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Biomedical subjects

D W Chang

Publications and source records attributed to D W Chang.

29 records · Page 2Linked to original sources
PubMed2000

The influence of patient age on primary care resident physician-patient interaction.

OBJECTIVES: To explore resident physician-patient interaction in primary care to address issues relevant to quality of care for older people. DESIGN: A sample of 509 new, adult, nonpregnant patients was assigned to the care of second- and third-year residents in primary care clinics. Care was compared for three subgroups of patients: older patients (65 years or older; n = 45), those aged 18 to 44 years (n = 320), and those aged 45 to 64 years (n = 144). SETTING: Observations were made at the family medicine and general internal medicine clinics at the University of California, Davis. MEASUREMENTS: Self-report by means of the Medical Outcomes Study Short Form-36 (MOS SF-36) was used to determine patient demographics and patient health status. Two measures of satisfaction were obtained gauging reaction to medical care in general and to the videotaped visit specifically. Videotapes were coded for content using the Davis Observation Code. RESULTS: Self-reported health status of older persons was poorer than that of younger groups as measured by the MOS SF-36. Differences in demographics were explored and then controlled, along with physical health status in subsequent analyses. Supporting prior studies, this study found that older patients had more return visits and reported higher levels of satisfaction than did younger comparison groups. Contrary to prior literature, older patients were found to have longer visits than did younger cohorts. The physician-patient interaction was significantly different in many areas between these three groups. Whereas older patients experienced more chatting in their visits, they were given less counseling, asked fewer questions, had less discussion about their families and their use of substances, were asked to change their health behavior habits less often, and were given less health education. For older patients, more of each visit was spent checking on compliance with earlier treatment and developing treatment plans. CONCLUSIONS: These results provide a new and more detailed view of how resident physician-patient interaction differs between older and younger groups and raise important issues on whether quality of care needs for this population are being adequately addressed, particularly regarding mental health issues.

Adolescent↗
PubMed2000

The c-Myc transactivation domain is a direct modulator of apoptotic versus proliferative signals.

We have assayed the oncogenic, proliferative, and apoptotic activities of the frequent mutations that occur in the c-myc gene in Burkitt's lymphomas. Some alleles have a modest (50 to 60%) increase in transforming activity; however, the most frequent Burkitt's lymphoma allele (T58I) had an unexpected substantial decrease in transforming activity (85%). All alleles restored the proliferation function of c-Myc in cells that grow slowly due to a c-myc knockout. There was discordance for some alleles between apoptotic and oncogenic activities, but only the T58A allele had elevated transforming activity with a concomitant reduced apoptotic potential. We discovered a novel missense mutation, MycS71F, that had a very low apoptotic activity compared to wild-type Myc, yet this mutation has never been found in lymphomas, suggesting that there is no strong selection for antiapoptotic c-Myc alleles. MycS71F also induced very low levels of cytochrome c release from mitochondria, suggesting a mechanism of action for this mutation. Phosphopeptide mapping provided a biochemical basis for the dramatically different biological activities of the transformation-defective T58I and transformation-enhanced T58A c-Myc alleles. Furthermore, the antiapoptotic survival factor insulin-like growth factor 1 was found to suppress phosphorylation of T58, suggesting that the c-Myc transactivation domain is a direct target of survival signals.

Animals↗
PubMed1999

Incision at nucleotide insertions/deletions and base pair mismatches by the SP nuclease of spinach.

Spinach leaves contain a highly active nuclease called SP. The purified enzyme incises single-stranded DNA, RNA, and double-stranded DNA that has been destabilized by A-T-rich regions and DNA lesions [Strickland et al. (1991) Biochemistry 30, 9749-9756]. This broad range of activity has suggested that SP may be similar to a family of nucleases represented by S1, P1, and the mung bean nuclease. However, unlike these single-stranded nucleases that require acidic pH and low ionic strength conditions, SP has a neutral pH optimum and is active over a wide range of salt concentrations. We have extended these findings and showed that an outstanding substrate for SP is a mismatched DNA duplex. For base-substitution mismatches, SP incises at all mismatches except those containing a guanine residue. SP also cuts at insertion/deletions of one or more nucleotides. Where the extrahelical DNA loop contains one nucleotide, the preference of extrahelical nucleotide is A >> T approximately C but undetectable at G. The inability of SP to cut at guanine residues and the favoring of A-T-rich regions distinguish SP from the CEL I family of neutral pH mismatch endonucleases recently discovered in celery and other plants [Oleykowski et al. (1998) Nucleic Acids Res. 26, 4597-4602]. SP, like CEL I, does not turn over after incision at a mismatched site in vitro. Similar to CEL I, the presence of a DNA polymerase or a DNA ligase allows SP to turn over and stimulate its activity in vitro by about 20-fold. The possibility that the SP nuclease may be a natural variant of the CEL I family of mismatch endonucleases is discussed.

Adenine↗
PubMed1998

Anticatabolic and anabolic strategies in critical illness: a review of current treatment modalities.

Critically ill patients characteristically exhibit a pronounced catabolism in addition to a down-regulation of normal anabolic activity, leading to major complications from loss of body protein stores. The marked decrease in lean body mass and protein stores leads to the loss of essential structural and functional proteins required for restoring and maintaining homeostasis. The standard management of the catabolic response to injury and illness has centered on optimizing nutrient intake that modulates but does not reverse the process. Complications of ongoing catabolism therefore remain a major cause of morbidity. Addition of anticatabolic and anabolic agents that may counteract "the stress response to injury or illness" may be of significant clinical benefit. Agents currently available for clinical use, which will be described, can be divided into two groups. The first group are nutrients and nutrient metabolites, namely protein and the specific amino acids, glutamine, arginine, and branched chain amino acids, especially leucine. The second group are anabolic hormones, namely growth hormone, testosterone, and the testosterone analog oxandrolone. The pros and cons of these agents, as to their anabolic and anticatabolic value, are described.

Anabolic Agents↗
PubMed1995

Using the split Latram for better breast projection in breast reconstruction.

Over the years, although methods of breast reconstruction have improved, the ability to build a symmetrical projecting breast has not. When stacked Meme implants were used, better projection was obtained. Folding the transverse rectus abdominis musculocutaneous flaps allows for good projection; however, the breast is then quite wide and large. For smaller breast women with projection and some larger breasted women as well, splitting and stacked flaps give a much better result. We now do this procedure with simultaneous Latram and mastectomy surgery in fewer than 3 hours.

Breast Neoplasms↗
PubMed1995

Pseudolymphoma of the breast.

A 27-year-old woman presented with a chronic mastitis treated by subcutaneous mastectomy and a deepithelialized TRAM flap reconstruction. The pathology indicated pseudolymphoma of the breast, a rare benign condition. The course of treatment and a brief description of the pathology are given.

Adult↗
PubMed1993

The Exo-gap method employing the phage f1 endonuclease generates a nested set of unidirectional deletions.

An Exo-gap method for producing a nested set of unidirectional deletions in a piece of cloned DNA is described. The protein (pII) encoded by gene II of phage f1 makes a single-stranded (ss) nick at the f1 origin of replication (ori) in supercoiled DNA. Many phagemids, such as pBluescriptSK+ contain this ori on one side of the multiple cloning site, thereby permitting purified pII endonuclease to create a nick at one end of a cloned DNA insert. The nick may be expanded into gaps of increasing size by the timed 3' to 5' exonuclease (Exo) activity of the Vent DNA polymerase. Double-stranded deletions are produced by subsequent treatment with ss-specific mung bean nuclease. After size fractionation by agarose-gel electrophoresis, the DNA from the melted gel slices is ligated and transfected into host cells to produce a set of plasmids that contain a unidirectional nested set of deletions. This deletion method is independent of restriction sites, requires only one universal DNA primer to sequence a cloned insert, and may be applied to virtually any cloned segment given the unique nature of the 46-bp recognition site for pII endonuclease.

Bacteriophages↗
PubMed1986

Syngeneic monoclonal internal image anti-idiotopes as prophylactic vaccines.

A syngeneic monoclonal anti-idiotope that behaves as an internal image of the mammalian reovirus type 3 cellular attachment protein (viral hemagglutinin) was used in the syngeneic host for the induction of a prophylactic anti-viral antibody response. These studies were performed without the aid of co-stimulation by viral antigens. The high stringency of this system enables us to define the maximum constraints on the use of anti-idiotopes as anti-viral vaccines. We have used the murine BALB/c monoclonal IgM anti-idiotope 87.92.6 to study the idiotope and antigen specificity, kinetics, dose dependence, adjuvant, carrier, and valency requirements of anti-idiotope-induced anti-viral antibody responses. These studies show that the production of high titer neutralizing antibody requires a lengthy (60 day) immunization protocol, which includes the use of adjuvant and multivalent anti-idiotope, and is dependent on anti-idiotope concentrations of greater than 50 micrograms. When administered in this manner anti-idiotope can stimulate serotype-specific antibody responses across species barriers at levels comparable with those obtained after inoculation with virus. The practical efficacy of these reagents and procedures is documented by the ability of maternal immunization with anti-idiotope to confer complete protection in neonates from a potentially lethal reovirus type 3 viral infection.

Animals↗
PubMed1984

[Skin tests in asthmatic patients in Taiwan].

During the 22-year period from February, 1961 to December, 1982, 3550 asthmatic patients who visited the Taipei Municipal Chung-shing Hospital were skin tested with 35 allergens. The following results were obtained: The patients showed high skin reactivity to only inhaled allergens with positive rates in the order of 90.2% for house dust, 79.9% for candida, 73.0% for alternaria, 71.7% for aspergillus, 65.5% for cladosporium, 58.4% for tatami, 54.5% for penicillum and 52.3% for ragweed. While the sex had no influence on the incidence of skin test positivity, the positive rate peaked at around 20 to 30 years of age and decreased gradually thereafter. There was a significant correlation between PK titer and antigen threshold (r = +0.68). Although the healthy controls also showed positive skin reaction to house dust, none of them had an antigen threshold of higher than 16 (i.e. 16,000 X final dilution). Therefore an antigen threshold of 16 was suggested to be used as the cut point for the diagnosis of house dust allergen.

Adolescent↗
PubMedDate not supplied

Microvascular reconstruction of the skull base.

Cranial base reconstruction is challenging, not only because of its technical difficulty, but also because of the potentially life-threatening complications that may arise in the case of reconstructive failure. Thus, a successful outcome following skull base tumor ablation often depends as much on the reconstruction as it does on the resection. Before the advent of free tissue transfers, cranial base surgery was often limited by our inability to repair defects adequately. Free tissue transfer has been shown to be safe and effective in skull base reconstruction, and provides an opportunity for wide surgical excision of dura and skull base structures to obtain tumor-free margins. With proper patient selection and with strict adherence to the basic principles of cranial base reconstruction, including watertight dural repair and the use of well-vascularized tissue to cover the exposed dura and obliterate the dead space, successful cranial base reconstruction can be achieved. Semin. Surg. Oncol. 19:211-217, 2000.

Dura Mater↗