The influence of water content on the longitudinal modulus of elasticity of maize stalk pith and rind tissues.

BACKGROUND: Modern computational modeling could provide the key to obtaining new insights into the mechanisms of maize stalk failure as well as suggesting new ways to improve stalk strength. However, a complete set of mechanical properties of maize tissues is required to enable computational modeling of maize stems. This study developed two compression test methods for obtaining the longitudinal modulus of elasticity of both rind and pith tissues, assessed the influence of water content on tissue properties, and investigated the relationship between rind modulus and pith modulus. These methods involved uniform 5-7 cm segments of maize stems which were scanned using a flatbed scanner then tested in compression using a universal testing machine in both intact and dissected (rind-only and pith-only) states. RESULTS: The modulus of elasticity of pith tissues was highest for fully turgid specimens and decreased as water was removed from the specimens. Water content was negatively correlated with the modulus of elasticity of the rind. Rind and pith tissues were found to be weakly correlated. The median ratio of rind modulus to pith modulus was found to be 17. Of the two methods investigated, the pith-only specimen preparation was found to be simple reliable while the rind-only method was found to be adversely affected by lateral bowing of the specimen. CONCLUSIONS: Researchers can use the information in this paper to improve computational models of maize stems in three ways: (1) by incorporating realistic values of the longitudinal modulus of elasticity of pith and rind tissues; (2) by selecting pith and rind properties that match empirically observed ratios; and (3) by incorporating appropriate dependencies between these material properties and water content. From an experimental perspective, the intact/pith-only experimental method outlined in this paper is simpler than previously reported methods and provides reliable estimates of both pith and rind modulus of elasticity values. Further research using this measurement method is recommended to more clearly understand the influence of water content and turgor pressure on tissue properties.

Multimodal ocular imaging of known and novel corneal stromal disorders in dogs.

BACKGROUND: Imaging features obtained with Fourier-domain optical coherence tomography (FD-OCT) and in vivo confocal microscopy (IVCM) for corneal stromal disorders have been sparsely reported in dogs. This case report is a compilation of imaging features for three cases of different stromal disorders of the canine cornea which have not yet been reported elsewhere. CASE PRESENTATION: Lipid deposition in case 1 appeared as needle-shaped hyperreflective lines along the collagen lamellae, which correlated histologically with lipid clefts. In case 2, glycosaminoglycan accumulation by mucopolysaccharidosis type 1 caused diffuse stromal hyperreflectivity and depletion of keratocytes on IVCM and was associated with secondary corneal degeneration presumed to be calcium deposition. In case 3, posterior corneal stromal opacities in the absence of ocular inflammation were identified. Hyperreflective particles were scattered in the middle and posterior corneal stroma on FD-OCT. With IVCM, hyperreflective deposits were identified within keratocytes and the number of enlarged keratocytes containing hyperreflective deposits increased towards the posterior stroma. The bilateral, non-inflammatory nature and unique appearance with IVCM is most consistent with a posterior stromal dystrophy reminiscent of pre-Descemet corneal dystrophy described in humans. CONCLUSIONS: In vivo multimodal corneal imaging facilitated instantaneous microstructural analysis and may be valuable in the differential diagnosis of corneal stromal disorders in veterinary clinical practice. The non-specific nature of imaging findings occurs in some conditions such as mucopolysaccharidosis, thus in vivo corneal imaging should be complemented with other gold standard methods of definitive diagnosis.

Canine endotheliitis: Clinical characteristics, advanced imaging features, and treatment.

OBJECTIVE: To describe the clinical findings, multimodal corneal imaging features and treatment in canine patients diagnosed with endotheliitis. ANIMALS STUDIED: Four canine patients met inclusion criteria for bilateral corneal disease with endothelial inflammation and secondary corneal edema that responded to topical anti-inflammatory treatment. METHODS: The patients selected underwent a complete ophthalmic examination with emphasis on the cornea including ultrasound pachymetry (USP), Fourier-domain optical coherence tomography (FD-OCT), in vivo confocal microscopy (IVCM), and digital slit lamp photography. RESULTS: All patients in this study demonstrated thickened corneas due to edema with USP and FD-OCT. With IVCM, mild to severe polymegathism and pleomorphism of corneal endothelial cells, reduced endothelial cell density, hyperreflective keratic precipitates (KPs), and extracellular debris as well as hyporeflective pseudoguttata were observed. With FD-OCT, hyperreflective KPs were commonly observed on the inferior cornea. Clinical examination and advanced imaging results were consistent with a diagnosis of endotheliitis. All patients initially responded to topical anti-inflammatory treatment and required continued therapy; two patients also received topical netarsudil, a rho-associated coiled-coil kinase inhibitor. CONCLUSION: Endotheliitis should be considered for canine patients with bilateral edema that is most severe in the inferior cornea. Careful inspection of Descemet's membrane-endothelial complex should be performed for KPs or inflammatory debris. Chronic administration of topical anti-inflammatories may be necessary to prevent flare-ups of endotheliitis.

Outcome of retinal reattachment surgery in dogs: a retrospective study of 145 cases.

OBJECTIVE: To summarize the clinical outcomes and complications of pars plana vitrectomy with perfluoro-n-octane (PFO)-silicone oil exchange and endolaser retinopexy for treatment of retinal detachment (RD) in dogs, at one surgical center. PROCEDURE: Records of 145 dogs (168 eyes) that underwent retinal reattachment surgery (RR) between 2005 and 2009 were reviewed. All surgeries were performed by the same surgeon (SS). Data collected from the medical records included signalment, duration of time from diagnosis of RD to surgical intervention, if prior lensectomy was performed, time from surgery to restoration of vision, and postoperative complications. The data was analyzed to test the effect of breed, prior lensectomy, and time from diagnosis to surgery on visual outcome, tendency for complications, and time of complication onset. RESULTS: One hundred thirty pure-bred dogs (36 breeds) and 15 mixed-breed dogs were represented. One hundred fifty-five of 168 eyes (92%) were visual after surgery. Six of 155 eyes (3.8%) were visual before the procedure and retained vision; one hundred forty-nine of 155 eyes (96%) were nonvisual before and regained vision afterward. Thirteen of 168 eyes (8%) that were nonvisual prior to the procedure did not regain vision. The most common complications in order of occurrence included: cataract development, silicone prolapse into the anterior chamber, corneal ulceration, retinal degeneration, glaucoma, and uveitis. CONCLUSIONS: Pars plana vitrectomy with PFO-silicone oil exchange and endolaser retinopexy for treatment of RD in dogs is highly successful and associated with overall good visual outcome.

Prepubic urethrostomy and vaginoplasty in a female cat.

A 1-year-old, intact female, domestic shorthaired cat was presented for dysuria resulting from perineal scarring subsequent to injuries incurred during a cat fight. A prepubic urethrostomy was performed to manage the dysuria. Eleven months later, the cat was re-presented with a 3-day history of pyrexia and inappetence. A pinpoint opening extending 0.5 cm ventral to the anus on midline, exuding a clear discharge, was noted in the perineal region. A contrast fistulogram was performed, and a vaginoperineal fistula was diagnosed. The fistulous tract was a result of vulvar stricture from the trauma of the cat fight. A vaginoplasty was performed to create an opening for vaginal secretions. This is the first published report of a prepubic urethrostomy performed in a female cat.

Tumoricidal activity of high-dose tumor necrosis factor-alpha is mediated by macrophage-derived nitric oxide burst and permanent blood flow shutdown.

This study investigates the role of tumor nitric oxide (NO) and vascular regulation in tumor ulceration following high-dose tumor necrosis factor-alpha (TNF) treatment. Using TNF-responsive (MethA) and nonresponsive (LL2) mouse tumors, tumor NO concentration was measured with an electrochemical sensor and tumor blood flow by Doppler ultrasound. Mice were also pretreated with a selective inducible nitric oxide synthase (iNOS) inhibitor, 1400 W. Tumors harvested from TNF-treated mice were cryosectioned and immunostained for murine macrophages, or/and iNOS. MethA tumor-bearing mice were depleted of macrophages. Pre- and post-TNF tumor NO levels were measured continuously, and mice were followed for gross tumor response. In MethA tumors, TNF caused a 96% response rate, and tumor NO concentration doubled. Tumor blood flow decreased to 3% of baseline by 4 hr and was sustained at 24 hr and 10 days post-TNF. Selective NO inhibition with 1400 W blocked NO rise and decreased response rate to 38%. MethA tumors showed tumor infiltration by macrophages post-TNF and the pattern of macrophage immunostaining overlapped with iNOS immunostaining. Depletion of macrophages inhibited tumor NO increase and response to TNF. LL2 tumors had a 0% response rate to TNF and exhibited no change in NO concentration. Blood flow decreased to 2% of baseline by 4 hr, recovered to 56% by 24 hr and increased to 232% by 10 days. LL2 tumors showed no infiltration by macrophages post-TNF. We conclude that TNF causes tumor infiltrating, macrophage-derived iNOS-mediated tumor NO rise and sustained tumor blood flow shutdown, resulting in tumor ulceration in the responsive tumor.