Subject(s)
Coronary Vessels , Absorptiometry, Photon/methods , Angiography , Coronary Angiography , Humans , Models, BiologicalABSTRACT
Radiopaque angiographic contrast agents are being used as indicators for the measurement of blood flow; the basic assumption for these measurements being that both blood and indicator flow nearly at the same rate. Indicators are injected into the circulation and recorded immediately by X-ray filming or video techniques; density changes at selected points along the recorded vessel are detected; dilution curves are plotted and blood flow is calculated graphically or by computer.
Subject(s)
Angiography/methods , Blood Flow Velocity , Arteries/physiology , Blood Circulation , Densitometry , Electromagnetic Phenomena , Humans , Mathematics , Models, Biological , Regional Blood Flow , UltrasonicsABSTRACT
Tritium-labelled disaggregated chick hypoblast cells were mixed with non-labelled epiblast cells and vice-versa. The mixtures were allowed to aggregate in a gyratory shaker and were transferred on to a solid culture medium for further incubation. The aggregates were fixed after various incubation times, sectioned and examined for sorting-out. There was already a tendency to sort out after 10 h of incubation, a process which was completed after 25 h. The hypoblast cells formed a continuous layer adjacent to the vitelline membrane, while the epiblast cells moved out to form the upper external layer. The position of the two layers was normal as far as the substrate and external environment are concerned, and reversed in relation to their relative position to the vitelline membrane. The hypoblast cells tended to migrate to the margins of the aggregate. The latter phenomenon seems to parallel the migration of hypoblast cells towards the extra-embryonal area during the formation of the primitive streak.
Subject(s)
Chick Embryo/cytology , Animals , Cell Aggregation , Female , Vitelline Membrane/cytologyABSTRACT
Magnesium ferrite, an inert ferrimagnetic material, was introduced as reference substances in absorption trials with ruminants. A method for assaying magnesium ferrite was based upon the difference between the weight of the test material on an analytic balance and that of the same material weighed below a permanent magnet. Four heifers in two pairs were in a feeding experiment lasting for 6 wk divided into two 3-wk periods. Each animal received once daily 12 g magnesium ferrite and, as control, 12 g shredded paper impregnated with 4.2 g chromium oxide. The rations were composed of chopped wheat straw and concentrates, given twice daily, with a different straw-concentrate ratio for each group. The treatments were reversed after the first experimental period. Mean recoveries of magnesium ferrite and chromic oxide in total collection of feces were 103 and 90.2%. Mean absorption coefficients of organic matter calculated by total collection and by the ratios of magnesium ferrite and chromic oxide in feces taken from the rectum were 68.1, 70.1, and 65.7%. The method is simple and accurate and may replace methods involving time consuming chemical determinations.
Subject(s)
Cattle/metabolism , Digestion , Ferric Compounds , Intestinal Absorption , Iron , Stomach, Ruminant/physiology , Animals , Chromium , Feces/analysis , Female , Magnesium , OxidesABSTRACT
The blood flow of iliac arteries was measrued by means of an improved angiographic chindensitometric technique. This consists of cineradiographic recording of contrast injection into the iliac arteries, followed by optical analysis of the "washout" phase of the contrast material at selected sites. In 25 pateints without perpheral vascular disease, undergoing abdominal angiography for different reasons, the blood flow measruements in left iliac arteries were within the limits of 371-766 ml
