Search PubMed⌕ Search

Biomedical subjects

M Sakuda

Publications and source records attributed to M Sakuda.

At least 145 records · Page 8Linked to original sources
PubMed1989

Isolation of mutants showing temperature-sensitive cell growth from embryonal carcinoma cells: control of stem cell differentiation by incubation temperatures.

Embryonal carcinoma(EC) cells, the undifferentiated stem cells of teratocarcinomas, have many properties in common with pluripotent embryonic cells, and thus provide an excellent system for studying the early events involved in embryonic development and stem cell differentiation. We have isolated three novel mutants with temperature-sensitive(ts) cell growth that were able to differentiate at a non-permissive temperature for cell growth. These mutations affect the progression of the cell cycle, leading to the transient accumulation of cells in a specific phase, the S phase, of the cell cycle, which is likely to be the primary cause of stem cell differentiation of EC cells at non-permissive temperature. Isolation of these mutants strongly supports the notion that there is a close association between the inhibition of DNA synthesis and EC cell differentiation.

Animals↗
PubMed1989

Inhibition of DNA synthesis causes stem cell differentiation: induction of teratocarcinoma F9 cell differentiation with nucleoside analogues of DNA-synthesis inhibitors and their inducing abilities counterbalanced specifically by normal nucleosides.

Nucleoside analogues inhibiting DNA synthesis can induce cell differentiation in teratocarcinoma cells. We have examined how their abilities to induce F9 cell differentiation were specifically counterbalanced by their corresponding normal nucleosides. We have also compared the differentiation inducing ability of the wild type F9 cells with that of its thymidine kinase-less mutant using plasminogen activator, as a differentiation marker, which is expressed at a very early stage of endodermal cell differentiation and can be assayed quantitatively. The results obtained were clearly explainable by the conventionally accepted action mechanisms of the nucleoside analogues, thus strongly suggesting that their abilities to induce cell differentiation were direct consequences of the inhibition of DNA synthesis; thus this confirms the notion that a close association exists between the inhibition of DNA synthesis and the induction of teratocarcinoma stem cell differentiation.

Animals↗
PubMed1989

Stimulation of cartilage-matrix proteoglycan synthesis by morphologically transformed chondrocytes grown in the presence of fibroblast growth factor and transforming growth factor-beta.

The effects of transforming growth factor-beta (TGF-beta) on the synthesis of cartilage-matrix proteoglycan by cultured rabbit chondrocytes were examined. Rabbit chondrocytes were seeded at low density and exposed to a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12 medium supplemented with 0.5% fetal bovine serum, 1% bovine serum albumin, 50 micrograms/ml ascorbic acid, and 2 x 10(-7) M hydrocortisone (Medium A). Various combinations of TGF-beta, insulin-like growth factor-I (IGF-I), and fibroblast growth factor (FGF) were also added to Medium A, and the chondrocytes were grown to confluency. Chondrocytes grown with TGF-beta or FGF alone became flat or fibroblastic, those grown with FGF and TGF-beta became very elongated and formed distinct foci, and those grown with FGF and IGF-I showed the spherical configuration characteristic of overtly differentiated chondrocytes. Nevertheless, the incorporation of 3H with glucosamine into the large, chondroitin sulfate proteoglycan synthesized by cultures with FGF and TGF-beta was similar to that in cells grown with FGF and IGF-I and five times that in cells cultured with FGF alone. The increases in incorporation of 3H reflected real increases in proteoglycan synthesis, because chemical analyses showed an increase in the accumulation of macromolecules containing uronic acid in cultures with FGF and TGF-beta or with FGF and IGF-I. However, FGF in combination with either TGF-beta or IGF-I had little effect on the incorporation of 3H into small proteoglycans or hyaluronic acid. These results indicate that chondrocytes morphologically transformed with TGF-beta and FGF fully express the differentiated proteoglycan phenotype rather than the transformed glycosaminoglycan phenotype.

Animals↗
PubMed1989

Three cases of oral squamous cancer associated with leukocytosis, hypercalcemia, or both.

Three examples of malignant neoplasms primary to the oral cavity and associated with paraneoplastic syndromes are presented. The first case is a squamous cell carcinoma of the maxilla associated with leukocytosis. The second case is a mandibular squamous cell carcinoma associated with hypercalcemia in the absence of bony metastases. The third case is a squamous cancer of the tongue that metastasized to the lumbar vertebrae and right second rib and was associated with both hypercalcemia and leukocytosis. There was no evidence of acute infection or leukemia that could be expected to account for leukocytosis. Hypercalcemia in the second case was defined as humoral hypercalcemia of malignancy by biochemical and clinical evaluations. To our knowledge, this is the first definitive report of a carcinoma primary to the oral cavity associated with humoral hypercalcemia of malignancy. In each case, the severity of hypercalcemia, leukocytosis, or both very closely correlated with tumor growth. Surgical excision of the tumors or regression of tumor mass due to aggressive anticancer drug administration resulted in decreases in leukocyte number, serum calcium level, or both. In contrast, recurrence or regrowth of tumors induced further development of hypercalcemia, leukocytosis, or both. It is therefore likely that humoral factors released by these oral carcinomas are responsible for the hypercalcemia, leukocytosis, or both.

Adult↗
PubMed1989

Biomechanical effect of anteriorly directed extraoral forces on the craniofacial complex: a study using the finite element method.

This study was designed to investigate the biomechanical effect of protractive maxillary orthopedic forces on the craniofacial complex by use of the three-dimensional finite element method (FEM). The three-dimensional FEM model was developed on the basis of a dry skull of a young human being. The model consisted of 2918 nodes and 1776 solid elements. Eighteen cranial and facial sutural systems were integrated in the model. An anteriorly directed 1.0-kg force was applied on the buccal surfaces of the maxillary first molars in both a horizontal parallel direction and a 30 degree obliquely downward direction to the functional occlusal plane. The nasomaxillary complex showed a forward displacement with upward and forward rotation in a horizontal protraction case, whereas a downward force produced almost translatory repositioning of the complex in an anterior direction. High stress levels were observed in the nasomaxillary complex and its surrounding structures. However, the pattern of stress distributions within the complex was different in two force systems. A downward protraction force produced relatively uniform stress distributions, indicating the importance of the force direction in determining the stress distributions from various orthopedic forces.

Biomechanical Phenomena↗
PubMed1989

Effects of directions of maxillary protraction forces on biomechanical changes in craniofacial complex.

The purpose of this study was to investigate the effect of directions of extraoral maxillary protraction forces on biomechanical changes in the craniofacial complex, using the three-dimensional finite element method (FEM). A three-dimensional FEM model was developed on the basis of a young, human dry skull. The model consisted of 2918 nodes and 1776 solid elements. An anteriorly directed 1.0 Kg force was applied to the buccal surface of the maxillary first molar in directions varying from -90 to 90 degrees to the occlusal plane. The displacement pattern of the entire craniofacial complex was evaluated. Further, the stress distributions were determined in three transverse planes associated with parallel, and 30 degrees upward and downward forces. As the force direction was more upward, repositioning of the craniofacial complex became larger in both the horizontal and vertical directions. Displacements were most translatory in loading with the forces applied in the directions ranging from -45 to -30 degrees to the occlusal plane. High stress levels were observed in the nasomaxillary complex and its surrounding structures. However, the patterns of stress distribution within the complex were different for three loading conditions. A downward protraction force produced the most uniform stress distribution. It is shown that the force direction plays an important role in determining the repositioning and the stress distributions in the craniofacial complex.

Biomechanical Phenomena↗
PubMed1989

Changes in [3H]nitrendipine binding and gamma-aminobutyric acid release in rat hippocampus following repeated morphine administration.

An antagonistic effect of calcium on the action of morphine was studied in rat hippocampal slices. The effect of repeated administration of morphine on gamma-aminobutyric acid (GABA) release and binding of [3H]nitrendipine, a calcium antagonist, was also examined. (1) In rat brain hippocampal slices, morphine enlarged the amplitude of the field potentials evoked in pyramidal neurons, disinhibiting them through basket cells. When the calcium concentration was elevated, potentiation of the field potentials by morphine was reduced. Decrease of the calcium concentration, on the other hand, enhanced the potentiating effect of morphine. Following repeated administration of morphine, its enhancing effect on the field potentials in slices was not observed. (2) In hippocampal membrane fractions obtained from rats repeatedly treated with morphine, enhancement of [3H]nitrendipine binding was observed. (3) In hippocampal slice preparations from rats receiving morphine repeatedly, K+ (45 mM)-stimulated [3H]GABA efflux was enhanced. The above results indicate that morphine antagonizes calcium, thereby reducing the release of transmitters. Furthermore, increase in calcium channels following repeated treatment of rats with morphine may explain the mechanism underlying development of tolerance.

Action Potentials↗
PubMed1989

[Mechanical properties of nickel-titanium alloy wire developed by the diffusion method].

The present study was conducted to investigate mechanical properties of the nickel-titanium (Ni-Ti) alloy wire developed by the diffusion method, in comparison with the previous Ni-Ti wires. Two types of the wire, work hardening and super elastic wires, were used for three experiments; three-point bending test, tension test and torque test. The following findings were obtained. 1. A newly developed work hardening wire exhibited lower force level with a generous reduction of force at various wire deflections, in comparison with the previous work hardening Ni-Ti wires. It was also found that tension strength and extension ratio of this wire were greater, and its modulus of longitudinal elasticity was smaller than those of the previous wires, indicating high resistibility to breakage. 2. A super elastic wire, developed by the diffusion method, showed similar pattern of force reduction associated with varying wire deflections, although magnitude of force was slightly larger than those of the previous super elastic wires. 3. An interesting finding was that force and its reduction with various deflections were varied by controlling how the wire was ligated onto a bracket, which was more obvious in the work hardening type of the present Ni-Ti wire. 4. Magnitudes of force exerted by Ni-Ti wires were around 200 gf at a deflection of 2 mm with an interbracket distance of 7 mm, and seemed to be beyond an optimal orthodontic force for anterior teeth. A further refinement is expected in terms of improving mechanical properties and/or developing finer wires.

Animals↗
PubMed1989

[Lymphoepithelial cyst of the upper neck: report of a case].

A case of lymphoepithelial cyst of the upper neck is presented. The patient was a 77-year-old woman. After her lesion was extirpated under clinical diagnosis of salivary gland tumor, identified as lymphoepithelial cyst (so-called branchial cyst). Histopathologically salivary gland was observed in the cyst wall composed of lymphoid tissue and was demonstrated highly active amylase-enzyme (S type) in the cyst fluid. These findings are convicted that our case originates ductal epithelium entrapped in cervical lymph node (inclusion theory of Bhaskar).

Aged↗
PubMed1989

Sensitivity analysis for GMDH correction modeling of MKG signals.

The purpose of this paper is to propose application of sensitivity analysis to the GMDH modeling for the correction of distorted kinesiographic signals recorded for inter-lattice points in space, and to evaluate its correction accuracy to estimate coordinates of an inter-lattice point, i.e., an observation, distorted coordinates of a nominal lattice point which is most adjacent to a given inter-lattice point is searched. Variations, i. e., differences, between distorted coordinates of the observations and their concomitant nominals are calculated. Instead of substituting kinesiographic measurements of the nominal and its neighbouring eight lattice points, the sum of the observation and its corresponding variation is substituted into the GMDH model which has been employed for the correction of distorted measurements of the aforementioned lattice point. A stereotaxic device is developed to stimulate mandibular jaw movement and determine position of a magnet transducer of a mandibular kinesiograph (MKG). Nominals of 3-D coordinates of the inter-lattice points are determined by the stimulator together with simultaneous recording of distorted output signals from the MKG which correspond to the nominals. Distorted signals are corrected on the basis of the sensitivity-oriented correction modeling. A mean estimation error of 0.16 mm (s. d., 0.19 mm) is determined for 24 inter-lattice coordinates. Thus, the application of sensitivity analysis to the GMDH modeling is confirmed to be effective.

Humans↗
PubMed1989

Biomechanical responses of tooth associated with different root lengths and alveolar bone heights: changes of stress distributions in the PDL.

The purpose of the present study was to elucidate the nature of stress distributions in the PDL varied by different root lengths and alveolar bone heights. A three-dimensional model of the upper central incisor was constructed for the finite element method (FEM). The model was modified to produce various root lengths and alveolar bone heights. A lingually directed 100 g horizontal force was applied at a point on the labial crown surface. Stress distributions were determined in the center of the PDL for various apicogingival levels. Stress levels in the PDL gradually decreased with a longer root. Rates of changes in stress levels to those with an original root length were approximately 1.5 at maximum and 0.8 at minimum. Patterns of stress distributions were varied by different alveolar bone heights in both the qualitative and quantitative aspects; i.e., apicogingival level of stress transition shifted more apical, and stress levels also increased following a reduction of the alveolar bone in the apicogingival direction, approaching about eight times with a half alveolar bone height as the original. It is found that the root length and alveolar bone height affect stress distributions in the PDL. Thus, it is shown that an orthodontic force application should be determined on the basis of anatomical variations in root length and alveolar bone height to induce an optimal stress level in the PDL, which is a key to desirable tooth movement.

Alveolar Process↗
PubMed1989

Associations between jaw-opening muscle activity and craniofacial morphology.

The purpose of this study was to investigate the relationship between jaw-opening muscle activity and craniofacial morphology in a sample of 64 adults with skeletal Class I malocclusions. EMG recordings from the inferior head of the right lateral pterygoid and the anterior belly of the right digastric muscle were analyzed together with mandibular displacement data sampled simultaneously with a kinesiograph. Incisor separation at the rest position and the threshold mandibular rotation position which corresponded to the onset of muscle activity in response to a graduated mandibular rotation were identified. Incisor separation was converted to a mandibular angle on lateral cephalograms. Anatomic points were digitized and sixteen traditional cephalometric variables were determined. The rest position angle did not correlate with the threshold angle for the anterior belly of the digastric muscle, but a significant correlation was identified with the inferior head of the lateral pterygoid muscle. One canonical correlation (r = 0.741; p less than 0.01) was identified between the mandibular rotation and dentoskeletal variables. Negative loadings with lateral pterygoid muscle threshold and rest position angles were obtained. The corresponding dentoskeletal variables had a positive loading with mandibular plane angle, total and lower anterior face height and gonial angle and a negative loading with lower posterior face height. The results suggest a possible relationship between lateral pterygoid muscle activity at two specific mandibular positions and the resultant form and posture of the mandible.

Cephalometry↗
PubMed1989

Longitudinal study on craniofacial growth following Le Fort I maxillary osteotomy in adolescent monkeys.

The present study was conducted to investigate the effects of Le Fort I maxillary osteotomy on craniofacial growth in adolescent monkeys. Twenty monkeys were used, of which eight served as control and twelve for experiment. All monkeys received tantalum implants, whereas experimental monkeys underwent Le Fort I osteotomy. Serial lateral cephalograms were taken before and immediately after surgery, and thereafter every month. Craniofacial growth was investigated by evaluating both repositionings of anatomical landmarks and implants, and dimensional changes. No significant differences between the experimental and control groups were observed in midfacial growth. Maxillary growth was not significantly affected excluding the posterior region of the maxilla. Condylar growth of the mandible was significantly influenced, and the overall length of the mandible in the experimental group was much less as compared to the controls. However, the length of the body of the mandible was not significantly affected, indicating a catch up growth of the mandible. It is shown that craniofacial growth is somewhat retarded, however, the maxilla and mandible experience harmonious growth even after surgery. Thus, it is indicated that the maxillary osteotomy is applicable to growing patients as well as adults, in terms of the craniofacial growth after surgery.

Animals↗
PubMed1989

Effect of moment to force ratios on stress patterns and levels in the PDL.

This study was conducted to investigate the effect of moment to force (M/F) ratios on stress distributions in the PDL. Three-dimensional finite element method (FEM) was applied to stress analysis, using a three-dimensional model of the upper central incisor. Five force systems were established to produce different M/F ratios with a constant 100 g lingual force and/or varying labial crown couples, applied at a point on the labial crown surface, 4 mm gingival to the incisal edge. Stresses were determined in the center of the PDL for eight apicogingival levels and at sixteen points around the root. Stress patterns and levels in the PDL changed in response to varying M/F ratios, however, stress values were invariable at the level of the center of resistance. M/F ratio for translation of a tooth produced the most uniform pattern of stress distributions and the minimum stress levels. It is found that the stress level induced in tooth translation is approximately 0.29 times as that in simple tipping of a tooth. Thus, it is shown that the M/F ratio is an important determinant for controlling the stress patterns and levels in the PDL and for achieving optimal tooth movement.

Bite Force↗
PubMed1989

[Adenoidcystic carcinoma of the palate in pregnancy: report of a case].

The Patient was a 28-year-old woman with 8th month of her pregnancy. She had noted a swelling of her palate (6-region) about 3 years before. Incisional biopsy was done in 8th month of her pregnancy and histological diagnosis was confirmed; adenoidcystic carcinoma. After normal health baby was born with cesarean section in 34 weeks, partial maxillectomy was performed. She is now free of the disease. The baby is now 1-year-old and enjoying the good health.

Adult↗
PubMed1989

[Case of skeletal open bite treated with orthognathic surgery, with special reference to morphological and functional analysis of the tongue].

Malfunction and abnormal posture of the tongue has been thought to be one of etiological factors for skeletal open-bite at length. In this study, an adult female patient with anterior open-bite is reported, who has been treated by means of posterior maxillary osteotomy and has obtained a good occlusion and profile, which is stable throughout the retention period. Electromyography was obtained from the tongue muscles by surface electrodes and the tongue muscle activity during deglutition was measured before and after surgery. The tongue posture was also analyzed on the basis of the roentgen cephalogram with the mandible at the rest position. Larger tongue muscle activities during swallowing was revealed compared to the control subjects. In addition, anteriorly and superiorly positioned tongue was seen in the initial stage. The amplitudes of the tongue muscle had decreased and tongue posture had shifted posteriorly and inferiorly following surgery, which approximated to the those observed in the control subjects. These improvements of the abnormal activity and posture of the tongue and the stability of occlusion after surgery confirmed that posterior maxillary osteotomy is an effective surgical operation for the anterior open-bite patients in terms of prognosis.

Adolescent↗