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!Kung San (Bushman) hunter-gatherers have unusually high levels of mother-infant contact and represent one of the environments
of human evolutionary adaptedness (EEAs). Studies among the !Kung show that levels of crying—the most basic sign of mammalian
infant distress—are low, and response to crying is high, and some suggest that responses are overwhelmingly maternal. We show
that although !Kung mothers respond to crying most often, one-third of crying bouts are managed solely by someone else. Mothers
responded to all bouts lasting ≥30 s, but in half of these responses they were joined by one or more others. Mothers are the
most consistent responders, but multiple caregiving is common. The mother is rarely alone when her baby cries; others often
substitute or join her in interventions. This social support may facilitate the high levels of maternal responsiveness characteristic
of the !Kung, and of hunter-gatherers generally, but it is also consistent with recent theory emphasizing nonmaternal care
(allocare) and cooperative breeding. 相似文献
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The aim of this work was to compare the coldlability of phosphofructokinase (EC 2.7.1.11) from tubers of potato cultivars
(cvs.) known to differ in their propensity to accumulate sugars at low temperature. When stored at 4°C for six weeks, the
sugar content of tubers ofSolanum tuberosum L. cv. Record doubled whereas the amount of sugar in tubers of cv. Brodick and an advanced breeding clone (13676) decreased
slightly. Tubers from each line contained four forms of phophofructokinase. Over the range 12°–16°C the temperature coefficients
of the four forms of phosphofructokinase from cvs. Record and Brodick were similar. In cv. Record the temperature coefficients
of three of the enzyme forms were significantly higher at 2°–6°C than at 12°–16°C, whereas those from cv. Brodick were unchanged.
These results are consistent with the proposal that inactivation of phosphofructokinase at low temperature results in the
accumulation of hexose phosphates leading to increased sucrose synthesis. 相似文献
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Here we show that fructose 2,6-bisphosphate cannot be reliably measured in mature leaves of tobacco (Nicotiana tabacum L.), potato (Solanum tuberosum L.), or stinging nettle (Urtica dioica L.) using conventional extraction techniques, since the recoveries of fructose 2,6-bisphosphate added during extraction are poor. However, fructose 2,6-bisphosphate could be extracted by boiling leaves in ethanol and aqueous buffer. Evidence for the reliability of this technique is provided by high recovery measurements of fructose 2,6-bisphosphate added to the leaves before extraction. This extraction method was used to measure changes in the level of fructose 2,6-bisphosphate throughout the photoperiod in tobacco and potato leaves. These changes are compared with the rate of accumulation of sucrose and starch in the leaf samples. Variations in the levels of fructose 2,6-bisphosphate, and the relationship between this metabolite and sucrose and starch accumulation in these leaves during the photoperiod are similar to the pattern observed in leaves of other plant species.Abbreviations BSA
bovine serum albumin
- Fru-2,6-P2
fructose 2,6-bisphosphate
This research was supported by the Agricultural and Food Research Council (Grant no. PG43/531), and the Royal Society. 相似文献
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