Biomedical subjects

T Masegi

Publications and source records attributed to T Masegi.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effects of atropine sulfate on rat harderian glands: correlation between morphological changes and porphyrin levels.

We examined the correlation between histopathological changes and porphyrin levels in the Harderian glands of male rats after treatment with atropine sulfate. After a single administration of atropine sulfate (250 mg/kg/day), the porphyrin levels in the Harderian glands gradually increased, beginning from 2 hr after administration, and at 36 hr reached a maximum level, which was about 7 times higher than that of the control animals. Histopathologically, the Harderian glands showed marked luminal dilatation and a brownish pigment accumulation in the lumina 6 hr after a single dose. Under daily repeated administrations of atropine sulfate (250 mg/kg/day), the highest porphyrin levels in the Harderian glands were observed 24 hr after the third dose, and were about 9 times higher than those of the control animals. However, beginning from one week after the initial dose, much lower peak porphyrin levels were observed 6 hr after each dose. The maximum porphyrin levels were only twice as high as those of the control animals, and they returned to the control levels 24 hr after each atropine dose. Histological examinations of the Harderian glands revealed that repeated administrations of atropine sulfate induced the same histopathological changes observed after a single atropine administration, and that no aggravated dilation of the lumina or pigmentation in the lumina appeared after such repeated administrations. The degree and incidence of the histopathological changes observed correlated well with the porphyrin levels. Some animals showed a degeneration of the glandular epithelium after 4 weeks of treatment, and the frequency increased slightly after 13 weeks of treatment. The present study suggests that atropine suppresses the expulsion of secretory materials, including porphyrin, from the glandular lumen of the Harderian glands, and thereafter an excessive accumulation of porphyrin induces luminal dilatation. These changes were gradually reduced by repeated administrations. The degeneration of the glandular epithelium after repeated administration might be a consequence of retention of an excessive accumulation of porphyrin.

Animals↗

PubMed2000

Large amount of vitamin A has no major effects on thyroidal hormone synthesis in two-stage rat thyroid carcinogenesis model using N-bis(2-hydroxypropyl)nitrosamine and thiourea.

In our previous investigation, which focused on two-stage carcinogenicity in the thyroid, rats were administered N-bis(2-hydroxypropyl)nitrosamine (DHPN), followed by thiourea (TU) over an experimental period of 19 weeks. Simultaneous treatment with a high level of vitamin A (VA) enhanced the induction of proliferative lesions that originated from the thyroidal follicular epithelium. To examine whether hormone synthesis in the thyroid could be inhibited by simultaneous treatment with a large amount of VA and TU, all of the rats were initially given a single subcutaneous injection of 2,800 mg DHPN/kg followed by a supply of 0% TU + 0% VA (DHPN only, control group), 0.2% TU in their drinking water (DHPN/TU group), 0.1% VA in their diet (DHPN/VA group), or 0.2% TU + 0.1% VA (DHPN/TU + VA group) during an experimental period of 4 weeks. Results obtained indicate that the iodine uptake and organification, namely iodination of tyrosine residue in thyroglobulin, of the thyroid, were significantly decreased in the DHPN/TU group compared to the DHPN control group. The variation in these values was attributable to the inhibitory effect of TU upon thyroid hormone synthesis. Results obtained from the DHPN/TU + VA and DHPN/TU groups were comparable. Therefore, the possibility that modification of hormone synthesis contributes to the enhancing effect of simultaneous treatment with a large amount of VA on thyroidal tumor induction by TU is considered to be very minimal.

Adenoma↗

PubMed2000

A hamster model of equine herpesvirus 9 induced encephalitis.

An acute and lethal infection of equine herpesvirus 9 (EHV-9), a new type of equine herpesvirus, was established in Syrian hamsters by intranasal inoculation. Clinical symptoms included the loss of body weight, nasal and ocular discharges and apparent neurological symptoms. Both LD50 and ID50 were equal at 33 plaque forming units. Histological and immunohistochemical examination demonstrated that the virus replicated in the olfactory mucosal cells and in the neurons of the olfactory bulbs, cerebrum and mesencephalon. The induction of encephalitis by intranasal but not by other routes of inoculation (i.v., i.p., i.m.) indicated that EHV-9 entered the brain via the olfactory nerve and then spread trans-synaptically to connecting neurons along the olfactory tract. This animal model should be useful for studying the pathogenesis and neurovirulence of this newly discovered neurotropic virus as well as other neurotropic herpesviruses.

Animals↗

PubMed1999

Detection of antibodies against Actinobacillus pleuropneumoniae serotypes 1, 2, 5 and 7 using the immunohistochemical staining.

Whole cells of Actinobacillus pleuropneumoniae (A. pleuropneumoniae) serotype 1, 2, 5 or 7 attached to fibrins were fixed in 10% neutral buffered formalin and embedded in paraffin. The sections on a slide glass were stained by the avidin-biotin complex immunoperoxidase (ABC) method. Test sera were applied to sections as primary antibodies. The serum antibodies against A.pleuropneumoniae (serotypes 1, 2, 5 and 7) were measured by the ABC method and complement fixation (CF) test. There was good correlation between the ABC and CF tests. The present results indicate that the immunohistochemical staining is as useful as the CF test for the detection and quantification of antibody in swine sera.

Actinobacillus Infections↗

PubMed1999

Clinicopathological study of canine oral epulides.

To clarify the clinicopathological features of canine epulides, 189 epulides were reviewed retrospectively. The incidence of the fibromatous, ossifying, acanthomatous and giant cell epulides were 56.6% (107/189), 23.3% (44/189), 18.0% (34/189) and 2.1% (4/189), respectively. The average ages of dogs with fibromatous, ossifying, acanthomatous and giant cell epulides were 8.8, 8.4, 7.8 and 8.7 years, respectively. The male/female ratio of dogs with the acanthomatous epulis (0.8) was lower than those of dogs with the fibromatous (1.9), ossifying (1.4) and giant cell epulis (3.0). There were slight breed differences among the types of epulides. The most noticeable result was that 38.2% of the acanthomatous epulis occurred in Shetland sheepdogs. 43.9% of the fibromatous epulis and 52% of the ossifying epulides arose around maxillary premolars, while 58.8% of the acanthomatous epulis arose around the mandibular canines. Dogs with the fibromatous and ossifying epulides had more severe dental plaque deposition than those with the acanthomatous epulides. Few of the fibromatous (6/104) or ossifying epulides (4/44) showed recurrence after excision, while the majority (21/23) of the acanthomatous epulides showed rapid and repeated recurrences after surgical excision. Epulides treated with hemimandibulectomy or bleomycin chemotherapy did not recur. Giant cell epulides showed no recurrence after surgical removal. These results indicate that the acanthomatous epulis differed from other types of epulides in biological and morphological features and poor prognosis.

Age Factors↗

PubMed1999

Proliferative potential of canine oral epulides and malignant neoplasms assessed by bromodeoxyuridine labeling.

The proliferative potential of canine oral lesions, including epulides, squamous cell carcinomas, a malignant melanoma, and a fibrosarcoma, was examined using a monoclonal antibody to bromodeoxyuridine (BrdU). Twenty-three dogs with oral masses were administered BrdU intravenously at a dose of 8 mg/kg 1 hour before surgery, and the BrdU labeling index (LI) of each lesion was determined immunohistochemically. The average BrdU LIs for the main proliferating elements in the fibromatous epulis (4 cases), ossifying epulis (2 cases), and acanthomatous epulis (10 cases) were 4.9, 3.0, and 8.8%, respectively. The squamous cell carcinomas (5 cases) had an average LI of 15.9%, and the LIs of the malignant melanoma and fibrosarcoma were 7.5 and 10.3%, respectively. All cases of acanthomatous epulides and squamous cell carcinoma treated with simple marginal surgical resection recurred within a short time. The higher LIs in the acanthomatous epulides, squamous cell carcinomas, and fibrosarcoma correlate well with their poor prognoses, reflected by rapid growth and frequent recurrence. Acanthomatous epulis is clearly distinguished from other epulides by its aggressive clinical behavior and high proliferative potential, which is equivalent to that of malignant tumors, despite a lack of cell atypia. The BrdU LI is a useful marker for evaluating the proliferative potential and prognosis of canine oral tumors.

Animals↗

PubMed1998

Ribozyme targeting of receptor for advanced glycation end products in mouse mesangial cells.

Accumulation of extracellular matrix is a characteristic of diabetic nephropathy, and advanced glycation end products (AGEs) are considered to play an important role in the mechanism. To investigate the involvement of the receptor for AGE (RAGE) in upregulation of type IV collagen by AGEs, we applied the hammerhead ribozyme for targeting RAGE. We established a stable mouse mesangial cell line that produces the RAGE-specific ribozyme (Rz-RAGE). Both the RAGE mRNA and protein were decreased in the cell line. The amount of type IV collagen mRNA increased by AGEs' treatment in control cells. In contrast, the increase of type IV collagen induced by AGEs was not observed in the Rz-RAGE-producing cells. We conclude that the induction of type IV collagen by AGEs is mediated by RAGE and this mechanism could be involved in diabetic nephropathy. This study also suggested the experimental/therapeutic potential of hammerhead ribozymes.

Animals↗

PubMed1998

Neuropathological study of gazelle herpesvirus 1 (equine herpesvirus 9) infection in Thomson's gazelles (Gazella thomsoni).

Gazelle herpesvirus (GHV-1), correctly designated as equine herpesvirus 9, is a new type of equine herpesvirus immunologically related to equine herpesvirus 1 (EHV-1). As a sequel to a virological study, the neuropathology of encephalitis caused by GHV-1 in Thomson's gazelles (Gazella thomsoni) was examined. Seven gazelles died with or without neurological symptoms between early September and mid-October in 1993. No gross abnormalities were observed at necropsy, but all animals had non-suppurative encephalitis, characterized by necrosis and degeneration of neurons, glial reactions and perivascular cuffing in the cerebrum. Five cases showed intranuclear inclusion bodies, with the appearance of herpesvirus in the degenerating neurons. Immunohistochemically, all seven animals showed a positive reaction to EHV-1 antigen in neurons in the necrotic areas of the cortex. The clinical course and morphological features of GHV-1 encephalitis were distinct from those of EHV-1-induced encephalitis in the horse, which is characterized by vasculitis, thrombosis, ischaemia, and lack of intranuclear inclusions in neurons.

Animals↗

PubMed1998

Immunohistochemical studies of TSH-producing cells in the pituitary and expression of growth factors in thyroidal proliferative lesions in rats treated with thiourea and excess vitamin A.

Changes of TSH-producing cells in the pituitary and thyroid expression of the growth factors, transforming growth factor alpha (TGF alpha) and epidermal growth factor receptor (EGFR), as well as cyclin D1, were investigated immunohistochemically in order to clarify their contribution to the enhancing effects of excess vitamin A (VA) on thyroidal carcinogenesis induced by thiourea (TU). Male rats were allocated to 4 groups, control, TU, VA, and TU + VA, respectively, receiving no treatment, water containing 0.2% TU, diet containing 0.1% VA, and both for 10 or 19 weeks after a single s.c. injection of DHPN (2800 mg/kg) for initiation. Immunohistochemistry using antibodies against TSH demonstrated enlargement of TSH-producing cells in the TU + VA group as compared to the TU group, supporting our conclusion that enhanced TSH stimulation is mainly responsible for promoting the effects of excess VA. Since the expression of TGF alpha, EGFR, and cyclin D1 in thyroid proliferative lesions did not exhibit any differences between the TU and TU + VA groups in the present study, these factors are unlikely to participate in VA enhancement of carcinogenesis.

Animals↗

PubMed1998

A fatal Pegosomum sp. (Trematoda: Echinostomatidae) infection in a wild cattle egret (Bubulcus ibis) from Japan.

An adult cattle egret (Bubulcus ibis) caught in Kobe of Hyogo Prefecture, Japan, in December 1995 died of a severe infection associated with the trematode parasite Pegosomum sp. At necropsy, 22 trematode parasites were found in the lumen of the bile duct, and the duct wall was markedly thickened. Histopathologically, severe cholangitis and cholecystitis were observed in close association with the parasites in the bile duct. Severe Pegosomum sp. infection may be one of the factors contributing to the mortality of wild cattle egrets. This is the first reported case of the genus Pegosomum infection in wild birds of Japan.

Animals↗

PubMed1997

Gazelle herpesvirus 1: a new neurotropic herpesvirus immunologically related to equine herpesvirus 1.

A herpesvirus was isolated from Thomson's gazelle (Gazella thomsoni) kept at a zoological garden in Japan during an outbreak of epizootic acute encephalitis. The virus, gazelle herpesvirus 1 (GHV-1), was serologically related to equine herpesvirus 1 (EHV-1). However, DNA fingerprints of GHV-1 were different from those of EHV-1 and other equine herpesviruses. Southern hybridization with probes of cloned BamHI fragments derived from UL and US segments of EHV-1 revealed differences in the DNA restriction profiles throughout the entire genome. Nucleotide sequences were determined for a conserved region of an essential envelope glycoprotein B (gB) gene and a type-specific glycoprotein G (gG) homologue gene. The predicted amino acid sequence of GHV-1 gB showed 97, 92, 61, and 57% identity to EHV-1, EHV-4, feline herpesvirus, and pseudorabies virus, respectively, indicating that GHV-1 was closer to EHV-1 than any other herpesvirus. The GHV-1 gG gene showed 93.2, 92.3, and 53% identity to EHV-1, EHV-8, and EHV-4 gGs, respectively. GHV-1 was virulent to suckling mice of the ICR strain by intracerebral inoculation and was virulent to 4-week-old BALB/c mice by intranasal inoculation, causing neurological symptoms and death. We conclude that GHV-1 is a new type of equine herpesvirus with strong neurotropism.

Amino Acid Sequence↗

PubMed1997

UDP-GT involvement in the enhancement of cell proliferation in thyroid follicular cell proliferative lesions in rats treated with thiourea and vitamin A.

The mechanisms underlying enhanced cell proliferation in thyroid proliferative lesions of rats simultaneously treated with large amounts of vitamin A (VA) and thiourea (TU) were investigated. Male F344 animals were initiated with N-bis(2-hydroxypropyl)nitrosamine (2800 mg/kg body weight, single s.c. injection). Starting 1 week later, groups received water containing 0.2% TU (TU group), diet containing 0.1% VA (VA group), both 0.2% TU and 0.1% VA (TU + VA group) or tap water/basal diet without supplement (control group) for 10 weeks. The serum levels of triiodothyronine (T3) and thyroxine (T4) were decreased and the thyroid stimulating hormone (TSH) levels were elevated in the TU and TU + VA groups, with the degree of change being significantly greater in the combined treatment group. The induction of P450 isoenzymes by TU was not enhanced by VA supplementation, but uridine diphosphate glucuronosyltransferase (UDP-GT) activity in the liver was significantly increased in the TU + VA group compared to the TU group. Thyroid weights were increased in both the TU and TU + VA groups, this being more pronounced with VA supplementation. Thyroid follicular cell hyperplasias and neoplasias were induced to similar extents in both TU treated groups, but their cell proliferation appeared to be increased by the VA supplementation. The results of the present study suggest that enhanced cell proliferation is due to increased TSH stimulation, resulting from the decrease in serum T3/T4 levels brought about by induction of liver UDP-GT activity with the combined action of TU + VA as well as inhibition by TU of thyroid hormone synthesis in the thyroid.

Animals↗

PubMed1997

Reduction of glutathione S-transferase P-form mRNA expression in remodeling nodules in rat liver revealed by in situ hybridization.

Glutathione S-transferase P-form (GST-P) mRNA levels and distribution were sequentially analyzed by in situ hybridization histochemistry (ISH) in rat livers during and after induction of preneoplastic foci and nodules in the Solt-Farber model. Dot blot analysis showed GST-P transcripts in the liver to be elevated coincidental with the development of GST-P-positive lesions. GST-P ISH indicated that the majority of early foci and some of the resultant lesions showed uniformly high levels of GST-P mRNA. However, the majority of foci and nodules after completion of the selection regimen exhibited a progressive loss of staining for GST-P mRNA. Similar results were obtained for gamma-glutamyltransferase (GGT) transcripts, indicating that phenotypic reversion is controlled by factors operating at the level of gene expression in both cases. Expression of GST-P mRNA was high in all hepatocellular carcinoma samples, whereas the levels of GGT transcripts varied considerably, so that the two enzymes showed a degree of independence in their regulation. The present data for transcription suggest that GST-P is a stable marker of preneoplastic and neoplastic cells, not only at the protein but also at the mRNA level, throughout hepatocarcinogenesis in the rat. The reason why transcription of GST-P mRNA is switched off as part of the reversion to a normal organization remains to be elucidated.

2-Acetylaminofluorene↗

PubMed1997

Sparse distribution of hepatocyte growth factor-producing cells inside hepatocellular foci in rats treated with hepatocarcinogens.

The distribution of hepatocyte growth factor (HGF)-synthesizing cells in rat liver during development of glutathione S-transferase P form (GST-P)-positive nodules after diethylnitrosamine initiation followed by promotion with 2-acetylaminofluorene plus partial hepatectomy (PH) was investigated using in situ hybridization. HGF-producing cells were non-parenchymal in nature, and were suspected to be mainly of Kupffer type. They were mostly located outside GST-P-positive lesions, in the surrounding parenchyma. In the oval cell proliferation phase 1 week after PH, they increased and they were mainly localized around the portal triads. It is concluded that HGF is directly involved in an endogenous paracrine growth pathway controlling proliferation in oval cells and in normal, but not GST-P-positive, hepatocytes.

2-Acetylaminofluorene↗

PubMed1997

Advanced gastric carcinoma in a de Brazza's guenon (Cercopithecus neglectus).

A necropsy case of advanced gastric carcinoma in a 20-year-old female de Brazza's guenon (Cercopithecus neglectus) was studied, Grossly, an excavated carcinoma mass, 60 x 55 x 35 mm in size, was located in the cardiac region of the stomach. Multiple disseminated nodules had implanted on the diaphragm and omentum. The tumor consisted of intestinal-type adenocarcinoma cells and showed infiltrative growth beyond the serosa. The morphologic features of this tumor closely resembled those of advanced gastric carcinomas in human patients.

Adenocarcinoma↗

PubMed1996

Immunohistochemical demonstration of S-phase cells by anti-bromodeoxyuridine monoclonal antibody in cattle tissues.

Bromodeoxyuridine (BrdU), a non-radioactive thymidine analogue, was administered to 15 cattle at a dosage of 1-10 mg/kg intravenously or intraperitoneally to demonstrate S-phase cells in the tissues. The organs and tissues were fixed in 10% neutral buffered formalin or in 70% ethanol, sectioned, denatured with hydrochloric acid, and treated with monoclonal antibody against BrdU. Immunohistochemical methods were used to "visualize" BrdU-labelled nuclei. BrdU-positive cells were satisfactorily demonstrated in both formalin- and ethanol-fixed tissues of animals given doses of 2 mg/kg or over, by either route of administration. Large numbers of BrdU-positive cells indicative of active cell production were found in the basal region of the stratified squamous epithelium, the neck between gastric pits and gastric glands in the abomasum, and the crypts of Lieberkühn of the small and large intestines. Moderate numbers of positive cells were observed amongst inflammatory cells in cases of nephritis and in granulation tissue. Numerous positive cells were detected in leukaemia cells. The study showed that BrdU can be used to measure proliferative S-phase cells in cattle, as in human beings, mice and rats.

Animals↗

PubMed1996

Bilateral giant myelolipoma in the adrenal of a cotton-top tamarin (Saguinus oedipus).

A rare case of bilateral adrenal myelolipomas in a female cotton-top tamarin is reported. Large bilateral masses in the adrenal glands were composed of mature adipose cells containing varying amounts of hematopoietic cells of the myeloid, erythroid, and megakaryocytic series. The gross and histologic features of this case closely resemble human "giant" adrenal myelolipomas.

Adrenal Cortex↗

PubMed1996

Ameloblastoma with prominent ossification in the mandible of a dog.

A rare case of ameloblastoma with prominent stromal ossification in an 8-year-old female dog was studied. A bony mass recurred rapidly in the right mandible at the first molar region. Histopathologic examination revealed the lesion to be an atypical variant of ameloblastoma. Epithelial cells showed marked cell atypia, and mitotic figures were rather common. The collagenous stroma was abundant, with prominent formation of bone trabecular rimmed by active osteoblasts. The tumor was highly proliferative and aggressive, and thought to be malignant in nature.

Ameloblastoma↗