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41.
42.
H. Zhang S. M. Reader X. Liu J. Z. Jia M. D. Gale K. M. Devos 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,103(4):518-525
Aegilops longissima Schw. et Musch. (2n= 2x=14, SlSl) and Aegilops sharonensis Eig. (2n=2x=14, SlSl) are diploid species belonging to the section Sitopsis in the tribe Triticeae and potential donors of useful genes for wheat breeding. A comparative genetic map was constructed
of the Ae. longissima genome, using RFLP probes with known location in wheat. A high degree of conserved colinearity was observed between the wild
diploid and basic wheat genome, represented by the D genome of cultivated wheat. Chromosomes 1Sl, 2Sl, 3Sl, 5Sl and 6Sl are colinear with wheat chromosomes 1D, 2D, 3D, 5D and 6D, respectively. The analysis confirmed that chromosomes 4Sl and 7Sl are translocated relative to wheat. The short arms and major part of the long arms are homoeologous to most of wheat chromosomes
4D and 7D respectively, but the region corresponding to the distal segment of 7D was translocated from 7SlL to the distal region of 4SlL. The map and RFLP markers were then used to analyse the genomes and added chromosomes in a set of ’Chinese Spring’ (CS)/Ae. longissima chromosome additions. The study confirmed the availability of disomic CS/Ae. longissima addition lines for chromosomes 1Sl, 2Sl, 3Sl, 4Sl and 5Sl. An as yet unpublished set of Ae. sharonensis chromosome addition lines were also available for analysis. Due to the gametocidal nature of Ae. sharonensis chromosomes 2Sl and 4Sl, additions 1Sl, 3Sl, 5Sl, 6Sl and 7Sl were produced in a (4D)4Sl background, and 2Sl and 4Sl in a euploid wheat background. The analysis also confirmed that the 4/7 translocation found in Ae. longissima was not present in Ae. sharonensis although the two wild relatives of wheat are considered to be closely related. The phenotypes of the Ae. sharonensis addition lines are described in an Appendix.
Received: 28 September 2000 / Accepted: 19 January 2001 相似文献
43.
Neurochemical Research - 相似文献
44.
Behavioural effects of tactile stimulation were investigated in newly-born lambs, which had, or had not, been suckled. A smooth or woolly, warm or cold stimulus which covered one side of the face elicited in unsuckled lambs a forceful response resembling its teat-seeking approach to the dam: vigorous forward and upward head movements, munching and sucking. Smaller amounts of tactile stimulation applied at discrete facial sites showed that most head movements occurred in response to touch on the upper surfaces of the face and most oral activity in response to touch on the muzzle. The response to touch was less in lambs which had been suckled, even when age was kept constant. Results are discussed in terms of the natural situation and of the response to touch in the 40–80 day foetus. 相似文献
45.
46.
T A Reader M Parisi E De Robertis 《Biochemical and biophysical research communications》1973,53(1):10-17
A special hydrophobic protein fraction from the electroplax of , when incorporated into artifical lipid membranes, induces a reactivity to acetylcholine. Uranyl ions increase 10–20 times the conductivity of such membranes, produce discrete current jumps, and strongly potentiate the effect of acetylcholine. The response to acetylcholine was studied in media containing KCl,NaCl, Choline-Cl and Na-Propionate in the presence or absence of uranyl ions. control membranes made of lipids or containing a non-cholinergic protein from the same tissue showed no reactivity to acetylcholine and had only a slight increase in conductance at very high concentrations of uranyl ions. 相似文献
47.
M. D. J. Sayer J. P. Reader T. R. K. Dalziel 《Reviews in Fish Biology and Fisheries》1993,3(2):95-132
Summary Over the last 20–30 years there has been a very extensive international research effort into freshwater acidification and the decline or loss of soft-water fisheries. The research includes many laboratory studies on physiology and survival of fish under the conditions caused by acidification. The causes of acidification have become increasingly well understood and accepted. In many countries, industrial and environmental management strategies are being implemented with the eventual aim of halting or reversing acidification in vulnerable areas. Attention has shifted away from research into the effects of acidification on fish, and the number of new papers on this subject is declining. Now appears a good time to review this research.As is often the case in research of this kind, it is difficult to compare work from different laboratories. Especially in earlier work, experimental conditions may not be fully relevant to the field (e.g. in the choice of ambient calcium concentration), experimental media may be inadequately specified (e.g. trace metal concentrations) and analytical techniques may be open to question (e.g. pH measurement). This may explain, in part, why agreement is lacking on many aspects of the physiological effects on the early life stages of fish, as well as the adult stages to some extent. If research is to continue in this field, then adoption of standard soft, acid water media would be of significant benefit. Nethertheless, some very general conclusions on fish early life stages can be reached.There is some evidence of impaired gametogenesis and spawning, but in this area there is still a need for systematic research. After fertilization, the chorionic membranes afford protection from the effects of low pH and especially the accompanying toxic trace metals, notably aluminium. Indeed, dissolved aluminium can ameliorate acid toxicity at this stage in development, possibly by helping to decrease membrane permeability and reduce H+ uptake. The main hazard seems to be impaired development (perhaps related to a decline in pH of the perivitelline fluid), often leading to a lack of ability to escape from the chorionic membranes on hatching.After hatching, vulnerability increases. Dissolved aluminium, and other trace metals associated with acidification, become more important. Some studies indicate continuing protection from low pH afforded by low concentrations of aluminium. The causes of death can still only be inferred: much attention has concentrated on mineral uptake and balance, and there is anecdotal evidence of respiratory impairment, although not as unequivocal as it is for postlarval fish. Comparison with the physiological effects on postlarval fish is not necessarily helpful. There seems to be at least one important difference. Unlike postlarvel fish, larvae do not find aluminium at around pH 5.5 (when respiratory effects are probably most important) the most hazardous combination; rather, the greatest danger to larvae seems to be when very low pH (<5.0) and trace metals (including aluminium) combine in some kind of joint toxic effect.There is a great increase in vulnerability once dependence on the yolk has come to an end. This period coincides with the movement from the incubation site in the substratum into the open water, where the relevant water chemistry is likely to fluctuate between greater extremes. However, it is earlier, during autumn rainstorms and spring snowmelt, that pH and concentrations of protective calcium ions usually reach their lowest and metals like aluminium their highest values. In waters where acidification is most likely to occur, the early life stages of many freshwater fish species will be close to their survival threshold and only a slight decline in water quality might result in the loss of a complete year class, which would affect recruitment and eventual population status.With gradual acceptance of the causes and effects of freshwater acidification, the research effort in relation to fish is declining or shifting towards attempts to re-establish fisheries in vulnerable areas. As outlined above, only very general conclusions can be reached on individual life stages, and the relative susceptibilities compared. However, in many respects the sequence of events in the loss of fisheries is not fully understood, and information is lacking on how events at significant stages of the life cycle affect subsequent survival, development and recruitment. Plenty of work is still required. 相似文献
48.
49.
Chitosan functional properties 总被引:7,自引:0,他引:7
Chitosan is a partially deacetylated polymer of N-acetyl glucosamine. It is essentially a natural, water-soluble, derivative
of cellulose with unique properties. Chitosan is usually prepared from chitin (2 acetamido-2-deoxy β-1,4-D-glucan) and chitin
has been found in a wide range of natural sources (crustaceans, fungi, insects, annelids, molluscs, coelenterata etc.) However
chitosan is only manufactured from crustaceans (crab and crayfish) primarily because a large amount of the crustacean exoskeleton
is available as a by product of food processing. Squid pens (a waste byproduct of New Zealand squid processing) are a novel,
renewable source of chitin and chitosan. Squid pens are currently regarded as waste and so the raw material is relatively
cheap. This study was intended to assess the functional properties of squid pen chitosan. Chitosan was extracted from squid
pens and assessed for composition, rheology, flocculation, film formation and antimicrobial properties. Crustacean chitosans
were also assessed for comparison. Squid chitosan was colourless, had a low ash content and had significantly improved thickening
and suspending properties. The flocculation capacity of squid chitosan was low in comparison with the crustacean sourced chitosans.
However it should be possible to increase the flocculation capacity of squid pen chitosan by decreasing the degree of acetylation.
Films made with squid chitosan were more elastic than crustacean chitosan with improved functional properties. This high quality
chitosan could prove particularly suitable for medical/analytical applications.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
50.
Control of homoeologous chromosomal pairing in hexaploid wheat stems from a balance between a number of suppressor and promoter
genes. This study used centromeric behaviour as a tool to investigate the mechanism. Fluorescent in situ hybridization employing
centromeric and telomeric sequences as probes was applied to pollen mother cells of wheat and wheat/alien hybrids having different
pairing gene combinations. It showed: association of centromeres during pre-meiotic interphase; decondensation of centromeric
structure; sister chromatid disjunction of univalent chromosomes in homoeologous pairing situations at anaphase I; and centromeric
stretching between univalent sister chromatids in wheat/rye hybrids deficient for pairing genes. The implications of these
results are discussed.
Received: December 1996 / in revised form: 11 March 1997 / Accepted: 14 March 1997 相似文献