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At least 1,279 records · Page 71Linked to original sources
PubMed1999

An overview of contemporary approaches to antiarrhythmic therapy.

This review discusses the evolution in the approach to the therapy of cardiac arrhythmias that has occurred during the past 2 decades. The major changes have been driven by advances in understanding arrhythmia mechanisms, in bioengineering, and in clinical trials. It seems likely that progress in understanding the cellular and molecular basis of arrhythmias and their response to drug therapy may allow further identification of patient subsets in which specific therapies are indicated or contraindicated.

Anti-Arrhythmia Agents↗
PubMed2005

A kinetic modeling of chondrocyte culture for manufacture of tissue-engineered cartilage.

For repairing articular cartilage defects, innovative techniques based on tissue engineering have been developed and are now entering into the practical stage of clinical application by means of grafting in vitro cultured products. A variety of natural and artificial materials available for scaffolds, which permit chondrocyte cells to aggregate, have been designed for their ability to promote cell growth and differentiation. From the viewpoint of the manufacturing process for tissue-engineered cartilage, the diverse nature of raw materials (seeding cells) and end products (cultured cartilage) oblige us to design a tailor-made process with less reproducibility, which is an obstacle to establishing a production doctrine based on bioengineering knowledge concerning growth kinetics and modeling as well as designs of bioreactors and culture operations for certification of high product quality. In this article, we review the recent advances in the manufacturing of tissue-engineered cartilage. After outlining the manufacturing processes for tissue-engineered cartilage in the first section, the second and third sections, respectively, describe the three-dimensional culture of chondrocytes with Aterocollagen gel and kinetic model consideration as a tool for evaluating this culture process. In the final section, culture strategy is discussed in terms of the combined processes of monolayer growth (ex vivo chondrocyte cell expansion) and three-dimensional growth (construction of cultured cartilage in the gel).

Animals↗
PubMed1994

Transgenic approaches for modifying the mammary gland to produce therapeutic proteins.

Bioengineering of the mammary gland to produce proteins of therapeutic and industrial value is the result of extensive investigation of the physiology of the mammary gland and the ability to generate transgenic animals. Targeting the expression of heterologous proteins to mammary tissue requires a thorough understanding of the biochemical events that coordinate growth and differentiation of the mammary gland and of the hormonal and developmental regulation of expression of milk protein genes. The characterization of mammary-specific promoter regions in milk protein genes and knowledge of the mechanisms that confer integration site-independent expression of transgenes have significantly contributed to modifying the mammary gland to produce heterologous proteins of therapeutic interest. The generation of large transgenic farm animals provides the opportunity for large-scale production of proteins in milk that have a therapeutic value but are naturally present at low concentrations in biological fluids. Transgenic mammary epithelial cells offer a versatile research model in biomedical, environmental health, and neonatal toxicology research.

Animals↗
PubMed2006

An agromedicine initiative for first-year medical students, 1998-2004: biochemistry seminar proves feasible.

This report describes a 20 class-hour, 10-session seminar on agromedicine-oriented topics, delivered as part of a basic science course for medical students (biochemistry) at the Medical University of South Carolina. The course was initiated in 1998 and continued through 2004. The preceptors are family medicine and agricultural research professors. Concepts from primary care, epidemiology, entomology, toxicology, and food science appeal strongly to the first-year medical student group (limited to 10 students). The agromedicine/environmental medicine seminar series is one of 16 research seminars available for in-depth study. As part of the course in biochemistry, this seminar has earned positive evaluations from medical students who expect to widen their perspective on global health and the environment. Seminar topics include food safety, farm trauma, nutraceuticals, crop protection, insect-borne disease, occupational health and safety, diet and cancer, birth defects, and bioengineering. Seventy medical students have participated in the interdisciplinary seminar. They perceive environmental science as affecting the health of their patients and as an essential part of their preparation for curative and preventive medicine. Readers may find medical school curriculum committees more receptive to accepting and continuing an agromedicine offering if it can be incorporated in a basic science course such as biochemistry or pharmacology.

Agriculture↗
PubMed2004

Multidomain synthetic peptide B2A2 synergistically enhances BMP-2 in vitro.

UNLABELLED: A multidomain, synthetic peptide designated B2A2 synergizes the activity of BMP-2. B2A2 interacts with BMP receptor isoforms, potentiating the action of BMP-2 in activating alkaline phosphatase and triggering Smad and MAPK signaling. B2A2's design permits its delivery as a local surface coating as well as a soluble co-factor, thus broadening potential bioengineering applications. INTRODUCTION: BMP-2 induces osteogenic differentiation and accelerates bone repair. Although BMP-2 inhibitors have been discovered, no BMP-2 mimetics or enhancers that function in the physiological range have yet been found. Here we report that a synthetic peptide designated B2A2, consisting of (1) a BMP receptor-targeting sequence, (2) a hydrophobic spacer, and (3) a heparin-binding sequence, is a positive modulator of recombinant BMP-2. MATERIALS AND METHODS: Cultures of mesenchymal cell lines C2C12 and C3H10T1/2 were given B2A2, recombinant BMP-2, or both. Alkaline phosphatase (ALP) activity was assayed by conversion of paranitrophenol phosphate (PNPP). Signaling through Smad and MAP kinase pathways was monitored by Western blot. Receptor binding was assessed by incubating immobilized B2A2 with soluble recombinant receptor-Fc chimeras and detecting bound receptor by anti-Fc antibody ELISA. Surface coating of medical device materials was done by first dip-coating with silyl-heparin, followed by B2A2. RESULTS AND CONCLUSIONS: Treatment of cells with B2A2 alone marginally increased ALP activity. However, B2A2 plus BMP-2 resulted in 5- to 40-fold augmentation of ALP compared with BMP-2 alone in C3H10T1/2 or C2C12 cells, respectively. This synergistic enhancement was observed over a broad concentration range (4-1000 ng/ml BMP-2). B2A2 interacted directly with BMP receptor isoforms (preferentially to BMPR-Ib and ActivinR-II). In cells, B2A2 + BMP-2 led to a repression of MAP kinase and an increase of Smad activation, consistent with known activation pathways of BMP-2. B2A2 was ineffective when paired with other cytokine/growth factors (basic fibroblast growth factor [FGF-2], TGF-beta1, vascular endothelial growth factor [VEGF]). Simultaneous co-administration was not strictly required. Pulse-chase experiments revealed that temporal separations up to 1 h were still effective. B2A2 was also effective when delivered in a polystyrene- or stainless steel-coated surface through a heparin platform (silyl-heparin) while BMP-2 was added exogenously in solution. These results suggest that B2A2 might promote aggregation of receptor subunits, enabling BMP-2 to activate signaling pathways at effectively lower concentrations. Synthetic multidomain constructs like B2A2 may be useful to accelerate bone repair/deposition through augmentation of endogenous levels of BMP-2 or through local BMP-2 contained in artificial or engineered matrices.

Alkaline Phosphatase↗
PubMed1996

Bronchoprovocation tests in the diagnosis of isocyanate-induced asthma.

Over the past 25 years, investigators have continued to improve on the approach to providing nonirritant exposures for the accurate diagnosis of isocyanate-induced asthma. Although the technology used in testing has become more sophisticated and may be fairly considered the domain of the bioengineer, the chemist, and the industrial hygienist, the requirements of the physician have remained unchanged. The physician must observe the level of exposure closely and monitor the worker's symptoms and lung function. Direct physician involvement in the testing procedure remains critical to the worker's safety and for the accurate diagnosis of isocyanate-induced asthma.

Asthma↗
PubMed2004

In vitro physical stimulation of tissue-engineered and native cartilage.

Because of the limited availability of donor cartilage for resurfacing defects in articular surfaces, there is tremendous interest in the in vitro bioengineering of cartilage replacements for clinical applications. However, attaining mechanical properties in engineered cartilaginous constructs that approach those of native cartilage has not been previously achieved when constructs are cultured under free-swelling conditions. One approach toward stimulating the development of constructs that are mechanically more robust is to expose them to physical environments that are similar, in certain ways, to those encountered by native cartilage. This is a strategy motivated by observations in numerous short-term experiments that certain mechanical signals are potent stimulators of cartilage metabolism. On the other hand, excess mechanical loading can have a deleterious effect on cartilage. Culture conditions that include a physical stimulation component are made possible by the use of specialized bioreactors. This chapter addresses some of the issues involved in using bioreactors as integral components of cartilage tissue engineering and in studying the physical regulation of cartilage. We first consider the generation of cartilaginous constructs in vitro. Next we describe the rationale and design of bioreactors that can impart either mechanical deformation or fluid-induced mechanical signals.

Animals↗
PubMed2005

Oxidation of glucose to gluconic acid by glucose oxidase in a membrane bioreactor.

Glucose oxidase (GO) (EC 1.1.3.4) was used as catalyst for oxidizing glucose into gluconic acid utilizing a 10-mL Bioengineering Enzyme Membrane Reactor or a 400-mL Millipore Stirred Ultrafiltration Cell (MSUC) coupled with a Millipore UF membrane (cutoff of 100 kDa) and operated for 12 h under an agitation of 100 rpm, pH 5.5, and 30 degrees C. The effect of feeding rate (0.10, 0.15, or 0.20 min-1), glucose (2.5 or 5.0 mM), and GO (1.0 or 2.0 mg/mL) concentrations on the catalysis were studied. A yield of about 75% was attained when the MSUC filled with 1.0 mg/mL of GO was fed with 2.5 mM glucose solution at a rate of 0.15 min-1.

Bioreactors↗
PubMed2000

Effects of initial pH on biological synthesis of xylitol using xylose-rich hydrolysate.

Sugarcane bagasse, an agricultural residue plentiful in Brazil, was utilized for xylitol production by a biotechnological process. A medium fermentation prepared with this xylose-rich biomass at an oxygen transfer volumetric coefficient of 10/h1 and different initial pH values was inoculated with cells of Candida guilliermondii FTI 20037. The maximum values of xylitol and cell volumetric productivities (Qp = 0.56 g/[L.h] and Qx = 0.11 g/[g.h]), xylitol yield factor (YP/S = 0.79 g/g), and xylose uptake rate (qs = 0.197 g/[g.h]) were attained at pH 7.0 without further pH control. The results show that the yeast performance was influenced by the pH, an important bioengineering parameter in this fermentation process.

Biological Transport↗
PubMed2004

Generation of new islets from stem cells.

Spain ranks number one in organ donors (35 per million per yr). Although the prevalence of diabetes is low (100,000 type 1 diabetic patients and 2 million type 2 diabetic patients), the expected number of patients receiving islet transplants should be estimated at 200 per year. Islet replacement represents a promising cure for diabetes and has been successfully applied in a limited number of type 1 diabetic patients, resulting in insulin independence for periods longer than 3 yr. However, it has been difficult to obtain sufficient numbers of islets from cadaveric donors. Interesting alternatives include acquiring renewable sources of cells using either embryonic or adult stem cells to overcome the islet scarcity problem. Stem cells are capable of extensive proliferation rates and are capable of differentiating into other cell types of the body. In particular, totipotent stem cells are capable of differentiating into all cell types in the body, whereas pluripotent stem cells are limited to the development of a certain number of differentiated cell types. Insulin-producing cells have been obtained from both embryonic and adult stem cells using several approaches. In animal models of diabetes, the therapeutic application of bioengineered insulin-secreting cells derived from stem cells has delivered promising results. This review will summarize the different approaches that have been used to obtain insulin-producing cells from embryonic and adult stem cells and highlights the key points that will allow in vitro differentiation and subsequent transplantation in the future.

Animals↗
PubMed2002

Stem cell and precursor cell therapy.

Strategies for cell replacement therapy have been guided by the success in the hematopoietic stem cell field. In this review, we discuss the basis of this success and examine whether this stem cell transplant model can be replicated in other systems where stem cell therapy is being evaluated. We conclude that identifying the most primitive stem cell and using it for transplant therapy may not be appropriate in all systems. We suggest alternative strategies such as progenitor cell replacement, inductive factors, bioengineering organs, in utero transplants, or any approach that takes advantage of the unique properties of the tissue and the stem cell type which, are more likely to provide effective functional replacement.

Animals↗
PubMed2004

Derivation of keratinocyte progenitor cells and skin formation from embryonic stem cells.

Despite numerous elegant transgenic mice experiments, the absence of an appropriate in vitro model system has hampered the study of the early events responsible for epidermal and dermal commitments. Embryonic stem (ES) cells are derived from the pluripotent cells of the early mouse embryo. They can be expanded infinitely in vitro while maintaining their potential to spontaneously differentiate into any cell type of the three germ layers, including epidermal cells. We recently reported that ES cells have the potential to recapitulate the reciprocal instructive ectodermal-mesodermal commitments, which are characteristic of embryonic skin formation. Derivation of epidermal cells from murine ES cells has been successfully established by exposing the cells to precisely controlled instructive influences normally found in the body, including extracellular matrix and the morphogen BMP-4. These differentiated ES cells are able to form, in culture, a multilayered epidermis coupled with an underlying dermal compartment similar to native skin. This bioengineered skin provides a powerful tool for studying the molecular mechanisms controlling skin development and epidermal stem cell properties.

Animals↗
PubMed2001

Where will the genome lead us? Dentistry in the 21st century.

BACKGROUND: Recent announcements of the deciphering and analysis of the human genome signal the inception of a new era of gene-based medicine. During the 21st century, patient treatment will be transformed and dentistry will be affected profoundly. METHODS: The author explains the importance of the decoding of the genome and how--based on this now completely depicted molecular structure--genes build, maintain and control all the biological functions of humans and all other living organisms. The potential application of this knowledge to the practice of dentistry is addressed, as well as the ethical, legal and moral challenges to the profession engendered by this new technology. CONCLUSION: During the next several decades, many of the current materials and methods will be abandoned in favor of emerging bioengineered technologies, genetically programmed for the prevention and treatment of oral disease as well as for the repair of damaged dental tissues. PRACTICE IMPLICATIONS: The development and implementation of these innovative dental therapies will require intensive education of current practitioners. Considerable restructuring of dental school curricula will need to take place, and the emergence of a new dental specialty is anticipated.

Bioethics↗
PubMed1998

Biofluid mechanics.

The flow behavior of biological fluids in living organisms plays a crucial role in determining the state of the tissue through which they flow. Biofluid mechanics, the study of the fundamentals of biological fluid flow, has been recognized to be extremely important for the understanding of how changes in the flow behavior within living tissue maybe affect both the fluid and the tissue. Fluids in living tissue include blood, water, air and bodily fluids of animals, as well as the fluids in plants. The movement and balance of forces in resting fluids and fluids in motion are among the basic subjects for research. Biofluid mechanics is a field whose importance to the field of bioengineering has increased over the last two decades as pharmaceuticals, biomaterials and non-invasive diagnostic and surgical procedures create changes in the fluid mechanics of biofluids. Biofluid mechanics is a complex field including one of the most important areas of study--blood flow and cardiovascular diseases.

Arteriosclerosis↗
PubMed2004

Poxvirus vaccines for cancer and HIV therapy.

The poxviridae have a long history of causing disease in society, and their biological effects in humans and other mammals have been extensively studied. In the 1980s, genetic engineering techniques were applied to vaccinia in order to create replicating recombinant vectors that could express inserted genes encoding influenza virus proteins. In animal models, these recombinant viruses were able to deliver their foreign antigens to the immune system and elicit a specific adaptive immune response. Since then, improvements in our understanding of immunobiology, as well as technical advances in bioengineering, have led to the creation and clinical testing of a large number of recombinant poxviruses as candidate vaccines. Poxviruses can infect a broad range of cells, replicate with high efficiency and elicit strong immune responses - factors that make them especially well-suited as vaccines for the prevention and treatment of human immunodeficiency virus (HIV) and cancer. Both of these diseases are characterised by chronic antigen expression in the setting of focal or global deficits in the immune system that hamper the generation of protective immunity. This review traces the history of poxviruses as pathogens and immunogens, examines some of the approaches that have been taken to design poxviral vaccines for HIV and cancer and summarises the results of existing clinical trials of these vectors. In addition, the review aims to identify some of the factors that may shape the development of future therapies based on recombinant poxviruses.

AIDS Vaccines↗
PubMed2006

Next-generation optical technologies for illuminating genetically targeted brain circuits.

Emerging technologies from optics, genetics, and bioengineering are being combined for studies of intact neural circuits. The rapid progression of such interdisciplinary "optogenetic" approaches has expanded capabilities for optical imaging and genetic targeting of specific cell types. Here we explore key recent advances that unite optical and genetic approaches, focusing on promising techniques that either allow novel studies of neural dynamics and behavior or provide fresh perspectives on classic model systems.

Animals↗
PubMed2004

Currently available metacarpophalangeal prostheses: their designs and prospective considerations.

Although implanted for over 40 years, finger prostheses have failed to match the success achieved by artificial hip and knee prostheses, despite a myriad of designs having been proposed and implanted. This article looks at the currently available designs of metacarpophalangeal prosthesis, both single-piece and multicomponent implants. An appraisal of their designs and the clinical results, where available, are provided. The review also considers the challenges that are still faced by bioengineers and surgeons concerned with improving the success of metacarpophalangeal prostheses. In addition, key current areas of concern such as in vitro testing and contemporary issues in rheumatology, which may be diminishing the amount of metacarpophalangeal arthroplasty taking place, are discussed.

Arthroplasty, Replacement, Finger↗
PubMed2007

Gastrointestinal tissue engineering.

Tissue engineering is an emerging discipline that combines engineering principles and the biological sciences toward the development of functional replacement tissue. Virtually every tissue in the body has been investigated and tremendous advances have been made in many areas. This article focuses on the gastrointestinal tract and reviews the current status of bioengineering gastrointestinal tissues, including the esophagus, stomach, small intestine and colon. Although progress has been achieved, there continues to be significant challenges that need to be addressed.

Biocompatible Materials↗