Biomedical subjects
Publications and source records attributed to T Kamikubo.
[structure: see text]. Two iridoid lactones, (-)-iridolactone and (+)-pedicularis-lactone, have been synthesized in an enantio- and diastereocontrolled manner starting from a tricyclic chiral building block serving as a synthetic equivalent of chiral 3-(hydroxymethyl)cyclopenta-2,4-dien-1-ol.
A previously healthy and asymptomatic 45-year-old woman was referred for evaluation of a heart murmur and an unusual dilatation in the aortic root. Transthoracic and transesophageal echocardiography, computed tomography, magnetic resonance imaging, and cardiac catheterization revealed an aneurysm with a maximum diameter of 6.0 cm in the right sinus of Valsalva. Aortic regurgitation and stenosis at the right ventricle outflow tract were associated with the aneurysm. Surgery and histological study demonstrated that the sinus of Valsalva aneurysm was enormously dilated with idiopathic degenerative change in the aortic media. The aneurysm was tremendously large compared to any previously reported. Decrease in pressure load during diastole caused by aortic regurgitation probably resulted in the growth of this huge aneurysm without rupture.
Intracranial hemangiopericytomas are hypervascular tumors. Consequently, resection of these tumors must occasionally be stopped owing to profuse bleeding. We report two cases of large intracranial hemangiopericytoma whose resection had to be stopped owing not to bleeding but to brain swelling. These patients were treated with large doses of barbiturate until the intracranial pressure had normalized. After preoperative irradiation therapy, the residual tumors were easily removed without serious complications. We speculate that the brain tissue around a large hemangiopericytoma might be under ischemia because of long-standing compression and deviation of blood to the hypervascular tumor. A large amount of blood flowing into these brain tissues due to external and internal decompression inverts cerebral perfusion acutely from ischemia to hyperemia. The brain swelling in the early operative stage would be evoked by this "inverted cerebral hyperemia". We found that brain swelling is sometimes encountered during the resection of a large hemangiopericytoma even in the early operative stage. If swelling occurs, tumor resection should be stopped immediately and intracranial pressure should be controlled. The residual tumor can then be easily removed without complications after preoperative irradiation therapy.
Succinyl-Leu-Leu-Val-Tyr-4-methylcoumaryl-7-amide (Suc-LLVY-MCA) hydrolyzing activities of the 20S and 26S proteasomes in the gerbil cortex following transient forebrain ischemia were examined. Using extraction solutions without ATP, only 20S proteasome activity was noted after separation with glycerol gradient centrifugation. When these extracts were incubated with ATP and an ATP-regenerating system prior to glycerol gradient separation, both 20S and 26S proteasome activities were detected. Following 10 min of ischemia, the activity of the 26S proteasomes decreased, whereas the 20S proteasome activity increased after 30 min of reperfusion. These changes returned to the control level after 1 h. The active 26S proteasomes were formed with ATP-dependent association with the 20S proteasomes and several subunits and the 26S proteasomes degraded ubiquitin-protein conjugates. These results indicate that proteasome activity might not be irreversibly impaired after transient ischemia. However, transient inhibition of ATP-dependent conversion of 20S to 26S proteasomes in vitro must be one of the causes of the accumulation of the ubiquitin-protein conjugates in the early reperfusion period.
Ubiquitin-conjugating activities in the soluble fractions of gerbil cortex and hippocampus following transient ischemia were examined in vitro. Ten minutes of ischemia did not affect the ubiquitination of heat-denatured lysozyme both in the cortex and in the hippocampus. No reduction of the conjugating activities following ischemia was also confirmed using the partially purified ubiquitin conjugating enzymes from the cortex. These results indicate that protein ubiquitination might not be impaired following transient ischemia.
Insoluble ubiquitin conjugates (UC) in the mitochondrial fraction of the gerbil cortex were analyzed following transient forebrain ischemia. At 1 h of reperfusion after 2-10 min of ischemia, UC increased as the duration of ischemia was prolonged. Pre-treatment with pentobarbital, rather than post-treatment immediately after recirculation, reduced the increase of UC at 1 h of reperfusion following 5 min of ischemia. Pentobarbital had no effect on in vitro ubiquitination of heat-denatured lysozyme by the extract of gerbil cortex. These results suggest that increase in UC is dependent on ischemic damage and pentobarbital attenuates the increase of UC by relieving injury during ischemia.
A case of visual allesthesia is reported. A thirty-year-old right-handed man with a right temporo-occipital arteriovenous malformation underwent the surgery for extirpation of the lesion. Postoperatively he had left homonymous hemianopsia. Approximately 6 months after the surgery, he experienced the initial spell of generalized convulsion, followed by the episodes of visual allesthesia. He experienced illusory left hemonymous transpositions of objects viewed in the right homonymous field. The transposition occurred from normal to the defective visual field. The illusory image was palinoptic, persisting for up to several minutes after the real object was no longer in view. It was equal in shape with the original, and caused monocular diplopia. MRI showed a large area of postoperative changes. The lesion was located from the posterior half of the middle and inferior gyri of the right temporal lobe to the occipital and a part of the parietal cortex. And it extended into the right fusiform and lingual gyri. The right lateral geniculate body and the posterior part of thalamus were also involved. We speculated that this phenomenon may result from irritation of the affected brain and its surrounding areas, since the episode took place following the seizure.
A 24-year-old housewife presented with weight gain of about 30 kg, constipation and pitting edema of extremity nine years after having a thyroidectomy. Hormonal examination revealed low levels of serum T3 and T4 and high levels of serum TSH and PRL. She also had enlarged pituitary gland (pituitary hyperplasia) with suprasellar extension on CT and MRI image. Thyroid replacement therapy and follow-up by MRI were performed without resort to surgery, because she had no visual disturbance. Within about 1 month after thyroid replacement therapy, serum TSH and PRL were normalized. And also thyroid function was normalized by thyronine (T3). Following this results, pituitary hyperplasia regression was seen on MRI image. About 1 year after thyroid replacement therapy, pituitary hyperplasia regression was more seen on MRI image. Prolonged hypothyroidism can result in hypertrophy of the pituitary thyrotropin-secreting cells and prolactin secreting cells. So, it can increase pituitary weight (pituitary hyperplasia). Radiological examination, abnormal sellar x-ray films suggesting intrasellar tumor are common in patients with primary hypothyroidism. Suprasellar extension of pituitary mass (pituitary hyperplasia) due to hypothyroidism was reported by radiological examination (PEG, CT and MRI image), and regression of pituitary hyperplasia was revealed by radiological examination after thyroid replacement therapy. The first choice of this type of pituitary hyperplasia is thyroid replacement therapy unless the patient has a visual disturbance. However, if this replacement therapy is not effective for diminution of the tumor, surgical removal of the tumor should be considered.
A case of solitary syringobulbia without syringomyelia diagnosed by MRI was reported. A 63-year-old female, who had a history of progressive gait disturbance for 9 months, was admitted to our department because of severe headache. Neurological examination revealed that the patient was suffering from right pyramidal sign as well as left deep sensory disturbance without apparent impairment of cranial nerves or nystagmus. The somatosensory evoked potential stimulated by the left median nerve showed delay in latency and low amplitude, however, the auditory brainstem response showed normal records bilaterally. A syringobulbia associated with platybasia, basilar impression, obstructive hydrocephalus and Arnold-Chiari malformation was diagnosed by the neuroradiological examinations including plain X-ray films of the skull, CT scan and MRI of the brain. Subsequent to the decompression around the cisterna magna by suboccipital craniectomy and laminectomy of the atlas, the opening of the Foramen Monro which was obstructed by a thick membrane was carried out, and prevention of communication between the fourth ventricle and the syrinx was accomplished by using a piece of muscle. This operative procedure was thought to be compatible with Gardner's operation for syringomyelia. The patient showed gradual improvement of gait disturbance as well as headache 3 months after surgery, and this neurological improvement was proved by decrease in the size of the known syringobulbia on MRI, and by normalized somatosensory evoked potential stimulated by the median nerve. Pathophysiology of the solitary syringobulbia with relatively acute onset of the neurological symptoms was assumed to have taken place in the following manner.(ABSTRACT TRUNCATED AT 250 WORDS)
Ribulose biphosphate carboxylase/oxygenase, with its large subunit encoded in the chloroplast and the small subunit in the nucleus, is induced by light. Accumulation of the enzyme, its two mRNA levels, and the synthesis rate of enzyme protein in pea leaves were followed during induction to understand the role of mRNA levels during greening subunit synthesis. The relative mRNA levels for the large and the small subunits increased coordinately up to 3-4 days, which almost corresponded to an inflection point of the accumulation profile of RuBisCO, and then the two mRNA levels gradually decreased. To obtain information of subunit synthesis, the extent of labelling of the two subunits were determined for both assembled and unassembled subunits using specific IgG. Unassembled subunits were found for both polypeptides, with a slight excess of the small one. The observed synthesis rates of the small and the large subunits were roughly coordinated without overproduction and almost stoichiometric amounts of the two polypeptides were found. The profiles of observed synthesis rate of the two subunits and the holoenzyme were similar to those of their mRNA levels. These results suggest that the synthesis of ribulose biphosphate carboxylase/oxygenase protein and its accumulation are dependent on the coordinated change of the two mRNA levels in greening pea leaves.
Etiolated pea seedlings (5 days old) were treated with red light for 5 min and grown for 2 days more in darkness. Effects of the red light on the mRNA levels of two subunits of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) (ribulose-P2 carboxylase), rate of enzyme synthesis and accumulation of the enzyme were examined for the plants. Increases of the two mRNA levels, encoded in nuclei and chloroplasts were observed. Red light followed by far-red light treatment for 5 min inhibited the increases. An increase parallel with the mRNA levels was found for the rate of the enzyme synthesis and accumulation of the enzyme. These results indicate that the induction of two mRNA levels is mediated by phytochrome and causes the red-light-inducible, far-red-light-reversible increase of ribulose-P2 carboxylase. When white light was irradiated to induce the enzyme, the effects of red light given in darkness were reinforced. These results indicate that light-induction of ribulose-P2 carboxylase is mediated by phytochrome and controlled by the two mRNA levels.
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To analyze the in vitro specificity of homologous and heterologous transcription systems, the template specificities of pea and cauliflower RNA polymerase II for pea chromatin were studied and compared with the specificity exhibited by the Escherichia coli holoenzyme. The results with pea chromatin show that the two eukaryotic enzymes compete with each other for the same recognition sites, but the E. coli enzyme utilizes different recognition sites. The data indicate that during transcription of chromatin in vitro, heterologous eukaryotic RNA polymerase II recognizes the same sites as the homologous enzyme, but the E. coli enzyme does not c enzymes compete with each other for the same recognition sites, but the E. coli enzyme utilizes different recognition sites. The data indicate that during transcription of chromatin in vitro, heterologous eukaryotic RNA polymerase II recognizes the same sites as the homologous enzyme, but the E. coli enzyme does not c enzymes compete with each other for the same recognition sites, but the E. coli enzyme utilizes different recognition sites. The data indicate that during transcription of chromatin in vitro, heterologous eukaryotic RNA polymerase II recognizes the same sites as the homologous enzyme, but the E. coli enzyme does not recognize these sites. In contrast to the situation with chromatin, all three enzymes utilize the same recognition sites on DNA. These results suggest the presence of proteins in chromatin which specifically interact with eukaryotic RNA polymerase II but not with the bacterial enzyme, or a possible template structure in chromatin which can be recognized by eukaryotic enzyme but not by E. coli enzyme.
DNA-dependent RNA polymerase II (EC 2.7.7.6) from pea seedlings (Pisum sativum var. Alaska) has been purified to homogeneity, as judged by native polyacrylamide electrophoresis. The procedure includes polyethyleneimine precipitation and elution, ammonium sulfate precipitation, DEAE-Sephadex chromatography, phosphocellulose chromatography, and heparin-Sepharose chromatography. The enzyme purified almost to homogeneity has a specific activity of 200 nmol/mg per 15 min at 30 degrees C with denatured calf thymus DNA as template. The enzyme activity is 50% inhibited in the presence of 0.05 migrograms/ml of alpha-amanitin. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicates that pea RNA polymerase II is composed of eight subunits with molecular weights and molar ratios (in parentheses) of 170 000 (0.9), 140 000 (1.0), 43 000 (1.5), 26 000 (2.0), 22 500 (1.2), 21 500 (0.6), 18 500 (1.6) and 17 500 (2.3). The structure is closely similar to that of cauliflower RNA polymerase II.
DNA-dependent RNA polymerase II (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) from cauliflower inflorescence (Brassica oleracae, var. botrytis) was highly purified by polyethyleneimine treatment on a large scale. The solubilized enzyme was partially purified by polyethyleneimine fractionation and subjected to chromatography on DEAE-Sephadex and phosphocellulose, and subsequently to sedimentation in a glycerol gradient. The specific activity (231 nmol/mg per 10 min) of this enzyme was comparable to that reported for other purified eukaryotic RNA polymerases. Analysis of the purified RNA polymerase II by polyacrylamide gel electrophoresis under nondenaturing conditions revealed a single band. The subunit composition of the enzyme was analyzed by electrophoresis under denaturing conditions. The RNA polymerase II contained subunits with molecular weights and molar ratios (in parentheses) of 180 000(1), 130 000(2), 48 000(2), 25 000(4), and 19 500(4).
Class III DNA-dependent RNA polymerase (EC 2.7.7.6) was highly purified from cauliflower (Brassica oleracea, var. bortytis) by using polyethyleneimine precipitation. The specific activity of the enzyme was comparable to that reported for mammalian enzymes. Glycerol gradient sedimentation analysis indicated that the sedimantation coefficient (23 S) was slightly higher than that of enzyme II from cauliflower. The class III enzyme was inhibited by alpha-amanitin at high concentrations (50% inhibition at 200 microgram/ml). The Km value for nucleoside triphosphate was determined. Template specificities for single synthetic polymers showed that the enzyme read pyrimidine homopolymers as templates and preferred poly(dT) to poly(dC). The enzyme transcribed both strands of homopolymer pairs of poly(dI). poly(dC) and poly(dA).poly(dT). The synthetic polyribonucleotides were not effectively read. Competition experiments with these synthetic polymers indicated that the enzyme had different binding specificities which were not the same as their template specificities. The different binding affinities and template specificites for synthetic templates of the three classes of enzyme suggest that the enzyme can discriminate among different template sequences.
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