Biomedical subjects

James D Lindsey

Publications and source records attributed to James D Lindsey.

At least 19 recordsLinked to original sources

PubMed2007

Magnetic resonance imaging of the visual system in vivo: transsynaptic illumination of V1 and V2 visual cortex.

Brain nuclei directly receiving retinal projections are readily labeled in magnetic resonance images following intraocular injection of manganese (Mn). To assess whether Mn in retinal ganglion cell axons can be transsynaptically delivered to visual cortex, mice that had previously received intraocular Mn injection were anesthetized with isoflurane, and T1-weighted data sets were acquired of the eyes and brain using a 7-T magnetic resonance imaging machine. Image intensity within contralateral brain structures was evaluated by assessing 1) signal-to-noise ratios, 2) mean image intensity, and 3) mean image intensity normalized to facial muscle intensity. Image intensity was increased throughout the visual pathway including within contralateral visual cortex areas V1 and V2L. Mean normalized image intensity was greater by 53% in the ipsilateral optic nerve and by 31% and 28% in the contralateral lateral geniculate nucleus and superior colliculus, respectively (N=5, P<0.02, paired t test). In contralateral visual cortex areas V1 and V2L, image intensity was increased by 7.5% and 6.8%, respectively (P<0.02 for both, paired t test). Power analysis of the different evaluation methods yielded evidence of superior sensitivity using the normalization method. Reconstruction of the visual system based upon threshold analysis allowed simultaneous visualization of all portions of the major retinal projections to the brain. These results support use of high magnetic field MRI imaging and data normalization for in vivo quantitative analysis of the mouse brain visual system including visual cortex.

Animals↗

PubMed2006

Comparison of invasive and non-invasive tonometry in the mouse.

Assessment of the accuracy of non-invasive rebound tonometry, and comparison with invasive cannulation tonometry. An in vivo calibration technique was devised to improve the accuracy of the rebound tonometer. IOP was then measured in SW mice using both rebound and cannulation tonometry. The ability of the rebound tonometer to accurately measure small IOP reductions after instillation of a topical prostaglandin was also determined. With the rebound method, mid-afternoon IOP in two groups of similar aged SW mice was 15.9+/-3.9 mmHg (mean+/-s.d., n=25) compared to 16.3+/-1.2 mmHg (n=32) using the cannulation technique. This difference was not statistically significant (p=0.6). For serial measurements using both techniques in the same eyes of a third group of SW mice (n=14), mean IOP was 15.0+/-3.9 mmHg for rebound tonometry but only 13.4+/-2.3 mmHg for subsequent cannulation tonometry. This effect was subsequently shown to be a consequence of the rebound tonometry, as multiple rebound measurements induced a statistically significant reduction in IOP. The average IOP reduction observed 2 hr after a single application of topical latanoprost (200 ng) was 2.8+/-1.3 mmHg (p<0.001) and 2.4+/-4.7 mmHg (p=0.03) with cannulation and rebound tonometers, respectively. These differences were not significantly different (p=0.8). In vivo calibration of the rebound tonometer increased measurement accuracy and provided IOP values within the physiological range that agreed closely with the IOP measured by cannulation tonometry. However, IOP measurement with the rebound tonometer had larger variability compared with the cannulation method. Repeat IOP measurements with the rebound tonometer led to a reduction in IOP. The rebound tonometer was sufficiently sensitive to detect a 2-3 mmHg reduction in IOP following application of topical latanoprost. Despite these limitations, the rebound tonometer has a significant advantage over cannulation tonometry in that it permits longitudinal IOP measurement in conscious mice.

Administration, Topical↗

PubMed2005

The importance of models in glaucoma research.

Experimental models have enhanced our understanding of the biology of glaucoma. Moreover, they have enabled the testing of potential therapies prior to the initiation of human trials. Each have advantages and limitations. In vitro cell and organ culture offer direct cellular accessibility and microenvironmental control, as well as efficient comparison between many experimental conditions or potential therapeutic compounds. However, they generally have less relevance to clinical glaucoma than in vivo models. Rat models allow moderate sized investigations of intact biological systems that have greater relevance to glaucoma than in vitro experiments, but less than primate experiments. Mouse models are similar to rat models but have the advantage of investigating mutant and transgenic strains mimicking specific aspects of glaucoma that are not available in other model systems. Primate models of glaucoma generally are the most relevant to human glaucoma but must be limited in scope because of availability and the high cost of experimentation.

Animals↗

PubMed2005

Elevated intraocular pressure and transgenic applications in the mouse.

Exploitation of the mouse as a model for glaucoma has been advanced by the development of methods to measure mouse intraocular pressure (IOP), identification of mutant mouse strains in which IOP spontaneously increases, and the development of treatments to induce elevated IOP. These developments enable investigations that directly test the influence of specific gene product alterations on the progression of glaucoma. Moreover, new transgenic mouse models have been produced with genetic mutations that parallel human gene mutations that have been linked to the onset of glaucoma. These new mouse models and technologies have potential for uncovering the biological basis of glaucoma as well as for evaluating new treatments.

Animals↗

PubMed2005

Effect of bimatoprost on intraocular pressure in prostaglandin FP receptor knockout mice.

PURPOSE: To determine the effect of bimatoprost on intraocular pressure in the prostaglandin FP receptor knockout mouse. METHODS: The IOP response to a single 1.2-microg (4 microL) dose of bimatoprost was measured in the treated and untreated fellow eyes of homozygote (FP+/+, n = 9) and heterozygote (FP+/-, n = 10) FP-knockout mice, as well as in wild-type C57BL/6 mice (FP+/+, n = 20). Serial IOP measurements were also performed after topical bimatoprost in a separate generation of homozygous FP-knockout mice and wild-type littermate control animals (n = 4 per group). Aqueous humor protein concentrations were measured to establish the state of the blood-aqueous barrier. Tissue, aqueous humor and vitreous concentrations of bimatoprost, latanoprost, and their C-1 free acids were determined by liquid chromatography and tandem mass spectrometry. RESULTS: A significant reduction in IOP was observed in the bimatoprost-treated eye of wild-type mice at 2 hours, with a mean difference and 95% confidence interval (CI) of the difference in means of -1.33 mm Hg (-0.81 to -1.84). Bimatoprost did not lead to a significant reduction in IOP in either the heterozygous knockout -0.36 mm Hg (-0.82 to +0.09) or homozygous FP-knockout mice 0.25 mm Hg (-0.38 to +0.89). The lack of an IOP response in the FP-knockout mice was not a consequence of blood-aqueous barrier breakdown, as there was no significant difference in aqueous humor protein concentration between treated and fellow eyes. Tissue and aqueous humor concentrations of bimatoprost, latanoprost, and their C-1 free acids indicate that latanoprost, but not bimatoprost, is hydrolyzed in the mouse eye after topical administration. CONCLUSIONS: An intact FP receptor gene is critical to the IOP response to bimatoprost in the mouse eye.

Amides↗

PubMed2004

Beta-catenin regulates the gene of MMP-26, a novel metalloproteinase expressed both in carcinomas and normal epithelial cells.

There are several unorthodox features, which distinguish the non-redundant and unique novel matrix metalloproteinase-26 (MMP-26) (an enzyme that has recently evolved and does not exist in rodents but is present in humans) from other members of the MMP superfamily. This report describes our recent efforts to gain a better understanding of the mechanisms which restrict expression of MMP-26 to certain cell/tissue types. We examined transcriptional regulation of the human MMP-26 gene in normal and malignant cells. The AP-1 and Tcf-4 sites of the MMP-26 promoter appear most potent in regulating the expression of the MMP-26-luciferase chimera in HEK293 embryonic kidney and MCF7 breast carcinoma cells. Key regulators of the Wnt pathway (beta-catenin and lymphoid enhancer-binding factor/T-cell factor with which beta-catenin associates) enhanced the transcriptional activity of MMP-26 suggesting that the MMP-26 gene is a likely target of the Wnt pathway. Immunostaining, gene arrays and reverse-transcriptase polymerase chain reaction (RT-PCR) confirm the presence of MMP-26 in normal cells, including the apical epithelial conjunctiva cells of the human eye, as well as in malignant cells of epithelial origin. MMP-26 predominantly accumulates in its proenzyme form in the intracellular milieu of the transfected breast carcinoma MCF7 cells. This study brings us a step forward towards a better understanding of the unconventional role, regulation and functions of epithelial cell MMP-26 in physiological conditions and in neoplasms.

Carcinoma↗

PubMed2004

Influence of molecular weight on intracameral dextran movement to the posterior segment of the mouse eye.

PURPOSE: Uveoscleral outflow provides a potential pathway to the posterior segment for drug delivery. In this study, the influence of molecular weight on the intraocular distribution of dextran molecules after intracameral injection in the mouse eye was investigated. METHODS: The anterior chambers of the eyes of 64 anesthetized NIH Swiss mice were perfused with various fluorescent dextran solutions (10, 40, 70, and 500 kDa) at 500 nL/min for 10 minutes. At 10, 20, or 60 minutes after the initiation of the anterior chamber perfusion, the mice were killed and tissue obtained for evaluation by fluorescence microscopy. RESULTS: Each of the different molecular weight dextrans were visible in the anterior chamber of the mouse eye after the termination of the experiments. The 10-kDa dextran was observed in the supraciliary space and the supraciliary sclera after 10 minutes and in the anterior sclera after 60 minutes of perfusion. The 40-kDa dextran was detected in the supraciliary space and the anterior sclera after 10 minutes and in the anterior choroid and sclera after 20 and 60 minutes, but not in the posterior segment. The 70-kDa dextran was observed in the supraciliary space and anterior choroid after 10 minutes. After 20 minutes, it was visible in the equatorial choroid. After 60 minutes, it was observed in the posterior choroid. The 500-kDa dextran was observed in the supraciliary space and the anterior choroid after 10 minutes and in the supraciliary sclera at 20 minutes. At 60 minutes, 500-kDa dextran was observed in the equatorial choroid, but not farther toward the posterior. CONCLUSIONS: The influence of molecular weight on the redistribution of macromolecules from the anterior chamber to the posterior globe in the mouse eye appears to be similar to primate eyes. These similarities include passage of all size dextrans through the proximal uveoscleral pathway, the dependence of the extent of posterior movement on the size of the dextran, and the absence of large dextran entry into the distal uveoscleral pathway.

Animals↗

PubMed2004

Effect of latanoprost on outflow facility in the mouse.

PURPOSE: To assess the early effect of latanoprost on outflow facility and aqueous humor dynamics in the mouse. METHODS: Aqueous humor dynamics in NIH Swiss White mice were assessed with an injection and aspiration system, using fine glass microneedles. A single 200-ng (4 microL) dose of latanoprost was applied to one eye 2 hours before measurement. The fellow eye served as a control. Intraocular pressure (IOP) was measured by using an established microneedle procedure. Outflow facility (C) was determined by constant-pressure perfusion measurements obtained at two different IOPs. Aqueous humor flow (Fa) was determined by a dilution method using rhodamine-dextran. Conventional and uveoscleral outflow (Fc and Fu) were calculated by the Goldmann equation. RESULTS: Average IOP, Fa, and C of control eyes were 15.7 +/- 1.0 mm Hg, 0.144 +/- 0.04 microL/min (mean +/- SD, n = 8), and 0.0053 +/- 0.0014 microL/min per mm Hg (n = 21), respectively. Average IOP, Fa, and C of treated eyes were 14.0 +/- 0.8 mm Hg, 0.138 +/- 0.04 microL/min (n = 8 for each), and 0.0074 +/- 0.0016 microL/min per mm Hg (n = 21), respectively. The differences between treated and control eyes were significant for IOP and total outflow facility only. CONCLUSIONS: These data indicate that the early hypotensive effect of latanoprost in the mouse eye is associated with a significant increase in total outflow facility. Alterations in the aqueous dynamics induced by latanoprost can be measured reproducibly in the mouse and may provide a useful model for further determining the mechanism by which latanoprost reduces IOP and alters outflow facility.

Animals↗

PubMed2004

Optic nerve damage in mice with a targeted type I collagen mutation.

PURPOSE: Transgenic (Col1a1(r/r)) mice gradually develop elevated intraocular pressure (IOP) with open angles. The present study was undertaken to evaluate optic nerve axonal loss with time in these mice. METHODS: The IOP of transgenic (Col1a1(r/r)) mice and control wild-type (Col1a1(+/+)) mice was measured at 7, 12, 16, 24, 36, and 54 weeks of age using a microneedle method. Transgenic Col1a1(r/r) and control Col1a1(+/+) mice at 24 and 54 weeks of age were randomly selected and their optic nerves were processed conventionally for electron microscopy. Optic nerve cross-sections were collected 300 micro m posterior to the globe. Low (200X) and high (10,000X) magnification images were collected systematically and were masked before analysis. For each nerve, cross-sectional area was measured in low magnification images, and axonal number was counted in high magnification images. RESULTS: Mean IOP of the transgenic Col1a1(r/r) mice was significantly higher than that of the control Col1a1(+/+) mice at 16, 24, 36, and 54 weeks by 21%, 42%, 41%, and 33% respectively (P < 0.05). The mean axonal density and total axonal number in the transgenic Col1a1(r/r) mice at 54 weeks of age (n = 10) was significantly less than those in the control Col1a1(+/+) mice at 24 weeks (n = 5) and 54 weeks (n = 5; P = 0.0081 and P = 0.020, respectively, analysis of variance, P < 0.05 for pair-wise comparisons). The mean axonal density and total axonal number in the transgenic Col1a1(r/r) mice at 54 weeks also were significantly less than in the transgenic Col1a1(r/r) mice at 24 weeks (n = 10). Mean axonal loss between 24 and 54 weeks of age in the transgenic Col1a1(r/r) mice was 28.7%. CONCLUSIONS: Transgenic Col1a1(r/r) mice develop sustained elevation of IOP and progressive optic nerve axon loss. This suggests that these mice may be useful as a mouse model of primary open angle glaucoma as well as for assessing the relationship between collagen type I metabolism and optic nerve axon loss.

Animals↗

PubMed2004

Effect of latanoprost on intraocular pressure in mice lacking the prostaglandin FP receptor.

PURPOSE: To determine whether latanoprost lowers IOP in prostaglandin FP receptor knockout mice. METHODS: Mean IOP difference between treated and untreated fellow eyes was measured on three separate occasions, 2 hours after a 200-ng dose of latanoprost to the right eye of homozygous (n = 9) and heterozygous (n = 15) FP knockout mice. C57BL/6 (n = 10) and NIH Swiss white mice (n = 17), which have normal FP receptor expression, provided the control population. The investigator was masked to the genotype of the FP knockout mice at the time of IOP measurement. RESULTS: Latanoprost had no effect on IOP in the homozygous FP knockout mice, with an average difference in IOP between treated and untreated fellow eyes of +0.25 mm Hg and a 95% confidence interval (CI) for the difference between means of -0.019 to +0.69. In contrast, latanoprost reduced IOP in the treated eye of the heterozygous FP knockout, C57BL/6, and Swiss white mice with mean differences and 95% CI of the difference in means of -0.52 (-0.91 to -0.14), -1.38 (-2.1 to -0.70), and -1.29 (-1.78 to -0.79) mm Hg, respectively. CONCLUSIONS: FP receptor signaling plays a crucial role in the early IOP response to latanoprost in the mouse eye.

Animals↗

PubMed2004

Regional optic nerve damage in experimental mouse glaucoma.

PURPOSE: To assess the relationship between regional variation of axon loss and optic nerve head anatomy in laser-induced experimental glaucoma in the mouse. METHODS: Experimental glaucoma was induced unilaterally in eight NIH Swiss black mice. Intraocular pressure (IOP) was measured for 12 weeks, and the mice were killed. The eyes were enucleated, and both optic nerves were dissected and processed conventionally for electron microscopy. Low- and high-magnification images of the optic nerve cross sections 300 microm posterior to the globe were collected systematically and masked before analysis. For each nerve, cross-sectional area was measured in low-magnification micrographs. Axon number and density were determined in the high-magnification micrographs. Loss of axonal density was compared between the superior and inferior and nasal and temporal areas of the optic nerve cross section. Additional cross-section micrographs were collected at 10- or 20-microm intervals throughout the optic nerve head. RESULTS: In the treated (glaucoma) eyes, mean IOP was 44% higher than that in the control eyes. The optic nerve cross-sectional area, mean axonal density, and total axonal number were significantly less than those in the control eyes (P < 0.01 for each). Axon loss in the superior optic nerve was greater than in the inferior optic nerve in each glaucomatous eye (P = 0.012). The ratio of axonal density in the superior and inferior optic nerve (superior-to-inferior [S/I] ratio) in all treated eyes was <1.0 and significantly lower than that in the control eyes (P = 0.012). The central retinal vessels occupied approximately 20% of the central optic nerve head cross-sectional area, gradually shifted position ventrally as they progressed toward the scleral foramen (the mouse does not have a lamina cribrosa), and exited the inferior retrobulbar optic nerve adjacent to the posterior of the globe. CONCLUSIONS: Ocular hypertension in the mouse eye sufficient to cause optic nerve damage induces preferential loss of superior optic nerve axons. Optic nerve axon loss appeared less among the axons that were near the major optic nerve blood vessels at the scleral foramen. Topographic differences in optic nerve axon loss should be considered when evaluating optic nerve damage in experimental laser-induced glaucoma in the mouse.

Animals↗

PubMed2004

Prostaglandin FP agonists alter metalloproteinase gene expression in sclera.

PURPOSE: The present study was undertaken to determine whether exposure of the sclera to prostaglandin (PG)F(2alpha) or to the PGF(2alpha) analogue latanoprost acid alters mRNA for matrix metalloproteinases. METHOD: Fifteen human eye bank eyes were studied. Circular pieces of sclera were either immediately preserved in a stabilization reagent or cultured in low-serum DMEM/F-12 medium. The cultures were treated for 24 hours with medium supplemented with PGF(2a), latanoprost acid, or vehicle. Total RNA was then isolated, and the expression of mRNA for matrix metalloproteinase (MMP)-1, -2, -3, -8, -9, -10, and -12 were determined by real-time PCR. All results were normalized according to the GAPDH mRNA in each sample. Altered mRNA expression after PG treatments also was evaluated with microarrays containing 19 MMP genes and 4 tissue inhibitor of matrix metalloproteinase (TIMP) genes. RESULTS: Real-time PCR results showed that 24 hours of exposure to 100 nM PGF(2alpha) significantly increased mRNA for MMP-1 and -9 (P < 0.06 Wilcoxon test) and that exposure to 100 nM latanoprost acid significantly increased mRNA for MMP-9 (P < 0.06 Wilcoxon test). Array analysis demonstrated increases of MMP-3 and -10 mRNA after exposure to 100 nM latanoprost and further increases after exposure to 200 nM latanoprost. The array results also showed that latanoprost induced dose-dependent increases in the expression of TIMP-1, -2, and -3 mRNA in the scleral cultures. CONCLUSIONS: PGF(2alpha) and latanoprost acid induce coordinated alterations of MMP gene transcription in scleral organ cultures. These results indicate that PGs can directly trigger MMP gene transcription changes within the sclera. These changes support a role for increased MMPs in the enhancement of uveoscleral outflow that occurs after topical treatment with latanoprost.

Aged↗

PubMed2003

Twenty-four-hour pattern of mouse intraocular pressure.

The 24-hr pattern of intraocular pressure in the mouse eye remains poorly characterized. The present study was undertaken to determine the magnitude, dynamic pattern, and synchrony of the 24-hr pattern of intraocular pressure (IOP) in NIH Swiss mice exposed to a 12-hr light/dark cycle or to constant light. IOP was measured every 3 hr using a microneedle method. Mice exposed to a 12-hr light /dark cycle were either measured repeatedly at 1 week interval (group 1) or were only measured once (group 2). A third group was exposed to constant light for 2 weeks prior to IOP measurements. The 24-hr IOP pattern in the first and second groups showed a similar rhythmic pattern that appeared to be sinusoidal. This IOP pattern declined in the morning until 12:00, and then increased in the early evening until 21:00. In contrast, IOP in the third group was asynchronous with some mice exhibiting multiple peaks and troughs during the 24-hr period. These results show that 24-hr IOP pattern in mouse eyes is biphasic and that extended exposure to constant light disrupts this 24-hr IOP pattern.

Animals↗

PubMed2003

Episcleral venous pressure of mouse eye and effect of body position.

PURPOSE: To measure the episcleral venous pressure (EVP) of the mouse eye and to investigate the effect of body position on EVP and intraocular pressure (IOP). METHODS: A microneedle connected to a pressure transducer was used to measure IOP in NIH Swiss white mice. To measure EVP, a reservoir connected to this transducer allowed modulation of the intracameral pressure by changing its height. As intracameral pressure was gradually lowered, there was an observable reflux of erythrocytes from an episcleral vein into Schlemm's canal. The IOP at which this occurred was the endpoint of the EVP measurement. EVP and IOP were measured in a horizontal body position (0 degrees ) analogous to an awake mouse and at 30 degrees and 60 degrees head-down body position from the horizontal position. EVP was measured twice in each eye of 6 mice. RESULTS: Mean IOP at 0 degrees, 30 degrees and 60 degrees of head-down position was 16.5 +/- 0.6, 18.2 +/- 0.6, and 19.5 +/- 1.8 mmHg, respectively. EVP (horizontal) was 9.6 +/- 1.3 mmHg (N = 6 eyes). EVP significantly increased with increasing degree of head-down position (SNK test, p < 0.05). EVP at 30 degrees and 60 degrees of head-down position was 11.2 +/- 1.3 and 13.3 +/- 1.5 mmHg, respectively. CONCLUSIONS: Mouse EVP was successfully measured based on the detection of erythrocyte reflux from an episcleral vein into Schlemm's canal. Both EVP and IOP increased with the degree of the head-down body position.

Animals↗

PubMed2003

Ocular hypertension in mice with a targeted type I collagen mutation.

PURPOSE: To evaluate intraocular pressure (IOP) in transgenic mice with a targeted mutation in the gene for the alpha1 subunit of collagen type I. METHODS: Homozygous B6; 129-Cola1(tm1Jae) mice and corresponding wild-type mice were anesthetized. A fluid-filled glass microneedle connected to a pressure transducer was then inserted through the cornea into the anterior chamber to measure IOP. All measurements were made between 11:30 AM and 1:30 PM. The IOP of seven Col1a1(r/r) and eight corresponding wild-type Col1a1(+/+) male mice was measured at 12, 18, 24, and 36 weeks after birth. The IOP of 5 to 24 additional Col1a1(r/r) mice was measured at 7, 12, 18, 24, and 36 weeks after birth. The structure of the anterior segment and the distribution of collagen I were assessed by immunohistochemistry. RESULTS: Mean IOP measurements of the control Col1a1(+/+) mice (IOP(c)) at 12 and 18 weeks after birth were relatively constant at 18.9 +/- 2.0 and 19.2 +/- 1.9 mm Hg, respectively. Mean IOP then decreased to 15.8 +/- 0.8 and 16.2 +/- 1.2 mm Hg at 24 and 36 weeks, respectively. In contrast, mean IOP measurements in the transgenic (Col1a1(r/r)) mice was 2.7 +/- 3.4 mm Hg higher at 12 weeks and increased to a maximum of 23.6 +/- 2.4 mm Hg at 24 weeks. The difference between mean IOP in these two groups gradually increased to a maximum of 4.8 mm Hg (30%) at 36 weeks and was significantly different from the control mice at both 24 and 36 weeks of age. No anterior segment abnormality was observed in Col1a1(r/r) mice and no difference between the anterior segment appearance of Col1a1(r/r) and Col1a1(+/+) mice was observed throughout the 36-week analysis period. However, collagen I immunoreactivity in sclera and associated structures was greater in Col1a1(r/r) mice than in Col1a1(+/+) mice. When the mean IOP measurements from the additional Col1a1(r/r) mice were included with these measurements, mean IOP at each age was 16.7 +/- 0.8, 21.8 +/- 3.9, 23.2 +/- 2.8, 23.5 +/- 2.4, and 22.1 +/- 3.6 mm Hg, respectively. Mean IOP in the Col1a1(r/r) mice was significantly higher than in the Col1a1(+/+) mice at 18, 24, and 36 weeks by 21%, 44%, and 36%, respectively (P < 0.05). CONCLUSIONS: These results demonstrate ocular hypertension in mice with a targeted type I collagen mutation and suggest there is an association between IOP regulation and fibrillar collagen turnover.

Animals↗

PubMed2003

Experimental mouse ocular hypertension: establishment of the model.

PURPOSE: To establish an experimental model of ocular hypertension in the mouse. METHODS: Twenty-two black Swiss mice were used. After anesthesia and pupil dilation, the anterior chamber was flattened by the aspiration of aqueous humor. Laser photocoagulation (532-nm wavelength, 200-mW power, 0.05-second duration, 200- micro m spot size) then was performed at the limbus. Intraocular pressure (IOP) was measured weekly for 4 weeks and biweekly for 12 weeks, by a microneedle method. Slit lamp biomicroscopy was performed throughout the period and the structural changes were assessed histologically. A treatment response was considered to be a success if either the mean of IOP measurements collected during the first 4 weeks was increased by 30% or more, or the mean of all measurements collected during the 12 week study period was increased by 30% or more. RESULTS: Laser-treated eyes showed significantly higher IOP than control eyes from 1 to 6 weeks (P < 0.001). The average IOP in treated eyes during the first 4 and 12 weeks was significantly higher than the control IOP (P < 0.001). These IOP increases were 7.1 and 3.8 mm Hg, respectively. During the first 4 weeks, sustained elevation of IOP was obtained in 64% (14/22) of the treated eyes. During the entire 12-week study, increased IOP was successfully maintained in 37% (7/19) of the treated eyes. After 6 weeks, elevated IOP often returned to normal or several mm Hg below normal. Histologic analysis at the end of the 12-week study showed no inflammatory cells in the anterior segment and confirmed that the angle was closed by the laser photocoagulation treatment. CONCLUSIONS: This method produces persistent IOP elevation in mouse eyes and may be a promising experimental model for the investigation of the biological mechanisms of glaucomatous optic neuropathy.

Animals↗

PubMed2003

Optic nerve damage in experimental mouse ocular hypertension.

PURPOSE: To evaluate optic nerve damage in mice after laser-induced ocular hypertension. METHODS: Ocular hypertension was induced unilaterally in 13 NIH Black Swiss mice by laser photocoagulation of the limbus. Over the following 12 weeks, intraocular pressure (IOP) was measured at regular intervals by the microneedle method. The optic nerves of these mice and of seven normal untreated mice were then processed conventionally for electron microscopy, and cross sections of the nerve 300 micro m posterior to the globe were collected. Low- and high-magnification images were collected systematically and masked before analysis. For each nerve, cross-sectional area was measured in low-magnification micrographs, and axon and glia numbers were counted in high-magnification micrographs. RESULTS: In normal untreated mice, the average number of axons was 59,597 +/- 3,112 (mean +/- SD). Variation among these measurements was 5.7% +/- 3.9%. After laser treatment, the duration of high IOP ranged from 2 to 12 weeks (6.2 +/- 3.6 weeks, mean +/- SD). The mean IOP in the treated eyes was 1.3 times greater than the mean IOP in the control eyes (P = 0.0012). The maximum IOP in the treated eyes was 1.6 times greater than that observed in the control eyes (P < 0.0001). The optic nerve cross-sectional area, mean axon density, and total number of axons in the treated eyes were significantly less than in the control eyes (28.5% +/- 23.4%, 57.8% +/- 37.8%, and 63.1% +/- 38.1%, respectively; P < 0.005 for each). The decrease in optic nerve cross-sectional area and the positive integral of elevated IOP and duration of IOP elevation correlated significantly with total axon loss (r(2) = 0.79, P < 0.0001 and r(2) = 0.36, P = 0.040, respectively). The number of astrocytes per cross section of optic nerve was significantly greater in the treated eyes than in the control eyes (P = 0.014). CONCLUSIONS: Laser-induced ocular hypertension in mouse eyes can induce optic nerve axon loss that correlates with the magnitude and duration of elevated IOP.

Animals↗

PubMed2003

Aqueous humor dynamics in mice.

PURPOSE: To assess aqueous humor dynamics in mouse eyes. METHODS: Aqueous humor dynamics of NIH Swiss White mouse were assessed with an injection and aspiration system, using fine glass microneedles. Intraocular pressure (IOP) was measured by a microneedle connected to a pressure transducer. Episcleral venous pressure (EVP) was measured by gradually lowering intracameral pressure until blood reflux into Schlemm's canal was observed. Outflow facility (C) was determined based on constant pressure perfusion measurements obtained at two different IOPs. Aqueous volume (V(a)) was determined by direct measurement of aspirated aqueous humor. Aqueous humor production (F(a)) was measured by the dilution method with rhodamine-dextran. Conventional and uveoscleral outflow (F(c) and F(u), respectively), as well as the turnover rate of aqueous humor, were also calculated. RESULTS: IOP and EVP were 15.7 +/- 2.0 and 9.5 +/- 1.2 mm Hg, respectively (n = 20). F(a) was 0.18 +/- 0.05 microL/min (mean +/- SD; n = 8). C was 0.0051 +/- 0.0006 microL/min per mm Hg (n = 8). Estimated F(c) and F(u) were 0.032 and 0.148 microL/min, respectively. F(c) was 18% of F(a). F(u) was 82% of F(a). V(a) was 5.9 +/- 0.5 microL (n = 8). The calculated turnover rate of aqueous humor was 2.5%. CONCLUSIONS: The mouse eye has similar aqueous production and aqueous humor turnover rate as the human eye. The presence of both conventional and uveoscleral outflow suggests that the mouse is a useful model system for further investigations of the biology of aqueous dynamics.

Animals↗