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PubMed2000

Genetic technologies. Bioengineered food--safety and labeling.

The safety and labeling of genetically engineered foods are two areas that have elicited considerable public concern and debate. This Policy Forum provides a legal analysis of these issues in the context of two bills that have been recently proposed in The U.S. Congress, the Genetically Engineered Food Safety Act and the Genetically Engineered Food Right to Know Act. Most transgenic components of foods currently on the market are plant-incorporated protectants or their inert ingredients. Therefore, they have been evaluated for safety by the Environmental Protection Agency (as well as the Food and Drug Administration), and their disclosure in labeling should not be required. If plant-incorporated protectants are considered safer than chemical pesticides, and chemical pesticides do not have to be disclosed in labels, then bioengineered foods should not be subject to stricter regulation, nor should they be required to be labeled. The two bills are inconsistent, in many respects, with well-established principles of food regulation.

Animals↗
PubMed1997

Bioengineering of emulsifier structure: emulsan analogs.

Strategies were investigated to modulate the side chain structure of emulsans formed by Acinetobacter calcoaceticus RAG-1. Analysis of emulsan fatty acid side chain groups by gas chromatography--mass spectrometry (GC-MS) revealed that by provoking the exogenous n-alkanoic fatty acids 15:0, 16:0, and 17:0, emulsan analogs were formed with 53, 46, and 44 mol%, respectively, of fatty acid substituents with chain lengths equal to that of the carbon source. In contrast, the increase in emulsan fatty acids of chain lengths less than 15 or greater than 17 by providing corresponding shorter and longer chain length fatty acids as carbon sources was not substantial. When [1-13C]-labeled (99% enriched) palmitic acid was used as a carbon source along with acetate, analysis of M/z 75/74 and 87/88 isotopomer ratios by GC-MS indicated that 84 and 86% of the 16:0 (9-cis) side groups, respectively, were incorporated intact from the 16:0 carbon source. The percentage of 14- 15-, 16-, 17-, and 18-carbon chain length fatty acid esters that were monounsaturated were 11, 26, 50, 70, and 85% respectively. Based on the observed percentage of unsaturated chain length dependence and almost identical enrichment at C-1 of 16:0 and 16:1 (9-cis) side groups from [1-13 C]-labeled experiments, it was concluded that desaturation of preformed n-alkanoic acids was the predominant mechanism of their formation. Further work established correlations between side chain structure and product emulsification specificity/activity, so that bioengineered emulsans with improved selectivity can now be formed.

Acinetobacter calcoaceticus↗
PubMed1999

Is occupational irritant contact dermatitis predictable by cutaneous bioengineering methods? Results of the Swiss Metalworkers' Eczema Study (PROMETES).

BACKGROUND: Since identification of subjects with high eczema risk by screening tests is desirable, different skin bioengineering methods were studied for their validity as predictive measures for the development of hand eczema. METHODS: 205 metalworker trainees were followed up over 2.5 years from the beginning of their apprenticeship to observe the occurrence of hand eczema. Within the first weeks of their training they underwent a number of noninvasive biophysical tests. Transepidermal water loss, skin moisture and skin roughness were measured, and irritation tests with dimethyl sulfoxide (DMSO), sodium hydroxide (NaOH) and sodium lauryl sulfate were conducted. Sensitivity, specificity and predictive values of the performed tests and test combinations were calculated. RESULTS: None of the observed single biophysical methods can be considered a valid screening test. CONCLUSION: A combination of short irritation tests (DMSO and NaOH tests) and the measurement of skin moisture, however, allows to identify individuals at high risk for hand dermatitis with a high sensitivity, though low specificity.

Adult↗
PubMed1985

Bioengineering changes in spastic cerebral palsy groups following cerebellar stimulation.

Quantitative bioengineering tests were performed on 30 spastic cerebral palsy (CP) patients who underwent chronic cerebellar stimulation (CCS) using the fully implantable pulse generator (Neurolith 601, 1.1-1.8 microC/cm2/phase). Using respiratory inductive plethysmography to measure 8 patients with paroxysmal and/or ataxic breathing patterns, 5 were shown to revert to normal with 3 others markedly improved within 5 months of CCS. Compliance testing of the ankle was performed on 4 patients who showed improvement in 9 of the 16 tests performed. Motor performance ability was evaluated with 9 comprehensive tests in 17 patients. Following 1-2 weeks of CCS, 52% showed performance increases greater than 10%, increasing to 62% during the first year.

Cerebellum↗
PubMed1991

Skin bioengineering in the noninvasive assessment of cutaneous aging.

Cutaneous changes induced by aging can be quantified and monitored noninvasively by means of bioengineering tools. Skin elasticity, hydration, skin blood flow and skin surface pattern show age-related changes reflecting the damage of cutaneous structures involved. Impairment and degeneration of elastic and collagen networks are responsible for the progressive decrease in skin elasticity recorded during aging. Reduction in blood flow and water supply with probably defective stratum corneum binding result in reduced stratum corneum water content and transepidermal water loss. Morphological changes such as increased skin roughness, pigmentation and alteration of skin surface pattern appearing from the age of 30 years onwards may be investigated at a subclinical level allowing the detection of early signs of aging.

Biomechanical Phenomena↗
PubMed2000

Bioengineered cardiac grafts: A new approach to repair the infarcted myocardium?

BACKGROUND: The myocardium is unable to regenerate because cardiomyocytes cannot replicate after injury. The heart is therefore an attractive target for tissue engineering to replace infarcted myocardium and enhance cardiac function. We tested the feasibility of bioengineering cardiac tissue within novel 3-dimensional (3D) scaffolds. METHODS AND RESULTS: We isolated and grew fetal cardiac cells within 3D porous alginate scaffolds. The cell constructs were cultured for 4 days to evaluate viability and morphology before implantation. Light microscopy revealed that within 2 to 3 days in culture, the dissociated cardiac cells form distinctive, multicellular contracting aggregates within the scaffold pores. Seven days after myocardial infarction, rats were randomized to biograft implantation (n=6) or sham-operation (n=6) into the myocardial scar. Echocardiography study was performed before and 65+/-5 days after implantation to assess left ventricular (LV) remodeling and function. Hearts were harvested 9 weeks after implantation. Visual examination of the biograft revealed intensive neovascularization from the neighboring coronary network. Histological examination revealed the presence of myofibers embedded in collagen fibers and a large number of blood vessels. The specimens showed almost complete disappearance of the scaffold and good integration into the host. Although control animals developed significant LV dilatation accompanied by progressive deterioration in LV contractility, in the biograft-treated rats, attenuation of LV dilatation and no change in LV contractility were observed. CONCLUSIONS: Alginate scaffolds provide a conducive environment to facilitate the 3D culturing of cardiac cells. After implantation into the infarcted myocardium, the biografts stimulated intense neovascularization and attenuated LV dilatation and failure in experimental rats compared with controls. This strategy can be used for regeneration and healing of the infarcted myocardium.

Alginates↗
PubMed1991

Bioengineering in the Department of Mechanical Engineering at the University of Western Australia.

Although bioengineering is not formally taught in the Department of Mechanical Engineering, University of Western Australia, undergraduate and postgraduate projects in this area are very popular among the students. Meetings of the research staff and students working in this area and in tribology in general are organized once a week where the research progress is reported and problems encountered are discussed. Very good collaboration has been established with the Royal Perth Hospital and the Departments of Anatomy and Pathology, University of Western Australia. The Department of Mechanical Engineering, University of Western Australia, has been most helpful over the years in meeting financial needs. The Department has also received over the years some support from the West Australian Arthritic Research Foundation.

Biomechanical Phenomena↗
PubMed2000

Multistep production of bioengineered skin substitutes: sequential modulation of culture conditions.

Many studies are being conducted to define the role of growth factors in cutaneous physiology in order to add cytokines in a timely fashion for optimal tissue engineering of skin. This study is aimed at developing a multistep approach for the production of bioengineered skin substitutes, taking into account the effects of various growth factors according to the culture time. The use of a serum-supplemented medium throughout the whole culture period of skin substitutes was compared to the sequential use of specific additives at defined culture steps. Histological analysis revealed that serum was necessary for keratinocyte proliferation and migration on dermal substitutes during the first 2 d after their seeding. However, the serum-free medium presented some advantages when supplemented with different additives at specific culture steps. Interestingly, ascorbic acid added to the dermal substitutes before and after keratinocyte seeding maintained their cuboidal morphology in the basal epidermal layer. In the absence of serum, collagen matrix degradation slowed down, and a better multilayered epidermal organization was obtained, notably with retinoic acid. Stratum corneum formation was also enhanced by fatty acids. Thus, sequential addition of exogenous factors to the medium used to produce skin substitutes can improve their structural features and functional properties in vitro.

Animals↗
PubMed2005

Development of a bioengineered tissue model and its application in the investigation of the depth selectivity of polarization gating.

Understanding the propagation of polarized light in tissue is crucial for a number of biomedical optics applications. Here we report the development of a bioengineered connective tissue model fabricated by the combination of scaffolding and cross-linking techniques to study light transport in biological tissue. It demonstrates great similarity to real connective tissue in its optical properties as well as microarchitecture. Moreover, the optical properties of the model can be reproducibly controlled. As an example, we report the utilization of this model to study the effect of epithelium and the underlying connective tissue on the depth selectivity of polarization gating.

Animals↗
PubMed2000

Beyond a code of ethics for bioengineers: the role of ethics in an integrated compliance program.

Developing a code of ethics for biomedical engineering professionals is a very important first step in clarifying their professional obligations and in helping to establish and maintain their professional autonomy. However, it is only that--a first step. Unless ways can be found to bring the principles contained in this code to bear on the everyday decision making of these professionals, this code will have little practical influence. One effective way to bring a code of ethics to bear on decision making is to integrate it into organizational compliance programs. Such programs often have company-specific codes of ethics attached to them, and these company-specific codes can either include the principles contained in the professional code of ethics or reference the code by title. After defining what I take to be the challenge of compliance, I consider four (4) roles that codes of ethics and ethics generally can play in helping to create and sustain programs at the organizational level that integrate ethics and compliance and thereby aim to make a practical difference in the everyday decision making of bioengineering professionals. These four roles include: framing the program, grounding the standards, achieving critical distance, and creating and sustaining an ethical organizational culture.

Biomedical Engineering↗
PubMed2000

What is life, and what is a machine? The ontology of bioengineering.

In his Keynote address to the First Conference at Clemson University on Ethical Issues in Biomedical Engineering, George Bugliarello suggested that a most important ethical issue for bioengineering "is the positioning of the bio-machine interface." "Where," he asked, "should the biological organism end and the machine begin?" Central to this question of the limits of life and engineering is the more fundamental question of how life differs and how it is similar to a machine. This paper argues that until very recently, science, by its very nature, has treated life as if it were a machine, or has treated the parts of living systems as if they were machines. The distinctive feature of a machine is that its behavior is linear and hence predictable. On the other hand, living organisms may not be linear, but rather nonlinear systems. Thus, the interface between organism and machine may be conceived as the interface between nonlinear and linear systems.

Biomedical Engineering↗
PubMed2002

Bilayered bioengineered skin substitute (Apligraf): a review of its use in the treatment of venous leg ulcers and diabetic foot ulcers.

UNLABELLED: The bilayered bioengineered skin substitute (BBSS) [Apligraf] is used for the treatment of venous leg ulcers and diabetic foot ulcers. It has an epidermal layer formed from human keratinocytes and a dermal layer composed of human fibroblasts in a bovine type I collagen matrix. BBSS does not contain any antigen-presenting cells such as Langerhans cells, dermal dendritic cells, endothelial cells or leucocytes. In clinical trials, there was no evidence of clinical rejection and immunological tests indicated no humoral or cellular response to the keratinocytes or fibroblasts of BBSS. Further clinical trials are required to identify the exact mechanism of action of BBSS in chronic wounds. BBSS plus compression therapy was well tolerated and was superior in efficacy to compression therapy alone in a multicentre, randomised trial in patients with venous leg ulcers. At 6 months' follow-up, complete wound healing occurred in 63 versus 49% of patients and the median time to wound closure was 61 versus 181 days. In a subgroup of patients with hard-to-heal ulcers (>1 year's duration), wound healing was achieved in significantly more patients (47 vs 19%) and the median time to wound healing was significantly shorter (181 days vs not attained). In a multicentre, randomised trial, BBSS was well tolerated and effective in patients with full-thickness neuropathic diabetic foot ulcers. Ulcer healing occurred in significantly more patients (56 vs 38%) and the median time to wound healing was shorter (65 vs 90 days) with BBSS than with saline-moistened gauze at 12 weeks' follow-up. Patients in both groups also received standard diabetic foot care. The cost effectiveness of BBSS in patients with chronic ulcers has yet to be examined in well designed, prospective clinical trials. However, according to a modelled analysis incorporating data from a multicentre randomised trial, BBSS was cost effective in patients with hard-to-heal venous leg ulcers. The average annual medical cost of managing patients with ulcers of >1 year's duration was estimated to be 20,041 US dollars per patient treated with BBSS plus compression therapy and 27,493 US dollars per patient treated with compression therapy alone (1996 costs). CONCLUSIONS: Clinical trials have shown that BBSS in conjunction with standard compression therapy was effective and well tolerated in patients with venous leg ulcers, especially patients with ulcers of >6 months' duration or that extended to the subcutaneous tissue. In addition, BBSS in conjunction with standard diabetic foot care was effective and well tolerated in patients with full-thickness neuropathic diabetic foot ulcers. BBSS represents a useful adjuvant to standard ulcer therapy in patients with venous leg ulcers or full-thickness neuropathic diabetic foot ulcers that do not respond to conventional ulcer therapy.

Clinical Trials as Topic↗
PubMed2001

Construction and physiological studies on a stable bioengineered strain of shengjimycin.

Shengjimycin is a group of 4"-acylated spiramycins with 4"-isovalerylspiramycin as the major component, produced by recombinant S. spiramyceticus F21 harboring a 4"-O-acyltransferase gene from S. mycarofaciens 1748. A stable bioengineered strain of Streptomyces spiramyceticus WSJ-1 was constructed by integrating the 4"-O-acyltransferase gene (ist) by homologous recombination into the chromosome of the spiramycin-producing strain S. spiramyceticus F21. In this construction, a Streptomyces/E. coli shuttle plasmid pKC1139 (AmR) was used as the vector with the tsr gene used as selection marker for homologous recombination. The constructed strain, S. spiramyceticus WSJ-1,was genetically stable in production titer and proportion of components of shengjimycin as well as in maintaining the tsr selective marker when grown without selection. Southern hybridization confirmed the integrated status of the ist gene in the host genome. The production and the proportion of major component of 4"-isovalerylspiramycin of S. spiramyceticus WSJ-1 was also improved comparing with the strain harboring an autonomous plasmid -S. spiramyceticus F21/pIJ680(311) as shown by HPLC analysis. Physiological studies indicated that increase of the VDH ( valine dehydrogenase ) and LDH ( leucine dehydrogenase ) activities of WSJ-1 may be involved in this improvement.

Amino Acid Oxidoreductases↗
PubMed1992

Scaling, dry skin and gender. A bioengineering study of dry skin.

Dry skin and scaling was studied in a group of 72 healthy volunteers by using subjective self-assessment and by clinical assessment by a dermatologist, as well as application of noninvasive bioengineering techniques to measure scaling and epidermal hydration. The study revealed that 67% of the volunteers had subjective complaints, while only 5.6% had definite clinical signs of dry skin at the time of examination. Subjective complaints were more common in women than in men (p < 0.001), though neither clinical nor objective measurements showed any sex difference, which suggests that other factors may play a role in the way men and women perceive dry skin. Subjective and clinical scores were correlated (p < 0.02), though neither was significantly correlated to objective measurements. Grading of skin scaling on D-squame tapes correlated with densitometry of the tapes (p < 0.001), as did the electrical capacitance (p < 0.001). Both clinical and objective methods can identify dry skin. However, the study showed that in healthy persons a number of irrational factors play a role in the use of moisturizers, and while these factors cannot be measured, they must be taken into account. Healthy, but dry skin is a vaguely defined clinical entity, which may explain the generally poor correlation between the two methods. This underlines the need for several methods to be used simultaneously in order to elicit complementary information.

Adult↗
PubMedDate not supplied

[Functional role' of hemodialysis equipment in the bioengineering system of artificial purification].

The paper deals with hemodialysis equipment as a constituent of the bioengineering system for artificial blood purification. This approach allows us to objectively evaluate its functional capacities and the usefulness of objective results of hemodialysis and to provide scientific evidence for the structure of hemodialysis equipment. The artificial purification of the biological organism is presented as a variety of interrelated controlling and diagnostic processes in the controlling and actuating elements of extracorporeal artificial organs.

Biomedical Engineering↗
PubMed1999

Construction of a stable bioengineered strain of biotechmycin.

A stable bioengineered strain of Biotechmycin (Streptomyces spiramyceticus WSJ-1) was constructed by integrating the 4"-isovaleryltransferase gene (ist) through homologous recombination into the chromosome of spiramycin-producing strain S.spiramyceticus F21. In this construction, a Streptomyces/E.coli shuttle plasmid pKC1139 (AmR) was used as the vector and tsr gene was inserted as the marker for selection of homologous recombination. This constructed strain, S.spiramyceticus WSJ-1, was genetically very stable in production titer and in the production of biotechmycin as well as in carrying tsr selective marker when grown without pressure. The fermentation of S.spiramyceticus WSJ-1 was also improved compared with the original strain harboring unintegrated plasmid. Southern hybridization confirmed the integrated status of the ist gene in the host genome.

Acyltransferases↗
PubMedDate not supplied

Interfacial bioengineering to enhance surface biocompatibility.

This article reviews recent developments in interfacial bioengineering to improve the biocompatibility of implanted materials. It includes a discussion of biomimetic approaches to bioinert and bioactive surface coatings to improve the in vivo performance of existing medical devices.

Biocompatible Materials↗
PubMed2002

Mechanical stretch regimen enhances the formation of bioengineered autologous cardiac muscle grafts.

BACKGROUND: Surgical repair of congenital and acquired cardiac defects may be enhanced by the use of autologous bioengineered muscle grafts. These tissue-engineered constructs are not optimal in their formation and function. We hypothesized that a mechanical stretch regimen applied to human heart cells that were seeded on a three-dimensional gelatin scaffold (Gelfoam) would improve tissue formation and enhance graft strength. METHODS AND RESULTS: Heart cells from children undergoing repair of Tetralogy of Fallot were isolated and cultured. Heart cells were seeded on gelatin-matrix scaffolds (Gelfoam) and subjected to cyclical mechanical stress (n=7) using the Bio-Stretch Apparatus (80 cycles/minute for 14 days). Control scaffolds (n=7) were maintained under identical conditions but without cyclical stretch. Cell counting, histology, and computerized image analysis determined cell proliferation and their spatial distribution within the tissue-engineered grafts. Collagen matrix formation and organization was determined with polarized light and laser confocal microscopy. Uniaxial tensile testing assessed tissue-engineered graft function. Human heart cells proliferated within the gelatin scaffold. Remarkably, grafts that were subjected to cyclical stretch demonstrated increased cell proliferation and a marked improvement of cell distribution. Collagen matrix formation and organization was enhanced by mechanical stretch. Both maximal tensile strength and resistance to stretch were improved by cyclical mechanical stretch. CONCLUSION: The cyclical mechanical stretch regimen enhanced the formation of a three-dimensional tissue-engineered cardiac graft by improving the proliferation and distribution of seeded human heart cells and by stimulating organized matrix formation resulting in an order of magnitude increase in the mechanical strength of the graft.

Absorbable Implants↗