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The formation of ectopic bone within skeletal muscle is a widely observed phenomenon. However, the source of the osteoprogenitor cells responsible for ectopic bone formation remains unknown. This study was designed to test for osteogenic differentiation among cells isolated from skeletal muscle tissue. Different subpopulations of cells derived from an adult mouse skeletal muscle were tested for induction of alkaline phosphatase activity after exposure to bone morphogenetic protein‐2 in vitro. A responsive subpopulation was identified, transduced with a retrovirus encoding for β‐galactosidase (Rv‐lacZ) and an adenoviral construct encoding for one bone morphogenetic protein‐2, and injected into the hindlimb of immune compromised (severe combined immunodeficient, or SCID) mice. The injected cells appeared to actively participate in the ectopic bone formation. The existence of lacZ‐positive muscle‐derived cells colocalized with osteocalcin‐producing cells within lacunae of newly formed bone matrix suggests osteoblast and osteocyte differentiation. Although a specific cell was not isolated, these data support the contentions that osteoprogenitor cells reside within skeletal muscle and that muscle may represent a source other than bone marrow for the harvest of these cells.

Transpiration of cuticular membranes isolated from the lower stomatous surface of Hedera helix (ivy) leaves was measured using a novel approach which allowed a distinction to be made between gas phase diffusion (through stomatal pores) and solid phase diffusion (transport through the polymer matrix membrane and cuticular waxes) of water molecules. This approach is based on the principle that the diffusivity of water vapour in the gas phase can be manipulated by using different gases (helium, nitrogen, or carbon dioxide) while diffusivity of water in the solid phase is not affected. This approach allowed the flow of water across stomatal pores ('stomatal transpiration') to be calculated separately from the flow across the cuticle (cuticular transpiration) on the stomatous leaf surface. As expected, water flux across the cuticle isolated from the astomatous leaf surface was not affected by the gas composition since there are no gas-filled pores. Resistance to flux of water through the solid cuticle on the stomatous leaf surface was about 11 times lower than cuticular resistance on the astomatous leaf surface, indicating pronounced differences in barrier properties between cuticles isolated from both leaf surfaces. In order to check whether this difference in resistance was due to different barrier properties of cuticular waxes on both leaf sides, mobility of 14C-labelled 2,4-dichlorophenoxy-butyric acid (14C-2,4-DB) in reconstituted cuticular wax isolated from both leaf surfaces was measured separately. However, mobility of 14C-2,4-DB in reconstituted wax isolated from the lower leaf surface was 2.6 times lower compared with the upper leaf side. The significantly higher permeability of the ivy cuticle on the lower stomatous leaf surface compared with the astomatous surface might result from lateral heterogeneity in permeability of the cuticle covering normal epidermal cells compared with the cuticle covering the stomatal cell surface.

A penetration study of 2-ethylhexyl-4-methoxycinnamate (EHMC), 4-methyl benzylidenecamphor (MBC), butyl methoxydibenzoylmethane (BMBM), 2-ethylhexyl-2,4,5-trimethoxycinnamate (EHTMC) and di(2-ethylhexyl)-2,4,5-trimethoxybenzalmalonate (TMB) through baby mouse skin (Mus musculus Linn.) was carried out using a vertical Franz diffusion cell. At 4.4 mg/cm 2 coverage of UV filter on the skin, 2.98 ± 0.38, 1.15 ± 0.14 and 0.80 ± 0.28% of the applied EHMC, MBC and BMBM were detected in the receptor fluid at 24 h after application. Penetrations of UV filter in an ethanolic solution and lotion forms were comparable. EHTMC and TMB showed insignificant penetration across the baby mouse skins. Baby mouse skins kept at 4, –20 and –80°C gave similar EHMC penetration results. Penetrations of EHMC, BMBM, EHTMC and TMB across human epidermis were carried out upon 5 volunteers using the suction blister technique. The results also confirmed the significant penetrations of EHMC and BMBM and the insignificant penetrations of EHTMC and TMB.

While a variety of in-vitro models have been employed to investigate the response of load-bearing tissues to hydrostatic pressure, long-term studies are limited by the need to provide for adequate gas exchange during pressurization. Applying compression in vitro may alter the equilibrium of the system and thereby disrupt the gas exchange kinetics. To address this, several sophisticated compression chamber designs have been developed. However, these systems are limited in the magnitude of pressure that can be applied and may require frequent media changes, thereby eliminating critical autocrine and paracrine signaling factors. To better isolate the cellular response to long-term compression, we created a model that features continuous gas flow through the chamber during pressurization, and a negative feedback control system to rigorously control dissolved oxygen levels. Monitoring dissolved oxygen continuously during pressurization, we find that the ensuing response exhibits characteristics of a second- or higher-order system which can be mathematically modeled using a second-order differential equation. Finally, we use the system to model chronic nerve compression injuries, such as carpal tunnel syndrome and spinal nerve root stenosis, with myelinated neuron-Schwann cell co-cultures. Cell membrane integrity assay results show that co-cultures respond differently to hydrostatic pressure, depending on the magnitude and duration of stimulation. In addition, we find that myelinated Schwann cells proliferate in response to applied hydrostatic compression.

To investigate the toxicity and mutagenicity of NO, methods are needed to deliver it to cell cultures at known, constant rates. To permit continuous exposures over lengthy periods, we fabricated a simple apparatus utilizing gas-permeable polydimethylsiloxane (Silastic) tubing to supply both NO and O2 to a stirred, cylindrical vessel. Mass transfer in this system was characterized by measuring the delivery rates of NO or O2 alone, and of NO to air-saturated solutions. The concentrations of NO, O2, and NO2- (the end product of NO oxidation) were monitored continuously. The total flux of nitrogen species into the liquid (as determined from the sum of NO and NO2- accumulation) was 50%-90% greater in the presence of O2, depending on the NO partial pressure in the gas. Also, the simultaneously measured mass transfer coefficients for NO and O2 differed greatly from the corresponding unreactive values. An analysis of the data using diffusion-reaction models showed that NO oxidation in the aqueous boundary layer contributed very little to the nitrogen flux increase or to variations in the mass transfer coefficients. However, the unusually strong dependence of the delivery rates on chemical reactions could be explained by postulating that partial oxidation of NO to NO2 occurred within the membrane. The rate constant we estimated for polydimethylsiloxane, 4.4 x 10(5) M-2 s(-1) at 23 degrees C, is only about one-fifth of values reported previously for water and nonpolar solvents, but the high solubilities of NO and O2 in the polymer are sufficient to make NO2 formation significant. Although considerable NO2 is calculated to enter the liquid, its reaction with aqueous NO is rapid enough to keep this undesired compound at trace levels, except within a few microns of the tubing. Thus, cells will have little exposure to NO2

Dermal papillae (DP) play a pivotal role in hair formation, growth and cycling. However, the number of DP is limited. In this study, we report the production of “reconstructed DP” by enclosing DP cells within an alginate–polylysine–alginate (APA) semipermeable membrane. MTT assay and electron microscopy showed that the microencapsulated dermal papilla cells retained normal activity. The microcapsules were implanted into rat footpads, which lack follicles and sebaceous glands, to assess their inductive properties. Histologic examination showed that numbers of follicle and sebaceous gland structures formed in the footpads within 6–10-week period. At the 10 weeks following transplantation, hair fibers were visible in the footpad. These findings indicate that the DP cell microcapsules retain the capacity to initiate follicle regeneration and could be considered a substitute for fresh isolated DPs.

Oral route offers an attractive mode of drug administration, although its applications are limited by poor stability of peptides and proteins in the gastrointestinal tract. In this article, we report a novel method based on intestinal patches for oral drug delivery. This method involves the use of millimeter size mucoadhesive patches that adhere to the intestinal wall and direct solute diffusion towards the wall similar to that observed in the case of a transdermal patch. Intestinal patches were prepared by sandwiching a film of cross-linked bovine serum albumin microspheres between a film of ethyl cellulose and Carbopol/pectin. Delivery of three model drugs, sulforhodamine B. phenol red, and dextran was assessed in vitro using rat intestine. In vitro tests confirmed substantial unidirectional diffusion of model drugs from the patch across the intestinal wall. The presence of ethyl cellulose layer minimized release from the edges as well as from the back side of the patch into the intestinal lumen. In vitro experiments with rat intestine showed that patches were effective in delivering model drugs across the intestine. Trans-lumenal flux of model drugs from intestinal patches was about 100-fold higher compared to that from a solution due to localization of the solute near the intestinal wall and due to minimization of drug loss into the intestinal lumen. Intestinal patches offer a novel approach for oral drug delivery.

The purpose of this work was to assess the molecular properties that influence solute permeation across siliconemembranes and to compare the results with transport across human skin. The permeability coefficients (log Kp) of a series of model solutes across silicone membranes were determined from the analysis of simple transport experiments using a pseudosteady-state mathematical model of the diffusion process. Subsequently, structure permeation relationships were constructed and examined, focusing in particular on the difference between solute octanol/water and 1,2 dichloroethane/water partition coefficients (deltalog P(oct-dce)), which re ported upon H-bond donor activity, and the computationally derived molecular hydrogen-bonding potential. The hydrogen-bond donor acidity and the lipophilicity of the compounds examined greatly influenced their permeation across sil cone membranes. Furthermore, for a limited dataset, a significant correlation was identified between solute permeation across silicone membranes and that through human epidermis. The key molecular properties that control solute perme ation across silicone membranes have been identified. For the set of substituted phenols and other unrelated compounds examined here a similar structure-permeation relationship has been derived for their transport through human epidermis, suggesting application of the results to the prediction of flux across biological barriers.

Lipid microparticles (lipospheres) loaded with butyl methoxydibenzoylmethane (BMDBM), a widely used UV-A sunscreen agent, were prepared by melt technique and evaluated for skin permeation both in vivo, by tape stripping method, and in vitro, by a flow-through diffusion chamber. Following in vivo human skin application of an O/W emulsion containing 2% of BMDBM loaded in lipospheres, 15% of the applied sunscreen accumulated in the uppermost layers of the stratum corneum without remarkably modifying the skin permeation of the unencapsulated sunscreen. These results were found to be predicted by an in vitro methodology involving the diffusion of BMDBM through a lipophilized synthetic membrane into a hydrophilic receptor phase, simulating the viable epidermis better than an ethanolic receptor phase.