Biomedical subjects

D G Greenhalgh

Publications and source records attributed to D G Greenhalgh.

At least 55 records · Page 3Linked to original sources

PubMedDate not supplied

Wound healing in the transforming growth factor-beta-deficient mouse.

To investigate the role of transforming growth factor-beta(1) in tissue repair, we performed wound healing studies in the transforming growth factor-beta(1)-deficient mouse with targeted disruption of the transforming growth factor-beta(1) gene. Transforming growth factor-beta(1)-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 x 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-beta(1)-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-beta(1), transforming growth factor-beta(2), platelet-derived growth factor A-chain and B-chain, interleukin-1beta and -6, and tumor necrosis factor-alpha 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-beta(1)-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-beta(1) was expressed in controls but not mutants. Transforming growth factor-beta(2), platelet-derived growth factor A-chain and B-chain, and tumor necrosis factor-alpha were constitutively expressed in unwounded skin, day 10 wounds, and liver of both controls and mutants. Interleukin-1beta and -6, however, were induced after wounding. Early wound healing in the transforming growth factor-beta(1)-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-beta(1) transmitted in milk. Loss of transforming growth factor-beta(1) 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-alpha, interleukin-1beta and 6). The severe wasting syndrome (marked by weight loss) undoubtedly has an adverse effect on wound healing.

Journal Article↗

PubMedDate not supplied

Capillary morphogenesis during healing of full-thickness skin grafts: an ultrastructural study.

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 x 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.

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PubMedDate not supplied

Surface electrical capacitance as an index of epidermal barrier properties of composite skin substitutes and skin autografts.

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.

Journal Article↗

PubMedDate not supplied

Mouse models to study wound closure and topical treatment of infected wounds in healing-impaired and normal healing hosts.

Full-thickness wounds were made on the backs of wound healing-impaired diabetic mice and their normally healing litter mates. The wounds were then inoculated with 10(4) colony-forming units of Pseudomonas aeruginosa. In both cases, the inoculum increased rapidly to between 10(9) and 10(10) colony-forming units/wound area. The infection caused a significant decrease in wound closure in the normally healing mice. In the wound healing-impaired diabetic mice, infection increased the size of the wound area over 100% by day 21. The wound became filled with inflammatory cells and serous fluid, and the mice lost significant amounts of weight, an additional sign of severe, ongoing infection. Early antimicrobial treatment of infected wounds in diabetic mice (1 hour after wounding and microbial inoculation) reversed the increase in wound size area, improved wound closure, and reduced to a significant degree the weight loss observed in untreated control mice. Delay in treatment for as little as 8 hours significantly reduces the efficacy of antimicrobial treatment. These models can be used to study the effects of infection as well as to determine the efficacy of topical antimicrobial and/or wound healing-enhancing substances on these wounds in both normally healing and healing-impaired hosts.

Journal Article↗

PubMedDate not supplied

Proteolytic activity in human burn wounds.

Wound healing is the result of a dynamic balance between synthetic and degradative processes. After a burn, proteolytic activity increases at the wound site. Excised burn wounds and donor skin were examined from 20 pediatric burn patients, to determine which of two classes of neutral proteinases, serine or metalloproteinases, accounts for the majority of this proteolytic activity in these tissues; to examine messenger RNA expression of three of the principal enzymes and inhibitors of this class; and to measure enzymatic activity of two of these metalloproteinases. The majority of the increased proteolysis was due to metalloproteinases. By polymerase chain reaction assays, messenger RNAs for matrix metalloproteinase-1, -3, and -9 were strongly expressed in burn tissue and absent or weakly expressed in unburned skin. Messenger RNA for tissue inhibitor of metalloproteinase-1 and -2 was consistently present in burned and unburned skin. By zymography, there was a significant increase in matrix metalloproteinase-2 (twofold to threefold) and matrix metalloproteinase-9 (20- to 30-fold) activity in burned versus unburned skin. We suggest that postburn there is an upregulation of some matrix metalloproteinases that exceeds the level of inhibitors with the net result of an increase in proteolysis in burned tissue. This increased proteolysis may play a role in wound repair and scar formation.

Journal Article↗

PubMedDate not supplied

Gelatinase activity in keloids and hypertrophic scars.

Keloids and hypertrophic scars are characterized by excessive deposition of collagen, which may result from insufficient protein degradation. Little is known about the levels of two gelatinases, matrix metalloproteinase-2 (72 kD type IV collagenase) and matrix metalloproteinase-9 (matrix metalloproteinase-9; 92 kD type IV collagenase) in these abnormal scars. The purpose of this study was to determine levels of these proteinases in tissue from hypertrophic scars, keloids, and donor skin. Ten hypertrophic scar samples, 9 keloid samples, and 10 donor skin samples were frozen, pulverized, homogenized, clarified by centrifugation, and analyzed for matrix metalloproteinases by quantitative zymography. Identity of matrix metalloproteinases was determined using a conditioned media reference standard, molecular weight ladders, and Western blotting. Levels of matrix metalloproteinase-9 activity were very low or undetectable in all samples. However, matrix metalloproteinase-2 activity was significantly elevated in keloids and hypertrophic scars vs. donor samples: 2.6 and 3.9-fold increases for latent matrix metalloproteinase-2, 7.8 and 6.9-fold increases for active matrix metalloproteinase-2, respectively. We conclude that little matrix metalloproteinase-9 activity (the gelatinase involved in early tissue repair) is present in keloids and hypertrophic scars, while matrix metalloproteinase-2 activity (the gelatinase involved in prolonged tissue remodeling) is present in donor skin and is significantly increased in hypertrophic scars and keloids.

Blotting, Western↗

PubMedDate not supplied

Expression and localization of p53 and bcl-2 in healing wounds in diabetic and nondiabetic mice.

In a healing wound, inflammatory cells undergo apoptosis immediately beneath the leading edge of migrating epithelium. A potential mediator of this apoptosis pattern is p53, a protein with antiproliferative effects. Another protein, bcl-2, is antagonistic to p53 and prevents apoptosis. The purpose of this study was to determine the expression and location of p53 and bcl-2 mRNA and protein in healing wounds of normal and genetically diabetic mice. At various time points, full-thickness skin wounds from nondiabetic and diabetic mice were evaluated for p53 and bcl-2 by immunohistochemistry and in situ hybridization. Apoptosis patterns were also determined using the TUNEL method. Messenger RNA for p53 and bcl-2 were quantitated by competitive reverse transcriptase-polymerase chain reaction. Protein and mRNA for p53 were expressed in the leading edge of migrating epithelium, with apoptosis patterns closely following those of p53 production. p53 mRNA levels decreased soon after wounding, but after a few days, levels increased to greater than baseline. bcl-2 was localized to the wound epithelium, but relative amounts tended to oppose levels of p53, i.e, when p53 increased, bcl-2 decreased and vice versa. Wounds in diabetic animals showed a delayed onset of p53 mRNA expression but had persistently greater levels for longer periods of time. bcl-2 mRNA expression was further delayed in diabetic mice and did not develop to levels as high as p53. Production of both proteins was delayed, consistent with the mRNA expression. Our data show that immediately after wounding, bcl-2 increases and p53 decreases to allow for the cellular proliferation that is required for tissue repair. Over time, bcl-2 levels decrease while p53 levels increase to shut down the inflammatory process and down-regulate the proliferative response. Diabetic animals appear to lose the indirect relationship between p53 and bcl-2. This loss may contribute to the altered apoptosis patterns observed in diabetic healing.

Animals↗

PubMedDate not supplied

Transcutaneous oxygen and carbon dioxide measurements for determination of skin graft "take".

The feasibility of using transcutaneous partial pressure of oxygen (TCPO2) and transcutaneous partial pressure of carbon dioxide (TCPCO2) measurements as a way of determining skin graft "take" was investigated in 13 patients who received partial-thickness sheet grafts. Transcutaneous measurements were obtained from the graft and an area of normal skin starting on the day of surgery and then daily for 2 weeks. No complications or discomfort resulted from the determinations. Initially, graft TCPO2 was extremely low (less than 8 mm Hg) and never rose above a value of 30 to 40 mm Hg, whereas skin levels ranged between 60 and 80 mm Hg. Graft TCPO2 levels never approached skin levels until graft maturity was achieved. Graft TCPCO2 levels were 80 to 100 mm Hg on the first few days after grafting but decreased to levels just above those of the skin (40 to 50 mm Hg) by 5 to 6 days after grafting. Graft TCPCO2 normalized at the time of clinical graft vascularization and remained levels just above those of the skin throughout the remainder of the study. Graft TCPCO2 determinations provide a noninvasive and objective measure of skin graft vascularization, and graft TCPO2 values reflect graft maturity.

Blood Gas Monitoring, Transcutaneous↗

PubMedDate not supplied

Comparison of back versus thigh donor sites in pediatric patients with burns.

To substantiate an observation that donor sites that are harvested from the back scar less than those that are harvested from thighs, donor sites from both areas were evaluated for the extent of scarring. For donor sites that were harvested more that 1 year before evaluation, no significant improvements were observed. Back donor sites that were evaluated less than or equal to 1 year after harvest had significant improvements in height, color, edema, suppleness, and cosmetic appearance than those harvested from thighs. Thirty-two patients had both back and thigh donor sites harvested at the same time. Back donor sites had significant improvement in scar height, color, and edema. Cosmetic improvements were also observed. Significantly more patients preferred the back donor site over that of the thigh. The back is the preferred donor site for skin grafts in the pediatric burn population.

Back↗

PubMedDate not supplied

A comparison of full-thickness versus split-thickness autografts for the coverage of deep palm burns in the very young pediatric patient.

From 1984 through 1989, 24 patients with 30 acute palmar burns (six were bilateral) that required skin grafting were evaluated to compare the efficacy of split-thickness versus full-thickness autografting. Sixteen of the palms had split-thickness skin grafts and 14 had full-thickness skin grafts. Normal range of motion was found in 8 of 14 palms that were treated with full-thickness skin grafts and in 4 of 16 for those that were treated with split-thickness skin grafts. Significantly fewer reconstructive surgical procedures were required in the palm burns that were treated with full-thickness skin grafts (full-thickness = 3 of 14 and split-thickness = 10 of 16). The results demonstrate improved function and decreased need for reconstructive procedures when full-thickness skin grafts are used for the treatment of deep palm burns in young pediatric patients.

Acute Disease↗

PubMedDate not supplied

The early release of axillary contractures in pediatric patients with burns.

In spite of the common teaching that contracture releases should be avoided until scars have matured, the Cincinnati Shriners Burns Institute has been releasing contractures in immature scars to prevent prolonged loss of range of motion. To evaluate the efficacy of axillary releases and, especially, to determine whether releases performed in immature scars were detrimental, axillary releases that were performed between January 1, 1988 and December 31, 1989 were evaluated for improvements in abduction and flexion. Overall, axillary releases significantly improved abduction and flexion, and the improvement was maintained for at least 1 year. Comparison of early (less than 1 year after burn injury) with late (more than 1 year after burn injury) releases revealed that the preoperative limitation was worse in the early release group but that the ultimate outcomes were similar. Waiting for scars to mature before performance of contracture releases is not necessary.

Adolescent↗

PubMedDate not supplied

Outcome and socioeconomic aspects of suspected child abuse scald burns.

Fifty-two children suffering from abuse-related scald burns were admitted between January 1, 1986, and June 30, 1991. Their clinical and socioeconomic aspects were compared with those of 50 nonabused scalded children. Patients were matched for age, total body surface area burn, and percentage of full-thickness burn. Patient characteristics and initial nutritional parameters were similar except for race; a higher percentage of black children were in the abused group. A significantly longer length of hospital stay was found in the abused children after using analyses of covariance to control for percentages of total and full-thickness body surface area burn. The number of operations and frequency of complications were increased in the abused group, but not significantly so. Several significant differences were found in the socioeconomic characteristics of the two groups. Children suspected of being scalded intentionally were more likely to be part of a broken home, belong to a single parent, and have a younger mother than were children in the control group. The majority of the parents of abused children were unemployed, and all but two earned less than $20,000/year. All but one of the abused children were discharged with a person other than their parents, and compliance with rehabilitation follow-up was significantly worse than with the control group. The person suspected of performing the abuse was always a family member, except in cases where the baby-sitter was the suspected abuser. Child abuse hurts not only the child but also society by increasing the need for resources to pay for extended hospital admissions.(ABSTRACT TRUNCATED AT 250 WORDS)

Black or African American↗

PubMedDate not supplied

Delivery and activity of antimicrobial drugs released from human fibrin sealant.

Engraftment and healing of native or cultured skin grafts depend on adherence, vascularization, and control of microbial contamination in the wound bed. Fibrin sealant is a biocompatible polymer that may be used to promote skin engraftment by serving as a delivery vehicle for antimicrobial drugs. Human fibrin sealant (25 mg/ml) was polymerized with antibacterial agents (mupirocin [32 micrograms/ml], nitrofurazone [0.02% wt/vol], polymyxin B [400 U/ml], or norfloxacin [20 micrograms/ml]) on nitrocellulose (nc) backing and was prepared as 6 mm diameter discs with skin punches. Discs (n = 6) were applied in the Wet Disc Assay to clinical isolates of Staphylococcus aureus (mupirocin, nitrofurazone) or Pseudomonas aeruginosa (polymyxin B, norfloxacin). Controls included drug applied to 6 mm paper discs (25 microliter) and nitrocellulose discs submerged in each drug, blotted, and applied to bacterial cultures on agar in petri dishes. Data were expressed as zone of clearing (mm diameter +/- SEM) after overnight incubation at 35 degrees C. Significant differences (ANOVA and Turkey's test, p < 0.05) were found for each drug released from the disc of fibrin sealant compared with other vehicles. Release from filter paper discs compared with nitrocellulose was significant for nitrofurazone and norfloxacin. Serial transfer of fibrin discs to fresh bacterial cultures after 24 hours showed no zones of clearing. The data show that fibrin sealant releases topical drugs with no inhibition of antimicrobial activity on burn organisms. Greater zones of clearing from fibrin sealant may result from passive fluid retention or from active binding to fibrin followed by protease digestion by burn organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Bacterial Agents↗

PubMedDate not supplied

The management of perineal contractures in children with burns.

A retrospective review of patients undergoing reconstruction for perineal scar contracture between 1980 and 1991 was performed to determine the surgical principles involved in perineal contracture release. Of the 5280 reconstructive admissions, 18 (0.34%) were for perineal contracture release. Fifty-six percent of patients received a local flap as an initial release, 28% underwent incisional release with split-thickness skin grafting (STSG), 5% had primary release and closure, and 11% had a combination of these techniques. Recurrences developed in 40% of the local flap group, 20% of the STSG group, and 50% of the combination group, with no statistical differences between groups. Although there was a higher rate of recurrence in the flap group, the procedure was much simpler to perform and recovery time was shorter. The use of STSG should be reserved for large bilateral contractures and recurrences, especially if normal skin for a flap is not available. Growth is an important variable in the development of perineal contractures in children with burns; thus these patients should be followed up closely during rapid-growth periods.

Adolescent↗

PubMedDate not supplied

Cardiac abnormalities in children with burns: an autopsy analysis.

After observing several cases of endocarditis-related deaths, we determined the contribution of cardiac abnormalities to burn mortality. Autopsy reports of all burn-related deaths between 1964 and 1992 (n = 212) were reviewed for cardiac disease. Cardiac abnormalities were categorized into infectious, acquired, or congenital. Cardiac abnormalities of all forms were associated with longer hospitalizations before death and affected a larger proportion of females than expected in the male-dominated burn population. The highest incidence of endocarditis (17.3% of all deaths) occurred in the past 5 years. The frequency of other forms of cardiac abnormalities has not changed over time. Improved burn management has resulted not only in improved survival but has also prolonged the duration of hospitalization of those patients who ultimately die of their injuries. As patients are kept alive for longer periods, the incidence of endocarditis and the cardiac manifestations of multiple organ failure have increased.

Autopsy↗

PubMedDate not supplied

A prospective study of burn scar maturation in pediatrics: does age matter?

A prospective study was performed to determine whether patterns of burn scar maturation varied among different pediatric age groups. Patients were divided into three groups according to age at the time of burn injury: birth to 3 years, 4 to 11 years, and 12 to 18 years. Scarring of sheet grafts on an extremity was assessed throughout the maturation process in three areas: vascularity, pliability, and height. A 1-inch square was selected on the graft edge adjacent to unburned skin. Two experienced therapists independently evaluated the test area and averaged their scores. There were no significant differences in rate of scar maturation between age groups. Burn scar maturation of sheet skin grafts in the pediatric patient with burns demonstrated a rapid peak of scarring (1 to 2 months) and scar maturation (9 to 13 months).

Adolescent↗

PubMedDate not supplied

Use of a helium-oxygen mixture in the treatment of postextubation stridor in pediatric patients with burns.

A mixture of helium and oxygen is less dense than room air. This property allows the gas to flow with less turbulence past airway narrowings, thereby decreasing airway resistance and increasing the volume of gas exchange. Previous studies demonstrated that airway obstruction that is manifested by stridor was present in 92% of patients requiring reintubation. Eight pediatric patients with burns in whom postextubation stridor or retractions unresponsive to racemic epinephrine developed, were treated with "heliox" (helium and oxygen) for 28 +/- 5 hours with an initial helium concentration between 50% and 70%. Of the eight patients treated with heliox, only two experienced respiratory distress and required reintubation. Both patients had stridor for a longer time before the initiation of heliox therapy compared with those patients who did not require reintubation. After initiation of heliox therapy, patients experienced a significant decrease in respiratory distress scores (6.8 +/- 0.7 vs 2.0 +/- 0.7). Heliox was able to relieve persistent stridor and thereby aid in the prevention of respiratory distress and reintubation.

Airway Obstruction↗

PubMedDate not supplied

The use of haloperidol in the agitated, critically ill pediatric patient with burns.

Haloperidol has become the drug of choice for sedation of the acutely agitated, delirious adult patient in the critical care setting because of its well-documented efficacy and lack of major side effects. Its use in the critically ill pediatric patient with burns has not been described. To determine the safety and efficacy of haloperidol in this population, the medical records of 30 critically ill pediatric patients with burns treated with haloperidol during the period 1986 to 1992 were reviewed. Our findings support the safe and effective use of haloperidol to treat severe agitation and delirium in the critically ill pediatric patient. The intravenous route appears to be more effective than the enteral route and should be considered when rapid, acute control of agitation is required.

Adolescent↗