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101.
The sibling species Drosophila melanogaster and D. simulans were collected at Laguna Verde, Veracruz, Mexico. D. melanogaster was found in significantly greater frequency than was D. simulans. Ten isofemale lines of each species were tested for egg to adult viability, desiccation resistance, and vagility. D. melanogaster surpassed D. simulans in all three characteristics. The findings are discussed with reference to the climatic conditions at Laguna Verde and the expected effect of such an environment on the relative frequencies of these species. The dichotomous results in regard to desiccation resistance and vagility that were observed between recently collected D. melanogaster and the Oregon-R laboratory stock of that species are also discussed. 相似文献
102.
Under stress of iron deficiency roots of sunflower (Helianthus annuus L.) increase proton efflux which acidifies the root medium, increase the ferric reducing capacity and the exudation of phenolic compounds. Differences have been found previously among sunflower inbred lines in the capacity of their roots to lower pH and it was also found that this character is under genetic control.This work presents the results of an inheritance study made by crossing two genotypes, one (CMS HA 89) without acidification capacity and another (RHA 271) with it. Plants were grown individually in 75 mL vessels with an aerated solution low in iron. After 4 days, solutions were changed to one without iron and the pH of the medium was measured during the following days. Results from F1, F2, and backcross generations can be explained with two pairs of alleles controlling the character, being the relation between alleles of complete dominance at both gene pairs, but either gene, when dominant is epistatic to the other. 相似文献
103.
I Lalowicz J Myka?a-Cie?la B Ber 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1990,45(8-9):174-176
Three cases of leiomyosarcoma are presented. The primary lesion to the stomach was seen in 2 patients while the small intestine in the remaining patient. Two patients underwent radical surgery. All patients were treated with multiple drug regimens. Radiotherapy was additionally carried out in one patient. One patient who underwent radical surgery and given maintaining chemotherapy is alive in the complete remission since 6 years while two remaining patients died within 3 and 6 years because of recurrence and haematopoietic proliferation. 相似文献
104.
Nitrogen-starved sunflower plants (Helianthus annuus L. cv. Peredovic) cannot absorb NO
3
–
or NO
2
–
upon initial exposure to these anions. Ability of the plants to take up NO
3
–
and NO
2
–
at high rates from the beginning was induced by a pretreatment with NO
3
–
. Nitrite also acted as inducer of the NO
2
–
-uptake system. The presence of cycloheximide during NO
3
–
-pretreatment prevented the subsequent uptake of NO
3
–
and NO
2
–
, indicating that both uptake systems are synthesized de novo when plants are exposed to NO
3
–
. Cycloheximide also suppressed nitrate-reductase (EC 1.6.6.1) and nitrite-reductase (EC 1.7.7.1) activities in the roots. The sulfhydryl-group reagent N-ethylmaleimide greatly inhibited the uptake of NO
3
–
and NO
2
–
. Likewise, N-ethylmaleimide promoted in vivo the inactivation of nitrate reductase without affecting nitrite-reductase activity. Rates of NO
3
–
and NO
2
–
uptake as a function of external anion concentration exhibited saturation kinetics. The calculated Km values for NO
3
–
and NO
2
–
uptake were 45 and 23 M, respectively. Rates of NO
3
–
uptake were four to six times higher than NO
3
–
-reduction rates in roots. In contrast, NO
2
–
-uptake rates, found to be very similar to NO
3
–
-uptake rates, were much lower (about 30 times) than NO
2
–
-reduction rates. Removal of oxygen from the external solution drastically suppressed NO
3
–
and NO
2
–
uptake without affecting their reduction. Uptake and reduction were also differentially affected by pH. The results demonstrate that uptake of NO
3
–
and NO
2
–
into sunflower plants is mediated by energy-dependent inducible-transport systems distinguishable from the respective enzymatic reducing systems.Abbreviations CHI
cycloheximide
- NEM
N-ethylmaleimide
- NiR
nitrite reductase
- NR
nitrate reductase
-
pHME
p-hydroxymercuribenzoate
This research was supported by grant PB86-0232 from the Dirección General de Investigatión Científica y Técnica (Spain). One of us (E.A.) thanks the Consejeria de Educación y Ciencia de la Junta de Andalucia for the tenure of a fellowship. We thank Miss G. Alcalá and Miss C. Santos for their valuable technical and secretarial assistance. 相似文献
105.
Different pathways mediate virus inducibility of the human IFN-alpha 1 and IFN-beta genes 总被引:26,自引:0,他引:26
N J MacDonald D Kuhl D Maguire D N?f P Gallant A Goswamy H Hug H Büeler M Chaturvedi J de la Fuente 《Cell》1990,60(5):767-779
106.
Huub J. M. Op den Camp Claudius K. Stumm Gerben Straatsma Piet J. L. Derikx Leo J. L. D. van Griensven 《Microbial ecology》1990,19(3):303-309
The interaction betweenAgaricus bisporus andScytalidium thermophilum on agar media was studied by differential interference contrast and phase contrast microscopy.A. bisporus combatively replacesS. thermophilum in culture on agar media. The antagonistic effect ofA. bisporus is transmissible through a cellophane membrane and causes irreversible disintegration ofS. thermophilum protoplasm, resulting in a total loss of viability after prolonged interaction between the two fungi. On compost extract agar, but not on other media, the growth rate ofA. bisporus increased from 2.7 to 5.3 mm·d–1 following contact withS. thermophilum mycelium. 相似文献
107.
P Alliet R B Lu J A Madrazo de la Garza R Santer E Lebenthal P C Lee 《Journal of steroid biochemistry》1989,33(6):1097-1102
The long-term effect of adrenalectomy (Adx) on the exocrine pancreas was examined in female adult rats. Pancreatic amylase concentration decrease to 50% of the control level starting 10 days after Adx, whereas the levels of trypsinogen and lipase remained unchanged. Replacement studies beginning 24 h after surgery with corticosterone (B, 1 mg/100 g body wt) or aldosterone (ALDO, 8 micrograms/100 g body wt) alone did not prevent the decline in amylase after Adx. However, when both hormones were administered together, pancreatic amylase concentration was maintained at a level similar to that of the control group. Serum corticosterone levels in the rats receiving B alone or B + ALDO were not different, and were comparable to levels found in normal rats. Both ALDO and B, given for 5 days starting 10 days after Adx, were required to restore amylase concentrations toward control values. When spironolactone (SPIRO, 3 mg/100 g body wt), a specific mineralocorticoid receptor blocker was administered bid together with ALDO + B, it blocked the increase in pancreatic amylase seen in ALDO + B treated rats but did not affect the serum corticosterone levels. These results suggest that mineralocorticoids are also involved in modulating the level of amylase in the rat exocrine pancreas. 相似文献
108.
D K Getman J H Eubanks S Camp G A Evans P Taylor 《American journal of human genetics》1992,51(1):170-177
Acetylcholinesterase (AChE) is a secreted enzyme essential for regulating cholinergic neurotransmission at neuronal and neuromuscular synapses. In view of the altered expression of AChE in some central neurological and neuromuscular disorders with a probable genetic basis, we have identified the chromosomal location of the gene encoding AChE. Chromosomal in situ suppression hybridization analysis revealed a single gene to be at 7q22, a result which was confirmed by PCR analysis of genomic DNA from a human/hamster somatic cell hybrid containing a single human chromosome 7. The AChE gene thus maps to the same region in which frequent nonrandom chromosome 7 deletions occur in leukemias of myeloid cell precursors known to express the enzyme during normal differentiation. 相似文献
109.
Acclimation of barley to changes in light intensity: photosynthetic electron transport activity and components 总被引:9,自引:0,他引:9
Barley seedlings (Hordeum vulgare L. Boone) were grown at 20°C with 16 h/8 h light/dark cycle of either high (H) intensity (500 mole m-2 s-1) or low (L) intensity (55 mole m-2 s-1) white light. Plants were transferred from high to low (H L) and low to high (L H) light intensity at various times from 4 to 8 d after leaf emergence from the soil. Primary leaves were harvested at the beginning of the photoperiod. Thylakoid membranes were isolated from 3 cm apical segments and assayed for photosynthetic electron transport, Photosystem II (PS II) atrazine-binding sites (QB), cytochrome f(Cytf) and the P-700 reaction center of Photosystem I (PS I). Whole chain, PS I and PS II electron transport activities were higher in H than in L controls. QB and Cytf were elevated in H plants compared with L plants. The acclimation of H L plants to low light occurred slowly over a period of 7 days and resulted in decreased whole chain and PS II electron transport with variable effects on PS I activity. The decrease in electron transport of H L plants was associated with a decrease in both QB and Cytf. In L H plants, acclimation to high light occurred slowly over a period of 7 days with increased whole chain, PS I and PS II activities. The increase in L H electron transport was associated with increased levels of QB and Cytf. In contrast to the light intensity effects on QB levels, the P-700 content was similar in both control and transferred plants. Therefore, PS II/PS I ratios were dependent on light environment.Abbreviations Asc
ascorbate
- BQ
2,5-dimethyl-p-benzoquinone
- DBMIB
2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone
- DCIP
2,6-dichlorophenolindophenol
- H
control plants grown under high light intensity
- H L
plants transferred from high to low light intensity
- L
low control plants grown under low light intensity
- L H
plants transferred from low to high light intensity
- MV
methyl viologen
- P-700
photoreaction center of Photosystem I
- QB
atrazine binding site
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
Cooperative investigations of the United States Department of Agriculture, Agricultural Research Service, and the North Carolina Agricultural Research Service, Raleigh, NC. Paper No. 11990 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC 27695-7643, USA. 相似文献
110.
Amelia K. Kivaisi Huub J. M. Op den Camp Henk J. Lubberding Jaap J. Boon Godfried D. Vogels 《Applied microbiology and biotechnology》1990,33(1):93-98
Summary The supernatants of effluents from an artificial rumen reactor degrading barley straw have been shown to contain lignin-derived compounds by UV spectral characteristics and pyrolysis mass spectrometry (PYMS). Most of these compounds were shown to be released by the action of rumen microorganisms. The compounds were quantified by measuring absorbance at 280 nm using bamboo-milled wood lignin as a standard. The concentration of the compounds rose from 0.5 mg·ml–1 at solid and liquid retention times (SRT and HRT) of 60 and 12 h, respectively, and a loading rate (LR) of 25 g total solids (TS)·l–1 per day to 3.5 mg·ml–1 at a SRT of 144 h, an HRT of 20 days and an LR of 15 g TS·1–1 per day. The highest concentration was below the level known to be toxic to rumen microorganisms in vitro. No indications were found for anaerobic lignin degradation in the rumen reactor.
Offprint requests to: H. J. M. Op den Camp 相似文献