Identification and immunohistochemical localization of annexin II in rat cornea

PURPOSE

We have identified annexin II mRNA expression in the rat cornea and demonstrated immunolocalization of annexin II in normal and injured corneas. Furthermore, to investigate possible interaction between annexin II and its extracellular ligand tenascin during corneal wound healing, we also examined tenascin expression simultaneously.

METHODS

Total RNA was extracted from the corneal tissue of male Wistar rats as well as from the cell cultures of corneal epithelial cells and keratocytes. cDNA was obtained by reverse transcription (RT). Annexin II mRNA expression was examined by polymerase chain reaction (PCR). Western blot analysis of annexin II protein was performed with protein samples that were obtained from the corneal tissue and cell cultures. In addition, the localization of annexin II and that of tenascin were clarified by immunohistochemical analysis, using both uninjured and epithelial scraped corneas.

RESULTS

RT-PCR analysis revealed that annexin II mRNA was expressed in corneal tissues, epithelial cells and keratocytes. Western blot analysis of corneal epithelium and keratocytes showed a 38kDa band that corresponded to the molecular weight of annexin II. Immunohistochemical study showed that annexin II was present in keratocytes as well as the basal cells of corneal epithelium in the central cornea, and basal/suprabasal cells of the limbal epithelium. Positive annexin II immunoreactivity is translocated from cytoplasm to the cell periphery/extracellular position during the epithelial wound healing process. Annexin II and tenascin are coexpressed on the basal surface of limbal epithelium and the leading edge of the healing epithelium. The reappearance of cytoplasmic annexin II staining at the periphery of the cornea correlated with the epithelial cell proliferation.

CONCLUSIONS

Annexin II is abundantly expressed in corneal tissue. The translocalization of annexin II protein suggests its role in the corneal epithelial migration during wound healing. The colocalization of annexin II and tenascin in migrating and proliferating corneal epithelial cells suggests that annexin II-tenascin interaction may play a role in epithelial wound healing.

Cone-beam CT angiography of the thorax: an experimental study

The authors recently developed a cone-beam computed tomography (CT) scanner and this report presents their evaluation of its potential for thoracic vascular imaging. An X-ray tube and a video-fluoroscopic system were rotated around the objects and 360 projected images were collected in a 12-s scan. Each image was digitized and a 3 dimensional (D) image (256x256x256 voxel volume with a voxel dimension of 0.9x0.9x0.9 mm) was reconstructed. Two different 3D-CT angiographies were investigated in 2 pigs: right atriography and thoracic aortography. Each pig was anesthetized, mechanically ventilated and positioned within the scanner. Contrast agent was infused through the right atrium or the aortic root at a rate of 3 ml/s during the scan. The right atriography scan clearly delineated the anatomy of the pulmonary artery, heart chambers and thoracic aorta. The thoracic aortography scan also clearly delineated the aortic anatomy including the internal thoracic and intercostal arteries. In conclusion, cone-beam CT angiography is potentially useful for thoracic vascular imaging.

Development of vascular networks during the morphogenesis of intestinal villi in the fetal mouse

The formation of villi was investigated in the proximal small intestine of fetal mice between 12 and 19 days of gestation in association with the development of vascular networks. Three-dimensional vascular networks were observed with confocal laser scanning microscopy after perfusing the fetuses with RITC-labelled gelatin. Some specimens were simultaneously stained for laminin by immunofluorescence to examine the epithelio-mesenchymal boundary. At 12 and 13 days of gestation, the epithelium of small intestine formed cylindrical tubes, and a loose plexus of large vessels formed in the mesenchyme. At 14 days of gestation, a dense plexus of smaller vessels was formed inside of the loose plexus and some capillary branches from this dense plexus developed beneath the epithelium. The epithelium began to make ingrowths in places where no capillaries were situated beneath the epithelium. The capillaries formed a loop in a concavity made between the ingrowths. As development proceeded, this concavity deepened and formed a villus. The top of the capillary loop always places at the top of the mesenchyme in the villus and the capillary loop then developed into a capillary network within the villus. These results suggest that the initial formation of intestinal villi in the fetal mouse occurs by an ingrowth of the epithelium and the developing vascular nets appear to play some role in villi formation. Throughout the villus formation, the top of the capillary loop in a villus would be anchored to the epithelial basement membrane or to the adjoining matrixes.

Chromosomal localization of a gene responsible for vestibulocochlear defects of BUS/Idr mice: identification as an allele of waltzer

Mice of the bustling mutant strain BUS/Idr have vestibulocochlear defects. bus/bus homozygotes, but not heterozygotes, are hyperactive and display an abnormal behavior such as circling, head bobbing and head tilting. To characterize BUS mice further, the auditory brain-stem response of the mutant was examined. In +/bus heterozygotes as well as control animals, the auditory brain-stem response was developmentally first recorded as early as 11 days of age and heterozygous and normal adults showed typical auditory brain-stem responses with five peaks in a threshold of 40-45 dB SPL. In contrast, bus/bus homozygotes showed no auditory brain-stem response at any age in response to stimuli up to 130 dB SPL, indicating that they are deaf throughout life. Linkage analysis revealed that the responsible gene, originally designated as bus, maps on chromosome 10, 1.09+/-0.9 cM distal to D10Mit127 and D10Mit59, and 0.72+/-0.51 cM proximal to three markers, D10Mit48, D10Mit112 and D10Mit258, at a site indistinguishable from that of the Albany waltzer, v(A/b). The results of allelism tests between BUS and Albany waltzer indicated that bus is allelic with v(Alb). From these data, we propose here that the bus mutation could represent another allele of waltzer, now designated v(bus).

Corneal wound healing in tenascin knockout mouse

PURPOSE

Tenascin (TN) is a large hexameric extracellular matrix glycoprotein that is expressed in developing organs and tumors. It has also been reported that TN is expressed in the embryonic cornea and during corneal wound healing. However, the role of TN in the cornea is not fully known. In this study, the role of TN in corneal wound healing was examined using the TN knockout (KO) mouse.

METHODS

Two different injuries (a linear perforation wound and two 10-0 nylon suture wounds) were made separately on the corneas of both TNKO and congenic wild-type mice. The corneal wound healing was compared histologically, and the expression of TN and fibronectin (FN) on the injured cornea was examined immunohistochemically and by immunoblot analysis.

RESULTS

Based on histologic analysis, there was no significant difference in the wound healing process between wild-type and TNKO mice in the linear incision experiment. However, the corneal stromata of TNKO mice were compressed prominently and devoid of migrating keratocytes in suture injury, which induced a more significant amount of TN than perforation wounds. Although FN expression on the sutured corneas of TNKO mice was upregulated during suture injury, the amount of FN protein was smaller than that of wild-type mice at the same time points after injury.

CONCLUSIONS

In suture wounds, TN appears to enhance the amount of FN expression, and a lack of TN may impair stromal cell migration. TN plays a significant role in corneal wound healing, especially for wounds with mechanical stress.

Identification of two Smad4 proteins in Xenopus. Their common and distinct properties

Smad family proteins have been identified as mediators of intracellular signal transduction by the transforming growth factor-beta (TGF-beta) superfamily. Each member of the pathway-restricted, receptor-activated Smad family cooperates and synergizes with Smad4, called co-Smad, to transduce the signals. Only Smad4 has been shown able to function as a common partner of the various pathway-restricted Smads in mammals. Here we have identified a novel Smad4-like molecule in Xenopus (XSmad4beta) as well as a Xenopus homolog of a well established Smad4 (XSmad4alpha). XSmad4beta is 70% identical to XSmad4alpha in amino acid sequence. Both of the Xenopus Smad4s can cooperate with Smad1 and Smad2, the pathway-restricted Smads specific for bone morphogenetic protein and TGF-beta, respectively. However, they show distinct properties in terms of their developmental expression patterns, subcellular localizations, and phosphorylation states. Moreover, XSmad4beta, but not XSmad4alpha, has the potent ability to induce ventralization when microinjected into the dorsal marginal region of the 4-cell stage of the embryos. These results suggest that the two Xenopus Smad4s have overlapping but distinct functions.

Tenascin-C in the cochlea of the developing mouse

Tenascin-C is a glycoprotein of the extracellular matrix that acts in vitro as both a permissive and a nonpermissive substrate for neurite growth. We analyzed, by immunocytochemistry, the distribution of tenascin-C along neural growth pathways in the developing mouse cochlea. In the spiral lamina, tenascin-C coexists in a region where nerve bundles arborize. In the organ of Corti, tenascin-C lines the neural pathways along pillar and Deiters' cells before and during the time of nerve fiber ingrowth. By embryonic day 16, tenascin-C is abundant on the pillar side of the inner hair cell but does not accumulate on the modiolar side until about birth, a time after the arrival of afferent fibers. The synaptic zones beneath outer hair cells are strongly labeled during the time when early events in afferent synaptogenesis are progressing but not during the time of efferent synaptogenesis. At the age when most neural growth ceases, tenascin-C immunoreactivity disappears. Faint tenascin-C immunolabeling of normal hair cells, strong tenascin immunolabeling in pathological hair cells of Bronx waltzer (bv/bv) mice, and staining for beta-galactosidase, whose gene replaces tenascin in a "knockout" mouse, indicate that hair cells supply at least part of the tenascin-C. The changing composition of the extracellular matrix in the synaptic region during afferent and efferent synaptogenesis is consistent with a role for tenascin in synaptogenesis. The presence of tenascin-C along the growth routes of nerve fibers, particularly toward the outer hair cells, raises the possibility that growth cone interactions with tenascin-C helps to guide nerve fibers in the cochlea.

Multipotent stem/progenitor cells with similar properties arise from two neurogenic regions of adult human brain

Recent in vitro studies have shown that the periventricular subependymal zone (SEZ) of the rodent brain is capable of de novo generation of neurons and glia. There is less information available on neurogenesis in the adult human brain, and no study has shown the clonal generation of neurons and glia from in vitro-generated "neurospheres." Here we describe the isolation of proliferative stem/progenitor cells within neurospheres from two different regions, the SEZ and the hippocampus, from surgical biopsy specimens of adult (24-57 years) human brain. Using light and electron microscopy; immunocytochemistry for a variety of neuronal, glial, and developmental (including extracellular matrix; ECM) markers; and the reverse transcriptase polymerase chain reaction to demonstrate different gene transcripts found in neurospheres, it is shown that the adult human brain harbors a complex population of stem/progenitor cells that can generate neuronal and glial progeny under particular in vitro growth conditions. These methods also show that these neurospheres contain both neurons and glia and demonstrate regional similarities at the mRNA level, indicating common stem/progenitor cell types within two different neurogenic regions of the adult human brain. In addition to the synthesis of developmentally regulated molecules such as the ECM protein tenascin-C, a variety of other genes (e.g., Pax 6) and proteins (e.g. , Bcl-2) involved in cell survival and differentiation are expressed by adult human brain neurospheres.

Spatial and temporal changes in chondroitin sulfate distribution in the sclerotome play an essential role in the formation of migration patterns of mouse neural crest cells

We have examined the roles of pertinent extracellular matrix molecules in the formation of the neural crest cell migration patterns in the sclerotome of the mouse embryo. The present data indicate that permissiveness for migration is inversely correlated with chondroitin sulfate content. Experimental removal of chondroitin sulfate proteoglycans in the embryo causes neural crest cells to migrate even within the posterior half of the somite, which they do not invade ordinarily. Moreover, three different sclerotomal regions defined by the presence or absence of the ventromedial and/or ventrolateral pathways are present along the anteroposterior axis and undergo systematic temporal changes that affect migration patterns. The most anterior portion of the sclerotome is conducive to both ventromedial and ventrolateral migration (Anterior Region). The intermediate portion is conducive to ventromedial migration only (Intermediate Region). No neural crest cells are seen within the posterior portion of the sclerotome (Posterior Region). At this level, they are observed exclusively in the dorsolateral space adjacent to the roof of the neural tube. With advancing embryonic development, the rostrocaudal length of the Anterior Region decreases and is accompanied by a corresponding enlargement of the Intermediate Region. These results suggest that temporal and regional differences in the sclerotome contribute to the neural crest cell migration patterns in the mouse. To refine our understanding of the underlying mechanisms, regional differences and temporal changes in the distribution of extracellular matrix molecules have been examined during migration. In the sclerotome, chondroitin sulfate displays distinct distribution patterns that are closely correlated with the migration patterns of mouse neural crest cells. Furthermore, their migration patterns are altered in embryos treated with the inhibitors of chondroitin sulfate proteoglycan biosynthesis, sodium chlorate, and beta-D-xyloside. In inhibitor-treated embryos, neural crest cell migration occurs even in the posterior portion of the sclerotome. The metameric organization of dorsal root ganglia is disturbed in these embryos. Our observations provide novel evidence for the importance of sclerotomal chondroitin sulfate distribution patterns in mouse crest cell migration patterns. We conclude that systematic spatiotemporal changes in the distribution of chondroitin sulfate proteoglycans are a key requisite for the formation of migration patterns of mouse neural crest cells in the sclerotome.

Effect of tenascin-C deficiency on chemically induced dermatitis in the mouse

Tenascin-C is a large extracellular matrix glycoprotein characterized by its spatiotemporal expression during embryogenesis, carcinogenesis, and wound healing. Many in vitro studies on tenascin-C have revealed its multifunctional properties; however, disruption of the tenascin-C gene did not reveal any obvious abnormalities during development, and its function in vivo remains unclear. Here, we investigated whether tenascin-C is involved in inflammatory dermatitis in adults by studying chemically induced dermatitis in tenascin-C knockout mice. An epicutaneous application of a hapten, 2,4-dinitrofluorobenzene, to the ear skin of BALB/CA mice resulted in inflammation and induced the expression of tenascin-C. In congenic tenascin-C knockout mice, the dermatitis occurred more severely than in wild-type mice; infiltration of polymorphonuclear cells in knockout mice persisted longer than in wild-type mice, and the elastosis-like disorganized extracellular matrix was also seen in the ear. These results suggest that tenascin-C plays a role in vivo in inflammatory responses in the skin, and that the genetic background has profound effects on the function of tenascin-C in mouse dermatitis.

Tenascin takes part in the progress of pathological severity in cerebral falciparum infection

We examined plasma level of circulating form of tenascin (TC) in falciparum malaria patients, cerebral malaria and non cerebral malaria, and compared them to uninfected healthy persons. Plasma level of TC examined were significantly higher in malaria patients than in control persons (p< 0.01). The results also show that among malaria patients, TC level was higher in the cerebral malaria patients compare to non cerebral malaria patients (p<0.10). Kinetics of TC level in plasma were related to kinetics of TNF-alpha level. Moreover, patients with higher level of TC showed higher level of parasitized erythrocytes binding ratio. Immunohistochemical study showed that TC was found in the cerebral microvessels of postmortem cerebral tissues from nine cerebral malaria cases. These results provide evidence that plasma level of TC correlates with the severity in cerebral malaria patients.

Embryoglycan ectodomains regulate biological activity of FGF-2 to embryonic stem cells

Basic fibroblast growth factor (FGF-2) functions as a natural inducer of mesoderm, regulator of cell differentiation and autocrine modulator of cell growth and transformation. The FGF-2 signals are transduced through receptors with intrinsic protein tyrosine kinase activity. However, receptor binding and activation is governed by extracellular matrix, cell surface or soluble proteoglycans. This paper focuses on the role of proteoglycans synthesized by embryonic cells, embryoglycans, in FGF-2 signaling via FGF receptor-1 (FGFR-1). We found that embryoglycan ectodomain Lewis X, analog of developmentally regulated embryonic cell surface epitope TEC 1, promotes oligomerization of FGF-2 in the cell free chemical crosslinking. In vitro assays show that a large molar excess of extracellular Lewis X does not inhibit binding of FGF-2 to embryonic stem (ES) cells, but prevents the mitogenic effect of FGF-2. Western blot analysis of ES cells revealed the presence of abundant 52 kDa and trace amounts of 67 and 125 kDa isoforms of FGFR-1. However, none of these isoforms undergo any detectable changes in tyrosine phosphorylation under the conditions that modulate the mitogenic effect of FGF-2. Rather, a primary substrate of all receptor tyrosine kinases, phospholipase C gamma (PLC gamma), is activated by both FGF-2 and Lewis X. The combination, FGF-2 plus Lewis X, leads to weak inhibition, when compared with the effects of FGF-2 and Lewis X, respectively. In accordance, the level of phosphorylation of non-receptor tyrosine kinase c-Src is reduced in a reversed pattern to PLC(gamma). Furthermore, in this particular cell type we show the presence of activated forms of extracellular signal-related kinase (ERK) in all nontreated and treated cells. These findings demonstrate that embryoglycan ectodomains may act as negative regulators of FGF-2-induced ES cell proliferation, most likely through the FGFR-1-independent signaling pathway.

The effects of central administration of neuropeptide Y on behavior of tenascin-gene knockout mice

Tenascin-C (TN), an extracellular matrix glycoprotein, plays a pivotal role in the regulation of neuronal pattern formation. TN-gene deficient mice produced by homologous recombination show hyperlocomotive activities. We have recently demonstrated that neuropeptide Y (NPY) mRNA expression is reduced in the limbic area of the TN-gene knockout mouse brain, compared to that in wild-type mice. We now report the effect of NPY on the behavior of TN mutant mice. Intracerebroventricular injection of NPY transiently decreased the hyperlocomotion of TN mutant mice. Concurrently, mice given NPY showed anxiolytic behavioral change as assessed by an exploratory model. The results presented here suggest that the hyperlocomotion of TN mutant mice is partially derived from severe tensity.

Cerebellar histogenesis as seen in identified cells of normal-reeler mouse chimeras

The potential contribution of cell-cell interactions and extracellular factors to cytoarchitectonic abnormalities in the cerebellum of the reeler mutant mouse was investigated by forming chimeras between the reeler and normal animals. The strain origin of Purkinje cells, granule cells and Golgi epithelial cells was immunohistologically identified with a strain-specific antibody. We analyzed 16 overt coat color chimeras, 10 reeler <--> C3H and 6 reeler <--> Balb/c. Abnormal behavioral traits of reeler were rescued in all chimeras. However, cerebellar histology was more affected in reeler <--> C3H chimeras than in reeler <--> Balb/c. Purkinje cells from the normal genotype occupy ectopic positions, and reeler genotype cells are arranged appropriately in the same chimeric cerebellum. We also obtained histologically normal chimeras with a significantly high contribution of the reeler genotype in Purkinje cells, Golgi epithelial cells and granule cells. These results clearly indicate that the abnormal cell positioning and cytoarchitecture of neurons and glia in the reeler is caused by a deficiency of extracellular environments, but is not determined cell-autonomously. The present data on chimeric mice suggest that Reelin is one of the important extracellular environmental factors that affects indirectly radial glial cells during cerebellar histogenesis.

Reduced mRNA expression of neuropeptide Y in the limbic system of tenascin gene disrupted mouse brain

Tenascin-C (TN), an extracellular matrix glycoprotein which reveals both neurite outgrowth-promoting and growth-inhibiting effects, is generated in the central nervous system. A previous study reported that TN-gene null mutant mice display hyperlocomotion and do not easily habituate to unfamiliar environments. Additionally, these mice display poor appetite, abnormal circadian rhythm and low pregnancy rate. The present study demonstrated that neuropeptide Y (NPY) mRNA expression is reduced in the limbic area of the TN gene-deficient mouse brain as compared to wild-type mice. NPY has been shown to affect emotion, circadian rhythm and food intake, and the present results suggest that the some behavioural abnormalities exhibited by TN-mutant mice may be in part due to the low level of expression of NPY mRNA in the limbic system.

Three-dimensional analysis of the developing pituitary gland in the mouse

Prenatal development of the mouse pituitary gland was analyzed in three-dimensions by using confocal laser-scanning microscopy. In any wholemount preparation of the fetal pituitary gland from day 10 to day 18, immunofluorescence of laminin was observed in the deeper regions of the organ and demarcated the boundary of the epithelial tissue from the surrounding mesenchyme. Three-dimensional capillary networks in the fetal pituitary gland at day 13, day 15, and day 18 were visualized clearly by perfusing the blood vessels with an fluorescein isothiocyanate-labelled gelatin solution. During days 12-14, cellular plates protruded from the anterior wall of the pituitary anlage and extended toward the base of the infundibulum. At the same time, the mesenchyme situated among the cellular plates separated from the surrounding mesenchyme except at the anteroventral portion of the anlage. In a posterior wall of the anlage, intercellular depositions of laminin were found among the epithelial cells, some of which reached the laminin sheet in the basement membrane of the anlage. From days 15-18, the pituitary gland enlarged, and the mesenchyme spread radially from the median anteroventral portion to the lateral, posterior, and dorsal regions and finally expanded throughout the entire organ. At the periphery, the mesenchyme in the pituitary gland connected with that surrounding the capsule. Laminin was still found in the intercellular spaces between the epithelial cells, and most of the intercellular depositions of laminin were combined with the laminin sheet in the epithelial basement membrane. An abundance of vessels entered the organ from its anteroventral portion, spread, and connected with one another throughout the gland, similar to the distribution of mesenchyme. Intercellular laminin would induce the polarization of the contacting epithelial cells, resulting in rearrangement of the epithelial cells. The mesenchyme might spread in the pituitary gland, providing the intercellular laminin a foothold, in order to cleave the epithelial cell mass into lobules. The development of capillary nets in the adenohypophysis corresponded well with that of the mesenchyme. Because laminin localizes mainly in the basement membrane in the fetal organs, immunostaining of laminin clearly indicates the boundary between epithelial tissue and the mesenchyme. Three-dimensional observation of laminin in wholemount preparation is very useful for studying morphogenesis.

Tenascin-C promotes healing of Habu-snake venom-induced glomerulonephritis: studies in knockout congenic mice and in culture

Mice without the gene for tenascin-C, a multifunctional extracellular matrix protein expressed in many important biological events, including wound healing, did not show any phenotype. However, it is now obvious that the phenotype of deletion of one gene frequently depends on the genetic background. Therefore, we have newly generated tenascin-C knockout mice (KO) by backcrossing original KO into three congenic lines: C57BL/6N, BALB/cA, and GRS/A (GR). And we investigated the disease course of reversible kidney injury, Habu-snake venom-induced proliferative glomerulonephritis. In all strains, the disease was more severe in KO, but the severity varied with the strain. The KO-GR showed irreversibility; all treated KO-GR died by the 4th month due to renal failure. The diseased KO-GR showed abnormal regenerative reactions, including reduced proliferation of mesangial cells, key players in glomerulonephritis, and reduced production of some kinds of cytokines and matrices, leading to poor formation of granulation tissue. In culture, the mesangial cells from the KO-GR had the same potential for proliferation and response to cytokines as controls, but interestingly, to achieve this potential, they required contact with tenascin-C. These reactions were blocked by an anti-tenascin monoclonal antibody. The results of the present study, the first report showing the most dramatic phenotype so far discovered, have strongly suggested the importance of tenascin-C in the resolution of the renal inflammation and that of the genetic background on which the KO was developed.

Characterization of gene expression in mouse blastocyst using single-pass sequencing of 3995 clones

To study the gene expression profile in the mouse blastocyst and to identify embryonic stage-specific genes, we randomly selected cDNAs derived from mouse blastocysts and sequenced a total of 3995 clones from one or both ends. Excluding the uninformative clones, 3395 clones were grouped as 937 different kinds of genes. Among these, 465 and 406 species showed similarity to known genes and expressed sequence tags (ESTs), respectively, whereas 66 species showed no significant similarity to any genes in known databases. Analysis of these cDNAs revealed that this library contained a variety of functional genes as well as genes that have not been detected in the human EST database; it should provide us with a useful resource for molecular analysis of developmental mechanisms. Although the human EST project is considered to represent roughly half of all genes, our findings indicate that many early stage developmental genes remain to be identified.

Simultaneous observation of capillary nets and tenascin in intestinal villi

BACKGROUND

In order to reveal the biological role of capillaries in a tissue, it is desirable to study the three-dimensional distribution of capillary nets in relation to tissue architecture. However, the simultaneous observation of the three-dimensional distribution of these nets and other substances has been rarely performed to date. In the present study, we have developed a novel method for investigating the three-dimensional distribution of capillary nets simultaneously with that of extracellular matrix components, such as tenascin, using the confocal laser scanning microscope.

METHODS

Adult male mice were perfused with TRITC-labelled gelatin. After perfusion, the intestine was irrigated with chilled fixative containing paraformaldehyde and picric acid, dissected, and returned to the same fixative. The intestine was further sectioned and indirectly immunostained for tenascin using an FITC-labelled antibody.

RESULTS

The three-dimensional distribution of capillary nets and tenascin in villi was simultaneously observed on stereo pairs of pseudo-colored and superimposed images. Tenascin was distributed at the basement membrane zone and in the underlying connective tissue but absent in some regions where capillary nets were running just beneath the epithelium. Substances other than tenascin also can be examined in correlation with capillary nets.

CONCLUSIONS

This method will be useful for investigating the biological role of capillary nets.

A methylation imprint mark in the mouse imprinted gene Grf1/Cdc25Mm locus shares a common feature with the U2afbp-rs gene: an association with a short tandem repeat and a hypermethylated region

We identified a sperm-specific methylation imprint mark (Site II) associated with a short tandem repeat sequence and a site/region methylated in both gametes (Site I) in the Grf1 locus on mouse chromosome 9, which shared a common feature with the U2afbp-rs gene. Sites or regions of gamete-specific methylation in imprinted genes are strong candidates for carrying information regarding the parental origin of alleles. The gamete-specific methylation pattern of Sites I and II was conserved after fertilization, but attained the somatic cell pattern by the blastocyst stage. In primordial germ cells, Site I was methylated, but Site II was unmethylated in both male and female embryos, suggesting that the sperm-specific methylation imprint mark in Site II was established during spermatogenesis. These common features in methylation imprint regions may be a clue to identifying regions carrying primary information for the imprinting regulation.

In vivo electrophysiological distinction of histochemically-identified cholinergic neurons using extracellular recording and labelling in rat laterodorsal tegmental nucleus

From indirect evidence we have proposed that cholinergic versus non-cholinergic neurons in the laterodorsal tegmental nucleus can be distinguished with the duration of their extracellularly recorded action potentials, "broad" spikes for the former, "brief" for the latter. To test this assumption more directly, we labelled single neurons recorded extracellularly in and around the laterodorsal tegmental nucleus with biocytin or neurobiotin, and processed the sections with reduced nicotinamide adenine dinucleotide phosphate-diaphorase, a proven marker for cholinergic neurons in the laterodorsal tegmental nucleus. Biocytin or neurobiotin which was deposited at the site of recording was incorporated into single neurons. Among 171 trials (91 for broad-spike and 80 for brief-spike neurons), marking was successful in 68 cases (29 for broad-spike and 39 for brief-spike neurons). Almost all (21/22) of the broad-spike neurons located within the laterodorsal tegmental nucleus were positive for reduced nicotinamide adenine dinucleotide phosphate-diaphorase staining, i.e. they were cholinergic, while all of the brief-spike neurons in and outside of the laterodorsal tegmental nucleus lacked the diaphorase activity, and were thus non-cholinergic. The present study shows that, after extracellular labelling of single neurons by biocytin or neurobiotin, cholinergic neurons in the laterodorsal tegmental nucleus are confidently distinguished from non-cholinergic ones in the corresponding area with their spike shapes. It is also shown that the cholinergic neurons distinguished by this criterion are characterized by their tonic firing at slightly lower rate and larger cell size than the brief-spike non-cholinergic ones.