IL-1 and iNOS gene expression and NO synthesis in the superior region of meniscal explants are dependent on the magnitude of compressive strains.

OBJECTIVE: Partial meniscectomy is known to cause osteoarthritis (OA) of the underlying cartilage as well as alter the load on the remaining meniscus. Removal of 30-60% of the medial meniscus increases compressive strains from a maximum of approximately 10% to almost 20%. The goal of this study is to determine if meniscal cells produce catabolic molecules in response to the altered loading that results from a partial meniscectomy. METHOD: Relative changes in gene expression of interleukin-1 (IL-1), inducible nitric oxide synthase (iNOS) and subsequent changes in the concentration of nitric oxide (NO) released by meniscal tissue in response to compression were measured. Porcine meniscal explants were dynamically compressed for 2 h at 1 Hz to simulate physiological stimulation at either 10% strain or 0.05 MPa stress. Additional explants were pathologically stimulated to either 0% strain, 20% strain or, 0.1 MPa stress. RESULTS: iNOS and IL-1 gene expression and NO release into the surrounding media were increased at 20% compressive strain compared to other conditions. Pathological unloading (0% compressive strain) of meniscal explants did not significantly change expression of IL-1 or iNOS genes, but did result in an increased amount of NO released compared to physiological strain of 10%. CONCLUSION: These data suggest that meniscectomies which reduce the surface area of the meniscus by 30-60% will increase the catabolic activity of the meniscus which may contribute to the progression of OA.

Proteoglycan breakdown of meniscal explants following dynamic compression using a novel bioreactor.

Motivated by our interest in examining meniscal mechanotransduction processes, we report on the validation of a new tissue engineering bioreactor. This paper describes the design and performance capabilities of a tissue engineering bioreactor for cyclic compression of meniscal explants. We showed that the system maintains a tissue culture environment equivalent to that provided by conventional incubators and that its strain output was uniform and reproducible. The system incorporates a linear actuator and load cell aligned together in a frame that is contained within an incubator and allows for large loads and small displacements. A plunger with six Teflon-filled Delrin compression rods is attached to the actuator compressing up to six tissue explants simultaneously and with even pressure. The bioreactor system was used to study proteoglycan (PG) breakdown in porcine meniscal explants following various input loading tests (0-20% strain, 0-0.1 MPa). The greatest PG breakdown was measured following 20% compressive strain. These strain and stress levels have been shown to correspond to partial meniscectomy. Thus, these data suggest that removing 30-60% of meniscal tissue will result in the breakdown of meniscal tissue proteoglycans.

In-situ monitoring of microbial biomass in wetland mesocosms.

The objective of the present investigation has been to combine tracer principles and a hydrolytic microbial activity assay using fluorescein diacetate to monitor changes in microbial biomass within subsurface flow wetland mesocosms. The mesocosm hydrolytic activity was referenced to activated sludge concentrations treating a typical domestic wastewater at full scale. Microbial biomass activity levels within four laboratory wetland mesocosms treating a synthetic domestic wastewater were routinely monitored over a 21-week period of plant growth and rhizosphere development. Although above ground plant mass and tracer dispersion numbers suggested progressive root zone development, plant growth did not result in any measurable enhancement in microbial activity when compared to a mesocosm operating without plants. Dispersion numbers also suggested a reduction in the mass transport kinetics in these planted mesocosms. In-situ biomass monitoring enabled the assessment of a characteristic response in terms of the steady-state food to microorganism (F/M) ratio that was observed in mesocosms receiving both low and high organic loading. Wetland treatment performance is sensitive to the degree to which bed volume is exploited in terms of wastewater flow to regions of bioactivity. The in-situ reactive tracer technique for mesocosm biomass monitoring provided an assessment of the collective substratum and rhizosphere microbial biomass in direct contact with wastewater contaminants. Thus, in-situ biomass monitoring has application in further understanding of plant function and strategies for plant implementation in wetland research and development.

Histopathology and ultrastructural examination of optic nerve sheath biopsies after optic nerve sheath decompression with and without mitomycin.

PURPOSE: We chose to compare histologically and ultrastructurally changes in the optic nerve sheath after optic nerve sheath decompression, initially after a second surgery and after treatment with mitomycin-C. The mechanism by which optic nerve sheath decompression alleviates papilledema can be further understood in consideration of the results. METHODS: Tissue was obtained by biopsy from 3 first-time surgical and 4 reoperative cases with and without mitomycin-C in patients with idiopathic intracranial hypertension. The sheaths were fixed in a mixture of 2% paraformaldehyde and 2% glutaraldehyde, osmicated and dehydrated in a series of ethanol, and finally embedded in epon. Tissue blocks were sectioned at 1 microm and stained with both PPD and toluidine blue. Thin sections were examined by transmission electron microscopy. RESULTS: Normal meningeal tissue obtained at the time at optic nerve sheath decompression consisted mainly of collagen, closely packed and roughly parallel to the axis of the optic nerve. Collagen deposition seen in scar tissue after secondary optic nerve sheath decompression was extremely disorganized and irregular, with the individual fibers laid down seemingly at random. There was little sense of layering or of parallel arrays. Mitomycin-C appeared to influence collagen deposition in such a way that the collagen was more regularly packed and more closely resembled unoperated tissue. CONCLUSIONS: The regular well-organized collagen packing seen in normal sheath tissue is disrupted and replaced by less organized but compact scar tissue after optic nerve sheath decompression. With mitomycin use, more regular collagen packing closely approximating that found in unoperated sheath occurs. This configuration of fibers lends support for the filtration mechanism of optic nerve sheath decompression in treating papilledema.

Overexpression of fra-2 in transgenic mice perturbs normal eye development.

The major components of transcription factor AP-1 (Activator Protein 1) are encoded by the two families of genes related to the proto-oncogenes c-fos and c-jun. The fos-related antigen-2 (fra-2) gene is the most recently described member of the Fos family. To determine the oncogenic potential of fra-2, transgenic mice were generated which over-express fra-2 in a number of tissues. No tumours were evident in any transgenic mice up to 18 months of age, although eye development was severely disrupted in these animals. Corneal abnormalities could be observed histologically as early as embryonic day 15.5 and eyelid fusion failed to occur. Adult eyes were characterized by generalized anterior segment dysgenesis similar to that previously reported in transgenic mice over-expressing transforming growth factor alpha (TGF alpha), and occasionally microphthalmia. Expression of fra-2 was shown to increase following TGF alpha treatment of cells in vitro, suggesting that AP-1 complexes containing Fra-2 contribute to TGF alpha signalling events.

Management of traumatic optic neuropathy.

Visual loss caused by trauma to the optic nerve is a well-recognized sequela to cranio-maxillofacial trauma. The authors reviewed their experience with 90 patients with pure traumatic optic neuropathy and optic nerve trauma with concomitant maxillofacial injuries. All patients were treated with intravenous steroids. Those not improving underwent extracranial optic canal decompression. Patients with initial visual acuity of 20/100 or better all responded favorably with improvement in visual acuity or visual field to a course of intravenous megadose corticosteroids. Patients with initial vision of 20/200 or worse who failed to respond to corticosteroids may have improved visual function after undergoing extracranial optic canal decompression. Preoperative and postoperative computed tomography scans on 6 patients enhanced with intrathecal iopamidol indicate the site of optic nerve compression to be at the optic canal. This article discusses the diagnosis and the medical and surgical treatment of pure and complex optic nerve injuries.

Subtenon's local anesthesia for optic nerve sheath fenestration.

PURPOSE: We used subtenon's local anesthesia for optic nerve sheath fenestration as an alternative to either general or retrobulbar anesthesia. METHODS: Thirty patients with pseudotumor cerebri, who were unresponsive to medical treatment, underwent optic nerve sheath fenestration after administration of topical and subtenon's local anesthesia. RESULTS: When topical tetracaine, in conjunction with subtenon's anesthesia, was administered at the beginning of the procedure, excellent anesthesia and maximal patient comfort were achieved. CONCLUSIONS: The use of local anesthesia allows for a pain-free, expeditious operation with fewer potential anesthetic complications.

Long-term results using adjunctive mitomycin C in optic nerve sheath decompression for pseudotumor cerebri.

PURPOSE: Up to 35% of patients undergoing optic nerve sheath decompression (ONSD) for pseudotumor cerebri who show initial improvement in visual function later show deterioration in visual field and acuity. Although repeat surgery can result in subsequent visual improvement, these procedures are technically difficult because of scarring and fibrosis. Attempting to improve the long-term success of ONSD, the authors sought to analyze the long-term success of ONSD by pretreating optic nerve sheaths with mitomycin C before incision. METHODS: Using a standard transconjunctival medial orbitotomy, optic nerve sheaths were exposed and treated for 5 minutes with mitomycin C (0.5 mg/ml)-soaked neurosurgical cottonoids before incision. RESULTS: Both eyes undergoing repeat ONSD with adjunctive mitomycin C had initial improvement and stable visual function for follow-up of more than 3 years. Four eyes that underwent primary ONSD all initially showed improvement in visual field. Three eyes with large cysts or fistulas remained stable. Another eye had gradual decline in visual function. Repeat ONSD in this eye showed no orbital scarring, and lysis of adhesions between dura-arachnoid and optic nerve resulted in improved, stable visual function for 31 months of follow-up. CONCLUSION: Mitomycin C appears to be a safe adjunct to ONSD in a series of six patients followed between 20 and 37 months. Fistulization and cyst formation are associated with improved visual function. Closure of cysts and fistulas may result in worsening visual function due to intersheath adhesions. Repeat surgery shows significantly less orbital scarring and allows for easier and successful repeat surgery. Adjunctive mitomycin C leads to less orbital scarring after ONSD, allowing for easier repeat surgery.

Long-term effectiveness of optic nerve sheath decompression for pseudotumor cerebri.

OBJECTIVE: To determine the long-term success of optic nerve sheath decompression in preserving visual function in patients with pseudotumor cerebri (PTC). DESIGN: To define stability of visual fields, we reviewed 32 series of postoperative visual fields in patients who were undergoing optic nerve sheath decompression for PTC who had stable visual acuity and four or more fields during 6 to 60 months of follow-up. The SD of these series was 0.80 dB (+/- 0.39 dB) of mean deviation. Fluctuations within 2 SDs of the 1-month postoperative field were +/- -1.60 dB. We therefore defined stability as a mean deviation within 2 dB of the preoperative visual field; improvement, greater than 2-dB mean deviation, and worsening, less than 2-dB mean deviation. We then extended our review to include all patients (54 patients, 75 eyes) who underwent optic nerve sheath decompression for PTC, who were followed up with serial automated perimetry (Humphrey 30-2). RESULTS: Fifty-one eyes (68%) showed improvement (36%) or stabilization (32%) of visual function. Twenty-four eyes (32%) experienced deterioration of visual function after an initially successful optic nerve sheath decompression. The probability of failure from 3 to 5 years was .35 by life-table analysis. CONCLUSION: Optic nerve sheath decompression effectively stabilizes or improves visual function in the majority of patients with PTC and visual loss. However, it may fail at any time after surgery. Patients with PTC need to be followed up routinely with automated perimetry to detect deterioration of visual function.

Progressive and static nonarteritic ischemic optic neuropathy treated by optic nerve sheath decompression.

PURPOSE: Optic nerve sheath fenestration has been advocated as an effective treatment for progressive nonarteritic ischemic optic neuropathy (NAION) and anecdotally effective for selected patients with NAION who have not had progressive visual loss. To determine whether optic nerve sheath decompression is of any benefit in patients with NAION, the authors reviewed their experience, surgically treating 23 patients with progressive NAION and 15 patients with static or nonprogressive NAION. RESULTS: Patients with progressive NAION had a significant improvement in visual function as measured by Snellen visual acuity after optic nerve sheath decompression (P = 0.0005). There was no statistically significant improvement in visual field mean deviation (P = 0.11). The 15 patients undergoing optic nerve sheath decompression for static NAION failed to demonstrate significant improvement in either visual acuity (P = 0.90) or visual field mean deviation (P = 0.87). Preoperative standardized echography was used to measure the optic nerve sheath diameter and ascertain its compressibility (30 degrees test). There was a significant difference in compressibility between eyes with static NAION and eyes with progressive NAION (P = 0.001). Accumulation of optic nerve sheath fluid was documented in three eyes initially presenting with NAION and then with development of progressive visual dysfunction. CONCLUSION: Optic nerve sheath decompression improves visual acuity but has little effect on overall visual function in patients with progressive NAION. Optic nerve sheath decompression does not improve visual field or acuity in patients with static NAION. Detection of significant intrasheath fluid by standardized echography helps to objectively differentiate patients with NAION who may benefit from optic nerve sheath decompression.

Scleral flap necrosis and infectious endophthalmitis after cataract surgery with a scleral tunnel incision.

BACKGROUND: Long scleral tunnel dissection techniques have been developed for cataract surgery incisions. These incisions reduce postoperative astigmatism and keratorefractive instability. If fashioned correctly, the internal lip of the incision produces a tight seal to the anterior chamber, permissible of sutureless surgery. The behavior of such a wound during intraocular infection is unknown. METHODS: The authors describe two elderly patients in whom postoperative bacterial endophthalmitis was accompanied by infectious scleritis, infectious sclerokeratitis or keratitis, and rapid scleral flap necrosis. One of the patients had a painless disease process. RESULTS: Intraocular isolates of Staphylococcus aureus and Streptococcus equinus were recovered from the two patients, respectively. Management was complicated by loss of tectonic integrity that followed scleral flap necrosis, by impaired vitreoretinal visualization associated with rapidly progressive sclerokeratitis or keratitis, and by bacterial scleritis in the base of the scleral flap. No light perception was retained in either eye. CONCLUSION: Scleral tunnel incisions create a potential abscess cavity. Although a rare occurrence, postoperative endophthalmitis in such an eye may present major surgical and therapeutic problems intrinsic to the wound design.