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Biomedical subjects

N Maeda

Publications and source records attributed to N Maeda.

At least 613 records · Page 34Linked to original sources
PubMed1983

Recombination and balanced chromosome polymorphism suggested by DNA sequences 5' to the human delta-globin gene.

Two types of chromosome (R and T) were found by cloning from six human individuals the 3.1-kilobase-pair EcoRI fragment that contains the bipolar Alu family repeat 5' to the delta-globin gene. Two type T fragments were identical in nucleotide sequence. Two type R fragments were identical except for one base. Both types are found in whites, blacks, and orientals. The differences between R and T sequences (16 base substitutions and two deletions) were mostly in the 5' domain of the fragment (0.91% difference in 1.7 kilobases), which contains the bipolar Alu repeat, whereas the 3' domain of the fragment was more conserved (0.14% difference in 1.4 kilobases). To help understand the history of this human polymorphism, the equivalent fragment from a chimpanzee was cloned and its sequence was determined. The chimpanzee sequence differed from both human sequences at 39 positions distributed almost uniformly along the whole 3.1-kilobase-pair fragment. Assuming that humans and chimpanzees diverged 4 to 5 million years ago, the data indicate that the divergence of the two types of human chromosome started about 3 million years ago but about 0.4 million years ago an interchromosomal recombination rendered the two types of human chromosome alike in their 3' domains. The two chromosomes have since remained discrete and have persisted in several populations. These observations suggest that factors are operating to maintain a balanced chromosomal polymorphism in this region 5' to the human delta-globin gene.

Animals↗
PubMed1983

The influence of deformation of transformed erythrocytes during flow on the rate of oxygen release.

The deoxygenation rates of transformed erythrocytes were compared with those of normal discocytes by both stopped-flow and continuous-flow methods. Echinocytic and spherostomatocytic transformations were induced by various anionic and cationic drugs, respectively, without altering the oxygen affinity of haemoglobin, the cell volume or the membrane fluidity. The echinocytic transformation reduced the deoxygenation rate at slow-flow velocities (50 cm/sec), as detected by the continuous-flow method. However, at higher flow velocities (150 cm/sec) the rate was similar to that seen in normal discocytes. A close correlation between the degree of echinocytosis, the retardation of deoxygenation rate and the increase of suspension viscosity were observed. Microscopic observation of flowing erythrocytes revealed that the echinocytes scarcely deformed at the slower flow velocity, but clearly deformed at the higher flow velocity to various shapes resembling the flowing discocytes. Transformation to spherostomatocytes had no effect on the deoxygenation rate, which was comparable with that of the discocytes, and even the higher flow force did not induce any deformation. The retarded deoxygenation and the increased viscosity of echinocytes was probably due to an augmented stagnant layer around the cells (i.e. an increase of the hydrodynamic effective volume); this layer was reduced when the echinocytes were deformed with increasing flow force.

Blood Flow Velocity↗
PubMed1983

Kinetics of rouleaux formation using TV image analyzer. II. Rat erythrocytes.

With the use of a rheoscope combined with a TV image analyzer, the kinetics of specific pathogen-free rat erythrocyte aggregation was studied. Under certain conditions (gamma 7.5 s-1, hematocrit 0.36%, in own plasma, at 25 degrees C) one-dimensional aggregates (rouleaux) were formed without the development of three-dimensional aggregates, perhaps because of very low concentration of gamma-globulin. The observed phenomena could be explained by 1) the erythrocyte sedimentation and 2) the rouleaux formation. The time courses, of the biphasic change in erythrocyte count and of the increments in total area and in the area/count, were successfully simulated by a kinetic model of linear polymerization, assuming a sedimentation rate constant and an association rate constant. Further, a Poissonlike distribution of the length of rouleaux was shown, as predicted theoretically on the basis of the same kinetic model.

Animals↗
PubMed1983

Protective effect of alpha-tocopherol on the morphological and rheological changes of rat red cells.

The effect of alpha-tocopherol on the rheological properties of rat red cells was studied. The suspension viscosity of red cells increased, as the alpha-tocopherol content in red cells decreased. The red cells gradually transformed to echinocytes in isotonic solution dependent on the alpha-tocopherol content. The unique correlations among the viscosity, the transformation, and alpha-tocopherol content were observed. It was shown that the increased suspension viscosity of alpha-tocopherol-deficient cells could have arisen from the difficulty of echinocytes to undergo high shear deformation. The possible mechanism is discussed.

Animals↗
PubMed1982

Functional impairments of human red cells, induced by dehydroepiandrosterone sulfate.

A study has been made on the incorporation of dehydroepiandrosterone sulfate (DHAS), one of the most abundant adrenal C-19 steroids, into human red cells, and of the resulting effects on red cell functions. 1. DHAS was incorporated into red cell membrane mainly by a partition mechanism: The apparent partition constant was small ([DHAS]cell/[DHAS]free = 1.34), indicating that DHAS in red cells would be easily removed by dilution. 2. At least part of the DHAS taken up was apparently bound to band 3 protein and thereby was able to inhibit the exchange of intracellular and extracellular SO4(2-) (Ki = 70 micro M). 3. Using a fatty acid spin label, it was established that the presence of DHAS in lipid bilayer of the membrane increased the acyl chain motion in the middle portion of the membrane. 4. DHAS induced echinocytosis of red cells. It is suggested that the increase in the viscosity of red cell suspension, the decreased deformability and the decrease in the deoxygenation rate of hemoglobin in the presence of DHAS probably reflect the presence of echinocytes. 5. In the presence of plasma proteins, the incorporation of DHAs into red cells was remarkably suppressed.

Blood Viscosity↗
PubMed1982

Isolation and amino acid sequence of a monomeric hemoglobin in heart muscle of the bullfrog, Rana catesbeiana.

A monomeric heme-containing protein was isolated from heart muscles of the bullfrog, Rana catesbeiana, by gel filtration on Sephadex G-75 followed by DE52 ion-exchange column chromatography. The protein is composed of 132 amino acid residues and has Mr = 14,000 estimated by gel filtration on Sephadex G-50. This is the shortest heme globin so far known. The complete amino acid sequence of the apoprotein was deduced from the amino acid sequences of cyanogen bromide fragments and tryptic peptides. In order to align its amino acid sequence with other proteins in the globin superfamily (Hunt, L. T., Hurst-Calderone, S., and Dayhoff, M. O. (1978) Atlas of Protein Sequence and Structure, Vol. 5, Suppl. 3, 229-249, National Biomedical Research Foundation, Washington, D.C.), three gaps common to alpha-hemoglobin are required plus three more gaps unique in this protein. Of the latter, one is at the end of the EF region, the second near the beginning of the H-region, and the third is at the COOH terminus. With 62 amino acid residues in common, the amino acid sequence of this monomer is more homologous to the alpha-hemoglobin of the tadpole of R. catesbeiana (Maruyama, T., Watt, K. W. K., and Riggs, A. (1980) J. Biol. Chem. 255, 3285-3293), than to any other globin. A phylogenetic study of it and other globins clearly reveals that it arose via a gene duplication of hemoglobin near the time of the duplication that gave rise to the alpha and beta genes. But residues in contact with the heme group are rather conserved while the residues in the alpha 1 beta 1, alpha 1 beta 2 subunit contact regions are significantly substituted, frequently reverting to a myoglobin-like residue. The absence of this monomeric protein from the blood and the absence of myoglobin in heart muscle may indicate the protein functions as a myoglobin.

Amino Acid Sequence↗
PubMed1982

Developmental changes in the activities of prolinase and prolidase in rat salivary glands, and the effect of thyroxine administration.

As the salivary glands are interesting tissues to study proliferation, we studied the activities of prolinase and prolidase using Pro-Ala and Pro-Hyp as substrates, respectively, in developing rat salivary glands between day 1 and week 10 after birth. Developmental changes of prolinase activity in the submandibular and sublingual glands were similar to those in the parotid gland, which steadily increased and reached the adult level by 20-25 days after birth. However, the changes in the activity of prolidase in the submandibular and sublingual glands were different from those in the parotid gland: the activity in the parotid gland slowly increased with maturation and reached a maximum level on day 30, but the activity in the submandibular and sublingual glands continuously increased with maturation. When thyroxine was injected every two days from day 1 to day 19, both enzyme activities were induced precociously in the parotid gland but not in the submandibular and sublingual glands. On the study of regional distribution in rat tissues, the correlation coefficient between prolinase and prolidase activities was high in the peripheral but not high in the brain regions. These results indicate that the physiological roles of prolinase and prolidase are very similar but not the same.

Aging↗
PubMed1982

Ontogenesis of monoamine-synthesizing enzyme activities and biopterin levels in rat brain or salivary glands, and the effects of thyroxine administration.

Neonatal changes in the activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TrpH) and in the content of the co-factor, biopterin, were studied in rat midbrain for the first 20 days after birth. Changes in TH activity in the parotid and submandibular glands were also examined. Changes in TH activity per unit weight in the developing rat brain were briefly similar to those in the salivary glands; the activity increased from day 2 or 4 to day 9 after birth, and remained constant or slightly decreased at day 12, then rapidly increased on day 16. TrpH activity in the midbrain increased about twofold up to day 16. The biopterin concentration in the brain increased, reached a maximum level on day 12 after birth, and thereafter decreased. The effect of hyperthyroidism in rats given 0.2 mg/kg i.p. of thyroxine every 2 days postnatally was studied on the activity of TH in rat salivary glands at 12-day-old rats. In parotid or submandibular gland of hyperthyroid rats, TH activity increased at day 12 postnatally. In comparison with the effect on TH activity in the salivary glands, TH activity in the midbrain on day 20 postnatally was not induced by hyperthyroidism. Furthermore, increase of the TrpH activity and biopterin and catecholamine levels in the midbrain of hyperthyroid rats was not found on day 20 after birth in comparison with the corresponding controls. From these data, we suppose that postnatal hyperthyroidism may cause precocious induction of TH in rat salivary gland, but may not increase the activity of TH or TrpH, and the level of their co-factor, biopterin, in rat midbrain.

Aging↗
PubMed1982

Decreased viscosity of human erythrocyte suspension due to drug-induced spherostomatocytosis.

The effect of two cationic drugs (chlorpromazine and isoxsuprine) on the suspension viscosity of human erythrocytes were examined, comparing with the effect of anionic drugs. (1) As increasing the drug concentrations, the cationic drugs transformed the erythrocytes to stomatocytes, then to spherostomatocytes, while trinitrobenzene sulfonate, dehydroepiandrosterone sulfate and lysolecithin induced echinocytes, as well known. (2) The suspension viscosity decreased in parallel with the appearance of spherostomatocytes, but it increased in echinocytosis. (3) The membrane fluidity, measured by spin label method, was not a major determinant for the suspension viscosity in these cases, because of no systematic correlation. (4) The rheoscopic observation under shear force demonstrated that the spherostomatocytes deformed easily to ellipsoid with smooth cell surface, while the echinocytes less easily deformed to ellipsoid on which the small spikes persisted at higher shear. These distinct difference in deformed shape under high shear force could be related to the decreased suspension viscosity of spherostomatocytes. (5) In addition, the transformation to spherostomatocytes, thus the decreased viscosity, was primarily determined by the intramembraneous drug concentration.

Blood Viscosity↗
PubMed1981

Amino acid sequence of a myoglobin from lace monitor lizard, Varanus varius, and its evolutionary implications.

Myoglobin was purified from a muscle extract of lace monitor lizard, Varanus varius, by Sephadex G-75, followed by DEAE-cellulose column chromatography. The apomyoglobin was cleaved with cyanogen bromide. The largest fragment was further digested with pepsin, trypsin, and alpha-chymotrypsin. From the amino acid sequence of the cyanogen bromide fragments, together with those of tryptic peptides of apomyoglobin, the complete amino acid sequence of lizard myoglobin was deduced. To investigate the tetrapod and amniote origins, many possible phylogenetic trees were constructed using the myoglobin sequences, including those of map turtle and lace monitor lizard. The tree that requires the minimum number of nucleotide substitutions in their genes for the myoglobin sequences to have evolved from a common ancestor was different from the similarly most parsimonious trees for cytochrome c or for alpha-hemoglobin. The trees were different from each other and from the tree that best reflects current biological opinions.

Amino Acid Sequence↗
PubMed1981

Amino acid sequence of a myoglobin isolated from map turtle, Graptemys geographica.

Myoglobin was isolated from the skeletal muscle of map turtle, Graptemys geographica, and purified by Sephadex G-75 and DEAE-cellulose column chromatography. The myoglobin was cleaved by cyanogen bromide treatment, by peptic digestion, and by tryptic digestion of myoglobin whose lysine residues had been modified with citraconic anhydride or 1,2,4-benzenetricarboxylic anhydride. From the amino acid sequences of these fragments, the complete amino acid sequence was deduced.

Amino Acid Sequence↗
PubMed1981

Postnatal development of masticatory organs in rats II. Effects of hormones on the postnatal development of the M. masseter superficialis.

The effects of L-thyroxine (T4; 0.2 microgram/g body weight) an hydrocortisone (HC 5 microgram/g body weight) on the M. masseter superficialis in developing rats were investigated. Administration of T4 and/or HC to rats for 5 consecutive days from day 5 after birth induced precocious increase in diameter of the muscle fibers, increase of SDH activity and differences of the activity in various fibers and precocious disappearance of fibers with EDTA-insensitive ATPase activity. The effects of these hormones on the muscle gradually decreased after the 10th postnatal day. In thyroidectomized-adrenalectomized rats. T4 increased the diameter and SDH-activity of the muscle fibers and induced differences in SDH activity between fibers, but HC did not. Thus HC may act permissively on the SDH activity and the diameter of the muscle fibers. On the other hand, muscle fibers with EDTA-insensitive ATPase activity did not disappear on treatment with T4 or HC alone, but did disappear on treatment with T4 plus HC. These results suggest that increases in the circulating levels of T4 and HC in suckling rats are involved in development of the M. masseter superficialis.

Adenosine Triphosphatases↗