Biomedical subjects

A Behrens

Publications and source records attributed to A Behrens.

At least 19 recordsLinked to original sources

PubMed2002

Expression, cellular distribution and induction of cytochrome p4501A (CYP1A) in gilthead seabream, Sparus aurata, brain.

The presence and induction of cytochrome p4501A (CYP1A) in the brain of a teleost fish, the seabream, Sparus aurata, was studied. Cerebral CYP1A expression of control fish or fish exposed to various concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was assessed at the enzyme activity level-measured as 7-ethoxyresorufin-O-deethylase; at the protein level-measured by means of Western blot and ELISA; and at the mRNA level-estimated by means of RT-PCR. Cellular localization of CYP1A in the brain tissue was studied using immunohistochemistry. In non-exposed control fish, expression of CYP1A could be demonstrated only in the olfactory bulbs. After TCDD exposure, the olfactory bulbs still showed the highest expression levels of CYP1A, however, other brain regions were now CYP1A-positive as well. Immunohistochemical examination of brain tissue sections from control fish demonstrated CYP1A immunoreactive fibers in the ventral telencephalon, in the glomerular layer of the olfactory bulbs, and in the endothelia of the cerebral vascular system. The same structures reacted positive in TCDD-exposed fish, but cell bodies and fibers from additional brain areas including telencephalon, diencephalon, mesencephalon and cerebellum showed CYP1A immunostaining. In the pituitary of TCDD-treated fish, putative GTH cells were positive for CYP1A, whereas in control fish no staining of the adenohypophysis was observed. The present findings provide evidence for basal expression of CYP1A in the telencephalon of Sparus aurata, and for the presence of inducible CYP1A in all other major brain regions, including the pituitary.

Animals↗

PubMed2002

Thiofunctional vanadium complexes.

The neutral tetradentate ligand 1,6-bis(2'-pyridyl)-2,5-dithiahexane (N(2)S(2)), containing two thioether functions, reacts with [VX(2)L(4)] (X = Br, L(4) = 2 tmeda (tmeda = Me(2)NCH(2)CH(2)NMe(2)); X = I, L = tetrahydrofuran (THF)) and [VX(3)(THF)(3)] (X = Br, I) to form the complexes [VX(2)(N(2)S(2))] (1) and [VX(2)(N(2)S(2))]X (2), respectively. [V(2)(mu-Cl)(3)(THF)(6)]I and N(2)S(2) yield the V(IV) complex [VOCl(N(2)S(2)]I (3). The pentadentate, dianionic ligand 2,6-bis(2'-mercaptophenylthio)dimethylpyridine, NS(2)S'(2)(2-), which contains two thioether (S) and two thiophenolate (S') functions, reacts with [VBr(3)(THF)(3)] to afford [VBr(NS(2)S'(2))] (4). The complex [VO(Cl)S'NS'] (5; H(2)S'NS' is the Schiff base formed between o-mercaptoaniline and o-mercaptobenzaldehyde) is obtained by redox interaction between [VCl(3)(THF)(3)] and 2,2'-dithiodibenzaldehyde in the presence of o-mercaptoaniline. The crystal and molecular structures have been obtained for 3. THF, 4. THF, and 5. n-C(5)H(12). The relevance of these compounds and their formation for the interaction between vanadium and thiofunctional biomolecules is addressed.

Journal Article↗

PubMed2001

Jun N-terminal kinase 2 modulates thymocyte apoptosis and T cell activation through c-Jun and nuclear factor of activated T cell (NF-AT).

The Jun N-terminal kinases (JNKs) recently have been shown to be required for thymocyte apoptosis and T cell differentiation and/or proliferation. To investigate the molecular targets of JNK signaling in lymphoid cells, we used mice in which the serines phosphorylated by JNK in c-Jun were replaced by homologous recombination with alanines (junAA mice). Lymphocytes from these mice showed no phosphorylation of c-Jun in response to activation stimuli, whereas c-Jun was rapidly phosphorylated in wild-type cells. Despite the fact that c-jun is essential for early development, junAA mice develop normally; however, c-Jun N-terminal phosphorylation was required for efficient T cell receptor-induced and tumor necrosis factor-alpha-induced thymocyte apoptosis. In contrast, c-Jun phosphorylation by JNK is not required for T cell proliferation or differentiation. Because jnk2-/- T cells display a proliferation defect, we concluded that JNK2 must have other substrates required for lymphocyte function. Surprisingly, jnk2-/- T cells showed reduced NF-AT DNA-binding activity after activation. Furthermore, overexpression of JNK2 in Jurkat T cells strongly enhanced NF-AT-dependent transcription. These results demonstrate that JNK signaling differentially uses c-Jun and NF-AT as molecular effectors during thymocyte apoptosis and T cell proliferation.

Animals↗

PubMed2001

Re-epithelialization in cornea organ culture after chemical burns and excimer laser treatment.

OBJECTIVE: To describe the epithelial healing rates observed in freshly cultured rabbit corneas chemically burned with high-concentration hydrochloric acid (HCl) and sodium hydroxide (NaOH) and subsequently treated with phototherapeutic keratectomy (PTK). METHODS: We obtained 126 fresh corneoscleral rims from cadaveric New Zealand white rabbits. Each cornea was exposed to 4-mm cellulose sponges soaked in a solution of topical 0.9% isotonic sodium chloride solution, 2M HCl, or 0.5M NaOH. A transepithelial PTK (6-mm zone; 100-microm ablation depth) was then performed using the excimer laser (150-mJ/cm(2) energy pulse; 20 nanosecond duration; and 10-Hz frequency). Corneas were placed in tissue culture, and 1 cornea from each group was taken out of culture each day after treatment. Re-epithelialization was monitored by means of fluorescein staining, slitlamp photography, and histopathological analysis. RESULTS: Corneas treated with HCl and NaOH exhibited immediate epithelial defects that slowly healed over time. In PTK-treated corneas, the re-epithelialization rate was accelerated compared with that of controls (P =.003 for the HCl group, and P<.001 for the NaOH group). The new epithelial layers were smoother in PTK-treated corneas, as confirmed by results of histopathological analysis. CONCLUSION: Corneal damage caused by HCl and NaOH may be modulated in vitro by PTK in this rabbit model. CLINICAL RELEVANCE: After corneal chemical damage, 193-nm excimer laser PTK accelerates epithelial wound healing.

Animals↗

PubMed2001

Simple organ cornea culture model for re-epithelialization after in vitro excimer laser ablation.

BACKGROUND AND OBJECTIVE: Most of the in vitro work to characterize the effects of clinical laser surgery on corneal tissues has concentrated on the effects on stromal keratocytes and endothelium with little attention being paid to corneal epithelium. Our purpose is to describe the epithelial healing rates observed in freshly cultured rabbit corneas treated with phototherapeutic keratectomy (PTK). STUDY DESIGN/MATERIALS AND METHODS: Corneas were placed in a simple organ culture system, with media change every 2 days. A clinical excimer laser was used to perform a 6 mm diameter, 100 microm depth transepithelial PTK on 24 cultured rabbit corneas, 1 day after culture initiation. For each post-treatment day, one experimental and one control cornea were removed from culture and stained with fluorescein, photographed, and fixed for histology. Epithelial defect area was measured with digital imaging software and analyzed statistically to assess the re-epithelialization rate. RESULTS: Control corneas, maintained in culture for 1-4 days, had no epithelial defects. Those corneas treated with PTK exhibited an immediate epithelial defect that slowly healed over 3 days. This was confirmed on histopathological analysis. A significant linear trend in re-epithelialization across the time points studied was found (F = 80.48, P = 0.0029). The slope of the linear regression model showed an estimate rate of re-epithelialization of -6.70 over the 3 days. CONCLUSION: We have described the development of a simple, whole organ, rabbit cornea culture model for re-epithelialization after PTK. Our rates of epithelial healing resemble those found in the literature in live rabbit models. Therefore, this model may possibly be used to monitor epithelial wound healing in different corneal diseases or injuries.

Animals↗

PubMed2001

Microkeratome-based limbal harvester for limbal stem cell transplantation: preliminary studies.

PURPOSE: To develop a mechanical device to perform limbal transplantation. This procedure is a valuable surgical technique for management of limbal stem cell deficiency. However, the freehand dissection to obtain donor tissue is laborious and time-consuming. METHODS: A manual microkeratome (LSK One; Moria/Microtech, Doylestown, Pennsylvania) using a redesigned head (200 microm thickness, 16-mm blade) was used to create partial thickness corneoscleral caps from human donor globes. RESULTS: Corneoscleral caps obtained from human donor globes included a ring of approximately 1 mm of perilimbal sclera in contiguity to the cornea. Scanning electron microscopy showed a smooth cut surface with some chatter at the margins. CONCLUSION: This instrument ensures an effective and straightforward method to dissect the area where stem cells have been indirectly localized.

Cell Transplantation↗

PubMed2001

Posterior corneal curvature changes after myopic laser in situ keratomileusis.

OBJECTIVE: To assess the posterior corneal power and asphericity changes after myopic laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. DESIGN: Prospective nonrandomized (self-controlled) comparative study. PARTICIPANTS: Fifty-seven eyes of 14 women and 15 men, mean age at the time of surgery 33 +/- 9 (range, 19-53) years with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (DI). INTERVENTION: All procedures were performed with the Keratom II Coherent-Schwind excimer laser and and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit scanning corneal topography analysis and pachymetry were performed before and 3 months after LASIK for myopia (n=35, -1.00 to -15.50 D, mean -4.75 +/- -3.07 D) or myopic astigmatism (n=22, sphere 0.00 to -9.75 D, mean -4.75 +/- 2.36 D; cylinder -0.75 to -3.50 D, mean -1.68 +/- 0.86 D). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters potentially indicative for detection of a "mild keratectasia" were derived. MAIN OUTCOME MEASURES: Posterior central corneal power and asphericity before and after LASIK were compared, and changes of these variables were correlated with the SEQ change (deltaSEQ)and the residual corneal bed thickness RBT). RESULTS: The mean RBT after LASIK was 280 +/- 42 microm. Overall, change of posterior power (-6.28 +/- 0.22 D/ -6.39 +/- 0.23 D, P=0.02) was statistically significant and change of asphericity (0.98 +/-0.07/1.14 +/- -.20, P<0.0001) was highly significant. In eyes with RBT < or =250 microm, the average change of posterior central power (-0.20 +/- 0.10 D vs. -0.08 +/- 0.18 D) was significantly greater than in eyes with RBT >250 microm (P=0.003). The change of posterior corneal power correlated significantly with deltaSEQ (P=0.004) and the RBT (P=0.002). CONCLUSIONS: Increased negative keratometric diopters and oblate asphericity of the posterior corneal curvature suggest that mild "keratectesia" of the cornea may be common early after LASIK. Further stuudies with longer follow-up are required to clarify whether this biomechanical deformation is progressive and whether a residual bed thickness of >250 microm can completely prevent it.

Adult↗

PubMed2001

Precision and accuracy of an artificial anterior chamber system in obtaining corneal lenticules for lamellar keratoplasty.

PURPOSE: To determine the precision and accuracy of an artificial anterior chamber and a manual microkeratome in obtaining corneal lenticules for lamellar keratoplasty. SETTING: Department of Ophthalmology, Cornea, External Diseases and Refractive Surgery Service, University of California Irvine, Irvine, California, USA. METHODS: A lamellar keratectomy was performed in 47 human corneoscleral rims. Three lenticule thicknesses (180, 300, and 360 microm heads) and 3 diameters (7.0, 8.0, and 9.0 mm) were attempted. Diameters and thicknesses were measured by planimetry and pachymetry, respectively. RESULTS: Peripheral lenticule thickness was more likely to be within +/-50 microm of the intended depth in thinner cuts (180 microm, 9/15 corneas, 60%; 300 microm, 6/16 corneas, 40%; 360 microm, 3/12 corneas, 33.3%) (P = .045). Eighty percent (32/40 corneas) were within +/-0.5 mm of the expected diameter. Accuracy was best in the 8.0 mm group, with 47.1% (8/17 corneas) within +/-0.2 mm of the expected diameter. A thickness/diameter correlation was not observed (r(s) < or = 0.28). CONCLUSIONS: The precision and accuracy of this system varied according to the attempted thickness and diameter.

Adolescent↗

PubMed2001

AP-1 mediated retinal photoreceptor apoptosis is independent of N-terminal phosphorylation of c-Jun.

Apoptosis is essential for retinal development but it is also a major mode of cell loss in many human retinal dystrophies. High levels of visible light induce retinal apoptosis in mice and rats. This process is dependent on the induction of the transcription factor AP-1, a dimeric complex composed of c-Fos and c-Jun/JunD phosphoproteins. While c-Fos is essential, JunD is dispensable for light-induced photoreceptor apoptosis. Here we show that N-terminal phosphorylation of c-Jun, the other main partner of c-Fos in induced AP-1 complexes is not required for programmed cell death during retinal development in vivo and is also dispensable for photoreceptor apoptosis induced by the exogenous stimuli "excessive light" and N-nitroso-N-methylurea (MNU). Mice expressing a mutant c-Jun protein (JunAA) that cannot be phosphorylated at its N-terminus are apoptosis competent and their retina is not distinguishable from wild-type mice. Accordingly, Jun kinase, responsible for phosphorylation of wild-type c-Jun protein is at best only marginally induced by the apoptotic stimuli "light" and MNU. Complex composition of light-induced AP-1 complexes is similar in wild-type and JunAA mice. This shows that the mutant c-Jun protein can be part of the DNA binding complex AP-1 and demonstrates that induction of the DNA binding activity of AP-1 after light insult does not depend on N-terminal phosphorylation of c-Jun. Our results suggest that transactivation of target genes by phosphorylated c-jun/AP-1 is not required for MNU- or light-induced apoptosis of photoreceptor cells.

Alkylating Agents↗

PubMed2001

Normal neurogenesis and scrapie pathogenesis in neural grafts lacking the prion protein homologue Doppel.

The agent that causes prion diseases is thought to be identical to PrPSc, a conformer of the normal prion protein PrPC. Recently a novel protein, termed Doppel (Dpl), was identified that shares significant biochemical and structural homology with PrPC. To investigate the function of Dpl in neurogenesis and in prion pathology, we generated embryonic stem (ES) cells harbouring a homozygous disruption of the Prnd gene that encodes Dpl. After in vitro differentiation and grafting into adult brains of PrPC-deficient Prnp0/0 mice, Dpl-deficient ES cell-derived grafts contained all neural lineages analyzed, including neurons and astrocytes. When Prnd-deficient neural tissue was inoculated with scrapie prions, typical features of prion pathology including spongiosis, gliosis and PrPSc accumulation, were observed. Therefore, Dpl is unlikely to exert a cell-autonomous function during neural differentiation and, in contrast to its homologue PrPC, is dispensable for prion disease progression and for generation of PrPSc.

Animals↗

PubMed2001

Polycyclic aromatic hydrocarbons as inducers of cytochrome P4501A enzyme activity in the rainbow trout liver cell line, RTL-W1, and in primary cultures of rainbow trout hepatocytes.

In order to investigate cell-specific differences in the response of in vitro models to environmental toxicants, we compared the capacity of nine polycyclic aromatic hydrocarbons (PAHs) to induce cytochrome P4501A (CYPIA) in primary rainbow trout (Oncorhynchus mykiss) hepatocytes and a rainbow trout liver cell line, RTL-W1. Induction of CYPIA was estimated from the catalytic activity of 7-ethoxyresorufin-O-deethylase (EROD) and compared by median effective concentration (EC50) values, induction spans, and benzo[a]pyrene induction equivalency factors for inducing PAHs. The influence of culture conditions was investigated with respect to the presence or absence of serum and varying exposure times. Both in vitro systems lead to an identical classification of the PAHs in noninducing (anthracene, fluoranthene, phenanthrene, and pyrene) and inducing compounds with a similar ranking of inducing PAHs. Mean EC50 values in RTL-W1 cells were, respectively, 343 and 266 nM for benzo[a]anthracene, 57 and 92 nM for BaP, 134 and 283 nM for benzo[b]fluoranthene, 455 and 270 nM for chrysene, and 98 and 116 nM for 3-methylcholanthrene. Compared to primary hepatocytes, the RTL-W1 cell line was more sensitive in its EROD response to the presence or absence of serum and to the increase in exposure time, which led to higher EC50 values.

Animals↗

PubMed2000

The EGF receptor provides an essential survival signal for SOS-dependent skin tumor development.

The EGF receptor (EGFR) is required for skin development and is implicated in epithelial tumor formation. Transgenic mice expressing a dominant form of Son of Sevenless (SOS-F) in basal keratinocytes develop skin papillomas with 100% penetrance. However, tumor formation is inhibited in a hypomorphic (wa2) and null EGFR background. Similarly, EGFR-deficient fibroblasts are resistant to transformation by SOS-F and rasV12, however, tumorigenicity is restored by expression of the anti-apoptotic bcl-2 gene. The K5-SOS-F papillomas and primary keratinocytesfrom wa2 mice display increased apoptosis, reduced Akt phosphorylation and grafting experiments imply a cell-autonomous requirement for EGFR in keratinocytes. Therefore, EGFR functions as a survival factor in oncogenic transformation and provides a valuable target for therapeutic intervention in a broader range of tumors than anticipated.

Animals↗

PubMed2000

Oncogenic transformation by ras and fos is mediated by c-Jun N-terminal phosphorylation.

The nuclear phosphoprotein c-Jun is a major component of the AP-1 transcription factor, whose activity is augmented by many oncogenes. An important mechanism to stimulate AP-1 function is N-terminal phosphorylation of c-Jun at the serine residues 63 and 73 by the c-JunN-terminal kinases (JNKs). Mice and cells harboring a mutant allele of c-jun, which has the JNK phosphoacceptor serines changed to alanines (junAA), were used to determine the function of c-Jun N-terminal phosphorylation (JNP) during oncogenic transformation in vitro and in vivo. JunAA immortalized fibroblasts expressing v-ras and v-fos showed reduced tumorigenicity in nude mice, but the efficiency of v-src transformation was unaffected by the lack of JNP. To assess the significance of JNP in tumour development in vivo, two transgenic mouse tumour models were employed. Skin tumour development caused by constitutive activation of the ras pathway by K5-SOS-F expression and c-fos-induced osteosarcoma formation were impaired in mice lacking JNP. Inhibition of JNP may, therefore, be a novel therapeutic strategy to inhibit tumour growth in vivo. Oncogene (2000).

Animals↗

PubMed2000

7,11-cyclobotryococca-5,12,26-triene, a novel botryococcene-related hydrocarbon occurring in natural environments

[formula: see text] With the unambiguous structural characterization of 7,11-cyclobotryococca-5,12,26-triene 1 by NMR, a novel C30 botryococcene-related hydrocarbon skeleton bearing a midchain five-membered ring has been identified in organic-rich sediments from Lake Cadagno (Switzerland). This compound may originate from the green alga Botryococcus braunii (race B) widespread in recent and past environments. Alternatively, it may also be a yet unreported lipid of green sulfur photosynthetic bacteria (Chlorobiaceae) or a microbial transformation product of the farnesol produced by the latter.

Journal Article↗

PubMed2000

Occurrence of precursors of regular tricyclopolyprenoids in recent sediments

[structure: see text] Two novel C24 tricyclic alkenes of the cheilanthane series have been isolated from the solvent extract of a sulfur-rich recent sediment and their structures determined by NMR studies. They represent the first example of functionalized tricyclic hydrocarbons structurally related to the tricyclopolyprenanes widespread in ancient sediments and petroleum identified in recent sediments.

Journal Article↗

PubMed2000

Inhibition of rabbit keratocyte and human fetal lens epithelial cell proliferation by retrovirus-mediated transfer of antisense cyclin G1 and antisense MAT1 constructs.

The aim of this study is to evaluate the potential of gene transfer of cell cycle control genes as treatment of corneal haze or secondary cataract formation. The guiding hypothesis is that strategic modulation of the cyclin G1 or MAT1 gene by retrovirus-mediated gene transfer will inhibit proliferation of rabbit keratocytes (RabK) and fetal human lens epithelial (FHLEpi) cells in vitro. RabK and FHLEpi cell cultures were transduced in triplicate with retroviral vectors bearing either a nuclear-targeted beta-galactosidase, an antisense cyclin G1 (aG1), an antisense MAT1 (aMAT1) construct, or the neo(r) gene. The presence of beta-galactosidase activity in the transduced cultures was detected by immunohistochemical X-Gal staining, while cyclin G1 and MAT1 protein expression levels were evaluated by Western analysis. Proliferation of RabKs and FHLEpi cells was analyzed by counting the number of cells in the aG1 and aMAT1 vector-transduced cultures over 5 days. The mean transduction efficiency was 34.4% (SD 1.41) for RabKs and 19.7% (SD 1.83) for FHLEpi cells. Downregulation of cyclin G1 and MAT1 protein expression was noted 24 hr after transduction of RabK cultures with the respective vectors. Cytostatic effects of the aG1 and aMAT1 vectors in both RabKs and FHLEpi cells were most pronounced on the fifth day (RabKs, p < 0.0007; FHEpi cells, p < 0.001). An increased incidence of apoptosis was identified in both aG1 and MAT1-transduced FHLEpi cells. Taken together, these data suggest the potential utility of developing aG1 and aMAT1 retroviral vectors in gene therapy protocols for corneal haze and secondary cataract formation.

Animals↗

PubMed2000

Thermal load of laser aperture masks in nonmechanical trephination for penetrating keratoplasty with the Er:YAG laser: comparison between stainless steel and ceramic masks.

PURPOSE: Thermal effects on the laser aperture mask may play a major role in the thermal loading of the cornea during nonmechanical trephination in penetrating keratoplasty. The purpose of this study was to assess the temperature increase on the laser mask using the 2.94-microm Er:YAG laser in order to find suitable parameters for avoidance of thermal damage to the cornea. METHODS: Thermal load measurements were performed on donor (7.5 mm trephination diameter, 0.7 mm thickness, central hole 3.0 mm) and recipient (7.5 mm trephination diameter, 0.7 mm thickness, outer diameter 13.0 mm) aperture masks. The masks were either mounted on a thermal isolator or fixed directly on porcine corneal samples. Temperature increase was measured either under static conditions in the ablation area (setup 1) and at the opposite side of the mask (setup 2) or in the ablation area under dynamic conditions, rotating the whole globe to simulate a constant trephination speed with the mask positioned directly on a porcine cornea (setup 3). We used the NWL Er:YAG solid-state laser in a 1.3-mm free-running spot mode focused on the trephination margin (half of the beam on the mask and half of it on the cornea) with a pulse energy of 200 or 400 mJ and 18CrNi10 stainless steel versus three different types of ceramic masks (silicium carbide, silicium nitrite, aluminum oxide). Temperature was assessed using an infrared pyrometer with automatic data acquisition software for a personal computer. RESULTS: Overall, the temperature rise ranged between 43.6 K (metal donor mask at the trephination area with 400 mJ pulse energy) and 3.3 K (silicium carbide recipient mask at the opposite side of the mask with 200 mJ pulse energy). With all setups and both energy levels, the heating of the metal mask was significantly higher (P<0.02) than the heating of the three types of ceramic masks. The silicium carbide masks revealed the lowest temperature rise. Comparing the three setups, the temperature rise was maximal under static conditions in the ablation area and minimal at the opposite side, with the dynamic setup ranging in between. Temperature rise was significantly greater (P<0.04) in donor masks than in recipient masks for each mask material and both energy levels. CONCLUSION: The physical characteristics of silicium carbide masks seem superior to those of metal masks with regard to minimizing the thermal load of the epithelium or superficial stroma during Er:YAG laser trephination of the cornea for penetrating keratoplasty.

Animals↗

PubMed2000

Experimental evaluation of two current-generation automated microkeratomes: the Hansatome and the Supratome.

PURPOSE: To compare flap dimensions, cut quality, and blade deterioration after reuse in an experimental setting using two current-generation microkeratomes for laser-assisted in situ keratomileusis. METHODS: Two pivoting-head principle microkeratomes, the Hansatome and the Supratome, were used to perform a corneal flap in 50 freshly enucleated pig cadaver eyes, with an intended thickness of 160 microm. Provided stainless steel blades were used from one to five times. Flap diameter was measured by planimetry and thickness calculated using ultrasonic pachymetry at three different locations. Scanning electron microscopy of stromal beds and blades' cutting edges were performed to assess the cut and blade deterioration after repeated use. RESULTS: Mean flap central thickness (Hansatome/Supratome) was 151 microm (SD 18)/192 microm (SD 32). Progressive thinning/thickening of the flap was observed in the direction toward the hinge (P = .003/P = .021). Mean vertical flap diameters of 8.9 mm (SD 0.3)/8.0 mm (SD 0.4) differed significantly (P = .001). No correlation was found between thickness and diameter (r = 0.03, P = .935/r = 0.12, P = .603). At scanning electron microscopy, smooth cuts were observed with both keratomes using a new blade. Periodical chatter lines at keratectomy edge were present and were more pronounced after blade reuse. Cut quality, blade deterioration, and small tissue remnants on the blade surface were noted with repeated blade use, especially using the Supratome. CONCLUSIONS: Local flap thickness and flap diameter variations are inherent to the instrument used. Comparable cut-surface quality can be obtained with new blades. Although cut and blade deterioration appears to be minor after two reuses, the presence of tissue remnants on the blade surface still limits its reuse.

Animals↗