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Biomedical subjects

J Olah

Publications and source records attributed to J Olah.

10 recordsLinked to original sources
PubMed1991

Fibre-optic oxygen sensor based on phosphorescence quenching.

A fibre-optic oxygen sensor is described which is based on an oxygen-sensitive luminescent film made from platinum octaethylporphyrin and polystyrene. The luminescence and quenching characteristics of such films were studied for their use in a fibre-optic oxygen biosensor. A prototype oxygen sensor was made from this material, and was tested in aqueous solutions and in the gaseous phase at physiological oxygen concentrations. Measurements of luminescence intensity and decay time were employed to determine oxygen concentration from luminescence quenching. The main working characteristics of this prototype oxygen sensor were studied.

Biosensing Techniques↗
PubMed1983

Major changes in the 5' and 3' chromatin structure of sea urchin histone genes accompany their activation and inactivation in development.

The major histone gene repeat (h22) of the sea urchin Psammechinus miliaris is transiently expressed for several hours during early embryonic development. Several major alterations in chromatin structure coincide with changes in the pattern of early histone gene expression and are reversed later. During the early (128-cell) blastula stages when h22 DNA is maximally expressed, promoter regions of all five histone genes are sensitive to both micrococcal nuclease and DNAase I. Hypersensitivity to micrococcal nuclease remains the same throughout the early hours of development, but disappears abruptly at hatching blastula stage when transcription has completely ceased. Some sequences near the 3' end of active histone genes are very resistant to micrococcal nuclease cutting and map just downstream of the inverted DNA repeats essential for generating faithful 3' ends of histone mRNAs. These same histone DNA sequences are readily cut in free DNA or when histone genes are transcriptionally inactive.

Animals↗
PubMed1981

Sequence of a yeast DNA fragment containing a chromosomal replicator and a tRNA Glu 3 gene.

The sequence of a 1.9 kb Bam x Hind III fragment from yeast has been determined. This fragment is part of a yeast 6.7 kb Hind III segment cloned into pBR322 (pY20). The fragment carries a single gene for a glutamate tRNA which has no intron. According to genetic analyses [1] this fragment also contains a yeast chromosomal replicator. We have analyzed the sequence for potential open reading frames and for several structural features which are thought to be involved in the initiation of DNA replication. Hybridization studies have revealed that portions of this sequence are repeated within the yeast genome.

Base Sequence↗
PubMed1981

Structural comparison of two yeast tRNA Glu 3 genes.

DNA sequences in a 1.7 kb Pst fragment from yeast have been determined. This fragment is part of a yeast 7.4 kb Hind III segment cloned ino pBR322 (pY 5). The fragment carries a single gene for a glutamate tRNA. The coding portion of this gene is identical in sequence to that of the tRNA Glu 3 gene from pY 20 [1]. The flanking regions differ in their sequences, but possible secondary structures within the 5'-flanking regions bear similar features. Sequence homologies between pY 5 and pY 20 were detected far outside the tRNA genes. More surprisingly, extended sequence homologies were seen between the flanking regions of the pY 20 tRNA Glu 3 gene and a tRNA Ser gene [2,3]. We have also checked the known tRNA genes for structural similarities. Hybridization studies indicate that portions of the Pst fragment are repeated within the yeast genome.

Base Sequence↗
PubMed1980

Structure of a yeast non-initiating methionine-tRNA gene.

4 to 8 kb Hind III fragments of yeast DNA were cloned into pBR322. One of these clones (pY6m3) containing a single tRNA3Met gene has been characterized in detail. The DNA sequence of the structural gene is colinear with the tRNA sequence, which means that in this case no intervening sequence is present. The 5'-leader and 3'-trailer sequences have also been determined. The 5'-flanking region can be folded up into possible secondary structures.

Base Sequence↗
PubMed1977

Classical nictitating membrane conditioning in the awake, normal, restrained cat.

Present knowledge of its central nervous system makes the cat a desirable subject for studies of brain-behavior relationships. Response frequencies and latency characteristics in conditioning and control groups indicate that the response of the nictitating membrane can be classically conditioned in a new restraint system in which detailed brain and behavior measures can be easily obtained.

Animals↗