Search

The binding model of cis -Ru II Cl 2 (DMSO) 3 (DMSO) ( cis -RDT, three out of the four DMSO's are S-bonded to the Ru, while the last one is O-bonded) with 5′-GMP and 5′-AMP in aqueous solution at physiological pH value were investigated by high-resolution 1 H and 31 P NMR. A 1 H NMR recognition probe, [ trans -en 2 Os(η-H 2 )](CF 3 SO 3 ) 2 , was used in order to verify further the results. 5′-GMP with cis -RDT formed two products, clearly indicating that the guanine N 7 and phosphate group bind to Ru II and form a chelate to the metal center; but binding of 5′-AMP to cis -RDT may only occur via the phosphate group.

The receptor-coupling efficiency for epinephrine (EPI) stimulated heterotrimeric G protein activation was studied at the G protein level in membranes prepared from PC12 cells expressing cloned alpha 2D-adrenergic receptors (alpha 2D-AR). After pretreatment with different concentrations of N-ethoxycarbonyl-1,2-dihydroquinoline, which irreversibly inactivates alpha 2D-AR, the portion of alpha 2D-ARs remaining active (q) was estimated from EPI-stimulated [35S]GTP gamma S binding. This function-derived estimate was close to the actual remaining number of receptors, as determined in saturation-binding studies using the selective alpha 2-AR antagonist [3H]rauwolscine in the same membranes. The agonist dissociation constant (KA) derived from EPI-stimulated [35S]GTP gamma S binding via Furchgott analysis was similar to the EC50 of EPI in the same assay, but 40-fold lower than its Ki measured from EPI competition for [3H]rauwolscine-binding sites in the presence of GTP gamma S and Na+. The occupancy-response relationship, calculated using Ki rather than KA, was markedly nonlinear, consistent with the high expression of alpha 2D-AR in these membranes. A nonlinear occupancy-response relationship was more directly confirmed by measuring the maximal level (i.e., full occupancy level) of G protein activation at graded densities of alpha AD-AR after N-ethoxycarbonyl-1,2-dihydroquinoline treatment. Determination of the number of G-proteins activated per receptor yielded lower values at higher receptor densities, indicating that overexpression of receptors can reduce their efficiency. Our results indicate the potential utility of using GTP-binding studies to assess agonist efficacy at the G protein level under conditions where receptor occupation can also be directly measured.

Taxus chinensis var. mairei is an endemic and endangered plant species in China. The resources of T. chinensis var. mairei have been excessively exploited due to its anti-cancer potential, accordingly, the extant T. chinensis var. mairei population is decreasing. In this paper, ultrasonic extraction and HPLC were adopted to determine the contents of active components paclitaxel, 7-xylosyltaxol and cephalomannine in cultivated and wild T. chinensis var. mairei plants, with the content distribution of these components in different parts of the plants having grown for different years and at different slope aspects investigated. There existed obvious differences in the contents of these active components between cultivated and wild T. chinensis var. mairei plants. The paclitaxel content in the wild plants was about 0.78 times more than that in the cultivated plants, whereas the 7-xylosyltaxol and cephalomannine contents were slishtly higher in the cultivated plants. The differences in the three active components contents between different parts and tree canopies of the plants were notable, being higher in barks and upper tree canopies. Four-year old plants had comparatively higher contents of paclitaxel, 7-xylosyltaxol and cephalomannine (0.08, 0.91 and 0.32 mg x g(-1), respectively), and the plants growing at sunny slope had higher contents of the three active components, with significant differences in the paclitaxel and 7-xylosyltaxol contents and unapparent difference in the cephalomannine content of the plants at shady slope. It was suggested that the accumulation of the three active components in T. chinensis var. mairei plants were closely related to the sunshine conditions. To appropriately increase the sunshine during the artificial cultivation of T. chinensis var. mairei would be beneficial to the accumulation of the three active components in T. chinensis var. mairei plants.

Aim: To test whether the genetic polymorphisms within the gene encoding the UGT2B7 gene may have an impact on methadone treatment. Materials & methods: Twelve SNPs in UGT2B7 were selected. 366 methadone maintenance treatment patients in Taiwan were recruited and genotyped. Results: In a genotype recessive model, rs6600879, rs6600880, rs4554144, rs11940316, rs7438135, rs7662029, rs7668258, rs7439366, rs4292394 and rs6600893 showed significant associations with severity of withdrawal symptoms (permutation p < 0.002), pupil size (permutation p < 0.048) and tremor (permutation p < 0.008). Haplotypes of GATCAGCCGC and CTCTGATTCT were significantly associated with pupil size score and tremor score (p < 0.034). Conclusion: These results suggest that SNPs of the UGT2B7 gene may play important roles in opiate withdrawal symptoms. Original submitted 10 February 2012; Revision submitted 23 April 2012

Permeabilized rat kidney cells rapidly released glucose 6-phosphate dehydrogenase (G6PD) following stimulation with peptide growth factors (Stanton, R.C., Seifter, J.L., Boxer, D.C., Zimmerman, E., and Cantley, L. C. (1991) J. Biol. Chem. 266, 12442-12448). To evaluate the signal transduction pathways mediating release of G6PD, two cell lines transfected with wild type or mutant platelet-derived growth factor (PDGF) receptors (PDGFR) were studied using two permeabilization protocols. G6PD release was evaluated by enzyme activity and Western blot analysis. PDGF caused a significant increase in G6PD release in 1 min in cells transfected with wild type PDGFR. PDGF did not stimulate G6PD release in cells transfected with tyrosine kinase-deficient PDGFR. PDGF did not stimulate G6PD release in cells transfected with partially autophosphorylation-deficient PDGFR in which four known signaling proteins do not associate with the PDGFR. The PDGF-stimulated release of G6PD was partially restored in PDGFR mutants in which either phosphatidylinositol-3-kinase or phospholipase C gamma 1 could associate with the PDGFR. Lastly, there was no basal or PDGF-stimulated phosphorylation of G6PD. We conclude that release of G6PD: 1) requires intrinsic PDGFR tyrosine kinase activity; 2) requires PDGFR autophosphorylation; 3) is mediated by signaling proteins that associate with the PDGFR; 4) is not mediated by direct phosphorylation of G6PD.

Methadone, a synthetic racemic opioid that primarily works as a μ-opioid receptor (OPRM1) agonist, is commonly used for the treatment of heroin addiction. Genetic association studies have reported that the OPRM1 gene is involved in the physiology of heroin and alcohol addiction. Our current study is designed to test the hypothesis that genetic polymorphisms in the OPRM1 gene region are associated with methadone dosage, plasma concentrations, treatment responses, adverse reactions and withdrawal symptoms in a methadone maintenance treatment (MMT) cohort from Taiwan. Fifteen OPRM1 single nucleotide polymorphisms (SNPs) were selected and genotyped using DNA samples from 366 MMT patients. The plasma concentrations of methadone and its metabolite were measured by high performance liquid chromatography. The results obtained using dominant model analysis indicate that the OPRM1 SNPs rs1074287, rs6912029, rs12209447, rs510769, rs3798676, rs7748401, rs495491, rs10457090, rs589046, rs3778152, rs563649, and rs2075572 are significantly associated with change-in-libido side effects (adjusted p0.042). Using recessive model analysis, these SNPs were also found to be significantly associated with insomnia side effects in this cohort (p0.009). The significance of the insomnia findings was mainly contributed by a subgroup of patients who had a positive urine morphine test (p0.022), and by individuals who did not use benzodiazepine hypnotics (p0.034). Our current data thus suggest that genetic polymorphisms in OPRM1 may influence the change-in-libido and insomnia side effects sometimes found in MMT patients.

Aim: Methadone maintenance therapy is one of the standard treatments for heroin addiction. The isozyme CYP3A4 of the CYP system is one of the metabolic enzymes, as well as CYP2B6, responsible for the metabolism of methadone. The aim of the present study is to evaluate the potential use of genetic polymorphisms in CYP3A4 as biomarkers for the prediction of methadone treatment responses. Materials & methods: A total of 366 Han Chinese methadone maintenance treatment patients in Taiwan were recruited in this study. Main clinical assessments included the clinical opioid withdrawal scale (COWS), the treatment emergent symptom scale (TESS) and the plasma concentrations of methadone and its metabolites. Genetic associations of six SNPs in the CYP3A4 gene were calculated using a general linear model. Results: Genotypes and allele types of rs4646440 and rs2242480 were found to be significantly associated with the severity of withdrawal symptoms rated by COWS (p = 0.012, 0.0096, 0.017 and 0.012, respectively) as well as the side effects rated by TESS (p = 0.0089, 0.028, 0.0027 and 0.0085, respectively). The allele types associated with more severe withdrawal symptoms are also associated with more severe side effects and less betel nut (Areca catechu) use (p = 0.009 for rs4646440, p = 0.0063 for rs2242480). Further analyses on specific withdrawal symptoms in COWS showed that the genetic variants in rs4646440 are significantly associated with heart rate (allele type p = 0.0019). Conclusion: These results suggested that genetic variants in the CYP3A4 gene may be useful indicators for the severity of side effects and withdrawal symptoms for methadone treatment. Original submitted 2 May 2011; Revision submitted 8 July 2011

Aim: Paroxetine is a drug of choice in the treatment of major depressive disorder (MDD). Its metabolism has recently been reported to be mediated through the CYP enzymes 1A2 and 2D6. In our current study, we tested whether genetic polymorphisms in CYP1A2 are associated with the treatment efficacy and side effects of paroxetine. Materials & methods: A total of 241 MDD patients who had taken paroxetine continually for 8 weeks were recruited, and their steady state paroxetine concentrations were measured at weeks 2, 4 and 8. The genotypes of these patients were then assessed for the presence of nine SNPs, which were selected from either the HapMap Chinese ethnic group, the literature report or through their functional role in the CYP1A2 gene. Results: The allele types for SNPs rs4646425 (permutation p = 0.03), rs2472304 (permutation p = 0.01) and rs2470890 (permutation p = 0.004) demonstrated significant associations with paroxetine treatment remission at week 8. Response rates in the Hamilton Rating Scale for Depression (HAM-D) and for The Hamilton Rating Scale for Anxiety (HAM-A) were significantly associated with the SNPs rs4646425 (p = 0.0126 and 0.0088 for HAM-D and HAM-A, respectively) and rs4646427 (p = 0.0067 and 0.0196 for HAM-D and HAM-A, respectively). The inducible SNP rs762551 had a significant association with paroxetine dose at week 4 (permutation p = 0.012). We did not find an association between these SNPs and the side effects or serum concentrations of paroxetine. Conclusion: Genetic variants in the CYP1A2 region may be indicators of treatment response in MDD patients to paroxetine.

By using O-ring statistics in point pattern analysis and Programita software, this paper studied the spatial distribution patterns and associations of different age-class individuals of Taxus chinensis var. mairei populations at Xianyu and Xiaxiang in the mountainous area of southern Anhui Province. The Xianyu population had a random spatial distribution at the scales from 2 m to 25 m but a clumped distribution at the scales2 m, while the Xiaxiang population distributed randomly at all the scales. As for Xianyu population, its individuals of age-class I had a clumped distribution at the scales5 m, while the individuals of elder age-classes tended to be non-randomly distributed at more scales than5 m, which might be related to the features of population regeneration. With increasingly enlarged age-class differences, the spatial association between younger and elder age-classes individuals turned to be negative, but less spatial association was observed between adjacent age-classes individuals. Such a spatial relationship between different age-classes individuals of T. chinensis was beneficial to the effective use of resources. With the growth of the individuals, T. chinensis population had a transition from clumped to random distribution.

To investigate the expression and the significance of toll-like receptor 3 (TLR-3) in placenta, tumor necrosis factor-alpha(TNF-alpha) in maternal and cord blood of idiopathic fetal growth restriction (IFGR), and their correlation with the pathogenesis of symmetric and asymmetric IFGR.From April 2008 to April 2009, 42 primiparae of singleton pregnancy and their IFGR babies, who delivered at term through cesarean section, in the Third Affiliated Hospital of Zhengzhou University were enrolled. All subjectects were divided into symmetric IFGR group (n = 20) and asymmetric IFGR group (n = 22). Another 42 non-IFGR pairs were randomly selected as the control group. The polink-2 plus polymerized horseradish peroxidase (HRP) immunohistochemical method and the enzyme linked immunosorbent assay (ELISA) were applied to detect TLR-3 and TNF-alpha levels.(1) The expression of TLR-3 protein were observed in all maternal placenta of the three groups. TLR-3 essentially expressed in syncytiotrophoblasts and hofbouer cells in the symmetric IFGR and control group, but expressed mostly in hofbouer cells and less in syncytiotrophoblasts in the asymmetric IFGR group. (2) The expression of TLR-3 in the syncytiotrophoblasts of the symmetric and asymmetric IFGR group was significantly lower than in the control group (111 +/- 14 and 118 +/- 11 vs. 156 +/- 9, P0.01). The number of TLR-3 positive in Hofbourer cell in the symmetric IFGR group was lower than the control group (8.9 +/- 2.8 vs 17.5 +/- 2.8, P0.01), but the number in the asymmetric IFGR group was higher (23.8 +/- 3.7) compared with the control group (P0.01). (3) The TNF-alpha levels in the maternal and cord blood of the symmetric and the asymmetric group were higher than that of the control group [maternal: (90 +/- 10) microg/L and (86 +/- 11) microg/L vs. (73 +/- 9) microg/L; cord blood: (92 +/- 12) microg/L and (96 +/- 8) microg/L vs. (79 +/- 9) microg/L; P0.01]. (4) Neither symmetric nor the asymmetric IFGR group showed any correlations between the maternal and cord blood levels of TNF-alpha (P0.05). (5) Significant correlation was found between the TNF-alpha level of the cord blood and TLR-3 expression in the placenta in both the symmetric and asymmetric IFGR group (P0.05), but no relationship was found between the maternal blood TNF-alpha level and TLR-3 expression in the placenta (P0.05).The variantions of TLR-3 expression in placenta and the increased expression of TNF-alpha in cord blood are associated with the genesis IFGR. The reduced expression of TLR-3 may related to symmetric IFGR, while the increased TLR-3 level in hofbouer cells may lead to asymmetric IFGR.

For increasing the classification accuracy of chest DR images between normal and lesion images, and improving the deficiencies of poor generalization ability of traditional statistical theory, a kind of medical image classification method adapting small samples was proposed. In order to get the decision-making function, SVM classifier was applied to study on training set of chest DR images. The test samples were divided into two categories, normal and lesion images. The experimental results show this approach simple and effective, and get good results in the case of small samples. In the medical conditions of limited clinical cases, this method can be used as a tool for early diagnosis and help doctors improving the recognition accuracy rate. The method has a good application value.

Prolonged exposure of tissues to hormone agonists results in a subsequent reduction in the sensitivity of the tissue through a process known as desensitization. The desensitization response, either homologous or heterologous, has been shown to be correlated with receptor phosphorylation. Recently we have provided evidence that protein kinase C, when activated by a phorbol ester, regulates α1-adrenoceptor coupling to a G-protein. In the present study, the effects of epinephrine (10 μM) pretreatment on the binding behavior of the α1-adrenoceptor were determined from radioligand binding assays at 25° and 2°C. Pretreatment of tissues with epinephrine for 25 min moderately decreased [3H]prazosin binding by 12% (Bmax 121.5 fmol/mg) in comparison to control (139.3 fmol/mg) with no change in its affinity. The second consequence of desensiization by epinephrine is a decrease in the affinity of agonist binding to α1-adrenoceptors associated with uncoupling of the receptors from the G-protein. In control membranes, at 25°C, epinephrine defined two different affinity states of the receptor, viz. high affinity (KDH 16.5 nM, % RH 21) and low affinity (KDL 710 nM, % RL 79). The high affinity state formed at 25°C is stabilized by forming a ternary complex with a G-protein. Addition of guanylylimidodiphosphate (Gpp(NH)p) reduced the stability of this complex resulting in a loss of high affinity sites in control membranes. On the other hand, epinephrine treated membranes exhibited only a single class of low affinity agonist binding (KDH 659 nM) and further, Gpp(NH)p had no significant effect on binding. In low-temperature binding studies, both treated and untreated preparations exhibited a large proportion of sites (% RH 88 and 87) in the high affinity state indicating that receptors retain the ability to achieve a high affinity conformation, as established by the reduced temperature. Our results indicate that epinephrine desensitization includes a selective loss in the ability of G-proteins to stabilize a high affinity state of the α1-adrenoceptor. This effect of agonist preexposure, thus, resembles receptor/G-protein uncoupling described previously following protein kinase C activation.

To investigate the clinical characteristics of moderate and severe Marcus-Gunn jaw winking synkinesis and it surgical management.Thirty-three patients with Marcus-Gunn syndrome were enrolled from 1997 to 2003 in Zhongshan Ophthalmic Center. The clinical characteristics were analyzed based on the records. Unilateral levator excision and frontalis flap suspension were performed for the correction of ptosis and the results were analyzed.The follow-up period varied from 1 to 6 years. Sixteen patients were male and 17 were female. The left eye was involved in 22 patients and the right eye in 11 patients. There was no family history. The amount of ptosis in each patient was more than 2 mm. At the end of observation, good results were achieved for ptosis correction in 26 (87%) of 30 patients, fair results in 3 (10%) patients.The ptosis of patients with moderate and severe Marcus-Gunn syndrome needs to be treated surgically. Unilateral frontalis flap suspension combined levator excision can correct ptosis very well for patients with moderate and severe Marcus-Gunn syndrome.

To study the effect and safety of polylacticglycolide acid copolymer (PLGA) and recombinant human bone morphogenetic protein 2 (rhBMP-2) as implanted biomaterials for reconstruction orbital floor defects in sheep and find the relationship between implant materials degradation and orbital floor defects restoration.Nine sheep (eighteen eyes) with orbital floor defect were divided into three groups randomly. Group A was the control without treatment. Group B was treated with PLGA and group C was received PLGA/rhBMP-2. Cosmetic appearances and complications were observed after surgery. CT scan, 3D reconstruction, defect area measurement and histological examination were performed on a week, three months and six months after operation.No complication was observed. The CT examinations showed that orbital floor defect in group C was almost disappeared by six months, however in group A and group B only partially orbital floor defect was repaired. Histological examinations showed that all materials were absorbed on six months. The orbit defects in group A were replaced by fiber tissue. The defect areas in group B were consisted of bone tissue in the peripheral and fiber tissue in the center. In group C the reconstructed areas were replaced by bone tissue, loose connective tissue and mucosal epithelia layers.The thick of 0.5 mm PLGA/rhBMP-2 sheet is a good substitute material of bone graft and may be used for orbital fracture defect reconstruction in clinic in the future.

Pot experiments with five legumes were conducted in five different amendment substrates for the reclamation of copper tailings in Tongling, Anhui province. The five tested legumes species are Glycine max, Phaseolus angularis, P. calcaratus, P. radiatus, P. mininus. The results showed that the main factors to restrict growing of the vegetation are poor nutrient and high concentration of Cu. The seeds of the legumes species could germinate, but they germinated later in the substrates with higher proportion of copper tailings than in the substrates with lower proportion of copper tailings. After clipping, G. max, P. angularis, P. calcaratus, P. radiatus were alive all the time, but some of the other two legumes species were dead because of the their non-adaptation to the copper tailings. At the same amendment group, the chlorophyll contents of G. max and P. calcaratus were higher than that of other three experimental species on the 50th day. The height and the biomass of G. max and P. calcaratus were higher than that of other three experimental species on the 70th day too. According to the biological characteristics of the five species during the growth periods about indexes of the seeding survival, chlorophyll content, height and biomass, G. max and P. calcaratus are more adaptive and tolerant than the other legumes and the TA75 amendment approach is the more reasonable for the reclamation of copper tailings.

Cancer is a genomic functional disease with features of oncogene activation and tumor suppressor inactivation. These genomic features have resulted in the limited effectiveness of conventional therapies and therefore forced considerable efforts to explore new types of anticancer agents. It has been clear that chemically synthesized or in vivo-expressed short interfering RNA (siRNA) can specifically and effectively direct homology-dependent post-transcriptional gene silencing. In the present study, we intended to investigate whether siRNA could suppress the proliferation of human cancer cells through interfering oncogene activities and recovering the functions of tumor-suppressor gene. Single siRNA or combinatorial siRNAs were successfully transfected into HeLa cells, lung adenocarcinoma cells, hepatoma cells, ovarian carcinoma cells, and melanoma cells with cationic lipid complexes. These siRNA molecules not only specifically knocked down their cognate targets such as bcl-2, cdk-2, mdm-2, pkc-alpha, tgf-beta1, H-ras, vegf, and GFP mRNAs, but also effectively suppressed the proliferation of cancer cells to different extents. These data suggest that (1) all these human cancer cells preserve RNAi machinery; (2) chemically synthesized and vector-driven siRNAs can be incorporated into intrinsic RNAi system for silencing target mRNA molecules; and (3) the combination of different siRNAs inhibits the growth and proliferation of cancer cells.

The intracellular redox potential plays an important role in cell survival. The principal intracellular reductant NADPH is mainly produced by the pentose phosphate pathway by glucose-6-phosphate dehydrogenase (G6PDH), the rate-limiting enzyme, and by 6-phosphogluconate dehydrogenase. Considering the importance of NADPH, we hypothesized that G6PDH plays a critical role in cell death. Our results show that 1) G6PDH inhibitors potentiated H2O2-induced cell death; 2) overexpression of G6PDH increased resistance to H2O2-induced cell death; 3) serum deprivation, a stimulator of cell death, was associated with decreased G6PDH activity and resulted in elevated reactive oxygen species (ROS); 4) additions of substrates for G6PDH to serum-deprived cells almost completely abrogated the serum deprivation-induced rise in ROS; 5) consequences of G6PDH inhibition included a significant increase in apoptosis, loss of protein thiols, and degradation of G6PDH; and 6) G6PDH inhibition caused changes in mitogen-activated protein kinase phosphorylation that were similar to the changes seen with H2O2. We conclude that G6PDH plays a critical role in cell death by affecting the redox potential.

The intracellular redox potential, which is determined by the level of oxidants and reductants, has been shown to play an important role in the regulation of cell growth. The principal intracellular reductant is NADPH, which is mainly produced by the pentose phosphate pathway through the actions of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway, and by 6-phosphogluconate dehydrogenase. Previous research has suggested that an increase in G6PD activity is important for cell growth. In this article, we suggest that G6PD activity plays a critical role in cell growth by providing NADPH for redox regulation. The results show the following: 1) inhibition of G6PD activity abrogated growth factor stimulation of [3H]thymidine incorporation in all cell lines tested; 2) overexpression of G6PD stimulated cell growth, as measured by an increase in [3H]thymidine incorporations as compared with cells transfected with vector alone; 3) inhibition of G6PD caused cells to be more susceptible to the growth inhibitory effects of H2O2; 4) inhibition of G6PD led to a 30-40% decrease in the NADPH/NADP ratio; and 5) inhibition of G6PD inhibited cell anchorage and significantly decreased the growth-related stimulation of tyrosine phosphorylation.

The ability of receptors (R) to activate G-proteins (G) is promoted by the binding of agonists, reflecting their induction of a receptor conformation which facilitates both the formation of a RG complex and guanine nucleotide exchange. Recent evidence from isolated membrane studies has indicated, however, that some receptors have the inherent ability to form RG complexes and promote GDP/GTP exchange in their unoccupied state. These receptors preferentially activate pertussis toxin-sensitive G-proteins (i.e. Gi/G(o)) and the interactions of R and G are modulated by monovalent cations (most notably Na+) both in the unoccupied and agonist-occupied states. Basal G-protein activation by such receptors is reduced both by increasing levels of cation and by antagonists which may act by inducing receptor conformations which are less favorable for RG complexation. This behaviour conforms to the predictions of a ternary complex model of receptor function and can be considered in structural terms for those receptors such as the alpha-2 adrenergic receptor where ligand binding and G-protein activation regions have been proposed.

Silicon oxide films were deposited in electron cyclotron resonance-radio frequency dual hybrid plasmas using a mixture of HMDSO and oxygen as source gases, and optical emission spectroscopy was employed to investigate the gas phase species in the plasma. It is found that both the deposition rate and the chemical bonds of films are significantly affected by the radio frequency bias. The deposition rate is slightly increased when a low direct current self-bias is applied, and is reduced with the increasing self-bias due to strengthened ion bombardment. The ratios of O to Si in the films deposited under the bias frequency of 400 kHz are above 2∶1, nearly the same as that under 13.56 MHz. However, the content of carbon under 400 kHz bias is much higher than that under 13.56 MHz. The reason is that the application of the high frequency bias of 13.56 MHz not only strengthens ion bombardment on the material surface, but also induces the variations of the bulk plasmas including the increase of O atom density, while the main effect of the bias of 400 kHz is only to strengthen ion bombardment.

Differences in epinephrine binding to alpha 1-adrenoceptors, epinephrine-induced contractile potency, susceptibility to phorbol ester (PDBu) modulation, and differences in membrane fluidity were studied in bovine aorta from young (3-8 weeks) and adult or mature (6-8 years) animals. Membranes prepared from aorta of adult animals exhibited a two-fold higher receptor density while [3H]prazosin affinity was unchanged. Epinephrine displacement studies revealed both high- and low-affinity binding in membranes from the aortas of young animals whereas, preparations from adult animals exhibited only a single class of low-affinity sites. In low-temperature binding studies, membranes prepared from aortas of adult animals exhibited both high- and low-affinity agonist binding, in proportions about equal to those of young animals. The ability of PDBu to uncouple alpha 1-adrenoceptor from G-protein interaction is demonstrable in young but not in adult animals which raises the possibility of prior phosphorylation of receptors in the latter tissues. Aortas from young animals showed increased contractile potency to epinephrine and, in addition, were significantly more fluid as compared to aortas from adult animals. Alterations in the membrane environment or phosphorylation state of the alpha 1-adrenoceptor may thus provide age-dependent modulation of its function.