Alpha-crystallin-mediated protection of lens cells against heat and oxidative stress-induced cell death

In addition to their key role as structural lens proteins, α-crystallins also appear to confer protection against many eye diseases, including cataract, retinitis pigmentosa, and macular degeneration. Exogenous recombinant α-crystallin proteins were examined for their ability to prevent cell death induced by heat or oxidative stress in a human lens epithelial cell line (HLE-B3). Wild type αA- or αB-crystallin (WT-αA and WT-αB) and αA- or αB-crystallins, modified by the addition of a cell penetration peptide (CPP) designed to enhance the uptake of proteins into cells (gC-αB, TAT-αB, gC-αA), were produced by recombinant methods. In vitro chaperone-like assays were used to assay the ability of α-crystallins to protect client proteins from chemical or heat induced aggregation. In vivo viability assays were performed in HLE-B3 to determine whether pre-treatment with α-crystallins reduced death after exposure to oxidative or heat stress. Most of the five recombinant α-crystallin proteins tested conferred some in vitro protection from protein aggregation, with the greatest effect seen with WT-αB and gC-αB. All α-crystallins displayed significant protection to oxidative stress induced cell death, while only the αB-crystallins reduced cell death induced by thermal stress. Our findings indicate that the addition of the gC tag enhanced the protective effect of αB-crystallin against oxidative but not thermally-induced cell death. In conclusion, modifications that increase the uptake of α-crystallin proteins into cells, without destroying their chaperone-like activity and anti-apoptotic functions, create the potential to use these proteins therapeutically.     

Effect of Combined Salt and Heat Treatments on Germination and Heat-Shock Protein Synthesis in Lentil Seeds

The germination of lentil seeds was gradually reduced when seeds were exposed to temperature of 30 or 40 °C, either alone or combined with 0.1, 0.2 or 0.3 M NaCl or 34.1 % (m/v) PEG 8000, during 6 –12 h imbibition. [³⁵S]-methionine incorporation in 12 h imbibed lentil axes also decreased with increasing NaCl concentration at 20 and 40 °C, whereas at 30 °C only 0.3 M NaCl treatment partially inhibited protein synthesis. An analysis of newly synthesized proteins by 1-D SDS PAGE, showed that the expression of most polypeptides decreased following increasing stress. Among these, low molecular mass heat-shock proteins declining, higher in 40 °C treated axes than those treated at 30 °C, supports the hypothesis that at this temperature maximal level of expression of these proteins was achieved.     

Oscillatory growth movements of roots in weightlessness

The gravitropic curvature of lentil roots ( Lens culinaris L. cv. Verte du Puy), grown in near weightlessness and stimulated on a 1-g centrifuge for 5 to 60 min was followed by time lapse photography. The experiment was carried out in the frame of the IML 1 Mission of Spacelab. Due to the applied acceleration field, the tip of the roots bent and reoriented with respect to the acceleration vector. However, visual inspection of the data could indicate an oscillatory movement superimposed on the gravitropic reorientation.
We applied two signal processing techniques, fast Fourier transform (FFT) and maximum entropy spectral analysis (MESA), to provide quantitative data about the oscillatory movements of the lentil roots under gravity free conditions. In the case with very few data points in the time series the MESA method is superior to the conventional FFT. In the lentil root movements, the Fourier analysis could not extract and resolve the oscillatory signals present in the time series. The MESA approach revealed oscillations with periods around 35 and 50 min for the present lentil roots.
Circumnutations are, therefore, present in roots also in weightlessness.     

An experimentally induced host shift in a seed beetle

Many insects use a fairly well-defined set of host plants, but are occasionally observed on an atypical host. The seed beetle Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae: Bruchinae) has rarely been reported to attack lentil, which is distantly related to its usual legume hosts. An initial assay of an Asian beetle population revealed that none of the 100 larvae entering lentil seeds survived to adult emergence. Nevertheless, three attempts at mass selection, in which more than 2 000 adults were added to lentil seeds, eventually yielded self-sustaining populations. In each case, a severe bottleneck was followed by a rapid increase in survival, which exceeded 65% after only five generations and surpassed 85% in <20 generations. Subsequent large-scale experiments indicated that survival in lentil is initially <2% and that most larvae die before they have completely entered a seed. The only potential trade-off associated with rapid adaptation to lentil was a modest increase in the time required to develop in the ancestral host, mung bean. Reciprocal crosses between a lentil-adapted line (F10) and a mung-bean line produced offspring with intermediate survival, very long development times, and small size. Although the Asian population has been kept under uniform laboratory conditions for more than 200 generations, it appears to maintain rare alleles that permit the colonization of an extremely poor host. Such standing genetic variation can account for the sporadic appearance of unusual 'biotypes' among herbivorous insects.     

Terrestrial optics in an aquatic eye: The sandlance,Limnichthytes fasciatus (Creediidae,Teleostei)

The sandlance, Limnichthyes fasciatus (Creediidae, Teleostei), behaves like a marine chameleon, with independent movements of its turret-like eyes, highly-effective camouflage and rapid strikes for isolated, mobile prey at close quarters. The optical system has a fixed circular pupil, a deep pit fovea and a flattened lens unlike any other teleost lens so far described. The convex, laminated structure of the cornea is also unparalleled in a teleost which suggests that the cornea may play a refractive role that might compensate for the reduced power of the flattened lens. This suggestion has been supported in the present investigation by four independent sets of observations:- i. Purkinje images formed underwater by the cornea; ii. Measurements of the magnification of intra-corneal iridophores viewed through the corneal lenticle; iii. Measurements of the magnification produced by the dissected corneal lenticle and lens when viewed over a grating; iv. Ray tracing experiments comparing the degree of refraction produced by the lens and by the corneal lenticle. All experimental observations confirm that the cornea of the sandlance has a significant refractive role, with a power of approximately 200 D compared with a power of 550 D for the lens. This is the first report of a significant refractive role played by the cornea in a teleost. The optical system of lens plus cornea, in combination with a deep pit fovea, may be more suitable for the detection and visual localisation of small, moving, underwater prey than the conventional wide-field spherical lens system of other teleosts. The evolutionary convergence of this marine optical system and lifestyle with those of the chameleon is remarkable, given the constraints imposed by underwater optics.     

亚硒酸钠诱发的晶状体上皮细胞DNA损伤及修复

观察了亚硒酸钠（Ｎａ２ＳｅＯ３）在体外作用于大鼠晶状体上皮细胞（ＲＬＥｃｅｌｌｓ）而造成的ＤＮＡ单链断裂（ｓｉｎｇｌｅｓｔｒａｎｄｂｒｅａｋｓ,ＳＳＢ）,并对其ＤＮＡ损伤、修复动力学做了初步研究．发现ＳＳＢ严重程度与亚硒酸钠的浓度呈线性相关,其ＳＳＢ重接修复约在３０～６０ｍｉｎ内完成．还作了有关非程序ＤＮＡ合成（ＵＤＳ）的检测,发现与ＳＳＢ相比,ＵＤＳ发生迟且持续时间更长,提示Ｎａ２ＳｅＯ３可能在体外对大鼠晶状体上皮细胞除造成ＳＳＢ以外,还可能造成其它种类的ＤＮＡ损伤．     

亚硒酸钠对大鼠晶体上皮细胞αA晶体蛋白基因转录的影响

在体外观察了亚硒酸钠（Ｎａ＿２ＳｅＯ＿３）作用于大鼠晶体上皮细胞（ＲＬＥｃｅｌｌｓ）而引起其晶体蛋白基因转录的改变,对不同浓度的硒在体外对αＡ晶体蛋白基因转录的影响作了初步的研究。结果发现,随着亚硒酸钠浓度的升高,αＡ基因的转录下降;而当亚硒酸钠浓度升至５×１０（－５）ｍｏ１／Ｌ时,αＡ基因的转录又呈反跳性回升。提示硒在致障过程中对晶体蛋白基因转录的影响作用不可忽视;同时αＡ晶体蛋白在晶体细胞内,至少应答于高浓度的硒,可能作为一种应激蛋白表达。     

Ectopic lens induction in fish in response to the murine homeobox gene Six3

Recent findings show an unexpected conservation of genes involved in vertebrate and insect eye development. The Drosophila homeobox gene sine oculis is crucial for eye development. Its murine homologue, Six3 is expressed in the anterior neural plate, a region which is involved in lens induction in Xenopus. To examine whether Six3 participates in the process of eye formation, mouse Six3 was ectopically expressed in fish embryos. The results show that Six3 is sufficient to promote ectopic lens formation in the area of the otic vesicle and that retinal tissue is not a prerequisite for ectopic lens differentiation. Our findings suggest a conserved function for Six3 in metazoan eye development.