Comparison of cerebrospinal fluid transport in fetal and adult sheep.

We quantified cerebrospinal fluid (CSF) transport (conductance) and CSF outflow resistance in late-gestation fetal and adult sheep using two methods, a constant pressure infusion method and a bolus injection technique into the lateral ventricles. No significant differences in CSF conductance (fetus 0.013 +/- 0.002, adult 0.014 +/- 0.003 ml x min(-1) x cm H(2)O(-1)) or CSF outflow resistance (fetus 83.7 +/- 9.8, adult 84.7 +/- 19.7 cm H(2)O x ml(-1) x min) were observed. To confirm CSF transport to plasma in fetal animals, (125)I- or (131)I-labeled human serum albumin (HSA) was injected into the lateral ventricles. The tracer entered fetal plasma with an average mass transport rate of 1.91 +/- 0.47% injected/h (n = 9). In two fetuses, we monitored the tracer appearance in plasma and cervical and thoracic duct lymph after injection of radioactive HSA into the ventricular CSF. As was the case in adult animals, fetal tracer concentrations increased in all three compartments over time, with the highest concentrations measured in lymph collected from the cervical lymphatics. These results 1) indicate that global CSF transport parameters in the late-gestation fetus and adult sheep are similar and 2) suggest an important role for extracranial lymphatic vessels in CSF transport before birth.

Equilibration of 6-[18F]fluoro-L-m-tyrosine between plasma and erythrocytes.

UNLABELLED: Intracranial or intraventricular blood pools have been suggested as noninvasive sources of an input function for quantitative PET. These techniques measure the concentration of the tracer in whole blood, but the concentration in plasma depends on the equilibration of the tracer between plasma and erythrocytes. METHODS: FDG, 6-[18F]fluoro-L-m-tyrosine (FmT), or its major metabolite, 6-[18F]fluoro-3-hydroxyphenylacetic acid (FHPAA), was added to blood samples obtained from healthy fasting volunteers along with radioiodinated human serum albumin (RIHSA). Samples were incubated at 37 degrees C for times between 10 s and 2 h and then plunged into an ice bath and centrifuged. Whole blood and plasma were counted for 18F and 125I activities. The resulting time courses were fit to successively more complex models, evaluated using an F test. RESULTS: All radioactivity associated with RIHSA remained in the plasma, whereas FDG equilibrated instantaneously between plasma and erythrocytes. FmT took about 1 h to equilibrate between plasma and erythrocytes; this time course could be described by a single exponential with a half-life of 10 min. FHPAA equilibrated within the first 5 min of the study. CONCLUSION: Our results show that, unlike FDG, the partitioning of FmT between plasma and erythrocytes is a relatively slow process. We present an analytic correction that may be applied to the measured time course of radioactivity in whole blood to obtain the time course of the tracer in plasma.

Brain-blood permeability: TNF-alpha promotes escape of protein tracer from CSF to blood.

The objective of this study was to determine the effect of tumor necrosis factor (TNF)-alpha on the efflux of protein from the central nervous system to blood based on assessing the clearance of radiolabeled albumin from the cerebrospinal fluid (CSF) to blood in rats. (125)I-labeled human serum albumin ((125)I-HSA) was injected into a lateral ventricle, and venous blood was sampled hourly to determine the basal CSF protein clearance into the blood. After this, rats were intraventricularly infused with 10 microliter TNF-alpha and 10 microliter (131)I-HSA (n = 6) or 10 microliter saline and 10 microliter (131)I-HSA (n = 6). Venous blood was sampled hourly for 3 h. (131)I-HSA tracer recovery increased threefold in the venous blood and was significantly higher in the spleen, muscles, and skin in animals treated with TNF-alpha. No significant changes were observed in control animals treated with saline. The data suggest that TNF-alpha promotes the clearance of protein macromolecules from the CSF to the venous blood.

Absorçäo de líquido de irrigaçäo na ressecçäo transuretral da próstata em cäes / Irrigating fluid absorption during transurethral resection of the prostate in dogs

Trinta e dois cäes submetidos a entubaçäo do ducto torácico e cateterismo bilateral dos ureteres, foram divididos em 3 grupos: A- 4 cäes inoculados com RISA 131 I ou EDTA 51 Cr por via intravenosa ou peri-prostática; B- controle de 8 cäes submetidos a irrigaçäo vesical e prostática com 8 litros de glicina a 1,2 por cento contendo os marcadores radioativos; C- 8 cäes manejados como em B mas sujeitos à RTU da próstata. Os cäes foram acompanhados por 5 horas. A absorçäo de líquido de irrigaçäo foi calculada pelos métodos volumétrico e radioisotópico. Em 5 horas, 97 por cento da RISA 131 I inoculada via intravenosa permanecia neste espaço enquanto apenas 4,6 por cento da injetada no espaço peri-prostático penetrou no compartimento vascular. Para o EDTA 51 Cr, 63,6 por cento da massa inoculada no espaço peri-prostático foi recuperada na urina após 5 horas. O método volumétrico mostrou absorçäo média de 22,7 ml no grupo B e 276 ml no C, e o radioisotópico de 6,3 ml e 165,4 ml, respectivamente. O modelo experimental tem similaridades com o ser humano

Drainage of CSF through lymphatic pathways and arachnoid villi in sheep: measurement of 125I-albumin clearance.

We investigated lymphatic drainage pathways of the central nervous system in conscious sheep and quantified the clearance of a cerebrospinal fluid (CSF) tracer into lymph and blood. In the first group of studies, 125I-HSA was injected into the lateral ventricles of the brain or into lumbar CSF and after 6 h, various lymph nodes and tissues were excised and counted for radioactivity. Multiple lymphatic drainage pathways of cranial CSF existed in the head and neck region defined by elevated 125I-HSA in the retropharyngeal/cervical, thymic, pre-auricular and submandibular nodes. Implicated in spinal CSF drainage were mainly the lumbar and intercostal nodes. In a second group of experiments, multiple cervical vessels and the thoracic duct were cannulated and lymph diverted from the animals. Transport of tracer through arachnoid villi was taken from recoveries in venous blood. Following intraventricular administration, the 6 h recoveries of 125I-HSA in the lymph (sum of cervical and thoracic duct) and blood were 8.2% +/- 3.0 and 12.5% +/- 4.5 respectively and at 22 h, 25.1% +/- 6.9 and 20.8% +/- 4.1 respectively. When 125I-HSA was injected into lumbar CSF, the 6 h recoveries of tracer in thoracic duct and blood were 11.6% +/- 2.7 and 16.3% +/- 3.7 respectively. Total lymph and blood recoveries were not significantly different in any experiment. We conclude that the clearance of 125I-HSA from the CSF is almost equally distributed between lymphatic and arachnoid villi pathways.

Transport of tracer albumin from peritoneum to plasma: role of diaphragmatic, visceral, and parietal lymphatics.

Using a technique to acutely seal off various parts of the peritoneal membrane surface, with or without evisceration, we investigated the role of diaphragmatic, visceral, and parietal peritoneal lymphatic pathways in the drainage of 125I-labeled albumin (RISA) from the peritoneal cavity to the plasma during acute peritoneal dialysis in artificially ventilated rats. The total RISA clearance out of the peritoneal cavity (Cl) as well as the portion of this Cl reaching the plasma per unit time (Cl--> P) were assessed. Under non-steady-state conditions, the Cl was fivefold higher than the Cl--> P. Evisceration caused a 25-30% reduction in both Cl--> P and Cl. Sealing of the diaphragm, however, reduced the Cl--> P by 55% without affecting the Cl. A further reduction in the Cl--> P was obtained by combining sealing of the diaphragm with evisceration, which again markedly reduced the Cl. However, the greatest reduction in the Cl was obtained when the peritoneal surfaces of the anterior abdominal wall were sealed off in eviscerated rats. The discrepancy between the Cl and the Cl--> P can be explained by the local entrance of fluid and macromolecules into periabdominal tissues, where fluid is rapidly absorbed through the capillary walls via the Starling forces, while macromolecules are accumulating due to their very slow uptake by tissue lymphatics under non-steady-state conditions. Of the portion of the total Cl that rapidly entered the plasma, conceivably by lymphatic absorption, 55% could be ascribed to diaphragmatic lymphatics 30% to visceral lymphatics, and only some 10-15% to parietal lymphatics.

Quantitation of lymphatic drainage of the peritoneal cavity in sheep: comparison of direct cannulation techniques with indirect methods to estimate lymph flow.

OBJECTIVE: It has been suggested that lymphatics may contribute to ultrafiltration failure in patients on continuous ambulatory peritoneal dialysis (CAPD) by absorbing dialysate and ultrafiltrate from the peritoneal cavity. In most studies lymphatic drainage has been estimated from the disappearance of an instilled tracer from the peritoneal cavity or estimated from the appearance of an intraperitoneally administered tracer in the bloodstream. However, in sheep it is possible to cannulate several of the relevant lymphatics that drain the peritoneal cavity and assess lymph drainage parameters directly. The purpose of this study was to estimate lymph drainage from the peritoneal cavity in sheep using the disappearance of tracer from the cavity and the appearance of intraperitoneally instilled tracer in the bloodstream and to compare these results with those obtained from our previous studies using cannulation techniques. DESIGN: Experiments were performed in anesthetized and nonanesthetized animals. Volumes of 50 mL/kg of Dianeal 4.25% containing 25 microCi of 125I-albumin were infused into the peritoneal cavity. RESULTS: In anesthetized sheep the calculated peritoneal lymph drainage from monitoring the disappearance of tracer from the peritoneal cavity over 6 hours was 1.873 +/- 0.364 mL/kg/hour. Monitoring the appearance of tracer in the blood gave significantly lower peritoneal lymph flow rates of 1.094 +/- 0.241 mL/kg/hour. Directly measured lymph flow rates from our earlier publication were lower still and ranged from 0.156 +/- 0.028-0.265 +/- 0.049 mL/hour/kg, depending on how we estimated the right lymph duct contribution to peritoneal drainage, since we could not cannulate this vessel. We repeated these experiments in conscious sheep. The value for lymph flow estimated from the disappearance of tracer from the peritoneal cavity was 2.398 +/- 0.617 mL/hour/kg and from the appearance of tracer in the blood, 1.424 +/- 0.113 mL/hour/kg. The lymph flow rates monitored from indwelling lymphatic catheters ranged from 1.021 +/- 0.186-1.523 +/- 0.213 mL/hour/kg (again, depending on our estimates for the right lymph duct). CONCLUSIONS: Lymph flow rates measured from indwelling lymphatic catheters provided the most conservative values for lymphatic drainage of the peritoneal cavity under dialysis conditions. Estimates of lymphatic drainage based on the appearance of tracer in the blood gave values that were on average higher. The method using the disappearance of tracer from the cavity to estimate lymph flows overestimated peritoneal lymph drainage. Fluid was lost from the peritoneal cavity, and the estimated proportion of liquid lost through lymphatic drainage depended on the technique used to measure lymph flow rates.

[A method for determining the body water compartments in patients with mechanical jaundice in the preoperative and postoperative periods]. / O metodike opredeleniia vodnykh prostranstv organizma u bol'nykh mekhanicheskoi zheltukhoi v predoperatsionnom i posleoperatsionnom periodakh.

Literature data concerning the techniques of body fluid determination in patients with mechanical jaundice in the pre- and postoperative periods have been briefly reviewed. A well-known technique of determining total, extra- and intracellular body fluid using urea, sodium rodonate and I13-albumin has been modified. The possibility of one-time determination of body fluids and the results of the author's studies are presented. It has been established that the preoperative period in patients with mechanical jaundice is characterized by considerable disturbances in fluid balance due mainly to total and extracellular body fluid; in the most severe cases there are changes in intracellular space volume. It has been established that upon correcting infusion therapy positive changes are observed on the second or third day of the postoperative period.

A simple, dual tracer method for the measurement of transvascular flux of albumin into the lung.

A simple, first-order model of albumin kinetics in the rat lung is presented and validated with a more sophisticated model. The simple model assumes that intravascular concentration of tracer albumin is constant over 30 min after injection and transvascular flux of tracer albumin is unidirectional and proportional to the permeability-surface area product (PS). 125I-albumin is injected initially and 131I-albumin at 20 min. At 30 min the rat is sacrificed and plasma and tissue samples are obtained for gamma counting. Simultaneous equations are set up for the two tracers and solved for PS and plasma volume. The accuracy of this approach is examined with data generated from a more complete model. This model uses the concepts of hydraulic conductivity, solvent drag, reflection coefficients, hydrostatic and osmotic pressures, exclusion volumes, and lymph flow, as well as PS. Based on known PS and clearance rates from the complex model, the simple model estimates tracer albumin leakage rate with less than 5% error over the range of PS encountered in rat studies.

Serum albumin decreases transendothelial permeability to macromolecules.

We examined the effects of serum albumin and other serum proteins on the fluxes of tracer 125I-albumin (MW 69 kDa) and 125I-haptoglobin (MW 100 kDa) across the pulmonary artery endothelial monolayer in vitro to test the role of serum proteins in modulating the endothelial barrier function. Replacement of control complete culture medium (20% fetal calf serum in DMEM) with DMEM alone increased the transendothelial 125I-albumin clearance rate (a measure of 125I-albumin permeability) by 83% of the control value. Repletion with 50% calf serum or with 2.0 g% albumin (i.e., the albumin concentration in 50% serum) decreased 125I-albumin permeability to the control value. This effect of serum or albumin was concentration-dependent since neither 12.5% serum nor 0.5 g% albumin (i.e., albumin concentration in 12.5% serum) altered 125I-albumin permeability from control values. The ammonium sulfate-precipitated serum protein fraction rich in albumin decreased 125I-albumin permeability from the control DMEM value, whereas serum fractions containing predominantly gamma-globulin or depleted of protein did not significantly alter 125I-albumin permeability. Other serum proteins that have been proposed to reduce endothelial permeability, alpha 1-acid glycoprotein (0.035-0.14 g/100 ml) and fibronectin (5 mg/100 ml), did not decrease 125I-albumin permeability from DMEM values. The endothelial permeability of 125I-haptoglobin of 4.63 +/- 0.53 x 10(-6) cm/sec in the presence of DMEM was 30% of the 125I-albumin permeability value. The addition of 2.0 g% albumin or 50% serum decreased 125I-haptoglobin permeability to 57 and 31%, respectively, of the DMEM value. These results indicate the critical role of serum albumin in regulating the restrictiveness of the endothelial barrier to macromolecules.

Initial plasma disappearance and tissue uptake of 131I-albumin in normal rabbits.

The simultaneous plasma disappearance curves of 131I-albumin and 125I-fibrinogen were recorded in normal rabbits for 1 hr. Using fibrinogen as a plasma reference, the disappearance curves of albumin were shown to contain two separate phases of efflux: one fast from zero to 10 min. comprising 8% of the total tracer; and one slow appearing in the interval of 10 to 60 min. containing another 9% of the tracer. Total albumin escape was analyzed to yield an initial slope of 0.024 +/- 0.004 min-1, corresponding to a wholebody unidirectional albumin clearance (Cl(0)) of 0.090 +/- 0.009 ml(min*100 g)-1. The distribution of efflux was assessed by biopsy uptakes using the same tracers in spleen, kidney, heart, lung, liver, intestine, skin, muscle, and brain. The disappearance curve generally reflects a biphasic pattern of uptake in peripheral tissue, predominantly by muscle and lung. The rapid phase has contributions from the fast near equilibration of liver, and intestine and skin are significant codeterminants of the slow phase. Due to their low body masses highly perfused organs such as kidney, spleen, and heart have little influence on the plasma disappearance. In accordance, the Cl(0) determined for the wholebody was higher than initial clearances found in skin (0.053 ml(min*100 g)-1 and muscle (0.054 ml(min*100 g)-1), but much lower than those found in the highly perfused organs. The initial (unidirectional) rates of peripheral albumin transfer demonstrated, ranged from 10 to 30 times higher than estimates of lymphatic return, suggesting that transcapillary albumin exchange is mediated by high-rate bidirectional diffusion. The rapid decrease of net albumin exchange rates suggests a second, highly significant barrier located within the interstitial matrix, which restricts plasma escape and reduces plasma to lymph albumin transport.

Influence of some inhibitors and activators of fibrinolysis on transcapillary transport of macromolecules.

The RISA transcapillary transport in the posterior paw was followed up under the influence of some substances inhibiting and activating fibrinolysis (Trasylol, EACA and Streptokinase and Salyrgan, respectively) in 11 dogs under narcosis with chloralose and the cannulation of the lymphatics in the popliteal space. It was found that EACA inhibits the transcapillary RISA transport and streptokinase activates it. Trasylol and Salyrgan produced no changes, the slope of the vanishing curve of the tracer being identical with that of the controls.

Absorption of the cerebrospinal fluid and intracranial compliance in an amphibian, Rana pipiens.

Experiments have been carried out to investigate the absorption of the cerebrospinal fluid (c.s.f.) and the intracranial compliance in an amphibian, Rana pipiens, using infusions into the c.s.f. system through glass micropipettes. Resistance to absorption of the c.s.f. was estimated by the constant rate infusion technique. Mean absorption resistance for infusions of artificial c.s.f. into the lateral ventricles and into the cerebral subarachnoid space were 15.48 and 16.52 mmH2O min microliter-1 respectively. This difference was not significant and it is concluded that the pores in the posterior tela situated in the roof of the fourth ventricle do not offer any resistance to the flow of c.s.f. out of the ventricles. The resistance to drainage of the c.s.f. in this amphibian is higher than that found for mammals. Mean resting c.s.f. pressure, estimated from the intercept of the regression line with the pressure axis at zero infusion rate was 18.0 mmH2O. Absorption resistance was measured from the cerebral subarachnoid space before and after injection of 4 microliter Indian ink solution. There was a 3-fold increase in resistance following ink injection. Two-way analysis of variance showed the difference to be significant (P less than 0.01) suggesting that the outflow sites can become partially blocked by particulate matter. During a continuous 3 h infusion of artificial c.s.f. containing [14C]dextran or [125I]-labelled human serum albumin (RISA) into the lateral ventricles, the mean percentage uptakes into the systemic circulation after the first 0.5 h of a 3 h period were 74.1 and 61.9% respectively. The difference is not significant. The rapid and high uptake into blood suggests there is a direct communication between c.s.f. and blood in amphibians. During continuous infusion of RISA into the lateral ventricles, simultaneous blood samples were taken from the femoral artery and the internal dorsal vertebral vein. Radioactivity was found to be 13.2% higher in venous samples. This suggests that at least some c.s.f. drainage takes place directly into the spinal venous system. Intracranial compliance was investigated by recording the peak pressure in response to a series of bolus injections of artificial c.s.f. into one lateral ventricle. Compliance was estimated to be 0.11, 0.10 and 0.09 microliter mmH2O-1 for injection rates of 12.74, 16.62 and 25.10 microliters min-1 respectively. The difference between these values is not significant. The results suggest that for injection volumes over 5 microliters the c.s.f. system behaves elastically.

Entry of [3H]norepinephrine, [125I]albumin and Evans blue from blood into brain following unilateral osmotic opening of the blood-brain barrier.

The blood-brain barrier in adult rats was opened unilaterally by infusing 1.58 M L (+)-arabinose in 0.9% NaCl solution into the internal carotid artery, via a catheter in the external carotid. The common carotid remained patent during the procedure. Osmotic barrier opening allowed entry into the brain of three intravascularly administered tracers--a visual tracer Evans blue (pulsely injected) and radioactive tracers [3H]norepinephrine (continuously infused) and [125I]albumin (pulsely injected). In osmotically perfused brain tissue, uptake of both 3H and 125I from blood was increased 2-5-fold above control, with maximal increases observed in the caudate nucleus, hippocampus and thalamus. In control brain regions, Evans blue and albumin remained intravascular, whereas norepinephrine was taken up, possibly by sympathetic nerve endings in cerebral vessels, as a function of blood plasma concentration and duration of exposure. The barrier closed within 4 h after intracarotid arabinose infusion, and barrier opening was not associated with edema as measured two days after infusion.