Is there a Role for Frozen Section Evaluation of Parotid Masses After Preoperative Cytology or Biopsy Diagnosis?

Fine-needle aspiration (FNA) biopsy reliably diagnoses parotid gland lesions preoperatively, whereas intraoperative frozen section (FS) has the additional benefit of assessing surgical margins and refining diagnoses; however, the role of FS in the setting of prior FNA diagnosis is not well established. Our aim was to determine whether FS should still be performed after a prior FNA/ CNB diagnosis. Parotid gland resections from January 2009 to January 2020 were identified; however, only patients who had both FNA and FS constituted our study population. For the purpose of statistical analysis, FNA diagnoses were classified into non-diagnostic (ND), non-neoplastic (NN), benign neoplasm (BN), indeterminate, and malignant. FS diagnoses were classified into benign, indeterminate, or malignant. Resections were dichotomized into benign and malignant and regarded as the gold standard to subsequently calculate diagnostic accuracy of FNA and FS. A total of 167 parotid gland resections were identified, but only 76 patients (45.5%) had both FNA and FS. In 35 cases deemed as benign preoperatively, three (8.6%) were reclassified as malignant on FS. Out of 18 lesions reported as malignant on FNA, four (22.2%) were interpreted as benign on FS, with three of these benign lesions confirmed on permanent slides. In addition, in patients with both FNA and FS, compared to FNA, FS was able to provide a definitive diagnosis in all five ND cases and in 61.1% (11/18) of indeterminate tumors. Intraoperative assessment provided a relative increase of 33.3% in specificity and 38.5% in positive predictive value when compared to preoperative FNA. The addition of FS to FNA was helpful to further refine the diagnoses of parotid gland lesions, which may provide better guidance for surgical intervention.

Salmonella typhimurium attachment to human intestinal epithelial monolayers: transcellular signalling to subepithelial neutrophils.

In human intestinal disease induced by Salmonella typhimurium, transepithelial migration of neutrophils (PMN) rapidly follows attachment of the bacteria to the epithelial apical membrane. In this report, we model those interactions in vitro, using polarized monolayers of the human intestinal epithelial cell, T84, isolated human PMN, and S. typhimurium. We show that Salmonella attachment to T84 cell apical membranes did not alter monolayer integrity as assessed by transepithelial resistance and measurements of ion transport. However, when human neutrophils were subsequently placed on the basolateral surface of monolayers apically colonized by Salmonella, physiologically directed transepithelial PMN migration ensued. In contrast, attachment of a non-pathogenic Escherichia coli strain to the apical membrane of epithelial cells at comparable densities failed to stimulate a directed PMN transepithelial migration. Use of the n-formyl-peptide receptor antagonist N-t-BOC-1-methionyl-1-leucyl-1- phenylalanine (tBOC-MLP) indicated that the Salmonella-induced PMN transepithelial migration response was not attributable to the classical pathway by which bacteria induce directed migration of PMN. Moreover, the PMN transmigration response required Salmonella adhesion to the epithelial apical membrane and subsequent reciprocal protein synthesis in both bacteria and epithelial cells. Among the events stimulated by this interaction was the epithelial synthesis and polarized release of the potent PMN chemotactic peptide interleukin-8 (IL-8). However, IL-8 neutralization, transfer, and induction experiments indicated that this cytokine was not responsible for the elicited PMN transmigration. These data indicate that a novel transcellular pathway exists in which subepithelial PMN respond to lumenal pathogens across a functionally intact epithelium. Based on the known unique characteristics of the intestinal mucosa, we speculate that IL-8 may act in concert with an as yet unidentified transcellular chemotactic factor(s) (TCF) which directs PMN migration across the intestinal epithelium.

Surface attachment of Salmonella typhimurium to intestinal epithelia imprints the subepithelial matrix with gradients chemotactic for neutrophils.

During intestinal disease induced by Salmonella typhimurium transepithelial migration of neutrophils (PMN) rapidly follows attachment of the bacteria to the epithelial apical membrane. Among the events stimulated by these interactions is the release of chemotaxins that guide PMN through the subepithelial matrix and subsequently through the epithelium itself (McCormick, B.A., S.P. Colgan, C. Delp-Archer, S.I. Miller, and J.L. Madara. 1993. J. Cell Biol. 123:895-907). Given the substantial volume flow that normally characterizes matrix compartments underlying transporting epithelia, it is unclear how such transmatrix signaling is sustained. Here we show that when underlying matrices are isolated from biophysically confluent polarized monolayers of the human intestinal epithelial cell line T84, they fail to support substantial transmatrix migration of PMN unless an exogenous chemotactic gradient is imposed. In contrast, such matrices isolated from confluent monolayers apically colonized with S. typhimurium support spontaneous transmatrix migration of PMN. Such chemotactic imprinting of underlying matrices is resistant to volume wash and is paralleled by secretion of the known matrix-binding chemokine IL-8. Chemotactic imprinting of the matrix underlying S. typhimurium-colonized monolayers is dependent on epithelial protein synthesis, is directional implying the existence of a gradient, and is neutralized by antibodies either to IL-8 or to the IL-8 receptor on PMN. An avirulent S. typhimurium strain, PhoPc, which attaches to epithelial cells as efficiently as wild-type S. typhimurium, fails to induce basolateral secretion of IL-8 and likewise fails to imprint matrices. Together, these observations show that the epithelial surface can respond to the presence of a luminal pathogen and subsequently imprint the subepithelial matrix with retained IL-8 gradients sufficient to resist washout effects of the volume flow that normally traverses this compartment. Such data further support the notion that the primary role for basolateral secretion of IL-8 by the intestinal and likely other epithelia is recruitment of PMN through the matrix to the subepithelial space, rather than directing the final movement of PMN across the epithelium.

Adhesion molecules involved in hepoxilin A3-mediated neutrophil transepithelial migration.

A common feature underlying active states of inflammation is the migration of neutrophils (PMNs) from the circulation and across a number of tissue barriers in response to chemoattractant stimuli. Although our group has recently established a discreet role for the PMN chemoattractant, hepoxilin A3 (HXA3) in the process of PMN recruitment, very little is known regarding the interaction of HXA3 with PMNs. To characterize further the event of HXA3-induced PMN transepithelial migration, we sought to determine the adhesion molecules required for migration across different epithelial surfaces (T84 intestinal and A549 airway cells) relative to two well-studied PMN chemoattractants, formyl-methionyl-leucyl-phenylalanine (fMLP) and leukotriene B4 (LTB4). Our findings reveal that the adhesion interaction profile of PMN transepithelial migration in response to HXA3 differs from the adhesion interaction profile exhibited by the structurally related eicosanoid LTB4. Furthermore, unique to PMN transepithelial migration induced by gradients of HXA3 was the critical dependency of all four major surface adhesion molecules examined (i.e. CD18, CD47, CD44 and CD55). Our results suggest that the particular chemoattractant gradient imposed, as well as the type of epithelial cell monolayer, each plays a role in determining the adhesion molecules involved in transepithelial migration. Given the complexities of these interactions, our findings are important to consider with respect to adhesion molecules that may be targeted for potential drug development.

Anaesthesia equipment for resource-poor environments.

The design of anaesthesia equipment for use in hospitals in the developing world must take into account the local conditions, particularly whether reliable supplies of compressed oxygen and electricity are available. Designs should ensure that maintenance is feasible locally. International standards should encourage the design of suitable equipment to ensure safe anaesthesia for patients worldwide.

Adhesive interactions in angiogenesis and metastasis.

A variety of adhesive interactions must take place between the tumor cell and the host vasculature in order to potentiate both tumor expansion and metastatic tumor spread. The study of tumor cell and blood vessel adhesive interactions becomes essential for our understanding of the malignant process, especially with regard to organ-specific tumor metastasis. In this article we will review recent progress made in our understanding of the nature of (i) receptor mediated adhesion of endothelial cells to extracellular matrix components and (ii) adhesion of tumor cells to endothelial adhesion molecules and to components of the subendothelial basement membrane.

New insights on molecular pathways utilized by salmonella species in cell binding.

Salmonella infections are a principal source of gastroenteritis and enteric fever in a variety of animals, including humans. An essential step in the development of Salmonella pathogenesis is the entry of bacteria into non-phagocytic cells, including those that line the intestinal epithelium. As a consequence of specific cues from the host intestinal micro-environment, Salmonella entry into the intestinal epithelium is the product of a multistep process that culminates in host cell membrane ruffling, and subsequent bacterial uptake. The events that trigger the internalization event appear to require an array of bacterial secreted proteins, exemplified by the formation of bacterial surface appendages (invasomes) which are important for the induction of host-cell signal transduction pathways that lead to membrane ruffling. In addition, during intestinal disease states induced by Salmonella typhimurium, transepithelial migration of neutrophils rapidly follows attachment of the bacteria to the epithelial membrane. Current evidence indicates that the intestinal epithelium plays a key role in orchestrating the inflammatory response to surface attached S. typhimurium. In this review, we explore current insights on the molecular pathways utilized by Salmonella spp. in cell binding that are important not only in the processes of Salmonella internalization but also in the generation of signals which lead to active states of intestinal inflammation.

Bronchopleural fistula complicating group A beta-haemolytic streptococcal pneumonia. Use of a Fogarty embolectomy catheter for selective bronchial blockade.

A 36-year-old woman developed severe group A Streptococcal pneumonia, complicated by a bronchopleural fistula, ARDS and multi-organ failure. We describe the use of selective middle lobe bronchus blockade, with a Fogarty embolectomy catheter, to localise and control the air leak. This allowed effective mechanical ventilation and oxygenation on intensive care and during right middle lobectomy. The patient made a prolonged, but full recovery.

Anaesthesia services in developing countries: defining the problems.

We describe the use of a questionnaire to define the difficulties in providing anaesthesia in Uganda. The results show that 23% of anaesthetists have the facilities to deliver safe anaesthesia to an adult, 13% to deliver safe anaesthesia to a child and 6% to deliver safe anaesthesia for a Caesarean section. The questionnaire identified shortages of personnel, drugs, equipment and training that have not been quantified or accurately described before. The method used provides an easy and effective way to gain essential data for any country or national anaesthesia society wishing to investigate anaesthesia services in its hospitals. Solutions require improvements in local management, finance and logistics, and action to ensure that the importance of anaesthesia within acute sector healthcare is fully recognised. Major investment in terms of personnel and equipment is required to modernise and improve the safety of anaesthesia for patients in Uganda.

Life-threatening pulmonary hypertension and right ventricular failure complicating calcium and phosphate replacement in the intensive care unit.

A 43-year-old man developed septic shock and acute lung injury after surgery to drain an ischiorectal abscess. In the intensive care unit he initially improved but developed severe hypoxaemia, right ventricular failure and pulmonary hypertension 90 min after receiving intravenous calcium gluconate and potassium phosphate, best explained by the formation of a calcium-phosphate precipitant that resulted in aggregate anaphylaxis. His rapid deterioration and lack of response to conventional therapies necessitated support with extracorporeal membrane oxygenation that was life saving. This adverse event has altered local practice regarding calcium and phosphate replacement and has implications for all intensive care units.

Neither motility nor chemotaxis plays a role in the ability of Escherichia coli F-18 to colonize the streptomycin-treated mouse large intestine.

Escherichia coli F-18, isolated from the feces of a healthy human in 1977, is an excellent colonizer of the streptomycin-treated mouse large intestine and displays normal motility and chemotaxis ability. A chemotaxis-defective derivative of E. coli F-18, E, coli F-18 CheA-, and a nonflagellated derivative, E. coli F-18 Fla-, were constructed. These strains were found to colonize the streptomycin-treated mouse large intestine as well as E. coli F-18 when mice were fed both E. coli F-18 and either the CheA- or Fla- derivative at high levels (10(10) CFU of each strain per mouse) or low levels (10(4) CFU of each strain per mouse). Furthermore, E. coli F-18 lost motility and chemotaxis ability when grown in colonic or cecal mucus in vitro despite retaining the ability to synthesize flagella. Thus, it appears that neither motility nor chemotaxis plays a role in the ability of E. coli F-18 to colonize because this strain becomes functionally nonmotile upon growth in the streptomycin-treated mouse large intestine.

Salmonella enterica serovar typhimurium-dependent regulation of inducible nitric oxide synthase expression in macrophages by invasins SipB, SipC, and SipD and effector SopE2.

When Salmonella enterica invades mammalian cells, it activates signals leading to increased expression of inflammatory mediators. One such mediator is nitric oxide (NO), which is produced under control of the enzyme inducible NO synthase (iNOS). Induction of iNOS in response to Salmonella infection has been demonstrated, but the bacterial effector molecules that regulate expression of the enzyme have not been identified. In the study reported here, an analysis of Salmonella-dependent iNOS expression in macrophages was carried out. Wild-type Salmonella strains increased the levels of both iNOS protein and mRNA in murine macrophage cell lines in an invasion-independent fashion. Mutant strains lacking a functional pathogenicity island 1-encoded type III secretion system, as well as strains lacking the invasins SipB, SipC, and SipD, were impaired in iNOS induction. Complementation experiments indicated that all three of the invasins were required for induction of iNOS expression. These results suggested that an effector protein, translocated into macrophages via the type III secretion system in a SipB-, SipC-, and SipD-dependent manner, might be the ultimate mediator of iNOS induction. In keeping with this idea, a mutant strain deficient in SopE2, a recently described homolog of SopE, was found to be impaired in the induction of iNOS expression. These observations suggest that iNOS expression is regulated by signals activated by SopE2 (and possibly SopE) and that the role of SipB, SipC, and SipD in this process is to facilitate translocation of the relevant effector.

Requirement of the Shigella flexneri virulence plasmid in the ability to induce trafficking of neutrophils across polarized monolayers of the intestinal epithelium.

Attachment of an array of enteric pathogens to epithelial surfaces is accompanied by recruitment of polymorphonuclear leukocytes (PMN) across the intestinal epithelium. In this report, we examine how Shigella-intestinal epithelium interactions evoke the mucosal inflammatory response. We modeled these interactions in vitro by using polarized monolayers of the human intestinal epithelial cell line, T84, isolated human PMNs, and Shigella flexneri. We show that Shigella attachment to T84-cell basolateral membranes was a necessary component in the signaling cascade for induction of basolateral-to-apical directed transepithelial PMN migration, the direction of PMN transepithelial migration in vivo. In contrast, attachment of Shigella to the T84-cell apical membrane failed to stimulate a directed PMN transepithelial migration response. Importantly, the ability of Shigella to induce PMN migration across epithelial monolayers was dependent on the presence of the 220-kb virulence plasmid. Moreover, examination of Shigella genes necessary to signal subepithelial neutrophils established the requirement of a functional type III secretion system. Our results indicate that the ability of Shigella to elicit transepithelial signaling to neutrophils from the basolateral membrane of epithelial cells represents a mechanism involved in Shigella-elicited enteritis in humans.

Roles of motility, chemotaxis, and penetration through and growth in intestinal mucus in the ability of an avirulent strain of Salmonella typhimurium to colonize the large intestine of streptomycin-treated mice.

Previously, it had been shown that an avirulent strain of Salmonella typhimurium, SL5316, with wild-type lipopolysaccharide (LPS) was a far better colonizer of the streptomycin-treated CD-1 mouse large intestine, was far more motile, did not bind to mouse intestinal mucus nearly as well as, but penetrated through a layer of intestinal mucus in vitro far better than an almost isogenic LPS-deficient transductant, SL5325. In the present investigation, a nonflagellated transductant, SL5681, and a nonchemotactic transductant, SL5784, were isolated from SL5316 and tested for relative colonizing ability versus SL5316 (smooth) and SL5325 (rough) in streptomycin-treated mice. In addition, the Salmonella strains were tested for their ability to grow together in cecal intestinal mucus and in cecal luminal contents, for their tumbling and swimming activities after growth in cecal mucus, and for their ability to adhere to and travel through cecal mucus in vitro. The data show that the nonflagellated and nonchemotactic derivatives colonized large intestine nearly as well as their parent and were far better colonizers than the LPS-deficient mutant, that all the strains grew equally well in cecal mucus but did not grow in cecal luminal contents, and that cecal mucus-grown strains lost tumbling and swimming activities. Furthermore, the LPS-deficient strain adhered to cecal mucus far better but penetrated mucus far worse than did the nonflagellated transductant, the nonchemotactic transductant, and the parent. Thus, motility and chemotaxis do not appear to play a major role in the ability of the avirulent S. typhimurium strains to colonize the mouse large intestine, colonization may require growth in cecal mucus but does not depend on growth in cecal luminal contents, growth in cecal mucus inhibits S. typhimurium motility, and increased adhesion of the LPS-deficient mutant to cecal mucus and its poor ability to penetrate cecal mucus may play a role in its poor intestine-colonizing ability.

Type 1 pili are not necessary for colonization of the streptomycin-treated mouse large intestine by type 1-piliated Escherichia coli F-18 and E. coli K-12.

Escherichia coli F-18, an excellent colonizer of the streptomycin-treated mouse large intestine, produces type 1 pili. E. coli F-18 FimA-, type 1 pilus negative, and E. coli F-18 FimH-, type 1 pilus positive but adhesin negative, were constructed by bacteriophage P1 transduction of defective fimA and fimH genes from the E. coli K-12 strains ORN151 and ORN133, respectively, into E. coli F-18. Adhesion of E. coli F-18 to an immobilized mannose-bovine serum albumin glycoconjugate was about sixfold greater than that of either E. coli F-18 FimA- or E. coli F-18 FimH-, and adhesion of E. coli F-18 to immobilized cecal epithelial cell brush border membranes was between two- and threefold greater than that of E. coli F-18 FimA- or E. coli F-18 FimH-. When either E. coli F-18 FimA- or E. coli FimH- was fed to streptomycin-treated mice together with E. coli F-18, the pilus-negative and adhesin-negative strains colonized as well as their type 1-piliated parent. Essentially the same result was observed when the type 1-piliated E. coli K-12 strain ORN152 was fed to streptomycin-treated mice together with a nearly isogenic K-12 FimA- strain, ORN151. Furthermore, when streptomycin-treated mice were fed E. coli F-18 FimA- or E. coli F-18 FimH- together with E. coli F-18 Col-, which also makes type 1 pili but is a poor colonizer relative to E. coli F-18 because it grows poorly in mucus in the presence of E. coli F-18, the F-18 FimA- and F-18 FimH- strains colonized well (10(6) to 10(7) CFU/g of feces), whereas the number of E. coli F-18 Col- in feces decreased rapidly to 10(2) CFU/g of feces. These data show that in streptomycin-treated mice, the inability to produce functional type 1 pili has no effect on the ability of E. coli F-18 and E. coli K-12 to colonize the large intestine.

Regulation of Salmonella-induced neutrophil transmigration by epithelial ADP-ribosylation factor 6.

Salmonella typhimurium elicits an acute inflammatory response in the host intestinal epithelium, characterized by the movement of polymorphonuclear leukocytes (PMN) across the epithelial monolayer to the intestinal lumen. It was recently shown that SipA, a protein secreted by S. typhimurium, is necessary and sufficient to drive PMN transmigration across model intestinal epithelia (Lee, C. A., Silva, M., Siber, A. M., Kelly, A. J., Galyov, E., and McCormick, B. A. (2000) Proc. Natl. Acad Sci. USA 97, 12283-12288). However, the epithelial factors responsible for this process have not been identified. Here, for the first time, we demonstrate that S. typhimurium-induced PMN transmigration across Madin-Darby canine kidney-polarized monolayers is regulated by the GTPase ARF6. Apically added S. typhimurium promoted the translocation of ARF6 and its exchange factor ARNO to the apical surface. Overexpression of a dominant-negative mutant of ARF6 inhibited Salmonella-induced PMN transmigration, which was due to a reduction in apical release of the PMN chemoattractant PEEC (pathogen-elicited epithelial chemoattractant), without affecting bacterial internalization. Furthermore, ARF6 and its effector phospholipase D (PLD) were both required for bacteria-induced translocation of protein kinase C (PKC) to membranes. These results describe a novel signal transduction pathway, in which Salmonella initiates an ARF6- and PLD-dependent lipid signaling cascade that, in turn, directs activation of PKC, release of PEEC, and subsequent transepithelial PMN movement.

Use of albumin in intensive care units in the United kingdom.

OBJECTIVE: To review the use of intravenous albumin solutions in intensive care units in the United Kingdom. METHODS: A postal questionnaire was sent to the clinical directors of all intensive care units in the United Kingdom (n = 292) asking about their use and indications for intravenous albumin solutions. RESULTS: Responses were received from 261 (89.4%) intensive care units (ICUs). The units were classified as general ICUs (n = 198), paediatric ICUs (n = 22) and combined intensive care/coronary care units (ICU/CCUs) (n = 41). Of the 261 units that replied, 181 (69.3%) reported using intravenous albumin, although the indications varied between units particularly in paediatric intensive care units. The alternatives to albumin also varied between the units. The general ICUs favoured hydroxyethyl starch (n = 129, 65.2%) and/or gelatin solutions (n = 87, 43.9%), as did the combined ICU/CCUs (n = 28, 68.3% and/or n = 23, 56.1% respectively). However, of the paediatric ICUs that used an alternative to albumin solutions (n = 21/22), 12 favoured crystalloid solutions (54.5%) and 9 favoured gelatin solutions (40.9%). We also assessed the impact of the recent review by the Cochrane Injuries Group Reviewers on the use of albumin and found that the respondents of 131 units (50.2%) reported that this study influenced their use of intravenous albumin. Of the 80 units that did not use albumin solutions, 33 units reported that they had ceased using intravenous albumin following the review from the Cochrane Injuries Group Reviewers. CONCLUSIONS: Approximately two-thirds of intensive care units in the United kingdom reported using intravenous albumin, although the indications varied between units. In many of these units the use of intravenous albumin had been influenced by the recent review by the Cochrane Injuries Group Reviewers on the use of albumin.

Transepithelial signaling to neutrophils by salmonellae: a novel virulence mechanism for gastroenteritis.

Salmonella serotypes which elicit human enteritis cannot be distinguished from those that do not on the basis of their in vitro interactions with eukaryotic cells. We have recently reported that an enteritis-producing strain of Salmonella typhimurium signals intact intestinal epithelium to recruit subepithelial neutrophils to migrate across the epithelial (B. A. McCormick, S. P. Colgan, C. D. Archer, S. I. Miller, and J. L. Madara, J. Cell Biol. 123:895-907, 1993). We now utilize a cell culture model of human intestinal epithelium (with T84 cells) to examine whether such transepithelial signaling to neutrophils by salmonellae is predictive of potential to elicit gastroenteritis. Various Salmonella serotypes, including S. typhimurium, S. enteritidis, S. pullorum, S. arizonae, S. typhi, and S. paratyphi, as well as invasion-defective mutants of S. typhimurium, were studied. Strains or serotypes which elicit diffuse enteritis in humans (defined histologically as transepithelial migration of neutrophils) exhibited transepithelial signaling to neutorphils across epithelial cell monolayers, while those which do not elicit diffuse enteritis in humans did not display transepithelial signaling. In contrast, the ability to enter the apical surface of T84 cells did not differentiate strains or serotypes which induce diffuse enteritis from those which do not. These results strongly suggest that the ability of salmonellae to elicit transepithelial signaling to neutrophils is a key virulence mechanism underlying Salmonella-elicited enteritis.

Inhibition of Shigella flexneri-induced transepithelial migration of polymorphonuclear leucocytes by cadaverine.

Dysentery caused by Shigella species is characterized by infiltration of polymorphonuclear leucocytes (PMNs) into the colonic mucosa. Shigella spp. evolved into pathogens by the acquisition of virulence genes and by the deletion of 'antivirulence' genes detrimental to its pathogenic lifestyle. An example is cadA (encoding lysine decarboxylase), which is uniformly absent in Shigella spp., whereas it is present in nearly all isolates of the closely related non-pathogen Escherichia coli. Here, using monolayers of T84 cells to model the human intestinal epithelium, we determined that the introduction of cadA into S. flexneri and the expression of lysine decarboxylase attenuated the bacteria's ability to induce PMN influx across model intestinal epithelium. Such inhibition was caused by cadaverine generated from the decarboxylation of lysine. Cadaverine treatment of model intestinal epithelia specifically inhibited S. flexneri induction of PMN transepithelial migration, while having no effect on the ability of Salmonella or enteropathogenic E. coli (EPEC) to induce PMN migration. These observations not only provide insight into mechanisms of S. flexneri pathogen evolution and pathogenesis, but also suggest a potential for the use of cadaverine in the treatment of dysentery.

Orchestration of neutrophil movement by intestinal epithelial cells in response to Salmonella typhimurium can be uncoupled from bacterial internalization.

Intestinal epithelial cells respond to Salmonella typhimurium by internalizing this pathogen and secreting, in a polarized manner, an array of chemokines which direct polymorphonuclear leukocyte (PMN) movement. Notably, interleukin-8 (IL-8) is secreted basolaterally and directs PMN through the lamina propria, whereas pathogen-elicited epithelial chemoattractant (PEEC) is secreted apically and directs PMN migration across the epithelial monolayer to the intestinal lumen. While most studies of S. typhimurium pathogenicity have focused on the mechanism by which this bacterium invades its host, the enteritis characteristically associated with salmonellosis appears to be more directly attributable to the PMN movement that occurs in response to this pathogen. Therefore, we sought to better understand the relationship between S. typhimurium invasion and epithelial promotion of PMN movement. First, we investigated whether S. typhimurium becoming intracellular was necessary or sufficient to induce epithelial promotion of PMN movement. Blocking S. typhimurium invasion by preventing, with cytochalasin D, the epithelial cytoskeletal rearrangements which mediate internalization did not reduce the epithelial promotion of PMN movement. Conversely, bacterial attainment of an intracellular position was not sufficient to induce model epithelia to direct PMN transmigration, since neither basolateral invasion by S. typhimurium nor apical internalization of an invasion-deficient mutant (achieved by inducing membrane ruffling with epidermal growth factor) induced this epithelial cell response. These results indicate that specific interactions between the apical surface of epithelial cells and S. typhimurium, rather than simply bacterial invasion, mediate the epithelial direction of PMN transmigration. To further investigate the means by which S. typhimurium induces epithelia to direct PMN movement, we investigated whether the same signaling pathways regulate secretion of IL-8 and PEEC. IL-8 secretion, but not PEEC secretion, was activated by phorbol myristate acetate and blocked by an inhibitor (mg-132) of the proteosome which mediates NF-kappabeta activation. Further, secretion of IL-8, but not PEEC, was activated by an entry-deficient (HilDelta) S. typhimurium mutant or by basolateral invasion of a wild-type strain. Together, these results indicate that distinct signaling pathways mediate S. typhimurium invasion, induction of IL-8 secretion, and induction of PEEC secretion in model intestinal epithelia.