Biomedical subjects

R Shibata

Publications and source records attributed to R Shibata.

At least 37 records · Page 2Linked to original sources

PubMed1999

Neutralizing antibody directed against the HIV-1 envelope glycoprotein can completely block HIV-1/SIV chimeric virus infections of macaque monkeys.

Virus-specific antibodies protect individuals against a wide variety of viral infections. To assess whether human immunodeficiency virus type 1 (HIV-1) envelope-specific antibodies confer resistance against primate lentivirus infections, we purified immunoglobulin (IgG) from chimpanzees infected with several different HIV-1 isolates, and used this for passive immunization of pig-tailed macaques. These monkeys were subsequently challenged intravenously with a chimeric simian-human immunodeficiency virus (SHIV) bearing an envelope glycoprotein derived form HIV-1DH12, a dual-tropic primary virus isolate. Here we show that anti-SHIV neutralizing activity, determined in vitro using an assay measuring loss of infectivity, is the absolute requirement for antibody-mediated protection in vivo. Using an assay that measures 100% neutralization, the titer in plasma for complete protection of the SHIV-challenged macaques was in the range of 1:5-1:8. The HIV-1-specific neutralizing antibodies studied are able to bind to native gp120 present on infectious virus particles. Administration of non-neutralizing anti-HIV IgG neither inhibited nor enhanced a subsequent SHIV infection.

Animals↗

PubMed1999

Human immunodeficiency virus type 1 neutralizing antibodies accelerate clearance of cell-free virions from blood plasma.

The concentration of human immunodeficiency virus type 1 (HIV-1) particles in blood plasma is very predictive of the subsequent disease course in an infected individual; its measurement has become one of the most important parameters for monitoring clinical status. Steady-state virus levels in plasma reflect a balance between the rates of virions entering and leaving the peripheral blood. We analyzed the rate of virus clearance in the general circulation in rhesus macaques receiving a continuous infusion of cell-free particles in the presence and absence of virus-specific antibodies. Here we show, by measuring virion RNA, particle-associated p24 Gag protein and virus infectivity, that the clearance of physical and infectious particles from a primary, dual-tropic virus isolate, HIV-1DH12, is very rapid in naive animals, with half-lives ranging from 13 to 26 minutes. In the presence of high-titer HIV-1DH12-specific neutralizing antibodies, the half-life of virion RNA was considerably reduced (to 3.9-7.2 minutes), and infectious virus in the blood became undetectable. Although physical virus particles were eliminated extravascularly, the loss of virus infectivity in the blood reflected the combined effects of extravascular clearance and intravascular inactivation of HIV-1 infectivity due to antibody binding.

Animals↗

PubMed1999

Abnormal expression of neurofilament proteins in dysmyelinating axons located in the central nervous system of jimpy mutant mice.

Myelination in the peripheral nervous system is considered to increase the phosphorylation level of neurofilament proteins in the axon, resulting in an increase in axonal calibre. To understand the relationship between myelination and neurofilament proteins in axons, we examined jimpy mutant mice with a point mutation in the proteolipid protein gene and dysmyelination in the central nervous system. The jimpy mice exhibited a characteristic similarity in neurofilament nature to the myelin-deficient mice in the peripheral nervous system reported previously. The following novel results were obtained in the jimpy mice: dysmyelinated axons, in which the amount of non-phosphorylated neurofilament-H was drastically increased without a significant reduction of the phosphorylated form, compared with the control myelinated axons, did not suffer any decrease in their diameters. Expression levels of all neurofilament subunit proteins and their mRNAs were enhanced in the central nervous system tissue. Because the above biochemical data were obtained from the cytoskeletal fraction, at least some of the increased neurofilament-H and -M proteins appeared to be coassembled into neurofilaments but remained non-phosphorylated. Axonal neurofilaments of the jimpy were, probably due to this abnormal stoichiometry and phosphorylation state in neurofilaments, more compact and random in alignment with less prominent cross-bridges than those of the control, providing possible evidence for disturbing the axonal transport of other organelles. These results suggest that myelination regulates both the expression and phosphorylation of neurofilament proteins, and is essential for the cytoplasmic organization of myelinated axons.

Animals↗

PubMed1999

Hippocampal neuronal position selectivity remains fixed to room cues only in rats alternating between place navigation and beacon approach tasks.

To study the relationship between brain representations and behaviour, we recorded hippocampal neuronal activity in rats repeatedly alternating between two different tasks on a circular platform with four reward boxes along the edge. In the beacon approach task, rewards were provided only at the pair of diametrically opposite boxes that was illuminated. In the place navigation task, rewards were available only at the boxes positioned near the north-east and south-west corners of the room. Performance levels were high and rats rapidly reoriented to changes in lamp cues in the beacon approach task. Neuropsychological studies show that rats with hippocampal lesions readily employ beacon approach strategies, while place navigation is severely impaired. Previous studies suggested that the neurons might change their behavioural correlates as the rat performed the respective tasks. However, of 34 hippocampal 'place cells' recorded, all showed position selectivity fixed with respect to room cues, even in the beacon approach task where coding the position of the rat in the room was of no use for locating rewards. Whether or not hippocampal signals are actually employed for ongoing behaviour would then be decided by structures downstream from the hippocampus. If this is the case, then the 'counterproductive' room referred place-related discharges in the beacon approach task would be a background representation. This would provide support for proposals of multiple memory systems underlying different types of information processing and contrasts with the popular notion that local neuronal activity levels are selectively increased to the degree that the brain region is required for the ongoing function.

Acoustic Stimulation↗

PubMed1999

Telomere dynamics in monkeys: increased cell turnover in macaques infected with chimeric simian-human immunodeficiency viruses.

To address the question of how cell turnover is affected by retroviral infections, we used the telomeric terminal restriction fragments (TRFs) as markers of cell replicative history and measured their length in macaques infected with chimeric simian-human immunodeficiency viruses (SHIVs). The TRF lengths of mononuclear cells in 104 samples, including longitudinal samples from nine cynomolgus and ten pig-tailed macaques infected with SHIV, and in samples from 26 uninfected macaques, were quantitated by an improved method, based on two-dimensional calibration of DNA sizes, pulsed field electrophoresis, and high-resolution Southern blot images. The average TRF lengths of peripheral blood mononuclear cells (PBMCs) from uninfected pig-tailed (14.9+/-1.6 kbp) and cynomolgus (14.1+/-1.8 kbp) macaques were about 3 and 5 kbp longer than those of human infants and 30-year-old adults, respectively. The rate of TRF length shortening in infected pig-tailed macaques was significantly (P = 0.035) higher (2.2-fold) than in uninfected monkeys. The TRFs in SHIV-infected cynomolgus monkeys, which, in general, had lower viral loads than pig-tailed macaques, shortened on average more rapidly (1.6-fold) than in uninfected animals, but the difference was not statistically significant. The TRFs of mononuclear cells from the lymph nodes of two rapidly progressing SHIV-infected macaques that developed AIDS and died also shortened in parallel but somewhat more rapidly than in the PBMCs. These results suggest that the rate of PBMC turnover in macaques could be increased several-fold during infections by immunodeficiency viruses, likely due to immune activation by SHIV antigens.

Animals↗

PubMed1999

Expression of Kv3.1 and Kv4.2 genes in developing cerebellar granule cells.

The expression of voltage-gated potassium channels plays an important role in the acquisition of membrane excitability in neurons. We examined the expression pattern of genes in developing cerebellar granule neurons in vivo and in vitro. In situ hybridization of Kv3.1 mRNA demonstrated that the gene was expressed at high levels in the external granule layer (EGL) as well as in the internal granule layer (IGL) at all postnatal stages (P) examined (from P3 to P10). In contrast, Kv4.2 mRNA was detected in the premigratory zone (PMZ) of the EGL, but not in the proliferative zone (PLZ), in addition to the IGL. This indicates that Kv4.2 gene expression initiates in the postmitotic migrating neurons. We also examined the expression of the channel genes in microexplant culture systems. Kv3.1 polypeptide was detected in parallel fibers of granule cells at 2 days in vitro, and the expression continued in later stages. The signal of Kv4.2 protein was very low at 2 days in vitro; however, the number of positive cells and the intensity of the signals were increased at 6 days in vitro. These in vitro observations matched those in vivo and our previous electrophysiological studies in which we demonstrated that delayed- rectifier-type current was predominant in the immature granule cells followed by the later appearance of A-type current. The patterns of K(+) channel expression suggest that sequential expression of these channel genes primarily determines the membrane excitability.

Aging↗

PubMed1998

Telomere dynamics in HIV-1 infected and uninfected chimpanzees measured by an improved method based on high-resolution two-dimensional calibration of DNA sizes.

We developed an improved method for accurately measuring telomere lengths based on two-dimensional calibration of DNA sizes combined with pulsed field electrophoresis and quantitative analysis of high-resolution gel images. This method was used to quantify the length of telomeres in longitudinal samples of peripheral blood mononuclear cells (PBMCs) from five chimpanzees infected with human immunodeficiency virus type 1 (HIV-1) and three uninfected animals, 14 to 27 years of age. The average length of the telomere restriction fragments (TRF) of infected and uninfected chimpanzees were 11.7 +/- 0.25 kbp, and 11.6 +/- 0.61 kbp, respectively, and were about 1 kbp and 3 kbp longer than those of human infants and 30 year old adults, respectively. There was a trend of a slight decrease (30-60 bp per year) in the TRF of two HIV infected chimpanzees over 30-35 months, while the TRF of one naive chimpanzee slightly increased over 20 months. Although the number of chimpanzees in this study is small and no statistically significant linear dependencies on time were observed, it appears that in chimpanzees, rates of shortening of the TRF are comparable or smaller than in adult humans and are not significantly affected by HIV-1 infection, which may be related to the inability of HIV-1 to cause disease in these animals.

Age Factors↗

PubMed1998

Administration of an anti-CD8 monoclonal antibody interferes with the clearance of chimeric simian/human immunodeficiency virus during primary infections of rhesus macaques.

Parenteral administration of a mouse anti-human CD8 monoclonal antibody (MAb) to rhesus macaques resulted in a transient depletion of CD8+ cells in both the peripheral blood and lymphoid tissues. When administered during primary chimeric simian/human immunodeficiency virus infections, the CD8 MAb caused marked elevations of plasma and cell-associated virus levels in both the peripheral blood and lymphoid tissues and led to prolonged depletion of CD4 cells. Taken together, these results directly demonstrate that CD8+ T lymphocytes are actively involved in controlling the acute phase of primate lentivirus infections.

Animals↗

PubMed1998

Anti-CD8 monoclonal antibody protects against spontaneous IgA nephropathy in ddY mice.

We investigated the effects of anti-CD4 monoclonal antibody (mAb) and/or anti-CD8 mAb in ddY mice, an animal model of spontaneous IgA nephropathy. Female ddY mice were treated with 18 intravenous injections of anti-CD4 and/or anti-CD8 mAb at 2-week intervals. This was based on our observation that a single injection of anti-CD4 mAb or anti-CD8 mAb caused a selective depletion in CD4+ T cells for 2 weeks and CD8+ T cells for 4 weeks, respectively. The level of proteinuria, serum IgA, and changes in the histopathological features of renal tissue samples were assessed in treated mice between the age of 4 and 40 weeks. The level of proteinuria increased with age, but there was not significant difference among the groups. No animal developed microhematuria throughout the study. Treatment with anti-CD4 mAb produced a mild to moderate level of mesangial hypertrophy at 20 and 40 weeks, similar to the results in untreated mice. The lowest degree of mesangial hypertrophy occurred in mice treated with anti-CD8 mAb up to the age of 40 weeks. Treatment with a combination of anti-CD4 and anti-CD8 mAbs produced effects that were similar to those observed on treatment with anti-CD8 mAb alone. Our results suggest that CD8+ T cells mediate mesangial proliferation and the progression of nephropathy in ddY mice.

Animals↗

PubMed1998

Stimulative effect of high-level hypergravity on differentiated functions of osteoblast-like cells.

The exposure of freshly isolated osteoblasts and osteoblast-like cells to high-level hypergravity caused the inhibition of cell growth, elevation of cAMP content, and the stimulation of differentiated functions such as alkaline phosphatase activity, collagen synthesis, and osteocalcin synthesis. Blockage of elevation of cAMP by SQ22536, an inhibitor of adenylate cyclase, resulted in the inhibition of the hypergravity-stimulated alkaline phosphatase activity, indicating that cAMP is the intracellular mediator of this action of hypergravity. H89, an inhibitor of cAMP-dependent protein kinase (PKA), further inhibited the cell growth that was already inhibited by the hypergravity, and further stimulated the alkaline phosphatase activity that was already stimulated by hypergravity. If cAMP acts through the PKA system, H89 should have blocked the changes in cell function effected by the exposure to hypergravity. Therefore the elevated intracellular cAMP by the exposure of hypergravity caused the changes in cell function by a PKA-independent pathway.

Adenine↗

PubMed1998

[A case of congenital myopathy with the pathologic transformation from fiber type disproportion to type 1 fiber predominance myopathy].

Many patients with a severe infantile form of congenital myopathies have respiratory and feeding difficulties from early infancy. We experienced a male patient who required an artificial ventilation soon after birth and showed marked generalized muscle weakness involving the facial muscles. He had skull deformity and mild mental retardation at the age of one year and 10 months. The first muscle biopsy at the age of 1 month showed small caliber fibers and an increase in the number of undifferentiated type 2C fibers, indicating muscle fiber immaturity. Since type 1 fibers were smaller than type 2 fibers, he was tentatively diagnosed as having congenital fiber type disproportion myopathy. The muscle biopsied findings improved significantly in the second biopsy at 1 year of age which showed type 1 fiber predominance but no cytoarchitectural abnormalities. Accordingly, he was diagnosed as having congenital myopathy with type 1 fiber predominance. A severe neonatal form of congenital myopathies may show striking muscle fiber immaturity in the early infancy. This may later develop into characteristic morphologic findings such as the formation of nemalines and cores, and abnormal fiber type distribution.

Biopsy↗

PubMed1998

[Bone and joint tuberculosis in the field of orthopedics].

In Japan the number of patients with bone and joint tuberculosis has been dramatically decreasing since the beginning of 1980's. The number of patients was 1626 in 1978 according to statistics of tuberculosis patient in Japan. This was only 2.02% of new tuberculosis patients of Japan in 1978. Since that time the number of patients with bone and joint tuberculosis, in Japan, has been in steady decline. The number was only 675 patients in 1996. This was only 1.34% of new tuberculosis patients. The rate of new infections also decreased. Recently due to the development of computed tomography, magnetic resonance imaging and so on, patients with bone and joint tuberculosis can be diagnosed early, with great certainty. Curettage of infected focus and bone grafting via anterior approach has resulted in consistently improved results. While there are many reports of about the operative treatment with spinal instruments for spinal tuberculosis, artificial materials must be implanted with great care.

Humans↗

PubMed1998

Coronary revascularization and abdominal aortic aneurysm repair in a patient with Behçet's diseases.

Behçet's disease is a systemic disease characterized by oral aphta, genital ulcer, and ocular lesion. Arterial involvement is an uncommon complication of Behçet's disease, and it most frequently affects the abdominal aorta followed by the femoral artery and the pulmonary artery. Coronary lesions in Behçet's disease have been little reported in the literature. In this communication, we present a case with coronary artery stenosis and with subsequently developed supra-renal abdominal aortic aneurysm. The coronary lesions were revasculized with gastroepiploic artery, right internal mammary artery, and saphenous vein graft. Abdominal aortic repair was performed with partial cardiopulmonary stand by, because of the risk of coronary ischemia during the cross clamp including the celiac artery. To our knowledge, this is the first report of successful repair of combined lesions of the coronary and the abdominal aorta in a patient with Behçet's disease.

Aortic Aneurysm, Abdominal↗

PubMed1997

Reactivation of HIV type 1 in chronically infected chimpanzees following xenostimulation with human cells or with pulses of corticosteroid.

Following resolution of a primary HIV-1 infection initially induced by inoculating a mixture of three different virus strains, a chimpanzee was exposed to both immunostimulatory and immunosuppressive agents in an attempt to assess the contributions of different components of the immune system in suppressing circulating virus. The infusion of human leukocytes as an xenogeneic stimulus induced the replication of one of the input virus strains that had not previously been isolated or detected by PCR. The administration of high-dose, 17-day courses of corticosteroids resulted in coordinate and transient increases of each of the three viruses present in the original inoculum and elevation of HIV-1-specific ELISA antibody levels. Steroids administered to a second chimpanzee, chronically infected with a single HIV-1 isolate, also induced elevations of cell-associated virus. These results highlight the intimate relationship between immune system activation/immunosuppression and HIV replication in an animal model.

Animals↗

PubMed1997

Infection and pathogenicity of chimeric simian-human immunodeficiency viruses in macaques: determinants of high virus loads and CD4 cell killing.

Chimeric simian-human immunodeficiency viruses (SHIVs) carrying envelope glycoproteins derived from a T cell-macrophage dual-tropic primary isolate (human immunodeficiency virus type 1 [HIV-1] strain DH12) were constructed. When inoculated into macaque monkeys, SHIV(MD14) carrying simian immunodeficiency virus-derived nef established significantly higher virus loads than did SHIV(MD1), which contains the HIV-1 nef gene. Three patterns of CD4 cell depletion were observed in infected monkeys: exponential and irreversible loss to undetectable levels within 10 weeks of infection; marked reduction during acute infection followed by partial recovery and stabilization (lasting from 10 weeks to > 1 year), with a later decline to undetectable levels in some animals; and a transient loss during acute infection. The induced immunodeficiency was accompanied by CD4 cell counts of < 50 cells/microL and was associated with Pneumocystis carinii pneumonia, cytomegalovirus meningoencephalitis, lymphoid depletion, and thymic atrophy.

Amino Acid Sequence↗

PubMed1997

Protection of monkeys vaccinated with vpr- and/or nef-defective simian immunodeficiency virus strain mac/human immunodeficiency virus type 1 chimeric viruses: a potential candidate live-attenuated human AIDS vaccine.

Two simian immunodeficiency virus strain mac (SIVmac)/human immunodeficiency virus type 1(HIV-1) chimeric viruses (SHIVs), designated NM-3 and NM-3n, with env derived from HIV-1 and defective vpr (plus defective nef for NM-3), were inoculated into seven macaques. These macaques were transiently or persistently infected and most of them produced long-lasting neutralizing antibodies and Env-specific killer T cells to HIV-1 with no AIDS-like symptoms. When they were challenged with another SHIV with intact vpr and nef (designated NM-3rN), all were protected as judged by virus recovery, DNA detection by PCR and antibody responses. Anti-HIV-1 Env-specific killer T cells were considered to have played a major role in this protection, but a non-specific defence mechanism as well as specific immunity also appeared to be involved. Thus, these two non-pathogenic SHIVs induced long-lasting protective immunities in macaques, suggesting the possibility of gene-defective SHIVs as attenuated live vaccines for human use.

AIDS Vaccines↗

PubMed1997

Live, attenuated simian immunodeficiency virus vaccines elicit potent resistance against a challenge with a human immunodeficiency virus type 1 chimeric virus.

Three rhesus macaques, previously immunized with SIVdelta3 or SIVdelta2, each an attenuated derivative of SIVmac239, and two naive monkeys were challenged with 30,000 50% tissue culture infective doses of SHIV, an SIV/human immunodeficiency virus type 1 (HIV-1) chimeric virus bearing the dual-tropic envelope of HIV-1DH12. By several criteria, including virus isolation, serological assays, and PCR (both DNA and reverse transcriptase), SHIV levels were reduced to barely detectable levels in the circulating blood of vaccinated animals. The resistant SIV-vaccinated macaques had no preexisting neutralizing antibodies directed against SHIV, nor did they produce neutralizing antibodies at any time over a 14-month observation period following SHIV challenge. Interestingly, SIV sequences, derived from the vaccine, could be amplified from numerous tissue samples collected at the conclusion of the experiment, 60 weeks postchallenge, but SHIV-specific sequences (viz., HIV-1 env) could not. These results demonstrate that live attenuated SIV vaccines provide strong long-term protection even against challenge strains with highly divergent envelope sequences.

Animals↗

PubMed1997

Hemodynamic effects of nicardipine and phentolamine in combination with norepinephrine in a canine low-output-state model.

Norepinephrine (NE) is one of the most potent positive inotropic drugs available for the treatment of low-output state following open-heart surgery. However, its inotropic effect is often masked by a significant increase of peripheral vascular resistance due to marked vasoconstriction. The purpose of the present study was to investigate whether the use of nicardipine (Nc) and phentolamine (Ph) in combination with NE could ameliorate the adverse vasoconstrictive action of NE. A low-output-state (LOS) model was produced by global myocardial ischemia due to electrically induced intermittent ventricular fibrillations in open-chest dogs. Twenty-eight dogs were divided into 6 groups according to the drugs infused after producing LOS. In the control group, hemodynamic changes similar to the clinical low-output state were observed, e.g., a decrease in cardiac output (CO) and left ventricular dp/dt, and an increase in the systemic vascular resistance (SVR). The use of NE alone produced marked increases in the systemic arterial pressure (SAP), heart rate, and SVR, with a slight increase in CO. The infusion of Nc alone produced decreases in SVR and SAP with a slight increase in CO. The concomitant infusion of NE and Nc produced increases in SV and CO, and decreases in SAP and SVR. The infusion of Ph alone produced no significant hemodynamic changes. The combined use of NE and Ph produced increases in CO, SAP and heart rate, but not to a significant extent. These results suggest that there are major advantages in the concomitant use of NE and Nc for the control of LOS.

Animals↗