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Abstract. Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction. 相似文献
5.
Thomas Jahns Alexandra Zobel Diethelm Kleiner Heinrich Kaltwasser 《Archives of microbiology》1988,149(5):377-383
Evidence for the existence of an energy-dependent urea permease was found for Alcaligenes eutrophus H16 and Klebsiella pneumoniae M5a1 by studying uptake of 14C-urea. Since intracellular urea was metabolized immediately, uptake did not result in formation of an urea pool. Evidence is based on observations that the in vivo urea uptake and in vitro urease activity differ significantly with respect to kinetic parameters, temperature optimum, pH optimum, response towards inhibitors and regulation. The K
m for urea uptake was 15–20 times lower (38 M and 13 M urea for A. eutrophus and K. pneumoniae, respectively) than the K
m of urease for urea (650 M and 280 M urea), the activity optimum for A. eutrophus was at pH 6.0 and 35°C for the uptake and pH 9.0 and 65°C for urease. Uptake but not urease activity in both organisms strongly decreased upon addition of inhibitors of energy metabolism, while in K. pneumoniae, potent inhibitors of urease (thiourea and hydroxyurea) did not affect the uptake process. Significant differences in the uptake rates were observed during growth with different nitrogen sources (ammonia, nitrate, urea) or in the absence of a nitrogen source; this suggested that a carrier is involved which is subject to nitrogen control. Some evidence for the presence of an energy-dependent uptake of urea was also obtained in Pseudomonas aeruginosa DSM 50071 and Providencia rettgeri DSM 1131, but not in Proteus vulgaris DSM 30118 and Bacillus pasteurii DSM 33.Non-standard abbreviations CCCP
Carbonylcyanide-m-chlorphenylhydrazone
- DCCD
dicyclohexylcarbodiimide
- DNP
2,4-dinitrophenole 相似文献
6.
Using a radioimmunoassay against the C-terminal sequence Arg-Pro-NH2 (RPamide), we have isolated the peptide Leu-Pro-Pro-Gly-Pro-Leu-Pro-Arg-Pro-NH2 (Antho-RPamide) from an extract of the sea anemone Anthopleura elegantissima. Antho-RPamide is located in neurons of sea anemones. Application of low concentrations of Antho-RPamide to tentacle preparations of sea anemones strongly increased the frequency and duration of spontaneous contractions, suggesting that this peptide is involved in neurotransmission. Antho-RPamide has a free N-terminus, yet its X-Pro-Pro sequence makes it relatively resistant to degradation by nonspecific aminopeptidases. Thus, we have discovered another strategy by which sea anemones protect the N-termini of their bioactive neuropeptides. 相似文献
7.
Sean Waters Muhammed Khamis Alexandra von der Decken 《Molecular and cellular biochemistry》1992,109(1):17-24
Atlantic salmon (Salmo salar) were treated with 17- estradiol to induce vitellogenin synthesis in liver. This led to an increase in liver wet weight and total DNA. After incubation with micrococcal nuclease (EC 3.1.31.1) less soluble chromatin was obtained from nuclei of the estradiol treated than the control fish, but active gene regions were solubilized by the nuclease. Thus, in the estradiol treated fish soluble mononucleosomes contained hybridizable vitellogenin gene sequences. As a result of estradiol treatment the content in total liver of putrescine rose 3-fold, that of spermidine 2-fold, while spermine was unchanged. In muscle no significant changes were observed. The regulatory functions of polyamines during gene expression were investigated by binding (14C)spermine to isolated liver nuclei depleted of endogenous polyamines. The number of binding sites was higher in nuclei of estradiol treated than control fish. (14C)spermine associated preferentially with micrococcal nuclease insensitive chromatin. Thus, the high content of putrescine and spermidine in liver supported the view of polyamine accumulation in proliferating tissues. The preferential binding to condensed chromatin indicated a stabilizing effect of polyamines on the organization of inactive chromatin structures.Abbreviations MNase
micrococcal nuclease
- PMSF
phenylmethylsulfonylfluoride 相似文献
8.
Mycoplasma, in particular species laidlawii and gallisepticum, are found to have a very small, low frequency conductivity as would be predicted by the dielectric model for bacteria and their apparent lack of cell wall structure. Membrane capacitance values for the two organisms are both about 0.9 μF/cm2, although electron micrographs show that the membrane of M. gallisepticum is 20-40 A thicker than that of M. laidlawii. 相似文献
9.
When ultrasound is absorbed by tissue, heat is produced which may be destructive or, if controlled, can be therapeutic. In addition, ultrasound produces biological effects which cannot be explained on the basis of heating alone. Under certain exposure conditions production of ultrasonic lesions in brain tissue can be explained on a purely thermal basis. Examples of nonthermal effects of ultrasound include changes in growth, mitotic index and the production of chromosomal aberrations in plant roots. 相似文献
10.
Passive Electrical Properties of Microorganisms: V. Low-Frequency Dielectric Dispersion of Bacteria 总被引:2,自引:0,他引:2 下载免费PDF全文
Very high dielectric constants have been observed for bacteria at low frequencies. High dielectric constants such as these can be explained by a theory which has been developed for the low-frequency dielectric dispersion of porous charged particles and which has been tested successfully through measurements with ion exchange resins. The bacterial cell wall is electrically similar to an ion exchange resin. Observations show that the theory provides a quantitative explanation for the low-frequency dielectric dispersion of bacteria. 相似文献