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Biomedical subjects

R E Baier

Publications and source records attributed to R E Baier.

At least 37 records · Page 2Linked to original sources
PubMed1989

Thin-section transmission electron microscopy of human saliva.

Thin sections (90-100 nm) of flash-frozen human saliva fractions and whole saliva were examined by transmission electron microscopy. Inside the major filamentous structural components numerous ultrastructural details were observed, especially for whole saliva and submandibular/sublingual fractions. An outer reticulated zone believed to contain the major salivary glycoproteins surrounded an inner core consisting of a continuous, more electron dense phase with multiple vacuoles and granules of different sizes, shapes, and electron densities. The observed structures suggest a complex microarchitectural model for whole saliva.

Actin Cytoskeleton↗
PubMed1988

Silicone rubber temporomandibular joint (TMJ) meniscal replacements: postimplant histopathologic and material evaluation.

Medical grade silicone rubber has long been considered a suitable meniscal replacement, but there has been increasing concern about migration of this material into adjacent tissues. The objectives of this study were to determine the definitive composition of tissue-incorporated material which is presumed by light microscopy to be silicone and to identify long term histopathologic sequelae of meniscal replacements. Adult female patients underwent meniscectomy and replacement with silicone rubber (Silastic) implants. After 12 to 18 months, recurrence of symptoms in 8% of these cases led to implant removal with excision of peri-implant fibrous pseudocapsules. Excised tissues, including one preauricular lymph node and implants were submitted for light microscopy, SEM, and energy dispersive x-ray microanalysis (EDX) for the identification of elemental composition, critical surface tension measurement, and internal reflection infrared spectroscopy. EDX revealed prominent peaks for silicon in both pseudocapsular and nodal tissues. Morphologic findings surrounding the long-term implants included foreign body reaction, synovitis, dystrophic calcification, fibrocartilaginous metaplasia, hyalinization, and scarring. Particulate silicone debris induced a pathologic response in the tissues and migrated to nodes. These findings suggest that periodic evaluation be performed over the life of such implants to rule out breakdown under function. These findings should intensify the search for improvements or replacements for silicone rubber as an interpositional material in the temporomandibular joint.

Calcinosis↗
PubMed1988

Role of temperature and shear forces on microbial detachment.

A flow cell system was used to assess the effects of shear stress and temperature on adhesion and retention of oral microorganisms from unstimulated whole human saliva. The saliva passed between two parallel mounted test plates, prepared and calibrated to present a surface energetic state similar to that of natural teeth and most restorative materials. The initial attachment of microorganisms occurred at a constant flow rate of 1 ml/min. Microbiota and biofilm material associated with the surface after 15 min of exposure were then challenged by introducing a cell-free rinsing fluid at increased flow rates. The remaining population was counted in a reflected light microscope and correlated to the calculated shear stress for each experiment. A reduction of 70-80% of attached microorganisms was seen after a 30-fold increase of the detaching force. No statistically significant differences could be detected in the proportions of initially attached or the remaining cocci and rods. The experiments were conducted at two temperature levels, both within a physiologic range representative of the oral environment. Temperature did not significantly affect the total numbers of attached or retained microorganisms, within the range of 22-37 degrees C. These findings demonstrate that non-specific attachment and detachment processes are important in the initial stage of microbial adhesion. Although biologically specific adhesive interactions were not addressed in this study, the data suggest that these may occur only after a minimum contact time of non-specifically surface associated cells.

Bacterial Adhesion↗
PubMed1988

Advanced biomaterials development from "natural products".

Natural substances and structures can serve increasingly well as biomedical products, given recent advances in understanding of requirements for biocompatibility and of methods for their preservation and surface tailoring. A successful example is the derivation of limb salvaging vessels, used in arterial reconstructive surgery, from human umbilical cords. There are numerous opportunities for additional product development from the umbilical cords' main ingredient, Wharton's gel, ranging from biolubricants to wound-healing aids. Major problems yet to be overcome with natural starting materials are their propensity for calcification and eventual biodeterioration. Surface modification of biomaterials to exhibit desired degrees of interaction with contacting viable tissues promises the greatest beneficial results. General principles of bioadhesion have broad applicability, predicting material behavior in environments as diverse as blood, saliva, and seawater.

Adhesiveness↗
PubMed1988

Future directions in surface preparation of dental implants.

Clean, intrinsically high-surface-energy dental implants are both safe and effective, but ambiguity remains with regard to the true surface qualities of many implant materials that have been sterilized and are about to be placed in properly instrumented host sites. Future dental implant requirements should include proper surface preparation and surface quality maintenance of the implants themselves. Recommended directions for research on dental implant materials include greater use of surface analytical techniques to identify, understand, and ultimately control common surface contaminants. Regulatory agencies should require specific reporting of critical surface parameters for all dental implant materials in their final, sterile states, including any changes from desirable initial values. Different implants demand different degrees of interaction with adjacent biological phases, for example, to promote or inhibit bioadhesion, and different surface preparations can assure these results.

Biocompatible Materials↗
PubMed1988

Investigation of tissue/implant interactions during the first two hours of implantation.

The objective of this study was to determine whether detectable differences exist in the initial process of tissue incorporation of implant materials of different original surface energies. Our earlier work focused on materials implanted for days to months; the experiments reported here addressed the initial 2 hours of implantation. Surface-treated metal implants were placed in the fascial plane in the back of New Zealand white rabbits for 5 minutes to 2 hours. Prior to implantation, the metal plates were characterized by infrared spectroscopy, ellipsometry, and contact potential methods; the same analytical techniques, as well as scanning electron microscopy and contact angle measurements were applied to the explanted samples. No significant cellular adhesion was observed within the first 2 hours of implantation. Films rich in lipids and proteins were detected on the implants, however, within 5 minutes. There is good evidence for specific film differentiation as a function of differing initial substratum surface energies.

Animals↗
PubMed1987

In vitro attachment of oral microorganisms to solid surfaces: evaluation of a controlled flow method.

A flow cell method was modified to provide shear-controlled experimental conditions for monitoring initial attachment and detachment of oral microorganisms to solid surfaces. Whole unstimulated human saliva was collected and circulated at a flow rate of 1 ml/min, through a cell composed of two parallel test plates. Infrared-transparent plates of medium surface energy served as test substrata in these initial calibration experiments. The plates presented a similar distribution of polar forces and dispersion forces at the surface as that of human tooth enamel and some restorative dental materials. Internal reflection infrared spectroscopy verified the presence of deposited organic material. After saliva had been circulated through the flow cells for 15 min at 37 degrees C, sterilized distilled water was introduced at the same flow rate and time of exposure to remove unattached microorganisms. Morphologic characterizations and counts of adherent Gram-stainable microorganisms were performed using incident light microscopy. Three different surface zones corresponding to the inlet area, the middle area and the outlet area of the flow cell were analyzed, and compared with enumerations of microorganisms in the whole saliva samples. Numbers of attached microorganisms in the three zones followed predictions from the laminar flow conditions, with a positive correlation shown between total numbers of microorganisms in saliva and total numbers of microorganisms attached. Cocci and rods were the only morphotypes observed on the plates, and no significant difference could be detected between the percentage of cocci and rods attached in the three different zones.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗
PubMed1987

Selected methods of investigation for blood-contact surfaces.

It is imperative that operating personnel and regulatory agencies have secure, advance, and accurate knowledge of the true surface properties of materials to be contacted with flowing blood. The actual devices must be characterized in their sterile, immediate pre-exposure states. Although very sensitive electronic instrumental analysis techniques are available, the requirements for small specimens exposed to high vacuums and energetic beams hinder their use with practical prosthetic implants. Thus, it remains important that classical estimation of the "wettability" of nonphysiologic materials by simple contact angle measurements can document their real surface qualities in the condition and environment of their intended application. These data, acquired quickly and nondestructively, together with confirming laboratory results from internal reflection infrared spectroscopy, scanning microscopy, and X-ray analysis, are the most useful indicators of material safety and effectiveness for blood contact uses. Experience has shown that the critical surface tensions of materials, determined from contact angle measurements in air rather than underwater, are generally predictive of the tenacity of bioadhesion at their boundaries with blood and other living tissues. Overall, it is now recommended that the surface chemistry of all implant materials be characterized before any exposure to flowing blood, as a minimum requirement of good practice.

Animals↗
PubMed1986

Compliance changes in glutaraldehyde-treated arteries.

Glutaraldehyde tanning of carotid arteries was used to develop a model for studying the effects of compliance on arterial graft performance, independent of other graft parameters. Canine carotid segments were filled with dilute phosphate-buffered glutaraldehyde (0-0.5%, pH 7.4), maintained at physiological pressure, and then immersed in either saline or 10.0% glutaraldehyde for up to 1 hr. After rinsing with saline, compliance was measured in vitro. All vessels which were immersed in 10% glutaraldehyde exhibited a significant reduction in compliance compared to native artery control [C = 11.8 +/- 1.3 (mean +/- SEM), % radial change/mm Hg X 10(-2), measured at 100 mm Hg], but maximum stiffness (C = 1.1 +/- 0.3) required that the lumen be specifically exposed to at least 0.025% glutaraldehyde in addition to simple immersion of the vessel segment in 10% fixative. Exposing the artery to 0.5% glutaraldehyde internally, without immersion of the entire structure, caused a decrease in compliance similar to that obtained after immersion in 10% glutaraldehyde, with only saline present in the lumen. Matched pairs of stiff and compliant grafts were generated by exposing the lumen to 0.025% glutaraldehyde and immersing the vessels in 10% fixative or saline, respectively. Light and scanning electron microscopy, internal reflection spectroscopy, and measurements of critical surface tension revealed nearly identical wall morphology and lumenal surface chemistry for these matched pairs. Differential tanning of the internal and external surfaces of carotid arteries thus provides a good model of arterial prostheses, wherein a substantial compliance mismatch can be studied without the complicating influences of varying diameter or differing flow surface properties.

Aldehydes↗
PubMed1984

Surface properties determine bioadhesive outcomes: methods and results.

This investigation developed experimental evidence for the influence of different surface energy states on tissue incorporation of biomedical materials. Implants of two smooth metals, each with three different surface energy states, were placed in the subdermal fascial plane of the backs of New Zealand White rabbits and were allowed healing times of 10 and 20 days. The implant surfaces were thoroughly characterized by physical-chemical criteria prior to surgical placement and again following removal from the tissue capsules generated by the host animals. Quantitative histopathologic analysis, using standard morphometric criteria, of the adjacent tissues revealed up to a threefold increase of fibroblastic-fibrocytic cells against the initially scrupulously cleaned, high-surface-energy materials. The cells were flattened and active, producing tenacious bonds through a thin pre-adsorbed protein-dominated "conditioning" film, that could be broken only by cohesive failure in the tissue itself. In contrast, the lower-surface-energy materials typical of standard dental implants were "walled off" by a cell-poor, nonadhesive capsule with a fibrous interface separated from a thicker "conditioning" film by a lipid-rich mucus zone. The advantages of proper surface treatment to favor the desired degree of biological adhesion are apparent.

Animals↗
PubMed1984

Biodegradation and aneurysm formation in umbilical vein grafts. Observations and a realistic strategy.

In a series of 756 glutaraldehyde-stabilized umbilical vein grafts implanted over a 7 1/2-year period, aneurysms were identified in seven cases. The earliest aneurysm was seen at 31 months after implantation and the remainder between 43 and 79 months after surgery. Corrective surgery was performed in five cases and succeeded in four. Although definite mechanisms have not been identified, mechanical fatigue, reversal of aldehyde crosslinks, and immunologic factors may be operative. The pathologic changes include: (1) actual dilation of both graft and mesh with or without intraluminal thrombus and, (2) maintenance of graft diameter with erosion of the umbilical vein and polyester mesh rupture leading to perigraft hematoma and false aneurysm formation. Microscopic examination and infrared spectral analysis confirmed the presence of host-contributed lipid in some specimens. Although this is a low incidence of aneurysm formation, umbilical vein grafts should be selected primarily for patients with limited life expectancy or for whom alternative materials with comparable or superior patency rates are not available or acceptable. Periodic angiography, particularly after 3 or 4 years, is recommended as a routine part of follow-up examinations. Improved graft materials and control of host environmental factors are potential means to reduce the noted degradation.

Aneurysm↗
PubMed1984

Fibroblastic activities post implantation of cobalt chromium alloy and pure germanium in rabbits.

Different preimplantation surface finishes were applied to surgical vitallium discs and germanium prisms implanted for 20 days within the back muscles of adult rabbits. Histopathologic analysis of the numbers of nuclei of active fibroblasts immediately adjacent to the implants was carried out. The mean apparent volume fractions (MAVF) for the subdermal implant sites were found to depend on the surface cleanliness of the implant, the cleanest or highest-surface-energy surfaces giving the highest MAVF values for active fibroblasts.

Animals↗
PubMed1984

In situ identification of bacterial species in marine microfouling films by using an immunofluorescence technique.

An immunofluorescence technique was developed for the in situ identification of specific bacteria in marine microfouling films. Microorganisms adherent to glass plates after 30 days of immersion in a synthetic seawater system were cultured and classified by biochemical tests, flagellar arrangement, and the API 20E system. All isolates were gram-negative aerobic or facultative motile rods, predominantly Pseudomonas spp. Rabbit antisera to the five dominant organisms including Achromobacter spp., Comamonas terrigena, P. putrefaciens, a yellow-pigmented Pseudomonas sp., and Vibrio alginolyticus were prepared. These antisera were shown to be species specific in indirect immunofluorescence assays against a battery of 26 marine isolates from 14 bacterial species, with the exception of antisera to the Pseudomonas spp, which cross-reacted with each other but not with test bacteria of other genera. These immunofluorescent reagents enabled the in situ identification of all five bacterial species in microfouling films. Low-surface-energy test plates had smaller numbers of adherent bacteria in microfouling films than medium-surface-energy test plates, suggesting that the degree of microfouling may be influenced by the surface energy. In addition, the reagents could identify up to 39% of the attached bacteria in microfouling films spontaneously formed on steel plates in flow cells deployed in different areas of the Atlantic Ocean. The microbial composition of the ocean-formed films varied with the geographical area of their formation. The present results indicate that immunofluorescence techniques may provide a rapid and reliable means to identify, in situ, specific bacteria in marine microfouling films.

Animals↗