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Biomedical subjects

N R Williams

Publications and source records attributed to N R Williams.

44 records · Page 3Linked to original sources
PubMed1989

Maternal zinc during oral iron supplementation in pregnancy: a preliminary study.

1. To investigate the possible effect of iron ingestion on maternal zinc status, one group of women was given 94 mg of iron per day as ferrous sulphate with multivitamins during the second and third trimesters of their pregnancies and another, control, group was given a placebo of multivitamins without iron. 2. The subjects given iron developed significantly lower plasma zinc concentrations than those in the control group. This effect on zinc was maximal by 6 weeks, whilst that on maternal iron status was slower. 3. There was no parallel decrease of zinc concentration in maternal mixed leucocytes, or of plasma heatlabile alkaline phosphatase activity, suggesting that there was a redistribution of zinc between plasma and tissues. 4. The results indicate that iron supplementation during pregnancy alters the disposition of zinc in the mother.

Adult↗
PubMed1986

A simple low-resistance flap valve for pulmonary ventilation studies.

Details of a simple low-resistance flap valve for pulmonary ventilation studies are presented. It has a space of 11 ml, weighs 28 g and is constructed from 3 mm thick perspex sheet. The opening pressure for both the inlet and the outlet is zero as its flaps normally remain open. The resistance of the valve to a flow of air at a rate of 20 l min-1 is 2.2 mm of water at the inlet and 4.2 mm of water at the outlet. At a rate of flow of 100 l min-1 the corresponding figures are 8.9 and 24.6 mm of water. All these values compare favourably with those obtained from three commercially available units. The valve has been in use over the past four years and the patient compliance has been found to be excellent.

Aerosols↗
PubMed1985

Measurements of the rubidium isotopic activities and the elution parameters of 81mKr generators using a standardized 114mIn source.

A method is described for measuring a number of parameters associated with an inorganic ion-exchange krypton generator. These are the activities of rubidium isotopes in inorganic ion-exchange krypton generators, the 81mKr extraction rate, the 81mKr activity delivered to patients during ventilation studies, the elution efficiency, and the radionuclide purity of the eluted gas. The method is based on the calibration of detectors, Ge(Li) and NaI(Tl), with a standardized 114mIn source at matching photon energies. The average activities present in our generators at the end of bombardment (EOB) were 14.6 +/- 3.8 mCi (81Rb), 6.2 +/- 1.6 mCi (82mRb) and 53 +/- 9.4 microCi (83Rb). The 81mKr extraction rate 2 h post-EOB was 10.2 +/- 2.3 mCi/min at an air flowrate of 1 l/min. The 81mKr activity delivered to patients during a ventilation study was 91 +/- 16 mCi. The elution efficiency of the generators averaged 50% +/- 7% at an air flowrate of 1 l/min. The eluted gas contained Rb radioisotopic impurities in trace quantities of approximately 0.06 microCi/l.

Humans↗
PubMed1985

Regional pulmonary distribution of krypton-81m gas delivered by different breathing systems.

Regional pulmonary distribution of 81mKr gas delivered by three breathing systems was determined. Data from 18 patients were analyzed. Posterior images were obtained using each breathing system in turn. Distribution of Kr gas was determined in terms of penetration and zonal indices. For penetration indices each lung was divided into a central, intermediate, and peripheral region and these indices, defined as the ratio of counts/cell in the intermediate or the peripheral region over those in the central region, were calculated. For the zonal indices each lung was divided equally into upper and lower zones and the percentage ratio of the counts in each zone to the total counts in both lungs was calculated. For all patients, in addition, the size, height, and width of each lung were determined from computer images. These parameters were compared between the breathing systems using a paired t-test. It was found that there were no statistical differences among the three breathing systems, either in the regional pulmonary distribution of the 81mKr gas or in the overall shapes of the lungs.

Humans↗
PubMed1984

A simple radioaerosol generator and delivery system for pulmonary ventilation studies.

Details of a simple radioaerosol generator and delivery system are presented. Aerosol streams of 99mTc-DTPA solution of different distributions were produced. The most useful distribution had an activity median aerodynamic diameter (AMAD) of 0.9 micron with a geometric standard deviation of 1.5. This distribution also had more than 96% of aerosol particles with aerodynamic diameter less than 2 micron. The system has been used for patient lung ventilation studies. The aerosol breathing-in period to achieve a satisfactory count rate was 1.8 +/- 0.38 min. The radioaerosol images were excellent and comparable to those obtained with 81mKr gas.

Aerosols↗