Biomedical subjects

A Sasaki

Publications and source records attributed to A Sasaki.

At least 55 records · Page 3Linked to original sources

PubMed2001

Identification of a dominant negative mutant of Sprouty that potentiates fibroblast growth factor- but not epidermal growth factor-induced ERK activation.

Various mitogenic stimuli such as epidermal growth factor (EGF), fibroblast growth factor (FGF), and phorbol 12,13-dibutyrate (PDBu) activate the Ras-Raf-MEK-ERK pathway, but the regulatory mechanism of this pathway remains to be investigated. Here we found that in 293 cells, mammalian Sprouty2 and Sprouty4 were rapidly induced by EGF, FGF, and PDBu in an ERK pathway-dependent manner. Forced expression of Sprouty2 and Sprouty4 inhibited FGF-induced ERK activation but did not affect EGF- or PDBu-induced ERK activation. To examine whether endogenous Sproutys were also selective inhibitors, we generated a dominant negative form of Sprouty2 (Y55A) and Sprouty4 (Y53A) in which conserved tyrosine residues were mutated. These mutants reverted the suppressive effect of both Sprouty2 and Sprouty4 but not that of RasGAP or SPRED (Sprouty-related EVH1 domain-containing protein), another Sprouty-related Ras suppressor. Expression of dominant negative Sprouty2 and Sprouty4 enhanced and prolonged FGF- but not EGF-induced ERK activation in 293 cells. In PC12 cells, endogenous Sprouty4 was also induced by FGF. Overexpression of wild-type Sprouty4 blocked FGF-induced differentiation, whereas Y53A-Sprouty4 enhanced it. These observations suggest that endogenous Sprouty2 and Sprouty4 are physiological negative feedback regulators of growth factor-mediated ERK pathway and that there are Sprouty-sensitive and -insensitive ERK activation pathways. Finding a dominant negative form of Sproutys will facilitate the study of the molecular mechanism and physiological function of Sproutys.

Animals↗

PubMed2001

Filamin associates with Smads and regulates transforming growth factor-beta signaling.

Members of the Smad proteins transmit signals triggered by the ligands of transforming growth factor (TGF)-beta superfamily. Ligand-activated receptors induce phosphorylation of so-called receptor-regulated Smads, which then accumulate in the nucleus to participate in target gene transcription, in collaboration with Smad-interacting proteins. We performed yeast two-hybrid screening and identified filamin, a cytoskeletal actin-binding protein 280, as a Smad5-interacting protein. Filamin was found to be associated not only with Smad5 but also with other Smad proteins, including TGF-beta/activin receptor-regulated Smad2. TGF-beta signaling was defective in filamin-deficient human melanoma cells M2 compared with a filamin-transfected subline A7, as determined by TGF-beta-responsive reporter gene activation and Smad2 nuclear accumulation. M2 cells restored TGF-beta responsiveness following transient transfection of full-length filamin encoding vector. The defective TGF-beta signaling in M2 cells seemed to be due to impaired receptor-induced serine phosphorylation of Smad2. These results suggest that filamin plays an important role in Smad-mediated signaling.

Cell Line↗

PubMed2001

Induction of epithelial differentiation and DNA demethylation in hamster malignant oral keratinocyte by ornithine decarboxylase antizyme.

The hamster ornithine decarboxylase antizyme (ODC-Az) cDNA was transfected into the hamster malignant oral keratinocyte cell line, HCPC-1. Ectopic expression of ODC-Az resulted in the reversion of malignant phenotypes and alteration of DNA methylation status of CCGG sites. The phenotypes examined include ODC enzymatic activity, doubling time, morphological change, anchorage dependent growth, tumorigenicity in nude mice, induction of epithelial differentiation marker protein (involucrin), and change of cell cycle position. Comparison of CCGG DNA methylation status of the ODC-Az and control vector transfectants revealed a significant increase in demethylation of 5-methyl cytosines (m5C) of CCGG sites in the ODC-Az transfectants. Ectopic expression of ODC-Az gene in hamster malignant oral keratinocytes led to reduce ODC activity and the subsequent demethylation of 5-methyl cytosines, presumably via the ODC/ polyamines/ decarboxylated S-adenosylmethionine (dc-AdoMet) pathways. Our data suggest that ODC-Az shared the same pathway of polyamines/ dc-AdoMet/DNA methyltransferase (DNA MTase). We propose that ODC-Az mediates a novel mechanism in tumor suppression by DNA demethylation and presumably re-activation of key cellular genes silenced by DNA hypermethylation during cancer development. Oncogene (2001) 20, 24 - 33.

Agar↗

PubMed2001

JAB/SOCS1/SSI-1 is an interleukin-2-induced inhibitor of IL-2 signaling.

JAB/suppressor of cytokine signaling 1 (SOCS1) STAT-induced STAT inhibitor-1 (SSI-1) (JAB/SOCS1/SSI-1) is an SH2-domain-containing protein that is induced by and negatively regulates signaling by a number of cytokines including interleukin-4 (IL-4), IL-6, interferon (IFN)-gamma, prolactin, growth hormone, and erythropoietin. The role of JAB/SOCS1/SSI-1 in IL-2 signaling has been analyzed. JAB/SOCS1/SSI-1 is strongly induced by IL-2 in peripheral blood T cells, and JAB/SOCS1/SSI-1 overexpression strongly inhibits IL-2-induced signal transducer and activator of transcription-5 (Stat5) phosphorylation and transcriptional activity. In cotransfection experiments, JAB/SOCS1/SSI-1 associates with both Jak1 and Jak3; however, JAB/SOCS1/SSI-1 had a greater effect on Jak1 tyrosine phosphorylation and kinase activity. JAB/SOCS1/SSI-1 also interacts with IL-2Rbeta, and this interaction requires the A region (residues 313-382) of IL-2Rbeta. However, this interaction was not essential for the inhibitory action of JAB. Thus, JAB/SOCS1/SSI-1 is an IL-2-induced inhibitor of IL-2 signaling that functions by inhibiting Jak kinase activity. This suggests an important role for JAB/SOCS1/SSI-1 in regulating T-cell responses.

Blotting, Western↗

PubMed2001

Clinicopathologic study of mixed hepatocellular and cholangiocellular carcinoma: modes of spreading and choice of surgical treatment by reference to macroscopic type.

BACKGROUND AND OBJECTIVES: Clinicopathologic features and the choice of surgical treatment for mixed hepatocellular and cholangiocellular carcinoma (MHC) remain controversial. METHODS: We evaluated the clinicopathological features of seven cases of MHC (one autopsied and six surgically resected cases). MHCs were divided into two classes by reference to macroscopic appearance: four were of the single nodular (SN) type and three were of the multinodular (MN) type. RESULTS: The mean age of patients and mean preoperative level of serum alpha-fetoprotein were 44.5 years and 56,457 ng/ml for the SN type and 63.7 years and 1,227 ng/ml for the MN type, respectively. Histologically, invasion of the portal vein, the hepatic vein, and the perineural space was found in three, two, and zero cases of SN type tumors and in three, three, and one cases of MN type tumors, respectively. Lymph node metastases were found only in two patients with MN type MHC. CONCLUSIONS: MHC of the SN type had a pattern of infiltration similar to hepatocellular carcinoma. By contrast, MHC of the MN type resembled intrahepatic cholangiocellular carcinoma. It is suggested that lymphadenectomy might be necessary for treatment of selected MHC, in particular MHC with a multinodular appearance.

Adult↗

PubMed2001

Antisense-mediated reduction in thrombospondin-1 expression reduces cell motility in malignant glioma cells.

Thrombospondin-1 (TSP-1) is a multifunctional matrix protein implicated in cancer cell adhesion, migration, invasion, inhibition of angiogenesis and activation of latent transforming growth factor-beta. The involvement of TSP-1 in the motility of malignant glioma cells was investigated by transfection of TSP-1 complementary deoxyribonucleic acid (cDNA) sense and antisense expression vectors into the glioblastoma cell line T98G-G7 that secretes high amounts of TSP-1. TSP-1 production in the 3 antisense cDNA-transfected clones was significantly reduced to 51%, 43% and 47% compared to the host T98G-G7 cells. Motility of the 3 clones was evaluated by invasion assay and compared to the motility of host T98G-G7 cells and 2 sense-transfected clones. Migration of cells was significantly reduced in the 3 antisense-transfected clones with reduced TSP-1 production to 56%, 61% and 43% compared to the host T98G-G7 cells. The host T98G-G7 and another TSP-1-secreting A172 and YMG5 glioblastoma cells were also treated with a synthetic peptide, WSHWSPWSSCSVTCG, which includes 3 consecutive sequences of the adhesion sites in the TSP-1 molecule and with a control peptide. The synthetic peptide significantly inhibited the migration of T98G-G7 and A172 cells in a dose-related manner. Maximum inhibition of migration was achieved by 100 microg/ml of the peptide and the reduction of cell motility compared to untreated cells was 34.6 % and 53.9 %, respectively. On the other hand, the inhibition of migration by the peptide was minimal in YMG5 cells, which secretes a smaller amount of TSP-1 than T98G-G7 and A172 cells. These results suggest that TSP-1 secreted by malignant glioma cells is involved in the motility of glioma cells.

Blotting, Western↗

PubMed2001

Variable timing of reproduction in unpredictable environments: adaption of flood plain plants.

We study the evolutionarily stable reproductive timing of annual plants that face unpredictable environmental disturbances. Plants living in a riverbed often experience a disturbance before they reproduce, suffering major fitness loss. Plants reproducing prior to the flood season are free from the risk of lost reproduction, but a small flowering plant can produce only a few numbers of seeds. If the date of disturbance is unpredictable, a mixed strategy of reproductive timing may evolve in which individuals of the same genotype have different reproductive dates. We calculate the evolutionarily stable phenotype distribution analytically. Depending on parameters, the ESS distribution is either (1) a timid strategy-the plant reproduces when small, prior to the major disturbance season; (2) a bold strategy-the plant reproduces only when it is fully grown; (3) a mixture of early and late reproduction; or (4) dates of reproduction spread over a wide interval. We also examine the effects of developmental and environmental noises that make realized flowering dates deviate from that programmed by the genotype, which follows the ESS distribution. In the presence of noise, the ESS distribution of programmed timing of reproduction is discrete.

Climate↗

PubMed2001

Analysis of interleukin-6 gene expression in primary human gliomas, glioblastoma xenografts, and glioblastoma cell lines.

Our previous study showed that high-grade astrocytomas often expressed high interleukin (IL)-1beta production. Coexpression of IL-1beta and IL-6 has been found in a number of glioma samples and glioma cell lines. To characterize the expression of IL-6 in the human glioma microenvironment, we investigated surgically excised human gliomas, human glioblastoma xenografts, and human glioblastoma cell lines using the reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA). In the 29 primary gliomas, transcripts of IL-6 were less frequently detectable (55.6%) than those of IL-1beta (72.4%) or those of IL-10, IL-8, or IL-1alpha (>80% each). As for IL-6 gene expression, little or no transcription was observed in low-grade astrocytomas, oligodendroglial tumors, and 1 ependymoma. Strong IL-6 gene expression was found in only 5 of 9 glioblastomas. Immunohistochemically, IL-6 antigen was localized in the tumor cells and macrophages in 4 of 7 glioblastomas. In 3 glioblastomas transplanted into nude mice, both IL-1beta and IL-6 were detected only in 1, but othercytokines (IL-8, IL-10, and IL-1alpha) were detected in all 3 xenografts by RT-PCR. Two cell lines both showed IL-6 expression at the mRNA level, and in a cell line with a high level of IL-6 and IL-1beta transcripts, significant production of IL-6 was observed by IHC and ELISA. We concluded that IL-6 produced in tumor tissue may be involved in tumor progression in some glioblastomas, but not in low-grade astrocytomas and oligodendroglial tumors, and that IL-6 gene expression is closely correlated with IL-1beta expression in biopsy tissue, xenografts, and cultures of human gliomas.

Animals↗

PubMed2001

Transient spontaneous regression of aggressive non-Hodgkin's lymphoma confined to the adrenal glands.

A 72-year-old-man with night sweats and a low-grade fever was found to have bilateral adrenal enlargement associated with incipient adrenal insufficiency. Without any intervention, these adrenal lesions regressed spontaneously, accompanied by disappearance of clinical symptoms. Seven months later, however, the lesions became enlarged and exceeded their initial size while remaining confined to the adrenals, associated with reappearance of nights sweats and overt adrenal insufficiency. Upon unilateral laparoscopic adrenalectomy, the lesion proved histopathologically to be diffuse large B cell non-Hodgkin's lymphoma (NHL). After contralateral laparoscopic adrenalectomy and adjuvant chemotherapy, the patient remains alive with no recurrence at 26 months. Treatment with bilateral adrenalectomy and chemotherapy is effective for aggressive NHL confined to bilateral adrenal glands. A transient clinical improvement without treatment was considered to be due to a spontaneous regression of NHL, although we could not confirm the histological results before the regression. Such tumor behavior showing spontaneous regression in spite of aggressive histology may also be related to the favorable outcome, even though regression was transient.

Adrenal Gland Neoplasms↗

PubMed2001

Complete nucleotide sequence of the linear DNA plasmid pRS224 with hairpin loops from Rhizoctonia solani and its unique transcriptional form.

The complete nucleotide sequence of the linear DNA plasmid (pRS224-1) from the plant-pathogenic fungus Rhizoctonia solani isolate H-16 was determined; and its unique RNA transcripts were characterized. The pRS224-1 DNA consists of 4,986 nucleotides. A computer-based study of the folding of pRS224-1 at both termini predicted hairpin-loop structures. The hairpin loops consisted of the left and right termini of 236 and 264 nucleotides, respectively, and share no sequence homology. Unique poly(A) RNAs, 4.7 kb and 7.4 kb in length and hybridizing with the pRS224 DNA, were found in mycelial cells of R. solani H-16. Transcript product-mapping allowed the prediction of the locations of different expression signals. The 7.4-kb transcript is generated from the left terminal region of the complementary strand, via the full-length sense-strand, to the right terminal region of the complementary strand. The 4.7-kb transcript is generated from the center region of the sense strand to the right terminal region of the complementary strand. One open reading frame (ORF) found in pRS224-1 is 887 amino acids long and has a potential coding capacity of 102 kDa. The ORF contains the highly conserved domains characteristic of reverse transcriptase sequences, including the highly conserved YXDD sequence.

Amino Acid Sequence↗

PubMed2001

Expansion of an ablated site and induction of apoptosis after microwave coagulation therapy in rat liver.

BACKGROUND/PURPOSE: Microwave coagulation therapy (MCT), one of the ablation therapies, has been widely used to treat liver cancers, yielding excellent clinical results. Despite its efficacy, the precise events that take place in the ablated liver after MCT remain unknown. We investigated sequential histologic changes around MCT sites and the relationship between MCT and apoptosis in rat liver. METHODS: One session of MCT at 30 W was applied to rat liver. The rats were killed at 0, 2, 6, 12, 24, 72, and 168 h after MCT. The liver surface area was measured for sequential evaluations of the size of the impaired field (i.e., the liver surface affected by MCT). The size of the impaired field was assessed by measuring the area that showed macroscopic changes in color with a relatively clear border. To assess apoptosis, we examined terminal deoxynucleotidyl transferase d-uridine triphosphate nick end labeling stained sections, determined the positive cell count for DNA fragmentation, and observed DNA ladder formation by gel electrophoresis. Caspase-3 activity at the ablated margin was measured for the enzymatic evaluation of apoptosis. RESULTS: The impaired field gradually expanded through 12 h after MCT. Caspase-3 activity increased four fold from the baseline, peaking at 2 h after MCT, and DNA fragmentation, confirmed by DNA ladder formation, was significantly increased at 6 h. CONCLUSIONS: Alterations in the ablated liver tissue indicated that the activation of caspase-3 around the MCT site was followed by apoptosis and expansion of the impaired field. The expansion continued until 12 h after MCT, and this may be beneficial for the local control of liver cancer.

Animals↗

PubMed2001

Endoscopic subtotal thyroidectomy for patients with Graves' disease.

Endoscopic thyroidectomy performed via the precordial approach leaves no scarring of the neck, and thus provided excellent results from a cosmetic viewpoint. We applied this technique to perform subtotal thyroidectomy in 12 patients with Graves' disease. Three trocars were inserted in the precordial region, and endoscopic surgery was performed with carbon dioxide insufflation. Vessel management and thyroidectomy were carried out using ultrasonic coagulation devices. The mean operative time was 259.8 min, and the mean blood loss was 90.2ml. There were no postoperative complications such as subcutaneous emphysema or hemorrhage, although hypoparathyroidism and recurrent laryngeal nerve paralysis occurred in one patient. Cosmetically esthetic results were achieved in all patients. These findings indicate that this surgical technique represents an effective method of treating Graves' disease that provides excellent cosmetic results.

Adolescent↗

PubMed2001

Inter-laboratory comparison of DNA preservation in archival paraffin-embedded human brain tissue from participating centres on four continents.

DNA extracted from formalin-fixed and paraffin-embedded brain tissue is known to contain as yet ill-characterized inhibitors of the PCR process. As part of a project that aims to clarify the role of mitochondrial DNA sequence variation in human neurodegenerative diseases using DNA from various ethnic backgrounds, we have investigated factors that influence the preservation of archival DNA and its suitability for PCR. In this study, neuropathological tissue samples were analysed that had been routinely processed in 18 international centres on four continents. Following DNA extraction, PCR amplification of mitochondrial and nuclear DNA sequences was performed with and without additional purification of the template DNA. In addition, the DNA used for PCR was analysed by HPLC. Phosphate-buffered formalin proved to be a superior fixative compared with unbuffered aldehyde: DNA extraction resulted in greater yields, the molecular weight of the isolated DNA was higher and PCR was more successful. PCR inhibitors were identified as (1) high concentrations of small (<300 bp) DNA fragments that competitively compete with template DNA and (2) contaminants of the DNA template solution including denatured protein that cannot be completely removed by phenolic extraction. HPLC analysis did not reveal significant qualitative differences between DNA isolated from fresh-frozen tissue samples and DNA recovered from formalin-fixed, paraffin-embedded brain tissue. The fact that DNA could be amplified from the majority of tissue specimens in this study suggests that rare diseases and diseases where ethnic background plays an important role can be sampled for genetic polymorphism analysis on a global scale using archival neuropathological collections.

Alzheimer Disease↗

PubMed2001

Biomechanical behaviour of bovine temporomandibular articular discs with age.

The purpose was to evaluate age-associated changes in the creep and restoration properties of bovine temporomandibular joint (TMJ) discs under and after sustained tensile stress. Forty discs were obtained from 7- and 10-year-old cattle, referred to as the adult and mature adult groups, respectively. Tension of 1.0 MPa was applied and sustained for 20 min to specimens from ten right discs and of 1.5 MPa to specimens from ten left discs. After the period of tension for the study of creep, the specimens were removed from the tension devices and their restoration observed for 20 min. For comparative purposes the relevant results for a young adult group were recruited from data on 3-year-old bovine TMJ discs reported in a previous study on viscoelastic properties. In all the specimens the time-dependent creep curves showed a marked change in strain during the initial 5 s, but the elastic moduli at the onset of stress were significantly larger in the mature adult group than in the other groups. After 20-min creep, the strains were decreased in relation to the age of the specimen and were significantly smaller in the mature adult than in the young adult. With regard to regional differences, the medial specimens exhibited significantly smaller strains than the central ones in all three age groups. Furthermore, the residual strains after 20-min restoration also decreased slightly with age. It is concluded that the bovine TMJ disc becomes stiff and acquires the capacity to recover from continuous deformation during growth and maturation. These findings suggest that the TMJ disc can modify its viscoelasticity in order to withstand extrinsic functional stresses.

Aging↗

PubMed2001

Effects of the administration of growth hormone-releasing peptide-2 (GHRP-2) orally by gavage and in feed on growth hormone release in swine.

The experiments were conducted to determine the effects of the administration of growth hormone-releasing peptide-2 (GHRP-2, also named KP102), both orally by gavage and in feed, on the release of growth hormone (GH) in swine and to investigate whether attenuation of the GH response occurs after short-term treatment with the peptide in feed. In the first experiment, saline or GHRP-2 at doses of 1, 4.5 and 9 mg/kg body weight (BW) was dissolved in 15 ml saline and administered orally as a bolus by gavage to cross-bred castrated male swine (n = 6). Orally administered GHRP-2 stimulated dose-related increases in peak concentrations of GH, with a return to basal by 120 min. After administering GHRP-2 orally, peak concentrations of GH and areas under the GH response curves (GH AUCs) for 180 min were higher (P < 0.05) than those in saline controls. In Experiment 2, GHRP-2 at doses of 0 (served as control), 1, 4.5 and 9 mg/kg BW was mixed in 150 g of feed and offered to cross-bred castrated male swine (n = 6) at 0900 hr and 1700 hr daily for a 3-d period. Administration of 1 mg/kg BW GHRP-2 to swine in feed failed to stimulate the release of GH, but GHRP-2 at doses of 4.5 and 9 mg/kg BW significantly (P < 0.05) increased plasma concentrations of GH after initial and final treatments at 0900 hr on Days 1 and 3 of treatment, respectively. Peak concentrations of GH and GH AUCs for 180 min after the initial and final treatments in the 4.5 and 9 mg/kg BW GHRP-2-treated swine were higher (P < 0.05) than those in controls. After 3 d of treatment with GHRP-2 in feed at doses of 4.5 and 9 mg/kg BW, GH responses to the peptide were maintained. The results of the present study indicate that the administration of GHRP-2 orally by gavage and in feed stimulates the release of GH in swine, and that the GH-releasing effect of the peptide does not become desensitized after short-term administration in feed.

Administration, Oral↗

PubMed2001

The nature of human craniofacial growth studied with finite element analytical approach.

The purpose of this study was to elucidate the nature of human craniofacial growth by means of finite element method (FEM), and to compare the results with the current concept derived from morphometric studies with roentgenographic cephalometry (RCM). Lateral cephalograms were taken of 20 males and 20 females, and traced on acetate paper. On the tracing, the craniofacial complex was divided into seven areas or elements. Growth analysis was executed with FEM for changes in the size and shape of each area during six developmental periods from 4 to 18 years old. The size change in the male group exhibited a peak from 10 to 12 years old for the cranial base and upper facial skeleton, from 8 to 10 years old for the maxillary complex, and from 12 to 14 years old for the mandible. On the other hand, in the females, the size change was almost invariable from 4 to 12 years old and completed suddenly at 12 years old, which was earlier by a few years than in the males. An interesting finding is that changes in the size and shape were the most substantial in the maxillary complex, followed by those in the mandible, and the smallest in the cranial base and upper facial skeleton. It is shown that growth of the cranial base lasted up to 14 years old and the maxillary complex exhibited the greatest growth changes in the size among various anatomic structures. These findings may provide a new concept of human craniofacial growth, somewhat different from the previously established principles by RCM.

Journal Article↗

PubMed2001

The expression of osteopontin with condylar remodeling in growing rats.

It is suggested that osteopontin may promote osteoclast binding to resorptive sites by interacting with the alphavbeta3 receptor on osteoclasts. However, the role of osteopontin in functional remodeling of bony structures remains unclear. The present study was conducted to examine the distribution of osteopontin on the condyle and explore the role in condylar remodeling in growing rats using an immunohistochemical method. Twenty Wistar strain male rats aged 7, 14, 28 and 56 days were used. In 7- and 14-day-old rats, no immunoreaction to osteopontin was detected in the cartilage cells. In 28-day-old rats initiating mastication, the thickness of condylar cartilage was decreased abruptly as compared to the younger rats. High immunoreaction to osteopontin was found in the cytoplasm of hypertrophic chondrocytes and on the trabecular bone surfaces of primary spongiosa adjacent to the osteoclasts or chondroclasts. The immunoreactions to osteopontin in the cytoplasm of hypertrophic chondrocytes were less in 56-day-old rats than in 28-day-old rats. It is shown that the alteration in mechanical loading on the mandibular condyle due to functional changes from weaning to mastication correlates with the localization of osteopontin in growing rats. Furthermore, it is suggested that osteopontin may stimulate osteoclastic resorption of calcified matrix by mediating the attachment of osteoclasts and/or chondroclasts during growth-related functional remodeling of the condyle.

Journal Article↗

PubMed2001

Photoconductive imaging in a photon scanning tunnelling microscope capable of point-contact current sensing using a conductive fibre probe.

A photoconductive photon scanning tunnelling microscope was developed to investigate the point-contact photoconductive properties of condensed matter. In order to detect the current and the optical signal at a local point on a surface, we coated the edge of a bent type fibre probe with indium tin oxide. Thus it was possible to measure both photocurrent and optical property with subwavelength resolution. The performance of the novel microscope was evaluated by analysing an organic thin film of copper phthalocyanine (CuPc), which is known to be an efficient photoconductive material. Photocurrent and current-voltage characteristics were observed at the local point on the CuPc thin films. Furthermore, photoconductive images were obtained with topography and near-field optical imaging using this system. The photoconductive PSTM shows potential in various areas of future optics and electronics.

Journal Article↗