Biomedical subjects

K Ikuta

Publications and source records attributed to K Ikuta.

At least 217 records · Page 12Linked to original sources

PubMed1995

Short photoperiod accelerates preoptic and ventral telencephalic salmon GnRH synthesis and precocious maturation in underyearling male masu salmon.

The temporal relationship between testicular maturation and salmon gonadotropin-releasing hormone (sGnRH) mRNA expression was investigated in underyearling precocious male masu salmon, Oncorhynchus masou. Testicular maturation could be experimentally manipulated by changing the length of the light-dark photoperiod; maturation was accelerated in the short photoperiod group (8L-16D) and delayed in the long photoperiod group (16-8D). sGnRH mRNA and total silver grains in these loci in individual fish, increased with advancing testicular maturation. They were maximal in the short photoperiod group in August and in the long photoperiod group in September, when spermiation occurred. In contrast, marked changes in sGnRH synthetic activity in relation to testicular maturation were not observed in the terminal nerve ganglion or in the olfactory bulbs. sGnRH neurons in the preoptic area and the ventral telencephalon are clearly influenced by photoperiod and are involved in the control of gonadal maturation probably via gonadotropin secretion.

Animals↗

PubMed1995

Prevalence of Borna disease virus RNA in peripheral blood mononuclear cells from blood donors.

The presence of Borna disease virus (BDV) in peripheral blood mononuclear cells (PBMC) of 100 blood donors from Sapporo and 72 blood donors from Tokyo was examined using nested reverse transcriptase/polymerase chain reaction amplification with specific-primers for BDV p24. Anti-BDV p24 antibodies in the plasma of the 100 blood donors from Sapporo also were studied by enzyme-linked immunosorbent assay and by Western blot. BDV RNA was detected in 3 (4.2%) of the 72 PBMC samples from Tokyo, and in 5 (5%) of the 100 PBMC samples from Sapporo. In contrast, anti-p24 antibodies were found in only 1 (1%) of the donors from Sapporo. These results suggest that BDV infection in humans may be more widespread than previously thought.

Adolescent↗

PubMed1995

Development of human precision grip. V. anticipatory and triggered grip actions during sudden loading.

When an object held by a precision gripis subjected to an abrupt vertical load perturbation, somatosensory input from the digits triggers an increase in grip force to restore an adequate safety margin, preventing frictional slips. In adults the response occurs after a latency of 60-80 ms. In the present study, children from 2 years old upward and adults grasped and lifted an object using a precision grip. Sudden, unpredicted increases in load force (tangential to the grip surfaces) were induced by the experimenter by dropping a small disc on to a receptacle attached to the object. The impact elicited a grip force response which in young children had a longer latency and a smaller amplitude than was seen in adults. The grip response latency gradually become shorter and its amplitude increased with increasing age, reaching adult values at 6-10 years. The muscle activity underlying the response could have several bursts. The adults showed one brisk response, appearing 40-50 ms after impact, in extrinsic and intrinsic hand muscles, while younger children also exhibited a short-latency burst, appearing about 20 ms after impact. It is suggested that the short-latency response was mediated via spinal pathways, and that these pathways are disengaged by supraspinal centers during development. In a predictable loading situation, when subjects dropped the disc themselves into the receptable using the contralateral hand, they changed strategy. Adults induced a well-timed anticipatory grip force increase prior to the impact that was scaled to the weight of the object. The youngest children did not time the force increase properly in relation to the impact. Yet, they could scale their anticipatory grip force increase with respect to the weight of the dropped disc. This suggests a well-developed capacity to use information about the weight of objects held by one hand to parameterize a programmed force output to the other hand.

Child↗

PubMed1995

Effects of erythropoietin, IL-3, IL-6 and LIF on a murine megakaryoblastic cell line: growth enhancement and expression of receptor mRNAs.

We examined the effects of recombinant human erythropoietin (rhEPO), recombinant murine interleukin 3 (rmIL-3), recombinant human interleukin 6 (rhIL-6), recombinant human interleukin 11 (rhIL-11), recombinant murine leukemia inhibitory factor (rmLIF) and recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the growth of murine megakaryocytic cell lines. In serum-free methylcellulose culture supplemented with bovine serum albumin (BSA), the addition of rhEPO (0.1-10 U/ml), rmIL-3 (10-500 U/ml), rhIL-6 (100-10,000 U/ml), rmLIF (100-10,000 U/ml), or rmGM-CSF (10-1000 U/ml) enhanced colony growth in L8057Y5 cells, which had been maintained in protein-free culture, mostly in a dose-dependent fashion; rhIL-11 did not have any stimulatory effect at the tested doses (10-1000 U/ml). In addition, colony growth of L8057 cells, which had been maintained in serum-containing culture, was enhanced, but to a lesser extent, by the addition of these cytokines except rhEPO (the cultures were supplemented with 1% fetal bovine serum. Among the cytokines that showed growth-enhancing effects on L8057 cells, the expression of mRNAs encoding receptors for EPO, IL-6 and IL-3 was examined by northern blot analysis or reverse transcription polymerase chain reaction (RT-PCR). In both cell lines, mRNAs for EPO-R, IL-6R, gp130, IL-3R alpha and beta chains were constitutively expressed. The results suggest that L8057 and L8057Y5 cell lines have characteristics of megakaryoblastic cells in their biological responses to cytokines, as well as in the expression of cytokine receptor mRNAs, and that the growth-enhancing effects of these cytokines on the cell lines may be achieved through specific receptors. Our findings show the value of these cell lines for investigating the mechanisms of growth signal transduction in megakaryopoiesis.

Animals↗

PubMed1995

High susceptibility of U937-derived subclones to infection with human immunodeficiency virus type 1 is correlated with virus-induced cell differentiation and superoxide generation.

The promonocytic human leukemic cell line U937, when infected with lymphotropic human immunodeficiency virus type 1 (HIV-1), becomes a continuous virus producer. A total of 46 U937-derived subclones in suspension was isolated and classified into three (2 high, 42 middle, and 2 low) types based on their susceptibility to the infection. By analyzing subclones before infection, we found that the high-type subclones expressed LFA-1 antigens at a relatively low level. In addition, the ability of these subclones to induce adherence after exposure to phorbol 12-myristate 13-acetate (PMA) was reduced. In contrast, a transition by HIV-1 infection to adherent macrophage-like cells was induced only in the high-type, but not in the low-type subclones. The high-type adherent cells obtained by HIV-1 infection were followed by further lineage to become retrodifferentiated suspension cells showing reduced syncytia formation ability. Superoxide was generated in the high-type subclones, without PMA-mediated differentiation, from the early stage of infection before HIV-1 replication, as well as during undifferentiated, differentiated and retrodifferentiated stages. In contrast, it was only transiently generated at acute phase of HIV-1 replication in low-type subclones. Long-term culture of the low-type subclones decreased the expression of major structural viral protein Gag and also virus production. Thus, the mechanism by which PMA differentiates U937 cells is not the same as that induced by HIV-1 infection. The latter mechanism results in high susceptibility to infection. The HIV-1 phenotypes of finally obtained persistently infected cells were also affected by the cell stages at the time of infection.

Cell Cycle↗

PubMed1995

Stimulation of human immunodeficiency virus type 1 infected cells with superoxide enhances the chemotactic motile response of CD4+ human T cells: implication for virus transmission by cell-to-cell interaction.

We previously showed that superoxide (O2-) significantly enhanced human immunodeficiency virus type 1 (HIV-1)-induced syncytia formation in co-cultured infected and uninfected human T cells. In this study, we describe a novel chemotactic response of uninfected CD4+ T cells by stimulating infected T cells with O2-. Syncytia formation was amplified only when persistently infected cells were stimulated by O2-. When the infected cells in lower well of microplate were cultured with uninfected cells in the upper well of a Boyden chamber with 8.0 microns pores, uninfected cell migration to the porous membrane was significantly amplified by stimulating infected cells with O2-. In contrast, similar functions were slight under the same assay conditions in the presence of known chemokines such as human RANTES and macrophage inflammatory protein 1 (MIP-1 alpha and beta), which all activate T lymphocytes. In addition, it is unlikely that the O2(-)-induced chemotactic response is due to soluble HIV-1 proteins from infected cells or to amplified expression levels of cell surface functional molecules such as CD4 and LFA-1 (CD11a and CD18) as well as HIV-1 Env gp120 on uninfected and/or infected cells. Thus, an unknown chemotactic factor could be generated from infected T cells by stimulation with O2- and it might contribute to viral transmission by activating cell-to-cell interactions.

Antigens, Surface↗

PubMed1995

Viral activation from latency during retrodifferentiation of U937 cells exposed to phorbol ester followed by infection with human immunodeficiency virus type 1.

To determine the mechanism underlying the human immunodeficiency virus type 1 (HIV-1) latency and its activation in monocyte/macrophage lineage, the human promonocytic cell line U937 was infected with HIV-1 after differentiation with varied doses of phorbol 12-myristate 13-acetate (PMA). Variously differentiated intermediate stages were generated in U937 cells in a dose-dependent manner. When these cells were infected with lymphotropic HIV-1, the kinetics of the production of HIV-1 DNA, the appearance of HIV-1 antigen-positive cells, and viral production in the conditioned media were slower at higher doses of PMA. This different susceptibility to the infection was not due to the rate of HIV-1 adsorption. Viral replication from latency in the differentiated cells was activated in proportion with the retrodifferentiation observed in long-term cultures of the host cells. Thus, our data demonstrate the close correlation between the regulation of HIV-1 replication and the differentiation stage of monocyte/macrophage lineage cells at the time of HIV-1 infection. The retrodifferentiation phenomenon in infected cells seems to be particularly important for understanding the mechanisms for HIV-1 activation from latency.

Base Sequence↗

PubMed1995

Demonstration of Borna disease virus RNA in peripheral blood mononuclear cells from healthy horses in Japan.

Borna disease (BD) is a progressive poliomeningoencephalomyelitis which occurs naturally in horses and sheep. Here, peripheral blood mononuclear cells (PBMC) derived from 57 healthy horses in Japan were examined by a nested reverse transcription-polymerase chain reaction to determine the prevalence of BD virus (BDV) infection. Seventeen (29.8%) of the samples were positive by this examination and the specificity of the amplified product was confirmed by hybridization with authentic oligomer probes. About 60% of the BDV RNA-positive individuals also showed seropositivity by Western blotting. This report is the first for the demonstration of BDV RNA in PBMC of healthy horses, as well as the first on the BDV infection in horses in Japan. Thus, BDV may be more widespread in healthy horses over the world as well as in Japan and the detection of BDV RNA in PBMC at a high rate indicates that the disease might develop in a part of the carriers only after long-incubation period.

Animals↗

PubMed1995

Maintenance of high virus load even after seroconversion in newborn cats acutely infected with feline immunodeficiency virus.

The viral loads in adult and newborn cats have been compared following injection with feline CD4+ FeL-039 line cells acutely infected with feline immunodeficiency virus (FIV). The level of virus genome in peripheral blood mononuclear cells (PBMC) increased progressively despite seroconversion in the newborn cats, whereas the virus genome was apparently cleared after seroconversion in the adult cats. Immunohistochemical staining of thymus of the FIV-infected newborn cats showed clusters of viral antigen-positive cells. These results indicate that FIV infection of the newborn cat results in higher virus loads than infection of the adult cat. We discuss these findings in relation to FIV as a model system for studies of the infection of neonates with an immunosuppressive retrovirus.

Acute Disease↗

PubMed1995

Contributions and co-ordination of individual fingers in multiple finger prehension.

The contributions and co-ordination of external finger grip forces were examined during a lifting task with a precision grip using multiple fingers. The subjects (n = 10) lifted a force transducer-equipped grip apparatus. Grip force from each of the five fingers was continuously measured under different object weight (200 g, 400 g and 800 g) and surface structure (plastic and sandpaper) conditions. The effect of five-, four-, and three-finger grip modes was also examined. It was found that variation of object weight or surface friction resulted in change of the total grip force magnitude; the largest change in finger force, was that for the index finger, followed by the middle, ring, and little fingers. Percentage contribution of static grip force to the total grip force for the index, middle, ring, and little fingers was 42.0%, 27.4%, 17.6% and 12.9%, respectively. These values were fairly constant for all object weight conditions, as well as for all surface friction conditions, suggesting that all individual finger force adjustments for light loads less than 800 g are controlled comprehensively simply by using a single common scaling value. A higher surface friction provided faster lifting initiation and required lesser grip force exertion, indicating advantageous effect of a non-slippery surface over a slippery surface. The results indicate that nearly 40% force reduction can be obtained when a non-slippery surface is used. Variation in grip mode changed the total grip force, i.e., the fewer the number of fingers, the greater the total grip force. The percent value of static grip force for the index, middle, and ring fingers in the four-finger grip mode was 42.7%, 32.5%, and 24.7%, respectively, and that for the index and middle fingers in the three-finger grip mode was 43.0% and 56.9%, respectively. Therefore, the grip mode was found to influence the force contributions of the middle and ring fingers, but not of the index finger.

Adolescent↗

PubMed1995

Superinfection of a defective human immunodeficiency virus type 1 provirus-carrying T cell clone with vif or vpu mutants gives cytopathic virus particles by homologous recombination.

The partially CD4-expressing T cell clone, Vpr-1, which carries a latent vpr-defective HIV-1 genome and expresses HIV-1 Nef protein only, was permissive to superinfection by HIV-1. Superinfection of Vpr-1 with vif- or vpu-defective mutants, which were noncytopathic, reactivated the vpr-defective virus and led to homologous recombination and cytopathogenesis. The data provide an experimental model for homologous recombination being an important mechanism whereby HIV-1 acquires genetic heterogeneity, and when occurring among defective virus in vivo bestows novel biological activities and virulence.

CD4-Positive T-Lymphocytes↗

PubMed1995

Naturally occurring accessory gene mutations lead to persistent human immunodeficiency virus type 1 infection of CD4-positive T cells.

Proviral DNA from cells surviving severe but transient cytopathic effects, mediated by infection with recombinant human immunodeficiency virus type 1 (HIV-1) carrying a single gene mutation at vif, vpr, or vpu, was characterized by use of HIV-1-specific primer pairs in a two-step PCR. Deletion mutations were detected in a region that spanned the vif and vpr open reading frames. Cloning and sequencing of the amplified DNA from this region revealed frequent large deletions in a limited number of nucleotide positions. Analyses of the deletions suggested that (i) genetic recombination, (ii) template-primer slippage, and (iii) misalignment of the growing point during reverse transcription of the HIV-1 genome might be the mechanisms that generated the mutations. Apart from the large deletions, smaller deletions that gave frameshift mutations in vif and/or vpr prevailed. In addition, cells infected with a triple mutant defective in vif, vpr, and vpu did not show any cytopathic effect. Thus, mutations generating multiple accessory gene defects during HIV-1 replication correlate with viral persistence and loss of cytopathogenicity.

Base Sequence↗

PubMed1995

Coronary artery aneurysms develop in weanling rabbits with serum sickness but not in mature rabbits. An experimental model for Kawasaki disease in humans.

The involvement of the cardiovascular system in rabbits with serum sickness is similar of that in Kawasaki disease, both with respect to the histologic changes of the myocardium, the valves, the coronary arteries, and the aorta and to the sequence with which they appear. Although coronary arteritis appears the same histologically, aneurysms did not occur in mature rabbits, even in case of necrosis of an arterial segment with deletion of muscle and elastic tissue. On the other hand, weanling rabbits with serum sickness had a tendency to develop aneurysms of coronary arteries, despite little cellular infiltration and reactive fibrocellular hyperplasia. The age factor thus appears to play an important role in the development of coronary aneurysms in Kawasaki disease, irrespective of the underlying mechanism, be it a markedly increased permeability to mediators through degenerated endothelial cells, or primary degenerated muscle cells with marked thinning of the media without much inflammatory cellular reaction. Furthermore, this study provides an insight into the long-term prognosis of transient dilatation of coronary arteries in the acute stage of Kawasaki disease.

Age Factors↗

PubMed1995

[The study of chemotherapy via the reservoir to colo-rectal cancer patients with liver metastases].

From January 1986 to December 1994, we administered intra-arterial chemotherapy via the reservoir to 26 colo-rectal cancer patients with liver metastases. The protocol of this chemotherapy was administration of ADM 30 mg/body/4 wks, MMC 10 mg/body/2 wks and 5-FU 500 mg/body/2 wks. Responses to this chemotherapy were PR in 8 cases, NC 3 cases, PD 14 cases and unknown 1 case. The rate of response was 32.0%. Side effects were shown in 12 cases (46.2%), and trouble with the reservoir in 5 cases (20.8%). Survival times of patients were from 5 months to 42 months (average 13.6). We think that this intra-arterial chemotherapy via the reservoir was effective for patients with liver metastases from colo-rectal cancer.

Adult↗

PubMed1994

The carboxyl-terminal region of HIV-1 Nef protein is a cell surface domain that can interact with CD4+ T cells.

Our previous studies have shown that the HIV-1 Nef Ag is expressed, at least in part, on the surface of infected cells. We demonstrated this by using membrane immunofluorescence and flow cytometry with Nef murine mAbs. To identify the domain of Nef exposed on the cell surface, epitope mapping of these and a new mAb was performed by ELISAs by using several recombinant truncated Nef fusion proteins and synthetic peptides. The results showed that mAbs F1, E7, E9, and 4H4 recognized Nef epitopes located at amino acid residues 148-157, 192-206, 158-206, and 1-33, respectively. The intensity of cell surface Nef staining was stronger with mAbs E7 and E9 than with F1, and there was no staining by 4H4, which indicates that the carboxyl-terminal region of Nef is predominantly exposed on the surface of HIV-1-infected T cell lines and PBMC. This surface Nef domain displayed high affinity for the surface of uninfected CD4+ T cells, because the binding of a soluble form of recombinant Nef protein to the cell surface was specifically blocked by the E7 and E9 mAbs or by synthetic peptides that contained the carboxyl-terminal region of Nef. In addition, syncytium formation between infected and uninfected cells also was specifically reduced by the same mAbs or peptides. Thus, the cell surface domain of Nef seems to play an important role in the interaction between HIV-1-infected and CD4+ uninfected T cells.

Antibodies, Monoclonal↗

PubMed1994

Nonsense mutations in the vpr gene of HIV-1 during in vitro virus passage and in HIV-1 carrier-derived peripheral blood mononuclear cells.

Long-term, persistent infection by HIV-1 is a prerequisite for the development of AIDS. However, little is known of the determinants required for HIV-1 to cause persistence. We have reported previously that persistent infection of a T cell line by a cytopathogenic strain of HIV-1 became increasingly likely with in vitro serial passage of the virus. DNA sequencing of the persistent strains revealed a nonsense mutation in the vpr gene in all isolates tested. Here, we report the development and use of a semi-quantitative PCR method to detect the vpr nonsense mutation within populations of virus. Our results show that vpr mutants also arise in cells during acute infection and increase progressively with serial passage of the virus. In addition, HIV-1-seropositive individuals were examined and found to carry the same vpr nonsense mutation at high frequency in virus-infected PBMC. These data are consistent with a mechanism of HIV-1 persistence in vivo and in vitro in which virus cytopathogenic potential is lost by the build up of nonsense mutations in vpr.

AIDS-Related Complex↗

PubMed1994

Salmon gonadotropin-releasing hormone and gonadotropin are involved in precocious maturation induced by photoperiod manipulation in underyearling male masu salmon, Oncorhynchus masou.

The relationship between gonadal maturation, salmon gonadotropin-releasing hormone (sGnRH), and gonadotropin (GTH) subunit contents in the brain and pituitary was investigated in underyearling masu salmon, Oncorhynchus masou. Gonadal maturation was manipulated by changing photoperiod to examine the involvement of these hormones in this process. Fish were divided into short (8 hr L: 16 hr D) and long photoperiod (16 hr L:8 hr D) groups in mid-June and maintained for 4 months until October. Gonadal maturation occurred in most males (precocious males), while a few remaining males and all females did not mature throughout the experiment irrespective of photoperiodic group. In precocious males, pituitary contents of sGnRH, GTH I beta, and GTH II beta increased faster under short photoperiod than under long photoperiod, and spermiation was observed in August. Under long photoperiod, these hormones gradually increased until October when spermiation occurred. sGnRH concentrations in the telencephalon of precocious males were high when spermiation occurred; in August, they were higher in the short photoperiod than in the long photoperiod group; in October, they were higher in the long photoperiod group. The increases of sGnRH and GTH in the pituitary and sGnRH in the brain appear to be involved in precocious maturation inducible by manipulation of photoperiod.

Animals↗

PubMed1994

Activation of salmon gonadotropin-releasing hormone synthesis by 17 alpha-methyltestosterone administration in yearling masu salmon, Oncorhynchus masou.

Juvenile salmonid pituitary gonadotropin (GTH) contents are elevated after steroid hormone treatment, but the involvement of gonadotropin-releasing hormone (GnRH) is unclear. Activation of salmon GnRH (sGnRH) synthesis by 17 alpha-methyltestosterone (MT) administration has been examined in the brain of yearling masu salmon (future precocious males and immature females) using an in situ hybridization technique combined with radioimmunoassay. Oral MT application markedly increased pituitary GTH II beta, but not GTH I beta, contents in both sexes. In future precocious males, MT treatment increased the number of cells expressing sGnRH mRNA in the preoptic area about threefold, whereas there were no significant differences in the olfactory bulbs and the ventral telencephalon. No significant changes were observed in cell sizes nor the numbers of silver grain per 100 microns2 cell in any of the brain regions. Thus, in future precocious males, preoptic sGnRH neurons may be activated by sex steroids. In contrast, no significant changes were observed in sGnRH mRNA levels of immature females after MT treatment. These differences in responses to sex steroids of sGnRH cells in the preoptic area between future precocious males and immature females suggest that MT has indirect actions via sGnRH and/or direct actions on the pituitary in the former, and that MT acts directly on the pituitary in the latter.

Animals↗