Hypoxia induces beta-amyloid in association with death of RGC-5 cells in culture

Beta-amyloid (Aβ) derived from amyloid precursor protein (APP) has been associated with retinal degeneration in Alzheimer’s disease (AD) and glaucoma. This study examined whether hypoxia exposure induces Aβ accumulation in RGC-5 cells. While levels of APP mRNA and protein significantly increased in the cells, elevated abundance of Aβ was also observed in cells and culture medium between 12 or 24 and 48 h after 5% O₂ hypoxia treatment. Additionally, there is a close relationship between induction of APP and Aβ and intracellular accumulation of ROS along with loss of mitochondrial membrane potential followed by the death of RGC-5 cells in culture under hypoxia. These results suggest a possible involvement of APP and Aβ in the death of RGCs challenged by hypoxia.     

Mnl2, a novel component of the ER associated protein degradation pathway

In eukaryotes, membrane and soluble proteins of the secretory pathway enter the endoplasmic reticulum (ER) after synthesis in an unfolded state. Directly after entry, most proteins are modified with glycans at suitable glycosylation sites and start to fold. A protein that cannot fold properly will be degraded in a process called ER associated degradation (ERAD). Failures in ERAD, either by loss of function or by premature degradation of proteins, are a cause of severe diseases. Therefore, the search for novel ERAD components to gain better insight in this process is of high importance. Carbohydrate trimming is a relevant process in ER quality control. In this work a novel putative yeast mannosidase encoded by the open reading frame YLR057W was identified and named Mnl2. Deletion of MNL2 diminished the degradation efficiency of misfolded CPY^* in the absence of the cognate mannosidase Mnl1, indicating a specific role in ERAD.     

Modeling the spontaneous initiation of the polymerization of methyl methacrylate

The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set. The Diels-Alder initiation mechanism (path (I) and path (II)) with remarkably high energy barriers is not applicable to MMA. Four favorable paths were found (path (III), path (IV), path (V) and path (VI)), which are supporting the Flory mechanism. Path (V) has the lowest active energy. Therefore this path is considered as the main path for the spontaneous polymerization of MMA. Figure The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set.     

Zebrafish β-adrenergic receptor mRNA expression and control of pigmentation

Beta adrenergic receptors (β-ARs) are members of the G-protein-coupled receptor superfamily and mediate various physiological processes in many species. The expression patterns and functions of β-ARs in zebrafish are, however, largely unknown. We have identified zebrafish β-AR orthologs, which we have designated as adrb1, adrb2a, adrb2b, adrb3a and adrb3b. adrb1 was found to be expressed in the heart and brain. Expression of adrb2a predominated in the brain and skin, whereas adrb2b was found to be highly expressed in muscle, pancreas and liver. Both adrb3a and adrb3b were exclusively expressed in blood. Knock-down of these β-ARs by morpholino oligonucleotides revealed a functional importance of adrb2a in pigmentation. Expression of atp5a1 and atp5b, genes that encode subunits of F1F0-ATPase, which is known to be involved in pigmentation, was significantly increased by knock-down of adrb2a. Our data suggest that adrb2a may regulate pigmentation, partly by modulating F1F0-ATPase.     

RAPD反应体系优化的研究

筛选随机扩增多态性DNA(RAPD)反应体系的最佳优化方案,以期获得稳定可靠的实验结果。选取对结果影响较大的4种因素(Taq酶、dNTP、引物、Mg2+)进行单因素设计,寻找最佳反应浓度。优化后得到4种因素的最佳反应浓度分别为Taq酶2.5U、dNTP 200μmol/L、引物1μmol/L、Mg2+2.5mmol/L。在优化的反应条件下,RAPD的稳定性和重复性均好。     

Kinetic studies on the reversible ring opening-closure reaction of the triazine ligand and structural properties of palladium(II) complexes

A Pd(II) complex containing didentate triazine ligand L¹ (2-(2-methylphenyl)-3-(2-pyridyl)-2,3-dihydronaphtho[2,1-e][1,2,4]triazine) [PdCl₂(L¹)] (1) was prepared, and the structure was determined by X-ray crystallography. The absorption spectrum of complex 1 in dichloromethane changed gradually with isosbestic points when methanol was added to the solution, and [PdCl(L²)] (2) (L² = N-[methoxy(2-pyridyl)methyl]-1-(2-methylphenylazo)-2-naphthylamide) was obtained from the resulting solution after the reaction was completed. Addition of hydrogen chloride to the solution of complex 2 led to the recovery of complex 1. Thus, a reversible ring opening and closure reaction of the triazine ligand was observed. The progress of the ring opening reaction was monitored by observing the absorbance changes at several wavelengths of the visible spectra as a function of the concentration of methanol. The absorbance plots were fitted successfully with a mechanism that includes the consumption of two methanol molecules and the release of HCl, whose concentration is equivalent to that of the produced Pd complex . In dichloromethane with a low dielectric constant, the polar HCl molecule will be stabilized by forming an adduct with methanol. The equilibrium constant was determined as at T = 25.0 °C. The kinetics of the reaction of [PdCl₂(L¹)] with methanol was investigated by monitoring the absorbance change of the reacting solution with time. We obtained rate constant values of k₁ = (2.40 ± 0.07) × 10⁻³ s⁻¹ and k₂ = (5.8 ± 0.1) × 10⁻³ M⁻¹ s⁻¹ at T = 25.0 °C on the observed pseudo-first-order rate constant of the forward reaction, k_f = k₁ + k₂ [CH₃OH].     

Sex-specific developmental plasticity of generalist and specialist predatory mites (Acari: Phytoseiidae) in response to food stress

We studied developmental plasticity under food stress in three female-biased size dimorphic predatory mite species, Phytoseiulus persimilis, Neoseiulus californicus, and Amblyseius andersoni. All three species prey on two-spotted spider mites but differ in the degree of adaptation to this prey. Phytoseiulus persimilis is a specialized spider mite predator, N. californicus is a generalist with a preference for spider mites, and A. andersoni is a broad generalist. Immature predators were offered prey patches of varying density and their survival chances, dispersal tendencies, age and size at maturity measured. Amblyseius andersoni dispersed earlier from and had lower survival chances in low density prey patches than N. californicus and P. persimilis. Age at maturity was not affected by prey density in the generalist A. andersoni, whereas both the specialist P. persimilis and the generalist N. californicus accelerated development at low prey densities. Species-specific plasticity in age at maturity reflects opposite survival strategies when confronted with limited prey: to prematurely leave and search for other food (A. andersoni) or to stay and accelerate development (P. persimilis, N. californicus). In all species, size at maturity was more plastic in females than males, indicating that males incur higher fitness costs from deviations from optimal body size.     

beta-cyclodextrin-immobilized (4S)-phenoxy-(S)-proline as a catalyst for direct asymmetric aldol reactions

beta-Cyclodextrin-immobilized (4S)-phenoxy-(S)-proline was prepared conveniently by simply heating the amino acid and beta-cyclodextrin in ethanol-water (1/1, v/v) and removal of the solvent. This proved to be an efficient catalyst for direct asymmetric aldol reactions, and the catalyst could be recycled four times without loss of enantioselectivity.     

Kinetics and subunit composition of NMDA receptors in respiratory-related neurons

NMDA receptors are involved in a variety of brainstem functions. The excitatory postsynaptic NMDA currents of pre-Botzinger complex interneurons and hypoglossal motoneurons, which are located in the medulla oblongata, show remarkably fast deactivation kinetics of approximately 30 ms compared with NMDA receptors in other types of neurons. Because structural heterogeneity might be the basis for physiological properties, we examined the expression of six NMDA receptor subunits (NMDAR1, NR2A-2D, and NR3A) plus eight NMDR1 splice variants in pre-Botzinger complex, hypoglossal and, for comparison, neurons from the nucleus of the solitary tract in young rats using single cell multiplex RT-PCR. Expression of NR2A, NR2B, and NR2D was observed in all three cell types while NR3A was much more abundant in pre-Botzinger complex interneurons, which belong to the rhythm generator of respiratory activity. In hypoglossal neurons, the NMDAR1 splice variants NMDAR1-4a and NMDAR1-4b were found. In neurons of the nucleus of the solitary tract, instead of NMDAR1-4b, the NMDAR1-2a splice variant was detected. This differential expression of modulatory splice variants might be the molecular basis for the characteristic functional properties of NMDA receptors, as neurons expressing a special NMDAR1 splice variant at the mRNA level show fast kinetics compared with neurons lacking this splice variant.