A Jordan control canonical form for singular systems

A canonical form for controllable singular systems modulo restricted system equivalence is presented. The canonical form respects the decomposition of the singular system into a regular and an impulsive part. The construction is based on Popov's control canonical form and on the Jordan canonical form recently developed by Hinrichsen and Prätzel-Wolters. Continuity properties are analysed and the cellular partition of the orbit space induced by the canonical form is briefly discussed.     

Biotin determination by three different methods: specificity and application to urine and plasma ultrafiltrates of patients with and without disorders in biotin metabolism

A microbiological, an avidin-binding and a streptavidin-binding method for biotin determination were compared. All three methods detected biotin equally well but they exhibit different specificities for derivatives of biotin. The microbiological assay has the highest specificity and is the method of choice for biotin determination in biotinidase-deficient patients. The specificity of streptavidin-binding has not been investigated so far. Application of the three methods to urine samples of patients with and without biotin therapy indicated that only 50% of biotin equivalents measured with the avidin method correspond to authentic biotin as previously shown. The other 50% comprise mainly bisnorbiotin and biotin-d-sulfoxide. HPLC-separation of urine samples prior to assay confirmed this finding and revealed a bisnorbiotin oxidation product and an unknown compound as further biotin metabolites. The latter was measurable by all three methods and not detectable in plasma ultrafiltrate. This was the only metabolite which was able to restore deficient 3-methylcrotonyl-CoA carboxylase activity in biotin-deficient fibroblasts. The combination of the three methods together with HPLC-separation proved to be a valuable analytical tool for the identification of the main biotin metabolites in biological fluids.     

Influence of short-term dietary measures on dioxin concentrations in human milk

Breast-feeding may expose infants to high levels of toxic chlorinated dioxins. To diminish intake of these lipophilic compounds by the baby, two diets were tested for their ability to reduce concentrations of dioxins in human milk. The diets were a low-fat/high- carbohydrate/low-dioxin diet. (about 20% of energy intake derived from fat) and a high fat /low-carbohydrate/low-dioxin diet. These diets were tested in 16 and 18 breast-feeding women, respectively. The test diets were followed for 5 consecutive days in the fourth week after delivery. Milk was sampled before and at the end of the dietary regimen, and dioxin concentrations and fatty acid concentrations were determined. Despite significant influences of these diets on the fatty acid profiles, no significant influence on the dioxin concentrations in breast milk could be found. We conclude that short-term dietary measures will not reduce dioxin concentration in human milk.     

Predictors of long-term smoking cessation in head and neck cancer patients

Cigarette smoking is a major risk factor for head and neck cancer, and individuals who continue to smoke past diagnosis and treatment are at elevated risk for further disease. In a randomized controlled trial, a state of the art provider-delivered smoking cessation intervention was compared to a usual care advice control condition. The intervention consisted of surgeon- or dentist-delivered advice to stop smoking, a contracted quit date, tailored written materials, and booster advice sessions. Subjects were 186 patients with newly diagnosed first primary squamous cell carcinomas of the upper aerodigestive tract who had smoked cigarettes within the past year. At randomization, 88.2% of subjects were current smokers. At 12-month follow-up, 70.2% of subjects completing the trial (n = 114) were continuous abstainers; among baseline smokers alone the continuous abstinence (CA) rate was 64.6%. The cotinine validation rate at 12 months was 89.6%. Modeling techniques were utilized in order to derive expected CA rates, which included noncompleter subjects (n = 72). The CA rate expected at 1 year for the entire patient population was 64.2%, and for smokers alone the expected CA rate was 59.4%. Logistic regression analysis carried out on baseline smokers identified predictors of 12-month CA status. These included medical treatment, stage of change, age, nicotine dependence, and race. The intervention effect was not significant, although the sign of the effect was positive. Based on these findings, we recommend systematic brief advice to stop smoking for head and neck cancer patients, with a stepped care approach for patients less able to quit.     

Identification of a gene that causes primary open angle glaucoma

Glaucoma is a major cause of blindness and is characterized by progressive degeneration of the optic nerve and is usually associated with elevated intraocular pressure. Analyses of sequence tagged site (STS) content and haplotype sharing between families affected with chromosome 1q-linked open angle glaucoma (GLC1A) were used to prioritize candidate genes for mutation screening. A gene encoding a trabecular meshwork protein (TIGR) mapped to the narrowest disease interval by STS content and radiation hybrid mapping. Thirteen glaucoma patients were found to have one of three mutations in this gene (3.9 percent of the population studied). One of these mutations was also found in a control individual (0.2 percent). Identification of these mutations will aid in early diagnosis, which is essential for optimal application of existing therapies.