Identification of lectin-purified neural glycoproteins, GPs 180, 116, and 110, with NMDA and AMPA receptor subunits: conservation of glycosylation at the synapse

The postsynaptic apparatus is associated with a number of glycoproteins with apparent molecular masses of 180, 116, and 110 kDa, which are highly concentrated in and may be uniquely associated with this structure. These glycoproteins, purified by concanavalin A lectin-affinity chromatography, showed immunoreactivity in the present study with subunit-specific antibodies to glutamate receptors as follows: GP 180, NMDA receptor subunits NR2A/NR2B; GP 116, NMDA receptor NR1 (1a); and GP 110, pan-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (pan-AMPA) receptors. Sensitivities to the glycosidases peptide N-glycosidase F and endo-beta-N-acetylglucosaminidase H on both western blots and silver-stained gels suggested that the glutamate receptors were at least major constituents of the glycoprotein bands. Similar detailed glycosylation was observed for all three glycoproteins, with neutral oligosaccharides being dominant. Oligomannosidic glycans (with from five to nine mannoses) accounted for approximately 50% of the neutral sugars, with Man 5 (at almost 20% of the neutral sugars) always the major glycan. Other abundant neutral oligosaccharides were of the complex type. Similar sensitivities to peptide N-glycosidase F and endo-beta-N-acetylglucosaminidase H were observed for cell line-expressed NMDA receptor subunits, suggesting that irrespective of the glycosylation processing available, the least highly processed oligosaccharides will be expressed. This may be indicative of glycosylation sites in these receptors that are inaccessible to the later processing enzymes and favours the oligomannosidic class of glycans in functional roles.

Understanding barriers to condom usage among HIV-infected African American women

Drawing on focus group discussions with adolescent and adult HIV-infected women between the ages of 16 and 45, this study explores the barriers to condom use among women infected with HIV. Although most of the participants were comfortable discussing condoms and sexuality, there was little, if any, negotiation of condom use with their male partners. Most of the participants used condoms inconsistently or not at all. Reasons for nonuse included a lack of trust in the reliability of condoms to protect them, a lack of desire for pregnancy prevention, and the male partner's refusal to use condoms. Women in discordant relationships explained their uninfected partner's refusal to use condoms as denial of the risk of contracting HIV or as a way of expressing their love for the infected partner. Women also had great difficulty in disclosing their HIV status to both family and partners. Prevention efforts to increase condom use among HIV-infected women should target both men and women and focus on negotiation and communication skills.

Digital mammography: hybrid four-channel wavelet transform for microcalcification segmentation

RATIONALE AND OBJECTIVES

The authors evaluated an algorithm for the automatic segmentation of microcalcification clusters (MCCs) at digital mammography. Two- and four-channel wavelet transforms were evaluated to determine whether sensitivity in the detection of MCCs can be improved and if the selective reconstruction of the higher-order M2 subimages allows better preservation of the segmented MCCs, which is required for their classification.

MATERIALS AND METHODS

The hybrid method involved the use of a nonlinear filter for image noise suppression coupled with wavelet transforms for image decomposition and an adaptive method for selective subimage reconstruction as a basis for segmentation of MCCs. The two- and four-channel wavelet transforms were implemented with different filter bank structures (i.e., polyphase quadrature mirror filters [QMFs], tree structure, and lattice structure) to determine if their computational efficiency can be improved while retaining properties such as near-perfect reconstruction. The hybrid wavelet transforms were applied to a common image database of biopsy-proved MCCs (100 images, 105-micron resolution, 12 bits deep; 52 cases with at least one MCC of varying subtlety [46 malignant and six benign cases] and eight normal cases).

RESULTS

The two- and four-channel wavelet transforms yielded sensitivities of 93% and 94% and false-positive (PP) detection rates of 1.58 and 1.35 MCCs per image, respectively. The lattice structure provided greater than fivefold improvement in computational speed compared to the polyphase QMF structure, particularly for the higher order of channels (M = 4).

CONCLUSION

The four-channel wavelet transform provided better sensitivity and FP detection rates and greater image detail preservation for the segmented MCCs.

Effect of asthma and its treatment on growth: four year follow up of cohort of children from general practices in Tayside, Scotland

OBJECTIVE

To investigate whether asthma or its treatment impairs children's growth, after allowing for socioeconomic group.

DESIGN

4 year follow up of a cohort of children aged 1-15.

SETTING

12 general practices in the Tayside region of Scotland.

SUBJECTS

3347 children with asthma or features suggestive of asthma registered with the general practices.

MAIN OUTCOME MEASURES

Height and weight standard deviation scores.

RESULTS

Children who lived in areas of social deprivation (assessed by postcode) had lower height and weight than their contemporaries (mean standard deviation score -0.26 (SD 1.02) and -0.18 (1.15) respectively, P < 0.001 for both). Children who were receiving > or = 400 micrograms daily of inhaled steroids and who were attending both hospital and general practice for asthma care had lower height and weight than average, independent of the effect of deprivation (mean standard deviation score -0.62 (1.01), P = 0.002, for height and -0.58 (0.94), P = 0.005, for weight). Children receiving high doses of inhaled corticosteroids also showed lower growth rates (mean change in standard deviation score -0.19 (0.51), P = 0.003). However, no other children with asthma showed growth impairment.

CONCLUSION

Most children with asthma were of normal height and weight and had normal growth rates. However, children receiving high doses of inhaled steroids and requiring both general practice and hospital services had a significant reduction in their stature. This effect was independent from but smaller than the effect of socioeconomic group on stature.

A three-dimensional collagen lattice activates NF-kappaB in human fibroblasts: role in integrin alpha2 gene expression and tissue remodeling

Normal adult human dermal fibroblasts grown in a three-dimensional collagen lattice increase mRNA level of collagen receptor integrin subunit alpha2 (Xu, J., and R.A.F. Clark. 1996. J. Cell Biol. 132:239- 249.) and DNA binding activity of a nuclear transcription factor, NF-kappaB (Xu, J., and R.A.F. Clark. 1997. J. Cell Biol. 136:473-483.). Here we present evidence that the collagen lattice induced the nuclear translocation of p50, one member of NF-kappaB family, and the degradation of an NF-kappaB inhibitor protein, IkappaB-alpha. The inhibition of NF-kappaB activity by SN50, a peptide inhibitor targeted at nuclear translocation of NF-kappaB, significantly reduced the induction of integrin alpha2 mRNA and protein by the collagen lattice. A region located between -549 and -351 bp in the promoter of integrin alpha2 gene conferred the inducibility by three-dimensional collagen lattice. The presence of either SN50 or IkappaB-alpha32, 36, a stable mutant of IkappaB-alpha, abrogated this inducibility, indicating that the activation of integrin alpha2 gene expression was possibly mediated by NF-kappaB through this region. Although there were three DNA-protein binding complexes forming in this region that are sensitive to the inhibition of NF-kappaB nuclear translocation, NF-kappaB was not directly present in the binding complexes. Therefore, an indirect regulatory mechanism by NF-kappaB in integrin alpha2 gene expression induced by three-dimensional collagen lattice is suggested. The involvement of NF-kappaB in reorganization and contraction of three-dimensional collagen lattice, a process that requires the presence of abundant integrin alpha2beta1, was also examined. The inhibition of NF-kappaB activity by SN50 greatly blocked the contraction, suggesting its critical role in not only the induction of integrin alpha2 gene expression by three-dimensional collagen lattice, but also alpha2beta1-mediated tissue-remodeling process.

L-Selectin ligands that are O-glycoprotease resistant and distinct from MECA-79 antigen are sufficient for tethering and rolling of lymphocytes on human high endothelial venules

During the process of lymphocyte recirculation, lymphocytes bind via L-selectin to sulfated sialyl-Lewisx (sLex)-containing carbohydrate ligands expressed on the surface of high endothelial venules (HEV). We have examined the expression of sLex on HEV using a panel of mAbs specific for sLex and sLex-related structures, and have examined the function of different sLex-bearing structures using an in vitro assay of lymphocyte rolling on HEV. We report that three sLex mAbs, 2F3, 2H5, and CSLEX-1, previously noted to bind with high affinity to glycolipid-linked sLex, vary in their ability to stain HEV in different lymphoid tissues and bind differentially to O-linked versus N-linked sLex on glycoproteins. Treatment of tissue sections with neuraminidase abolished staining with all three mAbs but slightly increased staining with MECA-79, a mAb to a sulfation-dependent HEV-associated carbohydrate determinant. Treatment of tissue sections with O-sialoglycoprotease under conditions that removed the vast majority of MECA-79 staining, only partially reduced staining with the 2F3 and 2H5 mAbs. Using a novel rolling assay in which cells bind under flow to HEV of frozen tissue sections, we demonstrate that a pool of O-sialoglycoprotease-resistant molecules is present on HEV that is sufficient for attachment and rolling of lymphocytes via L-selectin. This interaction is not inhibited by the mAb MECA-79. Furthermore, MECA-79 mAb blocks binding to untreated sections by only 30%, whereas the sLex mAb 2H5 blocks binding by approximately 60% and a combination of MECA-79 and 2H5 mAb blocks binding by 75%. We conclude that a pool of O-glycoprotease-resistant sLex-like L-selectin ligands exist on human HEV that is distinct from the mucin-associated moieties recognized by MECA-79 mAb. We postulate that these ligands may participate in lymphocyte binding to HEV.

Heterotopic muscle pulleys or oblique muscle dysfunction?

INTRODUCTION

The description of connective tissue sleeves that function as pulleys for the rectus extraocular muscles (EOMs) suggests that abnormalities of EOM pulley position might provide a mechanical basis for some forms of incomitant strabismus. Pulleys determine the paths and thus the pulling directions of EOMs.

METHODS

High-resolution magnetic resonance images spanning the orbits were obtained in primary position, upgaze, and downgaze for each subject. Paths of the EOMs were measured with reference to the orbital center and permitted inference of pulley locations.

RESULTS

Data from 18 orbits of orthotropic subjects defined means and SDs of normal EOM pulley coordinates. Eight patients, aged 17 to 60 years, had heterotopic EOM pulleys, defined as displaced at least 2 SDs from normal. We found one to eight heterotopic pulleys (considering both orbits) in each of four patients who had been diagnosed with marked superior oblique (SO) overaction and mild to marked inferior oblique (IO) underaction. Each patient had superior mislocation of at least one lateral rectus pulley by 1.8 to 4.9 mm. Three patients diagnosed with mild to moderate IO overaction and mild to moderate SO underaction in only one orbit had one to three heterotopic EOM pulleys. Each of those patients had at least one lateral rectus pulley inferiorly dislocated by 1.9 to 4.9 mm. The final patient, who was diagnosed with mild IO underaction and normal SO function bilaterally, had bilateral superior mislocation of the medial rectus pulleys by greater than 2 mm. Computer simulations using the Orbit program (Eidactics, San Francisco) incorporating individually measured pulley positions reproduced the clinical patterns of incomitant strabismus in all cases without postulating abnormalities of oblique muscle innervation or contractility.

CONCLUSION

Heterotopic EOM pulleys can cause patterns of incomitant strabismus that have been attributed to oblique muscle dysfunction. Even isolated mislocations of less than 2 mm, coupled with smaller mislocations of the other pulleys, can produce the clinical appearance of bilateral oblique dysfunction. Pulley heterotopy should be considered in the differential diagnosis of incomitant strabismus and oblique dysfunction.

Farming systems research: relevance to Australia

Summary. Farming systems research was introduced into many international and national agricultural research institutes in lower income countries in the 1970s and 1980s with the purpose of improving the relevance of research for small-scale farmers. This review outlines the origin, context, goals, principles and process of farming systems research in these countries, and aims to enable agricultural professionals to assess the relevance and value of farming systems research to their work in particular situations in Australia and overseas. The key elements of farming systems research include a holistic approach, orientation towards the needs of defined target groups, high levels of farmer participation and hence co-learning by farmers and specialists. There is guidance by facilitators, continuous evaluation and linkage to policy makers. The goal of farming systems research is to improve the well-being of farmers through development of farming systems. It involves application of methods from various disciplines, first to define the constraints and opportunities for development and then to overcome these in a research process involving farmers, with specialists and policy makers. A generalised farming systems research procedure and various research activities are described. Initially in lower income countries, a fairly standard farming systems research procedure was used, but farming systems research has evolved to encompass a range of activities commonly regarded as the realm of agricultural extension or rural development. Basic science, applied science and farming systems research are compared in terms of the roles and relationships of the people involved in the research process. The implications of selecting farming systems research as a model for rural research and development are discussed. Achieving adequate levels of farmer participation can be a major issue in farming systems research so it is important that the principal notions of participation are understood. Success of farming systems research in Australia will depend on developing innovative ways of achieving high levels of participation. Current trends in the philosophy, practice and funding of agricultural research and extension in Australia make it timely to consider the wider adoption of farming systems research principles and practices. Farming systems research could provide a valuable philosophical and practical basis for the trend towards greater participation by researchers with end-users and extension practitioners in agricultural development programs. However, it seems unwise to adhere strictly to any one particular model of research and development from other places: farming systems research concepts are being combined successfully with those from other models, such as systems learning and computer modelling, to suit the needs of particular situations. Implications of a wider adoption of farming systems research in Australia for agricultural research and development organisations and professional bodies include, the establishment of multidisciplinary teams with shared goals, and the sourcing of funding for periods long enough to achieve outcomes. There is also a need for training in systems concepts and facilitation, for reputable channels of publication of the results of farming systems research and for greater recognition of participatory activities as valid forms of agricultural research.

Displacement of the medial rectus pulley in superior oblique palsy

PURPOSE

The rectus extraocular muscles pass through fibromuscular connective tissue pulleys that stabilize muscle paths and control the direction of muscle pull. The authors investigated whether abnormal forces associated with superior oblique palsy can cause displacement of pulleys and muscle paths.

METHODS

Coronal magnetic resonance imaging (MRI) showing significantly reduced superior oblique cross-sectional areas and lack of contractile changes with vertical gaze confirms that seven subjects had superior oblique palsies. Binocular misalignment was quantified using the Hess test. In those seven subjects with palsies and in 18 normal orbits, coronal MRI scans corrected to standardized head position were analyzed digitally to determine muscle paths in primary gaze. Horizontal and vertical coordinates of the pulleys, known histologically to lie just posterior to the equator in primary gaze, were inferred from these muscle paths.

RESULTS

Normal pulley coordinates were highly uniform. Compared with both normal orbits and fellow orbits, orbits with superior oblique palsies showed a statistically significant 1.1 mm superior displacement of the medial rectus pulley. No other pulley was displaced significantly from normal. Computer simulation using a biomechanical model of ocular statics showed that, in each case, the pulley position shifts alone were insufficient to reproduce the clinical pattern of strabismus.

CONCLUSIONS

The excyclotorsion of the globe that accompanies superior oblique palsy does not systematically displace the pulleys of all the rectus muscles. The only significant rectus muscle path change is for the medial rectus muscle, and it may arise as a mechanical consequence of the atrophy of the adjacent superior oblique muscle belly. Biomechanical modeling suggests that this displacement of the medial rectus pulley alone does not account for the pattern of strabismus observed in superior oblique palsy.

What determines levels of passive smoking in children with asthma?

BACKGROUND

Children with parents who smoke are often exposed to high levels of environmental tobacco smoke, and children with asthma are particularly susceptible to the detrimental effects of passive smoking. Data were collected from parents who smoke and from their asthmatic children. The families are currently taking part in a randomised controlled trial to test an intervention designed to reduce passive smoking in children with asthma. This paper reports on the baseline data. Questionnaire data and cotinine levels were compared in an attempt to assess exposure and to identify factors which influence exposure of the children. The aim of the study was to identify the scope for a reduction in passive smoking by these children.

METHODS

A sample of 501 families with an asthmatic child aged 2-12 years was obtained. Factors influencing passive smoking were assessed by interviewing parents. Cotinine levels were measured from saliva samples using gas liquid chromatography with nitrogen phosphorous detection.

RESULTS

Cotinine levels in children were strongly associated with the age of the child, the number of parents who smoked, contact with other smokers, the frequency of smoking in the same room as the child, and crowding within the home. Parental cotinine levels, the amount smoked in the home, and whether the home had a garden also exerted an independent effect on cotinine levels in the children.

CONCLUSIONS

Many children are exposed to high levels of environmental tobacco smoke and their cotinine levels are heavily dependent upon proximity to the parent who smokes. Parents who smoke have a unique opportunity to benefit their child's health by modifying their smoking habits within the home.

Clinical manifestations and predictors of survival in older women infected with HIV

To review the natural history of HIV infection in older women, a retrospective review of women enrolled in the HIV Outpatient Program based at the Medical Center of Louisiana in New Orleans was performed. Eighty-four of the women were at least 40 years of age. Older women were more likely to be diagnosed with selected psychosocial illnesses (e.g., injection drug use, alcohol abuse, anxiety, depression, psychosis, dementia) compared with women <40 years of age. There was no association with age and other opportunistic processes or HIV-related symptoms, but cervical dysplasia and chlamydia cervicitis were less common in older women. In a multivariate proportional hazards model, characteristics predictive for death among older women included a CD4 cell count <200 cells/mm3 (relative risk [RR], 2.86; 95% confidence interval [CI], 1.18, 6.86; p < .02), a diagnosis of an opportunistic process (RR, 3.25; 95% CI, 1.24, 8.55; p < .02), antiretroviral combination therapy (RR, 0.36; 95% CI, 0.12, 1.13: p < .08), and hormone replacement therapy (HRT) (RR, 0.28; 95% CI, 0.07, 1.10; p < .06). HRT should be considered in the management of postmenopausal HIV-infected women for its known documented benefits shown in populations of persons not infected with HIV. Prospective studies to better evaluate risks and benefits of HRT in HIV-infected women are warranted.

Quantitative measurements of released amines from individual exocytosis events

Chemical analysis of single cells is an area of great interest in the biological sciences. Single-cell systems are being utilized as a model to understand in vivo processes better. One method that is moving to the forefront in cellular analysis is electrochemistry. Owing to their rapid response time and small dimensions, voltammetric microelectrode techniques, such as amperometry and fast-scan voltammetry, have made it possible to monitor minute amounts of biological compounds and transiently occurring chemical events in cellular systems. The application of these methods to the quantitation of individual vesicular release events from single cells is overviewed here. The application of electrochemical monitoring to several types of cultured cells, including bovine adrenal chromaffin cells, rat pheochromocytoma (PC12) cells, beige mouse mast cells, superior cervical ganglion neurons, and human pancreatic beta-cells, as well as to the invertebrate systems, the leech Hirudo medicinalis, and pond snail Planorbis corneus has provided a wealth of new information concerning exocytosis. Results obtained from the studies highlight the potential of electrochemical techniques in cellular analysis to contribute to our understanding of molecular and pharmacological effects on exocytosis. This article overviews work done on all the above cell types with an emphasis on PC12 cells.

PU.1 is essential for p47(phox) promoter activity in myeloid cells

Expression of the phagocyte cytosolic protein p47(phox), a component of NADPH oxidase, is restricted mainly to myeloid cells. To study the cis-elements and trans-acting factors responsible for its gene expression, we have cloned and characterized the p47(phox) promoter. A predominant transcriptional start site was identified 21 nucleotides upstream of the translation initiation codon. To identify the gene promoter sequences, transient transfections of HL-60 human myeloid cells were performed with a series of 5'-deletion p47(phox)-luciferase reporter constructs that extended as far upstream as -3050 bp relative to the transcriptional start site. The -224 and -86 constructs had the strongest p47(phox) promoter activity, whereas the -46 construct showed a major reduction in activity and the -36 construct a complete loss of activity. DNase I footprint analysis identified a protected region from -37 to -53. This region containing a consensus PU.1 site bound specifically both PU.1 present in nuclear extracts from myeloid cells and PU.1 synthesized in vitro. Mutations of this site eliminated PU.1 binding and abolished the ability of the p47(phox) promoter to direct expression of the reporter gene. The p47(phox) promoter was active in all myeloid cell lines tested (HL-60, THP-1, U937, PLB-985), but not in non-myeloid cells (HeLa, HEK293). Finally, PU.1 trans-activated the p47(phox)-luciferase constructs in HeLa cells. We conclude that, similar to certain other myeloid-specific genes, p47(phox) promoter activity in myeloid cells requires PU.1.

Calreticulin biosynthesis and processing in human myeloid cells: demonstration of signal peptide cleavage and N-glycosylation

Calreticulin is a soluble endoplasmic reticulum protein comprising the major storage reservoir for inositol trisphosphate-releasable calcium. Although its highly conserved primary structure and a wide range of functions have been well described, less attention has been paid to its biosynthesis, particularly in human tissues. We report analyses of synthesis, proteolytic processing and glycosylation of human calreticulin. In both HL-60 and PLB-985 myeloid cell lines calreticulin was immunoprecipitated as a single 60-kD species without evidence of precursor forms. However, in vitro cell-free synthesis produced a 62-kD primary translation product, which in the presence of microsomal membranes, was processed by cotranslational signal peptide cleavage to a 60-kD species that comigrated with mature calreticulin produced in myeloid cells. Neither tunicamycin treatment of the cells nor endoglycosidase digestion of calreticulin resulted in any forms other than the 60-kD protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, suggesting that the potential site for N-glycosylation at asparagine-327 was unmodified. However, oxidative derivatization of carbohydrate components with digoxigenin showed that human calreticulin produced in either HL-60 cells or Sf9 insect cells is glycosylated, indicating that glycosylated and nonglycosylated human calreticulin have indistinguishable electrophoretic mobilities. Direct measurement by phenol-H2SO4 confirmed the presence of carbohydrate on recombinant human calreticulin. These data show that human myeloid calreticulin undergoes cotranslational signal peptide cleavage and posttranslational N-linked glycosylation. Although glycosylation of calreticulin has been shown in rat liver and bovine liver and brain, it has been reported to be lacking in other tissues including human lymphocytes.

Tenascin supports lymphocyte rolling

Tenascin is a large extracellular matrix molecule expressed at specific sites in the adult, including immune system tissues such as the bone marrow, thymus, spleen, and T cell areas of lymph nodes. Tenascin has been reported to have both adhesive and anti-adhesive effects in static assays. We report here that tenascin supports the tethering and rolling of lymphocytes and lymphoblastic cell lines under flow conditions. Binding was calcium dependent and was not inhibited by treatment of lymphocytes with O-glycoprotease or a panel of glycosidases including neuraminidase and heparitinase but was inhibited by treatment of cells with proteinase K. Binding was to the fibrinogen-like terminal domain of tenascin as determined by antibody blocking studies and binding to recombinant tenascin proteins. When compared to rolling of the same cell type on E-selectin, rolling on tenascin was found to be smoother at all shear stresses tested, suggesting that cells formed a larger number of bonds on the tenascin substrate than on the E-selectin substrate. When protein plating densities were adjusted to give similar profiles of cell detachment under increasing shears, the density of tenascin was 8.5-fold greater than that of E-selectin. Binding to tenascin was not dependent on any molecules previously identified as tenascin receptors and is likely to involve a novel tenascin receptor on lymphocytes. We postulate that the ability of tenascin to support lymphocyte rolling may reflect its ability to support cell migration and that this interaction may be used by lymphocytes migrating through secondary lymphoid organs.

Does participation in distance learning and audit improve the care of patients with acute asthma attacks? The General Practitioners in Asthma Group

OBJECTIVE

To test whether general practitioners who completed an audit cycle encompassing a data recording exercise, distance learning programme and personalized feedback changed their management of patients with acute asthma attacks.

DESIGN, SETTING AND SUBJECTS

Practice and patient details from two national correspondence surveys of the management of acute asthma attacks in the United Kingdom in 1991-92 and 1992-93 were compared. Main outcome measures were use of nebulised bronchodilators, systemic steroids during an asthma attack, and increased use of prophylactic therapy after attacks.

RESULTS

Ninety-one general practitioners completed an audit cycle and reported data on 782 patients with asthma attacks in 1991-92 and 669 in 1992-93. There were no significant changes in practice resources during this time. Management changed in line with recommended guidelines and audit feedback suggestions leading to more use of nebulised bronchodilators [272 (35%) before, 268 (40%) after, Odds Ratio (OR) 0.80, 95% Confidence Intervals (CI) 0.64-0.99], systemic steroids [563 (72%) before, 506 (76%) after, OR 0.83, CI 0.65-1.06], and 'step-up' in preventative therapy [402 (51%) before, 382 (57%) after, OR 0.79, CI 0.64-0.98].

CONCLUSION

General Practitioners who completed an audit cycle showed changes in the management of acute asthma attacks in line with guidelines which may have been caused by participation in distance learning and clinical audit. However, general practitioners motivated to change clinical management may be similarly motivated to take part in audit. Audit may be the catalyst for change rather than the cause of change.

Human fibroblasts bind directly to fibrinogen at RGD sites through integrin alpha(v)beta3

Fibroblast migration into the blood clot initially filling a wound requires close interaction between fibroblasts and the matrix of the fibrin clot. However, very little is known about the specific receptor-ligand interactions that mediate fibroblast attachment to fibrin. Using an attachment assay developed to measure even relatively weak interactions, we demonstrate here that normal human dermal fibroblasts can attach to substrates coated with fibrinogen, fibrin, or the fibrinogen breakdown product I-9D. Fibroblast attachment to these ligands did not require the presence of fibronectin on the cell surface or as a component of the substrate. Cells treated with cycloheximide and monensin, to limit the synthesis and secretion of endogenous fibronectin, attached as well as untreated cells. The synthetic peptide GRGDS inhibited adhesion to fibrinogen, fibrin, and fibrinogen I-9D by about 60%, while the control peptide GRGES had no substantial effect. We conclude that attachment to these ligands is mediated at least partially by direct interactions between the substrates and one specific receptor, the integrin alpha(v)beta3. Affinity chromatography demonstrated that alpha(v)beta3 from detergent lysates of fibroblasts bound to a fibrinogen matrix and was eluted with EDTA. Furthermore, antibodies against the alpha(v)beta3 complex or against the alpha(v) subunit inhibited fibroblast attachment to fibrinogen and fibrin by 50-70%. An inhibitory antibody against the integrin beta1 subunit had no effect. The observation that integrin antagonists could not produce complete inhibition suggests that there may be other fibroblast cell surface proteins that can bind directly to fibrinogen.

Fibronectin provides a conduit for fibroblast transmigration from collagenous stroma into fibrin clot provisional matrix

After injury, the wound space is filled with a fibrin/fibronectin clot containing growth factors released by platelets and monocytes. In response to these factors, fibroblasts migrate into the fibrin clot and contribute to the formation of granulation tissue. The functional mechanisms allowing fibroblasts to leave the collagenous matrix of normal connective tissue and invade the provisional matrix of the fibrin clot have not been fully defined. To investigate these mechanisms we established a new in vitro model which simulates specific aspects of early wound healing, that is, the migration of fibroblasts from a three-dimensional collagen matrix into a fibrin clot. This transmigration could be induced by physiological concentrations of platelet releasate or platelet-derived growth factor BB (PDGF-BB) in a concentration-dependent manner. At 24 hours irradiated fibroblasts invaded the fibrin gel almost as well as non-irradiated cells, indicating that transmigration was independent of proliferation. Plasminogen and its activators appear to be necessary for invasion of the fibrin clot since protease inhibitors decreased the amount of migration. These serine proteases, however, were not necessary for exit from the collagen gel as fibroblasts migrated out of the collagen gel onto a surface coated with fibrin fibrils even in the presence of inhibitors. Removal of fibronectin (FN) from either the collagen gel or the fibrin gel markedly decreased the number of migrating cells, suggesting that FN provides a conduit for transmigration. Cell movement in the in vitro model was inhibited by RGD peptide, and by monoclonal antibodies against the subunits of the alpha5 beta1 and alpha v beta3 integrin receptor. Thus, the functional requirements for fibroblast transmigration from collagen-rich to fibrin-rich matrices, such as occurs in early wound healing, have been partially defined using an in vitro paradigm of this important biologic process.

Determination of factors associated with condom use among women infected with human immunodeficiency virus

To better understand potential barriers to condom use and the sexual behaviour of women infected with human immunodeficiency virus (HIV), an anonymous self-administered survey was performed on a convenience sample of 83 predominantly single HIV+ women. Most women had only one sexual partner who usually knew of the subject's serostatus. Only a minority of partners (26%) were known to also be HIV infected. Subjects were surprisingly more likely to use condoms with their main partner as opposed to other partners. Factors found to be associated with condom non-use included younger age, low education level, partner HIV+, history of a sexually transmitted disease (STD), and use of drugs or alcohol during sex. Although most subjects indicated the decision was mutual when deciding not to use a condom, 20% stated it a was a partner decision. Future intervention efforts should target these identified high-risk individuals and optimally involve the partners of HIV-infected women.

Reaudit of acute asthma admissions using a severity marker stamp and determinants of an outcome measure

Subsequent to the implementation of a severity marker stamp in case notes, an audit was performed in 86 admissions with acute asthma to a specialist centre over a 12 month period. Compared to previous audit the documentation of severity markers was significantly better (PEFR: 52% vs 83% p = 0.001, Respiratory rate: 44% vs 81% p = 0.001, ABG: 72% vs 80% p = 0.04, air entry: 58% vs 86% p = 0.001, speech: 27% vs 86% p = 0.001, exhaustion: 4% vs 86% p = 0.001). In contrast to the previous audit where no patient received FiO2 > 0.35, 66% of the cases in the repeat audit received FiO2 0.60 (p = 0.001). The mean duration of admission was five days and showed highest partial correlation (r = 0.6) to the time in hours for the pulse to fall to 80/min. Multiple linear regression showed that this was the only variable best predicting the duration of admission (R2 = 0.3). Admission pulse rate (p = 0.04) and serum K+ (p = 0.04) best discriminated between patients admitted for over and under five days. Logistic regression identified only the admission pulse as significant in calculating the odds of the patient staying in the hospital for > 5 days.

Role of computed tomographic arterial portography and intraoperative ultrasound in the evaluation of patients for resectability of hepatic lesions

Computed tomographic arterial portography (CTAP) has been shown to be the most sensitive preoperative test for determining resectability of hepatic lesions but we have shown it to have low specificity. Intraoperative ultrasound (IOUS) evaluation of the liver has also been proposed as an accurate means of assessing resectability. We sought to compare the effectiveness of the two modalities. Fifty-six patients who had been deemed candidates for liver resection based on CTAP findings underwent systematic exploration, liver mobilization, and IOUS examination. Ultrasound findings were compared with results of CTAP. In 46 patients the IOUS findings were in complete agreement with those of CTAP. In 10 patients CTAP lesions could not be verified by IOUS and these patients did not undergo resection. Follow-up of these 10 patients revealed eight who did not have progression of malignancy at the CTAP-predicted site (CTAP false positive). Two patients did have progression at a CTAP-positive IOUS-negative site (IOUS false negative). Sensitivity for CTAP and IOUS was 100% and 96%, respectively. Specificity for IOUS was 100%. These findings demonstrate the high sensitivity of CTAP and the high sensitivity and specificity of IOUS. CTAP may "overcall" hepatic lesions but IOUS can correctly identify these false positives in most instances. Because CTAP is useful for determining which patients might benefit from surgical exploration, we conclude that the two modalities are complementary for the assessment of resectability of hepatic lesions. The false positive rate for CTAP implies that caution must be used when declining to operate on patients on the basis of this test.