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1.
Craig Hadley 《American journal of physical anthropology》2007,132(1):160-161
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Inhibition of liver prenyltransferase by citronellyl and geranyl phosphonate and phosphonylphosphate
Citronellyl- and geranylphosphonic acids and the corresponding phosphonylphosphates were made and tested as inhibitors of liver prenyltransferase. Kinetic analysis showed that citronellyl- and geranylphosphonylphosphate were powerful inhibitors of the enzyme, and that they were competitive inhibitors with geranyl diphosphate and noncompetitive inhibitors with isopentenyl diphosphate. Two inhibition constants, representing the equilibria [E][I]/[EI] = K5 and [ES1][I]/[ES1I] = K9, have been defined for the inhibitors. For citronellylphosphonylphosphate, the value of K5 was 1.25 microM and K9 was 3.30 microM; for geranylphosphonylphosphate, K5 = 1.50 microM and K9 = 1.60 microM. The phosphonates were very poor linear mixed noncompetitive inhibitors with respect to both substrates of the transferase. 相似文献
4.
F W Johnson B A Matheson H Williams A G Laing V Jandial R Davidson-Lamb G J Halliday D Hobson S Y Wong K M Hadley et al. 《BMJ (Clinical research ed.)》1985,290(6468):592-594
A farmer''s wife who had helped with lambing aborted spontaneously in March after a short febrile illness in the 28th week of her pregnancy. She developed disseminated intravascular coagulation post partum with acute renal failure and pulmonary oedema. Recovery was complete after two weeks of hospital care. A strain of Chlamydia psittaci, probably of ovine origin, was isolated from the placenta and fetus. The patient''s serum showed rising titres of antibody against chlamydia group antigen; the placental and fetal isolates; and a known ovine abortion, but not a known avian, strain of C psittaci. IgG against both ovine abortion and enteric strains of C psittaci was detected, but IgM against only an abortion strain was detected. Histological examination showed pronounced intervillus placentitis with chlamydial inclusions in the trophoblast but no evidence of fetal infection or amnionitis. Laboratory evidence of chlamydial infection was found in an aborting ewe on the farm in January and in remaining sheep and lambs in July. Doctors should recognise the possible risk to pregnant women in rural areas where chlamydial infections in farm animals are widespread. 相似文献
5.
Summary Environmental and water relations parameters during fall were monitored for six conifer tree species common to the central Rocky Mountains growing naturally at the same location (Pinus contorta, Pinus ponderosa, Pinus flexilus, Pseudotsuga menziesii, Abies lasiocarpa, Picea engelmannii). Subsequent to what appeared to be the beginning of seasonal stomatal closure, leaf conductance to water vapor declined sharply following the onset of freezing air temperatures at night. A coincident rapid decline in morning xylem pressure potentials (p) also occurred which resulted in values that were considerably below afternoon p. Continuing decreases in maximum leaf conductance during the day were highly correlated with corresponding decreases in minimum nocturnal air temperatures of the preceding night. By mid-December, morning p returned to values very near afternoon p and were only slightly lower than before the onset of subfreezing nights. A preliminary model is proposed which interprets the qualitative interaction between air and soil temperatures, soil and plant water potentials, and leaf conductance during seasonal stomatal closure in fall. 相似文献
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Photosynthetic and respiratory rates were studied in Cetraria islandica, C. nivalis, and Cladonia rangiferina in the alpine zone of Mt. Washington, New Hampshire. Measurements were made in the field using an infrared gas analyzer; light, temperature, and thallus water content were varied. In all species, considerable reduction in photosynthesis and respiration occurred with drying, more rapidly in photosynthesis than respiration. Optimal photosynthetic rates in all 3 species occurred at 15–20 C with light levels of 1,600 ft-c. Light compensation points ranged from 200 to 350 ft-c. Optimal respiratory rates were attained at 15 C in the 2 species of Cetraria and at 20 C in Cladonia. The data indicate that these wide-ranging, arctic-alpine and arctic-temperate lichens on Mt. Washington are quite well adapted to a moist, foggy environment with cool temperatures and low light levels, conditions which predominate in summer. 相似文献
8.
Does the use of DM-nitrophen,nitr-5, or diazo-2 interfere with the measurement of indo-1 fluorescence? 总被引:1,自引:0,他引:1 下载免费PDF全文
Emission spectra of the photolabile Ca2+ chelators DM-nitrophen, nitr-5, and diazo-2 were studied alone, and in the presence of indo-1, to investigate potential interactions that would make the simultaneous manipulation and ratiometric measurement of the intracellular Ca2+ concentration difficult. Neither diazo-2 nor its photoproduct were found to be significantly fluorescent, and consequently concentrations of diazo-2 up to 20 times that of indo-1 did not distort the emission spectra of indo-1. DM-nitrophen was scarcely fluorescent, but its fluorescence did increase upon photolysis. In contrast to diazo-2 and DM-nitrophen, nitr-5 itself was found to be quite fluorescent, and this fluorescence was significantly increased upon photolysis. Thus, combined use of nitr-5 and indo-1 poses the most difficulty. The emission spectra of all the investigated compounds were used to define experimental conditions and calibration procedures that make possible simultaneous measurement and manipulation of the intracellular Ca2+ concentration. 相似文献
9.
M D Hirsch T L O'Donohue R Wilson T K Sawyer V J Hruby M E Hadley W L Cody J J Knittel J N Crawley 《Peptides》1984,5(6):1197-1201
Previous studies have identified the (4-10) heptapeptide sequence as the central core of alpha-MSH/ACTH peptides required for mediation of important biological activities. In the present study, the structure-activity relationships of Nle4-substituted and Cys4,Cys10-bridged cyclic alpha-MSH analogues, which were previously shown to exhibit a wide range of melanotropic potencies from weak agonism to super potency, were examined for grooming behavioral activity in the rat following intracerebroventricular injections. The results showed that stepwise C-terminal elongation of the linear Nle4-substituted Ac-alpha-MSH4-10-NH2 increased grooming potencies of the peptides in a manner similar to their actions on melanocytes. The most interesting finding was the observation that cyclization of the inactive linear "central (4-10) core" of alpha-MSH (Ac-alpha-MSH4-10) to form Ac-[Cys4,Cys10]-alpha-MSH4-10-NH2 resulted in a super potent agonist in the grooming assay. However, while cyclization of the (4-10) heptapeptide produced potent agonists on grooming behavior, the structure-activity relationships were different than the frog skin bioassay. These findings support the hypothesis that appropriate structural and confirmational modifications of alpha-MSH-related peptides can produce profound effects on the bioactivities of the peptides, and suggest that different structural-conformational requirements exist for alpha-MSH interactions with its various receptors. 相似文献
10.
Secretion of melanophore-stimulating hormone (MSH) in long-term cultures of pituitary neurointermediate lobes 总被引:1,自引:0,他引:1
Summary Neurointermediate lobes from pituitaries of the frog, Rana berlandieri forreri (Rana pipiens, sensu lato), were maintained in organ culture in media with and without serum for up to six months. The cultured tissues were examined periodically by light microscopy and transmission electron microscopy and by bioassay of the melanophore-stimulating hormone (MSH) secreted and present in the culture media. Light-microscopic observations revealed a high degree of preservation of the pars intermedia at four weeks with isolated areas of some glands maintaining histological integrity for the entire six months. Similarly, at the ultrastructural level the cells appeared morphologically intact and to be actively synthesizing and secreting hormone. Bioassays showed the glands to be continuously secreting MSH; however, larger yields of hormone were obtained in media lacking serum. No significant ultrastructural differences between cells grown in the presence or absence of serum were detected. The difference in concentration of MSH between the two groups therefore apparently results from enzymatic degradation of the hormone by the serum. Organ culture of the vertebrate neurointermediate lobe may provide a unique method for the production of large quantities of MSH and for the study of other melanotropic and opiate peptides as they may be synthesized and secreted by the pars intermedia. 相似文献