Host response to EBV infection in X-linked lymphoproliferative disease results from mutations in an SH2-domain encoding gene.

X-linked lymphoproliferative syndrome (XLP or Duncan disease) is characterized by extreme sensitivity to Epstein-Barr virus (EBV), resulting in a complex phenotype manifested by severe or fatal infectious mononucleosis, acquired hypogammaglobulinemia and malignant lymphoma. We have identified a gene, SH2D1A, that is mutated in XLP patients and encodes a novel protein composed of a single SH2 domain. SH2D1A is expressed in many tissues involved in the immune system. The identification of SH2D1A will allow the determination of its mechanism of action as a possible regulator of the EBV-induced immune response.

Thimet oligopeptidase: site-directed mutagenesis disproves previous assumptions about the nature of the catalytic site.

Zinc metallopeptidases that contain the His-Glu-Xaa-Xaa-His (HEXXH) motif generally have a third ligand of the metal ion that may be either a Glu residue (in clan MA) or a His residue (in clan MB) (Rawlings and Barrett (1995) Methods Enzymol. 248, 183-228). Thimet oligopeptidase has not yet been assigned to either clan, and both Glu and His residues have been proposed as the third ligand. We mutated candidate ligand residues in the recombinant enzyme and identified Glu, His and Asp residues that are important for catalytic activity and/or stability of the protein. However, neither of the Glu and His residues close to the HEXXH motif that have previously been suggested to be ligands is required for the binding of zinc. We conclude that thimet oligopeptidase is not a member of clan MA or clan MB and it is likely that the enzyme possesses a catalytic site and protein fold different from those identified in any metallopeptidase to date. The definitive identification of the third zinc ligand may well require the determination of the crystallographic structure of thimet oligopeptidase or one of its homologues.

Determination of norethindrone stability on red delicious apples.

A stability-indicating assay procedure for the determination of norethindrone on the surface of Red Delicious apple slices was developed. The apple slice is homogenized in pH 10 borate buffer solution and norethindrone is then partitioned into chloroform using a diffusion chamber that has a membrane that is permeable to hydrophobic compounds separating the buffer and chloroform. An aliquot of the chloroform extract is then evaporated to dryness and reconstituted in tetrahydrofuran. The reconstituted sample is then chromatographed on a C18 reversed-phase column using a mobile phase consisting of water:tetrahydrofuran:methanol (63:26:11, v/v/v). Detection is in the UV range at 254 nm. The chromatographic system is specific for norethindrone in the presence of its autoxidation products. Stability data indicate that norethindrone is stable for up to 6 h on the surface of Red Delicious apples.

pH-sensitive polymer hydrogels derived from morpholine to prevent the crystallization of ibuprofen.

Various pharmaceutical formulations of ibuprofen are available including oral tablets, suspensions, suppositories and transdermal gels and creams. Aqueous ibuprofen solubility is dependent on pH increasing solubility when increasing pH. The very low aqueous solubility of ibuprofen can lead to a segregation of the drug in to microdomains and possible crystallization which will affect the release profile even leading to possible damage of the mucous membrane of the stomach. Therefore, homopolymers and copolymers of N-ethylmorpholine methacrylamide (EMA) and N, N-dimethylacrylamide (DMA) hydrogels have been prepared to be applied as matrices for ibuprofen release as a method for minimizing these issues. The hydrogels were loaded with ibuprofen and the release over time was tested at 37°C and at different pH values: 2, 5 and 7.4. Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) was performed in order to identify the stretching vibrations of the carbonyl group for each component. Dissolution of the ibuprofen from the formulations at different pHs was studied using the ATR-FTIR spectroscopic imaging. The results showed that for DMA hydrogels, most of ibuprofen was released as non crystalline ibuprofen at pH 7.4 but it was not able to prevent crystallization at pH 2 and 5. In contrast, the EMA hydrogels were able to prevent crystallization of the ibuprofen at all pHs. Finally, it was demonstrated that there is a minimum concentration at which the polymer becomes ineffective.

An unusual complication of an inferior dental nerve block: a case report.

Local anaesthetic drugs are commonly used in dental practice, with few complications. We describe an unusual complication of an inferior dental nerve block where, as the needle was advanced through the mucosa, the patient experienced profound numbness and skin pallor in the distribution of the infra-orbital nerve. We discuss the possible mechanism for this complication.