Investigations on the Filter Capacity of the Dog's Brain

P, Prosenz

doi:10.1001/archneur.1972.00490120019001

Cited by 26 publications

(2 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast, the comparison of 15-and 10-~m spheres resulted in highly significant differences. Incomplete extraction of 8-~tm microspheres by the brain (16) and by the kidneys (17), however, was also found in dogs. This is surprising since good extraction was found in dogs for microspheres of sizes between 4 and 12 ~m in diameter (6).…”

Section: Discussionmentioning

confidence: 99%

Validation studies for the use of the microsphere method in cats and young minipigs

1980

View full text Add to dashboard Cite

Radioactive microspheres are suitable for measuring cardiac output, its distribution and organ blood flow if certain criteria are met. Cardiac output may be determined with the reference flow method if microspheres do not recirculate. In case 10 micron microspheres were extracted completely by the lungs. The use of microspheres for the determination of cardiac output is therefore not limited by recirculation of microspheres down to this size. Under baseline conditions we found no preferential streaming with 50 micron spheres in young minipigs and with 25 and 15 micron spheres in cats At high cardiac output values induced by the administration of 0.4 mg/kg of Dihydralazine in cats, 25 micron but not 15 micron microspheres showed a small, non significant tendency to stream preferentially into the upper body. Thus, under rapid flow conditions 15 micron microspheres may be preferable to larger ones from the rheological point of view. Under baseline conditions the distribution of cardiac output to a wide range of organs was very similar when comparing 25 and 15 micron microspheres in cats and 50 and 15 micron microspheres in minipigs, whereas 10 micron microspheres were poorly extracted by most organ in cats. 15 micron microspheres were found to be suitable for the determination of cardiac output and its distribution in both species provided that bronchial and arteriovenous shunt flows can be neglected.

show abstract

Section: Discussionmentioning

confidence: 99%

Validation studies for the use of the microsphere method in cats and young minipigs

1980

View full text Add to dashboard Cite

show abstract

“…Although the anti-5-HT nature of methysergide has been demonstrated in practically every vascular region, the regional haemodynamic effects of methysergide itself resemble those caused by 5-HT. Substantial arteriovenous shunt flow has been demonstrated in both ears (Warren & Ledingham, 1974) and intracranial structures (Gillilan & Markesbery, 1963;Rowbotham & Little, 1965;Prosenz, 1972) and 5-HT has been reported to reduce A-V shunting (Rondell, Palmer & Bohr, 1957). As we have found when using higher doses (10 pg kg-1 min-') of 5-HT (Saxena & others, 1978) methysergide also increased blood flow to the ears.…”

Section: Discussionmentioning

confidence: 99%

The influence of methysergide on 5-hydroxytryptamine-induced changes in regional distribution of blood flow

Forsyth

Saxena

1978

Journal of Pharmacy and Pharmacology

View full text Add to dashboard Cite

Systemic and regional haernodynamic variables were measured at the baseline and after saline or 5-HT infusions ( 5 p g kg-l min-l, i.v.) or methysergide injections (0.5 mg kg-l, i.v.). Cardiac output and its complete distribution were measured by the radioactive microsphere (15 p m diam.) technique. Although 5-HT did not change the systemic variables, methysergide caused a moderate increase in systolic and mean blood pressure and heart rate. 5-HT caused a substantial increase in gastric and a moderate increase in cerebral and myocardial blood flow at the expense of that to the lungs (arteriovenous shunt + bronchial flows), kidneys and skin. While rnethysergide was able to reduce the vascular responses to 5-HT in stomach, skin, kidneys, heart, lungs and brain, the drug itself, like 5-HT, decreased the number of microspheres reaching the lungs. Since a large number of 15 p m microspheres can escape through the arteriovenous anastomoses to lodge in the lungs it seems likely that both 5-HT and methysergide can reduce the 'non-nutrient' flow through these anastomoses.

show abstract

Brain Permeability of Water

Raichle¹,

Eichling²,

Grubb³

1974

Archives of Neurology

View full text Add to dashboard Cite

The equilibration of labeled water (H2 15O)with the exchangeable water pool of brain was examined during a single capillary transit. The labeled water did not equilibrate freely when cerebral blood flow (CBF) exceeded 20 (ml/100 gm)/min in the rhesus monkey. At normal CBF [.. 50 (ml/100 gm)/min] only 90% of the injected bolus freely equilibrated with brain. This value progressively declined as CBF increased.(30: [319][320][321] 1974) Radi oi sotopes of water have been widely assumed to equilibrate with the exchangeable water in brain during a single capillary transit.1-3For this reason, labeled water has been used as a standard for the eval¬ uation of the blood-brain barrier transport and brain distribution of other substances4 and as a tracer for the measurement of cerebral blood flow (CBF).' We present evidence that labeled water does not freely equilibrate with the exchangeable water in brain when mean CBF ex¬ ceeds 20 (ml/100 gm)/min. MethodsThe fraction of labeled water extracted by the brain during a single capillary tran¬ sit was determined subsequent to the in¬ ternal carotid injection of 0.2 ml of whole blood labeled with H21506 in 20 adult rhesus monkeys. To facilitate the injection of the radioisotope into the internal carotid ar¬ tery, all branches of the right external ca¬ rotid artery were ligated two weeks prior to the experiments. The radioisotope was then injected into the common carotid ar¬ tery through a small (0.021 cm) catheter positioned there under fluoroscopic control from the femoral artery.The monkeys were anesthetized with phencyclidine, paralyzed with gallamine triethiodide, and passively ventilated on 100% oxygen. The end-tidal carbon dioxide pressure (Pco2), arterial blood pressure, and rectal temperature were monitored continuously. Arterial pH, Pco,, and oxy¬ gen pressure were measured before and after each injection.The time course of labeled water through the brain was detected by a 3x2 inch sodium iodide, thallium impregnated scintillation detector appropriately posi¬ tioned and collimated to insure uniform detection efficiency. The signal from the detector, after suitable electronic process¬ ing including narrow pulse height analysis, was processed in a classic small laboratory computer where corrections were made for isotope decay and room background. Tem¬ poral resolution of the data was optimized

show abstract

Investigations on the Filter Capacity of the Dog's Brain

Cited by 26 publications

References 14 publications

Validation studies for the use of the microsphere method in cats and young minipigs

Validation studies for the use of the microsphere method in cats and young minipigs

The influence of methysergide on 5-hydroxytryptamine-induced changes in regional distribution of blood flow

Brain Permeability of Water

Contact Info

Product

Resources

About