Search PubMed⌕ Search

Biomedical subjects

B Dickson

Publications and source records attributed to B Dickson.

At least 37 records · Page 2Linked to original sources
PubMed1991

Importance of the position of TYR R boxes for repression and activation of the tyrP and aroF genes in Escherichia coli.

Tyrosine-mediated repression of aroF and tyrP was studied by inserting DNA sequences between the two adjacent TYR R boxes which, in each case, overlap the respective RNA polymerase binding sites of these genes. In both cases, repression was greatest when homologous regions of these two TYR R boxes were on the same face of the DNA helix and the boxes were directly adjacent. An insertion of 3 bases was sufficient to abolish repression, which was reestablished as the boxes became separated by one full turn of the helix. These observations, coupled with the results of in vitro DNase I protection studies, supported the hypothesis that the binding of TyrR protein to the downstream boxes required cooperative interaction with TyrR protein already bound to the upstream boxes. In the case of tyrP, moving the upstream box also affected activation. Maximal activation was observed when the box was moved 3 or 12 to 14 residues upstream. Practically no activation was seen at intermediate positions, such as +7 and -4. It is hypothesized that these results indicate positions allowing maximal interaction between TyrR protein bound to the upstream box and RNA polymerase bound to the RNA polymerase binding site.

Base Sequence↗
PubMed1989

The role of a static bend in the DNA of the aroF regulatory region of Escherichia coli.

DNA fragments containing the regulatory regions of two genes repressed by the tyrR gene product exhibit retarded electrophoretic mobility in polyacrylamide gels indicating the presence of static bends in the DNA. In the aroF gene this bend has been localized to a region containing two TyrR protein-binding sites. A point mutation between these two sites reduced the degree of bending observed but did not reduce the level of repression, indicating the static bend may not be an important component of the repression mechanism.

Base Sequence↗
PubMed1988

Law and medicine: conflict or collaboration? The 1988 Harvey Cushing oration.

Doctors and lawyers share the common goal of pursuit of the welfare of the patient and client. Even where litigation brings physicians into conflict with the law, collaboration must be our guide. The standard of care is defined by reference to the expertise of the medical profession. The need for informed consent is based upon the moral and ethical values our professions share. In assessing fair compensation, legal rules are shaped by the need to make the lives of the injured and disabled bearable, again an ethical value we hold in common. The nature of our day-to-day tasks and the methods we employ may be different, but we must never lose sight of the fact that the interests of society can only be met if we work closely together.

Canada↗
PubMed1988

A blinded endoscopic comparative study of misoprostol versus sucralfate and placebo in the prevention of aspirin-induced gastric and duodenal ulceration.

In a series of previous studies, we showed that misoprostol protects the gastric and duodenal mucosae against ulceration seen with the administration of both aspirin and the nonsteroidal antiinflammatory drug tolmetin. The purpose of this study was to confirm, in addition, that misoprostol protects the mucosae against aspirin-induced damage and, for the first time, to compare its cytoprotective properties with those of sucralfate. Thirty healthy volunteers were randomized into three equal groups receiving either misoprostol 200 micrograms, sucralfate 1 g, or placebo, co-administered with 650 mg of aspirin, four times a day for 7 days. All subjects had endoscopically normal mucosae on entry and were reendoscoped 2 h after a single final dose on day 7. The mucosae were graded on a 0-4 scale as follows: 0 = normal, 1 = single hemorrhage or erosion, 2 = 2-10 hemorrhages or erosions, 3 = 11-25 hemorrhages or erosions, 4 = more than 25 hemorrhages or erosions or an invasive ulcer of any size. Utilizing a previously established criterion of a score of 2 or less as a clinically significant degree of protection to the gastric mucosae, we found that the success rate for misoprostol was 100% (10/10), compared to 20% (2/10) for sucralfate and 0% (0/10) for placebo. Misoprostol was statistically significantly superior to both sucralfate (p = 0.0001) and placebo (p = 0.00001), with 95% confidence intervals on the difference in success rates between misoprostol and sucralfate and between misoprostol and placebo of (44%; 100%) and (61%; 100%), respectively. In the duodenum, nine of 10 subjects taking misoprostol showed no damage (0 grade), whereas this was seen in only five sucralfate and three placebo patients. Misoprostol was significantly superior to placebo (p = 0.020) and marginally superior to sucralfate (p = 0.141) with confidence intervals of (29%; 91%) and (-5%; 67%), respectively. Adverse experiences were minor and did not differ in the three groups.

Alprostadil↗
PubMed1988

Comparison of equal-weight oral dosages of verapamil hydrochloride and diltiazem hydrochloride in patients with mild to moderate hypertension.

The clinical efficacy, safety, and tolerability of oral verapamil and diltiazem, at total daily dosages of equal weight, were evaluated in a placebo-controlled, double-blind crossover study. Thirty-six ambulatory patients with chronic, stable, mild to moderate hypertension (supine diastolic blood pressure of 94-116 mm Hg) received a dosage of either verapamil or diltiazem 80 mg t.i.d. as the hydrochloride salt for one week after an antihypertensive-drug washout period. Each then received 120 mg of the same drug t.i.d. for one week. After another two-week washout period, the patients were crossed over to the other drug. Each patient had a 12-lead electrocardiogram and measurement of supine and standing blood pressure weekly. In the 32 patients completing the study, low-dose verapamil reduced supine diastolic blood pressure (DBP) from a mean of 101.5 +/- 5.2 to 95.3 +/- 9.5 mm Hg; high dose verapamil reduced DBP to 90.9 +/- 7.4 mm Hg. Standing DBP was reduced to a similar degree. Diltiazem showed an almost identical effect: Supine DBP was reduced from a mean of 101.7 +/- 5.3 to 94.0 +/- 10.1 mm Hg with the low dose and to 91.0 +/- 8.6 mm Hg with the high dose, with similar effects on standing DBP. The high dose of both drugs significantly increased the QTc interval, and both doses of diltiazem significantly increased the PR interval compared with baseline. Both drugs exhibited consistent efficacy with minimal adverse effects. The electrophysiologic safety profile of verapamil was superior to that of diltiazem.

Aged↗
PubMed1986

Pharmacokinetics of albendazole in man.

The pharmacokinetics of albendazole were investigated in healthy volunteers and in patients receiving albendazole for treatment of hydatid disease. Unchanged albendazole was below detectable limits in plasma, urine, bile and cyst fluid. The major metabolite present in all fluids was the sulfoxide. Maximum concentrations of albendazole sulfoxide in plasma were very variable, probably due to variable absorption of albendazole.

Absorption↗
PubMed1986

The effect of single intravenous doses of cimetidine or ranitidine on gastric secretion.

Intravenous cimetidine, 300 mg or 400 mg, or ranitidine, 50 mg, was administered as a single dose to 36 volunteers in a randomized, crossover fashion. Aspirates of gastric juice were obtained after dosing, and the pH, titratable acidity, gastric fluid volume, and gastric acid output were determined from baseline through 71/2 hours for each subject. Each intervention significantly increased pH and suppressed hydrogen ion concentration, gastric fluid volume, and gastric acid output. Both the magnitudes of the changes when compared with baseline and the time of the mean maximum effects were similar in all three drug regimens. The effect of all three interventions on gastric fluid volume and gastric acid output diminished sharply after 6 hours. The data indicate that the gastric secretory response to all three interventions did not differ substantially.

Adolescent↗
PubMed1986

The effect of age on theophylline clearance in normal subjects.

Dose-interval AUC and clearance of theophylline at steady-state were determined in healthy male subjects in each of three age groups (18-35, 36-54 and 55-70 years old). Mean AUC in the oldest group was significantly higher than in the youngest and clearance in both the middle and oldest groups was significantly lower than in the youngest. Though clearance was significantly correlated with age, age alone accounted for only 31% of the variability in clearance.

Adult↗
PubMed1986

Cimetidine, 800 mg once daily: preliminary European clinical data evaluation.

A multicenter study was carried out on a total of 574 patients to investigate the safety and efficacy of a 800-mg nighttime dose of cimetidine in comparison with 400 mg twice daily for 4 or 8 weeks in the treatment of patients with duodenal ulcer. No statistically significant differences were observed between the two regimens. Healing rates were as follows: at 4 weeks 212 of 269 patients (79%) healed with the once daily regimen whereas 200 of 270 patients (74%) healed with the twice daily dosage; at 8 weeks 242 of 251 patients (96%) healed with the once daily regimen as compared with 232 of 246 (94%) treated with the twice daily dosage. The dosages were equally effective in relief of pain during the study period. The results confirm that a single nighttime dose of cimetidine is as effective as the twice daily regimen.

Administration, Oral↗
PubMed1986

Australian National Health and Medical Research Council dietary salt study in mild hypertension.

Two-hundred-and-twelve untreated subjects (mean age 52.3 +/- 0.8 years; 181 males and 31 females) with a diastolic blood pressure between 90 and 100 mmHg were recruited to the study. Subjects were seen fortnightly and, after 4 pre-diet visits, were randomized into a normal diet group (A, 55 subjects), a high-potassium diet group (B, 52 subjects receiving greater than 100 mmol K+/day) a reduced-sodium diet group (C, 52 subjects receiving 50-75 mmol Na+/day) or a high-potassium and low-sodium diet group (D, 53 subjects receiving same Na+ and K+ as groups B and C). Two-hundred subjects completed the diet phase of 12 weeks. Urine sodium fell to 86 +/- 7 mmol/day in group C and 73 +/- 6 mmol/day in group D, while daily potassium excretion rose to 96 +/- 5 mmol in group B and 87 +/- 4 mmol in group C. Systolic and diastolic blood pressure fell by 3.8 +/- 1.0 and 1.6 +/- 0.6 mmHg respectively in the normal diet group. The falls in systolic and diastolic blood pressures (mmHg) in the diet phase were 7.7 +/- 1.1 and 4.7 +/- 0.7 (B), 8.9 +/- 1.0 and 5.8 +/- 0.6 (C) and 7.9 +/- 0.9 and 4.2 +/- 0.7 (D). These falls were all greater than those in the control group on an intention-to-treat analysis (P less than 0.005) but did not differ from each other. Factorial analysis confirmed that the falls in pressure attributable to the low-sodium diet and high-potassium diet were not additive.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1981

Null allele frequencies at allozyme loci in natural populations of Drosophila melanogaster.

We have sampled a London population of Drosophila melanogaster for null alleles at twenty-five allozyme loci. The same loci and biochemical techniques were used as in our previous survey of a North Carolina population (Voelker et al. 1980). This second survey is completely concordant with the first. No nulls were detected among the five X-linked loci. The mean frequency of nulls at the twenty autosomal loci was 0.0023. Although there is significant interlocus heterogeneity, the two populations appear to have the same frequencies at each locus. This suggests that null alleles at these allozyme loci are in mutation-selection balance, and we estimate the average heterozygous effect of an allozyme null to be 0.0015. Consideration of allozyme null-allele frequencies, the effects of allozyme null alleles on viability and fertility and the generally greater amount of genetic variability at allozyme loci determined by electrophoresis lead us to doubt the validity of generalizing from allozyme data to the whole genome.

Alleles↗