Molecular genetics of PKU in Eastern Europe: A nonsense mutation associated with haplotype 4 of the phenylalanine hydroxylase gene

Phenylketonuria (PKU) is a genetic disorder secondary to a deficiency of hepatic phenyalanine hydroxylase (PAH). Several mutations in thePAH gene have recently been reported, and linkage disequilibrium was observed between RFLP haplotypes and specific mutations. A new molecular lesion has been identified in exon 7 of thePAH gene in a Hungarian PKU patient by direct sequencing of PCR-amplified DNA. The C-to-T transition causes the substitution of Arg²⁴³ to a termination codon, and the mutant allele is associated with haplotype 4 of thePAH gene. The mutation is present in two of nine mutant haplotype 4 alleles among Eastern Europeans and is not present among Western Europeans and Asians. The rarity of this mutant allele and its restricted geographic distribution suggest that the mutational event occurred recently on a normal haplotype 4 background in Eastern Europe.     

A Guide to Immunotherapy of Genital Warts

Genital warts affect at least 1% of sexually active adults. Current therapies are inadequate because they are often painful, may fail to prevent recurrence and transmission of warts, and usually require either surgery or at least application by a physician. Investigation of immunotherapy for genital warts began with interferon. It has been studied in topical, intralesional, systemic and adjuvant applications. We review the major clinical trials of interferon for genital warts, and conclude that intralesional therapy with interferon-alpha or interferon-beta, with complete response rates of 36 to 63%, is the most successful route for interferon monotherapy. In choosing patients for therapy with interferon, major considerations include immune status, pregnancy and ability to return for frequent injections. Imiquimod is a new immune response enhancer that acts through stimulating host cytokine production. Interleukins-1, -2, -6, -8 and -12, interferons alpha, beta and gamma and tumour necrosis factor alpha have all been associated with the mechanism of action of imiquimod. Recently, 3 clinical trials have reported positive results using topical imiquimod to treat genital warts. Complete response rates ranged from 37 to 54% for these controlled trials of 5% imiquimod cream. Adverse effects reported include localised pruritis, erythema, erosion, burning and pain, which were rarely severe enough to cause discontinuation of the medication. Although further trials are necessary to identify the role of imiquimod in the therapy of genital warts, it appears to be an efficacious and well tolerated patient-controlled measure for wart therapy.     

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

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Automated radiosynthesis of [11C]UCB-J for imaging synaptic density by positron emission tomography

An automated radiosynthesis of carbon-11 positron emission tomography radiotracer [¹¹C]UCB-J for imaging the synaptic density biomarker synaptic vesicle glycoprotein SV2A was established using Synthra RNPlus synthesizer. Commercially available trifluoroborate UCB-J analogue was used as a radiolabelling precursor, and the desired radiolabelled product was isolated in 11 ± 2% (n = 7) nondecay corrected radiochemical yield and formulated as a 10% EtOH solution in saline with molar activities of 20 to 100 GBq/μmol. The method was based upon the palladium(0)-mediated Suzuki cross-coupling reaction and [¹¹C]CH₃I as a radiolabelling synthon. The isolated product was cGMP compliant as demonstrated by the results of quality control analysis.     

Theiler’s murine encephalomyelitis virus as an experimental model system to study the mechanism of blood–brain barrier disruption

Theiler’s murine encephalomyelitis virus is a widely used model to study the initiation and progression of multiple sclerosis. Many researchers have used this model to investigate how the immune system and genetic factors contribute to the disease process. Current research has highlighted the importance of cytotoxic CD8 T cells and specific major histocompatibility complex (MHC) class I alleles. Our lab has adopted this concept to create a novel mouse model to study the mechanism of blood–brain barrier (BBB) disruption, an integral feature of numerous neurological disorders. We have demonstrated that epitope-specific CD8 T cells cause disruption of the tight junction architecture and ensuing CNS vascular permeability in the absence of neutrophil support. This CD8 T cell-initiated BBB disruption is dependent on perforin expression. We have also elucidated a potential role for hematopoietic factors in this process. Despite having identical MHC class I molecules, similar inflammation in the CNS, and equivalent ability to utilize perforin, C57BL/6 mice are highly susceptible to this condition, while 129 SvIm mice are resistant. This susceptibility is transferable with the bone marrow compartment. These findings led us to conduct a comprehensive genetic analysis which has revealed a list of candidate genes implicated in regulating traits associated with BBB disruption. Future studies will continue to define the underlying molecular mechanism of CD8 T cell-initiated BBB disruption and may assist in the development of potential therapeutic approaches to ameliorate pathology associated with BBB disruption in neurological disorders.     

Experimental hypoglycemia is a human model of stress-induced hyperalgesia

Hypoglycemia is a physiological stress that leads to the release of stress hormones, such as catecholamines and glucocorticoids, and proinflammatory cytokines. These factors, in euglycemic animal models, are associated with stress-induced hyperalgesia. The primary aim of this study was to determine whether experimental hypoglycemia in humans would lead to a hyperalgesic state. In 2 separate 3-day admissions separated by 1 to 3 months, healthy study participants were exposed to two 2-hour euglycemic hyperinsulinemic clamps or two 2-hour hypoglycemic hyperinsulinemic clamps. Thermal quantitative sensory testing and thermal pain assessments were measured the day before and the day after euglycemia or hypoglycemia. In contrast to prior euglycemia exposure, prior hypoglycemia exposure resulted in enhanced pain sensitivity to hot and cold stimuli as well as enhanced temporal summation to repeated heat-pain stimuli. These findings suggest that prior exposure to hypoglycemia causes a state of enhanced pain sensitivity that is consistent with stress-induced hyperalgesia. This human model may provide a framework for hypothesis testing and targeted, mechanism-based pharmacological interventions to delineate the molecular basis of hyperalgesia and pain susceptibility.