Transgenic hepatocarcinogenesis in the rat

Although transgenic hepatocarcinogenesis has been accomplished in the mouse with a number of genetic constructs targeting the oncogene to expression primarily in the liver, no example of this process has yet been developed in the rat. Because our understanding of the multistage nature of hepatocarcinogenesis is most advanced in the rat, we have developed a strain of transgenic rats carrying the promoter-enhancer sequences of the mouse albumin gene linked 5' to the simian virus-40 T antigen gene. A line of transgenic rats bearing this transgene has been developed from a single founder female. Five to six copies of the transgene, possibly in tandem, occur within the genome of the transgenic animals, which are maintained by heterozygous matings. Livers of transgenic animals are histologically normal after weaning; at 2 months of age, small foci of vacuolated cells appear in this organ. By 4 months of age, all animals exhibit focal lesions and nodules consisting primarily of small basophilic cells, many of which exhibit considerable cytoplasmic vacuolization. Mating of animals each bearing the transgene results in rats with a demyelinating condition that develops acutely in pregnant females and more chronically in males. Ultrastructural studies of these cells indicate that the vacuoles contain substantial amounts of glycogen, with the cells resembling hepatoblasts. Malignant neoplasms with both a glandular and a hepatoblastoma/hepatocellular carcinoma pattern arise from the nodules. Enzyme and immunohistochemical studies of all lesions reveal many similarities in gene expression to comparable lesions in rats subjected to chemically induced hepatocarcinogenesis, with certain exceptions. The placental form of glutathione-S-transferase is absent from all lesions in the transgenic animal, as is the expression of connexin 32. A significant number of lesions express serum albumin, and many, but not all, exhibit the T antigen. Lesions expressing the T antigen also contain stainable amounts of the p53 gene product; by contrast, normal hepatocytes express only very low levels of the T antigen within their nuclei and no demonstrable p53. All of the animals develop hepatic lesions, and approximately one-third also develop adenomas and carcinomas derived from the islet cells of the pancreas. Although there are differences in the morphology, biology, and genetic expression in early and late hepatic lesions in this strain of transgenic rat, many similarities also occur, making this a potential model system with which to study the interactions of environmental factors with a genetic program for hepatocarcinogenesis.

Sphingosine 1-phosphate, a novel signaling molecule, stimulates DNA binding activity of AP-1 in quiescent Swiss 3T3 fibroblasts

Sphingosine and sphingosine 1-phosphate, metabolites of sphingolipids, stimulate cell proliferation in quiescent Swiss 3T3 fibroblasts and induce transient increases in intracellular free calcium (Zhang, H., Desai, N. N., Olivera, A., Seki, T., Brooker, G., and Spiegel, S. (1991) J. Cell Biol. 114, 155-167). However, little is yet known of the nuclear events that follow the early responses induced by sphingolipid metabolites. Using a gel retardation assay, we found that specific DNA binding activity of activator protein-1 (AP-1) was markedly increased after treatment of quiescent Swiss 3T3 fibroblasts with sphingosine 1-phosphate and sphingosine. The DNA binding specificity of AP-1 was confirmed with competing probes containing consensus sequences of AP-1, AP-2, AP-3, SP-1, and NF1/CTF. The c-fos gene product was detected in the AP-1 complex using anti-c-Fos antibody. The dose response for stimulation of DNA binding activity of AP-1 by sphingosine 1-phosphate correlated closely with its effect on DNA synthesis. Furthermore, an inhibitor of sphingosine kinase, DL-threo-dihydrosphingosine, which inhibits sphingosine-induced DNA synthesis and the formation of sphingosine 1-phosphate, also inhibited sphingosine-stimulated AP-1 DNA binding activity. This result further supports our proposal that sphingosine 1-phosphate mediates the mitogenic effect of sphingosine. Our results indicate that sphingosine 1-phosphate-induced DNA synthesis and cell division may result from activation of AP-1 protein, linking signal transduction by sphingolipid metabolites to gene expression.

[A murine model of mammary adenocarcinoma (VI TA2MA-891) with high rate of spontaneous metastases in the lungs]

The primary donor tumor was a spontaneous mammary tumor which arose in a 348-day-old female TA2 mouse. The pedigree number of that mouse was 0901-1423. The mouse was sacrificed for serial s.c. transplantation with 3 isogeneic hosts on January 19, 1989 and a total of 27 generations succeeded by the end of April, 1992. The primary donor tumor was diagnosed pathologically as a type B mouse mammary adenocarcinoma (Dunn 1959). The incidence of this serial s.c. transplantation tumor is 100% after inoculation. The latency period is 4-7 days and the lifetime of tumorbearing mice is about 47 days. The spontaneous metastatic rates in the lungs was 100% after the 11th generations. The earliest metastasis seen in the lung under light microscopy was on the 10th day after inoculation, and the earliest seen by gross examination was on about the 35th day. The transplanted tumor grew slowly from the 4th day to the 21st day after inoculation and then grew rather fast from the 22nd to the 47th day. The average size of the transplanted tumor obtained from 10 recipient mice on the 47th day after inoculation was 4.93cm3. Seven anticancer drugs were administered respectively for a sensitivity test. The taking rates of the transplanted tumor using 4 of the 7 drugs were as follows: 5-fluorouracil 29.27% (P < 0.05); thio-tepa 44.80% (P < 0.01); cyclophosphamide 95.31% (P < 0.01); and bleomycin 96.27% (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

GFAP promoter directs astrocyte-specific expression in transgenic mice

Glial fibrillary acidic protein (GFAP) is an intermediate-filament protein expressed abundantly and almost exclusively in astrocytes of the CNS. We are studying transcriptional regulation of the GFAP gene to gain insight into astrocyte function and also to develop an astrocyte-specific expression system for manipulating brain physiology. In this work, we have produced transgenic mice carrying the bacterial lacZ reporter gene linked to a 2.2 kilobase 5'-flanking sequence derived from the human GFAP gene that previously was shown to direct astrocyte-specific transcription in cultured cells. We report that this promoter directs expression to astrocytes in the CNS. In addition, the upregulation of GFAP gene activity that follows injury to the brain was mimicked by the transgene. One of the transgenes was found to be X-linked and appeared to undergo the usual random inactivation that achieves gene dosage compensation in females. The brains of hemizygous females stained uniformly rather than displaying mosaic patches, indicating that astrocytes intermingle following their formation. The specific expression of the GFAP-lacZ transgene means that it is now possible to target expression of other heterologous genes to astrocytes in vivo, and to study the mechanisms for reactive gliosis at the DNA level.

Design of a scanning ellipsometer by synchronous rotation of the polarizer and analyzer

We have designed and constructed a new type of spectroscopic ellipsometer to study the optical properties of materials in the 3500-8000-Å wavelength range. In the system, the analyzer and polarizer are driven 10(4) steps/revolution by two stepping motors that have hollow shafts and rotate synchronously with a speed ratio of 2:1, i.e., A = 2P. Both the polarizer and analyzer are mounted directly on the shafts to avoid mechanical transmission and vibration problems entirely and make the system simple and reliable. An additional source polarizer was placed in the optical path to reduce the slight polarization effects of the light source. The light intensity finally received by the detector contained five components, one dc and four ac, with frequencies of ω(0), 2ω(0), 3ω(0), and 4ω(0), respectively. One can independently obtain the ellipsometric parameters of ψ and Δ as well as the optical constants by calculating any one of the two sets of ac signals, with a raw data self-consistency of better than 0.5%. The incident angle, aligned precisely by a laser beam, was continuously variable through a mechanical system with a computercontrolled resolution of 0.001° or a visual resolution of 0.005°. The system operations, including data acquisition and reduction, high-voltage control of the photomultiplier, incident angle, as well as wavelength setting and scanning, were fully and automatically controlled by a 386-based microcomputer. We self-calibrated the system by adjusting and setting precisely the initial azimuthal angles of the prisms. The results from the measured spectra of the complex refractive index for a gold-film sample are presented, and we show that the data obtained at three different incident angles of 65°, 70°, and 75° are remarkably consistent with one another. A comparison of the two results from the ellipsometry and reflectance measurements is given. The experimental skills and system error reduction are discussed in detail.

Sphingosine-1-phosphate, a novel second messenger involved in cell growth regulation and signal transduction, affects growth and invasiveness of human breast cancer cells

This review will focus on the role of sphingosine and its phosphorylated derivative sphingosine-1-phosphate (SPP) in cell growth regulation and signal transduction. We will show that many of the effects attributed to sphingosine in quiescent Swiss 3T3 fibroblasts are mediated via its conversion to SPP. We propose that SPP has appropriate properties to function as an intracellular second messenger based on the following: it elicits diverse cellular responses; it is rapidly produced from sphingosine by a specific kinase and rapidly degraded by a specific lyase; its concentration is low in quiescent cells but increases rapidly and transiently in response to the growth factors, fetal calf serum (FCS) and platelet derived growth factor (PDGF); it releases Ca2+ from internal sources in an InsP3-independent manner; and finally, it may link sphingolipid signaling pathways to cellular ras-mediated signaling pathways by elevating phosphatidic acid levels. The effects of this novel second messenger on growth, differentiation and invasion of human breast cancer cells will be discussed.

The crystallographic structure of a human dihydropteridine reductase NADH binary complex expressed in Escherichia coli by a cDNA constructed from its rat homologue

A human dihydropteridine reductase (EC 1.6.99.10) has been created from a rat cDNA clone by a single five-oligonucleotide mutagenesis reaction and expressed in good yield in Escherichia coli. The enzyme has been purified to homogeneity, and kinetic identity to the naturally occurring enzyme has been proven. Crystallization has also been achieved, and the crystal structure was solved using 2.5 A data that was refined to an R value of 16.9%. The structure described in this report represents the first complete structural characterization of this important human enzyme.

(Pro)collagenase (matrix metalloproteinase-1) is present in rodent osteoclasts and in the underlying bone-resorbing compartment

Osteoclasts resorb the extracellular matrix of bone by secreting enzymes and acid into a sealed-off compartment that they form upon attachment to the bone surface. Although the lysosomal cysteine proteinases can degrade collagen after the demineralization of bone at low pH, several lines of evidence suggest that collagenase (matrix metalloproteinase-1, EC 3.4.24.7) may also be involved in this process. The question of whether collagenase is present in the osteoclast and/or in the bone-resorbing compartment has however not been resolved. We have prepared an anti-mouse collagenase antiserum and affinity-purified an IgG fraction that specifically immunoblots and immunoprecipitates (pro)collagenase. Using these antibodies, we demonstrate by immunolocalization the presence of (pro)collagenase both in the osteoclasts and in the extracellular subosteoclastic bone-resorbing compartment. These specific localizations were observed not only in mice but also in rat and rabbit osteoclasts and using not only the antibody we have prepared but also antibodies raised in other laboratories against rat (Jeffrey et al., J. Cell. Physiol. 143, 396–403, 1990) and rabbit (Brinckerhoff et al., J. Biol. Chem. 265, 22262–22269, 1990) collagenase. Intracellular collagenase was observed in the osteoclasts whether the cells were plated on bone or cultured on glass coverslips. It is proposed that osteoclastic collagenase is secreted in the resorbing compartment where it may cooperate with the lysosomal cysteine proteinases in the degradation of the collagen component of the matrix during the resorption of bone.

Possibility of signal transduction through microfilaments below the membrane following ligand-receptor interaction

In this paper, we describe the changes of microfilament assembly and 3H-TdR incorporation in mouse ascites liver cancer cells under the action of concanavalin A (ConA) and laminin (LN). We have also studied the variation of 3H-TdR incorporation induced by destroying microfilaments with cytochalasin B (CB) following ConA and LN binding with their membrane receptors. It was found that ConA and LN interactions with their membrane receptors could induce the assembly of microfilaments below the membrane and promote DNA synthesis in these cells, but this effect was inhibited when microfilaments were destroyed by CB treatment. These results suggest that microfilaments might play a role in transferring signals from the membrane to the nucleus.

Myelin protein zero gene mutated in Charcot-Marie-tooth type 1B patients

Autosomal dominant of Charcot-Marie-Tooth disease (CMT), whose gene is type 1B (CMT1B), has slow nerve conduction with demyelinated Schwann cells. In this study the abundant peripheral myelin protein zero (MPZ) gene, MPZ, was mapped 130 kb centromeric to the Fc receptor immunoglobulin gene cluster in band 1q22, and a major MPZ point mutation was found to cosegregate with CMT1B in one large CMT1B family. The MPZ point mutation in 18 of 18 related CMT1B pedigree 1 patients converts a positively charged lysine in codon 96 to a negatively charged glutamate. The same MPZ locus cosegregates with the CMT1B disease gene in a second CMT1B family [total multipoint logarithm of odds (lod) = 11.4 at theta = 0.00] with a splice junction mutation. Both mutations occur in MPZ protein regions otherwise conserved identically in human, rat, and cow since these species diverged 100 million years ago. MPZ protein, expressed exclusively in myelinated peripheral nerve Schwann cells, constitutes > 50% of myelin protein. These mutations are anticipated to disrupt homophilic MPZ binding and result in CMT1B peripheral nerve demyelination.

Virus-mediated induction of interferon A gene requires cooperation between multiple binding factors in the interferon alpha promoter region

Transcriptional activation of interferon A (IFNA) gene in virus-infected cells is controlled by a 35-nucleotide inducible element that is cell type specific. Within this region, two elements, alpha F1 and IRF-1 binding sites, were shown by mutation analysis to play a crucial role in the expression of inducible element. In this study, we have analyzed the binding of nuclear proteins to the alpha F1 sequence and have shown that the induction is associated with the formation of a novel complex alpha F1/B, which contains at least two DNA binding proteins of 68 and 96 kDa. In contrast, no binding of the purified interferon regulatory factor 1 (IRF-1) either to the alpha F1 or IRF-1 binding sites could be detected in vitro. However, the oligonucleotides corresponding to alpha F1 or IRF-1 binding sites competed efficiently for the induction of IFNA4 promoter region in a transient transfection assay. We suggest that the induction of IFNA promoter region requires cooperation between alpha F1 binding proteins and IRF-1. Interestingly, our data also show that the inability of IFNA6 promoter to be expressed in infected L-cells may be a result of a viral-induced repressor, which could act by binding and inactivating alpha F1 or by competing for the IRF-1 binding site. These results suggest that cell-specific expression of IFNA genes results from core-cruitment of trans-acting factors that bind to alpha F1 and the IRF-1 binding site with the cell-specific virus-induced activator or repressor.

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A by multicolor in situ hybridization

Genetic heterogeneity within the most common genetic neuropathy, Charcot-Marie-Tooth disease (CMT) results in about 70% slow nerve conduction CMT1 and 30% normal nerve conduction CMT2. Autosomal dominant CMT1A on chromosome 17p11.2 represents about 70% of CMT1 cases and about 50% of all CMT cases. Three different size CMT1A duplications with variable flanking breakpoints were characterized by multicolor in situ hybridization and confirmed by pulsed field gel electrophoresis and quantitative polymerase chain reaction (PCR) amplification. These different size duplications result in the same CMT1A phenotype confirming that trisomy of a normal gene region results in CMT1A. The smallest duplication does not include the 409 locus used previously to screen for CMT1A duplications. Direct analysis of interphase nuclei from fetuses and at-risk patients by multicolor in situ hybridization to a commonly duplicated CMT1A probe is informative more often than polymorphic PCR analysis, faster than pulsed field gel electrophoresis (PFGE), and faster, more informative, and more reliable than restriction enzyme analysis. CMT1B restriction enzyme analysis of CMT pedigrees without CMT1A is expected to diagnose another 8% of at-risk CMT1 patients (total: 78%).

Analysis of a segment of the human glial fibrillary acidic protein gene that directs astrocyte-specific transcription

To understand astrocyte-specific transcription, we have been studying the human gfa gene. This gene encodes glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed primarily in astrocytes. A survey of the gfa 5' flanking region showed it to contain several segments that contribute to expression of a chloramphenicol acetyltransferase reporter gene in transfected cells. The most active of these was the 124-bp B region, which spans bp -1612 to -1489. We have now used site-directed mutagenesis to analyze this region in greater detail, and show that the B region itself contains several important elements. The most crucial of these is a consensus AP-1 sequence, the binding site for the Fos and Jun families of transcription factors. The presence of members of both these families in the glial fibrillary acidic protein-expressing U251 cell line used for our transfection studies was verified by gel mobility-shift experiments. This is the first demonstration of the functioning of a specific transcription factor site for astrocytes, and provides a focus for future studies of glial fibrillary acidic protein regulation during development and reactive gliosis.

The effect of laminin on molecular motion in the cell membrane and on cell motility

We have studied the variation of lateral diffusion of proteins in the cell membrane, of membrane lipid fluidity and of the electrophoretic motility (EPM) of macrophages after treatment with extrinsic laminin. The results showed that the lateral diffusion coefficient D value of membrane proteins, the fluidity of membrane lipids and the EPM of macrophages were decreased after laminin had bound to its membrane receptor on the macrophages. These results are important for developing an understanding of the early reaction of plasma membranes and cells in the presence of laminin.

Crystallization of a deletion mutant of the R-subunit of cAMP dependent protein kinase

A single deletion (delta 1 to 91) mutant of the regulatory subunit of the cAMP dependent protein kinase was crystallized. The crystals are hexagonal P6(1)22 (P6(5)22) with a = b = 88.7 A and c = 179.9 A. The crystals diffract to 3 A resolution. There is one molecule per asymmetric unit.

Cerebral amino acid, norepinephrine and nitric oxide metabolism in CNS oxygen toxicity

CNS oxygen (O2) toxicity is complex, and the etiology of its most severe manifestation, O2 convulsions, is yet to be determined. A role for depletion of the brain GABA pool has been proposed, although recent data have implicated production of reactive O2 species, e.g. H2O2, in this process. We hypothesized that the production of H2O2 and NH3 produced by monoamine oxidase (MAO) would lead to depletion of GABA and production of nitric oxide (NO.) respectively, and thereby enhance CNS O2 toxicity. In this study, rats treated with an MAO inhibitor (pargyline) or a nitric oxide synthase inhibitor (LNNA) were protected against O2-induced convulsions. Selected cerebral amino acids including arginine were measured in control and O2 treated rats (6 ATA, 20 min) with or without drug pretreatment. After O2 exposure, the cerebral pools of glutamate, aspartate, and GABA decreased significantly while glutamine content increased relative to control (P < 0.05). After treatment with either enzyme inhibitor, glutamine, glutamate and aspartate concentrations were maintained near control levels. Remarkably, GABA depletion by O2 was not prevented despite protection from seizures by both pargyline and LNNA. The NO. precursor, arginine, was increased significantly in the brain by toxic O2 exposure, but both pargyline and LNNA inhibited this effect. Simultaneous norepinephrine measurements indicated that its storage substantially decreased during hyperoxia (P < 0.05), but this effect too was blocked by either pargyline or LNNA. These data indicate that protection against O2 by these inhibitors is not related to preservation of the GABA pool. More importantly, O2 dependent norepinephrine metabolism and NO. synthesis appear to be interactive during CNS O2 toxicity.

Exclusion of linkage between schizophrenia and the D2 dopamine receptor gene region of chromosome 11q in 112 Irish multiplex families

A leading theory hypothesizes that schizophrenia arises from dysregulation of the dopamine system in certain brain regions. As this dysregulation could arise from abnormal expression of D2 dopamine receptors, the D2 receptor gene (DRD2) on chromosome 11q is a candidate locus for schizophrenia. We tested whether allelic variation at DRD2 and five surrounding loci cosegregated with schizophrenia in 112 small- to moderate-size Irish families containing two or more members affected with schizophrenia or schizoaffective disorder, defined by DSM-III-R. Evidence of linkage was assessed using varying definitions of illness and modes of transmission. Assuming genetic homogeneity, linkage between schizophrenia and large regions of 11q around DRD2 could be strongly excluded. Assuming genetic heterogeneity, variation at the DRD2 locus could be rejected as a major risk factor for schizophrenia in more than 50% of these families for all models tested and in as few as 25% of the families for certain models. The DRD2 linkage in fewer than 25% of these families could not be excluded under any of the models tested. Our results suggest that the major component of genetic susceptibility to schizophrenia is not due to allelic variation at the DRD2 locus or other genes in the surrounding chromosomal region.

Molecular characterization of human prorenin isoelectric forms

OBJECTIVE

Mammalian renins and prorenins can be fractionated by isoelectric focusing into multiple species, the individual production and decay rates of which vary with certain physiological and pharmacological stimuli. The relative abundance of renin isoelectric species varies in certain pathological states, and the individual species have been reported to differ in their biological function. The present study was undertaken to clarify further the biochemical basis for isoelectric heterogeneity in human renin.

DESIGN

Previous data have suggested that differences in glycosylation contribute to isoelectric heterogeneity in human renin. To determine whether glycosylation was solely responsible for the observed isoelectric heterogeneity, the isoelectric focusing patterns of either native or non-glycosylated human prorenin were compared. The specific activities of the three most abundant isoelectric species of human prorenin were also compared.

METHODS

Tissue culture supernatants from transfected cells expressing either native recombinant human prorenin or human prorenin in which both glycosylation sites were eliminated were fractionated by isoelectric focusing. The expressed prorenins were detected in various fractions by trypsin activation and the angiotensin I generation assay. Specific activities of the various prorenins were estimated by direct comparison of immunoprecipitable radiolabeled prorenin and trypsin-activatable renin activity in the three most abundant fractions.

RESULTS

Native human recombinant prorenin was fractionated into at least five isoelectric species, whereas non-glycosylated human recombinant prorenin migrated as a single isoelectric species, the migration of which was unaffected by forskolin treatment. There was a direct correlation between immunoprecipitable and enzymatically determined prorenin in the three major isoelectric species of native prorenin.

CONCLUSIONS

The results suggest that isoelectric heterogeneity of human renin is due solely to differential glycosylation of the protein. The proposed different biological functions of the various isoelectric forms is not directly correlated with variations in their specific activities.

Biocompatibilities of organic solvents with Lactobacillus delbrueckii

In the search for biocompatible extractants for extractive fermentation of lactic acid, the effect of twelve organic solvents on the activity of L. delbrueckii were studied at different concentration levels. On this basis, the compatibilities of twelve solvents with L. delbrueckii were summarized into four classes: completely compatible, compatible at molecular level, partially compatible and non-compatible. The characteristics were described qualitatively for each class in terms of relative values between the solubility of organic solvent in water (Cs) and the toxicity of organic solvent, which is indicated by a newly defined concentration parameter (Cm). The classification was helpful for the selection of extractant in extractive fermentation.

Phosphofructokinase from white muscle of the rainbow trout, Oncorhynchus mykiss: purification and properties

Phosphofructokinase was purified and characterized from the white skeletal muscle of rainbow trout Oncorhynchus mykiss. Purification involved three steps: ion-exchange chromatography on hydroxyapatite and affinity chromatography on phosphocellulose and ATP-agarose. A final specific activity of 75 units per mg of protein at 22 degrees C and pH 7.2 with 40% recovery was obtained. The purified enzyme gave a single band on SDS-PAGE with a subunit molecular mass of 76.5 +/- 0.6 kDa. Based on gel filtration analysis, the active form of the enzyme was found to be composed of six identical subunits. A high isoelectric point (7.1) was found for this enzyme. Arrhenius plots of the enzyme activity showed a sharp transition at 15-16 degrees C. The pH optimum of the enzyme was 8.0-8.5 at physiological level of ATP and positive modulators shifted the optimum to lower pH values. Amino-acid analysis revealed a lower content of the aromatic residues Phe, Tyr and Trp and higher level of Ser residue than in the rabbit muscle enzyme.

Identification of regions in the rat serine dehydratase gene responsible for regulation by cyclic AMP alone and in the presence of glucocorticoids

Transcription of the rat serine dehydratase (SDH) gene is induced by glucagon, mediated by the action of cAMP. To identify the nucleotide sequences in the SDH gene responsible for this regulation, we constructed chimeric genes containing different portions of the 5' flanking region of the rat SDH gene fused to the structural sequence encoding the bacterial reporter enzyme, chloramphenicol acetyltransferase (CAT). The transcriptional activities of the fusion genes introduced into the rat hepatoma cell line 7AD-7 were assayed by measuring CAT activity in the cell lysates. Chlorophenylthio-cyclic AMP (CPT-cAMP), a potent protein kinase A activating agent, stimulated the expression of SDH-CAT fusion genes, and these inductions could be enhanced further by the addition of dexamethasone, although the glucocorticoid alone had no effect on CAT activity. Deletion analysis demonstrated that an 80 bp region located approximately 3.5 kb upstream from the transcription initiation site of the rat SDH gene was responsible for stimulation of transcription by CPT-cAMP, whereas the 120 bp region immediately upstream of the cAMP responsive element (CRE)-containing sequences is essential for the enhancement of CPT-cAMP induction by the glucocorticoid.

Application of automated DNA sizing technology for genotyping microsatellite loci

Highly polymorphic microsatellite loci offer great promise for gene mapping studies, but fulfillment of this potential will require substantial improvements in methods for accurate and efficient genotyping. Here, we report a genotyping method based on fluorescently labeled PCR primers and size characterization of PCR products using an automated DNA fragment analyzer. We capitalize on the availability of three distinct fluorescent dyes to label uniquely loci that overlap in size, and this innovation increases by threefold the number of loci that can be analyzed simultaneously. We label size standards with a fourth dye and combine these with the microsatellite PCR products in each gel lane. Computer programs provide very rapid and accurate sizing of microsatellite alleles and efficient data management. In addition, fluorescence signals are linear over a much greater range of intensity than conventional autoradiography. This facilitates multiplexing of loci (since signal intensities often vary greatly) and helps distinguish major peaks from artifacts, thereby improving genotyping accuracy.

Regulatory elements for the tissue-specific expression of the rat serine dehydratase-encoding gene

L-Serine dehydratase (SDH; EC 4.2.1.13), the key enzyme for serine utilization in the rat, is synthesized primarily in the liver. Cis-acting DNA elements required for liver-specific expression of the SDH gene were identified by two approaches: (1) transient expression assays in primary cultured rat hepatocytes, and in rat fibrosarcoma and normal rat kidney epithelial (NRK-52E) cell lines; and (2) in vitro transcription assays with nuclear extracts prepared from rat liver and spleen. Deletion analyses of the 5' flanking sequences of the gene have defined two functionally different regions: (a) a cell-type-specific promoter located between positions -62 and +10, which is sufficient for liver-specific expression; and (b) a distal promoter region between bp -133 and -63 containing positive cis-acting elements that regulate the promoter activity in a non-tissue-specific fashion. No other cis-acting elements essential for liver-specific expression were found in the region of -134 to 2.1 kb upstream relative to the cap site of SDH.

Differential effects of the 3',5'-cyclic adenosine monophosphate and protein kinase C pathways on the response of isolated rat osteoclasts to calcitonin

Calcitonin (CT) activates both the cAMP and the protein kinase C (PKC) pathways in the kidney cell line LLC-PK1. Although CT also activates cAMP in osteoclasts, its effects on PKC in this cell type are unknown. In order to determine whether the response of osteoclasts to CT also involves the PKC pathway, the effects of activators and inhibitors of PKC on bone resorption and cell surface area were analyzed in isolated rat osteoclasts. As expected, CT inhibited in a dose-dependent manner bone resorption by rat osteoclasts cultured for 24 h on devitalized bovine bone slices and this effect could be mimicked by cAMP. The inhibitory effect of CT could however also be mimicked by phorbol-12,13-dibutyrate (PDBu) and blocked by the PKC inhibitor sphingosine, as well as by the less specific inhibitors H7 and H8, none of which had detectable effects in the absence of CT. No changes in the number of attached osteoclasts were observed under any of these conditions. These results indicate that CT activates PKC in osteoclasts and that this activation, like the activation of cAMP-dependent protein kinase, leads to an inhibition of bone resorption. Quantitative time-lapse videomicroscopy showed that the CT-induced retraction of osteoclasts also involved activation of the PKC pathway and could therefore be induced by phorbol esters. In contrast, (Bu)2 cAMP (1-200 microM) failed to induce rapid cell retraction. It is concluded that, in osteoclasts, CT receptors are coupled to both the cAMP-dependent protein kinase and the PKC pathways. Although these two second messengers can have additive inhibitory effects on bone resorption, only activation of the PKC pathway induces rapid cell retraction. These two effects of calcitonin on osteoclasts are therefore independent and may be functionally unrelated.

Location and characterization of multiple glucocorticoid-responsive elements in the rat serine dehydratase gene

Transcription of the gene coding for serine dehydratase (SDH, EC 4.2.1.13) in the rat in vivo is dramatically increased by glucocorticoid hormones. To identify DNA elements mediating the glucocorticoid-regulated expression of the SDH gene, we transiently transfected 7AD-7 rat hepatoma cells with fusion genes consisting of various regions of the SDH 5' flanking sequence linked to the coding sequence of the gene for chloramphenicol acetyltransferase (CAT). Analysis of the CAT activities from these 5' deletion mutants identified three closely associated glucocorticoid-responsive elements (GREs), located more than 5 kb upstream relative to the cap site. Two distal GREs act synergistically to confer strong glucocorticoid inducibility to the gene, whereas the proximal GRE functions independently of the distal GREs and confers only a weak hormone response to the gene. The purified DNA-binding domain of rat glucocorticoid receptor binds to the sequence of each GRE as shown by footprinting experiments. However, only one of these sequences contains the TGTTCT consensus sequence reportedly associated with many other GREs.

Zaprionus tuberculatus: chromosome map and gene mapping by DNA in situ hybridization

The genus Drosophila has long been used as a model of karyotype evolution, demonstrating change by paracentric inversion and occasional centric fusion of an ancestral karyotype of five rod-shaped and one "dot" chromosome. This study shows, by mapping D. melanogaster probes hybridized to polytene chromosomes of Zaprionus tuberculatus, that this ancestral pattern extends beyond the genus Drosophila. A formal polytene chromosome map of Z. tuberculatus is presented.

Crystal structure of an actinidin-E-64 complex

E-64, 1-(L-trans-epoxysuccinylleucylamino)-4-guanidinobutane, is a potent and highly selective irreversible inhibitor of cysteine proteases. The crystal structure of a complex of actinidin and E-64 has been determined at 1.86-A resolution by using the difference Fourier method and refined to an R-factor of 14.5%. The electron density map clearly shows that the C2 atom of the E-64 epoxide ring is covalently bonded to the S atom of the active-site cysteine 25. The charged carboxyl group of E-64 forms four H-bonds with the protein and thus may play an important role in favorably positioning the inhibitor molecule for nucleophilic attack by the active-site thiolate anion. The interaction features between E-64 and actinidin are very similar to those seen in the papain-E-64 complex; however, the amino-4-guanidinobutane group orients differently. The crystals of the actinidin-E-64 complex diffracted much better than the papain-E-64 complex, and consequently the present study provides more precise geometrical information on the binding of the inhibitor. Moreover, this study provides yet another confirmation that the binding of E-64 is at the S subsites and not at the S' subsites as has been previously proposed. The original actinidin structure has been revised using the new cDNA sequence information.

Atrial natriuretic factor and renin synthesized in cultured aortic smooth muscle cells of rats

This study was designed to determine whether or not atrial natriuretic factor (ANF) is present in the vascular walls and to observe the differences in ANF between control (WKY) and stroke-prone spontaneously hypertensive rats (SHRsp). It was found that ANF is indeed present in the vascular wall of the distal aorta. HPLC analysis of the extracts from cultured aortic smooth muscle cells (ASMC) and medium revealed that intracellular ANF was mainly in the form of ANF(1-126), at levels of 0.82 +/- 0.03 (SHRsp) and 1.04 +/- 0.10 ng/10(6) cells (WKY), while the major form in the medium was ANF(99-126), at levels of 0.40 +/- 0.06 and 0.60 +/- 0.06 ng/10(6) cells, respectively. Both forms were present in smaller amounts in SHRsp than in WKY rats. On the contrary, both renin activity and angiotensin I concentrations in SHRsp cells were significantly higher than those in the WKY controls. In addition, immunocytochemistry showed positive ANF staining in cultured ASMC of both strains. The results suggest that ANF can be synthesized and secreted by cultured ASMC from rats.

Hormonal regulation of serine dehydratase gene expression in liver and kidney of the adrenalectomized rat

We have previously demonstrated that glucagon but not dexamethasone could induce serine dehydratase (SDH: EC.4.2.1.13) in liver, and either glucagon or dexamethasone could induce the enzyme in kidney of normal rats. The mechanism(s) of the hormonal regulation of SDH gene expression in liver and kidney was further studied using adrenalectomized rats. Simultaneous administration of glucagon and dexamethasone induced the activity, rate of SDH synthesis, and accumulation of SDH mRNA in both liver and kidney of the rat. The increased SDH activity was reflected by changes in the amount of enzyme protein and in the rate of SDH protein synthesis, both parameters closely paralleling the changes in the levels of SDH mRNA. The rates of transcription of the SDH gene as measured in run-on experiments with isolated nuclei were also increased by the administration of these hormones. These results indicate that the expression of the SDH gene was regulated primarily at the transcriptional level under these conditions. When glucagon or dexamethasone was injected separately into adrenalectomized rats, significant increases in the levels of SDH mRNA and the rate of SDH gene transcription were observed in liver. Although glucagon was more effective than dexamethasone, both hormones were required for the maximal induction of SDH gene transcription in liver. In contrast, dexamethasone alone effectively increased the rate of SDH gene transcription in kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Nutritional regulation and tissue-specific expression of the serine dehydratase gene in rat

The mechanism of dietary regulation and tissue-specific expression of the serine dehydratase gene in rat has been studied. The hepatic serine dehydratase activity and its mRNA showed a parallel increase with increasing protein content in the diet. However, when rats that had been maintained on a high protein diet were fed a protein-free diet, the mRNA level rapidly decreased to 0.5 in 3 h, whereas the enzyme activity gradually fell to a low level over a period of 5 days. With animals maintained on a high protein diet or on a protein-free diet, we examined the sites hypersensitive to DNase I in the 5'-flanking region of serine dehydratase gene in the liver chromatins. A series of DNase I-hypersensitive sites were located within 10.5 kilobase pairs upstream of the transcription start site. The DNA regions at -3050 and -3180 (region II) and -3600 to -3850 (region III) were more susceptible to the nuclease in the expressing than in the nonexpressing liver. A reverse situation obtained at -100 (region I). Kidney contained serine dehydratase mRNA at a level of 5% of liver as determined by Northern blotting. The kidney chromatin was found to be susceptible to DNase I only at region I. No conspicuous DNase I-hypersensitive sites were observed in the relevant regions of chromatins from brain and lung, in which serine dehydratase mRNA was scarcely transcribed. These results suggest that nutritional control and tissue-specific expression of the serine dehydratase gene is closely associated with the alteration of DNase I hypersensitivity at specific sites of the 5'-flanking region of the gene.

Effects of glucose, insulin, and cAMP on transcription of the serine dehydratase gene in rat liver

Starvation and diabetes both caused a dramatic induction of hepatic L-serine dehydratase (SDH) (EC 4.2.1.13) in rats. Increases in the activity of the enzyme which had been demonstrated in several previous studies were found to be associated with increases in the amount of SDH protein and its mRNA in our studies reported herein. Nuclear run-on experiments with isolated liver nuclei demonstrated that the increases in SDH activity were mainly the result of increases in the rate of SDH gene transcription. Refeeding of glucose to starved rats or the administration of insulin to diabetic rats caused a marked reduction in the amount of SDH mRNA. The rates of transcription as measured in isolated nuclei were reduced to uninduced levels within 30 min of either treatment. Following the administration of Bt2-cAMP, the transcription rates of the SDH gene returned to the original induced rates within 40 min both in glucose-refed rats and in diabetic rats administered insulin. The results of these experiments indicate that the induction of SDH in rat liver in vivo is controlled predominantly at the level of gene transcription by the reciprocal action of cAMP and insulin.

[Antihypertensive activity of monoclonal antibody to angiotensin II]

The antihypertensive effect of monoclonal antibody to angiotensin II (MAAII) was studied in renovascular hypertensive (RVH) rats. We found that MAAII could antagonize the pressor effect of exogenous angiotensin II but not of vasopressin in vivo. Five minutes after the administration of MAAII (15 mg/kg, i.v.), plasma angiotensin II could not be detected by radioimmunoassay and the mean blood pressure (MBP) decreased in RVH rats more than in normotensive rats (delta MBP: -5.33 +/- 0.12 and -1.17 +/- 0.29 kPa, respectively, P less than 0.01). The hypotensive effect of captopril was markedly inhibited by prior administration of MAAII, while that of nitroprusside and phentolamine was not. The results suggest that the antihypertensive effect of MAAII is mainly due to its specific binding to circulating angiotensin II.

Altered phosphorylation of tau protein in heat-shocked rats and patients with Alzheimer disease

Six hours after heat shocking 2- to 3-month-old male and female Sprague-Dawley rats at 42 degrees C for 15 min, we analyzed tau protein immunoreactivity in SDS extracts of cerebrums and peripheral nerves by using immunoblot analysis and immunohistochemistry with the anti-tau monoclonal antibody Tau-1, which recognizes a phosphate-dependent non-phosphorylated epitope, and with 125I-labeled protein A. In the cerebral extracts, we found altered phosphorylation of tau in heat-shocked females, characterized by a marked reduction in the amount of nonphosphorylated tau, a doubling of the ratio of total (phosphorylated plus nonphosphorylated) tau to nonphosphorylated tau, and the appearance of the slowest moving phosphorylated tau polypeptide (68 kDa). Similar, but milder, changes were observed in male rats. These changes progressively increased in females from 3 to 6 h after heat shocking. In contrast, both phosphorylated tau and nonphosphorylated tau were reduced in peripheral nerves after heat shocking. In immunoblots of SDS extracts from Alzheimer disease-affected brain, the two slowest moving phosphorylated tau polypeptides (62 kDa and 66 kDa, respectively) were detected by Tau-1 after dephosphorylation and by Tau-2 (an anti-tau-monoclonal antibody that recognizes a phosphate-independent epitope) without prior dephosphorylation only in regions that contained tau immunoreactivity in histologic preparations. In addition, quantitative immunoblot analysis of cortex and the underlying white matter with Tau-1 and 125I-labeled protein A showed that the amount of phosphorylated tau progressively increased in the Alzheimer disease-affected cerebral cortex, while concurrently a proportionally lesser amount of tau entered the white matter axons. The similar findings for the rat heat-shock model and Alzheimer disease suggest that life stressors may play a role in the etiopathogenesis of Alzheimer disease.

Numerical technique and computational procedure for isotachophoresis

This paper presents a new numerical method for computation of solutions of prototypical equations of isotachophoresis. Numerical computation is complicated because the Poisson equation, which relates electrostatic potential to space charge density, contains a small parameter. This parameter is usually assumed to have the value of zero. Under this assumption the Poisson differential equation is replaced by an algebraic equation, which is often called the equation of electroneutrality, because it indeed states that the electrolyte is electrically neutral this assumption were not studied in the past. Here we propose an iterative procedure which allows for computation of solutions without the assumption of electroneutrality. The accuracy is controlled by a number of iterations and is limited by a computer round-off error only. The method is based on our previously published theory of existence and uniqueness of solutions of isotachophoretic equations. Details of the computational algorithm for prototypical equations of isotachophoresis are given. A numerical example and comparison with previously published data are also provided.

Rat serine dehydratase gene codes for two species of mRNA of which only one is translated into serine dehydratase

With the previously obtained rat liver serine dehydratase cDNA (SDH2; Ogawa, H., Miller, D.A., Dunn, T., Su, Y., Burcham, J. M., Peraino, C., Fujioka M., Babcock, K., and Pitot, H. C. (1988) Proc. Natl. Acad. Sci. U.S. A. 85, 5809-5813) as a probe, we isolated a different species of cDNA (SDH3) from the same cDNA library from which SDH2 was obtained. Nucleotide sequence analysis has indicated that SDH3 has an open reading frame which encodes 327 amino acid residues and which is identical to that of the cDNA obtained by Noda et al. (Noda, C., Ito, K., Nakamura, T., and Ichihara, A., (1988) FEBS Lett. 234, 331-335). Primer extension analysis and RNase protection mapping clarified that the SDH3 mRNA was the major mRNA for serine dehydratase in the liver, and its transcription begins with a T residue located 23 nucleotides down-stream of a TATA-like box. In vitro transcription/translation experiment demonstrated that SDH3 encoded a polypeptide of 35 kDa, a size in agreement with that of the subunit of the purified protein, whereas SDH2, despite having a size larger than SDH3, produced a peptide of much smaller size that reacted with anti-serine dehydratase IgG. SDH2 was found to have a stop codon early in the sequence and is predicted to encode a polypeptide of 8.9 kDa. Also, SDH2 has a 5'-noncoding sequence different from that of SDH3. These results indicate that alternative transcription initiation and different modes of splicing of the primary transcripts of rat serine dehydratase gene result in the formation of two species of mRNA, of which only one is translated into the mature serine dehydratase protein.

Regulation of the expression of the serine dehydratase gene in the kidney and liver of the rat

Serine dehydratase was induced in the kidneys of normal rats by the administration of either glucagon or dexamethasone. The increase in enzyme activity was associated with an increase in both enzyme protein and its mRNA, which were determined respectively by Western blot and RNA blot analysis. No apparent differences were observed between kidney and liver in the molecular weights of serine dehydratase proteins and the sizes of their mRNAs. Although kidney serine dehydratase was dramatically induced by either glucagon or dexamethasone, the liver enzyme was induced by glucagon but not by dexamethasone alone in the intact rat. On the other hand, liver serine dehydratase was induced in starvation, diabetes mellitus, and a high-protein diet. The kidney enzyme could not be induced under any of these conditions.

[A survey of resources of Chinese medicinal materials in Dingxi District of Gansu Province]

A survey is given of the resources of Chinese medicinal materials in Dingxi district of Gansu province. Rational suggestions have been made with regard to the development and utilization of these resources.