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Biomedical subjects

J M Schwartz

Publications and source records attributed to J M Schwartz.

At least 19 recordsLinked to original sources
PubMed2001

Severe gastrointestinal bleeding after hematopoietic cell transplantation, 1987-1997: incidence, causes, and outcome.

OBJECTIVE: Severe GI bleeding after hematopoietic cell transplantation is commonly due to lesions that are unusual in nontransplant patients. The frequency of GI bleeding appears to have decreased over the last decade, but the reasons have not been readily apparent. We sought to determine the incidence of severe bleeding during two time periods, to describe the causes and outcomes of bleeding, and to analyze the reasons behind an apparent decline in severe bleeding over the decade covered. METHODS: During 1986-1987 and 1996-1997, we followed all patients with and without severe bleeding at our institution, a marrow transplant center. RESULTS: Over this decade, the incidence of severe bleeding declined from 50/467 (10.7%) to 15/635 (2.4%) (p < 0.0001). Overall mortality from intestinal bleeding declined from 3.6% to 0.9% (p = 0.002), but mortality in those with bleeding remained high (34% vs 40%). The onset (day 42 vs 47) and platelet counts (35,994 vs 37,600/microl) were similar, but the sites and causes of bleeding were different. During 1986-1987, 27/50 patients bled from multiple GI sites, viral and fungal ulcers, or graft-versus-host disease (GVHD). Over the decade, bleeding from GVHD had decreased 80% (p < 0.0001), and bleeding from viral (p < 0.0001) and fungal (p = 0.023) ulcers almost disappeared. CONCLUSIONS: The incidence of severe GI bleeding has declined significantly over the last decade because of prevention of viral and fungal infections and severe acute GVHD. However, severe bleeding after transplant remains a highly morbid event, particularly among patients with GVHD.

Adult↗
PubMed2000

Golvesin-GFP fusions as distinct markers for Golgi and post-Golgi vesicles in Dictyostelium cells.

Golvesin is a new protein associated with membranes of the Golgi apparatus and post-Golgi vesicles in Dictyostelium cells. An internal hydrophobic sequence of 24 amino-acid residues is responsible for anchoring golvesin to the membranes of these organelles. In an attempt to visualize organelle dynamics in vivo, we have used specific antibody and other labels to localize golvesin-green fluorescent protein (GFP) constructs to different cellular compartments. With a GFP tag at its N-terminus, golvesin shows the same localization as the untagged protein. It is transferred to two post-Golgi compartments, the endosomal and contractile vacuole systems. Endosomes are decorated with GFP-golvesin within less than 10 min of their internalisation, and keep the label during the acidic phase of the pathway. Blockage of the C-terminus with GFP causes entrapment of the protein in the Golgi apparatus, indicating that a free C-terminus is required for transfer of golvesin to any of the post-Golgi compartments. The C-terminally tagged golvesin proved to be a reliable Golgi marker in Dictyostelium cells revealing protrusion of Golgi tubules at peak velocities of 3 to 4 microm x s(-1). The fusion protein is retained in Golgi vesicles during mitosis, visualizing Golgi disassembly and reorganization in line with cytokinesis.

Amino Acid Sequence↗
PubMed2000

Monoclonal cryoglobulinemia with extensive gangrene of all four extremities--a case report.

The monoclonal immunoglobulin products of plasma cell neoplasm can give rise to a variety of manifestations including hyperviscosity, amyloidosis, cryoglobulinemia, neuropathy, and renal failure. A 50-year-old woman with monoclonal cryoglobulinemia developed extensive gangrene and ulceration of both hands and feet over several weeks requiring bilateral below-elbow and below-knee amputations. This case illustrates the importance of qualitative properties of paraprotein.

Amputation, Surgical↗
PubMed1999

Dynein motor regulation stabilizes interphase microtubule arrays and determines centrosome position.

Cytoplasmic dynein is a microtubule-based motor protein responsible for vesicle movement and spindle orientation in eukaryotic cells. We show here that dynein also supports microtubule architecture and determines centrosome position in interphase cells. Overexpression of the motor domain in Dictyostelium leads to a collapse of the interphase microtubule array, forming loose bundles that often enwrap the nucleus. Using green fluorescent protein (GFP)-alpha-tubulin to visualize microtubules in live cells, we show that the collapsed arrays remain associated with centrosomes and are highly motile, often circulating along the inner surface of the cell cortex. This is strikingly different from wild-type cells where centrosome movement is constrained by a balance of tension on the microtubule array. Centrosome motility involves force-generating microtubule interactions at the cortex, with the rate and direction consistent with a dynein-mediated mechanism. Mapping the overexpression effect to a C-terminal region of the heavy chain highlights a functional domain within the massive sequence important for regulating motor activity.

Animals↗
PubMed1999

Cytokinesis mediated through the recruitment of cortexillins into the cleavage furrow.

The fact that substrate-anchored Dictyostelium cells undergo cytokinesis in the absence of myosin II underscores the importance of other proteins in enabling the cleavage furrow to constrict. Cortexillins, a pair of actin-bundling proteins, are required for normal cleavage. They are targeted to the incipient furrow in wild-type and, more prominently, in myosin II-null cells. No other F-actin bundling or cross-linking protein tested is co-localized. Green fluorescent protein fusions show that the N-terminal actin-binding domain of cortexillin I is dispensable and the C-terminal region is sufficient for translocation to the furrow and the rescue of cytokinesis. Cortexillins are suggested to have a targeting signal for coupling to a myosin II-independent system that directs transport of membrane proteins to the cleavage furrow.

Actins↗
PubMed1999

The contractile vacuole network of Dictyostelium as a distinct organelle: its dynamics visualized by a GFP marker protein.

The contractile vacuole system is an osmoregulatory organelle composed of cisternae and interconnecting ducts. Large cisternae act as bladders that periodically fuse with the plasma membrane, forming pores to expel water. To visualize the entire network in vivo and to identify constituents of the vacuolar complex in cell fractions, we introduced a specific marker into Dictyostelium cells, GFP-tagged dajumin. The C-terminal, GFP-tagged region of this transmembrane protein is responsible for sorting to the contractile vacuole complex. Dajumin-GFP negligibly associates with the plasma membrane, indicating its retention during discharge of the bladder. Fluorescent labeled cell-surface constituents are efficiently internalized by endocytosis, while no significant cycling through the contractile vacuole is observed. Endosomes loaded with yeast particles or a fluid-phase marker indicate sharp separation of the endocytic pathway from the contractile vacuole compartment. Even after dispersion of the contractile vacuole system during mitosis, dajumin-GFP distinguishes the vesicles from endosomes, and visualizes post-mitotic re-organization of the network around the nucleus. Highly discriminative sorting and membrane fusion mechanisms are proposed to account for the sharp separation of the contractile vacuole and endosomal compartments. Evidence for a similar compartment in other eukaryotic cells is discussed.

Animals↗
PubMed1998

FDG-PET predictors of response to behavioral therapy and pharmacotherapy in obsessive compulsive disorder.

In subjects with obsessive-compulsive disorder (OCD), lower pre-treatment metabolism in the right orbitofrontal cortex (OFC) and anterior cingulate gyrus (AC) has been associated with a better response to clomipramine. We sought to determine pre-treatment metabolic predictors of response to behavioral therapy (BT) vs. pharmacotherapy in subjects with OCD. To do this, [18F]fluorodeoxyglucose positron emission tomography scans of the brain were obtained in subjects with OCD before treatment with either BT or fluoxetine. A Step-Wise Variable Selection was applied to normalized pre-treatment glucose metabolic rates in the OFC, AC, and caudate by treatment response (change in Yale-Brown Obsessive-Compulsive Scale) in the larger BT group. Left OFC metabolism (normalized to the ipsilateral hemisphere) alone was selected as predicting treatment response in the BT-treated group (F = 6.07, d.f. = 1,17, P = 0.025). Correlations between normalized left OFC metabolism and treatment response revealed that higher normalized metabolism in this region was associated with greater improvement in the BT-treated group (tau = 0.35, P = 0.04), but worse outcome (tau = -0.57, P = 0.03) in the fluoxetine-treated group. These results suggest that subjects with differing patterns of metabolism preferentially respond to BT vs. medication.

Adult↗
PubMed1998

Physician noncompliance with the 1993 National Cholesterol Education Program (NCEP-ATPII) guidelines.

BACKGROUND: We sought to determine the frequency with which physicians follow National Cholesterol Education Program (NCEP-ATPII) guidelines in screening for cardiovascular risk factors and treating hyperlipidemia. METHODS AND RESULTS: We conducted a retrospective chart review on randomly sampled charts of 225 patients admitted to the coronary care unit between January and June 1996. The main outcome measures were rates of physician screening for coronary heart disease risk factors; rates of counseling for cigarette cessation, diet, and exercise; and extent of use of NCEP algorithms for obtaining LDL cholesterol values and treating hypercholesterolemia. Screening rates for interns (who performed best) were: cigarette use (89%), known coronary heart disease (74%), hypertension (68%), hyperlipidemia (59%), family history (56%), diabetes (37%), postmenopausal hormone therapy (11%), and premature menopause (1%). Four percent of smokers were counseled to quit, 14% of patients were referred to dietitians, and 1% were encouraged to exercise. A full lipid panel was obtained in 50% of patients in whom it was indicated on the basis of NCEP criteria. Patients were more likely to receive lipid-lowering treatment if NCEP criteria indicated that they should, but 36% of hospitalized patients and 46% of patients who should have been treated on discharge were not. CONCLUSIONS: Physicians are poorly compliant with NCEP guidelines for risk factor assessment and counseling, even in patients at high risk for coronary heart disease. Physicians follow NCEP-ATPII algorithms for obtaining an LDL value, a key step in evaluating the need for treatment, only 50% of the time. NCEP criteria seem to influence the decision to initiate lipid-lowering therapy, but significant numbers of eligible patients remain untreated.

Aged↗
PubMed1998

G protein beta subunit-null mutants are impaired in phagocytosis and chemotaxis due to inappropriate regulation of the actin cytoskeleton.

Chemotaxis and phagocytosis are basically similar in cells of the immune system and in Dictyostelium amebae. Deletion of the unique G protein beta subunit in D. discoideum impaired phagocytosis but had little effect on fluid-phase endocytosis, cytokinesis, or random motility. Constitutive expression of wild-type beta subunit restored phagocytosis and normal development. Chemoattractants released by cells or bacteria trigger typical transient actin polymerization responses in wild-type cells. In beta subunit-null cells, and in a series of beta subunit point mutants, these responses were impaired to a degree that correlated with the defect in phagocytosis. Image analysis of green fluorescent protein-actin transfected cells showed that beta subunit- null cells were defective in reshaping the actin network into a phagocytic cup, and eventually a phagosome, in response to particle attachment. Our results indicate that signaling through heterotrimeric G proteins is required for regulating the actin cytoskeleton during phagocytic uptake, as previously shown for chemotaxis. Inhibitors of phospholipase C and intracellular Ca2+ mobilization inhibited phagocytosis, suggesting the possible involvement of these effectors in the process.

Actins↗
PubMed1998

Microtubule-mediated centrosome motility and the positioning of cleavage furrows in multinucleate myosin II-null cells.

To study centrosome motility and the interaction of microtubules with the cell cortex in mitotic, post-mitotic and interphase cells, (alpha)-tubulin was tagged in Dictyostelium discoideum with green fluorescent protein. Multinucleate cells formed by myosin II-null mutants proved to be especially suited for the analysis of the control of cleavage furrow formation by the microtubule system. After docking of the mitotic apparatus onto the cell cortex during anaphase, the cell surface is activated to form ruffles on top of the asters of microtubules that emanate from the centrosomes. Cleavage furrows are initiated at spaces between the asters independently of the positions of spindles. Once initiated, the furrows expand as deep folds without a continued connection to the microtubule system. Occurrence of unilateral furrows indicates that a closed contractile ring is dispensable for cytokinesis in Dictyostelium. The progression of cytokinesis in the multinucleate cells underlines the importance of proteins other than myosin II in specifying a cleavage furrow. The analysis of centrosome motility suggests a major role for a minus-end directed motor protein, probably cytoplasmic dynein, in applying traction forces on guiding microtubules that connect the centrosome with the cell cortex.

Anaphase↗
PubMed1998

Neuroimaging and frontal-subcortical circuitry in obsessive-compulsive disorder.

BACKGROUND: Neuroimaging studies provide strong evidence that the pathophysiology of obsessive-compulsive disorder (OCD) involves abnormal functioning along specific frontal-subcortical brain circuits. METHOD: A literature search was carried out for all brain imaging studies of patients with OCD. We also reviewed the basic science literature on the functional neuroanatomy of cortico-basal ganglia circuits, and integrated this information with neuroimaging data in OCD to formulate a theoretical model of brain mediation of OCD symptoms and response to treatment. RESULTS: At least a subgroup of patients with OCD may have abnormal basal ganglia development. Functional neuroimaging studies indicate that OCD symptoms are associated with increased activity in orbitofrontal cortex, caudate nucleus, thalamus and anterior cingulate gyrus. CONCLUSIONS: OCD symptoms are mediated by hyperactivity in orbitofrontal-subcortical circuits, perhaps due to an imbalance of tone between direct and indirect striato-pallidal pathways. We present a model which describes how frontal-subcortical brain circuitry may mediate OCD symptomatology, and suggest a hypothesis for how successful treatments may ameliorate symptoms, via their effects on circuit activity.

Brain Diseases↗
PubMed1998

Neuroanatomical aspects of cognitive-behavioural therapy response in obsessive-compulsive disorder. An evolving perspective on brain and behaviour.

BACKGROUND: Recent research has demonstrated that cognitive-behavioural therapy (CBT) for obsessive-compulsive disorder (OCD) can systematically modify cerebral metabolic activity in a manner which is significantly related to clinical outcome. METHOD: A substantial body of research is reviewed which supports an involvement of neural circuitry connecting the orbitofrontal cortex, cingulate gyrus and basal ganglia in the expression of the symptoms of OCD. RESULTS: Data are presented which expand upon previous work demonstrating effects of CBT on functional interactions between limbic cortex and the basal ganglia. CONCLUSIONS: The relevance of these effects of CBT on brain function is discussed in the context of recent advances in our knowledge of cortical-basal ganglia physiology. The clinical importance of these data is best appreciated when they are seen to reflect the interactive nature of the relationships between cognitive choice, behavioural output and brain activity.

Behavior Therapy↗
PubMed1997

Three-dimensional patterns and redistribution of myosin II and actin in mitotic Dictyostelium cells.

Myosin II is not essential for cytokinesis in cells of Dictyostelium discoideum that are anchored on a substrate (Neujahr, R., C. Heizer, and G. Gerisch. 1997. J. Cell Sci. 110:123-137), in contrast to its importance for cell division in suspension (DeLozanne, A., and J.A. Spudich. 1987. Science. 236:1086-1091; Knecht, D.A., and W.F. Loomis. 1987. Science. 236: 1081-1085.). These differences have prompted us to investigate the three-dimensional distribution of myosin II in cells dividing under one of three conditions: (a) in shaken suspension, (b) in a fluid layer on a solid substrate surface, and (c) under mechanical stress applied by compressing the cells. Under the first and second conditions outlined above, myosin II does not form patterns that suggest a contractile ring is established in the furrow. Most of the myosin II is concentrated in the regions that flank the furrow on both sides towards the poles of the dividing cell. It is only when cells are compressed that myosin II extensively accumulates in the cleavage furrow, as has been previously described (Fukui, Y., T.J. Lynch, H. Brzeska, and E.D. Korn. 1989. Nature. 341:328-331), i.e., this massive accumulation is a response to the mechanical stress. Evidence is provided that the stress-associated translocation of myosin II to the cell cortex is a result of the dephosphorylation of its heavy chains. F-actin is localized in the dividing cells in a distinctly different pattern from that of myosin II. The F-actin is shown to accumulate primarily in protrusions at the two poles that ultimately form the leading edges of the daughter cells. This distribution changes dynamically as visualized in living cells with a green fluorescent protein-actin fusion.

Actins↗
PubMed1997

Microfilament dynamics during cell movement and chemotaxis monitored using a GFP-actin fusion protein.

BACKGROUND: The microfilament system in the cortex of highly motile cells, such as neutrophils and cells of the eukaryotic microorganism Dictyostelium discoideum, is subject to rapid re-organization, both spontaneously and in response to external signals. In particular, actin polymerization induced by a gradient of chemoattractant leads to local accumulation of filamentous actin and protrusion of a 'leading edge' of the cell in the direction of the gradient. In order to study the dynamics of actin in these processes, actin was tagged at its amino terminus with green fluorescent protein (GFP) and observed with fluorescence microscopy in living cells of D. discoideum. RESULTS: Purified GFP-actin was capable of copolymerizing with actin. In the transfected cells of D. discoideum studied, GFP-actin made up 10-20% of the total actin. Microfilaments containing GFP-actin were capable of generating force with myosin in an in vitro assay. Observations of single living cells using fluorescence microscopy showed that the fusion protein was enriched in cell projections, including filopodia and leading edges, and that the fusion protein reflected the dynamics of the microfilament system in cells that were freely moving, being chemotactically stimulated, or aggregated. When confocal sections of fixed cells containing GFP-actin were labeled with fluorescent phalloidin, which binds only to filamentous actin, there was a correlation between the areas of GFP-actin and phalloidin fluorescence, but there were distinct sites in which GFP-actin was more prominent. CONCLUSIONS: Double labeling with GFP-actin and other probes provides an indication of the various states of actin in motile cells. A major portion of the actin assemblies visualized using GFP-actin are networks or bundles of filamentous actin. Other clusters of GFP-actin might represent stores of monomeric actin in the form of complexes with actin-sequestering proteins.

Actin Cytoskeleton↗
PubMed1997

Oral rehabilitation of a patient with amelogenesis imperfecta.

A patient with Type I hypoplastic patterned amelogenesis imperfecta, subtype D, presented for prosthodontic evaluation. This article describes the developmental and pathophysiological background of this disease. A clinical report describing the diagnosis, treatment planning, and dental rehabilitation of the patient is reviewed.

Adult↗
PubMed1996

Systematic changes in cerebral glucose metabolic rate after successful behavior modification treatment of obsessive-compulsive disorder.

BACKGROUND: We sought to determine in a new patient sample whether symptomatic improvement in obsessive-compulsive disorder treated with behavior modification is accompanied by significant changes in glucose metabolic rates in the caudate nucleus, measured with positron emission tomography, as seen in a previous study. Second, by combining samples from this and the previous study, we also examined whether there were pathologic correlational relationships among brain activity in the orbital cortex, caudate nucleus, and thalamus that obtained before behavioral treatment of obsessive-compulsive disorder, but that decreased significantly with symptom improvement. METHODS: Nine patients with obsessive-compulsive disorder were studied with positron emission tomography before and after 10 weeks of structured exposure and response prevention behavioral and cognitive treatment. Results were analyzed both alone and combined with those from nine similar subjects from the previous study. RESULTS: Behavior therapy responders had significant (P < .05) bilateral decreases in caudate glucose metabolic rates that were greater than those seen in poor responders to treatment. Before treatment, there were significant correlations of brain activity between the orbital gyri and the head of the caudate nucleus and the orbital gyri and the thalamus on the right. These correlations decreased significantly after effective treatment. CONCLUSIONS: These results replicate and extend previous findings of changes in caudate nucleus function with behavior therapy for obsessive-compulsive disorder. A prefrontal cortico-striato-thalamic brain system is implicated in mediation of symptoms of obsessive-compulsive disorder.

Adult↗
PubMed1994

Ischemic hepatitis in a patient with congestive cardiomyopathy: an innovative approach to therapy using intravenous dobutamine.

Patients who sustain a transient period of hypotension or low cardiac output can develop massive elevations of the serum transaminases without serum markers of acute hepatitis, a recent myocardial infarction or exposure to toxins and chemicals. This condition is often termed "ischemic hepatitis" (IH), with its pathological correlate being centrilobular necrosis. Recognition of IH can help in the appropriate management of these patients, and avoid unnecessary diagnostic testing. The authors describe a patient with congestive cardiomyopathy in whom IH developed as part of a complicated hospital course. The condition appeared to reverse with the administration of dobutamine, suggesting inotropic therapy as an appropriate treatment modality.

Adult↗