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Biomedical subjects

M Kumashiro

Publications and source records attributed to M Kumashiro.

At least 19 recordsLinked to original sources
PubMed2006

Genitalic autogrooming: a self-filling trash collection system in crickets.

Insects groom almost all parts of the body surface with their legs and mouth parts. However, some body regions are difficult to reach and keep clean. One is the genital chamber located in the last abdominal segment in males which houses the phallic complex for copulation and production of the spermatophore. In the male cricket, foreign substances can enter the genital chamber when it is opened during copulation and spermatophore formation. Moreover, the dorsal pouch and ventral lobes of the phallic complex, which mould the attachment plate, tube, and ampulla of the spermatophore, are inevitably soiled as a result of spermatophore production. We found a unique cleaning system in which foreign substances accumulated during copulation and spermatophore debris left in the dorsal pouch after copulation are quickly removed and collected in special pockets in the genital chamber. This trash is collected by undulation of the genital chamber's membranous floor which is entirely covered by small scales ( approximately 10 microm) similar to those in the ovipositor of female crickets. This self-filling trash collecting system may be used in some other insects which produce the spermatophore in a similar manner to that of crickets.

Animals↗
PubMed2004

Auto-spermatophore extrusion reveals that the reproductive timer functions in the separated terminal abdominal ganglion in the male cricket.

Auto-spermatophore extrusion is a kind of spermatophore extrusion without genital coupling in the male cricket. It rarely occurred in intact males paired with a female, while it frequently occurred in all the males with the connectives cut under restraint and dissection. The time interval (SPaSE) between spermatophore preparation and auto-spermatophore extrusion was found to be comparable to that (RS2) of the time-fixed sexually refractory stage measured by the calling song. According to extracellular spike recording, the dorsal pouch motoneuron (mDP), which singly innervates the dorsal pouch muscles and is responsible for spermatophore extrusion, showed a burst discharge in association with auto-spermatophore extrusion with an interval similar to RS2 in males with the connectives transected between the 6th abdominal ganglion and the terminal abdominal ganglion (TAG) after spermatophore preparation. These results strengthened our previous conclusion that the reproductive timer for RS2 is located in the TAG, and demonstrated that it functions normally even in the TAG separated from the rest of the central nervous system.

Abdomen↗
PubMed2001

Reproductive behaviour in the male cricket Gryllus bimaculatus DeGeer. I. Structure and function of the genitalia.

We have investigated the morphology and physiology of the genitalia of the male cricket to establish a basis for neuroethological study of its reproductive behaviour. First, the structure of the phallic complex, including the dorsal pouch, guiding rod, epiphallus, ventral lobes and median pouch, are described, as are the muscles, cuticle, membranes and biomechanics of copulation. The innervation and sensory receptors have also been examined. Second, the functional role of the muscle in each genital organ has been determined by direct observation of muscle contraction during spontaneous or evoked movements and by analysis of the changes in movements after the ablation of the muscle. Third, for the flexible membranous organs, the ventral lobes and median pouch, the passages for haemolymph and their dynamic properties have been examined using petroleum jelly. Fourth, the sequence of coordinated motor actions performed by the internal and external genital organs, which were induced in both restrained and dissected males using newly developed techniques, has been analyzed during tethered copulation and spermatophore formation. As a result, the mechanisms of copulation and spermatophore formation are now more fully understood.

Animals↗
PubMed2001

Reproductive behaviour in the male cricket Gryllus bimaculatus DeGeer. II. Neural control of the genitalia.

To understand the neural mechanisms of reproductive behaviour in the male cricket, we identified motor neurones innervating the muscles in each genital organ by backfilling with cobalt/nickel and recording their extracellular spike activity from nerve bundles of the terminal abdominal ganglion during tethered copulation and spermatophore formation. During tethered copulation, at least two motor neurones innervating two ipsilateral muscles were activated during projection of the guiding rod of the phallic dorsal pouch. Only one motor neurone, innervating four ipsilateral muscles of the dorsal pouch, was responsible for spermatophore extrusion by deforming the dorsal pouch. For spermatophore transfer, three motor neurones, singly innervating three epiphallus muscles, played a major role in opening passages for haemolymph to enter the ventral lobes and median pouch by bending the epiphallus. Two ventral lobe and 3-5 median pouch motor neurones seemed to play a role in expanding or folding the two membranous structures by relaxing or contracting their muscle fibres. After spermatophore transfer, most of the genital motor neurones exhibited a rhythmic burst of action potentials causing movement of the phallic complex coupled with strong abdominal contractions. For spermatophore formation, the genital motor neurones began to accelerate their rhythmic bursts approximately 30 s prior to subgenital plate opening and then changed their activity to tonic bursting or silence. The results have allowed us to describe the timing of the onset and termination of genital muscle contraction more precisely than before, to examine the neural mechanisms of copulatory motor control and to speculate on the neural organization of the reproductive centre for spermatophore extrusion and protrusion.

Action Potentials↗
PubMed2000

Ergonomics strategies and actions for achieving productive use of an ageing work-force.

In this report, a basic ERGOMA (Ergonomics in Industrial Management) strategy is proposed as a policy for corporate production and employment in countries where ageing populations and reduced birth rates are imminent, and a strategy related to this is proposed. Specifically, as a strategy at the company level, the results of survey studies aimed at the development of methods for determining job capacity, to enable effective use of the labour of ageing workers, were summarized. A number of the insights gained here are steps in the development of a foundational methodology for practical use, and in actual practice a number of these insights must be subjected to measurements. However, the theory and newly developed methodology described here are thought to represent significant changes from the approaches to job capacity diagnosis and assessment published in the past and from the stance towards utilization of an ageing work-force. The author is confident that this represents new progress in one of the ergonomics approach to dealing with the working environment of ageing workers and an ageing work-force in general.

Aged↗
PubMed1999

Differences in heart rate variability between young and elderly normal men during graded head up tilt.

An autoregressive spectral analysis of heart rate variability (HRV) was used to analyze the differences in autonomic functions during graded head up tilt (HUT) between young and elderly men. After recording at the 0 degree position, the table was rotated to an upright position. The incline of the table was increased progressively to 15 degrees, 30 degrees and 60 degrees. The data obtained from seven young subjects (mean age of 20.0 years) and nine elderly subjects (mean age of 63.3 years) were analyzed. The high frequency components expressed by normalized units (HFnu) were used as the parasympathetic indicators, and HFnu decreased with tilt angle in both age groups. These results suggested that parasympathetic withdrawal have an important role in adaptation to an upright posture in both age groups. However, mean HF amplitude at the 0 degree position in elderly men was not significantly different from that of young men at 60 degrees tilt. A significant interaction effect (age group x tilt angle) was found for mean HF amplitude. The increase of the low frequency components expressed by normalized units (LFnu) and the LF-to-HF ratio in elderly subjects from 0 degree to 15 degrees seemed to be larger than that in young subjects. Sympathetic activities may be sensitive to lower levels of orthostatic stress in the elderly, and the elderly workers are easily affected by a change in workload. Therefore, keeping the workload lower and constant may be recommended to avoid excessive sympathetic activation among the elderly.

Adolescent↗
PubMed1998

Power spectral analysis of heart rate variability in type A females during a psychomotor task.

This study investigated changes in autonomic nervous activities due to psychological stress in Type A females. Eight Type A and eight Type B females performed a psychomotor task for 30 minutes. Power spectral analysis of heart rate variability (HRV) was used to examine the autonomic nervous activities. Results showed the low frequency (LF) component and LF/HF ratio in Type A females increased after the onset of the task. There were no significant differences in task performance between Type A and Type B females. The subjective mental workload increased gradually in Type A females during the tasks, whereas in Type B females this parameter did not change in a consistent manner. The results suggest that the sympathetic nervous system in Type A females was more stimulated by the task and Type A females felt a greater subjective mental workload than did Type B females.

Adult↗
PubMed1998

Effects of armrests on workload with ten-key operation.

The constrained posture used for work using a visual display terminal (VDT), such as data entry, can produce static muscular fatigue. Based on the application of ergonomic principles, we conducted an experiment using a prototype VDT chair designed with an armrest adjustable to heights from 22 to 28 cm. The experiment--conducted to assess the static muscular strain based on varying heights of the armrest and distance from the keyboard--was performed with male subjects. The subjects were asked to input five-figure numbers using the 10 keys arranged on the right side. Using a surface electromyogram, we measured the strain imposed on the arm and the shoulder. This was followed up with a performance, weight-loading onto the armrests and a questionnaire. Results show that use of armrests is effective for the alleviation of muscles in one-handed keyboard operation where operators work on a desk whose height is unadjustable according to their body height or where operators are unable to rest their wrist on the desk. A chair with height-adjustable armrests is considered desirable when used by several people.

Adult↗
PubMed1997

Risk of serious adverse events in hypertensive patients receiving isradipine: a meta-analysis.

A meta-analysis was performed to compare the risk of serious adverse events associated with the use of all formulations of isradipine, when used as monotherapy in hypertension, to active drug or placebo controls. Eligible studies totalled 65 published and unpublished randomised controlled trials involving 9903 subjects and 10,675 treatment exposures: 4492 to isradipine, 1473 to isradipine sustained release, 2768 to other active drugs, and 1942 to placebo. Mortality, cardiovascular outcomes, other serious incident illnesses, such as cancer, and withdrawals were sought. Seventy-five per cent of the isradipine exposures were to standard-release formulations and 25% were to sustained-release formulations. Overall, isradipine therapy shows no difference in risk of major adverse events or withdrawals compared to other active controls or placebo (odds ratios [OR] 0.9; 95% CI 0.7-1.46 and 0.5; 95% CI 0.2-1.3). These major adverse events included angina, fatal and non-fatal myocardial infarction, stroke and overall mortality. Isradipine sustained release could be compared only to placebo, based on available data, and shows a lower risk of withdrawals (OR 0.5; 95% CI 0.3-0.9), and a similar trend was observed for major adverse events, (OR 0.8; 95% CI 0.3-2.5). Published and unpublished randomised controlled trials were analysed in separate meta-analyses and later combined when this sensitivity analysis of risk showed no differences between the groups. In conclusion, we find no evidence for increased risk of serious adverse events in patients receiving isradipine as monotherapy for hypertension.

Antihypertensive Agents↗
PubMed1995

Assessment of autonomic function in myotonic dystrophy by spectral analysis of heart-rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart-rate variability (HRV) of 10 myotonic dystrophy (MD) patients (4 men and 6 women, aged 37-53 years) and 10 age- and sex-matched healthy, sedentary humans (control) at rest in the supine position. All MD patients had no cardiac conduction disturbances (i.e., atrioventricular or intraventricular conduction defects) on 12-lead electrocardiogram and were able to walk and perform daily activities. In the MD group, the total power, the power of the low-frequency component (a marker of sympathetic and vagal modulation of heart rate) and that of the high-frequency component (a marker of vagal modulation of heart rate) were smaller than those in the control group (P < 0.01, P < 0.05 and P < 0.05, respectively). The results of this study suggest that the cardiovascular autonomic nervous system contributing to the HRV may be disturbed even in the MD patients who can walk and perform daily activities. Therefore, one must give careful consideration to the cardiovascular autonomic dysfunction, as well as the cardiac conduction disturbance in the MD patients.

Adult↗
PubMed1995

Assessment of autonomic function in traumatic quadriplegic and paraplegic patients by spectral analysis of heart rate variability.

We analyzed by means of autoregressive spectral analysis the spontaneous beat-to-beat heart rate variability (HRV) of quadriplegic and paraplegic male subjects at rest in the supine position. In agreement with our previous study, in nine of 15 quadriplegic patients only the high-frequency (HF: center frequency = respiratory frequency) component (a marker of vagal modulation of heart rate) was observed. In contrast, in six of the quadriplegic patients both the HF component and the low-frequency (LF: center frequency at approx. 0.1 Hz, 0.03-0.15 Hz in this study) component (a marker of sympathetic and vagal modulation of heart rate) were observed. However, in six quadriplegic patients who presented the LF component, (i) the center frequency of the LF component was lower than that in 10 healthy, sedentary, age-matched males (control I) (P < 0.01), (ii) the power of the HF component was smaller than that in the control-I group (P < 0.01) and (iii) the LF/HF power ratio (an index of sympathovagal balance) was larger than that in the control-I group (P < 0.05). On the other hand, in nine paraplegic patients with an intact 1st-4th thoracic spinal cord, from which the cardiac sympathetic nerves originate, the total power, the power of the LF component and that of the HF component were smaller than those in nine healthy, sedentary, age-matched males (control II) (P < 0.05, P < 0.01 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

How to benefit from ergonomic interventions through participation by workers, managers and the company: an example of a small- to medium-sized factory with no ergonomic knowledge.

Many of the managers, and supervisors in small- and medium-sized businesses are technicians. These are workers with many years of experience in one specialized technical area. They know, in their minds, what should be improved, and how, in order to make the work easier to do. However, their knowledge of work improvement techniques, and how to think together with the workers, and further how to best lead their troops, is nil. This report focuses on managers and supervisors who had never even heard the word "ergonomics," and touches on cases of successful implementation of ergonomic work improvements. The subject work-places are part of an automobile parts manufacturing plant operating under a typical production system of small amounts of many product types: cutting process machinery workshop, press workshop and packing and distribution workshop. At the stage when they became aware of ergonomics, the key words for improvement which they mentioned were "manual lifting" and "working posture." As a result of various observations, analysis techniques and meetings, they introduced a push car with lifters as support equipment. However, the most significant result was that they were able to convince the company's owner of its contribution to productivity improvement, using objective data. Also, with regard to the push car manufacturer, they designed the specifications for the push car themselves and participated in its production. Of course, they were also praised by the workers for achieving a work method involving no strain or waste.

Automobiles↗
PubMed1993

Menstrual cycle effects on a VDT-based simulation task: cognitive indices and subjective ratings.

It is unclear whether the menstrual cycle affects the basics of performance, mainly task performance and cognitive functions. We examined menstrual cycle effects on VDT-based task performance, cognitive indices based on the signal-detection theory, and subjective ratings in questionnaires. We experimented in three phases: premenstrual, menstrual and postmenstrual phases. Previous studies reported premenstrual tension syndrome (PMST) in the premenstrual phase. Women used physiological and psychological strategies to cope during the menstrual phase. However, task performance, cognitive indices and subjective ratings showed no menstrual cycle effects. Thus, we can conclude that the information processing for the VDT-based task was not affected by menstrual cycle.

Adult↗
PubMed1992

Power spectral analysis of heart rate variability in Type As during solo and competitive mental arithmetic task.

It has been reported that there are differences in autonomic balance between Type As and Type Bs. This study evaluated the sympathovagal interaction in Type A (N = 10) and Type B (N = 10) male students during mental arithmetic task in a solo and a competitive condition by the spectral component analysis of heart rate variability (HRV). The low-frequency (LF) component to high-frequency (HF) component ratio was significantly greater in Type As than in Type Bs, though no significant differences were found in task performance, heart rate change, and blood pressure between the two subject groups in both conditions. The present findings indicate that there was a significant difference in sympathovagal balance between Type As and Type Bs, and that Type As showed dominant sympathetic activity. The results suggest that the power spectral analysis of HRV, which is convenient and non-invasive, has enough sensitivity to discriminate differences in autonomic balance between Type A subjects and Type B subjects, not only during the solo and competitive task period but also during the resting period.

Heart Rate↗
PubMed1992

Ranges of dynamic motion of the wrist in healthy young and middle-aged men.

The difference in the range of dynamic motion of the wrist between young and middle-aged men was studied. To analyse wrist function easily, a new quantitative evaluation technique for wrist circumduction using a biaxial flexible electrogoniometer was introduced. A phase plane was made from two-channel signals of the electrogoniometer, and the 'ROM (range of motion) Index' for wrist circumduction was defined. Twelve healthy young men (age 19-31 years) and twelve healthy middle-aged men (age 45-63 years) were studied. Under forearm fixed conditions, there was no difference of the ROM Index between the two age groups. A significant decrease of the ROM Index in the middle-aged group was found in the non-dominant wrists without forearm fixation. The four quadrantal analysis of wrist circumduction clarified that this difference appeared especially in the radiodorsal direction. These results suggest that in the middle-aged men, the motor function involving the radiocarpal and midcarpal joints does not decrease, but that for the proximal and distal radioulnar joints in the non-dominant side drops.

Adult↗
PubMed1991

Power spectral analysis of blood pressure variability in traumatic quadriplegic humans.

A study was performed on seven traumatic neurologically complete quadriplegic (QP) males and seven age-matched healthy males (control) while they were at rest in the supine position in a climatic chamber (temperature 30 degrees C, relative humidity 60%). Arterial blood pressure waveforms were measured by a continuous noninvasive blood pressure-monitoring system based on arterial tonometry. Furthermore, the spontaneous beat-to-beat systolic blood pressure (SBP) variabilities of subjects were investigated by means of autoregressive power spectral analysis. As shown by earlier studies with an invasive (intra-arterial) blood pressure-monitoring system, in the control group there were two major spectral components: a high-frequency (HF) component [center frequency 0.27 +/- 0.02 (SE) Hz eq, power 0.9 +/- 0.2 mmHg2] and a low-frequency (LF) component (0.10 +/- 0.01 Hz eq, 5.2 +/- 1.4 mmHg2). On the contrary, in the QP group only the HF component was observed (0.28 +/- 0.03 Hz eq, 3.2 +/- 1.4 mmHg2). The results suggest that 1) in the QP subject the disappearance of the LF component in the SBP variability (i.e., the Mayer waves in humans) is presumably caused by the interruption of the spinal pathways linking supraspinal cardiovascular centers with the peripheral sympathetic outflow and 2) the cervical spinal sympathetic pathways may be instrumental in the genesis of the Mayer waves in humans.

Adult↗
PubMed1990

Power spectral analysis of heart rate variability in traumatic quadriplegic humans.

This study investigated the spontaneous beat-to-beat variabilities in R-R intervals of six traumatic neurologically complete quadriplegic (QP) males and six age-matched healthy males (control) while they were at rest in the supine position in a climatic chamber (temperature 30 degrees C, relative humidity 60%) by means of autoregressive power spectral analysis. As shown by earlier studies, in the control group there were two major spectral components, a high-frequency (HF) component [center frequency 0.30 +/- 0.02 (SE) Hertz equivalent (Hz eq), power 767.5 +/- 384.6 ms2] and a low-frequency (LF) component (0.11 +/- 0.01 Hz eq, 707.5 +/- 198.8 ms2). On the contrary, in the QP group, only the HF component was observed (0.30 +/- 0.02 Hz eq, 421.8 +/- 134.7 ms2). The results suggest that 1) the disappearance of the LF component in the QP subject is presumably caused by the interruption of the spinal pathways linking supraspinal cardiovascular centers with the peripheral sympathetic outflow, and 2) the cervical spinal sympathetic pathways may be instrumental in the genesis of the LF component in humans.

Adult↗