The role of nutrition on epigenetic modifications and their implications on health

Nutrition plays a key role in many aspects of health and dietary imbalances are major determinants of chronic diseases including cardiovascular disease, obesity, diabetes and cancer. Adequate nutrition is particularly essential during critical periods in early life (both pre- and postnatal). In this regard, there is extensive epidemiologic and experimental data showing that early sub-optimal nutrition can have health consequences several decades later.     

Evolutionary pathways to self-fertilization in a tristylous plant species

Evolutionary transitions from outcrossing to selfing occur commonly in heterostylous genera. The morphological polymorphisms that characterize heterostyly provide opportunities for different pathways for selfing to evolve. Here, we investigate the origins and pathways by which selfing has evolved in tristylous Eichhornia paniculata by providing new evidence based on morphology, DNA sequences and genetic analysis. The primary pathway from outcrossing to selfing involves the stochastic loss of the short-styled morph (S-morph) from trimorphic populations, followed by the spread of selfing variants of the mid-styled morph (M-morph). However, the discovery of selfing variants of the long-styled morph (L-morph) in Central America indicates a secondary pathway and distinct origin for selfing. Comparisons of multi-locus nucleotide sequences from 27 populations sampled from throughout the geographical range suggest multiple transitions to selfing. Genetic analysis of selfing variants of the L- and M-morphs demonstrates recessive control of the loss of herkogamy, although the number of factors appears to differ between the forms. Early stages in the establishment of selfing involve developmental instability in the formation of flowers capable of autonomous self-pollination. The relatively simple genetic control of herkogamy reduction and frequent colonizing episodes may often create demographic conditions favouring transitions to selfing in E. paniculata .     

Reexamination of the immature hominid maxilla from Tangier,Morocco

Reexamination of the immature Upper Pleistocene hominid maxilla from Mugharet el-'Aliya (Tangier), Morocco is undertaken in light of new evidence on the growth and development of Upper Pleistocene hominids. Metric and qualitative comparisons were made with 17 immature Upper Pleistocene maxillae, and with a recent Homo sapiens sapiens sample. No unambiguous criteria for aligning the maxilla with Neandertals were found, although one character, the degree of maxillary flexion on the zygoma, strongly suggests that this child could be a representative of H. s. sapiens. The probable lack of a canine fossa in Mugharet el-'Aliya 1, the primary criterion used previously to align it with Neandertals, cannot be accurately extrapolated to its adult form from this juvenile. The present evidence suggests that it is inappropriate to refer to this fossil as “Neandertal-like” or as a North African “neandertaloid.” Thus, the Tangier maxilla should not be cited as evidence for the presence of Neandertal facial features in North Africa during the Upper Pleistocene. © 1993 Wiley-Liss, Inc.     

Mapping autonomously replicating sequence elements in a 73-kb region of chromosome II of the fission yeast, Schizosaccharomyces pombe

Autonomously replicating sequence (ARS) elements are the genetic determinants of replication origin function in yeasts. They can be easily identified as the plasmids containing them transform yeast cells at a high frequency. As the first step towards identifying all potential replication origins in a 73-kb region of the long arm of fission yeast chromosome II, we have mapped five new ARS elements using systematic subcloning and transformation assay. 2D analysis of one of the ARS plasmids that showed highest transformation frequency localized the replication origin activity within the cloned genomic DNA. All the new ARS elements are localized in two clusters in centromere proximal 40 kb of the region. The presence of at least six ARS elements, including the previously reported ars727, is suggestive of a higher origin density in this region than that predicted earlier using a computer based search.     

亚油酸异构酶及其性质

共轭亚油酸（conjugated linoleic acids简称CLA）是一种具有多种生理活性的天然脂肪酸。亚油酸异构酶可将亚油酸转化成CLA,亚油酸异构酶可以特异性地转化合成CLA,克服了化学法催化合成CLA的缺点。本文介绍了亚油酸异构酶的来源、分离纯化;比较了Butyrivibrio fibrisolvens、Lactobacillus reuteri、Propionibacterium acnes、Clostridium sporogenes等来源的亚油酸异构酶的性质。     

Origin of bipedalism

Human and chimpanzee locomotor behaviors are described and compared using field patterns derived from measurements of the motions at the joints. Field patterns of human and ape bipedalism are so different that it is doubted whether the nonhuman type could ever have been a precursor of the human type. Chimpanzee quadrupedal vertical climbing and human bipedalism are, on the other hand, similar and a particular variety of this kind of climbing probably was the precursor of human bipedalism. Animals adapted to this variation would have had some brachiation-like morphological traits in their pectoral limbs and some hominid-like morphological traits in their pelvic limbs, traits anticipating the human condition. The australopithecines possessed these traits and must have been adapted to arboreal quadrupedal vertical climbing, having the capacity, at the same time, to perform facultative terrestrial bipedalism, moving on the ground in a manner visually identical to that of humans.     

Evolution of eye size and shape in primates

Strepsirrhine and haplorhine primates exhibit highly derived features of the visual system that distinguish them from most other mammals. Comparative data link the evolution of these visual specializations to the sequential acquisition of nocturnal visual predation in the primate stem lineage and diurnal visual predation in the anthropoid stem lineage. However, it is unclear to what extent these shifts in primate visual ecology were accompanied by changes in eye size and shape. Here we investigate the evolution of primate eye morphology using a comparative study of a large sample of mammalian eyes. Our analysis shows that primates differ from other mammals in having large eyes relative to body size and that anthropoids exhibit unusually small corneas relative to eye size and body size. The large eyes of basal primates probably evolved to improve visual acuity while maintaining high sensitivity in a nocturnal context. The reduced corneal sizes of anthropoids reflect reductions in the size of the dioptric apparatus as a means of increasing posterior nodal distance to improve visual acuity. These data support the conclusion that the origin of anthropoids was associated with a change in eye shape to improve visual acuity in the context of a diurnal predatory habitus.     

New primate first metatarsals from the Paleogene of Egypt and the origin of the anthropoid big toe

The specialized grasping feet of primates, and in particular the nature of the hallucal grasping capabilities of living strepsirrhines and tarsiers (i.e., ‘prosimians’), have played central roles in the study of primate origins. Prior comparative studies of first metatarsal (Mt1) morphology have documented specialized characters in living prosimians that are indicative of a more abducted hallux, which in turn is often inferred to be related to an increased ability for powerful grasping. These include a well-developed peroneal process and a greater angle of the proximal articular surface relative to the long axis of the diaphysis. Although known Mt1s of fossil prosimians share these characters with living non-anthropoid primates, Mt1 morphology in the earliest crown group anthropoids is not well known. Here we describe two Mt1s from the Fayum Depression of Egypt - one from the latest Eocene (from the ∼34 Ma Quarry L-41), and one from the later early Oligocene (from the ∼29-30 Ma Quarry M) - and compare them with a sample of extant and fossil primate Mt1s. Multivariate analyses of Mt1 shape variables indicate that the Fayum specimens are most similar to those of crown group anthropoids, and likely belong to the stem catarrhines Catopithecus and Aegyptopithecus specifically, based on analyses of size. Also, phylogenetic analyses with 16 newly defined Mt1 characters support the hypotheses that “prosimian”-like Mt1 features evolved along the primate stem lineage, while crown anthropoid Mt1 morphology and function is derived among primates, and likely differed from that of basal stem anthropoids. The derived loss of powerful hallucal grasping as reflected in the Mt1 morphology of crown anthropoids may reflect long-term selection for improved navigation of large-diameter, more horizontal branches at the expense of movement in smaller, more variably inclined branches in the arboreal environment.     

山顶洞人与现代华北人头骨非测量性特征比较及中国更新世晚期人类演化的一些问题

山顶洞人化石是迄今在东亚地区发现的数量最为丰富、保存状态最为完好的更新世晚期人类化石。多年来,山顶洞人作为东亚地区更新世晚期人类的代表,在研究东亚地区现代蒙古人种及美洲印第安人起源方面发挥着重要作用。随着对现代人起源与演化研究的深入,学术界对更新世晚期人类演化及现代人群形成过程的许多细节及演化机制予以了越来越多的注意,提出了现代人群出现时间及现代人群分化时间的概念。一些研究对山顶洞人的演化程度及其在东亚地区现代人群形成上的作用也提出了不同看法。为了深入探讨这些问题,本文对12项颅骨非测量特征在山顶洞人与现代中国人的表现情况进行了对比研究。发现有8项特征在山顶洞人与现代中国人之间具有不同的表现,作者认为山顶洞人在颅骨特征表现上较现代中国人具有更多的原始性。在此基础上,作者就更新世晚期人群内部变异、现代人群特征标准等问题进行了讨论。