The lipoxygenase metabolite 12(S)-HETE induces a cytoskeleton-dependent increase in surface expression of integrin alpha IIb beta 3 on melanoma cells

Integrin receptors are mediators of cell-extracellular matrix and cell-cell interactions. Biochemical and immunocytochemical evidence shows that the platelet integrin receptor alpha IIb beta 3 is present on the cell surface, at focal adhesion plaques and in the perinuclear region of metastatic B16a murine melanoma cells. Antibody to the fibronectin receptor alpha 5 beta i, inhibits basal adhesion by approx. 30%, whereas antibodies to alpha IIb beta 3 are ineffective. The surface immunoreactivity of tumor cells for alpha IIb beta 3 can be enhanced by pre-treatment (5 min) with a lipoxygenase metabolite of arachidonic acid [i.e. 12-(S)-HETE] in a dose-dependent manner (max. effect approx. 0.1 microM). Other lipoxygenase metabolites are ineffective. B16a cells possess a large intracellular pool of alpha IIb beta 3, from which the receptor complex translocates to the cell surface following 12-(S)-HETE pretreatment. This pre-treatment of tumor cells enhances their adhesion to fibronectin, which is mediated exclusively by alpha IIb beta 3 receptors. 12-(S)-HETE also facilitates the redistribution of alpha IIb beta 3 in the plasma membrane with localization at the focal adhesion plaques. The cytoskeleton of the B16a cell is characterized by an absence of distinct microtubules in interphase cells and the presence of prominent microfilaments and vimentin intermediate filaments. In B16a cells, the disruption of intermediate filaments and/or microfilaments prevents the 12-(S)-HETE-induced increase in plasma membrane alpha IIb beta 3 and enhanced tumor-cell adhesion to fibronectin. The microtubule-disrupting agent, colchicine, is ineffective in both respects. We conclude that the lipoxygenase metabolite of arachidonic acid, 12-(S)-HETE, regulates the surface expression and function of the alpha IIb beta 3 integrin in B16a cells. Further, these data support the hypothesis that microfilaments and intermediate filaments have a profound role in regulating the expression of a multifunctional integrin in B16a tumor cells.

Acute Helicobacter pylori infection: clinical features, local and systemic immune response, gastric mucosal histology, and gastric juice ascorbic acid concentrations

The symptomatology of a case of acute infection with Helicobacter pylori is described, together with the accompanying changes in gastric mucosal histology, local and systemic humoral immune response, and gastric ascorbic acid concentration. The patient was an endoscopist, previously negative for the carbon-14 urea breath test, who had a week of epigastric pain and then became asymptomatic. H pylori was detected by culture of antral biopsy specimens and was still present after 74 days. Five days after infection the histological findings showed acute neutrophilic gastritis; by day 74 changes of chronic gastritis were evident. The patient seroconverted by IgG enzyme linked immunosorbent assay by day 74, but a mucosal IgM and IgA response was evident as early as day 14. Infection was accompanied by a transient hypochlorhydria but a sustained fall in gastric juice ascorbic acid concentration.

EcoRV restriction endonuclease binds all DNA sequences with equal affinity

In the presence of MgCl2, the EcoRV restriction endonuclease cleaves its recognition sequence on DNA at least a million times more readily than any other sequence. In this study, the binding of the EcoRV restriction enzyme to DNA was examined in the absence of Mg2+. With each DNA fragment tested, several DNA-protein complexes were detected by electrophoresis through polyacrylamide. No differences were observed between isogenic DNA molecules that either contained or lacked the EcoRV recognition site. The number of complexes with each fragment varied with the length of the DNA. Three complexes were formed with a DNA molecule of 55 base pairs, corresponding to the DNA bound to 1, 2, or 3 molecules of the protein, while greater than 15 complexes were formed with a DNA of 381 base pairs. A new method was developed to analyze the binding of a protein to multiple sites on DNA. The method showed that the EcoRV enzyme binds to all DNA sequences, including the EcoRV recognition site, with the same equilibrium constant, though two molecules of the protein bind preferentially to adjacent sites on the DNA in a cooperative fashion. All of the complexes with a substrate that contained the EcoRV site dissociated upon addition of competitor DNA, but when the competitor was mixed with MgCl2, a fraction of the substrate was cleaved at the EcoRV site. The fraction cleaved was due mainly to the translocation of the enzyme from nonspecific sites on the DNA to the specific site.

Mucosal humoral immune response to Helicobacter pylori in patients with duodenitis

The humoral immune response to Helicobacter pylori infection in the duodenum has been investigated by short-term in vitro culture, ELISA, and immunoblotting techniques. H. pylori IgA secretion by duodenal bulb biopsies was significantly increased (P less than 0.001) in patients with duodenitis. The IgA response to H. pylori in patients with duodenitis was restricted to the first part of the duodenum; second part duodenal biopsies secreting significantly (P less than 0.001) less IgA during culture in vitro. H. pylori IgG antibody secretion by cultured biopsies was also significantly increased (P less than 0.01) in patients with duodenitis and those with gastric H. pylori infection but without duodenitis. Immunoblotting of duodenal bulb culture supernatants showed positive recognition by the mucosal IgA response of H. pylori antigens in the region of 120, 90, 61, and 31-26 kDa in patients with duodenitis. Serologically, such patients showed little evidence of IgA H. pylori antibodies by immunoblotting. These results demonstrate that the inflammatory response in the duodenal mucosa of patients with duodenitis represents a specific highly localized humoral response to H. pylori.

Molecular genetics of Pseudomonas syringae pathovar pisi: plasmid involvement in cultivar-specific incompatibility

A mutant (PF24) of the race 1 strain, 299A, of Pseudomonas syringae pv. pisi has been characterized in terms of its interactions with pea (Pisum sativum) cultivars. The mutant showed a changed reaction (avirulence to virulence) with a group of pea cultivars, including cvs. Belinda and Puget, previously thought to contain resistance genes R1 and R3. Avirulence towards cv. Puget was restored by transfer of any one of five cosmid clones from a race 3 (strain 870A) gene library to a rifampicin-resistant derivative of PF24. These observations were in agreement with a revised race-specific resistance genotype for Belinda and similar cultivars comprising a single resistance gene, R3. An incompatible interaction was observed between strain PF24 and cvs. Vinco (postulated to harbour race-specific resistance genes R1, R2, R3 and R5) and Hurst's Greenshaft (R4 and possibly R1), indicating that the mutant retains at least one avirulence gene (A1 or A1 and A4). Mutant PF24 showed loss of a cryptic plasmid (pAV212) compared with its progenitor, strain 299A. A subclone (pAV233) of one of the race 3 restoration clones showed strong hybridization with similar-sized digestion fragments in race 3 plasmid DNA, confirming the A3 gene to be plasmid-borne. Strong cross-hybridization was also observed with a single 3.27 kb EcoRI fragment of plasmid DNA present in strain 299A but absent from strain PF24. This is consistent with the corresponding A3 determinant being located on pAV212 in the race 1 strain 299A. The novel avirulence gene corresponding to A3 in strain 870A is provisionally designated avrPpi3.(ABSTRACT TRUNCATED AT 250 WORDS)

Immune responses to Helicobacter pylori in children with recurrent abdominal pain

The systemic immune response to Helicobacter pylori was examined in 69 children with recurrent abdominal pain and upper gastrointestinal symptoms. Twenty one (30%) children were histologically positive for H pylori. Eighteen of the 21 positive subjects and two H pylori negative subjects (one with normal mucosa, one with lymphocytic gastritis) were positive for H pylori IgG antibodies by enzyme linked immunosorbent assay (ELISA) (86% sensitivity, 98% specificity). In children with H pylori associated gastritis, there was a significant positive correlation (p less than 0.05) between IgG antibody titres and patient age. Intra-assay comparison of sera from histologically negative adults with those of histologically negative children showed that the cut off for positivity in the ELISA for adults was greater than that for children. Immunoblotting showed IgG positivity in 20 of the 21 patients with H pylori infection (95% sensitivity). Both ELISA and immunoblotting for IgA and IgM H pylori antibodies had poor discriminatory value for determining infection. Serological detection of H pylori IgG antibodies seems to be valuable in the assessment of children presenting with recurrent abdominal pain and other gastrointestinal symptoms, but assays must first be validated in paediatric populations.

Mucosal IgA recognition of Helicobacter pylori 120 kDa protein, peptic ulceration, and gastric pathology

The gastric IgA response to Helicobacter pylori was examined in 100 dyspeptic patients by means of immunoblotting of supernatants from antral biopsy and gastric mononuclear cell cultures. 76 of 78 patients with chronic gastritis, 2 of 8 with reactive gastritis, and 1 of 14 subjects with normal mucosa showed positive responses. Of patients with chronic gastritis, 75%, 83%, 97% and 76%, respectively, showed responses to the 120 kDa, 90 kDa, 61 kDa, and 31 kDa proteins. None of the 19 patients with chronic gastritis who did not recognise the 120 kDa protein had peptic ulcers, whereas 25 of 57 with positive recognition had peptic ulcers (p less than 0.001). Mucosal recognition of the H pylori 120 kDa protein was also positively associated with the activity of gastritis (polymorph infiltration) (p less than 0.002) and with the extent of surface degeneration (p less than 0.01). These findings suggest that 120-kDa-positive strains of H pylori have pathogenic features associated with active gastritis and peptic ulceration. Infection with 120-kDa-negative strains may explain why peptic ulceration develops in only a proportion of subjects infected with H pylori.

Complex regulation of macrophage colony-stimulating factor in the HL-60 promyelocytic cell line

The regulation of macrophage colony-stimulating factor (M-CSF) gene expression by phorbol esters and calcium ionophore (A23187) was studied in HL-60 cells. In untreated HL-60 cells, M-CSF transcripts were undetectable, but transcripts were present within 2 h of A23187 treatment or within 8 h of phorbol 12,13-dibutyrate (PdBu) treatment. Concurrent treatment of HL-60 cells with A23187 and cycloheximide (CHX) for 6 h led to a superinduction of message over A23187 treatment alone. But concurrent treatment with PdBu and CHX for 24 h abolished expression of the message normally present after 24 h of PdBu treatment. The role of new protein synthesis in transcriptional regulation of M-CSF was studied by run-on transcription assay. Untreated HL-60 cells or cells treated with CHX alone do not transcribe M-CSF mRNA. However, cells treated with A23187 for 6 h and CHX for 1, 3, or 6 h transcribed more M-CSF than cells treated with A23187 alone for 6 h. CHX also regulates M-CSF expression by message stabilization. The t1/2 of M-CSF mRNA was 45 min in cells treated with A23187 for 6 h or in cells treated with PdBu for 24 h, was over 2 h in HL-60 cells treated with A23187 for 6 h and CHX for 1 h, and was 3 h in cells treated with PdBu for 24 h and CHX for 1 h. We conclude that M-CSF gene expression can be differentially regulated in HL-60 cells and that new protein synthesis plays an important role in both the transcriptional and posttranscriptional regulation.

Complex regulation of macrophage colony-stimulating factor in the HL-60 promyelocytic cell line

The regulation of macrophage colony-stimulating factor (M-CSF) gene expression by phorbol esters and calcium ionophore (A23187) was studied in HL-60 cells. In untreated HL-60 cells, M-CSF transcripts were undetectable, but transcripts were present within 2 h of A23187 treatment or within 8 h of phorbol 12,13-dibutyrate (PdBu) treatment. Concurrent treatment of HL-60 cells with A23187 and cycloheximide (CHX) for 6 h led to a superinduction of message over A23187 treatment alone. But concurrent treatment with PdBu and CHX for 24 h abolished expression of the message normally present after 24 h of PdBu treatment. The role of new protein synthesis in transcriptional regulation of M-CSF was studied by run-on transcription assay. Untreated HL-60 cells or cells treated with CHX alone do not transcribe M-CSF mRNA. However, cells treated with A23187 for 6 h and CHX for 1, 3, or 6 h transcribed more M-CSF than cells treated with A23187 alone for 6 h. CHX also regulates M-CSF expression by message stabilization. The t1/2 of M-CSF mRNA was 45 min in cells treated with A23187 for 6 h or in cells treated with PdBu for 24 h, was over 2 h in HL-60 cells treated with A23187 for 6 h and CHX for 1 h, and was 3 h in cells treated with PdBu for 24 h and CHX for 1 h. We conclude that M-CSF gene expression can be differentially regulated in HL-60 cells and that new protein synthesis plays an important role in both the transcriptional and posttranscriptional regulation.

Treatment of blepharospasm and hemifacial spasm with botulinum A toxin: a Canadian multicentre study

Botulinum A exotoxin was recently approved for use in Canada. We describe the efficacy of botulinum toxin in the management of 235 patients with blepharospasm (mean age 64.3 years) and 130 patients with hemifacial spasm (mean age 60.4 years) treated at three Canadian ophthalmologic centres between 1984 and 1989. A total of 98% of the patients with blepharospasm and 100% of the patients with hemifacial spasm had significant relief of their symptoms; however, 11% of the former and 2% of the latter did not respond to the usual starting concentrations of the drug and needed stronger dosages for relief. The duration of relief varied widely in both groups. Up to 7% of patients had ineffective treatments but responded to subsequent injections. Analysis of variance and linear trend statistics showed that there were no changes in the mean duration of relief over the first several treatments for individual patients in either group. Side effects were transient and included ptosis, exposure keratitis, epiphora and strabismus.

Oral transmission of transmissible gastroenteritis virus by muscle and lymph node from slaughtered pigs

A study was conducted in the USA to determine whether transmissible gastroenteritis (TGE) virus could be transmitted from carcases of slaughtered pigs. Transmissible gastroenteritis virus was transmitted to 6-day-old piglets by dosing with homogenates of muscle and lymph node collected from 500 clinically normal pigs at the time of slaughter. All piglets in 2 separately housed litters showed clinical signs of TGE with 5 piglets dying within 10 d of oral dosing with homogenates. Transmissible gastroenteritis virus was isolated from 2 of these piglets and all piglets developed TGE antibody. Transmissible gastroenteritis virus was not isolated in tissue culture from muscle and lymph node homogenates, but was isolated from 4 (0.8%) of 500 tonsil samples collected from the same pigs. A survey of 250 serum samples provided an estimate of the prevalence of slaughtered pigs with TGE antibody of 34.8% in the sample population. The results indicate that carcases of some pigs from TGE endemic areas contain viable TGE virus, and that there would be a substantial risk of introducing TGE virus into Australia by the importation of uncooked pig meat from these areas.

Fidelity of DNA recognition by the EcoRV restriction/modification system in vivo

The EcoRV restriction/modification system consists of two enzymes that recognize the DNA sequence GATATC. The EcoRV restriction endonuclease cleaves DNA at this site, but the DNA of Escherichia coli carrying the EcoRV system is protected from this reaction by the EcoRV methyltransferase. However, in vitro, the EcoRV nuclease also cleaves DNA at most sites that differ from the recognition sequence by one base pair. Though the reaction of the nuclease at these sites is much slower than that at the cognate site, it still appears to be fast enough to cleave the chromosome of the cell into many fragments. The possibility that the EcoRV methyltransferase also protects the noncognate sites on the chromosome was examined. The modification enzyme methylated alternate sites in vivo, but these were not the same as the alternate sites for the nuclease. The excess methylation was found at GATC sequences, which are also the targets for the dam methyltransferase of E. coli, a protein that is homologous to the EcoRV methyltransferase. Methylation at these sites gave virtually no protection against the EcoRV nuclease: even when the EcoRV methyltransferase had been overproduced, the cellular DNA remained sensitive to the EcoRV nuclease at its noncognate sites. The viability of E. coli carrying the EcoRV restriction/modification system was found instead to depend on the activity of DNA ligase. Ligase appears to proofread the EcoRV R/M system in vivo: DNA, cut initially in one strand at a noncognate site for the nuclease, is presumably repaired by ligase before the scission of the second strand.

An in vivo study of the role of the tumor cell cytoskeleton in tumor cell-platelet-endothelial cell interactions

We recently reported that disruption of tumor cell microfilaments or intermediate filaments resulted in an inhibition of the ability of tumor cells to induce the aggregation of homologous platelets in vitro (H. Chopra et al., Cancer Res., 48: 3787-3800, 1988). Previous investigators demonstrated that disruption of the tumor cell cytoskeleton decreases the ability of these cells to form lung colonies. We proposed that this latter effect is due, in part, to decreased interaction of tumor cells with platelets, following their arrest in the microvasculature. To test this hypothesis, B16 amelanotic melanoma cell microtubules, microfilaments, or vimentin intermediate filaments were disrupted with colchicine (50 microns), cytochalasin D (50 microns), or cycloheximide (50 microns), respectively, and then cells were tail vein injected into syngeneic mice. Both cytochalasin D- and cycloheximide-treated cells formed fewer lung colonies than did control cells. Colchicine, however, failed to inhibit lung colony formation. Neither colchicine nor cycloheximide treatment altered initial pulmonary arrest; however, fewer cycloheximide-treated cells remained in the lungs 8 h postinjection. Greater than 90% of control or colchicine-treated cells were found to be associated with activated platelets, and they also demonstrated typical cell membrane process formation 10 min and 8 h post-tumor cell injection. In contrast, less than 10% of cycloheximide-treated cells were in contact with activated platelets 10 min postinjection. However, by 8 h approximately 90% of cycloheximide-treated cells were in contact with activated platelets. This recovery coincided with the reformation of the B16 amelanotic melanoma vimentin intermediate filament network and the reacquisition of the ability to induce platelet aggregation in vitro. Neither colchicine nor cycloheximide treatment altered initial B16 amelanotic melanoma cell adhesion to murine microvessel-derived endothelial cells. This study provides in vivo evidence in support of our previous findings that disruption of certain cytoskeletal elements (i.e., vimentin intermediate filaments) inhibits the tumor cell ability to activate platelets. This study also suggests that platelet activation may stabilize the initial tumor cell arrest in the microvasculature.

Chronic urinary retention postpartum

Three cases of chronic urinary retention postpartum are reported. All patients were primigravidas. Unrecognized urinary retention following epidural anaesthesia in labour was the likely cause. Abdominal ultrasound may have a place in early recognition of this complication. The early use of a suprapubic catheter hastens bladder recovery.

AIDS and hepatitis B and C: contamination risk at transurethral resection. A study using sodium fluorescein as a marker

The human immunodeficiency virus (HIV), hepatitis B virus (HBV) and hepatitis C virus (HCV) are all transmitted by minute amounts of infected blood. Surgeons are at risk of contracting these infections by a number of routes including splashes of blood on to the mucous membranes of eyes, nose and mouth, needle stick injuries and spillage of blood on chapped ungloved hands. The endoscopic surgeon is quite unaware of nearly all instances of facial contamination because the splashes are frequently both minute and dilute. Sodium fluorescein, an indelible fluorescent dye detectable in dilutions of one to two parts per million, has been used in this prospective study as a marker of irrigating fluid used during transurethral resection. In 17 out of 20 consecutive operations its presence on the face of the surgeon was revealed by photography, although only a few splashes were visible to the naked eye. There was a random distribution of splashes and also a recurring pattern of contamination of the orbit of the eye that looks through the telescope and the tip of the nose. Vaccination against hepatitis B is recommended for all endoscopic surgeons, together with the use of protective glasses and a mask that covers both the nose and mouth. The greatest danger to the health care team is from an infectious patient who is an unknown risk. It is recommended that high risk patients presenting for transurethral resection should first be screened for the presence of HBV, HCV and HIV antigens.

Effect of urine pH on the stability of doxorubicin and its recovery from bladder instillations

Doxorubicin (1 mg/ml) was shown to be stable when added to urine samples with a mean natural pH of 5.4 and in urine buffered to a mean pH of 4.6. However, at alkaline pH (mean = 8.1) there was a biphasic degradation of doxorubicin (mean t1/2 = 3.24 and 89 h respectively). The data indicate that buffering intravesical doxorubicin to pH 4.6 (acetate buffer) or pre-dosing of patients with ammonium chloride may minimise loss of active drug during the time for which the drug is retained in the bladder. Recovery of doxorubicin following 1 hour's retention in the bladder was similar (77%) for doses of 38/48 or 78 mg. It is suggested that a dose of 50 mg (1 mg/ml) is sufficient to ensure an adequate delivery of active drug to the bladder wall.

Partial characterization of a carotenoid droplet ATPase and its possible significance in carotenoid droplet dispersion in goldfish xanthophores

The dispersion of carotenoid droplets in permeabilized goldfish xanthophores is dependent on ATP, F-actin, and cytosol. We report here that the motor (ATPase, translocator) resides with the permeabilized cell remnants and not in the cytosol. We also report that the carotenoid droplets have an ATPase that is not conventional myosin, dynein, or an ion pump. Its activity appears to correlate with the actin content of the carotenoid droplet preparation. A carotenoid droplet protein of Mr 72,000 (p72) is shown to be labeled by irradiation with 8-azido-ATP with concomitant loss of ATPase activity of the carotenoid droplets. We propose that this protein may be the ATPase responsible for carotenoid droplet dispersion.

Actin-dependent carotenoid droplet dispersion in permeabilized cultured goldfish xanthophores

Organelle translocations are essential cellular processes. Although much progress has been made with regards to microtubule-dependent organelle translocations, little is known about actin-dependent organelle translocation(s) except cytoplasmic streaming in Nitella. On the other hand, there is indirect evidence that actin-dependent organelle translocation may be involved in secretion. We now present evidence that the dispersion of the pigment organelles carotenoid droplets in goldfish xanthophores is apparently actin dependent and that this process may be related to secretory processes. We show that, in digitonin-permeabilized goldfish xanthophores, the pigment organelles can be induced to disperse by a combination of cAMP, ATP, and xanthophore cytosol. This induced dispersion is inhibited by DNase I, phalloidin, or anti-actin, but not by anti-tubulin or anti-intermediate filament proteins, suggesting a dependence on F-actin. Since the dispersion of carotenoid droplets and secretion both involve outward translocation of organelles, we tested the possibility that cytosols of secretory tissues have similar activity. Such activity was indeed found in different tissues, apparently in parallel with the secretory activity of the tissues, suggesting that pigment dispersion in xanthophores and some secretory processes may share a common component.

Case four. Synergistic strategy development

Mercy Medical Center is a 467 bed, not-for-profit teaching hospital affiliated with a multispecialty group practice and health maintenance organization through contractual arrangements. Historically, strategy development was not helping the hospital remain viable while accomplishing its mission. Strategic planning was fragmented, not focused toward concern for balance of the overall product line, total growth of the organization or the best use of resources. The hospital did not involve the affiliated group practice or HMO in its planning. This last case in Chapter One describes the pursuit of synergy through strategy formulation. The case provides a good example of what Kanter describes as a post-entrepreneurial organization, striving for advantage through collaboration and linkage with "PALs."

Case seven. Managing mature operations in a competitive environment

In this case, a medical center learns how to evaluate each of its services along a Product Life Cycle curve. Each stage of the cycle has characteristics that suggest appropriate strategic growth and action orientations. When services were plotted along the Product Life Cycle curve, many of the services were found to be mature or making the transition from growth to maturity. At the time of the case, Memorial Medical Center's competitors were entering many of its traditional markets creating a strong competition for market share. Greater competitive emphasis on performance and price reduced profits in the medical center's mature services. The case reports the medical center's approach to modifying its action orientation in light of a better understanding of organizational competence.

Reversible dedifferentiation and redifferentiation of a melanized cell line from a goldfish tumor

We reported previously the isolation of a melanized cell line that can undergo reversible dedifferentiation and redifferentiation. A heavily pigmented cell line, designated as P15, originally isolated by fish serum-induced melanization of some GEM 81 cells, cloned and serially passaged in fish serum medium, became noticeably less pigmented after several months in fetal calf serum medium and completely unpigmented after another year in the same medium. Addition of fish serum to the medium of this dedifferentiated cell line, designated P15D, induced pigmentation within a week. This re-induced pigmented cell line, designated as P15DI, became unpigmented when cultured in fetal calf serum medium for one month. We report here that the dedifferentiation of P15 occurs in two stages. One week after withdrawal of fish serum, the specific activity of tyrosinase of the culture dropped by approximately 70% and remained at this reduced level for at least one month. After one year, the specific activity of tyrosinase had dropped to a barely detectable level and the culture became completely unpigmented (P15D). Electron microscopic studies showed that the P15D cells have no melanosomes, probably no large vesicles for melanosome formation, but some dopa-positive trans-Golgi network (TGN). Addition of fish serum to the growth medium of P15 cultures led to a steady increase in the specific activity of tyrosinase, detectable after one day. There was also an increase in the amount of dopa-positive TGN within one day. Melanosomes first appeared after three days and became numerous after one week. Upon removal of fish serum, these re-induced cells (P15D1) underwent a rapid decrease in the specific activity of tyrosinase, reaching, after eight days, the basal level seen in P15D cells. We also report that a protein designated as p75 (Mr approximately 75,000), previously shown to be associated with melanosomes in two melanized cell types of goldfish origin, is present in all melanized cell lines, including P15 and P15DI but absent in unmelanized cell lines, including P15D.

Enhanced tumor cell adhesion to the subendothelial matrix resulting from 12(S)-HETE-induced endothelial cell retraction

A 12-lipoxygenase metabolite of arachidonic acid, 12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE), which is produced by platelets and tumor cells, was tested for its ability to induce retraction of endothelial cell monolayers. The induction of endothelial cell retraction is a critical step in tumor cell metastasis. Endothelial cells demonstrated reversible retraction in response to 12(S)-HETE, but did not respond to the stereoisomer 12(R)-HETE or to unrelated 5-lipoxygenase (i.e., 5[S]-HETE) or 15-lipoxygenase (i.e., 15[S]-HETE) metabolites. Endothelial cells did not demonstrate loss of viability in response to 12(S)-HETE. The induction of retraction was both dose and time dependent. Scanning electron microscopy confirmed that 12(S)-HETE induced endothelial cell retraction and revealed collapsed filopodia on their surface, the appearance of spaces between endothelial cells and the underlying subendothelial matrix, in addition to large gaps between adjacent endothelial cells. Tumor cell adhesion to endothelial cell monolayers was enhanced 1 h after pretreatment of monolayers with 12(S)-HETE but not after pretreatment with other lipoxygenase metabolites. Tumor cell adhesion to endothelial cell monolayers 36 h after pretreatment with 12(S)-HETE was not different from adhesion to untreated monolayers. Therefore we suggest that 12(S)-HETE generated during tumor cell-platelet-endothelial cell interactions may induce reversible endothelial cell retraction, allowing tumor cell access to the subendothelial matrix, which is a critical step in their eventual extravasation from the microvasculature during hematogenous metastasis.