Autoradiographic analysis of L- and N-type voltage-dependent calcium channel binding in canine brain after global cerebral ischemia/reperfusion

Binding of antagonists to L- and N-type voltage-dependent calcium channels (VDCC) was measured in canine brain following global ischemia and reperfusion. Ischemia was induced by 10 min cardiac arrest, followed by restoration of spontaneous circulation for periods of up to 24 h. Binding of [3H]PN200-110 and [125I]omega-conotoxin GVIA to frozen sections from hippocampus, striatum, parietal cortex and temporal cortex was analyzed using quantitative receptor autoradiography. The binding patterns of the two radioligands were similar in cortex and striatum, but differed in hippocampus. In the latter tissue, [125I]omega-conotoxin GVIA binding was dense over synaptic regions, especially the presynaptic polymorph layer of the dentate gyrus, but was virtually absent over cell body layers. In contrast, [3H]PN200-110 binding was more homogenously distributed, with highest binding in the molecular layer of the dentate gyrus. The binding of [125I]omega-conotoxin GVIA was not different from sham controls at any time point following cardiac arrest. [3H]PN200-110 binding was decreased in each region immediately following ischemia, recovering within 30 min of recirculation. These findings are in contrast to earlier findings of rapid increases in L-type VDCC binding to membrane fractions obtained from cortex and striatum in this model, and suggest that the previously detected increases may be due to a redistribution of channels from subcellular compartments to the plasma membrane during ischemia.

Effect of norfloxacin and clonidine on human trabecular meshwork cells in vitro

We evaluated the effect of norfloxacin and clonidine on the morphology, DNA synthesis and phagocytic activity of cultured human trabecular meshwork cells in the 3rd-5th generations. Exposure to norfloxacin at a concentration of 1.5 x 10(-4) g ml-1 for 6 h led to retraction of cytoplasmic processes and rounding of cell profile, and exposure for 48 h caused cell death. Exposure to clonidine at 1.0 x 10(-3) g ml-1 for 12 h caused cell degeneration, and exposure for 72 h led to cell death. The morphologic changes were dose-time dependent. Tritiated thymidine incorporation was determined as an index of DNA synthesis, which was significantly inhibited by 1.5 x 10(-5) g ml-1 norfloxacin or 1.0 x 10(-3) g ml-1 clonidine, but obviously enhanced by 1.0 x 10(-4) and 1.0 x 10(-5) g ml-1 clonidine. Both drugs inhibited phagocytosis of latex microspheres in a dose-dependent mode. According to the presented results and the pharmacokinetic data reported in the literature, we suggest that the topical use of norfloxacin should not be too frequent or continued too long, especially when the corneal epithelium was not intact; clonidine has no deleterious effect on trabecular cells in its conventional use.

Genes in one megabase of the HLA class I region

To define the gene content of the HLA class I region, cDNA selection was applied to three overlapping yeast artificial chromosomes (YACs) that spanned 1 megabase (Mb) of this region of the human major histocompatibility complex. These YACs extended from the region centromeric to HLA-E to the region telomeric to HLA-F. In addition to the recognized class I genes and pseudogenes and the anonymous non-class-I genes described recently by us and others, 20 additional anonymous cDNA clones were identified from this 1-Mb region. We also identified a long repetitive DNA element in the region between HLA-B and HLA-E. Homologues of this element were located at several sites in the human genome outside of the HLA complex. The portion of the HLA class I region represented by these YACs shows an average gene density as high as the class II and class III regions. Thus, the high gene density portion of the HLA complex is extended to more than 3 Mb.

Intravitreal pharmacokinetics of liposome-encapsulated amikacin in a rabbit model

BACKGROUND

Intravitreal injection of antibiotics has become a standard therapy for bacterial endophthalmitis. The duration of effective antimicrobial levels in the vitreous after single injection, however, may not be long enough to get optimal response. The authors prepared liposome-encapsulated amikacin for prolonging the duration of intravitreal therapeutic concentrations and investigated the intravitreal pharmacokinetics of the liposomes and amikacin in phosphate buffer solution (PBS) as control.

METHODS

The liposome-encapsulated amikacin was prepared by reverse-phase evaporation method. The intravitreal pharmacokinetics of the liposomes was compared with amikacin in PBS by fluorescence polarization immunoassay. Albino rabbits were randomly distributed into 12 groups. Rabbits in groups 1 to 6 and in groups I to VI (control groups) received an intravitreal injection of the liposome-encapsulated amikacin and amikacin in PBS, respectively.

RESULTS

The encapsulation rate of amikacin was 91%. The time of 50% spontaneous degradation (half-life) of the liposomes in PBS (38 degrees C, pH 7.4) was 47.6 days, and the time of 50% release (half-life) of the drug from the liposomes in PBS was 84.8 hours. The vitreous amikacin concentrations in groups 1 to 6 were significantly greater (P < 0.05) than those in control groups I to VI in every time interval, except in groups 1 to 3 at 1 hour after injection. The difference was particularly obvious in the endophthalmitis groups. The clearance of encapsulated amikacin in vitreous appeared to be related to the state of blood-ocular barrier and to the structural integrity of vitreous. The distribution, the absorption, and the elimination of encapsulated amikacin in vitreous showed the first-order kinetics.

CONCLUSION

The liposome-encapsulated amikacin prolonged half-life of the drug in vitreous. The results of the pharmacokinetic analysis suggested that in endophthalmitis, especially in severe cases, the liposomes may be preferable to conventional preparation.

Relationship of oxidative events and DNA oxidation in SENCAR mice to in vivo promoting activity of phorbol ester-type tumor promoters

Reactive oxygen species (ROS) have been implicated as being involved in tumor promotion processes. However, the mechanism by which ROS modulate tumor promotion has not as yet been elucidated. In this report, we show that phorbol ester-type tumor promoters (12-O-tetradecanoylphorbol-13-acetate [TPA], mezerein and 12-O-retinoylphorbol-13-acetate [RPA]), which vary in their in vivo potencies, also differ in their effect on formation of hydrogen peroxide (H2O2) and oxidation of normal bases to 5-hydroxymethyl-2'-deoxyuridine [HMdU] and 8-hydroxyl-2'-deoxyguanosine [8-OHdG] in the DNA of SENCAR mouse epidermis, though they are equipotent in causing infiltration of polymorphonuclear leukocytes (PMNs). Treatment of SENCAR mice with the chemopreventive agents (-)-epigallocatechin gallate or tamoxifen (6.5 nmol) prior to application of TPA (6.5 nmol) diminished PMN infiltration, and formation of H2O2, HMdU and 8-OHdG. These results strengthen the evidence that ROS are involved in tumor promotion, and that generation of ROS and the subsequent oxidative DNA modification are related to the tumor-promoting potencies of the different phorbol ester-type promoters.

Sensitivity to tumor promotion of SENCAR and C57BL/6J mice correlates with oxidative events and DNA damage

Significant differences in sensitivity to multistage carcinogenesis have been noted between mice that are sensitive (SENCAR) and resistant (C57BL/6J) to 12-O-tetradecanoylphorbol-13-acetate (TPA). However, the mechanism of this sensitivity has not yet been established. Recent studies from this laboratory have shown that TPA significantly enhances formation of hydrogen peroxide (H2O2) and oxidized DNA bases in SENCAR mouse skin, as it increases the infiltration of polymorphonuclear leukocytes (PMNs), as quantitated by myeloperoxidase (MPO). In the studies reported here, we compared SENCAR and C57BL/6J mice with respect to TPA-mediated edema, hyperplasia, PMN infiltration, oxidant formation and oxidative DNA damage in mouse skin. Topical application of two TPA doses (2x2-40 micrograms, 20 h apart) dose-dependently increased PMN infiltration and oxidant formation in both mouse strains, which was consistent with TPA-induced morphological alterations (edema and hyperplasia). However, at low TPA doses (2-4 micrograms), the increases over controls in the SENCAR mice were significantly greater (P < 0.01) than those in C57BL/6J mice. Comparison of the net values indicated that 4 micrograms TPA enhanced PMN infiltration (MPO units/cm2) and oxidant formation (nmol H2O2/cm2) in SENCAR mice by 7.7- and 11-fold respectively over those present in TPA-treated C57BL/6J mouse skin. At the same dose, TPA also significantly increased formation of thymidine glycol (dTG; 5.5-fold), 5-hydroxymethyl-2'-deoxyuridine (HMdU; 4.9-fold) and 8-hydroxyl-2-deoxyguanosine (8-OHdG; 11.4-fold) in SENCAR mouse epidermis. Then, the levels of all three declined. In C57BL/6J mice, there were virtually no increases at 4 micrograms TPA, but their levels gradually increased with higher TPA doses and reached maxima at 10 micrograms TPA for dTG (1.9-fold increase), at 20 micrograms TPA for 8-OHdG (6.0-fold), and at 30 micrograms TPA for HMdU (1.8-fold). We conclude that the TPA-mediated oxidative events and oxidative DNA modification by different doses of TPA correlate with the promoting potencies of those doses in both mouse strains. Therefore, they could be, at least in part, responsible for the strain-dependent sensitivity to tumor promotion.

Study on initiation of human lung carcinogenesis

Cigarette smoking condensate and diethylnitrosamine can initiate human lung carcinogenesis as they are able to induce precancerous lesions of bronchioles and the transforming ability of human fetal lung (HFL) DNA. The induction of precancerous lesions in HFL and the acquirement of the transforming ability of HFL DNA by short-term exposure to carcinogens can be combined to yield an ideal model for the initiation of human lung carcinogenesis.

Inhibition of tumor promoter-mediated processes in mouse skin and bovine lens by caffeic acid phenethyl ester

Caffeic acid phenethyl ester (CAPE) was isolated from propolis (a product of honeybee hives) that has been used in folk medicine as a potent antiinflammatory agent. CAPE is cytotoxic to tumor and virally transformed but not to normal cells. Our main goal was to establish whether CAPE inhibits the tumor promoter (12-O-tetradecanoylphorbol-13-acetate)-induced processes associated with carcinogenesis. Topical treatment of SENCAR mice with very low doses (0.1-6.5 nmol/topical treatment) of CAPE strongly inhibits the following 12-O-tetradecanoylphorbol-13-acetate-mediated oxidative processes that are considered essential for tumor promotion: (a) polymorphonuclear leukocyte infiltration into mouse skin and ears, as quantified by myeloperoxidase activity; (b) hydrogen peroxide (H2O2) production; and (c) formation of oxidized bases in epidermal DNA, as measured by 5-hydroxymethyluracil and 8-hydroxylguanine. A 0.5-nmol dose of CAPE suppresses the oxidative burst of human polymorphonuclear leukocytes by 50%. At higher doses (1-10 mumol), CAPE inhibits edema and ornithine decarboxylase induction in CD-1 and SENCAR mice. Interestingly, we discovered that 12-O-tetradecanoylphorbol-13-acetate-induced H2O2 production in bovine lenses also is inhibited by CAPE. Cumulatively, these findings point to CAPE as being a potent chemopreventive agent, which may be useful in combating diseases with strong inflammatory and/or oxidative stress components, i.e., various types of cancer and possibly cataract development.

Inhibition of tumor promoter-induced hydrogen peroxide formation in vitro and in vivo by genistein

Here we report that genistein, a soybean isoflavone, strongly inhibits tumor promoter-induced H2O2 formation both in vivo and in vitro. Genistein suppressed H2O2 production by 12-O-tetradecanoylphorbol-13-acetate- (TPA) stimulated human polymorphonuclear leukocytes (PMNs) and HL-60 cells in a dose-dependent manner over the concentration range 1-150 microM. Human PMNs were more sensitive to the inhibitory effect of genistein than HL-60 cells (50% inhibitory concentration 14.8 and 30.2 microM, respectively). In addition, genistein moderately inhibited superoxide anion formation by HL-60 cells and scavenged exogenously added H2O2 under the same conditions as in cell culture. However, the H2O2-scavenging effect of genistein was about 50% lower than its inhibition of cell-derived H2O2 formation at all concentrations. In the CD-1 mouse skin model, genistein strongly inhibited TPA-induced oxidant formation, edema, and PMN infiltration in mouse skin. Inhibition of TPA-mediated H2O2 in vivo may result from decreased cell-derived H2O2 formation, scavenging of H2O2 produced, and/or suppression of PMN infiltration into the dermis. The antioxidant properties of genistein may be responsible for its anticarcinogenic effects, and the dietary availability of genistein makes it a promising candidate for the prevention of human cancers.

Hypothalamic-pituitary function assessment in children by a combined stimulation test

We utilized a combined stimulation test using insulin, thyrotropin-releasing hormone, gonadotropin-releasing hormone and levodopa to assess multiple pituitary hormones including growth hormone, thyrotropin, prolactin and gonadotropins in 32 children of short stature and 18 girls with early appearance of puberty. It was found that this combined stimulation test can assess multiple hormone responses with satisfactory results in a single 90-min test. Compared with any of those laborious classic stimulation tests alone, it is easier to be carried out and willingly accepted by children.

Activation of oncogenes and/or inactivation of anti-oncogenes by reactive oxygen species

Abundant evidence indicates that reactive oxygen species (ROS) are involved in mutagenesis and carcinogenesis. These chemical-generated or phagocyte-released ROS are known to cause a variety of genetic alterations which lie at the heart of the carcinogenic process. ROS have also been shown to cause malignant transformation of normal cells, and to increase expression of certain proto-oncogenes such as c-fos and c-jun. It is known that certain proto-oncogenes and anti-oncogenes may serve as the targets of carcinogens of various sorts. I hypothesize that ROS-mediated DNA damage may cause mutations and/or deletions in certain specific coding regions of tumor-related genes, and could be responsible for subsequent activation of oncogenes and/or inactivation of anti-oncogenes.

Suppression of tumor promoter-induced oxidative events and DNA damage in vivo by sarcophytol A: a possible mechanism of antipromotion

Sarcophytol A (Sarp A), a nontoxic compound isolated from marine soft coral, inhibits the in vivo effects of tumor promoters. However, the mechanism of its action is unknown. Our studies show that Sarp A suppresses oxidant formation and DNA oxidation in the epidermis of SENCAR mice exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA). In the short-term experiments, mice were topically pretreated with different doses of Sarp A before 6.5 nmol TPA, and the same treatment was repeated 20 h later. Sarp A significantly decreased the TPA-induced infiltration of neutrophils, the levels of myeloperoxidase in the dermis, and the formation of H2O2, cis-thymidine glycol, 8-hydroxyl-2'-deoxyguanosine, and 5-hydroxymethyl-2'-deoxyuridine in the epidermis. In the long-term studies, repeated TPA applications (3.2 nmol twice a week for 16 weeks) increased cis-thymidine glycol 2.7-fold, 5-hydroxymethyl-2'-deoxyuridine 3.4-fold, and 8-hydroxyl-2'-deoxyguanosine 3.3-fold in epidermal DNA over the basal levels. Application of 350 nmol Sarp A before each TPA treatment significantly decreased the formation of oxidized DNA bases even below those present in the control mouse skin. Histological examination showed that Sarp A also alleviated the TPA-induced inflammatory response and infiltration of phagocytes. Thus, it is possible that suppression of tumor promotion by Sarp A is due (at least in part) to its inhibitory effects on tumor promoter-mediated migration and activation of phagocytes, oxidant formation, and DNA base oxidation.

Experimental study of high-frequency two-way jet ventilation

BACKGROUND AND METHODS

A new mode of jet ventilation, high-frequency two-way jet ventilation, was devised and introduced to increase CO2 elimination. High-frequency two-way jet ventilation was achieved by adding reverse jet pulses inside the trachea through an intratracheal reverse jet system to the expiratory phase of common high-frequency jet ventilation. The ventilatory efficiency and features of high-frequency two-way jet ventilation were investigated and compared with those features of high-frequency jet ventilation in ten dogs in the same experimental condition. Random sample selection and randomized crossover trial were used for comparison between high-frequency two-way jet ventilation and high-frequency jet ventilation. Peak inspiratory pressure, end-expiratory pressure, and the arterial blood gas variables (PaO2, PaCO2, and pH) were measured during the study.

RESULTS

PaCO2 with high-frequency two-way jet ventilation was about 35% lower than that with high-frequency jet ventilation (from 45 to 29 torr [6.0 to 3.9 kPa], p less than .01). Simultaneously, peak inspiratory pressure and end-expiratory pressure during high-frequency two-way jet ventilation were significantly lower than those same variables measured during high-frequency jet ventilation. End-expiratory pressure of high-frequency two-way jet ventilation was a negative pressure (-2.45 +/- 0.45 cm H2O). The pH of high-frequency two-way jet ventilation was significantly higher than that of high-frequency jet ventilation.

CONCLUSIONS

Compared with high-frequency jet ventilation, high-frequency two-way jet ventilation demonstrated a ventilatory feature of increasing CO2 elimination and simultaneously decreasing airway pressure.

The screening diagnosis of tetrahydrobiopterin deficient phenylketonuria

Since 1990, 20 diagnostically confirmed phenylketonuria (PKU) patients have been screened with a tetrahydrobiopterin (BH4) loading test, in which plasma phenylalanine and urinary pterin metabolites were investigated, ind activity of dihydropteridine reductase (DHPR) was determined as well. The results showed that there was no statistical difference between the concentrations of plasma phenylalanine before and after BH4 (20mg/kg) administration in all patients, and values of urinary neopterin and biopterin were within the range of classic PKU. All patients but one had normal activity of DHPR in red cells. This suggests that incidence of BH4 deficiency in PKU patients amounts to five percent (1/20) which is almost the same as reported abroad.

Preparation and certification of lyophilized human urine for trace metals reference material in China

The preparation of lyophilized human urine certified reference material (CRM) was established on the basis of literature in other countries and domestic conditions. The homogeneity and stability of the CRM accord with the stipulations. The certified values were determined by 14 high level laboratories in China using nine methods with different principles and have been examined by the National Institute for Occupational Safety and Health (NIOSH) using Inductively Coupled Plasma--Mass Spectrometry (ICP-MS). This CRM has been approved as first grade national reference material. It can be used in quality control of routine analysis, test of new methods, and as standard material for calibration of analytical instruments and as certified reference material for quantity transmission and analysis arbitration.

Skeletal muscle amino acid and myofibrillar protein mRNA response to thermal injury and infection

Skeletal muscle changes associated with severe injury were investigated in male Wistar rats subjected to 30% full thickness scald injury (burn) and thermal injury followed by immediate colonization with 10(8) colony-forming units of Pseudomonas aeruginosa (BI). Freely fed animals (FF) and animals pair fed to the BI animals (PF) served as controls. Thermal injury in conjunction with infection produced a rapid and sustained muscle cellular membrane depolarization (transmembrane potential difference at 12 h after injury: FF 92.1 +/- 0.3 and BI 85.2 +/- 2.3 mV; P less than 0.05). This was followed by body weight loss and skeletal muscle protein wasting (gastrocnemius protein at 7 days: FF 0.35 +/- 0.01 and BI 0.16 +/- 0.03 g; P less than 0.05) and intracellular high-energy phosphate depletion (ATP at 10 days: FF 6.6 +/- 0.4 and BI 4.5 +/- 0.4 mumol/g tissue; P less than 0.05). These body and cellular changes were not accounted for by the anorexia alone. Marked alterations in intracellular free amino acids were also noted in the BI group characterized by increases in levels of all amino acids (total intracellular free amino acids at 7 days: FF 51 +/- 7 and BI 91 +/- 12 mM; P less than 0.05) except intracellular glutamine (at 7 days: FF 6.0 +/- 0.2 and BI 2.4 +/- 0.6 mM; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo formation of oxidized DNA bases in tumor promoter-treated mouse skin

There has been a paucity of evidence showing that 12-O-tetradecanoyl-phorbol-13-acetate (TPA), a potent tumor promoter, causes DNA damage in vivo. We show that oxidized DNA bases are formed in the epidermis of TPA-treated SENCAR mice in a dose- and time-dependent manner. As measured by high-performance liquid chromatography and acetylation of nucleosides with [3H]acetic anhydride, these oxidized DNA derivatives include cis-thymidine glycol, 5-hydroxymethyl-2'-deoxyuridine, and 8-hydroxyl-2'-deoxyguanosine. Their maximal formation induced by a single TPA dose occurred within 6-8 h (a 2-5-fold increase). The level of 8-hydroxyl-2'-deoxyguanosine was the lowest (3.2/10(5) bases) and remained almost unchanged for 18 h; thymidine glycol (29.1/10(4) bases) and 5-hydroxymethyl-2'-deoxyuridine (17.3/10(4) bases) declined gradually but were still above controls at 24 h. Reapplication of TPA 20 h after the first dose (time of the maximal polymorphonuclear leukocyte infiltration) enhanced the net formation of 8-hydroxyl-2'-deoxyguanosine by 3.8-fold (P less than 0.05), of cis-thymidine glycol by 1.9-fold (P less than 0.001), and of 5-hydroxymethyl-2'-deoxyuridine by 2.0-fold (P less than 0.01), as compared to those maximally produced by a single TPA dose. Thus, the infiltration of polymorphonuclear leukocytes into TPA-treated mouse skin, which was corroborated by histological examination and the presence of polymorphonuclear leukocyte-specific myeloperoxidase, might play an important role in TPA-induced DNA oxidation in vivo. Our findings provide proof that tumor promoters can induce genetic modification in vivo that is oxidative in nature. Hence, formation of oxidized DNA bases may be responsible for the genetic effects of tumor promoters in carcinogenesis.

The acute splanchnic and peripheral tissue metabolic response to endotoxin in humans

The in vivo alterations in organ-specific substrate processing and endogenous mediator production induced by endotoxin were investigated in healthy volunteers. An endotoxin bolus (20 U/kg) produced increased energy expenditure, hyperglycemia, hypoaminoacidemia, and an increase in circulating free fatty acids. These changes included increased peripheral lactate and free fatty acid output, along with increased peripheral uptake of glucose. Coordinately, there were increased splanchnic uptake of oxygen, lactate, amino acids, and free fatty acids, and increased splanchnic glucose output. There were no changes in circulating glucagon, or insulin and transient changes in epinephrine and cortisol were insufficient to explain the metabolic changes. Plasma cachectin levels peaked 90 min after the endotoxin infusion, and hepatic venous (HV) cachectin levels (peak 250 +/- 50 pg/ml) were consistently higher than arterial levels (peak 130 +/- 30 pg/ml, P less than 0.05 vs. HV). No interleukin 1 alpha or 1 beta was detected in the circulation. Circulating interleukin 6, measured by B.9 hybridoma proliferation, peaked 2 h after the endotoxin challenge (arterial, 16 +/- 2 U/ml; HV, 21 +/- 3 U/ml). The net cachectin efflux (approximately 7 micrograms) from the splanchnic organs demonstrates that these tissues are a major site for production of this cytokine. Hence, splanchnic tissues are likely influenced in a paracrine fashion by regional cachectin production and may also serve as a significant source for systemic appearance of this cytokine.

Inhibitory effect of apigenin, a plant flavonoid, on epidermal ornithine decarboxylase and skin tumor promotion in mice

This investigation studied the effect of topical application of apigenin on skin tumorigenesis initiated by 7,12-dimethylbenz(a)anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA) in SENCAR mice. Apigenin was a potent inhibitor of epidermal ornithine decarboxylase induction by TPA in a dose-dependent manner from 1 to 20 mumol. Two tumorigenesis studies were conducted. In the first study, 20 mumol of apigenin was applied topically and no effect on body weight was observed. By week 33 after DMBA initiation, 48% of DMBA/TPA-treated mice developed carcinomas, while none occurred in DMBA/apigenin/TPA-treated groups. In the second study, doses of 5 and 20 mumol of apigenin were used. The papilloma incidence for 0, 5, and 20 mumol apigenin at 26 weeks after DMBA was 93.3, 58, and 39.3%, and papilloma numbers per mouse were 7.5, 2.5, and 1.8, respectively. Apigenin prolonged by 3 weeks the latency period of tumor appearance. In addition, apigenin significantly inhibited the incidence of carcinoma and the numbers of carcinomas. The incidence of carcinomas per tumor-bearing animal and the ratio of carcinomas/papillomas in two apigenin-treated groups decreased although there were no significant differences between the three groups. These data indicate that apigenin inhibited skin papillomas and showed the tendency to decrease conversion of papillomas to carcinomas.

Serum cachectin/tumor necrosis factor in critically ill patients with burns correlates with infection and mortality

Serum cachectin/tumor necrosis factor (TNF), a cytokine implicated in the pathogenesis of septic shock, may appear in the circulation during serious infection, but the frequency of detection of elevated serum levels during protracted critical burn injury is unknown. Serial serum samples taken from 43 critically ill patients with burns with and without sepsis were analyzed for TNF using an enzyme-linked immunosorbent assay (ELISA). TNF was detectable (greater than 34 picograms per milliliter) at one or more time points in 69 per cent of the patients with sepsis versus 33 per cent of those without sepsis, in 71 per cent of the patients who died versus only 31 per cent of the survivors and in only one healthy normal control patient (n = 21). The frequency of the appearance of TNF correlated with both infection and mortality rate. Moreover, all three patients with TNF levels greater than 540 picograms per milliliter died. Neither the size of the burn nor injury from inhalation correlated with detection of TNF. A subset of 16 patients was studied longitudinally from admission until resolution of injury and these data demonstrate that TNF appears transiently and repetitively in the circulation of patients during infection and protracted critical burn injury. Also, serum cortisol levels were significantly higher during sepsis and death in the absence of serum TNF, compared with sepsis and death with detectable cachectin, suggesting that cortisol may interact with the production or detection of this cytokine during ongoing infection and lethal injury. In this study, we have demonstrated that serum TNF is detectable with greater frequency and in higher concentration in patients with sepsis and in those who ultimately succumb to the burn injury, that serum TNF appears transiently and repetitively in the circulation during injury and that higher serum cortisol levels are correlated with the absence of serum TNF during sepsis and lethal injury.