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Biomedical subjects

R Flickinger

Publications and source records attributed to R Flickinger.

6 recordsLinked to original sources
PubMed2001

Replication timing and cell differentiation.

Cell differentiation may depend in part upon a type of unbalanced growth in which several cell cycles occur with a reduced level of total protein synthesis. During this period the synthesis of the chromatin protein HMG-I/Y is reduced since its synthesis is correlated with that of total protein. The synthesis of histone H1 shows less reduction since its synthesis is entrained with that of DNA. This greater reduction of HMG-I/Y than of histone H1 is thought to delay or prevent replicon initiations within AT-enriched isochores. This shifts their time of replication from early to late S phase. This may restrict certain pathways of cell differentiation in multipotent progenitor cells and allow one particular type of differentiation.

Animals↗
PubMed1980

An alternate method of recording airflow during sleep.

Respiratory activity recordings in polysomnographic recordings are important in the identification of the sleep apnea syndrome. However, simultaneous recordings of both respiratory effort and airflow are necessary to accomplish this identification. We describe a relatively inexpensive and trouble-free face mask that makes use of a linear thermistor in the ventilation tube to accomplish the recording of airflow in a noninvasive manner.

Humans↗
PubMed1979

Post-transcriptional control of messenger RNA diversity in frog embryos.

The control of mRNA diversity during frog development has been investigated. Nuclear and messenger RNA from the early neurula and larval stages of Rana pipiens were hybridized in vast excess to labeled single-copy DNA and resistance to S1 nuclease was measured. Mixtures of RNA populations were also hybridized with single-copy DNA as a measurement of sequence overlap. Neurula and larval nuclear RNA hybridize to 11.3% and 12.1% of the single copy DNA. A mixture of both nuclear RNA populations hybridizes to 10.8% of the DNA, indicating a great amount of sequence overlap between the two populations. The mRNA complexity almost doubles during this developmental period from 4.7% of the single-copy DNA complexity at the early neurula to 8.7% at the larval stage. Mixtures of nuclear and messenger RNA were used to hybridize single-copy DNA and the results indicate that mRNA sequences present on neurula polysomes, but not on larval polysomes, are found in larval nuclei. Furthermore, mRNA sequences found on larval polysomes, but not on neurula polysomes, are found in the neurula nuclei. The data indicate that post-transcriptional events appear to play a role in the qualitative control of mRNA diversity during development.

Animals↗
PubMed1975

Relation of an evolutionary mechanism to differentiation.

It is believed that new gene products and differentiations arise during evolution by the creation of new members of families of repeated DNA sequences which undergo diversification and take on new functions, while still retaining some common sequences indicating their common ancestry. Since some of the sequences of such DNA families control differentiations that occur in present-day embryos, it appears that members of such families formed during evolution are active in development. The presence of partially homologous proteins in related types of cells, as well as the labile pattern of determination and differentiation of these cells, supports this idea. The ontogenetic sequence of differentiation follows the phylogenetic one and this may occur because the more conservative members of any family of DNA sequences are more reiterated and transcribe more copies of RNA.

Animals↗