A compact lighting system for use with portable leaf chambers to measure photosynthesis

Abstract. A compact, portable lighting system, developed for the measurement of photosynthesis in the field with portable chambers and applicable to the laboratory, is described. The system consists of a miniature 50-W, 12-V tungsten-halogen lamp and a light guide which is constructed with randomized fibre bundles and mounted above the window of a portable assimilation chamber. The light guide distributes light uniformly across the leaf surface; the photon irradiance at the leaf surface is monitored by measuring the irradiant emitted from one fibre-optic bundle using a sensor connected to the body of the light guide. Up to 1600 μmol quanta photosynthetic active radiation m⁻²s⁻¹ may be achieved at the leaf surface; irradiance may be varied by wire mesh screens of different densities. Leaf temperature follows air temperature outside the chamber to within ±2 °C over the range 10–30 °C and within the range of photon irradiances from 0 to 1600/μmol quanta m ⁻²s. The power supply for the lamp is a 12-V, 24-A h lead-acid battery and the photon irradiance at the leaf surface gradually decreases by c. 3% over 2.5 h of measurement. With this system, response of photosynthetic rate to irradiance and to CO₂ partial pressure at constant irradiance may be measured in the field, independent of natural variations in solar irradiance.     

Temperature gradient chambers for research on global environment change. I. Portable chambers for research on short-stature vegetation

Field temperature gradient chambers designed for experiments on short-stature plants such as wheat are deseribed. The chambers are portable, easily erected and dismantled, and are self-contained for control and measuring equipment. The design is modular, the modules being bolted together longitudinally although separated by slotted transparent septa which divide the chamber into zones of different temperature. Fresh air, which is blown in horizontally into one end of the chamber by two fans and extracted by a fan mounted vertically at the other end, passes sequentially through the modules. The air stream progressively heats when the sun is shining. Fans are automatically speed-controlled in 100 steps between 20 and 100% of full output to keep the end-to-end temperature difference to within 5°C. During darkness, when the fans are running at minimum speed, heaters mounted in the outlet module are turned on. The chambers in the configuration described enclose 6 × 8m rows of crop, are l-25m high and have side walls which are entirely composed of rigid, vertically sliding doors for crop access.     

A genetic role of isozyme types in plasma alkaline phosphatase activity in the young chicken

A genetic role of isozyme types in plasma alkaline phosphatase (AP) activity within dam families in the young chicken was investigated in a White Plymouth Rock strain kept in our laboratory since 1961. Plasma samples were obtained at 32 and 56 days of age and subjected to horizontal polyacrylamide gel electrophoresis and two methods of analysis.
A higher level of plasma AP activity of the fast (F) type relative to that of slow (S) type was re-confirmed. The F types of full-sib chicks had distinctly higher AP activity than the S types. Also within isozyme types, family differences were significant in the F type but not in the S type. The correlation of AP activities between 32 and 56 days of age was significant in the F type but not in the S type, which could be attributed to the effect of aging. The genetic control of plasma AP activity in young chickens were discussed under a hypothesis of two independent genetic systems, i.e. major genie and polygenic.     

Miniature RT-PCR system for diagnosis of RNA-based viruses

This paper presents an innovative portable chip-based RT-PCR system for amplification of specific nucleic acid and detection of RNA-based viruses. The miniature RT-PCR chip is fabricated using MEMS (Micro-electro-mechanical-system) techniques, and comprises a micro temperature control module and a PDMS (polydimethylsiloxane)-based microfluidic control module. The heating and sensing elements of temperature control module are both made of platinum and are located within the reaction chambers in order to generate a rapid and uniform thermal cycling. The microfluidic control module is capable of automating testing process with minimum human intervention. In this paper, the proposed miniature RT-PCR system is used to amplify and detect two RNA-based viruses, namely dengue virus type-2 and enterovirus 71 (EV 71). The experimental data confirm the ability of the system to perform a two-step RT-PCR process. The developed miniature system provides a crucial tool for the diagnosis of RNA-based viruses.     

A genetic role of isozyme types in plasma alkaline phosphatase activity in the young chicken.

A genetic role of isozyme types in plasma alkaline phosphatase (AP) activity within dam families in the young chicken was investigated in a White Plymouth Rock strain kept in our laboratory since 1961. Plasma samples were obtained at 32 and 56 days of age and subjected to horizontal polyacrylamide gel electrophoresis and two methods of analysis. A higher level of plasma AP activity of the fast (F) type relative to that of slow (S) type was re-confirmed. The F types of full-sib chicks had distinctly higher AP activity than the S types. Also within isozyme types, family differences were significant in the F type but not in the S type. The correlation of AP activities between 32 and 56 days of age was significant in the F type but not in the S type, which could be attributed to the effect of aging. The genetic control of plasma AP activity in young chickens were discussed under a hypothesis of two independent genetic systems, i.e. major genic and polygenic.     

A portable microelectrode array recording system incorporating cultured neuronal networks for neurotoxin detection

Cultured neuronal networks, which have the capacity to respond to a wide range of neuroactive compounds, have been suggested to be useful for both screening known analytes and unknown compounds for acute neuropharmacologic effects. Extracellular recording from cultured neuronal networks provides a means for extracting physiologically relevant activity, i.e. action potential firing, in a noninvasive manner conducive for long-term measurements. Previous work from our laboratory described prototype portable systems capable of high signal-to-noise extracellular recordings from cardiac myocytes. The present work describes a portable system tailored to monitoring neuronal extracellular potentials that readily incorporates standardized microelectrode arrays developed by and in use at the University of North Texas. This system utilizes low noise amplifier and filter boards, a two-stage thermal control system with integrated fluidics and a graphical user interface for data acquisition and control implemented on a personal computer. Wherever possible, off-the-shelf components have been utilized for system design and fabrication. During use with cultured neuronal networks, the system typically exhibits input referred noise levels of only 4-6 microVRMS, such that extracellular potentials exceeding 40 microV can be readily resolved. A flow rate of up to 1 ml/min was achieved while the cell recording chamber temperature was maintained within a range of 36-37 degrees C. To demonstrate the capability of this system to resolve small extracellular potentials, pharmacological experiments with cultured neuronal networks have been performed using ion channel blockers, tetrodotoxin and tityustoxin. The implications of the experiments for neurotoxin detection are discussed.     

Par-1 and Tau regulate the anterior-posterior gradient of microtubules in Drosophila oocytes

The formation of an anterior-posterior (AP) gradient of microtubules in Drosophila oocytes is essential for specification of the AP axis. Proper microtubule organization in the oocyte requires the function of serine/threonine kinase Par-1. The N1S isoform of Par-1 is enriched at the posterior cortex of the oocyte from stage 7 of oogenesis. Here we report that posterior restriction of Par-1 (N1S) kinase activity is critical for microtubule AP gradient formation. Egg chambers with excessive and ectopic Par-1 (N1S) kinase activity in the germline cells display phenotypes similar to those of egg chambers treated with the microtubule-depolymerizing drug colcemid: depolymerization of microtubules in the oocyte and disruption of oocyte nucleus localization. A phosphorylation target of Par-1, the microtubule-associated protein Tau, is also involved in oocyte polarity formation, and overexpression of Tau alleviates the phenotypes caused by ectopic Par-1 (N1S) kinase activity, suggesting that Par-1 regulates oocyte polarity at least partly through Tau. Our findings reveal that maintaining proper levels of Par-1 at correct position in the oocyte is key to oocyte polarity formation and that the conserved role of Par-1 and Tau is crucial for the establishment of an AP gradient of microtubules and for AP axis specification.     

Miniature RT–PCR system for diagnosis of RNA-based viruses

This paper presents an innovative portable chip-based RT–PCR system for amplification of specific nucleic acid and detection of RNA-based viruses. The miniature RT–PCR chip is fabricated using MEMS (Micro-electro-mechanical-system) techniques, and comprises a micro temperature control module and a PDMS (polydimethylsiloxane)-based microfluidic control module. The heating and sensing elements of temperature control module are both made of platinum and are located within the reaction chambers in order to generate a rapid and uniform thermal cycling. The microfluidic control module is capable of automating testing process with minimum human intervention. In this paper, the proposed miniature RT–PCR system is used to amplify and detect two RNA-based viruses, namely dengue virus type-2 and enterovirus 71 (EV 71). The experimental data confirm the ability of the system to perform a two-step RT–PCR process. The developed miniature system provides a crucial tool for the diagnosis of RNA-based viruses.     

Schizosaccharomyces pombe encodes a mutated AP endonuclease 1

Mutagenic and cytotoxic apurinic/apyrimidinic (AP) sites are among the most frequent lesions in DNA. Repair of AP sites is initiated by AP endonucleases and most organisms possess two or more of these enzymes. Saccharomyces cerevisiae has AP endonuclease 1 (Apn1) as the major enzymatic activity with AP endonuclease 2 (Apn2) being an important backup. Schizosaccharomyces pombe also encodes two potential AP endonucleases, and Apn2 has been found to be the main repair activity, while Apn1 has no, or only a limited role in AP site repair. Here we have identified a new 5' exon (exon 1) in the apn1 gene and show that the inactivity of S. pombe Apn1 is due to a nonsense mutation in the fifth codon of this new exon. Reversion of this mutation restored the AP endonuclease activity of S. pombe Apn1. Interestingly, the apn1 nonsense mutation was only found in laboratory strains derived from L972 h(-) and not in unrelated isolates of S. pombe. Since all S. pombe laboratory strains originate from L972 h(-), it appears that all experiments involving S. pombe have been conducted in an apn1(-) mutant strain with a corresponding DNA repair deficiency. These observations have implications both for future research in S. pombe and for the interpretation of previously conducted epistatis analysis.     

Minitron II system for precise control of the plant growth environment

A transparent, cylindrical chamber system was developed to allow measurement of gas-exchange by small crop canopies in the undisturbed plant growth environment. The system is an elaboration of the Minitron system developed previously to compare growth of small plants in different environments within the same general growth area. The Minitron II system described herein accommodates hydroponic culture and separate control of atmospheric composition in individual chambers. Root and shoot environments are compartmented separately to accommodate atmospheres of different flow rate and/or gaseous composition. A series of 0-rings and tension-adjustable springs allow carbon dioxide in the flowing atmosphere to be analyzed without cross-contamination between chamber compartments or from external gas sources. Carbon dioxide has been maintained at set point +/- 9 g m-3 over a range of CO2 concentrations from 382 to 2725 g m-3 and with an atmosphere turnover rate of 136.7 cm3 s-1 by computer-assisted mass flow controllers. Each chamber has dimensions large enough (61 cm internal diameter, 0.151 m3 internal volume) to allow adequate replication of individual plants for statistical purposes (e.g., up to 36 equally-spaced plant holders). No significant variation in growth or photosynthetic rate of leaf lettuce occurred between chambers for a given set of environmental conditions. Gas-exchange rates in different chambers changed to a similar extent as CO2 concentration in the flowing atmosphere or chamber temperature were varied by the same amount. When coupled with appropriate control systems, Minitron II chambers can provide separate controlled environments for multiple small plants with adequate precision and at relatively low cost.     

THE THERMAL SIGNIFICANCE OF THE NEST OF THE SOCIABLE WEAVER PHILETAIRUS SOCIUS: SUMMER OBSERVATIONS

Extending a previous study of the thermal significance of the nest of the Sociable Weaver carried out during the winter, we measured temperature and humidity in the matrix and chambers of a large nest of this species in the Kalahari Gemsbok National Park, South Africa, during the austral summer of December 1973. Air temperatures outside the nest ranged from 16 to 33.5°C but temperatures in occupied chambers varied over a range of only 7 or 8°C and remained well within the zone of thermal neutrality for a passerine bird of this size. Compared to outside air temperatures, those within the nest matrix were lower during the day and higher at night. Thus, the nest ameliorates the effects of external temperatures and allows maintenance inside the chambers of a range of temperature favourable to the birds. In winter we found up to five roosting adults per chamber, with some chambers left empty. In the same nest in summer we found no more than two adults per chamber but virtually all chambers were occupied. The principal mechanism for maintaining chambers within the zone of minimal energetic cost is changes in the number of birds in the nest chambers at night. Humidity inside the occupied and unoccupied chambers was somewhat higher in the former but always less than that of outside air in both cases. Air movement through the desiccated nest materials causes uptake by these materials of most of the water vapour introduced by the birds, and this moisture is dissipated to the outside during the day so that the nest remains dry. The highly social and colonial habits of the birds and their year-round occupancy and maintenance of the nest favour a system of opportunistic breeding that may be initiated by rainfall at any season. Larger nests provide the most favourable environment for energy conservation and successful reproduction. Even the largest nests, however, do not prevent predation during the warm season by snakes such as the Cape Cobra, which may consume all the eggs and young in all the chambers of a large nest. The effects of such heavy predation may be offset by the birds' capability for breeding during times too cold for reptile activity. It seems likely that in smaller nests such as those on telephone poles, lack of predation would favour summer breeding while thermal problems would limit breeding success in winter. In larger nests, breeding success may be lower in summer because of predation and higher in winter when reptile predation is lacking and thermal problems are minimized by the nest structure. The large nest not only makes possible the success of the Sociable Weaver in desert areas, but the nest could only exist in such areas and the species' range is thereby restricted. Higher humidity and heavier rainfall would cause fermentation within the nest mass, loss of its thermoregulatory advantages, and ultimately its decomposition and destruction. Therefore, the unique nesting system of the Sociable Weaver appears to be initially self-reinforcing and ultimately self-limiting.     

Quality indicators to detect pre-analytical errors in laboratory testing

Pre-analytical steps, the major source of mistakes in laboratory diagnostics, arise during patient preparation, sample collection, sample transportation, sample preparation, and sample storage. However, while it has been reported that the pre-analytical phase is error-prone, only recently has it been demonstrated that most errors occur in the 'pre-pre-analytical phase'. This comprises the initial procedures of the testing process performed by healthcare personnel outside the laboratory walls and outside the direct control of the clinical laboratory. Quality indicators (QIs) should therefore cover all steps in the pre-analytical phase, from test requesting to sample storage. In the present paper, the state-of-the-art of QIs in laboratory testing is described. The focus is on the experience of a working group of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) in developing a model of QIs, 16 of which concern the pre-analytical phase.     

Detection of endogenous alkaline phosphatase activity in intact cells by flow cytometry using the fluorogenic ELF-97 phosphatase substrate.

BACKGROUND: The alkaline phosphatase (AP) substrate 2-(5'-chloro-2'-phosphoryloxyphenyl)-6-chloro-4-(3H)-quinazolinone (ELF((R))-97 for enzyme-labeled fluorescence) has been found useful for the histochemical detection of endogenous AP activity and AP-tagged proteins and oligonucleotide probes. In this study, we evaluated its effectiveness at detecting endogenous AP activity by flow cytometry. METHODS: The ELF-97 phosphatase substrate was used to detect endogenous AP activity in UMR-106 rat osteosarcoma cells and primary cultures of chick chondrocytes. Cells were labeled with the ELF-97 reagent and analyzed by flow cytometry using an argon ultraviolet (UV) laser. For comparison purposes, cells were also assayed for AP using a Fast Red Violet LB azo dye assay previously described for use in detecting AP activity by flow cytometry. RESULTS: The ELF-97 phosphatase substrate effectively detected endogenous AP activity in UMR-106 cells, with over 95% of the resulting fluorescent signal resulting from AP-specific activity (as determined by levamisole inhibition of AP activity). In contrast, less than 70% of the fluorescent signal from the Fast Red Violet LB (FRV) assay was AP-dependent, reflecting the high intrinsic fluorescence of the unreacted components. The ELF-97 phosphatase assay was also able to detect very low AP activity in chick chondrocytes that was undetectable by the azo dye method. CONCLUSIONS: The ELF-97 phosphatase assay was able to detect endogenous AP activity in fixed mammalian and avian cells by flow cytometry with superior sensitivity to previously described assays. This work also shows the applicability of ELF-97 to flow cytometry, supplementing its previously demonstrated histochemical applications.     

A novel environmental chamber for neuronal network multisite recordings

Environmental stability is a critical issue for neuronal networks in vitro. Hence, the ability to control the physical and chemical environment of cell cultures during electrophysiological measurements is an important requirement in the experimental design. In this work, we describe the development and the experimental verification of a closed chamber for multisite electrophysiology and optical monitoring. The chamber provides stable temperature, pH and humidity and guarantees cell viability comparable to standard incubators. Besides, it integrates the electronics for long‐term neuronal activity recording. The system is portable and adaptable for multiple network housings, which allows performing parallel experiments in the same environment. Our results show that this device can be a solution for long‐term electrophysiology, for dual network experiments and for coupled optical and electrical measurements. Biotechnol. Bioeng. 2012; 109: 2553–2566. © 2012 Wiley Periodicals, Inc.     

Design and Construction of an Inexpensive Homemade Plant Growth Chamber

Plant growth chambers produce controlled environments, which are crucial in making reproducible observations in experimental plant biology research. Commercial plant growth chambers can provide precise controls of environmental parameters, such as temperature, humidity, and light cycle, and the capability via complex programming to regulate these environmental parameters. But they are expensive. The high cost of maintaining a controlled growth environment is often a limiting factor when determining experiment size and feasibility. To overcome the limitation of commercial growth chambers, we designed and constructed an inexpensive plant growth chamber with consumer products for a material cost of $2,300. For a comparable growth space, a commercial plant growth chamber could cost $40,000 or more. Our plant growth chamber had outside dimensions of 1.5 m (W) x 1.8 m (D) x 2 m (H), providing a total growth area of 4.5 m² with 40-cm high clearance. The dimensions of the growth area and height can be flexibly changed. Fluorescent lights with large reflectors provided a relatively spatially uniform photosynthetically active radiation intensity of 140–250 μmoles/m²/sec. A portable air conditioner provided an ample cooling capacity, and a cooling water mister acted as a powerful humidifier. Temperature, relative humidity, and light cycle inside the chamber were controlled via a z-wave home automation system, which allowed the environmental parameters to be monitored and programmed through the internet. In our setting, the temperature was tightly controlled: 22.2°C±0.8°C. The one-hour average relative humidity was maintained at 75%±7% with short spikes up to ±15%. Using the interaction between Arabidopsis and one of its bacterial pathogens as a test experimental system, we demonstrate that experimental results produced in our chamber were highly comparable to those obtained in a commercial growth chamber. In summary, our design of an inexpensive plant growth chamber will tremendously increase research opportunities in experimental plant biology.     

Microfluidic immunoaffinity separations for bioanalysis

Microfluidic devices often rely on antibody-antigen interactions as a means of separating analytes of interest from sample matrices. Immunoassays and immunoaffinity separations performed in miniaturized formats offer selective target isolation with minimal reagent consumption and reduced analysis times. The introduction of biological fluids and other complicated matrices often requires sample pretreatment or system modifications for compatibility with small-scale devices. Miniaturization of external equipment facilitates the potential for portable use such as in patient point-of-care settings. Microfluidic immunoaffinity systems including capillary and chip platforms have been assembled from basic instrument components for fluid control, sample introduction, and detection. The current review focuses on the use of immunoaffinity separations in microfluidic devices with an emphasis on pump-based flow and biological sample analysis.     

A fully automated and highly versatile system for testing multi-cognitive functions and recording neuronal activities in rodents

We have developed a fully automated system for operant behavior testing and neuronal activity recording by which multiple cognitive brain functions can be investigated in a single task sequence. The unique feature of this system is a custom-made, acoustically transparent chamber that eliminates many of the issues associated with auditory cue control in most commercially available chambers. The ease with which operant devices can be added or replaced makes this system quite versatile, allowing for the implementation of a variety of auditory, visual, and olfactory behavioral tasks. Automation of the system allows fine temporal (10 ms) control and precise time-stamping of each event in a predesigned behavioral sequence. When combined with a multi-channel electrophysiology recording system, multiple cognitive brain functions, such as motivation, attention, decision-making, patience, and rewards, can be examined sequentially or independently.     

Novel device for quick measurement of glucose in POCT areas without pre‐analytical steps based on a multi‐way glucose biosensor

Professional Point of Care testing demands rapid analysis and professional quality. To assure rapid analysis of high quality the analytical tool ideally should be able to work without sample pre‐treatment and should offer the opportunity to calibrate and/or control the analytical performance of the tool. In contrast to an enormous number of different disposable‐strips used for patient self monitoring today and based on an extended knowledge with respect to multi‐way biosensors used in laboratory analyzers we decided to develop a professional Point of Care Testing system for glucose analysis based on a multi‐way biosensor. The multi‐way glucose biosensor placed in the instrument for 30 days did reduce the lag time between blood withdrawal and availability of a result of lab quality in a bedside area to about 10 seconds. No pre‐analytical steps are necessary for measuring capillary whole blood, no crossing over was observed, and the data could be transferred into a laboratory information system or a hospital information system. Thus, we were able to realize tools for professional health control able to measure glucose values in laboratory quality at places outside laboratories: e.g., in doctor's offices, hospital wards, critical care units, and training units of athletes. By combining the advantages of laboratory analyzers (high quality and low sample price) and the advantages of disposable strips (simple procedure and immediate results after sample withdrawal) with the Glukometer 3000 and LactatProfi 3000 we did start to fill the gap between the two basic technologies available on the market for diagnosis today. Glukometer 3000 and LactatProfi 3000 are worldwide the first and only mobile glucose and lactate measuring instruments for decentralized locations based on multi‐way biosensors.     

A Battery‐Like Self‐Charge Universal Module for Motional Energy Harvest

Wearable and portable electronics have brought great convenience. These battery‐powered commercial devices have a limited lifetime and require recharging, which makes more extensive applications challenging. Here, a battery‐like self‐charge universal module (SUM) is developed, which is able to efficiently convert mechanical energy into electrical energy and store it in one device. An integrated SUM consists of a power management unit and an energy harvesting unit. Compared to other mechanical energy harvesting devices, SUM is more ingenious, efficient and can be universally used as a battery. Under low frequency (5 Hz), a SUM can deliver an excellent normalized output power of 2 mW g^?1. After carrying several SUMs and jogging for 10 min, a commercial global positioning system module is powered and works continuously for 0.5 h. SUMs can be easily assembled into different packages for powering various commercial electronics, demonstrating the great application prospects of SUM as a sustainable battery‐like device for wearable and portable electronics.     

Ultrasonic particle-concentration for sheathless focusing of particles for analysis in a flow cytometer.

BACKGROUND: The development of inexpensive small flow cytometers is recognized as an important goal for many applications ranging from medical uses in developing countries for disease diagnosis to use as an analytical platform in support of homeland defense. Although hydrodynamic focusing is highly effective at particle positioning, the use of sheath fluid increases assay cost and reduces instrument utility for field and autonomous remote operations. METHODS: This work presents the creation of a novel flow cell that uses ultrasonic acoustic energy to focus small particles to the center of a flowing stream for analysis by flow cytometry. Experiments using this flow cell are described wherein its efficacy is evaluated under flow cytometric conditions with fluorescent microspheres. RESULTS: Preliminary laboratory experiments demonstrate acoustic focusing of flowing 10-microm latex particles into a tight sample stream that is approximately 40 microm in diameter. Prototype flow cytometer measurements using an acoustic-focusing flow chamber demonstrated focusing of a microsphere sample to a central stream approximately 40 microm in diameter, yielding a definite fluorescence peak for the microspheres as compared with a broad distribution for unfocused microspheres. CONCLUSIONS: The flow cell developed here uses acoustic focusing, which inherently concentrates the sample particles to the center of the sample stream. This method could eliminate the need for sheath fluid, and will enable increased interrogation times for enhanced sensitivity, while maintaining high particle-analysis rates. The concentration effect will also enable the analysis of extremely dilute samples on the order of several particles per liter, at analysis rates of a few particles per second. Such features offer the possibility of a truly versatile low-cost portable flow cytometer for field applications.