Biomedical subjects

K Fujii

Publications and source records attributed to K Fujii.

At least 217 records · Page 12Linked to original sources

PubMed1999

MR fluid-attenuated inversion recovery imaging as routine brain T2-weighted imaging.

We tried to investigate if magnetic resonance (MR) fluid-attenuated inversion recovery (FLAIR) imaging can be used as a routine brain screening examination instead of spin-echo T2-weighted imaging. Three hundred and ninety-four patients with clinically suspected brain diseases were randomly selected and examined with both brain MR FLAIR and T2-weighted imaging on the axial plane. These two imaging techniques were evaluated by two neuroradiologists as to which imaging was better for routine brain T2-weighted imaging. In 123 of 394 cases (31%), FLAIR imaging was superior to spin-echo T2-weighted imaging. Especially in cases with inflammatory diseases, traumatic diseases and demyelinating diseases, FLAIR imaging was particularly useful. Small lesions bordering cerebrospinal fluid (CSF) are often detected only by FLAIR imaging. In 259 cases (66%), including 147 normal cases (37%), they were equally evaluated. Only in 12 cases (3%) was conventional T2-weighted imaging superior to FLAIR imaging. Cerebrovascular lesions like cerebral aneurysm and Moyamoya disease could not be detected on FLAIR images because these structures were obscured by a low signal from the CSF. Also, because old infarctions tend to appear as low signal intensity on FLAIR images, the condition was sometimes hard to detect. Finally, FLAIR imaging could be used as routine brain T2-weighted imaging instead of conventional spin-echo T2-weighted imaging if these vascular lesions were watched.

Adolescent↗

PubMed1999

Intravenous nicorandil can preserve microvascular integrity and myocardial viability in patients with reperfused anterior wall myocardial infarction.

OBJECTIVES: We assessed whether the intravenous administration of nicorandil, an adenosine triphosphate (ATP)-sensitive K+ channel opener, exerts beneficial effect on microvascular function and functional and clinical outcomes in patients with acute myocardial infarction (AMI). BACKGROUND: Experimental studies documented that ATP-sensitive K+ channel opener exerts cardioprotection after prolonged ischemia. METHODS: We randomly divided 81 patients with a first anterior AMI into two groups, nicorandil (n = 40) and control groups (n = 41). All patients received successful coronary angioplasty within 12 h after the symptom onset and underwent myocardial contrast echcardiography (MCE) with the intracoronary injection of sonicated microbubbles. In the nicorandil group, we injected 4 mg of nicorandil followed by the infusion at 6 mg/h for 24 h and by oral nicorandil (15 mg/day). RESULTS: The improvement in regional left ventricular function, wall motion score and regional wall motion was significantly better in the nicorandil group then in the control group. Intractable congestive heart failure, malignant ventricular arrhythmia and pericardial effusion were more frequently found in the control group than in the nicorandil group (15% vs. 37%, 5% vs. 20% and 8% vs. 37%, p < 0.05, respectively). The frequency of sizable MCE no reflow phenomenon was significantly lower in the nicorandil group than in the control group (15% vs. 33%, p < 0.05). CONCLUSIONS: Intravenous nicorandil in conjunction with coronary angioplasty is associated with better functional and clinical outcomes compared to angioplasty alone in patients with an anterior AMI. Myocardial contrast echocardiography findings imply that an improvement in microvascular function with nicorandil may be attributable to this better outcome.

Angioplasty, Balloon, Coronary↗

PubMed1999

Effects of adjunctive balloon angioplasty after intravascular ultrasound-guided optimal directional coronary atherectomy: the result of Adjunctive Balloon Angioplasty After Coronary Atherectomy Study (ABACAS).

OBJECTIVES: This study was conducted to evaluate: 1) the effect of adjunctive percutaneous transluminal coronary angioplasty (PTCA) after directional coronary atherectomy (DCA) compared with stand-alone DCA, and 2) the outcome of intravascular ultrasound (IVUS)-guided aggressive DCA. BACKGROUND: It has been shown that optimal angiographic results after coronary interventions are associated with a lower incidence ofrestenosis. Adjunctive PTCA after DCA improves the acute angiographic outcome; however, long-term benefits of adjunctive PTCA have not been established. METHODS: Out of 225 patients who underwent IVUS-guided DCA, angiographically optimal debulking was achieved in 214 patients, then theywere randomized to either no further treatment or to added PTCA. RESULTS: Postprocedural quantitative angiographic analysis demonstrated an improved minimum luminal diameter (2.88 +/- 0.48 vs. 2.6 +/- 0.51 mm; p = 0.006) and a less residual stenosis (10.8% vs.15%; p = 0.009) in the adjunctive PTCA group. Quantitative ultrasound analysis showed a larger minimum luminal diameter (3.26 +/- 0.48 vs. 3.04 +/- 0.5 mm; p < 0.001) and lower residual plaque mass in the adjunctive PTCA group (42.6% vs. 45.6%; p < 0.001). Despite the improved acute findings in the adjunctive PTCA group, six-month angiographic and clinical results were not different. The restenosis rate (adjunctive PTCA 23.6%, DCA alone 19.6%; p = ns) and target lesion revascularization rate (20.6% vs. 15.2%; p = ns) did not differ between the groups. CONCLUSIONS: With IVUS guidance, aggressive DCA can safely achieve optimal angiographic results with low residual plaque mass, and this was associated with a low restenosis rate. Although adjunctive PTCA after optimal DCA improved the acute quantitative coronary angiography and quantitative coronary ultrasonography outcomes, its benefit was not maintained at six months.

Aged↗

PubMed1999

Evidence for the delayed effect in human ischemic preconditioning: prospective multicenter study for preconditioning in acute myocardial infarction.

OBJECTIVES: This study aimed to investigate prospectively the protective effect of a first preinfarction angina attack against acute myocardial infarction (AMI) in human hearts without significant collaterals. BACKGROUND: Several retrospective studies and the prospective studies have demonstrated the existence of the preconditioning (PC) effect in humans. However, collaterals were not examined in the prospective studies. In animal models, the PC effect on myocardial infarct size appears soon after PC reperfusion (classic) but disappears within 1 to 2 h. It then reappears 24 to 48 h after reperfusion (the delayed PC effect). Meanwhile, the PC effect on stunning appears 12 h after PC reperfusion (the delayed PC effect). The concept of the classic and delayed PC effects has not been investigated in human AMI studies. If the above concept is also correct in humans, the infarct size and/or impairment of the left ventricular function should be inversely correlated with the time interval between the first preinfarction angina attack and the onset of AMI when that time interval is limited to between 2 and 48 h. METHODS: The subjects were 25 patients with first AMI of the proximal left anterior descending artery who underwent successful direct percutaneous transluminal coronary angioplasty (PTCA) 2 to 6 h after the onset and with no (or poor) collateral circulation (grade 0 or 1). They were divided into two groups: preinfarction angina (PA)(+) group: 11 patients with new onset preinfarction angina from 2 to 48 h before the onset, PA(-) group: 14 patients without angina before infarction. Peak creatine kinase (CK) and cumulative CK were examined, and the left ventricular ejection fraction (LVEF) and the regional wall motion (RWM) were determined from the left ventriculograms during the acute (immediately after the coronary reperfusion) and chronic (four weeks after the onset of AMI) phases. The RWM index (RWMI) was then calculated as the mean motion of chords (standard deviation [SD]/chord) lying in the area of chords of RWM < or = -2 SD in the acute phase (ischemic risk area). RESULTS The increase in the RWMI between the acute and chronic phases was significantly larger in the PA(+) group than in the PA(-) group (1.55 +/- 1.32 and 0.69 +/- 0.75, p < 0.05, respectively) although no significant difference in the enzymatic infarct size was seen between the two groups. The increases in the LVEF and the RWMI were significantly correlated with the time interval from the first preinfarction angina attack to the onset of AMI (r = 0.622, p < 0.05 and r = 0.646, p < 0.05, respectively), but the enzymatic infarct size was not. CONCLUSIONS: The beneficial effect of preinfarction angina on left ventricular wall motion, independently of collateral flows, indicates the existence of the PC effect in humans. The greater protective effect of a longer time interval between angina pectoris and AMI suggests that the protection is due to a delayed PC effect.

Angina Pectoris↗

PubMed1999

Neuroradiologic findings in glutaric aciduria type II.

The authors report a 3-year-old male with glutaric aciduria type II, whose magnetic resonance imaging studies revealed agenesis of the cerebellar vermis and hypoplastic temporal lobes. Proton magnetic resonance spectroscopy in the parietal white matter revealed a markedly increased choline/creatine ratio, suggesting a demyelinating process. Gas chromatographic analysis of urinary organic acids should be studied in any patient with agenesis of the cerebellar vermis and cystic renal disease to exclude glutaric aciduria type II.

Amino Acid Metabolism, Inborn Errors↗

PubMed1999

Neurocysticercosis case with a single cyst in the brain showing dramatic drop in specific antibody titers within 1 year after curative surgical resection.

We report on one Japanese case subject with neurocysticercosis (NCC) who had a single cyst in the brain and had undergone curative surgical resection. Pathological examination revealed that it was a cysticercus of Taenia solium. Serological examination of the pair serum samples just before and 1 year after surgery revealed that antibody responses against the glycoproteins, highly specific to NCC and detected in the serum sample just before surgery by both immunoblot and ELISA became negative within 1 year after the surgery. It is, therefore, strongly suggested that this case had a single cysticercus in his whole body and the presence of a single cysticercus was sufficient to evoke antibody responses against it.

Animals↗

PubMed1999

Leptomeningeal melanomatosis with multiple cutaneous pigmented nevi: tumor cell proliferation and malignant transformation in an autopsy case.

We experienced a rare case of leptomeningeal melanomatosis. The proliferative activity and nuclear accumulation of p53 in this tumor were examined, since the relationship between this tumor type and growth has not yet been elucidated. A 33-year-old Japanese man was shown to have leptomeningeal melanomatosis with multiple cutaneous pigmented nevi. The autopsy findings showed the presence not only of benign diffuse melanosis of the leptomeninges but also of leptomeningeal melanomatosis in the subarachnoid space and brain parenchyma. In the brain parenchyma, the direct invasion of tumor cells from the subarachnoid space and Virchow-Robin spaces filled with melanoma cells were observed. Multiple hemorrhagic areas invaded by melanoma cells were also present. Immunohistochemical staining with a monoclonal antibody to melanoma cells showed positivity in the tumor cells. Proliferation analysis using the MIB-1 antibody demonstrated that the labeling index of tumor cells invading brain parenchyma (2.54%) was higher than that in other lesions of the inner (0.89%) and outer layer (0.76%) of the subarachnoid space. Nuclear accumulation of p53 protein was rarely seen in the tumor cells. We reported a case of leptomeningeal melanomatosis. Higher proliferative activity was found in invading cells of the brain parenchyma. Malignant transformation of the tumor did not appear to be associated with p53 gene mutation.

Adult↗

PubMed1999

Pharmacological activities of TEI-8362, a novel inhibitor of human neutrophil elastase.

1. TEI-8362, 4-(N-(3-((3-carboxypropyl)amino)-8-methyl-1-oxo-4-azaisochromen-6- yl)carbamoyl)-4-((phenylmethoxy)carbonylamino)butanoic acid (C26H28N4O9) is a novel inhibitor of human neutrophil elastase (HNE). We evaluated its pharmacological profile in vitro and in vivo. 2. TEI-8362 demonstrated potent inhibition of HNE with a Ki value of 1.38 x 10(-9) M. Its selectivity for HNE among a variety of proteases ranged from 163 fold to 68,000 fold in favour of HNE. 3. The pulmonary haemorrhage that occurred after i.t. instillation of HNE to hamsters was inhibited by either i.t., i.v., or inhalant administration of TEI-8362. 4. Intratracheal administration of lipopolysaccharide induced pulmonary neutrophilia. Twenty-four hours after lipopolysaccharide administration, the additional treatment with formyl-methionyl-leucyl-phenylalanine resulted in a specific neutrophil-dependent acute lung injury. In this model, lung injury was significantly attenuated by i.t., i.v., or inhalant administration of TEI-8362. 5. These pharmacological actions of TEI-8362 suggest that this drug has therapeutic value in the treatment of destructive lung diseases due to neutrophils.

Animals↗

PubMed1999

Clinical evaluation of lymph node metastasis in gastric cancer defined by the fifth edition of the TNM classification in comparison with the Japanese system.

BACKGROUND: This study compared the classification of lymph node metastasis according to the number of involved nodes based on the new tumour node metastasis (TNM) system (fifth edition) with the classification by the Japanese Research Society for Gastric Cancer from an anatomical perspective. METHODS: The two classifications were related to long-term results in 1489 patients with gastric cancer who underwent gastrectomy with systematic extended lymphadenectomy. RESULTS: Both classifications performed well as prognostic indicators (5-year survival rates: pathological (p) N0, 89 per cent; pN1, 66 per cent; pN2, 34 per cent; pN3, nil; and M1, 10 per cent by the TNM classification; n0, 89 per cent; n1, 63 per cent; n2, 46 per cent; n3, 20 per cent; and n4, 8 per cent by the Japanese classification). For regional lymph nodes, the TNM classification was a better index of the prognosis. Significant survival differences were observed among patients with M1 disease according to the number of involved lymph nodes (between one and six nodes, 48 per cent; seven to 15 nodes, 12 per cent; more than 15 nodes, 2 per cent), indicating that patients with distant metastatic lymph nodes (M1) should also be classified by the number of involved nodes. On the other hand, the Japanese classification has the added benefit of being a good indicator of the anatomical extent of lymphadenectomy. CONCLUSION: The new TNM classification provided a better index of the prognosis of patients who underwent systematic lymph node dissection. However, both classifications have specific benefits in the surgical treatment of gastric cancer.

Female↗

PubMed1999

Clear cell chondrosarcoma: a pathological and immunohistochemical study.

AIM: Clear cell chondrosarcoma (CCC) is a rare malignant cartilaginous neoplasm of bone. CCC is characterized by clear cells (CCC cells), osteoclasts and osteoblasts. Many important questions concerning the varied histological features of CCC, and the interactions between CCC cells and coexisting osteoclasts and osteoblasts have not been fully investigated and remain controversial. The aim of this study is to clarify and explain the varied histological features and the possible interaction between tumour cells (CCC cells) and stromal cells such as osteoclasts and osteoblasts. METHODS AND RESULTS: Four cases of CCC were histologically and immunohistochemically studied in order to elucidate the biological nature and histological characteristics. A comparative study with chondroblastoma and grade I conventional chondrosarcoma (CC) was also performed. S100 protein and type II collagen were expressed in CCC cells, chondroblastoma cells and CC cells. CD68 and matrix metalloproteinase-9 were expressed in coexisting histiocytes and osteoclasts. Parathyroid hormone-like protein (PTH-LP) was expressed in histiocytes, osteoclasts, osteoblasts, chondroblastoma cells and CCC cells. Platelet-derived growth factor (PDGF) and its receptor (PDGF-R) were observed in osteoblasts, chondroblastoma cells and CCC cells. However, PTH-LP, PDGF and PDGF-R were not expressed in CC cells. PCNA (proliferating-cell nuclear antigen) was expressed more intensely in CCC than in chondroblastoma. CONCLUSION: These observations suggest that CCC cells trigger the varied histological changes in association with several cytokines. The difference of PCNA expression between CCC and chondroblastoma seemed to be related to the biological difference between the two tumours.

Adult↗

PubMed1999

Consistency of alginate impression materials and their evaluation.

The apparent viscosity of 17 commercially available alginate impression materials was examined using a rheometer. Each material was mixed for 15 s at a temperature of 23 +/- 0.5 degrees C, using a specially designed alginate mixing instrument. The water powder ratio was determined according to the manufacturer's instruction. The mixed alginate paste was immediately transferred to the sample stage of the rheometer or to a commercial perforated metal tray. Over the same time scale adjusted according to the rheometer test, a discrimination test (subjective test) was performed by 16 young dentists (each with more than 4 years experience). The apparent viscosity of all materials rose as a function of time after mixing and most of the material had properties similar to pseudoplastic fluids. The relationship between the results of the subjective test and the experimental values (objective test) with the rheometer was expressed in a quadratic equation. The maximum value of the apparent viscosity derived from this result was 1.52 x 10(3) Pa.s.

Alginates↗

PubMed1999

An evaluation of acrylic complete dentures using the discrimination of elastic bodies or viscous fluids.

The discrimination test on elastic bodies and viscous fluids was carried out for 16 young dentists and 13 denture patients, because it is considered that dentures affect the ability to discriminate food. The materials used in this test were six thermoplastic polyurethane elastomers with compressive elastic moduli from 11.8 to 62.0 MPa and six silicone impression pastes with coefficients of viscosity from 1.77 x 10(-2) to 23.0 x 10(-2) MPa x s. The subjects (dentists and patients) discriminated the materials based on differences in elastic moduli or coefficients of viscosity by chewing the materials for 10 s. From these experiments, it became clear that the ability to discriminate between elastic bodies or viscous fluids upon chewing, of subjects who use complete-dentures in combination with their own teeth and either an upper or lower complete-denture (S/D) or who have a set of complete-dentures in both jaws (D/D) decreased considerably, compared with that of subjects who have their own teeth in upper and lower jaws (S/S). The ratios of S/D and D/D against S/S were 0.5 and 0.3, respectively. This indicates that with an increase in the area occupied by dentures in the oral cavity, the value of the differential threshold increased markedly and made food discrimination more difficult. In addition, discriminating viscous fluids was 2.4 to 3.1 times more difficult compared with the discrimination of elastic bodies, independent of denture placement.

Acrylic Resins↗

PubMed1999

Direct and buffering effects of social support on depressive symptoms of the elderly with home help.

The purpose of the present study was to examine the prevalence of depressive symptoms on the Center for Epidemiologic Studies Depression Scale (CES-D) and the effect of life stressors or social support on depressive symptoms in 303 elderly people receiving social services at home. We conducted a questionnaire survey six times with a 1-month interval. In the initial wave of questionnaires, 92 (31%) scored 16 points or above on the CES-D, indicative of a risk for depression. Before life stressors, subjects with low-level support showed significantly more severe depressive symptoms than those with high-level support. Subjects with low-level support were significantly more depressive after life stressors than they had been before, whereas those with middle- and high-level support showed no such difference. The former and latter results seem to suggest the direct and buffering effects of social support on depressive symptoms, respectively.

Activities of Daily Living↗

PubMed1999

The role of cysteinyl leukotrienes in the pathogenesis of asthma: clinical study of leukotriene antagonist pranlukast for 1 year in moderate and severe asthma.

Clinical studies have shown that pranlukast (Ono Pharmaceutical Co., Osaka, Japan) is effective for mild and moderate asthma. However, it is not well known that pranlukast is also effective on moderate and severe persistent asthma in the long term. We studied the effect of pranlukast on moderate and severe asthmatics by evaluating the change of peak expiratory flow (PEF) and therapeutic scores for 1 year before and during pranlukast therapy. We gave pranlukast 225 mg twice daily orally to 25 patients who were receiving more than 400 micrograms/day beclomethasone inhalation and beta 2 stimulant inhalation with or without oral corticosteroid. Pranlukast increased PEF more than 10 L/min in 14 patients in the first 4 weeks. In these 14 patients, 10 patients continued to monitor PEF and kept asthma diaries for 1 year. We compared the data for 1 year before and during the pranlukast therapy. During the pranlukast therapy, PEF significantly increased, puffs of beta 2 stimulant inhalation significantly decreased. The incidence of oral corticosteroid rescue therapy reduced, and the mean daily dose of oral corticosteroid decreased; however, they were not statistically significant. During treatment with pranlukast, no side effect was observed. From these results, we suggest that pranlukast is effective for more than half of the moderate and severe persistent asthmatics, and that the effectiveness continues for more than 1 year.

Adult↗

PubMed1999

Spontaneous carotid cavernous fistulas with special reference to the influence of estradiol decrease.

The etiology of the dural arteriovenous fistula (AVF) involving the cavernous sinus is still unknown. However, it is of interest that this condition usually occurs in post-menopausal women. The purpose of the present study was therefore to clarify the relationship between sex hormone blood levels and the occurrence of dural AVFs in the cavernous sinus. Serum sex hormone levels and factors associated with atherosclerosis were examined in 26 consecutive patients with dural AVF involving the cavernous sinus presenting at our institute during the last eight years and compared with those of a post-menopause control group. Of the present patient series, 21 (81%) were women. All except five had passed menopause. Five (24%) of the women patients presented with symptoms consistent with cessation of menstruation, namely, a blood level of estradiol significantly lower than the control value. Hypertension was recognized in 10 (71%) of 14 females who had experienced menopause 10 or more years previously and in all male patients. A sudden abnormal decrease of blood estradiol levels in female patients demonstrating symptoms consistent with menopause may thus be an important precipitating factor in the occurrence of dural AVFs involving the cavernous sinus. Hypertension, in older female and male patients, with or without longstanding low blood estradiol levels, may cause atherosclerosis of the feeding vessels in the dura mater, resulting in the opening of a normal AV shunt to provide collateral circulation.

Aged↗

PubMed1999

Synovial sarcoma, histologically mimicking primitive neuroectodermal tumor/Ewing's sarcoma at distant sites.

We report a case of synovial sarcoma (SS) showing unusual histology at distant sites. A 47-year-old man was aware of a tumor on the sole of his left foot. After preoperative chemotherapy with a diagnosis of SS, wide excision was performed. During postoperative chemotherapy, multiple tumorous lesions developed in the bone (including the whole spine) and both lungs. The patient died 1 year later. Histologically, the excised tumor of the foot showed a biphasic cellular pattern typical of SS, whereas at autopsy the bone and lung lesions were composed only of undifferentiated small round cells with cytoplasmic fibrillar processes. Homer-Wright rosettes were also observed. Immunohistochemically, 80% of the bone and lung tumor cells expressed MIC2 protein homogeneously. To clarify whether the bone and lung round cell tumors were metastatic lesions or second malignancies, especially primary primitive neuroectodermal tumor (PNET)/Ewing's sarcoma (ES), we performed reverse transcription-polymerase chain reaction (RT-PCR) analysis of tumor type-specific fusion gene transcripts. The SYT/SSX fusion transcript was identified in both the foot and lung lesions, whereas the EWS/FLI1 transcript was not detected in either lesion. Therefore, we concluded that the multiple bone and lung tumors were poorly differentiated metastatic tumors, which arose from the SS of the foot. We also conclude that the identification of chimeric fusion transcripts can be successfully applied to poorly differentiated sarcomas and will help in the differential diagnosis of tumors that cannot be distinguished by conventional morphological examinations. Also, it should be remembered that cytoplasmic staining for MIC2 protein may occur in sarcomas other than PNET/ES.

12E7 Antigen↗

PubMed1999

The effect of carboxyl group modification on the chromophore regeneration of archaeopsin-1 and bacterioopsin.

Carboxyl group modification with DCCD and NCD-4 was employed to investigate the chemical environment of the side chains of archaeopsin-1 (aO-1) and bacterioopsin (bO). Some differences were observed between aO-1 and bO. Although DCCD or NCD-4 did not modify aO-1 in bleached membrane, they modified bO in bleached membrane and in mixed DMPC/CHAPS/SDS micelles at neutral pH, thereby affecting the opsin shift and the photocycle of the regenerated chromophore. On the contrary, after solubilization with SDS, aO-1 and bO were modified by DCCD and NCD-4, which decreased the chromophore regeneration. In particular, the reaction of aO-1 in SDS with NCD-4 proceeded in a 1:1 ratio at neutral pH. The fluorescence and CD spectra indicated that the modified site was located in the hydrophobic, asymmetrical region. Lysyl-endopeptidase digestion of NCD-4 modified aO-1 produced a fluorescent fragment and amino acid sequence analysis showed that Asp85 or Asp96 in helix C is a probable candidate for the modified residue at present. Kinetic CD measurements revealed that the introduction of N-acylurea at an Asp residue in helix C did not affect the formation of the transient intermediate but inhibited the side chain packing during refolding.

Amino Acid Sequence↗

PubMed1999

Genetic analysis of the peptide synthetase genes for a cyclic heptapeptide microcystin in Microcystis spp.

Peptide-synthetase-encoding DNA fragments were isolated by a PCR-based approach from the chromosome of Microcystis aeruginosa K-139, which produces cyclic heptapeptides, 7-desmethylmicrocystin-LR and 3,7-didesmethylmicrocystin-LR. Three open reading frames (mcyA, mcyB, mcyC) encoding microcystin synthetases were identified in the gene cluster. Sequence analysis indicated that McyA (315 kDa) consists of two modules with an N-methylation domain attached to the first and an epimerization domain attached to the second; McyB (242 kDa) has two modules, and McyC (147 kDa) contains one module with a putative C-terminal thioesterase domain. Conserved amino acid sequence motifs for ATP binding, ATP hydrolysis, adenylate formation, and 4'-phosphopantetheine attachment were identified by sequence comparison with authentic peptide synthetase. Insertion mutations in mcyA, generated by homologous recombination, abolished the production of both microcystins in M. aeruginosa K-139. Primer extension analysis demonstrated light-dependent mcy expression. Southern hybridization and partial DNA sequencing analyses of six microcystin-producing and two non-producing Microcystis strains suggested that the microcystin-producing strains contain the mcy gene and the non-producing strains can be divided into two groups, those possessing no mcy genes and those with mcy genes.

Amino Acid Sequence↗