Biomedical subjects

J G Spanier

Publications and source records attributed to J G Spanier.

10 recordsLinked to original sources

PubMed1998

Randomly amplified polymorphic DNA PCR analysis of bovine Cryptosporidium parvum strains isolated from the watershed of the Red River of the North.

Cryptosporidium parvum is a protozoan parasite that causes the disease cryptosporidiosis in a variety of mammals, including neonatal calves and humans. Millions of oocysts are shed during acute cryptosporidiosis, and zoonotic transmission is inferred, though not proven, to be a general phenomenon. Very little is known about the degree of strain variation exhibited by bovine and human isolates, though such knowledge would enable the amount of bovine-to-human transmission to be more precisely analyzed. This research was initiated to determine whether variations exist among bovine strains isolated from a localized geographic area, the watershed of the Red River of the North. Sixteen strains were isolated and compared to each other and to two human and two calf strains from Australia by randomly amplified polymorphic DNA PCR. A statistical analysis of the data indicated that the isolates belonged to four different groups of strains.

Animals↗

PubMed1995

Isolation and characterization of Pioneer1, a novel Chlamydomonas transposable element.

During the course of this study a novel family of Chlamydomonas mobile elements has been identified in natural isolate strain 224. The first member of this class to be characterized, a 2.8-kb element named Pioneer1, was trapped in an intron of the nitrate reductase structural gene, NIT1. This element has been cloned and completely sequenced and found to be unusual in structure. Pioneer elements are present in a very low-copy number of three per genome in strain 224. The copy number increased by one upon transposition of Pioneer1. Hybridization of Pioneer1 to a variety of Chlamydomonas strains confirmed that this element differed from previously described Chlamydomonas transposons. It also indicated that related elements are present in low-copy number in natural isolate strains 356 and S1D2, but not in the most commonly used laboratory strains 137c and 21 gr. For these reasons, members of the Pioneer family might prove useful as insertional mutagens.

Animals↗

PubMed1989

Nucleus-basal body connector in Chlamydomonas: evidence for a role in basal body segregation and against essential roles in mitosis or in determining cell polarity.

In the unicellular biflagellate green alga Chlamydomonas reinhardtii each basal body is linked to the nucleus by a fibrous nucleus-basal body connector (NBBC) that contains the calcium-binding protein centrin. (Wright et al.: Journal of Cell Biology 101:1903-1912.; Salisbury et al.: Journal of Cell Biology 107:635-642; Huang et al.: Journal of Cell Biology 107:121-131). In order to explore the cellular function of the NBBC we used antiserum directed against centrin to examine a number of mutants known to be defective for basal body assembly and/or localization. Of three variable flagella-number mutants examined, one, vfl-2, is dramatically defective with respect to the NBBC in that 1) the union between basal bodies and nucleus is very labile, 2) there is no detectible centrin in the NBBC region, and 3) total cellular centrin levels are reduced 75-80% relative to wild type. The existence of these defects in a mutant incapable of maintaining normal flagellar number supports the view that the NBBC plays an important role in determining proper basal body localization and/or segregation. In contrast to vfl-2, the mutants vfl-1, vfl-3, uni-1, and bald-2 contain approximately normal levels of centrin and possess stable NBBCs. The observation of NBBCs in the mutant bald-2, which lacks all but very rudimentary basal bodies, indicates that the assembly of the NBBC does not require fully formed basal bodies and that such assembly may not require basal bodies at all. Finally, the possibility that the NBBC is required for induction of gene expression following deflagellation was tested by examining vfl-2 for such induction. Results indicate that the connector does not play a necessary role in the induction process.

Animals↗

PubMed1987

Streptococcus pyogenes type 12 M protein gene regulation by upstream sequences.

A partial nucleotide sequence that included 1,693 base pairs of the M12 (emm12) gene of group A streptococci (strain CS24) and adjacent upstream DNA was determined. Type 12 M protein-specific mRNA of strain CS24 is transcribed from two promoters (P1 and P3) separated by 30 bases. The transcription start sites of the emm12 gene were located more than 400 bases downstream of a deletion that causes decreased M-protein gene transcription in strain CS64. Deletion analysis of M protein-expressing plasmids indicated that an upstream region greater than 1 kilobase is required for M-protein gene expression. The M-protein gene transcriptional unit appears to be monocistronic. Analysis of the emm12 DNA sequence revealed three major repeat regions. Two copies of each repeat, A and B, existed within the variable 5' end of the gene; repeat C demarcated the 5' end of the constant region shared by emm12 and emm6.

Antigens, Bacterial↗

PubMed1985

Integration of bacteriophage SP24 into the chromosome of group A streptococci.

The group A streptococcal bacteriophage SP24 contains a unique phage att site and integrates into a common chromosomal locus in two unrelated group A streptococcal strains, CS24 and CS112. Southern blot analysis suggested that the terminally redundant phage DNA recombines to form the unit-length genome observed in the prophage state. Phage DNA integration appears to be required for stable lysogen formation and conversion to the M+ state; however, the precise role of the bacteriophage and the relationship of phage integration to increased M protein synthesis are unclear.

Antigens, Bacterial↗

PubMed1984

Small DNA deletions creating avirulence in Streptococcus pyogenes.

The M protein is the antigen on the surface of group A streptococci that allows these bacteria to resist phagocytosis. DNA encoding the M12 protein was cloned into Escherichia coli and used as an isotopically labeled hybridization probe to compare genomic DNA's isolated from M+ and M- isogenic cultures in an effort to elucidate the genetic basis of this variation. DNA's from two spontaneous, independent M- variants contained small (approximately 50 base pairs) deletions which were mapped to identical restriction fragments within or adjacent to the M protein coding sequence. Taken together with the pleiotropic nature of these deletions, this suggests that they define a regulatory switch.

Antigens, Bacterial↗

PubMed1983

A restriction map and analysis of the terminal redundancy in the group a streptococcal bacteriophage SP24.

The DNA isolated from the group A streptococcal bacteriophage SP24 is a linear double-stranded molecule 42.0 kb in length. The DNA has been characterized by electron microscopy, and by agarose gel electrophoresis after cleavage with the restriction endonucleases SalI, BglII, XbaI, PvuI, HindIII, and BamHI. Analysis of SalI digests indicates that two fragments are present in submolar amounts and exist as a subset of sequences present in another SalI fragment. Moreover, overlapping endonuclease fragments suggested that the physical map is circular. This was confirmed when homoduplex phage DNA revealed circular structures with single-stranded tails that were 7.7% of the circumference of the genome length molecule. Tails were observed to be separated by as much as 42% of the circular homoduplex structure. These results indicate that the phage SP24 genome is terminally redundant and circularly permuted; and the data are consistent with a model in which DNA packaging into phage heads is initiated at a specific site on concatermeric DNA and proceeds sequentially to package up to five "headfuls" of DNA per concatemer.

Bacterial Proteins↗

PubMed1983

A DNA substitution in the group A streptococcal bacteriophage SP24.

When the group A streptococcal bacteriophage SP24 was propagated on an unrelated host strain CS112, it underwent a DNA rearrangement: the rearrangement involved a substitution of unique DNA (2.5 kb) from an unrelated endogenous prophage carried by strain CS112. This substitution event occurred reproducibly upon infection of strain CS112, as DNAs from a number of independent isolates were found to contain similar, but not identical, DNA sequences. Restriction endonuclease mapping suggested that recombination between homologous sequences shared by the infecting phage and the prophage produced the rearrangement. The recombinant phage was shown to adsorb more rapidly to CS112 cells than did wild type SP24 phage particles: It therefore has a selective advantage during multiple rounds of infection.

Adsorption↗

PubMed1980

Bacteriophage control of antiphagocytic determinants in group A streptococci.

At least two genes have been shown to be required for the expression of the antiphagocytic M protein molecule in group A streptococci. Evidence for phage involvement in the expression of M protein is that: (a) M- cultures of bacteria can be converted to the M+ state (resistant to phagocytosis) upon lysogenization with appropriate bacteriophages; (b) without those bacteriophages the M- recipient culture could not be detected to revert to the M+ state, even under our most stringent selective conditions; and (c) stable M+ lysogens cured of their bacteriophages returned to the M- state. Immunochemical analysis of lysogenically converted M+ strains demonstrated that they contain precipitating and antiphagocytic determinants of the parental M-76 strain (CS110) rather than M-12 determinants expressed by the phage donor strain. This information strongly suggests that the M- strain CS112 possesses the structural gene for M protein, but that it remains predominantly unexpressed. Quantitation of the M antigen produced by these strains supports the observation that the M- phage-recipient strain possesses a small amount of extractable M antigen and that phage activates its synthesis by some unknown mechanism. Various possibilities to account for the phage requirement in M protein synthesis and its role in the transition between M+ and M- states are discussed.

Antigens, Surface↗

PubMed1977

Bacteriophages of Streptococcus equi.

Bacteriophages were isolated from twelve lysogenic strains of Streptococcus equi. Based on sensitivity data and antiserum neutralization tests, the phage isolates were divided into two distinct but related groups. All twelve phage change the colonial morphology of S. equi from mucoid to matt. Possible phage-mediated effects on S. equi virulence are discussed.

Bacteriophage Typing↗