The histology of experimental pleural injury with tetracycline, empyema, and carrageenan

A Novel Rabbit Model of Retained Hemothorax with Pleural Organization

Retained hemothorax (RH) is a commonly encountered and potentially severe complication of intrapleural bleeding that can organize with lung restriction. Early surgical intervention and intrapleural fibrinolytic therapy have been advocated. However, the lack of a reliable, cost-effective model amenable to interventional testing has hampered our understanding of the role of pharmacological interventions in RH management. Here, we report the development of a new RH model in rabbits. RH was induced by sequential administration of up to three doses of recalcified citrated homologous rabbit donor blood plus thrombin via a chest tube. RH at 4, 7, and 10 days post-induction (RH4, RH7, and RH10, respectively) was characterized by clot retention, intrapleural organization, and increased pleural rind, similar to that of clinical RH. Clinical imaging techniques such as ultrasonography and computed tomography (CT) revealed the dynamic formation and resorption of intrapleural clots over time and the resulting lung restriction. RH7 and RH10 were evaluated in young (3 mo) animals of both sexes. The RH7 recapitulated the most clinically relevant RH attributes; therefore, we used this model further to evaluate the effect of age on RH development. Sanguineous pleural fluids (PFs) in the model were generally small and variably detected among different models. The rabbit model PFs exhibited a proinflammatory response reminiscent of human hemothorax PFs. Overall, RH7 results in the consistent formation of durable intrapleural clots, pleural adhesions, pleural thickening, and lung restriction. Protracted chest tube placement over 7 d was achieved, enabling direct intrapleural access for sampling and treatment. The model, particularly RH7, is amenable to testing new intrapleural pharmacologic interventions, including iterations of currently used empirically dosed agents or new candidates designed to safely and more effectively clear RH.

Predicting Complicated Parapneumonic Effusion in Community Acquired Pneumonia: Hospital Based Case-Control Study

OBJECTIVE

To identify predictors of complicated parapneumonic effusion (CPE)/empyema in patients of community acquired pneumonia (CAP) by using clinical and simple laboratory variables like hemoglobin (Hb), serum C-reactive protein (CRP), serum albumin (SA) levels and total leukocyte counts (TLC).

METHODS

This prospective case-control study was conducted after institutional ethical approval. Subjects between ages of 2-59 mo with World Health Organization (WHO) defined CAP with written, informed parental consent were included. Cases had CAP with CPE/empyema diagnosed by pleurocentesis. Controls had severe CAP without significant pleural collection on chest X-ray (CXR). Patients with congenital and chronic diseases/infections and possible immune deficiency were excluded. Variables with univariate association with case-control status were considered as potential predictors. Final prediction model was developed by Forward Stepwise Logistic Regression (FSLR). Adjusted odd's ratios (Adj OR) were smoothened into nearest whole numbers to develop KGMU-CPE score.

RESULTS

From 2016 to 17, 30 cases (66.6% males, age 38.7 + 14.9 mo) and 118 controls (78% males, age 17.8 + 16.9 mo) were included. In FSLR, predictors of CPE/empyema were ibuprofen intake (adj OR 6.8; 95%CI: 1.07-43.6), infective focus elsewhere (adj OR 28.2; 95%CI: 1.4-563.1), hypoalbuminemia <3.1 g/dL (adj OR 6.9; 95%CI: 1.22-39.3), serum CRP >20 mg/dL (adj OR 59; 95%CI: 1.86-1874.7), Hb <10 g/dL (adj OR 21.1; 95%CI: 2.8-158.1) and TLC >10,000 (adj OR 37; 95%CI: 5.7-239.8) and these six variables formed KGMU-CPE Score with a minimum score of 0 and maximum of 25. KGMU-CPE score area under the ROC curve was 0.97 and cut- off 15.55 had sensitivity of 80% and specificity of 94% for predicting CPE/empyema.

CONCLUSIONS

Using simple clinical and laboratory parameters it is possible to predict CAP with CPE/empyema. Use of ibuprofen is to be avoided in CAP as it associated with CPE. KGMU-CPE score had good diagnostic accuracy and needs external validation.

Targeting plasminogen activator inhibitor-1 in tetracycline-induced pleural injury in rabbits

Elevated active plasminogen activator inhibitor-1 (PAI-1) has an adverse effect on the outcomes of intrapleural fibrinolytic therapy (IPFT) in tetracycline-induced pleural injury in rabbits. To enhance IPFT with prourokinase (scuPA), two mechanistically distinct approaches to targeting PAI-1 were tested: slowing its reaction with urokinase (uPA) and monoclonal antibody (mAb)-mediated PAI-1 inactivation. Removing positively charged residues at the "PAI-1 docking site" (¹⁷⁹RHRGGS¹⁸⁴→¹⁷⁹AAAAAA¹⁸⁴) of uPA results in a 60-fold decrease in the rate of inhibition by PAI-1. Mutant prourokinase (0.0625-0.5 mg/kg; n = 12) showed efficacy comparable to wild-type scuPA and did not change IPFT outcomes ( P > 0.05). Notably, the rate of PAI-1-independent intrapleural inactivation of mutant uPA was 2 times higher ( P < 0.05) than that of the wild-type enzyme. Trapping PAI-1 in a "molecular sandwich"-type complex with catalytically inactive two-chain urokinase with Ser¹⁹⁵Ala substitution (S195A-tcuPA; 0.1 and 0.5 mg/kg) did not improve the efficacy of IPFT with scuPA (0.0625-0.5 mg/kg; n = 11). IPFT failed in the presence of MA-56A7C10 (0.5 mg/kg; n = 2), which forms a stable intrapleural molecular sandwich complex, allowing active PAI-1 to accumulate by blocking its transition to a latent form. In contrast, inactivation of PAI-1 by accelerating the active-to-latent transition mediated by mAb MA-33B8 (0.5 mg/kg; n = 2) improved the efficacy of IPFT with scuPA (0.25 mg/kg). Thus, under conditions of slow (4-8 h) fibrinolysis in tetracycline-induced pleural injury in rabbits, only the inactivation of PAI-1, but not a decrease in the rate of its reaction with uPA, enhances IPFT. Therefore the rate of fibrinolysis, which varies in different pathologic states, could affect the selection of PAI-1 inhibitors to enhance fibrinolytic therapy.

Mesothelial cells and peritoneal homeostasis

The mesothelium was traditionally thought to be a simple tissue with the sole function of providing a slippery, nonadhesive, and protective surface to allow easy movement of organs within their body cavities. However, our knowledge of mesothelial cell physiology is rapidly expanding, and the mesothelium is now recognized as a dynamic cellular membrane with many other important functions. When injured, mesothelial cells initiate a cascade of processes leading either to complete regeneration of the mesothelium or the development of pathologies such as adhesions. Normal mesothelial healing is unique in that, unlike with other epithelial-like surfaces, healing appears diffusely across the denuded surface, whereas for epithelium healing occurs solely at the wound edges. This is because of a free-floating population of mesothelial cells which attach to the injured serosa. Taking advantage of this phenomenon, intraperitoneal injections of mesothelial cells have been assessed for their ability to prevent adhesion formation. This review discusses some of the functions of mesothelial cells regarding maintenance of serosal integrity and outlines the mechanisms involved in mesothelial healing. In addition, the pathogenesis of adhesion formation is discussed with particular attention to the potential role of mesothelial cells in both preventing and inducing their development.

Differentiation of Lung Cancer, Empyema, and Abscess Through the Investigation of a Dry Cough

An acute dry cough results commonly from bronchitis or pneumonia. When a patient presents with signs of infection, respiratory crackles, and a positive chest radiograph, the diagnosis of pneumonia is more common. Antibiotic failure in a patient being treated for community-acquired pneumonia requires further investigation through chest computed tomography. If a lung mass is found on chest computed tomography, lung empyema, abscess, and cancer need to be included on the differential and managed aggressively.

This report describes a 55-year-old Caucasian male, with a history of obesity, recovered alcoholism, hypercholesterolemia, and hypertension, presenting with an acute dry cough in the primary care setting. The patient developed signs of infection and was found to have a lung mass on chest computed tomography. Treatment with piperacillin-tazobactam and chest tube placement did not resolve the mass, so treatment with thoracotomy and lobectomy was required. It was determined through surgical investigation that the patient, despite having no risk factors, developed a lung abscess.

Lung abscesses rarely form in healthy middle-aged individuals making it an unlikely cause of the patient's presenting symptom, dry cough. The patient cleared his infection with proper management and only suffered minor complications of mild pneumoperitoneum and pneumothorax during his hospitalization.

Evidence of Innervation in Talc-Induced Pleural Adhesions

STUDY OBJECTIVES

To conduct a detailed morphologic and ultrastructural study of pleural adhesions following talc pleurodesis.

METHODS

Talc with a main particle size of 8.36 +/- 0.2 mum (mean +/- SEM) and at a dose of 200 mg/kg in a 2-mL slurry was instilled via a small catheter into the pleural cavity of 10 male rabbits. Five rabbits were killed at 1 week, and five rabbits were killed at 1 month after instillation. At autopsy, after macroscopically observing the pleural cavity, adhesions were excised from opposing pleural surfaces and processed for histopathologic, immunocytochemical, and ultrastructural study.

RESULTS

At 1 week, all adhesions examined were mesothelium-covered fibrovascular bands containing well-developed blood and lymphatic vessels establishing a structural continuity between both pleural layers. Nerves were present in adhesions from 20% of the rabbits. They consisted of a single fascicle containing 5 to 20 thin myelinated axons of various diameters (1 to 6 microm) uniformly distributed throughout the nerve section. The anatomic location of the adhesion did not appear to influence its overall morphology.

CONCLUSIONS

As early as at 1 week, adhesions are well-formed structures more resembling newly formed pleural tissue than a simple scar. Nerve fibers in pleural adhesions are reported for the first time, which suggests that these adhesions are potentially capable of conducting pain stimuli. Further studies are required in order to confirm our results in human pleural adhesions.

Combination therapy with intrapleural doxycycline and talc in reduced doses is effective in producing pleurodesis in rabbits

BACKGROUND

It has been suggested that talc and doxycycline might be acting through different pathways in creating pleurodesis. We hypothesized that combining doxycycline and talc in half the usual doses would be synergistic in inducing pleurodesis.

METHODS

Thirty-two rabbits were equally allocated into four groups: group 1, half-dose combination (5 mg/kg of doxycycline and 200 mg/kg of talc slurry); group 2, quarter-dose combination (2.5 mg/kg of doxycycline and 100 mg/kg of talc slurry); group 3, half-dose doxycycline (5 mg/kg of doxycycline); and group 4, half-dose talc (100 mg/kg of talc slurry). The pleurodesis scores from historical groups that received a full dose of talc (400 mg/kg) or doxycycline (10 mg/kg) were also compared to those obtained in the current study. Pleural fluid lactate dehydrogenase and protein levels were measured 24 h after the injection. Pleurodesis was graded from 1 (none) to 8 (> 50% symphysis) by two observers blinded to treatment groups. All rabbits underwent an ultrasonic examination on each side of their chest for the evaluation of pleurodesis.

RESULTS

The mean pleurodesis score in the half-dose combination group was significantly higher than that in the half-dose talc group, half-dose doxycycline group, and the historical full-dose talc group (p = 0.009, p = 0.01, and p < 0.05, respectively). The quarter-dose combination group also had a significantly higher mean pleurodesis score compared to the half-dose talc group (p = 0.013). The difference between the historical full-dose doxycycline and the half-dose combination or quarter-dose combination groups was not significant (p > 0.05). A significantly positive correlation existed between the pleurodesis score and the ultrasound scores (r = 0.876, p = 0.000000005).

CONCLUSIONS

This study demonstrates that the combination of half doses of talc and doxycycline is more effective than the half dose of either drug alone or the full dose of talc in producing pleurodesis in rabbits. In addition, ultrasound is an accurate imaging modality for the evaluation of pleurodesis, in that the absence of pleural gliding on ultrasound correlates well with the presence of a pleurodesis in rabbits.

Polidocanol at Different Concentrations for Pleurodesis in Rats

PURPOSE

We previously found that 0.5% polidocanol was more effective than tetracycline for pleurodesis in rats. Thus, we conducted the present study to evaluate the efficacy of different concentrations of polidocanol for pleurodesis in rats.

METHODS

We divided 54 albino Wistar rats into six groups. Groups 1, 2, and 3 were given isotonic saline, 35 mg/kg tetracycline, and 0.6 mg of diluted polidocanol, respectively, being the daily recommended dose for humans. Groups 4, 5, and 6 were given 0.5%, 1%, and 2% polidocanol, respectively. All solutions were given intrapleurally in a volume of 0.5 ml. We examined the rats for macroscopic pleural adhesions and compared the mean values of macroscopic scoring among the six groups.

RESULTS

The rats given polidocanol and tetracycline had significantly more adhesions than the control group, and polidocanol at concentrations of 0.5%, 1%, and 2% was more effective for pleurodesis than tetracycline. The diluted polidocanol was not more effective than tetracycline. There was no difference between the effects of the 0.5% and 1% concentrations, but the 2% polidocanol group had significantly more adhesions than the other groups.

CONCLUSIONS

Polidocanol at concentrations of 0.5%, 1%, and 2% was a more effective sclerosing agent than tetracycline for pleurodesis. While 2% polidocanol was the most efficient sclerosing agent, the daily maximum recommended dose of polidocanol for humans was not more effective than tetracycline.

The efficacy of fibrin tissue adhesives in pleurodesis in rats

In search for a new sclerosing agent for pleurodesis, fibrin tissue adhesive is compared to tetracycline for its efficacy in rats. Twenty-four albino Wistar rats were divided into 3 groups. Groups 1, 2, and 3 were given intrapleural isotonic saline, 35 mg/kg tetracycline, and fibrin tissue adhesive with fibrinogen and thrombin concentrations of 30 mg/mL and 10 U/mL, respectively. Rats were evaluated for macroscopic pleural adhesions and mean values of macroscopic scoring were compared among the groups. Fibrin tissue adhesive- and tetracycline-treated rats had significantly more adhesions compared to the control group, whereas fibrin tissue adhesive was more effective for pleurodesis than tetracycline and no deaths or major side effects were observed in any rat. Thus, fibrin tissue adhesive was found as a more effective sclerosing agent than tetracycline for pleurodesis in rats.

Chemotherapeutic management of malignant pleural effusion

The management of malignant pleural effusions are a common, and sometimes difficult, therapeutic problem. This article reviews the currently available sclerosing agents and discusses novel agents that show promise for the future. Talc, tetracycline and bleomycin are currently the most widely used agents but none is an ideal sclerosant and certain adverse effects are of concern. Novel agents, particularly transforming growth factor (TGF)-beta(2) and metalloproteinase inhibitors, are being investigated, and the increase in knowledge into the mechanisms of pleural fluid formation and pleurodesis will hopefully lead to the development of targeted therapy in the future.

Inflammatory triggers of lymphangiogenesis

Inflammation is the common denominator to the postnatal events that overlap with lymphatic vessel growth, or lymphangiogenesis. Undoubtedly, inflammation and accompanying fluid overload are cardinal factors in wound healing, lymphedema, the pathogenesis of some forms of lymphangiomatosis, and solid tumor lymphangiogenesis. The assertion that inflammation actually triggers lymphangiogenesis lies in the evidence set forth below that inflammation is the usual precursor to tissue repair and regeneration. Moreover, the panel of pro-inflammatory and anti-inflammatory molecules that orchestrates the inflammatory response abounds with cytokines and chemokines that foster survival, migration, and proliferation of lymphatic endothelial cells. Finally, both interstitial fluid overload and increased demand for removal of leukocytes can benefit from lymphangiogenesis, although the mechanisms controlling the exit of leukocytes from tissues via the lymphatics are practically unknown. The pertinent question actually is how and why inflammation presents with formation of new lymph vessels in liver fibrosis but not in rheumatoid arthritis. One possible explanation is that organ-specific histological and functional properties of the lymphatic endothelium gauge their response to death, survival, and proliferative factors. Alternatively, the decision to remain quiescent, proliferate or regress resides within the stroma microenvironment.

Sonographically guided small-bore chest tubes and sonographic monitoring for rapid sclerotherapy of recurrent malignant pleural effusions

OBJECTIVE

To evaluate the role of sonographically guided small-bore chest catheters and sonographically based monitoring of fluid evacuation in rapid sclerotherapy of malignant pleural effusions.

METHODS

In 50 patients with recurrent malignant pleural effusions, a 9F catheter was inserted into the pleural space under sonographic guidance. When sonography documented complete fluid evacuation, bleomycin (0.75 mg/kg) was injected via the tube. Fluid drainage was monitored for 12 hours; if fluid output was less than 100 mL, the pleural catheter was removed; otherwise, a second dose of bleomycin was administered after 24 hours. If loculations or fluid reaccumulations due to tube malfunctioning were detected, they were evacuated by sonographically guided thoracentesis, and bleomycin (1.5 mg/100 mL of fluid) was injected through the thoracentesis needle. All patients were monitored for fluid recurrence with thoracic sonography.

RESULTS

Twenty-nine patients received 1 dose of bleomycin, and 21 received 2 doses. In 11 patients with residual loculations, sonographically guided thoracentesis was performed, and bleomycin was injected into the loculations. In 29 patients, pleurodesis was completed within 24 hours; in 21, it was completed within 48 hours. The 30-day response was 84%; the long-term response was 60%. No complications or serious side effects were observed.

CONCLUSIONS

Rapid pleurodesis can be accomplished within 24 to 48 hours, with good short- and long-term responses. Thoracic sonography plays a pivotal role. It guides placement of the pleural catheter and is valuable in the monitoring of fluid evacuation for determining the right time for sclerosing agent administration and in the detection and treatment of loculations or residual pleural fluid due to tube malfunctioning.

Rapid pleurodesis for malignant pleural effusions

STUDY OBJECTIVE

To determine the feasibility of rapid pleurodesis in patients with malignant pleural effusions in order to reduce hospital length of stay in patients with a limited life expectancy.

DESIGN

Prospective case series.

SETTING

Two university hospital programs.

PATIENTS

Thirty-eight patients with symptomatic pleural effusions associated with malignancy.

INTERVENTIONS

A 14F catheter was inserted percutaneously into the pleural space after radiographic confirmation of free fluid by lateral decubitus views. Following radiographic confirmation of complete fluid evacuation, a sclerosing agent (ie, talc slurry or bleomycin) was instilled into the pleural space. This was accomplished within 2 h of chest tube insertion, unless the tube was inserted in the evening or if the lung was trapped. After clamping the tube for 90 min, the pleural space was drained for 2 h, after which the chest tube was removed. The intervention was scored as "successful" if no radiographic evidence of fluid reaccumulation was noted at 4 weeks. A "partial successful" score indicated reaccumulation of fluid that did not produce symptoms and did not require repeat pleural drainage of any sort. All other outcomes were scored as "unsuccessful."

MEASUREMENTS AND RESULTS

Forty chest tubes were inserted into 38 patients. Four procedures revealed the presence of a trapped lung and did not result in any attempt at pleurodesis. Five patients who received pleurodesis died in less than 1 month and therefore were not evaluable. Two patients had technical problems with the chest tube and were not evaluable. Of the remaining 29 procedures, drainage procedures with pleurodesis were performed in 27 patients, a complete response was seen in 14 patients (48%), a partial response was seen in 9 patients (31%), and 6 patients (21%) did not respond to pleurodesis. Chemical pleurodesis was completed as an outpatient procedure in only two patients. In one of these, the outcome was unsuccessful. In the remainder, insertion of the chest tube in the evening or additional medical problems necessitated hospital admission, but the entire procedure was completed within 24 h.

CONCLUSIONS

Chemical pleurodesis can be accomplished with good results in < 24 h in the majority of patients with malignant pleural effusions.

Inflammatory cytokines mediate C-C (monocyte chemotactic protein 1) and C-X-C (interleukin 8) chemokine expression in human pleural fibroblasts

Current knowledge implicates pleural mesothelial cells as mainly responsible for inflammatory responses in the pleural space. However, a vast body of recent evidence underscores the important role of fibroblasts in the process of inflammation in several types of tissues. We hypothesize that HPFBs (human pleural fibroblasts) play an important role in pleural responses and also when activated by bacterial endotoxin LPS (lipopolysaccharide), IL-1 beta (interleukin-1 beta), or TNF-alpha (tumor necrosis factor-alpha) release of C-C and C-X-C chemokines-specifically, MCP-1 and IL-8. Our results show that pleural fluid-isolated human fibroblasts release IL-8 and MCP-1 upon stimulation with IL-1 beta, TNF-alpha, and LPS in both a concentration- and time-dependent manner. RT-PCR (reverse-transcriptase-polymerase chain reaction) studies have also confirmed IL-8- and MCP-1-specific mRNA expression in activated pleural fibroblasts. On the time-dependent response curve, IL-8 was found in maximum concentrations at 144 hr, whereas MCP-1 continued to increase even after 196 hr following stimulation. IL-1 beta induced the maximum release of IL-8 (800-fold) and MCP-1 (164-fold), as compared to the controls. TNF-alpha induced a 95-fold increase in IL-8 and an 84-fold increase in MCP-1 levels, as compared to the controls. Collectively, our results show that human pleural fibroblasts contribute to the inflammatory cascade in the pleural space.

Mesothelial cells in suspension expose an enriched integrin repertoire capable of capturing soluble fibronectin and laminin

Pleural cavities are lined by a polarized monolayer of mesothelial cells (MC). During pleuritis, MC are shed into effusions, and pleural obstruction may occur. Integrins are cell surface receptors mediating interactions with extracellular matrix (ECM) proteins. The distribution of beta 1-, beta 3-, beta 4-integrins and fibronectin and laminin in normal and chronically inflamed pleura and in/on MC from pleural effusions was examined by immunomorphology and flow cytometry. Adhesion assays of MC to fibronectin and laminin were performed. In situ, resting MC expressed beta 1-, beta 3-, and beta 4-, and alpha v-subunits. Activated MC were beta 1- and alpha v-positive and also expressed alpha 3 and alpha 6; beta 4 was confined to the basal surface of MC; beta 3 was absent. Floating MC from effusions neoexpressed alpha 5 and reexpressed beta 3. In vitro, MC surface expressed beta 1, beta 3, alpha 3, alpha 5, alpha 6, alpha v, and also alpha 1 and alpha 2. In normal pleura, fibronectin and laminin were components of the basement membrane. In pleuritis, the basement membrane was desintegrated. Instead, newly formed fibronectin/laminin containing fibrils extended into the submesothelial connective tissue. Floating MC freshly isolated from effusions carried fibronectin and laminin on their surface and showed specific binding to these ECM proteins. Binding was blocked by anti-beta 1 or anti-alpha 5 and anti-alpha 6 antibodies, respectively. MC incubated with fibronectin showed a clear shift to the S phase, while laminin had no effect. In conclusion, activated and detached MC progressively enrich their integrin repertoire. By capturing soluble fibronectin and laminin and by matrix-mediated bridging, readhering MC may contribute to pleural obstruction. Further, soluble fibronectin bound to alpha 5 beta 1 might be life-sustaining for floating MC by driving cells into cell cycle.

Characterization of indolinones which preferentially inhibit VEGF-C- and VEGF-D-induced activation of VEGFR-3 rather than VEGFR-2

VEGF-C and VEGF-D are lymphangiogenic factors that bind to and activate VEGFR-3, a fms-like tyrosine kinase receptor whose expression is limited almost exclusively to lymphatic endothelium in the adult. Processed forms of VEGF-C and VEGF-D can also activate VEGFR-2, a key player in the regulation of angiogenesis. There is increasing evidence to show that these receptor-ligand interactions play a pivotal role in a number of pathological situations. Inhibition of receptor activation by VEGF-C and VEGF-D could therefore be pharmaceutically useful. Furthermore, to understand the different roles of VEGF-C, VEGF-D, VEGFR-2 and VEGFR-3 in pathological situations it will be necessary to dissect the complex interactions of these ligands and their receptors. To facilitate such studies we cloned, sequenced and characterized the expression of rat VEGF-C and VEGF-D. We showed that Cys152-->Ser mutants of processed rat VEGF-C can activate VEGFR-3 but not VEGFR-2, while the corresponding mutation in rat VEGF-D inhibits its ability to activate both VEGFR-2 and VEGFR-3. We also synthesized and characterized indolinones that differentially block VEGF-C- and VEGF-D-induced VEGFR-3 kinase activity compared to that of VEGFR-2. These tools should be useful in analysing the different activities and roles of VEGF-C, VEGF-D and their ligands, and in blocking VEGFR-3-mediated lymphangiogenesis.

Tetracycline aspiration. Case report and review of the literature

A 74-year-old woman presented with a 2-day history of cough, dyspnea and wheezing following aspiration of a tetracycline tablet. She developed a left lower lobe pneumonitis, and bronchoscopy revealed left main bronchus narrowing and exudate. The course of this patient is discussed in reference to the available literature on toxic aspirations.

Increased levels of surgical adhesions in TGFbeta1 heterozygous mice

Adhesion formation and fibrosis represent a major complication of surgical intervention. Reducing the morbidity associated with adhesions requires an understanding of the mechanisms underlying their formation. Since increased levels of transforming growth factor-beta1 (TGFbeta1) have been associated with inflammation and adhesion production, we investigated the requirement of TGFbeta1 in peritoneal adhesion formation utilizing mice carrying a targeted disruption of the TGFbeta1 allele. Mice that were either wild-type (+/+), containing two normal alleles of TGFbeta1, or heterozygous (+/-) for the TGFbeta1 null allele received injections of magnesium silicate (talc), and the extent of abdominal adhesions was determined utilizing a standard grading score. Wild-type (+/+) animals had at least twofold more TGFbeta1 protein in peritoneal fluids at 2 h posttrauma compared to heterozygous (+/-) mice (727 vs. 243 pg TGFbeta1/mg protein by enzyme-linked immunosorbent assay (ELISA) in +/+ and +/- mice, respectively), and had significantly less scar and adhesion formation (p < .05) at 7 days posttrauma (1.8 +/- 0.8 vs. 3.4 +/- 1.4, graded from 0 to 5, in +/+ and +/- mice, respectively). These results demonstrate that haploid insufficiency in TGFbeta1 levels can lead to inappropriate matrix and adhesion production during inflammation, and together with previous studies suggest that any perturbation of normal TGFbeta1 levels can modulate the injury response that regulates the extent of adhesion formation.

An inhibitor of cell proliferation associated with adhesion formation is suppressed by N,O-carboxymethyl chitosan

Surgical adhesions are a major cause of morbidity and mortality. The ideal barrier agent will both minimize adhesions and provide a milieu for the regeneration of the mesothelium lining of the abdominal and thoracic cavities. N,O-Carboxymethylchitosan (NOCC), a derivation of chitin that markedly reduces adhesions, may function to modulate intracellular signals such as growth factors and cytokines in the inflammatory exudate. Since transforming growth factor-beta is implicated in the fibrotic process, we investigated the possibility that NOCC's effects on adhesion formation reflects a modulation of TGF-beta activity. Using a biological assay for inhibition of cell proliferation to detect TGF-beta activity, we demonstrate that NOCC suppresses the levels of an inhibitor of cell proliferation released into serum and peritoneal exudates after cecal abrasion in the rat. However, this activity was distinct from known forms of TGF-beta as determined using both TGF-beta-neutralizing antisera and a TGF-beta-resistant cell proliferation assay. Thus at least one potential effect of NOCC involves a mechanism distinct from TGF-beta inhibition.

Tissue factor expression in mesothelial cells: induction both in vivo and in vitro

Exudative pleural effusions are characterized by a high protein content and frequently progress to loculation and fibrosis. To test the hypothesis that tissue factor (TF) plays an integral role in this process, we investigated the expression of TF by human mesothelial cells (HMC) both in vivo and in vitro, and measured the effect of serum on HMC expression of TF in vitro. In vivo TF expression was not detected in HMC of normal pleura, but was detected in HMC of pleura overlying inflamed lung. In vitro, quiescent HMC demonstrated negligible levels of TF expression; however, upon serum stimulation there was a marked induction in both TF protein level and activity, peaking at 8-9 h. In contrast, treating quiescent HMC with plasma resulted in a further small, but significant, decrease in TF expression. This serum-induced rise in TF was also reflected in TF mRNA levels and did not require de novo protein synthesis. These results suggest that induction of HMC TF expression may be important in triggering both the intrapleural activation of prothrombin and the deposition of fibrin characteristic of inflammatory effusions.

Pleural mesothelioma mimics the integrin profile of activated, sessile rather than detached mesothelial cells

Mesothelial cells (MC) form a polarized monolayer lining serosal cavities. During serositis, the MC lining undergoes hyperplasia, and MC are shed into effusions. During these processes, contact with basement membrane and, ultimately, neighboring cells is at least temporarily lost, suggesting regulated alterations in cell/matrix and cell/cell adhesion. Such interactions are primarily mediated by integrins. Malignant mesothelioma has a growth pattern characterized by lateral, limited invasive but contiguous spread. During serositis, activated MC, both sessile and detached, expressed an extended spectrum of beta1, beta3 and beta4 integrins compared with resting MC, as shown by immunohistology. Malignant mesothelioma had an integrin repertoire and a subcellular distribution resembling that of activated sessile rather than floating MC. In vitro, MC exposed a more comprehensive pattern of integrins than that of the newly established mesothelioma cell lines ME-HD-1 and ME-HD-2, as shown by flow cytometry. MC consistently adhered better than mesothelioma cells to laminin, tenascin, fibronectin and collagen type IV. Adhesion of MC and mesothelioma cells to these matrix proteins was, at least in part, mediated via beta1 integrins. The different integrin profiles and adhesion properties of cultured MC and mesothelioma cells may reflect a limited functional differentiation of the latter.

A comparison of thoracoscopic talc insufflation, slurry, and mechanical abrasion pleurodesis

The purpose of this study was to compare the anatomic and histopathologic results of four different methods of pleurodesis in 10 dogs. Each animal was randomly assigned to receive two of the following methods of pleurodesis: thoracoscopic talc insufflation (poudrage), talc slurry administration, focal gauze abrasion by limited thoracotomy, and mechanical abrasion by thoracoscopy using a commercially available pleural abrader. Animals were killed 30 days after pleurodesis. At autopsy, the efficacy of pleurodesis was graded by evaluating the gross appearance of each pleural cavity and lung (pleurodesis score), and by determining the extent of adhesion formation (obliteration grade). Pleural and lung biopsy specimens were obtained from the areas most representative of adhesion formation for histopathologic evaluation. Pleurodesis scores (on a scale of 0 to 4) were 3.0 +/- 0.7 for talc poudrage (p < 0.05 when compared with talc slurry), 2.2 +/- 1.7 for thoracotomy, and 1.6 +/- 1.1 for talc slurry. Adhesions produced by gauze abrasion during thoracotomy were mostly peri-incisional. Thoracoscopic pleural abrasion using the pleural abrader was uniformly unsatisfactory. Granulation tissue formation was greatest in both talc models. The degree of parietal pleural thickening was greatest in the talc slurry model, but fibrosis and inflammation occurred mostly in gravity-dependent areas within the pleural cavity. Although differences were not statistically significant, thoracoscopic talc insufflation consistently produced the most widespread, firm fibrotic adhesions as evidenced by higher obliteration grades.

Pleural macrophages differentially alter pleural mesothelial cell glycosaminoglycan production

Glycosaminoglycans are produced in abundance by the pleural mesothelium and likely participate in the inflammatory response to pleural injury. Because intrapleural tetracycline (TCN) results in pleural macrophage influx and pleural fibrosis, this study attempted to define the role of pleural macrophage products on mesothelial glycosaminoglycan (GAG) production. Pleural macrophages were isolated 72 h after intrapleural TCN or intrapleural carrageenan (CAR), a substance that recruits pleural macrophages without producing pleural fibrosis. Macrophage cultured for 24 h produced a conditioned medium that was added to pleural mesothelial cell culture containing [3H]-glucosamine and was compared to control cultures treated with RPMI culture media alone or with the addition of TCN or CAR. After 72 h, GAGs were isolated by pronase digestion, cetyl pyridinium precipitation, and MgCl2 and ethanol extraction. The majority of GAGs were found in the culture media as compared to the combined mesothelial cell and basement membrane fractions of control mesothelial cells (883 +/- 33 vs. 216 +/- 16, cpm, counts per minute), TCN-treated (792 +/- 48 vs. 204 +/- 18 cpm), CAR-treated (849 +/- 45 vs. 223 +/- 13 cpm), and macrophage-conditioned media-treated mesothelial cells (TCN macrophage-conditioned media: 1420 +/- 42 vs. 356 +/- 11 cpm; CAR macrophage-conditioned media: 1241 +/- 38 vs. 339 +/- 10 cpm) (all p < .05). Media samples were enzymatically digested and individual GAG species were separated by Sephadex G-50 column chromatography. TCN macrophage-conditioned media induced more GAG production by the mesothelial cell into the cell media (1420 +/- 42 cpm) than CAR macrophage-conditioned media (1241 +/- 38 cpm) (p < .05), which was predominantly a difference in hyaluronate production (342 +/- 53 cpm vs. 186 +/- 7 cpm) (P. < .05). The results show that pleural macrophages modulate mesothelial GAG production during tetracycline pleural injury. Increases in mesothelial cell hyaluronate production may be important in the fibrotic response to chemical pleural injury.

Nitric oxide synthesis by rat pleural mesothelial cells: induction by growth factors and lipopolysaccharide

The purpose of this study was to determine if certain growth factors and bacterial products induce pleural mesothelial cells (PMC) to produce nitric oxide (NO). Confluent monolayers of rat PMC were exposed to epidermal growth factor (EGF), platelet-derived growth factor (PDGF), or lipopolysaccharide (LPS) individually and in various combinations for 24-72 h. Concentrations of nitrite and nitrate were quantified and used as an indirect measure of NO production. LPS stimulation resulted in a significant increase in nitrite/nitrate concentration, but neither EGF nor PDGF alone or combined had any significant effect relative to control. However, LPS combined with either EGF or PDGF caused a significant increase in nitrite/nitrate concentration relative to LPS alone and growth factor alone. The highest level level of nitrite/nitrate concentration was observed with the triple combination of LPS, EGF, and PDGF. Nitrite/nitrate accumulation was significantly increased at 24 h by all combinations, and continued to increase, with the highest concentration observed after 72 h of exposure. Nitrite/nitrate production was significantly inhibited by NG-nitro-L-arginine methyl ester and this inhibition was reversed by the addition of L-arginine, suggesting that nitrite and nitrate were derived from the L-arginine-dependent formation of NO. These data indicate that PMC can be induced to produce relatively large amounts of NO in response to growth factors combined with LPS.

Characterization of proteoglycans produced by rat pleural mesothelial cells in vitro

The mesothelial cell envelopes the surface of the parietal and visceral pleura. These cells are known to synthesize most of the protein constituents of the pleural basement membrane and interstitium. This study examined the ability of a rat pleural mesothelial cell line to synthesize proteoglycans in vitro. Cells were labeled with inorganic 35SO4 to label the glycosaminoglycan moiety of proteoglycans. The medium and combined cell membrane/extracellular matrix fractions contained 73 and 25% of the proteoglycan radioactivity, respectively. The medium contained a single chondroitin/dermatan sulfate proteoglycan of approximately 190 kDa, consistent with biglycan. As determined by Northern analysis of steady-state levels of messenger RNA, the cells contained message for biglycan. Stimulation of the cells with epidermal growth factor resulted in the appearance of a second chondroitin/dermatan sulfate proteoglycan of approximately 97 kDa, characteristic of decorin. The cell membrane/matrix contained a biglycan-like chondroitin/dermatan proteoglycan and several heparan sulfate proteoglycans. Pleural mesothelial cells in vitro are capable of synthesizing a variety of interstitial and basement membrane proteoglycans.

Talc slurry pleurodesis. Pleural fluid and histologic analysis

Although talc slurry pleurodesis is effective for control of malignant pleural effusions and recurrent pneumothorax, the mechanisms of pleurodesis remain incompletely defined. We instilled 70 mg/kg of sterile asbestos-free talc slurry into the pleural space of New Zealand white rabbits and studied the inflammatory response at 1, 2, 3, 7, 15, 30, 60, 90, and 120 days by observing pleural fluid and histologic characteristics. Talc slurry caused mesothelial denudement and an exudative neurotrophilic pleural effusion that resolved after 48 h. A transient mononuclear vasculitis was seen within the lung at 1, 2, and 3 days after instillation. Pleural adhesions were minimal and did not increase in number over time. Talc was found outside of the pleural space in mediastinal lymph nodes (4 of 23 animals examined), kidney (1 of 6), and spleen (4 of 10). The predominant cause of pleurodesis with talc slurry instillation is an acute pleural injury similar to the tetracycline class agents.

Histologic changes of doxycycline pleurodesis in rabbits. Effect of concentration and pH

The effects of doxycycline hyclate (DOXY) pleurodesis were compared with those of tetracycline hydrochloride (TCN) in 25 healthy New Zealand White rabbits. One group of rabbits received TCN (pH 2.0) in the left pleural space at a concentration of 35 mg/kg in 3.0 ml of saline solution. Four other groups of rabbits received DOXY in two concentrations (35 mg/kg or 10 mg/kg) and at two pHs (an acid of 2.0 and a NaOH neutralized pH of 7.6). No attempt was made to drain the pleural space after pleurodesis. At autopsy 2 weeks later, bloody fluid filled the pleural cavity and extensive intrapleural adhesions compressed the underlying lung. Microscopically, fibrin and collagen were diffusely deposited in the pleural connective tissue and in the intrapleural adhesions. The visceral pleural thickness increased from its normal value of 0.01 mm to values of 0.5 to 0.9 mm in the TCN and DOXY groups. Fibroblasts were the predominant inflammatory cell in the pleural connective tissue with few neutrophils or lymphocytes. No significant differences of histologic characteristics were observed between the TCN and DOXY groups. Alterations in pH or concentration in the DOXY groups produced similar changes in the gross and microscopic appearance of the pleural space. We conclude that DOXY is as effective as TCN in producing chemical pleurodesis. Doxycycline concentrations of 10 mg/kg were sufficient to substantially sclerose the pleural space in these healthy rabbits. Doxycycline pleurodesis was effective at neutral pH suggesting a mechanism of action independent of acid injury to the mesothelium.

Growth factor modulation of rat pleural mesothelial cell mitogenesis and collagen synthesis. Effects of epidermal growth factor and platelet-derived factor

This study examined the effects of an epithelial and a mesenchymal growth factor on pleural mesothelial cell proliferation and collagen synthesis, functions that may be important in the response of the pleura to injury. Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) added singly caused significant increases relative to control in both the uptake of [3H]thymidine into the cellular DNA of subconfluent monolayers and of [3H]proline into collagenase-sensitive protein. Combinations of EGF and PDGF resulted in more than additive increases in proliferation and additive increases in collagen production relative to each factor alone. Media from control and growth factor-stimulated PMC demonstrated no gelatinase or collagenase activity, suggesting that the increase in net collagen production was secondary to enhanced synthesis. These data demonstrate that both epithelial and mesenchymal growth factors can stimulate PMC proliferation and collagen synthesis and that these growth factors have even greater effects when combined, particularly in regard to cellular proliferation. Increases in PMC proliferation and collagen synthesis in response to these growth factors may be important in healing the pleura after injury by a variety of disease processes.

A comparison of rotation and nonrotation in tetracycline pleurodesis

Previously, we have shown rapid and complete dispersion of tetracycline hydrochloride in the pleural space following chest tube instillation. To assess the clinical relevance of this observation, we randomized patients with symptomatic pleural effusions to rotation (R) (n = 19) and nonrotation (NR) (n = 21) groups following administration of tetracycline hydrochloride, 20 mg/kg (n = 30); 300 mg of minocycline hydrochloride (n = 6); and 500 mg of doxycycline hydrochloride (n = 4) through a chest tube. Patients in the R group were maneuvered through six positions for the 2 h that the chest tube remained clamped. The NR patients remained supine for 2 h. Rotation and nonrotation groups were similar in demographics, source of pleural effusion, symptoms, and serum and pleural fluid analyses (all p = NS). A chest radiograph was scored based on pleural fluid recurrence throughout survival or up to 12 months. Survival, duration of chest tube instillation, and success of pleurodesis assessed by radiographic pleural fluid reaccumulation (73.7 vs 61.9 percent; R vs NR) were similar (p = NS). Rotational maneuvers appear to offer no benefit to the success of pleural symphysis after intrapleural instillation of tetracycline class agents.

Electron microscopic analysis of the normal and the activated pleural macrophage

Despite an apparent role in pleural pathophysiology, little information is known about pleural macrophage morphology. Intrapleural tetracycline (TCN) results in pleural macrophage influx and pleural fibrosis; intrapleural carrageenan (CAR) induces macrophage influx without ensuing fibrosis. Pleural macrophages collected from normal (NL) and TCN- or CAR-exposed rabbit pleural spaces were examined with electron microscopy. Cellular size; number of microvilli; pseudopods; coated pits (CP) and coated vesicles (CV); and prevalence of golgi, rough endoplasmic reticulum (RER), and intermediate filaments (IF) were determined. The means of each variable in each group were assessed by one-way analysis of variance, with post hoc testing performed by Scheffe F test; p < or = .05 was considered significant. TCN-stimulated pleural macrophages were characterized by their small perimeters. CAR-induced pleural macrophages were marked by their large size and abundant intracellular amorphous material. They had larger perimeters, areas, and diameters than the TCN-induced or normal macrophages and thus smaller numbers of CV + CP per area. The normal pleural macrophages were characterized by more IF, microvilli, and microvilli per perimeter than either the CAR- or TCN-induced pleural macrophages. No differences between groups were found in nuclear cytoplasmic ratios, number of pseudopods, and content of golgi or of RER. The results suggest that normal pleural macrophages and TCN- and CAR-induced pleural macrophages differ morphologically and that these morphologic differences reflect functional differences.

Early inflammatory response of minocycline and tetracycline on the rabbit pleura

The histopathologic findings were compared from 20 mg/kg intrapleural tetracycline hydrochloride (TCN) and three doses of intrapleural minocycline hydrochloride (5, 10, and 20 mg/kg) (MCN) in New Zealand white rabbits. Both TCN and MCN produced an early neutrophilic predominant pleural effusion that became mononuclear over 48 h. There was no difference in pleural fluid accumulation, number of adhesions, or histologically measured visceral and parietal pleural thickness between TCN and MCN (all p = ns). The TCN, 20 mg/kg, produced more visceral pleural plaque than MCN, 5 mg/kg (p < 0.05). Increasing MCN doses resulted in greater pleural fluid neutrophil accumulation. With higher dose MCN, greater mesothelial cell desquamation and fibroblast proliferation was evident compared to the 5 mg/kg dose. The MCN and TCN produce similar histopathologic condition in the rabbit pleura which suggests that MCN should cause a similar clinical response in humans.

Empyema thoracis: a problem with late referral?

BACKGROUND

Patients are often referred to thoracic units for management of empyema after the acute phase has been treated with antibiotics but without adequate drainage. This study evaluates the effects of delay in surgical treatment of empyema thoracis on morbidity and mortality.

METHODS

Thirty nine consecutive patients were studied from January 1991 to June 1992. Two groups (group 1, 16 patients; group 2, 23 patients) were compared depending on the time spent under the care of other specialists before referral to the thoracic unit (group 1, seven days or less; group 2, eight days or more). The reasons for delay in referral were analysed.

RESULTS

Four patients were treated conservatively with chest drainage alone (all in group 1). Thirty five patients required rib resection and drainage of their empyema (group 1, 12 patients; group 2, 23 patients). Nineteen (all in group 2) of the 35 patients who had rib resections went on to have decortication. The commonest cause of empyema was post-pneumonic (37 out of 39 patients). Staphylococcus aureus was the commonest organism isolated. Misdiagnosis (five patients), inappropriate antibiotics (six patients), and inappropriate placement of chest drainage tubes (three patients) all contributed to persistence and eventual progression of empyema. The overall mortality was 10% and mortality increased with age. The median stay in hospital was 9.5 days (range 7-12 days, n = 4) for patients treated with closed tube drainage only; 18 days (range 10-33 days, n = 16) for patients who had undergone rib resections and open drainage; and 28 days (range 22-49 days, n = 19) for patients who underwent decortication. The likelihood of having a staged procedure (antibiotics, closed tube drainage, open drainage with rib resection, and finally decortication) increased when closed tube drainage was persevered with for more than seven days. The total hospital stay was positively related with the time before referral for surgical treatment. Anaemia, low albumin concentrations, and worsening liver function were found in group 2 compared with group 1.

CONCLUSIONS

Early adequate operative drainage in patients with empyema results in low morbidity, shorter stays in hospital, and good long term outcome. These patients should be treated aggressively and early referral for definitive surgical management is recommended.

Intrapleural streptokinase in experimental empyema

Intrapleural streptokinase has been used in multiloculated empyemas to enhance pleural space drainage, presumably by causing fibrinolysis of the interlocular septae. We evaluated the efficacy and safety of daily administration of 10,000 U intrapleural streptokinase or equal volumes of saline to enhance resolution of experimental empyema in the rabbit pleural space. Seventy-two hours after intrapleural turpentine, 10(8) colony-forming units each of Escherichia coli, Peptostreptococcus anaerobius, and Bacteroides fragilis were injected into the sterile pleural effusion of all animals. Immediately after bacterial inoculation, and daily for 3 days, animals received 10,000 U streptokinase or saline intrapleurally. Animals that achieved a pleural fluid pH < 7.30 and either glucose < 50 mg/dl or LDH > 500 IU/L were included for data analysis. At Day 4 after bacterial inoculation, the streptokinase-treated empyemic rabbits had more pleural fluid (18.8 +/- 5.1 ml) (mean +/- SEM) than did saline-treated control animals (4.8 +/- 1.7 ml) (p = 0.015), fewer interpleural adhesions (8.2 +/- 2.7) than did saline-treated control animals (25.1 +/- 3.6) (p = 0.002), and comparable amounts of visceral and parietal pleural plaque than did saline-treated control animals (p = NS). No evidence of systemic fibrinolysis was observed at 1 h after intrapleural streptokinase administration. We conclude that intrapleural streptokinase decreases interpleural adhesion numbers but fails to reduce the amount of pleural plaque observed in experimental empyema in rabbits. The increases in pleural fluid volume observed after streptokinase administration may be due to mechanisms other than fibrinolytic activity.

Metalloproteinases and tissue inhibitor of metalloproteinases in mesothelial cells. Cellular differentiation influences expression

Mesothelial cells play a critical role in the remodeling process that follows serosal injury. Although mesothelial cells are known to synthesize a variety of extracellular matrix components including types I, III, and IV collagens, their potential to participate in matrix degradation has not been explored. We now report that human pleural and peritoneal mesothelial cells express interstitial collagenase, 72- and 92-kD gelatinases (type IV collagenases), and the counterregulatory tissue inhibitor of metalloproteinases (TIMP). Our initial characterization of the mesothelial cell metalloenzymes and TIMP has revealed: (a) they are likely identical to corresponding molecules secreted by other human cells; (b) they are secreted rather than stored in an intracellular pool; (c) a primary site of regulation occurs at a pretranslational level; (d) phorbol myristate acetate, via activation of protein kinase C, upregulates expression of collagenase, 92-kD gelatinase, and TIMP, but has no effect on expression of 72-kD gelatinase; and (e) lipopolysaccharide fails to upregulate the biosynthesis of either metalloproteinases or TIMP. Of particular interest is the observation that the state of cellular differentiation has a striking influence on the expression of metalloenzymes and TIMP, such that epitheloid cells display a more matrix-degradative phenotype (increased 92-kD gelatinase and decreased TIMP) than their fibroblastoid counterparts. We speculate that mesothelial cells directly participate in the extracellular matrix turnover that follows serosal injury via elaboration of metalloproteinases and TIMP. Additionally, the reactive cuboidal mesothelium which is characteristic of the early response to serosal injury may manifest a matrix-degenerative phenotype favoring normal repair rather than fibrosis.

Tetracycline and doxycycline inhibit pleural fluid metalloproteinases. A possible mechanism for chemical pleurodesis

We hypothesized that inhibition of matrix-degrading metalloproteinases (MMPs) accounts for a portion of the pleural fibrosis and adhesions of tetracycline pleurodesis. MMPs recently have been described in pleural fluid from patients with both exudative and transudative effusions. Since tetracyclines are recognized inhibitors of other metalloproteinases, we investigated their inhibitory capacity in pleural fluid. High concentrations of several different tetracyclines reduced MMP activity of pleural fluid by more than 75 percent. Lower concentrations (< or = 1 mg/ml) had only modest inhibitory effects. High concentration of of tetracyclines also inhibited cell synthesis of MMPs, in vitro, but other measures of vital cell function were also impaired. We conclude that tetracyclines are effective inhibitors of MMP activity in pleural fluid and may also reduce synthesis of MMPs via non specific cell injury. These data suggest a possible mechanism to account for tetracycline pleurodesis; ie, an inhibition of MMP activity in pleural fluid.

Pleural macrophages differentially alter mesothelial cell growth and collagen production

Intrapleural tetracycline (TCN) results in pleural macrophage influx and pleural fibrosis; intrapleural carrageenan (CAR) induces macrophage influx without fibrosis. Because macrophage products can modulate mesothelial cell activity, we investigated the role of TCN- and CAR-induced pleural macrophages on mesothelial cell growth can collagen production. Rabbit pleural macrophages, isolated by plastic adherence 72 h after 20 mg/kg TCN or 10 mg CAR instilled intrapleurally, were cultured for 20 h. Macrophage-conditioned media (MCM) from TCN-or CAR-induce pleural macrophages (TCN MCM, CAR MCM, respectively), were added to non-confluent or confluent rat visceral pleural mesothelial cells and compared to the effects of TCN and CAR. Nonconfluent mesothelial cells were harvested 72 h later for hemacytometry cell counts. A 20-h pulse of [3H] proline (1 mu Ci, 30 Ci/mM) preceded 72-h-cell harvesting of confluent cells. Collagen content was determined in the cell fraction and cell media separately after bacterial collagenase exposure. Mesothelial cells exposed to TCN MCM were found to have decreased numbers when compared to all groups (P < 0.05) except CAR. Cell media collagen content was increased in all macrophage-conditioned-media and chemical-exposed groups compared with control, with TCN MCM having a larger increase than TCN alone (P < 0.05). We conclude that stimulated pleural macrophages release a factor(s) that alters mesothelial cell growth and collagen production and that TCN- and CAR-stimulated pleural macrophages are functionally different. These in vitro mesothelial cell alterations may be important in the genesis of TCN pleurodesis.

The clinician's perspective on parapneumonic effusions and empyema

Respondents at an interactive symposium on pleural space infections (n = 339) at the 1991 American College of Chest Physicians Annual Scientific Assembly recorded their personal management preferences for hypothetical patients with empyema. The group's preference was to treat pleural sepsis from an anaerobic multiloculated empyema by pleural decortication (49 percent); however, open thoracotomy with directed chest tube placement (22 percent), chest tube placement with intrapleural streptokinase (14 percent), placement of a single chest tube into the largest pleural loculus (8 percent), and placement of multiple small-bore catheters with computed tomographic guidance (7 percent) all had proponents. In the case of a multiloculated empyema not completely drained by a first chest tube in a nontoxic patient, the preference was drainage by a second chest tube, either a small-bore (42 percent) or a large-bore (36 percent) tube. The heterogeneity of responses suggests that prospective trials comparing treatment modalities are needed.