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Biomedical subjects

J F Hansbrough

Publications and source records attributed to J F Hansbrough.

At least 37 records · Page 2Linked to original sources
PubMed1995

Soft tissue infection prophylaxis with gentamicin encapsulated in multivesicular liposomes: results from a prospective, randomized trial.

OBJECTIVES: Systemically administered antibiotic agents are not evenly distributed in the body, which frequently results in subtherapeutic regional drug concentrations, particularly in areas of poor vascularization, including wound sites. We have developed a lipid-based drug delivery system to provide prolonged levels of gentamicin in local tissues after local administration. Multivesicular liposomes are microspheres composed of lipid bilayer membranes surrounding multiple aqueous compartments that can contain drug. The preparation may be effective for the prevention and treatment of a variety of infections, including infections associated with indwelling vascular catheters. DESIGN: Prospective, randomized trial. SETTING: Animal laboratory. SUBJECTS: Mice, 6 to 12 wks of age, weighing 20 to 30 g. INTERVENTIONS: We administered 0.5 mg of gentamicin encapsulated in multivesicular liposomes to dorsal subcutaneous tissue in mice. Animals were inoculated with 10(5) to 10(7) colony-forming units (cfu) of Staphylococcus aureus 2, 4, 6, and 8 days later. The cfu/g of tissue values were determined 2 days after inoculation. MEASUREMENTS AND MAIN RESULTS: With a 10(7) cfu challenge, animals that received 2- and 4-day pretreatment with multivesicular liposome/gentamicin had a 4 log10 reduction in cfu/g of tissue compared with controls. When 10(5) cfu of Staphylococcus aureus were inoculated after 2- and 4-day pretreatment with multivesicular liposome/gentamicin, a 6 log10 reduction in bacteria colony-forming units was observed. CONCLUSION: Local injection of multivesicular liposome/gentamicin provides sustained drug concentrations in regional tissues that protect against a massive bacterial challenge for at least four subsequent days.

Animals↗
PubMed1995

Lipid-based slow-release formulation of amikacin sulfate reduces foreign body-associated infections in mice.

Treatment and prophylaxis of uncomplicated infections with standard systemic antibiotics are usually successful. However, standard systemic antibiotic therapy alone is frequently unsatisfactory in certain circumstances, such as the presence of a foreign body (FB), necrotic tissue, overwhelming bacterial inoculum, or poor vascular supply to the involved tissues. We have developed a lipid-based sustained release formulation of amikacin sulfate (DepoFoam encapsulated amikacin sulfate [DEAS]) as a biodegradable, locally injectable antibiotic for such circumstances. The encapsulated drug is released over 7 to 10 days. We tested the efficacy of this formulation in an FB infection model in which Teflon tubes (length, 1 cm; outside diameter, 1.6 mm) were implanted into the subcutaneous tissue in mice and the local site was inoculated with 0.87 x 10(7) CFU of Staphylococcus aureus 3 days later. Inoculation was followed by either no treatment or a local injection of DEAS, free amikacin sulfate, non-drug-containing DepoFoam, or systemic free amikacin sulfate. All drug applications contained 1 mg of amikacin. One group was implanted with the FB and left unchallenged with bacteria and untreated as a sterile control group. All animals were sacrificed 10 days following FB implantation. FBs were retrieved from tissues by an aseptic technique and incubated in liquid culture media for 7 days. Local wound tissue was excised and processed to determine the number of CFU per gram of tissue. Treatment with local or systemic free amikacin had no effect on the number of infected FBs or on the log CFU in wound tissue compared with the untreated or non-drug-containing DepoFoam group. Compared with local free amikacin therapy, the number of infected FBs was reduced from 86 to 25% (P=0.02) following treatment with DEAS, and log CFU per gram of tissue was significantly decreased from 4.8 +/- 0.9 to 1.3 +/- 0.6 (P<0.0005). DEAS may have clinical utility as locally injected antibiotic in certain infections.

Amikacin↗
PubMed1994

Treatment of burned mice with hyperbaric oxygen reduces mesenteric bacteria but not pulmonary neutrophil deposition.

OBJECTIVE: Hyperbaric oxygen (HBO) is used but unproven for many conditions, including burns. We hypothesized that HBO therapy might increase oxygen delivery to intestine during burn shock and decrease mucosal injury. SETTING: University research laboratory. DESIGN AND STUDY PARTICIPANTS: We studied the effects of HBO therapy (100% oxygen at 2.4 atm absolute) on mesenteric bacterial colonies (MBCs) in mice following 32% total body surface area burns. MBCs were counted 24 or 48 hours postburn by culturing mesenteric tissue. Intestinal histologic features were examined, acid-base balance was measured, and pulmonary neutrophil deposition was estimated by lung myeloperoxidase content. INTERVENTIONS: HBO delivered in a compression chamber. MAIN OUTCOME MEASURE: Numbers of mice with MBCs. RESULTS: With twice-daily HBO treatments, each treatment lasting 1.5 or 2 hours, fewer burned mice had MBCs. Three HBO treatments within 24 hours produced seizures, death, and increased numbers of mice with MBCs. Numbers of mice with MBCs were not influenced when compressed air (2.4 atm absolute) or 100% oxygen (1 atm absolute) was used. Villus histologic findings showed less damage in burned mice that received HBO therapy than in controls. Metabolic acidosis was not affected by HBO therapy, nor were lung myeloperoxidase levels. CONCLUSION: HBO therapy was associated with reduced numbers of mice with MBCs after burn injury and reduced histologic evidence of mucosal damage, but lung myeloperoxidase levels and metabolic acidosis were not affected. HBO therapy may increase oxygen delivery to ischemic intestine and improve cellular metabolism; alternatively, increased tissue oxygen may augment killing of translocated bacteria by phagocytic cells. HBO deserves further investigation for burn treatment, but because of the narrow therapeutic window and continued neutrophil sequestration in the lungs, we should proceed cautiously.

Acid-Base Equilibrium↗
PubMed1994

Supplementation of an elemental enteral diet with alanyl-glutamine decreases bacterial translocation in burned mice.

Although there are many reports of the importance of early enteral feeding in maintaining gastrointestinal integrity and preventing bacterial translocation (BT) following burn injury, no diet has been shown clinically to protect the GI tract postburn. Several studies suggest that glutamine (GLN) may benefit gut integrity following injury, shock and other stress. Unfortunately, the free amino acid GLN is unstable in solution. Alanyl-glutamine (ALA-GLN), a soluble form of GLN, maintains long-term stability in solution and could be supplemented to conventional liquid enteral diets. We studied the effects of ALA-GLN supplementation of the elemental diet Vivonex TEN on effecting BT in mice following 32 per cent TBSA full skin thickness burns. Groups A-D were burned. Group A (30 mice) was fed standard rodent chow, which contains extremely high (clinically non-useable) levels of protein. Group B (51 mice) was fasted 24 h, then fed chow 24 h. Group C (64 mice) was fed Vivonex TEN, and Group D (65 mice) received Vivonex TEN plus ALA-GLN (GLN equivalent, 14 g/l). A control group (Group E) consisted of 22 normal mice (no burn injury, chow diet). Mice were assessed for BT by sterile harvesting and plating of mesenteric lymph node tissue, 48 h postburn. Plates were considered positive if any bacterial growth was noted. Non-burned mice exhibited no BT, while burn-fasted mice showed a 64.3 per cent incidence of BT (P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Bacterial translocation in burned mice after administration of various diets including fiber- and glutamine-enriched enteral formulas.

OBJECTIVE: Severe burn injury can produce acute gastrointestinal derangements which may facilitate bacterial translocation to mesenteric lymph nodes. We studied the effects of feeding different dietary formulations on bacterial translocation in burned mice. DESIGN: Prospective, blinded, nonrandomized laboratory study. SETTING: Research laboratory. SUBJECTS: One hundred sixty-nine female, outbred, CF-1 mice, 8 to 12 wks of age. INTERVENTIONS: Anesthetized mice received a 32% total body surface area, full-thickness burn injury. Mice were then fed with: a) mouse chow; b) a low-residue enteral formula; c) a high-protein, high-fat enteral formula; d) an enteral formula with high concentrations of supplemental glutamine; or e) an enteral formula that contains soy fiber. MEASUREMENTS AND MAIN RESULTS: Burned mice that were fed the low-residue enteral formula demonstrated increased mortality rate (21.2%, p = .05) compared with chow-fed mice in the 2-day postburn period (0 mortality); other burn-diet groups had intermediate mortality rates. In surviving mice, bacterial translocation was found to be: a) lowest in the group fed chow (31.0%) and the high glutamine formula (30.8%); b) intermediate in the group fed formula and soy fiber (44.8%, NS compared with burn-chow group); and c) highest in the group receiving the low-residue enteral formula (73.1%, p < .005) and high-protein, high-fat enteral formula (59.3%, p < .05). CONCLUSIONS: Dietary composition markedly affects bacterial translocation in this animal burn model. Commercial enteral diets containing fiber and high concentrations of glutamine provide protection for the gut after burn injury and reduce the occurrence of bacterial translocation in this animal model.

Animals↗
PubMed1994

Reduction of bacterial translocation and intestinal structural alterations by heparin in a murine burn injury model.

Burn injury produces acute gastrointestinal (GI) derangements that may predispose the burn victim to bacterial translocation (BT). We studied the effects of heparin on gastrointestinal (GI) anatomic alterations and BT after 25% and 32% total body surface area (TBSA), full-thickness murine burn injuries. Heparin (100 U/kg) was administered with 1 mL of normal saline (NS) resuscitation solution immediately postburn and 4 hours and 18 hours postburn in volumes of 0.5 mL NS. Mice with 25% TBSA burns treated with heparin maintained small intestine weight, measured 24 hours postburn, and ileal mucosal height was preserved, whereas burned, untreated mice lost organ weight and mucosal height. Bacterial translocation was decreased in mice with 25% TBSA burn injuries treated with heparin (35.0% vs. 10.7%, p < 0.025). After 32% TBSA burn injuries, BT was also decreased in heparin-treated animals (64.3% vs. 31.6%; p < 0.025). Analysis of mixed venous blood gases showed that heparin did not affect the severe metabolic acidosis that follows burn injury in this animal model, indicating that general tissue perfusion was not improved. Heparin administered in the acute postburn period ameliorates GI structural and functional damage in this murine burn model and decreases BT.

Acid-Base Imbalance↗
PubMed1994

Ultrastructural features of composite skin cultures grafted onto athymic mice.

Skin substitutes composed of cultured keratinocytes with or without a dermal substrate are now being used in the treatment of burns and other cutaneous wounds. Composite skin cultures (Graftskin, LSE), consisting of epidermal keratinocytes seeded on a fibroblast-containing collagen matrix and maintained at the air-liquid interface, develop a well differentiated epidermis in vitro with many of the morphological and biochemical features of intact skin. Basement membrane-associated antigens, developing hemidesmosomes and short segments of lamina densa are present at the dermal-epidermal junction in vitro, although the LSE lacks a continuous basement membrane. As epidermal differentiation proceeds, the culture develops a stratum corneum composed of electron-dense corneocytes surrounded by extracellular lipid. However, the intercorneocyte lipid lamellae do not exhibit the repeating pattern of broad and narrow electron lucent bands observed in electron micrographs of the stratum corneum of intact skin. In this study, LSE were grafted onto full thickness wounds in athymic mice. Animals were killed 6, 15, 30 and 60 d after surgery for examination by light and electron microscopy to identify any ultrastructural changes which occurred in the culture in response to the host environment. The grafted LSE integrated well into the host tissue and remained intact throughout the 60 d study period. At the dermal-epidermal junction, a continuous basement membrane with a well defined lamina densa was established by 15 d after surgery. An extensive network of anchoring fibrils was present by 30 d after surgery. Collagen fibrils within the dermal matrix condensed by 6 d after surgery and began organising into loosely packed bundles by 15 d after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Development of a temporary living skin replacement composed of human neonatal fibroblasts cultured in Biobrane, a synthetic dressing material.

BACKGROUND: Preferred coverings for excised burn wounds when sufficient autograft skin is not available are fresh or cryopreserved cadaveric skin. Problems with supply, preservation, immune rejection, and potential infection transmission accompanying the use of allograft skin underscore the need for effective alternative temporary skin replacements. METHODS: We cultured human neonatal fibroblasts (HF) for 4 to 6 weeks in nylon mesh of Biobrane, a synthetic dressing consisting of a thin layer of silicone bonded to nylon mesh. Secreted matrix proteins were identified by immunostaining and quantitated, and growth factor-specific messenger RNAs were identified by reverse transcription-polymerase chain reaction. Living grafts (Biobrane/HF) were sutured to full-thickness, excised wounds on athymic mice; control animals received Biobrane alone. Wounds were observed and biopsy specimens were obtained at intervals during the subsequent 40 days. RESULTS: After 3 to 6 weeks of culture in Biobrane the HF proliferated and secreted matrix proteins including type I collagen, fibronectin, and decorin, as well as messenger RNA for several growth factors (acidic fibroblast growth factor, basic fibroblast growth factor, and keratinocyte growth factor). Biobrane/HF grafts were transferred to full-thickness wounds, resulting in rapid fibrovascular ingrowth from the wound and effective wound closure for up to 40 days with minimal inflammatory responses. Biobrane control grafts adhered initially to wounds, but within several days many grafts developed subgraft exudates; histologic sections revealed marked inflammatory responses in these wounds. By 20 days, most BB grafts were separating from the underlying wounds that were closing by epithelialization and contraction. CONCLUSIONS: The Biobrane/HF living skin replacement provides long-term biologic coverage of full-thickness wound defects in mice with rapid incorporation of a living tissue matrix into the wound bed. Because HF have been found to be relatively nonantigenic when transferred to allogeneic hosts, Biobrane/HF grafts could replace the use of cadaveric allograft skin for achieving temporary wound closure after burn wound excision. Biobrane/HF grafts may persist on human wounds for weeks or months, with long-term persistence perhaps primarily dependent on durability of the silicone rubber layer.

Animals↗
PubMed1993

Pharmacokinetics of DepoFoam gentamicin delivery system and effect on soft tissue infection.

Infections of burn and soft tissue wounds are often difficult to treat with systemic antibiotics since drug delivery to the wound may be suboptimal and high doses may result in toxicity. DepoFoam particles, a novel lipid-based drug delivery system, are composed of phospholipid membranes, enclosing multiple aqueous chambers into which pharmacologic agents can be encapsulated for local drug delivery. We encapsulated gentamicin (GENT) in DepoFoam particles with an average yield of 81% +/- 8 SD for 10 preparations. Encapsulated GENT was incubated in human plasma with t1/2 of 21 days, demonstrating stability in vitro. In vivo pharmacokinetics were determined by injecting CF-1 mice subcutaneously (sc) with a single dose of 0.5 mg of free (nonencapsulated drug) or DepoFoam GENT. At intervals postinjection the sc tissue was excised and blood was obtained by inferior cava puncture and both were assayed for GENT levels. At 0.5, 2, 6, and 24 hr following drug administration there was a significant difference between GENT levels in the tissue achieved with the encapsulated drug and free drug with n = 3-4 at each time point for each group (P < 0.01). By 24 hr following administration of free drug there was minimal detectable GENT in the tissues, while therapeutic levels of GENT remained in tissue at 24 hr following DepoFoam GENT injection. Serum GENT peaked at 30 min for both the DepoFoam (5 micrograms/ml) and free drug (10 micrograms/ml) and was undetectable by 2 hr (n = 3 each group).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Development of a device for measuring adherence of skin grafts to the wound surface.

Adherence of a biological graft to the wound surface is the most important factor influencing the ultimate success of graft viability. A machine has been developed to test the adherence of biological graft materials to a substrate such as a wound surface. The peeling mode, which yields reproducible quantitative measurements of adherence, is a standard method for testing adhesives. The device is designed to continuously measure the force required to peel the graft from the substrate at a constant rate. This force is a function of the energy of adhesion per unit area of adhered surface. This device has been used to measure the peeling force of (2 x 2 cm) skin grafts which are applied to full-thickness wounds on mice. Results of tests on adherence of autografts on mice show that the peeling force increases significantly with time over the first 9 days of healing. Thus, this device is useful in quantitative comparison of various skin grafting techniques and artificial grafts.

Adhesiveness↗
PubMed1993

Quantitation of cytokine levels in skin graft donor site wound fluid.

We quantified endogenous levels of multiple cytokines in skin graft donor site wounds in patients with small to moderate-sized burn injuries. Thirteen patients aged 11 months to 61 years with mean TBSA burn of 4 +/- 1 per cent underwent placement of occlusive wound dressings on partial skin thickness donor site wounds. Fluid was aspirated from beneath the dressing on postoperative day 1 and every subsequent 24 h until no further fluid could be obtained. Interleukin-1 alpha (IL-1) and tumour necrosis factor-alpha (TNF-alpha) levels were determined by enzyme-linked immunosorbent assay (ELISA). Epidermal growth factor (EGF), basic-fibroblast growth factor (bFGF), and platelet-derived growth factor (PDGF) were measured by an enzyme immunoassay (EIA). We found substantial levels of EGF and TNF-alpha in the donor site wound fluid in all 13 patients; detectable levels of bFGF in five patients; and elevated levels of IL-1 in three patients. There were no detectable levels of these cytokines in normal human serum. In contrast, there were no measurable levels of PDGF in any patient's wound fluid; the mean level in serum was 1.5 ng/ml +/- 0.2 s.e.m. Studies of cytokines in the normal wound healing environment may help in the design of future therapies to augment wound healing.

Adolescent↗
PubMed1993

Temporal analysis of human leucocyte surface antigen expression and neutrophil respiratory burst activity after thermal injury.

Sepsis, the major cause of morbidity and mortality after burn injury, is related to multiple immune derangements. Using monoclonal antibodies and two-colour flow cytometry to identify surface antigens, peripheral blood mononuclear cell (PBMC) populations were analysed and correlated with lymphocyte proliferation assays for 21 days postinjury. In addition, in vitro expression of activation antigens by mitogen-stimulated PBMCs was analysed during the time period. Twenty-nine burn patients were studied, with burn injuries ranging from 19 to 97 per cent TBSA; PBMCs from human volunteers were used for control cells. Patients received aggressive enteral nutritional support starting day 1 postburn and underwent early excision and grafting of wounds; no patients developed sepsis during the study period. The most consistent changes in PBMCs after thermal injury were decreased percentages of total T cells (CD3+), T helper/inducer cells (CD4+), and T suppressor/cytotoxic cells (CD8+); the percentages of natural killer (CD16+) cells were not altered. Expression of surface 'activation' antigens on CD4+ and CD8+ cells (HLA-DR, interleukin-2 receptor and transferrin receptor) after mitogen stimulation was significantly depressed as early as 1 day postburn. An early monocytosis was seen on day 1 postburn, but decreases were found on days 4 and 7. Monocyte expression of HLA-DR antigen was suppressed throughout the study. Lymphocyte proliferation after mitogen stimulation and the responses of lymphocytes in mixed lymphocyte culture were suppressed postburn. Neutrophil respiratory burst responses were supranormal on days 1 and 7 postburn, but the differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Effect of corticotropin releasing factor on acid-base alterations and bacterial translocation in a murine model of thermal injury.

Corticotropin-releasing factor (CRF) is a 41 amino acid polypeptide produced by the hypothalamus which has been shown to decrease inflammation and tissue oedema when administered following burns, cold and acid injuries in some animal models, and to increase mesenteric blood flow. We determined whether systemic administration of CRF to burned mice would decrease metabolic acidosis and protect the gastrointestinal (GI) tract from ischaemic injury leading to bacterial translocation (BT). Synthetic CRF was administered by intraperitoneal injection in doses of 20 and 200 micrograms/kg to mice immediately following 25 and 32 per cent TBSA burn injuries; the doses were repeated at 8 and 16 h postburn. Severe metabolic acidosis, measured 12 h after burn injury, was not improved in mice which received CRF treatment. Bacterial translocation, measured by quantifying bacteria in mesenteric lymph nodes harvested from animals 48 h postburn, was also not decreased with CRF treatment. CRF does not improve general tissue perfusion nor decrease GI derangements leading to bacterial translocation in this animal model of burn injury.

Acid-Base Equilibrium↗
PubMed1993

Direct comparison of a cultured composite skin substitute containing human keratinocytes and fibroblasts to an epidermal sheet graft containing human keratinocytes on athymic mice.

This study compares two techniques for making cultured skin substitutes: a composite graft made of human fibroblasts and keratinocytes on a collagen-glycosaminoglycan membrane (CG) and a cultured epidermal cell sheet graft (CEG), without a dermal component. The "take" and quality of these cultured skin substitutes were evaluated by placing them on full-thickness, excised wounds of athymic mice. These cultured skin substitutes were placed onto 2-X-2-cm wounds created on athymic mice. Mice were sacrificed at days 10, 20, and 42 with histologic sections obtained for light, electron, immunofluorescent, and immunohistochemical microscopy. "Take" was determined separately by a direct immunofluorescent stain for human leukocyte ABC antigens. There were ten mice of each graft type with at least two animals sacrificed at each time point. Results showed positive "take" for all animals. Grossly, there was little difference between the two graft types, with the CEG having occasional blister formation. By light microscopy, the CEG had a dissociation of dermis from epidermis until day 42, which was never apparent with the CG. By day 42, the CG had increased dermoepidermal interdigitations similar to rete ridges, with a mature epithelium. Neither of these findings were seen with the CEG. Immunofluorescent and immunohistochemical microscopy for type IV collagen and laminin, as well as electron microscopy, showed similar retardation of basement membrane formation with the CEG. Using this model, the composite graft had significant advantages over the epidermal sheet graft in the closure of full-thickness wounds.

Animals↗
PubMed1993

Epidermal growth factor limits structural alterations in gastrointestinal tissues and decreases bacterial translocation in burned mice.

BACKGROUND: Burn injury produces acute gastrointestinal derangements that may predispose to bacterial translocation (BT). We studied effects of recombinant human epidermal growth factor (r-HuEGF), a gastrointestinal trophic hormone, on gastrointestinal alterations and BT after murine burn injury. METHODS: r-HuEGF was administered 1 and 12 hours after burn injury in a dose of 4 micrograms per animal subcutaneously after 25% and 32% total body surface area (TBSA) scald burn. Small bowel and gastric weight and histologic factors were studied, and BT was measured by culturing mesenteric lymph nodes. RESULTS: Mice treated with r-HuEGF maintained gastric and small intestine weight measured 24 hours after burn injury, and ileal mucosal height was preserved, whereas burned-untreated mice lost organ weight and mucosal height. BT was decreased significantly in mice with 32% TBSA burn injury treated with r-HuEGF after injury (burn, 64.2% of animals had BT; burn-r-HuEGF, 34.6% had BT; p < 0.05). After 25% TBSA burn injury, BT was also decreased in r-HuEGF-treated animals (burn, 31.4% of animals had BT; burn-r-HuEGF, 14.3% had BT), but the difference was not statistically significant (p < 0.1). CONCLUSIONS: r-HuEGF improves intestinal and gastric structure in mice 24 hours after burn injury and decreases BT after 32% TBSA burn injury.

Absorption↗