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Biomedical subjects

R P Perry

Publications and source records attributed to R P Perry.

At least 91 records · Page 5Linked to original sources
PubMed1979

Nuclear transcripts of mouse heavy chain immunoglobulin genes contain only the expressed class of C-region sequences.

In plasmacytoma cells producing IgG, IgA, or IgM immunoglobulin heavy chains, the large precursors of the heavy chain messenger RNA's contain nucleotide sequences that specify only the expressed class of constant region. This indicates that the switch from one class of heavy chain to another during B cell ontogeny does not occur by altered processing of a complex gene transcript.

Animals↗
PubMed1979

Selective suppression of the transcription of ribosomal genes in mouse-human hybrid cells.

Mouse-human hybrid cells that preferentially segregate either mouse or human chromosomes were analyzed for their relative content of mouse and human rRNA genes and for their capacity to transcribe these genes. A distinctive Hind III restriction fragment containing 28S rRNA sequences was used to distinguish between mouse and human rDNA and a set of distinctive loop structures in the 45S pre-rRNA was used to distinguish between mouse and human gene transcripts. Our results indicate that the genes of only one species are transcriptionally active in these hybrid cells, even though both sets of genes are present.

Animals↗
PubMed1979

Comparison of mRNA precursors in plasmacytomas producing closely related kappa chains.

To help elucidate the mechanisms of formation and expression of active immunoglobulin genes, we have made a systematic study of the processing patterns of the mRNAs that code for a closely related family of kappa chains. Among the members of this family, represented by the V(kappa)21 group of plasmacytomas, are examples in which six different germ-line V genes are joined to four different J segments in various combinations. The mRNA precursors were identified by hybridizing a cloned kappa-cDNA probe to poly(A)-containing nuclear RNAs that were size fractionated on methylmercury-agarose gels and transferred to diazotized paper. Based on the length of the segment excised in the last detectable processing step, which presumably represents the removal of the J-C intron, the precursor patterns were classified into four primary categories that correlated well with the type of J segment being expressed. The J segments were thus located at distances ranging from 2.4 to 4.8 kilobases from the constant-region gene. Different V genes joined to the same J segment exhibited similar precursor patterns, suggesting that the size of the translocated V segment may be relatively uniform among members of the V(kappa)21 group. A large (9.1 kilobases) component, which is likely to represent a primary transcription product, was observed in all processing categories, regardless of which J segment was being utilized. This surprising observation leads to some interesting predictions about the mechanism of V-J translocation.

Animals↗
PubMed1979

An exploration of obese observational learning in modifying selected eating responses of obese children.

The present study investigated the effects of two observational learning paradigms in modifying the eating behavior of obese children. A total of 18 subjects ranging in age from seven to 12 years and in weight from 74 to 160 lb (33 to 72 kg) were randomly assigned to three conditions. Intervention consisted of four sessions in which subjects viewed videotapes of their baseline eating behaviors compared with a model eating at a reduced speed. Based on the assumption that children may acquire their parents' eating behaviors, one condition included videotapes of a same-sex adult model. In order to maximize model-observer similarity, subjects in a second treatment condition observed videotapes of themselves eating at a reduced speed. Subjects in the control condition viewed only their baseline eating behavior videotapes. Dependent measures of eating behavior were found to be significantly affected by both model treatments, while no significant differences were evidenced in the control group.

Behavior Therapy↗
PubMed1978

Isolation, purification, and properties of mouse heavy-chain immunoglobulin mRNAs.

A procedure is described for the isolation of highly purified heavy-chain immunoglobulin mRNAs from a variety of mouse plasmacytomas (IgA, IgG, and IgM producers). The use of fresh tissue and the rapid isolation and direct extraction of membrane-bound polyribosomes were found to be essential in obtaining large quantities of undegraded heavy-chain mRNAs. The individual mRNAs were purified by two cycles of oligo(dT)-cellulose chromatography, sodium dodecyl sulfate--sucrose gradient centrifugation, and electrophoresis on 98% formamide containing polyacrylamide gels. When added to a cell-free protein-synthesizing system from wheat germ, the MPC-11 gamma2b and H2020 alpha heavy-chain mRNAs efficiently directed the synthesis of a predominant product of 55 000 molecular weight, while the synthesis of a 70 000 dalton protein in addition to other lower molecular weight polypeptides were observed with MOPC 3741 mu mRNA. All of these proteins were immunoprecipitable with class-specific heavy-chain antisera, and in the case of the gamma2b in vitro products good correspondence in a comparative trypsin--chymotrypsin fingerpring with in vivo labeled gamma2b heavy chain was observed. The gamma2b and a alpha heavy-chain mRNAs possessed a chain length of approximately 1800 nucleotides and the mu mRNA a size of approximately 2150 nucleotides when examined under stringent denaturation conditions. The purities of the alpha, gamma2b, and mu mRNAs were estimated to be 60--80%, 50--70%, and 50--83%, respectively, on the basis of their hybridization rates with cDNA probes in comparison to mRNA standards of known complexity. Heavy-chain mRNAs of the same class isolated from different mouse strains (Balb/C or NZB) display no detectable sequence differences in cross hybridization experiments, even though the cDNA--mRNA hybrids are submitted to stringent S1 nuclease digestion. These results indicate that allotypic determinants represent only a minor fraction of the heavy-chain constant region sequence in the mouse.

Animals↗
PubMed1978

The synthesis and processing of the messenger RNAs specifying heavy and light chain immunoglobulins in MPC-11 cells.

The nuclear precursors of the immunoglobulin messenger RNAs of MPC-11 cells were characterized with respect to size, amount per cell and extent of polyadenylation. These cells produce three Ig mRNAs: a 1.8 kb component coding for a gamma2b heavy chain (H mRNA), a 1.2 kb mRNA coding for a k light chain (L mRNA) and a 0.8 kb mRNA coding for the constant region portion of the k light chain (Lf mRNA). To identify the pre-mRNAs without ambiguity, we constructed recombinant DNA plasmids containing H and L cDNA sequences, and used the cloned cDNAs as hybridization probes for analysis of steady state nuclear RNA and in DNA excess hybridization experiments with pulse-labeled nuclear RNA. The nuclear molecules containing Ig sequences consist of an 11 kb component (H1), which we believe to be the primary transcript of the H gene, 5.3 kb (L1), and 3.3 kb (L2) components, which seem to be primary transcripts of the L and L1 genes, components corresponding to mature size H, L and Lf mRNAs, and several intermediate-sized components which include the processing derivatives. The precursor role of these nuclear molecules was established by studies of their labeling kinetics and by appropriate pulse-chase experiments. All the pre-mRNA species including H1, L1 and L2 contain poly(A), thus suggesting that polyadenylation is an early event in the processing of these mRNAs. The MPC-11 cell contains about 30,000 and 40,000 cytoplasmic H and L mRNA molecules, respectively, which must be produced within one cell generation (approximately 24 hr). In comparison, the nucleus contains about 100-150 molecules of total pre-mRNA and only about 10-15 molecules of presumptive primary transcripts for each of these Ig species. These values indicate very rapid transcription rates (greater than 20 transcripts per min) and exceptionally fast processing rates (approximately 0.5 min for the primary transcripts and approximately 5 min for overall nuclear processing) for the Ig mRNAs. Thus rapid transcription and processing, together with high cytoplasmic stability, account for the high abundance of Ig mRNAs in the myeloma cell.

Animals↗
PubMed1978

Chromosomal locations of mouse immunoglobulin genes.

The chromosomal locations of the structural genes coding for the constant portions of mouse heavy (H) and light chain immunoglobulins were studied by molecular hybridization techniques. Complementary DNA probes containing the constant-region sequences of kappa and lambdaI light chain and alpha, gamma2b, and mu heavy chain mRNAs were annealed to a large excess of DNA from a series of eight mouse-human hybrid cell lines that are deficient for various mouse chromosomes. The lines were scored as positive when a high proportion of a probe annealed and negative when an insignificant proportion annealed. Some lines were clearly negative for H and lambda and clearly positive for kappa. Others were positive or intermediate for lambda, positive for kappa and negative for H. Still others, including a line that was selected for the absence of the mouse X chromosome, were positive for all immunoglobulin species. These results demonstrate that the Clambda, Ckappa, and CH genes are located on different autosomes in the mouse. In contrast, the three heavy-chain families exhibited consistently uniform hybridization results, suggesting that the genes for Calpha, Cgamma, and Cmu are located on the same chromosome. A comparison of karyotypic data with hybridization data has limited the possible locations of the Ig genes to only a few chromosomes.

Animals↗
PubMed1977

The 5'-termini of heterogeneous nuclear RNA: a comparison among molecules of different sizes and ages.

The composition of the 5' polyphosphorylated and capped termini of pulse labeled hnRNA from mouse L cells was analyzed by two-dimensional electrophoresis. Purine tri- and diphosphates: pppG, pppA, ppG and ppA; as well as four varieties of cap structure: m7GpppXm, Xm = Gm, (m6) Am, Cm and Um, were detected. With increasing labeling time the relative proportion of hnRNA molecules with tri- and diphosphorylated 5' ends decreases and the relative proportion of capped hnRNA increases, indicating that caps are metabolically more stable than the polyphosphate termini. About half of the hnRNA molecules that are labeled within 2 hr have capped ends. This finding, together with results of earlier kinetic and structural studies, implies that a relatively high proportion of the labeled hnRNA molecules are mRNA precursors. Large hnRNA molecules exhibit a higher proportion of capped ends and a lower proportion of 5'-triphosphate ends as compared to small hnRNA. Given the lower stability of triphosphate termini relative to caps, this result may mean that capping of some hnRNA molecules can occur before the completion of transcription.

Base Sequence↗
PubMed1976

Synthesis methylation, and capping of nuclear RNA by a subcellular system.

A subcellular system is described which is capable of in vitro synthesis of large nuclear RNA and the formation of both cap I [m7G(5')pppXmpYp] and capII [m7G(5')-pppXmpYmpZp] structures. This system, which consists of partially purified intact nuclei and residual cytoplasmic tags, carries out both guanosine addition, utilizing GTP, and the appropriate methylation reactions, utilizing S-adenosylmethionine as the methyl donor. The general structure of the caps was verified by analyses of methylated derivatives recovered after RNase T2 hydrolysis and after digestion with P1 nuclease, bacterial alkaline phosphatase,and nucleotide pyrophosphatase. Cap formation in large nuclear RNA species was found to be closely associated with transcription, as indicated by alpha-manitin sensitivity and a requirement for the presence of all four nucleoside triphosphates. Recovery of a class of cap II structures, in which only the methyl group at position Y is labeled, as well as capII structures in which all methylated constituents are labeled, indicates the presence of at least two independent methylation events in the in vitro system.

Amanitins↗
PubMed1976

Recruitment of college volunteers for community service organizations using the lecture method.

The present study was undertaken to determine those variables which best predict college students' reactions to lectures designed to solicit volunteers for a juvenile corrections program. One hundred and thirty-four students returned mailed questionnaires which assessed multiple variables related to: (1) audience characteristics, (2) recruiter (lecturer) characteristics, and (3) volunteer program (lecture content) characteristics. Results of canonical correlation analysis indicated that 8 of 17 predictor variables accounted for the majority of the variance in the volunteering behavior variate. Age of respondent, previous volunteer experience, overall lecture quality, understanding need for volunteer services, clarity and comprehension of volunteer roles, the value of the lecture as a significant learning experience, the opportunity for personal growth within the program, and the ability to influence existing structures were seen as important variables in predicting three volunteering behaviors. In particular, the data suggest that for recruitment programs using the lecture method recruiter characteristics have the greatest impact on soliciting volunteer personnel.

Adult↗
PubMed1976

Selective isolation of reversible cold sensitive variants from Chinese hamster ovary cell cultures.

Variants of the Chinese hamster ovary cell line CHO-KI (ATTCCCL61)which grow almost normally at 38.5C but very poorly or not at all at 30C were obtained after treatment with mutagens and application of an indirect selection procedure. Two kinds of variants were recovered. In the first of these, the cold sensitive phenotypw is expressed completely only at low cell densities. At higher cell desity, growth continues at the nonpermissive temperature, but at a reduced rate. In the second class, the cold snesitive phenotype is independent of cell density. Two members of the latter class were studied in detail. In both lines, after shift to the nonpermissive temperature, the rateof H-thymidine incorporation declines markedly; the rates of H-uridine and H-phenylalanine uptake are less drastically reduced. Autoradiographs indicate that the decline in thymidine uptake at the nonpermissive temperature is due to an elongation of part of the cell cycle, so that a smaller proportion of the cells lie in the synthetic (S) phase of the cell cycle with a consequent reduction in the fraction labeled cells. The uridine labeling patterns of the mutants appear to rule out a ribsomal lesion. Low temperature growth inhibition of both cell strains was reversible. In one of the cell lines, an apparent stretching of the cells at the low temperature produces substantial alterations in cell shape.

Cell Division↗
PubMed1976

Characterization of the 5' termini of hn RNA in mouse L cells: implications for processing and cap formation.

An analysis of the phosphorylated and capped 5' termini of the heterogenous nuclear RNA of mouse L cells has revealed four types of structure: pppXp..., ppXp..., pXp..., and m7/GpppXmp.... The 5'triphosphate termini consists exclusively of pppGp... and pppAp..., whereas a large proportion of the 5' monophosphate termini are pUp.... The 5'diphosphate termini contain all four species of nucleotide in relative proportions that are roughly similar to those found at the Xm position of cap structures. These results indicate that initiation of hnRNA transcription occurre exclusively with purine nucleotides, and consequently that the hnRNA molecules containing pyrimidines at the 5' termini very probably arise by cleavages at internal sites of larger primary transcripts. Taken together with previous results relating cap structures of hnRNA and mRNA, the data favor a model in which some mRNA sequences are located at transcriptionally initiated proportions and others in internal regions of their precursors. According to this model, both the mRNA segments derived from initial 5' end, and those derived by cleavage at internal sites could be converted to diphosphate-terminated derivatives, which then condense with GTP to form cap structures according to the mechanism previously described for vaccinia and reovirus mRNA.

Adenine↗