Impact of Particle Sedimentation in Pendant Drop Tensiometry.

Understanding the interface-stabilizing properties of surface-active components is key in designing stable macroscopic multiphase systems, such as emulsions and foams. When poorly soluble materials are used as an interface stabilizer, the insoluble material may sediment and interfere with the analysis of interfacial properties in pendant (or hanging) drop tensiometry. Here, the impact of sedimentation of particles on the interfacial properties determined by pendant drop tensiometry was evaluated using a model system of whey protein isolate and (non surface-active) glass beads (2.2-34.7 µm). Although the glass beads did not adsorb to the air-water interface, a 1% (w/w) glass bead solution appeared to decrease the surface tension by nearly 12 mN/m after 3 h. A similar effect was shown for a mixture of whey proteins and glass beads: the addition of 1% (w/w) of glass beads led to an apparent surface tension decrease of 31 mN/m rather than the 20 mN/m observed for pure whey proteins. These effects are attributed to the sedimentation of particles near the apex of the droplet, leading to droplet shape changes, which are interpreted as a decrease in surface tension using tensiometer software. The droplet density at the apex increases due to sedimentation, and this density increase is not accounted for when fitting the droplet shape with the Young-Laplace equation. The result is the observed apparent decrease in surface tension. In contrast to the significant impact of sedimenting material on the surface tension measurements, the impact on the results of oscillatory deformations was limited. These findings show that the impact of sedimentation should be considered when studying the interface-stabilizing properties of materials with reduced solubility, such as certain plant protein extracts. The presence of such particles should be carefully considered when conducting pendant drop tensiometry.

Hydrophobicity Enhances the Formation of Protein-Stabilized Foams.

Screening proteins for their potential use in foam applications is very laborious and time consuming. It would be beneficial if the foam properties could be predicted based on their molecular properties, but this is currently not possible. For protein-stabilized emulsions, a model was recently introduced to predict the emulsion properties from the protein molecular properties. Since the fundamental mechanisms for foam and emulsion formation are very similar, it is of interest to determine whether the link to molecular properties defined in that model is also applicable to foams. This study aims to link the exposed hydrophobicity with the foam ability and foam stability, using lysozyme variants with altered hydrophobicity, obtained from controlled heat treatment (77 °C for 0-120 min). To establish this link, the molecular characteristics, interfacial properties, and foam ability and stability (at different concentrations) were analysed. The increasing hydrophobicity resulted in an increased adsorption rate constant, and for concentrations in the protein-poor regime, the increasing hydrophobicity enhanced foam ability (i.e., interfacial area created). At higher relative exposed hydrophobicity (i.e., ~2-5 times higher than native lysozyme), the adsorption rate constant and foam ability became independent of hydrophobicity. The foam stability (i.e., foam collapse) was affected by the initial foam structure. In the protein-rich regime-with nearly identical foam structure-the hydrophobicity did not affect the foam stability. The link between exposed hydrophobicity and foam ability confirms the similarity between protein-stabilized foams and emulsions, and thereby indicates that the model proposed for emulsions can be used to predict foam properties in the future.

Enzymatic cross-linking of α-lactalbumin to produce nanoparticles with increased foam stability.

Hard colloidal nanoparticles (e.g. partly hydrophobised silica), are known to make foams with very high foam-stability. Nanoparticles can also be produced from proteins by enzymatic cross-linking. Such protein based particles are more suitable for food applications, but it is not known if they provide Pickering foam stabilisation to the same extent as hard colloidal particles. α-Lactalbumin (α-LA) was cross-linked with either microbial transglutaminase (mTG) or horseradish peroxidase (HRP) to produce α-LA/mTG and α-LA/HRP nanoparticles. With both enzymes a range of nanoparticles were produced with hydrodynamic radii ranging from 20-100 nm. The adsorption of nanoparticles to the air-water interface was probed by increase in surface pressure (Π) with time. In the beginning of the Π versus time curves, there was a lag time of 10-200 s, for nanoparticles with Rh of 30-100 nm, respectively. A faster increase of Π with time was observed by increasing the ionic strength (I = 0-125 mM). The foam-ability of the nanoparticles was also found to increase with increasing ionic strength. At a fixed I, the foam-ability of the nanoparticles decreased with increasing size while their foam-stability increased. Foams produced by low-shear whipping were found to be 2 to 6 times more stable for nanoparticles than for monomeric α-LA (Rh≈ 2 nm). At an ionic strength of 125 mM ionic strength and protein concentration ≥ 10 g L(-1), the foam-stability of α-LA/mTG nanoparticles (Rh = 100 nm, ρapp = 21.6 kg m(-3)) was 2-4 times higher than α-LA/HRP nanoparticles (Rh = 90 nm, ρapp = 10.6 kg m(-3)). This indicated that foam-stablity of nanoparticles is determined not only by size but also by differences in mesoscale structure. So, indeed enzymatic cross-linking of proteins to make nanoparticles is moving a step towards particle like behavior e.g. slower adsorption and higher foam stability. However, the cross-link density should be further increased to obtain hard particle-like rigidity and foam-stability.

Effect of glycation on the flocculation behavior of protein-stabilized oil-in-water emulsions.

Glycation of proteins by the Maillard reaction is often considered as a method to prevent flocculation of protein-stabilized oil-in-water emulsions. The effect has been suggested, but not proven, to be the result of steric stabilization, and to depend on the molecular mass of the carbohydrate moiety. To test this, the stabilities of emulsions of patatin glycated to the same extent with different mono- and oligosaccharides (xylose, glucose, maltotriose, and maltopentaose) were compared under different conditions (pH and electrolyte concentration). The emulsions with non-modified patatin flocculate under conditions in which the zeta potential is decreased (around the iso-electric point and at high ionic strength). The attachment of monosaccharides (i.e., glucose) did not affect the flocculation behavior. Attachment of maltotriose and maltopentaose (Mw > 500 Da), on the other hand, provided stability against flocculation at the iso-electric point. Since the zeta potential and the interfacial properties of the emulsion droplets are not affected by the attachment of the carbohydrate moieties, this is attributed to steric stabilization. Experimentally, a critical thickness of the adsorbed layer required for steric stabilization against flocculation was found to be 2.29-3.90 nm. The theoretical determination based on the DLVO interactions with an additional steric interaction coincides with the experimental data. Hence, it can be concluded that the differences in stability against pH-induced flocculation are caused by steric interactions.

Protein concentration and protein-exposed hydrophobicity as dominant parameters determining the flocculation of protein-stabilized oil-in-water emulsions.

DLVO theory is often considered to be applicable to the description of flocculation of protein-stabilized oil-in-water emulsions. To test this, emulsions made with different globular proteins (ß-lactoglobulin, ovalbumin, patatin, and two variants of ovalbumin) were compared under different conditions (pH and electrolyte concentration). As expected, flocculation was observed under conditions in which the zeta potential is decreased (around the isoelectric point and at high ionic strength). However, the extent of flocculation at higher ionic strength (>50 mM NaCl) decreased with increasing protein-exposed hydrophobicity. A higher exposed hydrophobicity resulted in a higher zeta potential of the emulsion droplets and consequently increased stability against flocculation. Furthermore, the addition of excess protein strongly increased the stability against salt-induced flocculation, which is not described by DLVO theory. In the protein-poor regime, emulsions showed flocculation at high ionic strength (>100 mM NaCl), whereas emulsions were stable against flocculation if excess protein was present. This research shows that the exposed hydrophobicity of the proteins and the presence of excess protein affect the flocculation behavior.

Production of tailor-made enzymes to facilitate lipid extraction from the oleaginous yeast Schwanniomyces occidentalis.

Due to the depletion of fossil fuel resources and concern about increasing atmospheric CO2 levels, the production of microbial oil as source for energy and chemicals is considered as a sustainable alternative. A promising candidate strain for the production of microbial oil is the oleaginous yeast Schwanniomyces occidentalis CBS 2864. To compete with fossil resources, cultivation and processing of S. occidentalis requires improvement. Currently, different cell wall disruption techniques based on mechanical, chemical, physiological, and biological methods are being investigated using a variety of oil producing yeasts and microalgae. Most of these techniques are not suitable for upscaling because they are technically or energetically unfavorable. Therefore, new techniques have to be developed to overcome this challenge. Here, we demonstrate an effective mild enzymatic approach for cell disruption to facilitate lipid extraction from the oleaginous yeast S. occidentalis. Most oil was released by applying 187 mg L-1 tailor-made enzymes from Trichoderma harzianum CBS 146429 against the yeast cell wall of S. occidentalis at pH 5.0 and 40 °C with 4 h of incubation time after applying 1 M NaOH as a pretreatment step.

Controlling the Ratio between Native-Like, Non-Native-Like, and Aggregated ß-Lactoglobulin after Heat Treatment.

The amount of heat-denatured whey protein is typically determined by pH 4.6 precipitation. Using this method, a significant amount of nondenatured protein was reported even after long heating times. Apparently, a fraction of the unfolded protein refolds into the "native" state rather than form aggregates. This fact is known and has been explained using kinetic models. How the conditions affect the refolding and aggregation is, however, not fully understood. Therefore, this study investigates the unfolding, refolding, and aggregation process of ß-lactoglobulin using circular dichroism and size-exclusion chromatography to characterize different folding variants and to quantify their content. The proteins remaining in solution at pH 4.6 were confirmed to be native-like. The nonaggregated fraction contains proteins with a native-like and two types of non-native-like conformations. The nonaggregated fraction increased with decreasing temperature (60-90 °C) and concentration (1-50 g/L) and increasing electrostatic repulsion (pH 7-8; 0-50 mM). The native-like fraction in the nonaggregated fraction was independent of pH, ionic strength, and concentration but increased with decreasing temperature.

Comparison of heat-induced aggregation of globular proteins.

Typically, heat-induced aggregation of proteins is studied using a single protein under various conditions (e.g., temperature). Because different studies use different conditions and methods, a mechanistic relationship between molecular properties and the aggregation behavior of proteins has not been identified. Therefore, this study investigates the kinetics of heat-induced aggregation and the size/density of formed aggregates for three different proteins (ovalbumin, ß-lactoglobulin, and patatin) under various conditions (pH, ionic strength, concentration, and temperature). The aggregation rate of ß-lactoglobulin was slower (>10 times) than that of ovalbumin and patatin. Moreover, the conditions (pH, ionic strength, and concentration) affected the aggregation kinetics of ß-lactoglobulin more strongly than for ovalbumin and patatin. In contrast to the kinetics, for all proteins the aggregate size/density increased with decreasing electrostatic repulsion. By comparing these proteins under these conditions, it became clear that the aggregation behavior cannot easily be correlated to the molecular properties (e.g., charge and exposed hydrophobicity).

Towards predicting the stability of protein-stabilized emulsions.

The protein concentration is known to determine the stability against coalescence during formation of emulsions. Recently, it was observed that the protein concentration also influences the stability of formed emulsions against flocculation as a result of changes in the ionic strength. In both cases, the stability was postulated to be the result of a complete (i.e. saturated) coverage of the interface. By combining the current views on emulsion stability against coalescence and flocculation with new experimental data, an empiric model is established to predict emulsion stability based on protein molecular properties such as exposed hydrophobicity and charge. It was shown that besides protein concentration, the adsorbed layer (i.e. maximum adsorbed amount and interfacial area) dominates emulsion stability against coalescence and flocculation. Surprisingly, the emulsion stability was also affected by the adsorption rate. From these observations, it was concluded that a completely covered interface indeed ensures the stability of an emulsion against coalescence and flocculation. The contribution of adsorption rate and adsorbed amount on the stability of emulsions was combined in a surface coverage model. For this model, the adsorbed amount was predicted from the protein radius, surface charge and ionic strength. Moreover, the adsorption rate, which depends on the protein charge and exposed hydrophobicity, was approximated by the relative exposed hydrophobicity (QH). The model in the current state already showed good correspondence with the experimental data, and was furthermore shown to be applicable to describe data obtained from literature.

Fallibility of Griess (nitrite) test.

The Griess (nitrite) test is a simple, inexpensive, and rapid method for detecting bacteriuria. However, a working knowledge of its limitation should be considered during its interpretation.

Polycystic horseshoe kidney.

Polycystic horseshoe kidney is a rare occurrence. Only 8 cases have been previously reported; we add another case to the literature.

New and rapid method for detection of pyuria by leukocyte esterase reaction.

A method for a rapid detection of leukocytes in the urine is available in the form of a "dipstick." The reaction (color change) occurs within one minute and has a high index of reliability.

Extraosseous myelomatosis. Clinical presentation with symptoms in lower urinary tract.

We believe this to be the first case reported of extraosseous myelomatosis seen clincally with lower urinary tract symptoms. Extraskeletal spread of myelomatosis which reportedly occurs in two thirds of cases is discovered postmortem. Immunoglobulin A prevails in this type of myelomatosis. Clinical course and autopsy findings are discussed.

Adenocarcinoma of rete testis.

Adenocarcinoma of the rete testis is a rare tumor of the genital tract. An advanced case of adenocarcinoma thought to arise from the rete testis is presented. We believe this is the eighteenth reported case.

A deficit of chondroitin sulfate proteoglycans on the bladder uroepithelium in interstitial cystitis.

OBJECTIVES: To investigate the abundance of chondroitin sulfate proteoglycans at the bladder lumenal and subepithelial surfaces in bladder biopsies derived from patients with interstitial cystitis (IC) and controls. METHODS: Tissue sections derived from biopsies from 31 IC patients and 24 pathologically normal control sections were labeled for proteoglycans using the 2B6 anti-"stub" antibody and detected by immunohistochemistry. RESULTS: On the lumenal surface, 5 of 31 (19%) IC sections were positive for proteoglycans versus 14 of 24 (58%) control sections (P = 0.00011). At the basal surface, 5 of 19 IC patients were positive versus 7 of 12 controls (P = 0.032). CONCLUSIONS: A deficit of bladder lumenal and basal proteoglycans is associated with IC. The deficit in basal layer proteoglycans suggests an altered urothelial differentiation program. The lumenal deficit suggests that the charge-dependent exclusion of ions from the bladder surface is compromised in IC.

Efficacy of finasteride is maintained in patients with benign prostatic hyperplasia treated for 5 years. The North American Finasteride Study Group.

OBJECTIVES: The purpose of this open-label study extension was to assess the long-term safety and efficacy of finasteride in the treatment of men with benign prostatic hyperplasia (BPH). METHODS: A Phase III North American BPH trial originally enrolled 895 men, 297 of whom were randomized to receive finasteride 5 mg. An enlarged prostate gland by digital rectal examination, symptoms of urinary obstruction, and a maximal urinary flow rate of less than 15 mL/s were required for entry. Patients who completed the initial 12-month, double-blind, placebo-controlled study were invited to participate in an open-label extension for 4 additional years. RESULTS: Of the 297 patients initially randomized to receive finasteride 5 mg, 259 completed 12 months in the double-blind period and 186 completed 48 months of open-label therapy. Prostate volume reached a nadir of -24.6% at month 24, and the effect was maintained through month 60. Compared with baseline values, month 60 prostate volume was decreased by 22.7% (P<0.001), the quasi-American Urological Association symptom score was decreased by 4.3 points, and maximal urinary flow was increased by 2.3 mL/s (P<0.001) on average. Finasteride was well tolerated, with no significant increase in the prevalence of sexual adverse events over time. CONCLUSIONS: Patients treated with finasteride 5 mg maintained an initial decrease in prostate volume and improvement in symptom score and maximal urinary flow rate over 5 years.

Contractile activity of vasotocin, oxytocin, and vasopressin on mammalian prostate.

The neurohypophyseal peptides arginine vasotocin, oxytocin and arginine vasopressin contracted guinea pig, rat, canine and human prostates with potencies and efficacies that were comparable to those of noradrenaline and methacholine. All three neuropeptides raised prostatic tone and elicited contractions at 10(-9) or 10(-8) M, with an order of efficacy: arginine vasotocin greater than oxytocin greater than arginine vasopressin. The findings suggest a physiological role for these peptides in prostatic smooth muscle contraction and possibly also in other aspects of male reproductive function.

The impact of 5-alpha-reductase inhibitors on the number of prostatectomies for benign prostatic hyperplasia.

To determine the impact of a 5-alpha-reductase inhibitor on the need for surgical treatment of symptomatic benign prostatic hyperplasia (BPH) in clinical urologic practice, we retrospectively reviewed records of 794 patients treated with pharmacotherapy or surgery (or both). The number of transurethral resections of the prostate (TURPs) performed during the 30 months since introduction of finasteride was compared with the number performed during the 30 months before finasteride became available. The alpha-blockers doxazosin and prazosin were used during both times for the treatment of BPH. Of the 619 patients treated with drugs, 88.5% received finasteride for a mean of 249.6 days. The alpha-blockers, either alone or combined with finasteride, were prescribed for 11.5% of patients for a mean of 179 days. In the 30 months after the introduction of finasteride, 65 patients underwent TURP: 28 of these men had initially received drug therapy. In contrast, 138 TURPs were performed in the 30 months prior to the availability of finasteride. The use of a 5-alpha-reductase inhibitor as primary medical therapy for symptomatic BPH decreased the number of prostatectomies by 52.9% (65 vs 138). This observation warrants corroboration through additional prospective studies.

Cancer of the prostate--an overview.

The prostate, so named because of its anatomical position, is a small, chestnut-sized gland. Despite its small size, it is the source of one of the most prevalent internal malignancies in man. Recently the incidence of prostate cancer has surpassed even cancer of the lung. Nonetheless, little if anything is known about its pathogenesis or its natural history.

Advances in the management of impotence.

With an estimated ten to twenty million men in the United States suffering from impotence, major advances have been made relative to the understanding of the pathophysiology of this disease. These advances have been translated into improved treatment options. Several exciting novel pharmacotherapeutic agents are in the final phase of their clinical trials. These should provide more favorable prospects for men with sexual dysfunction.