Simultaneous visible light optical coherence tomography and near infrared OCT angiography in retinal pathologies: A case study

A dual-channel optical coherence tomography system with wavelengths in the visible and near-infrared light ranges can provide both structural and functional information for retinal microvasculature simultaneously. We applied this integrated system in an ongoing clinical study of patients with various retinal pathologies. Here, we present case study results of patients with diabetic retinopathy, central retinal vein occlusion, and sickle cell retinopathy compared to a healthy subject. For the first time, this comparison validates the system’s ability to detect structural anomalies in both en face and B-scan images with simultaneous retinal optical coherence tomography angiography and measurement of sO₂ in parafoveal vessels that are around 20–30 µm in diameter. This integrated system represents a powerful instrument with potentially far-reaching clinical implications for the early detection and diagnosis of retinal vascular diseases.     

Acquisition of N by external hyphae of an arbuscular mycorrhizal fungus and its impact on physiological responses in maize under drought-stressed and well-watered conditions

This study examined the uptake of nitrogen by external hyphae of an arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck &; Smith) and its impact on physiological responses in maize plants subjected to well-watered or drought-stressed conditions. Plants were grown in compartmented boxes divided by a nylon mesh (40?μm) into a root compartment and a hyphal compartment. Maize plants (Zea mays cv. 'Tuxpeño sequia' selection cycle C0) were exposed to 2 weeks of drought 56 days after sowing. A ^[15]N tracer was applied as K^[15]NO_[3] to the hyphal compartment at a distance of 5?cm from the root compartment. Root and shoot samples were then analyzed for ^[15]N atom % excess (APE), glutamine synthetase (GS) activity, protein concentration and nutritional status. Evapotranspiration rate and stomatal resistance were monitored daily to determine the degree of drought stress. The APE values for AM shoots and roots were 32% and 33% higher than non-AM shoots and roots, respectively, under drought conditions. This provides clear evidence that the external mycelium of AM fungus transports considerable amounts of ^[15]NO_[3]^[– ]to the host plant under drought conditions. Drought-stressed AM roots had 28% higher GS activity, possibly as a consequence of higher hyphal acquisition of NO_[3]^[–] ions. Mycorrhizal colonization significantly increased the host plant P status regardless of soil moisture regime. In addition, the N status of drought-stressed AM shoots and roots was slightly higher than stressed non-AM shoots and roots. The improved nutritional status may assist AM plants to exploit available soil moisture more efficiently and to maintain higher leaf relative water content under moderate drought conditions.     

Telomere looping in P. sativum (common garden pea)

Telomeres vary greatly in size among plants and, in most higher plants, consist of a long array of 5'-TTTAGGG-3'/3'-AAATCCC-5' (TTTAGGG) repeats. Recently, telomeric DNA in human, mouse, oxytricha, and trypanosome chromosomes have been found arranged into loops (t-loops), proposed to sequester the telomere from unwanted repair events and prevent activation of DNA damage checkpoints. We have asked whether t-loops exist in the higher order plant Pisum sativum (garden pea). DNA was isolated from the shoots and root tips of germinating seeds. Analysis of the telomeric restriction fragments showed that DNA hybridizing to a (TTTAGGG)n probe migrated as a smear centering around 25 kb, and direct sequencing verified the repeat to be (TTTAGGG)n. Total DNA in isolated nuclei was photo-cross-linked, and the telomeric restriction fragments were purified by gel filtration. Electron microscopic (EM) analysis revealed DNA molecules arranged as t-loops with a size distribution consistent with that seen by gel electrophoresis. Some molecules had loops as large as 75 kb. These results show that the arrangement of telomeric DNA into loops occurs in higher plants.     

Basic studies on the role of components of Bacillus megaterium as flotation biocollectors in sulphide mineral separation

Studies were carried out to assess the utility of the cellular and extracellular constituents of Bacillus megaterium for the flotation of sphalerite and galena minerals. Based on the flotation results on the individual minerals, it was observed that sphalerite was preferentially floated compared to galena. A maximum selectivity index (SI) value of 11.7 was achieved in the presence of the soluble fraction of the thermolysed cells, which was higher than that obtained with the intact cells (SI of 6.5) and the insoluble fraction of the thermolysed cells (SI of 9.6). The results of the various enzymatic treatment tests revealed that extracellular DNA played a vital role in the selective flotation of sphalerite. A noteworthy finding was that the single-stranded DNA (ssDNA) had a higher biocollector capacity vis-à-vis the double-stranded DNA (dsDNA), leading to better flotation efficiency. About 95 % recovery of sphalerite could be achieved from the mineral mixture by the combined addition of the ssDNA with the non-DNA components of the bacterial cells, resulting in a maximum SI of 19.1. Calcium and phosphate components of the nutrient media were found to be essential for better selectivity of separation of sphalerite. The mechanisms of microbe–mineral interaction are discussed.     

Baseline toxicity of emamectin and spinosad to Helicoverpa armigera (Lepidoptera: Noctuidae) for resistance monitoring

Acute toxicity studies of emamectin and spinosad against Helicoverpa armigera revealed that the pest is highly susceptible to both the insecticides. The median lethal dose (LD₅₀) of emamectin is 3.86 × 10⁻³ µg per larva. The median lethal concentrations (LC₅₀) of emamectin and spinosad were found to be 0.09 and 2.94 ppm, respectively. The discriminating doses were fixed based on the LC₉₅ of the susceptible population of H. armigera as 0.80 ppm for emamectin and 10 ppm for spinosad. Resistance was not observed when the discriminating doses of emamectin and spinosad were applied on field-collected populations of H. armigera from two intensive cotton growing areas, Coimbatore and Madurai, India.     

The TPR domain of PgaA is a multifunctional scaffold that binds PNAG and modulates PgaB-dependent polymer processing

The synthesis of exopolysaccharides as biofilm matrix components by pathogens is a crucial factor for chronic infections and antibiotic resistance. Many periplasmic proteins involved in polymer processing and secretion in Gram-negative synthase dependent exopolysaccharide biosynthetic systems have been individually characterized. The operons responsible for the production of PNAG, alginate, cellulose and the Pel polysaccharide each contain a gene that encodes an outer membrane associated tetratricopeptide repeat (TPR) domain containing protein. While the TPR domain has been shown to bind other periplasmic proteins, the functional consequences of these interactions for the polymer remain poorly understood. Herein, we show that the C-terminal TPR region of PgaA interacts with the de-N-acetylase domain of PgaB, and increases its deacetylase activity. Additionally, we found that when the two proteins form a complex, the glycoside hydrolase activity of PgaB is also increased. To better understand structure-function relationships we determined the crystal structure of a stable TPR module, which has a conserved groove formed by three repeat motifs. Tryptophan quenching, mass spectrometry analysis and molecular dynamics simulation studies suggest that the crystallized TPR module can bind PNAG/dPNAG via its electronegative groove on the concave surface, and potentially guide the polymer through the periplasm towards the porin for export. Our results suggest a scaffolding role for the TPR domain that combines PNAG/dPNAG translocation with the modulation of its chemical structure by PgaB.     

Signals from the edges: The cortical hem and antihem in telencephalic development

The early cortical primordium develops from a sheet of neuroepithelium that is flanked by distinct signaling centers. Of these, the hem and the antihem are positioned as longitudinal stripes, running rostro-caudally along the medial and lateral faces, respectively, of each telencepahlic hemisphere. In this review we examine the similarities and differences in how these two signaling centers arise, their roles in patterning adjacent tissues, and the cells and structures they contribute to. Since both the hem and the antihem have been identified across many vertebrate phyla, they appear to be part of an evolutionary conserved set of mechanisms that play fundamental roles in forebrain development.     

Synthesis and pharmacological evaluation of (2-oxaadamant-1-yl)amines

The synthesis of several (2-oxaadamant-1-yl)amines is reported. They were evaluated as NMDA receptor antagonists and several of them were more active than amantadine, but none was more potent than memantine. None of the tested compounds displayed antiviral activity. Two of the derivatives showed a significant level of trypanocidal activity.