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Biomedical subjects

S F Ng

Publications and source records attributed to S F Ng.

23 records · Page 2Linked to original sources
PubMed1977

An ultrastructural investigation of 180 degrees-rotated ciliary meridians in Tetrahymena pyriformis.

An ultrastructural investigation has been carried out on 180 degrees-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (mo1b/mo1b), syngen 1, strain B. The longitudinal, transverse and post-ciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180 degrees angle to their normal positions or orientations. Other abnormalities are as follows: the first 2 basal bodies of the inverted meridian fail to organize into "couplets" and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines.

Animals↗
PubMed1977

Analysis of contractile vacuole pore morphogenesis in Tetrahymena pyriformis by 180 degree rotation of ciliary meridians.

The contractile vacuole pores (CVPs) in Tetrahymena pyriformis are usually found to the left of ciliary meridians (CVP meridians). When the CVP meridians are experimentally rotated 180 degrees ('inverted'), the CVPs are now found to the right of the rotated CVP meridians. In other words, the CVP is almost invariably found on the same side with respect to the CVP meridian. Thus, the 2 sides of the CVP meridian have different morphogenetic properties and such differences are determinative in the asymmetrical fine-positioning of the CVP. The number of CVPs per animal and their general placement on the animal (i.e. with which ciliary meridians the CVPs are associated) are known to be a function of the total number of ciliary meridians possessed by the animal. Rotation of the CVP meridians affects both the number of CVPs per animal and their general placement. The specificity of such effects appears to depend on whether both, or one, or which one, of the CVP meridians is rotated. Rotation of ciliary meridians may be used as a tool in analysing the mechanism determining the number of CVPs per animal and their general placement.

Animals↗
PubMed1976

Extra cytoproct mutant in Paramecium tetraurelia: morphogenetical analysis of proters and opisthes.

To account for the differences between proters and opisthes with regard to extra cytoproct morphogenesis in Paramecium tetraurelia, two hypotheses have been proposed and tested. (i) The differences may be a result of different actions of proter-macronucleus and opisthe-macronucleus. This hypothesis has been tested by cytoplasmically connecting the proter with the opisthe in the form of chains, some of which have only one macronucleus per chain. However, the connected proters and opisthes remain different in extra cytoproct morphogenesis, thus arguing against the hypothesis. (ii) The differences may be a result of differences between the proter and the opisthe with regard to the development of their posterior-ventral cortex: proters have a newly-developed posterior-ventral cortex whereas opisthes receive the posterior-ventral cortex from the pre-fission mother animal. This hypothesis has been tested by surgically producing an opisthe with a newly-regenerated posterior cortex. Such opisthes, however, remain different from proters in extra cytoproct morphogenesis. Thus no direct support for the second hypothesis is obtained. Also, proter-opisthe difference in morphogenesis may be understood in terms of Wolpert's positional information hypothesis, by assuming that the anterior and posterior ends of a dividing animal serve as reference points for establishing a gradient and that positional information before separation of the two daughter animals leads to differences in extra cytoproct morphogenesis between them after separation.

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