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Biomedical subjects

D J Osborne

Publications and source records attributed to D J Osborne.

At least 55 records · Page 3Linked to original sources
PubMed1977

Decline in ribonucleic acid and protein synthesis with loss of viability during the early hours of imbibition of rye (Secale cereale L.) embryos.

A decline in protein synthesis and slow germination accompanies loss of viability in embryos of rye (Secale cereale L.) grains. Associated with this, incorporation of precursors into all the major classes of RNA is decreased and the processing of precursor rRNA to 25S and 18S RNA is retarded. Embryos that just reach 0% viability still synthesize some low-molecular-weight non-nucleolar material, although they do not synthesize protein. It is suggested that early-synthesized RNA could play a major part in determining the extent of protein synthesis at early germination, and thereby regulate the rate at which germination can proceed.

Plant Proteins↗
PubMed1977

Analysis of nucleosomal deoxyribonucleic acid in a higher plant.

Comparisons of nuclease digestions of chromatin in nuclei from rye embryos and rat liver show that their nucleosomal DNA is similar, i.e. DNA subunits consist of 200 base-pair repeats with 140 base-pair cores of identical substructure. The identical nucleosome structure is present in nuclei from cells of rye embryos that have been non-viable (i.e. dead) for more than 7 years. These findings indicate a high degree of stability of the DNA-histone complex and are consistent with conservation of the nucleosomal structure of chromatin during evolution.

Base Sequence↗
PubMed1977

Mass spectral characterization of 6-oxo-OGF.

The mass spectra of eleven derivatives are presented to provide structural support for the recently discovered prostaglandin, 6-oxo-PGF1alpha, which we have isolated from incubations of arachidonic acid with ram seminal vesicles or released during isolated perfusions of sensitized guinea pig lungs.

Animals↗
PubMed1977

The identification of two novel prostaglandins and a thromboxane.

6,15-Dioxo-PGF1alpha, 6,15-dioxo-13,14-dihydro-PGF1alpha and 15-oxo-thromboxane B2 have been identified in incubates of ram seminal vesicle homogenates with added arachidonic acid or in the perfusate from sensitised challenged guinea pig lungs. These compounds are probably related to 6-oxo-PGF1alpha and thromboxane B2. The structures have been determined by gas chromatography mass spectrometry, following suitable chemical derivatisation.

Animals↗
PubMed1977

The pharmacology of prostaglandin-like substances released from guinea-pig lungs during anaphylaxis.

The pharmacology of the prostaglandins (PGs) and thromboxanes (Txs) released from immunologically challenged guinea-pig lungs is related to their roles in the anaphylactic response. 6-oxo-PGF1alpha probably contibutes substantially to bronchoconstriction during anaphylaxis. TxB2 may contribute to the anaphylactic response by increasing SRA-A release and by stimulating leucotaxis. The 15-oxo metabolites of PGE2 and PGF2alpha are rather weak spasmogens, but might modify respiratory muscle contractions and pulmonary vascular resistance. The 15-oxo 13,14 dihydro metabolites of PGE2 PGF2alpha and TxB2 were inactive in the systems studied, suggesting an important inactivating role for the 13:14 reductase enzyme.

Anaphylaxis↗
PubMed1976

Hormones and the growth of plants in response to gravity.

Plants are remarkable amongst living things in that all their parts (leaves, stems, roots and flowers) can orientate their position in response to gravity. Roots normally grow downwards towards the stimulus, shoots upwards away from the stimulus, while leaves and special kinds of stems like underground rhizomes or aerial runners have adaptations to grow horizontally, approximately at right angles to the gravitational field. This directional positioning of the organ in relation to gravity is achieved by a regulation of the growth of enlarging cells below the meristems or within the organ. Mature tissues in which further cell growth is precluded are therefore unable to reorientate if their position in the field is changed. Under conditions of zero gravity, roots and shoots continue to grow in opposite directions and the orientation of laterals with respect to the apex is essentially normal. This demonstrates the inherent polarity of plant cells and the internal correlative growth regulation that each organ exerts upon its neighbours. The perception of gravity, involving statoliths, membranes and "wound" ethylene, is discussed, together with the mechanisms by which the subsequent growth responses can be mediated by changes in endogenous hormones. Evidence for how such hormonal changes can lead to modifications of the rate, extent and reorientation of cell growth is reviewed for several geotropically responding systems.

Abscisic Acid↗
PubMed1975

Analysis of 1-(2-phenyladamant-1-yl)-2-methylaminopropane as its chlorodifluoroacetyl derivative.

The diastereoisomeric content of 1-(2-phenyladamant-1-yl)-2-methylaminopropane can be determined by gas chromatography following treatment with chlorodifluoroacetic anhydride. Racemisation occurs in the synthesis of 2-phenyladamantane from the corresponding 2-chloroadamantane in the Friedel-Crafts reaction with aluminium chloride, but fractionation of the diastereoisomers can occur in the purification steps. A method for determining 2-phenyladamantane in plasma and urine extracts at the nanogram level using an electron-capture detector is described and compared with a previously described radio-assay procedure.

Adamantane↗
PubMed1975

Early ribonucleic acid synthesis during the germination of rye (Secale cereale) embryos and the relationship to early protein synthesis.

Incorporation studies with radioactive precursors showed that synthesis of protein and RNA is initiated in germinating embryos of rye within the first hour of imbibition of water. By polyacrylamide-gel fractionations of radioactive nucleic acid components, the appearance of products of transcription of the genome was shown to follow the sequence: heterogeneous (ribonuclease-sensitive) RNA, 4S and 5S RNA by 20min, 31S and 25S rRNA by 40min, and 18S RNA by 60min. "Fingerprint' analysis of T1-ribonuclease digests show that all the large oligonucleotides present in 25S and 18S RNA are present in the 31S species, indicating that 31S RNA is the precursor rRNA molecule to both 25S and 18S RNA. The importance of these early RNA syntheses and in particular the possible template function of the heterogeneous RNA is discussed in relation to the concept of long-lived mRNA and the coding for protein synthesis in the first hours of germination.

Edible Grain↗
PubMed1975

Production of ethylene and other volatiles and changes in cellulase and laccase activities during the life cycle of the cultivated mushroom, Agaricus bisporus.

Nine volatile hydrocarbons, as well as methyl chloride, carbonyl sulphide and carbon disulphide, have been identified by mass spectrometry as products of Agaricus bisporus in the compost used in comerical mushroom beds. Of these, only ethylene showed a pattern of production that could be correlated with developmental phases of the crop, high levels being produced whenever fruit bodies were rapidly enlarging. In laboratory flask cultures, under controlled conditions, high levels of ethylene occurred whenever young fruit bodies entered the expansion phase. The enhanced rate of ethylene production continued over several days, irrespective of whether fruit bodies were removed. Production occurred within the colonized compost; no ethylene was evolved by the fruit body itself. When the first fruit bodies expanded, either in beds or culture flasks, laccase levels in the compost fell and those of a beta-1,4-glucanase (cellulase) rose. The enzyme switch occurred once only, during maturation of the first fruit bodies, whereas an elevated ethylene production was associated with each occasion when fruit body maturation took place. The low level of laccase and high of cellulase characterized the whole of the reproductive stage of A. bisporus, whereas the phasic periods of high ethylene production distinguished between periods of fruit body maturation and intervening resting periods.

Agaricales↗
PubMed1973

Protein synthesis and the viability of rye grains. Loss of activity of protein-synthesizing systems in vitro associated with a loss of viability.

A study was made of the integrity of some components of the protein-synthesizing system from viable and non-viable embryos of rye grains. In comparison with viable-embryo components both post-ribosomal supernatant and ribosomal fractions from non-viable embryos are impaired, for neither will fully support polyphenylalanine synthesis in poly(U)-directed cell-free systems. The lesion in the supernatant lies in components other than the tRNA or the aminoacyl-tRNA synthetase, for these are as functional as those present in the fully active cell-free systems from viable embryos. The ribosomes of embryos of lowered viability show considerable fragmentation and degradation of both 18S and 25S rRNA. This breakdown does not, however, account for the complete lack of polypeptide synthesis in the poly(U)-directed non-viable-embryo system, for if provided with viable-embryo supernatant, non-viable-embryo ribosomes will sustain 60% of the viable-embryo ribosome activity. A lesion in non-viable-embryo supernatant has been located in the binding of the aminoacyl-tRNA to the ribosome. The impaired components in both supernatant and ribosomes in systems in vitro may reflect the site of faults in protein synthesis in vivo in the early hours of germination. The development of these lesions during grain storage could contribute to senescence and loss of viability in the embryos of rye.

Amino Acids↗