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K Katahira

Publications and source records attributed to K Katahira.

79 records · Page 5Linked to original sources
PubMedDate not supplied

Effect of ouabain on hemodynamics in acute volume expanded hypertensive dogs.

To evaluate possible roles of endogenous Na+-K+-ATPase inhibitors in vasoconstricted blood pressure elevation produced by acute volume expansion, we administered ouabain (Na+-K+-ATPase inhibitor) intravenously (30 micrograms/kg) for 10 min to dogs, 3 h after volume expansion with dextran in lactated Ringer's solution (20 ml/kg, for 1 h). Acute volume expansion resulted in the elevation of blood pressure associated with an increase in cardiac output. In some dogs the blood pressure remained elevated with gradual increase in total peripheral resistance (Group I) or with sustained high cardiac output (Group II), and in other dogs (Group III) it returned to the control level. Ouabain administration elevated the blood pressure and total peripheral resistance in these groups and sham dogs which did not have volume expansion. And these effects of ouabain were not correlated with the degree of blood pressure or vasoconstriction produced by volume expansion. Thus, it is not likely that endogenous Na+-K+-ATPase inhibitors increased to produce vasoconstricted hypertension after acute volume expansion.

Animals↗
PubMedDate not supplied

Effect of cromakalim (BRL 34915) on hemodynamic and electrocardiographic changes induced by endothelin in dogs.

We evaluated whether cromakalim (BRL 34915), a vasorelaxant agent which acts by opening potassium channels, could affect the systemic effects of endothelin, a newly discovered vasoconstrictive peptide. Intravenous administration of endothelin alone (400 pmol/kg) to anesthetized dogs produced blood pressure elevation, which was associated with an increase in cardiac output in the early phase, and was associated with an increase in total peripheral resistance in the late phase. Electrocardiogram showed significant ST-elevation in II, III, and aVF, and ST-depression in aVR and aVL. The same dose of endothelin given to dogs pretreated with cromakalim did not induce these hemodynamic and electrocardiographic changes. Thus, cromakalim, a potassium activator, inhibited the hemodynamic and electrocardiographic actions of endothelin, suggesting that hyperpolarization due to potassium channel activation inhibited the voltage-dependent calcium channel, which is thought to be a major mechanism for the pressor action of endothelin.

Animals↗
PubMedDate not supplied

Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence.

PURPOSE: The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence. METHOD: Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences. RESULTS: The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01). CONCLUSION: The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.

Adult↗
PubMedDate not supplied

MR imaging of the anterior cruciate ligament: value of thin slice direct oblique coronal technique.

PURPOSE: The value of the thin slice direct oblique coronal technique, which is parallel to the anterior cruciate ligament (ACL), was assessed in the evaluation of ACL injury in comparison with conventional oblique sagittal and coronal images. MATERIAL AND METHODS: A thin slice direct oblique coronal technique was developed and applied clinically to 62 patients after conventional oblique sagittal and coronal images had been obtained. MR images of these 62 patients (24 with tears and 38 without tears) with an arthroscopic correlation were evaluated by three radiologists who were unaware of the arthroscopic results. The diagnostic accuracy of these new images was compared with that of oblique sagittal and coronal images by ROC analysis. RESULTS: Conventional oblique sagittal and coronal images for the diagnosis of ACL tears revealed accuracies of 82%, 84%, and 84%, sensitivities of 92%, 92%, and 96% and specificities of 76%, 79%, and 76% for the three reviewers, respectively. On thin slice direct oblique coronal images, specificities of 97%, 97%, and 97%, sensitivities of 96%, 96%, and 96%, and accuracies of 97%, 97%, and 97% were obtained, respectively. Diagnostic ability was significantly better with direct oblique coronal images (mean area under the ROC curve [Az]=0.99) than with conventional oblique sagittal and coronal images (Az=0.91) (p<0.05). CONCLUSION: The addition of thin slice direct oblique coronal images significantly improved specificity and accuracy in the diagnosis of ACL tears.

Adolescent↗
PubMedDate not supplied

Differential diagnosis of small round cervical lymph nodes: comparison of power Doppler US with contrast-enhanced CT and pathologic results.

PURPOSE: The purpose of this study was to differentiate reactive small round lymph nodes (SRLNs) from metastases by power Doppler ultrasonography (PD-US) and contrast-enhanced CT (CE-CT). MATERIALS AND METHODS: Both PD-US and CE-CT were performed in 99 cervical lymph nodes (LNs) with a maximum diameter of 1.5 cm or smaller and maximum longitudinal/transverse ratio of 1.5 or smaller in 76 patients with head and neck cancer. At pathologic examinations, 45 were reactive and 54 were metastatic LNs. The vascular patterns on PD-US were classified as hilar, avascular, peripheral, and miscellaneous vascular patterns. The enhancement patterns on CE-CT were classified as homogeneous, heterogeneous, and ring enhancement. RESULTS: On PD-US, the hilar pattern was more frequently associated with benignancy (91%) and the peripheral, miscellaneous vascular pattern with malignancy (91%). The avascular pattern included both benign (58%) and malignant (42%) LNs. On PD-US, accuracy was 85%. On CE-CT, ring enhancement showed metastasis (100%), and these LNs showed avascular or peripheral patterns on PD-US. On CE-CT, accuracy was 77%. When information on CE-CT results was added to PD-US results, the accuracy rate increased significantly, to 94% (p=0.01). CONCLUSION: Vascular patterns evaluated with PD-US and enhancement patterns on CE-CT can characterize SRLNs. For an avascular pattern on PD-US, information on CE-CT results can significantly increase the accuracy of characterization.

Adult↗
PubMedDate not supplied

Increased atrial natriuretic factor secretion after endothelin injection in dogs.

Hemodynamic and hormonal responses to bolus intravenous injections of synthetic porcine endothelin (pET) were examined in anesthetized dogs. There were no significant changes in mean blood pressure (MBP), right atrial pressure (RAP), or plasma atrial natriuretic factor (ANF) concentration in response to 40 pmol/kg of the peptide. However, responses to 400 pmol/kg of the peptide were significant: MBP rose from 114 +/- 6 mmHg (mean +/- SE) to 139 +/- 7 mmHg (p less than 0.01), RAP rose from 5.4 +/- 0.9 mmHg to 7.8 +/- 1.1 mmHg (p less than 0.01), and ANF increased from 45 +/- 10 pg/ml to 277 +/- 33 pg/ml (p less than 0.01). Peak value of RAP was observed 2.6 +/- 0.4 min, while peak of ANF was 11.4 +/- 0.9 min after peptide injection. There was a strongly positive correlation (r = 0.93, p less than 0.01) between the increase in RAP and the increase in ANF in dogs given 400 pmol/kg of pET. These results indicate that exogenously administered pET to anesthetized dogs alters hemodynamics and induces ANP release, and are compatible with a postulate that the ANF release is caused by elevated RAP.

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