Modifying the ‘pulse–reserve’ paradigm for deserts of North America: precipitation pulses,soil water,and plant responses

The ‘pulse–reserve’ conceptual model—arguably one of the most-cited paradigms in aridland ecology—depicts a simple, direct relationship between rainfall, which triggers pulses of plant growth, and reserves of carbon and energy. While the heuristics of ‘pulses’, ‘triggers’ and ‘reserves’ are intuitive and thus appealing, the value of the paradigm is limited, both as a conceptual model of how pulsed water inputs are translated into primary production and as a framework for developing quantitative models. To overcome these limitations, we propose a revision of the pulse–reserve model that emphasizes the following: (1) what explicitly constitutes a biologically significant ‘rainfall pulse’, (2) how do rainfall pulses translate into usable ‘soil moisture pulses’, and (3) how are soil moisture pulses differentially utilized by various plant functional types (FTs) in terms of growth? We explore these questions using the patch arid lands simulation (PALS) model for sites in the Mojave, Sonoran, and Chihuahuan deserts of North America. Our analyses indicate that rainfall variability is best understood in terms of sequences of rainfall events that produce biologically-significant ‘pulses’ of soil moisture recharge, as opposed to individual rain events. In the desert regions investigated, biologically significant pulses of soil moisture occur in either winter (October–March) or summer (July–September), as determined by the period of activity of the plant FTs. Nevertheless, it is difficult to make generalizations regarding specific growth responses to moisture pulses, because of the strong effects of and interactions between precipitation, antecedent soil moisture, and plant FT responses, all of which vary among deserts and seasons. Our results further suggest that, in most soil types and in most seasons, there is little separation of soil water with depth. Thus, coexistence of plant FTs in a single patch as examined in this PALS study is likely to be fostered by factors that promote: (1) separation of water use over time (seasonal differences in growth), (2) relative differences in the utilization of water in the upper soil layers, or (3) separation in the responses of plant FTs as a function of preceding conditions, i.e., the physiological and morphological readiness of the plant for water-uptake and growth. Finally, the high seasonal and annual variability in soil water recharge and plant growth, which result from the complex interactions that occur as a result of rainfall variability, antecedent soil moisture conditions, nutrient availability, and plant FT composition and cover, call into question the use of simplified vegetation models in forecasting potential impacts of climate change in the arid zones in North America.     

Evidence for a complex demographic history of chimpanzees

To characterize patterns of genomic variation in central chimpanzees(Pan troglodytes troglodytes) and gain insight into their evolution,we sequenced nine unlinked, intergenic regions, representinga total of 19,000 base pairs, in 14 individuals. When theseDNA sequences are compared with homologous sequences previouslycollected in humans and in western chimpanzees (Pan troglodytesverus), nucleotide diversity is higher in central chimpanzeesthan in western chimpanzees or in humans. Consistent with alarger effective population size of central chimpanzees, levelsof linkage disequilibrium are lower than in humans. Patternsof linkage disequilibrium further suggest that homologous geneconversion may be an important contributor to genetic exchangeat short distances, in agreement with a previous study of thesame DNA sequences in humans. In central chimpanzees, but notin western chimpanzees, the allele frequency spectrum is significantlyskewed towards rare alleles, pointing to population size changesor fine-scale population structure. Strikingly, the extent ofgenetic differentiation between western and central chimpanzeesis much stronger than what is seen between human populations.This suggests that careful attention should be paid to geographicsampling in studies of chimpanzee genetic variation.     

Preneoplastic changes in ovarian tissues

OBJECTIVE: To test whether histologically normal epithelium within ovarian inclusion cysts and stroma exhibit changes in nuclear chromatin pattern that indicate the presence of occult ovarian lesions. STUDY DESIGN: Ovaries were collected from 10 low-risk women,from 7 high-risk women and from 3 women with ovarian cancer. Histologic sections were cut at 5 microm and hematoxylin and eosin stained. High-resolution images were recorded from the epithelium lining inclusion cysts and from the underlying stroma of ovaries from these 20 subjects. A total of 2860 epithelial nuclei and 3610 stromal nuclei were recorded. Karyometric features and nuclear abnormality were computed. Discriminant analyses and unsupervised learning algorithms defined deviations from normal that were designated "above threshold" and used to compute average nuclear abnormality of a second nuclear phenotype. RESULTS: Histologically normal epithelium from inclusion cysts of ovaries harboring a malignant lesion was shown to exhibit changes in the nuclear chromatin pattern that were statistically significant using quantitative image analysis procedures. Similar changes were seen in the inclusion cyst epithelia of high-risk ovaries. A subpopulation of cells representing a new phenotype was detected in the underlying stroma of women harboring a malignant ovarian lesion and in women at high risk of ovarian cancer. CONCLUSION: The karyometric changes observed in the epithelia lining inclusion cysts and in the underlying stroma of ovaries either with ovarian cancer or at high risk of ovarian cancer suggest the presence of preneoplastic changes in histologically normal tissue.     

The science behind pre-Columbian evidence of syphilis in Europe: research by documentary

This article discusses the presentation of scientific findings by documentary, without the process of peer review. We use, as an example, PBS's "The Syphilis Enigma," in which researchers presented novel evidence concerning the origin of syphilis that had never been reviewed by other scientists. These "findings" then entered the world of peer-reviewed literature through citations of the documentary itself or material associated with it. Here, we demonstrate that the case for pre-Columbian syphilis in Europe that was made in the documentary does not withstand scientific scrutiny. We also situate this example from paleopathology within a larger trend of "science by documentary" or "science by press conference," in which researchers seek to bypass the peer review process by presenting unvetted findings directly to the public.     

First Evidence and Predictions of Plasmodium Transmission in Alaskan Bird Populations

The unprecedented rate of change in the Arctic climate is expected to have major impacts on the emergence of infectious diseases and host susceptibility to these diseases. It is predicted that malaria parasites will spread to both higher altitudes and latitudes with global warming. Here we show for the first time that avian Plasmodium transmission occurs in the North American Arctic. Over a latitudinal gradient in Alaska, from 61°N to 67°N, we collected blood samples of resident and migratory bird species. We found both residents and hatch year birds infected with Plasmodium as far north as 64°N, providing clear evidence that malaria transmission occurs in these climates. Based on our empirical data, we make the first projections of the habitat suitability for Plasmodium under a future-warming scenario in Alaska. These findings raise new concerns about the spread of malaria to naïve host populations.     

A 6 week randomized double-blind placebo-controlled trial of ziprasidone for the acute depressive mixed state

Objective

To examine the efficacy of ziprasidone vs. placebo for the depressive mixed state in patients with bipolar disorder type II or major depressive disorder (MDD).

Methods

73 patients were randomized in a double-blinded, placebo-controlled study to ziprasidone (40-160 mg/d) or placebo for 6 weeks. They met DSM-IV criteria for a major depressive episode (MDE), while also meeting 2 or 3 (but not more nor less) DSM-IV manic criteria. They did not meet DSM-IV criteria for a mixed or manic episode. Baseline psychotropic drugs were continued unchanged. The primary endpoint measured was Montgomery- Åsberg Depression Rating Scale (MADRS) scores over time. The mean dose of ziprasidone was 129.7±45.3 mg/day and 126.1±47.1 mg/day for placebo.

Results

The primary outcome analysis indicated efficacy of ziprasidone versus placebo (p = 0.0038). Efficacy was more pronounced in type II bipolar disorder than in MDD (p = 0.036). Overall ziprasidone was well tolerated, without notable worsening of weight or extrapyramidal symptoms.

Conclusions

There was a statistically significant benefit with ziprasidone versus placebo in this first RCT of any medication for the provisional diagnostic concept of the depressive mixed state.

Trial Registration

Clinicaltrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00490542","term_id":"NCT00490542"}}NCT00490542     

Retinal expression of Wnt-pathway mediated genes in low-density lipoprotein receptor-related protein 5 (Lrp5) knockout mice

Mutations in low-density lipoprotein receptor-related protein 5 (Lrp5) impair retinal angiogenesis in patients with familial exudative vitreoretinopathy (FEVR), a rare type of blinding vascular eye disease. The defective retinal vasculature phenotype in human FEVR patients is recapitulated in Lrp5 knockout (Lrp5(-/-)) mouse with delayed and incomplete development of retinal vessels. In this study we examined gene expression changes in the developing Lrp5(-/-) mouse retina to gain insight into the molecular mechanisms that underlie the pathology of FEVR in humans. Gene expression levels were assessed with an Illumina microarray on total RNA from Lrp5(-/-) and WT retinas isolated on postnatal day (P) 8. Regulated genes were confirmed using RT-qPCR analysis. Consistent with a role in vascular development, we identified expression changes in genes involved in cell-cell adhesion, blood vessel morphogenesis and membrane transport in Lrp5(-/-) retina compared to WT retina. In particular, tight junction protein claudin5 and amino acid transporter slc38a5 are both highly down-regulated in Lrp5(-/-) retina. Similarly, several Wnt ligands including Wnt7b show decreased expression levels. Plasmalemma vesicle associated protein (plvap), an endothelial permeability marker, in contrast, is up-regulated consistent with increased permeability in Lrp5(-/-) retinas. Together these data suggest that Lrp5 regulates multiple groups of genes that influence retinal angiogenesis and may contribute to the pathogenesis of FEVR.     

RNA interference of gonadotropin-inhibitory hormone gene induces arousal in songbirds

Gonadotropin-inhibitory hormone (GnIH) was originally identified in quail as a hypothalamic neuropeptide inhibitor of pituitary gonadotropin synthesis and release. However, GnIH neuronal fibers do not only terminate in the median eminence to control anterior pituitary function but also extend widely in the brain, suggesting it has multiple roles in the regulation of behavior. To identify the role of GnIH neurons in the regulation of behavior, we investigated the effect of RNA interference (RNAi) of the GnIH gene on the behavior of white-crowned sparrows, a highly social songbird species. Administration of small interfering RNA against GnIH precursor mRNA into the third ventricle of male and female birds reduced resting time, spontaneous production of complex vocalizations, and stimulated brief agonistic vocalizations. GnIH RNAi further enhanced song production of short duration in male birds when they were challenged by playbacks of novel male songs. These behaviors resembled those of breeding birds during territorial defense. The overall results suggest that GnIH gene silencing induces arousal. In addition, the activities of male and female birds were negatively correlated with GnIH mRNA expression in the paraventricular nucleus. Density of GnIH neuronal fibers in the ventral tegmental area was decreased by GnIH RNAi treatment in female birds, and the number of gonadotropin-releasing hormone neurons that received close appositions of GnIH neuronal fiber terminals was negatively correlated with the activity of male birds. In summary, GnIH may decrease arousal level resulting in the inhibition of specific motivated behavior such as in reproductive contexts.