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171.
Organization of the ribosomal ribonucleic acid genes in various wild-type strains and wild-collected strains of Neurospora 总被引:6,自引:0,他引:6
Peter J. Russell Sheryl Wagner Karin D. Rodland Rhonda L. Feinbaum Jennifer P. Russell Marion S. Bret-Harte Stephen J. Free Robert L. Metzenberg 《Molecular & general genetics : MGG》1984,196(2):275-282
Summary The organization of the ribosomal DNA (rDNA) repcat unit in the standard wild-type strain of Neurospora crassa, 74-OR23-1A, and in 30 other wild-type strains and wild-collected strains of N. crassa, N. tetrasperma, N. sitophila, N. intermedia, and N. discreta isolated from nature, was investigated by restriction enzyme digestion of genomic DNA, and probing of the Southern-blotted DNA fragments with specific cloned pieces of the rDNA unit from 74-OR23-1A. The size of the rDNA unit in 74-OR23-1A was shown to be 9.20 kilobase pairs (kb) from blotting data, and the average for all strains was 9.11+0.21 kb; standard error=0.038; coefficient of variation (C.V.)=2.34%. These data indicate that the rDNA repeat unit size has been highly conserved among the Neurospora strains investigated. However, while all strains have a conserved HindIII site near the 5 end of the 25 S rDNA coding sequence, a polymorphism in the number and/or position of HindIII sites in the nontranscribed spacer region was found between strains. The 74-OR23-1A strain has two HindIII sites in the spacer, while others have from 0 to at least 3. This restriction site polymorphism is strain-specific and not species-specific. It was confirmed for some strains by restriction analysis of clones containing most of the rDNA repeat unit. The current restriction map of the 74-OR23-1A rDNA repeat unit is presented. 相似文献
172.
A comparison of the effects of different substrata on chondrocyte morphology and the synthesis of collagen types IX and X 总被引:2,自引:0,他引:2
G. P. Bates S. L. Schor M. E. Grant 《In vitro cellular & developmental biology. Plant》1987,23(5):374-380
Summary Embryonic chick sternal chondrocytes were cultured either within three dimensional gels of type I collagen, type II collagen
or agar, or as monolayers on plastic dishes coated with air-dried films of these matrix macromolecules. It was observed that
cell shape and cell growth varied markedly between the different culture conditions. Flattened monolayers of cells on plastic
or films of type I or type II collagen, proliferated more rapidly and reached a higher final cell density per culture than
the more rounded cells found in the cultures on agar films or within three-dimensional gels. Biosynthetic studies demonstrated
that in addition to the synthesis of type II collagen, all the cultures were producing collagen types IX and X. Chondrocytes
cultured on plastic or films of the different matrix macromolecules all showed a similar expression of types IX and X collagen,
independent of whether they displayed a flattened or round cell morphology. In contrast, marked variations in the proportions
of the minor collagens, particularly type X collagen, were observed when the cells were cultured within three-dimensional
gels. The data suggest that direct interaction of the cell surface with matrix constituents displaying a particular spatial
array could be an important aspect in the control of type IX and X collagen expression by chondrocytes.
The financial support of the Arthritis & Rheumatism Council and the Medical Research Council is gratefully acknowledged. 相似文献
173.
Thermal adaptation in CHO cells at 40 degrees C: the influence of growth conditions and the role of heat shock proteins 总被引:1,自引:0,他引:1
The kinetics of thermal adaptation at the nonlethal temperature of 40 degrees C was studied in CHO (Chinese hamster ovary) cells in vitro. Thermal resistance, demonstrated as an increase in mean 45 degrees C killing time or as an increase in the shoulder of the 45 degrees C survival curve, was fully developed by 2 h. Control cells in early logarithmic phase were more heat sensitive than those in stationary phase. Corresponding 45 degrees C killing time frequency distributions were unimodal with an increase in mean killing time from early logarithmic to stationary phase. Cells which were thermally adapted at 40 degrees C for 6 h had biphasic 45 degrees C killing time frequency distributions, and as cells progressed from early logarithmic to stationary phase the heat-sensitive subpopulation progressively declined. Exposure to 40 degrees C produced a 30% increase in total protein synthesis. Proteins with molecular weights 72, 89, and 109 kDa which correspond to those induced by lethal heat shock were synthesized at 40 degrees C, but there was no close temporal correlation between the development of heat resistance at 40 degrees C and synthesis of the heat shock proteins. Cycloheximide (100 micrograms/ml) reduced the mean 45 degrees C killing time but did not totally prevent the development of heat resistance at 40 degrees C. 相似文献
174.
The mechanisms underlying Ir gene control of CMI were addressed by examining the DTH and Tprlf responses specific for the synthetic polymers GT, GAT, and GA. We show that BALB/c mice (GAT/GA responders, GT nonresponders) primed with GT fail to develop DTH and Tprlf responses specific for GT, GAT, or GA. GAT immunization resulted in DTH responses that could be elicited not only with GAT and GA but also with GT, demonstrating that GT-specific TDH are present in nonresponder mice. GT-specific DTH was transferred with Thy-1+ Lyt-1+2–, H-2 Irestricted, nylon wool nonadherent cells. GA-primed BALB/c mice developed GAT- and GA-, but not GT-apecific DTH responses, indicating that GA and GT do not cross-react at the T-cell level. The ability of GAT [but not a mixture of GA plus GT, or GT electrostatically complexed to the immunogenic carrier MBSA (GT-MBSA)] to induce GT-specific DTH suggested a requirement for covalent linkage of stimulatory GA and nonstimulatory GT determinants present on the GAT molecule. Similarly, GT-specific in vitro Tprlf responses could be demonstrated in GAT-primed mice exhibiting significant levels of GT-specific DTH but not in GT- or GT-MBSA-primed mice. Tolerization experiments also suggested that GT-specific Th were involved in the development of GT-specific DTH in GAT-primed mice. The GT nonresponsiveness of BALB/c mice for DTH and Tprlf responses could not be reversed by treatments designed to abrogate Ts activity (priming with GT-MBSA and CY injection), nor could GT-primed cells be shown to inhibit the development or elicitation of GT-specific CMI in GAT-primed mice during the afferent and/or efferent stages of DTH. Our results suggest that GT nonresponsiveness does not result from the absence of GT-specific T cells or preferential induction of Ts. The results are discussed in the context of hole-in-the-repertoire and antigen presentation (determinant selection) models of Ir gene control.Abbreviations used in this paper APC
antigen-presenting cells
- BSA
bovine serum albumin
- BSS
Mishell-Dutton balanced salt solution
- CFA
complete Freund's adjuvant
- CMI
cell-mediated immunity
- CY
cyclophosphamide
- DTH
delayed-type hypersensitivity
- GA
poly(Glu60Ala40)
- GAT
poly (Glu60Ala30Tyr10)
- GT
poly(Glu50Tyr50)
- GT-MBSA
GT complexed to methylated bovine serum albumin
- It
immune response
- LN
lymph node
- PPD
purified protein derivative of tuberculin
- TDH
DTH T cells
- Th
helper T cells
- Tprlf
T-cell proliferation
- Ts
suppressor T cells
- TsF
T-cell suppressor factor(s) 相似文献
175.
Daytime surface swarms of Meganyctiphanes norvegica in the Bayof Fundy were examined using a variety of techniques to providemeasurements of their shapes, sizes and densities. Shapes andsizes were determined from two aerial photographs: swarms werespherical, ribbon-like or amorphous. were up to 28 6 m longand ranged in area from 0.4111 7 m2. Densities were measuredby a bag-sampling device which gave figures of up to 41 000animals m3 by photographic methods which gave figuresof up to 770 000 animals m3 and by a plankton net whichgave maximum values of six animals m3 Using the photographicmethod the maximum euphausud biomass was estimated to be 154kg m3 within swarms and the largest swarm measured wasestimated to contain up to 2 1 tonnes of M. norvegica. Meanpatch biomass estimates for the two aerial photographs rangedfrom 77.8778 g m3 and 15 6155.6 g m3which are similar to figures obtained by other authors usingintegrating sampling techniques at depth. 相似文献
176.
Bernd Heinrich Stephen L. Buchmann 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(4):557-562
Summary The carpenter beesXylocopa varipuncta maintain thoracic temperatures of 33.0°C to 46.5°C during continuous free flight from 12°C to 40°C. Since the thoracic temperature excess is not constant (decreasing from 24°C at low air temperatures to 6°C at high) the bees are thermoregulating. We document physiological transfer of relatively large amounts of heat to the abdomen and to the head during pre-flight warm-up and during artificial thoracic heating. Most of the temperature increase of the head is due to passive conduction, while that of the abdomen is due to active physiological heat transfer despite a series of convolutions of the aorta in the petiole that anatomically conform to a counter-current heat exchanger. Although the thermoregulatory mechanisms during flight are far from clarified, our data suggest that thermoregulation involves a strong reliance on active convective cooling through increased flight speed. 相似文献
177.
The effects of endotoxaemia on protein metabolism in skeletal muscle and liver of fed and fasted rats. 总被引:15,自引:6,他引:9
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The response of muscle and liver protein metabolism to either a single or three successive daily injections of an endotoxin (Escherichia coli lipopolysaccharide, serotype 0127 B8; 1 mg/ml, 0.3 mg/100 g body wt.) was studied in vivo in the fed rat, and at 24 and 30 h after endotoxin treatment during fasting. In the fed rats there was a catabolic response in muscle, owing to a 60-100% increase in muscle protein degradation rate, and a 52% fall in the synthesis rate. Although there was a 20% decrease in food intake, the decrease in protein synthesis was to some extent independent of this, since rats treated with endotoxin and fasted also showed a lower rate of muscle protein synthesis, which was in excess of the decrease caused by fasting alone. The mechanism of this decreased protein synthesis involved decreased translational activity, since in both fed and fasted rats there was a decreased rate of synthesis per unit of RNA. This occurred despite the fact that insulin concentrations were either maintained or increased, in the fasted rats, to those observed in fed rats. In the liver total protein mass was increased in the fed rats by 16% at 24 h, and the fractional synthesis rate at that time was increased by 35%. In rats fasted after endotoxin treatment the liver protein mass was not decreased as it was in the control fasted rats, and the fractional synthesis rate was increased by 22%. In both cases the increased synthesis rate reflected an elevated hepatic RNA concentration. The extent of this increase in hepatic protein synthesis was sufficient at one point to compensate for the fall in estimated muscle protein synthesis, so that the sum total in the two tissues was maintained. 相似文献
178.
The effects of dopamine and octopamine on adenylate cyclase activity were studied on the head homogenate of adult Culex pipiens mosquitoes in vitro. Both dopamine and octopamine were shown to increase the cyclic AMP content in the homogenate. The antagonist haloperidol blocked the production of cyclic AMP induced from dopamine but had no effect on the production of cyclic AMP induced by octopamine at the concentrations tested. The opiate agonist etorphine was ineffective at reducing cyclic AMP levels induced by either dopamine or octopamine at the concentrations tested. 相似文献
179.
Kenneth R. Miller Jules S. Jacob Ursula Smith Stephen Kolaczkowski Michael K. Bowman 《Archives of microbiology》1986,146(2):111-114
The basic cellular organization of Heliobacterium chlorum is described using the freeze-etching technique. Internal cell membranes have not been observed in most cells, leading to the conclusion that the photosynthetic apparatus of these organisms must be localized in the cell membrane of the bacterium. The two fracture faces of the cell membrane are markedly different. The cytoplasmic (PF) face is covered with densely packed particles averaging 8 nm in diameter, while the exoplasmic (EF) face contains far fewer particles, averaging approximately 10 nm in diameter. Although a few differentiated regions were noted within these fracture faces, the overall appearance of the cell membrane was remarkably uniform. The Heliobacterium chlorum cell wall is a strikingly regular structure, composed of repeating subunits arranged in a rectangular pattern at a spacing of 11 nm in either direction. We have isolated cell wall fragments by brief sonication in distilled water, and visualized the cell wall structure by negative staining as well as deep-etching.Abbreviations PF
protoplasmic fracture face
- EF
exoplasmic fracture face 相似文献
180.
The anaerobic bacteriumClostridium butyricum is the major contributor to nitrogen gains by a cellulolytic/nitrogen-fixing population isolated from straw. Growth of the anaerobe is supported by the products of fungal cellulases. The facultative anaerobeEnterobacter cloacae does not make a significant direct contribution to nitrogen fixation but in association withC. butyricum allows the anaerobe to grow under aerobic conditions. The major function ofE. cloacae is though to be provision of oxygen-depleted microsites. 相似文献