Effect of chlorpromazine on hepatic perfusion and bile secretory function in the isolated perfused rat liver.

The hepatotoxicity of CPZ was studied in the isolated perfused rat liver in order to more closely define possible mechanisms of phenothiazine-induced cholestasis. Perfusate concentrations of CPZ were increased from 5 x 10(-6) M to 5 x 10(-4) M until bile secretion was significantly inhibited. Measurements were then made of determinants of bile secretory function, including the magnitude of lobar distribution of perfusate flow, BAIF, and liver plasma membrane enzyme activity, Na+,K+-ATPase, Mg++-ATPase and 5'-nucleotidase. BAIF diminished significantly from control values of 1.76 +/- 0.07 microliter min-1gm-1 of liver to 1.34 +/- 0.15 and 0.80 +/- 0.09 following 2.5 and 5 x 10(-4) M CPZ, respectively. Perfusate flow also diminished from 5.64 +/- 0.44 to 1.24 +/- 0.12 ml min-1 gm-1 of liver 20 min following 5 x 10(-4) M CPZ and was associated with reduced flow to peripheral areas of the hepatic lobes as demonstrated by Tc-HAM. By 30 min, perfusate flow had returned to baseline values. CPZ also transiently diminished the excretion of bile acids in livers receiving a constant infusion of 40 mumol hr-1 sodium taurocholate. Defects in hepatic perfusion could not account entirely for the impairment in BAIF, since comparable mechanical restriction of perfusate flow in controls only diminished BAIF to 1.49 +/- 0.08 microliter min-1gm-1 of liver. CPZ signofocamt;u rediced tje secofoc actovotu pf Mg++-ATPase and 5'-nucleotidase but did not affect Na+,K+-ATPase in liver plasma membrane isolated 20 min after 5 x 10(-4) M CPZ. CPZ also resulted in a profound shift in the recovery of protein in isolated liver plasma membrane fractions from the light (density = 1.16) to heavier (density = 1.18) fractions. These findings, together with previous observations demonstrating alterations in hepatic ultrastructure, indicate that CPZ interacts in a complex manner with hepatocyte plasma and cytoplasmic membrane components and suggest that these drug-membrane interactions independently result in diminished hepatic perfusion, impairment of bile acid excretion, and inhibition of bile acid-independent bile secretion.     

Effects of capsaicin on the endothelial permeability in isolated and perfused rabbit lungs

Summary— Changes in pulmonary endothelial permeability and in microvascular hemodynamics in response to capsaicin (10^?4M) were investigated in isolated, perfused rabbit lungs. Blood-free perfusate was recirculated through ventilated lungs in an isogravimetric state, under zone III conditions with a constant flow. Using the occlusions method, the total pressure gradient between the arterial and the venous levels (δPt) was partitioned into four components: arterial (δPa), pre- (δPa') and post-(δPv') capillary, and venous (δPv). The capillary filtration coefficient (Kf,c) was evaluated by measuring the amount of fluid filtering through the endothelium when arterial and venous pressures were suddenly increased. Capsaicin caused no changes in the vascular pressures at any level of the pulmonary circulation but induced a significant 3-fold increase in the Kf,c (P < 0.05). This reaction was accompanied by pulmonary oedema. The mechanisms involved in the permeability changes were investigated by testing the capacity of different drugs to block the response to capsaicin. Clonidine (10^?7M to 10^?5M), morphine (10^?6M), aspirin (10^?3M), ketanserin (10^?8M) and (±) CP 96,345 (10^?6M), an antagonist of neurokinin NK₁ receptor, completely prevented the effects of capsaicin on the Kf,c. In contrast, terfenadine (10^?7) together with cimetidine (10^?5M) had no protective effect against capsaicin. It was concluded that capsaicin-induced pulmonary oedema was due to an increase in the capillary filtration coefficient and not to hemodynamic changes. This alteration in the endothelium permeability is mediated by the release of endogenous peptides from C-fibers upon the action of capsaicin and subsequent activation of NK₁ receptors, probably by substance P. Moreover, 5-hydroxytryptamine receptors and arachidonic acid derivates are also involved in this reaction.     

Effect of tauroursodeoxycholic acid on bile acid-induced apoptosis in primary human hepatocytes

BACKGROUND/AIMS: The accumulation of endogenous bile acids contributes to hepatocellular damage during cholestatic liver disease. To evaluate the potential role of apoptotic cell death due to increased concentrations of bile acids, primary human hepatocytes were treated with hydrophobic and hydrophilic bile acids. Because the Fas receptor-ligand system may mediate apoptosis in human liver cells, the effect of toxic bile acids on hepatocellular Fas receptor expression was evaluated. MATERIALS AND METHODS: Primary human hepatocytes were incubated with 50 and 100 microM glycochenodeoxycholic acid (GCDCA) and co-incubated with equimolar concentrations of tauroursodeoxycholic acid (TUDCA). To evaluate cytolytic and apoptotic effects, morphological alterations, hepatocellular enzyme release, nuclear DNA fragmentation and hepatocellular Fas receptor expression were evaluated. RESULTS: Apoptotic cell death was significantly increased after exposure to 50 microM GCDCA. Bile acid-induced apoptosis was not accompanied by hepatocellular Fas receptor overexpression. Tauroursodeoxycholic acid reduced apoptosis, as indicated by a significant reduction of oligonucleosomal DNA cleavage. Fas receptor expression was not significantly affected by tauroursodeoxycholic acid. At higher concentrations, direct cytolytic cell destruction was observed. CONCLUSION: Primary human hepatocytes represent a suitable model to study bile acid-induced apoptotic cell death. In these hepatocytes, already low bile acid concentrations might induce apoptotic cell death, which is not triggered by hepatocellular Fas receptor overexpression. Apoptotic DNA fragmentation was significantly reduced by co-incubation with tauroursodeoxycholic acid. The reduction of bile acid-induced apoptosis by ursodeoxycholic acid and its conjugates may contribute to the beneficial effects of these hydrophilic bile acids used for medical treatment of several cholestatic liver diseases.     

Adenosine receptor-mediated alterations in prostacyclin production and cardiac function in the isolated rabbit heart.

The subtype of adenosine receptor linked to cardiac prostacyclin (PGI2) synthesis, measured as immunoreactive 6-keto-PGF1 alpha, was investigated in the rabbit heart perfused with Krebs' buffer at 20 ml/min. Adenosine (6.4-50 nmol) decreased 6-keto-PGF1 alpha synthesis, coronary perfusion pressure (PP) and myocardial contractility (dp/dt max), whereas higher doses (200 nmol) increased 6-keto-PGF1 alpha output and decreased PP, heart rate (HR) and dp/dt max. Injections (3.2-50 nmol) or infusion (0.6 microM) of A1 receptor agonist 1-deaza,2-chloro,N6 cyclopentyladenosine increased 6-keto-PGF1 alpha production and decreased HR and PP without affecting dp/dt max. 1-Deaza,2-chloro,N6 cyclopentyladenosine 100 to 200 nmol produced similar effects as lower doses except that it decreased transiently PP and reduced dp/dt max. 1,3-Dipropyl,8-cyclopentylxanthine (0.06 microM) prevented the effects of 1-deaza,2-chloro,N6 cyclopentyladenosine (50 mumol) and adenosine (10 microM) to increase 6-keto-PGF1 alpha output and decrease HR and minimized the decrease in dp/dt max. A2 receptor agonist 2-[p-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamido-ade nos ine (1.6-12.5 nmol) or 0.6 microM decreased 6-keto-PGF1 alpha output, PP and dp/dt max without changes in HR. 3,7-Dimethyl-1-propargylxanthine prevented 2-[p-(2-carboxyethyl)-phenethylamino]-5'-N-ethylcarboxamido adenosine-induced decrease in 6-keto-PGF1 alpha output, PP and dp/dt max; HR was not altered by this agent. These data suggest that stimulation of A2 receptors reduce cardiac PGI2 synthesis and PP, but activation of A1 adenosine receptors increased PGI2 synthesis, produced vasoconstriction and decreased HR.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of S-8666 on Cl- transport in the rabbit connecting tubule perfused in vitro.

S-8666, [6, 7-dichloro-5-(N, N-dimethylsulfamoyl)-2, 3-dihydrobenzofurancarboxylic acid] is a potent diuretic with uricosuric action. Although the major site of action of S-8666 has been proven by the in vitro microperfusion study to be the thick ascending limb of Henle's loop, clearance studies in the rat suggested that this drug has an additional thiazide-like action. To provide direct evidence that S-8666 acts also on distal nephron segments, we examined effect of S-8666 on Cl- flux across the rabbit connecting tubule perfused in vitro. The drug suppressed the lumen-to-bath Cl- flux by 96 +/- 41 (S.E.)pmol.mm-1.min-1 (n = 9) without affecting transmural voltage. To demonstrate that S-8666 acts on the connecting tubule cell, the target of thiazide diuretics, we compared effects of S-8666 and trichlormethiazide on the basolateral membrane voltage of the connecting tubule cell. Both drugs added to the lumen caused a small but significant hyperpolarization of the basolateral membrane without affecting transmural voltage. We conclude that S-8666 is a unique uricosuric diuretic having actions on both thick ascending limb of Henle's loop and connecting tubule.     

In vitro studies of ovarian function in the isolated perfused rabbit ovary

An in vitro model for studies of preovulatory follicle and ovulation is described, using a recirculating system for perfusion of isolated rabbit ovaries. The preovulatory follicle was studied by addition of human chorionic gonadotropin (hCG) to the perfusion medium 1.5 h after the start of perfusion. Ovulations occurred approximately 13 h after in vivo hCG injection to the animal and 5-10 h after the start of perfusion. The ultrastructural changes during the perfusion were similar to in vivo conditions. The release of estradiol and progesterone into the medium are consistent with in vivo measurements. This in vitro model is probably useful for further studies of the biochemistry and morphology of ovarian function.     

Hydraulic water permeability and transepithelial voltage in the isolated perfused rabbit cortical collecting tubule following acute unilateral ureteral obstruction.

Ureteral obstruction affects the kidney's ability to conserve water and sodium. Using the isolated perfused tubule technique, we studied cortical collecting tubules (CCT) taken from rabbits subjected to a sham operation or to 4 h of unilateral ureteral obstruction (UUO). Tubules were perfused in the presence of an osmotic gradient directed to promote water movement from lumen to bath, and volume flux (Jv), hydraulic water permeability (Lp), and transepithelial voltage (V1) were determined. In tubules from sham-operated and UUO animals, basal (before exposure to vasopressin) J, and Lp were not different from zero. After addition of 200 microU . ml-1 of arginine vasopressin (aVP) to the bath, Jv and Lp increased to 1.64 +/- 0.23 nl . mm-1 . min-1 and 127.9 +/- 19.8 cm . s-1 . atm-1 x 10(7), respectively, in tubules from sham-operated animals, but not only 0.27 +/- 0.09 nl . mm-1 . min-1 an 18.8 +/- 6.2 cm . s-1 . atm-1 . 10(7) in tubules from UUO animals. Pretreatment with desoxycorticosterone acetate (DOCA) or indomethacin in vivo did not prevent the blunted vasopressin response seen in tubules taken from UUO animals. The Jv and Lp responses to the cyclic AMP (cAMP) analogue, 8-Br-cAMP, were also diminished in tubules taken from UUO animals compared with shams. V1, measured during the basal period, was diminished in tubules from UUO kidneys (-5.0 +/- 2.1 mV) compared with shams (-21.9 +/- 4.1 mV), and pretreatment with DOCA did no prevent the effects of UUO on V1. In contrast, tubules taken from animals that received indomethacin prior to UUO developed voltages not different from voltages in tubules taken from sham-operated animals (-17.3 +/- 1.7 mV). We conclude that, although CCT from UUO animals can maintain osmotic gradients, their ability to respond to vasopressin by increasing Lp is impaired by an intrinsic defect located at a step beyond the generation of cAMP, and that prostaglandin inhibition or DOCA pretreatment do not reverse the decreased responsiveness of Lp to aVP. UUO also diminished V1, and this abnormality was prevented by previous treatment with indomethacin, suggesting that prostaglandins may mediate the effect of UUO on V1.     

Current advances in nanomaterials affecting morphology,structure, and function of erythrocytes

In recent decades, nanomaterials have been widely used in the field of biomedicine due to their unique physical and chemical properties, and have shown good prospects for in vitro diagnosis, drug delivery, and imaging. With regard to transporting nanoparticles (NPs) to target tissues or organs in the body intravenously or otherwise, blood is the first tissue that NPs come into contact with and is also considered an important gateway for targeted transport. Erythrocytes are the most numerous cells in the blood, but previous studies based on interactions between erythrocytes and NPs mostly focused on the use of erythrocytes as drug carriers for nanomedicine which were chemically bound or physically adsorbed by NPs, so little is known about the effects of nanoparticles on the morphology, structure, function, and circulation time of erythrocytes in the body. Herein, this review focuses on the mechanisms by which nanoparticles affect the structure and function of erythrocyte membranes, involving the hemocompatibility of NPs, the way that NPs interact with erythrocyte membranes, effects of NPs on erythrocyte surface membrane proteins and their structural morphology and the effect of NPs on erythrocyte lifespan and function. The detailed analysis in this review is expected to shed light on the more advanced biocompatibility of nanomaterials and pave the way for the development of new nanodrugs.

This review focuses on the way how nanoparticles affect the structure and function of erythrocyte membranes, and is expected to pave the way for development of new nanodrugs.     

Angiodysplasia in the colon and rectum. Endoscopic morphology, localisation and frequency

In a prospective study, the occurrence of angiodysplasia was investigated by total colonoscopy in 1938 patients. Angiodysplasia was found in 59 patients, i.e. 3%. 12 out of 59 patients were admitted for acute or chronic peranal hemorrhage or anemia. 47 out of 59 patients were asymptomatic. The site of the lesions was as follows: cecum 37%, ascending colon 17%, transverse colon 7%, descending colon 7%, sigmoid colon 18% and rectum 14%. Histological confirmation was obtained in 15 out of 37 biopsies. The endoscopic appearance was variable, most of the vascular dilatations being smaller than 5 mm (n = 47), with a homogeneous (n = 35) or inhomogeneous (n = 24) structure and a regular (n = 34) or irregular (n = 25) border. The lesions were single (n = 34) as well as multiple (n = 25), they were usually flat (n = 54), seldom slightly prominent (n = 5). Concomitant pathological findings in the bowel were diagnosed in 33 out of 59 patients: diverticula in 32%, adenomas in 24% and carcinomas in 8.5%. Right hemicolectomy for bleeding angiodysplasia is indicated only if endoscopic therapy has failed and other colorectal sources of bleeding, and especially angiodysplasia in the left colon and rectum have been excluded by endoscopy or angiography.     

Effect of terbutaline on lung mechanics and morphology in the preterm rabbit neonate

Summary. Lung morphology, surface properties of fetal pulmonary fluid, and lung mechanics during spontaneous breathing were studied in preterm newborn rabbits after antenatal administration of terbutaline (0 1 mg). The histological evaluation of lung sections revealed increased amounts of granular eosinophilic and sudanophilic material in the terminal airspaces. The amount of fetal pulmonary fluid was decreased in terbutaline-treated animals; the fetal pulmonary fluid also showed improved surface properties, evaluated by the pulsating bubble technique. Increased dynamic lung compliance without altered air-way resistance was found in terbutaline-treated animals during the first 30 min after onset of breathing. This report demonstrates that terbutaline has an initial beneficial influence on the preterm neonatal lung, probably due to release of preformed surfactant into the alveolar spaces and to dehydration of the lung.     

Beneficial effects of yohimbine on posthypoxic recovery of cardiac function and myocardial metabolism in isolated perfused rabbit hearts.

The present study was undertaken to elucidate the possible actions of yohimbine on cardiac function and metabolism in the hypoxic and subsequently reoxygenated myocardium. For this purpose, rabbit hearts were perfused for 20 min under hypoxic conditions, followed by 45 min reoxygenated perfusion, and their functional and metabolic alterations with and without yohimbine treatment were examined. Hypoxia induced cessation of cardiac contractile force, rise in resting tension and depletion of tissue high-energy phosphates, which were poorly recovered by subsequent reoxygenation. Hypoxia also induced release of creatine kinase and ATP metabolites from perfused hearts and increases in tissue calcium and sodium contents, which were further enhanced upon subsequent reoxygenation. When hypoxic hearts were treated with 3 to 30 microM yohimbine, several beneficial effects were observed in a concentration-dependent manner. This included enhancement of posthypoxic recovery of contractile function and suppression of the hypoxia- and reoxygenation-induced rise in resting tension. Hypoxia/reoxygenation-induced release of ATP metabolites was inhibited and restoration of myocardial high-energy phosphates enhanced. Inhibition of reoxygenation-induced rise in tissue calcium and sodium and creatine kinase release were also noted. The findings suggest that suppression of transmembrane flux of ions, substrates and enzymes during hypoxia/reoxygenation plays a role in the posthypoxic functional and metabolic recovery. Yohimbine (3-30 microM) significantly depressed the maximal stimulus frequency the left atria could follow. These results suggest a close relationship between depression in the maximal driving frequency of atria and enhancement of the posthypoxic contractile and metabolic recovery of perfused hearts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of 16,16-dimethyl PGE2 and indomethacin on bile acid-induced intestinal injury and restitution in rats

Topically administered 16,16-dimethyl prostaglandin E2 reduced bile acid-induced small intestinal mucosal injury; however, the time course of restitution after such injury and whether either exogenous or endogenous prostaglandins affect this restitution are unknown. To explore these questions, mucosal injury was produced in 50 cm small intestinal segments of anesthetized male Sprague-Dawley rats perfused in vivo for 0, 5, 15, 30, or 45 minutes with buffer containing 5 mmol/L chenodeoxycholic acid, and to assess mucosal restitution, additional rats were perfused for 45 minutes with chenodeoxycholic acid followed by 15, 30, 60 or 120 minutes with chenodeoxycholate-free buffer. The above studies were then repeated in rats receiving either intraperitoneal indomethacin (10 mg/kg) or 15 minutes of preperfusion with buffer containing 1.4 mumol/L (0.5 microgram/ml) 16,16-dimethyl prostaglandin E2. Prostaglandin pretreatment reduced and indomethacin pretreatment increased significantly the morphologic (as measured by quantitative histology) and functional (as measured by mannitol and water absorption) mucosal injury caused by chenodeoxycholic acid. However, neither pretreatment had a major impact on the time course of functional or morphologic mucosal restitution, with nearly complete restitution occurring within 1 hour. Thus, although both endogenous and exogenous prostaglandins have a significant impact on bile acid-induced small intestinal mucosal injury, this effect is not caused by an acceleration of the rate of mucosal restitution.     

Effect of nicotinic acid-induced insulin resistance on pancreatic B cell function in normal and streptozocin-treated baboons.

To study the interaction between insulin secretion and insulin action in maintaining glucose homeostasis, we induced experimental insulin resistance in eight normal baboons, in six baboons treated with 40 mg/kg streptozocin (STZ-40), and in six baboons treated with 200 mg/kg streptozocin (STZ-200). Insulin resistance was induced by a 20-d continuous intravenous infusion of nicotinic acid (NA). Normal animals showed compensatory increases in several measures of insulin secretion (fasting insulin [FI], acute insulin response to arginine [AIRarg], acute insulin response to glucose [AIRgluc], and glucose potentiation slope [delta AIRarg/delta G]), with no net change in fasting plasma glucose (FPG) or glycosylated hemoglobin (HbAtc). STZ-40 animals showed compensatory increases in FI, AIRarg, and AIRgluc, but delta AIRarg/delta G failed to compensate. Although FPG remained normal in this group during NA infusion, HbA1c rose significantly. STZ-200 animals failed to show compensatory changes in both AIRgluc and delta AIRarg/delta G, with both HbA1c and FPG rising. These animals showed a paradoxical inhibition of insulin secretion in response to intravenous glucose during NA infusion, at a time when they were hyperglycemic. These data indicate that a significant degree of insulin resistance does not cause hyperglycemia in the presence of normal B cell function but, in animals with reduced B cell mass and superimposed insulin resistance, the degree of hyperglycemia is proportional to the degree of pancreatic B cell dysfunction.     

Effect of polycations on the function of the isolated perfused rat kidney

1. In minimal change nephrotic syndrome the occurrence of heavy proteinuria can be explained on the basis of a reduction in charge selectivity of the glomerular filtration barrier, and it has been proposed that this might be caused by the neutralization of anionic groups by a circulating polycationic factor. 2. The effects of two polycations, protamine and poly-L-lysine, on the function of the isolated perfused rat kidney have been examined. 3. Poly-L-lysine polymers of relatively high molecular weight (8800 and 17,800) induced heavy proteinuria, while simultaneously causing a marked increase in renal vascular resistance and a fall in filtration rate. Protamine (approximate molecular weight 7000) at relatively high concentration induced modest proteinuria in the absence of effects on vascular resistance or filtration rate. 4. A poly-L-lysine polymer of lower molecular weight (3800) did not induce proteinuria. Protamine at a concentration of 40 micrograms/ml and below did not affect protein excretion either. Both provoked substantial natriuresis. This appeared to be largely due to an effect on the tubular handling of sodium since the filtration rate remained steady while fractional sodium excretion rose markedly. 5. The natriuretic effect of protamine was blocked by heparin, but not by indomethacin or verapamil, suggesting that the mechanism of natriuresis did not depend upon either prostaglandin production or entry of calcium through verapamil-sensitive channels.     

Effect of hemorrhagic shock on bacterial translocation, intestinal morphology, and intestinal permeability in conventional and antibiotic-decontaminated rats

Bacterial translocation and ileal and cecal injury have been shown to occur 24 h after limited periods of hemorrhagic shock. The present studies were performed to determine the temporal sequence of mucosal injury, permeability, and bacterial translocation after hemorrhagic shock. The results indicated that bacterial translocation and mucosal injury have occurred by 2 h after a 30-min episode of shock (mean arterial pressure 30 mm Hg). Although the histologic extent of the intestinal mucosal injury was less at 2 h postshock than at 24 h postshock, at both times intestinal barrier function was lost as measured by permeability to horseradish peroxidase. Since the role of translocating bacteria in potentiating the loss of intestinal barrier function after shock is unclear, the second goal was to determine whether the extent of shock-induced mucosal injury and permeability could be reduced or abrogated by antibiotic decontamination of the gut. The extent of shock-induced mucosal injury and intestinal permeability was similar between rats with a normal gut flora (greater than 10(6) bacteria/g cecum) and antibiotic-decontaminated rats (less than 10(3) bacteria/g cecum) 2 h postshock, although the incidences of bacterial translocation were 67% and 0, respectively. Thus, shock-induced mucosal permeability and injury appear not to be directly related to the presence of translocating bacteria.     

Early alterations in the morphology of cytomegalovirus-infected human fibroblasts.

Cytomegalovirus-infected human fibroblasts developed large numbers of fine microvilli within 90 min after addition of virus. The structure of these microvilli gradually changed as the infection proceeded, although the infected cells were easily detected by their large number of processes. These processes may be involved in the increased transport of ions and nutrients into the infected cell.     

超声发射方式对实验兔血脑屏障通透性的影响

目的探讨微泡介导下超声发射方式对实验兔血脑屏障通透性的影响。方法依据超声不同发射方式将20只清洁级新西兰大白兔随机分为两组,即连续发射组和间断触发组,各10只。观察在匀速注射微泡、相同超声能量参数下不同发射方式辐照兔脑组织情况,同时采用伊文思蓝示踪法评价血脑屏障通透性的变化情况。结果超声连续发射组、间断发射组靶区单位脑组织中伊文思蓝含量分别为(11.04±1.53)μg/g、(32.55±2.56)μg/g,两组比较差异有统计学意义(P<0.05)。结论在匀速注射微泡,相同超声能量参数辐照靶区脑组织时,间断触发方式较连续发射方式更能促进血脑屏障通透性增加。