首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
Homozygosity for Waardenburg syndrome.   总被引:3,自引:0,他引:3       下载免费PDF全文
In a large kindred including many individuals affected with Waardenburg (WS) type 1 (WS1) syndrome, a child affected with a very severe form of WS type 3 was born. This child presented with dystopia canthorum, partial albinism, and very severe upper-limb defects. His parents were first cousins, both affected with a mild form of WS1. Molecular analysis of PAX3, the gene that was determined by linkage to cause the disorder in the family, demonstrated a novel missense mutation (S84F) in exon 2 of PAX3 within the paired box. While individuals affected with WS1 were heterozygous for the mutation, the child with WS3 was homozygous for S84F. The observation that the PAX3 homozygote in humans may allow life at least in early infancy and does not cause neural tube defects was unexpected, since, in all the mutations known in mice (splotch), homozygosity has led to severe neural tube defects and intrauterine or neonatal death.  相似文献   

3.
4.
Lifetime reproductive success is difficult to obtain for adequate numbers of wild, long-lived animals because of incomplete knowledge of reproductive life histories and fates of offspring. A procedure is described that provides a standard estimate of lifetime reproductive success from either complete or incomplete reproductive life spans. For this procedure, reproductive success is defined as the following ratio: the number of offspring living to a criterion age in a given time period divided by the number expected for that age and period. The number expected is based upon the mean inter-birth interval of the population, the length of the time period, the age criterion of reproductive success chosen by the researcher (e.g., the average age of menarche), and the probability that an offspring will live to the criterion age. The effect of error upon the estimation of parameters is analyzed using the yellow baboons of Mikumi National Park as an example. The method can be used for both sexes, any litter (clutch) size, any mating system, any mean length of interbirth interval, any age criterion of reproductive success, and any study length that allows a reasonably sized sample of individuals for each of whom a substantial proportion of their reproductive life span is known. © 1992 Wiley-Liss, Inc.  相似文献   

5.
This 2nd part of our studies shows that the papilla foliata is fully developed in Pan, Cebus, and Macaca; in Prosimians the papilla foliata is well developed in Lemur and Chirogaleus. In Galago crassicaudatus, this papilla is missing. Among 3 individuals of Microcebus, the papilla foliata was differently developed: in 2 cases, the tongue exhibited only 2 on both sides and a very low folia. Taste buds were found in the epithelium of only one side of each folium. In the 3rd case, the folia of the papilla were developed only on one side of the tongue, whereas, on the other side, a typical papilla was missing. Instead of the papilla, the tongue of the same animal exhibited a hillock-like structure; it is a gustatory hillock which exhibited many taste buds. There were 3 gustatory hillocks in all of the specimens of Tupaia glis; they are situated on both sides of the tongue.  相似文献   

6.
Eukaryotes are endowed with multiple specialized DNA polymerases, some (if not all) of which are believed to play important roles in the tolerance of base damage during DNA replication. Among these DNA polymerases, Rev1 protein (a deoxycytidyl transferase) from vertebrates interacts with several other specialized polymerases via a highly conserved C-terminal region. The present studies assessed whether these interactions are retained in more experimentally tractable model systems, including yeasts, flies, and the nematode C. elegans. We observed a physical interaction between Rev1 protein and other Y-family polymerases in the fruit fly Drosophila melanogaster. However, despite the fact that the C-terminal region of Drosophila and yeast Rev1 are conserved from vertebrates to a similar extent, such interactions were not observed in Saccharomyces cerevisiae or Schizosaccharomyces pombe. With respect to regions in specialized DNA polymerases that are required for interaction with Rev1, we find predicted disorder to be an underlying structural commonality. The results of this study suggest that special consideration should be exercised when making mechanistic extrapolations regarding translesion DNA synthesis from one eukaryotic system to another.  相似文献   

7.
8.
The study of animal culture is a flourishing field, with culture being recorded in a wide range of taxa, including non-human primates, birds, cetaceans, and rodents. In spite of this research, however, the concept of culture itself remains elusive. There is no universally assented to concept of culture, and there is debate over the connection between culture and related concepts like tradition and social learning. Furthermore, it is not clear whether culture in humans and culture in non-human animals is really the same thing, or merely loose analogues that go by the same name. The purpose of this paper is to explicate core desiderata for a concept of culture and then to construct a concept that meets these desiderata. The paper then applies this concept in both humans and non-human animals.  相似文献   

9.
1. Molar concentrations of amino acids in the content of subsequent parts of alimentary tract of rainbow trout and common carp have been calculated. 2. The ratio of free amino acid concentration in intestinal content to blood of carp most commonly was between 10 and 20 and decreased as digestion proceeded. 3. Free amino acid concentration in gut content of fish appeared several times higher than that in reptiles or mammals. 4. Absorption rate of amino acids in carp was most intense during the first 3 hr after feeding and generally similar to that found in caymans. 5. Release rate of amino acids from dietary protein was most intense in the second segment of carp intestine where most of amino acids were also absorbed. 6. Requirements of essential amino acids based on their absorption rate were determined.  相似文献   

10.
Immunogenetic investigations on two serum beta-lipoprotein allotypes of rhesus monkeys (Macaca mulatta) are reported. The allotypes, designated Lmb1 and Lmb11, are associated with the main lipoprotein family, LP-B or beta-lipoprotein, expressed on independent beta-molecules, and classify rhesus monkeys into three phenotypes: Lmb1, Lmb11, and Lmb1,11. Genetic and molecular studies indicate that the allotypes are encoded by two codominant autosomal allelic genes, Lmb1 and Lmb11. Anti-Lmb1 cross-reacts with the sera of two other macaque species, whereas anti-Lmb11 with sera of all Old World monkeys. Heteroimmune sera, antihuman apo-B and antirhesus LP-B, showed high but diversified degrees of cross reactivity with other primates.  相似文献   

11.
12.
It has been suggested that primates utilize a compliant gait to help reduce peak locomotor stresses on their limbs (Schmitt [1994] J. Hum. Evol. 26:441-458; Schmitt [ 1998] Primate Locomotion, p. 175-200; Schmitt [ 1999] J. Zool. Lond. 248:149-160). However, the components of such a gait, i.e., increased step length, prolonged contact time, and substantial limb yield, have only been documented on a handful of primate species. In order to explore the generality of this claim, elbow and knee angles during walking were documented at touchdown, midstance, and liftoff in a sample of primates, carnivores, marsupials, rodents, and artiodactyls, all under 25 kg. Limb yield was calculated as the change in angle from touchdown to midstance, and re-extension as the change in angle from midstance to liftoff for both forelimbs and hind limbs. Use of a compliant gait (as reflected in significant limb yield) in primates was confirmed for both forelimbs and hind limbs. However, there was variability within primates in the degree of either elbow or knee yield. Surprisingly, marsupials were found to exhibit almost as much elbow yield and even greater knee yield than primates. Carnivores and rodents display a modest amount of limb yield during walking, while artiodactyls appear to display a relatively stiff gait. These data are consistent with the suggestion that the use of a compliant gait to attenuate peak substrate reaction forces may have facilitated the primate invasion of a small-branch niche. However, limb compliance (as reflected by elbow or knee yield) does not appear to be exclusive to the primate order.  相似文献   

13.
14.
In humans, placental corticotropin-releasing hormone (CRH) production has been linked to the determination of gestational length, and a late gestational fall in CRH-binding protein (CRH-BP) has been linked to the onset of parturition. Expression of placental CRH mRNA is limited to primates, and only in man has a circulating CRH-BP been described. As the fall in CRH-BP in late gestation has been associated with parturition in humans, we sought to determine whether a CRH-BP circulated in the plasma of other primates. It is unclear whether maternal plasma CRH concentrations are elevated in New World monkeys and prosimians. We have therefore performed CRH plasma measurements in the blood of pregnant marmosets, in several species of lemur, and in pregnant and fetal rhesus monkeys as a positive control. Using gel chromatography, CRH-BP was detected in the human, gorilla, chimpanzee, orangutan, gibbon, macaque, squirrel monkey, and marmoset, but was absent in the mandrill, spider monkey, and lemur. CRH was detected in the plasma of pregnant marmosets and rhesus monkeys. CRH was also detected in the fetal rhesus monkey, but at lower concentrations than in maternal plasma. CRH immunoreactivity was not detectable in the plasma of pregnant lemurs or in extracts of lemur placenta. In conclusion, a circulating binding protein for CRH exists in all species of apes but occurs variably among New World and Old World monkeys and is absent in lemurs. The variable occurrence of the CRH-BP does not support a role for this protein in the mechanism of parturition in primates. Maternal CRH is elevated in the pregnant marmoset and rhesus, and may play a role in the pregnancy of New and Old World monkeys.  相似文献   

15.
Magnetic alignment (MA) constitutes the simplest directional response to the geomagnetic field. In contrast to magnetic compass orientation, MA is not goal directed and represents a spontaneous, fixed directional response. Because animals tend to align their bodies along or perpendicular to the magnetic field lines, MA typically leads to bimodal or quadrimodal orientation, although there is also growing evidence for a fixed unimodal orientation not necessarily coinciding with the magnetic cardinal directions. MA has been demonstrated in diverse animals including insects, amphibians, fish, and mammals. Alignment can be expressed by animals during resting as well as on the move (e.g. while grazing, hunting, feeding, etc.). Here, we briefly survey characteristic features and classical examples of MA and review the current knowledge about the occurrence of MA in mammals. In addition, we summarize what is known about mechanisms underlying MA and discuss its prospective biological functions. Finally, we highlight some physiological effects of alignment along the magnetic field axes reported in humans. We argue that the phenomenon of MA adds a new paradigm that can be exploited for investigation of magnetoreception in mammals.  相似文献   

16.
We demonstrate the ease and utility of simulating heterogeneous interfacial systems with P2(1) and Pc periodic boundary conditions which allow, for example, lipids in a membrane to switch leaflets. In preliminary tests, P2(1) was shown to yield equivalent results to P1 in simulations of bulk water, a water/vacuum interface, and pure DPPC bilayers with an equal number of lipids per leaflet; equivalence of Pc and P1 was also demonstrated for the former two systems. P2(1) was further tested in simulations involving the spreading of an octane film on water, and equilibration of a DPPC bilayer from an initial condition containing different numbers of lipids in the two leaflets. Lastly, a simulation in P2(1) of a DOPC/melittin membrane showed significant passage of lipids to the melittin-containing leaflet from the initial distribution, and lends insight into the condensation of lipids by melittin.  相似文献   

17.
The products of RNA and synthetic polynucleotides degradation by intracellular RNAses Pc1 and Pc2 of the fungus Penicillium claviforme were studied. It was shown that the enzymes possess the endonuclease activity and are not specific for the bases vicinal to the cleaved PDE bonds (EC 3.1.4.23). The increase of binding of the dinucleoside monophosphates by Pc1 and Pc2 dependent on the nucleoside at the 3'-end of the PDE bond is: A greater than C greater than G greater than U. This order is opposite for the rates of these substrates cleavage by the RNAses. A homologous specificity of the intracellular RNAse Pc1 and the extracellular RNAse II of Pen. claviforme has been revealed.  相似文献   

18.
Photoperiodism in humans and other primates: evidence and implications   总被引:11,自引:0,他引:11  
Most of the anatomical and molecular substrates of the system that encodes changes in photoperiod in the duration of melatonin secretion, and the receptor molecules that read this signal, have been shown to be conserved in monkeys and humans, and the functions of this system appear to be intact from the level of the retina to the level of the melatonin-duration signal of change of season. While photoperiodic seasonal breeding has been shown to occur in monkeys, it remains unclear whether photoperiod and mediation of photoperiod's effects by melatonin influence human reproduction. Epidemiological evidence suggests that inhibition of fertility by heat in men in summer contributes to seasonal variation in human reproduction at lower latitudes and that stimulation of fertility by lengthening of the photoperiod in spring contributes to the variation at higher latitudes. Parallels between the seasonality of human reproduction and seasonal affective disorder suggest that they may be governed by common biological processes. Historical and experimental evidence indicates that human responses to seasonal changes in the natural photoperiod may have been more robust prior to the Industrial Revolution and that subsequently they have been increasingly suppressed by alterations of the physical environment.  相似文献   

19.
20.
The shy-bold continuum is a fundamental axis of behavioral variation in humans and at least some other species, but its taxonomic distribution and evolutionary implications are unknown. Models of optimal risk, density- or frequency-dependent selection, and phenotypic plasticity can provide a theoretical framework for understanding shyness and boldness as a product of natural selection. We sketch this framework and review the few empirical studies of shyness and boldness in natural populations. The study of shyness and boldness adds an interesting new dimension to behavioral ecology by focusing on the nature of continuous behavioral variation that exists within the familiar categories of age, sex and size.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号