Use of a muscle flap in lower blepharoplasty.

An adjunctive technique for lower lid blepharoplasty is presented. This operative procedure uses the principle of anchoring the upper margin of the lower lid by suturing a triangular muscle flap from it to the lateral-superior part of the orbital rim. This more effective support for the lower lid margin permits one to excise more redundant tissue without getting an ectropion.     

Restoring palpebral fissure shape after previous lower blepharoplasty

The youthful palpebral fissure can be described as long and narrow. Both the aging process and transcutaneous lower blepharoplasty can cause descent of the lower lid margin and medial migration of the lateral canthus, resulting in a rounding of the palpebral fissure. This article presents a technique to correct significant postsurgical lower lid malposition and palpebral fissure distortion without the use of outer or inner lamellar grafts. In overview, subperiosteal dissection frees scarred lid structures and cheek soft tissues, creating a continuous composite flap. Elevation of the cheek soft tissues recruits deficient outer lamellae and allows the sub-orbicularis oculi fat to be positioned between the orbital rim and scarred lid structures, filling this space and helping to support the repositioned lid margin. Titanium screws placed in the lateral orbit provide a point for secure fixation of elevated cheek tissues. Transosseous wire fixation securely repositions the lateral canthus. This procedure not only restores lower lid position and the vertical height of the palpebral fissure, but it also restores the palpebral fissure's horizontal length and the lateral canthal angle. It has been effective in correcting palpebral fissure distortion after lower blepharoplasty in 15 patients during a 6-year period.     

Lower eyelid reconstruction with a conchal cartilage graft

A conchal cartilage graft without skin or mucosa was used as a posterior lining for lower eyelid reconstruction in seven patients. The raw surface of the graft was smooth enough to cause no corneal irritation and was epithelialized from the surrounding mucosa about 3 to 4 weeks after the operation. The lower eyelid reconstructed in this method produced a stable lid margin.     

Retrospective analysis of reconstruction techniques after periocular basalioma excision

The paper presents our approach to reconstruction after periocular basalioma (pBCC) excision, especially of large lower lid (LL) and medial canthal (MC) pBCC. Retrospective analysis of data of 123 patients with pBCC, confirmed on histologic examination (HE), operated in period from 1998 to 2006, was performed. Oncologic safety margins of 3 mm were marked after local anesthesia was administered. Reconstruction was done in time of surgery. In pBCC away from a lid margin, adjacent myocutaneous flaps were used. For lid margin involving (LM) pBCC, size of 10 mm and less in horizontal diameter (HD), full-thickness lid excision was performed, combined with lateral canthotomy and/or Tenzel or McGregor flap. When size of LM pBCC was more than 10 mm in HD and it was on a LL, ipsilateral upper lid (UL) tarsoconjunctival (TC) graft combined with single pedicle transposition myocutaneous flap were used. The same size of LM pBCC on a UL required ipsilateral full-thickness LL "switch" flap and/or contralateral LL Hübner graft. In MC pBCC combined approach was used. The follow-up was up to 5 years. The 19 patients (15.4%) had positive tumor margin on HE. Five of them refused further surgery, but only two had recurrence. The rest of 121 patients had no recurrence during follow-up. In 5/14 patients, who underwent additional surgery, no tumor cells were found on HE. The 10/123 patients (8.1%) had complications. The imperative of our approach to reconstruction after pBCC was good functional and cosmetic result, avoiding prolonged lid closure. Accordingly, in large LL LM pBCC we used ipsilateral UL TC graft combined with single pedicle transposition myocutaneous flap. In MC pBCC combined approach was mandatory.     

Involutional entropion: a simple and stable repair

A simple technique for repair of involutional entropion is described. A 4 x 20 mm strip of cartilage is removed from the concha of the ear and placed in the lower lid, deep to the orbicularis muscle. Over the past 6 years, I have performed this procedure on 15 patients. Fourteen patients had an excellent result; one patient required a secondary lateral wedge resection. There have been no recurrences. The tarsal plate of the lower eyelid appears to soften and shrink with advancing age. As the tarsus shrinks, the lid becomes less rigid and the margin tends to roll inward. Creating a neotarsus out of ear cartilage provides a simple and stable repair for involutional entropion because it restores the structural rigidity of the lower lid. The operative procedure is technically simple. Its long-term effectiveness confirms the view, not widely held, that one primary cause of involutional entropion is a shrunken and atrophic tarsal plate.     

Human bites of the eyelid

Five patients with traumatic colobomas of the eyelid secondary to human bites were surgically repaired with retrieved autogenous tissue. All patients were treated with prophylactic intravenous antibiotics. Surgical repair consisted of debridement of the autograft, meticulous layered closure of the autograft to the wound, and placement of a lid margin suture. In two of the patients, mild upper eyelid retraction was noted, and two patients had loss of cilia.     

A simple method for reducing moisture condensation on Petri dish lids

Condensation on the lids of Petri dishes, used to culture plant tissues, can often obscure the view of the contents of the dish and interfere with data collection. Under the high humidity conditions that exist in the culture container, a small temperature drop causes water to condense on the inside lid and sides of the container. Mild condensation causes “fogging” while continual or repeated rounds of condensation result in the formation of water droplets. To control condensation in the standard plant tissue culture Petri dish, a simple method was developed whereby the lid of the culture dish was modified, to buffer the lid from temperature fluctuations. Polymer discs, which were the same diameter as the Petri dish lid, were either placed on the top of the lids of existing dishes or surface-sterilized and used in place of the lid. Polymer discs of varying thicknesses and type, and possessing different thermal conductivities, were evaluated for their abilities to reduce the rate of condensation formation. Petri dishes with modified lids were placed under reduced temperature conditions. Condensation, forming on the lids of the dishes was quantified over time using image analysis. Gray value determinations indicated that the thicker polymer discs with the lowest thermal conductivities provided the best protection against condensation. Placement of polymer discs on the top of Petri dishes is a relatively simple method that can be used to buffer the lid from small temperature changes and minimize condensation problems.     

Palatal grafts for eyelid reconstruction

A full-thickness graft of hard palate mucosa was used as the lining tissue for eyelid reconstruction in 11 patients over a 7-year period. An orbicularis musculocutaneous flap supplied cover and support. In all cases the mucosal graft was easily removed, convenient to handle, and took completely. The palate donor site reepithelialized by about 3 weeks postoperative and has remained healed and asymptomatic in all cases. In follow-up averaging 3 years, all the reconstructed lids have retained a stable and comfortable lid margin, with no instance of entropion or irritation. The outstanding virtue of palate mucosa for eyelid reconstruction is that it appears to retain most of its original size and stiffness over the long term and thus in a single layer can serve to replace both tarsus and conjunctiva.     

Eyelids and eye socket reconstruction using the expanded forehead flap and scapha composite grafting.

After trauma or excision of malignant tumor, it is difficult to achieve satisfactory results when reconstructing deformed eyelids and the socket for an ocular prosthesis. The authors demonstrate examples of successful reconstruction for a prosthetic eye that provided adequate and aesthetic soft-tissue support achieved by applying a three-step surgical procedure of reconstruction of the eye socket, the eyelids, and the tarsus and eyelid margin. Because it is highly vascularized and its distal end can be divided into two or three portions for easy three-dimensional reconstruction, the expanded forehead flap alone, with a galea flap, or with a free rectus abdominis muscle perforator flap was used. The expanded forehead flap also provides excellent thin upper lid contour and good color-matching with a recipient site. For the eye socket, sufficient volume of tissue was provided from the expanded forehead flap with or without a galea or a free rectus abdominis muscle perforator flap, and a deep and convex fornix was formed. This resulted in a good fit and in stability of the ocular prosthesis. The surface and the inner lining of the eyelids were reconstructed using portions of the expanded forehead flap. For the tarsus and eyelid margin, conventional reconstruction techniques use cartilage of the concha, which has limitations of length and which does not fit the shape of the tarsal margin. The authors used the scapha composite graft, and a natural shape and good elasticity resulted.     

Glands of the eyelids of rhesus monkeys (Macaca mulatta)

The various glands of rhesus monkey eyelids and human eyelids are similar. Numerous modified sebaceous glands are located along the tarsus. These conform with the meibomian glands, while typical sebaceous glands associated with the hair follicles of the lashes are consistent with the glands of Zeis. Lobules of accessory lacrimal tissue, corresponding to the glands of Krause and Wolfring, are located in the conjunctiva of the fornix and along the orbital border of the tarsal plate. Goblet cells are plentiful in the mucosa of the palpebral and bulbar conjunctiva, and along the lid margin are the sweat glands of Moll.     

The schizosaccharomyces pombe dim1(+) gene interacts with the anaphase-promoting complex or cyclosome (APC/C) component lid1(+) and is required for APC/C function

The Schizosaccharomyces pombe dim1(+) gene is required for entry into mitosis and for chromosome segregation during mitosis. To further understand dim1p function, we undertook a synthetic lethal screen with the temperature-sensitive dim1-35 mutant and isolated lid (for lethal in dim1-35) mutants. Here, we describe the temperature-sensitive lid1-6 mutant. At the restrictive temperature of 36 degrees C, lid1-6 mutant cells arrest with a "cut" phenotype similar to that of cut4 and cut9 mutants. An epitope-tagged version of lid1p is a component of a multiprotein approximately 20S complex; the presence of lid1p in this complex depends upon functional cut9(+). lid1p-myc coimmunoprecipitates with several other proteins, including cut9p and nuc2p, and the presence of cut9p in a 20S complex depends upon the activity of lid1(+). Further, lid1(+) function is required for the multiubiquitination of cut2p, an anaphase-promoting complex or cyclosome (APC/C) target. Thus, lid1p is a component of the S. pombe APC/C. In dim1 mutants, the abundances of lid1p and the APC/C complex decline significantly, and the ubiquitination of an APC/C target is abolished. These data suggest that at least one role of dim1p is to maintain or establish the steady-state level of the APC/C.     

Lid closure dynamics of porcine pancreatic lipase in aqueous solution

BackgroundPancreatic lipases hydrolyze fatty acids in dietary pathway. The activity of porcine pancreatic lipase (PPL) is controlled by lid domain along with a coenzyme, colipase. The active open-state conformation of the protein could be induced by detergents or bile salts which would be further stabilized by binding of colipase. In the absence of these interactions, the lid preferably attains a closed conformation in water.MethodsMolecular dynamic simulation was used to monitor the lid movement of PPL in open and closed conformations in water. Free energy surface was constructed from the simulation. Energy barriers and major structural changes during lid opening were evaluated.ResultsThe lid closure of PPL in water from its open conformation might be initiated by columbic interactions which initially move the lid away from domain 1. This is followed by major dihedral changes on the lid residues which alter the trajectory of motion. The lid then swirls back towards domain 1 to attain closed conformation. This is accompanied with conformational changes around β5- and β9-loops as well. However, PPL in closed conformation shows only the domain movements and the lid remains in its closed conformation.ConclusionsPPL in closed conformation is stable in water and the open conformation is driven towards closed state. The lid follows a swirling trajectory during the closure.General significanceConformational state of the lid regulates the activity and substrate specificity of PPL. Hence, it is essential to understand the lid dynamics and the role of specific amino acid residues involved.     

Late Cretaceous (Cenomanian to Campanian) paleoenvironmental history of the Eastern Canadian margin of the Western Interior Seaway: bonebeds and anoxic events

Upper Cretaceous strata in the Pasquia Hills of the northern Manitoba Escarpment, eastern Saskatchewan, Canada provide a detailed paleoenvironmental and sea-level record of the eastern margin of the Western Interior Seaway. Sediments deposited during the Cenomanian/Turonian Greenhorn marine cycle are dominantly black mudstones deposited in a stratified water column, with bottom-water anoxia recurrently reaching into the photic zone. A middle Cenomanian sea-level lowstand event followed by transgression left a series of bonebeds within the Belle Fourche Member of the Ashville Formation, indicating a sedimentary environment starved of coarse siliciclastics. Maximum sea level resulted in the formation of limestone beds within the Favel Formation, further favoured by reduced terrigenous sediment input compared to the western margin. Limestone sedimentation was followed by a phase of increased freshwater input under lower sea level conditions, and reducing zoo- and phytoplankton diversities. During final Greenhorn regression, eastern Saskatchewan probably turned into a restricted basin severely limiting marine circulation. Poor or absent benthic foraminiferal assemblages and biomarker analysis suggest prevailing watermass stratification throughout the Cenomanian/Turonian transgressive/regressive cycle. This was caused either by a freshwater lid, stratification of Boreal and Tethyan-derived watermasses, or both, to various intensities affected by changing sea level. Basin oxygenation during Niobrara time varies between localities along the eastern margin as documented by presence/absence of benthic and planktic foraminifera.     

Requirement of lid2 for interfacial activation of a family I.3 lipase with unique two lid structures

A family I.3 lipase from Pseudomonas sp. MIS38 (PML) is characterized by the presence of two lids (lid1 and lid2) that greatly change conformation upon substrate binding. While lid1 represents the commonly known lid in lipases, lid2 is unique to PML and other family I.3 lipases. To clarify the role of lid2 in PML, a lid2 deletion mutant (ΔL2-PML) was constructed by deleting residues 35-64 of PML. ΔL2-PML requires calcium ions for both lipase and esterase activities as does PML, suggesting that it exhibits activity only when lid1 is fully open and anchored by the catalytically essential calcium ion, as does PML. However, when the enzymatic activity was determined using triacetin, the activity of PML exponentially increased as the substrate concentration reached and increased beyond the critical micellar concentration, while that of ΔL2-PML did not. These results indicate that PML undergoes interfacial activation, while ΔL2-PML does not. The activities of ΔL2-PML for long-chain triglycerides significantly decreased while its activity for fatty acid ethyl esters increased, compared with those of PML. Comparison of the tertiary models of ΔL2-PML in a closed and open conformation, which are optimized by molecular dynamics simulation, with the crystal structures of PML suggests that the hydrophobic surface area provided by lid1 and lid2 in an open conformation is considerably decreased by the deletion of lid2. We propose that the hydrophobic surface area provided by these lids is necessary to hold the micellar substrates firmly to the active site and therefore lid2 is required for interfacial activation of PML. DATABASE: Triacylglycerol lipase (EC 3.1.1.3).     

Dissection of the assembly pathway of the proteasome lid in Saccharomyces cerevisiae

The 26S proteasome is a highly conserved multisubunit protease that degrades ubiquitinated proteins in eukaryotic cells. It comprises a 20S core particle and two 19S regulatory particles that are further divided into the lid and base complexes. The lid is a nine subunits complex that is structurally related to the COP9 signalosome and the eukaryotic initiation factor 3. Although the assembly pathway of the 20S and the base are well described, that of the lid is still unclear. In this study, we dissected the lid assembly using yeast lid mutant cells, rpn7-3, Δrpn9, and rpn12-1. Using mass spectrometry, we identified a number of lid subassemblies, such as Rpn3-Rpn7 pair and a lid-like complex lacking Rpn12, in the mutants. Our analysis suggests that the assembly of the lid is a highly ordered and multi-step process; first, Rpn5, 6, 8, 9, and 11 are assembled to form a core module, then a second module, consisting of Rpn3, 7, and Sem1, is attached, followed by the incorporation of Rpn12 to form the lid complex.     

Incorporation of the Rpn12 subunit couples completion of proteasome regulatory particle lid assembly to lid-base joining

The 26S proteasome, the central eukaryotic protease, comprises a core particle capped by a 19S regulatory particle (RP). The RP is divisible into base and lid subcomplexes. Lid biogenesis and incorporation into the RP remain poorly understood. We report several lid intermediates, including the free Rpn12 subunit and a lid particle (LP) containing the remaining eight subunits, LP2. Rpn12 binds LP2 in vitro, and each requires the other for assembly into 26S proteasomes. Stable Rpn12 incorporation depends on all other lid subunits, indicating that Rpn12 distinguishes LP2 from smaller lid subcomplexes. The highly conserved C terminus of Rpn12 bridges the lid and base, mediating both stable binding to LP2 and lid-base joining. Our data suggest a hierarchical assembly mechanism where Rpn12 binds LP2 only upon correct assembly of all other lid subunits, and the Rpn12 tail then helps drive lid-base joining. Rpn12 incorporation thus links proper lid assembly to subsequent assembly steps.     

Theoretical investigation of the dynamics of the active site lid in Rhizomucor miehei lipase.

Interfacial activation of Rhizomucor miehei lipase is accompanied by a hinge-type motion of a single helix (residues 83-94) that acts as a lid over the active site. Activation of the enzyme involves the displacement of the lid to expose the active site, suggesting that the dynamics of the lid could be of mechanistic and kinetic importance. To investigate possible activation pathways and to elucidate the effect of a hydrophobic environment (as would be provided by a lipid membrane) on the lid opening, we have applied molecular dynamics and Brownian dynamics techniques. Our results indicate that the lipase activation is enhanced in a hydrophobic environment. In nonpolar low-dielectric surroundings, the lid opens in approximately 100 ns in the BD simulations. In polar high-dielectric (aqueous) surroundings, the lid does not always open up in simulations of up to 900 ns duration, but it does exhibit some gating motion, suggesting that the enzyme molecule may exist in a partially active form before the catalytic reaction. The activation is controlled by the charged residues ARG86 and ASP91. In the inactive conformation, ASP91 experiences repulsive forces and pushes the lid toward the open conformation. Upon activation ARG86 approaches ASP61, and in the active conformation, these residues form a salt bridge that stabilizes the open conformation.     

Probing the opening of the pancreatic lipase lid using site-directed spin labeling and EPR spectroscopy

Access to the active site of human pancreatic lipase (HPL) is controlled by a surface loop (the lid) that undergoes a conformational change in the presence of amphiphiles and lipid substrate. The question of how and when the lid opens still remains to be elucidated, however. A paramagnetic probe was covalently bound to the lid via the D249C mutation, and electron paramagnetic resonance (EPR) spectroscopy was used to monitor the conformational change in solution. Two EPR spectral components, corresponding to distinct mobilities of the probe, were attributed to the closed and open conformations of the HPL lid, based on experiments performed with the E600 inhibitor. The open conformation of the lid was observed in solution at supramicellar bile salt concentrations. Colipase alone did not induce lid opening but increased the relative proportions of the open conformation in the presence of bile salts. The opening of the lid was found to be a reversible process. Using various colipase to lipase molar ratios, a correlation between the proportion of the open conformation and the catalytic activity of HPL was observed.