Aluminum salts in vaccines--US perspective

Aluminum in the form of aluminum hydroxide, aluminum phosphate or alum has been commonly used as an adjuvant in many vaccines licensed by the US Food and Drug Administration. Chapter 21 of the US Code of Federal Regulations [610.15(a)] limits the amount of aluminum in biological products, including vaccines, to 0.85 mg/dose. The amount of aluminum in vaccines currently licensed in the US ranges from 0.85-0.125 mg/dose. Clinical studies have demonstrated that aluminum enhances the antigenicity of some vaccines such as diphtheria and tetanus toxoids. Moreover, aluminum-adsorbed diphtheria and tetanus toxoids are distinctly more effective than plain fluid toxoids for primary immunization of children. There is little difference between plain and adsorbed toxoids for booster immunization. Aluminum adjuvants have a demonstrated safety profile of over six decades; however, these adjuvants have been associated with severe local reactions such as erythema, subcutaneous nodules and contact hypersensitivity.     

Primary closure of median sternotomy: techniques and principles

Understanding the biomechanics of midline sternotomy repair is important to successful surgical outcome. High-risk patients, particularly those with immunosuppression, diabetes, and osteoporosis, should be identified. Details of technique should be monitored, and closure should incorporate lateral support of the sternum in patients at risk. Sternal dehiscence can occur under physiologic loads. Closure techniques and materials should insure stable repair, with avoidance of material migration through the bone.     

Presynaptic congenital myasthenic syndrome due to quantal release deficiency

OBJECTIVE: To provide clinical, electrophysiologic, and ultrastructural findings in three patients with a presynaptic congenital myasthenic syndrome (CMS). BACKGROUND: Familial infantile myasthenia and paucity of synaptic vesicles are the only two fully characterized CMS. We are describing here three patients with another form of presynaptic CMS characterized by deficiency of the action potential-dependent release without reduction of the spontaneous release of neurotransmitter from the nerve terminal. METHODS: The authors performed electromyography and anconeus muscle biopsies that included intracellular recordings and electron microscopy of the neuromuscular junction in three patients with presynaptic CMS. They also sequenced part of the P/Q-calcium alpha(1)-subunit gene (CACNA1A) and the acetylcholine receptor subunit (AChR) genes in these patients. RESULTS: In these patients there were additional neurologic findings including nystagmus and ataxia. In all three patients the end-plate potential quantal content (m) was markedly reduced but neither the amplitudes nor the frequencies of miniature end-plate potentials were diminished. Ultrastructurally, postsynaptic end-plate folds, nerve terminal size, and synaptic vesicle number were normal but double-membrane-bound sacs containing synaptic vesicles were present in the nerve terminal of all three patients. The screening of reported pathogenic mutations in the CACNA1A and a mutational analysis of AChR subunit genes were negative. CONCLUSION: This form of CMS appears to result only from a deficiency of the quantal release of neurotransmitter that may be due to an abnormal calcium mechanism or impaired endocytosis and recycling of synaptic vesicles.     

A processive versus a distributive mechanism of action correlates with differences in ability of normal and xeroderma pigmentosum group A endonucleases to incise damaged nucleosomal DNA

A DNA endonuclease, isolated from the nuclei of normal human and xeroderma pigmentosum complementation group A (XPA) cells, which recognizes predominately pyrimidine dimers, was examined for the mechanism by which it locates sites of damage on UVC-irradiated DNA. In reaction mixtures with low ionic strengths (i.e. lacking KCl), the normal and XPA endonuclease locate sites of UV damage on both naked and reconstituted nucleosomal DNA by different mechanisms. On both of these substrates, the normal endonuclease acts by a processive mechanism, meaning that it binds non-specifically to DNA and scans the DNA for sites of damage, whereas the XPA endonuclease acts by a distributive one, meaning that it randomly locates sites of damage on DNA. However, while both the normal and XPA endonucleases can incise UVC irradiated naked DNA, they differ in ability to incise damaged nucleosomal DNA. The normal endonuclease showed increased activity on UVC treated nucleosomal DNA compared with naked DNA, whereas the XPA endonuclease showed decreased activity on the damaged nucleosomal substrate. Since a processive mechanism of action is sensitive to the ionic strength of the micro-environment, the KCl concentration of the reaction was increased. At 70 mM KCI, the normal endonuclease switched to a distributive mechanism of action and its ability to incise damaged nucleosomal DNA also decreased. These studies show that there is a correlation between the ability of these endonucleases to act by a processive mechanism and their ability to incise damaged nucleosomal DNA; the normal endonuclease, which acts processively, can incise damaged nucleosomal DNA, whereas the XPA endonuclease, which acts distributively, is defective in ability to incise this substrate.