Biomedical subjects

S K Williams

Publications and source records attributed to S K Williams.

At least 19 recordsLinked to original sources

PubMed2006

Effects of packaging systems on the natural microflora and acceptability of chicken breast meat.

The effect of 3 packaging systems on the spoilage microflora, objective color, and sensory characteristics of fresh commercial broiler chicken breast meat was investigated. Fresh skinless and boneless chicken broiler breasts were purchased from a local poultry processing plant and packaged in either (1) a conventional Styrofoam tray with polyvinyl chloride overwrap and absorbent pad, (2) a Styrofoam tray with polyvinyl chloride overwrap minus absorbent pad, or (3) a Fresh-R-Pax (FRP) container equipped with an absorbent liner-gel system. All packages were heat sealed and stored at 1.2 +/- 1 degrees C for 8 d. At each sampling period (0, 2, 4, 6, and 8 d), packages from each treatment were analyzed for Pseudomonas spp., psychrotrophic organisms, objective color, and sensory characteristics. In general, Pseudomonas spp. and psychrotrophic counts increased as storage time increased for all packaging systems. Color and overall appearance were similar (P >0.05) for all packaging systems. Although not significant, the off-odor scores for breast meat packaged in FRP were higher (P >0.05) after 6 and 8 d when compared with the breast meat packaged in a Styrofoam tray with polyvinyl chloride overwrap with or without an absorbent pad. Although the absorbent pad did not control microbial growth, it maintained aesthetic appeal by absorbing all visible moisture released from the meat during storage.

Animals↗

PubMed2005

The effect of electron beam irradiation on the survival of Salmonella enterica serovar typhimurium and psychrotrophic bacteria on raw chicken breasts stored at four degrees celsius for fourteen days.

The effect of high-energy electron beam irradiation on the survival of Salmonella enterica serovar Typhimurium and psychrotrophic bacteria on commercial chicken breast meat was evaluated. Fresh chicken breast meat was purchased from a local poultry processor, inoculated with 8 log10 cfu/mL Salmonella, packaged in Styrofoam trays and over wrapped with a polyvinyl chloride film, and subjected to 0, 1, 2, or 3 kGy of irradiation. The packaged samples were stored at 4 degrees C and analyzed for Salmonella Typhimurium and psychrotrophic organisms at 0, 2, 4, 6, 8, 10, 12, and 14 d of storage. Direct plating and enrichment methods were used for S. Typhimurium analyses. The direct plating method revealed a 4 log reduction in Salmonella for chicken breasts inoculated and treated with 1, 2, or 3 kGy of irradiation. Psychrotrophic counts were conducted at 7 degrees C for 10 d and 25 degrees C for 5 d to determine the effect of incubation methods on the recovery of psychrotrophic organisms. The enrichment method resulted in the repair of injured Salmonella cells and an elevated Salmonella Typhimurium count for all irradiation dosages when compared with data reported for the direct plating method. In general, psychrotrophic counts increased as storage time increased. However, psychrotrophic counts decreased (P < 0.05) as the irradiation dosage increased.

Animals↗

PubMed2001

Scaffold-based three-dimensional human fibroblast culture provides a structural matrix that supports angiogenesis in infarcted heart tissue.

BACKGROUND: We have developed techniques to implant angiogenic patches onto the epicardium over regions of infarcted cardiac tissue to stimulate revascularization of the damaged tissue. These experiments used a scaffold-based 3D human dermal fibroblast culture (3DFC) as an epicardial patch. The 3DFC contains viable cells that secrete angiogenic growth factors and has previously been shown to stimulate angiogenic activity. The hypothesis tested was that a viable 3DFC cardiac patch would stimulate an angiogenic response within an area of infarcted cardiac tissue. METHODS AND RESULTS: A coronary occlusion of a branch of the left anterior descending coronary artery was performed by thermal ligation in severe combined immunodeficient mice. 3DFCs with or without viable cells were sized to the damaged area, implanted in replicate mice onto the epicardium at the site of tissue injury, and compared with animals that received infarct surgery but no implant. Fourteen and 30 days after surgery, hearts were exposed and photographed, and tissue samples were prepared for histology and cytochemistry. Fourteen and 30 days after surgery, the damaged myocardium receiving viable 3DFC exhibited a significantly greater angiogenic response (including arterioles, venules, and capillaries) than nonviable and untreated control groups. CONCLUSIONS: In this animal model, viable 3DFC stimulates angiogenesis within a region of cardiac infarction and can augment a repair response in damaged tissue. Therefore, a potential use for 3DFC is the repair of myocardial tissue damaged by infarction.

Animals↗

PubMed2001

Analysis of self-assembled cationic lipid-DNA gene carrier complexes using flow field-flow fractionation and light scattering.

Self-assembled cationic lipid-DNA complexes have shown an ability to facilitate the delivery of heterologous DNA across outer cell membranes and nuclear membranes (transfection) for gene therapy applications. While the size of the complex and the surface charge (which is a function of the lipid-to-DNA mass ratio) are important factors that determine transfection efficiency, lipid-DNA complex preparations are heterogeneous with respect to particle size and net charge. This heterogeneity contributes to the low transfection efficiency and instability of cationic lipid-DNA vectors. Efforts to define structure-activity relations and stable vector populations have been hampered by the lack of analytical techniques that can separate this type of particle and analyze both the physical characteristics and biological activity of the resulting fractions. In this study, we investigated the feasibility of flow field-flow fractionation (flow FFF) to separate cationic lipid-DNA complexes prepared at various lipid-DNA ratios. The compatibility of the lipid-DNA particles with several combinations of FFF carrier liquids and channel membranes was assessed. In addition, changes in elution profiles (or size distributions) were monitored as a function of time using on-line ultraviolet, multiangle light scattering, and refractive index detectors. Multiangle light scattering detected the formation of particle aggregates during storage, which were not observed with the other detectors. In comparison to population-averaged techniques, such as photon correlation spectroscopy, flow FFF allows a detailed examination of subtle changes in the physical properties of nonviral vectors and provides a basis for the definition of structure-activity relations for this novel class of pharmaceutical agents.

DNA↗

PubMed2001

HER2/neu over-expression induces endothelial cell retraction.

Over-expression of the HER2/neu (HER2) proto-oncogene in breast carcinoma imparts an enhanced metastatic potential. Metastasis requires escape of the tumor cell from the vasculature into subjacent tissue, a transmigration event across an endothelial cell (EC) monolayer. EC retraction has been reported to precede transmigration in several tumor metastatic models. Using intact human iliac vein EC monolayers, we tested the abilities of MCF-7 breast cancer cells and HER cells, a transfected MCF-7 line over-expressing HER2, to induce EC retraction. We further analyzed whether HER2 signaling influenced cancer cell-induced EC retraction. MCF-7 or HER cells were co-cultured onto mature EC monolayers. More HER than MCF-7 cells induced EC retraction (76 +/- 19% vs. 17 +/- 12%, p < 0.001) with resultant exposure of subendothelial matrix (6.80 +/- 2.86% vs. 0.85 +/- 0.39%, p < 0.001). Blockade of HER2 signaling using Herceptin nearly eliminated EC retraction (p < 0.01), while stimulation of HER2 using heregulin-beta1-augmented EC retraction (p < 0.05). Further, there was no difference between cell lines in either the number of cells adhered or the strength of adherence to EC under shear stress. These data suggest that HER2 signaling enhances metastasis in breast cancer cells by inducing EC retraction, a process that appears to precede endothelial transmigration.

Antibodies, Monoclonal↗

PubMed2001

Unhydrolyzed vegetable sucrose polyester in broiler diets.

Duplicate 42-d broiler studies were conducted in pens with litter on the floor, beginning with 1-d-old chicks obtained from a commercial hatchery. Seven replicate pens, each starting with 12 male and 12 female chicks, received each dietary treatment in a randomized-block design. Dietary treatments comprised 0, 0.5, 1.0, 1.5, 2.0, or 2.5% unhydrolyzed vegetable sucrose polyester (UVSP) added to the starting and finishing diets at the expense of filler. In both studies, up to 2.5% UVSP did not have a significant negative effect on body weights, daily feed intake, feed conversion, or litter moisture. In Experiment 2, average body weights were significantly greater than control for groups that received 0.5, 2.0, or 2.5% UVSP. However, the degree of shank yellowness as measured with a Minolta Chroma-meter was consistently and significantly reduced by 0.5% or more UVSP. Although xanthophyll levels were intentionally lowered somewhat to improve sensitivity (7.9 and 9.6 mg/kg for starter and finished feeds, respectively), it is obvious that the utilization of xanthophyll was reduced somewhat by UVSP. Additional pigment titration trials could provide valuable information about the levels required to overcome this effect.

Animal Feed↗

PubMed2000

Comparison of neuregulin-1 expression in olfactory ensheathing cells, Schwann cells and astrocytes.

Recently we demonstrated that a member of the neuregulin-1 (NRG-1) family of growth factors is a mitogen and survival factor for olfactory ensheathing cells (OECs). OECs are specialized glial cells within the olfactory system that are believed to play a role in the continual nerve re-growth of this tissue. OECs share properties with both astrocytes and Schwann cells but are likely to be a distinct glial cell type. NRG-1s have been found to be important regulators of Schwann cells in vivo, but the role of NRG-1 for OECs is less clear. The nrg-1 gene produces at least 12 different isoforms, that are likely to have different functions, due to alternative splicing of its mRNA. In this study, the expression of NRG-1 mRNAs in OECs was compared with other glial cells and their corresponding tissue sources. Cultured glial cells, unlike their tissue sources, expressed NRG-1 mRNAs containing the alpha EGF-like domain and expressed only the type 1beta isoform that lacks the glycosylated spacer domain. This correlated with expression of these isoforms during olfactory nerve degeneration in vivo. Although OECs expressed mRNA for all NRG-1 isoforms, the protein could not be detected in concentrated supernatant, or on the cell surface by immunofluorescence, but was detected in the nucleus or cytoplasm (depending on the isoform). These data support the hypothesis that NRG-1s play a functional role in OEC biology.

Animals↗

PubMed2000

Cellular proliferation and macrophage populations associated with implanted expanded polytetrafluoroethylene and polyethyleneterephthalate.

The chronic inflammatory response associated with the abluminal surface of polymeric vascular grafts has been suggested to affect adversely graft neovascularization, the cellular response at the luminal surface of vascular grafts, and overall graft patency. To better understand the source for this chronic inflammation, this study examined two types of macrophages and the amount of cellular proliferation around two widely used graft materials, expanded polytetrafluoroethylene (ePTFE) and polyethyleneterephthalate (PET or Dacron) implanted in the rat for 3 and 5 weeks. Serial sections of explants were analyzed for recruited macrophages (ED1), resident macrophages (ED2), and proliferating cells (PCNA). Results show that Dacron is more inflammatory than ePTFE and that there is a segregated macrophage response; the first 54 micrometer of perigraft tissue were composed predominantly of recruited macrophages (ED1+) while the more distal tissue consisted of resident macrophages (ED2+). Proliferating cells were located predominantly in this same 54 micrometer perigraft region. In subcutaneous tissue they accounted for 23% of all cells present around Dacron after 3 weeks of implantation and 8% after 5 weeks. Conversely, cellular proliferation around ePTFE increased from 4% at 3 weeks to 21% at 5 weeks. In adipose tissue, proliferation levels around the implanted polymers were lower and more similar after 3 and 5 weeks. Serial sections revealed the coordinate expression of PCNA and ED1 antigens by the same individual cells, suggesting that proliferation is a mechanism used to perpetuate the chronic inflammatory response. These results suggest a new target for designing treatments to alter inflammation and improve the healing associated with these biomaterials.

Adipose Tissue↗

PubMed2000

The first year experience with the dual chamber ICD.

In July 1997, a dual chamber pacemaker combined with a tiered therapy implantable cardioverter defibrillator (ICD) first became available in the United States. We report the first-year experience of one center in the United States with this dual chamber ICD. Of a total of 174 ICDs, 95 (55%) were dual chamber devices and 79 (45%) were single chamber. New dual chamber ICD insertions averaged 57.4 +/- 8.9 minutes, though there was a learning curve as the last 30 implants averaged 45.1 +/- 6.1 minutes with a negative slope to the regression line of procedure duration (-0.52, P < 0.05). New single chamber ICD implants were 18.5 minutes quicker (38.9 +/- 7.2 minutes). The most challenging implants were dual chamber upgrades (mean procedure duration 64.9 +/- 15.8 minutes), especially if there was a previously implanted pacemaker and ICD at separate sites. Indications for a new dual chamber device were grouped into classic pacemaker indications (52.5%), which comprised the Class I ACC/AHA guidelines, ICD-specific indications (24.6%), and other (23.0%). In the 34 patients undergoing dual chamber upgrade, the classic and ICD-specific groups were equal (47.0% each). Complications were rare (2.8%), though 3 (8.8%) of 34 undergoing a dual chamber upgrade developed late infections requiring explantation. In its first year, the dual chamber ICD has become a common device at our institution comprising 55% of new implants. As experience grows, we anticipate similar usage at most institutions.

Aged↗

PubMed1999

Evaluation of an aqueous drainage glaucoma device constructed of ePTFE.

Aqueous drainage devices for the treatment of glaucoma are subject to the same limitations as most polymeric implants, namely a healing response comprised of chronic inflammation and fibrosis. The most widely used devices are currently made of silicone or polypropylene, materials that exhibit biocompatibility difficulties when they are implanted on the sclera underneath the conjunctiva of the eye. Decreased outflow of aqueous fluid to the conjunctival space caused by the development of a fibrous capsule around the device accounts for at least 20% of aqueous shunts failures. Clearly, the need exists to improve the healing response to aqueous drainage devices, and one approach is to develop new polymers or polymer modifications. Improved devices would elicit a limited fibrotic response while increasing neovascularization around the implant. Previous studies have indicated that denucleation markedly improves the healing characteristics and biocompatibility of expanded polytetrafluoroethylene (ePTFE). We reasoned that altering the design of drainage devices to allow the use of denucleated ePTFE in vivo might minimize fibrosis, thereby improving shunt function. We found that after 8 weeks in vivo, experimental shunt function was equivalent to the Baerveldt shunt, while there was less scarring with increased neovascularizatin. These findings suggest that ePTFE has potential as an improved, long-term alternative material for use in constructing glaucoma shunts.

Biocompatible Materials↗

PubMed1999

Endothelial cell transplantation into the corpus cavernosum: moving towards cell-based gene therapy.

PURPOSE: As a first step toward a cell based gene therapy for erectile dysfunction, we transplanted fluorescently labeled autologous microvessel endothelial cells (MVEC) into the rat corpus cavernosum. MATERIALS AND METHODS: MVEC were isolated from the epididymal fat pad, labeled with the membrane intercalating dye PKH 26, and injected into the corpus cavernosum. Two to 15 days after transplantation the penises were removed, cryosectioned, and examined under epifluorescent and phase contrast microscopy. RESULTS: In 7 consecutive animals transplanted fluorescent cells were identified in the corpora cavernosa. Bilateral distribution was noted in each animal, and staining with ED1 determined that the fluorescence was not due to engulfment of the MVEC by phagocytic cells. CONCLUSION: Transplanted endothelial cells adhere and persist in the corporal sinusoids and provide a rationale for cell-based gene therapy in the penis.

Animals↗

PubMed1999

Anastomotic tissue response associated with expanded polytetrafluoroethylene access grafts constructed by using nonpenetrating clips.

PURPOSE: The gross, light microscopic, and scanning microscopic appearance of arterial and venous anastomoses in expanded polytetrafluoroethylene (ePTFE) access grafts constructed with nonpenetrating clips were compared with that of those constructed with polypropylene suture. We hypothesized that clip-constructed anastomoses would provide controlled approximation of native vessel intimal and medial components with the ePTFE grafts. We further hypothesized that anastomotic healing with clips would involve primarily an intimal cellular response, as compared with suture-constructed anastomoses in which cells within the media and adventitia walls participate. METHODS: Femoral artery to femoral vein arteriovenous (AV) grafts were constructed in five dogs using 4-mm internal diameter ePTFE graft material. Each animal received one AV graft with anastomoses constructed by using polypropylene sutures in one leg and one AV graft with anastomoses constructed with Vascular Closure System clips in the contralateral leg. Animals were given aspirin for the duration of the study, and grafts were explanted at 5 weeks. At the time of explantation, graft segments were grossly evaluated and then underwent light and scanning electron microscopic analysis. RESULTS: At the time of explantation, all access grafts were patent. Joining the ePTFE grafts to the native vessels with clips resulted in minimal vessel wall damage. The lumenal contours of the discontinuous approximation were smooth and without gross endothelial disruption. These observations are in contrast to the lumenal compromise and endothelial disturbance associated with the sutured anastomoses. Furthermore, hemostasis was achieved immediately in the clipped grafts, decreasing the incidence of perianastomic hematoma. Finally, cellular reconstitution occurred at the anastomotic cleft in both the sutured and the clipped junctions. The neointima exhibited an endothelial cell lining on the lumenal surface and the presence of alpha-smooth muscle cell actin positive cells within the subendothelial layer. CONCLUSION: Vascular Closure System clips are a viable alternative to suture for the approximation of ePTFE AV access grafts to native blood vessels. The use of the clips resulted in a more streamlined anastomosis, with decreased vessel wall damage, immediate hemostasis, and a trend toward shorter procedure times.

Animals↗

PubMed1999

Characterization of cellular density and determination of neointimal extracellular matrix constituents in human lower extremity vein graft stenoses.

UNLABELLED: Arterial restenosis has been attributed to a hyperproliferative smooth muscle cell response. Paradoxically, studies of human coronary atherectomy and vein graft stenotic lesions have demonstrated a relatively low nuclear proliferative rate with the majority of the neointimal mass consisting of extracellular matrix. The purpose of the present study was to characterize the cellular density and determine the relative composition of the extracellular matrix protein constituents in stenotic, human lower extremity vein-bypass graft lesions. METHODS: Duplex surveillance of 148 consecutive infrainguinal bypass grafts identified 17 patients with 22 preocclusive autogenous vein graft stenoses (mean graft age 7 months). Morphological analyses of these stenotic lesions were compared with excised samples of 20 greater saphenous vein segments taken at the time of graft implantation from matched control patients. Intimal and medial areas were compared and cell density was determined with fluorescent nuclear (Bisbenzimide) staining. Differential light microscopy with pentachrome staining was performed to determine the relative percent composition of intimal matrix constituents by stereological morphometric (point-count) techniques. RESULTS: The intimal areas for control and stenotic vein segments were 1.64 x 10(6) microm2 and 3.85 x 10(6) microm2, P < 0.0001, whereas the intimal nuclear densities (cells/unit volume) were 1.42 x 10(3) and 1.70 x 10(3) cells/microm2, P = 0.03. respectively. The corresponding medial area and medial nuclear densities were 5.01 x 10(6) microm2, 3.31 x 10(6) microm2; P = 0.08, and 2.27 x 10(3), 3.29 x 10(3); P = 0.001, for control and stenotic specimens, respectively. The intima:media area ratios were much greater, whereas the intimal and medial cell densities were only slightly greater in the stenotic compared with control veins. The relative composition of intimal extracellular matrix proteins of stenotic vein graft segments consisted of 21% cellular (fibrous) material, 33% collagen, and 46% glycosaminoglycan ground substance. CONCLUSION: The intimal lesions responsible for lower extremity vein graft stenosis are more hypertrophic than hyperplastic. Therapies aimed at preventing arterial and vein graft restenosis may thus need to inhibit matrix biosynthetic processes in addition to cellular proliferation.

Aged↗

PubMed1999

Sensory and fatty acid profile of eggs from commercial hens fed rendered spent hen meal.

The objective of the study was to determine sensory characteristics and fatty acid profile of eggs from commercial laying hens fed rendered spent hen meal (RSHM). Eggs were collected on a daily basis from Single Comb White Leghorn hens between 43 and 60 wk of age. The hens were fed a layer diet containing either 0, 2.5, 5.0, 7.5, or 10.0% RSHM from 48 to 60 wk in Trial 1, and from 43 to 55 wk in Trial 2. Eggs were evaluated for sensory characteristics and fatty acid profile from hens fed the higher levels of RSHM (i.e., 7.5 and 10.0%). The RSHM treatments had no adverse effects (P > 0.05) on flavor, texture, and overall acceptability of the hard-boiled eggs. Fatty acid profile and total fat content of the eggs were similar for all treatments. Data demonstrated that up to 10% RSHM could be incorporated into the diets of laying hens, without altering the acceptability and fatty acid profile of the eggs produced.

Aging↗

PubMed1999

Denucleation promotes neovascularization of ePTFE in vivo.

Expanded polytetrafluoroethylene (ePTFE) implants are being increasingly used as vascular prostheses and other devices. However the tissue response associated with this and other polymer implants continues to limit any long-term function. One of the major approaches currently being investigated to improve biocompatibility involves surface modification of the base polymer. In this report, we attempted to alter the healing characteristics of ePTFE by denucleation, a process which removes air trapped within the interstices of the material. Additionally, adsorption of extracellular proteins on the denucleated polymer was also tested. After 5 weeks implanted in subcutaneous and epididymal fat sites of rats, the material was explanted and the healing around the implant evaluated histologically. We found that in skin implants, denucleation alone resulted in a substantial reduction in the fibrous capsule which has been previously reported for untreated ePTFE, and an increase in blood vessel development around and within the polymer. Absorption of extracellular matrix proteins prior to implantation resulted in a reduced vascularity of the implants compared with denucleation-only implants. Implants in fat tissue, regardless of treatment, showed very little tissue reaction, either in the number of inflammatory cells, development of a fibrous capsule or neovascularization. These results suggest that the presence of air nuclei within porous material may contribute to the inappropriate healing response associated with these polymers. In addition, they confirm earlier reports that healing around implanted polymers is tissue-specific.

Adipose Tissue↗

PubMed1998

Healing response associated with balloon-dilated ePTFE.

Deployment of endovascular grafts composed of a metallic stent surrounded by expanded polytetrafluoroethylene (ePTFE) stretches the polymer beyond its original dimensions, altering the structural characteristics of the ePTFE. We hypothesized this structural modification would alter the healing response associated with the implant. In this study, 4 mm i.d. of ePTFE (30 microns internodal distance) vascular grafts were balloon dilated using angioplasty balloons having final diameters of 6 (1.5X), 8 (2X), 10 (2.5X), 12 (3X), and 18 (4.5X) mm. Following balloon dilatation of the ePTFE, a circular punch (6 mm in diameter) was used to prepare polymer samples for implantation. The ePTFE circular patches were implanted within subcutaneous tissue and epididymal fat pads of male Sprague-Dawley rats. After 5 weeks, the implants were removed and analyzed for fibrous capsule formation, inflammation, and neovascularization associated with the material. Histological analysis revealed the formation of fibrous capsules only with control subcutaneous implants. The inflammatory response associated with subcutaneously implanted ePTFE was decreased significantly following balloon dilatation to at least 2.5 times the original diameter of the graft. In contrast, ePTFE implanted within adipose tissue demonstrated a significantly greater inflammatory response following balloon dilatation when compared to control implants. Only ePTFE balloons dilated to 6 mm and implanted within adipose tissue demonstrated neovascularization to any extent. These data suggest the structural modifications incurred by ePTFE following balloon dilatation dramatically affect the inflammatory response associated with an implant. Therefore, polymeric materials used for endovascular graft technology require designs that consider changes in polymer healing inherent to device design.

Adipose Tissue↗

PubMed1998

Particle size analysis of dilute environmental colloids by flow field-flow fractionation using an opposed flow sample concentration technique.

An on-line concentration method has been developed for the analysis of dilute suspensions of macromolecules and particles by flow field-flow fractionation (FFF). This method, termed opposed flow sample concentration (OFSC), uses two opposing flowstreams to focus sample into a narrow band near the inlet of the flow FFF channel. Large sample volumes (up to 1 L) have been successfully loaded, concentrated, and separated in a 1 mL volume flow FFF channel. Concentration factors as high as 10(5) have been achieved. The effectiveness of OFSC flow FFF was demonstrated using mixtures of monodispersed standards such as proteins and polystyrene latex beads. Retention times, peak areas, and resolution are comparable for a 10 mL and a typical 10 microL injection volume. The applicability of the method to environmental studies was demonstrated by a separation of river water colloids.

Automation↗

PubMed1998

Indications for implantation of a dual-chamber pacemaker combined with an implantable cardioverter-defibrillator.

Of 122 patients with single-chamber implantable cardioverter-defibrillators (ICDs) reviewed retrospectively, 35 had traditional indications, 14 had other indications, and 18 had ICD-specific indications for dual-chamber pacing therapy. Thus, 67 patients (55%) were potential candidates for dual-chamber pacing, which has only recently become available combined with ICD therapy.

Aged↗