Maria A. Bermudez

Time Course of Cold Cataract Development in Anesthetized Mice

Purpose: The aim of the present study was to study the time-course development of cold cataract in mice under general anesthesia. Methods: We anesthetized five groups of 10 mice (12 weeks old) with 400 mg/Kg intraperitoneal injections of chloral hydrate and exposed them to 0, 7, 15, 23, and 37°C for 1 hr. Cataract development was assessed and graded as no cataract, mild, medium, or severe at 10, 20, 30, 45, and 60 min after the exposure started. For quantification purposes, a value from 0 to 3 was assigned to each cataract grade, and the median value was calculated for each group and time point (cataract index, CI). Results: The CI for each temperature fitted a negative exponential equation. We found that four mice of the 37°C group, nine of the 23°C group, and all animals of the 15, 7, and 0°C groups developed cataract. The cataract started at 10 min after exposure to 0°C and at 20 min when exposed to 7, 15, and 23°C. The speed of development and CI significantly increased with lower temperatures. Similar results were observed when the procedure was repeated 48 hr later in the 15, 23, and 37°C groups. In all instances the cataract was reversible. Conclusion: Our findings show that cold cataract development is temperature dependent and that cataract formation starts between 10 and 20 min after exposure to low temperature. This finding is relevant for those experimental settings in which clear ocular media are required.

Putamen neurons process both sensory and motor information during a complex task

The putamen has classically been considered to be primarily a motor structure. It is involved in a broad range of roles and its neurons have been postulated to function as pattern classifiers of behaviourally significant events. However, its specific role in motor and sensory processing is still unclear. For the purpose of better categorizing putamen neurons, we trained two rhesus monkeys to perform multisensory operant tasks by using complex stimuli such as short videoclips. Trials involved image or soundtrack or both. Some stimuli required a motor response associated to reward, whereas others did not require response and produced no reward. We found that neurons in the putamen showed pure visual responses, action-related activity, and reward responses. Insofar as action-related activity, preparation of movement, movement execution, and withholding of movement involved three different putamen neuron populations. Moreover, our data suggest an involvement of putamen neurons in processing primary rewards and visual events in a complex task, which may contribute to reinforcement learning through stimulus-reward association.

Corneal epithelial wound healing and bactericidal effect of conditioned medium from human uterine cervical stem cells.

PURPOSE To evaluate the effect of conditioned medium from human uterine cervical stem cells (CM-hUCESCs) on corneal epithelial healing in a rat model of dry eye after alkaline corneal epithelial ulcer. We also tested the bactericidal effect of CM-hUCESCs. METHODS Dry eye was induced in rats by extraocular lacrimal gland excision, and corneal ulcers were produced using NaOH. Corneal histologic evaluation was made with hematoxylin-eosin (H&E) staining. Real-time PCR was used to evaluate mRNA expression levels of proinflammatory cytokines. We also studied the bactericidal effect of CM-hUCESCs in vitro and on infected corneal contact lenses (CLs) using Escherichia coli and Staphylococcus epidermidis bacteria. In addition, in order to investigate proteins from CM-hUCESCs that could mediate these effects, we carried out a human cytokine antibody array. RESULTS After injury, dry eyes treated with CM-hUCESCs significantly improved epithelial regeneration and showed reduced corneal macrophage inflammatory protein-1 alpha (MIP-1α) and TNF-α mRNA expression as compared to untreated eyes and eyes treated with culture medium or sodium hyaluronate ophthalmic drops. In addition, we found in CM-hUCESCs high levels of proteins, such as tissue inhibitors of metalloproteinases 1 and 2, fibroblast growth factor 6 and 7, urokinase receptor, and hepatocyte growth factor, that could mediate these effects. In vitro, CM-hUCESCs showed a clear bactericidal effect on both E. coli and S. epidermidis and CLs infected with S. epidermidis. Analyses of CM-hUCESCs showed elevated levels of proteins that could be involved in the bactericidal effect, such as the chemokine (C-X-C motif) ligands 1, 6, 8, 10, and the chemokine (C-C motif) ligands 5 and 20. CONCLUSIONS Treatment with CM-hUCESCs improved wound healing of alkali-injured corneas and showed a strong bactericidal effect on CLs. Patients using CLs and suffering from dry eye, allergies induced by commercial solutions, or small corneal injuries could benefit from this treatment.

Receptive field organization of disparity‐sensitive cells in Macaque medial superior temporal cortex

Binocular disparities are crucial for building an accurate three‐dimensional representation of the peripersonal environment in a viewer‐centred frame of reference. Previous studies have shown that visual cells of the medial superior temporal cortex (MST) have large receptive fields and that they are sensitive to disparities present in large surfaces. By using a reverse cross‐correlation technique in this study we tested 175 disparity‐sensitive units recorded from MST in the awake Macaca mulatta monkey to determine if these large receptive fields are homogeneous in terms of disparity sensitivity. We found that the receptive fields of 50 cells (50 out of 175, 29%) showed subregions with specific disparity sensitivity. These subregions presented eccentricities from 0.8 to 22.3° and their sizes varied from 1.6 to 15.3°2. This particular receptive field organization represents a suitable mechanism for encoding the location of small objects within our peripersonal space.

Cancer progression by breast tumors with Pit-1-overexpression is blocked by inhibition of metalloproteinase (MMP)-13.

IntroductionThe POU class 1 homeobox 1 transcription factor (POU1F1, also known as Pit-1) is expressed in the mammary gland and its overexpression induces profound phenotypic changes in proteins involved in cell proliferation, apoptosis, and invasion. Patients with breast cancer and elevated expression of Pit-1 show a positive correlation with the occurrence of distant metastasis. In this study we evaluate the relationship between Pit-1 and two collagenases: matrix metalloproteinase-1 (MMP-1) and matrix metalloproteinase-13 (MMP-13), which have been related to metastasis in breast cancer.MethodsWe began by transfecting the MCF-7 and MDA-MB-231 human breast adenocarcinoma cell lines with the Pit-1 overexpression vector (pRSV-hPit-1). Afterward, the mRNA, protein, and transcriptional regulation of both MMP-1 and MMP-13 were evaluated by real-time PCR, Western blot, chromatin immunoprecipitation (ChIP), and luciferase reporter assays. We also evaluated Pit-1 overexpression with MMP-1 and MMP-13 knockdown in a severe combined immunodeficiency (SCID) mouse tumor xenograft model. Finally, by immunohistochemistry we correlated Pit-1 with MMP-1 and MMP-13 protein expression in 110 human breast tumors samples.ResultsOur data show that Pit-1 increases mRNA and protein of both MMP-1 and MMP-13 through direct transcriptional regulation. In SCID mice, knockdown of MMP-13 completely blocked lung metastasis in Pit-1-overexpressing MCF-7 cells injected into the mammary fat pad. In breast cancer patients, expression of Pit-1 was found to be positively correlated with the presence of both MMP-1 and MMP-13.ConclusionsOur data indicates that Pit-1 regulates MMP-1 and MMP-13, and that inhibition of MMP-13 blocked invasiveness to lung in Pit-1-overexpressed breast cancer cells.

Binocular interaction and performance of visual tasks

Binocular vision implies the fusion of the right and left retinal images to perceive a single image. For this, interocular interaction is required. We measured the reaction times to carry out a visual fixation task in order to determine whether binocular interaction influences performance. Several combinations of test and distraction stimuli were monocularly and binocularly presented to one monkey and three human subjects. The overall median reaction times were 340 ms for the animal and 308, 342 and 381 for human subjects 1, 2 and 3 respectively. Reaction time was shorter when the test stimulus was presented binocularly. Moreover, we observed that the presence of a distraction stimulus increased the reaction time and that a correlated distraction stimulus had a greater influence on this increase than an uncorrelated distraction stimulus. These findings indicate that with binocular vision a more rapid performance of a visual task occurs.

Spatial frequency components influence cell activity in the inferotemporal cortex.

We studied the correlation between the spatial frequency of complex stimuli and neuronal activity in the monkey inferotemporal (IT) cortex while performing a task that required visual recognition. Single-cell activity was recorded from the right IT cortex. The frequency components of the images used as stimuli were analyzed by using a fast Fourier transform, and a modulus was obtained for 40 spatial frequency ranges from 0.3 to 11.1 cycles/deg. We recorded 82 cells showing statistically significant responses (analysis of variance, P < 0.05) to at least one of the images used as a stimulus. Seventy-eight percent of these cells (n = 64) showed significant responses to at least three images, and in two thirds of them (n = 42), we found a statistically significant correlation (P < 0.05) between cell response and the modulus amplitude of at least one frequency range present in the images. Our results suggest that information about spatial frequency of the visual images is present in the IT cortex.

Eye dominance and response latency in area V1 of the monkey

We measured the latency of 35 cells from V1 in two rhesus monkeys, to dynamic random dot stimuli monocular and binocularly presented. Mean latencies after non-dominant eye stimulation (97.9 ms) were longer than those for dominant eye (78.2 ms) and binocular (70.7 ms) stimulation. Differences between latencies for dominant eye and binocular stimulation were not statistically significant. For dominant eye, there was a significant statistical correlation between dominance strength and latency (R = -0.36; p = 0.03). We failed to find significant statistical differences between latencies for cells with temporal and nasal dominant receptive-field. We conclude that, in V1, the response latency is largely determined by the dominant eye, whereas interocular interactions do not seem to play a relevant role regarding response latency.

Sensitivity to direction and orientation of random dot stereobars in the monkey visual cortex.

We are able to judge the direction of movement and orientation of objects because they have contrast‐defined edges. However, we are also able to perceive the orientation and direction of movement of stereobars made of random dot stereograms in the absence of contrast‐defined edges. We recorded 207 disparity‐sensitive cells from visual areas V1 and V2 of two Macaca mulatta monkeys while performing an attentive fixation task. Luminance defined bars and random‐dot stereo‐defined bars were used to assess direction and orientation selectivity of these cells. Orientation and direction preference for luminance bars and for stereobars showed a statistically significant relationship (r = 0.83, P < 0.01 for direction; r = 0.63, P < 0.01 for orientation). However, disparity‐sensitive cells from these areas seem to be more sensitive to luminance than to stereobars regarding orientation and direction of movement. Similar results were obtained when the two areas were considered separately. Our results show that cells in areas V1 and V2 of the monkey visual cortex are able to detect the orientation and direction of movement of stereobars in a manner similar to those of luminance‐defined bars. This finding is relevant because to detect the direction and orientation of stereobars a comparison between left and right eye inputs is required.

Visual Perception in Anterior Temporal Lobectomy

PURPOSE To study visual perception in patients with anterior temporal lobectomy. MATERIALS AND METHODS We explored some aspects of visual perception and compared the results obtained from 14 control subjects and 14 patients with unilateral anterior temporal lobectomy. Each group included 7 men and 7 women and the same age distribution (patients and controls: age range 27-48 years; mean 37 years). All subjects underwent a conventional ophthalmic examination and were tested for color perception, stereopsis, texture perception, face recognition, and visual illusions. To quantify color, stereoscopic, and texture perception they performed a visuomotor task that required a rapid response to a visual stimulus. Reaction times were measured under several conditions. RESULTS Mild visual field defects involving the superior quadrant contralateral to the lobectomy were found in five patients; two other patients presented more severe defects. Lobectomized patients showed a lower number of correct trials than normal subjects when performing tasks involving color and texture perception. These patients also had longer reaction times for color, stereoscopic, and texture stimulus detection. Face recognition and perception of illusory images were preserved after unilateral anterior temporal lobectomy. CONCLUSION Our data indicate that patients with anterior temporal lobectomy show moderate deficits in color, stereo, and texture perception, with no impairment in complex visual stimuli perception.