After an invasion: understanding variation in grassland community recovery following removal of a high-impact invader

A pervasive problem in invasion ecology is the limited recovery of native communities following removal of invaders. Little evidence exists on the causes of variation in post-invasion recovery. In a 4-year experiment using 65 sets of matched plots, we imposed an invader removal treatment (with control) on heterogeneous grassland plots invaded or uninvaded by an aggressive recent arrival, Aegilops triuncialis (barb goatgrass). We tested the validity of plot matching using transplants and soil analyses. We analyzed the community-level correlates of invader impacts, removal treatment side effects, and community recovery, each defined in two ways: by compositional similarity to uninvaded plots, and by relative native species richness. Recovery of native species richness in invaded and treated plots was high (approaching 100 %) although recovery of composition was not high (median 71 % Bray–Curtis dissimilarity to uninvaded untreated plots). We measured resilience as the residuals of community recovery in models that controlled for invader impacts and removal treatment side effects. Compositional resilience was highest where the uninvaded communities had the least cover by other invaders in the same functional group as the focal invader. Richness resilience was highest where the uninvaded communities had the lowest native species richness. Our study suggests that the recovery of native species per se may be a more relevant goal than the recovery of the exact pre-invasion species composition of particular sites, particularly in cases where pre-invasion species composition included exotic species other than the focal invader.     

Dominant Mutations in GRHL3 Cause Van der Woude Syndrome and Disrupt Oral Periderm Development

Mutations in interferon regulatory factor 6 (IRF6) account for ∼70% of cases of Van der Woude syndrome (VWS), the most common syndromic form of cleft lip and palate. In 8 of 45 VWS-affected families lacking a mutation in IRF6, we found coding mutations in grainyhead-like 3 (GRHL3). According to a zebrafish-based assay, the disease-associated GRHL3 mutations abrogated periderm development and were consistent with a dominant-negative effect, in contrast to haploinsufficiency seen in most VWS cases caused by IRF6 mutations. In mouse, all embryos lacking Grhl3 exhibited abnormal oral periderm and 17% developed a cleft palate. Analysis of the oral phenotype of double heterozygote (Irf6^+/−;Grhl3^+/−) murine embryos failed to detect epistasis between the two genes, suggesting that they function in separate but convergent pathways during palatogenesis. Taken together, our data demonstrated that mutations in two genes, IRF6 and GRHL3, can lead to nearly identical phenotypes of orofacial cleft. They supported the hypotheses that both genes are essential for the presence of a functional oral periderm and that failure of this process contributes to VWS.     

Characteristics of temporal patterns of cortisol and luteinizing hormone in primiparous,postpartum, anovular,suckled, beef cows exposed acutely to bulls

Background  

The physiological mechanism by which bulls stimulate resumption of ovarian cycling activity in postpartum, anovular, suckled cows after calving may involve the concurrent activation of the hypothalamic-hypophyseal-ovarian (HPO) axis and hypothalamic-hypophyseal-adrenal (HPA) axis. Thus, the objectives of this experiment were to determine if characteristics of temporal patterns of cortisol and luteinizing hormone (LH) in postpartum, anovular, beef cows are influenced by acute exposure to bulls. The null hypotheses were that daily, temporal characteristics of cortisol and LH concentration patterns do not differ between cows exposed acutely to bulls or steers.     

Aggregation of human serum albumin during a thermal viral inactivation step

A terminal pasteurization step has been used for some plasma-derived protein products such as human serum albumin (HSA), which consists of heating the protein in solution at 60 °C for 10 h. Native and denaturing SDS-PAGE and dynamic light scattering were used to follow the stability of HSA during this process. It appears that a thermally unstable fraction, comprised primarily of haptoglobin, is involved in the formation of soluble aggregates of HSA. Therefore, it appears that aggregation during heat treatment is not due to conformational instability of HSA itself, but arises from unfolding of a thermally labile protein impurity. As haptoglobin aggregates, it entraps some HSA, which is present at much higher concentrations. This study emphasizes that, in a complex mixture of naturally occurring proteins, one thermally labile species can trigger aggregation of more stable proteins.     

Effects of hypo and hyperthyroidism on the response to glucose loading of blood glucose, ketones and insulin and liver glycogen as studied in the fasted rat

After receiving an i.p. glucose load, 24 h fasted thyroidectomized rats showed a progressive increase in blood glucose and a slow decrease in blood ketone bodies. Both liver glycogen and plasma insulin levels showed no differences within 60 min of the glucose administration. It is suggested that the glucose intolerance in these animals is partly due to an insulin deficiency. Thyroidectomized rats treated daily with 25 microgram of L-thyroxine/100 g body weight for 40 days responded to the glucose test with a supranormal and more persistent elevation of blood glucose but with a faster and a greater fall in blood ketone bodies, as compared to controls. Sixty min after the glucose loading, liver glucogen levels were lower and plasma insulin were slightly higher than controls. It is suggested that a diminished extraction of glucose during transhepatic passage can be responsible for the impaired glucose tolerance observed in the hyperthyroid animals.