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H Segawa

Publications and source records attributed to H Segawa.

At least 37 records · Page 2Linked to original sources
PubMed2000

Clinicopathological study of intracranial fusiform and dolichoectatic aneurysms : insight on the mechanism of growth.

BACKGROUND AND PURPOSE: Intracranial fusiform aneurysms can be divided into 2 clinically different subtypes: acute dissecting aneurysms and chronic fusiform or dolichoectatic aneurysms. Of these 2, the natural history and growth mechanism of chronic fusiform aneurysms remains unknown. METHODS: A consecutive series of 16 patients with chronic fusiform aneurysms was studied retrospectively to clarify patient clinical and neuroradiological features. Aneurysm tissues were obtained from 8 cases and were examined to identify histological features that could correspond to the radiological findings. RESULTS: Four histological features were found: (1) fragmentation of internal elastic lamina (IEL), (2) neoangiogenesis within the thickened intima, (3) intramural hemorrhage (IMH) and thrombus formation, and (4) repetitive intramural hemorrhages from the newly formed vessels within thrombus. IEL fragmentation was found in all cases, which suggests that this change may be one of the earliest processes of aneurysm formation. MRI or CT detected IMH, and marked contrast enhancement of the inside of the aneurysm wall (CEI) on MRI corresponded well with intimal thickening. Eight of 9 symptomatic cases but none of 7 asymptomatic cases presented with both radiological features. CONCLUSIONS: Data suggest that chronic fusiform aneurysms are progressive lesions that start with IEL fragmentation. Formation of IMH seems to be a critical event necessary for lesions to become symptomatic and progress, and this can be monitored on MRI. Knowledge of this possible mechanism of progression and corresponding MRI characteristics could help determine timing of surgical intervention.

Adult↗
PubMed2000

Estimation of the lethal toluene concentration from the accidental death of painting workers.

To determine the potentially lethal level of thinner concentration in the air, we measured the concentration of toluene in the blood and others of three patients who suffered severe acute thinner intoxication between 4 January 1996 and 21 April 1997 in Ube city. The concentration of toluene in blood were 30.2 mg/L in died patient, and 13.7 mg/L and 17.5 mg/L in recovered patients, respectively. By extrapolation from the results of our previous toxicokinetic research on toluene poisoning in anesthetized dogs, the fatal concentration of toluene was estimated to be approximately 1800 to 2000 ppm for 1-hour exposure.

Accidents, Occupational↗
PubMed2000

[Intraoperative autologous blood transfusion was effective in a massive blood loss during living-related donor liver transplantation].

We have experienced massive blood loss (> 80,000 g) during living-related donor liver transplantation (LRDLT) of a 14-year old girl with biliary atresia. As available homologous blood was not sufficient, we transfused autologous blood (13,400 ml) during operation. Although immunosuppressant was administered to the patient, severe infection did not occur for 10 days after the operation. Cold ischemia time of the graft liver was about 16 hr, but her postoperative liver function was well-maintained. The case suggests that intraoperative autologus blood transfusion is effective if homologous blood is insufficient during LRDLT.

Adolescent↗
PubMed2000

Secondary hyperparathyroidism and phosphate sensing in parathyroid glands.

Retention of inorganic phosphate (Pi) and associated hyperphosphatemia are important development of hyperparathyroidism secondary to renal failure. The beneficial effect of a low-Pi diet in the prevention of hyperparathyroidism can be attributed to the decrease in PTH secretion. This effect of Pi may be mediated by specific molecules in the parathyroid cell membrane. A complementary DNA encoding a Na(+)-Pi co-transporter, termed rat PiT-1, has been isolated from rat parathyroid. The amount of PiT-1 mRNA in the parathyroid is controlled by vitamin D and dietary Pi, which are the most important regulators of PTH secretion. The parathyroid Pi transporter may mediate the effects of extracellular Pi and PTH secretion in secondary hyperparathyroidism. In this study, we focus on the function of Na/Pi co-transporters in the parathyroid glands as inorganic Pi sensor.

Animals↗
PubMed1999

Regulation of intestinal Na+-dependent phosphate co-transporters by a low-phosphate diet and 1,25-dihydroxyvitamin D3.

In a study of the rat intestinal P(i) transport system, an activator protein for rat Na/P(i) co-transport system (PiUS) was isolated and characterized. We also investigated the effects of restriction of vitamin D and P(i) (two of the most important physiological and pathophysiological regulators of P(i) absorption in the small intestine) on intestinal P(i) transport activity and the expression of Na/P(i) co-transporters that are expressed in rat small intestine. Rat PiUS encodes a 424-residue protein with a calculated molecular mass of 51463 Da. The microinjection of rat PiUS into Xenopus oocytes markedly stimulated Na(+)-dependent P(i) co-transport activity. In rats fed with a low-P(i) diet, Na(+)-dependent P(i) co-transport activity was increased approx. 2-fold compared with that of rats fed a normal P(i) diet. Kinetic studies demonstrated that this increased activity was due to an elevation of V(max) but not K(m). The PiUS mRNA levels showed an approximate doubling in the rats fed with the low-P(i) diet compared with those fed with the normal P(i) diet. In addition, after the administration of 1, 25-dihydroxyvitamin D(3) [1,25-(OH)(2)D(3)] to vitamin D-deficient animals, the P(i) uptake was significantly increased in the Na(+)-dependent component in the brush border membrane vesicle (BBMV) at 24 and 48 h. In addition, we found a further high-affinity Na/P(i) co-transport system in the BBMV isolated from the vitamin D-replete animals. The levels of type III Na/P(i) co-transporter PiT-2 mRNA were increased 24 and 48 h after 1,25-(OH)(2)D(3) administration to vitamin D-deficient animals, whereas PiUS and the type IIb Na/P(i) co-transporter mRNA levels were unchanged. In conclusion, we first cloned a rat activator protein, PiUS, and then studied its role along with that of other type III Na/P(i) co-transporters. PiUS and PiT-2 might be important components in the regulation of the intestinal P(i) transport system by P(i) restriction and 1,25-(OH)(2)D(3).

Amino Acid Sequence↗
PubMed1999

Identification of an amino acid transporter associated with the cystinuria-related type II membrane glycoprotein.

We identified an amino acid transporter that is associated with the cystinuria-related type II membrane glycoprotein, rBAT (related to b(0,+) amino acid transporter). The transporter designated BAT1 (b(0, +)-type amino acid transporter 1) from rat kidney was found to be structurally related to recently identified amino acid transporters for system L, system y(+)L, and system x(-)C, which are linked, via a disulfide bond, to the other type II membrane glycoprotein, 4F2hc (4F2 heavy chain). In the nonreducing condition, a 125-kDa band, which seems to correspond to the heterodimeric complex of BAT1 and rBAT, was detected in rat kidney with anti-BAT1 antibody. The band was shifted to 41 kDa in the reducing condition, confirming that BAT1 and rBAT are linked via a disulfide bond. The BAT1 and rBAT proteins were shown to be colocalized in the apical membrane of the renal proximal tubules where massive cystine transport had been proposed. When expressed in COS-7 cells with rBAT, but not with 4F2hc, BAT1 exhibited a Na(+)-independent transport of cystine as well as basic and neutral amino acids with the properties of system b(0,+). The results from the present investigation were used to establish a family of amino acid transporters associated with type II membrane glycoproteins.

ATP-Binding Cassette Transporters↗
PubMed1999

Identification and functional characterization of a Na+-independent neutral amino acid transporter with broad substrate selectivity.

We have isolated a cDNA from rat small intestine that encodes a novel Na+-independent neutral amino acid transporter with distinctive characteristics in substrate selectivity and transport property. The encoded protein, designated L-type amino acid transporter-2 (LAT-2), shows amino acid sequence similarity to the system L Na+-independent neutral amino acid transporter LAT-1 (Kanai, Y., Segawa, H., Miyamoto, K., Uchino, H., Takeda, E., and Endou, H. (1998) J. Biol. Chem. 273, 23629-23632) (50% identity) and the system y+L transporters y+LAT-1 (47%) and KIAA0245/y+LAT-2 (45%) (Torrents, D., Estevez, R., Pineda, M., Fernandez, E., Lloberas, J., Shi, Y.-B., Zorzano, A., and Palacin, M. (1998) J. Biol. Chem. 273, 32437-32445). LAT-2 is a nonglycosylated membrane protein. It requires 4F2 heavy chain, a type II membrane glycoprotein, for its functional expression in Xenopus oocytes. LAT-2-mediated transport is not dependent on Na+ or Cl- and is inhibited by a system L-specific inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH), indicating that LAT-2 is a second isoform of the system L transporter. Compared with LAT-1, which prefers large neutral amino acids with branched or aromatic side chains, LAT-2 exhibits remarkably broad substrate selectivity. It transports all of the L-isomers of neutral alpha-amino acids. LAT-2 exhibits higher affinity (Km = 30-50 microM) to Tyr, Phe, Trp, Thr, Asn, Ile, Cys, Ser, Leu, Val, and Gln and relatively lower affinity (Km = 180-300 microM) to His, Ala, Met, and Gly. In addition, LAT-2 mediates facilitated diffusion of substrate amino acids, as distinct from LAT-1, which mediates amino acid exchange. LAT-2-mediated transport is increased by lowering the pH level, with peak activity at pH 6.25, because of the decrease in the Km value without changing the Vmax value. Because of these functional properties and a high level of expression of LAT-2 in the small intestine, kidney, placenta, and brain, it is suggested that the heterodimeric complex of LAT-2 and 4F2 heavy chain is involved in the trans-cellular transport of neutral amino acids in epithelia and blood-tissue barriers.

Amino Acid Sequence↗
PubMed1999

Schizosaccharomyces pombe UDP-galactose transporter: identification of its functional form through cDNA cloning and expression in mammalian cells.

The Schizosaccharomyces pombe UDP-galactose transporter cDNA (SpUGT cDNA), encoding the product of the gms1+ gene which consists of two exon sequences separated by a 173-bp intron, was cloned by RT-PCR. Its product, a hydrophobic protein of 353 amino acid residues resembling its human counterpart, was expressed in the Golgi membranes of UDP-galactose transporter-deficient Lec8 cells, and complemented the genetic defect of the mutant cells. This indicated that SpUGT cDNA encodes the functional S. pombe UDP-galactose transporter. The product of an ORF found in the second exon, which was previously assumed to be the S. pombe UDP-galactose transporter, thus represents an inactive, truncated form of the SpUGT protein.

Amino Acid Sequence↗
PubMed1999

Postoperative prognosis of Brown-Séquard-type myelopathy in patients with cervical lesions.

BACKGROUND: Postoperative prognosis of the hemihypalgesia in patients with Brown-Séquard-type myelopathy (BSM) caused by cervical lesions is of great interest to surgeons. However, there are very few reports discussing the postoperative prognosis of BSM. METHODS: We evaluated the prognosis of BSM using the criteria of the Japanese Orthopaedic Association (JOA) score in 16 (seven ossification of the posterior longitudinal ligament [OPLL], 5 cervical spondylosis [CS], and 4 disc herniation patients) out of 233 surgically treated patients with cervical diseases. The mean follow-up duration was 2 years and 11 months. RESULTS: After surgery, none of these patients showed complete resolution of hemihypalgesia, although the most rostral level of hemihypalgesia moved in a caudal direction in 13 patients (81%), whose recovery ratios of JOA score were significantly better than those of hemihypalgesia-level-persisted patients. In our BSM series, OPLL occurred most frequently and the anterior element compressing the spinal cord existed most frequently in the central area of the vertebra (44%). Postoperative improvement in the motor function of the legs in the disc herniation group was significantly better than in the OPLL and CS groups (p < 0.05, respectively). There were no significant differences in the functional prognosis between the BSM and non-BSM patient groups. CONCLUSIONS: BSM patients can expect almost the same functional outcome as non-BSM patients, with the exception of the disappearance of hemihypalgesia.

Adult↗
PubMed1999

Dexmedetomidine reduces seizure threshold during enflurane anaesthesia in cats.

Dexmedetomidine is an alpha 2 agonist and has been reported to have proconvulsant actions. To investigate the interaction of dexmedetomidine with convulsant anaesthetics, we studied effects on seizure threshold in cats during enflurane anaesthesia. Cats were prepared with chronic implantation of electrodes for recording of the cortical electroencephalogram (EEG) and midbrain reticular formation multi-unit activity (R-MUA). Seizure threshold, the reciprocal of the number of electrical stimuli required to induce generalized EEG seizure activity x 1000 (seizure induction index (SII)), was assessed. The effects of dexmedetomidine 1, 10 and 100 micrograms kg-1 i.v. and yohimbine 500 micrograms kg-1, an alpha 2 antagonist, on SII during 3.5% enflurane anaesthesia were investigated. Dexmedetomidine significantly increased SII at 10 and 100 micrograms kg-1, and this effect was reversed by yohimbine. We found that high-dose dexmedetomidine reduced seizure threshold during enflurane anaesthesia.

Adrenergic alpha-Agonists↗
PubMed1999

Living related donor liver transplantation in a patient with severe aortic stenosis.

We report the successful anaesthetic management of a young girl with Alagille's syndrome and severe aortic stenosis (resting pressure gradient 88 mm Hg) undergoing living related donor liver transplantation (LRDLT). The patient had end-stage liver disease and LRDLT was performed before replacement of the aortic valve. Anaesthesia was conducted uneventfully with the aid of a pulmonary artery catheter. Intra-aortic balloon pumping was used in the perioperative period for protection against myocardial ischaemia. Total clamping of the inferior vena cava was avoided during surgery and volume administration was guided by the pulmonary artery pressure. A stable circulation was maintained in the reperfusion period. The patient was discharged from hospital on day 54 after operation with normal liver function. Two years later her aortic valve was replaced successfully.

Alagille Syndrome↗
PubMed1999

Regulation of PiT-1, a sodium-dependent phosphate co-transporter in rat parathyroid glands.

A cDNA encoding an Na+-Pi co-transporter, termed rat PiT-1, has now been isolated from rat parathyroid. Expression of rat PiT-1 in Xenopus oocytes revealed that it possesses Na+-dependent Pi co-transport activity. The amount of PiT-1 mRNA in the parathyroid of vitamin D-deficient rats was reduced compared with that in normal animals, and increased markedly after administration of 1,25-dihydroxyvitamin D3. Furthermore, the abundance of PiT-1 mRNA in the parathyroid was much greater in rats fed a low-Pi diet than in those fed a high-Pi diet. Thus, rat PiT-1 may contribute to the effects of Pi and vitamin D on parathyroid function.

Animals↗
PubMed1999

Expression and activity of chimeric molecules between human UDP-galactose transporter and CMP-sialic acid transporter.

Human UDP-galactose transporter (hUGT1) and CMP-sialic acid transporter (hCST) are related Golgi proteins with eight putative transmembrane helices predicted by computer analysis. We constructed chimeric molecules in which segments of various lengths from the C- or N-terminus of hUGT1 were replaced by corresponding portions of hCST. The chimeras were transiently expressed in UGT-deficient mutant Lec8 cells, and their UGT activity was assessed by the binding of GS-II lectin to the transfected cells. The replacement of either the N- or C-terminal cytoplasmic segment by that of hCST did not affect the expression or activity of hUGT1. A chimera in which the eighth helix and the C-terminal tail were replaced also retained the UGT activity, indicating that this helix is not involved in the determination of substrate specificity. In contrast, three types of chimeras, in which the first helix, the first and the second helices, and a segment from the seventh helix to the C-terminus were replaced, respectively, were expressed very infrequently in the transfected cells, and had no UGT activity. They are likely folded incorrectly and degraded by a quality-control system, since the amounts of their mRNAs were normal and the proteins were mainly localized in the ER. The first and the seventh helices are important for the stability of the transporter protein.

Animals↗
PubMed1999

Xenon has greater inhibitory effects on spinal dorsal horn neurons than nitrous oxide in spinal cord transected cats.

UNLABELLED: Xenon (Xe) suppresses wide dynamic range neurons in cat spinal cord to a similar extent as nitrous oxide (N2O). The antinociceptive action of N2O involves the descending inhibitory system. To clarify whether the descending inhibitory system is also involved in the antinociceptive action of Xe, we compared the effects of Xe on the spinal cord dorsal horn neurons with those of N2O in spinal cord-transected cats anesthetized with alpha-chloralose and urethane. We investigated the change of wide dynamic range neuron responses to touch and pinch by both anesthetics. Seventy percent Xe significantly suppressed both touch- and pinch-evoked responses in all 12 neurons. In contrast, 70% N2O did not show significant suppression in touch- and pinch-evoked responses. These results suggest that the antinociceptive action of Xe might not be mediated by the descending inhibitory system, but instead may be produced by the direct effect on spinal dorsal horn neurons. IMPLICATIONS: Xenon (Xe) is an inert gas with anesthetic properties. We examined the antinociceptive effects of Xe and nitrous oxide (N2O) in spinal cord-transected cats. Our studies indicate that Xe has a direct antinociceptive action on the spinal cord that is greater than that of N2O.

Anesthetics, Inhalation↗
PubMed1999

New aneurysm clip and applier for narrow spaces: technical note.

OBJECTIVE: Aneurysm surgery carries considerable risk to the patient, in part because the surgical field can be so constricted that accurate placement of the aneurysm clip is impeded. In fact, most aneurysm clip appliers are so bulky that they can impair the surgeon's view, if the field is tight. We describe a system of aneurysm clips and appliers that have a very low profile and consequently allow better visualization of the operative field at critical moments during surgery. INSTRUMENTATION: A new system of clips for aneurysm surgery was developed to overcome some of the deficiencies of conventional sets. The new clip blades are opened from inside the spring, so the clip blades are clearly seen as they are applied across the base of the aneurysm. In addition, these clips can be angled in any desired direction in the applier, which makes their application easier. A third advantage is that the clip applier is used as a clip remover should adjustment or reapplication of the clip be necessary. RESULTS: Thirty aneurysms were obliterated with the new clips without any complications attributable to the clips. The new instruments allowed the safe application of clips to aneurysms in deep, confined, and anatomically complex spaces, such as aneurysms of the basilar tip and anterior communicating artery. CONCLUSION: The newly described system of aneurysm clips and appliers appears to have significant advantages over other currently available systems.

Animals↗