Microscale Distribution of Nitrification Activity in Sediment Determined with a Shielded Microsensor for Nitrate

Microprofiles of O₂ and NO₃^- were measured simultaneously in freshwater sediment with microsensors which were completely free from electrical interference because of coaxial designs. Depth profiles of nitrification (NO₃^- production) and denitrification (NO₃^- consumption) were subsequently determined by computer simulation of the measured microprofiles. The nitrifying bacterial community responded very quickly to changes in environmental conditions, and new steady-state microprofiles of O₂ and NO₃^- were usually approached within a few hours after perturbation. Nitrification started quickly after introduction of O₂ in previously anoxic layers, suggesting prolonged survival of the nitrifiers during anaerobiosis. Changes in the availability of O₂ and NH₄⁺ greatly affected the nitrification profile, and there was a high rate of coupled nitrification-denitrification under conditions in which nitrification occurred right above the oxic-anoxic interface. Addition of C₂H₂ rapidly removed the NO₃^- peaks, indicating that NO₃^- production was due mainly to autotrophic nitrification.     

木聚糖酶活力测定条件研究

用DNS法测木聚糖酶活力,分析测定条件对测定结果的影响。结果表明,在不同的条件下测定酶活力会得到不同的木聚糖酶活力测定值。其中,酶液用量、酶解反应的时间对测定结果的影响较大,酶液稀释度、DNS显色时间、DNS的用量,对测定结果也有一定的髟响。测定木聚糖酶活力的适宜条件为：酶液量/1％木聚糖液量1/9(V／V);酶解反应时间：10min;DNS用量2—2．5ml;DNS显色时间2—5min。     

Measurement of Larval Activity in the Drosophila Activity Monitor

Drosophila larvae are used in many behavioral studies, yet a simple device for measuring basic parameters of larval activity has not been available. This protocol repurposes an instrument often used to measure adult activity, the TriKinetics Drosophila activity monitor (MB5 Multi-Beam Activity Monitor) to study larval activity. The instrument can monitor the movements of animals in 16 individual 8 cm glass assay tubes, using 17 infrared detection beams per tube. Logging software automatically saves data to a computer, recording parameters such as number of moves, times sensors were triggered, and animals’ positions within the tubes. The data can then be analyzed to represent overall locomotion and/or position preference as well as other measurements. All data are easily accessible and compatible with basic graphing and data manipulation software. This protocol will discuss how to use the apparatus, how to operate the software and how to run a larval activity assay from start to finish.     

Predicting the Activity Coefficients of Free-Solvent for Concentrated Globular Protein Solutions Using Independently Determined Physical Parameters

The activity coefficient is largely considered an empirical parameter that was traditionally introduced to correct the non-ideality observed in thermodynamic systems such as osmotic pressure. Here, the activity coefficient of free-solvent is related to physically realistic parameters and a mathematical expression is developed to directly predict the activity coefficients of free-solvent, for aqueous protein solutions up to near-saturation concentrations. The model is based on the free-solvent model, which has previously been shown to provide excellent prediction of the osmotic pressure of concentrated and crowded globular proteins in aqueous solutions up to near-saturation concentrations. Thus, this model uses only the independently determined, physically realizable quantities: mole fraction, solvent accessible surface area, and ion binding, in its prediction. Predictions are presented for the activity coefficients of free-solvent for near-saturated protein solutions containing either bovine serum albumin or hemoglobin. As a verification step, the predictability of the model for the activity coefficient of sucrose solutions was evaluated. The predicted activity coefficients of free-solvent are compared to the calculated activity coefficients of free-solvent based on osmotic pressure data. It is observed that the predicted activity coefficients are increasingly dependent on the solute-solvent parameters as the protein concentration increases to near-saturation concentrations.     

Polygalacturonase Activity in Ripening Tomato Fruit Determined using Pericarp Discs

Discs prepared from the outer pericarp of tomato (Lycopersiconesculentum Mill. cv. Sunny) and placed in buffer exhibit anenzymic release of pectin fragments. Over a 2.5 h period at34 °C, discs from mature-green, 4 d and 10 d postbreakerfruit released approximately 90, 440 and 675 µg galacturonicacid equivalents (g^–1 disc fr. wt.), respectively. Bio-GelP-2 chromatography of the products revealed the presence ofpolymeric, oligomeric and monomeric uronic acids. The similarityof these products to those released from isolated, enzymatically-activecell walls and from enzymatically-inactive walls treated withpurified PG 2 provides evidence for the participation of polygalacturonase(PG, E. C. 3.2.1.15 [EC] ) in the release of pectin from disc tissue. The magnitude of pectin release from external pericarp discswas found to parallel ripening and increase progressively indiscs from the blossom, equatorial and shoulder regions, respectively.The use of discs and other systems to estimate in vivo PG activitywill be discussed. Key words: Cell wall, polyuronides     

Day-Night Rhythm of Rat Pineal Tyrosine Hydroxylase Activity as Determined by HPLC with Amperometric Detection

Tyrosine hydroxylase activity in the rat pineal gland was measured by means of HPLC determination of the amount of L-3,4-dihydroxyphenylalanine formed. Enzyme activity showed a clear day-night rhythm, paralleling that of plasma melatonin levels in the same animals, with values being high during the dark period apparently because of changes in Vmax. In animals maintained under constant illumination for 3 days, tyrosine hydroxylase activity and plasma melatonin level rhythms were completely abolished, a result indicating that both are under photoperiodic control.     

Reliability and Validity of the Transport and Physical Activity Questionnaire (TPAQ) for Assessing Physical Activity Behaviour

Background

No current validated survey instrument allows a comprehensive assessment of both physical activity and travel behaviours for use in interdisciplinary research on walking and cycling. This study reports on the test-retest reliability and validity of physical activity measures in the transport and physical activity questionnaire (TPAQ).

Methods

The TPAQ assesses time spent in different domains of physical activity and using different modes of transport for five journey purposes. Test-retest reliability of eight physical activity summary variables was assessed using intra-class correlation coefficients (ICC) and Kappa scores for continuous and categorical variables respectively. In a separate study, the validity of three survey-reported physical activity summary variables was assessed by computing Spearman correlation coefficients using accelerometer-derived reference measures. The Bland-Altman technique was used to determine the absolute validity of survey-reported time spent in moderate-to-vigorous physical activity (MVPA).

Results

In the reliability study, ICC for time spent in different domains of physical activity ranged from fair to substantial for walking for transport (ICC = 0.59), cycling for transport (ICC = 0.61), walking for recreation (ICC = 0.48), cycling for recreation (ICC = 0.35), moderate leisure-time physical activity (ICC = 0.47), vigorous leisure-time physical activity (ICC = 0.63), and total physical activity (ICC = 0.56). The proportion of participants estimated to meet physical activity guidelines showed acceptable reliability (k = 0.60). In the validity study, comparison of survey-reported and accelerometer-derived time spent in physical activity showed strong agreement for vigorous physical activity (r = 0.72, p<0.001), fair but non-significant agreement for moderate physical activity (r = 0.24, p = 0.09) and fair agreement for MVPA (r = 0.27, p = 0.05). Bland-Altman analysis showed a mean overestimation of MVPA of 87.6 min/week (p = 0.02) (95% limits of agreement −447.1 to +622.3 min/week).

Conclusion

The TPAQ provides a more comprehensive assessment of physical activity and travel behaviours and may be suitable for wider use. Its physical activity summary measures have comparable reliability and validity to those of similar existing questionnaires.     

Test System for Measurement of Translational Activity in Vivo

Abstract

A new plasmid which makes it possible to measure formation of a mature protein, as well as prematurely terminated gene products, has been constructed. It can be used for the analysis of translational efficiency of specified codon sequences in vivo.     

An H-ATPase Assay: Proton Pumping and ATPase Activity Determined Simultaneously in the Same Sample

A continuous spectrophotometric assay of H⁺-ATPase activity was developed by combining two well-known methods for measuring proton pumping and ATPase activity. Proton uptake into plasma membrane vesicles from Avena sativa L. (cv Rhiannon) was monitored as the absorbance decrease at 495 nm of the ΔpH probe acridine orange. Simultaneously, ATPase activity was measured by following the absorbance decrease at 340 nanometers by coupling ATP hydrolysis enzymatically to the oxidation of NADH. This H⁺-ATPase assay is convenient for determining the relative relationship between ATP hydrolysis and proton pumping.     

Standardized, Automated Procedure for Measurement of Serum Hemolytic Complement Activity

In the interest of standardizing and automating complement fixation procedures, an AutoAnalyzer manifold was designed in which the reagents are mixed in proportions similar to that of the Laboratory Branch Complement Fixation test. By bypassing the fixation stage, the manifold proved useful for measuring serum hemolytic complement activity (C'). As many as 21 serum samples per hour can be screened by testing two appropriate dilutions. Normal adult C' titers measured by the automated procedure ranged from 58 to 103 C'H(50) units per ml.     

Measurement of Fronto-limbic Activity Using an Emotional Oddball Task in Children with Familial High Risk for Schizophrenia

Adolescence is a critical developmental period where the early symptoms of schizophrenia frequently emerge. First-degree relatives of people with schizophrenia who are at familial high risk (FHR) may show similar cognitive and emotional changes. However, the neurological changes underlying the emergence of these symptoms remain unclear. This study sought to identify differences in frontal, striatal, and limbic regions in children and adolescents with FHR using functional magnetic resonance imaging. Groups of 21 children and adolescents at FHR and 21 healthy controls completed an emotional oddball task that relied on selective attention and the suppression of task-irrelevant emotional information. The standard oddball task was modified to include aversive and neutral distractors in order to examine potential group differences in both emotional and executive processing. This task was designed specifically to allow for children and adolescents to complete by keeping the difficulty and emotional image content age-appropriate. Furthermore, we demonstrate a technique for suitable fMRI registration for children and adolescent participants. This paradigm may also be applied in future studies to measure changes in neural activity in other populations with hypothesized developmental changes in executive and emotional processing.     

Earth Worm: Biomass Measurement: A Science Activity for Middle School

Ridgely, Robert S. A Guide to the Birds of Panama Princeton, N.J.: Princeton University Press, 1976 394 pp., $15.00. Reviewed by Karl L. Trever

Weiner, Michael A. Man's Useful Plants New York: Macmillan Co., 1976 137 pp., $6.95. Reviewed by Carolyn M. Levin

Bendick, Jeanne How Animals Behave New York: Parents Magazine Press, 1976 64 pp., $4.96. Reviewed by Robert Deitchman

Bayne, B. L., ed. Marine Mussels: The Ecology and Physiology New York: Cambridge University Press, 1976 506 pp., $49.50. Reviewed by Brother Nicholas Sullivan

Brown, Vinson The Explorer Naturalist Harrisburg, Pa.: Stackpole Books, 1976 288 pp., $10.00. Reviewed by Paul F. Connor

Sheldon, William G. The Wilderness Home of the Giant Panda Amherst: The University of Massachusetts Press, 1975 196 pp., $12.50. Reviewed by Harold W. Puffer

Rudolph, Joachim (translated by H. C. Grinter) Chemistry for the Modern Mind New York: Macmillan Publishing Co., 1973 359 pp., $8.95. Reviewed by Donald Schwartz     

Steady-state,Pre-steady-state,and Single-turnover Kinetic Measurement for DNA Glycosylase Activity

Human 8-oxoguanine DNA glycosylase (OGG1) excises the mutagenic oxidative DNA lesion 8-oxo-7,8-dihydroguanine (8-oxoG) from DNA. Kinetic characterization of OGG1 is undertaken to measure the rates of 8-oxoG excision and product release. When the OGG1 concentration is lower than substrate DNA, time courses of product formation are biphasic; a rapid exponential phase (i.e. burst) of product formation is followed by a linear steady-state phase. The initial burst of product formation corresponds to the concentration of enzyme properly engaged on the substrate, and the burst amplitude depends on the concentration of enzyme. The first-order rate constant of the burst corresponds to the intrinsic rate of 8-oxoG excision and the slower steady-state rate measures the rate of product release (product DNA dissociation rate constant, k_off). Here, we describe steady-state, pre-steady-state, and single-turnover approaches to isolate and measure specific steps during OGG1 catalytic cycling. A fluorescent labeled lesion-containing oligonucleotide and purified OGG1 are used to facilitate precise kinetic measurements. Since low enzyme concentrations are used to make steady-state measurements, manual mixing of reagents and quenching of the reaction can be performed to ascertain the steady-state rate (k_off). Additionally, extrapolation of the steady-state rate to a point on the ordinate at zero time indicates that a burst of product formation occurred during the first turnover (i.e. y-intercept is positive). The first-order rate constant of the exponential burst phase can be measured using a rapid mixing and quenching technique that examines the amount of product formed at short time intervals (<1 sec) before the steady-state phase and corresponds to the rate of 8-oxoG excision (i.e. chemistry). The chemical step can also be measured using a single-turnover approach where catalytic cycling is prevented by saturating substrate DNA with enzyme (E>S). These approaches can measure elementary rate constants that influence the efficiency of removal of a DNA lesion.     

Bacterial Activity in a Reservoir Determined by Autoradiography and its Relationships to Phyto- and Zooplankton

In the drinking water reservoir Římov (Southern Bohemia) bacterioplankton was studied during 1983. Special attention was given to the relationships between parameters of bacterial abundance, total and individual activity. Bacterial counts and biomass was assessed and autoradiographic determinations of the proportion of active bacteria incorporating thymidine (Th) and mixture of amino acids (AA) and total uptake rate of AA were made over a year in the surface layer and during summer stratification from the thermocline and 15 m depth. Specific activity of metabolically active bacteria (SAMAB) and specific activity per unit of biomass (SAUB) were negatively correlated with counts of metabolizing cells and with bacterial biomass, respectively. Total and individual heterotrophic activity and counts of bacteria coincided with the changes of phytoplankton biomass, whereas bacteria incorporating Th were more tightly correlated with primary production. The most significant relation of metabolically active bacteria was found to cladoceran biomass. Thus, this part of heterotrophic bacterial activity seems to be stimulated by leakage of dissolved organic matter from phytoplankton being disrupted and incompletely digested by cladocerans rather than from healthy photosynthetizing cells.     

Genetically Determined Measures of Striatal D2 Signaling Predict Prefrontal Activity during Working Memory Performance

Background

Variation of the gene coding for D2 receptors (DRD2) has been associated with risk for schizophrenia and with working memory deficits. A functional intronic SNP (rs1076560) predicts relative expression of the two D2 receptors isoforms, D2S (mainly pre-synaptic) and D2L (mainly post-synaptic). However, the effect of functional genetic variation of DRD2 on striatal dopamine D2 signaling and on its correlation with prefrontal activity during working memory in humans is not known.

Methods

Thirty-seven healthy subjects were genotyped for rs1076560 (G>T) and underwent SPECT with [¹²³I]IBZM (which binds primarily to post-synaptic D2 receptors) and with [¹²³I]FP-CIT (which binds to pre-synaptic dopamine transporters, whose activity and density is also regulated by pre-synaptic D2 receptors), as well as BOLD fMRI during N-Back working memory.

Results

Subjects carrying the T allele (previously associated with reduced D2S expression) had striatal reductions of [¹²³I]IBZM and of [¹²³I]FP-CIT binding. DRD2 genotype also differentially predicted the correlation between striatal dopamine D2 signaling (as identified with factor analysis of the two radiotracers) and activity of the prefrontal cortex during working memory as measured with BOLD fMRI, which was positive in GG subjects and negative in GT.

Conclusions

Our results demonstrate that this functional SNP within DRD2 predicts striatal binding of the two radiotracers to dopamine transporters and D2 receptors as well as the correlation between striatal D2 signaling with prefrontal cortex activity during performance of a working memory task. These data are consistent with the possibility that the balance of excitatory/inhibitory modulation of striatal neurons may also affect striatal outputs in relationship with prefrontal activity during working memory performance within the cortico-striatal-thalamic-cortical pathway.