Weihong Ji

Global DNA hypomethylation, rather than reactive oxygen species (ROS), a potential facilitator of cadmium-stimulated K562 cell proliferation

Cell proliferation plays a critical role in the process of cadmium (Cd) carcinogenesis. Although both induction of reactive oxygen species (ROS) and alteration of DNA methylation are involved in Cd-stimulated cell proliferation, the detailed mechanism of Cd-stimulated cell proliferation remains poorly understood. In this study, K562 cells pre-treated with N-acetylcysteine (NAC) or methionine (Meth) were exposed to Cd to investigate the potential contribution of ROS and global DNA methylation pathways in Cd-induced cell proliferation. The results showed that Cd-stimulated cell proliferation, increased ROS and DNA damage levels, and induced global DNA hypomethylation. The increases of ROS and DNA damage levels were attenuated by pre-treatment with NAC. Cd-stimulated cell proliferation did not appear to be suppressed through eliminating ROS by NAC. However, methionine was shown to prevent Cd-induced global DNA hypomethylation and Cd-stimulated cell proliferation. Our results suggest that global DNA hypomethylation, rather than ROS, is a potential facilitator of Cd-stimulated K562 cell proliferation.

Seasonal home range changes of the Sichuan snub-nosed monkey (Rhinopithecus roxellana) in the Qinling Mountains of China.

The seasonal changes in home range and habitat use of the Sichuan snub-nosed monkey, Rhinopithecus roxellana, have been studied by radio tracking and direct observation in the Qinling Mountains of China. The home range size was 14.1 km2 in spring, 9.5 km2 in summer, 12.1 km2 in autumn and 12.3 km2 in winter; the total area used was 22.5 km2. The area of the home range is closely correlated with the distribution and abundance of food resources. Seasonal change in the home range area is correlated with the phenology of the vegetation. An unusually large home range is a unique characteristic of this monkey.

Sex-biased dispersal and a density-independent mating system in the Australian brushtail possum, as revealed by minisatellite DNA profiling

Natal dispersal can have important effects on mammal population structure and dynamics following a local population crash. Such dispersal is of practical importance when applied to the control of pest species because dispersal may significantly, and undesirably, reduce the population recovery time following a control operation. The relative dispersal rate of the sexes is also critical because that too will affect the rate of population increase. Here, we describe a field experiment in which we reduce the density of two populations of the Australian brushtail possum, and use genetic similarity, as estimated by minisatellite DNA profiles, to investigate dispersal in the original (undisturbed) and recovering populations. Our results show that the genetic similarity within the undisturbed populations was lower between males than between females. Conversely, the genetic similarities between males and females in the two recovering populations were not significantly different, while relatedness among males was significantly higher in the recovering populations when compared with those in the pre‐removal populations. These data indicate two important characteristics of dispersal in possums: (i) that dispersal in established populations is sex biased towards males; and (ii) that within the first 3 years following population control, ‘the vacuum effect’, whereby individuals from areas adjacent to a control area expand their home range and invade the depopulated area, is the most important factor in the re‐colonization process for possums. We found no evidence that the mating system, which is polygynous, varied when the density was markedly reduced. These results indicate that drastic reductions in population density by conventional control will not affect the rate of spread of biological control agents that rely on sexual transmission for dissemination.

Social dynamics of the golden snub-nosed monkey (Rhinopithecus roxellana): female transfer and one-male unit succession.

Among primates that form multilevel societies, understanding factors and mechanisms associated with the movement of individuals between groups, clans, and one‐male social units offers important insight into primate reproductive and social strategies. In this research we present data based on an 8‐year field study of a multilevel troop of Sichuan snub‐nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains of China. Our study troop contained 78–126 individuals, and was usually organized into 6–8 one‐male units (OMU). The majority of OMUs were composed of networks of unrelated females and their offspring. We found that 59.7% (43/72) of subadult and adult females in our study troop transferred between OMUs (n=66) or disappeared (n=7) from the troop. In the majority of cases, two or more females transferred together into new OMUs or troops. In R. roxellana, new OMUs formed in several ways. During 2001–2008, 16 adult males appeared in the study troop. Over this period, we observed 13 different males who became harem leaders either by taking over an existing harem or by attracting females from other OMUs into their harem. We also observed four OMUs from a neighboring troop to successfully immigrate into the study troop. The number of individuals in these newly immigrated OMUs was significantly smaller than that number of individuals in resident OMUs. During harem formation, fighting between adult males was rarely observed, and female mate choice appeared to play a crucial role in harem male recruitment and replacement. These results suggest that golden snub‐nosed monkeys are organized in a nonmatrilineal social system. Female mate choice and possibly incest avoidance appear to play important roles in female transfer, male tenure, and OMU stability. Am. J. Primatol. 71:670–679, 2009.

Heavy metal concentrations in water, sediment, and tissues of two fish species (Triplohysa pappenheimi, Gobio hwanghensis) from the Lanzhou section of the Yellow River, China

In order to assess the condition of heavy metal pollution in the Yellow River, Lanzhou section, China, and to quantify heavy metal (copper, lead, zinc, and cadmium) contents in tissues (liver, kidney, gills, and muscles) of two fish species (Triplophysa pappenheimi and Gobio hwanghensis), levels of these four metals in the water body, sediment, and tissues of the two fish were measured using inductively coupled plasma-atomic emission spectrometry. The metal levels from this study were compared with the threshold values in the guidelines of water, sediment, and food given by the National Environmental Protection Agency of China, the National Oceanic and Atmospheric Administration of America, and the National Standards Management Department of China. We found the mean concentrations of Cu, Pb, Zn, and Cd in THE water body, sediment, and muscles of two fish species were far below the values in guidelines. We also found that the type of metals present and their concentrations varied in different tissues and species. The results suggested that (1) Cu, Pb, Zn, and Cd did not contaminate the aquatic ecosystem severely and did not threaten the safety of human consumption in the Yellow River, Lanzhou section, and (2) organs that are sensitive to accumulating heavy metals may be useful to develop bioindicators for monitoring metal contamination. Considering environmental variables, further study is necessary before deciding which fish species or tissue could be the ideal bioindicators for aquatic pollution.

Satellite telemetry and social modeling offer new insights into the origin of primate multilevel societies

Multilevel societies (MLS), in which polygynous reproductive units are nested in a larger social matrix, represent a highly complex social system documented only in a small number of mammalian species. Using long-term behavioural data, satellite telemetry and social network analysis, we present a new framework for understanding the function and social dynamics of the golden snub-nosed monkey MLS. Here we show that several one-male units form a cohesive breeding band that associates with one or more all-male units to form a herd. Herds seasonally aggregate and exchange members, thus facilitating gene flow and inbreeding avoidance. This MLS evolved from the aggregation of independent one-male, multifemale units that characterize ancestral Asian colobines; the evolutionary pathway leading to this MLS contrasts with that proposed for African papionins, which appear to have undergone internal fissioning of multimale–multifemale groups. The results suggest that both environmental and phylogenetic factors are important in the evolution of a primate MLS.

Molecular ecology and biological control: the mating system of a marsupial pest.

Many studies in molecular ecology have focused on the use of repeat DNA markers to determine the nature of mating systems in a wide variety of animal species. Whilst these studies typically have focused on important issues such as the evolutionary consequences of fitness variation among males, genetic studies of mating systems are potentially also important because they can generate information of significance to wider issues in wildlife management. For example, genetically modified, sexually transmitted viral diseases have been suggested as potential agents for the control of vertebrate pest species. An understanding of the epidemiology of such agents requires an intimate knowledge of the sexual contact rates between individuals of the target species. Here, we report the use of minisatellite DNA profiling to reveal the mating system in two New Zealand populations of the introduced Australian brushtail possum. The brushtail possum is New Zealand’s most important mammalian pest and a species for which control by a sexually transmitted immunocontraceptive has been proposed. Encouragingly, we report considerable variation in the reproductive success of males at both study sites, with one male siring offspring from four females in one year (mean no. of offspring/reproductively successful male/year at the two sites is 1.95–2.15), while many sired none. This bias in the pattern of reproductive success among males will probably facilitate the spread of an immunocontraceptive agent and thereby increase the power of this approach to biological control.

Response of a Group of Sichuan Snub-Nosed Monkeys to Commercial Logging in the Qinling Mountains, China

Habitat destruction is one of the greatest threats to primates worldwide. To understand the impact of forest logging on the habitat use of primates in temperate mixed forest, we compared the range, habitat used, population size, and diet of a troop (ERT) of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in the Qinling Mountains before (1989), during (1997), and after (2002-2003) commercial logging. Logging significantly changed the composition of the forest and the food supply for the troop. Some areas were heavily logged and formed patches in the forest that lacked canopy cover. The troop moved 7 km away from their original range when logging took place and returned to their original range after logging stopped, but they avoided heavily logged areas that lacked canopy cover. Their movement indicated some degree of site fidelity in this species. Diet and home range changed after logging, but the population size remained stable, which suggests that this species has some ability to adapt to habitat changes. Our results may reflect a natural flexibility in primates to adapt to the changing food resources in temperate areas with marked seasonal variations in food availability and distribution. This flexibility may have contributed to their higher degree of resilience to habitat alterations caused by human activities compared with tropical forest primates that have a more specialized diet. Our findings provide important baseline information that will help decision makers in their efforts to conserve primates, especially in temperate regions, and to sustainably manage primate habitat.

The mating system of the Sichuan snub-nosed monkey (Rhinopithecus roxellana).

This article reports the first genetic study of the mating system of the Sichuan snub‐nosed monkey (Rhinopithecus roxellana), an endemic and endangered species in China. The investigation was carried out in a population (WRT) in the Qinling Mountains using data from both field observation and paternity analysis through microsatellite DNA profiling. During a mating season, a male on an average copulated with 5.7 females. Approximately 18% of the females were observed to copulate with more than one male over the study period. The majority of copulations (94.5%) were initiated by females. Twenty‐eight of 430 observed matings were extra‐unit copulations. Eight polymorphic microsatellite loci were used for paternity analysis. The number of alleles at each locus ranged from 3 to 7 (mean=4.3). Observed heterozygosity ranged between 0.32 and 0.79. None of the loci showed significant deviation from Hardy–Weinberg equilibrium. Results from paternity exclusion showed that 12 of 21 (57.1%) immature individuals were sired by extra‐unit males. Although the basic social unit of snub‐nosed monkeys is consistent with a polygynous mating system, both field observation and genetic data suggests that their mating system is polygamous. Infanticide and inbreeding avoidance are the most likely explanations for the promiscuity of female snub‐nosed monkeys. Am. J. Primatol. 72:25–32, 2010.

Mate competition and reproductive correlates of female dispersal in a polygynous primate species (Rhinopithecus roxellana)

Different mating systems in group-living animals have characteristic behavioral correlates that are primarily related to mate competition. Mate competition may push individuals to selectively make dispersal decisions for the purpose of maximizing of opportunities for reproduction. The Sichuan snub-nosed monkey (Rhinopithecus roxellana) is a polygynous primate species endemic to China. We provide the first data on female dispersal in a free-ranging group of R. roxellana in the Zhouzhi National Nature Reserve, Qinling Mountains, China. Both adult and subadult female dispersal occurred. Immigration/emigration rates of adult females are higher than those of subadult females. Mate competition is one apparent driving force behind adult female dispersal, and inbreeding avoidance is the possible proximate factor influencing subadult female dispersal. Adult female R. roxellana employ various reproductive strategies related to dispersal, which may increase their reproductive success.