Biomedical subjects

C Wirbelauer

Publications and source records attributed to C Wirbelauer.

At least 19 recordsLinked to original sources

PubMed2006

[OCT-goniometry before and after iridotomy in angle-closure glaucoma].

PURPOSE: Visualization of the anterior chamber angle is an important diagnostic method in patients with angle-closure glaucoma. In this study, optical coherence tomography (OCT) was used to image the angle width, the iris configuration, and the iris thickness in patients with angle-closure glaucoma. METHODS: Thirteen eyes of 11 patients suffering from angle-closure glaucoma were studied with slitlamp-adapted OCT. All patients were treated with Nd:YAG laser iridotomy. The angle width ( degrees ), the angle opening distance (AOD) (microm), and the iris thickness (microm) were measured with OCT. The configuration of the iris was classified as steeply convex, convex, or flat. RESULTS: The mean angle width was preoperatively 5.1+/-5.0 degrees (0-15 degrees ) and enlarged significantly (p=0.007) to 10.4+/-5.5 degrees (0-19 degrees ) postoperatively. The AOD changed from 71+/-55 microm (0-157 microm) preoperatively to 143+/-74 microm (0-256 microm) postoperatively (p<0.001). The mean iris thickness was 338+/-33 microm. With the exception of two eyes the predominant iris configuration changed from convex to flat. CONCLUSIONS: OCT allowed visualization and noninvasive assessment of the anterior chamber angle region in patients with angle-closure glaucoma. Our results suggest that goniometry with OCT could improve the evaluation in patients with narrow or closed anterior chamber angles.

Adult↗

PubMed2006

[Optical quality of the cornea following incisional correction of astigmatism].

BACKGROUND: Unilateral lamellar keratotomy (LKT) and curved dual lamellar keratotomy (BLK) were compared to evaluate the influence of incisional correction of astigmatism on the optical quality of the cornea. PATIENTS AND METHODS: Forty-six patients with a preoperative astigmatism greater than 1.5 D were studied. LKT was performed on 30 eyes during cataract surgery and 20 eyes were treated with a BLK. Preoperatively and 4 weeks after surgery the corneal topographical data were analyzed with ray tracing in a 3-mm optical zone. The potential visual acuity (PVA) and the optical distortion (OD), which is represented by the width of the point spread in the optical center, were calculated as parameters for the optical quality. RESULTS: The mean surgically induced astigmatism was 2.6+/-1.5 D for the LKT group and 3.5+/-1.4 D for the BLK group. The PVA decreased significantly in the LKT group from 1.2+/-0.2 to 1.0+/-0.3 (p=0.008), whereas in the BLK group the PVA remained unchanged (p=0.916). The OD increased from 6.6+/-0.9 microm to 7.9+/-2.0 microm (p=0.007) in the LKT group. In the BLK group the values were stable (p=0.843). CONCLUSIONS: The optical quality of the cornea decreased after unilateral keratotomy in the early postoperative period. Thus, optical quality values should also be considered in incisional correction of astigmatism.

Adult↗

PubMed2006

[Influence of age on optical aberrations of the human eye].

BACKGROUND: Currently the influence of age on corneal and ocular aberrations is still insufficiently known. The aim of this clinical study was to compare age-related aberrations of human eyes. METHODS: In a prospective study 98 eyes of 49 healthy patients ranging from 17 to 65 years of age (38.6+/-10.0 years) were consecutively examined. The best corrected visual acuity ranged from 0.8 to 1.6; 48 eyes were emmetropic (SE+/-0.5 D), 42 eyes myopic (SE <-0.5 to -6.75 D), and 8 eyes hyperopic (SE >+0.5 to +3.88 D). The corneal aberrations were derived from corneal topography (Keratron Scout, Optikon). The measurement of ocular aberrations was performed with a Tscherning wavefront aberrometer (ORK, Schwind). The aberrations of the Zernike coefficients and RMS values (1st to 4th order) were determined. RESULTS: The mean corneal and ocular Zernike coefficients of higher order were smaller than 0.2 microm. There was an evident decrease of wavefront aberrations with increasing order. Higher order corneal aberrations were larger than the corresponding ocular aberrations. With increasing age higher optical errors increased in complexity, and the correlation of corneal and ocular aberrations decreased with significant differences. Although the corneal ocular RMS value of the 3rd and 4th order correlated in the younger group (r=0.51, p=0.0001), there was no correlation in the older group (r=-0.48, p=0.832). The influence of age caused a significant increase of ocular aberrations of the 3rd and 4th order, in particular a tenfold extension of coma (C07) (p=0.002), a twofold extension of spherical aberration (C12) (p=0.0001), and an increase of the 3rd and 4th order RMS values (p=0.001). CONCLUSIONS: Increased age induced an increase in optical aberrations of the eye, which demonstrates the influence of the lens on ocular aberrations. The combination of corneal and ocular diagnostic methods is recommendable for a better understanding of visual performance.

Adolescent↗

PubMed2006

[Cataract surgery in patients with end-stage glaucoma].

BACKGROUND: The purpose of this study was to assess the benefit of cataract surgery in patients with advanced cataract and glaucoma. METHODS: In a prospective study, we investigated 12 consecutive patients (12 eyes). Inclusion criteria were the diagnosis of cataract and end-stage glaucoma with a cup-disc ratio (CD) of 0.9-1.0 and marked visual field defects with partially preserved central function. Preoperatively, at the third postoperative day and after 6 months (2-11 months), the visual acuity (V), the intraocular pressure (IOP), the number of antiglaucomatous drugs and the visual fields were assessed. Furthermore, the surgical procedure and possible complications were noted. In all patients cataract surgery was performed with topical anaesthesia. RESULTS: 10 patients were treated with cataract surgery alone, whereas 2 patients underwent combined cataract and glaucoma surgery. The mean visual acuity improved significantly from 0.3 to 0.5 (p = 0.007). Additionally a significant intraocular pressure reduction of 4.4 mm Hg (p = 0.007) was observed. The number of antiglaucomatous drugs decreased from 1.5 preoperatively to 0.8 postoperatively. The mean deviation (MD) improved from -27.5 dB up to -26.4 dB (p = 0.036) after 6 months. CONCLUSION: Patients with progressive cataract and end-stage glaucoma can benefit from cataract surgery. Although marked visual field defects were present, an increase in visual acuity as well as a decrease of intraocular pressure may be achieved without worsening of the visual fields.

Aged↗

PubMed2006

[Covered sclerotomy for fistulating glaucoma surgery].

BACKGROUND: Covered sclerotomy was developed as a minimally invasive modification of filtering glaucoma surgery. In this prospective study the clinical results are compared after one year. PATIENTS AND METHODS: 58 eyes with advanced glaucoma were studied. 32 eyes had a covered sclerotomy (ST) and 26 had an ST with viscoelastic filling of the anterior chamber in order to reduce the postoperative hypotony rate (ST+H). The ST procedure consisted in the preparation of a 4-mm corneoscleral tunnel incision with a T-shaped 1.75-mm wide perforation and radial transection of the tunnel floor. RESULTS: The preoperative intraocular pressure (IOP) was on average 30 +/- 8.5 mmHg (ST) and 26 +/- 8.3 mmHg (ST+H). After 1 year the IOP decreased significantly (P < 0.05) to 17 +/- 3.7 mmHg (ST) and 17 +/- 2.9 mmHg (ST+H). The mean IOP reduction was 37 % (ST) and 30 % (ST+H). Revisions were required in 37 % (ST) and 15 % (ST+H) of the cases. The postoperative hypotony rate was 34 % in both groups. The number of morphologically functional filtering blebs was 60 % (ST) and 70 % (ST+H) after one year. CONCLUSIONS: The covered sclerotomy required minimal surgical manipulations of the conjunctiva and sclera. After 1 year a significant reduction of the IOP was achieved. However, the occurrence of bleb scarring could not be lowered compared to trabeculectomy. Therefore further modifications with the primary application of antimetabolites are planned.

Adult↗

PubMed2006

[Functional results after intraocular lens implantation with or without blue light filter: an intraindividual comparison].

BACKGROUND: The new generation of intraocular lenses (IOL) with an additional blue light filter has a slight yellowish colour (compared to the IOLs with only a UV filter) due to its different light transmitting properties. This could have an effect on contrast sensitivity and subjective visual perception. PATIENTS AND METHODS: In this intraindividual prospective comparative study including 14 cataract patients without further ocular pathology, a blue light filtering IOL (SN60AT, Alcon) was implanted in one eye and 1 month later a conventional single-piece IOL (SA60AT, Alcon) was fitted into the fellow eye. The visual acuity and the clinical findings were assessed at one day and four weeks post-operatively. Contrast sensitivity was tested under defined mesopic (6 cd/m(2)) and high mesopic (18.8 cd/m(2)) light conditions in the Ginsburg Box using the Functional Acuity Contrast Test (F.A.C.T.). Furthermore, subjective differences in the visual perception of both eyes were noted. RESULTS: The contrast sensitivity testing 1 day and 1 month postoperatively, revealed no statistically significant differences (P > 0.008) between both IOL types for all spatial frequencies (1.5/3/6/12/18 cpd) and light levels. 13 patients (85 %) reported no differences in the colour perception of both eyes, and none had visual disturbances. CONCLUSION: This intraindividual comparison revealed no relevant differences concerning mesopic contrast sensitivity and the subjective visual perception after implantation of one IOL with or without a blue light filter.

Aged↗

PubMed2005

[Evaluation of eye patching after cataract surgery in topical anesthesia].

BACKGROUND: Although postoperative eye patching is a common practice its background is not well known. Therefore the necessity of eye patching after cataract surgery in topical anesthesia from the medical point of view and the patients' subjective opinion was studied. PATIENTS AND METHODS: In this prospective and randomized study 133 patients received after cataract surgery either no covering of the eye (group1), a transparent eye shield for four hours (group 2), an eye pad for four hours (group 3) or an eye pad until the next morning (group 4). Clinical findings were noted and local symptoms, such as pain, foreign body sensation, tearing and photophobia were documented on a visual analogue scale (0 - 10). Furthermore, a questionnaire concerning the subjective opinion was handed out to the patient. RESULTS: The clinical findings revealed no significant differences between the groups. The mean values for local pain were 0.94 +/- 1.56, for the foreign body sensation 1.41 +/- 2.02, for tearing 0.99 +/- 1.8 and for photophobia 1.05 +/- 1.99. Comparing the groups there was significantly more pain and foreign body sensation reported by the patients in group 3, who received eye patching for 4 hours. 91 % of the unpatched patients had no discomfort, whereas 53 % of the patients wearing an eye pad until the next morning considered it as unnecessary. CONCLUSION: After cataract surgery in topical anesthesia only mild symptoms were noted. There were no significant differences between the groups in the objective clinical findings and the subjective feeling. These results indicate that after cataract surgery eye patching could be unnecessary.

Adolescent↗

PubMed2005

[Imaging of the anterior eye chamber with optical coherence tomography].

BACKGROUND: Optical coherence tomography (OCT) represents a high-resolution diagnostic method which can be used to precisely image the anterior eye segment. Further developments in scanning technology and data evaluation allowed to visualize the entire anterior eye segment in one image, and the purpose of this study was to clinically evaluate this new system. PATIENTS AND METHODS: The studied OCT system was adapted to a slit-lamp and allowed us to image the anterior segment with an axial resolution of 10 microm at a scanning rate of 200 Hz with a depth of 7 mm and a maximal width of 15 mm. In selected cases the clinical value of anterior segment OCT was assessed. The reproducibility and level of agreement of anterior chamber depth measurements were assessed during the preoperative examination in 49 cataract surgery patients and compared to ultrasound (US) biometry (10 MHz). RESULTS: The studied anterior segment OCT allowed the cross-sectional imaging of the entire anterior eye segment. Changes of the anterior chamber before and after cataract surgery or surgical iridectomy were visualised. Furthermore, the findings of the anterior chamber after implantation of an iris-fixated intraocular lens (IOL) and an iris prosthetic system could be assessed. The reproducibility of the anterior chamber depth measurement was +/- 22 microm (OCT) and +/- 76 microm (US). The mean difference between optical and acoustic values was 1 microm (0.03 % p = 0.921) and the limits of agreement (95 % confidence interval) were 260 microm (8.58 %). CONCLUSIONS: The anterior segment OCT proved to be a helpful diagnostic method. The cross-sectional visualisation of the entire anterior chamber allowed us to assess important values for the implantation of iris-fixated IOL and other changes after surgical procedures. The resolution and reproducibility were higher than for conventional ultrasound biometry.

Aged↗

PubMed2004

[Online optical coherence pachymetry in laser in situ keratomileusis].

PURPOSE: Currently the microkeratome incision and the ablation depth are unpredictable in laser in situ keratomileusis (LASIK). Online optical coherence pachymetry is a high-resolution and non-contact method, which enables the corneal thickness changes to be monitored intraoperatively. METHOD. In 12 patients undergoing myopic LASIK, online optical coherence pachymetry with a wavelength of 1310 nm and a measurement frequency of 74 Hz was studied. The central corneal thickness changes were determined continuously. RESULTS: Online optical coherence pachymetry enabled intraoperative visualization and assessment of the central corneal thickness, the flap thickness after the microkeratome pass, the time-resolved ablation and the residual stromal thickness. Intraoperatively the mean flap thickness was 113+/-31 microm and the residual stromal thickness was 277+/-49 microm. The optically determined ablation depth was 116+/-30 micro m, which corresponded to 33 microm higher mean values than the nominal ablation depth. CONCLUSIONS: Online optical coherence pachymetry enabled the flap and residual stromal thickness to be measured intraoperatively. Also the individual ablation depth and possible dehydration effects of the cornea were monitored continuously. Thus, online optical coherence pachymetry could contribute to improve the safety standards during LASIK.

Adult↗

PubMed2004

[Reproducibility of goniometry with slitlamp-adapted optical coherence tomography].

BACKGROUND: Visualization of the anterior chamber angle (ACA) is an important diagnostic part of evaluating patients with glaucoma. The purpose of this study was to evaluate the intra- and interobserver variability and reliability of the ACA and angle opening distance (AOD) measurements using optical coherence tomography (OCT). METHODS: To evaluate the intra- and interobserver variability, ACA and AOD were both measured five times and in three consecutive images in 22 patients (24 eyes) by two experienced observers. The intraclass correlation coefficient (ICC) as a measure of reliability was determined to estimate the intra- and interobserver variability. The main outcome measures were accuracy, reproducibility assessed with the coefficient of variation (CV), and the limits of agreement of ACA and AOD. RESULTS: The intraobserver variability of five replicate measurements was +/-1.4 degrees for ACA (CV 6.2%) and +/-11 micro m for AOD (CV 4%). The ICC for the intraobserver reliability was 0.99 for both ACA and AOD. The interobserver variability of three intersessional measurements was +/-2.5 degrees for ACA (CV 10.9%) and +/-24 micro m (CV 8.3%) for AOD. The ICC was 0.95 for ACA and 0.98 for AOD. There was no difference ( p>0.05) between the two observers measuring ACA and AOD. CONCLUSIONS: Two-dimensional visualization of the ACA and its assessment with slitlamp-adapted OCT yielded reliable ACA and AOD measurements in a clinical setting. Thus, OCT goniometry could provide an objective method to assess the anterior chamber angle.

Adult↗

PubMed2004

[Cataract surgery under topical anesthesia with oral anticoagulants].

BACKGROUND: Approximately 14 % of cataract surgery patients receive blood-thinning agents. In a prospective study, the influence of oral anticoagulants on intraoperative and postoperative hemorrhages in patients undergoing cataract surgery in topical anesthesia was investigated. PATIENTS AND METHODS: 128 patients presenting for cataract surgery under oral anticoagulation were included. The mean preoperative prothrombin time was 39 +/- 18 %. Most patients (81 %) continued their oral anticoagulation (prothrombin time 34 +/- 13 %). All surgeries were performed in topical anesthesia. RESULTS: In 9 patients (7 %) an ocular hemorrhagic event was observed. These were not sight-threatening and resorbed spontaneously within a few days. Only one patient (0.8 %) had a slight hemorrhage in the anterior chamber. There were no differences (P > 0.05) between patients with or without hemorrhagic complications in the postoperative visual acuity, the intraocular pressure, the prothrombin time or the discontinuation of oral anticoagulants. CONCLUSIONS: Cataract surgery in topical anesthesia under oral anticoagulation did not increase the risk of sight-threatening hemorrhages. The continuation of oral anticoagulation seems particularly indicated for ambulatory cataract surgery.

Administration, Oral↗

PubMed2003

[Piggyback lens implantation for anisometropia in pseudophakic eyes].

OBJECTIVE: Long standing pseudophakia or previous laser capsulotomy make lens exchange for anisometropia or incorrect target refraction difficult. Piggyback lens implantation might be a less traumatic surgical alternative. PATIENTS AND METHODS: Eight patients had a secondary posterior chamber lens implant (PMMA) into the ciliary sulcus. Lens power was estimated by the preoperative refraction according to the refractive vergence formula and was controlled intraoperatively by an automatic refractometer. Surgical access minimized preoperative astigmatism. RESULTS: All patients had disturbing anisometropia of 4.57+/-2.86 D and had undergone cataract surgery 1-13 years previously. Piggyback lens implantation was combined with surgical aspiration of the secondary cataract in three patients. Due to recurrent PVR retinal detachment, one patient received a silicon oil refilling procedure and piggyback lens implantation. The preoperative spherical equivalent was -3.34+/-4.9 D. Mean follow up time was 16.6 months. Postoperative anisometropia was reduced to 1.1+/-1.01 D. The mean absolute deviation from target refraction was 0+/-0.92 D. Elevated IOP or secondary cataract formation in the lens interface were not observed. One patient developed pigment dispersion. CONCLUSION: Secondary piggyback lens implantation into the ciliary sulcus in front of an existing posterior chamber lens is a safe and effective refractive surgical procedure for special cases with predictable refraction.

Aged↗

PubMed2003

Optical coherence tomography in malignant glaucoma following filtration surgery.

AIM: To assess the value of slit lamp adapted optical coherence tomography (OCT) for the management of malignant glaucoma following filtration surgery. METHODS: Two patients (three eyes) developed malignant glaucoma following filtration surgery for primary open angle glaucoma (POAG). With slit lamp adapted OCT it was possible to image non-invasively the anterior chamber angle structures during the malignant glaucoma episode, and after pars plana vitrectomy (PPV) with anterior chamber reformation. RESULTS: OCT revealed in both patients a markedly decreased anterior chamber angle with extreme shallowing of the anterior chamber depth during the acute malignant glaucoma phase. This critical closure of the anterior chamber angle resolved after PPV and deepening of the anterior chamber with viscoelastic. After PPV the quantitative values of the anterior chamber angle (ACA) and the anterior chamber opening distance (AOD) increased from 0 to an ACA of 35 degrees (SD 14 degrees ) and an AOD of 426 (SD 162) micro m. CONCLUSIONS: Non-contact slit lamp adapted OCT was helpful to evaluate the anterior chamber structures in malignant glaucoma, and thus could improve management of this serious clinical disorder.

Aged↗

PubMed2001

Quantitative distribution of glycosaminoglycans in young and senile (cataractous) anterior lens capsules.

The ocular lens is surrounded by the lens capsule, which is an elastic and unusually thick basal membrane. Anionic sites are thought to be responsible for charge-selective permeability barriers in basal membranes. We have used cationic colloidal gold as a tracer for anionic binding sites to investigate the distribution of glycosaminoglycans in young and senile (cataractous) lens capsules. Using electron microscopy, combined with the cationic colloidal gold post-embedding technique, glycosaminoglycans were localized distinctively in a continuous layer immediately apposed to the lens epithelium, which has been referred to as the lamina lucida. The amount of gold particles decreased from the internal (lenticular) side of the capsule, toward the center, followed by an increase of label intensity toward the external (humoral) side. The humoral surface is characterized by a highly anionic layer measuring 1.5--4 micro m. Immunofluorescence microscopy localized three main types of glycosaminoglycans (heparan-, chondroitin- and dermatan sulfate) within this distinctive layer. Quantitative electron microscopy demonstrated reduced amounts of glycosaminoglycans at the lenticular and humoral side of senile (cataractous) lens capsules. The distinctive spatial distribution of glycosaminoglycans in human lens capsules is discussed in terms of age-related structural and functional changes.

Adult↗

PubMed2001

[Biomorphometry of corneal epithelium with slit lamp-adapted optical coherence tomography].

INTRODUCTION: The purpose of this study was to evaluate the biomorphometry of the corneal epithelium with slitlamp-adapted optical coherence tomography (OCT). PATIENTS AND METHODS: In a clinical study, slitlamp-adapted OCT of the cornea was performed in 15 patients before and immediately after therapeutic corneal abrasion. Central corneal epithelium thickness measurements were compared to the pre- and postoperative central corneal thickness. RESULTS: Preoperatively, the corneal epithelium could be visualised from the highest OCT light reflections at the interfaces air-tear film and epithelium-Bowman's membrane. The preoperative mean geometrical central epithelial thickness determined with OCT ranged from 65 +/- 12 microns to 72 +/- 14 microns (45-92 microns). The mean difference of the pre- and postoperative central corneal thickness was 48 +/- 19 microns (9-79 microns). This resulted in a deviation from the direct epithelial thickness measurements of 26-33%. The reproducibility of the geometrical epithelial thickness was +/- 9 microns. CONCLUSIONS: Slitlamp-adapted OCT enabled a noncontact evaluation of the corneal epithelium. The difference between direct and indirect corneal epithelium thickness measurements could be related to the partial optical inclusion of the precorneal tear film and the Bowman's membrane. With some restrictions the biomorphometry of the corneal epithelium with slitlamp-adapted OCT seems to be a valuable technique to monitor therapeutical and refractive procedures of the cornea.

Adult↗

PubMed2001

[Examination of the cornea using optical coherence tomography].

INTRODUCTION: This study evaluated the clinical use of optical coherence tomography (OCT) for two-dimensional representation of the cornea. PATIENTS AND METHODS: Noncontact slitlamp-adapted OCT was used in selected cases to evaluate pathologically altered corneas and to measure the central corneal thickness and curvature. RESULTS: OCT provided correlation between differences in reflection and morphological changes. Scar tissue resulted in hyper-reflective light scattering, whereas cystic lesions were hyporeflective. Precise biomorphometry also allowed representation of intrastromal and retrocorneal changes. Central corneal thickness measured by OCT yielded reproducible values and corneal curvature could be calculated from the optical signals of the corneal surface. CONCLUSIONS: OCT provides high-resolution representation of the cornea and exact evaluation of its morphology, thickness, and curvature. Due to the noncontact, simple, and rapid examination using the slitlamp the corneal OCT method is a promising additional diagnostic modality.

Adolescent↗

PubMed2001

Immunohistochemical and charge-specific localization of anionic constituents in pseudoexfoliation deposits on the central anterior lens capsule from individuals with pseudoexfoliation syndrome.

BACKGROUND: Pseudoexfoliation (PSX) syndrome is a degenerative systemic disorder that is characterized primarily by deposits of distinct fibrillar material on the surface lining the anterior and posterior chambers of the eye and is often associated with cataract and glaucoma. Although some components of the PSX material have been identified, the precise composition is obscure. METHODS: High-resolution scanning electron microscopy in conjunction with colloidal cationic gold labeling was used to localize anionic constituents at the surface of PSX aggregates. Transmission electron microscopy was applied for the immunocytochemical detection of glycosaminoglycans, and to monitor the charge-specific distribution of colloidal thorium dioxide and ferritin in PSX material. The specific binding of antibodies was confirmed by immunohistological staining of paraffin-embedded specimens. RESULTS: Paraffin-embedded tissue sections revealed immunoreactivity for keratan sulfate and dermatan sulfate proteoglycan within PSX material deposited on the surface of the anterior lens capsule. Post-embedding immunogold labeling of keratan sulfate demonstrated an intense label of PSX aggregates primarily associated with mature PSX fibrils, whereas dermatan sulfate proteoglycon appeared to be present in low quantities. Additionally, keratan sulfate was found at the humoral periphery of the lens capsules. To further investigate the distribution of anionic sites in PSX material, we used cationic colloidal tracers of different size, such as gold, thorium dioxide and ferritin. PSX aggregates exhibited a strong negative charge, resulting very likely from glycosaminoglycan chains of proteoglycans. The density of anionic sites was higher at the interfibrillar matrix. Lens capsules associated with PSX material revealed a diminished accumulation of cationic ferritin at the humoral surfaces. CONCLUSIONS: Increased amounts of different glycosaminoglycans identified in PSX material suggest an important role of proteoglycans for the pathogenic pathway in PSX.

Aged↗

PubMed2000

The F-box protein Skp2 is a ubiquitylation target of a Cul1-based core ubiquitin ligase complex: evidence for a role of Cul1 in the suppression of Skp2 expression in quiescent fibroblasts.

The ubiquitin protein ligase SCF(Skp2) is composed of Skp1, Cul1, Roc1/Rbx1 and the F-box protein Skp2, the substrate-recognition subunit. Levels of Skp2 decrease as cells exit the cell cycle and increase as cells re-enter the cycle. Ectopic expression of Skp2 in quiescent fibroblasts causes mitogen-independent S-phase entry. Hence, mechanisms must exist for limiting Skp2 protein expression during the G(0)/G(1) phases. Here we show that Skp2 is degraded by the proteasome in G(0)/G(1) and is stabilized when cells re-enter the cell cycle. Rapid degradation of Skp2 in quiescent cells depends on Skp2 sequences that contribute to Cul1 binding and interference with endogenous Cul1 function in serum-deprived cells induces Skp2 expression. Furthermore, recombinant Cul1-Roc1/Rbx1-Skp1 complexes can catalyse Skp2 ubiquitylation in vitro. These results suggest that degradation of Skp2 in G(0)/G(1) is mediated, at least in part, by an autocatalytic mechanism involving a Skp2-bound Cul1-based core ubiquitin ligase and imply a role for this mechanism in the suppression of SCF(Skp2) ubiquitin protein ligase function during the G(0)/G(1) phases of the cell cycle.

Amino Acid Motifs↗