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Biomedical subjects

S Becker

Publications and source records attributed to S Becker.

At least 235 records · Page 13Linked to original sources
PubMed1995

Two CDC25 homologues are differentially expressed during mouse development.

The cdc25 gene product is a tyrosine phosphatase that acts as an initiator of M-phase in eukaryotic cell cycles by activating p34cdc2. Here we describe the cloning and characterization of the developmental expression pattern of two mouse cdc25 homologs. Sequence comparison of the mouse genes with human CDC25 genes reveal that they are most likely the mouse homologs of human CDC25A and CDC25B respectively. Mouse cdc25a, which has not been described previously, shares 84% sequence identity with human CDC25A and has a highly conserved phosphatase domain characteristic of all cdc25 genes. A glutathione-S-transferase-cdc25a fusion protein can hydrolyze para-nitro-phenylphosphate confirming that cdc25a is a phosphatase. In adult mice, cdc25a transcripts are expressed at high levels in the testis and at lower levels in the ovary, particularly in germ cells; a pattern similar to that of twn, a Drosophila homolog of cdc25. Lower levels of transcript are also observed in kidney, liver, heart and muscle, a transcription pattern that partially overlaps, but is distinct from that of cdc25b. Similarly, in the postimplantation embryo cdc25a transcripts are expressed in a pattern that differs from that of cdc25b. cdc25a expression is observed in most developing embryonic organs while cdc25b expression is more restricted. An extended analysis of cdc25a and cdc25b expression in preimplantation embryos has also been carried out. These studies reveal that cdc25b transcripts are expressed in the one-cell embryo, decline at the two-cell stage and are re-expressed at the four-cell stage, following the switch from maternal to zygotic transcription which mirrors the expression of string, another Drosophila homolog of cdc25. In comparison, cdc25a is not expressed in the preimplantation embryo until the late blastocyst stage of development, correlating with the establishment of a more typical G1 phase in the embryonic cell cycles. Both cdc25a and cdc25b transcripts are expressed at high levels in the inner cell mass and the trophectoderm, which proliferate rapidly prior to implantation. These data suggest the cdc25 genes may have distinct roles in regulating the pattern of cell division during mouse embryogensis and gametogenesis.

Amino Acid Sequence↗
PubMed1995

Contracting for outpatient surgical services.

This article provides a review of factors that influence a managed care entity's choice of a provider of outpatient surgical services. In reviewing issues, this article also provides practical guidance to the outpatient surgery center with respect to the pricing and marketing of its services. Finally, the article provides an overview of both business and legal issues relating to managed care contracting choices.

Contract Services↗
PubMed1995

[In vitro exposure of a human bronchial epithelial cell line with nitrogen dioxide induces enhanced transcription and liberation of pro-inflammatory cytokines].

Studies of in vivo inhalation of nitrogen dioxide (NO2) have demonstrated a transient pulmonary inflammation. This study was done to determine the contribution of airway epithelial cells to the release of inflammatory mediators following NO2 exposure. Confluent cultures of the human bronchial epithelial cell line BEAS-2B on Transwell-Col filters were exposed for 1 h to air or NO2 up to 1.5 ppm with the apical fluids removed with 5% CO2 at 37 degrees C. The cells were hydrated with Hanks' Balanced Salt Solution (HBSS) in the basolateral compartment. Sequential reverse transcription and quantitative cDNA amplification (RT-PCR) was used to measure inflammatory mediator mRNA abundance in BEAS-2B cultures. When compared to air-exposed cells, NO2 induced increases in IL-6 (23.4-fold) and IL-8 (30.9-fold) mRNA abundance. The NO2-dependent increases in mRNA expression reached a maximum between 0 and 1 h post exposure and returned to baseline levels within 24 h. IL-6 and IL-8 proteins as measured by enzyme-linked immunosorbent assays (ELISA) were also elevated in supernatants recovered from NO2-exposed BEAS-2B cells. These studies suggest that exposure to NO2 induces the synthesis and release of inflammatory mediators from airway epithelial cells that may participate in the pathogenesis of airway disease.

Bronchi↗
PubMed1995

O2-sensing and O2-dependent gene regulation in facultatively anaerobic bacteria.

Availability of O2 is one of the most important regulatory signals in facultatively anaerobic bacteria. Various two- or one-component sensor/regulator systems control the expression of aerobic and anaerobic metabolism in response to O2. Most of the sensor proteins contain heme or Fe as cofactors that interact with O2 either by binding or by a redox reaction. The ArcA/ArcB regulator of aerobic metabolism in Escherichia coli may use a different sensory mechanism. In two-component regulators, the sensor is located in the cytoplasmic membrane, whereas one-component regulators are located in the cytoplasm. Under most conditions, O2 can readily reach the cytoplasm and could provide the signal in the cytoplasm. The transcriptional regulator FNR of E. Coli controls the expression of many genes required for anaerobic metabolism in response to O2. Functional homologs of FNR are present in facultatively anaerobic Proteobacteria and presumably also in gram-positive bacteria. The target genes of FNR are mostly under multiple regulation by FNR and other regulators that respond to O2, nitrate, or glucose. FNR represents a 'one-component' sensor/regulator and contains Fe for signal perception. In response to O2 availability, FNR is converted reversibly from the aerobic (inactive) state to the anaerobic (active) state. Experiments suggest that the Fe cofactor is bound by four essential cysteine residues. The O2-triggered transformation between active and inactive FNR presumably is due to a redox reaction at the Fe cofactor, but other modes of interaction cannot be excluded. O2 seems to affect the site-specific DNA binding of FNR at target genes or the formation of an active transcriptional complex with RNA polymerase.

Bacterial Proteins↗
PubMed1995

Development of provider networks for specific diseases.

Carve out contracting for specific diseases and specialty services has become extremely common in a very short time. The goal of carve out contracting is simple: to place responsibility for managing care and its cost in the hands of those best suited to provide and manage care. This article provides an overview of carve out contracting for specific diseases. While the article focuses on business and legal issues relating to AIDS/HIV and ESRD, the principles discussed are applicable to numerous diseases.

Community Networks↗
PubMed1994

Theoretical and experimental epitope mapping of thymosin beta 4.

Two rabbit polyclonal antisera, one directed against thymosin beta 4 and the other one against the peptide fragment thymosin beta 4 (1-14) were characterised by epitope mapping. Hexapeptides representing the whole sequence of the native peptide and overlapping by one amino acid were synthesised on polystyrene pins. The antigenic determinants were identified in microtitre plates with an ELISA procedure. The polyclonal serum against thymosin beta 4 detected three epitopes (N-terminal, mid-region and C-terminal) whereas the polyclonal serum against the fragment contained only antibodies specific for the N-terminal epitope. These experimental results are consistent with theoretical predictions.

Amino Acid Sequence↗
PubMed1994

Interactions between respiratory epithelial cells and cytokines: relationships to lung inflammation.

Epithelial cells lining respiratory airways can participate in inflammation in a number of ways. They can act as target cells, responding to exposure to a variety of inflammatory mediators and cytokines by altering one or several of their functions, such as mucin secretion, ion transport, or ciliary beating. Aberrations in any of these functions can affect local inflammatory responses and compromise pulmonary defense. For example, oxidant stress can increase secretion of mucin and depress ciliary beating efficiency, thereby affecting the ability of the mucociliary system to clear potentially pathogenic microbial agents. Recent studies have indicated that airway epithelial cells also can act as "effector" cells, synthesizing and releasing cytokines, lipid mediators, and reactive oxygen species in response to a number of pathologically relevant stimuli, thereby contributing to inflammation. Many of these epithelial-derived substances can act locally, affecting both neighboring cells and tissues, or, via autocrine or paracrine mechanisms, affect structure and function of the epithelial cells themselves. Studies in our laboratories utilized cell cultures of both human and guinea pig tracheobronchial and nasal epithelial cells, and isolated human nasal epithelial cells, to investigate activity of respiratory epithelial cells in vitro as sources of cytokines and inflammatory mediators. Primary cultures of guinea pig and human tracheobronchial and nasal epithelial cells synthesize and secrete low levels of IL-6 and IL-8 constitutively. Production and release of these cytokines increases substantially after exposure to specific inflammatory stimuli, such as TNF or IL-1, and after viral infection.

Animals↗
PubMed1994

Dissecting differential binding in the forward and reverse reaction of Escherichia coli maltodextrin phosphorylase using 2-deoxyglucosyl substrates.

Substrate analogs are used in combination with site-directed mutagenesis to probe specific interactions between substrate and enzyme in the forward and reverse direction of the Escherichia coli maltodextrin phosphorylase reaction. In the phosphorolysis (degradation) mode, removal of the 2-OH group of the terminal glucose of the polysaccharide results in a 30-fold reduction of Km while similar changes were of no influence when the same polysaccharide was used for priming the synthesis. Mutation of active site residues Glu637 or Tyr538 does not change apparent affinity of substrates during degradation. In the synthesis mode, 2-deoxyglucose-1-P as substrate causes a 2-fold reduction of the wild-type kcat/Km while for the Y538F mutant a approximately 7-fold reduction is observed. In contrast, the mutation of Glu637 to Asp causes a 10-fold increase in kcat/Km. Therefore, different binding sites for the terminal glucose residue of the oligosaccharide and glucose-1-P exist. Glu637 and Tyr538 are part of the glucose-1-P binding site and do not interact with the terminal glucose residue. A 2-fold increase in rate was observed in both directions using the 2-deoxy derivatives. This confirms the role of intrinsic electronic effects in stabilizing the transition state. Uncompetitive substrate inhibition at high concentrations of maltoheptaose in the phosphorolysis direction is explained by inhibitory binding of the sugar in the synthesis mode.

Amino Acid Sequence↗
PubMed1994

Oxygen regulated gene expression in facultatively anaerobic bacteria.

In facultatively anaerobic bacteria such as Escherichia coli, oxygen and other electron acceptors fundamentally influence catabolic and anabolic pathways. E. coli is able to grow aerobically by respiration and in the absence of O2 by anaerobic respiration with nitrate, nitrite, fumarate, dimethylsulfoxide and trimethylamine N-oxide as acceptors or by fermentation. The expression of the various catabolic pathways occurs according to a hierarchy with 3 or 4 levels. Aerobic respiration at the highest level is followed by nitrate respiration (level 2), anaerobic respiration with the other acceptors (level 3) and fermentation. In other bacteria, different regulatory cascades with other underlying principles can be observed. Regulation of anabolism in response to O2 availability is important, too. It is caused by different requirements of cofactors or coenzymes in aerobic and anaerobic metabolism and by the requirement for different O2-independent biosynthetic routes under anoxia. The regulation mainly occurs at the transcriptional level. In E. coli, 4 global regulatory systems are known to be essential for the aerobic/anaerobic switch and the described hierarchy. A two-component sensor/regulator system comprising ArcB (sensor) and ArcA (transcriptional regulator) is responsible for regulation of aerobic metabolism. The FNR protein is a transcriptional sensor-regulator protein which regulates anaerobic respiratory genes in response to O2 availability. The gene activator FhlA regulates fermentative formate and hydrogen metabolism with formate as the inductor. ArcA/B and FNR directly respond to O2, FhlA indirectly by decreased levels of formate in the presence of O2. Regulation of nitrate/nitrite catabolism is effected by two 2-component sensor/regulator systems NarX(Q)/NarL(P) in response to nitrate/nitrite. Co-operation of the different regulatory systems at the target promoters which are in part under dual (or manifold) transcriptional control causes the expression according to the hierarchy. The sensing of the environmental signals by the sensor proteins or domains is not well understood so far. FNR, which acts presumably as a cytoplasmic 'one component' sensor-regulator, is suggested to sense directly cytoplasmic O2-levels corresponding to the environmental O2-levels.

Aerobiosis↗
PubMed1994

Lack of direct immunosuppressive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on human peripheral blood lymphocyte subsets in vitro.

A wide variety of immunosuppressive effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in experimental animals has been documented. In contrast, the impact of dioxin on the human immune system remains controversial, although adverse health effects have been reported in humans after occupational or accidental exposure to dioxin. Recently, Neubert et al. (1991) found that a dose-dependent decrease of peripheral blood lymphocyte (PBL) subpopulations in humans and non-human primates, including helper-inducer/memory cells (CD4+CD29+) and B cells (CD20+) occurred in pokeweed mitogen (PWM) stimulated cultures at concentrations as low as 10(-12)-10(-14) M TCDD. Therefore, the direct effects of dioxin on human PBL subpopulations have been studied, in order to determine their usefulness as sensitive biomarkers for human dioxin exposure. Lymphocyte cultures from healthy individuals were treated with 10(-7) M-10(-14) M TCDD in the absence and presence of stimulation with pokeweed mitogen (PWM) or anti-CD3 monoclonal antibody (moAb; OKT3) for 3 days. Cytochrome P450 (CYP1A1) enzyme induction, one of the best studied direct biological effects of TCDD on numerous cell types, was assayed in parallel by ethoxyresorufin-O-deethylase (EROD) activity. Percentages of the different lymphocytes subsets, including CD2 (T cells); CD4; CD45 RA (suppressor-inducer/virgin T cells); CD4 CD29; CD8; CD19 (B cells) as well as interleukin 2 (IL-2) receptor (CD25) and class II antigen (HLA-DR) expression, were analyzed by flow cytometry. DNA synthesis was determined by 3H-thymidine uptake after 3 days of culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

[Parenchymatous abscess in Streptococcus anginosus (Streptococcus milleri) septicemia. Value of their systematic search, apropos of 4 cases].

Streptococcus anginosus, the term suggested to cover a set of streptococci previously known under various names (milleri, MG, anginosus, intermedius, constellatus), is characterized by a propensity to create parenchymatous abscesses, essentially cerebral or hepatic, particularly within the terms of septicemia. These abscesses are sometimes difficult to detect due to a difficult or non-existent symptomatology. The authors report on four cases illustrating the necessity to search for them systematically by cerebral CT scan and abdominal echography or CT scan in all cases of septicemia caused by Streptococcus anginosus.

Aged↗
PubMed1994

Reliability study of reporting of days since last sexual intercourse in Matlab, Bangladesh.

The accuracy of responses to a question on the frequency of sexual intercourse in the 4-week period prior to an interview is expected to be low. This paper examines the reliability of an alternative question: 'How many days since you last had sexual intercourse?'. This was a part of a larger longitudinal study of fertility dynamics in Matlab, Bangladesh. The response pairs of 61 women who were asked the same question by an interviewer and on the next day by a supervisor, were analysed. Refusals were more common among older women and among women who gave a response at the extremes of the distribution for the other interview. Of the pairs of two responses, 78% had a difference of 3 days or less. Further study and use of the question on days since last intercourse is recommended.

Adolescent↗
PubMed1994

Mycobacterium abscessus pseudoinfection traced to an automated endoscope washer: utility of epidemiologic and laboratory investigation.

After 15 patients had positive cultures for Mycobacterium abscessus without evidence of infection (i.e., pseudoinfection) following endoscopy, retrospective cohort studies of patients undergoing endoscopy and microbiologic sampling of the environment were done to examine potential nosocomial transmission and to identify the source and risk factors for M. abscessus pseudoinfection. In the epidemic period, M. abscessus-positive cultures were significantly more likely to be obtained during bronchoscopy than gastroendoscopy (16/149 vs. 1/860, P < .001) and during procedures using bronchoscopes disinfected in an automated washer rather than by other methods (16/54 vs. 0/95, P < .001). M. abscessus was recovered from the automated washer, the inlet water feeding the washer, and a flexible bronchoscope. Environmental and case-patient isolates had identical large restriction fragment (LRF) patterns of genomic DNA separated by pulsed-field gel electrophoresis. Molecular typing using LRF analysis supported the epidemiologic results and demonstrate the utility of combined epidemiologic and laboratory investigations in nosocomial outbreaks of nontuberculous mycobacteria.

Adult↗
PubMed1994

The nucleoprotein of Marburg virus is phosphorylated.

The nucleoprotein (NP) of Marburg virus (MBG), a filovirus, is encoded by the gene closest to the 3' end of the non-segmented negative-strand RNA genome. Sequence comparison has indicated that NP is the functional equivalent to the nucleoproteins of paramyxoviruses and rhabdoviruses. Expression of recombinant NP in two eukaryotic systems using vaccinia virus and baculovirus (vectors pSC11 and pAcYMB1, respectively) and analysis of MBG-specific proteins have demonstrated that the NP of MBG is phosphorylated. The NP appeared in two forms differing in M(r) by about 2K (94K and 92K respectively). Dephosphorylation clearly demonstrated that the 94K form is phosphorylated whereas the 92K form is unphosphorylated. In virion particles NP was exclusively present in the phosphorylated form. These findings suggest that only the phosphorylated NP can form nucleocapsid complexes and interact with the genomic RNA.

Antibodies↗