Growth and grazing of a large heterotrophic dinoflagellate, Noctiluca scintillans, in laboratory cultures

Carbon (C) and nitrogen (N) content and growth/grazing characteristicsof the heterotrophic dinoflagellate Noctiluca scintillans wereexamined in laboratory cultures at 24°C. The C and N contentsof N.scintillans per unit cell volume were 2.3 x 10     

Impact of binocular vision impairments on reading skills in first-year schoolchildren with high visual acuity

The aim of this study was to investigate the state of binocular vision in first-year schoolchildren with high binocular visual acuity. The results have shown that only 5.1% of these children had normal binocular vision, whereas 25.7% of them had moderate impairments, and 67.9% had severe plus moderate impairments in binocular vision. Significant intergroup differences between schoolchildren with learning difficulties in reading and children with normal reading have been detected in the mean indicators for the distance of near-point of convergence (p < 0.001) and the visual behavior symptoms that confirmed binocular dysfunctions (p < 0.002).     

Dynamics of a stable, large volume, laboratory ecosystem containing Daphnia and phytoplankton

Daphnia magna and phytoplankton were maintained in stable, large-volume(3400 l), indoor, planktonic model ecosystems for up to 20 weeks.Ecosystem stability was demonstrated by damped oscillationsin population abundance, and by a return to steady-state conditionsif the system was perturbed. The steady-state biomass of daphniaand algae responded to variations in nutrient loading ratesand daphnia harvesting rates in accordance with predictionsfrom a mathematical model. Increased nutrient addition resultedin an increase in biomass of daphnia, but not phytoplankton,if both were present. Increased harvesting caused an increasein chlorophyll and decreased daphnia biomass. Phosphorus additionswere balanced by sedimentation losses which were proportionalto daphnia biomass. Increased harvesting rates resulted in decreasedphosphorus loss rates and increased efficiency of phosphorusconversion into harvested daphnia. Damped oscillations had aperiodicity of 3.5 weeks and could be successfully modelledassuming a half-saturation constant for phosphorus control ofalgal growth of 1 µg l^–1. The ecosystem became unstableif nutrient loading rates exceeded a defined limit which wasa function of harvesting rates. Steady-state chlorophyll anddaphnia biomass levels were similar to levels approached inLake Michigan in summer in 1983 and 1984, when the zooplanktonbiomass was dominated by Daphnia pulicaria.     

Design,construction, and validation of a large capacity rodent magnetic field exposure laboratory

A magnetic field exposure laboratory has been constructed to support National Toxicology Program studies for the evaluation of the toxicity and carcinogenicity of pure, linearly polarized, 60 Hz magnetic fields in rodents. This dual corridor, controlled access facility can support the simultaneous exposure of 1200 rats and 1200 mice. The facility contains fully redundant electrical and environmental control systems and was constructed using non‐metallic materials to maintain low levels of background (ambient), stray, and cross‐talk magnetic fields. The exposure module design provides for large uniform exposure volumes with good control of stray and cross‐talk fields, while allowing the use of roll‐around cage racks for simplified animal husbandry. Stray fields and cross‐talk have been further reduced by the inclusion of “steering coils” in each exposure module. Ambient 60 Hz fields (less cross‐talk) in all exposure rooms are <0.1 μT (1 mG), and static magnetic fields have been mapped extensively. Magnetic field strength, waveform, temperature, relative humidity, light intensity, noise level, vibration, and air flow in all animal holding areas are tightly regulated, and are monitored continuously during all studies. Field uniformity in the animal exposure volumes is better than ±10%; a systematic program of cage, rack, and room rotation controls for possible positional effects within the exposure system. Magnetic fields are turned on and off over multiple cycles to prevent the induction of transients associated with abrupt field level changes. Total harmonic distortion is <3% at all field strengths. The facility has been used to study magnetic field bioeffects in rodent model systems in experiments ranging in duration from 8 weeks to 2 years. Bioelectromagnetics 20:13–23, 1999. © 1999 Wiley‐Liss, Inc.     

Assessing the likely responses by fishes to stream bank rehabilitation in a large,urban estuary

Urban streams are under increasing threat from anthropogenic disturbances that alter their biological, chemical and physical characteristics. To attempt to repair the negative consequences of urbanization, management activities are commonly implemented with the aim of rehabilitating or restoring habitats. However, subsequent monitoring of these efforts is often done poorly or not at all. The setting of goals for these projects is also hindered by a lack of knowledge about the likely size of any potential response, and also the scope for undertaking activities at sufficient scales to override the likely larger‐scale effects of urbanization. In this study, we completed a series of surveys in a large, urban estuary to generate information that can be used to assess the likely responses of fish to management activities aimed at rehabilitating estuary bank habitats. Initially, we mapped the banks of the estuary to describe the distribution of different potential habitat types for fishes. Surveys were then carried out to assess associations between fish and these habitats, with a view to providing an indication of the likely effect size that management works might produce. We then initiated a BACI (Before‐After Control‐Impact)‐style monitoring design around management works aimed at stabilizing the banks of the estuary and increasing habitat complexity for fishes (the installation of coir logs and planting of native rushes). Power analyses based on the effect sizes and estimates of variability from our initial survey and subsequent monitoring respectively indicate that only large magnitude responses will be detectable. However, these are likely to be constrained by the influence of the larger‐scale effects of urbanization. Even if localized responses occur, wider‐scale manipulations to fish habitat in large urban estuaries are likely to be limited by a range of logistical, social and financial constraints that govern the scale and location of management activities.     

Performance of a new, liquid-based cervical screening technique in the clinical setting of a large French laboratory

OBJECTIVE: To compare the performance of liquid-based cytology with the CYTO-screen System (SEROA) with that of conventional smears through a secondary analysis of a large database covering the activity of an independent French laboratory during the period 1998-2002. STUDY DESIGN: The study was performed with a retrospective, comparative, historical design on 2 subgroups of women having been screened by gynecologists who switched from conventional smears to the CYTO-screen System in the period 1998-2002. The first cohort population consisted of women who had at least 4 subsequent screening tests over the period with half conventional and half with the CYTO-screen System. A control group consisted of smears collected by gynecologists who fully maintained activity with a conventional method over the same period. The second group consisted of women who had their first screening test performed over the study period by gynecologists who modified their technique. Specimen adequacy, endocervical cell content and epithelial cell abnormality detection rates were compared between the groups. RESULTS: As compared with the conventional smear, the CYTO-screen System showed a reduction in unsatisfactory reports, especially in the second group of first-screened (0.14% versus 1.3%, P < .0001). The rate of atypical squamous cells of undetermined significance increased significantly after the switch to the CYTO-screen System (2.5% versus 1.3%, P = .004) and in the second group of first-screened women (2.05% versus 1.4%, P = .0014), with higher histologic confirmation in both situations. There was a non-significant increase in the detection rates of low and high grade squamous intraepithelial lesions after the switch to the CYTO-screen System and in the second group of first-screened women. CONCLUSION: The CYTO-screen System gives higher-quality specimens and has a higher detection rate for squamous intraepithelial lesions, but that rate was significant only for atypical squamous cells of undetermined significance.     

Additional Watson-Crick interactions suggest a structural core in large subunit ribosomal RNA

Two new Watson-Crick type interactions in 23S-like ribosomal RNA have been identified by comparative sequence analysis. These interactions, A1269/U2011 and C1270/G2010 (E. coli numbering) along with the previously proposed A1262/U2017 suggest an anti-parallel helical arrangement characteristic of secondary structure in the 1265/2015 region of 23S rRNA. Nested within these three interactions are three universal juxtapositions which in principle allow the formation of an irregular helix containing two additional A-G interactions and a universal A-U pair. Whether or not this extended helix is biologically significant is uncertain. The proponderance of interactions in the 1265/2015 region and its location relative to the known structural domains of 23S rRNA suggest that this region may be part of a central structural core similar to that already known in 16S rRNA.     

Differential use of large summer rainfall events by shrubs and grasses: a manipulative experiment in the Patagonian steppe

In the Patagonian steppe, years with above-average precipitation (wet years) are characterized by the occurrence of large rainfall events. The objective of this paper was to analyze the ability of shrubs and grasses to use these large events. Shrubs absorb water from the lower layers, grasses from the upper layers, intercepting water that would otherwise reach the layers exploited by shrubs. We hypothesized that both life-forms could use the large rainfalls and that the response of shrubs could be more affected by the presence of grasses than vice versa. We performed a field experiment using a factorial combination of water addition and life-form removal, and repeated it during the warm season of three successive years. The response variables were leaf growth, and soil and plant water potential. Grasses always responded to experimental large rainfall events, and their response was greater in dry than in wet years. Shrubs only used large rainfalls in the driest year, when the soil water potential in the deep layers was low. The presence or absence of one life-form did not modify the response of the other. The magnitude of the increase in soil water potential was much higher in dry than in humid years, suggesting an explanation for the differences among years in the magnitude of the response of shrubs and grasses. We propose that the generally reported poor response of deep-rooted shrubs to summer rainfalls could be because (1) the water is insufficient to reach deep soil layers, (2) the plants are in a dormant phenological status, and/or (3) deep soil layers have a high water potential. The two last situations may result in high deep-drainage losses, one of the most likely explanations for the elsewhere-reported low response of aboveground net primary production to precipitation during wet years. Received: 23 January 1997 / Accepted: 19 November 1997     

Assessing sexual conflict in the Drosophila melanogaster laboratory model system

We describe a graphical model of interlocus coevolution used to distinguish between the interlocus sexual conflict that leads to sexually antagonistic coevolution, and the intrinsic conflict over mating rate that is an integral part of traditional models of sexual selection. We next distinguish the 'laboratory island' approach from the study of both inbred lines and laboratory populations that are newly derived from nature, discuss why we consider it to be one of the most fitting forms of laboratory analysis to study interlocus sexual conflict, and then describe four experiments using this approach with Drosophila melanogaster. The first experiment evaluates the efficacy of the laboratory model system to study interlocus sexual conflict by comparing remating rates of females when they are, or are not, provided with a spatial refuge from persistent male courtship. The second experiment tests for a lag-load in males that is due to adaptations that have accumulated in females, which diminish male-induced harm while simultaneously interfering with a male's ability to compete in the context of sexual selection. The third and fourth experiments test for a lag-load in females owing to direct costs from their interactions with males, and for the capacity for indirect benefits to compensate for these direct costs.     

Assessing accuracy and precision for field and laboratory data: a perspective in ecosystem restoration

Unlike most laboratory studies, rigorous quality assurance/quality control (QA/QC) procedures may be lacking in ecosystem restoration (“ecorestoration”) projects, despite legislative mandates in the United States. This is due, in part, to ecorestoration specialists making the false assumption that some types of data (e.g. discrete variables such as species identification and abundance classes) are not subject to evaluations of data quality. Moreover, emergent behavior manifested by complex, adapting, and nonlinear organizations responsible for monitoring the success of ecorestoration projects tend to unconsciously minimize disorder, QA/QC being an activity perceived as creating disorder. We discuss similarities and differences in assessing precision and accuracy for field and laboratory data. Although the concepts for assessing precision and accuracy of ecorestoration field data are conceptually the same as laboratory data, the manner in which these data quality attributes are assessed is different. From a sample analysis perspective, a field crew is comparable to a laboratory instrument that requires regular “recalibration,” with results obtained by experts at the same plot treated as laboratory calibration standards. Unlike laboratory standards and reference materials, the “true” value for many field variables is commonly unknown. In the laboratory, specific QA/QC samples assess error for each aspect of the measurement process, whereas field revisits assess precision and accuracy of the entire data collection process following initial calibration. Rigorous QA/QC data in an ecorestoration project are essential for evaluating the success of a project, and they provide the only objective “legacy” of the dataset for potential legal challenges and future uses.     

Sterilization of tissue-culture medium by filtration on a large laboratory scale

The design and operation of a permanently-piped plant for sterilizing 10–200 l. of tissue-culture media is described. The plant is sterilized in situ by steam injection, the filtration rate is 2–3 l./min., and the turn-around time for volumes of 100 l. is about 3 hr.     

A comprehensive internal quality control system for a large cytology laboratory

The British Columbia Cervical Cytology Program is operated through the Central Laboratory at the Cancer Control Agency in Vancouver and processes all of the gynecologic Papanicolaou smears collected by 3,200 physicians throughout the province of British Columbia. The laboratory receives approximately 2,400 smears per day, and the program currently processes in excess of 500,000 smears annually. This article describes the methods that have been developed for ensuring that adequate quality control is present in the screening and interpretation of half a million smears per year, both at the cytotechnologist and at the cytopathologist level. The results of the quality control program, which was considerably modified in 1985, are also presented. The modified program shows a significant improvement in the number of undercalled and overcalled cases detected in two comparable six-month periods.     

Effectiveness of IV cannulation skills laboratory training and its transfer into clinical practice: a randomized, controlled trial

Background

The effectiveness of skills laboratory training is widely recognized. Yet, the transfer of procedural skills acquired in skills laboratories into clinical practice has rarely been investigated. We conducted a prospective, randomised, double-blind, controlled trial to evaluate, if students having trained intravenous (IV) cannulation in a skills laboratory are rated as more professional regarding technical and communication skills compared to students who underwent bedside teaching when assessed objectively by independent video assessors and subjectively by patients.

Methodology and Principal Findings

84 volunteer first-year medical students were randomly assigned to one of two groups. Three drop-outs occurred. The intervention group (IG; n = 41) trained IV cannulation in a skills laboratory receiving instruction after Peyton''s ‘Four-Step Approach’. The control group (CG; n = 40) received a bedside teaching session with volunteer students acting as patients. Afterwards, performance of IV cannulation of both groups in a clinical setting with students acting as patients was video-recorded. Two independent, blinded video assessors scored students'' performance using binary checklists (BC) and the Integrated Procedural Protocol Instrument (IPPI). Patients assessed students'' performance with the Communication Assessment Tool (CAT) and a modified IPPI. IG required significantly shorter time needed for the performance on a patient (IG: 595.4 SD(188.1)s; CG: 692.7 SD(247.8)s; 95%CI 23.5 s to 45.1 s; p = 0.049) and completed significantly more single steps of the procedure correctly (IG: 64% SD(14) for BC items; CG: 53% SD(18); 95%CI 10.25% to 11.75%; p = 0.004). IG also scored significantly better on IPPI ratings (median: IG: 3.1; CG: 3.6; p = 0.015;). Rated by patients, students'' performance and patient-physician communication did not significantly differ between groups.

Conclusions

Transfer of IV cannulation-related skills acquired in a skills laboratory is superior to bedside teaching when rated by independent video raters by means of IPPI and BC. It enables students to perform IV cannulation more professionally on volunteer students acting as patients.     

Assessing the effects of chamber placement, manual sampling and headspace mixing on CH4 fluxes in a laboratory experiment

A laboratory experiment was conducted with two types of closed static chambers to estimate the effects of chamber placement, manual headspace sampling and headspace mixing on methane (CH₄) fluxes. Chamber fluxes were compared to a known reference flux in a chamber calibration system. The measurements were conducted with three types of soils (coarse dry, fine dry and fine wet quarts sand) at five flux levels ranging from 60 to 2000 ??g CH₄ m^?2 h^?1. We found that the placement of a non-vented chamber disturbed the initial CH₄ concentration development within the chamber headspace for 10 to 30 s. Excluding this short period from the flux calculation resulted in a lower flux estimate (mean±SE) of 126?±?26 ??g CH₄ m^?2 h^?1 compared to 134?±?26 ??g CH₄ m^?2 h^?1 if data from time zero of the enclosure were included. We also found that in non-mixed chambers (no fan mixing) the gas sampling by syringes or gas bottles disturbed the development of CH₄ concentration during the enclosure. Furthermore, flux estimates in non-mixed chambers were significantly underestimated (on average 36%) compared to the measured reference fluxes. However, the use of fans to constantly mix the chamber headspace during enclosure significantly improved the goodness-of-fit of the regression analysis used to calculate the flux and further eliminated the disturbance of the manual sampling on the concentration development. We recommend that chambers should be vented during the placement of the chamber, and that fans are used as an integrated part of static chambers while headspace mixing with syringes should be avoided.     

Using a module-based laboratory to incorporate inquiry into a large cell biology course

Because cell biology has rapidly increased in breadth and depth, instructors are challenged not only to provide undergraduate science students with a strong, up-to-date foundation of knowledge, but also to engage them in the scientific process. To these ends, revision of the Cell Biology Lab course at the University of Wisconsin-La Crosse was undertaken to allow student involvement in experimental design, emphasize data collection and analysis, make connections to the "big picture," and increase student interest in the field. Multiweek laboratory modules were developed as a method to establish an inquiry-based learning environment. Each module utilizes relevant techniques to investigate one or more questions within the context of a fictional story, and there is a progression during the semester from more instructor-guided to more open-ended student investigation. An assessment tool was developed to evaluate student attitudes regarding their lab experience. Analysis of five semesters of data strongly supports the module format as a successful model for inquiry education by increasing student interest and improving attitude toward learning. In addition, student performance on inquiry-based assignments improved over the course of each semester, suggesting an improvement in inquiry-related skills.     

Assessing the complex sponge microbiota: core,variable and species-specific bacterial communities in marine sponges

Marine sponges are well known for their associations with highly diverse, yet very specific and often highly similar microbiota. The aim of this study was to identify potential bacterial sub-populations in relation to sponge phylogeny and sampling sites and to define the core bacterial community. 16S ribosomal RNA gene amplicon pyrosequencing was applied to 32 sponge species from eight locations around the world''s oceans, thereby generating 2567 operational taxonomic units (OTUs at the 97% sequence similarity level) in total and up to 364 different OTUs per sponge species. The taxonomic richness detected in this study comprised 25 bacterial phyla with Proteobacteria, Chloroflexi and Poribacteria being most diverse in sponges. Among these phyla were nine candidate phyla, six of them found for the first time in sponges. Similarity comparison of bacterial communities revealed no correlation with host phylogeny but a tropical sub-population in that tropical sponges have more similar bacterial communities to each other than to subtropical sponges. A minimal core bacterial community consisting of very few OTUs (97%, 95% and 90%) was found. These microbes have a global distribution and are probably acquired via environmental transmission. In contrast, a large species-specific bacterial community was detected, which is represented by OTUs present in only a single sponge species. The species-specific bacterial community is probably mainly vertically transmitted. It is proposed that different sponges contain different bacterial species, however, these bacteria are still closely related to each other explaining the observed similarity of bacterial communities in sponges in this and previous studies. This global analysis represents the most comprehensive study of bacterial symbionts in sponges to date and provides novel insights into the complex structure of these unique associations.