Biomedical subjects

T Kubo

Publications and source records attributed to T Kubo.

At least 505 records · Page 28Linked to original sources

PubMed1995

Up-regulation of ferritin heavy chain mRNA expression in the rat skeletal muscle after denervation: detected by means of differential display.

The differential display method was applied to identify gene expression, which is especially up-regulated in denervated skeletal muscle. Total RNA from normal and denervated rat facial muscles (muscles zygomaticus, levator nasolabialis and caninus) was isolated, amplified by polymerase chain reaction (PCR) using certain primers and separated by electrophoresis on a polyacrylamide gel. PCR products, the amounts of which were significantly higher in the operated side than in the control side, were cut out from the gel and sequenced. One of the cDNA fragments obtained in the present study showed 100% identity in nucleotide sequence to the rat ferritin heavy chain (FHC) mRNA. Northern blot analysis and in situ hybridization histochemistry confirmed that FHC mRNA expression was up-regulated after denervation and was distributed throughout whole muscle cell bodies. The biological damage attributed to superoxide and hydrogen peroxide is dependent on the presence of intracellular free iron. Intracellularly, most of the iron that is not metabolized is sequestered in ferritin as a crystalline core of ferric irons (Fe3+). These findings suggest that alterations in the ferritin subunit composition after denervation play an important role in iron metabolism in skeletal muscle cells, resulting in restriction of the biological tissue damage caused by reactive oxygen species.

Animals↗

PubMed1995

8-OH-DPAT-induced hypotensive action and sympathoexcitatory neurons in the rostral ventrolateral medulla of the rat.

We examined whether the selective 5-hydroxytryptamine 1A (5-HT1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) injected systemically can act directly on sympathoexcitatory neurons located in the rostral ventrolateral medulla (RVLM) to cause the hypotensive effect of this agent in rats. Microinjections of 8-OH-DPAT and buspirone into the RVLM produced a dose-dependent decrease in blood pressure. Microinjections of spiperone and pindolol, 5-HT1A antagonists, into the RVLM inhibited the depressor response to 8-OH-DPAT intravenously injected or injected into the RVLM. Microiontophoretic application of 8-OH-DPAT onto RVLM sympathoexcitatory neurons inhibited the firing of RVLM sympathoexcitatory neurons and the inhibition of unit activity by 8-OH-DPAT was blocked by microiontophoretic spiperone. Intravenous administration of 8-OH-DPAT also inhibited the firing of these neurons. Microiontophoretic application of spiperone onto the RVLM sympathoexcitatory neurons reversed the inhibitory response to intravenous 8-OH-DPAT. These results are consistent with the hypothesis that 8-OH-DPAT may exert a portion of its hypotensive effect through a direct inhibition of RVLM sympathoexcitatory neurons in rats. The receptor involved is probably the 5-HT1A type.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1995

Endocytosis and transepithelial transport of endolymph in the endolymphatic sac.

The fate of cationized ferritin (CF) injected into the endolymphatic space of the endolymphatic sac was observed by transmission electron microscopy. At 10 min after the injection, CF particles bound to the apical plasma membrane of epithelial cells of the sac and were then endocytosed with coated pits. However, they never passed through the junctional complexes between the epithelial cells. At 30 min after the injection, the CF particles were transferred to endosomes and lysosomes by small vesicles of 100-150 nm in diameter. CF particles were also found in small vesicles close to Golgi cisternae and in multivesicular bodies. Acid phosphatase positive lysosomes were found close to endosomes containing CF particles. In addition, a small fraction of the small vesicles containing CF particles became inserted into the basolateral plasma membrane. At 60 min after the injection, many CF particles were found in acid phosphatase positive secondary lysosomes. These observations suggest that endocytosis of endolymph is actively performed by the epithelial cells of the sac, and transepithelial vesicular transport across the epithelial cells occurs.

Acid Phosphatase↗

PubMed1995

Serum levels of carboxyterminal propeptide of type I procollagen and pyridinoline crosslinked telopeptide of type I collagen in normal children and children with growth hormone (GH) deficiency during GH therapy.

In this study, we investigated age-related changes in serum levels of both the carboxyterminal propeptide of type I procollagen (PICP) and the pyridinoline crosslinked telopeptide of type I collagen (ICTP) to elucidate bone formation and resorption, respectively, in 200 normal Japanese children (141 males and 59 females, age range 0-16 years). Furthermore, to clarify the effect of GH on bone turnover, we measured serum PICP and ICTP in 26 growth hormone (GH)-deficient children (20 males and 6 females, age range 4-15 years) who showed significant bone growth during recombinant human GH therapy. In the normal children, the curves for age-related changes in both serum PICP and ICTP levels almost paralleled that of the standard height velocity curve in both sexes. The serum levels of both peptides were higher than those in adults, and the peak increases corresponded with the timing of the adolescent growth spurt. Furthermore, the serum levels of PICP and ICTP were significantly correlated with the height velocity. In the GH-deficient patients, the serum ICTP levels before GH therapy were lower than those in age- and sex-matched controls. Both PICP and ICTP levels in serum increased significantly at the beginning of GH therapy. Furthermore, the percent increase in PICP after 1 month of GH treatment was positively correlated with the percent increase in height velocity during 1 year of GH treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Chemosensitisation of spontaneous multidrug resistance by a 1,4-dihydropyridine analogue and verapamil in human glioma cell lines overexpressing MRP or MDR1.

Multidrug resistance phenotypes in human tumours are associated with the overexpression of the 170 kDa P-glycoprotein encoded by the multidrug resistance 1 (MDR1) gene, and also with that of the non-P-glycoprotein-mediated multidrug resistance gene, MRP, which encodes a 190 kDa membrane ATP-binding protein. We have previously reported that overexpression of MRP appears to be responsible for spontaneous multidrug resistance in some human glioma cell lines (Abe et al., Int. J. Cancer, 58, 860-864, 1994). In this study, we investigated whether chemosensitising agents of P-glycoprotein-mediated multidrug resistance such as verapamil, a biscoclaurine alkaloid (cepharanthine), and a dihydropyridine analogue (NIK250) could also reverse multidrug resistance in human glioma cells. The glioma cell lines were the two MRP-expressing cell lines, T98G and IN500, an MDR1-expressing cell line, CCF-STTG1, and the MRP1 MDR1-non-expressing cell line, IN157. Verapamil and NIK250 almost completely reversed drug resistance to vincristine, etoposide and doxorubicin in T98G cells, while they also reversed drug resistance to vincristine and etoposide, but only partially to doxorubicin in IN500 cells. Cepharanthine as well as verapamil and NIK250 reversed vincristine resistance in CCF-STTG1 cells, but cepharanthine only partially reversed drug resistance in T98G and IN500 cells. The cellular accumulation of [3H]etoposide increased about 2- and 3-fold compared with control in T98G cells in the presence of verapamil and NIK250 respectively. Furthermore, the release of doxorubicin from the nuclei of T98G cells was blocked by NIK250. However, NIK250 and verapamil caused no apparent increase in vincristine accumulation in T98G cells. NIK250 or verapamil might exert inhibitory effects upon MRP function, resulting in a reversal of MRP-mediated spontaneous multidrug resistance in cultured human glioma cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1995

Nucleotide sequence and restriction fragment length polymorphism analysis of the long terminal repeat of human T cell leukemia virus type II.

Molecular studies have demonstrated the existence of two major subtypes of human T cell leukemia virus type II: HTLV-IIa and HTLV-IIb. In attempts to further classify this family of viruses we have carried out nucleotide sequence and restriction fragment length polymorphism (RFLP) analysis of the long terminal repeat (LTR), a region that has been shown in previous studies to have the greatest intra- and intersubtype genomic divergence. Analysis of the nucleotide sequences suggested the existence of distinct phylogenetic groups in each subtype and, on the basis of predicted differences in restriction endonuclease sites, RFLP analysis allowed the identification of four groups within the IIa subtype (a1-a4) and six within the IIb subtype (b1-b6). Nucleotide sequence analysis also suggested the possible existence of HTLV-II quasispecies. However, this appeared not to be significant, and preliminary studies suggest that these would not be expected to influence the results of RFLP analysis appreciably. The validity of the RFLP method was demonstrated in an analysis of 36 randomly chosen samples from HTLV-II seropositive blood donors from the New York City Blood Center, where it could be shown that all could be successfully classified. Moreover, the RFLP analysis correctly matched the viruses in donors and recipients of contaminated blood in four situations in which HTLV-II was inadvertently transmitted by transfusion. RFLP analysis of the LTR appears to be a rapid and reliable method by which to identify HTLV-II infection. This should prove useful in studies of the epidemiology and the characterization of viruses present both in nonindigenous and indigenous populations.

Base Sequence↗

PubMed1995

Identification of human T cell lymphotropic virus type IIa infection in the Kayapo, an indigenous population of Brazil.

Human T cell lymphotropic virus type II (HTLV-II) infection is endemic in a number of indigenous populations in North, Central, and South America. In the present study we have employed serological and molecular methods to identify HTLV-II infection in Indian communities in the Amazon region of Brazil. Sera (1324) from 25 different Indian communities were analyzed by ELISA and Western blot. One hundred and four samples (7.8%) from a number of culturally distinct and geographically unrelated populations were found to have reactivities consistent with HTLV-II infection. Of these, 67 were from the Kayapo Indian communities, which had an overall seroprevalence rate of greater than 30%. In addition, high seroprevalence rates were observed in three other communities, the Munduruku, Arara do Laranjal and the Tyrio, suggesting that there are additional foci of endemic infection in the Amazon region. In the Kayapo, seroprevalence rates tended to increase with age, supporting the importance of sexual transmission of the virus, and family studies demonstrated that vertical transmission is also an important route of infection. Restriction fragment length polymorphism (RFLP) and nucleotide sequence analysis of a region of the env gene demonstrated that the Kayapo are infected with the HTLV-IIa subtype. Moreover, nucleotide sequence analysis of the LTR demonstrated that this belonged to a distinct HTLV-IIa phylogenetic group. The identification of HTLV-IIa in the Kayapo is, as far as we are aware, the first identified endemic focus of infection by this subtype of HTLV-II in the Americas.

Adolescent↗

PubMed1995

Suppression by prolactin of the electrically induced erectile response through its direct effect on the corpus cavernosum penis in the dog.

PURPOSE: Men become impotent when exposed to hyperprolactinemia. To clarify its mechanisms the effects of intracorporal infusion of prolactin on electrically induced penile erection were evaluated in 12 male dogs. MATERIALS AND METHODS: Prolactin (10 micrograms./ml.) or control saline was directly infused into the corpus cavernosum penis 5 minutes before electrical pulse stimulation of the pelvic nerve and the intracorporal pressure was monitored. RESULTS: In 8 dogs erection was markedly suppressed or completely abolished by prolactin. In the remaining 4, this effect of prolactin became manifest only when the ipsilateral internal pudenal artery was ligated. Saline infusion was without effect. CONCLUSIONS: An excess of prolactin directly inhibited the smooth muscle relaxation of corpus cavernosum penis.

Animals↗

PubMed1995

Acetylcholine release in the rostral ventrolateral medulla of spontaneously hypertensive rats.

1. Central acetylcholine (ACh) has been implicated in the pathogenesis of experimental hypertension and the rostral ventrolateral medulla (RVLM) is an important area for cardiovascular regulation. The purpose of this study was to determine whether cholinergic neurotransmission in the RVLM is altered in spontaneously hypertensive rats (SHR). 2. Experiments were performed on male SHR (12-16 weeks) and age-matched Wistar-Kyoto rats (WKY). The rats anaesthetized with pentobarbital were placed in a stereotaxic apparatus. For determining the release of ACh in the RVLM, a dialysis probe was introduced into the RVLM. 3. An RVLM microinjection of cholinergic agents elicited an increase in blood pressure. The pressor response to physostigmine was greater in SHR than that of WKY whereas there was no difference in the pressor response to ACh or carbachol between SHR and WKY. 4. The release of ACh in the RVLM was greater in SHR than that of WKY. Physostigmine (0.5 mg/kg, i.p.) produced increases in medulla ACh contents. The increase in ACh content of the rostroventral medulla including the RVLM was greater in SHR than that of WKY whereas there was no difference in ACh contents of the other three parts of the medulla oblongata between SHR and WKY. 5. Depressor responses to scopolamine injected bilaterally into the RVLM were greater in SHR than those of WKY. 6. These results suggest that ACh release is enhanced specifically in the RVLM of SHR. It appears that this enhanced release of ACh in the RVLM of SHR contributes to the maintenance of hypertension in SHR.

Acetylcholine↗

PubMed1995

A new computer network system for communicating perinatal decision support information via a telephone line.

OBJECTIVE: For fetal monitoring and assessment of high risk mother and fetus at regional hospitals, we developed a new computer network system. METHODS: The system incorporates a notebook-type personal computer (PC-9801nv) at regional hospital for communication in with 3 servers (IBM5580-YOC) connected via 2 Ethernet LANs to 2 host computers (IBM3080, IBM3174) and 5 workstations (IBM5521 V2b), and transmits the compressed data by telephone. When the data arrive, the doctor in perinatal center can immediately display and interpret the data on his workstation and give appropriate advice to the doctor at the regional hospital. RESULTS: The rate of reliable data transmission was 100%. Each 1 hour recording session and characteristic perinatal information was transmitted in less than 2 minutes. Regional medical institutions can easily access the center, and thereby can receive both simplified automatic diagnosis by fetal cardiotocography and pregnancy-risk evaluation. CONCLUSIONS: Because this system uses telephone circuits, it can be accessed from all regions of the country. Thus, our system is useful for perinatal management of high risk mother and fetus.

Adult↗

PubMed1995

Tokishakuyakusan effect on DNA polymerase alpha activity in relationship to DNA synthesis before and/or after the LH/FSH surge in rats.

DNA polymerase alpha activity in ovaries of mature cycling rats during the normal estrous cycle changed in a cyclic manner with a peak at 1800 h in proestrus. Tokishakuyakusan (TS) in vivo did not affect the changes in DNA polymerase alpha and beta activities during the estrous cycle. LH and FSH at 1000 or 1700 h in proestrus increased DNA polymerase alpha activity, but the DNA polymerase alpha activity induced by LH or FSH was not significantly affected by the addition of TS. DNA polymerase beta activity did not change with LH, FSH or TS. In PMS-treated or -untreated immature rats, TS enhanced ovarian DNA polymerase alpha activity but had no significant effect on LH or FSH action. In ovaries, incubated in vitro, in untreated mature or immature rats, TS enhanced ovarian DNA polymerase alpha activity but had no significant effect on LH or FSH action. These results suggest that TS stimulates ovarian DNA polymerase alpha activity in relationship to DNA synthesis and does not affect the effect of LH or FSH on the activity by preovulatory follicle before and/or after the LH/FSH surge.

Animals↗

PubMed1995

Vascular permeability of the stria vascularis and morphology of the endolymphatic sac in two types of experimental endolymphatic hydrops.

We produced two kinds of experimental endolymphatic hydrops. One was induced by obliteration of the endolymphatic sac (ES), and the other was induced by both systemic keyhole limpet hemocyanin immunization and secondary keyhole limpet hemocyanin challenge into the ES. The vascular permeability of the stria vascularis in acute and chronic phases was compared between both models by light and electron microscopy using the tracer method of horseradish peroxidase. Both models showed that the number of strial capillaries showing horseradish peroxidase leakage was significantly higher in the acute phase than in the chronic phase. In the acute phase, the ES showed acute inflammation in both models. In the chronic phase, extensive fibrosis occurred in the ES obliteration model, whereas the ES appeared to have a normal shape in the immunologically induced model. The mechanism of hydrops formation will be compared between the two models.

Acute Disease↗

PubMed1995

Urinary pyridinoline and deoxypyridinoline in healthy children and in children with growth hormone deficiency.

To assess the bone growth status in healthy children, urinary pyridinoline (PYR) and deoxypyridinoline (DPYR) levels, which are specific bone resorption markers, were studied in 192 healthy children, aged 3-14 yr. In healthy children ages 3-5 yr, the urinary PYR level was about 10 times higher than that in healthy adults (238.3 +/- 22.7 pmol/mumol Cr in boys and 261.8 +/- 14.2 pmol/mumol Cr in girls; mean +/- SE, and the level declined gradually with age. In boys, the urinary PYR level began to rise at about 10 yr of age and peaked 2 yr later, declining thereafter. In girls, urinary PYR level declined rapidly after 11 yr. The age-related changes in urinary DPYR levels closely resembled those in urinary PYR levels. We further studied PYR and DPYR levels in 17 GH-deficient children who were beginning treatment with GH. After 2-3 months of GH therapy, 1.3-fold significant increases in urinary PYR and DPYR levels were observed. These results indicate that the bone resorption in children is increased relative to that in adults, that urinary PYR and DPYR levels are increased during puberty when the growth rate is markedly elevated, and that bone resorption in children is accelerated by GH therapy.

Adolescent↗

PubMed1995

Up- and down-modulation of a cloned Aplysia K+ channel (AKv1.1a) by the activators of protein kinase C.

Modulation of a cloned Aplysia K+ channel, AKv1.1a, by protein kinase C (PKC) activators was examined in Xenopus oocytes expression system. Following the application of phorbol esters (phorbol 12-myristate 13-acetate, PMA; phorbol 12,13-dibutyrate, PDBu), or a diacylgrycerol analogue (1-oleoyl-2-acetyl-sn-glycerol, OAG), the fast inactivation of the AKv1.1a became slower and the peak current increased (up-modulation). However, the effect was transient. The expressed current was decreased even below control level about 15 to 20 min after the treatment (down-modulation). Both effects by PMA was blocked by the kinase inhibitor, H7, suggesting that phosphorylation by PKC is involved. The amino acid sequence of AKv1.1a contains three putative phosphorylation sites by PKC (Ser24, Thr345, Ser349). We tested their contributions to the PMA-induced modulation by site-directed mutagenesis. The results suggest that the up-modulation by PKC activators is due to the inhibition of the fast inactivation by the amino-terminal domain (N-type inactivation), thereby increase the time the channels are conductive. Phosphorylation of Ser24 may enhance the PKC-induced down-modulation, while phosphorylation of Thr345 may inhibit the down-modulation. By contrast, mutation of Ser349 did not affect the modulation. The N-type inactivation were not indispensable for the down-modulation because the amino-terminal deletion mutant also showed some down-modulation although its onset was quite slow. Thus, the down-modulation of AKv1.1a may be heterogeneous.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Time course of vestibular function in patients with menière's disease following vestibular nerve section.

Harmonic acceleration rotational test and vestibular autorotation test (VAT) were performed on 8 patients with Menière's disease before and after vestibular nerve section. Sinusoidal rotations of 0.01-0.64 Hz were used in the HA rotational test. VAT was performed at frequencies between 0.5 and 6 Hz. Two weeks after operation, almost all the patients consistently showed response asymmetry toward the healthy ear at all stimulus frequencies and a reduction in sensitivity to rotational stimuli at 0.01 Hz in the HA rotational test. Prior to surgery, the time constant of the vestibulo-ocular reflex (VOR) varied according to the residual vestibular function of each patient. The time constant then dropped to a mean of 4.2 s after the operation. In the VAT, almost all the patients showed a gain reduction at all frequency ranges on the seventh postoperative day. These findings suggest that response asymmetry and gain at 0.01 Hz in the HA rotational test are valuable for evaluating the time course of the compensation of the vestibular function after surgery and that the VOR time constant is useful in detecting whether the vestibular nerve has been sectioned correctly.

Adult↗

PubMed1995

Frequency analysis of evoked otoacoustic emissions in Meniére's disease.

Our study was designed to establish a diagnostic significance in Meniére's disease by means of evoked otoacoustic emissions (EOAEs). EOAEs were recorded from patients with Meniére, and the "main frequency" of the emissions, which shows the maximum peak in the frequency spectrum, was examined as a variable. The main frequencies in ears with Meniére ranged mainly from 0.8 kHz to 1.1 kHz and were to be found at lower frequencies than in ears with normal hearing whose range was mainly from 1.0 kHz to 1.6 kHz. Furthermore, in some ears with Meniére, the main frequencies changed from lower to higher after administration of osmotic diuretics such as glycerol or isosorbide. On the basis of these results it was speculated that in ears with Meniére, lower frequency dominant emissions might be elicited by modification of the basilar membrane in endolymphatic hydrops and that the main frequencies might change from lower to higher with reduction of endolymphatic hydrops induced by osmotic diuretics. It was considered that the EOAE testing might be useful for a diagnosis of endolymphatic hydrops in Meniére.

Adolescent↗

PubMed1995

Responses of locus coeruleus neurons to caloric stimulation in rats.

We examined the effects of caloric stimulation on the neuronal activity of the locus coeruleus (LC) and of the vestibular nucleus complex (VNC) in urethan-anesthetized rats. The single unit activity of neurons in the LC and VNC was extracellularly recorded. A polyethylene tube for caloric stimulation was inserted into the middle ear cavity on the ipsilateral side. Through the tube, the middle ear was irrigated by hot (44 degrees C), cold (30 degrees C), and ice (4 degrees C) water. The majority of neurons in the VNC showed excitation by middle ear irrigation with hot water and inhibition by ice-water irrigation. The responses occurred during caloric stimulation and disappeared immediately after the cessation of the stimulation. The results suggest that the responses of VNC neurons to caloric stimulation directly reflect changes in primary vestibular afferent activity. On the other hand, the predominant effect of caloric stimulation with hot and cold water on LC neuronal activity was inhibitory. The suppression of LC neuronal activity occurred approximately 1 min after the cessation of the caloric stimulation and persisted for 3-5 min. The results suggest that LC neurons receive processed vestibular signals. Motion sickness and vestibular dysfunction induced by caloric stimulation cause emesis, which is known as vestibulo-autonomic response. The vestibulo-autonomic syndrome can be prevented by amphetamine, a noradrenaline releaser. Therefore, the inhibitory response of noradrenergic LC neurons to vestibular stimulation may be involved in the vestibulo-autonomic response.

Afferent Pathways↗

PubMed1995

Clinical investigation of the vestibular cortex.

This study attempted to identify the vestibular cortex that is involved in the perception of vestibular vertigo in the human brain. We used single-photon emission computed tomography (SPECT) to measure regional cerebral blood flow (rCBF) in two cerebrovascular patients with nystagmus-sensation dissociation, which is known as brisk caloric nystagmus without simultaneous sensation of vertigo. Both patients had ischemic lesions involving mainly the parieto-temporal lobe in the nondominant hemisphere. It is suggested that the parieto-temporal lobe in the nondominant hemisphere contains the vestibular cortex which is a center for the perception of vertigo due to vestibular stimulation.

Aged↗