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At least 1,297 records · Page 72Linked to original sources
PubMed2003

A non-modular type B feruloyl esterase from Neurospora crassa exhibits concentration-dependent substrate inhibition.

Feruloyl esterases, a subclass of the carboxylic acid esterases (EC 3.1.1.1), are able to hydrolyse the ester bond between the hydroxycinnamic acids and sugars present in the plant cell wall. The enzymes have been classified as type A or type B, based on their substrate specificity for aromatic moieties. We show that Neurospora crassa has the ability to produce multiple ferulic acid esterase activities depending upon the length of fermentation with either sugar beet pulp or wheat bran substrates. A gene identified on the basis of its expression on sugar beet pulp has been cloned and overexpressed in Pichia pastoris. The gene encodes a single-domain ferulic acid esterase, which represents the first report of a non-modular type B enzyme (fae-1 gene; GenBank accession no. AJ293029). The purified recombinant protein has been shown to exhibit concentration-dependent substrate inhibition (K(m) 0.048 mM, K (i) 2.5 mM and V(max) 8.2 units/mg against methyl 3,4-dihydroxycinnamate). The kinetic behaviour of the non-modular enzyme is discussed in terms of the diversity in the roles of the feruloyl esterases in the mobilization of plant cell wall materials and their respective modes of action.

Amino Acid Sequence↗
PubMed1976

A statewide biomedical communications network for South Carolina.

In 1972, the Medical University of South Carolina was awarded a contract to establish 4 Area Health Education Centers in South Carolina. These centers, based in community hospitals, provide residency programs, clinical instruction for students, and continuing education programs for health professionals. In late 1974, contractual agreements between the Medical University of South Carolina's Library/Learning Resource Center and the Area Health Education Centers were negotiated to provide book and nonbook learning materials to all health practitioners in South Carolina. The history and the functions of the resulting network and evaluation of audiovisual and self-instructional learning materials procured and distributed by the network are described.

Area Health Education Centers↗
PubMed1976

Searching the literature and computerized services in ophthalmology.

The individual searching the literature of ophthalmology should not find this a time-consuming or frustrating activity. The basic guides to the literature are described, and methods for obtaining information are outlined. The value of orienting oneself to each guide before using it is stressed. Special attention in this communication is given to locating current material; however, guides for searching the older literature are presented also. Since several computerized searching services can be helpful, their programs are briefly described; addresses are given for current prices and additional information. Some of the online services may be accessible in your local or regional medical library. When you become conversant with these guides and methods you will be able to find more information than before, and you will be able to find it more quickly.

Abstracting and Indexing↗
PubMed1993

Prospects of using Drosophila for insect neuroendocrine research.

Classical and in vitro approaches for the analysis of the molecular components of neuroendocrine systems often disrupt their close interaction with other bodily systems, which is a crucial aspect of their function in vivo. "Genetic dissection" is an alternative, noninvasive approach which involves the systematic generation of mutations in individual genes, followed by in vivo analysis of the phenotypic effects of altering a single protein at a time avoiding extraneous disruptions. Among insects Drosophila melanogaster is the most suitable model for this approach. This paper explores the application of genetic and molecular techniques available in Drosophila for studying its neuroendocrine system with special emphasis on the production of ecdysone and juvenile hormone. Strategies are described for the generation and identification of endocrine mutations, especially those affecting hormone synthesis and regulation. Once identified by a specific mutation, a gene in Drosophila can be cloned either by chromosomal microdissection and "chromosomal walk" or by transposon tagging. Methods for molecular analysis of the structure and function of a cloned gene and of the protein it encodes are available for further study. Alternatively, a gene can be cloned using heterologous DNA probes or oligonucleotides designed according to the amino acid sequence of a protein. Genes may also be cloned via their pattern of expression (using stage- or tissue-specific cDNA libraries or through transposon-mediated "enhancer detection." Anti-sense RNA, the replacement of the gene by in vitro manipulated versions, or mutagenesis of its endogenous copies can then be used for studying its function in vivo. Information about endocrine genes in Drosophila as well as material such as cloned genes and antibodies should be useful for the analysis of endocrine systems in other insects which are not amenable to genetic manipulations. Such information should be helpful in designing novel means for pest control based on the specific intervention with endocrine systems regulating insect development and reproduction.

Animals↗
PubMed2005

Rapid identification of RoHS-relevant flame retardants from polymer housings by ultrasonic extraction and RP-HPLC/UV.

A rapid method was developed for the extraction and identification of RoHS-relevant organic flame retardants in polymer material. Extraction was carried out using ultrasonic supported solvent extraction (USSE) and isopropanol. HPLC separation was achieved using a reversed-phase phenylhexyl-modified column and methanol, containing 2-aminoethanol-buffered, alkaline water. Identification was carried out by scanning UV detection and comparison with a library assembled from spectra of reference substances. The method was used to extract and identify polymer additives in TV and PC monitor housings. The overall runtime required for extraction and chromatographic analysis is less than 10 min. The limits of detection comply with the recommendations set by the German draft law.

Chromatography, High Pressure Liquid↗
PubMed2004

Expanding the substrate repertoire of a DNA polymerase by directed evolution.

Nucleic acid polymerases are the most important reagents in biotechnology. Unfortunately, their high substrate specificity severely limits their applications. Polymerases with tailored substrate repertoires would significantly expand their potential and allow enzymatic synthesis of unnatural polymers for in vivo and in vitro applications. For example, the ability to synthesize 2'-O-methyl-modified polymers would provide access to materials possessing properties that make them attractive for biotechnology and therapeutic applications, but unfortunately, no known polymerases are capable of efficiently accepting these modified substrates. To evolve such enzymes, we have developed an activity-based selection method which isolates polymerase mutants with the desired property from libraries of the enzyme displayed on phage. In this report, mutants that could efficiently synthesize an unnatural polymer from 2'-O-methyl ribonucleoside triphosphates were immobilized and isolated by means of their activity-dependent modification of a DNA oligonucleotide primer attached to the same phage particle. In each case, directed evolution resulted in relocating a critical side chain to a different position in the polypeptide, thus re-engineering the overall active site while preserving critical protein-DNA interactions. Remarkably, one evolved polymerase is shown to incorporate the modified substrates with an efficiency and fidelity equivalent to that of the wild-type enzyme with natural substrates.

Amino Acid Sequence↗
PubMed2002

Synthetic hosts by monomolecular imprinting inside dendrimers.

Synthetic host systems capable of selectively binding guest molecules are of interest for applications ranging from separations and chemical or biological sensing to the development of biomedical materials. Such host systems can be efficiently prepared by 'imprinting' polymers or inorganic materials with template molecules, which, upon removal, leave behind spatially arranged functional groups that act as recognition sites. However, molecularly imprinted polymers have limitations, including incomplete template removal, broad guest affinities and selectivities, and slow mass transfer. An alternative strategy for moulding desired recognition sites uses combinatorial libraries of assemblies that are made of a relatively small number of molecules, interconverting in dynamic equilibrium; upon addition of a target molecule, the library equilibrium shifts towards the best hosts. Here we describe the dynamic imprinting of dendritic macromolecules with porphyrin templates to yield synthetic host molecules containing one binding site each. The process is based on our general strategy to prepare cored dendrimers, and involves covalent attachment of dendrons to a porphyrin core, cross-linking of the end-groups of the dendrons, and removal of the porphyrin template by hydrolysis. In contrast to more traditional polymer imprinting, our approach ensures nearly homogeneous binding sites and quantitative template removal. Moreover, the hosts are soluble in common organic solvents and amenable to the incorporation of other functional groups, which should facilitate further development of this system for novel applications.

Benzene↗
PubMed1994

Isolation and characterization of the principal ATPase associated with transitional endoplasmic reticulum of rat liver.

The transfer of membranes from the endoplasmic reticulum to the Golgi apparatus occurs via 50-70 nm transition vesicles which derive from part-rough, part-smooth transitional elements of the endoplasmic reticulum (TER). Vesicle budding from the TER is an ATP-dependent process both in vivo and in vitro. An ATPase with a monomer molecular weight of 100 kD by SDS-PAGE has been isolated from TER and designated as TER ATPase. The native TER ATPase has been characterized as a hexamer of six 100-kD subunits by gel filtration. The protein catalyzes the hydrolysis of [gamma 32-P]ATP and is phosphorylated in the presence of Mg2+. It is distinct from the classical transport ATPases based on pH optima, ion effects, and inhibitor specificity. Electron microscopy of negatively stained preparations revealed the TER ATPase to be a ring-shaped structure with six-fold rotational symmetry. A 19-amino acid sequence of TER ATPase having 84% identity with valosin-containing protein and 64% identity with a yeast cell-cycle control protein CDC48p was obtained. Anti-synthetic peptide antisera to a 15-amino acid portion of the sequence of TER ATPase recognized a 100-kD protein from TER. These antisera reduced the ATP-dependent cell-free formation of transition vesicles from isolated TER of rat liver. In a reconstituted membrane transfer system, TER ATPase antisera inhibited transfer of radiolabeled material from endoplasmic reticulum to Golgi apparatus, while preimmune sera did not. The results suggest that the TER ATPase is obligatorily involved in the ATP requirements for budding of transition vesicles from the TER. cDNA clones encoding TER ATPase were isolated by immunoscreening a rat liver cDNA library with the affinity-purified TER ATPase antibody. A computer search of deduced amino acid sequences revealed the cloned TER ATPase to be the rat equivalent of porcine valosin-containing protein, a member of a novel family of ATP binding, homo-oligomeric proteins including the N-ethylmaleimide-sensitive fusion protein.

Adenosine Triphosphatases↗
PubMed1994

An integrated YAC-overlap and 'cosmid-pocket' map of the human chromosome 21.

We describe here the construction of an ordered clone map of human chromosome 21, based on the identification of ordered sets of YAC clones covering > 90% of the chromosome, and their use to identify groups of cosmid clones (cosmid pockets) localised to subregions defined by the YAC clone map. This is to our knowledge the highest resolution map of one human chromosome to date, localising 530 YAC clones covering both arms of the chromosome, spanning > 36 Mbp, and localising more than 6300 cosmids to 145 intervals on both arms of the chromosome. The YAC contigs have been formed by hybridising a 6.1 equivalents chromosome 21 enriched YAC collection displayed on arrayed nylon membranes to a series of 115 DNA markers and Alu-PCR products from YACs. Forty eight mega-YACs from the previously published CEPH-Genethon map of sequence tagged sites (STS) have also been included in the contig building experiments. A YAC tiling path was then size-measured and confirmed by gel-fingerprinting. A minimal tiling path of 70 YACs were then used as probes against the 7.5 genome equivalents flow sorted chromosome 21 cosmid library in order to identify the lists of cosmids mapping to alternating shared--non-shared intervals between overlapping YACs ('cosmid pockets'). For approximately 1/5 of the minimal tiling path of YACs, locations and non-chimaerism have been confirmed by fluorescence in situ hybridisation (FISH), and approximately 1/5 of all cosmid pocket assignments have independent, confirmatory marker hybridizations in the ICRF cosmid reference library system. We also demonstrate that 'pockets' contain overlapping sets of cosmids (cosmid contigs). In addition to being an important logical intermediate step between the YAC maps published so far and a future map of completely ordered cosmids, this map provides immediately available low-complexity cosmid material for high resolution FISH mapping of chromosomal aberrations on interphase nuclei, and for rapid positional isolation of transcripts in the highly resolved regions of genetic interest.

Chromosome Mapping↗
PubMed1995

Expression cloning of cDNAs that render cancer cells resistant to Pseudomonas and diphtheria toxin and immunotoxins.

BACKGROUND: Several immunotoxins in which antibodies are coupled to plant or bacterial toxins are now in clinical trials for the treatment of cancer. One of these is B3-LysPE38 in which MAb B3 which reacts with many human cancers, is coupled with a genetically modified form of Pseudomonas exotoxin (PE). MATERIALS AND METHODS: To investigate how cells can become resistant to PE-derived immunotoxins, we constructed an immunotoxin-sensitive MCF-7 breast cancer cell line that contains SV40 T antigen and allows episomal replication of SV40 origin containing plasmids. We transfected a pCDM8/HeLa cDNA expression library into these cells, thereby causing over-expression of the plasmid-encoded genes. The transfected cells were treated with immunotoxin to select for resistance-mediating plasmids, which were reisolated from these cells and amplified in Escherichia coli. The resulting plasmid pool was transfected into cells for two further rounds of selection and plasmid reisolation. RESULTS: Several plasmids that caused immunotoxin resistance were enriched by this selection procedure. Four plasmids were stably transfected into MCF-7 cells and found to increase their resistance to PE-derived immunotoxins by 5- to 20-fold. These plasmids also confer resistance to native PE and to diphtheria toxin but not to ricin or cycloheximide. Thus, they appear to specifically interfere with the action of ADP-ribosylating toxins. CONCLUSION: Cancer cells can become resistant to immunotoxins by deregulated expression of normal genes. The clinical significance of this type of resistance will be evaluated in clinical trials.

ADP Ribose Transferases↗
PubMed1991

Health professionals' use of documents obtained through the Regional Medical Library Network.

The Pacific Southwest Regional Medical Library Service (PSRMLS) studied how health professionals use documents obtained through the regional medical library (RML) network and how various factors, such as delivery time, affected that use. A random sample of libraries in Region 7 of the RML network was selected to survey health professionals who had received documents through the interlibrary loan (ILL) network. The survey provided data about the purposes for which health professionals requested documents, how the immediacy of need for the items affected their usefulness, what effect the obtained information had on the health professionals' work, and whether the illustrations represented an important part of the information content of the items. Survey results provided a positive assessment of the ILL network. Results also verified the basic value of the materials provided to health professionals through ILL and identified some areas for consideration in future network development. Users of the documents indicated that the network works efficiently and effectively to provide timely and useful information needed by health professionals. Technological developments in electronic information transmission and imaging will further enhance network operation in the future.

Health Occupations↗
PubMed2004

Research on the value of medical library services: does it make an impact in the health care literature?

OBJECTIVE: To evaluate the impact in the health care literature of research articles that provided evidence of the value of library services (including MEDLINE) as an element of quality health care. DATA SOURCES/SELECTION: Four research articles on the relationship between use of library services and quality health care were selected as "primary articles" from a MEDLINE search using appropriate Medical Subject Heading. Primary articles met the following criteria: written in English, reported research, related to clinical care, and published before 1995. DATA EXTRACTION: The technique of citation analysis was used to measure the impact of the primary articles on the subsequent literature. The number, authorship, type, and publication venue of articles citing the primary articles were determined using ISI Web of Science, MEDLINE, other electronic resources, and the citing articles themselves. For the 146 English-language citing articles, the article type (i.e., advocacy, instructional, research) was noted; and, for those that reported research, the use to which the author put the cited material was determined. RESULTS: The primary articles were cited more often than the average articles published that year in the same journals. At the time of the study each article had been cited almost every year since publication. Of the 146 citing articles written in English, 43% were written by librarians, 38% by physicians, 12% by librarians with physicians. The majority were published in medical journals, followed in order of decreasing frequency by the Bulletin of the Medical Library Association, information science journals, and health administration journals. CONCLUSIONS: The results of this study demonstrate that published research on the value of medical library services has an impact on the literature. These articles are read and cited and continue to be of value.

Authorship↗
PubMed2004

Effect of TERT and ATM on gene expression profiles in human fibroblasts.

Telomeres protect chromosomes from degradation, end-to-end fusion, and illegitimate recombination. Loss of telomeres may lead to cell death or senescence or may cause genomic instability, leading to tumor formation. Expression of human telomerase reverse transcriptase (TERT) in human fibroblast cells elongates their telomeres and extends their lifespan. Ataxia telangiectasia mutated (ATM) deficiency in A-T human fibroblasts results in accelerated telomere shortening, abnormal cell-cycle response to DNA damage, and early senescence. Gene expression profiling was performed by serial analysis of gene expression (SAGE) on BJ normal human skin fibroblasts, A-T cells, and BJ and A-T cells transduced with TERT cDNA and expressing telomerase activity. In the four SAGE libraries, 36,921 unique SAGE tags were detected. Pairwise comparisons between the libraries showed differential expression levels of 1%-8% of the tags. Transcripts affected by both TERT and ATM were identified according to expression patterns, making them good candidates for further studies of pathways affected by both TERT and ATM. These include MT2A, P4HB, LGALS1, CFL1, LDHA, S100A10, EIF3S8, RANBP9, and SEC63. These genes are involved in apoptosis or processes related to cell growth, and most have been found to be deregulated in cancer. Our results have provided further insight into the roles of TERT and ATM by identifying genes likely to be involved in their function. Supplementary material for this article can be found on the Genes, Chromosomes and Cancer website at http://www.interscience.wiley.com/jpages/1045-2257/suppmat/index.html.

Ataxia Telangiectasia↗
PubMed1999

Toward controlling gene expression at will: selection and design of zinc finger domains recognizing each of the 5'-GNN-3' DNA target sequences.

We have taken a comprehensive approach to the generation of novel DNA binding zinc finger domains of defined specificity. Herein we describe the generation and characterization of a family of zinc finger domains developed for the recognition of each of the 16 possible 3-bp DNA binding sites having the sequence 5'-GNN-3'. Phage display libraries of zinc finger proteins were created and selected under conditions that favor enrichment of sequence-specific proteins. Zinc finger domains recognizing a number of sequences required refinement by site-directed mutagenesis that was guided by both phage selection data and structural information. In many cases, residues not expected to make base-specific contacts had effects on specificity. A number of these domains demonstrate exquisite specificity and discriminate between sequences that differ by a single base with >100-fold loss in affinity. We conclude that the three helical positions -1, 3, and 6 of a zinc finger domain are insufficient to allow for the fine specificity of the DNA binding domain to be predicted. These domains are functionally modular and may be recombined with one another to create polydactyl proteins capable of binding 18-bp sequences with subnanomolar affinity. The family of zinc finger domains described here is sufficient for the construction of 17 million novel proteins that bind the 5'-(GNN)6-3' family of DNA sequences. These materials and methods should allow for the rapid construction of novel gene switches and provide the basis for a universal system for gene control.

Animals↗
PubMed1992

A survey of expressed genes in Caenorhabditis elegans.

As an adjunct to the genomic sequencing of Caenorhabditis elegans, we have investigated a representative cDNA library of 1,517 clones. A single sequence read has been obtained from the 5' end of each clone, allowing its characterization with respect to the public databases, and the clones are being localized on the genome map. The result is the identification of about 1,200 of the estimated 15,000 genes of C. elegans. More than 30% of the inferred protein sequences have significant similarity to existing sequences in the databases, providing a route towards in vivo analysis of known genes in the nematode. These clones also provide material for assessing the accuracy of predicted exons and splicing patterns and will lead to a more accurate estimate of the total number of genes in the organism than has hitherto been available.

Animals↗
PubMed2003

Ceramic inlays for restoring posterior teeth.

BACKGROUND: In recent decades ceramic inlays have been used with the increasing requirements from patients for tooth-coloured restorations in posterior teeth. Ceramic inlays can offer an excellent appearance, however, their long-term prognosis is uncertain, as only a few studies have reported the long-term clinical performance of these restorations. OBJECTIVES: To compare the effectiveness of ceramic inlays in posterior teeth with other posterior restorations. SEARCH STRATEGY: We conducted an electronic search of the Cochrane Oral Health Group Trials Register, the Cochrane Central Register of Controlled Trials ( The Cochrane Library Issue 1, 2002), MEDLINE, and EMBASE from 1990 to 2001. Handsearching included relevant journals and bibliographies of all relevant papers and review articles from 1990 up to 2001. In addition, we contacted experts and companies conducting clinical research on ceramic restorations to find other trials or unpublished materials or to clarify ambiguous or missing data. SELECTION CRITERIA: Randomized controlled trials, in which the longevity of ceramic inlays is compared with those of other posterior restorations. DATA COLLECTION AND ANALYSIS: Screening of possible studies and data extraction were independently conducted by two reviewers (MH and AY) using a specially designed chart. Authors of studies were contacted for additional information. The methodological quality of studies was assessed in duplicate using individual components. The Cochrane Oral Health Group statistical guidelines were followed and the results expressed as Odds Ratio (OR) and 95% confidence interval for dichotomous outcomes. MAIN RESULTS: Two studies fulfilled the criteria to be included in the review. However, one of them was later excluded from the review, as the study design was not clearly described. The remaining, included study, evaluated the clinical performance of 60 ceramic inlays and 20 gold inlays for five years. Seven of the 60 ceramic inlays and two of the 20 gold inlays failed at five-year review. No ceramic inlays resulted in postoperative pain/discomfort after the treatment, however, one gold inlay did. The power of the included study was not great enough to detect an important difference in longevity and postoperative pain/discomfort between ceramic and gold inlays. REVIEWER'S CONCLUSIONS: There is no strong evidence available to support any differences in the clinical performance of ceramic inlays and other posterior restorations. There is a limited number of well-designed clinical trials within this research area. Greater attention to the design and reporting of studies should be given to improve the study quality of ceramic restoration trials.

Ceramics↗
PubMed1984

A 'hidden line' algorithm for 3D-reconstruction from serial sections--an extension of the NEUREC program package for a microcomputer.

An algorithm is described to generate pictures in arbitrary perspective from serially sectioned biological material. Only those parts of the object which lie on a direct line of sight to the observer are included into the computed paper-plot, while hidden lines are omitted. The program was written for an inexpensive Apple II+ microcomputer as an extension of an earlier program library (NEUREC) for three-dimensional reconstruction. Application examples of neuronal and cardiac tissues are presented.

Animals↗
PubMed1987

A DNA probe to distinguish the species Anopheles quadriannulatus from other species of the Anopheles gambiae complex.

DNA probes used previously to distinguish the species Anopheles gambiae sensu stricto, An.arabiensis, An.melas and An.merus were tested against An.quadriannulatus. Using these DNA probes, An.gambiae s.s. and An.quadriannulatus were indistinguishable. A genomic library was constructed for An.quadriannulatus. Differential screening of this genomic library with An.gambiae s.s. and An.quadriannulatus genomic DNAs identified a species-specific, repeated DNA sequence. When used as a hybridization probe, this DNA sequence clearly distinguished An.gambiae s.s. from An.quadriannulatus. A simplified protocol for the use of DNA probes is described which may be used to identify material squashed directly on to nitrocellulose filter paper.

Animals↗