Biomedical subjects

D H NORTHCOTE

Publications and source records attributed to D H NORTHCOTE.

At least 19 recordsLinked to original sources

PubMed1965

APPLE FRUIT PECTIC SUBSTANCES.

1. The pectic substances of apple have been extracted and separated into a pure pectinic acid and a neutral arabinan-galactan complex by precipitation of the acidic component with ethanol and with cetylpyridinium chloride. 2. The composition of the fractions has been determined. The pectinic acid contained galacturonic acid, arabinose, galactose, rhamnose, xylose and several trace sugars. 3. Transelimination degradation of the pectinic acid gave rise to two components completely separable by zone electrophoresis and by Sephadex gel filtration. Analysis of these components confirmed that the pectinic acid molecules contained long chains of esterified galacturonosyl residues, but showed in addition that more neutral portions containing a high proportion of arabinofuranose residues were attached to them. 4. The identification of rhamnose, galactose and xylose in aldobiouronic acids obtained from a partial hydrolysate of pectinic acid has shown that these sugars are covalently linked in the molecule, and it is suggested that the galacturonosyl-(1-->2)-rhamnose link is a general feature of pectinic acid structure. 5. The possible biological significance of pectinic acid structure has been discussed. 6. The arabinan-galactan complex contained nearly equal quantities of arabinose and galactose residues and some of its physical properties have been investigated.

Arabinose↗

PubMed1964

THE DEVELOPMENT OF THE SECONDARY WALL OF THE XYLEM IN ACER PSEUDOPLATANUS.

The development of the spirally thickened xylem element from a cambium initial of sycamore Acer pseudoplatanus has been traced by means of electron microscopy. The narrow elongated cambial initial undergoes considerable expansion in all dimensions. The cytoplasm at this stage is distributed in a thin skin between the cell wall and a large vacuole. No correlation has been observed between the distribution of any organelle and the pattern of the eventual thickenings. After the sites of thickening deposition have become apparent, the most conspicuous feature of the cell is the proliferation of Golgi bodies and vesicles. It is suggested that the material of the developing thickenings stems from direct apposition of the material in the Golgi vesicles. After glutaraldehyde fixation, microtubules (200 to 220 A in diameter) are seen to be sited in specific relation to the thickenings, the orientation of the tubules mirroring that of the fibrils seen in the thickenings. Possible reasons for absence of an observable pattern in the expanded but relatively undifferentiated cell are given, and the possible roles of the Golgi apparatus and microtubules in the thickening production are discussed

Acer↗

PubMed1964