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K Mochida

Publications and source records attributed to K Mochida.

At least 19 recordsLinked to original sources
PubMed1998

lefty-1 is required for left-right determination as a regulator of lefty-2 and nodal.

lefty-1, lefty-2, and nodal are expressed on the left side of developing mouse embryos and are implicated in left-right (L-R) determination. The role of lefty-1 was examined by analyzing mutant mice lacking this gene. The lefty-1-deficient mice showed a variety of L-R positional defects in visceral organs. Unexpectedly, however, the most common feature of lefty-1-/- mice was thoracic left isomerism (rather than right isomerism). The lack of lefty-1 resulted in bilateral expression of nodal, lefty-2, and Pitx2 (a homeobox gene normally expressed on the left side). These observations suggest that the role of lefty-1 is to restrict the expression of lefty-2 and nodal to the left side, and that lefty-2 or nodal encodes a signal for "leftness."

Animals↗
PubMed1998

Isolation of the rat spermatid manchette and its perinuclear ring.

The manchette is a transient structure that develops during spermiogenesis. It consists of three components: a perinuclear ring, a microtubule mantle inserted in the ring, and dense plaques attached at the distal end of the mantle. A procedure has been developed for the fractionation of intact manchettes from rat spermatids. Each fractionation step was monitored by indirect immunofluorescence using an antibody to unmodified alpha-tubulin. Indirect immunofluorescence and electron microscopy demonstrate that fractionated manchettes are relatively intact. A thermocleavage step was used to sever the microtubule mantle from the perinuclear ring. Microtubules of the mantle collected in a stabilizing buffer containing Taxol formed long bundles of side-by-side aligned microtubules. The perinuclear ring sample consisted of circular-shaped units of different diameter with truncated microtubules still attached to the ring, a property that enabled the initial recognition of the rings by alpha-tubulin antibody staining. Indirect immunofluorescence and immunoblotting experiments using isoform-specific antibodies to alpha-tubulins show that the manchette contains acetylated, tyrosinated, glutamylated alpha-tubulin and an alpha-3/7 tubulin isoform. The same alpha-tubulin isoforms were observed in the axoneme of the sperm tail. Two-dimensional polyacrylamide gel electrophoresis fractionation maps of silver-stained proteins of the intact manchette show four predominant proteins: alpha- and beta-tubulins, beta-actin, vimentin, and a 62-kDa protein. The latter persisted in thermocleaved perinuclear ring samples. Results of this study indicate that the newly developed procedure for the fractionation of manchettes will facilitate a direct characterization of posttranslationally modified tubulin variants, microtubule-associatedproteins, and the components of the perinuclear ring of this largely neglected structure of the spermiogenic process.

Animals↗
PubMed1998

Development of normal mice from metaphase I oocytes fertilized with primary spermatocytes.

Primary spermatocytes are the male germ cells before meiosis I. To examine whether these 4n diploid cells are genetically competent to fertilize oocytes and support full embryo development, we introduced the nuclei of pachytene/diplotene spermatocytes into oocytes that were arrested in prophase I (germinal vesicle stage), metaphase I, or metaphase II (Met II). Both the paternal and maternal chromosomes then were allowed to undergo meiosis synchronously until Met II. In the first and second groups, the paternal and maternal chromosomes had intermingled to form a large Met II plate, which was then transferred into a fresh enucleated Met II oocyte. In the third group, the paternal Met II chromosomes were obtained by transferring spermatocyte nuclei into Met II oocytes twice. After activation of the Met II oocytes that were produced, those microfertilized at metaphase I showed the best developmental ability in vitro, and three of these embryos developed into full-term offspring after embryo transfer. Two pups (one male and one female) were proven to be fertile. This finding provides direct evidence that the nuclei of male germ cells acquire the ability to fertilize oocytes before the first meiotic division.

Animals↗
PubMed1998

Regression of cervical disc herniation observed on magnetic resonance images.

STUDY DESIGN: A retrospective study of cervical disc herniation using results of repeated magnetic resonance imaging examinations. OBJECTIVES: To clarify the cervical disc herniation morphological changes over time in order to establish a strategy for treatment. SUMMARY OF BACKGROUND DATA: In the authors' previous magnetic resonance imaging follow-up study of patients with lumbar disc herniation, spontaneous regression was observed in the sequestration-type lesions, and it was found that the tendency toward regression differed based on the anatomic position of extruded disc material. METHODS: Thirty-eight patients with cervical disc herniation who underwent repeated magnetic resonance imaging examinations were studied. The changes over time in herniated disc size were evaluated using this imaging technique. Evaluation showed the characteristics of those in whom spontaneous regression was found, such as extrusion pattern, and the clinical outcome was evaluated by symptoms. RESULTS: In 15 patients (40%), the volume of herniated material was decreased. The interval from onset of symptoms to the initial examination was significantly shorter in the regression group than in the group that showed no change in disc herniation. By extrusion pattern, cervical disc herniation, which was divided into migration type on sagittal view and lateral type on axial view, most frequently exhibited spontaneous regression. All of the patients with radicular pain and upper limb amyotrophy were treated successfully with conservative therapy. CONCLUSION: Although the possibility of the combination of hemorrhage and disc material could not be denied, active resorption of herniated material probably occurred during the acute phase. Extruded material exposed to the epidural space may be resorbed more quickly than that beneath the ligament. Vascular supply probably plays a role in the mechanism of resorption. The phase and position of extrusion were the significant factors affecting cervical disc herniation resorption. It was demonstrated that examination performed during the acute phase using magnetic resonance imaging is necessary for elucidation of the pathogenesis of cervical disc herniation, and that migrating, lateral-type herniations regress so frequently that conservative treatment should be chosen not only for patients with radicular pain, but also for those with upper limb amyotrophy.

Adult↗
PubMed1998

Actions of cyclic esters, S-esters, and amides of phenyl- and phenylthiophosphonic acids on mammalian and insect GABA-gated chloride channels.

Cyclic esters, S-esters, and amides of phenyl(thio)phosphonic acid were synthesized to probe the interaction between noncompetitive antagonists of ionotropic gamma-aminobutyric acid (GABA) receptors and their binding site. Some of these compounds competitively inhibited the specific binding of [3H]EBOB, a noncompetitive GABA antagonist, to rat-brain and housefly-head membranes. The trans isomer of the ester bearing a tert-butyl group at the 5-position and a bromine atom at the p-position (5t) was most potent in rat receptors with an IC50 value of 40 nM, while the trans isomer of the S-ester bearing the same substituents (10t) was most potent in housefly receptors with an IC50 value of 55 nM. In both cases, the corresponding amide analogue (12t) was less potent. The potencies of 5t and 12t tended to decrease in the presence of GABA, particularly in housefly receptors, while that of 10t remained unchanged. The rank order of activity in inhibiting [3H]EBOB binding to housefly-head membranes in the presence of GABA (10t > 5t > 12t) was in accord with that of insecticidal activity. S-Ester 10t depressed 10 microM and 300 microM GABA-induced 36Cl- influx into mouse cerebral synaptoneurosomes, whereas ester 5t depressed 10 microM GABA-induced 36Cl- influx but not 300 microM GABA-induced flux. Amide 12t was inactive at both GABA concentrations. These findings indicate that six-membered cyclic phenylthiophosphonic acid derivatives act as noncompetitive antagonists of GABA receptors and suggest that 10t is able to bind to the receptor in the open, desensitized, and closed states, whereas the affinity of 5t and 12t is lower in the open and desensitized states than in the closed state. The derivatives have similar structures except for the heteroatoms at the 1- and 3-positions, so that the heteroatoms may play a unique role when antagonists bring the open state of the GABA-gated channel to the desensitized or closed state.

Affinity Labels↗
PubMed1998

Picrodendrin and related terpenoid antagonists reveal structural differences between ionotropic GABA receptors of mammals and insects.

Twenty-eight picrotoxane terpenoids, including picrodendrins isolated from the Euphorbiaceae plant, Picrodendron baccatum (L.) Krug and Urban, have been evaluated for their ability to inhibit the specific binding of [3H]EBOB, the noncompetitive antagonist of ionotropic GABA receptors, to rat-brain and housefly (Musca domestica L.)-head membranes. Picrodendrin Q was the most potent competitive inhibitor of [3H]EBOB binding, with IC50 values of 16 nM (rat) and 22 nM (Musca). We find that the spiro gamma-butyrolactone moiety at the 13-position, which contains a carbonyl group conjugated with an unsaturated bond, and the substituents at the 4-position play important roles in the interaction of picrodendrins with their binding site in rat receptors. In contrast, such structural features are not strictly required in the case of the interaction with Musca receptors; the spiro saturated gamma-butyrolactone moiety at the 13-position, which bears the 16-sp3 carbon atom, and the hydroxyl groups at various positions are somewhat tolerated. Quantitative structure-activity studies have clearly shown that the electronegativity of the 16-carbon atom and the presence or absence of the 4- and 8-hydroxyl groups are important determinants of the potency of nor-diterpenes in Musca receptors, while the negative charge on the 17-carbonyl oxygen atom is likely important in the case of rat receptors. These findings indicate that there are significant differences between the structures of the complementary binding sites in rat GABA receptors and Musca GABA receptors. We also infer differences between native Musca GABA receptors and the Drosophila Rdl subunit-containing homo-oligomeric GABA receptors in the structures of their binding sites.

Animals↗
PubMed1997

Evaluation of motor function during thoracic and thoracolumbar spinal surgery based on motor-evoked potentials using train spinal stimulation.

STUDY DESIGN: Using compound muscle action potentials after train spinal stimulation, intraoperative motor functional monitoring was performed during thoracic and thoracolumbar spinal surgery. OBJECTIVES: This study was designed to clarify the clinical usefulness of train spinal stimulation and to determine the critical point of compound muscle action potential change at which neurologic injury during surgery occurs. SUMMARY OF BACKGROUND DATA: In 1995 the authors reported that train spinal stimulation allows for the recording of compound muscle action potentials, even in animals and humans under general anesthesia. The facilitative effect of train stimulation overcomes the suppressive effects of anesthetics and allows potentials to pass through synapses, thereby enabling a reliable recording of lower extremity compound muscle action potential. METHODS: Multisegmental recording of compound muscle action potentials after train spinal stimulation was conducted on 34 patients Undergoing surgical treatment for thoracic or thoracolumbar lesions. During surgery, train stimuli (5 pulse, Interstimular Interval: 1 ms) were administered using an epidural electrode introduced transcutaneously. Compound muscle action potentials were recorded from a total of 128 muscles. Anesthesia was maintained using fentanyl and propofol or nitrous oxide with or without isoflurane. Muscle relaxation was attained mainly by controlled infusion of vecuronium bromide. The percent occurrence of recordable compound muscle action potentials was determined, and the potential changes were correlated with changes in muscle strength. RESULTS: Compound muscle action potentials could be recorded from at least one muscle in 94% of the patients, even in most patients with severe motor dysfunction. The compound muscle action potential changes before and after surgical maneuver were divided into four grades. All compound muscle action potential changes in deteriorated muscles belonged to Grade 2 (a 10% latency delay) or Grade 3 (disappearance). CONCLUSIONS: The success rate in obtaining muscle potentials was greatly enhanced when all of the following methods were used: train spinal stimulation, anesthetic with weak suppressive effect, multiple muscle recording, and percutaneous introduction of epidural electrode. The critical point of compound muscle action potential change should be defined as a 10% latency delay or disappearance. Multisegmental muscle potential after train spinal stimulation is the most appropriate method for thoracic and thoracolumbar spinal surgery.

Adult↗
PubMed1996

Fixed drug eruption due to colchicine.

A case of fixed drug eruption due to colchicine was reported. A 31-year-old man developed a dark purplish-red round macule on the glans penis 5 h after taking 2.5 mg of colchicine. An oral challenge test with 0.5 mg of colchicine provoked flare-up of the eruption.

Adult↗
PubMed1996

Lysosomal glycolipid storage in the renal tubular epithelium in mastomys (Praomys coucha).

The renal proximal tubular epithelium of MCC strain of mastomys (Praomys coucha) exhibited a number of cytoplasmic vacuoles after conventional paraffin-embedding procedures. These vacuoles were strongly PAS-positive in cryostat sections. Ultra-structurally, they were double membrane-bound structures filled with myelin figures and acid phosphatase-positive electron-dense matrix. Immunofluorescent microscopy revealed that these structures contained GM2 ganglioside. Other tissues or organs were histologically normal. Mating experiments indicated that the ganglioside storage in MCC mastomys is inherited as an autosomal recessive trait.

Animals↗
PubMed1996

Urodynamic and electrophysiologic study of the urinary disturbances caused by cervical myelopathy.

Urinary disturbance is one of the significant symptoms of cervical myelopathy. To make the diagnosis of urinary disturbance, preoperative urodynamic studies and evoked spinal cord potentials (ESCPs) recording were performed on 60 surgical patients with cervical myelopathy. Half (30) of this group complained of urinary disturbance, and 22 (37%) were diagnosed as having neurogenic bladder. The presence of neurogenic bladder was closely correlated with severe limb symptoms and relatively slow ESCP velocity. It was confirmed that neurogenic bladder was caused by severe spinal cord damage. However, for 47% of the patients with urinary complaints, findings of urodynamic examinations were negative; these patients probably had pathologic or psychosomatic factors other than neurogenic bladder due to cervical myelopathy. The prognosis of the neurogenic bladder appears to be influenced by irreversibility of the spinal cord lesions.

Aged↗
PubMed1996

Monitoring of anterior cervical spinal cord function.

Anterior surgery is frequently chosen for treatment of cervical myelopathy. However, intraoperative spinal cord recording has rarely been used to monitor the function of the ventral columns. We report a method of monitoring evoked spinal cord potentials useful for detection of minor injury of the anterior spinal cord. Evoked spinal cord potentials elicited in cats by thoracic spinal cord and labyrinth stimulation were studied. Evoked intraspinal field potentials recorded after labyrinth stimulation were confirmed to originate from the vestibulospinal tract in the ventral columns. Low-amplitude potentials were recorded from the posterior epidural space. However, this method has not been used clinically because of difficulty in obtaining selective stimulation in humans. Spinal cord potentials evoked by thoracic stimulation were recorded from the anterior and posterior epidural spaces. The amplitude of the potentials was large enough to permit quantitation of neural function. We confirmed that anterior recording was more sensitive in detecting ventral column injury than posterior recording was. Based on these findings, we used anterior recording from the disc clinically for anterior spinal cord monitoring during anterior cervical surgery.

Acoustic Stimulation↗
PubMed1995

Spinal cord monitoring of the ventral funiculus function. Analysis of spinal field potentials after galvanic vestibular stimulation.

STUDY DESIGN: This study was designed to examine the possibility of a new spinal cord monitoring method using galvanic vestibular stimulation to monitor the function of the ventral funiculus of the spinal cord. OBJECTIVES: To settle the problems of previous monitoring methods by using galvanic vestibular nerve stimulation, which is highly selective for monitoring the function of the ventral funiculus of the spinal cord. SUMMARY OF BACKGROUND DATA: Although various spinal cord monitoring methods have been used, there are still problems because potentials recorded by these methods do not reflect selectively the function of the ventral funiculus of the spinal cord, which is vulnerable during anterior spinal surgeries. METHODS: In anesthetized cats, field potentials evoked by galvanic stimulation of the labyrinth were recorded from the epidural space of the spinal cord. The origin of these potentials was determined by mapping field potentials from within the upper cervical spinal cord using a micropipette and by examining the effect of sectioning the brainstem on the evoked potentials. RESULTS: The spinal cord potentials evoked by galvanic stimulation between the bilateral labyrinths could be recorded from the epidural space, and these potentials mainly originated from the ventral and ventromedial funiculus of the spinal cord. The latency and intraspinal distribution of the evoked potentials and the effect of sectioning the medial longitudinal fascicle on the evoked potentials indicated that the earliest component of the evoked potentials reflects mainly the activity of the vestibulospinal tract. CONCLUSIONS: Recording spinal cord potentials evoked by galvanic vestibular stimulation from the epidural space appears to be a potential technique to monitor the functional state of the ventral funiculus during anterior spinal surgeries.

Animals↗
PubMed1995

A new method of multisegment motor pathway monitoring using muscle potentials after train spinal stimulation.

STUDY DESIGN: Evoked muscle and nerve action potentials after spinal stimulation for intraoperative monitoring were investigated using a modified stimulation technique. Animal experiments and clinical application were performed. OBJECTIVES: To contrive a useful method of intraoperative motor pathway monitoring under inhalation anesthesia. SUMMARY OF BACKGROUND DATA: Many different kinds of procedures have been reported. No reliable method that reflects pure motor tract function has been established. METHODS: Characteristic of our stimulating technique was the use of numbered consecutive pulses ("train stimulation"). In 16 cats, optimum condition of train stimulation, effects of anesthetic agents, and conductive pathway were examined. In 35 patients, muscle potentials evoked by train stimulation were recorded, and clinical usefulness was evaluated. RESULTS: In the experimental study, the optimum stimulus condition was determined 1 ms interstimulous interval train of five pulses. Conductive pathway of this method was identified as a lateral column by selective spinal cord transection. In the clinical application, by using train stimulation, multisegmental muscle potentials were obtainable even using inhalation anesthetics. CONCLUSIONS: The facilitative effects of train stimulation, attributed to temporal summation, are considered to overcome the suppression of inhalation anesthesia. The evoked muscle potentials by train spinal stimulation reflect the functions of pure motor tract and is the only, extremely efficient method for intraoperative motor pathway monitoring.

Action Potentials↗
PubMed1995

Six-membered cyclic phosphonate GABA antagonists, 2,5-disubstituted 1,3,2-dioxaphosphorinanes.

The trans isomer of 2-(4-bromophenyl)-5-tert-butyl-2-thiono-1,3,2-dioxaphosphorinane competitively inhibited the specific binding of 35S-tert-butylbicyclophosphorothionate to rat brain membranes with an IC50 value of 0.52 microM, and showed insecticidal activity against houseflies with an LD50 value of 2.4 micrograms/fly. This compound and its analogues acted as noncompetitive GABAA receptor antagonists (NGRAs), and phosphorus-containing cyclohexane skeletons may prove useful for the design of novel NGRAs.

Animals↗