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Biomedical subjects

H Segawa

Publications and source records attributed to H Segawa.

At least 73 records · Page 4Linked to original sources
PubMed1997

Preoperative and postoperative magnetic resonance imaging (MRI) findings of radiculomeningeal arteriovenous malformations: important role of gravity in the symptoms and MRI.

BACKGROUND: The symptoms of radiculomeningeal arteriovenous malformations (AVMs) are reported to be uniform, which suggests it to be a conus medullaris syndrome, and in fact, the lesions on magnetic resonance imaging (MRI) images usually include the conus medullaris. However, the reason why the conus medullaris is always involved in the lesion has not been discussed. METHODS: We encountered seven patients with spinal radiculomeningeal AVMs and operated on all of them. We evaluated the preoperative and postoperative MRI findings in these patients. Postoperative MRI was followed ranging from 6-32 months (mean: 21 months) after surgery. RESULTS: All of our patients showed swelling of the spinal cord, including the conus medullaris, on the preoperative magnetic resonance image. Postoperatively, MRI showed that the swelling of the spinal cord had resolved but that it had finally deteriorated into an atrophic condition. In all of five patients who could be followed up using multiple postoperative MRI scans, sequential T2-weighted images showed that the most rostral level of areas with increased signal in the spinal cord moved in a caudal direction with time. CONCLUSIONS: This and the fact that the conus medullaris was included in the swelling of the spinal cord regardless of the level of the nidus in all our patients, suggested that gravity played an important role in the etiology of radiculomen-ingeal AVM in these patients.

Aged↗
PubMed1997

Ocular and cerebellar defects in zebrafish induced by overexpression of the LIM domains of the islet-3 LIM/homeodomain protein.

Islet-3 is an LIM/homeodomain protein that is expressed specifically in the eyes and the presumptive tectum in the central nervous system of zebrafish (Danio rerio) embryos. Overexpression of the protein (LIM(Isl-3)) consisting only of the Islet-3 LIM domains in embryos specifically prevented formation of the optic vesicles; caused abnormal termination of the expression of wnt1, engrailed2, and pax2 in the mesencephalic and metencephalic region between 14 hr and 20 hr postfertilization; and severely impaired morphogenetic movement in this region between 20 hr and 26 hr, which should normally lead to formation of the cerebellar primordium. Such defects were all rescued by simultaneous overexpression of Islet-3, suggesting that LIM(Isl-3) acted as a specific dominant-negative variant of Islet-3. These data, combined with the results of mosaic analyses, suggest that Islet-3 is activated by putative LIM-binding cofactors and functions to promote evagination of the optic vesicles and to maintain reciprocal interaction between the mesencephalon and the mesencephalic-metencephalic boundary essential for normal development of this region.

Animals↗
PubMed1997

Acute regulation by dietary phosphate of the sodium-dependent phosphate transporter (NaP(i)-2) in rat kidney.

Alteration of the dietary intake of phosphate (P(i)) leads to rapid changes in renal P(i) transport activity. The present study, examined the underlying cellular mechanisms of the rapid regulation, with special reference to renal P(i) cotransporter. Rats were fed either a low-P(i) (0.02%) diet (CLP rats), the low-P(i) diet followed by a high-P(i) (1.2%) diet (AHP rats), or a normal (0.6%) diet (control rats). Na(+)-dependent P(i) transport activity in the brush border membrane was significantly increased in CLP rats compared with control rats, and this activity decreased rapidly within 2 h after the change of diet in AHP rats. Kinetic analysis of P(i) transport in the AHP rats indicated that the reduction was accompanied by a decrease in the apparent Vmax for Na(+)-dependent P(i) uptake. Northern blot analysis showed no difference in the abundance of NaP(i)-2 mRNA of the kidney between AHP and CLP rats. In contrast, Western blot analysis of renal brush border membrane proteins of AHP rats indicated a significant decrease in the abundance of NaP(i)-2 protein as compared with CLP rats. Immunoreactive signals for NaP(i)-2 were detected in lysosomal fractions of AHP and CLP rats. Immunohistochemical analysis showed that, NaP(i)-2 immunoreactivity in AHP rats was largely reduced in the apical membrane of the proximal tubular epithelial cells. Neither cycloheximide nor actinomycin D affected high-P(i)-induced reduction of NaP(i)-2 protein in the brush border membrane of AHP rats, indicating that de novo protein synthesis of an unidentified regulator protein was not involved in the mechanism of this reduction. In contrast, treatment with colchicine, which disrupts microtubulers, abolished the effect of high-P(i) diet on NaP(i)-2 expression. These results suggested that rapid endocytotic internalization of NaP(i)-2 may occur specifically in the brush border membrane following an acute increase in dietary P(i) intake.

Animals↗
PubMed1997

The effects of atrial natriuretic peptide infusion on hemodynamic, renal, and hormonal responses during gastrectomy.

UNLABELLED: Atrial natriuretic peptide (ANP) antagonizes the reninangiotensin-aldosterone, adrenocorticotropic hormone-cortisol, vasopressin, and endothelin systems. Surgical injury stimulates these systems and causes vasoconstriction and antidiuresis. We assessed the hemodynamic, renal, and endocrine effects of continuous intravenous infusion of ANP in patients anesthetized with sevoflurane undergoing gastrectomy. ANP (0.1 microgram.kg-1.min-1; ANP group, n = 9) or saline (control group, n = 9) was infused continuously for 3 h from the start of the operation. The ANP group showed much higher urinary volume and sodium, potassium, and chloride excretion than the control group, although the former had lower arterial blood pressure. ANP infusion slightly inhibited aldosterone secretion and initially tended to inhibit renin secretion stimulated by surgery, but it did not affect surgery-induced increases in the plasma concentrations of vasopressin, adrenocorticotropic hormone, cortisol, or endothelin. Two patients in the ANP group experienced excessive hypotension, one experienced bradycardia, and two experienced mild hypoxemia, which required treatment but were resolved easily. These findings suggest that ANP infusion may be used with caution for controlling renal function and arterial blood pressure during surgery. IMPLICATIONS: Continuous intravenous infusion of atrial natriuretic peptide, 0.1 microgram.kg-1.min-1, during gastrectomy was associated with higher water and sodium excretion and lower arterial blood pressure. It tended to inhibit the renin-angiotensin-aldosterone system compared with saline infusion, which suggests that atrial natriuretic peptide may be useful for intraoperative circulation control.

Adrenocorticotropic Hormone↗
PubMed1996

Effects of truncation of the COOH-terminal region of a Na+-independent neutral and basic amino acid transporter on amino acid transport in Xenopus oocytes.

To determine the role of a neutral and basic amino acid transporter (NBAT) in amino acid transport, we microinjected several COOH-terminal deletion mutants of NBAT cRNA into Xenopus oocytes and measured transport activity for arginine, leucine, and cystine in the presence and absence of sodium. Wild-type NBAT significantly stimulated the uptake of all three amino acids 10-20-fold compared with controls. On the other hand, no mutant, except a Delta511-685 mutant, stimulated the uptake of these amino acids. The Delta511-685 mutant significantly increased the uptake of arginine. In the presence of sodium, the Delta511-685 mutant also increased the uptake of leucine. The Delta511-685 mutant did not stimulate cystine uptake in the presence or absence of sodium. The stimulation of arginine uptake by the Delta511-685 mutant was inhibited by a 100-fold excess of unlabeled leucine in the presence of sodium. Inhibition of L-arginine uptake by L-homoserine was seen only in the presence of sodium, and an increase in the inhibition of L-arginine uptake by L-histidine was seen when the extracellular pH was decreased. Furthermore, an inward current in oocytes injected with the Delta511-685 mutant was recorded electrophysiologically when basic amino acids were applied. Homoserine was also taken up, but sodium was necessary for their transport. These properties of the Delta511-685 mutant correspond to those of the y+ amino acid transporter. If NBAT is a component of the b0,+-like amino acid transport system, it is unlikely that a mutant protein (Delta511-685) is able to stimulate an endogenous y+-like transport system. These results suggest that NBAT functions as a activator of the amino acid transport system in Xenopus oocytes.

Amino Acid Sequence↗
PubMed1996

The role of the phrenic nerves in stress response in upper abdominal surgery.

Previous studies have failed to demonstrate a block of the endocrine response to upper abdominal surgery by thoracic epidural analgesia. To clarify the bases for this failure, we compared the effects of epidural analgesia of different dermatome levels up to C8-T2 or C3-4. The patients who received general anesthesia alone showed significant increases of adrenocorticotropic hormone (ACTH) and arginine vasopressin (AVP) immediately after skin incision. The patients with C8-T2 blocked developed significant increases in these hormones, not after the skin incision, but after the intraabdominal procedure. Of the eight patients with C3-4 block, six developed no such responses throughout the study period. The responses of oxytocin (OXT) and prolactin (PRL) were more susceptible to epidural analgesia and were blocked at the C8-T2 level. Growth hormone (GH) showed no correlation with surgical procedures and epidural block. These findings indicate that the nociceptive neural information during upper abdominal surgery is conveyed by the sensory fibers included in both the thoracic and lumbar spinal nerves that innervate the abdominal wall and the intraabdominal viscera, and by the phrenic nerves that innervate the diaphragm. The rationale for postulating the involvement of the phrenic nerves can be referred to the embryonal descent of the diaphragm from the C3-5 myotomes that serves as the upper wall of the abdominal cavity.

Abdomen↗
PubMed1995

Mutations of the basic amino acid transporter gene associated with cystinuria.

To investigate the function of a basic and neutral amino acid transporter-like protein (rBAT) which is a candidate gene for cystinuria, we analysed the rBAT gene in cystinuric patients. Patient 1 is a compound heterozygote with mutations in the rBAT gene causing a glutamine-to-lysine transition at amino acid 268, and a threonine-to-alanine transition at amino acid 341, who inherited these alleles from his mother (E268K) and father (T341A), respectively. Injection of T341A and E268K mutant cRNAs into oocytes decreased transport activity to 53.9% and 62.5% of control (L-cystine transport activity in oocytes injected with wild-type rBAT cRNA), respectively. Co-injection of E268K and T341A into oocytes strongly decreased amino acid transport activity to 28% of control. On the other hand, co-injection of wild-type and mutant rBAT did not decrease transport activity. Furthermore, immunological studies have demonstrated that the reduction of amino acid transport is not due to a decrease in the amount of rBAT protein expressed in oocyte membranes. These results indicate that mutations in the rBAT gene are crucial disease-causing lesions in cystinuria. In addition, co-injection experiments suggest that rBAT may function as a transport activator or regulatory subunit by homo- or hetero-multimer complex formation.

Adolescent↗
PubMed1995

Parasellar Aspergillus granuloma extending from the sphenoid sinus: report of two cases.

BACKGROUND: Sphenoid sinus aspergillosis is a rare disease known to show an aggressive course with high mortality. Early diagnosis, though difficult, is required to prevent lethal fungal meningoencephalitis. CASE REPORT: We describe two cases of parasellar Aspergillus granuloma extending from the sphenoid sinus clinically indistinguishable from intracranial neoplasms. In the first patient, the fungus colony was visualized by computed tomography (CT) and magnetic resonance imaging (MRI) as a calcified concretion and total removal was curative. In the second patient, partial removal and subsequent antifungal therapy had minimal effect. CONCLUSIONS: The prognosis of the patients with this disease depends on prompt surgical treatment before intradural invasion occurs, and CT and MRI are useful diagnostic maneuvers for detecting calcified Aspergillus colonies.

Aged↗
PubMed1995

Effects of zinc on production of active oxygen species by rat neutrophils.

The effects of zinc on the production of active oxygen species were investigated in rat neutrophils by chemiluminescence and spectrophotometric assays. The luminol-dependent chemiluminescence in unstimulated neutrophils showed a single peak. Zinc at concentrations lower than 0.1 mM augmented the intensity of chemiluminescence and showed a bimodal pattern, the first peak of which was inhibited by superoxide dismutase and catalase, while the second peak disappeared in the presence of catalase, but was unaffected by superoxide dismutase. At the same concentrations of zinc, O2- and H2O2 production increased, but secretion and activity of myeloperoxidase were not affected. Zinc at 0.1 mM enhanced the second peak of luminol-dependent chemiluminescence, and concomitantly O2- and H2O2 production of neutrophils stimulated with formyl-methionyl-leucyl-phenylalanine. Homogenized neutrophils showed a bimodal pattern on induction by zinc, the second peak of which was inhibited slightly by catalase and completely by sodium azide, but was not inhibited by superoxide dismutase. Zinc-induced O2- production was inhibited by pertussis toxin, but was not significantly inhibited by a protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), or a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). These results suggest that zinc can augment luminol-dependent chemiluminescence by increasing O2- production through the classical signal transduction pathway, and by increasing H2O2 not via O2-.

Animals↗
PubMed1995

Delayed parent artery narrowing occurring months after aneurysm surgery: a complication after aneurysm surgery--technical case report.

The authors report two patients with a rare complication of parent artery narrowing that occurred 3 and 6 months after aneurysm surgery. In both cases, the stenosed arteries had been wrapped around their entire circumferences with neurosurgical sponge (cotton linter) and coated with plastic adhesive (cyanoacrylate compounds) and the aneurysmal neck had been clipped. This reinforcement procedure was considered to have caused the unusual delayed arterial narrowing. The importance of avoiding circumferential parent artery wrapping with plastic-adhesive coating is emphasized.

Aged↗
PubMed1995

Difinite-sequenced oligonucleotides shackled with tetraphenylporphyrin: syntheses and properties.

Oligonucleotides shackled with tetraphenylporphyrin at internucleotide phosphodiester linkage were synthesized and their properties were investigated. The derivatives can hybridize with the complementary oligonucleotide completely. Introduction of porphyrin into the oligonucleotide has little effect on the helix structure and hybridization entirely changes the electronic environment of the porphyrin moiety. Therefore, it is expected that the derivatives locate the photoactive phosphorus(V)porphyrin moiety in close proximity to the target site of DNA.

Base Sequence↗
PubMed1994

Zinc hydroxide induced respiratory burst in rat neutrophils.

The effects of zinc hydroxide on the respiratory burst and phagocytosis by rat neutrophils were examined. Zinc hydroxide induced an increase in oxygen consumption and O2- production. Electronmicroscopy showed that neutrophils engulfed zinc hydroxide particles by phagocytosis. Pertussis toxin (0.25, 0.5, 1.0 micrograms/ml) and EGTA (1, 2, 5 mM) inhibited zinc hydroxide-induced O2- production in a dose-dependent manner. The inhibitors of protein kinase C, 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine and N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide inhibited zinc hydroxide-induced O2- production with IC50 values ranging between 10 microM and 25 microM. The inhibitory study using an inhibitor of myosin light chain kinase, 1-(5-iodo-naphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine, showed IC50 values ranging from 5 microM to 10 microM. These findings indicate that zinc hydroxide induces respiratory burst and phagocytosis by rat neutrophils.

Animals↗
PubMed1994

Effect of IL-1 receptor antagonist and antiserum to TNF-alpha on LPS-induced plasma ACTH and corticosterone rise in rats.

Using an antiserum against tumor necrosis factor (TNF)-alpha and an interleukin (IL-1) receptor antagonist, we studied putative roles of these cytokines in mediating the endotoxin-induced elevation of plasma adrenocorticotropic hormone (ACTH) and corticosterone levels in freely moving rats. Intravenous administration of Escherichia coli lipopolysaccharide (LPS) increased plasma ACTH and corticosterone levels in a dose-dependent manner. The plasma corticosterone reached to its highest level among a series of experiments after the administration of even the smallest dose (0.03 microgram/kg) tested. Plasma ACTH and corticosterone levels in these rats were completely inhibited by the intravenous administration of anti-murine TNF-alpha-rabbit antiserum (anti-TNFAS) after the administration of LPS but not by the intravenous administration of IL-1 receptor antagonist (IL-1RA). On the other hand, both recombinant human IL-1RA and anti-TNFAS significantly inhibited plasma ACTH increase stimulated with 10 micrograms/kg LPS. These findings indicate that 1) when the plasma corticosterone increase induced by intravenous LPS remains below its maximum, the effect is exclusively mediated by TNF-alpha, and 2) when a larger amount of LPS is administered, both IL-1 beta and TNF-alpha participate at least in part in the hypothalamic-pituitary-adrenal axis activation.

Adrenocorticotropic Hormone↗
PubMed1994

[A case of polymyositis with ventricular tachycardia].

We reported a case of polymyositis with ventricular tachycardia. She had been suffering from proximal dominant muscle weakness and palpitation for 11 months. Holter EKG demonstrated 23 beats ventricular tachycardia. The noninvasive cardiac examination (Thalium cardiac scintigraphy, echocardiography, radionuclide ventriculography) demonstrated no abnormal findings. After initiation of steroid therapy, muscle strength and CK improved and ventricular tachycardia disappeared. Ventricular tachycardia is one of the important complications of polymyositis.

Adult↗
PubMed1994

[Practical CT classification for thalamic hemorrhage: relationship between localization of hematoma and prognosis].

It is not easy to predict functional outcome in patients with acute-stage thalamic hemorrhage. We analysed 100 cases of hypertensive thalamic hemorrhage less than 4 cm in diameter, and devised a practical CT classification for predicting the patients' prognoses. On an axial CT scan at the level of the pineal body, four lines were drawn as follows: line (a) between the lateral edge of the anterior horn and the midpoint of the third ventricle; line (b) vertical line to the sagittal line from the midpoint of the third ventricle; line (c) between the lateral edge of the trigone and the midpoint of the third ventricle; line (d) between the lateral edge of the anterior horn and the lateral edge of the trigone. The location of hematoma was divided into three types according to lateral extension as follows: type A (anterior type), center of hematoma located between line (a) and line (b); type P (posterior type), center of hematoma located between line (b) and line (c), and external margin of hematoma localized medial to line (d); type PL (postero-lateral type), center of hematoma located between line (b) and line (c), and showing lateral extension beyond line (d). Then, the correlation between hematoma location and severity of motor paresis at onset and its prognosis was investigated. Severe hemiparesis (MMT: 0-2) was observed in 15.3% of patients with type A, 21.8% with type P, and 59.3% with type PL hematoma in the acute stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

Brain stem haemorrhage during transsphenoidal surgery. Possible risk of the manoeuvre of increasing the endexpiratory pressure in a case of pituitary adenoma associated with dural arteriovenous malformation. Case report.

The authors report a case of pituitary adenoma associated with dural arteriovenous malformation (AVM), which caused brain stem haemorrhage during transsphenoidal surgery. The manoeuvre of increasing the endexpiratory pressure in order to push the suprasellar component of the adenoma down to the sella turcica could be the reason of this bleeding. The authors therefore recommend that in cases of such a combination any manoeuvres which are likely to increase the intracranial venous pressure or otherwise affect the intracranial pressure, are avoided. The dural AVM spontaneously regressed after haemorrhage.

Adenoma↗