Effects of Frequent Mowing on Survival and Persistence of Forbs Seeded into a Species-Poor Grassland

Many early attempts at tallgrass prairie reconstruction failed to achieve the high species diversity of remnant prairies, and instead consist primarily of C₄ grasses. We hypothesized that frequent mowing of established prairie grasses could create sufficient gaps in the aboveground and belowground environment to allow for the establishment of native forbs from seed. We studied forb seedling establishment in a 25‐year‐old prairie planting in northern Iowa that was dominated by native warm‐season grasses. In winter 1999, 23 species of native forbs were broadcast into the recently burned sod at a rate of 350 viable seeds/m². Treatment plots were mowed weekly for either one or two growing seasons, and control plots were unmowed. Mowed plots had greater light availability than controls, especially when warm‐season grasses began to flower. Overwinter seedling mortality was 3% in mowed treatments compared to 29% in the controls. Forbs in mowed plots had significantly greater root and shoot mass than those in control plots in the first and second growing seasons but were not significantly more abundant. By the fourth growing season, however, forbs were twice as abundant in the mowed treatments. No lasting negative impacts of frequent mowing on the grass population were observed. Mowing a second year influenced species composition but did not change total seedling establishment. Experimental evidence is consistent with the idea that mowing reduced competition for light from large established grasses, allowing forb seedlings the opportunity to reach sufficient size to establish, survive, and flower in the second and subsequent years.     

Mapping of Fhb2 on chromosome 6BS: a gene controlling Fusarium head blight field resistance in bread wheat (Triticum aestivum L.)

Fusarium head blight (FHB) is one of the most important fungal wheat diseases worldwide. Understanding the genetics of FHB resistance is key to facilitate the introgression of different FHB resistance genes into adapted wheat. The objective of this project was to study the FHB resistance QTL on chromosome 6B, quantify the phenotypic variation, and qualitatively map the resistance gene as a Mendelian factor. The FHB resistant parent BW278 (AC Domain*2/Sumai 3) was used as the source of the resistance allele. A large recombinant inbred line (RIL) mapping population was developed from the cross BW278/AC Foremost. The population segregated for three known FHB resistance QTL located on chromosomes 3BSc, 5A, and 6B. Molecular markers on chromosome 6B (WMC104, WMC397, GWM219), 5A (GWM154, GWM304, WMC415), and 3BS (WMC78, GWM566, WMC527) were amplified on approximately 1,440 F_2:7 RILs. The marker information was used to select 89 RILs that were fixed homozygous susceptible for the 3BSc and 5A FHB QTLs and were recombinant in the 6B interval. Disease response was evaluated on 89 RILs and parental checks in the greenhouse and field nurseries. Dual floret injection (DFI) was used in greenhouse trials to evaluate disease severity (DS). Macroconidial spray inoculations were used in field nurseries conducted at two locations in southern Manitoba (Carman and Glenlea) over two years 2003 and 2004, to evaluate disease incidence, disease severity, visual rating index, and Fusarium-damaged kernels. The phenotypic distribution for all five-disease infection measurements was bimodal, with lines resembling either the resistant or susceptible checks and parents. All of the four field traits for FHB resistance mapped qualitatively to a coincident position on chromosome 6BS, flanked by GWM133 and GWM644, and is named Fhb2. The greenhouse-DS trait mapped 2 cM distal to Fhb2. Qualitative mapping of Fhb2 in wheat provides tightly linked markers that can reduce linkage drag associated with marker assisted selection of Fhb2 and aid the pyramiding of different resistance loci for wheat improvement.     

Evidence that ethanol acts on a target in Loop 2 of the extracellular domain of alpha1 glycine receptors

Considerable evidence indicates that ethanol acts on specific residues in the transmembrane domains of glycine receptors (GlyRs). In this study, we tested the hypothesis that the extracellular domain is also a target for ethanol action by investigating the effect of cysteine substitutions at positions 52 (extracellular domain) and 267 (transmembrane domain) on responses to n-alcohols and propyl methanethiosulfonate (PMTS) in alpha1GlyRs expressed in Xenopus oocytes. In support of the hypothesis: (i) The A52C mutation changed ethanol sensitivity compared to WT GlyRs; (ii) PMTS produced irreversible alcohol-like potentiation in A52C GlyRs; and (iii) PMTS binding reduced the n-chain alcohol cutoff in A52C GlyRs. Further studies used PMTS binding to cysteines at positions 52 or 267 to block ethanol action at one site in order to determine its effect at other site(s). In these situations, ethanol caused negative modulation when acting at position 52 and positive modulation when acting at position 267. Collectively, these findings parallel the evidence that established the TM domain as a target for ethanol, suggest that positions 52 and 267 are part of the same alcohol pocket and indicate that the net effect of ethanol on GlyR function reflects the summation of its positive and negative modulatory effects on different targets.     

Docosahexaenoic acid induces an anti-inflammatory profile in lipopolysaccharide-stimulated human THP-1 macrophages more effectively than eicosapentaenoic acid

A number of studies have investigated the effects of fish oil on the production of pro-inflammatory cytokines using peripheral blood mononuclear cell models. The majority of these studies have employed heterogeneous blends of long-chain n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which preclude examination of the individual effects of LC n-3 PUFA. This study investigated the differential effects of pure EPA and DHA on cytokine expression and nuclear factor kappaB (NF-kappaB) activation in human THP-1 monocyte-derived macrophages. Pretreatment with 100 microM EPA and DHA significantly decreased lipopolysaccharide (LPS)-stimulated THP-1 macrophage tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta and IL-6 production (P<.02), compared to control cells. Both EPA and DHA reduced TNF-alpha, IL-1beta and IL-6 mRNA expression. In all cases, the effect of DHA was significantly more potent than that of EPA (P<.01). Furthermore, a low dose (25 microM) of DHA had a greater inhibitory effect than that of EPA on macrophage IL-1beta (P<.01 and P<.04, respectively) and IL-6 (P<.003 and P<.003, respectively) production following 0.01 and 0.1 microg/ml LPS stimulation. Both EPA and DHA down-regulated LPS-induced NF-kappaB/DNA binding in THP-1 macrophages by approximately 13% (P< or =.03). DHA significantly decreased macrophage nuclear p65 expression (P< or =.05) and increased cytoplasmic IkappaBalpha expression (P< or =.05). Although similar trends were observed with EPA, they were not significant. Our findings suggest that DHA may be more effective than EPA in alleviating LPS-induced pro-inflammatory cytokine production in macrophages - an effect that may be partly mediated by NF-kappaB. Further work is required to elucidate additional divergent mechanisms to account for apparent differences between EPA and DHA.     

Are the carotid bodies of the guinea-pig functional?

We have previously observed that the guinea-pig appears to have a relatively poor ventilatory (V (E)) response to hypoxia, compared to other mammals. Therefore, in this study, we questioned the ability of the carotid bodies (primary peripheral chemoreceptors) in the guinea-pig to detect hypoxia. The ventilatory responses to poikilocapnic hypoxia (8% O(2)), poikilooxic hypercapnia (8% CO(2)), hyperoxia (100% O(2)) and cyanide (NaCN - 200 mug/kg, i.v.) were assessed before and after carotid body denervation (CBD) in anaesthetized guinea-pigs. Although CBD attenuated the V (E) responses to hypercapnia and cyanide, it had no effect on normoxic breathing or the V (E) responses to hypoxia or hyperoxia. In a separate group of guinea-pigs, nerve activity was recorded from single or few-fibre preparations of the carotid sinus nerve (CSN). Basal chemoreceptor activity could not be detected from any of the nerve preparations. NaCN and hypercapnia consistently provoked an increase in neural activity. In contrast, hypoxia never clearly increased activity in any of the single or few-fibre preparations isolated from the CSN. In conclusion, although the carotid bodies of the guinea-pig, like those of other mammals, are able to detect hypercapnia and histotoxic hypoxia and elicit a reflex increase in V (E), they are essentially hypoxia-insensitive. The latter may explain, at least in part, the relatively poor V (E) response to hypoxia shown by the guinea-pig.     

The Aspergillus fumigatus metacaspases CasA and CasB facilitate growth under conditions of endoplasmic reticulum stress

We have examined the contribution of metacaspases to the growth and stress response of the opportunistic human mould pathogen, Aspergillus fumigatus, based on increasing evidence implicating the yeast metacaspase Yca1p in apoptotic-like programmed cell death. Single metacaspase-deficient mutants were constructed by targeted disruption of each of the two metacaspase genes in A. fumigatus, casA and casB, and a metacaspase-deficient mutant, DeltacasA/DeltacasB, was constructed by disrupting both genes. Stationary phase cultures of wild-type A. fumigatus were associated with the appearance of typical markers of apoptosis, including elevated proteolytic activity against caspase substrates, phosphatidylserine exposure on the outer leaflet of the membrane, and loss of viability. By contrast, phosphatidylserine exposure was not observed in stationary phase cultures of the DeltacasA/DeltacasB mutant, although caspase activity and viability was indistinguishable from wild type. The mutant retained wild-type virulence and showed no difference in sensitivity to a range of pro-apoptotic stimuli that have been reported to initiate yeast apoptosis. However, the DeltacasA/DeltacasB mutant showed a growth detriment in the presence of agents that disrupt endoplasmic reticulum homeostasis. These findings demonstrate that metacaspase activity in A. fumigatus contributes to the apoptotic-like loss of membrane phospholipid asymmetry at stationary phase, and suggest that CasA and CasB have functions that support growth under conditions of endoplasmic reticulum stress.     

Effects of helicopter net-gunning on survival of bighorn sheep

Wildlife capture, and the data collection associated with it, has led to major advancements in ecology that are integral to decision making pertaining to wildlife conservation. Capturing wildlife, however, can cause lethal and non-lethal risks to animals. Understanding the factors that contribute to the level of risk involved in wildlife capture is therefore important for the development and implementation of the safest and most effective methodologies. We used data from 736 animal captures of 389 individuals for 2 subspecies of female bighorn sheep (Rocky Mountain bighorn [Ovis canadensis canadensis], Sierra Nevada bighorn sheep [O. c. sierrae]) in Wyoming and California, USA, in 2002–2020 to evaluate the degree and extent of time that capture via helicopter net-gunning affects survival. We compared pre- and post-capture survival during a 10-week window centered on a capture event, and post-capture survival between captured animals and animals that were monitored but not captured during the 10-week window. Additionally, we evaluated the effects of handling techniques (number of times captured, season of capture event, handling time, chase time, and body temp) and biological factors (age and nutritional condition) on probability of capture mortality. Mean daily survival was 0.9992 during a 5-week pre-capture window, dropped to 0.9864 on the day of capture, and rebounded within 3 days of capture to pre-capture levels and that of sheep that were not captured. Overall, direct mortality resulting from capture was 1.36%, with 0.54% mortality occurring within the 3 days following a capture event for an overall 1.90% capture-related mortality. The only handling and biological metrics that influenced the probability of capture mortality were rectal temperature and nutritional condition; high initial rectal temperatures and poor body condition were associated with increased risk of mortality in the days following capture. Overall, helicopter net-gunning imposed low and short-term risk to survival of female bighorn sheep. To reduce bias in survival estimates, we recommend using a 3-day censorship window for post-capture mortalities as opposed to the common practice of a 2–5-week censor window. Helicopter net-gunning, including annual or seasonal recaptures, remains an effective and comparatively safe technique for capture and associated data collection of bighorn sheep.     

Effect of older age on treatment decisions and outcomes among patients with traumatic spinal cord injury

Background:

Older people are at increased risk of traumatic spinal cord injury from falls. We evaluated the impact of older age (≥ 70 yr) on treatment decisions and outcomes.

Methods:

We identified patients with traumatic spinal cord injury for whom consent and detailed data were available from among patients recruited (2004–2013) at any of the 31 acute care and rehabilitation hospitals participating in the Rick Hansen Spinal Cord Injury Registry. Patients were assessed by age group (< 70 v. ≥ 70 yr). The primary outcome was the rate of acute surgical treatment. We used bivariate and multivariate regression models to assess patient and injury-related factors associated with receiving surgical treatment and with the timing of surgery after arrival to a participating centre.

Results:

Of the 1440 patients included in our study cohort, 167 (11.6%) were 70 years or older at the time of injury. Older patients were more likely than younger patients to be injured by falling (83.1% v. 37.4%; p < 0.001), to have a cervical injury (78.0% v. 61.6%; p = 0.001), to have less severe injuries on admission (American Spinal Injury Association Impairment Scale grade C or D: 70.5% v. 46.9%; p < 0.001), to have a longer stay in an acute care hospital (median 35 v. 28 d; p < 0.005) and to have a higher in-hospital mortality (4.2% v. 0.6%; p < 0.001). Multivariate analysis did not show that age of 70 years or more at injury was associated with a decreased likelihood of surgical treatment (adjusted odds ratio [OR] 0.48, 95% confidence interval [CI] 0.22–1.07). An unplanned sensitivity analysis with different age thresholds showed that a threshold of 65 years was associated with a decreased chance of surgical treatment (OR 0.39, 95% CI 0.19–0.80). Older patients who underwent surgical treatment had a significantly longer wait time from admission to surgery than younger patients (37 v. 19 h; p < 0.001).

Interpretation:

We found chronological age to be a factor influencing treatment decisions but not at the 70-year age threshold that we had hypothesized. Older patients waited longer for surgery and had a substantially higher in-hospital mortality despite having less severe injuries than younger patients. Further research into the link between treatment delays and outcomes among older patients could inform surgical guideline development.Globally there has been an epidemiologic shift in the age of patients who sustain a traumatic spinal cord injury.^1–3 Although most people who have traumatic spinal cord injuries are 16–30 years old, there has been a progressive increase in the number who are over 70. The average age at injury has increased from 29 to 40 years.⁴ By 2032, patients over 70 are predicted to account for most patients with new traumatic spinal cord injuries.⁵ This change is attributed in part to aging baby boomers. It is unknown whether the management and outcomes of these older patients differ compared with younger patients.Older patients typically have more comorbid conditions, including cardiovascular disease, respiratory disorders, cerebrovascular disease and dementia, which are thought to increase their risk of perioperative adverse events.⁶ The use of anticoagulants for cardiac and cerebrovascular indications can delay timely surgical interventions. Older patients are also at increased risk of postoperative and medication-related adverse events, such as delirium.⁷ As a direct consequence of this perceived risk of perioperative adverse events and ambiguity about the optimal treatment for spinal cord injury in older patients, surgeons may deliberate for some time before making a clear therapeutic decision, they may choose nonoperative treatment,⁸ or they may delay the surgical treatment in an effort to optimize the patient’s condition medically.Given the increasing incidence of traumatic spinal cord injury in older adults, and the potential for differences in treatment among older and younger patients, we evaluated the impact of age on treatment decisions and outcomes among patients with traumatic spinal cord injury. We hypothesized that surgical management would differ at an age threshold of 70 years.