Motor unit recruitment for dynamic tasks: current understanding and future directions

Skeletal muscle contains many muscle fibres that are functionally grouped into motor units. For any motor task there are many possible combinations of motor units that could be recruited and it has been proposed that a simple rule, the ‘size principle’, governs the selection of motor units recruited for different contractions. Motor units can be characterised by their different contractile, energetic and fatigue properties and it is important that the selection of motor units recruited for given movements allows units with the appropriate properties to be activated. Here we review what is currently understood about motor unit recruitment patterns, and assess how different recruitment patterns are more or less appropriate for different movement tasks. During natural movements the motor unit recruitment patterns vary (not always holding to the size principle) and it is proposed that motor unit recruitment is likely related to the mechanical function of the muscles. Many factors such as mechanics, sensory feedback, and central control influence recruitment patterns and consequently an integrative approach (rather than reductionist) is required to understand how recruitment is controlled during different movement tasks. Currently, the best way to achieve this is through in vivo studies that relate recruitment to mechanics and behaviour. Various methods for determining motor unit recruitment patterns are discussed, in particular the recent wavelet-analysis approaches that have allowed motor unit recruitment to be assessed during natural movements. Directions for future studies into motor recruitment within and between functional task groups and muscle compartments are suggested.     

Interspike interval patterns of taste neurons in the hamster solitary nucleus

The central nervous system first processes taste informationin the solitary nucleus, which has been almost exclusively studiedin terms of average firing rate. We analyzed interspike intervals(ISI's) of 25 taste-responsive single units in the hamster (Mesocricetusauratus) solitary nucleus. ISI's were measured during spontaneousactivity and during stimulation with NaCl, KCl, sucrose, ora mixture of the three, and graphed on semi-logarithmic plots.Two different ISI patterns were evident: simple (13 units) andcomplex (12 units). Simple ISI patterns had a single broad peakat 284.7 ± 70.4 ms spontaneous and 78.8 ± 12.8ms stimulated. All complex ISI patterns had one distinct, sharppeak for an interval about 10 ms (11.3 ± 0.4 ms: spontaneous,9.3 ± 0.5 ms: stimulated), and a second, broader peakat 273.9 ± 45.9 ms spontaneous and 71.5 ± 14.6ms stimulated. As rate of firing increased peaks in ISI patternspredictably moved towards lower intervals, but ISI pattern-typedid not change. This constancy of ISI pattern held for responsesof a unit across all stimuli and did not depend upon the stimulusspecificity or location of the unit within the rostral poleof the solitary nucleus. Apparently, the pattern that a tasteneuron generates is intrinsic to the neuron and may relate tothe way it processes tast information.     

A comparison of resonance tuning with positive versus negative sensory feedback

We used a computational model of rhythmic movement to analyze how the connectivity of sensory feedback affects the tuning of a closed-loop neuromechanical system to the mechanical resonant frequency (ω_r). Our model includes a Matsuoka half-center oscillator for a central pattern generator (CPG) and a linear, one-degree-of-freedom system for a mechanical component. Using both an open-loop frequency response analysis and closed-loop simulations, we compared resonance tuning with four different feedback configurations as the mechanical resonant frequency, feedback gain, and mechanical damping varied. The feedback configurations consisted of two negative and two positive feedback connectivity schemes. We found that with negative feedback, resonance tuning predominantly occurred when ω_r was higher than the CPG’s endogenous frequency (ω_CPG). In contrast, with the two positive feedback configurations, resonance tuning only occurred if ω_r was lower than ω_CPG. Moreover, the differences in resonance tuning between the two positive (negative) feedback configurations increased with increasing feedback gain and with decreasing mechanical damping. Our results indicate that resonance tuning can be achieved with positive feedback. Furthermore, we have shown that the feedback configuration affects the parameter space over which the endogenous frequency of the CPG or resonant frequency the mechanical dynamics dominates the frequency of a rhythmic movement.     

Detecting Natural Selection at the Molecular Level: A Reexamination of Some “Classic” Examples of Adaptive Evolution

An important criterion used to detect adaptive evolution in DNA sequence data is ω_i > 1, where ω_i is the ratio of nonsynonymous to synonymous substitution rates in lineage i. However, the evaluation of multiple ω_i within a phylogenetic tree can easily inflate the statistical type I error rate. We developed two rigorous methods of analysis that avoid this and other potential pitfalls. We applied these methods to four published examples of adaptive evolution. One case was strongly supported by our reanalysis (abalone sperm lysin), and one was weakly supported (baboon α-globin), but two examples (primate lysozyme and Antarctic fish β-globin) did not show significant evidence of adaptive evolution. Our first method is a “bottom-up” hierarchical maximum likelihood approach, which (1) tests for significant heterogeneity in ω across the phylogeny, (2) locates its source using a sequence of planned comparisons, and (3) tests homogeneous groups of ω for ω > 1, using a modified level of significance that incorporates the pretesting. The second method is a “top-down” log-linear analysis based on estimates of nonsynonymous and synonymous substitutions in pairs of lineages. The log-linear test is applied to pairs of lineages joined at progressively deeper nodes. For each pair, the analysis simultaneously tests for adaptive evolution (ω > 1), a shift in natural selection (ω₁ ≠ω₂), and unequal evolution rate (the relative rate test). In both tests, we emphasized that the criterion ω₁ ≠ ω₂ is an important additional indicator of a phylogenetic shift in the balance between natural selection and genetic drift between two related lineages. [Reviewing Editor: Dr. John Huelsenbeck]     

Influence of macroinvertebrate sample size on bioassessment of streams

In order to standardise biological assessment of surface waters in Europe, a standardised method for sampling, sorting and identification of benthic macroinvertebrates in running waters was developed during the AQEM project. The AQEM method has proved to be relatively time-consuming. Hence, this study explored the consequences of a reduction in sample size on costs and bioassessment results. Macroinvertebrate samples were collected from six different streams: four streams located in the Netherlands and two in Slovakia. In each stream 20 sampling units were collected with a pond net (25×25 cm), over a length of approximately 25 cm per sampling unit, from one or two habitats dominantly present. With the collected data, the effect of increasing sample size on variability and accuracy was examined for six metrics and a multimetric index developed for the assessment of Dutch slow running streams. By collecting samples from separate habitats it was possible to examine whether the coefficient of variation (CV; measure of variability) and the mean relative deviation from the “reference” sample (MRD; measure of accuracy) for different metrics depended only on sample size, or also on the type of habitat sampled. Time spent on sample processing (sorting and identification) was recorded for samples from the Dutch streams to assess the implications of changes in sample size on the costs of sample processing. Accuracy of metric results increased and variability decreased with increasing sample size. Accuracy and variability varied depending on the habitat and the metric, hence sample size should be based on the specific habitats present in a stream and the metric(s) used for bioassessment. The AQEM sampling method prescribes a multihabitat sample of 5 m. Our results suggest that a sample size of less than 5 m is adequate to attain a CV and MRD of ≤ 10% for the metrics ASPT (Average Score per Taxon), Saprobic Index and type Aka+Lit+Psa (%) (the percentage of individuals with a preference for the akal, littoral and psammal). The metrics number of taxa, number of individuals and EPT-taxa (%) required a multihabitat sample size of more than 5 m to attain a CV and MRD of ≤ 10%. For the metrics number of individuals and number of taxa a multihabitat sample size of 5 m is not even adequate to attain a CV and MRD of ≤ 20%. Accuracy of the multimetric index for Dutch slow running streams can be increased from ≤ 20 to ≤ 10% with an increase in labour time of 2 h. Considering this low increase in costs and the possible implications of incorrect assessment results it is recommended to strive for this ≤ 10% accuracy. To achieve an accuracy of ≤ 10% a multihabitat sample of the four habitats studied in the Netherlands would require a sample size of 2.5 m and a labour time of 26 h (excluding identification of Oligochaeta and Diptera) or 38 h (including identification of Oligochaeta and Diptera). Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Treatment of dairy and swine manure effluents using freshwater algae: fatty acid content and composition of algal biomass at different manure loading rates

An alternative to land spreading of manure effluents is to mass-culture algae on the N and P present in the manure and convert manure N and P into algal biomass. The objective of this study was to determine how the fatty acid (FA) content and composition of algae respond to changes in the type of manure, manure loading rate, and to whether the algae was grown with supplemental carbon dioxide. Algal biomass was harvested weekly from indoor laboratory-scale algal turf scrubber (ATS) units using different loading rates of raw and anaerobically digested dairy manure effluents and raw swine manure effluent. Manure loading rates corresponded to N loading rates of 0.2 to 1.3 g TN m⁻² day⁻¹ for raw swine manure effluent and 0.3 to 2.3 g TN m⁻² day⁻¹ for dairy manure effluents. In addition, algal biomass was harvested from outdoor pilot-scale ATS units using different loading rates of raw and anaerobically digested dairy manure effluents. Both indoor and outdoor units were dominated by Rhizoclonium sp. FA content values of the algal biomass ranged from 0.6 to 1.5% of dry weight and showed no consistent relationship to loading rate, type of manure, or to whether supplemental carbon dioxide was added to the systems. FA composition was remarkably consistent among samples and >90% of the FA content consisted of 14:0, 16:0, 16:1ω7, 16:1ω9, 18:0, 18:1ω9, 18:2 ω6, and 18:3ω3.     

<Emphasis Type="Italic">Henriciella marina</Emphasis> gen. nov., sp. nov., a novel member of the family <Emphasis Type="Italic">Hyphomonadaceae</Emphasis> isolated from the East Sea

A bacterial strain, designated Iso4^T, was isolated from the East Sea of Korea and was subjected to a poly-phasic taxonomy study including phenotypic and chemotaxonomic characteristics as well as 16S rRNA gene sequence analysis. Cells of the strain were Gram-negative, motile, non-budding, non-stalked, and strictly aerobic. Strain Iso4^T grew optimally at 20°C in the presence of 1∼2% (w/v) NaCl and at pH 6.9∼7.6. The major respiratory quinone was Q-10 and the major cellular fatty acids were C_18:1 ω7c (53.5%), C_17:1 ω5c (11.7%), C_17:1 ω6c (8.1%), C_16:0 (7.8%), C_17:0 (4.8%), C_15:0 (2.9%), and C_16:1 ω5c (2.2%). The DNA G+C content of strain Iso4^T was 56.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Iso4^T formed a monophyletic clade in the family Hyphomonadaceae, supported by high bootstrap value and was most closely related to the genus Hyphomonas (92∼94%), a member of marine bacteria in the family. The phenotypic, genotypic, and chemotaxonomic evidences also suggest strain Iso4^T represents a novel genus and species in the family Hyphomonadaceae, for which the name Henriciella gen. nov., sp. nov. is proposed. The type strain is Iso4^T (=KCTC 12513^T =DSM 19595^T =JCM 15116^T).     

Carnitine palmitoyl transferase activity and whole muscle oxidation rates vary with fatty acid substrate in avian flight muscles

Birds primarily fuel migratory flights with fat, and the composition of that fat has the potential to affect overall lipid oxidation rates. We measured the whole muscle lipid oxidation rates in extensor digitorum communis muscles from white-throated sparrows (Zonotrichia albicollis Gmelin) incubated for 20 min at 20°C with radiolabeled stearate (18:0), oleate (18:1ω9), or linoleate (18:2ω6). Lipid oxidation rates were ~40% higher with linoleate than oleate (oleate: 36 ± 8.54 μmol CO₂ g⁻¹ h⁻¹), and ~75% lower with stearate compared with oleate, indicating that maximal lipid oxidation rates can indeed be affected by the type of fatty acid supplied to the muscle. Additionally, we investigated the activity of the mitochondrial fatty acid transport-associated enzyme carnitine palmitoyl transferase (CPT) in pectoralis muscles of 5 bird species (Zonotrichia albicollis, Philomachus pugnax, Sturnus vulgaris, Taeniopygia guttata, Passer domesticus). Activity was measured in homogenized samples using various fatty acyl-CoA substrates (16:0, 16:1, 18:0, 18:1ω9, 18:2ω6, 18:3ω3, 18:3ω6, 20:0, 20:4ω6, 22:6ω3) in a spectrophotometric assay. CPT activity increased with the degree of unsaturation and decreased with chain length. CPT activity did not differ between ω3 and ω6 isomers of 18:3, nor was the pattern of CPT substrate preference different between captive white-throated sparrows in a migratory (i.e., displaying Zugunruhe) or non-migratory state. These findings can explain previously observed differences in peak performance induced by dietary fat composition and suggest that lipid supply is limiting to maximal exercise performance in birds.     

Effects of aerobic exercise on the torque-velocity relationship in cycling

The kinetics of the torque-velocity (T-ω) relationship after aerobic exercise was studied to assess the effect of fatigue on the contractile properties of muscle. A group of 13 subjects exercised until fatigued on a cycle ergometer, at an intensity which corresponded to 60% of their maximal aerobic power for 50 min (MAP60%); ten subjects exercised until fatigued at 80% of their maximal aerobic power for 15 min (MAP80%). Of the subjects 7 exercised at both intensities with at least a 1-week interval between sessions. Pedalling rate was set at 60 rpm. The T-ω relationship was determined from the velocity data collected during all-out sprints against a 19 N · m braking torque on the same ergometer, according to a method proposed previously. Maximal theoretical velocity (ω₀) and maximal theoretical torque (T ₀) were estimated by extrapolation of the linear T-ω relationship. Maximal power (P _max) was calculated from the values of T ₀ and ω₀ (P _max = 0.25 ω₀ T ₀). The T-ω relationships were determined before, immediately after and 5 and 10 min after the aerobic exercise. The kinetics of ω₀, T ₀ and P _max was assumed to express the effects of fatigue on the muscle contractile properties (maximal shortening velocity, maximal muscle strength and maximal power). Immediately after exercise at MAP60% a 7.8% decrease in T ₀ and 8.8% decrease in P _max was seen while the decrease in ω₀ was nonsignificant, which suggested that P _max decreased in the main because of a loss in maximal muscle strength. In contrast, MAP80% induced a 8.1% decrease in ω₀ and 12.8% decrease in P _max while the decrease in T ₀ was nonsignificant, which suggested that the main cause of the decrease in P _max was probably a slowing of maximal shortening velocity. The short recovery time of the T-ω relationship suggests that the causes of the decrease of torque and velocity are processes which recover rapidly. Accepted: 25 November 1996     

A comparison of methods for converting rhizotron root length measurements into estimates of root mass production per unit ground area

Rhizotrons provide valuable information about plant root production, but measurements are usually made in units of root length per unit surface area of observation window surface. These measurement units are not easily comparable to above-ground plant growth. To address this deficiency, several techniques have been developed to convert rhizotron measurement units into root mass production per unit ground area. In this study, four different conversion methods were applied to the same dataset of rhizotron measurements. This data was used to reveal the effect of conversion method upon estimates of the temporal variation in, and annual magnitude of, gross root mass production. Application of four different conversion methods resulted in gross root production estimates ranging between 2.1 and 11.4 t ha⁻¹ year⁻¹. Temporal variation in gross root mass production also varied between methods. All current methods for quantifying root production are likely to cause some disturbance and bias. Based upon a comparison of the sources of error present in each conversion method, we assess which methods are likely to produce the most reliable estimates of root biomass production per unit ground area, and propose additional measurements which could further improve accuracy.     

Estimating genetic correlations in natural populations in the absence of pedigree information: accuracy and precision of the Lynch method

Usually, genetic correlations are estimated from breeding designs in the laboratory or greenhouse. However, estimates of the genetic correlation for natural populations are lacking, mostly because pedigrees of wild individuals are rarely known. Recently Lynch (1999) proposed a formula to estimate the genetic correlation in the absence of data on pedigree. This method has been shown to be particularly accurate provided a large sample size and a minimum (20%) proportion of relatives. Lynch (1999) proposed the use of the bootstrap to estimate standard errors associated with genetic correlations, but did not test the reliability of such a method. We tested the bootstrap and showed the jackknife can provide valid estimates of the genetic correlation calculated with the Lynch formula. The occurrence of undefined estimates, combined with the high number of replicates involved in the bootstrap, means there is a high probability of obtaining a biased upward, incomplete bootstrap, even when there is a high fraction of related pairs in a sample. It is easier to obtain complete jackknife estimates for which all the pseudovalues have been defined. We therefore recommend the use of the jackknife to estimate the genetic correlation with the Lynch formula. Provided data can be collected for more than two individuals at each location, we propose a group sampling method that produces low standard errors associated with the jackknife, even when there is a low fraction of relatives in a sample.     

On the parameter estimation for diffusion models of single neuron's activities

 For the Ornstein-Uhlenbeck neuronal model a quantitative method is proposed for the estimation of the two parameters characterizing the unkown input process, namely the neuron’s mean input per unit time μ and the infinitesimal standard deviation per unit time σ. This method is based on the experimentally observed first- and second-order moments of interspike intervals. The dependence of the estimates μ^ and σ^ on the moments of the observed interspike intervals and on the neuronal parameters is clarified, and a comparison is made between the estimates based on the classical Wiener model and those yielded by the Ornstein-Uhlenbeck model. Comprehensive tables are included in which the displayed values of μ^ and σ^ have been calculated in terms of physiologically realistic pairs of first- and second-order moments. Our method is finally applied to interspike interval data recorded from neurons in the mesencephalic reticular formation of the cat during hypothetical sleep, slow-wave sleep stage, and wake stage. Received: 10 October 1994/Accepted in revised form: 21 March 1995     

Confidence intervals for the mean of diagnostic test charge data containing zeros

In this paper, we consider the problem of interval estimation for the mean of diagnostic test charges. Diagnostic test charge data may contain zero values, and the nonzero values can often be modeled by a log-normal distribution. Under such a model, we propose three different interval estimation procedures: a percentile-t bootstrap interval based on sufficient statistics and two likelihood-based confidence intervals. For theoretical properties, we show that the two likelihood-based one-sided confidence intervals are only first-order accurate and that the bootstrap-based one-sided confidence interval is second-order accurate. For two-sided confidence intervals, all three proposed methods are second-order accurate. A simulation study in finite-sample sizes suggests all three proposed intervals outperform a widely used minimum variance unbiased estimator (MVUE)-based interval except for the case of one-sided lower end-point intervals when the skewness is very small. Among the proposed one-sided intervals, the bootstrap interval has the best coverage accuracy. For the two-sided intervals, when the sample size is small, the bootstrap method still yields the best coverage accuracy unless the skewness is very small, in which case the bias-corrected ML method has the best accuracy. When the sample size is large, all three proposed intervals have similar coverage accuracy. Finally, we analyze with the proposed methods one real example assessing diagnostic test charges among older adults with depression.     

The detuning factor in the dynamics of interlimb rhythmic coordination

 Dynamical models of two coupled biological oscillators interpret the detuning term as an arithmetic difference between the uncoupled frequencies, Δω= (ω₁−ω₂). This Δω interpretation of detuning was addressed in four experiments in which human subjects oscillated pendulums in their right and left hands in 1 : 1 frequency locking in antiphase (Experiments 1–3) or inphase (Experiment 4). Differences between the uncoupled frequencies were manipulated through differences in the equivalent simple pendulum lengths, and the effects of this manipulation on the detuning of relative phase from π or 0 and the standard deviation of relative phase SDφ were measured. In Experiment 1, the same values of ω _i were satisfied by several different physical configurations. The experiment confirmed that the detuning term is related strictly to the uncoupled frequencies rather than to other physical characteristics of the oscillators. Experiments 2, 3 and 4 showed, however, that the particular dependency of fixed point drift and SDφ on Δω depends on the particulars of ω₁ and ω₂. With variations in Δω brought about by different ω₁ and ω₂ that always formed a constant ratio, fixed point drift related inversely to Δω, and SDφ varied with Δω in ways that depended on the magnitude of the constant ratio. These outcomes do not conform to expectations from models of coordination dynamics that interpret detuning as (ω₁−ω₂). Received: 18 October 1993/Accepted in revised form: 2 December 1994     

Mutation rate and pattern of microsatellites in common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

Microsatellites are popular molecular markers in genetic and evolutionary studies. Their mutational dynamics have been extensively studied in humans and fruit flies, but few data were available in fish. By genotyping 55 individuals of a F1 pedigree, we investigated the mutation rates and patterns of 49 microsatellites in one of the most important fresh water fish species, the common carp (Cyprinus carpio L.). The overall mutation rate of the 49 loci was 5.56×10⁻⁴/locus/generation (95% confidence interval 1.52×10⁻⁴ and 1.63×10⁻³). The change of allele size was between +2 to −5 repeat units, assuming that the mutation allele arose from the parental allele most similar in size to the mutant.     

Cytochrome P450-dependent fatty acid hydroxylases in plants

In plants, hydroxy-fatty acid production is mainly the result of enzymatic reactions catalyzed by cytochrome P450 dependent fatty acid hydroxylases. One can distinguish ω-hydroxylases that catalyze the hydroxylation of the terminal methyl of aliphatics acids (ω position) and sub-terminal or in-chain hydroxylases that oxidize carbons in the chain (ω-n position). Since both types of enzymes were discovered about three decades ago, the majority of investigations have focused on the CYP94 and CYP86 families, which mediate ω-hydroxylations. The activities of ω-hydroxylases in cutin synthesis have been clearly established, but the studies of LCR (LACERATA) and att1 (aberrant induction of type three genes), which are the first Arabidopsis thaliana mutants with alterations in coding sequences of CYP86A8 and CYP86A2, show that these types of ω-hydroxylases can be involved in many aspects of plant development. The existence of different ω-hydroxylases in plants with distinct regulation patterns suggests that these enzymes mediate diverse biological processes. Much less information concerning in-chain hydroxylases is available despite the fact that they were initially reported along with ω-hydroxylases. This lack of information might be explained by the very few examples of sub-terminal hydroxy-fatty acids described in plants. We present here the best characterized fatty acid hydroxylases and we discuss their possible roles in plant defense and development, fatty acid catabolism, plant reproduction and detoxification.     

Isolation and characterization of wheat ω-gliadin genes

The DNA sequences of two full-length wheat ω-gliadin prolamin genes (ωF20b and ωG3) containing significant 5′ and 3′ flanking DNA sequences are reported. The ωF20b DNA sequence contains an open reading frame encoding a 30,460-Dalton protein, whereas the ωG3 sequence would encode a putative 39,210-Dalton protein except for a stop codon at amino-acid residue position 165. These two ω-gliadin genes are closely related and are of the ARQ-/ARE-variant type as categorized by the derived N-terminal amino-acid sequences and amino-acid compositions. The ω-gliadins were believed be related to the ω-secalins of rye and the C-hordeins of barley, and analyses of these complete ω-gliadin sequences confirm this close relationship. Although the ω-type sequences from all three species are closely related, in this analysis the rye and barley ω-type sequences are the most similar in a pairwise comparison. A comparison of ω-gliadin flanking sequences with respect to that of their orthologs and with respect to wheat gliadin genes suggests the conservation of flanking DNA necessary for gene function. Sequence data for members of all major wheat prolamin families are now available. Received: 24 August 2000 / Accepted: 15 December 2000     

Antioxidant activity of vegetable oils with different omega-6/omega-3 fatty acids ratio

The antioxidant activity and the oxidative stability of flax, sesame, silybum oils and seed blend oils with different ω-6/ω-3 fatty acid ratios have been investigated. The antioxidant content (AO) in crude oils and their reactivity towards peroxyl radicals were studied using the kinetic method based on oil addition to the model reaction of cumene oxidation. There were correlations between the ratio polyunsaturated fatty acids (PUFA)/ω-9 and thermal stability (50°C); between the effect of γ-tocopherol content and oil resistance to oxidative changes during long-term storage at (10 ± 2)°C.     

The Sec-1 locus on the short arm of chromosome 1R of rye (Secale cereale)

This paper describes a detailed sequence analysis of the ω-secalin gene array at theSec-1 locus on the short arm of chromosome 1 of rye. The analysis shows that the genes are separated by 8 kb of spacer sequence and that the gene/spacer units are arranged in a head to tail fashion. The boundaries of the array are identified, and a fragment containing the majority of the genes in the array is separated by PFG analysis. The sequence data of one 9.2 kb gene unit have been determined, and because of the similarity of the gene units within the array these data provide a detailed sequence analysis of 140 kb of theSec-1 locus. Fluorescence in situ hybridization, using lambda clones isolated for the structural analysis, identifies the position of the array on the rye chromosomes relative to the 5S rRNA genes. Edited by: W. Hennig     

Direct colorimetric assay of microcystin using protein phosphatase

A new direct colorimetric assay of microcystin in water and algal samples is proposed consisting of two procedures as follows: 1) the elimination of phosphorus in the sample and concentration of microcystin using a C₁₈ cartridge, 2) the detection of the released phosphorus by the ascorbic acid method and determination of protein phosphatase (PP) inhibition by microcystin. The optimum amounts of phosphorylase α and PP-1 in 50 μL concentrated sample were 50 μg/50 μL buffer and 1.0 unit/50 μL buffer, respectively, for the best assay. The pH for the maximum activity of PP-1 was 8. The minimum detectable concentration for this method was about 0.02 μg/L, which is sufficient to meet the proposed guideline level of 1 μg microcystin/L in drinking water. Consequently, it would seem that the proposed direct colorimetric assay using PP is a rapid, easy, and convenient method for the detection of microcystin in water and algal samples.