High-resolution mapping of crossovers reveals extensive variation in fine-scale recombination patterns among humans

Recombination plays a crucial role in meiosis, ensuring the proper segregation of chromosomes. Recent linkage disequilibrium (LD) and sperm-typing studies suggest that recombination rates vary tremendously across the human genome, with most events occurring in narrow "hotspots." To examine variation in fine-scale recombination patterns among individuals, we used dense, genome-wide single-nucleotide polymorphism data collected in nuclear families to localize crossovers with high spatial resolution. This analysis revealed that overall recombination hotspot usage is similar in males and females, with individual hotspots often active in both sexes. Across the genome, roughly 60% of crossovers occurred in hotspots inferred from LD studies. Notably, however, we found extensive and heritable variation among both males and females in the proportion of crossovers occurring in these hotspots.     

Comparative genome sequencing identifies a prophage-associated genomic island linked to host adaptation of Lawsonia intracellularis infections

Lawsonia intracellularis is an obligate intracellular bacterium and the causative agent of proliferative enteropathy (PE). The disease is endemic in pigs, emerging in horses and has also been reported in a variety of other animal species, including nonhuman primates. Comparing the whole genome sequences of a homologous porcine L. intracellularis isolate cultivated for 10 and 60 passages in vitro, we identified a 18-kb prophage-associated genomic island in the passage 10 (pathogenic variant) that was lost in the passage 60 (non-pathogenic variant). This chromosomal island comprises 15 genes downstream from the prophage DLP12 integrase gene. The prevalence of this genetic element was evaluated in 12 other L. intracellularis isolates and in 53 infected animals and was found to be conserved in all porcine isolates cultivated for up to 20 passages and was lost in isolates cultivated for more than 40 passages. Furthermore, the prophage region was also present in 26 fecal samples derived from pigs clinically affected with both acute and chronic forms of the disease. Nevertheless, equine L. intracellularis isolates evaluated did not harbor this genomic island regardless of the passage in vitro. Additionally, fecal samples from 21 clinically affected horses and four wild rabbits trapped in horse farms experiencing PE outbreaks did not show this prophage-associated island. Although the presence of this prophage-associated island was not essential for a virulent L. intracellularis phenotype, this genetic element was porcine isolate-specific and potentially contributed to the ecological specialization of this organism for the swine host.     

IMAGING DIAGNOSIS—AORTIC ANEURYSM AND URETERAL OBSTRUCTION SECONDARY TO UMBILICAL ARTERY ABSCESSATION IN A 5‐WEEK‐OLD FOAL

A 5‐week‐old foal was evaluated for fever and hematuria of 3 days duration. Cystoscopy localized the blood to be originating from the left ureter. Abdominal ultrasonography revealed left hydronephrosis, hydroureter, and omphaloarteritis of the left umbilical artery with abscess formation that communicated with an arterial structure. Computed tomography (CT) revealed a large aortic aneurysm within the center of the abscess. An exploratory celiotomy was performed and the infection was nonresectable. The prognosis for life was grave; therefore the colt was euthanized. Necropsy findings confirmed the antemortem diagnosis. Ultrasound and CT imaging in this case provided an accurate antemortem diagnosis.     

Post-wildfire seeding in forests of the western United States: An evidence-based review

Broadcast seeding is one of the most widely used post-wildfire emergency response treatments intended to reduce soil erosion, increase vegetative ground cover, and minimize establishment and spread of non-native plant species. We conducted an evidence-based review to examine the effectiveness and effects of post-wildfire seeding treatments on soil stabilization, non-native species invasion, and plant community recovery in the western U.S. We reviewed 94 scientific papers and agency monitoring reports identified using a systematic search protocol. As sampling designs have become more rigorous in recent years, evidence that seeding is effective in reducing erosion has decreased. Of highest and high quality studies evaluating soil erosion, 92% (11 of 12) were published since 2000, none of which showed an effective result. Before 2000, the majority of the studies (71%) fell into the lowest quality categories, of which 72% showed seeding to be effective. The majority of studies (20 of 27, 74%) evaluating soil erosion in seeded versus unseeded controls showed that seeding did not reduce erosion relative to unseeded controls. Even when seeding significantly increased vegetative cover, seeded sites rarely supported plant cover levels considered sufficient to stabilize soils within the first and second year post-wildfire. Of the 11 studies evaluating seeding effectiveness for curtailing invasions of non-native plant species, an almost equal percentage found seeding treatments to be either effective (54%, 6 studies) or ineffective (45%, 5 studies). However, the majority of effective and ineffective treatments (83% and 80%, respectively) used non-native species. Sixteen of 26 studies (62%) evaluating seeding effects on plant communities reported that seeding suppressed recovery of native plants, although data on long-term impacts of this reduction are limited. The literature suggests that post-wildfire seeding does little to protect soil in the short-term, has equivocal effect on invasion of non-native species, and can have negative effects on native vegetation recovery, although long-term studies are needed to assess lasting impacts of seeded species.     

Abundance and origins of plasma lipids in sexually maturing female coho salmon Oncorhynchus kisutch (Walbaum) in culture

Coho salmon Oncorhynchus kisutch are semelparous spawners with highly synchronized oocyte growth. Plasma was collected from maturing female fish and plasma lipids were quantified by lipoprotein class. Stable ¹³C isotopes were employed to investigate the origins of plasma lipids. Plasma lipoproteins were partitioned into the very low density (VLDL), low density (LDL), high density (HDL) and very high density (VHDL) lipoprotein classes. Lipids from all lipoprotein classes increased between the lipid droplet and early vitellogenesis stages of oocyte growth and VHDL lipids continued to increase through mid vitellogenesis (P < 0.05). During vitellogenesis, total plasma lipid concentrations were similar to the sum of lipoprotein lipids (P = 0.51). Plasma vitellogenin determined by an ELISA method was very well correlated with VHDL lipid during vitellogenesis (R² = 0.91, n = 15). In general, the δ¹³C values of plasma lipids reflected that of feed (exogenous) and muscle (endogenous) lipids when feed and muscle δ¹³C values were similar, and were intermediate when differences existed between the two lipid sources. With one exception, the δ¹³C values of lipids from all lipoprotein classes within a plasma sample were similar. Results indicate that during sexual maturity, lipids from all plasma lipoprotein classes originate from a common pool of exogenous and endogenous lipids.     

Prolonged survival after craniectomy with skull reconstruction and adjuvant definitive radiation therapy in three dogs with multilobular osteochondrosarcoma

Multilobular osteochondrosarcoma is an uncommon canine tumor but presents a treatment challenge when arising on the skull. This retrospective case series study aimed to describe outcome of a multimodality treatment approach involving aggressive surgical resection and adjuvant definitive radiation therapy in a group of dogs with multilobular osteochondrosarcoma of the calvarium. Clinical, imaging, treatment, and outcome data were collected from retrospective review of medical records. Three dogs met inclusion criteria. The presenting clinical complaint was the presence of a mass effect of the skull in all three dogs and concurrent neurologic abnormalities in one dog. Advanced imaging revealed aggressive lytic and proliferative tumors arising from the calvarium in all three dogs. All dogs were treated surgically with a modified craniectomy, repaired with a titanium mesh—polymethyl methacrylate bone cement implant or a low prolife titanium mesh plate and followed by adjuvant definitive radiation therapy with 2.5 Gy per fraction for 22 daily fractions. There were no major immediate surgical complications and radiation was well tolerated overall. Neurologic improvement was seen in the patient that presented with neurologic disease. Survival times from surgery were 387, 422, and 730 days and from the time of radiation were 358, 397, and 677 days. Findings in this sample of three dogs supported the use of aggressive therapy with a combination of surgical craniectomy and cranioplasty utilizing a titanium mesh implant and high dose definitive radiation therapy for local control and prolonged survival times in dogs with multilobular osteochondrosarcoma of the skull.     

Schooling and migration of large pelagic fishes relative to environmental cues

A kinesis model driven by high-resolution sea surface temperature maps is used to simulate Atlantic bluefin tuna movements in the Gulf of Maine during summer months. Simulations showed that individuals concentrated in areas of thermal preference. Results are compared to empirical distribution maps of bluefin tuna schools determined from aerial overflights of the stock during the same time periods. Simulations and empirical observations showed similar bluefin tuna distributions along fronts, although interannual variations in temperature ranges occupied suggest that additional foraging factors are involved. Performance of the model is further tested by simulating the relatively large-scale annual north–south migrations of bluefin tuna that followed a preferred thermal regime. Despite the model's relatively simple structure, results suggest that kinesis is an effective mechanism for describing movements of large pelagic fish in the expansive ocean environment.     

ELM,An Estuarine Nitrogen Loading Model: Formulation and Verification of Predicted Concentrations of Dissolved Inorganic Nitrogen

ELM is an Estuarine Loading Model that calculates mean annual concentration of dissolved inorganic nitrogen (DIN) available to producers in shallow estuaries by considering how different processes modify pools of nitrogen provided by inputs (streams, groundwater flow, atmospheric deposition, N₂ fixation, and regeneration), and losses (burial and denitrification), within components of the estuarine system (bare sediments, seagrass meadows, salt marshes, water column). ELM also considers the effect of flushing rate within an estuary. Its formulation was constrained to minimize demands of data needed to run the model. In spite of simplifications such as the use of loss coefficients instead of functional formulations of processes, and uncertainties in all the terms included in ELM, predictions of mean annual DIN in water were not significantly different than field measurements done in estuaries in Cape Cod, Massachusetts, subject to different rates of nitrogen (N) loading. This verification suggests that, in spite of its simple formulation, ELM captures the functioning of nutrient dynamics within estuaries. ELM may therefore be a reasonable tool for use in basic studies in nutrient dynamics and land/estuary coupling. Because of its simplicity and comprehensiveness in inclusion of components and processes, ELM may also be useful in efforts to manage N loads to estuaries and related management issues.