The protoconid: a key cusp in lower molars. Evidence from a recent modern human population.

BACKGROUND: The molar (M) size sequence in the genus Homo is decreasing and the general pattern in Homo sapiens is M1> M2 > M3. AIM: To gain a better understanding of the reduction patterns of M components (cusps), we aim to assess the area of the protoconid (Prd), the phylogenetically oldest cusp of the lower Ms. SUBJECT AND METHODS: We measured the Prd and the total crown area in the scaled photographs of a recent modern human sample of lower Ms (76 males and 39 females). The values were statistically analysed. RESULTS: The absolute size of the Prd increases significantly between M1 and M2/M3, whereas the relative size of this cusp increases significantly from M1 to M3. In the latter, reduction or disappearance of the cusps of the talonid is common. CONCLUSIONS: The results can be explained in the framework of the patterning cascade model. As the first cusp to appear developmentally, the Prd forms in response to signals from the primary enamel knot, likely contributing to its stability. Inhibitory signals emitted during the Prd formation may lead to the reduction or disappearance of the talonid cusps, if these do not have enough time to form before the end of the M morphogenetic process.

Testing the inhibitory cascade model in a recent human sample.

The Inhibitory Cascade Model was proposed by Kavanagh and colleagues (Nature, 449, 427-433 [2007]) after their experimental studies on the dental development of murine rodent species. These authors described an activator-inhibitor mechanism that has been employed to predict evolutionary size patterns of mammalian teeth, including hominins. In the present study, we measured the crown area of the three lower permanent molars (M1, M2, and M3) of a large recent modern human sample of male and female individuals from a collection preserved at the Institute of Anthropology of the University of Coimbra (Portugal). The main aim of the present study is to test if the size molar patterns observed in this human sample fits the Inhibitory Cascade Model. For this purpose, we first measured the crown area in those individuals preserving the complete molar series. Measurements were taken in photographs, using a planimeter and following well-tested techniques used in previous works. We then plot the M3 /M1 and M2 /M1  size ratios. Our results show that the premise of the Inhibitory Cascade Model, according to which the average of the crown area of M2 is approximately one-third of the sum of the crown area of the three molars, is fulfilled. However, our results also show that the individual values of a significant number of males and females are out of the 95% confidence interval predicted by the Inhibitory Cascade Model in rodents. As a result, the present analyses suggest that neither the sample of males, nor that of females, nor the pooled sample fits the Inhibitory Cascade Model. It is important to notice that, although this model has been successfully tested in a large number of current human populations, to the best of our knowledge this is the first study in which individual data have been obtained in a recent human population rather than using the average of the sample. Our results evince that, at the individual level, some factors not yet known could interfere with this model masking the modulation of the size on the molar series in modern humans. We suggest that the considerable delay in the onset of M3 formation in modern humans could be related to a weakening of the possible activation/inhibition process for this tooth. Finally, and in support of our conclusions, we have checked that the absolute and relative size of M1 and M2 is not related to the M3 agenesis in our sample. In line with other studies in primates, our results do not support the Inhibitory Cascade Model in a recent human sample. Further research is needed to better understand the genetic basis of this mechanism and its relationship to the phenotype. In this way, we may be able to find out which evolutionary changes may be responsible for the deviations observed in many species, including Homo sapiens.

Palliative Care and Oncology in Colombia: The Potential of Integrated Care Delivery.

Palliative care is on the global health agenda, as only approximately 14% of people who require palliative care receive it [...].

Infección grave por el virus del Chikungunya / Severe Chikungunya virus infection

Publicaciones recientes han desafiado la visión convencional sobre la naturaleza benigna de la infección por el virus de Chikungunya (VCHIK). Las manifestaciones clínicas son muy variables y pueden ser graves en algunos casos. Los estudios sugieren que la forma grave de la infección por el VCHIK puede ser asociada con disfunción orgánica múltiple, hepatitis, meningitis, nefritis, encefalitis, dermatitis ampollosa, miocarditis, arritmias cardiacas, entre otras. La fisiopatología subyacente para algunas de las complicaciones de la enfermedad por el VCHIK sigue siendo poco clara. Sin embargo, de acuerdo con las características clínicas de los casos graves o atípicos descritos a la fecha, el desarrollo de complicaciones podría agruparse principalmente en tres categorías: la exacerbación de condiciones médicas subyacentes, el deterioro de un trastorno no reconocido previamente y la respuesta inmunológica inadecuada a la infección. Se ha encontrado asociación entre las manifestaciones graves de la infección, niveles elevados de citoquinas y algunas secuencias genómicas específicas del VCHIK. La inmunoterapia pasiva puede constituir una estrategia eficaz en el tratamiento de individuos expuestos al VCHIK con riesgo de infección grave. Actualmente no existe evidencia clínica que soporte el uso de antivirales en la prevención o tratamiento de la infección por el VCHIK.

Recent publications have challenged the conventional view of the benign nature of the Chikungunya virus (CHIKV) infection. The clinical manifestations are highly variable and can be severe in some cases. Studies suggest that the severe form of CHIKV infection may be associated with multiple organ failure, hepatitis, meningitis, nephritis, encephalitis, bullous dermatitis, myocarditis, cardiac arrhythmias, among others. The underlying pathophysiology for some of these complications remains unclear. However, according to the clinical characteristics of severe or atypical cases reported to date, the development of complications could be grouped into three main categories, such as exacerbation of underlying medical conditions, deterioration of a previously unrecognized condition and inadequate immune response to infection. Some studies have found association between severe manifestations of infection and high levels of cytokines or some specific genomic sequences CHIKV. Experimental studies suggest that passive immunotherapy can be an effective strategy for the management of individuals at risk of severe CHIKV infection. Currently there is no clinical evidence to support antiviral drug use in the prevention or treatment of the disease.

Geometric morphometric analysis of the crown morphology of the lower first premolar of hominins, with special attention to Pleistocene Homo.

This article is the third of a series that explores hominin dental crown morphology by means of geometric morphometrics. After the analysis of the lower second premolar and the upper first molar crown shapes, we apply the same technique to lower first premolar morphology. Our results show a clear distinction between the morphology seen in earlier hominin taxa such as Australopithecus and African early Homo, as well as Asian H. erectus, and more recent groups such as European H. heidelbergensis, H. neanderthalensis, and H. sapiens. The morphology of the earlier hominins includes an asymmetrical outline, a conspicuous talonid, and an occlusal polygon that tends to be large. The morphology of the recent hominins includes a symmetrical outline and a reduced or absent talonid. Within this later group, premolars belonging to H. heidelbergensis and H. neanderthalensis tend to possess a small and mesiolingually-displaced occlusal polygon, whereas H. sapiens specimens usually present expanded and centered occlusal polygons in an almost circular outline. The morphological differences among Paranthropus, Australopithecus, and African early Homo as studied here are small and evolutionarily less significant compared to the differences between the earlier and later homin taxa. In contrast to the lower second premolar and the upper first molar crown, the inclusion of a larger hominin sample of lower first premolars reveals a large allometric component.

A new early Pleistocene hominin mandible from Atapuerca-TD6, Spain.

We present the description of a new mandibular specimen, ATD6-113, recovered in 2006 from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. A detailed study of the lithostratigraphy of the top sequence of this level, the section from where all human remains have been recovered so far, is also presented. We have observed that the hominin stratum, previously defined as Aurora Stratum, represents a condensed deposit of at least six layers, which could not be distinguished in the test pit made in 1994-95. Therefore, the human fossil remains were probably deposited during a discrete and undetermined time period. The new mandibular fragment exhibits a very similar morphology to that of the most complete specimen, ATD6-96, which was recovered in 2003 from a different layer. This suggests that both specimens represent the same biological population. The two mandibles, as well as the small mandibular fragment ATD6-5 (which constitutes part of the holotype of Homo antecessor), present a morphological pattern clearly derived with regard to that of the African early Homo specimens usually included in H. habilis and H. rudolfensis, the mandibles D211 and D2735 from Dmanisi, and most of the early Pleistocene mandibles from Sangiran. The TD6 mandibles also exhibit some derived features with regard to the African early Pleistocene specimens included in H. ergaster (or African H. erectus). Thus, the TD6 hominins seem to represent a lineage different from other African and Asian lineages, although some (metric in particular) similarities with Chinese middle Pleistocene mandibles are noted. Interestingly, none of the apomorphic mandibular features of the European middle and early late Pleistocene hominins are present in the TD6 mandibles.