Differential colon cancer cell adhesion to E-, P-, and L-selectin: role of mucin-type glycoproteins

E-, P-, and L-selectin support the adhesion of leukocytes to the vessel wall through the recognition of specific carbohydrate ligands, which often contain sialylated, fucosylated lactosamines such as sialyl Lewis x [sLex; Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc-]. E-selectin expressed by activated endothelium has been shown to support the adhesion of sLex-bearing colon cancer cells. In the present study, we examine the interactions of multiple colon cancer cell lines with all three selectins. Three colon cancer cell lines (LS 180, T84, and COLO 205) bound to recombinant purified E-, P-, and L-selectin. The colon cancer line COLO 320 bound to P- and L-selectin but not E-selectin; conversely, HT-29 cells bound E-selectin but not P- and L-selectin. Caco-2 showed little or no interaction with any of the three selectins. Treatment of the cells with O-sialoglycoprotease from Pasteurella haemolytica, an enzyme that selectively cleaves mucin-type O-linked glycoproteins, reduced binding to purified P- and L-selectin in all cases. In addition, recombinant soluble P- and L-selectin bound to affinity-purified mucins from all adherent tumor cell lines. Of the four tumor cell lines that interacted with E-selectin, O-glycoprotease treatment substantially diminished adhesion of LS 180 and T84, had little effect on COLO 205, and failed to inhibit the binding of HT-29. As predicted by these data, E-selectin showed substantial binding only to mucins purified from LS 180 and T84. These findings suggest that L- and P-selectin interact primarily with mucin-type ligands on colon cancers, whereas E-selectin can recognize both mucin and nonmucin ligands. Binding of the colon cancer lines to purified selectins correlates with their adhesion to activated endothelial cells (E-selectin-dependent), platelets (P-selectin-dependent), and neutrophils (L-selectin-dependent). These differential tumor cell-selectin interactions may influence metastatic spread and may also contribute to the observed variability in host response to tumor progression.

The role of an ethics committee in resolving conflict in the neonatal intensive care unit

What should be the role of an institutional ethics committee (IEC) in resolving conflict concerning patient care decisions in the neonatal intensive care unit (NICU)? This question takes on added importance in light of recent court decisions which suggest that IEC deliberations may serve as persuasive evidence in court, of proposed state regulations that would establish an IEC as an alternative to judicial review, and of recent Joint Commission on Accreditation of Healthcare Organizations (JCAHO) guidelines that require an institutional policy on limitation or withdrawal of treatment to include a specified mechanism for resolving conflict. Unfortunately, despite these developments, prospective case consultation remains one of the most controversial and poorly understood aspects of IEC functions. Questions and concerns persist about the relation the IEC has and should have to actual decisions in specific cases.

We briefly examine the clinical, organizational, and regulatory complexity of the NICU environment and suggest five potential sources of uncertainty, disagreement, and conflict among parent(s) and NICU staff.

Forgoing medically provided nutrition and hydration in pediatric patients

Discussion of the ethics of forgoing medically provided nutrition and hydration tends to focus on adults rather than infants and children. Many appellate court decisions address the legal propriety of forgoing medically provided nutritional support of adults, but only a few have ruled on pediatric cases that pose the same issue.

The cessation of nutritional support is implemented most commonly for patients in apermanent vegetative state(often referred to aspersistent vegetative state(hereinafter “PVS”)). An estimated 4,000 to 10,000 American children are in the permanent vegetative state, compared to 10,000 to 25,000 adults. Yet the dearth of literature, case reports, and court decisions suggests that physicians and families of pediatric patients stop medically provided nutrition or seek court orders much less frequently.

Inositol polyanions. Noncarbohydrate inhibitors of L- and P-selectin that block inflammation

Selectins are cell adhesion molecules known to support the initial attachment of leukocytes to inflamed vascular endothelium through their recognition of carbohydrate ligands such as the tetrasaccharide sialyl Lewisx (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)GlcNAc-). In the present study, we describe the inhibition of L- and P-selectin function by inositol polyanions, simple 6-carbon ring structures that have multiple ester-linked phosphate or sulfate groups. In a purified component competition assay, binding of L- and P-selectin-Ig fusion proteins to immobilized bovine serum albumin-sialyl Lewisx neoglycoprotein was inhibited by inositol hexakisphosphate (InsP6, IC50 = 2.1 +/- 1.4 microM and 160 +/- 40 microM), by inositol pentakisphosphate (InsP5, IC50 = 1.4 +/- 0.2 and 260 +/- 40 microM), and by inositol hexakissulfate (InsS6, IC50 = 210 +/- 80 microM and 2.8 +/- 0.9 mM); E-selectin-Ig binding was unaffected. Inositol polyanions diminished the adhesion of LS180 colon carcinoma cells to plates coated with L- and P-selectin-Ig but not with E-selectin-Ig. Inositol polyanions blocked polymorphonuclear leukocyte (PMN) adhesion to COS cells expressing recombinant transmembrane P-selectin but not to those expressing E-selectin. In addition, inositol polyanions diminished PMN adhesion to activated endothelial cells under rotation-induced shear stress, a process known to require L-selectin function. In vivo, the effects of inositol polyanions were studied in two murine models of acute inflammation. Intravenously administered InsP6 (two doses of 40 mumol/kg) inhibited PMN accumulation in thioglycolate-induced inflammation (55 +/- 10% inhibition) and in zymosan-induced inflammation (61 +/- 4% inhibition). InsP5 and InsS6 also inhibited inflammation in these models, although higher doses were required for InsS6. In conclusion, inositol polyanions are noncarbohydrate small molecules that inhibit L- and P-selectin function in vitro and inflammation in vivo.

Endothelial-leukocyte adhesion molecules in human disease

An effective host response to infection or tissue damage requires focal accumulation of leukocytes. Leukocyte adhesion to the vessel wall, a key step in this process, depends on the ordered expression of specific endothelial cell surface molecules. The endothelial molecules that support adhesion include selectins that recognize leukocyte cell surface glycoconjugates as well as members of the immunoglobulin superfamily that interact with leukocyte integrins. Although inflammation can occur with minimal damage to the vessel wall and surrounding tissues, control mechanisms sometimes appear to fail, and the inflammatory response itself becomes a significant clinical problem. In this review, we discuss endothelial-leukocyte adhesion molecules with particular emphasis on their expression and function in human disease. Pathophysiological processes presented include atherosclerosis, ischemia-reperfusion injury, acute lung injury, rheumatoid arthritis, and graft rejection. A more detailed description of the discovery and characterization of the key molecules appears in the antecedent article entitled "Endothelial-Leukocyte Adhesion Molecules".

Development of secondary sex characteristics in male rats after fetal and perinatal cimetidine exposure

Cimetidine has been reported to cause antiandrogenic effects in male pups of female rats receiving cimetidine during gestation. Because of conflicting reports of cimetidine causing permanent antiandrogenic effects in male rats, we studied the sexual development of male rats born to females receiving cimetidine. Water or water and cimetidine (194 mg/kg of body weight per day) were administered to pregnant rats from day 12 of gestation through weaning. A total of 130 male pups were studied. Testicular prostate gland/seminal vesicle weights, anogenital distance, serum testosterone and dihydrotestosterone levels, and seminiferous tubule areas were compared between the two groups. Transfer of cimetidine across the placenta and though breast milk was confirmed by HPLC analysis of serum from female littermates at 0, 10, and 20 days of age. With the exception of a smaller anogenital distance (p < 0.03) and a lower anogenital index (p < 0.05) in the cimetidine-exposed newborn rats, no statistically significant differences were observed in the measured parameters between the cimetidine-exposed and control groups. Cimetidine exposure during the fetal and perinatal periods did not alter the development of secondary sex characteristics in male rat pups.

Loop diuretic derivative L-644,711 inhibits K(+)-stimulated cellular injury in neonatal guinea pig cortical astrocytes

An early pathological rise in extracellular K+ following acute hypoxia results in Cl- uptake into astrocytes through the Cl/HCO3- exchanger with an osmotic equivalent of water. This study addressed effects of the anion transport inhibitor, L-644,711, (5,6,-dichloro-2,3, 9,9a-tetrahydro-3-oxo-9a-propyl-1H-fluroen-7-yl)oxyacetic acid. Confluent primary cultures from neonatal guinea pigs, characterized as > 95% astrocytes with antiserum to glial fibrillary acidic protein, were manipulated by incubation in either basal buffer (BB) with the ionic composition of Dulbecco's minimum essential media (DMEM) or one with high extracellular K+ (HiK). Incubation in 27 or 60 mM Hik significantly reduced cell viability and precipitated a time-dose dependent increase in lactate dehydrogenase (LDH) efflux (30 min to 4 h). L-644,711 was not cytotoxic, and significantly inhibited HiK-stimulated LDH efflux. The optimal effective dose of L-644,711 for preventing injury in guinea pig astrocytes was 10(-11)M when administered simultaneously with the HiK paradigm or in reversing injury when administered 30 min after exposing cells to HiK. These findings indicate the potential usefulness of agents which modify ion transport processes in hypoxic-ischemic cerebral injury.

Heparin oligosaccharides bind L- and P-selectin and inhibit acute inflammation

Initial attachment of leukocytes to the vessel wall at sites of inflammation is supported by a family of carbohydrate-binding adhesion molecules called the selectins. Selectin ligands include sialyl-Lewis x (sLex, Neu5Ac alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc--) and related structures. We report here that defined heparin oligosaccharides interact with the selectins. Heparin chains containing four or more monosaccharide residues inhibited the function of L- and P-selectin, but not E-selectin, in vitro. In a competition enzyme-linked immunosorbent assay measuring inhibition of solution-phase selectin-Ig fusion proteins (selectin-Ig) binding to immobilized bovine serum albumin-sLex neoglycoprotein, a heparin-derived tetrasaccharide mixture inhibited 50% of L- and P-selectin-Ig binding (IC50) at 200 +/- 40 mumol/L and 850 +/- 110 mumol/L, respectively. A single hexasulfated tetrasaccharide (delta UA2S alpha 1-4GlcNS6S alpha 1-4IdoA2S alpha 1-4GlcNS6S) was particularly active against L- and P-selectin-Ig (IC50 = 46 +/- 5 mumol/L and 341 +/- 24 mumol/L). By comparison, the tetrasaccharide sLex was not inhibitory at concentrations up to 1 mmol/L. In cell adhesion assays, heparin tetrasaccharides reduced binding of neutrophils to COS cells expressing P-selectin but not to COS cells expressing E-selectin. They also blocked colon cancer cell adhesion to L- and P-selectin but not E-selectin. In a model of acute inflammation, intravenously administered heparin tetrasaccharides diminished influx of neutrophils into the peritoneal cavities of thioglycollate-treated mice. We conclude that heparin oligosaccharides, including non-anticoagulant tetrasaccharides, are effective L- and P-selectin inhibitors in vitro and have anti-inflammatory activity in vivo.

Endothelial-leukocyte adhesion molecules in inflammation and metastasis

Vascular endothelium is an active tissue. In response to various mediators, it expresses specific cell surface glycoproteins that support the binding and extravasation of blood leukocytes. These events are essential for host defense against pathogens and for repair of tissue damage. Unfortunately, it appears that a number of blood borne tumor cells may be able to use the same adhesive structures to facilitate their metastasis. The development of agents designed to block the adhesion of leukocytes (or tumor cells) to the vessel wall may prove valuable in the treatment of a variety of human disease processes, including adult respiratory distress syndrome (ARDS), ischemic reperfusion injury, autoimmunity, and metastatic spread of cancer.

Plasma fentanyl levels in infants undergoing extracorporeal membrane oxygenation

Plasma levels of fentanyl were analyzed in 12 infants undergoing extracorporeal membrane oxygenation who received a fentanyl bolus (5 to 10 micrograms/kg) followed by infusion at 1 to 6.3 micrograms/kg/hr. Fentanyl levels, averaging 11 samples/infant, were measured by radioimmunoassay (mean 19.7 +/- 35.7 ng/ml; n = 140). Eight of the infants, all with a primary diagnosis other than congenital diaphragmatic hernia, survived with relatively short (< 7 days) courses on extracorporeal membrane oxygenation; this group of infants did not develop tolerance to fentanyl and could be maintained on infusion rates of < 5 micrograms/kg/hr throughout. The four infants with congenital diaphragmatic hernia had longer extracorporeal membrane oxygenation runs and three did not survive; their plasma fentanyl levels were consistently higher and while the infusion rates were higher early on extracorporeal membrane oxygenation, they did not exceed 7 micrograms/kg/hr and actually decreased after 5 days on extracorporeal membrane oxygenation. Five infants (42%) received lorazepam in addition to fentanyl for at least one sampling time. The fentanyl infusion dose and plasma level were higher in the congenital diaphragmatic hernia nonsurvivors who did not receive lorazepam (p < 0.001). A decrease in fentanyl clearance correlated with renal dysfunction (p < 0.01). A bolus of fentanyl followed by infusion of relatively low doses (1 to 5 micrograms/kg/hr) provides adequate analgesia for infants on extracorporeal membrane oxygenation, particularly when it is supplemented with intravenous lorazepam whenever needed to control infant movement.

The Opposition Effect of the Moon: The Contribution of Coherent Backscatter

The opposition effect, the sharp surge in brightness of an astronomical object observed near zero phase angle, which has been known for more than a century, has generally been explained by shadow hiding. The reflectances of several Apollo lunar soil samples have been measured as a function of phase angle in linearly and circularly polarized light. All samples exhibited a decrease in the linear polarization ratio and an increase in the circular polarization ratio in the opposition peak. This provides unequivocal proof that most of the lunar opposition effect is caused by coherent backscatter, not shadow hiding. This result has major implications for the interpretation of photometric observations of bodies in the solar system, including the Earth.

Higher-affinity oligosaccharide ligands for E-selectin

A series of synthetic oligosaccharides based on sialyl Lewis x (sLex; Neu5Ac alpha 2-3Gal beta 1-4[Fuc alpha 1-3]GlcNAc) and sialyl Lewis a (sLea; Neu5Ac alpha 2-3Gal beta 1-3[Fuc alpha 1-4]GlcNAc) was used to study the binding interactions of selectins. E-selectin-immunoglobulin fusion protein (E-selectin-Ig) bound to immobilized bovine serum albumin (BSA)-neoglycoproteins containing sLex or sLea in a Ca(2+)-dependent manner. Solution-phase sLex tetrasaccharide blocked this interaction by 50% at a concentration of 750 +/- 20 microM (IC50). sLea was more effective (IC50 = 220 +/- 20 microM), while nonsialylated, nonfucosylated derivatives showed little or no activity at concentrations up to 1 mM. Attachment of an 8-methoxycarbonyloctyl aglycone in a beta linkage to the anomeric carbon of the GlcNAc of sLex or sLea increased their blocking activity nearly twofold. Finally, replacement of the 2-N-acetyl substituent of the GlcNAc by an azido or amino group resulted in substantial increases in activity, with the most potent inhibitor being amino substituted sLea, which was 36-fold more active (IC50 = 21 +/- 3 microM) than the reducing tetrasaccharide sLex. In contrast to results obtained with E-selectin-Ig, P-selectin-Ig binding to immobilized BSA-sLea was blocked modestly by most oligosaccharides at 1 mM, with no substantial differences among them. IC50 values of soluble oligosaccharides determined in competitive binding studies accurately predicted blocking of leukocyte adhesion to recombinant E-selectin-Ig and to cytokine-activated endothelium.

Selectins

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Binding of protein S to C4b-binding protein. Mutagenesis of protein S

Protein S and C4b-binding protein (C4BP) form a tight complex (Kd approximately 0.6 nM) the physiologic purpose of which is unknown. The participation of protein S in this complex was investigated using site-specific mutagenesis. Normal recombinant human protein S (rHPS) and five specifically mutated protein S analogs were expressed in transformed human kidney 293 cells and the following properties were characterized: solution-phase C4BP binding, ability to be cleaved by thrombin, ability to act as a cofactor in the activated protein C-catalyzed inactivation of factor Va, and gamma-carboxyglutamic acid content. In some cases, beta-hydroxyaspartic acid plus beta-hydroxyasparagine content was also determined. Binding studies indicated that while clearly important for a high affinity interaction, the amino acid sequence Gly605-Ile614 identified by Walker (Walker, F J. (1989) J. Biol. Chem. 264, 17645-17648) does not account for all the binding energy of the HPS-C4BP interaction. All mutants perturbed in this region or lacking it altogether displayed reduced C4BP binding, and some retained anticoagulant cofactor function. Neither human factor X nor human steroid-binding protein had any measurable ability to compete with plasma HPS for C4BP binding. Furthermore, bovine protein S and a rHPS analog with bovine sequence from Gly597-Trp629 bound to human C4BP with the same affinity as did HPS, and both proteins substituted effectively for HPS as a cofactor for activated protein C in an otherwise human anticoagulation system. Together these results suggest that optimal binding of protein S to C4BP requires the putative alpha-helix Gly605-Ile614, as well as other undetermined regions of protein S, and that the regions of HPS responsible for C4BP binding and activated protein C cofactor function are structurally isolated.

The influence of harvesting technique on endothelial preservation in saphenous veins

To study optimal conditions of preparation of saphenous veins as coronary artery bypass grafts, segments of saphenous veins were obtained from 29 consecutive patients undergoing coronary artery bypass grafting. The saphenous vein segments were divided into three groups. In Group I, 10 saphenous vein segments were harvested using a "no-touch" technique without any other preparation aids. In Group II, 10 saphenous vein segments were removed while distended at 70-120 mm Hg with a balanced pH electrolyte solution at 37 degrees C. In Group III, consisting of 10 saphenous vein segments, nitroglycerin (1 microgram/ml) was added to the distending solution used in Group II. Samples of saphenous vein were assessed in a blind study using light and scanning electron microscopy to estimate endothelial cell preservation by the three harvest techniques. Saphenous veins receiving only a no-touch dissection technique without distention solution (Group I) revealed significantly better endothelial preservation (P less than 0.005). The administration of distention solution alone, or with nitroglycerin, to saphenous veins in situ using our operative technique during harvest does not appear to protect endothelial-integrity and may be harmful.

Justice and the moral acceptability of rationing medical care: the Oregon experiment

The Oregon Basic Health Services Act of 1989 seeks to establish universal access to basic medical care for all currently uninsured Oregon residents. To control the increasing cost of medical care, the Oregon plan will restrict funding according to a priority list of medical interventions. The basic level of medical care provided to residents with incomes below the federal poverty line will vary according to the funds made available by the Oregon legislature. A rationing plan such as Oregon's which potentially excludes medically necessary procedures from the basic level of health care may be just, for the right to publically-sponsored medical care is restricted by opposing rights of private property. However, the moral acceptability of the Oregon plan cannot be determined in the absence of knowing the level of resources to be provided. Finally, Oregon to date has failed to include the individuals being rationed in discussions as to how the scarce resources are to be distributed.

beta-Hydroxyaspartic acid and beta-hydroxyasparagine residues in recombinant human protein S are not required for anticoagulant cofactor activity or for binding to C4b-binding protein

Among the vitamin K-dependent plasma proteins, only protein S contains the post-translationally modified amino acid erythro-beta-hydroxyasparagine (Hyn). Protein S also contains erythro-beta-hydroxyaspartic acid (Hya). The function of these unusual amino acids, located in the epidermal growth factor-like domains, is unknown. To determine if these post-translational modifications contribute to the functional integrity of human protein S (HPS), recombinant human protein S lacking Hya and Hyn (rHPSdesHya/Hyn) was purified from the medium of human kidney 293 cells that were transfected with HPS cDNA and grown in the presence of the hydroxylase inhibitor 2,2'-dipyridyl. Solution-phase equilibrium binding studies revealed that rHPSdesHya/Hyn binds C4b-binding protein (C4BP) in a manner indistinguishable from recombinant HPS and plasma-derived HPS, exhibiting a Kd in the presence of 2 mM CaCl2 of approximately 0.7 nM and a Kd in the presence of 4 mM EDTA approximately 10-fold higher. In a purified component system, rHPSdesHya/Hyn displayed normal anticoagulant cofactor activity in the activated protein C-catalyzed inactivation of coagulation factor Va bound in the prothrombinase complex. In addition, digestion of rHPSdesHya/Hyn with thrombin in the presence of EDTA appeared normal, and 2 mM CaCl2 prevented the cleavage. Together these results suggest that the post-translational modifications of Asn and Asp residues are not necessary for the macromolecular or Ca2+ interactions associated with the anticoagulant and C4BP binding characteristics of HPS.

Plasma beta-endorphin in neonates: effect of prematurity, gender, and respiratory status

A consecutive cohort of 87 infants (46 infants less than 37 weeks gestational age and 41 term infants greater than or equal to 37 weeks gestation) admitted to the Neonatal Intensive Care Unit (NICU) and a convenience cohort of 27 term well babies at the University of Nebraska Medical Center (Omaha, NE) were evaluated for plasma beta-endorphin (beta E) levels during the first 4 h after birth. Demographic data, maternal history, and respiratory status at the time of sampling as well as development of documented apneic episodes during the initial hospitalization were analyzed for all infants. All NICU infants had higher plasma beta E levels than the control infants. Premature infants had significantly higher neonatal plasma beta E levels than term infants in either the control or NICU groups, but the response was gender specific; premature males had higher plasma beta E than premature females (P = 0.008). Perinatal stress, including respiratory problems, was associated with the increase in plasma beta E, but prematurity and being male were significantly predictors of an elevated plasma beta E level. Immaturity in respiratory control, as evaluated by the development of documented apneic episodes during the infant's initial hospitalization, did not correlate with an elevated perinatal plasma beta E level.

Fetal habituation to vibroacoustic stimulation in uncomplicated term pregnancies

The use of transabdominal vibroacoustic stimulation has been shown to improve the efficiency of antepartum fetal surveillance. The ability of the fetus to habituate to such a stimulus has also been suggested as a means of assessing the function of the central nervous system. The purpose of this blinded prospective investigation was to evaluate fetal habituation in a group of low-risk pregnancies anticipated to deliver within 1 week. One hundred sixteen uncomplicated pregnancies underwent repetitive vibroacoustic stimulation using a Corometrics Model 146 fetal acoustic stimulator. Fetal habituation was defined as a sustained elevation of the heart rate baseline for more than 15 minutes or a failure to produce an adequate acceleration of the fetal heart rate after an initial response. Habituation was present in 106 (91.4%) cases, whereas 10 (8.6%) failed to habituate to the stimulus. All infants failing to habituate in utero ultimately did well after delivery. Their birthweights, Apgar scores, umbilical artery blood gas determinations, and courses in the newborn nursery were similar to those of infants who responded to in utero sound stimulation. However, cesarean delivery for fetal distress and gross placental abnormalities (such as infarction and abruption) occurred more commonly in those fetuses failing to habituate. Additional investigations of fetal habituation to a vibroacoustic stimulus may be helpful in the intrapartum risk assessment of uncomplicated term pregnancies.

An electrodynographic study of foot function in shoes of varying heel heights

Forty-three female test subjects had electrodynographic gait analysis performed in barefoot, low-heel shoe, and high-heel shoe conditions. Comparisons of segmental foot function, actual pressures, and pressure durations were determined. The findings suggest that an increased duration of forefoot loading, rather than an increased actual pressure, is responsible for pedal pathology secondary to wearing high-heel shoes. Contrary to previous reports in the literature, evidence of abnormal pronation in high heels was not found in this study.