Biomedical subjects

F Berthiaume

Publications and source records attributed to F Berthiaume.

At least 19 recordsLinked to original sources

PubMed2005

Optimization of microbial DNA extraction and purification from raw wastewater samples for downstream pathogen detection by microarrays.

Numerous waterborne pathogens are difficult to detect and enumerate with accuracy due to methodological limitations and high costs of direct culturing. The purity of DNA extracted from wastewater samples is an important issue in the sensitivity and the usefulness of molecular methods such as polymerase chain reaction (PCR) and hybridizations on DNA microarrays. Ten different DNA extraction procedures, including physical and chemical extraction and purification steps, were examined to ascertain their relative effectiveness for extracting bacterial DNA from wastewater samples. The quality of the differentially extracted DNAs was subsequently assessed by PCR amplification and microarray hybridization. Our results showed that great differences existed among the ten procedures and only a few of the methods gave satisfactory results when applied to bacterial pathogens. This observation suggested that the extraction method needed to be carefully selected to produce significant and confident results in the detection of pathogens from environmental samples.

Bacteria↗

PubMed2004

Expression profiling analysis of the metabolic and inflammatory changes following burn injury in rats.

Burn injury initiates an inflammatory response as part of the healing process that is associated with extensive metabolic adjustments. While most studies have focused on understanding these changes from a biochemical perspective, not much work has been done to characterize these processes at the gene expression level. As a first step, we have comprehensively analyzed changes in gene expression in rat livers during the first 24 h after burn injury using Affymetrix GeneChips, which showed 339 genes to be differentially expressed at a statistical significance of P < 0.05 and changed at least twofold. Functional classification based on gene ontology terms indicated that two categories, metabolism (28%) and inflammation (14%), accounted for nearly 42%. Detailed analysis of the metabolism group of genes indicated that fatty acid (FA) and triglyceride (TG) biosynthesis in the liver were unchanged, whereas TG utilization, FA import, and beta-oxidation increased after burn injury. The increased FA pools after burn injury appear to serve as substrates for ATP production. Following burn injury, the cholesterol biosynthetic pathway was suppressed while cholesterol was increasingly imported and converted into bile acids. The inflammatory genes that were altered included several classic acute phase response markers, as well as genes involved in the complement, kinin, clotting, and fibrinolytic protein systems. These temporally coordinated changes in gene expression were also corroborated by biochemical measurements for FA, TG, cholesterol, and ATP. Together, these data indicate that FA are increasingly imported and oxidized in the liver to meet the enhanced energy demands arising from an inflammatory response during the first 24 h after burn injury.

Adenosine Triphosphate↗

PubMed2002

Critical issues in bioartificial liver development.

End-stage liver disease accounts for over 30,000 deaths annually in the United States. Orthotopic liver transplantation is the only clinically proven treatment for patients with end-stage liver failure. A limitation of this therapy is a shortage of donor organs available. This donor organ shortage is exacerbated by the fact that the number of patients listed for transplantation has continued to increase. As a result, there has been a continuing increase in the number of patients who die waiting for a donor liver. Extracorporeal bioartificial liver devices consisting of viable hepatocytes have the potential to provide temporary support for patients with fulminant hepatic failure, thereby serving as a "bridge" to transplantation. In some patients, this temporary support would allow the native liver to regenerate function, eliminating the need for transplantation and the resulting life-long immunosuppressive therapy, all of which translates into a cost savings to the health care system. Although the bioartificial liver device is a promising technology for the treatment of liver failure, significant technical challenges remain in order to develop systems with sufficient processing capacity and of manageable size. An overview of the critical issues in the development of bioartificial liver devices is discussed.

Animals↗

PubMed2001

Poloxamer-188 improves capillary blood flow and tissue viability in a cutaneous burn wound.

After cutaneous burn injury, an area of tissue 1-2 mm thick surrounding the wound is the site of a pronounced inflammatory response where blood flow is reduced. This "zone of stasis" undergoes progressive necrosis within 24-48 h, resulting in an expansion of the burn wound. Poloxamer-188 (P-188) is a surfactant that has been shown to prevent cell death due to electrical injury in vivo and heat shock in vitro. In this study, we investigated the effect of P-188 on blood flow within and around a burn wound and on the expansion of the wound area within 24 h after administration of a full-thickness burn injury. Results show that immediately (0-2 h) after the burn, red blood cell speed decreased to zero in a zone extending up to 1 mm from the center of the burn in both P-188 (200 mg/kg)- and saline (0.9%)-treated animals. Between 1 and 3 mm from the center of the burn, red blood cell speed decreased to 50% of preburn levels in saline controls (n = 5), while no decrease occurred in P-188-treated animals (n = 5). Beyond 3 mm from the center of the burn, red blood speed was equal to the preburn levels in saline controls, while it increased by about 10% in P-188 animals. Twenty-four hours after administration of burn, the "zero red blood cell speed zone," termed as the zone of coagulation, became smaller in P-188-treated animals, with an area of 2.4 +/- 0.5 mm(2) (n = 5) compared to 3.5 +/- 0.5 mm(2) (n = 4) in saline controls (P < 0.01). These results suggest that P-188 prevented the formation of a zone of stasis within 2 h after the burn injury and reduced the area of coagulation observed 24 h after cutaneous burn injury.

Animals↗

PubMed2001

Intrahepatic amino acid and glucose metabolism in a D-galactosamine-induced rat liver failure model.

A better understanding of the hepatic metabolic pathways affected by fulminant hepatic failure (FHF) would help develop nutritional support and other nonsurgical medical therapies for FHF. We used an isolated perfused liver system in combination with a mass-balance model of hepatic intermediary metabolism to generate a comprehensive map of metabolic alterations in the liver in FHF. To induce FHF, rats were fasted for 36 hours, during which they received 2 D-galactosamine injections. The livers were then perfused for 60 minutes via the portal vein with amino acid-supplemented Eagle minimal essential medium containing 3% wt/vol bovine serum albumin and oxygenated with 95% O(2)/5% CO(2). Control rats were fasted for 36 hours with no other treatment before perfusion. FHF rat livers exhibited reduced amino acid uptake, a switch from gluconeogenesis to glycolysis, and a decrease in urea synthesis, but no change in ammonia consumption compared with normal fasted rat livers. Mass-balance analysis showed that hepatic glucose synthesis was inhibited as a result of a reduction in amino acid entry into the tricarboxylic acid cycle by anaplerosis. Furthermore, FHF inhibited intrahepatic aspartate synthesis, which resulted in a 50% reduction in urea cycle flux. Urea synthesis by conversion of exogenous arginine to ornithine was unchanged. Ammonia removal was quantitatively maintained by glutamine synthesis from glutamate and a decrease in the conversion of glutamate to alpha-ketoglutarate. Mass-balance analysis of hepatic metabolism will be useful in characterizing changes during FHF, and in elucidating the effects of nutritional supplements and other treatments on hepatic function.

Amino Acids↗

PubMed2001

Expression of liver-specific functions by rat hepatocytes seeded in treated poly(lactic-co-glycolic) acid biodegradable foams.

Techniques of liver replacement would benefit patients awaiting donor livers and may be a substitute for transplantation in patients whose livers can regenerate. Poly(lactic-co-glycolic acid) (PLGA) copolymers are biodegradable and have been shown to be useful as scaffolds for seeding and culturing various types of cells. In this study, foam disks were prepared from PLGA (lactic-to-glycolic mole ratio of 85:15) by lyophilization of benzene (5% w/v) solutions. These disks were then used as scaffolds for rat hepatocyte culture. Foams were coated with either a type I collagen gel (0.1% w/v), coated with gelatin (5% w/v), or treated with oxygen plasma (25 W, 90 s) to modify their surface chemistry and wettability. The disks were then seeded with rat hepatocytes (10(6)/mL) and cultured for a period of 2 weeks. All surface treatments resulted in increased hydrophilicity, the greatest being obtained by collagen treatment (contact angle < 10 degrees ), and a minimal decrease in void fraction (5%). DNA content after a 2-week culture period increased proportionally with the wettability of the treated foam surface. Urea synthesis in untreated foams averaged 15.3 +/- 2.3 microg/h/microg DNA, which was significantly higher than that for controls, whereas gelatin and collagen treated foams exhibited urea synthetic rates below the control levels at all times. The DNA content decreased significantly by about 50% between days 1 and 12. PLGA foams, treated and untreated, represent a promising scaffold for scaling up hepatocyte cultures.

Animals↗

PubMed2001

Long-term maintenance of cytochrome P450 activities by rat hepatocyte/3T3 cell co-cultures in heparinized human plasma.

Little information on the effect of plasma on hepatocyte cytochrome P450 (CYP) activities is currently available. We characterized the effect of plasma on CYPs of hepatocyte-mesenchymal cell co-cultures, which exhibit stable liver specific functions and may be potentially useful for bioartificial liver design. Rat hepatocyte-mouse 3T3-J2 cell co-cultures were maintained for 6 days in medium, and then switched to heparinized human plasma containing 3-methylcholanthrene (3MC; 2 microM), phenobarbital (PB; 1 mM), or no inducer for up to 7 days. CYP activities were measured in situ based on the o-dealkylation of ethoxy- (EROD), methoxy- (MROD), pentoxy- (PROD), or benzyloxy- (BROD) resorufin. Plasma alone increased PROD/BROD but not EROD/MROD. The endogenous inducer was in the high molecular weight fraction (>5 kD) of plasma and inhibited by >5 nM okadaic acid and >10 microM dibutyryl cyclic AMP, two inhibitors of PB-inducible CYPs. Furthermore, plasma increased CYP1A1 and CYP2B1/2 mRNA levels. In plasma, 3MC induced EROD/MROD to about 60% of the level induced in culture medium while PB induced PROD/BROD that were three- to 10-fold above levels induced in medium. CYP activities decreased between days 2 and 7 of plasma exposure, but were enhanced by plasma supplementation with amino acids, insulin, glucagon, and hydrocortisone.

3T3 Cells↗

PubMed2000

Dynamics of tissue neutrophil sequestration after cutaneous burns in rats.

BACKGROUND: Neutrophil recruitment in organs after burns may cause local vascular damage, which can be reduced by agents blocking neutrophil adhesion to the vascular wall. Because these agents may increase susceptibility to infection, it is important to characterize the dynamics of neutrophil sequestration in order to optimize an eventual anti-adhesion therapy. MATERIALS AND METHODS: Rats were scald burned over 20 or 40% of their total body surface area (TBSA) and saline resuscitated. Sham controls were used. Myeloperoxidase (MPO) activity was measured in lungs, liver, kidney, gut, and burned skin up to 1 week postburn. Extravascular accumulation of (125)I-labeled bovine serum albumin ((125)I-BSA) was measured at 12 h postburn. RESULTS: MPO activity in lungs, liver, and kidney was increased within 3 h postburn and returned to normal within 24-48 h. Peak MPO levels occurred at 6-12 h postburn and were similar for both burn sizes. No MPO increase was observed in gut. MPO levels in burned skin did not increase before 6 h, peaked at 24 h, decreased at 48 h, but remained elevated for up to 7 days. Neutrophil recruitment in lungs and liver was confirmed histochemically. No neutrophils were found in kidneys. Extravascular (125)I-BSA was increased in lungs, liver, kidneys, and gut, in the 40% TBSA group only. CONCLUSIONS: Neutrophil sequestration in remote organs is a transient phenomenon while neutrophil homing into the wound site is sustained. Neutrophil accumulation dynamics are independent of burn size, although a minimum size is required to trigger vascular damage. Temporary early anti-adhesion therapy to reduce lung and liver neutrophil sequestration with little impact on neutrophil homing into the burn wound may be possible.

Animals↗

PubMed2000

Optimization of rat hepatocyte culture in citrated human plasma.

BACKGROUND: Maintenance of liver-specific functions in hepatocyte cultures during plasma exposure is critical for the clinical application of bioartificial liver assist systems. Sodium citrate is a common anticoagulant but has been shown to be cytotoxic to hepatocytes. We have tested the effect of various supplements on the viability and function of adult primary rat hepatocytes exposed to citrated plasma. MATERIALS AND METHODS: Freshly isolated rat hepatocytes were cultured in the collagen gel sandwich configuration in culture medium for 6 days followed by exposure to citrated human plasma with various supplements for 1 week. Controls were left in culture medium throughout. Viability and synthetic functions were evaluated. RESULTS: Hepatocytes exposed to unsupplemented citrated plasma lost significant viability and function within the first 2 days. Cells cultured in plasma supplemented with a fivefold concentrate of standard hepatocyte culture medium maintained urea (1. 2-2.1 micromol/day/10(6) cells) and albumin (51-62 microg/day/10(6) cells) synthesis rates equal to or higher than those of controls. Among the various components of the concentrated medium supplement, calcium chloride (1.8 mM), magnesium sulfate (0.8 mM), amino acids (fourfold Basal Medium Eagle amino acids including 4 mM glutamine), and glucagon (14 ng/ml) were found to be essential in maintaining urea synthesis. Maintenance of a high albumin synthesis rate also required the addition of hydrocortisone (7.5 microg/ml) and insulin (0.5 U/ml). CONCLUSIONS: Appropriate metabolic and hormonal supplementation of citrated human plasma prevents its cytotoxic effects and may be used in conjunction with in vivo use of bioartificial liver assist systems.

Albumins↗

PubMed2000

Metabolic flux analysis of postburn hepatic hypermetabolism.

The hepatic response to severe injury is characterized by a marked upregulation of glucose, fatty acid, and amino acid turnover, which, if persistent, predisposes the patient to progressive organ dysfunction. To study the effect of injury on liver intermediary metabolism, metabolic flux analysis was applied to isolated perfused livers of burned and sham-burned rats. Intracellular fluxes were calculated using metabolite measurements and a stoichiometric balance model. Significant flux increases were found for multiple pathways, including mitochondrial electron transport, the TCA and urea cycles, gluconeogenesis, and pentose phosphate pathway (PPP). The burn-induced increase in gluconeogenesis did not significantly increase glucose output. Instead, glucose-6-phosphate was diverted into the PPP. These changes were paralleled by increases in glucose-6-phosphate dehydrogenase (G6PDH) and glutathione reductase (GR) activities. Given that G6PDH and GR are the most significant NADPH producers and consumers in the liver, respectively, and that GR is responsible for recycling the free radical scavenger glutathione, these data are consistent with the notion that hepatic metabolic changes are in part due to the induction of liver antioxidant defenses.

Amino Acids↗

PubMed2000

Amino acid supplementation improves cell-specific functions of the rat hepatocytes exposed to human plasma.

Maintaining hepatocyte function during plasma exposure is critical for the successful development of hepatocyte-based bioartificial liver assist systems. Past attempts to culture hepatocytes in plasma yielded discouraging results. Using a stable culture model based on sandwiching hepatocytes between two layers of collagen gel, we investigated the effect of hormone and amino acid supplementation during exposure of rat hepatocytes to heparin-treated human plasma for 1 week. Morphology and hepatocyte-specific functions were evaluated for hepatocytes cultured in Dulbecco's Modified Eagle medium (DMEM), nonsupplemented plasma, plasma supplemented with hormones, or with hormones plus amino acids. Amino acids were supplemented at four-fold concentration of Basal Medium Eagle with 4 mM glutamine, whereas hormones included 7.5 microg/mL of hydrocortisone and 50 microU/mL of insulin. Cuboidal structure and bile canaliculi formation were observed throughout the 1-week exposure period for control hepatocytes in DMEM and for hepatocytes cultured in hormone supplemented plasma. Albumin and urea synthesis rates of hepatocytes in hormone plus amino acid supplemented plasma during the last day of plasma exposure were 60.4 +/- 13.7 and 75.6 +/- 6.5 (microg/day per 1 x 10(6) cells, mean +/- SD), respectively, comparable to cultures in standard culture medium. On the other hand, hepatocytes exposed to nonsupplemented plasma suffered significant morphological and functional damage. The results of this study indicate that hormone plus amino acid supplementation help to restore function in hepatocytes exposed to plasma.

Albumins↗

PubMed1999

Metabolic flux analysis: a powerful tool for monitoring tissue function.

In recent years, metabolic flux analysis has been widely used in bioprocess engineering to monitor cell viability and improve strain activity. Metabolic flux analysis refers to a methodology for investigating cellular metabolism whereby intracellular fluxes are calculated using a stoichiometric model for the major intracellular reactions and applying mass balances around intracellular metabolites. A powerful feature of this methodology is its ability to consider cellular biochemistry in terms of reaction networks. By considering the stoichiometry of biochemical reactions, it is possible to estimate the degree of engagement of each pathway participating in overall cellular activity, and hence obtain a comprehensive view of a cell s metabolic state. Given the potential impact of cellular energy metabolism on the function of engineered tissues, such comprehensive analysis of metabolic activity can be an extremely useful tool for tissue engineers. Estimates of intracellular fluxes under various environmental conditions could be used to optimize function in vivo as well as culture conditions in vitro. In this review, we provide a brief theoretical background of metabolic flux analysis and summarize the most widely used experimental approaches to obtain flux data. This review is intended as an overview of the field and as a starting point for tissue engineers wishing to learn about and eventually employ this methodology.

Animals↗

PubMed1999

Age- and disease-related decline in immune function: an opportunity for "thymus-boosting" therapies.

The thymus is the site of production of mature T lymphocytes and thus is indispensable for the development and maintenance of the T cell-mediated arm of the immune system. Thymic production of mature T cells is critically dependent on an influx of bone marrow-derived progenitor T cells that undergo replication and selection within the thymus. Thymus cellularity and thymic hormone secretion reach a peak during the first year of life and then decline gradually until the age of 50-60 years, a process known as "thymic involution." A rapid reduction of thymus cellularity occurs in young patients following injuries, chemotherapy, and other forms of stress. The mechanisms underlying the involution process appear to be dependent on factors intrinsic to the thymic tissue, such as the local production of cytokines and chemoattractants, promoting the recruitment, growth, and differentiation of bone marrow-derived T cell progenitors in the thymus, as well as extrinsic factors, such as systemic levels of endocrine hormones and mediators released by intrathymic nerves of the autonomic nervous system. Knowledge of these factors provides a rational basis for the development of an approach based on tissue engineering that could be used to provide either temporary or permanent reconstitution of thymic function.

Aging↗

PubMed1998

Genetically modified fibroblasts induce angiogenesis in the rat epigastric island flap.

METHODS: Gene therapy was tested for inducing functional angiogenesis in the superficial rat epigastric island flap to allow earlier pedicle division. Autologous rat fibroblasts were grown, harvested, cultured and retrovirally transfected to produce platelet-derived growth factor AA (PDGF-AA), an angiogenetically active protein. Stable gene expression was monitored by PDGF-AA enzyme-linked immunosorbent assay (ELISA). One hundred and eighty animals were divided into three groups (I-III) and a bilateral flap created in each animal. In all experiments, the right-sided flap was subjected to experimental treatment and the left-sided flap served as control (1ml saline 0.9%). During flap elevation, group I received 5X10(6) GMFB (genetically modified fibroblasts) plus 1 ml Dulbecco's modified Eagle's medium. Group II was treated with 5x10(6) NMFB (non-modified fibroblasts) plus 1 ml medium and group III received 1 ml medium only. The flaps were sutured back and the vascular pedicle was bilaterally ligated and divided in each of ten animals during the following 6 days. After 7 days, the flaps were harvested, the amount of necrosis measured and histologically examined. RESULTS: The GMFB produced up to 560 times more PDGF-AA than the NMFB, measured by ELISA. The GMFB-treated flaps tolerated surgical division of the vascular pedicle significantly earlier than groups II and III. Histologically, fibroblasts persisted in all flaps of groups I and II, without major inflammatory reaction. In all GMFB-treated flaps, massive angiogenesis could be demonstrated. CONCLUSION: By means of retroviral gene transfer, autologous rat fibroblasts can be genetically modified for stable expression of the PDGF-A gene to produce high amounts of PDGF-AA, which is angiogenetically active. After injection into the panniculus carnosus, these cells induce functional angiogenesis to permit earlier division of the vascular pedicle in this flap model.

Animals↗

PubMed1998

[Functional angiogenesis induction in epigastric islet flap rat model after genetic modification of fibroblasts].

Gene therapy was tested for inducing functional angiogenesis in the superficial rat epigastric island flap to allow earlier pedicle division. Autologous rat fibroblasts were grown, harvested, cultured and retrovirally transfected to produce PDGF-AA, an angiogenetically active protein. Stable gene expression was monitored by PDGF-AA ELISA. 180 animals were divided into 3 groups (I-III) and a bilateral flap created in each animal. In all experiments, the rightsided flap was subjected to experimental treatment and the left-sided flap served as control (1 ml saline 0.9%). During flap elevation, group I received 5 x 10(6) GMFB (genetically modified fibroblasts) plus 1 ml DMEM as medium. Group II was treated with 5 x 10(6) NMFB (non modified fibroblasts) plus 1 ml medium and group III received 1 ml medium alone. The flaps were sutured back and the vascular pedicle was bilaterally ligated and divided in each 10 animals during the following 6 days. 7 days later, the flaps were harvested, the amount of necrosis measured and histologically examined. The GMFB produced up the 560-times more PDGF-AA than the NMFB, measured by ELISA. The GMFB-treated flaps tolerated surgical division of the vascular pedicle significantly earlier than groups II and III. Histologically, fibroblasts persisted in all flaps of groups I and II without major inflammatory reaction. In all GMFB-treated flaps, massive angiogenesis could be demonstrated. By means of retroviral gene transfer autologous rat fibroblasts can be genetically modified for stable expression of the PDGF-A gene to produce high amounts of PDGF-AA, which is angiogenetically active. After injection into the panniculus carnosus, these cells induce functional angiogenesis to permit earlier division of the vascular pedicle in this flap model.

Animals↗

PubMed1997

Control of hypertrophic scar growth using selective photothermolysis.

BACKGROUND AND OBJECTIVE: Previous studies have shown a clinical improvement of hypertrophic scars (HS) after treatment with a pulsed dye laser. The objective of this study was to investigate the effects of variations in pulse wavelength and energy density on HS tissue using human HS implanted in athymic mice. STUDY DESIGN/MATERIALS AND METHODS: Small pieces (approximately 1 mm3) of HS tissue were implanted into athymic mice and allowed to grow for 5 days. The implant site was then exposed to a single 450 microseconds pulse, and implant growth and histology were monitored for an additional 12 days. Laser wavelength and energy density ranges tested were 585-600 nm and 2-10 J/cm2, respectively. RESULTS: Using a wavelength of 585 nm, laser treatment inhibited implant growth by 70% at 6 J/cm2 and 92% at 10 J/cm2, respectively. The inhibitory effect decreased as the laser wavelength was increased from 585 to 600 nm. A widespread destruction of the implant microvasculature with a minor effect on surrounding extracellular matrix at the highest light dose were observed. CONCLUSION: Pulsed laser treatment inhibits HS implant growth in nude mice. This effect is likely mediated by selective photo-thermolysis of the implant microvasculature.

Animals↗

PubMed1997

Control of fibroblast populated collagen lattice contraction by antibody targeted photolysis of fibroblasts.

BACKGROUND AND OBJECTIVE: Hypertrophic scarring and rigid scar contracture are disorders of wound healing for which there is presently no effective therapy. The dermal fibroblast plays a major role in scar fibrillogenesis and contracture. The objective of this study was to establish a selective and effective method to destroy fibroblasts. STUDY DESIGN/MATERIALS AND METHODS: An antifibroblast conjugate was synthesized by covalent attachment of the antifibroblast antibody PR2D3 to the photosensitizer Sn-chlorin e6. Fibroblasts were cultured in fibroblast-populated collagen lattices (FPCLs), incubated with the conjugate and exposed to light. The effect of the treatment on cell viability and the rate of contraction of the FPCL were assessed. RESULTS: The toxicity of antifibroblast conjugates increased with increasing conjugate concentration, light dose, and number of photosensitizers per antibody molecule, until nearly complete killing was achieved. The rate of lattice contraction after irradiation linearly correlated with the remaining viable fraction of fibroblasts. These conjugates were not cytotoxic to keratinocytes cultured on collagen lattices, and nonspecific conjugates could not cause significant fibroblast killing. Spatial selectivity was demonstrated using a light mask. CONCLUSIONS: Antibody-targeted photolysis is an effective and selective technique for controlling FPCL contraction in vitro and may have potential in vivo applications to modulate extracellular matrix remodeling by connective tissue cells.

Animals↗

PubMed1997

Effect of burn injury on glucose and nitrogen metabolism in the liver: preliminary studies in a perfused liver system.

BACKGROUND: The direct impact of burn injury on liver metabolism was studied in a rat liver perfusion system to remove the influence of systemic factors that modulate liver metabolism. METHODS: Seven animals received a burn injury covering 20% of the total body surface area, and seven were sham burned. The in situ liver perfusion studies were carried out in these animals after 3 days of isonitrogenous-isocaloric enteral feeding. In each study oxygen consumption and the rates of uptake and release of glucose, urea, and various amino acids were measured. RESULTS: Burn injury significantly increased urea production (18.5 +/- 0.4 versus 12.2 +/- 0.6 micromol/gm liver/hr and oxygen consumption (3.23 +/- 0.17 versus 1.21 +/- 0.03 micromol/gm liver/min) in the liver but did not alter the rate of gluconeogenesis. The change in amino acid concentrations in the perfusion medium implies an increased net protein breakdown. CONCLUSIONS: Our study indicates that (1) burn injury induces a hypermetabolic state in the liver, (2) the observed enhancement of gluconeogenesis in vivo after burn in probably regulated by factors outside the liver, and (3) the liver itself plays an active role in up-regulating urea production in burn injury. Identifying intrahepatic factors that up-regulate urea production may provide an "intrahepatic approach" to ameliorate the severe nitrogen loss after burn injury.

Amino Acids↗