PubMed · 7410141
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W J Kopecky, J A Purdy. 1980. Radiofrequency interference with Clinac 20.. https://doi.org/10.1016/0360-3016(80)90397-1
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UDPG-pyrophosphorylase (EC 2.7.7.9) from Saccharomyces cerevisiae was studied and the presence of isoforms investigated. Its activity was monitored during growth of cultures in rich media containing glucose, galactose, sucrose, maltose or glycerol as carbon sources. The results suggest that UDPG-pyrophosphorylase is subject to both catabolite repression and catabolite inactivation. The inactivation process seems to be complex: in order to produce maximum inactivation, glucose and ammonium sulfate must be added together. Addition of glucose or ammonium sulfate separately produced little effect upon enzyme activity. Adsorption to and elution from a DEAE-Sephacel column of a crude protein extract prepared from yeast cells collected in stationary phase from a glucose medium showed three activity peaks, which we denominated isoform I, II, and III. Isoform I is constitutive, it was the only form present during exponential growth on glucose medium, and did not suffer any alteration after glucose exhaustion, heat shock or by growing cells on maltose. On the other hand, isoforms II and III were shown to be repressed by glucose, and induced by heat shock. Furthermore, isoform II of UDPG-pyrophosphorylase was present together with isoform I when yeast cells were grown on maltose. The presence of a MAL4C allele rendered isoform II constitutive. Interestingly, a gal3 mutant strain had low UDPG-pyrophosphorylase activity and isoforms I and II were not expressed. These results are discussed in relation to trehalose metabolism.
Ultrasound of 1 MHz frequency is used routinely for patient treatment because it can penetrate to and heat deeply located tissue. Benefits are claimed for newly introduced 45 kHz ultrasound machines, yet little evidence is available to confirm these benefits. This paper compares claims supporting the therapeutic use of 45 kHz ultrasound with those supporting the traditional MHz frequencies. The results of an empirical study comparing the heating effects are also presented. Thermocouples placed at different tissue depths in nonliving pig tissue measured temperature variations over a 40-minute period. Direct heating produced by the 45 kHz ultrasound machine was very superficial. By contrast, the 1 MHz ultrasound machine produced direct heating at all tissue depths. The results confirmed that although 45 kHz ultrasound machines may be useful for heating superficial tissues, they have limited or no use in heating deeper tissues. For treatment of deeply located tissue, 1 MHz ultrasound should continue to be used.