SyncMRT: a solution to image-guided synchrotron radiotherapy for quality assurance and pre-clinical trials

In this work, a new image guidance system and protocols for delivering image-guided radiotherapy (IGRT) on the Imaging and Medical Beamline (IMBL) at the ANSTO Australian Synchrotron are introduced. The image guidance methods used and the resulting accuracy of tumour alignment in in vivo experiments are often under-reported. Image guidance tasks are often complex, time-consuming and prone to errors. If unchecked, they may result in potential mis-treatments. We introduce SyncMRT, a software package that provides a simple, image guidance tool-kit for aligning samples to the synchrotron beam. We have demonstrated sub-millimetre alignment using SyncMRT and the small-animal irradiation platform (the DynamicMRT system) on the IMBL. SyncMRT has become the standard for carrying out IGRT treatments on the IMBL and has been used in all pre-clinical radiotherapy experiments since 2017. Further, we introduce two quality assurance (QA) protocols to synchrotron radiotherapy on the IMBL: the Winston-Lutz test and hidden target test. It is shown that the presented QA tests are appropriate for picking up geometrical setup errors and assessing the end-to-end accuracy of the image guidance process. Together, these tools make image guidance easier and provide a mechanism for reporting the geometric accuracy of synchrotron-based IGRT treatments. Importantly, this work is scalable to other delivery systems, and is in continual development to support the upcoming veterinary radiotherapy trials on the IMBL.

Training injury incidence in an amateur women's rugby union team in New Zealand over two consecutive seasons

OBJECTIVES

To describe the training injury incidence in amateur women's rugby union in New Zealand over two consecutive seasons.

DESIGN

A prospective cohort observational study METHODS: A total of 69 amateur women's rugby 15s team playerswere observed. Training exposure and training injury incidence were calculated.

RESULTS

The 38 training injuries resulted in a total injury incidence of 11.4 (8.3-15.6) per 1,000 training-hours. There were 12 injuries that resulted in a time-loss injury incidence of 3.6 (95% CI: 2.0-6.3) per 1,000 training-hours. Forwards recorded more total (RR: 1.8 [95% CI: 0.9-3.5]; p=0.0516) and time-loss (RR: 2.0 [95% CI: 0.6-6.6]; p=0.2482) injuries than Backs. The tackle was the most common injury cause for total (3.0 [95% CI: 1.6-5.6] per 1,000 training-hours.) injuries, but collisions (1.5 [95% CI: 0.6-3.6] per 1,000 training-hours.) with the ground or another person were the most common cause for time-loss injuries.The training injuries occurred most often to the lower limb and during the latter part of training sessions. These injuries were mostly minor in nature resulting in minimal time-loss away from training.

DISCUSSION

The time-loss injury incidence (3.6 per 1,000 training-hours.) for the amateur women's rugby 15s team players was higher than that reported for National (1.2 per 1,000 training-hours.) and Rugby World Cup for women (0.2 to 3.0 per 1,000 training-hours.) competitions.

CONCLUSION

The training injury incidence in amateur women's rugby union in New Zealand was higher than that reported for national and international rugby union injury incidences.

The Interaction of Fibronectin (fn) with Native, Polymeric Collagen (Collagen Fibres): Comparison with von Willebrand Factor (vWf)-Binding by Collagen

The binding of fn to collagen (type I) fibres has been found to resemble that of vWf in the following respects: 1. Binding is rapid, specific, saturable, similar at 4 and 37°C, and reduced by increasing ionic strength.

2. Binding is not inhibited by native, monomeric collagen, suggesting a multivalent mechanism of interaction.

3. Binding of fn occurs to a variety of collagen fragments (after their renaturation and polymerization), including, for example, the collagenase-derived TCA and TCB 3A and lA molecular fragments and the peptides al(I)CB3, 6b, 7 and 8 obtained by cleavage with cyanogen bromide (CB), suggesting a wide distribution of binding sites on the native collagen molecule.

4. As judged by the effect of heat-treatment, the native conformation of fn is required.

5. Chemical modification indicates the involvement of arginyl residues in collagen and carboxyl groups in fn. However, fn and vWf did not compete with one another in binding to collagen, suggesting the participation of different collagen arginyl residues in the two interactions.

Fn-binding differed from that of vWf in that the former was inhibited by denatured rnonomeric collagen (gelatin). Fn-binding was also inhibited by the fragment TCA in denatured form. The inhibitory activity was lost after chemical modification of arginyl residues in gelatin. Our results suggest that fn binding to collagen fibres and gelatin involves the same widely-distributed spectrum of binding sites.

The Platelet Reactivity of Collagen Type I: Evidence for Multiple Platelet-Reactive Sites in the Type I Collagen Molecule

In this study, the ability of peptides, obtained by fragmentation of the collagen type I molecule, to induce platelet aggregation has been examined. In order to satisfy requirements for tertiary and quaternary structure, peptides were first renatured (where necessary) to restore triple-helical configuration and then polymerised. Fragmentation with mammalian collagenase indicated the presence of platelet-reactive sites in both the N-terminal three-quarter and C-terminal one quarter fragment of the collagen molecule. Cleavage with cyanogen bromide indicated the presence in the constituent cq^-chain of at least four platelet-reactive sites. Our results suggest a relatively wide distribution of platelet-binding sites situated throughout the length of the collagen (type I) molecule, each probably of relatively low affinity and low structural specificity, at least in terms of amino acid sequence, and probably of a similar nature to those that might be expected to exist in any collagen-like species.

The Interaction of von Willebrand Factor (vWf) with Collagen: Investigation of vWf-Binding Sites in the Collagen Molecule

Following fragmentation of the collagen molecule, we have examined the ability of the isolated fragments to bind vWf. In view of the importance of collagen tertiary and quaternary structure for binding, fragments were first renatured to restore triple-helical conformation and then polymerized. Results indicate the presence of specific vWf-binding sites in both the αl(I)-and α2(I)-chains of type I collagen. Cleavage of the αl(I)-chain with cyanogen bromide suggests the presence of at least four (conceivably several more) binding sites implying a wide distribution of sites along the length of the collagen type I molecule. Collagen type III appears to possess a similar wide distribution of sites. Chemical modification of specific amino acid residues indicates that interaction involves arginyl residues in collagen and carboxyl groups in vWf. Although interaction between fibronec-tin and collagen fibres also involves collagen arginyl residues and carboxyl groups in fibronectin (authors’ unpublished results), fibronectin does not compete with vWf in the binding to collagen fibres.

Does acute side-alternating vibration exercise enhance ballistic upper-body power?

The aim of this study was to investigate the effects of acute vibration exercise, at 2 different frequencies, on upper body power output. Muscle activity (EMG) and upper-body peak power was measured in 12 healthy males during ballistic bench press throws at 30% of 1-repetition maximum on a Smith machine. Measures were made prior to, 30 s and 5 min after one of 3 conditions performed for 30 s in a press-up position: side-alternating vibration at 20 Hz, 26 Hz and no vibration. EMG was recorded in the anterior deltoid, triceps brachii and pectoralis major during ballistic bench press throws as well as during application of each condition. While peak power output was higher at 5 min post condition across all conditions, compared to baseline measures (P<0.05), only 20 Hz vibration resulted in a significant increase in peak power output (P<0.05) compared to no vibration. EMG was greater during both vibration conditions, compared to no vibration (P<0.001). However, this difference was not evident during bench press throws when no difference was seen in muscle activity between conditions. These findings suggest that 20 Hz vibration has an ergogenic effect on upper-body power that may be due to peripheral, rather than central, mediated mechanisms.

Spatially-varying surface roughness and ground-level air quality in an operational dispersion model

Urban form controls the overall aerodynamic roughness of a city, and hence plays a significant role in how air flow interacts with the urban landscape. This paper reports improved model performance resulting from the introduction of variable surface roughness in the operational air-quality model ADMS-Urban (v3.1). We then assess to what extent pollutant concentrations can be reduced solely through local reductions in roughness. The model results suggest that reducing surface roughness in a city centre can increase ground-level pollutant concentrations, both locally in the area of reduced roughness and downwind of that area. The unexpected simulation of increased ground-level pollutant concentrations implies that this type of modelling should be used with caution for urban planning and design studies looking at ventilation of pollution. We expect the results from this study to be relevant for all atmospheric dispersion models with urban-surface parameterisations based on roughness.

Hypothalamic QRFP: regulation of food intake and fat selection

QRFP, a member of the RFamide-related peptide family, is a strongly conserved hypothalamic neuropeptide that has been characterized in various species. Prepro-QRFP mRNA expression is localized to select regions of the hypothalamus, which are involved in the regulation of feeding behavior. The localization of the peptide precursor has led to the assessment of QRFP on feeding behaviors and the orexigenic effects of QRFP have been detected in mice, rats, and birds. QRFP acts in a macronutrient specific manner in satiated rats to increase the intake of a high fat diet, but not the intake of a low fat diet, and increases the intake of chow in food-restricted rats. Studies suggest that QRFP's effects on food intake are mediated by the adiposity signal, leptin, and hypothalamic neuropeptides. Additionally, QRFP regulates the expression and release of hypothalamic Neuropeptide Y and proopiomelanocortin/α-Melanocyte-Stimulating Hormone. QRFP binds to receptors throughout the brain, including regions associated with food intake and reward. Taken together, these data suggest that QRFP is a mediator of motivated behaviors, particularly the drive to ingest high fat food. The present review discusses the role of QRFP in the regulation of feeding behavior, with emphasis on the intake of dietary fat.

Improved measurement of the positive-muon lifetime and determination of the Fermi constant

The mean life of the positive muon has been measured to a precision of 11 ppm using a low-energy, pulsed muon beam stopped in a ferromagnetic target, which was surrounded by a scintillator detector array. The result, tau(micro)=2.197 013(24) micros, is in excellent agreement with the previous world average. The new world average tau(micro)=2.197 019(21) micros determines the Fermi constant G(F)=1.166 371(6)x10(-5) GeV-2 (5 ppm). Additionally, the precision measurement of the positive-muon lifetime is needed to determine the nucleon pseudoscalar coupling g(P).

SINE insertion polymorphism on the X chromosome differentiates Anopheles gambiae molecular forms

Polymorphic SINE insertions can be useful markers for assessing population structure and differentiation. Maque is a family of SINE elements which, based on bioinformatic analysis, was suggested to have been active recently in Anopheles gambiae, the major vector of malaria. Here, we report the development of polymorphic Maque insertions as population genetic markers in A. gambiae, and the use of these markers to better characterize divergence on the X chromosome between A. gambiae M and S molecular forms in populations from Burkina Faso and Mali. Our data are consistent with the recent activity of Maque. Phylogenetic analysis suggests that at least two recently active lineages may have a role in mediating genome evolution. We found differences in element insertion frequency and sequence between the M and S populations analysed. Significant differentiation was observed between these two groups across a 6 Mb region at the proximal (centromeric) end of the X chromosome. Locus-specific F(ST) values ranged from 0.14 to 1.00 in this region, yet were not significantly different from zero in more distal locations on the X chromosome; the trend was consistent in populations from both geographical locales suggesting that differentiation is not due to local adaptation. Strong differentiation between M and S at the proximal end of the X chromosome, but not outside this region, suggests the action of selection counteracting limited gene flow between these taxa and supports their characterization as incipient species.

GnRH and gonadotropin release is decreased in chronic nitric oxide deficiency

Nitric oxide synthetase (NOS), the conversion enzyme for nitric oxide (NO) is localized in the anterior pituitary of female rats, particularly in gonadotrophs and folliculo-stellate cells, suggesting that NO regulates the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) from the anterior pituitary. The focus of this study was to determine the effect of chronic NO deficiency on the subsequent pituitary release of LH and FSH in vitro and the hypothalamic immunoexpression of GnRH in vivo. NO deficiency was induced by adding the NOS inhibitor, N-nitro-L-arginine (L-NNA, 0.6 g/L) to the drinking water of female Wistar rats. After 8 weeks, the animals were euthanized, the pituitaries were removed, and they were incubated in vitro. Pituitaries were perfused for 4 hr in the presence of pulsatile gonadotropin release hormone (GnRH, 500 ng/pulse) every 30 min. S-Nitroso-L-acetyl penicillamine (SNAP, an NO donor, 0.1 mM) or L-nitro-argine methyl ester (L-NAME, a NOS inhibitor, 0.1 mM) was added to the media and perfusate samples were collected at 10-min intervals. LH and FSH levels in the perfusate were measured by double antibody radioimmunoassays. Pituitaries from the NO-deficient rats had a significantly smaller GnRH-stimulated release of LH and FSH compared with proestrous control rats. The addition of S-NAP to the perfusate resulted in decreased LH and FSH secretion in the control group, but increased LH secretion in the NO-deficient group. The addition of L-NAME to the perfusate suppressed LH secretion from control pituitaries, but not in pituitaries from NO-deficient animals. Immunohistochemistry of brain slices demonstrated that NO-deficient rats had a large qualitative decrease of GnRH in the median eminence compared with their controls. This decrease was particularly evident in the external capillary plexus of the median eminence. We concluded that chronic NO deficiency is associated with a decreased GnRH in neurosecretory terminals in the external capillary layer of the median eminence, accompanied by a decrease in LH and FSH release from the pituitaries.

Synthesis and structure-activity relationships of guanine analogues as phosphodiesterase 7 (PDE7) inhibitors

The synthesis of a novel series of guanine analogues is reported. The compounds have been assessed in vitro and some analogues have been found to be inhibitors of phosphodiesterase type 7 (PDE7).

Integrin-independent tyrosine phosphorylation of p125(fak) in human platelets stimulated by collagen

Collagen fibers or a glycoprotein VI-specific collagen-related peptide (CRP-XL) stimulated tyrosine phosphorylation of the focal adhesion kinase, p125(fak) (FAK), in human platelets. An integrin alpha(2)beta(1)-specific triple-helical peptide ligand, containing the sequence GFOGER (single-letter nomenclature, O = Hyp) was without effect. Antibodies to the alpha(2) and beta(1) integrin subunits did not inhibit platelet FAK tyrosine phosphorylation caused by either collagen fibers or CRP-XL. Tyrosine phosphorylation of FAK caused by CRP-XL or thrombin, but not that caused by collagen fibers, was partially inhibited by GR144053F, an antagonist of integrin alpha(IIb)beta(3). The intracellular Ca(2+) chelator, BAPTA, and the protein kinase C inhibitor, Ro31-8220, were each highly effective inhibitors of the FAK tyrosine phosphorylation caused by collagen or CRP-XL. These data suggest that, in human platelets, 1) occupation or clustering of the integrin alpha(2)beta(1) is neither sufficient nor necessary for activation of FAK, 2) the fibrinogen receptor alpha(IIb)beta(3) is not required for activation of FAK by collagen fibers, and 3) both intracellular Ca(2+) and protein kinase C activity are essential intermediaries of FAK activation.

Roles of SLP-76, phosphoinositide 3-kinase, and gelsolin in the platelet shape changes initiated by the collagen receptor GPVI/FcR gamma-chain complex

How platelet shape change initiated by a collagen-related peptide (CRP) specific for the GPVI/FcR gamma-chain complex (GPVI/FcR gamma-chain) is coupled to SLP-76, phosphoinositide (PI) 3-kinase, and gelsolin is reported. As shown by video microscopy, platelets rapidly round and grow dynamic filopodial projections that rotate around the periphery of the cell after they contact a CRP-coated surface. Lamellae subsequently spread between the projections. All the actin-driven shape changes require SLP-76 expression. SLP-76 is essential for the Ca(++) mobilization induced by CRP, whereas PI 3-kinase only modulates it. The extension of lamellae requires net actin assembly and an exposure of actin filament barbed ends downstream of PI 3-kinase. Gelsolin expression is also required for the extension of lamellae, but not for the formation of filopodia. Altogether, the data describe the role of SLP-76 in the platelet activation initiated by GPVI/FcR gamma-chain and the roles of PI 3-kinase and gelsolin in lamellae spreading. (Blood. 2000;96:3786-3792)

Monoclonal antibodies identify residues 199-216 of the integrin alpha2 vWFA domain as a functionally important region within alpha2beta1

Integrin alpha2beta1 is the major receptor for collagens in the human body, and the collagen-binding site on the alpha2 subunit von Willebrand factor A-type domain (vWFA domain) is now well defined. However, the biologically important conformational changes that are associated with collagen binding, and the means by which the vWFA domain is integrated into the whole integrin are not completely understood. We have raised monoclonal antibodies against recombinant alpha2 vWFA domain for use as probes of function. Three antibodies, JA202, JA215 and JA218, inhibited binding to collagen, collagen I C-propeptide and E-cadherin, demonstrating that their function is important for structurally diverse alpha2beta1 ligands. Cross-blocking studies grouped the epitopes into two clusters: (I) JA202, the inhibitory antibody, Gi9, and a non-inhibitory antibody, JA208; (II) JA215 and JA218. Both clusters were sensitive to events at the collagen binding site, as binding of Gi9, JA202, JA215 and JA218 were inhibited by collagen peptide, JA208 binding was enhanced by collagen peptide, and binding of JA202 was decreased after mutagenesis of the cation-binding residue Thr(221) to alanine. Binding of cluster I antibodies was inhibited by the anti-functional anti-beta1 antibody Mab13, and binding of Gi9 and JA218 to alpha2beta1 was inhibited by substituting Mn(2+) for Mg(2+), demonstrating that these antibodies were sensitive to changes initiated outside the vWFA domain. Mapping of epitopes showed that JA202 and Gi9 bound between residues 212-216, while JA208 bound between residues 199-216. We have therefore identified two epitope clusters with novel properties; i.e. they are intimately associated with the collagen-binding site, responsive to conformational changes at the collagen-binding site and sensitive to events initiated outside the vWFA domain.

A method for mediastinal drainage after cardiac procedures using small silastic drains

BACKGROUND

It has been standard teaching in cardiac surgery that drainage of the mediastinum following cardiac surgical procedures is best accomplished using rigid large-bore chest tubes. Recent trends in cardiac surgery have suggested less invasive approaches to a variety of diseases. Difficult drainage problems in the field of general surgery including hepatic and pancreatic collections have been drained successfully with smaller flexible drains for many years. Additionally, many difficult to reach collections in the chest have been drained by invasive radiologists using small pigtail catheters.

METHODS

We have introduced drainage of the mediastinum using 10-mm flexible, flat, fluted Blake drains. To date, we have used these drains in more than 100 cardiac operations including coronary artery bypass grafting, valve repair/replacements, combined coronary artery bypass grafting/valve operations, heart transplants, septal defects, and mediastinal tumors.

RESULTS

We have demonstrated that this form of drainage is as good as using large-bore chest tubes with no significant risk of bleeding or tamponade. Additionally, use of these tubes is less painful, allows more mobility, and earlier discharge with functioning drains in place if necessary.

CONCLUSIONS

Larger chest tubes are not necessarily better when it comes to draining the mediastinum. The actual area of ingress through the sideholes is considerably less than the surface area provided by the fluted Blake drain. We believe that this system can replace standard chest tubes.

Micromolar Ca2+ concentrations are essential for Mg2+-dependent binding of collagen by the integrin alpha 2beta 1 in human platelets

Integrin receptor alpha(2)beta(1) requires micromolar Ca(2+) to bind to collagen and to the peptide GPC(GPP)(5)GFOGER(GPP)(5)GPC (denoted GFOGER-GPP, where O represents hydroxyproline), which contains the minimum recognition sequence for the collagen-binding alpha(2) I-domain (Knight, C. G., Morton, L. F., Peachey, A. R., Tuckwell, D. S., Farndale, R. W., and Barnes, M. J. (2000) J. Biol. Chem. 275, 35-40). Platelet adhesion to these ligands is completely dependent on alpha(2)beta(1) in the presence of 2 mm Mg(2+). However, we show here that this interaction was abolished in the presence of 25 microm EGTA. Adhesion of Glanzmann's thrombasthenic platelets, which lack the fibrinogen receptor alpha(IIb)beta(3), was also inhibited by micromolar EGTA. Mg(2+)-dependent adhesion of platelets was restored by the addition of 10 microm Ca(2+), but millimolar Ca(2+) was inhibitory. Binding of isolated alpha(2)beta(1) to GFOGER-GPP was 70% inhibited by 50 microm EGTA but, as with intact platelets, was fully restored by the addition of micromolar Ca(2+). 2 mm Ca(2+) did not inhibit binding of isolated alpha(2)beta(1) to collagen or to GFOGER-GPP. Binding of recombinant alpha(2) I-domain was not inhibited by EGTA, nor did millimolar Ca(2+) inhibit binding. Our data suggest that high affinity Ca(2+) binding to alpha(2)beta(1), outside the I-domain, is essential for adhesion to collagen. This is the first demonstration of a Ca(2+) requirement in alpha(2)beta(1) function.

Convulxin binding to platelet receptor GPVI: competition with collagen related peptides

Convulxin (CVX), a potent platelet aggregating protein from the venom of the snake Crotalus durissus terrificus, is known to bind to the platelet collagen receptor, glycoprotein VI (GPVI). CVX binding to human platelets was investigated by flow cytometry, using fluorescein labeled convulxin (FITC-CVX). Scatchard analysis indicated high and low affinity binding sites with Kd values of 0.6 and 4 nM and Bmax values of 1200 and 2000 binding sites per platelet. FITC-CVX binding was inhibited by collagen related peptides (CRPs) comprising a repeated GPO sequence, namely GCO(GPO)(10)GCOGNH(2) and GKO(GPO)(10)GKOGNH(2), which also bind to receptor GPVI. These peptides (monomeric or cross-linked forms) gave a high affinity inhibition of 10-20% for concentrations between 10 ng/ml and 5 microg/ml, followed by a second phase of inhibition at concentrations greater than 5 microg/ml. It was shown also that the inhibition of FITC-CVX binding by CRPs was independent on the time of preincubation of platelets with CRPs, and the same percentage of inhibition was seen with various concentrations of convulxin. Confocal microscopy of the distribution of FITC-CVX binding sites on platelets showed an homogeneous distribution of FITC-CVX bound to GPVI, although some limited clustering may exist.

Structural basis of collagen recognition by integrin alpha2beta1

We have determined the crystal structure of a complex between the I domain of integrin alpha2beta1 and a triple helical collagen peptide containing a critical GFOGER motif. Three loops on the upper surface of the I domain that coordinate a metal ion also engage the collagen, with a collagen glutamate completing the coordination sphere of the metal. Comparison with the unliganded I domain reveals a change in metal coordination linked to a reorganization of the upper surface that together create a complementary surface for binding collagen. Conformational changes propagate from the upper surface to the opposite pole of the domain, suggesting both a basis for affinity regulation and a pathway for signal transduction. The structural features observed here may represent a general mechanism for integrin-ligand recognition.

Development of a whole cell assay to measure methotrexate-induced inhibition of thymidylate synthase and de novo purine synthesis in leukaemia cells

The cellular pharmacology of methotrexate (MTX) is complex, involving the inhibition of both de novo thymidylate and purine biosynthesis. Measurement of MTX-induced inhibition of de novo thymidylate and purine biosynthesis may allow optimisation of MTX therapy, and the aim of this study was to develop an assay to measure the activity of both pathways in the same cell sample, and so determine the effects of MTX treatment. In situ thymidylate synthase (EC 2.1.1.45) activity was measured by the release of 3H2O from [5'-3H]deoxyuridine and de novo purine synthesis by the incorporation of [14C]formate into adenine and guanine. Incubation of human leukaemia CCRF-CEM cells for 22 hr with 50 nM MTX resulted in approximately 90% inhibition of in situ thymidylate synthase activity, relative to control untreated cells, and after exposure to 1000 nM MTX activity could not be detected. In contrast, de novo purine synthesis, measured in the same sample, was not inhibited by exposure to 50 nM MTX, although activity was again completely abolished by exposure to 1000 nM MTX. To demonstrate the utility of the assay, lymphoblasts isolated from a child with acute lymphoblastic leukaemia (ALL) were also incubated for 22 hr with 1000 nM MTX. Both in situ thymidylate synthase activity and de novo purine synthesis were significantly inhibited, by 70% and 60% respectively, relative to the activity in untreated cells.

HER-2/neu protein expression in breast cancer evaluated by immunohistochemistry. A study of interlaboratory agreement

Immunohistochemistry (IHC) is used commonly for evaluating HER-2/neu protein expression in breast cancer. Given the potential clinical importance of HER-2/neu status in patient management, interlaboratory variability in HER-2/neu IHC results in a matter of legitimate concern. We compared the results from 2 laboratories for HER-2/neu determined by IHC on paraffin sections of the same 100 consecutive invasive breast cancers. Both laboratories used the same primary antibody; however, different methods for heat-induced epitope retrieval (microwave or steam) and immunostaining (automated equipment from different manufacturers) and different scoring systems (positive-negative and 0-4+) were used. Slides were read in a blinded fashion and the results from the 2 laboratories were compared. Of the 93 cases evaluable in both laboratories, 24% were scored as HER-2/neu-positive at 1 laboratory, and 23% were scored as positive at the other. Complete concordance in categorization of HER-2/neu status between the 2 laboratories was achieved in 90 of 93 cases. Excellent interlaboratory agreement for HER-2/neu IHC was attained using the same primary antibody to HER-2/neu, even without standardization of assay method or scoring criteria. However, standardization of these parameters remains an important objective to optimize interlaboratory agreement.

The collagen-binding A-domains of integrins alpha(1)beta(1) and alpha(2)beta(1) recognize the same specific amino acid sequence, GFOGER, in native (triple-helical) collagens

We have previously assigned an integrin alpha(2)beta(1)-recognition site in collagen I to the sequence, GFOGERGVEGPOGPA (O = Hyp), corresponding to residues 502-516 of the alpha(1)(I) chain and located in the fragment alpha(1)(I)CB3 (Knight, C. G., Morton, L. F., Onley, D. J., Peachey, A. R., Messent, A. J., Smethurst, P. A., Tuckwell, D. S., Farndale, R. W., and Barnes, M. J. (1998) J. Biol. Chem. 273, 33287-33294). In this study, we show that recognition is entirely contained within the six-residue sequence GFOGER. This sequence, when in triple-helical conformation, readily supports alpha(2)beta(1)-dependent cell adhesion and exhibits divalent cation-dependent binding of isolated alpha(2)beta(1) and recombinant alpha(2) A-domain, being at least as active as the parent collagen. Replacement of E by D causes loss of recognition. The same sequence binds integrin alpha(1) A-domain and supports integrin alpha(1)beta(1)-mediated cell adhesion. Triple-helical GFOGER completely inhibits alpha(2) A-domain binding to collagens I and IV and alpha(2)beta(1)-dependent adhesion of platelets and HT 1080 cells to these collagens. It also fully inhibits alpha(1) A-domain binding to collagen I and strongly inhibits alpha(1)beta(1)-mediated adhesion of Rugli cells to this collagen but has little effect on either alpha1 A-domain binding or adhesion of Rugli cells to collagen IV. We conclude that the sequence GFOGER represents a high-affinity binding site in collagens I and IV for alpha(2)beta(1) and in collagen I for alpha(1)beta(1). Other high-affinity sites in collagen IV mediate its recognition of alpha(1)beta(1).

Impact of polyglutamation on sensitivity to raltitrexed and methotrexate in relation to drug-induced inhibition of de novo thymidylate and purine biosynthesis in CCRF-CEM cell lines

The aim of this study was to investigate the influence of folylpolyglutamyl synthetase (FPGS) activity on the cellular pharmacology of the classical antifolates raltitrexed and methotrexate (MTX) using two human leukemia cell lines, CCRF-CEM and CCRF-CEM:RC2Tomudex. Cell growth inhibition and drug-induced inhibition of de novo thymidylate and purine biosynthesis were used as measures of the cellular effects of the drugs. CCRF-CEM:RC2Tomudex cells had <11% of the FPGS activity of CCRF-CEM cells, whereas MTX uptake and TS activity were equivalent. In CCRF-CEM:RC2Tomudex cells, MTX polyglutamate formation was undetectable after exposure to 1 microM [3H]MTX for 24 h. After exposure to 0.1 microM raltitrexed, levels of total intracellular raltitrexed-derived material in CCRF-CEM:RC2Tomudex cells were 30- to 50-fold lower than in the CCRF-CEM cell line. CCRF-CEM: RC2Tomudex cells were >1000-fold resistant to raltitrexed and 6-fold resistant to lometrexol but sensitive to MTX and nolatrexed when exposed to these antifolates for 96 h. After 6 h of exposure, CCRF-CEM cells retained sensitivity to MTX and raltitrexed but were less sensitive to lometrexol-mediated growth inhibition. In contrast, CCRF-CEM: RC2Tomudex cells were markedly insensitive to raltitrexed, lometrexol, and to a lesser degree, MTX. Simultaneous measurement of de novo thymidylate and purine biosynthesis revealed 90% inhibition of TS activity by 100 nM MTX in both cell lines, whereas inhibition of de novo purine synthesis was only observed in CCRF-CEM cells, and only after exposure to 1000 nM MTX. Ten nM raltitrexed induced >90% inhibition of TS activity in CCRF-CEM cells, whereas in CCRF-CEM:RC2Tomudex cells, there was no evidence of inhibition after exposure to 1000 nM raltitrexed. These studies demonstrate that polyglutamation is a critical determinant of the cellular pharmacology of both raltitrexed and MTX, markedly influencing potency in the case of raltitrexed and locus of action in the case of MTX.

Adhesive domains in the collagen III fragment alpha1(III)CB4 that support alpha2beta1- and von Willebrand factor-mediated platelet adhesion under flow conditions

Seven overlapping peptides derived from the bovine alpha1(III)CB4 fragment of collagen III support static platelet adhesion, and an integrin alpha2beta1-recognition site has been assigned within this fragment to residues 522-528 of the collagen alpha1(III) chain; (25). In this study we found that two of the peptides, CB4(III)-6 and -7, were able to support platelet adhesion under flow conditions, whereas the other peptides showed either very little (CB4(III)-1 and -4) or no platelet adhesion at all (CB4(III)-2, -3 and -5). Using the recombinant leech anti-platelet protein (rLAPP), known to prevent both alpha2beta1 integrin- and von Willebrand factor (vWF)-binding to collagen, we observed almost complete inhibition of platelet adhesion to peptides CB4(III)-6 and -7. In solid-phase binding assays rLAPP bound to CB4(III)-6 and -7 and to CB4(III)-6/7, containing the peptide 6/7 overlap sequence, and not to any other peptide. Our results suggest that the overlap sequence GPP*GPRGGAGPP*GPEGGK (single-letter amino acid code, P* = hydroxyproline), corresponding to residues 523-540 of the alpha1(III) collagen chain, contains a binding site for rLAPP. Monoclonal antibodies (MoAbs) directed against the alpha2 subunit of integrin alpha2beta1 inhibited platelet adhesion to both CB4(III)-6 and -7 by about 50%, showing that the alpha2beta1-recognition site in this locality in alpha1(III)CB4 detected under static conditions is of sufficient affinity to withstand shear forces. Solid-phase binding studies indicated that vWF binds to CB4(III)-7 and to a lesser extent to CB4(III)-4. Furthermore, rLAPP competed with vWF in binding to CB4(III)-7. Our results indicate that residues 541-558 of the alpha1(III)-chain may contain one of the critical vWF-binding sites involved in the initial phase of platelet adhesion to collagen III. MoAbs against vWF (A1 and A3 domain) and glycoprotein (GP)Ib confirmed that vWF is involved in adhesion to CB4(III)-7 and showed that vWF is also involved in adhesion to CB4(III)-6 despite the absence of direct binding of vWF to the peptide. The existence of alpha2beta1-, vWF- and rLAPP-binding sites all in close proximity in alpha1(III)CB4 testifies to the importance of this locus in collagen III for its platelet reactivity.

Comparison of fluorescence in situ hybridization and immunohistochemistry for the evaluation of HER-2/neu in breast cancer

PURPOSE

To compare fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) in the determination of HER-2/neu status of breast cancers.

MATERIALS AND METHODS

FISH and IHC for HER-2/neu were performed on formalin-fixed paraffin sections of 100 consecutive invasive breast cancers. FISH was performed at Beth Israel Deaconess Medical Center, Boston, MA, using the Oncor/Ventana INFORM kit (Ventana Medical Systems, Tucson, AZ; formerly sold by Oncor, Inc, Gaithersburg, MD) in a laboratory certified as proficient in this procedure. IHC was performed at PhenoPath Laboratories, Seattle, WA, using a polyclonal antibody to the HER-2/neu protein. FISH and IHC were analyzed in a blinded fashion, and the results were then compared. Procedure and interpretation times and reagent costs for FISH and IHC were also compared.

RESULTS

HER-2/neu was amplified by FISH in 26% of cases, and 23% were HER-2/neu-positive by IHC. FISH and IHC were both assessable in 90 cases. Concordance between FISH and IHC results was seen in 82 of these cases (91%, P <.001). The FISH procedure required more technologist time and more interpretation time per case for the pathologist than IHC. Reagent costs were substantially higher for FISH than for IHC.

CONCLUSION

There is a high level of correlation between FISH and IHC in the evaluation of HER-2/neu status of breast cancers using formalin-fixed paraffin-embedded specimens. Although the choice of which assay to use should be left for individual laboratories to make based on technical and economic considerations, our results may make it difficult to justify the routine use of FISH for determination of HER-2/neu status in breast cancer.

Specificity of HercepTest in determining HER-2/neu status of breast cancers using the United States Food and Drug Administration-approved scoring system

PURPOSE

To evaluate the specificity of the HercepTest for Immunoenzymatic Staining (Dako Corp, Carpinteria, CA) for determining HER-2/neu protein expression in breast cancer.

MATERIALS AND METHODS

Forty-eight invasive breast cancers previously found to be HER-2/neu-negative by two different immunohistochemical (IHC) assays and not amplified for the HER-2/neu gene by fluorescence in situ hybridization were studied using the HercepTest kit. HercepTest was performed according to the manufacturer's guidelines, and the results were scored on a 0 to 3+ scale using the United States Food and Drug Administration (FDA)-approved grading system. In this system, cases scored as 2+ or 3+ are considered HER-2/neu-positive.

RESULTS

Among these 48 cases, the IHC score using the FDA-approved scoring system was 0 in four cases (8.3%), 1+ in 16 (33.3%), 2+ in 21 (43.8%), and 3+ in seven (14.6%). Therefore, 58.4% of these cases were categorized as HER-2/neu-positive, and the specificity of the HercepTest kit for HER-2/neu expression was 41.6%. However, with the use of a modified scoring system that took into account the level of staining of nonneoplastic epithelium, the specificity increased to 93.2%.

CONCLUSION

Our results indicate that the HercepTest kit, when used in accordance with the manufacturer's guidelines and the FDA-approved scoring system, results in a large proportion of breast cancers being categorized as positive for HER-2/neu protein expression and that many of these seem to be false-positives. Consideration of the level of staining of nonneoplastic epithelium resulted in improved specificity. The current FDA-approved scoring system for HercepTest results should be reevaluated before its widespread use in clinical practice.

Collagens and atherosclerosis

Smooth muscle cells in the atherosclerotic lesions of diseased arteries produce new extracellular matrix, largely collagenous in nature, which is responsible in part for the occlusion of the vessel lumen by the atherosclerotic plaque. These smooth muscle cells express a different phenotype, responsive to growth factors, to that of the differentiated, nondividing contractile cell in the media. Specific collagens may be involved in the regulation of phenotype and in the migration of the cells to the site of lesion growth. Collagens may also be involved in the calcification of lesions, in the retention of low-density lipoprotein in the vessel wall and in smooth muscle cell survival. Glycation of collagen may promote atherogenesis. Effects as summarized in this short review, are not always, at first sight, consistent. The following points should be kept in mind, though, when considering the response of a cell to collagen. Any effect may be governed not just by the identity of the collagen type as such but by its state of polymerization: monomeric collagen, for instance, whether in solution or immobilized on plastic, may express different effects to the same collagen type when presented in its native polymerized state, e.g., as fibers. The precise identity of the cell and its location may be important: SMCs in secondary culture may not necessarily respond to any given collagen exactly as SMCs within the lesion or possess precisely the same properties, albeit both types are regarded as expressing the same (synthetic) phenotype. Effects may not necessarily be directly attributable to collagen, but to some other matrix constituent bound to collagen.

Function of glycoprotein VI and integrin alpha2beta1 in the procoagulant response of single, collagen-adherent platelets

Various collagen-based materials were used to assess the structural requirements of collagen for inducing the procoagulant response of adhering platelets, as well as the collagen receptors involved. Cross-linked or monomeric collagen-related peptide (CRP), Gly-Cys-Hyp-(Gly-Pro-Hyp)10-Gly-Cys-Hyp-Gly was highly adhesive for platelets in a glycoprotein VI-(GpVI-)dependent manner. Adhesion was followed by a prolonged increase in cytosolic [Ca2+]i, formation of membrane blebs, exposure of phosphatidylserine (PS) and generation of prothrombinase-stimulating activity. Fibrils of type-I collagen were less adhesive but, once adhered, many of the platelets presented a full procoagulant response. Monomeric type-I collagen was unable to support adhesion, unless Mg(2+)-dependent integrin alpha2beta1 interactions were facilitated by omission of Ca2+ ions. With all surfaces, however, post-addition of CaCl2 to adhering platelets resulted in a potent Ca(2+)-influx signal, followed by PS exposure and bleb formation. The procoagulant response elicited by binding to CRP was inhibited by anti-GpVI Fab fragments, but not by impeding integrin alpha2beta1-mediated events. With fibrillar collagen, it was inhibited by blocking either the GpVI- or integrin alpha2beta1-mediated interactions. This suggests that the triple-helical Gly-Pro-Hyp repeat in CRP and analogous sequences in fibrillar collagen stimulate the procoagulant response of adherent platelets by acting as ligands for GpVI. Influx of Ca2+ is required for this response, and adhesion via integrin alpha2beta1 serves to potentiate the signaling effects of GpVI.

Monomeric (glycine-proline-hydroxyproline)10 repeat sequence is a partial agonist of the platelet collagen receptor glycoprotein VI

We have previously reported that a triple-helical, collagen-related peptide (CRP; also known as CRP-XL) containing a glycine-proline-hydroxyproline (GPP*) repeat motif and cross-linked through cysteine residues at its N-terminus and C-terminus is a powerful stimulus of platelet aggregation and secretion through the surface receptor glycoprotein VI (GPVI). The activation of platelets is associated with tyrosine phosphorylation of the tyrosine kinase Syk and phospholipase C gamma2 (PLCgamma2). We now report that the non-cross-linked backbone of CRP, monomeric CRP (mCRP), stimulates the tyrosine phosphorylation of Syk and PLCgamma2 in platelets and induces the weak secretion of [3H]5-hydroxytryptamine ([3H]5-HT) and aggregation. The action of mCRP does not seem to be due to spontaneous cross-linking, because alkylation of the cysteine residues leads to an increase in activity. The tripeptide backbone of CRP, GPP*10 (in which P* represents hydroxyproline) also stimulates platelet shape change and the weak tyrosine phosphorylation of Syk and PLCgamma2, but is unable to induce aggregation or secretion. The monomeric peptides partly inhibit the release of [3H]5-HT by CRP, suggesting that they are partial agonists of the collagen receptor GPVI. These results demonstrate that GPP* present as a repeat motif is sufficient to activate the platelet collagen receptor GPVI but that the cross-linking of monomers brings about an increase in activity.

Adenoviral gene therapy leads to rapid induction of multiple chemokines and acute neutrophil-dependent hepatic injury in vivo

Replication-deficient adenoviruses are known to induce acute injury and inflammation of infected tissues, thus limiting their use for human gene therapy. However, molecular mechanisms triggering this response have not been fully defined. To characterize this response, chemokine expression was evaluated in DBA/2 mice following the intravenous administration of various adenoviral vectors. Administration of adCMVbeta gal, adCMV-GFP, or FG140 intravenously rapidly induced a consistent pattern of C-X-C and C-C chemokine expression in mouse liver in a dose-dependent fashion. One hour following infection with 10(10) PFU of adCMVbeta gal, hepatic levels of MIP-2 mRNA were increased >60-fold over baseline. MCP-1 and IP-10 mRNA levels were also increased immediately following infection with various adenoviral vectors, peaking at 6 hr with >25- and >100-fold expression, respectively. Early induction of RANTES and MIP-1beta mRNA by adenoviral vectors also occurred, but to a lesser degree. The induction of chemokines occurred independently of viral gene expression since psoralen-inactivated adenoviral particles produced an identical pattern of chemokine gene transcription within the first 16 hr of administration. The expression of chemokines correlated as expected with the influx of neutrophils and CD11b+ cells into the livers of infected animals. At high titers, all adenoviral vectors caused significant hepatic necrosis and apoptosis following systemic administration to DBA/2 mice. To investigate the role of neutrophils in this adenovirus-induced hepatic injury, animals were pretreated with neutralizing anti-MIP-2 antibodies or depleted of neutrophils. MIP-2 antagonism and neutrophil depletion both resulted in reduced serum ALT/AST levels and attenuation of the adenovirus-induced hepatic injury histologically, confirming that this early injury is largely due to chemokine production and neutrophil recruitment. Our findings further clarify the early immune response against replication-deficient adenoviral vectors and suggest a strategy to prevent adenovirus-mediated inflammation and tissue injury by interfering with chemokine or neutrophil function.

Collagen-platelet interaction: Gly-Pro-Hyp is uniquely specific for platelet Gp VI and mediates platelet activation by collagen

OBJECTIVE

Peptides consisting of a repeat Gly-Pro-Hyp sequence are potent platelet agonists. The aim of this study was: (1) to examine the specificity of this sequence for platelet activation; (2) to confirm its recognition by platelet glycoprotein VI; and (3) to assess with suitable peptides the relative importance of glycoprotein VI and integrin alpha 2 beta 1 in platelet activation by collagen.

METHODS

Peptides were synthesized by standard Fmoc chemistry and tested for their ability to support adhesion of human platelets and HT 1080 cells, induce platelet aggregation, bind integrin alpha 2 subunit A-domain and to cause tyrosine phosphorylation of platelet proteins.

RESULTS

(1) Peptides consisting of a repeat Gly-Pro-Pro, Gly-Pro-Ala or Gly-Pro-Arg sequence exhibited little if any platelet-reactivity. (2) The platelet-reactive peptide consisting of a repeating Gly-Pro-Hyp sequence failed to induce tyrosine phosphorylation in glycoprotein VI-deficient platelets. Platelet adhesion to this peptide was inhibited by intact anti-glycoprotein VI antibody and its Fab fragment. The latter inhibited aggregation by the peptide and fibres of both collagens I and III. (3) A peptide containing a 15-mer alpha 2 beta 1-binding sequence in a repeat Gly-Pro-Pro structure supported alpha 2 beta 1-mediated platelet and HT 1080 cell adhesion and bound alpha 2 A-domain, but failed to activate platelets or to induce tyrosine phosphorylation. Conversely, a peptide containing this sequence but with an essential Glu replaced by Ala and inserted in a repeat Gly-Pro-Hyp structure did not recognize alpha 2 beta 1, but was highly platelet activatory.

CONCLUSIONS

Platelet activation by collagen involves the highly-specific recognition of the Gly-Pro-Hyp sequence by platelet glycoprotein VI. Recognition of alpha 2 beta 1 is insufficient to cause activation. Interaction between collagen and glycoprotein VI is unique since Gly-Pro-Hyp is common in collagens but occurs rarely in other proteins, and glycoprotein VI may be expressed solely by platelets. This sequence could provide a basis for a highly-specific anti-thrombotic reagent to control thrombosis associated with plaque rupture.

Identification in collagen type I of an integrin alpha2 beta1-binding site containing an essential GER sequence

The collagen type I-derived fragment alpha1(I)CB3 is known to recognize the platelet collagen receptor integrin alpha2beta1 as effectively as the parent collagen, although it lacks platelet-aggregatory activity. We have synthesized the fragment as seven overlapping peptides that spontaneously assemble into triple helices. On the basis of their capacity to bind purified alpha2 beta1 and the recombinant alpha2 A-domain, and their ability to support alpha2 beta1-mediated cell adhesion, we identified two peptides, CB3(I)-5 and -6, which contain an alpha2 beta1 recognition site. Synthesis of the peptide CB3(I)-5/6, containing the overlap sequence between peptides 5 and 6, allowed us to locate the binding site within the 15-residue sequence, GFP*GERGVEGPP*GPA (where P* represents hydroxyproline), corresponding to residues 502-516 of the collagen type I alpha1 chain. The Glu and Arg residues in the GER triplet were found to be essential for recognition since substitution of either residue with Ala caused a loss of alpha2 A-domain binding. By contrast, substitution of the Glu in GVE did not reduce binding, but rather enhanced it slightly. We were unable to detect significant recognition of alpha2 beta1 by the peptide CB3(I)-2 containing the putative alpha2 beta1 recognition sequence DGEA. Peptides CB3(I)-1 to -6, together with peptide CB3(I)-5/6, exhibited good platelet-aggregatory activity, in some cases better than collagen. However, peptide CB3(I)-7 was inactive, suggesting the presence of an inhibitory element that might account for the lack of aggregatory activity of the parent alpha1(I)CB3 fragment.

Major cervical spine injuries in children and adolescents

A population-based study of pediatric cervical spine trauma in the Auckland region over 7 years starting in March 1989 identified 32 patients younger than 15 years of age who sustained a fracture, dislocation, or major ligamentous injury including SCIWORA (spinal cord injury without radiographic abnormality). Thirty-one percent had associated injuries and 53% had abnormal neurologic findings on presentation. Children younger than 10 years of age with cervical spine trauma more commonly sustained the injury in a motor vehicle accident and had a preponderance of injuries of the upper cervical spine. Children 10 years of age or older were more often injured during sport or recreational activity and the injuries followed a more typically adult pattern. Treatment included closed reduction in two patients and posterior open reduction and stabilization in eight patients (25%) with one of these also requiring decompression. All patients treated surgically had a very satisfactory outcome.

The collagen-platelet interaction

Collagen-platelet interaction, occurring in hemostasis but also a cause of thrombosis, is a two-step process of adhesion and activation involving the sequential recognition of distinct receptors. Adhesion involves first the reversible recognition of collagen-bound von Willebrand factor by the platelet receptor complex Gp Ib/IX/V, followed by direct interaction between collagen and the platelet integrin receptor alpha2beta1, which binds to specific sequences in collagen in which the GER motif appears important. Platelet activation then follows from the recognition by the receptor Gp VI of GPP* sequences in collagen, culminating in signalling events unique to collagen as a platelet agonist: Gp VI leads via the novel platelet Fc receptor gamma-chain to p72syk and phospholipase Cgamma2.

Simple collagen-like peptides support platelet adhesion under static but not under flow conditions: interaction via alpha2 beta1 and von Willebrand factor with specific sequences in native collagen is a requirement to resist shear forces

The aim of this study was to define the need for specific collagen sequences and the role of their conformation in platelet adhesion to collagen under both static and flow conditions. We recently reported that simple triple-helical collagen-related peptides (CRPs), GCP*(GPP*)10GCP*G and GKP*(GPP*)10GKP*G (single-letter amino acid code, P* = hydroxyproline; Morton et al, Biochem J 306:337, 1995) were potent stimulators of platelet activation and were able to support the adhesion of gel-filtered platelets examined under static conditions. The present study investigated whether these same peptides were able to support platelet adhesion under more physiologic conditions by examining static adhesion with platelet-rich plasma (PRP) and adhesion under flow conditions. In the static adhesion assay, we observed 20% surface coverage with platelet aggregates. In marked contrast, there was a total lack of adhesion under flow conditions examined at shear rates of 50 and 300 s-1. Thus, the interaction of platelets with the CRPs is a low-affinity interaction unable on its own to withstand shear forces. However, the addition of CRPs to whole blood, in the presence of 200 micromol/L D-arginyl-glycyl-L-aspartyl-L-tryptophan (dRGDW) to prevent platelet aggregation, caused an inhibition of about 50% of platelet adhesion to collagens I and III under flow. These results suggest that the collagen triple helix per se, as defined by these simple collagen sequences, plays an important contributory role in the overall process of adhesion to collagen under flow. The monoclonal antibody (MoAb) 176D7, directed against the alpha2 subunit of the integrin alpha2 beta1, was found to inhibit static platelet adhesion to monomeric but not fibrillar collagens I and III. However, under flow conditions, anti-alpha2 MoAbs (176D7 anf 6F1) inhibited adhesion to both monomeric and fibrillar collagens, indicating that alpha2 beta1 is essential for adhesion to collagen under flow, independent of collagen conformation, whether monomeric or polymeric. To obtain further insight into the nature of the different adhesive properties of CRPs and native collagen, we investigated the relative importance of von Willebrand factor (vWF) and the integrin alpha2 beta1 in platelet adhesion to collagen types I and III, using the same shear rate (300 s-1) as used when testing CRPs under flow conditions. Our results, together with recent data of others, support a two-step mechanism of platelet interaction with collagen under flow conditions. The first step involves adhesion via both the indirect interaction of platelet glycoprotein (GP) Ib with collagen mediated by vWF binding to specific vWF-recognition sites in collagen and the direct interaction between platelet alpha2 beta1 and specific alpha2 beta1-recognition sites in collagen. This suffices to hold platelets at the collagen surface. The second step occurs via another collagen receptor (thought to be GPVI) that binds to simple collagen sequences, required essentially to delineate the collagen triple helix. Recognition of the triple helix leads to strengthening of attachment and platelet activation.

Glycoprotein VI is a major collagen receptor for platelet activation: it recognizes the platelet-activating quaternary structure of collagen, whereas CD36, glycoprotein IIb/IIIa, and von Willebrand factor do not

Simple collagen-related peptides (CRPs) containing a repeat Gly-Pro-Hyp sequence are highly potent platelet agonists. Like collagen, they must exhibit tertiary (triple-helical) and quaternary (polymeric) structure to activate platelets. Platelet signaling events induced by the peptides are the same as most of those induced by collagen. The peptides do not recognize the alpha 2 beta 1 integrin. To identify the signaling receptor involved, we have evaluated the response to the CRP, Gly-Lys-Hyp(Gly-Pro-Hyp)10-Gly-Lys-Hyp-Gly of platelets with defined functional deficiencies. These studies exclude a primary recognition role for CD36, von Willebrand factor (vWF), or glycoprotein (GP) IIb/IIIa. Thus, both CD36 and vWF-deficient platelets exhibited normal aggregation, normal fibrinogen binding, and normal expression of CD62 and CD63, measured by flow cytometry, in response to the peptide, and there was normal expression of CD62 and CD63 on thrombasthenic platelets. In contrast, GPVI-deficient platelets were totally unresponsive to the peptide, indicating that this receptor recognizes the Gly-Pro-Hyp sequence in collagen. GPVI-deficient platelets showed some fibrinogen binding in response to collagen but failed to aggregate and to express CD62 and CD63. Collagen, but not CRP-XL, contains binding sites for alpha 2 beta 1. Therefore, it is possible that collagen still induces some signaling via alpha 2 beta 1, leading to activation of GPIIb/IIIa. Our findings are consistent with a two-site, two-step model of collagen interaction with platelets involving recognition of specific sequences in collagen by an adhesive receptor such as alpha 2 beta 1 to arrest platelets under flow and subsequent recognition of another specific collagen sequence by an activatory receptor, namely GPVI.

Ethnicity, drug user status and academic performance

The impact of drug use and race on school performance was investigated. Data were collected retrospectively from a sample of 100 students in Grades 9 through 12, using a questionnaire devised by the authors. Most recent grades in English, mathematics, social studies, and science, and percentile scores on the mathematics portion of a recent Metropolitan Achievement Test, constituted achievement. Sufficient data were obtained for 38 students (11 black, 18 white, and 9 Latino). Results included significant main effects for both race (p < .05) and user status (p < .05). An interaction of race and user status was suggested. While black users and nonusers did not differ across academic areas, large differences for the two other ethnic groups emerged.

The platelet reactivity of synthetic peptides based on the collagen III fragment alpha1(III)CB4. Evidence for an integrin alpha2beta1 recognition site involving residues 522-528 of the alpha1(III) collagen chain

The platelet-reactive collagen III-derived fragment alpha1(III)CB4 has been synthesized as seven overlapping peptides, each as a homotrimeric triple-helical species covalently linked at the C terminus. Additional Gly-Pro-Hyp triplets were introduced at each end of the peptide sequence to ensure a stable triple-helical conformation at 20 degrees C, the temperature at which cell reactivity was measured. A Cys-containing triplet was included at each end to allow intermolecular cross-linking. All seven peptides in triple-helical, cross-linked form were able to cause platelet aggregation. Peptide 6, the most reactive species, was more aggregatory than collagen fibers. Platelet adhesion occurred to all peptides immobilized on plastic in monomeric form. Adhesion was integrin alpha2beta1-independent except in the case of peptide 6, adhesion to which was partially reduced by anti-integrin alpha2beta1 monoclonal antibodies. The presence of an alpha2beta1 recognition site in peptide 6 was confirmed using HT 1080 cells, which express alpha2beta1 as their major or sole collagen receptor. HT 1080 adhesion to both peptide 6 and collagen was strongly inhibited by anti-integrin alpha2beta1 monoclonal antibodies. These cells did not adhere to any of the other peptides. Comparison of the structure of peptide 6 with that of adjacent peptides indicates that the sequence Gly-Gly-Pro-Hyp-Gly-Pro-Arg, residues 522-528 of the collagen alpha1(III) chain, represents the minimum structure required for the recognition of alpha2beta1. Our findings support the view that the collagen triple helix possesses an intrinsic platelet reactivity that can be expressed independently of integrin alpha2beta1 and the precise level of which is governed by the exact nature of the primary sequence. Sequences such as those recognizing alpha2beta1 may potentiate the activity, whereas others may have the opposite effect.

A collagen-like peptide stimulates tyrosine phosphorylation of syk and phospholipase C gamma2 in platelets independent of the integrin alpha2beta1

Activation of platelets by collagen is mediated through a tyrosine kinase-dependent pathway that is associated with phosphorylation of the Fc receptor gamma chain, the tyrosine kinase syk, and phospholipase C gamma2 (PLC gamma2). We recently described a collagen-related triple-helical peptide (CRP) with the sequence GCP*(GPP*)GCP*G (single letter amino acid code: P* = hydroxyproline; Morton et al, Biochem J306:337, 1995). The cross-linked peptide is a potent stimulus of platelet activation but, unlike collagen, does not support alpha2beta1-mediated, Mg2+-dependent adhesion, suggesting that its action is independent of the integrin alpha2beta1. This finding suggests the existence of a platelet receptor other than alpha2beta1 that underlies activation. In the present study, we show that CRP stimulates tyrosine phosphorylation of the same pattern of proteins in platelets as collagen, including syk and PLC gamma2. Protein tyrosine phosphorylation induced by CRP is not altered in the absence of Mg2+ or the presence of monoclonal antibodies (MoAbs) to the integrin alpha2beta1 (MoAb 6F1 and MoAb 13), conditions that prevent the interaction of collagen with the integrin. In contrast, phosphorylation of syk and PLC gamma2 by collagen is partially reduced by MoAb 6F1 and MoAb 13 or by removal of Mg2+. This may reflect a direct role of alpha2beta1 in collagen-induced signaling events or an indirect role in which the integrin facilitates the binding of collagen to its signaling receptor. The results show an alpha2beta1-independent pathway of platelet activation by CRP that involves phosphorylation of syk and PLC gamma2. This pathway appears to contribute to platelet activation by collagen.