The red flour beetle, Tribolium castaneum, is a pest of stored products. It is also regarded as a model species for studying development, genetics, biology, physiology and biochemistry. Recently, it has become a model for use in RNA interference experiments. 20-hydroxyecdysone (20E) is involved in insect metamorphosis and its role in organ development in T. castaneum are based on hormonal treatment in conjunction with RNAi. However, information on the biological, morphological and physiological effects of 20E on T. castaneum is still limited. This study reveals the responses of T. castaneum larvae to injections with various doses of 20E (100, 200, 300, 400 and 500 ng / insect). The results show that larvae injected with 20E reached the prepupal, pupal and adult stages earlier than the control group. Different degrees of morphological change were observed in nine traits, including the appearance of pupal prothetelic organs in the larvae. Moreover, an injection of a high dose of 20E reduced the body weights of the resulting insects at each stage, as well as the length and width of elytra. The enzymatic activity of α-amylase in the resulting adults also decreased significantly. This indicates that injection of 20E caused precocious metamorphosis in T. castaneum by inducing changes in morphology and α-amylase activity, and the optimal concentrations that induce such phenomena were in the range of 100-200 ng / insect. Further investigations are needed to examine the roles of 20E in the regulation of α-amylase in T. castaneum., Nujira Tatun, Phiraya Kumdi, Jatuporn Tungjitwitayakul, Sho Sakurai., and Obsahuje bibliografii
Polyhydroxylated derivatives of 6-keto,7-dehydrocholesterol (ecdysteroids) are common constituents of various plants.
In 1965, they were accidentally discovered in the search for the insect moulting hormone. These biologically important natural
compounds are neither insect hormones nor inducers of insect ecdysis. Due to their strong anabolic, vitamin D-like effects in insects, domestic animals and humans, I propose the use of the arbitrary term vitamin D1
. The present paper describes the effects
of vitamin D1
on the growth and regeneration of excised epidermal cells of the tobacco hornworm, Manduca sexta (Sphingidae).
The periods of programmed cell death and cell proliferation (histolysis and histogenesis, respectively) exactly coincide in insects
with endogenous peaks of increased concentration of vitamin D1
. Epidermal cells communicate with each other, creating a mutually integrated tissue, connected by mechanical, chemical, electrical, ionic or other so far incompletely known factors. After natural
cell death, or after the artifi cial removal of some epidermal cells, the neighbouring cells that lose communication integrity, begin
to divide mitotically to replace the disconnected part. Cell divisions are arrested as soon as the integrity of the living tissue is
established. During insect ontogeny, the application of juvenile hormone causes regenerating epidermal cells to repeat the previous morphogenetic programme (i.e., development of patches of larval tissue on the body of a pupa, or metathetely). Conversely,
the application of vitamin D1
(20-hydroxyecdysone) caused the regenerating cells to prematurely execute a future morphogenetic
programme (i.e., development of patches of pupal tissue on the body of a larva, or prothetely). Among the key features of insect
regeneration, is the arrest of cell divisions when tissues resume living cell-to-cell integrity. This prevents the formation of aberrant groups of cells, or tumours. It is well established that the main physiological systems of insects (e.g., circulatory, respiratory,
neuro-endocrine) are structurally and functionally similar to corresponding systems in humans. Thus the basic principles of cell
regeneration and the role of vitamin D1
in insects may also be valid for humans. The common vitamins D2
(ergocalciferol) or D3
(cholecalciferol), are exclusively lipid soluble secosterols, which require activation by UV irradiation and hydroxylation in the liver.
By contrast, the neglected vitamin D1
is a natural derivative of polyhydroxylated 7-dehydrocholesterol of predominantly plant origin, which is both partly a water and partly a lipid soluble vitamin. It neither requires UV irradiation, nor hydroxylation due to 6 or
7 already built-in hydroxylic groups. Like other vitamins, it enters insect or human bodies in plant food or is produced by intestinal
symbionts. Vitamin D1
causes strong anabolic, vitamin D-like effects in domestic animals and in humans. I am convinced that
avitaminosis associated with a defi ciency of vitamin D1 in human blood may be responsible for certain hitherto incurable human
diseases, especially those related to impaired nerve functions and somatic growth, aberrant cell regeneration or formation of
malignant tumours.