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31.
32.
Activation of the gene coding for variant surface glycoprotein (VSG) 118 in Trypanosoma brucei proceeds via a duplicative transposition to a telomeric expression site. The resulting active expression-linked extra copy (ELC) is usually flanked by DNA that lacks sites for most restriction enzymes and that is thought to interfere with the cloning of the ELC as recombinant DNA in Escherichia coli. We have circumvented this problem by cloning an aberrant 118 ELC gene, flanked at the 3'-side by at least 1 kb DNA, that contains restriction enzyme sites. Our analysis shows that this DNA and the 3'-end of the 118 ELC gene are derived from another VSG gene (1.1006) that is permanently located at a telomeric position. We propose that the 3'-end of the 1.1006 gene and (all of) its 3' flanking sequence moved to the expression site by a telomere conversion. Such a telomere conversion can also account for the appearance of an extra copy of the 1.1006 gene detected in a sub-population of our trypanosome strain. 相似文献
33.
Theodore J. Smayda 《Journal of phycology》1969,5(2):150-157
The influence of 116 combinations of temperature (2, 7, 12, 16 C), salinity (5–35‰ at 5‰ intervals) and light (5 levels) on the mean daily cell division rate ( K ) of the Narragansett Bay clone of Detonula confervacea was examined following appropriate preconditioning. Growth did not occur at 16 C, but was excellent (K = 1.2–1.5) under certain combinations of light and salinity at 2, 7, and 12 C, being somewhat better at the 2 highest temperature levels. At 32%, and 1100–1200 ft-c, K increased approximately 2.5 fold from 0.6 to 1.5 between 2 and 12 C. A light-temperature relationship was found which had the general trend of an increased optimal light intensity with increasing temperature. Within the optimal salinity range of 15–30‰, the optimal light intensity was 200–600 ft-c at 2 C, 600–1200 ft-c at 7 C, and 1200–1800 ft-c at 12 C. The light-temperature relationship was most pronounced at 2 and 12 C. At 2 C, K decreased with increasing light intensity, but was independent of this factor at higher temperatures. The optimal salinity range of 15–30‰ was independent of temperature negligible growth occurred at 5‰. In situ and in vitro responses of Detonula confervacea to salinity were in general agreement but its pronounced cryophilic preference in nature (usually reaching maximum abundance below 1 C) contrasts with its excellent growth at 12 C in culture. The experiments suggest that termination of the bloom of Detonula confervacea in Narragansett Bay and elsewhere is not solely temperature-dependent. Temperature does not satisfactorily account for its apparent exclusion from waters contiguous to Narragansett Bay and from other more northerly portions of the northeastern coast of the U.S, or, together with light, for its equally surprising apparent unimportance in Norwegian coastal waters. 相似文献
34.
Changes in certain kinetic properties of hepatic microsomal aniline hydroxylase and ethylmorphine demethylase associated with postnatal development and maturation in male rats 总被引:2,自引:2,他引:0 下载免费PDF全文
Theodore E. Gram Anthony M. Guarino David H. Schroeder James R. Gillette 《The Biochemical journal》1969,113(4):681-685
1. Changes in certain kinetic properties (V(max.) and apparent K(m)) of hepatic microsomal mixed-function oxidases have been studied as a function of postnatal development and maturation in male rats. 2. Microsomal cytochrome P-450 content changed only slightly between 1 and 12 weeks of age. 3. Aniline hydroxylase activity (V(max.)) increased abruptly between 1 and 2 weeks of age to greater than adult activities and then returned to a plateau value between 4(1/2) and 12 weeks of age. Ethylmorphine demethylase activity remained low and relatively constant between 1 and 3 weeks of age and then increased markedly ( approximately 100%) between 3 and 4(1/2) weeks. 4. The apparent Michaelis constant (K(m)) for aniline hydroxylation increased almost linearly with time between 1 and 6 weeks of age and tended to reach a plateau value thereafter. The apparent K(m) for ethylmorphine demethylation increased between 1 and 3 weeks of age and then decreased abruptly to a constant value between 6 and 12 weeks. 5. The data indicate that developmental changes in the activity of these microsomal oxidases do not correlate temporally with each other or with changes in microsomal cytochrome P-450 content. 6. The most dramatic changes in enzyme activity were associated with early development (1-3 weeks) and weaning (3-4 weeks). 7. Changes in weight of seminal vesicle, a criterion of sexual maturation in male rats, were most prominent between 6 and 8 weeks of age and thus appeared to be separated in time from the prominent changes in enzyme activity. 相似文献
35.
Masashi Yamaguchi Theodore Yanos Tomoko Yamaguchi Abel Lajtha 《Developmental neurobiology》1969,1(4):419-433
When rat sciatic nerves were incubated with C14l-lysine, l- or d-glutamate, or d-l γ-aminoisobutyrate, the labeled compounds penetrated the nerve, and the level of lysine and leucine after 1 hr was higher in the nerve than in the medium. The level increased with time, and at 24 hr glutamate levels also were higher in the nerve than in the medium. Lowering the temperature strongly inhibited uptake, while other conditions such as absence of glucose, absence of sodium, or the presence of cyanide inhibited uptake by nerve less than uptake by brain slices. The uptake against a concentration gradient, and inhibitions of this uptake by metabolic inhibitors and by structural analogs, were interpreted as showing the presence of transport processes for amino acids in peripheral nerves with characteristics similar to such transport processes in the central nervous system. 相似文献
36.
Generic Identification of L-Forms by Polyacrylamide Gel Electrophoretic Comparison of Extracts from Parent Strains and Their Derived L-Forms 总被引:3,自引:1,他引:2 下载免费PDF全文
A polyacrylamide gel electrophoretic method was used for identification of L-forms in the genera Streptococcus, Staphylococcus, and Proteus, by comparing phenol-acetic acid-water extracts of homologous parent L-form pairs to one another and to other pairs. The method requires only milligram quantities of material for analysis. The standard patterns for the strains used in this study are shown as pictures of the gels and as densitometric tracings of appropriate gels. They show that, despite occasional minor differences in some organisms, the gel electrophoretic patterns of homologous L-forms and bacterial pairs are sufficiently similar-as well as sufficiently dissimilar from patterns of other genera-to permit generic identification of an unknown L-form by reference to patterns derived from possible parental bacteria. 相似文献
37.
Rapid Sulfonamide Disc Sensitivity Test for Meningococci 总被引:7,自引:1,他引:6
Minimal inhibitory concentrations (MIC) of 90 strains of Neisseria meningitidis were determined by a plate dilution technique that employed twofold changes in concentrations of sulfadiazine. The geometric mean of three MIC determinations on each strain was correlated with inhibition zones produced by a 300-mug sulfathiazole disc. The linear relationship between the logarithm of the geometric mean MIC values and the zone diameters was highly significant. Strains were separated into sensitive and resistant populations by both test procedures. Quantitative criteria for interpreting the sensitivity of a strain by the disc test were established. 相似文献
38.
The submicrosomal distribution of hepatic uridine diphosphate glucuronyltransferases in the rabbit 总被引:6,自引:3,他引:3 下载免费PDF全文
1. Rabbit liver microsomes were subfractionated into rough- and smooth-surfaced types, and glucuronyltransferase activity in each microsomal subfraction was determined with p-nitrophenol, o-aminophenol and phenolphthalein as substrates. The glucuronyltransferase activity measured with p-nitrophenol and o-aminophenol as substrates was localized predominantly in rough-surfaced microsomes. Glucuronyltransferase measured with phenolphthalein as substrate was equally present in rough- and smooth-surfaced microsomes. 2. Phenobarbital pretreatment of rabbits did not stimulate any of the glucuronyltransferase activities measured in either rough- or smooth-surfaced microsomes. 3. Preincubation of rabbit liver microsomes for 30-60min. at 37 degrees under oxygen did not cause any loss of glucuronyltransferase activity. Such preincubation caused either no change or increased enzyme activity in both submicrosomal fractions. The relative distribution of transferase activity in rough- and smooth-surfaced microsomes was not affected by preincubation. 相似文献
39.
Theodore Delevoryas 《American journal of botany》1960,47(9):778-786
Delevoryas , Theodore . (University of Illinois, Urbana.) Investigations of North American cycadeoids: trunks from Wyoming . Amer. Jour. Bot. 47(9): 778–786. Illus. 1960.—A study was undertaken of the cycadeoid trunks from Wyoming to more fully understand the morphology and evolutionary significance of these trunks and to determine the validity of the genus Cycadella. The stem named Cycadeoidea (or Cycadella) utopiensis is not the same morphologically as those from Carbon County, Wyoming, and because of its unknown source, it is not a reliable specimen for the study of cycadeoids from the Morrison formation. The Morrison, Carbon County specimens included in Ward's genus Cycadella were shown to have trunk structure, leaf bases, and cones like those in Cycadeoidea. The cone vascular bundle is derived from a fusion of 4 leaf traces. From the fused bundle complex, 4 leaf traces are separated farther out in the cortex, and 1 of these supplies the subtending leaf. In spite of the relatively complex pattern of cone trace formation, there does not seem to be any significant means of distinguishing specimens called Cycadella from the more common Cycadeoidea. Furthermore, it is evident that the genus Cycadeoidea represents a fairly homogeneous group with a wide geographic and geologic range. Pattern of formation of cone traces is interpreted as possible further evidence for regarding cycadeoid cones as portions of foliar systems. 相似文献