A standard method is described wliich gives reproducible blood volume values for rats and their various organs and tissues.

No abstract

and Oniocrdlg o f Waxkington, Seallle, Wmhinglon THIRTY-TTIBEE FIQURERSITES OF PUOTEII SYNTHESIS 227 yeast was added t,o 9 parts of the prepared diet formula arid then the expected weight gain was observed ( fig. 1). A few of the animals w-cre used in pilot expcrimcnts. The others werc treated as indicated below.'For radioa2~ictogru,phic observu.tions, DL-methionine-S35 (specific activity, 1 mc per 10.3 mg) 1va.s injoctcxi subcutaneously, 7.7 vc (0.0793 mg of methionine) per gram of body weight, 4 weeks after surgery. Injecti.ons were administered to three coat.rol. ruts which were sacrificed 4, 24 and 36 hours later respectively, and to t.wo rats from each of tlie tliyroidcct.omierd and thyroxine-tren,ted-thyroidectomized groups, which were sacrificed 4 and 36 hours latcr r.cspcc.t.ively. The tinimals were mc.st.l.ietizei1 with ether and killed by withdrawing a1.l the !)lootl oMainable from thc inferior vena cam.Blood smears ~v e i :~ niadc imniediatcly f o r each rat usi.rig 1 part of blood diluted with 3 p r t s of non-radi.oactive rat ser*um. 1.hc smears were a.ir dried, fixod f o r 4 niiniites in d)solutct methyl alcohol, arid stained for 1. hour with Wright ?s bl.ootl stain. Tlic wi(?xrs were t.ben coated wi.tl.1 unidlsioii €or mdioautography as indicated bclow and cxposed for 1' 2, 3 or 4 weeks.For fixat.io11, two pieccs of most, organs and tksues tverc r.cmoved and placed respec,tivcly i.n Rouin's fixative and. in 55: t.ri.chlorzlcetic acid. In order to insure obt.uining active hair follicles, skin samples extending from the dorm1 to the ventral midl.ine were taken from thc lower thoracic region. Tissues were kept in fixative for about a day wit,h the. cxccptioii of' head of tibia, lower jaw and tccth, foot pad, hppophysis, cerebrum and ccrcbellum, which were left in 5yj t,richloracct,ic acid for 3 weeks heforc processing.Sections were cut at 8 p and stained hy routine h,ematoxylineosin or kept unstained. Coated radioautographs (BQlaiiger and Lehlonci, '46 ; Gross ef al., '51) werc prepared by covering the scct.ions with melted KTR-3 emulsion (Eastman Kotlak) -Thc stained sets werc exposed for 10, 24 and 36 hours, the unstaincci set.s for 8,22, and 96 hours. r i

Crystalline insulin or glucagon labeled with I131 was injected intravenously in adult male Sprague-Dawley rats under ether anesthesia. The left kidney was removed at intervals ranging from 10 seconds to 6 minutes following the injection, and radioautographs of histological sections were prepared. Radioactivity was found to be concentrated in the cortex of the kidney. At intervals less than 2 minutes after injection, radioactivity was prominent in the lumina of proximal convoluted tubules. At later intervals radioactivity tended to become more concentrated in the cells of the proximal tubules than in the lumina. The observations support the hypothesis that proteins may be filtered through the glomerular membrane and reabsorbed in the tubules.