamide with the D-glucose transport system and to test the effect of other contrast media. Deoxyglucose was used as a marker for glucose. The first cellular system using rat hippocampus slices was designed to examine the effect of 15 mM and 80 mM metrizamide on deoxyglucose uptake. The second cell-free system, using isolated rat brain synaptosomes, was designed to evaluate more accurately the mechanism and kinetics of metrizamide's inhibitory effect on the uptake of deoxyglucose and to compare metrizamide to other nonionic contrast media (iohexol, iopamidol, iotrol, and iodixanol). These experiments demonstrate that there is inhibition of D-glucose uptake only in hippocampus slices and that the inhibition is dependent on the concentration of metrizamide. This does not, however, appear to be a competitive inhibitory effect on the carrier such as that between D-glucose and 2-deoxy-D-glucose. In synaptosomes, none of the contrast media had a significant effect on the uptake of 2-deoxyglucose.

In vitro models for testing the metabolic effects of myelographic contrast media.

Water-soluble nonionic x-ray contrast media have greatly improved the quality and safety of myelography. Toxic side effects are still observed however. The side effects are generally worse with the first nonionic agent, metrizamide, which has a glucoselike side group. Two in vitro models were developed to examine the effects of contrast media on glucose metabolism. Using rat hippocampus slices, the authors observed significant depression of carbon dioxide production by metrizamide and by deoxyglucose, a known metabolic inhibitor. Iohexol and iopamidol did not cause significant depressions. In rat brain synaptosomes the authors did not observe a depression of the uptake of deoxyglucose 14C by any media tested. These studies indicate that metrizamide can create metabolic depression but that it does not compete with glucose for the membrane glucose carrier.

Local blood-brain barrier penetration following systemic contrast medium administration. A case report and an experimental study.

The present study was initiated by a severe complication in a patient with renal dysfunction who developed cortical blindness and weakness of her left extremities 30 hours following renal and abdominal angiography. To evaluate the impact of prolonged high serum concentrations of contrast medium (CM) this clinical situation was simulated in a laboratory model using sheep with elevated serum levels of contrast medium maintained for 48 hours. The experimental data did not support the theory that the prolonged exposure to high circulating levels of contrast medium (4 ml/kg body weight of meglumine diatrizoate 60%) is sufficient alone to cause penetration of the blood-brain barrier.

Further support for the glucose hypothesis of metrizamide toxicity. The effect of metrizamide and glucose analogue-free contrast media on hexokinase.

Metrizamide neurotoxicity has been hypothesized to be caused by an inhibitory effect of the drug on glucose metabolism. Metrizamide contains a glucose side chain, and glucose analogues including metrizamide have been shown to be inhibitors of hexokinase, an enzyme that is central to cerebral glucose metabolism. We studied the effect of the nonionic contrast agents iohexol, iotrol, and iopamidol, and the ionic contrast meglumine diatrizoate, on hexokinase in vitro. Although metrizamide reproducibly caused competitive inhibition of the reaction, the nonglucose contrast agents had no significant effect on the enzyme. These results add further support for the glucose hypothesis of metrizamide neurotoxicity.

Iopamidol and neural tissue metabolism. A comparative in vitro study.

Metrizamide was the first water-soluble contrast medium with a neurotoxicity low enough to allow it to be used routinely in the entire subarachnoid space. However, neurologic complications are still observed in some patients following the use of metrizamide. The cause of this toxicity has not been established, but existing evidence suggests an interference with glucose metabolism. In previous studies, a depression in CO2 production in neural tissue slices was demonstrated when isotonic metrizamide was added but not isotonic iohexol. In addition to iohexol, there is another new, nonionic, monomeric, water-soluble CM, iopamidol, soon to be released for clinical use in the United States. Iopamidol, like iohexol, has shown fewer adverse reactions and seems to be safer for myelography than metrizamide. Direct comparative studies of iopamidol and iohexol are sparse and the cause of their toxicity is not yet understood. This study was performed to determine the effect of iopamidol on neural tissue glucose metabolism as compared with the effects of iohexol and metrizamide. Metrizamide decreased CO2 production in neural tissue slices by 23%. Iopamidol and iohexol did not produce significant depression. Moreover, this model could not demonstrate any significant difference between iopamidol and iohexol in direct comparisons. The new monomeric contrast media, iopamidol and iohexol, thus do not appear to interfere with glucose metabolism. Adverse reactions to these new media are most likely caused by other mechanisms.

Penetration of subarachnoid contrast medium into rabbit spinal cord. Comparison between metrizamide and iohexol.

The penetration into rabbit spinal cord of two nonionic contrast media, iohexol and metrizamide, and a reference tracer, technetium DTPA, were compared. The spinal subarachnoid space was perfused for 4 hours with a CSF solution to which technetium DTPA and either iohexol or metrizamide had been added. The contrast media and technetium DTPA concentrations reached a plateau level in CSF outflow within 80 minutes. The contrast media concentrations in CSF were higher than the technetium DTPA (P less than .001). In the cord tissue, technetium DTPA reached higher concentrations than the contrast media (P less than .001), and iohexol reached higher concentrations relative to technetium DTPA than metrizamide (P less than .001). The mean contrast media distribution volumes in the thoracic cord were 13% (iohexol) and 12% (metrizamide). The smaller distribution volume observed for metrizamide could be related to the larger effective size of "associated" metrizamide molecules or an interference with diffusion perhaps related to binding to glucose carriers.

Slipped capital femoral epiphysis co-existent with hypothyroidism.

Five patients with slipped capital femoral epiphysis were conclusively diagnosed as being hypothyroid. One was a cretin, who was diagnosed and begun on thyroid medication at four months of age but subsequently many years later developed the slip. Suspicion of hypothyroidism should exist for the clinician who finds himself with a child below age 12 with a delayed bone age, borderline mental status and a slipped capital femoral epiphysis. His attention in addition to the orthopedic management of the slip, should be directed towards laboratory studies to rule out hypothyroidism.