Real-Time Imaging of Rabbit Retina with Retinal Degeneration by Using Spectral-Domain Optical Coherence Tomography

Background: Recently, a transgenic rabbit with rhodopsin Pro 347 Leu mutation was generated as a model of retinitis pigmentosa (RP), which is characterized by a gradual loss of vision due to photoreceptor degeneration. The purpose of the current study is to noninvasively visualize and assess time-dependent changes in the retinal structures of a rabbit model of retinal degeneration by using speckle noise-reduced spectral-domain optical coherence tomography (SD-OCT). Methodology/Principal Findings: Wild type (WT) and RP rabbits (aged 4–20 weeks) were investigated using SD-OCT. The total retinal thickness in RP rabbits decreased with age. The thickness of the outer nuclear layer (ONL) and between the external limiting membrane and Bruch’s membrane (ELM–BM) were reduced in RP rabbits around the visual streak, compared to WT rabbits even at 4 weeks of age, and the differences increased with age. However, inner nuclear layer (INL) thickness in RP rabbits did not differ from that of WT during the observation period. The ganglion cell complex (GCC) thickness in RP rabbits increased near the optic nerve head but not around the visual streak in the later stages of the observation period. Hyper-reflective change was widely observed in the inner segments (IS) and outer segments (OS) of the photoreceptors in the OCT images of RP rabbits. Ultrastructural findings in RP retinas included the appearance of small rhodopsin-containing vesicles scattered in the extracellular space around the photoreceptors

Effect of Sex and Prior Exposure to a Cafeteria Diet on the Distribution of Sex Hormones between Plasma and Blood Cells

It is generally assumed that steroid hormones are carried in the blood free and/or bound to plasma proteins. We investigated whether blood cells were also able to bind/carry sex-related hormones: estrone, estradiol, DHEA and testosterone. Wistar male and female rats were fed a cafeteria diet for 30 days, which induced overweight. The rats were fed the standard rat diet for 15 additional days to minimize the immediate effects of excess ingested energy. Controls were always kept on standard diet. After the rats were killed, their blood was used for 1) measuring plasma hormone levels, 2) determining the binding of labeled hormones to washed red blood cells (RBC), 3) incubating whole blood with labeled hormones and determining the distribution of label between plasma and packed cells, discounting the trapped plasma volume, 4) determining free plasma hormone using labeled hormones, both through membrane ultrafiltration and dextran-charcoal removal. The results were computed individually for each rat. Cells retained up to 32% estrone, and down to 10% of testosterone, with marked differences due to sex and diet (the latter only for estrogens, not for DHEA and testosterone). Sex and diet also affected the concentrations of all hormones, with no significant diet effects for estradiol and DHEA, but with considerable interaction between both factors. Binding to RBC was non-specific for all hormones. Estrogen distribution in plasma compartments was affected by sex and diet. In conclusion: a) there is a large non-specific RBC-carried compartment for estrone, estradiol, DHEA and testosterone deeply affected by sex; b) Prior exposure to a cafeteria (hyperlipidic) diet induced hormone distribution changes, affected by sex, which hint at sex-related structural differences in RBC membranes; c) We postulate that the RBC compartment may contribute to maintain free (i.e., fully active) sex hormone levels in a way similar to plasma proteins non-specific binding

Effect of Sex and Prior Exposure to a Cafeteria Diet on the Distribution of Sex Hormones between Plasma and Blood Cells

It is generally assumed that steroid hormones are carried in the blood free and/or bound to plasma proteins. We investigated whether blood cells were also able to bind/carry sex-related hormones: estrone, estradiol, DHEA and testosterone. Wistar male and female rats were fed a cafeteria diet for 30 days, which induced overweight. The rats were fed the standard rat diet for 15 additional days to minimize the immediate effects of excess ingested energy. Controls were always kept on standard diet. After the rats were killed, their blood was used for 1) measuring plasma hormone levels, 2) determining the binding of labeled hormones to washed red blood cells (RBC), 3) incubating whole blood with labeled hormones and determining the distribution of label between plasma and packed cells, discounting the trapped plasma volume, 4) determining free plasma hormone using labeled hormones, both through membrane ultrafiltration and dextran-charcoal removal. The results were computed individually for each rat. Cells retained up to 32% estrone, and down to 10% of testosterone, with marked differences due to sex and diet (the latter only for estrogens, not for DHEA and testosterone). Sex and diet also affected the concentrations of all hormones, with no significant diet effects for estradiol and DHEA, but with considerable interaction between both factors. Binding to RBC was non-specific for all hormones. Estrogen distribution in plasma compartments was affected by sex and diet. In conclusion: a) there is a large non-specific RBC-carried compartment for estrone, estradiol, DHEA and testosterone deeply affected by sex; b) Prior exposure to a cafeteria (hyperlipidic) diet induced hormone distribution changes, affected by sex, which hint at sex-related structural differences in RBC membranes; c) We postulate that the RBC compartment may contribute to maintain free (i.e., fully active) sex hormone levels in a way similar to plasma proteins non-specific binding

Retinal pigment epithelium contains a distinctive strychnine-binding site.

Membranes prepared from the retinal pigment epithelium of several species possess a specific site which binds [3H]strychnine. This binding has a somewhat lower affinity and a much greater density than the corresponding interaction in the hindbrain or neural retina. Binding is not greatly altered in the presence of 10(-3) M glycine, L-alanine, beta-alanine, taurine, or serine. Thus, the receptor does not resemble the classical glycine receptor of the hindbrain and spinal cord. This new type of binding site appears to be confined to the pigment epithelial layer of the retina

Induction of dark-adaptive retinomotor movement (cell elongation) in teleost retinal cones by cyclic adenosine 3','5-monophosphate.

In the teleost retina, the photoreceptors and retinal pigment epithelium (RPE) undergo extensive movements (called retinomotor movements) in response to changes in light conditions and to an endogenous circadian rhythm. Photoreceptor movements serve to reposition the light-receptive outer segments and are effected by changes in inner segment length. Melanin granule movements within the RPE cells provide a movable melanin screen for rod outer segments. In the dark (night), cones elongate, rods contract, and pigment granules aggregate to the base of the RPE cell; in the light (day), these movements are reversed. We report here that treatments that elevate cytoplasmic cyclic adenosine 3',5'-monophosphate (cAMP) provoke retinomotor movements characteristic of nighttime dark adaptation, even in bright light at midday. To illustrate this response, we present a quantitative description of the effects of cyclic nucleotides on cone length in the green sunfish, Lepomis cyanellus. Cone elongation is induced when light-adapted retinas are exposed to exogenous cAMP analogues accompanied by phosphodiesterase (PDE) inhibitors (either by intraocular injection or in retinal organ culture). Cone movements is not affected by cyclic GMP analogies. Dose-response studies indicate that the extent, but not the rate, of cone elongation is proportional to the concentration of exogenous cAMP and analogue presented. As has been reported for other species, we find that levels of cAMP are significantly higher in dark- than in light-adapted green sunfish retinas. On the basis of these observations, we suggest that cAMP plays a role in the light and circadian regulation of teleost cone length

MATRIGEL PROMOTES RETINOBLASTOMA CELL-GROWTH INVITRO AND INVIVO

Cells derived from retinoblastomas grow slowly in vitro and only very rarely form tumors in nude mice. Matrigel, a mixture of components normally found in basement membranes, promotes the growth of Y-79 and WERI-RbI retinoblastoma (Rb) cells when added to suspension cultures of the 2 Rb cell lines. It also substantially increases cell adhesion in vitro. Y-79 cells, seeded into a Matrigel matrix, form round colonies over a 3-week period similar to those of control, weakly metastatic murine melanoma cells. In vivo, s.c. co-injection of Matrigel with either Y-79 or WERI-RbI cells into nude mice promotes retinoblastoma tumor formation. Transplantation of as few as 1,000 cells allows for xenografting under these conditions, while no tumors were observed in the absence of Matrigel, even at 10 x 10(6) cells/inoculum. The tumors produced have the expected morphology and express an mRNA for a highly specific retina/retinoblastoma marker protein, the interphotoreceptor retinoid-binding protein. Thus, the xenografts obtained maintain the original morphological and molecular characteristics of the injected cells and represent a useful model for in vivo studies of retinoblastoma growth and treatment