Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Bioengineering”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources
PubMed2007

Progress and potential for regenerative medicine.

Regenerative medicine focuses on new therapies to replace or restore lost, damaged, or aging cells in the human body to restore function. This goal is being realized by collaborative efforts in nonmammalian and human development, stem cell biology, genetics, materials science, bioengineering, and tissue engineering. At present, understanding existing reparative processes in humans and exploring the latent ability to regenerate tissue remains the focus in this field. This review covers recent work in limb regeneration, fetal wound healing, stem cell biology, somatic nuclear transfer, and tissue engineering as a foundation for developing new clinical therapies to augment and stimulate human regeneration.

Guided Tissue Regeneration↗
PubMed2005

The postnatal rat aorta contains pericyte progenitor cells that form spheroidal colonies in suspension culture.

Pericytes play an important role in modulating angiogenesis, but the origin of these cells is poorly understood. To evaluate whether the mature vessel wall contains pericyte progenitor cells, nonendothelial mesenchymal cells isolated from the rat aorta were cultured in a serum-free medium optimized for stem cells. This method led to the isolation of anchorage-independent cells that proliferated slowly in suspension, forming spheroidal colonies. This process required basic fibroblast growth factor (bFGF) in the culture medium, because bFGF withdrawal caused the cells to attach to the culture dish and irreversibly lose their capacity to grow in suspension. Immunocytochemistry and RT-PCR analysis revealed the expression of the precursor cell markers CD34 and Tie-2 and the absence of endothelial cell markers (CD31 and endothelial nitric oxide synthase, eNOS) and smooth muscle cell markers (alpha-smooth muscle actin, alpha-SMA). In addition, spheroid-forming cells were positive for NG2, nestin, PDGF receptor (PDGFR)-alpha, and PDGFR-beta. Upon exposure to serum, these cells lost CD34 expression, acquired alpha-SMA, and attached to the culture dish. Returning these cells to serum-free medium failed to restore their original spheroid phenotype, suggesting terminal differentiation. When embedded in collagen gels, spheroid-forming cells rapidly migrated in response to PDGF-BB and became dendritic. Spheroid-forming cells cocultured in collagen with angiogenic outgrowths of rat aorta or isolated endothelial cells transformed into pericytes. These results demonstrate that the rat aorta contains primitive mesenchymal cells capable of pericyte differentiation. These immature cells may represent an important source of pericytes during angiogenesis in physiological and pathological processes. They may also provide a convenient supply of mural cells for vascular bioengineering applications.

Actins↗
PubMed1993

Immunophysiology of the gut: a research frontier for integrative studies of the common mucosal immune system.

This review highlights work that, within the past decade, transformed mucosal immunophysiology from a hypothetical concept to a fully recognized interdiscipline. The regulation of epithelial and smooth muscle functions by the mucosal immune system represents an exquisitely sensitive adaptation to local antigenic challenge. Furthermore, immunologic cells communicate with nerves via paracrine secretions to rapidly transduce antigenic signals into panmucosal changes in function. These local immunocyte-nerve interactions are modulated by the autonomic and central nervous systems. Because of the common mucosal immune system, antigen-induced changes similar to those occurring in the intestine and colon are predicted to occur in mucosa of all hollow organs. The drawing together of fields as diverse as medicine and agriculture underscores the scope of areas encompassed by immunophysiology. Newly acquired knowledge has positioned the field to advance rapidly in both basic and applied directions. Forces that will remodel the field in the next decade will be derived from public concerns about human health maintenance and the explosive and novel use of new research tools stemming from molecular biology. These forces will draw on and advance our knowledge in areas as diverse as vaccine development and prevention of allergic reactions to foods, bioengineered foods in particular.

Animals↗
PubMed2000

Invited review: pulmonary capillary stress failure.

The pulmonary blood-gas barrier is an extraordinary bioengineering structure because of its vast area but extreme thinness. Despite this, almost no attention has been given to its mechanical properties. The remarkable area and thinness come about because gas exchange occurs by passive diffusion. However, the barrier also needs to be immensely strong to withstand the very high stresses in the capillary wall when capillary pressure rises during exercise. The strength of the thin region of the barrier comes from type IV collagen in the basement membranes. When the stresses in the capillary walls rise to high levels, ultrastructural changes occur in the barrier, a condition known as stress failure. Physiological conditions that alter the properties of the barrier include severe exercise in elite human athletes. Animals that have been selectively bred for high aerobic activity, such as Thoroughbred racehorses, consistently break their pulmonary capillaries during galloping. Pathophysiological conditions causing stress failure include high-altitude pulmonary edema and overinflation of the lung, which frequently occurs with mechanical ventilation. Remodeling of the capillary wall occurs in response to increased wall stress in diseases such as mitral stenosis. The barrier is able to maintain its extreme thickness with sufficient strength as a result of continual regulation of its wall structure. How it does this is a central problem in lung biology.

Animals↗
PubMed2001

Functional enhancement of electrofusion-derived BRIN-BD11 insulin-secreting cells after implantation into diabetic mice.

Electrofusion-derived BRIN-BD11 cells are glucose-sensitive insulin-secreting cells which provide an archetypal bioengineered surrogate beta-cell for insulin replacement therapy in diabetes mellitus. 5x10(6) BRIN-BD11 cells were implanted intraperitoneally into severely hyperglycaemic (>24 mmol/l) streptozotocin-induced insulin-treated diabetic athymic nude (nu/nu) mice. The implants reduced hyperglycaemia such that insulin injections were discontinued by 5-16 days (<17 mmol/l) and normoglycaemia (<9 mmol/l) was achieved by 7-20 days. Implanted cells were removed after 28 days and re-established in culture. After re-culture for 20 days, glucose-stimulated (16.7 mmol/l) insulin release was enhanced by 121% (p<0.001) compared to non-implanted cells. Insulin responses to glucagon-like peptide-1 (10(-9) mol/l), cholecystokinin-8 (10(-8) mol/l) and L-alanine (10 mmol/l) were increased by 32%, 31% and 68% respectively (p<0.05-0.01). Insulin content of the cells was 148% greater at 20 days after re-culture than before implantation (p<0.001), but basal insulin release (at 5.6 mmol/l glucose) was not changed. After re-culture for 40 days, insulin content declined to 68% of the content before implantation (p<0.01), although basal insulin release was unchanged. However, the insulin secretory responses to glucose, glucagon-like peptide-1, cholecystokinin-8 and L-alanine were decreased after 40 days of re-culture to 65%, 72%, 73% and 42% respectively of the values before implantation (p<0.05-0.01). The functional enhancement of electrofusion-derived surrogate beta-cells that were re-cultured for 20 days after implantation and restoration of normoglycaemia indicates that the in vivo environment could greatly assist beta-cell engineering approaches to therapy for diabetes.

Animals↗
PubMed2003

Can We Build Artificial Stem Cell Compartments?

Animals carry stem cells throughout their entire life, from embryogenesis to senescence. Their function during development and adulthood consists basically of forming and sustaining functional tissues while maintaining a small self-renewing population. They reside in a complex three-dimensional environment consisting of other nearby cells extracellular matrix components, endogenous or exogenous soluble factors, and physical, structural, or mechanical properties of the tissues they inhabit. Can we artificially recreate tissue development such that stem cells can both self-renew and be instructed to mature properly? The main factors required to regulate the maintenance and differentiation of some types of stem cells are known. In addition, new bioengineered synthetic materials that mimic extracellular matrix components can be used as initial scaffolding for building stem cell microenvironments.

Journal Article↗
PubMed1998

Influence of age, anatomic site and race on skin roughness and scaliness.

BACKGROUND: Variations in skin roughness and scaliness between age groups, anatomic sites and race have been assumed but minimally quantified. OBJECTIVE: We quantitatively investigated skin roughness, scaliness and stratum corneum hydration as a function of age, anatomic site and race (white and black). METHODS: Skin roughness, scaliness and stratum corneum hydration were determined in vivo by noninvasive bioengineering and image analysis techniques in 22 female subjects grouped according to age (young and aged) and race (white and black). RESULTS: Skin roughness, scaliness and stratum corneum hydration varied significantly in different anatomic areas and age groups. There was no racial variation in skin hydration between any anatomic site, nor significant differences in roughness and scaliness between races, except for the preauricular area. Skin roughness was significantly increased in the aged, compared to the young at the preauricle, volar forearm, lower back, thigh and lower leg. Older women demonstrated significantly more scaling at the preauricle than younger women. Stratum corneum hydration correlated with scaliness. No significant correlation between stratum corneum hydration and skin roughness was observed. CONCLUSION: Age and anatomic site but not race demonstrated a significant influence on skin roughness and scaliness. The desquamation index appears a good indicator of the status of stratum corneum hydration.

Adult↗
PubMed1999

Effect of topical antioxidants on UV-induced erythema formation when administered after exposure.

BACKGROUND: Photoprotective effects of topically applied antioxidants when applied before ultraviolet radiation (UVR) exposure are well known. Their protective effect when applied after UVR exposure is, however, less established. OBJECTIVE: In a randomized, double-blinded, placebo-controlled human study the short-term photoprotective effects of different antioxidants and of their combinations were evaluated when applied after UVR exposure. METHODS: Melatonin (N-acetyl-5-methoxytryptamine), vitamin E (alpha-tocopherol) and vitamin C (ascorbic acid) were topically administered alone or in combination following UVR exposure as single applications (immediately or 30 min after irradiation, respectively) or as multiple applications (three times: 30 min, 1 h and 2 h after irradiation). The erythemal reaction was evaluated visually and noninvasively with bioengineering methods (skin color and skin blood flow). RESULTS: No significant protective effect of melatonin or the vitamins when applied alone or in combination were obtained when antioxidants were applied after UVR exposure. No improved photoprotective effect was obtained when multiple applications were done. CONCLUSION: UVR-induced skin damage is a rapid event, and antioxidants possibly prevent such damage only when present in relevant concentration at the site of action beginning and during oxidative stress.

Administration, Cutaneous↗
PubMed2001

Platelet function and fibrinolytic agents: two sides of a coin?

Fibrinolytic therapy is the established treatment for the management of patients with ST elevation acute myocardial infarction (AMI). Present fibrinolytic regimens have a number of shortcomings, including the failure to produce early and sustained reperfusion, as well as failure to prevent reocclusion in at least some patients. Platelets play an important role in coronary thrombosis responsible for AMI. The effect of coronary fibrinolysis on platelets has been extensively debated in the literature with evidence of both platelet activation and inhibition. Among fibrinolytic agents, tissue plasminogen activator (t-PA) is considered to be the mainstay in the treatment of coronary artery disease. The native t-PA molecule has been modified in an attempt to achieve improved lytic characteristics with less risk of bleeding. The result is a group of mutant t-PA variants considered third-generation plasminogen activators. TNK-t-PA is one bioengineered variant of t-PA. Another third-generation plasminogen activator is reteplase (r-PA). Like TNK-t-PA, it is a variant of t-PA that has been developed to establish a more rapid, complete, and stable coronary artery patency, thus promising reduced mortality. Both r-PA and TNK-t-PA are effective when given as bolus therapy. This feature may facilitate more rapid treatment as well as decrease overall costs of treatment. New fibrinolytic regimens include potent antiplatelet agents that may improve sustained reperfusion. This review summarizes the latest and often confusing data on the interaction between fibrinolytic therapy and platelets in certain in vitro, animal and clinical scenarios.

Animals↗
PubMed2001

Facts and myths about electrical measurement of stratum corneum hydration state.

Some of the views presented in the chapter on 'Examination of stratum corneum hydration state by electrical methods' in Skin Bioengineering - Techniques and Applications in Dermatology and Cosmetology (Karger, 1998) are in strong disagreement with the results from basic research that has been conducted on skin impedance measurement over the last decades. This research has e.g. non-ambiguously shown that the frequency response of the stratum corneum does not obey the Cole equation and that measurement depth is strongly dependent on measurement frequency. One consequence of these findings is that multifrequency electrical measurements on stratum corneum are impossible to achieve in vivo with any electrode system known today. Hence, electrical measurements of stratum corneum hydration must be conducted at one single, low frequency.

Body Water↗
PubMedDate not supplied

In vivo tolerance assessment of skin after insertion of subcutaneous and cutaneous microdialysis probes in the rat.

The purpose of the study was to evaluate the trauma induced by insertion of the linear microdialysis probe in the subcutaneous and dermal tissue in the rat and to check if the microdialysis probe insertion affects transdermal drug delivery. Non-invasive bioengineering methods (TEWL, Laser Doppler Velocimeter, Chromameter) as well as histology were combined to characterize these effects. The results showed that the dermal and subcutaneous insertion of microdialysis probes did not change skin permeability, blood flow and color, confirming the safety of this technique. The probe depth did not influence the trauma. No significant physical damage after probe insertion was noticed. Thus, the present work validates the use of microdialysis in dermatopharmacokinetics studies after topical or systemic drug delivery.

Administration, Cutaneous↗
PubMedDate not supplied

Construction of a transplantable tissue-engineered artificial peritoneum.

BACKGROUND: Peritoneal defects lead to serious postoperative problems. Thus the development of physiological material to cover peritoneal defects is very desirable. AIM: The aim of this study was to develop a transplantable artificial peritoneum. METHOD: The artificial peritoneum consisted of collagen gel, fibroblasts, and mesothelial cells, and histological features were analyzed. The artificial peritoneum at the site of a peritoneal defect in the rat was transplanted to the abdominal wall. RESULTS: Histological examination revealed that the artificial peritoneum consisted of a flat mesothelial monolayer upon a stromal matrix. All transplanted artificial peritoneums adapted well to the host and prevented severe adhesion. CONCLUSION: Our artificial peritoneum may be a useful transplantable bioengineered material for repair of surgical peritoneal defects.

Abdominal Wall↗
PubMed2005

Protective effects of different marigold (Calendula officinalis L.) and rosemary cream preparations against sodium-lauryl-sulfate-induced irritant contact dermatitis.

In the present study, we evaluated the protective action of cream preparations containing seven different types of marigold and rosemary extracts in vivo in healthy volunteers with experimentally induced irritant contact dermatitis (ICD). Marigold and rosemary extracts in base cream DAC (Deutscher Arzneimittel-Codex = German Pharmaceutical Codex) were tested in a 4-day repetitive irritation test using sodium lauryl sulfate. The effect was evaluated visually and quantified by noninvasive bioengineering methods, namely chromametry and tewametry. When the test products were applied parallel to the induction period of ICD, a statistically significant protective effect of all cream preparations was observed by all methods. This effect, although not statistically significant, was superior to control by undyed marigold und faradiol ester-enriched extracts in chromametry and by dyed and undyed rosemary extracts in tewametry. The sequential treatment (postirritation) once a day for 5 days was without any effect. Thus, a protective effect of some marigold and rosemary extracts against ICD could be shown in the elicitation phase.

Administration, Cutaneous↗
PubMed1976

Mapping the brain. Historical trends in functional localization.

This essay presents a brief review and evaluation of some guiding concepts during the past century of inquiry into localization of brain functions. Mapping methods are described and discussed as one useful set of approaches to defining functional localization. Each neurobiological discipline: neuroanatomy, neurophysiology, neurochemistry neuropsychology, neuroethology, clinical neurology, biophysics and bioengineering, all use map-making strategies in their search for valid spatial and temporal definitions of the phenomena in their field of interest. Particular emphasis is given to neurophysiological mapping procedures. How these procedures have evolved to become important tools for testing hypotheses about the neuroelectric, behavioral and psychological functions of specific neuroanatomical structures is discussed. The continued importance is emphasized of neurophysiological mapping as a basic set of descriptive sampling strategies for testing hypotheses about specific neural mechanisms and their adaptive operations.

Animals↗
PubMed1996

Structural and architectural changes during arterial development and the role of hemodynamics.

Hemodynamics is a major determinant in the anatomical and mural architectural development of the arterial tree. Arterial intimal proliferation commences in utero at specific anatomical sites often appearing eccentric in transverse section and precedes more diffuse concentric thickening. Regarded as an inherent structural component of the wall or an adaptive mural response to increasing hemodynamic stresses concomitant with growth, its occurrence in utero and in lower animals, though generally supportive of this view, ignores qualitative changes. Further doubt derives from the retrogressive destructive nature of structural changes in the arterial wall in the young, individual differences and their continued progression after birth and maturation. It is postulated that concomitantly with arterial development the associated degenerative changes are attributable to hemodynamically induced bioengineering fatigue caused by longitudinal stretching and circumferential distensile effects of the pulse waves and by lesser vibrations generated by flow at sites of predilection for compensatory intimal thickening. This intimal proliferation is the compensatory reparative response to loss of tensile strength of mural constituents and of the vessel wall as a whole.

Animals↗
PubMed1997

Mechanisms underlying arterial fragility and the complications of atherosclerosis.

The etiology of atherosclerosis must explain the development of primary pathological complications (intimal tears, ectasia, tortuosity, aneurysms and stenoses). They are interrelated and associated with destruction of mural architecture and concomitant loss of tensile strength (fragility) attributable to bioengineering fatigue. The complications become manifested clinically by ischemia, hemorrhage and pressure effects developing with greater frequency in association with hypertension, arteriovenous shunts or connective tissue disorders. Moreover they are produced experimentally and iatrogenically by hemodynamic means but are unexplained by other current etiological hypotheses.

Adult↗
PubMed1996

Evaluation of topical antipsoriatic treatment by chromametry, visiometry and 20-MHz ultrasound in the psoriasis plaque test.

The antipsoriatic effects of two topical antipsoriatic agents, betamethasone valerate (Betnovate) and calcipotriol (Daivonex), and a pure nanocolloid gel were assessed in 10 patients with chronic plaque-type psoriasis in a modified psoriasis plaque test. Three noninvasive bioengineering methods were applied to measure antipsoriatic effects: chromametry for objective evaluation of erythema; visiometry, a method for profilometry, and 20-MHz skin ultrasound for the measurement of skin thickness as a parameter of inflammatory infiltration and psoriatic hyperproliferation of the epidermis. Regarding inflammation parameters such as skin thickness (infiltration) and erythema (dilatation of vessels and hyperperfusion), the steroid preparation Betnovate proved to be significantly most effective in our study. Daivonex showed significant decreases in the skin roughness parameters, underlining its antiproliferative effect. The nanocolloid carrier was significantly effective in thickness reduction, this effect being most probably due to occlusion. 20-MHz ultrasound, chromametry and visiometry proved to provide multiparameter assessment of treated and untreated psoriatic skin and can be recommended as objective and reproducible measurements for further studies.

Administration, Topical↗
PubMed1995

Influence of the test area on the mechanical properties of skin.

BACKGROUND: New advances in bioengineering have provided commercially available devices for measuring the mechanical properties of skin in vivo. Reproducibility of data and methodological approaches have not yet been thoroughly studied. OBJECTIVE: To study the reproducibility and the influence of the area of the test site on the values of biomechanical variables yielded in a normal population. METHOD: A 500-mbar suction was transmitted to the skin through Cutometer probes equipped with a 2- or 8-mm opening. RESULTS: The best reproducibility was obtained for the maximum distension of skin and for the biological elasticity. The values of the standard biomechanical ratios were almost the same for both probes. Linear correlations were found between parameters of elasticity. CONCLUSION: The Cutometer is a reliable device. A high degree of correlation exists between biomechanical variables related to elasticity. Under a suction of 500 mbar, both the 2- and 8-mm probes give results which correlate statistically in a large population. However, the two probes do not measure precisely the same aspect of skin mechanics. The 2-mm probe measures the capacity of superficial skin folding, and the 8-mm probe explores the biomechanical properties of the dermis itself and of its slipping mobility on the hypodermis. The biomechanical parameters which appear the most clinically relevant for a normal-looking skin are the maximum distension and the biological elasticity.

Adult↗