An improved Bradford protein assay for collagen proteins

Effects of elevated temperature and copper exposure on the physiological state of the coral Galaxea fascicularis

The co-occurrence of elevated seawater temperature and local stressors (heavy metal contamination) affects the ecophysiology of phototrophic species, and represents a risk to the environmental quality of coral reefs. Therefore, we investigated the effects of both Cu alone and Cu in combination with elevated temperature (ET) on the physiology of the coral Galaxea fascicularis, and measured the parameters related to the photo-physiology and oxidative state. G.fascicularis is one of the dominant coral species in the South China Sea which exhibits strong adaptability to environmental stress. We exposed the common coral species G.fascicularis to a series of environmentally relevant concentrations of Cu at 29 °C (normal temperature, NT) and 32 °C (elevated temperature, ET) for 96 h. Single polyps were used in the experiments, which reduced individual variability when compared to the coral colonies. The results suggested that: i) Cu or ET had significant negative effects on the actual operating ability of photosystem Ⅱ (PSII), but not on the maximal chlorophyll fluorescence in darkness (Fv/Fm). ii) Symbiodiniaceae density was significantly reduced by high Cu concentrations, for Cu-NT and Cu-ET, a high concentration of Cu (40 μg/L) significantly impacted Symbiodiniaceae density, causing a 75.4% and 81.0% decrease, respectively. iii) the content of malondialdehyde (MDA) in coral tissues increased significantly under Cu-ET. iv) a certain range of copper concentration (25-30 μg/L) increased the pigment content of the Symbiodiniacea. Our results indicated that the combined stressors of Cu and ET made the coral tissue sloughed, caused the coral tissue damaged by lipid oxidation, reduced the photosynthetic capacity of the Symbiodiniacea, and led to the excretion of Symbiodiniacea.

Tissue-specific collagen hydroxylation at GEP/GDP triplets mediated by P4HA2

Collagen, the most abundant organic compound of vertebrate organisms, is a supramolecular, protein-made polymer. Details of its post-translational maturation largely determine the mechanical properties of connective tissues. Its assembly requires massive, heterogeneous prolyl-4-hydroxylation (P4H), catalyzed by Prolyl-4-hydroxylases (P4HA1-3), providing thermostability to its elemental, triple helical building block. So far, there was no evidence of tissue-specific regulation of P4H, nor of a differential substrate repertoire of P4HAs. Here, the post-translational modifications of collagen extracted from bone, skin, and tendon were compared, revealing lower hydroxylation of most GEP/GDP triplets, together with fewer other residue positions along collagen α chains, in the tendon. This regulation is mostly conserved in two distant homeotherm species, mouse and chicken. The comparison of detailed P4H patterns in both species suggests a two-step mechanism of specificity. P4ha2 expression is low in tendon and its genetic invalidation in the ATDC5 cellular model of collagen assembly specifically mimics the tendon-related P4H profile. Therefore, P4HA2 has a better ability than other P4HAs to hydroxylate the corresponding residue positions. Its local expression participates in determining the P4H profile, a novel aspect of the tissue specificities of collagen assembly. Data availability: Proteomics data are available via ProteomeXchange with the identifier PXD039221. Reviewer account details.

Protein Quantitation and Analysis of Purity

The accurate quantitation of proteins and an analysis of their purity is essential in numerous areas of scientific research and is a critical factor in many clinical applications. The large number and variety of techniques employed for this purpose is therefore not surprising. The selection of a suitable assay is dependent on such factors as the level of sensitivity required, the presence of interfering agents, and the composition of the protein itself. In this chapter, protocols for the most commonly used protein determination methodologies are outlined, including an overview of the highly sensitive real-time quantitative immuno-polymerase chain reaction assay. In addition, an approach to validate the UV protein absorption assay is outlined, which can be applied to any procedure for method validation.

Optimizing Chitosan/Collagen Type I/Nanohydroxyapatite Cross-linked Porous Scaffolds for Bone Tissue Engineering

Bio-composite scaffolds mimicking the natural microenvironment of bone tissue offer striking advantages in material-guided bone regeneration. The combination of biodegradable natural polymers and bioactive ceramics that leverage potent bio-mimicking cues has been an active strategy to achieve success in bone tissue engineering. Herein, a competitive approach was followed to point out an optimized bio-composite scaffold in terms of scaffold properties and stimulation of osteoblast differentiation. The scaffolds, composed of chitosan/collagen type I/nanohydroxyapatite (Chi/Coll/nHA) as the most attractive components in bone tissue engineering, were analyzed. The scaffolds were prepared by freeze-drying method and cross-linked using different types of cross-linkers. Based on the physicochemical and mechanical characterization, the scaffolds were eliminated comparatively. All types of scaffolds displayed highly porous structures. The cross-linker type and collagen content had prominent effects on mechanical strength. Glyoxal cross-linked structures displayed optimum mechanical and structural properties. The MC3T3-E1 proliferation, osteogenic-related gene expression, and matrix mineralization were better pronounced in collagen presence and triggered as collagen type I amount was increased. The results highlighted that glyoxal cross-linked scaffolds containing equal amounts of Chi and Coll by mass and 1% (w/v) nHA are the best candidates for osteoblast differentiation and matrix mineralization.

Remote and Selective Control of Astrocytes by Magnetomechanical Stimulation

Astrocytes play crucial and diverse roles in brain health and disease. The ability to selectively control astrocytes provides a valuable tool for understanding their function and has the therapeutic potential to correct dysfunction. Existing technologies such as optogenetics and chemogenetics require the introduction of foreign proteins, which adds a layer of complication and hinders their clinical translation. A novel technique, magnetomechanical stimulation (MMS), that enables remote and selective control of astrocytes without genetic modification is described here. MMS exploits the mechanosensitivity of astrocytes and triggers mechanogated Ca2+ and adenosine triphosphate (ATP) signaling by applying a magnetic field to antibody-functionalized magnetic particles that are targeted to astrocytes. Using purpose-built magnetic devices, the mechanosensory threshold of astrocytes is determined, a sub-micrometer particle for effective MMS is identified, the in vivo fate of the particles is established, and cardiovascular responses are induced in rats after particles are delivered to specific brainstem astrocytes. By eliminating the need for device implantation and genetic modification, MMS is a method for controlling astroglial activity with an improved prospect for clinical application than existing technologies.

Biochemical Characterization of Cassiopea andromeda (Forsskål, 1775), Another Red Sea Jellyfish in the Western Mediterranean Sea

Increasing frequency of native jellyfish proliferations and massive appearance of non-indigenous jellyfish species recently concur to impact Mediterranean coastal ecosystems and human activities at sea. Nonetheless, jellyfish biomass may represent an exploitable novel resource to coastal communities, with reference to its potential use in the pharmaceutical, nutritional, and nutraceutical Blue Growth sectors. The zooxanthellate jellyfish Cassiopea andromeda, Forsskål, 1775 (Cnidaria, Rhizostomeae) entered the Levant Sea through the Suez Canal and spread towards the Western Mediterranean to reach Malta, Tunisia, and recently also the Italian coasts. Here we report on the biochemical characterization and antioxidant activity of C. andromeda specimens with a discussion on their relative biological activities. The biochemical characterization of the aqueous (PBS) and hydroalcoholic (80% ethanol) soluble components of C. andromeda were performed for whole jellyfish, as well as separately for umbrella and oral arms. The insoluble components were hydrolyzed by sequential enzymatic digestion with pepsin and collagenase. The composition and antioxidant activity of the insoluble and enzymatically digestible fractions were not affected by the pre-extraction types, resulting into collagen- and non-collagen-derived peptides with antioxidant activity. Both soluble compounds and hydrolyzed fractions were characterized for the content of proteins, phenolic compounds, and lipids. The presence of compounds coming from the endosymbiont zooxanthellae was also detected. The notable yield and the considerable antioxidant activity detected make this species worthy of further study for its potential biotechnological sustainable exploitation.

Dietary linoleic acid, antioxidants, and flight training influence the activity of oxidative enzymes in European Starlings (Sturnus vulgaris)

Multiple studies have demonstrated that diet (e.g., fatty acid composition, antioxidants) and exercise training affect the metabolic performance of songbirds during aerobic activity, although the physiological mechanisms that cause such an effect remain unclear. We tested the hypothesis that elevated proportions of dietary linoleic acid (18:2n6) and amounts of dietary anthocyanins (a hydrophilic antioxidant class) influence the activity and protein expression of oxidative enzymes in flight and leg muscle of European Starlings (Sturnus vulgaris N = 96), a subset of which were flown over 15 days in a wind tunnel. Carnitine palmitoyl transferase (CPT) and citrate synthase (CS) activity displayed 18:2n6-dependent relationships with soluble protein concentration. Lactate dehydrogenase (LDH) was similarly related to protein concentration although also dependent on both dietary anthocyanins and flight training. 3-Hydroxyacyl CoA Dehydrogenase (HOAD) activity increased throughout the experiment in flight muscle, whereas this relationship was dependent on dietary anthocyanins in the leg muscle. Soluble protein concentration also increased throughout the experiment in the flight muscle, but was unrelated to date in the leg muscle, instead being influenced by both dietary anthocyanins and flight training. Training also produced additive increases in CPT and leg muscle HOAD activity. FAT/CD36 expression was related to both dietary 18:2n6 and training and changed over the course of the experiment. These results demonstrate a notable influence of our diet manipulations and flight training on the activity of these key oxidative enzymes, and particularly CPT and CS. Such influence suggests a plausible mechanism linking diet quality and metabolic performance in songbirds.

Integrated interrogation of causes of membrane fouling in a pilot-scale anoxic-oxic membrane bioreactor treating oil refinery wastewater

Studies on membrane fouling during treatment of oil refinery wastewater (ORW) via membrane bioreactor (MBR) are currently lacking, and associated fouling challenges are largely undocumented. Using advanced chemical and Illumina sequencing approach, we investigated the complex bio-physiochemical interactions responsible for foulant-membrane interactions during treatment of ORW. After nearly 2 months of the MBR operation, COD removal reached maximal of 97.15 ± 1.85%, while oil and grease removal was maintained at 96.6 ± 2.6%, during the treatment duration. Most of the less or non-biodegradable oil moieties (>0.5 μm) progressively accumulated on the membrane as the influent oil concentration increased. Presence of relatively higher unsaturated extracellular polymers (100.6 mg/g VSS) like fulvic acid and aromatic-like compounds at high volumetric loading (~18.7 kg COD/m³/d), enhanced the adsorption of chemical elements (Fe = 88.9, Al = 63.4, and Ce = 0.56 mg/g dry-sludge, respectively). Moreover, shift in microbial community structure to hydrocarbon-utilizing and metals-tolerating genera, as Comamonas and Rhodanobacter, respectively, uncovers major membrane colonizers in ORW treatment via MBR.

Prophylactic application of laser light restores L-FABP expression in the livers of rats submitted to partial ischemia

OBJECTIVES

The objective of the present study was to evaluate the protective effect of pre-conditioning treatment with laser light on hepatic injury in rats submitted to partial ischemia using mitochondrial function and liver fatty acid binding protein as markers.

METHODS

Rats were divided into four groups (n=5): 1) Control, 2) Control + Laser, 3) Partial Ischemia and 4) Partial Ischemia + Laser. Ischemia was induced by clamping the hepatic pedicle of the left and middle lobes of the liver for 60 minutes. Laser light at 660 nm was applied to the liver immediately prior to the induction of ischemia at 22.5 J/cm2, with 30 seconds of illumination at five individual points. The animals were sacrificed after 30 minutes of reperfusion. Blood and liver tissues were collected for analysis of mitochondrial function, determination of malondialdehyde and analysis of fatty acid binding protein expression by Western blot.

RESULTS

Mitochondrial function decreased in the Partial Ischemia group, especially during adenosine diphosphate-activated respiration (state 3), and the expression of fatty acid binding protein was also reduced. The application of laser light prevented bioenergetic changes and restored the expression of fatty acid binding protein.

CONCLUSION

Prophylactic application of laser light to the livers of rats submitted to partial ischemia was found to have a protective effect in the liver, with normalization of both mitochondrial function and fatty acid binding protein tissue expression.

Inorganic polyphosphate induces accelerated tube formation of HUVEC endothelial cells

In this study, the effect of inorganic polyphosphate (polyP) on the initial phase of angiogenesis and vascularization was investigated, applying the HUVEC cell tube formation assay. PolyP is a physiological and high energy phosphate polymer which has been proposed to act as a metabolic fuel in the extracellular space with only a comparably low ATP content. The experiments revealed that polyP accelerates tube formation of human umbilical vein endothelial cells (HUVEC), seeded onto a solidified basement membrane extract matrix which contains polyP-metabolizing alkaline phosphatase (ALP) activity. This effect is abolished by co-addition of apyrase, which degrades ATP to AMP and inorganic phosphate. The assumption that ATP, derived from polyP, activates HUVEC cells leading to tube formation was corroborated by experiments showing that addition of polyP to the cells causes a strong rise of ATP level in the culture medium. Finally, we show that at a later stage of cultivation of HUVEC cells, after 3 d, polyP causes a strong enhancement of the expression of the genes encoding for the two major matrix metalloproteinases (MMPs) released by endothelial cells during tube formation, MMP-9 and MMP-2. This stimulatory effect is again abrogated by addition of apyrase together with polyP. From these results, we propose that polyP is involved either directly or indirectly in energy supply, via ALP-mediated transfer of energy-rich phosphate under ATP formation. This ATP is utilized for the activation and oriented migration of endothelial cells and for the matrix organization during the initial phases of tube formation.

Morphogenetically-Active Barrier Membrane for Guided Bone Regeneration, Based on Amorphous Polyphosphate

We describe a novel regeneratively-active barrier membrane which consists of a durable electrospun poly(ε-caprolactone) (PCL) net covered with a morphogenetically-active biohybrid material composed of collagen and inorganic polyphosphate (polyP). The patch-like fibrous collagen structures are decorated with small amorphous polyP nanoparticles (50 nm) formed by precipitation of this energy-rich and enzyme-degradable (alkaline phosphatase) polymer in the presence of calcium ions. The fabricated PCL-polyP/collagen hybrid mats are characterized by advantageous biomechanical properties, such as enhanced flexibility and stretchability with almost unaltered tensile strength of the PCL net. The polyP/collagen material promotes the attachment and increases the viability/metabolic activity of human mesenchymal stem cells compared to cells grown on non-coated mats. The gene expression studies revealed that cells, growing onto polyP/collagen coated mats show a significantly (two-fold) higher upregulation of the steady-state-expression of the angiopoietin-2 gene used as an early marker for wound healing than cells cultivated onto non-coated mats. Based on our results we propose that amorphous polyP, stabilized onto a collagen matrix, might be a promising component of functionally-active barrier membranes for guided tissue regeneration in medicine and dentistry.

Fabrication of a new physiological macroporous hybrid biomaterial/bioscaffold material based on polyphosphate and collagen by freeze-extraction

A macroporous hybrid biomaterial/bioscaffold material, eliciting morphogenetic activity, was fabricated with polyphosphate, chondroitin sulfate and collagen by the freeze-extraction technology.

Protein Quantitation and Analysis of Purity

The accurate quantitation of proteins and an analysis of their purity are essential in numerous areas of scientific research, and is a critical factor in many clinical applications. The large number and variety of techniques employed for this purpose is therefore not surprising. The selection of a suitable assay is dependent on such factors as the level of sensitivity required, the presence of interfering agents, and the composition of the protein itself. Here, protocols for the most commonly used protein determination methodologies are outlined, as well as for the more recently adapted technique of quantitative immuno-Polymerase Chain Reaction.

An investigation of folic acid-protein association sites and the effect of this association on folic acid self-assembly

The contribution of folic acid (FA)-tryptophan interactions to FA-protein association was investigated in the context of using FA as a drug carrier in protein delivery systems. Bovine serum albumin (BSA) and indolicidin were used as model proteins in the study. The FA-BSA complex was characterized by using the Bradford reagent to identify the impact of FA-BSA association on BSA-dye reagent interactions. UV-visible spectroscopic analysis of the FA-BSA mixture showed that the absorbance maximum of BSA-dye reagent occurred at 595 nm, even after the association of FA with BSA. This confirms that protonated amino acid groups of the protein are not involved in FA-BSA association. Moreover, molecular dynamics (MD) simulation confirmed the presence of an associative interaction between aromatic moieties in FA and tryptophan moieties in the indolicidin molecule, which disrupted FA self-assembly. An X-ray diffraction (XRD) study showed that there was limited disruption of FA self-assembly after the addition of BSA or tryptophan. This suggests that FA and BSA are compatible and associate with each other. Graphical Abstract Mechanism of folic acid and protein association.

Resveratrol induces cell cycle arrest via a p53-independent pathway in A549 cells

Resveratrol, a non-flavone polyphenol compound, has a chemopreventive and chemotherapeutic effect against the progression of multiple types of cancer, including lung cancer. However, the molecular mechanism underlying the effects of resveratrol on cancer remain to be elucidated. In the present study, using an MTT assay, it was demonstrated that resveratrol inhibited cell proliferation in a concentration- and time-dependent manner. In addition, morphological features were observed in the A549, human lung cancer cell line, which included cell shrinkage, cells became distorted, certain cells became rounded and there was a concentration-dependent increase in the number of sloughed cells. Cell cycle analysis revealed that resveratrol may induce cell cycle arrest in the G₀/G₁ phase by downregulating the expression levels of cyclin D1, cyclin-dependent kinase (CDK)4 and CDK6, and upregulating the expression levels of the CDK inhibitors, p21 and p27. The immunofluorescence and western blot analysis results revealed that resveratrol upregulated the nuclear expression of p53 in A549 cells. Further studies have demonstrated that p53 downregulation did not contribute to the G₀/G₁ cell cycle arrest induced by resveratrol. In addition, resveratrol had no effect on the expression of p21, through use of the p53 inhibitor, pifithrin-α. The present study may offer a scientific basis for the further in-depth evaluation of resveratrol in the association of p53 and cell cycle arrest.

Elastin based cell-laden injectable hydrogels with tunable gelation, mechanical and biodegradation properties

Injectable hydrogels made from extracellular matrix proteins such as elastin show great promise for various biomedical applications. Use of cytotoxic reagents, fixed gelling behavior, and lack of mechanical strength in these hydrogels are the main associated drawbacks. The aim of this study was to develop highly cytocompatible and injectable elastin-based hydrogels with alterable gelation characteristics, favorable mechanical properties and structural stability for load bearing applications. A thermoresponsive copolymer, poly(N-isopropylacrylamide-co-polylactide-2-hydroxyethyl methacrylate-co-oligo(ethylene glycol)monomethyl ether methacrylate, was functionalized with succinimide ester groups by incorporating N-acryloxysuccinimide monomer. These ester groups were exploited to covalently bond this polymer, denoted as PNPHO, to different proteins with primary amine groups such as α-elastin in aqueous media. The incorporation of elastin through covalent bond formation with PNPHO promotes the structural stability, mechanical properties and live cell proliferation within the structure of hydrogels. Our results demonstrated that elastin-co-PNPHO solutions were injectable through fine gauge needles and converted to hydrogels in situ at 37 °C in the absence of any crosslinking reagent. By altering PNPHO content, the gelling time of these hydrogels can be finely tuned within the range of 2-15 min to ensure compatibility with surgical requirements. In addition, these hydrogels exhibited compression moduli in the range of 40-145 kPa, which are substantially higher than those of previously developed elastin-based hydrogels. These hydrogels were highly stable in the physiological environment with the evidence of 10 wt% mass loss in 30 days of incubation in a simulated environment. This class of hydrogels is in vivo bioabsorbable due to the gradual increase of the lower critical solution temperature of the copolymer to above 37 °C due to the cleavage of polylactide from the PNPHO copolymer. Moreover, our results demonstrated that more than 80% of cells encapsulated in these hydrogels remained viable, and the number of encapsulated cells increased for at least 5 days. These unique properties mark elastin-co-PNHPO hydrogels as favorable candidates for a broad range of tissue engineering applications.

Controlled formation of cross-linked collagen fibers for neural tissue engineering applications

Fibrous scaffolds engineered to direct the growth of tissues can be important in forming architecturally functional tissue such as aligning regenerating nerves with their target. Collagen is a commonly used substrate used for neuronal growth applications in the form of surface coatings and hydrogels. The wet spinning technique can create collagen fibers without the use of organic solvents and is typically accomplished by extruding a collagen dispersion into a coagulation bath. To create well-controlled and uniform collagen fibers, we developed an automatic wet spinning device with precise control over the spinning and fiber collection parameters. A fiber collection belt allowed the continuous formation of very soft and delicate fibers up to half a meter in length. Wet-spun collagen fibers were characterized by tensile and thermal behavior, diameter uniformity, the swelling response in phosphate buffered saline and their biocompatibility with dorsal root ganglion (DRG) neurons and Schwann cells. Fibers formed from 0.75% weight by volume (w/v) collagen dispersions formed the best fibers in terms of tensile behavior and fiber uniformity. Fibers post-treated with the cross-linkers glutaraldehyde and genipin exhibited increased mechanical stability and reduced swelling. Importantly, genipin-treated fibers were conducive to DRG neurons and Schwann cell survival and growth, which validated the use of this cross-linker for neural tissue engineering applications.

Biomimetically mineralized salmon collagen scaffolds for application in bone tissue engineering

Biomimetic mineralization of collagen is an advantageous method to obtain resorbable collagen/hydroxy-apatite composites for application in bone regeneration. In this report, established procedures for mineralization of bovine collagen were adapted to a new promising source of collagen from salmon skin challenged by the low denaturation temperature. Therefore, in the first instance, variation of temperature, collagen concentration, and ionic strength was performed to reveal optimized parameters for fibrillation and simultaneous mineralization of salmon collagen. Porous scaffolds from mineralized salmon collagen were prepared by controlled freeze-drying and chemical cross-linking. FT-IR analysis demonstrated the mineral phase formed during the preparation process to be hydroxyapatite. The scaffolds exhibited interconnecting porosity, were sufficiently stable under cyclic compression, and showed elastic mechanical properties. Human mesenchymal stem cells were able to adhere to the scaffolds, cell number increased during cultivation, and osteogenic differentiation was demonstrated in terms of alkaline phosphatase activity.

Tissue-specific extracellular matrix coatings for the promotion of cell proliferation and maintenance of cell phenotype

Recent studies have shown that extracellular matrix (ECM) substitutes can have a dramatic impact on cell growth, differentiation and function. However, these ECMs are often applied generically and have yet to be developed for specific cell types. In this study, we developed tissue-specific ECM-based coating substrates for skin, skeletal muscle and liver cell cultures. Cellular components were removed from adult skin, skeletal muscle, and liver tissues, and the resulting acellular matrices were homogenized and dissolved. The ECM solutions were used to coat culture dishes. Tissue matched and non-tissue matched cell types were grown on these coatings to assess adhesion, proliferation, maintenance of phenotype and cell function at several time points. Each cell type showed better proliferation and differentiation in cultures containing ECM from their tissue of origin. Although subtle compositional differences in the three ECM types were not investigated in this study, these results suggest that tissue-specific ECMs provide a culture microenvironment that is similar to the in vivo environment when used as coating substrates, and this new culture technique has the potential for use in drug development and the development of cell-based therapies.

Quantitation of protein

The measurement of protein concentration in an aqueous sample is an important assay in biochemistry research and development labs for applications ranging from enzymatic studies to providing data for biopharmaceutical lot release. Spectrophotometric protein quantitation assays are methods that use UV and visible spectroscopy to rapidly determine the concentration of protein, relative to a standard, or using an assigned extinction coefficient. Methods are described to provide information on how to analyze protein concentration using UV protein spectroscopy measurements, traditional dye-based absorbance measurements; BCA, Lowry, and Bradford assays and the fluorescent dye-based assays; amine derivatization and detergent partition assays. The observation that no single assay dominates the market is due to specific limitations of certain methods that investigators need to consider before selecting the most appropriate assay for their sample. Many of the dye-based assays have unique chemical mechanisms that are prone to interference from chemicals prevalent in many biological buffer preparations. A discussion of which assays are prone to interference and the selection of alternative methods is included.

Cytotoxicity of 5-fluorouracil entrapped in gelatin microspheres

Gelatin microspheres were prepared by water/oil emulsion polymerization and by cross-linking with glutaraldehyde. For the microsphere preparation procedure, two different gelatin (5 or 10% w/v) and three different glutaraldehyde (5, 0.5 or 0.1% v/v) concentrations were used. The influence of preparation compositions on microsphere recovery, particle size and morphology, swelling and degradation, 5-fluorouracil loading and release, and cytotoxicity were investigated. The concentrations of gelatin and glutaraldehyde influenced the size and surface properties of microspheres. The decrease in gelatin concentration and the increase in glutaraldehyde concentration resulted in the formation of smaller (140.82-71.47 microm for gelatin microspheres with a 5% gelatin content; 297.67-97.44 microm for gelatin microspheres with a 10% gelatin content) microspheres with smoother surface properties. Swelling values were decreased as the amount of glutaraldehyde was increased. In particular, for microspheres with a high glutaraldehyde content (5% v/v), only about 15% were degraded in 12 days, whereas for those with 0.5% (v/v) glutaraldehyde, almost 97% degradation occurred in the same period. The most rapid 5-fluorouracil release was observed from uncross-linked microspheres (about 88% in 4 h), whereas a particular slower release (about 36% in 4 h) profile was obtained for the highly cross-linked ones. Cytotoxicity tests of free and entrapped 5-fluorouracil were carried out with MCF-7 breast cancer cell line. Free 5-fluorouracil produced an immediate effect, whereas entrapped 5-fluorouracil showed a prolonged cytotoxic effect.

Potential protein toxicity of synthetic pigments: binding of poncean S to human serum albumin

Using various methods, e.g., spectrophotometry, circular dichroism, and isothermal titration calorimetry, the interaction of poncean S (PS) with human serum albumin (HSA) was characterized at pH 1.81, 3.56, and 7.40 using the spectral correction technique, and Langmuir and Temkin isothermal models. The consistency among results concerning, e.g., binding number, binding energy, and type of binding, showed that ion pair electrostatic attraction fixed the position of PS in HSA and subsequently induced a combination of multiple noncovalent bonds such as H-bonds, hydrophobic interactions, and van der Waals forces. Ion pair attraction and H-bonds produced a stable PS-HSA complex and led to a marked change in the secondary structure of HSA in acidic media. The PS-HSA binding pattern and the process of change in HSA conformation were also investigated. The potentially toxic effect of PS on the transport function of HSA in a normal physiological environment was analyzed. This work provides a useful experimental strategy for studying the interaction of organic substances with biomacromolecules, helping us to understand the activity or mechanism of toxicity of an organic compound.

Interaction of brilliant red X-3B with bovine serum albumin and application to protein assay

The interaction of brilliant red X-3B (BRX) with bovine serum albumin (BSA) in three pH media has been characterized by the spectral correction technique. The binding number maximum of BRX was determined to be 102 at pH 2.03, 82 at pH 3.25 and 38 at pH 4.35 and the binding mechanism was analyzed in detail. The effects of ionic strength from 0 to 1 mol L(-1) and temperature from 20 to 70 degrees C on the binding were investigated. The results showed that the interaction of BRX with BSA responded to the Langmuir adsorption isothermal model and the binding constant was determined. From the correlation between the binding number and the number of basic amino acid residues, the ion-pair attraction induced the union of non-covalent bonds including H-bond, van der Waals force and hydrophobic bond and the binding model was illustrated. The binding of BRX to BSA has resulted in change of the BSA conformation confirmed by means of circular dichroism. Using this interaction at pH 2.03, a sensitive method named the absorbance ratio difference spectrometry was established and applied to the protein assay and the limit of detection of protein was only 6 microg L(-1). Two samples were determined and the results were in agreement with those obtained by the classical coomassie brilliant blue colorimetry.

Association of serum protein levels with egg productivity in Taiwan red-feathered country chickens

This study investigated the relationship between serum protein levels and egg productivity in Taiwan red-feathered country chickens (TRFCC). The total egg numbers of TRFCC (n=157) were recorded from 25 to 48 weeks of age. Serum samples were collected at 24 and 35 weeks of age, then classified by total egg number into four groups according to mean+/-1S.D. Serum X protein levels were evaluated by protein chip technology and with an insulin-like growth factor-I (IGF-I) immunoassay. Other serum proteins (apolipoprotein A-I, ovotransferrin and vitellogenin) were found at different levels between the most productive and the least productive groups of TRFCC, were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and were quantified by age. The results showed that levels of vitellogenin were positively correlated with total egg number at 24 and at 35 weeks old (p<0.01). Levels of apolipoprotein A-I and an IGF-1-related marker (termed X protein) in serum at 35 weeks old were correlated with total egg number (p<0.01). Serum ovotransferrin levels remained constant regardless of total egg number. To investigate the concentration differences among the four groups of TRFCC, serum protein levels of each group were analyzed by one-way ANOVA. The results showed that those protein levels, except for ovotransferrin, in the least productive group significantly differed from the other three groups (p<0.05). Although the correlation between those protein levels and the total egg number was not significant at the time of initial egg production, the selection strategy of those protein levels at later stages of egg production should provide a screening model to improve selection.

Preparation and characterization of a biodegradable drug targeting system for anticancer drug delivery: microsphere-antibody conjugate

Targeted delivery of anticancer drugs is one of the most actively pursued goals in anticancer chemotherapy. A major disadvantage of anticancer drugs is their lack of selectivity for tumour tissue, which causes severe side effects and results in low cure rates. Any strategy by which a cytotoxic drug is targeted to the tumour, thus increasing the therapeutic index of the drug, is a way of improving cancer chemotherapy and minimizing systematic toxicity. This study covers the preparation of the gelatin microsphere (GM)-anti-bovine serum albumin (anti-BSA) conjugate for the development of a drug targeting approach for anticancer drug delivery. Microspheres of 5% (w/v) gelatin content were prepared by crosslinking with glutaraldehyde (GTA) at 0.05 and 0.50% (v/v) concentration. Microspheres were in the size range of 71-141?microm. The suitability of these microspheres as drug carriers for anticancer drug delivery was investigated in vitro by studying the release profiles of loaded methotrexate (MTX) and 5-fluorouracil (5-FU) and the cytotoxicities on cancer cell lines. The in vitro MTX release profiles (approximately 22-46% released in 24 h depending on the amount of GTA used) were much slower compared to 5-FU (approximately 42-91% released in 24 h). Both drugs demonstrated an initial fast release, which was followed by gradual, sustained drug release. The MTT cytotoxicity test results of GMs loaded with 5-FU and MTX showed approximately 54-70% and approximately 52-67% cytotoxicities in 4 days. In general, incorporation of MTX and 5-FU in microspheres enhanced the cytotoxic effect in a more prolonged manner compared to the free drugs. Gelatin micospheres were chemically conjugated to anti-BSA and the antigen-antibody activities were studied by immunofluorescence. Results indicated approximately 80% binding with conjugated anti-BSA and BSA-FITC. Based on their low cytotoxicity and the high antigen binding efficiencies, anti-BSA conjugated gelatin microspheres could be suitable targeted drug carrier systems for selective and long-term delivery of anticancer drugs to a specific body compartment (i.e. bladder cancer).

Levels of pentosidine in the vitreous of eyes with proliferative diabetic retinopathy, proliferative vitreoretinopathy and retinal detachment

BACKGROUND

Advanced glycosylation end products (AGEs) are thought to play an important role in the pathophysiology of diabetes. Particularly, these products have been implicated in the pathogenesis of proliferative diabetic retinopathy. The majority of these products are formed from a vast range of precursor molecules, the variable chemical nature of which contributes to AGE heterogeneity. There is a growing population of structurally defined AGE adducts such as pyrraline, pentosidine, CML and crossline that have been found to be elevated in diabetic tissues. In the present study, the levels of the glycoxidation product pentosidine were determined in vitreous samples obtained during vitrectomy from eyes with proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and retinal detachment (RD). Samples from cadaveric control eyes were also included in the study. The levels of pentosidine were compared among the groups.

METHODS

Seventy-three vitreous samples were collected from eyes undergoing vitrectomy for PDR (n=33), PVR (n=28) and RD (n=12). Eighteen samples from cadaveric control eyes were also included in the study. A modified Bradford's method was used to assay protein content, and vitreous levels of pentosidine were determined by high-performance liquid chromatography after acid hydrolysis and pretreatment with SP-Sephadex. Statistical analyses were performed using a two-sided Mann-Whitney U test.

RESULTS

The levels of pentosidine [median (interquartile range)] were 0.92 (0.55-1.26) pmol/mg of protein in the PDR cases, 1.12 (0.46-1.80) pmol/mg of protein in PVR, and 1.02 (0.24-1.44) pmol/mg of protein in RD. In the cadaveric control eyes pentosidine levels were 0.97 (0.68-1.30) pmol/mg of protein. The pentosidine levels of the four groups did not differ significantly.

CONCLUSIONS

The levels of the glycoxidation product pentosidine (expressed as pmol/mg of protein) in the vitreous of eyes with PDR do not differ significantly from those in the vitreous of eyes with PVR, RD or cadaveric control eyes. Although these results do not refute the findings of previous studies that evaluated globally total AGE levels and the existence of diabetic vitreopathy, further investigation is needed to fully understand their relevance in this multifactorial disorder.

Ecteinascidin-743 drug resistance in sarcoma cells: transcriptional and cellular alterations

A human chondrosarcoma cell line, CS-1, was treated successively with increasing concentrations of the marine chemotherapeutic Ecteinascidin-743 (ET-743), yielding a variant cell line displaying a significant degree of resistance to the cytotoxic action of this drug. Various experiments were performed to discern molecular aberrations between the parent and resistant cell line, and also identify potential molecular markers indicative of drug resistance. Although no significant differences in the levels of membrane transporters such as P-glycoprotein or multidrug resistance protein 1 (MRP1) were detected, the cell migratory ability of the ET-743-resistant cell variant was reduced, as was its attachment capability to gelatin-coated cell culture dishes. Staining of the actin-containing cytoskeleton with fluorescent-labeled phalloidin revealed marked differences in the cytoskeleton architecture between the parent and ET-743-resistant CS-1 cell lines. Comparison of serum-free conditioned medium from both cell lines showed conspicuous differences in the levels of several proteins, including a quartet of high molecular weight proteins (> or =140 kDa). The protein sequences of two of these high molecular weight proteins, present at significantly higher concentrations in conditioned medium obtained from the parent cell line, corresponded to subunits of types I and IV collagen. Analysis of type I collagen alpha1 chain mRNA revealed a significantly lower level in the ET-743-resistant CS-1 cell line. Thus, prolonged exposure to ET-743 may cause changes in cell function through cytoskeleton rearrangement and/or modulation of collagen levels.

A simple and rapid assay of collagen-like polymer in crude lysate from Escherichia coli

An assay for the quantification of collagen-like polymer (CLP) in Escherichia coli cells utilizing the specific reaction between collagenase and CLP is presented. It involves thermal treatment to precipitate non-CLP proteins, digestion of CLP by collagenase and detection of the absorbance of the liberated amino acids and peptides from CLP by a ninhydrin-based method. CLP concentration is determined from the absorbance measurement.

Development and characterisation of a monoclonal antibody family against aquaporin 1 (AQP1) and aquaporin 4 (AQP4)

Recent studies have discovered the existence of water-channel molecules, the so called aquaporins (AQP) presumably involved in active, ATP dependent water transport between the intracellular and extracellular compartments. Both genetic and protein sequences and structures of the AQPs are known and crystallographic analyses of some members of the AQP family have been performed. Specific antibodies are required to examine their histological locations and analyse their roles in physiological and pathological pathways of water transportation and osmotic regulation. Until recently some polyclonal antibodies have been developed against certain members of the AQP family. However, to date highly specific monoclonal antibodies against aquaporins do not exist. We have developed a monoclonal antibody family against the aquaporin 1 (AQP1) and aquaporin 4 (AQP4) molecules. Well-conserved epitop sequences of AQP1 and AQP4 proteins were selected by computer analysis and their synthetic peptide fragments were used as the antigens of immunisation and the following screening. Antibodies were characterised by immunoserological methods (ELISA, dot-blot and immunoblot), flow cytometry and immunohistochemistry of formaldehyde-fixed and paraffin-embedded tissue samples. RT-PCR tests controlled the specificity of the immune reactions. Our monoclonal antibodies recognised AQP1 and AQP4 in all the techniques mentioned above and apparently they are useful both in various quantitative and qualitative measurements of the expressions of AQP1 and AQP4 in several species (human, rat, mouse, invertebrates, even plants). According to preliminary immunohistochemical studies our monoclonal anti-AQP1 and anti-AQP4 antibodies are appropriate tools of patho-morphological examinations on routine formol-paraffin tissue samples.

Modification of Lowry's method for collagen concentration measurement

A procedure for the determination of collagen concentration is described. It is simple and sensitive and is based on a modification of Lowry's method. The modification includes an initial heating of collagen samples in alkaline solution and changes in the concentrations of reagents used. It may be used for different collagen types, i.e. I, II, V and XI, from various sources as well as for gelatine. The influence of different buffers, salts, detergents, etc. on the precision of the method was studied. The precision of the measurements was not influenced by pH, the turbidity of the sample and the presence of certain salts, osmolytes and preservatives, routinely used in biochemical, microbiological and immunological experimental protocols. The modification is suitable for routine determinations of collagen concentration in a wide variety of samples.

Collagenolytic activity in human pancreatic tissue with different degrees of fibrosis

The present study was designed to establish a valid method for expressing collagenolytic activity in pancreatic tissue with different degrees of fibrosis. Collagenolytic activity was measured in pancreatic tissue of control and alcoholic chronic pancreatitis (CP) patients and data were expressed as percent digestion/mg tissue or as percent digestion/mg protein obtaining different results. The values were 18.4 +/- 4.7% digestion/mg tissue in the control group, and 8.4 +/- 3.2% digestion/mg tissue in the chronic pancreatitis group (p < 0.001). When collagenolytic activity was expressed as percent digestion/mg protein, measured by the Bradford assay, the values of the control group were 190.2 +/- 69.0% digestion/mg protein, and those of chronic pancreatitis patients were 187.2 +/- 61.7% digestion/mg protein (p = ns). Protein determination in pancreatic tissue of control and CP patients was seen to be influenced by the method assayed. Protein content per mg of fresh tissue, measured by the methods of Lowry, Bradford, and Bradford-SDS, were similar and twofold higher in controls than in CP samples. However, the Kjeldahl assay showed that protein content per mg of dry tissue was the same in both groups. The high degree of fibrosis in the pancreas of CP patients (60.2 +/- 28.0%) with regard to controls (4.7 +/- 1.8%) (p < 0.001) and the low response of collagen proteins to the Lowry and Bradford assays could explain the differences observed in protein content of human samples.(ABSTRACT TRUNCATED AT 250 WORDS)