Search PubMed⌕ Search

Biomedical subjects

K Masuda

Publications and source records attributed to K Masuda.

At least 469 records · Page 26Linked to original sources
PubMed1992

Mechanisms of antibacterial action of tachyplesins and polyphemusins, a group of antimicrobial peptides isolated from horseshoe crab hemocytes.

Tachyplesins I and II and polyphemusins I and II, cationic peptides isolated from the hemocytes of horseshoe crabs, show bactericidal activities with similar efficiencies for both gram-negative and gram-positive bacteria. Tachyplesin I inhibited bacterial growth irreversibly within 40 min. A subinhibitory concentration of tachyplesin I sensitized gram-negative bacteria to the bactericidal actions of novobiocin and nalidixic acid, although polymyxin B-resistant strains which have altered lipopolysaccharides were susceptible to tachyplesin I. This implies that tachyplesin permeabilizes the outer membrane and that the likely target of its action is outer membrane constituents other than lipopolysaccharides. On the other hand, a defensin-susceptible phoP strain of Salmonella typhimurium was also susceptible to tachyplesin I. Tachyplesin I rapidly depolarized the inverted inner-membrane vesicles of Escherichia coli. These results suggest that depolarization of the cytoplasmic membrane, preceded by the permeabilization of the outer membrane for gram-negative bacteria, is associated with tachyplesin-mediated bactericidal activity. The similarity between the actions of tachyplesin and those of defensin was discussed.

Animals↗
PubMed1992

Cerebrovascular responsiveness to hypercapnia in Alzheimer's dementia and vascular dementia of the Binswanger type.

BACKGROUND AND PURPOSE: Alzheimer's dementia is thought to be a primary degenerative dementia, whereas vascular dementia of the Binswanger type is an entity of vascular dementia. We evaluated the cerebrovascular responsiveness to hypercapnia to clarify the differences in the cerebral hemodynamics between two groups of patients. The subjects were eight younger control subjects, five age-matched control subjects, five Alzheimer's patients, and five patients with vascular dementia of the Binswanger type. SUMMARY OF REPORT: In the resting state, the regional cerebral blood flow was low in both Alzheimer's dementia and vascular dementia of the Binswanger type. The responsiveness to hypercapnia was preserved in Alzheimer's dementia, whereas it was impaired in vascular dementia of the Binswanger type in the cerebral cortices and in the deep white matter. CONCLUSIONS: These results suggest that small vascular lesions exist in vascular dementia of the Binswanger type but not in Alzheimer's dementia, even though regional cerebral blood flow was thought to decrease by hypometabolism in both types of dementia.

Adult↗
PubMed1992

Positron-emitting N-[18F]fluoroalkyl and [18F]fluoropyrrolidinyl analogues of eticlopride as potential in vivo radioligands for dopamine D2 receptors.

N-Fluoroalkyl and 4-fluoropyrrolidinyl eticlopride analogues with high affinity toward central nervous system dopamine D2 receptors in vitro were labelled with positron emitting fluorine-18 (t1/2 = 110 min), and their in vivo biodistribution was investigated in rats. N-[18F]Fluoro-ethyl and -propyl eticlopride derivatives showed poor in vivo selectivity in the rat brain. On the other hand, 4-[18F]fluoropyrrolidinyl eticlopride exhibited almost constant and relatively high striatal concentration. The striatal/cerebellar radioactivity ratio, which corresponds to the ratio of a brain D2 receptor-rich to poor region, gradually increased to 5.2-6.4, 90 min after the injection. The striatal accumulation was selectively inhibited by pre-injection of haloperidol, a dopamine D2 antagonist, without affecting accumulation in other tissues. Thus, the selective striatal accumulation of 4-[18F]fluoropyrrolidinyl eticlopride in striatal tissue appears to be due to the specific binding to dopamine D2 receptors.

Animals↗
PubMed1992

New application of human tumor clonogenic assay to in vitro evaluation of tumor-targeting efficiency of immunoconjugates.

This report proposes an efficient in vitro method for the evaluation of drug targeting with monoclonal antibody as a carrier to tumor cells. Monoclonal antibody (35G; IgG2a) selectively binding to alpha-fetoprotein (AFP) from human hepatoma cells (HuH-7) was conjugated with an anticancer drug, vindesine (VDS). Human tumor clonogenic assay (HTCA) with some modifications was applied to estimate the targeting efficiency of a conjugate (VDS-35G) for the first time. In this assay, VDS-35G was cytotoxically active against HuH-7 cells at a lower concentration (0.5 ng/ml) and for a shorter contact time than VDS (50 ng/ml), while 35G and VDS-normal mouse immunoglobulin conjugate (VDS-n-IgG) were not active against the cells. Both VDS-35G and VDS-n-IgG were inactive against HuH-13 cells established from a human hepatocellular carcinoma producing no AFP. In the conventional monolayer culture assay (MCA), VDS-35G showed little effect on HuH-7 cells at the concentration effective in HTCA. The cytotoxic activity of VDS in MCA was similar to that in HTCA but the cytotoxic activity of VDS-35G in MCA was considerably different from that in HTCA. This discrepancy could be explained by the hypothesis that VDS-35G was directed at stem cells of the HuH-7 cell population sensitively and selectively. HTCA was shown to be a useful in vitro evaluation method for drug targeting.

Animals↗
PubMed1992

Differential diagnosis of hepatic tumors (hepatoma, hemangioma, and metastasis) with CT: value of two-phase incremental imaging.

Two-phase dynamic incremental CT is a technique in which CT scans are obtained 45 sec and 6 min after commencing the rapid bolus injection of contrast medium. We analyzed the contrast enhancement patterns of three types of hepatic tumors (72 hepatomas, 39 hemangiomas, and 28 metastases) in 139 patients to determine if any differences in the patterns are useful in the differential diagnosis of these lesions. Dynamic incremental CT scanning was performed after 100 ml of iodinated contrast material was administered i.v. with a power injector at a rate of 2 ml/sec. A 1-sec scanning time was used with a 1.6-sec inter-scan delay, which allowed table motion between scans. CT scans (eight to 16 sections) were obtained 45-110 sec (early phase) and 6-7 min (delayed phase) after commencing the injection of contrast medium. The enhancement patterns of hepatomas were as follows: 32% were totally hyperdense in the early phase and totally hypodense in the delayed phase, while 24% were totally hypodense in both phases. Most of the hepatomas (88%) appeared as totally hypodense lesions in the delayed phase. In the case of hemangiomas, 56% were peripherally hyperdense in the early phase; in the delayed phase, 36% were isodense and 31% were totally hyperdense. Most hemangiomas (85%) were not totally hypodense in the early phase, and no hemangioma was totally hypodense in both phases. In the early phase, 61% of metastases were hypodense. In the delayed phase, 57% were hypodense. Metastases most commonly were totally hypodense in both phases (43%). We conclude that contrast enhancement patterns of hepatomas, hemangiomas, and metastases seen on two-phase dynamic incremental CT scans are useful in the differential diagnosis of these tumors.

Carcinoma, Hepatocellular↗
PubMed1992

Intramedullary spinal cord metastasis from lung cancer presenting with paraparesis: an autopsied case.

A 75-year-old male presented with paraparesis and pain in the thighs, which progressed rapidly. Five days later, he was unable to stand or to void urine. A lung cancer was found in the right upper lobe. A spinal cord metastasis from the lung cancer was suspected from the neurologic and pulmonary findings. After 2 weeks, motor dysfunction and a total sensory deficit were observed below the lumbar region, and the patient developed pneumonia, which resulted in death. Autopsy showed an extensive intramedullary metastasis at the third lumbar segment of the spinal cord. Histology revealed poorly differentiated adenocarcinoma of the lung.

Adenocarcinoma↗
PubMed1992

CT analysis of metastatic neoplasms of the kidney. Comparison with primary renal cell carcinoma.

The CT findings in 32 patients with pathologically proven metastases to the kidney were compared to findings in 74 patients with renal cell carcinoma. Fourteen CT criteria were chosen to describe and characterize the lesions and 2 radiologists evaluated the CT images retrospectively according to these criteria. Renal metastases were characterized as small, multiple, bilateral, wedge-shaped, less exophytic, and located within the renal capsule. Renal cell carcinomas were single, unilateral, nonwedge-shaped, and exophytic, and easily transgressed the renal capsule. The sensitivity of CT to discriminate renal cell carcinoma from renal metastasis was 93.2% for renal cell carcinoma, and to discriminate renal metastasis from renal cell carcinoma was 75.0% for renal metastases by computer posterior probabilities. This study indicates that CT is useful for distinguishing these clinically important tumors. By using posterior probability, some unnecessary biopsies may be avoided.

Adult↗
PubMed1991

[The management of stage I lymphomas of the B-cell type with special reference to the role of radiation therapy].

Fifty-one patients with clinical stage I B-cell lymphomas were treated between 1980 and 1988. For the entire group, the actuarial 5-year survival rate and 5-year freedom from relapse rate were 78% and 64%, respectively. Primary site, tumor bulk and performance status were the prognostic factors. Twenty-three patients were intensively treated with local radiotherapy alone, because (1) they had histologically low grade (7 patients) or follicular large cell (1 patients) tumors, (2) Waldeyer's ring was the site of the primary (11 patients) or (3) the tumor was less than 4 cm in maximum diameter (4 patients). Among them, only one patient died due to lymphoma (5-year survival rate: 95%), and 19 remained disease free (5-year freedom from relapse rate: 80%). In contrast, of the remaining 23 patients treated with both radiation therapy and combination chemotherapy (VEMP or CHOP), the 5-year survival rate and 5-year freedom from relapse rate were 70% and 54%, respectively. These results suggest that high-risk patients should be treated with more aggressive combination chemotherapy as well as radiotherapy. However, low-risk patients with stage I B-cell lymphomas can be treated by local radiotherapy alone.

Adult↗
PubMed1991

[MR imaging in paranasal and intracranial aspergillosis].

The MR findings in three patients with paranasal and intracranial aspergillosis were analyzed. Two patients had sphenoid sinus aspergillosis with mucocele, and one had aspergillosis in the maxillary sinus and pachymeningitis in the posterior fossa. In all patients with aspergillosis of the paranasal sinuses, a markedly hypointense area was present within the lesion on T2-weighted images. In the patient with pachymeningitis, contrast-enhanced MR images clearly demonstrated the extent of the lesion.

Aspergillosis↗
PubMed1991

[Role of MRI in diagnosis of adrenal tumors].

The authors evaluated the ability of magnetic resonance imaging (MRI) at 1.5 T to characterize 33 adrenal masses, using visual analysis and the following quantitative variables: signal intensity ratios of tumor/liver, tumor/muscle, and (tumor--muscle)/(fat--muscle) on T2- and T1-weighted images, and the calculated T2 relaxation time of the adrenal masses. All 15 tumors of less than 3 cm in diameter were visually homogeneous on all pulse sequences, whereas the other 18 tumors of over 3 cm appeared to be inhomogeneous. The signal intensity ratios of tumor/liver and tumor/muscle and the calculated T2 relaxation time were not helpful in distinguishing tumors from one another. The ratios of tumor/fat and (tumor--muscle)/(fat--muscle) were useful in distinguishing pheochromocytoma and myelolipoma from other tumors on T2- and T1-weighted images, respectively. However, differentiation among other adrenal tumors appeared to be difficult. The authors concluded that, although MRI might have considerable potential in characterizing adrenal masses, the use of conventional MRI in such analysis is still quite limited.

Adenoma↗
PubMed1991

Liver and muscle-fat type glucose transporter gene expression in obese and diabetic rats.

In order to investigate the regulation of glucose transporter gene expression in the altered metabolic conditions of obesity and diabetes, we have measured mRNA levels encoding GLUT2 in the liver and GLUT4 in the gastrocnemius muscle from various insulin resistant animal models, including Zucker fatty, Wistar fatty, and streptozocin(STZ)-treated diabetic rats. Northern blot analysis revealed that GLUT2 mRNA levels were significantly (P less than 0.001) elevated in 14 wk Zucker fatty and Wistar fatty rats relative to lean littermates but were similar in these two groups at 5 wk of age. Furthermore, there was significant increase (P less than 0.01) in GLUT2 mRNA levels in STZ diabetic rats at 3 wk after treatment. GLUT4 mRNA levels were not significantly different between control and insulin resistant rats in all animal models. These results indicate that neither hyperinsulinemia nor hyperglycemia affects GLUT4 mRNA levels in the muscle. However, GLUT2 mRNA levels in the liver were elevated in obesity and diabetes, although this regulatory event occurred independently from circulating insulin or glucose concentrations.

Animals↗
PubMed1991

[MRI of brain abscesses].

Four cases of brain abscess were examined on 1.5T MR and their findings were evaluated retrospectively. Preoperative cases had relatively characteristic findings, such as 1) peripheral edema producing hypointensity on T1-weighted images (T1WI) and hyperintensity on T2-weighted images (T2WI); 2) central necrosis with abscess fluid hypointense relative to white matter on T1WI and hyperintense on T2WI; 3) abscess rim iso- to hypointense on T2WI. Gd-DTPA enhanced T1WI carried further information; comparison of iso- to hypointense rim on T2WI (abscess rim) and enhanced area by Gd-DTPA on T1WI suggested that the former represented zone of macrophage infiltration.

Adult↗
PubMed1991

Tissue distribution and species difference of the brain type glucose transporter (GLUT3).

The complementary DNA for the human brain type glucose transporter (GLUT3) was used to determine its tissue specific expression in human, monkey, rabbit, rat, and mouse. Under high stringent conditions, 4.1 and 3.2 kilobase (kb) GLUT3 transcripts in monkey and a single 4.1 kb GLUT3 mRNA in rabbit, rat, and mouse were detected by RNA blot analysis. Although the GLUT3 transcripts were widely distributed, as are the erythrocyte type glucose transporter (GLUT1) transcripts, this mRNA is most abundant in the brain. However, the relative abundance of GLUT3 mRNA in the various regions of the monkey brain shows a different pattern from that of GLUT1 mRNA: GLUT3 is most highly expressed in the frontal lobe of the cerebrum, whereas GLUT1 is most abundant in the basal ganglia and the thalamus. Moderately higher GLUT3 mRNA levels were detected in the parietal lobe of the cerebrum, hippocampus, and cerebellum than the levels of GLUT1 transcripts. We also detected GLUT3 mRNA in adult human psoas major muscle, although it has been reported that the GLUT3 gene is scarcely expressed in adult human skeletal muscle of the thigh. In addition, in the rat and the mouse, no transcripts of the GLUT3 gene were detected in liver, kidney, small intestine, skeletal muscle, or fat besides in brain. Thus, the expression of the GLUT3 gene seems to be restricted to the brain in rodents. These results suggest that the expression of GLUT1 and GLUT3 genes might be regulated by different mechanisms.

Animals↗
PubMed1991

Arterioenteric fistulae: diagnosis and treatment by angiography.

Two cases of massive gastrointestinal haemorrhage caused by arterioenteric fistulae are presented. In both cases, bleeding was controlled by interventional angiography. In the first case, a fistula between an aberrant right subclavian artery and a reconstructed oesophagus was temporarily occluded with a balloon catheter as a pre-surgical measure. In the second case a communication between the external iliac artery and the colon in a patient with invasive cervical cancer was treated by embolization. An arterioenteric fistula should be considered as a possible cause of acute gastrointestinal haemorrhage in post-operative or cancer patients and aortography or pelvic arteriography may be required to make the diagnosis.

Catheterization↗