Fetal lung growth after tracheal ligation is not solely a pressure phenomenon

We investigated cell proliferation and cell death in the olfactory epithelium (OE) of mice from birth to maturity using bromodeoxyuridine and terminal deoxynucleotidyl transferase nick end labeling. We show that cell death events and proliferative activity diminish concomitantly with age in the OE. Thus, the age-dependent and coordinate diminution in cell proliferative activity and cell death events may serve to maintain the thickness of the OE as mice mature and age.     

Androgen regulation of epidermal growth factor receptor binding activity during fetal rabbit lung development

The luteolytic response to a prostaglandin F2 alpha analogue, cloprostenol, was investigated in vivo and in vitro at defined stages of the luteal phase. In vivo administration of cloprostenol to female marmoset monkeys on day 3 after ovulation had no effect on plasma progesterone concentrations, whereas administration on day 14 after ovulation reduced plasma progesterone to preovulatory concentrations within 4 h. To identify the cellular basis for this luteolytic action, marmoset luteal tissue obtained on days 3, 6 and 14 after ovulation was incubated in vitro and progesterone production, cAMP accumulation and phosphoinositide (PI) turnover measured in response to cloprostenol, human chorionic gonadotrophin (hCG) with or without cloprostenol, or dibutyryl-cAMP with or without cloprostenol. Progesterone production was stimulated by both hCG and dbcAMP at all stages of the luteal phase. Although neither hCG nor dbcAMP had any significant effects on PI turnover, hCG also increased cAMP accumulation. In marmoset luteal tissue obtained on day 3 after ovulation, cloprostenol had no significant effect on basal or hCG/dbcAMP-stimulated progesterone production but significantly stimulated PI turnover. In contrast, on days 6 and 14 after ovulation, cloprostenol significantly inhibited hCG- and dbcAMP-stimulated progesterone production and the cAMP response to hCG, but had no significant effect on PI turnover. Since progesterone production by the marmoset corpus luteum depends on the luteotrophic support of luteinizing hormone (LH), these observations suggest that the luteolytic action of cloprostenol in vivo involves the inhibition of LH/hCG action at sites both prior and subsequent to cAMP accumulation. However, such luteolytic effects do not appear to require the generation of inositol phosphates by increased PI turnover.     

Correction of congenital diaphragmatic hernia in utero VIII: Response of the hypoplastic lung to tracheal occlusion

Most fetuses with congenital diaphragmatic hernia (CDH) diagnosed before 24 weeks' gestation die despite optimal postnatal care. In fetuses with liver herniation into the chest, prenatal repair has not been successful. In the course of exploring the pathophysiology of CDH and its repair in fetal lambs, the authors found that obstructing the normal egress of fetal lung fluid enlarges developing fetal lungs, reduces the herniated viscera, and accelerates lung growth, resulting in improved pulmonary function after birth. They developed and tested experimentally a variety of methods to temporarily occlude the fetal trachea, allow fetal lung growth, and reverse the obstruction at birth. The authors applied this strategy of temporary tracheal occlusion in eight human fetuses with CDH and liver herniation at 25 to 28 weeks' gestation. With ongoing experimental and clinical experience, the technique of tracheal occlusion evolved from an internal plug (two patients) to an external clip (six patients), and a technique was developed for unplugging the trachea at the time of birth (Ex Utero Intrapartum Tracheoplasty [EXIT]). Two fetuses had a foam plug placed inside the trachea. The first showed dramatic lung growth in utero and survived; the second (who had a smaller plug to avoid tracheomalacia) showed no demonstrable lung growth and died at birth. Two fetuses had external spring-loaded aneurysm clips placed on the trachea; one was aborted due to tocolytic failure, and the other showed no lung growth (presumed leak) and died 3 months after birth. Four fetuses had metal clips placed on the trachea. All showed dramatic lung growth in utero, with reversal of pulmonary hypoplasia documented after birth. However, all died of nonpulmonary causes. Temporary occlusion of the fetal trachea accelerates fetal lung growth and ameliorates the often fatal pulmonary hypoplasia associated with severe CDH. Although the strategy is physiologically sound and technically feasible, complications encountered during the evolution of these techniques have limited the survival rate. Further evolution of this technique is required before it can be recommended as therapy for fetal pulmonary hypoplasia.     

Regulation of the beta 2 subunit chain of laminin in developing rabbit fetal lung tissue

Laminins are a family of basement membrane-associated heterotrimeric proteins that are important in mediating the growth, migration, and differentiation of a variety of cell types. The beta 2 subunit chain is a component of several laminin isoforms, e.g., laminin-3, laminin-4, laminin-7, and possibly other, as yet uncharacterized laminin isoforms. Utilizing monoclonal antibodies directed against the beta 2 subunit chain of laminin, we detected this protein in fetal, neonatal, and adult lung tissues. The relative amount of laminin beta 2 subunit chain in fetal lung tissue increased as gestation proceeded, reaching its peak around the time of alveolar type II cell differentiation in the rabbit. The laminin beta 2 subunit chain was localized in early gestational age rabbit fetal lung tissue primarily in basement membranes of prealveolar ducts, airways, and smooth muscle cells of airways and arterial blood vessels. A rabbit laminin beta 2 cDNA was generated using RT-PCR and utilized as a probe in northern blot analysis to characterize the levels of laminin beta 2 mRNA in developing rabbit lung tissue. Similar to the pattern of laminin beta 2 protein induction observed in fetal lung tissue, laminin beta 2 mRNA levels were maximal late in gestation. Utilizing a laminin beta 2 chain cRNA probe and in situ hybridization, we detected laminin beta 2 mRNA in the epithelial cells of prealveolar ducts, the alveolar wall, and airways, as well as in connective tissue cells, and the smooth muscle cells of airways and blood vessels in fetal and adult lung tissues. In addition, using an in vitro explant model, we determined that alveolar type II cells are capable of synthesizing laminin beta 2 subunit mRNA and depositing this laminin subunit chain in the basement membrane beneath type II cells. The results of this study are suggestive that the laminin beta 2 chain may be involved in alveolar epithelial cell differentiation.     

Temporal variations in the pattern of breathing

Breath-to-breath variations in the pattern of breathing can occur as uncorrelated random variations ("white noise"), correlated random changes, or as one of two types of nonrandom variations: periodic oscillations or nonrandom nonperiodic fluctuations. White noise is probably present in all physiological processes. In many cases, periodic variations are due to oscillations originating in chemoreflex feedback loops. It has long been hypothesized that correlated random variations in breathing pattern are due to central neutral "memory" mechanisms, but part of this behavior might be due to chemoreflex mechanisms. Recently it has been concluded that nonlinear interactions between pulmonary and airway afferent activities and integrative central respiratory mechanisms can produce nonrandom nonperiodic (and also periodic) variability of the respiratory pattern. These latter studies have provided new insights about the behavioral relevance of the integrative character of central respiratory mechanisms and the time-varying nature of pulmonary afferent activities and have emphasized the importance of identifying the physiological bases for these phenomena. These and other findings are interpreted assuming that respiratory rhythm generation/pattern formation occurs via a nonlinear oscillator, and novel inferences concerning temporal variations of the breathing pattern are proposed.     

The regulatory effect of estrogens on fetal growth. IV. Brain development in growth accelerated fetuses in rabbits

Brain weights and DNA, RNA, and total protein concentrations were determined on 31-day-old fetuses whose growth had been accelerated incidental to estrogen deficiency following maternal oophorectomy. Compared to controls, there were no differences in the DNA, RNA, or total protein concentrations, although the mean brain weight was increased. The higher mean brain weight in the growth accelerated fetuses was related to the increased mean fetal weight, and did not represent an independent response to the estrogen deficiency. A comparison of the influence of fetal weight versus gestational age on the weight of the fetal brain shows that gestational age exerts an effect apart from that of fetal weight.     

Pathohistological study of adriamycin-induced tracheal agenesis in the fetal rat

Mr 2266 [(-)-(1R,5R,9R)-5,9-diethyl-2-(3-furylmethyl)-2'-hydroxy-6,7-benzomorpha n] is an antagonist at kappa-opioid receptors and at ORL1 receptors as well. The aim of our study was to examine whether the known stereoselective antagonism of Mr 2266 at kappa-opioid receptors also extends to ORL1 receptors. In mouse brain cortex membranes, the binding of the ORL1 receptor agonist [3H]nociceptin was equipotently inhibited by Mr 2266 and its enantiomer Mr 2267 (pK(i) 4.82 and 5.14, respectively), whereas the binding of the kappa-opioid receptor agonist [3H]U-69,593 was inhibited by Mr 2266 more potently (pK(i) 9.11) than by its enantiomer Mr 2267 (pK(i)7.15). In mouse brain cortex slices preincubated with [3H]noradrenaline, the concentration-response curve of nociceptin for inhibition of the electrically evoked overflow of tritium was equipotently shifted to the right by Mr 2266 and Mr 2267 (pA2 5.77 and 5.64, respectively). On the other hand, the inhibitory effect of U-69,593 on the electrically evoked overflow of tritium in guinea-pig brain cortex slices preincubated with [3H]noradrenaline was more potently antagonized by Mr 2266 (pA2 8.81) than by Mr 2267 (pA2 7.15). These data show that the stereoselective antagonism of Mr 2266 at kappa-opioid receptors does not extend to ORL1 receptors.     

Blood flow in the rabbit tracheal mucosa under normal conditions and under the influence of tracheal intubation

Isotope labelled microspheres were used to study the capillary blood perfusion of the rabbit tracheal mucosa. Under resting conditions the perfusion was about 0.3 ml/min - g (i.e. about 60% of the relative cerebral blood flow). Irritation of the tracheal mucosa by an endotracheal tube caused a steep rise in blood flow, tenfold or more. This was probably due to relaxation of the arterioles caused by a release of histamine-like substances. When an endotracheal tube is equipped with a small cuff (small resting diameter, low residual volume), the part of the mucosa in contact with the cuff, i.e. the mucosa covering the surface and edges of the cartilages, will be ischaemic at a cuff to tracheal wall pressure (C-T pressure) of greater than 30 millimeters of mercury. This abrupt ischaemia threshold contributes to the risk of deep mucosal damage with subsequent tracheal scarring, possibly proceeding to stenosis. Our present studies indicate that the ideal large cuff, with properties resembling those of an air cushion, will allow the major part of the arterial pressure to be propagated as far down as the capillaries. Under these conditions the cuff would permit some of the capillary blood perfusion of the tracheal mucosa covering the cartilages also at C-T pressures exceeding 30 mmHg. Although this investigation supports the concept that the ideal thin-walled large cuff interferes much less with the mucosal blood perfusion than the small cuff, we recommend that the cuff pressure be monitored and kept below 20 mmHg.     

CD18-independent mechanism of neutrophil emigration in the rabbit lung after ischemia-reperfusion

BACKGROUND: Reperfusion of ischemic lung causes an inflammatory pulmonary vascular injury characterized by increased vascular permeability and migration of inflammatory cells into the alveoli. Migration of neutrophils into the alveolus during reperfusion after 24 hours of unilateral pulmonary artery occlusion has been shown to be in part dependent on the CD18 adhesion molecule on the cell surface. The current study investigated whether reperfusion lung injury after a 1-hour period of complete lung ischemia was CD18 dependent. METHODS: Eighteen rabbits were assigned to one of three groups. Groups 1 and 2 were subjected to one hour of in situ right hilar occlusion followed by 2 hours of reperfusion. Group 3 was subjected to identical surgical dissection but the right hilum was never occluded. Group 1 rabbits received saline solution (1 mL/kg) before hilar occlusion and group 2 rabbits, monoclonal antibody 60.3, a blocking antibody for the CD18 adhesion molecule on the neutrophil surface (2 mg/kg). In 3 of the antibody-treated rabbits, flow cytometry was performed on blood neutrophils before and after administration of the antibody and 120 minutes after reperfusion. RESULTS: The rabbits in groups 1 and 2 had significantly increased alveolar neutrophil infiltrate and increased pulmonary vascular resistance compared with the rabbits in group 3. However, there was no significant difference between group 1 (saline solution treated) and group 2 (antibody treated). Antibody treatment did not block migration of neutrophils into the alveoli. Flow cytometry of circulating neutrophils demonstrated that CD18 was upregulated after reperfusion and that CD18 was fully blocked after antibody treatment for the duration of the study. CONCLUSIONS: We conclude that a 1-hour period of warm ischemia followed by reperfusion results in upregulation of CD18 but that emigration of the neutrophils into the alveoli is not CD18 dependent in this injury.     

Changes in regional lung mechanics and ventilation distribution after unilateral pulmonary artery occlusion

Regional pneumoconstriction induced by alveolar hypocapnia is an important homeostatic mechanism for optimization of ventilation-perfusion matching. We used positron imaging of 13NN-equilibrated lungs to measure the distribution of regional tidal volume (VT), lung volume (VL), and lung impedance (Z) before and after left (L) pulmonary artery occlusion (PAO) in eight anesthetized, open-chest dogs. Measurements were made during eucapnic sinusoidal ventilation at 0.2 Hz with 4-cmH2O positive end expiratory pressure. Right (R) and L lung impedances (ZR and ZL) were determined from carinal pressure and positron imaging of dynamic regional VL. LPAO caused an increase in magnitude of ZL relative to magnitude of ZR, resulting in a shift in VT away from the PAO side, with a L/R magnitude of Z ratio changing from 1.20 +/- 0.07 (mean +/- SE) to 2.79 +/- 0.85 after LPAO (P < 0.05). Although mean L lung VL decreased slightly, the VL normalized parameters specific admittance and specific compliance both significantly decreased with PAO. Lung recoil pressure at 50% total lung capacity also increased after PAO. We conclude that PAO results in an increase in regional lung Z that shifts ventilation away from the affected area at normal breathing frequencies and that this effect is not due to a change in VL but reflects mechanical constriction at the tissue level.     

Is fetal neurologic and physical development accelerated in preeclampsia?

Tuberculosis remains a major health problem worldwide. The current role of video-assisted thoracoscopic surgery (VATS) in the management of this condition is unclear. We reviewed our experience over a 36-month period from a single institution. Thirty-seven patients (26 male, 11 female, with age ranging from 22 days to 71 years), in whom the final diagnosis was tuberculosis, underwent VATS procedures. There were 12 pleural biopsies, 3 decortications, 12 wedge lung resections, 5 drainages of empyema, and 5 lobectomies. All the patients were studied prospectively. There were no mortality or intraoperative complications. The overall median postoperative hospital stay was 4 days (range, 2 to 35 days). Postoperative parenteral narcotics requirement (mean, 310 mg meperidine hydrochloride [Pethidine]) was significantly less than a historic group of 30 patients who underwent conventional thoracotomy for lung resection or empyema drainage for tuberculosis (mean, 875 mg). Postoperative complications include 2 persistent air leaks over 7 days (5.4%) and 1 wound infection (2.7%). We conclude the following: (1) VATS is safe and effective in achieving the diagnosis of tuberculosis through pleural biopsies or wedge lung resection of indeterminate pulmonary nodules; it is particularly useful for those patients who are debilitated, thus making them poor candidates for conventional open surgery; (2) in patients with trapped lung or tuberculous empyema, VATS could achieve full lung reexpansion with minimal morbidity; and (3) therapeutic lung resection using VATS in patients with tuberculosis is technically demanding and potentially hazardous. Its role is, at present, limited.     

Peptide growth factors regulate insulin-like growth factor binding protein production by fetal rat lung fibroblasts

Insulin-like growth factor (IGF) binding proteins (IGFBPs) are expressed in fetal lung and may provide important post-translational regulation of IGF-induced mitogenesis during lung organogenesis. Because of the observation that growth factors can control cell growth through regulation of IGFBPs, we examined IGFBP production by fetal lung fibroblasts following stimulation by peptide growth factors important for fetal lung growth and development. Fetal lung fibroblasts were cultured in serum-free medium supplemented with various growth factors for up to 48 h, and IGFBPs in conditioned medium (CM) were analyzed by ligand blot and immunoblot techniques. Accumulation of CM IGFBP-3 was increased and IGFBP-2 decreased by incubation with either keratinocyte growth factor (KGF) or epidermal growth factor (EGF). The effect of these factors on IGFBP-3 accumulation increased with time but the effects of KGF on CM IGFBP-2 decreased over 48 h of incubation. CM IGFBP-4 was increased by 24 and 48 h incubation with basic fibroblast growth factor (bFGF; 2.1- and 2.7-fold increases at 24 and 48 h, respectively) and platelet-derived growth factor-BB (PDGF-BB; 4.2- and 14.9-fold increases at 24 and 48 h, respectively), and 48 h incubation with EGF (6.3-fold increase). In 48-h coincubation experiments, EGF in combination with PDGF-BB or with bFGF, and bFGF in combination with PDGF-BB, resulted in IGFBP-4 accumulations twice that expected from a summation of the effects of either growth factor alone (IGFBP-4 increased 9.8-, 4.0-, and 1.8-fold by PDGF-BB, EGF, and bFGF, respectively; and 27.1-, 37.3-, and 13.0-fold by PDGF-BB plus EGF, PDGF-BB plus bFGF, and EGF plus bFGF, respectively). These results suggest synergistic effects of these growth factors on IGFBP-4 accumulation in fetal lung fibroblast CM. Because IGFBPs are known to regulate DNA synthesis, we speculate that peptide growth factors may alter cell proliferation in fetal lung, in part through their effect on IGFBPs.     

Ultrasound enhanced thrombolysis in experimental retinal vein occlusion in the rabbit

Live virus vaccines have in many cases proven to be an extremely effective tool for the prevention of viral diseases. However, the production of conventional live vaccines in eukaryotic cell cultures has many disadvantages, including the potential for contamination with adventitious agents and genetic alterations during propagation, making it necessary to do extensive testing before distribution. Based on results obtained with a flavivirus (tick-borne encephalitis virus) in an experimental animal system, we propose a novel live attenuated virus vaccination strategy consisting of the application of in vitro-synthesized infectious RNA instead of the live virus itself. When administered using the GeneGun, less than 1 ng of RNA was required to initiate replication of virus that was attenuated by a specifically engineered deletion and this induced a protective immunity in laboratory mice. Because this approach uses RNA, it does not have the potential drawbacks of DNA vaccines and thus combines the advantages of conventional live virus vaccines (for example, mimicking natural infection and inducing long-lasting immunity) with those of nucleic acid-based vaccines (for example, ease of production without a requirement for eukaryotic cell culture, stability and purity).     

Spatial and temporal variability in the pattern of recovery of ventricular geometry and function after acute occlusion and reperfusion

Myocardial ischemia and infarction are known to cause changes in both ventricular shape and function. Little is known about the recovery of ventricular geometry after transient myocardial ischemia and its relationship to recovery of function. To examine the pattern of recovery of ventricular geometry following transient coronary artery occlusion and to assess the relationship of this to the return of systolic function, we used echocardiography to study 13 dogs following 15-minute occlusion of the left anterior descending coronary artery. During ischemia, total endocardial surface area (ESA) increased from 32.55 +/- 1.77 to 45.36 +/- 3.18 cm2 (p = 0.001). The most striking increase was at the apex, where circumference increased from 5.04 +/- 0.24 at baseline to 7.86 +/- 0.43 cm at the end of occlusion (p = 0.0001), an increase of 58%. During reperfusion, ventricular geometry rapidly returned toward normal (baseline), with recovery of 80% of the increase in ESA evident by 15 minutes of reperfusion. Recovery of systolic function was substantially slower (p < 0.005 for all periods of observation during the 2 hours of reperfusion). During reperfusion, recovery of ventricular geometry and function was not uniform throughout the ischemic bed. The apex recovered most slowly, with the centroid of the area of abnormal contraction progressively moving along the long axis of the left ventricle toward the apex. There was also a progressive decrease in the radius of the area of dysfunction, from 2.0 +/- 0.15 at end occlusion to 0.13 +/- 0.07 cm at 120 minutes of reperfusion (p = 0.0001). There was no difference in blood flow between the apical and anterior segments during ischemia or reperfusion. Reperfusion favorably reduced the ischemic zone dilation before recovery of active systolic function and geometric recovery thus may be important in determining ultimate functional recovery. In addition, recovery of function proceeded inward towards the center of the ischemic territory and in a wavefront from the base to apex. This heterogeneous and asymmetric recovery suggests that sampling at one point within the ischemic zone may not reflect the true temporal pattern of recovery.     

Heterogeneity of tachykinin receptors in the rabbit lung

The tachykinins, substance P (SP) and neurokinin A (NKA), are agonists for the NK(1) and NK(2) receptors, respectively. Tachykinins have various respiratory effects, including bronchoconstriction. This study characterizes tachykinin binding sites in the rabbit lung. We hypothesize that (2-[(125)I]iodohistidyl(1))Neurokinin A ([(125)I]NKA) interacts with NK1 and NK2 binding sites in the rabbit lung. The K d determined from saturation isotherms was 0.69 times/divided by 1.14 nM (geometric mean times/divided by SEM) and the B max was 4.15 + or - 0.22 femtomole/mg protein (arithmetic mean + or - SEM). Competitive inhibition studies with NKA, SP and various selective tachykinin agonists showed the rank order of potency; [beta-Ala(8)]-Neurokinin A 4-10 = SP > NKA > [Sar(9),Met(02)11]-Substance P. [beta-Ala(8)]-Neurokinin A 4-10, a selective NK(2) agonist, and SP inhibition of [(125)I]NKA binding were best described using a two-site model. Competitive inhibition studies using the selective nonpeptide NK(2) antagonist (SR 48968) and the selective nonpeptide NK(1) antagonist (CP 96,345) revealed Ki's of 5.5 nM and 8.1 nM, respectively. Our data therefore suggest that [(125)I]NKA binds to both the NK(1) and NK(2) receptors in the lung.     

Developmental pattern of fetal growth hormone, insulin-like growth factor I, growth hormone binding protein and insulin-like growth factor binding protein-3

AIMS: To evaluate the developmental pattern of fetal growth hormone (GH), insulin-like growth factor I (IGF-I), GH binding protein (GHBP) and IGF binding protein-3 (IGF-3); to determine the implications for fetal growth. METHODS: Serum GH, IGF-I, GHBP and IGFBP-3 were measured in 53 fetuses, 41 aged 20-26 weeks (group A) and 12 aged 31-38 weeks (group B). Fetal blood samples were obtained by direct puncture of the umbilical vein in utero. Fetal blood samples were taken to rule out beta thalassaemia, chromosome alterations, mother to fetus transmissible infections, and for maternal rhesus factor. GHBP was determined by gel filtration chromatography of serum incubated overnight with 125I-GH. GH, IGF-I and IGFBP-3 were determined by radioimmunoassay. RESULTS: Fetal serum GH concentrations in group A (median 29 micrograms/l, range 11-92) were significantly higher (P < 0.01) than those of group B (median 16.7 micrograms/l, range 4.5-29). IGF-I in group A (median 20 micrograms/l, range 4.1-53.3) was significantly lower (P < 0.01) than in group B (median 75.2 micrograms/l, range 27.8-122.3). Similarly, IGFBP-3 concentrations in group A (median 950 micrograms/l, range 580-1260) were significantly lower than those of group B (median 1920 micrograms/l, range 1070-1770). There was no significant difference between GHBP values in group A (median 8.6%, range 6.6-12.6) and group B (median 8.3%, range 6-14.3). Gestational age correlated positively with IGF-I concentrations (P < 0.0001) and IGFBP-3 (P < 0.0001) and negatively with GH (P < 0.0001). GHBP values did not correlate with gestational age. Multiple regression analysis showed a negative correlation between GH:IGF-I ratio and fetal growth indices CONCLUSIONS: The simultaneous evaluation of fetal GH, IGF-I, IGFBP-3 and GHBP suggests that the GH-IGF-I axis might already be functional in utero. The progressive improvement in the efficiency of this axis in the last part of gestation does not seem to be due to an increase in GH receptors.     

Temporal pattern of plasminogen activator activity in the developing chick cerebellum

Plasminogen activators are considered to be involved in several developmental events. The present work aims at characterizing the developmental pattern of expression of plasminogen activators in the chick cerebellum. Soluble fractions derived by ultracentrifugation from Triton X-100 treated membrane fractions were used for determination of the enzyme activity with a radial fibrinolytic assay. By using specific inhibitors and different anti-plasminogen activators antibodies it is shown that only one type of the enzyme, the urokinase-type plasminogen activator, is expressed during the cerebellum ontogeny. Our results show the existence of a bimodal pattern of enzyme activity with two peaks that temporally coincide with the processes of massive neuronal migration, neurite outgrowth and synapse formation and plasticity. It is proposed that plasminogen activator could play a role in these developmental events and that its pattern of variability is developmentally regulated.     

Increased endothelin-1 in the rabbit model of middle cerebral artery occlusion

Human neutrophils (5 x 10(4) incubated on fibronectin precoated wells released 2.83 +/- .25 nmoles of superoxide (0(2)-) (x +/- 1 SEM, n = 15) in response to 5.9 nM (100 ng/ml) Tumor Necrosis Factor Alpha (TNF). On the contrary, the 0(2)- production induced by interleukin-8 (IL-8) (doses ranging from 0.1 nM to 1 microM) was comparable to that of "resting" cells (< .6 nmoles/5 x 10(4) cells). IL-8 (100 nM) did not affect the TNF-dependent 0(2)- production when added with TNF at the beginning of the assay, but reduced it by approximately 80% when added with TNF on neutrophils previously incubated for 1 hour on fibronectin. As compared with IL-8, N-formyl-methionyl-leucyl-phenylalanine (FMLP, 100 nM) failed to suppress the TNF-triggering of the oxidative burst in neutrophils plated on fibronectin. The data suggest that the interaction of neutrophils with fibronectin uncovers the capacity of IL-8 to limit the cell response to TNF, without affecting the response to the combination of FMLP and TNF. Thus, although the chemotactic factors IL-8 and FMLP share the capacity of triggering the oxidative burst of neutrophils incubated in suspension, only IL-8 has the potential to down-regulate the responsiveness of fibronectin-adherent cells to TNF.