Biomedical subjects

T Lawton

Publications and source records attributed to T Lawton.

11 recordsLinked to original sources

PubMed2001

STR primer concordance study.

Over 1500 population database samples comprising African Americans, Caucasians, Hispanics, Native Americans, Chamorros and Filipinos were typed using the PowerPlex 16 and the Profiler Plus/COfiler kits. Except for the D8S1179 locus in Chamorros and Filipinos from Guam, there were eight examples in which a typing difference due to allele dropout was observed. At the D8S1179 locus in the population samples from Guam, there were 13 examples of allele dropout observed when using the Profiler Plus kit. The data support that the primers used in the PowerPlex 16, Profiler Plus, and COfiler kits are reliable for typing reference samples that are for use in CODIS. In addition, allele frequency databases have been established for the STR loci Penta D and Penta E. Both loci are highly polymorphic.

Alleles↗

PubMed2001

The impact of a multidisciplinary breast cancer center on recommendations for patient management: the University of Pennsylvania experience.

BACKGROUND: Advances in the diagnosis and treatment of breast carcinoma have led to a multidisciplinary approach to management for patients with breast carcinoma. To assess the effect of this approach, the authors performed an evaluation for a cohort of patients examined in a multidisciplinary breast cancer center. METHODS: An analysis was performed for the records of 75 consecutive women with 77 breast lesions examined in consultation in a multidisciplinary breast cancer center between January and June 1998. Each patient's case was evaluated by a panel consisting of a medical oncologist, surgical oncologist, radiation oncologist, pathologist, diagnostic radiologist, and, when indicated, plastic surgeon. A comprehensive history and physical examination was performed, and the relevant mammograms, pathology slides, and medical records were reviewed. Treatment recommendations made before this evaluation were compared with the consensus recommendations made by the panel. RESULTS: For the 75 patients, the multidisciplinary panel disagreed with the treatment recommendations from the outside physicians in 32 cases (43%), and agreed in 41 cases (55%). Two patients (3%) had no treatment recommendation before consultation. For the 32 patients with a disagreement, the treatment recommendations were breast-conservation treatment instead of mastectomy (n = 13; 41%) or reexcision (n = 2; 6%); further workup instead of immediate definitive treatment (n = 10; 31%); treatment based on major change in diagnosis on pathology review (n = 3; 9%); addition of postmastectomy radiation treatment (n = 3; 9%); or addition of hormonal therapy (n = 1; 3%). CONCLUSIONS: The multidisciplinary breast cancer evaluation program provided an integrated program in which individual patients were evaluated by a team of physicians and led to a change in treatment recommendation for 43% (32 of 75) of the patients examined. This multidisciplinary program provided important second opinions for many patients with breast carcinoma.

Adult↗

PubMed2000

Accuracy of sentinel lymph node biopsy in patients with large primary breast tumors.

BACKGROUND: Patients with large breast tumors are increasingly undergoing neoadjuvant treatment to downstage local disease; however, accurate staging of the axilla before the initiation of chemotherapy remains problematic. In the current study, the authors report on the accuracy of sentinel lymph node (SLN) biopsy in such patients to determine the feasibility of applying this technique before induction chemotherapy. METHODS: One hundred three patients with 104 tumors classified as American Joint Committee on Cancer (AJCC) T2 (tumor >/= 2 cm but </= 5 cm) or larger were recruited at the University of Pennsylvania and the Mayo Clinic. In the majority of cases, combined blue dye and radiotracer was used for SLN identification. After SLN identification, a completion axillary lymph node dissection was performed in 87 cases. The SLN was evaluated with hematoxylin and eosin and immunohistochemistry. RESULTS: The SLN was identified in 99% of cases. The overall rate of lymph node metastasis was 59% (95% exact confidence interval [95% CI], 49-68%) (61 of 104 cases). The SLN false-negative rate was 2% (95% exact CI, < 1-11.5%) (2 patients). In 56 tumors >/= 3 cm, 1 false-negative result (2% [95% exact CI, < 1-15%]) was identified, and the rate of lymph node metastasis was 62.5% (95% exact CI, 48. 5-75%) (35 of 56 tumors). Within 30 SLN positive patients with tumors >/= 3 cm and complete axillary lymph node dissection, 3 of 8 patients (37.5% [95% exact CI, 8.5-75.5%]) with micrometastasis (</= 2 mm) to the SLN had positive non-SLN compared with 21 of 22 patients (95.5% [95% exact CI, 77-100%]) with macrometastasis (> 2 mm) to the SLN (P = 0.002). CONCLUSIONS: SLN biopsy for patients with large breast tumors is technically feasible and highly accurate. SLN biopsy should be considered for the staging of clinically negative axilla in patients scheduled to receive neoadjuvant chemotherapy.

Adult↗

PubMed2000

Contrast-enhanced 3D MRA using SENSE.

Sensitivity encoding (SENSE) was used to improve the performance of three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA). Utilizing an array of receiver coils for sensitivity encoding, the encoding efficiency of gradient-echo imaging was increased by factors of up to three. The feasibility of the approach was demonstrated for imaging of the abdominal vasculature. On the one hand, using a SENSE reduction factor of two, the spatial resolution of a breath-hold scan of 17 seconds was improved to 1.0 x 2.0 x 2.0 mm(3). On the other hand, using threefold reduction, time-resolved 3D CE-MRA was performed with a true temporal resolution of 4 seconds, at a spatial resolution of 1.6 x 2.1 x 4.0 mm(3). CE-MRA with SENSE was performed in healthy volunteers and patients and compared with a standard protocol. Throughout, diagnostic quality images were obtained, showing the ability of sensitivity encoding to enhance spatial and/or temporal resolution considerably in clinical angiographic examinations.

Aged↗

PubMed1997

Analysis of estrogen receptor messenger RNA in breast carcinomas from archival specimens is predictive of tumor biology.

As the size of breast tumors continues to decrease, it has become more difficult to obtain adequate tumor tissue for molecular studies. We have used the estrogen receptor (ER) gene as a model to study the ability to perform a quantitative analysis of ER mRNA extracted from archival breast carcinoma specimens using reverse transcriptase polymerase chain reaction. Based upon ER mRNA abundance, tumors were characterized as having low, medium, or high ER mRNA expression. These data were compared with ER and progesterone receptor (PR) status determined by enzyme immunoassay, tumor histology, and Bloom-Richardson grade. Comparing the low and high ER mRNA groups, there were statistically significant differences in ER-positive status (10% versus 95%; P = 0.0001), PR-positive status (10% versus 90%; P = 0.0001), and tumor grade (2.67 +/- 0.12 versus 2.09 +/- 0.14; P = 0.0025). Of the 28 tumors in the high ER mRNA group, 5 (18%) were invasive lobular carcinomas whereas all 24 tumors with low ER mRNA were invasive ductal carcinomas. These data demonstrate that archival breast tumor specimens can be characterized for ER mRNA abundance. In addition, we conclude that the mechanisms regulating ER gene transcription influence the phenotype of breast carcinomas. These results also suggest that this technique can be designed to provide a quantitative analysis of gene expression for any gene of interest utilizing archival tumor specimens.

Blotting, Southern↗

PubMed1995

Primary structure and developmental expression of Fbn-1, the mouse fibrillin gene.

Previous studies have reported > 10 kilobases of human fibrillin-1 cDNA sequence, but a consensus regarding the 5' end of the transcript remains to be worked out. One approach to developing a clear consensus would be to search for regions of evolutionary conservation in transcripts from a related species such as mouse. As reported here, the mouse fibrillin-1 transcript encodes a highly conserved polypeptide of 2,871 amino acids. The upstream sequence that flanks the ATG is considerably less well conserved, however. Indeed, the ATG codon (which occurs in the context of a Kozak consensus sequence and is located just upstream of a consensus signal peptide) signals the point where human and mouse fibrillin-1 sequences cease to be nearly identical. Together, these results are consistent with previous efforts by Pereira et al. (Pereira, L., D'Alessio, M., Ramirez, F., Lynch, J. R., Sykes, B., Pangilinan, T., and Bonadio, J. (1993) Human Mol. Genet. 2, 961-968) to identify the human fibrillin-1 translational start site. Sequences immediately upstream of the ATG are GC-rich and devoid of TATA and CCAAT boxes, which suggests that the mouse fibrillin-1 gene will be broadly expressed. A survey of expression in mouse embryo tissues is consistent with this hypothesis and suggests two novel functions for fibrillin-associated microfibrils in non-elastic connective tissues.

Amino Acid Sequence↗

PubMed1993

In vitro alloreactivity against host antigens in an adult HLA-mismatched bone marrow transplant recipient despite in vivo host tolerance.

An adult recipient of an HLA-DR, DQ-mismatched, T cell-depleted bone marrow graft, who remains without graft versus host disease and who is not maintained on immunosuppressive therapy, was studied at 23 months posttransplantation for in vitro reactivity against the mismatched antigens of the host. The donor's PBMC's proliferated vigorously against the recipient's stimulators in the pretransplant mixed lymphocyte cultures (MLC). After transplant reconstitution, MLCs demonstrated that the in vitro response of engrafted donor T cells against host MHC class II antigens was equivalent to control allogeneic responses, while there was no detectable response against the donor's antigens. Posttransplantation limiting dilution analysis showed no difference between the precursor frequencies of antihost responders among populations of fresh donor PBMCs and among the engrafted cells of donor origin that are found circulating in the patient. This result suggests that clonal deletion is, at best, incomplete and that peripheral tolerance is essential in protecting this patient from GVHD. These findings also support the conclusion that bone marrow-derived thymic elements may be important for clonal deletion in human chimeras.

Adult↗

PubMed1992

Aggrecan core protein is expressed in membranous bone of the chick embryo. Molecular and biomechanical studies of normal and nanomelia embryos.

The recessive mutation nanomelia blocks the synthesis of a large aggregating proteoglycan (aggrecan) by avian embryo chondrocytes. Lack of aggrecan is associated with short stature, multiple morphological defects in cartilage, and embryo lethality. Bony defects have also been described, but were assumed to be a secondary consequence of the cartilage defect. However, two lines of evidence presented in this paper indicate that the aggrecan deficiency directly affects intramembranous bone. First, the morphology (i.e. projected area and shape) of certain membranous bones of nanomelia embryos was abnormal. Second, membranous bone from nanomelia embryos proved to be significantly stiffer in biomechanical tests that measured functional properties of the extracellular matrix. These findings were unexpected because intramembranous bones normally develop from mesenchyme and not from a cartilage intermediate, and they prompted a search for evidence of aggrecan expression in the bone of normal chick embryos. We report that: 1) aggrecan mRNA was identified by PCR analysis of total RNA isolated from day-13 chick embryo calvarium, 2) the PCR method successfully amplified aggrecan mRNA from primary chick embryo osteoblasts in culture, 3) in situ hybridization of membranous bone tissue sections demonstrated aggrecan expression by chick embryo osteoblasts in vivo, and 4) the aggrecan message was identified in Northern blots of calvarial mRNA probed at high stringency. The results of the molecular and biomechanical studies provide evidence that aggrecan is indeed expressed in membranous bone as well as cartilage. Altogether, these results suggest that aggrecan may contribute to the functional properties and the normal growth and development of avian membranous bone.

Aggrecans↗

PubMed1990

Role of interaction of CD2 molecules with lymphocyte function-associated antigen 3 in T-cell recognition of nominal antigen.

The role of the interaction of CD2 molecules with lymphocyte function-associated antigen 3 (LFA-3) in facilitating nominal antigen recognition by T lymphocytes was studied by utilizing an HLA-DR4-restricted CD4+ cytotoxic human T-cell clone specific for human immunodeficiency virus envelope glycoprotein gp120 as a responder and murine fibroblasts transfected with human class II major histocompatibility complex (MHC) and/or human LFA-3 molecules as antigen-presenting cells (APC). Although expression of the DR4 restriction element in fibroblasts is sufficient for T-cell recognition of a gp120 peptide as judged by induction of proliferation coexpression of human LFA-3 on DR4+ APC decreases the molar requirement of nominal antigen by greater than one order of magnitude. Both LFA-3 and the relevant class II MHC molecules are necessary for antigen-independent conjugate formation, but the binding is further enhanced by specific nominal antigen. CD2-LFA-3 interaction is independent of T-cell receptor-MHC interaction and contributes directly to the stabilized conjugate between the T cell and LFA-3-bearing APC; soluble CD2 and monoclonal antibodies to LFA-3 and CD2 reduce T-cell-APC binding to the level mediated by nominal antigen and MHC. During conjugate formation, CD2 but not CD3 molecules are reorganized into the cell-cell interaction site in an antigen-independent manner. Thus, reorganization and/or coassociation of CD2 with CD3 molecules is not essential for T-cell activation.

Animals↗

PubMed1989

Recognition of HIV glycoprotein gp120 by T cells. Role of monocyte CD4 in the presentation of gp120.

The HIV envelope glycoprotein gp120 binds with high affinity to CD4 and is responsible for the tropism of HIV for CD4+ T cells and monocytes. Efforts to develop HIV vaccines have focused on gp120 and, therefore, a detailed molecular understanding of human immune responses to gp120 is essential. In this report, we have used human T cell clones specific for gp120 to examine the processing and presentation of gp120 to T cells. In particular, we examined the role of the CD4 that is expressed at low levels on the surfaces of human monocytes in the presentation of gp120 by monocytes. The presentation of gp120 to gp120-specific human T cell clones was blocked by pretreatment of monocytes with anti-CD4 mAb. Blocking of monocyte CD4 with anti-CD4 did not inhibit presentation of other Ag or of synthetic peptides representing epitopes within gp120 recognized by gp120-specific T cell clones. These results indicated that the anti-CD4-mediated inhibition occurred at the level of the monocyte, was specific for the gp120 response, and was operative at the initial Ag uptake phase of the Ag-processing pathway. Definitive confirmation that monocyte CD4 functions in the initial uptake step of the gp120-processing pathway was obtained by using soluble CD4 to block the interaction of gp120 with monocyte CD4. These results demonstrate that gp120 expressed by human monocytes plays an important role in the initial uptake of gp120 by monocytes and that gp120 taken up via CD4 is subsequently processed to allow for exposure of epitopes recognized by gp120-specific human T cells. At limiting gp120 concentrations, uptake via CD4 is essential for the presentation of gp120.

Antigen-Presenting Cells↗

PubMed1988

Analysis of host-virus interactions in AIDS with anti-gp120 T cell clones: effect of HIV sequence variation and a mechanism for CD4+ cell depletion.

The primary human T cell response to HIV was analyzed by isolating from seronegative donors T cell clones specific for HIV gp120. T cell epitopes restricted by different MHC elements were identified within gp120, and synthetic peptides were used to address the fundamental problem of how HIV sequence variability affects T cell recognition. Even one conservative substitution can drastically reduce recognition; thus the interaction of gp120 epitopes with T cell receptors and MHC is precise and poorly crossreactive. Importantly, a subset of CD4+ gp120-specific clones manifest cytolytic activity and lyse uninfected autologous CD4+Ia+ T cells in the presence of gp120 in a process that is strictly dependent upon CD4-mediated uptake of gp120 by T cells. Assuming gp120 is shed from HIV-infected cells in vivo, this novel CD4-dependent autocytolytic mechanism may contribute to the profound depletion of CD4+ cells in AIDS.

Acquired Immunodeficiency Syndrome↗