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41.
Using cub growth as an index, I examine the influence of maternalnutrition, litter size, and cub sex on maternal care in cheetahs(Acinonyx jubatus) and compare cub and litter growth rates withthose of other large feilds. Seventy-nine free-living cheetahcubs in 21 litters from 15 mothers were weighed at least oncebetween 6 and 48 days of age. Eleven litters were weighed atthe beginning and end of a 5-day observation of their mothers.The mean cub growth rate varied significantly between litters,due primarily to differences in maternal food intake. Growthdeclined sharply when maternal food intake was less than 1.5kg/ day, but did not increase with greater levels of food intake.Lower limits of growth rates may therefore have been set bythe mother's food intake, whereas upper limits may be set bythe intrinsic physiological ability of cubs to grow. Althoughmale cubs were heavier than female cubs in the same litter whenfirst weighed, major differences in growth rate between thesexes were not apparent at this stage. Both cheetah cubs andlitters grow fast relative to other large felids, and I arguethat this may be an adaptation to the high rate of cheetah juvenilemortality from predation. 相似文献
42.
Graciela E. Santillán Marisa J. Sandoval Yuti Chernajovsky Patricia L. Orchansky 《Molecular and cellular biochemistry》1992,110(2):181-191
A number of cell-surface proteins are anchored in plasma membranes by a glycosylated phosphatidylinositol (PI) moiety that
is covalently attached to the carboxyl-terminal amino acid of the mature protein. We have previously reported the construction
of a cDNA clone of a truncated Platelet-derived growth factor (PDGF) receptor that consists of the extracellular domain without
the transmembrane and cytoplasmic domains. In the construction of the vector, a sequence of 51 base pairs (bp) from the 3′-untranslated
region of the receptor cDNA was linked in frame with the external domain coding sequence. The truncated receptor protein with
the peptide VTSGHCHEERVDRHDGE fused to its carboxyl terminus was covalently attached to the membrane by a PI linkage and it
was released by phosphatidylinositol specific-phospholipase C (PI-PLC). When the 51 bp sequence was deleted, the external
domain receptor protein was secreted into the media. To determine whether the PI linkage of the protein was due to the 17
amino acids added, the peptide was fused to the carboxyl terminus of the secreted protein human Interferon-β (hu-IFN-β). Chinese
hamster ovary (CHO) cells transfected with the hu-IFN-β cDNA secreted the protein to theconditioned media, whereas CHO cells
transfected with the carboxyl terminus modified-hu-IFN-β cDNA did not secrete detectable levels of protein. CHO cells expressing
the carboxyl terminus modified-hu-IFN-β were treated with PI-PLC, the media and cell lysates were analyzed by SDS-PAGE after
immunoprecipitation with antibodies against hu-IFN-β. The modified protein is anchored to the plasma membrane by a PI linkage
and it is specifically released by PI-PLC, whereas a control preparation of CHO cells expressing wild type hu-IFN-β does not
show the same pattern. The 17 amino acid peptide fused to the carboxyl terminus of IFN-β directs attachment of a PI anchor
and targets the fusion protein to the plasma membrane. 相似文献
43.
The poor solubility of polyene antibiotics in aqueous media limits their application in the therapy of systemic fungal infections.
In the present paper we have demonstrated that the ionic state (net electrical charge) of the antibiotic molecule is an important
factor in determining the aggregation and solubility properties of amphotericin B and its derivatives. A multi-step model
of polyene self-association in aqueous media has been proposed as an explanation for the fact that some major differences
are observed when aggregation is monitored by different techniques.
Offprint requests to: J. Mazerski 相似文献
44.
Long-term changes in growth and age at maturity of mackerel, Scomber scombrus L., from the North Sea
A.-L. Agnalt 《Journal of fish biology》1989,35(SA):305-311
Mean length and mean weight at age of Atlantic mackerel in the North Sea increased significantly between 1960 and 1979, then, decreased markedly during the 1980s. In contrast, median age at maturity decreased (c. 1-1.5 years) from 1960. Median length at maturity remained stable until the 1980s, when it declined sharply. The significance of these changes is discussed in relation to variation in sea temperature, food availability and stock size. It is speculated that the changes during the 1980s resulted from immigration of western stock mackerel. 相似文献
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46.
E. Wapstra 《Functional ecology》2000,14(3):345-352
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