HIV seroprevalence among military blood donors in Manica Province, Mozambique.

HIV seroprevalence data show an alarming HIV situation in central Mozambique, but little is known about the situation of HIV in Mozambican military personnel. This study is a retrospective analysis of laboratory records for voluntary blood donors at a rural hospital from January 1997 through December 1999. The hospital screened blood samples with HIV SPOT rapid test for HIV and rapid plasma reagin (RPR) serological test for syphilis. Of the 797 blood donors during this period, 110 (13.8%) were military personnel of whom 39.1% were HIV positive (35.0% in 1997, 33.3% in 1998 and 48.7% in 1999). Among the 687 nonmilitary donors 15.3% were HIV positive (P<0.0001 vs military). 74.4% of HIV-positive military personnel were also RPR positive. Conversely, only 3.0% of HIV-negative military donors were RPR positive. In light of the high rates of HIV and syphilis in military personnel, aggressive intervention measures must be taken to prevent and treat HIV and STDs in this population.

Intrathecal bupivacaine reduces pruritus and prolongs duration of fentanyl analgesia during labor: a prospective, randomized controlled trial.

UNLABELLED: Pruritus is a frequent complication (40%-100%) of intrathecal (IT) fentanyl 25 microg (F) for labor analgesia. The addition of IT bupivacaine 2.5 mg (B) to F has been reported in a nonrandomized series to have a 17.3% incidence of pruritus. This study prospectively evaluated the incidence and distribution of pruritus in laboring parturients receiving IT F + B. Sixty-five laboring parturients were randomly assigned to receive IT F, B, or F + B as part of a combined spinal-epidural technique. Visual analog scores, sensory level, motor strength, and pruritus were recorded before injection and at intervals thereafter. When present, the distribution of pruritus was evaluated. The duration of analgesia was determined as the time from IT drug administration until the patient requested supplemental analgesia. The median duration of analgesia in the F, B, and F + B groups was 62.5, 55.0, and 94.5 min, respectively. Compared with F alone, the combination of F + B led to a decreased frequency of pruritus (36.4% vs 95%). The incidence of facial pruritus (25%) was same in the F + B and F groups; however, the occurrence of pruritus distributed over the rest of the body was significantly more frequent in the F compared with the F + B group. The combination of F + B prolongs the duration of labor analgesia compared with IT F or B alone. F + B also leads to a decreased incidence of pruritus, except in the facial region. IMPLICATIONS: When administered intrathecally with fentanyl 25 microg in laboring parturients, bupivacaine 2.5 mg attenuates the frequency of pruritus on all parts of the body except the face. This combination also results in a rapid onset and prolonged duration of labor analgesia compared with either drug alone.

Pediatric wilderness recreational deaths in western Washington State.

STUDY OBJECTIVE: To determine the causes and characteristics of pediatric recreational wilderness deaths. METHODS: All deaths of children between 12 months and 20 years of age involving a wilderness recreational activity in 5 western Washington counties between 1987 and 1996 were identified by medical examiners' logs. Univariate analysis was used to examine variables such as age, gender, activity, mechanism of injury, adult presence, blood alcohol level, safety equipment, and mode of evacuation. RESULTS: Of 40 cases meeting inclusion criteria, 90% involved male subjects and 83% of victims were 13 to 19 years old. Hiking (33%), swimming (20%), and river rafting (10%) were the most common activities. Death was most often by drowning (55%) or closed head injury (26%). No victim was alone. All children younger than 10 years of age were accompanied by an adult, in contrast to only 26% of individuals 10 years or older. Only 4 victims had drugs or alcohol in their system. No victim wore a personal flotation device or helmet, and only 5% had foul weather gear. Although nearly one third of victims were transported by airlift, more than half of the victims were dead at the scene. CONCLUSION: Males and teenagers were the 2 major risk groups for recreational wilderness deaths. Traditional activities such as hiking and swimming were the most common causes of death. Children younger than 10 years died despite the presence of an adult, whereas teenagers were usually with groups of peers. The majority of victims were not prepared for adverse events with basic safety equipment.

An in vivo evaluation of four spinal needles used for the combined spinal-epidural technique.

UNLABELLED: The purpose of this study was to evaluate four pencil-point spinal needles commonly used for combined spinal-epidural (CSE) anesthesia. Four hundred-seven consecutive parturients undergoing cesarean delivery or labor analgesia received a CSE block with a randomly selected pencil-point spinal needle (Becton-Dickinson [B-D] 27-gauge, 119-mm Whitacre; B-D 27-gauge, 120-mm Durasafe; B-D 25-gauge, 120-mm Durasafe; or International Medical Devices' 26-gauge, 124-mm Gertie Marx). Success in obtaining cerebrospinal fluid (CSF) and the incidence of transient paresthesias and postdural puncture headache (PDPH) were compared by using chi2 testing; P < 0.05 was considered significant. Failure to obtain CSF (3%-5%) was not significantly different among spinal needles. The Gertie Marx 26-gauge needle was associated with significantly more paresthesias (29%) than the Whitacre 27-gauge needle (17%). The combined incidence of paresthesias with the Durasafe 25-gauge and Gertie Marx 26-gauge spinal needles (28%) was greater than the combined incidence of paresthesias with the Durasafe 27-gauge and Whitacre 27-gauge needles (18%). The incidence of PDPH did not differ among the four pencil-point spinal needles. We conclude that longer spinal needles are associated with a significantly more frequent incidence of transient paresthesias without residual effects. IMPLICATIONS: The use of four pencil-point spinal needles in the combined spinal-epidural technique is associated with an inconsequential incidence of spinal headache, a low incidence of paresthesias that are transient with no long-term effects, and a high degree of success independent of spinal needle length.

Severe respiratory depression in the obstetric patient after intrathecal meperidine or sufentanil.

Two cases of severe respiratory depression in the obstetric population are presented. The first occurred after intrathecal injection of a modest dose (50 mg) of meperidine. The second followed intrathecal administration of 10 microg of sufentanil after intravenous fentanyl. These cases illustrate the potential gravity of this complication and highlight the need for caution when giving intrathecal opioid following parenteral opioid administration.

Toluene 2-Monooxygenase-Dependent Growth of Burkholderia cepacia G4/PR1 on Diethyl Ether.

Aerobic bacterial growth on aromatic hydrocarbons typically requires oxygenase enzymes, which are known to fortuitously oxidize nongrowth substrates. In this study, we found that oxidation of diethyl ether by toluene 2-monooxygenase supported more rapid growth of Burkholderia cepacia G4/PR1 than did the aromatic substrates n-propylbenzene and o-xylene. The wild-type Burkholderia cepacia G4 failed to grow on diethyl ether. Purified toluene 2-monooxygenase protein components oxidized diethyl ether stoichiometrically to ethanol and acetaldehyde. Butyl methyl ether, diethyl sulfide, and 2-chloroethyl ethyl ether were oxidized by B. cepacia G4/PR1.

Transient radicular irritation after hyperbaric lidocaine spinal anesthesia in parturients.

Two cases of transient radicular irritation in pregnant patients are presented. Both cases involve the combination of spinal anesthesia employing hyperbaric 5% lidocaine and a small gauge pencilpoint needle as well as the surgery being performed in the lithotomy position. We recommend that until the potential for lidocaine-induced neuroradicular irritation under these circumstances is evaluated prospectively, hyperbaric lidocaine should not be used for cases in which a small gauge spinal needle is employed and the patient is placed in the lithotomy position.

Trichloroethylene oxidation by purified toluene 2-monooxygenase: products, kinetics, and turnover-dependent inactivation.

Trichloroethylene is oxidized by several types of nonspecific bacterial oxygenases. Toluene 2-monooxygenase from Burkholderia cepacia G4 is implicated in trichloroethylene oxidation and is uniquely suggested to be resistant to turnover-dependent inactivation in vivo. In this work, the oxidation of trichloroethylene was studied with purified toluene 2-monooxygenase. All three purified toluene 2-monooxygenase protein components and NADH were required to reconstitute full trichloroethylene oxidation activity in vitro. The apparent Km and Vmax were 12 microM and 37 nmol per min per mg of hydroxylase component, respectively. Ten percent of the full activity was obtained when the small-molecular-weight enzyme component was omitted. The stable oxidation products, accounting for 84% of the trichloroethylene oxidized, were carbon monoxide, formic acid, glyoxylic acid, and covalently modified oxygenase proteins that constituted 12% of the reacted [14C]trichloroethylene. The stable oxidation products may all derive from the unstable intermediate trichloroethylene epoxide that was trapped by reaction with 4-(p-nitrobenzyl)pyridine. Chloral hydrate and dichloroacetic acid were not detected. This finding differs from that with soluble methane monooxygenase and cytochrome P-450 monooxygenase, which produce chloral hydrate. Trichloroethylene-dependent inactivation of toluene 2-monooxygenase activity was observed. All of the protein components were covalently modified during the oxidation of trichloroethylene. The addition of cysteine to reaction mixtures partially protected the enzyme system against inactivation, most notably protecting the NADH-oxidoreductase component. This suggested the participation of diffusible intermediates in the inactivation of the oxidoreductase.

Multiple chemical exposures: synergism vs. individual exposure levels.

Exposure to single chemicals is known to produce congenital malformations in both pregnant animals and humans exposed at sufficiently high intensity. However, real life involves multiple, simultaneous exposures. Using as a database the 43 multiple chemical exposure studies located by Nelson (Teratology 49:33-71; 1994) where synergism was reported, we explored the degree to which such concerns may be realistic from the viewpoint of the current standard developmental toxicity safety evaluation process. Focusing on the assessment of the lowest tested dose of a given agent participating in synergistic activity as compared to its threshold level for eliciting toxicity when administered alone, we found that while the availability of adequate data was limited, all cases, with the possible exception of one, demonstrated synergistic toxic expression only when at least one, and usually both, compounds were used at or above their individual threshold for toxicity. These findings suggest that in animals such phenomena of synergistic chemical interactions are likely to occur only when at least one and more likely both agents are administered at or above their individual threshold for toxicity. To the extent animal studies are predictive of human developmental hazards due to single chemical exposures, available data do not establish multiple chemical exposures as a major human developmental concern.

Purification and characterization of toluene 2-monooxygenase from Burkholderia cepacia G4.

Recent in vivo studies indicate that ring monooxygenation is a widespread mechanism by which bacteria metabolize aromatic hydrocarbons and obtain carbon and energy. In this study, toluene 2-monooxygenase from Burkholderia (formerly Pseudomonas) cepacia G4 was purified to homogeneity and found to be a three-component enzyme system. The reconstituted enzyme system oxidized toluene to o-cresol and o-cresol to 3-methylcatechol, an important intermediate for growth of the bacterium on toluene. Steady-state kinetic parameters measured for the water-soluble substrate o-cresol were a Km of 0.8 microM and a Vmax of 131 nmol min-1 (mg of hydroxylase protein)-1. The three protein components were (1) a 40 kDa polypeptide containing one FAD and a [2Fe2S] cluster, (2) a 10.4 kDa polypeptide that contained no identifiable metals or organic cofactors, and (3) a 211 kDa alpha 2 beta 2 gamma 2 component containing five to six iron atoms. The 40 kDa flavo-iron-sulfur protein oxidized NADH and transferred electrons to cytochrome c, dyes, and the alpha 2 beta 2 gamma 2 component. It is analogous to other NADH oxidoreductase components found in a wide range of bacterial mono- and dioxygenases. The 10.4 kDa component, added to the other two components and NADH, increased toluene oxidation rates 10-fold. The alpha 2 beta 2 gamma 2 component was indicated to contain the site for toluene binding and hydroxylation by the following observations: (1) tight binding to a toluene affinity column; (2) oxidation of toluene after reduction of the protein with dithionite and adding O2; (3) H2O2-dependent toluene oxidation and catalase activity; and (4) spectroscopic studies of the iron atoms in the component. The alpha 2 beta 2 gamma 2 component had no significant absorbance in the visible region. EPR spectroscopy yielded a signal at g = 16 upon addition of > 2 equiv of electrons per 2 Fe atoms. Taken with the quantitation of five to six iron atoms, the data suggest that the alpha 2 beta 2 gamma 2 component contains two binuclear iron centers. In total, the structural, spectroscopic, and catalytic features of toluene 2-monooxygenase are reminiscent of soluble methane monooxygenase obtained from methanotrophic bacteria. The two enzyme systems also differ in many subtle ways; for example, they oxidize toluene with completely different regiospecificity.

Metabolism of polyhalogenated compounds by a genetically engineered bacterium.

The decomposition of organic compounds by bacteria has been studied for almost a century, during which time selective enrichment culture has generated microorganisms capable of metabolizing thousands of organic compounds. But attempts to obtain pure cultures of bacteria that can metabolize highly halogenated compounds, a large and important class of pollutants, have been largely unsuccessful. Polyhalogenated compounds are most frequently metabolized by anaerobic bacteria as a result of reductive dehalogenation reactions, the products of which are typically substrates for bacterial oxygenases. Complete metabolism of polyhalogenated compounds therefore necessitates the sequential use of anaerobic and aerobic bacteria. Here we combine seven genes encoding two multi-component oxygenases in a single strain of Pseudomonas which as a result metabolizes polyhalogenated compounds by means of sequential reductive and oxidative reactions to yield non-toxic products. Cytochrome P450cam monooxygenase reduces polyhalogenated compounds, which are bound at the camphor-binding site, under subatmospheric oxygen tensions. We find that these reduction products are oxidizable substrates for toluene dioxygenase. Perhalogenated chlorofluorocarbons also act as substrates for the genetically engineered strain.

Assessment of the effectiveness of animal developmental toxicity testing for human safety.

Evaluations of studies for four well-known human developmental toxicants clearly suggest that a margin of exposure of 1/100th the NOAEL for the most sensitive animal species tested provides adequate safety for the human conceptus. The lowest reported human teratogenic exposures occurred at doses at least one log above the estimated "safe" or acceptable daily exposure based on the most sensitive animal species, that is, 1/100th animal NOAEL. (The MOE ranged from < 1 to 10.). The data and analyses are consistent with the conclusion that, regardless of the type of in utero effect produced in animals, the margin of safety of 100 is likely to protect the human conceptus in utero from developmental perturbation, and it is a scientifically reasonable and conservative default number.

Cosubstrate effects in reductive dehalogenation by Pseudomonas putida G786 expressing cytochrome P-450CAM.

Cytochrome P-450CAM was shown to be the primary catalyst mediating reductive dehalogenation of polychlorinated ethanes by Pseudomonas putida G786. Under anaerobic conditions, the enzyme catalyzed reductive elimination reactions in vivo with the substrates hexachloroethane, pentachloroethane, and 1,1,1,2-tetrachlorethane; the products were tetrachloroethylene, trichloroethylene, and 1,1-dichloroethylene, respectively. In vivo reaction rates were determined. No reaction was observed with 1,1,2,2-tetrachloroethane or 1,1,1-trichloroethane. Purified cytochrome P-450CAM was used to measure dissociation constants of polychlorinated ethanes for the enzyme active site. Observed rates and dissociation constants were used to predict the course of a reaction with the three substrates simultaneously. Data obtained from experiments with P. putida G786 generally followed the simulated reaction curves. Oxygen suppressed the reductive dechlorination reactions and, in the case of 1,1,1,2-tetrachlorethane, 2,2,2-trichloroacetaldehyde was formed. Significant rates of reductive dechlorination were observed at 5% oxygen suggesting that these reactions could occur under partially aerobic conditions. These studies highlight the potential to use an aerobic bacterium, P. putida G786, under a range of oxygen tensions to reductively dehalogenate mixed wastes which are only degraded at very low rates by obligately anaerobic bacteria.

Organic peroxides inhibit neutrophil leukotriene B4 biosynthesis.

Leukotriene B4, an autacoid metabolite of arachidonic acid produced by polymorphonuclear neutrophils, induces chemokinesis, chemotaxis, and adhesion of these cells at sites of inflammation. Because neutrophil infiltration is a self-limited process, we hypothesized that oxidized lipid products of neutrophil-damaged tissue might inhibit leukotriene B4 biosynthesis, thereby preventing additional neutrophil infiltration and limiting peroxidative tissue damage. Erythrocyte ghosts exposed to a hydrogen peroxide-generating system served as a model of peroxidized tissue in inflammation and inhibited neutrophil leukotriene B4 production by 50% compared with unoxidized ghosts. Organic peroxides, including tert-butylhydroperoxide, peracetic acid, and linoleic hydroperoxide, resembling the product(s) of tissue membrane peroxidation in lipid solubility and catalase resistance, inhibited leukotriene B4 biosynthesis in a dose-dependent manner (50% inhibitory concentration of 3.9 microM compared to 530 microM for H2O2). Biosynthetic steps prior to the 5-lipoxygenase did not appear to be the site of inhibition. Likewise, the step after the 5-lipoxygenase, the leukotriene A4 hydrolase, was not primarily involved. Thus a possible mechanism for controlling the influx of neutrophils and their oxidative damage during inflammation may be inhibition of the 5-lipoxygenase by catalase-resistant lipid peroxides released by tissue membranes.