The effect of dextran to restore the activity of pulmonary surfactant inhibited by albumin

Pulmonary surfactant is crucial to maintain the proper functioning of the respiration system. Certain types of blood proteins (e.g. albumin) were found to inhibit the activity of pulmonary surfactant. Axisymmetric Drop Shape Analysis (ADSA) was used to study the effect of dextran to restore the activity of an albumin-inhibited pulmonary surfactant. It was found that dextran could effectively restore surface tension properties of the inhibited surfactant in vitro. Furthermore, dextran improved the performance of pulmonary surfactants when albumin was absent. It was found that when a surfactant film was under high compression (e.g. above 70% surface area reduction), the presence of dextran increased film stability, so that the film could sustain high surface pressures without being collapsing.

Characterization of virulence factors of mouse-adapted Helicobacter pylori strain SS1 and effects on gastric hydrophobicity

Gastric infection with Helicobacter pylori results in chronic active gastritis and in some individuals is associated with complications such as peptic ulceration and gastric cancers. A balance between bacterial factors and host responses may determine disease outcome. The mouse-adapted H. pylori strain SS1 has been utilized as a model to study disease pathogenesis. Although chronic gastritis is observed in this murine model of H. pylori infection, other complications of disease seen in the human host (such as peptic ulceration) are not identified. The objectives of this study were to characterize virulence factors of the mouse-adapted H. pylori strain SS1 and determine host responses to infection. Vacuolating cytotoxin activity of H. pylori strain SS1 was determined after incubation of HEp-2 cells with culture supernatant for 24 hr. Polymerase chain reaction was performed to detect the presence of the cagA and cagE genes. Chemokine responses from human gastric epithelial cells infected with H. pylori SS1 were assessed by measurement of the concentration of interleukin-8 in cell-free supernatants. C57BL/6 and gld mice were infected with strain SS1 or sham-infected. Eight weeks following infection, gastric tissues were obtained for histological analysis and surface hydrophobicity was measured by axisymmetric drop-shape analysis. H. pylori strain SS1 was cytotoxin negative, cagA positive, and cagE positive, but induced only a modest interleukin-8 response (684 +/- 140 pg/ml) from AGS gastric epithelial cells in comparison to a clinical isolate (4170 +/- 410 pg/ml, P < 0.0005). Increased inflammation was observed in the stomachs of H. pylori strain SS1-infected animals compared to uninfected controls. Gastritis was not associated with any disease complications. Despite mucosal inflammation, infected mice did not demonstrate alterations in gastric surface hydrophobicity (42.2 degrees +/- 2.2 degrees and 41.4 degrees +/- 3.2 degrees for C57BL/6 and gld, respectively) compared to uninfected mice (43.2 degrees +/- 2.3 degrees and 39.5 degrees +/- 1.6 degrees, respectively). In conclusion, murine infection with H. pylori SS1, which contains putative bacterial virulence factors, results in gastric inflammation. However, the mucosal changes are not associated with alterations in surface hydrophobicity. Therefore, the mouse model of infection with H. pylori, strain SS1 may not serve as an entirely appropriate model to study host factors associated with disease complications.

Study of binding of 12(S)-hydroxy-5(Z),8(Z),10(E), 14(Z)-eicosatetraenoic acid to bovine serum albumin using dynamic surface tension measurements

In a recent paper,(1) we demonstrated that molecular interactions between biopolymers and other smaller molecules can be detected by means of dynamic surface tension measurements. In the present paper, we demonstrate that the same methodology can be employed for investigating dose effects and specificity of molecular interactions. Three similar lipids were chosen for this study: 12(S)-hydroxy-5(Z), 8(Z),10(E),14(Z)-eicosatetraenoic acid (12(S)-HETE-free acid), methyl 12(S)-hydroxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoate (12(S)-HETE-methyl ester), and 5(Z),8(Z),11(Z), 14(Z)-eicosatetraenoic acid (arachidonic acid-free acid). These substances were added to a fatty acid free bovine serum albumin (BSA) aqueous solution at different lipid concentrations. The characteristic tension response indicates that molecular interactions between 12(S)-HETE-free acid and BSA exist. The detected interactions are concentration dependent: at a molecular ratio of lipid to protein of 1:1, the binding of 12(S)-HETE-free acid to BSA is hydrophobic in nature; at the molecular ratio of lipid to protein of 10:1, a secondary binding occurs and is hydrophilic in nature. Similar molecular interactions were not detected between 12(S)-HETE-methyl ester or arachidonic acid-free acid and BSA, indicating that the interactions between 12(S)-HETE-free acid and BSA are specific. As an independent means, surface elasticity is used to probe the molecular interactions at the interface. In the case of 12(S)-HETE-free acid but not its methyl ester or arachidonic acid, distinct higher surface elasticities were observed at lipid concentrations in excess of a molecular ratio of lipid to protein of 1:1. This finding reinforces the above stipulations.

Surface hydrophobicity is increased in the ileum and proximal colon of cystic fibrosis mice

Patients with cystic fibrosis (CF) have abnormal concentrations and composition of electrolytes and macromolecules in gastrointestinal secretions. Such alterations could change intestinal surface properties, such as surface hydrophobicity, and may influence the adhesion of macromolecules, bacteria, or microbial toxins to the intestinal surface. The objective of this study was to compare the surface hydrophobicity of the gastrointestinal tract in wild type and CF mice. We used axisymmetric drop shape analysis-contact diameter to determine surface hydrophobicity by measuring contact angles of sessile water droplets placed onto epithelial surfaces. In wild type mice, there were no differences in contact angles between the duodenum, upper jejunum, lower jejunum, and ileum. The contact angle of the gastric mucosa was lower than the rest of the gastrointestinal tract. Contact angles of the proximal colon and distal colon were both higher than that of the gastric mucosa and those of the small intestinal sections. In CF mice, contact angles along the gastrointestinal tract followed the same pattern as in wild type mice. However, contact angles in the ileum and proximal colon of CF mice were greater than those from wild type mice. This study of the murine intestine showed regional differences in surface hydrophobicity comparable to those observed in other mammalian species. In addition, we showed that the ileum and proximal colon of CF mice were more hydrophobic than the corresponding segments in wild type mice. These observations are of potential clinical relevance because patients with CF exhibit clinical manifestations of gastrointestinal disease primarily in the ileum and proximal colon.

Surface properties of Helicobacter mustelae and ferret gastrointestinal mucosa

Helicobacter mustelae is a gastric pathogen in ferrets that adheres to epithelial cells both in vitro and in vivo. In this study, the authors examine the role of surface hydrophobic properties in the adhesion of these organisms to eukaryotic cell surfaces. The surface properties of six H. mustelae strains were characterized by hydrophobic interaction chromatography (HIC), salt aggregation testing (SAT) and contact-angle measurement by axisymmetric drop-shape analysis (ADSA). Contact angles in multiple regions of the gastrointestinal tract, obtained from infected and uninfected ferrets, were also measured. The cell surface of H. mustelae was found to be hydrophilic by SAT but relatively hydrophobic by HIC. Contact-angle measurements for H.mustelae (mean 22.5 degrees, 95% confidence interval [CI] 9.3 degrees to 35.7 degrees) were higher than values previously reported for Helicobacter pylori (mean 12.1 degrees, 95% CI 2.0 degrees to 22.2 degrees, p < 0.05). The body of the stomach was more hydrophilic in infected ferrets (mean contact angle 59.9 degrees, 95% CI 52.5 degrees to 67.3 degrees) than in uninfected animals (mean contact angle 94.2 degrees, 95% CI 84.4 degrees to 104.0 degrees, p < 0.05). Reductions in the surface hydrophobicity of the ferrets' stomachs were correlated with the degree of mucosal inflammation (p < 0.01). These findings demonstrate that H. mustelae has surface properties comparable to those of H. pylori strains. Like the human stomach infected by H. pylori, there is a reduction in surface hydrophobicity of the ferret antrum associated with H. mustelae infection and the resulting mucosal inflammatory cell response.

Surface hydrophobicity properties of rabbit stomach in vitro

To quantitate surface hydrophobicity of the stomach, we measured contact angles formed with water droplets in different regions of rabbit stomach at varying ages (suckling, weanling, and adult). Contact angles were measured using novel methods: axisymmetric drop-shape analysis-contact diameter for contact angles < 90 degrees and axisymmetric drop-shape analysis-maximum diameter for contact angles > 90 degrees. To determine whether gastric mucus was responsible for the physical properties of the surface mucosa, the surface tension of mucus derived from the body of stomach was measured by axisymmetric drop-shape analysis on pendant drops. Contact angles of adult antrum 82.9 degrees +/- 5.5 degrees (mean +/- SEM) were greater than in the body of stomach (36.1 degrees +/- 2.6 degrees, p = 0.0001). Contact angles on mucosa obtained from the body of the stomach of both suckling rabbits (76.4 degrees +/- 2.7 degrees) and weanling rabbits (84.2 degrees +/- 2.9 degrees) were greater than in adult animals (ANOVA, p < 0.05). Pendant drop analysis of mucus derived from the body of stomach showed a high surface tension (57.72 +/- 0.06 mJ/m2, mean +/- SD). We conclude that there are maturational changes and regional differences in the surface hydrophobicity of the lapine stomach. These changes are likely caused by changes in the overlying mucus layer.

Surface hydrophobicity of the intestinal tract

To quantitate surface hydrophobicity of the intestine, we measured contact angles formed with water droplets in multiple regions of rabbit intestine at varying ages (suckling, weanling, and adult) and after dinitrochlorobenzene-induced colitis. Contact angles were measured using novel methods: axisymmetric drop-shape analysis-contact diameter for contact angles less than 90 degrees and axisymmetric dropshape analysis-maximum diameter for contact angles greater than 90 degrees. To determine whether mucus was present on the surface of intestine used, indirect immunofluorescence was performed using antibody specific to goblet cell mucin. To confirm that intestinal mucus could be responsible for the physical properties of surface mucosa, surface tensions of mucus prepared from distal ileum, distal colon, and inflamed distal colon of adult rabbits were measured by axisymmetric drop-shape analysis on pendant drops. Contact angles of adult small intestine [duodenum, 38.0 +/- 11.2 degrees (SD); jejunum, 44.0 +/- 22.9 degrees; ileum, 56.4 +/- 23.3 degrees] were less than proximal colon (93.2 +/- 6.7 degrees; P less than 0.05) and distal colon (86.4 +/- 24.2 degrees; P less than 0.05). Contact angles on proximal colon from suckling rabbits (53.2 +/- 8.4 degrees) were less than both weanling (93.2 +/- 23.3 degrees; P less than 0.05) and adult rabbits (93.2 +/- 6.7 degrees; P less than 0.05). Contact angles on inflamed adult distal colon (54.7 +/- 20.6 degrees) were decreased from values on normal distal colons (86.4 +/- 24.2 degrees). Indirect immunofluorescence demonstrated that mucin was present in both vacuoles of goblet cells and on the colonic surface.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro surface properties of the newly recognized gastric pathogen Helicobacter pylori

There appears to be a particular association between Helicobacter pylori and the gastric antrum, but the mechanisms by which the organism adheres to and colonizes the gastric mucosa are unclear. Surface hydrophobicity and surface charge mediate the adherence of other bacterial pathogens to mucosal epithelial cell surfaces. Therefore, in this study we characterized both the surface hydrophobicity and the surface charge of 10 H. pylori strains grown in broth culture. Four complementary methods were used to determine hydrophobicity: hydrophobic interaction chromatography, the salt aggregation test, comparison of bacterial adherence to polystyrene with adherence to sulfonated polystyrene, and measurement of contact angle with droplets of water. Three of the methods (salt aggregation test, adherence to polystyrene, and contact angles) indicated that each of the 10 strains expressed a relatively hydrophilic cell surface. In contrast, hydrophobic interaction chromatography determinations with both phenyl- and octyl-Sepharose suggested that the H. pylori strains were relatively hydrophobic. However, tetramethyl urea (0.4 M) did not reduce the binding of H. pylori to phenyl-Sepharose columns. DEAE-cellulose ion-exchange chromatography showed that each of the 10 strains of H. pylori had a surface which, overall, was highly negatively charged. We conclude that H. pylori expresses an overall relatively hydrophilic and negatively charged surface in vitro.

Bacterial cell surface hydrophobicity properties in the mediation of in vitro adhesion by the rabbit enteric pathogen Escherichia coli strain RDEC-1

The role of hydrophobicity in the attachment of enteropathogens to gastrointestinal mucosa is controversial. In vitro binding of Escherichia coli RDEC-1 to rabbit intestine is dependent on the expression of pili. We examined in vitro adherence of piliated RDEC-1 after altering either the hydrophobicity of the organisms, the hydrophobicity of the substrate for attachment, or the surface tension of the suspending liquid. Hydrophobicity of RDEC-1 was determined using four complementary methods. In each assay piliated RDEC-1 demonstrated relatively more hydrophobic properties compared with both organisms grown to suppress pilus expression and a mutant that cannot express mannose-resistant pili. When piliated RDEC-1 were pretreated with tetramethyl urea to disrupt hydrophobic bonds surface hydrophobicity decreased. Concurrently, bacterial adherence to rabbit ileal microvillus membranes, mucus and mucin was reduced. Binding of piliated organisms to hydrophobic surfaces was significantly higher compared to both nonpiliated bacteria and the adherence of piliated RDEC-1 to relatively hydrophilic surfaces. Addition of propanol reduced the surface tension of the suspending liquid, and decreased adhesion of piliated RDEC-1 to polystyrene by 80%. Conversely, adherence of piliated organisms to a hydrophilic surface increased 12-fold after lowering the surface tension of the suspending liquid. We conclude that hydrophobic properties have a role in mediating in vitro adherence of this E. coli enteric pathogen.

Determination of the surface tension of various species of erythrocytes by means of the solidification front technique

The solidification front technique is employed to determine the surface tension of fixed erythrocytes of dog, horse, human, chicken, and turkey. The results range from 65.5 erg/cm2 for dog erythrocytes to 67.6 erg/cm2 for turkey erythrocytes. A detailed error analysis shows that the differences obtained are statistically significant. Since cellular interactions are governed to a considerable extent by surface tension effects, it is concluded that caution needs to be exercised when results obtained for one species are used to predict the behavior of cells of another species.

Surface thermodynamics of bacterial adhesion

The adhesion of five strains of bacteria, i.e., Staphylococcus aureus (strain 049), Staphylococcus epidermidis (strain 047), Escherichia coli (strains 055 and 2627), and Listeria monocytogenes, to various polymeric surfaces was studied. The design of the experimental protocol was dictated by thermodynamic considerations. From the thermodynamic model for the adhesion of small particles from a suspension onto a solid substratum, it follows that the extent of adhesion is determined by the surface properties of all three phases involved, i.e., the surface tensions of the adhering particles, of the substrate, and of the suspending liquid medium. In essence, adhesion is more extensive to hydrophilic substrata (i.e., substrata of relatively high surface tension) than to hydrophobic substrata, when the surface tension of the bacteria is larger than that of the suspending medium. When the surface tension of the suspending liquid is larger than that of the bacteria, the opposite pattern of behavior prevails. Suspensions of bacteria at a concentration of 10(8) microorganisms per ml were brought into contact with several polymeric surfaces (Teflon, polyethylene, polystyrene, and acetal and sulfonated polystyrene) for 30 min at 20 degrees C. After rinsing, the number of bacteria adhering per unit surface area was determined by image analysis. The surface tension of the suspending medium. Hanks balanced salt solution, was modified through the addition of various amounts of dimethyl sulfoxide. It was found that the number of bacteria adhering per unit surface area correlates well with the thermodynamic predictions and that these data may be used to determine the surface tension of the different bacterial species. The surface tensions of the bacteria obtained in this fashion are in excellent agreement with those obtained by other methods.

Diurnal episodic pattern of insulin secretion in the dog

Sampling portal blood every 15 min by means of indwelling cannulae, we have found evidence that basal insulin secretion in nonanesthetized dogs takes place in six or seven major secretory episodes over a 24-h period. Reproducible patterns were obtained in four experiments conducted on three normal animals. When frequency of peaks was plotted against the log of insulin concentration, a normal distribution was obtained (lognormal distribution). The means and variances were nearly the same in the three animals. Low levels of insulin (10--25 microU/ml) alternated with peaks which were occasionally higher than 200 microU/ml. The average duration of a peak was 30 min and seemed to be independent of ambient glucose levels. It is suggested that these peaks are the result of surges in plasma growth hormone concentrations and/or spontaneous repetitive discharges along neuronal pathways functionally related to insulin secretion.

Effect of growth hormone on acute glucagon and insulin release

The aim was to clarify whether or not sudden spike concentrations of plasma growth hormone (GH) can affect the endocrine pancreas in vivo. The peaking of GH was reproduced by an injection (10 mg/kg iv) of bovine GH to anesthetized normal, pancreatectomized, and alloxan-diabetic dogs. In portal but not in peripheral blood, immunoreactive plasma glucagon (IRG), glucagon-like activity (GLI), and immunoreactive insulin (IRI), were significantly elevated within 10 min in normal and alloxan-diabetic dogs. In pancreatectomized dogs, GH did not affect either IRG or GLI. When a physiological dose of GH (6 microgram/kg) calculated to produce ambient peak plasma concentrations of 40 ng/ml was given to four conscious, normal dogs with indwelling portal catheters, a rise of IRG from 108 +/- 19 to 170 +/- 17 pg/ml and of IRI from 20 +/- 12 to 67 +/- 19 muU/ml (mean +/- SE) occurred within 2 min. GLI was not affected. Thus a sudden rise in GH concentration can stimulate the release of a) GLI in the presence but not in the absence of the pancreas, and b) pancreatic IRG and IRI but not extrapancreatic IRG.

Effect of ergot alkaloids on sulfonylurea-stimulated insulin secretion in dogs

The insulinogenic response to a standard i.v. dose of a sulfonylurea can be markedly augmented in normal, conscious dogs if they are given 30 min earlier a single i.v. dose of dihydroergotamine (DHE). Since the parent substance ergotamine posssed no such amplifying properties, further experiments were conducted to clarify the essential structural requirements that have to be fulfilled for an ergot alkaloid to act as an amplifier of sulfonylurea-stimulated insulin secretion. Amine alkaloids ergonovine, dihydroergonovone and dihydromethylergonovine had no amplifying potency, but the hydrogenated amino acid alkaloids dihydroergocornine, dihydroergocristine and dihydroergokryptine (Hydergine) were almost as potent amplifiers as was DHE. The data indicate that (a) DHE, Hydergine and by inference all hydrogenated amino acid alkaloids are potent amplifiers of sulfonylurea-stimulated insulin secretion; (b) saturation of the double bond at C9 and C10 of the lysergic acid moiety and the pressence of an amino acid side chain are essential structual requirements for an ergot alkaloid to function as an amplifier of the action of sulfonylureas; and (c) it appears that these compounds are acting chiefly by mechanisms other than alpha-adrenergic and serotonergic receptor blockade, perhaps as regulatory molecules inducing positive cooperative changes in integral proteins of the plasma membrane of beta cells.

Lipolysis as a function of cell numbers and fat content: comparison between isolated rat and dog adipocytes

The lipolytic responses to dihydroergotamine (5 mug/mi) of isolated rat adipocytes andto epinephrine (50 ng/m1 and 1 mug/m1) of both rat and dog adipocytes were measured over a period of two hours. Glycerol release was calculated as a function of either glycerol ester content or of cell number per incubation vial. The conventional calculation based on glyceride content gave the following results: a) epididymal fat cells from rats weighing less than 160 gm were more sensitive to dihydroergotamine and epinephrine than were fat cells from heavier animals weighing close to 200 gm; b) dog adipocytes from abdominal subcutaneous tissue were less sensitive to eipnephrine than were rat adipocytes. No such differences were noted when the same data were calculated on the basis of cell numbers per incubation vial: the lipolytic response was uniform with rat adipocytes obtained either from the lighter or the heavier weight groups, and so was the response of dog and rat cells. These results indicate that in the type of studies where receptor-dependent hormone and drug effects are measured, the number of cells per incubation vial is an important parameter to be considered in evaluating a lipolytic response.

Inhibition of sulphonylurea-stimulated insulin secretion by beta adrenergic blockage

Normal dogs were injected i.v. with a single dose of 0.25 mg/kg sodium salt of HB 419 (Glibenclamide). Plasma insulin and glucose concentrations were measured at stated intervals over a period of two hours. The rise in insulin, but not the hypoglycemic response was abolished in peripheral blood when the animals were pretreated with a single i.v. injection of either 0.1 mg/kg or 0.3 mg/kg dl-propranolol, 30 min prior to the administration of HB 419. The d-isomer of propranolol was ineffective in this respect. These results indicate that a) the mechanism by which propranolol inhibits sulphonylurea-stimulated insulin secretion involves beta adrenergic receptors; and b) the hypoglycemia produced by HB 419 in the presence of propranolol could be the result of extrapancreatic effects. Since the possibility of an early rise in the insulin concentration of portal blood was not excluded in our present series of experiments, final proof will have to be provided by studies in totally pancreatectomized dogs.

Failure of ergotamine to act as an amplifier of sulfonylurea-stimulated insulin secretion

Normal dogs were injected i.v. with 0.25 mg/kg sodium salt of HB 419 (glibenclamide) and plasma insulin concentrations were measured over a period of 2 hrs. When the animals were given a single i.v. injection of 0.2 mg/kg dihydroergotamine tartrate (DHE) 30 min prior to the administration of HB 419, the insulinogenic effect of the sulfonylurea was considerably amplified (192 muU/ml vs 34 muU/ml at 45 min). No augmentation of the insulinogenic effect of HB 419 was observed when the same experiments were conducted with 0.05, 0.025 or 0.01 mg/kg ergotamine tartrate. At the dose level of 0.1 mg/kg the insulinogenic effect of HB 419 was suppressed. Since the structural difference between these two ergot alkaloids consists of the presence or absence of the double bond at C9 and C10 of the lysergic acid moiety, it appears that saturation of this double bond is an essential structural requirement for DHE to function as an amplifier of sulfonylurea-stimulated insulin release.