Multicenter study to assess potential hazards from exposure to lipid peroxidation products in soya bean oil from Trilucent breast implants.

In response to a Hazard Notice by the Medical Devices Agency of the UK in 2000 regarding the Trilucent breast implant (TBI), an expert panel was convened to implement a research program to determine whether genotoxic compounds were formed in the soybean oil filler (SOF) of TBIs and whether these could be released to produce local or systemic genotoxicity. The panel established a research program involving six laboratories. The program recruited 47 patients who had received TBIs (9 patients had received silicone implants previously). A reference group (REBI) of 34 patients who had exchanged either silicone (17 patients) implants (REBI-E) or patients (17) who were to receive primary implantation augmentation with silicone (REBI-PIA), and who were included as needed to increase either the pre- or post-explantation sample number. Of the 17 REBI-E patients, 5 had silicone implants and 12 had saline implants previously (prior to the last exchange). Investigation was undertaken before and after replacement surgery in the TBI patients and before and after replacement or augmentation surgery in the REBI patients. The pre- to post-operative sample interval was 8-12 weeks. Pre-operative samples were collected within 7 days prior to the operation. Information on a variety of demographic and behavioral features was collected. Biochemical and biological endpoints relating to genotoxic lipid peroxidation (LPO) products potentially formed in the SOF, and released locally or distributed systemically, were measured. The SOF of explanted TBIs was found to have substantial levels of LPO products, particularly malondialdehyde (MDA), and low levels of trans-4-hydroxy-2-nonenal (HNE) not found in unused implants. Mutagenicity of the SOF was related to the levels of MDA. Capsules that formed around TBIs were microscopically similar to those of reference implants, but MDA-DNA adducts were observed in capsular macrophages and fibroblasts of only TBI capsules. These cell types are not progenitors of breast carcinoma (BCa) and the location of the implants precludes LPO products reaching the mammary epithelial cells which are progenitors of BCa. Blood levels of LPO products were not increased in TBI patients compared to REBI patients and did not change with explantation. In TBI patients, white blood cells did not show evidence of increased levels of LPO-related aldehyde DNA adducts. In conclusion, based on a number of measured parameters, there was no evident effect that would contribute to breast or systemic cancer risk in the TBI patients, and the recommended treatment of TBI patients involving explantation was judged appropriate.

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.

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.

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.

Perceptions of communicative disorders: verification and specification of rater variables.

UNLABELLED: 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.

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.

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.

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

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.

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.

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.

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.

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.