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1.
Mar Pollut Bull ; 123(1-2): 418, 2017 10 15.
Article in English | MEDLINE | ID: mdl-28545864
2.
Mar Pollut Bull ; 116(1-2): 9-40, 2017 Mar 15.
Article in English | MEDLINE | ID: mdl-28111002

ABSTRACT

Reductions of zooplankton biomasses and grazing pressures were observed during overfishing-induced trophic cascades and concurrent oil spills at global scales. Recent phytoplankton increments followed, once Fe-, P-, and N-nutrient limitations of commensal diazotrophs and dinoflagellates were also eliminated by respective human desertification, deforestation, and eutrophication during climate changes. Si-limitation of diatoms instead ensued during these last anthropogenic perturbations of agricultural effluents and sewage loadings. Consequently, ~15% of total world-wide annual asthma trigger responses, i.e. amounting to ~45 million adjacent humans during 2004, resulted from brevetoxin and palytoxin poisons in aerosol forms of western boundary current origins. They were denoted by greater global harmful algal bloom [HAB] abundances and breathing attacks among sea-side children during prior decadal surveys of asthma prevalence, compiled here in ten paired shelf ecosystems of western and eutrophied boundary currents. Since 1965, such inferred onshore fluxes of aerosolized DOC poisons of HABs may have served as additional wind-borne organic carriers of toxic marine MeHg, phthalate, and DDT/DDE vectors, traced by radio-iodine isotopes to potentially elicit carcinomas. During these exchanges, as much as 40% of mercury poisonings may instead have been effected by inhalation of collateral HAB-carried marine neurotoxic aerosols of MeHg, not just from eating marine fish. Health impacts in some areas were additional asthma and pneumonia episodes, as well as endocrine disruptions among the same adjacent humans, with known large local rates of thyroid cancers, physician-diagnosed pulmonary problems, and ubiquitous high indices of mercury in hair, pesticides in breast milk, and phthalates in urine.


Subject(s)
Climate Change , Food Chain , Harmful Algal Bloom , Aerosols , Animals , Asthma/epidemiology , Dinoflagellida , Global Health , Humans , Marine Toxins , Zooplankton
3.
Neuroscience ; 282: 101-8, 2014 Dec 12.
Article in English | MEDLINE | ID: mdl-24931766

ABSTRACT

The ventral tegmental area (VTA) in the brain's reward circuitry is composed of a heterogeneous population of dopamine, GABA, and glutamate neurons that play important roles in mediating mood-related functions including depression. These neurons project to different brain regions, including the nucleus accumbens (NAc), the medial prefrontal cortex (mPFC), and the amygdala. The functional understanding of these projection pathways has been improved since the extensive use of advanced techniques such as viral-mediated gene transfer, cell-type-specific neurophysiology and circuit-probing optogenetics. In this article, we will discuss the recent progress in understanding these VTA projection-specific functions, focusing on mood-related disorders.


Subject(s)
Amygdala/physiology , Mood Disorders/metabolism , Neural Pathways , Neurons/physiology , Nucleus Accumbens/physiology , Prefrontal Cortex/physiology , Reward , Ventral Tegmental Area/physiology , Animals , Humans , Neurons/metabolism , Ventral Tegmental Area/metabolism
4.
Angiogenesis ; 16(3): 503-24, 2013 Jul.
Article in English | MEDLINE | ID: mdl-23543223

ABSTRACT

Tumour vasculature targeting has been a very active area of cancer drug discovery over the last decade. Growth of solid tumours beyond a certain point requires a sufficient blood supply in order for them to develop and metastasise. While novel anti-angiogenic and vascular disrupting agents represent an important contribution to the armoury of anti-cancer agents they nevertheless usually require combination with standard cytotoxic therapy in order to demonstrate positive clinical outcomes. In line with this consensus, a new concept has arisen, namely the design of functional hybrids where at least one component of the design targets a tumour angiogenic/vasculature pathway. This review will outline examples of such hybrid/conjugate-based approaches. Emphasis will be placed on their preclinical evaluation with particular focus on the RGD/NGR-conjugates, heparin-related hybrids and antibody-drug conjugates. In conclusion, the benefits and shortcomings of hybrids under development will be discussed in the context of future directions and applications.


Subject(s)
Angiogenesis Inhibitors/pharmacology , Antineoplastic Combined Chemotherapy Protocols/pharmacology , Drug Design , Neoplasms/blood supply , Neoplasms/drug therapy , Neovascularization, Pathologic/drug therapy , Antineoplastic Combined Chemotherapy Protocols/chemistry , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Drug Evaluation, Preclinical/methods , Humans , Models, Biological , Molecular Structure
5.
Br J Pharmacol ; 170(1): 23-37, 2013 Sep.
Article in English | MEDLINE | ID: mdl-23441583

ABSTRACT

Mast cell stabilizing drugs inhibit the release of allergic mediators from mast cells and are used clinically to prevent allergic reactions to common allergens. Despite the relative success of the most commonly prescribed mast cell stabilizer, disodium cromoglycate, in use for the preventative treatment of bronchial asthma, allergic conjunctivitis and vernal keratoconjunctivitis, there still remains an urgent need to design new substances that are less expensive and require less frequent dosing schedules. In this regard, recent developments towards the discovery of the next generation of mast cell stabilizing drugs has included studies on substances isolated from natural sources, biological, newly synthesized compounds and drugs licensed for other indications. The diversity of natural products evaluated range from simple phenols, alkaloids, terpenes to simple amino acids. While in some cases their precise mode of action remains unknown it has nevertheless sparked interest in the development of synthetic derivatives with improved pharmacological properties. Within the purely synthetic class of inhibitors, particular attention has been devoted to the inhibition of important signalling molecules including spleen TK and JAK3. The statin class of cholesterol-lowering drugs as well as nilotinib, a TK inhibitor, are just some examples of clinically used drugs that have been evaluated for their anti-allergic properties. Here, we examine each approach under investigation, summarize the test data generated and offer suggestions for further preclinical evaluation before their therapeutic potential can be realized.


Subject(s)
Anti-Allergic Agents/pharmacology , Hypersensitivity/drug therapy , Mast Cells/immunology , Allergens/immunology , Animals , Anti-Allergic Agents/administration & dosage , Anti-Allergic Agents/economics , Biological Products/pharmacology , Drug Administration Schedule , Drug Costs , Drug Design , Humans , Hypersensitivity/immunology
6.
Curr Med Chem ; 17(7): 609-39, 2010.
Article in English | MEDLINE | ID: mdl-20088764

ABSTRACT

The targeting of tubulin is an important mechanism for cancer chemotherapy. However, limitations such as resistance, toxicity and incomplete tumour elimination associated with individual anti-cancer drugs have led to a need for combination therapy in cancer. It is therefore relevant to ask whether two or more drugs might be combined in a single hybrid molecule to advantageous effect. This review provides an overview of the hybrid drugs thus far investigated, in which at least one component targets tubulin. The rationale behind this approach is that the hybrid drug may have activity enhanced above and beyond that of the equivalent drug combination, or have an otherwise improved clinical outcome. Particular emphasis is placed on the investigation of activity in multidrug-resistant cancer cell lines. Attention is drawn to the difficulties encountered when developing hybrid drugs, with respect to in vivo metabolism-tracking, increased molecular bulk, and optimisation of the drug dosage ratio. The actual and potential advantages and disadvantages of such hybrid drugs when compared to single drugs or drug combinations are discussed critically and promising directions for future research is highlighted.


Subject(s)
Antineoplastic Agents/chemistry , Tubulin Modulators/chemistry , Antineoplastic Agents/therapeutic use , Drug Design , Drug Resistance, Neoplasm , Drug Therapy, Combination , Humans , Neoplasms/drug therapy , Tubulin/metabolism , Tubulin Modulators/therapeutic use
7.
Eur J Med Chem ; 44(12): 5018-22, 2009 Dec.
Article in English | MEDLINE | ID: mdl-19793620

ABSTRACT

Asthma is characterised by bronchoconstriction and inflammation, with infiltration and activation of inflammatory cells such as eosinophils and mast cells, and subsequent release of inflammatory mediators. Much of the therapy directed at the treatment of asthma is either to provide symptomatic relief through bronchodilation or to reduce inflammation to prevent or delay airway remodelling. In an attempt to address both of these issues, a novel series of 1,2-indane dimers has been synthesized and evaluated for smooth muscle relaxant and mast cell stabilising activities. We have identified two lead compounds, 5 and 15, which have substantial mast cell stabilisation activity.


Subject(s)
Indans , Mast Cells/physiology , Muscle Relaxation/physiology , Muscle, Smooth/physiology , Animals , Dimerization , Female , Guinea Pigs , Ileum/physiology , Indans/chemical synthesis , Indans/chemistry , Indans/pharmacology , Male , Molecular Structure
8.
Curr Pharm Des ; 15(25): 2970-85, 2009.
Article in English | MEDLINE | ID: mdl-19754373

ABSTRACT

Malaria continues to devastate much of the tropics and sub-tropics in spite of the availability of a number of antimalarial drugs. Part of this problem is due to the disadvantages of the drugs in use, which include (depending on the drug) side effects, reduced efficacy due to resistance, and high cost. Multiple traditional and novel approaches to the discovery and design of new antimalarial agents are likely to be required to furnish the new drugs necessary for improved malaria control. This review will address one novel and emerging approach, namely the development of hybrid antimalarial agents composed of two distinct antimalarial moieties joined covalently. Particular emphasis will be placed on the properties of the hybrids' design, including biological activity, advantages over other approaches, and the potential to address issues relating to resistance, solubility and formulation/delivery. The review will discuss the synthetic methodology used to form the hybrid and the ease by which it may be cleaved to form the independent components in vivo. The molecules discussed include hybrids of (i) artemisinins or other endoperoxide-based agents and quinolines (e.g. trioxaquines), (ii) chloroquine or other aminoquinolines and resistance-reversing or other agents, and (iii) peptidase inhibitors and other agents. The actual and potential advantages and disadvantages of such hybrids in relation to established single drugs or drug combinations will be discussed critically and promising future directions highlighted.


Subject(s)
Antimalarials/chemical synthesis , Drug Design , Prodrugs/chemical synthesis , Animals , Antimalarials/adverse effects , Antimalarials/pharmacology , Chemistry, Pharmaceutical , Drug Resistance , Humans , Molecular Structure , Prodrugs/adverse effects , Prodrugs/pharmacology , Structure-Activity Relationship
9.
Bioorg Med Chem ; 16(1): 248-54, 2008 Jan 01.
Article in English | MEDLINE | ID: mdl-17936628

ABSTRACT

A series of N-substituted 3-aminoindanones were synthesised and evaluated for smooth muscle relaxant activity and mediator release inhibition effects. A low level of smooth muscle relaxant activity has been identified in all derivatives. Data have revealed that the significant mediator release inhibition effects observed are related to the nature of the amine substituents. A structure activity relationship is proposed.


Subject(s)
Indans/chemical synthesis , Indans/pharmacology , Muscle Relaxation/drug effects , Amines , Animals , Female , Guinea Pigs , Histamine , Ileum , Mast Cells/drug effects , Mast Cells/metabolism , Muscle, Smooth/drug effects , Rats , Rats, Wistar , Structure-Activity Relationship
10.
J Geophys Res ; 111(C11003): 1-46, 2006 Nov 07.
Article in English | MEDLINE | ID: mdl-20411040

ABSTRACT

[1] Independent data from the Gulf of Mexico are used to develop and test the hypothesis that the same sequence of physical and ecological events each year allows the toxic dinoflagellate Karenia brevis to become dominant. A phosphorus-rich nutrient supply initiates phytoplankton succession, once deposition events of Saharan iron-rich dust allow Trichodesmium blooms to utilize ubiquitous dissolved nitrogen gas within otherwise nitrogen-poor sea water. They and the co-occurring K. brevis are positioned within the bottom Ekman layers, as a consequence of their similar diel vertical migration patterns on the middle shelf. Upon onshore upwelling of these near-bottom seed populations to CDOM-rich surface waters of coastal regions, light-inhibition of the small red tide of ~1 ug chl l(-1) of ichthytoxic K. brevis is alleviated. Thence, dead fish serve as a supplementary nutrient source, yielding large, self-shaded red tides of ~10 ug chl l(-1). The source of phosphorus is mainly of fossil origin off west Florida, where past nutrient additions from the eutrophied Lake Okeechobee had minimal impact. In contrast, the P-sources are of mainly anthropogenic origin off Texas, since both the nutrient loadings of Mississippi River and the spatial extent of the downstream red tides have increased over the last 100 years. During the past century and particularly within the last decade, previously cryptic Karenia spp. have caused toxic red tides in similar coastal habitats of other western boundary currents off Japan, China, New Zealand, Australia, and South Africa, downstream of the Gobi, Simpson, Great Western, and Kalahari Deserts, in a global response to both desertification and eutrophication.

11.
Nature ; 410(6830): 825-30, 2001 Apr 12.
Article in English | MEDLINE | ID: mdl-11298452

ABSTRACT

The early mammalian embryo is patterned by signals emanating from extraembryonic and embryonic signalling centres, most notably the anterior visceral endoderm (AVE) and the node, respectively. The AVE is responsible for anterior development, whereas further axis specification depends on the node, the equivalent of Spemann's organizer. Formation of the node, at the anterior primitive streak, depends on expression of the transcription factor HNF3beta (ref. 4). However, both the source and the nature of the signals responsible for inducing the node have been unknown. Here we describe a recessive lethal mutation, arkadia, generated using gene-trap mutagenesis. Mutant embryos establish an AVE but fail to maintain anterior embryonic structures and lack a node. The mutation has disrupted the Arkadia gene, which encodes a putative intracellular protein containing a RING domain. Arkadia is essential for HNF3beta expression in the anterior primitive streak. Analysis with chimaeras, however, shows that Arkadia functions within extraembryonic tissues, revealing that these are required to induce the node. Furthermore, our experiments show that Arkadia interacts genetically with the transforming growth factor (TGF)beta-like factor Nodal, implying that Nodal mediates the function of Arkadia in node induction.


Subject(s)
Body Patterning/physiology , Embryonic Induction , Embryonic and Fetal Development/physiology , Nuclear Proteins/physiology , Amino Acid Sequence , Animals , Body Patterning/genetics , Cell Line , Chick Embryo , Chimera , Ectoderm/physiology , Embryonic Induction/genetics , Genes, Lethal , Genetic Markers , Humans , Mice , Molecular Sequence Data , Mutagenesis , Nodal Protein , Nuclear Proteins/genetics , Organizers, Embryonic/physiology , Retroviridae/genetics , Transforming Growth Factor beta/genetics , Transforming Growth Factor beta/metabolism , Ubiquitin-Protein Ligases , Xenopus
12.
Nature ; 410(6830): 830-4, 2001 Apr 12.
Article in English | MEDLINE | ID: mdl-11298453

ABSTRACT

Nodal-related members of the transforming growth factor (TGF)-beta family regulate the induction of mesoderm, endoderm, and mesendoderm, a tissue specific to the Spemann organizer. How these different tissues form in response to the same signalling molecules is not completely understood. It has been suggested that concentration-dependent effects, mediated by extracellular cofactors and antagonists, are responsible for the differences. Here we show that the nuclear protein Arkadia specifically potentiates the mesendoderm-inducing activity of a subset of TGF-beta family members. The combined activities of Arkadia and Xenopus nodal-related-1 are sufficient to induce mesendoderm and suppress mesoderm. Arkadia dorsalizes ventral tissues, resulting in the induction of organizer-specific gene expression. Blocking nodal signalling extracellularly inhibits these effects. Arkadia influences nodal activity when co-expressed and can function in cells adjacent to those producing the nodal signal. Our findings, together with the observation that Arkadia mutant mice lack a node and node-derived mesendoderm, identify Arkadia as an essential modulator of the nodal signalling cascade that leads to induction of Spemann's organizer.


Subject(s)
Embryonic Induction , Mesoderm/physiology , Nuclear Proteins/physiology , Organizers, Embryonic/physiology , Repressor Proteins , Signal Transduction , Transcription Factors , Xenopus Proteins , Animals , Body Patterning/physiology , Bone Morphogenetic Protein 4 , Bone Morphogenetic Proteins/metabolism , Gene Expression Regulation, Developmental , Goosecoid Protein , Homeodomain Proteins/metabolism , Mice , Nuclear Proteins/chemistry , Nuclear Proteins/genetics , Protein Structure, Tertiary , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , T-Box Domain Proteins/metabolism , Transforming Growth Factor beta/metabolism , Transforming Growth Factor beta/physiology , Ubiquitin-Protein Ligases , Xenopus
13.
Hand Clin ; 16(3): 397-403, viii, 2000 Aug.
Article in English | MEDLINE | ID: mdl-10955213

ABSTRACT

Hamate hook fractures, although uncommon, are now recognized with increasing frequency because of the increase in popularity of racket sports and golf. Careful clinical evaluation and adjunctive radiologic investigation help establish the diagnosis. Acute nondisplaced fractures can heal with immobilization, while displaced fractures and nonunions typically require open reduction and internal fixation (acute fractures) or hook excision.


Subject(s)
Athletic Injuries/diagnosis , Athletic Injuries/therapy , Carpal Bones/injuries , Fracture Fixation/methods , Fractures, Bone/diagnosis , Fractures, Bone/therapy , Diagnosis, Differential , Diagnostic Imaging , Humans
14.
Cell Adhes Commun ; 5(4): 273-81, 1998 Jun.
Article in English | MEDLINE | ID: mdl-9762468

ABSTRACT

The alpha 2 beta 1 integrin functions as a cell surface receptor for collagen on some cells and as both a collagen and laminin receptor on a more restricted subset of cell types including endothelial and epithelial cells. The alpha 2 integrin subunit I domain binds collagen in a divalent cation-dependent manner. In contrast, I domain binding to laminin occurs via both divalent cation-dependent and -independent mechanisms. Saturable binding was observed in the presence of either Mn2+ or EDTA, although the extent of binding in Mn2+ was twice that observed in EDTA. Half-maximal binding occurred at about 22 nM I domain in either case. Whereas laminin binding was significantly enhanced by Mn2+, with half-maximal binding occurring at 1.9 mM Mn2+, Mg2+ was much less effective. Deletion of the N-terminal 35 residues of the I domain, including the DXSXS portion of the MIDAS motif, caused a significant diminution of laminin binding activity. Laminin binding by the I domain was significantly inhibited by the alpha 2 beta 1 function-blocking antibody 6F1 in the presence of either EDTA or Mn2+. The non-function-blocking antibody 12F1 had no effect. In contrast to the binding of the alpha 2 integrin I domain to collagen, the laminin binding activity of the I domain was not enhanced by the addition of the first EF hand motif of the integrin.


Subject(s)
Antigens, CD/chemistry , Antigens, CD/metabolism , Collagen/metabolism , Extracellular Space/metabolism , Laminin/metabolism , Antibodies, Monoclonal , Antigens, CD/genetics , Cations, Divalent/metabolism , Chelating Agents/pharmacology , Cloning, Molecular , Edetic Acid/pharmacology , Humans , Integrin alpha2 , Laminin/immunology , Ligands , Magnesium/pharmacology , Manganese/pharmacology , Mutagenesis/physiology , Protein Binding/drug effects , Protein Binding/physiology , Protein Structure, Tertiary
15.
Skeletal Radiol ; 27(4): 218-21, 1998 Apr.
Article in English | MEDLINE | ID: mdl-9592906

ABSTRACT

MR imaging of an anomalous hypothenar adductor muscle causing isolated deep ulnar nerve branch compression and producing a purely motor neuropathy is presented. The muscle appears to represent a type 1 variant of the intrinsic anomalous hypothenar adductor muscle.


Subject(s)
Magnetic Resonance Imaging , Muscle, Skeletal/abnormalities , Ulnar Nerve Compression Syndromes/diagnosis , Decompression, Surgical , Female , Humans , Middle Aged , Muscle, Skeletal/pathology , Muscle, Skeletal/surgery , Ulnar Nerve/pathology , Ulnar Nerve/surgery , Ulnar Nerve Compression Syndromes/surgery
16.
J Pediatr Orthop ; 18(2): 219-21, 1998.
Article in English | MEDLINE | ID: mdl-9531405

ABSTRACT

Reports in the literature suggest that there is an association between two childhood disorders: torticollis, an easily recognized clinical deformity, and developmental dislocation or dysplasia of the hip, an occult disorder. The identification of the obvious disease, torticollis, may prompt a search for the occult disease, developmental dislocation of the hip. If the association of these two disorders is common, it may be justified to expend resources to diagnose the occult disorder in all cases in which the more obviously noticed disorder is recognized. The reported association varies between 2 and 29%. We retrospectively reviewed 70 patients with the diagnosis of congenital muscular torticollis to determine the incidence of hip dislocation or subluxation in these patients. Fifty-four patients had radiographs of their hips. Forty-one patients were available for follow-up at an average of age 3+4 years. Six patients were noted to have hip subluxation or dislocation, all at presentation. Of these, four had been referred for diagnosed hip disease, whereas two were referred for torticollis, and the hip disease was then diagnosed by the pediatric orthopaedist. No patient had abnormal radiographs or physical findings at follow-up. We conclude that the rate of hip disease in those with torticollis is approximately 8% and is lower than the 20% often quoted.


Subject(s)
Hip Dislocation, Congenital/complications , Hip Dislocation, Congenital/epidemiology , Torticollis/complications , Child , Child, Preschool , Data Collection , Female , Follow-Up Studies , Hip Dislocation, Congenital/diagnostic imaging , Humans , Incidence , Infant , Infant, Newborn , Male , Radiography , Sex Distribution , Torticollis/congenital , Torticollis/epidemiology
17.
Biochem Mol Biol Int ; 42(3): 577-82, 1997 Jul.
Article in English | MEDLINE | ID: mdl-9247715

ABSTRACT

The adhesion of platelets and other cells to type I collagen is mediated by the alpha 2 beta 1 integrin. A binding site for the alpha 2 beta 1 integrin within the alpha 1(I) collagen chain has previously been localized to the cyanogen bromide fragment alpha 1(I)-CB3. We noe show by use of inhibitory monoclonal antibodies against the alpha 2 beta 1 integrin, that platelets also adhere to purified alpha 2(I) collagen chains by a mechanism mediated by the alpha 2 beta 1 integrin. Moreover, following isolation of cyanogen bromide fragments of the alpha 2(I) collagen chain by HPLC, we demonstrate that alpha 2 beta 1 integrin-mediated adhesion is restricted to the CB4 fragment of the alpha 2(I) collagen polypeptide. These findings indicate the presence of at least two spatially distinct binding sites for the alpha 2 beta 1 integrin on the native type I collagen triple helix.


Subject(s)
Collagen/metabolism , Integrins/metabolism , Peptide Fragments/metabolism , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/pharmacology , Binding Sites , Cattle , Cell Adhesion , Chromatography, High Pressure Liquid , Integrins/antagonists & inhibitors , Integrins/immunology , Protein Binding , Receptors, Collagen
18.
J Biol Chem ; 272(12): 7661-8, 1997 Mar 21.
Article in English | MEDLINE | ID: mdl-9065422

ABSTRACT

The alpha2beta1 integrin binds collagen in a Mg2+-dependent manner that is inhibited by Ca2+. Like the intact integrin, purified recombinant proteins containing the alpha2 integrin I domain, either alone or with variable numbers of alpha2 integrin EF hand metal binding sites, bound collagen in a Mg2+-dependent manner, and Ca2+ did not support binding. However, unlike the intact integrin, Ca2+ did not inhibit the Mg2+-dependent binding of any of the fusion proteins to collagen. Binding to collagen was saturable and blocked by the alpha2beta1 function blocking antibody 6F1. Deletional analysis demonstrated that residues present within the amino-terminal 35 amino acids contribute to the 6F1 epitope and are required for Mg2+-dependent collagen binding. The results indicate that the I domain contains a Mg2+ binding site that is essential for collagen binding and that the I domain alone is sufficient for collagen binding. Binding is markedly enhanced in a divalent cation-dependent manner by the addition of the first EF hand motif. Mutation of the EF hand to an inactive form completely abrogated the effect. The sites necessary for Ca2+ inhibition are not present within the I domain or the adjacent region containing the three EF hand sites.


Subject(s)
Calcium/metabolism , Collagen/metabolism , Integrins/metabolism , Magnesium/metabolism , Binding Sites , Humans , Protein Binding , Receptors, Collagen , Recombinant Proteins/metabolism
19.
Blood ; 81(7): 1778-86, 1993 Apr 01.
Article in English | MEDLINE | ID: mdl-8461464

ABSTRACT

Divalent cation-dependent platelet adhesion to fibronectin (FN) is mediated by the integrin receptors alpha 5 beta 1 (GP Ic-IIa) and alpha IIb beta 3 (GP IIb-IIIa), which recognize the RGD (Arg-Gly-Asp) sequence in the cell-binding domain. However, FN can also support divalent cation-independent platelet adhesion. To determine which domain of FN mediates divalent cation-independent adhesion, proteolysis with thermolysin and affinity chromatography were used to isolate the cell-binding, gelatin-binding, and heparin-binding domains of FN. Unactivated and thrombin-activated platelets adhered to intact FN and the 45-Kd gelatin-binding domain in the presence of either Ca2+ or EDTA. Platelet spreading was mediated only by the 105-Kd cell-binding domain and required divalent cations. The heparin-binding domains did not support platelet adhesion. Reduction of intrachain disulfide bonds or removal of carbohydrate side chains on the gelatin-binding domain did not alter the ability to support platelet adhesion. Divalent cation-independent adhesion to the 45-Kd gelatin-binding domain was not inhibited by RGDS (Arg-Gly-Asp-Ser) synthetic peptides or monoclonal antibodies (MoAbs) directed against known platelet receptors. We conclude that platelets can adhere but not spread on the gelatin-binding domain of FN by a novel divalent cation-independent mechanism.


Subject(s)
Calcium/blood , Carrier Proteins/blood , Fibronectins/blood , Gelatin/blood , Platelet Adhesiveness , Amino Acid Sequence , Cations, Divalent/blood , Cell Communication , Edetic Acid/pharmacology , Humans , Molecular Sequence Data , Peptide Fragments/blood , Platelet Adhesiveness/drug effects , Protein Binding
20.
Am J Respir Cell Mol Biol ; 8(4): 417-24, 1993 Apr.
Article in English | MEDLINE | ID: mdl-8476635

ABSTRACT

The type beta transforming growth factors (TGF-beta s) are a family of potent cytokines with diverse effects on proliferation, differentiation, turnover of extracellular matrix components, oncogene expression, and other aspects of cellular phenotype. Unlike lung fibroblasts of certain species, unstimulated human lung fibroblast lines produce little or no TGF-beta in culture. However, TGF-beta has been reported to autoregulate its own production in certain human tumor cells and in rodent cell lines. To test whether this phenomenon is operative in fibroblasts from normal human lung tissue, confluent cultures of IMR90 normal fetal lung fibroblasts were exposed to TGF-beta. Cultures were exposed briefly to purified TGF-beta 1 under serum-free conditions and secretion of newly synthesized TGF-beta over the ensuing 72 h was determined by immunoblotting and bioassays made specific with the use of neutralizing antibodies. Steady-state levels of mRNA for TGF-beta 1 were detected by Northern and slot blot hybridization analysis of total cellular RNA. The 2.5 kb TGF-beta 1 mRNA species rose within 1.5 h of exposure of IMR90 cells to TGF-beta 1 and reached maximal levels after 16 h. Increased levels of TGF-beta were detected in conditioned medium 9 h after the start of the exposure. Thereafter, TGF-beta continued to accumulate at an elevated rate (90 +/- 7 versus < or = 15 pg/10(6) cells/h in uninduced cells) for up to 72 h. As little as 1 ng/ml TGF-beta 1 auto-induced TGF-beta secretion.(ABSTRACT TRUNCATED AT 250 WORDS)


Subject(s)
Gene Expression Regulation , Lung/metabolism , Transforming Growth Factor beta/genetics , Animals , Blotting, Northern , Blotting, Western , Cell Line , Feedback , Fibroblasts/metabolism , Humans , Lung/cytology , Mink , Transforming Growth Factor beta/metabolism
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