Biomedical subjects

S Chiba

Publications and source records attributed to S Chiba.

At least 145 records · Page 8Linked to original sources

PubMed2000

Inotropic, chronotropic, and dromotropic effects mediated via parasympathetic ganglia in the dog heart.

Some parasympathetic ganglionic cells are located in the epicardial fat pad between the medial superior vena cava and the aortic root (SVC-Ao fat pad) of the dog. We investigated whether the ganglionic cells in the SVC-Ao fat pad control the right atrial contractile force, sinus cycle length (SCL), and atrioventricular (AV) conduction in the autonomically decentralized heart of the anesthetized dog. Stimulation of both sides of the cervical vagal complexes (CVS) decreased right atrial contractile force, increased SCL, and prolonged AV interval. Stimulation of the rate-related parasympathetic nerves to the sinoatrial (SA) node (SAPS) increased SCL and decreased atrial contractile force. Stimulation of the AV conduction-related parasympathetic nerves to the AV node prolonged AV interval. Trimethaphan, a ganglionic nicotinic receptor blocker, injected into the SVC-Ao fat pad attenuated the negative inotropic, chronotropic, and dromotropic responses to CVS by 33 approximately 37%. On the other hand, lidocaine, a sodium channel blocker, injected into the SVC-Ao fat pad almost totally inhibited the inotropic and chronotropic responses to CVS and partly inhibited the dromotropic one. Lidocaine or trimethaphan injected into the SAPS locus abolished the inotropic responses to SAPS, but it partly attenuated those to CVS, although these treatments abolished the chronotropic responses to SAPS or CVS. These results suggest that parasympathetic ganglionic cells in the SVC-Ao fat pad, differing from those in SA and AV fat pads, nonselectively control the atrial contractile force, SCL, and AV conduction partially in the dog heart.

Animals↗

PubMed2000

Impaired response of UCP family to cold exposure in diabetic (db/db) mice.

Impaired activity of the uncoupling protein (UCP) family has been proposed to promote obesity development. The present study examined differences in UCP responses to cold exposure between leptin-resistance obese (db/db) mice and their lean (C57Ksj) littermates. Basal UCP1 and UCP3 mRNA expression in brown adipose tissue was lower in obese mice compared with lean mice, but UCP2 expression in white adipose tissue (WAT) was higher. Basal skeletal muscle UCP3 did not change remarkably. The UCP family mRNAs, which were upregulated 12 and 24 h after cold exposure (4 degrees C), were returned to prior levels 12 h after rewarming exposure (21 degrees C) in lean mice. The accelerating effects of cold exposure on the UCP family were impaired in db/db obese mice. Together with these changes, WAT lipoprotein lipase mRNA was downregulated, and the concentration of serum free fatty acid was increased in response to cold exposure in the lean mice but not in db/db obese littermates. The impaired function of the UCP family and diminished lipolysis in response to cold exposure indicate that the reduced lipolytic activity may contribute to the inactivation of the UCP family in db/db obese mice.

Adipose Tissue↗

PubMed2000

Hereditary cerebellar ataxia with peripheral neuropathy and mental retardation.

We present here 5 patients with hereditary cerebellar ataxia with peripheral neuropathy and mental retardation as determined by clinical, pathological, and molecular studies. The most characteristic features of this disorder, in contrast to Friedreich's ataxia, were early onset of ataxic gait, mental retardation, and a marked atrophy of the cerebellum. Sural nerve biopsy showed a reduction of myelinated fibers. The expansion of a GAA triplet repeat within the first intron of the frataxin gene, which causes Friedreich's ataxia, was not identified in any of the patients. Hereditary cerebellar ataxia with peripheral neuropathy and mental retardation represents a specific clinical entity that so far has only been described in Japan.

Adolescent↗

PubMed2000

Endothelialization of the coils used to occlude a persistent ductus arteriosus: an angiographic study.

To assess the endothelialization of the coils used to close a persistent ductus arteriosus (PDA), the present study comprised a review of the follow-up aortograms and pulmonary angiograms in 25 patients who underwent coil occlusion. The minimal diameter and the length of the PDA were measured prior to the procedure, and the shortest distance between the aortic end of the deployed coil and the aortic end of the PDA was measured after coil deployment. Evidence of endothelial coverage of the coil was sought on follow-up angiograms performed 6-24 (15+/-5) months later and the factors that determined the thickness of the endothelial coverage on the aortic end were investigated. Separation of the coil and the contrast column were detected at the aortic end in all cases and at the pulmonary end in 18 of 25 cases. The thickness of the separation ranged from 0.4 to 1.3 (0.7+/-0.2) mm at the aortic end and 0.3 to 0.8 (0.6+/-0.2) mm at the pulmonary end. The length of the ductus and of the ampulla had a significant positive correlation with the thickness of the aortic end separation. Apparent endothelial coverage of the coil was completed by 6 months after coil occlusion. Infective endocarditis or thromboembolism is an unlikely complication once endothelium covers the implanted coil.

Angiography↗

PubMed2000

[ATP as a periarterial sympathetic transmitter in isolated vessel].

Double-peaked vasoconstrictor responses to periarterial nerve electrical stimulation (PNS) were readily induced in the condition of 30-s trains of pulses in isolated, perfused canine splenic artery, using the cannula insertion technique. P2X Prinoceptors have been shown to be involved mainly in the 1st peak response and alpha 1-adrenoceptors mostly in the 2nd one. A small dose of TTX did not affect the 1st peak, but strongly inhibited the 2nd one, although larger doses of TTX diminished either the 1st or 2nd response. A small dose of guanethidine also inhibited only the 2nd one. The 1st one was inhibited by prolonged cold storage of the vessel. On the other hand, omega CT produced parallel inhibitory effects on the 1st and 2nd peaked responses. A low pulse number of ES only caused the release of purinergic transmitters from sympathetic nerve terminals. The possible role as a transmitter of ATP is discussed in periarterial sympathetic transmission.

Adenosine Triphosphate↗

PubMed2000

A Na+/Ca2+ exchanger inhibitor, KB-R7943, caused negative inotropic responses and negative followed by positive chronotropic responses in isolated, blood-perfused dog heart preparations.

Effects of a Na+/Ca2+ exchanger inhibitor, KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl] isothiourea methanesulfonate), on the sinoatrial nodal pacemaker activity, atrial contractility and ventricular contractility were investigated in the isolated and blood-perfused right atrium and left ventricle of the dog. KB-R7943 (0.03- 3 micromol) induced negative inotropic effects and negative followed by positive chronotropic effects in the right atrium and negative inotropic effects in the left ventricle. Neither atropine nor hexamethonium affected the cardiac responses to KB-R7943. Propranolol attenuated the positive chronotropic response to KB-R7943 but imipramine did not. Tetrodotoxin potentiated the positive chronotropic response to KB-R7943 in 6 of 11 isolated atria. When NaCl infusion increased atrial contractile force and atrial rate, KB-R7943-induced negative inotropic and chronotropic responses were attenuated in a dose-dependent manner. CaCl2 infusion potentiated the negative chronotropic response to KB-R7943 but did not affect the inotropic response significantly. On the other hand, ouabain (17 nmol) attenuated the negative inotropic response, but not chronotropic response, to KB-R7943. These results suggest that KB-R7943-induced cardiac effects relate to the Na+ activity, probably mediated through the Na+/Ca2+ exchanger, and the Na+/Ca2+ exchanger modifies the pacemaker activity and myocardial contractility in the dog heart.

Animals↗

PubMed2000

Effects of neuropeptide Y on double-peaked constrictor responses to periarterial nerve stimulation in isolated, perfused canine splenic arteries.

The periarterial electrical nerve stimulation readily induced a double-peaked vasoconstriction in the isolated, perfused canine splenic artery. P2X-Purinoceptors have previously been shown to be involved mainly in the 1st-phase response and alpha 1-adrenoceptors, mostly in the 2nd-one. The dose used of neuropeptide Y (NPY) (0.01-0.1 microM) given into the preparation caused a slight but insignificant vasoconstriction. The treatment with NPY at concentrations of 0.01-0.1 microM produced a parallel inhibition on the 1st- and 2nd-phase responses following nerve stimulation at the frequencies used (1-10 Hz) in a dose-dependent manner. The vasoconstrictor responses to administered ATP (0.01-1 mumol) or noradrenaline (0.03-3 nmol) were slightly but not significantly potentiated by 0.1 microM NPY. The results indicate that NPY predominantly exerts a prejunctionally inhibitory modulation on the purinergic and adrenergic transmission in peripheral sympathetic nerves innervating the canine splenic artery.

Adenosine Triphosphate↗

PubMed2000

Perivascular purinergic nerve-induced vasoconstrictions in canine isolated splenic arteries.

We tried to induce selective perivascular purinergic nerve stimulation in isolated canine splenic arterial preparations, using the cannula insertion method. Under the conditions of periarterial electrical stimulation (ES), i.e., trains of 1, 3 and 10 pulses, 1-ms pulse duration and 10-V amplitude at 1 Hz, monophasic vasoconstriction was consistently induced. The ES-induced vasoconstriction was not influenced by prazosin in doses that completely inhibited noradrenaline-induced vasoconstrictions, but it was suppressed by alpha,beta-methylene ATP, a P2X purinoceptor desensitizer. Thus, it is indicated that a selective purinergic transmitter release is readily obtained in the isolated splenic arterial preparation.

Adenosine Triphosphate↗

PubMed2000

Dissociation of potentiation of Leu31 Pro34 neuropeptide Y on adrenergic and purinergic transmission in isolated canine splenic artery.

The present study observed the effects of an activation of neuropeptide Y (NPY) Y1 receptors on adrenergic and purinergic components of double-peaked vasoconstrictor responses to periarterial nerve stimulation in the isolated, perfused canine splenic arteries. The results showed that 3-30 nM Leu31 Pro34 neuropeptide Y (LP-NPY) produced a dose-dependent potentiation of double-peaked vasoconstrictor responses to trains of 30-s pulses at 1, 4 or 10 Hz of stimulation. The potentiation of LP-NPY of the nerve-stimulated vasoconstrictions were completely inhibited by subsequent blockade of alpha1-adrenoceptors or Y1 receptors with 0.1 microM prazosin or with 1 microM BIBP 3226 ((R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininami de), respectively. The remaining responses in the presence of LP-NPY and prazosin were abolished by P2X receptor desensitization with 1 microM alpha,beta-methylene ATP. Moreover, 30 nM LP-NPY failed to modify the vasoconstrictor responses to nerve stimulation after treatment with prazosin. A subsequent administration of alpha,beta-methylene ATP completely suppressed the remaining responses after prazosin and LP-NPY. The vasoconstrictions induced by 0.003-1 nmol noradrenaline and 0.003-1 micromol ATP were slightly, but not significantly enhanced by 30 nM LP-NPY. The observations indicated that activation of postjunctional NPY Y1 receptors may have an important role in the modulation of adrenergic rather than purinergic transmission of the sympathetic co-transmission.

Adenosine Triphosphate↗

PubMed2000

Acute desensitization of adenosine by adenosine infusion in isolated dog atria.

We investigated the effects of a continuous infusion of adenosine on responses of sinus rate and developed tension to bolus injections of adenosine and acetylcholine in isolated, blood-perfused canine right atria. Each drug was directly injected into the sinus node artery of the isolated atrium. During adenosine infusions, the negative chronotropic and inotropic responses to bolus injections of adenosine were significantly inhibited in a dose-related manner, while the negative responses to administered acetylcholine were consistently potentiated. These results indicate that adenosine infusion has an acute desensitizing action on subsequent bolus adenosine, although the cholinergic action is enhanced by a continuous infusion of adenosine.

Acetylcholine↗

PubMed2000

Periarterial electrical nerve stimulation-induced adrenergic vasoconstriction inhibited by adrenergic alpha1B-receptor blockade but not by alpha1A-blockade.

The periarterial electrical nerve stimulation at a frequency of 4 Hz (30-s trains of pulses) induced a double-peaked vasoconstriction in the canine splenic artery. The treatment with chloroethylclonidine (CEC, 60 microM) markedly inhibited the second-peaked constriction, whereas it produced an insignificant effect on the first-peaked response. The vasoconstriction to noradrenaline (NA, 1 nmol) was not significantly influenced by 60 microM CEC. On the other hand, WB 4101 (1 microM) consistently abolished the vascular response induced by NA (1 nmol), but rather potentiated the double-peaked constriction. The results indicate that neuronal NA may junctionally exert its vasoconstrictor effect via an activation of postjunctional alpha1B-receptors, whereas exogenous NA may extrajunctionally activate alpha1A-receptors for its vascular action in the canine splenic artery.

Adrenergic beta-Antagonists↗

PubMed2000

Purification and partial characterization of a novel glucanhydrolase from Lipomyces starkeyi KSM 22 and its use for inhibition of insoluble glucan formation.

A novel glucanhydrolase from a mutant of Lipomyces starkeyi ATCC 74054 was purified. The single protein (100 kDa) showed either dextranolytic or amylolytic activity. We referred to the glucanhydrolase as a DXAMase. The DXAMase was produced in a starch medium and it was 3.75-fold more active for hydrolysis of the purified insoluble-glucan of Streptococcus mutans than Penicillium funiculosum dextranase. Aggregation of S. mutans cells with dextran and adherence to glass were eliminated by incubating with the DXAMase. The addition of DXAMase (0.1 IU/ml) to the mutansucrase reaction digest with sucrose reduced the formation of insoluble-glucan about 80%. Also the DXAMase (0.5 IU/ml) removed 80% of the pre-formed sucrose-dependent adherent film. These in vitro properties of L. starkeyi KSM 22 DXAMase are desirable for its application as a dental plaque control agent.

Dental Materials↗

PubMed2000

Serum parathyroid hormone and calcitonin levels in racehorses with fracture.

Serum parathyroid hormone (PTH) and calcitonin (CT) levels in fractured racehorses were measured by radioimmunoassay. Racehorses with fracture of large bone such as the radius, third metacarpus, third carpus, digital bone or tibia, showed normal PTH level and elevated CT level in the serum. Serum PTH level was slightly higher in racehorses with sesamoid bone fracture compared to that of healthy racehorses, but not statistically significant. Moreover, serum CT level of racehorses with sesamoid bone fracture was significantly higher than that of healthy racehorses. Racehorses with sesamoid bone fracture and large bone fracture might be in different conditions of calcium regulation.

Animals↗

PubMed2000

Enhancement of vasoconstrictor responses to 5-HT but no to methoxamine by cooling in isolated dog lingual and mesenteric arteries.

The effect of temperature on submaximal vasoconstrictions to an intraluminal injection of serotonin (5-HT) and methoxamine was investigated in isolated and perfused canine lingual and mesenteric arteries, using the cannula insertion method. In both arteries cooling (from 37 degrees C to 27 degrees C) caused a remarkable enhancement of vasoconstriction to 5-HT, but did not to methoxamine. In lingual arteries, methoxamine-induced constrictions were strongly depressed, although those were slightly depressed in mesenteric arteries. It is assumed that 5-HT produces an important role to modulate vascular tonicity in low temperature conditions.

Adrenergic alpha-Agonists↗

PubMed2000

Serum levels of soluble interleukin-2 receptor after bone marrow transplantation: a true marker of acute graft-versus-host disease.

To examine whether serum levels of soluble interleukin-2 receptor (sIL-2R) may be a good marker of acute graft-versus-host disease (aGVHD), they were determined weekly in 56 patients receiving bone marrow transplantation (BMT). Because of wide variation in the pre-transplant sIL-2R levels (from 135 to 1918 IU/ml), we used a sIL-2R index in this study by comparing the peak levels with the pre-transplant levels. In agreement with previous reports, there was a significant correlation between the grade of aGVHD and the maximal sIL-2R index. The maximal sIL-2R index was 4.66 in patients with grade I to IV aGVHD, whereas it was 2.68 in patients without GVHD. This marker may be useful for monitoring the status of aGVHD. However, it was interesting that sIL-2R levels were elevated from the time of transplantation until the third week even in patients without GVHD or those who received autologous transplantation. Until the third week, no significant differences were observed in sIL-2R index between these patients and those who developed aGVHD during their clinical courses. After the fourth week, a higher sIL-2R index was observed in patients with aGVHD than in the other patients. Some factors other than GVHD contribute to the elevation of serum sIL-2R levels, and we should recognize the limitations of the measurement of this cytokine.

Adolescent↗

PubMed2000

[Essential thrombocythemia in transformation from myelodysplastic syndrome to acute myeloid leukemia with inv(3) after treatment for gastric cancer].

In March 1990, a 61-year-old man was given a diagnosis of essential thrombocythemia with a normal karyotype and subsequently treated with hydroxyurea. In November 1995, he underwent surgery for gastric cancer with thereafter received tegafur/uracil for 2 years. Refractory anemia with excess of blasts in transformation and chromosomal abnormalities including -5, -7, 20q-developed in August 1998. Combined chemotherapy with daunorubicin, cytarabine, mercaptopurine, and prednisolone, had only limited effectiveness. Acute myeloid leukemia was finally diagnosed in October 1998, and chromosomal analysis disclosed inv(3) in addition to -5 and -7. The appearance of inv(3) might be related to leukemic transformation of hematopoietic stem cell disease with an increase in the number of megakaryocytes and platelets.

Aged↗

PubMed2000

[A case of cadaveric kidney transplantation from a heart-beating donor].

We experienced a case of cadaveric kidney transplantation from a heart-beating donor, a 23-year-old man who became brain dead after a traffic accident. The recipient, a 39-year-old man, had been receiving regular hemodialysis since 1990, was admitted to our hospital on June 14, 1999. The number of human lymphocyte antigen mismatches was 3. The left kidney of the donor was transplanted to the right iliac fossa of the recipient 6 hours 28 minutes after the start of in situ cooling of the kidney. For the purpose of immunosuppressive induction, tacrolimus, azathioprine, antilymphocyte globulin, methylpredonisolone and deoxyspergualin were administered. Immediate function was obtained, moreover, the serum creatinine level of the recipient was normalized without hemodialysis. The histopathological examination of the transplant kidney biopsied 1 hour after transplantation revealed little damage of renal tubules. Since no rejection episode was recognized, the patient was discharged on the 48th day after transplantation. This is the third case of cadaveric kidney transplantation from a heart-beating donor after enforcement of the law concerning organ transplantations in Japan.

Adult↗

PubMed2000

[A case of left occipital lobe hemorrhage in a patient with progressive systemic sclerosis: evaluation of cerebral angiography and histology].

Involvement of the central nervous system is uncommon in progressive systemic sclerosis, with only 2 reported cases associated with intracerebral hemorrhage detected by neuroimaging. A 55-year-old woman with a 10-year history of scleroderma presented with left occipital lobe hemorrhage manifesting as headache and vomiting. She had no signs of hypertension, diabetes mellitus and hyperlipidemia. CT and MRI, on admission, showed left occipital lobe hemorrhage with ventricular rupture and acute left subdural hematoma. Serial cerebral angiography was performed on day 0, day 7 and day 14, and found no evidence of aneurysm, arteriovenous multiformation or tumor stain in the left occipital lobe. However, the bilateral anterior cerebral arteries showed increasing segmental narrowing suggestive of vasculitis. Histological examination of a section from the brain cortex adjacent to the hemorrhage revealed no evidence of vasculitis, fibrinoid degeneration or amyloid deposition. Focal vasculitis may have occurred secondary to the homorrhagic lesion.

Cerebral Angiography↗