Eukaryotic-like gephyrin and cognate membrane receptor coordinate corynebacterial cell division and polar elongation

The order Corynebacteriales includes major industrial and pathogenic actinobacteria such as Corynebacterium glutamicum or Mycobacterium tuberculosis . Their elaborate multi-layered cell wall, composed primarily of the mycolyl-arabinogalactan-peptidoglycan complex, and their polar growth mode impose a stringent coordination between the septal divisome, organized around the tubulin-like protein FtsZ, and the polar elongasome, assembled around the tropomyosin-like protein Wag31. Here, we report the identification of two new divisome members, a gephyrin-like repurposed molybdotransferase (GLP) and its membrane receptor (GLPR). We show that the interplay between the GLPR/GLP module, FtsZ and Wag31 is crucial for orchestrating cell cycle progression. Our results provide a detailed molecular understanding of the crosstalk between two essential machineries, the divisome and elongasome, and reveal that Corynebacteriales have evolved a protein scaffold to control cell division and morphogenesis similar to the gephyrin/GlyR system that in higher eukaryotes mediates synaptic signaling through network organization of membrane receptors and the microtubule cytoskeleton.

Simulation of arsenic retention in constructed wetlands

The software RCB-arsenic was developed previously to simulate the metalloid behavior in a constructed wetland (CW). The model simulates water flow and reactive transport by contemplating the major processes of arsenic (As) retention inside of CW. The objective of this study was to validate the RCB-arsenic model by simulating the behavior of horizontal flow CW for As removal from water. The model validation was made using data from a 122-day experiment. Two CWs prototypes were used: one planted with Eleocharis macrostachya (CW_planted) and another one unplanted (CW_unplanted) as a control. The prototypes were fed with synthetic water prepared using well water and sodium arsenite (NaAsO₂). In the RCB-arsenic model, a CW prototype was represented using a 2D mesh sized in accordance with the experiment. For simulation of As retention in CW, data addition was established in two stages that considered the mechanisms in the system: (1) aqueous complexation, precipitation/dissolution, and adsorption on granular media and (2) retention by plants: uptake (absorption) and rhizofiltration (adsorption). Simulation of As outlet (μg/L) in stage_1 was compared with CW_unplanted; the experimental mean was 40.79 ± 7.76 and the simulated 39.96 ± 6.32. As concentration (μg/L) in stage_2 was compared with CW_planted, the experimental mean was 9.34 ± 4.80 and the simulated 5.14 ± 0.72. The mass-balance simulation and experiment at 122 days of operation had a similar As retention rate (94 and 91%). The calibrated model RCB-arsenic adequately simulated the As retention in a CW; therefore, it constitutes a powerful tool of design.

MTHFR C677T, FII G20210A, FV Leiden G1691A, NOS3 Intron 4 Vntr, and APOE ε4 Gene Polymorphisms are Not Associated with Spontaneous Cervical Artery Dissection

Aims

The pathogenesis of spontaneous cervical artery dissection remains unknown. We examined the association between different polymorphisms frequently found in young patients with cryptogenic stroke [methylenetetrahydrofolate reductase ( MTHFR) C677T, factor II (prothrombin) G20210A, factor V G1691A (Leiden), nitric oxide synthase 3 ( NOS3) intron 4 VNTR, and apolipoprotein E ( APOE) ε4 gene] in patients with a cerebral infarct caused by spontaneous cervical artery dissection.

Methods

Forty-eight patients (27 males) and 96 matching control subjects were recruited. Clinical history, including cardiovascular risk factors, was assessed in all subjects. Genotypes were determined by a polymerase chain reaction with and without a restriction fragment length polymorphism. The genotypes and allele frequencies of the five genetic variants studied were compared between spontaneous cervical artery dissection cases and controls. We also incorporated our data into a meta-analysis of the MTHFR/C677T variant.

Results

Of 48 patients with spontaneous cervical artery dissection (28 vertebral and 20 carotid), the mean age of the patients was 36·6 ± SD 9·9 years. There were no significant associations between the alleles of the five genetic polymorphisms studied and spontaneous cervical artery dissection. In the meta-analysis of the MTHFR/C677T variant, a total of 564 individuals (231 cases and 333 controls) were analysed; no significant association was observed. Conclusions The results from this exploratory case-control study show the lack of an association between MTHFR, factor II G20210A, factor V G1691A, NOS3, intron 4 VNTR, and APOE ε4 gene polymorphisms and the development of spontaneous cervical artery dissection. Our findings contribute towards a better understanding of the genetic risk factors associated with spontaneous cervical artery dissection.

[Brain vasculitis associated with drugs]

INTRODUCTION

Vasculitis or angiitis is the term used to define the inflammation of the vessels, either blood or lymphatic, which causes may be primary related to immunological disorders, or secondary, with great variety of causal factors.

CASE REPORT

We present a very uncommon case of a 36 year old man with brain vasculitis associated with drugs with very peculiar characteristics in the imaging studies and with definite diagnosis through histopathology obtained by biopsy, which differs from the few reports in the literature until our days.

CONCLUSIONS

Our report is an uncommon case of cerebral vasculitis whose clinical features were confusing with impressing neuroimaging studies that showed possible lesions due to vasculitis that was confirmed through a cerebral biopsy and considering that the immunological tests were negative for a primary vasculitic process, we concluded that it was a vasculitis secondary to drug abuse which represents a special interest in view of the few existing reports in literature with definite diagnostic methods, such as cerebral biopsy or autopsy.

Treatment of a low concentration industrial chemicals mixture in an UASB reactor

A wastewater containing a mixture of methanol, isopropyl alcohol, ethylene glycol, acetic anhydride, methyl, ethyl and isopropyl acetate, acrylic acid, butyl and methyl acrylate, o, m and p-xylene and styrene was fed to an UASB reactor. Isopropanol addition diminished the removal efficiency to 60% and required a long adaptation time for its total mineralization. When acrylic acid was added to the mixture, the removal dropped to 83% and recovered after 40 days. As for the rest of the substrates, p-m-o-xylene addition had no effect on reactor performance, although in batch assays it showed low mineralization. Also the effect of volumetric organic load on removal efficiency was followed up. After diminishing the HRT to 4 and 3 h yielding 4.8 and 6.5 gCOD L(-1) d(-1), removal efficiencies decreased to 79 and 74% respectively.

Oncocalyxone A from Auxemma oncocalyx lacks genotoxic activity in phytohemagglutinin-stimulated lymphocytes

Inadequate doses or prolonged chemotherapy can be cytotoxic or genotoxic to cancer patients, increasing the risk for the development of a second cancer, particularly acute leukemia. The association between therapeutic and genotoxic properties of oncocalyxone A (Onco A), make cytotoxic tests (mitotic index and chromosomal aberrations) fundamental in the accompaniment of the effects of this active compound. Therefore, the aim of the present study was to determine the genotoxic action of Onco A in vitro, during different phases of the cell cycle, utilizing primary cultures of lymphocytes of healthy individuals. The results showed that Onco A is cytotoxic during the cell cycle phases G1, G1/S, and S, however, not in G2. Onco A did not demonstrate a genotoxic effect in any of the cell cycle phases at the concentration studied. It is concluded that during the period of exposure, this active substance inhibits DNA synthesis and consequently cell division. Therefore, the absence of such genotoxicity for Onco A in the tests performed in this study provides important information in regard to the therapeutic use of this agent. Further studies are necessary to better understand the molecular mechanism of action of Onco A.

High prevalence of human papillomavirus infection in Mexican males: comparative study of penile-urethral swabs and urine samples

BACKGROUND

Although extensive information has been gathered about the prevalence and determinants of human papillomavirus infection among women, little is known about the prevalence and natural history of this infection among males.

GOAL

To investigate the potential usefulness of urine specimens to assess the presence of genital human papillomavirus DNA infection.

STUDY DESIGN

The authors conducted a study of 120 healthy men from Cuernavaca, Mexico. A urine specimen and urethral and coronal sulcus swab samples were collected and tested for human papillomavirus using the GP5+/6+ polymerase chain reaction enzyme immunoassay method.

RESULTS

In 95% of the urethral-coronal sulcus samples, the beta-globin gene was detectable, indicating adequacy of the specimen for DNA amplification; however, only 14% of the urine specimens had detectable beta-globin. Removal of inhibitors by DNA purification in a sample of subjects produced beta-globin amplification, but no increase in human papillomavirus DNA positivity was detected. Human papillomavirus DNA was not detectable in penile-urethral swab samples in any of the subjects who reported not having engaged in sexual activity but was present in 43% of men who reported sexual activity, a strong indication of the sexual transmission of human papillomavirus.

CONCLUSIONS

Human papillomavirus is a common sexually transmitted infection among Mexican males, and urine sample specimens cannot adequately detect the presence of this infection in males.

Shark cartilage as source of antiangiogenic compounds: from basic to clinical research

The discovery that angiogenesis is a key condition for the growth of a tumor beyond a millimeter or two, brings about a new approach in the treatment of tumors using drugs able to inhibit the formation of new blood vessels. Also, it has been realized that antiangiogenic drugs can be useful in the treatment of other pathological processes, now classified as angiogenesis-dependent diseases. Initially, cartilage was considered as a possible natural source of antiangiogenic compounds due to its known avascular nature. To date, a number of in vitro and in vivo studies have suggested the existence of antiangiogenic and antitumor compounds in bovine and shark cartilage. However, the potential usefulness of shark cartilage in the treatment of cancer and other angiogenesis-dependent diseases have not been totally accepted due to (i) unsatisfactory patient outcome in clinical trials that have used shark cartilage in cancer patients, (ii) the lack of data that correlates bioavailability with pharmacological effects using oral shark cartilage. Thus, the objective of this review is to describe the main basic and clinical investigations reported in the literature, in which the antiangiogenic and/or antitumor properties of shark cartilage or of its extracts were evaluated. Possible explanations for conflicting results are discussed as well.

A conserved MYB transcription factor involved in phosphate starvation signaling both in vascular plants and in unicellular algae

Plants have evolved a number of adaptive responses to cope with growth in conditions of limited phosphate (Pi) supply involving biochemical, metabolic, and developmental changes. We prepared an EMS-mutagenized M(2) population of an Arabidopsis thaliana transgenic line harboring a reporter gene specifically responsive to Pi starvation (AtIPS1::GUS), and screened for mutants altered in Pi starvation regulation. One of the mutants, phr1 (phosphate starvation response 1), displayed reduced response of AtIPS1::GUS to Pi starvation, and also had a broad range of Pi starvation responses impaired, including the responsiveness of various other Pi starvation-induced genes and metabolic responses, such as the increase in anthocyanin accumulation. PHR1 was positionally cloned and shown be related to the PHOSPHORUS STARVATION RESPONSE 1 (PSR1) gene from Chlamydomonas reinhardtii. A GFP::PHR1 protein fusion was localized in the nucleus independently of Pi status, as is the case for PSR1. PHR1 is expressed in Pi sufficient conditions and, in contrast to PSR1, is only weakly responsive to Pi starvation. PHR1, PSR1, and other members of the protein family share a MYB domain and a predicted coiled-coil (CC) domain, defining a subtype within the MYB superfamily, the MYB-CC family. Therefore, PHR1 was found to bind as a dimer to an imperfect palindromic sequence. PHR1-binding sequences are present in the promoter of Pi starvation-responsive structural genes, indicating that this protein acts downstream in the Pi starvation signaling pathway.

Demonstration of inhibitory effect of oral shark cartilage on basic fibroblast growth factor-induced angiogenesis in the rabbit cornea

Several angiogenic inhibitors have been obtained from shark cartilage, some of these are currently in clinical trials for assessment of safety and therapeutic efficacy in humans. Still, shark cartilage taken orally is commonly used in alternative and complimentary medicine for various ailments including serious diseases such as cancer. However, only few studies of oral shark cartilage have demonstrated pharmacological effects in experimental animals or patients, to indicate safe doses with sufficient bioavailability. In the present study we demonstrated the antiangiogenic properties of oral shark cartilage in the rabbit cornea model. Slow-release, polymethylmetacrylate pellets containing basic fibroblast growth factor (bFGF) were surgically implanted in the rabbit cornea to stimulate neovascularization scored by stereo microscopy. Powdered shark cartilage (PSC; commercial product) was tested orally along with a water-soluble fraction (WSF) of this cartilage product which was tested by local application. Animals were treated with oral dosages of 100 mg/kg PSC or 200 mg/kg thalidomide as positive control. Pellets containing WSF (50, 100 or 200 microg/pellet) or bFGF-inhibitor pentosan polysulfate were implanted adjacent to the bFGF pellet. Oral shark cartilage inhibited bFGF-induced angiogenesis, as did oral thalidomide, in this in vivo model. WSF and pentosan polysulfate was shown to block neovascularization in the cornea when applied locally. This study demonstrates that in the rabbit, oral shark cartilage appears to produce systemic levels of angiogenesis inhibitors that can exert their effect at the cornea.

Influence of cytokinins on the expression of phosphate starvation responsive genes in Arabidopsis

The increase in the ratio of root growth to shoot growth that occurs in response to phosphate (Pi) deprivation is paralleled by a decrease in cytokinin levels under the same conditions. However, the role of cytokinin in the rescue system for Pi starvation remains largely unknown. We have isolated a gene from Arabidopsis thaliana (AtIPS1) that is induced by Pi starvation, and studied the effect of cytokinin on its expression in response to Pi deprivation. AtIPS1 belongs to the TPSI1/Mt4 family, the members of which are specifically induced by Pi starvation, and the RNAs of which contain only short, non-conserved open reading frames. Pi deprivation induces AtIPS1 expression in all cells of wild-type plants, whereas in the pho1 mutant grown on Pi-rich soils, AtIPS1 expression in the root was delimited by the endodermis. This supports the view that pho1 is impaired in xylem loading of Pi, and that long-distance signals controlling the Pi starvation responses act via negative control. Exogenous cytokinins repress the expression of AtIPS1 and other Pi starvation-responsive genes in response to Pi deprivation. However, cytokinins did not repress the increase in root-hair number and length induced by Pi starvation, a response dependent on local Pi concentration rather than on whole-plant Pi status. Our results raise the possibility that cytokinins may be involved in the negative modulation of long-distance, systemically controlled Pi starvation responses, which are dependent on whole-plant Pi status.

Antiproliferative effects of compounds derived from plants of Northeast Brazil

Ten compounds derived from plants indigenous to Northeast Brazil were examined for antiproliferative effects on human cells in vitro. The effects of these phytochemicals on cell growth were determined by the MTT microtitre assay with 3-day continuous drug exposure. Three human cell lines were used: CEM leukaemia, SW1573 lung tumour and CCD922 normal skin fibroblasts. Four active compounds were found with IC(50) values less than 10 microg/mL in the two cancer cell lines. Oncocalyxones A and C, both 1,4-anthracenediones from Auxemma oncocalyx (Boraginaceae), showed cytotoxicity with mean IC(50) values of 0.8-2, 7-8 and 12-13 microg/mL against CEM, SW1573 and CCD922, respectively. One diterpene and one flavonoid, both from Egletes viscosa (Compositae), were also active. 12-Acetoxy-hawtriwaic acid lactone was cytotoxic with mean IC(50) values of 6, 10 and 10 microg/mL, respectively. 4,5-Dihydroxy-3,3,7, 8-tetramethoxy flavone (ternatin) was only growth-inhibitory with mean IC(50) values of 2, 1 and 10 microg/mL, respectively. These four most active compounds were examined further for their effects on DNA integrity and on DNA synthesis. All but ternatin caused substantial DNA damage and marked inhibition of 5-bromo-2'-deoxyuridine incorporation within 24 h. This study demonstrated the antiproliferative activity of four novel phytochemicals, three of which are DNA-reactive and inhibit DNA synthesis. Further studies are warranted to evaluate these compounds for antitumour potential.

Oncocalyxones A and C, 1,4-anthracenediones from Auxemma oncocalyx: comparison with anticancer 1,9-anthracenediones

Oncocalyxones A and C are 1,4-anthracenediones isolated from Auxemma oncocalyx (Boraginaceae) that have been shown to be cytotoxic to tumor cells in vitro. The present study compared the cytotoxicity of these compounds with that of two conventional anticancer agents doxorubicin and mitoxantrone, both 1,9-anthracenediones, in a panel of human tumor cell lines. The effect on cell growth was examined using an MTT microtiter assay in two leukemia lines, five solid tumor lines of different histological origin, and two multidrug-resistant sublines of a lung tumor line. The oncocalyxones showed much lower potency than the 1,9-anthracenediones, but were similarly more cytotoxic to leukemia cells compared to solid tumor lines. However, in the multidrug-resistant cells with 10 to 500 times decreased sensitivity to doxorubicin, the cytotoxicity of oncocalyxones A and C was only modestly reduced by about twofold, 1,4-Anthracenediones may be a promising novel class of chemotherapeutic agents effective against multidrug resistant tumors.

A type 5 acid phosphatase gene from Arabidopsis thaliana is induced by phosphate starvation and by some other types of phosphate mobilising/oxidative stress conditions

Low phosphorous availability, a common condition of many soils, is known to stimulate phosphatase activity in plants; however, the molecular details of this response remain mostly unknown. We purified and sequenced the N-terminal region of a phosphate starvation induced acid phosphatase (AtACP5) from Arabidopsis thaliana, and cloned its cDNA and the corresponding genomic DNA. The nucleotide sequence of the cDNA predicted that AtACP5 is synthesised as a 338 amino acid-long precursor with a signal peptide. AtACP5 was found to be related to known purple acid phosphatases, especially to mammal type 5 acid phosphatases. Other similarities with purple acid phosphatases, which contain a dinuclear metal centre, include the conservation of all residues involved in metal ligand binding and resistance to tartrate inhibition. In addition, AtACP5, like other type 5 acid phosphatases, displayed peroxidation activity. Northern hybridisation experiments, as well as in situ glucuronidase (GUS) activity assays on transgenic plants harbouring AtACP5:GUS translational fusions, showed that AtACP5 is not only responsive to phosphate starvation but also to ABA and salt stress. It is also expressed in senescent leaves and during oxidative stress induced by H2O2, but not by paraquat or salicylic acid. Given its bifunctionality, as it displays both phosphatase and peroxidation activity, we propose that AtACP5 could be involved in phosphate mobilisation and in the metabolism of reactive oxygen species in stressed or senescent parts of the plant.

Tamoxifen inhibits particulate-associated protein kinase C activity, and sensitises cultured human glioblastoma cells not to etoposide but to gamma-radiation and BCNU

We investigated the potential mechanisms of tamoxifen cytotoxicity in the U-373, U-138, and U-87 human glioblastoma cell lines, namely interference with protein kinase C (PKC) activity, the oestrogen receptor, and/or the production of transforming growth factor beta 1 (TGF-beta 1). We further examined the effects of tamoxifen on the cytotoxicity exerted by gamma-radiation, 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and etoposide in this cell line panel. Thus, the cells were treated for 4 days with tamoxifen, gamma-radiation, purified recombinant human TGF-beta 1 (rhTGF-beta 1), BCNU, or etoposide, either alone or at certain combinations. Cellular responses were evaluated with the sulphorhodamine B assay, as well as by multiple drug effect analysis, and related to PKC activities in particulate and cellular fractions; cellular oestrogen receptor contents; and the influence of rhTGF-beta 1 on cell growth. Tamoxifen inhibited cell proliferation as well as the phosphorylation capacity of the particulate, but not of the cytosolic fractions dose-dependently, at comparable kinetics, and at IC50 values of approximately 15 microM. At these concentrations, tamoxifen acted synergistically with gamma-radiation (4- to 6-fold) and additively with BCNU (approximately 2-fold), but did not affect etoposide cytotoxicity. The cells were negative to immunostaining for the oestrogen receptor, and rhRGF-beta 1 did not influence their growth up to 100 nm. Our data suggest that tamoxifen can sensitise cultured glioblastoma cells not to etoposide but to gamma-radiation and BCNU, possibly through interference with membrane PKC, supporting its evaluation in experimental protocols for primary malignant gliomas.

Decreased resistance to gemcitabine (2',2'-difluorodeoxycitidine) of cytosine arabinoside-resistant myeloblastic murine and rat leukemia cell lines: role of altered activity and substrate specificity of deoxycytidine kinase

We determined the potential activity of 2',2'-difluorodeoxycytidine (gemcitabine, dFdC) in 1-beta-D-arabinofuranosylcytidine (ara-C)-sensitive and-resistant leukemia cell lines. Both drugs are phosphorylated by deoxycytidine kinase (dCK); the triphosphates, dFdCTP and ara-CTP, respectively, are incorporated into DNA. In the murine leukemia cell line L1210, induction of resistance to ara-C resulted in the 2200-fold resistant subline L4A6. The Brown Norway rat myelocytic leukemia ara-C-sensitive cell line (BCLO) was >300-fold more sensitive to ara-C than its variant Bara-C. In L1210 cells, gemcitabine was 8-fold more active than ara-C; in L4A6, BCLO, and Bara-C cells, gemcitabine was 16-, 28-, and more than 3-fold more active than ara-C, respectively. A partial explanation for these differences may be the higher dCK activity in the parental cell lines L1210 and BCLO with gemcitabine compared to ara-C as a substrate. DCK activity was not or hardly detectable in the resistant L4A6 and Bara-C cell. In the rat leukemia cell lines, deoxycytidine (dCyd) phosphorylation activity showed an aberrant pattern, since the activity with dCyd was 1.5-fold higher in the Bara-C cell line compared with BCLO, possibly due to thymidine kinase 2. The wild-type L1210 cells accumulated at least 3-fold more ara-CTP and dFdCTP than the rat leukemia cell line BCLO. The ara-C-resistant variants L4A6 and Bara-C did not accumulate dFdCTP or ara-CTP. In conclusion, gemcitabine was more active than ara-C in all leukemia cell lines tested. The sensitivity of the wild-type cell lines correlates with the accumulation of dFdCTP and ara-CTP, but is independent of dCK. However, both resistant variants had decreased dCK activities, but were relatively more sensitive to dFdC than to ara-C.

Towards functional characterisation of the members of the R2R3-MYB gene family from Arabidopsis thaliana

Transcription factors containing a conserved DNA-binding domain similar to that of the proto-oncogene c-myb have been identified in nearly all eukaryotes. MYB-related proteins from plants generally contain two related helix-turn-helix motifs, the R2 and R3 repeats. It was estimated that Arabidopsis thaliana contains more than 100 R2R3-MYB genes. The few cases where functional data are available suggest an important role of these genes in the regulation of secondary metabolism, the control of cell shape, disease resistance, and hormone responses. To determine the full regulatory potential of this large family of regulatory genes, a systematic search for the function of all genes of this family was initiated. Sequence data for more than 90 different A. thaliana R2R3-MYB genes have been obtained. Sequence comparison revealed conserved amino acid motifs shared by subgroups of R2R3-MYB genes in addition to the characteristic DNA-binding domain. No significant clustering of the genes was detected, although they are not uniformly distributed throughout the A. thaliana genome.

More than 80R2R3-MYB regulatory genes in the genome of Arabidopsis thaliana

Transcription factors belonging to the R2R3-MYB family contain the related helix-turn-helix repeats R2 and R3. The authors isolated partial cDNA and/or genomic clones of 78 R2R3-MYB genes from Arabidopsis thaliana and found accessions corresponding to 31 Arabidopsis genes of this class in databanks, seven of which were not represented in the authors' collection. Therefore, there are at least 85, and probably more than 100, R2R3-MYB genes present in the Arabidopsis thaliana genome, representing the largest regulatory gene family currently known in plants. In contrast, no more than three R2R3-MYB genes have been reported in any organism from other phyla. DNA-binding studies showed that there are differences but also frequent overlaps in binding specificity among plant R2R3-MYB proteins, in line with the distinct but often related functions that are beginning to be recognized for these proteins. This large-sized gene family may contribute to the regulatory flexibility underlying the developmental and metabolic plasticity displayed by plants.

More than 80R2R3-MYB regulatory genes in the genome of Arabidopsis thaliana

Transcription factors belonging to the R2R3-MYB family contain the related helix-turn-helix repeats R2 and R3. The authors isolated partial cDNA and/or genomic clones of 78 R2R3-MYB genes from Arabidopsis thaliana and found accessions corresponding to 31 Arabidopsis genes of this class in databanks, seven of which were not represented in the authors' collection. Therefore, there are at least 85, and probably more than 100, R2R3-MYB genes present in the Arabidopsis thaliana genome, representing the largest regulatory gene family currently known in plants. In contrast, no more than three R2R3-MYB genes have been reported in any organism from other phyla. DNA-binding studies showed that there are differences but also frequent overlaps in binding specificity among plant R2R3-MYB proteins, in line with the distinct but often related functions that are beginning to be recognized for these proteins. This large-sized gene family may contribute to the regulatory flexibility underlying the developmental and metabolic plasticity displayed by plants.

Characterization of a gene encoding a DNA-binding protein that interacts in vitro with vascular specific cis elements of the phenylalanine ammonia-lyase promoter

A study of the expression of a bean phenylalanine ammonia-lyase (PAL) promoter/beta-glucuronidase gene fusion in transgenic tobacco has shown that the PAL2 promoter has a modular organization. Expression of the PAL2 promoter in the vascular system involves positive and negative regulatory cis elements. Among these elements is an AC-rich motif implicated in xylem expression and a suppressing cis element for phloem expression. Using radiolabelled complementary oligonucleotides bearing the AC-rich motif, a cDNA clone encoding a DNA-binding protein has been isolated from a tobacco lambda gt11 expression library. This factor, named AC-rich binding factor (ACBF), showed binding specificity to the AC-rich region. The specificity of ACBF for the AC-rich region was also shown using a gel retardation assay with an ACBF recombinant protein extract. The deduced amino acid sequence from ACBF contains a long repeat of glutamine residues as found in well characterized transcription factors. Interestingly, ACBF shared sequence similarity to conserved amino acid motifs found in RNA-binding proteins. Genomic gel blot analysis indicated the presence of a small gene family of sequences related to ACBF within the tobacco nuclear genome. Analysis of tobacco mRNA using the ACBF cDNA as probe showed that while ACBF mRNA was present in all tissues examined, the highest transcript accumulation occurred in stem tissues. The functional characteristics of the AC-rich sequence were examined in transgenic tobacco. A heptamer of the AC-rich sequence, in front of a minimal 35S promoter from cauliflower mosaic virus (-46 to +4), conferred specific expression in xylem.

Seroepidemiological study of hepatitis E virus in different population groups

In order to determine the seroprevalence of hepatitis E virus, 1,993 sera (453 from healthy pregnant women, 491 from Moroccan subjects, 492 from blood donors, 321 from children, and 236 from intravenous drug users) were studied. IgG was measured by enzyme immunoassay (EIA), and positive results were confirmed by Western blot. The EIA detected antibodies in 3.96% of the subjects (5.6% of the Moroccans and drug users and 1.8% of the children). Fifty-four percent of these results were confirmed by Western blot, 11.4% were found to be negative, and 34.2% indeterminate. The overall prevalence after confirmation by Western blot decreased to 2.15%. When studying the Western blot pattern of the positive samples, 95% showed antibodies to SG-3, 65% to 8-5, and only 9.3% to CKS fusion protein. In the indeterminate Western blots, the results for these proteins were 96.3%, 62.9%, and 37%, respectively. When the epidemiological data were analysed, no statistically significant differences between women and men or between different age groups were found.

Spectroradiometer with wedge interference filters (SWIF): measurements of the spectral optical depths at Mauna Loa Observatory

A spectroradiometer with wedge interference filters (SWIF) (the filters were produced by Carl Zeiss, Jena, Germany) and a CCD matrix (which was of Russian production) that functions as the sensor has been designed and built for use in ground-based optical sensing of the atmosphere and the Earth's surface in the spectral range of 0.35-1.15 µm. Absolute calibration of this instrument was performed through a series of observations of direct solar radiation at Mauna Loa Observatory (MLO) in Hawaii in May and June 1993. Spectral optical depth (SOD) measurements that were made during these field experiments provided detailed spectral information about both aerosol extinction (scattering plus absorption) and molecular absorption in the atmosphere above the site at MLO. The aerosol-SOD measurements were compared with narrow-band radiometer measurements at wavelengths of 380, 500, and 778 nm The SWIF and narrow-band radiometer measurements are in agreement to within the experimental error. At a wavelength of 500 nm, the aerosol SOD was found to be approximately 0.045. Adescription of the SWIF instrument, its absolute calibration, and the determination of atmospheric SOD's at MLO are presented.

Low Temperature Induces the Accumulation of Phenylalanine Ammonia-Lyase and Chalcone Synthase mRNAs of Arabidopsis thaliana in a Light-Dependent Manner

Anthocyanins, which accumulate in leaves and stems in response to low temperature and changes in light intensity, are synthesized through the phenylpropanoid pathway that is controlled by key enzymes that include phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS). In this work we demonstrate that PAL and CHS mRNAs accumulate in leaves of Arabidopsis thaliana (L.) Heynh. upon exposure to low temperature in a light-dependent manner. The regulation of the PAL1 gene expression by low temperature and light was examined by analyzing the expression of the [beta]-glucuronidase (uidA) reporter gene in transgenic Arabidopsis plants containing the uidA gene of Escherichia coli under the control of the PAL1 promoter. The results indicate that the accumulation of PAL1 mRNA is transcriptionally regulated. Histochemical staining for [beta]-glucuronidase activity showed that the PAL1 promoter is preferentially activated in photosynthetically active cells, paralleling anthocyanin accumulation. Moreover, we show that light may also be implicated in the regulation of the CHS gene in response to bacterial infiltration. Finally, using two transparent testa Arabidopsis mutants that are unable to accumulate anthocyanins, we demonstrate that these pigments are not required for successful development of freezing tolerance in this species.

Influence of protein tyrosine phosphorylation on the expression of the c-myc oncogene in cancer of the large bowel

We tested the potential impact of tyrosine phosphorylation on the expression of the c-myc gene in two colon cancer cell lines, HCT8 and SW837. We found that the protein tyrosine kinase inhibitor genistein causes a decrease in the abundance of c-myc RNA and an inhibition of proliferation with a similar dose response. Geldanamycin, a mechanistically different tyrosine kinase inhibitor, also causes a decrease in both the expression of c-myc RNA and proliferation. Genistein has also been found to inhibit topoisomerase II, but the topoisomerase II inhibitor novobiocin did not lower the expression of c-myc. The most likely interpretation is that inhibition of protein tyrosine kinase activity caused a decrease in c-myc expression in these cells. The impact of tyrosine phosphorylation on the expression of the c-myc gene is further supported by the finding that inhibition of phosphotyrosine phosphatase using orthovanadate causes an increase in the level of c-myc RNA. The effect of genistein on HCT8 cells is not dependent on the synthesis of new protein and does not involve an alteration in the stability of the message. Analysis of transcription in the c-myc gene reveals a more complicated picture with a decrease in initiation and an increase in elongation but no net change in transcription. We speculate that the genistein induced reduction in myc expression is the result of a posttranscriptional intranuclear event(s).

Evaluation of enzyme immunoassay for hepatitis B virus DNA based on anti-double-stranded DNA

We have evaluated a new enzyme immunoassay technology to detect the products of PCR-based amplification that may be applicable to routine testing of hepatitis B virus (HBV) DNA. Two hundred eight serum samples were studied: 73 were basal samples and 135 were sequential serum samples from patients with chronic hepatitis, some of whom were being treated with alpha interferon. We compared the new detection method (PCR-DNA enzyme immunoassay [DEIA]) with dot blot hybridization performed without prior PCR amplification and with two other methods for detection of PCR products: agarose gel electrophoresis with ethidium bromide staining (PCR-EB) and dot blot (PCR-dot blot). For hepatitis B-antigen-positive basal samples, HBV DNA was detected in 70.4% by dot blot, 74.1% by PCR-EB, and 100% by PCR-DEIA and PCR-dot blot; for anti-hepatitis B e-antigen basal samples, HBV DNA was found in 10.5% by dot blot and PCR-EB and in 42.1% by PCR-DEIA and PCR-dot blot. Chi-square tests showed a strong association between dot blot and PCR-EB and between PCR-DEIA and PCR dot blot. Using PCR-dot blot as the reference, dot blot shows a 56.9% sensitivity and a 100% specificity, PCR-EB shows a 55.0% sensitivity and a 100% specificity, and PCR-DEIA shows a 95.4% sensitivity and a 97% specificity. We conclude that the technical advantages of the DEIA method and its high sensitivity and specificity may facilitate the use of PCR in routine testing for HBV DNA in clinical microbiology laboratories.

Hepatitis C virus RNA in patients with anti-HCV on hemodialysis. Relationship to transaminase levels

This study was performed in patients with hepatitis C virus (HCV) who were treated with hemodialysis to determine the relationships among alanine amino-transferase (ALT) levels, immunoglobulin (Ig) G anti-HCV, IgM anti-HCV core, and HCV RNA. Of 107 patients on hemodialysis, 27 had positive IgG anti-HCV. Eight of the patients who had HCV were evaluated every 8 months during a period of 2 years, using the following selection criteria: positive IgG against c-22, c33-c, 5-1-1, and c100-3 viral peptides; absence of infection by hepatitis A virus, hepatitis B virus, cytomegalo-virus, Epstein-Barr virus, herpes simplex virus, and human immunodeficiency virus, as well as absence of hepatotoxic drugs or cholelithiasis. We considered elevated ALT values as those more than 150% of the upper limit of normal. Three of the patients had persistent elevation of ALT levels, two had alternating elevation of ALT levels, and three had normal ALT levels in all blood samples. Of the 24 blood samples, 11 had elevation of ALT (45.8%) levels that showed positive IgM anti-HCV, but only 7 of these 11 had positive HCV RNA (63.6%). None of the 13 blood samples without elevation of ALT had positive IgM anti-HCV, but 5 had positive HCV RNA (38.5%). We found an excellent correlation between IgM anti-HCV and ALT levels (r = 0.81). There was no statistically significant difference between the mean ALT values on the 12 blood samples that had positive HCV RNA and the mean ALT values of the negative HCV RNA samples (53.5 +/- 28.0 IU/l vs. 37.4 +/- 17.5 IU/l, respectively). IgM anti-HCV is related to the elevation of ALT levels and can be used as a serologic marker to indicate the presence of active HCV induced liver damage. Serum ALT levels do not correlate with the detection of viral genome in sera. IgG anti-HCV is not necessarily associated with HCV RNA or IgM anti-HCV. The absence of IgM and HCV RNA in patients with IgG anti-HCV and normal ALT levels does not necessarily suggest the absence of active HCV infection.

Two related low-temperature-inducible genes of Arabidopsis encode proteins showing high homology to 14-3-3 proteins, a family of putative kinase regulators

We have isolated two Rare Cold-Inducible (RCI1 and RCI2) cDNAs by screening a cDNA library prepared from cold-acclimated etiolated seedlings of Arabidopsis thaliana with a subtracted probe. RNA-blot hybridizations revealed that the expression of both RCI1 and RCI2 genes is induced by low temperature independently of the plant organ or the developmental stage considered. However, RCI1 mRNA accumulates faster and at higher levels than the RCI2 one indicating that these genes have differential responsiveness to cold stress. Additionally, when plants are returned to room temperature, RCI1 mRNA decreases faster than RCI2. In contrast to most of the cold-inducible plant genes characterized, the expression of RCI1 and RCI2 is not induced by ABA or water stress. The nucleotide sequences of RCI1 and RCI2 cDNAs predict two acidic polypeptides of 255 and 251 amino acids with molecular weights of 29 and 28 kDa respectively. The alignment of these polypeptides indicates that they have 181 identical amino acids suggesting that the corresponding genes have a common origin. Sequence comparisons reveal no similarities between the RCI proteins and any other cold-regulated plant protein so far described. Instead, they demonstrate that the RCI proteins are highly homologous to a family of proteins, known as 14-3-3 proteins, which are thought to be involved in the regulation of multifunctional protein kinases.

A seroepidemiological study of human immunodeficiency virus infection in northeast Zaire

To evaluate the incidence of human immunodeficiency virus type 2 infections in an endemic African area, we have studied 134 patients from Northeast Zaire. Sera were tested for HIV-1 and HIV-2 antibodies to asses cross-reactivity or a possible double infection. Sixty five (48.5%) serum samples were reactive for HIV-1 and six (4.5%) for HIV-2 using specific Western blots. The enzyme immunoassays used to detect HIV-2 showed cross-reactivity with HIV-1 in 17 samples (16.5%). Tests based upon synthetic peptides corresponding to specific from human immunodeficiency viruses confirm their ability to discriminate antibodies directed against both viruses in 42/47 samples (89.4%); in 5/47 (10.6%) this test could not distinguish double infection from cross-reactivity. We suggest that the high number of sexual partners may be responsible for HIV transmission in our study group.

Serum hepatitis B virus DNA detection with S- and C-region-directed probes

Developments in molecular biology have offered a wide range of nucleic acid probes to detect the genome of hepatitis B virus (HBV). We have tested the ability of two enzyme-linked (alkaline phosphatase) probes to detect HBV-DNA. These hybridise with the S and C regions of the genome of HBV and are used to determine the clinical significance of detecting the two regions. A total of 66 serum samples from patients at different stages of HBV infection was examined. HBV-DNA was detected with at least one of the probes in 17 (85%) patients with HBeAg-positive chronic hepatitis, five (26.3%) with anti-HBe-positive chronic hepatitis and six (66.6%) with acute hepatitis. Although both probes were able to detect as little as 10 pg/ml (2.86 x 10(6) g.E./ml) of a full length HBV-DNA standard, the C-region-directed probe did not react in one patient with acute hepatitis, two with HBeAg-positive and three with anti-HBe-positive chronic hepatitis. When C-region-directed probes are used for diagnostic purposes, results should always be accompanied by hybridisation with probes directed against other regions showing less variability (e.g. S region).

Pharmacokinetics and biological responses after treatment of the rat R-1 rhabdomyosarcoma with methotrexate

Time relationships of drug concentrations in tissue of a transplantable rat rhabdomyosarcoma and of tumour responses up to 120 hr after treatment with methotrexate (MTX) were analysed and compared. MTX was shown to be retained within the tumour in a substantial concentration for several days, although no evidence of MTX polyglutamation was obtained. The response data confirm that MTX is active in the tumour for up to at least 3 days after injection. Within the first day after MTX treatment the nucleotide pools are only partly depleted. This indicates that the inhibition of DNA synthesis is still incomplete at the time when salvage precursors in increasing amounts are becoming available from decaying cells. From flow cytometric analysis of cell-cycle progression it is concluded that subsequent cohorts arriving in early S-phase were retarded, but not inhibited, in their progression through the S phase. At 3 days after MTX treatment the mean rate of cell-cycle progression as well as the relative clonogenic capacity were maximally reduced to 30% and 1% of control values, respectively. From 3 to 5 days the rate of cell-cycle progression was gradually restored, whereas from day 5 onwards the clonogenic capacity increased at a high rate corresponding to the proliferation rate of exponentially growing rhabdomyosarcoma cells in culture. However, a continuous reduction of cell recovery lasting for at least 12 days after treatment contributed to an 8-day delay in tumour volume growth.

Low Temperature Induces the Accumulation of Alcohol Dehydrogenase mRNA in Arabidopsis thaliana, a Chilling-Tolerant Plant

mRNA encoding alcohol dehydrogenase (ADH) increases in etiolated seedlings and leaves of Arabidopsis thaliana (L.) Heynh. upon exposure to low temperature. The analysis of this response after water stress and abscisic acid (ABA) treatments in Arabidopsis wild type and ABA-deficient and -insensitive mutants indicates that cold accumulation of ADH mRNA could be induced by both anaerobic metabolism and increase of ABA concentration resulting from low temperature exposure. By using one Arabidopsis ADH null mutant, we show that ADH activity is not required for successful development of freezing tolerance in this species.

Deoxycytidine kinase and deoxycytidine deaminase activities in human tumour xenografts

Deoxycytidine kinase (dCK) and deaminase (dCDA) are both key enzymes in the activation and inactivation, respectively, of several deoxycytidine antimetabolites. We determined the total dCK and dCDA activities using standard assays, in 28 human solid tumours grown as xenografts in nude mice, and four corresponding cell lines. dCK activities in colon tumours varied from 11 to 12 nmol/h/mg protein, in ovarian tumours from 3 to 10 nmol/h/mg protein, in soft tissue sarcomas from 2 to 7 nmol/h/mg protein and in squamous cell carcinomas of the head and neck about 45-fold, between 0.4 and 18 nmol/h/mg protein. The dCDA activities showed a larger variation, from 243 to 483, 14 to 1231, 3 to 7 and 1 to 222 nmol/h/mg protein, respectively. The ratios of dCK vs. dCDA activities in these tumours varied from 0.025 to 0.046, 0.004 to 0.240, 0.581 to 1.123 and from 0.012 to 4.227, respectively. In four cell lines (A2780, OVCAR-3, WiDr and UM-SCC-14C), sources for some of the above mentioned tumours, a different pattern in dCK and dCDA was observed than in the corresponding tumours. The variation in dCDA activities was in a smaller range (20-fold) than in the tumours (40-fold). In all cell lines dCK activity was higher than dCDA activity, in contrast to the corresponding tumours, in which the reverse pattern was observed. Previously, some of the tumours were tested for sensitivity to the deoxycytidine analogues 5-aza-deoxycytidine and 2',2'-difluorodeoxycytidine. In the sensitive tumours, both the highest and lowest dCK activity was observed, indicating that dCK activity in solid tumours is high enough to activate deoxycytidine analogues.

In vitro chemosensitivity testing of multilayered microcultures

A potential limitation of in vitro microtiter cytotoxicity assays as compared to in vivo antitumor studies is that the complex three-dimensional structure of the solid tumor is lost in monolayer cultures in vitro. We investigated whether more in vivo like cell-cell interactions could be easily and reproducibly obtained in an in vitro cytotoxicity assay. HT29 human colon adenocarcinoma cells were seeded in 96-well microtiter plates with "V"-shaped wells and allowed to form postconfluent multilayered cultures. Cross-sections of microcultures fixed after 2 and 3 weeks following plating revealed approximately 7 and 35 cell layers, respectively. Using a tetrazolium assay to assess cytotoxicity, the EC50 (drug concentration which gives absorbance readings 50% lower than those of non-treated wells) of multilayered cultures exposed to doxorubicin for 24 h was 12 times higher (p less than 0.05) than that determined for subconfluent monolayered cells simultaneously exposed to the drug. This system offers an alternative to study the chemosensitivity of three-dimensionally organized cells using semiautomated microtiter plate technology.

Etiologic study of patients with community-acquired pneumonia

Community-acquired pneumonias are difficult to diagnose. For this reason, we have attempted to evaluate the correct diagnosis by using noninvasive methods which are easy to follow outside the hospital environment. To achieve this, 165 patients exhibiting the clinical and roentgenographic symptoms characteristic of pneumonia, have been studied from a bacteriologic, serologic, and statistical stand point. The correct diagnosis was made in 75 percent of the cases. Of the total 124 cases, 69 (41.8 percent) were of bacterial origin. Streptococcus pneumoniae was the most common agent, followed by Gram-negative bacilli. In 73 cases showing positive serologic evidence, 22 (42 percent) could be attributed to the so-called atypical pneumonias, 18.18 percent to the viral, and 1.21 percent to the mycotic.

cis-element combinations determine phenylalanine ammonia-lyase gene tissue-specific expression patterns

The bean phenylalanine ammonia-lyase gene 2 (PAL2) is expressed in the early stages of vascular development at the inception of xylem differentiation, associated with the synthesis of lignin precursors. This is part of a complex program of developmental expression regulating the synthesis of functionally diverse phenylpropanoid natural products. Analysis of the expression of PAL2 promoter-beta-glucuronidase gene fusions in transgenic tobacco plants showed that functionally redundant cis elements located between nucleotides -289 and -74 relative to the transcription start site were essential for xylem expression, but were not involved in expression in leaf primordia and stem nodes or in establishing tissue specificity in petals. The -135 to -119 region implicated in xylem expression contains a negative element that suppresses the activity of a cryptic cis element for phloem expression located between -480 and -289. The functional properties of each vascular element are conserved in stem, petiole, and root, even though the xylem and phloem are organized in different patterns in these organs. We conclude that the PAL2 promoter has a modular organization and that tissue-specific expression in the vascular system involves a negative combinatorial interaction, modulation of which may provide a flexible mechanism for modification of tissue specificity.

A study of different parameters of cell-mediated immunity in patients with active and chronic tuberculosis

A study was carried out on cell-mediated immunity in healthy persons and patients with tuberculosis in order to extend the diagnostic capacity in tuberculosis. We studied the relation between baciloscopy and the state of specific cell-mediated immunity in vivo (Mantoux) and in vitro (leukocyte migration inhibition assay with PPD-RT 23 to evaluate specific cell-mediated immunity and PHA to evaluate nonspecific immunity) in 131 patients with active tuberculosis, in 63 patients with chronic tuberculosis, in 62 healthy persons and 10 individuals living with tuberculosis patients. The results demonstrate that the percentage of reaction was very low in both tests, being of no statistical significance the difference between patients with active or with chronic tuberculosis, although it was significant in the control group. In about half of the patients with active tuberculosis a positive baciloscopy could be observed; the percentage was much lower in patients suffering from chronic tuberculosis, the difference between the two groups significant from a statistical point of view. At the same time when we carried out an evolutionary study in 10 patients with positive baciloscopy, we observed a slight capacity of conversion of immunity when the baciloscopy was negative.

Differential expression of hydrogen uptake (hup) genes in vegetative and symbiotic cells of Rhizobium leguminosarum

The genetic determinants responsible for H2-uptake (hup genes) in Rhizobium leguminosarum are organized in six transcriptional units, designated regions hupI to hupVI, with region hupI coding for the hydrogenase structural genes (Leyva et al. 1990). Regulation of the expression of hup genes from R. leguminosarum was examined by using hup-lacZ fusions and mRNA dot-blot analysis. None of the six hup regions is transcribed in vegetative cells grown under normal aerobic conditions, whereas all six regions are transcribed in pea bacteroids. Additionally, exposure of cell cultures to low oxygen tensions specifically induces the expression of regions hupV and hupVI. By studying the expression of hupV- and hupVI-lacZ fusions in R. meliloti mutants it was determined that the microaerobic induction of these two regions is dependent on the regulatory fixLJ system, and that this control is exerted through fixK. Such expression was also shown to be nifA and ntrA independent. The functions of the hupV and hupVI gene products are unknown. The possibility that they play a regulatory role in hup gene expression is unlikely, since pea bacteroids from R. leguminosarum Hup- mutants carrying Tn5 insertions in regions hupV and hupVI contained normal levels of mRNA transcripts corresponding to the remaining hup regions.

Anti-tumor and differentiation-inducing activity of N,N-dimethylformamide (DMF) in head-and-neck cancer xenografts

The anti-tumor activity of the putative differentiation-inducing agent dimethylformamide (DMF) was assessed in 7 head-and-neck xenograft (HNX) lines transplanted into nude mice. The drug was administered intra-peritoneally at the maximum tolerated dose. A significant growth-inhibitory effect was observed in 3 out of 7 tumor lines tested. When compared with 5 conventional drugs active in patients with squamous-cell carcinoma of the head and neck (HNSCC), DMF was as effective as the most active drugs (cisplatin and bleomycin). The most sensitive xenograft line, the poorly differentiated tumor HNX-14C, was used to test the hypothesis that differentiation induction might play a role in the anti-tumor activity of DMF. Light microscopic examination did not show clear-cut alteration of differentiation characteristics such as keratin and keratin pearl formation. Furthermore, we used a monoclonal antibody to study the expression of cytokeratin 10 which is useful as a differentiation marker of human HNSCC tumors. Keratin 10, not present in HNX-14C tumors grown under control conditions, became expressed in some cells upon DMF treatment. Further evidence for a differentiation-inducing activity of DMF was found in electron-microscopic studies. In treated HNX-14C tumors, in addition to cells with normal ultrastructural features, better-differentiated cells were observed, as manifested by an increase in the number of tonofilaments and desmosomes. The results show that DMF has a potential value for the treatment of patients with head-and-neck cancer, and that differentiation induction might play a role in the anti-tumor action of the drug.

Reversal of 5-fluorouracil-induced myelosuppression by prolonged administration of high-dose uridine

The effect of high-dose uridine on 5-fluorouracil (5-FU)-induced toxicity was investigated. Nine patients were treated weekly with 5-FU at increasing dosages. Five patients developed dose-limiting leukopenia, and four patients developed thrombocytopenia. At dose-limiting toxicity, 5-FU treatment was repeated and followed after 3 hours by intermittent iv infusion of uridine (2 g/m2 per hr) during 72 hours. Leukopenia was reversed for several weeks but thrombocytopenia was not. Side effects consisted of mild rises in body temperature. The pharmacokinetics of uridine were similar to those observed with single-agent uridine. Our data indicate that high-dose uridine can reduce the severity of 5-FU-induced myelosuppression.

Preclinical antitumor activity of 5-aza-2'-deoxycytidine against human and neck cancer xenografts [corrected]

The antitumor activity of 5-aza-2'-deoxycytidine (5-aza-dCyd), a nucleoside analog, was established in human head and neck cancer xenografts, transplanted in nude mice. A significant response was noted in 3 of 5 lines, when the drug was injected intraperitoneally at a maximum tolerated dose of 2 mg/kg every four days for three doses. In two most sensitive lines 1 out of 6 tumors regressed completely. The antitumor activity of the drug may depend on the schedule used, as illustrated by the fact that just one of these two lines appeared to be sensitive when treated with low daily doses (0.25 mg/kg). In two lines, 5-aza-dCyd showed equal or better antitumor activity when compared to the conventional drugs known to produce remissions in patients with head and neck cancer (cisplatin, methotrexate, bleomycin, 5-fluorouracil and cyclophosphamide). 5-Aza-dCyd is a drug with potential value in the chemotherapeutic treatment of patients with head and neck cancer [corrected].

DUP 785 (NSC 368390): schedule-dependency of growth-inhibitory and antipyrimidine effects

DUP 785 (NSC 368390; Brequinar sodium) is a new inhibitor of pyrimidine de novo biosynthesis with antitumor activity against several experimental tumors. DUP 785 inhibits the mitochondrial enzyme dihydroorotate dehydrogenase, blocking the conversion of dihydroorotate to orotate. We examined the influence of exposure time to DUP 785 on its growth-inhibitory effects in L1210 murine leukemia and WiDR human adenocarcinoma cells and the effects of pyrimidine (deoxy) nucleosides on reversal of growth-inhibition. The results were correlated with changes in intracellular pyrimidine nucleotide pools and cell cycle distribution. In L1210 cells, a continuous exposure to 25 microM DUP 785 up to 96 hr caused complete growth inhibition. A 2 hr exposure of cells to the drug did not affect growth. In WiDR cells, exposure to the drug for 1-24 hr, followed by cultivation in drug-free medium resulted in recovery of growth. However, cells exposed to the drug for 48 hr or longer were not able to resume growth when recultured in drug-free medium. Reversal studies were performed to know whether selective depletion of one of the pyrimidine (deoxy) nucleotides might be related to the growth-inhibitory effects of DUP 785. Neither thymidine, deoxycytidine alone, deoxycytidine plus tetrahydrouridine; nor cytidine plus tetrahydrouridine added after 24 hr were able to reverse cell growth inhibition induced by 25 microM DUP 785. However, uridine and cytidine alone reversed growth inhibition. UTP and CTP pools in L1210 cells decreased to about 30-40% of control levels after 4 hr of drug exposure, while dTTP and dCTP pools decreased to about 30% of control levels. There were no significant changes in purine nucleotide pools. In WiDR cells, UTP and CTP pools decreased rapidly after drug exposure and were substantially depleted after 24 hr. Reculture of cells in drug-free medium resulted in a significant recovery of UTP and CTP levels only for cells exposed to DUP 785 for 1-24 hr. For cells exposed to the drug for 48 and 72 hr recovery of nucleotide pools was minimal. In L1210 cells, a 12-hr exposure to the drug caused an accumulation of cells in the early S-phase. In WiDR cells, there was a clear accumulation of cells in the S-phase of the cell cycle after 24 hr drug exposure.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation of the rapid automated tetrazolium dye based (MTT) assay for chemosensitivity testing in childhood leukemia

The reduction of the tetrazolium salt MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) to a blue-black formazan product by living but not by dead cells can be used to measure chemosensitivity of tumor cells. The main advantages of the MTT assay are its simplicity, rapidity, and the fact that the results are read automatically with a microplate spectrophotometer. Several reports on the use of the MTT assay in chemosensitivity testing have been published, but all these studies dealt with established cell lines and not with specimens obtained directly from patients. Here we present a study in which the MTT assay has been adapted to assess the effect of antineoplastic drugs on lymphoblasts of children with leukemia.

A study of the evolution of specific and non-specific immune complexes in acute hepatitis B and chronic hepatitis

Circulating immune complexes (ICs) containing IgG and HBsAg, and IgG and HBeAg, in sera from groups of patients with various liver diseases were sought by ELISA and immunodiffusion. A correlation was found between the absence of ICs and the disappearance of HBsAg in patients who had recovered from acute hepatitis B, but complexes containing HBsAg were always found in chronic hepatitis.

Activity of differentiation-inducing agents and conventional drugs in head and neck cancer xenografts

Three putative differentiation inducing agents and five conventional drugs which have been shown to be active in patients with squamous cell carcinoma of the head and neck (HNSCC), were tested for activity against HNSCC transplanted in nude mice. Drugs were administered at a maximum tolerated dose level. By testing the effect of conventional drugs the value of the nude mouse xenograft model for testing new drugs was assessed. Bleomycin as well as cisplatin showed antitumour effects in nude mice, although toxicity and thereby the effectiveness of cisplatin varied during the 5-year period in which the experiments were performed. Bleomycin caused responses in 4 out of 13 tumour lines and cisplatin, when administered at a high dose, was active in 2 out of 5 tumours. 5-Fluorouracil and cyclophosphamide were only moderately active, while methotrexate was inactive. These data indicate that the model might be of value in the detection of new anticancer drugs although it may have a tendency to underestimate the activity of some drugs. We used the nude mouse xenograft model to test the antitumour activity of three differentiation inducing agents, the polar-planar solvents hexamethylene bisacetamide (HMBA) and N,N-dimethylformamide (DMF) and the antimetabolite 5-aza-2'-deoxycytidine (5-aza-dCyd). HMBA appeared to be inactive. In contrast, DMF was active in 1 out of 4 tumour lines while 5-aza-dCyd was active in 2 out of 5 lines tested. Furthermore, the whole panel of differentiation inducers and conventional drugs was tested for antitumour activity against three HNSCC tumour lines.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro biochemical and in vivo biological studies of the uridine 'rescue' of 5-fluorouracil

The effect of delayed uridine administration on the in vitro growth inhibitory effects of 5-fluorouracil (5FU) and on the in vivo antitumour activity and toxicity was studied. In vitro growth inhibition of the human intestinal cell lines WiDr and Intestine 407 by 3 microM 5FU could be reversed by 1.0 mM uridine; the effect was more pronounced with WiDr cells. At 0.1 mM uridine an intermediate effect was observed. Inhibition of colony formation in both cell lines could also be reversed by delayed administration of uridine at 0.1 and 1 mM. Incorporation of 5FU into RNA of WiDr cells did not proceed after addition of uridine, in contrast to Intestine 407 cells. In these cells only a partial inhibition was observed. In vivo we studied the effect of uridine on two colon carcinoma tumour lines, the 5FU sensitive Colon 38 and the relatively resistant Colon 26. 5FU was administered i.p. in a weekly schedule. With Colon 26 delayed administration of uridine (3500 mg kg-1) at 2 and 20 h after 5FU enabled us to increase the 5FU dose from 100 to 250 300mg kg-1. The combination of high-dose 5FU and uridine resulted both in a superior antitumour effect and an increase in life span. In the 5FU sensitive Colon 38 we determined whether the sensitivity to 5FU was affected by uridine. Mice were treated at the non-lethal dose of 100 mg kg-1 which inhibited tumour growth almost completely. Delayed administration of uridine did not significantly affect the antitumour effect. In non-tumour bearing mice we studied the time course of the reversal of the haematological toxicity of 5FU. The effective dose of 100 mg kg-1 induced a significant decrease in leukocytes; in combination with delayed uridine the leukopenia was less severe and recovered more rapidly. 5FU also induced a decrease in haematocrit, which could be prevented by delayed administration of uridine. In conclusion, in cell culture the reversal of 5FU cytotoxicity could be achieved at a low concentration of 0.1 mM uridine, the extent of the reversal might be related to the 5FU incorporation into RNA. In vivo the relatively resistant tumour Colon 26 could be treated with a higher dose of 5FU in the presence of uridine. The sensitivity to 5FU of the sensitive Colon 38 was not affected by delayed administration of uridine, while the haematological toxicity of 5FU was less. So, delayed administration of uridine after 5FU resulted in an improved therapeutic effect in both a relatively resistant and sensitive tumour.