The role of immune pig colostrum,serum and immunoglobulins IgG,IgM, and IgA in local intestinal immunity against enterotoxic strain ofEscherichia coli 055 in germfree piglets

The protective effect of pig immune colostrum, serum and immunoglobulins IgG, IgM and IgA against the enterotoxic strain ofEscherichia coli O55, was studied in newborn germfree piglets. This strain produced accumulation of fluid and dilatation of intestine when injected into the ligated ileal segment of germfree piglets, which is considered to be the typical effect of enterotoxins. Erosion of the intestinal epithelium and penetration of bacteria into the submucosa were also observed. Immune serum, colostrum and all the immunoglobulin classes used produced a local protective effect, IgA being most effective. The mechanism of protection conferred by these immunoglobulins is discussed with respect to the possible pathogenic action of enterotoxicEscherichia coli O55 in the intestinal tract of immunologically virgin germfree piglets.     

Steric Hindrance Mutagenesis in the Conserved Extracellular Vestibule Impedes Allosteric Binding of Antidepressants to the Serotonin Transporter

The serotonin transporter (SERT) controls synaptic serotonin levels and is the primary target for antidepressants, including selective serotonin reuptake inhibitors (e.g. (S)-citalopram) and tricyclic antidepressants (e.g. clomipramine). In addition to a high affinity binding site, SERT possesses a low affinity allosteric site for antidepressants. Binding to the allosteric site impedes dissociation of antidepressants from the high affinity site, which may enhance antidepressant efficacy. Here we employ an induced fit docking/molecular dynamics protocol to identify the residues that may be involved in the allosteric binding in the extracellular vestibule located above the central substrate binding (S1) site. Indeed, mutagenesis of selected residues in the vestibule reduces the allosteric potency of (S)-citalopram and clomipramine. The identified site is further supported by the inhibitory effects of Zn²⁺ binding in an engineered site and the covalent attachment of benzocaine-methanethiosulfonate to a cysteine introduced in the extracellular vestibule. The data provide a mechanistic explanation for the allosteric action of antidepressants at SERT and suggest that the role of the vestibule is evolutionarily conserved among neurotransmitter:sodium symporter proteins as a binding pocket for small molecule ligands.     

Leaf n‐Alkanes as Characters Differentiating Coastal and Continental Juniperus deltoides Populations from the Balkan Peninsula

The composition of the cuticular n‐alkanes isolated from the leaves of nine populations of Juniperus deltoides R.P.Adams from continental and coastal areas of the Balkan Peninsula was characterized by GC‐FID and GC/MS analyses. In the leaf waxes, 14 n‐alkane homologues with chain‐lengths ranging from C₂₂ to C₃₅ were identified. n‐Tritriacontane (C₃₃) was dominant in the waxes of all populations, but variations between the populations in the contents of all n‐alkanes were observed. Several statistical methods (ANOVA, principal component, discriminant, and cluster analyses) were used to investigate the diversity and variability of the cuticular‐leaf‐n‐alkane patterns of the nine J. deltoides populations. This is the first report on the n‐alkane composition for this species. The multivariate statistical analyses evidenced a high correlation of the leaf‐n‐alkane pattern with the geographical distribution of the investigated samples, differentiating the coastal from the continental populations of this taxon.     

Trends of Superoxide Dismutase and Soluble Protein of Aquatic Plants in Lakes of Different Trophic Levels in the Middle and Lower Reaches of the Yangtze River,China

A limnological study was carried out to determine the responses of superoxide dismutase (SOD) activities and soluble protein (SP) contents of 11 common aquatic plants to eutrophication stress.Field investigation in 12 lakes in the middle and lower reaches of the Yangtze River was carried out from March to September 2004.Our results indicated that nonsubmersed (emergent and floating-leafed) plants and submersed plants showed different responses to eutrophication stress.Both SOD activities of the non-submersed and submersed plants were negatively correlated with their SP contents (P < 0.000 1).SP contents of non-submersed plants were significantly correlated with all nitrogen variables in the water (P < 0.05),whereas SP contents of submersed plants were only significantly correlated with carbon variables as well as ammonium and Secchi depth (SD) in water (P<0.05).Only SOD activities of submersed plants were decreased with decline of SD in water (P < 0.001).Our results indicate that the decline of SOD activities of submersed plants were mainly caused by light limitation,this showed a coincidence with the decline of macrophytes in eutrophic lakes,which might imply that the antioxidant system of the submersed plants were impaired under eutrophication stress.     

Terpene chemodiversity of relict conifers Picea omorika, Pinus heldreichii, and Pinus peuce, endemic to Balkan

Terpenes are often used as ecological and chemotaxonomic markers of plant species, as well as for estimation of geographic variability. Essential oils of relic and Balkan endemic/subendemic conifers, Picea omorika, Pinus heldreichii, and P. peuce, in central part of Balkan Peninsula (Serbia and Montenegro), on the level of terpene classes and common terpene compounds were investigated. In finding terpene combinations, which could show the best diversity between species and their natural populations, several statistical methods were applied. Apart from the content of different terpene classes (P. omorika has the most abundant O-containing monoterpenes and sesquiterpenes; P. heldreichii and P. peuce have the largest abundance of sesquiterpene and monoterpene hydrocarbons, resp.), the species are clearly separated according to terpene profile with 22 common compounds. But, divergences in their populations were established only in combination of several compounds (specific for each species), and they were found to be the results of geomorphologic, climatic, and genetic factors. We found similarities between investigated species and some taxa from literature with respect to terpene composition, possibly due to hybridization and phylogenetic relations. Obtained results are also important regarding to chemotaxonomy, biogeography, phylogeny, and evolution of these taxa.     

On the shape of a DNA molecule

Due to the lack of direct X-ray evidence for base pairing being the only mechanism for the formation of double helix in a DNA crystal, an alternative explanation is suggested so that the observed DNA loop becomes essential. This work was sponsored at Brown University under a grant from Speidel Corporation.     

Neuroprotective Potential and Chemical Profile of Alternatively Cultivated Ganoderma lucidum Basidiocarps

Various neurodegenerative diseases are the main challenges to the modern medicine and there is a great need for novel, natural, neuroprotective agents. Ganoderma lucidum is a well‐known medicinal mushroom, which health benefits have been confirmed by numerous studies. As demand for its basidiocarps is increased and traditional cultivation on hardwoods is not environmentally friendly and economically justified, finding of alternative substrates is necessary. The aim of the study was to assess the effect of alternative cultivation substrates on the chemical profile of G. lucidum basidiocarps and their capacity to inhibit acetylcholinesterase and tyrosinase, which higher activity is directly associated with neurodegenerative processes. Extracts of basidiocarps cultivated on alternative substrates, especially on clear wheat straw, showed significantly higher inhibition capacities than extracts of commercially‐grown ones. These extracts were considerably different chemically from commercial basidiocarps extracts and even nine new compounds were isolated from them. Our results suggest that cultivation substrate greatly affect the chemical profile and neuroprotective capacity of obtained basidiocarps and wheat straw is a promising cultivation substrate.     

A novel intact circular dsDNA supercoil

A novel intact circular dsDNA supercoil is proposed as an alternative to the conventional DNA supercoil, so that the two complementary strands of ssDNA circles are separable without any covalent bond breakage. This new structure can be visualized by using two tubings: one black and one clear. Twist the black tubing a number of times and connect its two ends. Do the same for the clear tubing. Then wrap the two tubings together. This forms the separable or novel supercoil. On the other hand, the conventional supercoil can be modeled by twisting the black and clear tubings together and then connect their respective ends, so that the two tubings are not separable unless one of them is cut. Experimentally, in the absence of any enzyme, many intact plasmid dsDNA circles give two bands on agarose gel electrophoresis under a certain given condition, while the same plasmid molecules after cutting once by a restriction enzyme give only one band under the same, condition. In the case of intact pUC19 plasmids, these two bands can then be, recovered and sequenced separately, using two primers in opposite directions. Each band gives mostly one sequence which is complementary to that of the other band. The combination of the above theoretical model and experimental results strongly suggests that there is an alternative structure of DNA which does not have the usual difficulty of unwinding, rewinding and requiring numerous covalent bond breakages and ligations during semiconservative replication.     

An efficient model development strategy for bioprocesses based on neural networks in macroscopic balances

In the serial gray box modeling strategy, generally available knowledge, represented in the macroscopic balance, is combined naturally with neural networks, which are powerful and convenient tools to model the inaccurately known terms in the macroscopic balance. This article shows, for a typical biochemical conversion, that in the serial gray box modeling strategy the identification data only have to cover the input-output space of the inaccurately known term in the macroscopic balances and that the accurately known terms can be used to achieve reliable extrapolation. The strategy is demonstrated successfully on the modeling of the enzymatic (repeated) batch conversion of penicillin G, for which real-time results are presented. Compared with a more data-driven black box strategy, the serial gray box strategy leads to models with reliable extrapolation properties, so that with the same number of identification experiments the model can be applied to a much wider range of different conditions. Compared to a more knowledge-driven white box strategy, the serial gray box model structure is only based on readily available or easily obtainable knowledge, so that the development time of serial gray box models still may be short in a situation where there is no detailed knowledge of the system available. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 549-566, 1997.