Bibliothek

Notizen: The observation that many chronic wounds are ischemic has spurred a series of studies evaluating the response of cells exposed to hypoxia. To date, these studies have shown largely beneficial effects from hypoxia, such as increased cellular replication and procollagen synthesis. These findings are counter-intuitive from a clinical standpoint because cellular growth and synthetic function are known to be retarded in chronic ischemic wounds. We have established an in vitro system in which human dermal fibroblasts grown chronically at 5 ± 3 mm Hg will proliferate at a rate three times slower than those fibroblasts grown under standard culture conditions (namely an oxygen partial pressure of 150 mm Hg). No phenotypic changes are noted in chronically hypoxic cells, and the growth-retarding effects are reversible when the cells are returned to standard oxygen conditions. Competitive reverse transcription-polymerase chain reaction showed that acute exposure to hypoxia (up to 1 week) results in a 6.3-fold increase in the relative expression of transforming growth factor-β1 messenger RNA, whereas chronic exposure to hypoxia leads to a 3.1-fold decrease in this message. Collagen production measured at both the mRNA and protein level is also decreased in the setting of chronic hypoxia. We propose that this system may be the most appropriate setting for studying the role of oxygen on dermal fibroblasts in ischemic, nonhealing wounds.

Notizen: Impaired wound healing as a result of age is a well-documented phenomenon. However, the overall deficit in healing is substantially increased when the healing wound of an aged animal is ischemic. We hypothesized that both of these deficits are cytokine mediated. We have studied the messenger RNA expression of platelet-derived growth factor receptor-β, using the rabbit dermal ulcer model of wound repair, in young (3 to 6 months) and aged (48 months and 60 months) rabbits under normal and ischemic conditions. Platelet-derived growth factor receptor-β mRNA expression was measured with the use of quantitative reverse transcriptase-polymerase chain reaction with incorporation of a synthetic, nonhomologous DNA fragment complementary to platelet-derived growth factor receptor-β primers as a competitive internal standard. Results in young rabbits showed a large upregulation of platelet-derived growth factor receptor-β mRNA expression after wounding. In both aged animal groups, platelet-derived growth factor receptor-β expression was found to be significantly decreased in nonischemic wounds relative to young nonischemic controls. Ischemia was found to have little effect on platelet-derived growth factor receptor-β mRNA expression in young animals relative to matched controls. However, ischemia induced a large decrease in the platelet-derived growth factor receptor-β mRNA levels of wounds of aged animals relative to paired aged nonischemic wounds. Results suggest an age-related delay in platelet-derived growth factor receptor-β mRNA expression in healing wounds, as well as an age-related decline in responsiveness to confounding ischemia.

Notizen: Purpose This study evaluated the tensile bond strength of a bisphenol glycidyl methacrylate (Bis-GMA) resin luting cement with four different surface treatments of a high Pd-Cu alloy.Materials and Methods For each surface treatment type (tin-plated, porcelain furnace oxide, air-abraded, and finished-only), 15 opposing half-dumbbell-shaped samples were cast and prepared in new Pd?Cu alloy. Samples were luted with a Bis-GMA resin luting cement at a film thickness of 80 μm using a custom alignment apparatus. Samples were stored in distilled water at 37°C for 24 hours, thermocycled for 1,000 cycles, and then stored for 30 days in distilled water at 37°C. Samples were then subjected to fracture in tension at a loading rate of 0.5 cm/min with the bond strengths calculated in megapascals (MPa). The fractured surfaces were examined using stereomicroscopy and scanning electron microscopy at various magnifications ranging from 5.5x to 500x to determine the type of bond failure (adhesive, cohesive, or mixed).Results Tensile bond strengths (mean ± SD MPa) were: tin-plated, 30 ± 15.7; porcelain furnace oxide, 23 ± 8.6; air-abraded, 8 ± 8.1; and finished-only, 4 ± 4.5. Statistical analysis of the tensile bond values using an ANCOVA and Tukey's multiple comparison test at a significance level of 0.05 indicated that there was no difference between the tin-plated and the furnace oxide groups, as well as between the air-abraded and the furnace oxide groups. However, there was significant difference between the tin-plated, the air-abraded, and the finished-only groups. The observed bond failures were predominantly mixed and cohesive in nature with only one adhesive failure.Conclusions There was no significant difference in the tensile bond strengths between the tin-plated group or the porcelain furnace oxide surface group. This suggests that the less-technique-sensitive porcelain furnace oxide surface treatment offers an alternative for achieving high metal-resin bonds to a high Pd?Cu alloy.

Notizen: Abstract: Aromatic l-amino acid decarboxylase (AADC) is found in both neuronal cells and nonneuronal cells, and a single gene encodes rat AADC in both neuronal and nonneuronal tissues. However, two cDNAs for this enzyme have been identified: one from the liver and the other from pheochromocytoma. Exons 1a and 1b are found in the liver cDNA and the pheochromocytoma cDNA, respectively. In the third exon (exon 2), there are two alternatively utilized splicing acceptors specific to these exons, 1a and 1b. Structural analysis of the rat AADC gene showed that both alternative promoter usage and alternative splicing are operative for the differential expression of this gene. To demonstrate whether alternative promoter usage and splicing are tissue specific and whether the exons 1a and 1b are differentially and specifically transcribed in nonneuronal and neuronal cells, respectively, in situ hybridization histochemistry for the rat brain, adrenal gland, liver, and kidney was carried out using these two exon probes. The exon 1a probe specifically identified AADC mRNA only in nonneuronal cells, including the liver and kidney, and the exon 1b probe localized AADC mRNA to monoaminergic neurons in the CNS and the adrenal medulla. Thus, both alternative promoter usage and differential splicing are in fact operative for the tissue-specific expression of the rat AADC gene.

Notizen: Background: The current use of collagen vascular hemostasis devices to percutaneously seal femoral arteriotomy sites is limited by a significant incidence of vascular complications. The purpose of the present study was to assess the efficacy of new collagen plug specifically designed to avoid these complications by accurately gauging the depth of the femoral artery and by minimizing the risk of intra-arterial collagen deployment. Methods: The hemostasis device used in this study consists of a multicomponent collagen plug with an external rigid collagen tube lined by an inner layer of absorptive sponge collagen. Placement of this plug is facilitated with a specialized two-lumen dilator, which localizes the arterial surface using a “bleedback” mechanism from one of the lumens, and prevents the placement of collagen through the arteriotomy site. The acute efficacy of this device was assessed in 26 adult dogs in which 36 collagen plugs were used to seal 8Fr femoral arteriotomies. An additional 16 arteriotomies treated with standard manual compression served as study controls. Following plug placement or manual compression, all puncture sites were observed for bleeding and hematoma formation over a 45-minute period. Patency of each instrumented artery was assessed with serial femoral angiography and localization of each plug was confirmed with surgical cutdown at the puncture site. The chronic efficacy of this device was assessed in three pigs in which three collagen plugs were used to seal 8Fr femoral arteriotomies. The three animals were subsequently sacrificed at 7,14, and 30 days, respectively, for histologic analysis. Results: In acute animals, all 36 plugs were successfully placed without evidence of vascular compromise or intra-arterial collagen deployment. In nonanticoagulated animals, hemostasis was achieved within 5 minutes in 10 of 10 plugs placed with a skin-to-arlery distance 〉 1.8 cm, in 4 of 7 plugs with a skin-to-artery distance of 1.2–1.7 cm, and in 0 of 9 plugs with a skin-to-artery distance 〈 1.2 cm. In anticoagulated animals, hemostasis within 5 minutes was demonstrated with 8 of 10 plugs with a skin-to-artery distance 〉 1.8 cm; small hematomas occurred in the remaining two animals in the setting of a PTT 〉 100 seconds. Time to hemostasis was significantly less for collagen plugs than manual compression in both nonanticoagulated animals (plug 17 ± 16 minutes; manual compression 28 ± 5 minutes; P 〈 0.03) and anticoagulated animals (plug 6 ± 2 minutes; manual compression 42 ± 4 minutes; P 〈 0.01). Chronic studies demonstrated femoral artery patency in all three pigs. Histologic analysis demonstrated progressive collagen resorption with no difference between collagen plug placement or manual compression at 30 days. Conclusions: The local hemostasis device utilized in this study resulted in accurate placement of a collagen plug immediately adjacent to the arteriotomy site with no evidence of acute or chronic vascular compromise or intra-arterial collagen deposition. Hemostasis with shorter compression times than with standard manual techniques was achieved at puncture sites in which the skin-to-artery distance was 〉 1.8 cm and the anticoagulation profile was not excessive. At 1 month postplacement, there is no histologic difference between plug use and standard manual compression. (J Interven Cardiol 1996;9:25–33)

Notizen: The purpose of this paper is to investigate the impact of locational and individual characteristics upon interstate retiree migration, particularly in state-level public policy variables. Data regarding the characteristics of individual movers are drawn from the 1990 US. Census of Population and Housing 5% Public Use Microdata Sample. The household data are merged with location-specific attributes including both natural amenities and local fiscal variables. Three specifications of the model are estimated. The “push” model analyzes the impact of origin characteristics upon migration between states, while the “pull” model demonstrates the influence of destination characteristics upon interstate migration. The final specification is the “difference” model, which measures the actual changes in site characteristics experienced by migrants in their location decisions. The results indicate that both personal and locational characteristics are important factors determining the decision of elderly migrants to change their state of residence. While there is some limited support for the push and pull specifications, the difference model is found to provide the best overall fit.

Notizen: Variation in the fatty acid profile of Staphylococcus aureus WRRC B124 grown at varying temperatures was determined. The range of incubation temperatures tested induced both qualitative and quantitative differences in S. aureus fatty acid profile. While branched chained saturated fatty acids were the predominate species at 37C, C18:1 and C16:1 monounsaturated fatty acids were predominant at lower temperatures (12 and 19C). Iso-branched C14:0, C16:0 and C18:0 saturated fatty acids were expressed exclusively at 37C and several C17:0 and C20:0 fatty acids were suppressed at 12C. Results demonstrated that S. aureus had altered fatty acid profile in response to changes in growth temperature.

Notizen: The prognostic value of serial measurements of serum albumin concentration during the first 72 h after admission to a general adult intensive care unit was retrospectively reviewed in 348 consecutive critically ill patients over a one year period. The accuracy of the admission APACHE II (Acute Physiology And Chronic Health Evaluation) score in correctly predicting patient outcome was compared with the serum albumin concentration measured at different times after intensive care unit admission. Multiple logistical regression analyses were performed to evaluate whether combining APACHE II and serum albumin into a unified risk index improved prognostic accuracy. Serum albumin concentration on admission was lower in non-survivors than in survivors and decreased more rapidly in non-survivors (p 〈 0.001). The admission serum albumin concentration was found to be an insensitive prognostic indicator. However, serum albumin measured after 24 h was as accurate as the admission APACHE II score in correctly classifying patients according to outcome. There was a good correlation between the admission APACHE II score and serum albumin measured after 24 h but not between the admission APACHE II and the admission serum albumin. Combining the APACHE II score and serial albumin concentrations into a unified risk of death equation did not improve the accuracy of outcome prediction.

Notizen: Urea and creatinine clearances achieved using continuous veno-venous haemofiltration were calculated in 16 critically ill patients, during 50 episodes of filtration. The effects of filter life and the volume of ultrafiltrate on these clearances were also evaluated. Clearances were calculated from urea and creatinine concentrations in blood and ultrafiltrate and the volume of ultrafiltrate produced. The overall mean (SD) urea clearance was 26.6 (6.0) ml.min-1 and the overall creatinine clearance was 30.1 (6.3) ml.min-1. The mean (SD) ultrafiltrate production was 29.6 (5.9)ml.min-1. Creatinine clearance was significantly lower in, filters that failed within 24 h (filters 〈 24h 27.5 (6.3) ml. min 1, filters 〉 24 h 32.2 (5.5) ml.min-1). The clerance of both solutes increased with increasing ulfrafiltrate volume (p 〈 0.001). We conclude that satisfactory clearance of urea and creatinine can be achieved using continuous two-venous haemofiltration. Increases in ultrafiltrate production lead to similar increases in urea and creatinine clearance. Prolongation of filter life may improve creatinine clearance.