Developmental regulation of cardiac MAP4 protein expression.

It has been shown that the level of expression of microtubule-associated protein 4 (MAP4) mRNAs changes throughout neonatal heart development [Chapin SJ, et al. 1995. Biochemistry 34:2289]. In the present study, both immunofluorescence and western blotting methods were used to monitor MAP4 protein expression levels in the developing heart. By both methods, it was shown that the levels of total MAP4 protein were maximal during the first postnatal week, and then declined progressively to adulthood. In addition, four major electrophoretic species that reacted with MAP4-specific antibodies (called bands 1-4) were observed in all heart tissue samples. Three of the four bands decreased in abundance throughout postnatal development, but at different rates. The fourth band remained relatively constant in abundance with increasing postnatal age. To determine if phosphorylation events might contribute to this heterogeneity, western blotting experiments using phospho-specific antibodies and phosphatase digestion of extract samples were performed. No phosphorylation-specific antibody staining was observed and no significant changes were demonstrated in the bands after phosphatase treatment, implying that the observed complexity was due mainly to alternative start site or differential isoform expression. Finally, it was discovered that cardiomyocyte MAP4 associated with drug- and cold-stable microtubules in early neonatal myocytes. Thus, the complex regulation of MAP4 protein expression may play a key role in the functional differentiation of myocyte microtubules during heart development.

Toxicity of infliximab in the course of treatment of Crohn's disease.

Infliximab is a monoclonal antibody directed against the pro-inflammatory mediator TNF-alpha, which was approved in the US in 1998 for treatment-resistant Crohn's disease. Since that time, the indications have dramatically expanded to include rheumatoid arthritis, ankylosing spondylitis, psoriasis and most recently, active ulcerative colitis. Although the safety profile in the initial studies was quite favourable, subsequent studies have shown that a small percentage of patients reported severe side effects, including pneumonia, tuberculosis, lymphoma, drug-induced lupus and hepatotoxicity. Although these complications are rare, it is important to properly screen patients for predisposing conditions before beginning treatment. Furthermore, concurrent use of other immunosuppresive agents, such as 6-mercaptopurine, may reduce the incidence of less serious side effects, such as arthralgias, myopathies and other antibody-associated diseases. Since its approval, infliximab has revolutionised the treatment of Crohn's disease and has shown benefit in a variety of other inflammatory conditions, but significant toxicities can occur that necessitate thorough screening protocols and periodic clinical evaluation.