Filling in the retinal image

The optics of the eye form an image on a surface at the back of the eyeball called the retina. The retina contains the photoreceptors that sample the image and convert it into a neural signal. The spacing of the photoreceptors in the retina is not uniform and varies with retinal locus. The central retinal field, called the macula, is densely packed with photoreceptors. The packing density falls off rapidly as a function of retinal eccentricity with respect to the macular region and there are regions in which there are no photoreceptors at all. The retinal regions without photoreceptors are called blind spots or scotomas. The neural transformations which convert retinal image signals into percepts fills in the gaps and regularizes the inhomogeneities of the retinal photoreceptor sampling mosaic. The filling-in mechamism plays an important role in understanding visual performance. The filling-in mechanism is not well understood. A systematic collaborative research program at the Ames Research Center and SRI in Menlo Park, California, was designed to explore this mechanism. It was shown that the perceived fields which are in fact different from the image on the retina due to filling-in, control some aspects of performance and not others. Researchers have linked these mechanisms to putative mechanisms of color coding and color constancy

Specific and highly efficient condensation of GC and IC DNA by polyaza pyridinophane derivatives

Two bis-polyaza pyridinophane derivatives and their monomeric reference compounds revealed strong interactions with ds-DNA and RNA. The bis-derivatives show a specific condensation of GC- and IC-DNA, which is almost two orders of magnitude more efficient than the well-known condensation agent spermine. The type of condensed DNA was identified as psi-DNA, characterized by the exceptionally strong CD signals. At variance to the almost silent AT(U) polynucleotides, these strong CD signals allow the determination of GC-condensates at nanomolar nucleobase concentrations. Detailed thermodynamic characterisation by ITC reveals significant differences between the DNA binding of the bis- derivative compounds (enthalpy driven) and that of spermine and of their monomeric counterparts (entropy driven). Atomic force microscopy confirmed GC-DNA compaction by the bis-derivatives and the formation of toroid- and rod-like structures responsible for the psi-type pattern in the CD spectra

Global wealth disparities drive adherence to COVID-safe pathways in head and neck cancer surgery

Peer reviewe

THE ANOMALOUS CONE PHOTOPIGMENTS OF PROTANOMALOUS AND DEUTERANOMALOUS TRICHROMATS

Abstract not availabl

Implant loss and sinusitis after sinus lift ‐ an underestimated complication

Background: Sinus lift is designed to enable the placement of maxillary implants in situations with vertically reduced alveolar bone. It has become a more frequently performed procedure. Possible complications comprise sinusitis, failing grafts and failing of the dental implant. More severe problems and chronic sinusitis have been reported. Aim/Hypothesis: To report on 76 patients with implant loss after sinuslift. To report the reasons, the possibilities for repair in routine cases and in more severe situations of sinusitis with multiple implant loss and damage to surrounding structures. To report the long‐term outcome. Materials and Methods: Between 2000 and 2020 76 patients with failing implants after sinuslift were referred to four Oral Surgery and ENT services in Switzerland. Of 169 implants originally placed 71 implants were already lost before the first consultation. 14 patients had no complaints other than implant loss. The other 62 patients complained about varying degrees of pain, swollen midface, pussy exudates, paresthesia etc. In 3 patients implants had been failing repeatedly. CBCT showed in 58 patients maxillary sinusitis, in 4 patients half‐sided pan‐sinusitis. In 11 patients, nasal fiberoptic endoscopy was carried out. Further investigations consisted of bacteriology, mycology and histology. Reasons for sinusitis were attributable to postoperative blowing of the nose, infection of the graft, antiresorptive drugs, peri‐implantitis reaching the floor of the sinus and allergic reaction to sinus grafting material mixed with collagen. Another reason for implant loss was a failing graft without signs of sinusitis. Results: 53 implants had to be removed under Local Anaesthesia (LA), 9 implants could be left in situ. 8 patients did not need surgical intervention for sinusitis but only antibiotic treatment. 41 patients needed surgical intervention under LA for cleaning the sinus of infected graft material and closing of fistula. 27 patients needed surgical intervention under General Anaesthesia (GA) because of more extensive disease, removal of debris, fungi, dislocated dental implants and nasal endoscopy. 51 patients became pain free. In 11 patients some chronic pain remained. In 18 patients the sinus did not heal to a degree that re‐sinuslift was deemed appropriate. Whilst 29 patients were subsequently treated with dentures, 47 patients underwent a second surgery for new grafting procedures with autologous bone, followed by implant insertion. This was possible in 28 patients under LA, whilst 19 patients needed GA for reconstruction of lost maxillary structures with large mandibular or with hip bone graft. Conclusions and Clinical Implications: Whilst many complications after sinus lift are not severe and can be treated locally, some patients exhibit more severe problems with e.g. pan‐sinusitis and chronic sinusitis. Multidisciplinary cooperation between dentists, oral surgeons, and ear, nose and throat specialists can be very helpful in diagnosing and treating these cases. To estimate the chance for success of redo of sinus lift is rather difficult, especially when bone substitutes were used beforehand which may not have integrated

Dipeptides Containing Pyrene and Modified Photochemically Reactive Tyrosine: Noncovalent and Covalent Binding to Polynucleotides

Dipeptides 1 and 2 were synthesized from unnatural amino acids containing pyrene as a fluorescent label and polynucleotide binding unit, and modified tyrosine as a photochemically reactive unit. Photophysical properties of the peptides were investigated by steady-state and time-resolved fluorescence. Both peptides are fluorescent (Φf = 0.3–0.4) and do not show a tendency to form pyrene excimers in the concentration range −5 M, which is important for their application in the fluorescent labeling of polynucleotides. Furthermore, both peptides are photochemically reactive and undergo deamination delivering quinone methides (QMs) (ΦR = 0.01–0.02), as indicated from the preparative photomethanolysis study of the corresponding N-Boc protected derivatives 7 and 8. Both peptides form stable complexes with polynucleotides (log Ka > 6) by noncovalent interactions and similar affinities, binding to minor grooves, preferably to the AT reach regions. Peptide 2 with a longer spacer between the fluorophore and the photo-activable unit undergoes a more efficient deamination reaction, based on the comparison with the N-Boc protected derivatives. Upon light excitation of the complex 2·oligoAT10, the photo-generation of QM initiates the alkylation, which results in the fluorescent labeling of the oligonucleotide. This study demonstrated, as a proof of principle, that small molecules can combine dual forms of fluorescent labeling of polynucleotides, whereby initial addition of the dye rapidly forms a reversible high-affinity noncovalent complex with ds-DNA/RNA, which can be, upon irradiation by light, converted to the irreversible (covalent) form. Such a dual labeling ability of a dye could have many applications in biomedicinal sciences

Session Participants

draft copy of this article was sent to all members of the Roundtable for their input regarding any revisions, changes, additions, and editing purposes. The article presented here represents the integration of input received from all participants of the Roundtable, and forms the final product of this Special Session. The Roundtable contributors, i.e. managers, engineers, industrial consultants, and researchers, are listed in alphabetical order