Characterization of mutations induced by 300 and 320 nm UV radiation in a rat fibroblast cell line

The cytotoxic and mutagenic activities of monochromatic ultraviolet light (UV) at four wavelengths (254, 290, 300 and 320 nm) were determined using a rat fibroblast cell line CREF stably infected with a retroviral vector carrying the neo and HSV-tk markers. In this system, mutations can be positively detected as acyclovir-resistant colonies. Although the action spectra for these activities closely fit some of the previously reported spectra for photochemical DNA modifications, erythema, cell killing and mouse skin carcinogenesis, they diverge at 320 nm from the absorption spectrum for DNA and the action spectrum for bacterial inactivation and mutagenesis. Structural comparison of the HSV-tk mutants detected after irradiation with 300 and 320 nm UV revealed (1) CC dimers and C oligomers as predominant targets at both wavelengths; (2) increased incidence of relatively large deletions at 300 nm; and (3) greatly increased frequency of tandem double mutations at both wavelengths and of clustered multiple mutations at 320 nm. These results suggest the involvement of distinct mechanisms specifically operating, or becoming evident, in UV-mediated mutagenesis at these different wavelengths in mammalian cells.

Long-term alcohol intake enhances ADP-ribosylation of the multifunctional enzyme, phosphoglucomutase, in rat liver

Adenosine diphosphate (ADP)-ribosylation is a posttranslational protein modification that, in turn, alters several regulatory proteins in mammalian cells. We demonstrated that long-term alcohol intake enhanced the ADP-ribosylation of a 58-kd protein in rat liver plasma membranes. To assess the biological significance of this phenomenon, we partially purified the 58-kd acceptor protein from solubilized rat liver homogenates by two sequential preparative high-pressure liquid chromatographies. Microsequencing revealed that it was phosphoglucomutase (PGM) (EC 5,4,2,2). This enzyme underwent negligible auto ADP-ribosylation, but the ADP-ribosylation was remarkably increased by adding rat liver plasma membranes. The extent of the increase was greater in alcohol-fed rats than in pair-fed controls, suggesting enhanced enzyme activities toward ADP-ribosylation of PGM after chronic alcohol consumption. Several important enzymes are ADP-ribosylated, after which their activities are modified. The results of this study showed that PGM is a novel substrate for ADP-ribosylation in the liver and that the ADP-ribosylation is increased after chronic alcohol consumption. In view of the variety of roles of PGM in the liver (carbohydrate metabolism and Ca2+ homeostasis), specific roles of this modification in terms of the effects of alcohol on hepatocytes may deserve further investigation.

Establishment of a novel chondrocyte-like cell line derived from transgenic mice harboring the temperature-sensitive simian virus 40 large T-antigen gene

We established a clonal chondrocyte-like cell line (TC6, TC stands for large T immortalized chondrocyte-like cell line) derived from articular cartilage of transgenic mice harboring a temperature-sensitive simian virus 40 large T-antigen gene. TC6 cells exhibited spindle-like or polygonal morphology and grew well at 33 degrees C in alpha-minimal essential medium supplemented with 0.5% fetal bovine serum. After confluence, these cells formed nodules that were positive for staining with alcian blue. Northern blot analysis demonstrated that these cells expressed messenger RNAs (mRNA) of the genes encoding cartilage-specific proteins such as type II procollagen, link protein, and aggrecan. Furthermore, the expression of type II procollagen and link protein genes in TC6 cells was regulated by parathyroid hormone and basic fibroblast growth factor, suggesting the presence of the receptors for the hormone and cytokine. The expression of link protein mRNA in TC6 cells was regulated in a time-dependent manner and was enhanced in culture within a week and increased continuously up to 10-fold by the end of 4 weeks. Expression of mRNAs encoding type II procollagen and versican/PG-M also increased moderately during the culture period. TC6 cells expressed type I procollagen mRNA, however, its level declined along with time in culture in contrast to the enhancement of the genes encoding cartilage-specific molecules in these cells. Interestingly, alkaline phosphatase mRNA expression was barely detectable in the TC6 cells in their growing phase while it was enhanced dramatically more than 7-fold by day 14 in culture. These results indicate that the TC6 cells could serve as an excellent model for the studies on chondrocyte physiology.

[Role of Na(+)-glucose cotransport in fluid absorption across alveolar epithelium in isolated rat lungs]

To evaluate the role of Na(+)-glucose cotransport in fluid absorption across alveolar epithelial walls in isolated rat lungs, we measured the inhibitory effects of amiloride (a Na+ channel blocker) and phlorizin (a Na(+)-glucose cotrasport blocker) on the fluid absorption rate in fluid-filled lungs. Amiloride (10(-5)-10(-4) M) reduced alveolar fluid absorption by 30%. This value was similar to that obtained in the presence of 10(-3) M phlorizin. The coefficient of Na(+)-glucose cotransport was estimated to be 2.5. The strong correlation between Na+ escape and fluid absorption (r = 0.907) was not affected by phlorizin. These findings suggest that the impact of Na(+)-glucose cotransport was similar to that of Na+ transport alone, and that glucose molecules transported by Na(+)-glucose cotransport do not play an important role in alveolar fluid absorption across rat alveolar epithelium.

Expression and functional characterization of the P-selectin glycoprotein ligand-1 in various cells

We have examined the expression and function of P-selectin glycoprotein ligand-1 (PSGL-1), which is a high affinity ligand for P-selectin. Northern blot and flow cytometric analysis demonstrated that a variety of hematopoietic cells and cell lines expressed PSGL-1. However, P-selectin binding ability was dependent on the additional expression of a carbohydrate structure, sialyl Lewis x (sLex). All the peripheral lymphocytes expressed PSGL-1 and subpopulation expressed sLex. Two color analysis showed that the majority of the cells that bound P-selectin were sLex-negative I lymphocytes, and most of the sLex-positive cells were B lymphocytes that did not blind P-selectin, indicating that the carbohydrate on T lymphocytes recognized by P-selectin is not sLex, and that the sLex on B lymphocytes is not readily presented for P-selectin recognition. Transfected 293 cells detectably bound P-selectin only when the cells expressed both PSGL-1 and sLex. When cysteine 310 of PSGL-1 was mutated to alanine, P-selectin binding was markedly reduced, suggesting the importance of dimerization of PSGL-1. These findings indicate that a preferable conformation of both carbohydrate and protein structure is necessary for a functional P-selectin ligand.

An adipogenic basic helix-loop-helix-leucine zipper type transcription factor (ADD1) mRNA is expressed and regulated by retinoic acid in osteoblastic cells

ADD1 is a recently identified basic helix-loop-helix leucine zipper-type transcription factor that acts as a positive regulator of adipocyte-specific gene expression. Since adipocytes may share their precursor with osteoblasts, we examined the expression of ADD1 mRNA in osteoblast-like cells. In osteoblastic MC3T3-E1 cells, the level of the ADD1 mRNA expression was low at the early period of cultures while it subsequently increased with time up to more than 10-fold in the later period of cultures along with the expression of alkaline phosphatase, a differentiation marker of these cells. In ROS17/2.8 cells, which represent mature osteoblasts, ADD1 mRNA was expressed constitutively. Treatment with retinoic acid (RA) enhanced the ADD1 mRNA expression several fold in these cells within 4 h in a dose-dependent manner. This RA effect on the ADD1 mRNA expression was blocked by dichloro-D-ribofuranosylbenzimidazole but not by cycloheximide. RA treatment did not affect the ADD1 mRNA stability, suggesting the involvement of transcriptional control. Electrophoretic mobility shift assay revealed that proteins in the crude nuclear extracts prepared from ROS17/2.8 cells were bound to the E box-containing ADD1 recognition DNA sequence, E/C, and that this binding activity was enhanced by the RA treatment. Neither the E2A protein recognition sequence nor the Myo-D/E12 recognition sequence competed against the E/C sequence for the binding, indicating the sequence specificity of the binding activity. Furthermore, RA treatment enhanced the transactivation activity of the chloramphenicol acetyltransferase construct containing the E/C sequence in the transient transfection assay in ROS17/2.8 cells. RA treatment also enhanced the ADD1 mRNA expression in another rat calvaria-derived cell line, RCT1, and in the primary cultures of newborn rat calvaria cells. Overexpression of ADD1 in ROS17/2.8 enhanced the level of the osteocalcin mRNA expression. These results indicated that the adipogenic basic helix-loop-helix leucine zipper-type transcription factor (ADD1) mRNA was expressed in osteoblastic cells and that its expression was associated with the expression of an osteoblastic phenotype-related gene.

[Isolation and analysis of amino acid sequence of V3 region of HIV-1 from patients with HIV-infection in Hiroshima]

Isolation of HIV-1 was tried in PBMCs separated from 27 blood samples which were sent to Hiroshima Prefectural Institute for Health & Environment Science for anti-HIV antibody-test. 18 samples were positive for HIV-isolation (4 samples were Rapid/High type, 12 samples were Slow/Low type and 2 samples were intermediate). Compared with clinical stages of patients, samples from patients in CDC-II were 64% (14/22) positive and those in CDC-IV were 100% (3/ 3) positive in HIV-isolation. Improvement of the methods is to be required to isolate HIV from the samples of patient in the latent phase. Removal of CD8 positive cells from PBMCs of patients did not affect the efficiency of HIV-isolation by our methods. Three parts in amino acid sequence of V3 region in proviruses were different between Rapid/High type isolated and Slow/Low type isolates. The difference of amino acid may be related to the different phenotypes of the two viruses.

Hepatic artery-biliary fistula during infusion chemotherapy

A 52-year-old man with rectal cancer and liver metastasis underwent tumor resection with hepatic arterial catheterization. During adjuvant chemotherapy, he developed epigastric pain, nausea, and melena. Digital subtraction angiography revealed a hepatic artery-biliary fistula and a pseudoaneurysm at the catheter tip. This rare complication of intra-arterial chemotherapy is reported in detail.

Inositol trisphosphate/Ca2+ as messengers of bradykinin B2 and muscarinic acetylcholine m1-m4 receptors in neuroblastoma-derived hybrid cells

Neuroblastoma x glioma hybrid NG 108-15 and neuroblastoma x fibroblast hybrid NL308 cells possess endogenous bradykinin B2 receptors and m4 muscarinic acetylcholine receptors (mAChRs), which couple to phospholipase C and adenylate cyclase, respectively. Four genetic subtypes of mAChRs differed in their effects when stimulated in NG108-15 and NL308 cells overexpressing mAChRs. Broadly speaking, the principal effects fell into two categories: the odd-numbered receptors (m1 and m3) activated phospholipase C and increased inositol trisphosphate/Ca2+, as bradykinin did, whereas the even-numbered receptors (m2 and m4) inhibited adenylate cyclase via a pertussis toxin (PTx)-sensitive G-protein in NG108-15 cells. But all four types of NL308 cells overexpressing each m1, m2, m3 and m4 receptor activated phospholipase C, while keeping the PTx-sensitivity in m2/m4, but not in m1/m3 receptors. Coupling to ion channel effectors showed a comparable dichotomy in NG108-15 cells, while cross-activation occurred in NL308 cells.

6B4 proteoglycan/phosphacan, an extracellular variant of receptor-like protein-tyrosine phosphatase zeta/RPTPbeta, binds pleiotrophin/heparin-binding growth-associated molecule (HB-GAM)

A major chondroitin sulfate proteoglycan in the brain, 6B4 proteoglycan/phosphacan, corresponds to the extracellular region of a receptor-like protein-tyrosine phosphatase, PTPzeta/RPTPbeta. Here, we purified and characterized 6B4 proteoglycan-binding proteins from rat brain. From the CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid) extract of brain microsomal fractions, 18-, 28-, and 40-kDa proteins were specifically isolated using 6B4 proteoglycan-Sepharose. N-terminal amino acid sequencing identified the 18-kDa protein as pleiotrophin/heparin-binding growth-associated molecule (HB-GAM). Scatchard analysis of 6B4 proteoglycan-pleiotrophin binding revealed low (Kd = 3 nM) and high (Kd = 0.25 nM) affinity binding sites. Chondroitinase ABC digestion of the proteoglycan decreased the binding affinities to a single value (Kd = 13 nM) without changing the number of binding sites. This suggested the presence of two subpopulations of the proteoglycan with different chondroitin sulfate structures. Heparin potently inhibited binding of 6B4 proteoglycan to pleiotrophin (IC50 = 3.5 ng/ml). Heparan sulfate and chondroitin sulfate C inhibited moderately (IC50 = 150 and 400 ng/ml, respectively), but, in contrast, chondroitin sulfate A and keratan sulfate were poor inhibitors (IC50 > 100 microg/ml). Immunofluorescence and immunoblotting analyses indicated that both 6B4 proteoglycan and PTPzeta are located on cortical neurons. Anti-6B4 proteoglycan antibody added to the culture medium suppressed pleiotrophin-induced neurite outgrowth of cortical neurons. These results suggested that interaction between 6B4 proteoglycan and pleiotrophin is required for the action of pleiotrophin, and chondroitin sulfate chains on 6B4 proteoglycan play regulatory roles in its binding.

The S29 ribosomal protein increases tumor suppressor activity of K rev-1 gene on v-K ras-transformed NIH3T3 cells

The human S29 ribosomal protein (S29 rp) cDNA has been isolated from differential hybridization screening of a colon carcinoma cDNA library. Northern blot analysis showed that the level of S29 rp mRNA was higher in undifferentiated HT29 human colon carcinoma cells than in a morphologically differentiated subclone under the same growth condition. Furthermore, the level of S29 rp mRNA was downregulated in rapidly proliferating HT29 cells, as compared to the contact inhibited cells. Interestingly, the amount of Krev-1 mRNA was inversely correlated with respect to the amount of S29 rp mRNA in these cells. To examine a functional link between S29 rp and Krev-1 protein, we co-transfected the expression vectors containing wild-type or mutant S29 rp and mutationally activated Krev-1(63E) cDNAs into the v-Ki-ras-transformed NIH3T3 (DT) cells, and observed the induction of flat revertants. Krev-1(63E) induced a certain amount of flat colonies, while S29 rp alone also induced flat colonies at low frequencies. Interestingly, revertant-inducing activity of Krev-1(63E) was significantly enhanced by S29 rp. We have also demonstrated that a zinc finger-like domain of S29 rp indeed has a zinc binding activity and a derivative, S29 rp(ms), which was unable to bind zinc ion but still retained revertant inducing activity by itself, could not functionally interact with Krev-1(63E) protein.

Visual projection map specified by topographic expression of transcription factors in the retina

Topographical maps of neuronal connectivity occur in various brain regions. In the visual system of birds, retinal ganglion-cell axons from the anterior retina connect to a posterior part of the optic tectum, and posterior retinal axons connect to the anterior part, thereby establishing a point-to-point projection map. The chemoaffinity theory predicts that the orderly retinotectal projection is generated by a topographical arrangement of molecules. We report here that we have found several genes topographically expressed along the nasotemporal (anterior-posterior) axis in the embryonic chicken retina. Among these, two transcriptional regulators, belonging to the winged-helix family are expressed in a mutually exclusive manner in either the nasal or temporal part of the retina. Misexpression of each factor causes misprojection on the tectum along the rostrocaudal axis, showing that topographical expression of these transcription factors controls formation of the retinotectal map.

Angiographic findings of Takayasu arteritis: new classification

Having proposed a new classification on angiographic findings of patients with Takayasu arteritis, we evaluated the angiographic findings of 80 Japanese patients and 102 Indian patients according to this classification. Japanese patients showed a higher frequency of involvement of the ascending aorta, aortic arch and its branches than did the Indians (P < 0.01). On the other hand, the frequency of involvement of the abdominal aorta and/or renal arteries was higher in Indian patients (P < 0.01). Type III cases of the new classification which involves the thoracic descending aorta, abdominal aorta and/or renal arteries were observed in 3% of the Indian patients, but not at all in the Japanese. In conclusion, in Japanese patients, vascular lesions tend to occur primarily in the ascending aorta, aortic arch and/or its branches and extend into the abdominal aorta. On the other hand, in Indian patients, the tendency is primarily in the abdominal aorta including renal arteries and extending into the thoracic aorta.

BMP-4 mediates interacting signals between the neural tube and skin along the dorsal midline

BACKGROUND

The neural tube and its overlying tissues (skin and mesenchyme) interact along the dorsal midline during early development. This has been previously demonstrated experimentally in chicken embryos by the fact that the dorsal neural tube transplanted ectopically induced expression of Msx 2 in the adjacent tissues. It is important to identify the molecules responsible for these interactions.

RESULTS

We observed that BMP-4, a member of the TGFbeta-family, is expressed in the dorsal neural tube in a pattern closely correlated with that of Msx 2. In order to investigate whether BMP-4 mediates the signal between the neural tube and the skin/mesenchyme, BMP-4 was ectopically administered in ovo either by implantation of the recombinant protein or transplantation of COS cells producing BMP-4. Both manipulations resulted in ectopic induction of Msx 2 expression in the adjacent skin/mesenchyme. In addition, the activity of BMP-4 in inducing Msx 2 was counteracted by the floor plate.

CONCLUSION

These data suggest that BMP-4 positively mediates the signals from the neural tube to the adjacent tissues and that this signal may be an essential step for the establishment of the dorsal midline structures.

New hydrolyzable tannins, shephagenins A and B, from Shepherdia argentea as HIV-1 reverse transcriptase inhibitors

Two new hydrolyzable tannins, shephagenins A and B, were isolated along with hippophaenin A and strictinin from the leaf extract of Shepherdia argentea, which showed a remarkable inhibitory activity against human immunodeficiency virus (HIV)-1 reverse transcriptase. Their structures, having a gluconic acid core, have been elucidated on the basis of spectroscopic and chemical methods. The inhibitory effect of the leaf extract on HIV-1 reverse transcriptase was found to be due to tannins, and their activities were stronger than that of (-)-epigallocatechin gallate as a positive control.

Design and synthesis of C-linked fucosides as inhibitors of E-selectin

Two series of C-linked fucosides as mimetics for the tetrasaccharide sialyl Lewis X have been synthesized and tested as inhibitors of E-Selectin. The fucopeptides have been prepared from three key intermediates, including alpha-C-allyl fucose, natural and unnatural amino acids bearing hydroxyl groups and an alpha, omega-diacid moiety for the imitation of the essential three parts of SLex, i.e., the Fuc, Gal, and NeuAc. The nature and distance of the linkage of the fucose moiety to the amino acids as well as the distance between the amino acids and the terminal carboxylic acid group turned out to be crucial for the biological activity. In addition the necessity of both OH groups (4- and 6-OH) in the Gal part could be confirmed. Conformational NMR study of the most active mimetic supports the structure-activity relationship. A second series of mimetics was prepared, where Fuc and Gal moieties were purely C-linked. In the synthesis of beta-C-allyl galactose an intramolecular 1,2-hydride shift led to an interesting side product. However, the substituted glycosidic oxygens led to a substantial loss of conformational constrain, which could not be compensated and resulted in low activity.

Mechanical force regulation of vascular parathyroid hormone-related peptide expression

Parathyroid hormone-related peptide (PTHrP) was originally identified as a factor responsible for the syndrome of humoral hypercalcemia of malignancy. PTHrP has a vasodilator activity and is produced in vascular smooth muscle. However, the exact physiological role of PTHrP and the regulation of its gene expression in the vascular system have not been understood. We found that the mechanical stretch of rat aortic smooth muscle cells in vitro induced a marked increase in PTHrP expression through a protein kinase C-dependent mechanism. We further examined whether PTHrP expression in blood vessels in vivo is regulated by mechanical forces. Mechanical stretch of isolated aortic strips increased the expression of PTHrP mRNA. The PTHrP mRNA expression levels in aortae from hypertensive 18-week-old spontaneously hypertensive rats (SHR) was twofold higher than age-matched control Wistar-Kyoto (WKY) rats, while the PTHrP mRNA level in the aortae from normotensive 4-week-old SHR was not different from that of age-matched control WKY rats. Moreover, treatment of hypertensive SHR with an angiotensin II type 1 receptor antagonist or hydralazine caused a decrease in PTHrP expression in the aortae with the lowering of blood pressure. These results indicate that the gene expression of the vasoleraxant PTHrP in blood vessels is under the regulation of mechanical forces, and suggest a modulatory role for PTHrP in the regulation of vascular tone.

Visceral leishmaniasis misdiagnosed as malignant lymphoma

Visceral leishmaniasis is a chronic infectious disease caused by a protozoan parasite of the genus Leishmania, characterized by intermittent fever, monocytosis, hepatosplenomegaly and hypergammaglobulinemia. This morbid condition is rather difficult to diagnose correctly, especially at its early stage, because it is rarely encountered in Japan. Recently we treated a case of visceral leishmaniasis in which the patient was misdiagnosed as malignant lymphoma, and went through splenectomy and steroid administration, which made the diagnosis more difficult.

Characterization of a human MSX-2 cDNA and its fragment isolated as a transformation suppressor gene against v-Ki-ras oncogene

A cDNA (termed CT124) encoding a carboxyl-terminal fragment of the human homeobox protein MSX-2 was found to induce flat reversion when expressed in v-Ki-ras-transformed NIH3T3 cells. Although the expression of endogenous MSX-2 gene is low in most of the normal adult tissues examined, it is frequently activated in carcinoma-derived cell lines. Likewise, the gene is inactive in NIH3T3 cells but is transcriptionally activated after transformation by v-Ki-ras oncogene, suggesting that the intact MSX-2 may play a positive, rather than suppressive, role in cell transformation. To test this possibility, we isolated a near full-length human MSX-2 cDNA and tested its activities in two cell systems, i.e. fibroblast and myoblast. In NIH3T3 fibroblasts, although the gene by itself failed to confer a transformed phenotype, antisense MSX-2 cDNA as well as truncated CT124 cDNA interfered with the transforming activities of v-Ki-ras oncogene. In C2C12 myoblasts, MSX-2 was found to suppress MyoD gene expression, as do activated ras oncogenes, under certain culture conditions, and CT124 was found to inhibit the activities of both MSX-2 and ras in this system as well. Our findings not only suggest that CT124 may act as a dominant suppressor of MSX-2 but also raise the possibility that MSX-2 gene may be an important downstream target for the Ras signaling pathways.

[A study of surgical treatment in lung cancer over 75 years of age-effect of epidural anesthesia for protection of postoperative coughing disturbance]

29 patients over 75 years of age in 221 patients undergoing resection of lung cancer from January of 1990 through December of 1994 were studied for the occurrence of expectoration disturbance (atelectasis), the effect of epidural anesthesia for protection of it. Atelectasis was observed in 8 (27.6%) of 29. In a group received epidural anesthesia (EA) during the early postoperative phase, 1 of 5 patients developed atelectasis. In 192 patients below 75 years of age, atelectasis was observed in 40 (20.8%) of them, so in a group received epidural anesthesia (EA) during the early postoperative phase, only 2 of 42 patients (4.8%) developed atelectasis. This value was significantly lower than that value (25.3%) in a group without EA. In conclusion, in the group below 75 years of age, EA during the early postoperative phase may be useful in inhibiting the occurrence of atelectasis, an important one of the postoperative lung complications.

MCC, a cytoplasmic protein that blocks cell cycle progression from the G0/G1 to S phase

The MCC gene was isolated from the human chromosome 5q21 by positional cloning and was found to be mutated in several colorectal tumors. In this study, we prepared specific antibodies and detected the MCC gene product as a cytoplasmic 100-kDa phosphoprotein in mouse NIH3T3 cells. Immunoelectron microscopic analysis showed that the MCC protein is associated with the plasma membrane and membrane organelles in mouse intestinal epithelial cells and neuronal cells. The amount of the MCC protein remained constant during the cell cycle progression of NIH3T3 cells, while its phosphorylation state changed markedly in a cell cycle-dependent manner, being weakly phosphorylated in the G0/G1 and highly phosphorylated during the G1 to S transition. Overexpression of the MCC protein blocked the serum-induced cell cycle transition from the G1 to S phase, whereas a mutant MCC, initially identified in a colorectal tumor, did not exhibit this activity. These results suggest that the MCC protein may play a role in the signaling pathway negatively regulating cell cycle progression.

A membrane-bound heparan sulfate proteoglycan that is transiently expressed on growing axons in the rat brain

Monoclonal antibodies were raised to membrane-bound proteoglycans derived from rat brain and three monoclonal antibodies that recognized a 200-kDa heparan sulfate proteoglycan (designated H5-PG) with a core glycoprotein of 140 kDa were obtained. The expression of H5-PG was spatially and temporally regulated in the central nervous system. In the cerebellar cortex, H5-PG was associated mainly with the actively growing parallel fibers of granule cells. The expression was abruptly down-regulated in parallel with the formation of synapses on dendrites of Purkinje cells. In the cerebral cortex, the proteoglycan was widely distributed throughout the cortex. The temporal pattern of expression was similar to that in the cerebellar cortex; the peak level of expression was observed during the period from postnatal days 0 to 20 when neuritogenesis and synaptogenesis occur most extensively in the rat cerebral cortex. H5-PG in the central nervous system disappeared prior to adulthood except in the olfactory bulb. High-level expression was recognized on the olfactory nerves and glomeruli, where the renewal of both axons and synapses is occurring constantly. The data suggest that H5-PG is a glycoconjugate on axonal surface that is involved in axonal outgrowth and/or synaptogenesis.

Cell surface-associated extracellular distribution of a neural proteoglycan, 6B4 proteoglycan/phosphacan, in the olfactory epithelium, olfactory nerve, and cells migrating along the olfactory nerve in chick embryos

The immunocytochemical and immuno-electron microscopic distribution of a neural proteoglycan (PG) was investigated with a monoclonal antibody, MAb 6B4, in the olfactory epithelium, the olfactory nerve, and the cells originating the epithelium and migrating along the olfactory nerve toward the forebrain in chick embryos. The PG recognized by MAb 6B4, that is 6B4 PG, in the brain of early postnatal rats, is identical to phosphacan. In chick embryos, immunoreactivity to 6B4 PG appeared on embryonic day (ED) 3-3.5 in a thin layer beneath the olfactory epithelium. It disappeared immediately, then becoming apparent in the bundles of the olfactory nerve. The immunoreactivity in the nerve bundles gradually increased during ED 5-11. On the other hand, cell surface-associated extracellular localization of the immunoreactivity was seen in the olfactory epithelium on ED 6 and afterwards. Immunofluorescent double-labeling of 6B4 PG and gonadotropin-releasing hormone (GnRH) revealed that the cell bodies of both GnRH-containing cells and other cells migrating along the olfactory nerve were surrounded by a rim immunoreactive to the PG. Under an electron microscope, the surfaces of the cell bodies and of the neurites in the nerve bundles were surrounded by deposits immunoreactive to 6B4 PG. These results indicate that 6B4 PG in chick embryos is one type of cell surface-associated extracellular matrix molecule, and that 6B4 PG covered the surfaces of migrating cells and of elongating olfactory nerve. The cell surface-associated extracellular localization of 6B4 PG found in the nasal region, taken together with the binding properties of this PG with cell adhesion molecules shown in rat brains, suggested that 6B4 PG played a role in guiding the migration of cells along the olfactory nerve in chick embryos.