Eye Capsule Research Articles

Upregulated NOTCH Signaling in the Lens of Patients With Pseudoexfoliation Syndrome Compared With Pseudoexfoliation Glaucoma Suggests Protective Role.

NOTCH signaling is significantly upregulated in the lens capsules of eyes with pseudoexfoliation syndrome (PXF) but not in those with pseudoexfoliation glaucoma (PXG) when compared with healthy controls. NOTCH signaling has neuroprotective functions and altered NOTCH signaling is associated with neurodegenerative diseases with protein aggregation such as Alzheimer disease. As PXG is also a protein aggregate disease associated with neural degeneration, NOTCH molecular expression was explored in the lens capsules of patients with PXF, PXG, primary open-angle glaucoma (POAG), and healthy controls. Anterior lens capsules were collected from 106 patients (27 PXF, 24 PXG, 22 POAG, and 33 controls) undergoing cataract surgery. Gene expression profiling for NOTCH pathway molecules (ligands, receptors, and downstream target genes) was performed on the tissue using a quantitative reverse transcription-polymerase chain reaction. The results were confirmed by protein analysis using dot-blot or immunostaining techniques. There was no difference in the demographic characteristics between the groups. There was an increase in NOTCH4 receptor expression (>14-fold) in the PXF group as compared with the controls. Similarly, the Delta-like 3 and Delta-like 4 ligands were significantly elevated in the PXF group compared with controls (P<0.05). Downstream targets HES3, HES5, and HEY1 expression were significantly elevated (P<0.005) in PXF lens capsules, confirming a higher activity of NOTCH signaling in this cohort. Immunostaining also corroborated the gene expression profile. The finding that NOTCH signaling is significantly upregulated in the lens capsule of eyes with PXF and not in PXG or POAG patients suggests a possible protective role in the development of glaucoma.

Laser treatment of the anterior capsulorhexis shrinkage syndrome in patients with pseudophakia

The article describes results of laser treatment applied in seven patients (eleven eyes) due to capsulorhexis margin shrinkage and the subsequent wrinkling of the anterior capsule in eyes with pseudophakia. Almost total loss of the anterior capsulorhexis aperture caused a significant decrease in visual acuity, to the level of counting fingers right in front of the eyes in three patients (four eyes). The laser cut of the anterior capsulorhexis margin using the Nd-Yag laser led to an immediate increase in the capsulorhexis size in each case. Visual acuity improved in the eyes with an extreme decrease in the capsulorhexis size. In the remaining eyes, where the decrease of the capsulorhexis size did not lead to the appearance of anterior capsule wrinkling, visual acuity did not change. The progressive decrease in the capsulorhexis size, accompanied by the appearance of white tissue on its margin, containing shrinking elements, constitutes an indication for the implementation of laser therapy.

Cloning and expression of Hoxc6 gene from Pampus argenteus and its relationship with pelvic fin absence

Hoxc6 gene can be described as having roles in axial patterning in early embryogenesis, and in at least some species, having a contribution to limb positioning. In this study, we cloned and characterised Pampus argenteus Hoxc6. The highly conserved HOXC6 protein sequence contains a homeodomain and a low-complexity region. Expression of Hoxc6 mRNA was measured at different developmental stages and in different tissues by real-time PCR (p < 0.05), and was high during eye capsule and brain differentiation stages, but low in 7 and 13-day-old larvae. Hoxc6 mRNA was more abundant in fin tissue than brain and eye tissues. Western blotting showed that HOXC6 protein levels were high at embryonic stages, but decreased significantly in 7, 13, 16 and 19-day-old larvae, and levels were essentially consistent with those of mRNA measured by real-time PCR in different tissues. In situ hybridisation showed that the Hoxc6 transcript was strongly expressed in the whole brain and anterior part of the body axis in 1-day-old larvae, but in the hindbrain, pectoral fin, mandible and hypothetical pelvic fin region in 7, 13, 16 and 19-day-old organisms. These results clarify the expression and localisation characteristics of Hoxc6 gene in P. argenteus, and provide a theoretical basis for the molecular mechanism of pelvic fin loss in silver pomfret.

MANUAL AND YAG-LASER ANTERIOR CAPSULORHEXIS SURGERY OF CONGENITAL ECTOPIA OF THE LENS IN MARFAN SYNDROME IN CHILDREN

Purpose. is to optimize the tactics of performing anterior capsulorhexis in children with congenital lens subluxation in Marfan syndrome with the use of manual and YAG - laser technique. Material and methods. There were observed 25 patients (34 eyes) aged 4 to 11 years old with lens subluxation: 7 children (10 eyes) with congenital cataract and 18 patients (24 eyes) of the clear crystalline lens in Marfan syndrome. The degree of ectopia was different: 14 eyes - 1 degree, 16 eyes-2 degree and 4 eyes-3 degree of crystal ectopia. Manual circular continuous capsulorexis performed 15 eyes in 12 childrens, YAG-laser capsulectomy-19 eyes in 13 children. Results. Use of YAG - laser equipment allowed to excise planned part of of the anterior capsule without mechanical pressure on not fixed lens. Full of YAG-laser anterior capsulorhexis could not be executed in eyes with 3 degree subluxation of the lens (a significant portion of the anterior capsule is covered with an iris). Manual method allowed to execute anterior capsulorhexis at any degree of subluxation of the lens, but required multiple manipulations on the anterior capsule because of clinical and anatomical features anterior capsule in eyes with subluxation of the lens, which significantly prolonged the time of surgery, increasing the risk of developing exudative and proliferative reactions. YAG - laser anterior capsulotomy (dissection of the anterior capsule by YAG laser) with the completion of capsulotomy with the help of instrumental method increases the quality of the surgery. Conclusion.To perform anterior capsulorhexis in children with lens subluxation 1 and 2 degrees can be applied a manual and YAG-laser methods, each of which has its advantages and disadvantages.

Новые возможности мониторинга пациентов с миопией

Purpose: to study the changes of axial length and distension of the posterior pole retina of the eye in patients with myopia, using two optical methods: contactless biometrics and optical coherence tomography (OCT). Material and methods. We conducted a combined clinical and instrumental examination of 83 patients (166 eyes) with low and moderate myopia aged 10-19 (ave. 13.8 ± 2.5 years). The examination included the measurement of axial length, using a Lenstar contactless laser biometer Lenstar, and retinal nerve fiber layer (RNFL) thickness using optical coherent tomography (OCT Stratus). 32 patients (64 eyes) with emmetropia aged 7 to 18 (ave. 11.7 ± 2.6 years) served as control. Results. The analysis of contactless biometrics and OCT results collected for 1 year helped specify four clinical groups: Myopia progression, Latent myopia progression, Myopic refractogenesis, and Stable myopia. It was also found that RNFL thickness in different retinal sectors is decreasing unevenly in latent myopia progression. To facilitate the evaluation of myopia progression, a structural indicator of progression was proposed. Conclusion. Progressing myopia monitoring by two modern optical methods: biometrics (for AL) and OCT (for RNFL thickness) enables the detection of changes in the fibrous eye capsule and identification of individual features of myopic progression. For citation: Strakhov V.V., Makhova M.V., Klimova O.N. New opportunities of monitoring patients with myopia. Russian ophthalmological journal. 2018; 11 (3): 30-5 (In Russian). doi: 10.21516/2072-0076-2018-11-3-30-35

Distribution of chemical compounds of Fufang Xueshuantong capsule in eyes and kidney of beagle dogs

Diabetic retinopathy(DR) and diabetic nephropathy(DN) are the most common complications of diabetes, and the main causes of death and disability of diabetes. Clinical reports showed that Fufang Xueshuantong capsule(FXT) had effective curative effect on DR and DN, but there was no report on the distribution of chemical compounds of FXT in beagle dog eyes and kidneys. In this study, FXT was given by gavage administration in Beagle dogs for 3 days, and then their eyeballs and kidneys were taken. The chemical compounds in beagle dog eyes and kidneys were detected by HPLC LTQ-Orbitrap technology. Furthermore, by comparing with the data from retrieving literature and references, the chemical compounds were identified by the accurate mass, retention time (tR), and MS/MS. Fourteen and 19 types of notoginsenosides were respectively identified in eyeballs and kidneys in this study, and these results could lay foundation for clarifying the effective ingredients of FXT in treatment of DR and DN.

Comparative analysis of brilliant blue G and an intracameral illuminator in assisting visualization of the anterior capsule in eyes with vitreous hemorrhage

To compare the safety and efficacy of 0.025mg/mL brilliant blue G (BBG) and an intracameral illuminator for visualizing the anterior capsule. University-based tertiary referral center, South Korea. Retrospective cases series. The medical records of patients with vitreous hemorrhage for which they had pars plana vitrectomy and cataract surgery were retrospectively reviewed. The patients were classified into 2 groups. The BBG group comprised patients having capsule staining with BBG. The illuminator group comprised patients who had capsulorhexis assisted with an intracameral illuminator. The status of the endothelial cells was analyzed. There were 27 eyes in the BBG group and 35 eyes in the illuminator group. In the BBG group, endothelial cell density (ECD) was reduced 3months after surgery (10.6% loss) (P=.003). The illuminator group had no significant loss (1.5% loss) (P=.264). The ECD loss was greater in the BBG group than the illuminator group 3months after surgery (P=.01). There was no statistically significant difference in the coefficient of variation of cell area or percentage of hexagonal cells between the 2 groups. The ECD loss was higher in eyes with 0.025mg/mL BBG staining than in eyes using an intracameral illuminator. Further studies are necessary to establish the safety profile of BBG on the endothelium. None of the authors has a financial or proprietary interest in any material or method mentioned.

Accuracy of 3 imaging modalities for evaluation of the posterior lens capsule in traumatic cataract

To compare the accuracy of 3 imaging modalities for preoperative evaluation of the posterior lens capsule in traumatic cataract. Farabi Eye Hospital, Tehran, Iran. Case series. The study comprised eyes with traumatic cataract opaque enough to prevent visualization of the posterior lens capsule on slitlamp examination. To detect posterior lens capsule rupture before surgery, imaging was performed with 20 MHz echography (Eye Cubed), anterior segment optical coherence tomography (AS-OCT) (Visante model 1000), and Scheimpflug imaging (Pentacam). All patients subsequently had cataract extraction, and the intraoperative findings of the posterior lens capsule were compared with the preoperative findings of the imaging modalities. The study enrolled 21 eyes of 21 patients (20 men, 1 woman) with a mean age of 31.5 years ± 1.45 (SD). The nature of trauma was blunt (5 eyes) or sharp (16 eyes). To detect posterior lens capsule rupture, the sensitivity and specificity were, respectively, 80% and 86% for 20 MHz echography, 71% and 77% for AS-OCT, and 62% and 57% for Scheimpflug imaging (95% confidence intervals: sensitivity, 30.00-90.32; specificity, 54.81-92.95). Insufficient resolution for posterior lens capsule evaluation occurred in 33.3% cases for AS-OCT and 57.1% cases for Scheimpflug imaging. The accuracy of 20 MHz echography, AS-OCT, and Scheimpflug imaging was 76.1%, 61.9%, and 42.9%, respectively. In the evaluation of the posterior lens capsule in eyes with traumatic cataract, 20 MHz echography had higher accuracy than AS-OCT and Scheimpflug imaging. No author has a financial or proprietary interest in any material or method mentioned.

Soft–part preservation in heteromorph ammonites from the Cenomanian–Turonian Boundary Event (OAE 2) in north–west Germany

Abstract: From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north‐west Germany), 17 sediment‐compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstätte, upper jaws and anaptychi of ammonites rank among the commonest fossils.

Surgical approaches to posterior polar cataract: a review

The aim of this study is to provide a comprehensive overview of surgical methods used in the emulsification of posterior polar cataracts (PPCs) that have been devised to minimize the risk of posterior capsule rupture (PCR) and its consequences. A Pubmed and Medline search of relevant literature on PPC was done. Only articles relevant to the treatment of PPC were included. The posterior capsule in eyes with PPC are known to have an abnormal adhesion to the polar opacity or a pre-existing weakness of the capsule that predisposes the eye to PCR. To circumvent the consequences of cleaving the abnormal adhesion, a majority of the surgeons use the anterior approach through the limbus, whereas some advocate the posterior approach through the pars plana. Emulsifying the nucleus and cleaving the central opacity of the PPC off the posterior capsule without disrupting its integrity provides optimal surgical outcomes. To achieve this, various modifications have been applied by surgeons during different phases of surgery. The advantages, disadvantages, complications, and results of each method have been discussed. Phacoemulsification is the preferred technique for removing PPC. This review will provide methods to avoid and /or deal with intraocular surgical difficulties that can arise during emulsification. Employing these would result in least ocular morbidity and satisfactory visual outcomes for the patient. This is particularly relevant given the major advancements in technology and refinements in surgical techniques in phacoemulsification.

Experimental study on effects of matrix metalloproteinase inhibitor on posterior capsule opacification in rabbits

To determine whether matrix metalloproteinase (MMP) inhibitor can provide therapeutic effects for rabbits posterior capsule opacification in vivo and to observe the side effects of this drug on surrounding intraocular structures. Experimental research. New Zealand white rabbits were undertaken phacoemulsification operation. GM6001 at different concentrations (100, 200 and 500 µmol/L) and GM6001 negative control liqueur were infused into the capsule bags of the rabbits at the end of operation and two days after the operation. The incidence of posterior capsule opacification was assessed and the histological sections of posterior capsules were observed under microscope 12 weeks after the surgery. The anterior chamber response was observed on day 2 post-operatively. The changes of intraocular pressure were measured by day 2 and day 7. Corneal endothelial cells were observed under scanning electron microscope and iris, ciliary body and retina were observed under microscope on day 7. GM6001 significantly prevented posterior capsule opacification (P = 0.007). No opacification occurred on the rabbit posterior capsule in eyes with 200 and 500 µmol/L GM6001 on week 12 post-operatively in vivo. No cells were found on posterior capsule in 500 µmol/L group, whereas lens epithelial cells and fibroblasts were found in the controls under microscope. No difference of anterior chamber flare between the eyes with GM6001 at different concentrations and the control group (P = 0.380) by day 2 after the operation. The intraocular pressure in eyes with GM6001 was the same as that in the control 2-days (F = 0.642, P = 0.597) and 7-days (F = 0.179, P = 0.909) post-operation. The corneal endothelial cells in eyes with 500 µmol/L GM6001 arranged regularly and did not show any difference from that in the control eyes under scanning electron microscope 7-day after the operation. The iris, ciliary body and retina in eyes with 500 µmol/L GM6001 were normal in appearance 7-day after the operation. MMP inhibitor can prevent posterior capsule opacification effectively in rabbits in vivo and does not cause damage to surrounding intraocular structures, suggesting that MMP inhibitor may become a medication used for the prevention of lens posterior capsule opacification.

Bionic soft crystalline lens materials for MEMs applications based on self-assembling amphiphilic block copolymer/nanoparticle hybrids

In this study, a biomimetic crystalline lens with properties that combine the softness of a hydrogel comparable to that of a human lens for adjustable focus and the property for image aberration correction with gradient refractive index (GRIN) was developed by the self-organization of an amphiphilic block copolymer blended with high refractive index titanium nanoparticles (TiO2). The hydrogel lens was prepared by using a thermally responsive poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PPO–PEO–PPO) triblock copolymer (Poloxamer 407) with the lower-critical solution temperature (LCST) property that can be injectable into the eye capsule as a liquid below its LCST and solidifies as a soft gel above the LCST at the human body temperature. By chemical modification of the triblock copolymer with double bonds on its chain-ends (Poloxamer 407A), the soft lens network can be made by using UV crosslinking of the hydrogel. To further increase the refractive index (RI) of the hydrogel lens network and to match its RI to that of the human lens (=1.41), highly visible-light transparent titanium dioxide (TiO2) nanoparticles were introduced into the hydrogel lens network. To create a biomimetic GRIN lens as in the human’s eyes, an electric field method was also used to induce an axial diffusion of TiO2 nanoparticles from the center of the lens where TiO2 nanoparticles were first injected to the edge. The above method demonstrates the potential to use the hydrogel/nanoparticle hybrid as an injectable replacement for a soft optical lens system with an adjustable focus for future MEMs application.

Transmission electron microscopy of the rabbit posterior capsule irrigated with thapsigargin and 5-fluorouracil in a sealed-capsule irrigation device

To investigate, by transmission electron microscopy (TEM), the effect on the posterior capsule of a young rabbit eye of 5-fluorouracil (5-FU) or thapsigargin in a sealed-capsule irrigation device. St Erik's Eye Hospital, Stockholm, Sweden. Clear lens extraction was performed unilaterally in eight 4-week-old rabbits. A sealed-capsule irrigation device was irrigated for 2 min with 20 ml of one of the following: balanced salt solution (BSS; n=2), thapsigargin 300 muM (n=2), 5-FU 50 mg/ml (n=2), or 5-FU 25 mg/ml (n=2). The substances were washed out for 10 s with BSS. The eyes were left aphakic. Six weeks postoperatively, the animals were killed, and the posterior capsule was extracted and fixed for TEM. As a control, we also evaluated the capsules from the two fellow eyes in the BSS group that did not undergo surgery. The ultrastructure of the posterior capsule in eyes irrigated with 5-FU or thapsigargin did not differ from that in the eyes irrigated with BSS or in the eyes that did not have surgery. The membranes had the same ultrastructure with thin collagen fibres on the anterior and posterior face of the posterior capsule and an amorphic matrix. Thapsigargin or 5-FU used in a sealed-capsule irrigation device does not seem to harm the posterior capsule, which appeared similar to when the capsule is irrigated with BSS.

Fine structure of the lateral eyes in the tiny marine Antarctic mite Halacarellus thomasi : an ultrastructural study

The lateral eyes of the tiny marine /-Vntarclic mite, Halacarellus iliomasi, consist of two entities in the same eye capsule. The oplical axes of the two eyes point in different directions and the two eyes are of different sizes- The larger of the two is covered by a circular lens of approximately 13 |im diameter, with considerably greater inner than outer convex curvature. The cover of the smaller eye consists of little else than a circular 10-).m'i-\vide transparent patch of cuticle. Both eyes have an everted retina with few (4-6) retinula cells, and their microvilli, which are oriented perpendicular to the light' path, have diameters of 55 nm. Screening pigments in the form of lipid-like, electron-opaque cell inclusions, measuring 1-2 um in size, are abundant on the proximal side of the retina. A small l-)im-thick muscle is in con­ tact with the eye capsule. On the basis of our structural data and comparisons with other mite species, we con­ clude that form, colour and polarization vision would play no role in the eye of /-/, ihouiasi. More likely, (he function of the eye is to monitor seasonal daylength changes to allow synchronization of reproductive activities.

Preservation of anterior capsule during vitrectomy and lensectomy for retinal detachment with proliferative vitreoretinopathy

Purpose To report a series of 15 eyes with rhegmatogenous retinal detachment and proliferative vitreoretinopathy (PVR) or at high risk for advanced PVR, which underwent pars plana vitrectomy (PPV) and lensectomy (PPL) with preservation of the anterior capsule. Design Retrospective noncomparative case series. Participants Fifteen consecutive patients with retinal detachment and varying degrees of PVR in one eye. Methods All eyes had undergone PPV and PPL with preservation and polishing of the anterior capsule and had at least 6 months of follow-up. Of the 15 eyes, grade C PVR was present preoperatively in 11 and was anterior in 5. Seven of 15 eyes had gas and 8 of 15 had silicone oil tamponade. Eight of 15 eyes had subsequent posterior chamber intraocular lens (PCIOL) placement; 5 eyes had simultaneous silicone oil removal. One eye had a PCIOL placed at the time of the PPL. Main outcome measures Visual acuity, retinal reattachment, complications of gas or silicone oil tamponade, and anterior capsular clarity. Results Fourteen eyes had complete retinal reattachment at the final visit (1 of 15 had macular redetachment only). Final visual acuity was better or equal to preoperative acuity in all eyes, improving by 4 ± 4 lines overall. No eyes had corneal decompensation, pupillary block, or other vision-threatening anterior segment complication. The anterior capsule remained centrally clear in the 13 eyes that did not have a primary central capsulotomy. One eye with minimal preoperative PVR developed hypotony. Conclusions Vitreoretinal surgeons can preserve the anterior capsule in eyes with retinal detachment and PVR to help prevent intraoperative and postoperative complications of gas or silicone oil, simplify future PCIOL placement, and maintain a normal iris appearance.

Survey of large branchiopods on Aruba and observations on taxonomic characters in Leptestheria (Spinicaudata)

A survey of more than 60 ephemeral pools during March 1989 resulted in finding three large branchiopods not previously known to occur on the Caribbean Island of Aruba. These were two Anostraca, Dendrocephalus spartaenovae Margalef, 1967 and Thamnocephalus venezuelensis Belk & Pereira, 1982, and one Spinicaudata, Leptestheria venezuelica Daday, 1923. The notostracan previously reported from Aruba, Triops longicaudatus (LeConte, 1846), was also collected from several pools. All of these species occur also in Venezuela, which is separated from Aruba by an ocean gap of about 25 km. Comparison of Leptestheria venezuelica with Leptestheria compleximanus (Packard, 1877) demonstrated that cephalic morphology provides useful taxonomic features including length of rostrum, depth of occipital notch, shape of the occipital region, and protrusion of the eye capsule. These features may prove useful in studying other species of Leptestheria.

Directional filtering in edge detection

Two-dimensional (2-D) edge detection can be performed by applying a suitably selected optimal edge half-filter in n directions. Computationally, such a two-dimensional n-directional filter can be represented by a pair of real masks, that is, by one complex-number matrix, regardless of the number of filtering directions, n. Specific calculations of the edge strength were conducted using a 2-D tridirectional filter based on a Petrou-Kittler one-dimensional (1-D) detector optimized for the ramp edges, which are characteristic of posterior eye capsule images that were used here as a test set. In applications to image segmentation, tridirectional filtering results in co-occurrence arrays of low dimensionality.

Light and scanning electron microscopy of rabbit lens capsules with intraocular lenses

Purpose: To examine postoperative changes in the lens capsules of rabbit eyes after phacoemulsification and aspiration of the crystalline lens and implantation of posterior chamber intraocular lenses (IOLs) using light and scanning electron microscopy.Setting: Research Laboratory, Department of Ophthalmology, Wakayama Medical College, Japan.Methods: The crystalline lens was emulsified and aspirated and an IOL implanted in the capsular bag or ciliary sulcus of each eye in adult albino rabbits under general anesthesia. Animals were killed after 4 weeks, and the lens capsules were removed. The specimens were observed under phase-contrast microscopy and processed for light and scanning electron microscopy.Results: Phase-contrast microscopy revealed presumed lens epithelial cells (LECs) on the central posterior capsules in association with regenerating lenticular fibers and Elschnig pearls in the peripheral capsules. Scanning electron microscopy showed the accumulation of fibrous extracellular matrix on the surface of the posterior capsule in eyes in which the IOL was implanted in the ciliary sulcus. Deposition of packed material attached to the surface of IOLs and of Soemmering's ring were observed in eyes with in-the-bag IOL fixation. At a higher magnification, a parallel arrangement of lenticular fibers was seen in the regenerated lens structure on posterior capsules. An identical structure was observed under light microscopy. Outgrowth of presumed LECs from residual anterior lens capsules and adhesion of macrophages and giant cells were observed on the IOL surface.Conclusion: Two types of postoperative changes were observed in lens capsules after implantation of IOLs: accumulation of fibrous extracellular matrix and newly formed lenticular fibers. These changes are attributed to the proliferation of LECs and can induce posterior capsule opacification after IOL implantation.

Soft anatomy and the affinities of conodonts

Recent claims that conodonts are members of the Craniata or Vertebrata are based in part upon soft tissue features that have been preserved in a small number of specimens. These features include what appear to be radials in the caudal fin and paired structures that have been identified as eye remnants. The evidence for radials is limited, but credible. However, the anatomy of extant cyclostomes suggests that the paired structures are more reasonably interpreted as otic capsules than the remnants of sclerotic eye capsules. Moreover, even if these structures are the remnants of eyes, conodonts might equally well be a sister group to the craniates as a member of that group. Aside from these paired structures, conodont fossils exhibit no features that are suggestive of a cartilaginous skeleton. Given that cyclostome fossils sometimes show evidence of the cartilages of the head, the apparent absence of a similar skeleton in conodont animals calls into question the claim that they are craniates. The simple single chevron shape of conodont myomeres also suggests that they lie outside of the Craniata. All living craniates have double-chevron myomeres as adults, whereas simple myomeres of the conodont type are found in the non-craniate cephalochordates. Thus the available soft tissue evidence suggests that conodonts are best regarded as the sister group of the craniates.

A truncated bone morphogenetic protein 4 receptor alters the fate of ventral mesoderm to dorsal mesoderm: roles of animal pole tissue in the development of ventral mesoderm.

The biological effects of endogenous bone morphogenetic protein 4 (BMP-4), a member of the transforming growth factor beta family, on embryonic development of Xenopus laevis were investigated by using a functionally defective mutant of the BMP-4 receptor (delta mTFR11), which blocks the BMP signaling pathway. Injection of delta mTFR11 RNA into either the animal pole area or ventral marginal cells at the two-cell stage induced a dorsal phenotype in the explant of ventral mesoderm with animal pole tissue from stage 10+ embryo, even though the normal fate of this explant is a "mesenchymal ball" containing blood cells. These explants with the dorsal phenotype contained muscle, neural tissue, eye capsule, and cement gland. Northern blot analysis showed an increase of cardiac alpha-actin mRNA and a decrease of T alpha-globin mRNA expression, providing further evidence of a conversion from ventral to dorsal phenotype. Although injection of delta mTFR11 RNA did not induce mesoderm in an animal cap culture, the same tissue injected with delta mTFR11 RNA can alter the differentiation fate of uninjected ventral mesodermal explant from ventral to dorsal type, suggesting specific interaction of animal pole tissue and prospective ventral mesoderm in vivo.