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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 811 records · Page 45Linked to original sources
PubMed1982

Ocular defocus, spurious resolution and contrast reversal.

With the increasing popularity of periodic gratings in vision research, the effects of ocular defocus, such as spurious resolution and the presence of more than one maximum in the contrast - defocus level function, are very important. Optical transfer function theory is used to develop graphs and formulae that can be used to predict the presence of spurious resolution for given levels of defocus and spatial frequency in aberration-free optical system. Geometrical optical approximations are used extensively, as these lead to very simple formulae. These general equations, applying to any optical system, are extended to the particular case of ocular defocus. Formulae are presented that can be used to predict the presence of spurious resolution, in terms of such variables as pupil size and longitudinal focus error. Conditions for the observation of spuriously resolved gratings are also discussed. An example is presented for observing spurious resolution and contrast reversal and this example can be presented as a "pseudo" visual illusion.

Humans↗
PubMed1982

The minimum alveolar concentration of nitrous oxide in man.

The potency and anesthetic state produced by nitrous oxide alone were investigated in order to clarify its contribution to the effect of other anesthetic agents. Seven volunteers anesthetized with 1.55 atm absolute N2O in a pressure chamber displayed muscle rigidity with jerking movements, labored and rapid breathing, sweating, and dilated pupils. At 1.1 atm absolute N2O, relaxation and quiescence occurred, sweating ceased, and pupil size decreased. Determination of MAC (using tetanic electrical impulses as the noxious stimulus) produced a mean value of 1.04 +/- 0.10 (SE) atm absolute. All subjects complained of nausea and vomiting after anesthesia.

Adult↗
PubMed1981

Effect of oral diazepam on lower oesophageal sphincter pressure.

The effect of diazepam 10 mg orally was investigated on lower oesophageal sphincter pressure in a random double-blind study of nine healthy volunteers. Barrier pressure decreased to a small but statistically significant extent. The reduction in barrier pressure was not related to the level of drowsiness.

Administration, Oral↗
PubMed1981

Single and combined effects of atropine and metoclopramide on the lower oesophageal sphincter pressure.

The effects of atropine and metoclopramide on the lower oesophageal sphincter pressure (LOSP) were studied in 12 healthy volunteers using oesophageal pressure transducers. Atropine decreased LOSP significantly at 5 min after i.v. injection (P less than 0.005) and this change was sustained for 60 min. Metoclopramide increased LOSP significantly at 3 min after administration i.v. (P less than 0.05) and this change was sustained for 40 min. Following consecutive administration of the drugs the effects of atropine predominated.

Adult↗
PubMed1981

Comparison of the effects of atropine and glycopyrrolate on lower oesophageal sphincter pressure.

Lower oesophageal sphincter pressure (LOSP) has been measured on three separate occasions in nine healthy volunteers using oesophageal pressure transducers. Atropine 0.6 mg decreased LOSP significantly at 5 min after i.v. injection (P less than 0.025) and this change was sustained for 40 min. Glycopyrrolate 0.3 mg or 0.2 mg decreased LOSP significantly at 3 min after i.v. injection (P less than 0.0025). This change was sustained for 60 min and was similar for both doses and also similar in magnitude to the change produced by atropine.

Adult↗
PubMed1981

Partition coefficients of some aromatic alcohols in an n-heptane/water system and their relationship to minimum inhibitory concentration against Pseudomonas aeruginosa and Staphylococcus aureus.

The partition coefficients of the homologous series of aromatic alcohols were determined in an n-heptane/water system. The minimum inhibitory concentrations of benzyl alcohol, 2-phenylethanol, 3-phenylpropanol, 4-phenylbutanol and 5-phenylpentanol were elucidated against Pseudomonas aeruginosa and Staphylococcus aureus. The linear relationship log1/C = a log P + b postulated by Hansch was found to apply.

Alcohols↗
PubMed1981

The effect of 5-fluorouracil and 5-fluorocytosine on the development of the filarial nematodes Brugia pahangi and Dirofilaria immitis.

5-fluorouracil and 5-fluorodeoxyuridine at 30 mg/kg body weight daily for four days inhibit microfilarial production in Brugia pahangi in the jird. Disruption of intrauterine embryogenesis was observed in treated female worms but the compounds were not macrofilaricidal or microfilaricidal under the conditions employed. 5-fluorocytosine possessed no filaricidal or embryostatic activity. The inhibition of microfilaria production by 5-fluorouracil was temporary and larval production was resumed within nine weeks. The compound also inhibited the development of B. pahangi and Dirofilaria immitis larvae in the mosquito Aedes aegypti, when administered to cages of mosquitoes as a 0.01 or 0.001% solution in a 10% aqueous sucrose solution on cotton wool wicks. The development of infective larvae of B. pahangi in the jird was inhibited by 5-fluorouracil.

Animals↗