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At least 541 records · Page 30Linked to original sources
PubMed2000

Photorepair prevents ultraviolet-induced apoptosis in human cells expressing the marsupial photolyase gene.

Photolyase absorbs blue light and employs the energy to remove UV-induced DNA damage, cyclobutane pyrimidine dimers, or pyrimidine pyrimidone (6-4) lesions. These enzymes have been found in many living organisms ranging from bacteria to aplacental mammals, but their photoreactivation effect, such as survival increase of UV-irradiated cells by light-illumination, has not been identified in placental mammals, including humans. Therefore, we introduced a photolyase gene derived from the marsupial rat kangaroo, Potorous tridactylus, into HeLa cells and established the first human cell line capable of photorepairing UV-induced pyrimidine dimers. Several clones were found to increase cell survival after UV irradiation when illuminated by fluorescent light. The induction of apoptosis by UV irradiation was investigated in these photoreactivation-proficient cells. Several typical features of the programmed cell death, such as internucleosomal DNA degradation, presence of subdiploid cells, loss of membrane integrity, and chromosomal condensation, were found to be induced by UV in the HeLa cells, but they can be reduced by photorepair. This implicates that cyclobutane pyrimidine dimers cause UV-induced apoptosis in human cells.

Animals↗
PubMedDate not supplied

[Virus-specific syntheses in cells infected with the virions from standard and "defective" populations of the influenza virus (author's transl)].

The structure of influenza virus virions from the standard and "Magnus" populations as well as intracellular syntheses induced by them were studied. Virions of influenza virus were shown to be heterogeneous with respect to the set of fragments in them. This heterogeneity was more marked in virions of the "Magnus" population and consisted in a relatively greater deficiency of large fragments. A marked induction of light RNA fractions in the cell by defective influenza virus was demonstrated. Synthesis of protein and the polypeptide composition of virions were found to be similiar in standard and "Magnus" viruses.

Animals↗
PubMedDate not supplied

[Obtaining bioluminescent bacterial strains for detection of thallium ions].

The possibility of Alcaligenes eutrophus T1 luxphenotype creation by temperature induced mutagenesis has been shown. These mutants are able to emit light after induction by thallium ions. This biological method of thallium detection possesses high specificity and sensitivity (0.5 microM of metal). Such microbial cells can be used to quantify bioavailability of thallium part in the environment.

Biological Availability↗
PubMed1989

Influence of exogenous thymidine on killing and mutation of Chinese hamster V-79 cells by X-rays, ultraviolet light and N-methyl-N'-nitro-N-nitrosoguanidine.

V-79 cells when exposed to thymidine (5 micrograms/ml) in growth medium after treatment with X-rays, UV light and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), responded differently depending upon the agent. For treatment with X-rays and UV light, only induction of mutation was potentiated, but for MNNG treatment, both killing and mutation induction were potentiated. The increase in killing of MNNG exposed cells could be reversed by simultaneous addition of deoxycytidine with thymidine, but, for all the three mutagenic treatments, enhancement in mutation induction could not be suppressed by deoxycytidine.

Animals↗
PubMed1986

Anti-idiotypic antibodies to monoclonal antibody CO17-1A.

Anti-idiotypic antibodies (Ab2) raised during the course of monoclonal antibody (MAb) therapy against anti-colorectal carcinoma (CRC) MAb CO17-1A were characterized in 142 patients with carcinomas of the colon, rectum or pancreas. Ab2 comprised between 21 and 80% of the total human anti-mouse IgG antibodies in various patients, and up to 42 micrograms of Ab2 were isolated per ml serum. In one patient significant levels of Ab2 could be detected for greater than 770 days. Between 20 and 70% of Ab2 in various patients bound to the combining site of MAb CO17-1A and may therefore bear the internal image of the 17-1A tumor antigen. Furthermore, Ab2 isolated from different patients showed considerable cross-reactivities. A beneficial role of the Ab2 responses in the cancer patients who improved clinically following MAb immunotherapy is discussed in light of induction by Ab2 of anti-anti-idiotypic antibodies (Ab3) with tumor-binding activities.

Animals↗
PubMed1984

Full recovery after different anesthesia techniques for short diagnostic procedures.

When suitable, local anesthetic techniques are preferable for ambulatory short diagnostic procedures. If general anesthesia is used no or only very light premedication, induction with a short acting i.v. agent and the maintenance of anesthesia with nitrous oxide plus oxygen plus an inhalational agent or alternatively with short acting i.v. anesthetic and analgesic seems today to provide fastest recovery. Patients should always arrange for a responsible adult to accompany them home. Minimal requirements for safe discharge should in addition to stable vital signs and the ability to maintain oral fluids include that patients are able to dress themselves and able to walk out. These criteria, however, do not indicate that patients are fully recovered after anesthesia. In most cases patients are not fully recovered when discharged from hospital after even brief anesthesia and they should refrain from driving, operating machinery, and delay making important decisions for at least 24 hours after anesthesia.

Adjuvants, Anesthesia↗
PubMed1984

Differential acylation in vitro with tetradecanoyl coenzyme A and tetradecanoic acid (+ATP) of three polypeptides shown to have induced synthesis in Photobacterium phosphoreum.

Acylation of extracts of Photobacterium phosphoreum at different stages of growth with [3H]tetradecanoic acid (+ATP) has shown that two polypeptides found in the fatty acid reductase complex, the fatty acid activating enzyme (50K) and the 34K polypeptide, were specifically labeled during induction of the luminescent system. An alternate method for in vitro acylation of polypeptides in the luminescent system was developed using tetradecanoyl-CoA. Both the 34K polypeptide and, to a lesser extent, the acyl-CoA reductase component (58K) in the complex, were acylated with [3H]tetradecanoyl-CoA. In contrast, the fatty acid activating enzyme (50K) was not labeled. Labeling of both the 34K and 58K polypeptides with [3H]tetradecanoyl-CoA as well as the acyl-CoA reductase activity in extracts paralleled the induction of luciferase during growth. Differential labeling of P. phosphoreum cells with [35S]methionine before luminescence induction and with [3H]methionine after the onset of luminescence followed by purification of luciferase and the polypeptides in the fatty acid reductase complex demonstrated that the alpha and beta subunits of luciferase and the 34K, 50K, and 58K polypeptides of the complex had 3H/35S ratios at least 7-fold higher than the constitutive proteins. These results give evidence that the synthesis of the component polypeptides of the fatty acid reductase are induced during the development of bioluminescence and may be under the same control as luciferase. The experiments also showed that P. phosphoreum may have the highest content of luciferase of any luminescent bacterium, constituting approximately 20% of the total soluble protein in extracts.

Acyl Coenzyme A↗
PubMed1994

Isolation and characterization of cDNA clones for chloroplast translational initiation factor-3 from Euglena gracilis.

A complete cDNA clone encoding Euglena gracilis chloroplast translational initiation factor 3 (IF-3chl) has been obtained. Analysis of the sequence indicates that the IF-3chl mRNA contains the spliced leader found at the 5' end of nuclear encoded mRNAs in E. gracilis. The open reading frame for IF-3chl encodes a 537-amino acid protein. IF-3chl appears to be divided into four domains. The first 140 amino acids correspond to a transit peptide required for the import of IF-3chl into the chloroplast. The mature form of IF-3chl encompasses domains 2-4 and is about twice the size of Escherichia coli IF-3. The second domain has no homology to other known proteins. It begins with a stretch of 35 residues, of which about 30% are proline. Downstream from this region is a stretch of about 25 amino acids with a repeating (GX)n motif followed by a very acidic region. The third domain comprises a region of about 175 residues and has between 31 and 37% homology to the IF-3s found in other organisms. The IF-3 homology domain is followed by an acidic region which has no detectable homology to other sequences. Analysis of E. gracilis genomic DNA suggests that there are about four copies of the IF-3chl gene, one of which is probably a pseudogene. The activity of IF-3chl is inducible by light. However, the IF-3chl mRNA is present in approximately equal amounts in both dark- and light-grown cells, suggesting that the light-dependent induction of IF-3chl activity is post-transcriptional.

Amino Acid Sequence↗
PubMed1997

Quipazine and light have similar effects on c-fos induction in the rat suprachiasmatic nucleus.

The effects of the serotonin agonist, quipazine, on the induction of c-fos in the suprachiasmatic nucleus of the rat was examined at different times of the 24 h cycle. Quipazine administered at night induced Fos production in a dose dependent manner (1, 3, 10, 30 mumol/kg) in the ventrolateral portion of the suprachiasmatic nucleus at ZT18. Administration of the highest dose at other times resulted in c-fos induction at ZT15 but not at other times of the day or subjective day examined (CT6 and ZT12). When compared to the effects of light pulses (2 lux/1 min), quipazine only caused c-fos induction at times when light caused induction. Our results support a role of serotonergic pathways in the transmission or modulation of photic information from the retina to the suprachiasmatic nucleus of the rat.

Animals↗
PubMed1996

Induction of cyclobutane pyrimidine dimer photolyase in cultured fish cells by UVA and blue light.

The cyclobutane pyrimidine dimer (CPD) photolyase in fish cells is known to be regulated by environmental factors, such as light, hydrogen peroxide and growth inhibition. The induction of CPD photolyase by light in cultured goldfish cells was dependent on the wavelength of the light, and UVA and blue light had high inductive activity. The spectrum for CPD photolyase activity was different from that for the induction. Treatment with blue or yellow light for a short time, which did not induce any CPD photolyase, induced high CPD photolyase activity in the presence of the photosensitizers, TPPS (monosulfonated meso-tetraphenyl porphine) and ALPS (aluminum phthalocyanine tetrasulfonate), respectively. These results suggest that the induction of CPD photolyase might be triggered by active oxygen produced by light and cellular photosensitizers. We also found that immediately after treatment with UVA, blue light or a photosensitizer in combination with light, cellular attachment to the substratum was enhanced, as was the CPD photolyase activity. Pretreatment with a flavonoid, quercetin, inhibited both photoinduction of CPD photolyase and enhancement of cellular attachment. Vitamin E inhibited only photoinduction of CPD photolyase activity. Treatment with H7, a strong inhibitor for protein kinase C, after light treatment inhibited photoinduction of CPD photolyase activity, but an analogue of H7, Ha1004, which is a weak inhibitor of protein kinase C, did not have such an effect.

Animals↗
PubMed1996

Integration of circadian and phototransduction pathways in the network controlling CAB gene transcription in Arabidopsis.

The transcription of CAB genes, encoding the chlorophyll a/b-binding proteins, is rapidly induced in dark-grown Arabidopsis seedlings following a light pulse. The transient induction is followed by several cycles of a circadian rhythm. Seedlings transferred to continuous light are known to exhibit a robust circadian rhythm of CAB expression. The precise waveform of CAB expression in light-dark cycles, however, reflects a regulatory network that integrates information from photoreceptors, from the circadian clock and possibly from a developmental program. We have used the luciferase reporter system to investigate CAB expression with high time resolution. We demonstrate that CAB expression in light-grown plants exhibits a transient induction following light onset, similar to the response in dark-grown seedlings. The circadian rhythm modulates the magnitude and the kinetics of the response to light, such that the CAB promoter is not light responsive during the subjective night. A signaling pathway from the circadian oscillator must therefore antagonize the phototransduction pathways controlling the CAB promoter. We have further demonstrated that the phase of maximal CAB expression is delayed in light-dark cycles with long photoperiods, due to the entrainment of the circadian oscillator. Under short photoperiods, this pattern of entrainment ensures that dawn coincides with a phase of high light responsiveness, whereas under long photoperiods, the light response at dawn is reduced.

Arabidopsis↗
PubMed1979

Orthophosphate control of glucose-6-phosphate dehydrogenase light modulation in relation to the induction phase of chloroplast photosynthesis.

High concentrations of orthophosphate (Pi) inhibited CO(2)-dependent O(2) evolution and prevented the inactivation of glucose-6-P dehydrogenase by light in intact spinach and barley chloroplasts. Addition of glycerate-3-P to chloroplasts inhibited by Pi in the light, induced O(2) evolution and caused rapid inactivation of glucose-6-P dehydrogenase. The activity of phosphofructokinase detected in chloroplast preparations was not affected by light or by Pi.Dihydroxyacetone-P was a major product of chloroplast photosynthesis when optimum concentrations of Pi were used. Chloroplasts continued to form dihydroxyacetone-P at a slow rate in the presence of Pi at concentrations (2 to 4 millimolar) that gave complete inhibition of CO(2)-dependent O(2) evolution. Formation of dihydroxyacetone-P in the presence of 4 millimolar Pi was stimulated by light and either O(2) (150 micromolar) or sparker amounts of oxaloacetate.Conditions that favored dihydroxyacetone-P formation (high O(2) or low O(2) plus oxaloacetate) increased the optimum Pi concentration for CO(2)-dependent O(2) evolution and stimulated O(2) evolution at high concentrations of Pi. The stimulation of O(2) evolution at superoptimal concentrations of Pi by O(2) or oxaloacetate was prevented by dithiothreitol.The results suggested that formation of pentose-P pathway intermediates via the oxidative pentose-P pathway may be limited by availability of NADP in the light but may occur at significant rates and thereby contribute to termination of the induction phase of O(2) evolution.

Journal Article↗
PubMed1992

Mutagenesis after exposure of bacteria to ultraviolet light and delayed photoreversal.

The induction of mutations by ultraviolet light and delayed photoreversal in bacteria defective for SOS mutagenesis is discussed in terms of two models: the two-step misincorporation and bypass model, and the model involving simple deamination of cytosine-containing dimers. In phage S13 the latter appears to be the predominant mechanism. In Escherichia coli there is little evidence that the simple deamination mechanism is of any significance except in ung strains lacking uracil glycosylase where uracils left after photoreversal are not removed. Deamination might, however, occur during the operation of translesion synthesis via the two-step model and if it did, subsequent photoreversal would lead to the "mutation" being extended from one to both strands by uracil glycosylase repair rather than being removed.

Coliphages↗