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Biomedical subjects

F Cao

Publications and source records attributed to F Cao.

At least 19 recordsLinked to original sources
PubMed2003

Medical image security in a HIPAA mandated PACS environment.

Medical image security is an important issue when digital images and their pertinent patient information are transmitted across public networks. Mandates for ensuring health data security have been issued by the federal government such as Health Insurance Portability and Accountability Act (HIPAA), where healthcare institutions are obliged to take appropriate measures to ensure that patient information is only provided to people who have a professional need. Guidelines, such as digital imaging and communication in medicine (DICOM) standards that deal with security issues, continue to be published by organizing bodies in healthcare. However, there are many differences in implementation especially for an integrated system like picture archiving and communication system (PACS), and the infrastructure to deploy these security standards is often lacking. Over the past 6 years, members in the Image Processing and Informatics Laboratory, Childrens Hospital, Los Angeles/University of Southern California, have actively researched image security issues related to PACS and teleradiology. The paper summarizes our previous work and presents an approach to further research on the digital envelope (DE) concept that provides image integrity and security assurance in addition to conventional network security protection. The DE, including the digital signature (DS) of the image as well as encrypted patient information from the DICOM image header, can be embedded in the background area of the image as an invisible permanent watermark. The paper outlines the systematic development, evaluation and deployment of the DE method in a PACS environment. We have also proposed a dedicated PACS security server that will act as an image authority to check and certify the image origin and integrity upon request by a user, and meanwhile act also as a secure DICOM gateway to the outside connections and a PACS operation monitor for HIPAA supporting information.

California↗
PubMed2003

Trends in PACS image storage and archive.

PACS is widely used in hospitals and is considered a mission critical system for around-the-clock daily clinical operation. Scheduled or unscheduled downtime of the main PACS archive storage or server could potentially cripple the entire PACS operation. This is especially the case in a filmless hospital environment. Therefore, in a downtime event, it is most desirable for users to have only a minimal performance impact without interruption of clinical data flow or loss of data and to have available historical PACS studies. This paper summarizes some of the developments in the design and implementation of a reliable PACS that insures maximum uptime for end users while preserving the integrity of the PACS data and making it available during downtime events. It also details strategy for developing proper clinical workflow contingency procedures when a scheduled downtime event to the main archive storage and server occurs. Specifically, the design and implementation of a fault-tolerant (FT) main archive server, the development of a FT back-up archive using an application service provider (ASP) model, and the clinical experiences while upgrading a main archive server and migrating the stored PACS data to new storage media will be discussed.

California↗
PubMed2002

[CaSRB9, a novel Candida albicans gene, plays a role in morphogenesis of Saccharomyces cerevisiae].

Candida albicans is the most frequently isolated fungal pathogen in humans. Many factors are involved in its morphological transition. Flo8 plays an important role in morphogenesis of Saccharomyces cerevisiae. In this work, a C.albicans genomic DNA library was introduced into an S.cerevisiae flo8/flo8 mutant to screen genes which could complement its invasive growth defect. In this screening, a novel gene was isolated and designated CaSRB9 (Candida albicans SRB9 gene). The CaSRB9 gene had an ORF of 4 998 bp, encoding a putative protein of 1 665 amino acids. The CaSrb9 shared highest similarity in amino acids (38%) with Srb9 of S.cerevisiae. Ectopic expression of the CaSRB9 gene in diploid S. cerevisiae suppressed defect in filamentous growth of some mutants in filamentation MAPK pathway (ste7/ste7, ste 12 / ste 12, and tec 1 / tec 1) and flo 8 / flo 8 mutant under nitrogen starvation conditions. In haploid S. cerevisiae, ectopic expressed CaSrb9 complemented the invasive growth defect of flo8 mutant but failed to complement the invasive growth defects of the mutants in filamentation MAPK pathway.

Amino Acid Sequence↗
PubMed2001

Nuclear aggregation of huntingtin is not prevented by deletion of chaperone Hsp104.

Polyglutamine expansion causes the disease proteins to aggregate, resulting in stable insoluble aggregates in the nucleus. The in vitro aggregation and cellular toxicity of polyglutamine proteins are reduced by chaperone heat shock proteins (Hsp). In polyglutamine disease animal models, however, polyglutamine inclusions remain in the nucleus despite the suppression of neurodegeneration by Hsp. Studies using yeast genetic approach revealed that the balance of Hsp is important for regulating protein aggregation in the cytoplasm of yeast cells. Here we report that N-terminal fragments of huntingtin with an expanded polyglutamine tract form aggregates only in the cytoplasm of yeast cells and, when tagged with nuclear localization sequences (NLS), are able to aggregate in the nucleus. Deletion of the Hsp104 gene prevents the aggregation of huntingtin in the cytoplasm but is unable to eliminate the aggregation of NLS-tagged huntingtin in the nucleus. The inhibitory effect of Hsp104 deletion on the cytoplasmic aggregation of huntingtin only occurs in viable yeast cells, as aggregates can be formed in Hsp104 deletion cells that have been frozen for 72 h. Fresh cytosolic extracts of the Hsp104 deletion strain inhibit the aggregation of huntingtin in vitro, suggesting that the deletion of Hsp104 may alter the activities of other cytoplasmic factors to inhibit polyglutamine aggregation in the cytoplasm. We propose that the regulatory effects of chaperones may mainly be restricted to the cytoplasm and have much less influence on polyglutamine-containing aggregates in the nucleus.

Cell Nucleus↗
PubMed2001

A comparative study of the effects of magnetic stimulation and electric stimulation on peripheral nerve injury in rat.

The influence of pulsed magnetic stimulation (MS) on the sciatic nerve injury was investigated. Thirty rats were divided into three groups equally: MS group (A), electric stimulation (ES) group (B) and the control group (C). The MS and ES were applied immediately after the first 10 min of the sciatic nerve crush. Sciatic function index (SFI), toe spreading reflex (TSR), muscular weight and volume were measured after the experiment. The TSR of in the groups A and B occurred at 4th day while in the control group it occurs at 10th day. There was statistically significant difference in SFI between groups A and B (P < 0.01). The weight and volume of the gastrocnemius muscle were statistically greater in the groups A and B than in the control group (P < 0.01). The effect of MS was similar to that of ES. It was suggested that the application of MS immediately after the nerve injury might have an important clinical value as it can accelerate functional recovery and prevent or minimize muscle atrophy. The technique is easily to operate, non-invasion, painless and permits tolerance of high intensity output to be used.

Animals↗
PubMed2001

Computer automated approach to the extraction of epiphyseal regions in hand radiographs.

Epiphyseal region is the most sensitive region to developmental changes of the skeletal system. Extraction of this area is the very first step in any computerized image analysis. In this report a fully automated analysis of a hand radiograph resulting in extraction of distal and middle regions of the II, III, and IV phalanx is presented. The processing is performed in 3 stages. First, the trend of background is removed from radiograph to obtain a binary hand mask. At this stage a labeling procedure is necessary to eliminate artifacts (markers). Then, II, III, and IV phalanges are identified in the binary image, and the phalangeal axes are drawn. Finally, the intensity profile along each phalangeal axis is analyzed, and, on its basis, distal and middle regions are located. The presented procedure is designed as a part of currently developed system for automatic bone age assessment; however, it also can be as a preprocessing step in other diseases the diagnoses of which may require a computer assistance.

Adolescent↗
PubMed2001

Computer-assisted bone age assessment: image preprocessing and epiphyseal/metaphyseal ROI extraction.

Clinical assessment of skeletal maturity is based on a visual comparison of a left-hand wrist radiograph with atlas patterns. Using a new digital hand atlas an image analysis methodology is being developed. To assist radiologists in bone age estimation. The analysis starts with a preprocessing function yielding epiphyseal/metaphyseal regions of interest (EMROIs). Then, these regions are subjected to a feature extraction function. Accuracy has been measured independently at three stages of the image analysis: detection of phalangeal tip, extraction of the EMROIs, and location of diameters and lower edge of the EMROIs. Extracted features describe the stage of skeletal development more objectively than visual comparison.

Adolescent↗
PubMed2001

[Studies on mimotopes of hepatitis C virus E1 protein].

OBJECTIVE: To study the B-cell epitope of E1 protein of hepatitis C virus. METHODS: By induction of IPTG, the E.coli M15 strains harboring the pQE30-HCVe118 expressed truncated C-terminal HCV E1 protein (Pte1). The proteins were purified with preparative electrophoreses system, which captured anti-E1 IgG in HCV (+) sera. By applying the antibodies as selective molecular 12 mers random peptide libraries were panned, and positive clones were obtained by ELISA. Amino acid sequences of display peptide were compared with that of HCV E1 protein. RESULTS: The purified HCV E1 proteins could react specifically with partly anti-HCV sera by ELISA. Among 10 phage display peptides, 6, 6, 2 were the most homologous to HCV E1 protein at position 320-336aa, 251-263aa, 225-248, respectively. CONCLUSIONS: There exist multiple B-cell epitopes in HCV E1 protein. At least one preponderant epitope is mapped at residues 320-336 of HCV E1 protein.

Amino Acid Motifs↗
PubMed2000

Nucleotide sequence analyses of partial envgp46 gene of human T-lymphotropic virus type I from inhabitants of Fujian Province in Southeast China.

Partial sequences from the env(gp46) gene of two human T-lymphotropic virus type I (HTLV-I) isolates (LIN and WEN) obtained from inhabitants of Fujian Province in southeast China were analyzed. A phylogenetic tree was constructed from these sequence data and those of other known HTLV-I isolates from all over the world. Comparisons of the LIN and WEN nucleotide sequences with other HTLV-I isolates showed diversity ranging from 0.73 to 7.00% for LIN and from 0.87 to 7.00% for WEN. Sequences of isolates LIN, WEN, MT-2, TSP1, and CH were most closely related, and the phylogenetic tree showed that all belong to the widespread subtype A of the cosmopolitan group. These preliminary data indicate that HTLV-I isolates from Fujian Province, China are closely related to HTLV-I strains from Japan and the Caribbean.

Base Sequence↗
PubMed2000

The molecular basis of selective permeability of connexins is complex and includes both size and charge.

Although gap junction channels are still widely viewed as large, non-specific pores connecting cells, the diversity in the connexin family has led more attention to be focused on their permeability characteristics. We summarize here the current status of these investigations, both published and on-going, that reveal both charge and size selectivity between gap junction channels composed of different connexins. In particular, this review will focus on quantitative approaches that monitor the expression level of the connexins, so that it is clear that differences that are seen can be attributed to channel properties. The degree of selectivity that is observed is modest compared to other channels, but is likely to be significant for biological molecules that are labile within the cell. Of particular relevance to the in vivo function of gap junctions, recent studies are summarized that demonstrate that the connexin phenotype can control the nature of the endogenous traffic between cells, with consequent effects on biological effects of gap junctions such as tumor suppression.

Animals↗
PubMed2000

High levels of E-/P-cadherin: correlation with decreased apical polarity of Na/K ATPase in bovine RPE cells in situ.

PURPOSE: The adherens junction protein E-cadherin induces a basolateral polarity of Na/K ATPase in most epithelial cells that express it, whereas in retinal pigment epithelium (RPE) cells, Na/K ATPase is largely apical. The purpose of this study was to determine whether the distribution of Na/K ATPase differs in RPE cells in situ, that differ in levels of junctional E-cadherin. METHODS: Bovine RPE cells in situ were immunostained with an E-cadherin antibody (which has some cross-reactivity with the closely related epithelial cadherin P-cadherin), and RPE cells with different levels of junctional stain were identified. RPE cells with low and high E-/P-cadherin were costained in various combinations with Na/K ATPase and interacting proteins of the membrane cytoskeleton (ankyrin, fodrin, and actin) and analyzed by confocal imaging. RESULTS: Individual RPE cells within the same monolayer differed in amount of Na/K ATPase, with a lower frequency of high expressing cells in the area centralis. High expressing Na/K ATPase cells were found among cells with both low and high E-/P-cadherin levels. In cells with low E/P-cadherin, Na/K ATPase localized to apical microvilli, whereas in high E-/P-cadherin cells, Na/K ATPase was on basolateral surfaces in addition to microvilli. Actin staining showed that microvillar domains were smaller and that lateral membrane domains were taller in high E-/P-cadherin cells. In high but not low E-/P-cadherin cells, ankyrin and fodrin levels varied among cells, with a subset of cells showing distinctly higher expression. Both ankyrin and fodrin had complex subcellular distribution patterns, although they tended to be enriched basal to rather than apical to the adherens junction. Cells with high Na/K ATPase did not necessarily have commensurately higher levels of ankyrin or fodrin. Where both Na/K ATPase and ankyrin were high, they codistributed weakly in apical microvilli but more prominently on the basal cell surface. CONCLUSIONS: Within the same RPE monolayer, the polarity of Na/K ATPase differs among cells, with a more basal polarity found in cells with high levels of junctional E-/P-cadherin. The increased basal Na/K ATPase was due to a combination of a smaller microvillar domain, a taller lateral domain, and more basolateral staining for Na/K ATPase, perhaps because of an enrichment of a basal ankyrinfodrin membrane cytoskeleton with which Na/K ATPase is known to associate.

Actins↗
PubMed2000

Time at confluence for human RPE cells: effects on the adherens junction and in vitro wound closure.

PURPOSE: To determine how time at confluence affects the properties of cultured human retinal pigment epithelium (RPE) cells, with emphasis on the adherens junction. METHODS: Cultures were maintained at confluence without passage for intervals to several months. Adherens junction proteins (N-cadherin, E-cadherin, alpha-catenin, beta-catenin, plakoglobin, and actin) and the proliferation marker Ki-67 were localized in the cultures by fluorescence microscopy, and in vitro wound healing was compared. Adherens junctions were analyzed for protein solubility in detergent buffers and sensitivity to disruption by treatment with anti-cadherin antibodies and low calcium conditions. RESULTS: Compared with cultures in early-confluence (2-3 days), postconfluent cultures (weeks) had more mature adherens junctions characterized by a circumferential (rather than linear) actin organization, and a zonular (rather than punctate) distribution of more detergent resistant cadherin and catenins. Postconfluent cultures also had fewer Ki-67-positive cells and a higher cell packing density. Early-confluence cells migrated into in vitro wounds as dissociated single cells, whereas postconfluent cells moved as contiguous sheets, retaining an intact junction during wound-induced cell migration and proliferation. Mature junctions were not disrupted by treatment of living cells with N-cadherin antibodies, which bound to and remained detectable at junctions for several days. Calcium withdrawal displaced N-cadherin from mature junctions and rendered it more soluble, but the dominant circumferential pattern of actin was stable. Restoration of medium calcium resulted in a rapid (hours) recovery of a nearly complete zonular pattern of insoluble N-cadherin. CONCLUSIONS: Over long postconfluent periods, cultured RPE cells became more growth quiescent, and intercellular cadherin adhesions became more stable, exhibiting increased resistance to calcium removal and greater retention of junctional integrity during in vitro wound closure. Consideration should be given to whether the behavior of RPE cells in postconfluent cultures, where intercellular adhesions are more mature, more closely simulates RPE cells in situ than cells in early-confluence cultures, which are more commonly used for analysis.

Adolescent↗
PubMed1999

Progressive association of a "soluble" glycolytic enzyme with the detergent-insoluble cytoskeleton during in vitro morphogenesis of MDCK epithelial cells.

In MDCK epithelial cells, cell contact at confluency initiates a protracted process of morphogenesis during which several proteins known to bind the cytoskeleton become progressively associated with the detergent-resistant cell fraction and distributed to their characteristic polarized domains. Using extraction protocols that identify this tight cytoskeletal linkage, here we show a similar but slower, time-dependent enrichment in the detergent resistant fraction of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), a highly abundant glycolytic enzyme that is traditionally considered soluble. Similar enrichment did not occur for two other glycolytic enzymes, phosphoglycerate mutase or lactate dehydrogenase. Insoluble GAPDH was not homogeneously distributed in the cytoplasm but rather displayed several discrete patterns that varied within and among MDCK cells. It also localized prominently to a few nuclei in the phenotypically heterogeneous cells of late confluency cultures. Disruptors of cytoskeletal filaments were relatively ineffective in the postconfluent epithelial monolayers, although use of disrupting agents implicated actin as the cytoplasmic filament that tethers insoluble GAPDH. Catalytic activity could be demonstrated in the insoluble fraction of GAPDH from postconfluent cultures, but only after release by mechanical disruption of insoluble extracts. Treatment of postconfluent cells with agents that deplete ATP diminished the fraction of cytoskeletally associated GAPDH, and levels of insoluble GAPDH were restored with ATP repletion, suggesting that ATP levels may regulate cytoskeletal linkage and thereby local enzyme activity. We conclude that the highly abundant and ubiquitous enzyme GAPDH becomes progressively enriched in detergent stable subcellular compartments during the process of epithelial morphogenesis. The process that produces GAPDH compartments is slow, suggesting that epithelial cells just at confluency, when they are typically analyzed, have not yet maximized the organizational state that can be attained in monolayer culture.

Acrylamide↗
PubMed1999

Expression of E-cadherin by human retinal pigment epithelium: delayed expression in vitro.

PURPOSE: To determine whether retinal pigment epithelial (RPE) cells, which reportedly express N-cadherin as their major cadherin cell adhesion protein, also express the more common epithelial cadherin, E-cadherin. METHODS: Cadherins expressed by human RPE cells in situ were examined by western blot analysis of extracts prepared from the RPE of human adult eyes. Cadherins expressed in vitro were examined by analysis of confluent and postconfluent human RPE cultures, using the methods of reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis. Protein distribution was examined by conventional fluorescence microscopy, confocal imaging, or both. Proteins whose expression, distribution, or both correlated with E-cadherin expression in other epithelial cells were examined by similar methods in cultured RPE cells. RESULTS: In addition to N-cadherin, E-cadherin (and P-cadherin) was found in adult human RPE in situ. In cultured human RPE cells, N-cadherin was ubiquitous, but E-cadherin was limited to patches of cells and was not expressed until several weeks after confluence, a time when several phenotypic variants become prominent. E-cadherin was absent from RPE cells of fusiform shape but was found in only a subset of epithelioid RPE cells. Unlike epithelial cell lines expressing E-cadherin, cultured RPE cells with E-cadherin did not show diminished coexpression of N-cadherin, increased expression of desmosomal proteins, or a preferential expression of the alphaE- (rather than alpha-N) isoform of the cadherin linker protein alpha-catenin. Na/K ATPase distributed to both apical and basolateral membranes in RPE cells with junctional E-cadherin and not preferentially to the basolateral domain as in most epithelial cells with E-cadherin. CONCLUSIONS: RPE cells express E-cadherin, a cadherin found in most other epithelial cells, but which was believed to be absent from RPE. In RPE in vitro, E-cadherin expression is a late developmental event, occurring in late confluence in cells that already express N-cadherin. E-cadherin is an established epithelial morphoregulatory protein, but it does not induce the same properties in RPE cells as in other epithelial cells, suggesting tissue-specific differences in the potential of E-cadherin to determine an epithelial phenotype.

Adult↗
PubMed1999

[Can esophagogastric anastomosis prevent gastroesophageal reflux].

OBJECTIVE: To investigate the possible anti-reflux function of esophagogastric anastomosis in the patients after receiving resection of cardiac cancer. METHODS: One hundred and ninety-two patients were studied by video-assisted gastroscopy, manometry, 24-h pH esophageal monitoring, radioscintigraphy and scanning electron microscopy. RESULTS: Abnormalities were found in 90.2% of patients through endoscopy. Resting pressure in esophageal body was higher than that in normal controls, and in the stomach, lower. Twenty-four hour pH monitoring demonstrated that gastroesophageal reflux (GER) did not occur when the patients slept in semi-reclining position, and occurred in all patients when slept in supine position. Scintigraphic study showed that 2/3 of the patients had reflux, occurrence of which was not affected by the length of postoperative period. Scanning electron microscopic examination showed that degeneration, exfoliation of esophageal mucosal epithelial cell, and derangement of micro-fold and inflammatory oedema of cytomembrane may be directly caused by reflux. CONCLUSIONS: GER exists in the majority of the patients after esophagogastrectomy and esophagogastrostomy for cardiac cancer. The occurrence of GER is not affected by the length of postoperative period. Some detecting methods fail to show the existence of GER, and 24-h pH monitoring is the most reliable method for detecting GER. Sleep in semireclining position is an effective method of preventing GER in postoperative patients.

Adult↗
PubMed1999

[Functional improvement of remnant stomach after proximal subtotal gastrectomy for cardiac cancer].

OBJECTIVE: To evaluate the function of the remnant stomach after proximal subtotal gastrectomy for cardiac cancer and to improve the life quality of post-surgical patients. METHODS: 17 patients with cardiac cancer underwent proximal subtotal gastrectomy combined with disconnection of pyloric sphincter (PSG + DPS) by finger pressing. Intraoperative pyloric manometric studies were performed in the 17 patients before and after DPS. Five subjects who underwent laparotomy for non-esophagogastric reasons was taken as controls. Total bile acids (TBA) in gastric juice was tested in the 17 patients at 5th postoperative day, and radionuclide gastric emptying was also studied from the 18th to 20st postoperative day. RESULTS: Both pyloric resting pressure and pyloric contracting pressure were significantly decreased after DPS (P > 0.01). In comparison with normal subjects, PCP was increased before DPS (P > 0.01) and decreased after the procedure (P < 0.05). However, PRP did not show significant differences before (P > 0.05) and after (P > 0.05) DPS. There were no significant differences regarding TBA content in gastric juice in PSG + DPS group, PSG group, and normal subjects (P > 0.05). The time required for the stomach to empty half of its radioactive contents (T1/2) was longer in the patients having PSG only than those undergoing PSG + DPS (P < 0.01) and normal controls (P < 0.05). However, there were no significant differences regarding T1/2 between the patients with PSG + DPS and normal controls (P > 0.05). CONCLUSIONS: The emptying of remnant stomach after subtotal gastrectomy for cardiac cancer is delayed because of the increase of emptying-resistance and decrease of peristalsis. PSG combined with DPS not only improves gastric emptying, but also prevents duodenogastric reflux. Consequently, postoperative life quality of the patients with cardiac cancer can be effectively improved.

Aged↗