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PubMed1989

[Structural and functional investigation of polymyxins. Structure and biological properties of polymyxin M analogs].

The effect of proteinases of plant and microbial origin on polymyxin M was studied. It was shown that this antibiotic was absolutely stable to the effect of papain and ficin. On hydrolysis with subtilisin there formed polymyxin decyclized analogs not described earlier. Their isolation, purification and biological activity are described. The structure of these compounds was assessed by one- and two-dimensional 1H NMR spectroscopy. The role of various functional groups, their space orientation and impact on antimicrobial activity of the compounds are discussed.

Ficain↗

PubMed2006

Aquaporins in the hepatobiliary system.

The review focuses on the potential physiological and pathophysiological roles of aquaporins (AQPs), a family of water channel proteins, in the hepatobiliary system. Among 13 aquaporins (AQP0-AQP12) cloned in mammals, seven AQPs have been identified in the liver and biliary tree. Accumulating evidence suggests that AQPs are likely involved in canalicular and ductal bile secretion, gluconeogenesis and microbial infection and may have other novel roles that affect liver function.

Animals↗

PubMed1997

Rat dihydroorotate dehydrogenase: isolation of the recombinant enzyme from mitochondria of insect cells.

Mammalian dihydroorotate dehydrogenase (EC 1.3.99.11), the fourth enzyme of pyrimidine de novo synthesis is located in the mitochondrial inner membrane with functional connection to the respiratory chain. From the cDNA of rat liver dihydroorotate dehydrogenase cloned in our laboratory the first complete sequence of a mammalian enzyme was deduced. Two hydrophobic stretches centered around residues 20 and 357, respectively, and a short N-terminal mitochondrial targeting sequence of 10 amino acids was proposed. A recombinant baculovirus containing the rat liver cDNA for dihydroorotate dehydrogenase was constructed and used for virus infection and protein expression in Trichoplusia ni cells. The targeting of the recombinant protein to mitochondria of the insect cells was monitored by activity determination of dihydroorotate dehydrogenase in subcellular compartments in comparison to succinate dehydrogenase activity (EC 1.3.5.1), which is a specific marker enzyme of the inner mitochondrial membrane. The results of subcellular distribution were verified by Western blotting with anti-dihydroorotate dehydrogenase immunoglobulins. The activity of the recombinant enzyme in the mitochondria of infected insect cells was found to be about 570-fold above the level of dihydroorotate dehydrogenase in rat liver mitochondria. By cation exchange chromatography of the Triton X-114 solubilisate of mitochondria, dihydroorotate dehydrogenase was purified to give a specific activity of 15 U/mg at pH 8.0. This was a marked progress over the six-step purification procedure of the enzyme from rat liver which resulted in a specific activity of 0.7 U/mg at pH 8.0. The characteristic flavin absorption spectrum obtained with the recombinant enzyme gave strong evidence that the rodent enzyme is a flavoprotein. By enzyme kinetic studies K(m) values for dihydroorotate and ubiquinone were 6.4 and 9.9 microM with the recombinant enzyme, and were 5.0 and 19.7 microM, respectively, with the rat liver enzyme. After expression of only truncated forms of human dihydroorotate dehydrogenase, the present successful generation of the complete rodent enzyme using insect cells and the efficient procedure will promote structure and function studies of the eukaryotic dihydroorotate dehydrogenases in comparison to the microbial enzyme.

Amino Acid Sequence↗

PubMed2026

PGPR inoculation and growth enhancement of crops cultivated in hydroponic systems.

Plant growth-promoting rhizobacteria (PGPR) are ubiquitous rhizosphere microorganisms that promote plant health through various mechanisms. Although the study of PGPR inoculants in soil has been done for ages, their application in hydroponic systems has received relatively limited attention. This review identifies PGPR inoculants that are commonly used in hydroponics, methods of application, and their effects on plant growth and nutrient use efficiency. Literature shows that PGPR inoculants improve plant performance in controlled hydroponic systems through the production of growth-stimulating substances, nitrogen fixation, and improved nutrient acquisition. However, the plant growth responses are highly variable depending on the composition of nutrient solutions, environmental factors, crop and microbe species, and the type of hydroponic system. The review identifies various challenges of PGPR inoculation in hydroponic systems and future research directions to address the current gaps. Generally, the productivity of hydroponic systems can be enhanced through advanced inoculation strategies and the development of suitable carrier materials to improve inoculant survival, viability, and functions. Emphasis should also be placed on designing system-specific microbial consortia and Synthetic communities that are tailored to the unique ecological conditions of hydroponic systems.

Hydroponics↗

PubMed2006

Toll-like receptors: from the discovery of NFkappaB to new insights into transcriptional regulations in innate immunity.

Toll-like receptors (TLRs) are key components of the innate immune system, functioning as pattern recognition receptors that recognise a wide range of microbial pathogens. TLRs represent a primary line of defence against invading pathogens in mammals, plants and insects. Recognition of microbial components by TLRs triggers a cascade of cellular signals that culminates in the activation of NFkappaB which leads to inflammatory gene expression and clearance of the infectious agent. The history of NFkappaB began with the TLR4 ligand lipopolysaccharide (LPS), a component of the cell wall of Gram-negative bacteria, since this was the stimulus first used to activate NFkappaB in pre-B-cells. However, since those early days it has been a circuitous route, made possible by drawing on information provided by many different fields, that has led us not only to the discovery of TLRs but also to an understanding of the complex pathways that lead from TLR ligation to NFkappaB activation. In this review we will summarize the current knowledge of TLR-mediated NFkappaB activation, and also the recent discoveries that subtle differences in kappaB binding sequences and NFkappaB dimer formation result in specific gene expression profiles.

Animals↗

PubMed1990

On the two-compartment model for estimating the rate and extent of feed degradation in the rumen.

An analysis of the compartmental scheme used to determine the rate and extent of ruminal degradation of feeds is presented. Attention is given to the kinetic representation of the degradation of the potentially degradable fraction. Changing the kinetic order of the rate, and introducing indigestible substrate inhibition and microbial activity into its representation, are investigated. This leads to response functions such as the Gompertz and logistic for describing the cumulative disappearance of potentially degradable substrate during in-sacco and in-vitro incubation.

Animals↗

PubMed2002

Transcription factors controlling plant secondary metabolism: what regulates the regulators?

Plants produce secondary metabolites, among others, to protect themselves against microbial and herbivore attack or UV irradiation. Certain metabolite classes also function in beneficial interactions with other organisms. For example, anthocyanin pigments and terpenoid essential oils have key roles in attraction of flower pollinators. Secondary metabolites also have direct uses for man. Flavonoids and terpenoids for example have health-promoting activities as food ingredients, and several alkaloids have pharmacological activities. Controlled transcription of biosynthetic genes is one major mechanism regulating secondary metabolite production in plant cells. Several transcription factors involved in the regulation of metabolic pathway genes have been isolated and studied. There are indications that transcription factor activity itself is regulated by internal or external signals leading to controlled responses. The aim of this review is to discuss the regulation of transcription factors involved in secondary metabolism in plants at gene and protein levels, using phenylpropanoid and terpenoid indole alkaloid pathways as two well-studied examples.

Alkaloids↗

PubMed1999

Influence of age and plasma treatment on neutrophil phagocytosis and CD18 expression in foals.

The aim of this study was to evaluate the influence of age and plasma treatment on neutrophil phagocytosis, CD18 expression and serum opsonic capacity in foals in field settings. Microbial infections constitute a large threat in young foals and neutrophil functions are crucial for the defense. Blood samples were obtained from 13 foals at seven time points between the ages of 2 and 56 days and once from 16 adult horses. Six of the foals were treated with adult plasma at the age of 1 week. Neutrophil phagocytosis of yeast after various opsonizations and the expression of complement adhesion receptor CD18 were analysed by flow cytometry. Autologous serum opsonization resulted in 52+/-6.1% phagocytic neutrophils in 2-day-old foals (n = 12), a significantly lower rate than in adult horses (mean 84+/-3.1%; n = 16). In foals, yeast ingestion per neutrophil was also lower than in adults. Opsonic capacity increased with age (p < 0.05), reaching adult levels at 3-4 weeks. An increase in serum opsonic capacity followed plasma treatment (p < 0.05). The phagocytic capacity of foal neutrophils at the time-points studied was equal to or higher than that in the adults, when pooled adult horse serum or anti-yeast IgG was used as opsonin. In foals, serum IgG concentration was negatively correlated to serum opsonic capacity. CD18 receptor expression was higher in neutrophils from foals (<21 days old) than in those from adult horses (p < 0.05). The results indicate that foals are transiently deficient in serum opsonic capacity, which negatively affects their capacity for neutrophil phagocytosis. These changes in serum opsonins, unrelated to IgG, may be important factors in susceptibility to infections in foals.

Actinomycetales Infections↗

PubMed1999

Expression and role of heat-shock protein 65 (HSP65) in macrophages during Trypanosoma cruzi infection: involvement of HSP65 in prevention of apoptosis of macrophages.

The 65-kDa heat-shock protein (HSP65) is thought to play a role in host defense against infections with various microbial pathogens and in autoimmune inflammatory disorders. We investigated the biological function and expression mechanism of HSP65 in macrophages of mice infected with Trypanosoma cruzi. BALB/c mice, which are susceptible to T. cruzi, showed high levels of parasitemia, and 80% of these mice died within 42 days after the infection, whereas resistant C57BL/6 or DBA/2 mice showed low levels of transient parasitemia and all survived. HSP65 expression was correlated with resistance to T. cruzi infection; HSP65 was more strongly expressed in macrophages of resistant C57BL/6 and DBA/2 mice than in macrophages of susceptible BALB/c mice. Immunodeficient BALB/c-nu/nu (nude) and C.B-17 scid/scid (SCID) mice were shown to be highly susceptible to this infection, and they did not express detectable levels of HSP65, suggesting that T cells play essential roles in the expression of HSP65 as well as in protective immunity against the infection. CD4(+) T cells, but not CD8(+) T cells or gammadelta T cells, were the cell population responsible for the induction of HSP65 expression in macrophages. Furthermore, depletion of asialo GM-1(+) NK cells made resistant C57BL/6 mice more susceptible to the infection, and HSP65 expression in their macrophages was abolished. Semiquantitative reverse transcription PCR analyses showed that both interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) mRNA levels in CD4(+) T cells became low when resistant C57BL/6 mice were depleted of NK cells, suggesting that NK cells contribute to functional differentiation of CD4(+) T cells and thereby affect the induction of HSP65 expression. To determine the function of HSP65, macrophages were treated in vitro with antisense oligonucleotide for HSP65 prior to inducing HSP65 with IFN-gamma plus TNF-alpha or T. cruzi infection. This treatment did not affect the production of nitric oxide following activation, but the treated macrophages became susceptible to apoptosis. These results indicate that HSP65 plays a role in preventing the apoptosis of macrophages and thereby contributes to host resistance against T. cruzi infection.

Animals↗

PubMed2000

Reactive nitrogen intermediates and the pathogenesis of Salmonella and mycobacteria.

Over the past decade, reactive nitrogen intermediates joined reactive oxygen intermediates as a biochemically parallel and functionally non-redundant pathway for mammalian host resistance to many microbial pathogens. The past year has brought a new appreciation that these two pathways are partially redundant, such that each can compensate in part for the absence of the other. In combination, their importance to defense of the murine host is greater than previously appreciated. In addition to direct microbicidal actions, reactive nitrogen intermediates have immunoregulatory effects relevant to the control of infection. Genes have been characterized in Mycobacterium tuberculosis and Salmonella typhimurium that may regulate the ability of pathogens to resist reactive nitrogen and oxygen intermediates produced by activated macrophages.

Animals↗

PubMed2026

Exploring biohydrogen producing potential of Arctic ice and water through metagenomics and dark fermentation kinetics.

Cryospheric ecosystems in the high Arctic harbor largely unexplored microbiomes with significant biotechnological potential. The present study evaluates the biohydrogen production capabilities of the indigenous microbiome of Ny-Ålesund, Svalbard, using glacial ice and surface water samples. Dark fermentation batch assays were performed at 4 °C and 20 °C with 2-bromoethanesulfonate (BES), a methanogenic inhibitor, to track the succession of metabolic and taxonomic diversity. Metagenomic and functional analyses revealed that under 20 °C and BES conditions, psychrotolerant microbial communities maximize biohydrogen production to 85% of the total biogas produced, with an acetate-dominant fermentation pathway, as inferred from volatile fatty acid (VFA) analysis. This evolves into a highly coordinated system utilizing a coupled Rnf-nitrogenase route alongside Formate Hydrogenlyase and [FeFe]-hydrogenase pathways. Kinetic modelling using the Modified Gompertz equation, along with Q10 temperature-sensitivity indices, demonstrated a very high latent catalytic potential in these cold-adapted microbiomes. This study indicates that Arctic microbiomes are highly elastic thermodynamically and could serve as highly efficient, manipulatable biocatalysts for the environmental recovery of bioenergy through engineered low-temperature systems.

Fermentation↗

PubMed2003

Skin immunity.

As the major barrier of the body to the outside, the skin is constantly confronted with microbial, chemical and physical insults. However, the skin does not only function as a mechanical barrier but also uses the immune system for protection. Therefore, the skin is endowed with the capacity to generate immune responses of the innate as well as of the adaptive type.

Antigen-Presenting Cells↗

PubMed2002

Cystatin M / E expression in inflammatory and neoplastic skin disorders.

BACKGROUND: Cystatins are natural and specific inhibitors of endogenous mammalian lysosomal cysteine proteinases and exogenous microbial cysteine proteinases. Cystatins were shown to provide regulatory and protective functions against uncontrolled proteolysis in several disease processes. Recently we reported that cystatin M/E, which is a novel member of the cystatin gene family, has an unusually restricted expression pattern that is limited to skin. Although cystatin M/E possesses two distinct biochemical properties (it is a proteinase inhibitor and a substrate for transglutaminase) its physiological function is unknown. Disturbance of the balance between proteinases and their inhibitors can lead to irreversible damage as in chronic inflammatory reactions and tumour invasion. OBJECTIVES: To examine the expression pattern of cystatin M/E in inflammatory conditions and neoplastic skin disorders in order to obtain possible clues on its function. Furthermore, we wished to determine whether cystatin M/E expression could discriminate between various types of neoplasia. METHODS: Biopsy material of normal skin, atopic dermatitis and psoriatic lesional skin, healing excisional wounds in healthy volunteers, and several types of epidermal neoplasia (keratoacanthoma, actinic keratosis, basal cell carcinoma and squamous cell carcinoma) were used in this study. For comparison we studied the expression of cystatin M/E in squamous neoplasias from non-cutaneous origin. Affinity-purified polyclonal antibodies against cystatin M/E were used for immunohistochemical detection. RESULTS: Cystatin M/E is constitutively expressed in the stratum granulosum of normal skin, sebaceous glands, eccrine sweat glands and the infundibular epithelium of hair follicles. Expression in atopic dermatitis and psoriasis was found to extend to several layers of the stratum spinosum. In wound healing, cystatin M/E was not found in the edge of migrating keratinocytes, but it was strongly expressed in the suprabasal layers of the neo-epidermis. In epidermal neoplasias cystatin M/E expression was only found in differentiated cells and keratinized cell nests. CONCLUSIONS: Inflammation causes cystatin M/E to be expressed in the spinous cell layers where it colocalizes with transglutaminase for which it serves as a substrate. Speculatively, increased expression of cystatin M/E is compatible with a role in controlling increased levels of cysteine proteinases during inflammation and infection. Cystatin M/E expression in neoplastic epidermis is confined to well-differentiated cells and as such does not discriminate between benign and (pre)malignant epidermal neoplasias.

Carcinoma, Squamous Cell↗

PubMed1997

Exercise immunology and neutrophils.

Neutrophils play important roles in host defense against infectious agents but, paradoxically, they are also involved in the pathology of various inflammatory conditions. Their microbicidal armory consists of oxidative and nonoxidative processes that are activated simultaneously upon phagocytosis. While destruction of infectious agents occurs intracellularly, release of cytotoxic molecules into the extracellular milieu can damage body tissues. Neutrophils are not a homogeneous cell population. Subpopulations exist in various stages from dormant to primed to fully activated. The activities of neutrophils are modulated by cytokines, hormones and bioactive lipids. As neutrophils represent 60% of the circulating leukocyte pool, they are readily accessible to experimental investigation. The sequence of events that occurs in the neutrophil response to microbial invasion includes adherence, chemotaxis, phagocytosis, the oxidative burst, degranulation and microbial killing. In general, high-intensity exercise suppresses most neutrophil functions both acutely and chronically while the effects of moderate exercise have been conflicting. This review will summarize where the field is now and present some suggestions for future research. Emphasis will be placed on resolving conflicting results that may be due to biological and technical variability, and determination of the regulatory events that may mediate exercise-induced changes in neutrophil function.

Adrenocorticotropic Hormone↗

PubMed2006

Reduced nitrate leaching and enhanced denitrifier activity and efficiency in organically fertilized soils.

Conventional agriculture has improved in crop yield but at large costs to the environment, particularly off-site pollution from mineral N fertilizers. In response to environmental concerns, organic agriculture has become an increasingly popular option. One component of organic agriculture that remains in question is whether it can reduce agricultural N losses to groundwater and the atmosphere relative to conventional agriculture. Here we report reduced N pollution from organic and integrated farming systems compared with a conventional farming system. We evaluated differences in denitrification potential and a suite of other soil biological and chemical properties in soil samples taken from organic, integrated, and conventional treatments in an experimental apple orchard. Organically farmed soils exhibited higher potential denitrification rates, greater denitrification efficiency, higher organic matter, and greater microbial activity than conventionally farmed soils. The observed differences in denitrifier function were then assessed under field conditions after fertilization. N(2)O emissions were not significantly different among treatments; however, N(2) emissions were highest in organic plots. Annual nitrate leaching was 4.4-5.6 times higher in conventional plots than in organic plots, with the integrated plots in between. This study demonstrates that organic and integrated fertilization practices support more active and efficient denitrifier communities, shift the balance of N(2) emissions and nitrate losses, and reduce environmentally damaging nitrate losses. Although this study specifically examines a perennial orchard system, the ecological and biogeochemical processes we evaluated are present in all agroecosystems, and the reductions in nitrate loss in this study could also be achievable in other cropping systems.

Agriculture↗

PubMed2002

Transcriptional modulation of bacterial gene expression by subinhibitory concentrations of antibiotics.

Antibiotics such as erythromycin and rifampicin, at low concentrations, alter global bacterial transcription patterns as measured by the stimulation or inhibition of a variety of promoter-lux reporter constructs in a Salmonella typhimurium library. Analysis of a 6,500-clone library indicated that as many as 5% of the promoters may be affected, comprising genes for a variety of functions, as well as a significant fraction of genes with no known function. Studies of a selection of the reporter clones showed that stimulation varied depending on the nature of the antibiotic, the promoter, and what culture medium was used; the response differed on solid as compared with liquid media. Transcription was markedly reduced in antibiotic-resistant hosts, but the presence of mutations deficient in stress responses such as SOS or universal stress did not prevent antibiotic-induced modulation. The results show that small molecules may have contrasting effects on bacteria depending on their concentration: either the modulation of bacterial metabolism by altering transcription patterns or the inhibition of growth by the inhibition of specific target functions. Both activities could play important roles in the regulation of microbial communities. These studies indicate that the detection of pharmaceutically useful natural product inhibitors could be effectively achieved by measuring activation of transcription at low concentrations in high-throughput assays using appropriate bacterial promoter-reporter constructs.

Anti-Bacterial Agents↗

PubMed2002

Complementation of pulmonary abnormalities in SP-D(-/-) mice with an SP-D/conglutinin fusion protein.

Surfactant protein D (SP-D) and serum conglutinin are closely related members of the collectin family of host defense lectins. Although normally synthesized at different anatomic sites, both proteins participate in the innate immune response to microbial challenge. To discern the roles of specific domains in the function of SP-D in vivo, a fusion protein (SP-D/Cong(neck+CRD)) consisting of the NH(2)-terminal and collagenous domains of rat SP-D (rSP-D) and the neck and carbohydrate recognition domains (CRDs) of bovine conglutinin (Cong) was expressed in the respiratory epithelium of SP-D gene-targeted (SP-D(-/-)) mice. While SP-D/Cong(neck+CRD) fusion protein did not affect lung morphology and surfactant phospholipid levels in the lungs of wild type mice, the chimeric protein substantially corrected the increased lung phospholipids in SP-D(-/-) mice. The SP-D/Cong(neck+CRD) fusion protein also completely corrected defects in influenza A clearance and inhibited the exaggerated inflammatory response that occurs following viral infection. However, the chimeric protein did not ameliorate the ongoing lung inflammation, enhanced metalloproteinase expression, and alveolar destruction that characterize this model of SP-D deficiency. By contrast, a single arm mutant (RrSP-D(Ser15,20)) partially restored antiviral activity but otherwise failed to rescue the deficient phenotype. Our findings directly implicate the CRDs of both SP-D and conglutinin in host defense in vivo. Our findings also strongly suggest that the molecular mechanisms underlying impaired pulmonary host defense and abnormal lipid metabolism are distinct from those that promote ongoing inflammation and the development of emphysema.

Administration, Inhalation↗

PubMed1979

The effects of malnutrition on secretory and cellular immune processes.

About 15 million children under 5 years of age die each year due to suppressed immunity and the resulting increased infection. In severely malnourished children and animals some immune systems such as T-cell function, secretory IgA and complement are significantly suppressed. Other systems, such as the serum IgG or IgA, are normal or even elevated. Some of these changes are apparently caused by nutritional stress while others may be due to stimulation by increased incidence of infection and antigen load. On the other hand, marginal malnutrition stimulates increased phagocytosis and T-cell function with increased immunity to cancer but decreased resistance to certain microbial agents. The mechanisms of immune suppression by malnutrition, persistence of these effects after renutrition, and the effect of maternal malnutrition on newborn immunity are critically reviewed. Possible non-nutritional means of rapid immunological restoration of malnourished children are described.

Adolescent↗