Biomedical subjects

Kunio Doi

Publications and source records attributed to Kunio Doi.

At least 55 records · Page 3Linked to original sources

PubMed2005

Microarray analysis of genes in fetal central nervous system after ethylnitrosourea administration.

BACKGROUND: Ethylnitrosourea (ENU), a monofunctional alkylating agent, induces apoptosis and cell cycle arrest in neuroepithelial cells, neural stem cells in the fetal central nervous system (CNS). These effects occur immediately after the administration of ENU to pregnant animals resulting in fetal brain anomalies and long-term effects include brain tumors in the offspring. METHODS: Changes in gene expression were investigated in the fetal CNS after ENU administration to pregnant rats using microarray to identify the genes involved in the injury and recovery of the fetal CNS. RESULTS: The up-regulation of 21 genes in injury and 15 genes in recovery phases and down-regulation of 5 genes in injury and 3 genes in recovery phases were identified. The genes up-regulated in the injury phase contained p53-target genes that mediate apoptosis and cell cycle arrest, and those in the recovery phase contained cell proliferation-promoting genes. The genes down-regulated in the injury phase contained cholesterol biosynthesis-related genes. In addition, there were some genes that have not been identified to be involved in the CNS injury and recovery. CONCLUSIONS: The present study will provide a better understanding of the mechanisms of development, regeneration and carcinogenesis of the CNS as well as the mechanisms of ENU-induced fetal CNS injury and recovery.

Alkylating Agents↗

PubMed2005

Evaluation of automated lung nodule detection on low-dose computed tomography scans from a lung cancer screening program(1).

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the performance of a fully automated lung nodule detection method in a large database of low-dose computed tomography (CT) scans from a lung cancer screening program. Because nodules demonstrate a spectrum of radiologic appearances, the performance of the automated method was evaluated on the basis of nodule malignancy status, size, subtlety, and radiographic opacity. MATERIALS AND METHODS: A database of 393 thick-section (10 mm) low-dose CT scans was collected. Automated lung nodule detection proceeds in two phases: gray-level thresholding for the initial identification of nodule candidates, followed by the application of a rule-based classifier and linear discriminant analysis to distinguish between candidates that correspond to actual lung nodules and candidates that correspond to non-nodules. Free-response receiver operating characteristic analysis was used to evaluate the performance of the method based on a jackknife training/testing approach. RESULTS: An overall nodule detection sensitivity of 70% (330 of 470) was attained with an average of 1.6 false-positive detections per section. At the same false-positive rate, 83% (57 of 69) of the malignant lung nodules in the database were detected. When the method was trained specifically for malignant nodules, a sensitivity of 80% (55 of 69) was attained with 0.85 false-positives per section. CONCLUSION: We have evaluated an automated lung nodule detection method with a large number of low-dose CT scans from a lung cancer screening program. An overall sensitivity of 80% for malignant nodules was achieved with 0.85 false-positive detections per section. Such a computerized lung nodule detection method is expected to become an important part of CT-based lung cancer screening programs.

Adult↗

PubMed2005

Investigation of misfiled cases in the PACS environment and a solution to prevent filing errors for chest radiographs.

RATIONALE AND OBJECTIVE: The aim of the study was to survey misfiled cases in a picture archiving and communication system environment at two hospitals and to demonstrate the potential usefulness of an automated patient recognition method for posteroanterior chest radiographs based on a template-matching technique designed to prevent filing errors. MATERIALS AND METHODS: We surveyed misfiled cases obtained from different modalities in one hospital for 25 months, and misfiled cases of chest radiographs in another hospital for 17 months. For investigating the usefulness of an automated patient recognition and identification method for chest radiographs, a prospective study has been completed in clinical settings at the latter hospital. RESULTS: The total numbers of misfiled cases for different modalities in one hospital and for chest radiographs in another hospital were 327 and 22, respectively. The misfiled cases in the two hospitals were mainly the result of human errors (eg, incorrect manual entries of patient information, incorrect usage of identification cards in which an identification card for the previous patient was used for the next patient's image acquisition). The prospective study indicated the usefulness of the computerized method for discovering misfiled cases with a high performance (ie, an 86.4% correct warning rate for different patients and 1.5% incorrect warning rate for the same patients). CONCLUSION: We confirmed the occurrence of misfiled cases in the two hospitals. The automated patient recognition and identification method for chest radiographs would be useful in preventing wrong images from being stored in the picture archiving and communication system environment.

Database Management Systems↗

PubMed2005

False-positive reduction in computer-aided diagnostic scheme for detecting nodules in chest radiographs by means of massive training artificial neural network.

RATIONALE AND OBJECTIVE: We developed a technique that uses a multiple massive-training artificial neural network (multi-MTANN) to reduce the number of false-positive results in a computer-aided diagnostic (CAD) scheme for detecting nodules in chest radiographs. MATERIALS AND METHODS: Our database consisted of 91 solitary pulmonary nodules, including 64 malignant nodules and 27 benign nodules, in 91 chest radiographs. With our current CAD scheme based on a difference-image technique and linear discriminant analysis, we achieved a sensitivity of 82.4%, with 4.5 false positives per image. We developed the multi-MTANN for further reduction of the false positive rate. An MTANN is a highly nonlinear filter that can be trained with input images and corresponding teaching images. To reduce the effects of background levels in chest radiographs, we applied a background-trend-correction technique, followed by contrast normalization, to the input images for the MTANN. For enhancement of nodules, the teaching image was designed to contain the distribution for a "likelihood of being a nodule." Six MTANNs in the multi-MTANN were trained by using typical nodules and six different types of non-nodules (false positives). RESULTS: Use of the trained multi-MTANN eliminated 68.3% of false-positive findings with a reduction of one true-positive result. The false-positive rate of our original CAD scheme was improved from 4.5 to 1.4 false positives per image, at an overall sensitivity of 81.3%. CONCLUSION: Use of a multi-MTANN substantially reduced the false-positive rate of our CAD scheme for lung nodule detection on chest radiographs, while maintaining a level of sensitivity.

False Positive Reactions↗

PubMed2005

How can a massive training artificial neural network (MTANN) be trained with a small number of cases in the distinction between nodules and vessels in thoracic CT?

RATIONALE AND OBJECTIVES: To demonstrate that a massive training artificial neural network (MTANN) can be adequately trained with a small number of cases in the distinction between nodules and vessels (non-nodules) in thoracic computed tomography (CT) images. MATERIALS AND METHODS: An MTANN is a trainable, highly nonlinear filter consisting of a linear-output multilayer artificial neural network model. For enhancement of nodules and suppression of vessels, we used 10 nodules and 10 non-nodule images as training cases for MTANNs. The MTANN is trained with a large number of input subregions selected from the training cases and the corresponding pixels in teaching images that contain Gaussian distributions for nodules and zero for non-nodules. We trained three MTANNs with different numbers (1, 9, and 361) of training samples (pairs of the subregion and the teaching pixel) selected from the training cases. In order to investigate the basic characteristics of the trained MTANNs, we applied the MTANNs to simulated CT images containing various-sized model nodules (spheres) with different contrasts and various-sized model vessels (cylinders) with different orientations. In addition, we applied the trained MTANNs to nontraining actual clinical cases with 59 nodules and 1,726 non-nodules. RESULTS: In the output images for the simulated CT images by use of the MTANNs trained with small numbers (one and nine) of subregions, model vessels were clearly visible and were not removed; thus, the MTANNs were not trained properly. However, in the output image of the MTANN trained with a large number of subregions, various-sized model nodules with different contrasts were represented by light nodular distributions, whereas various-sized model vessels with different orientations were dark and thus were almost removed. This result indicates that the MTANN was able to learn, from a very small number of actual nodule and non-nodule cases, the distinction between nodules (spherelike objects) and vessels (cylinder-like objects). In nontraining clinical cases, the MTANN was able to distinguish actual nodules from actual vessels in CT images. For 59 actual nodules and 1,726 non-nodules, the performance of the MTANN decreased as the number of training samples (subregions) in each case decreased. CONCLUSIONS: The MTANN can be trained with a very small number of training cases (10 nodules and 10 non-nodules) in the distinction between nodules and non-nodules (vessels) in CT images. Massive training by scanning of training cases to produce a large number of training samples (input subregions and teaching pixels) would contributed to a high generalization ability of the MTANN.

Algorithms↗

PubMed2005

Gene expression profiling in streptozotocin treated mouse liver using DNA microarray.

Streptozotocin (SZ) is known to exert toxic effects not only on pancreatic islet beta cells but also on other organs including liver. For analyzing changes in genes expression associated with SZ toxicity, we performed DNA microarray analyses on the liver obtained from SZ-treated mice. Eight-week-old male ICR mice were treated i.p. with 200 mg/kg of SZ, and the blood and liver were taken at 6, 24 and 48 h after the treatment. Labeled cRNA prepared from total RNA of the liver was hybridized to the GeneChip Murine Genome U74A V.2 (Affymetrix). The number of the probe sets, which were clearly up-regulated or down-regulated, were over 100 at 6 and 24h after the SZ-treatment, and it decreased at 48 h after the treatment. Many of the up-regulated genes were categorized into cell cycle/apoptosis related genes, immune/allergy related genes and stress response/xenobiotic metabolism related genes. On the other hand, genes related to glucose, lipid and protein metabolisms were down-regulated. These changes started prior to the elevation of the serum glucose levels, indicating the direct action of SZ on the liver rather than the secondary effect of diabetes. This may be related with the previously reported hepatic changes such as lipid peroxidation, mitochondrial swelling and inhibition of hepatocyte proliferation observed before the development of hyperglycemia.

Animals↗

PubMed2005

Morphological and gene expression analysis in mouse primary cultured hepatocytes exposed to streptozotocin.

Streptozotocin (SZ) is known to exert toxic effects not only on pancreatic islet beta cells but also on other organs including the liver. For analyzing direct effects of SZ on hepatocytes, we performed morphological analysis and DNA microarray analysis on mouse primary cultured hepatocytes. Hepatocytes were taken from non-treated Crj:CD-1(ICR) mice. The primary cultured hepatocytes were treated with SZ at concentrations of 0, 1, 3, 10, 30 and 100 mM. After the treatment for about 6 or 24h, cell survival assay using tetrazolium salt (WST-1), light microscopic/electron microscopic analysis and gene expression analysis were performed. For the gene expression analysis, target (labeled cRNA) prepared from total RNA of the hepatocytes was hybridized to the GeneChip Murine Genome U74A V.2 (Affymetrix). The signal intensity calculation and scaling were performed using Microarray Suite Software Ver 5.0. IC50 of the cell survival assay was around 62 mM at 6 h exposure and 7 mM at 24 h exposure. Marked chromatin margination was observed in nuclei of the hepatocytes treated with SZ at concentrations of 3 or 10mM. Gene expression analysis revealed similar expression changes to those of in vivo, i.e. up-regulation in cell proliferation/ apoptosis related genes, and down-regulation of lipid metabolism related genes. These results potently supported the hypothesis that many of the hepatic alteration including histopathological and gene expression changes are induced by direct effect of SZ rather than by the secondary effect of the hyperglycemia or hypoinsulinemia.

Animals↗

PubMed2005

Nitrofurazone-induced gene expressions in rat hepatocytes and their modification by N-acetylcysteine.

The antibiotic nitrofurazone (NF) at a subtoxic dose has been shown to increase hepatocyte DNA synthesis with no preceding cell damage or necrosis. This was suppressed by concomitant administration of the antioxidant N-acetylcysteine (NAC), which suggests that free radical production is involved in the process. In this study, male F344 rats were given a single oral subtoxic dose of NF to investigate the changes in genes implicated in hepatocyte proliferation between 1 and 20h postdose by real-time PCR. Some rats were also given NAC to examine the involvement of free radicals. There were transient and sequential increases in mRNA levels of c-myc and c-jun shortly after the administration, followed by tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha), c-Ha-ras, and cyclin E. The increases were blocked by concomitant administration of NAC. In contrast, there were no NF-specific increases in c-fos, hepatocyte growth factor, epidermal growth factor or cyclin D1 mRNAs. These results indicate that the induction of hepatocyte proliferation by NF is triggered by free radicals, with a pathway involving increases in c-jun, c-myc, TNF-alpha, TGF-alpha, c-Ha-ras, and cyclin E. The results also indicate that NF-induced proliferation resembles that of other mitogens.

Acetylcysteine↗

PubMed2005

Microarray analysis of T-2 toxin-induced liver, placenta and fetal liver lesions in pregnant rats.

Pregnant rats on day 13 of gestation were treated orally with 2 mg/kg of T-2 toxin and sacrificed at 1, 3, 6, 9 and 12 h after the treatment (HAT). Histopathologically, the number of apoptotic cells was increased in the liver, placenta and fetal liver (peaked at 6, 12 and 9-12 HAT, respectively). To examine the gene expression profiles, we performed microarray analysis of these tissues at two selected time points based on the results of the TdT-mediated dUTP nick end labeling (TUNEL) staining. Increased expression of oxidative stress- and apoptosis-related genes was detected in the liver of dams, placenta and fetal liver of pregnant rats treated with T-2 toxin at the peak time point of apoptosis. Decreased expression of lipid metabolism- and drug-metabolizing enzyme-related genes was also detected in these tissues. The results suggested that the mitogen-activated protein kinase (MAPK) pathway might be involved in the mechanism of T-2 toxin-induced apoptosis. In addition, increased expression of the c-jun gene was consistently observed in these tissues. Our results suggest that the mechanism of T-2 toxin-induced toxicity in pregnant rats is due to oxidative stress followed by the activation of the MAPK pathway, finally inducing apoptosis. The c-jun gene may play an important role in T-2 toxin-induced apoptosis.

Administration, Oral↗

PubMed2005

Ethylnitrosourea induces neural progenitor cell apoptosis after S-phase accumulation in a p53-dependent manner.

Neural progenitor cells populate the ventricular zone of the fetal central nervous system. In this study, immediately after the administration of ethylnitrosourea (ENU), an alkylating agent, an accumulation of neural progenitor cells in the S phase was observed. This event was caused by the inhibition or arrest of DNA replication rather than acceleration of the G1/S transition. Soon after this accumulation reached its peak, the number of cells in the G2/M phase decreased and the apoptotic cell count increased. In p53-deficient mice, both ENU-induced apoptosis and S-phase accumulation were almost completely abrogated. These findings indicate that ENU inhibits or arrests DNA replication in neural progenitor cells during the S phase and then evokes apoptosis before the cells enter the G2 phase. Furthermore, these data also demonstrate that both ENU-induced apoptosis and cell cycle perturbation in the S phase require p53.

Animals↗

PubMed2005

Induction of cytochrome P450 isozymes by phenobarbital in pregnant rat and fetal livers and placenta.

Cytochrome P450 (CYP) isozymes are important in metabolizing xenobiotics. They are found in extrahepatic tissues such as placenta as well as liver. Previously, we reported that CYP3A1 was detected in the cytoplasm of giant cells in the trophoblastic region of placenta of rats through pregnancy. In this study, we examined the changes in the expression of CYP proteins in the pregnant rat and fetal livers and placenta after treatment with phenobarbital (PB), one of the antiepileptic drugs which is well known to induce several phase I and phase II drug metabolizing enzymes in the liver. Namely, F344 pregnant rats were treated with PB (80 mg/kg, i.p.) from 13 days of gestation (DG) to 16 DG. All animals were sacrificed on 17 DG, and Western blot analysis and immunohistochemical staining on nine CYP proteins (CYP1A1, CYP2B1, CYP2C6, CYP2C12, CYP2D1, CYP2D4, CYP2E1, CYP3A1, and CYP4A1) and histological examination were done in the dam's liver, placenta, and the fetal liver. Western blot analysis revealed that CYP3A1 protein was significantly induced, CYP2B1 protein was detected, and CYP2D1 protein was significantly decreased in the dam's liver after PB-treatment. In placenta, only CYP3A1 was detected with no difference between control and PB-treated animals. The results of immunohistochemical staining corresponded closely to those of Western blot analysis in the dam's liver and placenta. In the fetal liver, CYP3A1 and CYP2C6 proteins were significantly induced after the PB-treatment, but their immunostainability was not prominent. The present results are considered useful as a basis for further investigation of drug metabolism in pregnant animals.

Animals↗

PubMed2005

T-2 toxin-induced apoptosis in rat keratinocyte primary cultures.

T-2 toxin, a kind of trichothecene mycotoxins produced by the genus Fusarium, induces apoptosis in basal keratinocytes when topically applied to the dorsal skin of rats. In the present study, direct effects of T-2 toxin on keratinocyte primary cultures obtained from newborn rats were examined after the third passage. Keratinocyte medium containing 0.25 microg/ml of T-2 toxin dissolved in dimethyl sulfoxide or solvent alone was added to 4-day cultures and incubated at 37 degrees C. At 0.5, 1, 3, 5, 7, and 9 h after treatment (h), feeder layer was separated from flasks, and cells were trypsinized. Cell viability was estimated by trypan blue exclusion method. In addition, RNA was obtained and RT-PCR was performed. Samples obtained from slide cultures at 3, 6, 9, and 12 h were fixed in 4% paraformaldehyde or 2.5% glutaraldehyde for morphological examination. After T-2 toxin application, cell viability decreased to 40% at 3 h. At 6 h, small-sized keratinocytes showed pyknosis or karyorrhexis, resulting in detachment from slides. The number of such cells increased until 12 h. These small-sized keratinocytes showed ultrastructural changes characteristic for apoptosis. At the same time, large squamous keratinocytes showed intracytoplasmic edema. The expression of apoptosis-related genes (c-fos and c-jun) and cytokines (TNF-alpha and IL-1beta) mRNAs markedly increased before the development of apoptosis. These findings indicate that c-fos and c-jun oncogenes and TNF-alpha and IL-1beta play an important role in the development of T-2 toxin-induced apoptosis in keratinocytes.

Animals↗

PubMed2005

Microarray analysis on CYPs expression in pregnant rats after treatment with pregnenolone-16alpha-carbonitrile and phenobarbital.

We previously reported the protein expression profiles of nine cytochrome P450 isozymes (CYPs) in pregnant rat's liver, fetal liver, and placenta after treatment with pregnenolone-16alpha-carbonitrile (PCN), dexamethasone (DEX), or phenobarbital (PB). In this study, the gene expression of 40 CYPs and 2 orphan nuclear receptors for CYP inducers, that is, Nr1i2 (CYP3A subfamily inducible by PCN) and Nr1i3 (CYP2B subfamily inducible by PB), in pregnant rat's liver, fetal liver, and placenta was investigated at one time. Fischer 344 (F344) pregnant rats were daily treated intraperitoneally with 50 mg/kg of PCN or 80 mg/kg of PB from 13 to 16 days of gestation (DG). They were sacrificed on 17 DG, and microarray analysis using Affymetrix Rat Expression Array 230A was performed. Ten genes expression significantly increased in dam's liver in PCN group, and seven genes expression in PB group. On the other hand, four genes expression increased in fetal liver in PCN group, and three genes expression increased in PB group. Being common to dam's and fetal livers, the gene expression of Cyp3A1 (CYP3A subfamily) and cytochrome P-450e (CYP2B subfamily) increased in both PCN and PB groups. In placenta, the expression of Cyp3A1 gene was significantly induced in PB group, and it also showed a tendency to increase in PCN group. The expression of Nr1i2 gene was significantly elevated only in dam's liver of PCN group, while the expression of Nr1i3 gene showed no changes in all groups. The results of the present study of 40 CYPs gene expression mostly corresponded to our previous reports on 9 CYPs protein expression.

Animals↗

PubMed2005

Effects of pregnancy on CYPs protein expression in rat liver.

A body of evidence suggests that pregnancy may be responsible for the depression in the microsomal enzyme activity and the reduction in the total content of cytochrome P450 (CYP) in the rat liver. However, changes in expression of individual CYP isozyme remain poorly known. The current study was designed to examine the changes in CYPs protein expression in the liver of F344 rats in midpregnancy and late pregnancy by Western blot analysis and immunohistochemistry. Total nine antirat CYPs antibodies (CYP1A1, CYP2B1/CYP2B2, CYP2C6, CYP2C12, CYP2D1, CYP2D4, CYP2E1, CYP3A1, and CYP4A1) were used. In comparison with age-matched nonpregnant control rats, there were significant decreases in hepatic levels of CYP2B2, CYP2C6, and CYP4A1 in midpregnancy (day 13) and CYP2B2, CYP2C6, CYP4A1, CYP1A1, CYP2B1, and CYP2E1 in late pregnancy (day 19). The expression of CYP2C12, CYP2D1, and CYP 3A1 did not differ between nonpregnant and pregnant rats, and CYP2D4 was not detectable in microsomal proteins obtained from nonpregnant and pregnant rats at a protein loading of 20 mug total protein per lane. Immunohistochemistry showed that there were no differences in the distribution and degree of immunostainability for the abovementioned antibodies to nine CYPs between pregnant and nonpregnant rats.

Animals↗

PubMed2005

Encephalomyocarditis (EMC) virus-induced sialodacryoadenitis in mice.

The mode of occurrence of the D variant of encephalomyocarditis (EMC-D) virus-induced acute sialodacryoadenitis was investigated using three strains of mice differing in their sensitivity to EMC-D virus-induced diabetes (C57BL/6: resistant; BALB/c: moderately sensitive; DBA/2: highly sensitive). Mice were intranasally inoculated with high (10(5) PFU/mouse) or low dose (10(2) PFU/mouse) of EMC-D virus. Although there were individual differences, the blood virus titer generally reached the peak earlier in the high-dose group than in the low-dose group. Signals of viral RNA and histopathological changes were seen in parotid glands and intraorbital and extraorbital lachrymal glands. In these glands, signals of viral RNA and histopathological changes were detected only in acinar cells and initial lesions were characterized by pyknosis of acinar cells. Coagulative necrosis with interstitial inflammatory cell infiltration developed later in parotid glands of BALB/c mice of the high-dose group and in intraorbital and extraorbital lachrymal glands of all groups except for C57BL/6 mice of the low-dose group. Such changes were not observed in epithelial cells of the ductal system. The present results indicate that EMC-D virus shows clear tissue and cell tropism within the salivary and lachrymal glands, probably due to the distribution of receptors for EMC virus.

Animals↗

PubMed2005

Computer-aided diagnosis in thoracic CT.

Computer-aided diagnosis (CAD) provides a computerized diagnostic result as a "second opinion" to assist radiologists in the diagnosis of various diseases by use of medical images. CAD has become a practical clinical approach in diagnostic radiology, although, at present, primarily in the area of detection of breast cancer in mammograms. Currently, a large research effort has been devoted to the detection and classification of various lung diseases in thoracic computed tomography (CT) images. We describe in this article the current status of the development of CAD schemes in thoracic CT, including nodule detection, distinction between benign and malignant nodules, and detection, characterization, and differential diagnosis of diffuse lung disease. Observer performance studies indicate that these CAD schemes would be useful in clinical practice by providing radiologists with computer output as a "second opinion."

Humans↗

PubMed2005

Temporal reduction in size of salivary acinus in rats induced by theophylline.

Repeated administration of theophylline, a phosphodiesterase inhibitor, induces the enlargement of the salivary glands in rats. Time-course changes after a single administration of theophylline were examined in the salivary glands, including phosphodiesterase enzyme activity, and the expression of aquaporin 5 (AQP5), a water channel. We also examined the contribution of beta-adrenergic receptors to theophylline-induced salivary changes. Male F344 rats were given 50 mg/kg of theophylline intraperitoneally either alone or concurrently with a 10 mg/kg subcutaneous injection of propranolol. After treatment with theophylline alone, the weight and histology of the submaxillary and parotid glands were examined. Phosphodiesterase activity and AQP5 were detected by enzyme- and immuno-histochemistry, respectively. At 4 hours, 8 hours, or both, organ weights were decreased with depletion of secretory vesicles in the acinar cells. In the submaxillary glands, reduced activity of phosphodiesterase and increased expression of AQP5 in the intercalated ducts were observed at 4 hours. When co-administered, propranolol partially abolished theophylline-induced glandular reduction. These results suggest that the theophylline-induced transient reduction in size of the salivary glands is attributable not only to phosphodiesterase inhibition but also to beta-adrenergic receptor activation and that the intercalated ducts in submaxillary glands play a role in the production of saliva.

Adrenergic beta-Antagonists↗

PubMed2005

Histopathological study of time course changes in PTHrP-induced incisor lesions of rats.

Parathyroid hormone related peptide (PTHrP) was discovered as a causative factor of humoral hypercalcemia of malignancy (HHM). In the present study using HHM model rats, the time course of odontoblastic response to PTHrP and its relation to incisal fracture were elicited. Nude rats were implanted with PTHrP-expressing tumor (LC-6) cells, mandibular incisors were collected at several time points. Microscopically 3 distinctive types of odontoblastic/dentin lesions were observed. Hypercalcfied dentin, which was reported as hypercalcemia-induced lesion in previous reports, observed in all areas of the dentin from week 5-10 samplings. Dentin niche, observed solely in week-10 sampling point, exhibited a nature identical to that of reparative odontoblast reported in the literatures of various cytotoxic agents. Since cytotoxicites were neither observed prior to the lesions nor reported as a role of PTHrP, the reparative response may have derived from highly sustained levels of PTHrP. Loss of columnar odontoblasts height was initially observed at week-5 time point in the middle section of the incisor. This primary loss of cell height prior to incisor fracture was considered to be the earliest response to the increased PTHrP levels of this model.

Animals↗