Delta and Serrate are redundant Notch ligands required for asymmetric cell divisions within the Drosophila sensory organ lineage

Asymmetric divisions allow a precursor to produce four distinct cells of a Drosophila sensory organ lineage (SOL). Whereas this process requires cell-cell communication via Notch (N) receptor, mitotic recombination that removes the N ligand Delta (Dl) or Serrate (Ser) in the SOL had mild or no effect. Removal of both Dl and Ser, however, led to cell fate transformations similar to the N phenotype. Cell fate transformation occurred even when a single SOL cell lost both Dl and Ser. Thus, Dl and Ser are redundant in mediating signaling between daughter cells to specify their distinct cell fates.

[Processing of ceramiclike xenogeneic bone and experimental study of its bone formation from composite graft combined with bone marrow]

Ceramiclike xenogeneic bone (CXB) was obtained from the fresh bone of pig ribs being treated by physical and chemical methods to deprive of its organic substance. The CXB possessed the same natural porous network system as that of the human. The CXB was cultured with the bone marrow stromal cells of rabit. When the marrow cells had integrated with the CXB, thus a new material was obtained. (CXB-BM), and was implanted sacro-spinal muscle of rabbit. The specimens were observed under phase microscope, light microscope and electronic scanning microscope. The results showed that: at the 2nd week after the implantation of CBX-BM composite material there began the new bone formation, and the rate of bone formation was increased with time. There was evident new bone formation after 24 weeks. The process of the new bone formation were quite similar to the composite graft of HAP red autogenous and marrow, but the former degraded faster and formed typical cancellous structure earlier. There was no new bone formation when CXB was implanted alone in the control. Both the mechanism of osteogenetic potential and its clinical application were discussed.

Intranuclear targeting of AML/CBFalpha regulatory factors to nuclear matrix-associated transcriptional domains

The AML/CBFalpha runt transcription factors are key regulators of hematopoietic and bone tissue-specific gene expression. These factors contain a 31-amino acid nuclear matrix targeting signal that supports association with the nuclear matrix. We determined that the AML/CBFalpha factors must bind to the nuclear matrix to exert control of transcription. Fusing the nuclear matrix targeting signal to the GAL4 DNA binding domain transactivates a genomically integrated GAL4 responsive reporter gene. These data suggest that AML/CBFalpha must associate with the nuclear matrix to effect transcription. We used fluorescence labeling of epitope-tagged AML-1B (CBFA2) to show it colocalizes with a subset of hyperphosphorylated RNA polymerase II molecules concentrated in foci and linked to the nuclear matrix. This association of AML-1B with RNA polymerase II requires active transcription and a functional DNA binding domain. The nuclear matrix domains that contain AML-1B are distinct from SC35 RNA processing domains. Our results suggest two of the requirements for AML-dependent transcription initiation by RNA polymerase II are association of AML-1B with the nuclear matrix together with specific binding of AML to gene promoters.

Glycosylation provides both stimulatory and inhibitory effects on cell surface and soluble CD44 binding to hyaluronan

Glycosylation has been implicated in the regulation of CD44-mediated cell binding of hyaluronan (HA). However, neither the relative contribution of N- and O-linked glycans nor the oligosaccharide structures that alter CD44 affinity for HA have been elucidated. To determine the effect of selective alteration of CD44 oligosaccharide composition on the affinity of CD44 for HA, we developed a novel strategy based on the use of affinity capillary electrophoresis (ACE). Soluble recombinant CD44-immunoglobulin fusion proteins were overproduced in the mutant CHO cell line ldl-D, which has reversible defects in both N- and O-linked oligosaccharide synthesis. Using this cell line, a panel of recombinant glycosidases, and metabolic glycosidase inhibitors, CD44 glycoforms with defined oligosaccharide structures were generated and tested for HA affinity by ACE. Because ldl-D cells express endogenous cell surface CD44, the effect of any given glycosylation change on the ability of cell surface and soluble CD44 to bind HA could be compared. Four distinct oligosaccharide structures were found to effect CD44-mediated HA binding: (a) the terminal alpha2,3-linked sialic acid on N-linked oligosaccharides inhibited binding; (b) the first N-linked N-acetylglucosamine residue enhanced binding; (c) O-linked glycans on N-deglycosylated CD44 enhanced binding; and (d) N-acetylgalactosamine incorporation into non-N-linked glycans augmented HA binding by cell surface CD44. The first three structures induced up to a 30-fold alteration in the intrinsic CD44 affinity for HA (Kd = 5 to >150 microM). The fourth augmented CD44-mediated cellular HA avidity without changing the intrinsic HA affinity of soluble CD44.

Signal transduction pathways leading to spore differentiation in Dictyostelium discoideum

Cells that overexpress PKA as a consequence of carrying multiple copies of the gene encoding the catalytic subunit can be induced to sporulate when developing as single cells. A peptide phosphorylated by PKA, termed SDF-1, has recently been shown to stimulate this process (Anjard et al., 1997). Several genes have been implicated in a signal transduction pathway by which prestalk cells induce encapsulation of prespore cells during terminal differentiation including a prestalk-specific putative membrane protease (TagC) and a two-component system consisting of a receptor-histidine kinase (DhkA) and a response regulator with cAMP phosphodiesterase activity (RegA). To determine whether SDF-1 uses this pathway, strains carrying null mutations in the pertinent genes were transformed with a pkaC plasmid such that they can overexpress PKA. Since these mutant strains all sporulated efficiently when SDF-1 was added, it appears that other gene products mediate the response. However, we found that regA- mutant cells release a distinct factor, SDF-2, that rapidly induces encapsulation of test cells overexpressing pkaC. Since cells in which tagC is disrupted do not form SDF-2 and cells in which dhkA is disrupted do not respond to SDF-2, this peptide appears to use the two-component system that regulates PKA activity. SDF-2 is a small peptide released by prestalk cells in a manner dependent on TagC. It appears to act on prespore cells through the DhkA receptor to inhibit the cAMP phosphodiesterase of RegA, thereby activating PKA via cAMP. The process of induction by SDF-2 can be shown to be distinct from that by SDF-1. SDF-2 appears to stimulate prestalk cells to release additional SDF-2 by acting through a signal transduction pathway that also involves DhkA, RegA, and PKA. Based on these results we present a model for the signal transduction cascade regulating spore differentiation.

The mechanism of regulation of hexokinase: new insights from the crystal structure of recombinant human brain hexokinase complexed with glucose and glucose-6-phosphate

BACKGROUND

Hexokinase I is the pacemaker of glycolysis in brain tissue. The type I isozyme exhibits unique regulatory properties in that physiological levels of phosphate relieve potent inhibition by the product, glucose-6-phosphate (Gluc-6-P). The 100 kDa polypeptide chain of hexokinase I consists of a C-terminal (catalytic) domain and an N-terminal (regulatory) domain. Structures of ligated hexokinase I should provide a basis for understanding mechanisms of catalysis and regulation at an atomic level.

RESULTS

The complex of human hexokinase I with glucose and Gluc-6-P (determined to 2.8 A resolution) is a dimer with twofold molecular symmetry. The N- and C-terminal domains of one monomer interact with the C- and N-terminal domains, respectively, of the symmetry-related monomer. The two domains of a monomer are connected by a single alpha helix and each have the fold of yeast hexokinase. Salt links between a possible cation-binding loop of the N-terminal domain and a loop of the C-terminal domain may be important to regulation. Each domain binds single glucose and Gluc-6-P molecules in proximity to each other. The 6-phosphoryl group of bound Gluc-6-P at the C-terminal domain occupies the putative binding site for ATP, whereas the 6-phosphoryl group at the N-terminal domain may overlap the binding site for phosphate.

CONCLUSIONS

The binding synergism of glucose and Gluc-6-P probably arises out of the mutual stabilization of a common (glucose-bound) conformation of hexokinase I. Conformational changes in the N-terminal domain in response to glucose, phosphate, and/or Gluc-6-P may influence the binding of ATP to the C-terminal domain.

The roles of glycine residues in the ATP binding site of human brain hexokinase

Mutants of hexokinase I (Arg539 --> Lys, Thr661 --> Ala, Thr661 --> Val, Gly534 --> Ala, Gly679 --> Ala, and Gly862 --> Ala), located putatively in the vicinity of the ATP binding pocket, were constructed, purified to homogeneity, and studied by circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and initial velocity kinetics. The wild-type and mutant enzymes have similar secondary structures on the basis of CD spectroscopy. The mutation Gly679 --> Ala had little effect on the kinetic properties of the enzyme. Compared with the wild-type enzyme, however, the Gly534 --> Ala mutant exhibited a 4000-fold decrease in kcat and the Gly862 --> Ala mutant showed an 11-fold increase in Km for ATP. Glucose 6-phosphate inhibition of the three glycine mutants is comparable to that of the wild-type enzyme. Inorganic phosphate is, however, less effective in relieving glucose 6-phosphate inhibition of the Gly862 --> Ala mutant, relative to the wild-type enzyme and entirely ineffective in relieving inhibition of the Gly534 --> Ala mutant. Although the fluorescence emission spectra showed some difference for the Gly862 --> Ala mutant relative to that of the wild-type enzyme, indicating an environmental alteration around tryptophan residues, no change was observed for the Gly534 --> Ala and Gly679 --> Ala mutants. Gly862 --> Ala and Gly534 --> Ala are the first instances of single residue mutations in hexokinase I that affect the binding affinity of ATP and abolish phosphate-induced relief of glucose 6-phosphate inhibition, respectively.

[Determination of demethylvancomycin in neonate serum by high performance liquid chromatography]

A rapid high performance liquid chromatography for determination of demethylvancomycin in neonate serum has been developed. The procedure involved a simple protein precipitation by acetonitrile-isopropanol (1:1) and then the sample was chromatographed on a reversed phase C18 column with UV detection at 236 nm. The mobile phase was CH3CN: 0.05 mol/L KH2PO4 = 8:92 (V/V). The calibration curve was Y = 35,721.89X - 13,031.54, r = 0.9998 and he detection limit was 0.3 mg/L. The average recovery was 94.7% +/- 1.2%. Intra-day and inter-day RSD were 2.23% and 2.62% respectively. It can be concluded that this method meets the requirement for routine clinical application. This method has been used to determine serum concentration of demethylvancomycin in neonates. The data obtained showed that the method was simple, rapid, sensitive and precise.

[Gas chromatographic analysis of methyl methacrylate and methanol in its esterification mixture]

A fast, simple and accurate gas chromatographic method is established for determining the content of methyl methacrylate (MMA) and methanol in the esterification mixture of methacrylic acid with methanol in the presence of sulfuric acid. In the measurement, polyethylene glycol-20M/sodium hydroxide was adopted as liquid phase, coated on the acid-washed 201 pink support. n-Heptane was used as the internal standard and the correction factors of MMA and methanol obtained were 1.65 and 4.10, respectively. It is significant for this method to be used to control MMA production by acetone cyanohydrin method and to improve the production technology.

[Study on culture and osteogenic potential of stromal cell of bone marrow in vitro]

The osteogenc potential of bone marrow has been proved by experiment. To investigate more in details, bone marrow was obtained from the trochanteric region of femur of New-Zealand rabbit in 4 to 8 weeks old. After being cultured in vitro for one week, the hematopoietic component of the bone marrow had disappeared, thus the stromal cells were obtained. Then the stromal cells were subcultured in cultural fluid containing dexamethasone (10(-8) mol/L) and natrium glycerophosphate (10 mmol/L). Under the phase-contrast microscope, it was found that being cultured for 15 days. The stromal cells were lined up in one layer and late the secretion activity was increased and gradually transformed into multilayer structure and was congregated into diffused opaque clusters in twenty days. During culture, the cells were examined by tetracycline fluorescence label, histochemistry stains, transmission electron microscopy, scanning electron microscopy and energy dispersive X-ray microanalysis. The results showed that the morphological and biological characteristics of the cultured stromal cells derived from the bone marrow were similiar to those of osteoblasts and could synthesized mineralized new bone tissue in vitro.

Identification of a nuclear matrix targeting signal in the leukemia and bone-related AML/CBF-alpha transcription factors

Transcription factors of the AML (core binding factor-alpha/polyoma enhancer binding protein 2) class are key transactivators of tissue-specific genes of the hematopoietic and bone lineages. Alternative splicing of the AML-1 gene results in two major AML variants, AML-1 and AML-1B. We show here that the transcriptionally active AML-1B binds to the nuclear matrix, and the inactive AML-1 does not. The association of AML-1B with the nuclear matrix is independent of DNA binding and requires a nuclear matrix targeting signal (NMTS), a 31 amino acid segment near the C terminus that is distinct from nuclear localization signals. A similar NMTS is present in AML-2 and the bone-related AML-3 transcription factors. Fusion of the AML-1B NMTS to the heterologous GAL4-(1-147) protein directs GAL4 to the nuclear matrix. Thus, the NMTS is necessary and sufficient to target the transcriptionally active AML-1B to the nuclear matrix. The loss of the C-terminal domain of AML-1B is a frequent consequence of the leukemia-related t(8;21) and t(3;21) translocations. Our results suggest this loss may be functionally linked to the modified interrelationships between nuclear structure and gene expression characteristic of cancer cells.

Dynamic relocation of transcription and splicing factors dependent upon transcriptional activity

Recent interest in understanding the spatial organization of gene expression has focused attention on nuclear structures known as speckles or interchromatin granule clusters (IGCs) revealed by immunofluorescence or electron microscopy. Staining of nuclear factors involved in pre-mRNA splicing or, more recently, transcription, reveals 20-40 speckles per nucleus, resulting in the intriguing suggestion that speckles are nuclear sites of transcription and processing. In contrast, other investigations have observed transcription in other areas of the nucleus. In this study, we have examined the localization of active transcription as detected by uridine incorporation and recently developed RNA polymerase II antibodies, and compared this pattern with that of known splicing and polyadenylation factors. Our results indicate that in actively transcribing cells, transcription and splicing factors are dispersed throughout the nucleus with abundant sites of preferred localization. In contrast, in poorly transcribing cells, polymerase II and splicing factors localize to speckles. In nuclei inactivated for transcription by drugs or heat shock, the speckle type of co-localization is accentuated. These observations suggest that bulk transcription and splicing occur throughout the nucleus during periods of active transcription; and that factors involved in these two processes re-locate to minimal speckle domains during periods of inactive transcription.

[Mean corpuscular volume and red blood cell volume distribution width in the diagnosis of iron deficiency anemia in pregnancy]

OBJECTIVE

To evaluate the value of combined measurement of mean corpuscular volume (MCV) and red blood cell volume distribution width (RDW) in the diagnosis of iron deficiency anemia in pregnancy.

METHODS

Hemoglobin concentration (HGB), MCV, RDW, serum iron concentration (Fe), total iron binding capacity (TIBC) and transferrin saturation percentage (TS%) were simultaneously assayed in 605 pregnant women at prenatal examination. The results in different groups were analysed.

RESULTS

There were 68 cases in iron deficiency anemia group, 57 cases in non-iron deficiency anemia group and 480 pregnant women in normal group. RDW was significantly increased and MCV greatly decreased in iron deficiency anemia group as compared with that in normal group and non-iron deficiency anemia group. There were no differences in both MCV and RDW between normal group and non-iron deficiency anemia group.

CONCLUSIONS

Low MCV and high RDW were the characteristic changes of iron deficiency anemia in pregnancy. We recommend the use of RDW and MCV in the initial classification of anemia in pregnancy.

ATP-binding site of human brain hexokinase as studied by molecular modeling and site-directed mutagenesis

The interaction of ATP with the active site of hexokinase is unknown since the crystal structure of the hexokinase-ATP complex is unavailable. It was found that the ATP binding site of brain hexokinase is homologous to that of actin, heat shock protein hsc70, and glycerol kinase. On the basis of these similarities, the ATP molecule was positioned in the catalytic domain of human brain hexokinase, which was modeled from the X-ray structure of yeast hexokinase. Site-directed mutagenesis was performed to test the function of residues presumably involved in interaction with the tripolyphosphoryl moiety of ATP. Asp532, which is though to be involved in binding the Mg2+ ion of the MgATP2- complex, was mutated to Lys and Glu. The kcat values decreased 1000- and 200-fold, respectively, for the two mutants. Another residue, Thr680 was proposed to interact with the gamma-phosphoryl group of ATP through hydrogen bonds and was mutated to Val and Ser. The kcat value of the Thr680Val mutant decreased 2000-fold, whereas the kcat value of the Thr680Ser decreased only 2.5-fold, implying the importance of the hydroxyl group. The Km and dissociation constant values for either ATP or glucose of all the above mutants showed little or no change relative to the wild-type enzyme. The Ki values for the glucose 6-phosphate analogue 1,5-anhydroglucitol 6-phosphate, were the same as that of the wild-type enzyme, and the inhibition was reversed by inorganic phosphate (Pi) for all four mutants. The circular dichroism spectra of the mutants were the same as that of the wild-type enzyme. The results from the site-directed mutagenesis demonstrate that the presumed interactions of investigated residues with ATP are important for the stabilization of the transition state.

Anchoring of c-myc on nuclear matrix proteins in process of mouse thymic T lymphocyte proliferation induced by ConA

Isolation and characterization of functional nuclear matrix proteins involved in DNA anchoring and gene expression is one of the major subjects of current nuclear matrix research. Southwestern blotting (DNA-protein hybridization) was applied to studying the anchoring of c-myc on the nuclear matrix proteins in mouse thymic T lymphocytes. The results showed that c-myc bound to the lamin, p34 and p36 nuclear matrix proteins specifically. In the process of mouse thymic PNA-T lymphocytes proliferation induced by ConA, the anchoring of c-myc on p34 and p36 nuclear matrix proteins changed dynamically.

Biological model of ED01 hepatocarcinogenesis

The ED01 bioassay on 2-acetylaminofluorene (2-AAF)-induced hepatocarcinogenesis in BALB/c mice was analyzed using a biologically based, two-mutation model of the oncogenic process. Computer simulations indicate that 2-AAF-induced hepatocarcinogenesis has both genotoxic and promotional components. However, contrary to the current paradigm, we find that the genotoxic component of 2-AAF plays a minor role in its carcinogenicity. The ED01 hepatocarcinogenicity can be explained almost entirely to result from the promotional influence of 2-AAF on an existing pool of spontaneously initiated cells.

Identification of an active site residue of the R1 subunit of ribonucleotide reductase from Escherichia coli: characterization of substrate-induced polypeptide cleavage by C225SR1

Incubation of the C225S mutant of the R1 subunit of ribonucleotide reductase from Escherichia coli with the R2 subunit and nucleoside diphosphates leads to fragmentation of the polypeptide backbone of R1 [Mao, S. S., Holler, T. P., Bollinger, J.M., Jr., Yu, G. X., Johnston, M.I., & Stubbe, J. (1992) Biochemistry 31, 9744--9751]. The 26 and 60 kDa cleavage fragments were purified to homogeneity. The 26 kDa polypeptide was digested with Lys-C, and the peptides were partially purified by RP-HPLC. Mass spectrometric analysis (MALDI-TOF) of the HPLC fractions allowed the identification of the C-terminal peptide. The molecular mass of this peptide (2176) revealed that serine-224 constitutes its C-terminus, and further analysis of the distribution of its monoisotopic masses by FAB-MS indicated that Ser224 possesses a carboxamide rather than a carboxylate group. Treatment of the 60 kDa cleavage fragment with cyanogen bromide and subsequent MALDI-TOF analysis of the partially RP-HPLC purified peptides yielded a fraction containing its N-terminal peptide. This peptide was digested with trypsin, and the digestion mixture was purified by HPLC. Analysis of the fractions by MALDI-TOF identified the N-terminal peptide and determined a mass of 2222. This mass suggested valine 226 was the N-terminal residue (modified by an adduct of 28 mass units). Larger amounts of the C-terminal tetrapeptide of the 60 kDa fragment (V226LIE229) were obtained by complete digestion of the crude reaction mixture with endoproteinase Glu-C. The peptide mixture was then purified on an immunoadsorbent column containing immobilized antibodies raised against a synthetic peptide with the sequence KVLIE. After elution of the affinity-bound peptide, it was analyzed by CID-MS verifying that an adduct of 28 mass units was attached to valine 226. These results indicated that the amino group of Val226 is formylated. The localization of the residues at the cleavage site of C225SR1 provides a biochemical identification of the active site region of the R1 subunit of RDPR from E.coli. The details of the mechanism of cleavage remain to be elucidated.

Crystallization and preliminary X-ray analysis of human brain hexokinase

Human brain hexokinase type I, expressed in Escherichia coli, has been crystallized from polyethylene glycol 8000 in the presence of inorganic phosphate. The crystals are hexagonal needles of diameter 0.25 mm, diffracting to a resolution of 3.5 A on a rotating-anode/area-detector system. The crystals belong to the space group P3(1)21/P3(2)21 with cell dimensions a = b = 171.5 A and c = 99.4 A. The specific volume of the crystal is 4.2 A3/Da, suggesting an asymmetric unit with a single 100 kDa molecule and a solvent content of 71% by volume or two molecules of hexokinase with a solvent content of 41%. The complex of hexokinase with glucose crystallizes under similar conditions, giving crystals of the same morphology.

A human axillary odorant is carried by apolipoprotein D

The characterization of the source of the odor in the human axillary region is not only of commercial interest but is also important biologically because axillary extracts can alter the length and timing of the female menstrual cycle. In males, the most abundant odor component is known to be E-3-methyl-2-hexenoic acid (E-3M2H), which is liberated from nonodorous apocrine secretions by axillary microorganisms. Recently, it was found that in the apocrine gland secretions, 3M2H is carried to the skin surface bound to two proteins, apocrine secretion odor-binding proteins 1 and 2 (ASOB1 and ASOB2) with apparent molecular masses of 45 kDa and 26 kDa, respectively. To better understand the formation of axillary odors and the structural relationship between 3M2H and its carrier protein, the amino acid sequence and glycosylation pattern of ASOB2 were determined by mass spectrometry. The ASOB2 protein was identified as apolipoprotein D (apoD), a known member of the alpha2mu-microglobulin superfamily of carrier proteins also known as lipocalins. The pattern of glycosylation for axillary apoD differs from that reported for plasma apoD, suggesting different sites of expression for the two glycoproteins. In situ hybridization of an oligonucleotide probe against apoD mRNA with axillary tissue demonstrates that the message for synthesis of this protein is specific to the apocrine glands. These results suggest a remarkable similarity between human axillary secretions and nonhuman mammalian odor sources, where lipocalins have been shown to carry the odoriferous signals used in pheromonal communication.

[Transcriptional expression of oncogenes and Rb antioncogene in experimental atherosclerotic lesions]

Atherosclerosis (AS) is characterized by the proliferation of the smooth muscle cells (SMC) in the arterial wall. Its pathogenesis might be associated with overexpression of oncogenes in SMC. Gorden and Barrett et al found that sis mRNA level elevated in human atherosclerotic plaques 5-12 fold above level present in normal artery. But the transcriptional expression of c-fos, c-myc, c-jun, H-ras, v-erb-B oncogenes and Rb antioncogene in atherosclerotic lesion has not yet been reported. A study on these oncogenes and Rb gene expression in artherosclerotic lesions in rabbits fed on high cholesterol diet were assayed by the dot blot hybridization using alpha-32P-labelled oncogenes and Rb gene fragments as the probes. After fed with the high cholesterol diet for six months, the plasma cholesterol levels in AS rabbits were significantly increased (1300 +/- 240 mg/dl vs 67.1 +/- 11.5 mg/dl). The atherosclerotic plaques covered 91% +/- 11% of the intimal aortic surface of aorta thoracalis. The results showed that the atherosclerotic plaques contained 3-4 fold more v-sis, c-fos and c-myc mRNA (P < 0.01), 2 fold more c-jun and H-ras mRNA (P < 0.01), and less Rb mRNA (P < 0.05) than those in the normal aortic arteries. But the expression of v-erb-B gene in atherosclerotic plaques remained unchanged. These results indicate that the abnormal expression of v-sis, c-myc, c-fos, c-jun, and H-ras oncogenes and Rb antioncogene may play an important role in arterial SMC proliferation and pathogenesis of atherosclerosis.

Nuclear matrix proteins as structural and functional components of the mitotic apparatus

The eukaryotic nucleus is a membrane-enclosed compartment containing the genome and associated organelles supported by a complex matrix of nonhistone proteins. Identified as the nuclear matrix, this component maintains spatial order and provides the structural framework needed for DNA replication, RNA synthesis and processing, nuclear transport, and steroid hormone action. During mitosis, the nucleoskeleton and associated chromatin is efficiently dismantled, packaged, partitioned, and subsequently reassembled into daughter nuclei. The dramatic dissolution of the nucleus is accompanied by the assembly of a mitotic apparatus required to facilitate the complex events associated with nuclear division. Until recently, little was known about the fate or disposition of nuclear matrix proteins during mitosis. The availability of specific molecular probes and imaging techniques, including confocal microscopy and improved immunoelectron microscopy using resinless sections and related procedures, has enabled investigators to identify and map the distribution of nuclear matrix proteins throughout the cell cycle. This chapter will review the structure, function, and distribution of the protein NuMA (nuclear matrix mitotic apparatus) and other nuclear matrix proteins that depart the nucleus during the interphase/mitosis transition to become structural and functional components within specific domains of the mitotic apparatus.

Effects of antisense epidermal growth factor and its receptor retroviral expression vectors on cell growth of human pancreatic carcinoma cell line

A 150 bp epidermal growth factor (EGF) cDNA fragment and a 1024 bp epidermal growth factor receptor (EGFR) cDNA fragment were inserted into 5.05 kb pBabe-puro retroviral vectors between BamH I and EcoR I sites in 3'-5' and/or 5'-3' orientation. The vectors were ligated with EGF and EGFR fragments by T-4 Ligase. The recombinant retroviral vectors were then packaged with packaging cell line PA317 through calcium phosphate mediated transfection. The viral supernatant of transfected PA317 cell lines were used to infect the human pancreatic carcinoma cell line PC-7. The resultant transformant cell lines: PC-7/AS-EGF, PC-7/S-EGFR, PC-7/AS-EGFR and PC-7/pBabe were tested for their endogenous EGF and EGFR mRNA expressions, cell growth rate, 3H-TdR incorporation rate, soft agar colony formation and tumorigenicity in nude mice. The results showed that there were noticeable inhibitions of cell growth, 3H-TdR incorporation rate, soft agar colony formation and tumorigenicity in nude mice in PC-7/AS-EGF and PC-7/AS-EGFR transformant cell lines. The endogenous EGF mRNA expression was blocked in PC-7/AS-EGF cell line and the endogenous EGFR mRNA was significantly down-regulated in PC-7/AS-EGFR cell line.