Suppression of pacemaker activity by Ginkgo biloba extract and its main constituent, bilobalide in rat sino-atrial nodal cells

Effects of Ginkgo biloba extract (GBE) and bilobalide (a main constituent) on the pacemaker activity and the underlying ionic currents in rat sino-atrial (SA) nodal cells were investigated using patch-clamp techniques. Both GBE and bilobalide depressed the pacemaker activity in a concentration-dependent manner. At both 0.03 mg/ml GBE and 0.3 microM bilobalide, a negative chronotropic effect was produced. Dysrhythmias often occurred. The L-type Ca(2+) current (I(Ca)) and the hyperpolarization-activated inward current (I(f)) decreased by 69.7+/-3.2% (n=6, P<0.001) and by 12.6+/-2.1% (n=7, P<0.05) at 0.03 mg/ml GBE, and by 51.2+/-3.3% (n=6, P<0.01) and by 19.8+/-2.2 % (n=6, P<0.05) at 0.3 microM bilobalide, respectively. The delayed rectifier K(+) current (I(K)) also decreased. The inhibition was 12.3+/-2.0% (n=6, P<0.05) at 0.03 mg/ml GBE, and was 28.0+/-2.9% (n=6, P<0.05) at 0.3 microM bilobalide. These results indicate that cardiac ionic channels contributing to the pacemaking are highly sensitive to GBE and bilobalide, which can sufficiently modify the spontaneous activity in rat SA nodal cells.     

Cryosurvival of bovine blastocysts is enhanced by culture with trans-10 cis-12 conjugated linoleic acid (10t,12c CLA)

An excessive lipid content in embryo cells is a consequence of embryo culture in the presence of serum which is suggested to be responsible for their high susceptibility to cryopreservation. The objective of the present study was to examine the effects of supplementing serum-containing culture media with trans-10 cis-12 conjugated linoleic acid (10t,12c CLA) on embryo lipid accumulation and its subsequent cryopreservation. Abattoir-derived oocytes were matured and fertilized in vitro (IVF=day 0). On day 1, presumptive zygotes (n=3390) were randomly placed in: (I) (MS), granulosa cell monolayer cultured with M199 and 10% serum; (II) (SCLA), granulosa cell monolayer cultured with M199, 10% serum and 100 microM 10t,12c CLA and (III) (SOF), modified synthetic oviduct fluid, where embryo culture proceeded for 8 days. Cleavage rates or D7/D8 embryo quality did not vary among treatments. D7/D8 embryo production rate was significantly (P<0.001) lower in SOF (17.9+/-1.6%) than in groups MS (29.8+/-2.5%) and SCLA (27.8+/-2.0%). After cytoplasmic lipid droplets observation under Nomarski microscopy, classified embryos were the leanest when cultured in SOF, intermediate in SCLA and the fattest in MS (P<0.02). Post-thawing intact blastocyst rates where significantly higher in the SCLA group (84.7+/-4.1%) than in SOCS (50.3+/-4.8%, P=0.0007) or SOF (65.3+/-6.9%, P=0.03) groups. Post-thawing re-expanding rates were significantly lower when embryos were cultured in MS (34.7+/-3.7%) than in SCLA (63.7+/-5.3%, P=0.0006) or SOF (49.0+/-4.6%, P=0.04). Moreover, re-expanding rates were lower (P=0.05) in SOF than in SCLA cultured embryos. These results clearly show that addition of CLA to serum-containing media reduced lipid accumulation during in vitro culture and significantly improved cryopreservation survival.     

The micronucleus assay in exfoliated buccal cells: application to occupational exposure to polycyclic aromatic hydrocarbons.

Many polycyclic aromatic hydrocarbons (PAHs) have been identified as cancer-inducing chemicals for animals and/or humans. Also, there is sufficient evidence that exposures in the occupational settings are carcinogenic or probably carcinogenic to human. Engine exhaust and used engine oils are major PAH sources in engine repair workshops and traffic. Analysis of micronucleus (MN) in exfoliated buccal cells is a sensitive method for monitoring genetic damage in human populations. In our study, we used three different occupational groups (Group 1; engine repair workers, Group 2; taxi drivers, Group 3; traffic police) and two controls (Control I for Group 1 and Control II for Group 2 and Group 3) for the exposed groups. We analysed MN frequencies in exfoliated buccal cells and compared the exposed groups (Group 1; n=34, Group 2; n=17, Group 3; n=15) and subjects not occupationally exposed to PAH (Control I; n=28, Control II; n=20). The mean (+/-S.D.) MN (%) frequencies in exfoliated buccal cells from Group 1 and Control I were 0.07+/-0.05 and 0. 05+/-0.04, respectively (p>0.05; Table 2). The mean (+/-S.D.) MN (%) frequencies in exfoliated buccal cells from Group 2, 3 and Control II were 0.12+/-0.05, 0.10+/-0.05 and 0.03+/-0.03, respectively (p<0. 0001, p<0.05; Table 2) Smokers and nonsmokers do not differ with respect to the incidence of MN in all groups.     

Taurine content of isolated rat alveolar type I cells.

1. Rat alveolar type I cells were isolated by enzymatic digestion and purified by centrifugal elutriation and specific surface adsorption. 2. The identity of the harvested cells was confirmed using electronic cell sizing and transmission electron microscopy. 3. Purified cell preparations contained 4.6 +/- 2.3 x 10(6) type I cells/rat lung with a purity of 79 +/- 3%. 4. Isolated type I cells exhibited the following characteristics: mean cell volume = 716 +/- 48 microns 3; diameter = 11.1 +/- 0.7 microns; and cell water content = 0.50 +/- 0.03 microliter/10(6) cells. 5. Taurine content of these alveolar type I cells was measured by HPLC. 6. The intracellular taurine concentration of type I cells was 0.14 +/- 0.07 mM, a value close to that of plasma (0.1 mM).     

Membrane bilayer balance and erythrocyte shape: a quantitative assessment

When human erythrocytes are incubated with certain phospholipids, the cells become spiculate echinocytes, resembling red cells subjected to metabolic starvation or Ca2+ loading. The present study examines (1) the mode of binding of saturated phosphatidylcholines and egg lysophosphatidylcholine to erythrocytes and (2) the quantitative relationship between phospholipid incorporation and red cell shape. We find that the phospholipids studied become intercalated into erythrocyte membranes, not simply adsorbed to the cell surface. Spin-labeling and radiolabeling data show that the incorporation of (4 +/- 1) X 10(6) molecules of exogenous phosphatidylcholine per cell converts discocytes to stage 3 echinocytes with about 35 conical spicules. This amount of lipid incorporation is estimated to expand the red cell membrane outer monolayer by 1.7% +/- 0.6%. Calculations of the inner and outer monolayer surface areas of model discocytes and stage 3 echinocytes yield an estimated difference of 0.7% +/- 0.2%.     

Pyrene fluorescence probing of unsaturated lipids in Phytophthora infestans zoospores.

Pyrene rapidly penetrates into isolated zoospores of phytopathogenic fungus Phytophthora infestans localizing predominantly in lipid bodies. An analysis of steady-state monomer and excimer fluorescence spectra, as well as of vibronic structure has suggested a considerable part of the fluorescent probe to be located in a lipid environment. Pyrene partition into hydrophilic phase was observed at its high concentrations. Catalytic hydrogenation of unsaturated lipids in zoospores in situ reduced excimer production. The kinetics of changes of pyrene excimerization suggest that hydrogenation affects both the surface and the intrinsic lipids of the zoospores. The usefulness of pyrene as a fluorescent probe for unsaturated lipids in membranes and lipid bodies of intact cells, and the possible role of eicosapolyunsaturated fatty acids in induction of immune response in potato plants are discussed.     

Expression of nanomolar-affinity binding sites for melatonin in Syrian hamster RPMI 1846 melanoma cells.

Pharmacological studies indicate that Syrian hamster melanoma (RPMI 1846) cells possess a melatonin binding site similar to that found in normal hamster cells. A high correlation was observed for a series of compounds between the Ki in hamster hypothalamic membranes vs. RPMI 1846 membranes (r = 0.94, slope = 0.93, P less than 0.01, n = 14). Scatchard analysis of saturation binding of 2-[125I]-iodomelatonin to membranes (at 0 degrees C) indicated: Kd = 0.89 +/- 0.08 nM, Bmax = 6.2 +/- 2.9 fmol/mg protein (n = 3). Melatonin did not alter basal or forskolin-stimulated adenylate cyclase activity in RPMI 1846 membranes or intact cells. Therefore, in contrast to the picomolar-affinity receptor for melatonin in the mammalian hypothalamus and pars tuberalis, the putative nanomolar-affinity receptor is not coupled to adenylate cyclase. The RPMI 1846 cell line provides a useful model system for further studies of signal transduction via the nanomolar-affinity site for melatonin.     

Comparison of [125I]Iodolysergic Acid Diethylamide Binding in Human Frontal Cortex and Platelet Tissue

The human platelet contains a functional 5-hydroxytryptamine (5-HT) receptor that appears to resemble the 5-HT2 subtype. In this study, we have used the iodinated derivative [125I]iodolysergic acid diethylamide ([125I]iodoLSD) in an attempt to label 5-HT receptors in human platelet and frontal cortex membranes under identical assay conditions to compare the sites labelled in these two tissues. In human frontal cortex, [125I]iodoLSD labelled a single high-affinity site (KD = 0.35 +/- 0.02 nM). Displacement of specific [125I]iodoLSD binding indicated a typical 5-HT2 receptor inhibition profile, which demonstrated a significant linear correlation (r = 0.97, p less than 0.001, n = 17) with that observed using [3H]ketanserin. However, [125I]iodoLSD (Bmax = 136 +/- 7 fmol/mg of protein) labelled significantly fewer sites than [3H]ketanserin (Bmax = 258 +/- 19 fmol/mg of protein) (p less than 0.001, n = 6). In human platelet membranes, [125I]iodoLSD labelled a single site with affinity (KD = 0.37 +/- 0.03 nM) similar to that in frontal cortex. The inhibition profile in the platelet showed significant correlation with that in frontal cortex (r = 0.96, p less than 0.001, n = 16). We conclude that the site labelled by [125I]iodoLSD in human platelet membranes is biochemically similar to that in frontal cortex and most closely resembles the 5-HT2 receptor subtype, although the discrepancy in binding capacities of [125I]iodoLSD and [3H]ketanserin raises a question about the absolute nature of this receptor.     

Thromboxane receptors in human kidney tissues.

Thromboxane (TX) A2 effects in the kidneys include contraction of glomerular mesangial cells and intrarenal vascular tissue. A kidney cDNA encoding a TX receptor expressed in rat renal glomeruli and rat renal arterial smooth muscle cells has been reported. However, TXA2 receptors in human kidneys have not been documented. The purpose of this study was to identify and characterize TXA2 receptors in glomeruli and intrarenal arteries isolated from human kidneys. Normal kidneys, not used for transplant because of technical reasons, were kept at -70 degrees C and used for research purposes. The glomeruli and intrarenal arteries were isolated from renal cortical tissue by a mechanical sieving technique. The equilibrium dissociation constant and receptor number were determined by nonlinear analysis of binding inhibition data. The data were generated in radioreceptor assays using [125I]-BOP, a stable analog of TXA2. The dissociation constants (mean +/- SEM) for binding of I-BOP to human glomeruli and intrarenal arterial membranes were 6.6 +/- 1.1 nM (n = 7) and 20 +/- 6 nM (n = 7), respectively (p < 0.05). The receptor number was 311 +/- 91 fmol/mg protein (n = 7) in glomeruli and 74 +/- 16 fmol/mg protein (n = 7) in intrarenal arterial membranes (p < 0.04). The order of specificity of TXA2 analogs for [125I]-BOP binding sites was similar in glomeruli and in arterial membranes and was I-BOP > or = U46619 > or = pinane TXA2 > or = carbocyclic TXA2 > or = PGH2. These findings provide direct evidence for the presence of specific, high-affinity [125I]-BOP binding sites in human renal glomeruli and extraglomerular vascular tissue. These data also indicate that the human binding sites have higher affinity for the TXA2 agonist I-BOP than for PGH2.     

Levels of glycosylated haemoglobin in the Arabian camel (Camelus dromedarius)

Proportions of glycosylated haemoglobin (Hb) were determined in 10 Arabian camels (Camelus dromedarius) and were compared with normal controls (n = 59) and diabetic patients (n = 47) using the thiobarbituric acid (TBA) method. The level of glycosylated haemoglobin (5.5%) in camels is significantly different from that of normal healthy humans (4.9%) (P less than 0.001). Whereas the glucose levels were comparable, this difference in percentages of glycosylated haemoglobin may be explained by the difference in survival time between human and camel red blood cells.     

Effect of some polypeptide hormones on the lateral mobility in plasma membranes of rat testes, L-cells and liver. Influence of development and ageing

1. The effect of different doses of six polypeptide hormones on pyrene diffusion in rat testes and liver plasma membranes was tested. Pyrene mobility was reduced in membranes possessing respective receptors. 2. An incubation time of 15 min of testes plasma membranes with 10(-5) M lutropin (LH) reduced pyrene and diphenyl hexatriene mobilities by 10-20%. 3. The addition of 10(-5) M LH to a suspension of intact L-cells from rats at different ages decreased the diffusion of membrane fluorescently labelled lipids and proteins by ca 60%. Diffusion was measured by fluorescence recovery after photobleaching. 4. Observed LH effects were independent of development and ageing.     

Simultaneous determination of low free Mg2+ and pH in human sickle cells using 31P NMR spectroscopy

The concentrations of free magnesium, [Mg(2+)](free), [H(+)], and [ATP] are important in the dehydration of red blood cells from patients with sickle cell anemia, but they are not easily measured. Consequently, we have developed a rapid, noninvasive NMR spectroscopic method using the phosphorus chemical shifts of ATP and 2,3-diphosphoglycerate (DPG) to determine [Mg(2+)](free) and pH(i) simultaneously in fully oxygenated whole blood. The method employs theoretical equations expressing the observed chemical shift as a function of pH, K(+), and [Mg(2+)](free), over a pH range of 5.75-8.5 and [Mg(2+)](free) range 0-5 mm. The equations were adjusted to allow for the binding of hemoglobin to ATP and DPG, which required knowledge of the intracellular concentrations of ATP, DPG, K(+), and hemoglobin. Normal oxygenated whole blood (n = 33) had a pH(i) of 7.20 +/- 0.02, a [Mg(2+)](free) of 0.41 +/- 0.03 mm, and [DPG] of 7.69 +/- 0.47 mm. Under the same conditions, whole sickle blood (n = 9) had normal [ATP] but significantly lower pH(i) (7.10 +/- 0.03) and [Mg(2+)](free) (0.32 +/- 0.05 mm) than normal red cells, whereas [DPG] (10.8 +/- 1.2 mm) was significantly higher. Because total magnesium was normal in sickle cells, the lower [Mg(2+)](free) could be attributed to increased [DPG] and therefore greater magnesium binding capacity of sickle cells.     

The blood group U antigen is not located on glycophorin B

Erythrocytes from twelve individuals with the S-s-U- phenotype and from ten with the S-S-U+ phenotype were analyzed and compared to control cells with S+/s+U+ determinants. No red cell abnormality was detected in S-s-U+ or S-s-U- carriers. Sialic acid content was similar (P greater than 0.05) for S-s-U+ and S-s-U- erythrocytes (74.6 +/- 7.14 and 71.4 +/- 8.53 nmol/10(9) red blood cells, respectively) but significantly less (P less than 0.001) than controls with 89.5 +/- 11.4 nmol/10(9) red blood cells, n = 16. Fluorographs of SDS-polyacrylamide gels showed no glycophorin B in membranes from S-s-U+ and S-s-U- erythrocytes labeled with NaB3H4. Glycophorins were extracted from red cell membranes in chloroform/methanol, labeled with 125I and analyzed by SDS-polyacrylamide gel electrophoresis. Periodic acid Schiff stain and autoradiographs of these gels also showed absence of glycophorin B in both S-s-U+ and S-s-U- cells. These findings suggested that the U antigen is not located on glycophorin B. This hypothesis was tested by determining blood group antigenicity on red cell membranes and on extracted sialoglycoproteins by the hemagglutination inhibition technique. Although U and S/s activities were detected in control red cell membranes, extracted glycoproteins demonstrated S/s activity but no U activity. Together the data indicate that both S-s-U+ and S-s-U- erythrocytes lack glycophorin B and that the U antigen is not located on glycophorin B. This deletion does not seem to affect the structure-function of the red cell.     

cAMP regulation of Cl(-) and HCO(-)(3) secretion across rat fetal distal lung epithelial cells

We isolated and cultured fetal distal lung epithelial (FDLE) cells from 17- to 19-day rat fetuses and assayed for anion secretion in Ussing chambers. With symmetrical Ringer solutions, basal short-circuit currents (I(sc)) and transepithelial resistances were 7.9 +/- 0.5 microA/cm(2) and 1,018 +/- 73 Omega.cm(2), respectively (means +/- SE; n = 12). Apical amiloride (10 microM) inhibited basal I(sc) by approximately 50%. Subsequent addition of forskolin (10 microM) increased I(sc) from 3.9 +/- 0.63 microA/cm(2) to 7.51 +/- 0.2 microA/cm(2) (n = 12). Basolateral bumetanide (100 microM) decreased forskolin-stimulated I(sc) from 7.51 +/- 0.2 microA/cm(2) to 5.62 +/- 0.53, whereas basolateral 4,4'-dinitrostilbene-2,2'-disulfonate (5 mM), an inhibitor of HCO secretion, blocked the remaining I(sc). Forskolin addition evoked currents of similar fractional magnitudes in symmetrical Cl(-)- or HCO(-)(3)-free solutions; however, no response was seen using HCO(-)(3)- and Cl(-)-free solutions. The forskolin-stimulated I(sc) was inhibited by glibenclamide but not apical DIDS. Glibenclamide also blocked forskolin-induced I(sc) across monolayers having nystatin-permeablized basolateral membranes. Immunolocalization studies were consistent with the expression of cystic fibrosis transmembrane conductance regulator (CFTR) protein in FDLE cells. In aggregate, these findings indicate the presence of cAMP-activated Cl(-) and HCO(-)(3) secretion across rat FDLE cells mediated via CFTR.     

肾上腺素能受体阻断剂预防慢性压力超负荷左心室的电重构

研究长期使用肾上腺素能受体阻断剂治疗对慢性压力超负荷左心室电重构的影响。新西兰兔通过肾上腹主动脉次全结扎诱发慢性压力超负荷,10周后行心脏超声检查,并采用全细胞膜片钳技术分别记录腹主动脉结扎组(简称结扎组)、腹主动脉结扎 Carvedilol 干预组(简称Carvedilol组)及正常对照组(简称对照组)动物左室肌中层细胞的动作电位(action potential,AP)、内向整流钾电流(inward rectifier potassium current,IKi)、延迟整流钾电流(delayed rectifier potassium current,IK)及Na /Ca2 交换体电流。结果表明,结扎组的左室质量指数较对照组明显升高,Carvedilol组较结扎组明显降低(P<0.01)。在2 s的基础周长下,动作电位持续时间(以90％的复极时间表示,简称APD90)在对照组、结扎组及Carvedilol组分别为522.0±19.5 ms(n=6)、664.7± 46.2 ms(n=7)、567.8±14.3 ms(n=8),结扎组同对照组相比,P<0.01,Carvedilol组同结扎组相比,P<0.05。在测试电位为-100mV时,IKi电流密度(pA/pF)在对照组、结扎组及Carvedilol组分别为-11.8±0.50(n=8),-8.07±0.28 (n=8),-10.69±0.35(n=8),结扎组与对照组及Carvedilol组相比,P<0.01。在测试电位为 50 mV时,IK尾电流密度(pA/pF)在对照组、结扎组及Carvedilol组分别为0.59±0.40(n=     

Adenosine transporters in chromaffin cells: subcellular distribution and characterization

Adenosine transporters in freshly isolated and cultured chromaffin cells were quantified by the [3H]dipyridamole binding technique, showing a maximal bound capacity of 0.4 +/- 0.05 pmol/10(6) cells (240,000 +/- 20,000 transporters by cell). Scatchard analysis showed a similar affinity for [3H]dipyridamole in isolated cells and subcellular fractions (Kd = 5 +/- 0.6 nM). For enriched plasma membrane preparations and chromaffin granule membranes, the maximal binding capacities were also very similar, 2.3 +/- 0.3 and 1.8 +/- 0.4 pmol/mg protein, respectively. When [3H]nitrobenzylthioinosine was employed as a radioligand, the maximal bound capacity in cultured chromaffin cells was 0.053 +/- 0.004 pmol/10(6) cells (32,000 +/- 3000 transporters per cell) with a high affinity constant (Kd = 0.25 +/- 0.03 nM); similar values were obtained in all subcellular fractions (Kd = 0.1 +/- 0.01). Also, plasma and chromaffin granule membranes showed similar maximal binding values (0.4 +/- 0.06 pmol/mg protein). Photoincorporation studies with [3H]nitrobenzylthioinosine into plasma membrane polypeptides showed the presence of three molecular species of 115 +/- 10; 58 +/- 6 and 42 +/- 5 kDa. Chromaffin granule membranes showed only the 105 +/- 9 and 51 +/- 4 molecular species.     

Increased cathepsin D-like activity in cortex, tubules, and glomeruli isolated from rats with experimental nephrotic syndrome.

We have examined the activity and distribution of cathepsin D (EC 3.4.23.5), a major renal lysosomal endoproteinase, in the various anatomical and functional areas of normal rat kidney. Cathepsin D-like activities (delta A280/h per mg of protein) in normal rat tissues were: cortex, 0.78 +/- 0.05, n = 37; medulla, 0.62 +/- 0.03, n = 12; papilla, 0.63 +/- 0.04, n = 12; tubules, 0.74 +/- 0.04, n = 28; glomeruli, 0.59 +/- 0.03, n = 28; and liver, 0.41 +/- 0.02, n = 28. Enzyme activity was maximal at pH 3.0-3.5 and inhibited more than 90% by pepstatin (6.7 micrograms/ml), suggesting that the enzyme is cathepsin D. In subsequent experiments we measured cathepsin D-like activity in cortex, tubules and glomeruli isolated from rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome. Treated animals (15 mg of PAN/100g body wt., intraperitoneally) developed proteinuria beginning 4 days after injection and exceeding 900 mg/24h on day 9. In two separate experiments involving 52 animals we observed a significant increase in cathepsin D-like activity in cortex (+82.7%), tubules (+109.6%) and glomeruli (+54.7%) isolated from PAN-treated rats killed during marked proteinuria (day 9, mean total urinary protein excretion: 937 +/- 94 mg/24h). This increase was observed whether the activity was expressed per mg of DNA or per mg of protein. Increased cathepsin D-like activity was first observed in cortex and tubules coincident with the onset of proteinurea (day 4, mean total urinary protein excretion: 112 +/- 23 mg/24h). In contrast with the significant elevation of renal cathepsin D-like activity, the activity (nmol/h per mg of protein) of alpha-L-fucosidase (EC 3.2.1.51), a non-proteolytic enzyme, was markedly decreased in the identical samples used for the measurement of cathepsin D-like activity: cortex (-46.4%); tubules (-46.1%); and glomeruli (-38.5%). In addition to changes in renal enzyme activities, PAN-treated rats excreted large amounts of cathepsin D-like activity in their urine (beginning on day 3) compared with nearly undetectable cathepsin D-like activity in the urine from control rats. The significant increases in glomerular and tubular cathepsin D activity may reflect an important role for this enzyme in the pathophysiology associated with PAN-induced nephrotic syndrome.     

Elevated capillary tube hematocrit reflects degradation of endothelial cell glycocalyx by oxidized LDL

Proteoglycans and plasma proteins bound to the endothelial cell glycocalyx are essential for vascular function, but at the same time, they lower capillary tube hematocrit by reducing capillary volume available to flowing blood. Because oxidized low-density lipoproteins (oxLDL) reduce the effective thickness of the glycocalyx (Vink H, Constantinescu AA, and Spaan JAE. Circulation 101: 1500-1502, 2000), we designed the present study to determine whether this is caused by pathological degradation of glycocalyx constituents or increased glycocalyx deformation by elevated shear forces of flowing blood. Capillaries from the right cremaster muscle of 24 hamsters were examined by using intravital microscopy after systemic administration of normal LDL (n = 4), moderate oxLDL (6-h oxidation with CuSO(4), n = 7), severe oxLDL (18-h oxidation, n = 5), and moderate oxLDL plus superoxide dismutase (SOD) and catalase (n = 8). Capillary tube hematocrit increased from 0.16 +/- 0.03 to 0.37 +/- 0.05 and from 0.15 +/- 0.01 to 0.31 +/- 0.03 after moderate oxLDL and severe oxLDL, respectively. These changes were paralleled by increases in red blood cell flux from 8.7 +/- 1.9 to 13.8 +/- 3 and from 10.7 +/- 2.1 to 16.3 +/- 3.2 cells/s after moderate oxLDL and severe oxLDL, respectively, in the absence of changes in anatomic capillary diameter. Red blood cell velocity, as a measure for the shear forces on the glycocalyx, was not affected by oxLDL, whereas tissue pretreatment with SOD and catalase completely abolished the effects of oxLDL on glycocalyx thickness, capillary hematocrit, and red blood cell flux. We conclude that elevation of capillary tube hematocrit by oxLDL reflects degradation of the endothelial glycocalyx by oxygen-derived free radicals.     

Stroma-free hemoglobin: its presence in plasma does not improve oxygen supply to the resting hindlimb vascular bed of hemodiluted dogs.

In hemodilution, red cell spacing in the microcirculation is increased, flow distribution may become more heterogeneous, and, as a result, oxygen supply to tissues may suffer. We tested the hypothesis that oxygen extraction from diluted blood may be enhanced by the presence of hemoglobin in the plasma phase in relatively low concentrations. In anesthetized dogs, the hindlimb vascular bed was isolated and perfused with the animal's own blood by a roller pump. One group of dogs (n = 6) was hemodiluted (hematocrit = 15.0 +/- 1.0%) with a 6% solution of dextran. A second group of dogs (n = 6) was similarly hemodiluted (hematocrit = 16.0 +/- 0.4%) with dextran containing stroma-free hemoglobin solution whereby plasma-phase hemoglobin concentration was raised to 1.1 +/- 0.1 g.dL-1. Systemic hemodynamic observations were made repeatedly over the subsequent 2.5 h, while blood flow to the hindlimb was progressively reduced in stepwise decrements. The hemoglobin-hemodiluted group showed increased systemic arterial blood pressure and total peripheral resistance when compared with the control (dextran diluted) group. The isolated hindlimb also showed evidence of increased vascular resistance in the hemoglobin-treated group. In each individual animal, critical oxygen delivery and extraction were determined by finding the intercept of the supply-independent and supply-dependent portions of the oxygen uptake/oxygen delivery relationship. Neither the critical oxygen delivery rates (5.75 +/- 0.83 vs. 6.41 +/- 0.53 mL.kg-1.min-1) nor critical oxygen extraction ratios (0.75 +/- 0.03 vs. 0.76 +/- 0.04) were found to be significantly different in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Determination of the surface area and viscosity of membranes in T- and B-lymphocytes by means of fluorescent probes

The surface area of lymphocyte membranes was measured by registering F?rster's energy transfer on fluorescent probes. Pyrene served as donor, 4-(n-hydroxystyryl)-N-tetradecylpiridinium (HSP) was the acceptor. The surface area B-lymphocyte membranes was shown to be 1,2 times larger than that of T-lymphocytes. The mean value of lymphocyte membranes viscosity was measured using the excimerization effect of pyrene. This value was the same in all the cells investigated Fluorescence of the probe 3-methoxybenzanthrone (MBA) was 2-2.5 times higher in B-lymphocytes and was not proportional to the surface area of T- and B-cells membranes. MBA fluorescence may imply some differences in physical structures of these cells which are not connected with the viscosity of their membrane lipid phase.