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Biomedical subjects

Y Iwai

Publications and source records attributed to Y Iwai.

At least 73 records · Page 4Linked to original sources
PubMed1998

Rupture mechanism of a thrombosed slow-growing giant aneurysm of the vertebral artery--case report.

A 76-year-old male developed left hemiparesis in July 1991. The diagnosis was thrombosed giant vertebral artery aneurysm. He showed progressive symptoms and signs of brainstem compression, but refused surgery and was followed up without treatment. He died of rupture of the aneurysm and underwent autopsy in March 1995. Histological examination of the aneurysm revealed fresh clot in the aneurysmal lumen, old thrombus surrounding the aneurysmal lumen, and more recent hemorrhage between the old thrombus and the inner aneurysmal wall. The most important histological feature was the many clefts containing fresh blood clots in the old thrombus near the wall of the distal neck. These clefts were not lined with endothelial cells, and seemed to connect the lumen of the parent artery with the most peripheral fresh hemorrhage. However, the diameter of each of these clefts is apparently not large enough to transmit the blood pressure of the parent artery. Simple dissection of the aneurysmal wall by blood flow in the lumen through many clefts in the old thrombus of the distal neck may be involved in the growth and rupture of thrombosed giant aneurysms of the vertebral artery.

Aged↗
PubMed1998

[Indications for external ventricular drainage after clipping of ruptured aneurysms in the acute stage].

The indication for external ventricular drainage after clipping of ruptured aneurysms in the acute stage is evaluated. Since 1990, 234 patients who presented with subarachnoid hemorrhage (SAH) and underwent aneurysmal clipping in the acute stage were evaluated retrospectively. Patients with ventricular dilatation had intraoperative placement of a ventriculostomy to obtain intraoperative brain relaxation, but the ventricular catheter was removed at the end of the surgery. All these patients were managed postoperatively in a similar fashion with no ventricular drainage, avoidance of dehydration complemented by a course of sodium ozagrel and nicardipine or fasudil hydrochloride. Acute hydrocephalus was defined as clinically and radiographically demonstrated ventricular dilatation that developed within 2 weeks of the onset of SAH and that required ventricular drainage. Three surgical approaches were employed; pterional approach (PA) for the aneurysms of the anterior circulation and upper basilar artery in 207 patients, interhemispheric approach (IHA) for the aneurysms of the pericallosal artery in 11 patients and lateral suboccipital approach (LSA) for the aneurysms of the vertebral arteries in 16 patients. No significant differences were found among these three approach groups in Fisher CT classification and the Hunt & Kosnik gradings. Four patients developed acute hydrocephalus within two weeks of surgery: three patients were operated on via LSA and one through IHA. Compared to the IHA or LSA, PA was superior for reestablishing cerebrospinal fluid circulation, because it is possible to remove more subarachnoid clot in the basal cisterns than to do so in the other two approaches. Opening of the lamina terminalis and the Liliequist membrane are also possible using PA. In conclusion, PA can prevent development of acute hydrocephalus, whereas postoperative ventricular drainage may be necessary in patients operated upon via IHA or LSA.

Acute Disease↗
PubMed1998

[Antimicrobial activity of macrolides against clinical isolates].

Antimicrobial activity of 6 macrolides was determined using a micro-broth dilution method, against 535 clinical isolates of 22 species, which were isolated in 1996 from 325 facilities in Japan. Results were as follows. 1. In general, antimicrobial activities of 14-membered macrolides were higher than those of 16-membered macrolides. The antimicrobial activities of 14-membered macrolides were in the order of clarithromycin (CAM), erythromycin (EM), roxithromycin (RXM). Among 16-membered macrolides, rokitamycin (RKM) was the most potent, josamycin (JM) was next potent followed by midecamycin (MDM). More numbers of highly-resistant strain of > 100 micrograms/ml were recognized in 14-membered macrolides than in 16-membered macrorides. 2. Most of S. pyogenes (group A) strains were distributed in the susceptible range and almost none was found in the resistant range. 3. S. pneumoniae strains were distributed widely from the susceptible range to the highly resistant range, and as high as 37.1% fell into the high resistance of > 100 micrograms/ml range. 4. Against Peptostreptococcus spp. and MRSA, 16-membered macrolides were more effective than 14-membered macrorlides, and their antibacterial activities were in the order of RKM, JM, MDM. Ratio of high-resistant strains of > 100 micrograms/ml against 14-membered macrolides was much higher than that against 16-membered macrolies. 5. Most of M. (B.) catarrhalis strains were distributed in the susceptible range of < or = 1.56 micrograms/ml, and most of H. influenzae strains were distributed within the moderately resistant and the resistant ranges. 6. In M. (B.) catarrhalis and H. influenzae, no correlation between macrolide resistance and beta-lactamase production was recognized. 7. Most of C. jejuni strains were susceptible to all macrolides used in this study.

Anti-Bacterial Agents↗
PubMed1998

[Type A acute aortic dissection: late reoperations for dilatation of the distal false lumen and aortic regurgitation].

From January 1990 to December 1996, 71 patients aged 33 to 79 years (mean 60 +/- 11) underwent an emergency operation for type A acute aortic dissection. Fifty-three (74.6%) survived, and were followed 7 to 94 months (mean follow up 2.9 +/- 1.8 years) after the first operation. Five patients underwent reoperation for dilatation of the distal false lumen 7 to 52 months (mean period, 25 months) after primary repair. One patient underwent replacement of the arch and descending aorta, three patients underwent replacement of the descending aorta, and one patient underwent the stented graft implantation, resulting in closure of the entry site. Three patients underwent reoperation for severe aortic valve regurgitation 12 to 31 months (mean period, 24 months) after primary repair. Two patients underwent aortic valve replacement, and one patient underwent aortic root replacement. The actuarial freedom from reoperations was 81 +/- 6.9% at 3 years, and 73 +/- 9.9% at 5 years.

Adult↗
PubMed1998

[Management of elderly patients with incidentally discovered unruptured aneurysms].

Long-term natural history of unruptured cerebral aneurysms is not found frequently. Hence, the indications for surgery on unruptured asymptomatic cerebral aneurysms are still unclear. The benefit of treatment ultimately depends on the relative risk of subsequent aneurysm rupture in untreated patients versus the risk involved in surgery. Clinical features of fourteen elderly patients aged over 70 years with incidentally discovered unruptured aneurysms were analyzed. Two were male and 12 were female, with ages ranging from 70 to 82 years (mean: 74.5 years). Aneurysms were located in the anterior circulation in 13 patients and in the posterior circulation in 1 patient. One patient had multiple aneurysms, that is, bilateral middle cerebral aneurysms. The size of all these aneurysms was less than 10 mm. The indication for surgery was determined case by case. General information about the natural history of incidentally discovered aneurysms was given to the patients and their relatives. Informed consent was based on the fact that subarachnoid hemorrhage was associated with a poor prognosis, while excellent operative results were common in patients with unruptured aneurysms. Five patients agreed to surgical treatment. Four of them, their ages being 70, 70, 72 and 72 years old, with aneurysms located on the middle cerebral arteries, underwent neck clipping of their aneurysms with no operative morbidity or mortality. However, the remaining one patient was not recommended for surgery in spite of her consent to having it, because of her high age (82 years) and the location of her aneurysm (intracavernous internal carotid artery). Consequently, 10 patients who didn't receive surgery were followed-up at periods ranging from 3 months to 7 years. Two patients developed rupture of the aneurysms, either proven (one patient) or presumed (one patient). The former patient made an uneventful recovery after surgery, but the latter died. None of the remaining eight patients have experienced rupture of the aneurysms. It is our clinical impression, however, that they harbor an unruptured aneurysm with at least mild trepidation. With the rapid aging of the population, withholding aneurysm surgery merely because a patient is elderly may not necessarily be the most appropriate decision. Our conclusions are as follows: (1) Elderly patients in their early seventies are apt to agree to having surgical treatment for their unruptured aneurysms. (2) The cases reported herein show that asymptomatic middle cerebral artery aneurysms were able to be clipped very safely. (3) Most patients have experienced a decrease in quality of life from knowing they are living with an unruptured aneurysm.

Age Factors↗
PubMed1998

[Report of four cases of lymphocytic infundibuloneurohypophysitis].

We reported 4 cases of lymphocytic infundibuloneurohypophysitis. All four patients had diabetes insipidus as initial symptoms without anterior pituitary dysfunction. All patients showed pituitary stalk swelling and two patients showed enlargement of the pituitary gland. No patients were operated on for a histological diagnosis. No patients received corticosteroid treatment for this pathology. The mean follow-up period was 36 months. The diabetes insipidus continued in all cases, but radiological findings showed improvement in all cases. In one case, adrenal insufficiency occurred after 10 months, but had disappeared 6 months later. We think lymphocytic infundibuloneurohypophysitis can be diagnosed without histological examinations and can be treated conservatively without corticosteroid treatment. It seems to be a self-limiting disease. This disease can be distinguished from lymphocytic adenohypophysitis, but in some cases, both the anterior and posterior pituitary glands are invaded, and in this situation lymphocytic hypophysitis may be an appropriate name. Even if the initial symptom is diabetes insipidus, careful follow-up is needed for the duration of the disease.

Aged↗
PubMed1998

[Application of ultrafast 3D-CT in cervical spine injury].

The authors investigated the usefulness of the ultrafast three-dimensional computed tomography (UF-3D-CT) in cervical spine injury. At Osaka City General Hospital, between April 1995 and March 1998, the authors examined 38 patients with cervical spine injury using UF-3D-CT. The ultrafast CT reduces scanning time. There were no complications associated with the examination. We examined 12 patients with vertebral body fracture, 11 patients with lamina fracture, 8 cases with subluxation including locking facet, 2 patients with atlanto-axial dislocation and 8 patients without bony abnormality. Results suggested that UF-3D-CT was very useful for helping us to understand the bony deformity and the relationship between the bone and the important vessels. UF-3D-CT is very useful for preoperative evaluation and pathophysiological evaluation in cervical spin injury.

Adolescent↗
PubMed1997

Vertebral artery occlusion after subarachnoid hemorrhage from a dissecting aneurysm of the vertebral artery: case report.

BACKGROUND: Generally speaking, occlusion of the vertebral artery is a finding of a dissecting aneurysm associated with completed stroke. We present a case of a vertebral dissecting aneurysm that produced subarachnoid hemorrhage (SAH). Angiography on the day of hemorrhage, however, demonstrated complete occlusion of the vertebral artery. CASE PRESENTATION: A 44-year-old hypertensive woman suffered a sudden onset of headache and vomiting followed by loss of consciousness due to SAH. Angiography on the day of hemorrhage revealed a complete occlusion of the right vertebral artery just distal to the dissecting aneurysm. This is the first report of such a case. The patient was still considered to be at significant risk of rerupture. Craniotomy and clip occlusion of the right vertebral artery and the origin of the right posterior inferior cerebellar artery were carried out to trap the thin-walled sac. At discharge, the patient had recovered completely except for some left limb ataxia, which subsequently disappeared. CONCLUSIONS: Two options are available for the treatment of such a case: surgical or medical treatment. We employed surgery. Which is the preferred approach, however, is a difficult judgment to make at this juncture.

Adult↗
PubMed1997

Fluorescence polarization study of a salt bridge between a single-chain Fv and its antigen ribonuclease A.

The interaction between a single-chain Fv (sFv) of the monoclonal antibody 3A21 and its antigen, bovine pancreatic ribonuclease A (RNase A), was studied by site-directed mutagenesis of the hypervariable regions and fluorescence polarization analysis. The affinity constants of wild-type sFv and a mutant sFv D31A (Asp31 of heavy chain was replaced by Ala) for RNase A were found to be 2.7 x 10(7) and 4.7 x 10(6) M-1 in PBS at pH 7.2 and 37 degrees C, respectively. While the affinity constant of D31A is not affected by NaCl concentration, that of wild-type sFv is almost the same as that of D31A in the presence of more than 1 M NaCl. These results demonstrate that Asp31 of the heavy chain interacts electrostatically with a positively charged amino acid residue of RNase A.

Alanine↗
PubMed1997

Axon patterning requires DN-cadherin, a novel neuronal adhesion receptor, in the Drosophila embryonic CNS.

We identified DN-cadherin, a novel Drosophila cadherin that is expressed in axons and in the mesoderm. Although DN-cadherin has diverged from vertebrate classic cadherins in terms of its extracellular structure, it still can form a complex with catenins and induce cell aggregation, as do the vertebrate molecules. Loss-of-function mutations of the gene resulted in either embryonic lethality or uncoordinated locomotion of adults. In the central nervous system of null mutant embryos, subsets of ipsilateral axons displayed a variety of aberrant trajectories including failure of position shifts, defective bundling, and errors in directional migration of growth cones. These results suggest that processes of axon patterning critically depend on DN-cadherin-mediated axon-axon interactions.

Animals↗
PubMed1997

Novel detoxification of the trichothecene mycotoxin deoxynivalenol by a soil bacterium isolated by enrichment culture.

A mixed microbial culture capable of metabolizing deoxynivalenol was obtained from soil samples by an enrichment culture procedure. A bacterium (strain E3-39) isolated from the enrichment culture completely removed exogenously supplied deoxynivalenol from culture medium after incubation for 1 day. On the basis of morphological, physiological, and phylogenetic studies, strain E3-39 was classified as a bacterium belonging to the Agrobacterium-Rhizobium group. Thin-layer chromatographic analysis indicated the presence of one major and two minor metabolites of deoxynivalenol in ethyl acetate extracts of the E3-39 culture filtrates. The main metabolite was identified as 3-keto-4-deoxynivalenol by mass spectroscopy and 1H and 13C nuclear magnetic resonance analysis. The immunosuppressive toxicity of 3-keto-4-deoxynivalenol was evaluated by means of a bioassay based on the mitogen-induced and mitogen-free proliferations of mouse spleen lymphocytes. This compound exhibited a remarkably decreased (to less than one tenth) immunosuppressive toxicity relative to deoxynivalenol, indicating that the 3-OH group in deoxynivalenol is likely to be involved in exerting its immunosuppressive toxicity. Strain E3-39 was also capable of transforming 3-acetyldeoxynivalenol but not nivalenol and fusarenon-X.

Animals↗
PubMed1997

Amphistin, a new melanogenesis inhibitor, produced by an actinomycete.

A new melanogenesis inhibitor, named amphistin, was isolated from the fermentation broth of an actinomycete strain KP-3052. Amphistin was purified from the culture filtrate by the combination of cation exchange, gel filtration, and aminosilyl silica gel chromatographic methods. The structure of amphistin was elucidated as gamma-(beta-histidinoalanino)homoalanine by NMR experiments including 1H-15N HMBC experiment and other spectroscopic analyses. Amphistin inhibited the melanogenesis of B16 melanoma cells at concentration of 6.8 microM.

Actinomycetaceae↗
PubMed1997

[Interstitial tubercle in Chinese and Japanese young adults]

A comparative study on the incidence of interstitial tubercle from standardized stone casts of 160 Chinese and 190 Japanese young adults,ages from 20-30.The following results were obtained:(1)No significant difference in the incidence of interstitial tubercle on maxillary first premolar between Chinese and Japanese groups(P>0.05),but on maxillary second premolar,Japanese is higher than Chinese(P<0.05).(2)The incidence of interstitial tubercle on maxillary first premolar is higher than second premolar in two groups(P<0.05).(3)The intestitial tubercle occurs in unilateral more frequently than in bilateral.The incidence of maxillary first premolar in mesial of occlusal is higher than in distal.No difference between mesial and distal on occlusal of maxillary second premolar in the Chinese group,and the incidence in mesial is higher than in distal in the Japanese group.

Journal Article↗
PubMed1997

[Intraoperative aneurysmal rupture at the neck].

Intraoperative rupture of an aneurysm can lead to disastrous results when the rupture occurs at the neck. The authors have encountered eight cases (5%) of intraoperative rupture in a series of 155 patients. All patients were operated on in the acute stage by one of the authors of this paper (T.Y.). In six cases, the aneurysm ruptured at the dome and in two, at the neck. We report these two patients with intraoperative rupture at the neck. The first case, a 50-year-old female, developed SAH, but a 4-vessel study failed to show an aneurysm. The second series of angiograms obtained ten days later showed a broad-based, left proximal A1 aneurysm. It was decided to employ a right pterional approach. The aneurysm was arising from the right A1 segment just proximal to the anterior communicating artery. The neck was wide, with thin walls. Thus, it seemed better to apply a clip parallel to the A1 segment axis than to apply it from a direction perpendicular to the A1 segment axis. However, the right pterional approach precluded a parallel clipping, so the blades of a clip were applied perpendicularly. The clip seemed not to be completely across the neck of the aneurysm. After applying a temporary clip to the A1 segment proximal to the aneurysm, the clip blades were opened and advanced just when bursting of the sac at the base occurred and microvascular suture repair was required to control the bleeding. The second case, a 57-year-old female, underwent clipping of a right IC-PC aneurysm. However, two years postoperatively, the patient again suffered SAH. Cerebral angiography at this time revealed a relatively large recurrent IC-PC aneurysm in which the old clip was situated on the dome of the aneurysm. Aneurysmal clipping was performed on the day of rupture. Tough granular tissue was removed from the ICA, PcomA, aneurysmal neck, and the old clip. After the true neck was identified, a straight clip was applied to the neck parallel to the ICA. Soon after the clipping, arterial bleeding occurred near the neck. The ruptured aneurysm was trapped using two temporary clips. A curved clip was applied to the ruptured neck, including the wall of the ICA, to control the bleeding. This clipping caused a substantial stenosis of the ICA. Both patients demonstrated postoperative neurological deficits due to ischemia caused by temporary clipping. These encounters dramatically demonstrated that a very thin-walled aneurysm or a recurrent aneurysm has a fragile neck. In surgical treatment of these unusual aneurysms, a clip should be placed on the neck parallel to the parent artery. Furthermore, temporary clipping is advisable when dissecting the neck or applying the clip to the neck to reduce the damage to the neck.

Aneurysm, Ruptured↗
PubMed1997

[Rupture of previously documented asymptomatic saccular intracranial aneurysms].

The authors report four cases of patients with documented asymptomatic intact aneurysms that subsequently ruptured. Case 1 involves a 64-year-old woman who had two unruptured aneurysms, i.e., an anterior communicating artery aneurysm and a posterior inferior cerebellar aneurysm, both were discovered during evaluation of cerebral ischemic symptoms. At that time, only the posterior inferior cerebellar aneurysm was clipped. Seven years later, the patient bled fatally from a 5-mm untreated anterior communicating artery aneurysm that had measured approximately 3 mm on an angiogram obtained 7 years earlier. Case 2 is that of a 50-year-old woman who bled from an anterior communicating artery aneurysm that had been discovered 6 years earlier when she suffered subarachnoid hemorrhage (SAH) from a left middle cerebral artery aneurysm. At that time, she had refused surgery for the anterior communicating artery aneurysm. She recovered well from the second SAH. Case 3 is that of a 74-year-old woman who bled from a left paraclinoid internal carotid artery aneurysm that had been discovered incidentally 3 years earlier during evaluation of vertigo. She had not agreed to have a clipping at that time the aneurysm was first discovered because of her age and the difficult location of the aneurysm. She eventually made an uneventful recovery. In the fourth case, during evaluation of cerebral ischemic symptoms, a 59-year-old man was discovered to have a large basilar bifurcation aneurysm. He underwent a craniotomy for clipping of the aneurysm. The aneurysm, however, was unclippable and was instead coated with Bemsheet. Four months later, the patient bled from the aneurysm and entered a vegetative state. The indications for surgery on unruptured asymptomatic cerebral aneurysms are still unclear. The cases reported herein show that asymptomatic aneurysms, especially anterior communicating aneurysms and aneurysms once exposed surgically, do carry a certain risk for future hemorrhage and should not be dismissed as innocuous. Neurosurgeons have recognized the importance of considering life expectancy in managing patients with asymptomatic, unruptured, intracranial aneurysms. With the rapid aging of the population, withholding aneurysm surgery merely because a patient is elderly may not necessarily be the most appropriate decision.

Aged↗
PubMed1997

[Management of subarachnoid hemorrhages without detectable aneurysm].

In this study, 21 patients with subarachnoid hemorrhage (SAH) but negative angiography were evaluated. Angiography was performed twice on each patient, that is, on admission and at 2 weeks following admission. All patients had severe headache of sudden onset, a characteristic manifestation of SAH. Clinical grades on admission (Hunt and Kosnik classification) were generally good: 17 patients were in grade I or II and 4 patients were in grade III. SAH was confirmed by the presence of subarachnoid clot on CT in all cases. Based on the distribution of SAH, CT findings were classified into two patterns, i.e., perimesencephalic and non-perimesencephalic patterns. Four patients showed the perimesencephalic pattern and the remaining 17 the non-perimesencephalic. The period of follow-up ranged from 20 days to 11 years 6 months, with a mean of 6 years 10 months. Except for three recent cases, the mean follow-up period in 8 years 9 months. Exploratory craniotomies probing for aneurysms have been performed in four patients, but no aneurysms have been found in any of these cases. Clinical deterioration associated with vasospasm was observed in one patient. A communicating hydrocephalus requiring a shunting procedure was observed in three patients showing the non-perimesencephalic type CT pattern. Rebleeding occurred in one patient who subsequently died of what may be a dissecting aneurysm of the vertebral artery. One patient who was able to return to full activity experienced symptoms attributable to SAH such as frequent headaches and increased fatigability. Complete recovery was observed in the remaining 19 patients. Two of them, however, later died due to myocardial infarction and aging, respectively. Given these generally positive outcomes, it should be possible to inform such patients of the benignity of their condition. Angiography may not demonstrate a ruptured aneurysm on initial examination in all cases of aneurysmal SAH. Serial angiography, however, can provide a definite diagnosis of the dissecting aneurysm. Therefore, repeat angiography, particularly, when possible, digital subtraction angiography, is necessary to rule out aneurysmal SAH. While small aneurysms or microaneurysms are often found through exploratory craniotomy, we do not agree with the opinion that surgery may be appropriate for certain patients with SAH but with negative angiography. The natural history concerning rebleeding in such cases, as well as morbidity and mortality associated with hemorrhage, remains to be defined. Furthermore, there are reservations regarding whether coagulation of these abnormalities with bipolar cautery constitutes definitive treatment.

Adult↗
PubMed1997

Direct extracranial-intracranial bypass for children with moyamoya disease.

To improve cerebral hypoperfusion in the ischemic type of Moyamoya disease, we have applied superficial temporal artery-middle cerebral artery (STA-MCA) double anastomoses in combination with encephalo-myo-synangiosis (EMS) for 19 hemispheres of 10 children (age from 5 to 11 years at surgery). Two branches of the STA were anastomosed to the two cortical arteries which were selected in the watershed area of the cerebral hemisphere estimated as a hypoperfusion area on the preoperative angiograms. Before surgery transient ischemic attacks (TIAs) developed from every month to every 6 months in association with hyperventilation or sobbing. No perioperative completed stroke or wound complications was observed, although single TIA developed in four patients within 1 month after surgery. Postoperative angiogram demonstrated that, not only the preoperative watershed area, but also the most of the middle cerebral artery territory was oppacified via the 2 branches of the STA in all 19 hemispheres. In a mean follow-up period of 4 years, no ischemic episode was induced by hyperventilation, and there was no mental or neurological deterioration. STA-MCA double anastomoses, to the cerebral watershed area, in combination with EMS are safe and effective even for younger children with Moyamoya disease.

Anastomosis, Surgical↗