[Quantifying stenosis of the internal carotid artery: which ultrasound criteria are relevant?]

Therapeutic decisions in cases of arteriosclerotic stenosis of the internal carotid artery usually depend mainly on the degree of stenosis. However, the recommendations with regard to suitable ultrasonographic criteria are so controversial that even authors of repute describe "confusion" and "chaos in methodology".

AIM

The aim of this study is to assess which of the most frequently recommended sonographic criteria for stenosis best fulfill the requirements of an exact quantification of stenoses of the internal carotid artery.

METHOD

In 42 consecutive cases the preoperative ultrasound findings were compared with the degree of stenosis in surgically removed specimens. The sonographic technique employed consisted of the analysis of 2 direct and 3 indirect hemodynamic criteria of stenosis. In 34 of these cases planimetry was performed, too. The specimens were obtained by eversion thrombendarteriectomy or arteriotomy; for determination of the degree of stenosis a Paladur molded cylinder was prepared and measured.

RESULTS

Quantification of the haemodynamic criteria carries provided well with the endarterectomy specimens. Only in two cases there was a deviation of more than 10 %; however, in these two cases a change with time in the degree of stenosis was probably responsible for the discrepancy. In contrast, planimetry usually underestimated the degree of stenosis: In 61 % of the findings the ultrasonographic results differed by more than 10 % from the reference standard.

CONCLUSION

Quantification of stenosis of the internal carotid artery should be made using a combination of direct and indirect haemodynamic ultrasonographic criteria.

Detoxification of ferulic acid by ectomycorrhizal fungi

The ectomycorrhizal fungi Laccaria amethystina and Lactarius deterrimus grown in liquid culture were used to study the fate of added ferulic acid. Laccaria amethystina degraded ferulic acid to the major metabolite vanillic acid. The intermediate vanillin was not detected. Lactarius deterrimus showed a completely different detoxification pattern. Two dimers and one trimer of ferulic acid could be identified as polymerization products of this fungus. A bioassay of the possible biological activities of ferulic acid and vanillic acid on these fungi revealed that vanillic acid was less toxic than ferulic acid for Laccaria amethystina but that both phenolic acids were toxic for Lactarius deterrimus. The results are discussed with respect to ectomycorrhizal fungal growth in the organic layer of forest soils and between living root cells of ectomycorrhizas.

Laccase-catalysed synthesis of coupling products of phenolic substrates in different reactors

Substrate oxidation of aromatic substances by the enzyme laccase followed by a heteromolecular coupling with a co-substrate is a promising possibility for the synthesis of new compounds. To find a suitable reactor for the effective production of new compounds, the laccase-catalysed coupling of 3-(3,4-dihydroxyphenyl)propionic acid with 4-aminobenzoic acid was investigated as a model system. Based on the kinetic parameters, a mathematical model was used to predict the reaction yield and oxygen demand in a discontinuously stirred tank reactor and a continuously operated stirred tank reactor. Membrane processes were used for bubble-free aeration of the system and to recover the soluble enzyme.

Molecular analysis of aerobic phenylacetate degradation in Azoarcus evansii

The Azoarcus evansii gene which codes for phenylacetate-CoA ligase, an enzyme involved in the aerobic degradation of phenylacetate, was isolated from a genomic library, using as the probe a fragment of the gene which encodes the isoenzyme that is induced under anaerobic conditions. By this means both the gene and its flanking sequences were recovered. The gene is homologous to the phenylacetate-CoA ligase genes of Pseudomonas putida U and Escherichia coli W. Induction by phenylacetate under aerobic growth conditions was demonstrated using lacZ fusions. Western analysis showed that phenylacetate-CoA ligase is involved in the degradation of the aromatic amino acid phenylalanine. Genes coding for the phenylacetate-CoA ligase and for the putative hydroxylating enzyme were expressed in E. coli. Detection of 2-hydroxyphenylacetate in the recombinant E. coli strain indicated hydroxylation of phenylacetyl-CoA. The gene pacL, which codes for the putative ring-opening enzyme was mutated to enable the isolation of intermediates in aerobic phenylacetic acid degradation, which were characterized by GC-MS and NMR analyses.

Cometabolic ring fission of dibenzofuran by Gram-negative and Gram-positive biphenyl-utilizing bacteria

Thirty-five strains of soil bacteria were grown with biphenyl (BP) and tested for their capacity to cooxidize dibenzofuran (DBF). During metabolism of DBF, the culture medium of 17 strains changed from colorless to orange, indicating a meta-cleavage pathway of DBF degradation. The ring cleavage product of these isolates was shown to be 2-hydroxy-4-(3'-oxo-3' H-benzofuran-2'-yliden)but-2-enoic acid (HOBB). The strain SBUG 271, studied in detail and identified as Rhodococcus erythropolis, degraded DBF via 1,2-dihydroxydibenzofuran. The ensuing meta-cleavage yielded HOBB and salicylic acid. In addition, the four monohydroxylated monomers of DBF and two metabolites, which were not further characterized, were detected. Thus, our results demonstrate that the metabolic mechanism involves lateral dioxygenation of DBF followed by meta-cleavage and occurs in Gram-negative as well as in Gram-positive BP-degrading bacteria.

High-throughput site-directed mutagenesis in ES cells

Introduction of nonselectable mutations into the genome of embryonic stem cells by homologous recombination allows to investigate the function of genes at the molecular level and has been achieved, however, at very low efficiencies by the Hit and Run, Tag and Exchange, and Double Replacement strategies. Comparing those strategies at a single locus with vectors derived from a single fragment of the desmin gene led to the improvement of two strategies by employing a new selection cassette and modified selection procedures. Modified strategies resulted in the introduction of nonselectable point-mutations in 53% of the Hit and Run derived embryonic stem cell clones and in 0.7% of the Tag and Exchange clones. Efficiency of intrachromosomal recombination at Hit alleles outscored replacement-type recombination at the tagged alleles making the modified Hit and Run strategy the method of choice for the efficient introduction of nonselectable point mutations into the genome of embryonic stem cells.

Formation of glucoside conjugates during biotransformation of dibenzofuran by Penicillium canescens SBUG-M 1139

Penicillium canescens oxidises dibenzofuran (DBF) to produce monohydroxylated derivatives and other more hydrophilic metabolites. These substances are water-soluble but unstable in organic solvents such as ethyl acetate, acetone or dichloromethane. Both extraction with ethyl acetate and enzymatic treatment of the aqueous culture filtrate with beta-glucuronidase led to decay of the hydrophilic metabolites and indicated these products to be glycoside conjugates. The glycosyl residue was identified as glucose both by liquid chromatography and by the use of glucose oxidase. The conjugate pattern formed was the same in type and amount, independent of the carbon source used for cultivation of the fungus. Clearly, DBF transformation in P canescens occurred in two phases: first the conversion to 2-, 3-, and 4-hydroxydibenzofuran (phase I), followed by the formation of the corresponding glucosyl conjugates (phase II). In contrast, 2,3-dihydroxydibenzofuran added to the cultures was transformed by ring cleavage producing a muconic acid-like dead-end product.

Novel ring cleavage products in the biotransformation of biphenyl by the yeast Trichosporon mucoides

The yeast Trichosporon mucoides, grown on either glucose or phenol, was able to transform biphenyl into a variety of mono-, di-, and trihydroxylated derivatives hydroxylated on one or both aromatic rings. While some of these products accumulated in the supernatant as dead end products, the ortho-substituted dihydroxylated biphenyls were substrates for further oxidation and ring fission. These ring fission products were identified by high-performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance analyses as phenyl derivatives of hydroxymuconic acids and the corresponding pyrones. Seven novel products out of eight resulted from the oxidation and ring fission of 3,4-dihydroxybiphenyl. Using this compound as a substrate, 2-hydroxy-4-phenylmuconic acid, (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)acetic acid, and 3-phenyl-2-pyrone-6-carboxylic acid were identified. Ring cleavage of 3,4,4'-trihydroxybiphenyl resulted in the formation of [5-oxo-3-(4'-hydroxyphenyl)-2,5-dihydrofuran-2-yl]acetic acid, 4-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid, and 3-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid. 2,3,4-trihydroxybiphenyl was oxidized to 2-hydroxy-5-phenylmuconic acid, and 4-phenyl-2-pyrone-6-carboxylic acid was the transformation product of 3,4,5-trihydroxybiphenyl. All these ring fission products were considerably less toxic than the hydroxylated derivatives.

Dehalogenation of chlorinated hydroxybiphenyls by fungal laccase

We have investigated the transformation of chlorinated hydroxybiphenyls by laccase produced by Pycnoporus cinnabarinus. The compounds used were transformed to sparingly water-soluble colored precipitates which were identified by gas chromatography-mass spectrometry as oligomerization products of the chlorinated hydroxybiphenyls. During oligomerization of 2-hydroxy-5-chlorobiphenyl and 3-chloro-4-hydroxybiphenyl, dechlorinated C---C-linked dimers were formed, demonstrating the dehalogenation ability of laccase. In addition to these nonhalogenated dimers, both monohalogenated and dihalogenated dimers were identified.

Oxidation of triphenylarsine to triphenylarsineoxide by Trichoderma harzianum and other fungi

Arsenic resistant strains of bacteria and fungi were isolated from soil contaminated by chemical warfare agents. Until now, no metabolic products of microbial attack against the phenyl residues of the model substrate triphenylarsine (TP) were found if it was incubated together with these strains in liquid culture assays. However, one of the isolated fungi, Trichoderma harzianum As 11, was found to oxidize TP to triphenylarsineoxide (TPO). The yeast Trichosporon mucoides SBUG 801 and the white-rot fungus Phanerochaete chrysosporium were also able to oxidize the As(III) in TP. In addition, P. chrysosporium transformed phenylarsineoxide (PAO) to phenylarsonic acid (PAA) under O2-atmosphere. By means of a respirometer system, the oxidation of TP by T. harzianum As 11 was confirmed by a significantly higher consumption of oxygen in the presence of these compounds. HPLC analysis of the oxidation products TPO and PAA in the medium of the assays provided evidence for the transfer reaction of As(III) to As(V) in organic bonds. The oxidation products TPO and PAA are more hydrophilic than TP and PAO. Therefore, it was concluded that particular fungi contribute to the mobilization of arsenic in soil contaminated by chemical warfare agents.

Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290-320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290-380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge. Lethality was ameliorated by filtration of UV-B radiation alone, demonstrating that ambient UV-B radiation is sufficient to cause mortality. Although several studies have qualitatively demonstrated the lethality of UV-B to early life stage amphibians this study demonstrates that the larval life stages of the three species tested are more sensitive than the embryonic stages. This suggests that previous reports that have not included the larval life stage may underestimate the risk posed to some anuran populations by increasing UV-B exposure. Furthermore, this study reports quantitative UV-B dosimetry data, collected in conjunction with the exposures, which can be used to begin the assessment of the impact of environmental changes which increase UV-B exposure of these anurans.

Biotransformation of biphenyl by Paecilomyces lilacinus and characterization of ring cleavage products

We examined the pathway by which the fungicide biphenyl is metabolized in the imperfect fungus Paecilomyces lilacinus. The initial oxidation yielded the three monohydroxylated biphenyls. Further hydroxylation occurred on the first and the second aromatic ring systems, resulting in the formation of five di- and trihydroxylated metabolites. The fungus could cleave the aromatic structures, resulting in the transformation of biphenyl via ortho-substituted dihydroxybiphenyl to six-ring fission products. All compounds were characterized by gas chromatography-mass spectroscopy and proton nuclear magnetic resonance spectroscopy. These compounds include 2-hydroxy-4-phenylmuconic acid and 2-hydroxy-4-(4'-hydroxyphenyl)-muconic acid, which were produced from 3,4-dihydroxybiphenyl and further transformed to the corresponding lactones 4-phenyl-2-pyrone-6-carboxylic acid and 4-(4'-hydroxyphenyl)-2-pyrone-6-carboxylic acid, which accumulated in large amounts. Two additional ring cleavage products were identified as (5-oxo-3-phenyl-2,5-dihydrofuran-2-yl)-acetic acid and [5-oxo-3-(4'-hydroxyphenyl)-2,5-dihydrofuran-2-yl]-acetic acid. We found that P. lilacinus has a high transformation capacity for biphenyl, which could explain this organism's tolerance to this fungicide.

Characterisation of coupling products formed by biotransformation of biphenyl and diphenyl ether by the white rot fungus Pycnoporus cinnabarinus

Cells of the white rot fungus Pycnoporus cinnabarinus grown in glucose were able to hydroxylate biphenyl and diphenyl ether, although growth was inhibited by these substrates at concentrations above 250 microM. 2- and 4-Hydroxybiphenyl were detected as products of biphenyl metabolism and 2- and 4-hydroxydiphenyl ether as products of diphenyl ether metabolism in the culture media. After addition of 2-hydroxydiphenyl ether and 2-hydroxybiphenyl to cell-free supernatants containing laccase as the only ligninolytic enzyme, different coloured precipitates were formed. HPLC analysis revealed the formation of additional hydrophobic metabolites with one major product per transformation. Mass spectrometric analysis of the methyl derivatives of the polymer mixture indicated dimers and trimers with different binding types. The main products were identified as dimers with carbon-carbon bonds in para-position to the hydroxyl group of the monomers by mass spectroscopy and nuclear magnetic resonance spectroscopy.

Hydroxylation of biphenyl by the yeast Trichosporon mucoides

Hydroxylation of biphenyl by the dibenzofuran-degrading yeast Trichosporon mucoides SBUG 801 was studied. Glucose-grown cells degraded 40% of the biphenyl added within the first 24 h of incubation. The first step in the biotransformation pathway was the monohydroxylation of the biaryl compound to produce 2-, 3-, and 4-hydroxybiphenyl. Further oxidation produced seven dihydroxylated intermediates; the second hydroxyl group was added either on the aromatic ring already hydroxylated or on the second ring. Of all metabolites, 2,5-dihydroxybiphenyl accumulated in the supernatant in the highest concentration. The initial hydroxylation favors the 4-position to produce 4-hydroxybiphenyl, which is subsequently hydroxylated to form 3,4-dihydroxybiphenyl. When biphenyl was replaced as a substrate by 4-hydroxybiphenyl, further hydroxylation of the intermediate 3,4-dihydroxybiphenyl resulted in 3,4,4'-trihydroxybiphenyl. Incubation of T. mucoides with biphenyl and 18O2 indicated a monooxygenase-catalyzed reaction in the oxidation of biphenyl. The hydroxylation was inhibited by 1-aminobenzotriazole and metyrapone, known cytochrome P450 inhibitors. These results are very similar to those observed in the biotransformation of biphenyl in mammals.

Cometabolic degradation of dibenzofuran by biphenyl-cultivated Ralstonia sp. strain SBUG 290

Cells of the gram-negative bacterium Ralstonia sp. strain SBUG 290 grown in the presence of biphenyl are able to cooxidize dibenzofuran which has been 1,2-hydroxylated. Meta cleavage of the 1, 2-dihydroxydibenzofuran between carbon atoms 1 and 9b produced 2-hydroxy-4-(3'-oxo-3'H-benzofuran-2'-yliden)but-2-enoic acid, which was degraded completely via salicylic acid. The presence of these intermediates indicates a degradation mechanism for dibenzofuran via lateral dioxygenation by Ralstonia sp. strain SBUG 290.

Transformation of triclosan by Trametes versicolor and Pycnoporus cinnabarinus

We investigated the ability of Trametes versicolor and Pycnoporous cinnabarinus to metabolize triclosan. T. versicolor produced three metabolites, 2-O-(2,4,4'-trichlorodiphenyl ether)-beta-D-xylopyranoside, 2-O-(2,4,4'-trichlorodiphenyl ether)-beta-D-glucopyranoside, and 2,4-dichlorophenol. P. cinnabarinus converted triclosan to 2,4, 4'-trichloro-2'-methoxydiphenyl ether and the glucoside conjugate known from T. versicolor. The conjugates showed a distinctly lower cytotoxic and microbicidal activity than triclosan did.

Methyl ketone formation during degradation of phenoxybutyric acid by Penicillium canescens SBUG-M 1139

Penicillium canescens SBUG-M 1139 was shown to be able to grow using phenoxybutyric acid as the sole carbon source. The rapid conversion of the phenoxyalkanoic acid resulted in the formation of phenol, which was metabolized completely. These reactions were accompanied by an accumulation of the methyl ketone phenoxypropan-2-one. Furthermore, during the metabolism of phenoxybutyric acid, 4-phenoxy-2,3-dehydrobutyric acid, 4-phenoxy-3-hydroxybutyric acid, phenoxyacetic acid, and phenoxypropan-2-ol accumulated in minor amounts. Clearly, fungi can metabolize phenoxyalkanoic acids to produce methyl ketones in a manner analogous to that used for the conversion of short- or medium-chain fatty acids by fungi.

Analysis of both TSC1 and TSC2 for germline mutations in 126 unrelated patients with tuberous sclerosis

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of multiple hamartomas involving many organs. About two-thirds of the cases are sporadic and appear to represent new mutations. With the cloning of two causative genes, TSC1 and TSC2 it is now possible to analyze both genes in TSC patients and identify germline mutations. Here we report the mutational analysis of the entire coding region of both TSC1 and TSC2 genes in 126 unrelated TSC patients, including 40 familial and 86 sporadic cases, by single-stranded conformational polymorphism (SSCP) analysis followed by direct sequencing. Mutations were identified in a total of 74 (59%) cases, including 16 TSC1 mutations (5 sporadic and 11 familial cases) and 58 TSC2 mutations (42 sporadic and 16 familial cases). Overall, significantly more TSC2 mutations were found in our population, with a relatively equal distribution of mutations between TSC1 and TSC2 among the familial cases, but a marked underrepresentation of TSC1 mutations among the sporadic cases (P = 0.0035, Fisher's exact test). All TSC1 mutations were predicted to be protein truncating. However, in TSC2 13 missense mutations were found, five clustering in the GAP-related domain and three others occurring in exon 16. Upon comparison of clinical manifestations, including the incidence of intellectual disability, we could not find any observable differences between TSC1 and TSC2 patients. Our data help define the distribution and spectrum of mutations associated with the TSC loci and will be useful for both understanding the function of these genes as well as genetic counseling in patients with the disease.

Anaerobic formation and degradation of toxic aromatic compounds in agricultural and communal sewage deposits

Relatively high concentrations of phenol, p-cresol, phenylacetic acid and other aromatic compounds were found in agricultural and communal sewage deposits. These toxic aromatic compounds are products of the bacterial degradation of aromatic amino acids under anaerobic conditions. In laboratory experiments at 26 degrees C and under N2-atmosphere, the same aromatics were formed from the amino acid tyrosine and from gelatine in assays inoculated with sewage sludge. After exhaustion of tyrosine and gelatine, respectively, concentrations of the accumulated phenol and other aromatics remained stable for months, i.e., phenol, p-cresol, phenylacetic acid etc. are dead-end products of the bacterial metabolism under these conditions. After addition of sodium nitrate the aromatic compounds are metabolically decomposed by denitrification within weeks.

[Spontaneous vertebral arteriovenous fistula. Detection and treatment follow-up with color-coded duplex ultrasound]

Spontaneous or traumatic arteriovenous fistulae between vertebral artery and the surrounding venous plexus may cause vertebrobasilar hypoperfusion by steal effects. We report on a 71-year-old man presenting with vertigo. Duplex sonography revealed a vertebral arteriovenous fistula at the C4/5 level with the typical perivascular color Doppler artifact and hyperperfusion in the supplying arteries and draining veins. Angiography confirmed the findings; the consequently performed endovascular embolization using platin coils and silicon balloon removed the symptoms immediately. Ultrasonographic follow-up examinations within 5 months demonstrated the success of therapy showing only low-flow fistula yet. This case demonstrates that early detection of a vertebral arteriovenous fistula by duplex sonography is highly beneficial because efficient treatment modalities are available.

Biodegradation of biphenyl by the ascomycetous yeast Debaryomyces vanrijiae

Cells of the yeast strain Debaryomyces vanrijiae SBUG 770, grown with glucose, converted biphenyl to 4-hydroxybiphenyl as the major metabolite. In addition, 2-hydroxybiphenyl was formed in minor amounts. No further degradation of these substances was detected. However, these monohydroxylated derivatives were oxidised by alkane-grown cells in the presence of the co-metabolic substrate, tetradecane. Under these conditions 2-hydroxybiphenyl was oxidised to 2,5-dihydroxybiphenyl, and 4-hydroxybiphenyl was rapidly metabolised by formation of two major metabolites. One was identified as 3,4-dihydroxybiphenyl. Characterisation of the second product as 4-phenylmuconolactone points to a further metabolism of the initially formed dihydroxylated biphenyl via ortho-ring fission.

Isolation and characterization of a dibenzofuran-degrading yeast: identification of oxidation and ring cleavage products

We characterized the ability of a yeast to cleave the aromatic structure of the dioxin-like compound dibenzofuran. The yeast strain was isolated from a dioxin-contaminated soil sample and identified as Trichosporon mucoides. During incubation of glucose-pregrown cells with dibenzofuran, six major metabolites were detected by high-performance liquid chromatography. The formation of four different monohydroxylated dibenzofurans was proven by comparison of analytical data (gas chromatography-mass spectrometry) with that for authentic standards. Further oxidation produced 2, 3-dihydroxydibenzofuran and its ring cleavage product 2-(1-carboxy methylidene)-2,3-dihydrobenzo[b]furanylidene glycolic acid, which were characterized by mass spectrometry and 1H nuclear magnetic resonance spectroscopy. These two metabolites are derived from 2-hydroxydibenzofuran and 3-hydroxydibenzofuran, as shown by incubation experiments using these monohydroxylated dibenzofurans as substrates.