Seed dispersal in changing landscapes McConkey, Kim R.; Prasad, Soumya; Corlett, Richard T. ...
Biological conservation,
02/2012, Letnik:
146, Številka:
1
Journal Article
Recenzirano
► We review the effects of major drivers of biodiversity change on seed dispersal. ► Fragmentation, harvests, invasions and climate change alter seed dispersal patterns. ► Synergistic interactions ...between drivers are likely to exacerbate impacts. ► Understanding seed dispersal can help identify robust conservation solutions.
A growing understanding of the ecology of seed dispersal has so far had little influence on conservation practice, while the needs of conservation practice have had little influence on seed dispersal research. Yet seed dispersal interacts decisively with the major drivers of biodiversity change in the 21st century: habitat fragmentation, overharvesting, biological invasions, and climate change. We synthesize current knowledge of the effects these drivers have on seed dispersal to identify research gaps and to show how this information can be used to improve conservation management. The drivers, either individually, or in combination, have changed the quantity, species composition, and spatial pattern of dispersed seeds in the majority of ecosystems worldwide, with inevitable consequences for species survival in a rapidly changing world. The natural history of seed dispersal is now well-understood in a range of landscapes worldwide. Only a few generalizations that have emerged are directly applicable to conservation management, however, because they are frequently confounded by site-specific and species-specific variation. Potentially synergistic interactions between disturbances are likely to exacerbate the negative impacts, but these are rarely investigated. We recommend that the conservation status of functionally unique dispersers be revised and that the conservation target for key seed dispersers should be a population size that maintains their ecological function, rather than merely the minimum viable population. Based on our analysis of conservation needs, seed dispersal research should be carried out at larger spatial scales in heterogenous landscapes, examining the simultaneous impacts of multiple drivers on community-wide seed dispersal networks.
Previous reviews of smoking prevalence among individuals with primary psychosis have largely been internationally focused, with little attention given to within- and among subgroup comparisons of ...U.S. individuals with such disorders. Nationally, smoking prevalence has been decreasing among the general population. We aimed to review national and divisional samples to determine if this downward trend is being reflected among individuals with primary psychotic disorders, if geographical differences exist, and which demographic characteristics are associated with reported rates. We conducted a systematic search of the PubMed, PsycINFO, and Cochrane databases using a floor of 2010. Studies found during a review of references, and studies previously known to the authors but not found during the initial search, were also reviewed. We found 7 papers which reported the prevalence of smoking among individuals with psychotic disorders, and 2 papers which reported the prevalence of general tobacco and/or vaped nicotine use in this population. One eligible paper was excluded due to the same authors publishing more recent data of the same sample. In all, 1 national and 7 divisional samples were included for analysis. Individuals with psychotic disorders still smoke at rates far higher than the general population. We did not find strong support for a downward trend in smoking in this population but did find support for geographical heterogeneity. Smoking interventions must be tested and implemented nationwide.
Aberrant subclavian arteries (aSCAs), with or without aortic pathology, are uncommon. The purpose of the present study was to review our experience with the surgical management of aSCA.
We performed ...a retrospective review of patients who had undergone surgery for an aSCA between 1996 and 2020. Symptomatic and asymptomatic patients were included. The primary end points were ≤30-day and late mortality. The secondary end points were ≤30-day complications, graft patency, and reinterventions.
A total of 46 symptomatic and 3 asymptomatic patients with aSCA had undergone surgery (31 females 62%; median age, 45 years). An aberrant right subclavian artery was present in 38 (78%) and an aberrant left subclavian artery in 11 patients (22%). Of the 49 patients, 41 (84%) had had a Kommerell diverticulum (KD) and 11 (22%) had had a concomitant distal arch or proximal descending thoracic aortic aneurysm. Symptoms included dysphagia (56%), dyspnea (27%), odynophagia (20%), and upper extremity exertional fatigue (16%). Five patients (10%) had required emergency surgery. The aSCA had been treated by transposition in 32, a carotid to subclavian bypass in 11, and an ascending aorta to subclavian bypass in 6. The KD was treated by resection and oversewing in 19 patients (39%). Fifteen patients (31%) had required distal arch or proximal descending thoracic aortic replacement for concomitant aortic disease and/or KD treatment. Thoracic endovascular aortic repair was used to exclude the KD in six patients (12%). Seven patients (14%) had undergone only bypass or transposition. The 30-day complications included one death from pulseless electrical activity arrest secondary to massive pulmonary embolism. The 30-day major complications (14%) included acute respiratory failure in three, early mortality in one, stroke in one, non–ST-elevation myocardial infarction in one, and temporary dialysis in one patient. The other complications included chylothorax/lymphocele (n = 5; 10%), acute kidney injury (n = 2; 4%), pneumonia (n = 2; 4%), wound infection (n = 2; 4%), atrial fibrillation (n = 2; 4%), Horner syndrome (n = 2; 4%), lower extremity acute limb ischemia (n = 1; 2%), and left recurrent laryngeal nerve injury (n = 1; 2%). At a median follow-up of 53 months (range, 1-230 months), 40 patients (82%) had had complete symptom relief and 9 (18%) had experienced improvement. Six patients had died at a median of 157 months; the deaths were not procedure or aortic related. The primary patency was 98%. Reintervention at ≤30 days had been required for two patients (4%) for ligation of lymphatic vessels and bilateral lower extremity fasciotomy after proximal descending thoracic aorta replacement. One patient had required late explantation of an infected and occluded carotid to subclavian bypass graft, which was treated by cryopreserved allograft replacement.
Surgical treatment of the aSCA can be accomplished with low major morbidity and mortality with excellent primary patency and symptom relief.
The literature demonstrates that obtaining a biopsy of the physis may be beneficial for diagnostic purposes. A small biopsy of the epiphyseal plate may allow for earlier detection of certain ...conditions and be used to monitor the healing of diseased and/or damaged physes. However, due to the fear of a growth arrest in a growing child, biopsies are not currently performed. In this study, we investigated the effects of a biopsy of the epiphyseal plate in 3‐month‐old lambs. A total of 4.2 mm biopsy samples were captured in the proximal tibiae and distal femora physes. The lambs were monitored 12‐ and 24‐week post‐biopsy. Computed tomography (CT) and micro‐CT scans were obtained to determine if any angular deformities occurred, while scanning electron microscope (SEM) and histological analysis were utilized to assess the bone response due to the biopsy. The contralateral limbs served as unaltered controls for direct comparison within each lamb. The data demonstrated no signs of angular deformities following a 4.2 mm biopsy of the physis. Bone growth/elongation was confirmed by CT, SEM, and fluorochrome analyses and indicated that the lambs were in fact immature and still growing at the time of the biopsy. Clinical Significance: This investigation demonstrated that a small biopsy of the epiphyseal plate can be obtained safely without the cause of growth arrest and angular deformities. The ability to precisely diagnose, treat, and/or monitor at‐risk children at an earlier timepoint by way of a biopsy sample could be an important advancement in regard to researching diseased and/or damaged physes.
We investigated the effects of a biopsy of the epiphyseal plate in 3‐month old lambs. A 4.2 mm biopsy sample was captured in the proximal tibiae and distal femora physes. The lambs were monitored for 12‐ and 24‐week. The data demonstrated no signs of angular deformities following a 4.2 mm biopsy of the physis. Bone growth/elongation was confirmed by computed tomography, scanning electron microscope (SEM), and fluorochrome analyses. This investigation demonstrated that a small biopsy of the epiphyseal plate can be obtained safely for diagnostic purposes.
Abstract
Resilience is the ability of ecosystems to maintain function while experiencing perturbation. Globally, forests are experiencing disturbances of unprecedented quantity, type, and magnitude ...that may diminish resilience. Early warning signals are statistical properties of data whose increase over time may provide insights into decreasing resilience, but there have been few applications to forests. We quantified four early warning signals (standard deviation, lag-1 autocorrelation, skewness, and kurtosis) across detrended time series of multiple ecosystem state variables at the Hubbard Brook Experimental Forest, New Hampshire, USA and analyzed how these signals have changed over time. Variables were collected over periods from 25 to 55 years from both experimentally manipulated and reference areas and were aggregated to annual timesteps for analysis. Long-term (>50 year) increases in early warning signals of stream calcium, a key biogeochemical variable at the site, illustrated declining resilience after decades of acid deposition, but only in watersheds that had previously been harvested. Trends in early warning signals of stream nitrate, a critical nutrient and water pollutant, likewise exhibited symptoms of declining resilience but in all watersheds. Temporal trends in early warning signals of some of groups of trees, insects, and birds also indicated changing resilience, but this pattern differed among, and even within, groups. Overall, ∼60% of early warning signals analyzed indicated decreasing resilience. Most of these signals occurred in skewness and kurtosis, suggesting ‘flickering’ behavior that aligns with emerging evidence of the forest transitioning into an oligotrophic condition. The other ∼40% of early warning signals indicated increasing or unchanging resilience. Interpretation of early warning signals in the context of system specific knowledge is therefore essential. They can be useful indicators for some key ecosystem variables; however, uncertainties in other variables highlight the need for further development of these tools in well-studied, long-term research sites.
Summary
Two‐component systems (TCS) are universal among bacteria and play critical roles in gene regulation. Our understanding of the contributions of TCS in the biology of the Borrelia is just now ...beginning to develop. Borrelia burgdorferi, a causative agent of Lyme disease, harbours a TCS comprised of open reading frames (ORFs) BB0419 and BB0420. BB0419 encodes a response regulator designated Rrp1, and BB0420 encodes a hybrid histidine kinase–response regulator designated Hpk1. Rrp1, which contains a conserved GGDEF domain, undergoes phosphorylation and produces the secondary messenger, cyclic diguanylate (c‐di‐GMP), a critical signaling molecule in numerous organisms. However, the regulatory role of the Rrp1–Hpk1 TCS and c‐di‐GMP signaling in Borrelia biology are unexplored. In this study, the distribution, conservation, expression and potential global regulatory capability of Rrp1 were assessed. rrp1 was found to be universal and highly conserved among isolates, co‐transcribed with hpk1, constitutively expressed during in vitro cultivation, and significantly upregulated upon tick feeding. Allelic exchange replacement and microarray analyses revealed that the Rrp1 regulon consists of a large number of genes encoded by the core Borrelia genome (linear chromosome, linear plasmid 54 and circular plasmid 26) that encode for proteins involved in central metabolic processes and virulence mechanisms including immune evasion.
Fenestrated/branched endovascular aortic repair (F/BEVAR) in patients with occluded iliac arteries is challenging owing to limited access for branch vessel catheterization and increased risk for leg ...and spinal ischemic complications. The aim of this study was to analyze technical strategies and outcomes of F/BEVAR in patients with unilateral iliofemoral occlusive disease.
We performed a retrospective review of all consecutive patients treated by F/BEVAR in two institutions (2003-2021). Patients with unilateral iliofemoral occlusive disease were included in the analysis. All patients had one patent iliac artery that was used for advancement of the fenestrated-branch component. Preloaded catheter/guidewire systems or steerable sheaths were used as adjuncts to facilitate catheterization. Primary endpoints were technical success, mortality, major adverse events (stroke, spinal cord injury, dialysis or decrease in the glomerular filtration rate of more than 50%, bowel ischemia, myocardial infarction, or respiratory failure), primary iliac patency, and freedom from reinterventions.
There were 959 patients treated with F/BEVAR. Of these, 15 patients (1.56%; mean age, 74 years; 80% male) had occluded iliac arteries and 1 patent iliofemoral access and were treated for a thoracoabdominal aortic aneurysm (n = 8) or juxtarenal abdominal aortic aneurysm (n = 7). Brachial access was used in 14 of the 15 patients and preloaded systems in 7 of the 15 patients (47%). The remaining 53% had staggered deployment of stent grafts. There were seven physician-modified endovascular grafts, seven custom-made devices, and one off-the-shelf device used. Thirteen patients (87%) had distal seal using aortouni-iliac stent grafts and two (13%) had distal seal in the infrarenal aorta. Concomitant femoral crossover bypass (FCB) was performed in two patients and six patients had a prior FCB. Technical success was 100%. There were no intraoperative complications or early lower extremity ischemic complications, and all FCB were preserved. There was one mortality (7%) within 30 days owing to retrograde type A dissection. Major adverse events occurred in 20% of patients. The median follow-up was 12 months (range, 0-85 months). Two patients (13%) required three reinterventions. One patient required proximal stent graft extension for an acute type B dissection (3 months) and another required iliac extension for type Ib endoleak of an aortouni-iliac graft (21 months) and thrombolysis of that extension (50 months). At last follow-up, all patients had primary graft patency except one with secondary graft patency without new claudication. One patient had a single renal artery stent occlusion at follow-up with no r-intervention. The overall survival rate was 60%, without aortic-related deaths.
Although challenging, F/BEVAR with unilateral femoral/brachial approach is feasible in patients with occluded iliac limbs, with an important rate of ischemic complications, but satisfactory outcomes.
Summary
Rrp1 is the sole c‐di‐GMP‐producing protein (diguanylate cyclase) of Borrelia burgdorferi. To test the hypothesis that Rrp1 regulates critical processes involved in the transmission of ...spirochetes between ticks and mammals, an rrp1 deletion mutant (B31‐Δrrp1) and a strain that constitutively produces elevated levels of Rrp1 (B31‐OV) were constructed. The strains were assessed for progression through the enzootic cycle using an Ixodes tick/C3H‐HeJ mouse model and tick immersion feeding methods. B31‐Δrrp1 infected mice as efficiently as wild type but had altered motility, decreased chemotactic responses to N‐acetylglucosamine (NAG) and attenuated ability to disseminate or colonize distal organs. While this strain infected mice, it was not able to survive in ticks. In contrast, B31‐OV displayed normal motility patterns and chemotactic responses but was non‐infectious in mice. Using immersion feeding techniques, we demonstrate that B31‐OV can establish a population in ticks and survive exposure to a natural bloodmeal. The results presented here indicate Rrp1, and by extension, c‐di‐GMP, are not strictly required for murine infection, but are required for the successful establishment of a productive population of B. burgdorferi in ticks. These analyses provide significant new insight into the genetic regulatory mechanisms of the Lyme disease spirochetes.
Medullary thyroid cancer is a neuroendocrine malignancy that can occur sporadically or as the result of genomic rearranged during transfection mutations. Medullary thyroid cancer has a higher rate of ...metastasis than well-differentiated thyroid cancer. Lateral neck dissection is often performed, and its prophylactic use is controversial.
Single-center, retrospective review (2000–2017) of patients undergoing primary surgical treatment for medullary thyroid cancer who had negative lateral neck imaging preoperatively. Demographics, genetic associations, clinical, and imaging findings were analyzed. Locoregional recurrence, overall recurrence, and overall survival were examined.
A total of 110 patients were identified, of which 18 underwent prophylactic lateral neck dissection and 92 did not. Age, sex distribution, preoperative calcitonin levels, and follow-up were similar among groups. Overall recurrence was 20% for no prophylactic lateral neck dissection and 39% for prophylactic lateral neck dissection (P = .46). Most recurrences were locoregional recurrence, 7.6% for no prophylactic lateral neck dissection versus 22% for prophylactic lateral neck dissection (P = .08), half of it being to the lateral neck in both groups. A total of 7 patients from the no prophylactic lateral neck dissection group required treatment for recurrences versus 4 patients in prophylactic lateral neck dissection group (P = .57). Overall survival at 5 years was similar, 43% the no prophylactic lateral neck dissection group and 31% for prophylactic lateral neck dissection group (P = .52).
Lateral neck dissection has no effect in decreasing locoregional or overall recurrences in medullary thyroid cancer and has no effect in overall survival when performed prophylactically at index surgical intervention.
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