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Biomedical subjects

Mark A Agius

Publications and source records attributed to Mark A Agius.

6 recordsLinked to original sources
PubMed2004

Current approved options for treating patients with multiple sclerosis.

Multiple sclerosis (MS), a neurologic disorder that affects 400,000 persons in the United States, consists of an inflammatory and a neurodegenerative phase. Treatment options now approved by the FDA specifically target the inflammatory phase of MS and include immunomodulators (i.e., interferon betas and glatiramer acetate) and an immunosuppressant, mitoxantrone. This article discusses the methods of monitoring disease progression using disability scales and MRI and reviews the clinical efficacy and tolerability of the FDA-approved therapies. All of the immunomodulators are approved for the treatment of relapsing forms of MS. Only mitoxantrone is approved for the treatment of worsening relapsing-remitting MS, secondary progressive MS, and progressive-relapsing MS. Early treatment with these disease-modifying agents is desirable to reduce the progression of the disease and to limit long-term disability.

Clinical Trials as Topic↗
PubMed2003

Treatment of autoimmune myasthenia gravis.

Autoimmune myasthenia gravis (MG) is associated with antibodies directed against the nicotinic acetylcholine receptor (AChR) in 85% of patients. Other postsynaptic neuromuscular junction antigens are implicated, e.g., muscle-specific receptor tyrosine kinase (MuSK), in a number of the remaining 15% of patients, so-called seronegative MG. The autoimmune attack generally leads to decreased concentrations of the AChR and damage to the structure of the endplate itself. This information has guided the empiric treatment of patients with MG and has suggested new treatment strategies. Whereas the outcome of patients with MG has improved because of more effective symptomatic treatment, including advances in critical care medicine and the use of cholinesterase inhibitors, the greatest advances have come from therapies that directly reduce the autoimmune attack or modify its effects on the AChR and the surrounding endplate. Immune-directed treatment of patients with MG, which is guided by this information and by data from the management of other autoimmune disease, is aimed at inducing an immunologic remission and then maintaining that remission. Remission induction is usually accomplished through the use of high-dose corticosteroids, frequently in conjunction with IV immunoglobulin or plasmapheresis. Maintenance of the remission is usually accomplished by slow tapering of the corticosteroids along with the use of "steroid-sparing" agents, which include azathioprine, thymectomy, and possibly mycophenolate. Therapy usually begins with cholinesterase inhibitors. If necessary, immune-directed treatment is added, beginning with either thymectomy or high-dose corticosteroids. The short-term therapies, i.e., IV immunoglobulin or plasmapheresis, may be effective in the early stages of treatment or later during an exacerbation. Steroid-sparing medications are usually added to facilitate the tapering phase.

Adrenal Cortex Hormones↗
PubMed2003

Agonist-induced transitions of the acetylcholine receptor.

Anti-acetylcholine receptor (AChR) monoclonal antibody 383C binds to the beta-hairpin loop alpha(187-199) of only one of the two Torpedo AChR alpha subunits. The loop recognized is associated with the alpha subunit corresponding to the high-affinity d-tubocurarine (dTC) binding site. Desensitization of the receptor with carbamylcholine completely blocks the binding of 383C. Mild reduction of AChR alpha subunit cys 192-193 disulfide with DTT and subsequent reaction with 5-iodoacetamidofluorescein label only the high-affinity dTC alpha subunit. Rhodamine-labeled alpha-bungarotoxin (R-Btx) binds to the unlabeled AChR alpha subunit as monitored by fluorescence resonance energy transfer between the fluorescein and rhodamine dyes. A 10-A contraction of the distance between the dyes is observed following the addition of carbamylcholine. In a small angle X-ray diffraction experiment exploiting anomalous X-ray scattering from Tb(III) ions titrated into AChR Ca(II) binding sites, we find evidence for a change in the Tb(III) ion distribution in the region of the ion channel following addition of carbamylcholine to the AChR. The carbamylcholine-induced loss of the 383C epitope, the 10-A contraction of the beta-hairpin loop, and the loss of multivalent cations from the channel likely represent the first molecular transitions leading to AChR channel opening.

Animals↗
PubMed2003

Three forms of immune myasthenia.

We propose a new classification for immune myasthenia based on antibody pattern. The types of immune myasthenia presently characterized by known antibody targets segregate into three groups: type 1, in which the muscle target is the acetylcholine receptor only; type 2, in which titin antibodies are present in addition to acetylcholine receptor antibodies; and type 3, in which muscle-specific kinase antibodies are present in the absence of acetylcholine receptor antibodies. The immune target is unknown in the patients with immune myasthenia not associated with these antibodies. This classification has advantages over the present classifications as regards homogeneity of groups, etiology, mechanism of disease, and prognosis.

Antibodies↗
PubMed2003

Treatment principles in the management of autoimmune myasthenia gravis.

The pathogenesis of myasthenia gravis (MG) involves a T cell-directed antibody-mediated autoimmune attack on the nicotinic acetylcholine receptor (AChR) or, occasionally, on other postsynaptic antigens. The antibodies induce their effects through complement-mediated destruction of the postsynaptic endplate membrane with resultant reduction in endplate AChR, and to a lesser degree by increased turnover of endplate AChR or blockade of AChR function. Considerable progress in the treatment of MG has accrued from so-called symptomatic treatments, including improved critical care of seriously ill patients and medications (e.g., cholinesterase inhibitors) increasing the concentration of acetylcholine at the remaining endplate AChRs. Information from other autoimmune diseases and from the response of the normal immune system to invading pathogens supports the view that the course of MG is characterized by exacerbations and remissions. Therefore, the goal in MG treatment is to induce and maintain a remission. This usually involves combinations of short-term and long-term immunosuppressive agents. Selection of the particular combinations of agents in a given patient is guided by the goal of minimizing the cost/benefit ratio of the regimen in an individual patient. In general, the plan involves an initial forceful attack followed by a slow and measured withdrawal.

Adrenal Cortex Hormones↗