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Biomedical subjects

H Iwanaga

Publications and source records attributed to H Iwanaga.

At least 37 records · Page 2Linked to original sources
PubMed1993

Initial flow of tissue conditioners--influence of composition and structure on gelation.

The effects of the molecular weight of polymer powders, the ethyl alcohol content of the liquids, the type of plasticizer and the polymer powder/liquid ratio on viscoelastic properties during gelation of tissue conditioners were studied with an oscillating rheometer. The results showed that: (i) The gelation time decreased exponentially with increases in molecular weight of the polymer powder and with powder/liquid ratio. There were linear relationships between the log of gelation time, and both the molecular weight of the polymer powder and the powder/liquid ratio. (ii) In general, gelation time decreased exponentially with increases in ethyl alcohol content. However, the relationship between the log of the gelation time and ethyl alcohol content fitted a second-order polynomial. (iii) The type of plasticizer affected gelation time. The order of gelation times was: benzyl benzoate < dibutyl phthalate < butyl phthalyl butyl glycolate. The initial flow of tissue conditioners could be controlled over a wide range by varying the molecular weight of the polymer powders, the ethyl alcohol content, the powder/liquid ratio and the type of plasticizer.

Acrylic Resins↗
PubMed1993

The effect of nicardipine on carotid blood flow velocity, local cerebral blood flow, and carbon dioxide reactivity during cerebral aneurysm surgery.

We studied the effects of nicardipine (initial infusion rate 0.5 micrograms.kg-1 x min-1) on blood flow velocity in the internal carotid artery, local cerebral blood flow (LCBF), and carbon dioxide reactivity in 20 patients undergoing craniotomy for cerebral aneurysm clipping under isoflurane anesthesia. The blood flow velocity in the internal carotid artery was measured at T0 and T3 by a 20-MHz pulsed ultrasound Doppler flowmeter. LCBF was measured by the thermal gradient blood flow meter. Group A consisted of 10 patients with a good neurologic status (Hunt and Kosnik Grade I); Group B consisted of 10 patients with a poor status (Grades II-IV). Nicardipine was infused until the mean arterial blood pressure decreased to about 75% of the initial value and was maintained at this level until the completion of aneurysm clipping. The measurements of hemodynamics and LCBF were performed after the exposure of the internal carotid artery (T0), and 10 and 30 min after the start of nicardipine (T1 and T2, respectively), before aneurysm clipping (T3), and 30 min after its discontinuation (T4). Carbon dioxide reactivity [% ALCBF/APaCO2 (%/mm Hg)] was evaluated at T0, T3, and T4. Mean arterial blood pressure decreased after nicardipine infusion in both groups. LCBF did not change during nicardipine infusion in either group. Blood flow velocity increased significantly in Group A after nicardipine infusion from 45.1 +/- 6.9 to 51.5 +/- 6.4 cm/s (P < 0.05), but in Group B flow velocity did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Dissecting aneurysm of the posterior inferior cerebellar artery--case report.

A 29-year-old male presented with a dissecting aneurysm of the left posterior inferior cerebellar artery manifesting as left lateral medullary syndrome due to brainstem ischemia. Extirpation of the aneurysm and anastomosis of the occipital artery to the posterior inferior cerebellar artery were performed simultaneously. The dissecting aneurysm was confirmed by histological examination of the surgical specimen.

Adult↗
PubMed1993

Clinicopathological characteristics of colorectal submucosal carcinoma with lymph node metastasis.

The clinicopathological characteristics of colorectal submucosal carcinoma with lymph node metastasis are described. Lymph node positive metastasis was found in 10 (11%) of 87 cases. The depth of submucosal invasion was classified as sm1, sm2 or sm3. Lymph node positive metastases were found in 18% of the cases at sm2 or more, in 31% of those without adenomatous components, in 39% of those with positive lymphatic permeation, in 41% of those with positive budding, and in 56% of all the moderately differentiated adenocarcinomas. These characteristics are risk factors and are important for the prediction of lymph node metastasis from colorectal submucosal carcinoma. Bowel resection with lymphadenectomy is indicated in the presence of any one or more risk factors.

Adult↗
PubMed1993

[The effect of nicardipine on internal carotid artery blood flow velocity, local cerebral blood flow and carbon dioxide reactivity].

To study the effect of nicardipine on the blood flow velocity of the internal carotid artery, on local cerebral blood flow (LCBF), and on carbon dioxide reactivity, an initial dose of 0.5 microgram/kg/min of nicardipine was administered in patients for scheduled craniotomy for cerebral aneurysm clipping under isoflurane anesthesia. This agent was administered until the mean arterial blood pressure decreased and could be maintained at about 75% of the initial value until the completion of aneurysm clipping. The measurements of hemodynamics and LCBF were performed after the exposure of the internal carotid artery (T0), and 10 min, 30 min after the starting of nicardipine (n = 13), (T1, T2 respectively), before aneurysm clipping (T3) and 30 min after its discontinuation (T4). Local cerebral blood flow was measured by the thermal gradient blood flow meter. The blood flow velocity of the internal carotid artery was measured at T0 and T3 by a 20MHz pulsed ultrasound Doppler Flow-meter under surgical microscope. Carbon dioxide reactivity was evaluated with % delta LCBF/delta PaCO2 (%/mmHg) at T0, T3 and T4. Mean arterial blood pressure decreased after nicardipine infusion. Local cerebral blood flow did not change during nicardipine infusion, but blood velocity increased significantly after nicardipine infusion from 43 +/-12 to 55 +/- 12 cm/sec (p = 0.024). Carbon dioxide reactivity did not change after nicardipine infusion but had a close correlation with LCBF before (rs = 0.64, p < 0.05), during (rs = 0.84, p < 0.01) and after hypotension (rs = 0.65, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Effect of nicardipine on the blood flow velocity in the vessel near a cerebral aneurysm of the internal carotid artery during cerebral aneurysm surgery: its therapeutic use for intra-operative hypertension.

Seven patients scheduled for clipping of an aneurysm of the internal carotid artery after subarachnoid haemorrhage, were studied in order to evaluate the efficacy of a bolus injection of nicardipine (2 mg) in the treatment of intra-operative hypertension on the blood flow velocity of vessel near the aneurysm under isoflurane anaesthesia. The blood flow velocity of the vessel near the aneurysm was measured using a 20 MHz ultrasound Doppler flowmeter. Nicardipine bolus significantly decreased the mean arterial blood pressure by about 30% (P < 0.01). The blood flow velocity of the internal carotid artery increased after the nicardipine bolus (from 43.3 +/- 9.9 to 51.7 +/- 15.0 cm s-1) (P < 0.05) but returned to the pre-injection level within 30 min (43.9 +/- 10.4 cm s-1). Nicardipine proved effective for control of intra-operative hypertension during aneurysm clipping.

Blood Flow Velocity↗
PubMed1992

Successful surgical obliteration of a huge intradural arteriovenous fistula of the spinal cord in a child.

We report the case of an 8-year-old boy with a huge intradural spinal arteriovenous fistula (AVF), which was successfully obliterated by surgery. The symptoms were episodic headaches and progressive motor and sensory deficits. He had suffered a subarachnoid hemorrhage twice before but no ensuing neurological deficits. Neuroradiological examinations revealed an intradural AVF with a huge venous aneurysm ventral to the spinal cord of C7 to T2, which was fed by the left 5th intercostal artery and the right thyrocervical artery. These two feeding arteries were occluded intradurally just at the venous aneurysm emerging point. MR images taken sequentially after surgery demonstrated complete thrombosis and subsequent disappearance of the thrombosed malformation. Neurological symptoms improved gradually. Treatment of such malformations is discussed.

Angiography↗
PubMed1992

Carbon dioxide reactivity and local cerebral blood flow during prostaglandin E1- or nitroglycerin-induced hypotension.

The aims of this randomized study were to determine the effect of prostaglandin-(PGE1) or nitroglycerin-(TNG) induced hypotension on local cerebral blood flow (LCBF) and carbon dioxide reactivity during isoflurane anaesthesia in 20 patients after subarachnoid haemorrhage (SAH) scheduled for aneurysm clip ligation. Mean arterial blood pressure decreased immediately, after giving either PGE1 or TNG. The LCBF, measured using a thermal gradient blood flowmeter, was unchanged after PGE1, while the LCBF increased after TNG infusion (control; 47.6 + 10.0, 60 min after infusion; 55.1 +/- 6.5 (P < 0.05), before clipping; 55.5 +/- 7.8 (P < 0.05)) but returned to control values after its discontinuation. Carbon dioxide reactivity, calculated from % delta LCBF/delta PaCO2 was unchanged during PGE1- or TNG-induced hypotension (PGE1; 2.13 +/- 0.9, 2.48 +/- 0.68 and 2.31 +/- 0.79%/mmHg for before, during and after hypotension respectively) (TNG; 2.08 +/- 0.68, 2.17 +/- 0.64 and 2.02 +/- 0.69%/mmHg for before, during and after hypotension respectively). Carbon dioxide reactivity correlated with presurgical neurological status (rs = -0.7, -0.648 and -0.458 for before, during and after hypotension respectively) and the initial LCBF (rs = -0.605). These results suggest that both PGE1 and TNG are useful drugs for induced hypotension for cerebral aneurysm surgery, because neither decreased LCBF.

Adult↗
PubMed1992

In vitro evaluation of Candida albicans adherence to soft denture-lining materials.

The adherence of Candida albicans to seven commercial soft denture-lining materials was studied in vitro with BCA protein assay reagent. A good correlation was observed between the amount of protein in yeast cells and the number of yeasts (r = 0.993, p < 0.01), and it was revealed that the adherence of C. albicans to bare surfaces of these soft denture-lining materials correlated well with their relative hydrophobic properties (r = 0.905, p < 0.01); thus there was consistency with the thermodynamic theory. These results combined corroborated the accuracy of this method. To know the effect of pellicle on fungal adherence, the adherence of C. albicans to saliva-coated samples was examined. It was revealed that neither the amount of protein adsorbed by substrates nor the adherence of yeast to saliva-coated substrates correlated with the relative hydrophobic properties of these samples, suggesting that factors other than hydrophobic interaction play an important role in the adherence of C. albicans to pellicle-coated soft liners and tissue conditioners.

Analysis of Variance↗
PubMed1992

Use of plastic bar molded casting in the modification of variably expanding investment to compensate for casting shrinkage of nickel-chromium alloy.

Trial plastic bar molded castings were compared for accuracy with cast crowns by means of a nickel-chromium alloy, which was used to establish the liquid density of variably expanding investments. The plastic bars were invested to evaluate the change of expansion rate in a wide range of six liquid densities from 0% to 100%, and the distances between the sections were measured before and after casting. Wax crowns were cast to obtain a more detailed relation around 0% expansion at seven liquid densities, and the gaps between the base of the die and the margin of the crown were measured before and after casting. The expansion rates of both castings were calculated and thus were proportional to the liquid density; both regression curves indicated high correlation coefficients. As a result of the statistics of the Student's t-test, the difference between the two methods was not significant. The trial plastic bar was useful in establishing the variably expanding investment for precise casting of artificial crowns.

Chromium Alloys↗
PubMed1992

[Local cerebral blood flow and its CO2 reactivity in the ischemic cerebrovascular diseases before and after bypass].

We evaluated the effects of the STA-MCA anastomosis on local cerebral blood flow (LCBF) and CO2 cerebrovascular reactivity (CVR) in ischemic cerebrovascular diseases (CVD). [Patients and Methods] We examined the LCBF and CVR of 21 patients with ischemic CVD subjected standard STA-MCA anastomosis. During surgery, LCBF was continuously measured using the thermal diffusion method sometimes in a state of decreased PaCO2 (median: 7.2mmHg) before and after bypass. CVR was represented as % delta LCBF/delta CO2. [Results] 1) In the control group (with non-ruptured aneurysm, n = 7), LCBF was 58.6 +/- 14.1 ml/100g/min and % delta LCBF/delta CO2 was 4.68 +/- 1.68%/mmHg. 2) Before bypass, LCBF was 46.7 +/- 10.3ml/100g/min. It was significantly (p < 0.05) lower than control level. After bypass, LCBF increased significantly (p < 0.05) to 62.0 +/- 14.3 ml/100g/min. 3) Before bypass, % delta LCBF/delta CO2 was -1.36 +/- 4.34%/mmHg. In the 14 cases (66.7%), % delta LCBF/delta CO2 was below the 0%/mmHg (inverse steal effect). 4) After bypass, it increased to 0.08 +/- 2.73%/mmHg. 11 cases (52.4%) showed % delta LCBF/delta CO2 was above the 0%/mmHg. 5) In the group with a preoperative % delta LCBF/delta CO2 of less than 0%/mmHg, preoperative LCBF was 43.6 +/- 9.3 ml/100g/min, which was significantly low (p < 0.01) compared to that in the group with higher % delta LCBF/delta CO2. After bypass, LCBF and % delta LCBF/delta CO2 remarkably increased in the group with % delta LCBF/delta CO2 below 0%/mmHg. [Conclusion] Before bypass, LCBF was low and CVR was severely disturbed. In the 14 cases % delta LCBF/delta CO2 was below 0%/mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Influence of stellate ganglion resection on intracranial pressure].

This study was designed to investigate the influence of stellate ganglion resection on intracranial pressure and blood flow through common carotid and vertebral arteries in 10 mongrel dogs. Following anesthesia with diazepam and pancuronium, each dog was intubated and ventilated to maintain normocapnia. Intracranial pressure was measured with a subdural catheter (Nihon Koden) inserted through right and left temporal burr holes. The right and left common carotid and vertebral arteries were surgically identified, and blood flow estimated with an ultrasonic probe (Transonic T201). After baseline measurement, the stellate ganglion was resected on the right side in 5 dogs, and on the left in the remaining animals. There were no significant change in intracranial pressure. After stellate ganglion resection, there was a significant increase in blood flow through the ipsilateral common carotid and vertebral arteries, but there were significant decreases in flow through the contralateral vessels.

Animals↗
PubMed1990

Ruptured cerebral aneurysms missed by initial angiographic study.

The authors reviewed the computed tomographic (CT) scans of patients with subarachnoid hemorrhage whose initial angiograms were negative, to investigate the validity of CT scans in predicting the presence of an angiographically missed aneurysm in such patients. During the past 14 years, additional angiograms have been obtained for 38 of the 45 patients with subarachnoid hemorrhage whose initial angiograms disclosed no aneurysm. Aneurysms were found in 8 patients; 7 on the anterior communicating artery and 1 at the junction of the internal carotid and posterior communicating arteries. CT scans were taken within 4 days after subarachnoid hemorrhage in 31 patients. Analysis of these scans showed that the second angiogram revealed 1) an aneurysm in 21% of the patients with a thin layer of subarachnoid blood and in 63% of those with a thick layer; 2) no aneurysm in the patients without subarachnoid blood; and 3) an aneurysm of the anterior communicating artery in 70% of the patients who showed a considerable amount of blood in the basal frontal interhemispheric fissure. These results suggest that if CT scans show thin or thick subarachnoid blood, angiographic study should be repeated early in the course. If a considerable amount of blood is shown in the basal frontal interhemispheric fissure, it is highly probable that an aneurysm is hidden on the anterior communicating artery, even if the angiogram is negative for an aneurysm.

Adult↗