An objective scatter index based on double-pass retinal images of a point source to classify cataracts

Purpose

To propose a new objective scatter index (OSI) based in the analysis of double-pass images of a point source to rank and classify cataract patients. This classification scheme is compared with a current subjective system.

Methods

We selected a population including a group of normal young eyes as control and patients diagnosed with cataract (grades NO2, NO3 and NO4) according to the Lens Opacities Classification System (LOCS III). For each eye, we recorded double-pass retinal images of a point source. In each patient, we determined an objective scatter index (OSI) as the ratio of the intensity at an eccentric location in the image and the central part. This index provides information on the relevant forward scatter affecting vision. Since the double-pass retinal images are affected by both ocular aberrations and intraocular scattering, an analysis was performed to show the ranges of contributions of aberrations to the OSI.

Results

We used the OSI values to classify each eye according to the degree of scatter. The young normal eyes of the control group had OSI values below 1, while the OSI for subjects in LOCS grade II were around 1 to 2. The use of the objective index showed some of the weakness of subjective classification schemes. In particular, several subjects initially classified independently as grade NO2 or NO3 had similar OSI values, and in some cases even higher than subjects classified as grade NO4. A new classification scheme based in OSI is proposed.

Conclusions

We introduced an objective index based in the analysis of double-pass retinal images to classify cataract patients. The method is robust and fully based in objective measurements; i.e., not depending on subjective decisions. This procedure could be used in combination with standard current methods to improve cataract patient surgery scheduling.     

Seed germination ecology of the threatened endemic Iberian <Emphasis Type="Italic">Delphinium fissum</Emphasis> subsp. <Emphasis Type="Italic">sordidum</Emphasis> (Ranunculaceae)

Seeds of Delphinium fissum subsp. sordidum are physiologically dormant at maturity, with underdeveloped embryos; thus they have morphophysiological dormancy (MPD). The aims of this study were to determine the requirements for embryo growth, dormancy break and germination, to characterise the type of seed dormancy and to evaluate the effects of light, seed age, pollination mechanism, and inter-annual and inter-population variability on germinative ability. After 3 months of incubation at 5°C (cold stratification) in darkness conditions, the mean embryo length increased from 5.6 to 2.07 mm, with 76% of seeds germinating. Conversely, embryos of seeds incubated during 3 months at 20/7 or 28/14°C hardly grew and no germination was recorded. Since cold stratification was the only requirement for the loss of MPD, and both dry storage in laboratory conditions and warm stratification prior to cold stratification shortened the cold stratification period required for germination, it could be concluded that D. fissum subsp. sordidum seeds have intermediate complex MPD. Cold stratification and incubation in darkness conditions promoted higher germination percentages than those in light. In addition, germinative ability increased with seed age up to 8 months (reaching 96% at 5°C in darkness), showed a pronounced inter-annual and inter-population variability, as well as a significant decrease in seeds coming from pollination by geitonogamy. High temperatures (25/10 or 28/14°C) induced seeds to secondary dormancy, so seedling emergence in the greenhouse was restricted to February–March. The requirements for dormancy break and germination reflect an adaptation to trigger germination in late winter. This study is the first one to document a gradual increase in germination percentage with seed age for plant species with intermediate complex MPD.     

Chinese hamster apurinic/apyrimidinic endonuclease (chAPE1) expressed in sf9 cells reveals that its endonuclease activity is regulated by phosphorylation

Apurinic/apyrimidinic endonuclease (APE), an essential DNA repair enzyme, initiates the base excision repair pathway by creating a nick 5' to an abasic site in double-stranded DNA. Although the Chinese hamster ovary cells remain an important model for DNA repair studies, the Chinese hamster APE (chAPE1) has not been studied in vitro in respect to its kinetic characteristics. Here we report the results of a kinetic study performed on cloned and overexpressed enzyme in sf9 cells. The kinetic parameters were fully compatible with the broad range of kinetic parameters reported for the human enzyme. However, the activity measures depended on the time point of the culture. We applied inductivity coupled plasma spectrometry to measure the phosphorylation level of chAPE1. Our data showed that a higher phosphorylation of chAPE1 in the expression host was correlated to a lower endonuclease activity. The phosphorylation of a higher activity batch of chAPE1 by casein kinase II decreased the endonuclease activity, and the dephosphorylation of chAPE1 by lambda phosphatase increased the endonuclease activity. The exonuclease activity of chAPE1 was not observed in our kinetic analysis. The results suggest that noticeable divergence in reported activity levels for the human APE1 endonuclease might be caused by unaccounted phosphorylation. Our data also demonstrate that only selected kinases and phosphatases exert regulatory effects on chAPE1 endonuclease activity, suggesting further that this regulatory mechanism may function in vivo to turn on and off the function of this important enzyme in different organisms.     

A unique case of a discontinuous duplication 3q26.1-3q28 resulting from a segregation error of a maternal complex chromosomal rearrangement involving an insertion and an inversion

Until now, few cases of partial trisomy of 3q due to segregation error of parental balanced translocation and segregation of a duplicated deficient product resulting from parental pericentric inversion have been reported so far. Only five cases of chromosomal insertion malsegregation involving 3q region are available yet, thus making it relatively rare. In this case report, we are presenting a unique case of discontinuous partial trisomy of 3q26.1-q28 region which resulted from a segregation error of two insertions involving 3q26.1 to 3q27.3 and 3q28 regions with ~ 21 Mb and ~ 2 Mb sizes, respectively. The maternally inherited insertion was cytogenetically characterized as der(8)(8pter → 8p22::3q26 → 3q27.3::3q28 → 3q28::8p22 → 8qter) and the patient's major clinical features involved Dandy Walker malformation, sub-aortic ventricular septal defect, upslanting palpebral fissures, clinodactyly, hirsutism, and prominent forehead. Besides, a review of the literature involving cases with similar chromosomal imbalances and cases with “3q-duplication syndrome” is also provided.     

Neurogenic differentiation of human adipose-derived stem cells: Relevance of different signaling molecules,transcription factors,and key marker genes

Since numerous diseases affect the central nervous system and it has limited self-repair capability, a great interest in using stem cells as an alternative cell source is generated. Previous reports have shown the differentiation of adipose-derived stem cells in neuron-like cells and it has also been proved that the expression pattern of patterning, proneural, and neural factors, such as Pax6, Mash1, Ngn2, NeuroD1, Tbr2 and Tbr1, regulates and defines adult neurogenesis. Regarding this, we hypothesize that a functional parallelism between adult neurogenesis and neuronal differentiation of human adipose-derived stem cells exists. In this study we differentiate human adipose-derived stem cells into neuron-like cells and analyze the expression pattern of different patterning, proneural, neural and neurotransmitter genes, before and after neuronal differentiation. The neuron-like cells expressed neuronal markers, patterning and proneural factors characteristics of intermediate stages of neuronal differentiation. Thus we demonstrated that it is possible to differentiate adipose-derived stem cells in vitro into immature neuron-like cells and that this process is regulated in a similar way to adult neurogenesis. This may contribute to elucidate molecular mechanisms involved in neuronal differentiation of adult human non-neural cells, in aid of the development of potential therapeutic tools for diseases of the nervous system.     

Analysis of Trunk Neural Crest Cell Migration using a Modified Zigmond Chamber Assay

Neural crest cells (NCCs) are a transient population of cells present in vertebrate development that emigrate from the dorsal neural tube (NT) after undergoing an epithelial-mesenchymal transition ^1,2. Following EMT, NCCs migrate large distances along stereotypic pathways until they reach their targets. NCCs differentiate into a vast array of cell types including neurons, glia, melanocytes, and chromaffin cells ^1-3. The ability of NCCs to reach and recognize their proper target locations is foundational for the appropriate formation of all structures containing trunk NCC-derived components ³. Elucidating the mechanisms of guidance for trunk NCC migration has therefore been a matter of great significance. Numerous molecules have been demonstrated to guide NCC migration ⁴. For instance, trunk NCCs are known to be repelled by negative guidance cues such as Semaphorin, Ephrin, and Slit ligands ^5-8. However, not until recently have any chemoattractants of trunk NCCs been identified ⁹. Conventional in vitro approaches to studying the chemotactic behavior of adherent cells work best with immortalized, homogenously distributed cells, but are more challenging to apply to certain primary stem cell cultures that initially lack a homogenous distribution and rapidly differentiate (such as NCCs). One approach to homogenize the distribution of trunk NCCs for chemotaxis studies is to isolate trunk NCCs from primary NT explant cultures, then lift and replate them to be almost 100% confluent. However, this plating approach requires substantial amounts of time and effort to explant enough cells, is harsh, and distributes trunk NCCs in a dissimilar manner to that found in in vivo conditions. Here, we report an in vitro approach that is able to evaluate chemotaxis and other migratory responses of trunk NCCs without requiring a homogenous cell distribution. This technique utilizes time-lapse imaging of primary, unperturbed trunk NCCs inside a modified Zigmond chamber (a standard Zigmond chamber is described elsewhere¹⁰). By exposing trunk NCCs at the periphery of the culture to a chemotactant gradient that is perpendicular to their predicted natural directionality, alterations in migratory polarity induced by the applied chemotactant gradient can be detected. This technique is inexpensive, requires the culturing of only two NT explants per replicate treatment, avoids harsh cell lifting (such as trypsinization), leaves trunk NCCs in a more similar distribution to in vivo conditions, cuts down the amount of time between explantation and experimentation (which likely reduces the risk of differentiation), and allows time-lapse evaluation of numerous migratory characteristics.     

Precipitation and predation risk alter the diversity and behavior of pollinators and reduce plant fitness

Biotic and abiotic factors may individually or interactively disrupt plant–pollinator interactions, influencing plant fitness. Although variations in temperature and precipitation are expected to modify the overall impact of predators on plant–pollinator interactions, few empirical studies have assessed if these weather conditions influence anti-predator behaviors and how this context-dependent response may cascade down to plant fitness. To answer this question, we manipulated predation risk (using artificial spiders) in different years to investigate how natural variation in temperature and precipitation may affect diversity (richness and composition) and behavioral (visitation) responses of flower-visiting insects to predation risk, and how these effects influence plant fitness. Our findings indicate that predation risk and an increase in precipitation independently reduced plant fitness (i.e., seed set) by decreasing flower visitation. Predation risk reduced pollinator visitation and richness, and altered species composition of pollinators. Additionally, an increase in precipitation was associated with lower flower visitation and pollinator richness but did not alter pollinator species composition. However, maximum daily temperature did not affect any component of the pollinator assemblage or plant fitness. Our results indicate that biotic and abiotic drivers have different impacts on pollinator behavior and diversity with consequences for plant fitness components. Even small variation in precipitation conditions promotes complex and substantial cascading effects on plants by affecting both pollinator communities and the outcome of plant–pollinator interactions. Tropical communities are expected to be highly susceptible to climatic changes, and these changes may have drastic consequences for biotic interactions in the tropics.