Entire Tracts Research Articles

Disrupted white matter microstructure correlates with impulsivity in children and adolescents with bipolar disorder

Altered white matter (WM) microstructure likely occurs in children with bipolar disorder (BD) with impulsivity representing one of the core features. However, altered WM microstructures and their age-related trendlines in children with BD and those at high-risk of developing BD, as well as correlations of WM microstructures with impulsivity, have been poorly investigated. In this study, diffusion MRI, cognitive, and impulsivity assessments were obtained from children/adolescents diagnosed with BD, offspring of individuals with BD (high-risk BD) and age-matched healthy controls. A novel atlas-based WM skeleton measurement approach was used to quantify WM microstructural integrity with all diffusion-tensor-imaging (DTI) metrics including fractional anisotropy, axial, mean and radial diffusivity to survey entire WM tracts and ameliorate partial volume effects. Among all DTI-derived metric measures, radial diffusivity quantifying WM myelination was found significantly higher primarily in corpus callosum and in the corona radiata in children with BD compared to controls. Distinguished from age-related progressively decreasing diffusivities and increasing fractional anisotropy in healthy controls, flattened age-related trendlines were found in BD group, and intermediate developmental rates were observed in high-risk group. Larger radial diffusivity in the corpus callosum and corona radiata significantly correlated with shorter response times to affective words that indicate higher impulsivity in the BD group, whereas no such correlation was found in the healthy control group. This work corroborates the progressive nature of pediatric BD and suggests that WM microstructural disruption involved in affective regulation and sensitive to impulsivity may serve as a biomarker of pediatric BD progression.

Ex vivo development of the entire mouse fetal reproductive tract by using microdissection and membrane-based organ culture techniques

Ex vivo explant culture is an appealing alternative to in vivo studies on fetal reproductive organ development. There is extensive literature on ex vivo methods of growing the fetal gonad. However, a method for culturing the whole fetal reproductive tract that has a different shape and size has not been documented. Here, with careful dissection and proper tissue orientation, we successfully cultured the entire bicornuate reproductive tracts from mouse embryos of both sexes on the Transwell insert membrane. The cultured reproductive tract system undergoes sexually dimorphic establishment and region-specific morphogenesis comparable to in vivo development of their counterparts. To test this culture method's applications, we used chemical treatment (dihydrotestosterone and BMS 564929) and genetic cellular ablation mouse model (Gli1-CreER; Rosa-DTA) to investigate the roles of androgen signaling and Gli1+ mesenchyme in Wolffian duct development. Dihydrotestosterone and BMS 564929 promoted the ectopic maintenance of Wolffian ducts in cultured XX tissues. The efficient and specific elimination of Gli1+ mesenchyme was successfully achieved in the cultured tissues, resulting in defective coiling of Wolffian ducts. These results demonstrate the amenability of this organ culture method for chemical and genetic manipulations that are otherwise difficult to study in vivo. Taken together, the establishment of this organ culture method provides a valuable tool complementary to in vivo studies for understanding fetal reproductive tract development in mice.

Asymmetric Phenotypes of Sterile Hybrid Males From Reciprocal Crosses Between Species of the Anopheles gambiae Complex

Haldane’s rule of speciation states that sterility or inviability affects the heterogametic sex of inter-species hybrids. Darwin’s corollary to Haldane’s rule implies that there are asymmetric phenotypes in inter-species hybrids from reciprocal crosses. Studying the phenotypes of F1 hybrids among closely related species of malaria mosquitoes can assist researchers in identifying the genetic factors and molecular mechanisms of speciation. To characterize phenotypes of sterile hybrid males in the Anopheles gambiae complex, we performed crosses between laboratory strains of An. merus and either An. gambiae or An. coluzzii. The reproductive tracts had normal external morphology in hybrid males from crosses between female An. merus and male An. gambiae or An. coluzzii. Despite being sterile, these males could copulate with females for a normal period of time and could transfer a mating plug to induce female oviposition and monogamy. In contrast, the entire reproductive tracts in hybrid males from crosses between female An. gambiae or An. coluzzii and male An. merus were severely underdeveloped. These males had atrophic testes and reduced somatic organs of the reproductive system including male accessary glands and ejaculatory duct. In addition, hybrid males with underdeveloped reproductive tracts displayed a shorter copulation time with females and failed to induce female oviposition and monogamy due to their inability to form and transfer a plug to females during mating. The asymmetry of the phenotypes associated with hybrid male sterility suggests that different genetic factors and molecular mechanisms are responsible for reproductive isolation in reciprocal crosses among species of the An. gambiae complex.

Investigation of Local White Matter Properties in Professional Chess Player: A Diffusion Magnetic Resonance Imaging Study Based on Automatic Annotation Fiber Clustering

This article investigates whether the white matter (WM) anatomical changes exist in the brain of professional chess players. Diffusion magnetic resonance imaging (dMRI) and fiber tracking provide a unique, noninvasive technique to study brain WM microstructures in vivo. However, existing methods focused on the entire tracts without detailed anatomical annotation, which depended on expert neuroanatomical knowledge to subdivide and annotate fiber tracts. This article used an automatically annotated fiber clustering method to identify anatomically meaningful WM structures from the whole brain's tractography. Each fiber was resampled to 200 equally spaced nodes along the whole tract to detect local differences. We calculated diffusion characteristics for 4 regions and 64 fiber clusters of professional chess players ( n = 28) and matched controls ( n = 29). The experimental results showed that there were significant differences in the diffusion characteristics of continuous locations in the thalamofrontal tracts and left superior longitudinal fasciculus. Pearson correlation analysis was also performed to prove our results. Professional chess players are significantly correlated with training duration and training frequency. Their brain structures have changed due to cognitive aspects, such as learning and memory. It is very meaningful to study the cognitive mechanism of change, which can improve high-level cognitive ability.

Exclusive predation of sea turtle hatchlings by juvenile blacktip reef sharks Carcharhinus melanopterus at a turtle nesting site in Malaysia

This study reports the discovery of the exclusive predation of sea turtle hatchlings by several juvenile blacktip reef sharks (Carcharhinus melanopterus) in Chagar Hutang bay on Redang Island, Malaysia, in the South China Sea. Three dead specimens of C. melanopterus were retrieved from ghost nets, and the entire digestive tracts of these sharks solely contained the partially digested bodies of sea turtle hatchlings, with no evidence of the remains of any other prey. Thus, juvenile C. melanopterus may opportunistically feed primarily on turtle hatchlings during times when hatchling abundance is high.

Gastro-intestinal helminths in the red-bellied squirrel introduced in Argentina: accidental acquisitions and lack of specific parasites

Introduced species may lose their natural parasites when invading a new habitat, may acquire new, local parasites or may introduce parasites from their native range. We studied the gastro-intestinal helminth fauna associated with the red-bellied squirrel Callosciurus erythraeus (Pallas, 1778) introduced in Argentina to evaluate its role as a host of either specific or acquired parasites in two invasion foci. We analyzed entire digestive tracts of 72 red-bellied squirrels captured in the main invasionfocus(Lujan, provinceofBuenosAires)betweenFebruaryandMay2011, andinasecondary focus (Canada de Gomez, province of Santa Fe) in December 2008. We only found two nematode specimens: an adult male belonging to the genus Pterygodermatites (Paucipectines) Quentin, 1969 and another adult male belonging to the genus Stilestrongylus (Freitas, Lent and Almeida, 1973). None of these genera were previously listed for the red-bellied squirrel in introduced areas, but a species of the genus Pterygodermatites was previously reported for this squirrel in its native habitat. These results indicate that, to date, the red-bellied squirrel in Argentina is accidentally parasitised by nematodes acquired in its new environment and has no specific gastro-intestinal helminths. This could be related with a “founder eect” and/or the lack of sciurid rodents that prevent the red-bellied squirrel to be colonized by pre-adapted helminth taxa. Other factors that may play a role are the small number of mammals with arboreal habits and some “encounter barriers” in the new environment that prevent the acquisition of helminths with a wide host spectrum.

Remarkable complexity and variability of corticospinal tract defects in adult Semaphorin 6A knockout mice

The corticospinal tract (CST) has a complex and long trajectory that originates in the cerebral cortex and ends in the spinal cord. Semaphorin 6A (Sema6A), a member of the semaphorin family, is an important regulator of CST axon guidance. Previous studies have shown that postnatal Sema6A mutant mice have CST defects at the midbrain–hindbrain boundary and medulla. However, the routes the aberrant fibers take throughout the Sema6A mutant brain remain unknown. In this study, we performed 3D reconstruction of immunostained CST fibers to reevaluate the details of the abnormal CST trajectories in the brains of adult Sema6A mutant mice. Our results showed that the axon guidance defects reported in early postnatal mutants were consistently observed in adulthood. Those abnormal trajectories revealed by 3D analysis of brain sections were, however, more complex and variable than previously thought. In addition, 3D analysis allowed us to identify a few new patterns of aberrant projections. First, a subset of fibers that separated from and descended in parallel to the main bundle projected laterally at the caudal pons, subsequently changed direction by turning caudally, and extended to the medulla. Second, some abnormal fibers returned to the correct trajectory after deviating substantially from the original tract. Third, some fibers reached the pyramidal decussation normally but did not enter the dorsal funiculus. Section immunostaining combined with 3D reconstruction is a powerful method to track long projection fibers and to examine the entire nerve tracts of both normal and abnormal animals.

Description of epithelial granular cell in catshark spiral intestine: Immunohistochemistry and ultrastructure.

We evaluated the histology of the spiral intestine of the blackmouth catshark (Galeus melastomus), a small shark distributed in the eastern Atlantic and Mediterranean Sea basin. Entire digestive tracts of 10 G. melastomus were studied using histochemical, immunohistochemical, and ultrastructural methods. Our studies identified a unique, large granular cell type in the intestinal epithelium. Transmission electron microscopy showed that the epithelial granular cell type made intimate contact, by means of junctional complexes, with adjacent epithelial and mucous cells. Several histochemical staining methods showed that the cytoplasmic granules were strongly eosinophilic. Immunostaining of intestinal sections revealed immunoreactivity of the granular cell to tumor necrosis factor-α (TNF-α) antibody. However, no reactivity to inducible-nitric oxide synthase (i-NOS), interleukin-6 (IL-6), interleukin IL-1β, lysozyme, serotonin 5-HT antibodies was detected.

Histomorphometrics and quantitative unbiased stereology in canine uteri treated with medroxyprogesterone acetate

This article describes the effects of MPA use on the canine uterus using stereological methods. Entire reproductive tracts were removed from normal healthy canine bitches (Canis lupus familiaris) and grouped as: nulliparous (n = 11), multiparous (n = 11) and MPA-treated (n = 11; nulliparous; two treatments; 5 mg/kg). 1 cm samples were cut from the corpus, horn and uterine tube and fixed in 10% formaldehyde. Sections of each were mounted on slides and stained with hematoxylin-eosin. We assessed the fraction area for components of endometrium and myometrium and VV (volume density) and SV (surface density) of the gland and stroma using the M36 test system provided by the STEPanizer Stereological Tool. No gross histological differences were observed between study groups in the uterine tube, uterine corpus and horn. The wall of the uterine corpus and horn in MPA-treated bitches was characterized as being thicker than in the other groups. A cross-section of the uterine corpus revealed no differences between components of uterine wall in the corpus and horn; however, differences were observed in the volume density [VV; %] in variables such as: VV[str.vasc/uterus] (nulliparous vs. multiparous; p = 0.0019) and VV[str.supravasc/uterus] (multiparous vs. nulliparous and MPA; p = 0.0035). In the endometrial gland, differences were detected in SV[gland/endom] (multiparous vs. MPA, p = 0.0442). In the uterine horn, differences were only observed in the variable VV[lumen.gland/endom] (multiparous vs. MPA; p = 0.0019). This study shows quantitative changes in the architecture of the endometrium and myometrium in all the uterine segments, mainly morphological endometrial gland changes of the uterine corpus, increasing the surface area per unit of volume; however, these changes usually do not differ quantitatively from those observed in the uterus of multiparous bitches.

White Matter Correlates of Auditory Comprehension Outcomes in Chronic Post-Stroke Aphasia

Neuroimaging studies have shown that speech comprehension involves a number of widely distributed regions within the frontal and temporal lobes. We aimed to examine the differential contributions of white matter connectivity to auditory word and sentence comprehension in chronic post-stroke aphasia. Structural and diffusion MRI data were acquired on 40 patients with chronic post-stroke aphasia. A battery of auditory word and sentence comprehension tests were administered to all the patients. Tract-based spatial statistics were used to identify areas in which white matter integrity related to specific comprehension deficits. Relevant tracts were reconstructed using probabilistic tractography in healthy older participants, and the mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of the entire tracts were examined in relation to comprehension scores. Anterior temporal white matter integrity loss and involvement of the uncinate fasciculus related to word-level comprehension deficits (RFA = 0.408, P = 0.012; RMD = −0.429, P = 0.008; RAD = −0.424, P = 0.009; RRD = −0.439, P = 0.007). Posterior temporal white matter integrity loss and involvement of the inferior longitudinal fasciculus related to sentence-level comprehension deficits (RFA = 0.382, P = 0.02; RMD = −0.461, P = 0.004; RAD = −0.457, P = 0.004; RRD = −0.453, P = 0.005). Loss of white matter integrity in the inferior fronto-occipital fasciculus related to both word- and sentence-level comprehension (word-level scores: RFA = 0.41, P = 0.012; RMD = −0.447, P = 0.006; RAD = −0.489, P = 0.002; RRD = −0.432, P = 0.008; sentence-level scores: RFA = 0.409, P = 0.012; RMD = −0.413, P = 0.011; RAD = −0.408, P = 0.012; RRD = −0.413, P = 0.011). Lesion overlap, but not white matter integrity, in the arcuate fasciculus related to sentence-level comprehension deficits. These findings suggest that word-level comprehension outcomes in chronic post-stroke aphasia rely primarily on anterior temporal lobe pathways, whereas sentence-level comprehension relies on more widespread pathways including the posterior temporal lobe.

Single-molecule, antibody-free fluorescent visualisation of replication tracts along barcoded DNA molecules.

DNA combing is a standard technique to map DNA replication at the single molecule level. Typically, replicating DNA is metabolically labelled with nucleoside or nucleotide analogs, purified, stretched on coverslips and treated with fluorescent antibodies to reveal tracts of newly synthesized DNA. Fibres containing a locus of interest can then be identified by fluorescent in situ hybridization (FISH) with DNA probes. These steps are complex and the throughput is low. Here, we describe a simpler, antibody-free method to reveal replication tracts and identify the locus of origin of combed DNA replication intermediates. DNA was replicated in Xenopus egg extracts in the presence of a fluorescent dUTP. Purified DNA was barcoded by nicking with Nt.BspQI, a site-specific nicking endonuclease (NE), followed by limited nick-translation in the presence of another fluorescent dUTP. DNA was then stained with YOYO-1, a fluorescent DNA intercalator, and combed. Direct epifluorescence revealed the DNA molecules, their replication tracts and their Nt.BspQI sites in three distinct colours. Replication intermediates could thus be aligned to a reference genome map. In addition, replicated DNA segments showed a stronger YOYO-1 fluorescence than unreplicated segments. The entire length, replication tracts, and NE sites of combed DNA molecules can be simultaneously visualized in three distinct colours by standard epifluorescence microscopy, with no need for antibody staining and/or FISH detection. Furthermore, replication bubbles can be detected by quantitative YOYO-1 staining, eliminating the need for metabolic labelling. These results provide a starting point for genome-wide, single-molecule mapping of DNA replication in any organism.

Investigating the descending motor tracts in patients with chronic ischemic stroke with diffusion tensor imaging

To evaluate the relationship between structural integrity of descending motor tracts and motor status in patients with chronic ischemic stroke using diffusion tensor imaging (DTI). From April 2012 to December 2013, 47 patients with chronic ischemic strok were recruited along with 20 matched normal controls. The DTI data was acquired and preprocessed. Bilateral descending motor tracts includingcorticospinal tract (CST) and alternate motor fibers (aMF) were constructed. The descending motor tracts numberswere acquired and the relationships between laterality indices(LI) of descending motor tracts numbers and FMA were assessed. The patients were grouped into (CST + aMF) group (group1), no (CST + aMF) group (group2), CST group (group3) and aMF group (group4) according to the damage morphology of descending motor tracts. Observing the changes of each group. Ipsilesional CST and theentiredescending motor tracts numbers (aMF + CST) were lower in the patient group as compared to the control group (P < 0.01, CST: 26 ± 30, CST + aMF: 37 ± 37). The FMA were statistically different between group 1, 2, 3 (55 ± 12, 16 ± 10, 34 ± 15, F = 24.2, P < 0.01). The LI of CST and (CST + aMF) significantly diagnosed motor impairment (P < 0.01, r = -0.653; r = -0.692). Meanwhile, it is a stronger parameter when entire descending motor tracts were combined comparing to using the CST only. The integrity of entire descending motor tracts, not merely the CST, appears to account for stroke recovery. Our results highlight the role of aMFin compensatory function, which may be used as a target in future rehabilitative treatmentsto promoting motor function recovery at the most extent.

Abstract T MP118: Microinfarct Disruption of Cerebral White Matter: A Longitudinal Diffusion Tractography Analysis

Introduction: Cerebral microinfarcts (CMI) are associated with cognitive decline in clinico-pathological studies. Acute CMI can be detected by diffusion-weighted imaging (DWI). We prospectively evaluated the effect of incidental CMI on white matter (WM) ultrastructure using longitudinal diffusion tensor imaging (DTI)-based tractography. Methods: Nine incidental DWI lesions were identified in six subjects (all males, age 67±9 years, mean pre-to-post lesional scan interval 19±4 months). All patients were diagnosed with probable cerebral amyloid angiopathy and underwent at least three MRIs as part of a prospective study. Silent DWI lesions were observed on the middle scan, enabling longitudinal analysis. Control regions-of-interest (ROIs) were generated in the contralateral hemisphere using semi-automated coregistration, and the lesion/control ROIs were coregistered to the pre- and post-lesional scans. DTI parameters [fractional anisotropy (FA); mean diffusivity (MD)] were measured within each ROI, along a short-segment of WM fiber tracts (within 6mm of the ROI), and along the entire tract. For the lesional scan, we compared DTI parameters between lesion and control ROIs. For the longitudinal analysis, we compared the ratio of lesion-to-control FA and MD at the pre-lesional and post-lesional scans. Results: On the lesional scan, FA within the lesion ROI was significantly lower than in the control ROI (0.28±0.13 vs. 0.40±0.20, p=0.04) and MD was non-significantly reduced in the lesion ROI versus the control ROI (p=0.09). A significant decline within lesion ROI in FA ratio (1.22±0.45 vs. 0.91±0.439, p=0.04) and an increase in MD ratio (0.96±0.14 vs. 1.25±0.37, p=0.02) were observed between the pre-lesional and post-lesional scans. There was no difference in FA ratio or MD ratio for the short segment or entire tracts at the time of the lesion and in the longitudinal analysis. Conclusion: We demonstrate persistent microstructural alterations of WM caused by incidental DWI lesions. Although these alterations do not extend outside the lesional ROI to associated fiber tracts, their accumulation over time may explain their association with cognitive decline.

A patient with Cronkhite-Canada syndrome whose entire digestive tracts was examined endoscopically

A 60-year-old woman was referred to our hospital with nausea, vomiting, taste disorder, alopecia, onichodystrophy and epigastric pain. Laboratory examination showed under-nutritionand abdominal computed tomography showed a thickened stomach wall. Endoscopic examination of the entire digestive tract showed multiple salmon roe-like polyp in the stomach, duodenum, ileum, and colon. Pathologically, biopsy specimens from the polyp-like lesions and mucosa revealed edematous change of the intestitium and cystic dilatation of the glands. We diagnosed the patient as having Cronkhite-Canada syndrome because of the polyposis associated with abnormalities of the ectoderm. Prednisolone therapy was initiated at 40 mg per day, with tapering of the dose subsequently. The clinical symptoms, laboratory data and polyposis improved with the prednisolone therapy. The prognosis of patients with Cronkhite-Canada syndrome treated with prednisolone is favorable, however, it has been reported recently that Cronkhite-Canada syndrome is associated with a risk of carcinogenesis. Therefore, it is necessary to conduct periodic screening of the entire digestive tract even after mucosal improvement.

Church Immunities in Practice during the Reign of Ivan IV

This article examines the dynamic and interactive relationship between the central governmental authorities in Moscow and regional church institutions, especially monasteries, during Ivan IV’s reign (1533-1584). This relationship is plainly visible in the texts of immunity charters—official exemptions from taxes or other fees exacted on churches, monasteries, and entire tracts of land. Based on the complete corpus of surviving immunity charters, this article demonstrate that regional officials sometimes violated these charters by collecting taxes and fees from persons or institutions that were supposed to be exempt from them, but that these abuses prompted immediate and stern responses from the tsar’s officials and clerics affected by these infractions, and by central authorities in (sometimes) distant Moscow. The disputes over these immunities generated a lively crisscrossing dialogue between church and state officials in the provinces and in the capital, showing the links between the Muscovite center and periphery.

Are Big Cities More Segregated? Neighbourhood Scale and the Measurement of Segregation

Many studies show that larger metropolitan areas are more segregated than smaller ones. To some extent, this tendency is part of the conventional wisdom. However, the reason for this tendency is not apparent. This paper suggests that the correlation between segregation and metropolitan scale is spurious. Segregation measures based on census data will tend to rank larger cities higher because larger cities have more neighbourhoods that are big enough to 'fill up' entire census tracts, while smaller cities with equally homogeneous, but smaller, neighbourhoods have to pair neighbourhoods to fill up a census tract. This bias will be reduced at smaller levels of spatial aggregation. This prediction is tested by comparing segregation measures computed at several levels of spatial aggregation and with American Housing Survey data. The results suggest that spatial aggregation effects are important: the correlation between city size and measured segregation appears to be at least partly spurious.

Quantitative unbiased estimates of endometrial gland surface area and volume in cycling cows and heifers

Entire reproductive tracts were removed from seven normal healthy heifers and qualitative unbiased estimates made of endometrial gland volume density and glandular surface density. After examining approximately 55 microscopic fields of endometrium from each tract, a mean glandular surface density value of 10.2 mm 2/ mm 3 (CE 3.1%) was obtained. The stereological method was then employed in optimising the design of the main study. The endometrial height was measured for 17 healthy cycling heifers and 19 similar cows. Subsequently, unbiased estimates were made of intercaruncular endometrial gland volume per unit surface for all cattle were investigated; differences between heifers and cows generally, and the possible effect of the follicular and luteal phases of the oestrous cycle were compared. The mean surface area of glands per unit area of endometrium at the intercaruncular site in heifers and cows was approximately 18 mm 2/ mm 2 in the follicular phase and 26 mm 2/ mm 2 in the luteal phase, figures similar to the gland area found in women. The intercaruncular gland volume increased significantly, by about 30% during the luteal phase of the bovine oestrous cycle in heifers, from 0.01 to 0.13 per mm 3. The differences in endometrial anatomy between site of sampling and either follicular or luteal phases of the oestrous cycle were always more significant in heifers than cows. The endometrial thickness in cows was always greater than for heifers, irrespective of the site of sampling. It was concluded that the intercaruncular endometrium of cattle was far more active physiologically than recognised previously.

Divergence of noncoding sequences and of insertions encoding nonglobular domains at a genomic region well conserved in plasmodia.

To identify conserved features in the rapidly diverging portions of a well-conserved locus, completely sequenced in Plasmodium falciparum and Plasmodium berghei, a computational method based on recurrence analysis was exploited. At the level of the genomic sequence, in both species, introns and intergenic sequences-though subject to rapid diversification-do not drift without constraints, but rather coevolve, in the sense that they maintain not only an AT-rich base composition, but also a consistent use of recurring (AT)(n) tracts. One of the two genes present in the conserved locus encodes a protein that exhibits blocks of high similarity to the first enzyme in glutathione biosynthesis (gamma-glutamylcysteine synthetase) but bears long low-complexity insertions, absent in other organisms. From an analysis of the aminoacid sequence, different constraints appear to act on the borders and on the central part of the insertions. Albeit maintaining a strong bias toward hydrophilic residues, central portions diverge more rapidly than borders, through point mutation and differential presence of entire tracts.

Expression of myelin proteins in the opossum optic nerve: Late appearance of inhibitors implicates an earlier non‐myelin factor in preventing ganglion cell regeneration

The pattern of appearance of myelin-associated proteins in the visual system of the Brazilian opossum Monodelphis domestica is described. Whole mounts of optic nerve, chiasm, and optic tract were sectioned horizontally and incubated with antibodies to myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein, (MAG), “Rip,” and the neurite inhibitory protein (IN-1), followed by visualization with diaminobenzidine and a peroxidase-conjugated secondary antibody. PLP is first detectable 24 days after birth (P24) at the centre of the optic chiasm. MBP, MAG, Rip, and IN-1 appear first in the same area at P26. By P28 the distribution of all proteins is similar, occupying the entire chiasm, optic tracts, and prechiasmatic portion of the optic nerves. Protein expression progresses along the optic nerve to reach the lamina cribrosa by P34, coincident with the time of eye opening. A critical period in which the retinofugal pathway has a regenerative capacity has recently been observed in Monodelphis. This period ends at P12, 2 weeks before the appearance of the myelin-associated inhibitory proteins MAG and IN-1. These results therefore suggest that regeneration in the developing retinofugal projection of the opossum is restricted by an earlier non-myelin factor, which is in contrast to current literature on the spinal cord. © 1996 Wiley-Liss, Inc.

Expression of myelin proteins in the opossum optic nerve: late appearance of inhibitors implicates an earlier non-myelin factor in preventing ganglion cell regeneration.

The pattern of appearance of myelin-associated proteins in the visual system of the Brazilian opossum Monodelphis domestica is described. Whole mounts of optic nerve, chiasm, and optic tract were sectioned horizontally and incubated with antibodies to myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG), "Rip," and the neurite inhibitory protein (IN-1), followed by visualization with diaminobenzidine and a peroxidase-conjugated secondary antibody. PLP is first detectable 24 days after birth (P24) at the centre of the optic chiasm. MBP, MAG, Rip, and IN-1 appear first in the same area at P26. By P28 the distribution of all proteins is similar, occupying the entire chiasm, optic tracts, and prechiasmatic portion of the optic nerves. Protein expression progresses along the optic nerve to reach the lamina cribrosa by P34, coincident with the time of eye opening. A critical period in which the retinofugal pathway has a regenerative capacity has recently been observed in Monodelphis. This period ends at P12, 2 weeks before the appearance of the myelin-associated inhibitory proteins MAG and IN-1. These results therefore suggest that regeneration in the developing retinofugal projection of the opossum is restricted by an earlier non-myelin factor, which is in contrast to current literature on the spinal cord.