Spirostomum ambiguum: a protozoan model for primordial musculoskeletal exchange?
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1
University of Leeds, IMSB, FBS, United Kingdom
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2
University of Leeds, IMBE, United Kingdom
The skeleton is responsive to mechanical usage, yet the basis for its remarkable sensitivity remains uncertain. Abundant osteocytes seem central. Their cytoplasmic syncitium is pervasive and well placed to bridge the gap between mechanical signal transduction and cellular. However, its calcified entombment limits accessibility, while isolation or manipulation may alter its specific threshold characteristics. Insight into the rudiments of musculoskeletal exchange may be found in certain protozoa from which the metazoan pathway apparently evolved (Pautard 1960, 1970; Ruffalo 1978). In particular is the organism Spirostomum ambiguum (a cigar-shaped creature visible to the naked eye) which fabricates and accumulates calcium phosphate particles resembling those found in bone. Moreover, their intracellular, golgi-directed synthesis (Fallon, Garner and Aaron, in press) is determined by their active life-cycle. This modulates between a free-swimming state when calcified particles are few and a burrowing stage when calcified particles are many. Thus when the mineral of cultured S. ambiguum was labelled with the fluorochrome tetracycline the green fluorescence intensity (AU), mapped using laser confocal microscopy, recorded a high mineral level in the burrowing animals (138.0 + SD4.0) compared with the free-swimmers (89.7 SD 3.3). Similarly when the live organisms were transfected with a GFP construct (Fallon, 2006) the resulting mannosidase II enzyme, as an expression of Golgi activity, differed significantly (p<0.0001) between tunnelling (104.6 SD 2.7) and free-swimming (74.5 6.7) by the two-sample t-test. Also it was observed that the distribution of the calcified particles was not random. A proportion related in disposition to a regular and well-defined pattern of contractile muscle myonemes, the fibres of which were arranged longitudinally within the high stress burrowers in contrast to their transverse alignment in the low stress swimmers. The capacity exhibited by this animal model not only to package bone-like mineral in response to changing environmental pressures, but also to relate them to their intracellular contractile elements may suggest an early integrated musculoskeletal system that substantially predated the vertebrates which eventually exploited this major advantage. The protozoan model described may therefore serve as a valuable tool for future fundamental investigation of osteocyte ancestry, mechanotransduction, perception and response.
Keywords:
Bones,
Bone Research
Conference:
2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society, Cambridge, United Kingdom, 27 Jun - 29 Jun, 2011.
Presentation Type:
Oral
Topic:
Abstracts
Citation:
Garner
P,
Garner
P,
Fallon
V and
Aaron
J
(2011). Spirostomum ambiguum: a protozoan model for primordial musculoskeletal exchange?.
Front. Endocrinol.
Conference Abstract:
2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society.
doi: 10.3389/conf.fendo.2011.02.00021
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Received:
30 Sep 2011;
Published Online:
30 Sep 2011.
*
Correspondence:
Prof. PE Garner, University of Leeds, IMSB, FBS, United Kingdom, bms2peg@leeds.ac.uk