Biomedical subjects

David George

Publications and source records attributed to David George.

7 recordsLinked to original sources

PubMed2003

Gene expression profiling reveals a highly specialized genetic program of plasma cells.

The formation of terminally differentiated plasma cells represents the critical final step in B-cell differentiation. In this study, utilizing oligonucleotide microarray analysis, we describe the highly specialized genetic profile exhibited by terminally differentiated plasma cells. A total of 1476 known genes were differentially expressed by plasma cells compared with B cells. Plasma cells displayed an up-regulation, induction, or a selective retention of a unique constellation of transcription factors, including members of the AP-1, nuclear factor-kappaB (NF-kappaB), nuclear factor of activated T cells (NFAT), and octamer binding factor families. Interestingly, plasma cells also displayed a down-regulation of several RNA polymerase I- related factors, consistent with terminal differentiation, and exhibited a down-regulation of the TATA box binding protein. Furthermore, plasma cells displayed alterations in multiple components of the Wnt and Notch signaling pathways and showed a unique pattern of apoptosis and proliferation-associated genes. Unexpectedly, plasma cells displayed an up-regulation of 2 factors normally associated with microenvironmental positioning of neuronal cells, reelin and neuropilin-1. These results supply insight into the developmental genetics of plasma cell differentiation and provide a foundation for further analysis of plasma cell biology.

Animals↗

PubMed2002

Interaction of the extracellular domain of the epidermal growth factor receptor with gangliosides.

Ganglioside GM3 inhibits epidermal growth factor (EGF)-dependent cell proliferation in a variety of cell lines. Both in vitro and in vivo, this glycosphingolipid inhibits the kinase activity of the EGF receptor (EGFR). Furthermore, membrane preparations containing EGFR can bind to GM3-coated surfaces. These data suggest that GM3 may interact directly with the EGFR. In this study, the interaction of gangliosides with the extracellular domain (ECD) of the EGFR was investigated. The purified human recombinant ECD from insect cells bound directly to ganglioside GM3. The ganglioside interaction site appears to be distinct from the EGF-binding site. In agreement with previous reports on the effects of specific gangliosides on EGFR kinase activity, the ECD preferentially interacted with GM3. The order of relative binding of other gangliosides investigated was as follows: GM3 GM2, GD3, GM4 > GM1, GD1a, GD1b, GT1b, GD2, GQ1b > lactosylceramide. These data suggest that NeuAc-lactose is essential for binding and that any sugar substitution reduces binding. In agreement with the specificity of soluble ECD binding to gangliosides, GM3 specifically inhibited EGFR autophosphorylation. Identification of a ganglioside interaction site on the ECD of the EGFR is consistent with the hypothesis that endogenous GM3 may function as a direct modulator of EGFR activity.

Animals↗

PubMed2002

Immunophenotypic differences between uveal and cutaneous melanomas.

OBJECTIVE: To determine the immunophenotypic differences between uveal and cutaneous melanomas, employing standard melanoma markers as well as p75 neurotrophin receptor (p75NTR) and microphthalmia transcription factor (MITF). DESIGN: Fifteen uveal melanomas (5 spindle, 5 epithelioid, and 5 mixed uveal subtypes) were immunolabeled with a panel of antibodies that included S100, tyrosinase, melan-A, HMB-45 and HMB-50 combination, MITF, and p75NTR. The results were tabulated on the basis of intensity and pervasiveness of the labeling and compared with a prior study on cutaneous spindle and epithelioid melanomas. RESULTS: In contrast to its strong labeling of cutaneous melanomas, S100 immunolabeling of uveal melanomas was weak and variable. p75NTR, known to differentiate spindle from epithelioid melanomas of the skin, did not immunolabel uveal melanomas. HMB-45, HMB-50, tyrosinase, melan-A, and MITF immunolabeled all uveal melanomas strongly, irrespective of the histologic subtype, but not cutaneous melanomas. Microphthalmia transcription factor was especially clear in its labeling of uveal melanomas. CONCLUSIONS: Although cutaneous and uveal melanomas share many molecular markers in common, there are differences between the 2 types of melanoma. First, the level of expression of S100 differs between cutaneous and uveal melanomas. Second, while cutaneous melanomas can be further subdivided into spindle and epithelioid types based on their immunophenotype, the uveal melanomas cannot.

Antigens, Neoplasm↗

PubMed2002

Clinical-pathological study of levodopa complications.

We sought to determine the continued benefit and the pattern of motor complications of long-term levodopa treatment in Parkinson's disease. Patients were evaluated between 1968 and 1996. Only those who had an adequate levodopa trial and in whom autopsy revealed Lewy body Parkinson's disease were included. Total levodopa and mean daily dose were calculated in each case. Dyskinesia, wearing-off and on-off were collectively classified as motor adverse effects and reported as cumulative incidence. Forty-two patients (male, 30; female, 12) with mean 15.9 years of illness and 9.1 years follow-up received on average 500-mg levodopa daily over 9.8 years. Seventeen of 21 patients assessed during the last 18 months of life reported some motor benefit. Adverse effects were seen in 71.4% of patients. The most common was dyskinesia, in 61.9%; wearing-off in 35.7%; and on-off in 16.7% of patients. The earliest adverse effect was dyskinesia and the last to emerge was on-off. Isolated dyskinesia was seen in 35.7% and wearing-off in 7.1% of patients; 15.5% of patients developed dyskinesia after 2.6 years and 31% after 6.4 years on levodopa. We concluded that levodopa benefit declined and adverse effects increased with time. Dyskinesia was the earliest and the most common isolated adverse effect.

Aged↗

PubMed2002

Progressive supranuclear palsy diagnosis and confounding features: report on 16 autopsied cases.

We evaluated 16 (15 men, 1 woman) autopsy-verified progressive supranuclear palsy (PSP) cases during 31 years (1969-2000) for clinical diagnosis and the course of the disease. The onset was gait difficulty or postural instability in 9 (56.3%), general motor slowing in 3 (18.8%), and tremor in 2. One case had onset with cognitive decline and 1 as hemidystonia. Four cases had supranuclear ophthalmoplegia (SNO) at the first assessment and were diagnosed as PSP. By last assessment, PSP diagnosis was made in 4 additional cases, but in 8 (50%) who never manifested ophthalmoplegia (mean 9.8 years after onset), PSP diagnosis was not made. Other manifestations included bulbar symptoms in 13 (81.3%), and cognitive impairment in 10 (62.5%) during the course of illness. Fifteen cases received levodopa, amantadine, anticholinergics, dopamine agonists, and selegiline in different combinations with symptomatic benefit in 9 of 15 (60%). Five had some improvement on levodopa alone and 3 showed more improvement when a dopamine agonist was added to levodopa. In general, the benefit was minimal and occurred only early in the course of illness. The mean age at onset was 63.7 (range, 53-85) years. Mean duration at PSP diagnosis was 4.8 (range, 2-11) years. Mean survival was 8.6 (range, 3-24) years and mean age at death was 72.3 (range, 60-89) years. When the different diagnostic criteria recommended in the literature were used, the accuracy of clinical diagnosis did not improve substantially.

Aged↗

PubMed2002

Engraftment assessment in human and mouse liver tissue after sex-mismatched liver cell transplantation by real-time quantitative PCR for Y chromosome sequences.

Transplanted hepatocytes can engraft, proliferate, and function permanently in host animals. After one cell infusion, however, engrafted hepatocytes constitute only between 1 in 200 to 1 in 3,000 host liver cells. Although transplanted cells can be identified using biochemical and molecular techniques, more accurate methods are needed to evaluate interventions that could improve cell engraftment rates. Real-time polymerase chain reaction (PCR) was done using primers and probes complementary to human testis determining gene (SRY) and mouse testis-specific Y-encoded protein (TSPY) pseudogene. Tissue samples from human or mouse recipients of liver cell transplantation were used to determine the test ability to detect transplanted cell DNA. Real-time PCR for the human SRY and mouse TSPY were species- and sex-specific. These two tests were sensitive in the detection of male DNA. Test sensitivity was consistently found at minimum 1:10,000 of male and female DNA mixing curve in both human SRY and mouse TSPY assays. The optimal amount of sample DNA per reaction to produce the highest sensitivity was 300 ng to 1 microg. Real-time PCR gave similar results whether standard male-female mixtures were prepared from liver cells or mononuclear cells. Engraftment of male liver cells in female liver tissues in mice and humans ranging from 0.125% to 0.257% was successfully measured using this method. Real-time PCR for SRY and TSPY affords a specific, sensitive, and reproducible tool for chimerism analysis in transplanted human and mouse liver tissues. This method could be used to optimize current models of cell transplantation.

Animals↗

PubMed2002

Clinical evaluation of a 15% in-office hydrogen peroxide tooth-whitening touch-up agent.

The success of tooth whitening has increased public demand for quicker results of the tooth-whitening process. More and more patients are opting for in-office treatments, if available, to expedite the process, and they are looking for ways to re-whiten quickly when they feel their teeth have reverted from their after-treatment results. This article will discuss the use of a commercially available product as a touch-up procedure for patients who had been previously treated with a 2-week carbamide peroxide whitening regimen.

Adolescent↗