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Biomedical subjects

J Lawler

Publications and source records attributed to J Lawler.

At least 37 records · Page 2Linked to original sources
PubMed2000

Unpacking the 'black box' of a nurse-led stroke support service.

OBJECTIVES: To describe in detail the nature of the specialist nurse interventions; to increase understanding of the principal problems facing stroke patients and their care-givers in the first year following stroke and to demonstrate how these problems may change over time; and to investigate the value of qualitative research methodologies within the context of a randomized trial. METHODS: Specialist nurses providing support in the year following stroke were asked to maintain comprehensive written records of their involvement with all patients and care-givers participating in a randomized controlled trial. Qualitative methods were used to examine the problems faced by stroke patients and their care-givers, and the actions taken by nurses in response. RESULTS: Specialist nurses commenced 120 records. As 19 patients died or left the area during the year-long interventions, we obtained 101 complete records. The problems encountered by stroke patients and their care-givers were numerous, diverse, complex and changed over time. Initially, practical difficulties were noted; over time, these were accompanied by growing numbers of psychological needs. The nurses responded by providing information, advice, support and monitoring using a flexible, individualized approach. The nurses also collaborated or liaised with 17 other professional groups and provided direct support to care-givers. CONCLUSION: The need for many stroke patients and their care-givers to be professionally supported during the stages of stroke adjustment, for at least the first year and probably beyond, was emphasized by this study.

Female↗
PubMed1999

Inhibition of angiogenesis by thrombospondin-1 is mediated by 2 independent regions within the type 1 repeats.

BACKGROUND: Suppression of tumor growth by thrombospondin-1 (TSP-1) has been associated with its ability to inhibit neovascularization. The antiangiogenic activity of TSP-1, as defined by cornea pocket assays, was previously mapped to the amino-terminal portion of the protein within the procollagen region and the type 1 repeats. METHODS AND RESULTS: We evaluated the specificity and efficacy of different regions of TSP-1 using recombinant fragments of the protein on chorioallantoic membrane (CAM) angiogenesis and endothelial cell proliferation assays. In both assays, fragments containing the second and third type 1 repeats but not the procollagen region inhibited angiogenesis and endothelial cell proliferation. To further define the sequences responsible for the angiostatic effect of TSP-1, we used synthetic peptides. The CAM assay defined 2 sequences that independently suppressed angiogenesis. The amino-terminal end of the type 1 repeats showed higher potency for inhibiting angiogenesis driven by basic fibroblast growth factor (FGF-2), whereas the second region equally blocked angiogenesis driven by either FGF-2 or vascular endothelial growth factor (VEGF). Modifications of the active peptides revealed the specific amino acids required for the inhibitory response. One sequence included the conserved tryptophan residues in the amino-terminal end of the second and third type 1 repeats, and the other involved the amino acids that follow the CSVTCG sequence in the carboxy-terminus of these repeats. Both inhibition in the CAM assay and inhibition of breast tumor xenograft growth in nude mice were independent of the TGF-beta-activating sequence located in the second type 1 repeat. CONCLUSIONS: These results indicate that the type 1 repeats of TSP-1 contain 2 subdomains that may independently inhibit neovascularization. They also identify 2 independent pathways by which TSP-1 can block FGF-2 and VEGF angiogenic signals on endothelial cells.

Amino Acid Sequence↗
PubMed1999

Cooperation between thrombospondin-1 type 1 repeat peptides and alpha(v)beta(3) integrin ligands to promote melanoma cell spreading and focal adhesion kinase phosphorylation.

CD47-binding sequences from the carboxyl-terminal domain of thrombospondin-1 (TSP1) are known to regulate activity of the alpha(v)beta(3) integrin (Gao, G., Lindberg, F. P., Dimitry, J. M., Brown, E. J., and Frazier, W. A. (1996) J. Cell Biol. 135, 533-544). Here we show that peptides from the type 1 repeats of TSP1 also stimulate alpha(v)beta(3) integrin function in melanoma cells. Addition of soluble peptide 246 (KRFKQDGGWSHWSPWSS) enhances spreading of A2058 melanoma cells on several alpha(v)beta(3) integrin ligands, including vitronectin, recombinant TSP1 fragments containing the Arg-Gly-Asp sequence, and native TSP1. This activity requires the Trp residues and is independent of CD36-binding sequences in the type 1 repeats. Recombinant type 1 repeats expressed as a glutathione S-transferase fusion protein also enhance spreading on vitronectin and TSP1. Activation of alpha(v)beta(3) integrin by the soluble peptide 246 stimulates organization of F-actin and increases tyrosine phosphorylation of focal adhesion kinase. In contrast, direct adhesion of melanoma cells on immobilized peptide 246 inhibits tyrosine phosphorylation of focal adhesion kinase. Stimulation of alpha(v)beta(3) integrin function by the type 1 repeat peptide differs from that induced by CD47-binding TSP1 peptides in that heparan sulfate proteoglycans are required and pertussis toxin does not inhibit the former activity. Thus, the type 1 repeats contain a second sequence of TSP1 that can enhance alpha(v)beta(3) integrin signaling, and these two sequences stimulate recognition of both vitronectin and TSP1 by the alpha(v)beta(3) integrin.

Amino Acid Sequence↗
PubMed1999

Plasmodium falciparum-infected erythrocyte adhesion to the type 3 repeat domain of thrombospondin-1 is mediated by a modified band 3 protein.

Previously, the binding site for the Plasmodium falciparum-infected erythrocyte (PE) was determined to be the C-terminal 120 or 140 kDa region but not the N-terminal 25 kDa domain of thrombospondin (TSP). In this work, we have localized the TSP binding site for PE more precisely. PE adhered to glutathione-S-transferase-fusion proteins containing the type 3 repeat (T3) of TSP, but not to other functional domains of TSP (i.e. N-terminal domain, procollagen domain, type 1 and 2 repeat, and C-terminal domain). Soluble T3 inhibited PE binding to immobilized TSP. PE binding to immobilized T3 was inhibited by soluble TSP, a monoclonal antibody directed against the T3, glycine-arginine-glycine-aspartic acid-serine-proline (GRGDSP) peptide, and *cysteine-GRGDSP-cysteine*, where *cysteine and cysteine* form a disulfide linkage, suggesting involvement of an RGD-containing motif in the T3. In support of this, a fusion protein which excluded the RGD motif showed no PE binding activity. Earlier it was shown that the amino acid sequence of the band 3 protein, histidine-proline-leucine-glutamine-lysine-threonine-tyrosine (HPLQKTY), was exposed on PE and mediated PE binding to TSP. Monoclonal antibodies, which recognize HPLQKTY and inhibit PE binding to TSP, also inhibited PE binding to the T3. The involvement of the sequence was confirmed by the fact that an octamer of HPLQKTY-containing peptide bound to the T3 but not to the RGD motif-excluded fusion protein and the binding to T3 was inhibited by GRGDSP peptide. Thus, PE binding to the T3 domain of TSP is mediated by the peptidic sequence HPLQKTY of band 3 which is exposed on PE.

Animals↗
PubMed1999

Thrombospondin-1 and neural crest cell migration.

Using a monoclonal antibody raised against human platelet thrombospondin, we found anti-thrombospondin immunoreactivity in the extracellular matrix of avian embryos, coincident with the ventral pathways followed by trunk neural crest cells. To confirm that the antibody recognized thrombospondin-1 and to determine the tissue of origin of the thrombospondin matrix, a thrombospondin-1 cRNA probe was used for whole mount in situ hybridization. This probe revealed thrombospondin-1 mRNAs in the developing myotome before and during neural crest cell migration. The effect of thrombospondin-1 on neural crest cell migration, morphology, and adhesion was assayed in vitro. Quail trunk neural crest cells cultured on 4 microg/ml of thrombospondin-1 migrate at 1.14 +/- 0.54 microm/min, which is significantly greater than the rate of cell migration on tissue culture plastic. Using a shaker-based adhesion assay, a significantly greater number of neural crest cells remain attached to dishes coated with 4 microg/ml of thrombospondin-1 than to tissue culture plastic alone. The number of neural crest cells that remain attached to 4 microg/ml of thrombospondin-1 is similar to the number that remain attached to dishes coated with 10 microg/ml of fibronectin. These observations indicate that neural crest cells migrate through a thrombospondin-filled extracellular matrix, and that thrombospondin-1 promotes neural crest cell migration and adhesion. Thus, thrombospondin-1 is the first somite-derived extracellular matrix molecule with properties consistent with a role in the promotion of migration into the anterior somite, as opposed to the repulsion of neural crest cells from the posterior half of the somite.

Animals↗
PubMed1999

The thrombospondin-4 gene.

Thrombospondins are a family of extracellular, adhesive proteins that are widely expressed in vertebrates. Five distinct gene products, designated thrombospondin-1 through -4 and cartilage oligomeric matrix protein (COMP), have been identified. With the exception of thrombospondin-4, the structure and location of thrombospondin genes have been determined in the human and/or mouse genomes. In this study, the structure and location of the murine thrombospondin-4 gene and the location of the human thrombospondin-4 gene are reported. The murine thrombospondin-4 gene is approximately 4.5 kb in length and includes 22 exons. Interspecific backcross analysis of progeny derived from matings of (C57BL/6J x Mus spretus)F(1) x C57BL/6J mice indicates that the thrombospondin-4 gene is tightly linked to the Dhfr locus on murine Chromosome (Chr) 13. The human gene maps to Chr 5 in band q13 by in situ hybridization to human metaphase chromosomes. The thrombospondin-4 promoter is similar to promoters of some housekeeping, growth control, and other thrombospondin genes in that it contains multiple GC box sequences and lacks a CAAT box. The presence of multiple E-box sequence motifs is consistent with thrombospondin-4 expression in muscle and bone tissue.

Animals↗
PubMed1999

Overexpression of thrombospondin-1 decreases angiogenesis and inhibits the growth of human cutaneous squamous cell carcinomas.

The function of the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1) in epithelial tumor development has remained controversial. We studied the in vitro growth characteristics and the in vivo tumor xenograft growth of the human squamous cell carcinoma cell lines A431 and SCC-13, stably transfected to overexpress human TSP-1. Overexpression of TSP-1 inhibited tumor growth of A431 xenotransplants, and completely abolished tumor formation by SCC-13 cells. TSP-1 overexpressing A431 tumors were characterized by extensive areas of necrosis and by decreased tumor vessel number and size. The effects of TSP-1 on tumor cell growth were indirect since tumor cell proliferation rates in vivo and in vitro, anchorage-dependent and -independent growth in vitro, and susceptibility to induction of apoptosis by serum withdrawal were unchanged in TSP-1 overexpressing tumor cells. However, TSP-1 overexpression up-regulated the TSP-1 receptor CD36, leading to enhanced adhesion of A431 cells to TSP-1. These findings establish TSP-1 as a potent inhibitor of angiogenesis and tumor growth in carcinomas of the skin.

Animals↗
PubMed1999

Use of dipyridyl-dithio substrates to measure directly the protein disulfide-thiol interchange activity of the auxin stimulated NADH: protein disulfide reductase (NADH oxidase) of soybean plasma membranes.

Dipyridyl-dithio substrates were cleaved by isolated vesicles of plasma membranes prepared from etiolated hypocotyls of soybean. The cleavage was stimulated by auxins at physiological concentrations. The substrates utilized were principally 2,2'-dithiodipyridine (DTP) and 6,6'-dithiodinicotinic acid (DTNA). The DTP generated 2 moles of 2-pyridinethione whereas the 6,6'-dithiodinicotinic acid generated 2 moles of 6-nicotinylthionine. Both products absorbed at 340 nm. The auxin herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D) stimulated the activity approximately 2-fold to a maximum at about 10 microM. Concentrations of 2,4-D greater than 100 microM inhibited the activity. Indole-3-acetic acid stimulated the activity as well. The growth-inactive auxin, 2,3-dichlorophenoxyacetic acid (2,3-D), was without effect. DTNA cleavage correlated with oxidation of NADH and reduction of protein disulfide bonds reported earlier in terms of location at the external plasma membrane surface, absolute specific activity, pH dependence and auxin specificity. The dipyridyl-dithio substrates provide, for the first time, a direct measure of the disulfide-thiol interchange activity of the protein previously measured only indirectly as an auxin-dependent ability of isolated plasma membrane vesicles to restore activity to scrambled and inactive RNase.

2,2'-Dipyridyl↗
PubMed1999

Recovering from stroke: a qualitative investigation of the role of goal setting in late stroke recovery.

This article examines the role of goal setting in the continuing relationship between specialist nurse and patients recovering from stroke. The nurse intervention was intended to ease the patient through the stages of recovery from stroke, focusing on emotional and social recovery rather than physical function. Literature on the use of goals in the nursing process is discussed. The article uses data from contemporary nurse records and from interviews with nurses and with patients and caregivers. The data from each of these elements were subjected to content analysis and were then synthesized using a grounded theory approach to interpret their significance. The perspective of patients and caregivers provides an additional insight into the use and limitations of goal setting which is largely developed in the literature from a nursing perspective. Nurses were found to have different interpretations of the use of goal setting. Some used it explicitly in their relationships with patients, whilst others used the concept to inform their actions whilst being less explicit and more informal. In all cases they demonstrate the tension between establishing and supporting progress towards realistic recovery goals and recognizing the limitations now placed on stroke victims.

Adaptation, Psychological↗
PubMed1999

Biofeedback-assisted relaxation training with brain injured patients in acute stages of recovery.

There are few published accounts or empirical studies of biofeedback-assisted relaxation training with brain injured patients still in acute stages of recovery. Given the efficacy of biofeedback-assisted relaxation training with other medical populations, brain injured patients in acute stages of recovery with anxiety-based symptoms may also stand to gain some benefits from this form of treatment. It has yet to be determined, however, if severe cognitive impairment or disorientation contraindicate biofeedback treatment. The cases profiled here tentatively suggest that consideration of biofeedback-assisted relaxation training, even for severely cognitively impaired brain injured patients in acute stages of recovery, may be appropriate. Empirical investigations will be needed to determine selection criteria and contraindications for biofeedback treatment in the acute brain injury population.

Acute Disease↗
PubMed1999

Mouth care practices in nursing and research-based education: an historical analysis of instructional nursing texts 1870-1997.

In this paper we examine 68 nursing textbooks published between 1870 and 1997 to examine the historical background to contemporary mouth care practice(s) in nursing and the extent to which they are based on research evidence. The analysis shows that, although there has been some variation in the types of equipment and preparations recommended for use over the past 120 years, descriptions of the actual nursing practices themselves have not varied greatly; nor has the discourse varied noticeably. Since the 1970s, there is a progressive increase in references to research. However, the instructional style and discursive frames in which mouth care is discussed reflect an approach to body care that is relatively unchanged in over a century. Individual nursing practices appear as decontextualised and procedurally oriented. With the exception of assessment techniques, written accounts of mouth care practices do not reflect the influence of more recent conceptual or rhetorical standpoints in nursing.

Education, Nursing↗
PubMed1998

Muskelin, a novel intracellular mediator of cell adhesive and cytoskeletal responses to thrombospondin-1.

We have used an expression cloning strategy based on a cell-attachment assay screen to seek identification of molecules required in cellular responses to thrombospondin-1, a regulated macromolecular component of extracellular matrix. We report the identification and functional characterization of a novel, widely expressed, intracellular protein, named muskelin, which contains dispersed motifs with homology to the tandem repeats first identified in the Drosophila kelch ORF1 protein. In adherent C2C12 cells, muskelin localizes in the cytoplasm and at cell margins. Over-expression of muskelin in C2C12 cells promotes cell attachment to the thrombospondin-1 C-terminal domain, alters the mechanisms of attachment to intact thrombospondin-1 and correlates with decreased formation of fascin microspikes and increased assembly of focal contacts by cells adherent on thrombospondin-1. Reciprocally, cell attachment, spreading and cytoskeletal organization are specifically reduced in TSP-1-adherent cells after antisense depletion of muskelin. These results establish a requirement for muskelin in cell responses to thrombospondin-1 and demonstrate that such responses involve a novel process which is integrated into the regulation of cell-adhesive behaviour and cytoskeletal organization.

Amino Acid Sequence↗
PubMed1998

Differential roles of protein kinase C and pertussis toxin-sensitive G-binding proteins in modulation of melanoma cell proliferation and motility by thrombospondin 1.

Thrombospondin 1 (TSP1) is an angiogenesis inhibitor that decreases tumor growth. We now report that TSP1 directly inhibits the proliferation of human melanoma cells. TSP1, peptides, and a recombinant fragment from the type I repeats, but not peptides that bind CD36 or CD47, inhibit the proliferation of A2058 melanoma cells. In contrast, chemotaxis is mediated by peptides or recombinant fragments from the procollagen, type I, type II, and cell-binding domains. The antiproliferative activity of TSP1 is mediated by a different signal transduction pathway than those mediating motility responses to the same protein. Activators of protein kinase A and protein kinase C inhibit chemotaxis but not the antiproliferative activity of TSP1, whereas the antiproliferative activity is reversed by inhibiting the tyrosine kinase or phosphatase activities. TSP1-mediated chemotaxis is partially dependent on a pertussis toxin (PT)-sensitive G-binding protein, whereas haptotaxis is not. Chemotaxis stimulated by the procollagen domain and the CD47-binding sequences from the COOH-terminal domain are also sensitive to PT, but responses to the type I and type III domains are not sensitive to PT. Residual chemotaxis to TSP1 in the presence of PT may therefore be mediated by the activities of the type I or type III repeats. Thus, TSP1 elicits several intracellular signals in melanoma cells that result from interactions with several domains of this protein and differentially affect growth and motility.

Blood Platelets↗
PubMed1998

Thrombospondin-1 is a major activator of TGF-beta1 in vivo.

The activity of TGF-beta1 is regulated primarily extracellularly where the secreted latent form must be modified to expose the active molecule. Here we show that thrombospondin-1 is responsible for a significant proportion of the activation of TGF-beta1 in vivo. Histological abnormalities in young TGF-beta1 null and thrombospondin-1 null mice were strikingly similar in nine organ systems. Lung and pancreas pathologies similar to those observed in TGF-beta1 null animals could be induced in wild-type pups by systemic treatment with a peptide that blocked the activation of TGF-beta1 by thrombospondin-1. Although these organs produced little active TGF-beta1 in thrombospondin null mice, when pups were treated with a peptide derived from thrombospondin-1 that could activate TGF-beta1, active cytokine was detected in situ, and the lung and pancreatic abnormalities reverted toward wild type.

Animals↗
PubMed1998

A human fibrosarcoma inhibits systemic angiogenesis and the growth of experimental metastases via thrombospondin-1.

Concomitant tumor resistance refers to the ability of some large primary tumors to hold smaller tumors in check, preventing their progressive growth. Here, we demonstrate this phenomenon with a human tumor growing in a nude mouse and show that it is caused by secretion by the tumor of the inhibitor of angiogenesis, thrombospondin-1. When growing subcutaneously, the human fibrosarcoma line HT1080 induced concomitant tumor resistance, preventing the growth of experimental B16/F10 melanoma metastases in the lung. Resistance was due to the production by the tumor cells themselves of high levels of thrombospondin-1, which was present at inhibitory levels in the plasma of tumor-bearing animals who become unable to mount an angiogenic response in their corneas. Animals carrying tumors formed by antisense-derived subclones of HT1080 that secreted low or no thrombospondin had weak or no ability to control the growth of lung metastases. Although purified human platelet thrombospondin-1 had no effect on the growth of melanoma cells in vitro, when injected into mice it was able to halt the growth of their experimental metastases, providing clear evidence of the efficacy of thrombospondin-1 as an anti-tumor agent.

Animals↗
PubMed1998

Thrombospondin-1 is required for normal murine pulmonary homeostasis and its absence causes pneumonia.

The thrombospondins are a family of extracellular calcium-binding proteins that modulate cellular phenotype. Thrombospondin-1 (TSP-1) reportedly regulates cellular attachment, proliferation, migration, and differentiation in vitro. To explore its function in vivo, we have disrupted the TSP-1 gene by homologous recombination in the mouse genome. Platelets from these mice are completely deficient in TSP-1 protein; however, thrombin-induced platelet aggregation is not diminished. TSP-1-deficient mice display a mild and variable lordotic curvature of the spine that is apparent from birth. These mice also display an increase in the number of circulating white blood cells, with monocytes and eosinophils having the largest percent increases. The brain, heart, kidney, spleen, stomach, intestines, aorta, and liver of TSP-1-deficient mice showed no major abnormalities. However, consistent with high levels of expression of TSP-1 in lung, we observe abnormalities in the lungs of mice that lack the protein. Although normal at birth, histopathological analysis of lungs from 4-wk-old TSP-1-deficient mice reveals extensive acute and organizing pneumonia, with neutrophils and macrophages. The macrophages stain for hemosiderin, indicating that diffuse alveolar hemorrhage is occurring. At later times, the number of neutrophils decreases and a striking increase in the number of hemosiderin-containing macrophages is observed associated with multiple-lineage epithelial hyperplasia and the deposition of collagen and elastin. A thickening and ruffling of the epithelium of the airways results from increasing cell proliferation in TSP-1-deficient mice. These results indicate that TSP-1 is involved in normal lung homeostasis.

Animals↗
PubMed1998

Thrombospondins in early Xenopus embryos: dynamic patterns of expression suggest diverse roles in nervous system, notochord, and muscle development.

The thrombospondins (TSPs) are a family of extracellular matrix (ECM) glycoproteins that modulate many cell behaviors including adhesion, migration, and proliferation. Here we report the molecular cloning of the Xenopus homologs of TSP-1 and TSP-3, and the developmental patterns of expression of Xenopus TSP-1, TSP-3, and TSP-4 mRNAs. Xenopus TSP-1 and TSP-3 protein sequences each share approximately 80% amino acid identity with their mammalian counterparts. TSP-1 mRNAs are detectable at low levels in fertilized eggs indicating that this TSP is a maternally deposited transcript. Zygotic expression of TSP-1, TSP-3, and TSP-4 begins at the end of gastrulation and transcripts encoding each protein accumulate through the tadpole stages of development. Whole mount in situ hybridizations reveal that each TSP mRNA is localized in the embryo with distinct, developmentally regulated patterns of expression. TSP-1 mRNAs are detected in a wide range of tissues including the floor plate of the neural tube, epidermis, somites, notochord and, most notably, alternating rhombomeres. Transcripts encoding TSP-3 are expressed in the notochord, floor plate, sensorial layer of the epidermis and sensory epithelia. TSP-4 mRNAs are restricted to somitic mesoderm and skeletal muscle. These data suggest that the TSPs represent a functionally diverse family of ECM proteins with tissue-specific functions during embryogenesis.

Amino Acid Sequence↗