Biomedical subjects

Peng Liu

Publications and source records attributed to Peng Liu.

At least 55 records · Page 3Linked to original sources

PubMed2006

[Effects of shading on the growth, development and grain yield of summer maize].

Under field condition, this paper studied the effects of shading on the growth, development, and grain yield of summer maize varieties ND108 and YD13. The results showed that shading decreased maize yield significantly, and the effect was differed with different shading period and intensity. With a shading intensity of 50% and 90%, the grain yield of ND108 and YD13 was decreased by 67.5% and 79.4%, and 82.9% and 86.7% when shading at flowering-maturing stage, and by 34.1% and 55.3%, and 47.2%, 65.7% when shading at joining-flowering stage, respectively. Shading at seedling-joining stage had a relatively smaller effect, with the grain yield decreased by 16.9% and 24.5%, and 18.9% and 24.3%, respectively. Shading had a larger effect on YD13 than on ND108, and the effect of shading period was larger than that of shading intensity. Under shading, the growth and development of maize was retarded, and the effect was increased with increasing shading intensity. Shading at joining-flowering stage affected spike differentiation significantly, reflecting in the marked decrease of the numbers of silks and tassels, and the effect was also larger on YD13 than on ND108. The leaf and plant growth was restrained significantly when shading at seedling stage and at flowering-maturing stage.

Biomass↗

PubMed2006

[Efficacy of once-per-cycle administration pegylated recombinant human granulocyte colony-stimulating factor in chemotherapy-induced neutropenia in a phase I trial].

OBJECTIVE: To explore the efficacy of pegylated recombinant human granulocyte colony-stimulating factor (PEG-rhG-CSF) in the prophylaxis of chemotherapy-induced neutropenia. METHODS: Patients with previously untreated non-small cell lung cancer or breast cancer and with normal bone marrow function were eligible for the trial. In the phase I trial, patients were to treated with two cycles of paclitaxel/carboplatin chemotherapy every 21 days. In cycle 1, if absolute neutrophil count (ANC) dropped below 1.0 x 10(9)/ L with fever and/or ANC dropped below 0.5 x 10(9)/L, rhG-CSF 150 microg/d was administrated until WBC > or = 10 x 10(9)/L or ANC > or = 5.0 x 10(9)/L. In cycle 2, patients were to receive a single injection of PEG-rhG-CSF (30, 60, 100, or 200 microg/kg) 48 hours after chemotherapy. Pharmacodynamic analyses were performed. RESULTS: All the 16 patients enrolled (4 in each group) were eligible for efficacy evaluation. In cycle 1, 7 patients received rhG-CSF administration because of grade 4 neutropenia, while in cycle 2, there was only 1 episode of grade 4 neutropenia, which were in the 30 microg/kg group. In cycle 1, the mean ANC nadir of 1.37 x 10(9)/L occurred on day 13 in the 9 patients who received no rhG-CSF administration. In cycle 2, the mean ANC nadirs were 0.77 x 10(9)/L, 4.54 x 10(9)/L, 3.00 x 10(9)/L, and 5.56 x 10(9)/L, respectively, in 30, 60, 100, or 200 microg/kg group. The nadirs of the first two groups occurred on day 8 of cycle 2, while those of the other two groups appeared on day 7. After PEG-rhG-CSF administration, two mean ANC peaks were observed. The first one ranging from 20.87 x 10(9)/L to 33.61 x 10(9)/L in the 4 groups appeared on day 3 to day 4. In the 30 microg/ kg group, the mean ANC reached the second peak at 5.03 x 10(9)/L on day 14. The second peaks on day 10 in the other groups were 12.42 x 10(9)/L, 11.59 x 10(9)/L, and 18.92 x 10(9)/L, respectively. Pharmacodynamic analyses showed sustained serum concentrations of PEG-rhG-CSF during the period of neutropenia. CONCLUSIONS: PEG-rhG-CSF administration may decrease the incidence of grade 4 neutopenia and result in earlier and higher nadir ANCs. PEG-rhG-CSF has a potential of once-per-cycle administration. The ANC and serum concentration of PEG-rhG-CSF are consistent with neutrophil receptor-mediated clearance.

Adolescent↗

PubMed2006

Prevention of retinoic acid-induced early craniofacial abnormalities by folinic acid and expression of endothelin-1/dHAND in the branchial arches in mouse.

Prevention of retinoic acid-induced craniofacial abnormalities by folinic acid, and endothelin-1 (ET-1)/dHAND protein and mRNA expression were investigated in mouse embryos using the whole embryo culture, streptavidin-biotin peroxidase complex method, and whole-mount in situ hybridization. In the whole embryo culture, 1.0 and 0.1 mm-folinic acid dose dependently prevented branchial region malformations and decreased defects by 93 % and 77 %, respectively. Folinic acid at concentrations of 1.0 and 0.1 mm significantly increased ET-1 and dHAND protein expression levels compared to retinoic acid-exposed values in embryonic branchial areas. Folinic acid also increased ET-1 and dHAND mRNA levels in the same region. The present results suggest that folinic acid may prevent retinoic acid-induced craniofacial abnormalities via increasing ET-1 and dHAND levels in the branchial region during the organogenic period.

Animals↗

PubMed2006

[Clinical application of medical grade calcium sulfate as a bone graft substitute].

OBJECTIVE: To investigate the clinical effect of medical grade calcium sulfate(Osteoset) as a bone graft substitute. METHODS: From December 2004 to May 2005, 9 cases of bone defect(limb group) were repaired with Osteoset pellets; bone defect was caused by benign tumor in limbs, including 3 cases of fibroma xanthomas in humerus (1 case) and acetabulum (2 cases), 2 cases of bone cysts in humerus (1) and radius (1), 1 case of nonossifying fibroma, 1 case of ossifying fibroma and 2 cases of osteofibrous dysplasia in femurs. Five cases of lumbar posterolateral fusion (spine group) were treated with Osteoset pellets as autograft volume expander, including 2 cases of lumbar spinal stenosis, 2 cases of lumbar spondylolisthesis and 1 case of lumbar spondylolysis. Radiological method was used to evaluate the repair effect of Osteoset pellets. RESULTS: The mean follow-up time was 6.2 months (3 to 9 months). Osteoset pellets began to be absorbed after 1 to 3 months of operation, and were totally absorbed and replaced by osseous tissue after 4 to 6 months. No local recurrence was detected in limb group and the function of limbs was normal. At 6 months after operation, all patients in spine group got bony fusion. CONCLUSION: Medical grade calcium sulfate (Osteoset) is an ideal bone graft substitute with excellent bone repair effect.

Adolescent↗

PubMed2005

Nanosecond time-resolved IR emission from molecules excited in a supersonic jet: intramolecular dynamics of NO2 near dissociation.

IR emission from NO2 cooled in a supersonic jet and excited to a single, B 2B1 state rovibronic level at 22 994.92 cm(-1) above the ground-state zero point was detected with 10(-8)-s time resolution. The IR emission together with the laser-induced fluorescence decay measurement allows the deduction of the relaxation dynamics near the dissociation of NO2. Following the excitation this single rovibronic B 2B1 level decays on 1.0-s time scale primarily through electronic radiation. Collisions induce internal conversion with a rate constant of 3.0 x 10(7) Torr(-1) s(-1) to the mixed AX states. Collisions further induce internal conversion of the AX mixed states into highly vibrationally excited levels in the X states with a rate constant at least one order of magnitude slower. This mechanism results in the observation of a double-exponential decay in the laser-induced fluorescence and a rise in the IR emission intensity corresponding to the fast decay in the fluorescence intensity. The IR emission rate of the highly vibrationally excited X-state levels is estimated to be about one order of magnitude larger than the isoenergetic AX mixed states and much larger than the B 2B1 level, both with much less vibrational excitation.

Journal Article↗

PubMed2005

[Quality of life of malignant patients after autologous stem cell transplantation].

OBJECTIVE: To investigate the quality of life of Chinese malignant patients who treated with the high dose chemoradiotherapy combined with autologous stem cell transplantation (ASCT). METHODS: The data of 89 patients who answer the EORTC QLQ-C30 Chinese version 3.0 after finished ASCT and disease free were analyzed using SPSS 10.0. RESULTS: The score of global health status and functional assessment were near or over 80, more than 80 percent of patient had good or very good global health status or function, the patients who were experiencing moderate or severe financial dysfunction, fatigue, dyspnea, sleeping disturbance and diarrhea were in 72.5% (65/89), 50.6% (45/89), 42.7% (38/89), 33.7% (30/89) and 32.5% (29/89) respectively. The score of dyspnea in female patients was significant higher than male patients (P = 0.024). The score of global health status (P = 0.000), physical function (P = 0.000), role function (P = 0.031) and social function (P = 0.029) became higher significantly with time from transplantation and the score of fatigue became lower (P = 0.020). The Hodgkin's lymphoma patients had higher score significantly in nausea & vomiting (P = 0.002) and dyspnea (P = 0.006) than NHL. The age at transplantation and evaluation took none effect on the score. CONCLUSION: Most patient have good global health status and function after autologous stem cell transplantation, they are more suffered from financial dysfunction, fatigue, dyspnea, sleeping disturbance and diarrhea. Females have more dyspnea symptoms, the quality of life of patient will improve gradually with the time from transplantation, the Hodgkin's lymphoma patients have more symptoms than non-Hodgkin's lymphoma patients, we do not find any effect of age at transplantation and assessment on the quality of life.

Adolescent↗

PubMed2005

Effects of ginsenoside Rg1 on postimplantation rat and mouse embryos cultured in vitro.

GRg1 is one of the most important active agents extracted from ginseng. Although there are numerous reports in the medical literature concerning the beneficial effects of GRg1, little is known about its effects on embryonic development. In our study, whole embryo culture was applied to explore the effects of GRg1 on SD rat and ICR mouse embryos during their critical period of organogenesis. All embryos were exposed to different concentrations of GRg1, and scored for their growth and differentiation at the end of the 48-h culture period. Total morphological score decreased significantly at the concentration of GRg1 of 50 microg/ml to mice and at 30 microg/ml to rats. The whole embryonic growth was affected, represented as reduced crown-rump length and head length, and decreased number of somites from 10 microg/ml both in mice and rats. Morphological development was influenced relatively late. To rats, the scores of flexion, forelimb bud and hindlimb bud were significantly reduced at 30 microg/ml, and heart was among the affected organs. However, the effect on heart was not observed in mice, and flexion and limb buds were influenced at 50 microg/ml. These results demonstrate that GRg1 has embryotoxicity during both rat and mouse organogenetic period and rats might be more sensitive than mice. We suggest that pregnant women of first trimester should use ginseng with caution before the exact conclusion is obtained.

Animals↗

PubMed2005

Dkk2 has a role in terminal osteoblast differentiation and mineralized matrix formation.

Human and mouse genetic and in vitro evidence has shown that canonical Wnt signaling promotes bone formation, but we found that mice lacking the canonical Wnt antagonist Dickkopf2 (Dkk2) were osteopenic. We reaffirmed the finding that canonical Wnt signaling stimulates osteogenesis, including the differentiation from preosteoblasts to osteoblasts, in cultured osteoblast differentiation models, but we also found that canonical Wnts upregulated the expression of Dkk2 in osteoblasts. Although exogenous overexpression of Dkk before the expression of endogenous canonical Wnt (Wnt7b) suppressed osteogenesis in cultures, its expression after peak Wnt7b expression induced a phenotype resembling terminal osteoblast differentiation leading to mineralization. In addition, osteoblasts from Dkk2-null mice were poorly mineralized upon osteogenic induction in cultures, and Dkk2 deficiency led to attenuation of the expression of osteogenic markers, which could be partially reversed by exogenous expression of Dkk2. Taken together with the finding that Dkk2-null mice have increased numbers of osteoids, these data indicate that Dkk2 has a role in late stages of osteoblast differentiation into mineralized matrices. Because expression of another Wnt antagonist, FRP3, differs from Dkk2 expression in rescuing Dkk2 deficiency and regulating osteoblast differentiation, the effects of Dkk2 on terminal osteoblast differentiation may not be entirely mediated by its Wnt signaling antagonistic activity.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Deficient hippocampal neuron expression of proteasome, ubiquitin, and mitochondrial genes in multiple schizophrenia cohorts.

BACKGROUND: Hippocampal dentate granule neurons are altered in schizophrenia, but it is unknown if their gene expressions change in schizophrenia or other psychiatric diseases. METHODS: Laser-captured dentate granule neurons from two groups of schizophrenia and control cases and from major depression and bipolar disease cases were examined for alterations in gene expression using complementary DNA (cDNA) microarrays and reverse transcription polymerase chain reaction (RT-PCR). RESULTS: Compared with 24 control cases, the 22 schizophrenia patients in both groups revealed decreases in clusters of genes that encode for protein turnover (proteasome subunits and ubiquitin), mitochondrial oxidative energy metabolism (isocitrate, lactate, malate, nicotinamide adenine dinucleotide [NADH], and succinate dehydrogenases; cytochrome C oxidase; adenosine triphosphate [ATP] synthase), and genes associated with neurite outgrowth, cytoskeletal proteins, and synapse plasticity. These changes were not obtained in 9 bipolar cases or 10 major depression cases and were not associated with age, sex, brain weight, body weight, postmortem interval, or drug history. Brain pH contributed to the variance of some genes but was mostly independent of the disease effect. CONCLUSIONS: Decreases in hippocampal neuron gene expression are consistent with brain imaging and microarray studies of the frontal cortex in schizophrenia. A mitochondrial and ubiquitin-proteasome hypofunctioning of dentate granule neurons may contribute to the deficits of schizophrenia.

Analysis of Variance↗

PubMed2005

Gamma knife radiosurgery for tumors involving the cavernous sinus.

OBJECTIVE: To study the features of diagnosis and radiosurgery of tumors involving the cavernous sinus. METHODS: From December 1994 to the end of 2000, 175 patients with cavernous sinus lesions were treated by Leksell gamma knife (GK) in our Institute. Ninety patients (51.4%) had had open surgery previously. Our experience of treating cavernous sinus tumors by GK was analyzed retrospectively. RESULTS: A Hundred and forty-four (82.3%) patients were followed from 1 to 84 months (median 32.5 months); total tumor control rate was 94%. Surgery was performed after radiosurgery in 3 patients because of tumor enlargement. Metastatic tumor in the cavernous sinus was highly sensitive to irradiation. These lesions shrunk markedly on MRI 2-3 months after GK surgery. The median survival time was 12.2 months, and patients died of noncavernous sinus lesions. CONCLUSION: With high tumor control rate and few complications, GK surgery could become a main option for small benign or residual tumors involving the cavernous sinus. It is also very useful as part of comprehensive therapy for metastatic tumors in the cavernous sinus.

Adenoma↗

PubMed2005

Crystal structure of human vacuolar protein sorting protein 29 reveals a phosphodiesterase/nuclease-like fold and two protein-protein interaction sites.

Vacuolar protein sorting protein 29 (Vps29p), which is involved in retrograde trafficking from prevacuolar endosomes to the trans-Golgi network, performs its biological functions by participating in the formation of a "retromer complex." In human cells, this complex comprises four conserved proteins: hVps35p, hVps29p, hVps26p, and sorting nexin 1 protein (SNX1). Here, we report the crystal structure of hVps29p at 2.1 Angstroms resolution, the first three-dimensional structure of the retromer subunits. This novel structure adopts a four-layered alpha-beta-beta-alpha sandwich fold. hVps29p contains a metal-binding site that is very similar to the active sites of some proteins of the phosphodiesterase/nuclease protein family, indicating that hVps29p may carry out chemically similar functions. Structure and sequence conservation analysis suggests that hVps29p contains two protein-protein interaction sites. One site, which potentially serves as the interface between hVps29p and hVps35p, comprises 5 conserved hydrophobic and 8 hydrophilic residues. The other site is relatively more hydrophilic and may serve as a binding interface with hVps26p, SNX1, or other target proteins.

Amino Acid Sequence↗

PubMed2005

[Feasibility of breast conservation surgery after neoadjuvant chemotherapy for breast cancer].

OBJECTIVE: To investigate the efficacy of neoadjuvant chemotherapy (NCT) and the feasibility of conservative breast surgery after reducing the size of a primary tumor by NCT in patients with operable breast cancer. METHODS: Thirty patients with stage IIB and IIIA breast cancer underwent NCT including epirubicin 60 mg/m(2) by intravenous injection on day 1 and paclitaxel 150 mg/m(2) by 3-hour continuous infusion on day 2 with 21 days as a cycle from July 2001 to April 2003. All patients received 3 - 4 cycles of NCT. Breast conservation treatment or modified mastectomy was performed after the tumor was reduced to less than 3 cm in diameter. The nonresponders received modified mastectomy. RESULTS: The overall response rate (ORR) was 93% (28/30) for the primary tumors of breast, Fifteen patients (50%) obtained clinical complete response (cCR), including 7 cases (23%) with pathologic complete response (pCR). Thirteen cases (43%) achieved clinical partial response (cPR), and 2 (7%) no change (NC). No case showed progression of disease. Twenty-six (87%) cases were downstaged according to the TNM system classification. The median initial tumor size was 4 cm (3 - 10 cm) before NCT and was reduced to 0.8 cm (0 - 6 cm) after NCT. All 30 patients received operation. Eighteen (60%) of them were candidates for breast conserving therapy, and actually only 11 (37%) selected such surgery. CONCLUSION: An effective treatment for operable breast cancer, NCT with epirubicin plus paclitaxel results in significant downstaging or eliminating of primary tumors in breast cancer, thus expanding the indication of breast conservation therapy.

Adult↗

PubMed2005

Sclerostin binds to LRP5/6 and antagonizes canonical Wnt signaling.

The loss of the SOST gene product sclerostin leads to sclerosteosis characterized by high bone mass. In this report, we found that sclerostin could antagonize canonical Wnt signaling in human embryonic kidney A293T cells and mouse osteoblastic MC3T3 cells. This sclerostin-mediated antagonism could be reversed by overexpression of Wnt co-receptor low density lipoprotein receptor-related protein (LRP) 5. In addition, we found that sclerostin bound to LRP5 as well as LRP6 and identified the first two YWTD-EGF repeat domains of LRP5 as being responsible for the binding. Although these two repeat domains are required for transduction of canonical Wnt signals, canonical Wnt did not appear to compete with sclerostin for binding to LRP5. Examination of the expression of sclerostin and Wnt7b, an autocrine canonical Wnt, during primary calvarial osteoblast differentiation revealed that sclerostin is expressed at late stages of osteoblast differentiation coinciding with the expression of osteogenic marker osteocalcin and trailing after the expression of Wnt7b. Given the plethora of evidence indicating that canonical Wnt signaling stimulates osteogenesis, we believe that the high bone mass phenotype associated with the loss of sclerostin may be attributed, at least in part, to an increase in canonical Wnt signaling resulting from the reduction in sclerostin-mediated Wnt antagonism.

3T3 Cells↗

PubMed2005

Impaired development of mitochondria plays a role in the central nervous system defects of fetal alcohol syndrome.

BACKGROUND: Alcohol consumption during pregnancy can induce a wide spectrum of adverse effects in offspring. Microcephaly and mental retardation are two major defects of central nervous system (CNS). Most mechanism studies of alcohol-related CNS defects have been focused on the morphologically abnormal tissues, and more attention has been paid to nuclear alteration as opposed to organelle development. METHODS: A mouse model of fetal alcohol syndrome (FAS) was used to investigate the effect of alcohol on fetal cerebral mitochondria development. Pregnant mice were given different doses of ethanol intragastrically from GD6 to GD15. Fetal cerebral mitochondria were isolated and analyzed on GD18. RESULTS: Excessive cell apoptosis was found in the cerebra of prenatal alcohol exposure fetuses. Proliferation and differentiation of fetal cerebral mitochondria were inhibited by alcohol. Affected mitochondrial volume constriction and adenosine triphosphate (ATP) accumulation, reduced activities of respiratory chain complex I and IV and ATP synthase were detected in the cerebral tissue without obvious malformed appearance. CONCLUSIONS: Impaired mitochondria development plays a role in the CNS defects induced by prenatal alcohol exposure.

Animals↗

PubMed2005

Developmental toxicity research of ginsenoside Rb1 using a whole mouse embryo culture model.

BACKGROUND: Ginseng has been widely used around the world for many years. Knowledge is limited, however, on its effects on embryonic development. METHODS: Whole embryo culture was used to explore the developmental toxicity of ginsenoside Rb1 (GRb1) on mouse embryos. All embryos were exposed to different concentrations of GRb1, and scored for their growth and differentiation at the end of the 48-hr culture period. RESULTS: Total morphological score decreased significantly at the concentration of GRb1 of 30 microg/ml and was further reduced at 50 microg/ml. Yolk sac was affected at the lower concentration of 15 microg/ml. Developments of midbrain, forebrain, and optic system were relatively sensitive to GRb1 and were affected at the concentration of 30 microg/ml. Allantois, flexion, branchial arch, and limb buds were affected at 50 microg/ml. At this concentration, the embryonic crown-rump length, head length, and somite number were also reduced significantly compared to the control group. CONCLUSIONS: These results suggest that GRb1 has teratogenic effect during the mouse organogenetic period. We suggest that before more data in humans is available, ginseng should be used with caution by pregnant women in the first trimester.

Abnormalities, Drug-Induced↗

PubMed2005

Preparation and characterization of core/shell SiO(x)/PAM nanospheres with 'graft from' method.

The core/shell SiO(2) encapsulated with polyacrylamide (SiO(x)/PAM) nanospheres were successfully prepared by the radical copolymerization of acrylamide (AM) and a macromonomer, methacryloxypropyl SiO(x) (MP-SiO(x)) nanoparticles, initiated with AIBN via a facile precipitation polymerization method in ethanol. The percentage of encapsulating (PE%) and the conversion of the AM (C%) of 327.5% and 93%, respectively, were achieved after a polymerizing time of 3 h. The formation mechanism of the core/shell SiO(x)/PAM nanospheres was explained. The nanospheres were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), X-ray photoelectron spectrometer (XPS) and transmission electron microscope (TEM).

Acrylic Resins↗

PubMed2005

Elevated plasma levels of vascular endothelial growth factor is associated with marked splenomegaly in chronic myeloid leukemia.

Recent investigations support the idea that angiogenesis is involved in the pathophysiology of hematologic malignancies, including chronic myeloid leukemia (CML). The aim of the present study was to evaluate plasma levels of VEGF and bFGF in a cohort of 51 chronic-phase CML patients at the time of diagnosis, as well as to investigate the effect of imatinib therapy on VEGF amounts in CML patients. Plasma VEGF levels were significantly higher in patients studied as compared with the 20 healthy subjects (p<0.001), the median plasma VEGF level detected in patients analysed and healthy controls was 433.4 pg mL(-1) (range 65.2-2,452.7 pg mL(-1)) and 81.6 pg mL(-1) (range 44.2-338.7 pg mL(-1)), respectively. On the other hand, no difference in bFGF plasma levels could be found between chronic-phase CML patients and the control group. There were significant associations between plasma VEGF levels and some characteristics of patients evaluated, with trends for higher VEGF values in patients with enlarged spleens (p = 0.02) and those with higher platelet count (p<0.001). Of the patients, 11 received imatinib treatment. The initial VEGF levels markedly decreased after 6 months of imatinib therapy in each patient (p<0.001). These data support the important pathophysiological role of VEGF in CML. Further studies aiming to explore the detailed angiogenic profile of CML may help in developing new therapeutic strategies for this myeloproliferative disorder.

Biomarkers↗

PubMed2005

M opsin phosphorylation in intact mammalian retinas.

The deactivation of visual pigments involved in phototransduction is critical for recovering sensitivity after exposure to light in rods and cones of the vertebrate retina. In rods, phosphorylation of rhodopsin by rhodopsin kinase (GRK1) and the subsequent binding of visual arrestin completely terminates phototransduction. Although signal termination in cones is predicted to occur via a similar mechanism as in rods, there may be differences due to the expression of related but distinct gene products. While rods only express GRK1, cones in some species express only GRK1 or GRK7 and others express both GRKs. In the mouse, cone opsin is phosphorylated by GRK1, but this has not been demonstrated in mammals that express GRK7 in cones. We compared cone opsin phosphorylation in intact retinas from the 13-lined ground squirrel (GS) and pig, cone- and rod-dominant mammals, respectively, which both express GRK7. M opsin phosphorylation increased during continuous exposure to light, then declined between 3 and 6 min. In contrast, rhodopsin phosphorylation continued to increase during this time period. In GS retina homogenates, anti-GS GRK7 antibody blocked M opsin phosphorylation by 73%. In pig retina homogenates, only 20% inhibition was observed, possibly due to phosphorylation by GRK1 released from rods during homogenization. Our results suggest that GRK7 phosphorylates M opsin in both of these mammals. Using an in vitro GTPgammaS binding assay, we also found that the ability of recombinant M opsin to activate G(t) was greatly reduced by phosphorylation. Therefore, phosphorylation may participate directly in the termination of phototransduction in cones by decreasing the activity of M opsin.

Adaptation, Physiological↗