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81.
A study of the epideictic behaviour patterns of male Xiphophorus helleri Heckel was made, and the social rank of individual fish in 12 groups of three was assessed over a ten-day period. Straight-line hierarchies were established in most groups. An anatomical study was made to locate the adrenocortical tissue, and the adrenocortical activity of each fish was assessed by measuring mean nuclear diameter of 25 adrenocortical cells. Although results were somewhat variable, the highest-ranking fish in 7 out of 12 groups showed the least adrenocortical activity. The remaining two fish showed no significant difference from each other in adrenocortical activity, though their rank was in most cases clearly distinguishable on behavioural grounds. 相似文献
82.
John F. Brandts Richard D. Taverna Easwara Sadasivan Kathryn A. Lysko 《生物化学与生物物理学报:生物膜》1978,512(3):566-578
Differential scanning calorimetry has been used to study several structural transitions of the human erythrocyte membrane. Earlier studies have shown that one of these transitions (the A transition) is due to the thermal unfolding of spectrin on the membrane. In this paper, it is shown that two of the other transitions (B and C) exhibit a high sensitivity to a local anesthetic, benzyl alcohol. Increasing the ionic strength of the suspending medium results in a splitting of the B transition into two independent transitions (B1 and B2). It is found that one of these (B2) is associated with titrating groups, since the midpoint for the transitions shifts by about 20°C, with an apparent near 7.5. Extensive bilateral proteolysis by papain causes a drastic decrease in the size of all transitions except the C transition, which remains unaltered. On the other hand, treatment with phospholipase A2 largely affects the C transition, causing its disappearance. Because of the lack of sensitivity to proteolysis and the high sensitivity to phospholipase, it appears that the C transition has a large extent of ‘lipid involvement’. It might result from the melting of a small fraction of phospholipid which exists in a crystalline state under physiological conditions. Alternatively, the C transition could arise from changes in protein-lipid interactions or from lipid-dependent changes in protein-protein interactions, providing one assumes that only protease-resistant portions of membrane proteins are participating. 相似文献
83.
In the presence of MgCl2, amounts of detergents which disrupted phospholipid vesicles caused lipopolysaccharide I from Proteus mirabilis to aggregate and form vesicular, membrane-like structures. Vesicle formation with P. mirabilis lipopolysaccharide II containing longer O-polysaccharide chains was extremely poor. Lipopolysaccharides of Salmonella minnesota R mutants (chemotypes Ra, Rc and Re) displayed a growing tendency for vesicle formation with increasing deficiency of the R core polysaccharide. Lipopolysaccharides of chemotypes Rc and Re produced vesicles even in the absence of MgCl2 and detergent. Spherical aggregates consisting of P. mirabilis lipopolysaccharide I, MgCl2 and detergent were unable to either entrap or retain [14C]-sucrose, [3H]inulin or [3H]dextran. On the other hand, S. minnesota R mutant lipopolysaccharides of chemotypes Rc and Re could entrap all three saccharides and retain them for at least short periods of time. Leakage of [3H]-inulin out of Re-lipopolysaccharide vesicles was greatly retarded by addition of MgCl2 to the vesicle system. Incorporation of P. mirabilis lipopolysaccharide I or S. minnesota Rc lipopolysaccharide into phospholipid vesicles protected these model membranes from disruption by detergent. This suggested a similar protective function of lipopolysaccharide in the outer membrane of enteric bacteria against the action of surfactants occuring in their normal intestinal habitat. 相似文献
84.
Alfonso L. Pogolotti Kathryn M. Ivanetich Hans Sommer Daniel V. Santi 《Biochemical and biophysical research communications》1976,70(3):972-978
Studies are reported on the FdUMP-CH2-H4 folate-peptide obtained upon proteolysis of the complex formed from thymidylate synthetase, FdUMP and 5,10-CH2-H4folate. Contrary to a previous report from this laboratory, the peptide does contain a cysteine residue. The sequence of the largest peptide obtained is Ala-Leu-Pro-Pro-(His,Cys)-Thr. Quantitative modification of the histidine residue with the Pauly reagent indicates that imidazole is not directly linked to the nucleotide. The stability of the peptide indicates the covalent bond to the cofactor involves its 5-nitrogen; from this, it may be concluded that the reactive form of the cofactor is the 5-iminium ion. 相似文献
85.
F R Ellis I M Clarke M Modgill S Currie D G Harriman 《BMJ (Clinical research ed.)》1975,3(5982):511-513
Evidence is presented that serum creatinine phosphokinase (CPK) activity is of no direct value in screening patients for susceptibility to malignant hyperpyrexia and does not correlate with halothane-induced muscle contracture or the presence of myopathy. Widely differing CPK values were found at different times in the same people. In most "malignant hyperpyrexia" families the susceptible patients had either normal or inconsistently raised CPK values. 相似文献
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ABSTRACT Investigators generally pool observations of males and females in studies of the foraging behavior of sexually monochromatic songbirds. However, such pooling can obscure possible intersexual differences. We compared the foraging behavior of male and female Western Wood‐Pewees (Contopus sordidulus), a sexually monochromatic species, in the Sierra Nevada Mountains of California during the breeding seasons of 2007 and 2008. We recorded 143 foraging observations (male N= 74, female N= 69). Overall, mean foraging rates of females (2.8 attacks/min) were higher (P < 0.001) than those of males (1.1 attacks/min). In addition, female foraging rates were significantly higher during incubation than during the nest building, nestling, and fledgling periods. When foraging, males perched higher above ground than females (means = 17.1 and 6.7 m, respectively). Differences between male and female Western Wood‐Pewees in foraging rates and perch heights suggest that males may spend more time on vigilance while females focus on foraging quickly during incubation and when feeding nestlings. Because metrics such as foraging attack rates are sometimes used as indicators of habitat quality and we found that rates can differ between the sexes and among nesting stages, investigators should consider the possibility of such differences when assessing habitat quality, especially for sexually monochromatic species of birds. 相似文献
90.
Relationships between plasma flow and plasma concentrations of prostaglandin F were examined in the utero-ovarian veins of three pregnant goats. Plasma flow, measured by veno-arterial dilution of para-Aminohippurate in two goats, was unchanged or increased slightly when PGF concentrations were elevated by short-term infusions of PGF2α into a uterine vein. Utero-ovarian plasma flow was measured during labor in two goats. Flow doubled during advanced labor and then decreased sharply to very low rates during the terminal expulsive phase of stage II labor.A total of 8.3 and 9.5 mg PGF was released into the utero-ovarian vein of two goats during the last 6 hours before fetal delivery and maximal release rates of approximately 100 ug. min−1 were obtained some 5–10 minutes before delivery was completed. The highest plasma concentrations of PGF were detected immediately after completion of fetal delivery when utero-ovarian plasma flows were lowest. 相似文献