Activated clotting time as a screening test prior to catheter-based cardiovascular procedures

The activated clotting time (ACT) was investigated as a rapid, inexpensive, point-of-service screening test for coagulation abnormalities prior to catheter-based procedures. A total of 963 patients were screened by obtaining a history, standard coagulation profile, and activated coagulation time. The prevalence of normal patients (normal ACT and coagulation profile) was 94% (sensitivity = 91%; specificity = 27%). A normal ACT had a positive predictive value of 95%. The ACT was an acceptable screening test due to its ability to predict positively a low rate of bleeding complication and normal coagulation studies. Patients with ACT > 150 sec should be further evaluated with a screening coagulation panel. Additionally, given its low specificity, coagulation studies should be obtained in high-risk patients since an abnormal ACT does not effectively correlate with abnormal coagulation studies.

Bile acid transport in the anhepatic rat

Hepatocyte dysfunction eventually results in the loss of canalicular bile formation. Without canalicular flow, intestinal bile acid may originate from plasma by reverse transport. Anhepatic rats with preserved intestinal function permit evaluation of such transport. In the present study, plasma taurocholate clearance was markedly decreased in anhepatic rats. The relative proportion of free cholate increased with time. Peripheral tissues contained virtually only cleared taurocholate, but the intestinal contents were mainly free cholate. This indicates the intestinal contents as the source of the plasma cholate and shows an equilibrium between intestinal and plasma bile acid even without bile flow. The enteral administration of an anion exchange resin to anhepatic rats increased intestinal bile acid recovery and decreased the bile acid recovery in tissue. Plasma bile acid concentration was decreased and fractional loss increased threefold, confirming the anhepatic plasma-intestine bile acid equilibrium. However, the enhanced plasma clearance produced by the resin was less than 1% of the fractional loss found in the intact rat. These data show a very limited bile acid flux between intestine and plasma without bile flow, which could be modestly influenced by an intestinal bile acid sequestrant.

Serum factors influencing cultured hepatocyte exogenous and endogenous triglyceride

Rat hepatocyte monolayer triglyceride content was increased modestly by incubations with apolipoprotein E-containing triglyceride emulsions or chylomicrons (exogenous) and was increased substantially by increasing media free fatty acid concentrations (endogenous). The secretion of both endogenous and exogenous triglyceride into media was enhanced by additions of serum and serum components. These additions not only enhanced hepatocyte triglyceride secretion but also, because of the absence of media lipolysis, more triglyceride was recovered in the system. Lipoprotein-free serum replicated the effect of whole serum. Lipoprotein produced a more modest secretory response. The apolipoprotein C components were the only ones that enhanced hepatic triglyceride secretion. Both lipoprotein-free plasma and lipoprotein enhanced the in vitro transfer of hepatocyte exogenous triglyceride to fibroblast.

High-density lipoproteins (HDL) stimulate placental lactogen secretion in pregnant ewes: further evidence for a role of HDL in placental lactogen secretion during pregnancy

Previous studies from our laboratory showed that high-density lipoproteins (HDL) stimulate the release of human placental lactogen (PL) from cultured trophoblast cells from normal pregnant women. To determine whether HDL stimulates PL secretion in vivo, ovine HDL was infused over 2-5 min into 11 pregnant ewes (22 separate experiments) at 86-130 days of gestation via an indwelling catheter into the maternal jugular vein. The HDL, freshly prepared from the plasma of pregnant ewes by differential flotation ultracentrifugation, was greater than 99% purified as judged by SDS-PAGE. Plasma samples were obtained from the ewes before and at 0.5-h intervals for 6 h following the infusions and were assayed for PL by a specific homologous radioimmunoassay. The maternal infusion of HDL at doses of 302-784 mg (5.3-13.8 mg/kg body weight) stimulated significant increases in maternal plasma PL concentrations in six out of eight experiments (six ewes), and the infusion of 108-264 mg (1.9-4.6 mg/kg) stimulated plasma PL concentrations in two out of six experiments. In contrast, HDL at doses less than 100 mg were without effect in eight experiments. The response to the HDL infusions was characterized by a sustained increase in plasma PL concentrations beginning 1.5-2.5 h after the infusions, reaching a maximum 274.2 +/- 21.9% of the baseline value (P less than 0.001). In contrast, the maternal infusion of lipoprotein-free plasma proteins or saline had no effect on maternal plasma PL concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

A simplified single stage total hepatectomy in the rat with maintenance of gastrointestinal absorptive function

A technique is described to remove the entire liver in a single stage with preservation of intestinal absorptive function. An inverted V-shape polyethylene cannula, either heparin bonded or silicon coated, was inserted into the portal vein and inferior vena cava to maintain venous return from the splanchnic and lower caval regions of the anhepatic rat. Blood glucose fell at a rate of 7 to 11 mg per hr per total plasma volume (4% body weight), usually resulting in hypoglycemia within the initial 2 hr. Euglycemia could be maintained in the first 3 hr after hepatectomy with hourly intravenous infusions of 2.5 to 5 mg per 100 gm body weight of glucose. Larger infusions of glucose (10 to 12.5 mg per hr per 100 gm body weight) were necessary for normal levels at later times. A 0.5 gm per 100 gm rat weight intestinal glucose bolus restored euglycemia for at least a 2-hr interval. Intestinal absorption of cholesterol and oleic acid was demonstrated in the anhepatic rat, although the latter was not so efficiently absorbed as in the control. The plasma cholesterol decreased with time in the anhepatic rat. Prompt increases were observed in plasma free fatty acid and glycerol concentrations after hepatectomy. Progressive increases in both direct and indirect plasma bilirubin levels were noted after hepatectomy. With appropriate maintenance of blood sugar, survival of 36 hr was observed. This procedure for single stage total hepatectomy in the rat can be performed in less than 30 min. The model is particularly useful for studies of the influence of the liver on postabsorptive metabolism.

Characterization of placental lactogen release from perifused human trophoblast cells

The dynamics of the release of human placental lactogen (hPL) under basal conditions and response to various secretogogues has been studied in perifused enriched hPL-producing cells from term placentae prepared by the isopycnic centrifugation of collagenase/hyaluronidase-dispersed placental cells on Percoll gradients. Under basal conditions, the perifused cells released hPL at a relatively constant rate for up to 24 h in culture. The mean rates of hPL release from cells (5 x 10(6) cells) from 18 normal full-term placentae varied from 1.8 to 20.2 ng/5 min (mean 7.7 ng/5 min). The cells from term placentae, however, did not release detectable amounts of chorionic gonadotrophin or the cytosolic enzymes lactic dehydrogenase and alkaline phosphatase. The amounts of hPL released by the perifused cells were inversely related to cell density with mean rates of hPL release by 2, 5, and 10 x 10(6) cells of 15.8, 8.6, and 5.7 ng/10(6) cells/0.5 h. The perifused cells responded to provocative stimuli (high-density lipoproteins (HDL), apolipoproteins AI, AII, and CI, partially purified hPL-releasing factor, phorbol esters, sn-1,2-diacylglycerol, and cAMP) in a manner qualitatively similar to enriched trophoblast cells and placental explants in static culture. Release of hPL in response to HDL, apoproteins AI, AII, and CI, and partially purified hPL-releasing factor was dose-dependent and occurred within 5 min of exposure. Basal and stimulated hPL release by perifused trophoblast cells that had been previously frozen at -70 degrees C for four weeks was identical to that of freshly dispersed cells from the same placenta. These experiments indicate that perifused trophoblast cells may be used as a model system to examine the dynamics of hPL release under basal conditions and in response to provocative stimuli.

Effect of apoE on triglyceride emulsion interaction with hepatocyte and hepatoma G2 cells

The uptake and internalization of a triglyceride emulsion by rat hepatocytes in culture less than 24 hr was either inhibited or uninfluenced by apoE. ApoE significantly increased the uptake of these emulsions in later cultures. Specific low density lipoprotein (LDL) binding was similar for hepatocyte monolayers prior to and after 24 hr. Rat hepatocytes in culture for 2 days, which were treated with collagenase, detached and then replated within 1 hr and were apoE-responsive in 2 hr. Heparin inhibited the apoE stimulation in both hepatocytes and hepatoma monolayers. Heparin wash of hepatocytes or hepatoma cells incubated with apoE-[14C]triolein emulsions at 4 degrees C resulted in a considerable loss in radiolabeled cell lipid. A similar wash after 37 degrees C incubations produced little loss suggesting internalization. Hepatocytes had lower affinity but similar apoE-emulsion binding capacity compared to hepatoma cells. Triolein emulsions with apoE were significantly more rapidly metabolized by the hepatocyte than unsupplemented emulsions. The apoE-mediated hepatocyte lipid uptake was inhibited by apoC proteins. High molar ratios of free fatty acid/albumin also suppressed hepatocyte apoE-mediated lipid uptake. Both rat high density lipoprotein (HDL) and LDL inhibited with a potency directly related to their content of apoE. Human LDL and HDL without apoE also inhibited the interaction with less potency than the rat lipoproteins. Human HDL inhibition was diminished after removal of apoC proteins.

Apolipoproteins AI, AII, and CI stimulate placental lactogen release from human placental tissue. A novel action of high density lipoprotein apolipoproteins

High density lipoproteins (HDL) stimulated a dose-dependent increase in the release of placental lactogen (hPL) from human placental explants. The stimulation was not prevented by delipidation of HDL but was completely blocked by tryptic digestion. Delipidated apolipoproteins (Apo) AI, AII, and CI also stimulated hPL release but other apolipoproteins were without effect. HDL and Apo CI had no effects on the release of luteinizing hormone and follicle-stimulating hormone from rat pituitary cells or the release of prolactin from human decidual cells. Because placental cells have specific HDL receptors and plasma HDL concentrations increase during pregnancy, these results strongly suggest a role for HDL in the regulation of hPL release during pregnancy possibly independent of their usual role in plasma lipid transport.

The relevance of glycosaminoglycan sulfates to Apo E induced lipid uptake by hepatocyte monolayers

The binding of Apolipoprotein E supplemented triglyceride emulsions to sulfated glycosaminoglycans demonstrated specificity for the carbohydrate polymers. Glucosamine containing glycosaminoglycans with relatively less sulfate had little affinity for the Apo E emulsion whereas those with more sulfate (i.e. heparin and sulfated heparans) effectively bound the emulsion. Galactosamine containing glycosaminoglycans (chondroitin 4 sulfate and dermatan sulfate) demonstrated no binding. The Apo E induced uptake of triglyceride emulsions by hepatocytes was inhibited by highly sulfated polysaccharides (i.e. heparin, dextran sulfate) but other glycosaminoglycans which did not bind the emulsion were ineffective in this inhibition. The same sulfated compounds which inhibited the hepatocyte Apo E emulsion interaction effectively released hepatic lipase from isolated heptic perfusions. Glycosaminoglycan sulfates which did not bind the Apo E supplemented emulsions and did not inhibit hepatocyte association were ineffective in releasing lipase. A heparan mixture isolated from human liver was much less effective in inhibiting Apo E induced association of emulsions with hepatocytes, than heparin. A highly sulfated octasaccharide fraction isolated from bovine liver heparin inhibited more effectively than the human heparans but less than the heparin. Inhibition of Apo E mediated hepatocyte emulsion association was produced by a one hour exposure of the cells to either heparinase or heparanase. The heparanase was more active than the heparinase and both were effective in the presence of protease inhibitors. Enzymes hydrolyzing chondroitin sulfates and hyaluronic acid were ineffective in inhibiting the Apo E induced association. The specific binding of human low density lipoprotein to the hepatocyte was much less effected by the heparanase exposure than the Apo E mediated binding.

Selective biliary secretion of basal and glucagon-inhibited neutral sterol after triparanol administration

Biliary cholesterol secretion was studied in dogs with chronic bile fistulas, using glucagon, an inhibitor of biliary cholesterol secretion, and triparanol, an inhibitor of cholesterol synthesis. Glucagon inhibited neutral sterol secretion before and after triparanol administration. Triparanol caused a significant accumulation in bile of the cholesterol precursor desmosterol which comprised a significant portion of the neutral sterol in bile but not in blood. Glucagon inhibited both biliary desmosterol and cholesterol secretions to a similar degree. These findings suggest that biliary cholesterol is derived from newly synthesized hepatic sterol as well as from equilibrated sources. Furthermore, glucagon suppressed biliary secretion of both equilibrated as well as newly synthesized neutral sterol, suggesting that glucagon inhibits the movement of neutral sterol to or through the canalicular membrane.

The uptake of high density lipoprotein cholesteryl ester in the perfused rat liver

The hepatic uptake of high density lipoprotein cholesteryl ester was determine in a nonrecycling isolated rat liver perfusion. High density lipoprotein rich in the E apoprotein (apoE) showed about 10 times more uptake of the ester on a single pass than the bulk of the high density lipoproteins rich in the A-I protein. The apoportein recoveries in the liver paralleled the ester for both lipoproteins. The uptake appeared to occur primarily in the hepatic parenchymal cell. Addition of human C-III-1 apoprotein to the rat apoE-rich high density lipoprotein inhibited the hepatic uptake of its constituents.

Effect of apoproteins on hepatic uptake of triglyceride emulsions in the rat

The addition of apoprotein E isolated from human very low density lipoproteins to both rat lymph chylomicrons and a triglyceride emulsion significantly increased the hepatic uptake of these particles in a nonrecycling isolated rat liver perfusion system. The cleared triglyceride was removed without apparent hydrolysis by the hepatocyte. When lymph chylomicrons were loaded with both Apo E and Apo C proteins by exposure to rat plasma, no increment in hepatic clearance was observed. Sequential evalutions of the influence of the C apoproteins on the hepatic clearance of both emulsions and chylomicrons revealed that the CIII (CIII-1) protein had a pronounced inhibitory effect on hepatic removal. The inhibition was observed for both Apo E-enriched chylomicrons and those containing little of this apoprotein.

The sources of rat biliary cholesterol and bile acid

The precursor sources of bile acid and bile neutral sterol were evaluated in the rat using Triparanol to inhibit the terminal reduction in the synthesis of cholesterol. During the initial period of Triparanol administration, the accumulation of hepatic desmosterol acts to segregate relatively newly synthetic hepatic sterol from the bulk of the equilibrated sterol mass. Biliary excretion of newly synthetic sterol can then be determined in acute studies, assuming no great differences between desmosterol and cholesterol as precursors of biliary neutral sterol or bile acid. It has been determined in this model that newly synthetic sterol comprises a mean of about 28% of the total biliary neutral sterol output. This fraction fell when hepatic cholesterogenesis was suppressed by prior cholesterol feeding. By using this approach in conjunction with the administration of labeled mevalonate to a renal pedicle-ligated rat, it was possible to calculate the amount of bile acid produced from either newly synthesized sterol or the equilibrated sterol pool. It has been estimated that the bulk of bile acid synthesis arises from this equilibrated source when these determinations were made within two hours of creating the fistula. With more prolonged fistula times, more of the bile acid originated from the newly synthesized sterol.

On thelipoprotein abnormality in type 3 hyperlipoproteinemia

Two lipoprotein species were isolated by starch block electrophoresis from the very low density lipoproteins (VLDL) (S(f) 20-400) of patients with type III hyperlipoproteinemia. One of these, alpha(2)-VLDL, had a content of lipid and protein and physical characteristics similar to VLDL from normal subjects or patients with other forms of hyperglyceridemia. The other species, beta-VLDL, contained more cholesterol and less triglyceride in relation to the protein, than normal VLDL. Only the apoprotein of low density lipoprotein was immunochemically detectable in the beta-VLDL; the proteins in the alpha(2)-VLDL reacted with antisera specific for low density lipoprotein and high density lipoprotein. The electrophoretic mobility of beta-VLDL was similar to that of low density lipoprotein and significantly less than that of alpha(2)-VLDL. Isolated beta-VLDL had a lesser mean flotation rate than alpha(2)-VLDL, but both alpha(2)- and beta-VLDL were found throughout the S(f) 20-400 flotation range.The relative quantities of alpha(2)- and beta-VLDL could be varied by changing the diet or by heparin administration. Most of the VLDL from type III patients on a high carbohydrate diet was in the alpha(2)-VLDL form. During fasting, alpha(2)-VLDL fell and beta-VLDL increased becoming the predominant species of VLDL. Heparin-induced acceleration of triglyceride clearance also increased beta-VLDL and decreased alpha(2)-VLDL. These findings suggest a precursor-product relationship between the alpha(2)- and beta-forms of VLDL.