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At least 235 records · Page 13Linked to original sources
PubMed1988

Retroviral gag gene amber codon suppression is caused by an intrinsic cis-acting component of the viral mRNA.

In some type C retroviruses, translation of the pol gene appears to require translational suppression of the proximal gag amber codon. To identify the region of the viral nucleic acid responsible for synthesis of the pol gene products, a 300-base-pair DNA fragment containing the stop codon from a type C murine virus (AK virus) was inserted into the Escherichia coli lacZ gene such that the translational reading frame was maintained. Introduction of the resulting fusion gene into cells resulted in the suppression of the viral stop codon. As measured by beta-galactosidase production, suppression occurred at a frequency of approximately 10%. Suppression could occur in at least several vertebrate cell types and was not augmented by virus replication or the expression of viral gene products. This indicates that gag amber codon suppression does not require augmented levels of suppressor tRNA species.

Acetyltransferases↗
PubMed1988

AMBER: a scanning multiple-beam equalization system for chest radiography.

Conventional chest radiography is limited by the small useful exposure range of radiographic film. The wide variation in absorption thickness of different parts of the chest results in areas of under- and over-exposure. An advanced multiple-beam equalization system, AMBER, controls local exposure delivered to the film. The system has a row of 20 modulators in front of the x-ray tube, each able to change the height of the local slit beam during scanning. Changes are made in response to measurements from a linear detector array in front of the film cassette. This array consists of 20 individually functioning detectors coupled through electronic feedback loops to the 20 modulators. A scan is obtained in 0.8 second with a local exposure time of approximately 50 msec. AMBER results in radiographs with significantly improved exposure of the mediastinum without overexposure of the lungs.

Humans↗
PubMed2006

[Effect of amber acid on the kidney function in gentamycin-induced nephropathy in white rats].

The amber acid neutralized by 10 % solution of NaOH in a concentration of 250 mmoL/L was administered subcutaneously simultaneously with intraperitonal injection of gentamycin in a doze of 10 mg/kg(bw) once a day during 7 days to the ten nonlinear white male rats, weight 100-120 g exposed to the water-induced diuresis. In these experiments the positive action of an amber acid as energy substratum on some renal function tests was shown: improvement of reabsorbtion in proximal tubules, proved by proteinuria decrease, subsequent normalization of glomerular filtrations followed by uremia reduction and diminishing of other signs of acute renal failure.

Acute Kidney Injury↗
PubMed1989

Suppression of amber codons in vivo as evidence that mutants derived from Escherichia coli initiator tRNA can act at the step of elongation in protein synthesis.

The absence of a Watson-Crick base pair at the end of the amino acid acceptor stem is one of the features which distinguishes prokaryotic initiator tRNAs as a class from all other tRNAs. We show that this structural feature prevents Escherichia coli initiator tRNA from acting as an elongator in protein synthesis in vivo. We generated a mutant of E. coli initiator tRNA in which the anticodon sequence is changed from CAU to CUA (the T35A36 mutant). This mutant tRNA has the potential to read the amber termination codon UAG. We then coupled this mutation to others which change the C1.A72 mismatch at the end of the acceptor stem to either a U1:A72 base pair (T1 mutant) or a C1:G72 base pair (G72 mutant). Transformation of E. coli CA274 (HfrC Su- lacZ125am trpEam) with multicopy plasmids carrying the mutant initiator tRNA genes show that mutant tRNAs carrying changes in both the anticodon sequence and the acceptor stem suppress amber codons in vivo, whereas mutant tRNA with changes in the anticodon sequence alone does not. Mutant tRNAs with the above anticodon sequence change are aminoacylated with glutamine in vitro. Measurement of kinetic parameters for aminoacylation by E. coli glutaminyl-tRNA synthetase show that both the nature of the base pair at the end of the acceptor stem and the presence or absence of a base pair at this position can affect aminoacylation kinetics. We discuss the implications of this result on recognition of tRNAs by E. coli glutaminyl-tRNA synthetase.

Amino Acyl-tRNA Synthetases↗
PubMed1986

Variation in light transmission properties of amber oral syringes.

Four brands of amber oral syringes were tested for compliance with compendial standards for light-resistant packaging. United States Pharmacopoeia (USP) specifications state that light-resistant packaging must not transmit more than 10% of incident light with wavelengths of 290-450 nm. The amount of light transmitted by samples of the barrels of 200 amber plastic oral syringes from each of four manufacturers was determined by spectrophotometry. Samples of both the printed and unprinted sides of the barrel were tested (after removal of all ink). The thickness of each syringe-barrel sample was measured, and the apparent density was determined. All of the Becton-Dickinson syringes tested met the USP standard for light transmittance, and none of the syringes from Baxa or Solopak met the compendial standards. Of the Burron syringes tested, 70 syringes met the standard, 83 did not meet the standard, and 47 could not be classified. The samples of the printed side of the syringe barrel had light transmission properties similar to those of the unprinted side with the exception of the syringes from Baxa, which had substantially higher apparent densities at all wavelengths for the printed side. Only one manufacturer's oral syringes consistently met the USP standard for light-resistant packaging. Further testing is needed to determine the clinical importance of these findings.

Color↗
PubMed1976

[Mutator effect of suppressed amber-alleles of early genes of bacteriophage T4].

The mutator effect of amber alleles of three early genes (43, 32, 47), which were suppressed by the bacterial suppressor gene, was studied. There are some advantages in using the suppressed amber alleles instead of ts, because in this case definite amino acid substitutions take place in the protein due to certain suppressor gene effect. For example, in Escherichia coli CR63(Su+-1) the replacement of the original amino acid by serine takes place. Studying the mutator effect of 43 alleles of DNA polymerase gene of phage T4 with tester mutant r131 showed that in condition of suppression by the gene Su+ -1 only 13,9% of alleles possessed the mutator activity. In the same experiments with mutants of genes 32 and 47 the mutator effect was not observed.

Alleles↗
PubMed1993

Pacemaker wires. Difference in performance between AMBER and conventional chest radiography.

Evaluation of pacemaker wires were performed by comparing Advanced Multiple Beam Equalization Radiography (AMBER) with conventional chest radiography. The scanning equalization technique of the AMBER unit makes it superior to conventional technique in the depiction of different structures in the mediastinum or in the pleural sinuses. So far motion artifacts have not been considered clinically important. The longer exposure time, however, may impair the assessment of pacemaker wires. The motion artifact described may not only make adequate evaluation impossible but may even give a false impression of a lead fracture. The difference between the two systems was significant.

Artifacts↗
PubMed1993

[New imaging methods in thoracic diagnosis. A study to evaluate digital storage screen radiography, the slit technique ("AMBER"), asymmetric ("InSight") and conventional film-screen techniques].

New methods have been introduced in recent years in chest imaging to achieve high image quality simultaneously in the mediastinum and in the lung field. In this study the clinical value is assessed for four techniques: digital storage phosphor radiography, slit-technique ("AMBER"), asymmetrical film/screen ("InSight") and conventional film/screen. 43 patients were examined with these techniques within one day. Seven readers of four universities graded the image quality according to ten criteria of the mediastinum and the lung field. The slit-technique ("AMBER") showed the best image quality in both areas. Compared to conventional film/screen, storage phosphor radiography and asymmetrical film/screen ("InSight") yield better image quality only in the mediastinum.

Adult↗
PubMed1996

Selection of tRNA(Asp) amber suppressor mutants having alanine, arginine, glutamine, and lysine identity.

Elements that confer identity to a tRNA in the cellular environment, where all aminoacyl-tRNA synthetases are competing for substrates, may be delineated by in vivo experiments using suppressor tRNAs. Here we describe the selection of active Escherichia coli tRNAAsp amber mutants and analyze their identity. Starting from a library containing randomly mutated tRNA(CUA)Asp genes, we isolated four amber suppressors presenting either lysine, alanine, or glutamine activity. Two of them, presenting mainly alanine or lysine activity, were further submitted to a second round of mutagenesis selection in order to improve their efficiency of suppression. Eleven suppressors were isolated, each containing two or three mutations. Ten presented identities of the two parental mutants, whereas one had switched from lysine to arginine identity. Analysis of the different mutants revealed (or confirmed for some nucleotides) their role as positive and/or negative determinants in AlaRS, LysRS, and ArgRS recognition. More generally, it appears that tRNAAsp presents identity characteristics closely related to those of tRNALys, as well as a structural basis for acquiring alanine or arginine identity upon moderate mutational changes; these consist of addition or suppression of the corresponding positive or negative determinants, as well as tertiary interactions. Failure to isolate aspartic acid-inserting suppressors is probably due to elimination of the important G34 identity element and its replacement by an antideterminant when changing the anticodon of the tRNAAsp to the CUA triplet.

Alanine↗
PubMed2007

Using electrospray-assisted pyrolysis ionization/mass spectrometry for the rapid characterization of trace polar components in crude oil, amber, humic substances, and rubber samples.

We describe the use of electrospray-assisted pyrolysis ionization/mass spectrometry (ESA-Py/MS) to selectively ionize trace polar compounds that coexist with large amounts of nonpolar hydrocarbons in crude oil, amber, humic substances, and rubber samples. Samples of different origins are distinguished rapidly by their positive ion ESA-Py mass spectra without prior separation or chemical pretreatment. During ESA-Py analysis, the samples in their solid or liquid states were pyrolyzed at 590, 630 or 940 degrees C using a commercial Curie-point pyrolysis probe. The gaseous pyrolysates were transferred into a glass reaction cell. The polar compounds (M) in the pyrolysates were then ionized by electrospray ionization (ESI), yielding protonated molecules (MH+). Although the major components of the pyrolysates are nonpolar hydrocarbons, their lack of functional groups that can receive a proton in the ESA-Py source results in no hydrocarbon ion signals being produced; thus, the positive ions detected in ESA-Py mass spectra all result from trace polar components in the pyrolysates.

Amber↗
PubMed2005

Plasmodium dominicana n. sp. (Plasmodiidae: Haemospororida) from Tertiary Dominican amber.

Plasmodium dominicana n. sp. is described from Tertiary Dominican Republic amber. The description is based on oocysts, sporozoites and possible microgametes and an ookinete in the body-cavity of a female Culex mosquito (Diptera: Culicidae: Culicinae). The large pedunculated oocysts, together with the culicine vector, align the fossil with the extant avain malaria species, P. juxtanucleare Versiani & Gomes, 1941. Based on the host range of P. juxtanucleare, a possible primary host would have been a member of the order Galliformes. This discovery establishes a minimum age for the genus Plasmodium Marchiafava & Celli, 1885 and places avian malaria in the Americas by the mid-Tertiary. It also supports earlier theories that some species of primate malaria could have evolved in the Americas.

Amber↗
PubMed2006

Nematode (Nematoda: Mermithidae) and hairworm (Nematomorpha: Chordodidae) parasites in Early Cretaceous amber.

The present report describes a mermithid nematode (Nematoda: Mermithidae) and a gordiid hairworm (Nematomorpha: Chordodidae) from Early Cretaceous Burmese amber dated at 100-110 million years. The mermithid, Cretacimermis protus sp. n., is emerging from a biting midge (Diptera: Ceratopogonidae) while the hairworm, Cretachordodes burmitis, gen. n., sp. n. had already emerged from its host. These rare specimens represent the first fossil mermithid parasite of a ceratopogonid midge and second oldest described nematode and the earliest known and only Mesozoic fossil of the phylum Nematomorpha. A list of previously described fossil mermithids is included.

Amber↗
PubMed2003

Sooty moulds from European tertiary amber, with notes on the systematic position of Rosaria ('Cyanobacteria').

Sooty moulds are described and illustrated from European amber dating back to 22-54 Myr. All the fossils are fragments of superficial subicula composed of brown moniliform hyphae with markedly tapering distal ends. The subglobose cells are identical to those of extant Metacapnodium (Metacapnodiaceae, Capnodiales) species. Also other preserved features, like the type of apical growth, wide-angled branching and the production of two distinctive conidial states, supports a placement in this genus. The fossils demonstrate that Metacapnodium hyphae have remained unchanged for tens of millions of years. This confirms that hyphal morphology and conidial states should be accorded considerable classificatory significance in this group of fungi. The following nomenclatural change is made: Metacapnodium succinum comb. nov. (syn. Rosaria succina). The type specimen was initially described as a filamentous cyanobacterium, due to similarities with Rosaria ramosa. Also the systematic position of this attribute is shortly discussed.

Amber↗
PubMed2003

A non-gilled hymenomycete in Cretaceous amber.

Palaeoclavaria burmitis gen. et sp. nov. (Palaeoclavariaceae fam. nov, Hymenomycetes) is described from a series of fruit bodies and hyphae in Cretaceous amber from Burma (about 100 Myr). This is the first fossil record of the Aphyllophorales and establishes certain basic morphological and ecological characters for the group.

Amber↗
PubMed2005

A new species of Stigmatomyces from Baltic amber, the first fossil record of Laboulbeniomycetes.

A fossil ascomycete was found attached to the thorax of a stalk eyed fly (Diopsidae: Prosphyracephala succini) in a fragment of Baltic amber. The fungus is assigned to the extant genus Stigmatomyces and described as S. succini sp. nov. This find is the first fossil record of the order Laboulbeniales. At the same time it constitutes the oldest record of a parasitic fungus on an insect. The palaeohabitat is discussed with regard to the find.

Amber↗
PubMed2003

A new genus of hard ticks in Cretaceous Burmese amber (Acari: Ixodida: Ixodidae).

A hard tick larva in Cretaceous Burmese amber is described as Cornupalpatum burmanicum n. g., n. sp. Diagnostic characters include a subcircular body with a marginal groove, 11 festoons, elongate four-segmented palpi with the fourth segment distinct and apical, the absence of an anal groove and eyes, and the presence of claws on palpal segment 3. The last character is unique for all members of the Ixodida, both fossil and extant. Aside from the palpal claws and marginal groove, features of the tick larva closely resemble those of members of the genus Aponomma Neumann 1899, considered one of the most primitive tick lineages today, whose hosts are primarily reptiles.

Amber↗
PubMed2004

A new phlebotomine fossil species Trichopygomyia killickorum sp. n. (Diptera: Psychodidae) found in the Dominican Republic amber.

A description is given of male sandfly found in a piece of amber from Dominican Republic that dates from the Miocene period (20-15 m.y.a). It is assigned to the genus Trichopygomyia Barreto. The position of the spines on the style and the shape of the dorsal lobes of the paramere separate this fly from other species of the genus: it is here named Trichopygomyia killickorum sp. n.

Amber↗