Biogenic volatile emissions from the soil.

Volatile compounds are usually associated with an appearance/presence in the atmosphere. Recent advances, however, indicated that the soil is a huge reservoir and source of biogenic volatile organic compounds (bVOCs), which are formed from decomposing litter and dead organic material or are synthesized by underground living organism or organs and tissues of plants. This review summarizes the scarce available data on the exchange of VOCs between soil and atmosphere and the features of the soil and particle structure allowing diffusion of volatiles in the soil, which is the prerequisite for biological VOC-based interactions. In fact, soil may function either as a sink or as a source of bVOCs. Soil VOC emissions to the atmosphere are often 1-2 (0-3) orders of magnitude lower than those from aboveground vegetation. Microorganisms and the plant root system are the major sources for bVOCs. The current methodology to detect belowground volatiles is described as well as the metabolic capabilities resulting in the wealth of microbial and root VOC emissions. Furthermore, VOC profiles are discussed as non-destructive fingerprints for the detection of organisms. In the last chapter, belowground volatile-based bi- and multi-trophic interactions between microorganisms, plants and invertebrates in the soil are discussed.

Partial purification and characterization of the short-chain prenyltransferases, gernayl diphospate synthase and farnesyl diphosphate synthase, from Abies grandis (grand fir).

In the conifer Abies grandis (grand fir), a secreted oleoresin rich in mono-, sesqui-, and diterpenes serves as a constitutive and induced defense against insects and pathogenic fungi. Geranyl diphosphate (GPP) and farnesyl diphosphate (FPP) synthase, two enzymes which form the principal precursors of the oleoresin mono- and sesquiterpenes, were isolated from the stems of 2-year-old grand fir saplings. These enzymes were partially purified by sequential chromatography on DEAE-Sepharose, Mono-Q, and phenyl-Sepharose to remove competing phosphohydrolase and isopentenyl diphosphate (IPP) isomerase activities. GPP and FPP synthase formed GPP and E,E-FPP, respectively, as the sole products of the enzymatic condensation of IPP and dimethylallyl diphosphate (DMAPP). The properties of both enzymes are broadly similar to those of other prenyltransferases. The apparent native molecular masses are 54 +/- 3 kDa for GPP synthase and 110 +/- 6 kDa fo

Chlorella virus PBCV-1 encodes a functional homospermidine synthase.

Sequence analysis of the 330-kb genome of chlorella virus Paramecium bursaria chlorella virus 1 (PBCV-1) revealed an open reading frame, A237R, that encodes a protein with 34% amino acid identity to homospermidine synthase from Rhodopseudomonas viridis. Expression of the a237r gene product in Escherichia coli established that the recombinant enzyme catalyzes the NAD(+)-dependent formation of homospermidine from two molecules of putrescine. The a237r gene is expressed late in PBCV-1 infection. Both uninfected and PBCV-1-infected chlorella, as well as PBCV-1 virions, contain homospermidine, along with the more common polyamines putrescine, spermidine, and cadaverine. The total number of polyamine molecules per virion ( approximately 539) is too small to significantly neutralize the virus double-stranded DNA (>660,000 nucleotides). Consequently, the biological significance of the homospermidine synthase gene is unknown. However, the gene is widespread among the chlorella viruses. To our knowledge, this is the first report of a virus encoding an enzyme involved in polyamine biosynthesis.

Purification, molecular cloning and expression in Escherichia coli of homospermidine synthase from Rhodopseudomonas viridis.

Homospermidine synthase (HSS) catalyzes the synthesis of the polyamine homospermidine from 2 mol putrescine in an NAD(+)-dependent reaction. In this study, the enzyme was purified from anaerobically grown cultures of the photosynthetic bacterium Rhodopseudomonas viridis to electrophoretic homogeneity using a three-step procedure. The enzyme was shown to be a homodimer of 52-kDa subunits. Six endopeptidase LysC fragments were sequenced from the purified protein. With the aid of degenerate primers designed against these peptides, specific PCR products from R. viridis DNA were obtained that were used as hybridization probes to isolate the hss gene from a library constructed in lambda EMBL4. The hss gene and flanking regions were sequenced and were shown to exist as a single copy in the R. viridis genome. HSS is translated from a monocistronic mRNA and possesses no detectable similarity to previously sequenced gene products. Escherichia coli, which lacks HSS activity, was transformed with an expression plasmid containing the hss coding region under the control of a bacteriophage T7 promoter. Upon induction, transformed F. coli cells accumulate enzymatically active and highly stable R. viridis HSS at levels corresponding to 40-50% of the soluble protein in crude extracts.

Improved metabolic action of a bacterial lysine decarboxylase gene in tobacco hairy root cultures by its fusion to a rbcS transit peptide coding sequence.

The gene of a bacterial lysine decarboxylase (ldc) fused to a rbcS transit peptide coding sequence (tp), and under the control of the CaMV 35S promoter, was expressed in hairy root cultures of Nicotiana tabacum. The fusion of the ldc to the targeting signal sequence improved the performance of the bacterial gene in the plant cells in many respects. Nearly all transgenic hairy root cultures harbouring the 35S-tp-ldc gene contained distinctly higher lysine decarboxylase activity (from 1.5 to 30 pkat LDC per mg protein) than those which had been transformed with constructs in which the gene had been directly cloned behind the CaMV 35S promoter. The higher enzyme activity led to the accumulation of up to 0.7% cadaverine on a dry mass basis. In addition, part of the cadaverine pool was used for increased biosynthesis of anabasine, an alkaloid which was hardly detectable in control cultures. The best line contained anabasine levels of 0.5% dry mass, which could be further be enhanced by feeding of lysine.

Morphine use and adverse effects in a neonatal intensive care unit.

Prescribing patterns and appropriateness of morphine use in a neonatal intensive care unit (NICU) were evaluated in a concurrent drug-use evaluation (DUE). Data were collected for 99 infants who received morphine over a six-month period. Patient charts were reviewed to collect the following data: patient's age, weight, dosage schedule, concurrent sedatives, ventilatory status, whether adequacy of analgesia was documented, and descriptions of adverse drug reactions (ADRs). The physicians' orders were reviewed to determine whether NICU morphine dosage guidelines were followed and whether the indication for use was noted. Seven ADRs occurred in six of the patients; three of the ADRs occurred after ophthalmic cryosurgery. Indications for use were noted in 79 of 285 physician orders (27.7%). The adequacy of sedation or analgesia was documented on 60 of the 360 patient days (16.7%). The DUE results prompted several changes: physicians were asked to select indications from a list in the computerized order-entry system, an analgesia or sedation assessment scale was added to nursing flow sheets, and endotracheal intubation became a requirement before ophthalmic cryosurgery. A follow-up DUE showed nearly complete compliance with the new guidelines for morphine use and a reduction in the number of adverse reactions to morphine. A DUE prompted policy changes that improved documentation of indications for and efficacy of morphine use and reduced adverse reactions to the drug in an NICU.

Meta-analysis of phenobarbital usage for prevention of intraventricular hemorrhage in premature infants: factors related to variation in outcome.

PURPOSE: To assess the efficacy of phenobarbital for the prevention of intraventricular hemorrhage (IVH) in premature infants and to identify study characteristics that were associated with beneficial or adverse effects. DATA IDENTIFICATION: Studies published from 1981 to 1994 were identified through a computerized search, and by searching the bibliographies of all identified articles. STUDY SELECTION: Ten randomized, controlled clinical trials were selected. DATA EXTRACTION: Data were extracted from each article, including the percentage of patients in the control and treatment groups with IVH, and key patient and study characteristics. RESULTS OF DATA ANALYSIS: Seven studies showed no statistically significant effects, two studies showed a beneficial effect of phenobarbital, and one study showed an adverse effect. The meta-analysis showed no significant difference in the percentage of IVH in treated and untreated infants when treatment effects were combined across all studies. However, prenatal administration of phenobarbital in two studies was associated with a beneficial effect. CONCLUSIONS: Overall, we did not find a significant beneficial effect of postnatal phenobarbital administration. The data suggests that prenatal phenobarbital is beneficial. Further evaluations of the efficacy of prenatal phenobarbital are warranted.

Can pharmacokinetic dosing decrease nephrotoxicity associated with aminoglycoside therapy.

A randomized, controlled clinical trial was performed to determine whether individualized dosing by use of Bayesian pharmacokinetic modeling could decrease nephrotoxicity accosted with aminoglycoside therapy. Two hundred forty-three patients receiving aminoglycosides for suspected or proven infection were randomly assigned to one of three groups: usual physician-directed dosing (Group 1), pharmacist-assisted dosing (Group 2), or pharmacist-directed dosing (Group 3). Dosing in Groups 2 and 3 was based on a Bayesian pharmacokinetic dosing program, whereas Group 1 served as the control group. Individualized dosing resulted in higher mean postinfusion (peak) serum aminoglycoside levels, higher ratios of mean peak level to minimum inhibitory concentration (peak/MIC ratios), and a trend toward lower trough serum levels. Milligrams per dose were higher and number of doses per day was lower in the pharmacist-dosed groups. However, the incidence of nephrotoxicity (> or = 100% increase in serum creatinine) was not different among the three groups (16, 27, and 16% in Groups 1, 2, and 3, respectively). Similarly, severity of toxicity was not affected by the dosing intervention. Risk factors for toxicity included duration of therapy, shock, treatment with furosemide, older age, and liver disease. After controlling for these factors, the dosing intervention still had no effect on nephrotoxicity. It was concluded that Bayesian pharmacokinetic dosing did not decrease the risk of nephrotoxicity associated with aminoglycoside therapy.

Physiologic response of stress and aminoglycoside clearance in critically ill patients.

OBJECTIVE: To examine the relationships between aminoglycoside clearance and physiologic parameters associated with the physiologic response to injury. DESIGN: Cross-sectional study of surgical patients receiving aminoglycoside pharmacokinetic monitoring and parenteral nutritional support. SETTING: An adult surgical ICU. PATIENTS: Fifty-four surgical/trauma patients who had Gram-negative sepsis. INTERVENTIONS: Measurements of the physiologic stress response to injury were associated with aminoglycoside clearance in 54 surgical/trauma patients who had Gram-negative sepsis. Measurements used to estimate the magnitude of the stress response included a 24-hr urinary urea nitrogen excretion, blood urea nitrogen, peak temperature, serum albumin, bilirubin, and transferrin concentrations. MEASUREMENTS AND MAIN RESULTS: Mean drug clearance rate (4.4 +/- 2.5 [SD] L/hr) was related to the physiologic measurements using correlation and regression techniques. Collectively, all physiologic indices (utilized) explained 59% of the variance in drug clearance (p < .001), an amount similar to the variance explained by creatinine clearance alone (53%). When all six physiologic measurements were included into a multiple regression model that included creatinine clearance, the total variance explained increased to 73%. CONCLUSIONS: Along with renal function estimates, the physiologic response to stress should be considered when treating critically ill patients with aminoglycosides and other, similar, renally eliminated drugs.

Activated charcoal for theophylline toxicity in a premature infant on the second day of life.

A premature infant received an overdose of aminophylline on the 2nd day of life and was successfully treated with activated charcoal. The use of activated charcoal this early postnatally has never been reported.

Methotrexate disposition following disruption of the blood-brain barrier.

Intracarotid drug administration after osmotic blood-brain barrier disruption (BBBD) enhances drug delivery to brain tumors. Despite clinical use, the pharmacokinetics of drugs following BBBD has not been described to date. Since methotrexate exhibits a concentration-toxicity response relationship, methotrexate disposition was determined following BBBD and intracarotid administration in seven patients with nonoperable brain tumors. Following a 1.5-5 g intracarotid methotrexate injection, 12 blood samples and 9 urine collections were obtained. Methotrexate concentrations in serum and urine were determined by fluorescence polarization immunoassay. The serum concentration-time data were best described by a three-compartment model. Systemic and renal clearances were consistent with previous studies. However, a prolonged mean terminal half-life of 51.5 h was observed. Serum methotrexate concentrations at 72 h exceeded 0.1 mumol/L in five of seven patients. Stomatitis occurred in one patient. Relative to previous reports, prolonged methotrexate half-life and cytotoxic methotrexate concentrations were observed in the serum of patients receiving intracarotid methotrexate following BBBD. Due to the prolonged cytotoxic methotrexate concentrations observed, extended leucovorin therapy may be indicated following BBBD and intracarotid methotrexate.