Aging is a progressive physiological deterioration of an organism, which induces morphological change and increases the probability of death. Morphological change is obvious measurements that can be monitored by observing the animals under the microscope, analyzed as a valuable biomarker for aging research. Here we offer a number of morphological measurements using the powerful model system C. elegans to help our customers study mutations, drugs, diet, environmental conditions, and other factors that influence aging.
The regulation of body size is an important aspect of animal development. In C. elegans, the body size is determined by the composition of the extracellular cuticle and the nuclear DNA content of the underlying hypodermis. Changes in the nematode body size are largely dependent on cell size rather than cell number due to an essentially invariant cell lineage. Previous studies demonstrate that adult C. elegans display an age-related increase in size, which may be an example of programmed growth rather than a degenerative change.
The pharynx is a tubular neuromuscular organ, which consists of six kinds of cells, including epithelial cells, muscle cells, marginal cells, gland cells, neurons and posterior valve cells. In young adults C. elegans, the pharynx is the character of enlargements in the midsection at the metacorpus and the posterior terminal bulb. The pharynx is 100 µm long and 20 µm at its widest region in the terminal bulb. The structural changes of the pharynx are dramatic during the adult lifespan, the organ is progressively more disorganized and swollen.
C. elegans is typically cultured with live E. coli. It is reported that the microbial environment influences the host's aging and longevity. By contrast, the number of bacteria gives an index to the age-related changes through detection in the pharynx and the anterior and posterior intestine.
Functional body wall muscle is essential for C. elegans maintaining the sinusoidal movement on semi-solid surfaces or the c-shaped thrashing in liquid. C. elegans has striated and non-striated muscles. And most studies have been performed on the striated body wall muscle cells, due to the high conservation between nematodes and vertebrates in structure, composition, and function of the sarcomere. Moreover, the optical transparency of the nematode allows better visualization of muscle structure. Studies demonstrate that C. elegans undergoes sarcopenia, an age-related decline in muscle structure and function.
The C. elegans germline contains germ cell proliferation that is maintained by a niche, the distal tip cell. Like mammalian stem cells, the C. elegans germline appears to be quite plastic and responsive to changing physiological conditions. The germline viewed by microscopy appears to progressively deteriorate with the age-related regulation, such as increased spacing of mitotic nuclei, nucleoplasm disrupted by cavities and grainy material, and nuclei that appeared to be cellularized.
|Age-related morphology||Description||Method of measurement||Quantitative|
|Body size||The perimeter of the lateral image of animals is measured and analyzed.||Dissecting scope||Yes|
|Pharynx||Analyze age-related changes in tissue appearance in the region of the head and pharynx.
The extent of deterioration categories: none, low, medium, high, and very high.
|Bacterial content||Detect the number of bacteria in the pharynx and the anterior and posterior intestine.||Nomarski microscopy||No|
|Body wall muscles||Visualizing muscle morphology: GFP is expressed in the nuclei of body wall muscle cells,
Visualizing muscle structure: GFP is localized to the sarcomeres of the body wall muscles.
|Electron and fluorescence microscopy using GFP tagged proteins||No|
|Germline||Five categories of germline deterioration:
Stage 1, the gonad is full sized and youthful in appearance;
Stage 2, the gonad is still intact, but shows slight signs of atrophy and deterioration;
Stage 3, the gonad shows clear atrophy and signs of impending disintegration;
Stage 4, fragmentation had occurred in gonad;
Stage 5, the gonad is occasionally seen.
Scoring germline disintegration on day 1, 8 and 12 of adult animals at 20°C.
* For research use only.