Crude Supernatant Research Articles

Setting-up a fast and reliable cytokinin biosensor based on a plant histidine kinase receptor expressed in Saccharomyces cerevisiae

Cytokinins (CK) have been extensively studied for their roles in plant development. Recently, they also appeared to ensure crucial functions in the pathogenicity of some bacterial and fungal plant pathogens. Thus, identifying cytokinin-producing pathogens is a prerequisite to gain a better understanding of their role in pathogenicity. Taking advantage of the cytokinin perception properties of Malus domestica CHASE Histidine Kinase receptor 2 (MdCHK2), we thereby developed a selective and highly sensitive yeast biosensor for the application of cytokinin detection in bacterial samples. The biosensor is based on the mutated sln1Δ Saccharomyces cerevisiae strain expressing MdCHK2. The biosensor does not require any extraction or purification steps of biological samples, enabling cytokinin analysis directly from crude bacterial supernatants. For the first time, the production of cytokinin was shown in the well-known plant pathogenic bacteria Erwinia amylovora and was also revealed in human pathogens Staphylococcus aureus and Streptococcus agalactiae. Importantly, this biosensor was shown to be an efficient tool for unraveling certain steps in cytokinin biosynthesis by micro-organisms since this it was successfully used to unveil the role of ygdH22, a LOG-like gene, that is probably involved in cytokinin biosynthesis pathway in Escherichia coli. Overall, we demonstrated that our biosensor displays several advantages including time- and cost-effectiveness by allowing a rapid and specific detection of cytokinins in bacterial supernatants These results also support its scalability to high-throughput formats.

3D polyelectrolyte scaffolds to mimic exocrine glands: a step towards a prostate-on-chip platform

Abstract We report our approach to creating a microfluidic chip (namely UroLOC) that mimics the acinar/tubular structure and the luminal microenvironment of exocrine glands. The chip utilises a nanostructured membrane that is designed to provide a 3-dimensional supporting scaffold for the growth of exocrine acinus epithelial cells. The nanostructured membrane was produced using layer-by-layer assembly of polyelectrolytes, and formed into 3-dimensional hemispherical cavities and “finger-like” structures in order to mimic the natural architecture of acini found in exocrine glands. We utilised normal (PNT2) and cancerous (PC3, LNCaP) prostate epithelial cells to demonstrate the proof-of-concept of using MALDI (Matrix Assisted Laser Desorption Ionisation) profiling of secretions collected after 48 hours of cell growth, with no concentration or purification steps and without any a priori on the knowledge of targeted proteins. This MALDI profiling analysis of the crude supernatants from 3 different cell lines (PNT2, PC3 and LNCaP) demonstrated the capacity of the MALDI profiling approach to discriminate between the different secretome signatures. The UroLOC concept and secretome profiling that we describe opens new opportunities in terms of liquid-biopsy based diagnosis, particularly for the early stages of carcinogenesis.

Microbial assisted (Bacillus mojavensis) production of bio-surfactant lipopeptide with potential pharmaceutical applications and its characterization by MALDI-TOF-MS analysis

Lipopeptides are a fascinating group of biosurfactants possess remarkable surface properties. Functional groups on the surface of these molecules can combine with other substances leading to obtain applicable materials. The aim of the present study is the isolation of an anionic lipopeptide- producing bacterium and verifying its potential for pharmaceutical applications. A Bacillus mojavensis strain capable of producing a great amount of lipopeptide biosurfactant was selected from a number of isolated Bacillus using oil spreading technique, blood agar hemolysis, drop collapsing assay, pH sensitivity and biuret test. Anionic extracellular lipopeptides compound was extracted using metal salt precipitation method and its properties were investigated by TLC, FTIR and SDS page. HPLC-amino acid analysis showed that negative- charge amino acids were dominant in the peptidyl part of the crude supernatant and purified anionic fraction. Furthermore Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS) analysis was applied to detect the lipopeptides harvested from the most anionic fraction obtained from anion- exchange chromatography and the results revealed the presence of surfactin isoform in the extracted substance. The extracted lipopeptides showed surface tension reducing ability, antibacterial activity and lack of toxicity to PC12 and PBMC cells. Also with negative nature interacted with basic molecules to make new compounds, so these surfactants can be considered as a natural product with potential pharmaceutical applications.

Xylanase and feruloyl esterase from actinomycetes cultures could enhance sugarcane bagasse hydrolysis in the production of fermentable sugars.

The addition of enzymes that are capable of degrading hemicellulose has a potential to reduce the need for commercial enzymes during biomass hydrolysis in the production of fermentable sugars. In this study, a high xylanase producing actinomycete strain (Kitasatospora sp. ID06-480) and the first ethyl ferulate producing actinomycete strain (Nonomuraea sp. ID06-094) were selected from 797 rare actinomycetes, respectively, which were isolated in Indonesia. The addition (30%, v/v) of a crude enzyme supernatant from the selected strains in sugarcane bagasse hydrolysis with low-level loading (1 FPU/g-biomass) of Cellic® CTec2 enhanced both the released amount of glucose and reducing sugars. When the reaction with Ctec2 was combined with crude enzymes containing either xylanase or feruloyl esterase, high conversion yield of glucose from cellulose at 60.5% could be achieved after 72h-saccharification.

Enhanced methane production from wheat straw with the assistance of lignocellulolytic microbial consortium TC-5

The major obstacle of methane production from lignocellulose lies in the inefficient deconstruction of biomass. In this study, an anaerobic microbial consortium TC-5 was enriched with high lignocellulose-degradation capacity to enhance methane production from wheat straw. High degradation ratio of 45.7% of un-pretreated wheat straw was achieved due to a multi-species lignocellulolytic enzyme presented in the crude culture supernatant. The specific activity of xylanase, xylan esterase and β-xylosidase reached the highest level of 4.23, 0.15 and 0.48 U/mg, while cellobiohydrolase, endoglucanase and β-glucosidase showed the highest specific activity of 0.36, 0.22 and 0.41 U/mg during 9 days’ degradation. Inoculation of TC-5 in digestion sludge during anaerobic digestion of wheat straw resulted in remarkable enhancement of 22.2% and 36.6% in methane yield under mesophilic and thermophilic conditions, respectively. This work demonstrates the potential of TC-5 for enhancing the production of biogas and other chemicals through biomass based biorefinery.

Update on the emergence and pathogenesis of necrotic enteritis in broiler chickens

Necrotic enteritis (NE) is a disease of broiler chickens, which is caused by Clostridiumperfringens type A or C and is characterized by high mortality and severe intestinal lesions. NE is described as a disease of high economical importance which affects health and welfare of broilers and also may pose a threat to public health. Although NE was known as a disease since 1930, it did not cause serious problems to the poultry industry. The emergence of the disease occurred after 1986 in Scandinavia and 2000 in the European Union and was related with the ban of in-feed antimicrobial growth promoter. Furthermore, the ban of meat meal and bone meal from the feed of broiler chickens and their replacement by fishmeal increased further the occurrence of NE. NE breaks the Koch's postulate, which supports that "a disease-causing organism should not be present in healthy individuals", because C perfringens may be detected in high populations in the gut of birds with no visible signs of NE. Moreover, challenge of birds with C perfringens does not \eadperse to the development of the disease. It is very well accepted that NE is a multi-factorialdisease in which a number of co-factors are usually required for the proliferation and toxinogenesis of C. perfringens and manifestation of the disease. Toxin -a, since 2006, has been proposed to be the main virulence factor for NE in poultry. The origin of this assumption seems to lie to observation that crude supernatant from C perfringens type A cultures induced necrotic lesions in broilers. Moreover, the development of NE lesions prevented partially by antibodies against C. perfringens toxin -a. The interpretation of these early studies is not clear, because they used crude supernatant and the assumption was made that the effects were caused by the dominant protein present (i.e. toxin -a). However, many other proteins are also present in the supernatant ofC perfringens cultures. The most convincing evidence, that toxin -a is not essential virulence factor for the pathogenesis of NE, comes from studies using a toxin -a negative mutant (epa mutant) of a C perfringens strain from NE outbreak, which was able to produce characteristic NE lesions. Recently, netB, a novel toxin that is associated with broiler NE, has been described. A netB mutant of C perfringens was unable to cause necrotic lesions in the gut of experimentally infected broilers, but a complemented netB mutant was virulent, like the wild-type strain. However, netB per se, might not be an essential component of virulence factor for the pathogenesis of NE, because not all strains isolated from diseased birds carry the netB gene. The presence of the toxin -β2, although it has been linked with increased incidence of bovine enterotoxaemia, intestinal disorders in human, horses and diarrhea in piglets, does not seem to be involved in the pathogenesis of NE in broiler. Most C. perfringens strains isolated from cases of NE do not carry the gene (cpb2) which is responsible for the production of toxin -β2. The efficacy of antitoxin -a toxoid vaccines, the high concentration of toxin-a at the supernatant of C. perfringens culture and feces of diseased birds, as well as the high titer of antibodies against toxin-a in birds with NE, indicate that toxin -a definitely play a role, major or minor, on the pathogenesis of NE in broilers.

Isolation and molecular characterization of antifungal metabolite producing actinomycete from mangrove soil

The main object of the present study is to isolate and characterize the actinomycetes from Koringa mangrove soil samples near Kakinada, Andhra Pradesh, India. Isolated actinomycetes were assessed for antagonistic activity against various bacteria and fungi. The potent strain KMFA-1 having activity against dermatophytes Candida albicans and Pectinotrichum llanense was characterized. Based on physiological, morphological characteristics and 16s rRNA gene sequencing the isolated strain was identified as Streptomyces hydrogenans. Extraction was done with different solvents and the activity was evaluated for each solvent extract. The antibiotic that is responsible for activity is found to be highly water soluble. The bioactive metabolite present in crude supernatant was found to be stable at 80 °C for 1 h, 90% activity was retained after boiling at 100 °C for 1 h, but 53.4% activity was reduced after autoclaving (at 121 °C for 15 min). The activity was not lost when the crude supernatant was subjected to wide range of pH (2–10). Furthermore, analytical techniques must be employed to isolate the molecule of interest. The result of present study revealed that the Streptomyces hydrogenans produced an interesting antifungal metabolite.

Cell-free one-pot conversion of (+)-valencene to (+)-nootkatone by a unique dye-decolorizing peroxidase combined with a laccase from Funalia trogii.

A combined system of a unique dye-decolorizing peroxidase (Ftr-DyP) and a laccase obtained from the basidiomycete Funalia trogii converted the precursor (+)-valencene completely to the high-value grapefruit flavour constituent (+)-nootkatone, reaching a concentration maximum of 1100mg/L. In the presence of 1mM Mn2+ and 2.5mM p-coumaric acid, (+)-nootkatone was the predominating volatile product, and only traces of substrate and the nootkatols were detectable after 24h. Hence, the two-enzyme-system reproduced the oxidizing activity observed before for the crude culture supernatant. The newly discovered Ftr-DyP was purified, sequenced and further characterized as a thermostable, non-glycosylated protein with a pH-optimum in the acidic range and a calculated mass of 52.3kDa. Besides the typical activity of DyPs towards anthraquinone dyes, Ftr-DyP also oxidized Mn2+ and showed activity in the absence of hydrogen peroxide. Neither the DyP from Mycetinis scorodonius nor the manganese peroxidase from Nematoloma frowardii were able to replace Ftr-DyP in this reaction. A hypothetical reaction mechanism is presented.

Simple Multiplexed Antibody-Binding Assay.

This simple protocol tests antibody binding to target antigens on the surface of cells. This assay is powerful because negative controls are built into each well of the screening plates. It can be used to screen crude supernatants from hybridomas, as well as bacterial periplasmic extracts when screening phage libraries. Using cell-permeant dyes allows the negative and positive cell lines to be color-coded and screened in the same well. A variant enzyme-linked immunosorbent assay can be performed where the target antigen is presented on beads.

An esterase from Penicillium decumbens P6 involved in lignite depolymerization

In this study, lignite was degraded using a purified esterase from Penicillium decumbens P6 for the first time. The esterase was purified using ammonium sulfate precipitation, anion exchange and gel filtration chromatography. The recovery and purification yield of the enzyme were 15% and 83 folds, respectively. The molecular weight of the purified enzyme was about 45 kDa. Both crude and purified esterases were studied for lignite depolymerization. The tendency of depolymerization by crude enzyme was consistent with the enzyme secreted in the medium. Along with the increased purified esterase concentration from 8 to 50 mg/ml, A450 value increased from 0.38 to 2.08. The contribution of esterase to the depolymerization was about 40% in the crude supernatant. Compared with aHA (crude lignite humic acid), bHA (esterase degraded lignite humic acid) has a lower percentage of aromatic carbon and ester groups, but a higher percentage of aliphatic carbon. bHA can promote the growth of asparagus lettuce. The results demonstrated that lignite was depolymerized by the purified esterase and evidenced the potential of esterase application in conversion of lignite into compounds with high bioactivities.

Continuous laccase concentration in an aqueous two-phase system

An approach to describe continuous partitioning of Cerrena unicolor laccase in a PEG 6000—phosphate aqueous two-phase system was proposed. The laccase was separated from crude supernatant of C. unicolor-submerged culture, and all the experiments were carried out in 25 °C and pH 7 conditions. Masses of both phases and their compositions at phase equilibrium, as well as laccase activity concentrations at different mixing points, were measured in batch experiments. An empirical short-cut method was developed which allows for calculation of mass and volume fractions of the phases, laccase concentration factors, and laccase recoveries. Theoretical predictions were verified by several experiments carried out in a special mixer-settler unit with automatic substrate feed and continuous collection of separated phases. Required concentration of the laccase was possible to achieve in a one-step extraction process in the mixer-settler unit. The predictions of the short-cut method were compared to the results of experimental measurements of phase compositions, phase volume fractions, concentration factors and enzymatic yields at steady-state operation of the extraction unit. The values of experimental results lay well within the 10% error range of the predicted values.

Production of fibrinolytic protease from Streptomyces lusitanus isolated from marine sediments

This study aim was to isolate, screen, characterize and optimize marine Streptomyces for fibrinolytic enzyme production. The potent actinomycete isolate was subjected to optimization. The parameters for optimization included pH, temperature, carbon, nitrogen sources. The crude supernatant produced was purified using size exclusion gel filtration chromatography. The optimized parameters for maximum productivity were found to be pH 7, 37°C, maltose and peptone respectively. The molecular weight of the purified enzyme was found to be 21kDa.

Halophilic viruses with varying biochemical and biophysical properties are amenable to purification with asymmetrical flow field-flow fractionation.

Viruses come in various shapes and sizes, and a number of viruses originate from extremities, e.g. high salinity or elevated temperature. One challenge for studying extreme viruses is to find efficient purification conditions where viruses maintain their infectivity. Asymmetrical flow field-flow fractionation (AF4) is a gentle native chromatography-like technique for size-based separation. It does not have solid stationary phase and the mobile phase composition is readily adjustable according to the sample needs. Due to the high separation power of specimens up to 50µm, AF4 is suitable for virus purification. Here, we applied AF4 for extremophilic viruses representing four morphotypes: lemon-shaped, tailed and tailless icosahedral, as well as pleomorphic enveloped. AF4 was applied to input samples of different purity: crude supernatants of infected cultures, polyethylene glycol-precipitated viruses and viruses purified by ultracentrifugation. All four virus morphotypes were successfully purified by AF4. AF4 purification of culture supernatants or polyethylene glycol-precipitated viruses yielded high recoveries, and the purities were comparable to those obtained by the multistep ultracentrifugation purification methods. In addition, we also demonstrate that AF4 is a rapid monitoring tool for virus production in slowly growing host cells living in extreme conditions.

Lipase immobilization on functionalized mesoporous TiO 2 : Specific adsorption, hyperactivation and application in cinnamyl acetate synthesis

Abstract According to the purification characteristics of lipase from Burkholderia ambifaria YCJ01, mesoporous TiO 2 was functionalized by phenylaminopropyl trimethoxysilane (Ph-TiO 2 ) for lipase immobilization. This support permitted one step immobilization and purification of lipase YCJ01 via hydrophobic interactions from crude fermentation supernatant. The activity of immobilized lipase was 6119.2 U/g support with 12.8 mg/g support of enzyme loading. The ratio of the activity of immobilized lipase to decrease activity in the supernatant after immobilization reached 2.2, which indicated that the immobilized lipase molecules exhibited a dramatic hyperactivation. In comparison with free lipase, immobilized lipase showed significantly improved pH stability and thermalstability. The Ph-TiO 2 /YCJ01 biocomposite was analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The result indicated lipase was efficiently immobilized on Ph-TiO 2 surface. Finally, the research about cinnamyl acetate synthesis suggested that Ph-TiO 2 /YCJ01 had enhanced catalytic efficiency compared with free lipase. In solvent free medium, the yield of 96.9% was obtained after one operation, and maintained more than 80% of yield after ten reaction cycles.

Purification and characterization of macrolactins and amicoumacins from Bacillus licheniformis BFP011: a new source of food antimicrobial substances

ABSTRACTIn this study, Bacillus licheniformis BFP011 has been cultivated for producing antimicrobial compounds, which were concentrated from the crude supernatant and purified using thin-layer chromatography. The antimicrobial activity was investigated in the presence of several organic solvents and detergents, and inhibiting effects to various Gram-negative and Gram-positive human pathogenic and food spoilage bacteria were observed. Three bands (F4, F5 and F6) showing antimicrobial activity against Salmonella typhi ATCC 5784 were subjected to reversed-phase high-performance liquid chromatography purification. Two peaks of fraction F5, F5-P3 and F5-P4, showed 100% inhibition against S. typhi ATCC 5784. The contained mixture of antimicrobial compounds consists of macrolactins and amicoumacins, which induced the collapse and breaking of S. typhi ATCC 5784 cell membranes in a time-dependent manner. Taken collectively, the results indicate that these compounds may represent promising candidates for the development of food preservative agents of natural origin, as well as novel antimicrobial drug candidates against multiresistant bacterial strains.

Overexpression of functional human FLT3 ligand in Pichia pastoris

Growth factors and cytokines including FLT3 Ligand (FLT3L) have many applications in cellular and molecular biology studies, and also as therapeutical agents. FLT3L was expressed in Pichia pastoris through cloning from human leukemic K562 cell line as well as using a codon-optimized synthetic construct. Codon adaptation index (CAI) was increased from 55 in the native sequence up to 95 after optimization. Significant changes occurred in the codons for Pro, Arg, Leu and Ser toward the favored codons in P. pastoris. Both forms of expressed FLT3L (from the native and optimized sequences) were capable of stimulating proliferation of the FDC-P1 cells expressing human wild-type FLT3 (FD–FLT3–WT). Sequence optimization resulted in 55-fold increase in the yield of active FLT3L (290 μg/mL of product in the crude supernatant). Amino acid residues 27–162 are sufficient for the biological function of human FLT3L. Pichia pastoris is a highly efficient and cost-effective system for expression of endotoxin-free FLT3L; however, codon optimization is necessary for its optimal expression.

Enzymatic phosphorylation of mannose by glucomannokinase from Mycobacterium phlei using inorganic polyphosphate.

Mannose-6-phosphate is an important phosphor-sugar, which is involved in many physiological functions and it is used to treat many diseases. Its production is however expensive since it requires costly substrate ATP as phosphorylation agent. This study has focused upon the direct synthesis of M6P by glucomannokinase using inorganic polyphosphate without involvement of ATP. The gene cloned for glucomannokinase has been sequenced from Mycobacterium phlei and it is transformed into Escherichia coli for expression. After purification involving affinity chromatography, a band of 30kDa corresponding to the enzyme has been isolated from induced crude supernatant. A total amount of 0.69mg/ml of enzyme has been successively obtained and the purity exceeds 90%. The kinetic assay studies show that this enzyme has more affinity towards polyphosphate and glucose than ATP and mannose respectively. The KM values of the enzyme for glucose, mannose, ATP and hexametaphosphate derived from experiments are 9.5, 203.7, 4.6, 1.7μM, respectively. The enzyme has shown a maximum production of mannose-6-phosphate at optimized conditions of pH 8.5, 25°C, poly(P)/mannose ratio 3:1 and in the presence of bivalent ion Mg2+. The results reveal that the glucomannokinase from Mycobacterium phlei suitable for further production of mannose-6-phosphate.

Effective mosquito and arbovirus surveillance using metabarcoding.

Effective vector and arbovirus surveillance requires timely and accurate screening techniques that can be easily upscaled. Next‐generation sequencing (NGS) is a high‐throughput technology that has the potential to modernize vector surveillance. When combined with DNA barcoding, it is termed ‘metabarcoding.’ The aim of our study was to establish a metabarcoding protocol to characterize pools of mosquitoes and screen them for virus. Pools contained 100 morphologically identified individuals, including one Ross River virus (RRV) infected mosquito, with three species present at different proportions: 1, 5, 94%. Nucleic acid extracted from both crude homogenate and supernatant was used to amplify a 269‐bp section of the mitochondrial cytochrome c oxidase subunit I (COI) locus. Additionally, a 67‐bp region of the RRV E2 gene was amplified from synthesized cDNA to screen for RRV. Amplicon sequencing was performed using an Illumina MiSeq, and bioinformatic analysis was performed using a DNA barcode database of Victorian mosquitoes. Metabarcoding successfully detected all mosquito species and RRV in every positive sample tested. The limits of species detection were also examined by screening a pool of 1000 individuals, successfully identifying the species and RRV from a single mosquito. The primers used for amplification, number of PCR cycles and total number of individuals present all have effects on the quantification of species in mixed bulk samples. Based on the results, a number of recommendations for future metabarcoding studies are presented. Overall, metabarcoding shows great promise for providing a new alternative approach to screening large insect surveillance trap catches.

Lactose-inducted production of a complete lignocellulolytic enzyme system by a novel bacterium Bacillus sp. BS-5 and its application for saccharification of alkali-pretreated corn cob

In this study, with combined carboxymethyl cellulose agar plate, xylan agar plate and filter paper hydrolysis assay, a novel cellulase and xylanase-producing strain identified as Bacillus sp. was isolated. Using lactose as the only carbon source, a complete and balanced lignocellulolytic enzyme system containing at least endoglucanase (9.6 U/ml), exoglucanase (0.8 U/ml), Fpase (1.4 U/ml), xylanase (3.8 U/ml) and β-glucosidase (1.2 U/ml) was produced. Interestingly, a zymogram of the crude culture supernatant displayed a multifunctional lignocellulolytic enzyme system including at least four bonds with both endoglucanase activity and xylanase activity at 21.2, 23.8, 28.9 and 31.2 kDa, respectively, indicating that these enzymes might be bifunctional. More gratifyingly, according to the binding affinity analysis and scanning electron microscopy, the crude enzyme complex produced by strain BS-5 was capable of hydrolyzing not only pure insoluble polysaccharides, but also agricultural residues such as corn cob. At 5% substrate concentration and 20 FPU/g enzyme loading, the reducing sugar was 350.8 mg/g of alkali-pretreated corn cob after 72 h enzymatic hydrolysis. These results suggested that this strain could be a good candidate for the development of a more cost-effective and efficient lignocellulolytic enzyme cocktail for the saccharification of lignocellulosic biomass.

Effect of Histophilus somni on Heart and Brain Microvascular Endothelial Cells.

Histophilus somni is a pathogenic gram-negative bacterium responsible for pneumonia and septicemia in cattle. Sequelae include infectious thrombotic meningoencephalitis (ITME), myocarditis, arthritis, and abortion. These syndromes are associated with widespread vasculitis and thrombosis, implicating a role for endothelium in pathogenesis. Histopathologic and immunohistochemical investigation of 10 natural cases of bovine H. somni myocarditis and 1 case of ITME revealed intravascular H. somni in large biofilm-like aggregates adherent to the luminal surface of microvascular endothelium. Ultrastructurally, bacterial communities were extracellular and closely associated with degenerating or contracted endothelial cells. Histophilus somni was identified by bacterial culture and/or immunohistochemistry. Western blots of the bacterial isolates revealed that they expressed the immunodominant protective 40 kDa OMP and immunoglobulin-binding protein A (IbpA) antigens. The latter is a large surface antigen and shed fibrillar antigen with multiple domains. The cytotoxic DR2Fic domain of IbpA was conserved as demonstrated by polymerase chain reaction. Treatment of endothelial cells in vitro with IbpA in crude culture supernatants or purified recombinant GST-IbpA DR2Fic (rDR2) cytotoxin induced retraction of cultured bovine brain microvascular endothelial cells. By contrast, no retraction of bovine endothelium was induced by mutant rDR2H/A with an inactive Fic motif or by a GST control, indicating that the cytotoxic DR2Fic motif plays an important role in endothelial cell retraction in vasculitis. The formation of biofilm-like aggregates by H. somni on bovine microvascular endothelium may be fundamental to its pathogenesis in heart and brain.