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991.
The allometric relationships between canine base area, first molar and summed molar crown area, and the glabella–opisthocranion distance, and the direct allometric relationships between canine and molar size have been established in five primate taxa. Separate sex and combined sex ‘intraspecific’, and ‘interspecific’ regression and ‘best fit’ allometry coefficients were computed. This analysis showed that for any increase in glabella–opisthocranion length, the rate of increase in canine size exceeds the rate of increase in molar area, and ‘best fit’ solutions indicate that canine base area is positively allometric when related directly to molar crown area. These results were compared with data available for the ‘gracile’ australopithecine, A. africanus, and two ‘robust’ australopithecine taxa, A. boisei and A. robustus. The differences in canine and molar size which occur between the ‘gracile’ taxon and the two ‘robust’ taxa do not correspond to any of the trends in the comparative allometric models. Data on glabella–opisthocranion length for the fossils, meagre though they are, show that while the proportional increase in molar crown area between the taxa corresponds to comparative allometry models, the reduced canine size in the ‘robust’ taxa is against comparative allometric trends. These results indicate that, at least in terms of canine/molar proportions, the differences between the ‘gracile’ and ‘robust’ australopithecines are not merely allometric and may indicate significant dietary or behavioural differences. 相似文献
992.
A new class of Phycomyces behavioral mutants with enhanced tropic responses has been analyzed genetically to determine the number of genes involved and the nature of their expression. These hypertropic mutants carry pleiotropic nuclear mutations. Besides their effects on sensory behavior, they also affect morphology and meiotic processes. Behavioral analyses of heterokaryons containing hypertropic and wild-type nuclei in varying proportions show that the hypertropic mutations in strains L82, L84, L86, and L88 are strongly dominant. Conversely, the hypertropic mutations carried by the strains L83, L85, and L87 are strongly recessive. We performed recombination analyses between hypertropic mutants and mutants with diminished phototropism, affected in the seven genes madA to madG. We found no evidence of linkage between the hypertropic mutations and any of these mad mutations. From crosses, we isolated double mutants carrying hypertropic mutations together with madC (night blind) and madG (stiff) mutations. The behavioral phenotypes of the double mutants are intermediate between those of the parentals. Complementation analyses show that the three recessive hypertropic mutations affect the same gene, which we call madH. The expression of the recessive hypertropic allele becomes dominant in heterokaryons carrying madC and madH nuclei; the madC gene has been implicated separately with the photoreceptor at the input to the sensory pathway, while the madH gene is associated with the growth control output. This result suggests the physical interaction of both gene products, madH and madC, in a molecular complex for the photosensory transduction chain. 相似文献
993.
994.
995.
The effects of mechanical injury on the skin, connective tissue, muscle and bone of the goldfish is described 28 days following the injury. There is evidence of a dynamic response but the apparent inability of muscle regeneration to any degree is noted. 相似文献
996.
Pressure-flow relationships in the isolated canine trachea 总被引:1,自引:0,他引:1
997.
Phenylacetic, 3-phenylpropionic, -hydroxyphenylacetic and 3 (-hydroxyphenyl) propionic acids together with the series of C2 to C6 saturated fatty acids previously reported in the anal sac secretion of the red fox () are identified as constituents of the anal sac secretion of the lion (Panthera leo). All these compounds are also observed in the anal sac secretion of the red fox using gas chromatography. The aerobic microflora of red fox and domestic dog () anal sac secretion samples invariably consisted predominantly of and . The hypothesis that the secretion volatiles so far identified may be microbiologically produced is examined. 相似文献
998.
999.
F. Fontaine E. Kiefer C. Clément M. Burrus J. L. Druelle 《Trees - Structure and Function》1999,14(2):83-90
In the present work, we described the fate of proventitious epicormic buds on the trunks of 40-year-old Quercus petraea trees and in parallel the vascular trace they produced in the wood. Our results show that small and large individual epicormic
buds can survive as buds for 40 years and that both are composed of a terminal meristem and scales. Meristematic areas are
detected in the scale axils of small buds; in addition to these meristems the large buds also have secondary bud primordia.
The small buds are connected to the pith of the main stem by a unique trace, whereas the large buds are connected by one or
multiple traces. A single trace might imply that the whole bud is still alive and multiple traces might indicate that the
terminal meristem has died. In the latter case, each trace is connected to a secondary bud of the large bud. The buds found
in a cluster are composed of a terminal meristem and scales with axillary meristems in the scale axils. A cluster is connected
to the pith of a stem either by a unique trace when it seems to be the result of partial abscission of an epicormic shoot
or multiple traces when it might have originated from an epicormic bud in which the terminal meristem has died. Whatever the
type of the bud, the vascular trace in the bark is composed of a cambium, secondary xylem and parenchyma cells and the trace
present in the wood had parenchyma cells with vestiges of secondary xylem. Each year, the vascular trace should be produced
in the bark by the cambium of the tree but not by the bud itself. On 40-year-old Q. petraea, we observed a proliferation of epicormic buds and in parallel a multiplication of the number of vascular traces in the trunk,
but the knots caused by the traces of epicormic buds in the wood, either as individuals or in clusters, are minor since their
colours are only slightly darker than those of woody rays and they are less than 2 mm in diameter. The knots will appear when
epicormic buds develop into shoots.
Received: 30 March 1999 / Accepted: 09 June 1999 相似文献
1000.
A. V. Timofeev 《Plasma Physics Reports》2003,29(8):683-687
The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field. 相似文献