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PubMed2003

H2 consumption during the microbial reductive dehalogenation of chlorinated phenols and tetrachloroethene.

Competition for molecular hydrogen exists among hydrogen-utilizing microorganisms in anoxic environments, and evidence suggests that lower hydrogen concentrations are observed with more energetically favorable electron-accepting processes. The transfer of electrons to organochlorines via reductive dehalogenation reactions plays an important role in hydrogen dynamics in impacted systems. We studied the flux of aqueous hydrogen concentrations in methanogenic sediment microcosms prior to and during reductive dehalogenation of a variety of substituted chlorophenols (CP) and tetrachloroethene (perchloroethylene, PCE). Mean hydrogen concentrations during reductive dehalogenation of 2,4-CP, 2,3,4-CP, and PCP were 3.6 nM, 4.1 nM, and 0.34 nM, respectively. Sediment microcosms that were not dosed with chlorophenols yet were actively methanogenic maintained a significantly higher mean hydrogen concentration of 9.8 nM. During active PCE dehalogenation, sediment microcosms maintained a mean hydrogen concentration of 0.82 nM. These data indicate that during limiting hydrogen production, the threshold ecosystem hydrogen concentration is controlled by microbial populations that couple hydrogen oxidation to thermodynamically favorable electron accepting reactions, including reductive dehalogenation of chloroaromatic and chloroaliphatic compounds. We also present revised estimates for the Gibbs free energy available from the reductive dehalogenation of a variety of substituted chlorophenols based on recently published values of vapor pressure, solubility, and pKa for these compounds.

Bacteria↗
PubMedDate not supplied

Evaluation of a new antiseptic-containing alginate impression material.

A comparison was made of the disinfection achieved in impressions taken in Blueprint Asept alginate impression material and those taken in the plain brand of this material disinfected by immersion in 1% Hycolin solution for one minute. The plain Blueprint impression material without disinfection was used as a control. Impressions were taken of dies which had been contaminated with 0.75 ml of saliva from each of 20 volunteers. The surfaces of the impressions were used to inoculate Wilkins-Chalgren agar plates immediately and after 1 and 2 hours' storage of the impressions. The number of organisms recovered from the surface of the Blueprint Asept impressions was 1.5% of the control immediately after removal from the dies and complete disinfection was observed within one hour. In contrast, the number of organisms recovered from the surface of the impressions disinfected with 1% Hycolin solution was 30% of the control immediately after disinfection, and viable organisms could still be recovered after 2 hours' storage. Blueprint Asept impression material appears, therefore, to provide a high degree of disinfection when compared with the plain material treated with 1% Hycolin solution for one minute.

Adult↗
PubMed2002

Environmental agents as cause of health disorders in children presented at an outpatient unit of environmental medicine.

There are no publications on the frequency of environmental agents causing diseases in children presented at centers of environmental medicine. The aim of this study was to perform a statistical analysis of the data of children who visited the outpatient Unit of Environmental Medicine (UEM) at the University Hospital of Aachen, Germany. Data of all UEM patient files from January 1988 to September 1996 were evaluated. From a total of 682 patients, 75 were children (40 girls, 35 boys, age range 1-12 years). Forty-six children were presented with unspecific health disorders, 12 to examine a possible relationship between environmental agents and a current condition, mostly atopy (n = 10). Complaints were mucosal irritations (n = 38), unspecific (n = 19), dermatological (n = 16), gastrointestinal (n = 4), heart/circulation-related (n = 2), musculoskeletal (n = 1) and neurological (n = 1) symptoms. Wood preservatives were mentioned as suspected environmental causative agents in 22 cases, followed by unspecific indoor factors (n = 15), factories/disposal sites near homes (n = 9), formaldehyde (n = 5) and unspecific exposures (n = 5). Biomonitoring was done in 44 cases, local inspections and ambient monitoring in 10 cases. No evidence for a cause-and-effect relationship was found in 55 children, but was deemed possible in nine cases. In nine other children, a relatively high degree of exposure was determined by chemical analysis, but clinical relevance remained unclear. One child suffered from subclinical mercury poisoning caused by inadequate homeopathic medication. In most children referred to an environmental medicine center, it is difficult or impossible to verify an environmental cause using the diagnostic instruments currently available.

Age Distribution↗
PubMed1986

Metabolism and disposition of ortho-benzyl-para-chlorophenol in male rats.

The metabolism and disposition of ortho-benzyl-para-chlorophenol (BCP) has been investigated in the male rat following an oral dose of 69 mg/kg or 206 mg/kg. BCP was rapidly eliminated at both dose levels with 45-49% of the dose appearing in the urine and 44-49% in the feces during the 5-d period after dosing. After 5 d only 0.28-0.3% of the dose remained in the body, with almost half this value accounted for in the liver and kidney. The dynamics for the overall elimination of radioactivity from the body was biphasic at both dose levels. The initial rapid alpha phase had a well defined half-life of 8-9 h, and the slower beta phase had an estimated half-life of approximately 52-140 h. Analysis of the 12-24-h urine indicated that a majority of the radioactivity (41-61%) was present as sulfate and/or glucuronide conjugates. Treatment with purified aryl sulfatase suggested that sulfate esters were the predominate conjugate. Gas chromatography-mass spectroscopy (GC/MS) of the products isolated after enzymatic hydrolysis of the conjugates and purification by thin-layer chromatography (TLC) identified BCP, as well as two metabolites in which the benzyl ring was modified. One metabolite contained a hydroxyl substituent on the benzyl ring, and the other contained a hydroxyl and a methoxyl substituent. Preliminary analysis of the 12-24-h feces demonstrated the presence of BCP and two other components with chromatographic properties identical to the metabolites identified in the urine. A metabolic pathway for BCP has been proposed to account for the observed metabolites.

Animals↗
PubMed1990

An improved procedure for derivatization of controlled-pore glass beads for solid-phase oligonucleotide synthesis.

A simplified and economical method for the attachment of 2'-deoxyribo, ribo and arabinonucleosides onto long-chain alkylamidopropanoic acid controlled-pore glass (LCAAP-CPG, P-3) is described. In this procedure, 5'-O-tritylated nucleosides are coupled directly to LCAAP-CPG in excellent yields using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (DEC) as coupling reagent. The conventional and time-consuming preparation of nucleoside-3'-O-succinates is no longer required.

Acetic Anhydrides↗
PubMed1983

Environmental hazards of interest to the forensic pathologist.

The hazards associated with occupational exposure to various workplace contaminants (lead, silica, etc.) have been known for a number of years. Until recently, the potential toxic effects of exposures on the male reproductive system had not been appreciated. This article not only discusses recent studies in that area, but gives clinical examples of how environmental exposures (water, soil, air, and dwellings) can affect various organs in the human body. Awareness that these injuries can occur without obvious relationship to these environmental exposures may help the forensic pathologist discover previously unsuspected hazards.

Adult↗