A ninhydrin-based assay to quantitate the total protein content of tissue samples

NMR and bioinformatics discovery of exosites that tune metalloelastase specificity for solubilized elastin and collagen triple helices

The catalytic domain of metalloelastase (matrix metalloproteinase-12 or MMP-12) is unique among MMPs in exerting high proteolytic activity upon fibrils that resist hydrolysis, especially elastin from lungs afflicted with chronic obstructive pulmonary disease or arteries with aneurysms. How does the MMP-12 catalytic domain achieve this specificity? NMR interface mapping suggests that α-elastin species cover the primed subsites, a strip across the β-sheet from β-strand IV to the II-III loop, and a broad bowl from helix A to helix C. The many contacts may account for the comparatively high affinity, as well as embedding of MMP-12 in damaged elastin fibrils in vivo. We developed a strategy called BINDSIght, for bioinformatics and NMR discovery of specificity of interactions, to evaluate MMP-12 specificity without a structure of a complex. BINDSIght integration of the interface mapping with other ambiguous information from sequences guided choice mutations in binding regions nearer the active site. Single substitutions at each of ten locations impair specific activity toward solubilized elastin. Five of them impair release of peptides from intact elastin fibrils. Eight lesions also impair specific activity toward triple helices from collagen IV or V. Eight sites map to the "primed" side in the III-IV, V-B, and S1' specificity loops. Two map to the "unprimed" side in the IV-V and B-C loops. The ten key residues circumscribe the catalytic cleft, form an exosite, and are distinctive features available for targeting by new diagnostics or therapeutics.

Mechanisms of emphysema in autosomal dominant cutis laxa

Heterozygous elastin gene mutations cause autosomal dominant cutis laxa associated with emphysema and aortic aneurysms. To investigate the molecular mechanisms leading to cutis laxa in vivo, we generated transgenic mice by pronuclear injection of minigenes encoding normal human tropoelastin (WT) or tropoelastin with a cutis laxa mutation (CL). Three independent founder lines of CL mice showed emphysematous pulmonary airspace enlargement. No consistent dermatological or cardiovascular pathologies were observed. One CL and one WT line were selected for detailed studies. Both mutant and control transgenic animals showed elastin deposition into pulmonary elastic fibers, indicated by increased desmosine levels in the lung and by colocalization of transgenic and endogenous elastin by immunostaining. CL mice showed increased static lung compliance and decreased stiffness of lung tissue. In addition, markers of transforming growth factor-β (TGFβ) signaling and the unfolded protein response (UPR) were elevated together with increased apoptosis in the lungs of CL animals. We conclude that the synthesis of mutant elastin in CL activates multiple downstream disease pathways by triggering a UPR, altered mechanical signaling, increased release of TGFβ and apoptosis. We propose that the combined effects of these processes lead to the development of an emphysematous pulmonary phenotype in CL.

Purinergic effects of a hydroalcoholic Agaricus brasiliensis (A. blazei) extract on liver functions

The effects of a hydroalcoholic extract of Agaricus brasiliensis (A. blazei) on functional parameters in the perfused rat liver were examined with emphasis on its content of nucleotides and nucleosides. Several nucleosides and nucleotides were identified in the A. brasiliensis extract, which was active on several liver functions. A significant part of the effects is the result of the purinergic action of nucleosides and nucleotides: pressure increment, glycogenolysis stimulation, transient inhibition of oxygen consumption, and redox state changes. Other phenomena such as the stimulation of gluconeogenesis, ureogenesis, and oxygen consumption are more likely consequences of the metabolic transformation of substrates contained within the extract, especially amino acids. It seems apparent that consumption of A. brasiliensis represents not only the ingestion of metabolic precursors but also the ingestion of substances that, even at low concentrations, can exert important signaling functions in the liver as well as in the organism as a whole.

PPARgamma deficiency results in reduced lung elastic recoil and abnormalities in airspace distribution

Background

Peroxisome proliferator-activated receptor (PPAR)-γ is a nuclear hormone receptor that regulates gene expression, cell proliferation and differentiation. We previously described airway epithelial cell PPARγ deficient mice that develop airspace enlargement with decreased tissue resistance and increased lung volumes. We sought to understand the impact of airspace enlargement in conditionally targeted mice upon the physio-mechanical properties of the lung.

Methods

We measured elastic recoil and its determinants, including tissue structure and surface forces. We measured alveolar number using radial alveolar counts, and airspace sizes and their distribution using computer-assisted morphometry.

Results

Air vs. saline-filled pressure volume profiles demonstrated loss of lung elastic recoil in targeted mice that was contributed by both tissue components and surface tension, but was proportional to lung volume. There were no significant differences in surfactant quantity/function nor in elastin and collagen content between targeted animals and littermate controls. Importantly, radial alveolar counts were significantly reduced in the targeted animals and at 8 weeks of age there were 18% fewer alveoli with 32% more alveolar ducts. Additionally, the alveolar ducts were 19% larger in the targeted animals.

Conclusions

Our data suggest that the functional abnormalities, including loss of recoil are secondary to altered force transmission due to differences in the structure of alveolar ducts, rather than changes in surfactant function or elastin or collagen content. These data further define the nature of abnormal lung maturation in the absence of airway epithelial cell PPARγ and identify a putative genetic determinant of dysanapsis, which may serve as a precursor to chronic lung disease.

The effect of isolated lignins, obtained from a range of pretreated lignocellulosic substrates, on enzymatic hydrolysis

The influence of the residual lignin remaining in the cellulosic rich component of pretreated lignocellulosic substrates on subsequent enzymatic hydrolysis was assessed. Twelve lignin preparations were isolated by two isolation methods (protease treated lignin (PTL) and cellulolytic enzymatic lignin (CEL)) from three types of biomass (corn stover, poplar, and lodgepole pine) that had been pretreated by two processes (steam and organosolv pretreatments). Comparative analysis of the isolated lignin showed that the CEL contained lower amounts of carbohydrates and protein than did the PTL and that the isolated lignin from corn stover contained more carbohydrates than did the lignin derived from the poplar and lodgepole pine. The lower yields of acid insoluble lignin (AIL) obtained from the corn stover when using the PTL method indicated that the lignin from the corn stover had a higher hydrophilicity than did the lignin from the poplar and lodgepole pine. The isolated lignin preparations were added to the reaction mixture containing crystalline cellulose (Avicel) and their possible effects on enzymatic hydrolysis were assessed. It was apparent that the lignin isolated from lodgepole pine and steam pretreated poplar decreased the hydrolysis yields of Avicel, whereas the other isolated lignins did not appear to decrease the hydrolysis yields significantly. The hydrolysis yields of the pretreated lignocellulose and those of Avicel containing the PTL showed good correlation, indicating that the nature of the residual lignin obtained after pretreatment significantly influenced hydrolysis.

The applicability of urinary creatinine as a method of specimen normalization in the cystic fibrosis population

BACKGROUND

Urine specimens are commonly used in biomarker research. Urinary creatinine (UCr) is often used to adjust for urine analyte concentration. We aim to explore the applicability of UCr as a normalization method in a cystic fibrosis (CF) population during hospitalization.

METHODS

Multiple spot urine samples were collected from CF patients hospitalized for a pulmonary exacerbation. Single spot specimens were obtained from asthmatics and healthy children for comparison. The assumptions and implications from the use of UCr as a normalization factor for urinary desmosine measurements were investigated.

RESULTS

UCr differed significantly across disease groups and decreased significantly over time in the CF population. Differing results were obtained when contrasting normalization by UCr with specific gravity.

CONCLUSIONS

UCr levels are not completely attributable to simply variations in urine concentration. Analysis of urinary biomarker measurements should be initiated with an understanding of the relative effects of the normalization process on the results.

Cell-induced alignment augments twitch force in fibrin gel-based engineered myocardium via gap junction modification

A high-potential therapy for repairing the heart post-myocardial infarction is the implantation of tissue-engineered myocardium. While several groups have developed constructs that mimic the aligned structure of the native myocardium, to date no one has investigated the particular functional benefits conferred by alignment. In this study we created myocardial constructs in both aligned and isotropic configurations by entrapping neonatal rat cardiac cells in fibrin gel. Constructs were cultured statically for 2 weeks, and then characterized. Histological staining showed spread cells that express typical cardiac cell markers in both configurations. Isotropic constructs had higher final cell and collagen densities, but lower passive mechanical properties than aligned constructs. Twitch force associated with electrical pacing, however, was 181% higher in aligned constructs, and this improvement was greater than what would be expected from merely aligning the cells in the isotropic constructs in the force measurement direction. Our hypothesis was that this was due to improved gap junction formation/function facilitated by cell alignment, and further analyses of the twitch force data, as well as Western blot results of connexin 43 expression and phosphorylation state, support this hypothesis. Regardless of the specific mechanism, the results presented in this study underscore the importance of recapitulating the anisotropy of the native tissue in engineered myocardium.

Proteolysis during long-term glucose starvation in Staphylococcus aureus COL

A combination of pulse-chase experiments and 2-D PAGE revealed that protein degradation appears to play a crucial role for the cell physiology of Staphylococcus aureus COL during extended periods of glucose starvation. The synthesis rate of virtually all cytosolic and radioactively labeled proteins from growing cells seemed dramatically reduced in the first 3.5 h of glucose starvation. The stability of proteins synthesized in growing cells was monitored by a pulse-chase approach on a proteome wide scale. Especially, enzymes involved in nucleic acid and amino acid biosyntheses, energy metabolism and biosynthesis of cofactors were found rather rapidly degraded within the onset of the stationary phase, whereas the majority of glycolytic and tricarboxylic acid cycle enzymes remained more stable. Furthermore, single enzymes of biosynthetic pathways were differentially degraded. A metabolite analysis revealed that glucose completely depleted from the medium in the transient phase, and amino acids such as alanine and glycine were taken up by the cells in the stationary phase. We suggest that vegetative proteins no longer required in non-growing cells and thus no longer protected by integration into functional complexes were degraded. Proteolysis of putative non-substrate-bound or "unemployed" proteins appears to be a characteristic feature of S. aureus in order to access nutrients as an important survival strategy under starvation conditions.

Fibrillin-1 staining anomalies are associated with increased staining for TGF-beta and elastic fibre degradation; new clues to the pathogenesis of emphysema

We recently demonstrated aberrant staining of fibrillin-1 in lung tissue specimens with emphysematous lesions. In this study, we have extended this observation by an elaborate analysis of the elastic fibre. Using domain-specific antibodies to fibrillin-1, and to other elastin fibre-associated molecules, lung tissue derived from patients without obvious clinical emphysema, but harbouring various degrees of microscopical emphysematous lesions, was analysed. In addition, the fibrillin-regulated growth factor TGF-beta was studied. Electron microscopy and biochemical analysis of desmosine (a marker for elastin) were also performed. Results were compared with lung tissue derived from patients with clinical emphysema. Domain-specific antibodies recognizing the C-terminal, N-terminal, and middle part of fibrillin-1 showed aberrant staining patterns associated with increasing degrees of microscopical emphysema. Staining for elastin, emilin-1, and fibulin-2 was, however, not aberrant. TGF-beta staining was markedly increased. On the electron microscopic, but not light microscopical, level, initial elastic fibre degradation was noticed in specimens with microscopical emphysema. Lung specimens from patients with clinical emphysema also displayed fragmented fibrillin-1 staining and, in addition, displayed extensive degradation of the elastic fibre. The results suggest that fibrillin-1 anomalies and TGF-beta overexpression are associated with initial events occurring during the emphysematous process. Based on these and other data, a mechanism for emphysematogenesis is proposed.

ELASTIN DEFECTS IN THE LUNGS OF AVIAN AND MURINE MODELS OF HOMOCYSTEINEMIA

Homocysteinemia in animals is associated with disruption of the elastic fiber component of the extracellular matrix, resulting in vascular complications. The authors have utilized both avian and murine models to investigate the effects of homocysteinemia on lung development and repair following injury. Days old chicks were fed a diet containing 2% methionine for 3 weeks. Pregnant mice were given 2% methionine in the diet and feeding continued for up to 6 weeks after birth. The lungs were removed and examined for defects in elastin fiber formation. Methionine levels were elevated 20-fold in the serum from chicks receiving the methionine and 10-fold in pregnant mice. The elastic fibers in the parabronchi and air capillaries of chicks receiving methionine were thin and clearly disrupted. In the 2% methionine neonatal pups, normal lung development was prevented and the alveoli were significantly enlarged. However, after the pups reached 10 days of age the 2% methionine lungs did not differ histologically from the normal controls. Fetal mice reflected the same serum methionine levels as the dams fed the 2% methionine diet, yet after birth the serum levels of the neonates returned to control levels within 3 days. The authors found that the high serum methionine levels of the dams were not transferred to the milk, allowing the pups to reverse the histopathology observed early and then develop normally. The ability of the lung to replace elastin following elastase injury was not different in mice raised on the 2% methionine diet compared to controls. The studies show that continuous exposure of the developing lung to high circulating levels of methionine/homocysteine can result in major disruptions of elastic fibers and lung architecture. However, young mammals such as the mouse are protected from extended lung pathology because toxic levels of methionine are not transferred through the mothers milk.

Sputum desmosine during hospital admission for pulmonary exacerbation in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) lung disease is characterized by structural changes in the airways and parenchyma. No sputum biomarker exists to measure the degree of active structural destruction during pulmonary exacerbation in patients with CF. The noninvasive measurement of desmosine, a breakdown product of elastin, may reflect ongoing lung injury and serve as a biomarker of short-term damage. Our objectives were to measure desmosine in the sputum of patients with CF hospitalized for treatment of a pulmonary exacerbation and to explore the correlation between desmosine levels and other markers of clinical improvement, including lung function and inflammatory mediators, following hospitalization.

METHODS

Sputum and blood samples collected and lung function measurements were made at multiple time points during hospitalization. We used a repeated measures model, adjusted for age and time between measurements, to compare log-transformed sputum desmosine levels across multiple time points and to correlate those levels with related variables.

RESULTS

Desmosine levels were measured by radioimmunoassay in 71 expectorated sputum samples from 19 patients with CF hospitalized for 26 pulmonary exacerbations (range of results, 0 to 200 pmol/L desmosine/mL). Sputum desmosine levels decreased significantly during the first week of hospitalization (p = 0.04). Desmosine levels were positively associated with plasma C-reactive protein (rho = 0.59; p = 0.03), sputum interleukin-8 (rho = 0.86; p < 0.01), and sputum neutrophil elastase (rho = 0.78; p < 0.01).

CONCLUSIONS

Sputum desmosine, a novel measure of acute structural lung injury, may serve as a marker of structural lung damage occurring during exacerbations of lung disease in CF.

Purification and characterization of an efficient poultry feather degrading-protease from Myrothecium verrucaria

The purpose of this work was to characterize an alkaline protease from the filamentous fungus Myrothecium verrucaria and to explore its capability to degrade native poultry feathers. The enzyme was purified to homogeneity using a single chromatographic step. Recovery was high, 62%, with a specific activity of 12,851.8 U/mg protein. The enzyme is a small monomeric protein with a molecular mass of 22 +/- 1.5 kDa. It presented pH optimum of 8.3 and was stable over a broad pH range (5.0-12.0). The temperature optimum was 37 degrees C, with thermal stability at temperatures up to 45 degrees C. The enzyme presented an efficiency of 80.3% in the degradation of poultry feather meal, releasing amino acids and soluble peptides. It was able to hydrolyze beta-keratin without necessity of chemical or enzymatic reduction of the disulphide bonds. Considering that, everyday, poultry-processing plants produce feathers as a waste products, this protease can be useful in biotechnological processes aiming to improve the transformation of poultry feathers through solubilization of beta-keratin into usable peptides. Furthermore, it can also be useful in processes aiming to reduce the environmental pollution caused by the accumulation of feathers.

Starch granule biosynthesis in Arabidopsis is abolished by removal of all debranching enzymes but restored by the subsequent removal of an endoamylase

Several studies have suggested that debranching enzymes (DBEs) are involved in the biosynthesis of amylopectin, the major constituent of starch granules. Our systematic analysis of all DBE mutants of Arabidopsis thaliana demonstrates that when any DBE activity remains, starch granules are still synthesized, albeit with altered amylopectin structure. Quadruple mutants lacking all four DBE proteins (Isoamylase1 [ISA1], ISA2, and ISA3, and Limit-Dextrinase) are devoid of starch granules and instead accumulate highly branched glucans, distinct from amylopectin and from previously described phytoglycogen. A fraction of these glucans are present as discrete, insoluble, nanometer-scale particles, but the structure and properties of this material are radically altered compared with wild-type amylopectin. Superficially, these data support the hypothesis that debranching is required for amylopectin synthesis. However, our analyses show that soluble glucans in the quadruple DBE mutant are degraded by alpha- and beta-amylases during periods of net accumulation, giving rise to maltose and branched malto-oligosaccharides. The additional loss of the chloroplastic alpha-amylase AMY3 partially reverts the phenotype of the quadruple DBE mutant, restoring starch granule biosynthesis. We propose that DBEs function in normal amylopectin synthesis by promoting amylopectin crystallization but conclude that they are not mandatory for starch granule synthesis.

The role of caveolin-1 in pulmonary matrix remodeling and mechanical properties

Caveolin-1 (cav1) is a 22-kDa membrane protein essential to the formation of small invaginations in the plasma membrane, called caveolae. The cav1 gene is expressed primarily in adherent cells such as endothelial and smooth muscle cells and fibroblasts. Caveolae contain a variety of signaling receptors, and cav1 notably downregulates transforming growth factor (TGF)-beta signal transduction. In pulmonary pathologies such as interstitial fibrosis or emphysema, altered mechanical properties of the lungs are often associated with abnormal ECM deposition. In this study, we examined the physiological functions and the deposition of ECM in cav1(-/-) mice at various ages (1-12 mo). Cav1(-/-) mice lack caveolae and by 3 mo of age have significant reduced lung compliance and increased elastance and airway resistance. Pulmonary extravasation of fluid, as part of the cav1(-/-) mouse phenotype, probably contributed to the alteration of compliance, which was compounded by a progressive increase in deposition of collagen fibrils in airways and parenchyma. We also found that the increased elastance was caused by abundant elastic fiber deposition primarily around airways in cav1(-/-) mice at least 3 mo old. These observed changes in the ECM composition probably also contribute to the increased airway resistance. The higher deposition of collagen and elastic fibers was associated with increased tropoelastin and col1alpha2 and col3alpha1 gene expression in lung tissues, which correlated tightly with increased TGF-beta/Smad signal transduction. Our study illustrates that perturbation of cav1 function may contribute to several pulmonary pathologies as the result of the important role played by cav1, as part of the TGF-beta signaling pathway, in the regulation of the pulmonary ECM.

Neuraminidase-1 is required for the normal assembly of elastic fibers

The assembly of elastic fibers in tissues that undergo repeated cycles of extension and recoil, such as the lungs and blood vessels, is dependent on the proper interaction and alignment of tropoelastin with a microfibrillar scaffold. Here, we describe in vivo histopathological effects of neuraminidase-1 (Neu1) deficiency on elastin assembly in the lungs and aorta of mice. These mice exhibited a tight-skin phenotype very similar to the Tsk mouse. Normal septation of Neu1-null mice did not occur in neonatal mice, resulting in enlarged alveoli that were maintained in adults. The abnormal development of elastic fibers was remarkable under electron microscopy and confirmed by the overlapping distribution of elastin, fibrillin-1, fibrillin-2, and fibulin-5 (Fib-5) by the light microscopy immunostainings. Fib-5 fibers appeared diffuse and unorganized around the alveolar walls and the apex of developing secondary septal crests. Fibrillin-2 deposition was also abnormal in neonatal and adult lungs. Dispersion of myofibroblasts appeared abnormal in developing lungs of Neu1-null mice, with a random distribution of myofibroblast around the alveolar walls, rather than concentrating at sites of elastin synthesis. The elastic lamellae in the aorta of the Neu1-null mice were thinner and separated by hypertrophic smooth muscle cells that were surrounded by an excess of the sialic acid-containing moieties. The concentration of elastin, as measure by desmosine levels, was significantly reduced in the aorta of Neu1-null mice. Message levels for tropoelastin and Fib-5 were normal, suggesting the elastic fiber defects in Neu1-null mice result from impaired extracellular assembly.

Functional tissue-engineered valves from cell-remodeled fibrin with commissural alignment of cell-produced collagen

Heart valve replacements composed of living tissue that can adapt, repair, and grow with a patient would provide a more clinically beneficial option than current inert replacements. Bioartificial valves were produced by entrapping human dermal fibroblasts within a fibrin gel. Using a mold design that presents appropriate mechanical constraints to the cell-induced fibrin gel compaction, gross fiber alignment (commissure-to-commissure alignment in the leaflets and circumferential alignment in the root) and the basic geometry of a native aortic valve were obtained. After static incubation on the mold in complete medium supplemented with transforming growth factor beta 1, insulin, and ascorbate, collagen fibers produced by the entrapped cells were found to coalign with the fibrin based on histological analyses. The resultant tensile mechanical properties were anisotropic. Ultimate tensile strength and tensile modulus of the leaflets in the commissural direction were 0.53 and 2.34 MPa, respectively. The constructs were capable of withstanding backpressure commensurate with porcine aortic valves in regurgitation tests (330 mmHg) and opened and closed under physiological pressure swings of 10 and 20 mmHg, respectively. These data support proof of principle of using cell-remodeled fibrin gel to produce tissue-engineered valve replacements.

A Protein Dye-Binding Assay on Cellulose Membranes for Tear Protein Quantification

PURPOSE

To develop a method to quantify tear protein concentration with the sensitivity to measure this variable in the restricted volumes of single human tear samples.

METHODS

Aliquots of tear fluid from healthy subjects and a solution of standard bovine serum albumin (BSA) were spotted on cellulose membranes. Membranes were fixed, stained for protein with Coomassie blue, and washed until they displayed clear backgrounds. Stained spots were excised and eluted in a defined volume of methanol-ammonia, and the absorbance was determined spectrophotometrically at 610 nm. Membranes were calibrated by calculating their apparent thickness from the areas of stained spots and the corresponding aliquot volumes of either tear fluid or BSA solution.

RESULTS

In our dye-binding assay, absorbance (0-1.00 OD) was found to have a linear relation with tear fluid volume (1-7 microL). In a study involving samples from 33 healthy subjects, aliquots (3 microL) of tear fluid were found to yield absorbances in the linear range. Protein concentrations in tear fluid were found to be distributed over the range of 2.20-6.37 mg/mL (mean, 4.11 +/- 1.00 mg/mL) with no apparent sex differences. The assay can be applied successfully to quantify protein concentrations in tear fluid by using calibrated Schirmer strips after a tear test. Electrophoretic profiles of proteins present in tear fluid sampled from different healthy individuals were nearly identical when normalized for protein load by using this method.

CONCLUSIONS

The protein dye-binding assay we developed by using cellulose membranes or Schirmer strips is an efficient and convenient method for measuring tear protein concentration.

Dietary iron deficiency compromises normal development of elastic fibers in the aorta and lungs of chicks

Elastic fibers play a key role in the structure and function of numerous organs that require elasticity. Elastogenesis is a complex process in which cells first produce a microfibrillar scaffold, composed of numerous structural proteins, upon which tropoelastin assembles to be cross-linked into polymeric elastin. Recently, it was demonstrated that low concentrations of free iron upregulate elastin gene expression in cultured fibroblasts. The present studies were conducted to assess whether low-iron diets would affect the deposition of elastic fibers in an in vivo model. One-day-old chicks were fed semipurified diets containing 1.3 (low), 12 (moderate), and 24 (control) mg/kg of iron. After 3 wk, chicks in the low-iron group were underweight and anemic. Their aortas were smaller with significantly thinner walls than control chicks, yet elastin or collagen content did not decrease relative to total protein. They also demonstrated a significantly lower stress-strain resistance than the controls. Electron microscopy demonstrated that aortic and lung smooth muscle cells were vacuolated and surrounded by loose extracellular matrix and disorganized elastic lamellae with diffuse and fragmented networks of elastic fibers and microfibrils. Immunohistology demonstrated that fibrillin-3 (FBN3) was disorganized and markedly reduced in amount in aortas of the low-iron chicks. Elastin messenger RNA levels were not downregulated in the tissues from the low-iron-fed chicks; however, there was a significant reduction in expression of the FBN1 and FBN3 genes compared with control chicks. The studies indicate that iron deficiency had a pronounced negative effect on elastic fiber development and suggests that fibrillin may have an important role in this pathology.

Distinct steps of cross-linking, self-association, and maturation of tropoelastin are necessary for elastic fiber formation

Elastic fibers play an important role in the characteristic resilience of many tissues. The assembly of tropoelastin into a fibrillar matrix is a complex stepwise process and the deposition and cross-linking of tropoelastin are believed to be key steps of elastic fiber formation. However, the detailed mechanisms of elastic fiber assembly have not been defined yet. Here, we demonstrate the relationship between deposition and the cross-linking/maturation of tropoelastin. Our data show that a C-terminal half-fragment of tropoelastin encoded by exons 16-36 (BH) is deposited onto microfibrils, yet we detect very limited amounts of the cross-linking amino acid, desmosine, an indicator of maturation, whereas the N-terminal half-fragment encoded by exons 2-15 (FH) was deficient for both deposition and cross-linking, suggesting that elastic fiber formation requires full-length tropoelastin molecules. A series of experiments using mutant BH fragments, lacking either exon 16 or 30, or a deletion of both exons showed that self-association of tropoelastin polypeptides was an early step in elastic fiber assembly. Immunofluorescence and Western blot assay showed that the treatment of cell culture medium or conditioned medium with beta-aminopropionitrile to inhibit cross-linking, prevented both the deposition and polymerization of tropoelastin. In conclusion, our present results support the view that self-association and oxidation by lysyl oxidase precedes tropoelastin deposition onto microfibrils and the entire molecule of tropoelastin is required for this following maturation process.

Degradation of keratinous materials by the plant pathogenic fungus Myrothecium verrucaria

In this paper it is described for the first time the capability of Myrothecium verrucaria to grow in submerged and solid state cultures using poultry feathers as the only substrate. The fungus produced a protease with an unusual keratinolytic activity among plant pathogenic fungi. Its crude protease hydrolyzed keratinous substrates at pH 9.0 and 40 degrees C in the following order: poultry feather keratin > sheep wool keratin > human nail keratin > human hair keratin. Protease activity was highly sensitive to phenylmethyl sulphonyl fluoride (PMSF) indicating that the enzyme belonged to the serine protease family.

Crosslinking of discrete self-assembled collagen threads: Effects on mechanical strength and cell-matrix interactions

Bundles of threads extruded from type I collagen have been researched extensively as scaffolds to promote the repair and regeneration of torn tendons and ligaments. The success of these scaffolds has been limited by insufficient tissue ingrowth from the wound margin, which may be inhibited by the chemical or physical crosslinking treatment used to increase the mechanical properties and decrease the degradation rate of these scaffolds. Recently, self-assembled collagen threads extruded from solutions of type I collagen molecules were shown to possess ultimate tensile strengths and structural properties comparable to native tendon fibers; however the tissue response to these threads has yet to be determined. The goal of this study was to investigate the effects of various crosslinking techniques on the mechanical properties as well as the in vitro rate of new tissue ingrowth on these threads. Our findings indicate that the physical crosslinking techniques, dehydrothermal (DHT) or ultraviolet light (UV), most significantly improve the mechanical strengths of the threads, but most significantly decrease the rate of cell migration. In contrast, carbodiimide (EDC) crosslinking achieved sub-optimal strength generation, but demonstrated improved cell migration rates. Future studies will investigate the design of threads with surface biochemistries that maximize tissue ingrowth while maintaining the mechanical stability of the scaffold.

An efficient protein preparation for proteomic analysis of developing cotton fibers by 2-DE

Preparation of high-quality proteins from cotton fiber tissues is difficult due to high endogenous levels of polysaccharides, polyphenols, and other interfering compounds. To establish a routine procedure for the application of proteomic analysis to cotton fiber tissues, a new protocol for protein extraction was developed by optimizing a phenol extraction method combined with methanol/ammonium acetate precipitation. The protein extraction for 2-DE was remarkably improved by the combination of chemically and physically modified processes including polyvinylpolypyrrolidone (PVPP) addition, acetone cleaning, and SDS replacement. The protocol gave a higher protein yield and vastly greater resolution and spot intensity. The efficiency of this protocol and its feasibility in fiber proteomic study were demonstrated by comparison of the cotton fiber proteomes at two growth stages. Furthermore, ten protein spots changed significantly were identified by MS/tandem MS and their potential relationships to fiber development were discussed. To the best of our knowledge, this is the first time that a protocol for protein extraction from cotton fiber tissues appears to give satisfactory and reproductive 2-D protein profiles. The protocol is expected to accelerate the process of the proteomic study of cotton fibers and also to be applicable to other recalcitrant plant tissues.

Measurement of skin desmosine as an indicator of altered cutaneous elastin in draft horses with chronic progressive lymphedema

BACKGROUND

Chronic progressive lymphedema in Clydesdale and Shire draft horses causes severe disability of the limbs which leads to premature death of these horses. Since appropriate function of lymph vessels is dependent on the presence of viable elastin fibers, the goal of this study was to document differences in skin elastin fibers in affected horse breeds, compared to a nonaffected draft horse breed.

METHODS AND RESULTS

Biochemical analysis of cutaneous desmosine, a cross-linking amino acid found only in elastin, was used to measure elastin in the skin from 110 draft horses. This included 7 normal, 38 mildly affected, 30 moderately, and 15 severely affected horses, and 20 horses of a nonaffected draft breed. Desmosine concentrations in neck, considered a nonaffected skin region, and left forelimb, an affected skin region, were compared between the groups. A significantly lower desmosine concentration was found in the skin of the neck and limb of clinically normal animals of affected draft breeds compared to a nonaffected draft horse breed. During the progression of the disease in the affected breeds, cutaneous desmosine concentrations most prominently increased in the skin of the distal limbs.

CONCLUSIONS

Chronic progressive lymphedema in draft horses was associated with an initially systemic lower cutaneous elastin level and a deposition of elastin during the progression of the disease. A failure of elastic fibers to appropriately support the skin and its lymphatics is proposed as a possible contributing factor for chronic progressive lymphedema in Shires and Clydesdales.

Refolding hydrogels self-assembled from N-(2-hydroxypropyl)methacrylamide graft copolymers by antiparallel coiled-coil formation

A novel hybrid hydrogel system based on N-(2-hydroxypropyl)methacrylamide copolymers was proposed. It consisted of the hydrophilic polymer backbone and a pair of oppositely charged peptide grafts. Two distinct pentaheptad peptides (CCE and CCK) were anticipated to create a dimerization motif and serve as physical cross-linkers. Consequently, the graft copolymers CCE-P and CCK-P self-assembled into hybrid hydrogels in situ; the process was modulated by the formation of antiparallel heterodimeric coiled-coils. This approach possesses an advantage to decrease the steric hindrance of the polymer backbone on the "in-register" alignment of peptide grafts. Indeed, equimolar mixtures of the graft copolymers, CCE-P/CCK-P, have been observed to self-assemble into hydrogels in PBS solution at neutral pH at concentrations as low as 0.1 wt %. Circular dichroism spectroscopy, sedimentation equilibrium experiments, and microrheology revealed that the self-assembly process corresponded to the two-stranded alpha-helical coiled-coil formation between CCE and CCK. Moreover, the formation of hybrid hydrogels was reversible. Denaturation of the coiled-coil domains with guanidine hydrochloride (GdnHCl) solutions resulted in disassembly of the hydrogels. Removal of GdnHCl by dialysis caused coiled-coil refolding and hydrogel reassembly. Scanning electron microscopy results demonstrated that the concentration of the graft copolymers had a significant impact on the structure and morphology of self-assembled hydrogels.

Cell Sourcing and Culture Conditions for Fibrin-Based Valve Constructs

Cell sourcing for tissue-engineered heart valves remains a critical issue. In this work, human dermal fibroblasts (HDF) or porcine valve interstitial cells (PVIC) were entrapped in adherent fibrin disk constructs and harvested at 3 and 5 weeks. We compared the fibrin remodeling abilities of each cell type in Dulbecco's Modified Eagle's Medium (DMEM) and DMEM/F12 supplemented with transforming growth factor beta (TGF), and the response of PVIC to DMEM/F12 supplemented with fibroblast growth factor (FGF), a combination of FGF and TGF, and TGF with varying ascorbic acid (AA) concentrations. Culture media were supplemented with serum, insulin, AA, a fibrinolysis inhibitor, and antibiotics. DMEM maximized collagen and elastin deposition by HDF, while DMEM/F12 with FGF yielded the highest fibrin remodeling response by PVIC. HDF degraded fibrin slower than PVIC, and PVIC constructs had higher cellularity than HDF constructs in DMEM and DMEM/F12 at 3 weeks. FGF addition increased collagen content, collagen deposited per cell, and collagen as percentage of total protein compared to medium supplemented with TGF or TGF and FGF. AA addition increased collagen deposition by PVIC, but there was no dose dependence between 50 and 150 microg/mL AA. These results collectively show that PVIC are able to remodel fibrin faster and exhibit greater mechanical stiffening compared to HDF. Conditions for increased collagen deposition are also identified toward the engineering of valve constructs.

Postnatal alterations in elastic fiber organization precede resistance artery narrowing in SHR

Resistance artery narrowing and stiffening are key elements in the pathogenesis of essential hypertension, but their origin is not completely understood. In mesenteric resistance arteries (MRA) from spontaneously hypertensive rats (SHR), we have shown that inward remodeling is associated with abnormal elastic fiber organization, leading to smaller fenestrae in the internal elastic lamina. Our current aim is to determine whether this alteration is an early event that precedes vessel narrowing, or if elastic fiber reorganization in SHR arteries occurs because of the remodeling process itself. Using MRA from 10-day-old, 30-day-old, and 6-mo-old SHR and normotensive Wistar Kyoto rats, we investigated the time course of the development of structural and mechanical alterations (pressure myography), elastic fiber organization (confocal microscopy), and amount of elastin (radioimmunoassay for desmosine) and collagen (picrosirius red). SHR MRA had an impairment of fenestrae enlargement during the first month of life. In 30-day-old SHR, smaller fenestrae and more packed elastic fibers in the internal elastic lamina were paralleled by increased wall stiffness. Collagen and elastin levels were unaltered at this age. MRA from 6-mo-old SHR also had smaller fenestrae and a denser network of adventitial elastic fibers, accompanied by increased collagen content and vessel narrowing. At this age, elastase digestion was less effective in SHR MRA, suggesting a lower susceptibility of elastic fibers to enzymatic degradation. These data suggest that abnormal elastic fiber deposition in SHR increases resistance artery stiffness at an early age, which might participate in vessel narrowing later in life.

Impact of Cryopreservation on Extracellular Matrix Structures of Heart Valve Leaflets

BACKGROUND

Transplantation of cryopreserved allografts represents a well-established valve replacement option. Despite their clinical use for more than 40 years, the integrity of the extracellular matrix (ECM) of these valves after thawing has not been determined. The purpose of this study was to investigate and compare ECM structures of fresh and cryopreserved porcine heart valve leaflets with special emphasis on the condition of collagenous and elastic fibers.

METHODS

Pulmonary valves were excised from unprocessed porcine hearts under sterile conditions. After treatment with antibiotics, the valves were incubated in a cryoprotective solution, cryopreserved stepwise, and stored at -196 degrees C for 1 week. Two groups of heart valves (fresh untreated and thawed cryopreserved [each, n = 8]) were analyzed using biochemical (collagen, elastin, desmosine), histologic (hematoxylin-eosin, Movat-pentachrome, resorcin-fuchsin), and immunohistochemical (antibodies against collagen I, III, IV, and elastin) methods. Near-infrared femtosecond multiphoton laser scanning microscopy and second harmonic generation were used for high-resolution three-dimensional imaging of ECM structures.

RESULTS

Biochemical testing demonstrated similar amounts of collagen and desmosine, but a minor loss of elastin in the cryopreserved specimens. Conventional histology revealed almost comparable cell and ECM formations in fresh and cryopreserved valve leaflets. In contrast, laser-induced autofluorescence imaging showed substantial ultrastructural deterioration and disintegration of most collagenous structures. Second harmonic generation was not inducible.

CONCLUSIONS

Conventional cryopreservation of heart valves is accompanied by serious alterations and destruction of leaflet ECM structures, specifically demonstrated by multiphoton imaging. Further in-depth studies to clarify the impact of alternative cryopreservation techniques proposed for clinical use, such as vitrification, are crucial.

Dermal connective tissue development in mice: an essential role for tenascin-X

Deficiency of the extracellular matrix protein tenascin-X (TNX) causes a recessive form of Ehlers-Danlos syndrome (EDS) characterized by hyperextensible skin and hypermobile joints. It is not known whether the observed alterations of dermal collagen fibrils and elastic fibers in these patients are caused by disturbed assembly and deposition or by altered stability and turnover. We used biophysical measurements and immunofluorescence to study connective tissue properties in TNX knockout and wild-type mice. We found that TNX knockout mice, even at a young age, have greatly disturbed biomechanical properties of the skin. No joint abnormalities were noted at any age. The spatio-temporal expression of TNX during normal mouse skin development, during embryonic days 13-19 (E13-E19), was distinct from tropoelastin and the dermal fibrillar collagens type I, III, and V. Our data show that TNX is not involved in the earliest phase (E10-E14) of the deposition of collagen fibrils and elastic fibers during fetal development. From E15 to E19, TNX starts partially to colocalize with the dermal collagens and elastin, and in adult mice, TNX is present in the entire dermis. In adult TNX knockout mice, we observed an apparent increase of elastin. We conclude that TNX knockout mice only partially recapitulate the phenotype of TNX-deficient EDS patients, and that TNX could potentially be involved in maturation and/or maintenance of the dermal collagen and elastin network.

Increased Fibulin-5 and Elastin in S100A4/Mts1 Mice With Pulmonary Hypertension

Transgenic mice overexpressing the calcium binding protein, S100A4/Mts1, occasionally develop severe pulmonary vascular obstructive disease. To understand what underlies this propensity, we compared the pulmonary vascular hemodynamic and structural features of S100A4/Mts1 with control C57Bl/6 mice at baseline, following a 2-week exposure to chronic hypoxia, and after 1 and 3 months “recovery” in room air. S100A4/Mts1 mice had greater right ventricular systolic pressure and right ventricular hypertrophy at baseline, which increased further with chronic hypoxia and was sustained after 3 months “recovery” in room air. These findings correlated with a heightened response to acute hypoxia and failure to vasodilate with nitric oxide or oxygen. S100A4/Mts1 mice, when compared with C57Bl/6 mice, also had impaired cardiac function judged by reduced ventricular elastance and decreased cardiac output. Despite higher right ventricular systolic pressures with chronic hypoxia, S100A4/Mts1 mice did not develop more severe PVD, but in contrast to C57Bl/6 mice, these features did not regress on return to room air. Microarray analysis of lung tissue identified a number of genes differentially upregulated in S100A4/Mts1 versus control mice. One of these, fibulin-5, is a matrix component necessary for normal elastin fiber assembly. Fibulin-5 was localized to pulmonary arteries and associated with thickened elastic laminae. This feature could underlie attenuation of pulmonary vascular changes in response to elevated pressure, as well as impaired reversibility.

A model two-component system for studying the architecture of elastin assembly in vitro

Tropoelastin is encoded by a single human gene that spans 36 exons and is oxidized in vivo by mammalian lysyl oxidase at the epsilon amino group of available lysines to give the adipic semialdehyde, which then facilitates covalent cross-link formation in an enzyme-free process involving tropoelastin association. We demonstrate here that this process is effectively modeled by a two protein component system using purified lysyl oxidase from the yeast Pichia pastoris to facilitate the oxidation and subsequent cross-linking of recombinant human tropoelastin. The oxidized human tropoelastin forms an elastin-like polymer (EL) that is elastic, shows hydrogel behavior and contains typical elastin cross-links including lysinonorleucine, allysine aldol, and desmosine. Protease digestion and subsequent mass-spectrometry analysis of multiple ELs allowed for the identification of specific intra- and inter-molecular cross-links, leading to a model of the molecular architecture of elastin assembly in vitro. Specific intra-molecular cross-links were confined to the region of tropoelastin encoded by exons 6-15. Inter-molecular cross-links were prevalent between the regions encoded by exons 19-25. We find that assembly of tropoelastin molecules in ELs are highly enriched for a defined subset of cross-links.

Mutations in the GTP-binding and synergy loop domains of Mycobacterium tuberculosis ftsZ compromise its function in vitro and in vivo

The Mycobacterium tuberculosis FtsZ (FtsZ(TB)), unlike other eubacterial FtsZ proteins, shows slow GTP-dependent polymerization and weak GTP hydrolysis activities [E.L. White, L.J. Ross, R.C. Reynolds, L.E. Seitz, G.D. Moore, D.W. Borhani, Slow polymerization of Mycobacterium tuberculosis FtsZ, J. Bacteriol. 182 (2000) 4028-4034]. In an attempt to understand the biological significance of these findings, we created mutations in the GTP-binding (FtsZ(G103S)) and GTP hydrolysis (FtsZ(D210G)) domains of FtsZ and characterized the activities of the mutant proteins in vitro and in vivo. We show that FtsZ(G103S) is defective for binding to GTP and polymerization activities, and exhibited reduced GTPase activity whereas FtsZ(D210G) protein is proficient in binding to GTP, showing reduced polymerization activity but did not show any measurable GTPase activity. Visualization of FtsZ-GFP structures in ftsZ merodiploid strains by fluorescent microscopy revealed that FtsZ(D210G) is proficient in associating with Z-ring structures whereas FtsZ(G103S) is not. Finally, we show that Mycobacterium smegmatis ftsZ mutant strains producing corresponding mutant FtsZ proteins are non-viable indicating that mutant FtsZ proteins cannot function as the sole source for FtsZ, a result distinctly different from that reported for Escherichia coli. Together, our results indicate that optimal GTPase and polymerization activities of FtsZ are required to sustain cell division in mycobacteria and that the same conserved mutations in different bacterial species have distinct phenotypes.

Influence of elastin on rat small artery mechanical properties

We have previously developed a method for estimating elastin content and organization in resistance arteries, where it is a minor component. The aim of the present study was to validate the method against a quantitative assay and to determine the relative importance of elastin content and organization for intrinsic elasticity of small arteries. Mesenteric third order branches (from 10-day-old, 1- and 6-month-old rats) and middle cerebral arteries (from 6-month-old rats) were pressurized. beta-Values were calculated from stress-strain relationships and used as indicators of intrinsic stiffness. The same pressure-fixed arteries were used to estimate elastin content and organization in the internal elastic lamina with confocal microscopy. Collagen and elastin contents were determined by Picrosirius Red staining and radioimmunoassay for desmosine, respectively. Confocal and desmosine assays gave similar results: no difference in elastin content of mesenteric vessels from 1- and 6-month-old rats, and a significant reduction in cerebral compared to mesenteric arteries. For all parameters (elastin and collagen content, fenestrae area and internal elastic lamina thickness) the best correlation was found between beta-values and fenestrae size. These data suggest that in small arteries: (1) confocal microscopy can be used as a method for the simultaneous study of changes in elastin content and organization; and (2) elastin organization might be a key determinant of intrinsic elastic properties.

Poly(D,L-lactic acid)-block-(ligand-tethered poly(ethylene glycol)) copolymers as surface additives for promoting chondrocyte attachment and growth

The poly(D,L-lactic acid)-block-(ligand-tethered poly(ethylene glycol)) copolymer was explored to engineer poly(D,L-lactic acid) (PLA) material to promote chondrocyte attachment and growth. The poly(D,L-lactic acid)-block-poly(ethylene glycol) copolymer (PLE) was synthesized by a coupling reaction between PLA and poly(ethylene glycol) (PEG) (M(n) 1000, 2000, and 4000 respectively), with the use of 4,4'-methylenediphenyl diisocyanate (MDI). Then the PLE was activated by methyl sulfonyl chloride and the amino acids or arginine-glycine-aspartic acid tripeptide (RGD) was attached, which was verified by the ninhydrin-UV method. The modified PLA films were simply prepared by blending PLA with PLE derivatives. ATR-FTIR, XPS, contact angle, and AFM results clearly showed that the PEG chain stably enriched on the surface of PLE-modified PLA films. The chondrocyte cytocompatibility test showed the modified PLA films could significantly improve chondrocyte attachment and proliferation.

Development of UV-induced squamous cell carcinomas is suppressed in the absence of SPARC

SPARC (Secreted Protein Acidic and Rich in Cysteine) is a multifunctional glycoprotein belonging to a group of matrix-associated factors that mediate cell-extracellular matrix interactions but have no structural roles. In the present study we investigated the contribution of SPARC to factors that influence the development of skin tumors in response to UV irradiation. A hairless SPARC-null mouse was developed and compared to control SKH1 hairless mice in terms of skin tumor induction and extracellular matrix changes occurring in response to UV-irradiation. Following 23 weeks of exposure to UVB totaling 14.5 J per cm(2), tumor development in the wild-type mice was severe, with an average of over 20 tumors per mouse, many of which were squamous cell carcinomas. Conversely, the SPARC-null mice were strikingly tumor-resistant, developing no squamous cell carcinomas and averaging less than one small papilloma per mouse. SPARC was undetectable immunohistochemically in skin from the non-irradiated control group yet was present in relatively high quantities in the basal and superficial areas of the tumor mass. The SPARC-null mice also exhibited a limited contact hypersensitivity response and were refractory to UV induced immune suppression. In conclusion, SPARC appears to have a crucial role in mediating tumor formation in response to UV irradiation.

Detection and quantification of protein residues in food grade amino acids and nucleic acids using a dot-blot fluorescent staining method

Food allergies represent an important health problem in industrialized countries, such that detection and quantitative analysis of the protein considered to be the main allergen is crucial. A dot-blot fluorescent staining method for the detection and quantitative analysis of protein residues in food grade amino acids and nucleic acids is presented. This method combines fluorescence staining with dot-blotting onto PVDF membrane. Several standard proteins, such as bovine serum albumin (66 kDa), lysozyme (14 kDa), ubiquitin (8.6 kDa), bovine insulin (5.7 kDa), and oxidized insulin B chain (3.5 kDa), were detectable at 0.1 ppm using SYPRO Ruby blot stain. Twenty-five different amino acids and two different nucleic acids of food grade were analyzed using this method combined with an internal standard addition method using BSA as an internal standard. All amino acids and nucleic acids were dissolved in 3.6% aqueous HCl and dot-blotted onto PVDF membrane before a large amount of amino acids and nucleic acid were removed. Protein residues and the internal standard protein immobilized on the membrane were stained using SYPRO ruby blot stain. The internal standard in all samples was detectable at 0.1 ppm. Samples were dissolved at 120 or 70 mg/mL, according to their solubility under acidic conditions. The detection limit of protein residues per weight was 0.8-1.4 ppm in amino acids and nucleic acids; residual protein was not detected in any sample.

Surface tailoring of poly(dl-lactic acid) by ligand-tethered amphiphilic polymer for promoting chondrocyte attachment and growth

The ligand-tethered poly(ethylene oxide-propylene oxide-ethylene oxide) (PEO-PPO-PEO) triblock copolymer was explored to engineer poly(DL-lactic acid) (PDL-LA) material to promote cell attachment and growth. The PEO-PPO-PEO was activated by methyl sulfonyl chloride and the amino acid, and peptide were attached. By blending the PDL-LA with the ligand-tethered PEO-PPO-PEO derivatives, the surface of modified PDL-LA film was investigated by ATR-FTIR, XPS and contact angle. The chondrocytes test on different PDL-LA films indicated that the PEO-PPO-PEO amino acid and RGD derivatives modified PDL-LA films could promote chondrocyte attachment and growth. This simple surface treatment method may have potentials for tissue engineering and other biomedical applications.

Characterization of two classes of pancreatic shock factors: functional differences exhibited by hydrophilic and hydrophobic shock factors

Pancreatic tissue homogenate induces a powerful pathophysiologic response sufficient to produce lethal shock in a rat. However, limited progress has been made in the biochemical characterization of these pancreas-derived active factors or their mechanisms of action. It has been shown that the pancreas is a major source of these shock-inducing factors and that they are generated by pancreatic proteinases. Porcine pancreas was homogenized and the filtered homogenate was subjected to organic extraction both before and after incubation for 2.5 h at 37 degrees C. The aqueous and lipid extracts of pancreatic homogenates were collected and analyzed for their ability to activate human neutrophils and to induce lethal shock in the rat. Neutrophil activation, a presumed hallmark of shock, was determined by chemiluminescence and myeloperoxidase (MPO) release. Only the intact homogenate and lipid extracts stimulated the neutrophils, and the aqueous extracts proved to be inactive. Neutrophils exhibited enhanced cellular activation when exposed to substimulatory levels of either formyl-methionyl-leucyl-phenylalanine (FMLP) or platelet-activating factor (PAF) followed by substimulatory levels of the lipid extracts, but not by the aqueous extracts. Both the lipid and aqueous extracts induced dramatic decreases in heart rate and blood pressure when injected in the rat, often resulting in lethal shock. In all cases, incubation of the homogenates at 37 degrees C enhanced the potency of the extracts. Our results demonstrated that the pancreas-derived homogenate and lipid factors were capable of inducing both neutrophil activation and shock. These results support the hypothesis that shock is produced via neutrophils that have been activated by inflammatory components. However, the shock-inducing factors in the aqueous extracts (i.e., hydrophilic fraction of the homogenate) apparently function via a pathway independent of neutrophil activation. This is the first evidence that there are both hydrophobic and hydrophilic factors generated in tissue homogenates capable of inducing shock, and that these different chemical classes of factors appear to function via separate mechanisms.