Little is known about the regulatory signals involved in tendon and ligament formation, and this lack of understanding has hindered attempts to develop biologically based therapies for tendon and ligament repair. Here we report that growth and differentiation factors (GDFs) 5, 6, and 7, members of the TGF- gene superfamily that are most related to the bone morphogenetic proteins, induce neotendon/ligament formation when implanted at ectopic sites in vivo. Analysis of tissue induced by GDF-5, 6, or 7, containing implants by currently available morphological and molecular criteria used to characterize tendon and ligament, adds further evidence to the idea that these GDFs act as signaling molecules during embryonic tendon/ligament formation. In addition, comparative in situ localizations of the GDF-5, 6, and 7 mRNAs suggest that these molecules are important regulatory components of synovial joint morphogenesis. ( J.
The experiments described in this report were designed to determine the possible influence of plasma and salivary constituents on dentin permeability, in vitro. The results indicate that plasma, serum, and whole (mixed) saliva are all capable of causing immediate reductions in dentin permeability. Individual plasma protein fractions and several different types of bacteria were also effective in reducing the ease with which fluid can move across dentin. These observations may provide a mechanism for the "spontaneous" reductions in dentin sensitivity seen by clinicians following periodontal therapy. J Dent Res 61 (8): 978-981, August 1982 Introduction.Several clinical studies of the efficacy of various treatments for hypersensitive dentin have reported that about 20-30% of the control groups which received either no treatment or sham treatment showed distinct decreases in the magnitude of dentin sensitivity.'4 Similar clinical impressions have been reported by numerous periodontists. They report that dentin sensitivity is a frequent complication of periodontal therapy, but that it rapidly improves in most patients over a period of days to weeks without any treatment.Based on the hydrodynamic theory of dentin sensitivity,5 these observations suggest that the resistance to fluid flow across dentin has increased in those patients who experienced "spontaneous" recovery. According to the hydrodynamic theory of dentin sensitivity, the common denominator of all painful stimuli is fluid movement within dentinal tubules. Removal of cementum from dentin obviously exposes the tubules to stimuli from the oral environment. Conversely, decreases in dentin sensitivity must be due to decreases in the ability of fluid to move within dentinal tubules.6 The most important variable influencing fluid movement through dentin tubules is the functional radius of the tubules,7 since fluid flow varies with the fourth power of the radius. There are several possible mechanisms which may be responsible for decreasing the fluid permeability of hypersensitive dentin. Brannstrdm and Garberoglio8 recently demonstrated that saliva is capable of forming mineralized deposits within exposed dentinal tubules in crown segments worn in removable dentures for three yr. Saliva has the same access to tubules in exposed hypersensitive dentin. The presence of large numbers of bacteria in plaque or saliva offers another mechanism of blocking fluid flow through tubules. Michelich et al. 9 reported that filtration of bacterial suspensions across dentin resulted in an almost total removal of the bacteria from the solution. The bacteria lodged within the tubules decreased the ability of fluid to move across dentin. If this occurred in hypersensitive dentin, the occlusion of tubules would tend to make it less sensitive. Whether this dentin would ever develop active carious lesions is a moot point. A third mechanism that may be responsible for spontaneous recovery of hypersensitive dentin is the adsorption of salivary and/or plasma proteins gaining access to tubu...
In routine dental practice, anesthetic solutions are injected into tissue sites of widely different distensibilities, under a variety of pressures. The purpose of the present study, during simulated dental practice, was to determine the maximum injection pressures obtained by clinicians during injections in dogs. Regular aspirating dental syringes were used together with dental anesthetic cartridges filled with isotonic saline. Maximum operator injection pressures ranged from 330 to 660 psi (17,061-34,122 mmHg). Those injection sites that were least distensible gave the highest maximum injection pressures: interosseous (21,559 mmHg); incisive papilla (18,224 mmHg); periodontal (17,630 mmHg); hard palate (11,322 mmHg); and intrapulpal (8918 mmHg). More distensible tissue sites gave much lower pressures. The data indicate that dental injection pressures vary widely from several hundred mmHg to several hundred psi, depending on the clinician's physical effort and the distensibility of the tissue.
Swarm cells of Thiothrix nivea were found to possess a group of fimbriae at one pole. The other pole either was bare or possessed from one to three fimbriae. By using this polarity as a marker, it was found that the initial step in attachment of swarm cells involves the fimbriated pole and that this initial step is followed by the production of holdfast material.
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