Impact of prestorage leucoreduction of autologous whole blood on length of hospital stay with a subgroup analysis in bilateral hip arthroplasty

BACKGROUND

Although prestorage leucoreduction (LR) of blood components for transfusion has gained favour around the world, evidence of its beneficial clinical effects is ambiguous.

STUDY DESIGN AND METHODS

To reveal whether leucocytes and/or platelets in transfused blood are related to transfusion-related adverse effects, a prospective randomized crossover study was performed on patients who donated autologous blood prior to elective surgery. Among 1487 primary enrolees, a total of 192 patients undergoing two-stage, bilateral total hip arthroplasty were randomized to receive autologous blood that was either prestorage leucoreduced, or not, for the first procedure. For the second procedure, each patient was crossed over to receive alternatively processed autologous blood. Length of hospital stay served as a primary end-point, with perioperative infectious/thrombotic complications, pre- and postoperative laboratory values, and body temperature serving as secondary endpoints.

RESULTS

No significant differences emerged between prestorage LR and non-LR cohorts in length of hospital stay, as well as perioperative infectious/thrombotic complications, postoperative body temperature and duration of fever. Postoperative laboratory values including white blood cell counts and C-reactive protein levels had no significant differences.

CONCLUSION

This study could not prove any superiority of prestorage LR over non-LR for autologous whole blood among patients who underwent total hip arthroplasty.

A unique sequence of the laminin alpha 3 G domain binds to heparin and promotes cell adhesion through syndecan-2 and -4

Laminin-5, consisting of the alpha 3, beta 3, and gamma 2 chains, is localized in the skin basement membrane and supports the structural stability of the epidermo-dermal linkage and regulates various cellular functions. The alpha chains of laminins have been shown to have various biological activities. In this study, we identified a sequence of the alpha 3 chain C-terminal globular domain (LG1-LG5 modules) required for both heparin binding and cell adhesion using recombinant proteins and synthetic peptides. We found that the LG3 and LG4 modules have activity for heparin binding and that LG4 has activity for cell adhesion. Studies with synthetic peptides delineated the A3G75aR sequence (NSFMALYLSKGR, residues 1412--1423) within LG4 as a major site for both heparin and cell binding. Substitution mutations in LG4 and A3G75aR identified the Lys and Arg of the A3G75aR sequence as critical for these activities. Cell adhesion to LG4 and A3G75aR was inhibited by heparitinase I treatment of cells, suggesting that cell binding to the A3G75aR site was mediated by cell surface heparan sulfate proteoglycans. We showed by affinity chromatography that syndecan-2 from fibroblasts bound to LG4. Solid-phase assays confirmed that syndecan-2 interacted with the A3G75aR peptide sequence. Stably transfected 293T cells with expression vectors for syndecan-2 and -4, but not glypican-1, specifically adhered to LG4 and A3G75aR. These results indicate that the A3G75aR sequence within the laminin alpha 3 LG4 module is responsible for cell adhesion and suggest that syndecan-2 and -4 mediate this activity.

Search for a W' boson via the decay mode W'-->munumu in 1.8 TeV pp collisions

We report the results of a search for a W' boson produced in pp collisions at a center-of-mass energy of 1.8 TeV using a 107 pb-1 data sample recorded by the Collider Detector at Fermilab. We consider the decay channel W'-->&munumu and search for anomalous production of high transverse mass munumu lepton pairs. We observe no excess of events above background and set limits on the rate of W' boson production and decay relative to standard model W boson production and decay using a fit of the transverse mass distribution observed. If we assume standard model strength couplings of the W' boson to quark and lepton pairs, we exclude a W' boson with invariant mass less than 660 GeV/c2 at 95% confidence level.

The ActR-I activin receptor protein is expressed in notochord, lens placode and pituitary primordium cells in the mouse embryo

ActR-I is a type I serine/threonine kinase receptor which has been shown to bind activin and bone morphogenetic proteins (BMPs). To study the function of ActR-I, we have generated novel monoclonal antibodies that specifically recognize the extracellular domain of mouse ActR-I. We examined the level of ActR-I protein during mouse development by immunohistochemistry. We found that in the embryonic body, ActR-I protein first appears in a restricted part of the primitive streak region and is present throughout the length of notochord. Furthermore, ActR-I protein is expressed in the facial sensory organ primordia, including eye area, otic vesicle and olfactory placode, which all contain invaginating ectoderm. In addition, ActR-I is produced in pituitary primordium (Rathke's pouch), mammary buds and the epithelial layer of branchial arches. Interestingly, in the lens placodes and in early Rathke's pouch, ActR-I protein is transiently localized at the apical surface of the epithelial cells, indicating the presence of an apical-basal asymmetry in these cells.

Vinexin forms a signaling complex with Sos and modulates epidermal growth factor-induced c-Jun N-terminal kinase/stress-activated protein kinase activities

Vinexin, a novel protein that plays a key role in cell spreading and cytoskeletal organization, contains three SH3 domains and binds to vinculin through its first and second SH3 domains. We show here that the third SH3 domain binds to Sos, a guanine nucleotide exchange factor for Ras and Rac, both in vitro and in vivo. Point mutations in the third SH3 domain abolished the vinexin-Sos interaction. Stimulation of NIH/3T3 cells with serum, epidermal growth factor (EGF), or platelet-derived growth factor (PDGF) decreased the electrophoretic mobility of Sos and concomitantly inhibited formation of the vinexin-Sos complex. Phosphatase treatment of lysates restored the binding of Sos to vinexin, suggesting that signaling from serum, EGF, or PDGF regulates the vinexin-Sos complex through the Sos phosphorylation. To evaluate the function of vinexin downstream of growth factors, we examined the effects of wild-type and mutant vinexin expression on extracellular signal-regulated kinase (Erk) and c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) activation in response to EGF. Exogenous expression of vinexin beta in NIH/3T3 cells enhanced JNK/SAPK activation but did not affect Erk activation. Moreover mutations in the third SH3 domain abolished EGF activation of JNK/SAPK in a dominant-negative fashion, whereas they slightly stimulated Erk. Together these results suggest that vinexin can selectively modulate EGF-induced signal transduction pathways leading to JNK/SAPK kinase activation.

Molecular diversity of cell-matrix adhesions

In this study we have examined for molecular heterogeneity of cell-matrix adhesions and the involvement of actomyosin contractility in the selective recruitment of different plaque proteins. For this purpose, we have developed a novel microscopic approach for molecular morphometry, based on automatic identification of matrix adhesions, followed by quantitative immunofluorescence and morphometric analysis. Particularly informative was fluorescence ratio imaging, comparing the local labeling intensities of different plaque molecules, including vinculin, paxillin, tensin and phosphotyrosine-containing proteins. Ratio imaging revealed considerable molecular heterogeneity between and within adhesion sites. Most striking were the differences between focal contacts, which are vinculin- and paxillin-rich and contain high levels of phosphotyrosine, and fibrillar adhesions, which are tensin-rich and contain little or no phosphotyrosine. Ratio imaging also revealed considerable variability in the molecular substructure of individual focal contacts, pointing to a non-uniform distribution of phosphotyrosine and the different plaque constituents. Studying the quantitative relationships between the various components of the submembrane plaque indicated that the levels of vinculin, paxillin and phosphotyrosine in adhesion sites are positively correlated with each other and negatively correlated with the levels of tensin. Tyrosine phosphorylation of focal contacts was highly sensitive to cellular contractility, and was diminished within 5 minutes after treatment with the kinase inhibitor H-7, an inhibitor of actomyosin contractility. This was followed by the loss of paxillin and vinculin from the focal adhesions. Tensin-rich fibrillar adhesions were relatively insensitive to H-7 treatment. These findings suggest a role for contractility in the generation of matrix adhesion diversity.

Cooperative activity of alpha4beta1 and alpha4beta7 integrins in mediating human B-cell lymphoma adhesion and chemotaxis on fibronectin through recognition of multiple synergizing binding sites within the central cell-binding domain

We have quantitated the relative contributions of the constitutively active alpha4beta1 and alpha4beta7 integrins and the domains embodying their cognate binding sites in mediating human B-cell lymphoma adhesion and chemotaxis on fibronectin. By cooperating, the central cell-binding and IIICS carboxy-terminal domains were entirely responsible for the adhesion activity displayed by fibronectin, and their relative contribution to this process was estimated to be 30% versus 70%. Assessment of the leukocyte-substrate binding strength (ie, dynes/cell) indicated a 10-fold higher avidity of the cell-IIICS domain interaction. The two integrins interchangeably recognized both domains, but differed quantitatively in their participation in the adhesive event, as well as in domain preference. The use of 3Fn (according to the nomenclature proposed by Bork and Koonin [Curr Opin Struct Biol 6:366, 1996] for the type III fibronectin modules) module-specific antibodies and recombinant polypeptides showed that alpha4 integrins recognized both the RGD sequence (3Fn10) and an apparently novel synergistic site located within the 3Fn8 module; even in this case, the integrins displayed a distinct binding site preference. Interleukin-1beta (IL-1beta)/IL-2-induced chemotaxis also involved cooperative function of the central cell-binding and IIICS domains, but the mechanisms regulating this phenomenon differed markedly from those controlling cell adhesion. First, the relative contribution of the individual domains was comparable, but neither of the individual domains promoted migration to the extent observed on intact fibronectin. Secondly, alpha4beta1 and alpha4beta7 integrins were both involved in the domain-binding necessary for initiation of migration, but the relative contribution of each receptor in the chemotactic process was less disparate than for initial cell adhesion. Thirdly, the mode by which chemotactic B-lymphoma movement was supported by the central cell-binding domain differed from that sustaining cell adhesion in that it involved independent recognition of either the 3Fn8 or the 3Fn9 module, which acted in synergy with the 3Fn10 module. Our data provide novel evidence concerning the relative importance of the constitutively active alpha4beta1 and alpha4beta7 integrins for the interaction of B-cell lymphoma cells with fibronectin, and they emphasize a multiple and diverse recognition of sites responsible for either anchorage or locomotion of tumor leukocytes on this matrix molecule.

Vinexin: a novel vinculin-binding protein with multiple SH3 domains enhances actin cytoskeletal organization

Using the yeast two-hybrid system and an in vitro binding assay, we have identified a novel protein termed vinexin as a vinculin-binding protein. By Northern blotting, we identified two types of vinexin mRNA that were 3 and 2 kb in length. Screening for full-length cDNA clones and sequencing indicated that the two mRNA encode 82- and 37-kD polypeptides termed vinexin alpha and beta, respectively. Both forms of vinexin share a common carboxyl-terminal sequence containing three SH3 domains. The larger vinexin alpha contains an additional amino-terminal sequence. The interaction between vinexin and vinculin was mediated by two SH3 domains of vinexin and the proline-rich region of vinculin. When expressed, vinexin alpha and beta localized to focal adhesions in NIH 3T3 fibroblasts, and to cell-cell junctions in epithelial LLC-PK1 cells. Furthermore, expression of vinexin increased focal adhesion size. Vinexin alpha also promoted upregulation of actin stress fiber formation. In addition, cell lines stably expressing vinexin beta showed enhanced cell spreading on fibronectin. These data identify vinexin as a novel focal adhesion and cell- cell adhesion protein that binds via SH3 domains to the hinge region of vinculin, which can enhance actin cytoskeletal organization and cell spreading.

Age-depending effects of methotrexate treatment on systemic bone turnover in experimental adjuvant arthritis

Adjuvant arthritis was induced in rats in the growth stage (aged 6 weeks) and those in the mature stage (aged 4 months), and changes in the systemic bone turnover and the effects of methotrexate (MTX, CAS 133073-73-1) were compared. After induction of adjuvant arthritis, the paw edema ratio and the urinary deoxypyridinoline (u-Dpy) level increased in both age groups. No marked changes were observed in the serum osteocalcin (s-OC) level in either group. In the 6-week-old rats, arthritis completely inhibited the bone mass, and strength of the femur and lumbar vertebral body. The 4-month-old rats showed more marked changes than the 6-week-old rats in the bone mass and strength of the lumbar, vertebral body. MTX administration (0.05, 0.1 and 0.2 mg/kg/day) resulted in significant dose-dependent inhibition of arthritis-induced changes, and the effects of MTX were similar between the two age groups. MTX was useful at each age. These results suggest that 4-month-old rats with arthritis are more appropriate as a model for evaluation of drugs for bone metabolic turnover in human chronic rheumatoid arthritis.

Prednisolone prevents decreases in trabecular bone mass and strength by reducing bone resorption and bone formation defect in adjuvant-induced arthritic rats

We examined the effects of prednisolone (PSL) administration in normal female Sprague Dawley rats and adjuvant-induced arthritic rats at the age of 6 weeks. Rats were intramuscularly injected with PSL twice a week at doses of 0 (control), 10, 30, 90, or 270 mg/kg body weight (b.w.). In the normal rats, serum osteocalcin level at 14 days and serum carboxyterminal pyridinoline cross-linked telopeptide of type 1 collagen (1CTP) level at 28 days in the 270 mg/kg dose group was lower than the respective value in control animals. The BMC and the trabecular bone formation rate (BFR/BS) of the lumbar body (L-4) in the 270 mg/kg dose group at 14 and 28 days were significantly lower than the values in the control rats. In the arthritic rats, however, serum osteocalcin levels in the PSL-treated groups did not differ compared with arthritic controls. The serum 1CTP levels in all of the PSL-treated groups were significantly reduced at 28 days. The age-dependent increases in the L4 BMC, BMD, and L-3 ultimate compressive load values were maintained. The BFR/BS values in the 90 mg/kg and 270 mg/kg dose groups were significantly higher than those in the arthritic control rats. The trabecular osteoclast number and surface values in all of the PSL-treated groups were significantly lower than the values in arthritic controls. These data demonstrate that PSL administration prevented reduction in bone mass and strength of the lumbar trabecular bone in adjuvant-induced arthritic rats by reducing the increase in bone resorption and the decrease in bone formation at both the local and systemic levels.

Green fluorescent protein labeling of cytoskeletal structures--novel targeting approach based on leucine zippers

Green fluorescent protein (GFP) is a valuable marker for intracellular protein localization. However the fusion of GFP with structural proteins can alter their properties, resulting in a loss of fusion protein localization, decreased GFP fluorescence or both. We describe a novel targeting approach based on noncovalent heterodimerization of GFP and cytoplasmic structural proteins. The formation of structural protein/GFP complexes was mediated by modified leucine zipper protein spacers designed to form high-affinity heterodimers. The complexes localized accurately to specific sites within cells, providing selective fluorescence labeling of subcellular structures such as microfilaments or focal contacts.

Formation of amyloid-like fibrils by self-association of a partially unfolded fibronectin type III module

The ninth type III module of murine fibronectin was expressed in E. coli and folded into a compact homogeneous monomer whose unfolding and refolding were then investigated by fluorescence, circular dichroism, calorimetry and electron microscopy. The isolated module is unusually labile under physiological conditions. When heated at 1 deg. C/minute it exhibits an irreversible endothermic transition between 35 and 42 degrees C depending on the protein concentration. The transition is accompanied by changes in secondary and tertiary structure with partial exposure of the single tryptophan and increased binding of the hydrophobic probe, 1,8-anilinonaphthalene-sulfonate. The partially unfolded intermediate undergoes rapid self-association leading to the formation of large stable multimers that, like the original monomer, contain substantial amounts of beta sheet structure. The multimers melt and dissociate reversibly in a second endothermic transition between 60 and 90 degrees C also depending on the protein concentration. This second transition destroys the remaining secondary structure and further exposes the tryptophan. Visualization of negatively stained specimens in the electron microscope reveals that partially unfolded rmIII-9 slowly forms amyloid-like fibrils of approximately 10 nm width and indeterminate length. A subdomain swapping mechanism is proposed in which beta strands from one partially unfolded molecule interact with complementary regions of another to form oligomers and polymers. The possibility that similar interactions could play a role in the formation of fibrils by fibronectin in vivo is discussed.

Inhibition of cell migration, spreading, and focal adhesions by tumor suppressor PTEN

The tumor suppressor PTEN is a phosphatase with sequence similarity to the cytoskeletal protein tensin. Here the cellular roles of PTEN were investigated. Overexpression of PTEN inhibited cell migration, whereas antisense PTEN enhanced migration. Integrin-mediated cell spreading and the formation of focal adhesions were down-regulated by wild-type PTEN but not by PTEN with an inactive phosphatase domain. PTEN interacted with the focal adhesion kinase FAK and reduced its tyrosine phosphorylation. Overexpression of FAK partially antagonized the effects of PTEN. Thus, PTEN phosphatase may function as a tumor suppressor by negatively regulating cell interactions with the extracellular matrix.

Solution structure and dynamics of linked cell attachment modules of mouse fibronectin containing the RGD and synergy regions: comparison with the human fibronectin crystal structure

We report the three-dimensional solution structure of the mouse fibronectin cell attachment domain consisting of the linked ninth and tenth type III modules, mFnFn3(9,10). Because the tenth module contains the RGD cell attachment sequence while the ninth contains the synergy region, mFnFn3(9,10) has the cell attachment activity of intact fibronectin. Essentially complete signal assignments and approximately 1800 distance and angle restraints were derived from multidimensional heteronuclear NMR spectra. These restraints were used with a hybrid distance geometry/simulated annealing protocol to generate an ensemble of 20 NMR structures having no distance or angle violations greater than 0.3 A or 3 degrees. Although the beta-sheet core domains of the individual modules are well-ordered structures, having backbone atom rmsd values from the mean structure of 0.51(+/-0.12) and 0.40(+/-0.07) A, respectively, the rmsd of the core atom coordinates increases to 3.63(+/-1.41) A when the core domains of both modules are used to align the coordinates. The latter result is a consequence of the fact that the relative orientation of the two modules is not highly constrained by the NMR restraints. Hence, while structures of the beta-sheet core domains of the NMR structures are very similar to the core domains of the crystal structure of hFnFn3(9,10), the ensemble of NMR structures suggests that the two modules form a less extended and more flexible structure than the fully extended rod-like crystal structure. The radius of gyration, Rg, of mFnFn3(9,10) derived from small-angle neutron scattering measurements, 20.5(+/-0.5) A, agrees with the average Rg calculated for the NMR structures, 20.4 A, and is ca 1 A less than the value of Rg calculated for the X-ray structure. The values of the rotational anisotropy, D ||/D perpendicular, derived from an analysis of 15N relaxation data, range from 1.7 to 2.1, and are significantly less than the anisotropy of 2.67 predicted by hydrodynamic modeling of the crystal coordinates. In contrast, hydrodynamic modeling of the NMR coordinates yields anisotropies in the range of 1.9 to 2.7 (average 2.4(+/-0.2)), with NMR structures bent by more than 20 degrees relative the crystal structure having calculated anisotropies in best agreement with experiment. In addition, the relaxation parameters indicate that several loops in mFnFn3(9,10), including the RGD loop, are flexible on the nanosecond to picosecond time-scale. Taken together, our results suggest that, in solution, the limited set of interactions between the mFnFn3(9,10) modules position the RGD and synergy regions to interact specifically with cell surface integrins, and at the same time permit sufficient flexibility that allows mFnFn3(9,10) to adjust for some variation in integrin structure or environment.

Methotrexate maintains bone mass by preventing both a decrease in bone formation and an increase in bone resorption in adjuvant-induced arthritic rats

We examined the effects of low doses methotrexate (MTX) and indomethacin (IND) on bone mass and turnover in normal male Sprague-Dawley rats and those with adjuvant-induced arthritis. Normal and the adjuvant (heat-killed mycobacterium)-injected rats, 6 weeks of age, were given MTX at daily doses of 0.05, 0.1, or 0.2 mg/kg body weight (BW) or IND at a daily dose of 1.0 mg/kg BW. Rats were killed at the start, or at 14 and 28 days. In normal rats, the administration of these agents did not change the lumbar and femoral BMD values, nor did the serum osteocalcin or urinary deoxypyridinoline (D-Pyr) levels. Lumbar trabecular osteoclast number (Oc.N/BS) and osteoclast surface (Oc.S/BS) were decreased in the rats given IND. In the arthritic rats, the administration of MTX did not prevent an early increase of paw edema in the adjuvant-injected limb, but late inflammatory edema was alleviated in the non-injected limb. However, MTX administration at a dose of 0.1-0.2 mg/kg BW maintained an age-dependent increase in the lumbar and femoral BMD values. While serum osteocalcin levels were decreased and urinary D-Pyr values were increased in the arthritic control rats, these bone markers remained at the levels of the normal rats. Decreases in mineral apposition rate (MAR) and bone formation rate (BFR/BS) and increases in the trabecular Oc.N/BS and Oc.S/BS values were prevented by MTX. While IND almost completely prevented inflammatory paw edema, it did not improve the parameters of bone formation. An increase in osteoclasts was prevented and the osteopenia in the lumbar and the femoral bone was only partially prevented by IND. These data suggest that MTX improves bone mass and turnover in the arthritic rat, in which several cytokines that affect bone cells are involved. An increase in bone resorption may be due to prostaglandins, but bone formation defect was suggested to be due to other cytokines such as IL-1, IL-6, and TNF-alpha in this model.

Effects of indomethacin administration on bone turnover and bone mass in adjuvant-induced arthritis in rats

We examined the bone turnover and bone mass in adjuvant-induced arthritis in rats and assessed the effects of indomethacin in this model. One hundred ten SD rats, 6 weeks of age, were assigned to 11 groups and injected with adjuvant or solvent in the right foot. Adjuvant-injected rats were orally administered indomethacin at doses of 0 (vehicle), 0.1 (low), 0.5 (medium), and 1.5 (high) mg/kg body weight from the start (day 0). Animals were sacrificed on days 0, 14 (acute phase), and 28 (chronic phase). In the arthritic-control group, serum osteocalcin level and bone mineral content of the fourth lumbar body (L4) and the femur were significantly reduced on day 14. Serum alkaline-phosphatase was increased on day 28. Trabecular bone volume of L4 was decreased on day 14, and the value was further decreased on day 28. Bone formation rate (BFR/BS) was significantly reduced on day 14, and then osteoclast number (Oc.N/BS) increased on day 28. Indomethacin treatment dose-dependently prevented increases in paw volume and osteoclast number. In the high dose group, these indices were maintained at the same level with those in the normal group. However, indomethacin treatments were not able to maintain the parameters of bone formation such as serum osteocalcin and BFR/BS values, and the trabecular bone mass decrease was only partially prevented. These data clearly indicated both reduced bone formation and increased bone resorption as the causes of bone loss in adjuvant-induced arthritis in rats. Increased bone resorption seemed to be due to the increased activity of prostaglandins, but bone formation defect would be related to other factors in this animal model.

Fibronectin regulates calvarial osteoblast differentiation

The secretion of fibronectin by differentiating osteoblasts and its accumulation at sites of osteogenesis suggest that fibronectin participates in bone formation. To test this directly, we determined whether fibronectin-cell interactions regulate progressive differentiation of cultured fetal rat calvarial osteoblasts. Spatial distributions of alpha 5 integrin subunit, fibronectin, osteopontin (bone sialoprotein I) and osteocalcin (bone Gla-protein) were similar in fetal rat calvaria and mineralized, bone-like nodules formed by cultured osteoblasts. Addition of anti-fibronectin antibodies to cultures at confluence reduced subsequent formation of nodules to less than 10% of control values, showing that fibronectin is required for normal nodule morphogenesis. Anti-fibronectin antibodies selectively inhibited steady-state expression of mRNA for genes associated with osteoblast differentiation; mRNA levels for alkaline phosphatase and osteocalcin were suppressed, whereas fibronectin, type I collagen and osteopontin were unaffected. To identify functionally relevant domains of fibronectin, we treated cells with soluble fibronectin fragments and peptides. Cell-binding fibronectin fragments (type III repeats 6–10) containing the Arg-Gly-Asp (RGD) sequence blocked both nodule initiation and maturation, whether or not they contained a functional synergy site. In contrast, addition of the RGD-containing peptide GRGDSPK alone did not inhibit nodule initiation, although it did block nodule maturation. Thus, in addition to the RGD sequence, other features of the large cell-binding fragments contribute to the full osteogenic effects of fibronectin. Nodule formation and osteoblast differentiation resumed after anti-fibronectin antibodies or GRGDSPK peptides were omitted from the media, showing that the inhibition was reversible and the treatments were not cytotoxic. Outside the central cell-binding domain, peptides from the IIICS region and antibodies to the N terminus did not inhibit nodule formation. We conclude that osteoblasts interact with the central cell-binding domain of endogenously produced fibronectin during early stages of differentiation, and that these interactions regulate both normal morphogenesis and gene expression.

Cardiovascular effects of adrenomedullin in teleost fishes

Adrenomedullin is a fifty-two-amino acid polypeptide that was first discovered in pheochromocytoma cells, and later in the normal adrenal medullae, lungs, kidneys, and blood. In mammals, adrenomedullin has vasodepressive effects, mainly by decreasing peripheral vascular resistance. I investigated the effects of adrenomedullin in fish to see if this novel neuropeptide would have an effect in lower vertebrates, or if its actions were limited to the higher vertebrates. Bolus injections of adrenomedullin resulted in a reduction of heart rate and dorsal aortic pressure in the rainbow trout Oncorhynchus mykiss. However, adrenomedullin had no effect in the Atlantic cod, Gadus morhua. The effects of adrenomedullin in trout appear to be due to a direct action on the peripheral vasculature, as pre-treatment of celiac artery strips with tetrodoxin had no effect on the ability of adrenomedullin to relax the strip.

Requirement for the synergy site for cell adhesion to fibronectin depends on the activation state of integrin alpha 5 beta 1

We investigated the influence of the activation state of integrin alpha 5 beta 1 on its dependence on the PHSRN synergy site for binding to RGD in fibronectin. K562 and MV3 cells lacked alpha v beta 3 expression and adhered to fibronectin through alpha 5 beta 1. Mel57 cells adhered through alpha v beta 3 and alpha 5 beta 1. A recombinant fibronectin polypeptide, containing five type III repeats from the central cell binding domain 3Fn6-10, and a mutated polypeptide lacking the synergy site were equally effective in promoting Mel57 adhesion. For K562 and MV3, the mutated polypeptide was not or poorly active compared to the control polypeptide. Expression of alpha v beta 3 in MV3 induced strong adhesion to the mutated polypeptide. TS2/16 stimulatory beta 1-integrin antibodies or Mn2+ induced alpha 5 beta 1-mediated adhesion of K562 and MV3 to GRGDSP. In the presence of TS2/16 or Mn2+, alpha 5 beta 1-mediated MV3 adhesion to the mutated polypeptide was equally strong as adhesion to the control polypeptide. Mn2+ or TS2/16 induced weak K562 binding to the mutated polypeptide, and in the presence of a combination of phorbol 12-myristate 13-acetate, Mn2+, and TS2/16, alpha 5 beta 1-mediated K562 adhesion to the mutated and control polypeptide was equally strong. Our findings demonstrate that requirement for the PHSRN synergy site for alpha 5 beta 1-mediated adhesion to RGD in fibronectin depends on the activation state of the integrin.

Changes in urinary deoxypyridinoline level and vertebral bone mass in the development of adjuvant-induced arthritis in rats

This study was designed to determine the effect of bone resorption on the development of generalized osteopenia in adjuvant-induced arthritic rats. Thirty of a total of sixty male SD rats, 6 weeks of age, were injected with killed mycobacterium butyricum suspended in mineral oil into the right hind paw and assigned to six groups of 5 animals each. The other thirty animals served as the age-matched noninjected controls. Animals were sacrificed at 4, 7, 10, 14, 21, and 28 days post-injection after measuring the bilateral hind-paw volumes. Twenty-four-hour urinary samples were obtained before sacrifice and the levels of deoxypyridinoline (D-Pyr) and creatinine (CR) were measured. Plasma intact osteocalcin levels were measured by a sandwich enzyme immunoassay at the start, 14 and 28 days after injection. Bone mineral measurement and histomorphometrical analyses were performed on specimens of the third lumbar vertebral body. On the seventh day after injection, arthritic rats showed significant decreases in the values of bone mineral content (BMC) and density (BMD) when compared to controls. Urinary D-Pyr/Cr ratios, however, did not increase on the seventh day, showing a significant increase on the tenth day after injection. The serum osteocalcin level was significantly reduced on the fourteenth day. The trabecular bone volume (BV/TV) in the arthritic rats showed a significant decrease from the seventh day. The trabecular thickness (Tb.Th) value significantly decreased on the seventh day after injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Function and receptor specificity of a minimal 20 kilodalton cell adhesive fragment of fibronectin

Previous studies have reached conflicting conclusions about the minimal size and sequences of the fibronectin cell-adhesive domain necessary for retention of high cell adhesive activity. We have expressed a recombinant 20 kDa cell-binding fragment of human fibronectin consisting of the ninth and tenth type III modules, which includes the Arg-Gly-Asp (RGD) cell recognition site and a second cell adhesive domain that acts synergistically with the RGD site. This polypeptide retained a similar activity as a larger 110 kDa fibronectin fragment when used in soluble form in inhibition assays, but it displayed low cell adhesive activity if assayed after direct adsorption to a plastic substrate. However, adhesive function was restored if the fragment was bound to a non-inhibitory anti-fibronectin antibody pre-adsorbed to the plastic substrate. The antibody-bound fragment also promoted cell migration. Both cell spreading and migration were specifically mediated by the alpha 5 beta 1 integrin. Affinity columns containing immobilized 20 kDa cell-binding fragment effectively bound alpha 5-, alpha 3-, and alpha v-containing fibronectin-binding integrins. In contrast, an immobilized 11.5 kDa fragment that contained the RGD sequence but lacked the synergistic sequence was bound only poorly by alpha 5-containing fibronectin receptor integrins, even though the alpha 3- and alpha v-containing integrins bound readily. Our results indicate that the manner in which adhesion proteins are presented to cells is important and that most cell adhesive activity is retained in a minimal 20 kDa segment of fibronectin.

Why is there no carbonic anhydrase activity available to fish plasma?

Carbonic anhydrase (CA) is absent from the plasma of vertebrates. In vitro, CA in fish plasma will short-circuit the effect of catecholamines, which is to increase red blood cell (RBC) pH and volume, both of which enhance the affinity of hemoglobin for O2. CA was infused into trout for a period of 6 h and injected after 48 h, during which the animal was submitted to deep hypoxia (PO2=30­35 mmHg; 4.0­4.7 kPa). O2 content, lactate content, catecholamine levels, hematocrit, hemoglobin concentration and pHi were similar to those in the saline-infused control group. In contrast, cell volume was significantly higher and pHe, total CO2 content and organic phosphate levels were significantly lower than in the control group. The concentration of CA was not high enough completely to short-circuit the increase in pHi and red blood cell volume caused by catecholamines. The lower pHe in the CA-infused animals could enhance the activity of the Na+/H+ pump, which would keep the nucleotide triphosphate levels low. pH is a balance between acid loading at the muscle and acid excretion at the gills or the kidneys; we cannot distinguish between which of these resulted in a decrease of plasma pH. In conclusion, CA in plasma did not cause the expected reduction in blood oxygen content but did have a marked effect on plasma total CO2 content.

The short amino acid sequence Pro-His-Ser-Arg-Asn in human fibronectin enhances cell-adhesive function

Synergistic sites in the central cell-adhesive domain of fibronectin (FN) substantially enhance cell adhesion mediated by the alpha 5 beta 1 integrin receptor for fibronectin. We characterized a critical minimal sequence needed for synergistic activity using site-directed mutagenesis and homology scanning using intramolecular chimeras. The minimal cell-binding domain of FN consisting of the 9th and 10th type III FN repeat was expressed in an Escherichia coli expression system. This protein retained high biological activity when assayed using a competitive inhibition assay for FN-mediated adhesion of baby hamster kidney or HT-1080 cells. In contrast, a construct consisting of the 8th and 10th repeat displayed very low biological activity. By replacing various portions of the 8th repeat with homologous 9th repeat segments, we mapped the synergistic region to the center of the 9th repeat. When a very short peptide sequence, Pro-His-Ser-Arg-Asn (PHSRN), from the 9th repeat was substituted for the homologous pentapeptide site in the 8th repeat sequence, the recombinant protein showed markedly enhanced activity. Further mutagenesis analysis suggested that the arginine residue of this pentapeptide sequence is important for function. We also identified a weaker adjacent synergy region other than the PHSRN region. Epitope mapping of an anti-FN monoclonal antibody that inhibits FN-mediated adhesion identified the same critical regions. A synthetic peptide containing the PHSRN sequence showed neither competitive inhibitory activity in solution nor synergy with a soluble RGD-containing peptide. However, when the same synthetic peptide was positioned via a covalent bond at the corresponding site of the normally inactive 8th repeat, it mediated an enhancement of adhesive activity. These results identify a pentapeptide site that synergistically enhances the cell-adhesive activity of the FN RGD sequence.

Effects of changes in plasma pH, CO2 and ammonia on ventilation in trout

We investigated ventillatory responses to a plasma alkaloids and hypocapnia,a nd the basis for the ventilatory response to sodium bicarbonate (NaHCO3) infusion in rainbow trout. Plasma alkalosis and hypocapnia created by infusion of sodium hydroxide (NaOH) did not cause hypoventilation, whereas infusion of hydrochloric acid (HCl) caused vigorous hyperventilation, associated with an acidosis, a reduction in blood O2 content (CaO 2) and a release of circulating catecholamines. Infusion of NaHCO3 stimulated ventilation and caused an increase in plasma pH, total carbon dioxide content (CaCO 2) and catecholamine levels, and a reduction in oxygen tension (PaO 2). Infusion of ammonium bicarbonate (NH 4HCO3) caused hyperventilation and was associated with an increase in CaCO 2 and plasma total ammonia (Camm) and ammonia gas (NH3) concentration. Infusion of sodium chloride (NaClI) and Cortland's saline had no effect on ventilation. The results indicate that trout do not exhibit the ventilatory sensitivity to pH seen in terrestrial vertebrates. Ventilatory responses to NaHCO3 appear to have been a result of reductions in PaO 2, a release of catecholamines and an increase in CaCO 2 whereas responses to NH4HCO3 appear to have been a result of increases in CaCO 2 and Camm.

PROPRANOLOL IMPAIRS THE HYPERVENTILATORY RESPONSE TO ACUTE HYPERCAPNIA IN RAINBOW TROUT

This study investigated the possible role of catecholamines in the ventilatory response of rainbow trout (Oncorhynchus mykiss) to acute external hypercapnia. The ventilatory response to hypercapnia [partial pressure of CO2 in water (PwCO2=0.76 kPa)] of fish pre-treated with the selective beta-adrenoceptor antagonist, d,l-propranolol, was compared with that of d-propranolol (an isomer with minimal beta-antagonistic activity) and saline pre-treated fish (sham). A sustained 3.6- fold increase in gill ventilation volume (V(dot)w) was observed in the sham and d-propranolol-treated groups during the 30 min interval of hypercapnia. Fish pre-treated with d,l-propranolol displayed a blunted hyperventilatory response to hypercapnia (1.9-fold increase at 30 min). These results indicate that the beta-component of an adrenergic response is involved in the usual hyperventilatory response to external hypercapnia. It is suggested that the impaired hyperventilatory response of the d,l- propranolol-treated group reflects an inhibition of central adrenergic mechanism(s) involved in the hyperventilatory reflex to respiratory acidosis.