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Biomedical subjects

S Fields

Publications and source records attributed to S Fields.

At least 19 recordsLinked to original sources
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↗
PubMed1995

A centralized communication system.

Patient care redesign involves people, processes and technology coming together to meet or exceed patient expectations. A centralized communication system promotes professional nursing practice and optimizes all the team members' roles through more efficient use of staff.

Hospital Communication Systems↗
PubMed1995

Protein-protein interactions: methods for detection and analysis.

The function and activity of a protein are often modulated by other proteins with which it interacts. This review is intended as a practical guide to the analysis of such protein-protein interactions. We discuss biochemical methods such as protein affinity chromatography, affinity blotting, coimmunoprecipitation, and cross-linking; molecular biological methods such as protein probing, the two-hybrid system, and phage display: and genetic methods such as the isolation of extragenic suppressors, synthetic mutants, and unlinked noncomplementing mutants. We next describe how binding affinities can be evaluated by techniques including protein affinity chromatography, sedimentation, gel filtration, fluorescence methods, solid-phase sampling of equilibrium solutions, and surface plasmon resonance. Finally, three examples of well-characterized domains involved in multiple protein-protein interactions are examined. The emphasis of the discussion is on variations in the approaches, concerns in evaluating the results, and advantages and disadvantages of the techniques.

Carrier Proteins↗
PubMed1995

Alprazolam for tinnitus.

There is insufficient evidence to support the use of alprazolam in the treatment of tinnitus. The Johnson trial is the only study to date assessing the role of alprazolam, and at best it is an open-label trial demonstrating activity. There is a need for definitive double-blind, controlled, crossover studies of sufficient statistical power to resolve the issue. Furthermore, once efficacy is demonstrated, further studies are needed to determine the appropriate length of therapy, the necessity for maintenance therapy, the role of "drug holidays," appropriate dose tapering schedules, and a more careful delineation of which populations of patients are more likely to respond to alprazolam.

Alprazolam↗
PubMed1995

Radiologic spectrum of localized Castleman's disease.

We report seven patients with the localized form of Castleman's disease, diagnosed by surgical biopsy; four had the plasma cell type and three the hyaline vascular type. A variety of nonspecific clinical and radiologic findings were identified in these patients. Precise clinical staging is important to separate the widespread from the localized form of Castleman's disease, as the localized form may be successfully treated surgically. Percutaneous core needle biopsy is not helpful in the diagnosis of Castleman's disease. Significant computerized tomography enhancement with intravenous contrast in the hyaline vascular type is indicative of increased vascularity which may cause surgical complications when resection is attempted.

Adolescent↗
PubMed1994

Activated Ras interacts with the Ral guanine nucleotide dissociation stimulator.

The yeast two-hybrid system was used to identify proteins that interact with Ras. The H-Ras protein was found to interact with a guanine nucleotide dissociation stimulator (GDS) that has been previously shown to regulate guanine nucleotide exchange on another member of the Ras protein family, Ral. The interaction is mediated by the C-terminal, noncatalytic segment of the RalGDS and can be detected both in vivo, using the two-hybrid system, and in vitro, with purified recombinant proteins. The interaction of the RalGDS C-terminal segment with Ras is specific, dependent on activation of Ras by GTP, and blocked by a mutation that affects Ras effector function. These characteristics are similar to those previously demonstrated for the interaction between Ras and its putative effector, Raf, suggesting that the RalGDS may also be a Ras effector. Consistent with this idea, the RalGDS was found to inhibit the binding of Raf to Ras.

Amino Acid Sequence↗
PubMed1994

Two cellular proteins that bind to wild-type but not mutant p53.

p53 is a tumor-suppressor protein that can activate and repress transcription. Using the yeast two-hybrid system, we identified two previously uncharacterized human proteins, designated 53BP1 and 53BP2, that bind to p53. 53BP1 shows no significant homology to proteins in available databases, whereas 53BP2 contains two adjacent ankyrin repeats and a Src homology 3 domain. In vitro binding analyses indicate that both of these proteins bind to the central domain of p53 (residues 80-320) required for site-specific DNA binding. Consistent with this finding, p53 cannot bind simultaneously to 53BP1 or 53BP2 and to a DNA fragment containing a consensus p53 binding site. Unlike other cellular proteins whose binding to p53 has been characterized, both 53BP1 and 53BP2 bind to the wild-type but not to two mutant p53 proteins identified in human tumors, suggesting that binding is dependent on p53 conformation. The characteristics of these interactions argue that 53BP1 and 53BP2 are involved in some aspect of p53-mediated tumor suppression.

Amino Acid Sequence↗
PubMed1994

[Percutaneous, CT-guided excision of femoral osteoid osteoma].

An osteoid osteoma in the distal femur of a 10-year-old girl was excised, percutaneously, under CT guidance. Location of the nidus was by insertion of a Kirshner wire under CT control. Hollow Mill was used to excise the nidus by drilling over the Kirshner wire, with CT guidance during each stage. There were no complications and pain ceased overnight. Follow-up after 4 months showed complete recovery and no pain.

Child↗
PubMed1994

Magnetic resonance imaging and spectroscopy of MCF7 human breast cancer: pathophysiology and monitoring of treatment.

Magnetic resonance imaging at high spatial resolution, dynamic-contrast enhanced imaging, and localized 31P magnetic resonance spectroscopy were applied to monitor in vivo growth and tamoxifen treatment of MCF7 human breast tumors implanted in athymic mice. Correlation of the imaging data with histological findings demonstrated significant differences between viable carcinoma, fibrous, and necrotic regions on T2 weighted images. At an early stage after tamoxifen treatment rapid necrosis preceded tumor regression suggesting tamoxifen inhibition of angiogenesis. The necrosis was followed by growth of reperative fibrous tissue at the boundary of the viable cancer cells and the necrotic regions. The dynamic of contrast enhancement after tamoxifen treatment revealed high permeability of microvessels at this boundary cord. In parallel to the induction of the repair process the tumor energy profile changed, showing a significant increase in the ratio of ATP to inorganic phosphate. Initial attempts to use MRI for evaluating the response of breast cancer patients to treatment are also described.

Adenosine Triphosphate↗
PubMed1994

The two-hybrid system: an assay for protein-protein interactions.

The two-hybrid system is a yeast-based genetic assay for detecting protein-protein interactions. It can be used to identify proteins that bind to a protein of interest, or to delineate domains or residues critical for an interaction. Variations on this methodology have been developed to clone genes that encode DNA-binding proteins, to identify peptides that bind to a protein and, potentially, to screen for drugs.

DNA-Binding Proteins↗
PubMed1994

Phase I and pharmacokinetic studies of topotecan administered as a 72 or 120 h continuous infusion.

Topotecan (SK&F 104864-A, NSC 609699) is a water-soluble, semi-synthetic analog of camptothecin which is an inhibitor of topoisomerase I. Since topoisomerase I is cell specific for S phase, we undertook a phase I study to determine the maximum tolerated dose and toxicities of continuous infusion (CI) topotecan. This phase I trial first explored a 5 day CI every 21 day schedule. Doses of topotecan included 0.17, 0.34 and 0.68 mg/m2/day. Fourteen patients [median age 60; median performance status (PS) of 1] with refractory malignancies received 59 courses of drug. Hematologic toxicities occurred only at the highest dose level; NCI grade 3-4 granulocytopenia and thrombocytopenia occurred in 4/8 and 3/8 patients, respectively. The protocol was amended to a 3 day infusion in an effort to ameliorate toxicity and obtain greater dose intensity (DI). Doses of 0.68, 0.85, 1.05, 1.3 and 1.6 mg/m2/day were evaluated. Thirty-two patients (median age 60; median PS of 1) received a total of 115 courses. The major toxicity seen was hematologic with 9/32 and 5/32 patients demonstrating grade 3-4 granulocytopenia and thrombocytopenia, respectively. Non-hematologic toxicities were mild (grade 1-2) in the two schedules and included nausea, vomiting, fatigue and alopecia. At the maximum tolerated dose (MTD) on the 5 day schedule, patients received 0.87 mg/m2/week, whereas they received 1.08 mg/m2/week at the MTD on the 3 day schedule (24% increase in relative dose intensity). A steady-state plasma lactone concentration of 5.5 mg/ml of topotecan was achieved at the phase II recommended dose of 1.6 ng/m2/day as a 3 day continuous infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Phase I clinical trial of ormaplatin (tetraplatin, NSC 363812).

Ormaplatin is a platinum analog that was developed because of an altered toxicity profile and non-cross resistance to cisplatin in both in vitro and in vivo models. To determine the toxicities and maximum tolerated dose of ormaplatin on a daily times five schedule, patients with refractory solid tumors received ormaplatin on five consecutive days at nine dose levels ranging from 1.0 to 15.0 mg/m2/day. A total of 35 patients received 70 cycles of therapy. Nausea and vomiting and myelosuppression were moderate and not dose-limiting. Dose-limiting neurotoxicity, consisting of a sensory peripheral neuropathy, was seen in all five patients who received cumulative doses greater than or equal to 165 mg/m2. This neurotoxicity was symptomatic in all patients and caused significant functional impairment in four patients with inability to walk in two patients. A sensitive atomic absorption spectroscopy analysis performed for one patient at the 13.0 mg/m2/day dose level showed a Cpmax of 163 ng/ml and a t1/2 of 10.9 min for free platinum. A phase II dose could not be determined due to the onset of peripheral neuropathy at low cumulative doses and not at absolute dose levels.

Adult↗
PubMed1994

Distinct residues of human p53 implicated in binding to DNA, simian virus 40 large T antigen, 53BP1, and 53BP2.

We identified a minimal domain of human p53 required for the transactivation of a p53 response element in Saccharomyces cerevisiae. This domain contains the central region of p53 sufficient for specific DNA binding, which colocalizes with the region responsible for binding simian virus 40 large T antigen, 53BP1, and 53BP2. Thirty amino acid positions, including natural mutational hot spots (R175, R213, R248, R249, and R273), in the minimal DNA-binding domain were mutated by alanine substitution. Alanine substitutions at positions R213, R248, R249, D281, R282, R283, E286, and N288 affected transactivation but allowed binding to at least one of the three interacting proteins; these amino acids may be involved in amino acid-base pair contacts. Surprisingly, alanine substitution at the mutational hot spot R175 did not affect DNA binding, transactivation, or T-antigen binding, although it nearly eliminated binding to 53BP1 and 53BP2. Mutation of H168 significantly affected only T-antigen binding, and mutation of E285 affected only 53BP1 binding. Thus, we implicate specific residues of p53 in different DNA and protein interactions.

Amino Acid Sequence↗