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Review |
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Abstract
Angiogenesis depends on the adhesive interactions of vascular cells. The adhesion receptor integrin alpha v beta 3 was identified as a marker of angiogenic vascular tissue. Integrin alpha v beta 3 was expressed on blood vessels in human wound granulation tissue but not in normal skin, and it showed a fourfold increase in expression during angiogenesis on the chick chorioallantoic membrane. In the latter assay, a monoclonal antibody to alpha v beta 3 blocked angiogenesis induced by basic fibroblast growth factor, tumor necrosis factor-alpha, and human melanoma fragments but had no effect on preexisting vessels. These findings suggest that alpha v beta 3 may be a useful therapeutic target for diseases characterized by neovascularization.
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Comparative Study |
31 |
2248 |
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Clark R, Anderson NB, Clark VR, Williams DR. Racism as a stressor for African Americans. A biopsychosocial model. AMERICAN PSYCHOLOGIST 1999; 54:805-16. [PMID: 10540593 DOI: 10.1037/0003-066x.54.10.805] [Citation(s) in RCA: 1308] [Impact Index Per Article: 50.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Various authors have noted that interethnic group and intraethnic group racism are significant stressors for many African Americans. As such, intergroup and intragroup racism may play a role in the high rates of morbidity and mortality in this population. Yet, although scientific examinations of the effects of stress have proliferated, few researchers have explored the psychological, social, and physiological effects of perceived racism among African Americans. The purpose of this article was to outline a biopsychosocial model for perceived racism as a guide for future research. The first section of this article provides a brief overview of how racism has been conceptualized in the scientific literature. The second section reviews research exploring the existence of intergroup and intragroup racism. A contextual model for systematic studies of the biopsychosocial effects of perceived racism is then presented, along with recommendations for future research.
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26 |
1308 |
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Meraz MA, White JM, Sheehan KC, Bach EA, Rodig SJ, Dighe AS, Kaplan DH, Riley JK, Greenlund AC, Campbell D, Carver-Moore K, DuBois RN, Clark R, Aguet M, Schreiber RD. Targeted disruption of the Stat1 gene in mice reveals unexpected physiologic specificity in the JAK-STAT signaling pathway. Cell 1996; 84:431-42. [PMID: 8608597 DOI: 10.1016/s0092-8674(00)81288-x] [Citation(s) in RCA: 1292] [Impact Index Per Article: 44.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The JAK-STAT signaling pathway has been implicated in mediating biological responses induced by many cytokines. However, cytokines that promote distinct cellular responses often activate identical STAT proteins, thereby raising the question of how specificity is manifest within this signaling pathway. Here we report the generation and characterization of mice deficient in STAT1. STAT1-deficient mice show no overt developmental abnormalities, but display a complete lack of responsiveness to either IFN alpha or IFN gamma and are highly sensitive to infection by microbial pathogens and viruses. In contrast, these mice respond normally to several other cytokines that activate STAT1 in vitro. These observations document that STAT1 plays an obligate and dedicated role in mediating IFN-dependent biologic responses and reveal an unexpected level of physiologic specificity for STAT1 action.
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29 |
1292 |
5
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Bailey JA, Gu Z, Clark RA, Reinert K, Samonte RV, Schwartz S, Adams MD, Myers EW, Li PW, Eichler EE. Recent segmental duplications in the human genome. Science 2002; 297:1003-7. [PMID: 12169732 DOI: 10.1126/science.1072047] [Citation(s) in RCA: 979] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Primate-specific segmental duplications are considered important in human disease and evolution. The inability to distinguish between allelic and duplication sequence overlap has hampered their characterization as well as assembly and annotation of our genome. We developed a method whereby each public sequence is analyzed at the clone level for overrepresentation within a whole-genome shotgun sequence. This test has the ability to detect duplications larger than 15 kilobases irrespective of copy number, location, or high sequence similarity. We mapped 169 large regions flanked by highly similar duplications. Twenty-four of these hot spots of genomic instability have been associated with genetic disease. Our analysis indicates a highly nonrandom chromosomal and genic distribution of recent segmental duplications, with a likely role in expanding protein diversity.
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23 |
979 |
6
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Abstract
During wound healing, angiogenic capillary sprouts invade the fibrin/fibronectin-rich wound clot and within a few days organize into a microvascular network throughout the granulation tissue. As collagen accumulates in the granulation tissue to produce scar, the density of blood vessels diminishes. A dynamic interaction occurs among endothelial cells, angiogenic cytokines, such as FGF, VEGF, TGF-beta, angiopoietin, and mast cell tryptase, and the extracellular matrix (ECM) environment. Specific endothelial cell ECM receptors are critical for these morphogenetic changes in blood vessels during wound repair. In particular, alpha(v)beta3, the integrin receptor for fibrin and fibronectin, appears to be required for wound angiogenesis: alpha(v)beta3 is expressed on the tips of angiogenic capillary sprouts invading the wound clot, and functional inhibitors of alpha(v)beta3 transiently inhibit granulation tissue formation. Recent investigations have shown that the wound ECM can regulate angiogenesis in part by modulating integrin receptor expression. mRNA levels of alpha(v)beta3 in human dermal microvascular endothelial cells either plated on fibronectin or overlaid by fibrin gel were higher than in cells plated on collagen or overlaid by collagen gel. Wound angiogenesis also appears to be regulated by endothelial cell interaction with the specific three-dimensional ECM environment in the wound space. In an in vitro model of human sprout angiogenesis, three-dimensional fibrin gel, simulating early wound clot, but not collagen gel, simulating late granulation tissue, supported capillary sprout formation. Understanding the molecular mechanisms that regulate wound angiogenesis, particularly how ECM modulates ECM receptor and angiogenic factor requirements, may provide new approaches for treating chronic wounds.
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Review |
25 |
888 |
7
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Bangsberg DR, Perry S, Charlebois ED, Clark RA, Roberston M, Zolopa AR, Moss A. Non-adherence to highly active antiretroviral therapy predicts progression to AIDS. AIDS 2001; 15:1181-3. [PMID: 11416722 DOI: 10.1097/00002030-200106150-00015] [Citation(s) in RCA: 722] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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24 |
722 |
8
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Martin GA, Viskochil D, Bollag G, McCabe PC, Crosier WJ, Haubruck H, Conroy L, Clark R, O'Connell P, Cawthon RM. The GAP-related domain of the neurofibromatosis type 1 gene product interacts with ras p21. Cell 1990; 63:843-9. [PMID: 2121370 DOI: 10.1016/0092-8674(90)90150-d] [Citation(s) in RCA: 711] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The neurofibromatosis type 1 (NF1) protein contains a region of significant sequence similarity to ras p21 GTPase-activating protein (GAP) and the yeast IRA1 gene product. A fragment of NF1 cDNA encoding the GAP-related domain (NF1 GRD) was expressed, immunoaffinity purified, and assayed for effects on N-ras p21 GTPase activity. The GTPase of wild-type ras p21 was stimulated by NF1 GRD, but oncogenic mutants of ras p21 (Asp-12 and Val-12) were unaffected, and the GTPase of an effector mutant (Ala-38) was only weakly stimulated. NF1 GRD also down-regulated RAS function in S. cerevisiae. The affinity of NF1 GRD for ras p21 was estimated to be 250 nM: this is more than 20-fold higher than the affinity of GAP for ras p21. However, its specific activity was about 30 times lower. These kinetic measurements suggest that NF1 may be a significant regulator of ras p21 activity, particularly at low ras p21 concentrations.
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35 |
711 |
9
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Borregaard N, Heiple JM, Simons ER, Clark RA. Subcellular localization of the b-cytochrome component of the human neutrophil microbicidal oxidase: translocation during activation. J Cell Biol 1983; 97:52-61. [PMID: 6408102 PMCID: PMC2112494 DOI: 10.1083/jcb.97.1.52] [Citation(s) in RCA: 707] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We describe a new method for subcellular fractionation of human neutrophils. Neutrophils were disrupted by nitrogen cavitation and the nuclei removed by centrifugation. The postnuclear supernatant was applied on top of a discontinuous Percoll density gradient. Centrifugation for 15 min at 48,000 g resulted in complete separation of plasma membranes, azurophil granules, and specific granules. As determined by ultrastructure and the distribution of biochemical markers of these organelles, approximately 90% of the b-cytochrome in unstimulated cells was recovered from the band containing the specific granules and was shown to be in or tightly associated with the membrane. During stimulation of intact neutrophils with phorbol myristate acetate or the ionophore A23187, we observed translocation of 40-75% of the b-cytochrome to the plasma membrane. The extent of this translocation closely paralleled release of the specific granule marker, vitamin B12-binding protein. These data indicate that the b-cytochrome is in the membrane of the specific granules of unstimulated neutrophils and that stimulus-induced fusion of these granules with the plasma membrane results in a translocation of the cytochrome. Our observations provide a basis for the assembly of the microbicidal oxidase of the human neutrophil.
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research-article |
42 |
707 |
10
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Sharp AJ, Locke DP, McGrath SD, Cheng Z, Bailey JA, Vallente RU, Pertz LM, Clark RA, Schwartz S, Segraves R, Oseroff VV, Albertson DG, Pinkel D, Eichler EE. Segmental duplications and copy-number variation in the human genome. Am J Hum Genet 2005; 77:78-88. [PMID: 15918152 PMCID: PMC1226196 DOI: 10.1086/431652] [Citation(s) in RCA: 688] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2005] [Accepted: 05/04/2005] [Indexed: 01/15/2023] Open
Abstract
The human genome contains numerous blocks of highly homologous duplicated sequence. This higher-order architecture provides a substrate for recombination and recurrent chromosomal rearrangement associated with genomic disease. However, an assessment of the role of segmental duplications in normal variation has not yet been made. On the basis of the duplication architecture of the human genome, we defined a set of 130 potential rearrangement hotspots and constructed a targeted bacterial artificial chromosome (BAC) microarray (with 2,194 BACs) to assess copy-number variation in these regions by array comparative genomic hybridization. Using our segmental duplication BAC microarray, we screened a panel of 47 normal individuals, who represented populations from four continents, and we identified 119 regions of copy-number polymorphism (CNP), 73 of which were previously unreported. We observed an equal frequency of duplications and deletions, as well as a 4-fold enrichment of CNPs within hotspot regions, compared with control BACs (P < .000001), which suggests that segmental duplications are a major catalyst of large-scale variation in the human genome. Importantly, segmental duplications themselves were also significantly enriched >4-fold within regions of CNP. Almost without exception, CNPs were not confined to a single population, suggesting that these either are recurrent events, having occurred independently in multiple founders, or were present in early human populations. Our study demonstrates that segmental duplications define hotspots of chromosomal rearrangement, likely acting as mediators of normal variation as well as genomic disease, and it suggests that the consideration of genomic architecture can significantly improve the ascertainment of large-scale rearrangements. Our specialized segmental duplication BAC microarray and associated database of structural polymorphisms will provide an important resource for the future characterization of human genomic disorders.
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Research Support, N.I.H., Extramural |
20 |
688 |
11
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Clark R, Anderson NB, Clark VR, Williams DR. Racism as a stressor for African Americans. A biopsychosocial model. THE AMERICAN PSYCHOLOGIST 1999. [PMID: 10540593 DOI: 10.1037//0003-066x.54.10.805] [Citation(s) in RCA: 576] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Various authors have noted that interethnic group and intraethnic group racism are significant stressors for many African Americans. As such, intergroup and intragroup racism may play a role in the high rates of morbidity and mortality in this population. Yet, although scientific examinations of the effects of stress have proliferated, few researchers have explored the psychological, social, and physiological effects of perceived racism among African Americans. The purpose of this article was to outline a biopsychosocial model for perceived racism as a guide for future research. The first section of this article provides a brief overview of how racism has been conceptualized in the scientific literature. The second section reviews research exploring the existence of intergroup and intragroup racism. A contextual model for systematic studies of the biopsychosocial effects of perceived racism is then presented, along with recommendations for future research.
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Journal Article |
26 |
576 |
12
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Abstract
Wound repair of the integument is reviewed in the context of new developments in cell biology and biochemistry. Injury of the skin and concomitant blood vessel disruption lead to extravasation of blood constituents, followed by platelet aggregation and blood clotting. These events initiate inflammation and set the stage for repair processes. The macrophage plays a pivotal role in the transition between wound inflammation and repair (granulation tissue formation), since this cell both scavenges tissue debris and releases a plethora of biologically active substances that include growth factors. Although concrete evidence is lacking, growth factors are probably at least partially responsible for the angiogenesis and fibroplasia (granulation tissue) that gradually fill the wound void. If the epidermal barrier is disrupted during injury, reepithelialization begins within 24 hours and proceeds first over the margin of residual dermis and subsequently over granulation tissue. The signals for angiogenesis, fibroplasia, neomatrix formation, and reepithelialization in wound repair are not known, but a number of possibilities are discussed. Matrix remodeling is the last stage of wound repair and gradually increases the scar tensile strength to 70% to 80% of normal skin.
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Review |
40 |
478 |
13
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Levine JD, Clark R, Devor M, Helms C, Moskowitz MA, Basbaum AI. Intraneuronal substance P contributes to the severity of experimental arthritis. Science 1984; 226:547-9. [PMID: 6208609 DOI: 10.1126/science.6208609] [Citation(s) in RCA: 430] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
There is evidence that substance P is a peptide neurotransmitter of some unmyelinated primary afferent nociceptors and that its release from the peripheral terminals of primary afferent fibers mediates neurogenic inflammation. The investigators examined whether substance P also contributes to the severity of adjuvant-induced arthritis, an inflammatory disease in rats. They found that, in the rat, joints that developed more severe arthritis (ankles) were more densely innervated by substance P-containing primary afferent neurons than were joints that developed less severe arthritis (knees). Infusion of substance P into the knee increased the severity of arthritis; injection of a substance P receptor antagonist did not. These results suggest a significant physiological difference between joints that develop mild and severe arthritis and indicate that release of intraneuronal substance P in joints contributes to the severity of the arthritis.
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41 |
430 |
14
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Clark RA, Lanigan JM, DellaPelle P, Manseau E, Dvorak HF, Colvin RB. Fibronectin and fibrin provide a provisional matrix for epidermal cell migration during wound reepithelialization. J Invest Dermatol 1982; 79:264-9. [PMID: 6752288 DOI: 10.1111/1523-1747.ep12500075] [Citation(s) in RCA: 421] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Factors regulating the attachment and directional migration of a regenerating epidermis in wound healing are poorly understood. In studies of guinea pig 4-mm skin wounds, left uncovered for 1-28 days, biopsied and processed for 1-micrometer section and immunofluorescence, the epidermis migrated over an irregular thickened provisional matrix containing fibrin and fibronectin. The provisional matrix lacked two major components of normal basement membrane, laminin and type IV collagen, which can mediate tenacious epithelial attachment to plastic in vitro and may limit epidermal cell migration in vivo. Upon completion of wound reepithelialization at 7-9 days after wounding, the basement membrane zone lost its thickened appearance, fibronectin and fibrinogen disappeared, and type IV collagen and laminin reappeared. Although these findings do not prove that epidermal cell migration during reepithelialization required a fibrin and fibronectin matrix, they demonstrate that epidermal cells do move over such a substratum during in vivo wound repair.
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43 |
421 |
15
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Clark RA, Volpp BD, Leidal KG, Nauseef WM. Two cytosolic components of the human neutrophil respiratory burst oxidase translocate to the plasma membrane during cell activation. J Clin Invest 1990; 85:714-21. [PMID: 2155923 PMCID: PMC296487 DOI: 10.1172/jci114496] [Citation(s) in RCA: 326] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The superoxide-forming respiratory burst oxidase of human neutrophils is composed of membrane-associated catalytic components and cytosolic constituents required for oxidase activation. This study concerns the hypothesis that cytosolic oxidase components translocate to a membrane fraction when neutrophils are stimulated and the oxidase is activated. A polyclonal antiserum that recognizes two discrete cytosolic oxidase components of 47 and 67 kD was used to probe transfer blots of electrophoresed membrane and cytosol fractions of resting and stimulated neutrophils. In contrast to their strictly cytosolic localization in unstimulated cells, both proteins were detected in membrane fractions of neutrophils activated by phorbol esters and other stimuli. This translocation event was a function of stimulus concentration as well as time and temperature of exposure to the stimulus. It was inhibited by concentrations of N-ethylmaleimide that blocked superoxide formation but was unaffected by 2-deoxyglucose. There was a correlation between translocation of the cytosolic proteins and activation of the oxidase as determined by superoxide formation. Quantitative analyses suggested that approximately 10% of total cellular p47 and p67 became membrane-associated during phorbol ester activation of the oxidase. Analysis of Percoll density gradient fractions indicated that the target membrane for translocation of both proteins was the plasma membrane rather than membranes of either specific or azurophilic granules. In the cell-free oxidase system arachidonate-dependent but membrane-independent precipitation of the cytosolic oxidase proteins was demonstrated. The data show that activation of the respiratory burst oxidase in stimulated human neutrophils is closely associated with translocation of the 47- and 67-kD cytosolic oxidase components to the plasma membrane. We suggest that this translocation event is important in oxidase activation.
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research-article |
35 |
326 |
16
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Mohr IJ, Clark R, Sun S, Androphy EJ, MacPherson P, Botchan MR. Targeting the E1 replication protein to the papillomavirus origin of replication by complex formation with the E2 transactivator. Science 1990; 250:1694-9. [PMID: 2176744 DOI: 10.1126/science.2176744] [Citation(s) in RCA: 321] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The mechanism by which transcription factors stimulate DNA replication in eukaryotes is unknown. Bovine papillomavirus DNA synthesis requires the products of the viral E1 gene and the transcriptional activator protein encoded by the E2 gene. Experimental data showed that the 68-kilodalton (kD) E1 protein formed a complex with the 48-kD E2 transcription factor. This complex bound specifically to the viral origin of replication, which contains multiple binding sites for E2. Repressor proteins encoded by the E2 open reading frame failed to complex with E1 suggesting that the 162-amino acid region of E2 that participates in transactivation contained critical determinants for interaction with E1. The physical association between a replication protein and a transcription factor suggests that transcriptional activator proteins may function in targeting replication initiator proteins to their respective origins of replication.
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35 |
321 |
17
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Abstract
Although hemostasis is the major role of fibrin in wound repair, once the clot is present the wound cells must deal with it. The invasion and clearing of fibrin by these cells involves multiple complex processes that may go array XXX and delay wound repair. A good example, of the latter is leg ulcers. These chronic wounds contain a plethora of proteases that digest fibronectin and growth factors in the fibrin clot resulting in a corrupt provisional matrix that no longer supports reepithelialization or granulation tissue formation. Every good wound care provider knows that these wounds will not heal unless the corrupt matrix is removed by vigorous debridement that stimulates the accumulation of a competent provisional matrix.
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Review |
24 |
302 |
18
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Leto TL, Lomax KJ, Volpp BD, Nunoi H, Sechler JM, Nauseef WM, Clark RA, Gallin JI, Malech HL. Cloning of a 67-kD neutrophil oxidase factor with similarity to a noncatalytic region of p60c-src. Science 1990; 248:727-30. [PMID: 1692159 DOI: 10.1126/science.1692159] [Citation(s) in RCA: 291] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Chronic granulomatous diseases (CGDs) are characterized by recurrent infections resulting from impaired superoxide production by a phagocytic cell, nicotinamide adenine dinucleotide phosphate (reduced) (NADPH) oxidase. Complementary DNAs were cloned that encode the 67-kilodalton (kD) cytosolic oxidase factor (p67), which is deficient in 5% of CGD patients. Recombinant p67 (r-p67) partially restored NADPH oxidase activity to p67-deficient neutrophil cytosol from these patients. The p67 cDNA encodes a 526-amino acid protein with acidic middle and carboxyl-terminal domains that are similar to a sequence motif found in the noncatalytic domain of src-related tyrosine kinases. This motif was recently noted in phospholipase C-gamma, nonerythroid alpha-spectrin (fodrin), p21ras-guanosine triphophatase-activating protein (GAP), myosin-1 isoforms, yeast proteins cdc-25 and fus-1, and the 47-kD phagocyte oxidase factor (p47), which suggests the possibility of common regulatory features.
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Comparative Study |
35 |
291 |
19
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Volpp BD, Nauseef WM, Clark RA. Two cytosolic neutrophil oxidase components absent in autosomal chronic granulomatous disease. Science 1988; 242:1295-7. [PMID: 2848318 DOI: 10.1126/science.2848318] [Citation(s) in RCA: 290] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Neutrophils kill microorganisms with oxygen radicals generated by an oxidase that uses the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as substrate. This system requires both membrane and cytosolic components and is defective in patients with chronic granulomatous disease. A cytosolic complex capable of activating latent membrane oxidase was eluted from guanosine triphosphate-agarose and was used to raise polyclonal antiserum that recognized 47- and 67-kilodalton proteins. These proteins were restricted to the cytosol of myeloid cells. Both proteins were associated with NADPH oxidase-activating capacity when neutrophil cytosol was purified on nucleotide affinity matrices or molecular sizing columns. Neutrophils from patients with two different forms of autosomal chronic granulomatous disease lacked either the 47- or 67-kilodalton protein.
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37 |
290 |
20
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Heyworth PG, Curnutte JT, Nauseef WM, Volpp BD, Pearson DW, Rosen H, Clark RA. Neutrophil nicotinamide adenine dinucleotide phosphate oxidase assembly. Translocation of p47-phox and p67-phox requires interaction between p47-phox and cytochrome b558. J Clin Invest 1991; 87:352-6. [PMID: 1985107 PMCID: PMC295061 DOI: 10.1172/jci114993] [Citation(s) in RCA: 289] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Two of the cytosolic NADPH oxidase components, p47-phox and p67-phox, translocate to the plasma membrane in normal neutrophils stimulated with phorbol myristate acetate (PMA). We have now studied the translocation process in neutrophils of patients with chronic granulomatous disease (CGD), an inherited syndrome in which the oxidase system fails to produce superoxide due to lesions affecting any one of its four known components: the gp91-phox and p22-phox subunits of cytochrome b558 (the membrane-bound terminal electron transporter of the oxidase), p47-phox, and p67-phox. In contrast to normal cells, neither p47-phox nor p67-phox translocated to the membrane in PMA-stimulated CGD neutrophils which lack cytochrome b558. In one patient with a rare X-linked form of CGD caused by a Pro----His substitution in gp91-phox, but whose neutrophils have normal levels of this mutant cytochrome b558, translocation was normal. In two patients with p47-phox deficiency, p67-phox failed to translocate, whereas p47-phox was detected in the particulate fraction of PMA-stimulated neutrophils from two patients deficient in p67-phox. Our data suggest that cytochrome b558 or a closely linked factor provides an essential membrane docking site for the cytosolic oxidase components and that it is p47-phox that mediates the assembly of these components on the membrane.
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research-article |
34 |
289 |
21
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Li Y, Bollag G, Clark R, Stevens J, Conroy L, Fults D, Ward K, Friedman E, Samowitz W, Robertson M. Somatic mutations in the neurofibromatosis 1 gene in human tumors. Cell 1992; 69:275-81. [PMID: 1568247 DOI: 10.1016/0092-8674(92)90408-5] [Citation(s) in RCA: 285] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The neurofibromatosis 1 (NF1) gene product, neurofibromin, contains a GTPase-activating protein (GAP)-related domain, or NF1 GRD, that is able to down-regulate p21ras by stimulating its intrinsic GTPase. Since p21ras.GTP is a major regulator of growth and differentiation, mutant neurofibromins resulting from somatic mutations in the NF1 gene might interfere with ras signaling pathways and contribute to the development of tumors. We describe an amino acid substitution in the NF1 GRD, altering Lys-1423, that has occurred in three tumor types: colon adenocarcinoma, myelodysplastic syndrome, and anaplastic astrocytoma, and in one family with neurofibromatosis 1. The GAP activity of the mutant NF1 GRD is 200- to 400-fold lower than that of wild type, whereas binding affinity is unaffected. Thus, germline mutations in NF1 that cause neurofibromatosis 1 can also occur in somatic cells and contribute to the development of sporadic tumors, including tumors not associated with neurofibromatosis 1.
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33 |
285 |
22
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Abstract
Wound repair requires a continually evolving network of interactions among cells, cytokines and the extracellular matrix. Cell-surface integrins provide a mechanical connection between matrix components and the cytoskeleton, and integrins can transduce an astonishing variety of signals along pathways that may intercept the pathways triggered by cytokine receptors.
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Review |
31 |
284 |
23
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Duerr RL, Huang S, Miraliakbar HR, Clark R, Chien KR, Ross J. Insulin-like growth factor-1 enhances ventricular hypertrophy and function during the onset of experimental cardiac failure. J Clin Invest 1995; 95:619-27. [PMID: 7860746 PMCID: PMC295527 DOI: 10.1172/jci117706] [Citation(s) in RCA: 244] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
To determine whether additional hypertrophy would be beneficial or maladaptive in cardiac failure, the effects of insulin-like growth factor (IGF-1) were investigated in rats with left ventricular (LV) dysfunction. In normal rats, 3 mg/kg per d of recombinant human IGF-1 for 14 d augmented LV wt (32%) and increased LV/body wt ratio (P < 0.01). 2 d after coronary occlusion, rats were randomized to IGF-1 (3 mg/kg per d) or placebo. After 2 wk, IGF-1-treated rats showed significant increases in LV wt (13%) and LV wt/tibial length ratio, but LV/body wt ratio was unchanged. By microangiography, compared with controls (n = 12) IGF-1-treated rats (n = 16) showed increased LV end-diastolic volume (19%) and stroke volume (31%) (both significant normalized to tibial length, but not to body wt). Average infarct size did not differ between groups. The LV ejection fraction (EF) was not significantly different between groups, but estimated cardiac output was higher in treated rats; there was a significant interaction for the EF between infarct size and treatment (P = 0.029) and a trend for EF to be higher in treated rats with large infarctions (EF 33.4 vs 25.1% in controls). Myocyte cross-sectional areas in noninfarcted LV zones tended to be larger in treated rats (232.1 vs 205.4 microns 2; P = 0.10), but there was no difference in capillary density and collagen content did not differ between groups. In conclusion, IGF-1 administration caused hypertrophy of the normal heart in vivo. When stimulated by IGF-1, the severely dysfunctional heart in evolving myocardial infarction is capable of undergoing additional hypertrophy with evidence of improved function, suggesting a beneficial effect. Further investigation of the potential role of growth factor therapy in heart failure appears warranted.
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research-article |
30 |
244 |
24
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Nauseef WM, Volpp BD, McCormick S, Leidal KG, Clark RA. Assembly of the neutrophil respiratory burst oxidase. Protein kinase C promotes cytoskeletal and membrane association of cytosolic oxidase components. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(19)67684-2] [Citation(s) in RCA: 242] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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34 |
242 |
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Welch MP, Odland GF, Clark RA. Temporal relationships of F-actin bundle formation, collagen and fibronectin matrix assembly, and fibronectin receptor expression to wound contraction. J Biophys Biochem Cytol 1990; 110:133-45. [PMID: 2136860 PMCID: PMC2115975 DOI: 10.1083/jcb.110.1.133] [Citation(s) in RCA: 240] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Wound contraction can substantially reduce the amount of new tissue needed to reestablish organ integrity after tissue loss. Fibroblasts, rich in F-actin bundles, generate the force of wound contraction. Fibronectin-containing microfibrils link fibroblasts to each other and to collagen bundles and thereby provide transduction cables across the wound for contraction. The temporal relationships of F-actin bundle formation, collagen and fibronectin matrix assembly, and fibronectin receptor expression to wound contraction have not been determined. To establish these relationships, we used a cutaneous gaping wound model in outbred Yorkshire pigs. Granulation tissue filled approximately 80% of the wound space by day 5 after injury while wound contraction was first apparent at day 10. Neither actin bundles nor fibronectin receptors were observed in 5-d wound fibroblasts. Although fibronectin fibrils were assembled on the surfaces of 5-d fibroblasts, few fibrils coursed between cells. Day-7 fibroblasts stained strongly for nonmuscle-type F-actin bundles consistent with a contractile fibroblast phenotype. These cells expressed fibronectin receptors, were embedded in a fibronectin matrix that appeared to connect fibroblasts to the matrix and to each other, and were coaligned across the wound. Transmission EM confirmed the presence of microfilament bundles, cell-cell and cell-matrix linkages at day 7. Fibroblast coalignment, matrix interconnections, and actin bundles became more pronounced at days 10 and 14 coinciding with tissue contraction. These findings demonstrate that granulation tissue formation, F-actin bundle and fibronectin receptor expression in wound fibroblasts, and fibroblast-matrix linkage precede wound contraction.
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