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Biomedical subjects

S Fields

Publications and source records attributed to S Fields.

At least 19 recordsLinked to original sources
PubMed1997

A conserved RNA-binding protein that regulates sexual fates in the C. elegans hermaphrodite germ line.

The nematode Caenorhabditis elegans has two sexes, males and hermaphrodites. Hermaphrodites Initially produce sperm but switch to producing oocytes. This switch appears to be controlled by the 3' untranslated region of fem-3 messenger RNA. We have now identified a binding factor (FBF) which is a cytoplasmic protein that binds specifically to the regulatory region of fem-3 3'UTR and mediates the sperm/oocyte switch. The RNA-binding domain of FBF consists of a stretch of eight tandem repeats and two short flanking regions. This structural element is conserved in several proteins including Drosophila Pumilio, a regulatory protein that controls pattern formation in the fly by binding to a 3'UTR. We propose that FBF and Pumilio are members of a widespread family of sequence-specific RNA-binding proteins.

Amino Acid Sequence↗
PubMed1997

[CT-guided core needle biopsy of abdominal, pelvic and retroperitoneal masses].

CT-guided core needle biopsy of abdominal, pelvic and retroperitoneal masses is accurate and safe and can be performed on an outpatient basis. Between 1987 and 1995, 809 patients (age range 1-87 years) underwent 851 biopsies (minimal lesion diameter 1 cm). Cutting needles were always used, facilitating both cytological and histological diagnosis while minimizing risk of complications. A positive result (malignant, inflammatory or infectious) was obtained in 69% of the 809 and a negative result (normal tissue) in 17.4%, while in 13.6%, material for diagnosis was insufficient. Biopsy was repeated in 42 of them in whom radiological or clinical suspicion of malignancy was high. In 24 (60%) a positive result was obtained after the second biopsy. Significant complications occurred in 7 (0.8%). 1 hemo-rrhaged following liver biopsy and required blood transfusion. Pancreatitis occurred in 6 (2.6%) following pancreatic biopsy. An intraabdominal fluid collection in 1 necessitated percutaneous drainage. There was no mortality following the procedure and no documented case of needle-tract seeding of tumor. All outpatients were discharged within 3 hours of completion of the biopsy, without ill effects.

Abdominal Neoplasms↗
PubMed1997

Mapping pathophysiological features of breast tumors by MRI at high spatial resolution.

Magnetic resonance imaging (MRI) is a noninvasive method that reveals anatomical details in vivo and detects lesions for diagnosis. Although standard breast MRI cannot clearly delineate breast cancer, contrast-enhanced MRI enables the detection of breast masses with high sensitivity. Dynamic studies demonstrated that malignant lesions were characterized by a faster signal enhancement rate than benign ones. Dynamic MRI of human breast cancer in mice revealed high heterogeneity in the distribution of contrast-enhanced curves and derived pathophysiological features, indicating the importance of high spatial resolution. With clinical MRI, it is difficult to achieve simultaneously high spatial and temporal resolution. In previous dynamic studies, the emphasis was on high temporal resolution and mainly empiric analyses. We describe here a new model-based method that optimizes spatial resolution by using only three time points, and yet characterizes tumor heterogeneity in terms of microvascular permeability and extracellular fraction. Mapping these pathophysiological features may aid diagnosis and prognosis assessment, while the high spatial resolution may improve the capacity to detect smaller lesions. The method was tested in human breast tumors implanted in mice and in a limited number of benign and malignant breast lesions of patients.

Animals↗
PubMed1997

The complete set of predicted genes from Saccharomyces cerevisiae in a readily usable form.

Nearly all of the open reading frames (ORFs) of the yeast Saccharomyces cerevisiae have been synthesized by PCR using a set of approximately 6000 primer pairs. Each of the forward primers has a common 22-base sequence at its 5' end, and each of the back primers has a common 20-base sequence at its 5' end. These common termini allow reamplification of the entire set of original PCR products using a single pair of longer primers-in our case, 70 bases. The resulting 70-base elements that flank each ORF can be used for rapid and efficient cloning into a linearized yeast vector that contains these same elements at its termini. This cloning by genetic recombination obviates the need for ligations or bacterial manipulations and should permit convenient global approaches to gene function that require the assay of each putative yeast gene.

DNA Primers↗
PubMed1997

Transcriptional activation upon pheromone stimulation mediated by a small domain of Saccharomyces cerevisiae Ste12p.

In the yeast Saccharomyces cerevisiae, Ste12p induces transcription of pheromone-responsive genes by binding to a DNA sequence designated the pheromone response element. We generated a series of hybrid proteins of Ste12p with the DNA-binding and activation domains of the transcriptional activator Gal4p to define a pheromone induction domain of Ste12p sufficient to mediate pheromone-induced transcription by these hybrid proteins. A minimal pheromone induction domain, delineated as residues 301 to 335 of Ste12p, is dependent on the pheromone mitogen-activated protein (MAP) kinase pathway for induction activity. Mutation of the three serine and threonine residues within the minimal pheromone induction domain did not affect transcriptional induction, indicating that the activity of this domain is not directly regulated by MAP kinase phosphorylation. By contrast, mutation of the two tyrosines or their preceding acidic residues led to a high level of transcriptional activity in the absence of pheromone and consequently to the loss of pheromone induction. This constitutively high activity was not affected by mutations in the MAP kinase cascade, suggesting that the function of the pheromone induction domain is normally repressed in the absence of pheromone. By two-hybrid analysis, this minimal domain interacts with two negative regulators, Dig1p and Dig2p (also designated Rst1p and Rst2p), and the interaction is abolished by mutation of the tyrosines. The pheromone induction domain itself has weak and inducible transcriptional activity, and its ability to potentiate transcription depends on the activity of an adjacent activation domain. These results suggest that the pheromone induction domain of Ste12p mediates transcriptional induction via a two-step process: the relief of repression and synergistic transcriptional activation with another activation domain.

Amino Acid Sequence↗
PubMed1996

A three-hybrid system to detect RNA-protein interactions in vivo.

RNA-protein interactions are pivotal in fundamental cellular processes such as translation, mRNA processing, early development, and infection by RNA viruses. However, in spite of the central importance of these interactions, few approaches are available to analyze them rapidly in vivo. We describe a yeast genetic method to detect and analyze RNA-protein interactions in which the binding of a bifunctional RNA to each of two hybrid proteins activates transcription of a reporter gene in vivo. We demonstrate that this three-hybrid system enables the rapid, phenotypic detection of specific RNA-protein interactions. As examples, we use the binding of the iron regulatory protein 1 (IRP1) to the iron response element (IRE), and of HIV trans-activator protein (Tat) to the HIV trans-activation response element (TAR) RNA sequence. The three-hybrid assay we describe relies only on the physical properties of the RNA and protein, and not on their natural biological activities; as a result, it may have broad application in the identification of RNA-binding proteins and RNAs, as well as in the detailed analysis of their interactions.

Base Sequence↗
PubMed1996

A protein linkage map of Escherichia coli bacteriophage T7.

Genome sequencing projects are predicting large numbers of novel proteins, whose interactions with other proteins must mediate the function of cellular processes. To analyse these networks, we used the yeast two-hybrid system on a genome-wide scale to identify 25 interactions among the proteins of Escherichia coli bacteriophage T7. Among these is a set of six interactions connecting proteins that function in DNA replication and DNA packaging. Remarkably, two genes, arranged such that one entirely overlaps the other and uses a different reading frame, encode interacting proteins. Several of the interactions reflect intramolecular associations of different domains of the same polypeptide, suggesting that the two-hybrid assay may be useful in the analysis of protein folding. This global approach to protein-protein interactions may be applicable to the analysis of more complex genomes whose sequences are becoming available.

Amino Acid Sequence↗
PubMed1996

A phase I clinical and pharmacokinetic study of the angiogenesis inhibitor, tecogalan sodium.

BACKGROUND: Tecogalan sodium is an angiogenesis inhibitor isolated from a sulfated polysaccharide produced by the bacterium Arthrobacter. The antiangiogenic effect of tecogalan sodium is thought to be mediated by the inhibition of binding of basic fibroblast growth factor to cellular receptors. PATIENTS AND METHODS: A phase I study was conducted in thirty-three patients with refractory malignancies, including AIDS-associated Kaposi's sarcoma. Patients received a single i.v. infusion every three weeks with the infusion duration ranging from one to twenty-four hours. Seven different dosage levels were studied (125, 185, 240, 300, 390, 445, and 500 mg/m2). RESULTS: The primary dose-limiting toxicity was prolongation of the activated partial thromboplastin time with peak times being between 1.0-4.0 times the upper limit of normal. This toxicity was ameliorated at a given dose level by prolonging the infusion time. Other common toxicities included fever (40%) and rigors (31%) which were well controlled with acetominophen and meperidine. The serum half-life of tecogalan sodium was between 1-1.5 hours and < 25% of unchanged drug was excreted in the urine. CONCLUSIONS: The recommended phase II dose of tecogalan sodium on this schedule is 390 mg/m2 over 24 hours. Other schedules including continuous administration should be investigated to maximize the efficacy of this novel angiogenesis inhibitor.

Antineoplastic Agents↗
PubMed1996

Image-guided core-needle biopsy in malignant lymphoma: experience with 100 patients that suggests the technique is reliable.

PURPOSE: In an initial evaluation of 1,500 computed tomography (CT)-guided core-needle biopsies performed at our institute during the period from 1989 to 1994, we encountered 100 patients with the diagnosis of lymphoma. Here, we review the clinical impact of 109 image-guided needle biopsies in these 100 patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). PATIENTS AND METHODS: NHL was diagnosed in 71 patients, and 29 had HD. Among the NHL patients, 17 (24%) had proven lymphoma diagnosed before the biopsy was performed; in 54 (76%) core-needle biopsy was performed as the first diagnostic procedure. Of 29 HD patients, nine (31%) were already established cases of HD, and in 20 (69%) core-needle biopsy was the first diagnostic procedure attempted. Most of the biopsies were performed under CT control using a 20- or 18-gauge Turner biopsy needle. RESULTS: Eighty-six patients received therapy based on the results of the needle biopsy alone. Fourteen patients received therapy after undergoing surgical biopsy for a suspected diagnosis of lymphoma, which could not be established with certainty on the basis of an earlier core-needle biopsy alone. In 78% of the patients, the needle biopsy saved a further surgical procedure that may have been difficult to perform because of the primary location of the tumor. CONCLUSION: From our experience in this study, image-guided core-needle biopsies provide sufficient information for the diagnosis of and subsequent therapeutic decision to treat most cases of lymphoma.

Adolescent↗
PubMed1995

Dissociation of transcriptional activation and oncogenic transformation by v-Myb.

The nuclear oncoprotein v-Myb is a transcriptional activator in both animal cells and the budding yeast Saccharomyces cerevisiae. Previous studies have suggested that an acidic domain of approximately 50 amino acids (amino acids 204-254 of v-Myb) is necessary and sufficient for transcriptional activation by v-Myb, c-Myb and GAL4-Myb fusion proteins. However, we find that first, none of the acidic residues within this region is essential for transcriptional activation in either animal cells or yeast. Second, transcriptional activation requires cooperation among multiple domains of v-Myb. In animal cells, transcriptional activation by v-Myb requires a central domain (amino acids 234-295), a C-terminal domain (amino acids 295-356), plus either of two more N-terminal domains (amino acids 163-197 or 198-232); in yeast, it requires the central domain plus either the C-terminal domain or a more N-terminal domain (amino acids 163-233). Third, although various subsets of these domains are sufficient for transcriptional activation by v-Myb, all of the domains must be present for transformation of primary hematopoietic cells. These results demonstrate that transcriptional activation by v-Myb is not sufficient for oncogenic transformation.

Amino Acid Sequence↗
PubMed1995

Protein-peptide interactions analyzed with the yeast two-hybrid system.

The yeast two-hybrid system was used to screen a library of random peptides fused to a transcriptional activation domain in order to identify peptides capable of binding to the retinoblastoma protein (Rb). Seven peptides were identified, all of which contain the Leu-X-Cys-X-Glu motif found in Rb-binding proteins, although their activity in the yeast assay varied over a 40-fold range. Mutagenesis of the DNA encoding two of these peptides followed by screening in the two-hybrid system allowed the delineation of residues apart from the invariant Leu, Cys and Glu that affect binding to Rb. Binding affinities of a peptide and one of its variants to Rb, determined by surface plasmon resonance, correlated with results from the two-hybrid assay. This method offers several advantageous features compared to existing technology for screening peptide libraries: in vivo detection of protein-peptide interactions, high sensitivity, the capacity for rapid genetic screening to identify stronger and weaker binding peptide variants, and the use of a simple assay (transcriptional activity) as a means to assess binding affinity.

Amino Acid Sequence↗
PubMed1995

Interrater agreement in the interpretation of microscopic urinalysis.

To determine the reliability of specimen interpretation by outpatient laboratories, 150 consecutive specimens from three family practice centers were analyzed by either two laboratory technicians (n = 99) or two family physicians (n = 51). The results showed good to excellent agreement for contamination (defined as five or more epithelial cells per high-power field) or significant pyuria (five or more white blood cells per high-power field) or hematuria (five or more red blood cells per high-power field). Agreement between laboratory technicians did not differ significantly from agreement between physicians for the interpretation of contamination or pyuria, but for hematuria, agreement was higher between technicians (P = .02). These results suggest that outpatient interpretation of microscopic urine specimens shows levels of interrater agreement similar to or better than other tests that have been evaluated.

Humans↗
PubMed1995

A phase I and pharmacokinetics study of 2-chlorodeoxyadenosine in patients with solid tumors.

Preclinical studies of 2-chlorodeoxyadenosine (2-CdA) against solid tumors in the human tumor cloning assay and evidence that 2-CdA is active against slow-growing or resting tumor cells have stimulated interest in the clinical activity of this agent against solid tumors. This study sought to estimate the maximum tolerated dose, dose-limiting toxicity, and plasma and urine pharmacokinetics accompanying the intravenous administration of 2-CdA by 120-h continuous infusion in patients with solid tumors. Treated patients were also assessed for other toxicities of therapy and for antitumor response. A total of 23 patients received 35 courses of treatment given at doses of 3.5, 5.3, 6.5 and 8.1 mg/m2 per day by continuous intravenous infusion for 5 days and repeated every 28 days. Blood and urine specimens were collected before, during, and after drug infusion. The dose-limiting toxicity at 8.1 mg/m2 per day manifested as granulocytopenia in 2 of 5 patients (3 of 7 courses of treatment) and as thrombocytopenia in 3 of 5 patients (3 of 7 courses of treatment). At the dose levels of 6.5 and 8.1 mg/m2 per day, recovery from thrombocytopenia was often delayed. Severe lymphocytopenia (< 1,000/microliters) was observed at all dose levels of 2-CdA. Dose-related anemia and leukopenia were observed and were infrequently severe. Non-hematological toxicities were confined to mild-to-moderate nausea, vomiting, fatigue, and anorexia. Fever of 37 degrees-40 degrees C was induced during drug infusion in 19 patients. No antitumor response was observed. Average plasma concentrations at steady-state (Cpss) ranged from 3 ng/ml at the initial dose level to 13 ng/ml at the dose level of 8.1 mg/m2 per day. Both the Cpss and the area under the plasma concentration-time curve (AUC) were proportional to the dose. A relationship was observed between the percentage of change in absolute neutrophil count and the AUC. Renal excretion accounted for only 18% of the elimination of 2-CdA over the 5-day infusion period. The maximum tolerated dose for 2-CdA given by 5-day continuous infusion was 8.1 mg/m2 per day in this study. The recommended dose on this schedule for phase II studies is 6.5 mg/m2 per day. Granulocytopenia and thrombocytopenia were dose-limiting. No antitumor activity was observed during this study. On the basis of the plasma concentrations of 2-CdA observed, it is unlikely that this schedule of drug administration will permit achievement of the concentrations consistent with antitumor activity observed in preclinical studies.

Adult↗