Self-cloning of the Catalase Gene in Environmental Isolates Improves Their Colony-forming Abilities on Agar Media.

Hydrogen peroxide (H2O2) inhibits microbial growth at a specific concentration. However, we previously isolated two environmental bacterial strains that exhibited sensitivity to a lower H2O2 concentration in agar plates. Putative catalase genes, which degrade H2O2, were detected in their genomes. We herein elucidated the characteristics of these putative genes and their products using a self-cloning technique. The products of the cloned genes were identified as functional catalases. The up-regulation of their expression increased the colony-forming ability of host cells under H2O2 pressure. The present results demonstrated high sensitivity to H2O2 even in microbes possessing functional catalase genes.

Genome Sequences of Comamonadaceae Bacteria OS-1 and OS-4, Two Highly H2O2-Sensitive Strains Isolated from Pond Water.

The Comamonadaceae bacterial strains OS-1 and OS-4 were isolated from pond water and were found to be highly sensitive to hydrogen peroxide in the agar plates. Here, we report the nearly complete and complete genome sequences, respectively, of these two strains.

Critical Effect of H2O2 in the Agar Plate on the Growth of Laboratory and Environmental Strains.

We previously showed that autoclaving in preparing agar media is one of the sources of hydrogen peroxide (H2O2) in the medium. This medium-embedded H2O2 was shown to lower the total colony count of environmental microorganisms. However, the critical concentrations of H2O2 detrimental to colony formation on the agar plate remain largely undetermined. Herein, we elucidated the specific effect of H2O2 on microbial colony formation on solid agar medium by external supplementation of varying amounts of H2O2. While common laboratory strains (often called domesticated microbes) formed colonies in the presence of high H2O2 concentrations (48.8 µM or higher), microbes from a freshwater sample demonstrated greatly decreased colony counts in the presence of 8.3 µM H2O2. This implies that environmental microbes are susceptible to much lower concentrations of H2O2 than laboratory strains. Among the emergent colonies on agar plates supplemented with different H2O2 concentrations, the relative abundance of betaproteobacterial colonies was found to be lower on plates containing higher amounts of H2O2. Further, the growth of the representative betaproteobacterial isolates was completely inhibited in the presence of 7.2 µM H2O2. Therefore, our study clearly demonstrates that low micromolar levels of H2O2 in agar plates critically affect growth of environmental microbes, and large portions of those are far more susceptible to the same than laboratory strains. IMPORTANCE It is well-known that most of environmental microorganisms do not form colonies on agar medium despite that agar medium is the commonly used solidified medium. We previously demonstrated the negative effects of H2O2 generation during agar medium preparation on colony formation. In the present study, we investigated the independent effect of H2O2 on microbial growth by adding different concentrations of H2O2 to agar medium. Our results demonstrate for the first time that even low micromolar levels of H2O2 in agar plates, that are far lower than previously recognized as significant, adversely affect colony number obtained from freshwater inoculum.

Accuracy of Heart Rate and Respiratory Rate Measurements Using Two Types of Wearable Devices.

Objectives: Wearable devices such as fitness trackers have become popular in the healthcare field. Tracking heart rate and respiratory rate, in addition to physical activity, may provide an accurate picture of daily health. We believe that a combination of two types of devices can simultaneously measure and record physical activity, heart rate, and respiratory rate. However, the measurement accuracies of these two types of devices are not clear. This study aimed to determine the measurement accuracies of two wearable devices for heart and respiratory rate measurements. Methods: Ten healthy men performed incremental load tests (ILTs) and constant load tests (CLTs) on a cycle ergometer. The heart and respiratory rates were measured using wrist-worn (Silmee W22, TDK, Japan, Tokyo) and respiratory tracking devices (Spire Stone, Spire Health, San Francisco, CA, USA), respectively. A 12-lead electrocardiograph and the breath-by-breath method were used as external standards for heart and respiratory rates, respectively. Results: Bland-Altman analysis showed that heart rate had a fixed bias at rest and during ILT and CLT and had a proportional bias during CLT. The standard error values of the regression at rest and during CLT were less than 10 bpm for heart rate and less than 5.0 /min for respiratory rate. During ILT, the standard error was greater than 10 bpm for heart rate and approximately 5.0 /min for respiratory rate. Conclusions: The heart and respiratory rate measurements obtained using wearable devices were accurate within the practical margin of error.

Development of a Gait Rehabilitation Robot Using an Exoskeleton and Functional Electrical Stimulation: Validation in a Pseudo-paraplegic Model.

OBJECTIVE: We have developed a robot for gait rehabilitation of paraplegics for use in combination with functional electrical stimulation (FES). The purpose of this study was to verify whether the robot-derived torque can be reduced by using FES in a healthy-person pseudo-paraplegic model. METHODS: Nine healthy participants (22-36 years old) participated in this study. The robot exoskeleton was designed based on the hip-knee-ankle-foot orthosis for paraplegia. Participants walked on a treadmill using a rehabilitation lift to support their weight. The bilateral quadriceps femoris and hamstrings were stimulated using FES. The participants walked both with and without FES, and two walking speeds, 0.8 and 1.2 km/h, were used. Participants walked for 1 min in each of the four conditions: (a) 0.8 km/h without FES, (b) 0.8 km/h with FES, (c) 1.2 km/h without FES, and (d) 1.2 km/h with FES. The required robot torques in these conditions were compared for each hip and knee joint. The maximum torque was compared using one-way analysis of variance to determine whether there was a difference in the amount of assist torque for each gait cycle. RESULTS: Walking with the exoskeleton robot in combination with FES significantly reduced the torque in hip and knee joints, except for the right hip during extension. CONCLUSIONS: In the healthy-participant pseudo-paraplegic model, walking with FES showed a reduction in the robot-derived torque at both the hip and knee joints. Our rehabilitation robot combined with FES has the potential to assist paraplegics with various degrees of muscle weakness and thereby provide effective rehabilitation.

Complete Genome Sequence of Alphaproteobacteria Bacterium Strain SO-S41, Isolated from Forest Soil.

The complete genome of hydrogen peroxide-sensitive alphaproteobacterial strain SO-S41 was sequenced. The complete genome contains a single chromosome, is 4,443,179 bp in length, contains a total of 4,632 genes, and has a G+C content of 66.2%.

Development of a Rehabilitation Robot Combined with Functional Electrical Stimulation Controlled by Non-disabled Lower Extremity in Hemiplegic Gait.

OBJECTIVE: We developed a rehabilitation robot to assist hemiplegics with gait exercises. The robot was combined with functional electrical stimulation (FES) of the affected side and was controlled by a real-time-feedback system that attempted to replicate the lower extremity movements of the non-affected limb on the affected side. We measured the reproducibility of the non-affected limb movements on the affected side using FES in non-disabled individuals and evaluated the smoothness of the resulting motion. METHOD: Ten healthy men participated in this study. The left side was defined as the non-affected side. The measured hip and knee joint angles of the non-affected side were reproduced on the pseudo-paralytic side using the robot's motors. The right quadriceps was stimulated with FES. Joint angles were measured with a motion capture system. We assessed the reproducibility of the amplitude from the maximum angle of flexion to extension during the walking cycle. The smoothness of the motion was evaluated using the angular jerk cost (AJC). RESULTS: The amplitude reproduction (%) was 87.9 ± 6.2 (mean ± standard deviation) and 71.5 ± 10.7 for the hip and knee joints, respectively. The walking cycle reproduction rate was 99.9 ± 0.1 and 99.8 ± 0.2 for the hip and knee joints, respectively. There were no statistically significant differences between results with FES versus those without FES. The AJC of the robot side was significantly smaller than that of the non-affected side. CONCLUSIONS: A master-slave gait rehabilitation system has not previously been attempted in hemiplegic patients. Our rehabilitation robot showed high reproducibility of motion on the affected side.

Postcontraction hyperemia after electrical stimulation: potential utility in rehabilitation of patients with upper extremity paralysis.

The purpose of this study was to compare postcontraction hyperemia after electrical stimulation between patients with upper extremity paralysis caused by upper motor neuron diseases and healthy controls. Thirteen healthy controls and eleven patients with upper extremity paralysis were enrolled. The blood flow in the basilic vein was measured by ultrasound before the electrical stimulation of the biceps brachii muscle and 30 s after the stimulation. The stimulation was performed at 10 mA and at a frequency of 70 Hz for 20 s. The mean blood flow in the healthy control group and in upper extremity paralysis group before the electrical stimulation was 60 ± 20 mL/min (mean ± SD) and 48 ± 25 mL/min, respectively. After the stimulation, blood flow in both groups increased to 117 ± 23 mL/min and 81 ± 41 mL/min, respectively. We show that it is possible to measure postcontraction hyperemia using an ultrasound system. In addition, blood flow in both groups increased after the electrical stimulation because of postcontraction hyperemia. These findings suggest that evaluating post contraction hyperemia in patients with upper extremity paralysis can assess rehabilitation effects.

The impact of high-frequency magnetic stimulation of peripheral nerves: muscle hardness, venous blood flow, and motor function of upper extremity in healthy subjects.

The purpose of this study was to investigate the impact of high-frequency peripheral nerve magnetic stimulation on the upper limb function. Twenty-five healthy adults (16 men and 9 women) participated in this study. The radial nerve of the non-dominant hand was stimulated by high-frequency magnetic stimulation device. A total of 600 impulses were applied at a frequency of 20 Hz and intensity of 1.2 resting motor threshold (rMT). At three time points (before, immediately after, and 15 min after stimulation), muscle hardness of the extensor digitorum muscle on the stimulated side was measured using a mechanical tissue hardness meter and a shear wave imaging device, cephalic venous blood flow on the stimulated side was measured using an ultrasound system, and the Box and Block test (BBT) was performed. Mechanical tissue hardness results did not show any significant differences between before, immediately after, and 15 min after stimulation. Measurements via shear wave imaging showed that muscle hardness significantly decreased both immediately and 15 min after stimulation compared to before stimulation (P < 0.05). Peripheral venous blood flow and BBT score significantly increased both immediately and 15 min after stimulation compared to before stimulation (P < 0.01). High-frequency peripheral nerve magnetic stimulation can achieve effects similar to electrical stimulation in a less invasive manner, and may therefore become an important element in next-generation rehabilitation.