Alpha 1-adrenoceptors in the conduction system of rat hearts.

1. We have characterized alpha 1-adrenoceptor in the conduction systems of the rat heart by quantitative autoradiography. 2. Consecutive 20 micron thick sections from a single rat heart containing the sinoatrial (SA) node and atrioventricular (AV) node were incubated with increasing concentrations of [3H]-prazosin with or without 10 microM phentolamine. After exposure to 3H-Ultrofilm, optical densities corresponding to the SA node and AV node were determined by computerized densitometry after comparison with 3H standards. 3. The SA node and AV node were stained heavily for cholinesterase and they contained a higher concentration of alpha 1-adrenoceptors than the adjacent myocardium without a significant change in the affinity. 4. These results support the hypothesis that alpha 1-adrenoceptors may play an important role not only in inotropism but also in chronotropism of rat hearts.

Identification of a receptor type guanylyl cyclase in the antennal lobe and antennal sensory neurons of the silkmoth, Bombyx mori.

Sensory neuron-specific guanylyl cyclases (GC), which were recently identified in rodents and nematodes, are thought to be a new family of odorant/pheromone receptors. In the antennae of the male silkmoth Bombyx mori, receptor type GC are supposed to mediate signaling of pheromone. Structure of receptor type GC expressed in insect sensory neurons has remained unidentified. Here we report the isolation of cDNA of the receptor type GC, designated BmGC-I, from the male silkmoth antennae. The deduced amino acid sequence indicates that BmGC-I appears to consist of four domains: an extracellular, single transmembrane, kinase-like and a guanylyl cyclase domain. BmGC-I is most closely related to the mammalian natriuretic peptide hormone receptor A (GC-A) and retains all the cysteine residues that are conserved within the extracellular domain of the mammalian GC-As. Transcripts of the BmGC-I gene were detected in various tissues; the flight muscles, midgut, legs, ganglion, Malpighian tubules, testis and the head. Immunohistochemical study revealed that the BmGC-I protein localizes in the antennal-lobe glomerulus and in the soma and axon of sensory neurons. We thus suggest that BmGC-I plays functional roles in the odorant information processing and the modulation of excitability in the antennal sensory neurons.

Histomorphometric analysis of the response of rat tibiae to shape memory alloy (nitinol).

The bone reaction to nitinol (Ni-Ti), a metal with shape memory, and other materials inserted transcortically and extending into the medullary canal of rat tibiae was quantitatively assessed using an image processing system. The materials examined were implants, all of the same shape and size, composed of nitinol, pure titanium (Ti), anodic oxidized Ti (AO-Ti), a titanium alloy (Ti-6Al-4V) and pure nickel (Ni). While the other four implant materials were progressively encapsulated with bone tissues, Ni was encapsulated with connective tissues through the 168-day experimental period, and the Ni implants showed no bone contact at any time during the experimental period. Histometric analysis revealed no significant difference among the tissue reactions to Ti, AO-Ti and Ti-6Al-4V, but Ni-Ti implants showed significantly (P < 0.01) lower percentage bone contact and bone contact area than any of the other titanium or titanium alloy materials.

Study of bone formation around dense hydroxyapatite implants using light microscopy, image processing and confocal laser scanning microscopy.

The bone reaction to hydroxyapatite (HA) implants inserted transcortically and extending into the medullary canal of rat tibiae was quantitatively assessed using light microscopy, confocal laser scanning microscopy and an image processing system. Sixty-five male rats (6 weeks old) were divided into two groups, 60 for histological observation and image analysis and five for time-labelling. In the histological observation, control sections of 168 days showed a few bone trabeculae in the fatty bone marrow, and Ti implants had become gradually encapsulated with a thick bone tissue layer; however, HA implants became almost completely encapsulated with a thin bone tissue layer during the 168 day experimental period. Histometrical analysis of the percent bone contact revealed that Ti implants showed a continuous increasing curve, and HA implants showed rapid increase in the initial healing period up to 14 days, with 96% bone contact reaching a plateau at 84 days after operation. There was a significant difference in the percent of bone contact between Ti and HA implants throughout the experimental period. Confocal laser scanning microscopic observations revealed the presence of calcein at the 14th day and only slight alizarin colour layer in the bone tissue at the 28th day, both indicating bone formation. These findings suggest that the activity of bone formation was higher at the 14th day than at the 28th day. Also, the percentage of bone contact of HA is superior to titanium throughout the experimental period, and the ascending patterns of both implants are quite different to each other.

Fractures of hydroxyapatite-coated blade implants connected with natural teeth. A histological study using SEM, light microscopy, and an image processing system.

A clinical study was conducted of 59 patients treated with 78 hydroxyapatite (HA)-coated blade implants from August 1986. Five implants in 5 patients were broken at the neck portion, and one implant in one patient was removed from the jaw bone. The histological findings around a broken implant which was removed from the mandible are presented. These sections showed good adaptation of the bone to the implant without a fibrous layer. Histomorphometric evaluation of bone-to-implant contact showed 73.5%. The scanning electron microscopy image of the fractured surface revealed a fatigue fracture. The suspected cause of the fracture was stress concentration at the cervix portion, because of excessive mobility or deleterious change of abutment teeth. Consequently, the osseointegration/biointegration implants should not be connected with natural teeth.

Failing hollow implants examined by light microscopy and image processing.

The purpose of this study was to evaluate the radiologic, histologic, and histometric findings of three failing hollow implants. On periapical radiographs, these implants showed vertical bone loss up to the hollow portion around the implant. Examination of the histologic sections disclosed that the hollow portions of all the implants were almost filled with bone tissue, although slight bone resorption and presence of granulation tissue infiltrated with inflammatory cells was observed coronal to the hollow portion. Histometric analysis disclosed that the average percent bone contact was 93.1% in case 1, 90.9% in case 2, and 84.3% in case 3 and the average percent bone filling was 42.1%, 50.5%, and 33.8%, respectively. Consequently, there seems to be some potential for successful treatment of these implants because the destructive changes were limited to the coronal aspects of the implant.

Abscess formation around a hydroxyapatite-coated implant placed into the extraction socket with autogenous bone graft. A histological study using light microscopy, image processing, and confocal laser scanning microscopy.

The purpose of this study was to evaluate the radiologic, histologic, and histometric findings for a retrieved hydroxyapatite (HA)-coated implant which had been placed into a fresh extraction socket with autogenous bone graft 3 months previously. A periapical radiography disclosed a vertical bone loss around the implant cervix. Examination of histologic section disclosed that granulation tissue including bone chips around the cervix, and newly-formed bone tissue around the grafted bone tissue on the HA coated surface. In the confocal laser scanning microscopic findings toluidine blue-negative bone tissue showed autofluorescence. Histometric analysis indicated that the average percent bone contact was 29.2% (ranged 26.4% to 34.1%). Suspected reasons for failure were an early exposure of the barrier membrane, its early removal, the implant placement into an infected site, inadequate antibiotic premedication, and/or poor control of infections around teeth prior to implant surgery and around implants before and after placement of barrier membrane.

A histologic evaluation of retrieved hydroxyapatite-coated blade-form implants using scanning electron, light, and confocal laser scanning microscopies.

We histologically examined seven hydroxyapatite-coated (HA) blade implants removed from patients. Four of them radiologically showed severe bone loss and were easily removed with an elevator. Three radiologically showed vertical bone loss and were removed by surgical procedure. Our histological evaluation indicated that coating separation from the HA implants had occurred, and HA coating resorption by bone tissues was suspected in an implant left in situ for 8 years. Several multinucleated giant cells were seen with a few released particles of HA coating at the point lacking bone contact with the HA coating. The presence of microorganisms on and in the HA coating layer was also noted.

Histological comparison of early wound healing following dense hydroxyapatite granule grafting and barrier placement in surgically-created bone defects neighboring implants.

The purpose of this study was to examine early wound healing following grafting of dense hydroxyapatite granules (HA granules) and barrier placement in surgically-created bone defects surrounding implants. Eight healthy adult dogs with an average weight of 15 kg were used in this study. Thirty-two bone defects measuring 4 mm x 4 mm were removed with a surgical bur to form continuous bucco-lingual bone defects and 32 implants (16 titanium [Ti]) and 16 hydroxyapatite-coated [HA]) were then placed into the defects. Four implant groups were created: 1) grafting HA; 2) covering with an expanded polytetrafluoroethylene (ePTFE) membrane; 3) grafting HA and covering with ePTFE membrane; and 4) control (no treatment). Animals were sacrificed 28 days after surgery. Histological sections revealed large amounts of newly-formed bone in all bone defects surrounding the implants treated with ePTFE membranes alone. Fibrous encapsulation of HA granules was observed in the defects of the HA granules grafting group. In the group with grafting of HA granules and covering with ePTFE membranes, small amounts of bone tissue were observed among HA granules, but most HA granules were surrounded with fibrous tissue. Bone defects were completely filled with connective tissue in the control group. There were no differences in the histological findings between Ti and HA-coated implants in all cases. Histomorphometric data disclosed that the presence of HA granules in the bone defects significantly arrested bone formation. Our study suggests that the grafting of dense HA into bone defects surrounding implants will result in fibrous healing during the early healing stage.

Uncontrolled diabetes hinders bone formation around titanium implants in rat tibiae. A light and fluorescence microscopy, and image processing study.

This study examined the influence of diabetes mellitus on bone formation around cylindrical titanium (Ti) implants (1.0 mm in diameter and 1.5 mm in length) inserted transcortically and extending into the medullary canal of rat tibiae using light and fluorescence microscopies and image processing. Forty-eight male Wistar King A rats (age 5 weeks) were used in this experiment. Streptozotocin was injected intraperitoneally to induce diabetes and the serum glucose concentration was checked to ensure the induction of diabetes prior to implant placement and at the time of sacrifice. The animals were sacrificed 7, 28, 56, or 84 days after placement. Toluidine blue-stained undecalcified sections were prepared for histological observation and image analysis. The Ti implants in the control group became increasingly encapsulated with a bone layer. The implants in the diabetes-induced (DI) group were also surrounded with a thin bone layer. Abundant adipocytes were observed in the DI group as compared with the control group. Quantitative evaluation indicated that the control group showed a significantly higher percent of bone contact, and thickness of surrounding bone and area than the DI group. Consequently, the present study suggests that uncontrolled diabetes would hinder bone formation around Ti implants in rats.

An immunocytochemical study for lysosomal cathepsins B and D related to the intracellular degradation of titanium at the bone-titanium interface.

The morphological relationship between titanium and lysosomal proteinases, cathepsins B and D, at the bone-titanium interface using titanium-coated plastic implants placed for 28 days in the tibiae of 6-week-old rats was immunocytochemically investigated by the colloidal immunogold-silver method. Under light microscopy the titanium layer appeared to make direct contact with the bone and one or a few layers of slender cells were interposed between the bone and titanium. Ultrastructurally, the titanium came in contact with the bone or the slender cell layer through a 20 to 40 nm thin amorphous zone. The slender cells at the bone-titanium interface consisted of two types; one was an osteoblast type with glycogen granules which was found along the newly-formed bone facing titanium layer. The other was a fibroblast type which came in contact with the titanium layer and occasionally endocytosed the detached titanium fragments. In addition, some of the slender cells also showed degenerative changes. Immunocytochemically, cathepsins B and/or D were sometimes colocalized in some phagolysosomes with titanium fragments. These findings suggested that the fibroblast types at the bone-titanium interface may act as scavengers to remove both cell debris and titanium by means of some endocytotic ability, and lysosomal cathepsins also developed in response to the endocytosed titanium. The osteoblast type also appears to show a high degree of osteogenic activity around the titanium-coated plastic implants.

The effects of diabetes on the interface between hydroxyapatite implants and bone in rat tibia.

We examined the influence of diabetes on the implant-bone interface of hydroxyapatite (HA) implants inserted transcortically and extending into the medullary canal of rat tibiae, and quantitatively assessed the differences in bone reaction using an image processing system. Forty male Wistar King A rats (aged 5 weeks) were used in this experiment; they were sacrificed 84 days after implant placement. Toluidine blue-stained undecalcified sections were prepared for histological observation and image analysis, and the labeled sections were observed by confocal laser scanning microscopy. The HA implants in the bone marrow area in the control group were completely encapsulated with a bone layer, and there were some osteoblast-like cells in the bone lacunae apposing the implant surface. The HA implants in the diabetes-induced (DI) group were partially surrounded with a thin bone layer, and there were some fibroblasts running parallel to the implant surface at areas of no bone contact. Quantitative evaluation indicated that the control group showed significantly higher bone contact rate, bone contact thickness, and bone contact area than the DI group. The DI group showed approximately 30% reduction in the percentage of bone contact and 50% reduction in the thickness and the area of surrounding bone tissue.

A study of the regional distribution of bone formed around hydroxyapatite implants in the tibiae of streptozotocin-induced diabetic rats using multiple fluorescent labeling and confocal laser scanning microscopy.

The present study was designed to compare the amount and regional distribution of bone formation around hydroxyapatite (HA) implants in normal (control) rats with that of animals with diabetes mellitus (DM), induced by streptozotocin 2 weeks prior to implant placement. Calcein (CAL), alizarin complexone (AL), and tetracycline (TC) were injected on the 7th, 14th, and 21st days after implantation, respectively, and the rats were sacrificed on the 28th day after implantation. Seventy-microns undecalcified sections of the HA-bone interface in both groups were then prepared for confocal laser scanning microscopy (CLSM) observation. In both groups, bone formation developed from the HA surface to the endosteum, periosteum, or bone marrow. In the control group, around the HA close to the endosteum and periosteum, the new bone showed an extensive lamination pattern of three color layers (CAL, AL, and TC), but in the DM group the labeling density of TC on the 21st day was low. In contrast, on the lateral part of the HA surface (away from the endosteum and periosteum), there was considerably less bone formation in the control group, and in the DM group it was almost completely suppressed. These findings indicate that bone formation around the HA was initiated from the HA surface in the control group, while in the DM group, bone formation along the lateral part of the HA away from the endosteum and periosteum was almost completely suppressed. Furthermore, it is also suggested that in the new bone along the HA close to the endosteum and periosteum, only calcification on the 21st day was depressed.

Histopathologic observation of seven removed endosseous dental implants.

Seven failed endosseous dental implants that were removed from humans were examined histologically. Results suggest that the hollow-basket portion or the vent should be located as far from the gingiva as possible, and that an adequate healing period is needed for implant placement following tooth extraction. In addition, findings also suggest that the hollow-basket implant is not suitable for a healing socket, that periodic inspection is necessary for two-stage implants to evaluate adaptation of the embedded junction between the abutment and implant in the gingiva, and that there is risk of coating separation from hydroxyapatite-coated implants and possibilities of coating resorption.

Histologic study of failed hollow implants.

Nine hollow dental implants that were removed from patients were examined histologically to determine whether there was a common mechanism of failure with this implant design. When a hollow implant showed saucerized bone loss at the neck portion radiologically, the hollow portion was divided histologically into soft tissue and bone tissue. In advanced cases, stratified flattened epithelium that had invaded the hollow and the dead space at the top was observed. The condition of bone tissue located in the bottom of the basket can be adversely affected by an unfavorable crown-root ratio. The presence of an empty basket may cause fracture of the basket portion. The hollow portion can foster the growth of pathogenic bacteria. The hollow-type implant may not be suitable for immediate placement because surrounding soft tissues can invade the basket immediately.

Correlation between inclination of occlusal plane and masticatory movement.

OBJECTIVES: The purpose of this study was to investigate the relationship between the inclination of the occlusal plane and masticatory movement. METHODS: Masticatory movements of 41 young adults were measured using the three-dimensional Mandibular Movement Analyzing System. The inclination of the occlusal plane was measured in the sagittal plane using a three-dimensional digitizer. RESULTS: In the sagittal plane, the masticatory closing path and the occlusal plane were consistent in maintaining a perpendicular relation with each other regardless of the inter-individual variation of the inclination of the occlusal plane. Subjects with an anteriorly inclined occlusal plane showed a vertical closing path, and subjects with a posteriorly inclined occlusal plane showed a flat closing path in the frontal plane. These characteristics were explained by the variation of the timing on the balancing-side condylar return correlated with the inclination of the occlusal plane. CONCLUSIONS: There is a significant correlation between the inclination of the occlusal plane and the direction of the closing path during mastication.

Fourteen-year survival in a case of ventricular septal perforation after myocardial infarction.

We treated a case of ventricular septal perforation (VSP) who survived for 14 years after myocardial infarction. Nine years after the onset of myocardial infarction, an apparent cardiac murmur was discovered by chance, and following further examination, the patient was diagnosed as having VSP. The patient is still in the NYHA functional class I, and requiring no surgical treatment. In general, the prognosis of myocardial infarction complicated with VSP is so poor that there have only been 14 reported cases of long survival without surgical treatment. Among these patients, only 2 survived for more than 10 years. The present case is extremely rare, and evidently is the longest living survivor with this condition yet reported.

Histologic investigation of hollow implants retrieved for psychological reasons.

OBJECTIVE: The purpose of this study was to radiologically, histologically, and histometrically evaluate bone in the hollow portion of three implants retrieved for psychological reasons. STUDY DESIGN: Three hollow implants retrieved from two patients were studied. We investigated the radiologic and histologic changes of these implants with the use of radiographs, light microscopy, image processing, and fluorescent microscopy. RESULTS: There were no radiologic and histologic degeneration around the implants. Histometric analysis of the hollow indicated that the average percentage of bone contact rate was 33.5% in case 1, 74.5% in case 2, and 18.4% in case 3; the average percentage of bone filling was 25.1%, 33.9%, and 6.6%, respectively. There was a great variation among the three cases in bone to implant contact and bone filling. CONCLUSION: The hollow portion in case 1 that penetrated into the maxillary sinus was encapsulated with fibrous tissue. The amount of bone tissue in the hollow portion seems to depend on the initial bone quality of the recipient sites.

Various designs of ceramometal crown for implant restorations.

The posterior design of the implant superstructure (the ceramometal crown) was classified into four categories: a ceramometal crown with an access hole on top; a cemented ceramometal crown; a ceramometal crown retained with a lingual screw; and a telescopic ceramometal crown. Cemented ceramometal crowns and telescopic ceramometal crowns are considered simpler, more esthetic, and more resistant to fracture among the four models.

Improved method using a bubble-free adhesion technique for the preparation of semi-serial undecalcified histologic sections containing dental implants.

The preparation technique, with the minimum of artifacts for the semi-serial undecalcified histologic sections containing dental implants, is presented in this study. The sections enabled finer light-microscopic observations to be made. A formalin-fixed tissue block containing a dental implant was dehydrated in ethanol and acetone, and then embedded in polyester resin under 76 cm Hg reduced pressure. The embedded block was trimmed by a cutter and ground by abrasive paper. In a 1.5 Kg f/cm2 pressurized chamber, its polished surface was bonded to a methacrylate slide by means of ethylcyanoacrylate used in an adhesion loading device. This meant that no bubbles could arise in the interface between the slide and the block. The slide-block was then attached to an adsorptive specimen-holder of a hard-tissue cutting machine and cut to a thickness of approximately 50 microns, with use of a diamond blade. The slide-section was ground to 15-40 microns with wet-type abrasive paper and film on a polishing table. Etching with weak acid and surface staining with toluidine blue and methylene blue/basic fuchsin/light green were performed on the section.