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41.
Catherine Digonnet-Kerhoas Gilles Gay Jean Claude Duplan Christian Dumas 《Planta》1989,179(2):165-170
During ageing of the short-lived pollen grains of Cucurbita pepo L., water loss was examined in relation to viability using biophysical (1H-nuclear magnetic resonance, NMR) and cytological methods (fluorochromatic reaction test, freezefracture and scanning electron microscopy). A semi-logarithmic representation of the pollen weight loss demonstrated the complexity of the dehydration process. A the study of proton loss using 1H-NMR indicated that two major releases water of had taken place, each with different flux rates. Pulse 1H-NMR experiments showed the occurrene of non-exponential signal decay as a function of time, indicating the existence of different fractions of water in a pollen grain sample. These fractions leave the pollen grain at different times during pollen dehydration, and one of them (that of the so-called vital water) can be related to pollen viability. The quantity of protons giving a signal during pulse 1H-NMR experiments was very low when the pollen grains were judged to be dead according to the fluorochromatic test. Freeze-fracture replicas of these dead pollen grains (less than 25% water content) showed that the plasma membrane had become detached from the intine surface; this ultrastructural feature might therefore be involved in the loss of pollen viability.Abbreviations A
initial amplitude of the NMR signal
- A2
quantity of water charcterized by T2-2
- A5
quantity of water characterized by T2–5
- FCR
fluorochromatic reaction
- NMR
nuclear magnetic resonance
- T2
transverse relaxation time
- T2-2
T2 measured with 2 ms between each pulse of radiofrequency
- T2–5
T2 measured with 5 ms between each pulse of radiofrequency 相似文献
42.
Päivi Heikkilä Arvi I. Kahri Christian Ehnholm Petri T. Kovanen 《Cell and tissue research》1989,255(3):487-494
Summary The choroid plexus consists of the choroidal epithelium, a derivative of the neural tube, and the choroidal stroma, which originates from the embryonic head mesenchyme. This study deals with epithelio-mesenchymal interactions of these two components leading to the formation of the organ. Grafting experiments of the prospective components have been performed using the quail-chicken marker technique. Prospective choroidal epithelium of quail embryos, forced to interact with mesenchyme of the body wall of chicken embryos, gives rise to a choroid plexus showing normal morphogenesis and differentiation. The choroidal epithelium induces the differentiation of organtypical fenestrated capillaries, which are highly permeable to intravenously injected horseradish peroxidase. The choroidal epithelium of the grafts constitutes a blood-cerebrospinal fluid barrier. On top of the choroidal epithelium, there are epiplexus cells displaying a typical ultrastructure. The experimental results show that these cells do not originate from the transplanted neural epithelium. Prospective choroidal stroma of chicken embryos does not exert a choroid plexus-inducing influence upon a quail embryo's neural epithelium isolated from parts of the brain that normally do not develop a choroid plexus. The experiments show that the choroidal epithelial cells are determined at least three days before the first organ anlage is detectable.This work was supported by the Deutsche Forschungsgemeinschaft (grant Ch 44/7-1) 相似文献
43.
Christian Schütt 《Microbial ecology》1989,17(1):49-62
Sixty-two aerobic bacterial strains isolated from the unproductive dystrophic Lake Skärshultsjön (South Sweden) were screened for plasmids. The lake is considered to be an extreme environment because of its high concentration of persistent but nontoxic humic compounds. One-third of the isolates harbored multiple plasmids usually of similar high molecular weights (>25 Mdal). The plasmid-bearing strains were members of the common aquatic taxaPseudomonas spp.,Acinetobacter sp.,Alcaligenes sp.,Aeromonas/Vibrio group, andEnterobacteriaceae (taxonomy is tentative). The majority of isolates displayed multiple resistance to antibiotics and heavy metals. Some of them were capable of degrading aromatic compounds. Three isolates were chosen for curing experiments. Only strain S-68, anAlcaligenes sp., could be cured of one of its two plasmids. It harbored the two cryptic plasmids pQQ32 and pQQ70 of 32 and ca. 70 Mdal, and the latter was segregated during ethidium bromide treatment. Parental strain S-68 was capable of degrading some of nonchlorinated phenolic compounds and displayed resistance to a broad spectrum of antibiotics and the heavy metals Co2+, Ni2+, Zn2+, Cd2+, and Hg2+. Derivative strain S-68-41 lost its resistance to nickel, suggesting segregated plasmid PQQ70 coded for nickel resistance. Transformation experiments to restore nickel resistance in the cured derivative strain were not successful. 相似文献
44.
Karl Hagspiel Doris Haab Christian P. Kubicek 《Applied microbiology and biotechnology》1989,32(1):61-67
Summary The secretion of multiple forms of cellulolytic enzymes by a Trichoderma reesei QM 9414 selectant exhibiting high protease activity (T. reesei QM 9414/A 30) was investigated using monoclonal, domain-specific antibodies against cellobiohydrolase (CBH) I, CBH II and -glucosidase, and a polyclonal antibody against endoglucanase I. The pattern of appearance of these proteins was followed during growth of the fungus on Avicel cellulose, using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting/immunostaining. Evidence was obtained that, at late cultivation stages, CBH I and II became partially modified to lower molecular weight components, whereas -glucosidase and endoglucanase I appeared to remain largely intact. Modification of CBH I appeared to commence from the carboxy-terminal AB region, whereas CBH II appeared to become modified both from the amino- (ABB') and the carboxy-terminal. Evidence for a protease activity that modifies the already truncated cellobiohydrolases in the culture filtrate was obtained. These results show that proteolysis at late culture stages may contribute to the multiplicity of cellulases found in T. reesei culture fluids. Initial proteolytic cleavage of CBH I and II may, however, involve an unusual protease not detectable by the azocasein method.Offprint requests to: C. P. Kubicek 相似文献
45.
J C Christian P L Yu C W Slemenda C C Johnston 《American journal of human genetics》1989,44(3):429-433
Midshaft radial bone mass was first measured from 1970 through 1972 by photon absorptiometry in 42 pairs of monozygotic (MZ) and 38 pairs of dizygotic (DZ) male Caucasian twins (age 44-55 years). The MZ intraclass correlation (rMZ) of .70 was significantly larger (P less than .05) than the DZ correlation (rDZ) of .45, providing evidence for genetic influences (Smith et al. 1973). Radial bone mass measurements repeated 16 years later (1986-87) on 25 of the MZ pairs and on 21 of the DZ pairs revealed an rMZ of .61 and an rDZ of .44, but the difference was not significant (P greater than .05). The twins had an average radial mass loss of 0.49%/year between the two examinations. The rMZ (.52) and rDZ (.49) values for the 16-year loss in radial mass were both significantly different from zero, but their similar size indicated that the correlations were due to nongenetic factors. In a search for the source of genetic influences on adult radial mass, heritability was estimated by the formula 2(rMZ - rDZ) for radial width and was found to be .66 and .76 (P less than .05) for examinations 1 and 2, respectively. An index of radial density (mass/width) was calculated, and the differences between rMZ and rDZ were not significant at either examination. The intraclass correlations (rMZ = .35; rDZ = .43) were both significant for the loss of bone density between examinations but provided no evidence for genetic influences, results similar to the findings for the loss of mass.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
46.
Seeds of the root parasitesStriga (several spp.) andBuchnera americana were examined by means of SEM. The surface patterns of the seeds in both genera resemble each other closely, especially those ofS. angustifolia andB. americana. SomeStriga spp. can be clearly distinguished by their surface characteristics, while this is quite difficult in others. The taxonomic value of the seed surface features ofStriga andBuchnera is discussed. 相似文献
47.
Michelle Lesimple Christian Dournon Charles Houillon 《Development genes and evolution》1990,198(7):420-429
Summary In urodele amphibians, the lack of a reliable germ cell marker restricts the experimental study of the germ lineage. In the present work, we conducted genetic and histological analyses in order to demonstrate that melanin from oocytes constitutes a germ cell marker available for intraspecific experiments in Ambystoma mexicanum. Then, using this marker, we implanted germ cells from undifferentiated gonads (stage 48) into the blastocoel of host embryos and investigated their fate and determined state. Our results show that, from this stage on, the donor cells do not differentiate into other cell types; therefore, they are restricted in developmental capacity and irreversibly determined as germ cells. On the other hand, exogenous germ cells were found in an isotopic position until the young tail-bud stage, and then were found in an ectopic position; these results suggest that, from the middle tail-bud stage on, an active process contributes to migration of primordial germ cells to the gonadal territory. 相似文献
48.
Carolyn M. Giles Beatrice Uring-Lambert Joelle Goetz Georges Hauptmann Angela H. L. Fielder William Ollier Christian Rittner Tracy Robson 《Immunogenetics》1988,27(6):442-448
The antigenic determinants of human C4 have been defined by human IgG antisera, Rodgers (Rg) and Chido (Ch), in hemagglutination-inhibition assays (HAI). Eight (2 Rg and 6 Ch) are of high frequency, > 90% , and 1, WH, is of low frequency, 15 %. The phenotypic combinations are complex; generally, C4A expresses Rg, and C4B has Ch, but reverse antigenicities have been established both by HAI and by sequence data of selected C4 allotypes. A study of 325 families provides data on the antigenic expression of each C4 allotype and demonstrates strong associations. A structural model for the antigenic determinants of C4 proteins has been proposed and is completely supported by the family material. Of the 16 possible antigenic combinations for C4 proteins, only 3 are undetected. A new Ch combination has been recorded in two French families. The reported sequence variation within the C4d region can account for the antigenic determinants but leaves the location of electrophoretic variation in C4 still unclear. 相似文献
49.
Christian Larroche Chantal Desfarges Jean-Bernard Gros 《Applied microbiology and biotechnology》1988,28(1):85-92
Summary The effect of substrate (buckwheat seeds) pretreatment on the growth and the sporulation behaviour of Penicillium roqueforti is presented. When a saccharifying enzyme (-amylase) is added to a medium which exhibits a low water content (0.46 g water/g initial dry matter, IDM), a more rapid internal colonization of the seeds occurs, but the final spore production does not increase and remains close to 8.109 spores/g dry matter (DM) at 500 h. No carbon source limitation is then observed. The addition of casein hydrolysate to this medium gives rise to a great increase of the sporulation, since 14.5 109 spores/g DM are obtained after 600 h. This result is attained by a better spore yield from the mycelium, the substrate colonization being unchanged. High water content (0.60 g water/g IDM) of buckwheat seeds induces a shorter cultivation time along with a higher biomass production. However, the spore content of the medium remains close to the low water content one, but 60% total spores are external against 30% to 35% in the other media. 相似文献
50.
Luc Mejean Alena Bicakova-Rocher Marianne Kolopp Christian Villaume Francis Levi Gerard Debry Alain Reinberg Pierre Drouin 《Chronobiology international》1988,5(3):227-236
The circadian and ultradian variations of blood glucose and plasma insulin have been characterized individually and as a group phenomenon in five healthy young adults studied while adhering as closely as possible to their usual routine of sleep, activity, meal content and timing. Three complementary methods were used to analyze the data: displaying raw data as a function of time; cosinor method according to Nelson and Halberg; and time series analyses as proposed by De Prins and Malbecq. The subjects were studied in the laboratory and their life routine were controlled, but very close to that of their habitual routine. They had mainly ultradian rhythms of blood glucose (mainly about 6 hr) and circadian rhythms of immunoreactive insulin (I.R.I.). Blood glucose ultradian rhythms seem to be mainly but not exclusively mealtime dependent, while I.R.I, circadian rhythms appear to be primarily endogenous in origin. Therefore, the role played by insulin in the control of blood glucose levels seems to be programmed on a circadian basis rather than by a time independent feedback phenomenon as postulated by the conventional homeostatic hypothesis. The advantage of this chronophysiologic approach is to consider circadian rhythms of both I.R.I. and insulin effectiveness as an adaptive phenomenon able to maintain blood sugar changes in the ultradian domain of rhythms. 相似文献