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12 recordsLinked to original sources
PubMed1978

Cloning of the phr gene and amplification of photolyase in Escherichia coli.

A new technique is developed for physically enriching recombinant DNA molecules in an in vitro recombination mixture. UV-irradiation of the donor DNA before recombination enables photoreactivating enzyme (PRE) (deoxyribodipyrimidine photolyase, EC 4.1.99.3) to attach to the donor segments in recombinant molecules. This attached protein causes retention of the recombinant molecules on a nitrocellulose filter, while molecules not containing donor DNA pass through. The bound DNA is repaired of its UV damage and released for insertion into cells by exposure to photoreactivating light in situ, yielding approx. 350-fold enrichment. Although applicable to any gene, this procedure has been used in cloning the Escherichia coli phr gene itself, permitting 100-fold amplification of the gene product in vivo.

DNA Repair↗
PubMed1979

Graded changes in central chemoceptor input by local temperature changes on the ventral surface of medulla.

1. In cats under pentobarbitone anaesthesia the effects of focal temperature changes of the ;chemoceptive' areas on the ventral surface of medulla, described by Loeschcke and his associates, were studied with respect to tidal volume, V(T), tidal variation in efferent phrenic activity, Phr(T), and respiratory rate. The cats were either paralysed and ventilated at various constant P(A,CO2) and P(a,O2) levels, or breathing spontaneously.2. It was confirmed that focal bilateral cooling of the intermediate, ;I((S))', areas caused rapid depression of respiration even at constant artificial ventilation. In normocapnic and normoxic conditions apnoea usually ensued at brain surface temperatures of 20-22 degrees C.3. The effects were graded along continuous temperature-response curves with enhancements of ventilation above and depression below normal body temperature.4. The strongest effects on V(T) and Phr(T) were obtained from the I((S)) areas with no or only small effects on inspiratory or expiratory timing in the vagotomized animal. The Hering-Breuer inflation reflex and its effects on timing and amplitudes were not affected by cooling this area.5. Focal cooling of the caudal or the rostral ;chemoceptive' areas, ;C((L))' and ;R((M))' areas, caused smaller effects on V(T) and Phr(T) but produced significant effects on respiratory rate even after vagotomy.6. The effects of focal cooling of these areas could be mimicked by topical application of procaine solution which has been shown not to penetrate deeper than 100 mum from the surface.7. Moderate focal cooling of area I((S)) to temperatures above 28-30 degrees C caused a parallel shift in the CO(2)-response (V(T), Phr(T)) curves to the right with little change in slope. The P(CO2) thresholds for apnoea were correspondingly raised. These focal temperature effects could be compensated by changes in P(CO2) with, on the average, 2.7 torr/ degrees C. Focal temperatures below 28 degrees C usually caused some decrease in slope of the CO(2)-response curves in addition to further shifts.8. Added hypoxic stimulus or electrical stimulation of the carotid sinus nerves caused an almost parallel increase of Phr(T) at all P(CO2) levels and all focal temperatures suggesting an additive type of interaction between the input from the peripheral chemoreceptors and that from the central (CO(2), H(+)) sensing structures whether the latter was altered by changing P(CO2) or by focal temperature changes on the I((S)) areas.9. In contrast to these effects of hypoxia and stimulation of the carotid sinus nerves the reflex increase of inspiratory activity caused by lung deflation or by electrical stimulation of the glossopharyngeal nerve distal to the carotid sinus nerves was CO(2) dependent. These reflex effects decreased with focal cooling of the I((S)) areas as with hypocapnia, suggesting a mainly multiplicative or ;gain-changing' type of interaction with the central chemoceptive drive.10. The close similarities in effect of focal cooling and of hypocapnia on the different respiratory parameters even during constant artificial ventilation indicate that focal temperature changes of the I((S)) areas intervene effectively with the normal ventilatory response to CO(2) without changing the chemical or physical environment of those neural structures in the brain stem which set respiratory pattern.

Animals↗
PubMed1979

Dependence of phrenic motoneurone output on the oscillatory component of arterial blood gas composition.

1. The hypothesis that respiratory oscillations of arterial blood gas composition influence ventilation has been examined. 2. Phrenic motoneurone output recorded in the C5 root of the left phrenic nerve and the respiratory oscillations of arterial pH in the right common carotid artery were measured in vagotomized anaesthetized dogs which had been paralysed and artificially ventilated. 3. The effect of a change in tidal volume for one or two breaths on phrenic motoneurone output was measured with the inspiratory pump set at a constant frequency similar to, and in phase with, the animal's own respiratory frequency. A reduction of tidal volume to zero or an increase by 30% led to a corresponding change of mean carotid artery pH level. The changes of carotid artery pH resulted in a change of phrenic motoneurone output, predominantly of expiratory time (Te) but to a lesser extent of inspiratory time (T1) and also peak amplitude of 'integrated' phrenic motoneurone output (Phr). Denervation of the carotid bifurcation blocked this response. 4. The onset of movement of the inspiratory pump was triggered by the onset of phrenic motoneurone output. When a time delay was interposed between them, the phase relationship between respiratory oscillations of arterial pH and phrenic motoneurone output altered. The dominant effect was to alter Te; smaller and less consistent changes of Phr and T1 were observed. 5. When the inspiratory pump was maintained at a constant frequency but independent of and slightly different from the animal's own respiratory frequency (as judged by phrenic motoneurone output), the phase relationship between phrenic motoneurone output and the respiratory oscillations of pH changed breath by breath over a sequence of 100-200 breaths, without change of the mean level of arterial blood gas composition. Te varied by up to 30% about its mean value depending on the phase relationship. Ti and Phr were also dependent on the phase relationship but varied to a lesser extent. The changes were comparable to the results obtained in paragraph 4. 6. It was concluded that phrenic motoneurone output is dependent in part on its relationship to the respiratory oscillations of arterial blood gas composition. 7. Information concerning a transient ventilatory disturbance is stored in the arterial blood in the form of an altered pattern of the respiratory oscillations of blood gas composition; this in turn can change breathing by an effect on the carotid bodies.

Action Potentials↗
PubMed1979

Multiple loci affecting photoreactivation in Escherichia coli.

Sutherland et al. mapped a phr gene in Escherichia coli at 17 min and found that induction of an E. coli strain lysogenic for a lambda phage carrying this gene increased photoreactivating enzyme levels 2,000-fold. Recently, Smith and Youngs and Sancar and Rupert located a phr gene at 15.9 min. We have therefore investigated the properties of photoreactivating enzyme and cellular photoreactivation in cells containing deletions of the gene at 17 min. Cells with this deletion photoreactivated ultraviolet-induced killing at a rate 20% of normal; they also contained approximately 20% of the normal photoreactivating enzyme level. The residual enzyme in these cells was characterized to determine whether the reduced cellular photoreactivation rate and photoreactivating enzyme levels resulted from reduced numbers of normal enzymes or from an altered enzyme. Photoreactivating enzymes from strains carrying a deletion of the region at 17 min had an apparent Km about two- to threefold higher than normal enzyme and showed markedly increased heat lability. The gene at 17 min thus contains information determining the function of the E. coli photoreactivating enzyme rather than the quantity of the enzyme. It is proposed that the gene at 17 min be termed phrA and that located at 15.9 min be termed phrB.

DNA Repair↗
PubMed1979

Penicillin selection of Escherichia coli deoxyribonucleic acid repair mutants.

A rapid method has been developed for isolation of ultraviolet-sensitive mutants of Escherichia coli, by inducing delay in the growth and/or division of repair-deficienct cells with low fluences of far-ultraviolet radiation, and killing with penicillin the repair-proficient cells, which continue to grow and divide. With this technique, we have achieved about a 3,000-fold enrichment for photoreactivation less (phr) cells and have isolated and characterized three phr mutants.

DNA Repair↗
PubMed1978

Some features of the reaction of intracellular bacteriophages T1 to UV irradiation.

The reaction of complexes pf phage T1-cells of E. coli B or E. coli Bs-1 to UV irradiation was investigated. The complexes were irradiated at various stage of infection, and their survival, extent of Hcr and Phr, were evaluated. It was found that the UV resistance of phage DNA in the second half of the latent period fluctuates. Hcr after UV exposure at these stages of infection operates in a small volume. The ability of intracellular phage to photoreactivate when cells of E. coli B were infected is constant after irradiation at many stages of infection, except the early ones. In the complexes of phage T1-bacteria of E. coli Bs-1 this ability declines while infection is promoted. The daughter phage particles released from UV irradiated complexes undergo Phr and Hcr only after irradiation at the late stages of infection. This was not the cases when complexes of phage-bacteria were irradiated during the first half of the latent period. A possible tole of UV-damaged phage DNA in propagation of infection and in maturation of phage particles is discussed.

Coliphages↗
PubMed2026

The link between phosphate starvation-triggered anthocyanin biosynthesis and jasmonate-driven regulation in tomato.

Phosphate Starvation Response (PSR) in plants integrates inorganic phosphate (Pi) sensing with hormonal and metabolic reprogramming. Recent evidence supports a PSR-jasmonate (JA)-anthocyanin axis in which the PSR-associated PHOSPHATE STARVATION RESPONSE (PHR)/PHR-like-SYG1-PHO81-XPR1-inositol pyrophosphate 8 (PHR/PHL-SPX-InsP8) module gates transcriptional activation, while the core JA components JASMONATE ZIM-DOMAIN (JAZ) and MYELOCYTOMATOSIS 2 (MYC2) mediate hormone-induced activation of secondary metabolism. In Solanum lycopersicum, PHR/PHL transcription factors (TFs) serve as core PSR hubs, with expanded regulatory networks and InsP-associated control layers that tune SPX buffering and transcriptional output. Downstream, JA signaling and MYC2-dependent transcription interface with anthocyanin regulators, including key MYB and bHLH TFs that form the MYB-basic helix-loop-helix (bHLH)-WD40 repeat (MBW) complex, thereby regulating tissue capacity for pigmentation under Pi starvation (PiS). Anthocyanin-rich tomato cultivars such as 'Indigo Rose' exemplify how genetic configuration can enhance MBW responsiveness and potentiate pigment accumulation under PiS. Here, we collate recent advances linking PSR gating, JA response, and anthocyanin biosynthesis regulation in tomato, and propose a working model with testable predictions to accelerate causal validation, and enable breeding strategies targeting phosphorus use efficiency and nutritional quality.

Solanum lycopersicum↗
PubMed1979

Relative effectiveness of the 300--320 NM spectral region on sunlight for the production of primary lethal damage in E. coli cells.

Cell inactivation by sunlight exposure has been studied in E. coli CSR 603 (uvrA recA phr), a K12 derivative which is deficient in all known repair systems. Under suitable conditions, unfiltered sunlight inactivates these cells to 10(-3) survival within 30 sec. The effects of unfiltered sunlight have been compared with those of sunlight filtered through 1-cm layers of aqueous caffeine solutions ranging in concentration from 1 to 20 mg/ml. In the wavelength region of solar emission below 320 nm, which is most critical for DNA damage, the transmission of these liquid filters changes from 10 to 90% within 8-nm intervals. Thus our results permit minimum estimates for the fraction of lethal lesions produced by the solar spectrum below certain wavelenghts. In an experiment analyzed in this manner more than 80% of primary lethal lesions are caused by wavelengths less than 321 nm, and more than 50% by wavelengths less than 306 nm, while the contribution of wavelengths greater than 380 nm to primary lethal damage is below 1%.

DNA Repair↗
PubMed2026

A complete genome for the common marmoset.

The common marmoset is a New World monkey widely used to study primate evolution and human disease. We present a telomere-to-telomere (T2T) reference assembly for the species, plus three near-T2T haplotypes. These resolve previously inaccessible regions, including the centromeres, sex chromosomes, subterminal satellites, acrocentric chromosomes, and the major histocompatibility complex (MHC). We find marmoset centromeres carry dimeric alpha satellites with chromosomal specificity, flanked by inactive layers interpreted as ancestral centromere remnants. We assemble gene-poor, satellite-rich short arms of the acrocentrics and find that most can harbor rDNA and all share pseudo-homolog regions (PHRs). PHR-sharing chromosomes also share closely related centromeric satellites, consistent with a model of ongoing rDNA-facilitated recombinational exchange between heterologous chromosomes. We further identify over 500 marmoset-lineage-specific transcribed genes with previously unknown transcript models or expansions. These resources, along with a preliminary pangenome, improve the utility of the marmoset as a model organism and address gaps in primate genome evolution.

Animals↗
PubMed1978

Expression of the uvrB gene of Escherichia coli: in vitro construction of a pMB9 uvrB plasmid.

Bacteriophage lambdab2att2 [lambdab2cI857intam6(deltabioAB)bioFCD+uvrB+phr+] codes for a function(s) that confers UV resistance (Uvr+) and reactivation of irradiated phage (Hcr+) to an Uvr-Hcr-Escherichia coli strain. It was demonstrated that these functions are expressed under the control of bacterial regulatory elements located on lambdab2att2 DNA. The location of the E. coli uvrB gene on the DNA of this transducing phage was established by heteroduplex and restriction-enzyme analyses. Recombinant DNA molecules were constructed in vitro from plasmid pMB9 (Tcr), as the vector, and an EcoRI fragment (Eco-RI-F) of lambdab2att2 DNA. The resulting plasmid, designated pNP5, has a molecular weight of 5.1 X 10(6) and replicates in a relaxed fashion. Transformation of E. coli uvrB with plasmid pNP5 resulted in clones that are Uvr+ Tcr. Irradiation of bacteria transformed with plasmid pNP5 with low UV doses revealed a complete restoratation of the Uvr+ phenotype by the presence of the cloned EcoRI-F DNA, while only a partial restoration was observed after irradiation with high UV doses. Likewise, the Hcr+ character was also partially restored due to the presence of pNP5. No correlation was found between the acquired Uvr+, Hcr+ properties, and the presence of correndonuclease II activity in an extract of bacteria that harbor plasmid pNP5.

Chromosome Mapping↗
PubMed1978

[Photically released trains of potentials following local application of ethosuximide into the corpus geniculatum laterale].

The influence of ethosuximide injected into the lateral geniculate body (LGB) on photically evoked afterdischarges (PhAD) and recruiting responses (PhR) after 0,3/s or 7/s light flash series was compared with the effect of intraperitoneally administered ethosuximide in freely moving albino rats with chronic electrodes. Whereas i. p. application of ethosuximide reduces or abolishes photically evoked afterdischarges and recruiting, administration into the LGB does not change these potentials or the photic evoked potential. This points to an action not immediately in the LGB.

Animals↗