The Relationship Between Visual Sensitivity and Eccentricity,Cone Density and Outer Segment Length in the Human Foveola

PurposeThe cellular topography of the human foveola, the central 1° diameter of the fovea, is strikingly non-uniform, with a steep increase of cone photoreceptor density and outer segment (OS) length toward its center. Here, we assessed to what extent the specific cellular organization of the foveola of an individual is reflected in visual sensitivity and if sensitivity peaks at the preferred retinal locus of fixation (PRL).MethodsIncrement sensitivity to small-spot, cone-targeted visual stimuli (1 × 1 arcmin, 543-nm light) was recorded psychophysically in four human participants at 17 locations concentric within a 0.2° diameter on and around the PRL with adaptive optics scanning laser ophthalmoscopy-based microstimulation. Sensitivity test spots were aligned with cell-resolved maps of cone density and cone OS length.ResultsPeak sensitivity was at neither the PRL nor the topographical center of the cone mosaic. Within the central 0.1° diameter, a plateau-like sensitivity profile was observed. Cone density and maximal OS length differed significantly across participants, correlating with their peak sensitivity. Based on these results, biophysical simulation allowed to develop a model of visual sensitivity in the foveola, with distance from the PRL (eccentricity), cone density, and OS length as parameters.ConclusionsSmall-spot sensitivity thresholds in healthy retinas will help to establish the range of normal foveolar function in cell-targeted vision testing. Because of the high reproducibility in replicate testing, threshold variability not explained by our model is assumed to be caused by individual cone and bipolar cell weighting at the specific target locations.     

Über Myokardschäden bei der Maul- und Klauenseuche des Rindes

Ohne Zusammenfassung Mit 19 Abbildungen im Text und 1 graphischen Tabelle.     

Bilaterale diffuse uveale melanozytäre Proliferation bei metastasierendem Mammakarzinom

A 64-year-old female patient with a history of metastatic breast cancer presented with bilateral deterioration of visual acuity over a period of several weeks. Examination revealed patchy fundus pigmentation, serous retinal detachment and cataract in both eyes. After diagnosis of a bilateral diffuse uveal melanocytic proliferation (BDUMP) and due to disease progression, a course of plasmapheresis three times a week over a period of 2 weeks was initiated. Apart from the occurrence of peripheral edemas the therapy was well-tolerated by the patient. Treatment success could not be evaluated because the patient died a short time later. This is the first reported case of BDUMP due to breast cancer.     

Ein Retinoidbestandteil von Lipofuszin, A2-E, ist ein Photosensitizer in humanen RPE-Zellen

Hintergrund. A2-E, ein fluoreszierender Bestandteil von Lipofuszin, beeintr?chtigt den lysosomalen Stoffwechsel humaner retinaler Pigmentepithel- (RPE-)Zellen. Als weiterer m?glicher Sch?digungsmechanismus wurde hier das phototoxische Potenzial des Retinoidanteils untersucht.     

Experimental external irradiation of corneal neovascularization

The clinical effect of ionidizing radiation on ocular neovascularizations is controversial not only because of the variety of treatment modalities. The aim of our study was to investigate an experimental model which allows to evaluate radiation parameters and to study the mechanism of the inhibitory effect on neoangiogenesis. METHODS: Corneal angiogenesis was induced by use of a micropocket assay in NZW rabbits. Pellets with 500 ng bFGF in 2% methylecellulose were implanted into the stroma 2.0 mm from the limbus. Initiation of vessel growth occurred on day 3. At this time radiation was performed with different doses (single dose of 15 to 30 Gy or fractionated 5 x 5 Gy) using a 6 MeV linear accelerator. Vascular growth was quantified. RESULTS: Irradiation with a total dose of 25 Gy applied in a fractionated regimen or as single-dose irradiation on the day of surgery or on day 6 after surgery did not significantly reduce neovascular growth. In contrast, postoperative radiation therapy on day 3 was able to reduce the area of ingrowing vessels significantly (P < 0.01). In spite of the relatively high dose there were no significant side effects during the observation period of 8 weeks. CONCLUSION: Our results show that single-dose radiation (> or = 25 Gy) is sufficient to inhibit the growth of corneal neovascularizations. With this model it might be possible to investigate parameters for therapy of ocular neovascularizations as well as the underlying mechanisms.     

Substitution of amino acids Asp-85, Asp-212, and Arg-82 in bacteriorhodopsin affects the proton release phase of the pump and the pK of the Schiff base.

Photocycle and flash-induced proton release and uptake were investigated for bacteriorhodopsin mutants in which Asp-85 was replaced by Ala, Asn, or Glu; Asp-212 was replaced by Asn or Glu; Asp-115 was replaced by Ala, Asn, or Glu; Asp-96 was replaced by Ala, Asn, or Glu; and Arg-82 was replaced by Ala or Gln in dimyristoylphosphatidylcholine/3-[(3-cholamidopropyl)dimethylammonio]-1- propanesulfonate micelles at pH 7.3. In the Asp-85----Ala and Asp-85----Asn mutants, the absence of the charged carboxyl group leads to a blue chromophore at 600 and 595 nm, respectively, and lowers the pK of the Schiff base deprotonation to 8.2 and 7, respectively, suggesting a role for Asp-85 as counterion to the Schiff base. The early part of the photocycles of the Asp-85----Ala and Asp-85----Asn mutants is strongly perturbed; the formation of a weak M-like intermediate is slowed down about 100-fold over wild type. In both mutants, proton release is also slower but clearly precedes the rise of M. The amplitude of the early (less than 0.2 microseconds) reversed photovoltage component in the Asp-85----Asn mutant is very large, and the net charge displacement is close to zero, indicating proton release and uptake on the cytoplasmic side of the membrane. The data suggest an obligatory role for Asp-85 in the efficient deprotonation of the Schiff base and in the proton release phase, probably as proton acceptor. In the Asp-212----Asn mutant, the rise of the absorbance change at 410 nm is slowed down to 220 microsecond, its amplitude is small, and the release of protons is delayed to 1.9 ms. The absorbance changes at 650 nm indicate perturbations in the early time range with a slow K intermediate. Thus Asp-212 also participates in the early events of charge translocation and deprotonation of the Schiff base. In the Arg-82----Gln mutant, no net transient proton release was observed, whereas, in the Arg-82----Ala mutant, uptake and release were reversed. The pK shift of the purple-to-blue transition in the Asp-85----Glu, Arg-82----Ala, and Arg-82----Gln mutants and the similarity in the photocycle and photoelectrical signals of the Asp-85----Ala, Asp-85----Asn, and Asp-212----Asn mutants suggest the interaction between Asp-85, Arg-82, Asp-212, and the Schiff base as essential for proton release.     

Clinical evaluation of four amalgam alloys: a five-year report

In this study 96 teeth of 12 patients were restored with either the conventional alloy Premix, the blended non-gamma 2 amalgam Dispersalloy, or one of the spherical alloys Sybraloy and Tytin. To ascertain an objective comparison of the clinical performance of these alloys, two different alloys were used in each of at least two dental arch quadrants in the same patient and consequently were placed in the same oral environment. Clinical performance of the restorations was evaluated by macrophotography and scanning electron microphotography of replicas made after placement and 2, 3, and 5 years thereafter. Standard criteria were used for the evaluation of anatomic form, surface condition, and marginal adaptation of the fillings. In addition, the filling-enamel interface was assessed from the microphotographs. The three high-copper alloys performed better clinically than the conventional alloy, and the spherical alloys had the best qualifications. In addition to visual examination and photographic evaluation of restorations, the micrometric assessment of replica photographs from the scanning electron microscope may render clinical trials of amalgam alloys measurable and less subjective.     

Vertebral autograft used as bone transplant for anterior cervical corpectomy: technical note

OBJECTIVE: In this prospective patient study, we used a surgical technique for autograft bone fusion during anterior cervical corpectomy (ACC) in patients experiencing cervical spondylotic myelopathy. We packed the resected bone material of the corpectomy into a titanium mesh cage. To evaluate the efficacy of our autograft technique, we analyzed the results according to neurological outcome, radiological outcome, and complications. METHODS: Between 1995 and 1998, 27 ACC operations were performed for cervical spondylotic myelopathy caused by multisegmental cervical spondylosis. In all patients, decompression of the cervical canal and/or spinal nerve roots was performed by a median cervical corpectomy by an anterior approach. After the ACC was completed, a titanium mesh cage, which was variable in diameter and length, was filled with morselized and impacted bone material from the cervical corpectomy and was then implanted. An anterior cervical plate was placed in all patients to achieve primary stability of the cervical vertebral column. Age, sex, pre- and postoperative myelopathy, number of decompressed levels, radiological results, and complications were assessed. The severity of myelopathy was graded according to the scoring system of the Japanese Orthopaedic Association. RESULTS: Symptomatic improvement of neurological deficits was achieved in 80% of the patients. The mean preoperative Japanese Orthopaedic Association score improved from 13.1 to 15.2 postoperatively (P < 0.05). No patient demonstrated worsening of myelopathic symptoms. Radiological follow-up studies demonstrated complete bony fusion in all patients. A vertical movement of 2.25 +/- 0.43 mm of the titanium cage into the adjacent vertebral bodies was observed in 24 patients. In patients with either a lordotic or neutral cervical spinal axis postoperatively, the axis remained unchanged during the entire follow-up period. CONCLUSION: The results of this study demonstrate that transplantation of autograft bone material harvested during the ACC integrated well in the cage and in the adjacent vertebral bodies. Thus, complications associated with explantation of autograft material from other donor sites, e.g., the iliac crest, could be avoided. The early postoperative and midterm follow-up periods provided no evidence of morphological or functional instability of the operated cervical segments when this autograft technique was used in combination with cervical instrumentation.