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41.
Corien C. Verschuuren-Bemelmans Ewout R. P. Brunt Margaret Burton Rob G. J. Mensink Martin A. van der Meulen Nico H. Smit Irene Stolte-Dijkstra Charles H. C. M. Buys Hans Scheffer 《Human genetics》1995,96(6):691-694
The autosomal dominant cerebellar ataxias (ADCA) are clinically and genetically heterogeneous. To date, several loci (SCAI-V) have been identified for ADCA type I. We have studied two large families from the northern part of The Netherlands with ADCA type I with a broad intra-familial variation of symptoms. In both families significant linkage is shown of the disease to the markers of the SCA3 locus on chromosome 14. Through recombinations, the candidate region for SCA3 could be refined to a 13-cM range between D14S256 and D14S81. No recombinations were detected with the markers D14S291 and D14S280, which suggests that the SCA3 gene lies close to these loci. This finding will benefit the individuals at risk in these two families who are seeking predictive testing or prenatal diagnosis. 相似文献
42.
The effect of ethylene on petiole growth of the Fringed Waterlily (Nymphoides peltata (S.G. Gmelin) O. Kuntze) changes during leaf ontogeny. During early development (before expansion of laminae), ethylene causes an increase in both cell number and cell size; later in development, promotion of rapid cell expansion is the dominant effect. The early effects may contribute to the accommodation of new leaves to water columns of different depth. The later effects on cell expansion only are shown to contribute to the rapid accommodation of floating leaves when changes in water level submerge the laminae. This kind of accommodation results from an interaction between accumulated ethylene, which increases wall extensibility, and the tension in petioles due to natural buoyancy which, it is suggested, supplements the driving force for cell expansion. Cell age (position) within a petiole and age of the whole petiole influence the growth response to ethylene alone and the amount of extra growth produced by applying tension when ethylene is present. In young petioles, apical cells are highly sensitive to ethylene and tension causes little further growth; older cells in both immature and mature petioles show little response to ethylene unless the petiole is under tension. Young (but not mature) petioles respond slowly to applied tension even in the absence of ethylene. It is concluded that as cells age the driving force for expansion limits increasingly their capacity to respond to the wall-loosening effects of ethylene. Dual sensitivity to ethylene and buoyant tension facilitates rapid accommodation responses but sensitivity of young petioles to tension alone may exclude Nymphoides from habitats where current velocity is appreciable. 相似文献
43.
Gemma A.J. Kuijpers Irene G.P. Van Nooy Jan Joep H.H.M. De Pont Sjoerd L. Bonting 《生物化学与生物物理学报:生物膜》1984,774(2):269-276
The isolated rabbit pancreas secretes a fluid containing chloride and bicarbonate in about equal concentrations. Replacement of bicarbonate by acetate, phosphate or isethionate, replacement of Na+ by Li+ and addition of ouabain to the bathing medium of the pancreas inhibit the secretion of fluid, chloride and bicarbonate in a similar fashion and by maximally 100%. Replacement of chloride by isethionate inhibits fluid secretion by maximally 50%, chloride secretion by 90% and bicarbonate secretion by 20%. It is concluded that fluid secretion is based on a Na+-gradient-dependent bicarbonate influx or proton efflux in the ductular cell, and that the secretion of chloride is secondary to that of bicarbonate. 相似文献
44.
Juan Alberto Claver Irene von Lawzewitsch Orestes Jorge Colillas 《Primates; journal of primatology》1984,25(3):362-371
The microscopic structure of theAlouatta caraya ovary is studied in different ages and reproductive stages. The most significant feature seems to be the presence in adult
ovaries of abundant glandular interstitial tissue which occupies both the cortex and medulla. It seems to be derived from
the theca interna of atretic follicles. Discrete luteinized masses are present in the medulla in all the ovaries observed.
Invaginations of the surface epithelium are seen only in infant and juvenile ovaries. The development of cystic follicles
seems to be a common pathway of atresia. 相似文献
45.
46.
R.L. Jones P.J. Kerry N.L. Poyser Irene C. Walker N.H. Wilson 《Prostaglandins & other lipid mediators》1978,16(4):583-589
Arachidonic acid is converted by washed platelets from man, horse and dog into a mixture of 8, 9, 12-trihydroxyeicosa-5, 10, 14-trienoic acid and 8, 11, 12-trihydroxyeicosa-5, 9, 14-trienoic acid (termed 8, 9, 12-THETA and 8, 11, 12-THETA respectively and THETA collectively). Gas chromatographic — mass spectrometric evidence of structure is discussed. 相似文献
47.
Guanosine 5′-triphosphate and guanosine 5′-[βγ-imido]triphosphate effect a collision coupling mechanism between the glucagon receptor and catalytic unit of adenylate cyclase 总被引:7,自引:6,他引:1 下载免费PDF全文
1. GTP, but not p[NH]ppG (guanosine 5′-[βγ-imido]triphosphate), abolishes the sensitivity of glucagon-stimulated adenylate cyclase to the lipid-phase separations occurring in the outer half of the bilayer in liver plasma membranes from rat. 2. When either GTP or p[NH]ppG alone stimulate adenylate cyclase, the enzyme senses only those lipid-phase separations occurring in the inner half of the bilayer. 3. Trypsin treatment of intact hepatocytes has no effect on the basal, fluoride-, GTP- or p[NH]ppG-stimulated adenylate cyclase activity. However, 125I-labelled-glucagon specific binding decays with a half-life matching that of the decay of glucagon-stimulated adenylate cyclase activity. 4. When GTP or p[NH]ppG are added to assays of glucagon-stimulated activity, the half-life of the trypsin-mediated decay of activity is substantially increased and the decay plots are no longer first-order. 5. Trypsin treatment of purified rat liver plasma membranes abolishes basal and all ligand-stimulated adenylate cyclase activity, and 125I-labelled-glucagon specific binding. 6. Benzyl alcohol activates the GTP- and p[NH]ppG-stimulated activities in an identical fashion, whereas these activities are affected differently when glucagon is present in the assays. 7. We suggest that guanine nucleotides alter the mode of coupling between the receptor and catalytic unit. In the presence of glucagon and GTP, a complex of receptor, catalytic unit and nucleotide regulatory protein occurs as a transient intermediate, releasing a free unstable active catalytic unit. In the presence of p[NH]ppG and glucagon, the transient complex yields a relatively stable complex of the catalytic unit associated with a p[NH]ppG-bound nucleotide-regulatory protein. 相似文献
48.
Two commonly used time-sampling techniques in studying animal behavior, namely, fixed interval time point technique and fixed
interval time span technique have been investigated, in which their statistical properties and the estimators for frequency
and duration have been discussed. Three simple numerical examples have been used to illustrate the calculation of estimates.
Finally, a sketch of a stochastic approach to the problem and the resultant estimators are presented, in which all the possible
transitions are considered. Therefore, both total frequency and duration of a certain behavior can be estimated by summing
up the estimators during each fixed intervening interval with only two end-points being observed. 相似文献
49.
50.
The period length of the leaf movement rhythm of Trifolium repens L. is lengthened by continuously offered cAMP (0.5–1.0 mol m-3) and theophylline (0.5–4 mol m-3). At the higher concentrations this effect is more pronounced and the rhythm damps out faster. Imidazole (0.5 and 1 mol m-3) has no effect on the period length; however, after 5 mol m-3 the rhythm is abolished. Offered as 4 h pulses the resulting phase response curves for cAMP and imidazole are similar and show delays of up to 4 h during the day position of the leaves. Theophylline pulses lead to delays of up to 5 h during closure and advances of up to 3 h during opening. No phase shift is brought about by 4-(3,4-dimethoxybenzyl)-2-imidazolidone. The results do not support the cAMP-model of the circadian clock which has been proposed by Cummings (J. theor. Biol. 55, 455–470; 1975). The effect of the substances tested could, however, be based upon influences on the transport of Ca2+.Abbreviations ATP
adenosine triphosphate
- cAMP
cyclic adenosine 35 monophosphate
- AMP
adenosine 5 monophosphate
- AC
adenyl cyclase
- PDE
phosphodiesterase
- LL
continuous light 相似文献