Different characteristics of endothelial cells from central and peripheral human cornea in primary culture and after subculture

Summary Several methods for isolation and cultivation of human corneal endothelial cells have been described during the last few decades. In contrast to the situation in vivo, the cultured cells show mitogenic activity but often lose their typical morphological appearance. In this paper, we describe a technique to isolate and cultivate morphologically unchanged endothelium from the human cornea. This method revealed different characteristics of endothelial cells according to their position within the human cornea. Endothelial cells isolated from the central part have a morphology similar to that of cells in vivo (i.e., they are densely packed and show no mitogenic activity). In contrast, endothelial cells derived from the peripheral part of the cornea are characterized by mitogenic activity but their cell-to-cell attachment seems to be less tight than in vivo. The significance of these two different endothelial cell types for wound healing in the human cornea is discussed.     

CORNEAL SURFACE PROPERTIES OF TWO MARINE MAMMAL SPECIES1

Compared to the anterior surface of the normal human cornea, all Tursiops showed pronounced random, local curvature changes typical of old keratitis and scarring. Comparable but less severe findings apply to Zalophus. These irregularities were superimposed on the mild regular astigmatism of the spoon-shaped Tursiops cornea (mean central power is 26.8 D, SD = 3.8, N = 82). All Zalophus corneas showed no reliable regular astigmatism (overall mean power is 21.7 D, SD = 4.4, N = 53) but exhibited a flat, circular region about 6.5 mm in diameter along the nasal aspect of the horizontal meridian. Refraction through this cornea1 region showed aerial emmetropia, which accounts for equivalent marine and aerial visual resolution in this species.     

Correlation of histology and linear and nonlinear microscopy of the living human cornea

The morphology and the function of cellular and non‐cellular structures in the living human cornea can be determined with modern correlative linear and nonlinear optical microscopic techniques and histology. Correlative microscopy is based on the use of different optical techniques to study the same specimen, ideally at the same location within the specimen, in order to increase the functional and/or morphological understanding of the specimen. A case study to assess the effect of overnight lid‐closure on in vivo human corneal morphology is presented to illustrate correlative linear microscopy and optical low‐coherence reflectometry. Nonlinear multiphoton excitation microscopy provides functional information on cellular metabolism based on the intrinsic fluorescence from the reduced pyridine nucleotides and the oxidized flavoproteins. Second‐harmonic generation microscopy, a scattering process that does not deposit net energy into the tissue, provides structural information on corneal collagen organization. Molecular third‐harmonic generation microscopy generates a signal in all materials and it an emerging technique. Coherent anti‐Stokes Raman scattering microscopy provides chemical imaging for biology and medicine. The comparison and limitations of these microscopic modalities, linear and nonlinear microscopy applied to the cornea, and a review of some key findings is analyzed. A correlative integration and correlation of linear and nonlinear microscopies to study corneal function and structure is proposed to validate the clinical interpretation of microscopic images of the cornea. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the true intraocular pressure and modulus of elasticity of the human cornea in vivo

The purpose of this study was to determine the true intraocular pressure and modulus of elasticity of the human cornea in vivo. The cornea was modeled as a shell, and the equations for the deformations of a shell due to applanating and intraocular pressures were combined to model the behavior of the cornea during applanation tonometry. At certain corneal dimensions called the calibration dimensions, the applanating and intraocular pressures are considered to be equal. This relationship was used to determine the modulus of elasticity of the cornea and the relationship between the applanating and intraocular pressures. The true intraocular pressure (IOPT) was found to be related to Goldmann’s applanating pressure (IOPG) as (IOPT = IOPG/K, where K is a correction factor. For the calibration corneal thickness of 0.52 mm, the modulus of elasticity E in MPa of the human cornea was found to be related to the true intraocular pressure IOPT in mmHg as E = 0.0229IOPT. The generalization of the Imbert—Fick law that takes into account the effect of corneal dimensions and stiffness was found to be given by IOPT = 73.5W/(K A), where W is the applanating weight in gf (gram force) and A is the applanated area in mm². The calculated true intraocular pressure and modulus of elasticity were found to agree with published experimental results. The mathematical model developed may therefore be used to improve results from applanation tonometry and to estimate the mechanical property of the cornea in vivo.     

Morphology and evolution of the snake cornea

To investigate whether the thickness of the cornea in snakes correlates with overall anatomy, habitat or daily activity pattern, we measured corneal thickness using optical coherence tomography scanning in 44 species from 14 families (214 specimens) in the collection at the Natural History Museum (Denmark). Specifically, we analyzed whether the thickness of the cornea varies among species in absolute terms and relative to morphometrics, such as body length, spectacle diameter, and spectacle thickness. Furthermore, we examined whether corneal thickness reflects adaptation to different habitats and/or daily activity patterns. The snakes were defined as arboreal (n = 8), terrestrial (n = 22), fossorial (n = 7), and aquatic (n = 7); 14 species were classified as diurnal and 30 as nocturnal. We reveal that the interspecific variation in corneal thickness is largely explained by differences in body size, but find a tendency towards thicker corneas in diurnal (313 ± 227 μm) compared to nocturnal species (205 ± 169 μm). Furthermore, arboreal snakes had the thickest corneas and fossorial snakes the thinnest. Our study shows that body length, habitat, and daily activity pattern could explain the interspecific variation in corneal morphology among snakes. This study provides a quantitative analysis of the evolution of the corneal morphology in snakes, and it presents baseline values of corneal thickness of multiple snake species. We speculate that the cornea likely plays a role in snake vision, despite the fact that results from previous studies suggest that the cornea in snakes is not relevant for vision (Sivak, Vision Research, 1977, 17, 293–298).     

Structural specializations of the cornea and retina at the dorsal rim of the compound eye in hymenopteran insects

Summary Structurally specialized ommatidia at the dorsal rim of the compound eyes of honey bees have been shown to be indispensable for polarized skylight navigation. In this study numerous other hymenopteran genera belonging to various superfamilies are shown to exhibit similar specializations in this part of the eye: (1) The cornea is penetrated by pore canals, which affect the optics of the ommatidia by scattering the light falling into the eye. In Andrena and Ammophila the cornea contains extensive cavities. (2) Each retinula contains 9 long receptor cells as opposed to 8 long ones in the adjacent dorsal area, and the rhabdom area is increased by a factor of up to 2. In all ant species examined there are no corneal but only retinal specializations at the dorsal rim of the eye. They include a specially shaped rhabdom as in Cataglyphis, in which polarization vision has also been demonstrated.     

Understanding cornea epithelial stem cells and stem cell deficiency: Lessons learned using vertebrate model systems

Animal models have contributed greatly to our understanding of human diseases. Here, we focus on cornea epithelial stem cell (CESC) deficiency (commonly called limbal stem cell deficiency, LSCD). Corneal development, homeostasis and wound healing are supported by specific stem cells, that include the CESCs. Damage to or loss of these cells results in blindness and other debilitating ocular conditions. Here we describe the contributions from several vertebrate models toward understanding CESCs and LSCD treatments. These include both mammalian models, as well as two aquatic models, Zebrafish and the amphibian, Xenopus. Pioneering developments have been made using stem cell transplants to restore normal vision in patients with LSCD, but questions still remain about the basic biology of CESCs, including their precise cell lineages and behavior in the cornea. We describe various cell lineage tracing studies to follow their patterns of division, and the fates of their progeny during development, homeostasis, and wound healing. In addition, we present some preliminary results using the Xenopus model system. Ultimately, a more thorough understanding of these cornea cells will advance our knowledge of stem cell biology and lead to better cornea disease therapeutics.     

In vivo determination of young's modulus for the human cornea

The present paper describes a calculation technique to determine a value of Young's modulus for the cornea when the intraocular pressure, the shape of the cornea and the thickness variation along the cornea are known fromin vivo measurements. Twenty-eight persons were examined in both eyes and a mean value of Young's modulus for the cornea was calculated to 2.45×10⁴±0.57×10⁴ N/m² (S.D.).     

A new maximum size for the family Nomeidae and the third record of a longfin cigarfish,Cubiceps paradoxus (Stromateoidei: Nomeidae) from California,USA

We report the largest specimen from the stromateoid family Nomeidae. The specimen, measuring 1283 mm total length unpreserved, was caught on hook and line from shore in Port Hueneme, California, USA in June 2019. Despite scavenging damage, the specimen was identified as a longfin cigarfish, Cubiceps paradoxus, using morphological characters and molecular techniques. This is the third record of C. paradoxus from California. We also provide an account of a previously unreported C. paradoxus collected off the US-Mexico Border in 1999 that was examined but not preserved.     

Last evidence of Lates (Perciformes,Latinae) in the latest Miocene of the Eastern Paratethys

An articulated series of centra from latest Miocene deposits of Ukraine is described and identified as a species of Lates. The specimen comes from a locality with an estimated age of 6.04–4.7 Ma, representing the northernmost reach of the Paratethys during the Pontian. The specimen almost certainly represents a distinct species, but because it is incomplete we do not formally name it. The specimen can be differentiated from other species of Lates by features of the centra, including the relative size of the primary lateral fossa of the second centrum, the broadened neural spine of the third centrum, and the relative position of the upper and primary lateral pits on both the fifth and sixth centra. The Ukrainian specimen documents the presence of Lates in the northern Paratethys in the latest Miocene. After this time, species of Lates persisted in freshwaters in the Mediterranean area (Israel and Africa), but are no longer found in the marine waters of the region. We suggest that latines were extirpated from the Mediterranean and Paratethys by the rapidity of the changes in salinity that occurred in the Tethys Mediterranean basin and Paratethys as a result of the Messinian Salinity Crisis.     

Typification of the Linnaean name Ononis crispa and the related O. zschackei (Fabaceae)

The typification of the Linnaean name Ononis crispa and the related O. zschackei (Fabaceae) is discussed. Original material for O. crispa was traced at LINN, but found to be heterogeneous. In addition, the illustration by Magnol cited in the protologue represents O. aragonensis. The name is lectotypified using a specimen at LINN to preserve the current usage of the name and to avoid any ambiguity in the interpretation of the lectotype, an epitype is selected. Since no original material is extant for the name O. zschackei, a neotype is designated from a specimen preserved at P and collected in Mallorca (Balearic Islands, Spain).     

Apparently contradictory routes in the expansion of two fish species in the Eastern Atlantic

One specimen of the boreal Clupea harengus (Clupeidae) was caught southerly, in the Gulf of Cádiz (southern Spain), whereas a specimen of the subtropical Epinephelus aeneus (Serranidae) was caught northerly, in Galician waters (north-west of Spain). These catches represent a new southernmost record in the eastern Atlantic for C. harengus and the second northernmost for E. aeneus. The co-occurrence of warm and cold affinity fishes in temperate latitudes is unusual, but the existence of anomalies in the temperature of the Atlantic waters could be behind these findings.     

Monognathus berteli sp. nov. from the Indian Ocean (Pisces,Monognathidae)

A new deepsea monognathid species,Monognathus berteli, is described based on one specimen collected pelagically in the northwestern Indian Ocean at 1440–1018 meters of depth. LikeM. taningi andM. bertini, it belongs to the short-skulled species-group and has very long pectoral fins, but differs from these species by several meristic characters. The described specimen has a very long caudal filament (53% SL) which is not known from otherMonognathus. However, the fragile filament is not used as a diagnostic character since it could easily be broken.     

The first known neonate Ichthyosaurus communis skeleton: a rediscovered specimen from the Lower Jurassic,UK

Numerous specimens of Ichthyosaurus are known, but only very few small examples (total length of <1 m) have been assigned beyond Ichthyosaurus sp. Here, we report on a very small specimen (preflexural length of 560 mm) that can be unequivocally assigned to Ichthyosaurus communis due to possessing a unique combination of diagnostic skull and postcranial characters that are found in larger examples of the species. Furthermore, the specimen is identified as a neonate because of the small size, large sclerotic ring relative to the orbital region, and poorly ossified (highly cancellous) bones of the skull and postcranium. It is not an embryo as it is not preserved within an adult specimen and stomach contents are clearly evident. This is therefore the first neonate Ichthyosaurus communis skeleton to be described. The specimen, in the Lapworth Museum of Geology, University of Birmingham, has no provenance data associated with it. A microfossil analysis of the matrix in which the ichthyosaur skeleton is preserved strongly suggests a stratigraphic range of uppermost Hettangian to lowermost Sinemurian age (Lower Jurassic), but does not provide any geographical information.     

Cranial anatomy,taxonomic implications and palaeopathology of an Upper Jurassic Pliosaur (Reptilia: Sauropterygia) from Westbury,Wiltshire, UK

Abstract: Complete skulls of giant marine reptiles of the Late Jurassic are rare, and so the discovery of the 1.8‐m‐long skull of a pliosaur from the Kimmeridge Clay Formation (Kimmeridgian) of Westbury, Wiltshire, UK, is an important find. The specimen shows most of the cranial and mandibular anatomy, as well as a series of pathological conditions. It was previously referred to Pliosaurus brachyspondylus, but it can be referred reliably only to the genus Pliosaurus, because species within the genus are currently in need of review. The new specimen, together with another from the same locality, also referred to P. brachyspondylus, will be crucial in that systematic revision, and it is likely that the genus Pliosaurus will be found to include several genera. The two Westbury Pliosaurus specimens share many features, including the form of the teeth, but marked differences in the snout and parietal crest suggest sexual dimorphism; the present specimen is probably female. The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual. An erosive arthrotic condition of the articular glenoids led to prolonged jaw misalignment, generating a suite of associated bone and dental pathologies. Further damage to the jaw joint may have been the cause of death.     

Preparation and physical properties of a novel biocompatible porcine corneal acellularized matrix

This study was to investigate the stability, physico-mechanical property and biocompatibility of porcine corneal acellularized matrix (PCAM) that was prepared using human sera treatment to decellularize corneas. The stability (the rate of biodegradation) and physico-mechanical property (water uptake, density, and porosity) of PCAM were not compromised, compared with porcine fresh cornea matrix (PFCM, p > 0.05). The contact and extract cytotoxicity tests with human corneal epithelial cells and human keratocytes showed that PCAM has a good biocompatibility ex vivo and no cytotoxic effect. These results present the ability to create safety scaffolds that function as cornea grafts and provide a novel experimental approach for the study of cornea tissue engineering using acellular porcine cornea.     

Avian corneal innervation: Inhibition of nerve ring formation by 6-diazo-5-oxo-l-norleucine

Normal innervation of embryonic avian cornea is achieved in two distinct phases. During phase I, nerves extend from the ventrotemporal region both dorsally and ventrally around the cornea, but not into it, ultimately encircling the 10th-day cornea. Phase II commences as nerves extend radially from the ring into the corneal stroma and from there into the epithelium. The effect of the glutamine analog, 6-diazo-5-oxo-l-norleucine (DON), on this normal sequence of events has been examined. In ovo administration of 5 μg DON on the 5th day of development inhibits the incorporation of [³⁵S]sulfate in sulfated glycosaminoglycans in both the cornea and control tissues and inhibits the completion of phase I. Phase II of corneal innervation appears to be affected only indirectly and extension of nerves into the cornea does occur. However, the number of nerves entering the DON-treated cornea is dramatically reduced. Administration of DON on the 7th or 9th days of development does not affect corneal innervation, but does demonstrate a clear effect on [³⁵S]sulfate incorporation in sulfated glycosaminoglycans by the cornea and control tissues. These data suggest that nerve ring completion is not a prerequisite for extension of nerves into the cornea and suggest an integral role for glycosaminoglycans in facilitating phase I, but not phase II, of corneal innervation.     

LEPIDODENDRON ACULEATUM WITH ATTACHED FOLIAGE: EVIDENCE OF STEM MORPHOLOGY AND FOSSILIZATION PROCESSES

A 6 m long specimen of Lepidodendron aculeatum Sternberg with attached leaves is described. The preserved portion of this axis gradually tapers from 38 cm wide at the lower end to 33.5 cm at the top. Ligule pit casts are present immediately above the leaf scars; they are similar to those of Lower Carboniferous lycophytes Angarodendron, Eskdalia, Tomiodendron, Ursodendron, and Meyenodendron and the Upper Carboniferous Bothrodendron. No such casts have beeen reported previously from Lepidodendron, although ligule pit cuticles have been prepared from Ulodendron, Lepidodendron, and Lepidophloios. This specimen is also unusual in that leaves are attached to the large stem. The specimen consists of external and internal molds, details of which show that the stem increased in width during burial and compression and prior to fossilization. The width of the specimen does not equal the original diameter of the stem but more closely corresponds to one half the circumference of the axis. This flattened log provides further details of overall Lepidodendron morphology and an insight into fossilization processes.