Molded porous poly (L-lactide) membranes for guided bone regeneration with enhanced effects by controlled growth factor release

The aim of this study was to develop platelet-derived growth factor (PDGF-BB) loaded moldable porous poly (L-lactide) (PLLA)-tricalcium phosphate (TCP) membranes for guided bone regeneration (GBR) therapy. The membranes were designed to fit various types of bone defect sites. PDGF-BB-dissolved PLLA-TCP in methylene chloride-ethyl acetate solution was cast on a dome shaped metallic mold to fabricate a model membrane. The release rate of PDGF-BB, the osteoblast attachment test, and guided bone regeneration potential were evaluated with PDGF-BB-loaded PLLA-TCP membranes. Regular pores were generated throughout the membrane mainly due to phase inversion of PLLA-methylene chloride-ethyl acetate solution. A therapeutic amount of PDGF-BB was released from the membrane. The release rate could be controlled by varying the initial loading content of PDGF-BB. A significant amount of cells attached onto the PDGF-BB-loaded membrane rather than onto the unloaded membrane. Dome shaped bone formation was achieved in rabbit calvaria at 4 weeks. This indicated that restoration of bone defects to the bone's original shape can be made possible by using molded membranes, which guide bone regeneration along with providing sufficient spaces. Bone forming efficiency was increased remarkably due to PDGF-BB release from PLLA-TCP membranes. These results suggested that the PDGF-BB releasing molded PLLA-TCP membrane may potentially improve GBR efficiency in various types of bone defects.

Clinical application of computer-aided rapid prototyping for tooth transplantation

The maintenance of healthy periodontal ligament cells in the donor tooth is one of the most important factors for successful tooth transplantation. This is achieved by minimizing the extraoral time during the surgical procedure. If a duplicate form of donor tooth could be obtained before extraction, it would be possible to precontour the recipient alveolar bone compatible with the donor tooth, and thereby reduce the extra-oral time of the donor tooth. We obtained a three-dimensional image with the real dimensions of the donor tooth from a CT Highspeed Advantage, allowing a life-sized resin model of the tooth to be fabricated. From 22 clinical cases, we achieved an average total transplantation time of 7.7 min. The average distance between the transplanted root surface and the alveolar bone from 12 available cases was 0.87 mm at the mesial cervix, 0.91 mm at the mesial apex, 0.98 mm at the distal cervix and 1.16 mm at the distal apex on the postoperative radiographs. Clinical data indicate that computer-aided rapid prototyping may be of value in minimizing the extra-oral time and possible injury to transplanted tooth during the process of autotransplantation.

Cardiac arrhythmias in F-16 pilots during aerial combat maneuvers (ACMS): a descriptive study focused on G-level acceleration

INTRODUCTION

It is well known that acceleration during centrifuge training provokes cardiac arrhythmias. However, there is little research regarding cardiac arrhythmia during actual flight. Therefore, to identify the kinds of cardiac arrhythmias that occur in response to the Aerial Combat Maneuvers (ACM) environment, we analyzed electrocardiograms (ECG) of 35 male pilots.

METHODS

ECGs were recorded from 35 pilots (mean age 31 yr, range 27-39) from 1 h before take-off to 1 h after landing. G-load was simultaneously recorded. To see the patterns of the arrhythmia as Gz force increased, ECG data of each subject were classified into three G levels: a) G-level A was < +3 G; b) G-level B was > or = +3 G but < +6 G lasting longer than 3 s; and c) G-level C was > or = +6 G lasting longer than 3 s.

RESULTS

Mean total flying time of the 35 pilots was 1475 h (range 578-3300). Arrhythmias were observed in 17 of the pilots (49%) during ECG recording. Four pilots (11.4%) experienced arrhythmias before take-off, 16 pilots (45.7%) inflight and 4 pilots (11.4%) after landing. Arrhythmias were recorded in 13 of 35 pilots (37.1%) at G-level A, in 10 of 35 pilots (28.6%) at G-level B and in 1 of 21 pilots (5%) at G-level C. During flight, unifocal premature ventricular contractions (PVC) were experienced by three of the subjects (8.6%); supraventricular premature beats (SVPB) by four subjects (11.4%), and PVCs with bigeminy by one subject (2.9%). Eight subjects (22.9%) experienced combined arrhythmias.

CONCLUSION

There were no clinically significant arrhythmias recorded during ACM in these experienced pilots.

Melittin exerts multiple effects on the release of free fatty acids from L1210 cells: lack of selective activation of phospholipase A2 by melittin

Melittin is known as a phospholipase A2 (PLA2) activator, but the selectivity of its effect on PLA2 is uncertain. We examined the selectivity of melittin effect on the release of free fatty acids (FFAs) from L1210 cells using various inhibitors. A systemic lipid analysis by HPLC and GLC revealed that melittin induced release of various FFAs including saturated, monounsaturated, and polyunsaturated FFAs. Various PLA2 inhibitors examined exerted only minimal effects on the melittin-induced arachidonic acid (AA) and palmitic acid (PAL) releases. Specific inhibitors of phosphatidylinositol-phospholipase C (U73122) and diacylglycerol lipase (RHC80267) exerted significant inhibitory effects on both AA and PAL releases. These results suggest that melittin-induced FFA release is most likely due to multiple participations of various types of lipases. Since BAPTA/AM, an intracellular Ca2+ chelator, did not influence the FFA release, the Ca2+ influxed by melittin appeared not to be a key factor for the FFA release. The mimicking of the melittin-induced FFA release by digitonin, a membrane-permeabilizing agent, implies that the membrane-perturbing action of melittin is likely the cause of the FFA release. Melittin also induced release of multiple FFAs from other cell lines including P388D1 and HL60. The rapid melittin-stimulated phospholipase D (PLD) observed in L1210 cells appeared not directly related to the steady release of FFA, as indicated by the fact that the PLD was not blocked by RHC80267. In view of melittin's multiple effects on the composition of cellular lipids, we conclude that melittin does neither exclusively release any single FFA nor selectively activate PLA2 in L1210 cells. The problem of using melittin as a PLA2 activator is discussed.

Bounds on the CP asymmetry in like-sign dileptons from B(0)B*(0) meson decays

We have measured the charge asymmetry in like-sign dilepton yields from B(0)B*(0) meson decays using the CLEO detector at the Cornell Electron Storage Ring. We find a(0)(ll) identical with[N(l(+)l(+))-N(l(-)l(-))]/[N(l(+)l(+))+N(l(-)l(-))] = +0.013+/-0.050+/-0.005. We combine this result with a previous, independent measurement and obtain Re(epsilon(B))/(1+ the absolute value of epsilon(B)(2)) = +0.0035+/-0.0103+/-0.0015 (uncertainties are statistical and systematic, respectively) for the CP impurity parameter, epsilon(B).

Sigma38 (rpoS) RNA polymerase promoter engagement via -10 region nucleotides

Band shift assays using DNA probes that mimic closed and open complexes were used to explore the determinants of promoter recognition by sigma38 (rpoS) RNA polymerase. Duplex recognition was found to be much weaker than that observed in sigma70 promoter usage. However, binding to fork junction probes, which attempt to mimic melted DNA, was very strong. This binding occurs via the non-template strand with the identity of the two conserved junction nucleotides (-12T and -11A) being of paramount importance. A modified promoter consensus sequence identified these two nucleotides as among only four (underlined) that are highly conserved, and all four were in the -10 region (CTAcacT from -13 to -7). The remaining two nucleotides were shown to have different roles, -13C in preventing recognition by the heterologous sigma70 polymerase and -7T in directing enzyme isomerization. These -10 region nucleotides appear to have their primary function prior to full melting because probes that had a melted start site were relatively insensitive to substitution at these positions. These results suggest the sigma38 mechanism differs from the sigma70 mechanism, and this difference likely contributes to selective use of sigma38 under conditions that exist during stationery phase.

Study of tau decays to six pions and a neutrino

The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.

Observation of new states decaying into Lambda+(c)pi(-)pi(+)

Using 13.7 fb(-1) of data recorded by the CLEO detector at the Cornell Electron Storage Ring, we investigate the spectrum of charmed baryons which decay into Lambda+(c)pi(-)pi(+) and are more massive than the Lambda+(c)(2625) baryon. We find evidence for two new states: one is broad and has an invariant mass roughly 480 MeV above that of the Lambda+(c) baryon; the other is narrow with an invariant mass of 596+/-1+/-2 MeV above the Lambda+(c) mass.

Evidence of New States Decaying into Xi(*)(c)pi

Using 13.7 fb(-1) of data recorded by the CLEO detector at Cornell Electron Storage Ring, we report evidence of two new charmed baryons: one decaying into Xi(0')(c)pi(+) with the subsequent decay Xi(0')(c)-->Xi(0)(c)gamma, and its isospin partner decaying into Xi(+')(c)pi(-) followed by Xi(+')(c)-->Xi(+)(c)gamma. We measure the following mass differences for the two states: M(Xi(0)(c)gammapi(+))-M(Xi(0)(c)) = 318.2+/-1.3+/-2.9 MeV and M(Xi(+)(c)gammapi(-))-M(Xi(+)(c)) = 324.0+/-1.3+/-3.0 MeV. We interpret these new states as the J(P) = 1 / 2(-) Xi(c1) particles, the charmed-strange analogs of the Lambda(+)(c1)(2593).

Psychometric evaluation of a Chinese (Taiwanese) version of the SF-36 health survey amongst middle-aged women from a rural community

To test the psychometric properties of the Chinese (Taiwanese) version of the short form 36 health survey (SF-36), 1,439 women, aged 40-54 years and living in Kinmen (a Taiwanese island reflecting a predominantly rural community) were recruited to participate in this survey. The rate of unavailable data points for the 36 tested items remained consistently low, and item-discriminate validity was high (95%) for all subscales. Cronbach's alpha coefficient remained above the 0.70 threshold criterion for all scales except for social functioning and bodily pain. Principal components analysis supported the two major dimensions of health, physical and mental, in the internal structure of the SF-36 scales, although the dimensions did not match the hypothesized association very well. Poorer health profiles were associated with physical and mental conditions. The mental health subscores in the SF-36 test correlated highly with the associated hospital anxiety and depression score (Spearman rank correlation coefficient = -0.62). In conclusion, the reliability and validity tests performed on the data collected support the cross-cultural application of the Chinese (Taiwanese) version of the SF-36 test.

Today's dental student is training for tomorrow's elderly baby boomer

We are constantly reminded of the exploding elderly population and the increasing demand to meet their needs. But do we fully understand and appreciate the impact that this fastest-growing segment of the population will have upon our profession? Whether we realize it or not, today's dental student is training for tomorrow's elderly baby boomer. The baby boomer generation is 76 million strong, representing 19 years worth of births spanning from 1946-1964. That makes the oldest baby boomer 55 years old and the youngest 37 years old. What does this all mean? That from 2011-2030, the age group of 65 years of age and older will make up approximately 22% of the population, vastly changing our patient population, not to mention a significant increase in patient load. The future holds promise for not only a busy career, but also potentially a financially rewarding one as well. To some extent, we are all going to be geriatric clinicians. There is little doubt that there will be a great demand for services in restorative dentistry, prosthodontic dentistry, endodontics, periodontics, oral surgery, and perhaps orthodontics. As the baby boomers benefited from fluoride and sanitation, more people have been able to maintain their dentition and health into their older years. Dental students graduating today will be only beginning the prime of their careers as the baby boomers make their introduction in full force in the year 2011.

Continuous culture of immobilized streptomyces cells for kasugamycin production

Continuous cultures of immobilized Streptomyces kasugaensis, a kasugamycin producer, were carried out on Celite beads. When using a prototype separator for immobilized-cell separation and recycling, the continuous operation could not be sustained for an extended period as a result of an excessive loss of immobilized cells caused by the poor performance of the separator. Accordingly, the immobilized-cell separator was revised to provide better immobilized-cell settling and thus recycling into the reactor. In a subsequent culture using the revised separator, a stable operation was maintained for over 820 h with a high kasugamycin productivity. The kasugamycin productivity ranged from 9.8 to 16.1 mg/L/h, which was about 14- to 23-fold higher than that in a batch suspended-cell culture. When the original feeding medium concentration was doubled at the end of the continuous culture, the productivity became severely impaired for several reasons, which will be discussed. An excessive formation of free cells and loss of immobilized cells through the separator were also observed.

Correlation of hematopoietic progenitor cell count determined by the SE-automated hematology analyzer with CD34(+) cell count by flow cytometry in leukapheresis products

The yield of stem cell collection after mobilization is crucial for autologous peripheral blood stem cell (PBSC) transplantation. Quantitative determinations of CD34(+) cells using flow cytometry or stem cell culture have been used, but these methods require much time, technical experience, and expensive reagents. The automated hematology analyzer (Sysmex SE-9000trade mark, TOA, Japan) equipped with the Immature Information (IMI) channel for immature myeloid cells can detect IMI(+) cells within 90 sec. Detection is made possible by the combination of a special reagent system and direct current/radiofrequency biosensors. We studied the relation of IMI(+) cells and variable cell counts with CD34(+) cell yield in autologous stem cell harvest. In a series of 32 patients (median age, 44 years; M:F = 11:21), 184 leukaphereses were performed after mobilization regimens with chemotherapy and G-CSF or G-CSF alone. Full blood cell counts were enumerated on peripheral blood (PB) samples taken prior to each leukapheresis. Mononuclear cell (MNC) and IMI(+) cell counts by automated hematology analyzer and flow cytometry based CD34(+) cell yield were measured on the harvested product. The relationship among PB white blood cells (WBC), PB monocytes, IMI(+) cells, MNC, and CD34(+) cell yield in a single leukapheresis was estimated by Pearson correlation analysis. PB WBC count showed no correlation with CD34(+) cell yield in a single leukapheresis (r = 0.02, P = 0.81). PB monocyte count showed a weak correlation (r = 0.21, P = 0.01) and MNC in harvest also showed a weak correlation (r = 0.36, P = 0.0001) with CD34(+) cell yield. In contrast, CD34(+) cell yield correlated well with IMI(+) cell count (r = 0.68, P = 0.0001), and data could be fitted by a linear regression equation, y = 0.330 + 0.974x. IMI(+) cell assay by the automated hematology analyzer correlated well with the CD34(+) cell yield in a mobilized autologous stem cell harvest. The IMI(+) cell count might be used as a simple and efficient indicator of blood stem cell mobilization and collection.

Microencapsulation of theophylline in composite wall system consisting of whey proteins and lipids

Theophylline was microencapsulated in composite whey protein-based wall systems containing different proportions of dispersed apolar filler, anhydrous milkfat. Wall emulsions exhibited uni-modal particle size distribution and had a mean particle size of 0.36-0.38 microm. Microcapsules were cross-linked by glutaraldehyde-saturated toluene via an organic phase. Spherical microcapsules ranging in diameter from 150 to larger than 700 microm were obtained and exhibited some surface cracks that could be attributed to the fragile nature of a peripheral, highly cross-linked 'shell' layer around the capsules. Core content ranged from 46.9-56.6% (w/w) and filler content ranged from 12.0-33.4% (w/w). Core and filler retention during microencapsulation ranged from 84.9-96.9%) and from 85.1-89.6%, respectively. Core retention was proportionally related to the proportion of filler embedded in the wall matrix. Core release into SGF and SIF was affected by microcapsule size, type of dissolution medium and wall composition. Rate of core release was inversely proportional to filler content of the wall matrix. This could be attributed to effects of filler content on diffusion through the wall matrix and probably on swelling properties of microcapsules. Results indicated that incorporation of apolar filler in wall matrix of whey protein-based capsules provided the means to enhance retention of a water-soluble core during the microencapsulation process and to decrease the rate of core release into aqueous dissolution media.

Disodium cromoglycate inhibits production of immunoglobulin E

Disodium cromoglycate (DSCG) has been shown to inhibit the release of mediators from mast cells. In the present study, the effect of DSCG on active anaphylactic reaction was studied in mice. DSCG dose-dependently inhibited the active systemic anaphylactic reaction and serum immunoglobulin (Ig)E production induced by immunization with ovalbumin, Bordetella pertussis toxin and aluminum hydroxide gel. DSCG strongly inhibited IL-4-dependent IgE production by lipopolysaccharide-stimulated murine whole spleen cells. In the case of U266 human IgE-bearing B cells, DSCG also showed an inhibitory effect on the IgE production. These results suggest that DSCG has an anti-anaphylactic activity by inhibition of IgE production from B cells.

Observation of B --> phiK and B --> phiK*

We have studied two-body charmless hadronic decays of B mesons into the final states straight phiK and phiK(*). Using 9.7 million B&Bmacr; pairs collected with the CLEO II detector, we observe the decays B- --> phiK- and B0--> phiK(*0) with the following branching fractions: B(B--->phiK-) = (5.5(+2.1)(-1.8)+/-0.6)x10(-6) and B(B0--> phiK(*0)) = (11.5(+4.5+1.8)(-3.7-1.7))x10(-6). We also see evidence for the decays B0-->phiK0 and B---> phiK(*-). However, since the statistical significance is not overwhelming for these modes, we determine upper limits of <12.3x10(-6) and <22.5x10(-6) ( 90% confidence level), respectively.

Observation of the Omega(0)(c) Charmed Baryon at CLEO

The CLEO experiment at the CESR collider has used 13.7 fb(-1) of data to search for the production of the Omega(0)(c) (css ground state) in e(+)e(-) collisions at square root of (s) approximately 10.6 GeV. The modes used to study the Omega(0)(c) are Omega(-)pi(+), Omega(-)pi(+)pi(0), Xi-K-pi(+)pi(+), Xi0K-pi(+), and Omega(-)pi(+)pi(+)pi(-). We observe a signal of 40.4+/-9.0(stat) events at a mass of 2694.6+/-2.6(stat)+/-1.9(syst) MeV/c(2), for all modes combined.

Development of a frequency-dependent-type apex locator with automatic compensation

Among apex locators, the frequency dependent type is more accurate and convenient to use than others. However, the accuracy of the apex locator is still influenced by the presence of various electrolytes used in root canal treatments. In this study, we developed a frequency-dependent electronic apex locator minimizing the influence of electrolytes on the measurement of root canal lengths. It was confirmed that the two frequencies of 0.5 and 10 kHz are better than the conventional ones of 0.4 and 8 kHz. The impedance ratio of the two different frequencies represents the position of the file in root canal, and the voltage difference of the two frequencies represents the status of the fluid in the root canal. As a result of compensation using the voltage differences of the two frequencies, the errors decreased significantly on average from +0.54 mm to +0.18 mm in H2O2 solution (p < 0.01), and from -0.33 mm to -0.01 mm in NaOCl solution (p < 0.01) in the tooth model experiments.

The immunomodulatory effects of a novel agent, leflunomide, in rat cardiac allotransplantation

We assessed the immunomodulatory effect of leflunomide (LEF) in a heterotopic abdominal model of rat heart transplantation using a major histocompatibility mismatch (DA X LEW). The endpoint of this study was cardiac rejection assessed by abdominal palpation of the ventricular impulse and confirmed by laparotomy and histology. In this study, LF was investigated using four dosages (5, 10, 20 and 30 mg/kg per day orally) against cyclosporine (CsA) (15 mg/kg per day orally) and FK 506 (1 mg/kg per day orally). The ability of LEF to prevent rejection and reverse ongoing acute rejection was assessed. The results showed that untreated hearts were fully rejected by day 5 and that LEF at 5 mg/kg was significantly better than any other dose tested, was superior to FK 1 mg/kg, and was as effective as CsA 15 mg/kg in preventing rejection after a short course of treatment. After a longer course, 10 and 20 mg/kg LEF proved more effective than 5 mg/kg in controlling rejection and as efficacious as 1 mg/kg FK and 15 mg/kg CsA. In the control of ongoing established early rejection. LEF proved to be equally effective, even at lower doses (5 mg/kg), to CsA 15 mg/kg and FK 1 mg/kg. In the control of ongoing established late rejection, 20 mg/kg LEF proved to be superior to 10 mg/kg LEF and 15 mg/kg CsA, and was as effective as FK 1 mg/kg. However, when higher doses of CsA (25 mg/kg) and FK (2 mg/kg) were tested against 20 mg/kg LEF in this mode of rescue, LEF proved as effective as CsA and superior to FK. In the assessment of drug toxicity using body weight as a parameter, 20 mg/kg LEF proved safer than any other LEF dose tested, and safer than 15 mg/kg CsA and 1 mg/kg FK in both short- and long term administration. We conclude that LEF is a relatively safe and potent immunosuppressant with promising clinical potential.

Entropic stabilization of the tryptophan synthase alpha-subunit from a hyperthermophile, Pyrococcus furiosus. X-ray analysis and calorimetry

The structure of the tryptophan synthase alpha-subunit from Pyrococcus furiosus was determined by x-ray analysis at 2.0-A resolution, and its stability was examined by differential scanning calorimetry. Although the structure of the tryptophan synthase alpha(2)beta(2) complex from Salmonella typhimurium has been already determined, this is the first report of the structure of the alpha-subunit alone. The alpha-subunit from P. furiosus (Pf-alpha-subunit) lacked 12 and 6 residues at the N and C termini, respectively, and one residue each in two loop regions as compared with that from S. typhimurium (St-alpha-subunit), resulting in the absence of an N-terminal helix and the shortening of a C-terminal helix. The structure of the Pf-alpha-subunit was essentially similar to that of the St-alpha-subunit in the alpha(2)beta(2) complex. The differences between both structures were discussed in connection with the higher stability of the Pf-alpha-subunit and the complex formation of the alpha- and beta-subunits. Calorimetric results indicated that the Pf-alpha-subunit has extremely high thermostability and that its higher stability is caused by an entropic effect. On the basis of structural information of both proteins, we analyzed the contributions of each stabilization factor and could conclude that hydrophobic interactions in the protein interior do not contribute to the higher stability of the Pf-alpha-subunit. Rather, the increase in ion pairs, decrease in cavity volume, and entropic effects due to shortening of the polypeptide chain play important roles in extremely high stability in Pf-alpha-subunit.

Psychological stress may induce increased humoral and decreased cellular immunity

Stress alters immune function and affects different immune cell populations in different ways. The authors examined whether psychological stress has different effects on the production of macrophage, T-helper 1(Th1) cell, and T-helper 2(Th2) cell-derived cytokines. Forty-two college students were recruited and their blood was sampled on the day they were to take a stressful academic examination and again 4 weeks after the examination. The stress from the academic examination significantly increased IL-1 beta, IL-6, and IL-10 and decreased IFN-gamma production. These findings suggest that examination stress may increase Th2 cell-mediated humoral immunity and macrophage activities and may decrease Th1 cell-mediated cellular immunity.

Search for B --> tau(nu) and B --> K(nu)nu

We report results of a search for B-->tau(nu) in a sample of 9.7 x 10(6) charged B meson decays. We exclusively reconstruct the companion B decay to suppress background. We set an upper limit on the branching fraction B(B-->tau(nu))<8.4 x 10(-4) at 90% confidence level. We also establish B(B+/--->K+/-nu(nu))<2.4 x 10(-4) at 90% confidence level.

Seasonal variation and indirect monitoring of microcystin concentrations in Daechung reservoir, Korea

Physicochemical and biological water quality, including the microcystin concentration, was investigated from spring to autumn 1999 in the Daechung Reservoir, Korea. The dominant genus in the cyanobacterial blooming season was Microcystis. The microcystin concentration in particulate form increased dramatically from August up to a level of 200 ng liter(-1) in early October and thereafter tended to decrease. The microcystin concentration in dissolved form was about 28% of that of the particulate form. The microcystins detected using a protein phosphatase (PP) inhibition assay were highly correlated with those microcystins detected by a high-performance liquid chromatograph (r = 0.973; P < 0.01). Therefore, the effectiveness of a PP inhibition assay for microcystin detection in a high number of water samples was confirmed as easy, quick, and convenient. The microcystin concentration was highly correlated with the phytoplankton number (r = 0.650; P < 0.01) and chlorophyll-a concentration (r = 0.591; P < 0.01). When the microcystin concentration exceeded about 100 ng liter(-1), the ratio of particulate to dissolved total nitrogen (TN) or total phosphorus (TP) converged at a value of 0.6. Furthermore, the microcystin concentration was lower than 50 ng liter(-1) at a particulate N/P ratio below 8, whereas the microcystin concentration varied quite substantially from 50 to 240 ng liter(-1) at a particulate N/P ratio of >8. Therefore, it seems that the microcystin concentration in water can be estimated and indirectly monitored by analyzing the following: the phytoplankton number and chlorophyll-a concentration, the ratio of the particulate and the dissolved forms of N and P, and the particulate N/P ratio when the dominant genus is toxigenic Microcystis.