Exclusive transabdominal trans-amniotic approach for chorionic villus sampling in posterior placenta: a novel approach for prenatal diagnosis of genetic disorders

Background: The objective of the study was to evaluate role and safety of transabdominal trans-amniotic approach for Chorionic villus sampling (CVS) for prenatal diagnosis of genetic disorders.Methods: Retrospective analytical study carried out on data form couples coming for pre-natal diagnosis from January 2010 to February 2021. Patient related parameters like age, gestational age; procedure related parameters like amount of sample, number of attempts required; different genetic disorder diagnosed and complications by both the approaches of CVS were recorded and analyzed.Results: Total 2287 patients undergoing CVS with mean age of 27±3.3 years were included. Majority (1621;70.9%) had CVS procedure at gestational age of 12-14 weeks. On analyzing physician’s perception, 663 (29%) patients having complete posterior placenta could not be accessible with routine trans-abdominal CVS and opted for trans-amniotic approach. Amount of sample yield and number of attempts were not statistically significant (p>0.05) by both methods of CVS. Thalassemia major was found in 948 (41.45%) followed by thalassemia minor in 525 (22.96%) patients. No statistically significant difference was found for developing complications by both the methods (p>0.05). Most common complication was pain and discomfort which was relieved by simple analgesics. Out of total 17 (0.74%) abortions; 13 (0.80%) from routine transabdominal and 4 (0.60%) from trans-amniotic route CVS with no statistically significant difference among them (p>0.05). No case of post procedure infection was observed.Conclusions: In complete posterior placenta CVS procedures usually postponed by most physicians leading to delay in diagnosis of genetic disorders. The novel method transabdominal trans-amniotic approach for CVS is effective and safe in skilled hands and can help in early prenatal diagnosis of genetic disorders.

Pooling signals from vertically and non-vertically orientation-tuned disparity mechanisms in human stereopsis

AbstractTo understand the role that orientation-tuned disparity-sensitive mechanisms play in the perception of stereoscopic depth, we measured stereothresholds using two sets of random-dot stimuli that produce identical stimulation of disparity mechanisms tuned to vertical orientation but dissimilar stimulation of disparity mechanisms tuned to non-vertical orientations. Either 1 or 1.5D of astigmatic blur was simulated in the random-dot images presented to both eyes, using two axis configurations. In the parallel-axis conditions, the axis of simulated astigmatic blur was same in the two eyes (0, 45 or 135 o[rientation]deg). In the orthogonal-axis conditions, the axes of astigmatic blur were orthogonal in the two eyes (LE: 180, RE: 90; LE: 90, RE: 180; LE: 45, RE: 135; and LE: 135, RE: 45). Whereas the stimulation of disparity mechanisms tuned to near-vertical orientations should be similar in the oblique parallel- and orthogonal-axis conditions, the stimulation of non-vertically tuned disparity mechanisms should be dissimilar. Measured stereothresholds were higher in the orthogonal compared to the parallel-axis condition by factors of approximately 2 and 5, for 1 and 1.5D of simulated oblique astigmatic blur, respectively. Further, for comparable magnitudes of simulated astigmatic blur, stereothresholds in the (LE: 180, RE: 90 and LE: 90, RE: 180) conditions were similar to those in the (LE: 45, RE: 135 and LE: 135, RE: 45) conditions. These results suggest that the computation of horizontal disparity includes substantial contributions from disparity mechanisms tuned to non-vertical orientations. Simulations using a modified version of a disparity-energy model [Qian, N., & Zhu, Y. (1997). Physiological computation of binocular disparity. Vision Research, 37, 1811–1827], show (1) that pooling across disparity mechanisms tuned to vertical and non-vertical orientations is required to account for our data and (2) that this pooling can provide the spatial resolution needed to encode spatially changing horizontal disparities

Attenuation of perceived motion smear during vergence and pursuit tracking

AbstractWhen the eyes move, the images of stationary objects sweep across the retina. Despite this motion of the retinal image and the substantial integration of visual signals across time, physically stationary objects typically do not appear to be smeared during eye movements. Previous studies indicated that the extent of perceived motion smear is smaller when a stationary target is presented during pursuit or saccadic eye movements than when comparable motion of the retinal image occurs during steady fixation. In this study, we compared the extent of perceived motion smear for a stationary target during smooth pursuit and vergence eye movements with that for a physically moving target during fixation. For a target duration of 100 ms or longer, perceived motion smear is substantially less when the motion of the retinal image results from vergence or pursuit eye movements than when it results from the motion of a target during fixation. The reduced extent of perceived motion smear during eye movements compared to fixation cannot be accounted for by different spatio-temporal interactions between visual targets or by unequal attention to the moving test spot under these two types of conditions. We attribute the highly similar attenuation of perceived smear during vergence and pursuit to a comparable action of the extra-retinal signals for disjunctive and conjugate eye movements

Relationship between threshold and suprathreshold perception of position and stereoscopic depth.

We seek to determine the relationship between threshold and suprathreshold perception for position offset and stereoscopic depth perception under conditions that elevate their respective thresholds. Two threshold-elevating conditions were used: (1) increasing the interline gap and (2) dioptric blur. Although increasing the interline gap increases position (Vernier) offset and stereoscopic disparity thresholds substantially, the perception of suprathreshold position offset and stereoscopic depth remains unchanged. Perception of suprathreshold position offset also remains unchanged when the Vernier threshold is elevated by dioptric blur. We show that such normalization of suprathreshold position offset can be attributed to the topographical-map-based encoding of position. On the other hand, dioptric blur increases the stereoscopic disparity thresholds and reduces the perceived suprathreshold stereoscopic depth, which can be accounted for by a disparity-computation model in which the activities of absolute disparity encoders are multiplied by a Gaussian weighting function that is centered on the horopter. Overall, the statement equal suprathreshold perception occurs in threshold-elevated and unelevated conditions when the stimuli are equally above their corresponding thresholds describes the results better than the statement suprathreshold stimuli are perceived as equal when they are equal multiples of their respective threshold values

Color and motion: which is the tortoise and which is the hare?

AbstractRecent psychophysical studies have been interpreted to indicate that the perception of motion temporally either lags or is synchronous with the perception of color. These results appear to be at odds with neurophysiological data, which show that the average response-onset latency is shorter in the cortical areas responsible for motion (e.g., MT and MST) than for color processing (e.g., V4). The purpose of this study was to compare the perceptual asynchrony between motion and color on two psychophysical tasks. In the color correspondence task, observers indicated the predominant color of an 18°×18° field of colored dots when they moved in a specific direction. On each trial, the dots periodically changed color from red to green and moved cyclically at 15, 30 or 60 deg/s in two directions separated by 180°, 135°, 90° or 45°. In the temporal order judgment task, observers indicated whether a change in color occurred before or after a change in motion, within a single cycle of the moving-dot stimulus. In the color correspondence task, we found that the perceptual asynchrony between color and motion depends on the difference in directions within the motion cycle, but does not depend on the dot velocity. In the temporal order judgment task, the perceptual asynchrony is substantially shorter than for the color correspondence task, and does not depend on the change in motion direction or the dot velocity. These findings suggest that it is inappropriate to interpret previous psychophysical results as evidence that motion perception generally lags color perception. We discuss our data in the context of a “two-stage sustained-transient” functional model for the processing of various perceptual attributes

Mechanisms of perceptual learning of depth discrimination in random dot stereograms.

Perceptual learning is a training induced improvement in performance. Mechanisms underlying the perceptual learning of depth discrimination in dynamic random dot stereograms were examined by assessing stereothresholds as a function of decorrelation. The inflection point of the decorrelation function was defined as the level of decorrelation corresponding to 1.4 times the threshold when decorrelation is 0%. In general, stereothresholds increased with increasing decorrelation. Following training, stereothresholds and standard errors of measurement decreased systematically for all tested decorrelation values. Post training decorrelation functions were reduced by a multiplicative constant (approximately 5), exhibiting changes in stereothresholds without changes in the inflection points. Disparity energy model simulations indicate that a post-training reduction in neuronal noise can sufficiently account for the perceptual learning effects. In two subjects, learning effects were retained over a period of six months, which may have application for training stereo deficient subjects

The temporal impulse response function in infantile nystagmus.

Despite rapid to-and-fro motion of the retinal image that results from their incessant involuntary eye movements, persons with infantile nystagmus (IN) rarely report the perception of motion smear. We performed two experiments to determine if the reduction of perceived motion smear in persons with IN is associated with an increase in the speed of the temporal impulse response. In Experiment 1, increment thresholds were determined for pairs of successively presented flashes of a long horizontal line, presented on a 65-cd/m2 background field. The stimulus-onset asynchrony (SOA) between the first and second flash varied from 5.9 to 234 ms. In experiment 2, temporal contrast sensitivity functions were determined for a 3-cpd horizontal square-wave grating that underwent counterphase flicker at temporal frequencies between 1 and 40 Hz. Data were obtained for 2 subjects with predominantly pendular IN and 8 normal observers in Experiment 1 and for 3 subjects with IN and 4 normal observers in Experiment 2. Temporal impulse response functions (TIRFs) were estimated as the impulse response of a linear second-order system that provided the best fit to the increment threshold data in Experiment 1 and to the temporal contrast sensitivity functions in Experiment 2. Estimated TIRFs of the subjects with pendular IN have natural temporal frequencies that are significantly faster than those of normal observers (ca. 13 vs. 9 Hz), indicating an accelerated temporal response to visual stimuli. This increase in response speed is too small to account by itself for the virtual absence of perceived motion smear in subjects with IN, and additional neural mechanisms are considered

A study of bacteriological profile and antibiotic sensitivity of culture proven neonatal sepsis

Background: Neonatal sepsis is the second most common cause of neonatal mortality in India. Early detection and proper treatment of sepsis are important in reducing neonatal mortality. The emergence of antibiotic resistance among pathogens that infect newborns is of great concern. Hence, this study was done to identify the bacterial agents causing neonatal septicemia along with their antibiotic sensitivity pattern. Methods: This was a prospective study carried out at neonatal intensive care unit of a tertiary care teaching hospital of western Gujarat, India, from October 2018 to August 2020. 2739 neonates were admitted with probable sepsis during the study period. 299 neonates with positive blood cultures were recruited for the study. Antibiotic sensitivity of organisms was noted and compared with other studies. Results: Out of 299 blood culture proven sepsis, most common organism was Klebsiella pneumoniae, isolated in 98 patients (32.7%), followed by coagulase negative staphylococcus aureus in 90 patients (30.2%). Candida was the third most common organism isolated in 45 (15.1%) patients. Other bacteria isolated were Enterococcus in 33 (11.1%), Staphylococcus aureus in 17 (5.6%), Escherichia coli in 7 (2.3%), Acinetobacter spp in 6 (2%) and Pseudomonas in 3 (1%) patients. Gram positive bacteria were isolated in 140 (46.8%) patients, while, gram negative bacteria and fungus were isolated in 114 (38.2%) and 45 (15%) patients respectively. Klebsiella demonstrated maximum sensitivity to Meropenem (95%) and Piperacillin-Tazobactam (73.1%), while it showed high resistance to ampicillin (97.9%) and Cefoperazone (95.9%). Among non-beta lactam antibiotics, Klebsiella showed maximum sensitivity to colistin (100%) and Vancomycin (80%), while showed high resistance to Aminoglycosides and Quinolones. CONS showed maximum sensitivity to Cefoperazone (81.4%) and Cefotaxim (62.4%), but they showed high resistance to Ampicillin (86.5%) and Meropenem (86.9%). Among non-beta lactam antibiotics, CONS showed maximum sensitivity to Linezolid (100%) and Vancomycin (98%), while showed high resistance to Aminoglycosides and Quinolones. Conclusions: The most common organism isolated was Klebsiella and it showed high resistance to 1st, 2nd and 3rd line antibiotics (Ampicillin, Aminoglycosides, Cefoperazone and Quinolones). Due to the emergence of antibiotic resistance in NICU, it is important to know antibiotics sensitivity and resistant pattern of various organisms for neonatal sepsis