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Biomedical subjects

Michael Weinstein

Publications and source records attributed to Michael Weinstein.

At least 19 recordsLinked to original sources
PubMed2006

Granulocyte macrophage colony-stimulating factor regulates dendritic cell content of atherosclerotic lesions.

OBJECTIVE: Recent evidence suggests that dendritic cells may play an important role in atherosclerosis. Based primarily on previous in vitro studies, we hypothesized that granulocyte macrophage colony-stimulating factor (GM-CSF)-deficient mice would have decreased dendritic cells in lesions. METHODS AND RESULTS: To test this, we characterized gene targeted GM-CSF(-/-) mice crossed to hypercholesterolemic low-density lipoprotein receptor null mice. Our results provide conclusive evidence that GM-CSF is a major regulator of dendritic cell formation in vivo. Aortic lesion sections in GM-CSF(-/-) low-density lipoprotein receptor null animals showed a dramatic 60% decrease in the content of dendritic cells as judged by CD11c staining but no change in the overall content of monocyte-derived cells. The GM-CSF-deficient mice exhibited a significant 20% to 50% decrease in the size of aortic lesions, depending on the location of the lesions. Other prominent changes in GM-CSF(-/-) mice were decreased lesional T cell content, decreased autoantibodies to oxidized lipids, and striking disruptions of the elastin fibers adjacent to the lesion. CONCLUSION: Given that GM-CSF is dramatically induced by oxidized lipids in endothelial cells, our data suggest that GM-CSF serves to regulate dendritic cell formation in lesions and that this, in turn, influences inflammation, plaque growth and possibly plaque stability.

Animals↗
PubMed2006

Mll partial tandem duplication induces aberrant Hox expression in vivo via specific epigenetic alterations.

We previously identified a rearrangement of mixed-lineage leukemia (MLL) gene (also known as ALL-1, HRX, and HTRX1), consisting of an in-frame partial tandem duplication (PTD) of exons 5 through 11 in the absence of a partner gene, occurring in approximately 4%-7% of patients with acute myeloid leukemia (AML) and normal cytogenetics, and associated with a poor prognosis. The mechanism by which the MLL PTD contributes to aberrant hematopoiesis and/or leukemia is unknown. To examine this, we generated a mouse knockin model in which exons 5 through 11 of the murine Mll gene were targeted to intron 4 of the endogenous Mll locus. Mll(PTD/WT) mice exhibit an alteration in the boundaries of normal homeobox (Hox) gene expression during embryogenesis, resulting in axial skeletal defects and increased numbers of hematopoietic progenitor cells. Mll(PTD/WT) mice overexpress Hoxa7, Hoxa9, and Hoxa10 in spleen, BM, and blood. An increase in histone H3/H4 acetylation and histone H3 lysine 4 (Lys4) methylation within the Hoxa7 and Hoxa9 promoters provides an epigenetic mechanism by which this overexpression occurs in vivo and an etiologic role for MLL PTD gain of function in the genesis of AML.

Animals↗
PubMed2006

Pro- and antiinflammatory cytokine signaling: reciprocal antagonism regulates interferon-gamma production by human natural killer cells.

Activated monocytes produce proinflammatory cytokines (monokines) such as interleukin (IL)-12, IL-15, and IL-18 for induction of interferon-gamma (IFN-gamma) by natural killer (NK) cells. NK cells provide the antiinflammatory cytokine transforming growth factor (TGF)-beta, an autocrine/negative regulator of IFN-gamma. The ability of one signaling pathway to prevail over the other is likely important in controlling IFN-gamma for the purposes of infection and autoimmunity, but the molecular mechanism(s) of how this counterregulation occurs is unknown. Here we show that in isolated human NK cells, proinflammatory monokines antagonize antiinflammatory TGF-beta signaling by downregulating the expression of the TGF-beta type II receptor, and its signaling intermediates SMAD2 and SMAD3. In contrast, TGF-beta utilizes SMAD2, SMAD3, and SMAD4 to suppress IFN-gamma and T-BET, a positive regulator of IFN-gamma. Indeed, activated NK cells from Smad3(-/-) mice produce more IFN-gamma in vivo than NK cells from wild-type mice. Collectively, our data suggest that pro- and antiinflammatory cytokine signaling reciprocally antagonize each other in an effort to prevail in the regulation of NK cell IFN-gamma production.

Animals↗
PubMed2006

Anatomy of the percutaneous presacral space for a novel fusion technique.

OBJECTIVES: Lumbar fusion has been widely used to treat unstable spinal disorders. Methods are evolving from open procedures to less invasive methods to avoid soft tissue trauma. Recently, a soft tissue sparing method to access the axial lumbosacral spine has been developed. It is crucial to determine structures potentially at risk for injury during this fusion technique. The anatomy of the presacral space and safety of the paracoccygeal approach were evaluated through cadaveric dissection and radiographic studies. The objective was to evaluate the safety of a paracoccygeal approach to the axial lumbosacral spine and determine structures that could potentially be injured. METHODS: The paracoccygeal approach was performed on two cadavers, followed by dissection. Distances from the midline trajectory of the approach to surrounding vascular structures were determined. Similar distances were also measured on computed tomography (CT) and magnetic resonance imaging (MRI) of 12 patients, as well as CT images of two additional patients. A "safe zone" was determined using the sagittal length of the presacral space and the distance between the most medial internal iliac vessel on the right and left, respectively. RESULTS: The coronal safe zone averaged 6.9 and 6.0 cm on MRI and CT, respectively. The mean distance from the anterior sacral margin to the rectum at the S3-S4 level was 1.2 and 1.3 cm on MRI and CT, respectively. CONCLUSION: In this study, we defined the "coronal safe zone" within the presacral space. This "safe zone" may guide surgeons when utilizing the percutaneous paracoccygeal approach.

Cadaver↗
PubMed2006

Seizures and encephalopathy as the presenting sign of viral gastroenteritis.

OBJECTIVES: To determine the incidence, nature, and outcome of encephalopathy associated with viral gastroenteritis in hospitalized children. METHODS: Retrospective chart review of all children during a 4-year period with viral gastroenteritis identified by International Classification of Diseases, Ninth Revision, Clinical Modification/International Classification of Diseases, Tenth Revision (ICD-9-CM/ICD-10) codes. Children with encephalopathy were defined as cases; the remainder served as controls. RESULTS: Thirteen (7.2%) of 181 children presented with encephalopathy (typical febrile seizures, 4; atypical febrile seizures, 4; afebrile seizures, 3; with alteration in level of consciousness alone, 2). Between cases and controls, the mean age (17.4 vs. 14.9 months, respectively) and temperature (38.4 degrees C vs. 38.5 degrees C, respectively) were not significantly different (mean age, P = 0.52; temperature, P = 0.61). The mean length of hospital stay was longer in children with encephalopathy (7 vs. 4.3 days; P = 0.03). All children recovered without sequelae. CONCLUSIONS: Encephalopathy, including afebrile seizures and nonconvulsive encephalopathy, is a relatively common presenting sign of acute viral gastrointestinal tract infection in hospitalized children, has a good outcome, but is associated with increased diagnostic testing and length of stay.

Female↗
PubMed2006

TGIF inhibits retinoid signaling.

TGIF (TG-interacting factor) represses transforming growth factor beta (TGF-beta)-activated gene expression and can repress transcription via a specific retinoid response element. Mutations in human TGIF are associated with holoprosencephaly, a severe defect of craniofacial development with both genetic and environmental causes. Both TGF-beta and retinoic acid signaling are implicated in craniofacial development. Here, we analyze the role of TGIF in regulating retinoid responsive gene expression. We demonstrate that TGIF interacts with the ligand binding domain of the RXRalpha retinoid receptor and represses transcription from retinoid response elements. TGIF recruits the general corepressor, CtBP, to RXRalpha, and this recruitment is required for full repression by TGIF. Interaction between TGIF and RXRalpha is reduced by the addition of retinoic acid, consistent with a role for TGIF as an RXRalpha transcriptional corepressor. We created a Tgif null mutation in mice and tested the sensitivity of mutant mice to increased levels of retinoic acid. Tgif mutant embryos are more sensitive to retinoic acid-induced teratogenesis, and retinoid target genes are expressed at a higher level in tissues from Tgif null mice. These results demonstrate an important role for TGIF as a transcriptional corepressor, which regulates developmental signaling by retinoic acid, and raises the possibility that TGIF may repress other RXR-dependent transcriptional responses.

Animals↗
PubMed2006

Efficacy of an individualized adherence support program with contingent reinforcement among nonadherent HIV-positive patients: results from a randomized trial.

OBJECTIVE: To evaluate the efficacy of a program designed to improve adherence to antiretroviral therapy among patients with poor adherence. METHODS: A randomized intervention trial was conducted among 90 HIV-positive patients experiencing treatment failure as a result of noncompliance with their medication regimen. Eligible participants were randomly assigned to an adherence case management intervention with monetary reinforcement (CM) or to a standard of care group (SC). The CM participants met regularly with a treatment advocate for individualized adherence support. Efficacy was measured in terms of reductions in viral load and improvements in immune function at weeks 12, 24, and 48. RESULTS: After 48 weeks, 55% (n=26) of those in the CM achieved at least a 1-log10 drop in viral load as compared to 28% (n=12) in the SC group (P=.0089). Furthermore, the mean CD4 count was 209 cells/mm3 for the CM group as compared to 150 cells/mm3 in the SC group (P=.0333). Based on logistic regression analysis, being in the CM was an independent predictor of reduction in viral load (odds ratio=2.49; P=.0514). CONCLUSION: The individualized adherence intervention is feasible and effective in reducing viral load and improving immune function.

Adult↗
PubMed2005

CDG-IL: an infant with a novel mutation in the ALG9 gene and additional phenotypic features.

We describe the second case of congenital disorder of glycosylation type IL (CDG-IL) caused by deficiency of the ALG9 a1,2 mannosyltransferase enzyme. The female infant's features included psychomotor retardation, seizures, hypotonia, diffuse brain atrophy with delayed myelination, failure to thrive, pericardial effusion, cystic renal disease, hepatosplenomegaly, esotropia, and inverted nipples. Lipodystrophy and dysmorphic facial features were absent. Magnetic resonance imaging of the brain showed volume loss in the cerebral hemispheres and cerebellum and delayed myelination. Laboratory investigations revealed low levels of multiple serum proteins including antithrombin III, factor XI, and cholesterol. Hypoglycosylation was confirmed by the typical CDG type 1 pattern of serum transferrin analyzed by isoelectric focusing. A defect in the ALG9 enzyme was suggested by the accumulation of the DolPP-GlcNAc2Man6 and DolPP-GlcNAc2Man8 in the patient's fibroblasts and confirmed by mutation analysis: the patient is homozygous for the ALG9 mutation p.Y286C. The causal effect of the mutation was shown by complementation assays in alg9 deficient yeast cells. The child described here further delineates the clinical spectrum of CDG-IL and confirms the significant clinical overlap amongst CDG subtypes.

Cathepsin A↗
PubMed2005

Baalc, a marker of mesoderm and muscle.

Transcripts of the Brain and Acute Leukemia, Cytoplasmic (BAALC) gene are expressed in human neuroectodermal tissues and in CD34-positive bone marrow cells. High transcript levels occur in leukemic blasts from some patients with acute myeloid leukemia (AML), where high expression is an independent marker of poor prognosis. To gain insight into the hitherto unknown function of BAALC/Baalc, we studied its protein expression in embryonic and adult mouse tissue by immunohistochemical analysis. Baalc protein was mainly expressed in developing and mature muscle cells (cardiac, skeletal, and smooth) beginning on day E9 (heart). Signal was seen in the pre-muscle mesodermal cells of the dermatomyotome regions, and the derivatives of the lateral plate and intermediate mesoderm such as smooth muscle wall of the esophagus, stomach, the gut tube, bronchi, small blood vessels, and urinary bladder. This pattern continued through the late embryonic stages into adulthood. Baalc appeared to localize in the cytoplasm, adjacent to the cell membrane. This is distinctly observed in adult skeletal muscle cells. Baalc co-localized with known muscle-associated proteins but not with neural crest or neuronal markers. Scattered expression in adult bone marrow hematopoietic cells and weak expression in the brain neuropil also occurred. In conclusion, BAALC/Baalc is a marker of the mesodermal lineage, especially muscle.

Animals↗
PubMed2005

Smad1 and Smad8 function similarly in mammalian central nervous system development.

Smads 1, 5, and 8 are the intracellular mediators for the bone morphogenetic proteins (BMPs), which play crucial roles during mammalian development. Previous research has shown that Smad1 is important in the formation of the allantois, while Smad5 has been shown to be critical in the process of angiogenesis. To further analyze the BMP-responsive Smads, we disrupted the murine Smad8 gene utilizing the Cre/loxP system. A Smad8 hypomorphic allele (Smad8(Deltaexon3)) was constructed that contains an in-frame deletion of exon 3, removing one-third of the MH2 domain and a small portion of the linker region. Xenopus injection assays indicated that this Smad8 deletion allele is still functional but has reduced ventralizing capability compared to the wild type. Although Smad8(Deltaexon3/Deltaexon3) embryos are phenotypically normal, homozygotes of another hypomorphic allele of Smad8 (Smad8(3loxP)) containing a neomycin cassette within intron 3, phenocopy an embryonic brain defect observed in roughly 22% of Smad1(+/)(-) embryos analyzed at embryonic day 11.5. These observations suggest that BMP-responsive Smads have critical functions in the development of the mammalian central nervous system.

Alleles↗
PubMed2004

Smad2 and Smad3 coordinately regulate craniofacial and endodermal development.

Ligands of the transforming growth factor-beta (TGF-beta) superfamily are involved in numerous developmental and disease processes. TGF-beta, activins, and nodal ligands operate through the highly homologous Smad2 and Smad3 intracellular mediators. Smad2 mutants exhibit early embryonic lethality, while Smad3 mutants are viable, but show a plethora of postnatal phenotypes, including immune dysfunction and skeletal abnormalities. Previously, we have shown that the Smad2 and Smad3 genes function cooperatively during liver morphogenesis. Here we show that Smad2 and Smad3 are required at a full dosage for normal embryonic development. Animals lacking one allele of each gene exhibit a variably penetrant phenotype in which structures in the anterior and ventral midline are reduced or lost; additionally, we demonstrate that this craniofacial defect and the previously reported hepatic phenotypes are both due to defects in the definitive endoderm. A reduction of endodermal gene expression as well as a failure to displace the visceral endoderm occurs despite the formation of a normal foregut pocket. This precedes any defects in anterior patterning and likely causes the abnormalities observed in craniofacial and midline development, as well as hepatogenesis.

Animals↗
PubMed2004

The inositol 3-phosphatase PTEN negatively regulates Fc gamma receptor signaling, but supports Toll-like receptor 4 signaling in murine peritoneal macrophages.

Fc gamma R clustering in macrophages activates signaling events that result in phagocytosis. Phagocytosis is accompanied by the generation harmful byproducts such as reactive oxygen radicals and production of inflammatory cytokines, which mandate that the phagocytic process be subject to a tight regulation. The molecular mechanisms involved in this regulation are not fully understood. In this study, we have examined the role of the inositol 3-phosphatase and tensin homologue deleted on chromosome 10 (PTEN) in Fc gamma R-induced macrophage function. We demonstrate that in ex vivo murine peritoneal macrophages that are deficient in PTEN expression, Fc gamma R-induced Akt and extracellular signal-regulated kinase phosphorylation are enhanced. Notably, PTEN(-/-) macrophages showed constitutively high phosphorylation of Akt. However, PTEN did not seem to influence tyrosine phosphorylation events induced by Fc gamma R clustering. Furthermore, PTEN(-/-) macrophages displayed enhanced phagocytic ability. Likewise, Fc gamma R-induced production of TNF-alpha, IL-6, and IL-10 was significantly elevated in PTEN(-/-) macrophages. Surprisingly, LPS-induced TNF-alpha production was down-regulated in PTEN(-/-) macrophages. Analyzing the molecular events leading to PTEN influence on LPS/Toll-like receptor 4 (TLR4) signaling, we found that LPS-induced activation of mitogen-activated protein kinases is suppressed in PTEN(-/-) cells. Previous reports indicated that LPS-induced mitogen-activated protein kinase activation is down-regulated by phosphatidylinositol 3-kinase through the activation of Akt. Our observation that Akt activation is basally enhanced in PTEN(-/-) cells suggests that PTEN supports TLR4-induced inflammatory responses by suppressing the activation of Akt. Thus, we conclude that PTEN is a negative regulator of Fc gamma R signaling, but a positive regulator of TLR4 signaling. These findings are the first to demonstrate a role for PTEN in Fc gamma R- and TLR4-mediated macrophage inflammatory response.

Animals↗
PubMed2004

Generation of novel conditional and hypomorphic alleles of the Smad2 gene.

Smad2 is an intracellular mediator of the transforming growth factor beta signaling (TGFbeta) pathway. It has been previously shown that, in the mouse, ablation of functional Smad2 results in embryonic lethality due to gastrulation defects. To circumvent the early lethality and study the spatially and temporally specific functions of Smad2, we utilized the Cre-loxP system to generate a Smad2 conditional allele. Here we show that a conditional allele, Smad2(flox), was generated. In this allele, exons 9 and 10 are flanked by loxP sites and the gene is functionally wildtype. Cre-mediated recombination results in a deletion allele which phenocopies our previously reported Smad2(DeltaC) null mutation. To generate this conditional allele, we first made a targeted mutation which introduced a floxed neo cassette into intron 10. This allele (Smad2(3loxP)) functions hypomorphically when placed opposite a null allele, and unlike the other published Smad2 hypomorphic allele, can be maintained in the homozygous state.

Alleles↗
PubMed2004

Effectiveness and safety of tissue plasminogen activator in the management of complicated parapneumonic effusions.

OBJECTIVE: The management of parapneumonic effusions in children is controversial. The objective of this study was to evaluate the effectiveness and safety of intrapleural tissue plasminogen activator (tPA) in children who require tube thoracostomy for drainage of a complicated parapneumonic effusion. METHODS: An observational cohort study was used to compare children who were treated with intrapleural tPA (either early or late administration) with children who were treated with thoracostomy tube drainage alone. RESULTS: Over a 6-year period, 12 children received early tPA (within 24 hours of diagnosis), 18 children received late tPA (>24 hours after diagnosis), and 23 children received thoracostomy tube drainage alone for the management of a complicated parapneumonic effusion. Total pleural fluid drainage was highest for the late tPA group (691 mL vs 360 mL in the control group); however, the rate of pleural fluid drainage was highest for the early tPA group (7 mL/h vs 3 mL/h in the control group). The duration of chest tube placement was 84 hours for the early tPA group, 209 hours for the late tPA group, and 130 hours for the control group. There was a significant difference in duration of chest tube placement between the early and late tPA groups. No child who was treated with tPA developed local or systemic bleeding. CONCLUSIONS: Early administration of intrapleural tPA seems to be a safe and potentially effective treatment in children with complicated parapneumonic effusions. Randomized controlled trial evidence is needed to confirm this finding.

Chest Tubes↗