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Biomedical subjects

F Kawasaki

Publications and source records attributed to F Kawasaki.

7 recordsLinked to original sources
PubMed1995

Structure and innervation of longitudinal and transverse abdominal muscles of the cricket, Gryllus bimaculatus.

Detailed morphological and physiological studies on the insect abdominal muscles, including their innervation and neuromuscular transmission, are essential for understanding their important role in respiratory movements. There are both longitudinal and transverse muscles in the ventral abdominal segments of the cricket, Gryllus bimaculatus. Muscle 202 was selected as an example of a longitudinal muscle. This muscle is, on average, 1.4 mm long, paired on both sides of the abdomen, and consists of 127 fibers whose mean maximum diameter is 32 microns; the average sarcomere length is 8.1 microns. It is innervated by two ipsilateral motoneurons in the second abdominal ganglion, the axons of which run in the ipsilateral first nerve root of the third abdominal ganglion. Two motor axons run in parallel from the two cell bodies and innervate in close proximity. Accordingly, large and small excitatory junctional potentials (EJPs) are recorded from the same fiber with slightly different thresholds when the first nerve root of the third abdominal ganglion is stimulated. Muscle 203, which is a transverse muscle that extends across the fifth abdominal sternum and is located over the fourth abdominal ganglion and muscle 202 on both sides, is, on average, 2.9 mm long and consists of 86 fibers with a maximum diameter of 33 microns. The average sarcomere length is 7.9 microns. The right or left half of the muscle is innervated mainly by a contralateral motoneuron in the third abdominal ganglion through the ipsilateral first nerve root of the third abdominal ganglion. Nerve branches of the first nerve root also reach muscles 188 and 218. Muscle 203 is additionally innervated by the first nerve roots of abdominal ganglia 1, 2, and 4. These innervations were ascertained both electrophysiologically and histologically. Individual muscle fibers of muscle 203 produced small EJPs in response to stimulation of the first nerve roots of abdominal ganglia 2, 3, and 4 and large EJPs in response to stimulation of the root from the first abdominal ganglion. The large and small EJPs in muscle 203 have properties similar to those in muscle 202.

Abdominal Muscles↗
PubMed1990

Spontaneous and evoked transmitter releases after concanavalin A treatment are affected differently by hypertonic low calcium solutions at frog neuromuscular junction.

Adding sucrose to the low calcium bathing solution made with no added calcium but containing Mg2+ EGTA to increase the tonicity elevated the basal frequency of miniature end-plate potentials (MEPPs) in the frog. The hypertonic low calcium solution also increased the rate at which the MEPP frequency rose in response to tetanic stimulation and elevated the level of the maximum frequency, which approached an asymptote. Pretreatment with concanavalin A (con A) greatly reduced the elevation in the basal frequency produced by hypertonic solutions. However, tetanic stimulation gave the same results as in untreated preparations when the tonicity was increased. Pretreatment with colchicine before the con A treatment eliminated the blocking action of con A on the MEPP frequency when the preparation was exposed to hypertonic solutions. Tetanic stimulation produced increases in MEPP frequency similar to those observed in normal junctions immersed in hypertonic solutions. Caffeine elevated the basal level of the MEPP frequency. Tetanic stimulation in the caffeine solution caused the increase in the MEPP frequency; the higher the basal level rose, the higher the maximum level became. However, the rate at which the MEPP frequency rose remained unchanged. The present results indicate that hypertonicity increases not only the basal frequency of MEPPs but also the slope at which the MEPP frequency is elevated by tetanic stimulation, both mechanisms being different and that the rate and magnitude of the tetanic potentiation of MEPP frequency are not simply determined by the pre-tetanus frequency.

Action Potentials↗
PubMed1990

Mn and Mg influxes through Ca channels of motor nerve terminals are prevented by verapamil in frogs.

At frog neuromuscular junctions immersed in solutions containing 0.5 mM Mn2+, verapamil (40 microM) reduced the increase in miniature end-plate potential (MEPP) frequency produced by tetanic stimulation (50 Hz, 2 min) of the motor nerve to 5% of that in the absence of verapamil. In solutions containing 5 mM Mg2+, verapamil reduced the tetanic increase in MEPP frequency to 8% of that in the absence of verapamil. Verapamil added to solutions containing 0.15 mM Ca2+ decreased the tetanic rise in MEPP frequency to 6% of the control value. In low Ca2+ (nominally Ca2(+)-free) solutions, verapamil decreased the tetanic rise to 70% of the control value. The present results suggest that Mn2+ and Mg2+, as well as Ca2+, enter the nerve terminal through Ca2+ channels during nerve stimulation and promote transmitter release. In addition to its effect on the Ca2+ channel, verapamil at higher concentrations appears to have inhibitory effects on the acetylcholine-gated end-plate channel and on the Na+ channel as suggested by its depressive effects on the amplitudes of MEPPs, end-plate potentials and nerve terminal action potentials.

Action Potentials↗
PubMed1989

[Study on hybrid materials compounded with porous hydroxyapatite and culture cells. 1. Attachment and the invasion of cultured cells to porous hydroxyapatite].

The purpose of this study was to investigate the effects of hybrid material compounded with periodontal ligament cells on human teeth and porous hydroxyapatite. As the first step, we tried to produce hybrid materials compounded with periodontal ligament cells and porous hydroxyapatite, and to observe the attachment and invasion of periodontal ligament cells porous hydroxyapatite. Human periodontal ligament cells which had been scraped off the root with a disposable blade were cultured at 37 degrees C in alpha-MEM plus 10% fetal calf serum. The culture cells were attached to the porous hydroxyapatite in vitro. After 3 and 14 days of incubation, the specimens were fixed in gluteraldehyde and examined using SEM. Other specimens were embedded in paraffin and successive specimens were prepared for to remodelling of the attachment and invasion. Many cells attached to the P-HAP granules, and some cells invaded the P-HAP granules. The results suggest that when these hybrid materials are implanted in bone defects, the cells remain in the defect for a certain period, and exhibit the functions and characteristics of itself.

Bone Regeneration↗