Twenty years of biochemistry of human P450s: purification, expression, mechanism, and relevance to drugs

Today cytochrome P450 (P450) research is accepted as an integral part of drug development and discovery. Work leading to this point included biochemical studies on P450 in experimental animal models and application to human systems. The development of recombinant expression systems has been an important part of the progress, and in this article we describe some recently developed bacterial systems that can be used for the production of metabolites, genotoxicity testing, and screening in random mutagenesis work. Rate-limiting aspects of P450 reactions vary with particular systems, and further investigations are in order. Non-ionic detergents have been utilized widely in P450 purification work; these compounds are now shown to be substrates for P450s. These oxidations are not only of fundamental interest in expanding the repertoire of P450 substrates but have significance in light of human exposure to these compounds.     

Attitudes of 47 mothers of pediatric oncology patients toward genetic testing for cancer predisposition

PURPOSE: To assess attitudes toward testing for cancer susceptibility genes, we interviewed mothers of pediatric oncology patients about their cancer causation theories, interest in hypothetical predisposition testing for themselves and their healthy children, and anticipated impact of testing. PATIENTS AND METHODS: The subjects were 47 mothers of two or more living children, one of whom was 6 to 24 months postdiagnosis of cancer. Potential risks and benefits of hypothetical genetic predisposition testing for cancer susceptibility were described. A semistructured interview assessed the following: (1) recall of discussions with the pediatric oncologist about the possible role of heredity in causing the child's cancer; (2) mothers' personal theories of the etiology of their child's cancer; (3) family cancer history; (4) interest in genetic predisposition testing for themselves and unaffected (cancer-free) children; and (5) expected sequelae of testing. RESULTS: If genetic cancer predisposition tests were available, 51% of mothers would test themselves and 42% would test healthy children, even with no medical benefit. With established medical benefit, an additional 36% of mothers would seek testing for themselves and another 49% would test their healthy children. Interest in cancer predisposition testing among mothers extended far beyond those with significant family histories of cancer. Most mothers would consider minor children's wishes in the decision about testing and would tell children under age 18 their test results. CONCLUSION: As increasing numbers of cancer susceptibility genes are identified, parents of pediatric oncology patients may be receptive to opportunities to test themselves and their healthy children. Counseling will be important to aid in decisions about testing. Research is essential to evaluate the long-term impact of predisposition testing.     

Amizon in the treatment of nervous system involvement in herpes zoster

The authors submit results of treatment of patients having suffered from postherpetic pain syndrome (herpetic ganglionitis of the cervical, thoracic, lumbosacral localization, postherpetic intercostal neuralgia, ganglionitis of the trigeminal nerve). In viral diseases, amizone has marked analgetic, antiinflammatory, and immunomodulating effects. The drug is well tolerated by patients, is not associated with side effects under prescribed doses (0.25-0.75 as one dose on a three- or four-times daily schedule during the course of treatment lasting three or four weeks). The drug preparation in question is less effective in the treatment of chronic recurring post-therapeutic intercostal neuralgias, radiculalgia.     

Pulmonary involvement in primary Sj?gren''s syndrome

Knowledge of normal adjustment of heart rate and its response to exercise is essential for understanding and management of chronotropic incompetence. The autonomic nervous system plays an important role in the modulation of normal heart rate. Chronotropic responses of a normal heart to exercise are associated with parallel hemodynamic changes in order to meet the metabolic demand of the body. Determination of chronotropic incompetence is widely based on the assessment of maximal heart rate. However, maximal effort should always be confirmed before an attempt to measure a maximal heart rate is made.     

The muscarinic M1 agonist xanomeline increases soluble amyloid precursor protein release from Chinese hamster ovary-m1 cells

The functionally selective M1 agonist xanomeline, which is currently undergoing clinical trials as a therapy for Alzheimer's disease, was compared to the muscarinic agonist carbachol for effects on secretion of soluble amyloid precursor protein (APPs) from Chinese hamster ovary cells transfected with the human m1 receptor (CHO-m1). Release of APPs from CHO-m1 cells was increased maximally (4-10 fold) by 100 microM carbachol (EC50 = 11 microM) and by 100 nM xanomeline (EC50 = 10 nM). Stimulation of APPs secretion by xanomeline and carbachol was blocked by preincubation with 1 microM atropine. Carbachol did not stimulate APPs secretion from non-transfected CHO cells. Pilocarpine at 1 mM also increased APPs release. The efficacy of carbachol, xanomeline and pilocarpine for stimulating APPs secretion did not differ significantly. Activation of protein kinase C (PKC) in m1 transfected cell lines by 1 microM phorbol dibutyrate (PDBu) increased APPs release, and this was inhibited 97% by the PKC inhibitor bisindolemalemide. The PKC inhibitor decreased xanomeline and carbachol-stimulated APPs secretion by only 25-30%. These results demonstrate that xanomeline increased APPs release by activation of m1 muscarinic receptors and support the possibility that cholinergic replacement therapy for Alzheimer's Disease may reduce amyloid deposition.     

Misincorporation of dNTPs opposite 1,N2-ethenoguanine and 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine in oligonucleotides by Escherichia coli polymerases I exo- and II exo-, T7 polymerase exo-, human immunodeficiency virus-1 reverse transcriptase, and rat polymerase beta

1,N2-Ethenoguanine (1,N2-epsilon-Gua) and 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine (HO-ethanoGua) are two modified bases formed in the reaction of DNA with 2-chlorooxirane, the epoxide derivative of vinyl chloride. The oligonucleotides (19-mers), 5'-CAGTGGGTG*TCCGAATTGA-3', were prepared, with each of these modified bases substituted for G at G*. HO-ethanodeoxyguanosine exists predominantly as a mixture of diastereomers of the closed cyclic hemiaminal form, 5,6,7,9-tetrahydro-7-hydroxy-9-oxoimidazo[1,2-a]purine, shown by H2(18)O experiments to be in equilibrium with the open form, N2-(2-oxoethyl)Gua. Both adducts retarded the 3'-extension of a complementary 10-mer primer by all of the polymerases examined, but in every case, some full-length product was obtained. Nucleotide sequence analysis indicated misincorporation of dGTP and dATP across from both 1,N2-epsilon-Gua and HO-ethanoGua, with the extent varying considerably among the polymerases. Similar results were obtained when the abilities of the polymerases to incorporate a single dNTP were evaluated. In addition, -1 and -2 base frame shifts were detected with both 1,N2-epsilon-Gua and HO-ethanoGua with some of the polymerases. Steady-state kinetic experiments with Escherichia coli polymerase I exo- and T7 polymerase exo-/thioredoxin showed large decreases in k(cat) for all dNTP incorporations compared to the normal G x dCTP pair and high misincorporation frequencies for dATP and dGTP with both adducts (compared to dCTP). Collectively, the results indicate that both of these adducts have considerable miscoding potential with some of these polymerases, that there are a number of differences between the 1,N2-epsilon-Gua and HO-ethanoGua adducts (which formally differ only in the presence of the elements of water), and that misincorporation of dNTPs at a single modified base can vary considerably among different polymerases even in the absence of exonuclease activity.     

Riedel's thyroiditis: a case report and review of the literature

Riedel's thyroiditis is a very rare disease of unknown aetiology, occasionally associated with retroperitoneal and mediastinal fibrosis. It is a benign condition, but may be confused with an anaplastic carcinoma of the thyroid. The differential diagnosis with anaplastic carcinoma is assured only by intraoperative biopsy. The Authors report a clinical case: symptoms were a progressive enlargement of the thyroid gland, left recurrential palsy, dyspnoea and dysphagia. The surgical treatment was total thyroidectomy, performed with bilateral neurolysis of recurrent nerves. The patient was also under adjuvant corticosteroid treatment.