Response of small pulmonary arteries to unilobar hypoxia and hypercapnia

We measured the internal diameters of small muscular pulmonary arteries in the right and left lower lobes of lungs rapidly frozen in the anesthetized, open-thorax cat. In every cat the right lower lobe was ventilated with the test gas and all other lobes were ventilated with O 2 . In 4 cats, the test gas supplied to the right lower lobe was also O 2 (control experiments); in 6, it was 100% N 2 and in 6 it was 90% N 2 -10% CO 2 . In the 4 controls, there was no difference between the internal diameters of corresponding arteries in the right and left lower lobes. In the other 12 cats, there was a highly significant decrease in the diameter of arteries in the right lower lobe that correlated well with a large decrease in blood flow to that lobe, calculated using a shunt equation. Ventilation of the right lower lobe with 10% CO 2 in air (4 cats) did not affect the diameter of arteries and ligation of the pulmonary artery to the right lower lobe resulted in only a slight decrease in arterial dimensions in 3 of 4 cats.

These data show that in regional alveolar hypoxia without systemic hypoxia the muscular pulmonary arteries of the terminal respiratory units in the hypoxic region actively constrict. The constriction occurs with or without alveolar hypercapnia.

Fatty acids in Drosophila melanogaster. II. Separation and identification of saturated fatty acids in Drosophila melanogaster

The component saturated fatty acids of the lipids extracted from the pupal tissues of Drosophila melanogaster have been determined. Treating the mixture of acids with p-bromophenacyl bromide and 2,4-dinitrophenylhydrazine permitted the separation of the saturated from the unsaturated acids. The derivatives were separated by reversed-phase paper chromatography.The following saturated fatty acids were found in the pupal extracts: n-octadecanoic (stearic), n-hexadecanoic (palmitic), n-tetradecanoic (myristic), n-dodecanoic (lauric), n-decanoic (capric), n-octanoic (caprylic), n-hexanoic (caproic), and n-butanoic (butyric) acids.

Distribution of sodium-plus-potassium-stimulated adenosine-triphosphatase activity in isolated nerve-ending particles

1. A rapid method for the isolation of nerve-ending particles from brain is described. This involved the centrifugation of the large-granule fraction over a discontinuous density gradient consisting of 3% (w/v) and 13% (w/v) Ficoll dissolved in 0.32m-sucrose. The results of the biochemical as well as morphological identification of nerve-ending particles are given. 2. Approx. 20% of the (Na(+)+K(+))-stimulated adenosine-triphosphatase activity originally present in the cerebral grey-matter suspension was recovered in the fraction consisting principally of large nerve-ending particles (approx. 1mu in diameter). The activity of the adenosine triphosphatase/mg. of protein in the nerve-ending fraction approximated to that in the small-granule fraction after the treatment with glycol ether diamine-tetra-acetic acid. The conclusion was drawn that the synaptic structure, supposedly the limiting membrane of the nerve-ending particle, is one of the feasible sites of localization of the (Na(+)+K(+))-stimulated adenosine-triphosphatase activity in cerebral tissues. Adenosine triphosphatase in purified cerebral mitochondria was not stimulated by Na(+). 3. No qualitative differences were found between the (Na(+)+K(+))-stimulated adenosine-triphosphatase activities exhibited by the nerve-ending particles and by the cerebral small-granule fraction with respect to pH-dependence, cation requirements and susceptibility to ouabain.