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Biomedical subjects

N Maeda

Publications and source records attributed to N Maeda.

At least 631 records · Page 35Linked to original sources
PubMed1981

Postnatal development of masticatory organs in rats. I. consecutive changes in histochemical properties and diameter of muscle fibers of the M. masseter superficialis.

At birth, the diameter of muscle fibers in the M. masseter superficialis of rats has a narrow range. The diameters begin to increase rapidly from day 10 after birth, and on day 30 the diameters range between about 25 and 55 micrometers, and can be distinguished into 3 groups. SDH activity also increases in some fibers from day 10 and on day 15, 2 types of fibers can be distinguished on the basis of SDH activity, fibers of larger diameter having high activity. From day 30 to 60, 3 types of fibers can be distinguished on the basis of diameter and SDH activity. During this period, the diameter of fibers with the lowest SDH activity increases rapidly, the diameter of fibers with the highest SDH activity decrease transiently, and the diameter of fibers with intermediate SDH activity increases slightly. After day 60, the diameter of fibers with the highest SDH activity begins to increase again. Some fibers show high EDTA-insensitive ATPase activity for the first 15 days. This activity begins to decrease from day 15 after birth, and after day 25 it is no longer detectable in any fibers. No relation between SDH activity and EDTA-insensitive ATPase activity was found in serial sections of fibers. These results indicate that histochemical differences between muscle fibers of the M. masseter superficialis first appear during the late suckling period and develop gradually over a comparatively long period after weaning during use of the muscle for mastication.

Animals↗
PubMed1981

Postnatal development of masticatory organs in rats. III. Effects of mastication on the postnatal development of the M. masseter superficialis.

When suckling of rats was continued on days 17--25 after birth, the development of the M. masseter superficialis was inhibited: increase in the diameter and SDH activity of its muscle fibers was retarded. Conversely, forced weaning of rats on 17 after birth stimulated the development of the muscle. These results suggest that mastication after weaning is involved in the further postnatal development of the M. masseter superficialis in rats.

Animals↗
PubMed1980

Effect of cholesterol on human erythrocyte membrane. A spin label study.

The effect of cholesterol on the membrane fluidity of human erythrocytes has been studied by electron spin resonance (ESR) spectroscopy, sensing the motion of androstane and fatty acid spin labeles in the cell membrane and in vesicles made from extracted phospholipids. 1. Androstane spin label (ASL) was incorporated from ASL-containing phospholipid vesicles into the erythrocyte membrane, essentially by a partition mechanism in proportion to their phospholipid contents. 2. On increasing the cholesterol or ASl content in the cell membrane, the spin label was gradually immobilized. 3. ASL motion in the cell membrane seemed to be primarily determined by the cholesterol/phospholipid molar ratio, regardless of the membrane protein-lipid interaction, as judged from the temperature effects on the ESR spectra of both membranes. 4. However, glutaraldehyde pretreatment induced considerable changes of the cholesterol-lipid interaction in the cell membrane, i.e., strong immobilization and cluster formation of ASL were observed.

Androstanes↗
PubMed1980

Functional restoration of ACD-blood by pyrodoxal 5'-phosphate.

Successful application of pyridoxal 5'-phosphate (PLP) to restore the oxygen transport function of ACD-stored blood is described. PLP is readily incorporated into ACD-erythrocytes by both carrier-mediated transport (in which ATP may participate) and passive diffusion. Plasma proteins (up to 2.5%) and inorganic phosphate (up to 40 mM) do not affect the incorporation of PLP, though more than 25 mM inorganic phosphate is necessary for the maintenance of ATP levels. Increasing the PLP concentration and/or decreasing the packed cell volume in the medium, increases the incorporation of PLP. Incubation of erythrocytes with PLP at pH 7.0 is most suitable for incorporation of PLP and the maintenance of ATP levels. PLP incorporated into erythrocytes restores the oxygen transport function of the ACD-erythrocytes, though decreased haem--haem interaction is observed. A procedure for the clinical application of PLP-loaded erythrocytes is suggested.

Adenosine Triphosphate↗
PubMed1980

A method for studying oxygen diffusion barrier in erythrocytes: effects of haemoglobin content and membrane cholesterol.

1. In order to study the kinetics os the oxygen egress from human red cells in the 50 sec-20 min time range, an apparatus for measuring the oxygen dissociation process was constructed, combining a spectrophotometer with an oxygen electrode of quick response. 2. Starting from air-saturated haemolysate or red cell suspensions, the velocity of oxygen dissociation from oxyhaemoglobin (Vdiss) and of oxygen disappearance in the medium (Vobs) after addition of bakers' yeast (consuming the dissolved oxygen at the velocity of Vconsump) were recorded. A parameter (r) was defined as the ratio of two velocities, Vegress (the velocity of oxygen egress into the medium) and Vdiss, r identical to Vegress/Vdiss = (Vconsump -Vobs)/Vdiss. Vcomsump could be calculated by the Michaelis-Menten equation as follows, Vconsump = Vmax [O2]/(Km + [O2]), where Vmax was the maximal velocity of oxygen consumption of bakers' yeast. 3. The r value was always 1.0 for the haemolysate, but it was less than 1.0 for the normal red cells. Further, the oxygen dissociation curve of red cells obtained at higher Vmax was distorted, due to the non-equilibration between intra- and extracellular oxygen concentrations. 4. The r value was (i) independent of the amounts of the allosteric effectors (2,3-diphosphoglycerate and H+) but (ii) dependent on the haemoglobin contents and (iii) dependent on the amounts of the membrane cholesterol. Therefore, the r value reflected only the process of the oxygen diffusion but not the "chemical reaction' rate. The "barrier' of the oxygen diffusion decreased at lower haemoglobin contents, but increased at higher cholesterol contents in the membrane.

Biological Transport↗
PubMed1980

Permissive role of L-thyroxine in induction of pancreatic amylase by cortisol in neonatal rats.

The effect of L-thyroxine (T4) on amylase activity in the developing rat pancreas has been investigated. Administration of T4 (0.2 microgram/g body wt) alone to intact rats on days 5-10 after birth did not induce pancreatic amylase but the enzyme was induced significantly by daily injection of cortisol (10 microgram/g body wt) alone into intact rats over the same period. In thyroidectomized, adrenalectomized rats pancreatic amylase was not induced by the injection of cortisol alone but it was induced by the administration of cortisol plus T4. Increase in enzyme activity was much less in thyroidectomized animals than in intact animals. These results suggested that T4 does not have a direct effect in increasing pancreatic amylase activity but plays a permissive role in increasing enzyme activity.

Adrenalectomy↗
PubMed1980

L-Thyroxine, cortisol and diet affect the level of amylase in the parotid gland of developing rats.

The effects of cortisol (10 microgram/g body weight) and L-thyroxine (T4; 0.2 microgram/g body weight) on the activity of parotid gland amylase in young rats were investigated. Administration of cortisol or T4 for 5 consecutive days from day 5 after birth caused the precocious appearance of amylase, T4 having almost twice the effect of cortisol. Cortisol and T4 did not have synergistic effects. In thyroidectomized-adrenalectomized rats, T4 increased amylase activity but cortisol did not. The increase in enzyme activity after day 20 was much less in rats thyroidectomized on day 10 than in rats adrenalectomized on day 10. These results suggest that T4 has a direct effect on the early increase of amylase activity (days 15-25) and that the action of glucocorticoid requires the presence of endogenous thyroid hormones. The hormone-induced level of amylase in intact rats was less than that of normal adult rats. Forced weaning of intact rats resulted in a further increase in amylase activity, suggesting that further amylase accumulation (after day 25) may be due to dietary factors.

Adrenalectomy↗
PubMed1980

Permissive role of L-thyroxine in the induction of stomach pepsinogen by cortisol in neonatal rats.

Subcutaneous injection of cortisol (10 micrograms/g body wt daily for 5 days) into normal neonatal rats increased the activity of stomach pepsinogen after day 5. L-Thyroxine (T4; 0.2 microgram/g body wt daily for 5 days) alone did not affect the activity but it somewhat enhanced the effect of cortisol. Even before day 5, when no effect of cortisol alone was observed, T4 plus cortisol increased pepsinogen activity. In adrenalectomized, thyroidectomized neonatal rats, injection of cortisol alone did not induce enzyme activity but cortisol together with T4 did induce it. Moreover, the increase in pepsinogen activity was depressed in rats thyroidectomized on day 10 but not in those thyroidectomized on day 15. These results suggest that T4 does not have a direct effect on the stomach but plays an important role in making the stomach responsive to glucocorticoids, resulting in increased pepsinogen activity.

Adrenalectomy↗
PubMed1980

Factors influencing long-term survival after aortic valve replacement.

In the aortic stenosis group, the left ventricular (LV) muscle mass index was a good parameter for predicting the prognosis. Associated mitral valve disease had no influence on long term survival after aortic valve replacement. In the aortic insufficiency group, associated mitral valve disease had a marked influence on the results of aortic valve replacement. In general, the aortic insufficiency group had less clinical improvement postoperatively than the aortic stenosis group. In the annuloaortic ectasia group, left ventricular enddiastolic pressure (LVEDP) might be the predictor to the prognosis. This group had the worst prognosis, of the three groups. Early operation should be considered for patients who have no, or only mild symptoms of, aortic valve disease.

Adolescent↗
PubMed1980

Anaerobic, gram-positive, pleomorphic rods in human gingival crevice.

Sixty-two strains of anaerobic, gram-positive, pleomorphic rods were isolated from the gingival crevice of individuals clinically free from peridontal disease, and examined for biochemical characteristics, cellular and colonial morphology, and acid end-products from glucose fermentation. None of them produced indole, hydrogen sulfide, or catalase, but all hydrolysed esculin. Seven, 10 and 45 of 62 strains were identified as Bifidobacterium, Actinomyces naeslundii, and Actinomyces israelii, respectively, on the basis of biochemical characteristics.

Actinomyces↗