Biomedical subjects

M Yamamoto

Publications and source records attributed to M Yamamoto.

At least 19 recordsLinked to original sources

PubMed1992

Expression of scavenger receptors on renal cell carcinoma cells in vitro.

Messenger RNAs and proteins of scavenger receptor thought to be macrophage specific protein were expressed in renal cell carcinoma (RCC) cells in vitro. Acetyl LDL was taken up into RCC cells and promoted the production of interleukin-6 (IL-6), an in vitro autocrine growth factor to proliferate the cells. These results suggested that RCC cells might have a scavenger pathway which has not yet been demonstrated except for macrophages.

Blotting, Northern↗

PubMed1992

Quercetin arrests human leukemic T-cells in late G1 phase of the cell cycle.

The effect of quercetin, a flavonoid found in many plants, on the proliferation of human leukemic T-cells was analyzed. Quercetin reversibly blocked the cell cycle at a point 3-6 h before the start of DNA synthesis. Expression of the growth-related genes histone H4, cyclin A and B, and p34cdc2 was suppressed in cells blocked with quercetin. Comparison of the quercetin arrest points with those of the cell cycle inhibitors aphidicolin and mimosine revealed a temporal order of arrest points in G1 of quercetin, mimosine, and aphidicolin. Mimosine and aphidicolin did not inhibit the expression of cyclin A or p34cdc2, whereas all three reagents inhibited expression of cyclin B. Low concentrations of the protein inhibitor cycloheximide inhibited release of the quercetin but not the mimosine or aphidicolin block. A [35S]methionine-labeled M(r) 60,000 protein disappeared in quercetin-treated cells and was rapidly synthesized after removal of quercetin, suggesting the possibility that the M(r) 60,000 protein induces DNA synthesis after the cell is released from a quercetin block. These results suggest the usefulness of quercetin in studies of the regulation of late G1 phase.

Aphidicolin↗

PubMed1992

Animal histo-blood group ABO genes.

Sequences homologous to the human histo-blood group ABO genes are present in the genomic DNA of various mammals. We have PCR-amplified, subcloned, and sequenced a portion of these genes from several species of primates and found high conservation of the nucleotide as well as the deduced amino acid sequences during evolution.

ABO Blood-Group System↗

PubMed1992

CD5 acts as a tyrosine kinase substrate within a receptor complex comprising T-cell receptor zeta chain/CD3 and protein-tyrosine kinases p56lck and p59fyn.

T-cell antigens including CD2, CD4, CD6, CD8, and CD28 serve as coreceptors with the T-cell receptor (TCR)/CD3 complex in control of T-cell growth. The molecular basis by which these antigens fulfill this role has remained a major issue. An initial clue to this question came with our finding that the sensitivity of in vitro kinase labeling (specifically using protein-tyrosine kinase p56lck) allowed detection of a physical association between CD4-p56lck and the TCR/CD3 complexes. Another T-cell antigen, CD5, is structurally related to the macrophage scavenger receptor family and, as such, can directly stimulate and/or potentiate T-cell proliferation. In this study, we reveal that in Brij 96-based cell lysates, anti-CD5 antibodies coprecipitated TCR zeta chain (TCR zeta)/CD3 subunits as well as the protein-tyrosine kinases p56lck and p59fyn. Conversely, anti-CD3 antibody coprecipitated CD5, p56lck, and p59fyn. Indeed, anti-CD5 and anti-CD3 gel patterns were virtually identical, except for a difference in relative intensity of polypeptides. Anti-CD4 coprecipitated p56lck, p32, and CD3/TCR zeta subunits but precipitated less CD5, suggesting the existence of CD4-TCR zeta/CD3 complexes distinct from the CD5-TCR zeta/CD3 complexes. Consistent with the formation of a multimeric CD5-TCR zeta/CD3 complex, anti-CD5 crosslinking induced tyrosine phosphorylation of numerous T-cell substrates, similar to those phosphorylated by TCR zeta/CD3 ligation. Significantly, as for TCR zeta, CD5 was found to act as a tyrosine kinase substrate induced by TCR/CD3 ligation. The kinetics of phosphorylation of CD5 (t1/2 = 20 sec) was among the earliest of activation events, more rapid than seen for TCR zeta (t1/2 = 1 min). CD5 represents a likely TCR/CD3-associated substrate for protein-tyrosine kinases (p56lck or p59fyn) and an alternative signaling pathway within a multimeric TCR complex.

Antibodies, Monoclonal↗

PubMed1992

Marked enhancement of rat urinary bladder carcinogenesis by heat-killed Escherichia coli.

Chronic urinary tract infection is an important risk factor for the development of carcinoma in the human urinary bladder. To test the effect of chronic persistent inflammation on bladder carcinogenesis, we instilled heat-killed Escherichia coli (1 x 10(8) cells suspended in 0.5 ml of phosphate-buffered 2.1% NaCl solution) twice a week into the heterotopically transplanted rat urinary bladders in which carcinogenesis was initiated by a single dose (0.25 mg) of N-methyl-N-nitrosourea. When compared with the control animals, the rats treated with killed E. coli showed significantly enhanced bladder tumorigenesis, as reflected by an increase in the incidence of tumor (P = 0.05) and a 6- to 40-fold increase in the number of tumors per bladder (P less than 0.0001). The tumors were characterized by intraepithelial clusterings of neutrophils and by chronic inflammation and marked capillary proliferation in the tumor stroma. All of these features were rare in tumors in the control groups. The accelerated cell proliferation induced by killed E. coli treatment appears to play a significant role in the enhancement of tumorigenesis.

Administration, Intravesical↗

PubMed1992

Tissue factor-dependent autoactivation of human blood coagulation factor VII.

We recently showed that single-chain zymogen factor VII is converted to two-chain factor VIIa in an autocatalytic manner following complex formation with either cell-surface or solution-phase relipidated tissue factor apoprotein (Nakagaki, T., Foster, D. C., Berkner, K. L., and Kisiel, W. (1991) Biochemistry 30, 10819-10824). We have now performed a detailed kinetic analysis of the autoactivation of human plasma factor VII in the presence of relipidated recombinant tissue factor apoprotein and calcium. Incubation of factor VII with equimolar amounts of relipidated tissue factor apoprotein resulted in the formation of factor VIIa amidolytic activity coincident with the conversion of factor VII to factor VIIa. The time course for the generation of factor VIIa amidolytic activity in this system was sigmoidal, characterized by an initial lag phase followed by a rapid linear phase until activation was complete. The duration of the lag phase was decreased by the addition of exogenous recombinant factor VIIa. Relipidated tissue factor apoprotein was essential for factor VII autoactivation. No factor VII activation was observed following complex formation between factor VII and a recombinant soluble tissue factor apoprotein construct consisting of the aminoterminal extracellular domain in the presence or absence of phospholipids. Kinetic analyses revealed that factor VII activation in the presence of relipidated tissue factor apoprotein can be defined by a second-order reaction mechanism in which factor VII is activated by factor VIIa with an apparent second-order rate constant of 7.2 x 10(3) M-1 S-1. Benzamidine inhibited factor VII autoactivation with an apparent Ki of 1.8 mM, which is identical to the apparent Ki for the inhibition of factor VIIa amidolytic activity by this active site competitive inhibitor. Our data are consistent with a factor VII autoactivation mechanism in which trace amounts of factor VIIa rapidly activate tissue factor-bound factor VII by limited proteolysis.

Benzamidines↗

PubMed1992

Biphasic effects of alcohols on the phase transition of poly(L-lysine) between alpha-helix and beta-sheet conformations.

Poly(L-lysine) exists as a random-coil at neutral pH, an alpha-helix at alkaline pH, and a beta-sheet when the alpha-helix poly(L-lysine) is heated. The present Fourier-transform infrared (FTIR) study showed that short-chain alcohols (methanol, ethanol, and 2-propanol) partially transformed alpha-helix poly(L-lysine) to beta-sheet when their concentrations were low. At higher concentrations, however, these alcohols reversed the reaction, and the alcohol-induced beta-sheet was transformed back to alpha-helix structure. The reversal occurred at 1.40 M methanol, 0.96 M ethanol, and 0.55 M 2-propanol. The alcohol effects on the secondary structure were further investigated by circular dichroism (CD) on the thermally induced beta-sheet poly(L-lysine). Methanol, ethanol, and 1-propanol, but not 1-butanol, shifted the negative mean-residue ellipticity at 217 nm of the beta-sheet poly(L-lysine) to the positive side at low concentrations of the alcohols and to the negative side at high concentrations. With 1-butanol, only the positive-side shift was observed. The positive-side shift at low concentrations of alcohols indicates enhancement of the hydrophobic interactions among the side chains of the polypeptide in the beta-sheet conformation. The negative-side shift indicates a partial transformation to alpha-helix. The shift from the positive to negative side occurred at 7.1 M methanol, 4.6 M ethanol, and 3.1 M 1-propanol. The alcohol concentrations for the beta-to-alpha transition were higher in the CD study than in the IR study.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Propanol↗

PubMed1992

Parathyroid hormone-related protein in the rat urinary bladder: a smooth muscle relaxant produced locally in response to mechanical stretch.

Parathyroid hormone-related protein (PTHrP) gene expression in the pregnant rat uterus has been shown to be dependent on occupancy of the uterus by the fetus. To further test the hypothesis that the synthesis of PTHrP in smooth muscle tissue is regulated by mechanical stretch, we conducted experiments using the rat urinary bladder as a model of an expansible hollow organ. The results indicate that PTHrP mRNA levels do change in response to the stretch of the bladder wall. Under normal conditions PTHrP mRNA levels in the bladder correlated with the urine volume-namely, the extent of bladder distension. When bladders were maintained empty in vivo, PTHrP mRNA levels decreased gradually. Conversely, when bladders were distended by the accumulation of urine, levels of PTHrP mRNA increased dramatically with time. When distension was limited to one-half of the bladder, the increase in PTHrP mRNA was observed only in the distended portion. Histochemical studies performed on distended bladder tissue indicated the presence of PTHrP immunoreactivity in smooth muscle cells. Isolated organ bath studies were used to examine the possible physiological role of PTHrP in smooth muscle tonicity. In vitro responsiveness of bladder muscle strips to exogenous PTHrP was dependent on the in vivo condition of the bladder. In muscle strips obtained from bladders kept empty in vivo, PTHrP-(1-34)-NH2 relaxed carbachol-induced contraction in a dose-dependent manner but failed to relax the contraction in muscle strips from distended bladders that had high endogenous PTHrP expression. These results and the previous findings in the rat uterus suggest a physiological role of PTHrP in bladder smooth muscle function.

Animals↗

PubMed1992

Detection of a new mutant alpha-1-antichymotrypsin in patients with occlusive-cerebrovascular disease.

A new mutant alpha-1-antichymotrypsin (variant ACT) was found by direct sequencing and PCR-single strand conformation polymorphism (PCR-SSCP). This variant ACT was a point mutation of exon V of ACT, with the substitution of Met by Val. Four out of six individuals with this variant ACT had occlusive-cerebrovascular disease, leading to one hypothesis that there might be an association between this mutation and occlusive-cerebrovascular disease.

Base Sequence↗

PubMed1992

Endocrine cells and prognosis in patients with colorectal carcinoma.

Using chromogranin (CG) immunohistochemical staining, the prognostic significance of endocrine differentiation was investigated in 212 patients with primary colorectal adenocarcinoma (including 6 patients with mucosal carcinoma). CG-immunoreactive cells were found to be an integral component of the tumor in 67 of 206 patients (32.5%, excluding mucosal carcinoma). The intracellular localization of CG in the CG-immunoreactive cells in cancer tissue was completely different from that in the normal endocrine cells of the large bowel. In addition, morphologic changes such as nuclear hyperchromasia and pleomorphism also indicated that the CG-immunoreactive cells in the cancer tissue were malignant. The tumors were divided into three groups based on the frequency of CG-immunoreactive cells: Group I (n = 139), negative; Group II (n = 38), less than 1 positive cell/mm2; and Group III (n = 29), more than 1 positive cell/mm2. No correlation was observed between CG-immunoreactivity (CG-IR) and tumor location, grade, depth of invasion, or stage, regardless of lymph node involvement. However, patients with numerous endocrine tumor cells (Group III) had a significantly worse prognosis compared with patients without endocrine cells (Group I) (multivariate Cox's model, P less than 0.01). Similar findings were observed in patients with node-negative tumor (multivariate Cox's model, P less than 0.05). These results indicated that the neuroendocrine differentiation is an independent prognostic factor and that CG-immunohistochemistry is useful for detecting a subgroup with a worse prognosis among patients with colorectal cancer.

Biomarkers, Tumor↗

PubMed1992

Compartmentation in mammalian cerebellum: Zebrin II and P-path antibodies define three classes of sagittally organized bands of Purkinje cells.

The respective roles of genetic and epigenetic factors in generation of pattern formation in the vertebrate nervous system are still poorly elucidated. The mammalian cerebellum is subdivided in parasagittal modules defined by anatomical, physiological, and biochemical criteria. Immunostaining of adult mouse cerebellum with two monoclonal antibodies, P-path, which recognizes 9-O-acetylated glycolipids, and Zebrin II, which recognizes a 36-kDa protein, reveals three classes of sagittally organized bands of Purkinje cells: two complementary groups distinctly immunoreactive to one antibody but not the other and a third group that contains double-labeled cells. No Purkinje cells could be detected that were unreactive to either antibody. The specific and reproducible topography of these three classes of Purkinje cells may be related to the compartmentation of the cerebellum into developmental genetic modules.

Animals↗

PubMed1992

Expression of thymosin beta 4 gene during Xenopus laevis embryogenesis.

In order to investigate the molecular events which take place during gastrulation, extracts from developing Xenopus embryos were analyzed for temporal peptide distribution by high performance liquid chromatography. One peptide peak which became increasingly dominant after gastrulation was purified and partially characterized. The amino acid sequence of enzymic digests showed the peptide is extremely similar to mammalian thymosin beta 4. The peptide was capable of binding actin monomers like mammalian counterparts. Cloning of the Xenopus thymosin beta 4 cDNA showed that only three amino acid substitutions occurred between amphibian and bovine. Northern blot analysis revealed the mRNA is maternally present at a low level and the transcript becomes abundant after gastrulation, supporting the distribution of the peptide.

Amino Acid Sequence↗

PubMed1992

Insulin stimulates novel protein kinase C in rat adipocytes.

Insulin is known to rapidly stimulate and/or translocate Ca2+/phospholipid-dependent protein kinase (conventional PKC; cPKC) in rat adipocytes. Presently we examined whether insulin also stimulates/translocates Ca(2+)-independent, phospholipid-dependent protein kinase (novel PKC; nPKC). Total Mono Q column-elutable nPKC (like cPKC) activities were decreased in cytosolic and increased in membrane fractions with insulin treatment. Immunoblot study of novel PKC epsilon also showed insulin-induced translocation of immunoreactive PKC from cytosol to membrane, similar to the translocation of cPKC, PKC beta. These results suggest that nPKC has an important role in insulin-induced signal transduction.

Adipose Tissue↗

PubMed1992

Purification and structural analysis of hippocampal cholinergic neurostimulating peptide.

Hippocampal soluble fraction stimulates acetylcholine (AcCho) synthesis of medial septal nuclei in explant culture system. This stimulating activity was purified from 10-12-day-old rat hippocampus. During purification, the activity was separated into two fractions and a previously unreported peptide was purified from one fraction. The structure of this novel peptide is acetyl-Ala-Ala-Asp-Ile-Ser-Gln-Trp-Ala-Gly-Pro-Leu and we designated it as hippocampal cholinergic neurostimulating peptide (HCNP). Synthesized HCNP and de-acetylated HCNP (free-HCNP) stimulated AcCho synthesis of medial septal nuclei culture, in a dose-dependent manner, but not cultures of corpus striatum or anterior spinal cord. Mean half-maximal concentrations of HCNP and free-HCNP in AcCho synthesis of medial septal nuclei culture were 1.0 +/- 0.3 x 10(-10) M and 1.0 +/- 0.6 x 10(-11) M, respectively. Affinity purified polyclonal antibody to the free-HCNP neutralized the activity of crude hippocampal extract, as well as synthetic HCNP and free-HCNP. These observations suggested that HCNP was present in the hippocampal extract and was involved in development of specific cholinergic neuron in central nervous system.

Amino Acid Sequence↗

PubMed1992

Association interneurons of embryonic rat spinal cord transiently express the cell surface glycoprotein SNAP/TAG-1.

SNAP/TAG-1 is a 135 kDa glycoprotein of the immunoglobulin superfamily that is transiently expressed upon the surfaces of developing axons. In the embryonic rodent spinal cord, this molecule is expressed by motor neurons, dorsal root ganglion cells, and commissural neurons (Yamamoto et al.: J. Neurosci. 6:3576-3594, 1986; Dodd et al.: Neuron 1:105-116, 1988). The commissural cells are a subset of early-forming dorsal horn interneurons whose axons follow a circumferential course in the embryonic spinal cord. The axons of commissural neurons cross the developing ventral commissure to terminate on contralateral synaptic targets, whereas those of the other subset of circumferential cells, the association interneurons, remain on the same side of the spinal cord to form ipsilateral, terminal synaptic fields. The difference between the axonal trajectories of these two subsets of nerve cells raised the question of whether or not association interneurons would also express the SNAP/TAG-1 epitope and, if so, how would this expression be related to that of the commissural cells. Immunocytochemistry for SNAP/TAG-1 and choline acetyltransferase (ChAT) was used to answer these questions. The results indicated that association interneurons expressed SNAP/TAG-1 epitopes and that this expression began later and lasted longer than that of the commissural neurons. Other new findings of this study included the identification of a lateral subgroup of commissural fibers that expressed SNAP/TAG-1 later than their more medially located counterparts, and these lateral fibers were more pronounced in the thoracic spinal cord than at cervical levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Differential induction responses of delta-aminolevulinate synthase mRNAs during erythroid differentiation: use of nonradioactive in situ hybridization.

Expression of mRNAs encoding the erythroid-specific delta-aminolevulinate synthase (ALAS-E) and the nonspecific delta-aminolevulinate synthase (ALAS-N) were examined in murine Friend virus-transformed erythroleukemia (MEL) cells using nonradioactive in situ hybridization. Following dimethyl sulfoxide (DMSO) treatment, ALAS-E mRNA increased markedly, while ALAS-N mRNA did not increase in wild-type MEL cells. In contrast, in a DMSO-resistant clone of MEL cells, ALAS-E was not detectable before and after DMSO treatment. These findings suggest that ALAS-E and ALAS-N mRNAs are under separate controls and that the expression of ALAS-E mRNA is a critical event in erythroid differentiation.

5-Aminolevulinate Synthetase↗

PubMed1992

Nerve growth factor receptor (NGFR)-like immunoreactivity in the perineurial cell in normal and sectioned peripheral nerves of rats.

The occurrence of nerve growth factor receptor (NGFR)-like immunoreactivity in the perineurial cells of sympathetic and sensory nerves was analyzed in normal controls and after surgical severance. In the normal nerve trunk, no cellular elements exhibited NGFR-like immunoreactivity. Immunoreactivity was induced in the innermost perineurial cells and in all Schwann cells distal to a severed nerve. The acquisition of immunoreactivity in perineurial cells was also seen in deafferented sympathetic ganglia. On the other hand, the perineurial cells as well as axonal endings showed NGFR-like immunoreactivity consistently in the terminal region of normal nerves, and this immunoreactivity was enhanced by nerve section. The present study clearly showed that different types of nerve terminals are ensheathed to different extents by perineurial cells which were first clearly identified by their NGFR-like immunoreactivity: 1) nerve terminals were free of the perineurium far away from targets in the iris, 2) they were free of the perineurium at sites close to targets in the lingual epithelium, and 3) the perineurium ensheathed nerve terminals together with targets in Meissner's sensory corpuscle. The functional significance of the three different patterns of perineurial enclosure requires further examination.

Animals↗

PubMed1992

Intestinal intraepithelial lymphocyte T cells are resistant to lpr gene-induced T cell abnormalities.

The mucosal immune system of the gastrointestinal (GI) tract consists of Peyer's patches (PP), which are IgA inductive sites, and more diffuse effector regions which include cells in the intraepithelial lymphocyte (IEL) compartment. Since autoimmune MRL lpr/lpr (MRL/lpr) mice develop a proliferating CD3+, CD4-, CD8- (double negative; DN), B220+ T cell subset in systemic lymphoid tissue, we have initiated studies to determine the distribution of CD3+, DN, B220+ T cells (B220+ T cells or lpr/lpr T cells) in the GI immune system. Specifically, we examined T cell subsets separated according to expression of CD4, CD8, Thy-1, B220, alpha/beta T cell receptor (TcR) and gamma/delta TcR in PP and IEL of MRL/lpr mice at 6, 12 and 21 weeks of age. Increased numbers of CD3+ T cells were noted in both PP and spleen of 12- and 21-week-old mice in which the development of autoimmune disorders were also evident. However, normal numbers of CD3+ IEL T cells were seen in MRL/lpr mice in all three age groups tested. When the presence of T cell lymphadenopathy was examined in both IgA inductive and effector tissues, the PP followed the B220+ T cell pattern seen in the spleen, where approximately 30%-50% of CD3+ T cells in the PP of 12- and 21-week-old MRL/lpr mice expressed the phenotype of lpr/lpr T cells and greater than 90% were alpha/beta TcR+. On the other hand, B220+ T cells had not developed in PP or spleen of 6-week-old MRL/lpr mice. Of interest was the finding that IEL from lpr/lpr homozygous mice did not contain B220+ T cells in any age group tested. In this regard, the IEL of MRL/lpr mice comprised an identical pattern and frequency of CD4-/CD8+, CD4+/CD8-, DN and CD4+/CD8+ (double positive, DP) T cell subsets as their normal counterparts (i.e. MRL +/+, BALB/c and C3H/HeN mice) which consisted of approximately 75%, approximately 7.5%, approximately 7.5% and approximately 10%, respectively. Further, Thy-1, gamma/delta TcR and alpha/beta TcR expression in these four subsets of MRL/lpr IEL were very similar to normal mice. These results suggest that the intestinal IEL compartment is minimally affected by the lpr/lpr mutation which induces T cell abnormalities and indicate that B220+ T cells do not preferentially home to IEL. Further, our results support the concept that IEL T cells develop as a separate T cell lineage from thymus-derived cells.

Animals↗