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At least 91 records · Page 5Linked to original sources

PubMed1992

Genetic analysis of the interaction between bacteriophage T7 DNA polymerase and Escherichia coli thioredoxin.

Gene 5 protein of bacteriophage T7 is a nonprocessive DNA polymerase. During infection of Escherichia coli, T7 annexes the host protein thioredoxin for use as a processivity factor for T7 DNA polymerase. We describe here a genetic method to investigate the interaction between T7 gene 5 protein and E. coli thioredoxin. The strategy is to use thioredoxin mutants that are unable to support the growth of wild-type T7 phage to select for T7 revertant phage that suppress the defect in thioredoxin. A thioredoxin mutation that replaces glycine at position 74 with aspartic acid fails to support the growth of wild-type T7. This mutation is suppressed by six different mutations within T7 gene 5, each of which results in a single amino acid substitution within gene 5 protein. Three of the suppressor mutations are located within the putative polymerization domain of gene 5 protein, and three are located within the putative 3'-to-5' exonucleolytic domain. Each suppressor mutation alone is necessary and sufficient to confer the revertant phenotype.

DNA Replication↗

PubMed1977

Selection of medical specialties: preferences versus choices.

This study was undertaken to examine the extent to which there are differences between preferences and choices of specialty areas among medical students. A total of 350 medical students completed a questionnaire dealing with various aspects of a career in medicine, including specialty preference and choice decisions. The Intolerance of Ambiguity Scale was included as part of the questionnaire. Differences between specialty preference and choice were found for the total group as well as for male and female comparisons. Intolerance of ambiguity was found to be associated with the specialty decision process. Factors contribution to the differences were examined and recommendations for further research were discussed.

Career Choice↗

PubMed1979

Decreased splenic perfusion without functional asplenia.

Although functional asplenia may be associated with decreased splenic perfusion, two cases are presented which illustrate that the converse is not necessarily true. That is, two patients with markedly reduced splenic perfusion still showed splenic extraction of radiocolloid. These cases clearly demonstrate the dissociation of splenic blood flow and the radiocolloid extraction processes. Factors which might have contributed to the decreased perfusion are discussed.

Adolescent↗

PubMed1978

Temporal integration and children's understanding of social information of television.

Recent studies are reviewed that suggest that preschool and young grade-school children often have incomplete or distorted impressions of social portrayals on television. It is suggested that cognitive-processing factors in understanding television dramas may put these younger viewers at special risk for deleterious effects of television viewing.

Age Factors↗

PubMed1992

trans-acting requirements for replication of Epstein-Barr virus ori-Lyt.

Epstein-Barr virus (EBV) utilizes a completely different mode of DNA replication during the lytic cycle than that employed during latency. The latency origin of replication, ori-P, which functions in the replication of the latent episomal form of the EBV genome, requires only a single virally encoded protein, EBNA-1, for its activity. During the lytic cycle, a separate origin, ori-Lyt, is utilized. Relatively little is known about the trans-acting proteins involved in ori-Lyt replication. We established a cotransfection-replication assay to identify EBV genes whose products are required for replication of ori-Lyt. In this assay, a BamHI-H plasmid containing ori-Lyt was replicated in Vero cells cotransfected with the BamHI-H target, the three EBV lytic-cycle transactivators Zta, Rta, and Mta, and the EBV genome provided in the form of a set of six overlapping cosmid clones. By removing individual cosmids from the cotransfection mixture, we found that only three of the six cosmids were necessary for ori-Lyt replication. Subcloning of the essential cosmids led to the identification of six EBV genes that encode replication proteins. These genes and their functions (either known or predicted on the basis of sequence comparison with herpes simplex virus) are BALF5, the DNA polymerase; BALF2, the single-stranded DNA-binding protein homolog; BMRF1, the DNA polymerase processivity factor; BSLF1 and BBLF4, the primase and helicase homologs; and BBLF2/3, a potential homolog of the third component of the helicase-primase complex. In addition, ori-Lyt replication in this cotransfection assay was also dependent on one or more genes provided by the EBV SalI-F fragment and on the three lytic-cycle transactivators Zta, Rta, and Mta.

Amino Acid Sequence↗

PubMed1988

Structure and function of nonhistone phosphoproteins.

Many nonhistone nuclear proteins have been shown to be phosphorylated and associated with a diverse range of cellular activities. The aim of this present review is to update the most recent developments in this field with respect to the traditional roles that these proteins have been postulated to play as enzymes, DNA-binding proteins, hormonal receptors, nucleosome associated proteins, and nucleolar associated proteins. In addition, evidence is presented suggesting that these proteins may also function as nuclear oncogene protein products, structural constituents of nuclear organization (e.g., lamina-nuclear matrix associated proteins), and RNA processing factors.

Animals↗

PubMedDate not supplied

Platelet secretory products increase low density lipoprotein oxidation, enhance its uptake by macrophages, and reduce its fluidity.

Oxidized low density lipoprotein (Ox-LDL) is considered to be involved in the atherogenic process. Factors influencing the formation of Ox-LDL are thus of importance. Oxidation of LDL in a cell-free system in the presence of copper ions was significantly increased (up to 60%) by the presence of platelet-conditioned medium, (PCM) obtained from collagen-activated platelets for the duration of the oxidation period. The effect was time- and dose-dependent and was related to hydrogen peroxide and superoxide production, since PCM-induced enhanced LDL oxidation was inhibited by catalase and by superoxide dismutase, but not by protease treatments. PCM also reduced the fluidity of oxidized LDL by 45%. Upon incubation with a J-774 macrophage-like cell line, PCM-treated Ox-LDL enhanced cellular cholesteryl ester synthesis by 47% and lipoprotein degradation by 41%. Thus platelet secretory products appeared to enhance LDL oxidation through the involvement of oxidative agents. The resulting Ox-LDL demonstrated increased atherogenic properties.

Blood Platelets↗

PubMed1988

Antibiotic resistance and production of inhibitory substances among bacterial strains isolated from the oral cavities of BALB/c mice.

In the oral cavities of BALB/c mice, microbial population levels are regulated by multifactorial processes. Factors include the production of inhibitory substances and the exchange of genetic material. In this work, 371 isolates from different sites (saliva, tongue, teeth, and mucosa) of the oral cavities of BALB/c mice were screened for resistance to antibiotics and antimicrobial activity. Antibiotic-resistant strains represented 25% of the total flora. Among the predominant species, all the S. faecalis isolates showed multiresistance, and 23% of the Lactobacillus murinus isolates and 15% of the Staphylococcus aureus were resistant to at least one antibiotic. Resistance to aminoglycosides (neomycin, streptomycin, kanamycin, and gentamicin) was most frequently encountered. In S. faecalis, high levels of resistance were recorded to neomycin and streptomycin but not to gentamicin or kanamycin. Macrolides (M), lincosamides (L), streptogramin B (S), tetracycline (Tc), and chloramphenicol (Cm) resistance was also present in multiresistance patterns, especially among S. faecalis isolates. Hemolytic (Hly+) streptococci were less resistant to MLS, Tc, and Cm than were non-hemolytic (Hly-) isolates. Resistance to beta-lactam antibiotics was detected only among staphylococci and with a low prevalence (4%). The frequencies of strains producing antimicrobial substances against the indicator strains (S. mutans LG-1, S. sanguis Ny 101, and A. viscosus Ny 1) were high for L. murinus (76%) and S. faecalis (57% for Hly- and 90% for Hly+), but low for S. aureus (7%). These results indicate that the indigenous oral flora could interfere with colonization by allochthonous micro-organisms and that resistance patterns should be taken into account for the elimination of the oral indigenous flora by antibiotic treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

[Various clinical characteristics of remission in patients with recurrent schizophrenia].

Altogether 194 patients suffering from attack-like schizophrenia lasting not less than 15 years since the manifest attack were examined for the clinico-dynamic features of the remission conditions as dependent on a number of endogenous and process factors: the disease period, disease duration from the manifest attack, the number of the attacks suffered by the patient. The data obtained can be used in elaboration of the socio-rehabilitation and medicamentous measures in patients suffering from attack-like schizophrenia.

Adult↗

PubMed1991

Paramyxovirus tropism dependent on host proteases activating the viral fusion glycoprotein.

An essential step in paramyxovirus fusion (F) glycoprotein biosynthesis is the posttranslational endoproteolytic cleavage of the inactive precursor glycoprotein Fo by host cell proteases. When the Fo possesses a pair or a cluster of basic residues at the cleavage site, cleavage is catalyzed by a ubiquitous protease(s) and the infection is consequently pantropic. When the site is monobasic with a single arginine, cleavage is allowed to occur only by the enzyme(s) expressed in limited tissue types and the infection is localized there. We have isolated from chick embryo an example of the latter type of endoprotease specific for the single arginine motif and demonstrate its identity with the clotting factor Xa. The ectopic expression of the FXa appeared to be the sole determinant for the viral tropism in chick embryo. The latter type of protease specific for a paired or multiple basic cleavage motif have neither been identified nor characterized extensively. We show here that this cleavage can be induced by the yeast KEX2 protease, a unique subtilisin-like serine protease, responsible for pro factor processing at the paired basic sites.

Amino Acid Sequence↗

PubMed1991

[Insomnia and its treatment in aged persons: a new approach].

Existing hypotheses regarding psychological mediation of disorders in initiating and maintaining sleep only partially explain the phenomenon of insomnia, particularly in aging individuals. In this article we review existing nonpharmacological treatments of insomnia and propose a new way of conceptualizing and treating disorders of initiating and maintaining sleep. The model, based on cognitive and information processing factors, is then used to propose novel approaches to intervention. Because of the prevalence of sleep disruptions in older adults and the limitations of existing pharmacological and psychological treatments with this population, the assumptions of the model and the proposed intervention are explored with particular reference to aging individuals.

Aged↗

PubMed1979

[Possibilities and limits for palsied children in the general polytechnical school (author's transl)].

Some children with cerebral palsy attend the ten-form general polytechnical school. To this end, several prerequisites have to be fulfilled and other essential arrangements to be developed in cooperation with specially trained teachers. The learning conditions have to be fitted to the improving abilities of children during the educational process. Factors of influence and cooperation modes are discussed.

Adolescent↗

PubMed1979

[The psychophysiology of the visual thought perception of visually evoked brain potentials and recognition mechanisms].

The study tries to demonstrate, that the combination of the actualgenetic method (Sander, Froehlich), and the VEP, allows a systematic and differentiated analysis of the psychophysiological process of visual thinking. A student group was compared with mental retardates in VEP and EOG, watching actualgenetically manipulated picture series. Phasic EEG-changes are significantly related to the identification process. Most sensitive are amplitude changes about 120 to 270 msec. The mental retardates had significant VEP changes 180--270 msec, the students 128--192 msec after picture presentation. The process factor analysis (Pawlik) elaborated an illumination factor and two factors being labelled general reaction set. VEP averaging over the persons revealed different attention and/or discrimination behavior for the student group and the mental retardates, identifying the picture objects.

Adult↗

PubMed1991

Cleavage of the membrane precursor for transforming growth factor alpha is a regulated process.

Transforming growth factor alpha (TGF-alpha) is generated by cleavage of a membrane-anchored precursor protein, proTGF-alpha. ProTGF-alpha is cleaved at a slow rate and accumulates on the cell surface, thereby mediating cell-cell adhesion and mitogenic stimulation. We show here that cleavage of membrane proTGF-alpha by an elastase-like enzyme constitutes an important regulatory step in the generation of soluble TGF-alpha. Cleavage is activated in response to serum factors and tumor-promoting phorbol esters, leading to depletion of cell surface proTGF-alpha, which disperses as soluble factor. Activation of proTGF-alpha cleavage is mediated by protein kinase C-dependent and -independent mechanisms. The results demonstrate the existence of mechanisms that control the switch of TGF-alpha from a juxtacrine to a paracrine growth factor.

Animals↗

PubMed1992

[Role of cytokines and growth factors in joint destruction processes].

Cytokines and growth factors are important mediators of inflammatory reactions and play a central role in the physiologic regulation of bone and cartilage cell activities and in joint destruction. The net effects of cytokines on target tissues depend on the relative pericellular concentrations of several cytokines and their inhibitors in the inflammatory tissue. It is possible to suppress the effects of cytokines with natural or synthetic inhibitory molecules. The measurement of cytokines and their inhibitors may be useful to understand the pathogenesis and to develop new therapies for inflammatory joint diseases. In this review the following cytokines will be reviewed: interleukin 1 and its inhibitor, tumor necrosis factor alpha and its inhibitor, interleukin 6, interferon gamma, transforming growth factor beta, colony-stimulating factors, fibroblast growth factors, platelet derived growth factor and prostaglandins.

Arthritis↗

PubMed1977

The styloid process syndrome: aetiological factors and surgical management.

The literature on the syndromes associated with the styloid process is reviewed. The anatomy and embryology of the styloid apparatus are then discussed in relation to the development of these conditions; attention is drawn to the significance of elongation of the process. Eighty styloids measured at post-mortem examination enabled a mean length to be determined as well as a range of normals. The possible aetiological factors are then listed. Four cases of elongated styloid process are described, three treated by excision via an external approach and the fourth presenting as an asymptomatic lump in the neck, not requiring treatment. The authors' preference for the external approach is explained.

Congenital Abnormalities↗

PubMed1989

Identification of mRNA coding for factor VII protein in human alveolar macrophages--coagulant expression may be limited due to deficient postribosomal processing.

Clotting factors synthesized by monocytes and macrophages may initiate coagulation reactions during inflammation. Functional vitamin K-dependent coagulation factors have been found to be associated with human monocytes/macrophages, but there are no reports identifying mRNA coding for vitamin K-dependent proteins in these cells. In the present studies, factor VII mRNA was found in total RNA extracted from freshly isolated human alveolar macrophages using hybridization with a complementary DNA probe. On the other hand, vitamin K-dependent carboxylase activity which is required for postribosomal modification of the protein, was not detectable in the macrophages before or after culture, and human blood mononuclear leukocytes also lacked this enzyme activity. Control human and rat hepatoma cells exhibited high levels of carboxylase activity within the same experiments. Using sensitive kinetic assays, no increase in factor VII activity was detected during culture of alveolar macrophages under conditions promoting 1.78 +/- .24 (n = 8) fold increases of tissue factor activity. These findings with freshly isolated cells demonstrate that alveolar macrophages synthesize factor VII mRNA in vivo. However, the mRNA was found in the absence of evidence for gamma-carboxylase activity or processing of the factor into a functional clotting enzyme. The results imply that functional expression of any synthesized coagulation factor VII in alveolar macrophages may be limited or prevented due to a cellular deficiency at the level of postribosomal processing.

Carbon-Carbon Ligases↗

PubMed1990

Antigen processing and presentation in vivo: the microenvironment as a crucial factor.

Antigen processing and presentation in vitro is an increasingly well understood phenomenon. However, in vivo, a large number of variables conspire to obscure and confuse. In this article, Nico van Rooijen attempts to bring order to events that occur in the spleen after antigenic challenge: starting with the large body of reliable in vitro data he incorporates information on splenic anatomy, cell trafficking and the cellular microenvironment to arrive at a physiological model for antigen handling in vivo.

Animals↗