Katsuichiro Ohsaki

Histological reaction to hydroxyapatite in the middle ear of rats

OBJECTIVE Present study was performed to evaluate the histological response of rat middle ear mucosa following implantation of Apaceram granules, a synthetic dense hydroxyapatite [Ca10(PO4)6(OH)2], prepared from commercially available synthetic auditory ossicle, and to assess the precise histological response of the rat middle ear to implantation of Apaceram granules, by microscopic examination of mucosal tissue at various time points after implantation. METHODS Apaceram granules were implanted in the temporal bulla of 32 rats. As control, sham surgery was performed in a group of ten rats. Bulla specimens were removed at 1, 3, 7, 14, and 30 days after surgery in the implant and control groups, and at 90, 180 and 300 days in the implant group. Specimens were decalcified, sectioned at a thickness of 6 microm, and stained with haematoxylin and eosin, and Mallorys azan for histological examination of mucosal tissue. RESULTS Evidence of inflammatory reaction was slightly greater in the implant group than in controls. Lymphocyte and macrophage counts were higher in the implant group 1 day after surgery, but decreased to similar levels by day 3, and continued to decrease thereafter, and few were observed in the implant group at 300 days. Neutrophils observed at 1 day after surgery were not evident in either group at 3 days. Gradual fibrosis development continued in both groups over all time points studied. Foreign body giant cells were never observed in either group. No bony reaction was observed in any specimen. CONCLUSION The results of this study suggest that Apaceram is biocompatible and suitable for reconstructive ear surgery.

Thickness of fibrous capsule after implantation of hydroxyapatite in subcutaneous tissue in rats

The present study evaluates in rats the histomorphometrical thickness of fibrous capsules that surround hydroxyapatite (HA) disks after implantation. HA disks were implanted into the subcutaneous tissue of 79 rats for 1 day to 20 months. Decalcified histological sections stained with hematoxylin and eosin were examined. Fibrous capsule thickness (FCT) was measured using an objective micrometer. On the fourteenth day, primary fibrous capsules formed around implants. From that time point FCT increased with time of implantation. Within a given sample, FCT differed from one portion of the fibrous capsule to another, depending on which site faced the disks. FCT was thickest at the upper and lower portions of the disks, thinner at the lateral portions, and thinnest at the upper and lower ring-shaped portions. Two possible explanations for the above findings are discussed in this paper: (1) The area of contact between disk and tissue differs. (2) Chemical stimulation of implanted material caused by demineralization and remineralization may result from the varying thicknesses of fibrous capsules. FCT from upper and lower portions of HA disks increased by over 200% in the first 10 months and steadily increased about 20% over the next 10 months. Many studies have concluded that HA is useful for reconstructive surgery, so the long-term effects of FCT need further study.

MALIGNANT FIBROUS HISTIOCYTOMA OF THE MAXILLARY SINUS

A case of malignant fibrous histiocytoma arising primarily in the left maxillary sinus is described. The patient, a 39‐year‐old male, who had suffered from sinusitis for 20 years, began to have paresthesia or sharp pain of the left side of the face and toothaches of the left maxilla. At operation a white fibrous tumor developing extensively from the lateral wall to the upper and medial walls of the left maxillary sinus and into the ethmoidal sinus was noted. Following gradual progression of dyspnea, he died approximately one year after the onset in spite of radiation therapy and anticancer chemotherapy. An autopsy revealed recurrence of the tumor in the left maxillary sinus with wide‐spread metastases to the lungs, pleurae, pancreas, kidneys and bone marrows. The direct cause of death was respiratory failure due to extensive growths of the pulmonary and pleural metastases.

Long-term observation of subcutaneous tissue reaction to synthetic auditory ossicle (Apaceram) in rats

The present study evaluates histological characteristics of the soft tissue response to long-term implantation of Apaceram discs composed of dense hydroxyapatite in rats. Discs were implanted into the subcutaneous tissue of 76 rats for six to 20 months. Decalcified histological sections stained with haematoxylin and eosin (H & E) and Mallorys azan were examined. Different cell types surrounding implants were counted. The greatest proportion of macrophages was found at six months (13.5 per cent). This proportion gradually decreased to four per cent at 20 months. Small numbers of lymphocytes and foreign body giant cells were observed in every group, but neither neutrophils nor osteogenesis were observed in any specimens. Results of the present study and previous related studies indicate that despite reappearance of a small number of macrophages six months after implantation, Apaceram is useful for reconstructive surgery.

Subcutaneous tissue reaction to synthetic auditory ossicle (Apaceram ® ) in rats

A study was carried out in order to obtain further information about the soft tissue response to thin Apaceram discs of dense hydroxyapatite (HA) implanted in rats for various periods of time between one day and 10 months. The Apaceram discs were implanted subcutaneously into the interscapular region of 33 rats. A sham operation was performed on eight rats used as controls. Decalcified histological sections stained with haematoxylin and eosin and Mallorys azan were examined and the different cell types found around the implants were counted. It was found that an acute inflammatory reaction occurred after one day and disappeared at about two weeks after implantation. In the test groups, macrophages and lymphocytes disappeared about one week later, and no inflammatory reaction was observed from one to three months. However, a tissue reaction occurred at six months with the appearance of macrophages and lymphocytes, and decreased gradually at 10 months. Meanwhile, a few foreign body giant cells at the Apaceram-tissue interface and a thick layer of fibrous connective tissue around the Apaceram disc were observed at 10 months. No osteogenesis was observed in any specimen. The results obtained so far suggest that Apaceram is still a useful material for reconstructive surgery, despite the possible appearance of a slight macrophage reaction at six months.

Mechanism of bone destructiondue to middle ear cholesteatoma as revealed by laser-Raman spectrometry

In an investigation of the mechanism of bone destruction caused by chronic otitis media complicated with cholesteatoma, both the processes of demineralization and remineralization were studied in an animal model and clinically at the molecular level, using a laser-Raman spectrometer. From this investigation, it is proposed that the mechanism of bone destruction associated with cholesteatoma is a form of demineralization.

Subcutaneous inflammatory reaction to a synthetic auditory ossicle (Bioceram) in rats.

Cellular response and inflammatory reaction to synthetic auditory ossicle (Bioceram) made from aluminium oxide are investigated. Local inflammatory effects are important in wound healing and in determining biocompatibility of an implant, necessitating the study of biologic effects of implants, especially inflammation and fibrous capsule formation. Bioceram discs were implanted subcutaneously in the interscapular region of rats for various periods of time, ranging from 1 day to 300 days. Histological sections 6 microns thick were stained with haematoxylin and eosin. Cell types around the implants were examined quantitatively by light microscopy. Inflammatory cell reaction to Bioceram decreased rapidly within 14 days, similar to the reaction in control groups. From 30 days to 300 days after implantation, there was continuous reduction to very low levels for macrophages and lymphocytes, but fibrous connective tissue capsule around implants matured. Preliminary results suggest that Bioceram is a satisfactory biocompatible material for reconstructive surgery from the viewpoint of cellular response. We also briefly discuss the different tissue responses in light of our previous study on hydroxyapatite (Apaceram).

Fibrinolytic activity of middle ear fluid in otitis media with effusion.

In order to investigate the prolonged factors of otitis media with effusion, hydrolytic activities for specific substrates of plasmin and plasminogen activator (P.G.-activator) and the activity for fibrin degradation (fibrinolysis) were measured. Materials were middle ear fluids of 36 cases diagnosed as unilateral otitis media with effusion. Age of the patients were from 28 to 88 years old (mean: 61.3). Using specific substrates, determinations of P.G.-activator activity and plasmin activity were made by the method of Claeson et al. and fibrinolysis was determined by the standard fibrin plate. The results are shown below: 1) Both activities for decomposition of amide against the specific substrates of plasmin and of P.G.-activator were revealed. 2) Concerning fibrinolysis in all cases, we divided them into 3 groups; fibrinolysis (-) group of 8 cases (22.2%) which could not dissolve fibrin at all, fibrinolysis (+) group of 17 cases (47.2%) which could dissolve fibrin. Fibrinolysis (+/-) group of 11 cases (30.6%) of which the presence of fibrin dissolution was unknown. 3) The progress of fibrinolysis was observed by serial collection of middle ear fluid in the same side ear of 5 cases out of 17 cases having much activity for fibrin degradation, and lowering of fibrinolytic activity was revealed in 4 out of these 5 cases as the result. On the basis of these results, we discussed on the process of prolongation in this disease from the standpoint of the presence of fibrinolytic activity in the middle ear fluid.

The effect of tranexamic acid on cochlear blood flow in guinea pigs measured by laser Doppler flowmetry

OBJECTIVE This study investigated the vasoactive effect of tranexamic acid on the cochlear blood flow in guinea pigs. METHOD 3 ml solution (infusion speed, 0.5 ml/min) containing different concentrations of tranexamic acid was intravenously infused into 15 guinea pigs under general anesthesia. The guinea pigs were grouped according to four levels of dosage of the medicine (470 mg/kg, n=6; 220 mg/kg, n=3; 4 mg/kg, n=3; 1 mg/kg, n=3). Before administering medicine, saline solution was administered in similar volume and speed as a control. The cochleas were surgically exposed and laser Doppler flowmetry monitored cochlear blood flow volume (CBF). The left femoral artery was cannulated to permit a transducer to monitor systemic blood pressure (BP). RESULTS (1) Stimulatory effect of tranexamic acid on CBF was dose-dependent at concentrations of 1-470 mg/kg and, (2) the time course of changes in CBF was almost identical to that in BP following tranexamic acid administration. CONCLUSION Preliminary findings suggest that intravenous administration of tranexamic acid increases CBF due to vasomotorial mechanism effect on BP.

Reproducibility of pitch-matching test for tinnitus. Using a heptatonic scale.

We evaluated the reproducibility of measured values obtained using a heptachord pitch-matching test (PMT). Investigation of the measured values by considering the minimum unit width limits of the testing scale revealed that the coincidence ratios of the measured values of intra-daily variations, intra-weekly variations and eight values measured consecutively in one test were as high as 100%, 94.8% and 83.3%, respectively. We therefore concluded that the reproducibility of this method is satisfactory. The measured values obtained by both ordinary one-octave-interval and heptachord PMT are compared in this article.