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Biomedical subjects

A Yoshida

Publications and source records attributed to A Yoshida.

At least 415 records · Page 23Linked to original sources
PubMed1996

Physical and clinical evaluation of a 2,048 x 2,048-matrix image intensifier TV digital imaging system in bone radiography.

RATIONALE AND OBJECTIVES: To evaluate the potential utility of a 2,048 x 2,048-matrix image intensifier television digital radiography (DR) system versus a conventional screen-film (S-F) system for bone radiography. METHODS: Basic imaging properties were evaluated including resolution properties, Wiener spectra, and detectabilities of low-contrast signals. DR images were obtained with the same exposure (iso-dose) or one-third the exposure (low-dose) used with the S-F system. The visibility of pathologic details of metastatic disease on bone radiographs of 27 patients was evaluated subjectively by six radiologists. RESULTS: Resolution properties of the DR system were slightly superior to those of the S-F system at low-frequency range, but the S-F system showed considerably higher resolution properties at the high-frequency range. The noise levels for iso-dose DR were slightly greater than those for S-F imaging at low spatial frequency; however, low-dose digital radiographs showed higher noise levels. Visibility of details of diagnostic features on bone radiographs was similar with both systems, but the low-dose digital radiographs were slightly inferior. CONCLUSION: High-resolution image intensifier television DR systems may be clinically useful for bone radiography.

Bone Neoplasms↗
PubMed1996

Effect of staphylococcal enterotoxin B-induced anergy on cytokine gene expression: anergy-sensitive and resistant mRNA expression.

We examined the effect of staphylococccal enterotoxin B (SEB)-induced anergy on expression of six different cytokine genes in T cells restimulated with SEB in vitro. We found that although IL-2, IL-3, and IL-4 mRNA levels are substantially reduced in anergic T cells, mRNAs for IL-6, IL-10, IFN-gamma, and TNF-alpha are expressed normally. Thus, there appeared both anergy-sensitive and resistant cytokine mRNA expression in restimulated anergic T cells. The same pattern of cytokine mRNA responses was observed in anergic CD4+ T cells, indicating that the preferential induction of anergy in Th1-like cells is not evident in this in vivo model. Employing TCR V beta 8.2 transgenic mice in which almost all T cells become anergic, we found that the TCR/CD3 complex can transduce both anergy-sensitive and resistant signals. Furthermore, a series of experiments using FK506, A23187, and PMA suggests that signals between TCR and activation of calcineurin and protein kinase C may be blocked in anergic T cells. This is supported by our gel mobility shift assays indicating that calcineurin and/or PMA-inducible NF-ATp, OAP40, and AP-1, but not calcineurin-independent Oct-2, are repressed in anergic spleen T cells upon restimulation with SEB. Taken together, these results suggest that, among signals elicited by stimulation of TCR with SEB, a Ca2+/calcineurin-NF-ATp pathway and other signals, including protein kinase C, are repressed in anergic T cells upstream of their activation, which are essential for the cytokine mRNA expression of the anergy-sensitive type but are dispensible for those of the anergy-resistant type.

Animals↗
PubMed1996

Diagonistic dyspraxia. Clinical characteristics, responsible lesion and possible underlying mechanism.

We present three patients who showed, in addition to signs of callosal interruption, a variety of abnormal motor behaviour of the left hand dissociated from conscious volition, in the absence of pathological grasping phenomena. The abnormal movements of the left hand consisted of (i) antagonistic movements to the right; (ii) non-antagonistic, irrelevant movements to the right; (iii) symmetric movements to the right in which the left hand sometimes preceded the right, and (iv) occasional inability to move at will during a bimanual task. From these observations and a review of previous publications, we propose that, in most right-handed subjects; diagonistic dyspraxia could be defined as abnormal motor behaviour of the left hand activated by voluntary movements of the right hand. Motor phenomena similar to diagonistic dyspraxia but attributable to impulsive groping movements induced by medial frontal lobe pathology should be excluded from diagonistic dyspraxia. Comparison of MRIs of the three patients with those of five patients who developed no diagonistic dyspraxia following an infarction of the corpus callosum, with or without medial hemispheric involvement, revealed that damage to the ventral part of the posterior end of the body of the corpus callosum was crucial for the development of diagonistic dyspraxia. Since the commissural fibres between the superior parietal lobules pass through the caudal part of the body of the corpus callosum, and also since there is accumulating evidence that the human superior parietal lobule is concerned with selection of movement based on the integration of visual and/or somatosensory information, we infer that diagonistic dyspraxia is produced by a disconnection of the right superior parietal lobule from the left which is dominant for volitional control of movement in most right-handed subjects.

Apraxias↗
PubMed1996

Ascorbic acid deficiency reduces hepatic apolipoprotein A-I mRNA in scurvy-prone ODS rats.

Using the ODS rat (genotype od/od) as a model, we investigated the effect of ascorbic acid deficiency on the expression of the apolipoprotein A-I gene. Male ODS rats (7 wk old, body weight approximately 140 g) were fed a basal diet containing ascorbic acid (300 mg/kg) or a diet without ascorbic acid for 14 d. Ascorbic acid deficiency lowered the serum apolipoprotein A-I concentration. The apolipoprotein A-I mRNA level in the liver of ascorbic acid-deficient rats was lowered to about 40% (P < 0.05) of that of control rats fed sufficient ascorbic acid. The mRNA level in jejunum was not affected by ascorbic acid deficiency. Ascorbic acid deficiency did not change the transcriptional rate of the hepatic apolipoprotein A-I gene, suggesting that post-transcriptional regulation was involved in lowering the mRNA level. The low level of hepatic apolipoprotein A-I mRNA was restored to the control level within 3 d after the administration of sufficient ascorbic acid. These data indicate that ascorbic acid deficiency lowers serum apolipoprotein A-I concentration through lowering its mRNA level and subsequent depression of its synthesis in liver.

Animals↗
PubMed1996

Optimal beam quality for chest computed radiography.

RATIONALE AND OBJECTIVES: Optimal x-ray beam quality for chest computed radiography (CR) has not been determined. To investigate the optimal beam quality for chest CR, the authors measured the radiographic contrasts and compared the image quality of chest CR and screen-film (SF) radiographs using various x-ray tube voltages. METHODS: Chest CR and SF radiographs were obtained on a phantom lung and human volunteers with or without a variety of simulated lung opacities using various x-ray tube voltage levels. Exposures were set to maintain identical patient exposure doses for all images. The contrast between peripheral lung and rib or heart was measured on these images and the differences were compared. The quality of the images of each simulated opacity was evaluated by five radiologists using a five-point grading scale. RESULTS: Contrast between peripheral lung and rib or heart increased on CR images obtained by lowering the tube voltage from 140 to 80 kV, but the degree of increase was less than half the increase on SF images. The CR images of the simulated opacities obtained using a lower tube voltage were judged to be superior to those obtained with a higher tube voltage. Scattered radiation was reduced on CR images with a lower tube voltage. CONCLUSION: The image quality of chest CR was improved by using a lower tube voltage than that used for conventional SF chest radiography. Considering the problem of tube loading in clinical applications, a tube voltage of 100 kV is recommended for chest CR.

Evaluation Studies as Topic↗
PubMed1996

Assessment of cerebral fat embolism by magnetic resonance imaging in the acute stage.

The authors assessed the characteristic appearance of magnetic resonance imaging (MRI) of cerebral fat embolism in three patients. The MRI features in the acute stage were characterized by widespread, spotty lesions in the white matter, which appeared hyperintense on T2-weighted images and iso- or hypointense on T1-weighted images. The relation between clinical features and MRI findings are discussed.

Acute Disease↗
PubMed1996

Do epidermal Langerhans cells, migrating from skin lesions, induce the paracortical hyperplasia of dermatopathic lymphadenopathy?

In the present study, immunohistochemical and immuno-electron microscopic techniques were used to differentiate Langerhans cells (LC) from interdigitating cells (IDC) in the lymph nodes (LN) of dermatopathic lymphadenopathy. The majority of the dendritic cells that existed in the LN of dermatopathic lymphadenopathy were positive for OKT-6 (CD 1a) antibody. It was concluded that these dendritic cells were not IDC, but LC. Electron microscopically, LC in these LN contained a few Birbeck granules (BG). In order to prove the fact that these dendritic cells were LC, the existence of BG was investigated ultrastructurally by examining serial sections, and immunoelectron microscopically for CD 1a positive cells. Most of the LC in the lymph nodes we examined were negative for the anti-proliferating nuclear antigen (PCNA) antibody. This finding may mean that LC in the LN are fully developed cells and do not divide in the LN. Langerhans cells may migrate from the skin lesions to the paracortical areas in the LN, which then may become enlarged.

Antibodies, Monoclonal↗
PubMed1996

Clinical features of measles in immunocompromised children.

Measles is often fatal for immunocompromised hosts. Protective immunity against measles has been studied but is still not completely understood. Recently, five cases of measles were encountered in immunocompromised children. Two of these were allogeneic bone marrow transplanted cases (one common variable immunodeficiency and one severe aplastic anemia) in remission, one Wilms' tumor case in remission, one hepatoblastoma case after cytotoxic therapy at disease onset and one exaggerating hemophagocytic syndrome case with suppressed natural killer cell activity. Clinical symptoms, laboratory findings and the immunologic backgrounds of these five patients were investigated. One of the patients, an 8 year old boy with hemophagocytic syndrome, died of giant cell pneumonia which was confirmed in the section of necropsy lung specimen. Two other patients who received allogeneic bone marrow transplants were not immune to measles, despite their own and their donors' immunizations. Their clinical symptoms were rather severe but both patients recovered and have remained seropositive for as long as 13 months. This fatality from measles is the first reported in a patient with hemophagocytic syndrome. Suppressed natural killer cell activity may be a poor prognostic factor. Also, secondary immunization failure for measles can occur in bone marrow transplanted patients with rather severe clinical symptoms.

Adult↗
PubMed1996

Basic imaging properties of a new screen-film system for chest radiography.

To evaluate the potential clinical usefulness of a new screen-film system (advanced screen-film system; AD system) for chest radiography, its fundamental imaging properties compared with a conventional screen-film system (HR-4/HR-S) were investigated. The basic imaging properties were evaluated by measuring characteristic (H&D) curves, relative speeds, MTFs (modulation transfer functions), WS (Wiener spectra), and x-ray attenuations of screens. The detail visibilities and pathological details of various diseases in chest radiographs of patients were evaluated subjectively. The film gradient of the AD system was slightly lower at low radiographic density, and higher at high density, as compared with a conventional screen-film system. The screen speed of the AD system was 212% greater than that of the conventional system, and the film speed was 53% that of the conventional film. As the result, the total speed of the AD system was slightly higher compared with the conventional system. The spatial resolution of the AD system was comparable to or slightly lower than that of the conventional system. The noise level of the AD system was considerably lower than that of the conventional system at low (D = 0.5) and middle (D = 1.0) radiographic density levels. However, it was high at high radiographic density (D = 1.8). The radiographic densities in the underpenetrated areas with the AD system were greater than those of the conventional system when the lung densities are matched comparable. Improvement in noise level with the AD system at low and middle density levels may be useful for detection of various diseases in chest radiographs.

Equipment Design↗
PubMed1996

Mechanism of differential activities of ofloxacin enantiomers.

Ofloxacin, a potent quinolone antibacterial agent, has a tricyclic ring structure with a methyl group attached to the asymmetric carbon at the C-3 position on the oxazine ring. The S isomer (DR-3355) of ofloxacin has antibacterial activity up to 2 orders of magnitude greater than that of the R isomer (DR-3354). This differential antibacterial activity was not due to different drug transport mechanisms of the two isomers but was found to be derived from the inhibitory activity against the target enzyme, DNA gyrase. Previous mechanistic studies have suggested that the bactericidal effect of the drug is mediated through the stabilization of a cleavable complex via a cooperative drug binding process to a partially denatured DNA pocket created by DNA gyrase. The drug binds to supercoiled DNA in a manner similar to that to which it binds to the enzyme-DNA complex. In the present studies, we first examined the binding of the two radiolabeled ofloxacin enantiomers to supercoiled pUC9 plasmid DNA. Surprisingly, the two enantiomers possessed similar apparent binding affinities and binding cooperatives. The major difference in binding between the two stereoisomers was the molar binding ratio: 4 for the more active S isomer versus 2 for the less active R isomer. We next examined the relative binding potencies of the stereoisomers to the DNA-DNA gyrase complex. The results of a competition assay showed that (S)-ofloxacin binds 12-fold better to the complex than (R)-ofloxacin. The binding potencies of the two enantiomers and two other quinolones correlated well with their respective concentrations causing 50% inhibition against DNA gyrase. The results are interpreted by a stacking model by using the concept of the cooperative drug-DNA binding mechanism, indicating that the potencies of quinolones cannot be determined solely by the DNA binding affinity and cooperativity but can also be determined by their capability in maximally saturating the binding site. The capability of the drug in saturating the binding pocket manifests itself in an increased efficacy at inhibiting the enzyme through a direct interaction between the drug and the enzyme. The results augment the previous suggestion that the binding pocket in the enzyme-DNA complex involves multiple receptor groups including not only DNA bases but also a gyrase subunit. The higher level of potency of (S)-ofloxacin is proposed to derive from the fact that a greater number of molecules are assembled in the pocket. This greater number of molecules optimizes the interaction between the drug and the enzyme, possibly through a contact between the C-7 substituent and the quinolone pocket on the B subunit of DNA gyrase.

Anti-Infective Agents↗
PubMed1996

Retinal blood flow increases following short-term aspirin usage in type I diabetics with no or minimal retinopathy.

In a double-masked, randomized, placebo-controlled, two-period crossover study, we measured the effect of aspirin on retinal blood flow in 8 type I diabetic patients, 5 with no observable retinopathy, and 3 with 1-10 observable microaneurysms and no other signs of retinopathy. Each patient ingested 1 capsule/day of either aspirin (650 mg) or placebo for 14 days. Following a 1-month washout period, the treatment was reversed. The bidirectional laser Doppler technique and monochromatic photography were used to measure the blood flow rate in a major temporal retinal artery in 1 eye of each patient at baseline and on the 14th day of each treatment period. Retinal blood flow increased following aspirin in 7 of the 8 patients. Using a standard crossover analysis we found a mean aspirin-placebo treatment difference of 21 +/- 17% (mean +/- 95% CI), which was statistically significant (p = 0.03). Retinal blood flow increased following aspirin by 44 +/- 10% (mean +/- SEM) in the 5 patients with no retinopathy (p = 0.04), but only by 8 +/- 10% (n.s.) in the 3 patients with minimal retinopathy.

Adult↗
PubMed1996

Lenticular autofluorescence in normal tree shrews.

Lenticular autofluorescence was measured in vivo in 25 normal tree shrews using a fluorophotometer with a specially designed small animal adapter to assess the usefulness of this model of lens pathology. The average variability in the lenticular autofluorescence measurements was 8.7%. The average ratio between lenticular autofluorescence of the left eye and that of the right eye was 0.99 +/- 0.13 SD. There was a strong correlation between age and mean lenticular autofluorescence in both eyes (correlation coefficient, 0.988; p < 0.001). The calculated annual increase in lenticular autofluorescence was 23.7 ngEq/ml. This method of measurement is reliable, and lenticular autofluorescence in tree shrews varies little among animals other than a variation caused by aging. Moreover, the tree shrew, which is believed to be a primate, is small and easy to breed. This could be a useful animal model to study various lens pathologies in humans.

Aging↗
PubMed1996

Retinal hemodynamics in middle-aged normal subjects.

The laser Doppler technique and monochromatic photography were used to measure the total retinal blood flow, temporal/nasal differences in blood flow and the relationship between blood flow and vessel diameter in 5 healthy subjects, aged 54-58 years. Systemic blood pressure (BP) and intraocular pressure were also measured, and the retinal perfusion pressure was calculated. The measurements were compared to those previously obtained from a younger group of 7 healthy subjects, aged 25-38 years. Total retinal blood flow was 73 +/- 13 microliters/min in the middle-aged subjects and was not significantly different from the value measured in young subjects (80 +/- 12 microliters/min). Retinal perfusion pressure was significantly higher in the older subjects, primarily due to elevated systemic BP. The similarity in total flow between the two groups, even though the retinal perfusion pressures were higher in the older group, is an indication of an increased vascular resistance to flow. The increase may be an aging phenomenon or an indication of a well-functioning autoregulatory capacity in the retinal vasculature of the older subjects.

Adult↗
PubMed1996

A new type of familial central diabetes insipidus caused by a single base substitution in the neurophysin II coding region of the vasopressin gene.

We studied the genetic basis of familial neurohypophyseal diabetes insipidus in a Japanese family. The members had polyuria and a deficiency of plasma vasopressin (AVP). Polymerase chain reaction (PCR) amplified exons of the AVP-neurophysin-II gene were subcloned and sequenced. Exons 1 and 3 were normal, but nucleotide 1884 Guanine (G) in exon 2 was substituted with Thymine (T), which induced a substitution of glycine (Gly) for valine (Val). To examine the presence of this mutation in the affected subjects, we designed two mutated primers. One of them induced a new endonuclease restriction site in the PCR fragments from normal, and the other induced a new endonuclease restriction site from patients with the mutation. DNA fragments from two affected members of this family were amplified with this primer, and the PCR products were digested by endonuclease and resolved by electrophoresis. The results indicated that these subjects had both normal and mutant alleles, indicating that the mutation was heterozygous. We concluded that this mutation caused neurohypophyseal diabetes insipidus in this family.

Arginine Vasopressin↗
PubMed1996

Vasoactive intestinal peptide enhances immunoglobulin production and growth in human plasma cells via mechanisms that may involve protein kinase C.

The effects of various neuropeptides on human plasma cells were studied. Of the various neuropeptides tested, vasoactive intestinal peptide (VIP) enhanced Ig production and growth in human plasma cell lines, IM-9 and AF-10, and in plasma cells generated in vivo (four out of four patients with plasma cell leukemia) and in vitro. In contrast, other neuropeptides (neuropeptide Y, somatostatin, substance P, peptide YY, neurokinin A, calcitonin gene-related peptide, chole-cystokinin octapeptide, and beta-endorphin) were ineffective. Moreover, VIP-induced enhancement was specifically blocked by VIP receptor antagonist. Among the various cytokines, IL-6, GH, and insulin-like growth factor I (IGF-I) also enhanced Ig production and thymidine uptake in plasma cells. However, VIP-induced enhancement was not mediated by IL-6, GH, or IGF-I because antibodies to these cytokines failed to block VIP-induced enhancement. Phorbol 12,13 dibutyrate enhanced Ig production and thymidine uptake in plasma cells, and the Phorbol 12,13 dibutyrate-induced enhancement was blocked by H7 (a protein kinase C inhibitor) but not by H8 (a protein kinase A inhibitor). Similarly, VIP-induced enhancement was blocked by H7 but not by H8. Collectively, VIP enhances plasma cell responses via mechanisms that may involve protein kinase C.

Cell Division↗