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61.
Sidney W. Fox 《Origins of life and evolution of the biosphere》1984,14(1-4):485-488
The primal role of the origins of proteins in molecular evolution is discussed. On the basis of this premise, the significance of the experimentally established self-sequencing of amino acids under simulated geological conditions is explained as due to the fact that the products are highly nonrandom and accordingly contain many kinds of information. When such thermal proteins are aggregated into laboratory protocells, an action that occurs readily, the resultant protocells also contain many kinds of information. Residue-by-residue order, enzymic activities, and lipid quality accordingly occur within each preparation of proteinoid (thermal protein).In this paper are reviewed briefly the phenomenon of self-sequencing of amino acids, its relationship to evolutionary processes, other significance of such self-ordering, and the experimental evidence for original polyfunctional protocells. 相似文献
62.
Improved techniques for use of the triploid cell marker in the axolotl, Ambystoma mexicanum 总被引:1,自引:0,他引:1
Techniques for using the triploid cell marker for studying cell lineage during the development and regeneration of the axolotl limb are described. Triploid animals possess cells with three nucleoli while diploid animals possess cells with two nucleoli. We have developed a technique for isolating the limb dermis as a sheet of cells for whole-mount analysis of cellular ploidy. Whole-mount tissue preparations as well as paraffin-embedded sectioned tissues were stained specifically for nucleoli with bismuth. Cell counts from a number of triploid and diploid dermal preparations show that (1) diploid dermal cells never possess three nucleoli, (2) the frequency of trinucleolate cells in whole-mount triploid dermal preparations is not 100% but varies between animals from 30 to 76%, (3) within a single triploid animal, the frequency of trinucleolate cells in different dermal preparations is constant. These data establish the usefulness of this technique and emphasize the need for appropriate control cell counts when using the triploid cell marker in the axolotl. 相似文献
63.
Propylene glycol (PG), glycerol (G), or a combination of both were introduced into and eluted from 116 rabbit kidneys. The function of the kidneys was then studied on an ex vivo shunt by determining bloodflow and creatinine clearance. The cryoprotective agents (CPAs) were introduced and eluted at the rate of about 30 mM/min in an albumin-Ringer's lactate perfusate. In this system, 1.75 to 2.25 M cryoprotectant could be introduced and removed with no demonstrable loss of function. Significant injury was incurred at and above 2.5 M concentrations. When a combination of PG and G (equal proportions) was utilized, both 2.5 and 2.75 M total concentrations were tolerated by the kidney, with no loss of function. These studies demonstrate that in this very rigorous test system, cryoprotectant-induced injury can be significantly diminished by combining two agents of low toxicity. This suggests that osmotic injury may be enhanced by specific toxicities of cryoprotective agents, which can be minimized by using combinations, such as was done in these studies. Also, it has been shown that PG is at least as low in toxicity in the rabbit kidney as is G. 相似文献
64.
To determine what proportion of head injuries in children under 24 months of age who presented to an emergency department were related to the use of baby walkers, we reviewed the charts of 52 such children. Walkers were involved in 42% of the head injuries in the children under 12 months of age and in none of those in the children aged 12 to 24 months. All walker-related injuries, including skull fractures in three children, involved stairs (p less than 0.001). Questionnaires were also sent to all families with children aged 3 to 18 months attending a private pediatric practice to determine the prevalence of falls involving baby walkers among these children and the factors associated with such falls. Of the 152 responding families 82% reported using or having used a walker. Thirty-six percent of the families reported that their child had a fall while in a walker, with 8.8% of the falls resulting in contact with a doctor. Walker-related falls were directly associated with time spent in the walker (p less than 0.001) and with a previous fall from the walker by an older sibling (p less than 0.03). Since there is no demonstrated benefit of walkers, their use should not be encouraged, and parents should be advised of their potential danger. 相似文献
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Data from the 1971 census population were used to evaluate the effects of age differences of married partners on mortality rates. Different age groups were isolated to highlight the association between mortality and age of spouse for specific ages of married men and women. Men married to much younger or to older women exhibited a higher mortality rate than men married to women who were only a few years younger than themselves. A similar trend was observed among women married to much younger or much older men compared with those whose spouses were a few years older or of similar ages as themselves. Trends for other age groups (women aged 60-69 years, men below 40, and women below 30) did not exhibit a clear pattern. Although statistical biases within age groups may in part account for the differences in the findings, the trend which emerged from the analysis suggests that lower morbidity is associated with the most common age combinations (husbands same age or slightly older than wives). Other factors could also account for the differences (e.g., selection of healthy partners in 1st marriages, differences in lifestyles between married and single). 相似文献