Data-driven predictions of complex organic mixture permeation in polymer membranes

Membrane-based organic solvent separations are rapidly emerging as a promising class of technologies for enhancing the energy efficiency of existing separation and purification systems. Polymeric membranes have shown promise in the fractionation or splitting of complex mixtures of organic molecules such as crude oil. Determining the separation performance of a polymer membrane when challenged with a complex mixture has thus far occurred in an ad hoc manner, and methods to predict the performance based on mixture composition and polymer chemistry are unavailable. Here, we combine physics-informed machine learning algorithms (ML) and mass transport simulations to create an integrated predictive model for the separation of complex mixtures containing up to 400 components via any arbitrary linear polymer membrane. We experimentally demonstrate the effectiveness of the model by predicting the separation of two crude oils within 6-7% of the measurements. Integration of ML predictors of diffusion and sorption properties of molecules with transport simulators enables for the rapid screening of polymer membranes prior to physical experimentation for the separation of complex liquid mixtures.

The developing occlusion of children and young people in general practice: when to watch and when to refer

This paper discusses the assessment of the developing occlusions of children and adolescents in the general practice setting; that is, reviewing the potential of interceptive orthodontics. In particular we will illustrate the management of these individuals with case examples. We have also provided a handy pull-out guide with this issue of the Journal which can be used in the GDP's surgery for quick reference.

Using degrees of rate control to improve selective n-butane oxidation over model MOF-encapsulated catalysts: sterically-constrained Ag3Pd(111)

Metal nanoparticles encapsulated within metal organic frameworks (MOFs) offer steric restrictions near the catalytic metal that can improve selectivity, much like in enzymes. A microkinetic model is developed for the regio-selective oxidation of n-butane to 1-butanol with O₂ over a model for MOF-encapsulated bimetallic nanoparticles. The model consists of a Ag₃Pd(111) surface decorated with a 2-atom-thick ring of (immobile) helium atoms which creates an artificial pore of similar size to that in common MOFs, which sterically constrains the adsorbed reaction intermediates. The kinetic parameters are based on energies calculated using density functional theory (DFT). The microkinetic model was analysed at 423 K to determine the dominant pathways and which species (adsorbed intermediates and transition states in the reaction mechanism) have energies that most sensitively affect the reaction rates to the different products, using degree-of-rate-control (DRC) analysis. This analysis revealed that activation of the C–H bond is assisted by adsorbed oxygen atoms, O*. Unfortunately, O* also abstracts H from adsorbed 1-butanol and butoxy as well, leading to butanal as the only significant product. This suggested to (1) add water to produce more OH*, thus inhibiting these undesired steps which produce OH*, and (2) eliminate most of the O₂ pressure to reduce the O* coverage, thus also inhibiting these steps. Combined with increasing butane pressure, this dramatically improved the 1-butanol selectivity (from 0 to 95%) and the rate (to 2 molecules per site per s). Moreover, 40% less O₂ was consumed per oxygen atom in the products. Under these conditions, a terminal H in butane is directly eliminated to the Pd site, and the resulting adsorbed butyl combines with OH* to give the desired 1-butanol. These results demonstrate that DRC analysis provides a powerful approach for optimizing catalytic process conditions, and that highly selectivity oxidation can sometimes be achieved by using a mixture of O₂ and H₂O as the oxidant. This was further demonstrated by DRC analysis of a second microkinetic model based on a related but hypothetical catalyst, where the activation energies for two of the steps were modified.

A Conceptual Model to Describe the Decline of European Blackberry (Rubus anglocandicans), A Weed of National Significance in Australia

Human activities have had an adverse impact on ecosystems on a global scale and have caused an unprecedented redispersal of organisms, with both plants and pathogens moving from their regions of origin to other parts of the world. Invasive plants are a potential threat to ecosystems globally, and their management costs tens of billions of dollars per annum. Rubus anglocandicans (European blackberry) is a serious invasive species in Australia. Herbicide and cultural control methods are generally inefficient or require multiple applications. Therefore, a biological control program using stem and leaf rust strains is the main option in Australia. However, biological control using rusts has been patchy, as host factors, climate, and weather can alter the impact of the rust at different locations. In 2007, Yeoh and Fontanini noticed that blackberry plants on the banks of the Donnelly and Warren rivers in the southwest of Western Australia were dying in areas that were being regularly monitored for the impact of rust as a biological control agent. The symptoms on blackberry became known as the disease "blackberry decline". Continuous and intensive investigations are required to discover the different biotic and abiotic components associated with specific declines in plant populations. The only agent so far introduced to Australia for the biological control of blackberry is the rust Phragmidium violaceum.

The effect of long term storage on tobacco smoke particulate matter in in vitro genotoxicity and cytotoxicity assays

Particulate matter (PM) collected from mainstream tobacco smoke is a test article commonly used for in vitro genotoxicity and cytotoxicity testing of combustible tobacco products. However, little published data exists concerning the stability of PM. We completed a 2 year study to quantify the effect of PM storage at -80 °C, on the genotoxicity and cytotoxicity of PM generated from 3R4F and M4A reference cigarettes. The Ames test, Micronucleus assay (MNvit), Mouse Lymphoma assay (MLA) and the Neutral Red Uptake assay (NRU) were used. The majority of M4A and 3R4F PMs were genotoxic and cytotoxic at the timepoints tested. Some minor but statistically significant differences were observed for stored versus freshly prepared PM, but the magnitude of changes were within the variability observed for repeat testing.

Upper lip blanching and diplopia associated with local anaesthesia of the inferior alveolar nerve

A case of transient left lateral rectus nerve palsy, following an inferior alveolar nerve block to enable the surgical removal of a permanent mandibular left third molar tooth, is reported. The anatomy related to this case is considered together with suggestions for management of such patients.

Identification and characterization of a peptide that specifically binds the human, broadly neutralizing anti-human immunodeficiency virus type 1 antibody b12

Human monoclonal antibody (MAb) b12 recognizes a conformational epitope that overlaps the CD-4-binding site of the human immunodeficiency virus type 1 (HIV-1) envelope. MAb b12 neutralizes a broad range of HIV-1 primary isolates and protects against primary virus challenge in animal models. We report here the discovery and characterization of B2.1, a peptide that binds specifically to MAb b12. B2.1 was selected from a phage-displayed peptide library by using immunoglobulin G1 b12 as the selecting agent. The peptide is a homodimer whose activity depends on an intact disulfide bridge joining its polypeptide chains. Competition studies with gp120 indicate that B2.1 occupies the b12 antigen-binding site. The affinity of b12 for B2.1 depends on the form in which the peptide is presented; b12 binds best to the homodimer as a recombinant polypeptide fused to the phage coat. Originally, b12 was isolated from a phage-displayed Fab library constructed from the bone marrow of an HIV-1-infected donor. The B2.1 peptide is highly specific for b12 since it selected only phage bearing b12 Fab from this large and diverse antibody library.

Homodimeric peptides displayed by the major coat protein of filamentous phage

Peptide libraries displayed by filamentous bacteriophage have proven a powerful tool for the discovery of novel peptide agonists, antagonists and epitope mimics. Most phage-displayed peptides are fused to the N terminus of either the minor coat protein, pIII, or the major coat protein, pVIII. We report here that peptides containing cysteine residues, displayed as N-terminal fusions to pVIII, can form disulfide-bridged homodimers on the phage coat. Phage clones were randomly selected from libraries containing one or two fixed Cys residues, and surveyed for the presence of peptide-pVIII homodimers by SDS-PAGE analysis that involved pretreatment of the phage with reducing or thiol-modifying agents. For all phage whose recombinant peptide contained a single Cys residue, a significant fraction of the peptide-pVIII molecules were displayed as dimers on the phage coat. The dimeric form was in greater abundance than the monomer in almost all cases in which both forms could be reliably observed. Occasionally, peptides containing two Cys residues also formed dimers. These results indicate that, for a given pVIII-displayed peptide bearing a single Cys residue, a significant fraction of the peptide (>40 %) will dimerize regardless of its sequence; however, sequence constraints probably determine whether all of the peptide will dimerize. Similarly, only occasionally do peptides bearing two Cys residues form intermolecular disulfide bridges instead of intramolecular ones; this indicates that sequence constraints may also determine dimerization versus cyclization. Sucrose-gradient analysis of membranes from cells expressing pVIII fused to a peptide containing a single Cys residue showed that dimeric pVIII is present in the cell prior to its assembly onto phage. A model of the peptide-pVIII homodimer is discussed in light of existing models of the structure and assembly of the phage coat. The unique secondary structures created by the covalent association of peptides on the phage surface suggest a role for homo- and heterodimeric peptide libraries as novel sources of bioactive peptides.

Characterization of murine coronavirus neutralization epitopes with phage-displayed peptides

Phage-displayed peptide libraries were used to map immunologically relevant epitopes on the surface (S) glycoprotein of a neurotropic murine coronavirus (MHV-A59). Three in vitro virus-neutralizing and in vivo protective mAbs against either continuous or discontinuous epitopes on the S glycoprotein were used to screen 12 different peptide libraries expressed on the pVIII major coat protein of the fd filamentous bacteriophage. Consensus sequences that matched short sequences within the S glycoprotein were identified. The sequence of a tight-binding, mAb-selected peptide suggested the location of a discontinuous epitope within the N-terminal S1 subunit. Several tightly binding phage were amplified and used directly as immunogens in BALB/c and C57BL/6 mice. Partial protection of C57BL/6 mice against a lethal acute virus infection was achieved with a phage preparation that displayed a linear epitope. Protection correlated with the presence of sufficient levels of specific antiviral antibodies recognizing the same immunodominant domain and 13-mer peptide, located within the C-terminal S2 subunit, as the selecting mAb. Thus, the direct use of phage-displayed peptides to evaluate protective antiviral immune responses complements their use to characterize antibody-binding epitopes. This is the first evaluation of protective immunization induced by mAb-selected phage-displayed peptides.

NSP4 elicits age-dependent diarrhea and Ca(2+)mediated I(-) influx into intestinal crypts of CF mice

Homologous disruption of the murine gene encoding the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) leads to the loss of cAMP-mediated ion transport. Mice carrying this gene defect exhibit meconium ileus at birth and gastrointestinal plugging during the neonatal period, both contributing to high rates of mortality. We investigated whether infectious mammalian rotavirus, the recently characterized rotaviral enterotoxin protein NSP4, or its active NSP4(114-135) peptide, can overcome these gastrointestinal complications in CF (CFTR(m3Bay) null mutation) mice. All three agents elicited diarrhea when administered to wild-type (CFTR(+/+)), heterozygous (CFTR(+/-)), or homozygous (CFTR(-/-)) 7- to 14-day-old mouse pups but were ineffective when given to older mice. The diarrheal response was accompanied by non-age-dependent intracellular Ca(2+) mobilization within both small and large intestinal crypt epithelia. Significantly, NSP4 elicited cellular I(-) influx into intestinal epithelial cells from all three genotypes, whereas both carbachol and the cAMP-mobilizing agonist forskolin failed to evoke influx in the CFTR(-/-) background. This unique plasma membrane halide permeability pathway was age dependent, being observed only in mouse pup crypts, and was abolished by either the removal of bath Ca(2+) or the transport inhibitor DIDS. These findings indicate that NSP4 or its active peptide may induce diarrhea in neonatal mice through the activation of an age- and Ca(2+)-dependent plasma membrane anion permeability distinct from CFTR. Furthermore, these results highlight the potential for developing synthetic analogs of NSP4(114-135) to counteract chronic constipation/obstructive bowel syndrome in CF patients.

The recognition of a noncanonical RNA base pair by a zinc finger protein

BACKGROUND

The zinc finger (ZF) is the most abundant nucleic-acid-interacting protein motif. Although the interaction of ZFs with DNA is reasonably well understood, little is known about the RNA-binding mechanism. We investigated RNA binding to ZFs using the Zif268-DNA complex as a model system. Zif268 contains three DNA-binding ZFs; each independently binds a 3 base pair (bp) subsite within a 9 bp recognition sequence.

RESULTS

We constructed a library of phage-displayed ZFs by randomizing the alpha helix of the Zif268 central finger. Successful selection of an RNA binder required a noncanonical base pair in the middle of the RNA triplet. Binding of the Zif268 variant to an RNA duplex containing a G.A mismatch (rG.A) is specific for RNA and is dependent on the conformation of the mismatched middle base pair. Modeling and NMR analyses revealed that the rG.A pair adopts a head-to-head configuration that counterbalances the effect of S-puckered riboses in the backbone. We propose that the structure of the rG.A duplex is similar to the DNA in the original Zif268-DNA complex.

CONCLUSIONS

It is possible to change the specificity of a ZF from DNA to RNA. The ZF motif can use similar mechanisms in binding both types of nucleic acids. Our strategy allowed us to rationalize the interactions that are possible between a ZF and its RNA substrate. This same strategy can be used to assess the binding specificity of ZFs or other protein motifs for noncanconical RNA base pairs, and should permit the design of proteins that bind specific RNA structures.

The role of structure in antibody cross-reactivity between peptides and folded proteins

Peptides have the potential for targeting vaccines against pre-specified epitopes on folded proteins. When polyclonal antibodies against native proteins are used to screen peptide libraries, most of the peptides isolated align to linear epitopes on the proteins. The mechanism of cross-reactivity is unclear; both structural mimicry by the peptide and induced fit of the epitope may occur. The most effective peptide mimics of protein epitopes are likely to be those that best mimic both the chemistry and the structure of epitopes. Our goal in this work has been to establish a strategy for characterizing epitopes on a folded protein that are candidates for structural mimicry by peptides. We investigated the chemical and structural bases of peptide-protein cross-reactivity using phage-displayed peptide libraries in combination with computational structural analysis. Polyclonal antibodies against the well-characterized antigens, hen eggwhite lysozyme and worm myohemerythrin, were used to screen a panel of phage-displayed peptide libraries. Most of the selected peptide sequences aligned to linear epitopes on the corresponding protein; the critical binding sequence of each epitope was revealed from these alignments. The structures of the critical sequences as they occur in other non-homologous proteins were analyzed using the Sequery and Superpositional Structural Assignment computer programs. These allowed us to evaluate the extent of conformational preference inherent in each sequence independent of its protein context, and thus to predict the peptides most likely to have structural preferences that match their protein epitopes. Evidence for sequences having a clear structural bias emerged for several epitopes, and synthetic peptides representing three of these epitopes bound antibody with sub-micromolar affinities. The strong preference for a type II beta-turn predicted for one peptide was confirmed by NMR and circular dichroism analyses. Our strategy for identifying conformationally biased epitope sequences provides a new approach to the design of epitope-targeted, peptide-based vaccines.

Phage-displayed peptide libraries

Over the past year, significant advances have been achieved through the use of phage-displayed peptide libraries. A wide variety of bioactive molecules, including antibodies, receptors and enzymes, have selected high-affinity and/or highly-specific peptide ligands from a number of different types of peptide library. The demonstrated therapeutic potential of some of these peptides, as well as new insights into protein structure and function that peptide ligands have provided, highlight the progress made within this rapidly-expanding field.

Epitope mapping of a function-blocking beta 1 integrin antibody by phage display

Integrins are a major class of cell surface receptors involved in cell-cell and cell-matrix adhesion and communication. Ha2/11 is a function-blocking anti-rat beta 1 integrin hamster IgM that should be a useful reagent for understanding beta 1 integrin function. We demonstrate that Ha2/11 cross reacts with human, Xenopus, and Drosophila beta 1 integrins, and use phage display to map the epitope for Ha2/11 to residues within the sequence LRSGEPQTF which lies 18 amino acids proximal to the putative I domain in beta 1 integrins. Monoclonal antibody mapping experiments, mutational analyses, and direct binding assays have implicated integrin I domains in both cation and ligand binding. Our data therefore suggest that Ha2/11 blocks beta 1 integrin function by interfering with I domain-mediated ligand binding.

Assaying phage-borne peptides by phage capture on fibrinogen or streptavidin

There is no simple and efficient method for assaying phage isolated from libraries without having to resort to PEG purification of the phage, or to the biotinylation or other labelling of the target molecule. We report here a method for producing 'bifunctional' phage that express two types of peptide; one peptide, fused to pVIII, will bind to immobilized fibrinogen, allowing capture of the phage out of culture supernatants; this allows the other peptide, fused to pIII or pVIII to be assayed by simple ELISA. This system has also been developed for the capture of phage bearing a streptavidin-binding peptide. The bifunctional phage are produced by bacterial cells bearing a plasmid that expresses pVIII fused either to the fibrinogen-binding peptide or to the streptavidin-binding one. Thus, when these cells are infected with a phage clone or pool to be assayed, phage will be produced whose 'capture-peptide' is produced from the plasmid and whose 'assay-peptide' is produced from the phage genome. We show here that, by this method, bifunctional phage can be produced that will bind to immobilized streptavidin or fibrinogen.

Exploring the basis of peptide-carbohydrate crossreactivity: evidence for discrimination by peptides between closely related anti-carbohydrate antibodies

To investigate the molecular basis of antigenic mimicry by peptides, we studied a panel of closely related mAbs directed against the cell-wall polysaccharide of group A Streptococcus. These antibodies have restricted V-gene usage, indicating a shared mechanism of binding to a single epitope. Epitope mapping studies using synthetic fragments of the cell-wall polysaccharide supported this conclusion. All of the mAbs isolated crossreactive peptides from a panel of phage-displayed libraries, and competition studies indicated that many of the peptides bind at or near the carbohydrate binding site. Surprisingly, the peptides isolated by each mAb fell into distinct consensus-sequence groups that discriminated between the mAbs, and in general, the peptides bound only to the mAbs used for their isolation. Similar results were obtained with polyclonal antibodies directed against synthetic oligosaccharide fragments of the streptococcal cell-wall polysaccharide. Thus, the peptides appear to be specific for their isolating antibodies and are not recognized by the same mechanism as their carbohydrate counterparts.

Probing the basis of antibody reactivity with a panel of constrained peptide libraries displayed by filamentous phage

The structural requirements for peptide binding to an antibody may be elucidated by probing it with a variety of peptides having different constraints. To this end, we have constructed and screened a panel of peptide libraries displayed by filamentous bacteriophage. The peptides in most of the libraries have the potential for constraint by fixed Cys residues, which have been placed at different sites within a randomized amino acid sequence of varying length. When taken together, the binding data obtained from screening the panel with a given antibody allow one to determine the types of constraints that promote binding, as well as the residues that are critical for binding. We describe the construction of 11, pVIII-displayed, peptide libraries, whose sizes range from 150 million to 10 billion clones. The libraries were screened with a number of polyclonal and monoclonal antibodies against peptides, proteins and carbohydrates. Cross-reactivity with peptides was always found for antibodies produced against peptides, linear epitopes on folded proteins and, surprisingly, carbohydrates, whereas antibodies against discontinuous epitopes on proteins were found less frequently. The implications of these results are discussed in terms of the structural basis for cross-reactivity with peptides.

International medicine and air pollution

Environmental pollution worldwide has been increasing rapidly as a result of massive increases in industrial production, especially since 1950. Although the United States has begun to address the problem, many nations have not been able to, such as those formerly part of the Communist bloc and many emerging nations. The International Society of Doctors for the Environment was established to promote the information flow about environmental impacts on health. The National Association of Physicians for the Environment is a member of that organization.

International Medicine and Air Pollution

Environmental pollution worldwide has been increasing rapidly as a result of massive increases in industrial production, especially since 1950. Although the United States has begun to address the problem, many nations have not been able to, such as those formerly part of the Communist bloc and many emerging nations. The International Society of Doctors for the Environment was established to promote the information flow about environmental impacts on health. The National Association of Physicians for the Environment is a member of that Organization.

Random peptide libraries

Over the past year, great strides have been made in the design of peptide libraries, and new approaches have been developed for identifying peptide ligands. The libraries comprise large collections of peptides, ranging from 1 million to 1 billion different sequences, which can be screened using monoclonal and polyclonal antibodies, receptors, enzymes or other target molecules. The power of this technology stems from the chemical diversity of the amino acids coupled with the large number of sequences in a library. As such, peptide libraries may be useful for finding ligands that can serve as leads for pharmaceutical development and other purposes.

Discovering peptide ligands using epitope libraries

Epitope libraries are large collections of peptides. Each peptide is displayed on the surface of a bacteriophage particle and is encoded by a randomly mutated region of the phage genome, thus associating each unique peptide with the DNA molecule encoding it. Antibodies and other binding proteins are used to select specifically for rare, phage-bearing peptide ligands; sequencing of the corresponding viral DNA will reveal their amino acid sequences. Relatively high-affinity peptides for a variety of peptide- and non-peptide-binding ligates have been affinity-isolated from epitope libraries. This technology has been used to map epitopes on proteins and to find peptide mimics for non-peptide-binding ligates. The current challenge lies in developing epitope library technology so that tight-binding peptide ligands can be detected for a wider variety of ligates, including those that recognize folded proteins. Should this be accomplished, many powerful applications can be envisioned in the areas of drug design and the development of diagnostic markers and vaccines.

A family of concanavalin A-binding peptides from a hexapeptide epitope library

The lectin concanavalin A (Con A) binds methyl alpha-D-mannopyranoside (Me alpha Man) as well as alpha-D-mannosyl groups at the nonreducing terminus of oligosaccharides. Ligand peptides that mimic the binding of Me alpha Man to Con A were identified from screening an epitope library composed of filamentous phage displaying random hexapeptides. A consensus sequence was identified among affinity-purified phage; Con A binds phage bearing this sequence and is inhibited from doing so by Me alpha Man. When tested for binding against a panel of lectins, phage bearing this sequence bind only weakly to a closely related D-mannose-binding lectin, indicating that binding to Con A is highly selective. A synthetic peptide bearing the consensus sequence blocks the precipitation of Con A by dextran with an inhibition strength equivalent to that of methyl alpha-D-glucopyranoside. These results demonstrate that the specificity of Con A is not limited to carbohydrates and that highly selective sugar-mimics for lectins of plant, animal, or bacterial origin may be identified from epitope libraries.

Searching for peptide ligands with an epitope library

Tens of millions of short peptides can be easily surveyed for tight binding to an antibody, receptor or other binding protein using an "epitope library." The library is a vast mixture of filamentous phage clones, each displaying one peptide sequence on the virion surface. The survey is accomplished by using the binding protein to affinity-purify phage that display tight-binding peptides and propagating the purified phage in Escherichia coli. The amino acid sequences of the peptides displayed on the phage are then determined by sequencing the corresponding coding region in the viral DNA's. Potential applications of the epitope library include investigation of the specificity of antibodies and discovery of mimetic drug candidates.

Evidence that the familial adenomatous polyposis gene is involved in a subset of colon cancers with a complementable defect in c-myc regulation

Human colorectal carcinomas frequently express elevated levels of c-myc mRNA in the absence of a gross genetic change at the c-myc locus. To test the hypothesis that these tumors are defective in a gene function necessary for the regulation of c-myc expression, we fused an osteosarcoma cell line that exhibits normal c-myc regulation with two colon carcinoma cell lines that express deregulated levels of c-myc mRNA. The levels of c-myc transcripts in all of the hybrid clones examined were normal and were induced normally by a mitogenic stimulus. Since rates of c-myc mRNA turnover in the colon carcinoma cells were found to be comparable to those in normal cells, increased message stability cannot account for the increased steady-state levels of transcripts. Our findings suggest that loss of function of a trans-acting regulator is responsible for the deregulation of c-myc expression in a major fraction of colorectal carcinomas. Analysis of restriction fragment length polymorphisms in tumor/normal tissue pairs from patients with primary colorectal lesions indicated that deregulation of c-myc expression in the tumors is correlated with frequent loss of alleles of syntenic markers on chromosome 5q; allele loss on 5q could be detected in 9 of 19 tumors expressing deregulated levels of c-myc mRNA, but not in any of 8 tumors expressing normal levels of c-myc RNA. Chromosome 5q is the region known to contain the gene for familial adenomatous polyposis, an inherited predisposition to colon cancer. These findings, together with the earlier finding that the colonic distribution of tumors exhibiting deregulated c-myc expression is similar to that reported for familial polyposis, provide evidence that loss of function of the familial adenomatous polyposis gene is involved in a subset of colorectal cancers in which c-myc expression is deregulated.

Resolution of a missense mutant in human genomic DNA by denaturing gradient gel electrophoresis and direct sequencing using in vitro DNA amplification: HPRT Munich

The combination of denaturing gradient gel electrophoresis (DGGE) and in vitro DNA amplification has allowed us to (1) localize a DNA mutation to a given 100-bp region of the human genome and (2) rapidly sequence the DNA without cloning. DGGE showed that a mutation had occurred, but the technique revealed little about the nature or position of that mutation. The region of the genome containing the mutation was amplified by the polymerase chain-reaction technique, providing DNA of sufficient quality and quantity for direct sequencing. Amplification was performed with a 32P end-labeled primer that allowed direct Maxam-Gilbert sequencing of the amplified product without cloning. HPRTMunich was found to contain a single-base-pair substitution, a C-to-A transversion at base-pair position 397. We report the generation of a 169-bp, wild-type DNA probe that encompasses most of exon 3 of the human hypoxanthine guanine phosphoribosyltransferase (HPRT) gene and contains a low-temperature melting domain of approximately 100 bp. HPRTMunich, an HPRT mutant isolated from a patient with gout, has a single amino acid substitution; the corresponding DNA sequence alteration must lie within the low-temperature melting domain of exon 3. We report the separation of HPRTMunich from the wild-type sequence using DGGE. In addition to base-pair substitutions, DGGE is also sensitive to the methylation state of the molecule. The cDNA for HPRT was cloned into a vector and propagated in Escherichia coli dam+ and dam- strains; thus, methylated and unmethylated HPRT cDNA was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

The c-myc protein is constitutively expressed at elevated levels in colorectal carcinoma cell lines

In this study, we have employed both indirect immunofluorescence and ELISA assays to compare the relative levels of c-myc protein in cell lines derived from normal human colon and colon adenocarcinomas. We show that the levels of protein found in the majority of carcinoma cell lines are consistent with the levels of mRNA expressed, and that both are significantly elevated with respect to the levels found in normal cells. Growing populations of fibroblastic and epithelial cell lines derived from normal colonic mucosa exhibit small numbers of steady-state transcripts and immunofluorescence signals which are weak and confined to the nucleus. The adenocarcinoma cell lines, however, express 5- to 10-fold elevated levels of c-myc mRNA and exhibit correspondingly intense immunofluorescence signals which appear to reside principally in the nucleus. Quantitation of c-myc protein levels in these tumor cell lines by ELISA assay indicates that they are 8- to 37-fold higher than the levels of protein in normal cells. Elevated expression of the c-myc gene at both the mRNA and protein levels occurs constitutively in the colorectal carcinoma cell lines during their growth in culture, in contrast to the transiently elevated levels of expression observed in normal cells which have been subjected to a mitogenic stimulus. The constitutively elevated expression of the c-myc protein in colorectal carcinoma cell lines is not typically accompanied by gross rearrangement or amplification of the gene.

The Impact of Destructive Insects on Reproduction in Six Species of Banksia L.f. (Proteaceae)

Six species of Banksia (Proteaceae) were examined at two study sites near Perth for insect larvae that destroy flowers and seed. All species, B. attenuata, B grandis, B. ilicifolia, B. littoralis, B. menziesii and B. telmatiaea, showed some damage to the conflorescence (flowering spike) while all except B, grandis and B. ilicifolia had damage to the infructescence (fruit). Six lepidopteran larvae and a curculionid larva damaged conflorescences, and five lepidopteran larvae and three curculionid larvae consumed seed. The insects were found only on Banksia and were mostly host-specific. The insects prevent about one-third of conflorescences from developing seed, but only one-third of the total conflorescences develop into infructescences. It is not known why the remaining one-third of conflorescences do not set seed. Insects destroy up to 60% of the follicles, which contain one or two seeds, on these infructescences. Examples of possible adaptations of the conflorescence and infructescence for avoiding this insect damage are suggested.

Selective Predation by White-Tailed Black Cockatoos on Fruit of Banksia Attenuata Containing the Seed-Eating Weevil Alphitopis Nivea

The cockatoo Calyptorhynchus funereus latirostris excavates the seed-eating weevil Alphitopis nivea from young fruits of Banksia attenuata trees but discards the immature seed. The birds attacked similar proportions of trees in 3 nearby areas that differed, due to previous histories of fires, in number of reproductive structures per tree. However, within areas the cockatoos attacked trees with larger numbers of fruits. In addition, the proportion of fruits containing weevils was greater in those fruits that the cockatoos attacked than in those they did not. The weevils mostly occurred in larger fruits and large size could be a clue enabling selection of fruits by the birds. The birds removed between 1 and 2 weevils per fruit, but if the weevils were absent the birds still destroyed follicles and often the whole fruit.

A comparison of measles and canine distemper virus polypeptides

The polypeptides induced by canine distemper virus (CDV) strains have been characterized by polyacrylamide slab gel electrophoresis of infected cell lysates labelled with 35S-methionine, 14C-amino acids, 3H-glucosamine and 3H-mannose, or 32P-orthophosphate. Seven virus-induced polypeptides have been asigned the following nomenclature and mol. wt.: a large polypeptide L (180,000); a large glycoprotein G (77,000); a nucleocapsid-associated protein P (73,000); the nucleocapsid protein N (60,000); the smaller glycoprotein F0 (59,000); a membrane protein M (35,000) and a small polypeptide S (15,000). During pulse-chase experiments with 3H-glucosamine and 14C-amino acids the intensity of the F0 band decreases and that of the F1 and F2 bands increases; the H polypeptide band becomes more diffuse and the S-protein disappears. The N- and P- but not the M-proteins have been found to be phosphorylated. The polypeptide pattern of the Onderstepoort strain of CDV has been compared with that of two other CDV and with 17 measles and subactue sclerosing panencephalitis (SSPE) strains. Differences in the mobilities of various polypeptides have been observed between CDV and measles and SSPE strains; however, the only consistent difference is the mol. wt. of the M-protein of CDV strains which is smaller by 2000 than that of MV and this may be a biochemical marker to distinguish CDV from measles and SSPE virus strains.

Comparison of cefamandole nafate to cefamandole by microbiological assay

Before microbiological assay, cefamandole nafate should be hydrolyzed for 1 h at 37 degrees C in pH 8 buffer (0.1 M) or for 30 min at room temperature in aqueous solutions containing 1.25 molar equivalents of sodium carbonate.

Diagnostic pneumoperitoneum

Pneumoperitoneum as a diagnostic procedure has been practised for many years but there is a reluctance to make use of it. The author believes that this is due in some degree to lack of clearly defined indications and partly to lack of confidence in the safety of the procedure. In this paper the technique of diagnostic pneumoperitoneum is described and the risks are examined. Indications for its use are described. Finally, three case histories of special relevance are described and a summary of the results is tabulated with a view of giving an estimate of the diagnostic value which may be expected.

Mechanical property changes of barium titanate (ceramic) after in vivo and in vitro aging

Since barium titanate (BaTi03) can be made piezoelectric, it may be used to substitute hard tissues directly. As a first step in testing this concept, a series of in vivo and in vitro aging and biocompatibility studies were performed. The mean compressive strength of samples implanted subcutaneously in the backs of rabbits decreased to 138 MPa after 20 weeks from a control value of 281 MPa. Similar, though less drastic losses of strength were seen when specimens were aged in distilled water (182 MPa at 28 weeks) and Ringer's solution (159 MPa at 28 weeks). The most rapid decrease of strength in all cases was seen prior to 4 weeks. Thereafter, the decrease was much slower. Histological evaluation of the tissue surrounding the implant revealed a thin fibrous capsule and no evidence of tissue inflammation.

S-carboxymethylcysteine in the fluidification of sputum and treatment of chronic airway obstruction

The clinical results and changes in sputum found in both a short-term inpatient trial and a subsequent long-term outpatient investigation (three-month double-blind controlled study) of 82 patients with chronic bronchitis treated with a new mucolytic agent, S-carboxymethylcysteine (Mucodyne), are reported. Fluidification of sputum with reduction in certain measurements of the viscosity of morning sputum aliquots, associated with improvement in the ability to cough up bronchial secretions, significant increase in sputum volume output, and improvement in ventilation (as estimated by the forced expiratory volume in one second), were observed in both trials as dose-related responses, with an increase in the ease of expectoration and a reduction in cough frequency and dyspnea. Therapy with S-carboxymethylcysteine was well tolerated, and there were no serious adverse effects, either immediate or delayed. We suggest that the effect of the drug in fluidifying sputum may be due to a mucoregulatory mechanism which reverses the sputum macromolecular disturbances seen in chronic bronchitis.

Surgical emphysema, bilateral pneumothorax, pneumomediastinum and pneumoperitoneum complicating intubation for anaesthesia

A combination of surgical emphysema, bilateral pneumothorax, pneumomediastinum and pneumoperitoneum complicating anaesthesia using endotracheal intubation has been reported only once before. Its occurrence twice in a recent period of 4 months at one hospital suggests that it may not be rare. Recognition of the early signs should enable steps to be taken before irreversible cerebral damage has occurred.