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PubMed2001

Glycosaminoglycan synthesis in the separate layers of the chick sclera during myopic eye growth: comparison with mammals.

PURPOSE: Studies in animal models of refractive development have shown that the development of and recovery from induced myopia is associated with visually-guided changes in scleral glycosaminoglycan synthesis. The present study sought to determine whether differential patterns of scleral glycosaminoglycan synthesis are present in the fibrous scleral layer of the chick during myopia development or recovery, as has previously been reported in the mammalian sclera. METHODS: Myopia was induced in young chicks by monocular deprivation of pattern vision over 5 days. Other animals underwent monocular deprivation, then had the occluder removed and were allowed 2 days of recovery. A group of age-matched normal animals served as a control. Newly synthesised glycosaminoglycans in the scleral layers were labelled in vivo, using a [(35)S]-labelled precursor delivered intraperitoneally on the final experimental day. Incorporation of this sulphate into glycosaminoglycans of the fibrous and cartilaginous scleral layers was assessed in proteinase K digests by selective precipitation with alcian blue. RESULTS: Glycosaminoglycan synthesis in the fibrous scleral layers of myopic and recovering eyes was not significantly different to contralateral control eyes (+14 +/- 7%, p = 0.09 and -2 +/- 4%, p = 0.64 respectively). In contrast, glycosaminoglycan synthesis was significantly elevated, relative to controls, in the cartilaginous scleral layer of eyes developing myopia (+63 +/- 18%, p < 0.02), whereas in recovering eyes there was found to be a significant decrease in synthesis in the cartilaginous layer (-40 +/- 6%, p < 0.001). CONCLUSIONS: The results of the current study demonstrate that the fibrous scleral layer of the chick does not display the characteristic differential patterns of glycosaminoglycan synthesis that are found in the mammalian sclera during myopia development and recovery. However, as has previously been reported, the cartilaginous layer of the chick sclera does display differential glycosaminoglycan expression, although the direction of regulation is opposite to that found in the fibrous sclera of mammals.

Animals↗
PubMed2004

Influences of osmotic agents in diffusion layer on drug release from multilayer coated pellets.

Nonpareil beads were coated with three different functional layers, namely inner chlorpheniramine maleate-loaded hydroxypropylmethylcellulose (HPMC, 4 mPa x s) deposition layer, middle HPMC (400 mPa x s) diffusion layer, and outer polyacrylic polymer (Eudragit RS30D) retention layer. The osmotic agents, including sodium chloride, glycine, citric acid, and disodium hydrogen phosphate, were incorporated in different amounts into the diffusion layer and the influences on drug release were studied. The osmotic agent competed with HPMC for imbibed water and subsequently caused more water influx owing to the osmotic pressure gradient. An appropriate amount of osmotic agent in the diffusion layer was necessary to exert its effect on retarding drug release. The osmotic effect on drug release was compromised with pellets at a higher coating level of the diffusion layer due to the extensive swelling and rupture of coat. The release parameters, including dissolution T50% and mean dissolution time, showed linear relationship with osmolalities of osmotic agents studied. The effect of the osmotic agent in the diffusion layer played an important role in determining the unique multiphase drug release profiles, particularly in the initial phase of dissolution, and reduced with depletion of the osmotic agent in the later phase of dissolution.

Acrylic Resins↗
PubMed1985

Light-evoked increases in extracellular K+ in the plexiform layers of amphibian retinas.

Recordings of light-evoked changes in extracellular K+ concentration (delta[K+]o) were obtained in the retinas of frog and mudpuppy. In eyecup preparations, various recording approaches were used and provided evidence for a K increase near the outer plexiform layer (distal K increase). This distal K increase could be pharmacologically dissociated from the well-known, large K increase in the proximal retina by the application of ethanol and gamma-aminobutyric acid. The distal K increase also often showed surround antagonism. A retinal slice preparation was used to permit electrode placement into the desired retinal layers under direct visual control and without the risk of electrode damage to adjacent layers. In the slice, a distinct distal K increase was found in the outer plexiform layer, in addition to the prominent K increase in the inner plexiform layer. Compared with eyecups, only weak K increases were found in the nuclear layers of the slice. This suggests that the K responses observed in the nuclear layers of eyecups may be generated by K+ diffusing along the electrode track from the plexiform layers. In the context of current models of ERG b-wave generation, the magnitude of the recorded distal K increase, compared with the proximal K increase, seems too small to give rise to the b-wave. However, the distal K increase may be differentially depressed by electrode dead space. It is also possible that if certain aspects of the models of b-wave generation were modified, then the observed distal K increase could give rise to the b-wave.

Animals↗
PubMed2005

A four-layer attenuation compensated PET detector based on APD arrays without discrete crystal elements.

Scintillation detectors developed for PET traditionally use relatively thick crystals coupled to photomultiplier tubes. To ensure good efficiency the crystals typically measure between 10 and 30 mm thick. Detectors also require good spatial resolution so the scintillator is normally made up of a densely packed array of long thin crystals. In this paper, we present a novel design in which the detection crystal is divided into a number of layers along its length with an avalanche photo diode (APD) inserted between each layer. With thin layers of crystal, it is possible to use a continuous rather than a pixelated crystal. The potential advantages of this design over a conventional PMT-based detector are: (i) improved light collection efficiency, (ii) reduced dependency on dense crystal to achieve good stopping power, (iii) ease of crystal manufacture, (iv) reduced detector dead-time and increased count rate, and (v) inherent depth of interaction. We have built a four-layer detector to test this design concept using Hamamatsu S8550 APD arrays and LYSO crystals. We used the centre 16 pixels of each of the arrays to give an active area of 9.5 mm x 9.5 mm. Four crystals 9.5 mm x 9.5 mm were used with thickness increasing from 2 mm at the front to 2.5 mm, 3.1 mm and 4.3 mm at the back, to ensure a similar count rate in each layer. Calculations for the thickness of the four layers were initially made using the linear attenuation coefficient for photons at 511 keV of LYSO. Experimental results and further simulation demonstrated that a correction to the thickness of each layer should be considered to take into account the scattered events. The energy resolution for each of the layers at 511 keV was around 15%, coincidence-timing resolution was 2.2 ns and the special resolution was less than 2 mm using a statistical-based positioning algorithm.

Crystallization↗
PubMed2001

The effects of aging on layer 1 of primary visual cortex in the rhesus monkey.

The effect of age on layer 1 in primary visual cortex was determined in 19 rhesus monkeys of various ages. Twelve of the monkeys had been behaviorally tested. With age layer 1 becomes thinner and the glial limiting membrane becomes thicker. In the neuropil of layer 1 many of the dendrites in old monkeys appear to be degenerating and, as a consequence, electron micrographs from old monkeys display fewer dendritic and spine profiles per unit area than in young monkeys. As determined using both the disector and size-frequency methods, there is also a concomitant decrease in the numerical density of synapses with age. Although there is a significant correlation between the thinning of layer 1 in area 17 and age, there is no significant correlation between either the thinning of layer 1 or its loss of synapses and any of the behavioral measures of memory function obtained from the 12 behaviorally tested monkeys. Similar morphological changes with age occur in layer 1 of prefrontal cortex of these same monkeys, but in area 46 both the thinning of layer 1 and the loss of synapses show a significant correlation with behavioral measures of memory function. These differences between layer 1 in these two cortical areas presumably relate to the fact that prefrontal cortex has a greater role in subserving cognition than does primary visual cortex.

Aging↗
PubMed2003

Emerging complexity of layer I in human cerebral cortex.

In this study we examine possible origins and migratory routes of human cortical neurons, with special emphasis on the preplate and layer I. In embryonic stages, two main cell types, Cajal-Retzius cells, and cells labeled with interneuron markers (calretinin, calbindin and GABA), were present in the preplate layer. In addition, a number of preplate GABAergic cells co-expressed either Nkx2.1 or Dlx transcription factors, findings consistent with their origin in the ganglionic eminence and subsequent tangential migration to the layer I. The orientation of the leading process indicates that some of these cells descend to the cortical plate. However, the finding of radially oriented GABAergic, NKX2.1+ and DLX+ cells in the cortical ventricular zone, argues that, unlike in rodents, a significant subpopulation of these cells originates in the cortical ventricular zone. In embryonic stages, expression of Reelin in Cajal-Retzius cells as well as Reelin/DLX2+ cells in the embryonic ganglionic eminence and the olfactory region, suggest that these cells in human may have diverse origins. In later fetal stages in human (17-22 gestational weeks) layer I and the newly formed subpial granular layer, contained a population of small interneurons that originated mainly in the lateral ganglionic eminence, since the majority of these cells were double-labeled with DLX/GABA, and rarely with NKX2.1/GABA. Therefore, neurons in the human cortical layer I are heterogeneous, with more complex origin and migratory routes than in rodents. In addition to the ganglionic eminence, both the expended subventricular zone and subpial granular layer, contribute to the neuronal population of the developing layer I and underlining cortical plate.

Cerebral Cortex↗
PubMed2006

Comparative analysis of layer-specific genes in Mammalian neocortex.

We examined the expression patterns of 4 layer-specific genes in monkey and mouse cortices by fluorescence double in situ hybridization. Based on their coexpression profiles, we were able to distinguish several subpopulations of deep layer neurons. One group was characterized by the expression of ER81 and the lack of Nurr1 mRNAs and mainly localized to layer 5. In monkeys, this neuronal group was further subdivided by 5-HT2C receptor mRNA expression. The 5-HT2C(+)/ER81(+) neurons were located in layer 5B in most cortical areas, but they intruded layer 6 in the primary visual area (V1). Another group of neurons, in monkey layer 6, was characterized by Nurr1 mRNA expression and was further subdivided as Nurr1(+)/connective tissue growth factor (CTGF)(-) and Nurr1(+)/CTGF(+) neurons in layers 6A and 6B, respectively. The Nurr1(+)/CTGF(+) neurons coexpressed ER81 mRNA in monkeys but not in mice. On the basis of tracer injections in 3 monkeys, we found that the Nurr1(+) neurons in layer 6A send some corticocortical, but not corticopulvinar, projections. Although the Nurr1(+)/CTGF(-) neurons were restricted to lateral regions in the mouse cortex, they were present throughout the monkey cortex. Thus, an architectonic heterogeneity across areas and species was revealed for the neuronal subpopulations with distinct gene expression profiles.

Animals↗
PubMed2004

Comparison between broilers and layers for growth and protein use by embryos.

Three experiments were conducted to compare the growth and protein utilization of embryo between broilers and layers. In experiments 1 and 2, the average weight of eggs was the same for broilers and layers. Nothing or an amino acid (AA) solution was injected into the eggs of broilers at d 7 of incubation, and the plasma AA concentration of newly hatched chicks was determined in broilers in experiment 1. In experiment 2, the same treatments as experiment 1 were used on layer breeder eggs. Plasma Tau, Thr, and Lys concentrations of hatched chicks increased when AA solution was injected in broilers breeder eggs (P < 0.05) but not in layers (P > 0.05). The AA ratio to Lys was reduced by AA injection in broilers but not in layers. In experiment 3, weights of embryos and egg were recorded, and CP contents were analyzed over time during incubation (d 0, 7, 14, and 19 of incubation) in broilers and layers using eggs of the same weight. There were no differences in the weights and CP contents of embryos and eggs from broilers and layers. On d 14 and 19 of incubation, weights and CP contents of embryo were higher in broilers than layers (P < 0.05). These results suggested that the egg protein content might be adequate for hatching but insufficient for maximum growth of embryos from broilers.

Amino Acids↗
PubMedDate not supplied

Reconstruction of a hybrid vascular graft hierarchically layered with three cell types.

Hybrid grafts with hierarchically incorporated endothelial cells (ECs), smooth muscle cells (SMCs), and fibroblasts (FCs), were developed, and the cellular behavior and ultrastructure of the regenerated extracellular matrix (ECM) of the grafts were investigated in vivo. Two models of hybrid vascular grafts were constructed on knitted Dacron grafts (internal diameter, 4 mm; length, 6 cm) in vitro. Model I grafts were hierarchically structured with a confluent monolayer of ECs, a middle layer of SMCs, and an outer layer of FCs. Model II consisted of a confluent EC monolayer and a homogeneously mixed layer composed of SMCs and FCs prelabeled with fluorescent lipids. The designed artificial ECM was a mixed gel of type I collagen and dermatan sulfate. Both grafts were implanted bilaterally in the carotid arteries of 11 dogs for up to 12 weeks without anticoagulant. Regardless of model type, patent grafts (n = 18 of 22 implanted grafts) were completely endothelialized. In model II grafts at 4 weeks, SMCs migrated to the subendothelial layer, whereas labeled FCs migrated to an outer layer. Observation of model I grafts at 12 weeks showed that most of the collagen fibers in the luminal surface layer were longitudinally oriented, but those in deeper layers tended to orient circumferentially, and that newly generated elastic tissues were composed of many concentric laminae. SMCs of both grafts at 12 weeks were predominantly of the contractile phenotype. Thus, hybrid grafts incorporating intimal-, medial-, and adventitial-type layers can enhance the process of arterial wall reconstruction.

Animals↗
PubMed2000

Bowman's layer structure and function: critical or dispensable to corneal function? A hypothesis.

PURPOSE: The purpose of this article is to review available information regarding development, structure, and function of Bowman's layer in the cornea. Disease-related abnormalities of Bowman's layer are described. A hypothesis is advanced to explain the development and maintenance of Bowman's layer. METHODS: Literature review and hypothesis formulation based on previous studies. RESULTS: Information is presented that supports the hypothesis that Bowman's layer forms as a result of cytokine-mediated interactions occurring between corneal epithelial cells and keratocytes that include chemotactic and apoptotic effects on the keratocytes. This hypothesis suggests that Bowman's layer results from such interactions beginning in early development and continuing into adulthood in humans and other animals, such as chickens. CONCLUSIONS: Bowman's layer may be a visible indicator of ongoing stromal-epithelial interactions in the human and have no critical function in corneal physiology. Bowman's layer is commonly destroyed in diseases such as advanced bullous keratopathy where stromal-epithelial interactions may be interrupted. Bowman's-like layers often form in response to epithelium, for example when epithelial plugs extend into the stroma in corneas with radial keratotomy incisions.

Animals↗
PubMedDate not supplied

Two-phase helical CT for detection of early gastric carcinoma: importance of the mucosal phase for analysis of the abnormal mucosal layer.

PURPOSE: To evaluate the efficacy of two-phase dynamic helical computed tomography (CT), including the gastric mucosal phase, for detection of early gastric carcinoma with typical hyperattenuating and atypical nonhyperattenuating enhancement patterns. METHOD: Two-phase helical CT scanning was performed using the water-filling method as negative oral contrast material for 212 patients with proven adenocarcinoma on endoscopic biopsy. Two gastrointestinal radiologists prospectively analyzed the focal alterations of the inner hyperattenuating mucosal layer and the outer hypoattenuating layer before the information obtained at barium study and pathologic examination was available. The first, so-called mucosal phase was obtained at 38-45 seconds after the start of intravenous injection of contrast material for a total of 150 ml/sec at a rate of 4 ml/sec to obtain maximum enhancement of the inner mucosal layer. The second delayed phase was obtained at 3 minutes. RESULTS: Fifty-four cases of early gastric cancer were suspected on two-phase helical CT preoperatively. Postoperatively, 49 cases of early gastric cancer were pathologically confirmed. The detection rate for the typical hyperattenuating early gastric cancer, that is the type I enhancement pattern defined as the localized thickening of the inner hyperattenuating layer, using two-phase helical CT was 18% (9/49 patients). The type 2 enhancement pattern, defined as the focal interruption of the inner hyperattenuating mucosal layer without abnormal enhancement of the outer hypoattenuating layer on the mucosal phase, was seen in 15 cases. These were pathologically confirmed as early gastric cancer IIb + IIc (three patients), IIc (four patients), IIc + IIa (one patient), IIc + III (three patients), IIb + IIc (one patient), and advanced cancer (T2) lesions (three patients). The type 3 enhancement pattern was defined as the focal polypoid protrusion of the inner hyperattenuating layer without abnormal enhancement of the outer thickened hypoattenuating layer on the mucosal phase, and was seen in seven patients who were pathologically confirmed with early gastric cancer IIb + IIc (three patients), IIc + IIa (one patient), and IIc + lIb (three patients). The lesions became less distinct on the delayed phase. Five T2 advanced gastric cancers were falsely interpreted as early gastric cancer. The detection rate for early gastric cancer after considering type 2 and 3 atypical enhancement patterns was increased to 57% (28/49 patients). CONCLUSION: Helical CT with two-phase scan including the mucosal phase was efficient for identifying the enhancement patterns of early gastric cancer.

Adenocarcinoma↗
PubMed2001

Oronasal fistula repair with three layers.

We present an innovative method for closure of oronasal fistulas involving a three-layer repair, consisting of septal mucosa flap, bone or cartilage graft, and palatal mucosa flap. The septal mucosa flap closes the nasal side of the defect. This is an inferiorly based flap along the nasal floor and consists of septal mucosa from the side opposite the oronasal fistula. A slit is created in the remaining layers of the nasal septum, allowing the flap to be delivered into the defect. When the septal flap is folded down in this fashion, it exposes nasal septal bone and cartilage. The bone and cartilage are harvested and are used to create the middle layer of the three-layer fistula repair. The oral layer of the repair is provided by a palatal mucosa transposition flap. This method allows the bone/cartilage graft to be sandwiched between two vascular layers. We have successfully used the three-layer repair on three patients. All of the oronasal defects were 2 cm in size. All patients are at least 1 year after repair with 100 percent closure; thus, no oronasal leakage. The flaps both septal and palatal resulted in no morbidity once healed. Specifically, the surgically created slit in the nasal septum is well mucosalized and barely discernible. Also, no nasal obstruction occurs from the septal flap on the floor of the nose. We perform the procedure on an outpatient basis. The three-layer repair can be used in adult patients with oronasal fistulas of the middle and posterior hard palate up to 3 cm in size. This technique is not recommended for children.

Aged↗
PubMed2001

Senile schisis detachment with posterior outer layer breaks.

BACKGROUND: Senile retinoschisis with associated retinal detachment in the presence of multiple or large posterior outer layer breaks is rare. Despite many and significant developments in vitreoretinal surgery for this situation, no definitive therapeutic guidelines exist. In an observational study three different approaches performed by two of the authors are presented. METHODS: Eighteen eyes of 18 patients with symptomatic schisis detachment and large posterior outer layer breaks were analyzed retrospectively. The fovea was detached in six eyes. Four eyes had laser photocoagulation and/or transscleral cryopexy (Group I), and five eyes had extensive scleral buckling (Group II). In nine eyes primary vitrectomy and gas endotamponade were performed, including inner layer resection in two eyes (Group III). The median follow-up period was 13 months. RESULTS: Initial anatomic success, which was defined as complete reattachment of the outer retinal layer, was achieved in two of four eyes of Group I, in four of five eyes of Group II, and in seven of nine eyes of Group III. Inner layer separation persisted in 11 of 16 eyes. Visual acuity improved in 3 of 18 eyes, remained unchanged in 9 of 18 eyes, and worsened in 6 of 18 eyes. Complications included in Group I were persistent outer retinal layer detachment (two eyes); in Group II, proliferative vitreoretinopathy (PVR) detachment (one eye), CME (one eye), diplopia (one eye), late redetachment (one eye); in Group III, secondary rhegmatogenous detachment (one eye) PVR detachment (two eyes), macular pucker (one eye), preexisting CME (two eyes), subretinal perfluorocarbon liquid (one eye), transient central serous detachment (one eye), and nuclear sclerosis (five of eight eyes). CONCLUSION: Photocoagulation alone may be considered a first approach in selected cases of schisis detachment complicated by large posterior outer layer breaks. By use of present surgical techniques, today pars plana vitrectomy is the most rational approach allowing an exact evaluation of the complex retinal architecture, a controlled coagulation, and an adequate tamponade of the involved area. Resection of the inner layer seems to increase the risk for epiretinal membrane formation.

Adult↗
PubMed1999

Attachments of the posterior layer of lumbar fascia.

STUDY DESIGN: Superficial and deep laminae of the posterior layer of lumbar fascia were dissected. The lumbar portion was measured for evidence of segmental thickenings. Superior attachments were dissected, documented, and photographed. OBJECTIVES: To verify the existence of posterior accessory ligaments and establish the superior attachments and fiber angles of the posterior layer of lumbar fascia. SUMMARY OF BACKGROUND DATA: There have been two small dissection studies on the posterior layer. Their findings are conflicting in several areas of clinical significance. Thickenings in the lumbar region were described in one study, but have not been verified. The superior attachments of the posterior layer have not been formally documented. METHODS: Study 1: In 21 embalmed cadavers, the lumbar region of the posterior layer was dissected. The lumbar spinous processes and adjacent fascia were marked. The fascia was removed and examined, and its thickness measured with a manual micrometer. Results were statistically analyzed. Study 2: Superior attachments of the posterior layer in 20 cadavers were dissected and photographed. Capacity to transmit tension was estimated and documented photographically, and fiber angles measured in situ. RESULTS: Study 1: There was no evidence of macroscopic segmental thickening in the posterior layer. Study 2: The superficial lamina was continuous superiorly with the rhomboids, and the deep lamina with the tendons of splenius cervices and capitis. These previously undocumented attachments were of variable thickness and fibrosity, and capable of transmitting tension. CONCLUSIONS: Both superficial and deep laminae of the posterior layer are more extensive superiorly than previously thought. This may have implications for certain tests used in assessment and management of low back pain such as the slump and "nonorganic" tests. The thickness of the superior attachments is variable. Their capacity for load bearing is yet to be quantified.

Aged↗
PubMed2003

Evaluation of retinal nerve fiber layer thickness in the area of apparently normal hemifield in glaucomatous eyes with optical coherence tomography.

PURPOSE: The authors investigated the correlation between visual field defects detected by automated perimetry and the thickness of the retinal nerve fiber layer measured with optical coherence tomography, and examined whether there is a decrease in retinal nerve fiber layer thickness in the apparently normal hemifield of glaucomatous eyes. PATIENTS AND METHODS: Forty-one patients with glaucoma and 41 normal control subjects were included in this study. Statistical correlations between the sum of the total deviation of 37 stimuli of each hemifield and the ratio of decrease in retinal nerve fiber layer thickness were evaluated. The statistical difference between the retinal nerve fiber layer thickness of the apparently normal hemifield in glaucomatous eyes and that of the corresponding hemifield in normal subjects was also evaluated. RESULTS: There was a statistically significant correlation in the sum of the total deviation and retinal nerve fiber layer thickness decrease ratio (superior hemifield, P = 0.001; inferior hemifield, P = 0.003). There was no significant decrease in retinal nerve fiber layer thickness in the area that corresponded to the normal visual field in the hemifield defect with respect to the horizontal meridian in glaucomatous eyes (superior side, P = 0.148; inferior side, P = 0.341). CONCLUSIONS: Optical coherence tomography was capable of demonstrating and measuring retinal nerve fiber layer abnormalities. No changes in the retinal nerve fiber layer thickness of the apparently normal hemifield were observed in glaucomatous eyes.

Adult↗
PubMed2005

Mammary ducts with and without focal myoepithelial cell layer disruptions show a different frequency of white blood cell infiltration and growth pattern: implications for tumor progression and invasion.

The authors' previous studies revealed that a subset of ductal carcinoma in situ (DCIS) contained focally disrupted myoepithelial (ME) cell layers and basement membrane (BM). As the disruption of these two structures is a prerequisite for tumor invasion, and white blood cells (WBCs) contain digestive enzymes capable of degrading both the BM and damaged host cells, this study was designed to assess the possible roles of WBC in ME cell layer disruptions and tumor invasion. A total of 23 DCIS containing ducts with focally disrupted ME cell layers were selected from 94 such cases identified in the authors' previous studies. Two consecutive sections from each case were double immunostained, one with leukocyte common antigen (LCA) plus smooth muscle actin (SMA) and the other with Ki-67 plus SMA. Ducts lined by at least 50 epithelial cells and distinct ME cell layers were examined. A total of 191 duct cross-sections were found to contain focal ME cell layer disruptions; of these, 186 (97.4%) were with and 5 (2.6%) were without WBC infiltration. Of 207 morphologically similar sections without ME disruptions, 46 (22.2%) were with and 161 (77.8%) were without WBC infiltration. Ki-67-positive cells in ducts with focally disrupted ME cell layers were generally subjacent to ME cell layers, and more than 30 clusters of multiple proliferating cells were seen directly overlying or near focally disrupted ME cell layers. In contrast, Ki-67-positive cells in ducts without ME disruptions were scattered over the entire epithelial compartment. The significantly different frequency of WBC infiltration and clusters of multiple proliferating cells in ducts with and without ME disruptions suggests that WBCs might play important roles in ME disruption and tumor invasion.

Basement Membrane↗
PubMed2006

Retinal nerve fiber layer analysis in the diagnosis of glaucoma.

PURPOSE OF REVIEW: The detection of optic disc and retinal nerve fiber layer damage and change is the cornerstone of glaucoma management. Assessment of the retinal nerve fiber layer for localized and diffuse damage has been traditionally based on clinical examination, with documentation of change primarily qualitative. With the latest improvements in optical imaging instruments, objective and quantitative measurements of the retinal nerve fiber layer are now possible. This review summarizes the results from recent cross-sectional studies evaluating the discriminating ability of automated retinal nerve fiber layer measurements to detect glaucoma, and from longitudinal studies assessing the ability to predict and monitor glaucomatous changes. RECENT FINDINGS: Numerous cross-sectional studies have documented good diagnostic accuracy of a scanning laser polarimeter (GDx VCC), the optical coherence tomograph (Stratus), and the Heidelberg Retina Tomograph retinal nerve fiber layer measurements for differentiating between healthy and glaucoma eyes. There are only limited data available on the ability of these retinal nerve fiber layer measurements to document change over time. SUMMARY: It is essential that the clinician understand the specific strengths and weaknesses of each technique so that only good quality retinal nerve fiber layer information will be used in conjunction with careful clinical examination and visual function testing for glaucoma management decisions. Longitudinal studies are needed to evaluate the ability of these instruments to document retinal nerve fiber layer change over time.

Diagnostic Imaging↗
PubMed2004

Between the sheets: inter-cell-layer communication in plant development.

The cells of plant meristems and embryos are arranged in an organized, and sometimes extremely beautiful, layered pattern. This pattern is maintained by the controlled orientation of cell divisions within layers. However, despite this layered structure, cell behaviour during plant development is not lineage dependent, and does not occur in a mosaic fashion. Many studies, both classical and recent, have shown that plant cell identity can be re-specified according to position, allowing plants to show remarkable developmental plasticity. However, the layered structure of meristems and the implications of this during plant development, remain subjects of some speculation. Of particular interest is the question of how cell layers communicate, and how communication between cell layers could allow coordinated developmental processes to take place. Recent research has uncovered several examples both of the molecular mechanisms by which cell layers can communicate, and of how this communication can infringe on developmental processes. A range of examples is used to illustrate the diversity of mechanisms potentially implicated in cell-layer communication during plant development.

Cell Communication↗