Single-cell RNA sequencing identifies molecular targets associated with poor in vitro maturation performance of oocytes collected from ovarian stimulation.

STUDY QUESTION: What is the transcriptome signature associated with poor performance of rescue IVM (rIVM) oocytes and how can we rejuvenate them? SUMMARY ANSWER: The GATA-1/CREB1/WNT signalling axis was repressed in rIVM oocytes, particularly those of poor quality; restoration of this axis may produce more usable rIVM oocytes. WHAT IS KNOWN ALREADY: rIVM aims to produce mature oocytes (MII) for IVF through IVM of immature oocytes collected from stimulated ovaries. It is not popular due to limited success rate in infertility treatment. Genetic aberrations, cellular stress and the absence of cumulus cell support in oocytes could account for the failure of rIVM. STUDY DESIGN, SIZE, DURATION: We applied single-cell RNA sequencing (scRNA-seq) to capture the transcriptomes of human in vivo oocytes (IVO) (n = 10) from 7 donors and rIVM oocytes (n = 10) from 10 donors. The effects of maternal age and ovarian responses on rIVM oocyte transcriptomes were also studied. In parallel, we studied the effect of gallic acid on the maturation rate of mouse oocytes cultured in IVM medium with (n = 84) and without (n = 85) gallic acid. PARTICIPANTS/MATERIALS, SETTING, METHODS: Human oocytes were collected from donors aged 28-41 years with a body mass index of <30. RNA extraction, cDNA generation, library construction and sequencing were performed in one preparation. scRNA-seq data were then processed and analysed. Selected genes in the rIVM versus IVO comparison were validated by quantitative real-time PCR. For the gallic acid study, we collected immature oocytes from 5-month-old mice and studied the effect of 10-µM gallic acid on their maturation rate. MAIN RESULTS AND THE ROLE OF CHANCE: The transcriptome profiles of rIVM/IVO oocytes showed distinctive differences. A total of 1559 differentially expressed genes (DEGs, genes with at least 2-fold change and adjusted P < 0.05) were found to be enriched in metabolic processes, biosynthesis and oxidative phosphorylation. Among these DEGs, we identified a repression of WNT/ß-catenin signalling in rIVM when compared with IVO oocytes. We found that oestradiol levels exhibited a significant age-independent correlation with the IVO mature oocyte ratio (MII ratio) for each donor. rIVM oocytes from women with a high MII ratio were found to have over-represented cellular processes such as anti-apoptosis. To further identify targets that contribute to the poor clinical outcomes of rIVM, we compared oocytes collected from young donors with a high MII ratio with oocytes from donors of advanced maternal age and lower MII ratio, and revealed that CREB1 is an important regulator. Thus, our study identified that GATA-1/CREB1/WNT signalling was repressed in both rIVM oocytes versus IVO oocytes and in rIVM oocytes of lower versus higher quality. Consequently we investigated gallic acid, as a potential antioxidant substrate in human rIVM medium, and found that it increased the mouse oocyte maturation rate by 31.1%. LARGE SCALE DATA: Raw data from this study can be accessed through GSE158539. LIMITATIONS, REASONS FOR CAUTION: In the rIVM oocytes of the high- and low-quality comparison, the number of samples was limited after data filtering with stringent selection criteria. For the oocyte stage identification, we were unable to predict the presence of oocyte spindle, so polar body extrusion was the only indicator. WIDER IMPLICATIONS OF THE FINDINGS: This study showed that GATA-1/CREB1/WNT signalling was repressed in rIVM oocytes compared with IVO oocytes and was further downregulated in low-quality rIVM oocytes, providing us the foundation of subsequent follow-up research on human oocytes and raising safety concerns about the clinical use of rescued oocytes. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Collaborative Research Fund, Research Grants Council, C4054-16G, and Research Committee Funding (Research Sustainability of Major RGC Funding Schemes), The Chinese University of Hong Kong. The authors have no conflicts of interest to declare.

Morphometric sex determination of Milky and Painted Storks in captivity.

Logistic regression was applied to develop a morphometric sexing method of two closely related stork species that were previously sexed through amplification of the CHD gene. Tarsus length (TL) and bill length (BL) measurements were recorded from captive populations of adult Milky Stork (Mycteria cinerea) (n = 60) and Painted Stork (Mycteria leucocephala) (n = 58) at Zoo Negara Malaysia. Despite having monomorphic plumages, both stork species exhibited normal sexual size dimorphism in which males were significantly larger than females in the tested variables. Based on logistic regression analysis, BL correctly classified the sex of sampled individuals from Painted and Milky stork with an overall predicted accuracy of 94.8 and 90.0%, respectively. However, TL measurements generated a lower predicted accuracy level of 86.2% and a same accuracy level of 90% on the sex classification of individuals from Painted and Milky stork, respectively. By comparing the measurements of both species, only the average BL measurements of the Milky storks were significantly lower than that of Painted storks (t-test, P80.001). The logistic regression equation in this study may serve as a simple and more practical option for sexing Milky and Painted storks for their breeding and conservation programmes.

An evolutionarily conserved nested gene pair - Mab21 and Lrba/Nbea in metazoan.

The embedding of one gene in another as a nested gene pair is a unique phenomenon of gene clustering in the metazoan genome. A gene-centric paralogous genomic sequence comparison strategy was used in this study to align these paralogous nested pairs, Mab21l2-Lrba and Mab21l1-Nbea, to identify the associated paralogous non-coding elements (pNEs) they shared. A majority of these pNEs in the Mab21l2-Lrba locus display tissue-specific enhancer activities recapitulating the expression profiles of Mab21l2 and Mab21l1. Since these enhancers are spread into the introns of Lrba, dissociation of the two genes will likely disrupt the function of at least one of them. Phylogenetic analysis of this complex locus in different species suggests that Mab21 was probably locked in the Lrba/Nbea intron in the ancestral metazoan species, in which the cis-elements uncovered in this study may act as a selective force to prevent the dissociation of this gene pair in vertebrates.

Development of rabbit visual cortex: late appearance of a class of receptive fields.

In young rabbits before the age at which the eyes open, only three of the seven receptive field types described in the adult visual cortex are detectable. The remaining four receptive field types-which share the property of having radially asymmetric fields-appear later, coincident with a decline in the percentage of cells that are visually responsive but not classifiable as to receptive field type.

Ruptured Superficial Femoral Artery Anastomotic Pseudoaneurysm after 30 Years.

INTRODUCTION: Anastomotic pseudoaneurysms are a complication of vascular reconstructive surgery with the majority in the femoral region. Although rare, ruptured femoral anastomotic pseudoaneurysms have high mortality and require emergency surgery. CASE PRESENTATION: A 60-year-old male with a history of a left leg crush injury was treated with a superficial femoral artery interposition vein graft 30 years ago. He presented nowadays with a three-day history of severe pain in his left thigh. CT angiography demonstrated a ruptured anastomotic pseudoaneurysm with contrast extravasation into an intramuscular hematoma. He had significant scarring from his previous surgeries which made the leg hostile for an open repair. Therefore, percutaneous access selectively cannulated the left iliofemoral vasculature. An angiogram showed a distal superficial femoral artery pseudoaneurysm. Subsequently, two 10mmx15cm Viabahn covered stents (Gore & Associates, Flagstaff, AZ) were placed bridging healthy superficial femoral artery. A completion angiogram demonstrated no extravasation into the pseudoaneurysm. The patient recovered and was discharged home two days postoperatively. CONCLUSION: Ruptured femoral anastomotic pseudoaneurysms are traditionally repaired with open pseudoaneurysm excision and arterial reconstruction, although endovascular repair has been reported. Furthermore, most femoral anastomotic pseudoaneurysms form less than 10 years after initial operation. We present a unique case of ruptured superficial femoral artery pseudoaneurysm, 30 years after the initial operation. Endovascular stents offer effective treatment for ruptured anastomotic pseudoaneurysms.

mab-7 encodes a novel transmembrane protein that orchestrates sensory ray morphogenesis in C. elegans.

The tapered sensory rays of the male Caenorhabditis elegans are important for successful male/hermaphrodite copulation. A group of ram (ray morphology abnormal) genes encoding modifying enzymes and transmembrane protein have been reported as key regulators controlling ray morphogenesis. Here we report the characterization of another component essential for this morphogenetic process encoded by mab-7. This gene is active in the hypodermis, structural cells, the body seam and several head neurons. It encodes a novel protein with a hydrophobic region at the N-terminus, an EGF-like motif, an ShKT motif and a long C-terminal tail. All these domains are shown to be critical to MAB-7 activity except the EGF-like domain, which appears to be regulatory and dispensable. MAB-7 is shown to be a type II membrane protein, tethered on the cell surface by the N-terminal transmembrane domain with the remainder of the protein exposed to the extracellular matrix. Since ectopic mab-7 expression in any ray cell or even in touch neurons of non-ray lineage can rescue the mutant phenotype, mab-7 is probably acting non-autonomously. It may facilitate intercellular communication among ray cells to augment normal ray morphogenesis.

Case reports of atrial and pericardial rupture from blunt cardiac trauma.

BACKGROUND: Blunt cardiac trauma is diagnosed in less than 10% of trauma patients and covers the range of severity from clinically insignificant myocardial contusions to lethal multi-chamber cardiac rupture. The most common mechanisms of injury include: motor vehicle collisions (MVC), pedestrians struck by motor vehicles and falls from significant heights. A severe complication from blunt cardiac trauma is cardiac chamber rupture with pericardial tear. It is an exceedingly rare diagnosis. A retrospective review identified only 0.002% of all trauma patients presented with this condition. Most patients with atrial rupture do not survive transport to the hospital and upon arrival diagnosis remains difficult. CASE PRESENTATION: We present two cases of atrial and pericardial rupture. The first case is a 33-year-old female involved in a MVC, who presented unresponsive, hypotensive and tachycardic. A left sided hemothorax was diagnosed and a chest tube placed with 1200 mL of bloody output. The patient was taken to the OR emergently. Intraoperatively, a laceration in the right pericardium and a 3 cm defect in the anterior, right atrium were identified. Despite measures to control hemorrhage and resuscitate the patient, the patient did not survive. The second case is a 58-year-old male involved in a high-speed MVC. Similar to the first case, the patient presented unresponsive, hypotensive and tachycardic with a left sided hemothorax. A chest tube was placed with 900 mL of bloody output. Based on the output and ongoing resuscitation requirements, the patient was taken to the OR. Intraoperatively, a 15 cm anterior pericardial laceration was identified. Through the defect, there was brisk bleeding from a 1 cm laceration on the left atrial appendage. The injury was debrided and repaired using a running 3-0 polypropylene suture over a Satinsky clamp. The patient eventually recovered and was discharged home. CONCLUSIONS: We present two cases of uncontained atrial and pericardial rupture from blunt cardiac trauma. Contained ruptures with an intact pericardium present as a cardiac tamponade while uncontained ruptures present with hemomediastinum or hemothorax. A high degree of suspicion is required to rapidly diagnose and perform the cardiorrhaphy to offer the best chance at survival.

A combination of closely associated positive and negative cis-acting promoter elements regulates transcription of the skeletal alpha-actin gene.

The chicken skeletal alpha-actin gene promoter region provides at least a 75-fold-greater transcriptional activity in muscle cells than in fibroblasts. The cis-acting sequences required for cell type-restricted expression within this 200-base-pair (bp) region were elucidated by chloramphenicol acetyltransferase assays of site-directed Bg/II linker-scanning mutations transiently transfected into primary cultures. Four positive cis-acting elements were identified and are required for efficient transcriptional activity in myogenic cells. These elements, conserved across vertebrate evolution, include the ATAAAA box (-24 bp), paired CCAAT-box-associated repeats (CBARs; at -83 bp and -127 bp), and the upstream T+A-rich regulatory sequence (at -176 bp). Basal transcriptional activity in fibroblasts was not as dependent on the upstream CBAR or regions of the upstream T+A-rich regulatory sequence. Transfection experiments provided evidence that positive regulatory factors required for alpha-actin expression in fibroblasts are limiting. In addition, negative cis-acting elements were detected and found closely associated with the G+C-rich sequences that surround the paired CBARs. Negative elements may have a role in restricting developmentally timed expression in myoblasts and appear to inhibit promoter activity in nonmyogenic cells. Cell type-specific expression of the skeletal alpha-actin gene promoter is regulated by combinatorial and possibly competitive interactions between multiple positive and negative cis-acting elements.

Activation of skeletal alpha-actin gene transcription: the cooperative formation of serum response factor-binding complexes over positive cis-acting promoter serum response elements displaces a negative-acting nuclear factor enriched in replicating myoblasts and nonmyogenic cells.

Three upstream CBAR cis-acting promoter elements, containing the inner core CC(A/T)6GG of the serum response element (SRE), are required for myogenic cell type-restricted expression of the avian skeletal alpha-actin gene (K.L. Chow and R.J. Schwartz, Mol. Cell. Biol. 10:528-538, 1990). These actin SRE elements display differential binding properties with two distinct nuclear proteins, serum response factor (SRF) and another factor described here as F-ACT1. SRF is able to bind to all actin SREs with various affinities. This multisite interaction is marked by cooperative binding events in that the two high-affinity proximal and distal SREs facilitate the weak central-site interaction with SRF, leading to the formation of a higher-order SRF-promoter complex. Functional analyses reveal that undisrupted multiple SRF-DNA interactions are absolutely essential for promoter activity in myogenic cells. F-ACT1, present at higher levels in nonmyogenic cells and replicating myoblasts than in myotubes, binds solely to the proximal SRE, and its binding is mutually exclusive with that of SRF owing to their overlapping base contacts. The cooperative promoter binding by SRF, however, can effectively displace prebound F-ACT1. In addition, an intact F-ACT1 binding site acts as a negative promoter element by restricting developmentally timed expression in myoblasts. F-ACT1 may therefore act as a repressor of skeletal alpha-actin gene transcription. This interplay between F-ACT1 and SRF may constitute a developmental as well as a physiologically regulated mechanism which modulates sarcomeric actin gene expression.

Heterodimers of myogenic helix-loop-helix regulatory factors and E12 bind a complex element governing myogenic induction of the avian cardiac alpha-actin promoter.

Recent studies have shown that two genes regulating myogenesis (MyoD and myogenin) are coexpressed with cardiac alpha-actin during early stages of skeletal muscle development. Myogenin and MyoD are members of a family of regulatory proteins which share a helix-loop-helix (HLH) motif required for dimerization and DNA binding. Myogenin and MyoD form heterodimers with the ubiquitous HLH protein E12 which bind cis-acting DNA elements that have an E box (CANNTG) at their core. E boxes are present in the control regions of numerous muscle-specific genes, although their functional importance in regulating many of these genes has not yet been evaluated. In this report we examine the possibility that myogenin (or MyoD) directly transactivates the cardiac alpha-actin promoter. Heterodimers of myogenin and E12 (or MyoD and E12) specifically bound a restriction fragment extending from -200 to -103 relative to the start of cardiac alpha-actin transcription. Methylation interference footprints pinpointed the site of interaction to an E box immediately adjacent to a previously identified CArG box (CArG3). Site-directed mutations to the DNA-binding site revealed that either an intact E box or an intact CArG3 is required for induction of the cardiac alpha-actin promoter in myoblasts and for transactivation by myogenin in cotransfected fibroblasts. However, deletion and substitution experiments indicate that the complex E box/CArG3 element alone does not confer muscle-specific expression to a minimal promoter. These results suggest that direct and indirect pathways involving multiple cis-acting elements mediate the induction of the cardiac alpha-actin promoter by myogenin and MyoD.

Developmental expression of Mab21l2 during mouse embryogenesis.

mab-21 has been identified as a critical component required for sensory organ identity establishment in Caenorhabditis elegans. [Chow, K.L., Emmons, S.W., 1994. Development 120, 2579-2592; Chow, E. L., Hall, D.H., Emmons, S.W., 1995. Development 121, 3615-3625]. Human and mouse homologs of this gene have been isolated and their transcripts are predominantly detected in the eye and cerebellum [Margolis, R.L., Stine, O.C., McInnis, M.G., et al., 1996. Hum. Mol. Genet 5, 607-616; Mariani, M., Corradi, A., Baldessari, D., et al., 1998. Mech. Dev. 79, 131-135. We report here the expression profile of a second murine mab-21 homolog, Mab21l2 [Wong, R.L.Y., Wong, H.T., Chow, K.L., 1999. Cyto. Cell Genet., [in press]. Whole mount in situ hybridization data from embryonic day 8.5 to day 15 revealed that Mab21l2 expression patterns partially overlapped with that of Mab21l1. In addition, its strong expression in the mid- and hindbrain, otic vesicle, optic vesicle, maxillary and mandibular process, paraxial mesoderm, dorsal midline, limb bud and developing digits suggest that Mab21l2 has more diverse functions in vertebrate development.

Anatomical studies of a temporal visual area in the rabbit.

Using Fink-Heimer, autoradiographic and horseradish peroxidase techniques, the connections of a temporal visual cortical region of the rabbit were explored. The temporal visual area covers portions of areas T1 and T2, and is reciprocally connected with the posterior nucleus and suprageniculate nuclei of the thalamus. It was also shown that the temporal visual area projects to a similar region in the opposite hemisphere, and to intermediate laminae of the superior colliculus. The temporal visual area is discussed in comparison to other similar regions in the cortex of primate species. It is pointed out that recent evidence indicates visual areas in the occipital cortex of non-primate species may be no less numerous and complex than those in primate species.

The ipsilateral retinocollicular projection in the rabbit: an autoradiographic study of postnatal development and effects of unilateral enucleation.

The postnatal development of the ipsilateral retinocollicular projection in the rabbit and the effects of unilateral enucleation (performed on the day of birth, day 0) on that development were studied by using the anterograde axonal transport of tritiated proline injected intraocularly. Material from 1-, 6-, and 10-day-old (i.e., at days 1, 6, and 10) and adult animals was examined. On day 1, autoradiographically labelled optic fibers from the ipsilateral eye formed distinct patches and bands within the superior colliculus (SC), which were restricted primarily to the lateral one-half and anterior one-third to one-half of the nucleus. At subsequent ages no major changes in the location of this projection were found for normal animals or animals enucleated on day 0 (0-DE animals). From dorsal-view reconstructions, the pattern of the ipsilateral projection appeared wedge-shaped with a broad base aligned with the lateral SC border for all normal and 0-DE animals at the various postnatal ages examined. In normal animals the surface area of this projection increased with age and maintained a constant proportion of the increasing surface area of the total SC. In 0-DE animals the surface area of the projection initially increased more rapidly than in normal animals. Thus, by day 6 the area was already within the normal adult range but did not exceed this range at later postnatal ages. The only obvious difference in the appearance of the ipsilateral retinocollicular projection between normal and 0-DE animals at corresponding ages was an enhanced radial distribution of the projection across laminae in the 0-DE animals. Taken together these findings suggest that, in the rabbit, once topographically appropriate connections are established between the SC and the ipsilateral retinal projection, they are maintained regardless of substantial postnatal growth of the SC and removal of the contralateral retinal projection to the SC.

Receptive field characteristics of neurons in a visual area of the rabbit temporal cortex.

In a program of surveying the characteristics of visual receptive fields of neurons in rabbit brain, we have explored cortical sectors beyond the striate and occipital cortices and found cells in a part of the temporal lobe that were responsive to visual stimulation. Using evoked potential and unit-cluster methods, this temporal visual area was mapped to be roughly oval-shaped, 3 mm x 2mm in size, and at about the level posterior to the apex region of auditory area 1. It is located ventral to and continuous with visual area 11, at about the caudal half of M. Rose's temporal cortices 1 and 2 (T1 and T2). Only about two-thirds of 96 units studied responded to some sort of moving light stimulation. These motion-sensitive cells were divided into four groups. Cells in the first group (22) responded best to a large light spot or shadow sweeping quickly across the field. Cells in the second group (29) responded to slow moving, jerking spot. Nine cells responded to a narrow, dark bar thrusting into a lighted field. Four cells are "direction-selective," responding to light stimulus moving in one direction and showing either no response or decreased background discharges in the opposite direction. In addition, three cells required unusual stimulus features. Of the 38 cells tested, nine of them were found to be binocularly driven. These receptive field characteristics are quite different from those described for other visual centers of the rabbit. The significance of these results together with data on the anatomical connections of this cortical area as reported in the following paper were discussed.

Anomalous uncrossed retinal projections fail to activate superior colliculus neurons in rabbits unilaterally enucleated by fetal surgery.

Previous studies have shown that unilateral enucleation of rabbit pups produces an aberrant uncrossed retinotectal projection. These fibers failed to drive collicular units when stimulated with either light or electric shock. The present study attempts to assess the possibility that enucleation at earlier stages of development would lead to a greater degree of morphological and physiological reorganization in the uncrossed retinotectal projection. Rabbit fetuses were unilaterally enucleated at day 20 or 25 of gestation. Birth is at day 31. After 3 months, the degree of reorganization of the uncrossed retinotectal projection was assessed using the following techniques: (1) autoradiographic demonstration of the projection from the remaining eye, (2) electrophysiological recording of collicular unit activity, and (3) a combination of these methods. Autoradiographic data indicated a much greater expansion of the anomalous uncrossed projection in fetally enucleated animals than in those enucleated at birth. Labelled terminals were found to occupy more than the anterior third of the ipsilateral colliculus and were distributed to the entire depth of the stratum griseum superficiale and stratum opticum. Electrode penetrations within the boundaries of the expanded projection failed to locate collicular units which could be driven by either light stimulation of the eye or electric shock of the optic nerve. Only a few cells encountered in the lateral border area, receiving the normal uncrossed retinal projection, could be driven by light stimulation. These negative findings are in contrast to the data reported for the rat and hamster where anomalous retinal projections are capable of forming functional connections. Further comparative studies of reorganization are needed.

The origin and terminal arbors of individual uncrossed retinogeniculate fibers in rabbits.

The distribution and morphology of individual uncrossed retinogeniculate fibers in both normal and monocularly enucleated adult Dutch-belted rabbits were studied using horseradish peroxidase and wheat germ agglutinin conjugated to horseradish peroxidase as neuronal markers. The results showed that the uncrossed retinogeniculate fibers were distributed almost entirely in the ipsilateral segment of the dorsal nucleus of the lateral geniculate body, and the extent of terminal distribution of the fibers observed in rabbits with one eye enucleated during the young adult stage was essentially the same as that in the normal rabbit. Most of the uncrossed retinogeniculate fibers appeared to arise as collateral branches of optic tract fibers which were apparently destined for the pretectum or the superior colliculus. The uncrossed retinogeniculate fibers labeled by the wheat germ agglutinin conjugated to horseradish peroxidase passed through the dorsal nucleus of the lateral geniculate body without any branching until they reached the ipsilateral segment. There they could be divided into several morphological types although the possibility that they may represent different classes of a continuum cannot be ruled out.

Velocity-tuning of motion-sensitive and direction-selective cells in the rabbit striate cortex.

The receptive field characteristics of 268 striate cortical cells were classified in 10 Dutch-belted rabbits. From the 66 motion-sensitive and direction-selective units encountered, quantitative data describing the responses of 41 motion-sensitive, and 10 direction-selective cells to moving gratings were obtained. The results showed that all cells responded with increased spike discharges to increased velocities of the moving gratings up to a maximum, then they became less responsive to further increase of the velocities. The patterns of the response curves varied from cell to cell. When the 51 cells were taken as a whole, there were more cells responding to the velocities of 10-30 deg/sec than to higher or lower velocities. The total range over which these cells responded was 0.1-300 deg/sec. The preferred velocities for individual cells ranged from 1.5 to 150 deg/sec, showing a moderate concentration at the 6-40 deg/sec region. The extent of the effective velocities for individual cells formed a continuous distribution. No segregation into groups was seen in either of the two cell types studied or in all cells taken as a group. These data were compared with those reported for the rabbit retinal ganglion cells and the cells in the nucleus of the optic tract, as well as the cells in the cat visual system.

Movement discrimination in the rabbit.

In a two-choice discrimination box, rabbits were trained to discriminate vertical vs horizontal striations. After criterion was reached, the same striations were presented again, but now the patterns moved sinusoidally. All animals immediately transferred to moving patterns. After that, it was attempted to train the animals to discriminate between moving vs non-moving vertical striations. Even after prolonged training, none of the animals learned this discrimination task.

Receptive field development in the dorsal lateral geniculate nucleus in rabbits subjected to monocular eyelid suture.

Receptive field properties of cells in the dorsal lateral geniculate nucleus (LGNd) were examined in 3 groups of rabbits, each subjected to monocular visual deprivation by lid suture at differing age periods. Monocular deprivation occurring from 6--8 to 20--25 days of age affected the normal development of LGNd receptive fields. A significant proportion of the cells in the deprived LGNd were either unresponsive to visual stimulation or had vague, indefinite receptive fields. Significantly fewer cells with uniform fields were found in the deprived LGNd than in the control. Percentages of concentric, motion and directional cells did not differ between the deprived and control LGNd. The diameters of receptive fields for concentric cells with sustained response properties, however, were smaller in the deprived than in the control LGNd. When deprivation was continued to 87--121 days of age, the percentage of uniform, indefinite and non-responsive cells found in the deprived LGNd approached more normal levels. Percentages of concentric, motion and directional cells were also normal. Monocular deprivation commencing at 21--22 days of age also had disruptive effects on LGNd receptive field organization, as reflected in the lower percentage of uniform and increased percentages of indefinite and non-responsive cells. These deficits, however, were not as severe as those seen in the animals deprived at an early age. A fourth group of adult rabbits subjected to monocular lid suture showed no such detrimental deficits in receptive field organization. These results demonstrated that visual deprivation affects the predominantly monocular LGNd of the rabbit, and that a critical period exists for such effects.