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R Taga

Publications and source records attributed to R Taga.

31 records · Page 2Linked to original sources
PubMed1991

Hydroxyl radical participation in the in vitro effects of gram-negative endotoxin on cardiac sarcolemmal Na,K-ATPase activity.

The effect of in vitro exposure of sarcolemmal membrane (SL) vesicles to Gram-negative endotoxin lipopolysaccharides (LPS) was studied. LPS decreased the Na,K-ATPase activity of SL vesicles; this effect was inhibited by hydroxyl radical (.OH) scavengers such as dimethylthiourea and dimethyl sulfoxide, but not by superoxide dismutase, a scavenger of superoxide anion radicals or by the hydrogen peroxide scavenger catalase. ESR spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide verified the generation of .OH from LPS itself under the conditions used; .OH generated from LPS was not affected by deferoxamine, a powerful iron chelator. The Na,K-ATPase activity was reduced by an .OH radical generating system consisting of dihydroxyfumarate and Fe3(+)-ADP. Furthermore, exposure of SL vesicles to LPS caused an increase in malondialdehyde formation. It can be concluded that LPS damages cardiac SL by an oxygen free radical mechanism by the generation of .OH, due to inhibition of Na,K-ATPase activity and peroxidation of lipids, and that the effect of LPS is not dependent on the presence of contaminating iron.

Animals↗
PubMed1988

The effect of oxygen free radicals on calcium permeability and calcium loading at steady state in cardiac sarcoplasmic reticulum.

It has been proposed that oxygen free radical production is an important mediator of the myocardial dysfunction during the course of acute ischemia. We tested this hypothesis by characterizing the pathway of calcium efflux across sarcoplasmic reticulum (SR) membranes affected by oxygen free radicals. The effect of oxygen free radicals on the steady state calcium load, calcium permeability, and Ca,Mg-ATPase activity of isolated canine cardiac SR vesicles was investigated at pH 7.0. In vitro generation of oxygen free radicals by xanthine oxidase (0.09 units/ml), acting on xanthine in doses up to 50 microM as a substrate, increased the permeability of the SR vesicles to calcium, determined by measuring net efflux of calcium after stopping pump-mediated fluxes, and decreased total intravesicular calcium and free intravesicular calcium with no effect on Ca,Mg-ATPase activity. The effect of oxygen free radicals on calcium permeability was calcium gradient-dependent. Xanthine alone or xanthine plus denatured xanthine oxidase had no effect on this system. Superoxide dismutase (SOD, 56 units/ml), but not denatured SOD, significantly inhibited the effect of xanthine-xanthine oxidase reaction. The calcium permeability of the SR membrane decreased with decreasing calcium load. In addition, inasmuch as extravesicular calcium exerts only a slight effect on calcium permeability, the decrease in the permeability with calcium load is specifically related to the calcium load. Oxygen free radical-induced increase in calcium permeability was unaffected by Mg concentration between 2.1 and 21 mM. In summary, our data reveal that .O2- can produce a diminished level of accumulated calcium, which is reflected by the decreased calcium load and an increase in passive calcium permeability, and that the decreased calcium accumulation in the presence of the xanthine-xanthine oxidase system may not be mainly due to an inhibited calcium pump but due to an increased calcium permeability. Our results also suggest that increased SR membrane passive calcium permeability induced by oxygen free radicals is not carrier mediated. It is postulated that, with the oxygen free radical-mediated progressive increase in calcium permeability, free cytosolic calcium concentrations would increase in ischemic myocardium.

Animals↗
PubMed1979

Morphometric evaluation of the number of exocrine pancreatic cells during early postnatal growth in the rat.

The number of the various cell categories of the exocrine pancreas of the rat was evaluated by morphometric methods in paraffin sections of glands from rats aged 2, 5, 15, 20 and 33 days. The evolution of these cell types could be properly expressed by equations of the type y = aoek.x, where y = cell number, and x = age in days. The time necessary for each cell type to duplicate was thus obtained. The percentages (y') of acinar, intercalated duct and connective tissue cells also proved to be age-dependent and could be expressed by second-degree equations.

Age Factors↗
PubMed1979

Ultrastructural studies on developing parotid gland of the rat at early postnatal periods.

An electron microscopic study of the exocrine and myoepithelial cells of the parotid gland of the rat between days 2 and 40 of the postpartum was undertaken. Besides confirming morphological data of the literature on the evolution of the acinar cells, the following observations are reported. 1. At early postnatal development in some acini "mucous-like" cells containing secretory granules with light and dense parts may be observed. Cells with these types of granules were not found after day 20. 2. Morphological differentiation and maturation of the myoepithelial cells were followed. A parallelism was observed between the maturation of these myoepithelial cells and of the acinar cells. Myofilaments first appear around the nucleus at day 5 and between days 20 and 30 a considerable amount of these filaments is found in the already typical myoepithelial cells. 3. Active morphogenesis seems to be occurring in all cellular compartments namely at very early postnatal periods, e.g., between days 2 to 15. 4. The distribution and amount of thin and intermediate sized microfilaments in cells of these compartments varied visibly by various orders of magnitude.

Animals↗
PubMed1978

Ultrastructural morphometric study on developing acinar cells of the rat pancreas and parotid gland.

The fraction of cellular volume occupied by the cytoplasm has been assessed by point-counting volumetry in 0.5 micrometer araldite sections. Measurement of the transection radius of the nuclei of acinar cells allowed the assessment of the mean nuclear volume according to the method of Bach. With these data, the cytoplasm volume was calculated in cubic micrometers. Ultrastructural morphometric data were obtained by means of superimposing on the electron photomicrographies (x 21,000 or x 28,500) a test system of 84 evenly spaced segments according to Weibel et al. The analysis of the values obtained for the pancreas and parotid gland allowed for the supposition that the process of maturation in the rat, either for the pancreas or the parotid gland, occurs simultaneously with the mitotic process, this last being held as the predominating one in the first 3--4 postnatal weeks. The cytodifferentiation process becomes more marked in the last phases studied and on the 40th day it already shows parameters held as similar to those of the adult animal.

Animals↗
PubMed1978

Histological study on the prenatal development of the cheek-teeth of rabbits (Oryctolagus cuniculus).

The prenatal development of cheek-teeth of rabbits was studied by histological methods. Females from 15 to 30 days of gestation were sacrificed and their fetuses were collected and decapitated. The heads were fixed in buffered neutral formalin and paraffin embedded. Sagittal and frontal sections of 7 mu were obtained and stained with hematoxylin-eosin. The first tooth-germs observed were the m3 and m3, in the animal of 16 days of fetal life. One day after the m4 and m4 are observed in the bud stage. The last teeth to initiate development in the fetal rabbits are the M3 and M3 at 30 days. Only the m3, m4, m3 and m4 start cementogenesis in the prenatal stage.

Animals↗
PubMed1976

Histological study on the postnatal development and sequence of eruption of the mandibular cheek-teeth of rabbits (Oryctolagus cuniculus).

The postnatal development and sequence of eruption of mandibular cheek teeth of rabbits were studied by histological methods. Hemi-mandibles were dissected and sectioned in longitudinal sections of 7 mu and stained with hematoxylin-eosin and Masson's trichrome. The presence of two mandibular deciduous molars which are replaced by corresponding premolars and of three mandibular permanent monofisary molars was confirmed. Eruption of deciduous molars of the mandible begins at 4 days after birth and of the mandibular permanent molars at 9 days, while that of mandibular premolars occurs at 23 days, replacing the mandibular deciduous molars which have exfoliated. At 32 days all the mandibular permanent cheek-teeth are erupted. At birth the mandibular deciduous molars are completely developed and at 4 days their root resorption is initiated. At the first day P3 is in the bell stage and the P4 has begun dentinogenesis. In M1 and M2 amelogenesis is observed.

Amelogenesis↗
PubMed1975

Histological study on the postnatal development and sequence of eruption of the maxillary cheek-teeth of rabbits (Oryctolagus cuniculus).

The development and sequence of eruption of the maxillary cheek-teeth of rabbits were studied by histological methods. The presence of three deciduous molars which were replaced by correspondent premolars and of three permanent molars without predecessors was confirmed. The eruption of the maxillary deciduous molars was shown to begin at 4 days postnatally and that of the permanent molar at 9 days, while the eruption of the premolars occurs from 24 days on, replacing the deciduous molars which are exfoliated. The last tooth to erupt is the M3. At 32 days all the permanent cheek-teeth are erupted. The deciduous molars are completely developed at birth, root resorption starting at 4 days. On the first day the premolars are in the bell stage and in the M1 and M2 amelogenesis is taking place. After 27 days the development of the permanent maxillary cheek-teeth is completed. Dentinogenesis, amelogenesis and cementogenesis were observed in all of them.

Age Factors↗
PubMedDate not supplied

Morphometric dimensions of the mouse parotid glands of both sexes.

The goal of this research was to evaluate the morphometric dimensions of the different structures of male and female albino mouse parotid glands. The following morphometric dimensions were evaluated for the acini, intercalated ducts, striated ducts, excretory ducts and stroma: volume density, total compartmental volume, surface density, total external surface, surface-to-volume ratio, cell volume and absolute number of cells. Analysis of the results showed that the parotid gland mass was 43.7% greater (P < 0.01) in the male mice than in the females. This difference was due to the fact that the compartmental volumes of the acini, intercalated ducts and striated ducts were markedly higher in the male mice, 57.6% (P < 0.01), 253.1% (P < 0.01) and 91.1% (P < 0.05), respectively. The higher volume of the acinar morphological compartment was due to the total number of cells and average cell volume being higher in the male mice, 24.8% P < 0.01) and 47.7% (P < 0.01), respectively. Based on the results obtained, it was concluded that there are morphological differences between male and female parotid glands. These differences are detectable through morphometry, mainly in the morphological acinar and intercalated ducts compartments, which are more developed in male mice.

Animals↗
PubMedDate not supplied

Rabbit bone marrow response to bovine osteoinductive proteins and anorganic bovine bone.

The effects caused by the implantation of bioabsorbable hydroxyapatite (HA) bound to a pool of bone morphogenetic proteins (BMPs) and other bone noncollagenous hydrophobic proteins mixed with anorganic bovine bone inside rabbit bone marrow were assessed. Within the interior of hollow cylindric titanium prototypes, the following biomaterials were inserted: (1) test group: HA containing a pool of BMPs and noncollagenous hydrophobic proteins mixed with anorganic bovine bone; (2) control group: HA without any protein mixed with anorganic bovine bone; and (3) negative control group: blood clot. The cylinders were placed surgically into the medial portion of the tibiae of 7 rabbits in a manner that allowed the biomaterials to contact just the bone marrow. Morphometric analysis showed that: (1) the biomaterials containing the protein mixture resulted in significantly less new bone than the biomaterials without such a mixture; (2) the group without the protein pool formed larger amounts of bone within the cylinder when compared to the negative control (blood clot only); and (3) the biomaterials containing the protein pool did not show any difference in relation to the negative control. It was concluded that a pool of BMPs and other bone noncollagenous hydrophobic proteins had an inhibitory effect on osteogenesis, and that the biomaterials without a protein pool formed a favorable substrate to bone formation.

Animals↗