PubMed Health⌕ Search

Biomedical subjects

J Sturtevant

Publications and source records attributed to J Sturtevant.

13 recordsLinked to original sources
PubMed2000

Applications of differential-display reverse transcription-PCR to molecular pathogenesis and medical mycology.

The host-fungus interaction is characterized by changes in gene expression in both host and pathogen. Differential-display reverse transcription PCR (DDRT-PCR) is a PCR-based method that allows extensive analysis of gene expression among several cell populations. Several limitations and drawbacks to this procedure have now been addressed, including the large number of false-positive results and the difficulty in confirming differential expression. Modifications that simplify the reaction time, allow the use of minute quantities of RNA, or address unusual species- or gene-specific sequences have been reported. DDRT-PCR has been used to address biological questions in mammalian systems, including cell differentiation, cell activation, cell stress, and identification of drug targets. In microbial pathogenesis and plant pathogenesis, DDRT-PCR has allowed the identification of virulence factors, genes involved in cell death, and signaling genes. In Candida albicans, DDRT-PCR studies identified TIF-2, which may play a role in the upregulation of phospholipases, and the stress-related genes, CIP1 and CIP2. In Histoplasma capsulatum and C. albicans, genes involved in the host-pathogen interaction, including a member of the 100-kDa family in Histoplasma and an ALS and 14-3-3 gene in Candida, were potentially identified by DDRT-PCR. Although very few reports have been published in medical mycology, studies in mammalian, nonfungal microbial, and plant pathogen systems are easily applied to basic questions in fungal pathogenesis and antifungal therapeutics.

Animals↗
PubMed1999

Identification and cloning of GCA1, a gene that encodes a cell surface glucoamylase from Candida albicans.

Adherence of yeast cells of Candida albicans to human oesophageal cells is greater when cells are grown in 500 mM D-galactose in comparison to D-glucose at the same concentration. Moreover, a 190 kDa mannoprotein (MP190) from a yeast cell wall preparation is highly expressed when cells are grown in the presence of galactose but less so in glucose. We now report on the identification of the MP190 and the isolation of its encoding gene. MP190 was purified, and three internal peptides were isolated and sequenced. Each of the three peptides showed significant homology (65-85%) with a glucoamylase (GAM1) from the yeast, Schwanniomyces occidentalis. In order to isolate the C. albicans homologue of GAM1 (GCA1), we probed a genomic library with a 0.9-kb internal fragment of the S. occidentalis GAM1 and isolated a 2.3-kb clone that corresponded to the 5' region of the gene. Polymerase chain reaction (PCR) amplification was used to isolate the remainder of the open reading frame. GCA1 encodes a 946 amino acid protein containing three putative hydrophobic, membrane-spanning domains and 15 potential N-glycosylation sites. Both Gca1p and GAM1 are novel to the family of glycosyl hydrolases. Northern analysis indicated that GCA1 is transcribed to a greater extent in galactose than in sucrose or glucose. Also, using reverse transcriptase (RT)-PCR, we observed expression of GCA1 in a rat model of oral candidiasis, indicating that Gca1p is expressed during disease development.

Amino Acid Sequence↗
PubMed1999

NSAID-induced bronchospasm--a common and serious problem. A report from MEDSAFE, the New Zealand Medicines and Medical Devices Safety Authority.

Between 8-20 percent of adult asthmatics experience bronchospasm following ingestion of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs). Termed aspirin-induced asthma, this reaction is potentially fatal. Asthmatics with chronic rhinitis or a history of nasal polyps are at greater risk. The reaction rarely occurs in children. Patients initially present with an acute episode of vague malaise, sneezing, nasal obstruction, rhinorrhoea, and often a productive cough. Persistent rhinitis and nasal polyps may then develop. Asthma and aspirin sensitivity may appear in the following months. Within 20 minutes to 3 hours of taking a NSAID, aspirin-sensitive asthmatics can develop symptoms such as bronchospasm, rhinorrhoea, dyspnoea, cough, or urticaria-angiodema. NSAIDs (systemic or topical) should be used with caution in asthmatics and avoided in asthmatics with nasal polyps. Asthmatics should be told to seek medical help if symptoms worsen on initiation of a NSAID.

Adult↗
PubMed1998

Molecular mechanisms of virulence in fungus-host interactions for Aspergillus fumigatus and Candida albicans.

Research on fungi that cause opportunistic infections has increased dramatically during the past few years, largely because these organisms cause significant morbidity and mortality. Most of this research has focused on defining the virulence factors produced by these pathogens, as well as developing methods for the diagnosis of fungal diseases. With regard to studies on the biology of Candida albicans, it is now possible to isolate genes, disrupt their expression, and observe the specific effects of gene disruption on virulence and growth of the organism. Moreover, growth and virulence of this pathogen is also being studied and the effect of environmental factors on gene expression investigated. This subject is especially important in view of the fact that C. albicans can colonize and invade a number of sites in the human body. Thus, its ability to grown in the oral and vaginal tracts, as well as in blood, requires the organism to adapt to a variety of environmental stresses. Here we present observations on the growth, morphogenesis and virulence of the opportunistic fungi C. albicans and Aspergillus fumigatus.

Amino Acid Sequence↗
PubMed1995

Expression of Candida albicans SAP1 and SAP2 in experimental vaginitis.

Several strains of Candida albicans were compared for their ability to cause vaginal infection in a rat model, and their vaginopathic potentials were correlated with the expression of two aspartyl proteinases genes (SAP1 and SAP2) and adherence in vivo to the vaginal epithelium. Dot blot reactions and Northern blot analysis with RNA extracted from the vaginal fluid of rats infected with the highly vaginopathic strains H12 and 10261 demonstrated the expression of both SAP1 and SAP2 during the first week of infection. In contrast, neither gene was expressed during infection by a nonvaginopathic strain (N), even though the organism could be recovered during the first 24 h postinfection. A moderately vaginopathic strain (P) also expressed both genes, but the level of SAP1 mRNA appeared to decrease prior to that of SAP2. Neither gene was expressed, even by the highly vaginopathic strains, after the first week of infection, concomitant with a decrease in the number of organisms recovered from the vaginas. Analysis of in vivo adherence showed that the nonvaginopathic strain (N) adhered to vaginal epithelial cells less readily than the highly vaginopathic strain (H12) and moderately vaginopathic strain (P). Thus, in addition to its inability to express SAP1 and SAP2 in vivo, the nonvaginopathic strain does not colonize host cells to the same extent as the other strains tested. Our results demonstrate the early in vivo expression of two aspartyl proteinase gene during candidal vaginitis and suggest its association with the establishment of a vaginal infection.

Animals↗
PubMed1994

Macrophage interactions with Candida.

The monocyte/macrophage, in comparison to the neutrophil, would appear to have a limited role in protection against C. albicans. This statement is based on the observations of several investigators who report that these cells have very little killing capacity unless they are activated by cytokines such as IFN-gamma and GM-CSF. The mechanisms of killing by these cells appear to include both oxidative and nonoxidative mechanisms, the latter perhaps being more important. The mechanisms of killing may be different for monocytes and macrophages. Granulocyte-macrophage colony-stimulating factor and its effect on monocytes has been studied using Candida as a target organism. Two explanations for the enhancement of monocyte killing by this cytokine have been proposed: GM-CSF augments both superoxide anion and the level of mannose receptors on treated monocytes. Both of these changes could be significant in the increased killing capacity of these cells.

Animals↗
PubMed1992

Participation of complement in the phagocytosis of the conidia of Aspergillus fumigatus by human polymorphonuclear cells.

Nonspecific immunity plays a major role in the clearance of the opportunistic fungal pathogen, Aspergillus fumigatus. However, the mode of recognition of Aspergillus conidia by the different elements of an intact phagocyte system remains poorly understood. This study concentrated on the initial interaction between infective conidia and human polymorphonuclear cells (PMNL) using a double-label immunofluorescent method. At 37 degrees C, association was rapid. Although ingestion rates were slower than association, both association and ingestion plateaued at 90 min and were considerably reduced in the presence of fetal calf serum. In the presence of autologous plasma, association increased as the conidia-to-cell ratio increased, but the percentage of associated conidia that were ingested decreased. At 4 degrees C, phagocytosis was negligible. Phagocytosis experiments in the presence of plasma treated in various ways to inhibit the complement pathways demonstrated that optimal association was dependent on an active alternative complement pathway.

Analysis of Variance↗
PubMed1991

Global suppression of protein folding defects and inclusion body formation.

Amino acid substitutions at a site in the center of the bacteriophage protein P22 tailspike polypeptide chain suppress temperature-sensitive folding mutations at many sites throughout the chain. Characterization of the intracellular folding and chain assembly process reveals that the suppressors act in the folding pathway, inhibiting the aggregation of an early folding intermediate into the kinetically trapped inclusion body state. The suppressors alone increase the folding efficiency of the otherwise wild-type polypeptide chain without altering the stability or activity of the native state. These amino acid substitutions identify an unexpected aspect of the protein folding grammar--sequences within the chain that carry information inhibiting unproductive off-pathway conformations. Such mutations may serve to increase the recovery of protein products of cloned genes.

Amino Acid Sequence↗
PubMed1970

Pigeon control by chemosterilization: population model from laboratory results.

Reproductivity of pigeons is inhibited with mestranol incorporated in a synthetic grit; continual erosion releases daily doses. Young squabs may be permanently sterilized when fed crop milk by treated birds. A theoretical model of pigeon population dynamics using laboratory-obtained data shows the advantages of chemosterilization over killing as a means of pigeon control.

Animals↗