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F Spencer

Publications and source records attributed to F Spencer.

At least 37 records · Page 2Linked to original sources
PubMed1997

Temporal glucocorticoid treatment: modulation of periodic endometrial responses during decidualization and pregnancy in rats.

The synthetic glucocorticoid, dexamethasone (Dex) was administered subcutaneously (1.5 mg/day/rat) in 3-days pretreatment regimens (Days 2-4, 4-6, 6-8, 8-10 and 10-12) to pseudopregnant rats in which decidualization was surgically induced and to pregnant rats. Variability in endometrial growth during decidualization and in the fetoplacental homeostasis of pregnancy was assessed at the end of each treatment period (Days 4, 6, 8, 10 and 12). During decidualization, endometrial growth (wet weight, protein and DNA) displayed significant (p < 0.05) time-dependent inhibitory profiles which rose steeply from Day 4 to Day 6 and declined thereafter to Day 10 in fairly well defined linear patterns. For the endometrial enzymes (isocitrate dehydrogenase, alkaline phosphatase and the matrix metalloproteinases--72 and 92 kDa), although the inhibitory patterns were inconsistent, a Days 6-8 treatment regimen seemed to be critical. By contrast Dex treatment induced progressive inhibition in serum progesterone concentrations from Day 2, to peak levels by Day 12. This indicates that time-related Dex inhibition of endometrial growth appeared not to be progesterone-mediated since the endometrial and progesterone inhibitory profiles were not in synchrony. The inhibitory effect of Dex under the pregnancy status demonstrated that birth potentials, fetal and placental weights, all had similar response patterns which rose from Day 4 to Day 8 and then underwent reductions to Day 12. Collectively, the results indicate that there was time dependency in growth inhibition by Dex at the endometrial and fetoplacental levels. Maximal sensitivity to drug exposure essentially coincided with the immediate post-traumal (decidualization) and postimplantation (pregnancy) periods.

Animals↗
PubMed1997

Genome cross-referencing and XREFdb: implications for the identification and analysis of genes mutated in human disease.

Comparative genomics approaches and multi-organismal biology are valuable tools for genetic analysis. Cross-species connections between genes mutated in human disease states and homologues in model organisms can be particularly powerful, as model-organism gene function data and experimental approaches can shed light on the molecular mechanisms defective in the disease. We describe a project that is systematically identifying novel expressed sequence tag (EST) sequences that are highly related to genes in model organisms and mapping them to positions on the mouse and human maps. This process effectively cross-references model organism genes with mapped mammalian phenotypes, facilitating the identification of genes mutated in human disease states via the positional candidate approach. A public database, XREFdb (http:@www.ncbi.nlm.nih.gov/XREFdb/), disseminates similarity search, mapping and mammalian phenotype information and increases the rate at which these cross-species connections are established.

Animals↗
PubMed1996

Anticoagulation in Congestive Cardiomyopathy: Steps Toward Defining the Great Unknown.

It is generally agreed that congestive cardiomyopathy predisposes to the formation of cardiac thrombus and in turn systemic thromboembolism. Several uncontrolled studies have confirmed this association and have prompted wide-scale recommendations for long-term anticoagulation in these patients. Clinical studies have also attempted to identify patients at high risk for embolic events. The presence of cardiac thrombus, its topographic characteristics, the severity of left ventricular dysfunction, and decreased apical flow velocities may each represent markers of increased risk.Driven by the lack of definitive data addressing this issue, several pleas from the medical community have come forth for a large, randomized controlled trial of anticoagulation in congestive cardiomyopathy. Accordingly, a multicenter trial comparing aspirin, warfarin, or placebo as prophylaxis against thromboembolism has been proposed and if conducted will provide valuable information regarding the management of patients with congestive cardiomyopathy.

Journal Article↗
PubMed1996

Abnormal kinetochore structure activates the spindle assembly checkpoint in budding yeast.

Saccharomyces cerevisiae cells containing one or more abnormal kinetochores delay anaphase entry. The delay can be produced by using centromere DNA mutations present in single-copy or kinetochore protein mutations. This observation is strikingly similar to the preanaphase delay or arrest exhibited in animal cells that experience spontaneous or induced failures in bipolar attachment of one or more chromosomes and may reveal the existence of a conserved surveillance pathway that monitors the state of chromosome attachment to the spindle before anaphase. We find that three genes (MAD2, BUB1, and BUB2) that are required for the spindle assembly checkpoint in budding yeast (defined by antimicrotubule drug-induced arrest or delay) are also required in the establishment and/or maintenance of kinetochore-induced delays. This was tested in strains in which the delays were generated by limited function of a mutant kinetochore protein (ctf13-30) or by the presence of a single-copy centromere DNA mutation (CDEII delta 31). Whereas the MAD2 and BUB1 genes were absolutely required for delay, loss of BUB2 function resulted in a partial delay defect, and we suggest that BUB2 is required for delay maintenance. The inability of mad2-1 and bub1 delta mutants to execute kinetochore-induced delay is correlated with striking increases in chromosome missegregation, indicating that the delay does indeed have a role in chromosome transmission fidelity. Our results also indicated that the yeast RAD9 gene, necessary for DNA damage-induced arrest, had no role in the kinetochore-induced delays. We conclude that abnormal kinetochore structures induce preanaphase delay by activating the same functions that have defined the spindle assembly checkpoint in budding yeast.

Anaphase↗
PubMed1996

Faithful chromosome transmission requires Spt4p, a putative regulator of chromatin structure in Saccharomyces cerevisiae.

A chromosome transmission fidelity (ctf) mutant, s138, of Saccharomyces cerevisiae was identified by its centromere (CEN) transcriptional readthrough phenotype, suggesting perturbed kinetochore integrity in vivo. The gene complementing the s138 mutation was found to be identical to the S. cerevisiae SPT4 gene. The s138 mutation is a missense mutation in the second of four conserved cysteine residues positioned similarly to those of zinc finger proteins, and we henceforth refer to the mutation of spt4-138. Both spt4-138 and spt4 delta strains missegregate a chromosome fragment at the permissive temperature, are temperature sensitive for growth at 37 degrees C, and upon a shift to the nonpermissive temperature show an accumulation of large budded cells, each with a nucleus. Previous studies suggest that Spt4p functions in a complex with Spt5p and Spt6p, and we determined that spt6-140 also causes missegregation of a chromosome fragment. Double mutants carrying spt4 delta 2::HIS3 and kinetochore mutation ndc10-42 or ctf13-30 show a synthetic conditional phenotype. Both spt4-138 and spt4 delta strains exhibit synergistic chromosome instability in combination with CEN DNA mutations and show in vitro defects in microtubule binding to minichromosomes. These results indicate that Spt4p plays a role in chromosome segregation. The results of in vivo genetic interactions with mutations in kinetochore proteins and CEN DNA and of in vitro biochemical assays suggest that Spt4p is important for kinetochore function.

Amino Acid Sequence↗
PubMed1994

A versatile method for efficient YAC transfer between any two strains.

The ability to transfer yeast artificial chromosome (YAC) clones among yeast hosts greatly enhances their utility as cloned DNAs by increasing the range of methods available for experimental manipulation. An effective method for the transfer of YACs between strains in Kar1- matings is described in the accompanying paper (F. Spencer et al., 1994, Genomics 22, 118-126). To evaluate the general nature of the new methodology, we compare YAC transfer in matings in which the YAC donor, the recipient, or both partners carry the kar1 mutation. A set of four universal kar1 intermediary strains that allow YAC transfer from any source to any target strain of the same or of opposite mating type is described. The procedure requires elementary microbial manipulations, including yeast culture and replica plating, and pulsed-field gel electrophoresis for verification of the YAC transfer and integrity. Transfer of YACs by Kar1- mating provides an efficient, reliable, and highly flexible technique that will greatly facilitate YAC manipulation required for a wide variety of applications.

Animals↗
PubMed1994

Yeast kar1 mutants provide an effective method for YAC transfer to new hosts.

Yeast artificial chromosome (YAC) clones propagate large segments of exogenous DNA in a host organism with well-developed classical and molecular genetics. Most extant YAC clones are from libraries created in a single yeast host (AB1380). The application of techniques allowing the manipulation and/or restructuring of these cloned DNA segments often requires a change in the yeast genetic background to introduce desirable genetic markers. Transfer methods in current use require extremely high yeast transformation efficiencies or require access to equipment for yeast tetrad analysis. We have developed an alternative method for moving YAC clones from one yeast strain to another, taking advantage of the properties of kar1 mutants altered in a gene required for normal karyogamy (nuclear fusion) during mating. Transfer by this method requires generally accessible methods, including yeast cell culture, replica plating, and pulsed-field gel electrophoresis. We present data demonstrating efficient transfer of nine different YACs from their original host (AB1380) to a kar1 recipient strain (YPH925) with genetic markers that facilitate the use of existing homologous recombination-based modification methods. The enhanced ability to transfer clones to this new host will accelerate the pace of refinement and fine-structure mapping of the YAC contigs currently under construction and facilitate gene manipulation on YACs for subsequent functional analysis.

Chromosomes, Artificial, Yeast↗
PubMed1994

Efficient manipulation of the human adenovirus genome as an infectious yeast artificial chromosome clone.

A yeast artificial chromosome (YAC) containing a complete human adenovirus type 2 genome was constructed, and viral DNA derived from the YAC was shown to be infectious upon introduction into mammalian cells. The adenovirus YAC could be manipulated efficiently using homologous recombination-based methods in the yeast host, and mutant viruses, including a variant that expresses the human analog of the Saccharomyces cerevisiae CDC27 gene, were readily recovered from modified derivatives of the YAC. The application of powerful yeast genetic techniques to an infectious adenovirus clone promises to significantly enhance the genetic analysis of adenovirus and to simplify the construction of adenovirus-based vectors for vaccines or for gene transfer to mammalian cells or whole animals. The adenovirus YAC was produced by homologous recombination in vivo between adenovirus 2 virion DNA and YAC vector plasmids carrying segments of the viral left and right genomic termini. This recombinational cloning strategy is generally applicable to the construction of YACs containing other DNA segments, such as the genomes of other viruses. Further, it is very efficient and may permit the targeted cloning of segments of the genomes of higher organisms directly from genomic DNA.

Adenoviruses, Human↗
PubMed1994

Radiographic measurement of hallux valgus in the rheumatoid arthritic foot.

OBJECTIVE: To develop a method which is objective and quantifiable, as well as reliable and valid for measuring the severity and progression of hallux valgus deformity (HVD). HVD is defined as an increase in the hallux abductus angle (HAA). METHODS: HAA drawn on plain anterioposterior radiographs of the foot was measured in 94 patients with rheumatoid arthritis. The intra and interrater reliability were analyzed. RESULTS: Findings were significant with interclass correlation coefficients ranging from 0.9 to 0.99. Detection of changes in HAA using this method were comparable to the judgment of a panel of experienced clinicians. CONCLUSION: This method is useful in detecting progression of HVD.

Arthritis, Rheumatoid↗
PubMed1993

Identification of essential components of the S. cerevisiae kinetochore.

We have designed and utilized two in vivo assays of kinetochore integrity in S. cerevisiae. One assay detects relaxation of a transcription block formed at centromeres; the other detects an increase in the mitotic stability of a dicentric test chromosome. ctf13-30 and ctf14-42 were identified as putative kinetochore mutants by both assays. CTF14 is identical to NDC10/CBF2, a recently identified essential gene that encodes a 110 kd kinetochore component. CTF13 is an essential gene that encodes a predicted 478 amino acid protein with no homology to known proteins. ctf13 mutants missegregate chromosomes at permissive temperature and transiently arrest at nonpermissive temperature as large-budded cells with a G2 DNA content and a short spindle. Antibodies recognizing epitope-tagged CTF13 protein decrease the electrophoretic mobility of a CEN DNA-protein complex formed in vitro. Together, the genetic and biochemical data indicate that CTF13 is an essential kinetochore protein.

Amino Acid Sequence↗
PubMed1993

Identification and genetic mapping of CHL genes controlling mitotic chromosome transmission in yeast.

Eight independent chl (chromosome loss) mutants were isolated using yeast haploid strain disomic for chromosome III. In these mutants, chromosome III is lost during mitosis 50-fold more frequently than in the wild-type strains. chl mutants are also incapable of stable maintenance of circular and linear artificial chromosomes. Seven of the eight mutations are recessive, and one is semidominant. Complementation tests placed these mutants into six complementation groups (chl11 through chl16). Based on tetrad analysis, chl12, chl14 and chl15 correspond to mutations in single nuclear genes. Tetrad analysis of the other mutants was not possible due to poor spore viability. Complementation analysis was also carried out between collection of chl mutants and ctf mutants (chromosome transmission fidelity) (Spencer et al., 1990). The chl3, chl4, chl8, chl12 and chl15 mutants were unable to complement ctf3, ctf17, ctf12, ctf18 and ctf4, respectively. Three CHL genes were mapped by tetrad analysis. The CHL3 gene is placed on the right arm of chromosome XII, between the ILV5 (33.3 cM) and URA4 (21.8 cM) loci. The CHL10 gene is located on the left arm of chromosome VI, 12.5 cM from the centromere. The CHL15 gene is tightly linked to the KAR3 marker of the right arm of chromosome XVI (8.8 cM). The mapping data indicate that these three genes differ from other genes known to affect chromosome stability in mitosis. Therefore, the total number of the CHL genes identified (including those described by us earlier) is 13 (CHL1-CHL10, CHL12, CHL14 and CHL15).

Chromosomes, Fungal↗
PubMed1992

Centromere DNA mutations induce a mitotic delay in Saccharomyces cerevisiae.

Cytological observations of animal cell mitoses have shown that the onset of anaphase is delayed when chromosome attachment to the spindle is spontaneously retarded or experimentally interrupted. This report demonstrates that a centromere DNA (CEN) mutation carried on a single chromosome can induce a cell cycle delay observed as retarded mitosis in the yeast Saccharomyces cerevisiae. A 31-base-pair deletion within centromere DNA element II (CDEII delta 31) that causes chromosome missegregation in only 1% of cell division elicited a dramatic mitotic delay phenotype. Other CEN DNA mutations, including mutations in centromere DNA elements I and III, similarly delayed mitosis. Single division pedigree analysis of strains containing the CDEII delta 31 CEN mutation indicated that most (and possibly all) cells experienced delay in each cell cycle and that the delay was not due to increased chromosome copy number. Furthermore, a synchronous population of cells containing the CDEII delta 31 mutation underwent DNA synthesis on schedule with wild-type kinetics, but subsequently exhibited late chromosomal separation and concomitant late cell separation. We speculate that this delay in cell cycle progression before the onset of anaphase provides a mechanism for the stabilization of chromosomes with defective kinetochore structure. Further, we suggest that the delay may be mediated by surveillance at a cell cycle checkpoint that monitors the completion of chromosomal attachment to the spindle.

Alleles↗