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1.
The effect of changes in ambient oxygen concentration on the bioelectric properties of middle ear mucosa 总被引:2,自引:0,他引:2
Mandell DL Devor DC Madia JV Lo CY Hake H Hebda PA 《American journal of physiology. Cell physiology》2003,285(3):C618-C622
The purpose of the present study was to compare the effect of 24 h of exposure to 7% O2 (normal middle ear physiological conditions) vs. 21% O2 (found in the middle ear after ventilation tube placement) on transepithelial Na+ absorption and Cl secretion in cultured gerbil middle ear epithelial cell monolayers. Although no difference in apical Na+ absorption was identified, the UTP-induced stimulation of apical Cl secretion in the presence of apical Na+ channel blockade with amiloride was significantly enhanced after exposure to 21% O2 compared with 7% O2 exposure. In the presence of a calcium-activated Cl channel inhibitor, DIDS, UTP-induced stimulation of Cl secretion after 21% O2 exposure was decreased, suggesting a role for calcium-activated Cl channels in middle ear Cl secretion in response to relative hyperoxia. ion channels; sodium; chloride; hypoxia 相似文献
2.
The principal collagen types synthesized during two distinct phases of regeneration in rabbit ears have been investigated, in order to relate altered phenotypic expression in connective tissue cells to regeneration of cartilage. To do this, radioactively labeled collagens synthesized in short-term culture by selected regenerating ear tissues were analyzed by ion-exchange chromatography and SDS-gel electrophoresis of the intact collagens and of the cyanogen bromide peptides derived from them. Prior to the appearance of cartilage, rabbit ear holes are filled by an outgrowth of mesenchyme-like cells derived locally from adjacent tissues. These cells produce a mixture of collagens including type I, [α1(I)]2α2, and the type I trimer, [α1(I)]3, but not type II collagen. Trimer production represents about one-fourth of the collagen synthesized in either a 4-, 10-, or a 24-hr incubation. Trimer is not made by tissues from healing skin wounds nor is it present in normal, uninjured ear tissues. Type II collagen synthesis was detected in tissues taken from late regenerates containing histologically recognizable cartilage, and direct analysis of regenerated cartilage confirmed the presence of type II collagen in the matrix. Thus, regenerated cartilage in the rabbit ear system contains the normal cartilage collagen, type II, while the proliferating cell mass from which the cartilage develops synthesizes the unusual collagen, [α1(I)]3. 相似文献
3.
Rajendra S. Bhatnagar M. Zamirul Hussain Jerome A. Streifel Maximita Tolentino Belma Enriquez 《Biochemical and biophysical research communications》1978,83(2):392-397
Organ cultures of neo-natal rat lungs continue to accumulate collagen at a nearly linear rate for 5 days, when maintained in an atmosphere consisting of 5% CO2 in air. Nearly 70% of the collagen synthesized in these cultures is Type I and 30%, Type III. When these cultures are maintained in 5% CO2 + 95% O2, the per cell accumulation of collagen increased. Although there is no significant change in the amount of radiolabeled proline incorporated, the rate of incorporation per cell is increased since there appear to be fewer cells in the O2-treated cultures. These parameters of collagen synthesis parallel lung O2 injury in vivo. There is a shift in the type of collagen synthesized, nearly 70% being Type III and 30%, Type I in O2-exposed cultures. This finding is reminiscent of tissue repair after injury. Such changes in collagen may contribute to pulmonary connective tissue disorders in oxidant-induced lung injury. 相似文献
4.
C. S. Degoute C. Dubreuil M. J. Ray J. Guitton M. Manchon V. Banssillon J. L. Saumet 《European journal of applied physiology and occupational physiology》1994,69(5):414-420
Studies by laser-Doppler flowmetry of middle ear microcirculation changes induced by physical and chemical stimuli in the animal have only recently been made. This prospective study, performed in humans, was designed to compare the effects of a postural manoeuvre (headup tilt 30°), hypotension and locally applied vasoconstriction on middle ear blood flow during anaesthesia. Circulatory changes provoked by a headup tilt of 30°, and successive intravenous boluses of potent vasodilators, were compared with circulatory changes provoked by locally applied adrenaline, in ten healthy patients in good physical states undergoing middle ear surgical repair. Heart rate and direct arterial pressure were continuously recorded via a radial artery cannula. Middle ear blood flow was continuously recorded via a laser-Doppler probe placed on the promontorium cavi tympani. Metabolic parameters (partial pressure of O2 and CO2 in arterial blood, pH, arterial lactate concentrations) and arterial concentrations of propofol were measured just before and just after the experiment. Headup tilt did not modify heart rate, mean arterial pressure or middle ear blood flow. Vasodilators (nicardipine, nitroprusside, nitroglycerin) provoked a fall in arterial pressure (P<0.0001,P<0.0001,P<0.019, respectively), but did not induce any significant variations in heart rate; variations occurred in middle ear blood flow (P>0.05, not significant) which were different according to patients and agents. Locally applied adrenaline provoked a fall in the middle ear blood flow (P<0.0012), with no effect on heart rate and arterial pressure. There were no significant changes in metabolic values, or propofol serum concentrations. The behaviour of the middle ear blood flow submitted to hypotension, posture, or to vasoconstriction could be related to counteracting regulatory responses and/or to direct vascular effects. 相似文献
5.
Philip Needleman Sharon L. Key Peter C. Isakson Prasad S. Kulkarni 《Prostaglandins & other lipid mediators》1975,9(1):123-134
In isolated perfused rabbit hearts, coronary vasodilation, produced by reduced oxygen tension seems to be independent of myocardial prostaglandin biosynthesis. a) Anoxia (N2: CO2 95: 5%) produced coronary vasodilation without causing prostaglandin-like substance (PLS) biosynthesis and release; b) the decrease in coronary resistance during hypoxia (N2:O2:CO2 — 80:15:5 %) was sustained during myocardial perfusion with the low oxygen media despite the transitory nature of its PLS release; and c) indomethacin, which abolished basal or ADP stimulated myocardial PLS release, did not abolish the coronary vasodilation produced by ischemia, hypoxia, or anoxia. 相似文献
6.
C. -W. Zhu J. -G. Zhu G. Liu Q. Zeng Z. -B. Xie J. Pang Z. -Z. Feng H. -Y. Tang L. Wang 《Photosynthetica》2008,46(2):318-320
Net photosynthetic rate (P
N) of ear and flag leaf during grain filling stage and grain yield of plants with non-darkened or darkened flag leaf or darkened
ear were examined in two different CO2 concentrations: ambient (AC) and AC+200 μmol mol−1 (EC). Ear showed much higher enhancement (56 %) of P
N than flag leaf (23 %) under EC. Moreover, CO2 enrichment shortened the photosynthetic duration of flag leaf relative to ear. In this way the ratio of ear to flag leaf
contribution to grain yield increased from 1.18 (AC) to 1.39 (EC). 相似文献
7.
Kakiomenou K. Tassou C. Nychas G.-J. 《World journal of microbiology & biotechnology》1998,14(3):383-387
The influence of initial head-spaces of air – 4.9% CO2/2.1% O2/93% N2 and 5% CO2/5.2% O2/89.8% N2 – on Salmonella enteritidis and Listeria monocytogenes, and on microbial association with shredded carrots and lettuce was studied at 4 °C. Both these pathogens survived but did not grow in any vegetable regardless of the packaging system used. Total viable count, lactic acid bacteria and pseudomonads were also monitored. Lactic acid bacteria were the predominant organisms in all samples. The pH dropped significantly during the storage of vegetables. 相似文献
8.
Charles W. Leffler David W. Busija Donathan G. Beasley Anthony M. Fletcher Robert S. Green 《Prostaglandins & other lipid mediators》1986,31(2)
We determined the effect of breathing 9% CO2/10% O2/81% N2 (asphyxia) on cardiac output distribution (microspheres) in 4–5 day old unanesthetized, chronically instrumented piglets prior to and following intravenous indomethacin administration. Thirty minutes of asphyxia caused PaCO2 to increase from 35 ± 2 mmHg to 66 ± 2 mmHg, PaO2 to decrease form 73 ± 4 mmHg to 41 ± 1 mmHg, and pH to decrease from 7.52 ± 0.05 to 7.21 ± 0.07. Arterial pressure was increased slightly but cardiac output was not changed significantly. Asphyxia caused blood flow to the brain, diaphragm, liver, heart, and adrenal glands to increase while causing decreases in blood flow to the skin, small intestine, and colon. Blood flows to the stomach and kidneys tended to decrease, but the changes were not significant. Treatment with indomethacin during asphyxia did not alter arterial pressure or cardiac output but decreased cerebral blood flow to the preasphyxiated level and decreased adrenal blood flow about 20%. Indomethacin did not alter blood flow to any other systemic organ. At this time the piglet was allowed to breathe air for 2.5 hr undisturbed. Two and a half hours after indomethacin administration, blood flows to all organs returned to the preasphyxia control levels with the exception of cerebral blood flow which was reduced (93 ± 13 to 65 ± 5 ml/100 g·min. Three hours after indomethacin administration, the cerebral hyperemia caused by asphyxia was less (134 ± 17b ml/100 g·min) than prior to indomethacin (221 ± 15 ml/100 g·min. Indomethacin did not alter the asphyxia-induced changes to any other systemic organ. We conclude that in newborn pigs, systemic treatment with indomethacin decreases cerebral blood flow and cerebral hyperemia in response to asphyxia, without affecting blood flow to any other systemic organ. 相似文献
9.
Diana Rigueur Ryan R. Roberts Lauren Bobzin Amy E. Merrill 《Genesis (New York, N.Y. : 2000)》2019,57(1)
The skeletal structure of the mammalian middle ear, which is composed of three endochondral ossicles suspended within a membranous air‐filled capsule, plays a critical role in conducting sound. Gene mutations that alter skeletal development in the middle ear result in auditory impairment. Mutations in fibroblast growth factor receptor 2 (FGFR2), an important regulator of endochondral and intramembranous bone formation, cause a spectrum of congenital skeletal disorders featuring conductive hearing loss. Although the middle ear malformations in multiple FGFR2 gain‐of‐function disorders are clinically characterized, those in the FGFR2 loss‐of‐function disorder lacrimo‐auriculo‐dento‐digital (LADD) syndrome are relatively undescribed. To better understand conductive hearing loss in LADD, we examined the middle ear skeleton of mice with conditional loss of Fgfr2. We find that decreased auditory function in Fgfr2 mutant mice correlates with hypoplasia of the auditory bulla and ectopic bone growth at sites of tendon/ligament attachment. We show that ectopic bone associated with the intra‐articular ligaments of the incudomalleal joint is derived from Scx‐expressing cells and preceded by decreased expression of the joint progenitor marker Gdf5. Together, these results identify a role for Fgfr2 in development of the middle ear skeletal tissues and suggest potential causes for conductive hearing loss in LADD syndrome. 相似文献
10.
The photosynthetic CO2 fixation by spinach leaf (Spinacia oleracea L. var. Kyoho) protoplasts was inhibited by substituting an atmosphere of N2 with one of either air (21% O2) or 100% O2. The inhibitory effect of 100% O2 was greater than that of air. The mode of inhibition by 100% O2 and air was competitive with respect to CO2; Ki(O2) value was 0.32 mM at pH 7 and 0.28 mM at pH 8.5 The labeling patterns of compounds in protoplasts exposed to 14CO2 in light after transferring them from N2 to O2 atmospheres were examined. There was no detectable 14CO2 incorporation into glycolate under anaerobic and O2 atmospheres; a more marked labeling of glycine occurred under an oxidative environment compared to that under the anaerobic condition, presumably because of a rapid transformation of glycolate to glycine in the protoplasts. 相似文献
11.
Shin Jchi Nakamura 《Journal of plant research》1976,89(3):211-218
The seedling of an achlorophyllous orchid,Galeola septentrionalis, requires for its early growth anomalous atmospheric conditions appropriate to each process of development.
The most favorable atmosphere for the enlargement of protocorm consists of 10% O2, 6% CO2 and 84% N2 at a pressure of 1.4 kg/cm2. Tolerable ranges of atmospheric pressure, concentrations of O2 and CO2 were 1.1–2.0 kg/cm2, 5–12% and 2–10%, respectively. Such a range for culture temperatures was 20–26 C.
Subsequent development of the seedlings was little influenced by atmospheric pressure (1.0–1.8 kg/cm2) and concentration of CO2 (0–8%), but influenced by O2 concentration. Optimum and tolerable concentrations of O2 were 10–15% and 5–19.7%, respectively.
These atmospheres are discussed hypothetically as the conditions required to pass an inevitable process specific to the epigenetic
ontogeny of scobiform (sawdusty) seeds. 相似文献
12.
Survival of Aspergillus flavus and Fusarium moniliforme in High-Moisture Corn Stored Under Modified Atmospheres 总被引:1,自引:1,他引:1
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Freshly harvested high-moisture corn with 29.4% moisture and corn remoistened to 19.6% moisture were inoculated with Aspergillus flavus Link ex Fr. and stored for 4 weeks at about 27 C in air (0.03% CO2, 21% O2, and 78% N2) and three modified atmospheres: (i) 99.7% N2 and 0.3% O2; (ii) 61.7% CO2, 8.7% O2, and 29.6% N2; and (iii) 13.5% CO2, 0.5% O2, and 84.8% N2. Kernel infections by A. flavus, Fusarium moniliforme (Sheld.) Snyd. et Hans., and other fungi were monitored weekly. The modified-atmosphere treatments delayed deterioration by A. flavus and F. moniliforme, but their growth was not completely stopped. A. flavus survived better in the remoistened than in the freshly harvested corn. F. moniliforme survived in both. A. flavus and F. moniliforme were the dominant fungi in corn removed from the modified atmospheres and exposed to normal air for 1 week. 相似文献
13.
Response of gas exchange and yield components of field-grown Triticum aestivum L. to elevated ozone in China 总被引:1,自引:0,他引:1
To assess photosynthesis and yield components’ response of field-grown wheat to increasing ozone (O3) concentration (based on diurnal pattern of ambient O3) in China, winter wheat (Triticum aestivum L.) cv. Jia 403 was planted in open top chambers and exposed to three different O3 concentrations: O3-free air (CF), ambient air (NF), and O3-free air with additional O3 (CF+O3). Diurnal changes of gas exchange and net photosynthetic rate (P
N) in response to photosynthetic photon flux density (PPFD) of flag leaves were measured at the filling grain stage, and yield
components were investigated at harvest. High O3 concentration altered diurnal course of gas exchange [P
N, stomatal conductance (g
s), and intercellular CO2 concentration (C
i)] and decreased significantly their values except for C
i. Apparent quantum yield (AQY), compensation irradiance (CI), and saturation irradiance (SI) were significantly decreased,
suggesting photosynthetic capacity was also altered, characterized as reduced photon-saturated photosynthetic rate (P
Nmax). The limit of photosynthetic activity was probably dominated by non-stomatal factors in combination with stomatal closure.
The significant reduction in yield was observed in CF+O3 treatment as a result of a marked decrease in the ear length and the number of grains per ear, and a significant increase
in the number of infertile florets per ear. Even though similar responses were also observed in plants exposed to ambient
O3 concentration, no statistical difference was observed at current ambient O3 concentration in China. 相似文献
14.
L. V. Antonova V. G. Matveeva M. N. Chernova E. A. Velikanova A. V. Ponasenko A. S. Golovkin 《Cell and Tissue Biology》2014,8(3):204-212
In this study, we examined the impact of 3-day hypoxia of different degrees on the viability, proliferation, and secretory activity of endothelial cells from human umbilical vein (HUVEC). A gas mixture of three components was used (%): 1) 10 O2, 5 CO2, and 85 Ar; 2) 5 O2, 5 CO2, and 80 Ar; and 3) 1 O2, 5 CO2, and 94 Ar. Cells cultivated in a CO2 incubator in atmospheric oxygen (21% O2) served as control. It was found that 3-day HUVEC cultivation at 1% O2 increased NO synthesis; enhanced secretion of endothelin-1, IL-6, IL-8, TNF-alpha, sVCAM-1, sE-cadherin, sE-selectin, VEGF-A, and bFGF; and inhibited proliferation. HUVEC cultivated under 10% O2 and 5% O2 exhibited the lowest level of basal secretion of these substances and increased proliferative activity. These cells cultivated under conditions of atmospheric oxygen for 3 days displayed activated secretion of NO, IL-6, IL-8, and von Willebrand factor; the activation was higher than at 10% O2 and 5% CO2. Thus, the gaseous medium with reduced oxygen content (5%) is a more physiological condition for HUVEC cultivation. An increase in the amount of oxygen up to the atmospheric level causes endotheliocyte activation; the cells exhibit the features of endothelial dysfunction. Oxygen content reduced to 1% induces endothelial dysfunction and reduced proliferative potential. 相似文献
15.
Z. Flagella R. G. Campanile M. C. Stoppelli A. De Caro N. Di Fonzo 《Physiologia plantarum》1998,104(4):753-759
The quantum yield of photosynthetic electron transport (ΦPSII), evaluated by means of chlorophyll (Chl) fluorescence analysis, has proven to be a useful screening test for drought tolerance in durum wheat (Triticum durum Desf.). To explore the potential of this parameter further in detecting drought-tolerant genotypes, three cereal species were studied; ΦPSII measurements were carried out under two different gas mixtures, at three points of the induction curve (to obtain the maximal ΦPSII and both the transient and steady-state actual ΦPSII), and at three different water stress levels (moderate, severe and drastic). The species investigated were durum and bread wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.); two cultivars per species, characterized by different levels of drought tolerance, were tested. The two gas mixtures used were normal air (21% O2, 0.035% CO2 in N2) to monitor the whole photosynthetic process under physiological conditions, and CO2 enriched-low O2 air (1% O2, 5% CO2 in N2) to monitor ΦPSII reduction under stress mainly related to Calvin cycle activity. When ΦPSII related to both assimilatory and non-assimilatory metabolism was evaluated, the cultivar differences observed under normal Air were more representative of the agronomic performance upon drought stress than under high CO2-low O2 air. Maximal ΦPSII showed no difference among either cultivars, gas mixtures or stress levels, the efficiency of excitation capture being highly resistant to drought. The ΦPSII evaluated during the transient yielded predictable values in respect of drought tolerance for durum wheat and barley cultivars, highlighting the key role of regulatory processes such as the Mehler peroxidase reaction and possibly also cyclic electron transport, in preventing overreduction under stress. The results clearly show that when Chl fluorescence analysis is used as a parameter in plant breeding, different experimental conditions should be used depending on the physiological mechanism that is bred or selected for. 相似文献
16.
B. J. Mulholland J. Craigon C. R. Black J. J. Colls J. Atherton† G. Landon 《Global Change Biology》1998,4(2):121-130
Spring wheat cv. Minaret was grown to maturity under three carbon dioxide (CO2) and two ozone (O3) concentrations in open-top chambers (OTC). Green leaf area index (LAI) was increased by elevated CO2 under ambient O3 conditions as a direct result of increases in tillering, rather than individual leaf areas. Yellow LAI was also greater in the 550 and 680 μmol mol–1 CO2 treatments than in the chambered ambient control; individual leaves on the main shoot senesced more rapidly under 550 μmol mol–1 CO2, but senescence was delayed at 680 μmol mol–1 CO2. Fractional light interception (f) during the vegetative period was up to 26% greater under 680 μmol mol–1 CO2 than in the control treatment, but seasonal accumulated intercepted radiation was only increased by 8%. As a result of greater carbon assimilation during canopy development, plants grown under elevated CO2 were taller at anthesis and stem and ear biomass were 27 and 16% greater than in control plants. At maturity, yield was 30% greater in the 680 μmol mol–1 CO2 treatment, due to a combination of increases in the number of ears per m–2, grain number per ear and individual grain weight (IGW). Exposure to a seasonal mean (7 h d–1) of 84 nmol mol–1 O3 under ambient CO2 decreased green LAI and increased yellow LAI, thereby reducing both f and accumulated intercepted radiation by ≈ 16%. Individual leaves senesced completely 7–28 days earlier than in control plants. At anthesis, the plants were shorter than controls and exhibited reductions in stem and ear biomass of 15 and 23%. Grain yield at maturity was decreased by 30% due to a combination of reductions in ear number m–2, the numbers of grains per spikelet and per ear and IGW. The presence of elevated CO2 reduced the rate of O3-induced leaf senescence and resulted in the maintenance of a higher green LAI during vegetative growth under ambient CO2 conditions. Grain yields at maturity were nevertheless lower than those obtained in the corresponding elevated CO2 treatments in the absence of elevated O3. Thus, although the presence of elevated CO2 reduced the damaging impact of ozone on radiation interception and vegetative growth, substantial yield losses were nevertheless induced. These data suggest that spring wheat may be susceptible to O3-induced injury during anthesis irrespective of the atmospheric CO2 concentration. Possible deleterious mechanisms operating through effects on pollen viability, seed set and the duration of grain filling are discussed. 相似文献
17.
1. The effects of O2, CO2, and pressure were studied in two very different species of protozoa, a flagellate, Chilomonas paramecium, grown in acetate-ammonium solution and a ciliate, Tetrahymena geleii, grown in 2 per cent proteose-peptone solution. 2. Chilomonas and Tetrahymena live and reproduce in solutions exposed to a wide range of O2 concentrations, but Chilomonas is killed at high O2 tensions in which Tetrahymena grows best. The optimum O2 concentration for Chilomonas is about 75 mm. pressure but it lives and reproduces in O2 tensions as low as 0.5 mm. while Tetrahymena fails to grow in concentrations below 10 mm. O2 pressure. 3. With a constant O2 tension of 50 mm. pressure, it was found that there is no significant variation in growth in Chilomonas between 50 mm. and 740 mm. total pressure. In Tetrahymena, however, under the same conditions, an optimum total pressure was found at about 500 mm. and growth is comparatively poor at 50 mm. total pressure. 4. Tetrahymena does not live very long in CO2 tensions over 122 mm., although Chilomonas grows as well at 400 mm. CO2 as in air at atmospheric pressure (0.2 mm. CO2). Tetrahymena grows best in an environment minus CO2, but the optimum for Chilomonas is 100 mm. CO2 at which pressure an average of 668,600 ± 30,000 organisms per ml. was produced (temperature, 25 ± 1° C.). 5. Chilomonads grown in high CO2 concentrations (e.g., 122 mm.) produce larger starch granules and more starch than those grown in ordinary air at atmospheric pressure. 6. In solutions exposed to 75 mm. O2 tension (optimum) and 122 mm. CO2 plus 540 mm. N2 pressure, chilomonads contain very little, if any, fat. This phenomenon seems to be due to the action of CO2 on the mechanisms concerned with fat production. 7. In Tetrahymena exposed to pure O2, there is very little fat compared to those grown in atmospheric air. This may be due to the greater oxidation of fat in the higher O2 concentrations. 8. Further evidence is presented in support of the contention that Chilomonas utilizes CO2 in the production of starch. 相似文献
18.
Johan Smitz Rita Cortvrindt Andr C. van Steirteghem 《Molecular reproduction and development》1996,45(4):466-475
This study compares the effects of reduced (5%) or normal (5% CO2 in air; 20% O2) oxygen tension on the in vitro maturation of early preantral ovarian follicles isolated from 14-day-old (C57BI/6J × CBAca) F1 mice. Intact follicles (100–130 μm) are singly cultured in 20 μl droplets α-MEM enriched with FCS and rFSH under mineral oil at 37°C and 100% humidity. In this culture system the follicles are allowed to attach to the bottom of the petri dishes. Follicle in vitro growth, hormone secretory capacity, and in vitro ovulation were studied under the two oxygen tensions. Spontaneous oocyte release from the follicle during a 16-day culture period was observed significantly more under 5% oxygen. Antrallike cavity formation was not observed under 5% O2. The follicles in the 5% O2 cultures reaching day 16 were stripped of their granulosa cell layers, and 83% of the retrieved oocytes had already undergone spontaneous germinal-vesicle breakdown (GVBD). Under 20% O2, the GV stage was maintained until day 16 in 77% of the oocytes. Under 5% O2, intact follicle survival up to day 12 was significantly reduced as compared to the 5% CO2 in air conditioning. The hCG stimulus on day 12 induced mucification in a significantly larger proportion of follicles cultured under 20% O2 (79% vs. 47%). Germinal-vesicle breakdown (20% O2:95%, 5%, O2:42%) and first polar body extrusion (20% O2:40%, 5% O2:15%) were significantly more prevalent under normal oxygen tension. A reduced secretory capacity of E2 and inhibin was demonstrated for follicles cultured under 5% O2. The histological study of serially sectioned follicles showed increased areas of centrally located granulosa cell necrosis and pyknosis in the cumulus cells. Gassing follicle cultures using 5% CO2 in air provided appropriate conditions for normal growth, enhanced whole-follicle survival, differentiation, and hormone production, and improved the yield of meiotic competent oocytes. © 1996 Wiley-Liss, Inc. 相似文献
19.
A mutant strain of Chlamydomonas reinhardtii, designated 18-7F, has been isolated and characterized. 18-7F requires a high CO2 concentration for photoautrophic growth in spite of the apparent induction of a functional CO2 concentrating mechanism in air-adapted cells. In 2% O2 the photosynthetic characteristics of 18-7F and wild type are similar. In 21% O2, photosynthetic O2 evolution is severely inhibited in the mutant by preillumination in limiting CO2, although the apparent photosynthetic affinity for inorganic carbon is similar in preilluminated cells and in cells incubated in the dark prior to O2 evolution measurements. Net CO2 uptake is also inhibited when the cells are exposed to air (21% O2, 0.035% CO2, balance N2) for longer than a few minutes. [14C]Phosphoglycolate accumulates within 5 minutes of photosynthetic 14CO2 fixation in cells of 18-7F. Phosphoglycolate does not accumulate in wild type. Phosphoglycolate phosphatase activity in extracts from air-adapted cells of 18-7F is 10 to 20% of that in wild-type Chlamydomonas. The activity of phosphoglycolate phosphatase in heterozygous diploids is intermediate between that of homozygous mutant and wild-type diploids. It was concluded that the high-CO2 requiring phenotype in 18-7F results from a phosphoglycolate phosphatase deficiency. Genetic analyses indicated that this deficiency results from a single-gene, nuclear mutation. We have named the locus pgp-1. 相似文献
20.
Effects of N2-O2 and CO2-O2 Tensions on Growth of Fungi Isolated from Damaged Flue-Cured Tobacco
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Ten fungi, Aspergillus niger, A. flavus, A. ochraceus, A. ruber, A. repens, A. amstelodami, Alternaria tenuis, Penicillium brevi-compactum, Cladosporium herbarum, and Chaetomium dolicotrichum, were isolated from moldy flue-cured tobacco and grown in various mixtures of N2-O2 or CO2-O2. A 1 to 5% concentration of O2 in an N2 atmosphere caused the greatest change in growth of the nine species, and a 10 to 20% concentration of O2 for A. flavus. All species, except A. amstelodami and A. ruber, grew faster in air than in mixtures containing 10% O2. High O2 concentrations generally inhibited furrow production in the mycelial mats. In an atmosphere of 5 to 40% O2 in the N2 atmosphere, furrows formed in mycelial mats between 5 and 40% O2 in the species except for A. ruber, A. repens, and A. amstelodami, which produced none in any concentration. As O2 decreased below 20%, spore production was progressively decreased, colony color faded to white, and cleistothecia formation was suppressed. In CO2-O2 mixtures radial growth of all species increased with each quantitative decrease of CO2. All species except A. niger grew faster in air than in 10% CO2. In contrast to N2-O2 mixtures, the fungi formed furrows, sporulation and cleistothecial formation were suppressed, and colony color changed to white in higher O2 concentrations. 相似文献