Field testing of an enzymatic quorum quencher coating additive to reduce biocorrosion of steel

Microbial colonization can be detrimental to the integrity of metal surfaces and lead to microbiologically influenced corrosion. Biocorrosion is a serious problem for aquatic and marine industries in the world and severely affects the maritime transportation industry by destroying port infrastructure and increasing fuel usage and the time and cost required for maintenance of transport vessels. Here, we evaluate the potential of a stable quorum quenching lactonase enzyme to reduce biocorrosion in the field. Over the course of 21 months, steel samples coated with lactonase-containing acrylic paint were submerged at two different sites and depths in the Duluth-Superior Harbor (Lake Superior, MN, USA) and benchmarked against controls, including the biological biocide surfactin. In this experiment, the lactonase treatment outperformed the surfactin biocide treatment and significantly reduced the number of corrosion tubercles (37%; P < 0.01) and the corroded surface area (39%; P < 0.01) as compared to the acrylic-coated control coupons. In an attempt to evaluate the effects of signal disruption of surface microbial communities and the reasons for lower corrosion levels, 16S rRNA sequencing was performed and community populations were analyzed. Interestingly, surface communities were similar between all treatments, and only minor changes could be observed. Among these changes, several groups, including sulfate-reducing bacteria (SRB), appeared to correlate with corrosion levels, and more specifically, SRB abundance levels were lower on lactonase-treated steel coupons. We surmise that these minute community changes may have large impacts on corrosion rates. Overall, these results highlight the potential use of stable quorum quenching lactonases as an eco-friendly antifouling coating additive. IMPORTANCE Biocorrosion severely affects the maritime transportation industry by destroying port infrastructure and increasing fuel usage and the time and cost required to maintain transport vessels. Current solutions are partly satisfactory, and the antifouling coating still largely depends on biocide-containing products that are harmful to the environment. The importance of microbial signaling in biofouling and biocorrosion is not elucidated. We here take advantage of a highly stable lactonase that can interfere with N-acyl homoserine lactone-based quorum sensing and remain active in a coating base. The observed results show that an enzyme-containing coating can reduce biocorrosion over 21 months in the field. It also reveals subtle changes in the abundance of surface microbes, including sulfate-reducing bacteria. This work may contribute to pave the way for strategies pertaining to surface microbiome changes to reduce biocorrosion.

Correction: Evaluation of biological and enzymatic quorum quencher coating additives to reduce biocorrosion of steel

[This corrects the article DOI: 10.1371/journal.pone.0217059.].

Evaluation of biological and enzymatic quorum quencher coating additives to reduce biocorrosion of steel

Microbial colonization can be detrimental to the integrity of metal surfaces and lead to microbiologically influenced corrosion (MIC). Biocorrosion is a serious problem for aquatic and marine industries in the world. In Minnesota (USA), where this study was conducted, biocorrosion severely affects the maritime transportation industry. The anticorrosion activity of a variety of compounds, including chemical (magnesium peroxide) and biological (surfactin, capsaicin, and gramicidin) molecules were investigated as coating additives. We also evaluated a previously engineered, extremely stable, non-biocidal enzyme known to interfere in bacterial signaling, SsoPox (a quorum quenching lactonase). Experimental steel coupons were submerged in water from the Duluth Superior Harbor (DSH) for 8 weeks in the laboratory. Biocorrosion was evaluated by counting the number and the coverage of corrosion tubercles on coupons and also by ESEM imaging of the coupon surface. Three experimental coating additives significantly reduced the formation of corrosion tubercles: surfactin, magnesium peroxide and the quorum quenching lactonase by 31%, 36% and 50%, respectively. DNA sequence analysis of the V4 region of the bacterial 16S rRNA gene revealed that these decreases in corrosion were associated with significant changes in the composition of bacterial communities on the steel surfaces. These results demonstrate the potential of highly stable quorum quenching lactonases to provide a reliable, cost-effective method to treat steel structures and prevent biocorrosion.

Decay of genetic markers for fecal bacterial indicators and pathogens in sand from Lake Superior

Beach sands impact water quality and pathogen loads, however, the comparative decay of the fecal indicator bacteria (FIB) Enterococcus spp. and Escherichia coli, and pathogens in freshwater sand have not been examined. In this study, freshwater sand microcosms were inoculated with sewage and pure cultures of bacterial pathogens to compare relative decay rates. The abundance of culturable Enterococcus spp. and E. coli, genetic markers for Enterococcus spp. (Entero1), total Bacteroides (AllBac), and human-specific Bacteroides (HF183), and genetic markers for the pathogens Campylobacter jejuni, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enterica subsp. enterica serovar Typhimurium, and Shigella flexneri were monitored over the course of two weeks using conventional culture methods and quantitative PCR (qPCR). The effect of moisture on the persistence of culturable FIB and all genetic markers was also determined. In addition, propidium monoazide (PMA) treatment was used to examine differences in the persistence of total genetic markers and those from live cells. Decay rates were statistically compared using Tukey's test. Moisture had a significant (p ≤ 0.05) effect on the decay rates of culturable indicator bacteria, total AllBac markers, and genetic markers for FIB, Salmonella, and MRSA from live cells. At 14% sand moisture, the decay rate of total markers was slower than that of live cells for all qPCR assays, but at 28% moisture, there was no difference in the decay rates of total and live markers for any assay. AllBac and MRSA markers increased in sand at 28% moisture, probably indicating cellular growth. Overall, culturable FIB and HF183 had decay rates that were most comparable to the bacterial pathogen markers examined in this study, whereas Entero1 and AllBac rarely exhibited decay rates similar to the bacterial pathogens in this study. The choice of FIB for assessment of fecal contamination in freshwater sand should take into account the pathogen of concern and sand moisture conditions.

Distribution of genetic markers of fecal pollution on a freshwater sandy shoreline in proximity to wastewater effluent

Water, sand, and sediment from a Lake Superior harbor site continuously receiving wastewater effluent was sampled monthly for June to October 2010 and from May to September 2011. Understanding the dynamics of genetic markers of fecal bacteria in these matrices is essential to accurately characterizing health risks. Genetic markers for enterococci, total Bacteroides, and human-associated Bacteroides were measured in site-water, sand, and sediment and in final effluent by quantitative PCR. The similarity between the quantity of molecular markers in the water column and effluent indicated that the abundance of genetic markers in the water column was likely controlled by effluent inputs. Effluent turbidity was positively correlated (p ≤ 0.05) with AllBac and HF183 in final effluent and AllBac in the water column. In sand and sediment, Entero1 and AllBac were most abundant in the upper 1-3 cm depths, whereas HF183 was most abundant in the upper 1 cm of sand and at 7 cm in sediment. The AllBac and Entero1 markers were 1- and 2-orders of magnitude more abundant in sand and sediment relative to the water column per unit mass. These results indicate that sand and sediment may act as reservoirs for genetic markers of fecal pollution at some freshwater sites.

Waterfowl abundance does not predict the dominant avian source of beach Escherichia coli

The horizontal, fluorophore enhanced, rep-PCR (HFERP) DNA fingerprinting technique was used to identify potential sources of in water, nearshore sand, and sediment at two beaches in the Duluth-Superior Harbor, near Duluth, MN, and Superior, WI, during May, July, and September 2006. An animal or environmental source could be identified for 35, 29, and 30% of strains in water, sand, and sediments, respectively. Waterfowl, including Canada geese, ring-billed gulls, and mallard ducks, were the largest source of that could be identified in water (55-100%), sand (59-100%), and sediment (92-100%) at both beaches. Although ring-billed gulls were more abundant in this harbor, Canada geese were usually the dominant source of waterfowl found at these beaches. The percentage of identified from treated wastewater was always less than the percentage of originating from waterfowl. At both beaches, the percentage of in water contributed by treated wastewater was higher in May compared with July and September. The larger proportion of wastewater-derived seen in May probably reflected a smaller contribution of from geese when these birds were less abundant rather than an absolute increase in from treated wastewater. Microbial source analysis and bird census data both indicated that waterfowl were a major source of at beaches in the Duluth-Superior Harbor. These data also indicated it is risky to assume that the most abundant waterfowl species present in waterways will also be the largest source of avian-derived in water, nearshore sand, and sediments at beaches.

Presence and sources of fecal coliform bacteria in epilithic periphyton communities of Lake Superior

Epilithic periphyton communities were sampled at three sites on the Minnesota shoreline of Lake Superior from June 2004 to August 2005 to determine if fecal coliforms and Escherichia coli were present throughout the ice-free season. Fecal coliform densities increased up to 4 orders of magnitude in early summer, reached peaks of up to 1.4x10(5) CFU cm-2 by late July, and decreased during autumn. Horizontal, fluorophore-enhanced repetitive-PCR DNA fingerprint analyses indicated that the source for 2% to 44% of the E. coli bacteria isolated from these periphyton communities could be identified when compared with a library of E. coli fingerprints from animal hosts and sewage. Waterfowl were the major source (68 to 99%) of periphyton E. coli strains that could be identified. Several periphyton E. coli isolates were genotypically identical (>or=92% similarity), repeatedly isolated over time, and unidentified when compared to the source library, suggesting that these strains were naturalized members of periphyton communities. If the unidentified E. coli strains from periphyton were added to the known source library, then 57% to 81% of E. coli strains from overlying waters could be identified, with waterfowl (15 to 67%), periphyton (6 to 28%), and sewage effluent (8 to 28%) being the major potential sources. Inoculated E. coli rapidly colonized natural periphyton in laboratory microcosms and persisted for several weeks, and some cells were released to the overlying water. Our results indicate that E. coli from periphyton released into waterways confounds the use of this bacterium as a reliable indicator of recent fecal pollution.

Beach sand and sediments are temporal sinks and sources of Escherichia coli in Lake Superior

The Duluth Boat Club (DBC) Beach, located in the Duluth-Superior harbor of Lake Superior, is frequently closed in summer due to high counts of Escherichia coli, an indicator of fecal contamination. However, the sources of bacteria contributing to beach closure are currently unknown. In this study, we investigated the potential sources of E. coli contaminating the DBC beach by using modified rep-PCR (HFERP) DNA fingerprinting. Over 3600 E. coli strains were obtained from 55 lake water, 25 sediment, and 135 sand samples taken from five transects at the DBC beach at 11 different times during the summer through fall months of 2004 and 2005. Potential sources of E. coli at this beach were determined by using a known-source DNA fingerprint library containing unique E. coli isolates from wildlife, waterfowl, and treated wastewater obtained near Duluth, MN. Amounts E. coli in the samples were enumerated by membrane filtration counting, and the presence of potentially pathogenic E. coli was determined by using multiplex PCR. E. coli counts in all samples increased during the summer and early fall (Julyto September). While E. coli in spring samples originated mainly from treated wastewater effluent, the percentage of E. coli from waterfowl increased from summer to fall. DNA fingerprint analyses indicated that some E. coli strains may be naturalized, and autochthonous members of the microbial community in the beach sand and sediments were examined. However, multiplex PCR results indicated that <1% of the E. coli strains at the DBC was potentially pathogenic. Our results also suggest that wave action may influence the early colonization and homogeneous distribution of E. coli in beach sand and the subsequent release of sand or sediment-borne E. coli into lake water. Taken together, these results indicate that sand and sediment serve as temporal sources and sinks of human and waterfowl-derived E. coli that contribute to beach closures.

Presence and growth of naturalized Escherichia coli in temperate soils from Lake Superior watersheds

The presence of Escherichia coli in water is used as an indicator of fecal contamination, but recent reports indicate that soil populations can also be detected in tropical, subtropical, and some temperate environments. In this study, we report that viable E. coli populations were repeatedly isolated from northern temperate soils in three Lake Superior watersheds from October 2003 to October 2004. Seasonal variation in the population density of soilborne E. coli was observed; the greatest cell densities, up to 3 x 10(3) CFU/g soil, were found in the summer to fall (June to October), and the lowest numbers, < or =1 CFU/g soil, occurred during the winter to spring months (February to May). Horizontal, fluorophore-enhanced repetitive extragenic palindromic PCR (HFERP) DNA fingerprint analyses indicated that identical soilborne E. coli genotypes, those with > or =92% similarity values, overwintered in frozen soil and were present over time. Soilborne E. coli strains had HFERP DNA fingerprints that were unique to specific soils and locations, suggesting that these E. coli strains became naturalized, autochthonous members of the soil microbial community. In laboratory studies, naturalized E. coli strains had the ability to grow and replicate to high cell densities, up to 4.2 x 10(5) CFU/g soil, in nonsterile soils when incubated at 30 or 37 degrees C and survived longer than 1 month when soil temperatures were < or =25 degrees C. To our knowledge, this is the first report of the growth of naturalized E. coli in nonsterile, nonamended soils. The presence of significant populations of naturalized populations of E. coli in temperate soils may confound the use of this bacterium as an indicator of fecal contamination.

Presence and growth of naturalized Escherichia coli in temperate soils from Lake Superior watersheds

The presence of Escherichia coli in water is used as an indicator of fecal contamination, but recent reports indicate that soil populations can also be detected in tropical, subtropical, and some temperate environments. In this study, we report that viable E. coli populations were repeatedly isolated from northern temperate soils in three Lake Superior watersheds from October 2003 to October 2004. Seasonal variation in the population density of soilborne E. coli was observed; the greatest cell densities, up to 3 x 10(3) CFU/g soil, were found in the summer to fall (June to October), and the lowest numbers, < or =1 CFU/g soil, occurred during the winter to spring months (February to May). Horizontal, fluorophore-enhanced repetitive extragenic palindromic PCR (HFERP) DNA fingerprint analyses indicated that identical soilborne E. coli genotypes, those with > or =92% similarity values, overwintered in frozen soil and were present over time. Soilborne E. coli strains had HFERP DNA fingerprints that were unique to specific soils and locations, suggesting that these E. coli strains became naturalized, autochthonous members of the soil microbial community. In laboratory studies, naturalized E. coli strains had the ability to grow and replicate to high cell densities, up to 4.2 x 10(5) CFU/g soil, in nonsterile soils when incubated at 30 or 37 degrees C and survived longer than 1 month when soil temperatures were < or =25 degrees C. To our knowledge, this is the first report of the growth of naturalized E. coli in nonsterile, nonamended soils. The presence of significant populations of naturalized populations of E. coli in temperate soils may confound the use of this bacterium as an indicator of fecal contamination.

Seasonal virus removal by alternative onsite wastewater treatment systems

Viral contamination of public waters is a leading health concern around the world, including in Minnesota where cold climate, abundant onsite systems on poor or thin soils, and abundant surface water resources present a significant risk of wastewater pathogens reaching sensitive water sources. Three alternative onsite treatment systems, a sand filter, peat filter and subsurface-flow constructed wetland (CW) at a field research site were evaluated for seasonal virus removal by seeding each with MS2 bacteriophage. The sand and peat filters and CW removed 2.7, 7.0, and 1.4 log10 of MS2, respectively, during summer and 1.8 and 6.9 log for the sand and peat filter during winter (CW not seeded). Somatic coliphage reductions for the sand filter, peat filter and CW were 2.9, 3.5, 1.0 log10 in summer, and 1.5, 2.8, 0.7 log10 during winter, respectively over a 3 year period. During this period, fecal coliform log10 reductions were 2.9, 4.6, 2.0 in summer for the sand and peat filters and CW, and 2.0, 4.6, 1.6 in winter. The peat filter was the most effective system for removing MS2, somatic coliphage and fecal coliforms during both winter and summer but all systems removed > 90% of viruses throughout the year.

Effect of alternative on-site wastewater treatment on the viability and culturability of Salmonella choleraesuis

The objective of this study was to determine how alternative on-site wastewater treatment systems (i.e. subsurface flow constructed wetlands, intermittent sand filters and intermittent peat filters) affect the viability and culturability of Salmonella choleraesuis (serotype typhimurium, ATCC 23567). Influent was a high strength septic tank effluent (BOD5 240-344 mgL(-1), TN approximately 100 mgL(-1), TP approximately 15 mgL(-1)) at the Natural Resources Research Institute's (NRRI) alternative treatment system test facility in northern Minnesota. Treatment systems were inoculated with cultures of S. choleraesuis for 5-7 consecutive days in summer and winter during 1998-99. After the seeding, outflow samples were taken until Salmonella counts were sustained at background levels. In addition to culture-based enumeration, S. choleraesuis abundances were also measured using fluorescent in situ hybridization (FISH) alone and in combination with the direct viable count method (DVC) to determine if plate counts underestimated total and viable Salmonella abundances and if the Salmonella cell viability changed after passing through the treatment systems. In most cases, total and viable cell abundances in treatment system effluents were several orders of magnitude higher than cultured cell abundances. Our results indicate that the culture-based method underestimated viable concentrations of the model pathogen, S. choleraesuis. Salmonella cell viability decreased in effluents during the summer but increased during the winter. Using a culture-based enumeration method alone to determine removal efficiencies of bacterial indicators and pathogens for wastewater treatment systems may result in artificially high estimates of effective treatment.

Effects of freezing and storage temperature on MS2 viability

Monitoring human enteric virus levels in domestic wastewater effluent is crucial to protecting human health. Occasionally, during intensive sampling, wastewater samples must be stored for later viral analysis. Little data exist regarding how enteric viruses survive during storage at different temperatures in secondary treated wastewater. During a field-scale study assessing pathogen removal performance by various onsite treatment technologies, the MS2 bacteriophage, an indicator of enteric viruses, was inoculated into septic tank (STE), sand filter, peat filter and constructed wetland (CW) effluents to determine virus decay at various storage temperatures. Virus stored at temperatures > or =10 degrees C and at -20 degrees C decayed nearly twice as fast as those stored at 4 degrees C or -80 degrees C. Decreased water quality decreased viral decay rates at 4 degrees C and -80 degrees C, with slowest decay occurring in STE and the fastest in sterile PBS and low pH peat effluent. In CW effluent after 8 days, less MS2 was inactivated when stored at 4 degrees C (20%) compared to -80 degrees C (58%); however, during extended storage (approximately 300 days), less MS2 was inactivated at -80 degrees C (75%) compared to 4 degrees C (93%). We recommend that viruses in wastewater be stored in the dark at 4 degrees C unless storage for >40 days is necessary.

Archaeal nucleic acids in picoplankton from great lakes on three continents

Phylogenetic analysis of PCR-amplified 16S rRNA genes revealed the presence of archaea in picoplankton collected from the Laurentian Great Lakes in North America, Africa's Lake Victoria, and Lakes Ladoga and Onega in northeastern Eurasia. From 1 to 10% of the rRNA extracted from size-fractionated picoplankton (>0.2 microm but <1.2 microm) collected in the epilimnion and hypolimnion of these lakes was specific to the Archaea, whereas the majority of rRNA was derived from Bacteria. Analysis of the 16S rRNA genes cloned from these samples indicated they were closely related to crenarchaeal sequences that have been widely characterized from marine environments. The presence of nearly identical 16S rDNA clones in several of these geographically disparate lakes suggests a cosmopolitan distribution of specific subgroups of these Archaea in freshwater environments. Despite their abundance in the water column of freshwater lakes, we have no representatives of these crenarchaea in pure culture, and so their physiological characteristics and ecological role remain unknown.

Salmonella typhimurium survival and viability is unaltered by suspended particles in freshwater

Rolling microcosm experiments were conducted to determine whether suspended particles affect the survival and viability of a model pathogen, Salmonella choleraesuis, serotype typhimurium (American Type Culture Collection no. 23567), in a freshwater microbial community. Water from the Duluth, MN harbor of Lake Superior (including native microorganisms) was inoculated with clay, silt, or flocculent organic particles in a range of concentrations and a streptomycin-resistant strain of S. typhimurium. Microcosms (incubated at 20 degrees C) were rolled horizontally (3 rpm) and sampled periodically for total bacteria and total, viable, and culturable S. typhimurium. Total S. typhimurium abundance decreased rapidly in all experiments (8.5-73.1% d-1). Total bacteria did not decrease as rapidly as the S. typhimurium population in any experiment, suggesting that a microcosm effect was not responsible for the decline in S. typhimurium populations. Loss rates of attached and free cells were similar, indicating that attachment to particles did not enhance the persistence of Salmonella cells beyond our minimum detectable differences. After eight days, only 0.1 to 11.9% of the initial S. typhimurium inocula were detected by direct counts. Suspended particles had a minimal effect on the survival and viability of S. typhimurium; the losses of total, viable, or culturable Salmonella were generally the same across particle treatments and concentrations. Silt and flocculent particles affected loss rates of total and viable S. typhimurium similarly to inorganic particles (clay). It appears unlikely that suspended particles would provide a means for S. typhimurium to persist at hazardous levels in freshwater.

Specifying the relations between affect and heavy alcohol use among young adults

Current reformulations of the tension reduction hypothesis posit that only a subset of vulnerable individuals are at risk for drinking in response to negative affect. To further specify this model, this study examined the types of mood and social contexts under which affect and alcohol use are associated. Participants were 74 college students who completed repeated assessments of mood, alcohol use, friendship quality, and social support. A complex pattern of findings supported the moderating influences of gender, friendship factors, and the timing of behavior (i.e., weekends vs. weekdays) on the relation between affect and alcohol use. Young adults with less intimate and supportive friendships, as compared with their peers, showed risk for greater drinking following relative elevations in sadness and hostility. Such drinking episodes, in turn, predicted subsequent elevations in these same negative moods the following week. Gender differences in such a cyclical pattern of affect and alcohol use were found to vary across differing emotional experiences. Recommendations for a more refined theory of affect and alcohol use are discussed.

Specifying the relations between affect and heavy alcohol use among young adults

Current reformulations of the tension reduction hypothesis posit that only a subset of vulnerable individuals are at risk for drinking in response to negative affect. To further specify this model, this study examined the types of mood and social contexts under which affect and alcohol use are associated. Participants were 74 college students who completed repeated assessments of mood, alcohol use, friendship quality, and social support. A complex pattern of findings supported the moderating influences of gender, friendship factors, and the timing of behavior (i.e., weekends vs. weekdays) on the relation between affect and alcohol use. Young adults with less intimate and supportive friendships, as compared with their peers, showed risk for greater drinking following relative elevations in sadness and hostility. Such drinking episodes, in turn, predicted subsequent elevations in these same negative moods the following week. Gender differences in such a cyclical pattern of affect and alcohol use were found to vary across differing emotional experiences. Recommendations for a more refined theory of affect and alcohol use are discussed.

Cannabis, atropine, and temporal information processing

In experiment 1, subjects judged time by duration production under no-counting instructions. The productions were made following intravenous injection of atropine sulfate or saline, and after smoking cigarettes with and without (-)-delta 9-tetrahydrocannabinol (THC). THC increased the subjective time rate (STR); i.e., the rate at which subjective time passes relative to clock time, whereas atropine had no effect on STR. Thus, reduction in central acetylcholine activity is not a sufficient explanation of THC's effect on STR. Experiment 2 replicated the THC effect on STR when subjects were counting subjective seconds. This result indicates that THC affects the experience of time as it is passing, and not solely the memory for duration experience after a time period.

Ethanol, monoamines, and affect

Evidence suggests that ethanol self-administration is directly related to central norepinephrine (NE) activity and inversely related to central serotonin (5-HT) activity. Normal male volunteers participated in a placebo controlled crossover design to assess the effects of 1-tyrosine (TY) and 1-tryptophan (TP) (precursors of catecholamines and 5-HT, respectively) in combination with ethanol, on several neurobehavioral measures. Ethanol by itself produced negative effects on several dimensions of mood. Dysphoria was potentiated by TP in combination with ethanol and either unchanged or attenuated by the combination of TY and ethanol. Ethanol impaired verbal recall, and neither TP nor TY in combination with ethanol altered that impairment. The results are consistent with the hypothesis that 5-HT mediates some of the negative mood effects produced by ethanol or antagonizes some of its positive effects, while NE at least partly mediates ethanol's positive effects on mood. Ethanol's impairment of verbal memory appears to be mediated by mechanisms outside the monoamine systems.

Removal of Contaminants from Soils by Electric Fields

Application of a direct-current electric field in soils that contain contaminated liquid is expected to produce an important in situ means of environmental restoration. The electric field induces a motion of the liquid and dissolved ions that transports the contaminant to wells for removal. Electrode chemistry plays an important role, and reagents can be introduced at the electrodes to enhance contaminant removal rates. Experiments and modeling demonstrate high degrees of contaminant removal, propagation of sharp acid and base wave fronts from the electrodes, and a "focusing" effect by which metals accumulate in regions of the soil.

Interaction between ethanol and calcium channel blockers in humans

The purpose of this study was to test the hypothesis that pretreatment with Ca2+ channel blockers would antagonize the effects of ethanol intoxication in humans. The Ca2+ channel blockers verapamil and nifedipine were chosen because preclinical research has shown them to decrease certain behavioral effects of ethanol in animals. Sixteen healthy, male, paid volunteers, moderate users of ethanol, participated in the study (six in the verapamil and 10 in the nifedipine paradigms). Gelatin capsules containing verapamil (80 mg, 160 mg, or placebo) were administered orally 90 min before ethanol ingestion; whereas, gelatin capsules containing nifedipine (10 mg, 20 mg, or placebo) were administered 30 min before ethanol ingestion. Ethanol (0.85 g/kg or placebo) was administered over a 30-min interval. Subjects were tested in a single-blind, latin-square, cross-over design with each of the following six conditions: placebo ethanol-placebo blocker, placebo ethanol-low dose blocker, placebo ethanol-high dose blocker, ethanol-placebo blocker, ethanol-low dose blocker, and ethanol-high dose blocker. The variables measured in this study were subjective rating of ethanol intoxication, Addiction Research Center Inventory alcohol scale, heart rate, blood pressure, short-term memory, accuracy and latency of response in the Simulator Evaluation of Drug Impairment task, and blood ethanol concentrations by breath analyzer. Results indicate that pretreatment with either verapamil or nifedipine failed to antagonize the inebriating effects of ethanol including its decremental effects on short-term memory and psychomotor performance.

Dual staining of natural bacterioplankton with 4',6-diamidino-2-phenylindole and fluorescent oligonucleotide probes targeting kingdom-level 16S rRNA sequences

A method for quantifying eubacterial cell densities in dilute communities of small bacterioplankton is presented. Cells in water samples were stained with 4',6-diamidino-2-phenylindole (DAPI), transferred to gelatin-coated slides, and hybridized with rhodamine-labeled oligonucleotide probes specific for kingdom-level 16S rRNA sequences. Between 48 and 69% of the cells captured on membrane filters were transferred to gelatin-coated slides. The number of DAPI-stained cells that were visualized with eubacterial probes varied from 35 to 67%. Only 2 to 4% of these cells also fluoresced following hybridization with a probe designed to target a eukaryotic 16S rRNA sequence. Between 0.1 and 6% of the bacterioplankton in these samples were autofluorescent and may have been mistaken as cells that hybridized with fluorescent oligonucleotide probes. Dual staining allows precise estimates of the efficiency of transfers of cells to gelatin films and can be used to measure the percentage of the total bacterioplankton that also hybridize with fluorescent oligonucleotide probes, indicating specific phylogenetic groups.

Interaction between ethanol and dextroamphetamine: effects on psychomotor performance

The objective of this study was to investigate the interaction between ethanol and dextroamphetamine with regard to psychomotor performance. Twelve healthy, male, paid volunteers, moderate users of ethanol and amphetamines, participated in this study. Ethanol (0.85 g/kg or placebo) was administered over a 30-min interval. Five minutes before the termination of ethanol or placebo ingestion, dextroamphetamine elixir (0.09 mg/kg, 0.18 mg/kg or placebo) diluted in 50 ml of orange juice was administered. Subjects were tested in a single-blind, latin-square, crossover design with each of the following six conditions: placebo ethanol/placebo dextroamphetamine; placebo ethanol/low-dose dextroamphetamine; placebo ethanol/high-dose dextroamphetamine; ethanol/placebo dextroamphetamine; ethanol/low-dose dextroamphetamine; and ethanol/high-dose dextroamphetamine. The variables measured in this study were: subjective rating of ethanol and dextroamphetamine intoxication, accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI task), blood ethanol concentration by breath analyzer, and plasma concentrations of dextroamphetamine by gas chromatography. Results indicate ethanol induced decrements in performance of the skills necessary to drive an automobile were significantly decreased by dextroamphetamine in a dose-response fashion. The administration of dextroamphetamine did not decrease the subjective ratings of ethanol intoxication.

Behavioral and endocrine interactions between thyrotropin-releasing hormone and ethanol in normal human subjects

Thyrotropin-releasing hormone (TRH) has been shown to antagonize the depressant effects of ethanol in animals, but conflicting findings have been reported in humans. To test whether TRH counteracts any of a variety of ethanol-sensitive behavioral measures in normal human subjects and for an effect of ethanol on TRH-induced thyrotropin (TSH) and prolactin (PRL) response, we administered TRH (500 micrograms) or placebo over 1 min intravenously, 30 min after subjects had ingested 0.8 g/kg of ethanol or a placebo drink. Blood samples for TSH and PRL were drawn prior to and 15 and 30 min after injection. Eight male subjects were studied in a balanced, crossover design with each subject receiving placebo-placebo, TRH-placebo, placebo-ethanol, and TRH-ethanol. Whereas ethanol had significant and expected effects on subjective measures, memory, disinhibition, reaction time and time perception, TRH failed to counteract any ethanol effect, except for a small effect in one memory task. Similarly, no effect of ethanol on TRH-induced TSH or PRL response was found. Though the behavioral findings could be interpreted to indicate that TRH does not alter ethanol sensitive behaviors in humans it will be necessary to utilize higher dosages of TRH and/or TRH analogues before firmly drawing this conclusion.

The pharmacologic effects of daily marijuana smoking in humans

Six healthy male, paid volunteers smoked one NIDA cigarette containing 1.0% THC each day for 13 consecutive days. They were tested before and after the period of drug administration by the following procedure: the subjects smoked one NIDA marijuana cigarette containing 1.0% THC followed 15 minutes later by the intravenous infusion of 52 micrograms/min of deuterated THC for 50 minutes. The THC plasma concentrations, ratings of "high" and heart rate effects produced by the combined drug administration were measured, and absolute bioavailability of smoked THC was calculated on Days 1 and 22. Statistical analyses indicate that the only significant changes induced by daily marijuana exposure were in cardioacceleration.

Clinical effects of daily methamphetamine administration

This study investigated alterations in the disposition and pharmacodynamics of methamphetamine HCl after daily administration. Six male paid volunteers familiar with the use of amphetamines participated. Each subject was administered 10 mg of methamphetamine HCl as a slow-release preparation (Desoxyn Gradumets) at 9 a.m. for 13 consecutive days (days 2-14 of the study). On days 1 and 15 the subjects were challenged with 10 mg of oral deuterated methamphetamine HCl. Deuterated drug was used to differentiate plasma concentrations of challenge doses from those of daily doses. The heart rate, subjective perception of "high," and plasma concentrations of methamphetamine were examined on days 1 and 15. Repeated ANOVA measures indicate that a significant decrease in heart-rate acceleration in response to methamphetamine challenge occurred on day 15 [F(1,5) = 8.26, p less than or equal to 0.035]. However, no significant change in either the subjective ratings of "high" or the plasma concentrations of deuterated methamphetamine occurred. These findings indicate that the disposition of methamphetamine and its subjective effects were not altered by this period of daily exposure to a low dose of the drug. In contrast, tolerance to the heart-rate accelerating effect was observed.

Dose-response studies with thyrotropin-releasing hormone (TRH) in abstinent male alcoholics: evidence for selective thyrotroph dysfunction?

A reduced thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) has been reported in subjects with a history of alcoholism whereas prolactin (PRL) responses have generally been normal. One hypothesis proposed to explain the reduced TSH response is down-regulation of pituitary TRH receptors. If this is correct, PRL response should also be diminished. To account for the different dose-response characteristics of TSH/PRL we have given four dosages of TRH (25, 100, 500 and 800 micrograms) to eight noncirrhotic, male alcoholics abstinent from ethanol a minimum of 28 days and to seven male control subjects. Across the TRH dose range the alcoholic subjects exhibited reduced basal TSH (p = .01) and a reduced TSH response (p = .0023) but no differences in basal and stimulated PRL levels. Alcoholic subjects had higher basal T4, T3 and FT4I values than did control subjects but covarying for T4, T3 and FT4I did not change the significance of either TSH or PRL findings. No significant differences in estradiol, estrone, testosterone, cortisol or glucose were noted between groups. The present study confirms the observation of a lower TSH response to TRH in abstinent alcoholics and indicates that the lower response cannot be overcome by increasing TRH dosage. The similar PRL response between groups suggests normal lactotroph function in noncirrhotic abstinent alcoholics and argues against the pituitary TRH receptor down-regulation hypothesis.

Ethanol inhibits NMDA-evoked electrophysiological activity in vivo

Recent studies have demonstrated that ethanol blocks N-methyl-D-aspartate (NMDA) responses in vitro. In the present study, evidence is provided that ethanol, when administered by the systemic route to rats, also inhibits NMDA-evoked electrophysiological activity in vivo at behaviorally relevant doses. Ethanol, at doses in rats ranging from those producing minimal changes in spontaneous behavioral activity (0.75 g/kg) to those producing marked suppression of behavioral activity (2.5 g/kg), produced a dose-dependent inhibition of the ability of NMDA, when iontophoresed onto neurons of the medial septum (MS), to activate MS neurons. However, at all doses of ethanol tested, a proportion of MS neurons responded to ethanol with essentially complete inhibition of NMDA-evoked activity, whereas other MS neurons responded to ethanol with little or no inhibition of NMDA-evoked activity. By way of comparison, MK-801, a non-competitive NMDA antagonist, antagonized NMDA-evoked activity in all MS neurons tested. In contrast to the actions of ethanol, MK-801 increased, rather than decreased, behavioral activity even at doses that completely inhibited NMDA-evoked activity in all MS neurons tested. These latter findings provide evidence that inhibition of NMDA-evoked activity cannot account for all of the behavioral effects of ethanol. In conclusion, while the present results demonstrate for the first time that ethanol can inhibit NMDA-evoked neuronal activity in vivo, they also indicate that additional neural actions must contribute to ethanol's pharmacological profile.

Antagonism of marihuana effects by indomethacin in humans

To investigate whether the nonsteroidal anti-inflammatory drug (NSAID) indomethacin antagonized the effects of marihuana, an exploratory single-blind, placebo-controlled study was conducted. Subjects (n = 4) smoked marihuana after pre-treatment with placebo and indomethacin. The subjective rating of marihuana "high", heart rate, word recall, time estimation/production, and plasma concentrations of THC and PGE2 were measured. It was found that: 1) indomethacin pre-treatment decreased the elevation of prostaglandins induced by THC; 2) indomethacin significantly attenuated the subjective "high" and the heart rate accelerating effects of THC, although the magnitude of this effect was modest; 3) indomethacin abolished the profound effect of THC on time estimation and production; and 4) indomethacin pretreatment did not affect the decremental effects of THC on word recall. We conclude that prostaglandins are involved in the neurophysiologic mechanisms that mediate some of the typical clinical effects of THC, particularly the distortion of time perception.

Differential psychopharmacology of methylphenidate and the neuropsychology of childhood hyperactivity

The principle of rate-dependency has been proposed to explain the therapeutic effects of stimulant drugs in hyperactive children (HAC). This paper is a critical discussion of the salience of rate-dependency to childhood hyperactivity, on mathematical, theoretical and clinical levels. The results of a stimulant drug trial in 55 HAC are presented; the data are analyzed using analysis of variance to describe main drug effects, and these are compared to results derived from a traditional rate dependency analysis. The latter are found to have little salience to the actual clinical effects of stimulant drugs on a wide variety of behavioral, physiological and laboratory measures. The weakness of the rate dependency hypothesis, however, is not necessarily fatal to the idea that the state of the organism prior to drug administration influences the response profile of the drug. The heterogeneity of stimulant effects, and the relationship between stimulant effects and the predrug state of the organism, especially in electrophysiological paradigms, are clear. A hypothesis is presented to suggest that HAC may be characterized by a trait of excessive variability. Homeostatic stimulant effects in reducing response variability may be central to the therapeutic action of the drug. A neural substrate for the abnormal oscillations which characterize HAC, the correction of which is germane to therapeutic stimulant effects, is presented in terms of the regulatory functions of the frontal lobe. A neuroanatomic locus of childhood hyperactivity is proposed in terms of disorder or dysmaturation of frontal striatal systems.

Interaction between marihuana and ethanol: effects on psychomotor performance

This is a report of the results of a placebo-controlled study in which the effects of the interaction between ethanol and marihuana on drug plasma concentrations, subjective ratings of intoxication, heart rate acceleration, and psychomotor performance were investigated. Six healthy, male, paid volunteers, moderate users of ethanol and marihuana, participated in the study. Ethanol (0.42 g/kg, 0.85 g/kg, or placebo) was administered over a 30-min interval. Fifteen minutes later the subjects smoked, in their customary manner, NIDA cigarettes containing 2.4% or 0.0004% (placebo) delta-9-tetrahydrocannabinol (THC). Each subject was tested in a single-blind, latin-square crossover design with the following six conditions: placebo ethanol/placebo marihuana; low dose ethanol/placebo marihuana; high dose ethanol/placebo marihuana; placebo ethanol/marihuana; low dose ethanol/marihuana; and high dose ethanol/marihuana. The variables measured in the study were: (a) subjective rating of ethanol and/or marihuana intoxication; (b) heart rate; (c) accuracy and latency of response in the Simulator Evaluation of Drug Impairment (SEDI) task; (d) blood ethanol concentration by gas chromatography; and (e) plasma concentration of THC by radioimmunoassay. The results indicate that the decrements due to ethanol in performance of skills necessary to drive an automobile were significantly enhanced by marihuana in an additive and perhaps synergistic manner. The administration of ethanol prior to marihuana smoking did not produce significant effects on the subjective rating of "high," heart rate acceleration, or THC plasma concentration.

A neuropathic substrate for stimulant drug effects in hyperactive children

Behavioral, physiological, and cognitive data are presented from a sample of 55 hyperactive children undergoing methylphenidate treatment. Consistent with previous research, considerable variability exists on these measures in this clinical population with little evidence for a consistent profile on any of these dimensions. A theoretical discussion is offered reflecting these findings with reference to a proposed pathophysiologic basis for the disorder. The proposed model postulates a particular emphasis on the functional responsibilities of the frontal-striatal system. A neural substrate for the abnormal oscillations that characterize hyperactive children, the correction of which is germane to therapeutic stimulant effects, is presented in terms of the regulatory functions of the frontal lobe.

Tardive dyskinesia in young mentally retarded individuals

The results of a systematic neuroleptic withdrawal study in 38 mentally retarded children, adolescents, and young adults are described. The focus of the study was the occurrence of side effects of chronic neuroleptic treatment: tardive dyskinesia, transient withdrawal dyskinesia, nondyskinetic withdrawal symptoms, and a possible behavioral analogue of withdrawal dyskinesia. Transient side effects were noted in 34% of the subjects, and tardive dyskinesia in an equal proportion. The data suggest that cumulative neuroleptic dose may play a role as a risk factor in the development of severe tardive dyskinesia.

Methylphenidate and exercise: additive effects on motor performance, variable effects on the neuroendocrine response

It has been suggested that the effects of intensive environmental stressors and of psychostimulant drugs may be interchangeable. A specific test of this hypothesis was undertaken in a double-blind, placebo controlled, cross-over study of the stimulant drug, methylphenidate (MPH), and of intense exercise, alone and in combination. On measures of motor performance the effects of MPH and of exercise were additive while on measures of neuroendocrine response the individual and interactive effects were variable. The effects of MPH and of intense exercise are probably mediated by mechanisms that overlap to a degree but are by no means identical.

Neuropharmacology of methylphenidate and a neural substrate for childhood hyperactivity

What began as a simple chemical question about the clinical utility of MPH SL measurement has led our group across a broad expanse of research endeavors, from the problem of nonintercorrelated stimulant effects to a theory of hyperactivity as a dysregulatory disorder based on frontal-striatal dysfunction or dysmaturation. The transition has been from a traditional and fairly circumscribed question in psychopharmacology to a new interest in the neuropsychological approach to hyperactivity and its treatment. Biologic psychiatry and neuropsychology have developed as distinct disciplines well insulated from one another, but a degree of cross-fertilization is beginning to occur. Rather than thinking of childhood hyperactivity in terms of vague metapsychological concepts such as "attention" or "arousal," it will be perhaps more constructive to base a model for the disorder on the foundation of known elements of brain function. Perhaps the most interesting research areas to pursue will be neuropsychological and neurodiagnostic (for example, PET). The specific locus of disorders, such as the HKS and the specific mechanisms of drug action, may not be so elusive after all.

Clinical correlates of methylphenidate blood levels

The clinical correlates of methylphenidate blood levels in hyper-active children and normal adults were examined in five studies. Although occasional correlations between blood levels and neuroendocrine response were noted within subjects along the pharmacokinetic time profile of the drug, no significant associations were found between blood levels and clinical response in behavioral measures or laboratory tests of attention or activity. It is unlikely that routine methylphenidate blood level determinations will become a part of the routine clinical management of hyperactive children.

Pathological left-handedness and familial sinistrality in relation to degree of mental retardation

The relationship between personal and familial hand preference and mental retardation was examined. Six unimanual tasks were performed by 232 subjects within four mental retardation severity groups. Family handedness histories were obtained. Right hand preference varied inversely with severity of mental retardation. The handedness of mentally retarded groups at the different functional levels paralleled, but tended much more to the sinistral, than that of the corresponding parent groups. The parent-proband handedness correlations were largely insignificant, especially in lower functioning groups. The findings support both pathological left-handedness theory and an association between brain damage causing mental retardation and familial sinistrality.

Influence of sex of antecedent siblings on the human sex ratio

Analysis of family configurations in a population of 649,366 American secondary school students confirmed that sex of later-born children is influenced by the sex of antecedent siblings. Antecedent brothers decrease the probability of subsequent male births. This observation, a confirmation of an earlier report in a substantially smaller sample, is consistent with an immunologic influence on human sex determination.

A developmental study of temporal duration judgments

First, third, fifth, and seventh graders and college students (18 per grade) made four serial reproductions of each of three time intervals, 8, 13, and 32 sec. The results paralleled those of other studies using only adults since both the psychophysical function and the Weber fraction were typical, and magnitude of judgments was an increasing, negatively accelerated function of trials. None of these effects was a function of age nor were there any age effects in an analysis of variable errors. Analysis of first-degree sequential dependency of judgments (using lag correlations) revealed a slight negative recency which was also invariant with age of Ss.

The persistence of stimulant effects in chronically treated children: further evidence of an inverse relationship between drug effects and placebo levels of response

Seventeen hyperactive children who had been treated for 1-5 years with methylphenidate were studied in a double-blind placebo-controlled crossover study. Specific measures of stimulant response were found to be inversely related to the subject's level of response in the placebo condition. This inverse relationship was previously found to characterize the clinical effects of hyperactive children in an acute-treatment paradigm. It is equally valid in a chronic-treatment study. "State-contingency" is not, therefore, simply a function of the "novelty" of initial drug treatment.

Tardive dyskinesia and other clinical consequences of neuroleptic treatment in children and adolescents

Of 41 children, adolescents, and young adults who were withdrawn from chronic neuroleptic treatment, 18 developed tardive dyskinesia, withdrawal dyskinesia, nondyskinetic withdrawal symptoms, or transient behavior deterioration. Development of neuroleptic-related problems seemed to be associated with cumulative neuroleptic dose and possibly with the sex of the subject. Only 12 of the 41 subjects required resumption of neuroleptic treatment after a prolonged trial withdrawal period.