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L Mei

Publications and source records attributed to L Mei.

83 records · Page 5Linked to original sources
PubMed1988

The cloned murine M1 muscarinic receptor is associated with the hydrolysis of phosphatidylinositols in transfected murine B82 cells.

A rat genomic DNA clone was isolated by its homology with a conserved primary sequence among the mammalian and avian beta adrenergic and porcine muscarinic receptors. A gene identified in this clone was highly homologous to the rat M1 muscarinic receptor. Stable expression of this gene was achieved in an established murine fibroblast cell line, B82. The gene product exhibits M1 type muscarinic receptor characteristics, as it has high affinity for PZ but low affinity for AF-DX 116. Carbachol stimulated the hydrolysis of phosphatidylinositols in the transfected cells. Pirenzepine had a more potent inhibitory effect on this response than AF-DX 116 since their functional inhibition constants were 13 nM and 480 nM, respectively, which is consistent with an M1 pharmacological profile. These data suggest that the M1 muscarinic receptor encoded by the gene is coupled to the hydrolysis of phosphatidylinositols after transfecting this gene into the B82 cells.

Animals↗
PubMed1988

The intact human neuroblastoma cell (SH-SY5Y) exhibits high-affinity [3H]pirenzepine binding associated with hydrolysis of phosphatidylinositols.

The binding of [3H]pirenzepine to a human neuroblastoma cell line (SH-SY5Y) and its correlation with hydrolysis of phosphatidylinositols were characterized. Specific [3H]pirenzepine binding to intact cells was rapid, reversible, saturable, and of high affinity. Kinetic studies yielded association (k+1) and dissociation (k-1) rate constants of 5.2 +/- 1.4 X 10(6) M-1 min-1 and 1.1 +/- 0.06 X 10(-1) min-1, respectively. Saturation experiments revealed a single class of binding sites (nH = 1.1) for the radioligand with a total binding capacity of 160 +/- 33 fmol/mg protein and an apparent dissociation constant of 13 nM. The specific [3H]pirenzepine binding was inhibited by the presence of selected muscarinic drugs. The order of antagonist potency was atropine sulfate greater than pirenzepine greater than AF-DX 116, with K0.5 of 0.53 nM, 2.2 nM, and 190 nM, respectively. The binding properties of [3H](-)-quinuclidinyl benzilate and its quaternary derivative [3H](-)-methylquinuclidinyl benzilate were also investigated. The muscarinic agonist carbachol stimulated formation of inositol phosphates which could be inhibited by muscarinic antagonists. The inhibition constants of pirenzepine and AF-DX 116 were 11 nM and 190 nM, respectively. In conclusion, we show that the nonclassical muscarinic receptor antagonist [3H]pirenzepine identifies a high-affinity population of muscarinic sites which is associated with hydrolysis of phosphatidylinositols in this human neuroblastoma cell line.

Atropine↗
PubMed1987

Solubilization with digitonin alters the kinetics of pirenzepine binding to muscarinic receptors from rat forebrain and heart.

The binding properties of the putative M1 selective antagonist pirenzepine (PZ) to muscarinic acetylcholine receptor (mAChR) embedded in membranes and freed by solubilization with digitonin have been studied in the rat forebrain and heart. In the forebrain membranes, the k+1 and k-1 of [3H]PZ binding was 7.05 X 10(5) min-1 M-1 and 1.84 X 10(-3) min-1 (Kd = 3.34 nM), respectively, whereas those in heart membranes were estimated to be 1.21 X 10(5) min-1 M-1 and 7.46 X 10(-3) min-1 (Kd = 66 nM) by an indirect method. After solubilization, the kinetic parameters were determined as 3.17 X 10(5) min-1 M-1 and 2.23 X 10(-3) min-1 (Kd = 7.16 nM) in the forebrain and 2.41 X 10(5) min-1 M-1 and 1.41 X 10(-3) min-1 (Kd = 6.35 nM) in the heart. Similar dissociation constants were obtained from equilibrium saturation binding studies of [3H]PZ. Both high and low affinity binding sites for PZ were found in the forebrain membranes, whereas only one low affinity site was detected in the heart membranes. After solubilization, the inhibition curves in both tissues were better fitted to a one-site model with similar Ki values. The affinity of the agonist carbachol was decreased greatly in the heart and decreased slightly in the forebrain after solubilization to IC50 values that were similar in both tissues. Although 5'-guanylylimidodiphosphate was able to reduce the affinity of carbachol for membrane bound mAChR and to increase slightly the binding of (-)-[3H]quinuclidinyl benzilate it had no effect on ligand binding to the solubilized mAChR. The affinities of classic antagonists (-)-[3H]quinuclidinyl benzilate and atropine were not altered significantly by solubilization. Our results suggest that several different factors appear to be involved in the association and dissociation processes of PZ binding to the putative M1 (in forebrain) and M2 (in heart) mAChR in membranes. Most of these factors were separated from the receptors by solubilization under our conditions.

Animals↗
PubMed1987

Thermodynamic analyses of pirenzepine binding to membrane-bound and solubilized muscarinic receptors from rat forebrain and heart.

The thermodynamic properties of pirenzepine (PZ) binding to membrane-bound and digitonin-solubilized muscarinic receptors (mAChR) from the rat forebrain and heart were evaluated. Apparent dissociation constants (Kd) of PZ were measured from saturation studies using [3H]PZ for forebrain membrane-bound mAChR and from inhibition studies of (-)-[3H]quinuclidinyl benzilate binding using unlabeled PZ, at five different temperatures from 4 degrees C to 37 degrees C. The Kd values of PZ binding to both membrane-bound and solubilized mAChR decreased with decreasing temperature whereas the maximum receptor density was unchanged. The heterogeneity of membrane-bound mAChR characterized by PZ binding to mAChR from both tissues disappeared upon digitonin-solubilization of the mAChR. The magnitude of changes of the Kd values with temperature was greater in the solubilized mAChR, suggesting that some constituents in the membrane constrained the affinity changes. The Gibbs free energy of PZ binding to membrane-bound and solubilized mAChR were both negative. The Gibbs free energy for membrane-bound receptors decreased (more negative) whereas those for solubilized receptors increased (less negative) with increasing temperature. The change in entropy was the apparent major driving force for PZ binding to membrane-bound receptors with the change in enthalpy also being favorable. The change in enthalpy was the apparent major driving force for PZ binding to solubilized receptors at all temperatures with the change in entropy being unfavorable above 17 degrees C in the rat forebrain mAChR and above 10 degrees C in the heart mAChR. Our results suggest an important role for the biomembrane microenvironment and possible topographical differences in the binding sites which may contribute to the mechanism of muscarinic subtypes.

Animals↗
PubMed1983

The gravitational field and brain function.

The frontal cortex is recognized as the highest adaptive control center of the human brain. The principle of the "frontalization" of human brain function offers new possibilities for brain research in space. There is evolutionary and experimental evidence indicating the validity of the principle, including it's role in nervous response to gravitational stimulation. The gravitational field is considered here as one of the more constant and comprehensive factors acting on brain evolution, which has undergone some successive crucial steps: "encephalization", "corticalization", "lateralization" and "frontalization". The dominating effects of electrical responses from the frontal cortex have been discovered 1) in experiments under gravitational stimulus; and 2) in processes potentially relating to gravitational adaptation, such as memory and learning, sensory information processing, motor programing, and brain state control. A brain research experiment during space flight is suggested to test the role of the frontal cortex in space adaptation and it's potentiality in brain control.

Acceleration↗
PubMedDate not supplied

Brain interleukin-1 is involved in generation of the serum suppressive factor induced by restraint stress in mice.

Our previous work showed that a factor (a protein with a high molecular weight) in serum was induced by restraint stress in mice and rats, and suppressed lymphocyte proliferation induced by concanavalin A. It was also found that the generation of the serum suppressive factor was under the control of the central nervous system. The present work was designed to investigate the role of interleukin-1 (IL-1) in the brain in the serum suppressive factor. IL-1 receptor antagonist (IL-1ra) was injected intracerebroventricularly in mice and the generation of the serum suppressive factor was found to be significantly decreased in a dose-dependent manner. When the dose of IL-1ra reached 5 micrograms, the generation of the suppressive factor was almost totally abolished. Intracerebroventricular injection of IL-1 beta (1.0 pg) enhanced the generation of the suppressive factor. Taken together, these results indicate the involvement of IL-1 in the brain in mediating generation of the suppressive factor.

Animals↗
PubMedDate not supplied

A factor in lymph node and spleen induced by restraint stress in mice and rats suppresses lymphocyte proliferation.

Extracts from lymph node and spleen in mice and rats subjected to restraint stress significantly suppressed lymphocyte proliferation, but extracts from brain, skeletal muscle, and thymus gland had no effect on lymphocyte proliferation, suggesting that a suppressive factor for lymphocyte proliferation might selectively be induced in lymph node and spleen. Further experiments showed that biochemical properties, molecular weight, correlation between suppressive factors in serum and in extract of the lymph tissue from stressed animals, and control of the generation, all indicated that under the conditions of restraint stress and under the control of central nervous system a suppressive factor was generated in peripheral lymph tissue and then released into the blood-stream, which acted as a strong suppressor of lymphocyte proliferation.

Animals↗
PubMedDate not supplied

[Ultrasonic assessment of the state of the cervical canal at the term of pregnancy].

BACKGROUND: To assess if ultrasonic measurement of the cervical canal has carries, at term of pregnancy, a relationship with the onset of labour. To assess if cervical length identifies women at risk to deliver beyond 42 completed weeks of gestation (287 days). METHODS: Prospective case-control study, carried out between 37 and 40 weeks of gestation in uncomplicated, singleton, cephalic presentation, pregnant women. SETTING: outpatient ultrasound Department of a tertiary referral centre, serving > 1000 pregnancies. Weekly measurements of the cervical canal by transvaginal ultrasound probe. RESULTS: Inverse relationship between sonographic measurements and advancing gestational age. At 38 weeks of gestation, significant difference in the ultrasonic recordings between patients delivered before and beyond 41 completed weeks. CONCLUSIONS: It is possible to identify as early as 38 weeks of gestation those women that will deliver beyond 41 weeks. There is a subgroup of nulliparous patients that will probably be candidates to induction of labour.

Cervix Uteri↗
PubMedDate not supplied

Angiotensin II receptor binding and actions in NG108-15 cells.

NG108-15 cells were grown in culture to confluency and membranes were prepared from the cells to test for the presence of angiotensin II (Ang II) receptors using 125I-sarcosine1, isoleucine8 angiotensin II (125I-SI Ang II). These radioligand binding studies indicated a single class of binding sites with high affinity (KD = 221 +/- 54 pM) that were saturable (Bmax = 27.2 +/- 1.6 fmol/mg protein) and showed characteristic specificity (SI Ang II greater than Ang II greater than Sar1Thr8 Ang II greater than Ang III greater than Ang I greater than des Phe8 Ang II greater than des Asp1, Arg2, Val3 pentapeptide Ang II). To see if these putative receptor binding sites were associated with a functional response, the effect of Ang II on phosphatidylinositide (PtdIns) hydrolysis, expressed as inositol monophosphate (IP1) formation in intact NG108-15 cells preloaded with 3H-myoinositol, was determined. Ang II inhibited IP1 formation up to 35% below the basal rate in a dose related manner. The inhibition of PtdIns hydrolysis was prevented by pre-exposure of the cells to SI Ang II, an Ang II receptor antagonist. These results indicate that undifferentiated NG108-15 cells possess Ang II receptors that mediate a reduction in PtdIns hydrolysis.

Angiotensin II↗