作者机构：
[R D H Boyd; A P Weedon; R H T Ward; T E Stacey] Depts. Paediatrics & Obstetrics U.C.H. Medical School, London, England
摘要：
The sheep placenta behaves as a relatively impermeable barrier. It has an equivalent pore size of 0.45 nm to polar solutes, a low permeability to Na+ , and can maintain an electrical potential difference across it. In order to establish the site of this barrier, volumes of distribution of a vascular marker (125I- or 131I-albumen) were compared with those of an E.C.F. marker (24Na, 22Na, or 51CrEDTA) in 6 chronically catheterised pregnant ewes. Isotopes were injected into fetal, maternal or both circulations between 30 and 250 minutes before rapid induction of anaesthesia and removal of up to 20 cotyledons for isotope counting. Results for isotope spaces, expressed as ml plasma per 100g cotyledon wet weight [mean ± SEM(n)] were:- (i) Fetal: sodium 19.7 ± 1.5(5), CrEDTA 19.3 ± 1.4(3) and albumen 1.75 ± 0.29(4); (ii) Maternal: sodium 23.3 ± 1.7(3) and albumen 5.07 ± 1.52(3). Total cotyledon water content by dessication was 81 ml/100g. We conclude that the anatomical barrier to Na and CrEDTA is the same, and is not in the capillary endothelia, but most probable resides in maternal syncytium or trophoblast junctional complexes.
期刊：
American Journal of Physics,1970年38(1):65 ISSN：0002-9505
作者机构：
B. C. Institute of Technology, Burnaby, British Columbia
摘要：
A method is presented in which topics of a direct technological application are studied by students in technology taking a general physics course. It is found that student motivation is enhanced, and their interest in the over-all course increased, by such a presentation. The development of the specific laboratory projects also gives the staff member of a technical teaching institute the opportunity to spend some time on work close to his own field of specialization. A list of the project labs is available, and specific comments on an example of each of three types offered (paper, bench top model, and field) are given.
