Biomedical subjects

Yin Wang

Publications and source records attributed to Yin Wang.

At least 37 records · Page 2Linked to original sources

PubMed2006

[Effect of balanced diet on the nutrition status of schoolchildren in the mountain area].

OBJECTIVE: To study the effect of balanced diet on the nutrition status of primary schoolchildren in the mountain area in November 2004. METHODS: All the subjects aged 7-9 years old were divided into intervention group and control group. The balanced diet was provided for the intervention group and the control group was maintained on their usual diet for 30 days in December. The anthropometric and nutritional status of the subjects were checked before and after the study. RESULTS: The growth and nutritional status of the intervention group improved significantly. However the unbalanced diet in the control group affects the normal growth of the children because the usual diet can not meet the nutrient requirement. CONCLUSION: The nutrition intervention can improve the growth and nutritional status of the primary schoolchildren in the mountain area.

Child↗

PubMed2005

[The influence of mycophenolate mofetil upon the maturation and allostimulatory activity of cultured dendritic cell progenitors and the effects of tolerance induction in allograft recipients].

OBJECTIVE: To investigate the influence of mycophenolate mofetil (MMF) on the maturation and allostimulatory activity of cultured dendritic cell progenitors (DCPs) and to evaluate the efficacy of pretreatment of donor dendritic cells (DCs) with MMF in tolerance induction in allograft recipients and its possible mechanism. METHODS: DCPs of Balb/c mice were cultured in culture fluid containing recombinant mouse granulocyte-macrophage colony stimulating factor (GM-CSF), and then divided into 4 groups: control group, MMF group, lipopolysaccharide (LPS) group, and MMF + LPS group. Seven days later, flow cytometry was used to analyze the phenotypes of the DCs. ELISA was used to examine the level of IL-12 in the supernatant. T cells from the spleens of C57/BL6 mice were cultured together with inactivated DCs from Balb/c mice, and added with [(3)H]-TdR. Mixed lymphocyte reaction (MLR) was analyzed. The DCs and MMF-DCs cultured for 5 days were co-cultured with T hybridoma cells of the line MF2.2D9 in culture fluid containing ovalbumin (OVA). Twenty-four hours later, the supernatant was collected and ELISA was used to measure the level of interleukin (IL)-12 so as to reflect the antigen-presenting ability of the DCs. OVA immunized C57/BL6 mice for 4 times. 21 days after T cells were collected from the spleens and co-incubated with DCs and MMF-DCs, [(3)H]-TdR was added and the values of counts per minute (cpm) were calculated so as to analyze the antigen-specific proliferation. Twenty-four Balb/c mice were randomly divided into 3 groups: group A (without treatment), group B (treatment with intravenous injection of untreated DCs of Balb/c mice), and group C (treatment with intravenous injection of DCs of Balb/c mice treated with MMF), and then transplanted with the hearts of C57/BL6 mice. The functions of the transplanted hearts were evaluated by touching the arterial pulse and histological examination. ELISA was used to detect the levels of Th1 cytokines, such as IL-12, IL-4, IL-10, IL-2, and IFN-gamma, in the cultured DCs and in the sera of the recipients 7 and 14 days after culture or transplantation. RESULTS: The immunophenotypic analysis showed that in comparison with those in the control group and the LPS group the expressions of the costimulatory molecules, Ia(d), CD80, and CD86, of the DCPs were significantly weaker in the MMF-group and MMP + LPS group. The IL-12 levels in the supernatant of the MMF and MMF + LPS groups of DCPs were significantly lower than those in the other groups (P < 0.01). The IL-12 level of the MF2.2D9 cells treated with MMF-treated DCs was significantly lower than control group (P < 0.01). The ability to stimulate proliferation of T cells of the same genotype in the MMF-DC group was significantly inhibited (P < 0.01). The survival time of the transplanted heart was 30.50 +/- 3.25 days in the C57/BL6 mice injected with untreated DCPs of Balb/c mice (21.25 +/- 2.12, P < 0.01) and that in the control C57/BL6 mice (8.63 +/- 1.06 days, P < 0.01) and with a significant difference between the latter 2 groups too (P < 0.01). The levels of, such as IL-2 and IFN-gamma, 7 and 14 days after heart transplantation of the group B were all significantly lower than those of the group A (both P < 0.05). The IL-2 and IFN-gamma levels 7 days after the heart transplantation were similar to those in the group B (both P > 0.05) and even lower than those of the group C (both P < 0.05). The IL-10 level in the groups B and C were all higher than those in the group A (all P < 0.05) with a significant difference between the group B and group C. The level of IL-4 was not significantly different among the 3 groups. CONCLUSION: MMF has a significant suppressive effect on the maturation and function of DCs, which leads to a donor-specific tolerance in transplant recipients.

Animals↗

PubMed2005

The effects of PPAR-gamma ligand pioglitazone on platelet aggregation and arterial thrombus formation.

BACKGROUND: It has been suggested that peroxisome proliferator-activated receptor (PPAR)-gamma ligands reduce the development of atherosclerosis and myocardial ischemia-reperfusion injury; both of these phenomena are associated with platelet activation. We postulated that PPAR-gamma activation would inhibit platelet activation and intra-arterial thrombus formation. METHODS AND RESULTS: Sprague-Dawley rats were fed chow mixed with pioglitazone (1 or 10 mg/kg/day) for 7 to 10 days. A filter soaked in 30% FeCl(3) was applied around the abdominal aorta to study the patterns of arterial thrombogenesis. The aortic blood flow was continuously monitored using an ultrasonic Doppler flow probe. ADP and arachidonic acid-induced platelet aggregation and the expression of constitutive nitric oxide synthase (cNOS) and thrombomodulin in aorta were measured. Pioglitazone feeding delayed the time to occlusive thrombus formation by 40% (P<0.01 vs. control, n=9) without affecting the weight of the thrombus. ADP- as well as arachidonic acid-induced platelet aggregation was also inhibited by pioglitazone feeding (P<0.01 vs. control, n=9). Pioglitazone feeding also upregulated the aortic expression of cNOS and thrombomodulin; both are considered important factors in platelet aggregation and thrombus formation in vivo. The effect of a high dose (10 mg/kg/day) of pioglitazone was not more potent than that of a low dose (1 mg/kg/day). CONCLUSION: These results indicate that pioglitazone administration decreases platelet aggregation and delays intra-arterial thrombus formation in rats, at least partially, by an increase in the expression of cNOS and thrombomodulin.

Animals↗

PubMed2005

Papillary endothelial hyperplasia (Masson tumor) of the petrous and jugulare region: case report and literature review.

OBJECTIVE: Intracranial papillary endothelial hyperplasia (PEH) is rare, and only 13 cases have been reported intracranially in the literature. In this article, we present a case of PEH involving petrous and jugular foramen region due to the uncommon incidence. CASE DESCRIPTION: A 49-year-old female patient with a 4-year history of left-sided hearing loss and facial palsy. Magnetic resonance (MR) imaging disclosed the presence of a 6 x 6 x 5 cm lobular mass occupying the left petrous and jugulare region. This mass was hyperintense on both T1 and T2 weighted MR images and was enhanced strongly with gadolinium. No edema was found around the lesion. Preoperative digital subtraction angiogram examination showed that the lesion had a rich blood supply. Therefore, polyvinyl alcohol embolization was carried out to reduce bleeding during operation. A left-sided suboccipital extreme lateral approach was applied for craniotomy. The lesion was extradural and highly vascular with extension into the petrous bone. It was subtotally removed. Postoperative course of the patient was stable. Her neurologic evaluation was the same as preoperatively. CONCLUSION: Surgical excision of the lesion is the main therapy. Radiotherapy should be given to patients whose lesion cannot be totally removed.

Brain Neoplasms↗

PubMed2005

Activated protein C, a natural anticoagulant protein, has antioxidant properties and inhibits lipid peroxidation and advanced glycation end products formation.

INTRODUCTION: Activated protein C (APC) is an important natural anticoagulant that is proteolytically generated from protein C (PC) by the modulation of thrombin activity in the presence of thrombomodulin on an endothelial surface. Recent studies have demonstrated that, beyond its anticoagulant acitivities, APC had anti-inflammatory and cytoprotective properties. The mechanisms underlying APC's anti-inflammatory effects remain unknown. Our goal was to elucidate and confirm these mechanisms. METHODS: We first examined the effect of APC on reactive oxygen species (ROS) and inflammatory cytokine production in murine macrophage-like RAW264.7 cells. We further examined the effect of APC on chemically induced lipid peroxidation and advanced glycation end-products (AGE) formation. RESULTS AND CONCLUSIONS: APC in the range of 10-50 microg/mL could reduce lipopolysaccharide (LPS)-induced ROS generation, nuclear factor kappaB (NF-kappaB) activation and resultant proinflammatory cytokine production. Additional cell-free experiments revealed that APC (10-50 microg/mL) had inhibitory effects on lipid peroxidation and AGE formation. These findings suggest that APC, via its intrinsic anti-oxidant properties, may, in settings of oxidant stress, exert important cytoprotective and anti-inflammatory effects that are distinct from its anticoagulant activity as an antioxidant protein. If that is true, APC may contribute to ROS-related chronic disorders including atherosclerosis and diabetes as well as acute shock conditions.

Animals↗

PubMed2005

[Effects of processing Phellodendron amurense with salt on anti-gout].

OBJECTIVE: To investigate the effects of processing Phellodendron anurene with salt on anti-gout. METHOD: The mouse serum uric acid level and liver xanthine oxidase activity were used to evaluate anti-gout effects of raw and processing P. amurense with salt. RESULT: Both raw and processing P. amurense with salt reduced serum uric acid levels in the in hyperuricemic mice, and inhibited activities of liver xanthine oxidase at the low and high doses respectively, thus exhibiting anti-gout effects. Moreover, they showed the tendency to decrease the uric acid levels in the normal animal only at the high dose. The latter was a little weaker than the former. CONCLUSION: Processing with salt might not significantly change anti-gout effect of P. amurense.

Animals↗

PubMed2004

CD24 controls expansion and persistence of autoreactive T cells in the central nervous system during experimental autoimmune encephalomyelitis.

In the development of experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS), autoreactive T cells must be activated and clonally expand in the lymphoid organs, and then migrate into the central nervous system (CNS) where they undergo further activation. It is unclear whether the autoreactive T cells further expand in the CNS and if so, what interactions are required for this process. We have demonstrated previously that expression by the host cells of the heat-stable antigen (CD24), which was recently identified as a genetic modifier for MS, is essential for their susceptibility to EAE. Here we show that CD24 is essential for local clonal expansion and persistence of T cells after their migration into the CNS, and that expression of CD24 on either hematopoietic cells or nonhematopoietic antigen-presenting cells in the recipient is sufficient to confer susceptibility to EAE.

Adoptive Transfer↗

PubMed2004

B7-CD28 interaction promotes proliferation and survival but suppresses differentiation of CD4-CD8- T cells in the thymus.

Costimulatory molecules play critical roles in the induction and effector function of T cells. More recent studies reveal that costimulatory molecules enhance clonal deletion of autoreactive T cells as well as generation and homeostasis of the CD25(+)CD4(+) regulatory T cells. However, it is unclear whether the costimulatory molecules play any role in the proliferation and differentiation of T cells before they acquire MHC-restricted TCR. In this study, we report that targeted mutations of B7-1 and B7-2 substantially reduce the proliferation and survival of CD4(-)CD8(-) (double-negative (DN)) T cells in the thymus. Perhaps as a result of reduced proliferation, the accumulation of RAG-2 protein in the DN thymocytes is increased in B7-deficient mice, which may explain the increased expression of TCR gene and accelerated transition of CD25(+)CD44(-) (DN3) to CD25(-)CD44(-) (DN4) stage. Qualitatively similar, but quantitatively less striking effects were observed in mice with a targeted mutation of CD28, but not CTLA4. Taken together, our results demonstrate that the development of DN in the thymus is subject to modulation by the B7-CD28 costimulatory pathway.

Animals↗

PubMed2004

Phenylthiourea as a weak activator of aryl hydrocarbon receptor inhibiting 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced CYP1A1 transcription in zebrafish embryo.

The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor that can be activated by a diverse synthetic and naturally-occurring chemicals, such as the halogenated aromatic hydrocarbons (HAHs) and the non-halogenated polycyclic aromatic hydrocarbons (PAHs). The liganded AHR modulates the genetic activity of a variety of xenobiotic-responsive genes, including cytochrome P4501A1 (CYP1A1). The tyrosinase inhibitor 1-phenyl-2-thiourea (PTU) is widely used in zebrafish research to suppress pigmentation in developing embryos/fry. Here we showed that 0.2 mM PTU induced a basal level of CYP1A1 transcription in zebrafish embryonic integument as early as 24 h postfertilization (hpf) stage. Subsequently, PTU induced CYP1A1 transcription in blood vessels at 36 hpf. During larval stage, the liver and all pharyngeal arch vessels of PTU-treated embryos exhibited CYP1A1 transcription as well. Comparing to TCDD, PTU induces CYP1A1 transcription with much lower efficacy in zebrafish embryos. Coincubating the embryos with PTU and TCDD led to repressing TCDD-induced CYP1A1 transcription. Mechanistic studies indicated that both of PTU- and TCDD-mediated CYP1A1 transcriptions are modulated by the same AHR-ARNT signaling pathway.

Animals↗

PubMed2004

An evaluation of erythrocytes as plasma glutamate scavengers for enhanced brain-to-blood glutamate efflux.

Several acute brain pathological conditions are characterized by the presence of excess glutamate in brain interstitial fluid. We have previously shown that decreasing blood glutamate levels increases the driving force for an enhanced brain-to-blood efflux of glutamate. The present study investigated the glutamate pumping ability of glutamate-depleted erythrocytes both in vitro and in vivo to determine whether the latter could potentially be used in a blood exchange procedure for neuroprotection. We have observed that glutamate is taken up in red blood cells only via a passive diffusive process with a diffusion constant of 0.144/h. When glutamate-depleted blood cells resuspended in 6% hetastarch were injected into recipient rats, using a blood exchange protocol, a decrease of blood glutamate was observed but attributed to plasma dilution. These observations are discussed in light of a novel neuroprotective strategy based on blood glutamate scavenging.

Animals↗

PubMed2004

Inhibitors of 5-lipoxygenase inhibit expression of intercellular adhesion molecule-1 in human melanoma cells.

AIM: To study the effect of 5-lipoxygenase inhibitors on the expression of intercellular adhesion molecule-1 (ICAM-1) in melanoma cells. METHODS: ICAM-1 protein of human melanoma cell a375 was detected by enzyme-linked immunosorbent, flow cytometry and Western blot analysis. Level of ICAM-1 mRNA in a375 was evaluated by Northern blot analysis. Adhesion of a375 to endothelial cell EC304 was analyzed by isotopic tracing. RESULTS: 5-Lipoxygenase inhibitors nordihydroguaiaretic acid, AA861 and MK886, could suppress the expression of ICAM-1 protein as well as of its mRNA in a375 cells and reduce the adhesion of a375 to EC304. CONCLUSION: 5-Lipoxygenase inhibitors can inhibit the expression of ICAM-1 in human melanoma cells and may be valuable for treatment of melanoma metastasis.

Benzoquinones↗

PubMed2003

Mechanism of three inhibitors of TACE in blocking the converting of pro-TNF alpha into sTNF alpha.

The effects of inhibitors of TNF alpha converting enzyme (TACE) on TNF alpha secretion were studied to develop an approach to interfere inflammation processes. The HL-60 cell lines were stimulated in vitro with LPS intravenously for different time to establish the cellular model of inflammation and simultaneously induce in vivo inflammation animal model by LPS The cytotoxic effects of soluble TNF alpha were checked using MTT colorimetric method to determine the rate of cell proliferation. The level of expression of TACE was detected by using RT-PCR, FCM and immuno-histochemical technique respectively. It was found Chinese medicine Reduqing (RDQ) could inhibit the transcription of TNF alpha mRNA induced by LPS stimulation (P < 0.01, compared with the control). The antioligodeoxyribonucleotide (anti-ODN) of TNF alpha mRNA could inhibit 78.9% of TNF alpha secretion. The mimic peptides of TACE substrates with hydroxamine group showed potency in vivo and in vitro against converting of pro-TNF alpha. It was concluded that all the three types of TACE inhibitors can regulate the expression of TACE at different levels and inhibit sTNF alpha secretion, indicating TACE is a novel target for inflammation therapy.

ADAM Proteins↗

PubMed2003

Blood-mediated scavenging of cerebrospinal fluid glutamate.

The maintenance of brain extracellular glutamate (Glu) at levels below its excitotoxic threshold is performed by Glu transporters present on glia and neurons as well as on brain capillary endothelial cells which remove brain Glu into blood. The feasibility of accelerating the naturally occurring brain-to-blood Glu efflux was studied using paradigms based on the fate of Glu present in the cerebrospinal fluid or infused into the brain ventricles and monitored before, during, and after decreasing blood Glu levels with pyruvate and oxaloacetate, the respective Glu co-substrates of the blood resident enzymes glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase. Results from cerebroventricular perfusions with [3H]Glu, intracerebroventricular injections of [3H]Glu, and measurements of the basal CSF Glu levels point out to the same conclusion that the intravenous administration of pyruvate and oxaloacetate which decreases blood Glu levels accelerates the brain-to-blood Glu efflux. We conclude that the brain extracellular Glu levels can be controlled in part by the blood Glu levels. The results may provide not only a rational explanation for the inhibition of Glu release and neuroprotective effects of parentally administered pyruvate in hemorrhagic shock and forebrain ischemia but could also outline a potential strategy for the removal of excess Glu in various neurodegenerative disorders.

Animals↗

PubMed2003

[Reproductive toxicity of metadoxine in rats].

OBJECTIVE: To study the reproductive toxicity of metadoxine. METHODS: Male and female rats were given metadoxine before pregnancy and early gestation, i.e. to feed metadoxine to male rats for 60 days before copulation and continue feeding during copulation, and feed metadoxine to female rats for 14 days before copulation. RESULTS: No significant toxic effect was observed in the 400 mg/kg group. A few rats showed paralysis of hind leg in the 800 mg/kg group. The dosage of 1 600 mg/kg caused significant paralysis of hind legs, emaciation, and reduced weight gain. In the 1600 mg/kg group, the mating rate of male rats was significantly affected (P < 0.01). In the 800 and 1 600 mg/kg group, fertility of male rats was markedly reduced (P < 0.01). In the 800 mg/kg group, the effect on sperm counts of epididymis of male rats was markedly reduced (P < 0.05). In the 1 600 mg/kg group, testicle weight and body weight ratio and sperm counts of epididymis rate were significantly (P < 0.001) reduced. In the 1 600 mg/kg group, the fertility rate of female rats was remarkably (P < 0.001) reduced. In the 800 mg/kg group, the weight gain of pregnant rats was significantly reduced (P < 0.001). In both the 800 and 1 600 mg/kg groups, the gestation rate was greatly reduced (P < 0.001). In the 800 mg/kg group, mortality rate before nidation (P < 0.001) and average live fetus number were significantly reduced (P < 0.05). In the 400 mg/kg group, the fetal weight was significantly reduced (P < 0.001). In the 800 mg/kg group, body length, tail length, body weight and sternum development of fetal rats were significantly affected (P < 0.001). CONCLUSION: Under the presented experimental conditions, metadoxine has no teratogenic effects on SD rats and the no effect dose is 400 mg/kg. And the no effect dose for the developmental toxicity is less than 400 mg/kg.

Animals↗

PubMed2003

[Combination therapy with losartan and fosinopril for early diabetic nephropathy].

OBJECTIVE: To observe the effects of combined use of losartan and fosinopril in the treatment of early diabetic nephropathy. METHODS: Fifty-seven patients with diabetic nephropathy were divided equally into group A with treatment with losartan (50 mg) and fosinopril (10 mg) daily, group B with daily losartan treatment (50-100 mg), and group C with fosinopril treatment at the daily dose of 10-20 mg. After the 6-month medication, the patients underwent examinations for changes in the mean arterial blood pressure (MABP), serum creatinine (SCr), blood urea nitrogen (BUN) and 24-h urine protein excretion. RESULTS: Losartan or fosinopril used alone or in combination significantly lowered MABP, 24-h urine protein excretion, SCr and BUN in the patients ( P < 0.05 or P < 0.01). In spite of the absence of significant differences between the patient groups, combination use of the two drugs produced the most obvious reduction of the parameters measured. CONCLUSION: Combined use of losartan and fosinopril may decrease MABP, 24-h urine protein excretion, SCr and BUN to a greater extent than the use of losartan or fosinopril alone.

Blood Urea Nitrogen↗

PubMed2003

[Study on the effect of micronutrients supplementation on health status of children].

To study the effect of multi-micronutrients supplementation on nutritional status of children, 220 students aged 8-12 years were observed for 6 months. A half of them were given the supplements, another half placebo. The results showed that in comparison with the placebo, the supplemented children had a higher urine excretion of vitamin B2 and vitamin C after loading; a higher concentration of serum 25-OH-D3, a high content of hydroxy-proline and hydroxy-proline/creatinine ratio in fast urine, and a higher bone mineral content and bone mass density of the mid-ulna. The supplemented children performed significantly better than the placebo in reading speed, learning capacity and arithmetic examinations. It is concluded that micronutrients supplementation played a notable rule in resulting better nutritional status and learning ability of school children.

Ascorbic Acid↗

PubMed2002

Comparison between continuous accelerated hyperfractionated and late-course accelerated hyperfractionated radiotherapy for esophageal carcinoma.

PURPOSE: To compare the treatment results and toxicity of continuous accelerated hyperfractionated (CAHF) and late-course accelerated hyperfractionated (LCAF) radiotherapy (RT) for esophageal carcinoma. METHODS AND MATERIALS: Between August 1996 and March 1999, 101 patients with squamous cell carcinoma of the esophagus were randomized into two groups: 49 to the CAHF group and 52 to the LCAF group. Patients in the CAHF group received RT at 1.5 Gy/fraction b.i.d. (6-h interval), 5 d/wk, to a total dose 66 Gy in 44 fractions during 4.4 weeks. The patients in the LCAF group received conventional fractionation RT, 1.8 Gy/fraction, to a dose of 41.4 Gy in 23 fractions during 4.6 weeks, followed by accelerated fractionation RT using reduced fields, b.i.d., at 1.5 Gy/fraction, with a minimal interval of 6 h between fractions. The total dose was 68.4 Gy in 41 fraction during 6.4 weeks. Patient age, gender, performance score, diet, lesion location, lesion length, stage, and fractionation (CAHF or LCAF) were entered into the univariate and multivariate analyses. RESULTS: All patients finished the treatment course, except for 1 patient in the CAHF group because of severe acute esophagitis. The rate of Grade I, II, and III acute bronchitis was 18.4% (9 of 49), 30.6% (15 of 49), and 8.2% (4 of 49) in the CAHF group and 13.5% (7 of 52), 21.2% (11 of 52), and 3.8% (2 of 52) in the LCAF group, respectively. However, the difference between the two groups was not statistically significant (p = 0.084). The rate of Grade I, II, III, and IV acute esophagitis was 6.1% (3 of 49), 32.7% (16 of 49), 46.9% (23 of 49), and 14.3% (7 of 49) in the CAHF group and 26.9% (14 of 52), 32.7% (17 of 52), 7.7% (4 of 52), and 1.9% (1 of 52) in the LCAF group, respectively. The difference was statistically significant (p < 0.001). The local control rate at 1, 2, and 3 years was 88.7%, 83.9%, and 55.9% in the CAHF group and 80.7%, 71.4%, and 57.1% in the LCAF group, respectively (p = 0.1251). The 1-, 2-, and 3-year survival rate was 79.6%, 51.6%, and 37.6% in the CAHF group and 80.0%, 57.6%, and 41.2% in the LCAF group, respectively (p = 0.5757). Multivariate analysis showed that age and lesion length were independent significant prognostic factors for local control rate, and age was for the overall survival rate. The fractionation schedule had no significant prognostic effect. CONCLUSION: CAHF and LCAF result in similar 1-, 2-, and 3-year local control and survival rates. CAHF resulted in more severe acute esophagitis and may be less well tolerated than LCAF. The treatment results after the CAHF and LCAF regimens were better than those of historical conventional RT.

Adult↗

PubMed2002

Electrostatic properties of membrane lipids coupled to metarhodopsin II formation in visual transduction.

Changes in lipid composition have recently been shown to exert appreciable influences on the activities of membrane-bound proteins and peptides. We tested the hypothesis that the conformational states of rhodopsin linked to visual signal transduction are related to biophysical properties of the membrane lipid bilayer. For bovine rhodopsin, the meta I-meta II conformational transition was studied in egg phosphatidylcholine (PC) recombinants versus the native rod outer segment (ROS) membranes by means of flash photolysis. Formation of metarhodopsin II was observed by the change in absorbance at 478 nm after a single actinic flash was delivered to the sample. The meta I/meta II ratio was investigated as a function of both temperature and pH. The data clearly demonstrated thermodynamic reversibility of the transition for both the egg PC recombinants and the native ROS membranes. A significant shift of the apparent pK(a) for the acid-base equilibrium to lower values was evident in the egg PC recombinant, with little meta II produced under physiological conditions. Calculations of the membrane surface pH using a Poisson-Boltzmann model suggested the free energies of the meta I and meta II states were significantly affected by electrostatic properties of the bilayer lipids. In the ROS membranes, phosphatidylserine (PS) is needed for full formation of meta II, in combination with phosphatidylethanolamine (PE) and polyunsaturated docosahexaenoic acid (DHA; 22:6omega3) chains. We propose that the PS surface potential leads to an accumulation of hydronium ions, H(3)O(+), in the electrical double layer, which drive the reaction together with the large negative spontaneous curvature (H(0)) conferred by PE plus DHA chains. The elastic stress/strain of the bilayer arises from an interplay of the approximately zero H(0) from PS and the negative H(0) due to the PE headgroups and polyunsaturated chains. The lipid influences are further explained in terms of matching of the bilayer spontaneous curvature to the curvature at the lipid/rhodopsin interface, as formulated by the Helfrich bending energy. These new findings guide current ideas as to how bilayer properties govern the conformational energetics of integral membrane proteins. Moreover, they yield knowledge of how membrane lipid-protein interactions involving acidic phospholipids such as PS and neutral polyunsaturated DHA chains are implicated in key biological functions such as vision.

Animals↗