Inoculation with adapted bacterial communities promotes development of full scale slow sand filters for drinking water production

Gravity-driven filtration through slow sand filters (SSFs) is one of the oldest methods for producing drinking water. As water passes through a sand bed, undesired microorganisms and chemicals are removed by interactions with SSF biofilm and its resident microbes. Despite their importance, the processes through which these microbial communities form are largely unknown, as are the factors affecting these processes. In this study, two SSFs constructed using different sand sources were compared to an established filter and observed throughout their maturation process. One SSF was inoculated through addition of sand scraped from established filters, while the other was not inoculated. The operational and developing microbial communities of SSFs, as well as their influents and effluents, were studied by sequencing of 16S ribosomal rRNA genes. A functional microbial community resembling that of the established SSF was achieved in the inoculated SSF, but not in the non-inoculated SSF. Notably, the non-inoculated SSF had significantly (p < 0.01) higher abundances of classes Armatimonadia, Elusimicrobia, Fimbriimonadia, OM190 (phylum Planctomycetota), Parcubacteria, Vampirivibrionia and Verrucomicrobiae. Conversely, it had lower abundances of classes Anaerolineae, Bacilli, bacteriap25 (phylum Myxococcota), Blastocatellia, Entotheonellia, Gemmatimonadetes, lineage 11b (phylum Elusimicrobiota), Nitrospiria, Phycisphaerae, subgroup 22 (phylum Acidobacteriota) and subgroup 11 (phylum Acidobacteriota). Poor performance of neutral models showed that the assembly and dispersal of SSF microbial communities was mainly driven by selection. The temporal turnover of microbial species, as estimated through the scaling exponent of the species-time relationship, was twice as high in the non-inoculated filter (0.946 ± 0.164) compared to the inoculated filter (0.422 ± 0.0431). This study shows that the addition of an inoculum changed the assembly processes within SSFs. Specifically, the rate at which new microorganisms were observed in the biofilm was reduced. The reduced temporal turnover may be driven by inoculating taxa inhibiting growth, potentially via secondary metabolite production. This in turn would allow the inoculation community to persist and contribute to SSF function.

Biofilm colonization and succession in a full-scale partial nitritation-anammox moving bed biofilm reactor

BACKGROUND

Partial nitritation-anammox (PNA) is a biological nitrogen removal process commonly used in wastewater treatment plants for the treatment of warm and nitrogen-rich sludge liquor from anaerobic digestion, often referred to as sidestream wastewater. In these systems, biofilms are frequently used to retain biomass with aerobic ammonia-oxidizing bacteria (AOB) and anammox bacteria, which together convert ammonium to nitrogen gas. Little is known about how these biofilm communities develop, and whether knowledge about the assembly of biofilms in natural communities can be applied to PNA biofilms.

RESULTS

We followed the start-up of a full-scale PNA moving bed biofilm reactor for 175 days using shotgun metagenomics. Environmental filtering likely restricted initial biofilm colonization, resulting in low phylogenetic diversity, with the initial microbial community comprised mainly of Proteobacteria. Facilitative priority effects allowed further biofilm colonization, with the growth of initial aerobic colonizers promoting the arrival and growth of anaerobic taxa like methanogens and anammox bacteria. Among the early colonizers were known 'oligotrophic' ammonia oxidizers including comammox Nitrospira and Nitrosomonas cluster 6a AOB. Increasing the nitrogen load in the bioreactor allowed colonization by 'copiotrophic' Nitrosomonas cluster 7 AOB and resulted in the exclusion of the initial ammonia- and nitrite oxidizers.

CONCLUSIONS

We show that complex dynamic processes occur in PNA microbial communities before a stable bioreactor process is achieved. The results of this study not only contribute to our knowledge about biofilm assembly and PNA bioreactor start-up but could also help guide strategies for the successful implementation of PNA bioreactors. Video Abstract.

Marine sediments are identified as an environmental reservoir for Escherichia coli: comparing signature-based and novel amplicon sequencing approaches for microbial source tracking

Viable Escherichia coli were detected in sediments near a point of wastewater discharge in a marine coastal environment in Sweden. Since high concentrations were found in the sediments nearest the pipe, this suggested that treated wastewater effluent was the source of the microbes. In order to examine this hypothesis, different bioinformatics approaches were applied using 16S rRNA gene V3-V4 amplicon sequences from the sediments. Both signature-based source tracking using sequence libraries describing known sources of fecal water pollution (SourceTracker); and, a curated source tracking method, indicated that sediments were contaminated with wastewater. The results from the curated approach were independently confirmed using differential abundance analysis (DESeq2). A number of taxa originating from wastewater were identified which can be used to describe contamination of the sediments, and examine the spread of these specific taxa, even at low relative abundance, along the urban coast. Sequences of phylum Bacteroidetes (such as Bacteroides and Prevotella) and Firmicutes (such as Romboutsia) increased in sediments with higher concentrations of E. coli. In addition, sequences from Trichococcus are proposed as an indicator for treated wastewater. All three source tracking approaches, and the detection of viable E. coli, suggest that urban sediments can be a reservoir for indicator bacteria.

Characterizing natural degradation of tetrachloroethene (PCE) using a multidisciplinary approach

A site in mid-western Sweden contaminated with chlorinated solvents originating from a previous dry cleaning facility, was investigated using conventional groundwater analysis combined with compound-specific isotope data of carbon, microbial DNA analysis, and geoelectrical tomography techniques. We show the value of this multidisciplinary approach, as the different results supported each interpretation, and show where natural degradation occurs at the site. The zone where natural degradation occurred was identified in the transition between two geological units, where the change in hydraulic conductivity may have facilitated biofilm formation and microbial activity. This observation was confirmed by all methods and the examination of the impact of geological conditions on the biotransformation process was facilitated by the unique combination of the applied methods. There is thus significant benefit from deploying an extended array of methods for these investigations, with the potential to reduce costs involved in remediation of contaminated sediment and groundwater.

Monitoring biofilm function in new and matured full-scale slow sand filters using flow cytometric histogram image comparison (CHIC)

While slow sand filters (SSFs) have produced drinking water for more than a hundred years, understanding of their associated microbial communities is limited. In this study, bacteria in influent and effluent water from full-scale SSFs were explored using flow cytometry (FCM) with cytometric histogram image comparison (CHIC) analysis; and routine microbial counts for heterotrophs, total coliforms and Escherichia coli. To assess if FCM can monitor biofilm function, SSFs differing in age and sand composition were compared. FCM profiles from two established filters were indistinguishable. To examine biofilm in the deep sand bed, SSFs were monitored during a scraping event, when the top layer of sand and the schmutzdecke are removed to restore flow through the filter. The performance of an established SSF was stable: total organic carbon (TOC), pH, numbers of heterotrophs, coliforms, E. coli, and FCM bacterial profile were unaffected by scraping. However, the performance of two newly-built SSFs containing new and mixed sand was compromised: breakthrough of both microbial indicators and TOC occurred following scraping. The compromised performance of the new SSFs was reflected in distinct effluent bacterial communities; and, the presence of microbial indicators correlated to influent bacterial communities. This demonstrated that FCM can monitor SSF performance. Removal of the top layer of sand did not alter the effluent water from the established SSF, but did affect that of the SSFs containing new sand. This suggests that the impact of the surface biofilm on effluent water is greater when the deep sand bed biofilm is not established.

Bacterial community analysis of drinking water biofilms in southern Sweden

Next-generation sequencing of the V1-V2 and V3 variable regions of the 16S rRNA gene generated a total of 674,116 reads that described six distinct bacterial biofilm communities from both water meters and pipes. A high degree of reproducibility was demonstrated for the experimental and analytical work-flow by analyzing the communities present in parallel water meters, the rare occurrence of biological replicates within a working drinking water distribution system. The communities observed in water meters from households that did not complain about their drinking water were defined by sequences representing Proteobacteria (82-87%), with 22-40% of all sequences being classified as Sphingomonadaceae. However, a water meter biofilm community from a household with consumer reports of red water and flowing water containing elevated levels of iron and manganese had fewer sequences representing Proteobacteria (44%); only 0.6% of all sequences were classified as Sphingomonadaceae; and, in contrast to the other water meter communities, markedly more sequences represented Nitrospira and Pedomicrobium. The biofilm communities in pipes were distinct from those in water meters, and contained sequences that were identified as Mycobacterium, Nocardia, Desulfovibrio, and Sulfuricurvum. The approach employed in the present study resolved the bacterial diversity present in these biofilm communities as well as the differences that occurred in biofilms within a single distribution system, and suggests that next-generation sequencing of 16S rRNA amplicons can show changes in bacterial biofilm communities associated with different water qualities.

Characterization of the properties of Pediococcus parvulus for probiotic or protective culture use

Pediococcus parvulus 2.6 (previously Pediococcus damnosus 2.6, here confirmed as P. parvulus by 16S DNA sequencing) displayed antibacterial activity toward several bacterial species, including isolates found as contaminants in oats, herein genetically identified as Bacillus cereus. No inhibition of Listeria monocytogenes was found under the conditions used. Antibacterial activity was retrieved after ammonium sulfate or acetone precipitation showed it to be peptide mediated. P. parvulus 2.6 has previously shown good technological properties in oat-based products. This, together with the currently found inhibition of food spoilage microorganisms like B. cereus, makes it suitable as a food protective culture. Survival trials of P. parvulus 2.6 at conditions mimicking the gastrointestinal tract were prompted by previously found cholesterol-lowering effects in humans after consumption of oat products cofermented by using P. parvulus 2.6 and Bifidobacterium spp. Viability was measured with in vitro, gutlike simulations at 37 degrees C. High survival was shown under two of three conditions (gastric juice, bile, and small intestine juice), defined as main obstacles of the gastrointestinal tract. The critical step was bile exposure. At a concentration of 20%, viability was low, but 0.3% bile (mean concentration in the intestine) did not have a major influence on growth. Viability of P. parvulus 2.6 was significantly decreased in gastric juice at pH 1.5 (with pepsin), but it was not significantly affected at pH 2.5, and was also improved at a lower pH in 20% oat milk. Viability was judged sufficient for colonization at gutlike conditions, qualifying the strain for further probiotic studies.

Independent evolution of neurotoxin and flagellar genetic loci in proteolytic Clostridium botulinum

Background

Proteolytic Clostridium botulinum is the causative agent of botulism, a severe neuroparalytic illness. Given the severity of botulism, surprisingly little is known of the population structure, biology, phylogeny or evolution of C. botulinum. The recent determination of the genome sequence of C. botulinum has allowed comparative genomic indexing using a DNA microarray.

Results

Whole genome microarray analysis revealed that 63% of the coding sequences (CDSs) present in reference strain ATCC 3502 were common to all 61 widely-representative strains of proteolytic C. botulinum and the closely related C. sporogenes tested. This indicates a relatively stable genome. There was, however, evidence for recombination and genetic exchange, in particular within the neurotoxin gene and cluster (including transfer of neurotoxin genes to C. sporogenes), and the flagellar glycosylation island (FGI). These two loci appear to have evolved independently from each other, and from the remainder of the genetic complement. A number of strains were atypical; for example, while 10 out of 14 strains that formed type A1 toxin gave almost identical profiles in whole genome, neurotoxin cluster and FGI analyses, the other four strains showed divergent properties. Furthermore, a new neurotoxin sub-type (A5) has been discovered in strains from heroin-associated wound botulism cases. For the first time, differences in glycosylation profiles of the flagella could be linked to differences in the gene content of the FGI.

Conclusion

Proteolytic C. botulinum has a stable genome backbone containing specific regions of genetic heterogeneity. These include the neurotoxin gene cluster and the FGI, each having evolved independently of each other and the remainder of the genetic complement. Analysis of these genetic components provides a high degree of discrimination of strains of proteolytic C. botulinum, and is suitable for clinical and forensic investigations of botulism outbreaks.

A unique restriction site in the flaA gene allows rapid differentiation of group I and group II Clostridium botulinum strains by PCR-restriction fragment length polymorphism analysis

Clostridium botulinum produces the potent botulinum neurotoxin, the causative agent of botulism. Based on distinctive physiological traits, strains of C. botulinum can be divided into four groups: however, only groups I and II are associated with human illness. Alignment of the flaA gene sequences from 40 group I and 40 group II strains identified a single BsrG1 restriction cut site that was present at base pair 283 in all group II flaA sequences and was not found in any group I sequence. The flaA gene was amplified by rapid colony PCR from 22 group I strains and 18 group II strains and digested with BsrGI restriction enzyme. Standard agarose gel electrophoresis with ethidium bromide staining showed two fragments, following restriction digestion of group II flaA gene amplicons with BsrGI, but only a single band of uncut flaA from group I strains. Combining rapid colony PCR with BsrGI restriction digest of the flaA gene at 60 degrees C is a significant improvement over current methods, such as meat digestion or amplified fragment length polymorphism, as a strain can be identified as either group I or group II in under 5 h when starting with a visible plated C. botulinum colony.

Genome sequence of a proteolytic (Group I) Clostridium botulinum strain Hall A and comparative analysis of the clostridial genomes

Clostridium botulinum is a heterogeneous Gram-positive species that comprises four genetically and physiologically distinct groups of bacteria that share the ability to produce botulinum neurotoxin, the most poisonous toxin known to man, and the causative agent of botulism, a severe disease of humans and animals. We report here the complete genome sequence of a representative of Group I (proteolytic) C. botulinum (strain Hall A, ATCC 3502). The genome consists of a chromosome (3,886,916 bp) and a plasmid (16,344 bp), which carry 3650 and 19 predicted genes, respectively. Consistent with the proteolytic phenotype of this strain, the genome harbors a large number of genes encoding secreted proteases and enzymes involved in uptake and metabolism of amino acids. The genome also reveals a hitherto unknown ability of C. botulinum to degrade chitin. There is a significant lack of recently acquired DNA, indicating a stable genomic content, in strong contrast to the fluid genome of Clostridium difficile, which can form longer-term relationships with its host. Overall, the genome indicates that C. botulinum is adapted to a saprophytic lifestyle both in soil and aquatic environments. This pathogen relies on its toxin to rapidly kill a wide range of prey species, and to gain access to nutrient sources, it releases a large number of extracellular enzymes to soften and destroy rotting or decayed tissues.

Flagellin diversity in Clostridium botulinum groups I and II: a new strategy for strain identification

Strains of Clostridium botulinum are traditionally identified by botulinum neurotoxin type; however, identification of an additional target for typing would improve differentiation. Isolation of flagellar filaments and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that C. botulinum produced multiple flagellin proteins. Nano-liquid chromatography-tandem mass spectrometry (nLC-MS/MS) analysis of in-gel tryptic digests identified peptides in all flagellin bands that matched two homologous tandem flagellin genes identified in the C. botulinum Hall A genome. Designated flaA1 and flaA2, these open reading frames encode the major structural flagellins of C. botulinum. Colony PCR and sequencing of flaA1/A2 variable regions classified 80 environmental and clinical strains into group I or group II and clustered isolates into 12 flagellar types. Flagellar type was distinct from neurotoxin type, and epidemiologically related isolates clustered together. Sequencing a larger PCR product, obtained during amplification of flaA1/A2 from type E strain Bennett identified a second flagellin gene, flaB. LC-MS analysis confirmed that flaB encoded a large type E-specific flagellin protein, and the predicted molecular mass for FlaB matched that observed by SDS-PAGE. In contrast, the molecular mass of FlaA was 2 to 12 kDa larger than the mass predicted by the flaA1/A2 sequence of a given strain, suggesting that FlaA is posttranslationally modified. While identification of FlaB, and the observation by SDS-PAGE of different masses of the FlaA proteins, showed the flagellin proteins of C. botulinum to be diverse, the presence of the flaA1/A2 gene in all strains examined facilitates single locus sequence typing of C. botulinum using the flagellin variable region.

The structure and biological characteristics of the Spirochaeta aurantia outer membrane glycolipid LGLB

In an attempt to isolate lipopolysaccharide from Spirochaeta aurantia, Darveau-Hancock extraction of the cell mass was performed. While no lipopolysaccharide was found, two carbohydrate-containing compounds were detected. They were resolved by size-exclusion chromatography into high molecular mass (LGLA) and low molecular mass (LGLB) fractions. Here we present the results of the analysis of the glycolipid LGLB. Deacylation of LGLB with hydrazine and separation of the products by using anion-exchange chromatography gave two major products. Their structure was determined by using chemical methods, NMR and mass spectrometry. All monosaccharides had the D-configuration, and aspartic acid had the L-configuration. Intact LGLB contained two fatty groups at O-2 and O-3 of the glycerol residue. Nonhydroxylated C14 to C18 fatty acids were identified, which were predominantly unsaturated or branched. LGLB was able to gel Limulus amebocyte lysate, albeit at a lower level than that observed for Escherichia coli O113 lipopolysaccharide. However, even large amounts of LGLB were unable to stimulate any Toll-like receptor (TLR) examined, including TLR4 and TLR2, previously shown to be sensitive to lipopolysaccharide and glycolipids from diverse bacterial origins, including other spirochetes.

Nature of the genome of the saprophytic spirochete Spirochaeta aurantia and its ribosomal RNA operons

Using restriction endonucleases DraI, AseI, and I-CeuI in conjunction with pulsed-field gel electrophoresis, we have shown that Spirochaeta aurantia M1 possesses a circular 3.98-Mb genome. This is the second largest spirochete chromosome yet analyzed. The observation that the latter enzyme cuts in 3 places suggests the presence of 3 copies of the large subunit (23S) rRNA gene (rrl), which was confirmed by Southern hybridizations. The complete sequence of 2 of the ribosomal RNA operons was determined, revealing that their structure resembled that of the typical member of the bacterial superkingdom: rrs (16S; 1561 bp), tRNA, rrl (23S; 2972 bp), and rrf (5S; 110 bp). The S. aurantia rrs-rrl intergenic regions, as with Treponema denticola, contain genes specifying a 73-nt tRNA(Ala) (anticodon TGC) and a 77-nt tRNA(Ile) (anticodon GAT).

Influence of mutations in the mexR repressor gene on expression of the MexA-MexB-oprM multidrug efflux system of Pseudomonas aeruginosa

Several nalB-type multidrug-resistant mutants of Pseudomonas aeruginosa overexpressed MexAB-OprM and carried mutations in the local regulatory gene, mexR. Others, dubbed nalC types, carried mutations elsewhere and overexpressed MexAB-OprM less extensively than the nalB strains. Available evidence showed that MexR acted solely as repressor. Disruption of the mexR gene at various places suggested that the 5' end of mexR may be a part of the mexAB-oprM promoter.

Metabolism and disposition of phenazopyridine in rat

1. The blood profile, tissue distribution, biliary and urinary excretion, and metabolism of 14C-phenazopyridine (PAP) was studied in male Wistar rats. 2. Based on the blood profile of 14C the absorption of PAP from the gastrointestinal tract was rapid; the t1/2 of elimination was 7.35 h. 3. Biliary excretion was a major route of elimination with 40.7% dose excreted by this route in bile duct-cannulated rats over the 0-8 h period. The predominant metabolite was conjugated 4'-hydroxy-PAP. 4. Liver and kidney showed the highest tissue levels of PAP-derived 14C, and significant covalent binding was found in these two tissues. 5. The major urinary metabolite of PAP was 4-acetylaminophenol (NAPA) followed in order by 5,4'-dihydroxy-PAP, 5-hydroxy-PAP, 4'-hydroxy-PAP and 2'-hydroxy-PAP; unchanged PAP accounted for < 1% dose. 6. Doubling the dose of PAP to 200 mg/kg caused a proportionate decrease in urinary NAPA excretion and an increase in 5-hydroxy-PAP.

Enalapril cytotoxicity in primary cultures of rat hepatocytes. II. Role of glutathione

The cytotoxicity of enalapril maleate (EN) in primary cultures of rat hepatocytes, at concentrations of 0.5 mM or greater, was measured by the release of lactate dehydrogenase (LDH) into the culture medium. Pretreatment of the hepatocytes with L-buthionine-(S,R)-sulfoximine (BSO) and diethyl maleate (DEM) potentiated the toxicity whereas N-acetyl-L-cysteine (NAC) provided protection. EN produced a dose-dependent reduction in intracellular glutathione (GSH) concentration. This was an early effect, apparent after only 1 h of exposure to the drug, whereas loss of cell viability occurred after 6-18 h. These results suggest that the mechanism of EN cytotoxicity involves a GSH-dependent detoxification pathway.

Enalapril cytotoxicity in primary cultures of rat hepatocytes. I. Effects of cytochrome P450 inducers and inhibitors

Enalapril maleate (EN) incubated with primary cultures of rat hepatocytes was cytotoxic in concentrations of 0.5 mM or greater. Toxicity was measured by release of lactate dehydrogenase (LDH) into the culture medium at 24 h. SKF525A, alpha-naphthoflavone (alpha NF) and metyrapone (MTP) reduced the toxicity of EN. In vivo pretreatment with phenobarbital (PB) and beta-naphthoflavone (beta NF) had minor protective effects on the responses of hepatocytes to EN exposure. However, in vivo pretreatment with pregnenolone-16 alpha-carbonitrile (PCN) substantially potentiated EN cytotoxicity. These results suggest that the cytocidal hepatotoxicity of EN in primary culture depends to some degree on metabolic activation by a cytochrome P450 species.

Hepatic effects of ketoconazole in the male Swiss Webster mouse: temporal changes in drug metabolic parameters

There have been conflicting observations regarding the effects of ketoconazole on hepatic metabolism. The objectives of these studies were to determine whether ketoconazole was an enzyme inducer or inhibitor in the mouse and then to establish the time frame of these ketoconazole-induced enzyme changes. Ketoconazole was administered (150 mg/kg p.o. X 4 days) to male Swiss Webster mice. Biochemical observations over a period of 6 days following treatment indicated that ketoconazole had a temporal biphasic effect on the liver. Although liver weight and microsomal protein were elevated, all other parameters monitored were lower at 2 h following ketoconazole treatment. At 24 h after the last dose of ketoconazole, hepatic biochemical parameters (liver wt., % liver wt./body wt., microsomal protein, and cytochrome P-450) were statistically elevated, while enzyme activities (benzphetamine N-demethylation, 6 beta- and 7 alpha-hydroxylation of testosterone, formation of androstenedione and UDP-glucuronyltransferase) were inhibited. At 72 h the ketoconazole-induced changes in the hepatic biochemical parameters were comparable to those observed at 24 h, and enzymatic parameters generally appeared to be induced by ketoconazole, with the exception of benzphetamine N-demethylase and UDP-glucuronyltransferase, which exhibited lower enzyme activities. Ethoxyresorufin O-deethylase, 7 alpha-hydroxylation of testosterone and glutathione S-transferase, on the other hand, were unaltered by ketoconazole treatment. The opposing effects of ketoconazole on benzphetamine N-demethylase and ethylmorphine N-demethylase at 72 h were further examined. Enzyme kinetics studies indicated that ketoconazole did not effect the Michaelis constants (Km) of the two substrates, but the maximum velocity (Vmax) of the reactions was altered.(ABSTRACT TRUNCATED AT 250 WORDS)

Antinociceptive activity of propionyl esters of morphine: a reevaluation

The antinociceptive activity of the propionyl homologues of 3-O- and 6-O-acetyl- and 3,6-O-diacetylmorphine was re-investigated using materials of unequivocally established structure. Testing was in male Wistar rats at 60 min following subcutaneous administration by the rat tail-flick method. Results indicate that the antinociceptive activity of 3-O-propionylmorphine was similar to that of 3-O-acetylmorphine. 6-O-Propionylmorphine and 3,6-O-dipropionylmorphine had similar antinociceptive activity and, like 6-O-acetylmorphine, 6-O-propionylmorphine may be the pharmacologically active principle responsible for the antinociceptive activity of its disubstituted homologue.

Excretion of phenazopyridine and its metabolites in the urine of humans, rats, mice, and guinea pigs

The metabolism of the urinary tract analgesic phenazopyridine [2,6-diamino-3-(phenylazo)pyridine; PAP] was studied in the urine of humans, rats, mice, and guinea pigs. Urinary excretion was rapid in human and guinea pig, but in the rat and mouse it was slower and there was significant fecal excretion. Metabolism of PAP was extensive in all four species, and there were marked quantitative differences in the routes of metabolism. The extent of azo bond cleavage was high in the mouse and guinea pig, moderate in the rat, and low in humans. Hydroxylation of both the phenyl and pyridyl rings of PAP was observed in all species. In the human, 5-hydroxyl PAP was the major metabolite (48.3% of the dose). It was concluded that there are marked species differences in the metabolism of PAP, and that none of the species studied resembles the human; the rat comes closest, but cannot be considered a particularly good model.

Ketoconazole-induced hepatic lysosomal phospholipidosis: the effect of concurrent barbiturate treatment

An unusual hepatic phospholipidosis produced by repeated high doses of ketoconazole in the mouse was investigated. This abnormal phospholipid accumulation was dose dependent after seven days of daily oral treatment over a 150-350 mg/kg ketoconazole dose range. The accumulation continued after 21 days at the 250 mg/kg dose level. Ultrastructural and biochemical studies revealed that ketoconazole produced a hepatic lysosomal accumulation of concentric lamellar bodies, as typically produced by many cationic amphiphilic drugs. Ketoconazole administered orally in mice at 250 mg/kg also induced total hepatic protein, microsomal protein, cytochrome p-450, and ethylmorphine N-demethylation. Concurrent phenobarbital and ketoconazole administration appeared to further increase hepatic drug metabolizing parameters and to reduce the extent of the hepatic phospholipid accumulation.

Plasma sorbitol dehydrogenase determination in experimental hepatotoxicity using the Abbott Bichromatic Analyzer

An automated single reagent micro-assay for the determination of sorbitol dehydrogenase (EC 1.1.1.14) catalytic activity concentration in mouse plasma was developed for the Abbott Bichromatic Analyzer (ABA-100). The kinetic rate determination was linear up to 250 U/l, had a CV of 2.65%, and required only 25 microliters of sample. Experimentally induced hepatotoxicity in the mouse by acetaminophen produced a dose dependent increase in blood sorbitol dehydrogenase activity.

Vasculitic leg ulcers associated with diltiazem

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Metastatic Crohn's disease responding to metronidazole

Metastatic Crohn's disease is a rare cutaneous manifestation of intestinal Crohn's disease, for which existing treatment is unsatisfactory. We report a case of perianal and vulval Crohn's disease which cleared completely on a 4-month course of metronidazole without adverse effects. The patient remained in remission I year later. The merits of long-term treatment with metronidazole are discussed.

Postabsorption antidotal effects of N-acetylcysteine on acetaminophen-induced hepatotoxicity in the mouse

Male Swiss Webster mice, treated with N-acetylcysteine (NAC, 500 mg/kg po) 1 h following acetaminophen (NAPA, 350 mg/kg po) administration, had control levels of transaminases indicating that NAC protects against NAPA-induced hepatotoxicity by postabsorption antidotal mechanism(s). Hepatic congestion induced by NAPA was reduced by NAC. Significantly higher elimination rate constants (K) for indocyanine green (500 micrograms/kg, iv) in mice treated with NAPA and NAC (K = 0.676 +/- 0.062) than in animals receiving NAPA alone (0.341 +/- 0.105) suggested NAC improved or preserved the hepatic circulation of the compromised liver. This NAC-induced improvement and (or) preservation of hepatic circulation was reflected in biliary and urinary excretion of acetaminophen and its metabolites by a general increase in elimination during the first 6 h (70.2 +/- 2.6 vs. 32.6 +/- 7.1%), and in the repletion of glutathione (GSH) in the liver by a return to control levels more quickly (3 vs. greater than 5 h) following depletion by NAPA. The metabolic consequences of the postabsorption antidotal effect of NAC in the compromised liver was a preferential excretion of sulphydryl-derived metabolites in the 1-4 h bile (GSH conjugate 11.30 +/- 1.25 vs. 7.25 +/- 0.39%) which was subsequently observed in the urine by preferential excretion of glutathione degradation products.

Devil's Claw (Harpagophytum procumbens): no evidence for anti-inflammatory activity in the treatment of arthritic disease

Devil's Claw (Harpagophytum procumbens), an herbal product being marketed in Canada as a home remedy for the relief of arthritic disease, was screened for efficacy with standard preclinical screening methods. At doses 100 times or greater than the recommended daily dose for humans, Devil's Claw was completely ineffective in reducing edema of the rat hind foot induced by either lambda-carrageenan or Mycobacterium butyricum. At concentrations of up to 1 x 10(5) microgram/ml, Devil's Claw was also ineffective as an in-vitro inhibitor of prostaglandin synthetase. These results indicate that Devil's Claw lacks the anti-inflammatory properties possessed by all antiarthritic drugs of the nonsteroidal, anti-inflammatory analgesic type.

Isoniazid-induced hepatic steatosis in rabbits: an explanation for susceptibility and its antagonism by pyridoxine hydrochloride

Steatosis was induced in rabbits by subacute administration of isoniazid (INH, 50 mg/kg po). Concomitant treatment with pyridoxine (vitamin B6, 25 mg/kg po) antagonized both development of the hepatic lesions and the elevation of plasma concentrations of lipids. Rabbit acetylating ability was sixfold that of male Wistar rats, a species susceptible to hepatic cell necrosis, whereas hepatic cytochrome P-450 and NADPH-cytochrome c reductase were significantly lower than that observed in control or phenobarbital-induced rats. Examination of the hepatic hydrolysis of the amide bonds of INH and acetylisoniazid (AcINH) indicated that the isonicotinoyl bond of AcINH was the bond most susceptible to amidase hydrolysis in both species; but rabbits possessed the greater amidase activity: 5- to 20-fold greater than control rats and 2- to 7-fold greater than the phenobarbital-induced rats. Consequently, INH-induced hepatic fatty degeneration in rabbits was attributed to increased hepatic exposure to INH-derived primary amine functional groups, and its antagonism by vitamin B6 was attributed to the deactivation of the primary amine by pyridoxal hydrazone formation.

Pathways of disposition of acetaminophen conjugates in the mouse

After a single dose of [14C]acetaminophen (50 mg/kg) was administered orally to bile duct cannulated mice, 13.9% of the radioactivity was recovered in the bile while 41.2% was found in the urine in the first 3 h after administration. Analyses of biles revealed that the major biliary metabolite was acetaminophen glutathione (AG) conjugate which was derived from the hepatotoxic acetaminophen intermediate. Examination of urines showed that they contained mostly glucuronide and sulfate conjugates with no AG or its degradation products (cysteine and mercapturate). Analysis of urines collected from non-cannulated animals at 4 h showed that they contained glucuronide, sulfate, cysteine and mercapturate metabolites. Our results suggest that after formation in the liver, the majority of the glucuronide and sulfate conjugates were directly eliminated by the kidney. On the other hand, the pathway for the disposition of the glutathione conjugate was first into the bile, then reabsorption, and finally disposition into the urine as cysteine and mercapturate metabolites.

Incorporation of D-(3H)glucosamine into normal and psoriatic epidermal glycoconjugates

Samples of normal, uninvolved and involved psoriatic skin were maintained for 18 h in organ culture in the presence of D-(6-3H) glucosamine which is a precursor of cell-surface associated carbohydrates in the epidermis. The total incorporation into involved psoriatic epidermis (solubilized with 8 mol/l urea, 5% sodium dodecyl sulphate, 10 mmol 2-mercaptoethanol) was less than into normal or uninvolved epidermis. This decrease was found whether specific radioactivities were expressed in terms or area, wet weight or protein content of the epidermis. Electrophoresis revealed that the major labelled component in normal and uninvolved epidermis had a high molecular weight. The labelling of this material was significantly reduced in involved psoriatic epidermis. Using pig epidermis we have shown previously that this material represents mainly extracellular glycosaminoglycans and proteoglycans. The decrease labelling (and presumable synthesis) of these extracellular carbohydrates may be related to the failure of mechanisms controlling cell proliferation and to the altered cell interactions which are found in psoriatic epidermis. Electrophoresis also showed that a non-glycosylated protein, molecular weight approximately 50,000, which was present as a singly band in both normal and uninvolved epidermis was always present as a doublet band in the involved psoriatic epidermis.

N-acetylcysteine-induced inhibition of gastric emptying: a mechanism affording protection to mice from the hepatotoxicity of concomitantly administered acetaminophen

Swiss Webster male mice, 22 +/- 3 g, killed 17-18 h following the concomitant oral administration of acetaminophen (350 mg/kg) and N-acetyl-cysteine (NAC, 100-500 mg/kg, treated) had statistically significant lower plasma transaminases (GOT and GPT) than control mice (acetaminophen + water). Possible mechanisms underlying this protective effect of NAC were examined. NAC (500 mg/kg) reduced [14C]acetaminophen-derived radioactivity in the blood and tissues but increased the percentage of the dose in the gastrointestinal tract. Depletion of hepatic sulphydryl compounds below 75% of the control value was prevented by NAC treatment, whereas urinary excretion of mercapturate and sulfate, metabolites derived from sulphydryls, were proportionally increased and excretion of unchanged drug was decreased by NAC. Absorption of acetaminophen from the small intestine was prevented by NAC and this was attributed to an inhibition in gastric emptying. Since all changes observed following NAC treatment could be attributed to inhibition of gastric emptying, it was considered the major mechanism responsible for affording in mice protection from acetaminophen-induced hepatocellular damage following concomitant oral administration.

Effect of a concomitant single dose of ethanol on the hepatotoxicity and metabolism of acetaminophen in mice

A concomitant single dose of ethanol (1 g/kg) protected mice from hepatic injury induced by acetaminophen (250 mg/kg) as evidenced by the lowering of plasma transaminases. Pharmacokinetic studies with [14C]acetaminophen indicated that ethanol enhanced the initial blood concentrations of radiolabel and its rate of elimination. A tissue distribution study suggested that these effects were probably due to an ethanol-induced inhibition of the biliary clearance of acetaminophen from the blood. Examination of the urinary and biliary metabolites indicated that ethanol inhibited the excretion of the degradation products derived from the glutathione-deactivated hepatotoxic acetaminophen intermediate. The decrease in acetaminophen induced hepatotoxicity was therefore attributed to an inhibitory effect of ethanol on the biotransformation of acetaminophen to the toxic intermediate.

Pathological fracture of tibia in patient with corticosteroid-dependent psoriasis treated by functional bracing

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A semi-automated Bratton & Marshall micromethod for determining acetylator phenotype of rabbits using the Abbott Bichromatic Analyzer-100

A micromethod for the determination of acetylator phenotype using the method of Bratton & Marshall (1939) J. Biol. Chem. 128, 537--550) was adapted to the Abbott Bichromatic Analyzer (ABA-100). Advantages of this procedure include: (a) the requirement for small blood samples (20 microliter) making it a suitable pediatric method and eliminating the need for venipunctures; (b) elimination of tedious manual reading of absorbances of samples and mathematical manipulation of data by the automated capabilities of the ABA-100; (c) an increase in the accuracy of the assay by reading samples at two wavelengths thereby correcting for differences in background.

Micro-scale enzymic determination of ethanol in plasma with a discrete analyzer, the ABA-100

An enzymic method for estimating ethanol has been adapted to the Abbott Bichromatic Analyzer-100. Fully automated, the method can accommodate up to 192 assays per hour. It requires only 2.5 muL of plasma and therefore is applicable to analysis for ethanol in blood sampled by finger-prick.

Micro-scale enzymic determination of ethanol in plasma with a discrete analyzer, the ABA-100

An enzymic method for estimating ethanol has been adapted to the Abbott Bichromatic Analyzer-100. Fully automated, the method can accommodate up to 192 assays per hour. It requires only 2.5 muL of plasma and therefore is applicable to analysis for ethanol in blood sampled by finger-prick.

Effect of aspirin on a subtoxic dose of 14C-acetaminophen in mice

The interaction of 14C-acetaminophen, 150 mg/kg (20 muCi/kg), and aspirin, 200 mg/kg po, was studied in male mice. The radiolabel was rapidly absorbed from the GI tract, achieving maximum blood levels 0.25 hr after oral dosing. Radioactivity in the blood equilibrated rapidly with the tissues and was concentrated in the liver and kidney. At 14 hr, most of the dose was eliminated in urine as the glucuronide, cysteine, sulfate, free drug, and mercapturate. Pretreatment with aspirin tended to reduce the rate and extent of acetaminophen absorption and altered the percentage of the dose excreted in the urine as sulfate, mercapturate, glucuronide, and cysteine. Interpretation of these data toxicologically as an indication of the potentiation of either toxicity or protection was not possible.

Metabolic basis for the supra-additive effect of the ethanol-diazepam combination in mice

1 The comination of ethanol and diazepam elicits additive or supra-additive pharmacological effects in animals and humans. Since the mouse appeared to be a reasonably good animal model for man, this species was examined to determine if a biochemical basis for these effects could be established.2 The effect of ethanol (3 g/kg, orally), administered 0.5 h before [(14)C]-diazepam (5 mg/kg, orally), on the pharmacokinetics of diazepam in male Swiss Webster mice was examined.3 At 4, 6, 8 and 12 h after dosing, blood levels of (14)C were higher in ethanol pretreated mice than in vehicle pretreated controls. A tissue distribution study indicated that ethanol had similar effects on levels of (14)C in most tissues at 2, 6 and 12 hours.4 Both pretreated and control mice eliminated approximately 25% of the dose of isotope in the urine and 50% in the faeces by 48 hours.5 Biliary excretion was the major route of clearance in mice in which the bile ducts had been cannulated and ethanol reduced excretion at all time periods examined up to 12 hours.6 Oxazepam (the glucuronide in bile) and desmethyl diazepam were the major metabolites identified in bile, plasma and brain. Ethanol reduced oxazepam levels but increased desmethyl diazepam levels, suggesting that 3-hydroxylation of desmethyl diazepam was inhibited by ethanol.7 The accumulation of the pharmacologically active desmethyl diazepam in the brains of ethanol pretreated mice offers an explanation for the supra-additive effect of the ethanol-diazepam combination on motor coordination.

Effect of ethanol on diazepam distribution in rat

The effect of an acute oral dose of ethanol (3 g/kg), administered 30 min prior to oral administration of 14C-diazepam (5 mg/kg), on the fate of radioactivity in rats was examined. Ethanol pretreated rats possessed higher tissue levels at 60, 90 and 120 min than control animals. Blood, liver, kidney and plasma tissues showed 1.5 fold differences, adipose tissue exhibited a 2.4 to 3.6-fold increase, with brain showing 3.9, 4.5 and 5.4 fold higher levels of 14C at 60, 90 and 120 min respectively. Octanol extraction of plasma and ethyl acetate extraction of brain tissues indicated ethanol pretreated animals possessed a higher percentage of extractable radioactivity than controls. Thin-layer chromatography of the extracts suggested that biotransformation of 14C-diazepam was inhibited by ethanol, causing brain levels of 14C-diazepam at 60 min to be 6.4 fold higher than that observed in controls.

Poikiloderma atrophicans vasculare as a pointer to reticulosis of the skin

A case of reticulosis of the skin (mycosis fungoides) terminating in reticulum cell sarcoma is described where the features of poikiloderma atrophicans vasculare had been present for 40 years. The likelihood of reticulosis eventually developing after such a change in the skin is believed to be around 50%.