| pubmed-article:1282699 | pubmed:abstractText | The purpose of this study was to determine if the newborn pig brain had a reserve of unperfused capillaries during normoxia. To accomplish this, a method was developed to determine the volume fraction, surface area, and number of both total and perfused capillaries in the newborn pig brain. Newborn pigs of either sex, 2-7 d old, were used. FITC-dextran, molecular weight 147,000, was used as a plasma marker to visualize the perfused capillaries. Alkaline phosphatase staining was used to stain the total capillary bed of the brain. Our results showed that FITC-dextran stayed within the vascular compartment, as it was not seen in areas that were not subsequently visualized with alkaline phosphatase staining. Eighty-four to 86% of the alkaline phosphatase-stained capillaries could be visualized with perfusion markers (india ink or FITC-dextran) in different brain regions. Similar results were obtained in two animals using a basement membrane stain, silver methenamine. The total volume fraction of capillaries (mm3/mm3) was cortex 0.055 +/- 0.012, cerebellum 0.062 +/- 0.011, and medulla 0.039 +/- 0.012. Capillary surface area (mm2/mm3) of different brain regions averaged cortex 23.2 +/- 1.8, cerebellum 24.8 +/- 2.5, and medulla 15.8 +/- 2.9. The total number of capillaries (per mm2) was cortex 375 +/- 37, cerebellum 329 +/- 37, and medulla 216 +/- 32. The time course of filling of the capillaries indicated that approximately 50% were perfused at 6 s, which increased to over 80% at 12 s and remained unchanged thereafter.(ABSTRACT TRUNCATED AT 250 WORDS) | lld:pubmed |
