Kinematic characteristics during gait in frail older women identified by principal component analysis.

Frailty is associated with gait variability in several quantitative parameters, including high stride time variability. However, the associations between joint kinematics during walking and increased gait variability with frailty remain unclear. In the current study, principal component analysis was used to identify the key joint kinematics characteristics of gait related to frailty. We analyzed whole kinematic waveforms during the entire gait cycle obtained from the pelvis and lower limb joint angle in 30 older women (frail/prefrail: 15 participants; non-frail: 15 participants). Principal component analysis was conducted using a 60 × 1224 input matrix constructed from participants' time-normalized pelvic and lower-limb-joint angles along three axes (each leg of 30 participants, 51 time points, four angles, three axes, and two variables). Statistical analyses revealed that only principal component vectors 6 and 9 were related to frailty. Recombining the joint kinematics corresponding to these principal component vectors revealed that frail older women tended to exhibit greater variability of knee- and ankle-joint angles in the sagittal plane while walking compared with non-frail older women. We concluded that greater variability of knee- and ankle-joint angles in the sagittal plane are joint kinematic characteristics of gait related to frailty.

Effects of footwear fixation on joint angle variability during straight gait in the elderly.

BACKGROUND: Various types of footwear fixation can dramatically alter gait characteristics, and could potentially contribute to an increased risk of falls in the elderly. However, no studies have been conducted to analyze the effects of footwear fixation on joint angle variabilities, particularly during the entire gait cycle. RESEARCH QUESTION: Does the fixation of footwear significantly affect the lower limb joint angle variabilities during the gait cycle? METHODS: Principal component analysis (PCA) was conducted on 20 healthy adults using 3D spatio-temporal data of the pelvis and lower limb joint angle that were collected during the entire gait cycle with the footwear in various conditions (well-fixated footwear, less-fixated footwear, slippers, and bare feet). Kinematic waveforms were reconstructed from the PCA data, which were used to determine the distinct differences in joint angle variabilities between footwear conditions. RESULTS: The results showed large variability in the knee- and ankle-joint angles on the sagittal plane when walking in the loose condition (less-fixated footwear, slippers, and bare feet) compared with those in the well-fixated footwear condition. SIGNIFICANCE: These results demonstrate the effect of footwear fixation on the joint angle variabilities of the elderly while walking. The increase in the knee- and ankle-joint angle variabilities when walking with less-fixated footwear could be a risk factor for falls.

Application of the novel estimation method by shear wave elastography using vibrator to human skeletal muscle.

In recent years, non-invasive measurement of tissue stiffness (hardness) using ultrasound elastography has attracted considerable attention. It has been used to evaluate muscle stiffness in the fields of rehabilitation, sports, and orthopedics. However, ultrasonic diagnostic devices with elastography systems are expensive and clinical use of such devices has been limited. In this study, we proposed a novel estimation method for vibration-based shear wave elastography measurement of human skeletal muscle, then determined its reproducibility and reliability. The coefficient of variation and correlation coefficient were used to determine reproducibility and reliability of the method by measuring the shear wave velocities in konjac phantom gels and agar phantom gels, as well as skeletal muscle. The intra-day, day-to-day, and inter-operator reliabilities were good when measuring the shear wave velocities in phantom gels. The intra-day and day-to-day reliabilities were good when measuring the shear wave velocities in skeletal muscle. The findings confirmed adequate reproducibility and reliability of the novel estimation method for vibration-based shear wave elastography. Therefore, the proposed measurement method may be a useful tool for evaluation of muscle stiffness.

New approach to a practical quartz crystal microbalance sensor utilizing an inkjet printing system.

The present work demonstrates a valuable approach to developing quartz crystal microbalance (QCM) sensor units inexpensively for reliable determination of analytes. This QCM sensor unit is constructed by inkjet printing equipment utilizing background noise removal techniques. Inkjet printing equipment was chosen as an alternative to an injection pump in conventional flow-mode systems to facilitate the commercial applicability of these practical devices. The results demonstrate minimization of fluctuations from external influences, determination of antigen-antibody interactions in an inkjet deposition, and quantification of C-reactive protein in the range of 50-1000 ng∙mL-1. We thus demonstrate a marketable application of an inexpensive and easily available QCM sensor system.

Simultaneous immunoassay analysis of plasma IL-6 and TNF-α on a microchip.

Sandwich enzyme-linked immunosorbant assay (ELISA) using a 96-well plate is frequently employed for clinical diagnosis, but is time-and sample-consuming. To overcome these drawbacks, we performed a sandwich ELISA on a microchip. The microchip was made of cyclic olefin copolymer with 4 straight microchannels. For the construction of the sandwich ELISA for interleukin-6 (IL-6) or tumor necrosis factor-α (TNF-α), we used a piezoelectric inkjet printing system for the deposition and fixation of the 1st anti-IL-6 antibody or 1st anti-TNF-α antibody on the surface of the each microchannel. After the infusion of 2 µl of sample to the microchannel and a 20 min incubation, 2 µl of biotinylated 2nd antibody for either antigen was infused and a 10 min incubation. Then 2 µl of avidin-horseradish peroxidase was infused; and after a 5 min incubation, the substrate for peroxidase was infused, and the luminescence intensity was measured. Calibration curves were obtained between the concentration and luminescence intensity over the range of 0 to 32 pg/ml (IL-6: R(2) = 0.9994, TNF-α: R(2) = 0.9977), and the detection limit for each protein was 0.28 pg/ml and 0.46 pg/ml, respectively. Blood IL-6 and TNF-α concentrations of 5 subjects estimated from the microchip data were compared with results obtained by the conventional method, good correlations were observed between the methods according to linear regression analysis (IL-6: R(2) = 0.9954, TNF-α: R(2) = 0.9928). The reproducibility of the presented assay for the determination of the blood IL-6 and TNF-α concentration was comparable to that obtained with the 96-well plate. Simultaneous detection of blood IL-6 and TNF-α was possible by the deposition and fixation of each 1st antibody on the surface of a separate microchannel. This assay enabled us to determine simultaneously blood IL-6 and TNF-α with accuracy, satisfactory sensitivity, time saving ability, and low consumption of sample and reagents, and will be applicable to clinic diagnosis.

Determination of calprotectin in gingival crevicular fluid by immunoassay on a microchip.

OBJECTIVES: Gingival crevicular fluid (GCF) contains calprotectin, which appears to be a useful biomarker for periodontal diseases because of its high level in GCF from periodontally diseased pockets. To determine calprotectin in GCF that has a very small volume, sandwich enzyme-linked immunosorbent assay (ELISA) on a microchip was performed and its utility was estimated. DESIGN AND METHODS: Anti-calprotectin primary antibody was discharged on a microchip using a piezoelectric inkjet printing system. Calprotectin standard and calprotectin in GCF samples from eleven subjects were determined by the ELISA method with the prepared microchip and their values were compared with those obtained by conventional ELISA. RESULTS: Using the ELISA on a microchip, a reasonable standard curve of calprotectin protein (1.56-100 ng/mL) was obtained. Calprotectin in GCF samples was quantified and showed reasonable values in accordance with the condition of periodontal diseases. The values determined by the microchip method and conventional ELISA showed a significant linear relationship (R(2)=0.981). CONCLUSIONS: Calprotectin in GCF was determined using the ELISA on a microchip with high efficiency and this ELISA method for calprotectin determination may become a useful method for diagnosing periodontal diseases.

Differential effects of cold exposure on gene expression profiles in white versus brown adipose tissue.

The thermogenic function of brown adipose tissue (BAT) is known to be markedly elevated when animals are exposed to the cold, and intensive studies have been carried out to understand the molecular basis enabling effective thermogenesis in cold-exposed animals. In this study, we used microarray analysis to examine the effects of cold exposure of animals on their gene expression profiles in white adipose tissue (WAT), which seems to function as a counterpart tissue of BAT. The results indicate that the effects of cold exposure on the gene expression profiles of WAT were much more moderate than the effects on those of BAT. Possible reasons for the different responses of BAT and WAT to cold exposure are discussed.

Quantitative analysis of serum procollagen type I C-terminal propeptide by immunoassay on microchip.

BACKGROUND: Sandwich enzyme-linked immunosorbent assay (ELISA) is one of the most frequently employed assays for clinical diagnosis, since this enables the investigator to identify specific protein biomarkers. However, the conventional assay using a 96-well microtitration plate is time- and sample-consuming, and therefore is not suitable for rapid diagnosis. To overcome these drawbacks, we performed a sandwich ELISA on a microchip. METHODS AND FINDINGS: The microchip was made of cyclic olefin copolymer with straight microchannels that were 300 µm wide and 100 µm deep. For the construction of a sandwich ELISA for procollagen type I C-peptide (PICP), a biomarker for bone formation, we used a piezoelectric inkjet printing system for the deposition and fixation of the 1st anti-PICP antibody on the surface of the microchannel. After the infusion of the mixture of 2.0 µl of peroxidase-labeled 2nd anti-PICP antibody and 0.4 µl of sample to the microchannel and a 30-min incubation, the substrate for peroxidase was infused into the microchannel; and the luminescence intensity of each spot of 1st antibody was measured by CCD camera. A linear relationship was observed between PICP concentration and luminescence intensity over the range of 0 to 600 ng/ml (r(2) = 0.991), and the detection limit was 4.7 ng/ml. Blood PICP concentrations of 6 subjects estimated from microchip were compared with results obtained by the conventional method. Good correlation was observed between methods according to simple linear regression analysis (R(2) = 0.9914). The within-day and between-days reproducibilities were 3.2-7.4 and 4.4-6.8%, respectively. This assay reduced the time for the antigen-antibody reaction to 1/6, and the consumption of samples and reagents to 1/50 compared with the conventional method. CONCLUSION: This assay enabled us to determine serum PICP with accuracy, high sensitivity, time saving ability, and low consumption of sample and reagents, and thus will be applicable to clinic diagnosis.

Analysis of DNA ligation by microchip electrophoresis.

We describe the potential of microchip electrophoresis with a Hitachi SV1100, which can be used to determine DNA sizes between 500 and 5000 bp with good quantification (DNA concentration, <8 ng/l) within 5 min, for the analysis of DNA ligation. On analysis of an electropherogram of a ligation mixture of the pTAC1-T vector and a 789 bp PCR-amplified DNA fragment, the presence of recombinant DNA was easily detected by comparison with an electropherogram obtained without ligase. On analysis of a ligation mixture of pUC19/Eco RI without alkaline phosphatase treatment and a 667 bp Eco RI-digested fragment of foreign DNA, several peaks observed in the electropherogram corresponded to the formation of monomeric and polymeric insert DNAs, self-ligated vector DNA, and recombinant DNA. On the other hand, several peaks were also observed in the electropherogram of the ligation mixture of pUC19/Eco RI with alkaline phosphatase treatment and the 667 bp Eco RI-digested fragment of foreign DNA, the fluorescence intensity corresponding to recombinant DNA apparently being increased. These results indicate the potential of microchip electrophoresis for the analysis of DNA ligation, it offering high resolution in a short time.

Measuring the length distribution of self-assembled lipid nanotubes by orientation control with a high-frequency alternating current electric field in aqueous solutions.

The present work addresses the length distribution of self-assembled lipid nanotubes (LNTs) by controlling the orientation of the LNTs using an alternating current (ac) electric field in aqueous solutions. The effect of the ac field on the orientation and rotation of individual LNTs was examined to evaluate the optimum orientation frequency by visualizing the individual LNTs in real time. By using the high-frequency ac field, we have successfully measured the length distribution for two different types of LNTs and have quantitatively analyzed the maximum occurrences of the length distribution as well as the extension of the longer length region.

Laser damage to marine plankton and its application to checking biofouling and invasion by aquatic species: a laboratory study.

In this laboratory study, the ability of low-power pulsed laser irradiation to kill planktonic organisms in a flowing water system was examined, thus, to test the possibility of using this technique as a water treatment strategy to reduce biofouling growth in condenser tubes of power plants and to reduce bioinvasion via the ballast water of ships. Two flow rates (4.6 and 9.0 l h(-1)) were tested on three planktonic organisms: two marine centric diatoms viz. Skeletonema costatum and Chaetoceros gracilis and a dinoflagellate, Heterocapsa circularisquama. A low-power pulsed laser irradiation at 532 nm with a fluence of 0.1 J cm(-2) from a frequency-doubled Nd:YAG laser was used as the irradiation source. The laser irradiation resulted in a heavy mortality of the test cells. The mortality observed was >90% for S. costatum and H. circularisqama and >70% for C. gracilis. The results suggest that laser irradiation has the potential to act as a water treatment strategy to reduce biofouling of condenser tubes in power plants as well as to reduce species invasion via the ballast water of ships.

Importance of probe location for quantitative comparison of signal intensities among genes in microarray analysis.

In our previous studies, we demonstrated that expression levels of genes determined by Agilent oligoarray system, code G4130A, could be quantitatively evaluated by spike-in of synthetic full-length mRNAs as standards [Kakuhata R, Watanabe M, Yamamoto T, Akamine R, Yamazaki N, Kataoka M, et al. Possible utilization of in vitro synthesized mRNAs specifically expressed in certain tissues as standards for quantitative evaluation of the results of microarray analysis, J Biochem Biophys Methods 2007;70:755-60]. However, in its successor version (Agilent oligo array system, code G4131F), which was established to enable gene expression analysis over a much wider dynamic range, multiple probes are often utilized for evaluation of expression levels of individual genes; and they showed markedly distinct signal intensities. This result indicates that the observed signal intensities in this new version seemed not to simply reflect the transcript levels of individual genes. To understand the factors influencing the signal intensities of probes, we characterized the properties of the probes used in this new array system and the cRNAs formed during the labeling process. Analysis of cRNAs in the reaction mixture, which were hybridized with the arrays, revealed that the cRNAs were not fully transcribed under the conditions used. For this reason, probes located at the 5' side of the message were found to give lower signals than those at the 3' end; and the observed signal intensities were dependent upon the location of probes in the mRNA. Analysis of the correlation between signal intensities and locations on mRNAs for larger numbers of probes also supported the idea that probe location is one of the major determinants of signal intensities of probes in microarray analysis.

Possible utilization of in vitro synthesized mRNAs specifically expressed in certain tissues as standards for quantitative evaluation of the results of microarray analysis.

To examine the possible usefulness of in vitro synthesized RNA as standards in microarray analysis, we prepared full-length mRNAs encoded by 3 rat metabolic genes for heart/muscle type carnitine palmitoyltransferase I (M-CPTI), uncoupling protein (UCP1), and heart/muscle type fatty acid-binding protein (H-FABP). Artificial RNA samples were prepared by adding known amounts of these synthetic mRNAs to total RNA from rat liver, and transcript levels of various genes were compared between the prepared artificial RNA samples and total RNA samples of rat liver by using an Agilent oligo microarray system. Upon the addition of these synthetic RNAs, signals from the DNA spots corresponding to these 3 genes were elevated, but those from the DNA spots representing other genes were not markedly influenced. Using the ratio of the increase in signal intensity of DNA spot to the amount of added RNA, we estimated the expression levels of several genes and compared them with the absolute expression levels determined by calibrated Northern analysis. As a result, the absolute transcript levels of 3 genes encoding acidic ribosomal phosphoprotein P0, type-1 voltage-dependent anion channel (VDAC1), and type-2 glucose transporter (GLUT2) were successfully estimated by this procedure. Furthermore, genes specifically expressed in certain tissues such as UCP1 were concluded to be good candidates as standards for use in microarray analysis.

Usefulness of the 5' region of the cDNA encoding acidic ribosomal phosphoprotein P0 conserved among rats, mice, and humans as a standard probe for gene expression analysis in different tissues and animal species.

Housekeeping genes are often used as internal standards for gene expression analysis. When steady-state transcript levels of 4 typically used housekeeping genes, i.e., beta-actin, glyceraldehyde 3-phosphate dehydrogenase, cyclophilin, and acidic ribosomal phosphoprotein P0 (36B4), were evaluated in various rat tissues, the 36B4 gene seemed to be the most suitable as a standard to compare the expression levels of genes among different tissues. Next, for possible quantitative comparison of the expression level of this gene among different animal species, we compared the nucleotide sequence of the cDNA of 36B4 among rats, mice, and humans. As a result, highly conserved regions showing more than 97.5% identities were observed in the 5' portion of its open reading frame. When samples of synthesized mRNA encoding rat, mouse, and human 36B4 were hybridized with the entire cDNA encoding rat 36B4 as a probe, hybridization signals of mRNAs of mouse and human 36B4 were much weaker than those of mRNA encoding rat 36B4. However, when they were hybridized with an oligonucleotide probe corresponding to the highly conserved regions, they showed similar signal intensities. Thus, these highly conserved regions of the cDNA encoding 36B4 were concluded to be an effective standard for use in gene expression analysis.

In vitro laser ablation of natural marine biofilms.

We studied the efficiency of pulsed low-power laser irradiation of 532 nm from an Nd:YAG (neodymium-doped yttrium-aluminum-garnet) laser to remove marine biofilm developed on titanium and glass coupons. Natural biofilms with thicknesses of 79.4 +/- 27.8 microm (titanium) and 107.4 +/- 28.5 microm (glass) were completely disrupted by 30 s of laser irradiation (fluence, 0.1 J/cm2). Laser irradiation significantly reduced the number of diatoms and bacteria in the biofilm (paired t test; P < 0.05). The removal was better on titanium than on glass coupons.

In vitro laser ablation of laboratory developed biofilms using an Nd:YAG laser of 532 nm wavelength.

We studied the laser ablation of laboratory-developed biofilm on titanium and glass surfaces. Specifically, Pseudoalteromonas carrageenovora, a marine biofilm forming bacterium was used to generate laboratory biofilm. Two fluences, 0.05 and 0.1 J/cm(2) and three durations of irradiation, 30 s, 5 min, and 10 min were tested using an Nd;YAG laser of 532 nm wavelength (in the green light area). Nonirradiated coupons with biofilm served as control. The biofilm removal efficiency increased with the increase in laser fluence and duration of irradiation. The maximum biofilm area cover on control coupons of glass and titanium was 62.5 and 76.0%, respectively. Upon irradiation with fluence 0.1 J/cm(2) for the very short duration of 30 s, this reduced to 5.6 and 12.4% and at 10 min to 2.17 and 0.7% on glass and titanium coupons, respectively, while the controls did not show any reductions (62.5 and 76.0% respectively, for glass and titanium coupons). The biofilm TRC (Total Resuscitated Cells) reduction during this period was even more prominent than the area cover, indicating that the remaining biofilm portions on coupons after irradiation were largely composed of dead bacterial cells. The TRC in the irradiation chamber medium for short durations of irradiation showed a significant increase, indicating that the laser irradiation removed live bacteria from the biofilm. The re-growth of the resuscitated cells showed they could grow like the control cells but with a significant lag. The laser's efficiency in the removal of biofilm was better seen on titanium coupons than on glass. Our results showed that a low-power pulsed laser irradiation could be used to remove biofilm formed on hard surfaces.

Laser impact on bacterial ATP: insights into the mechanism of laser-bacteria interactions.

The mechanisms of laser action on bacteria are not adequately understood. Here, an attempt has been made to study the fluctuation in ATP (adenosine triphosphate) concentration following laser irradiation from a pulsed Nd:YAG laser on a marine biofilm-forming bacterium Pseudoalteromonas carrageenovora. A stationary phase bacterial suspension (density 10(7-8) ml-1) was exposed to pulsed laser irradiations at a fluence of 0.1 J cm-2 (pulse width 5 ns, repetition rate 10 Hz) for different durations, ranging from 2 s to 15 min. The total viable count (TVC) and ATP concentration of the irradiated samples were determined immediately after the laser irradiation. While the maximum reduction in the TVC observed with respect to the control was 59% immediately after 15 min irradiation, the ATP concentration showed a reduction of about 86% for the same duration. The ATP concentration showed an abrupt reduction from 3 min of laser irradiation and continued to reduce significantly with increasing duration of irradiation. Thus, 3 min irradiation at a fluence of 0.1 J cm-2 is considered as an approximate threshold for ATP production in this bacterium. As the decreased level of ATP production continued, bacterial mortality resulted. The reduction in ATP production could be due to damage caused by the laser irradiations on bacterial metabolic processes such as cellular respiration.

Laser impact on marine planktonic diatoms: an experimental study using a flow cytometry system.

A flow cytometry system was used to evaluate the impact of pulsed laser irradiations from an Nd:YAG laser on two marine coastal water diatoms, Chaetoceros gracilis and Skeletonema costatum. Three flow speeds, i.e. 9, 18 and 27 ml min-1 and three laser fluences, i.e. 0.025, 0.05 and 0.1 J cm-2 pulse-1 were tested during this study. The reduction in cell density and chlorophyll a (chl a) concentrations were monitored by reference to non-irradiated samples as controls. Upon irradiation, the cell density and the chl a concentrations became reduced significantly compared to the control (one way ANOVA p < 0.001 for the cell density in both the species and p < 0.05 for chl a concentrations in both species). A maximum mortality of 0.77 log10 (about 83%) for C. gracilis and 0.68 log10 (about 78%) for S. costatum was observed at 9 ml min-1 flow speed and 0.1 J cm-2 laser fluence. The maximum reduction observed in the chl a concentration was about 26% (control 0.413 and sample 0.306 mg ml-1) for C. gracilis and 27% (control 0.222 and sample 0.16 mg ml-1) for S. costatum, when the flow rate was 9 ml min-1 and the fluence 0.1 J cm-2. In general, mortality increased with an increase in the laser fluence. The results thus show if the cooling water is laser-irradiated to mitigate biofouling, this could result in significant damage to the planktonic flora of the flowing seawater system, which in turn might reduce algal biofilm formation on industrially important structures. The reduction in the chl a concentration showed that the laser irradiations also could result in a significant reduction in the primary productivity of the cooling water.

Lethal and sub-lethal impacts of pulsed laser irradiations on the larvae of the fouling barnacle Balanus amphitrite.

Laboratory experiments were conducted to study the impact of laser irradiation on the larvae of the fouling barnacle Balanus amphitrite. Research pertaining to fouling invertebrate larvae-laser interaction is sparse and, hence, data on this aspect were thought significant in order to consider pulsed low power laser irradiations as a possible future antifouling tool. Lethal and sub-lethal impacts of four very low laser fluences, viz. 0.013, 0.025, 0.05 and 0.1 J cm-2 for three different durations, viz. 2, 10 and 30 s were investigated. Three growth stages of barnacle larvae, viz. nauplii stage II, nauplii stage IV and cyprids were exposed to the mentioned laser fluences for different durations. While lethal impact was assessed immediately after and 1 d after irradiation, sub-lethal impacts were studied by monitoring the success rate of the irradiated nauplii in reaching the cyprid stage. In addition, the swimming speed of VIth stage nauplii after irradiation was studied. In the case of cyprids, in addition to the mortality measurement immediately after and 1 d after irradiation, the settlement rate was investigated. In all the above experiments, non-irradiated larvae served as controls. The results showed an increase in mortality with increasing laser fluence and duration of irradiation. Irradiation for 2 s resulted in significant mortality in nauplii, while it was less in the case of cyprids. In IInd stage nauplii, the mortality immediately after irradiation for 2 s varied from 14.8 +/- 2.12 to 97.1 +/- 4.1% for laser fluences of 0.013 and 0.1 J cm-2, respectively. However, in cyprids, the mortality immediately after irradiation for 2 s varied from 12.2 +/- 3 to 13.4 +/- 1.2% for fluences of 0.013 and 0.1 J cm-2, respectively. The mortality in IVth stage nauplii was less than that for IInd stage nauplii but more than that for cyprids. There was a significant increase in mortality with time after irradiation. The formation of cyprids from the irradiated larvae was significantly less than that observed for non-irradiated larvae. Also, the irradiated larvae showed a significantly slower swimming speed compared to the control samples. The settlement rate in cyprids was reduced significantly by the laser irradiation. This was true even for the lowest fluence and shortest period of irradiation tested. Thus, the results of the experiment showed that even a low power pulsed laser irradiation of 0.013 J cm-2 for 2 s can cause significant damage to fouling barnacle larvae.

Pulsed laser irradiation impact on two marine diatoms Skeletonema costatum and Chaetoceros gracilis.

The ability of pulsed laser irradiations to cause damage on the biofouling organisms is recently being investigated. If this technique is employed in industries such as power generation wherein a large quantity of water is being used for the cooling purpose, many organisms other than the targeted would get affected. In this study, we have investigated the damage caused by the pulsed laser irradiations from an Nd:YAG laser (fluence 0.1J/cm(2)) for varying durations such as 2, 5, 10, 30, 60 and 300 s on two marine diatom species namely Skeletonema costatum and Chaetoceros gracilis. Upon exposure to low power laser irradiations, these diatom species showed mortalities between 52.6+/-9.3% to 97.7+/-3.1% in the case of S. costatum and 57.8+/-2.5% to 98.9+/-0.6% in the case of C. gracilis for 2 and 300 s of irradiations, respectively. The mortality increased with the increase in the duration of laser irradiation. The estimation of the chlorophyll a concentration in the irradiated samples showed a considerable reduction varying between 9.8% and 57% in C. gracilis and 3% and 70.3% in S. costatum for 2 and 300 s of irradiations, respectively. The laser-survived cells grew as the non-irradiated (control) samples. C. gracilis frustules were broken by the laser whilst, the cell materials were drained out of the frustules in the case of S. costatum. The study therefore showed that the low power pulsed laser irradiations could cause significant damage on the two species of planktonic diatoms.