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Biomedical subjects

H Gomi

Publications and source records attributed to H Gomi.

At least 55 records · Page 3Linked to original sources
PubMed1995

The role of gamma delta T cells in priming macrophages to produce tumor necrosis factor-alpha.

The secretion of tumor necrosis factor (TNF)-alpha from macrophages is regulated by both priming and triggering signals. We found that macrophages from mice lacking gamma delta T cells [T cell receptor (TCR) delta-/- mice], which lack the gene encoding the delta chain, produced only small amounts of TNF-alpha in response to lipopolysaccharide (LPS) and showed a reduced level of expression of CD14. Pre-incubation of macrophages from TCR delta-/- mice with gamma delta T cells from their TCR delta +/- littermates restored their capacity to produce TNF-alpha in response to LPS. The priming activity of gamma delta T cells was in part inhibited by neutralizing anti-interferon (IFN)-gamma monoclonal antibodies. Collectively, these results suggest that gamma delta T cells play a role in priming macrophages to a steady state of activation via IFN-gamma secretion, which allows them to produce TNF-alpha when exposed to LPS.

Animals↗
PubMed1995

Mice devoid of the glial fibrillary acidic protein develop normally and are susceptible to scrapie prions.

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein specifically expressed in astrocytes in the CNS. To examine the function of GFAP in vivo, the Gfap gene was disrupted by gene targeting in embryonic stem cells. Mice homozygous for the mutation were completely devoid of GFAP but exhibited normal development and showed no obvious anatomical abnormalities in the CNS. When inoculated with infectious scrapie prions, the mutant mice exhibited neuropathological changes typical of prion diseases. Infectious prions accumulated in brains of the mutant mice to a degree similar to that in control littermates. These results suggest that GFAP is not essential for the morphogenesis of the CNS or for astrocytic responses against neuronal injury. The results argue against the hypothesis that GFAP plays a crucial role in the pathogenesis of prion diseases.

Animals↗
PubMed1994

Antioxidant enzymes in the brain of zitter rats: abnormal metabolism of oxygen species and its relevance to pathogenic changes in the brain of zitter rats with genetic spongiform encephalopathy.

Zitter rats develop a genetic spongiform encephalopathy characterized by edematous changes in their brains. In order to elucidate the involvement of reactive oxygen species in this process we examined age-related alterations of the activities of the enzymes which metabolize reactive oxygen species. Activities of superoxide dismutase (SOD), D-amino acid oxidase (D-AAO), glutathione peroxidase (GSH-Px) and catalase in the brain and the liver of zitter rats are compared with those of control SD/J rats. In the brain of adult zitter rats which show degenerative changes, significantly enhanced activities of SOD and D-AAO were obtained, whereas activity of catalase was lower than that of the SD/J rats. Prominent abnormalities in catalase and D-AAO but not in SOD activity were demonstrated before or at the same time as the appearance of the morphological vacuolation in the brain of suckling zitter rats. There was no difference in GSH-Px activity between the brains from zitter and SD/J rats. These results suggest that the alteration of hydrogen peroxide (H2O2)-metabolism in microperoxisomes may play an important role in the initiation of degenerative changes in the brain of zitter rats. Enhanced SOD activity observed in the brain of adult zitter rats may be a compensatory response to the high superoxide anion produced in the course of cell damage caused by the H2O2 stagnation. Also, more SOD might produce more H2O2.

Animals↗
PubMed1994

Antigen-binding glycosylation inhibiting factor from a human T-cell hybridoma specific for bee venom phospholipase A2.

We obtained human T-cell hybridomas that are specific for bee venom phospholipase A2 (PLA2) and constitutively secrete glycosylation inhibiting factor (GIF). Upon crosslinking of CD3, the hybridoma produced GIF having affinity for PLA2. When affinity-purified PLA2-binding GIF was used as an immunogen, monoclonal antibodies specific for the antigen-binding GIF were obtained. Monoclonal antibody 110BH3 bound the antigen-binding GIF but failed to bind the 13-kDa nonspecific GIF, as determined by both bioassay and ELISA. In contrast, 388F1, a monoclonal antibody against nonspecific GIF, gave ELISA signals with both the nonspecific GIF and the antigen-binding GIF. Gel filtration of affinity-purified antigen-binding GIF revealed the presence of a 72- to 80-kDa protein which gave ELISA signals with both 110BH3 and 388F1 and contained GIF bioactivity. Upon reduction and alkylation, the antigen-binding GIF dissociated into a 62- to 64-kDa protein which gave positive ELISA with antibody 110BH3 but no signal with antibody 388F1, and a 15-kDa protein, which gave ELISA signal with the 388F1 but not with 110BH3. Immunoblotting of a PLA2-binding GIF preparation revealed that under reducing conditions, the antigen-binding GIF dissociated a 13-kDa peptide which reacted with polyclonal antibodies against recombinant GIF. The results indicate that the 13-kDa nonspecific GIF is a subunit of antigen-binding GIF. The PLA2-binding GIF has affinity for an epitope, representing amino acid residues 19-28 in PLA2 which appears to be an external structure in the antigen.

Animals↗
PubMed1994

Prion protein (PrP) is not involved in the pathogenesis of spongiform encephalopathy in zitter rats.

In order to elucidate the relationship between the prion protein (PrP) structure and the development of spongiform encephalopathy in zitter rats, we analyzed the nucleotide sequences and restriction fragment length variation (RFLV) of the Prn gene encoding PrP in zitter rats and inbred SD/J rats as a control. Prn genes from two strains had identical nucleotide sequences in their coding sequences. Obvious RFLV on the locus was not detected in zitter rats by a Southern blot hybridization. Consistently, zitter rat brains express the normal cellular PrP (PrPC), but do not accumulate the protease-resistant modified isoform (PrPSC). These results indicate that PrP is not involved in the pathogenesis of spongiform encephalopathy in zitter rats.

Amino Acid Sequence↗
PubMed1994

Humanization of mouse anti-human IL-2 receptor antibody B-B10.

Mouse monoclonal anti-human IL-2 receptor antibody (B-B10) inhibits IL-2-dependent human T-cell proliferation. It has been used in clinical trials in the transplantation field and promising results are being accumulated. Mouse B-B10 antibody was humanized by grafting all CDRs and some framework amino acid residues onto human antibodies, KAS for VH and PAY for V kappa. Nine humanized B-B10s with differently grafted framework residues were constructed and assessed for their biological activities. One of these humanized B-B10, M5, showed nearly the same activity as the mouse B-B10. The 49th residue of V kappa was demonstrated to play a crucial role in the antigen-antibody interaction by 3-D structure analysis with a computer modeling system.

Amino Acid Sequence↗
PubMed1994

Protein H--a surface protein of Streptococcus pyogenes with separate binding sites for IgG and albumin.

Protein H, a molecule expressed at the surface of some strains of Streptococcus pyogenes, has affinity for the constant (IgGFc) region of immunoglobulin (Ig) G. In absorption experiments with human plasma, protein H-sepharose could absorb not only IgG but also albumin from plasma. The affinity constant for the reaction between albumin and protein H was 7.8 x 10(9) M-1, which is higher than the affinity between IgG and protein H (Ka = 1.6 x 10(9) M-1). Fragments of protein H were generated with deletion plasmids and polymerase chain reaction (PCR) technology. Using these fragments in various protein-protein interaction assays, the binding of albumin was mapped to three repeats (C1-C3) in the C-terminal half of protein H. On the albumin molecule, the binding site for protein H was found to overlap the site for protein G, another albumin- and IgGFc-binding bacterial surface protein. Also IgGFc-binding could be mapped with the protein H fragments and the region was found N-terminally of the C repeats. A synthetic peptide (25 amino acid residues long) based on a sequence in this region was shown to inhibit the binding of protein H to immobilized IgG or IgGFc. This sequence was not found in previously described IgGFc-binding proteins. However, two other cell surface proteins of S. pyogenes exhibited highly homologous regions. The results identify IgGFc- and albumin-binding regions of protein H and further define and emphasize the convergent evolution among bacterial surface proteins interacting with human plasma proteins.

Amino Acid Sequence↗
PubMed1994

Autoerythrocyte sensitization syndrome with thrombocytosis.

A case of autoerythrocyte sensitization syndrome in a 59-year-old female is reported. She had several episodes of circular ecchymoses on her left thigh. Intradermal injection of autoerythrocytes reproduced a similar ecchymosis. Thrombocytosis was detected and treated with busulfan which induced a delayed improvement of the ecchymosis outbreaks over 2 years of follow-up.

Autoimmunity↗
PubMed1994

Characteristics of anemia in patients with nephrotic syndrome.

Primary nephrotic syndrome can, although infrequently, cause severe anemia. However, the mechanisms of the anemia remain unknown. We investigated the mechanism of anemia in nephrotic syndrome by measuring parameters of nephrotic syndrome and anemia in 44 nephrotic patients (male: female; 21:23, average age; 43.6 +/- 20.3 years). Nephrotic patients had significantly lower hematocrits than did healthy controls (43.3 +/- 3.7 vs. 46.8 +/- 3.4% in males, 37.4 +/- 3.5 vs. 40.8 +/- 2.8% in females). Serum erythropoietin (Epo) concentrations were correlated inversely with hemoglobin (Hb), hematocrit (Hct), and red blood cell corpuscle (RBC) counts. Furthermore, serum Epo correlated with the serum iron concentration, but not with the other parameters, such as reticulocytes, serum protein and proteinuria. However, the maximum Epo concentration was less than 100 mU/ml in spite of severe anemia, and this was thought to be inappropriate. On the contrary, urine Epo was not detected by the same method of serum Epo determination in spite of aggressive dialysis with distilled water. When four patients with severe anemia were subcutaneously administered recombinant Epo 6,000 unit two times a week, they showed marked improvement in Hb/Hct/RBC. The precise mechanism of anemia in NS was not elucidated by this investigation, but further study should clarify the causes of the inappropriately low concentration of serum Epo in patients with primary nephrotic syndrome.

Adult↗
PubMed1994

[Pregnancy and delivery in patients with lupus nephritis].

To investigate some of the problems associated with pregnancy and delivery in lupus nephritis, 13 pregnancies in 7 patients with inactive lupus nephritis and 5 pregnancies in one patient with primary antiphospholipid syndrome (PAPS) were compared with 36 pregnancies in 22 patients with primary nephrotic syndrome (NS). Furthermore, a follow-up survey during 0-8 years was made with 12 babies born to mothers with lupus nephritis. Some pregnancies during lupus nephritis were accompanied by disease exacerbation and worsening of renal function. There was a higher incidence of babies born with a low birth weight, and the incidences of fetal loss or premature birth and toxemia were higher in lupus nephritis than in NS. The number of babies with a low birth weight was significantly higher in patients with pregnancy-induced hypertension or skin lesion due to lupus erythematosus. The presence of antibodies against SSA/RO in the mother was associated with the occurrence of congenital heart block. Birth weight of babies born to mothers with lupus nephritis was low, but there were no statistical differences in the growth of babies after 6 months of age compared with babies born to normal women.

Adult↗
PubMed1993

Molecular cloning and functional expression of a cDNA encoding glycosylation-inhibiting factor.

By using probes based on partial amino acid sequence of glycosylation-inhibiting factor (GIF) from a mouse T-cell hybridoma, a full-length cDNA encoding mouse GIF was isolated. A cDNA clone encoding human GIF was isolated from cDNA libraries of a GIF-producing human T-cell hybridoma by using mouse GIF cDNA as a probe. The cDNAs encode a putative 12.5-kDa peptide of 115 amino acids. Northern blot analysis demonstrated a single, 0.6-kb transcript. Polyclonal rabbit antibodies against the Escherichia coli-derived recombinant 13-kDa peptide bound hybridoma-derived GIF. Although the peptide did not contain a signal peptide sequence, transfection of the cDNA into COS-1 cells resulted in secretion of 13-kDa peptide, but the peptide had substantially less bioactivity than the hybridoma-derived GIF. However, expression of a chimeric cDNA encoding a fusion protein consisting of the N-terminal pro region of calcitonin precursor and human GIF and cotransfection with furin cDNA to allow intracellular cleavage of the fusion protein resulted in secretion of 13-kDa peptide that was comparable to hybridoma-derived GIF in its bioactivity. Both the 13-kDa peptide and GIF bioactivity in the transfected COS-1 supernatant bound to a monoclonal antibody against hybridoma-derived human GIF. These results indicate that the 13-kDa peptide represents recombinant GIF, but posttranslational modification of the peptide is important for generation of the bioactivity. The GIF cDNA had high homology with the cDNA encoding macrophage migration inhibitory factor. However, the recombinant GIF failed to inhibit migration of human monocytes, and recombinant human macrophage migration inhibitory factor did not have GIF bioactivity.

Amino Acid Sequence↗
PubMed1993

Inverse-dynamics model eye movement control by Purkinje cells in the cerebellum.

Many lines of evidence suggest that the cerebellum is involved in motor control. But what features of these movements are encoded by cerebellar neurons? For slow-tracking eye movements, the activity of Purkinje cells in the ventral paraflocculus of the cerebellum is known to be correlated with eye velocity and acceleration. Here we show that the complex temporal pattern of the firing frequency that occurs during the ocular following response elicited by movements of a large visual scene can be reconstructed by an inverse-dynamics representation, which uses the position, velocity and acceleration of eye movements. Further analysis reveals that the velocity and acceleration components can provide appropriate dynamic drive signals to ocular motor neurons, whereas the position component often has the wrong polarity. We conclude that these Purkinje cells primarily contribute dynamic command signals.

Action Potentials↗
PubMed1992

Convergent evolution among immunoglobulin G-binding bacterial proteins.

Protein G, a bacterial cell-wall protein with high affinity for the constant region of IgG (IgGFc) antibodies, contains homologous repeats responsible for the interaction with IgGFc. A synthetic peptide corresponding to an 11-amino acid-long sequence in the COOH-terminal region of the repeats was found to bind to IgGFc and block the interaction with protein G. Moreover, two other IgGFc-binding bacterial proteins (proteins A and H), which do not contain any sequences homologous to the peptide, were also inhibited in their interactions with IgGFc by the peptide. Finally, a decapeptide based on a sequence in IgGFc blocked the binding of all three proteins to IgGFc. This unusually clear example of convergent evolution emphasizes the complexity of protein-protein interactions and suggests that bacterial surface-protein interaction with host protein adds selective advantages to the microorganism.

Amino Acid Sequence↗
PubMed1992

Serologic, biologic and western blot analysis of human IgE-binding factor derived from a T cell hybridoma maintained in protein-free medium.

The human T cell hybridoma AC5 has been shown to produce an IgE-binding factor (IgEBF) upon stimulation with T cell mitogens, or anti-CD3 antibody. In this study, the line was established, propagated long term in a newly available serum-free, protein-free medium, and the factor it produced was analyzed. Serologic analysis, utilizing an ELISA assay and biotin-labeled human Ig of various isotypes, revealed that the IgEBF thus obtained was highly specific for the Ig epsilon-chain and was released primarily within the first 24 h after mitogen stimulation. Using biotin-labeled IgE as the detecting reagent, Western blot analysis of this factor demonstrated that the molecule was a single chain moiety of m.w. 64,000, and could be purified to apparent homogeneity by either DEAE or affinity (IgE column) chromatography. Detection of the IgEBF by ELISA and Western blot correlated well with activity in the previously employed rosette inhibition assay. Finally, purified IgEBF was found to suppress in vitro the production of IgE in the monoclonal human myeloma line U266, but not IgA or IgM-producing myelomas, providing evidence for the direct and specific regulatory action of this molecule on IgE-producing cells.

Antibody Specificity↗
PubMed1992

Glycosylation-inhibiting factor from human T cell hybridomas constructed from peripheral blood lymphocytes of a bee venom-sensitive allergic patient.

Human T cell hybridomas, which constitutively secrete glycosylation inhibiting factor (GIF), were constructed from PBL of an allergic individual who was sensitive to honey bee venom. PBMC of the patient were stimulated with either denatured or cyanogen bromide-treated bee venom phospholipase A2 (PLA2), and Ag-activated cells were propagated by IL-2 in the presence of human recombinant lipocortin I. T cells obtained in the cultures were fused with a HAT-sensitive mutant of the human lymphoblastoid cell line CEM. Approximately one-third of hybridoma clones constitutively secreted GIF. The GIF-producing hybridomas were CD3+ and bore TCR-alpha beta. GIF formed by unstimulated hybridomas lacked affinity for bee venom PLA2. Upon cross-linking of CD3, however, a majority of the GIF-producing hybridomas formed IgE-binding factors and GIF, the latter of which had affinity for bee venom PLA2. Both nonspecific GIF and Ag-binding GIF from the hybridomas bound to an immunosorbent coupled with the anti-lipomodulin mAb 141-B9. Using an affinity-purified GIF as an immunogen, we established mouse B cell hybridomas that secreted monoclonal anti-human GIF. In order to characterize human nonspecific GIF, one of the GIF-producing hybridomas was adapted to a serum-free medium, and culture supernatant was fractionated by DEAE-Sepharose column chromatography and by gel filtration. The majority of nonspecific GIF in the culture supernatant was recovered from DEAE-Sepharose by elution of the column with 10 mM Tris-HCl buffer, pH 8.0, containing 50 mM NaCl. Affinity-purification of GIF in the DEAE Sepharose fraction by using anti-GIF-coupled Affigel, and analysis of the purified GIF by SDS-PAGE revealed that human GIF is a single polypeptide chain of 14 to 15 kDa. Gel filtration of both crude and affinity-purified GIF preparations confirmed the molecular size of the cytokine.

Antibodies, Monoclonal↗
PubMed1992

A computational model of four regions of the cerebellum based on feedback-error learning.

We propose a computationally coherent model of cerebellar motor learning based on the feedback-error-learning scheme. We assume that climbing fiber responses represent motor-command errors generated by some of the premotor networks such as the feedback controllers at the spinal-, brain stem- and cerebral levels. Thus, in our model, climbing fiber responses are considered to convey motor errors in the motor-command coordinates rather than in the sensory coordinates. Based on the long-term depression in Purkinje cells each corticonuclear microcomplex in different regions of the cerebellum learns to execute predictive and coordinative control of different types of movements. Ultimately, it acquires an inverse model of a specific controlled object and complements crude control by the premotor networks. This general model is developed in detail as a specific neural circuit model for the lateral hemisphere. A new experiment is suggested to elucidate the coordinate frame in which climbing fiber responses are represented.

Animals↗
PubMed1992

Adaptive feedback control models of the vestibulocerebellum and spinocerebellum.

We extend the cerebellar learning model proposed by Kawato and Gomi (1992) to the case where a specific region of the cerebellum executes adaptive feedback control as well as feedforward control. The model is still based on the feedback-error-learning scheme. The proposed adaptive feedback control model is developed in detail as a specific neural circuit model for three different regions of the cerebellum and the learning of the corresponding representative movements: (i) the flocculus and adaptive modification of the vestibulo-ocular reflex and optokinetic eye-movement responses, (ii) the vermis and adaptive posture control, and (iii) the intermediate zones of the hemisphere and adaptive control of locomotion. As a representative example, simultaneous adaptation of the vestibulo-ocular reflex and the optokinetic eye-movement response was successfully simulated while the Purkinje cells receive copies of motor commands through recurrent neural connections as well as vestibular and retinal-slip parallel-fiber inputs.

Animals↗