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Biomedical subjects

A W Wong

Publications and source records attributed to A W Wong.

At least 19 recordsLinked to original sources
PubMed1999

Anion dopant for oligosaccharides in matrix-assisted laser desorption/ionization mass spectrometry.

A new anion dopant for oligosaccharides is developed for use in matrix-assisted laser desorption/ionization mass spectrometry. Two types of sulfate-attached quasimolecular ions are formed in the negative ion mode when neutral oligosaccharides are doped with dilute H2SO4 solutions. Under mild conditions, i.e., low H2SO4 concentration (approximately 10(-3) M) and threshold laser fluence, a sulfate adduct [M + HSO4]- is formed. With more concentrated H2SO4 solutions (approximately 10(-2) M) and higher laser fluence, in situ derivatization of the oligosaccharides occurs to produce an ion whose m/z corresponds to a sulfate derivative [M + HSO4 - H2O]-. Hydrogen sulfate appears to be a general anion dopant because it forms complexes with a wide variety of neutral oligosaccharides. Conversely, anionic oligosaccharides form neither the adduct nor the derivative. The combination of complex formation (with neutral oligosaccharides) and the deprotonation of acidic oligosaccharides allows simultaneous detection of the respective mixture.

Anions↗
PubMed1998

Identification of Glu-540 as the catalytic nucleophile of human beta-glucuronidase using electrospray mass spectrometry.

Human beta-glucuronidase is a member of the Family 2 glycosylhydrolases that cleaves beta-D-glucuronic acid residues from the nonreducing termini of glycosaminoglycans. The enzyme is shown to catalyze glycoside bond hydrolysis with net retention of anomeric configuration, presumably via a mechanism involving a covalent glucuronyl-enzyme intermediate. Incubation of human beta-glucuronidase with 2-deoxy-2-fluoro-beta-D-glucuronyl fluoride resulted in time-dependent inactivation of the enzyme through the accumulation of a covalent 2-deoxy-2-fluoro-alpha-D-glucuronyl-enzyme, as observed by electrospray mass spectrometry. Regeneration of the free enzyme by hydrolysis or transglycosylation and removal of excess inactivator demonstrated that the covalent intermediate was kinetically competent. Peptic digestion of the 2-deoxy-2-fluoro-alpha-D-glucuronyl-enzyme intermediate and subsequent analysis by liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry indicated the presence of a 2-deoxy-2-fluoro-alpha-D-glucuronyl peptide. Sequence determination of the labeled peptide by tandem mass spectrometry in the daughter ion scan mode permitted the identification of Glu-540 as the catalytic nucleophile within the sequence SEYGAET.

Affinity Labels↗
PubMed1998

Catamenial fevers associated with a uterine smooth muscle tumor of undetermined malignant potential.

BACKGROUND: Pyrexia associated with solid and hematogenous neoplasms are a well-recognized clinical condition. Menstrually related (catamenial) fevers have not been reported previously. CASE: A 52-year-old woman with a history of stage I breast cancer on adjuvant tamoxifen citrate presented with recurrent fevers associated with menses. An extensive evaluation of possible causes, including recurrent breast cancer and infectious, collagen-vascular, and drug-related sources, initially was unrevealing. A gynecologic evaluation identified a uterine tumor, which appeared to be a cellular leiomyoma on hysteroscopic biopsy. The catamenial fevers resolved immediately after hysterectomy. A uterine smooth muscle tumor of undetermined malignant potential was identified on pathology. CONCLUSION: Smooth muscle tumors of the myometria are a rare cause of menstrual fevers.

Female↗
PubMed1996

Clinical experience with a second-generation hospital-integrated picture archiving and communication system.

In a previous report we described a second-generation hospital-integrated picture archiving and communication system (HI-PACS) developed in-house. This HI-PACS had four unique features not found in other PAC systems. In this report, we will share some of our clinical experiences pertaining to these features during the past 12 months. We first describe the usage characteristics of two 2,000-line workstations (WSs), one in the in-patient and the second in the out-patient neuroradiology reading area. These two WSs can access neuro-images from 10 computed tomographic and magnetic resonance scanners located two medical centers through an asynchronous transfer mode network connection. The second unique feature of the system is an intensive care unit (ICU) server, which supports three WSs in the pediatric, medical surgery, and cardiac ICUs. The users' experiences and requests for refinement of the WSs are given. Another feature is physician desk-top access of PACS data. The HI-PACS provides a server connected to more than 100 Macintosh users for direct access of PACS data from their offices. The server's performance and user critiques are described. The last feature is a digital imaging and communication in medicine (DICOM) connection of the HI-PACS to a manufacturer's ultrasound PACS module. The authors then outline the interfacing process and summarize some of the difficulties encountered. Developing an in-house PACS has many advantages but also some drawbacks. Based on experience, the authors have formulated three axioms as a guide for in-house PACS development.

Computer Communication Networks↗
PubMed1996

Design and implementation of a picture archiving and communication system: the second time.

This report describes the authors' experience in the design and implementation of two large scale picture archiving and communication systems (PACS) during the past 10 years. The first system, which is in daily clinical operation was developed at University of California, Los Angeles from 1983 to 1992. The second system, which continues evolving, has been in development at University of California, San Francisco (UCSF) since 1992. The report highlights the differences between the two systems and points out the gradual change in the PACS design concept during the past 10 years from a closed architecture to an open hospital-integrated system. Both systems focus on system reliability and data integrity, with 24-hour on-line service and no loss of images. The major difference between the two systems is that the UCSF PACS infrastructure design is a completely open architecture and the system implementation uses more advanced technologies in computer software, digital communication, system interface, and stable industry standards. Such a PACS can withstand future technology changes without rendering the system obsolete, an essential criterion in any PACS design.

Diagnostic Imaging↗
PubMed1995

Asynchronous transfer mode technology for radiologic image communication.

Image communication is an important component in picture archiving and communication systems (PACS) and teleradiology applications. Currently, local area networks (LANs) and wide area networks (WANs) use different technologies for image communication. Asynchronous transfer mode (ATM) is an emerging technology that can be used for both LANs and WANs. This article describes experimental results using an ATM network to transmit CT scans and digitized radiographs between the University of California, San Francisco (UCSF) and Mount Zion Hospital, an affiliated community hospital in the San Francisco Bay area. The WAN connection between the two hospitals is via an ATM main switch at Pacific Bell, a local communication carrier located in Oakland, CA, which uses single-mode optical fibers. Preliminary results show that, using the ATM Optical Carrier Level 3 (OC3) (155 Mbits/sec) specification, it takes 1.3 sec and 2.7 sec to transmit a 10-Mbyte digitized radiograph and a 20-Mbyte CT scan, respectively, between the two locations. Encouraged by these results, we have designed and implemented an ATM WAN and LAN between UCSF and Mount Zion Hospital. This is the first of a three-phase project of installing a WAN serving four hospitals and one clinic in the San Francisco Bay area.

Computer Communication Networks↗
PubMed1994

Digital archive system for radiologic images.

Use of a picture archiving and communication system (PACS) for clinical review requires rapid access to patient images. The authors have developed a second-generation archive system for a departmental PACS that optimizes access time for both current and historical images. The system is based on a composite staging mechanism that uses multiple storage media: magnetic disks, erasable magneto-optical disks, and write-once-read-many (WORM) disks. A two-tiered communication network composed of a standard Ethernet network and a gigabit bandwidth fiberoptic UltraNet network is used for distributing images to remote display stations. The system currently archives 1.5 Gbytes of radiologic images daily from three magnetic resonance imagers, two computed tomographic scanners, one computed radiographic system, and one laser film digitizer. The system features (a) multiple optical drives and robotic arms, which support concurrent archival and retrieval operations; (b) a stacking mechanism, which provides fast retrieval of current images; (c) a pre-fetch mechanism, which minimizes on-line image retrieval, hence relieving peak-hour workload of the optical disk library and the networks; (d) studies grouping and platter management, which optimize retrieval of a patient's images from multiple examinations; and (e) a job-prioritizing control, which minimizes waiting time for radiologists and referring physicians to review images at the display stations. This system is suitable for a large-scale PACS to serve the clinical and research staff.

Radiology Information Systems↗
PubMed1994

Accessing picture archiving and communication system text and image information through personal computers.

Recent advances in storage technology have made possible the archiving of tremendous amounts of text and image information within a picture archiving and communication system (PACS). However, a radiologist's access to this information typically has been limited to viewing workstations designed primarily to support clinical activities. Unfortunately, these workstations often overlook the benefits of PACS in teaching and research applications, which are of significant importance in an academic institution. To support such activities at our own institution, we have included two major objectives in our second-generation PACS development: (1) to provide access to text and image information archived within our PACS in an environment that is easily accessible to and comfortable for our radiologists, namely, their own Macintosh (Apple Computer, Cupertino, CA) personal computers; and (2) to provide this information in standard Macintosh formats, so that tools with which radiologists are already familiar can be used in frequently performed teaching activities--the production of slides and prints, the maintenance of personal teaching and research files, and specialized image analysis and processing.

Computer Communication Networks↗
PubMed1993

O-linked glycosylation modifies the association of apolipoprotein A-II to high density lipoproteins.

O-linked glycosylation is a common post-translational modification of apolipoproteins, but no structural or functional role for it has been identified. We examined the biosynthesis of apolipoprotein (apo) A-II in Hep G2 cells and in glycosylation-defective Chinese hamster ovary (CHO) cell mutants transfected with apoA-II cDNA. Three monomeric isoforms of apoA-II with an apparent molecular mass of 8.5, 9.8, and 11.4 kDa were synthesized by Hep G2 cells and transfected wild-type CHO cells. The 9.8- and 11.4-kDa isoforms were sialylated but not the 8.5-kDa isoform. Transfected 1dlD cells, which are defective in the biosynthesis of galactose and N-acetylgalactosamine, only produced the 8.5-kDa isoform; however, when grown in media supplemented with these sugars, ldlD cells produced all three isoforms of apoA-II. Pulse-chase analysis of ldlD cells showed that glycosylation was not necessary for secretion of apoA-II. Glycosylation did modify the association of apoA-II with nascent high density lipoprotein (HDL) secreted by Hep G2 cells. The sialylated isoforms were lipid-poor and were present in the lipoprotein-deficient density range, whereas the nonsialylated 8.5-kDa isoform was associated with LpA-I, A-II lipoprotein particles in the HDL density range. ApoA-II from transfected ldlD cells, regardless of glycosylation, were lipid-poor. When preincubated with HDL from serum, however, sialylated apoA-II from both ldlD cells and Hep G2 cells associated with lipoprotein particles within the HDL3 density, whereas nonsialylated apoA-II was found throughout the HDL density range. In summary, O-linked glycosylation is not necessary for the secretion of apoA-II but does modify the association of apoA-II to HDL and may, therefore, play an important role in the metabolism of HDL.

Animals↗
PubMed1992

Subsystem throughputs of a clinical picture archiving and communications system.

We measured the throughtput rates of individual picture archiving and communications system (PACS) subsystems including the acquisition, archive, display, and communication network as a basis of evaluation the overall throughput of our clinical PACS. The throughput rate of each PACS subsystem was measured in terms of average residence time of individual images in the subsystem. The residence time of an image in a PACS subsystem was determined by the total time the image was required to be processed within the subsystem. The overall throughput of the PACS was measured as the total residence time of an image in the various subsystems. We also measured throughputs of the PACS subsystems using three types of networks (Ethernet; fiber distributed data interface; and UltraNet, UltraNetwork Technologies, San Jose, CA), and the results were compared. Approximately 200 gigabytes of data transactions including magnetic resonance, computed tomography and computed radiography images from our PACS were analyzed. Results showed that PACS throughput was limited by three major factors: (1) low-speed data interface used in the radiologic imaging devices and archive devices; (2) competition for systems processing time among the PACS processes; and (3) network degradation caused by heavy network traffic. We concluded that PACS performance could be improved with a well-designed network architecture, a job prioritizing mechanism, and an image routing strategy. However, device-dependent low-speed data interface has limited PACS performance.

Computer Communication Networks↗
PubMed1992

Digital archive center: implementation for a radiology department.

OBJECTIVE: In this article, we describe the implementation of a digital archive center for a radiology department in a 700-bed teaching hospital. MATERIALS AND METHODS: The archive center consists of two identical archive systems, each comprising five components: an archive server, a data-base server, an optical disk library, a stand-alone optical disk drive, and a communication network. An image management system controls the image traffic from acquisition devices to display stations. A fault-tolerant mechanism was built into the archive center to achieve a 100% uptime. RESULTS: The center has been in operation for over 6 months. We have not experienced a single total system failure during this period. It currently archives all digital images from three MR units and four CT scanners and selected images from three computed radiographic systems and two laser film digitizers. The center archives between 1.5 and 2.0 gigabytes of images per workday. CONCLUSION: With its built-in fault-tolerant mechanism, we believe that the implemented archive center is very reliable and is suitable for a radiology department to archive its digital images.

Hospital Bed Capacity, 500 and over↗
PubMed1990

Trends in pulmonary embolism death rates for Canada and the United States, 1962-87.

To investigate the effect of advances in the prevention and treatment of pulmonary embolism, we examined the rates of death from pulmonary embolism in Canada for 1965-87 and compared them with those for the United States for 1962-84. The direct method of age standardization was used on sex-specific and age-specific death rates, with the 1960 US population as the standard. In both countries the death rates increased then decreased, although the changes in the Canadian rates occurred later and were less pronounced than those in the US rates. Men and elderly people were at higher risk of death from pulmonary embolism than women and younger people. Prevention strategies, possibly including encouraging a more active lifestyle and targetting high-risk groups, may further reduce pulmonary embolism death rates in both countries.

Adolescent↗
PubMedDate not supplied

Implementation of a large-scale picture archiving and communication system.

This paper describes the implementation of a large-scale picture archiving and communication system (PACS) in a clinical environment. The system consists of a PACS infrastructure, composed of a PACS controller, a database management system, communication networks, and optical disk archive. It connects to three MR units, four CT scanners, three computed radiography systems, and two laser film digitizers. Seven display stations are on line 24 h/day, 7 days/wk in genitourinary radiology (2K), pediatric radiology in-patient (1K and 2K) and outpatient (2K), neuroradiology (2K), pediatric ICU (1K), coronary care unit (1K), and one laser film printing station. The PACS is integrated with the hospital information system and the radiology information system. The system has been in operation since February 1992. We have integrated this PACS as a clinical component in daily radiology practice. It archives an average of 2.0-gigabyte image data per workday. A 3-mo system performance of various components are tabulated. The deployment of this large-scale PACS signifies a milestone in our PACS research and development effort. Radiologists, fellows, residents, and clinicians use it for case review, conferences, and occasionally for primary diagnosis. With this large-scale PACS in place, it will allow us to investigate the two critical issues raised when PACS research first started 10 yrs ago: system performance and cost effectiveness between a digital-based and a film-based system.

Computer Communication Networks↗
PubMedDate not supplied

Multimedia in the radiology environment: current concept.

Multimedia has different meanings according to its context. Here, multimedia in the radiology environment is defined as the integration of multiple radiology and medical information systems to facilitate the practice of radiology. These information systems include the hospital information system, radiology information system, picture archiving and communication systems, voice reporting, library information systems, and electronic mail and file systems. The concept of multimedia within the context of integration of these database systems will be presented. An example is given on how to access these information systems by a radiologist's desktop personal computer.

Database Management Systems↗
PubMedDate not supplied

Performance of asynchronous transfer mode (ATM) local area and wide area networks for medical imaging transmission in clinical environment.

Asynchronous transfer mode (ATM) technology emerges as a leading candidate for medical image transmission in both local area network (LAN) and wide area network (WAN) applications. This paper describes the performance of an ATM LAN and WAN network at the University of California, San Francisco. The measurements were obtained using an intensive care unit (ICU) server connecting to four image workstations (WS) at four different locations of a hospital-integrated picture archiving and communication system (HI-PACS) in a daily regular clinical environment. Four types of performance were evaluated: magnetic disk-to-disk, disk-to-redundant array of inexpensive disks (RAID), RAID-to-memory, and memory-to-memory. Results demonstrate that the transmission rate between two workstations can reach 5-6 Mbytes/s from RAID-to-memory, and 8-10 Mbytes/s from memory-to-memory. When the server has to send images to all four workstations simultaneously, the transmission rate to each WS is about 4 Mbytes/s. Both situations are adequate for radiologic image communications for picture archiving and communication systems (PACS) and teleradiology applications.

Computer Communication Networks↗