Biomedical subjects

Y Mishima

Publications and source records attributed to Y Mishima.

At least 19 recordsLinked to original sources

PubMed1995

Formation of a parallel-stranded DNA homoduplex by d(GGA) repeat oligonucleotides.

The GGA9-H molecules consisting of a double helical stretch followed by a single-stranded 3'-terminal overhang of nine GGA sequence repeats exhibited a gel mobility-shifted band in a concentration-dependent manner, suggestive of the intermolecular complex formation. The position of the shifted band in a gel was almost identical to that of the Y-shaped dimer marker of the same molecular weight that had the two double-helices at one side. This suggests that GGA9-H dimerizes in a parallel orientation without the formation of four-stranded hairpin structure. Since the GGA9-H homoduplex was stably formed at pH 4, 7 and 9, the formation does not require protonation or deprotonation of the N1 position of adenines. Neither does it require the N7 group of guanines responsible for Hoogsteen base pairing from the methylation interference and modification studies. Modification of the N7 group of guanines with dimethyl sulfate (DMS) did not inhibit the association and also the N7 group in the homoduplex was not protected from DMS. On the other hand, the GAA9-H having the G to A base substitution did not show such an association with either GGA9-H or GAA9-H. These results suggest that the homoduplex formation may be due to G.G base pairing through non-Hoogsteen hydrogen bonds.

Base Composition↗

PubMed1995

Site-specific crosslinking of 4-thiouridine-modified human tRNA(3Lys) to reverse transcriptase from human immunodeficiency virus type I.

We have mapped specific RNA-protein contacts between human immunodeficiency virus (HIV) type I reverse transcriptase (RT) and its natural primer, human tRNA(3Lys), using a site-specific crosslinking strategy. Four different tRNA(3Lys) constructs with a single 32P-labeled 4-thiouridine (4-thioU) residue at positions -1, 16, 36 or 41 were synthesized. After incubation with RT followed by irradiation, crosslinks were localized to either the p66 or p51 subunit of RT by digestion with nuclease and SDS gel fractionation. 4-thioU at position -1 or 16 transferred label to the p66 subunit almost exclusively (> 90%), whereas position 36 labeled both p66 and p51 (3:1). Position 41 yielded no detectable crosslinks. The region of p66 contacted by position -1 of tRNA(3Lys) was localized to the 203 C-terminal amino acids of RT by CNBr cleavage, whereas a 127 amino acid-CNBr peptide (residues 230-357) from both p66 and p51 was labeled by position 36. Functionality of the 4-thioU-modified tRNA(3Lys)(-1) crosslinked to RT in the presence of an RNA but not a DNA template was demonstrated by the ability of the tRNA to be extended. These results localize the 5' half of the tRNA on the interface between the two RT subunits, closer to the RNase H domain than to the polymerase active site, in accord with previous suggestions. They argue further that a specific binding site for the 5' end of the primer tRNA(3Lys) may exist within the C-terminal portion of the p66 subunit, which could be important for the initiation of reverse transcription.

Base Sequence↗

PubMed1995

High-performance liquid-chromatographic analysis of dopachrome and dihydroxyphenylalanine.

A high-performance liquid-chromatographic system for the determination of dopachrome and dihydroxy-phenylalanine (dopa) is described. The retention of dopa and dopachrome on C18 reversed-phase columns was investigated as a function of pH in the mobile phase, and as expected the capacity factors were found to be pH dependent. The chromatographic behavior is explained by the change in net charge and polarity of dopachrome and dopa when pH varies. Satisfactory separation of dopachrome and dopa was obtained. An advantage of the method is that the measurements of dopachrome stability and disappearance are uninfluenced by concomitant formation of melanochromes which, however, is the case when the disappearance is followed by measurement of the decrease in absorbance at 475 nm. The utility of the method is illustrated by following the disappearance of dopachrome as a measure of dopachrome tautomerase activity.

Animals↗

PubMed1995

Correlation between the number of melanosomes, tyrosinase mRNA levels, and tyrosinase activity in cultured murine melanoma cells in response to various melanogenesis regulatory agents.

Tyrosinase is the rate limiting enzyme critically associated with melanin synthesis. The melanosomes are specialized membrane-bound organelles within melanocytic cells in which melanin polymers are ultimately deposited. To determine whether tyrosinase correlates with the number of melanosomes, we examined the relationship between tyrosinase activity, tyrosinase mRNA levels, and the number of melanosomes in B16 murine melanoma cells, using melanogenesis regulatory agents. 12-O-Tetradecanoylphorbol-13-acetate (TPA) or linoleic acid decreased tyrosinase activity, while dibutyryl cyclic adenosine monophosphate (dbcAMP) or palmitic acid increased it. The tyrosinase mRNA levels were not always correlated with tyrosinase activity, i.e., TPA down-regulated, dbcAMP upregulated, while linoleic acid or palmitic acid did not alter the message levels, indicating that fatty acid regulation of melanogenesis was due to post-transcriptional events. The number of melanosomes changed when agents which modulate the tyrosinase gene expression were added, since TPA decreased, dbcAMP increased, and linoleic acid or palmitic acid did not alter their number. These results suggest that the number of melanosomes changed in relation to tyrosinase mRNA level but not to tyrosinase activity in response to melanogenesis regulatory agents.

Animals↗

PubMed1995

Experiences with the linear cutter technique for performing Roux-en-Y anastomosis following total gastrectomy.

The use of stapling devices for performing gastro-intestinal anastomosis has recently gained wide acceptance. In fact, since 1991, we have been using linear cutter devices for performing the Roux-en-Y anastomosis, transection of the duodenum, and closure of the jejunal stump (except following esophagojejunostomy), and are no longer employing hand-sewn procedures. In this report, the linear cutter technique used after total gastrectomy is described and the differences in anastomotic leakage, morbidity, operating time, and reconstruction time are evaluated in comparison with those following hand-sewn anastomoses. A total of 22 patients undergoing total gastrectomy within a 2-year period were randomized into two groups of 11, to have reconstruction performed by either a stapled or hand-sewn Roux-en-Y anastomosis. One patient from the stapled group died of acute myocardial infarction 6 days after the operation. Anastomotic leakages from the esophagojejunostomy region occurred in 18% of the patients in the stapled group, but fortunately no leakage was apparent from the Y-anastomosis when the linear cutter technique was used. The most obvious significance was the short mean reconstruction time in the stapled group of 19.1 +/- 3.56 min (P < 0.01) being 31 min shorter than that of the hand-sewn group (n = 11). Thus, we proposed that the linear cutter technique is a safe technique for performing anastomosis following total gastrectomy, which would significantly reduce the reconstruction time.

Adenocarcinoma↗

PubMed1995

Spontaneous dissecting aneurysm of the main trunk of the superior mesenteric artery: report of a case.

A 47-year-old man with a sudden onset of abdominal pain was diagnosed as having an aneurysm of the main trunk of the superior mesenteric artery (SMA), which induced ischemic colitis of the transverse colon probably because of a transient decrease in the SMA blood flow. The patient was successfully treated by resection of the aneurysm and an end-to-side anastomosis of the SMA to the aorta. A histological examination revealed a spontaneous dissecting aneurysm of the SMA.

Aortic Dissection↗

PubMed1995

Inhibitory effects of melanin monomers, dihydroxyindole-2-carboxylic acid (DHICA) and dihydroxyindole (DHI) on mammalian tyrosinase, with a special reference to the role of DHICA/DHI ratio in melanogenesis.

DOPAchrome tautomerase (DCT) is known to control the ratio of DHICA/DHI formed within the melanocyte, but physiologic significance of this activity is not yet fully elucidated. In this study the two melanin monomers are shown to inhibit with different efficacy the initial, tyrosinase-controlled, melanogenic reaction, namely conversion of L-tyrosine to DOPAchrome (2-carboxy-2,3-dihydroindole-5,6-quinone). This is demonstrated in the test tube assay system whereby formation of DOPAchrome is catalyzed by i) isolated premelanosomes (PMS), ii) tyrosinase-rich PMS glycoproteins, or iii) tyrosinase purified from fibroblasts transfected with human tyrosinase gene. Both DHI and DHICA suppress the conversion of L-tyrosine to DOPAchrome when added to reaction mixture but the inhibitory effect is far more strongly pronounced by DHI. DHI inhibits both activities of tyrosinase--tyrosine-hydroxylation and DOPA-oxidation--more strongly than DHICA. The different extent of inhibition is shown to reflect i) the ability of the two monomers to compete with tyrosinase substrates for the enzyme's active center and ii) the rate of interaction between melanin monomers and DOPAquinone. Consequently, we demonstrate that the tyrosinase-catalyzed DOPAchrome formation can be modulated by the ratio of DHICA/DHI among melanin monomers with the increased proportion of DHICA resulting in more efficient DOPAchrome formation. These results raise the possibility that DOPAchrome tautomerase plays a role in positive control of the tyrosinase-catalyzed early phase of melanogenesis.

Animals↗

PubMed1995

[Expression of E-cadherin as related to prognostic factors and survivals in breast cancer].

E-cadherin (E-CD) expression and its clinicopathological implication were investigated in 26 patients with breast cancer by immunohistochemical staining. 12 out of 26 primary lesions (46%) express strong and homogeneous expression of E-cadherin (preserved type), while in 14 cases (54%), degree of E-CD expression was reduced, i.e., 8 patients with heterogeneous staining, 2 cases with weak but homogeneous, and 4 cases with lost expression of E-CD (reduced type). However, there was no statistically significant correlation among decrease of E-CD expression, histological features, and advanced stages of breast cancer. Analysis on survivals showed better prognosis in the group with preserved E-CD expression than without E-CD (follow up was more than 96 months or until death). These findings suggests that the patients with decreased E-CD expression may be associated with metastasis resulting in poor prognosis, and E-CD expression could be one of the prognostic factors.

Breast Neoplasms↗

PubMed1995

[Interferon production in peripheral blood cells of patients with pulmonary mycobacterial disease].

Production of interferon (IFN)-alpha and IFN-gamma were examined in 31 patients with acute tuberculosis, 12 patients with atypical mycobacterial disease. IFN production was examined in cultures of unseparated fresh whole blood. Production of IFN-alpha was induced by hemagglutinating virus of Japan and production of IFN-gamma was induced by PHA. Patients with mycobacterial disease produced significantly less IFN-alpha than healthy subjects. In patients with acute tuberculosis, effective chemotherapy for 2 months restored IFN-alpha production. Patients produced less IFN-gamma than healthy subjects, but the difference was not significant. Patients with high serum CRP levels tended to produce little IFN-alpha. These results suggest that measurement of IFN production is useful for immunological evaluation of patients with mycobacterial disease.

Acute Disease↗

PubMed1994

Mortality in young first-degree relatives of patients with familial adenomatous polyposis.

BACKGROUND: Mortality and cancer deaths among young family members of patients with familial adenomatous polyposis (FAP) were investigated. METHODS: The subjects were 1764 members of 628 families with FAP registered at the authors' Polyposis Registry. They consisted of first-degree relatives of patients with FAP, excluding the propositus. These 1764 subjects were born between 1960 and 1978. Their survival times and causes of death were certified mainly by the National Family Registry and death certificates. Relative mortality rates were calculated based on the calendar year, age sex, and cause-specific death rate of Japanese people in the Vital Statistics, (Ministries of Health and Welfare, Japan. Vital statistics, Japan, Vol. 1960-1990. Tokyo: Statistics and Information Department, Minister's Secretariat, Ministry of Health and Welfare.) 1960-1990, Japan. RESULTS: There were 69 deaths before the age of 25 years. Deaths from malignant tumor were observed in 20 cases. Overall relative mortality rate in the subject group younger than age 20 years was 1.48. Relative cancer mortality in the age group between 1 and 4 years was significantly higher, because the relative mortality from hepatoblastoma in this age group was 176. Relative cancer mortality rate was significantly higher among males 15-19 years of age (15.4) and 20-24 years of age (male, 33.3; female, 150) due to colorectal cancer. CONCLUSIONS: Hepatoblastoma was a specific cancer in the 1- to 4-year-old age group in first-degree family members of patients with FAP. The incidence of colorectal cancer considerably increased, starting around the age of 20 years.

Adenomatous Polyposis Coli↗

PubMed1994

Production of immunoreactive atrial natriuretic polypeptide in neuroendocrine tumors.

BACKGROUND: Peptide hormone synthesis in neuroendocrine tumors is a well-recognized phenomenon. However, production in neuroendocrine tumors of atrial natriuretic polypeptide (ANP), a newly discovered peptide hormone from the heart, has not been studied extensively. METHODS: The presence of immunoreactive human ANP (IR-hANP) in neuroendocrine tumors was determined using a specific human ANP radioimmunoassay. Neuroendocrine tumors examined included 9 small cell carcinomas of the uterus, 28 small cell carcinomas of the lung, 20 carcinoid tumors, 54 pancreatic endocrine tumors, 17 neuroblastic tumors, 14 pheochromocytomas, and 14 medullary carcinomas of the thyroid. Twenty atrial tissues also were examined as the control. Molecular size of IR-hANP in the extracts of atrial and tumor tissues was determined by gel chromatography. RESULTS: IR-hANP was detected in the extracts of small cell carcinoma of the uterus, small cell carcinoma of the lung, and carcinoid tumor, with concentrations ranging from 3.1 to 210 ng/g wet weight tissue. No IR-hANP was detected in the extracts of pancreatic endocrine tumor, neuroblastic tumor, pheochromocytoma, and medullary carcinoma of the thyroid. The frequency of production of IR-hANP in neuroendocrine tumors was highest in small cell carcinoma of the uterus (44%), followed by small cell carcinoma of the lung (18%) and carcinoid tumor (15%). IR-hANP present in the extracts of small cell carcinomas of the uterus had molecular size heterogeneity, with three fragments in addition to alpha-, beta- and gamma-human ANP. CONCLUSIONS: These results indicate that IR-hANP is produced by neuroendocrine tumors and that the molecular size of IR-hANP in tumor tissues is different from that in atrial tissues.

Atrial Natriuretic Factor↗

PubMed1994

The significance of portal vein chemotherapy for liver micrometastases: an experimental study of a rat model.

To clarify the significance of prophylactic portal vein chemotherapy for hepatic metastases, the correlation between the timing of the portal infusion and the growth of liver micrometastases was examined in a rat model. Male Donryu rats weighing 160-180 g were first inoculated intraportally with 5 x 10(6) ascites hepatoma AH60C cells, following which an intraportal infusion of 5-fluorouracil (5-FU) 20 mg/kg/day with heparin 100 U/kg/day was given over 5 days, commencing on day 0, 3, and 6, in groups A, B, and C, respectively. Compared with a control group of rats which received no treatment, a significant inhibition of tumor growth and prolongation of survival time were observed in groups A (P < 0.01) and B (P < 0.05); however, group C, in which the mean diameter of the micrometastases was 0.52 +/- 0.10 mm at the commencement of the portal infusion, showed no therapeutic response. These results suggest that prophylactic portal vein chemotherapy should be given to prevent the lodgement of tumor cells in the portal system and inhibit their initial proliferation, rather than to destroy established micrometastases.

Animals↗

PubMed1994

Factors affecting the risk of rectal cancer following rectum-preserving surgery in patients with familial adenomatous polyposis.

PURPOSE: Rectum-preserving surgery is one of the most common surgeries for familial adenomatous polyposis (FAP). It is appropriate to analyze factors influencing risk of rectal cancer after rectum-preserving surgery in FAP patients. METHODS: Three hundred twenty-two patients with FAP (169 males, 153 females) who had undergone rectum-preserving surgery and were part of 1050 FAP patients registered at our FAP registry were included in the study. Postoperative survival was investigated and cause of death was elucidated from the death certificate or by inquiry to the hospitals that registered the patients. For risk analysis, log-rank tests were used. RESULTS: Forty-four cases developed invasive cancer within a mean interval of 119 months after surgery. Cumulative risk of rectal cancer was 24.2 +/- 7 percent (mean +/- limit of 95 percent confidence interval) at 15 years. Influencing risk factors for rectal cancer were a postoperative period over ten years or age over 44 years, a rectum longer than 7 cm, and dense polyposis. Other factors such as sex and cancer in the colon at initial surgery were not correlated with risk. CONCLUSION: The rectum may be reasonably preserved in patients with FAP when polyps in the rectum are sparse, ileorectal anastomosis is made on or below the peritoneal reflection, and patients continue having rectal examinations for life.

Adenomatous Polyposis Coli↗

PubMed1994

Bombesin enhances experimental carcinogenesis induced in rat colon by 1,2-dimethylhydrazine.

The effects of bombesin on the colonic mucosa and on the incidence, number, size and histology of colon cancers induced by 1,2-dimethylhydrazine (DMH) were studied in Fischer 344 rats. In experiment 1, rats were randomized into three groups to receive either saline or bombesin (10 or 30 micrograms/kg body wt) to determine the labeling index of normal colonic mucosa. In experiment 2, rats were given 20 weekly injections of DMH (20 micrograms/kg body wt) and received either saline or bombesin (10 or 30 micrograms/kg body wt) every other day for 24 weeks. Administration of bombesin significantly increased the labeling indices of colonic mucosa in a dose-dependent manner. Chronic administration of bombesin at both dosages with DMH caused significant increases in the incidence, number and depth of involvement of colon cancers; however, it did not affect the size and histological type of colon cancers. In addition, bombesin at the dose of 30 micrograms/kg significantly increased the labeling index of colon cancer. These results suggest that bombesin stimulates the cell proliferation of colonic mucosa and colon cancer and enhances colon carcinogenesis in rats.

1,2-Dimethylhydrazine↗

PubMed1994

Lack of effect of cholecystokinin receptor antagonist (CR1505) on recovery of experimental pancreatitis after pancreatic duct occlusion in rats.

The effect of long term administration of a synthetic cholecystokinin (CCK) receptor antagonist CR1505 (loxiglumide) on pancreatitis was examined in rats after pancreatic duct ligation (PL) with an internal bile fistula. All rats were given both 6 mg/day of CR1505 continuously infused intraduodenally with an osmotic pump and 32 mg/day introduced into the stomach with an orogastric tube. Rats were killed 7, 14, and 28 days after PL, and changes of body weight, pancreatic wet weight, daily food intake, pancreatic protein content, and histology, plasma amylase concentration, and both plasma and duodenal CCK concentrations were examined. Administration of CR1505 for 7 days from immediately after PL, resulted in decrease of body weight, increase of daily food intake, and significant increases of intestinal CCK concentration and the level of CCK mRNA. However, its administration from day 7 to day 14 or 28 did not improve any of the parameters examined except inflammatory infiltration of the pancreas on the 14th postoperative day. These results suggest that CR1505 may have a beneficial effect on recovery from pancreatitis when administered during the early stage, but not when administered during a later stage.

Animals↗

PubMed1994

Selective boron accumulation in human ocular melanoma vs surrounding eye components after 10B1-p-boronophenylalanine administration. Prerequisite for clinical trial of neutron-capture therapy.

We have developed neutron-capture therapy (NCT) for cutaneous malignant melanoma using a melanoma-seeking 10B-dopa, analogue, 10B1-para-boronophenylalanine (10B1-BPA). In order to explore the feasibility of applying NCT further to ocular melanoma, we investigated the boron concentrations in ocular melanomas and normal ocular tissues by 10B1-BPA administration to three patients, because success of NCT depends mainly upon selective boron accumulation in melanoma. In the first and second ocular melanoma patients, to whom 10B1-BPA fructose complex (total dose of 10B1-BPA: 170 mg/kg body weight) was administered orally in two divided doses, the boron concentrations in blood, vitreous body, sclera and retina choroidea were lower than that in melanoma examined. In the third conjunctival melanoma patient, to whom 10B1-BPA fructose complex (dose of 10B1-BPA: 85 mg/kg body weight) was administered by intravenous drip infusion, the average boron concentration in four melanoma samples was 17.7 ppm, which was estimated to be within the range necessary for melanoma eradication by thermal neutron irradiation. Boron uptake by lens, vitreous body, retina choroidea and sclera was much lower than that by melanoma. It was suggested that such a superficial ocular melanoma as iris melanoma can be destroyed by NCT, although vision may be affected--mainly due to cataract formation.

Boron↗

PubMed1994

Melanogenesis investigation leading to selective melanoma neutron capture therapy and diagnosis.

Basic investigation into the nature of melanin monomer and polymer synthesis in pigment cells has revealed many of the new underlying factors involved in its regulation and control by three melanogenesis-related genes, tyrosinase, TRP-1 and TRP-2, and other non-tyrosinase glycoproteins. Pigment cells can undergo clinically and biologically recognizable progressive multi-step carcinogenesis. Generally parallel to this progressive cancerization is accentuated melanogenesis. Using this accentuated melanogenesis to develop a specific diagnosis and cure for melanoma (Mm) has long been a challenge. However, until recently, no success was achieved. As an example, attempting to utilize the fact that dopa accumulates as a melanin substrate within Mm cells, hybrid compounds of dopa and cytotoxic drugs were developed. However, these compounds were found to have severe systemic side effects and were therefore unusable. Another newer Mm treatment involves high energy radiation such as fast neutrons. But this is quite non-selective, killing both the target cancer and the normal surrounding tissue. Since 1972, I have developed the idea of coupling the high energy releasing system of thermal neutron irradiation with the non-toxic 10B-dopa analogue, 10B1-L-p-boronophenylalanine (10B1-L-BPA). Thermal neutrons are essentially harmless, but, after specific absorption by 10B, release high LET alpha-particles and 7Li-atoms with an energy of 2.33 MeV up to a distance of 14 mu, the diameter of Mm cells, thus selectively killing them without damaging surrounding normal tissue. After the synthesis of 10B1-L-BPA, exhaustive in vitro and in vivo radiological studies on its enhanced killing effect were done to develop optimal Mm Boron Neutron Capture Therapy (NCT).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1994

Light and electron microscopic analysis of liver sinusoids during hepatocarcinogenesis with 2-acetylaminofluorene in rats.

To clarify the sequential changes and morphological differences of the sinusoidal structures between hepatocellular carcinoma (HCC) and hepatocellular adenoma (HA), we examined morphological changes of sinusoidal cells and related structures such as basement membrane during hepatocarcinogenesis in the rat. During continuous feeding of carcinogenic diets containing 2-acetylaminofluorene to rats, HA appeared at the 8th week in the peripheral area and then extended toward the centrolobular area. The appearance of HCC was recognized at the 27th week. In the HA lesion, the morphology of sinusoidal cells and related structures was basically the same as that of normal liver except for a slight thickening of the basement membrane and a decreased amount of vitamin A-lipid droplets of stellate cells. In HCC, the fenestrations of endothelial cells disappeared and the basement membrane became continuous, thick and often multilayered. Stellate cells contained almost no vitamin A-lipid droplets and were associated with abundant collagen fibers. Kupffer cells and pit cells were not seen inside the sinusoid. All these features of the sinusoids in HCC resembled the morphological characteristics of the capillary. The present study has revealed that HCC possesses sinusoid structures distinct from those of HA. This suggests that HCC may not derive directly from HA but may develop newly within the HA.

2-Acetylaminofluorene↗