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At least 127 records · Page 7Linked to original sources

PubMed1990

Mechanism of escape of endogenous murine leukemia virus emv-14 from recognition by anti-AKR/Gross virus cytolytic T lymphocytes.

It was previously shown that spleen cells from endogenous ecotropic murine leukemia virus emv-14+ AKXL-5 mice fail to stimulate an anti-AKR/Gross virus cytolytic T-lymphocyte (CTL) response in a mixed lymphocyte culture with primed C57BL/6 responder spleen cells, whereas spleen cells from AKXL strains carrying the very similar emv-11 provirus do stimulate a response (Green and Graziano, Immunogenetics 23:106-110, 1986). We wished to determine whether the lack of response with AKXL-5 spleen cells was at the level of recognition between effector cell and target cell and whether the relevant mutation was within the emv-14 provirus. It is shown here that EMV-negative SC-1 fibroblast cells transfected with the major histocompatibility complex class I Kb gene and infected with virus isolated from the AKXL-5 strain (SC.Kb/5 cells) were not lysed by H-2b-restricted anti-AKR/Gross virus CTL. SC.Kb cells infected with virus isolated from emv-11+ strains, however, were efficiently lysed by anti-AKR/Gross virus CTL, indicating that there is nothing intrinsic to EMV-infected SC.Kb cells that would prevent them from being recognized and lysed efficiently by anti-AKR/Gross virus CTL. Analysis of virus expression for the infected SC.Kb cells by XC plaque assay and by flow cytometry indicated that emv-14 virus expression for SC.Kb/5 cells was not significantly different from that for emv-11-containing SC.Kb/9 or SC.Kb/21 cells. These data show that the mutation responsible for the lack of CTL recognition and lysis is at the level of recognition between target cell and effector cell. Furthermore, these data strongly suggest that the mutation is within the emv-14 genome. Flow cytometry experiments with monoclonal antibodies against a number of viral determinants indicated that there was no gross mutation detectable in the viral determinants analyzed. The data suggest that the relevant mutation may be a point mutation or a small insertion or deletion within a coding sequence that is critical for CTL recognition.

AKR murine leukemia virus↗

PubMed1991

Allospecific recognition of hemic cells in vitro by natural killer cells from athymic rats: evidence that allodeterminants coded for by single major histocompatibility complex haplotypes are recognized.

We have previously shown that large granular lymphocyte (LGL)-enriched cell populations have the capacity to spontaneously recognize and kill allogeneic small lymphocytes and bone marrow cells (BMC) in vitro in certain strain combinations of rats. Here, we have studied the alloreactivity of natural killer (NK) cells from PVG nude (RT1c) rats against a panel of major histocompatibility complex (MHC) incompatible hemic cells. Both lymphocytes and BMC from the AO (RT1u), DA (RT1a), BN (RT1n) as well as the MHC-congenic PVG-RT1u (RT1u) rat strains were efficiently killed in vitro, whereas cells from syngeneic PVG rats were spared. The structures recognized on lymphocytes and BMC were probably similar since the two cell populations inhibited each other in cross-competition experiments. A number of features aligned the alloreactive effector cells with NK cells and not T cells. (a) Only about 5% of the effector cells from nude spleens expressed the T cell antigens CD3, CD5 or T cell receptor (TcR) alpha/beta whereas greater than 50% of the cells expressed markers present on NK cells (CD2, CD8, OX52 and the rat NK cell-specific marker NKR-P1 recognized by the monoclonal antibody 3.2.3). (b) The alloreactive cells were granular since pretreatment of nude spleen cells with the lysosomotropic agent L-leucine methyl ester which eliminated LGL, simultaneously abolished the cytolysis of both allogeneic lymphocytes and YAC-1 tumor cells. (c) Nude spleen cells stimulated with human recombinant interleukin 2 for 1 week in vitro generated large granular proliferating cells which were CD3-, CD5-, TcR alpha/beta-, but greater than 95% 3.2.3+. These cells efficiently killed allogeneic hemic cells from the same rat strains as did freshly isolated effector cells. (d) The cytolysis of allogeneic hemic cells could effectively be inhibited with unlabelled NK-sensitive (YAC-1 and K-562), but not NK-resistant (Roser leukemia) tumor cells. Cross-competition studies showed that PVG nude NK cells discriminated between AO, BN and DA BMC, suggesting that different alloantigens were positively recognized by subsets of NK cells. The mode of inheritance of the allodeterminant specifically recognized on AO BMC was investigated in crosses and backcrosses between AO and BN or DA rats. A gene dosage effect was observed in that this determinant was expressed at a slightly reduced level in F1 hybrids.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Advanced cardiac life support refresher course using standardized objective-based Mega Code testing.

The American Heart Association (AHA) recommends that those whose daily work requires knowledge and skills in advanced cardiac life support (ACLS) not only be trained in ACLS, but also be given a refresher training at least every 2 yr. However, AMA offers no recommended course for retraining; no systematic studies of retraining have been conducted on which to base these recommendations. In this paper we review and present our recommendation for a standardized approach to refresher training. Using the goals and objectives of the ACLS training program as evaluation criteria, we tested with the Mega Code a sample population who had previously been trained in ACLS. The results revealed deficiencies in ACLS knowledge and skills in the areas of assessment, defibrillation, drug therapy, and determining the cause of an abnormal blood gas value. We combined this information with our knowledge of other deficiencies identified during actual resuscitation attempts and other basic life-support and ACLS teaching experiences. We then designed a refresher course which was consistent with the overall goals and objectives of the ACLS training program, but which placed emphasis on the deficiencies identified in the pretesting. We taught our newly designed refresher course in three sessions, which included basic life support, endotracheal intubation, arrhythmia recognition and therapeutic modalities, defibrillation, and Mega Code practice. In a fourth session, using Mega Code testing, we evaluated knowledge and skill learning immediately after training. We similarly tested retention 2 to 4 months later. Performance immediately after refresher training showed improvement in all areas where performance had been weak.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical Care↗

PubMed1985

Tactual perception of embossed Morse code and braille: the alliance of vision and touch.

In three experiments observers made visual matches to tangible embossed patterns. Stained glass was used to blur vision and thus allow the effect of visual guidance of tactual exploration on the accuracy of symbol recognition to be evaluated. Stained glass rendered the embossed code invisible, but allowed sight of the hand. In the first experiment subjects identified patterns made up of dots and dashes drawn from Morse code; in the second and third experiments they studied braille. The results show that subjects are more accurate in 'reading' tangible codes when provided with visual guidance. Performance was higher for braille than for Morse code. Vision aided touch through the provision of a frame of reference and through sight of scanning movements. Naive sighted observers were able to identify invisible braille dots by watching other individuals touch the symbols, suggesting the importance of vision of kinesthetic patterns.

Female↗

PubMed1992

Comparison of speech recognition ability with different speech processing strategies by Korean cochlear implantees.

Many variables affect the audiologic performance of cochlear implantees. With current methods of evaluation, it is difficult to directly compare auditory function with different speech coding strategies. We compared the audiologic performance directly with F0F1F2 and multipeak speech coding strategies in the same implanted ear of eight Korean cochlear implantees. We tested word and phoneme recognition abilities using Korean word lists for speech audiometry and two-syllable nonsense words, respectively. With the multipeak coding strategy, a significant difference in discrimination ability was found in the initial fricative consonant phonemes (/s/,/ss/,/h/). Our results suggest that the improvement of speech recognition ability with the multipeak coding strategy comes primarily from the better understanding of the initial fricative consonants.

Adult↗

PubMed1987

In vitro sodium bisulfite mutagenesis of restriction endonuclease recognition sites.

Sodium bisulfite treatment of single-stranded DNA deaminates exposed cytosine residues to form uracil, resulting in cytosine-to-thymidine transition mutations following DNA replication. We have used this reaction in vitro to destroy the recognition sequences for the restriction endonucleases HindIII and XmaI in the aminoglycoside 3'-phosphotransferase I coding region of plasmid pUC4K. This procedure should be applicable to the mutation of any recognition sequence of restriction endonucleases which generate cytosine-containing single-stranded ends. The possibility of mutagenesis of restriction sites to generate stop codons in coding regions is discussed.

Base Sequence↗

PubMed1992

Reading isolated words: no evidence for automatic incorporation of the phonetic code.

Backward masking with a homophonic mask induces better target recognition than backward masking with a graphemic mask that shares the same letters with the target as the homophonic mask. From this, the existence of automatic prelexical phonological recoding in silent word reading has been inferred. The present experiments, however, show that the advantage of homophonic masks in a backward-masking task only arises if a considerable proportion of the masks are phonologically related to the targets (at least for Dutch). The results are in line with findings of lexical-decision tasks and number-processing tasks, and constitute a further argument for the dominance of the orthographic route over the phonological route in processing isolated written words.

Adult↗

PubMed1986

RAM, a gene of yeast required for a functional modification of RAS proteins and for production of mating pheromone a-factor.

We have identified a gene (SUPH) of S. cerevisiae that is required for both RAS function and mating by cells of a mating type. supH is allelic to ste16, a gene required for the production of the mating pheromone a-factor. Both RAS and a-factor coding sequences terminate with the potential acyltransferase recognition sequence Cys-A-A-X, where A is an aliphatic amino acid. Mutations in SUPH-STE16 prevent the membrane localization and maturation of RAS protein, as well as the fatty acid acylation of it and other membrane proteins. We propose the designation RAM (RAS protein and a-factor maturation function) for SUPH and STE16. RAM may encode an enzyme responsible for the modification and membrane localization of proteins with this C-terminal sequence.

Acylation↗

PubMed1977

Cytotoxic T-cell response to Ectromelia virus-infected cells. Different H-2 requirements for triggering precursor T-cell induction or lysis by effector T cells defined by the BALB/c-H-2db mutation.

The T(c)-cell response to ectromelia virus infection was studied in BALB/c-H-2(db) mice which carry a loss mutation in the H-2D region that results in the absence from cell surfaces of a molecule (D') bearing certain public H-2 specificities. When infected, these mice showed a poor response of T(c) cells that recognize H-2D(d) plus virus-specific determinants on infected macrophage targets, but gave a normal response to H-2K d plus virus-specific antigens. However, their own infected macrophages do display wild-type antigenic patterns involving virus and H-2D(d) since they were killed as efficiently as wild-type (BALB/c,H- 2(d))-infected cells by T(c) cells specific only for H-2D(d) plus viral antigens. When tested in vitro, infected BALB/c-H-2(db) cells stimulated a poor T(c)-cell response to H-2D plus virus-specific antigens, but stimulated a normal response (in comparison with infected BALB/c macrophages) to H-2K(d) plus viral antigens. Uninfected BALB/c-H-2(db) cells stimulated a normal T(c)-cell response to minor H antigens or trinitrophenyl in association with H-2D(d), thus suggesting that the defective response to infection may reside in a failure of the relevant H-2D(d) antigens of mutant cells to physically associate with viral antigens. Close association of viral and H-2D-coded molecules was also suggested by ability of specific anti-H-2K or -H-2D to partially block T(c)-cell-mediated lysis of infected targets. These results were interpreted to mean that H-2Dd-dependent, virus- immune T(c) cells recognized an antigenic pattern consisting of virus- specific and H-2D(d) determinants with the latter borne on an H-2D molecule carrying serologically-defined H-2D(d) private specificities. A second H-2D(d)-coded molecule (D') was not required for recognition and lysis by activated T(c) cells, but was apparently necessary for efficient stimulation of precursor T(c) cells, perhaps by promoting appropriate physical association of viral and H-2D(d) molecules.

Animals↗

PubMed1987

Blocking of delivery of the antigen-mediated signal to the nucleus of T cells by cyclosporine.

Cyclosporine (CsA) inhibits release of interleukin 2 (IL-2) and hemopoietic growth activities such as interleukin 3 (IL-3) from major histocompatibility complex (MHC)-antigen-activated T cells. Production of both lymphokines appears to be coordinately regulated; the antigen dose response, T cell dose response, and time course of lymphokine appearance are similar. The triggering of lymphokine production by these cells is solely dependent on T cell-target cell interaction, as the T cell dose response curve indicates that no cooperation occurs between T cells, and any metabolic contribution by the target cell was eliminated by ultraviolet irradiation. This interaction triggers the transcription of lymphokine-encoding mRNA. The process of lymphokine release can be divided into 4 steps: Antigen binds to the T cell; a signal is transferred to the cell nucleus; transcription of lymphokine-encoding mRNA occurs; and intact lymphokine is synthesized and secreted. CsA inhibits antigen triggered lymphokine production. However, it does not inhibit lymphokine release from the constitutively producing tumor cell lines WEHI-3 (which releases IL-3) and MLA 144 (which produces IL-2). Thus CsA has no effects on the lymphokine secretion process or any direct action upon lymphokine-coding mRNA. CsA does not affect antigen recognition during cell-mediated cytotoxicity. Therefore, CsA acts after antigen binding and before transcription of lymphokine-encoding mRNA. That is CsA blocks the transmission of the antigen signal. This information is used to show that this CsA-sensitive signal is required continuously to maintain the T cell in a lymphokine-secreting state.

Animals↗

PubMed1987

Cytotoxic T cell specificity for respiratory syncytial virus proteins: fusion protein is an important target antigen.

We examined the specificity of BALB/c cytotoxic T (Tc) cells for respiratory syncytial virus (RSV) components, using recombinant vaccinia viruses (VV) coding for several individual RSV proteins. We found that immunization with the different VVs yielded the following Tc memory cell populations: high levels of RSV-specific Tc cells were induced with the fusion protein VV, but low levels were induced with VV coding for the RSV nucleoprotein. Tc cell recognition of attachment glycoprotein, part of the matrix molecule or 1A internal protein was poor. While high levels of fusion protein-specific Tc cells were induced by the fusion protein VV, they showed poor cross-reactivity between the A2 and 8/60 RSV strains compared with Tc cells primed by RSV infection.

Animals↗

PubMed1988

Inhibition of self-binding antibodies (autobodies) by a VH-derived peptide.

The self-binding properties of a dominant idiotypic antibody (T15) and a minor idiotypic antibody (M603), both specific for phosphorylcholine, were examined as models of self-binding antibodies (autobodies). Observed differences in the self-binding affinity of T15 and M603 relate to variable sequence differences in their respective heavy and light chains. A molecular recognition theory based on the translation of coding and noncoding DNA strands was used to identify complementary amino acid sequences responsible for self-binding. The second hypervariable region of the heavy chain domain, extending into the third framework region, was predicted as the primary self-binding locus. Among peptides synthesized with different variable heavy and light chain regions, a 24-residue peptide spanning the second hypervariable and third framework regions of the heavy chain of T15 was nearly as effective as phosphorycholine in inhibiting the self-binding complexes.

Amino Acid Sequence↗

PubMed1990

Evidence that modulation requires sequences downstream of the promoters of two vir-repressed genes of Bordetella pertussis.

Gene expression in Bordetella pertussis is altered by environmental signals in a process called antigenic modulation. In the presence of modulating signals, expression of several known virulence factors and outer membrane proteins is coordinately reduced. From a bank of TnphoA fusions, we have identified five genes whose expression profiles are reciprocal of those of the major virulence determinants; that is, alkaline phosphatase activity is maximal during growth in the presence of the modulators nicotinic acid and MgSO4 (S. Knapp and J. J. Mekalanos, J. Bacteriol. 170:5059-5066, 1988). We have called these loci vir-repressed genes (vrg). Two of these gene fusions (vrg-6 and vrg-18) have been cloned in Escherichia coli, returned on low-copy-number plasmids to several strains of B. pertussis, and found to be regulated similarly to the fusions harbored on the chromosome. Deletions of the two vrg promoters were constructed and returned to B. pertussis. Regulation was maintained even when all but 24 nucleotides upstream of the vrg-18 initiation codon and 60 nucleotides upstream of the vrg-6 initiation codon were deleted, suggesting that cis-acting regulatory elements of these genes lie very near or within the coding region. We observed a 21-base palindromic sequence overlapping an 8-base direct repeat within the signal sequence coding region of vrg-6; insertion of a 6-bp linker in this region abolished regulation. These repetitive sequences are also at the site of greatest primary sequence identify between vrg-6 and vrg-18 and correspond to the signal sequence coding region. We propose models that involve recognition of this region by a vir-regulated gene product.

Alkaline Phosphatase↗

PubMed1992

Phoneme recognition by deaf individuals using the multichannel nucleus cochlear implant.

Experiments have been carried out to determine which cues are used in phoneme identification by deaf individuals using a cochlear implant. Five deaf individuals with a Nucleus 22-channel cochlear implant were tested with open set speech audiometry in free field without lipreading. Speech material consisted of lists of Dutch words of the Consonant-Vowel-Consonant type (CVC-words). Word scores ranged from 0 to 22%, phoneme scores from 11 to 54%. For each subject the responses to the initial consonant, the vowel and the final consonant were entered into separate confusion matrices. Kruskal analysis, which provided a geometric representation of these confusions, showed that in the recognition of consonants the feature of voicing is all important. Vowels were identified on the basis of the frequencies of the first and second formants. In one subject the electrode array could only partially be inserted into the cochlea, leaving roughly half the second formant area of the electrode array outside the cochlea. For this subject vowel identification was based upon the first formant and vowel duration; there was no contribution of second formant information to vowel identification. Compressing the first and second formant frequency to the limited intracochlear array did not enhance transmission of second formant information and did not improve performance. The basic findings for consonant and vowel recognition could be explained by the speech coding strategy of the Nucleus speech processor in which voicing determines stimulus periodicity and formant frequencies determine channel selection. Kruskal analysis of phoneme confusions may aid in programming and evaluating the performance of the Nucleus cochlear implant.

Adult↗

PubMed1991

Degradation of MYCN oncoprotein by the ubiquitin system.

Nuclear oncoproteins are among the most rapidly degraded intracellular proteins. Previous work has implicated the ubiquitin-mediated proteolytic system in the turnover of short-lived intracellular proteins as a class. In the present study, we have evaluated the potential role of the ubiquitin system in the degradation of the specific nuclear oncoproteins encoded by the MYCN gene. The oncoproteins were synthesized in vitro by transcription of an MYCN cDNA, and translation of the resulting single species of mRNA in the presence of 35S-methionine. Degradation of labeled proteins was monitored in a cell-free system derived from rabbit reticulocytes. ATP stimulated the degradation of the MYCN protein more than 10 fold. ATP-dependent degradation was completely inhibited by neutralizing antibody directed against E1, the first enzyme in the ubiquitin-mediated proteolytic cascade. Moreover, ATP-dependent degradation in E1-depleted lysate could be restored by the addition of affinity-purified E1. These data suggest that the ubiquitin system mediates the ATP-dependent degradation of MYCN oncoproteins in vitro, and that these proteins possess signals that target them for rapid turnover by this proteolytic pathway. Although MYCN in neuroblastomas is activated primarily by amplification, it may be activated by other mechanisms in aggressive tumors with a single copy of MYCN. Mutations in protein coding sequence that alter the signals for recognition by protein degradation systems represent a potential mechanism by which oncogene activation might occur.

Animals↗

PubMedDate not supplied

[Role of nonspecific complex formation in protein-nucleic acid recognition].

Combinatory mathematical model of equilibrium binding of recognising proteins to DNA has been considered. The expression for the ratio of specific and unspecific complex as the function of a number of nucleotides in DNA, a number of centers of recognition, concentration of recognising molecules and a code number have been obtained. The analysis of obtained expression for the repressor--operator system showed that binary code would preferable than quartic one. The specificity of binding corresponding to experimental results have been observed by the number of centers more than twenty, in the narrow interval of the energy value and by high limitation on the number of combinations of error centers.

Base Sequence↗

PubMed1990

Place coding of vowel formants for cochlear implant patients.

Four multiple-channel cochlear implant patients were tested with synthesized versions of the words "hid, head, had, hud, hod, hood" containing 1, 2, or 3 formants, and with a natural 2-formant version of the same words. The formant frequencies were encoded in terms of the positions of electrical stimulation in the cochlea. Loudness, duration, and fundamental frequency were kept fixed within the synthetic stimulus sets. The average recognition scores were 47%, 61%, 62%, and 79% for the synthesized 1-, 2-, and 3-format vowels and the natural vowels, respectively. These scores showed that the place coding of the first and second formant frequencies accounted for a large part of the vowel recognition of cochlear implant patients using these coding schemes. The recognition of the natural stimuli was significantly higher than recognition of the synthetic stimuli, indicating that extra cues such as loudness, duration, and fundamental frequency contributed to recognition of the spoken words.

Attention↗

PubMed1992

Experimental studies on the origin of the genetic code and the process of protein synthesis: a review update.

This article is an update of our earlier review (Lacey and Mullins, 1983) in this journal on the origin of the genetic code and the process of protein synthesis. It is our intent to discuss only experimental evidence published since then although there is the necessity to mention the old enough to place the new in context. We do not include theoretical nor hypothetical treatments of the code or protein synthesis. Relevant data regarding the evolution of tRNAs and the recognition of tRNAs by aminoacyl-tRNA-synthetases are discussed. Our present belief is that the code arose based on a core of early assignments which were made on a physico-chemical and anticodonic basis and this was expanded with new assignments later. These late assignments do not necessarily show an amino acid-anticodon relatedness. In spite of the fact that most data suggest a code origin based on amino acid-anticodon relationships, some new data suggesting preferential binding of Arg to its codons are discussed. While information regarding coding is not increasing very rapidly, information regarding the basic chemistry of the process of protein synthesis has increased significantly, principally relating to aminoacylation of mono- and polyribonucleotides. Included in those studies are several which show stereoselective reactions of L-amino acids with nucleotides having D-sugars. Hydrophobic interactions definitely play a role in the preferences which have been observed.

5'-Nucleotidase↗