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Biomedical subjects

N Maeda

Publications and source records attributed to N Maeda.

At least 415 records · Page 23Linked to original sources
PubMed1992

Junctions between genes in the haptoglobin gene cluster of primates.

To investigate the nature of the recombination that generated the haptoglobin three-gene cluster in Old World primates, we sequenced the region between the second gene (HPR) and the third gene (HPP) in chimpanzees (15 kb), as well as the region 3' to the cluster in humans (14 kb). Comparison to the previously sequenced human haptoglobin (HP) and HPR genes showed that the junction point between HP and HPR in humans (junction 1) was not identical to the junction point between the HPR and HPP genes of the chimpanzee (junction 2). An Alu sequence was found at each junction, but both Alu sequences lacked short direct repeats of the flanking genomic DNA. The lack of direct repeats implies that both junction Alu sequences are the products of recombination between different Alu elements. In addition, other insertion and deletion events are clustered in the regions near the junction Alu sequences. The observation that Alu sequences define the junctions between genes in the haptoglobin gene cluster emphasizes the importance of Alu sequences in the evolution of multigene families.

Animals↗
PubMed1992

Production of chimeric hamsters by aggregation of eight-cell embryos.

Chimeric animals were produced by aggregation of 8-cell-stage embryos from two strains of hamsters (LVG and Bio 1.5). Two series of experiments were performed. In the first series, embryo pairs in contact with each other were classified as aggregates even if 2 distinct embryos could still be distinguished. Of 88 aggregates transferred, 2 chimeras were obtained. Pregnancy rate was 25%, and embryo survival was 35%. In the second set of experiments, only embryo pairs that had coalesced to form a single giant blastocyst were classified as aggregates. Of 56 aggregates transferred, 6 chimeras were obtained. Pregnancy rate was 83%, and embryo survival was 30%. Of the 8 chimeras, 6 were phenotypic males, and 2 were phenotypic females. Both females were germ line chimeras. Of the 6 males, 4 reproduced normally, 1 had abnormal external genitalia but normal spermatogenesis, and 1 was sterile and had atrophic testes. Each of the fertile males transmitted only a single component, either the LVG or the Bio 1.5. Examination of the testes from the sterile chimera revealed that in excess of 80% of the seminiferous cords were devoid of germ cells. These results demonstrate that hamster chimeras can be obtained by aggregation of 8-cell-stage embryos.

Animals↗
PubMed1992

Etiological implication of autoantibodies to zona pellucida in human female infertility.

PROBLEM: Autoantibodies to zona pellucida (ZP) have been implicated as a cause of infertility in woman by three lines of clinical and laboratory evidence. METHOD: First, positive anti-zona activities, as assessed by the passive hemagglutination reaction (PHAR) using bovine red blood cells sensitized with porcine zona antigen, were detected in 45 of 1,872 serum samples collected from infertile women, but in only three (two nonpregnant and one pregnant) of 592 serum samples from control subjects. Their incidence in 320 women with unexplained infertility (5.6%) was much higher than that in 1,552 women with infertility of known cause (1.7%, P < 0.01), which was comparable to the incidence observed in 193 age-matched fertile nonpregnant and pregnant women (1.5%, P < 0.05). None of the serum samples from 292 age-matched adult men and 100 children of between 5 and 10 years old gave a positive PHAR. Second, follow-up study for a minimum of 2 years with treatment revealed that no pregnancy occurred in 11 infertile women with a consistently positive PHAR, and only three pregnancies in 19 infertile women with a fluctuating positive PHAR. Third, three of seven serum samples from women who gave a consistently positive PHAR produced strong immunofluorescence reactions on human ZP even after adsorption with porcine and human AB blood cells. Pre-exposure of human ZP to the sera showing positive immunofluorescence, including that of one patient undergoing an in vitro fertilization program, greatly diminished the number of spermatozoa of normal quality that bound to and penetrated across human ZP. CONCLUSIONS: The observed high incidence of anti-zona activities and long-term resistancy to treatment in women with unexplained infertility may be closely correlated with inhibition of sperm-egg interaction by anti-zona autoantibodies produced in these women.

Antibody Formation↗
PubMed1992

A method for measuring the rate of oxygen release from single microvessels.

A system determining the rate of oxygen release from erythrocytes flowing in single microvessels was constructed with an inverted microscope by connecting 1) a scanning/grating spectrophotometer equipped with a photon-counting detector through a thin light guide, to obtain the visible absorption spectrum of a spot (5 microns in diameter) focused on a microvessel, 2) two photomultipliers (connected to a microcomputer via an analog-to-digital converter) through two light guides, to determine the flow velocity of erythrocytes by calculating the cross correlation between the light-intensity changes of two spots (3 microns in diameter, 5 microns apart from each other) focused on the microvessel, and 3) an image processor through a video camera, to estimate the diameter of microvessel from the digitized video images. The rate of oxygen release from single microvessels 7-25 microns in diameter in rat mesentery was measured under the superfusion of deoxygenated solution: 1) The maximal rate was obtained in capillaries, and the rate in arterial microvessels was larger than that in venous microvessels, when similar diameters were compared. 2) The rate was maximum at pH 7.0-7.2, and it decreased in more acidic and alkaline pH values. 3) The rate decreased with a decrease in temperature. The reliability of the measurement using the present apparatus was tested in detail.

Animals↗
PubMed1992

[A steroid-effective case with "prolonged" cerebellar ataxia].

We reported a girl with "prolonged" cerebellar ataxia for whom steroid was effective. At the age of 9 months, she developed gait disturbance, tremor and abnormal eye movements following exanthema subitum. Her symptoms were prolonged for more than 4 months and she was admitted to our hospital. The symptoms were successfully suppressed with repeated ACTH treatment but recurred in a few weeks after cessation of the therapy. Steroid was also effective but reduction of the dosage resulted in worsening of symptoms. Immunological mechanism was suspected for her disorder because of her response to steroid and ACTH.

Adrenocorticotropic Hormone↗
PubMed1992

Effect of FR121196, a novel cognitive enhancer, on the memory impairment of rats in passive avoidance and radial arm maze tasks.

Passive avoidance performance was impaired in young rats by scopolamine (1.0 mg/kg) or by nucleus basalis magnocellularis lesions and in aged rats (24-26 months old). FR121196[N-(4-acetyl-1-piperazinyl)-4-fluorobenzenesulfonamide+ ++], a newly introduced cognitive enhancer, ameliorated the failure in memory retention with bell-shaped dose-response curves in doses ranging from 0.1 to 10 mg/kg. Similar dose-response curves also were obtained with methamphetamine (0.1-10 mg/kg), whereas physostigmine (0.01-1.0 mg/kg) attenuated the amnesia in scopolamine-treated rats, but hardly affected that in nucleus basalis magnocellularis-lesioned or aged rats. In radial arm maze tasks, behavioral indices of spatial memory, such as first correct choices and number of errors, were impaired by an injection of scopolamine (0.5 mg/kg) or by lesions of the medial septum or fimbria-fornix. FR121196 ameliorated the scopolamine-induced memory deficit with a bell-shaped dose-response curve, whereas methamphetamine had the opposite effect. These two drugs had little effect on memory deficits brought about by medial septum or fimbria-fornix lesioning, whereas physostigmine ameliorated these deficits in scopolamine-treated and medial septum-lesioned rats, but not in fimbria-fornix-lesioned rats. Behavioral studies using Animex demonstrated that FR121196, in contrast with methamphetamine, does not increase locomotor activities in rats up to a dose of 10 mg/kg. These results are discussed in relation to the cholinergic and dopaminergic mechanisms of memory.

Aging↗
PubMed1992

[Development of specific immunotherapy for cancer].

We developed CTL therapy against cancer as an cancer specific immunotherapy. The primary CTL therapy showed certain efficacy on advanced cancer patients. However, when ratio of monocyte population in peripheral blood lymphoid cells (PBL) of advanced cancer patients increases more than that of CD8+ T cell population, so that CD8+ T cell/M3 ratio is less than 1, CTL directed to cancer cannot be induced in PBL and the primary CTL therapy is not materialized for these patients. Monocyte-macrophages in these patients release a suppressive factor(s) capable of inhibiting CTL induction and proliferation at induction phase but not inhibiting cytotoxic activity in target cell lysis at effector phase. Furthermore, these monocytes expressed strong message of TGF beta. If most of increased monocytes of PBL from advanced cancer patients are removed by a nylon wool column method from the PBL, CTL directed to cancer cells can be induced even in PBL of advanced cancer patients with high frequency, this improved CTL therapy against cancer showed remarkable efficacy as the cancer specific immunotherapy in various advanced cancer patients without any side effects.

Adult↗
PubMed1992

Assignment of the pig apolipoprotein B locus (APOB) to chromosome region 3q24-qter.

The locus for apolipoprotein-B (APOB) has been chromosomally assigned in swine by in situ hybridization of a genomic probe to metaphase chromosomes. As expected based on the observation of extensive linkage conservation and based on the previous assignment of the malate dehydrogenase locus (MDH1) in swine, APOB maps to chromosome 3, specifically to region 3q24-qter. Variations at APOB may represent both in humans and in swine risk factors for hypercholesterolaemia and atherosclerosis. Evidence presented here that the human and porcine APOB occupy evolutionarily conserved chromosome regions provides a basis for using the pig as an animal model to study the APOB associated atherosclerosis risk.

Animals↗
PubMed1992

[Vitreous oxygen tension of proliferative diabetic retinopathy].

The authors investigated the vitreous oxygen tension in 30 eyes of 29 cases of proliferative diabetic retinopathy patients in order to determine the distribution of oxygen tension and the possible role of neovascular tissue in tissue oxygenation. Vitreous oxygen tension was measured using a polarographic oxygen electrode and a PO2 monitoring system (PO-2080). Prior to pars plana vitrectomy, the oxygen electrode was inserted into the vitreous cavity under microscopic observation with dim illumination transmitted fiberoptically. The respective oxygen tension at the mid-vitreous cavity, above the optic disc, above the macula, above the neovascular tissue, in the peripheral vitreous, above the photocoagulated retina and above the non-photocoagulated retina were 15.8 +/- 4.7 mmHg, 31.2 +/- 10.0 mmHg, 17.1 +/- 4.0 mmHg, 32.0 +/- 9.9 mmHg, 15.6 +/- 5.1 mmHg, 16.5 +/- 5.5 mmHg and 18.6 +/- 4.9 mmHg. The oxygen tension values above the neovascular tissue and above the optic disc showed statistically significantly higher values than that of midvitreous cavity. We assume this to be due to differences between the oxygen demand and supply on the neovascular tissue, because in these tissues there are large amounts of vessels and blood flow compared to oxygen consumption. Therefore residual oxygen causes oxygen flow from the neovascularization to the mid-vitreous. This outcome is one of the facts which supports the hypothesis that neovascular tissues develop in order to compensate for retinal ischemia by releasing oxygen.

Adult↗
PubMed1991

A dominant positive and negative selectable gene for use in mammalian cells.

We have constructed three different fusion genes containing the herpes simplex virus thymidine kinase (HSV tk) and the bacterial neomycin phosphotransferase (neo) genes. All three fusion genes utilize the HSV tk promoter but differ at the junction of their components. We have determined if the fusion genes are bifunctional by introducing them into mammalian cells and testing for function of the individual components. One of the fusion genes, TNFUS 69, produced a bicistronic message and a fusion protein that has TK and NEO protein functions. This and other fusion genes of a similar nature could serve as dominant positive and negative selectable markers in mammalian cells.

Amino Acid Sequence↗
PubMed1991

Differential effects of physostigmine and pilocarpine on the spatial memory deficits produced by two septo-hippocampal deafferentations in rats.

Rats that had received two kinds of septo-hippocampal deafferentations, medial septum (MS) lesion and fimbria-fornix (FF) transection, were assayed for brain cholineacetyltransferase (ChAT) activity and spatial memory in an 8-arm radial maze task. Both lesions produced profound and long-lasting spatial memory impairments, which were characterized by a reduction in the numbers of correct arm choices and first correct choices, a reduction in the percent of correct choices and an increase in the number of errors. The degree of memory impairment was severer in FF- than in MS-lesioned rats, and paralleled that of decreases in ChAT activity in the hippocampus. MS lesion reduced ChAT activity in the hippocampus by approximately 45%, while FF lesion almost completely depleted the activity. An intraperitoneal injection of physostigmine (0.0032-0.32 mg/kg), an acetylcholinesterase (AChE) inhibitor, significantly ameliorated the spatial memory deficit induced by MS lesion, but hardly affected that by FF lesion. In contrast, intraperitoneal doses (0.032-3.2 mg/kg) of pilocarpine, a muscarinic agonist, showed a significant improvement of both types of memory deficit with bell shaped dose-response curves. The drug was more potent in the FF- than in the MS-lesioned rats. These results suggest that the septo-hippocampal cholinergic system plays a crucial role in the maintenance of spatial memory, and that the degree of septo-hippocampal deafferentation affects the efficacy of cholinergic drugs.

Animals↗
PubMed1991

Erythrocyte aggregation: bridging by macromolecules and electrostatic repulsion by sialic acid.

Relation between aggregating force (of fibrinogen and IgG) and disaggregating force (due to electrostatic repulsion among erythrocytes) in erythrocyte aggregation was investigated with a rheoscope combining a video camera, an image analyzer and a computer. (i) Erythrocyte aggregation was augmented with the increase of molecular weight of bridging macromolecules as far as examined for fibrinogen and the degradation products and IgG and the related macromolecules, and the augmentation seemed to be dependent on the molecular length of macromolecules. In accelerating the erythrocyte aggregation, fibrinogen was more effective than IgG, and some interaction between fibrinogen and IgG in their coexistence was suggested. (ii) The decrease of sialic acid content on the erythrocyte surface accelerated IgG-induced erythrocyte aggregation much greater than fibrinogen-induced one. (iii) Counteraction between aggregating force and disaggregating force in leading to erythrocyte aggregation was discussed relating to molecular length of bridging macromolecule and electrostatic repulsive force by sialic acid.

Adult↗
PubMed1991

Involvement of the C-terminus of the inositol 1,4,5-trisphosphate receptor in Ca2+ release analysed using region-specific monoclonal antibodies.

We have studied the effects of monoclonal antibodies that recognize different epitopes of the cerebellar Ins(1,4,5)P3 receptor on Ins(1,4,5)P3-induced Ca(2+)-release activity. Ins(1,4,5)P3 stimulated Ca2+ flux from cerebellar microsomes, and half-maximal Ca2+ release occurred at 112 +/- 8 nM-Ins(1,4,5)P3 [concentration causing half-maximal effect (EC50) = 112.8 nM]. The minimum concentration of Ins(1,4,5)P3 necessary to initiate Ca2+ release (threshold concentration) was 20 +/- 5 nM. A monoclonal antibody (mAb) 18A10 (50 micrograms/ml), which recognizes the C-terminal region of the Ins(1,4,5)P3 receptor, suppressed Ins(1,4,5)P3-induced Ca2+ release: the EC50 and threshold concentration shifted to 460 +/- 56 nM and 61 +/- 6 nM respectively. On the other hand, the antibody at the same concentration raised the affinity of the receptor for binding to Ins(1,4,5)P3, and the Kd value decreased from 43 +/- 12 nM to 25 +/- 4 nM without a change in the number of Ins(1,4,5)P3-binding sites. However, mAbs that recognize the N-terminal domain affected neither Ca2+ release nor Ins(1,4,5)P3 binding. Among the various synthetic peptides, only the 12-residue-long peptide from the most C-terminal portion of the receptor (amino acid residues 2736-2747) reacted strongly with mAb18A10. From these findings, combined with the Immunogold localization of the cerebellar Ins(1,4,5)P3 receptor [Otsu, Yamamoto, Maeda, Mikoshiba & Tashiro (1990) Cell Struct. Funct. 15, 163-173], we concluded that the C-terminus of the Ins(1,4,5)P3 receptor is exposed to the cytoplasmic side of the smooth endoplasmic reticulum and plays an important role in the regulation of both Ins(1,4,5)P3-binding affinity and channel gating.

Amino Acid Sequence↗
PubMed1991

The primary structure of chicken ribosomal protein L5.

The nucleotide sequence of a cDNA for chicken ribosomal protein L5, which is considered to associate with 5S rRNA, was determined. The cDNA is 975 bp long. The deduced protein has 297 amino acids and has a molecular mass of 34,090 Da. A comparative analysis of the amino acid sequences of chicken L5 and its homologous proteins revealed an extremely conserved region which contains a cluster of basic amino acids.

Amino Acid Sequence↗