Surface properties and biocompatibility of solvent-cast poly[-caprolactone] films

Poly(epsilon-caprolactone) (PCL) was dissolved in four solvent systems, chloroform, tetrahydrofuran, acetone and ethyl acetate, and cast onto glass Petri dishes. The surface properties of the resulting films were investigated. The extent to which their properties were determined by the solvent used in each case was quantified in terms of contact angle, surface morphology, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and the adhesion and proliferation of fibroblasts by direct contact. The surface of the PCL film in contact with glass was denoted the SG surface, and the other, which was exposed to the gas phase, a mixture of air and residual solvent vapour, was denoted the SA surface. In the case of hydrophobic solvent systems, the advancing contact angle of the SG surface was always lower than that of the SA surface. With hydrophilic solvent systems, on the other hand, the advancing contact angle of the SG film surface was higher when the contact angle of the Petri dish was higher than that of the gaseous mixture of the air and solvent vapour, otherwise it was lower or equal to that of the surface on which it was cast. The surface morphology was dictated by the solubility of PCL in the respective solvent systems: high dissolution solvents such as chloroform and tetrahydrofuran produced films that comprised PCL aggregates, the particles being larger in the case of chloroform, whereas the less efficient solvents (acetone and ethyl acetate) resulted in a filamentous structure. The ATR-FTIR results confirmed that the chemistry of the SA surfaces differed according to the solvent system used. Preliminary cell culture experiments carried out with the PCL films established that murine (L929) fibroblasts grew well on all surfaces regardless of the solvent used, although the rates of adhesion and proliferation were not as great as on tissue culture plastic controls. Of all the surfaces examined in this study, the cells favoured the SG aspect of ethyl acetate cast PCL films, the surface of which had the finest pore size and relatively low contact angle.

Preparation of non-thrombogenic materials using 2-methacryloyloxyethyl phosphorylcholine

This review addresses the non-thrombogenic characteristics of copolymers based on 2-methacryloyloxyethyl phosphorylcholine (MPC), originally developed by Nakabayashi and colleagues. The hypothesis underlying these developments was that such materials would adsorb phospholipids from blood, yielding surfaces with good natural blood compatibility. Methacrylates were found to have excellent properties for this copolymerisation. The characteristics of the MPC copolymers relevant to the improved blood compatibility were minimisation of protein adsorption through an increase in the amount of free water in the MPC hydrogels, which prevents protein conformational change and increased protein stability in solution. Non-thrombogenicity has been evaluated by in vitro, ex vivo and in vivo procedures. Non-thrombogenic dialysis membranes and a durable glucose biosensor have been developed using this MPC copolymer.

Influence of test protocol in determining the blood response to model polymers

A multi-parametric, multi-center evaluation of three polymers was performed measuring their response to blood contact. The purpose of this study was to pinpoint differences in tests performed for assessing "basic" hemocompatibility on identical materials at different centers and attempt to rationalize. Assays for platelet adhesion, activation, aggregability and activation of the coagulation system in addition to an ex vivo patency assay were performed at four centers across Europe, using protocols favored by each center for determining the blood-contacting performance of a biomaterial. Three polymers were chosen for their expected blood response spanning the range of undesirable to desirable: ethylenevinylacetate (EVA), polyvinylchloride (PVC) and PVC modified with polyethylene oxide (PEO). The assays were ranked in terms of their efficacy compared to cost and simplicity. A correlation between assays was calculated, indicating the ability of one test to correctly determine the blood response compared to another. Some assays were unable to distinguish between materials, but of the assays which could, the materials were ranked in the following order: EVA; PVC; PVC-PEO, EVA producing the most undesirable response. It is concluded that many commonly used assays for determining hemocompatibility are inappropriate, but there are simple and reliable test methods available which correlate well with the more sophisticated protocols.

A study of tissue interface membranes from revision accord knee arthroplasty: the role of T lymphocytes

Despite four decades of advances in the design of orthopaedic devices aseptic loosening remains a major cause for the revision of total joint arthroplasty. This study used the techniques of immunohistochemistry and reverse transcription polymerase chain reaction to identify the inflammatory cell types, cytokines and chemokines within the interface tissue surrounding failed Accord Knee prostheses. Many T cells were identified within the tissue: however, the classical marker of activation, CD25 was expressed on very few cells. Molecular analysis failed to detect the synthesis of either Th1 or Th2 cytokines. These results suggest that the T cells are being actively recruited to the site of inflammation along the chemokine gradients but are not participating in a classical immune response.

Evidence of intracolony transmission of Thelohania solenopsae (Microsporidia: Thelohaniidae) in red imported fire ants (Hymenoptera: Formicidae) and the first report of spores from pupae

Red imported fire ant, Solenopsis invicta, colonies were infected horizontally by introducing live brood (mainly larvae and pupae) infected with Thelohania solenopsae. Live, infected brood introduced into uninfected colonies were adopted and raised to adulthood instead of being executed by the recipient colony. Introductions of infected larvae with uninfected pupae, which eclose into adult worker caste fire ants, resulted in an 80% infection rate of the inoculated colonies. Infections from introductions of infected pupae with uninfected larvae resulted in a 37.5% infection of inoculated colonies. Infections were also detected in 11.6 and 3.7% of the adult worker caste ants that eclosed from uninfected large larvae and pupae, respectively, that were held with infected adult workers. Microscopic examination of infected brood revealed sporoblasts and large numbers of spores of T. solenopsae in S. invicta pupae.

Perceptions of communicative disorders: verification and specification of rater variables

Using semantic differential scales with nine trait pairs, 600 students at three universities rated five descriptions, one depicting an individual without a disorder and four portraying individuals with communicative disorders. Statistical analyses indicated that the description with no disorder was rated as significantly less ambitious than the described articulation disorder. Other differences emerged when raters were divided by gender and age. Male subjects rated the portrayed individuals as more highly stressed than did females. A significant negative correlation was found for age of respondent and ratings of self-esteem. Results support previous research suggesting that rater gender and age impact perceptions of communicative disorders.

LEARNING OUTCOMES

As a result of this activity, the participant will be able to: (1) identify the different means by which investigators have studied the stereotyping of people with communicative disorders, (2) discuss how listeners perceive those with and without communicative disorders, and (3) identify listener traits that may be associated with negative perceptions of people with communicative disorders.

Hydrodynamic function of a biostable polyurethane flexible heart valve after six months in sheep

Survival to six months for sheep with a non-biostable polyurethane mitral heart valve prosthesis has been reported previously, however, with surface degradation and accumulation of calcified fibrin/thrombus that impaired leaflet motion and compromised hydrodynamic function. Newly available biostable polyurethanes may overcome this problem. Six adult sheep with biostable polyurethane trileaflet heart valve prostheses of documented hydrodynamic performance, implanted in the mitral position, were allowed to survive for 6 months. Explanted valves were photographed, resubmitted to hydrodynamic function testing, and studied by light and electron microscopy. Explanted valves were structurally intact and differed little in appearance from their preimplant state. Hydrodynamic testing showed no deterioration in pressure gradient or energy losses compared with pre-implant values. Biostable polyurethanes demonstrated improved blood compatibility leaving leaflets flexible and valve function unimpaired. Biostable polyurethanes may thus improve prospects for prolonged function of synthetic heart valve prostheses.

A new design for polyurethane heart valves

BACKGROUND AND AIM OF THE STUDY

The synthetic flexible tri-leaflet heart valve offers considerable potential for improvement in both hydrodynamic and biomechanical performance of replacement heart valves. To date, success with the synthetic leaflet heart valve has been limited, partly due to limitations in the biostability of the polyurethanes used. With the synthesis of new biostable polyurethanes, the integration of advancing technology, and better knowledge of the functional and biomechanical design requirements necessary to increase the long-term durability of the polyurethane heart valve, novel clinical solutions are now in sight.

METHODS

This study describes the design characteristics, hydrodynamic and biomechanical performance of a new design of polyurethane heart valve. The function and durability characteristics of this novel design of heart valve, manufactured using a proven durable non-biostable polyurethane, was compared with that of a single AorTech porcine bioprosthetic heart valve and a single tilting disc mechanical heart valve, the Björk-Shiley Monostrut valve (BSM), of similar size.

RESULTS

For equivalent sizes of valve, the new polyurethane heart valve design had significantly lower pressure gradients compared with the porcine valve at all flow rates and to the BSM valve at the higher flow rates. The effective orifice area of the polyurethane valve was greater than the other two valves studied; regurgitation and total energy loss were less. The new polyurethane valve design reached over 360 million cycles in an accelerated durability tester, without failure.

CONCLUSION

This new design of polyurethane heart valve showed improved hydrodynamic function in comparison with either the porcine bioprosthetic or the BSM mechanical heart valve. The pulsatile flow results showed a lower total energy loss associated with this valve, indicating improved potential patient benefit. The durability of this new design of polyurethane heart valve was demonstrated when manufactured using a medical-grade polyurethane.

Bait distribution among multiple colonies of Pharaoh ants (hymenoptera: Formicidae)

Pharaoh ant, Monomorium pharaonis (L.), infestations often consist of several colonies located at different nest sites. To achieve control, it is desirable to suppress or eliminate the populations of a majority of these colonies. We compared the trophallactic distribution and efficacy of two ant baits, with different modes of action, among groups of four colonies of Pharaoh ants. Baits contained either the metabolic-inhibiting active ingredient hydramethylnon or the insect growth regulator (IGR) pyriproxyfen. Within 3 wk, the hydramethylnon bait reduced worker and brood populations by at least 80%, and queen reductions ranged between 73 and 100%, when nests were in proximity (within 132 cm) to the bait source. However, these nest sites were reoccupied by ants from other colonies located further from the bait source. The pyriproxyfen bait was distributed more thoroughly to all nest locations with worker populations gradually declining by 73% at all nest sites after 8 wk. Average queen reductions ranged from 31 to 49% for all nest sites throughout the study. Even though some queens survived, brood reductions were rapid in the pyriproxyfen treatment, with reductions of 95% at all locations by week 3. Unlike the metabolic inhibitor, the IGR did not kill adult worker ants quickly, thus, more surviving worker ants were available to distribute the bait to all colonies located at different nest sites. Thus, from a single bait source, the slow-acting bait toxicant provided gradual, but long-term control, whereas the fast-acting bait toxicant provided rapid, localized control for a shorter duration.

Patients with existing pressure ulcers admitted to acute care

PURPOSE

This study describes the characteristics of patients with pressure ulcers present on admission to the hospital and predictors of pressure ulcer presence and severity.

DESIGN

Prospective cohort study.

SETTING AND SUBJECTS

Adults (n = 267) admitted to a Pacific Basin military hospital who were expected to stay more than 24 hours.

INSTRUMENTS

Braden scale, portable vital sign machine, and pulse oximeter.

METHODS

Pressure ulcer risk was evaluated and skin inspection was performed. Demographic, physiologic, and laboratory data were obtained. Medical history and patient acuity were recorded.

RESULTS

Thirty-four of 267 subjects (12.8%) had a pressure ulcer. Most were male and white. Their mean age was 65.7 years; mean albumin level, 2.9 g/dL: mean hematocrit level, 31.9 vol%; mean oxygen saturation, 95.3 mm Hg; and mean hemoglobin level, 10.7 g/dL. The mean Braden scale score for subjects without ulcers on admission was 19.7, and it was 15.9 for those with ulcers (P < .05). Analysis of variance showed that subjects with pressure ulcers had a significantly lower albumin level, total lymphocyte count, hematocrit level, and hemoglobin level. These subjects were significantly older and had a longer hospital length of stay. Regression showed that albumin level, oxygen saturation, and length of stay (P < .01) accounted for 11.3% of the variance of pressure ulcer presence and that albumin level and length of stay (P < .001) accounted for 11.2% of the variance in ulcer severity.

CONCLUSIONS

Poorer nutritional status and decreased oxygen perfusion were predictors of pressure ulcers on admission. Nutrition and length of stay were predictors of ulcer severity. Further research is warranted.

Relentless placoid chorioretinitis: A new entity or an unusual variant of serpiginous chorioretinitis?

OBJECTIVE

To characterize an unusual clinical entity resembling acute posterior multifocal placoid pigment epitheliopathy (APMPPE) and serpiginous choroiditis but with an atypical clinical course.

PATIENTS

We describe 6 patients, aged 17 through 51 years, exhibiting this unusual entity who were seen at 6 different centers from 1984 to 1997.

RESULTS

The acute retinal lesions in this series were similar to those of APMPPE or serpiginous choroiditis, both clinically and on fluorescein and indocyanine green angiography. However, the clinical course, number of lesions, and location of these lesions were atypical. These patients had evidence of numerous posterior and peripheral retinal lesions predating or occurring simultaneously with macular involvement. Older, healing pigmented lesions were often accompanied by the appearance of new active white placoid lesions. Additionally, these cases all demonstrated prolonged periods of activity resulting in the appearance of more than 50 and sometimes hundreds of lesions scattered throughout the fundus. Growth of subacute lesions and the appearance of new lesions continued for 5 to 24 months after initial examination, and relapses were common.

CONCLUSIONS

This entity has clinical features similar to APMPPE and serpiginous choroiditis but has a prolonged progressive clinical course and widespread distribution of lesions. It may represent a variant of serpiginous choroiditis or may be a new entity. We call it relentless placoid chorioretinitis. Arch Ophthalmol. 2000;118:931-938

Biomaterial-induced sarcoma: A novel model to study preneoplastic change

In the study of carcinogenesis most interest has focused on carcinomas, as they represent the majority of human cancers. The recognition of the adenoma-carcinoma sequence both in humans and in animal experimental models has given the field of basic oncology the opportunity to elucidate individual mechanisms in the multistep development of carcinoma. The relative scarcity of human sarcomas coupled with the lack of adequate animal models has hampered understanding of the molecular genetic steps involved. We present an experimental model in the rat in which a high incidence of malignant mesenchymal tumors arise around a subcutaneously implanted biomaterial. Nine commercially available biomaterials were implanted in a total of 490 rats of the Fischer strain for 2 years. On average, macroscopic tumors were found in 25.8% of implantation sites over a period from 26 to 110 weeks after implantation. The most frequent tumors were malignant fibrous histiocytomas and pleomorphic sarcomas, although fibrosarcomas, leiomyosarcomas, and angiosarcomas readily developed, the latter especially around polyurethane implants. Of particular interest are the results of a detailed histological study of the capsules around the implanted biomaterials without tumors. Here a spectrum of change from focal proliferative lesions through preneoplastic proliferation to incipient sarcoma could be observed. A parallel immunohistochemical study of peri-implant capsules showed that proliferating cell nuclear antigen was of particular help in identifying these atypical proliferative lesions. To our knowledge this is the first description of a sarcoma model in which preneoplastic lesions can be readily identified and also reproducibly induced. This model provides the molecular biologist with defined stages in the development of mesenchymal malignancy, with which the multistage tumorigenesis hypothesis can be tested, analogous to the well-known adenoma-carcinoma sequence.

Expanding habitat of the imported fire ant (Solenopsis invicta): a public health concern

Residents in the southeastern United States would hardly describe life with the aggressive imported fire ant as peaceful coexistence. The continued spread of these insects has produced agricultural problems, changes in the ecosystem, and increasing numbers of subjects with sting sequelae, including hypersensitivity reactions, secondary infections, and rare neurologic sequelae. Evolutionary changes have facilitated their expansion northward into Virginia and westward into California, and increasing urbanization will likely permit further expansion. Recent reports of building invasion with sting attacks inside occupied dwellings, including health care facilities, heighten public health concerns. This article reviews the medically important entomology, clinical aspects of stings, and the current approaches to chemical control of fire ants. We also propose directions for future research and treatment.

Effects of mesh modification on the structure of a mandrel-grown biosynthetic vascular prosthesis

Mandrel-grown, mesh-reinforced vascular prostheses require adequate tissue coverage of the mesh for effective clinical function, particularly in low blood flow situations. Development of the ovine collagen-based Omniflowtrade mark vascular prosthesis has shown that the extent of this tissue cover is dependent on the interactions of the mandrel and the mesh with the sheep host. In the present study, the effects of chemical changes to the mesh have been examined. These data indicate that certain treatments of the mesh, particularly collagen or heparin, lead to increased tissue coverage while the number of sheep cells present and the ultrastructure of the resulting vessel remain unchanged.

In vivo evaluation of modified mandrel-grown vascular prostheses

The Omniflowtrade mark Vascular Prosthesis (OVP) has been manufactured and extensively tested in animal and human trials. It has mechanical and biological qualities superior to synthetic and biological conduits, particularly in low flow conditions. For further development into the smaller diameter coronary prostheses, the inner luminal surface is of paramount importance. In a previous study this inner surface was modified to produce a more uniformly thicker nonundulating surface. In this study the mandrels of these modified OVPs were treated with either collagen or heparin; the OVPs were evaluated for patency, tissue integration and wound healing, and endothelialization using a dog model comparable to that used to evaluate the unmodified OVP. In all instances, each of the modified prostheses were fully patent and had no signs of any deleterious effects caused by these modifications; no thrombus or aneurysms were visible. The tissue response was rapid with excellent new host collagen deposition within the vessel wall and minimal inflammatory and foreign body giant cells. Endothelialization was noted at the earliest explant time point in central regions of the prostheses, albeit that the histological picture at this time point appeared to reflect a complex atypical intimal layer.

Fire ant attacks on residents in health care facilities: a report of two cases

BACKGROUND

Imported fire ants now infest more than 310 million acres in the United States and Puerto Rico. Colonies have been found in Arizona, California, New Mexico, and Virginia. Available reports suggest that each year, fire ants sting more than 50% of persons in endemic areas, resulting in a variety of medical consequences.

OBJECTIVE

To describe fire ant attacks among patients in health care facilities.

DESIGN

Case series and literature review.

SETTING

Two nursing homes in Mississippi.

PATIENTS

Two nursing home residents.

MEASUREMENTS

Clinical records to describe clinical sequelae of multiple stings.

RESULTS

With the 2 incidents reported here, the total number of reported indoor fire ant attacks on humans since 1989 is 10. Six of the persons attacked, including the 2 nursing home residents described here (who died after the stings), had preexisting neurologic impairment. Eight of the 10 attacks have been reported in the past 4 years.

CONCLUSIONS

The presence of fire ants in occupied dwellings indicates the presence of active fire ant colonies in the immediate proximity. Efforts to eradicate these insects should be undertaken immediately, especially if immobile persons are present. These persons should be considered at risk for fire ant attacks as long as the ants are present.

The corrosion behaviour of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr in protein solutions

Ti alloys are used in orthopaedic applications owing to their appropriate mechanical properties and their excellent corrosion resistance. The release of titanium and the other alloying elements into the surrounding tissue has been reported due either to passive corrosion or accelerating processes such as wear. Since the passive layer can be broken down in certain circumstances by wear it is important to study the ability of these alloys to repassivate in biological environments, in particular in the presence of proteins, and evaluate how the repassivated surface may vary from the original surface. In this study we investigated the ability of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr to repassivate in phosphate buffered saline (PBS), bovine albumin solutions in PBS and 10% foetal calf serum in PBS at different pH values and at different albumin concentrations. It was found that an increase in pH had a greater effect on the corrosion behaviour of Ti-6Al-4V and Ti-6Al-7Nb than on Ti-13Nb-13Zr in PBS and that the addition of protein to the PBS reduced the influence of pH on the corrosion behaviour of all the alloys. The effect of the corrosion and repassivation was investigated by measuring changes in the surface hardness of the alloys and it was found that corrosion reduced the hardness of the surface oxides of all the alloys. In PBS the reduction was smallest for Ti-6Al-4V and largest for Ti-13Nb- 3Zr and that corrosion in protein solutions further reduced the hardness of the surface oxides. This effect was greater for Ti-6Al-4V and Ti-6Al-7Nb than for Ti-13Nb-13Zr. In conclusion, proteins in the environment appear to interact with the repassivation process at the surface of these alloys and influence the resulting surface properties.

Conjoint corrosion and wear in titanium alloys

When considering titanium alloys for orthopaedic applications it is important to examine the conjoint action of corrosion and wear. In this study we investigate the corrosion and wear behaviour of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr in phosphate buffered saline (PBS), bovine albumin solutions in PBS and 10% foetal calf serum solutions in PBS. The tests were performed under four different conditions to evaluate the influence of wear on the corrosion and corrosion on the wear behaviour as follows: corrosion without wear, wear-accelerated corrosion, wear in a non-corrosive environment and wear in a corrosive environment. The corrosion behaviour was investigated using cyclic polarisation studies to measure the ability of the surface to repassivate following breakdown of the passive layer. The properties of the repassivated layer were evaluated by measuring changes in the surface hardness of the alloys. The amount of wear that had occurred was assessed from weight changes and measurement of the depth of the wear scar. It was found that in the presence of wear without corrosion the wear behaviour of Ti-13Nb-13Zr was greater than that of Ti-6Al-7Nb or Ti-6Al-4V and that in the presence of proteins the wear of all three alloys is reduced. In the presence of corrosion without wear Ti-13Nb-13Zr was more corrosion resistant than Ti-6Al-7Nb which was more corrosion resistant than Ti-6Al-4V without proteins whereas in the presence of protein the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb was reduced and that of Ti-6Al-4V increased. In the presence of corrosion and wear the corrosion resistance of Ti-13Nb-13Zr is higher than that of Ti-6Al-7Nb or Ti-6Al-4V in PBS but in the presence of proteins the corrosion resistance of Ti-13Nb-13Zr and Ti-6Al-7Nb are very similar but higher than that of Ti-6Al-4V. The wear of Ti-13Nb-13Zr is lower than that of Ti-6Al-7Nb and Ti-6Al-4V with or without the presence of proteins in a corrosive environment. Therefore the overall degradation when both corrosion and wear processes are occurring is lowest for Ti-13Nb-13Zr and highest for Ti-6Al-4V and the presence of proteins reduces the degradation of all three alloys.

Welding metallurgy's putative influence on Björk-Shiley convexo-concave valve outlet strut failures

BACKGROUND AND AIM OF THE STUDY

Multiple reports of convexo-concave valve outlet strut fractures have focused on the welds, often implicating putative defects of uncertain character and significance. This study differs from all others in that it systematically assesses a large number (n = 60) of intact and fractured valves and clearly differentiates findings on the critical, tensile-stressed, inflow side of the outlet strut leg from those on the outflow side, which are subject only to compression.

METHODS

Each valve was examined by scanning electron microscopy and subjected to multiple metallographic sectioning of each strut-flange interface. All fractures and selected intact valves were further analyzed with X-ray dispersive spectroscopy.

RESULTS

Fatigue striations were seen in all fractured valves, and their orientation indicated that every fracture initiated in an area on the inflow side, spreading out progressively towards the outflow side. Data indicated that 22% of the first-to-fail leg separations and 17% of all fractures initiated outside of the weld. Element segregation areas were seen in 40% of welds, significantly more commonly in intact valves, invariably located on the outflow side, and typically (85%) apart from the fracture path. Microporosity was identified in 15% of welds, usually near the outflow side, and in the same proportion of intact and fractured valves. One fracture surface had a 38 microns, inflow-side void that might have been a factor in crack initiation in this valve, which was highly stressed.

CONCLUSIONS

With this singular exception, no metallurgical feature of any weld was found that appeared to have contributed, even in a minor way, to the process of outlet fracture.

A quantitative-trait locus on chromosome 6p influences different aspects of developmental dyslexia

Recent application of nonparametric-linkage analysis to reading disability has implicated a putative quantitative-trait locus (QTL) on the short arm of chromosome 6. In the present study, we use QTL methods to evaluate linkage to the 6p25-21.3 region in a sample of 181 sib pairs from 82 nuclear families that were selected on the basis of a dyslexic proband. We have assessed linkage directly for several quantitative measures that should correlate with different components of the phenotype, rather than using a single composite measure or employing categorical definitions of subtypes. Our measures include the traditional IQ/reading discrepancy score, as well as tests of word recognition, irregular-word reading, and nonword reading. Pointwise analysis by means of sib-pair trait differences suggests the presence, in 6p21.3, of a QTL influencing multiple components of dyslexia, in particular the reading of irregular words (P=.0016) and nonwords (P=.0024). A complementary statistical approach involving estimation of variance components supports these findings (irregular words, P=.007; nonwords, P=.0004). Multipoint analyses place the QTL within the D6S422-D6S291 interval, with a peak around markers D6S276 and D6S105 consistently identified by approaches based on trait differences (irregular words, P=.00035; nonwords, P=.0035) and variance components (irregular words, P=.007; nonwords, P=.0038). Our findings indicate that the QTL affects both phonological and orthographic skills and is not specific to phoneme awareness, as has been previously suggested. Further studies will be necessary to obtain a more precise localization of this QTL, which may lead to the isolation of one of the genes involved in developmental dyslexia.

Cuspal deflection during polymerisation of composite lutes of ceramic inlays

OBJECTIVE

The purpose of this study was to measure the cuspal deflection that occurs in teeth as a result of the dimensional changes of resin-based lutes during polymerisation.

METHODS

Standardised MOD cavities were cut in 15 intact human premolar teeth using a custom paralleling device. A ceramic inlay was machined by the CEREC 2 system for each tooth ensuring an interface width of 50 microns (SD = 17.5) at the cavity margin. The 15 teeth were divided into three groups of five according to the cementation system employed: a microfilled hybrid posterior composite; a compomer restorative; a dual-cure luting composite. The inter-cuspal tooth dimension was recorded continuously with a laser micrometer assembly during a 2 min photoactivation period and a further 30 min post-activation period.

RESULTS

A clear overall reduction in tooth dimension was detectable for the first 10 min of polymerisation. The mean changes ranged from -0.02% to -0.06% depending on the nature of the luting material. In addition, all samples exhibited a slight expansion of 0.03% during the time of light-activation.

CONCLUSIONS

The dimensional changes that teeth experience during the polymerisation of resin-based lutes are clearly detectable. It can be postulated that an increase in the dimensions of the teeth during photoactivation occurs as a result of expansion of the lute due to the thermal energy delivered.

Albumin-binding surfaces: in vitro activity

Immobilized monoclonal antibodies (Mabs) have been used to attract specific molecules to a solid surface from complex mixtures such as blood, plasma or serum, thereby directing the response to the modified substrate, a key goal in rational biomaterial design. The nature of the Mab dictated the nature of the response: anti-albumin antibodies were used to prevent cell and platelet adhesion in vitro, whilst anti-fibronectin Mabs promoted attachment. Patterned surfaces could be formed, bearing Mabs that generated adhesive and non-adhesive regions. Fibrinogen adsorption from plasma showed a Vroman peak on unmodified control polymer, which was reduced by 64% in the presence of surface-bound anti-albumin Mab. Immobilization of a control Mab reduced fibrinogen adsorption only slightly, implying an albumin-mediated effect. In static tests, platelet adhesion from human platelet rich plasma was significantly reduced by the immobilization of anti-HSA Mab when compared to the untreated FEP surface (p < 0.0001). This effect was also seen with citrated blood flowing through Mab-treated polyurethane tubing at a shear rate of 132 s(-1) (p=0.034). Since platelets and proteins (as blood, plasma or serum) were introduced to the surface simultaneously, the generation of a defined protein film must have been sufficiently rapid as to shape the platelet or cell response.

Quantification of the bone-related mRNAs at the bone/prosthetic interface

Aseptic loosening is one of the major reasons for failure of joint prostheses. The periprosthetic tissue has previously been described microscopically; however, little work has been devoted towards quantitating genes expressed by cells at the materials/tissue interface. This study aims to characterize the phenotypic expression of osteoblasts and test the feasibility of quantifying the level of gene expression in periprosthetic tissue sections by combining in situ hybridization and image analysis techniques. There are many factors to consider when quantifying mRNA, in that comparing labeling between different cDNA probes, these should have comparable length and base comparison. The probes should be labeled with the same specific activity, that is the amount of probe to label added is the same, both between different probes and between batches of the same probe. Chromagen color reactions are variable in that the color development is not always linear and more likely follows a sigmoidal curve. Samples should only be compared when it is known that the reaction has been in the linear range. The image analysis of such staining introduces further factors which should be considered and controlled. Color analysis is a very complex problem with respect to reproducibly analyzing histological sections. The brightness component of the image should be independent of the colors within the image, in conventional RGB (red, green and blue) signalling mode this is not possible, while when using HSI (hue saturation and intensity) mode this becomes possible, and factors like staining intensity and brightness of the image become much more accountable and controllable. With these factors identified, we consider that the quantitative image analysis approach does allow comparison of patterns of bone-related mRNAs and demonstrates differences in expression in these osteogenic factors depending on distance from the prosthesis, tissue type, patient and device.

Semisynthetic resorbable materials from hyaluronan esterification

In recent years, research on new, biocompatible, degradable materials has seen the development of a series of modified natural polymers. Among these, a new class of materials consisting of different hyaluronan derivatives promises to be useful in a whole range of clinical applications thanks to their varied biological properties. These new materials are obtained by chemical modification of purified hyaluronan consisting of the partial or total esterification of the carboxyl groups of this natural polymer. This review on the properties of the new materials reports some of their biocompatibility and characterization aspects based on findings from studies conducted on the ethyl and benzyl hyaluronan esters, two representative members of this new class of compounds, and is intended to arouse interest in the potential of other, as yet unexplored derivatives. From the results of a number of investigations, the various derivatives appear to possess different physico-chemical properties, especially as far as the degree of hydration and polymer stability are concerned. In addition, the type of esterification and extent of chemical esterification of hyaluronan considerably affects the biological properties of these materials, offering a range of polymers either favouring or, conversely, inhibiting the adhesion of certain types of cell.

Platelet reactions to modified surfaces under dynamic conditions

The influence of surfaces on the reactions of platelets in whole blood under laminar flow was investigated in a cone and plate viscometer. Citrated whole blood was exposed to steel, PMMA and PMMA modified with PEO at low (500 s(-1)) and high (4000 s(-1)) wall shear rates at room temperature for a period of 100 s. Treated blood samples were fixed with paraformaldehyde, stained with a monoclonal antibody for CD41 (platelet GPIIb/IIIa) conjugated with phycoerythrin and analyzed by flow cytometry. The reactions of platelets (microparticle generation and formation of platelet-platelet, platelet-red blood cell and red blood cell-microparticle aggregates) to these environments were quantified. Additionally, the size of platelet-platelet aggregates was assessed. The percentage platelet aggregation and numbers of microparticles generated were independent of surface type at any shear rate. The composition of the aggregates formed was influenced by the surface: at low and high shear rates PMMA caused the generation of platelet-platelet aggregates of the greatest size. The numbers of red blood cell-platelet and red blood cell-microparticle aggregates also varied depending on the surface. Fewer red blood cell-platelet aggregates were formed at higher shear rates, whereas the reverse was true for red blood cell-microparticle aggregates. It is concluded that these variations may help to explain the differential effects of surfaces to the induction of distant thrombotic events: microparticles may be protected from loss from the blood stream by their association with red blood cells at high shear rates.

Management of complications in eyes containing two intraocular lenses

OBJECTIVE

To describe the management of complications in eyes containing two intraocular lenses (IOLs).

DESIGN

A retrospective noncomparative case series.

PARTICIPANTS

Eight patients having a dislocated posterior chamber intraocular lens (PC IOL) and a secondary anterior chamber intraocular lens (AC IOL) participated.

INTERVENTION

Surgical treatment of complications, including mobile dislocated PC IOLs in five eyes and retinal detachment in three eyes, was performed.

MAIN OUTCOME MEASURES

Visual acuity and anatomic status were evaluated.

RESULTS

Dislocated PC IOLs were removed through a pars plana incision in five eyes and a limbal incision in three eyes. Retinal detachments were repaired in three eyes. With follow-up from 7 months to 6.5 years, visual acuities ranged from 20/25 to 20/40 in five eyes and 20/60 to 20/400 in the three eyes undergoing retinal detachment repair.

CONCLUSION

Eyes in which dislocation of a PC IOL occurs during or after cataract surgery may have significant complications develop. Successful surgical repair is more complex in the presence of a secondary AC IOL.

Discovery of thelohania solenopsae from the red imported fire ant, solenopsis invicta, in the united states

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Macrophage subpopulation differentiation by stimulation with biomaterials

Macrophages were elicited by the subcutaneous implantation of ultra high molecular weight polyethylene (UHMWPE) for periods of 2, 7, and 14 days in rats. Exudates of varying volumes were produced that was comprised of granulocytes, monocytes, immature and mature macrophages, and T-lymphocytes. No B-lymphocytes were observed at any time periods. Cell types were identified by their granularity and positivity to the following antibodies: leucocyte common antigen (LCA, pan leucocyte); CD11b/c (macrophage/monocyte); CD5 (T-lymphocyte); CD45RA (B-lymphocyte); HIS48 (granulocyte); ED2 (mature macrophage); and MCP-1 (monocyte chemoattractant protein 1). Monocytes isolated from control rat blood demonstrated a size slightly larger than that of granulocytes but with less granularity. Their size and granularity were followed over increasing time periods. The macrophages elicited by UHMWPE showed a similar pattern, with the exception of an apparently highly granular subpopulation with volumes similar to that of granulocytes but significantly more granular. The granular macrophage subset had a very high degree of ED2 and MCP-1 positivity, and their proportion, compared with other macrophages, was greatest at 2 days. The high MCP-1 expression was accounted for by MCP-1 molecules bound to the surface of a small proportion of macrophages that were activated. It is postulated that this subpopulation was responsible for the synthesis of the MCP-1 and could indicate a mechanism by which monocytes are attracted to the site of an implanted material.

From cytotoxicity to biocompatibility testing in vitro: cell adhesion molecule expression defines a new set of parameters

Determination of potential cytotoxicity is a central issue in current biocompatibility testing standards such as ISO and ASTM. Most of these tests do not assess biocompatibility of a biomaterial with regard to cell function. This study was aimed at screening a number of potential parameters that could be included in assessment of cell functional aspects of biocompatibility. Human umbilical vein endothelial cells (HUVEC) were seeded directly on titanium, NiCr alloy, CoCr alloy, PMMA, PE, PU, PVC, and silicone, or were exposed to the material extracts. Cytotoxicity was assessed for these materials through MTT conversion, crystal violet protein determination and Ki67 expression. In addition, expression of the cell adhesion molecules E-selectin, cadherin-5 and PECAM, as well as of the adhesion-associated proteins fibronectin and vinculin (focal adhesions), was determined by immunocytochemistry and western blotting. Cytotoxicity was not detected with the material extracts. Cells were able to adhere to bare metals, but not polymers. Fibronectin preadsorption resulted in adhesion and spreading also on the polymers. Cells were able to establish cell-cell contacts and focal adhesions. Western blotting, in combination with differential detergent extraction, indicated that linkage of cell-cell adhesion markers to the cytoskeleton may be used as an additional parameter relevant to cell function.

The effect of temperature and shear rate on platelet aggregation

Samples of whole blood were obtained from male volunteers and exposed to combinations of shear rates and temperatures representative of cardiopulmonary bypass (CPB) in a modified computer-controlled concentric cylinder rotational viscometer for a period of 100 s. Blood sampled from the chamber was fixed in paraformaldehyde, stained with CD41 and analysed by flow cytometry. Only platelet-positive particles were acquired, each individual cell, or aggregate of cells, identified by analysis of its fluorescence and forward light scatter characteristics. Little platelet aggregation was observed at shear rates of less than 4000 s(-1) for temperatures of greater than 24 degrees C, but large numbers of aggregates were formed at all temperatures at 4000 s(-1) (p<0.05), with more aggregates forming at 24 and 30 degrees C than at 37 and 42 degrees C (p<0.05). We conclude that the process of aggregation is dependent on both temperature and shear rate. We note that a large number of platelets become involved in aggregates under conditions of temperature and shear-rate typical of CPB.

Activation status of platelet aggregates and platelet microparticles shed in sheared whole blood

The role of temperature and shear rate in the activation status of aggregating platelets and platelet microparticles (MPs) was investigated in a modified concentric-cylinder rotational viscometer. Whole blood anticoagulated with citrate was exposed to a range of shear rates typical of cardiopulmonary bypass circuits (0, 1000, 2000 and 4000 s(-1)) over four temperatures spanning hypothermic to mildly hyperthermic conditions (24, 30, 37 and 42 degrees C) for short durations (100 s). Aliquots of blood were double-stained for CD41 (platelet GPIIb/IIIa) and CD62 (P-selectin). Platelets, platelet aggregates, MPs and red blood cell-platelet and -MP aggregates were identified by flow cytometry by acquiring only CD41-positive particles and differentiating on a plot of CD41 versus forward light scatter. The activation status of each particle was quantified by measuring CD62 expression (alpha-granule release). A degree of correlation between the shedding of MPs and the formation of platelet-platelet aggregates was observed for the data as a whole (r=0.85 for p<0.01), although this trend was not observed for a shear rate of 4000 s(-1). The mean expression of CD62 on both platelets and MPs was maintained at a very low level for all temperature and shear rate combinations. There was, however, a number of very highly activated MPs associated with red blood cells at high shear rates.

Hydrophilicity of polymers and soft tissue responses: a quantitative analysis

This study investigates the effect of changing the hydrophilicity of polyurethane on the soft tissue inflammatory response after implantation into rats. A series of five polyurethanes were made from the macrodiols poly(ethylene oxide) (PEO), poly(tetramethylene oxide) (PTMO), poly (hexamethylene oxide) (PHMO), poly(octamethylene oxide) (POMO), and poly(decamethylene oxide) (PDMO). In the sequence the macrodiols become less polar and phase separation in the polymer increases, creating a range of hydrophilicity. These five polyurethanes were studied along with commercial Pellethane 2363-80A. The materials were implanted intramuscularly into rats for 7 days, 1 month, and 3 months. The inflammatory response was analyzed using a combination of immunohistochemistry, enzyme histochemistry, and image analysis to determine the specific cell types involved in the response and to quantify these cellular responses. The presence of three cytokines also was investigated. The cell types targeted were neutrophils, monocytes, macrophages, and T and B lymphocytes. The cytokines target were tumor necrosis factor alpha (TNF alpha), interleukin 6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). All samples were positive for macrophages and activated macrophages, TNF alpha, and MCP-1, and negative for all other antibodies. The response was sustained throughout the implantation period with no significant difference among the samples except at the 7-day time point. The study demonstrated an absence of lymphocytes and neutrophils in a response that was sustained in terms of macrophages with the presence of TNF alpha and MCP-1 and the absence of IL-6. The position of subsets of macrophages with respect to increasing distance from the implants was demonstrated to be significant and consistent within this series of polyurethanes.

A study of cell behaviour on the surfaces of multifilament materials

Since many fibres are very strong, they are considered to have useful potential for fibre reinforcement of orthopaedic and dental implant materials. Fibres exposed on the surface of composites may significantly influence the cellular response not only due to the chemistry but also due to the fibre size and shape. This study has concentrated on investigation of cellular responses to fibre-specific aspects of fibre-reinforced composites. Four multifilament materials with diameter less than 20 microm were used: Kevlar 29(K), silicon carbide(SiC), nylon 66(N), and polyethylene terephthalate(PET). Established cell line L929 fibroblasts were used as the cell model. Cell behaviour on the surfaces of fibres was examined using direct cell counting (after 3, 5, 8 h and 1, 2, 3 days), scanning electron microscopy (SEM) (after 2 h and 2 days), and fluorescent staining of F-actin, which was analysed by confocal laser scanning microscopy (CLSM) (after 2 h and 2 days). The results showed that fibroblasts adhered and grew very well on all fibre surfaces, although less cells were observed on PET from direct cell counting. Significant orientational behaviour of cells was found on all fibre surfaces from the SEM and CLSM analysis, independent of the bulk chemistry of the fibres.

Sterile versus clean technique in postoperative wound care of patients with open surgical wounds: a pilot study

PURPOSE

This study was completed to determine whether there were differences between sterile versus clean dressing change technique for open surgical wounds in the postoperative period with respect to (1) rate of wound healing and (2) cost of supplies.

METHODS

A two-group design was used for this pilot study. Of a sample of 30 patients undergoing elective gastrointestinal operations with wounds healing by secondary intention, 15 were men and 15 were women. Mean age was 40.6 years (SD 13.0 years). Patients were randomly assigned to receive clean or sterile dressings, and the intervention was begun on the first postoperative day and repeated three times a day until discharge from the hospital. Analysis of rate of healing was performed with the Mann-Whitney U test: cost analysis was completed with a t test.

FINDINGS

Subjects were studied for 3 to 9 days. Groups were homogeneous of the start of treatment with respect to age, length of operation, wound volume, nutritional status, and perfusion. There was no difference in rate of wound healing between the clean and sterile groups. Mean cost was significantly less for the clean group than for the sterile group.

CONCLUSION

These pilot study data show no difference in rate of wound healing with clean versus sterile technique, and clean technique is less expensive. These findings need to be confirmed with a larger sample; type II error cannot be ruled out.