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PubMed1984

Performance, ruminal and serum characteristics of steers fed lasalocid on pasture.

Seventy-two growing steers were used in a 126-d study to determine the influence of varying levels of lasalocid on performance, ruminal and serum characteristics of animals grazing pasture. Treatments consisted of: 1) control; 2) 200 mg lasalocid/d and 3) 300 mg lasalocid/d. Each treatment was replicated three times and each replicate of eight steers was maintained on 3.0 ha of pasture. Pastures consisted of a mixture of tall fescue, orchard grass and ladino clover. In addition to pasture, each replicate of steers was group fed ground corn at a rate of .91 kg X head-1 X d-1 with the lasalocid incorporated into the grain. Average daily gains were .50, .60 and .57 kg, respectively, for steers on the control, and for the 200 and 300 mg lasalocid treatments, which differed (P less than .05) from controls. Ruminal acetate (mol/100 mol) was lower (P less than .05) in steers fed lasalocid at 28 d, but similar for all treatments at 56 and 112 d. Molar proportion of propionate was higher (P less than .05) and butyrate and valerate were lower (P less than .10) in rumen fluid of steers receiving 200 or 300 mg/d of lasalocid. Plasma glucose concentrations were similar for controls and steers receiving 200 mg lasalocid/d, but higher (P less than .05) in steers fed 300 mg lasalocid/d. Serum Mg concentrations were lower (P less than .01) in steers receiving lasalocid. Potassium concentrations in serum were slightly lower (P less than .01) in animals fed lasalocid at 112 d, but not at 28 or 56 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Origins of replication and gene regulation.

Eukaryotic chromosomes appear to consist of many replicons, the time of replication of which is probably controlled by specific origins. However, plasmids without specific eukaryotic origins may also replicate in some cells when injected into nuclei or transferred during transformation. The efficiency and the mechanisms of their initiation are still uncertain. A number of reports are cited which indicate that natural eukaryotic DNAs initiate their replication from specific origins. The nature of these origins are known in only a few instances and no general conclusions can yet be given about the nucleotide sequences involved. Short dispersed repeats of the Alu type appear to function as origins since they enhance the efficiency of replication of vector plasmids in Xenopus eggs. Certain sequences from a variety of eukaryotic DNAs also enhance the replicative potential of plasmids in yeast cells. The common features of such initiators or enhancers is uncertain. If dispersed repeats are origins in mammalian chromosomes, the number appears to be excessive. Either only a subset are functional, or the functional ones are only suborigins in larger replicons in which master origins (not yet isolated) function in the regulation of the timing of replication. Evidence is cited which indicates that the regulation of the time of replication of a gene or gene cluster is part of a regulatory system that makes the DNA available for transcription or leaves it in an inactive state. About one-half the DNA in mammalian cells is replicated in the first half of S phase (SE). After a brief pause in mid-S phase, the remainder of the DNA is replicated in what is designated late S (SL). The fractions replicated in SE and SL may vary in other phylogenetic groups, but wherever division of differentiated cells occurs such fractions are likely to be found. The following hypothesis is proposed. The DNA replicated in SL is suppressed in transcription, if it has the appropriate promoter regions, because the newly replicated DNA is complexed with proteins that suppress transcription. These proteins are only available during SL. Those genes replicated in SE are complexed with a different set of proteins which leave the promoter regions open for transcription when the appropriate regulatory molecules are available. In this way an inactive state or potentially active state can be transmitted from one cell generation to the next. Evidence is cited which indicates that genes which are active in all cells at some stage in the cell cycle are replicated in SE.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1973

Control of F'lac replication in Escherichia coli B-r.

The timing of replication of an F'lac plasmid during the division cycle of Escherichia coli B/r lac(-)/F'lac was examined in relation to the timing of initiation of chromosome replication. This was accomplished by measuring the induction of beta-galactosidase and the incorporation of radioactive thymidine into cells at different ages in cultures growing exponentially at various rates. In cells growing with interdivision times of 27, 36, and 55 min, the F'lac replicated at various stages in the division cycle but always at approximately the same time as initiation of chromosome replication. In cells growing with an interdivision time of 85 min, the F'lac episome replicated midway through the division cycle, whereas chromosome replication initiated at the start of the cycle. Measurements of absorbance at 450 nm per cell suggested that the F'lac replicated when the cells reached a mass which was a constant multiple of the number of episomes per cell at each growth rate. In contrast, the mass per cell at initiation of chromosome replication in cells with an 85-min interdivision time was significantly lower than this constant value. A possible explanation for the apparent coupling between F'lac replication and initiation of chromosome replication at the higher growth rates, and the lack of coupling at the lowest growth rate, is discussed.

Carbon Isotopes↗
PubMed1990

Time-delay discrimination training: replication with different stimuli and different populations.

Two time-delay conditions for teaching complex visual discriminations to normal preschoolers and children with mild and moderate intellectual handicaps were compared. One condition involved spatially separating the distinctive components from the redundant parts of both stimuli (multiple dynamic distinctive-feature prompts). The other condition involved adding a colored field to the correct stimulus (single static nondistinctive-feature prompt). The effect of the latter condition was assessed with unlearned and learned tasks. The study consisted of four experiments. In one experiment, children were also required to use the prompts for self-monitoring responses given before prompting had occurred. The results indicated that for all populations and stimuli (a) time delay of multiple dynamic distinctive-feature prompts consistently produced learning, and (b) time delay of the single static nondistinctive-feature prompt almost never produced learning and frequently led to a complete loss of discriminative performance on previously learned tasks. The resistance to disruption was a function of the training history (i.e., with or without time delay) and IQ level. Self-monitoring increased the efficacy of time delay when multiple dynamic distinctive-feature prompts were used but not when the single static nondistinctive-feature prompt was used.

Adolescent↗
PubMed1984

The beta-major and beta-minor globin genes in murine erythroleukemia cells replicate during the same early interval of the S phase.

The time of replication in S phase was determined for the 7.3 kb EcoRI segment containing the beta-major globin gene and the 14 kb EcoRI segment containing the beta-minor globin gene in a murine Friend erythroleukemia virus transformed (MEL) cell line. Cells were obtained from different intervals of S phase by centrifugal elutriation to avoid artifacts of chemical synchronization. Newly synthesized DNA from different parts of S phase were obtained by isolation of 5-bromouracil (BU) labelled DNA from these cells. The BU-DNA synthesized during four different intervals of S was transferred to diazobenzyloxymethyl (DBM) paper and hybridized with a beta-globin cDNA probe. Quantitation showed that both beta-globin segments were replicated in the first quarter of the S phase with no significant difference in their time of replication in this MEL cell line.

Animals↗
PubMed1992

Escherichia coli cells lacking methylation-blocking factor (leucine-responsive regulatory protein) have precise timing of initiation of DNA replication in the cell cycle.

A protein that is required for specific methylation inhibition of two GATC sites in the papBA pilin promoter region, known as methylation-blocking factor (Mbf) and recently shown to be identical to the leucine-responsive regulatory protein (Lrp), is not responsible for the delayed methylation at oriC implicated in an eclipse period following initiation of DNA replication. Cells containing a transposon mutation within the mbf (lrp) gene initiate DNA replication at the correct time during the cell cycle, whereas cells with increased amounts of the Dam methyltransferase initiate DNA replication randomly throughout the cell cycle.

Bacterial Proteins↗
PubMed1992

The efficiency and timing of plasmid DNA replication in Xenopus eggs: correlations to the extent of prior chromatin assembly.

Injection of the circular plasmid FV1 (derived from type I bovine papilloma virus) into Xenopus eggs before the start of the first cell cycle dramatically increases the efficiency of plasmid replication once eggs are chemically activated. We call this the preloading effect and report kinetic and quantitative characterization of this phenomenon here. The timing and the amount of FV1 synthesis were measured by both BrdUTP density labelling and an optimized method of selective enzymatic digestion of replicated and unreplicated molecules using the three methyladenosine-sensitive isoschizomers, DpnI, MboI and Sau3a. DpnI in 100 mM NaCl proved particularly useful for distinguishing and quantitating unreplicated, once-replicated, and repeatedly replicated molecules accumulated over several cell cycles. Our results reveal that both the amount of DNA replicated and the timing of synthesis during the first S-phase correlate with the length of the preloading period. Longer preloading leads to larger amounts of DNA being replicated sooner. In fact, up to 30-50% of 1 ng injected plasmid can replicate in a semiconservative cell cycle-dependent manner during the first S-phase. But such high levels of synthesis during the first cell cycle appear to limit the egg's ability to rereplicate this material in subsequent cell cycles. The preloading effect does not depend on synthesis of either viral or egg proteins, but does appear to correlate with the extent of plasmid assembly into chromatin before the start of the cell cycle. We postulate that each plasmid molecule must achieve a critical degree of chromatin assembly before it can proceed along the replication pathway. These observations illuminate some of the difficulties inherent in building a vector for gene insertion into Xenopus embryos, but also suggest an experimental strategy toward this aim.

Animals↗
PubMed1993

Pathogenesis of HSV-1/2 induced vaginitis/vulvitis of the mouse: dependence of lesions on genetic properties of the virus and analysis of pathohistology.

A scoring system for herpes simplex virus (HSV) induced vaginitis/vulvitis in Balb/c mice was delineated from vaginal infections. Four degrees of vaginitis/vulvitis could be distinguished after infection with suitable strains of HSV despite nearly identical replication rates. The time course of replication, inflammation and pathohistology was compared further. Grade 0 was defined by lack of symptoms despite presence of strong replication, which was detectable at days 3-6. Focal necrotic lesions of the epithelial layer were present containing HSV-specific antigens. DNA could be detected by hybridization only in the outer zone of these areas. At day 6 these zones began to be re-epithelialized. In the vaginal lumen abundant detached epithelial cells and granulocytes were already present by day 2. Grade 1 was macroscopically characterized by a slight inflammation commencing on days 5-6. Replication and antigens in the epithelium were found on days 2-6. HSV-antigens were only detected above the basal membrane, and some infiltration with granulocytes and lymphocytes was observed below the basal membrane at day 4. Grade 2 showed strong redness and inflammation as well as hyperemia. Cellular infiltrates were present in the large antigen containing epithelial lesions and below the basal membrane. From day 4 on, neurons were HSV-antigen and DNA positive and macrophages in the stroma contained antigen. The vulva was also shown to be involved. Grade 3 exhibited prolonged severe hyperemia, and destruction of the epithelium and the stroma with necrosis and infiltration, especially of the vulva. This grading system was shown to depend on certain unknown genetic properties of HSV-strains. Neither thymidine-kinase activity, replication in macrophages, fusion activity of strains nor presence or absence of the Hpa I P-fragment were shown to be of importance for severity of vaginitis/vulvitis. Vaginitis/vulvitis was shown to be an all or none response to HSV independent of the rate of replication. The set of virus genes responsible for neuroinvasiveness after vaginal or i.p. inoculation was found to be different. The time course of replication (mainly days 3-6) and inflammation (days 5-10) indicates that inflammation seems to be a secondary immunological phenomenon induced later by the replication phase of HSV. Our system could be useful for separately testing drugs with antiviral and anti-inflammatory properties.

Animals↗
PubMed1990

Centromere separation. Early replication of repetitive DNA associated with inactive centromeres.

Four types of stable dicentric and one octacentric chromosomes from mouse brain tumor cells and L-929 cells were analyzed for the timing of replication of repetitive deoxyribonucleic acid (DNA) located in the centric and pericentric regions associated with active versus inactive centromeres. The repetitive DNA present in the heterochromatin blocks of inactive centromeres replicates much earlier than similar DNA associated with the active centromeres. The former appears to replicate during early to mid S when several euchromatic segments are still replicating. There seems to be little or no overlap in the timing of replication of the repetitive DNA present in the vicinity of prematurely separating centromeres (which are accessory and nonfunctional) and those that separate at meta-anaphase junction (which are the functional centromeres). In the absence of any information about the mechanism(s) controlling initiation and completion of DNA synthesis in the two types of heterochromatic blocks, the differential timing of replication of the DNA with similar base composition remains an enigma.

Animals↗
PubMed1992

Adaptation to juvenile rheumatic disease: a controlled evaluation of functional disability with a one-year follow-up.

Compared the adaptation of 165 patients with juvenile rheumatic disease (JRD) to that of their healthy siblings. Patients were divided into those with mild functional disability and those with moderate/severe disability. Adaptation in several domains was assessed by parents and children on two occasions 1 year apart. The adjustment difficulties of the JRD children were limited primarily to social functioning but appeared also in the psychological and family problems domains. Compared to "mild" patients, "moderate/severe" patients had more adjustment difficulties; in some areas, mild patients functioned as well as their healthy siblings. Some Time 1 differences were replicated at Time 2. The results help to delineate (a) the specific domains in which children with chronic disease have adjustment difficulties and (b) the factors that put children at risk for developing adjustment problems.

Activities of Daily Living↗
PubMed1990

Evaluation of the dietary interaction of calcium and phosphorus in the high producing laying hen.

1. In a 6 x 7 factorial experiment using 2688 22-week-old laying hens of the Lohmann-SL strain kept in cages (4 birds/cage), diets containing six calcium (20, 25, 30, 35, 40, 45 g calcium/kg) and seven phosphorus concentrations (3.2, 4.2, 5.2, 6.2, 7.2, 8.2, 16.2 g total phosphorus/kg (Pt)) were combined orthogonally. The resulting 42 treatments were replicated 8 times so that a replicate consisted of a double cage of 2 x 4 hens. The experiment lasted 40 weeks (10 x 28 days). 2. The experimental diets, based on maize and soyabean meals contained 11.5 MJ metabolisable energy/kg and 175 g/kg protein. Different dietary calcium and phosphorus contents were obtained by substituting oat hulls with limestone and dicalcium phosphate. 3. Mortality, egg production, egg weight, egg mass, food intake and food conversion efficiency were determined as well as the breaking strength, thickness of shells and the percentage of eggs with defective shells. 4. All responses measured were significantly influenced by the variance sources (calcium, phosphorus, interaction). Most of the production traits responded asymptotically to increasing dietary phosphorus concentration, the greatest increases or decreases generally being seen between 3.2 and 5.2 g Pt/kg. Further but weaker increases were seen between 5.2 and 8.2 or 16.2 g Pt/kg. 5. Increases in dietary calcium content always resulted in curvilinear responses. In all cases optimal effects were obtained with diets containing 25 g calcium/kg and the worst values at 45 g calcium/kg. The interaction between calcium and phosphorus was recognised by strong performance depressions and a high mortality at combinations of the lowest phosphorus concentration (3.2 g/kg) with high calcium contents (35 to 45 g/kg). These were largely offset by increasing dietary phosphorus. Thus, between 7.2 and 16.2 g Pt/kg and 25 and 45 g Ca/kg a plateau was formed where only small differences in egg production were observed. 6. From the three egg shell characteristics measured, breaking strength and shell thickness responded differently to the percentage of eggs with defective shells. While breaking strength and shell thickness were respectively negatively and positively influenced by increasing dietary phosphorus and calcium contents, both elements affected the proportion of eggs with defective shells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1974

Ultraviolet mutagenesis and its repair in an Escherichia coli strain containing a nonsense codon.

Ultraviolet mutagenesis and its repair were studied mainly in WU36-10-89, a uvr(-) strain of Escherichia coli containing a UAG mutation in a gene for leucine biosynthesis. Following ultraviolet (UV) irradiation revertants appearing with or without direct photoreactivation (PR) were classified according to the presence and type of suppressor they contained. We find UV mutation production to be quite specific. An analysis of revertants produced by UV indicates they are formed mainly from GC --> AT and that the miscoding is due to a cytosine residue at the site of mutation in a cytosine-thymine (CT) dimer. We propose that the dimer serves as template during some aspects of repair replication and at the time of replication the C in the dimer directs the insertion of A in the complementary strand. We also note that C --> A and T -->G changes caused by a CT dimer occur much less frequently.

Base Sequence↗
PubMed1981

alpha-Globulin sequences are located in a region of early-replicating DNA in murine erythroleukemia cells.

The time of replication in the S phase of regions of the mouse genome including the alpha-globin genes was determined in the murine erythroleukemia cell line transformed by Friend virus. Cells grown for short times in the presence of BrdUrd were fractionated into synchronous populations by centrifugal elutriation. The DNA was cleaved by restriction endonucleases, and fragments containing bromouracil (BrU-DNA) were isolated in density gradients of Cs2SO4. BrU-DNA fractions replicated during selected S-phase intervals were subjected to electrophoresis in agarose gels, transferred to diazobenzyloxymethyl-paper, and hybridized to an alpha-globin probe. Reconstruction experiments using a cloned mouse EcoRI fragment including one alpha-globin gene demonstrated that the extent of hybridization provides an accurate measurement that the extent of hybridization provides an accurate measurement of the concentrations of specific fragments in a DNA sample. The alpha-globin fragments were detected primarily in the BrU-DNA replicated during early S phase (approximately the first quarter of S). This result was confirmed in other synchrony experiments and by Cot analysis. (Cot is the initial concentration of DNA in mol of nucleotide per liter multiplied by the time in sec.) The temporal replication of mouse satellite sequences, already known from previous studies, was used as an internal control for cell synchrony. To show that the globin sequences were not lost from the cells in late S phase during isolation of the DNA, we quantitated th alpha-globin fragments in BrU-DNA prepared from a mixture of cells in early and late S phase. The results demonstrate that the alpha-globin gene regions in these cells are replicated during early S phase.

Animals↗
PubMed1979

Carbon monoxide and human time discrimination: failure to replicate Beard-Wertheim experiments.

Beard and Wertheium described a dose-related deficit in human time perception during low level CO exposure. Two other laboratories were unable to replicate this finding, although methodological differences could explain these failures. This study more precisely repeated the original experiment, but failed again to obtain any CO-related deficit. The bulk of evidence, therefore, does not indicate any adverse effect of low level CO exposure on time perception in healthy young adults.

Acoustic Stimulation↗
PubMed1989

Temporal order of gene replication in Chinese hamster ovary cells.

To investigate the molecular basis of the regulatory mechanisms responsible for the orderly replication of the mammalian genome, we have developed an experimental system by which the replication order of various genes can be defined with relative ease and precision. Exponentially growing CHO-K1 cells were separated into populations representing various stages of the cell cycle by centrifugal elutriation and analyzed for cell cycle status flow cytometry. The replication of specific genes in each elutriated fraction was measured by labeling with 5-mercuri-dCTP and [3H]dTPP under conditions of optimal DNA synthesis after cell permeabilization with lysolecithin. Newly synthesized mercurated DNA from each elutriated fraction was purified by affinity chromatography on thiol-agarose and replicated with the large fragment of Escherichia coli DNA polymerase I by using [alpha-32P]dATP and random primers. The 32P-labeled DNA representative of various stages of the cell cycle was then hybridized with dot blots of plasmid DNA containing specific cloned genes. From these results, it was possible to deduce the nuclear DNA content at the time each specific gene replicated during S phase (C value). The C values of 29 genes, which included single-copy genes, multifamily genes, oncogenes, and repetitive sequences, were determined and found to be distributed over the entire S phase. Of the 28 genes studied, 19 had been examined by others using in vivo labeling techniques, with results which agreed with the replication pattern observed in this study. The replication times of nine other genes are described here for the first time. Our method of analysis is sensitive enough to determine the replication time of single-copy genes. The replication times of various genes and their levels of expression in exponentially growing CHO cells were compared. Although there was a general correlation between transcriptional activity and replication in the first half of S phase, examination of specific genes revealed a number of exceptions. Approximately 25% of total poly(A) RNA was transcribed from the late-replicating DNA.

Animals↗
PubMed1993

Correlation of gene transcription with the time of initiation of chromosome replication in Escherichia coli.

Transcriptional levels of the Escherichia coli mioC and gidA genes, which flank the chromosomal origin of replication (oriC) and the dnaA gene, were correlated with the time of initiation of chromosome replication. The transcripts were measured either in dnaC2(ts) mutants that had been aligned for initiation of chromosome replication by a temperature shift or in synchronous cultures of cells obtained using the baby machine technique. In both types of experiments, mioC transcription was inhibited prior to initiation of chromosome replication and resumed several minutes after initiation. Conversely, gidA and dnaA transcription were both inhibited after initiation of replication, coincident with the period of hemimethylation of oriC DNA. It is proposed that mioC transcription prevents initiation of chromosome replication, and must terminate before replication can begin. It is further proposed that the eclipse period between rounds of replication, i.e. the minimum interval between successive initiations, encompasses the time required to methylate GATC sequences in newly replicated oriC plus the time required to terminate mioC transcription. Conversely, the active transcription of gidA and dnaA prior to initiation is consistent with their positive effects on initiation, and their shutdown after initiation could serve to limit premature reinitiation.

Algal Proteins↗
PubMed1991

The effect of pelleting, salt, and pentosanase on the viscosity of intestinal contents and the performance of broilers fed rye.

An experiment was conducted to determine the impact of pelleting of rye, dietary salt (.39 and .57%), and crude pentosanase supplementation (0 and .2%) on the viscosity of intestinal contents and the concomitant performance of broiler chicks fed rye-based diets. Each treatment was replicated six times with six birds per replicate. Test diets were fed from 1 day to 3 wk of age, at which time body weight, feed intake, intestinal viscosity, and molecular weight distribution of carbohydrate complexes were determined in fore and hind gut sections. Enzyme supplementation in all treatment combinations significantly increased weight gains and feed conversion efficiency (FCE). Pelleting and salt did not influence weight gain or FCE, although feed intake was increased through the addition of salt. The viscosity of fore and hind gut contents was significantly reduced with pentosanase supplementation, whereas the effects of salt or pelleting were not as clearly defined. Weight gain and FCE correlated with fore but not hind gut viscosity. The viscosity of gut samples was found to be best described by the concentration of carbohydrate complexes with an average molecular weight greater than 500,000 Da. Pentosanase treatment reduced lumenal concentration of these complexes, thereby reducing viscosity and stimulating improvements in growth and FCE.

Animal Feed↗