Possible association of actin filaments with chloroplasts of spinach mesophyll cells in vivo and in vitro.

In palisade mesophyll cells of spinach (Spinacia oleracea L.) kept under low-intensity white light, chloroplasts were apparently immobile and seemed to be surrounded by fine bundles of actin filaments. High-intensity blue light induced actin-dependent chloroplast movement concomitant with the appearance of a couple of long, straight bundles of actin filaments in each cell, whereas high-intensity red light was essentially ineffective in inducing these responses. The actin organization observed under low-intensity white light has been postulated to function in anchoring chloroplasts at proper intracellular positions through direct interaction with the chloroplasts. Intact chloroplasts, which retained their outer envelopes, were isolated after homogenization of leaves and Percoll centrifugation. No endogenous actin was detected by immunoblotting in the final intact-chloroplast fraction prepared from the leaves kept under low-intensity white light or in darkness. In cosedimentation assays with exogenously added skeletal muscle filamentous actin, however, actin was detected in the intact-chloroplast fraction precipitated after low-speed centrifugation. The association of actin with chloroplasts was apparently dependent on incubation time and chloroplast density. After partial disruption of the outer envelope of isolated chloroplasts by treatment with trypsin, actin was no longer coprecipitated. The results suggest that chloroplasts in spinach leaves can directly interact with actin, and that this interaction may be involved in the regulation of intracellular positioning of chloroplasts.

[Usefulness of spiral CT in the detection of hypovascular, well-differentiated hepatocellular carcinoma].

Whole liver scanning during artery-dominant phase using spiral CT was performed in 14 patients with 17 histologically proven well-differentiated HCCs, which were not depicted by hepatic digital subtraction angiography but by CT during arterial portography. The density of HCC relative to the liver was evaluated with conventional precontrast CT, spiral CT, and following conventional CT during the equilibrium phase. Comparison between spiral CT and magnetic resonance (MR) imaging of dynamic contrast studies was also investigated. Four tumors of 17 HCCs (24%) were shown as a high-density area by the artery-dominant phase using spiral CT. Consequently, the total sensitivity of these three kinds of CT techniques was elevated to 82%. The sensitivity of dynamic MR imaging was slightly greater than that of spiral CT. However, spiral CT sometimes made the diagnosis more conspicuous by it's good spatial resolution. Our results indicate that spiral CT has a potential benefit in the detection of hypovascular well-differentiated HCC, and MR imaging and spiral CT may be complement each other.

Comparison between conventional and spiral CT in patients with hypervascular hepatocellular carcinoma.

To determine the usefulness of spiral CT in the detection of hypervascular hepatic lesions, we compared conventional contrast enhanced CT (CECT) with whole liver dynamic scanning during the artery-dominant phase by spiral CT (SDCT), using hypervascular hepatocellular carcinoma (HCC) as a model. Twenty-nine patients with 56 hypervascular nodular type HCCs detected by hepatic digital subtraction angiography were examined by both CT techniques. These nodular type HCCs were divided into three groups according to diameter: < 10 mm (n = 7), 10-20 mm (n = 17), and over 20 mm (n = 32). None of seven lesions less than 10 mm in diameter was seen by either technique. Of 17 lesions 10-20 mm in diameter, four (24%) were detected by precontrast CT plus CECT, whereas 14 (82%) were detected by precontrast CT plus SDCT. There were no lesions detected by CECT only, whereas 10 lesions were detected by SDCT only (P < 0.01 by signed test). For 32 lesions over 20 mm in diameter, there was no significant difference in detection rates between the CT techniques. Our results indicate that spiral CT is useful for the detection of relatively small hypervascular hepatic lesions such as hypervascular HCCs.

Small PACS for digital medical images--reliability and security in a clinical setting.

Recently we introduced a small Picture Archiving Communication System (PACS) for handling CT and MRI data. Our experience with this system has been useful in identifying potential problems in a clinical setting. Since the use of PACS raises both medical and social concerns, it cannot be instituted without addressing concerns related to the reliability and security issues. Although PACS is useful in the management of medical images, there are concerns about their reliability and security in a clinical setting. Reliability encompassed image quality, timeliness of the reports, and the PACS to the Radiological Information System (RIS) interface including the retrieval of the previously obtained images. The security of the patient's medical data is also essential.

Pleural invasion by peripheral bronchogenic carcinoma: assessment with three-dimensional helical CT.

PURPOSE: To evaluate the potential role of three-dimensional (3D) computed tomography (CT) in assessment of pleural invasion by peripheral bronchogenic carcinoma. MATERIALS AND METHODS: Twenty-four-second helical CT scans were obtained during a single breath hold in 42 consecutive patients with peripheral bronchogenic carcinoma. Conventional two-dimensional (2D) images and 3D reconstruction images were reviewed independently by three blinded observers, who reached a decision by consensus. All patients underwent surgical resection of the tumor, and CT findings were correlated with the findings in pathologic specimens. RESULTS: Twelve patients had visceral pleural invasion, five had parietal pleural invasion, and 25 had no evidence of pleural invasion. Visceral pleural invasion was identified on 2D CT images in two patients and on 3D reconstructions in 11. Parietal pleural invasion was identified on 2D CT images in two patients and on 3D reconstructions in three. CONCLUSION: 3D reconstruction imaging is superior to conventional 2D CT in assessment of pleural invasion by peripheral bronchogenic carcinoma.