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Biomedical subjects

M Nakai

Publications and source records attributed to M Nakai.

At least 271 records · Page 15Linked to original sources
PubMed1990

Chemical stimulation of the nucleus tractus solitarii decreases cerebral blood flow in anesthetized rats.

In anesthetized (chloralose and urethane), paralyzed and artificially ventilated rats, the neurons in the nucleus tractus solitarius (NTS) were chemically stimulated by microinjections of L-glutamate and the cerebral blood flow (CBF) was determined using a combination of labeled microspheres (either 57Co, 113Sn and 46Sc or 141Ce, 85Sr and 46Sc). Unilateral chemical stimulation of the NTS (n = 14) decreased CBF significantly in most brain areas. The decrease in CBF was not due to the decrease in arterial blood pressure (ABP) because the CBF of the whole cerebral cortex during the chemical stimulation of the NTS was significantly smaller (P less than 0.05) than the CBF during controlled hemorrhagic hypotension (n = 10). In another group of rats (n = 6), moderate hypertension was induced by blood transfusion. Unilateral chemical stimulation of the NTS in these rats decreased ABP but it remained within normotensive range. A significant (P less than 0.05) decrease in CBF (from 62 +/- 28 (mean +/- S.D.) to 48 +/- 23 ml.min-1.(100 g)-1) and increase in cerebrovascular resistance (from 1.9 +/- 1.2 to 2.6 +/- 1.2 mm Hg per [ml.min-1.(100 g)-1]) was observed in the whole cerebral cortex of these rats. Chemical stimulation of the NTS did not affect the reactivity of the cerebral vessels to hypercapnea (n = 5). These results suggest that the cell bodies within the NTS may play a role in the control of cerebral circulation.

Animals↗
PubMed1990

A minimally invasive technique for multiple measurement of regional blood flow of the rat brain using radiolabeled microspheres.

To observe the rat brain blood flow with microspheres, a left ventricular catheter for sphere introduction was threaded into position via the right brachial artery. Cross-circulation with a donor rat was employed to prevent any mismatch between the infused and sampled blood volumes. Multiple measurements yielded stable flow data, and the responsiveness to hypercapnia was well preserved, irrespective of the dose of injected spheres (48 x 10(3) and 130 x 10(3)).

Animals↗
PubMed1990

Human PTH-(3-34) inhibited the effects of human parathyroid hormone-related protein on phosphate uptake in a cultured renal cell line (OK cells).

The action mechanism of hPTH and hPTHrP-(1-34) on phosphate uptake in opossum kidney (OK) cells was studied using [Nle8,18Tyr34]hPTH-(3-34)-NH2, a potent competivie inhibitor of adenylate cyclase-coupled PTH receptor. We examined the effects of hPTH-(1-34), hPTHrP-(1-34), and hPTH-(3-34) separately or in combination on the change in renal cyclic AMP production and phosphate uptake in OK cells. Both hPTH-(1-34) and hPTHrP-(1-34) stimulated intracellular cyclic AMP production to the same degree at concentrations between 10(-10) and 10(-7) M and inhibited phosphate uptake equipotently on a molar basis (27.5 +/- 2.0 and 33.2 +/- 1.2% inhibition at 10(-7) M, respectively). Both exogenous addition of (Bu)2cAMP and endogenous stimulation of cAMP by forskolin inhibited phosphate uptake in a dose-dependent manner. Cyclic AMP production induced by either hPTH-(1-34) or hPTHrP-(1-34) was inhibited by both [Nle8,18Tyr34]-hPTH-(3-34)-NH2 and [Tyr34]-hPTH-(7-34)-NH2. However, [Nle8,18Tyr34]hPTH-(3-34)-NH2 and [Tyr34]-hPTH-(7-34)-NH2 inhibited hPTH-induced cAMP production more strongly. The inhibitory action of phosphate uptake by hPTH-(1-34) and hPTHrP-(1-34) was prevented in the presence of a 100-fold greater concentration of [Nle8,18Tyr34]hPTH-(3-34)-NH2. The antagonistic action of [Nle8,18Tyr34]hPTH-(3-34)-NH2 on the inhibition of phosphate uptake induced by hPTH-(1-34) and hPTHrP-(1-34) became weaker with time (0-120 minutes), and [Nle8,18Tyr34]hPTH-(3-34)-NH2 did not antagonize the inhibition of phosphate uptake induced by hPTHrP-(1-34) at 120 minutes of incubation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The budding of defective human immunodeficiency virus type 1 (HIV-1) particles from cell clones persistently infected with HIV-1.

Three cell clones producing large numbers of infectious or noninfectious particles of human immunodeficiency virus type 1 (HIV-1), designated M 10/LAV-2, M 16/LAV-3, and MT/LAV-17, were isolated from persistently HIV-1-infected MT-4 cells. In M 10/LAV-2, the HIV-1 proteins were defective in the cleavage of gag precursor protein, and the particles were doughnut-shaped with a double-ring structure. These particles were produced by budding at the cell surface from crescentic structures followed by the formation of double-ring structures. The viral proteins in M 16/LAV-3 were defective in the cleavage of env precursor protein. The morphology of the virus particles was intact, and an electron dense bar-shaped core was seen inside a single-ring enveloped structure. The intact particles were released from the cell surface by a budding process in which crescent shape structures first appeared at the cell membrane, then subsequently just before release matured to a complete structure with an electron dense core. In MT/LAV-17, the synthesis of HIV-1 proteins was normal, and the particles were teardrop-shaped with an intact core structure. These particles were produced by budding with an electron dense core at the cell surface. Thus, it was suggested that the morphological maturation of HIV-1 particles was completed just before release from the cell surface in several cell clones producing HIV-1 particles of different morphology.

Antibodies, Monoclonal↗
PubMed1990

Amplification and high-level expression of a cDNA for human granulocyte-macrophage colony-stimulating factor in human lymphoblastoid Namalwa cells.

We have achieved high-level expression of human granulocyte-macrophage colony-stimulating factor (GM-CSF) in human lymphoblastoid Namalwa cells by introducing and subsequently amplifying an expression vector encoding human GM-CSF and mouse dihydrofolate reductase (DHFR). Transformants expressing elevated levels of both GM-CSF and DHFR were selected by a step-wise increase in the concentration of methotrexate (MTX). Several cell lines resistant in 800 nM MTX have been established that express GM-CSF at a rate of 10-20 micrograms/10(6) cells/day. The amplified genes are integrated and stably maintained in the chromosomes of these cell lines. Analysis of the GM-CSF produced in the amplified Namalwa cells revealed that the molecular-size distribution due to varied degrees of glycosylation was similar to that observed in the naturally-occurring molecules.

Cloning, Molecular↗
PubMed1990

Replacement of putative axial ligands of heme iron in yeast cytochrome c1 by site-directed mutagenesis.

The His-44 and Met-164 residues of yeast cytochrome c1 are evolutionally conserved and regarded as heme axial ligands bonding to the fifth and sixth coordination sites of the heme iron, which is directly involved in the electron transfer mechanism. Oligonucleotide-directed mutagenesis was used to generate mutant forms of cytochrome c1 of yeast having amino acid replacements of the putative axial ligands of the heme iron. When a cytochrome c1-deficiency yeast strain was transformed with a gene encoding the Phe-44, Tyr-44, Leu-164, or Lys-164 protein, none of these transformants could grow on the non-fermentable carbon source. These results suggest that the His-44 and Met-164 residues have a critical role in the function of cytochrome c1 in vivo, most probably as axial ligands of the heme iron. Further analysis revealed that the mutant yeast cells with the Phe-44, Tyr-44, or Leu-164 protein lacked the characteristic difference spectroscopic signal of cytochrome c1. However, in the Lys-164 mutant cells, partial recovery of the cytochrome c1 signal was observed. Moreover, the Lys-164 protein retained a low but significant level of succinate-cytochrome c reductase activity in vitro. The possibility that the nitrogen of Lys-164 served as the sixth heme ligand is discussed in comparison with cytochrome f of a photosynthetic electron-transfer complex, in which lysine has been proposed to be the sixth ligand.

Base Sequence↗
PubMed1990

[HIV isolation and clinical markers on the seropositive subjects].

We investigated 18 anti-HIV seropositive subjects with respect to the isolation of HIV from peripheral blood mononuclear cells (PBMC) and cellular and serologic markers for progression to AIDS. The subjects included homosexuals and recipients of blood products. Three had AIDS, an asymptomatic subject developed AIDS during the study and 14 of the remaining have remained asymptomatic. HIV was isolated from all AIDS patients and 7 asymptomatic subjects. Moreover HIV was detected significantly sooner in symptomatic patients than in asymptomatic subjects. The reductions in CD4 lymphocytes number and CD4/CD8 ratio, as well as anti-HIV core (p24, p17) antigens negativity correlated with deterioration of clinical symptoms and successful HIV isolation. The isolates from AIDS patients and from an asymptomatic subject who 9 months later developed AIDS were infective and cytotoxic to MT-4 cells, however isolates from asymptomatic subjects were not infective. These findings indicate that disease progression correlates with the appearance of variant viruses that are more infective and cytopathic.

Biomarkers↗
PubMed1990

Transplantation of autologous superior cervical ganglion into the brain of parkinsonian monkeys.

Autologous transplantation of the superior cervical ganglion (SCG) into the caudate nuclei of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonian monkey was studied in regard to animal behavior and catecholamine (CA) metabolites in cerebrospinal fluid. Monkeys which had undergone autotransplantation of the SCG revealed an apparent improvement in motor activity. The homovanillic acid content in cerebrospinal fluid increased following the SCG transplantation and was correlated with an increase in motor activity. CA histofluorescence studies confirmed the long-term survival of the SCG graft in which many CA fibers and cells were observed. The present experiment indicates that dopamine released from the graft improved the symptoms of parkinsonism in the monkey.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

Transplantation of peripheral cholinergic neurons into Alzheimer model rat brain.

The effect of transplantation of peripheral cholinergic neurons was examined in rats with a lesion of the nucleus basalis Meynert (NBM). The rats with an NBM lesion showed abnormal increase of spontaneous activity, disturbance of memory retention, and disturbance of learning acquisition. In contrast, the rats which had received transplantation of cholinergic neurons into the cerebral cortex displayed amelioration of abnormal behavior produced by the destruction of the NBM. Morphological study (acetylcholinesterase) clearly showed survival of many transplanted cholinergic cells. The present study suggests that autotransplantation of peripheral cholinergic cells may be a possible therapy for Alzheimer's disease.

Acetylcholinesterase↗
PubMed1990

Coronary hemodynamics in diabetic spontaneously hypertensive rats.

We investigated the coronary hemodynamics in conscious spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats 4 and 20 weeks after streptozotocin or vehicle injection. The hemodynamic parameters were measured at rest and during maximal coronary vasodilation with dipyridamole. Streptozotocin, 40 or 60 mg/kg, produced moderate or severe diabetes in both strains, but resulted in a mortality of 11.3 or 40.8% in SHR alone. The left and right ventricular weights were decreased with no change in their ratios to body weight in both strains. Severely diabetic SHR and WKY revealed hypotension, bradycardia, an increased cardiac index and decreased total peripheral resistance index at both weeks. Moderately diabetic SHR revealed similar changes except for an unaltered cardiac index. Short-term severely diabetic SHR alone displayed an increased basal bi-ventricular coronary flow (per unit mass). The maximal coronary flow was unaltered in any group by diabetes. The left ventricular transmural flow distribution was also unaltered in any group. However, severe diabetes in SHR diminished a coronary flow reserve (maximal minus basal flow) of the left ventricle at 4 weeks, and that of both ventricles at 20 weeks. Thus, the severity and duration of diabetes had a strain-related influence on the systemic and coronary hemodynamics, with deaths and a reduced coronary flow reserve in SHR alone. The minimal coronary vascular resistance in both ventricles (per unit mass) showed no increase in each group by diabetes, suggesting no overall decrease in functional cross-sectional area of the coronary vasculature.

Animals↗
PubMed1990

Autologous transplantation of the superior cervical ganglion into the brain of parkinsonian monkeys.

The effect of autologous transplantation of the superior cervical ganglion (SCG) into the brain of parkinsonian monkeys was studied through quantitative measurement of animal behavior. The motor activity of the monkey was measured with a telemetry system during the experiment. After experimental parkinsonism was induced by repeated intravenous injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), three monkeys were treated with autologous transplantation of the SCG into both caudate nuclei. One monkey served as a control without SCG transplantation after MPTP treatment. Three SCG-transplanted monkeys showed biphasic (acute and chronic) behavioral amelioration of parkinsonism after transplantation. In the acute stage, the animals showed transient hyperkinesia with aggressive behavior and loss of circadian rhythm. In the chronic stage following acute hyperkinesia, the animals regained normal behavior and circadian rhythm without aggressiveness. In contrast with the transplanted monkeys, the control monkey failed to show recovery of the bradykinesia and muscle rigidity.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1990

Isolation and characterization of cell clones persistently producing teardrop-shaped particles of human immunodeficiency virus type 1.

Several cell clones producing teardrop-shaped human immunodeficiency virus type 1 (HIV-1) particles were isolated from MT-4 cells that survived HIV-1 infection after extensive cell lysis. Most of the teardrop-shaped particles contained an electron-dense core structure, and the particles could replicate in MT-4 cells. No significant structural difference in the HIV-1 proteins was observed between these cell clones and the MOLT-4 cells producing intact HIV-1 particles, although their envelope structure is morphologically abnormal.

Acetylglucosaminidase↗
PubMed1990

[Three adult intussusception cases with colorectal cancer; CT diagnosis and its characteristic findings].

We have experienced three adult intussusception cases with colorectal cancer. In all three cases CT studies were performed prior to administering a barium enema, where we could make the exact diagnosis of the lesions in both the plain and the contrast studies. In the CT studies, the intussusception lesions showed the characteristic eccentric layered pattern. It was difficult to distinguish the tumors from the edematous intestinal walls at the proceeding portion in two cases. While in one case, the proceeding portion (the tumor itself) was pointed out as the enhanced soft tissue density mass of layered pattern with the irregular margins.

Aged↗
PubMed1989

Ultrastructural features of the AIDS virus (HIV) and its morphogenesis.

HIV particles were usually seen on the surface of established lymphoid cells derived from AIDS patients or on CEM cells infected with HIV, and sometimes in cytoplasmic vacuoles. The virus particles were formed by a budding process from the plasma membrane of an infected cell. The budding particles were of a doughnut form. Various profiles of virus particles were seen extracellularly: type 1 had a bar-shaped, electron-dense core, type 2 had a central and type 3 an eccentric electron-dense round core, type 4 was doughnut-shaped, and type 5 had a layered core. However, projection patterns of the AIDS virus model suggested that type 1, 2 and 3 particles are similar. Therefore, the AIDS virus may be one of three main types: with or without a dense core, and with a layered core. It is thought that a particle with a layered core and a doughnut-type particle may be immature viruses.

Cell Line↗
PubMed1989

Transcription of a region downstream from lambda ori is required for replication of plasmids derived from coliphage lambda.

DNA replication of lambda phage depends on transcriptional activation at or around the lambda ori region by RNA polymerase. To elucidate the function of the transcriptional activation, we constructed several plasmids carrying lambda ori and lacP, whose relative locations and directions were different from each other, and studied replication activity of these recombinant plasmids. Transcription in a region immediately downstream from lambda ori, but not in the lambda ori region, was found to be essential for plasmid replication. Transcription proceeding over a certain minimal length was required and only rightward-directed transcription was effective for the activation.

Bacteriophage lambda↗