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S Alper

Publications and source records attributed to S Alper.

18 recordsLinked to original sources
PubMed1997

Is resting state HCO3- secretion in frog gastric fundus mucosa mediated by apical Cl(-)-HCO3- exchange?

1. We have tested the widely accepted hypothesis that resting-state bicarbonate secretion of gastric fundus mucosa is mediated by Cl(-)-HCO3- exchange in the apical membrane of surface epithelial cells (SECs). To this end, SECs of isolated fundus mucosa of Rana esculenta were punctured with double-barrelled microelectrodes to measure intracellular pH (pHi). 2. No significant pHi changes were observed in response to changing luminal HCO3- and/or Cl- concentrations. The change in pHi (delta pHi) in response to luminal chloride substitution averaged 0.00 +/- 0.01 pH units (mean +/- S.E.M.; n = 48), and did not change after blocking putative basolateral acid/base transporters which could have masked the pHi response. 3. On the other hand, pHi responded readily and reversibly to luminal perfusion with either low-pH (pH 2.5) solution (delta pHi = -0.36 +/- 0.05; n = 4; P < 0.01) or CO2-free HCO3- Ringer solution (delta pHi = +0.10 +/- 0.01; n = 29; P < 0.001). These observations demonstrate that the solution change was effective and complete within 1 min and show that the apical membrane of SECs is permeable to CO2. 4. The apical membrane of frog SECs could not be stained with an antibody against the C-terminal end of the mouse Cl(-)-HCO3- exchanger isoform AE2, although this antibody readily stained the basolateral membrane of the oxyntopeptic cells (OCs). 5. In conclusion, the presence of a Cl(-)-HCO3- exchanger in the apical membrane of SECs of frog gastric fundus mucosa in the resting state could not be confirmed, but other models of HCO3- secretion cannot be fully excluded. Observations from electrical measurements, favouring a model of conductive HCO3- secretion, point to the OCs rather than the SECs as a site of origin of HCO3- secretion.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

SpoIIAA governs the release of the cell-type specific transcription factor sigma F from its anti-sigma factor SpoIIAB.

The Bacillus subtilis transcription factor sigma F is a cell-type specific regulatory protein whose activity is governed by SpoIIAB and SpoIIAA and the nucleotides ATP and ADP. SpoIIAB is an anti-sigma factor that binds to sigma F in a manner that is stimulated by ATP, thereby trapping sigma F in an inactive complex. Alternatively, SpoIIAB binds to SpoIIAA in a manner that is stimulated by ADP to form a SpoIIAB.SpoIIAA complex in which SpoIIAB is sequestered from sigma F. SpoIIAB is also a protein kinase that uses ATP to phosphorylate, and thereby inactivate, SpoIIAA. Thus, ATP inhibits sigma F activity both by promoting formation of the SpoIIAB.sigma F complex and by phosphorylation of SpoIIAA. In extension of previous results, we use affinity chromatography to show that SpoIIAB is capable of forming long-lived complexes with sigma F and SpoIIAA and that the formation of these complexes is dependent on ATP and ADP, respectively. Using a DNA template lacking adenosine residues on the non-transcribed strand, we demonstrate that ATP is required for SpoIIAB-mediated inhibition of sigma F-directed RNA synthesis and that this inhibition is prevented by SpoIIAA in a manner that is stimulated by ADP. We show that ADP acts by protecting SpoIIAA from phosphorylation by SpoIIAB and that a mutant protein bearing an amino acid substitution at the site of phosphorylation in SpoIIAA is capable of preventing the inhibition of sigma F in a manner that does not depend on ADP. A principal finding from the investigation is that SpoIIAA restores activity to sigma F that had previously been inhibited by SpoIIAB. This is demonstrated both by the capacity of SpoIIAA to reverse SpoIIAB-mediated inhibition of sigma F-directed RNA synthesis and by its capacity to interact with and disrupt the SpoIIAB. sigma F complex. The results are consistent with a model in which sigma F is controlled by the cellular concentration of unphosphorylated SpoIIAA.

Adenosine Diphosphate↗
PubMed1996

Role of adenosine nucleotides in the regulation of a stress-response transcription factor in Bacillus subtilis.

The RNA polymerase sigma factor sigma B is a stress-response regulatory protein in Bacillus subtilis. The activity of sigma B is controlled in part by RsbW, a protein that inhibits sigma B, and RsbV, a protein that counteracts this inhibition. We now demonstrate that purified RsbW is capable of forming alternative complexes with either sigma B or RsbV. Sigma B in the RsbW. sigma B complex was transcriptionally inactive. RsbV reversed this inhibition by sequestering RsbW in a RsbW-RsbV complex, thereby allowing sigma B to remain free and active. In contrast to interactions among the components of the homologous regulatory system for the sporulation transcription factor sigma F, the binding of RsbW to RsbV and sigma B did not require adenosine nucleotides. Experiments involving the exchange of proteins between the two regulatory systems demonstrated that RsbW and its homolog in the sigma F system, SpoIIAB, exhibit strong preference in binding to RsbV and sigma B, and SpoIIAA and sigma F, respectively, and that the difference in nucleotide-dependence of binding between these two systems is attributable to a difference between RsbW and SpoIIAB. In confirmation and extension of previous results, we show that RsbW is also a protein kinase that uses ATP to phosphorylate RsbV, thereby blocking the capacity of RsbV to bind to RsbW and activate transcription. A close correlation was observed between the concentration of ATP required for efficient RsbW-mediated phosphorylation of RsbV, inhibition of RsbW.RsbV comlex formation, and inhibition of sigma B-directed transcription. These results are consistent with the hypothesis that activation of sigma B under certain stress condition is due to a decrease in cellular ATP levels.

Adenosine Diphosphate↗
PubMed1996

SpoIIE governs the phosphorylation state of a protein regulating transcription factor sigma F during sporulation in Bacillus subtilis.

Cell-specific activation of the transcription factor sigma F during sporulation in Bacillus subtilis is controlled by a regulatory pathway involving the proteins SpoIIE, SpoIIAA, and SpoIIAB. SpoIIAB is an antagonist of sigma F, and SpoIIAA, which is capable of overcoming SpoIIAB-mediated inhibition of sigma F, is an antagonist of SpoIIAB. SpoIIAA is, in turn, negatively regulated by SpoIIAB, which phosphorylates SpoIIAA on serine 58. SpoIIAA is also positively regulated by SpoIIE, which dephosphorylates SpoIIAA-P, the phosphorylated form of SpoIIAA. Here, isoelectric focusing and Western blot analysis were used to examine the phosphorylation state of SpoIIAA in vivo. SpoIIAA was found to be largely in the phosphorylated state during sporulation in wild-type cells but a significant portion of the protein that was unphosphorylated could also be detected. Consistent with the idea that SpoIIE governs dephosphorylation of SpoIIAA-P, SpoIIAA was entirely in the phosphorylated state in spoIIE mutant cells. Conversely, overexpression of spoIIE led to an increase in the ratio of unphosphorylated SpoIIAA to SpoIIAA-P and caused inappropriate activation of sigma F in the predivisional sporangium. We also show that a mutant form of SpoIIAA (SpoIIAA-S58T) in which serine 58 was replaced with threonine was present exclusively as SpoIIAA-P, a finding that confirms previous biochemical evidence that the mutant protein is an effective substrate for the SpoIIAB kinase but that SpoIIAA-S58T-P cannot be dephosphorylated by SpoIIE. We conclude that SpoIIE plays a crucial role in controlling the phosphorylation state of SpoIIAA during sporulation and thus in governing the cell-specific activation of sigma F.

Bacillus subtilis↗
PubMed1996

Antigen retrieval in cryostat tissue sections and cultured cells by treatment with sodium dodecyl sulfate (SDS).

A simple method for antigen retrieval in tissue sections and cell cultures is described. Because many antibodies recognize denatured proteins on western blots, but are poorly reactive by immunocytochemistry, the effect of applying sodium dodecyl sulfate (SDS) to cryostat sections of tissues and to cell cultures prior to immunostaining was examined. In many cases, a 5-min pretreatment with 1% SDS produced a dramatic increase in staining intensity by indirect immunofluorescence. Among the antibodies tested that showed a positive effect of SDS were an anti-Na/K-ATPase monoclonal antibody, an anti-AE1/2 anion exchanger polyclonal antipeptide antibody, a monoclonal anti-caveolin antibody, and an anti-rab4 monoclonal antibody. In other cases, including antibodies against gp330, aquaporin 1, and aquaporin 2, no effect of SDS was detected. The results show that SDS treatment can be used as a simple method of antigen retrieval in cryostat sections and on cultured cells. In some cases, antigens were not detectable without pretreatment with SDS.

Animals↗
PubMed1996

Subcellular localization of proteins governing the proteolytic activation of a developmental transcription factor in Bacillus subtilis.

BACKGROUND: Spore formation in Bacillus subtilis takes place in a sporangium consisting of two compartments called the forespore and the mother cell. Late in development, when the forespore is wholly contained within the mother cell, gene transcription is coordinated between the compartments by an intercellular signal transduction pathway. This pathway operates at the level of proteolytic processing of the proprotein precursor (pro-sigma K to the mother-cell transcription factor sigma K. The conversion of pro-sigma K to sigma K is governed by the putative processing enzyme SpoIVFB and its negative regulator SpoIVFA, which are produced in the mother cell. RESULTS: We used fluorescence microscopy in conjunction with antibodies against SpoIVFA and SpoIVFB and a fusion of SpoIVFB to the Green Fluorescent Protein from Aquorea victoria to visualize these proteins in the sporangium. Both proteins were found to co-localize with the forespore region of the sporangium, a finding consistent with the idea that SpoIVFA and SpoIVFB, which are inferred to be integral membrane proteins, are located in the mother cell membrane that surrounds the forespore. CONCLUSIONS: We conclude that SpoIVFA and SpoIVFB are situated at the boundary between the forespore and the mother cell, at which location SpoIVFB could be activated by a signalling protein produced in the forespore.

Antibodies, Bacterial↗
PubMed1995

Activation of cell-specific transcription by a serine phosphatase at the site of asymmetric division.

Cell fate is determined by cell-specific activation of transcription factor sigma F after asymmetric division during sporulation by Bacillus subtilis. The activity of sigma F is governed by SpoIIAA, SpoIIAB, and SpoIIE, a membrane protein localized at the polar septum. SpoIIAB binds to and inhibits sigma F, and SpoIIAA inhibits SpoIIAB, which prevents SpoIIAB from binding to sigma F. SpoIIAB is also a serine kinase that inactivates SpoIIAA. Here, it is demonstrated that SpoIIE dephosphorylates SpoIIAA-P and overcomes SpoIIAB-mediated inhibition of sigma F. The finding that SpoIIE is a serine phosphatase links asymmetric division to the pathway governing cell-specific gene transcription.

Adenosine Triphosphate↗
PubMed1994

An adenosine nucleotide switch controlling the activity of a cell type-specific transcription factor in B. subtilis.

The sigma F factor establishes cell type-specific gene transcription during sporulation in B. subtilis. sigma F is negatively regulated by SpollAB, which forms complexes with sigma F or SpollAA. ATP and its nonhydrolyzable analogs stimulate the formation of the SpollAB.sigma F complex, whereas ADP stimulates the formation of the SpollAB.SpollAA complex. Which protein SpollAB associates with is determined by the concentrations of the two nucleotides, on which basis we propose a partner-switching model for the regulation of sigma F: [formula: see text] Consistent with this model, SpollAA reverses SpollAB-mediated inhibition of sigma F-directed transcription in a manner that depends on ADP. Cell-specific activation of sigma F could be due to an alteration in adenosine nucleotide levels in one cell of the sporangium.

Adenosine Diphosphate↗
PubMed1994

Establishment of cell type specific gene transcription during sporulation in Bacillus subtilis.

Asymmetric cell division during the process of sporulation in the bacterium Bacillus subtilis generates dissimilar progeny that exhibit distinct programs of gene transcription. Recent work reveals a partner switching mechanism that governs the activity of the sporulation regulatory protein sigma F and that may be responsible for the establishment of cell type specific gene transcription.

Adenine Nucleotides↗
PubMed1994

Allergy to sodium hypochlorite during root canal therapy: a case report.

Sodium hypochlorite (NaOCl), is the most popular irrigation solution used in root canal treatment but it is known to be an irritant to vital tissues. There have been many case reports dealing with toxic effects of this material. Although the allergic potential of NaOCl has been described in the medical literature, only one case of known hypersensitivity to NaOCl has been reported in the dental literature. In this paper a case is presented, describing both local and systemic adverse tissue reactions, caused by an allergic response, after NaOCl irrigation.

Adult↗
PubMed1994

Duplication of 10 nucleotides in the erythroid band 3 (AE1) gene in a kindred with hereditary spherocytosis and band 3 protein deficiency (band 3PRAGUE).

We describe a duplication of 10 nucleotides (2,455-2,464) in the band 3 gene in a kindred with autosomal dominant hereditary spherocytosis and a partial deficiency of the band 3 protein that is reflected by decreased rate of transmembrane sulfate flux and decreased density of intramembrane particles. The mutant allele potentially encodes an abnormal band 3 protein with a 3.5-kD COOH-terminal truncation; however, we did not detect the mutant protein in the membrane of mature red blood cells. Since the mRNA levels for the mutant and normal alleles are similar and since the band 3 content is the same in the light and dense red cell fractions, we conclude that the mutant band 3 is either not inserted into the plasma membrane or lost from the membrane prior to the release of red blood cells into circulation. We further show that the decrease in band 3 content principally involves the dimeric laterally and rotationally mobile fraction of the band 3 protein, while the laterally immobile and rotationally restricted band 3 fraction is left essentially intact. We propose that the decreased density of intramembrane particles decreases the stability of the membrane lipid bilayer and causes release of lipid microvesicles that leads to surface area deficiency and spherocytosis.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1994

Using self-recording, evaluation, and graphing to increase completion of homework assignments.

This article describes the use of self-monitoring procedures to increase the number of daily homework assignments completed by eight students with learning disabilities. Students ranged in age from 13 to 16 years and attended Grades 7 through 10. The experimental procedure involved the use of a sheet listing all daily assignments given by regular classroom teachers. A multiple-baseline design across subjects demonstrated a clear relationship between the introduction of self-monitoring of assignments and an increase in assignments completed. Goal setting and self-graphing of data appeared to increase this effect.

Adolescent↗
PubMed1994

Reducing disruptive behaviors by training students to request assistance.

Disruptive behaviors of students with disabilities can have a communicative function. They may aid the learner in escaping from aversive situations, and they may also serve to produce positive events. Disruptive behaviors that have a communicative function may be eliminated by teaching an alternative prosocial response. This study compared the relative effectiveness of two teaching methods for reducing disruptive behaviors exhibited by two primary age students with moderate disabilities. The first method consisted solely of a hierarchy of prompts. The second method combined the prompting hierarchy with a cue to request assistance. A multiple baseline design across students with alternating treatments was used to evaluate performance. Results demonstrated a clear relationship between teaching participants to request assistance and a reduction in disruptive behaviors.

Behavior Therapy↗
PubMed1993

Extended school year programs: a community-driven curriculum model.

Appropriate education guaranteed to children with disabilities under P.L. 94-142 has been translated by the courts to mean more than 180 days of education. There is now a strong legal precedent establishing the right to an extended school year (summer school) for students with severe disabilities. The courts have left open to interpretation, however, issues related to the program implementation. Descriptions of extended school year programs vary widely and include respite for parents, continuation of the regular school year curriculum, and remediation in skill areas. The only consensus seems to be that these programs should be tailored to individual needs. In the present article a systematic approach to curriculum development for students with severe disabilities enrolled in extended school year programs was described. This approach is (a) community driven, (b) consistent with each student's IEP objectives for the regular school year, (c) tailored to the individual student, and (d) consistent with current best practices of teaching functional skills performed by individuals without disabilities in a variety of integrated nonschool settings. Student progress data were presented.

Activities of Daily Living↗
PubMed1977

The effects of a seven day camping experience on volunteer student counselors.

An investigation of the effects of a seven-day camp experience with disturbed adolescents on approximately sixty undergraduate "camp counselors" was conducted. Measures of the types of reinforcement preferred and used as well as an overall attitude toward disturbed adolescents were obtained and evaluated. The results indicated that the student counselors did not use the type of reinforcement that they felt was most important and they did not change their attitudes toward disturbed adolescents as a result of experience. The limitations of the study are discussed as well as some suggestions for future research into practicum sites for programs training teachers of the severely disturbed.

Adolescent↗