Impact of the COVID-19 pandemic on the incidence of surgical site infection after orthopaedic surgery: an interrupted time series analysis of the nationwide surveillance database in Japan.

BACKGROUND: During the COVID-19 pandemic, hygiene awareness was increased in communities and hospitals. However, there is controversy regarding whether such circumstances affected the incidence of surgical site infections (SSIs) in the orthopaedic surgical field. AIM: To examine the impact of the COVID-19 pandemic on the incidence of SSIs after orthopaedic surgery. METHODS: The medical records of patients having undergone orthopaedic surgery were extracted from the nationwide surveillance database in Japan. The primary outcomes were the monthly incidences of total SSIs, deep or organ/space SSIs, and SSIs due to meticillin-resistant Staphylococcus aureus (MRSA). Interrupted time series analysis was conducted between pre-pandemic (January 2017 to March 2020) and pandemic (April 2020 to June 2021) periods. RESULTS: A total of 309,341 operations were included. Interrupted time series analysis adjusted for seasonality showed no significant changes in the incidence of total SSIs (rate ratio 0.94 and 95% confidence interval 0.98-1.02), deep or organ/space SSIs (0.91, 0.72-1.15), or SSIs due to MRSA (1.07, 0.68-1.68) along with no remarkable slope changes in any parameter (1.00, 0.98-1.02; 1.00, 0.97-1.02; and 0.98, 0.93-1.03, respectively). CONCLUSIONS: Awareness and measures against the COVID-19 pandemic did not markedly influence the incidence of total SSIs, deep or organ/space SSIs, or SSIs due to MRSA following orthopaedic surgery in Japan.

Design of microfluidic channels to prevent negative filtration in implantable hemofiltration devices.

In order to improve the quality of life of dialysis patients, our group have been developing an implantable hemofiltration device (IHFD) composed of multiple layers of dialysis membranes and microfluidic channels. To improve the hemodialysis performance of IHFD, preventing the negative filtration, which is caused by the oncotic pressure of blood, is mandatory. In this study, we fabricated IHFDs with five different microchannel designs and experimentally investigated the performance of each device in in vitro experiment. In addition, the successful IHFD was further evaluated by ex vivo experiments with a beagle dog. The experiments verified the effectiveness of the microchannel design, which will be used for the IHFD for in vivo experiments with pigs in the future.

Analysis of the pattern of suprahyoid muscle activity during pharyngeal swallowing of foods by healthy young subjects.

We previously developed the T(P) technique to discriminate between the activity patterns of skeletal muscles. In this study we aim to identify the T(P) value(s) that can be used to sensitively evaluate the activity patterns of the suprahyoid (SH) muscles during swallowing. We also analyse the effect of food textural properties on the activity patterns of the SH muscle during oral and pharyngeal swallowing. Three test foods consisting of 3%, 6% and 9% of a thickening agent, Mousse-up (MU) were prepared. Their textural properties differed significantly. Swallowing of 9% MU involved a significantly longer average duration than 3% MU. The average T(50) value for 6% MU was significantly larger than that for 3% MU. However, the average T(20) and T(80) values of the test foods did not differ. Thus, the T(50) value is particularly suitable for evaluating SH muscle swallowing patterns. Moreover, test foods that vary in their textural properties elicit different durations and patterns of SH muscle activity.

Activity patterns of the suprahyoid muscles during swallowing of different fluid volumes.

Influences of bolus volumes on activity patterns of the suprahyoid muscles during swallowing were examined using the T(P) technique (which quantitatively evaluates muscle activity patterns and indicates a negatively skewed pattern at lower T(P) values) in healthy young adults (eight men and four women). One of six volumes of tea ranging from 10 to 32 mL was delivered randomly to each subject while recording an electromyogram of the suprahyoid muscles and a laryngeal mechanogram with a piezoelectric sensor. Each subject was asked to swallow the full volume of liquid in a gulp if possible. T(P) values were calculated as deciles from T(0) to T(100) during intervals that were defined by the trajectory of the laryngeal mechanogram recorded during swallowing. Seven significant differences were detected in the average T(P) values from T(30) to T(60): between 16 mL (e.g., 0.448 in T(30)) and 25 mL (0.408 in T(30)) and between 20 mL (0.453 in T(30)) and 25 mL. There were significant differences among the 12 subjects for all of the nine average T(P) values (Ps < 0.001), suggesting a notable intersubject variation in the suprahyoid (SH) activity patterns. The average peak amplitudes of the integrated suprahyoid activity differed significantly among the six volumes (P < 0.001), while the average durations measured by the laryngeal mechanogram did not. The present results suggest that the swallowing volume mainly affects SH activity patterns, which were evaluated by the T(P) technique, during the early period of each swallow.

Activity pattern of swallowing-related muscles, food properties and body position in normal humans.

Activity patterns of the swallowing-related muscles were examined in normal subjects at different four body positions during swallowing of foods with different textural properties. Surface electromyograms were recorded from two muscle groups, the anterior tongue and suprahyoid muscles. The T(P) technique we developed was applied to the electromyograms for quantitative analysis of the activity patterns. Three test foods were prepared by dissolving 2.0% (low), 5.7% (middle) and 9.1% (high concentration) of a thickening agent into distilled water. Each subject was delivered randomly, one of the test foods to swallow at one of the four body positions i.e. horizontal supine, 30 degrees inclined, 60 degrees inclined and upright. In this study, T(50) values were calculated in activity data of the two muscle groups, and the T(50) values were statistically examined analysis of variance with a linear model including four fixed effects of 'concentrations', 'body positions', 'subjects' and 'sessions'. Three major findings obtained were that (i) the activity pattern of the anterior tongue was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the upright to the horizontal supine position, (ii) the activity pattern of the suprahyoid muscles was altered from a decrementing discharge pattern to an incrementing discharge pattern by shifting from the low concentration food to the higher ones and (iii) two subgroups were detected in subjects with the significant effects of 'concentrations' and 'body positions'. These findings lead a conclusion that activity patterns of the swallowing-related muscles are affected by food properties and body positions.

Effects of damage of the l-XII nerve that innervates tongue retractive muscles in rats.

The aim of this study was to examine whether sectioning of the lateral branches of the hypoglossal nerves (l-XII) in young male rats affects regulation of body weight, food intake and water intake in their period of growth by using a linear fixed effects model or not. Three groups of the rats were prepared according to treatments applied at about 4 weeks after birth to the l-XII innervating the hyoglossus, styloglossus and inferior longitudinal muscles: bilaterally sectioned (n = 9), unilaterally sectioned (n = 3) and sham-operated (n = 6) groups. Changes in body weight, food intake and water intake of the rats in the three groups were measured for 32 days before and after the treatments. To test the abilities of eating and drinking, the amounts of food and water intake were also measured for 1 and 2 min, respectively, after 20 h food and water deprivation at the final stage of the experiment. The major findings obtained were that (i) bilateral sectioning of the l-XII in the young rats significantly reduced body weight and the amount of water, not food, intake consumed and (ii) the bilateral sectioning affected the ability of eating and bilateral and unilateral sectioning affected that of drinking. The results suggest that bilateral sectioning of the lateral branches of XII nerve in young male rats affects regulation of body weight and water intake in their period of growth.

Comparison of video-recorded laryngeal movements during swallowing by normal young men with piezoelectric sensor and electromyographic signals.

The movement of the larynx in five young men during the swallowing of a liquid was examined by simultaneously recording a video-movie, the trajectory of a piezoelectric sensor, and the surface electromyogram of the suprahyoid muscles (SH). The movies revealed swallowing was associated with four characteristic spatial points of laryngeal movement: (1) a slight movement in the superior posterior direction (1.9 +/- 1.2 s; mean +/- SD of the time elapsed after the command to swallow was issued); (2) the initiation of anterosuperior elevation (2.3 +/- 1.3 s); (3) the turn at the highest position (3.2 +/- 1.2 s); and (4) the return to the initial position (4.1 +/- 1.4 s). The piezoelectric sensor and the SH electromyogram also detected characteristic temporal points that closely corresponded to the characteristic temporal points captured by the video. The advantages of using movies in swallowing research are discussed.

Applicability of piezoelectric sensors for speech rehabilitation.

The applicability of piezoelectric sensors for speech rehabilitation was examined by setting vocalizing tasks for seven healthy young adults (four men and three women). A piezoelectric sensor was attached to the front of the neck and each seated subject was instructed to vocalize /a/ with subjective low and high tones and /pa/, /ta/, and /ka/ with a subjective middle tone. The three major findings were: (1) slow potential changes recorded at the start of these tasks were followed by rapid changes; (2) the tasks did not differ in the average range of the slow changes; (3) female subjects had higher average frequencies of rapid changes than male subjects. The frequencies and phases of the rapid changes paralleled the sound waves recorded in the neck during the tasks. Swallowing tasks verified the appropriateness of the recording system. The advantages of using piezoelectric sensors in the clinic are discussed.

Influence of food properties and body position on swallowing-related muscle activity amplitude.

This study was designed to examine the effect of different food properties and body positions on electromyographic amplitudes of the anterior tongue (AT) and suprahyoid (SH) muscles during swallowing in normal subjects (six men and three women; 21-30 years old). Each subject was asked to swallow three foods (consisting of 2.0%, 5.7% or 9.1% of a thickening agent dissolved in water) with different textural properties in one of four body positions: upright, inclined at 60 degrees or 30 degrees , or supine. Surface electromyograms (EMG) were recorded from the anterior tongue and SH muscles, and the integrated and cumulated EMG were used to evaluate the amplitude changes. The increases in food hardness and adhesiveness elevated the integrated and cumulated EMGs of both the AT and SH muscles during swallowing in a stepwise manner (P < 0.0001, one-way anova) that was independent of the body position. There was a linear relationship between the concentrations of the thickening agent and the logarithmic values of the food hardness. There was also a parallel relationship between the logarithmic hardness values and the final logarithmic values of the cumulated muscle activity during swallowing. Unlike these simple amplitude responses of the AT and SH muscles to the different food properties, our previous studies have shown that the durational responses of these muscle activities to different food properties are more complicated. Possible neural mechanisms responsible for the amplitude responses observed are discussed.

A new method of simulating surface electromyograms using probability density functions.

A new method based on probability density functions (inverse Gaussian distributions) to simulate surface electromyograms (sEMGs) was developed for the specific use of the 'T(P) technique', which discriminates sEMG activity patterns. First, four prototypes with different activity patterns were generated from inverse Gaussian distributions by changing their geometrical parameters, which were derived from actual recorded sEMGs. Then, four simulated sEMGs were produced on the basis of the prototypes. The validity of the simulation method in relation to the T(P) technique was statistically examined and verified. The new simulation method will be useful.

Influence of food properties and body posture on durations of swallowing-related muscle activities.

The purpose of this study was to determine (i) whether or not textural properties of foods and body positions affect the durations of anterior tongue and suprahyoid muscle activities during swallowing, and (ii) if such changes occur, is the 'pre-peak' or the 'post-peak' duration of integrated muscle activity responsible. We used two test foods with different properties of hardness and adhesiveness. We recorded electromyograms (EMGs) from the anterior tongue and suprahyoid muscles as well as the laryngeal movement associated with swallowing in normal subjects (six men and three women; 21-30-years old). The subjects swallowed the test foods in four randomly set postures: upright, two inclined (60 degrees and 30 degrees to horizontal), and supine. None of the measured durations for the anterior tongue and suprahyoid EMGs were different among the four positions during swallowing of either food. The 'total' duration, from the start to the end of the integrated EMG, of anterior tongue activity was significantly (P<0.001, anova) longer during the swallowing of the tougher and more adhesive food than during swallowing of the other food, but the 'total' duration of suprahyoid activity was unchanged. The 'post-peak' duration of anterior tongue activity, which stretched from the peak to the end of the integrated EMG, was also significantly longer (P<0.001, anova) during swallowing of the tougher and more adhesive food. The results indicate that tougher and more adhesive foods prolong the duration, especially the 'post-peak' duration, of anterior tongue activity during swallowing in the upright, inclined and supine positions.

Influences of body posture on duration of oral swallowing in normal young adults.

The primary purpose of this study was to determine whether body posture altered the duration of oral swallowing. To answer this question, we recorded electromyograms (EMGs) from the anterior tongue and suprahyoid (SH) muscles as well as laryngeal movement associated with swallowing in nine normal young subjects. The subjects swallowed a test food after receiving a signal while in four randomly set postures: upright, two inclined (60 degrees and 30 degrees to the horizontal), and supine positions. We measured the durations from the start to the peak and from the peak to the end of the integrated tongue and SH EMGs. We assumed that the duration from the start to the peak of the integrated SH EMG would correspond to the duration of oral swallowing. The average duration from the start to the peak of the integrated SH EMG decreased after moving from the upright to the inclined and supine positions. The decrease in the duration was statistically significant and consistent for three experimental sessions. The duration from the start to the peak of the integrated tongue EMG during swallowing tended to decrease after lying down, but not significantly. The postural changes did not affect the remaining four durations. The decrease in the duration of oral swallowing induced by lying down suggests that the gravitational force placed on the test food facilitates the swallowing reflex. Large variation in the tongue activity during swallowing among the subjects can probably be attributed to the lack of a significant decrease in the duration of the tongue activity.

Analysis of head movements coupled with trunk drift in healthy subjects.

Accelerometers were used to measure sequential head tilt and trunk drift in 14 healthy young subjects while they performed three kinds of head task. First, maximum inclination angles in anterior, posterior, right and left directions were measured to estimate cervical ranges of motion for flexion-extension and lateral bending. The inclination angles measured (61.2 degrees on average for flexion, 51.7 degrees for extension, 42.7 degrees for right bending and 43.9 degrees for left bending) were consistent with previous findings. Secondly, cross-correlation analysis was applied to evaluate the degree of functional coupling between the head and trunk during flexion-extension and lateral bending. Significantly higher correlation coefficients were found between head tilt and trunk drift when these movements were in the same (iso-) directional condition than in a different (allo-) directional condition. The coupled trunk drift in flexion-extension for the iso-directional condition (10.3 degrees on average) was much larger than for the allodirectional condition (2.3 degrees). Finally, head turning was recorded as oval traces in a biaxial plane. In both clockwise and counter-clockwise head turning conditions, the maximum inclination angles of the traces were larger in the anterior-posterior direction (59.8 degrees anterior and 58.2 degrees posterior, in the clockwise condition, and 47.4 degrees and 47.4 degrees in the counter-clockwise condition) than in the right-left direction (36.3 degrees right and 39.0 degrees left, in the clockwise condition, and 40.5 degrees and 36.7 degrees in the counter-clockwise condition), and the angles in the four directions were almost equal to flexion-extension and lateral bending. The characteristics of the traces recorded and a possible application of the present recording system are discussed.

Barrett's oesophagus with predominant intestinal metaplasia correlates with superficial cyclo-oxygenase-2 expression, increased proliferation and reduced apoptosis: changes that are partially reversed by non-steroidal anti-inflammatory drugs usage.

BACKGROUND: Cyclo-oxygenase-2 expression has been reported to play an important role in the metaplasia-dysplasia-carcinoma sequence in Barrett's oesophagus. However, the existence of cyclo-oxygenase-2 expressing cells in Barrett's epithelium is still uncertain. AIM: To identify the cells that express cyclo-oxygenase-2 protein and to investigate the relationship between cyclo-oxygenase-2 expression and mucin-phenotype of Barrett's epithelium. METHODS: Sections from 466 biopsy samples of Barrett's epithelium from 358 non-medicated patients were immunohistochemically examined for the cyclo-oxygenase-2 expression, mucin-phenotype, cell proliferation and apoptosis. RESULTS: Cyclo-oxygenase-2 expression was detected in 71.0% of Barrett's epithelium biopsy samples. In Barrett's epithelium with the gastric predominant mucin-phenotype, cyclo-oxygenase-2 expression was mainly found in stromal and deep epithelial cells, whereas in intestinal predominant mucin-phenotype, it was mostly in superficial epithelial cell. A significant elevation of proliferating cell nuclear antigen index and suppression of apoptotic index was observed in Barrett's epithelium with superficial epithelial cyclo-oxygenase-2 expression. Neither such elevation of proliferating cell nuclear antigen index nor the suppression of apoptotic index could be found in chronic non-steroidal anti-inflammatory drugs users. CONCLUSIONS: Barrett's epithelium with intestinal mucin and superficial epithelial cyclo-oxygenase-2 expression possess a higher proliferation potential, but this risk may be thwarted by non-steroidal anti-inflammatory drugs administration.

Head movement associated with performance of mandibular tasks.

The present study was designed to examine the hypothesis that the motor system controlling phonation is functionally coupled with the motor system controlling posture of the head and neck, as previously suggested (U. Haddar, T.J. Steiner, E.C. Grant and F.C. Rose Human Movement Science 2: 35 and Language and Speech 26: 117). Head tilt and trunk drift in the antero-posterior and right-left directions were measured simultaneously for 20 s before and during three types of speech sounds (/pa/, /ta/ and /ka/) as well during a maximum jaw open-close task in 14 healthy young subjects. The major findings obtained in all of the four tasks were: (i) the trunk drift measured in both directions was negligible in comparison with the head tilt; (ii) the head tilt in the antero-posterior direction was much larger than in the right-left direction and (iii) the head tilt during performance of the four tasks consisted of 'initial' and 'sustained' phases. In the initial phase, the head tilted posteriorly in association with the start of individual tasks. In the sustained phase, the head tilted either anteriorly or posteriorly when the task progressed. The magnitude of the net head tilt in the sustained phase negatively correlated with that of the initial head tilt. These findings indicate that phonation, in the form of jaw open-close, accompanies head movement in two consecutive phases.

Expression of midkine and receptor-like protein tyrosine phosphatase (RPTP)-beta genes in the rat stomach and the influence of rebamipide.

BACKGROUND: Midkine has been reported to bind to receptor-like protein tyrosine phosphatase (RPTP)-beta and to play important roles in growth and differentiation of various cells. Midkine is expressed in rat stomach during experimental ulcer healing, suggesting that the midkine-RPTP-beta system has some physiological functions in the stomach. Rebamipide is a mucoprotective drug used for the treatment of gastric ulcers. We have tested the hypothesis that the ulcer healing mechanism stimulated by rebamipide is linked physiologically to the gastric midkine-RPTP-beta system. MATERIALS AND METHODS: Seven-week-old-male Wistar rats were used. Midkine and RPTP-beta gene expression in rat stomach was investigated by laser capture microdissection coupled with the reverse transcription-polymerase chain reaction (RT-PCR). The effects of rebamipide on midkine and RPTP-beta expression in rat stomach and the gastric epithelial cell line RGM1 were evaluated by RT-PCR and Northern blot analyses. RESULTS: Midkine and RPTP-beta expression was detected in the gastric mucosal, submucosal and muscle layers. Rebamipide stimulated both midkine and RPTP-beta expression in rat stomach and RGM1 cells. CONCLUSION: Rebamipide may protect the gastric mucosa by regulating midkine and RPTP-beta expression.

Activation of prostaglandin E2-receptor EP2 and EP4 pathways induces growth inhibition in human gastric carcinoma cell lines.

The effect of prostaglandin E2 (PGE2) on the proliferation of gastric cancer cells is still unclear. PGE2 receptors are divided into four subtypes - EP1, EP2, EP3, and EP4 - which are coupled to three different intracellular signal-transduction systems. Stimulation of EP2 and EP4 is linked with cyclic adenosine 3', 5'-monophosphate (cAMP)-dependent protein kinase A (PKA). In some human gastric cancer cells, PGE2 has been suggested to have an antiproliferative effect by way of increased cAMP production. Expression of EP2 and EP4 in human gastric carcinoma cells, however, has not been examined. We examined the expression of EP2 and EP4 and the antiproliferative effects of specific EP2 and EP4 agonists on four different human gastric cancer cell lines. Our data clarified that all the cell lines investigated in this study expressed EP2 and EP4 and that the specific agonists of these receptors induced growth inhibition with an accompanying increase in cAMP production. In summary, gastric cancer cells have EP2 and EP4 receptors, and their selective activation is linked with the decreased cell proliferation.

Graphic analysis of the relationship between skin colour change and variations in the amounts of melanin and haemoglobin.

BACKGROUND/AIMS: The L*a*b* coordinate is the most commonly used colour system to measure skin colour in dermatology and cosmetology. In this system, a* and L* are often used for quantification of the degrees of erythema and pigmentation. The aim of this study was to examine whether a* and L* can be used as specific scales to indicate the amount of haemoglobin and melanin, respectively, in the skin. METHODS: The a* and L* values were examined with a reflectance spectrometer in various skin conditions or lesions caused by a change in the amount of either melanin or haemoglobin, i.e. vitiligo, ultraviolet-induced pigmentation (PG), erythema resulting from slapping (ER), corticosteroid-induced blanching, erythema due to stasis by arm lowering, and a combination of PG and ER. The differences in values between the test sites and the adjacent normal skin, deltaa* and deltaL*, were plotted on the deltaa*-deltaL* plane and analysed statistically and geometrically. RESULTS: L* depended substantially not only on melanin but also on haemoglobin, especially if the oxygen saturation level was expected to be low. a* was also influenced by melanin. The results of graphic analysis indicated that a linear transformation of (deltaa*, deltaL*) into (deltaHb = 1.68 deltaa* + 0.60 deltaL*, deltaMel =-1.06 deltaa*-1.44 deltaL*) was suitable for separately estimating the change in the amount of haemoglobin (deltaHb) and in that of melanin (deltaMel). CONCLUSION: The results of this study may be of value for understanding the relationship between colour coordinates of the skin and the quantities of haemoglobin and melanin, and may be of use when pigmented lesions of the face are monitored by tristimulus colourimetry, as facial skin colour is affected considerably by the rich and easily variable cutaneous blood flow.

Skin reflectance-spectra and colour-value dependency on measuring-head aperture area in ordinary reflectance spectrophotometry and tristimulus colourimetry.

BACKGROUND/AIMS: Measurement of skin colour has become increasingly popular in the study of dermatology with the increased availability of portable instruments. However, different instruments have been reported as giving different results from measurement of the same skin region. The aim of this study was to examine the effects of differences in measuring-head aperture area on skin reflectance spectra and colour values. METHODS: We measured both reflectance spectra and CIE-L*a*b* values of the skin in five different anatomical regions on 10 subjects using two MINOLTA reflectance spectrometers that were identical apart from the aperture area of the measuring heads (diameters: 5 and 11 mm). For comparison, data were also obtained from a skin-coloured tile. RESULTS: Skin reflectance values measured with the wider-aperture instrument were higher than those measured with the other, irrespective of anatomical location. The differences between the two were near zero at an incident light wavelength of 400 nm, but increased to around 10% of the reflectance value at 700 nm, increasing exponentially with incident light of increasing wavelength. Skin colour was observed to be brighter, redder and yellower, in CIE-L*a*b* expression, when measured with the wider-aperture instrument. The differences between measurements obtained from the skin-coloured tile were much smaller. CONCLUSION: Skin reflectance and colour values measured with reflectance instruments are not absolute data but depend on the aperture area of the measuring head. This is probably due to variations in the proportion of longer-wavelength light reflected from the skin and collected by the instrument.

Changes in jaw reflexes by stimulation of the hypothalamus in anesthetized rabbits.

Changes in the masseteric monosynaptic reflex (MMR) and jaw-opening reflex (JOR) responses resulting from conditioning stimulation in the hypothalamus were studied in anesthetized rabbits. Stimulation of the lateral hypothalamus evoked a facilitation of the MMR and an inhibitory or facilitatory effect on the JOR. The facilitatory effect on JOR was stronger than that on the MMR. The facilitatory effective site for the JOR was in the dorsal and lateral directions as compared to the inhibitory field. The results suggest two functionally distinct regions in the lateral hypothalamus that separately project to the jaw-opening muscles.