Including phylogenetic conservatism of shortgrass prairie restoration species does not improve species germinability prediction

Premise

We investigated whether phylogenetic conservatism can improve the performance of seed germinability prediction models. Previous studies in tallgrass prairie and alpine meadow revealed that seed morphological traits demonstrate phylogenetic conservatism. We hypothesized that phylogenetic conservatism in seed traits could help predict the seed germinability, under the assumption that seed traits contain phylogenetic signals.

Methods

We measured seed germination percentage and seed morphological traits (seed mass, seed height, and seed surface area) on 34 native species from shortgrass prairie in North America. We supplemented these data with similar data from the literature on 11 more species. We calculated the robustness of the phylogenetic signal of each trait to the number of species sampled. We also compressed the phylogenetic distance matrix to a two-dimensional space, and applied the Akaike information criterion to evaluate the effects of phylogeny on seed germinability prediction models.

Key results

We found weak but significant phylogenetic signals in seed mass and seed height in the full data set. These phylogenetic signals were not able to improve seed germinability prediction model performance among shortgrass prairie species. Our robustness tests of phylogenetic signals using random sub-sampling showed that the detection rate of phylogenetic signals in seed mass was increased along with the expansion of species pool, and nearly 100% at 40 species. However, the detection rate of phylogenetic signals in seed height was constantly low, around 20%.

Conclusion

When the phylogenetic signals are weak, the phylogenetic position does not improve germinability prediction model performance. Therefore, phylogenetic signals detected during a single species pool calculation may not accurately reflect the phylogenetic conservatism of the trait in a plant community. We suggest testing for robustness of phylogenetic signals using random sub-sampling tests.

Airborne environmental DNA metabarcoding detects more diversity, with less sampling effort, than a traditional plant community survey

Background

Airborne environmental DNA (eDNA) research is an emerging field that focuses on the detection of species from their genetic remnants in the air. The majority of studies into airborne eDNA of plants has until now either focused on single species detection, specifically only pollen, or human health impacts, with no previous studies surveying an entire plant community through metabarcoding. We therefore conducted an airborne eDNA metabarcoding survey and compared the results to a traditional plant community survey.

Results

Over the course of a year, we conducted two traditional transect-based visual plant surveys alongside an airborne eDNA sampling campaign on a short-grass rangeland. We found that airborne eDNA detected more species than the traditional surveying method, although the types of species detected varied based on the method used. Airborne eDNA detected more grasses and forbs with less showy flowers, while the traditional method detected fewer grasses but also detected rarer forbs with large showy flowers. Additionally, we found the airborne eDNA metabarcoding survey required less sampling effort in terms of the time needed to conduct a survey and was able to detect more invasive species than the traditional method.

Conclusions

Overall, we have demonstrated that airborne eDNA can act as a sensitive and efficient plant community surveying method. Airborne eDNA surveillance has the potential to revolutionize the way plant communities are monitored in general, track changes in plant communities due to climate change and disturbances, and assist with the monitoring of invasive and endangered species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-021-01947-x.

Reduction of fibrillar strain-rate sensitivity in steroid-induced osteoporosis linked to changes in mineralized fibrillar nanostructure

As bone is used in a dynamic mechanical environment, understanding the structural origins of its time-dependent mechanical behaviour - and the alterations in metabolic bone disease - is of interest. However, at the scale of the mineralized fibrillar matrix (nanometre-level), the nature of the strain-rate dependent mechanics is incompletely understood. Here, we investigate the fibrillar- and mineral-deformation behaviour in a murine model of Cushing's syndrome, used to understand steroid induced osteoporosis, using synchrotron small- and wide-angle scattering/diffraction combined with in situ tensile testing at three strain rates ranging from 10-4 to 10-1 s-1. We find that the effective fibril- and mineral-modulus and fibrillar-reorientation show no significant increase with strain-rate in osteoporotic bone, but increase significantly in normal (wild-type) bone. By applying a fibril-lamellar two-level structural model of bone matrix deformation to fit the results, we obtain indications that altered collagen-mineral interactions at the nanoscale - along with altered fibrillar orientation distributions - may be the underlying reason for this altered strain-rate sensitivity. Our results suggest that an altered strain-rate sensitivity of the bone matrix in osteoporosis may be one of the contributing factors to reduced mechanical competence in such metabolic bone disorders, and that increasing this sensitivity may improve biomechanical performance.

The detection of a non-anemophilous plant species using airborne eDNA

Genetic analysis of airborne plant material has historically focused (generally implicitly rather than as a stated goal) on pollen from anemophilous (wind-pollinated) species, such as in multiple studies examining the relationship of allergens to human health. Inspired by the recent influx of literature applying environmental DNA (eDNA) approaches to targeted-species and whole-ecosystem study, we conducted a proof-of-concept experiment to determine whether airborne samples reliably detect genetic material from non-anemophilous species that may not be releasing large plumes of pollen. We collected airborne eDNA using Big Spring Number Eight dust traps and quantified the amount of eDNA present for a flowering wind-pollinated genus (Bouteloua) and insect-pollinated honey mesquite (Prosopis glandulosa) that was not flowering at the time of the study. We were able to detect airborne eDNA from both species. Since honey mesquite is insect-pollinated and was not flowering during the time of this study, our results confirm that airborne eDNA consists of and can detect species through more than just pollen. Additionally, we were able to detect temporal patterns reflecting Bouteloua reproductive ecology and suggest that airborne honey mesquite eDNA responded to weather conditions during our study. These findings suggest a need for more study of the ecology of airborne eDNA to uncover its potential for single-species and whole-community research and management in terrestrial ecosystems.

Interactive effects of severe drought and grazing on the life history cycle of a bioindicator species

We used the lesser prairie-chicken (Tympanuchus pallidicinctus), an iconic grouse species that exhibits a boom-bust life history strategy, on the Southern High Plains, USA, as a bioindicator of main and interactive effects of severe drought and grazing. This region experienced the worst drought on record in 2011. We surveyed lesser prairie-chicken leks (i.e., communal breeding grounds) across 12 years that represented 7 years before the 2011 drought (predrought) and 4 years during and following the 2011 drought (postdrought). Grazing was annually managed with the objective of achieving ≤50% utilization of aboveground vegetation biomass. We used lek (n = 49) count data and covariates of weather and managed grazing to: (a) estimate long-term lesser prairie-chicken abundance and compare abundance predrought and postdrought; (b) examine the influence of annual and seasonal drought (modified Palmer drought index), temperature, and precipitation on long-term lesser prairie-chicken survival and recruitment; and (c) assess and compare the influence of grazing on lesser prairie-chicken population predrought and postdrought. Lesser prairie-chicken abundance was nearly seven times greater predrought than postdrought, and population declines were attributed to decreased survival and recruitment. The number of days with temperature >90th percentile had the greatest effect, particularly on recruitment. The population exhibited a substantial bust during 2011 and 2012 without a boom to recover in four postdrought years. Adaptive grazing positively influenced the population predrought, but had no effects postdrought. Results suggest that the severe drought in 2011 may have been beyond the range of environmental conditions to which lesser prairie-chickens, and likely other species, have adapted. Land management practices, such as grazing, should remain adaptive to ensure potential negative influences to all species are avoided. Increasing habitat quantity and quality by reducing habitat loss and fragmentation likely will increase resiliency of the ecosystem and individual species.

Bone matrix development in steroid-induced osteoporosis is associated with a consistently reduced fibrillar stiffness linked to altered bone mineral quality

Glucocorticoid-induced osteoporosis (GIOP) is a major secondary form of osteoporosis, with the fracture risk significantly elevated - at similar levels of bone mineral density - in patients taking glucocorticoids compared with non-users. The adverse bone structural changes at multiple hierarchical levels in GIOP, and their mechanistic consequences leading to reduced load-bearing capacity, are not clearly understood. Here we combine experimental X-ray nanoscale mechanical imaging with analytical modelling of the bone matrix mechanics to determine mechanisms causing bone material quality deterioration during development of GIOP. In situ synchrotron small-angle X-ray diffraction combined with tensile testing was used to measure nanoscale deformation mechanisms in a murine model of GIOP, due to a corticotrophin-releasing hormone promoter mutation, at multiple ages (8-, 12-, 24- and 36 weeks), complemented by quantitative micro-computed tomography and backscattered electron imaging to determine mineral concentrations. We develop a two-level hierarchical model of the bone matrix (mineralized fibril and lamella) to predict fibrillar mechanical response as a function of architectural parameters of the mineralized matrix. The fibrillar elastic modulus of GIOP-bone is lower than healthy bone throughout development, and nearly constant in time, in contrast to the progressively increasing stiffness in healthy bone. The lower mineral platelet aspect ratio value for GIOP compared to healthy bone in the multiscale model can explain the fibrillar deformation. Consistent with this result, independent measurement of mineral platelet lengths from wide-angle X-ray diffraction finds a shorter mineral platelet length in GIOP. Our results show how lowered mineralization combined with altered mineral nanostructure in GIOP leads to lowered mechanical competence.

SIGNIFICANCE STATEMENT

Increased fragility in musculoskeletal disorders like osteoporosis are believed to arise due to alterations in bone structure at multiple length-scales from the organ down to the supramolecular-level, where collagen molecules and elongated mineral nanoparticles form stiff fibrils. However, the nature of these molecular-level alterations are not known. Here we used X-ray scattering to determine both how bone fibrils deform in secondary osteoporosis, as well as how the fibril orientation and mineral nanoparticle structure changes. We found that osteoporotic fibrils become less stiff both because the mineral nanoparticles became shorter and less efficient at transferring load from collagen, and because the fibrils are more randomly oriented. These results will help in the design of new composite musculoskeletal implants for bone repair.

Misidentification of copperhead and cottonmouth snakes following snakebites

INTRODUCTION

Copperhead (Agkistrodon contortrix) and cottonmouth or water moccasin (Agkistrodon piscivorus) snakes account for the majority of venomous snakebites in the southern United States. Cottonmouth snakes are generally considered to have more potent venom. Copperheads are considered less venomous and there is some controversy as to whether or not bites from copperhead snakes need to be treated with antivenom. Copperhead and juvenile cottonmouth snakes are both brown in color. The purpose of this study was to evaluate the accuracy of identification by the public and healthcare providers between these two species.

METHODS

Snakebite victims sometimes bring dead snakes to the hospital or have taken pictures of the snake. When this occurred, ED personnel were asked to take a picture of the snake, and forward the picture to the state poison control center. The identification of the snake by witnesses and/or hospital personnel was compared to the identification by the state herpetologist.

RESULTS

During the study period, there were 286 cases of snakebites reported to the state poison control center. Pictures were obtained on 49 of the responsible snakes. All copperhead snakes were identified correctly by callers. However, only 21% of cottonmouth snakes were identified correctly, with 74% of cottonmouth snakes being identified as copperheads. Both public and medical personnel performed poorly on identification of cottonmouth snakes.

CONCLUSIONS

Forty percent of the snakes identified as copperheads were actually cottonmouth snakes. Juvenile cottonmouth snakes were often identified as copperhead snakes.

Air Ambulance Delivery and Administration of Four-factor Prothrombin Complex Concentrate Is Feasible and Decreases Time to Anticoagulation Reversal

OBJECTIVES

The objective was to evaluate the feasibility, safety, and preliminary efficacy of four-factor prothrombin complex concentrate (4-factor PCC) administration by an air ambulance service prior to or during transfer of patients with warfarin-associated major hemorrhage to a tertiary care center for definitive management (interventional arm) compared to patients receiving 4-factor PCC following transfer by air ambulance or ground without 4-factor PCC treatment (conventional arm).

METHODS

This was a retrospective chart review of patients presenting to a large academic medical center. All patients presenting to the emergency department (ED) treated with 4-factor PCC from April 1, 2014, through June 30, 2016, were identified. For this study, only transfer patients with an International Normalized Ratio (INR) > 1.5 actively treated with warfarin were included. The primary outcome was the proportion of patients with an INR ≤ 1.5 upon tertiary care hospital arrival, and the secondary efficacy outcome was difference in time to achievement of INR ≤ 1.5. Additional safety and efficacy objectives included difference in thromboembolic complications, length of stay, intensive care unit length of stay, and inpatient mortality between groups.

RESULTS

Of the 72 included patients, a higher proportion of patients in the interventional group had an INR ≤ 1.5 on ED arrival (proportion difference = 0.82, 95% confidence interval = 0.64-0.92, p < 0.0001) and significantly reduced time to observed INR ≤ 1.5 (181 minutes vs. 541 minutes, p = 0.001). No differences were observed in thromboembolic complications or patient-centered outcomes with the exception of mortality, which was significantly higher in patients in the interventional group. This group was also observed to have lower Glasgow Coma Scale score and higher intubation rates prior to transfer and treatment.

CONCLUSIONS

Dispatch of an air ambulance carrying 4-factor PCC with administration prior to transfer is feasible and leads to more rapid improvement in INR among patients with warfarin-associated major hemorrhage.

Longitudinal Trends in the Prevalence of Diabetes Mellitus in an Urban Emergency Department

OBJECTIVE

The objective of this study was to examine the longitudinal trends in diabetes mellitus (DM) in emergency department (ED) patients and evaluate the factors associated with those trends.

METHODS

We conducted a retrospective analysis of all patients who presented to the ED from 2006 to 2011. The presence of DM, height, and weight were recorded prospectively. The study was conducted in the ED of an urban, academic hospital with an average yearly volume of approximately 62,000 patients. Inclusion criteria were age 16 years and older; presentation to the ED for any reason; and documentation of height, weight, and history of DM. Data were analyzed in 1-year blocks, then examined for trends using linear regression analysis. Data also were examined by obesity class: normal (body mass index [BMI] 20-24.9 kg/m(2)), overweight (BMI 25-29.9 kg/m(2)), obese (BMI 30-39.9 kg/m(2)), and extreme obesity (BMI >40 kg/m(2)).

RESULTS

There was a statistically significant increase in the prevalence of type 2 DM during the study period. The percentage of type 2 DM for all patient visits increased progressively from 10.7% to 16.1% (r(2) 0.97). Progressive increases in yearly type 2 DM prevalence were observed for all BMI classes. The rate of change in the increase of DM was related directly to the degree of obesity. For the normal weight category, the percentage of patients with DM increased 0.5%/year (r(2) 0.92), overweight 0.7%/year (r(2) 0.88), obesity 1.0%/year (r(2) 0.90), and extreme obesity 1.4%/year (r(2) 0.94). Patient age increased slightly for all obesity groups, accounting for a 0.2% to 0.4%/year increase in the prevalence of DM in the population.

CONCLUSIONS

In this longitudinal analysis, we found an increase in the prevalence of patients with DM and an increase in ED visits by patients with DM. Our results indicate that these increases are influenced most significantly by the obesity level of the patient.

Multiscale alterations in bone matrix quality increased fragility in steroid induced osteoporosis

A serious adverse clinical effect of glucocorticoid steroid treatment is secondary osteoporosis, enhancing fracture risk in bone. This rapid increase in bone fracture risk is largely independent of bone loss (quantity), and must therefore arise from degradation of the quality of the bone matrix at the micro- and nanoscale. However, we lack an understanding of both the specific alterations in bone quality n steroid-induced osteoporosis as well as the mechanistic effects of these changes. Here we demonstrate alterations in the nanostructural parameters of the mineralized fibrillar collagen matrix, which affect bone quality, and develop a model linking these to increased fracture risk in glucocorticoid induced osteoporosis. Using a mouse model with an N-ethyl-N-nitrosourea (ENU)-induced corticotrophin releasing hormone promoter mutation (Crh(-120/+)) that developed hypercorticosteronaemia and osteoporosis, we utilized in situ mechanical testing with small angle X-ray diffraction, synchrotron micro-computed tomography and quantitative backscattered electron imaging to link altered nano- and microscale deformation mechanisms in the bone matrix to abnormal macroscopic mechanics. We measure the deformation of the mineralized collagen fibrils, and the nano-mechanical parameters including effective fibril modulus and fibril to tissue strain ratio. A significant reduction (51%) of fibril modulus was found in Crh(-120/+) mice. We also find a much larger fibril strain/tissue strain ratio in Crh(-120/+) mice (~1.5) compared to the wild-type mice (~0.5), indicative of a lowered mechanical competence at the nanoscale. Synchrotron microCT show a disruption of intracortical architecture, possibly linked to osteocytic osteolysis. These findings provide a clear quantitative demonstration of how bone quality changes increase macroscopic fragility in secondary osteoporosis.

Symmetrically reduced stiffness and increased extensibility in compression and tension at the mineralized fibrillar level in rachitic bone

In metabolic bone diseases, the alterations in fibrillar level bone-material quality affecting macroscopic mechanical competence are not well-understood quantitatively. Here, we quantify the fibrillar level deformation in cantilever bending in a mouse model for hereditary rickets (Hpr). Microfocus in-situ synchrotron small-angle X-ray scattering (SAXS) combined with cantilever bending was used to resolve nanoscale fibril strain in tensile- and compressive tissue regions separately, with quantitative backscattered scanning electron microscopy used to measure microscale mineralization. Tissue-level flexural moduli for Hpr mice were significantly (p<0.01) smaller compared to wild-type (~5 to 10-fold reduction). At the fibrillar level, the fibril moduli within the tensile and compressive zones were significantly (p<0.05) lower by ~3- to 5-fold in Hpr mice compared to wild-type mice. Hpr mice have a lower mineral content (24.2±2.1Cawt.% versus 27.4±3.3Ca wt.%) and its distribution was more heterogeneous compared to wild-type animals. However, the average effective fibril modulus did not differ significantly (p>0.05) over ages (4, 7 and 10weeks) between tensile and compressive zones. Our results indicate that incompletely mineralized fibrils in Hpr mice have greater deformability and lower moduli in both compression and tension, and those compressive and tensile zones have similar moduli at the fibrillar level.

A mutation in KCNJ11 causing human hyperinsulinism (Y12X) results in a glucose-intolerant phenotype in the mouse

AIMS/HYPOTHESIS

We identified a mouse with a point mutation (Y12STOP) in the Kcnj11 subunit of the K(ATP) channel. This point mutation is identical to that found in a patient with congenital hyperinsulinism of infancy (HI). We aimed to characterise the phenotype arising from this loss-of-function mutation and to compare it with that of other mouse models and patients with HI.

METHODS

We phenotyped an N-ethyl-N-nitrosourea-induced mutation on a C3H/HeH background (Kcnj11 ( Y12STOP )) using intraperitoneal glucose tolerance testing to measure glucose and insulin plasma concentrations. Insulin secretion and response to incretins were measured on isolated islets.

RESULTS

Homozygous male and female adult Kcnj11 ( Y12STOP ) mice exhibited impaired glucose tolerance and a defect in insulin secretion as measured in vivo and in vitro. Islets had an impaired incretin response and reduced insulin content.

CONCLUSIONS/INTERPRETATION

The phenotype of homozygous Kcnj11 ( Y12STOP ) mice is consistent with that of other Kcnj11-knockout mouse models. In contrast to the patient carrying this mutation homozygously, the mice studied did not have hyperinsulinaemia or hypoglycaemia. It has been reported that HI patients may develop diabetes and our mouse model may reflect this clinical feature. The Kcnj11 ( Y12STOP ) model may thus be useful in further studies of K(ATP) channel function in various cell types and in investigation of the development of hyperglycaemia in HI patients.

Blood lead levels in Mississippi children

Lead is toxic to the nervous system and has been shown to have deleterious effects on the developing nervous systems of children. Widespread exposure to lead has occurred in the past due to the use of lead as a gasoline additive and as a paint additive. Children are usually exposed to lead in the home. Prevention of exposure to lead through monitoring is the most effective way to reduce childhood toxicity. Lead levels were determined in 24,736 children in Mississippi. The percentage of 1-5-year-old children with blood lead levels >10 microg/dL in Mississippi is less than those seen nationally, and mean levels are comparable to national ones. In Mississippi, the age of housing is not a viable predictor of risk for elevated lead levels in children.

A missense mutation in the non-neural G-protein alpha-subunit isoforms modulates susceptibility to obesity

OBJECTIVE

The Gnas transcription unit located within an imprinting region encodes several proteins, including the G-protein alpha-subunit, Gsalpha, its isoform XLalphas and their variant truncated neural forms GsalphaN1 and XLN1. Gsalpha and GsalphaN1 are expressed predominantly from the maternally derived allele in some tissues, whereas XLalphas and XLN1 are expressed exclusively from the paternally derived allele. The relative contribution of full-length Gsalpha and XLalphas, and truncated forms GsalphaN1 and XLN1 to phenotype is unknown. The edematous-small point mutation (Oed-Sml) in exon 6 of Gnas lies downstream of GsalphaN1 and XLN1, but affects full-length Gsalpha and XLalphas, allowing us to address the role of full-length Gsalpha and XLalphas. The aim of this study was therefore to determine the metabolic phenotypes of Oed and Sml mice, and to correlate phenotypes with affected transcripts.

METHODS

Mice were fed standard or high-fat diets and weighed regularly. Fat mass was determined by DEXA analysis. Indirect calorimetry was used to measure metabolic rate. Glucose was measured in tolerance tests and biochemical parameters in fasted plasma samples. Histological analysis of fat and liver was carried out post mortem.

RESULTS

Oed mice are obese on either diet and have a reduced metabolic rate. Sml mice are lean and are resistant to a high-fat diet and have an increased metabolic rate.

CONCLUSION

Adult Oed and Sml mice have opposite metabolic phenotypes. On maternal inheritance, the obese Oed phenotype can be attributed to non-functional full-length Gsalpha. In contrast, on paternal inheritance, Sml mice were small and resistant to the development of obesity on a high-fat diet, effects that can be attributed to mutant XLalphas. Thus, the neural isoforms, GsalphaN1 and XLN1, do not appear to play a role in these metabolic phenotypes.

Nicotinamide nucleotide transhydrogenase: a link between insulin secretion, glucose metabolism and oxidative stress

This paper reviews recent studies on the role of Nnt (nicotinamide nucleotide transhydrogenase) in insulin secretion and detoxification of ROS (reactive oxygen species). Glucose-stimulated insulin release from pancreatic beta-cells is mediated by increased metabolism. This elevates intracellular [ATP], thereby closing KATP channels (ATP-sensitive potassium channels) and producing membrane depolarization, activation of voltage-gated Ca2+ channels, Ca2+ influx and, consequently, insulin secretion. The C57BL/6J mouse displays glucose intolerance and reduced insulin secretion, which results from a naturally occurring deletion in the Nnt gene. Transgenic expression of the wild-type Nnt gene in C57BL/6J mice rescues the phenotype. Knockdown of Nnt in the insulin-secreting cell line MIN6 with small interfering RNA dramatically reduced Ca2+ influx and insulin secretion. Similarly, mice carrying ENU (N-ethyl-N-nitrosourea)-induced loss-of-function mutations in Nnt were glucose intolerant and secreted less insulin during a glucose tolerance test. Islets isolated from these mice showed impaired insulin secretion in response to glucose, but not to the KATP channel blocker tolbutamide. This is explained by the fact that glucose failed to elevate ATP in Nnt mutant islets. Nnt is a nuclear-encoded mitochondrial protein involved in detoxification of ROS. beta-Cells isolated from Nnt mutant mice showed increased ROS production on glucose stimulation. We hypothesize that Nnt mutations enhance glucose-dependent ROS production and thereby impair beta-cell mitochondrial metabolism, possibly via activation of uncoupling proteins. This reduces ATP production and lowers KATP channel activity. Consequently, glucose-dependent electrical activity and insulin secretion are impaired.

A metabolomic comparison of urinary changes in type 2 diabetes in mouse, rat, and human

Type 2 diabetes mellitus is the result of a combination of impaired insulin secretion with reduced insulin sensitivity of target tissues. There are an estimated 150 million affected individuals worldwide, of whom a large proportion remains undiagnosed because of a lack of specific symptoms early in this disorder and inadequate diagnostics. In this study, NMR-based metabolomic analysis in conjunction with multivariate statistics was applied to examine the urinary metabolic changes in two rodent models of type 2 diabetes mellitus as well as unmedicated human sufferers. The db/db mouse and obese Zucker (fa/fa) rat have autosomal recessive defects in the leptin receptor gene, causing type 2 diabetes. 1H-NMR spectra of urine were used in conjunction with uni- and multivariate statistics to identify disease-related metabolic changes in these two animal models and human sufferers. This study demonstrates metabolic similarities between the three species examined, including metabolic responses associated with general systemic stress, changes in the TCA cycle, and perturbations in nucleotide metabolism and in methylamine metabolism. All three species demonstrated profound changes in nucleotide metabolism, including that of N-methylnicotinamide and N-methyl-2-pyridone-5-carboxamide, which may provide unique biomarkers for following type 2 diabetes mellitus progression.

Type-2 diabetes: a cocktail of genetic discovery

Diabetes is one of the most challenging health problems of the 21st century with an alarming increase in the prevalence of type-2 diabetes mellitus (T2DM) and associated conditions such as hypertension, dyslipidemias and obesity. T2DM is a complex genetic disease comprised of many metabolic disorders with a common phenotype of glucose intolerance. Patients with T2DM would have inherited a variety of different genetic factors that together with environmental factors combine as the primary cause. This complicates the genetic study of the disease and means that different methodological approaches are needed if we hope to identify susceptibility genes and genetic variants. The biochemical and physiological processes that underpin T2DM are still unclear although most certainly involve impairment in insulin secretion and insulin action. In this review, we will discuss the most exciting advances in understanding the genetics of T2DM by looking at recent discoveries employing human association studies and candidate genes arising from animal models.

SNP haplotypes in the angiotensin I-converting enzyme (ACE) gene: analysis of Nigerian family data using gamete competition models

Gamete competition models were used to explore the relationships between 13 ACE gene polymorphisms and plasma ACE concentration in a set of Nigerian families. Several markers in the 5' and 3' regions of the gene were significantly associated with ACE concentration (P < 10(-4)). Multi-locus genotypes comprising different combinations of markers from the 5' UTR and the 3' region of the gene were also analysed; in addition to G2350A, in the 3' region, two markers from the 5' UTR (A-5466C and A-240T) were found to be associated with ACE concentration. These results are consistent with reports that have suggested the presence of at least two ACE-linked QTLs, and demonstrate the utility of gamete competition models in the exploratory investigation of the relationship between a quantitative trait and multiple variants in a small genomic region.

A genetic and physiological study of impaired glucose homeostasis control in C57BL/6J mice

AIMS/HYPOTHESIS

C57BL/6J mice exhibit impaired glucose tolerance. The aims of this study were to map the genetic loci underlying this phenotype, to further characterise the physiological defects and to identify candidate genes.

METHODS

Glucose tolerance was measured in an intraperitoneal glucose tolerance test and genetic determinants mapped in an F2 intercross. Insulin sensitivity was measured by injecting insulin and following glucose disposal from the plasma. To measure beta cell function, insulin secretion and electrophysiological studies were carried out on isolated islets. Candidate genes were investigated by sequencing and quantitative RNA analysis.

RESULTS

C57BL/6J mice showed normal insulin sensitivity and impaired insulin secretion. In beta cells, glucose did not stimulate a rise in intracellular calcium and its ability to close KATP channels was impaired. We identified three genetic loci responsible for the impaired glucose tolerance. Nicotinamide nucleotide transhydrogenase (Nnt) lies within one locus and is a nuclear-encoded mitochondrial proton pump. Expression of Nnt is more than sevenfold and fivefold lower respectively in C57BL/6J liver and islets. There is a missense mutation in exon 1 and a multi-exon deletion in the C57BL/6J gene. Glucokinase lies within the Gluchos2 locus and shows reduced enzyme activity in liver.

CONCLUSIONS/INTERPRETATION

The C57BL/6J mouse strain exhibits plasma glucose intolerance reminiscent of human type 2 diabetes. Our data suggest a defect in beta cell glucose metabolism that results in reduced electrical activity and insulin secretion. We have identified three loci that are responsible for the inherited impaired plasma glucose tolerance and identified a novel candidate gene for contribution to glucose intolerance through reduced beta cell activity.

Evaluation of potential adverse health effects resulting from chronic domestic exposure to the organophosphate insecticide methyl parathion

Methyl parathion (MP) was used illegally to spray homes for insect control over approximately an 8-yr period. In an attempt to determine if there were any adverse health effects from this, health-screening evaluations were performed on 353 individuals living in homes that were illegally sprayed. The average subject spent 15.5 h a day in the home. Subjects from homes with high levels of MP (exposure group) were compared to controls that lived in homes with minimal or no MP. Subjects were aware of the levels of MP found in their homes and recall bias was likely. There were no significant differences in the symptoms reported or by the physician assessment of subacute or chronic toxicity between those in the exposure group and controls. No significant differences were found in growth and developmental evaluations. Three subjects were identified who most likely suffered acute toxicity from the initial exposure and were not appropriately diagnosed and treated. Cholinesterase determinations also did not differ between those in the exposure group and controls. When subjects from the exposure group were stratified by the level of MP in their home, those from homes with the highest levels appeared to have an increased likelihood of subacute toxicity and reported an increased number of neuropsychiatric symptoms (OR 2 for both evaluations).

Ethylene Glycol Toxicity

Ethylene glycol is an inexpensive, readily available substance that may be associated with accidental or intentional toxicity. Toxicity from this substance may be encountered in the military and civilian populations. Because it is highly toxic and can result in death if not treated appropriately, it is imperative to recognize the signs and symptoms of intoxication. Two cases are presented and the diagnosis and treatment of ethylene glycol toxicity are discussed. Fomepizole, a new medication for ethylene glycol toxicity, has changed the management of this poisoning. It increases the elimination half-life of ethylene glycol, thus delaying the formation of toxic metabolites.

Association between droperidol use and sudden death in two patients intoxicated with illicit stimulant drugs

Illicit drug intoxication is often a cause of extreme agitation in the emergency department and prehospital settings. Chemical restraint is often required to protect patient as well as health-care providers. Droperidol has commonly been used to sedate extremely agitated patients in the emergency department and psychiatric settings. Its safety has been demonstrated in these settings and in patients who's agitation has been attributed to amphetamine toxicity. We present 2 cases of sudden death following the use of droperidol to sedate 1 patient who was extremely agitated secondary to cocaine intoxication and another secondary to phencyclidine intoxication.

Blunt trauma in the obstetric patient: monitoring practices in the ED

This study was undertaken to determine the usually used approach to fetal monitoring in the emergency department (ED) of the less severely injured obstetric patient who has sustained blunt trauma. A written survey was sent to clinical directors of teaching programs in emergency medicine (EM) with inquiries on the usual way of monitoring, what studies were performed, and the usual disposition of the less-injured obstetric patient. From the 112 teaching programs surveyed in early 1996, there were 87 responses (78%). Seventy-eight percent of programs generally have fetal monitoring performed for 2 to 4 hours in obstetric trauma patients when the trauma is more than minor extremity injury. In 68%, fetal monitoring was not performed in the ED from the time of the initial assessment of fetal heart tones until the mother went to an obstetric area even though the average estimated time to radiographically clear a cervical spine was 36 minutes. In 92% of programs residents are taught cardiotocographic changes indicative of fetal distress but only 15% have such monitoring equipment in their department. However, 51% do have sonographic equipment in their department. Given a patient with a viable fetus who has no abdominal pain, 46% routinely use fetal monitoring if the mechanism is a simple fall whereas 92% use monitoring only if the mechanism is a rollover motor vehicle collision or a strike to the abdomen. It is generally recognized that fetal distress may occur subtly without overt clinical signs and that obstetric area monitoring for a period of several hours should take place. However, most teaching programs do not institute continuous fetal monitoring during the first 30 to 60 minutes that the mother is undergoing her work-up even though residents are taught such monitoring.

Injuries sustained during competitive white-water paddling: a survey of athletes in the 1996 Olympic trials

To examine injury prevalence in competitive paddlers, a cross-sectional, retrospective, written survey of the athletes competing in the four regional Olympic canoe and kayak qualifying races for the United States Canoe and Kayak Team was conducted in the spring of 1996. A total of 375 questionnaires were distributed, of which 54 were completed and returned. Results were reported as the percentage of total injuries. A composite of 271 separate injuries was reported by kayakers during their careers. While 56% of the injuries occurred during training, 40% happened during recreation and 4% during competition. The most frequent injuries were sprains (32%), tendonitis (20%), and chronic musculoskeletal pain (14%). Simple bruises (9%) and infections (8%) occurred with moderate frequency, while severe injuries, such as dislocations (3%) and lacerations (2%), were even less common. About 10% of the paddlers noted a near-drowning event during their careers. Of the injuries noted, 70% were reported as recurrent or chronic. Treatment included rest (37%), physical therapy (23%), medical intervention (34%), and surgical intervention (6%). White-water paddling of canoes and kayaks is a potentially dangerous sport, and competitive paddlers frequently suffer a range of injuries. Most injuries occurred during training; however, the short intense work of racing produced a greater frequency of injuries.

A radiation hybrid transcript map of the mouse genome

Expressed-sequence tag (EST) maps are an adjunct to sequence-based analytical methods of gene detection and localization for those species for which such data are available, and provide anchors for high-density homology and orthology mapping in species for which large-scale sequencing has yet to be done. Species for which radiation hybrid-based transcript maps have been established include human, rat, mouse, dog, cat and zebrafish. We have established a comprehensive first-generation-placement radiation hybrid map of the mouse consisting of 5,904 mapped markers (3,993 ESTs and 1,911 sequence-tagged sites (STSs)). The mapped ESTs, which often originate from small-EST clusters, are enriched for genes expressed during early mouse embryogenesis and are probably different from those localized in humans. We have confirmed by in situ hybridization that even singleton ESTs, which are usually not retained for mapping studies, may represent bona fide transcribed sequences. Our studies on mouse chromosomes 12 and 14 orthologous to human chromosome 14 show the power of our radiation hybrid map as a predictive tool for orthology mapping in humans.

Comparison of fluorescent single-strand conformation polymorphism analysis and denaturing high-performance liquid chromatography for detection of EXT1 and EXT2 mutations in hereditary multiple exostoses

EXT1 and EXT2 are two genes responsible for the majority of cases of hereditary multiple exostoses (HME), a dominantly inherited bone disorder. In order to develop an efficient screening strategy for mutations in these genes, we performed two independent blind screens of EXT1 and EXT2 in 34 unrelated patients with HME, using denaturing high-performance liquid chromatography (DHPLC) and fluorescent single-strand conformation polymorphism analysis (F-SSCP). The mutation likely to cause HME was found in 29 (85%) of the 34 probands: in 22 of these (76%), the mutation was in EXT1; seven patients (24%) had EXT2 mutations. Nineteen of these disease mutations have not been previously reported. Of the 42 different amplicon variants identified in total in the cohort, 40 were detected by DHPLC and 39 by F-SSCP. This corresponds to mutation detection efficiencies of 95% and 93% respectively. We have also found that we can confidently distinguish between different sequence variants in the same fragment using F-SSCP but not DHPLC. In light of this, and the similarly high sensitivities of the two techniques, we propose to continue screening with F-SSCP.

Studies of the lethargic (lh/lh) mouse model of absence seizures: regulatory mechanisms and identification of the lh gene

To understand the cellular and molecular mechanisms that underlie generalized absence seizures sufficiently well to design rational, efficacious new therapies for patients, it is necessary to turn to animal models to gain insights into these mechanisms. The lethargic (lh/lh) mutant mouse expresses spontaneous absence seizures that share behavioral, electrographic, and anticonvulsant profiles with absence seizures in patients. This validates its use to study the mechanisms that underlie absence seizures. This chapter discusses two scientific approaches that involve the use of lh/lh mice. The first part of the chapter discusses neurobiologic approaches used to investigate critical mechanisms that regulate the synchronized burst firing within the thalamocortical network that generates absence seizures. Two of these critical mechanisms have been studied in detail with lh/lh mice. The first critical mechanism involves the required activation of gamma-aminobutyric acid B (GABAB) receptors to generate absence seizures. Because the numbers of GABAB receptors are increased in thalamocortical populations among lh/lh mice compared with littermates without epilepsy, these receptors appear to play a pathophysiologic role in the expression of absence seizures among lh/lh mice. Moreover, there may be a role for GABAB receptors in the generation of absence seizures among humans, because administration of compounds that activate GABAB receptors can produce absence seizures among humans. These findings suggest that GABAB receptor antagonists may represent a new class of antiabsence compounds that will be efficacious against absence seizures among patients. A second critical mechanism that regulates generation of absence seizures involves GABAA receptors in the nucleus reticularis thalami (NRT), a nucleus that sends GABA-ergic afferents to thalamic relay nuclei. Activation of GABAA receptors in the NRT appears to suppress the generation of absence seizures among lh/lh mice and in other models. Moreover, clonazepam may exert its antiabsence actions through this mechanism. Together, these findings suggest that compounds that selectively activate GABAA receptor isoforms expressed in NRT may represent a class of antiabsence drugs that could have fewer side effects than compounds currently used to treat patients. The second part of the chapter discusses a molecular genetic approach to delineation of the mechanisms that underlie absence seizures. Absence seizures among lh/lh mice are caused by a single-gene defect on chromosome 2. If positional cloning and gene isolation techniques are successful, it will be possible to identify the lh disease gene. Subsequent studies of the lh gene product should greatly increase not only our understanding of the pathophysiologic basis for absence seizures among lh/lh mice but also our ability to seek similar mutations in homologous genes in human families that express absence seizures. Accordingly, strategies and progress in cloning and identifying the lh disease gene are presented.

Refined linkage disequilibrium and physical mapping of the gene locus for X-linked dystonia-parkinsonism (DYT3)

X-linked dystonia-parkinsonism (XDP) is a recessive disorder characterized by generalized dystonia with some patients exhibiting parkinsonism. The disease gene, DYT3, is located between DXS453 (DXS993) and DXS559, and strongest linkage disequilibrium is found distal to DXS7117 and proximal to DXS559. We have isolated and analyzed four novel polymorphic markers between DXS7117 and DXS559 and, by haplotype analysis, have narrowed the candidate interval to <350 kb. A sequence-ready contig of 700 kb has been constructed spanning DXS7117 to DXS559 and is composed of 35 PACs, BACs, and cosmids. Nine genes and novel ESTs have been mapped into this contig, and mutations in the coding regions and intron-exon borders of two genes have been excluded as the cause of XDP. Several of the other genes and ESTs located within the contig code for proteins implicated in normal brain development and function and are candidates for DYT3.

Bridging the gap: linking a legacy hospital information system with a filmless radiology picture archiving and communications system within a nonhomogeneous environment

A health level 7 (HL7)-conformant data link to exchange information between the mainframe hospital information system (HIS) of our hospital and our home-grown picture archiving and communications system (PACS) is a result of a collaborative effort between the HIS department and the PACS development team. Based of the ability to link examination requisitions and image studies, applications have been generated to optimise workflow and to improve the reliability and distribution of radiology information. Now, images can be routed to individual radiologists and clinicians; worklists facilitate radiology reporting; applications exist to create, edit, and view reports and images via the internet; and automated quality control now limits the incidence of "lost" cases and errors in image routing. By following the HL7 standard to develop the gateway to the legacy system, the development of a radiology information system for booking, reading, reporting, and billing remains universal and does not preclude the option to integrate off-the-shelf commercial products.

Contrasting effects of ENU induced embryonic lethal mutations of the quaking gene

Multiple alleles of the quaking (qk) gene have a variety of phenotypes ranging in severity from early embryonic death to viable dysmyelination. A previous study identified a candidate gene, QKI, that contains an RNA-binding domain and encodes at least three protein isoforms (QKI-5, -6 and -7). We have determined the genomic structure of QKI, identifying an additional alternative end in cDNAs. Further we have examined the exons and splice sites for mutations in the lethal alleles qkl-1, qkkt1, qkk2, and qkkt3. The mutation in qkl-1 creates a splice site in the terminal exon of the QKI-6 isoform. Missense mutations in the KH domain and the QUA1 domains in qkk2 and qkkt3, respectively, indicate that these domains are of critical functional importance. Although homozygotes for each ENU induced allele die as embryos, their phenotypes as viable compound heterozygotes with qkv differ. Compound heterozygous qkv animals carrying qkkt1, qkk2, and qkkt3 all exhibit a permanent quaking phenotype similar to that of qkv/qkv animals, whereas qkv/qkl-1 animals exhibit only a transient quaking phenotype. The qkl-1 mutation eliminates the QKI-5 isoform, showing that this isoform plays a crucial role in embryonic survival. The transient quaking phenotype observed in qkv/qkl-1 mice indicates that the QKI-6 and QKI-7 isoforms function primarily during myelination, but that QKI-5 may have a concentration-dependent role in early myelination. This mutational analysis demonstrates the power of series of alleles to examine the function of complex loci and suggests that additional mutant alleles of quaking could reveal additional functions of this complex gene.

Transparent image access in a distributed picture archiving and communications system: the Master Database broker

A distributed design is the most cost-effective system for small-to medium-scale picture archiving and communications systems (PACS) implementations. However, the design presents an interesting challenge to developers and implementers: to make stored image data, distributed throughout the PACS network, appear to be centralized with a single access point for users. A key component for the distributed system is a central or master database, containing all the studies that have been scanned into the PACS. Each study includes a list of one or more locations for that particular dataset so that applications can easily find it. Non-Digital Imaging and Communications in Medicine (DICOM) clients, such as our worldwide web (WWW)-based PACS browser, query the master database directly to find the images, then jump to the most appropriate location via a distributed web-based viewing system. The Master Database Broker provides DICOM clients with the same functionality by translating DICOM queries to master database searches and distributing retrieval requests transparently to the appropriate source. The Broker also acts as a storage service class provider, allowing users to store selected image subsets and reformatted images with the original study, without having to know on which server the original data are stored.

Evolution of a filmless digital imaging and communications in medicine-conformant picture archiving and communications system: design issues and lessons learned over the last 3 years

This presentation describes our experience and lessons learned over the first 3 years of developing and operating a filmless picture archiving and communications system (PACS) for all computed tomography (CT), magnetic resonance (MR), ultrasound, and nuclear medicine studies in our hospital. The PACS conforms to the Digital Imaging and Communications in Medicine (DICOM) standard and includes a sophisticated Worldwide Web (WWW)-based interface to complement the regular DICOM services. The PACS has undergone many design modifications from its inception, which have addressed performance, functionality, support, and maintenance issues. The lessons we have learned through making these modifications are described here and may prove to be helpful to anyone planning to deploy a PACS of their own.