Regulation of the neural crest cell fate by N-myc: promotion of ventral migration and neuronal differentiation

During neural crest development in avian embryos, transcription factor N-myc is initially expressed in the entire cell population. The expression is then turned off in the period following colonization in ganglion and nerve cord areas except for the cells undergoing neuronal differentiation. This was also recapitulated in the culture of Japanese quail neural crest, and the cells expressing N-myc eventually coincided with those expressing neurofilaments. These findings suggested that N-myc is involved in regulation of neuronal differentiation in the neural crest cell population. In fact, transient overexpression of N-myc in the neural crest culture by transfection resulted in a remarkable promotion of neuronal differentiation. An experimental procedure was developed to examine the effect of exogenous N-myc expression in the neural crest cells in embryos. Neural crest cell clusters still attached to the neural tube were excised from Japanese quail embryos, transfected and grafted into chicken host embryos. Using this chimera technique, we were able to analyze the consequence of transient high N-myc during the early phase of neural crest migration. Two effects were demonstrated in the embryos: first, high N-myc expression provoked massive ventral migration of the neural crest population and, second, those cells that migrated to the ganglion-forming areas underwent neuronal differentiation with the cell type determined by the nature of the ganglion. Thus, N-myc is involved in regulation of the neural crest fate in two different aspects: ventral migration and neuronal differentiation.

Impairment of T cell development in deltaEF1 mutant mice

Using the method of gene targeting in mouse embryonic stem cells, regulatory function of deltaEF1, a zinc finger and homeodomain-containing transcription factor, was investigated in vivo by generating the deltaEF1 mutant mice. The mutated allele of deltaEF1 produced a truncated form of the deltaEF1 protein lacking a zinc finger cluster proximal to COOH terminus. The homozygous deltaEF1 mutant mice had poorly developed thymi with no distinction of cortex and medulla. Analysis of the mutant thymocyte showed reduction of the total cell number by two orders of magnitude accompanying the impaired thymocyte development. The early stage intrathymic c-kit+ T precursor cells were largely depleted. The following thymocyte development also seemed to be affected as assessed by the distorted composition of CD4- or CD8-expressing cells. The mutant thymocyte showed elevated alpha4 integrin expression, which might be related to the T cell defect in the mutant mice. In the peripheral lymph node tissue of the mutant mice, the CD4-CD8+ single positive cells were significantly reduced relative to CD4+CD8-single positive cells. In contrast to T cells, other hematopoietic lineages appeared to be normal. The data indicated that deltaEF1 is involved in regulation of T cell development at multiple stages.

A binding site for Gli proteins is essential for HNF-3beta floor plate enhancer activity in transgenics and can respond to Shh in vitro

The floor plate plays important roles in ventral pattern formation and axonal guidance within the neural tube of vertebrate embryos. A critical event for floor plate development is the induction of a winged helix transcription factor, Hepatocyte Nuclear Factor-3beta (HNF-3beta). The enhancer for floor plate expression of HNF-3beta is located 3′ of the transcription unit and consists of multiple elements. HNF-3beta induction depends on the notochord-derived signal, Sonic hedgehog (Shh). Genetic analysis in Drosophila has led to the identification of genes involved in the Hh signalling pathway, and cubitus interruptus (ci), encoding a protein with five zinc finger motifs, was placed downstream. In the present work, we test the involvement of Gli proteins, the mouse homologues of Ci, in activation of the floor plate enhancer of HNF-3beta. Transgenic analysis shows that a Gli-binding site is required for the activity of the minimal floor plate enhancer of HNF-3beta in vivo. Three Gli genes are differentially expressed in the developing neural tube. Gli expression is restricted to the ventral part, while Gli2 and Gli3 are expressed throughout the neural tube and dorsally, respectively. Strong Gli and Gli2, and weak Gli3 expressions transiently overlap with HNF-3beta at the time of its induction. Consistent with ventrally localized expression, Gli expression can be up-regulated by Shh in a cell line. Finally, the Gli-binding site acts as a Shh responsive element, and human GLI, but not GLI3, can activate this binding site in tissue culture. Taken together, these findings suggest that Gli, and probably also Gli2, are good candidates for transcriptional activators of the HNF-3beta floor plate enhancer, and the binding site for Gli proteins is a key element for response to Shh signalling. These results also support the idea that Gli/Ci are evolutionary conserved transcription factors in the Hedgehog signalling pathway.

Time and flow study results before and after installation of a hospital information system and radiology information system and before clinical use of a picture archiving and communication system

The effectiveness of a hospital information system (HIS) and a radiological information system (RIS) was evaluated to optimize preparation for the planned full clinical operation of a picture archiving and communication system (PACS), which is now linked experimentally to the HIS and the RIS. One thousand IC (integrated circuit) cards were used for time studies and flow studies in the hospital. Measurements were performed on image examination order entry, image examination, reporting, and image delivery times. Even though after the HIS and the RIS operation only a small amount of time savings were realized in each time fraction component, such as in the patient movement time, examination time, and film delivery time, the total turn-around time was shortened markedly, by more than 23 hours on average. It was verified that the HIS and the RIS was beneficial in the outpatient clinics of the orthopedic department. Our method of measurement employing IC cards before and after HIS and RIS operations can be applied in other hospitals.

Mouse fibroblast expressing human tyrosinase with DHICA-oxidase activity produces predominantly pheomelanin deposit in lysosome

The melanogenic gene-transfected cell system serves as a useful tool for the study of the symphonic relation between melanin synthesis and intracellular organelles such as melanosomes in melanocytes. We constructed melanin-producing mouse fibroblasts by transfection of human tyrosinase cDNA to investigate the intracellular changes caused by tyrosinase expression. DHICA-oxidase (5,6-dihydroxyindole-2-carboxylic acid oxidase) activity without TRP-1 (Tyrosinase Related Protein-1) expression in the cells suggested that human tyrosinase also possesses a DHICA-oxidase activities different from mouse tyrosinase. Electron microscopic observation indicated that melanin-deposit organelles have some lysosomal features. These properties of melanin-deposit organelles in tyrosinase expressing fibroblasts provide one evidence for the hypothesis that melanosome is the specialized lysosome in melanocytes.

Impairment of endothelium-dependent relaxation of the isolated basilar artery from streptozotocin-induced diabetic rats

In the isolated rat basilar artery, acetylcholine (ACh) caused concentration-dependent relaxation. The relaxation induced by ACh was significantly inhibited by NG-nitro-L-arginine (L-NNA) (10(-4) M) or isotonic high K+ medium (30 mM) but not by treatment with indomethacin (3 x 10(-5) M) or glibenclamide (10(-6) M). The relaxation was abolished by the combined treatment with L-NNA and isotonic high K+ (30 mM). The relaxation caused by ACh was significantly attenuated in the basilar artery from streptozotocin (STZ)-induced diabetic rats. L-NNA caused contractile response in the isolated basilar artery and this response was significantly attenuated in diabetic rats. IBMX (3-isobutyl-1-methylxanthine)-induced relaxation response was slightly but significantly attenuated in diabetic rats. The relaxation of the basilar artery caused by sodium nitroprusside was not significantly different between control and diabetic rats. In the present study, we were the first to report that the endothelium-dependent relaxation of the isolated rat basilar artery in response to ACh was significantly impaired during STZ-induced diabetic rats.

Organization of the gene encoding transcriptional repressor deltaEF1 and cross-species conservation of its domains

DeltaEF1 (delta-crystallin/E2-box factor 1) is a widely distributed repressor of transcription which binds at the E2-box sequence, CACCTG. It carries seven zinc fingers (Zf) in two clusters and a homeodomain in the middle as potential DNA-binding domains. We cloned the genomic gene encoding chicken deltaEF1 and analyzed its organization. The gene consisted of nine exons, the N-proximal Zf were encoded by exons 5 through 7, and the C-proximal Zf by exons 8 and 9. Exon 7 also coded for the large middle portion of the protein including the homeodomain. Promoter analysis and RNase-protection assay indicated that the gene is driven by a G+C-rich promoter without a TATA box, and the transcription start points (tsp) cluster around 20 bp from the start codon located in exon 1. cDNA and genomic sequences of the mouse delta EF1 were cloned and compared with the chicken sequence. The deduced amino acid (aa) sequence was highly conserved between the chicken and mouse deltaEF1, no only in DNA-binding motifs but also in other blocks (78% overall aa identity). More recently reported DNA-binding proteins, AREB6 (human) ZEB (human) and BZP (hamster), were attributed to homologues of deltaEF1, among which only AREB6 represented full-length sequence. It was also indicated that rodent deltaEF1 lacked exon 3.

High-level secretion of fungal glucoamylase using the Candida boidinii gene expression system

The methylotrophic yeast, Canadida boidinii, was investigated as an expression host for secretory enzyme production. The cDNA of Rhizopus oryzae glucoamylase was placed under the C. boidinii alcohol oxidase (AODl) promoter. A transformant integrated with a single-copy expression cassette to the chromosome produced glucoamylase into the medium to a high amount when the cells were grown on methanol or methanol plus glycerol as (a) carbon source(s). The transformant C. boidinii cells were grown up to ca. 95 g dry cell weight/liter medium, and the concentration of glucoamylase in the medium reached 3.4 g/liter. This showed that the signal sequence from Rhizopus glucoamylase functioned very efficiently in C. boidinii. Next, secreted glucoamylase from C. boidinii was purified and compared with the enzyme produced in S. cerevisiae. The enzyme produced in C. boidinii was found to have higher molecular weight than that produced in S. cerevisiae, which was due to the difference of the N-linked glycosylated sugar structure of the produced proteins.

Detection of subtle interstitial abnormalities of the lungs on digitized chest radiographs: acceptable data compression ratios

OBJECTIVE

To determine acceptable compression ratios for digital radiography, we evaluated the effect of data compression on the detection of subtle interstitial lung abnormalities using digitized chest radiographs.

MATERIALS AND METHODS

Screen-film chest radiographs of 38 patients with subtle interstitial lung abnormalities and 40 patients with normal lung parenchyma were digitized (spatial resolution, 0.175 mm; 2000 x 2000 pixels; 10 bits per pixel) and compressed with the discrete cosine transform method at ratios of 10:1, 20:1, and 30:1. Five chest radiologists and five radiology residents examined the uncompressed and compressed digital images and rates the presence of interstitial lung abnormalities with a five-level scale of confidence. Results were analyzed by receiver operating characteristic methods.

RESULTS

Overall, the interpretation of images with a compression ratio of 30:1 was significantly less accurate than that of uncompressed images (p < .05). For the five chest radiologists, interpretation of images with a compression ratio of 20:1 or 30:1 was significantly less accurate than that of uncompressed images (p < .05). However, for the five residents, no significant difference between interpretations of compressed and uncompressed images was noted (p > or = .05).

CONCLUSION

These results suggest that a 10:1 data compression ratio does not influence the detection of subtle interstitial lung abnormalities. However, information that is lost with a 20:1 data compression ratio might be essential for interpretation by experienced chest radiologists.

[Effect of preoperative oral 5-fluorouracil on cell cycle of advanced cervical squamous cell carcinoma]

Using flow cytometry, we examined the correlations between the tumor stage and the cell cycle in subjects with advanced cervical squamous cell carcinoma as well as between the changes of cell cycle caused by 5-FU and their prognoses. Before 5-FU treatment, 75.9 +/- 9.6% of the patients were at G1 phase, 16.8 +/- 3.9% at S and 7.3 +/- 4.5% at G2/M. The change of cell cycle was not accompanied by the progression of tumor stage. Sixteen patients received oral 5-FU (300 mg/day) for at least 2 weeks before operation. In the patients at stage I, the cell cycle was not changed even after 5-FU treatment. They have been cancer-free for 3 postoperative years. While early recurrence was found in 4 of 5 cases at stage II or III showing progression at G1, all 6 cases who had regressed or remained unchanged at G1 were free from recurrence (p = 0.0152). These results suggested that the cell cycle is not necessarily correlated with the progression of tumor stage in patients with this kind of carcinoma, and that the change of cell cycle due to preoperative oral 5-FU could be a predictive indicator for their prognoses. Especially for those with poor prognoses who had shown progression at G1, more potent adjuvant chemotherapy should be planned.

Regionalized expression of the Dbx family homeobox genes in the embryonic CNS of the mouse

Here we report the identification of a novel homeobox gene family Dbx in mouse, which consists of Dbx and Dbx2. The two genes share similar structural organization and are encoded by different chromosomes. The predicted Dbx and Dbx2 proteins share 85% identity in their homeodomain amino acid sequences, but otherwise showed no significant similarity. Characterization of the expression of these two genes in the embryos suggested their role in the development of the CNS. In the forebrain, Dbx is expressed in various regions, while Dbx2 showed a more restricted pattern of expression. In the midbrain, the expression domains of Dbx and Dbx2 overlap along the dorso-lateral wall of the ventricle. In the hindbrain and spinal cord, both genes are expressed in the boundary separating the basal and alar plates, which seems to correspond to the sulcus limitans. Expression of the Dbx/Dbx2 genes is restricted to the ventricular region of the embryonic CNS except for that of Dbx in the septum of the telencephalon. Together these observations indicate possible participation of the members of the Dbx family in regionalization of the CNS. While the expression of Dbx was restricted to the CNS, Dbx2 was also expressed in some of the mesenchymal cells, such as limb buds and tooth germs.

Composition of mammalian eumelanins: analyses of DHICA-derived units in pigments from hair and melanoma cells

The proportions in which two eumelanin monomers, namely 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and 5,6-dihydroxyindole (DHI), compose the eumelanin polymer are believed to determine properties of the pigment including its color. These proportions are, however, not well elucidated for naturally occurring eumelanins, largely because of methodological difficulties. In this study we estimate the content of DHICA-derived units in mammalian eumelanins using a combination of two analytical techniques: 1) quantitation of DHICA-derived eumelanin by measuring the yield of pyrrole-2,3,5-tricarboxylic acid (PTCA index) and 2) spectrophotometrical quantitation of total (DHI + DHICA) eumelanin at 350 nm (A350 index). The ratio of PTCA/A350 measured for melanins synthesized from DHI and DHICA mixed in various molar proportions correlates well with the content of DHICA in synthetic polymers. Using this relationship as a standard curve we estimated the proportion of DHICA-derived units in mammalian eumelanins from hair and melanoma cells and found it to be much higher in rodent pigments (58.8%-98.3%; two species, mouse and hamster were examined) as compared to human eumelanins (19.2%-41.8%; one Caucasian and one Oriental individual were examined). No relationship between proportion of DHICA-derived units in eumelanin and hair color is found. The latter seems to be determined predominantly by the ratio of pheo- to eumelanin synthesis.

Dynamic range control processing of digital chest images. A clinical evaluation

PURPOSE

The clinical usefulness of an advanced image-processing system called "dynamic range control processing" was investigated, with which selected parts of the dynamic range of digital chest images could be controlled.

MATERIAL AND METHODS

A comparative study of 3 different post-processed formats of storage phosphor (SR) images was performed in 35 patients with abnormalities in the chest. The 3 formats were SR images with standard mode (SR-standard), SR images with strong edge-enhancement (SR-enhanced), and dynamic range controlled SR images (SR-controlled).

RESULTS

For lung abnormalities, there was no difference among the 3 SR image formats. For normal mediastinal structures and lung abnormalities covered by the heart or diaphragm, SR-controlled and SR-enhanced images were significantly superior to SR-standard images, while no difference was found between SR-controlled and SR-enhanced images except for the trachea and bony structures.

CONCLUSION

Dynamic range control processing appears to be a useful method for displaying SR chest images with an extremely wide dynamic range.

The regulatory subunits of fission yeast protein phosphatase 2A (PP2A) affect cell morphogenesis, cell wall synthesis and cytokinesis

BACKGROUND

Protein phosphatase 2A (PP2A) holoenzymes have a trimeric structure, consisting of a catalytic subunit C and two regulatory subunits A (PR65) and B (PR55). In fission yeast the C subunits, being 80% identical to their mammalian counterparts, are essential for viability and negatively regulate the entry into mitosis. Genetic analyses in budding yeast and Drosophila show that the regulatory subunits are implicated in chromosome segregation, cell morphogenesis and/or cytokinesis.

RESULTS

We isolated fission yeast genes paa1+ and pab1+ encoding the regulatory subunits PR65 and PR55, respectively. Gene disruption showed that the paa1+ gene was essential for viability while pab1+ was not required at 26-33 degrees C. Microtubule and actin distributions were anomalous in gene disrupted delta paa1 cells which were incapable of forming a polarized cell shape. Gene disrupted delta pab1 cells were pear- or round-shaped, and lost the polar distributions of actin and microtubules. In addition, delta pab1 cells were defective in cell wall synthesis and sporulation at permissive temperatures. At restrictive temperatures, delta pab1 cells showed an osmoremedial temperature-sensitive phenotype and delayed in cytokinesis. However, chromosome segregation was normal.

CONCLUSION

Fission yeast PP2A regulatory subunit plays a critical role in cell morphogenesis, probably through regulation of the cytoskeletal network and cell wall synthesis.

Overexpression of a membrane protein, neuropilin, in chimeric mice causes anomalies in the cardiovascular system, nervous system and limbs

Neuropilin is a type 1 membrane protein, which is highly conserved among Xenopus frog, chicken and mouse. The extracellular part of the neuropilin protein is composed of three unique domains, each of which is thought to be involved in molecular and/or cellular interactions. In mice, neuropilin is expressed in the cardiovascular system, nervous system and limbs at particular developmental stages. To clarify the roles of neuropilin in morphogenesis in vivo, we generated mouse embryonic stem (ES) cell clones that constitutively expressed exogenous neuropilin, then produced chimeras using these ES cell clones. The chimeras overexpressed neuropilin and were embryonic lethal. The chimeric embryos exhibited several morphological abnormalities; excess capillaries and blood vessels, dilation of blood vessels, malformed hearts, ectopic sprouting and defasciculation of nerve fibers, and extra digits. All of these abnormalities occurred in the organs in which neuropilin is expressed in normal development. The variety of abnormalities occurring in these chimeric embryos suggested diverse functions of neuropilin in embryonic morphogenesis, which may be ascribed to multiple interaction domains identified in the molecule. Correct spatiotemporal expression of neuropilin seems to be essential for normal development of the cardiovascular system, nervous system and limbs.

Involvement of SOX proteins in lens-specific activation of crystallin genes

We have studied the mechanism of delta 1-crystallin gene activation, which occurs early in lens cell differentiation, and have previously shown that an essential element of the delta 1-crystallin enhancer is bound by a group of nuclear factors, delta EF2, among which delta EF2a is highly enriched in lens cells. In this report we show that the cDNA of delta EF2a codes for the chicken SOX-2 protein (cSOX-2), which is structurally related to the sex-determining factor SRY. Sox-2 is expressed at high levels in the early developing lens in both chicken and mouse embryos. Overexpression of delta EF2a/cSOX-2 increased delta 1-crystallin enhancer activity to a plateau in lens cells, but not in fibroblasts, consistent with the previously drawn conclusion that delta EF2a activates transcription only in concert with another factor present in the lens. This result supports the model that SOX proteins act as architectural components in the activating complex formed on an enhancer, as indicated for another HMG domain protein, lymphoid enhancer binding factor 1 (LEF-1). We also show that SOX protein binding is essential for lens-specific promoter activity of the mouse gamma F-crystallin gene. This work is the first to show delta- and gamma-crystallin genes as examples of direct regulatory targets of SOX proteins and provides evidence that diversified crystallin genes are regulated, at least partly, by a common mechanism.

Enhancement of hematopoietic uptake by granulocyte colony-stimulating factor in Ga-67 scintigraphy

The authors report on two non-Hodgkin's lymphoma cases which showed markedly enhanced Ga-67 uptake of granulopoietic area induced by recombinant human granulocyte colony-stimulating factor (rhG-CSF) administration. The rhG-CSF is a newly developed agent for reduction of infections, which stimulates the proliferation and differentiation of granulopoiesis. Use of rhG-CSF is becoming increasingly frequent because the indications are so broad that most patients with intensive chemotherapy for malignancies benefit from undergoing this treatment. In this study, the results of the two cases were: 1) G-CSF enhanced the accumulation of Ga-67 citrate in the granulopoietic area; 2) the marked uptake of red marrow looked like involvement; and 3) in contrast, the involved area became relatively "cold." These findings should be considered in the interpretation of Ga-67 scintigraphy.

A murine Thy-1.2 reporter vector containing a SV40 origin for rapid cloning and analysis of eukaryotic promoters

A new vector, pATO, was constructed for rapid cloning and analysis of eukaryotic promoters. When a recombinant pATO, carrying a promoter sequence in its multiple cloning site, was introduced into COS cells, Thy-1.2 protein was produced on the cell surface, and was easily identified by an fluorescein-conjugated anti-Thy-1.2 antibody. The intensity of the fluorescence reflected the strength of the inserted promoter. Since pATO could replicate efficiently in COS cells, the recombinant plasmids recovered from a single COS cell were sufficient to transform Escherichia coli cells. This plasmid is applicable for the rapid and labor saving cloning of promoter elements.

bcl-2 deficiency in mice leads to pleiotropic abnormalities: accelerated lymphoid cell death in thymus and spleen, polycystic kidney, hair hypopigmentation, and distorted small intestine

Transgenic mice homozygously lacking in the bcl-2 gene were generated using homologous recombination in embryonal stem cells. The complete absence of Bcl-2 alpha and -beta proteins did not interfere with normal embryonic development. Abnormalities became evident after birth, although the severity varied among homozygous null mice, bcl-2-/- mice displayed pleiotropic abnormalities similar to those in the previously described bcl-2-/- mice, including growth retardation, smaller ears, short lives, polycystic kidney, atrophic thymus and spleen with accelerated apoptotic cell death of lymphocytes, and hair hypopigmentation in the second hair follicle cycle. Our bcl-2-/- mice also revealed novel defects in the small intestine, characterized by retarded development, accelerated exfoliation of epithelial cells, and very few mitotic progenitor cells.

Developing a new picture archiving and communication system for the new Osaka University Hospital

Osaka University Hospital moved into a new hospital building on the suburban Suita campus in October 1993. A newly developed hospital information system, a new radiologic information system and phase I of a completely new Picture Archiving and Communication System (PACS) also began operating. Work began in 1986 on this PACS. The PACS effort has been guided by one working group and two committees during the last 7 years. A survey of the previous diagnostic and image delivery system was performed as part of the preamble to designing an optimal PACS. Extensive analysis and measurement of pre-existing operational conditions was undertaken. These studies and technical research projects are described in a companion paper in this issue. The phase I hardware installation and initial testing were completed in March 1994. Subsequent phases will build incrementally until the completely new, hospital-wide PACS is realized.