Partially oxidized polycyclic aromatic hydrocarbons show an increased bioavailability and biodegradability.

Polycyclic aromatic hydrocarbons have a low water solubility and tend to adsorb on soil particles, which both result in slow bioremediation processes. Many microorganisms, known for their ability to degrade polycyclic aromatic hydrocarbons, only partially oxidize these compounds. White rot fungi, for instance, convert polycyclic aromatic hydrocarbons to more water soluble and bioavailable products. Polycyclic aromatic hydrocarbon metabolites were more readily mineralized by natural mixed bacterial cultures, like activated sludge and soil, than the parent polycyclic aromatic hydrocarbon compounds. These results suggest that sequential breakdown by white rot fungi followed by indigenous bacteria leads to an effective polycyclic aromatic hydrocarbon bioremediation process.

Degradation of 3-nitrophenol by Pseudomonas putida B2 occurs via 1,2,4-benzenetriol.

Growth of Pseudomonas putida B2 in chemostat cultures on a mixture of 3-nitrophenol and glucose induced 3-nitrophenol and 1,2,4-benzenetriol-dependent oxygen uptake activities. Anaerobic incubations of cell suspensions with 3-nitrophenol resulted in complete conversions of the substrate to ammonia and 1,2,4-benzenetriol. This indicates that P. putida B2 degrades 3-nitrophenol via 1,2,4-benzenetriol, via a pathway involving a hydroxylaminolyase. Involvement of this pathway in nitroaromatic metabolism has previously only been found for degradation of 4-nitrobenzoate. Reduction of 3 nitrophenol by cell-free extracts was strictly NADPH-dependent. Attempts to purify the enzymes responsible for 3-nitrophenol metabolism were unsuccessful, because their activities were extremely unstable. 3-Nitrophenol reductase was therefore characterized in cell-free extracts. The enzyme had a sharp pH optimum at pH 7 and a temperature optimum at 25 degrees C. At 30 degrees C, reductase activity was completely destroyed within one hour, while at 0 degrees C, the activity in cell-free extracts was over 100-fold more stable. The Km values for NADPH and 3-nitrophenol were estimated at 0.17 mM and below 2 microM, respectively. The substrate specificity of the reductase activity was very broad: all 17 nitroaromatics tested were reduced by cell-free extracts. However, neither intact cells nor cell-free extracts could convert a set of synthesized hydroxylaminoaromatic compounds to the corresponding catechols and ammonia. Apparently, the hydroxylaminolyase of P. putida B2 has a very narrow substrate specificity, indicating that this organism is not a suitable biocatalyst for the industrial production of catechols from nitroaromatics.

Purification and partial characterization of a thermostable trithionate hydrolase from the acidophilic sulphur oxidizer Thiobacillus acidophilus.

Cell-free extracts of Thiobacillus acidophilus catalysed the quantitative conversion of trithionate (S3O6(2-) to thiosulphate and sulphate. A continuous assay for quantification of experimental results was based on the difference in absorbance between trithionate and thiosulphate at 220 nm. Trithionate hydrolase was purified to near homogeneity from cell-free extracts of T. acidophilus. The molecular masses of the native enzyme and the subunit were 99 kDa (gel filtration) and 34 kDa (SDS/PAGE). The purified enzyme has a pH optimum of 3.5-4.5 and a temperature optimum of 70 degrees C. Enzyme activity was stimulated by sulphate. The stimulation of the enzyme activity by sulphate was half maximal at a concentration of 0.23 M. The Km for trithionate is 70 microM at 30 degrees C and 270 microM at 70 degrees C. Enzyme activity was lost after 36 days at 0 degrees C, 27 days at 70 degrees C; but after 97 days at 30 degrees C, 40% of the initial activity was still present: The enzyme activity was inhibited by mercury chloride, N-ethylmaleimide, thiosulphate and tetrathionate. Tetrathionate S4O6(2-) was not hydrolysed by trithionate hydrolase.

Burning mouth syndrome: a possible etiologic role for local contact hypersensitivity.

BACKGROUND: The pathogenesis of the burning mouth syndrome (BMS) is not yet understood. Apart from psychologic factors, several etiologic "somatic" factors have been reported. OBJECTIVE: In 22 patients (19 women, 3 men, mean age 56 years) classified with BMS, clinical and laboratory investigations were performed, with particular emphasis on the role of contact hypersensitivity. Twenty of the 22 patients wore a complete or partial denture. METHODS: Besides clinical and laboratory investigations patch testing was performed with a standard routine series and a standardized denture-dental (acrylate and metal) series. RESULTS: Folate, iron, pyridoxine deficiency, and Candida infections were found, but correction of the deficiency or treatment of the infection was of no benefit. Contact allergy to allergens used in the production of acrylate-based dentures was observed in six (27%) of the cases (all wore a denture); positive reactions were seen to N,N,-dimethyl-4-toluidine (3 cases), to 4-tolyldiethanolamine (2 cases), to benzoylperoxide (2 cases), and to oligotriacrylate (1 case). In six cases (27%) a possible relevant sensitization was seen to dental metals and in particular to gold chloride (four cases). CONCLUSION: The possible role of local hypersensitivity reactions to denture or dental components as etiologic factors in BMS must be considered.

Psychologic characteristics of men with alopecia androgenetica and their modification.

Psychologic characteristics were studied in a sample of 168 men with alopecia androgenetica who participated in a clinical trial on the efficacy of minoxidil gel. In general, no evidence of psychologic malfunctioning was found. Instead, a slightly more adequate psychologic state was indicated. However, specific problems associated with hair loss were reported by a substantial number of men. Responders with cosmetic improvement in the group over 35 years of age improved more regarding general psychologic maladjustment, inadequacy, and self-evaluation than those who did not respond. A reverse trend was, however, found in the group younger than 35 years of age, where the nonresponders improved more. An explanation for these findings is derived from the theory of cognitive dissonance.

Mixotrophic and Autotrophic Growth of Thiobacillus acidophilus on Glucose and Thiosulfate.

Mixotrophic growth of the facultatively autotrophic acidophile Thiobacillus acidophilus on mixtures of glucose and thiosulfate or tetrathionate was studied in substrate-limited chemostat cultures. Growth yields in mixotrophic cultures were higher than the sum of the heterotrophic and autotrophic growth yields. Pulse experiments with thiosulfate indicated that tetrathionate is an intermediate during thiosulfate oxidation by cell suspensions of T. acidophilus. From mixotrophic growth studies, the energetic value of thiosulfate and tetrathionate redox equivalents was estimated to be 50% of that of redox equivalents derived from glucose oxidation. Ribulose 1,5-bisphosphate carboxylase (RuBPCase) activities in cell extracts and rates of sulfur compound oxidation by cell suspensions increased with increasing thiosulfate/glucose ratios in the influent medium of the mixotrophic cultures. Significant RuBPCase and sulfur compound-oxidizing activities were detected in heterotrophically grown T. acidophilus. Polyhedral inclusion bodies (carboxysomes) could be observed at low frequencies in thin sections of cells grown in heterotrophic, glucose-limited chemostat cultures. Highest RuBPCase activities and carboxysome abundancy were observed in cells from autotrophic, CO(2)-limited chemostat cultures. The maximum growth rate at which thiosulfate was still completely oxidized was increased when glucose was utilized simultaneously. This, together with the fact that even during heterotrophic growth the organism exhibited significant activities of enzymes involved in autotrophic metabolism, indicates that T. acidophilus is well adapted to a mixotrophic lifestyle. In this respect, T. acidophilus may have a competitive advantage over autotrophic acidophiles with respect to the sulfur compound oxidation in environments in which organic compounds are present.

Why men with hair loss go to the doctor.

Consultations, motives, experience, and attitudes were explored in 201 men with alopecia androgenetica who had two years before shown interest in hair treatment using minoxidil. During the past two years, one-third consulted a professional on account of hair loss. General practitioners were consulted by 60% and other professionals by about 75%. The main motive for the consultation was hair treatment, which was offered to half of the consulting subjects. Medical professionals were generally considered to be more suitable than other professionals for consultation on minoxidil treatment. The perceived chance of the treatment being successful and the amount of hair problems experienced seemed more important factors for consulting than the views on the suitability of a professional or the extent of baldness. There were indications that subjects who consulted both general practitioners and other professionals had also more general problems.