P glycoprotein regulated transport of glutamate at blood brain barrier

AIM

To study whether efflux of glutamate (Glu) at blood brain barrier (BBB) was regulated by P-glycoprotein (P-gp).

METHODS

1) After intracerebral microinjection [3H]Glu 5 min, recoveries were determined in injected cerebrums in presence of multidrug-resistant(MDR) reversing agents verapamil (Ver), vincristine(VCR), an d cyclosporin A(CsA); 2) apparent transfer constants (Kin) of [3H]Glu from plasma to brain were determined after the in situ rat brain perfusion 2 min us ing solution containing MDR-reversing agents; 3) uptake amount of [3H]Glu by prima ry cultured bovine brain capillary endothelial cells(BCEC) was analyzed; and 4) In presence of MDR-reversing agents and antibody of P-gp, C(219), uptake amount of [3H]Glu by luminal membrane vesicles derived from BCEC was also determined.

RESULTS

In control rats, remaining percentage of [3H]Glu in inject ed cerebrums was 25 %+/-16 % at 5 min after intracerebral injection. After pre-treating with CsA 10, 100 micromol/L, VCR 20 micromol/L and Ver 100 micromol/L, the remaining percentages of [3H]Glu were increased to about 2.2, 2.5, 2.3, a nd 2.7 folds of control, respectively. In the in situ rat brain per fusion experiment, VCR and CsA in perfusion medium concentration-dependently increased [3H]Glu BBB permeability to brain. Co-administration o f CsA 40 micromol/L mad e BBB permeability of [3H]Glu in cerebral cortex, hippocampus and striatum increase to about 9, 3, 7, and 4.6 folds of control, respectively. Steady-state uptake of [3H]Glu by BCEC was also increased up to 2.5 folds in presence of 100 micromol/L CsA. MDR-reversing agents and antibody of P-gp, C219, level-dependently inhibited the uptake of [3H]Glu by luminal membrane vesicles of BCEC. And this process is ATP-dependent.

CONCLUSION

Efflux of Glu at BBB may be regulated by P-gp.

Contraction of fibroblast-containing collagen gels: initial collagen concentration regulates the degree of contraction and cell survival

Remodeling of extracellular matrix involves a number of steps including the recruitment, accumulation, and eventual apoptosis of parenchymal cells as well as the production, organization, and rearrangement of extracellular matrix produced by these cells. The culture of fibroblasts in three-dimensional gels made of type I collagen has been used as a model of tissue contraction which characterizes both wound repair and fibrosis. The current study was designed to determine the effect of initial collagen concentration on the ability of fibroblasts to contract collagen gels and on cell survival. Native type I collagen was extracted from rat tail tendons and used to prepare collagen gels with varying collagen concentrations (0.75-2.0 mg/ml). Human lung fibroblasts (HFL-1) were cast into the gels and cultured in Dulbecco modified Eagle medium with 0.1% fetal calf serum for 2 wk. The gel size, collagen content, and deoxyribonucleic acid (DNA) content were determined. Gels prepared with an initial concentration of 0.75 mg/ml contracted more rapidly and to a smaller final size than gels prepared from 2 mg/ml initial collagen concentration (final size 7.1 versus 36.4% of initial size, P < 0.01). There was no significant degradation of the collagen in the gels under either condition. Hence, the dramatically increased contraction of the lower density gels resulted in a higher final density (P < 0.01). Cell density was estimated from DNA content. In low initial density gels, the final DNA content was significantly less than that in higher initial density gels (0.73 versus 1.88 microg/gel, P < 0.05). This was accompanied by an increased percentage of apoptotic cells at day 14 (43.3 versus 34.1%, P < 0.05). If the gels were maintained in the attached state which largely prevents contraction, apoptosis was significantly reduced, suggesting that contraction rather than matrix composition was a requirement for the increased apoptosis. In summary, these findings indicate that the initial matrix composition can lead to differing outcomes during fibroblast-mediated wound contraction.

Blood monocytes attenuate lung fibroblast contraction of three-dimensional collagen gels in coculture

Mononuclear phagocytes can interact with mesenchymal cells and extracellular matrix components that are crucial for connective tissue rearrangement. We asked whether blood monocytes can alter matrix remodeling mediated by human lung fibroblasts cultured in a three-dimensional collagen gel. Blood monocytes from healthy donors (>95% pure) were cast into type I collagen gels that contained lung fibroblasts. Monocytes in coculture inhibited the fibroblast-mediated gel contractility in a time- and concentration-dependent manner. The concentration of PGE(2), a well-known inhibitor of gel contraction, was higher (P < 0.01) in media from coculture; this media attenuated fibroblast gel contraction, whereas conditioned media from either cell type cultured alone did not. Three-dimensional cultured monocytes responded to conditioned media from cocultures by producing interleukin-1beta and tumor necrosis factor-alpha, whereas fibroblasts increased synthesis of PGE(2). Antibodies to interleukin-1beta and tumor necrosis factor-alpha blocked the monocyte inhibitory effect and reduced the amount of PGE(2) produced. The ability of monocytes to block the fibroblast contraction of matrix may be an important mechanism in regulating tissue remodeling.

Endothelial cell-mediated type I collagen gel contraction is regulated by hemin

The contraction of three-dimensional type I collagen gels is regarded as a model of contraction during wound healing and tissue remodeling. Because such a process could contribute to vessel narrowing, we hypothesized that endothelial cells may be able to mediate gel contraction. To demonstrate this, type I collagen was extracted from rat tail tendon and used to prepare collagen gels. Bovine arterial endothelial cells (BAECs) or human pulmonary artery endothelial cells (HPAECs) were then plated on the top of the gels in serum-free Ham's F-12 medium or 2% fetal calf serum-endothelium growth medium-2 (FCS-EGM2), respectively. After 48 hours of attachment, gels were released and floated in 0.2% FCS-Ham's F-12 medium (BAECs) or 2% FCS-EGM2 (HPAECs). Gel size was measured with an image analyzer daily for 5 consecutive days. Gels were then digested with collagenase to quantify DNA and hydroxyproline. BAECs contracted the gels in a time-dependent manner over the 5 days. Contraction was dependent on cell density (gel size was 100% of initial size after 5 days with no cells vs. 66.4%+/-0.5% with 0.9x10(4) cells/cm2 and 22.1%+/-0.3% with 7.5x10(4) cells/cm2) and was inversely related to collagen concentration (gel size was 22.3%+/-0.05%, 46.4%+/-0.9%, 72.3%+/-0.4%, and 87.4% +/-0.3% of initial size for gels prepared with 0.5 mg/mL, 0.75 mg/mL, 1 mg/mL, and 2 mg/mL of collagen, respectively). Hemin (a precursor for CO) and cytochalasin D inhibited collagen gel contraction mediated by both bovine and human endothelial cells without changing cell number or hydroxyproline content. In contrast, prostaglandin E2, an inhibitor, and transforming growth factor-beta1, a stimulator of fibroblast-mediated gel contraction, had no effect on endothelial cell-mediated contraction. These findings demonstrate that endothelial cells are able to contract native type I collagen gels and that this process can be modulated by exogenous mediators. Such a capability may cause remodeling of subjacent matrix of endothelial cells and may contribute to vessel narrowing.

Cyclodextrin encapsulation to prevent the loss of l-menthol and its retention during drying

The taste and flavor of spray-dried powdered products are the most important quality factors. In the present study, molecular encapsulation in cyclodextrin was applied to prevent the loss of a hydrophobic flavor compound (l-menthol) during the drying of a droplet. beta-Cyclodextrin appeared to be a better encapsulant for menthol than alpha- and gamma-cyclodextrin. The retention of menthol increased with increasing concentration of both cyclodextrin and maltodextrin. A simple mathematical model is proposed for estimating the flavor retention. The theoretical results by this model estimated well the final retention of menthol encapsulated in a blend of beta-cyclodextrin and maltodextrin.

Gender difference in letrozole pharmacokinetics in rats

AIM

To study gender difference in letrozole (Letr) pharmacokinetics in rats.

METHODS

Letr concentrations in plasma and tissues were determined after ig administration of Letr 2 mg/kg. Recoveries of Letr in urine and feces were also analyzed.

RESULTS

Marked gender differences were found 6 h after ig Letr 2 mg/kg, the plasma concentrations of Letr in male rats were significantly (P < 0.01) lower than those in female rats. For example, at 24, 36, 48, and 72 h after administration, plasma concentrations in female rats were about 3.3, 5.6, 10.5, and 7.4-fold of that of male rats, respectively. AUC value of Letr in male was only about one-third of that in female rats. Estimated terminal phase half-lives (T1/2) were 10.5 and 40.4 h, respectively. In female rats, cumulative excreted fractions of Letr in urine and feces were 5.8% +/- 1.4% and 6.6% +/- 1.1% within 120 h after administration, respectively, but in male rats, the excreted fractions of Letr in urine and feces were only 1.30% +/- 0.59% and 0.87% +/- 0.31%. Letr concentrations in female rat tissues were significantly (P < 0.01) higher than those in male rat tissues 24 h after administration.

CONCLUSION

There are marked gender differences in Letr pharmacokinetics in rats.

Isospin fractionation in nuclear multifragmentation

Isotopic distributions for light particles and intermediate mass fragments have been measured for 112Sn+112Sn, 112Sn+124Sn, 124Sn+112Sn, and 124Sn+124Sn collisions at E/A = 50 MeV. Isotope, isotone, and isobar yield ratios are utilized to estimate the isotopic composition of the gas phase at freeze-out. Analyses within the equilibrium limit imply that the gas phase is enriched in neutrons relative to the liquid phase represented by bound nuclei. These observations suggest that neutron diffusion is commensurate with or more rapid than fragment production.

Intracarotid infusion of hypertonic mannitol changes permeability of blood-brain barrier to methotrexate in rats

AIM

To study whether infusion of hypertonic mannitol through internal carotid artery could enhance methotrexate (MTX) concentration in rat cortex and to study the time-course of this process.

METHODS

Hypertonic mannitol was infused into the rat left internal carotid artery, ten minutes later, MTX was injected from the left femoral vein (i.v.) or left common carotid artery (ia), and the concentration of MTX was assayed 1 h later. Rats were given MTX at different time interval after infusion of mannitol, and the concentration of MTX was assayed 1 h after drug administration. At the same time, the rat cortex's density was analyzed.

RESULTS

After mannitol infusion, MTX's concentration in rat cortex increased 2.54 times (i.v.) and 3.41 times (ia) as compared to control, respectively. After 10 min, such effect reached its peak, and almost disappeared after 6 h. There was no significant change in rat cortex's density.

CONCLUSION

Mannitol can make blood-brain barrier (BBB) reversibly permeable, and increase MTX concentration in brain without any obvious injury to the brain.

Impaired nitric oxide-mediated vasodilation in transgenic sickle mouse

Transgenic sickle mice expressing human beta(S)- and beta(S-Antilles)-globins show intravascular sickling, red blood cell adhesion, and attenuated arteriolar constriction in response to oxygen. We hypothesize that these abnormalities and the likely endothelial damage, also reported in sickle cell anemia, alter nitric oxide (NO)-mediated microvascular responses and hemodynamics in this mouse model. Transgenic mice showed a lower mean arterial pressure (MAP) compared with control groups (90 +/- 7 vs. 113 +/- 8 mmHg, P < 0.00001), accompanied by increased endothelial nitric oxide synthase (eNOS) expression. N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective inhibitor of NOS, caused an approximately 30% increase in MAP and approximately 40% decrease in the diameters of cremaster muscle arterioles (branching orders: A2 and A3) in both control and transgenic mice, confirming NOS activity; these changes were reversible after L-arginine administration. Aminoguanidine, an inhibitor of inducible NOS, had no effect. Transgenic mice showed a decreased (P < 0.02-0.01) arteriolar dilation in response to NO-mediated vasodilators, i.e., ACh and sodium nitroprusside (SNP). Indomethacin did not alter the responses to ACh and SNP. Forskolin, a cAMP-activating agent, caused a comparable dilation of A2 and A3 vessels ( approximately 44 and 70%) in both groups of mice. Thus in transgenic mice, an increased eNOS/NO activity results in lower blood pressure and diminished arteriolar responses to NO-mediated vasodilators. Although the increased NOS/NO activity may compensate for flow abnormalities, it may also cause pathophysiological alterations in vascular tone.

[Early cracked teeth: clinical analysis of 70 cases]

OBJECTIVE

To determine the clinical features and x-ray findings in early cracked teeth,in order to provide theoretical basis.

METHODS

86 cracked teeth in 70 cases were reviewed. Analysis of x-ray and articulation paper examination was combined. The teeth were repaired with composite resins.

RESULTS

The study showed that the incidence of cracked first maxillary molar was highest in patients aged form 40 to 50 years. X-ray demonstrated characteristic changes of the diseased periodontal tissues in 57% teeth. Contour deformities were found in 19% affected roots. The efficacy rate 1 year after treatment was 90.9%.

CONCLUSION

The features of periodontal supporting tissues illustrating on x-ray films are considered to be useful to aid the diagnosis and treatment of early cracked teeth.

Sodium nitroprusside augments human lung fibroblast collagen gel contraction independently of NO-cGMP pathway

Nitric oxide (NO) relaxes vascular smooth muscle in part through an accumulation of cGMP in the target cells. We hypothesized that a similar effect may also exist on collagen gel contraction mediated by human fetal lung (HFL1) fibroblasts, a model of wound contraction. To evaluate this, HFL1 cells were cultured in three-dimensional type I collagen gels and floated in serum-free DMEM with and without various NO donors. Gel size was measured with an image analyzer. Sodium nitroprusside (SNP, 100 microM) significantly augmented collagen gel contraction by HFL1 cells (78.5 +/- 0.8 vs. 58.3 +/- 2. 1, P < 0.01), whereas S-nitroso-N-acetylpenicillamine, 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium chloride, NONOate, and N(G)-monomethyl-L-arginine did not affect the contraction. Sodium ferricyanide, sodium nitrate, or sodium nitrite was not active. The augmentory effect of SNP could not be blocked by 1H-[1,2, 4]-oxadiazolo-[4,3-a]-quinoxalin-1-one, whereas it was partially reversed by 8-(4-chlorophenylthio) (CPT)-cGMP. To further explore the mechanisms by which SNP acted, fibronectin and PGE(2) production were measured by immunoassay after 2 days of gel contraction. SNP inhibited PGE(2) production and increased fibronectin production by HFL1 cells in a concentration-dependent manner. CPT-cGMP had opposite effects on fibronectin and PGE(2) production. Addition of exogenous PGE(2) blocked SNP-augmented contraction and fibronectin production by HFL1 cells. Therefore, SNP was able to augment human lung fibroblast-mediated collagen gel contraction, an effect that appears to be independent of NO production and not mediated through cGMP. Decreased PGE(2) production and augmented fibronectin production may have a role in this effect. These data suggest that human lung fibroblasts in three-dimensional type I collagen gels respond distinctly to SNP by mechanisms unrelated to the NO-cGMP pathway.

A double-site absorption model fits to pharmacokinetic data of repaglinide in man

The plasma concentrations of repaglinide in 16 male subjects were determined after an oral dose of 4 mg. Two-peak concentrations in plasma were observed. A type of one-compartment model with double sites of drug absorption was developed and successfully used to fit the data. A good agreement between observed and predicted data was found in all subjects with correlation index r2 > 0.97. The corresponding pharmacokinetic parameters were estimated as follows: Tmax1 0.61 +/- 0.14 h, Tmax2 1.45 +/- 0.43 h, Cmax1 40.60 +/- 20.57 ng/ml, Cmax2 42.70 +/- 17.54 ng/ml, T1 0.12 +/- 0.07 h, T2 0.67 +/- 0.30 h and T3 1.03 +/- 0.35 h.

Monoclonal antibodies to alphaVbeta3 (7E3 and LM609) inhibit sickle red blood cell-endothelium interactions induced by platelet-activating factor

Abnormal interaction of sickle red blood cells (SS RBC) with the vascular endothelium has been implicated as a factor in the initiation of vasoocclusion in sickle cell anemia. Both von Willebrand factor (vWf) and thrombospondin (TSP) play important roles in mediating SS RBC-endothelium interaction and can bind to the endothelium via alphaVbeta3 receptors. We have used monoclonal antibodies (MoAb) directed against alphaVbeta3 and alphaIIbbeta3 (GPIIb/IIIa) integrins to dissect the role of these integrins in SS RBC adhesion. The murine MoAb 7E3 inhibits both alphaVbeta3 and alphaIIbbeta3 (GPIIb/IIIa), whereas MoAb LM609 selectively inhibits alphaVbeta3, and MoAb 10E5 binds only to alphaIIbbeta3. In this study, we have tested the capacity of these MoAbs to block platelet-activating factor (PAF)-induced SS RBC adhesion in the ex vivo mesocecum vasculature of the rat. Infusion of washed SS RBC in preparations treated with PAF (200 pg/mL), with or without a control antibody, resulted in extensive adhesion of these cells in venules, accompanied by frequent postcapillary blockage and increased peripheral resistance units (PRU). PAF also caused increased endothelial surface and interendothelial expression of endothelial vWf. Importantly, pretreatment ofthe vasculature with either MoAb 7E3 F(ab')(2) or LM609, but not 10E5 F(ab')(2), after PAF almost completely inhibited SS RBC adhesion in postcapillary venules, the sites of maximal adhesion and frequent blockage. The inhibition of adhesion with 7E3 or LM609 was accompanied by smaller increases in PRU and shorter pressure-flow recovery times. Thus, blockade of alphaVbeta3 may constitute a potential therapeutic approach to prevent SS RBC-endothelium interactions under flow conditions. (Blood. 2000;95:368-374)

Rate of deoxygenation modulates rheologic behavior of sickle red blood cells at a given mean corpuscular hemoglobin concentration

Although the mean corpuscular hemoglobin concentration (MCHC) plays a dominant role in the rheologic behavior of deoxygenated density-defined sickle red blood cells (SS RBCs), previous studies have not explored the relationship between the rate of deoxygenation and the bulk viscosity of SS RBCs at a given MCHC. In the present study, we have subjected density-defined SS classes (i.e., medium-density SS4 and dense SS5 discocytes) to varying deoxygenation rates. This approach has allowed us to minimize the effects of SS RBC heterogeneity and investigate the effect of deoxygenation rates at a given MCHC. The results show that the percentages of granular cells, classic sickle cells and holly leaf forms in deoxygenated samples are significantly influenced by the rate of deoxygenation and the MCHC of a given discocyte subpopulation. Increasing the deoxygenation rate using high K+ medium (pH 6.8), results in a greater percentage of granular cells in SS4 suspensions, accompanied by a pronounced increase in the bulk viscosity of these cells compared with gradually deoxygenated samples (mainly classic sickle cells and holly leaf forms). The effect of MCHC becomes apparent when SS5 dense cells are subjected to varying deoxygenation rates. At a given deoxygenation rate, SS5 dense discocytes show a greater increase in the percentage of granular cells than that observed for SS4 RBCs. Also, at a given deoxygenation rate, SS5 suspensions exhibit a higher viscosity than SS4 suspensions with fast deoxygenation resulting in maximal increase in viscosity. Although MCHC is the main determinant of SS RBC rheologic behavior, these studies demonstrate for the first time that at a given MCHC, the rate of deoxygenation (hence HbS polymerization rates) further modulates the rheologic behavior of SS RBCs. Thus, both MCHC and the deoxygenation rate may contribute to microcirculatory flow behavior of SS RBCs.

The mammalian HSF4 gene generates both an activator and a repressor of heat shock genes by alternative splicing

The expression of heat shock genes is controlled at the level of transcription by members of the heat shock transcription factor family in vertebrates. HSF4 is a mammalian factor characterized by its lack of a suppression domain that modulates formation of DNA-binding homotrimer. Here, we have determined the exon structure of the human HSF4 gene and identified a major new isoform, HSF4b, derived by alternative RNA splicing events, in addition to a previously reported HSF4a isoform. In mouse tissues HSF4b mRNA was more abundant than HSF4a as examined by reverse transcription-polymerase chain reaction, and its protein was detected in the brain and lung. Although both mouse HSF4a and HSF4b form trimers in the absence of stress, these two isoforms exhibit different transcriptional activity; HSF4a acts as an inhibitor of the constitutive expression of heat shock genes, and hHSF4b acts as a transcriptional activator. Furthermore HSF4b but not HSF4a complements the viability defect of yeast cells lacking HSF. Moreover, heat shock and other stresses stimulate transcription of target genes by HSF4b in both yeast and mammalian cells. These results suggest that differential splicing of HSF4 mRNA gives rise to both an inhibitor and activator of tissue-specific heat shock gene expression.

The yeast Hsp110 family member, Sse1, is an Hsp90 cochaperone

In eukaryotes, production of the diverse repertoire of molecular chaperones during normal growth and in response to stress is governed by the heat shock transcription factor HSF. The HSC82 and HSP82 genes, encoding isoforms of the yeast Hsp90 molecular chaperone, were recently identified as targets of the HSF carboxyl-terminal activation domain (CTA), whose expression is required for cell cycle progression during prolonged heat stress conditions. In the present study, we have identified additional target genes of the HSF CTA, which include nearly all of the heat shock-inducible members of the Hsp90 chaperone complex, demonstrating coordinate regulation of these components by HSF. Heat shock induction of SSE1, encoding a member of the Hsp110 family of heat shock proteins, was also dependent on the HSF CTA. Disruption of SSE1 along with STI1, encoding an established subunit of the Hsp90 chaperone complex, resulted in a severe synthetic growth phenotype. Sse1 associated with partially purified Hsp90 complexes and deletion of the SSE1 gene rendered cells susceptible to the Hsp90 inhibitors macbecin and geldanamycin, suggesting functional interaction between Sse1 and Hsp90. Sse1 is required for function of the glucocorticoid receptor, a model substrate of the Hsp90 chaperone machinery, and Hsp90-based repression of HSF under nonstress conditions. Taken together, these data establish Sse1 as an integral new component of the Hsp90 chaperone complex in yeast.

Glucocorticoids augment fibroblast-mediated contraction of collagen gels by inhibition of endogenous PGE production

Glucocorticoids are currently regarded as the drug of choice in the treatment of inflammatory airway and lung diseases, however, they are not routinely effective in fibrotic phases of inflammation. In the current study, glucocorticoids were investigated for their ability to affect fibroblast mediated contraction of a three dimensional collagen gel, a measure of one aspect of tissue remodeling. Dexamethasone, budesonide, hydrocortisone and fluticasone propionate were all able to significantly augment fibroblast contractility in a concentration dependent manner. Glucocorticoids also had an augmentative effect on collagen gel contraction mediated by fibroblasts from bronchi, skin and bone marrow. The increased contractility was not due to cell proliferation or to collagen degradation, since the glucocorticoids did not alter the amounts of DNA and hydroxyproline in the gels. The concentration of prostaglandin E2 (PGE2) in supernatant media was lower from glucocorticoid-treated gels compared to control gels. Consistent with this, addition of exogenous PGE2 to the culture system restored the contractile properties and indomethacin augmented contraction similar to the glucocorticoids suggesting that inhibition of prostaglandins or related eicosanoids may be the mechanism by which the increased contractility occurs. DBcAMP, forskolin and the long lasting beta2-agonist formoterol were able to reverse the effect of the glucocorticoids on fibroblast mediated collagen gel contraction suggesting that enhancers of cAMP can counteract the effect of glucocorticoids. Thus, we provide evidence that glucocorticoids have the ability to directly augment fibroblast contractility by inhibiting fibroblast endogenous PGE synthesis. The findings could be one possible mechanism to explain the poor therapeutic response to glucocorticoids on the later stages of fibrotic diseases.

Efflux transport of [3H]GABA across blood-brain barrier after cerebral ischemia-reperfusion in rats

AIM

To study whether the efflux transport of [3H]GABA across the blood-brain barrier (BBB) would be enhanced after cerebral ischemia-reperfusion.

METHODS

Brain efflux index (BEI) of [3H]GABA was determined in ischemic-reperfused rats after [3H]GABA or [3H]GABA combined with unlabeled GABA or probenecid (Pro) was microinjected into the parietal cortex area 2 (Par 2), and brain uptake of Evans blue (EB) was assessed after i.v. EB.

RESULTS

BEI in rats subjected to 10-min ischemia and 30-min, 2-h, 6-h, or 24-h reperfusion were 67%, 83%, 92%, and 87%, respectively, which were higher than that in control (58%). The brain uptake of EB was also considerably increased. Unlabeled GABA or Pro obviously decreased BEI in normal or 6-h reperfused rats, but GABA had no obvious effect on that in 5-min reperfused rats.

CONCLUSION

The efflux transport of [3H]GABA was markedly enhanced after cerebral ischemia-reperfusion in rats.

Anionic polysaccharides inhibit adhesion of sickle erythrocytes to the vascular endothelium and result in improved hemodynamic behavior

The abnormal adherence of sickle red blood cells (SS RBC) to vascular endothelium may play an important role in vasoocclusion in sickle cell anemia. Thrombospondin (TSP), unusually large molecular weight forms of von Willebrand factor, and laminin are known to enhance adhesion of SS RBC. Also, these endothelial proteins bind to sulfated glycolipids and this binding is inhibited by anionic polysaccharides. Reversible sickling may expose normally cryptic membrane sulfatides that could mediate this adhesive interaction. In this study, we have investigated the effect of anionic polysaccharides, in the presence or absence of TSP, on SS RBC adhesion to the endothelium, using cultured human umbilical vein endothelial cells (HUVEC) (for the adhesion assay) and the ex vivo mesocecum of the rat (for hemodynamic evaluation). The baseline adhesion (ie, without added TSP) of SS RBC to HUVEC was most effectively inhibited by high molecular weight dextran sulfate (HDS), whereas low molecular weight dextran sulfate (LDS) and the glycosaminoglycan chondroitin sulfate A (CSA) also had significant inhibitory effects. Heparin was mildly effective whereas other glycosaminoglycans (chondroitin sulfates B and C, heparan sulfate, and fucoidan) were ineffective. Similarly, HDS and CSA resulted in an improved hemodynamic behavior of SS RBC. Soluble TSP caused significant increases in SS RBC adhesion and in the peripheral resistance. Both HDS and CSA prevented TSP-enhanced adhesion and hemodynamic abnormalities. Thus, anionic polysaccharides can inhibit SS RBC-endothelium interaction in the presence or absence of soluble TSP. These agents may interact with RBC membrane component(s) and prevent TSP-mediated adhesion of SS RBC to the endothelium.

[Pharmacokinetics and disposition of triptonide in rats]

Triptonide, isolated from Tripterygium wilfordii Hook., was found to show significant antiinflammatory, immunosuppression and antitumor activities. A RP-HPLC method was applied to determine the plasma concentration of triptonide at different times in rats. Concentration-time curves after i.v., 0.7, 1.4 and 2.8 mg.kg-1 of triptonide were fitted to a two-compartment open model with T1/2 alpha of 0.167-0.195 h and T1/2 beta of 4.95-6.49 h. The area under curves (AUCs) were linearly related to the dosages (gamma = 0.9894). Systematic clearances (CLs) were independent of dosages. Mean residence time (MRT) of the three doses was 3.26-5.14 h by noncompartmental (the statistical moment method) analyses. The tissue distribution of triptonide in rats appeared to be wide throughout the body. The triptonide levels were high in the lung and liver, moderate in the heart, kidney, spleen and muscle and low in the testis, intestine and brain. Data of the urine and bile excretion indicated that only a small percent of unchanged triptonide was excreted. Plasma protein binding of triptonide rate was about 75%.

[Two-site absorption model fits to pharmacokinetic data of gemfibrozil in man]

The plasma concentration-time data of gemfibrozil in 8 male subjects were determined after an oral dose of 600 mg. Two-peak concentrations in plasma were observed. A kind of one-compartment model with two-sites of drug absorption was proposed and used to fit these data. A good agreement between observed and predicted data was found in all subjects with correlation indexes (gamma 2) > 0.99. The corresponding pharmacokinetic parameters were estimated as follows: Tmax1, 1.10 +/- 0.46 h; Tmax2, 2.60 +/- 0.73 h; Cmax1, 13.62 +/- 4.30 micrograms.ml-1; Cmax2, 17.22 +/- 3.83 micrograms.ml-1; T1, 0.06 +/- 0.06 h; T2, 1.42 +/- 0.57 h and T3, 1.79 +/- 0.60 h.

[Pharmacokinetic and electocardiographic study of oral verapamil sustained-release tablet in 10 Chinese volunteers]

Both verapamil pharmacokinetics and electrocardio graphic changes in 10 Chinese volunteers were studied after po 240 mg of verapamil sustained release tablet. A one-compartment model with zero-order absorption gave a better fitting to concentration--time data with values of r2 > 0.96. The main pharmacokinetic parameters obtained were: Tmax, 5.9 +/- 1.6 h; Cmax, 118.9 +/- 37.2 micrograms.L-1; T1, 5.4 +/- 1.5 h; k0, 30.5 +/- 17.5 micrograms.L-1.h-1; T1/2, 10.8 +/- 4.9 h; MRT, 15.4 +/- 3.2 h and AUC. 1.96 +/- 0.82 mg.h.L-1. There were significant prolongations of PR intervals after dose. Relationships between PR interval changes and plasma concentrations of verapamil were better fitted to sigmoidal model, with r2 > 0.98. The corresponding pharmacodynamic parameters were estimated. EC50, 64.6 +/- 16.9 micrograms.L-1, Emax, 54 +/- 11 ms and s, 1.68 +/- 0.66.

Microvascular hemodynamics and in vivo evidence for the role of intercellular adhesion molecule-1 in the sequestration of infected red blood cells in a mouse model of lethal malaria

The cytoadherence of infected red blood cells (IRBCs) to the vascular endothelium is the major cause of IRBC sequestration and vessel blockage in the cerebral form of human malaria. Among the rodent models of malaria, Plasmodium yoelii 17XL-infected mice show many similarities with the human cerebral malaria caused by P. falciparum. In both, the sequestration of IRBCs in the brain vessels is secondary to the cytoadherence of IRBCs to the vascular endothelium. Similar to P. falciparum infection in the human but in contrast to P. berghei ANKA infection in mice, P. yoelii 17XL results in little, if any, accumulation of monocytes in the brain. In vivo microcirculatory studies reported here were designed to further understand the hemodynamic aspects and mechanisms underlying cytoadherence of IRBCs in the P. yoelii model using the easily accessible cremaster muscle vasculature. The results show significant decreases in arteriovenous red blood cell velocities (Vrbc) and wall shear rates in the microcirculation of P. yoelii-infected mice, with a maximal decrease occurring in small-diameter postcapillary venules, the main sites of cytoadherence. This reflects contributions from IRBC cytoadherence as well as from increased rigidity of parasitized red blood cells. No cytoadherence is observed in arterioles of the infected mice despite decreased wall shear rates, indicating that endothelial receptors for cytoadherence are restricted to venules. Infusion of a monoclonal antibody (MAb) against the intercellular adhesion molecule-1 (ICAM-1) resulted in significant increases in both arteriolar and venular Vrbc and wall shear rates, accompanied by detachment of adhered IRBCs at some venular sites. The peripheral blood smears taken after the MAb infusion showed a distinct increase in the percentage of schizonts, again indicating detachment and/or prevention of cytoadherence. An MAb against the vascular cell adhesion molecule-1 (VCAM-1) as well as an irrelevant control antibody had no effect on these parameters. These results provide the first in vivo microcirculatory evidence indicating involvement of ICAM-1, but not of VCAM-1, in the sequestration of IRBCs in a rodent model of cerebral malaria.

Human bronchial epithelial cells modulate collagen gel contraction by fibroblasts

Connective tissue contraction is an important aspect of both normal wound healing and fibrosis. This process may contribute to small airway narrowing associated with certain airway diseases. Fibroblast-mediated contraction of a three-dimensional collagen gel has been considered a model of tissue contraction. In this study, the ability of primary cultured human bronchial epithelial cells (HBEC) obtained by bronchial brushings to modulate fibroblast gel contraction was evaluated. Human lung fibroblasts (HFL1) were cast into type I collagen gels. The gels were floated both in dishes containing a monolayer of HBEC or in dishes without HBEC. Contraction assessed by measuring the area of gels was increased at all time points from 24 h up to 96 h of coculture. At 48 h, coculture of HBEC with fibroblasts resulted in significantly more contraction than fibroblasts alone (36.6 +/- 1.2 vs. 20.4 +/- 1.7%, P < 0.05). Lipopolysaccharide (LPS, 10 micrograms/ml) stimulation of the HBEC augmented the contraction (44.9 +/- 1.0%, P < 0.05 vs. HBEC). In the presence of indomethacin, the augmentation by LPS was increased further (52.2 +/- 4.3%, P < 0.05 vs. HBEC with LPS), suggesting that prostaglandins (PGs) are present and may inhibit contraction. Consistent with this, PGE was present in HBEC-conditioned medium. Bronchial epithelial cell conditioned medium had an effect similar to coculturing. SG-150 column chromatography revealed augmentive activity between 20 and 30 kDa and inhibitory activity between 10 and 20 kDa. Measurement by enzyme-linked immunosorbent assay confirmed the presence of the active form of transforming growth factor (TGF)-beta 2. The stimulatory activity of conditioned medium was blocked by adding anti-TGF-beta antibody. These data demonstrate that, through the release of factors including TGF-beta 2 which can augment and PGE which can inhibit, HBEC can modulate fibroblast-mediated collagen gel contraction. In this manner, HBEC may modulate fibroblast activities that determine the architecture of bronchial tissue.