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Biomedical subjects

J Iwai

Publications and source records attributed to J Iwai.

At least 55 records · Page 3Linked to original sources
PubMed1992

Interferon gamma attenuates hypertensive renal injury in salt-sensitive Dahl rats.

Evidence has been provided that the immunological mechanism is involved in the genesis or maintenance of hypertension. In the present study, we investigated the effects of interferon gamma, a potent immunomodulator derived from lymphocytes, on hypertension and organ damage in Dahl salt-sensitive rats and in spontaneously hypertensive rats. Subcutaneous injection of interferon gamma (5 x 10(4) units/kg body wt once a week for 10 weeks) reduced blood pressure in Dahl salt-sensitive rats fed a 4% high salt diet (174 versus 194 mm Hg, p less than 0.025). This blood pressure reduction was associated with an improvement of renal functions, an increase in glomerular filtration rate (690 versus 569 ml/day/100 g body wt, p less than 0.05), and decreases in urinary protein excretion (48 versus 78 mg/day/100 g body wt, p less than 0.025) and urinary N-acetyl-beta-D-glucosaminidase excretion (143 versus 183 milliunits/day/100 g body wt, p less than 0.05). Morphological investigation showed a marked resolution of the vascular injuries seen in untreated Dahl salt-sensitive rats, e.g., intimal and medial hyperplasia, with infiltration of inflammatory cells, and significant amelioration of the glomerular sclerotic changes. In contrast, interferon gamma affected neither blood pressure nor renal functions in spontaneously hypertensive rats. These data indicate that interferon gamma ameliorates the development of hypertension and vascular and renal injuries in Dahl salt-sensitive rats. The resolution of vascular and renal injuries contributes, in part, to the antihypertensive action of interferon gamma.

Acetylglucosaminidase↗
PubMed1992

[Efficacy of magnetic resonance imaging in treatment of neuroblastoma].

Magnetic resonance imaging (MRI) was performed in 36 children with neuroblastoma at Chiba University from 1984 through 1989, and 29 patients of them were discussed about efficacy of MRI in treatment of neuroblastoma in this paper and the results were as follows. 1) MRI was difficult to differentiate tumor from normal kidney in the image intensity and was more efficient in determining the relationship of tumor to liver and to vascular structures. 2) MRI was better than CT in detecting the size and extent of tumor mass and in identifying lymph node spread using multiple planes. 3) MRI was more efficient than CT in defining displacement and encasement of renal vessels by tumor. It was useful to predict to reserve kidney before surgery. 4) MRI was useful to monitor tumor response to combined modalities of therapy. A favorable response was seen as a change in the image intensity in bone marrow metastases of neuroblastoma.

Adrenal Gland Neoplasms↗
PubMed1991

Expression of N-myc and c-src protooncogenes correlating to the undifferentiated phenotype and prognosis of primary neuroblastomas.

Genomic amplification of the N-myc protooncogene in neuroblastomas correctly predicts poor outcome for the patients. However, the prognosis for neuroblastomas with a single copy of N-myc is also poor in cases diagnosed after 1 year of age but good in infantile cases. To elucidate the different prognoses depending upon the age of the patients with neuroblastoma, we performed an analysis of the expression of protooncogenes related to neural differentiation. We examined the genomic amplification of N-myc in 26 specimens of neuroblastomas and further analyzed 22 of the 26 cases for expression of N-myc, c-src, c-Ha-ras, and c-fos. Consequently, we observed frequent overexpression of N-myc in undifferentiated neuroblastomas and enhanced expression of c-src and c-Ha-ras in infantile neuroblastomas with favorable prognosis and in neuroblastomas differentiated by chemotherapy. These findings suggest that c-src and c-Ha-ras play important roles in the neural differentiation of infantile neuroblastomas.

Blotting, Northern↗
PubMed1991

Vascular eicosanoid production in experimental hypertensive rats with different mechanisms.

This study investigated the release of prostacyclin (PGI2) and thromboxane A2 (TXA2) from the aortic walls of various experimental hypertensive rats, e.g. spontaneously hypertensive rats (SHR), Dahl salt-sensitive (Dahl S) rats, deoxycorticosterone (DOCA)-salt hypertensive rats and renovascular (2-kidney, 1-clip (2K1C) and 1-kidney, 1-clip (1K1C] hypertensive rats. The PGI2 generation was increased significantly in these hypertensive models, irrespective of the hypertensive mechanisms, when they developed established hypertension. Dahl S rats, having an impaired PGI2 production on a low salt diet, restored PGI2 generating capacity to the control level of Dahl salt-resistant rats when they were fed a high salt diet and developed salt-induced hypertension. On the other hand, the TXA2 generation in the vascular walls was enhanced particularly in rat models for genetic hypertension, and this system was unaltered in the models for secondary hypertension, e.g. DOCA-salt and renovascular hypertension. Thus, it is suggested that the elevation of blood pressure is associated with an increase in vascular PGI2 production, and that the increased vascular TXA2 production is a characteristic feature of genetic hypertension.

Animals↗
PubMed1991

Antihypertensive effects of cicletanine and renal protection in Dahl salt-sensitive rats.

We designed experiments to reveal the antihypertensive properties of cicletanine, a novel antihypertensive drug, in Dahl salt-sensitive (Dahl-S) rats. Cicletanine (39 mg/kg body weight per day for 6 weeks) ameliorated the development of hypertension in Dahl-S rats fed a high-salt (4% NaCl) diet. This blood pressure reduction was associated with a decrease in heart weight and vascular wall thickness. Moreover, urinary prostacyclin (PGl2) excretion was increased with cicletanine treatment, being inversely related to systolic blood pressure. Proteinuria and urinary excretion of n-acetyl-beta-D-glucosaminidase were decreased and glomerular filtration rate was increased with this treatment. Morphological investigation revealed an improvement in glomerulosclerosis, renal tubular damage and intrarenal arterial injury in the salt-induced hypertensive rats. In contrast, trichloromethiazide, which decreased blood pressure to the same extent as cicletanine, lowered urinary PGl2 excretion and generally did not ameliorate the deteriorated renal functions and morphological abnormalities. Thus, these data indicate that cicletanine ameliorates the development of hypertension in Dahl-S rats and protects the cardiovascular and renal systems against the injuries seen in the hypertension. The enhanced vasodepressor PGl2 synthesis probably participates, to some extent, in these beneficial properties of long-term cicletanine treatment.

Animals↗
PubMed1991

Evidence for medial-mass regression in the vascular wall of Dahl hypertensive rats by cicletanine treatment.

We designed experiments to investigate the effects of cicletanine, a novel antihypertensive drug, on medial hypertrophy in Dahl rats susceptible to salt-induced hypertension (Dahl S rats). Cicletanine treatment (500 mg of cicletanine/kg of chow) for 6 weeks lowered blood pressure by 19% in Dahl S rats challenged with a high-salt (4%) diet. The blood pressure reduction was associated with a significant decrease in weight of the aortic vessels. Morphological examination revealed that this treatment decreased medial hypertrophy and expansion of intimal tissue, in concert with resolution of the periarteritis in the intrarenal arteries. In fact, the content of actin in the aortic wall, analyzed by SDS-PAGE, was decreased significantly with this treatment and myosin content was reduced to the same extent as well. Moreover, cicletanine per se lowered protein synthesis in randomly cycling cultured vascular smooth muscle cells (VSMCs) from Sprague-Dawley rats. Actin formation by VSMCs was decreased with cicletanine. Thus, these data indicate that chronic cicletanine treatment produces regression of the medial hypertrophy in Dahl S rats. Direct inhibitory effects on cytoskeleton protein synthesis, as well as its antihypertensive action, are partly responsible for this regression in vivo.

Animals↗
PubMed1991

[The role of magnetic resonance imaging for treatment in children with malignant solid tumor].

Magnetic resonance imaging (MRI) was performed in 126 children with malignant solid tumor between April 1984 and December 1990. The criteria of tumor visualization, localization, staging, prediction of kidney preserving and monitoring treatment were compared by MRI and CT for 47 children with neuroblastoma, Wilms' tumor, hepatoblastoma, rhabdomyosarcoma and teratoma, MRI and CT were viewed together and an assessment was made as to whether the studies yielded equivalent information or whether one study was superior to the other. 1) The tumor were better visualized in 47% cases by MRI than CT. 2) MRI was superior to CT in 43% cases in evaluating the local spread of tumor. 3) There was little difference between MRI and CT in identification of lymph node metastases. 4) Without requiring the injection of intravenous contrast agents, MRI accurately defined displacement, invasion of renal vessels by neuroblastoma. MRI was excellent in prediction of kidney preserving. 5) MRI was useful to detect bone marrow metastases in neuroblastoma. The best imaging plane for a demonstration of bone marrow involvement was coronal in lower limbs.

Abdominal Neoplasms↗
PubMed1990

Relevance of vascular PGI2 synthase to vascular prostacyclin production in Dahl rats susceptible to salt-induced hypertension.

To assess the roles of prostacyclin (PGI2) synthase in vascular PGI2 generation, the enzymatic activity was examined in the mesenteric artery of Dahl S rats in the prehypertensive or hypertensive stage. Elevation of blood pressure in Dahl S rats was accompanied by an increase of vascular PGI2 synthase activity. The enzymatic activity was positively correlated to the blood pressure value. Similarly, impaired vascular capacity to generate PGI2, which was observed in prehypertensive Dahl S rats, was restored to the control level of Dahl R rats with the elevation of blood pressure. These data indicate that vascular PGI2 synthase activity is increased with blood pressure elevation, thereby contributing to the restoration of vascular capacity to generate PGI2 in Dahl S rats.

Animals↗
PubMed1989

Management of defecation in spina bifida.

The main presenting complaint in defecational disorders in spina bifida is constipation. The principal cause of this complaint is hypofunction or paralysis of muscles in the pelvic floor as a result of the spinal cord injuries. To evaluate the present status of defecation, anorectal manometry with special reference to the anorectal pressure profile has been useful. The possibility of using anorectal manometry for the research of anorectal movement and participation of spinal cord was discussed.

Anal Canal↗
PubMed1989

How is the NaCl signal transmitted in NaCl-induced hypertension?

Is the NaCl signal perceived as a small increase in the concentration of NaCl in extracellular fluid? We used 8 g NaCl/100 g soluble nutrients and fed only a hypertonic (1.4% NaCl) or a hypotonic (0.45% NaCl) drink to Dahl salt-sensitive (DS) rats. After 12 weeks, 11 rats receiving the hypertonic drink had a mean blood pressure of 195 mm Hg versus 195 mm Hg in 12 rats receiving the hypotonic drink. Thus, the high-NaCl signal seems unrelated to a higher NaCl concentration in extracellular fluid, thereby suggesting volume signals. Most volume controls are near the third brain ventricle (3V). As a working hypothesis, high dietary NaCl may swell the tissues surrounding 3V, which is slitlike. Such swelling would partially close the upper part of the slit and cause ependymal cells and nerve fibers on opposite walls to touch, possibly leading to hypertension in susceptible humans or rats. To test this, we stereotaxically blocked the aqueduct with inert silicone to produce hydrocephalus of 3V in DS rats and thus prevent ependymal cells and nerve fibers from touching. After blocking or sham-blocking the aqueduct, either a 6% NaCl diet or a 0.23% NaCl diet was started. Intra-arterial blood pressure was taken after 6 weeks. A group of 28 sham-blocked rats and a group of 29 blocked rats, all fed a 0.23% low NaCl diet, had equal blood pressures averaging 130 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Alpha-adrenoceptors in Dahl hypertensive and normotensive rats: effect of sodium.

Sodium ions play an important role in vitro and in vivo in the regulation of alpha 2-adrenoceptors. The in vitro effect of sodium on cerebral and renal alpha-adrenoceptors was investigated in Dahl salt-sensitive and salt-resistant rats. Cerebral alpha 2-adrenoceptor densities were higher in Dahl salt-resistant rats. In contrast, the renal alpha 2-adrenoceptor density was higher in Dahl salt-sensitive than in Dahl salt-resistant rats. No difference in cerebral and renal alpha 1-adrenoceptor densities was observed between the two types of rat. Noradrenaline contents in the cerebral and renal cortex were also similar in these two rat substrains. An influx of sodium ions markedly increased cerebral and renal high-affinity alpha 2-adrenoceptor densities in Dahl salt-sensitive but not in Dahl salt-resistant rats. Under these conditions alpha 1-adrenoceptor densities remained unchanged. The absence of sodium regulation in Dahl salt-resistant rats may be linked either to a particular receptor conformation or to an abnormal structure of the alpha 2-adrenoceptor system. We conclude from the present study that there are marked differences in density and in the role of sodium regulation of cerebral and renal alpha 2-adrenoceptors from salt-sensitive and salt-resistant Dahl rats. These differences may play a primary role in the resistance or in the sensitivity of salt-induced hypertension.

Animals↗
PubMed1988

[Diagnosis of anterior perineal anus (APA)--significance of electromyographic evaluation of the external anal sphincter location].

APA is a common cause of constipation, and is the mild case of the imperforated anus. On diagnosing APA, anterior displacement of the anus and normal distribution of the external anal sphincter to the anus are essential. To determine the location of the anus in the perineum simple clinical technique was developed. In 61 normal cases, the result of measurement was almost same in each sex, but in 3 APA cases the location were anteriorly dislocated than normal cases. Distribution of the external anal sphincter was evaluated with electromyographic technique, and location map of the sphincter was made. In 3 APA cases, the anus was totally surrounded by the external anal sphincter, but in 17 ano-cutaneous fistula cases, the opening was anteriorly dislocated to the sphincter distribution map. As a conclusion, newly proposed simple clinical technique to determine anal location and electromyographic examination of the external and sphincter distribution are very useful in objective diagnosis of APA.

Anal Canal↗
PubMed1988

Heterogeneous ventilation and perfusion: a sensitive indicator of lung impairment in nonsmoking coal miners.

Twenty life-long nonsmoking West Virginia coal-miners participated in a study to amplify the role of focal irregularities on regional ventilation (V) and perfusion (Q) and to develop an improved method for the early detection of coal-workers' pneumoconiosis. Their mean age was 59.3 yr and they averaged 35.2 years' exposure to coal dust. Conventional pulmonary function tests were supplemented by measurement of V, Q and lung volume (V), using radioactive Kr-81m, Tc-99m MAA and Xe-127, respectively, to determine regional abnormalities in lung function. A computer analysis of the regional distributions of V/V, Q/V and V/Q was performed, and their topographical distributions and indices of heterogeneity (HI) computed. V/V and Q/V were significantly reduced in the lower third, and increased in the upper two-thirds of the miners' lungs; V/Q was reduced in the upper half. The miners' V/V and Q/V were more heterogeneous (p less than 0.001) than that of eleven age-matched controls, with mean ventilation HI values of 0.190 +/- 0.027 and 0.133 +/- 0.011, respectively, and mean perfusion HI values of 0.206 +/- 0.022 and 0.164 +/- 0.041, respectively. P(A-a)O2 correlated positively (r = 0.72; p less than 0.001) with ventilation HI. Gas exchange was the most significant functional measurement, being abnormal in 19/20 subjects. In contrast, conventional spirometric measurements were within the predicted normal limits in all but four miners.

Adult↗
PubMed1987

Alterations of vascular prostacyclin and thromboxane A2 in Dahl genetical strain susceptible to salt-induced hypertension.

To assess the implications of vascular eicosanoids system in the hypertension of Dahl salt-sensitive (Dahl S) strain, we investigated the production of vascular vasodepressor and vasoconstrictor eicosanoids in Dahl S rats. 14-week-old Dahl S rats on a 0.11% NaCl diet (normotension) or a 0.3% NaCl diet (borderline hypertension) had a significantly lowered generation of vascular prostacyclin (PGI2), compared with Dahl salt-resistant (Dahl R) rats. The impairment of vascular PGI2 in Dahl S rats was restored to the normal level of Dahl R rats with the elevation of blood pressure induced by a high salt diet (4% NaCl). The production of vascular PGI2 was closely related to the height of blood pressure. The deterioration of vascular PGI2 was also found in 4-week-old Dahl S rats with normotension. Conversely, vascular thromboxane A2 (TXA2) was significantly enhanced in 14-week-old Dahl S rats in all of the feeding groups. Thus, it seems possible that the proved alterations of the vasodepressor and vasoconstrictor eicosanoids partially contribute to the genesis of salt hypertension. Although the exact mechanisms remain obscure, the adaptation of vascular PGI2 on a high salt diet may be suitable to compete with the high blood pressure and to protect against the vascular damage.

Aging↗
PubMed1986

Platelet thromboxane inhibition by plasma polypeptides in prehypertensive Dahl rats.

Plasma from Dahl rats susceptible to salt-induced hypertension (Dahl S rats) contains inhibitory factors that reduce the release of thromboxane A2 from thrombin-activated platelets. Platelet-rich plasma from Dahl S rats on either low salt (0.11 or 0.3% NaCl) or high salt (4% NaCl) diets released about 50% less thromboxane A2 than comparable plasma from Dahl rats that are resistant to hypertension (Dahl R rats). This inhibitory activity was present even in the blood of 4-week-old completely normotensive Dahl S rats on a diet containing 0.11% low NaCl. The inhibitory activity could be transmitted to platelets of normal Sprague-Dawley rats by incubating these platelets in boiled and dialyzed plasma from Dahl S rats. Moreover, the inhibitory activity could be completely washed off the Dahl S platelets by incubation in Dahl R plasma. Thus, Dahl S plasma contains inhibitory factors that reduce platelet thromboxane A2 release. The factors are found in low concentrations even in Dahl R plasma; and in Dahl S or Dahl R plasma the factors are increased 25 to 32% by a 4% high NaCl diet. Digestion of Dahl S and Dahl R plasma with either trypsin or chymotrypsin destroyed the inhibitory factors, which have a molecular weight between 2,000 and 3,500. Twenty-four hours after bilateral nephrectomy, dialyzed plasma from both Dahl S and Dahl R rats was completely devoid of thromboxane A2 inhibitory activity. Thus, the factors appear to be heat-stable polypeptides either produced in the kidney or greatly influenced by the presence of renal tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗