Biomedical subjects

T Kuroiwa

Publications and source records attributed to T Kuroiwa.

At least 19 recordsLinked to original sources

PubMed1996

Nuclear encoding of a chloroplast RNA polymerase sigma subunit in a red alga.

A chloroplast RNA polymerase sigma factor is encoded by a nuclear gene, sigA, in the red alga Cyanidium caldarium RK-1. The encoded protein functions as an RNA polymerase sigma factor in vitro and it is localized to the chloroplast in vivo. SigA shows high sequence similarity to the sigma factors of cyanobacteria, which is indicative of the ancestral endosymbiotic event and subsequent transfer of the sigA gene to the nuclear genome.

Amino Acid Sequence↗

PubMed1996

The pyramidal cell layer of sector CA 1 shows the lowest hippocampal succinate dehydrogenase activity in normal and postischemic gerbils.

We examined regional differences in the activity of a mitochondrial respiratory enzyme, succinic dehydrogenase (SDH), in the hippocampi of normal and postischemic gerbils, using a quantitative imaging method. Gerbils (n = 21) without ischemia, and gerbils which had experienced 5 min of bilateral common carotid artery occlusion 12 h or 2 days previously, were sacrificed. Coronal sections of the brains were prepared for quantitative imaging of SDH activity and histological examination. In the control gerbils, SDH activity in the pyramidal cell layer of the CA 1 sector (Sommer's sector) was 106.3 +/- 10.3% (mean +/- SD; SDH activity as a percentage of the cerebellar SDH activity), which was lower than in the other subfields of the hippocampus. SDH activity in the oriens layer, stratum radiatum and lacunosum molecular layer of the CA 1 sector was lower than in the corresponding layers of the CA 2 and CA 3 sectors. After transient ischemia, SDH activity remained unchanged in the CA 1 sector. Histologically, selective neuronal necrosis was observed in the pyramidal cell layer of the CA 1 sector 2 days after ischemia. The observed low level of this mitochondrial respiratory enzyme in the pyramidal cell layer of the CA 1 sector should be taken into account as a possible trigger of the selective vulnerability of the region to ischemia.

Animals↗

PubMed1996

Reinitiation of protein translocation across the endoplasmic reticulum membrane for the topogenesis of multispanning membrane proteins.

The reinitiation of the translocation of the growing nascent chain across the endoplasmic reticulum membrane is essential for the topogenesis of multispanning membrane proteins. We investigated the requirements for the reinitiation process using model proteins in which systematically designed sequences were inserted after two preceding topogenic sequences, namely the N-terminal signal sequence (S) and stop transfer sequence (St). The model proteins were translated in vitro in the presence of rough microsomes, and the final topology of the proteins in the microsomal membrane was examined by proteolytic digestion. The structural requirements for S and the reinitiation sequence (R) overlapped to some extent, but substantial differences were noticed. When St and R were separated by a short cytoplasmic segment (58 amino acids), the efficiency of the reinitiation was not affected by the concentration of the signal recognition particle (SRP) in the translation system, even though the sequence inserted as R was an SRP-dependent signal sequence. However, when the cytoplasmic segment was longer (100 amino acids), the reinitiation efficiency was reduced, and the SRP improved the overall efficiency as well as impaired the accessibility of the processing site after the R to the signal peptidase.

Amino Acid Sequence↗

PubMed1996

Radiosurgery for cerebral arteriovenous malformations: assessment of early phase magnetic resonance imaging and significance of gadolinium-DTPA enhancement.

PURPOSE: To evaluate the initial changes within the nidus of arteriovenous malformations (AVMs) and to assess the reaction to the brain tissue surrounding AVMs after radiosurgery by serial magnetic resonance (MR) imaging. METHODS AND MATERIALS: Twenty-one patients, treated using 60Co gamma knife unit with cerebral AVMs, were retrospectively evaluated. Forty-seven follow-up MR images of the 21 patients were performed including 10 patients with two or more serial gadolinium enhanced studies (Gd-MR). Two or more sequential MR angiographies (MRA) were obtained in 13 patients. Three-dimensional (3D) time-of-flight MRA and two-dimensional (2D) phase contrast MRA were used in 13 patients for evaluating the flow changes of AVMs. The follow-up period after radiosurgery ranged from 3 to 30 months (average 10.8 months) and the interval time of MRI ranged from 34 days to 13 months (average 4.9 months). RESULTS: Reduction of nidus size was observed in 14 of 21 patients (67%) between 4 to 13 months on spin echo (SE) images. Complete obliteration was observed on SE images in 4 of these 14 patients; three were confirmed by conventional angiography. New hyperintense areas surrounding the nidus on T2s-weighted images (T2WI) developed in 9 of the 14 patients who showed nidus reduction between 5 to 17 months after radiosurgery; in three patients, size of the hyperintense area started to decrease between 6 to 7 months after its appearance. Probable radiation necrosis of pons developed in one patient 26 months after radiosurgery. The irradiated area within the AVM nidus was significantly enhanced in 8 of the 10 patients who underwent Gd-MR. The degrees of enhancement within the nidus increased with time in 7 of the 10 patients. Overall, total enhancement of irradiated areas was observed in four of the 10 patients; in three of the four, the enhancement decreased in size and degree, indicating nidus reduction. In three patients who had a partial volume irradiation within the nidus, the enhancing areas corresponded with the exact portions of irradiated volume. The nidus reduction was observed in 7 of the 13 patients on MRA during 5 to 13 months after radiosurgery. MRA was more useful compared to SE images in four of the seven patients in evaluating the size change of AVM nidus, feeding arteries, and draining veins. CONCLUSION: Magnetic resonance imaging and MRA were useful in assessing the progress of nidus reduction. T2-weighted imaging was sensitive to radiation-induced reaction in and around the AVM nidus. The enhancement within the AVM nidus on Gd-MR may represent the initial sign of nidus reduction and demonstrates the exact location of irradiation in the nidus. The changes of the enhancement pattern are presumed to represent the processes of nidus reduction and irradiated reaction within the AVM nidus.

Adolescent↗

PubMed1996

Changes in lCBF, morphology and related parameters by fluid percussion injury.

We investigated the pathophysiological and morphological responses of anaesthetized rats to fluid percussion brain injury generated by an original midline fluid percussion injury device. Following different grades of trauma, lCBF was measured continuously in the right parietal cortex through a burr hole using laser Doppler flowmeter, and physiological parameters were monitored. Pathological changes also were evaluated microscopically. During the first 2 hours following trauma, we found four patterns of cerebral circulatory responses. Little measurable pathophysiological response occurred after percussion pulses of less than 1.33 atmospheres (atm). In animals subjected to pulses of greater than 4.30 atm, lCBF increased synchronously with blood pressure, and then both parameters decreased continuously until death. In animals subjected to pulses of 1.53 to 2.33 atm, trauma produced a transient increase in lCBF with no synchronous rise in blood pressure. In animals subjected to pulses of 2.70 to 3.87 atm, lCBF increased synchronously with blood pressure immediately following the injury, but had decreased markedly by 60 seconds and remained below the pre-injury baseline. Blood pressure recovered to baseline within 4 minutes of the injury. The transient increase in lCBF occurred within 5 seconds following percussion pulses of greater than 1.53 atm and appeared to be independent of the rise in systemic blood pressure. Apnoea occurred in animals subjected to pulses of greater than 1.53 atm, and the duration of apnoea and mortality rate correlated with the magnitude of the applied injury. A power decrease in the electroencephalogram post-injury and a delay in its recovery, both depended on the magnitude of the injury with few regional differences in the beta-2 band power. The distribution and extent of blood-brain barrier disruption and small haemorrhages also correlated with the magnitude of the injury. The number of neurons decreased significantly in both hippocampi by 2 weeks following moderate trauma. The four patterns of lCBF changes demonstrated in the present study, as well as the other responses to injury, may be useful for studying graded models of various diffuse brain injuries.

Animals↗

PubMed1996

Rearrangements of mitochondrial DNA and the mitochondrial fusion-promoting plasmid (mF) are associated with defective mitochondrial fusion in Physarum polycephalum.

A specific linear mitochondrial plasmid (mF) is genetically associated with the fusion of mitochondria in the true slime mould, Physarum polycephalum. In matings between mF+ and mF- strains, which respectively carry and do not carry the mF plasmid, mitochondrial fusion occurs in the zygote. Mitochondrial fusion induces recombination between specific sites in the mitochondrial DNA (mtDNA) and in the mF plasmid. To detect a region which is associated with the mitochondrial fusion in the mF plasmid, we isolated, by fluorescence microscopy, strains which showed defective mitochondrial fusion (delta mif-) from those which showed normal mitochondrial fusion (mif+). Analysis of the mitochondrial genomes of delta mif- strains showed only mtDNA which recombined with the mF plasmid in mitochondria. Comparison of this recombinant mtDNA in one delta mif- strain (NG 15) with that of a mif+ strain showed that a 2.2-kbp region, which included the integration site of the mF plasmid, was deleted in the delta mif- strain by recombination between the main mtDNA and the mF plasmid. In other strains, in addition to this deletion, a 6-kbp region which included both termini was deleted by recombination at six repeats of AAT sequences in the mF plasmid. Moreover, transcripts of the mF plasmid were not detected in NG15 by slot hybridization.

Animals↗

PubMed1996

Selective hypothermic perfusion of canine brain.

A method for selective brain cooling by profound hemodilution with cold Ringer's lactate solution was previously reported in 1992. We recently modified this technique by combining it with an ultrafiltration and rewarming circuit between the left jugular vein and the inferior vena cava. We used 12 beagle dogs to study the efficacy of selective cerebral hypothermia induced by this modified technique. The brain temperature decreased to 28 degrees C within 5.4 +/- 2.7 minutes and to 20 degrees C within 15.5 +/- 9.4 minutes. The lowest brain and rectal temperatures were 17.0 +/- 1.8 degrees C and 32.1 +/- 2.2 degrees C, respectively. All animals survived in good condition without evidence of neurological deficits until they were killed at 10 weeks. Histological examination of the brains with 2,3,5-triphenyltetrazolim chloride demonstrated no evidence of ischemic lesions, and even in the hippocampus, there was no evidence of ischemic neuronal damage.

Animals↗

PubMed1996

Exophytic intraspinal extension of cerebellar glioma--case report.

A 49-year-old female presented with a 2-year history of occipitalgia, a 3-month history of dysesthesia, and dull sensation of the left upper extremity. T1-weighted magnetic resonance (MR) imaging revealed a low-intensity mass without gadolinium-diethylenetriaminepenta-acetic acid enhancement extending from the cisterna magna to the spinal canal. T2-weighted MR imaging revealed a high-intensity mass. Neuroradiological findings were inadequate to establish the mass as intra-axial or extra-axial. Operative findings discovered an intra-axial mass which was totally removed. Histological examination found the mass was an oligoastrocytoma. Cerebellar glioma developing exophytically is very rare. Adequate surgical removal is possible and likely to be curative if total.

Cerebellar Neoplasms↗

PubMed1995

Isolation, characterization and chromosomal mapping of an actin gene from the primitive red alga Cyanidioschyzon merolae.

Based on the results of cytological studies, it has been assumed that Cyanidioschyzon merolae does not contain actin genes. However, Southern hybridization of C. merolae cell-nuclear DNA with a yeast actin-gene probe has been suggested the presence of an actin gene in the C. merolae genome. In the present study, an actin gene was isolated from a C. merolae genomic library using a yeast actin-gene probe. The C. merolae actin gene has no intron. The predicted actin is composed of 377 amino acids and has an estimated molecular mass of 42 003 Da. Southern hybridization indicated that the C. merolae genome contains only one actin gene. This gene is transcribed at a size of 2.4 kb. When Southern hybridization was performed with C. merolae chromosomes separated by pulsed-field gel electrophoresis, a band appeared on unseparated chromosomes XI and XII. A phylogenetic tree based on known eucaryote actin-gene sequences revealed that C. merolae diverged after the division of Protozoa, but before the division of Fungi, Animalia and Chlorophyta.

Actins↗

PubMed1995

Significance of ST segment elevation in electrocardiograms in patients with ruptured cerebral aneurysms.

Twenty-three patients with aneurysmal subarachnoid haemorrhage (SAH), who showed an ST segment elevation in their electrocardiograms (ECG), were examined. There were 12 males and 11 females, with a mean age of 61 years. The clinical condition on admission was Hunt and Kosnik grade II in four, III in seven, IV in one, and V in 11 patients. Computerized tomography (CT) also revealed many cases of diffuse, thick SAH or intracerebral or intraventricular haematoma. Laboratory examinations including serum electrolyte, pH, and PaO2 revealed no abnormalities that might have influenced the ECG. Elevation in the levels of myocardial enzymes in serum was observed in two of the nine patients examined, although the elevation was only slight in one of them. Echocardiography, which was performed on several occasions on all patients, and cardiac catheterization, which was performed on eight patients, revealed a reduction in the motion of the left ventricular apex that was synchronous with ST segment elevation. This is the first report about these phenomena. No abnormalities were observed in the coronary artery. The elevated ST segment was normalized within one week in all patients, accompanied by normalization of the apical wall motion recorded on echocardiograms. In four patients, however, T wave inversion accompanied the improvement of the ST segment and was normalized within three months after the onset. These results suggest that ST segment elevation in the acute stage of SAH reflects transient cardiac dysfunction rather than myocardial injury. In some patients, however, the elevated serum levels of myocardial enzymes or T wave inversion suggested the presence of myocardial injury. Close follow-up seems to be necessary in such cases.

Adult↗

PubMed1995

Phase II study of a new combined primary chemotherapy regimen, intravenous methotrexate and vincristine and intraarterial adriamycin and cisplatin, for locally advanced urinary bladder cancer: preliminary results.

A phase II study of a new combination therapy was performed using intraarterial (i.a.) cisplatin and Adriamycin in combination with i.v. methotrexate and vincristine for 27 patients with invasive urinary bladder carcinoma of stages T2-3NOMO, and the therapeutic effects were assessed. Methotrexate (20 mg/m2) was given i.v. on days 1,15, and 22, and vincristine (0.7 mg/m2) was injected i.v. on day 2 before i.a. infusion therapy and on days 15 and 22. The i.a. chemotherapy was performed after both superior gluteal arteries had been embolized using 3- or 5-mm stainless-steel coils. A mixture of cisplatin (50-70 mg/m2) and Adriamycin (20 mg/m2) was infused i.a. via both internal iliac arteries over a period of 20-30 min. Angiotensin II (mean dose, 21 micrograms) was simultaneously infused i.a. in 15 of 27 patients. In 24 of the 27 patients, at least 2 cycles of full-dose chemotherapy were completed. The dose was decreased in the remaining 3 patients because of their poor health status and advanced age. Among the 27 patients, 9 and 14 had complete (CR) and partial responses (PR), respectively; 3 manifested no change (NC), and 1 had progressive disease (PD). The objective response rate (CR+PR) was 85.2%. Among the 27 patients staged T2-3 NOMO, 6 (CR, 1; PR, 5) underwent total cystectomies and 18 (CR, 8; PR, 8; NC, 2) had transurethral resection of a bladder tumor (TUR-Bt) or partial resections following chemotherapy. The remaining 3 diminished-dose patients had no surgery. Of the 27 patients, 22 were alive after a median follow-up period of 21+ (range, 7-48+) months. No significant side effect was observed except for lower extremity paresthesias in 5 patients (18.5%). These results point to the effectiveness of this therapy and to the possibility of urinary bladder preservation in patients with invasive, advanced urinary bladder cancers.

Adult↗

PubMed1995

Traumatic basilar impression: case report.

A very rare case of traumatic basilar impression is reported. The patient, a 57-year-old man, was hit on the head vertically in the parietal region. X ray of the cervical spine and computed tomography (CT) scans showed intracranial indentation of the atlas and the odontoid process with a depressed fracture around the foramen magnum. There are no previous reports about this type of fracture.

Cranial Fossa, Posterior↗

PubMed1995

Chopstick penetration of the posterior cranial fossa: case report.

A very rare case of wooden foreign body intrusion into the posterior cranial fossa is reported. The patient, a 16-month-old girl, fell down while holding chopsticks and was injured in the right pre-auricular region. Computed tomographic scans revealed a linear low-density area ranging from the right external auditory meatus to the fourth ventricle through the petrous portion of the temporal bone, passing near the middle cerebellar peduncle. Right temporal craniotomy was performed to abrade the petrous bone, resulting in removal of the chopstick fragment. The patient had an uneventful postoperative course and was discharged in ambulant condition, only with right hearing difficulty.

Accidental Falls↗

PubMed1995

Sexuality of mitochondria: fusion, recombination, and plasmids.

Mitochondrial fusion, recombination, and mobile genetic elements, which are essential for mitochondrial sexuality, are well established in various organisms. The recombination of mitochondrial DNA (mtDNA) depends upon fusion between parental mitochondria, and between their mtDNA-containing areas (mt-nuclei), to allow pairing between the parental mtDNAs. Such mitochondrial fusion followed by recombination may be called "mitochondrial sex." We have identified a novel mitochondrial plasmid named mF. This plasmid is apparently responsible for promoting mitochondrial fusion and crosses over with mtDNA in successive sexual crosses with mF- strains. Only in mF+ strains carrying the mF plasmid did small spherical mitochondria fuse which subsequently underwent fusion between the mt-nuclei that contained the mtDNA derived from individual mitochondria. Several successive mitochondrial divisions followed, accompanied by mt-nuclear divisions. The resulting mitochondria contained recombinant mtDNA with the mF plasmid. Such features remind us also of the bacterial conjugative plasmids such as F plasmid. Therefore, in the final part of this chapter, we discuss the origin of sex and its relationship to the sexuality of mitochondria.

Animals↗

PubMed1995

Small hepatocellular carcinomas undetected on two-phased incremental computed tomography. Angiographic and clinicopathologic findings.

RATIONALE AND OBJECTIVES: To elucidate the characteristic clinicopathologic features of hepatocellular carcinomas (HCCs) undetected on two-phased incremental computed tomography (CT). METHODS: Computed tomographic scans of 115 surgically resected small (< or = 3 cm) HCCs from 83 patients were performed 45 seconds and 6 minutes after the administration of contrast material. These scans were compared with corresponding angiographic and histopathologic findings. RESULTS: Eighty HCCs (70%) were depicted on the early images; 73 (63%) on the delayed images; and 89 (77%) using two-phased incremental CT. The small HCCs undetected on the early images but seen histologically had the following characteristics: (1) absence of a fibrous capsule, (2) well-differentiated tumor, (3) replacing growth patterns of the tumors, (4) lack of fatty metamorphosis and/or clear cell changes, (5) hypovascular on angiography. Those not seen on delayed images had the following characteristics: (1) absence of a fibrous capsule, (2) replacing growth patterns, and (3) presence of portal tracts in the tumors. CONCLUSIONS: The replacing growth pattern and the presence of portal tracts correlate with the undetectability on CT. For HCCs undetected on CT, treatment methods must be considered carefully, because the HCCs may be receiving transsinusoidal and portal blood supplies.

Adult↗

PubMed1995

Radiologic appearance of the dysembryoplastic neuroepithelial tumor.

PURPOSE: To evaluate the computed tomographic (CT) and magnetic resonance (MR) imaging features of dysembryoplastic neuroepithelial tumor (DNT). MATERIALS AND METHODS: Six CT studies (four with contrast material enhancement) and 10 MR imaging studies (seven with gadolinium enhancement) obtained in 10 patients with a history of seizures and pathologically proved DNT were retrospectively reviewed. RESULTS: All tumors were intracortical or subcortical. CT showed a low-attenuation mass in all cases except one of mixed isoattenuation and low attenuation. The DNT had decreased signal intensity on T1-weighted MR images and well-demarcated increased signal intensity on T2-weighted images without peritumoral edema. Prominent MR imaging features were a gyriform configuration on T1- or T2-weighted images in 10 patients (100%), well-demarcated lobular tumor margins on T2-weighted images in eight (80%), and a high rate of bone remodeling of the adjacent calvaria on MR (60% [n = 6]) and CT (67% [n = 4]) images. CONCLUSION: Diagnosis of DNT with imaging modalities alone may be difficult, but these radiologic features may aid in differentiating DNT from other gliomas.

Adolescent↗

PubMed1995

Diffuse leptomeningeal enhancement, "ivy sign," in magnetic resonance images of moyamoya disease in childhood: case report.

We report three cases of children with moyamoya disease who revealed prominent leptomeningeal enhancement on postcontrast magnetic resonance (MR) images. Two of the children underwent bilateral extracranial-intracranial bypass operations because of ischemic symptoms. During the operations, a profuse pial arterial network was observed, which was considered to be the origin of the enhancement. The ischemic episodes disappeared after the operations, and the follow-up MR images showed marked reduction of the leptomeningeal enhancement. One of the three patients had an extracranial-intracranial bypass operation on one side, but postoperative MR images have not yet been obtained. We named this finding on postcontrast MR images "ivy sign," because it resembles ivy creeping on stones. Ivy sign seems to be a unique, characteristic feature of the pial network observed in moyamoya disease.

Brain Ischemia↗

PubMed1995

[Clinical analysis of 14 patients with anti-myeloperoxidase antibody positive rapid progressive glomerulonephritic syndrome].

We investigated the clinical features and outcome of 14 patients with anti-myeloperoxidase antibody (MPO-ANCA) positive rapidly progressive glomerulonephritic syndrome. Underlying diseases included microscopic polyarteritis in 6 patients, idiopathic crescentic glomerulonephritis with lung hemorrhage in 2 patients, idiopathic glomerulonephritis in 3 patients, rapidly progressive glomerulonephritic syndrome without renal biopsy in 1 patient, crescentic glomerulonephritis associated with Sjögren syndrome and progressive systemic sclerosis in 1 patient and crescentic glomerulonephritis associated with sarcoidosis in 1 patient. Five patients were male (mean age, 59.2 years) and 9 were female (mean age, 54.0 years). On admission, most patients had anemia, leukocytophilia, and marked elevation of C-reactive protein (CRP). Average hemoglobin, white blood cell count and CRP levels on admission were 8.1 mg/dl, 11,500/mm3 and 14.7 mg/dl, respectively. Average serum creatinine was 4.0 mg/dl. All patients were treated with steroids either with or without cyclophosphamide. As the patients recovered clinically, the MPO-ANCA titers declined. Although most patients responded well to immunosuppressive therapy, some died of serious complications (such as acute respiratory distress syndrome, fungal infection, and pneumocystis pneumonia). The prognosis of patients with severe renal failure was especially poor. We conclude that early diagnosis, treatment and intensive care during immunosuppressive therapy are very important in the management of MPO-ANCA-positive rapidly progressive glomerulonephritis.

Adolescent↗