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A review of the literature reveals a long history of disagreement on the interpretation of the lower deciduous and permanent dentition of the Indriidae. This disagreement has centered on the existence and/or replacement of a canine as a member of the indriid toothcomb. The presence of a pair of canines in the toothcomb of lemurids and lorisids has rarely been questioned, and there is no evidence to indicate that this interpretation is incorrect. There has, however, been no consistency nor substantiating evidence presented for any interpretation of the indriid toothcomb. By comparing the morphology of the teeth of the lemurid, lorisid, and indriid toothcomb, both deciduous and permanent, comparing the mode of dental development in these three families, identifying the indriid lower deciduous dentition, and by relating the data to an ontogenetic and phylogenetic framework, this study proposes: (1) in all three families, the lateral teeth of the toothcomb are canines, (2) the dental formula for the lower deciduous teeth of indriids is 1.1.4, (3) the dental formula for the lower permanent teeth of indriids is 1.1.2.3, and (4) that decrease in number of incisors during primate evolution was most likely I1 to I2 to I3.  相似文献   

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The possible role of various potential chemical mediators in the production of fever is reviewed. A major problem in this field is the very considerable conflict of evidence, let alone interpretation. On the existing evidence, it appears unlikely that monoamines, acetyl choline, or alterations in relative concentrations of sodium and calcium play any major role in the production of fever. Recent evidence makes it unlikely that prostaglandins have a direct role in this mechanism, though the involvement of other metabolites of arachidonic acid has not been excluded. It is possible that protein synthesis may play a part in the central action of leukocyte pyrogen.  相似文献   

5.
The development of resistance in response to interferon depends on cellular RNA synthesis and probably also on cellular protein synthesis. The evidence for these requirements is reviewed, as well as the proposal that this evidence indicates the existence of a specific response of the cell to interferon, involving the induced synthesis of an antiviral protein. Direct evidence for such an interpretation has not been obtained, and alternative explanations are discussed which do not require quantitative or qualitative differences in the RNA and protein made in cells exposed to interferon. The possible role of the ribosome in the antiviral action of interferon is also discussed.  相似文献   

6.
A. G. Morris 《Human Evolution》2002,17(3-4):231-240
The debate between the proponents of the Recent African Origin and the Multiregional Evolution models for the origin of anatomically modern humans has not been of great importance to the interpretation of late Pleistocene human fossils in South Africa. The main reason is that both models propose that evidence of anatomically moderns should happen in South Africa at an early date. A more important issue to the African context is whether or not those early transitions to modernity were accompanied by the development of the distinctive local populations known today as the Khoisan. Serogenetic evidence suggests a relative antiquity for the origins of living Khoisan peoples, but this may simply reflect the longer time that anatomically modern peoples have lived in the sub-continent. A search for features of distinctive Khoisan morphology in the early remains may be of more value as it might indicate the presence of a local adaptive pattern to the special environment conditions of the region.  相似文献   

7.
Tony Thulborn 《Ichnos》2017,24(1):1-18
A remarkable assemblage of dinosaur trackways in the Winton Formation (Albian–Cenomanian) at Lark Quarry, in western Queensland, Australia, has long been regarded as evidence of a stampede involving small theropods, whose tracks were classified in the ichnogenus Skartopus, and small ornithopods, whose tracks represented a second ichnogenus, Wintonopus. However, one recently-published study has claimed that existing interpretation of Lark Quarry is incorrect: it maintains that all the track-makers were ornithopods, that the ichnogenus Skartopus is a variant form of Wintonopus, and that most of the Lark Quarry track-makers were not running but more probably swimming downstream in a current of water. Those iconoclastic claims are investigated here and shown to be untenable. They derive from overgeneralized interpretation of the Lark Quarry track assemblage and invoke ad hoc auxiliary hypotheses which are either untestable or demonstrably incorrect. Closer inspection of the evidence underpinning those claims corroborates the existing interpretation of Lark Quarry as the site of a dinosaurian stampede and confirms the validity of the original distinction between theropod tracks (Skartopus) and ornithopod tracks (Wintonopus).  相似文献   

8.
Cortical neurons show irregular but structured spike trains. This has been interpreted as evidence for 'temporal coding', whereby stimuli are represented by precise spike-timing patterns. Here, we suggest an alternative interpretation based on the older concept of the cell assembly. The dynamic evolution of assembly sequences, which are steered but not deterministically controlled by sensory input, is the proposed substrate of psychological processes beyond simple stimulus-response associations. Accordingly, spike trains show a temporal structure that is stimulus-dependent and more variable than would be predicted by strict sensory control. We propose four signatures of assembly organization that can be experimentally tested. We argue that many observations that have been interpreted as evidence for temporal coding might instead reflect an underlying assembly structure.  相似文献   

9.
The genetic load disclosed by inbreeding has been analyzed in a multiple regression model for a population involving several localities in the state of Espírito Santo, Brazil. The inbreeding load has been estimated for number of pregnancies, abortions, stillbirths, children born alive, anomalies in general, sex ratio, infant mortality, post-infant mortality, and sterility and infertility of the couple. There was no evidence of either maternal or paternal inbreeding effects on the variables analyzed. The effect of inbreeding of the zygote was significant only for anomalies in general (B = 2.29 +/- 0.45) and infant mortality (B = 3.19 +/- 1.39). The latter result must be accepted with caution because of the many environmental causes affecting infant mortality. The B/A ratio suggested a predominantly mutational load for anomalies in general (B/A = 25), but with respect to infant mortality (B/A = 6), the ratio is regarded as an underestimate because of the environmental contribution to A and therefore not supportive of the segregational interpretation.  相似文献   

10.
Mites and ticks (Acari) have been found in a variety of archaeological situations. Their identification has enabled data on habitat and dietary preferences to be obtained, and these have been used to interpret study sites. Despite this, Acari are not routinely considered in analyses in the way that other environmental components are. Like forensic science, archaeology draws on biological material to rebuild past human activity, and acarology has the potential to provide a much greater amount of evidence to both than is currently the case. As an aid to workers in these fields, an overview is presented of the Acari that have been extracted from archaeological samples, the situations in which they were found and the contribution their presence can make to the interpretation of sites.  相似文献   

11.
A characteristic relationship between infection and host age, with levels of infection reaching a peak in particular age classes, has been reported for many parasites. However, several field studies have shown that this relationship is not invariant: if age-infection data are compared across host populations, the peak level of infection is higher and occurs at a younger age when the transmission rate is high, and is lower and occurs at an older age when it is low. This pattern is called the ;peak shift'. Here, Mark Woolhouse reviews the evidence for and the implications of the peak shift. The peak shift is consistent with the predictions of mathematical models that assume gradually acquired protective immunity, and this interpretation is supported by experimental studies using animals. This agreement between theory, experimental evidence and field studies strongly suggests that acquired immunity has a major impact on epidemiological patterns not only for parasites such as malaria, where the importance of acquired immunity is not in doubt, but also for many parasitic helminths, where the role of acquired immunity is less widely accepted.  相似文献   

12.
Both woody and herbaceous plant species are known to respond to wind loading, with consequences for growth and morphology. Wind has usually been classified as a mechanical stress which is detrimental to plant growth. Few experiments exist whereby plants and, in particular, woody species are exposed to wind, as opposed to mechanical perturbation by touching, flexing or shaking. Such experiments have always been short term and often carried out in wind tunnels in a controlled greenhouse environment. This study introduces an experiment to test the responses of Maritime pine (Pinus pinaster A?t.) seedlings to recurrent and short wind loading in the field, over two growing seasons. These experiments provide evidence that periodic short-term exposure to wind can induce phototropic responses in the early stage of pine seedlings' development. An interpretation is proposed in terms of efficiency to light tracking and hypotheses are discussed concerning the underlying physiological process.  相似文献   

13.
Cytoplasmic and nuclear incorporation of 125I triiodothyronine by thymic lymphocytes has been demonstrated by electron microscopic autoradiography. Incorporation was significantly more pronounced in the newborn than in the adult age. The information emerging from the experime,tal observations contributes further evidence to the more precise interpretation of receptor maturation.  相似文献   

14.
Due to its apparent absence in archaeologically derived skeletons, rheumatoid arthritis (RA) has generally been believed to be of fairly recent origin. A growing body of evidence now demonstrates that erosive lesions typical of RA are present in archaeological populations and that the antiquity of RA may be greater than previously expected. In support of this argument, a case of erosive arthritis is reported in a skeleton from Kulubnarti, Republic of the Sudan (c. 700-1450 A.D.). Lytic, erosive lesions and subchondral cysts are present bilaterally in the carpal and metacarpal joints of a female skeleton with an estimated age at death of 50+ years. These lesions are typical of those seen in clinically diagnosed rheumatoid patients. While their expression and distribution are highly suggestive of RA, interpretation must be made with due consideration for problems of differential diagnosis of this disease in archaeological material.  相似文献   

15.
Pie MR 《Genetika》2007,43(3):427-429
It has been recently suggested that the C-value paradox, the lack of an obvious association between organismal complexity and genome size, can result simply from biases in insertion and deletion rates--the DNA loss hypothesis. This hypothesis has been heavily criticized, particularly because its evidence, a negative relationship between genome size and DNA loss rate, is based on a highly selective use of the available data. In this study it is show that even the even the most favorable interpretation of the data favoring the DNA loss hypothesis is largely an artifact of phylogenetic nonindependence, supporting the assertion made by other authors that the mechanisms underlying genome size evolution might be more complex than envisioned by the DNA loss hypothesis.  相似文献   

16.
Daff S 《Biochemistry》2004,43(13):3929-3932
The diflavin reductases exemplified by mammalian cytochrome P450 reductase catalyze NADPH dehydrogenation and electron transfer to an associated monooxygenase. It has recently been proposed that double occupancy of the NADPH dehydrogenation site inhibits the NADPH to FAD hydride transfer step in this series of enzymes. This has important implications for the mechanism of enzyme turnover. However, the conclusions are drawn from a series of pre-steady-state stopped-flow experiments in which the data analysis and interpretation are flawed. Recent data published for P450-BM3 reductase show a decrease in the rate constant for pre-steady-state flavin oxidation with increasing NADP(+) concentration. This is interpreted as evidence of inhibition by multiple substrate binding. A detailed reanalysis shows that the data are in fact consistent with a simple single-binding-site model in which reversible hydride transfer causes the observed effect. Data for the related systems are also discussed.  相似文献   

17.
Mary Jane West-Eberhard has suggested that plasticity may be of primary importance in promoting evolutionary innovation and diversification. Here, we explore the possibility that the diversification of phytophagous insects may have occurred through such a process, using examples from nymphalid butterflies. We discuss the ways in which host plant range is connected to plasticity and present our interpretation of how West-Eberhard’s scenario may result in speciation driven by plasticity in host utilization. We then review some of the evidence that diversity of plant utilization has driven the diversification of phytophagous insects and finally discuss whether this suggests a role for plasticity-driven speciation. We find a close conceptual connection between our theory that the diversification of phytophagous insects has been driven by oscillations in host range, and our personal interpretation of the most efficient way in which West-Eberhard’s theory could account for plasticity-driven speciation. A major unresolved issue is the extent to which a wide host plant range is due to adaptive plasticity with dedicated modules of genetic machinery for utilizing different plants.  相似文献   

18.
《Plains anthropologist》2013,58(79):69-74
Abstract

Traditionally, Arikara mortuary practice has been described as direct interment soon after death in wood-covered pits. This interpretation explains most of the ethnohistorical and archeological data, but not all. Some ethnohistorical, archeological, and entomological evidence suggests scaffolding prior to burial.  相似文献   

19.
There is convincing evidence that the patterns formed by microtubules and by other fibres and organelles in ciliates are partly determined by non-genic inherited information, the so-called cytotactic information. There is also some evidence that this exists in metazoan cells and is perhaps involved in neoplastic transformation. On this background a cytotactic model of transformation which allows new interpretation of several characteristics of cancer cells has been developed. It proposes (a) that most cells contain cytotactic information, (b) that mechanisms to repair modifications of this information exist, and (c) that transformation may result when the cytotactic information is modified beyond repair. The model further proposes that (d) the modified cytotactic information is unevenly distributed between daughter cells at the following divisions so that cells with abnormal patterns, increasing pleomorphy and malignancy, and possibly altered gene functions are formed. The cytotactic transformation is proposed to take place in one or in two steps and to be inducible not only by many usual carcinogens but also by for example aborted cell divisions. A cytotactic interpretation of cancers induced by asbestos and of certain other observations is attempted.  相似文献   

20.
An nmr spectral comparison of a model cyclic pentapeptide cyclo(Gly-Pro-Gly-D-Phe-Pro) with an analogous pseudopeptide has been made. The pseudopeptide contains a ψ[CH2S] amide bond replacement at the only amide linkage that, in the model, is not involved in an intramolecular hydrogen bond. Both proton and carbon-13 nmr spectral evidence confirms the retention of β- and γ-turns in the pseudopeptide in chloroform. Characteristic chemical shifts, temperature dependence, and glycine α-resonances support this interpretation. However, evidence of a more flexible conformation involving cistrans proline isomerism is seen on addition of dimethylsulfoxide.  相似文献   

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