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T J Simon

Publications and source records attributed to T J Simon.

25 records · Page 2Linked to original sources
PubMed1987

The dual task paradigm: speech dominance or manual dominance?

Two hundred and sixty monolinguals divided into subgroups based on gender, handedness, and familial left-handedness, were given a concurrent task, verbal-manual interference paradigm. The primary purpose of the study was to test whether the dual task interference effects were more related to hemispheric speech or manual dominance factors. The dominant hand, regardless of handedness, underwent relatively more tapping interference than the nondominant hand. The obtained results seriously question the basic assumptions underlying the interpretation of the dual task paradigm as an assessment index for hemispheric language lateralization. A possible explanation of this result that is in keeping with known hemispheric language representation proportions in left-handers is offered based on left hemisphere ipsilateral control of the left hand.

Female↗
PubMed1985

Chronic ethanol increases liver plasma membrane fluidity.

Purified plasma membrane fractions of cultured well-differentiated Reuber H35 hepatoma cells were studied after growth in the presence or absence of ethanol. Growth of cells in the presence of ethanol significantly increased plasma membrane 5'-nucleotidase activity but did not influence sodium-potassium adenosinetriphosphatase activity. Fluorescence polarization of lipophilic probes was used to study membrane lipid structure. Steady-state polarization of diphenylhexatriene (DPH), a probe of the hydrophobic core, was significantly lower in plasma membranes from cells grown in 80 mM ethanol for 3 weeks, compared to controls. Decreased polarization of DPH in plasma membranes was observed after 3-weeks growth of cells in as little as 1 mM ethanol. A 1-h exposure to 80 mM ethanol had no effect. Altered DPH polarization was due to a decrease in the order parameter of the probe. The rotational correlation time of the probe was virtually unchanged. Chronic ethanol treatment of cells did not alter the polarization of the membrane surface probe trimethylammoniodiphenylhexatriene. Plasma membranes from cells grown in 80 mM ethanol had decreased contents of both phospholipid and unesterified cholesterol, but the cholesterol to phospholipid ratio was unchanged. The percentages of sphingomyelin and phosphatidylserine in plasma membrane phospholipids were significantly decreased after ethanol treatment, while the phosphatidylcholine/sphingomyelin ratio was increased by 42%. Vesicles prepared from total plasma membrane lipids of ethanol-treated cells, as well as vesicles prepared from polar lipids alone, showed the same alterations in DPH polarization as did plasma membranes. The importance of ethanol metabolism in the observed plasma membrane changes was demonstrated in two ways.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Binding of T4 endonuclease V to deoxyribonucleic acid irradiated with ultraviolet light.

Endonuclease V of bacteriophage T4 binds to UV-irradiated deoxyribonucleic acid (DNA) but not to unirradiated DNA. We have developed an assay to detect this binding, based on the retention of enzyme--DNA complexes on nitrocellulose filters. The amount of complex retained, ascertained by using radioactive DNA, is a measure of T4 endonuclease V activity. The assay is simple, rapid, and specific, which makes it useful for detecting T4 endonuclease V activity both in crude lysates and in purified preparations. We have used it to monitor enzyme activity during purification and to study binding of the enzyme to DNA under conditions that minimize the ability of the enzyme to nick DNA. From our data we conclude that (1) T4 endonuclease V binds to UV-irradiated DNA but not to DNA that has been previously incised by the endonuclease, (2) equilibrium between the free and complexed form of the enzyme is attained under our reaction conditions, (3) dissociation of enzyme--DNA complexes is retarded by sodium cyanide, and (4) retention of enzyme--DNA complexes on nitrocellulose filters is enhanced by high concentrations of saline--citrate.

Cyanides↗
PubMed1975

Action of bacteriophage T4 ultraviolet endonuclease on duplex DNA containing one ultraviolet-irradiated strand.

Previous studies have indicated that the ultraviolet endonuclease of bacteriophage T4 acts specifically at pyrimidine dimer sites in ultraviolet-irradiated DNA. At such sites the enzyme could conceivably catalyze endonucleolytic incision of the DNA either on the dimer-containing strand or on the strand directly opposite to the dimer. In the present work, a direct test of these alternatives was made. Substrate molecules containing one irradiated and one unirradiated strand were prepared from differentially isotopically labeled purified complementary strands of bacteriophage lambdaDNA. Following incubation with the enzyme, the sedimentation profiles of the DNA strands in alkaline sucrose density gradients were compared. The results show that the enzyme selectively nicks the irradiated strand.

Centrifugation, Density Gradient↗
PubMed1975

Repair replication in permeabilized Escherichia coli.

We have examined the modes of DNA synthesis in Escherichia coli strains made permeable to nucleoside triphosphates by treatment with toluene. In this quasi in vitro system, polymerase-I-deficient mutants exhibit a nonconservative mode of synthesis with properties expected for the resynthesis step of excision-repair. This UV-stimulated DNA synthesis can be performed by either DNA polymerase II or III and it also requires the uvrA gene product. It requires the four deoxynucleoside triphosphates; but, in contrast to the semiconservative mode, the ATP requirement can be partially satisfied by other nucleoside triphosphates. The ATP-dependent recBC nuclease is not involved. The observed UV-stimulated mode of DNA synthesis may be part of an alternate excision-repair mechanism which supplements or complements DNA-polymerase-I-dependent repair in vivo.

Adenosine Triphosphate↗
PubMedDate not supplied

Acid suppression by famotidine 20 mg twice daily or 40 mg twice daily in preventing relapse of endoscopic recurrence of erosive esophagitis.

Control of esophageal acid exposure is important in treating patients with gastroesophageal reflux disease (GERD). After complete healing of esophagitis, most patients will relapse within 6 months if left untreated. This multicenter, randomized, double-masked, placebo-controlled trial, conducted in the United States, examined whether two famotidine dosing regimens are effective in extending the time in remission for patients with moderate-to-severe erosive esophagitis. Of 172 patients enrolled, 31 received placebo, 69 received famotidine 20 mg twice daily (BID) , and 72 received famotidine 40 mg BID. Endoscopy was scheduled at baseline and at months 3 and 6. Patients assessed global heartburn and symptom relief at months 3 and 6 relative to the start of the study. Life table (Kaplan-Meier) relapse rates at 6 months were 22% (P < 0.001 vs placebo) for famotidine 20 mg BID, 11% (P < 0.001 vs placebo) for famotidine 40 mg BID, and 62% for placebo. Compared with placebo, patients in the famotidine groups were significantly less likely to note global symptomatic deterioration, as measured by the distribution of global assessment responses. The incidence of clinical and laboratory adverse experiences was similar among treatment groups. For maintenance treatment of GERD, famotidine 20 mg BID and 40 mg BID are more effective than placebo in extending the time in remission.

Adolescent↗