Average Cell Density Research Articles

Characteristics of phytoplankton community structures in Ningwu subalpine lakes, Shanxi Province

通过对山西宁武亚高山湖群浮游植物群落结构的调查研究,共鉴定出浮游植物291个种、变种及变型,隶属于8门,45科,108属.各采样站点间种数相差较大,以马营海种类最多,干海最少.硅藻门、绿藻门和蓝藻门明显占优势,优势科、优势属和优势种也都较为明显.优势种有蓝藻门的细小隐球藻(Aphanocapsa elachista)、铜绿微囊藻(Microcystis aeruginisa)和小席藻(Phormidium tenue),硅藻门的库津小环藻(Cyclotella kuetzingii)、肘状脆杆藻(Fragilaria ulna)、尖针杆藻(Synedra acus),绿藻门的狭形纤维藻(Ankistrodesmus angustus)和小球藻(Chlorella vulgaris).浮游植物平均密度为3.49×106cells/L.水面下0.5 m处比水表层的细胞密度高.综合4种生物多样性指数,宁武亚高山湖群水质总体为轻污染.;The phytoplankton community structures in Ningwu subalpine lakes have been studied and 291 taxa, belonging to 8 divisions, 45 families and 108 genera, have been identified. The species numbers of each sampling station are quite different. The most abundant species are occurred in Lake Mayinghai, and the least in Lake Ganhai. Bacillariophyta, Chlorophyta and Cyanophyta dominate the area, in addition, dominant families, dominant genera and dominant species are also relatively clear. There are 8 dominant species and they are Aphanocapsa elachista, Microcystis aeruginosa, Phormidium tenue, Cyclotella kuetzingii, Fragilaria ulna, Synedra acus, Ankistrodesmus angustus and Chlorella vulgaris. The average phytoplankton cell density is 3.49×10⁶ cells/L in the lakes. The cell density in 0.5 m depth was higher than that on the surface. The initially assessment by four biodiversity indexes is that the water quality in Ningwu subalpine lakes is light-polluted.

Long-term effect of LASEK for the treatment of low to moderate myopia with thin cornea

Objective To evaluate the long term effect and safety of laser subepithelial keratomileusis( LASEK)for the treatment of low to moderate myopia with thin cornea( central corneal thickness ＜ 500 μm) Methods To analyze patients with low to moderate myopia in 5 -7 years after LASEK,and compare the refraction,visual acuity,contrast sensitivity,glare contrast sensitivity,corneal endothelium and corneal topography between pateints with thin cornea and normal thickness cornea.Results Thin cornea group had 27 cases (52 eyes).Normal thickness cornea group had 31 cases (62 eyes).No keratoconus had been observed during the follow-up period in the two groups.The corrected visual acuity of both groups were ≥1.0 ;In the thin cornea group,49 eyes' uncorrected visued acuity were ≥ 1.0,and 3 eyes were ＜ 1.0.In the normal cornea group,58 eyes' uncorreeted visued acuity were ≥ 1.0,and 4 eyes were ＜ 1.0 (x2 ＝ 0.0228,P ＞ 0.05).In the thin cornea group,49 eyes had 0 degree of cornea Haze,and 3 eyes had 0.5 degrees of cornea Haze.On the other hand,in the normal thickness cornea group,60 eyes had 0 degree of cornea Haze,and 2 eyes had 0.5 degrees of cornea Haze(x2 =0.4416,P ＞ 0.05 ).The shapes of the corneal endothelium of bothgroups were quite consistent and appear to be hexagonal,and the cell edge was neat.The average endothelial cell density:(2330±294)/mm2 in the thin cornea group,and (2413 ±320)/mm2 in the normal corneal thickness group; The average endothelial cell area:(420 ± 78 )μm2 in the thin cornea group,and (447 ± 92 ) μm2 ( t =1.6875,P ＞ 0.05 ) in the normal thickness cornea group.The contrast sensitivity of two groups with or without glare condition had significant difference for every spatial frequencies (P ＞ 0.05 ).Conclusion LASEK for the treatment of low to moderate myopia with thin cornea is tested to be safe,stable and with no keratoconus. Key words: Laser subepithelial keratomileusis; Corneal thickness; Keratoconus

Optimization of microalgal productivity using an adaptive, non-linear model based strategy

The optimization of biomass and oil productivities in heterotrophic cultures of Auxenochlorella protothecoides was achieved using a non-linear model-based approach. A 10-fold increase in the average biomass productivity, and a 16-fold increase in the maximum productivity, was observed with respect to batch cultures as a result of the proposed optimization strategy. Final cell density in the optimized culture was 144g/L (dry weight), with 49.4%w/w oil content. Maximum lipid productivity was 20.16g/Ld, achieved during the exponential growth phase at an average cell density of 86g/L. Lipid productivity in the optimized microalgal culture was higher than previously reported values for other oleaginous microorganisms. Oil composition analysis showed that the oil has a high quality as biodiesel precursor. The higher productivity and excellent lipid profile of the optimized microalgal culture make A. protothecoides an exceptional source for biodiesel production and a potential source of single cell oil for other applications.

Dynamic behavior of nucleation in supercritical N2 foaming of polystyrene-aluminum oxide nanocomposite

In this study, dynamic behaviour of nucleation was investigated during foaming process of polystyrene in presence of nano aluminium oxide. Nano aluminium oxide played a role of a bubble nucleating agent within polystyrene matrix. Foaming process was visually observed in conjunction with supercritical N2. Furthermore, the effect of nano Al2O3 compositions on the growth rate was studied. Also, final density per unit area and the average size in the latest growth steps were assessed. The obtained data were compared with foaming process for unfilled polystyrene under the same conditions. The results demonstrated that the final sizes of bubbles as well as the average cell density of the foam were reduced by using of nucleating agent. The growth rate of bubbles was also decreased by increasing the nano Al2O3 particles content. In addition, influence of temperature on foam density of nanocomposite specimens was greater than unfilled polystyrene foam. In presence of nano particle, the cell density was uniformly distributed in nanocomposites specimens. The article is published in the original.

Effects of wood fiber content on the rheological properties, crystallization behavior, and cell morphology of extruded wood fiber/HDPE composites foams

When increasing the wood fiber (WF) content in extruded wood fiber/plastic composites (WPC) foams, a good balance between reducing the cost and obtaining good cell morphology should be maintained. This study examines the relationship between WF content and the foam morphology in WPC foams. The role of WF as cell nucleating agent at low concentrations (10 wt.%) was observed, as WPC foam with 10 wt.% WF had lower average cell size and higher cell density than neat HDPE foams. Increasing the WF content further, decreased the average cell size and cell density, and increased the foam density of WPC foams. These results were linked to the rheological properties and crystallization behavior of HDPE and WPC with different WF content.

Preparation and characterization of lignocellulosic material filled polyethylene composite foams

In this study, the effects of foaming agent loading on the physical, mechanical and morphological properties of composites were investigated. Composites based on high-density polyethylene, rice husk flour, foaming agent and coupling agent were melt compounded using twin-screw extruder. The samples were foamed via a batch process using a compression molding machine at180°C. The mass ratio of rice husk flour to high-density polyethylene was controlled at 40:60 for all blends. The concentration was set to vary between 0, 1, 2 and 3 per hundred resins (phr) for foaming agent. The amount of coupling agent was fixed at 2% for all formulations. Results indicated that the cell size and average cell density of samples increased with an increase of foaming agent content. Also, by increasing the chemical foaming agent content the density, tensile modulus and flexural strength of the rice husk flour filled high-density polyethylene composites were decreased. However, the water absorption and thickness swelling of the composites increased by addition of the foaming agent. Scanning electron microscopy confirmed that the chemical foaming agent had a significant effect on the density reduction of foamed composites. This project has shown that the strategy of foaming wood plastic composites can be a good solution to overcome the high density of these composites.

Density Graded Linear Medium Density Polyethylene Foams Produced under a Temperature Gradient with Expancel Microbeads

In this work, density graded foams were produced using linear medium density polyethylene as the matrix and different grades of Expancel microbeads. Local density inside the foams was controlled by setting independently the top and bottom plates of a compression mould at different temperatures and by controlling moulding time. Due to the temperature gradient, complex density profiles were produced and a complete morphological analysis was performed to extract average cell diameter and cell density across foam thickness. Finally, the tensile and flexural moduli are reported and discussed in relation with foam structure.

Influence of chemical foaming agent on the physical, mechanical, and morphological properties of HDPE/wood flour/nanoclay composites

In this study, the effects of chemical foaming agent and nanoclay on the physical, mechanical, and morphological properties of composites based on HDPE and WF were described. To meet this objective, the nanoclay, HDPE and the coupling agent were compounded and granulated and mixed with WF and blowing agent in a twin-screw extruder. Consequently, the foaming process was completed in the injection stage. The amount of WF was fixed at 50 wt% for all samples. For nanoclay (organomodified montmorillonite) and CBA (azodicarbonamide), different levels of 0, 2, 4, 6 per hundred resins (phr) and 0, 0.5, 1, 1.5 phr were considered, respectively. Results indicate that the cell size and the average cell density of samples increased with the increase in the chemical foaming agent content. However, on addition of nanoclay to HDPE/WF composite foams, the cell size was decreased and their cell density increased. SEM confirmed that the chemical foaming agent and nanoclay contents had significant influence on density reduction of foamed composites. Finally, by increase in the chemical foaming agent content, the tensile modulus decreased and the water absorption and thickness swelling of HDPE/WF nanocomposite increased. The nanoclay dispersion quality is quite an important factor for the physical and mechanical properties of both foamed and unfoamed wood plastic nanocomposites. It was found that the optimal condition was attained by incorporating 0.5 phr foaming agent and 4 phr nanoclay in composite formulation.

Mass out-door culture of the micro-alga Chaetoceros gracilis

The mass culture of the micro-alga, Chaetoceros gracilis, a live-food for feeding the larval stages of Black Tiger shrimp, Penaeus monodon, was carried out in the in-door shrimp hatchery of Nigerian Institute for Oceanography and Marine Research. Guillard modified f/2 medium was used in the production of starter culture and maintenance of the pure algal culture in an indoor laboratory. Mass cultures of C. gracilis were thereafter developed in 1.5 m3 out-door plastic tanks using Guillard modified f/2 medium and Liao and Huang modified medium. The culture reached the stationary phase within 120 hours when exposed to sunlight. Three phases of cell growth of C. gracilis were observed during the culture periods which were lag phase followed by exponential and stationary phases. Average cell density of the out-door culture of the micro-alga was 780,000 cells/mL and the culture remained in this phase for 120-144 hours with a brown colouration. The highest cell density was 1,039,145 cells/mL recorded in the month of October while the lowest was 248,154.7 cells/mL recorded in the month of July. High cell density of the species occurred during the months of January to May and in October. These months were characterized by low humidity and higher temperature. Water temperature and salinity of the mass culture medium ranged from 25-29oC and 28-30 ppt respectively. The culture was sustained by semi-continuous culture throughout the study-period which lasted for ten months. The use of enrichment media enhanced sustained continuous culture for all year round alga production. The results obtained in this study indicated that mass culture and all year round production of C. gracilis is feasible in Nigeria.Keywords: Chaetoceros gracilis, mass culture, marine algae, Guillard modified f/2 growth medium, Liao and Huang modified growth medium.

Reproducible High Yields of Recombinant Adeno-Associated Virus Produced Using Invertebrate Cells in 0.02- to 200-Liter Cultures

The large amounts of recombinant adeno-associated virus (rAAV) vector needed for clinical trials and eventual commercialization require robust, economical, reproducible, and scalable production processes compatible with current good manufacturing practice. rAAV produced using baculovirus and insect cells satisfies these conditions; however, recovering rAAV particles from 200-liter bioreactors is more complicated than bench-scale vector preparations. Using a variety of processing media, we developed a reliable and routine downstream procedure for rAAV production that is scalable from 0.02- to 200-liter cultures. To facilitate the upstream process, we adapted the titerless infected-cell preservation and scale-up process for rAAV production. Single-use aliquots of cryopreserved baculovirus-infected insect cells (BIIC) are thawed and added to the suspension culture to achieve the desired ratio of BIIC to rAAV-producer cells. By using conditions established with small-scale cultures, rAAV was produced in larger volume cultures. Strikingly consistent rAAV yields were attained in cultures ranging from 10 liters to 200 liters. Based on the final yield, each cell produced 18,000 ± 6,800 particles of purified rAAV in 10-, 20-, 100-, and 200-liter cultures. Thus, with an average cell density of 4.32 × 10(6) cells/ml, ≥ 10(16) purified rAAV particles are produced from 100 to 200 liters. The downstream process resulted in about 20% recovery estimated from comparing the quantities of capsid protein antigen in the crude bioreactor material and in the final, purified product. The ease and reproducibility of rAAV production in 200-liter bioreactors suggest that the limit has not been reached, and 500-liter productions are planned.

Cell Pattern in Adult Human Corneal Endothelium

A review of the current data on the cell density of normal adult human endothelial cells was carried out in order to establish some common parameters appearing in the different considered populations. From the analysis of cell growth patterns, it is inferred that the cell aging rate is similar for each of the different considered populations. Also, the morphology, the cell distribution and the tendency to hexagonallity are studied. The results are consistent with the hypothesis that this phenomenon is analogous with cell behavior in other structures such as dry foams and grains in polycrystalline materials. Therefore, its driving force may be controlled by the surface tension and the mobility of the boundaries.

Study on Formula for Glass Fiber/Microcellular Unsaturated Polyester Composites Preparation

Formula for glass fiber/microcellular unsaturated polyester composites (GF/MCUP) using supersaturated gas technology was studied by the way of orthogonal experiment. The results showed that these factors affecting average cell size from strongly to weakly were styrene content, accelerant content, glass fiber length, curing agent and glass fiber content, respectively. The factors affecting average cell density from strongly to weakly were accelerant content, styrene content, glass fiber content, curing agent content and glass fiber length, respectively. Curing agent content was the major factor affecting impact strength of GF/MCUP. The factors revealed no obvious difference in affecting tensile strength. Under the optimizing processing condition, the average cell size of GF/MCUP was about 8 μm and the cell density was 1.19×109 cells/cm3. The 153.70 and 255.84 % increase in impact strength were gained over that of GF/UP and UP, respectively. The corresponding 20.24 and 82.51% increase in tensile strength-to-weight ratio were gained over that of GF/UP and UP, respectively.

Research on Glass Fiber/Microcellular Unsaturated Polyester Composites

Glass fiber/microcellular unsaturated polyester composites (GF/MCUP) were prepared using the supersaturated gas technology. Technological process included three stages. The effect of processing parameters on average cell size, cell density, impact strength and tensile strength was investigaed by orthogonal experiment. The results indicated that the major factor affecting them was the temperature in stageⅡ(T2). Under the optimizing processing condition, the average cell size of GF/MCUP was about 8 μm and the cell density was 1.57×109 cells/cm3. It was found that impact strength of GF/MCUP increased 88.81 and 188.12 % than that of glass fiber/unsaturated polyester composites (GF/UP) and unsaturated polyester plastics (UP), respectively. The corresponding 16.56 and 69.25 % increase in tensile strength-to-weight ratio were gained over that of GF/UP and UP, respectively.

Descemet’s Stripping with Endothelial Keratoplasty for Special Fuchs’ Endothelial Dystrophy in Phakic Eyes

Background: To determine the efficacy and postoperative complications of simple Descemet’s stripping endothelial keratoplasty (DSEK) for treatment of special Fuchs’ endothelial dystrophy in phakic eyes. Methods: Six eyes with clear crystalline lenses in 5 consecutive patients with Fuchs’ endothelial dystrophy underwent DSEK and were followed up for 12–27 months. The pupil was constricted preoperatively to 1.5 mm in diameter. The anterior chamber was deepened intraoperatively by injection of balanced salt solution to unfold the donor graft and to protect the crystalline lens. Best corrected visual acuity, corneal astigmatism, corneal curvature, corneal thickness, and anterior chamber depth were recorded preoperatively and at 6 and 12 months postoperatively. Average endothelial cell density and endothelial cell loss (ECL) were recorded at 6 and 12 months postoperatively. Results: DSEK was successfully performed in all 6 eyes. No graft dislocation or lens injury occurred. One of the 6 eyes presented with mild cataract at 12 months after surgery but showed no sign of progressive cataract development during the follow-up. All grafts were clear during the last follow-up: best corrected visual acuity ranged from 20/50 to 20/30, average corneal astigmatism was 2.2 ± 0.6 dpt, average corneal curvature was 46.0 ± 2.4 dpt, and average central corneal thickness was 583.0 ± 21.5 µm. At 6 and 12 months postoperatively, average endothelial cell density was 2,070.7 ± 206.1 cells/mm² (28.0 ± 7.5% of ECL) and 1,838.3 ± 194.5 cells/mm² (36.1 ± 6.2% of ECL), respectively. Conclusions: Simple DSEK might be a feasible option for Fuchs’ endothelial dystrophy in young patients with clear crystalline lenses.

Influences of particle sizes and contents of chemical blowing agents on foaming wood plastic composites prepared from poly(vinyl chloride) and rice hull

This research aims to investigate the effects of chemical blowing agent (CBA) contents and particle sizes on the properties of foamed poly(vinyl chloride) (PVC)/rice hull (RH) composites. Fine particles of azodicarbonamide (AC) at 5, 8, 11 and 22 μm were modified with 20% by weight of ZnO and used at 0–3.0% by weight. The average cell size and density of the PVC/RH foamed profiles were reduced as the content of modified azodicarbonamide (mAC) increased. Larger mAC particles lowered the density more effectively. Maximum reduction of density by 46% was achieved when mAC 22 μm was applied at 2.0% by weight. Larger blowing particles led to PVC/RH foam with greater flexural modulus and strength. Greater impact strength, observed when 5 μm mAC was applied, resulted from the rather thick cell wall created abundantly when fine mAC was applied.

Reaction engineering analysis of hydrogenotrophic production of acetic acid by Acetobacterium woodii

Great interest has emerged in biological CO₂-fixing processes in the context of current climate change discussions. One example for such a process is the hydrogenotrophic production of acetic acid by anaerobic microorganisms. Acetogenic microorganisms make use of carbon dioxide in the presence of hydrogen to produce acetic acid and biomass. In order to establish a process for the hydrogenotrophic production of acetic acid, the formation of acetate by Acetobacterium woodii was studied in a batch-operated stirred-tank bioreactor at different hydrogen partial pressures (pH₂) in the gas phase. The volumetric productivity of the batch processes increased with increasing hydrogen partial pressure. A maximum of the volumetric productivity of 7.4 g(acetate) L⁻¹ day⁻¹ was measured at a pH₂ of 1,700 mbar. At this pH(2) a final acetate concentration of 44 g L⁻¹ was measured after a process time of 11 days, if the pH was controlled at pH 7.0 (average cell density of 1.1 g L⁻¹ cell dry weight). The maximum cell specific actetate productivity was 6.9 g(acetate) g(cdw)⁻¹ day⁻¹ under hydrogenotrophic conditions.

Mast cells have a protumorigenic role in human thyroid cancer

In different human carcinoma types, mast cell infiltrate increases with respect to normal tissue and mast cell density correlates with a bad prognosis. To assess the role of mast cells in human thyroid cancer, we compared the density of tryptase-positive mast cells in 96 papillary thyroid carcinomas (PTCs) versus normal thyroid tissue from 14 healthy individuals. Mast cell density was higher in 95% of PTCs (n=91) than in control tissue. Mast cell infiltrate correlated with extrathyroidal extension (P=0.0005) of PTCs. We show that thyroid cancer cell-line-derived soluble factors induce mast cell activation and chemoattraction in vitro. Different mast cell lines (HMC-1 and LAD2) and primary human lung mast cells induced thyroid cancer cell invasive ability, survival and DNA synthesis in vitro. The latter effect was mainly mediated by three mast-cell-derived mediators: histamine, and chemokines CXCL1/GROα and CXCL10/IP10. We show that xenografts of thyroid carcinoma cells (8505-C) could recruit mast cells injected into the tail vein of mice. Co-injection of human mast cells accelerated the growth of thyroid cancer cell (8505-C) xenografts in athymic mice. This effect was mediated by increased tumor vascularization and proliferation, and was reverted by treating mice with sodium cromoglycate (Cromolyn), a specific mast cell inhibitor. In conclusion, our study data suggest that mast cells are recruited into thyroid carcinomas and promote proliferation, survival and invasive ability of cancer cells, thereby contributing to thyroid carcinoma growth and invasiveness.

T1688 Decrease in Parietal Cell Density at Squamo-Columnar Junction With Increasing Age in Asymptomatic Healthy Volunteers

Introduction The gastric cardia is an important site of pathology with a high incidence of inflammation, metaplasia and neoplasia. However the area is poorly understood and cardia mucosa may itself be pathological. Previous autopsy studies show a near absence of cardia epithelium in neonates and an increase in length with age. Aims: To1 investigate whether parietal cell density in the columnar mucosa at the squamocolumnar junction (SCJ) changes with age and2 determine the association of parietal cell density with distal oesophageal acid exposure. Methods 25 healthy volunteers (14 males, 5 Helicobacter pylori positive) were studied. Biopsies were taken from the macroscopic SCJ, 1 cm distal to the SCJ, gastric body and antrum. Biopsies were embedded in paraffin and 5-micron sections cut for immunohistochemistry. Parietal cells were stained and visualised using a standardised monoclonal anti-H+/K+ATPase antibody. Slides were digitally scanned and uploaded onto a slide server. An image analysis programme was used to quantify parietal cell density expressed as intracellular positive pixels. The average parietal cell density in a minimum of four sections of columnar mucosa per slide was reported as the percentage of the total cells per section. In 20 subjects pH studies were performed before and after a standardised meal. Acid exposure was calculated as per cent time pH Results There was a significant negative correlation between age and parietal cell density in the columnar mucosa at the level of the SCJ (R=−0.530, p=0.008). There was no significant correlation between age and parietal cell density 1 cm distal to the SCJ (R=0.153, p=0.5), in the gastric body (R=0.386, p=0.08) or antrum (R=0.117, p=0.6). In the HP negative subgroup, parietal cell density at the SCJ of volunteers under 30 years old was significantly greater than those aged 30 years and over (6.8% vs 0.4%, p=0.05). In contrast, gastric body parietal cell density was lower in the younger group (30.0% vs 34.5%, p=0.019). There was no significant correlation between distal oesophageal acid exposure and parietal cell density at the SCJ (R=0.223, p=0.3). Conclusion Parietal cell density decreases with age in the columnar mucosa at the SCJ. This effect appears to be localised to the SCJ and is not seen 1 cm distal to this or within the stomach. There was no correlation between parietal cell density and acid exposure. These results support cardiac mucosa being acquired and due to mechanisms other than traditional gastro-oesophageal reflux.

PWE-082 Decrease in parietal cell density at squamo-columnar junction with increasing age in asymptomatic healthy volunteers

<h3>Introduction</h3> The gastric cardia is an important site of pathology with a high incidence of inflammation, metaplasia and neoplasia. However the area is poorly understood and cardia mucosa may itself be pathological. Previous autopsy studies show a near absence of cardia epithelium in neonates and an increase in length with age. Aims: To¹ investigate whether parietal cell density in the columnar mucosa at the squamocolumnar junction (SCJ) changes with age and² determine the association of parietal cell density with distal oesophageal acid exposure. <h3>Methods</h3> 25 healthy volunteers (14 males, 5 <i>Helicobacter pylori</i> positive) were studied. Biopsies were taken from the macroscopic SCJ, 1 cm distal to the SCJ, gastric body and antrum. Biopsies were embedded in paraffin and 5-micron sections cut for immunohistochemistry. Parietal cells were stained and visualised using a standardised monoclonal anti-H+/K+ATPase antibody. Slides were digitally scanned and uploaded onto a slide server. An image analysis programme was used to quantify parietal cell density expressed as intracellular positive pixels. The average parietal cell density in a minimum of four sections of columnar mucosa per slide was reported as the percentage of the total cells per section. In 20 subjects pH studies were performed before and after a standardised meal. Acid exposure was calculated as per cent time pH&lt;4. Spearman9s σ correlation and Mann-Whitney U tests were used for analysis of non-parametric data. <h3>Results</h3> There was a significant negative correlation between age and parietal cell density in the columnar mucosa at the level of the SCJ (R=−0.530, p=0.008). There was no significant correlation between age and parietal cell density 1 cm distal to the SCJ (R=0.153, p=0.5), in the gastric body (R=0.386, p=0.08) or antrum (R=0.117, p=0.6). In the HP negative subgroup, parietal cell density at the SCJ of volunteers under 30 years old was significantly greater than those aged 30 years and over (6.8% vs 0.4%, p=0.05). In contrast, gastric body parietal cell density was lower in the younger group (30.0% vs 34.5%, p=0.019). There was no significant correlation between distal oesophageal acid exposure and parietal cell density at the SCJ (R=0.223, p=0.3). <h3>Conclusion</h3> Parietal cell density decreases with age in the columnar mucosa at the SCJ. This effect appears to be localised to the SCJ and is not seen 1 cm distal to this or within the stomach. There was no correlation between parietal cell density and acid exposure. These results support cardiac mucosa being acquired and due to mechanisms other than traditional gastro-oesophageal reflux.

Comparison of Data From the Rostock Cornea Module of the Heidelberg Retina Tomograph, the Oculus Pentacam, and the Endothelial Cell Microscope

The aim of this study was to validate data arising from the Rostock Cornea Module (RCM) of the Heidelberg Retina Tomograph. Morphological parameters of the cornea were analyzed according to their dependency on patient's age. RCM measurements of 60 healthy eyes within 2 different age groups (group 1 <35 years, group 2 >50 years) were compared with the corneal thickness determined by the Oculus Pentacam and the endothelial cell density measured by the Tomey endothelial microscope, EM-2000. The mean corneal thickness measured with the Heidelberg Retina Tomograph/RCM was 517 +/- 31 microm and 542 +/- 30 microm with the Oculus Pentacam (correlation coefficient, R = 0.78). Group 1 showed a corneal thickness of 509 +/- 24 microm with the RCM and 531 +/- 27 microm with the Pentacam. In group 2, the corneal thickness was 525 +/- 34 microm and 553 +/- 29 microm, respectively. A significant increase in corneal thickness for older patients could be shown. The differences between the methods and the age groups were statistically significant (P < 0.0001). The average endothelial cell density measured with the RCM was 2779 +/- 472 cells per square millimeter. Between the age groups and the methods (RCM and endothelial microscope), no statistically significant differences could be found. Cell densities for the epithelial cell layers and keratocytes showed no significant correlation with age and sex of the patients. The RCM provides a reliable procedure for the evaluation of all corneal layers including morphological parameters. Endothelial cell densities either determined with the RCM or the EM-2000 are generally comparable to each other and showed no significant differences. It is suggested that lower corneal thickness measurements of the RCM can be caused by pressure during examination. An increased corneal thickness in the older group could be determined with the RCM and the Oculus Pentacam.