Reproducibility Of Experimental Results Research Articles

Herbaria and Botanic Gardens as the memory of biological diversity

Abstract In order to fully understand biological diversity of plants, it is necessary to study their genetic and metabolic-functional aspects. However, it is also necessary to identify with utmost precision the kind of organism under study, to allow the reproducibility of experimental results. Within this context, a major role is played by Botanic Gardens and Herbaria, where the investigated specimens are cultivated and kept as exsiccata, respectively, as a memory of plant diversity. After pointing out the role of herbaria in reference to the typologic concept of species, the author mentions the recent advances made possible by PCR techniques and RAPD markers in the analysis of the species and of the evolutionary relationships amongst allied taxa. Systematics, as study of diversity, is a modern and fascinating science.

Experimental Strategy to Study the pH Dependence of the Kinetic Behavior of Enzymes: Practical Application to Chicken Liver Xanthine Dehydrogenase

An experimental strategy has been developed to analyze the pH dependence of kinetic parameters in two-substrate enzyme kinetics based upon model discrimination, parameter refinement, and optimal discrete design. The experimental protocol proposed includes obtaining reproducible experimental results in different sessions, replicates of each experimental determination, and rejection of outliers. This strategy leads to an empirical kinetic equation that fits the experimental results. As a practical application of this strategy we studied the pH dependence of kinetic parameters of chicken liver xanthine dehydrogenase. We obtained an empirical rate law from the determination of the initial rates at different substrate concentrations and pH. Finally, we have proposed a plausible kinetic mechanism that may explain the experimental findings. This model is not the only one leading to the empirical equation, but it is based on previous experimental findings (Bruguera, P., López-Cabrera, A., and Canela, E. I., 1988, Biochem. J. 249, 171-178).

The Use of Robots and Computers in the Organisation of Studies on the orcadian Variation of β2-Adrenoceptor Sites in Peripheral Mononuclear Leucocytes

We have developed a partially automated method for the performance of equilibrium radioligand binding studies which is applied by our group in investigations on circadian variations and stimulation studies on beta 2-adrenoceptor sites in human peripheral mononuclear leucocytes (pMNL). Using a Tecan Robotic Sample Processor, binding assays with 12 concentrations of 125iodocyanopindolol (1-150 pmol/l, total binding in triplicates, unspecific binding in the presence of 10(-5) mol/l timolol in duplicates) are prepared automatically with all titer tubes per experiment arranged in a microtiterplate-sized rack. After incubation in a waterbath for 2hr at 37 degrees C, the whole rack is centrifuged at 5000g and transferred back to the lab robot. Bound radioactivity is separated from the unbound ligand by removing the supernatant by the machine. The radioactive counts are evaluated using personal computers. The lab robot enhances reproducibility of experimental results and frees lab workers from time-consuming pipetting jobs. Radioactive exposure is minimized to the time preparing the radioligand working solution and transferring the sample tubes from the robot to the waterbath, to the centrifuge and back to the robot. The variability of our software allows easy adaptation to other binding studies with intact cells.

A Steady‐State Multiplicity Analysis of a Kinetic Model for Zinc Electrodeposition: Mapping of Parameter Regions with Specific Numbers of Solutions

The application of singularity theory to the investigation of the steady‐state multiplicity features of electrochemical systems is demonstrated by an analysis of a nonlinear kinetic model of zinc electrodeposition proposed previously by Epelboin and co‐workers. This analysis systematically determines and maps the regions in [Zn2+]‐pH or E‐pH space where different numbers of solutions for the steady‐state current can exist. This information is crucial for the understanding of certain electrode behavior, such as oscillations, fluctuations, and chaos, that is often observed experimentally during the electrodeposition of zinc and other metals. It can also explain why it is often difficult to achieve reproducible experimental results and why hysteresis effects can occur. Examples of current‐potential curves predicted by the model for zinc electrodeposition are also discussed.

Characterization of Micro-Babington and Cross-Flow Type Nebulizers for Inductively Coupled Plasma Atomic Emission Spectrometry

The use of Inductively Coupled Plasma Atomic Emission Spectrometry (ICP/AES) for the analysis of samples which contain either low or high amounts of dissolved solids and/or suspended particles has become common in recent years because of the high sensitivities and multielement capability of this technique. One of the major concerns associated with ICP/AES is the reproducible introduction of the sample aerosol into the plasma. This parameter is commonly thought of as the limiting factor in the reproducibility of experimental results. Although traditional pneumatic nebulizers, such as crossflow or concentric types, can be used for samples containing low amounts of dissolved solids, such nebulizers cannot be used for samples which contain suspended particles and/or high amounts of dissolved solids, because of the possible clogging of the sample capillary. For such samples, either frit, ultrasonic, or Babington-type nebulizers are commonly employed.

Optimum DC current resolution of a ferromagnetic-core flux transformer coupled SQUID instrument

This paper describes theoretical and reproducible experimental results for a ferromagnetic-core (VITROVAC) flux transformer coupled SQUID instrument with equivalent noise temperatures x Al 1−x As heterostructures.

Selective removal of water in purge and cold‐trap capmary gas chromatographic analysis of volatile organic traces in aqueous samples

AbstractThe design and features of an on‐line purge and cold‐trap pre‐concentration device for rapid analysis of volatile organic compounds in aqueous samples are discussed. Excessive water is removed from the purge gas by a condenser or a water permeable membrane in order to avoid blocking of the capillary cold‐trap. Synthetic mixtures covering concentrations ranging from tenths to tens of ppb's and different chemical classes are used to study the effect of various process factors on the efficiency and selectivity of water removal as well as on the purging recovery. The importance of the concentration of the solutes, the flow rate in conjunction with the volume of the purge gas, and the temperature of the condenser, the cold‐trap and the sample is emphasized. Theoretical models describing the purge process and the blocking of the cold‐trap agree fairly well with the highly reproducible experimental results (σ = 2–4%). Both the condenser and the Nafion membrane successfully remove water, although some compounds, dependent on volatility and polarity, are partly or completely lost. It is shown that non‐polar volatile organic compounds are efficiently enriched so that recoveries between 80–100% and a detection limit of 1 ppt can be obtained. The applicability of the system is illustrated on some examples.

CHANGES IN SERUM IMMUNOGLOBULIN LEVELS AND NEUTROPHILIC PHAGOCYTOSIS AFTER EXERCISE

This paper is intended to give the information we need about personal reactivity to transient loads for the object of estimating human physical fitness. For this purpose, both serum immunoglobulin levels and neutrophilic phagocytosis were assayed as indices to self-defense activities.To determine the later described reproducibility of experimental results, two independent experiments were made on two different groups -one consisting of twelve and the other of fourteen male voluntary students of our college- exercised in the playgroud. The serum levels of three immunoglobulins (IgG, IgA and IgM) and two complements (C3 and C4), prior to and immediately after exercise, were compared with each other. They rose without exception after exercise.Paired T-test revealed that in the group of twelve students, rises in IgG, IgA, C3, α-1-antitrypsin and transferrin were significant at P<0.1%, 5%, 5%, 5% and 0.1%, and in the group of fourteen rises in IgG, IgA, IgM, C 3, C 4, α-1-antitrypsin and transferrin were significant at P<1%, 0.1%, 1%, 0.1%, 0.1%, 0.1% and 0.1%, respectively.In the meantime, the neutrophilic phagocytosis (%) was significantly decreased immediately after exercise in both groups (P-<1% and P-<0.1% respectively) .

Studies on the mechanics of the normal human middle ear.

The middle ear was studied in temporal bone preparations using a laser-Doppler interferometer. For measurements at a sound level of 80 dB SPL this method proved to be very reliable, as was shown by good reproducibility of results in experiments over more than 6 hours. The vibrations of the tympanic membrane and stapes footplate were studied from 200 Hz to 10 KHz and the results demonstrate a piston-like movement of the stapes footplate up to 120 dB SPL. The damping effect of the normal ear is located mainly at the footplate/cochlea level and the middle ear cavity per se does not contribute significantly to the stiffness of the middle ear system.

Malfunction of intestinal mucus and mucus production.

The mucus layer is a complex, frustrating, sheet of proteins, glycoproteins, cells, bacteria, ions and water which covers and presumably protects, underlying epithelial cells, while remaining sufficiently porous to permit the passage of vital nutrients and secretions. The possibilities for malfunction are real and varied. It seems evident that thinning of the layer may predispose the intestine to ulceration and inflammation, while thickening may lead to obstruction of bronchi and small ductules as in cystic fibrosis. Porosity may be affected by cross-linking agents such as drugs (Kellaway and Marriot, 1975; Braybrooks, et al., 1975) and in unknown ways a change in porosity may affect the passage of spermatozoa causing infertility fDavajan, et al., 1971)- The mechanisms underlying these disorders are not well understood partially because of the nature of mucus itself. It is too heterogeneous and varied for simple characterization, and without an adequate description of each batch, reproducibility of experimental results beyond the most superficial level of enquiry is almost impossible. Fortunately the major glycoprotein or mucin components can be isolated, purified and manipulated in a reproducible manner and examination of these molecules can tell us much about the behaviour of the mucus.KeywordsCystic FibrosisSialic AcidMucus LayerMucus ProductionIntestinal MucusThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Ignition on catalytic wires: Kinetic parameter determination by the heated‐wire technique

AbstractA new analysis is presented for the extraction of Arrhenius parameters from experimental measurements of ignition temperatures during catalytic oxidation over electrically‐heated metal wires. Butane oxidation on high purity platinum wires has yielded reproducible experimental results for the reaction rate and has provided consistent estimates of the Arrhenius parameters. First‐order kinetics was assumed. The present treatment contains explicit consideration of: (1) the ohmic heating term; and (2) the end conduction heat loss from the catalytic wire. The effects of wire length, diameter, and configuration are reconciled when the ignition phenomenon is refferred to the center‐point temperature of the wire.

INTERORGANISMIC AND ENVIRONMENTAL INFLUENCES THROUGH EXTREMELY WEAK ELECTROMAGNETIC FIELDS

1. The mean rate of water uptake by beans during the first four hours of their submergence in water varies substantially from day to day, even when in presumed "constant" conditions. 2. The variations in rate in independent samples at different laboratory sites and even at widely different geographic ones may show a strong positive correlation not explicable in terms of variations in any obvious factor. 3. Superimposed on a major positively correlating state, is a secondary, shorter period fluctuation wherein the correlation between different groups of samples may exhibit either a positive or a negative correlation. 4. Groups of organisms in closely juxtaposed vessels may bias one another to adopt opposite sign of correlation under some conditions and the same sign under others. 5. This interorganismic biasing may be prevented by having the paired vessels in the very weak field of a very slowly rotating (2 rpm, CW) horizontal bar magnet, or by separating the vessels by 70 cm or more. In either case, the separate vessels then appear to correlate positively and negatively with about equal frequency, indicating independence of one another. 6. Pairs of vessels upon rotating tables at 6 rpm are modified in their interactions in manners dependent upon direction of rotation. Other factors equal, CW rotation appears to favor positive correlation between members of pairs, CCW rotation favors negative correlation. 7. Platform rotation even at the very slow rate of one revolution a day (CW) appears to effect an alteration in the character of the interaction between closely apposed bean samples. 8. Partial electrical shielding by copper plates and experimental alteration of the ambient background radiation by a lead plate modify the rate of water uptake by beans. 9. The interactions between organisms and organisms and their subtle physical environment as they determine positively and negatively correlating states are able to yield biological differences, even on the order of a 2-fold range, concurrently and under the same conditions of all obvious environmental factors. 10. Parallel and concurrent variations in bean samples as widely separated as Woods Hole, Massachusetts and Evanston, Illinois, suggest wide geographic scope of at least one of the major effective subtle parameters. 11. The nature of the phenomenon for beans is of such character that it appears probable that the living embryo within the dried seed possesses the capacity to regulate to a substantial degree the rate of water absorption by the seed upon its submergence. 12. On the presumption that the phenomenon that has been treated herein is a universal biological one, the implications of these findings are great. They relate to (a) reproducibility of experimental results, (b) biological influence of the weak fields of diverse facilities and equipment employed for measurement of biological phenomena, (c) additional and subtle means through which man's alteration of his environment may influence living creatures and (d) potential practical applications of knowledge of the subject for the health sciences.

An Apparatus for the Microslide Immunodiffusion

Immunological methods of analysis have recently come to be used more and more in food inspections. These methods require the availability of high-grade anti-sera, and they also demand farreaching standardization of all parameters, important to the method. The author describes an apparatus which makes it possible to carry out immuno-chemical separation in the microscale. In food inspection, substances such as milk, soybean and egg protein, blood plasma, bacterial toxins such as staphylococcal enterotoxins etc., which are difficult to determine, become more easily and more specifically detectable when this method is used. It is also possible to obtain qualitative as well as quantitative information. By making available highly standardized and strictly controlled parts and reagents, it is possible to ensure reproducible experimental results in both research and routine work. If all the parameters of importance to an immunological system are fully utilized, 0.0005 μg antigen or less can be detected. Eine Apparatur für die “Micro-Slide-Immundiffusion” Immunologische Analysenverfahren finden in letzter Zeit in immer stärkerem Maße Eingang in die Lebensmittelüberwachung. Diese Verfahren setzen voraus, daß hochwertige Antiseren zur Verfügung stehen, aber auch eine weitgehende Standardisierung aller für dieses Verfahren wichtiger Parameter. In der folgenden Arbeit wird eine Apparatur beschrieben, die es gestattet, im Mikromaßstab immunochemische Trennungen durchzuführen. Für die Lebensmittelüber-wachung werden damit sonst nur schwierig zu bestimmende Stoffe wie Milch-, Soja- und Hühner- eiweiß, Blutplasma, Bakterientoxine, wie Staphylokokken-Enterotoxine usw., leichter und spezifischer nachweisbar. Dabei ist sowohl eine qualitative als auch eine quantitative Aussage möglich. Durch Zurverfügungstellung von hoch standardisierten und streng genormten Teilen und Reagentien ist die Gewähr gegeben, Untersuchungsergebnisse in Routine und Forschung reproduzierbar zu machen. Bei Optimaler Ausnutzung aller für ein immunologischer System wichtigen Parameter lassen sich 0.0005 μg Antigen und weniger eindeutig erfassen.

Effect of Potential and Stress on Time to Failure of Austenitic Stainless Steels in Magnesium Chloride Solutions

Abstract Investigations were carried out on effect of cathodic and anodic polarization and applied tensile stress on time-to-failure of Types 302 and 304 austenitic stainless steels in MgCl2 under conditions leading to a better reproducibility of experimental results than those usually observed using boiling 42 w/o MgCl2 and uniformly stressed test specimens. Instead, boiling 35 w/o MgCl2 and specimens with a narrow part situated below the liquid level were used. Results show that slight cathodic polarization by an external current stops sec, whereas anodic polarization enhances corrosion. This finding confirms some earlier observations but contradicts another viewpoint concerning the effect of hydride phase formation. For both Types 302 and 304 steels the effect of stress on time to failure is found to differ considerably from typical plots heretofore reported. At loads higher than the yield strength, susceptibility to sec initially increases with stress and then decreases before finally increasing again...