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Biomedical subjects

M Hart

Publications and source records attributed to M Hart.

At least 19 recordsLinked to original sources
PubMed2004

Transgenic mice overexpressing both amyloid beta-protein and perlecan in pancreatic acinar cells.

Heparan sulfate proteoglycans such as perlecan are thought to facilitate amyloid fibril formation. Tg3695 mice overexpress perlecan core protein in many tissues including the brain and pancreas. Tg13592 mice overexpress the signal plus 99-amino acid carboxyl terminal sequences (C99) of amyloid beta-protein precursor in multiple tissues and develop amyloid deposits in the pancreas. To investigate a role of perlecan in beta-amyloidosis, we established doubly transgenic mice by crossing the two lines of transgenic mice. The expression levels of the two transgenes remained unchanged in the brain and pancreas and the doubly transgenic mice did not develop amyloid deposits in the brain up to 19-months of age. Amyloid load detected by thioflavine S in the pancreas of the doubly transgenic mice was not significantly different from that in the transgenic littermates expressing only C99. Amyloid load in the pancreas increased during aging. We found a positive correlation between the Abeta-immunoreactive (non-fibrillar and fibrillar) and thioflavine S-positive (fibrillar) Abeta deposits in the single (C99) but not doubly transgenic mice. Our results suggest that perlecan does not independently influence amyloid formation in the pancreas of the transgenic mice and that there may be other factors that may modulate amyloid formation together with perlecan.

Aging↗
PubMed2001

Utility of azapeptides as major histocompatibility complex class II protein ligands for T-cell activation.

Major histocompatibility complex class II (MHC II) protein binding and antigen specific activation of CD4+ "helper" T cells are demonstrated with peptides composed of the antigenic hen egg ovalbumin 325-339 peptide (OVA) substituted with azaamino acids. AzaAla and azaGly substitutions were made at 10 sequential peptide positions (326Ala-335Asn) that lie in the binding groove. The peptide positions substituted with azaamino acids encompass almost the entire binding groove, including positions where the identity of the amino acid side chain is known to have the most significant effect on MHC binding and the least effect on T-cell recognition. In addition, the T-cell contact 333Glu was substituted with azaGlu to generate a partial agonist ligand for the 3DO-54.8 T-cell hybridoma. Binding to MHC II protein was assayed by measuring the kinetic stability of complexes formed between detergent-solubilized MHC II I-A(d) protein and fluorescein-labeled OVA peptides using a fluorescence-HPLC assay. T-cell activation was also evaluated for aza-substituted peptides with azaamino acid substitutions at the peptide positions known to interact with the MHC II protein. All aza-substituted peptides showed detectable MHC binding, and some were found to show T-cell activation potency equal to the native peptide. Several of these were also found to be weak or partial agonists. Our results demonstrate that azaamino acids substituted into an antigenic peptide cause a subtle, global effect on peptide conformation that can be used to design altered peptide ligands (APL) as T-cell partial agonists. These may have potential as T-cell epitopes for synthetic vaccines and therapeutic agents for autoimmune diseases.

Amino Acid Sequence↗
PubMed2001

Ureteral obstruction in a transplant kidney caused by an ovarian tumor.

Ureteral obstruction in the transplant recipient can provide a diagnostic challenge. We report a case of ureteral obstruction 5 years after cadaveric renal transplantation due to an ovarian tumor. Magnetic resonance imaging provided essential anatomic information that eventually led to the diagnosis. To our knowledge, this is the first reported case of ureteral obstruction in a transplant kidney caused by an ovarian tumor.

Adult↗
PubMed2001

Overproduction of perlecan core protein in cultured cells and transgenic mice.

Heparan sulphate proteoglycan (HSPG) and amyloid P component are the only macromolecules consistently associated with all varieties of amyloid, irrespective of the type of amyloid protein, suggesting that HSPG may play a pathogenetic role in amyloid formation through a common mechanism. In the case of Alzheimer's disease (AD), HSPG, such as perlecan, co-accumulates with amyloid-beta protein (Abeta), a main constituent of amyloid plaques, and paired helical filaments (PHFs). Additionally, in vitro, HSPG accelerates both Abeta fibril and PHF formation and protects Abeta from degradation. Therefore, this study first established lines of P19 mouse embryonic carcinoma cells stably carrying an expression vector encoding the complete perlecan core protein (approximately 400 kD). In the cell lysates, overexpressed perlecan was identified as an approximately 400 kD protein without glycosaminoglycan side-chains, while in the media, secreted perlecan was mostly glycosylated, suggesting that the secretion and glycosylation of perlecan are coupled. Next, transgenic mice were produced using the same expression vector. Marked perlecan overexpression occurred in the cytoplasm of multiple tissues including the brain, heart, kidney, and pancreas, without a discernible increase of perlecan in extracellular matrices. The transgenic mice up to 18 months of age did not develop amyloid or AD-like pathology in the brain or elsewhere, based on histochemical and immunohistochemical analyses. Thus, overproduction of perlecan core protein is insufficient to lead to amyloidosis and AD-like pathology.

Alzheimer Disease↗
PubMed2000

Generalized strategies in the minority game.

We show analytically how the fluctuations (i.e., standard deviation sigma) in the minority game can decrease below the random coin-toss limit if the agents use more general, stochastic strategies. This suppression of sigma results from a cancellation between the actions of a crowd, in which agents act collectively and make the same decision, and those of an anticrowd, in which agents act collectively by making the opposite decision to the crowd.

Journal Article↗
PubMed2000

A t(2;19)(p13;p13.2) in a giant invasive cardiac lipoma from a patient with multiple lipomatosis.

Cardiac lipomas occur infrequently but account for a significant portion of rare cardiac tumors. Common cutaneous lipomas have previously been associated with rearrangements of chromosome band 12q15, which often disrupt the high-mobility-group protein gene HMGIC. In this report, we describe the cytogenetic analysis of an unusual giant cardiac lipoma that exhibited myocardial invasion in a patient with a history of multiple lipomatosis (cutaneous lipoma, lipomatous gynecomastia, lipomatous hypertrophy of the interatrial septum, and dyslipidemia). Cytogenetic studies of cells derived from the cardiac lipoma demonstrated no abnormalities of chromosome 12, but did reveal a t(2;19)(p13;p13.2). A liposarcoma-derived oncogene (p115-RhoGEF) previously mapped to chromosome 19 and the low-density lipoprotein receptor gene (LDLR) previously mapped to chromosome band 19p13 were evaluated to determine whether they were disrupted by this translocation. Fluorescence in situ hybridization analyses assigned p115-RhoGEF to chromosome 19 in bands q13.2-q13.3 and mapped the LDLR to chromosome arm 19p in segment 13.2, but centromeric to the t(2;19) breakpoint. Thus, these genes are unlikely to be involved in the t(2;19)(p13;p13.2). Further studies of the regions of chromosomes 2 and 19 perturbed by the translocation in this unusual infiltrating cardiac lipoma will identify gene(s) that participate in adipocyte growth and differentiation and may provide insight into syndromes of multiple lipomatosis.

Chromosomes, Human, Pair 19↗
PubMed2000

Epstein-Barr virus-dependent lymphoproliferative disease: critical role of IL-6.

Epstein-Barr virus (EBV)-induced lymphoproliferative disease (lpd) is a B cell neoplasm that affects patients who are immunosuppressed in the context of organ transplantation or HIV infection. A model for the aggressive form of this entity was generated by xenotransplantation of SCID mice with human peripheral blood leukocytes from individuals with prior contact with EBV. This model, where large B cell lymphoma occurs, was used to test the hypothesis that IL-6 has a major role in EBV-induced B cell tumorigenesis. IL-6 is known to differentiate B cells into immunoglobulin-secreting plasma cells and induce EBV replication, and xenochimeric animals have detectable serum levels of human IL-6. Human IL-6 inhibition with a neutralizing monoclonal antibody decreased tumor incidence from 62 % to 27 %. In addition, anti-IL-6 treatment significantly improved xenotransplanted animal survival, with median survival at > 245 days when compared to that of controls at 132 days. In conclusion, IL-6 plays a critical role in the pathogenesis of EBV-induced human lpd, and IL-6 inhibition may represent a new and promising preventive or therapeutic approach against this malignancy.

Animals↗
PubMed2000

Phylogenetic analyses of mode of larval development.

Phylogenies based on morphological or molecular characters have been used to provide an evolutionary context for analysis of larval evolution. Studies of gastropods, bivalves, tunicates, sea stars, sea urchins, and polychaetes have revealed massive parallel evolution of similar larval forms. Some of these studies were designed to test, and have rejected, the species selection hypothesis for evolutionary trends in the frequency of derived larvae or life history traits. However, the lack of well supported models of larval character evolution leave some doubt about the quality of inferences of larval evolution from phylogenies of living taxa. Better models based on maximum likelihood methods and known prior probabilities of larval character state changes will improve our understanding of the history of larval evolution.

Animals↗
PubMed2000

Accumulation of amyloid-beta protein in exocrine glands of transgenic mice overexpressing a carboxyl terminal portion of amyloid protein precursor.

Amyloid-beta protein (Abeta) and its precursor (betaPP) play important roles in the pathogenesis of Alzheimer disease and inclusion-body myositis. In humans, Abeta deposits are found in brain, skeletal muscle, and skin. Therefore, we have investigated possible Abeta deposits in multiple tissues of two transgenic mouse lines overexpressing the signal plus Abeta-bearing 99-amino acid carboxyl terminal sequences of betaPP under the control of a cytomegalovirus enhancer/beta-actin promoter. One of the lines developed Abeta-immunoreactive intracellular deposits consistently in the pancreas and lacrimal gland, and occasionally in gastric, DeSteno's, and lingual glands. Although the Abeta deposits increased during ageing and degenerative changes of the tissues were observed, little or no extracellular Abeta deposits were observed up to the age of 25 months. These lines of transgenic mice are useful for studying the molecular mechanisms of development and clearance of intracellular Abeta deposits.

Aging↗
PubMed2000

Case management model for a community-based multiple sclerosis clinic.

This article describes the process from inception to successful operation of a case management model of a community-based multiple sclerosis clinic. The article includes information regarding the pathophysiology, diagnosis, and clinical manifestations of multiple sclerosis. The assessment, planning, and intervention stages of the process are explained, and a case study of one clinic patient is provided.

Adult↗
PubMed2000

Utilization and outcome in an overnight psychiatric observation program at a Veterans Affairs Medical Center.

OBJECTIVE: The effectiveness of an overnight psychiatric observation program was evaluated. The program was designed to avoid unnecessary hospitalization of patients experiencing acute psychiatric crises. METHODS: Of 110 patients admitted to the observation unit at a Veterans Affairs medical center over a six-month period in 1996, the charts of 92 patients were retrospectively reviewed. Characteristics of patients referred to the program were documented, inpatient hospitalization rates and suicide rates in the six-month periods before and after admission to the observation unit were examined, and variables related to the need for hospitalization immediately after observation were explored. RESULTS: Most of the 92 patients (98 percent) were referred from the medical center's emergency room. At the time of observation, 80 percent of the patients were unemployed, 55 percent expressed suicidal or homicidal ideation, 49 percent were intoxicated or at risk for alcohol withdrawal, and 41 percent were homeless. The most frequent psychiatric diagnosis was substance abuse or dependence (77 percent). The large majority of patients (88 percent) were referred the next day to other outpatient programs for follow-up and treatment, which avoided costly inpatient treatment. In the six months before admission to the observation program, the mean number of inpatient psychiatric bed days was 9.8, compared with 2.7 days in the six-month period after discharge from the observation program. No increase in suicide gestures or attempts was noted among the patients. No variables significantly predicted admission to inpatient care after the observation period. CONCLUSIONS: Overnight observation programs may provide a cost-effective alternative to traditional inpatient treatment for some individuals with psychiatric disorders.

Adult↗
PubMed1999

A tyrosine-phosphorylated protein that binds to an important regulatory region on the cool family of p21-activated kinase-binding proteins.

The p21-activated kinases (Pak) are major targets of the small GTPases Cdc42 and Rac. We, and others, recently identified a family of proteins termed Cool/Pix, which interact with Pak3. In cells, p50(Cool-1) suppresses Pak activation by upstream activators; p85(Cool-1) has a permissive effect on Pak activation, and we now show that the closely related Cool-2 stimulates Pak kinase activity. To understand the differential regulation of Pak by Cool proteins, we screened for Cool-interacting proteins by affinity purification and microsequencing. This has led to the identification of two closely related proteins called Cat (Cool-associated, tyrosine phosphorylated), which contain a zinc finger followed by three ankyrin repeats. Cat-1 is identical to the recently identified binding partner for the beta-adrenergic receptor kinase (betaARK or GRK-2), which was shown to have Arf-GAP activity. Cat-1 and Cat-2 both bind to the COOH-terminal region of p85(Cool-1) and p85(Cool-2) but do not bind to p50(Cool-1). Cat-1 is tyrosine-phosphorylated in growing NIH 3T3 fibroblasts, and its tyrosine phosphorylation is increased following cell spreading on fibronectin, decreased in cells arrested in mitosis, and increased in the ensuing G(1) phase. Cat proteins are tyrosine-phosphorylated when co-expressed in cells with the focal adhesion kinase Fak and Src. These findings suggest that in addition to playing a role in Cool/Pak interactions, Cat proteins may serve as points of convergence between G protein-coupled receptors, integrins, Arf GTPases, cell cycle regulators, and Cdc42/Rac/Pak signaling pathways.

Adaptor Proteins, Signal Transducing↗
PubMed1999

The F-box protein beta-TrCP associates with phosphorylated beta-catenin and regulates its activity in the cell.

Defects in beta-catenin regulation contribute to the neoplastic transformation of mammalian cells. Dysregulation of beta-catenin can result from missense mutations that affect critical sites of phosphorylation by glycogen synthase kinase 3beta (GSK3beta). Given that phosphorylation can regulate targeted degradation of beta-catenin by the proteasome, beta-catenin might interact with an E3 ubiquitin ligase complex containing an F-box protein, as is the case for certain cell cycle regulators. Accordingly, disruption of the Drosophila F-box protein Slimb upregulates the beta-catenin homolog Armadillo. We reasoned that the human homologs of Slimb - beta-TrCP and its isoform beta-TrCP2 (KIAA0696) - might interact with beta-catenin. We found that the binding of beta-TrCP to beta-catenin was direct and dependent upon the WD40 repeat sequences in beta-TrCP and on phosphorylation of the GSK3beta sites in beta-catenin. Endogenous beta-catenin and beta-TrCP could be coimmunoprecipitated from mammalian cells. Overexpression of wild-type beta-TrCP in mammalian cells promoted the downregulation of beta-catenin, whereas overexpression of a dominant-negative deletion mutant upregulated beta-catenin protein levels and activated signaling dependent on the transcription factor Tcf. In contrast, beta-TrCP2 did not associate with beta-catenin. We conclude that beta-TrCP is a component of an E3 ubiquitin ligase that is responsible for the targeted degradation of phosphorylated beta-catenin.

Animals↗
PubMed1999

Defects in the regulation of beta-catenin in colorectal cancer.

The molecular events that contribute to the progression of colon cancer are beginning to unravel. An initiating and probably obligatory event is the oncogenic activation of beta-catenin. This can come about by the loss of its negative regulator the adenomatous polyposis coli (APC) protein, or by mutations in the beta-catenin gene that result in a more stable protein product. The interaction between APC and beta-catenin, and additional proteins that affect assembly and signaling along this pathway, are discussed.

Animals↗
PubMed1999

Patients with systemic lupus erythematosus with high plasma levels of sFas risk relapse.

OBJECTIVE: We related soluble Fas (sFas) levels to the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) in a longitudinal series of plasma samples of patients with SLE to evaluate the relation between excessive production of sFas and disease activity. METHODS: We generated 21 monoclonal antibodies against Fas. Two of these were used to develop and validate a sensitive sandwich ELISA for the longitudinal analysis of sFas levels in plasma of 30 patients and 25 controls. RESULTS: At the start of followup, a significant elevation (p<0.0001) was found in sFas levels in SLE (1167+/-347 pg/ml sFas) compared to controls (618+/-98 pg/ml sFas). Also, at the start of the followup a significant difference (p = 0.0028) existed between patients who were going to have a relapse (1236+/-402 pg/ml sFas) during followup and patients who were not (809+/-276 pg/ml sFas). While sFas did not fluctuate with disease activity in individual patients, we found a strong correlation (r = 0.75, p<0.0001) between sFas and SLEDAI, but only at the time of relapse, when we analyzed the patients as a group. CONCLUSION: In individual patients with SLE, sFas does not fluctuate with disease activity. However, patients with high plasma levels of sFas are at risk of relapse.

Biomarkers↗
PubMed1998

Alzheimer's disease and heparan sulfate proteoglycan.

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder. Cardinal histopathologic changes of AD are neurofibrillary tangles (NFTs) and deposits of beta-amyloid protein (A-beta) in the form of neuritic plaques (NPs). Several different mutations found in patients with familial AD have been demonstrated to increase A-beta production, resulting in a common pathological cascade of beta-amyloidosis in the brain. Heparan sulfate proteoglycan (HSPG) has been co-localized with both A-beta in the NPs and NFTs. The proteoglycans are a family of complex macromolecules consisting of a protein core to which glycosaminoglycan (GAG) chains are covalently attached. HSPG has been shown to bind to A-beta, accelerate its fibril formation, and maintain its fibril stability. In AD and other neurodegenerative disorders, tau becomes hyperphosphorylated hence it is unable to bind to microtubules which results in the production of paired helical filaments, a building unit of NFTs. It has been shown in vitro that sulfated GAGs induce the formation of paired helical-like filaments under physiological conditions from tau. Furthermore, an interaction between HSPG and apolipoprotein E (a potent risk factor of AD) has been shown to be involved in neurodegeneration. Thus, substantial evidence exists to underscore important roles of HSPG in the etiology of AD.

Alzheimer Disease↗