• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 947
  • 334
  • 334
  • 334
  • 334
  • 334
  • 333
  • 181
  • 99
  • 20
  • 1
  • Tagged with
  • 1723
  • 1723
  • 393
  • 229
  • 220
  • 175
  • 175
  • 175
  • 174
  • 154
  • 83
  • 62
  • 60
  • 59
  • 56
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

STRUCTURE AND REVERSE TRANSCRIPTION OF THE DOUBLE-STRANDED-RNA OF A SUPERKILLER YEAST

Unknown Date (has links)
Killer strains of Saccharomyces cerevisiae secrete a toxin which kills sensitive strains. The toxin and immunity are encoded by a cytoplasmically inherited double-stranded (ds) RNA plasmid 1.8 kbp in length designated M. Nearly all strains of S. cerevisiae contain another dsRNA 4.8 kbp in length designated L. Killer strains always contain L and M. / This study describes the discovery and characterization of four new species of dsRNA in the superkiller strain, T158C. The new species were found to be 1.4, 1.2, 1.1 and 0.9 kbp in length. Growth at elevated temperature resulted in the loss of the four additional species as well as the M dsRNA. Northern hybridization analysis demonstrated that the extra components possess sequence homology to M. / Analysis of polyadenylate enriched (+poly A) single-stranded (ss)RNA preparations from T158C by Northern "dot" hybridization demonstrated the presence of ssRNA that is complementary to dsRNA. Single-stranded RNA homologous to L and M was found to represent about 1.0% and 5.0% of the +poly A RNA, respectively. / A further analysis of the killer system was made by the use of the four oligodeoxyribonucleotide primers oligo dT(,12-18), oligo dA(,12-18), oligo dG(,12-18), and oligo dC(,12-18) as primers for avian myeloblastosis virus reverse transcriptase using denatured dsRNA as templates. Oligo dT and oligo dA were found to prime the synthesis of 1.1 kb, and 1.0 kb reverse transcripts, respectively, using denatured M dsRNA as a template. The oligo dT and oligo dA primed cDNAs of M dsRNA hybridized to the region of the M dsRNA that encodes the killer toxin and to each other. Addition of oligo dT to reverse transcription reactions of denatured L dsRNA produced a 4.3 kb cDNA. / During the course of this investigation oligo dC was observed to be a highly efficient primer for reverse transcription of yeast 18S ribosomal RNA. Oligo dC primed the synthesis of a 1.0 kb reverse transcript of 18S rRNA which hybridized to the large Eco RI fragment of the yeast 18S rRNA gene cluster which contains the 5'-terminus of the mature 18S rRNA. / Source: Dissertation Abstracts International, Volume: 43-07, Section: B, page: 2104. / Thesis (Ph.D.)--The Florida State University, 1982.
12

MULTIPLE FORMS OF BETA-GALACTOSIDASE IN NEUROSPORA CRASSA

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 30-05, Section: B, page: 2036. / Thesis (Ph.D.)--The Florida State University, 1969.
13

DNA REPAIR IN HAEMOPHILUS INFLUENZAE

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 40-09, Section: B, page: 4115. / Thesis (Ph.D.)--The Florida State University, 1979.
14

MEMBRANE FUNCTION IN CYSTIC FIBROSIS: CHARACTERIZATION OF A CYSTIC FIBROSIS FACTOR FRACTIONATED FROM FIBROBLAST MEDIA WITH RESPECT TO THE EFFLUX OF PUTRESCINE

Unknown Date (has links)
In this study, a polycationic substance which is produced by cystic fibrosis fibroblasts and secreted into the growth medium has been identified and characterized with respect to its action on the efflux of putrescine from normal fibroblasts. Comparison of medium extracts from various cystic fibrosis homozygotes, heterozygotes and where possible normal fibroblasts from family groups have been undertaken in order to determine the relationship of this factor to the putative abnormal gene in cystic fibrosis. Physiological characterization of the factor secret-by cystic fibrosis homozygotes into fibroblast medium with respect to its effect on putrescine efflux in normal fibroblasts, including comparisons with the known membrane active substance polygalactosamine, has been pursued in order to delineate the possible role of cystic fibrosis factor in the pathophysiology of the disease. / The cystic fibrosis factor from medium is capable of causing the efflux of exogenously supplied putrescine. This activity is enhanced in the presence of extracellular calcium. Efflux of exogenously supplied putrescine is used as a bioassay for the cystic fibrosis factor. The putrescine efflux assay can be used as a quantitative bioassay for the cystic fibrosis factor. The response of the cystic fibrosis factor in the presence of calcium distinguishes it from polygalactosamine. The cystic fibrosis factor is found in medium from all homozygote and heterozygote cell lines tested but not in media from normal cell lines. It is proposed that the ability of the cystic fibrosis factor to alter the membrane permeability of cells and allow influx of extracellular calcium may be the underlying lesion which expresses itself phenotypically as cystic fibrosis. A model for the mode of action of the cystic fibrosis factor is presented. / Source: Dissertation Abstracts International, Volume: 41-03, Section: B, page: 0819. / Thesis (Ph.D.)--The Florida State University, 1980.
15

THE NUCLEOTIDE SEQUENCE AND EVOLUTIONARY IMPLICATIONS OF ASPARTIC ACID TRANSFER-RNA FROM THE CHLOROPLAST OF EUGLENA GRACILIS

Unknown Date (has links)
The nucleotide sequence of aspartic acid tRNA from the chloroplast of Euglena gracilis has been determined. In resembling prokaryotic tRNA, the sequence of the chloroplast tRNA('asp) represents additional evidence in support of the prokaryotic endosymbiotic theory of the origin of the chloroplast. The accuracy of this sequence determination has been buttressed by the independent use of two techniques, conventional angular mobility shift analysis and the recently developed rapid print-readout method. Further, these methods have been combined in a novel approach to support the proposed sequence. / Source: Dissertation Abstracts International, Volume: 41-12, Section: B, page: 4380. / Thesis (Ph.D.)--The Florida State University, 1980.
16

A KCL EXTRACTABLE L- AMINO ACID OXIDASE FROM NEUROSPORA CRASSA

Unknown Date (has links)
An L-amino acid oxidase is extracted from whole Neurospora crassa conidia when they are treated with saturated (4.8 M) KCL. This procedure preferentially extracts cell surface molecules, many of which are components of the amino acid transport system and leaves the cells completely viable. / The L-amino acid oxidase has a molecular weight of 160,000 daltons by gel filtration chromatograhy and 85,000 daltons by SDS polyacrylamide gel electrophoresis. The oxidase is sensitive to zinc ions, and not to the sulfhydryl reagent, iodoacetic acid. The neutral (N) amino acid transport system in Neurospora crassa is also sensitive to zinc ions. The similarity between the concentration dependence of zinc inhibition of the oxidase and the transport system suggests that the oxidase may be involved in the membrane-mediated transport process. / Source: Dissertation Abstracts International, Volume: 41-11, Section: B, page: 4003. / Thesis (Ph.D.)--The Florida State University, 1980.
17

BIOCHEMICAL CHARACTERIZATION OF SEROLOGICALLY-DEFINED RABBIT HEAVY CHAIN VARIABLE REGION ALLOTYPES OF THE A AND Y SUBGROUPS (IMMUNOGLOBULIN, IDIOTYPE, PEPTIDE MAPPING)

Unknown Date (has links)
Structural studies on the serologically-defined rabbit VHa('+) (a1, a2, and a3) and VHa('-) (y33,30 and y33,-) immunoglobulins have been performed in order to establish that these genetic markers reflect the presence of different primary gene products. In addition, biochemical studies were carried out on induced non-a2 anti-a1-reactive molecule in order to determine whether these molecules represent latent allotypes or are an internal image idiotype. / Initially, allotype-defined heavy chains were prepared from the affinity-purified IgG molecules. These were then subjected to tryptic digestion and were analyzed by HPLC. Approximately 38-40 distinct peptides were resolved from each heavy chain, of which about 30 peptides were derived from Fc fragment (CH2 and CH3) and 8-10 peptides were derived from Fd region (VH1 and CH1). Seven Fd peptides were shared by all VHa('+) and VHa('-) heavy chains. Each of the a1 and the a2 digests had one allotype-specific peptide (in addition to the common peptides), whereas no allotype-specific peptides were observed for a3 heavy chain. No differences were detected between y33,30 and y33,- peptides, however, both expressed a common y-specific peptide. / Comparison of the nominal a1 digest with non-a2 anti-al-reactive heavy chain digest revealed that non-a2 anti-a1-reactive molecule expressed an a1-specific peptide. This observation, together with previous immunoelectron microscopic data, suggests that non-a2 anti-a1-reactive molecule are possibly latent a1 allotype. / Amino acid analyses of the isolated a1 and y-specific peptides indicate that the y-specific peptide is very similar to the first 19 N-terminal amino acid residues of the previously reported pooled VHa('-) molecule (e.g., the two peptides matched at 16 residues out of 19 residues). The a1-specific peptide was very similar (except one extra amino acid) to the N-terminal 10 amino acid residues of the VHa1 molecule. These data indicate that both a1 and y-specific peptides are located in the first VH framework region. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0052. / Thesis (Ph.D.)--The Florida State University, 1984.
18

GENES OF THE RABBIT VH SUBGROUP III

Unknown Date (has links)
The rabbit VH region has been the subject of extensive and continued serological and biochemical analysis during the past three decades. Four VH subgroups (a, x, y, w) have been characterized, each of which displays a distinct set of allelic products (allotypes). However, despite years of study, certain basic phenomena associated with VH allotype expression remain unexplained. For these, and other reasons we have undertaken the analysis of the rabbit VH gene complex at the level of the DNA. / In this report, we present the sequence of a rabbit VH gene (pRVH831), which was selected from a rabbit genomic library using the mouse VH gene, pS107V1, as a cross-species hybridization probe. Our analysis reveals that pRVH831 is a highly defective VH pseudogene. It contains three deletions toward the 3' end, which cause a frameshift mutation in FR3 and cripple the D region splice site. / We have determined that pRVH831 is a member of the VH subgroup III. When used as a probe in filter hybridization experiments pRVH831 reveals 10-15 VH subgroup III genes, a number consistent with results obtained in human and murine systems. Furthermore, our analysis of the predicted translational product of pRVH831 confirms that at least some rabbit VHa-negative genes are members of the VH subgroup III. We have also examined genomic DNA obtained from pedigreed rabbits of different VH haplotypes. These data reveal haplotype specific hybridization patterns and support previous indications that recombination in the rabbit VH gene complex is extremely rare. / When the sequence of pRVH831 was analysed for internal repetitiveness, three similar copies (73-90%) of a 14-15 bp sequence were detected. These sequences are located in FR1, CDR1, and CDR2. Our analysis indicates that this repeat is homologous to a portion of a primordial VH sequence. However, this is also the same sequence which appears in the human D minigenes and in some CDR2s. We have determined that this sequence occurs in many VH genes, T cell receptor genes, and can contain Chi and Chi-like recombination sequences from lambda phage. / Source: Dissertation Abstracts International, Volume: 46-01, Section: B, page: 0056. / Thesis (Ph.D.)--The Florida State University, 1984.
19

A comparative analysis of a major repeat DNA sequence prevalent among Anatidae (waterfowl)

Unknown Date (has links)
The evolution of a 190 bp tandemly organized, highly repeated DNA sequence (AMR), prevalent among Anatidae (waterflow), was extensively studied. Monomeric units of the AMR repeat family were cloned and sequenced from the American Merganser (Mergus merganser), Barrows Goldeneye (Bucephela islandica), Comb Duck (Sarkidiornis melanotos), North American Wood Duck (Aix sponsa) and Mallard (Anas platyrhynchos). Data provided from intra and interspecific sequence comparisons was analyzed with respect to the modes of evolution previously proposed for other non-avian repeat families. To estimate the importance of primary DNA structure with regard to function and evolution, the AMR sequence was compared to three different nonhomologous, tandemly organized, highly repetitive DNA sequences. These repeat sequences were isolated from the Blue Fronted Amazon (Amazona aestiva), Goffins Cockatoo (Cacatua goffini) and Flamingo (Phoenicopterus indus). / Source: Dissertation Abstracts International, Volume: 51-09, Section: B, page: 4171. / Major Professor: Siwo R. de Kloet. / Thesis (Ph.D.)--The Florida State University, 1990.
20

THE BIOSYNTHESIS OF HIGH MOLECULAR WEIGHT RIBOSOMAL AND HETEROGENEOUS RIBONUCLEIC ACID IN EUKARYOTES

Unknown Date (has links)
Source: Dissertation Abstracts International, Volume: 32-11, Section: B, page: 6228. / Thesis (Ph.D.)--The Florida State University, 1971.

Page generated in 0.0858 seconds