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Notes: Restoration of the epidermal barrier is a requirement for burn wound closure. A rapid, reliable, and noninvasive measure of the rate of restoration of the epidermal barrier is not readily available. To monitor the reformation of the epidermal barrier, we measured surface electrical capacitance on cultured skin substitutes (human keratinocytes and fibroblasts attached to collagen-glycosaminoglycan substrates) and split-thickness skin autografts grafted to patients. Data were collected from four patients with burns and one pediatric patient with a congenital hairy nevus comprising 〉 60% total body surface area. Capacitance measurements were performed at days 7, 10, 12, 14, and 28 by direct contact of the capacitance probe for 10 seconds to the cultured skin substitutes or split-thickness autograft. On postoperative days 7, 10, 12, 14, 21, and 28, the surface electrical capacitance of cultured skin substitutes after 10 seconds of sampling was 2468 ± 268, 1443 ± 439, 129 ± 43, 200 ± 44, 88 ± 20, and 74 ± 19 picofarads (mean ± standard error of the mean), respectively. Surface electrical capacitance for split-thickness autograft on the same days was 1699 ± 371, 1914 ± 433, 125 ± 16, 175 ± 63, 110 ± 26, 271 ± 77 picofarads, respectively. Surface electrical capacitance in all of the grafts decreased with time. Cultured skin substitutes had approximately the same 10-second capacitance values as split-thickness autograft during 3 weeks of healing and approached values for uninjured skin (32 ± 5 picofarads) by 12 days. Measurement of surface electrical capacitance is a direct, inexpensive, and convenient index for noninvasive monitoring of epidermal barrier formation.

Notes: To investigate the role of transforming growth factor-β1 in tissue repair, we performed wound healing studies in the transforming growth factor-β1—deficient mouse with targeted disruption of the transforming growth factor-β1 gene. Transforming growth factor-β1—deficient mice exhibit no obvious developmental defects and are phenotypically normal until approximately 3 weeks of age when a severe wasting syndrome develops, accompanied by an overwhelming inflammatory response resulting in multisystem organ failure and death. Full-thickness 0.5 × 0.5 cm skin wounds were created on the backs of 10-day-old mice (wild type or heterozygous controls versus homozygous transforming growth factor-β1—deficient mutants) and covered with a nonabsorbent dressing (OpSite). Serial wound measurements were made, and percentage of wound closure over time was determined. On day 10, wounds and liver were harvested for histologic and molecular analysis. Histologic scores were assigned (1 [no healing] to 12 [complete healing]) on the basis of granulation tissue formation, vascularity, collagen deposition, and epithelialization. Reverse transcription—polymerase chain reaction was performed to detect messenger RNA transcripts for transforming growth factor-β1, transforming growth factor-β2, platelet-derived growth factor A-chain and B-chain, interleukin-1β and -6, and tumor necrosis factor-α in unwounded skin, day 10 wounds, and liver. No significant differences in wound closure were observed until day 10. Weight gain, however, was significantly decreased in the mutant animals as early as day 6. Histologic scores were significantly lower in the transforming growth factor-β1—deficient mutants (5.4 ± 0.6 versus 11.1 ± 0.3, p 〈 0.01, Wilcoxon rank-sum test) and showed decreased granulation tissue formation, vascularity, collagen deposition, and epithelialization and a marked inflammatory infiltrate. As expected, transforming growth factor-β1 was expressed in controls but not mutants. Transforming growth factor-β2, platelet-derived growth factor A-chain and B-chain, and tumor necrosis factor-α were constitutively expressed in unwounded skin, day 10 wounds, and liver of both controls and mutants. Interleukin-1β and -6, however, were induced after wounding. Early wound healing in the transforming growth factor-β1—deficient mouse proceeds relatively normally because of upregulation or functional redundancy of other growth factors or possibly because of maternal rescue by means of transforming growth factor-β1 transmitted in milk. Loss of transforming growth factor-β1 regulation ultimately results in a marked inflammatory response, as evidenced by the histologic appearance of the wound and increased expression of the inflammatory cytokines (tumor necrosis factor-α, interleukin-1β and 6). The severe wasting syndrome (marked by weight loss) undoubtedly has an adverse effect on wound healing.

Notes: Biologic mechanisms by which skin grafts become revascularized after transplantation are poorly understood. To investigate graft revascularization, we examined the pattern of capillary growth in full-thickness skin grafts at serial time points. Full-thickness skin (2 × 2 cm) was excised to muscle fascia from the bilateral hind limbs of adult male Lewis rats. The graft/wound base boundary was identified by placement of a polypropylene mesh on the wound beneath the graft. Excised skin was replaced in its original orientation and secured with silk sutures tied over a gauze bolster dressing. After 3, 5, 7, and 10 days, animals were killed, and their aortas were cannulated and infused with an acrylic polymer to generate vascular casts. Grafts were excised, tissues were digested, and casts were examined with the use of scanning electron microscopy. Transmission electron microscopy was performed on tissues infused with the acrylic polymer that were not digested. At day 3, an immature lobular pattern was observed extending from the neovascular plexi on the graft side of the polypropylene mesh. At day 5, defined vessels with lobular ends occurred with high frequency. At day 7, the number of observed lobular structures was greatly reduced, and high frequencies of depressions in acrylic casts suggested protrusion of endothelial cell nuclei. By day 10, lobular structures were rare, well-defined microvascular plexi were contiguous with larger vessels, and depressions from endothelial cell nuclei appeared more shallow and less frequent. These findings suggest that (1) an immature lobular pattern representing either capillary outgrowth or extracapillary leakage occurs at day 3; (2) these immature lobules decrease, and more discrete capillaries increase by day 5; (3) vascular integrity is reestablished by day 7; (4) vascular plexi has regained full continuity, and there are suggestions that endothelial cell proliferation has subsided by day 10.

Notes: Purpose The maximum preload torque of implant prosthetic retaining screws from four manufacturers and of two alloy types was measured to determine one index of interchangeability of intersystem components.Materials and Methods Implant prosthetic retaining screws from four manufacturers (3i Implant Innovations Inc, West Palm Beach, FL; Impla-Med Inc, Sunrise, FL; Nobelpharma USA Inc, Chicago, IL; and Implant Support Systems Inc, Irvine, CA) and of two metal types (gold and titanium) were investigated using an in vitro simulation model. Five screws of each type were tightened down against a gold cylinder using a Tohnichi BTG-6 torque gauge (Tohnichi American Corporation, Northbrook, IL) until fracture occurred.Results The 3i Implant Innovations gold and the Nobelpharma gold were not significantly different. The 3i Implant Innovations titanium and the Impla-Med gold were able to withstand less preload torque than the 3i Implant Innovations gold and the Nobelpharma gold. The Implant Support Systems titanium was able to withstand significantly more preload torque than all of the other screws.Conclusions Interchanging implant prosthetic retaining screws could introduce new and unknown variables that may affect the long-term survival of implant fixtures and/or the implant prostheses.

Notes: Abstract: KCl-evoked glutamate exocytosis from cerebrocortical synaptosomes can be inhibited by the adenosine A1 receptor agonist cyclohexyladenosine (CHA). Inhibition is associated with a decreased KCl-evoked Ca2+ level elevation, and the effect of the agonist is occluded by prior incubation with the Agelenopsis aperta neurotoxin ω-agatoxin-IVA at 250 nM. The inhibition is suppressed in the presence of 3 nM phorbol dibutyrate (PDBu) or by activation of the protein kinase C (PKC)-coupled metabotropic glutamate receptor by 100 µM (1S,3R)-1-aminocyclopentane-1,3-dicarboxylate [(1S,3R)ACPD]. A tonic inhibition of release by leaked exogenous adenosine can be reversed by adenosine deaminase or by PDBu addition. The CHA-induced inhibition can be enhanced by the PKC inhibitor Ro 31-8220. The mechanism for the suppression of the adenosine A1 receptor-mediated inhibition is distinct from that previously described for the (1S,3R)ACPD-evoked, PKC-mediated, facilitatory pathway, which enhances phosphorylation of the MARCKS protein, 4-aminopyridine-induced action potentials, and release of glutamate because the latter requires at least 100 nM PDBu [or the combination of (1S,3R)ACPD and arachidonic acid] and is not seen following KCl depolarization. Both PKC-mediated pathways may be involved in the presynaptic events associated with the establishment of synaptic plasticity.

Notes: Abstract: The effects of age on basal and lesion-induced changes in astrocyte RNA messages reported to respond to neurodegeneration were examined in the mouse brain. The first study found an age-related increase in glial fibrillary acidic protein RNA throughout the brain. Other astrocyte RNAs remained generally stable with age. We hypothesize this increase is due to astrocytes undergoing a mild reaction to the small amount of synaptic degeneration occurring with usual aging. To test this theory, we used an experimental model of modest synaptic loss in the hippocampus by transecting the fimbria/fornix bundle in mice and examined the same series of messages. In situ hybridization revealed the expected increase in glial fibrillary acidic protein RNA after the lesion; however, we unexpectedly found that aged mice showed a greater magnitude of this response, which appeared to develop more slowly. There was no significant change in the hippocampus for any of the other messages, although responses were observed at the site of transection. This study supports the idea that the age-related increase in glial fibrillary acidic protein may be secondary to modest synaptic degeneration. We also demonstrated an exaggerated reactive astrocytic response in aged mice, which may be associated with age-related deficits in reactive synaptogenesis and behavioral recovery in normal aging.