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Biomedical subjects

H Momoi

Publications and source records attributed to H Momoi.

At least 19 recordsLinked to original sources
PubMed1995

Progressive decrease in heteronymous monosynaptic Ia facilitation with human ageing.

To evaluate functional change in the spinal reflex pathway with ageing, we studied heteronymous Ia facilitation from the quadriceps to soleus muscle in 30 normal volunteers (aged 24-68 years). The size of the test H-reflex of the soleus muscle was adjusted to 25% that of the maximal M-response. The conditioning stimulus was adjusted to 1.5-fold the motor threshold to stimulate all the Ia fibres in the femoral nerve. Facilitation was quantified as the slope of the very early part of facilitation, within 0.8 ms of onset. This procedure enabled us to evaluate the extent of monosynaptic Ia facilitation without contamination by other effects. The extent of facilitation decreased linearly with age. This decrease in facilitation could reflect a decrease in the number of Ia fibres and in their conduction velocities, and an increase in presynaptic inhibition on Ia terminals. The increase in presynaptic inhibition may be an adaptive phenomenon in the ageing of the neuromuscular system or, alternatively, a deteriorating process with decreasing flexible supraspinal modulation.

Adult↗
PubMed1994

A fission yeast gene encoding a protein that preferentially associates with curved DNA.

We searched for fission yeast (Schizosaccharomyces pombe) proteins that preferentially bind to a synthetic curved DNA sequence, by means of a DNA-binding gel shift assay in the presence of an excess amount of a non-curved DNA sequence as a competitor. We identified such a protein in S. pombe. The protein, thus purified, has an apparent molecular weight of 42,000, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was suggested that this protein (42 K-protein) recognizes and binds to a curved DNA structure in a given nucleotide sequence, although it also binds to a non-curved DNA sequence with lower affinity. As its putative coding sequence, a 1.9-kilobase genomic DNA from S. pombe was cloned and sequenced. Sequencing of a cDNA clone also revealed the existence of an open reading frame, with no intron, encoding a 381-amino-acid protein with a calculated molecular mass, 41,597. This protein appears to be located in the nucleus. The predicted protein sequence revealed that the 42 K-protein exhibits no significant similarity to any other known proteins, except to a hypothetical protein of Caenorhabditis elegans.

Amino Acid Sequence↗
PubMed1993

Sequence of a fission yeast gene encoding a protein with extensive homology to eukaryotic elongation factor-1 gamma.

A polypeptide with an apparent molecular mass of 23 kDa was identified, that exhibited an affinity to a 491-bp DNA derived from one of the Schizosaccharomyces pombe centromeric DNAs (cen1). After determining its N-terminal amino acid (aa) sequence, a Sz. pombe genomic DNA encompassing the coding sequence of the isolated protein was cloned, and a 2.3-kb genomic DNA region sequenced. Further sequence analysis of cDNA clones, originating from this particular genomic region, confirmed the existence of an open reading frame with a short intron, which encodes a 409-aa protein with striking homology to eukaryotic elongation factor-1 gamma.

Amino Acid Sequence↗
PubMed1993

Distribution of bent DNA structures in the fission yeast centromere.

To gain a clue as to the functional significance of DNA curvature, we experimentally characterized the distribution of bent DNA structures throughout the 35-kb cen1 sequence, one of the isolated functional centromeric DNA of the fission yeast, Schizosaccharomyces pombe. It was revealed that a relatively large central portion of cen1, covering a 2.2-kb DNA sequence, displays a remarkable DNA curvature.

Centromere↗
PubMed1992

Phosphotransfer signal transduction between two regulatory factors involved in the osmoregulated kdp operon in Escherichia coli.

The proteins KdpD and KdpE are regulatory factors critically involved in the osmotic regulation of the kdpABC operon that is responsible for a high-affinity transport system in Escherichia coli. In this study, we obtained biochemical evidence supporting the view that the KdpD protein is a sensory protein kinase that exhibits autophosphorylation and KdpE-phosphotransfer characteristics. During the course of such studies we established a procedure for purifying the KdpE protein in large quantities. We also developed a procedure for preparing cytoplasmic membrane enriched with the KdpD protein that exhibits in vitro ability with regard to phosphorylation of KdpE protein.

Bacterial Proteins↗
PubMed1992

Multiple hemangiopericytomas of the spleen.

Splenic tumors are uncommon. Described is a 58-yr-old man with multiple hemangiopericytomas of the spleen. Hemangiopericytoma is categorized as a benign vascular tumor, but has a relatively high malignant potential. A review of the literature shows that the case we present is only the second ever reported of a tumor originating from the spleen. Radiological findings and the treatment of the tumor are discussed.

Hemangiopericytoma↗
PubMed1984

Monoclonal antibodies to poly(adenosine diphosphate ribose) recognize different structures.

Two hybridomas producing monoclonal antibodies to poly(adenosine diphosphate ribose) [poly(ADP-Rib)] were established. One antibody, 10H (IgG3, kappa), bound to most of the poly(ADP-Rib) preparation, which consisted of molecules of various sizes of more than 20 ADP-Rib residues. The binding of this antibody was inhibited by not only poly-(ADP-Rib) but also a monomer unit of poly(ADP-Rib), Ado(P)-Rib-P. The sites protected by antibody 10H were isolated and analyzed by hydrolysis with alkaline phosphomonoesterase and then snake venom phosphodiesterase. The sites contained the same amounts of monomer units and branched portions [Ado(P)-Rib(P)-Rib-P] as the original poly(ADP-Rib) molecules but a lower average number of branched portions per molecule than in the original molecules. The other antibody, 16B (IgM, lambda), reacted with only 50% of the radioactive poly(ADP-Rib), and its binding was not inhibited by a monomer unit. This antibody protected 25% of all the poly(ADP-Rib) molecules from hydrolysis by snake venom phosphodiesterase. The protected sites contained twice as many branched portions per molecule as the original poly(ADP-Rib) molecules. These results show that the two monoclonal antibodies recognize different structures of poly-(ADP-Rib); 10H antibody recognizes the linear structure with ribose-ribose linkages, and 16B antibody may recognize specific structures, including the branched portions of poly-(ADP-Rib).

Animals↗
PubMed1984

Binding of benzo(a)pyrene with peroxidase and its oxidation by peroxidase-H2O2 intermediate.

The oxidation of benzo(a)pyrene (BP) by horseradish peroxidase (HRP) (EC 1.11.1.7) was examined spectrophotometrically by the decomposition of peroxidase-H2O2 intermediate "compound II." The rate constant of the oxidation of BP was 9.5 X 10(4) M-1 sec-1. The oxidation of BP by HRP was inhibited at high BP concentrations, and the hydrogen donor (BP) inhibition constant, KA', was 1.48 microM. The association constant, Kassoc, of the formation of a complex of BP and HRP at 403 nm was 4.37 X 10(4) M-1. The oxidation products of BP have been identified as 1,6-, 3,6- and 6,12-quinone BP. These products showed no mutagenicity in the mutagenicity assay.

Benzo(a)pyrene↗
PubMed1983

Electrophysiologic study on atrioventricular nodal reetrant tachycardia with special reference to recent controversies.

Electrocardiographic and electrophysiologic studies were performed in 21 patients with atrioventricular (A-V) nodal reentrant tachycardia (AVNRT). Patients were classified into three types according to the patterns during the tachycardia, i.e., (1) type I; an atrial echo (Ae) occurred simultaneously with a ventricular electrogram (VE) (14 patients), (2) type II; an Ae occurred in front of the next VE (four patients) and (3) type III; an Ae followed immediately after the preceding VE (three patients). All patients with type I AVNRT showed discontinuous A-V and continuous ventriculoatrial (V-A) conduction curves. "Enhanced V-A conduction" (1:1 V-A conduction at the ventricular paced rate of 200 beats/min) was demonstrated in five of the 14 and after verapamil in two of the five patients. In type II AVNRT the tachycardia was initiated with a minimal amount of A-V nodal conduction delay and second degree A-V or V-A block was observed in all four patients. V-A conduction was poor in these patients. In type III AVNRT A-V conduction curves were discontinuous and retrograde study revealed the presence of retrograde dual A-V nodal pathways. In conclusion, A-V and V-A conduction in patients with AVNRT were variable and this variability seemed to be responsible for different patterns of AVNRT.

Adolescent↗
PubMed1983

Effect of cholinergic stimulation on the distribution of amylase activity.

The amylase activity was measured in the several tissues and plasma after pancreatectomy in the rat. Pancreatectomy decreased the alpha-amylase content of the blood and several tissues in the rat, whereas the amylase activity did not change in the submandibular gland. Especially, the content of the small intestine lost about 99% of its amylase activity as did the small intestinal mucosa. After cholinergic stimulation, the amylase activity in several tissues and plasma tended to increase but the increase was not statistically significant. Only the enzyme activity in the lumen of the small intestine and distal intestine increased substantially after cholinergic stimulation. However, the maximal concentration in the small intestine was still only 2% of that in the normal non-pancreatectomized animal. The data suggest that the absence of the dramatic increase in the amylase activity in the plasma and several tissues that was observed in the normal rat after this pattern of cholinergic stimulation was due to the absence of the potential source of amylase, the pancreas.

Animals↗