Growth responses

Although riboflavin can be assayed more readily by chemical or microbiological methods than by animal methods, the latter are preferred for nutritional studies and as the basis of other techniques. Such assays depend upon a growth response the rat or chick is the preferred experimental animal. This method is particularly useful for assaying riboflavin derivatives, since the substituents frequently reduce or eliminate the biological activity. 

Biological, spectroscopic, and chromatographic methods have been used to assay vitamin A and the carotenoids. Biological methods have traditionally been based on the growth response of vitamin A—deficient rats. The utiUty and shortcomings of this test have been reviewed (52,53). This test has found apphcabiUty for analogues of retinol (54,55). Carotenoids that function as provitamin A precursors can also be assayed by this test (56). 

Bioassays are based on the growth response of vitamin-depleted rats or chicks to graded amounts of vitamin B 2 added in the diet. These assays are not specific for vitamin B 2 because factors, other than vitamin B 2 present in biological materials, produce a growth response. Because coen2yme primary form of natural vitamin 2 is light sensitive, assays should be carried out in subdued light. 

Pao, P. S., Wei, W. and Wei, R. P., Effect of frequency on fatigue crack growth response of AISl 4340 steel in water vapour , Proc. of Environment Sensitive Fracture of Engineering Materials, 24-26 Oct. 1977, Chicago, USA, The Metallurgical Society of the AIME, pp. 565-580 (1977)... 

Family of transcription factors that modulate the expression of genes which control immune, inflammatory, and acute-phase responses, as well as cell growth, responses to stress, apoptosis, and oncogenesis. All members of this family have a Rel-homology domain that contains sequences responsible for dimerization and DNA binding. In vertebrates, this family includes NF-kB1 (also known as p50), NF-kB2 (also known as p52), Rel (also known as cRel), Rel-A (also known as p65), and Rel-B. 

The growth requirement for EGF is a good example in this regard. EGF stimulates the growth of many different types of animal cells in culture. In order to initiate the growth response, EGF interacts with specific EGF receptors localized in the plasma membrane, activating a tyrosine-specific protein kinase, which is an intrinsic part of the receptor (Figure 12). As a consequence, specific proteins are phosphorylated at tyrosine residues, and some of these proteins (which are also... 

Knapp PE, Maderspach K, Hauser KF (1998) Endogenous opioid system in developing normal and jimpy oligodendrocytes p, and k opioid receptors mediate differential mitogenic and growth responses. Glia 22 189-201... 

M. A. Adams and P. M. Attiwill, Nitrate reductase activity and growth response of forest species to ammonium and nitrate sources of nitrogen. Plant Soil 66 373 (1982). 

Figure 3. Histograms showing growth response of cress, barnyard grass, and cucumber to 347 microbial isolates bioassayed on solid medium. Growth response 1) seedling growth minimal or germination nil, 2) pronounced inhibition, 3) slight inhibition, 4) growth comparable to controls, 5) stimulation over controls.

Phycocymes shows a positive UV-induced light-growth-response (Fig. 3 3) as well as a negative phototropic curvature, as depicted in Fig. 5 1. The exceptionally good fit of this action spectrum and auxin absorption (Fig. 5 2) might indicate that auxin is the UV-photoreceptor. 

Fig. 22. (A) Comparison of flavin triplet -> triplet absorption spectra (downwards drawn) with bluelight-induced (440 nm) phototropic curvature of aVena coleoptiles as inhibited by strong monochromatic light in the long wave visible region 154). (B) Comparison of the growth response of Phycomyces induced by strong laser light of wavelength longer than 590nm46, with the flavin phosphorescence spectrum los)...

Fig. 23. Comparison of physiological action spectra with action spectra for light-induced absorbance changes in the same organisms, (1) Bluelight-induced light growth response of Phycomyces45 (2) Action spectrum for the light-induced absorbance change in the C2-mutant of Phycomyces109) ...

Autochemotropism is also known as the avoidance response. Sporangiophores which are placed near an obstacle, e.g., a glass or metal wall, a wire or a silk thread, bend away from these objects. A closely related response to autochemotropism is the so-called house response. If a sporangiophore is covered with a house , e.g., a cuvette, the specimen responds with a transient increase of the growth rate similar in quantity and duration to the light growth response (Cohen et al., 1975). 

Ethylene and ethane cause transient growth responses (Russo et al., 1977). Addition of carbon dioxide or diminution of the oxygen concentration (from 20% to 10%) trigger a transient diminution of the growth rate (unpublished results). 

Fig. 4. Pleiotropism of Phycomyces strains selected as phototropic defective mutants. Mutants madA and madB are defective in all photoresponses, mutants madD, E, F, G only in tropic and growth responses...

Other related phenomena are a double barrier will induce a transient growth response in still air (very small house 2.5 2.5 7.5 cm) there is no avoidance response the avoidance response is restored if an air current is artificially created in this small house (Johnson and Gamow, 1971). 

Light-and Dark-Growth Responses aj Concept of Level of Adaptation... 

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