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91.
The utility of various techniques for assessing dominance relations within captive primate groups has been repeatedly debated.
The present research compared status rankings derived from observations of spontaneous agonism with rankings based on success
in experimental competitions within two groups of captiveSaimiri. Observation of social agonism revealed stable dyadic dominance relations in both groups. Status rankings derived from the
competitive Water Dominance tests were neither temporally stable nor concordant with observational rankings. Thus the utility
of the Water Dominance test as an index of dominance among captive squirrel monkeys seems questionable. Results are discussed
in terms of ecological factors in group adaptation which lead to species-specific differences in the relationship between
social conflict and competition. 相似文献
92.
David John Harris 《Zoomorphology》1977,88(1):37-63
Summary The mechanoreceptive and chemoreceptive hairs on the legs of the cribellate spiderCiniflo similis were examined during the moulting cycle. In mechanoreceptive hairs the new hair shaft is formed around the extended dentrites, which emerge from near the tip of the newly forming hair and continue to the old sensillum within the extended dendritic sheath. Thus there is no ecdysial canal in the base of the hair shaft as found in insect mechanoreceptive hairs. The dendritic connection with the old hair is maintained until shortly before ecdysis by which time new tubular bodies have developed in the same dendrites at the base of the new hair. In chemoreceptive sensilla the new hair shaft is also formed around the elongated outer segment of the dendrites (19 chemosensitive and 2 mechanosensitive). The two mechanosensitive dendrites develop new tubular bodies at the base of the hair. As ecdysis occurs the old dendritic sheath and dendrites are snapped off at the tip of the new hair but the pore remains open. The ultrastructural evidence indicates that the roles of the three main enveloping cells are as follows: The dendritic sheath cell secretes the dendritic sheath, the middle enveloping cell forms the hair shaft while the outer enveloping cell forms the socket. This pattern corresponds closely to that observed in insecta sensilla. The extreme length of the chemoreceptive dendrites during moulting is mentioned in connection with receptor function. The unique multi-layered nature of the middle enveloping cell is seen as a device for the formation of regularly occurring rows of small spines on the shaft of the hair. 相似文献
93.
In an attempt to study mutagenesis in human diploid fibroblasts, clones derived from mass cultures treated with mutagen have been examined by starch-gel electrophoresis for 43 different enzyme loci. A technique of mutagen treatment was devised which facilitated the cloning and which enabled the cells to be exposed to very high doses of EMS and MNNG. Two alterations in phenotype, presumably the result of mutation, were observed, one involving peptidase D (PEPD) and the other phosphoglucomutase (PGM1). 相似文献
94.
B B Farmer R A Harris W W Jolly D R Hathaway A Katzberg A M Watanabe A L Whitlow H R Besch 《Archives of biochemistry and biophysics》1977,179(2):545-558
Adult rat heart muscle cells were isolated after simultaneous perfusion of multiple (two to eight) hearts with buffered salt solutions containing collagenase and hyaluronidase. Yields (35 to 50% of ventricular weight with approximately 70% viability) are quantitatively suitable for metabolic studies. Viability has been determined by the ability of intact cells to exclude trypan blue and the inability of intact cells to oxidize exogenous succinate. Micrographs show that the fine structure of the isolated cells is well ordered. Cell concentrations of glycogen, glucose 6-phosphate, citrate, and various enzymes were similar to those of intact heart. ATP and creatine phosphate concentrations were lower than in whole hearts. Adenosine 3′,5′-monophosphate concentrations were somewhat elevated. Deoxyribonucleic acid was lower than in whole tissue. The isolated cells retain certain metabolic control mechanisms. The uncoupler of oxidative phosphorylation, 2,4-dinitrophenol, increased oxygen consumption severalfold, whereas exogenous ADP had no effect on respiration. Under anaerobic conditions the rates of glucose utilization and lactate production were faster than in the presence of oxygen, indicating retention of the Pasteur effect. The addition of glucose and insulin caused a decrease in oxygen uptake or the Crabtree effect. Exogenously added pyruvate decreased glycolytic flux and produced a pronounced increase in intracellular citrate and glucose 6-phosphate. Isoproterenol stimulated adenylate cyclase activity of the isolated cells at the same concentrations effective with intact heart preparations. Isoproterenol and glucagon caused the activation of phosphorylase. The cells deteriorated as a function of incubation time, as indicated by a decrease in ATP content and a loss of lactate dehydrogenase into the medium. Cell deterioration was greatly accelerated by Ca2+ at concentrations greater than 10?5m. 相似文献
95.
96.
Results of activity and spectral studies using fluorescence and circular dichroism show that AMP and fructose 2,6-bisphosphate (F-2,6-P2) activate Ascaris suum phosphofructokinase through specific and similar conformational changes. Inorganic compounds like (NH4)2SO4 and KH2PO4 also induce structural alterations in the enzyme in a manner different from those caused by AMP and F-2,6-P2. The enzyme is activated by both AMP and F-2,6-P2, in 20 mM phosphate buffer, pH 6.6, with 0.2 mM ATP and 1 mM F-6-P. The Kact values for AMP and F-2,6-P2 are 25 +/- 3 microM and 1.5 +/- 0.2 microM, respectively. Both effectors quench enzyme tryptophan fluorescence in phosphate, pH 6.6, in a concentration-dependent manner. The Kd values determined from the decrease in emission intensity at 342 nm as a function of effector concentration are 24 +/- 3 microM for AMP and 1.00 +/- 0.15 microM for F-2,6-P2, in excellent agreement with the values of Kact. Both effectors also produce dramatic changes in the CD spectrum of the enzyme, in the region from 240 to 190 nm representing the peptide backbone. Secondary structure calculations suggest an increase in the alpha-helical content of the enzyme in the presence of either effector. The Kd values obtained from the concentration dependence of the decrease in ellipticity at 210 nm are 22.8 +/- 5.3 microM and 1.3 +/- 0.2 microM, respectively, for AMP and F-2,6-P2, once again in close agreement with the Kact values for these effectors. The data imply that activation of phosphofructokinase by these effectors is concomitant with structural changes in the enzyme. Further, comparison of the difference CD spectra for the effects of AMP and F-2,6-P2 show that both of them produce similar conformational changes and probably stabilize a similar final activated state of the enzyme. Other hexose phosphate analogues such as fructose 6-phosphate, glucose 1,6-bisphosphate, and fructose 1,6-bisphosphate do not affect the CD spectrum of the enzyme. Ammonium sulfate has no effect on the CD spectrum of the enzyme in phosphate buffer but does cause a significant alteration in the spectrum obtained in Mes. Gel filtration high performance liquid chromatography using a Borosil TSK 400 column shows that the tetrameric state of the native enzyme is not affected by the presence of the effectors. 相似文献
97.
Uncemented femoral total hip components rely entirely on contact with the prepared femur for their initial fixation. The contact areas and stresses between a straight tubular bone and a metal cylindrical prosthesis 12.5 cm long and 13 mm in diameter were calculated in a finite element model which includes uniform diametral gaps varying from 20 to 500 microns, using transverse loads from 100 to 2000 N. Frictionless three-dimensional contact elements were used between the bone and the prosthesis. Contact stresses were high and irregular in all cases, and the contact areas were small. Two regions of contact were apparent for lower loads and larger gaps. A third region of contact occurred near the distal tip of the implant at higher loads. This region of contact markedly increased the contact stresses at the distal tip of the prosthesis. A 20 microns overlap between bone and implant was modelled to assess a slight interference fit. The contact stress distribution in this case was markedly different from the stress distribution with a 20 microns diametral gap. The data collectively indicates that gaps of less than 20 microns between bone and implant can substantially change contact stress distributions. 相似文献
98.
The evolution of placental mammals. 总被引:2,自引:0,他引:2
J R Harris 《FEBS letters》1991,295(1-3):3-4
Based on morphological, virological, biochemical and molecular biological data, it is proposed that the presence of endogenous retrovirus particles in the placental cytotrophoblasts of many mammals is indicative of some beneficial action provided by the virus in relation to cell fusion, syncytiotrophoblast formation and the creation of the placenta. Further, it is hypothesised that the germ line retroviral infection of some primitive mammal-like species resulted in the evolution of the placental mammals. 相似文献
99.
100.