Biomedical subjects

K Ojima

Publications and source records attributed to K Ojima.

At least 19 recordsLinked to original sources

PubMed1998

Suppressive effect of vagal afferents on the activity of the trigeminal spinal neurons related to the jaw-opening reflex in rats: involvement of the endogenous opioid system.

The purpose of the present study is to test the hypothesis that via the endogenous pain control system, vagal afferent input modulates the activity of the trigeminal spinal nucleus oralis (TSNO) related to the tooth pulp (TP)-evoked jaw-opening reflex (JOR). Extracellular single-unit recordings were made from 36 TSNO units responding to TP electrical stimulation with a constant temporal relationship to a digastric electromyogram (dEMG) signal in 26 pentobarbital-anesthetized rats. The activity of 36 TSNO neurons and the amplitude of the dEMG increased proportionally during 1.0-3.5 times the threshold for JOR. Some of these neurons (4 out of 5) were also excited by chemical stimulation (bradykinin, 1-2 microl, 1 mM) of TP. In 31 out of 36 TSNO neurons (86%), their activities during tooth pulp stimulation were suppressed by conditioning stimulation of the right vagus nerve. The suppressive effect of vagal afferent stimulation occurred at conditioning-test intervals of 20-150 ms after the onset of the stimulation, and its maximal suppressive effect occurred at approximately 50 ms. The mean time course of this suppressive effect paralleled that of the dEMG. After administration of naloxone (0.5 and 1.0 mg/kg, i.v.), an opiate receptor blocker, the suppressive effect on the activity of TSNO neurons (6 out of 8) was significantly attenuated at the conditioning-test interval of 50 ms compared to the control (p < 0.01). These results suggested that vagal afferent input inhibits nociceptive transmission in the TSNO related to TP-evoked JOR and this inhibitory effect may occur via the endogenous opioid system in rats.

Afferent Pathways↗

PubMed1998

Elevated serum lipoprotein(a) is a risk factor for left atrial thrombus in patients with chronic atrial fibrillation: a transesophageal echocardiographic study.

BACKGROUND: Patients with chronic atrial fibrillation have an increased risk of thromboembolism. Apoprotein(a) has a structural homology with plasminogen, suggesting that lipoprotein(a) [Lp(a)] may produce thrombogenic effects by modulating the fibrinolytic system. However, the role of Lp(a) level in the formation of left atrial thrombus has not been studied. We sought to evaluate whether Lp(a) is a risk factor for left atrial thrombus in patients with chronic atrial fibrillation. METHODS AND RESULTS: The consecutive series of 150 patients (mean age 67 +/- 8 years) with chronic atrial fibrillation underwent transesophageal echocardiography. Left atrial thrombus was diagnosed by transesophageal echocardiography. Clinical, biochemical, and echocardiographic variables were prospectively collected. Univariate analysis showed that patients with left atrial thrombus (n = 29, 19%) had higher frequency of spontaneous echo contrast (93% vs 55%, P <.0001) than patients without left atrial thrombus (n = 121). Patients with left atrial thrombus also had a significantly higher serum concentration of Lp(a) (34.5 +/- 24.1 vs 17.9 +/- 13.5 mg/dL, P <.0001), a larger left atrium (5.4 +/- 0.9 vs 4.8 +/- 0.7 cm, P <.001), and a lower left atrial appendage peak flow velocity (11.1 +/- 5.4 vs 23.5 +/- 14.6 cm/s, P <.0001). Multivariate regression analysis showed that the Lp(a) concentration (P <.0001) was a significant positive predictor and the left atrial appendage peak flow velocity (P =.0125) was a significant negative predictor of left atrial thrombus. Left atrial thrombus was present in 16 (48%) of 33 patients with Lp(a) level >/=30 mg/dL. CONCLUSIONS: Elevated serum levels of Lp(a) are strongly associated with left atrial thrombus. These findings suggest that Lp(a) level may be a novel risk factor for left atrial thrombus in patients with chronic atrial fibrillation.

Aged↗

PubMed1998

Effects of methylenechloride-soluble fraction of Japanese angelica root extract, ligustilide and butylidenephthalide, on pentobarbital sleep in group-housed and socially isolated mice.

We previously showed that the extract of Japanese angelica root (JAR-E) reversed the decrease in pentobarbital (PB) sleep induced by isolation stress and yohimbine and methoxamine, stimulants of central noradrenergic systems, in mice. Here, we tested the effects of several fractions from JAR-E and ligustilide and butylidenephthalide, phthalide components of JAR-E, on PB sleep in isolated mice to elucidate the mechanism of the action of JAR-E. Methanol-soluble (Met-S) and -insoluble (Met-IS) fractions were obtained from JAR-E. Methylenechloride-soluble (MC-S) and -insoluble fractions (MC-IS) were prepared from Met-S. MC-S (11.4-76 mg/kg, p.o.) reversed the isolation stress-induced decrease in PB sleep, but neither Met-IS (0.8-2.4 g/kg, p.o.) nor MC-IS (0.7-2 g/kg, p.o.) had the same effect. The i.p. administration of MC-S exhibited a similar activity to that observed after the p.o. administration of the same fraction. Ligustilide (5-20 mg/kg, i.p.) and butylidenephthalide (10-30 mg/kg, i.p.) reversed PB sleep decrease in isolated mice. Both components (20 mg/kg, i.p.) attenuated the suppressive effects of yohimbine (30 nmol, i.c.v.), methoxamine (200 nmol, i.c.v.) and a benzodiazepine inverse agonist FG7142 (10 mg/kg, i.p.) on PB sleep in group-housed mice. These results suggest the contribution of ligustilide and butylidenephthalide to the effect of JAR-E on PB sleep in isolated mice, and implicate central noradrenergic and/or GABA(A) systems in the effects of these components.

4-Butyrolactone↗

PubMed1998

Excitatory mechanism of veratridine on slowly adapting pulmonary stretch receptors in anesthetized rabbits.

The excitatory effects of veratridine on slowly adapting pulmonary stretch receptors (SARs) were studied before and after administration of ouabain (a Na+-K+ ATPase inhibitor) in anesthetized, artificially ventilated rabbits after vagus nerve section. Administration of veratridine (40 microg/kg) stimulated SAR activity but did not significantly alter tracheal pressure. Administration of ouabain (50 microg/kg) initially stimulated SAR activity during both inflation and deflation, but after 20 min, two different types of SAR responses were observed; one became silent at the peak, of inflation only, and the other maintained excitatory activity during both inflation and deflation phases. Veratridine usually inhibited SAR activity in ouabain-treated animals, irrespective of the difference of ouabain effects. These results suggest that veratridine-induced stimulation of SARs is closely related to the change in the Na+ ion gradient, which is regulated by Na+ pump activity.

Anesthesia↗

PubMed1998

Angioarchitectural structure and functional distributive pattern of the filiform papillae on the meso-dorsal surface of the rabbit tongue.

The angioarchitectural classification and distributive patterns were investigated in the filiform papillae (FiP) on the meso-dorsal surface of the rabbit tongue by using microvascular cast specimens (MVCS) and the scanning electron microscope (SEM). The author examined the microvascular network structures, which consisted of ascending and descending branches entering the FiP. They inclined in a posterior (pharynx) direction, and densely and geometrically covered the meso-dorsal surface, directing the spoon-like concave face in an anterior direction. FiPs could be classified into three types: a small filiform papilla (SfP) covering on the meso-dorsal surface except for the marginal part of the intermolar eminence (MIME) and the intermolar eminence itself (IME): a spoon-like concave structure facing in an anterior (apex) direction with an arrowhead-like top: a middle filiform papilla (MfP) on the MIME, made up of a long triangle-like concave structure with a sharp arrowhead-like top and inclined at right angles to the IME. A large filiform papilla (LfP) on the whole swelling dorsal area of the IME was formed by a long triangle-like concave structure with a sharper arrowhead-like top. LfPs are longer and larger than MfPs and inclined towards the pharynx.

Animals↗

PubMed1998

Quantitative and distributive study of the fungiform papillae in the cat tongue in microvascular cast specimens.

The number of fungiform papillae (FuP) has been counted, and distribution has been observed on the tongue of 55 adult cats. FuP were sampled from the whole region of the tongue surface, and the number and variation in distribution were determined in microvascular cast specimens (MVCS) of four types of FuP (Ojima et al. 1996) by scanning electron microscopy (SEM). There were approximately 35 (female) and 42 (male) FuP (mean number 38) on the whole tongue dorsal surface. FuP were most numerous in the peripheral region, and the number tended to decrease progressively from the peripheral to the medial region. There were no FuP in the central region of the tongue, in which there were types I and II filiform papillae (FiP) (Ojima and Lowe 1995). Their number differed significantly between the sexes and the regions.

Animals↗

PubMed1998

Saphenous vein graft shrinkage as a mechanism of stenosis soon after bypass surgery.

A 63-year-old man with left main coronary artery disease underwent aortocoronary bypass surgery using saphenous vein grafts. Less than 1 month later, severe narrowing occurred in the mid-portion of the vein graft to the left anterior descending coronary artery. Preintervention intravascular ultrasonography revealed prominent vein graft shrinkage. Percutaneous transluminal angioplasty failed because the stenotic lesion could not be dilated, even by high-pressure balloon inflation. Saphenous vein graft shrinkage appears to be one of the mechanisms of early saphenous vein graft stenosis, and balloon angioplasty to the vein graft stenosis with prominent shrinkage may be of only limited value.

Coronary Artery Bypass↗

PubMed1997

Flumazenil but not FG7142 reverses the decrease in pentobarbital sleep caused by activation of central noradrenergic systems in mice.

Central noradrenergic systems have been shown to modulate the hypnotic activity of pentobarbital in mice. To determine whether the GABA(A)/benzodiazepine receptor system is involved in the decrease in pentobarbital sleep caused by activation of central noradrenergic systems, we examined in mice the effects of the benzodiazepine receptor ligands flumazenil and FG7142 on pentobarbital-induced sleep, and on adrenoceptor ligand modulation of pentobarbital sleep. The intracerebroventricular (i.c.v.) administration of methoxamine (8-200 nmol), an alpha1-adrenoceptor agonist, and yohimbine (1-30 nmol), an alpha2-adrenoceptor antagonist, produced a dose-dependent decrease in sleeping time induced by pentobarbital (50 mg/kg, intraperitoneally (i.p.)). The i.c.v. administration of flumazenil (16.5 and 33 nmol), a selective benzodiazepine receptor antagonist, had no effect on pentobarbital sleep, whereas an i.p. injection of FG7142, a selective benzodiazepine receptor inverse agonist, shortened pentobarbital sleep. Flumazenil (33 nmol, i.c.v.) caused the pentobarbital sleep time, shortened by methoxamine (200 nmol, i.c.v.) and yohimbine (30 nmol, i.c.v.), to return to the control level, while FG7142 (10 mg/kg, i.p.) had no effect on the methoxamine- and yohimbine-shortened pentobarbital sleep. These results suggest that putative endogenous benzodiazepine receptor ligands with an inverse agonist-like property are involved in the methoxamine- and yohimbine-induced decrease in pentobarbital sleep in mice.

Animals↗

PubMed1997

Central corticotropin-releasing factor and benzodiazepine receptor systems are involved in the social isolation stress-induced decrease in ethanol sleep in mice.

Social isolation stress has been demonstrated to decrease the hypnotic activity of ethanol in rodents. In this study, the role of central corticotropin-releasing factor (CRF) and GABA(A)/benzodiazepine (BZD) receptor systems in the social isolation stress-induced decrease in the hypnotic activity of ethanol in mice was investigated by examining the effect of alpha-helical CRF(9-41) (alpha hCRF) and flumazenil, antagonists of CRF and BZD receptors, respectively, on ethanol-induced sleep in group-housed and socially isolated mice. We also tested whether social isolation stress affects the ability of ethanol to enhance the GABA-induced 36Cl- influx into a synaptoneurosomal preparation of mouse forebrain. Social isolation stress significantly decreased both the ethanol (4 g/kg i.p.)-induced and pentobarbital (50 mg/kg i.p.)-induced sleeping times, while this stress had no effect on chloral hydrate (325 mg/kg i.p.)-induced sleep. The i.c.v. injection of alpha hCRF (6.5 nmol) and flumazenil (33 nmol) antagonized the social isolation stress-induced decrease in the ethanol sleep without affecting ethanol sleep in group-housed animals. Social isolation stress significantly attenuated the ability of GABA to stimulate 36Cl- influx but this stress had no effect on the ability of ethanol to enhance GABA-induced 36Cl- influx. These results suggest that the functional changes in central CRF and GABA(A)/BZD receptor systems are involved in the social isolation stress-induced decrease in the hypnotic activity of ethanol in mice.

Animals↗

PubMed1997

Flumazenil reverses the decrease in the hypnotic activity of pentobarbital by social isolation stress: are endogenous benzodiazepine receptor ligands involved?

Long-term social isolation stress has been shown to cause a decrease in pentobarbital (PB)-induced sleeping time in mice. In the present study, to clarify whether the GABAA/benzodiazepine (BZD) receptor system is involved in the decrease in the hypnotic activity of PB by social isolation stress, we examined the effects of BZD receptor ligands on the PB-induced sleep in group-housed and socially isolated mice. Moreover, we also tested whether social isolation stress affects the ability of GABA to stimulate 36Cl- uptake or the modulatory effect of diazepam and PB and GABA-induced stimulation of 36Cl- uptake into synaptoneurosomes prepared from mouse brain. Social isolation stress significantly decreased the PB-induced sleeping time in mice. The BZD receptor diazepam (0.1-0.8 mg/kg, i.p.) dose-dependently prolonged PB sleep in group-housed and isolated mice, but the effect was weaker in isolated mice. In contrast, FG7142 (5-10 mg/kg, i.p.), a BZD receptor inverse agonist, shortened the sleep in group-housed but not in isolated mice. Flumazenil (16.5-33 nmol, i.c.v.), a selective BZD receptor antagonist, caused PB sleep in isolated mice to return to the level of group-housed mice, at the dose that antagonized the effects of diazepam and FG7142 on PB sleep in group-housed mice. However, this antagonist alone produced no effect on PB sleep in group-housed mice. Social isolation stress decreased the ability of GABA (0.6-200 microM) to stimulate 36Cl- uptake into synaptoneurosomes but this stress had no effect on PB- and diazepam-induced enhancement of GABA-stimulated 36Cl- uptake. These results suggest that endogenous substance(s) with an inverse BZD receptor agonist-like property and the changes in the ability of GABA to stimulate chloride ion channels are involved in the decrease in the hypnotic activity of pentobarbital following social isolation stress.

Animals↗

PubMed1997

Effects of vagal and carotid chemoreceptor afferents on the frequency and pattern of spontaneous augmented breaths in rabbits.

We investigated the effects of vagal afferents and carotid chemoreceptors on the frequency and pattern of spontaneous augmented breaths in anesthetized rabbits by analyzing the changes in the phrenic nerve discharge. Blockade of vagal C-fiber conduction by capsaicin treatment greatly reduced the frequency of spontaneous augmented breaths but had no significant effect on the pattern of the augmented breaths. Inhalation of sulfur dioxide, which abolished the Hering-Breuer inflation reflex, suppressed the frequency of spontaneous augmented breaths but did not significantly alter the pattern of the augmented breaths. Carotid sinus denervation diminished both the frequency and amplitude of spontaneous augmented breaths. The occurrence of spontaneous augmented breaths was not observed in rabbits after bilateral vagotomy. In other experiments we examined the relationship between rapidly adapting pulmonary stretch receptors (RARs) and dynamic lung compliance during the spontaneous augmented breath. The stimulation of RARs occurred at the first phase of spontaneous augmented breaths, and augmentation of transpulmonary pressure seen at the second phase coincided with vigorous stimulation of the receptor activity. These results suggest that spontaneous augmented breaths may be mediated by the summation of several facilitatory inputs from vagal and carotid chemoreceptor afferents.

Action Potentials↗

PubMed1997

Developmental expression of extracellular matrix components in intramuscular connective tissue of bovine semitendinosus muscle.

We have investigated the expression patterns of extracellular matrix components in intramuscular connective tissue during the development of bovine semitendinosus muscle by means of indirect immunofluorescence techniques. Types I, III, V, and VI collagen and fibronectin were located in the endomysium and the perimysium. Type IV collagen, laminin, and heparan sulfate proteoglycans (PGs) were exclusively located in the endomysium, and dermatan sulfate PGs existed only in the perimysium. The localization of these components in the intramuscular connective tissue of semitendinosus muscle remained unchanged throughout prenatal and postnatal growth of cattle, suggesting that they are essential for forming and maintaining structures of the endomysium and perimysium in bovine semitendinosus muscle. On the other hand, decorin was undetectable in the endomysium of neonates, although other matrix components were already expressed. It was expressed slightly in the endomysium of 2-month-old calves, and clearly detectable in the endomysium of cattle more than 6 months old. Chondroitin sulfate PGs were barely detectable in the perimysium of fetuses and neonatal calves, and progressively appeared during postnatal development of the muscle. It seems likely that these PGs are closely related to the postnatal development of the endomysium and perimysium.

Aging↗

PubMed1997

An investigation into the distributive pattern, classification and functional role of the conical papillae on the posterodorsal surface of the cat tongue using SEM.

In order to examine the relationship between their distributive patterns, classification and functional roles, three-dimensional structures in the microvascular network of the conical papillae (CoP) on the posterior third of the central dorsal surface of the cat tongue were observed by the corrosion cast method under a scanning electron microscope (SEM). CoP can be classified into two types: small conical papillae (SCoP) and large conical papillae (LCoP), according to their shape, size and distributive pattern. On the posterior third of the central dorsal surface of the tongue, SCoPs are arranged in the form of six-eight straight lines running regularly from the posterior third of the central zone towards the pharynx. LCoPs are also arranged in the form of a V, with the point directed posteriorly, in oblique lines running in an orderly fashion from both the antero-peripheral zones to the central zone. To summarize CoPs play an important role in the drinking of milk and water, after mixing the food with saliva, in the transport of the food mass towards the pharynx and in swallowing it.

Animals↗

PubMed1997

Microvascular fin-like structure of the foliate papillae of the rabbit tongue using scanning electron microscopic specimens.

Although many morphological studies have been undertaken on the lingual papillae of the rabbit tongue, relatively few have dealt with the microvascular structure and classification of the foliate papillae (FoP) by means of microvascular cast specimens (MVCS) and using scanning electron microscopy (SEM). For the present study, a three dimensional observation and classification was carried out by SEM. The morphological characteristics of the outer frame structure were observed by means of MVCS of FoP which were located on both posteroperipheral parts of the tongue. They showed a bead-like appearance and consisted of 14-18 transverse and slightly bent fin-like structures, running from the dorsal surface to both peripheral sides symmetrically. These are effectively increased on the surface areas and play the functional role of receiving the taste sense. FoPs can be classified into three types: type I (14 fins), type II (16 fins), type III (18 fins) according to the fin numbers.

Animals↗

PubMed1997

Angioarchitectural classification of the fungiform papillae on the dorsal surface of the bullfrog tongue.

In this study, the three-dimensional anatomy of the microvascular structure of fungiform papillae (FuP) on the dorsal surface of the bullfrog tongue has been investigated using scanning electron microscopy (SEM), and angioarchitectural classification has been carried out by means of the capillary loop (L. s) and intra-bridge structure (I. b). FuP from 30 sound bullfrog tongues were used. The following research methods were applied: SEM observation on microvascular cast specimens (MVCS) of bullfrog tongue's FuP were injected with synthetic resin (Mercox). Observation of MVSC showed that the bullfrog tongue FuP consisted of an ascending branch (A. b), L. s, I. b and a descending branch (D. b). Based upon SEM observations of MVCS, FuP can be classified into four types: A, B, C, D types according to A. b, L. s, I. b and D. b. A-type (none I. b) formed from A. b, L. s, D. b only and with no I. b. B-type (one I. b) consisted of A. b, L. s, D. b and one I. b. C-type (two I. b) were composed of A. b, L. s, D. b and two I. b. D-type (three I. b) were composed of A. b, L. s, D. b and three I. b, A. b, L. s, I. b and D. b on each. A, B, C, D types were all same thickness.

Animals↗

PubMed1997

Angioarchitectural structure of the fungiform papillae on the anterodorsal surface of the rat tongue.

To ascertain whether the microvascular morphological differences of fungiform papillae (FuP) on the anterodorsal surface of the rat tongue are locationally and functionally related, this study aimed at examining and comparing, in greater detail, the comparative morphological characteristics of FuP. FuP were sporadically and consistently scattered among numerous filiform papillae (FiP) in three parts: the apical, central and in front of the intermolar eminence on the anterodorsal surface. We studied these by means of the microvascular cast specimen (MVCS) of FuP using scanning electron microscopy (SEM). The results obtained in this study showed that in all three parts on the anterodorsal region, the capillary bed of FuP presented as a netbasket-like and cylindrical figure with a central hole consisting of 4-5 horizontal rings of several ascending and descending roots. FuP in the central part on the anterodorsal region were relatively larger in size and more cylindrical in shape than those of both the other parts, and they play the leading part as sensory organs for the taste sense and were regarded as taste receptive organs.

Animals↗

PubMed1997

Functional role of V form distribution seen in microvascular cast specimens of the filiform and fungiform papillae on the posterior central dorsal surface of the cat tongue.

The relationship between the functional role and three-dimensional structures of the microvascular network of the filiform papillae (FiP) and fungiform papillae (FuP) on the posterior central surface of the cat tongue were observed by the corrosion cast method under a scanning electron microscope (SEM). FiP can be classified into five types; types I-V (Ojima and Lowe 1995), and FuP, found to be distributed sporadically among FiP (I-V), into four types; types I-IV (Ojima et al. 1996 b) according to the shape and size of the main process (MP) and the number of the accessory processes (AP). Each of the types I-V of FiP were arranged in the form of a V as oblique lines running in an orderly and geometrical fashion from the posterior central zone to the anterior peripheral zone in both directions. Each of the types I-IV of FuP were scattered throughout the line of FiPs arranged in the form of a V, the point of which is directed towards the pharynx. FiPs play an important role in the drinking of milk and water, holding, masticating and swallowing the food and, after mixing the food with saliva, in the transporting of the food mass towards the pharynx. The MP of FuPs is considered to be a modified form of the MP of FiP of the cat tongue function (Ojima et al. 1996 c) as part of a sense organ for taste.

Animals↗

PubMed1997

Angioarchitectural structure of the fungiform papillae on rabbit tongue anterodorsal surface.

The relationships between the functional and morphological characteristics and the positional difference of the microvascular cast specimen (MVCS) of the fungiform papillae (FuP) on the antero-dorsal surface of the rabbit tongue were examined and compared using a scanning electron microscope (SEM). The sporadic FuPs scattered among the numerous small filiform papillae (SfP) were found to be distributed irregularly over the antero-dorsal surface. FuPs consisted of the ascending and descending capillary loops, forming margins of the central opening at the top of FuP. They resembled flower-like configurations (carnations), the petals of which ranged from eight to twelve, and they were larger in width and more complex in shape than SfPs with morphological differences. FuPs can be classified into three types: type I (consisting of eight petals), type II (ten petals), type III (twelve petals) according to the shape of FuP, and to the petal number of the flower-like aspect on the eight points of MVCS of FuPs observed by SEM. These results suggest that the petals of the ascending and descending capillary loops of FuP expanded the flower-like figure, increased in the surface areas and effectively play a role in receiving the sense of taste.

Animals↗