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Biomedical subjects

A Royal

Publications and source records attributed to A Royal.

33 records · Page 2Linked to original sources
PubMed1987

Expression of new proteins of the intermediate filament protein family in differentiating F9 embryonal carcinoma cell cytoskeleton.

Differentiation of F9 embryonal carcinoma cells by retinoic acid treatment results in extraembryonic endoderm-like cells. The effects of this process on the protein composition of the intermediate filaments were studied by two-dimensional gel electrophoresis and by immunoblotting. By this approach, two new proteins induced in differentiating cells, p57 and p54, were identified in cytoskeletal preparations enriched in intermediate filaments. The 57-kDa protein could be resolved into at least three components (pI 5.6-5.9), and the 54-kDa protein into at least two components (pI approximately 5.6). Both proteins reacted with a monoclonal antibody which recognizes an antigenic determinant common to all intermediate filaments. Based on these results, the two proteins were identified as members of the intermediate filament protein family. Partial digestion with V8 protease showed that p57 was different from vimentin, another intermediate filament protein present in these cells. p57 and p54 were also immunodetected by a polyclonal anti-keratin anti-serum, which suggests that these proteins share some homology with the keratins. These two proteins are different from the endodermal cytoskeletal protein A and B (endo A and endo B) keratins, which are known to be present in extraembryonic endoderm-like cells. They were also more abundant than endo A and endo B in differentiating F9 embryonal carcinoma cells, but almost undetectable in terminally differentiated extraembryonic endoderm-like cells, where endo A and endo B are readily detectable. This suggests that p57 and p54 have a different pattern of expression than endo A and endo B.

Animals↗
PubMed1987

Lamins A and C appear during retinoic acid-induced differentiation of mouse embryonal carcinoma cells.

The lamin complement of nuclear matrix isolated from F9 embryonal carcinoma cells was studied during retinoic acid-induced differentiation in culture. Differentiation of the original cells into parietal endoderm-like cells was accompanied by the gradual appearance of lamins A and C while lamin B was present throughout all stages. Lamins were identified by their molecular masses, isoelectric points, recognition by a monoclonal antibody and a polyclonal antiserum, and by peptide mapping. The increase in the amounts of lamins A and C found in the matrix was due to de novo synthesis as no extranuclear pools of these lamins were detected in the undifferentiated cells. These results provide biochemical evidence that, as in amphibian embryogenesis, there are variations in nuclear lamina composition during mammalian development.

Animals↗
PubMed1986

Differential expression of keratin genes during mouse development.

Suprabasal layers of the newborn mouse epidermis contain two mRNAs of 2.0 and 2.4 kb which are translated into keratins of 59 and 67 kDa, respectively. To study their expression during development, cDNA sequences corresponding to the 2.0- and the 2.4-kb mRNAs were cloned, characterized by hybridization selection assay, and used as probes to detect keratin sequences in polyadenylated RNA from Day 11, 13, 15, and 17 embryos. In RNA from Day 11 of gestation, two RNAs of 2.8 and 1.8 kb were identified. They were found to have homologies with both epidermal RNAs, suggesting that they are coding for proteins of the keratin family. These two sequences were not detected in sample of later stages. RNAs comigrating with the two epidermal keratin RNAs were identified only in Day 15 and 17 embryos indicating that their expression was induced between Day 13 and 15. Finally, the localization of the 59-kDa keratin mRNA was examined by in situ hybridization. The spinous and granulous cell layers were found to be heavily covered with grains while other regions of the tissue sections were unlabeled. All these results support the hypothesis of a sequential expression of keratins during differentiation of epidermal cells and suggest that proteins related to the keratins expressed specifically in keratinizing cells are expressed earlier during development.

Animals↗
PubMed1986

Herpes simplex virus type 2 mutagenesis: characterization of mutants induced at the hprt locus of nonpermissive XC cells.

In a previous report, herpes simplex virus type 2 (HSV-2) was shown to increase the frequency of mutation at the hypoxanthine phosphoribosyltransferase (hprt) locus of nonpermissive rat XC cells (L. Pilon, A. Royal, and Y. Langelier, J. Gen. Virol. 66:259-265, 1985). A series of 17 independent mutants were isolated after viral infection together with 12 spontaneous noninfected mutants to characterize the nature of the mutations induced by the virus at the molecular level. The DNA of the mutants isolated after viral infection was probed with cloned HSV-2 fragments representing the entire genome. In these mutants, no authentic HSV-2 hybridization could be detected. This was indicative of a mechanism of mutagenesis which did not require the permanent integration of viral sequences in the host genome. The structure of the hprt gene was determined by the method of Southern (J. Mol. Biol. 98:503-517, 1975), and the level of hprt mRNA was analyzed by Northern blots. Except for the identification of one deletion mutant in each of the two groups, the HPRT- clones showed no evidence of alteration in their hprt gene. A total of 7 of 12 spontaneous mutants and 11 of 15 mutants isolated from the infected population transcribed an hprt mRNA of the same size and abundance as did the wild-type cells. Thus, the majority of the mutants seemed to have a point mutation in their hprt structural gene. Interestingly, the proportion of the different types of mutations was similar in the two groups of mutants. This analysis revealed that HSV-2 infection did not increase the frequency of rearrangements but rather that it probably induced a general increase of the level of mutations in the cells. This type of response is thought to be compatible with the biology of the virus, and the possible mechanisms by which HSV-2 induces somatic mutations in mammalian cells are discussed.

Animals↗
PubMed1986

Evaluation of a cardiac arrest simulation.

Prior to using a simulation strategy for educational and/or research purposes, it is essential to assess whether or not the simulation elicits responses one would expect in the "real" situation. The purpose of this study was to evaluate the stress-eliciting capacity of two variations of a simulated cardiac arrest situation. Twenty-seven senior baccalaureate students in nursing volunteered to participate in the study. Each subject was randomly assigned either to a simulation containing interpersonal stressors or a simulation containing environmental stressors. The simulations took place in a videotape studio equipped as an intensive care unit. All subjects were instructed via an audiotape recording to perform tasks similar to those undertaken by intensive care nurses in the context of a cardiac arrest situation. Pre-post measurements included: self-reported anxiety as measured by the State Trait Anxiety Inventory (A-State), pulse rate, and diastolic and systolic blood pressure. Task performance on cardiopulmonary resuscitation (CPR) and on a medication memory activity also were measured. Since no significant differences in the dependent measures were found between the two groups, data from both groups were analyzed together. Univariate analyses showed significant pre-post increases in pulse rate (p less than .0001), systolic blood pressure (p less than .03), and self-reported anxiety (p less than .0001). No significant change was noted in diastolic blood pressure. Ratings on CPR performance and a medication memory task were well below expected performance standards. The implications of these findings for educational and research purposes are discussed.

Education, Nursing, Baccalaureate↗
PubMed1985

Detection in BHK cells of a precursor form for lamin A.

Lamins are structural proteins found in the fibrous lamina underlining the nuclear envelope. In vitro translation of polyadenylated RNA or polysomes followed by immunoprecipitation with a serum raised against BHK nuclear matrix proteins showed that lamin A (72 kD) is synthesized as a high molecular weight precursor (74 kD) (Laliberté et al., J Cell Biol 98 (1984) 980) [23]. We have thus investigated the presence in BHK cells of this putative precursor by in vivo labelling with [35S]methionine and immunoprecipitation of lamin proteins. Short labelling times, ranging from 5 to 60 min reveal the presence of the 74 kD protein. Pulse-chase experiments indicate that the half-life of the precursor is about 60 min. On two-dimensional gel, the 74 kD protein is resolved in a cluster of isovariants between pH 7.4 and 6.6, which are generally slightly more alkaline than their counterparts in lamin A. These results indicate that lamin A is synthesized as a precursor of 74 kD; the long half-life further suggests that pre-lamin A might accumulate in some sort of cellular pool before undergoing post-transcriptional modification(s) to give the mature form of lamin A.

Animals↗
PubMed1985

Increased mutation frequency after herpes simplex virus type 2 infection in non-permissive XC cells.

The effect of herpes simplex virus type 2 (HSV-2) infection on the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus was studied in the non-permissive XC cell line. When the cells were infected with 20 to 800 p.f.u./cell, there was initially a lag in cell growth and cell death, but after 4 days there was no difference in growth rate between infected and control cultures. However, the mutation frequency, as determined by the number of 6-thioguanine-resistant colonies, was increased in infected cultures by factors ranging from 2.5 to 10.3. This effect was found to be dependent on the multiplicity of infection. The maximum effect was obtained between 20 and 100 p.f.u./cell while further increase in the amount of virus resulted in a drop in the yield of mutants. The optimum multiplicity of infection was a reproducible characteristic but was variable between viral stocks. When a number of mutant clones were examined they were found to have HGPRT activities ranging from undetectable to 6.9% of wild-type, indicating that the mutations were in the HGPRT gene. These results show that, in a non-productive infection, HSV-2 particles can increase the mutation frequency. The possible mechanisms by which this effect is brought about in the host genome are discussed.

Animals↗
PubMed1984

Identification of distinct messenger RNAs for nuclear lamin C and a putative precursor of nuclear lamin A.

The lamins are the major components of the nuclear matrix and are known as lamins A, B, and C with Mr 72,000, 68,000, and 62,000 when analysed by SDS PAGE. These three polypeptides are very similar, as determined by polypeptide mapping and immunological reactivity. Lamins A and C are so homologous that a precursor-product relationship has been proposed. Using an antiserum against nuclear matrix proteins that specifically immunoprecipitates the three lamins, we examined their synthesis in the rabbit reticulocytes lysate. Four bands of Mr 62,000, 68,000, 70,000, and 74,000 were specifically immunoprecipitated when polysomes or polyadenylated RNA were translated in vitro. By two-dimensional gel electrophoresis, the 68,000- and the 62,000-mol-wt proteins were identified as lamins B and C, respectively, and the 74,000-mol-wt polypeptide had properties of a precursor of lamin A. The mRNAs of lamin C and of the putative precursor of lamin A were completely separated by gel electrophoresis under denaturing conditions, and their respective sizes were determined. These results suggest that lamin A is not a precursor of lamin C.

Animals↗
PubMed1981

DNA organisation in the chicken lysozyme gene region.

DNA sequences surrounding the lysozyme gene of the chicken have been cloned in several recombinants which define a region of 40 Kb. We have detected no other gene with a sequence related to that of the lysozyme gene, nor any gene expressed in the oviduct in these recombinants. This situation contrasts with that of the ovalbumin gene, in the vicinity of which lie two other genes of related structure expressed in the oviduct under hormonal control. The lysozyme gene region, however contains a complex array of repeated sequences, which have been resolved into at least five classes. An inverted repeat overlaps the lysozyme gene itself.

Animals↗
PubMed1979

Isolation of the lysozyme gene of chicken.

The lysozyme gene has been purified by molecular cloning from two chicken gene libraries. Several recombinant phages harbouring sequences homologous to a plasmid carrying a double stranded lysozyme cDNA have been isolated. One recombinant appears to carry an entire lysozyme gene. Electron microscopic studies show that the latter is split by at least three introns. The length of the gene is about 3.9 kb, 6 times longer than lysozyme mRNA.

Animals↗
PubMed1979

The ovalbumin gene region: common features in the organisation of three genes expressed in chicken oviduct under hormonal control.

Two large DNA fragments overlapping the chicken ovalbumin gene have been isolated by molecular cloning. Analysis of these fragments provided a map of a 46,000-base pair region of the chicken genome. This region contains the complete ovalbumin gene (including its mRNA leader-coding sequence) and at least two other genes of unknown function. All three genes are orientated in the same direction and their expression in chicken oviduct is under hormonal control. The three genes share some sequence homologies, suggesting that duplications have occurred in the ovalbumin gene region in the course of evolution.

Animals↗
PubMed1979

Organisation and sequences at the 5' end of a cloned complete ovalbumin gene.

A clone which contains the complete chicken ovalbumin gene, including its leader coding sequences, has been isolated. From electron microscopic analysis of this DNA we conclude that the minimal size of the transcriptional unit for ovalbumin is 7.7 kilobases. The DNA sequence of the region surrounding the 5' end of the ovalbumin gene is presented. Comparison of this sequence with those of other eukaryotic genes reveals striking similarities, possibly related to a promoter region, approximately 30 base pairs upstream from the site coding for the 5' end of the mRNA.

Animals↗
PubMed1975

RNA synthesis in the ultrastructural and biochemical components of the nucleolus of Chinese hamster ovary cells.

A correlated autoradiographic and biochemical study of RNA synthesis in the nucleoli of chinese hamster ovary cells has been made. Quantitative analysis of the labeling indicates that the fibrillar ribonucleoprotein (RNP) component is labeled faster than 80S RNP and 45S RNA molecules, but approaches simultaneously a steady-state 3H to 14C ratio or grains/mum2 after 30 min of [3H]uridine incorporation. On the other hand, the 55S RNP, the 36S + 32S RNA, and the granular RNP components have the same kinetic of labeling with [3H]uridine. These results suggest that the fibrillar and granular RNP components of the nucleolus are the ultrastructural substratum of, respectively, the 80S RNP (45S RNA) and 55S RNP (36S + 32S RNA). The possibility that precursors to 80S RNP exist also in the fibrillar region of the nucleolus is strongly suggested by the rapid labeling of the fibrils on the autoradiographs.

Animals↗