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Biomedical subjects

F J Taylor

Publications and source records attributed to F J Taylor.

6 recordsLinked to original sources
PubMed1979

Symbionticism revisited: a discussion of the evolutionary impact of intracellular symbioses.

Wallin (1927) first published the notion that the fusion of bacteria with host cells was the principal source of genetic novelty for speciation. He suggested that mitochondria are transitional elements in this process. While the significance that he attributed to symbiosis now seem excessive, he was one of the first authors to be aware of the evolutionary potential of symbiotic events and his view of mitochondria may not seem strange to many cell biologist today. The most significant evolutionary development which has been attributed to intracellular symbiosis is the origin of eukaryotic cellular organization. The current status of the 'serial endosymbiosis hypothesis' is briefly review. The case for the symbiotic origin of the chloroplast, based principally on 16 S RNA oligonucleotide cataloguing, is very strong. Mitochondrial origins are more obscure but also appear to be symbiotic due to recent 18 S cataloguing from wheat embryos. The probablility of the multiple origin of some eukaryotic organelles is also examined, the processes in question being the acquisition of distinct stocks of chloroplasts from disparate photosynthetic prokaryotes and the secondary donation of organelles from degenerate eukaryotic endosymbionts to their hosts, with specific reference to the dinoflagellates Peridinium balticum, Kryptoperidinium foliaceum and the ciliate Mesodinium rubrum. It is concluded that the evolutionary potential of intracellular symbiosis ('cytobiosis': a term introduced in this paper) is great, with the best established influence being on the origin of eukaryotic chloroplasts. Together with the potential effects of viral vectors, symbiosis serves as a supplementary speciation mechanism capable of producing directed evolutionary changes. It is likely that these processes will explain some of the apparent anomalies in evolutionary rates and direction which are not readily explicable by the conventional synthetic theory of evolution.

Animals↗
PubMed1978

Problems in the development of an explicit hypothetical phylogeny of the lower eukaryotes.

A semi-explicit arrangement of the lower eukaryotes is provided to serve as a basis for phyletic discussions. No single character is used to determine the position of all the groups. The tree provides no ready separation of protozoa, algae and fungi, groups assigned to these traditional assemblages being considered to be for the most part inextricably interwoven. Photosynthetic forms, whose relationships seem to be more readily discernable, are considered to have given rise repeatedly to nonphotosynthetic forms. The assumption that there are primitive "preflagellar" eukaryotes (red algae, non-flagellated fungi) is adopted. The potential value of mitochondrial features as indicators of broad affinities is emphasised, particularly in determining the probable affinities of non-photosynthetic forms, and this criterion is contra-indicative of a ciliate ancestry for the Metazoa. In the arrangement provided the distributions of chloroplast, mitochondrial and flagellar features match one another well, suggesting their probable co-evolution.

Animals↗
PubMed1976

The propulsive mechanism of the dinoflagellate transverse flagellum reconsidered.

As a result of the recent discovery that the transverse flagellum of dinoflagellates does not beat helically within the cingulum it has been necessary to formulate a new model for the manner in which this flagellum can impart a forward motion to the cell. It is theorised that the contribution to forward propulsion by the transverse flagellum can only arise directly from an asymmetry of the flagellar wave. In addition we have drawn attention to topographic features of the cell, and particularly of the left sulcal list, which may augment this thrust by redirecting cingular flow down the sulcus.

Dinoflagellida↗
PubMed1975

Taxonomic difficulties in red tide and paralytic shellfish poison studies: the "tamarensis complex" of Gonyaulax.

The type illustrations of the dinoflagellate Gonyaulax tamarensis contain an apparent reversal of the epithecal plates. Furthermore a culture from the type locality has been found not to be toxigenic. These two features have led a recent author to doubt the appropriateness of the allocation of toxic populations in the North Atlantic to this species or a variety of it (var. excavata Braarud). The latter has been raised to the status of a distinct species but the wrong name has been applied to it (G. excavata) as, according to the rules of priority, it should be G. phoneus (Woloszynska & Conrad) nov. comb. A history of this confused situation is provided. The criteria by which other similar species are recognised are summarised. The necessity for further study on the specific distinction of these taxa is stressed. G. conjuncta has been so inadequately described or rejected. Variability in the plate pattern of a culture of G. tamarensis var. excavata from British Columbia is illustrated and its bearing on the taxonomy of the group discussed. The presence of this toxic variety on the west coast of N. America is a new record for the Pacific Ocean.

Animals↗