The Arabidopsis leaf quantitative atlas: a cellular and subcellular mapping through unified data integration

Quantitative analyses and models are required to connect a plant's cellular organisation with its metabolism. However, quantitative data are often scattered over multiple studies, and finding such data and converting them into useful information is time-consuming. Consequently, there is a need to centralise the available data and to highlight the remaining knowledge gaps. Here, we present a step-by-step approach to manually extract quantitative data from various information sources, and to unify the data format. First, data from Arabidopsis leaf were collated, checked for consistency and correctness and curated by cross-checking sources. Second, quantitative data were combined by applying calculation rules. They were then integrated into a unique comprehensive, referenced, modifiable and reusable data compendium representing an Arabidopsis reference leaf. This atlas contains the metrics of the 15 cell types found in leaves at the cellular and subcellular levels.

Improving photosynthetic efficiency toward food security: Strategies, advances, and perspectives

Photosynthesis in crops and natural vegetation allows light energy to be converted into chemical energy and thus forms the foundation for almost all terrestrial trophic networks on Earth. The efficiency of photosynthetic energy conversion plays a crucial role in determining the portion of incident solar radiation that can be used to generate plant biomass throughout a growth season. Consequently, alongside the factors such as resource availability, crop management, crop selection, maintenance costs, and intrinsic yield potential, photosynthetic energy use efficiency significantly influences crop yield. Photosynthetic efficiency is relevant to sustainability and food security because it affects water use efficiency, nutrient use efficiency, and land use efficiency. This review focuses specifically on the potential for improvements in photosynthetic efficiency to drive a sustainable increase in crop yields. We discuss bypassing photorespiration, enhancing light use efficiency, harnessing natural variation in photosynthetic parameters for breeding purposes, and adopting new-to-nature approaches that show promise for achieving unprecedented gains in photosynthetic efficiency.

Temporal segregation of biosynthetic processes is responsible for metabolic oscillations during the budding yeast cell cycle

Many cell biological and biochemical mechanisms controlling the fundamental process of eukaryotic cell division have been identified; however, the temporal dynamics of biosynthetic processes during the cell division cycle are still elusive. Here, we show that key biosynthetic processes are temporally segregated along the cell cycle. Using budding yeast as a model and single-cell methods to dynamically measure metabolic activity, we observe two peaks in protein synthesis, in the G1 and S/G2/M phase, whereas lipid and polysaccharide synthesis peaks only once, during the S/G2/M phase. Integrating the inferred biosynthetic rates into a thermodynamic-stoichiometric metabolic model, we find that this temporal segregation in biosynthetic processes causes flux changes in primary metabolism, with an acceleration of glucose-uptake flux in G1 and phase-shifted oscillations of oxygen and carbon dioxide exchanges. Through experimental validation of the model predictions, we demonstrate that primary metabolism oscillates with cell-cycle periodicity to satisfy the changing demands of biosynthetic processes exhibiting unexpected dynamics during the cell cycle.

Isotopically non-stationary metabolic flux analysis of heterotrophic Arabidopsis thaliana cell cultures

Fluxes are the ultimate phenotype of metabolism and their accurate quantification is fundamental to any understanding of metabolic networks. Steady state metabolic flux analysis has been the method of choice for quantifying fluxes in heterotrophic cells, but it is unable to measure fluxes during short-lived metabolic states, such as a transient oxidative load. Isotopically non-stationary metabolic flux analysis (INST-MFA) can be performed over shorter timescales (minutes - hours) and might overcome this limitation. INST-MFA has recently been applied to photosynthesising leaves, but agriculturally important tissues such as roots and storage organs, or plants during the night are heterotrophic. Here we outline the application of INST-MFA to heterotrophic plant cells. Using INST-MFA we were able to identify changes in the fluxes supported by phosphoenolpyruvate carboxylase and malic enzyme under oxidative load, highlighting the potential of INST-MFA to measure fluxes during short-lived metabolic states. We discuss the challenges in applying INST-MFA, and highlight further development required before it can be routinely used to quantify fluxes in heterotrophic plant cells.

Measuring ROS and redox markers in plant cells

Reactive oxygen species (ROS) are produced throughout plant cells as a by-product of electron transfer processes. While highly oxidative and potentially damaging to a range of biomolecules, there exists a suite of ROS-scavenging antioxidant strategies that maintain a redox equilibrium. This balance can be disrupted in the event of cellular stress leading to increased ROS levels, which can act as a useful stress signal but, in excess, can result in cell damage and death. As crop plants become exposed to greater degrees of multiple stresses due to climate change, efforts are ongoing to engineer plants with greater stress tolerance. It is therefore important to understand the pathways underpinning ROS-mediated signalling and damage, both through measuring ROS themselves and other indicators of redox imbalance. The highly reactive and transient nature of ROS makes this challenging to achieve, particularly in a way that is specific to individual ROS species. In this review, we describe the range of chemical and biological tools and techniques currently available for ROS and redox marker measurement in plant cells and tissues. We discuss the limitations inherent in current methodology and opportunities for advancement.

Shining a light on NAD- and NADP-based metabolism in plants

The pyridine nucleotides nicotinamide adenine dinucleotide [NAD(H)] and nicotinamide adenine dinucleotide phosphate [NADP(H)] simultaneously act as energy transducers, signalling molecules, and redox couples. Recent research into photosynthetic optimisation, photorespiration, immunity, hypoxia/oxygen signalling, development, and post-harvest metabolism have all identified pyridine nucleotides as key metabolites. Further understanding will require accurate description of NAD(P)(H) metabolism, and genetically encoded fluorescent biosensors have recently become available for this purpose. Although these biosensors have begun to provide novel biological insights, their limitations must be considered and the information they provide appropriately interpreted. We provide a framework for understanding NAD(P)(H) metabolism and explore what fluorescent biosensors can, and cannot, tell us about plant biology, looking ahead to the pressing questions that could be answered with further development of these tools.

A catalog of associations between rare coding variants and COVID-19 outcomes

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes coronavirus disease-19 (COVID-19), a respiratory illness that can result in hospitalization or death. We investigated associations between rare genetic variants and seven COVID-19 outcomes in 543,213 individuals, including 8,248 with COVID-19. After accounting for multiple testing, we did not identify any clear associations with rare variants either exome-wide or when specifically focusing on (i) 14 interferon pathway genes in which rare deleterious variants have been reported in severe COVID-19 patients; (ii) 167 genes located in COVID-19 GWAS risk loci; or (iii) 32 additional genes of immunologic relevance and/or therapeutic potential. Our analyses indicate there are no significant associations with rare protein-coding variants with detectable effect sizes at our current sample sizes. Analyses will be updated as additional data become available, with results publicly browsable at https://rgc-covid19.regeneron.com.

In Vivo NADH/NAD+ Biosensing Reveals the Dynamics of Cytosolic Redox Metabolism in Plants

NADH and NAD+ are a ubiquitous cellular redox couple. Although the central role of NAD in plant metabolism and its regulatory role have been investigated extensively at the biochemical level, analyzing the subcellular redox dynamics of NAD in living plant tissues has been challenging. Here, we established live monitoring of NADH/NAD+ in plants using the genetically encoded fluorescent biosensor Peredox-mCherry. We established Peredox-mCherry lines of Arabidopsis (Arabidopsis thaliana) and validated the biophysical and biochemical properties of the sensor that are critical for in planta measurements, including specificity, pH stability, and reversibility. We generated an NAD redox atlas of the cytosol of living Arabidopsis seedlings that revealed pronounced differences in NAD redox status between different organs and tissues. Manipulating the metabolic status through dark-to-light transitions, respiratory inhibition, sugar supplementation, and elicitor exposure revealed a remarkable degree of plasticity of the cytosolic NAD redox status and demonstrated metabolic redox coupling between cell compartments in leaves. Finally, we used protein engineering to generate a sensor variant that expands the resolvable NAD redox range. In summary, we established a technique for in planta NAD redox monitoring to deliver important insight into the in vivo dynamics of plant cytosolic redox metabolism.

Thermal transport of helium-3 in a strongly confining channel

The investigation of transport properties in normal liquid helium-3 and its topological superfluid phases provides insights into related phenomena in electron fluids, topological materials, and putative topological superconductors. It relies on the measurement of mass, heat, and spin currents, due to system neutrality. Of particular interest is transport in strongly confining channels of height approaching the superfluid coherence length, to enhance the relative contribution of surface excitations, and suppress hydrodynamic counterflow. Here we report on the thermal conduction of helium-3 in a 1.1 μm high channel. In the normal state we observe a diffusive thermal conductivity that is approximately temperature independent, consistent with interference of bulk and boundary scattering. In the superfluid, the thermal conductivity is only weakly temperature dependent, requiring detailed theoretical analysis. An anomalous thermal response is detected in the superfluid which we propose arises from the emission of a flux of surface excitations from the channel.

Discovery of novel plasma biomarkers for future incident venous thromboembolism by untargeted synchronous precursor selection mass spectrometry proteomics

Essentials Discovery of predictive biomarkers of venous thromboembolism (VTE) may aid risk stratification. A case-control study where plasma was sampled before the occurrence of VTE was established. We generated untargeted plasma proteomic profiles of 200 individuals by use of mass spectrometry. Assessment of the biomarker potential of 501 proteins yielded 46 biomarker candidates.

ABSTRACT

Background Prophylactic anticoagulant treatment may substantially reduce the incidence of venous thromboembolism (VTE) but entails considerable risk of severe bleeding. Identification of individuals at high risk of VTE through the use of predictive biomarkers is desirable in order to achieve a favorable benefit-to-harm ratio. Objective We aimed to identify predictive protein biomarker candidates of VTE. Methods We performed a case-control study of 200 individuals that participated in the Tromsø Study, a population-based cohort, where blood samples were collected before the VTE events occurred. Untargeted tandem mass tag-synchronous precursor selection-mass spectrometry (TMT-SPS-MS3)-based proteomic profiling was used to study the plasma proteomes of each individual. Results Of the 501 proteins detected in a sufficient number of samples to allow multivariate analysis, 46 proteins were associated with VTE case-control status with P-values below the 0.05 significance threshold. The strongest predictive biomarker candidates, assessed by statistical significance, were transthyretin, vitamin K-dependent protein Z and protein/nucleic acid deglycase DJ-1. Conclusions Our untargeted approach of plasma proteome profiling revealed novel predictive biomarker candidates of VTE and confirmed previously reported candidates, thereby providing conceptual support for the validity of the study. A larger nested case-control study will be conducted to validate our findings.

Fabrication of microfluidic cavities using Si-to-glass anodic bonding

We demonstrate the fabrication of ∼1.08 μm deep microfluidic cavities with characteristic size as large as 7 mm × 11 mm or 11 mm diameter, using a silicon-glass anodic bonding technique that does not require posts to act as separators to define cavity height. Since the phase diagram of ³He is significantly altered under confinement, posts might act as pinning centers for phase boundaries. The previous generation of cavities relied on full wafer-bonding which is more prone to failure and requires dicing post-bonding, whereas these cavities are made by bonding a pre-cut piece of Hoya SD-2 glass to a patterned piece of silicon in which the cavity is defined by etching. Anodic bonding was carried out at 425 °C with 200 V, and we observe that pressurizing the cavity to failure (>30 bars pressure) results in glass breaking, rather than the glass-silicon bond separation. In this article, we discuss the detailed fabrication of the cavity, its edges, and details of the junction between the coin silver fill line and the silicon base of the cavity that enables a low internal-friction joint. This feature is important for mass coupling torsional oscillator experimental assays of the superfluid inertial contribution where a high quality factor (Q) improves frequency resolution. The surface preparation that yields well-characterized smooth surfaces to eliminate pinning sites, the use of transparent glass as a cover permitting optical access, low temperature capability, and attachment of pressure-capable ports for fluid access may be features that are important in other applications.

Joint effects of prothrombotic genotypes and body height on the risk of venous thromboembolism: the Tromsø study

Essentials Body height and prothrombotic genotypes are associated with risk of venous thromboembolism (VTE). The joint effect of prothrombotic genotypes and tall stature on VTE risk is scarcely investigated. We investigated the joint effect of prothrombotic genotypes and tall stature on VTE risk. Prothrombotic genotypes did not yield excess risk of VTE in subjects with a tall stature.

SUMMARY

Background Studies have reported synergistic effects of prothrombotic single-nucleotide polymorphisms (SNPs) and obesity on the risk of venous thromboembolism (VTE). Tall stature is associated with an increased VTE risk, but the joint effect of prothrombotic genotypes and tall stature on the VTE risk is unknown. Aims To investigate the joint effects of prothrombotic genotypes and tall stature on the VTE risk. Methods Cases with incident VTE (n = 676) and a randomly selected age-weighted subcohort (n = 1842) were sampled from the Tromsø study (cohort follow-up: 1994-2012). DNA was genotyped for rs6025 (factor V Leiden), rs1799963 (FII), rs8176719 (ABO blood group), rs2066865 (fibrinogen-γ), and rs2036914 (FIX). Age-adjusted and sex-adjusted hazard ratios (HRs) of VTE were calculated by categories of risk alleles (de Haan 5-SNP score: 0-1, 2-3, and ≥ 4) and body height (< 40th, 40th-80th and > 80th percentiles). Results The VTE risk increased by increasing category of body height, and subjects with height ≥ 178 cm had a two-fold higher VTE risk (HR 2.03; 95% confidence interval [CI] 1.51-2.73) than those with height ≤ 165 cm. The VTE risk also increased across categories of risk alleles. However, the combination of a tall stature and risk alleles, either individual SNPs or risk score, did not result in an excess VTE risk. Subjects with four or more risk alleles and height ≥ 178 cm had a two-fold (HR 2.08; 95% CI 1.24-3.52) higher VTE risk than subjects ≤ 165 cm with no risk allele or one risk allele. Conclusions In contrast to obesity, the presence of prothrombotic genotypes did not result in an excess VTE risk in subjects with a tall stature.

Observation of a new superfluid phase for 3He embedded in nematically ordered aerogel

In bulk superfluid ³He at zero magnetic field, two phases emerge with the B-phase stable everywhere except at high pressures and temperatures, where the A-phase is favoured. Aerogels with nanostructure smaller than the superfluid coherence length are the only means to introduce disorder into the superfluid. Here we use a torsion pendulum to study ³He confined in an extremely anisotropic, nematically ordered aerogel consisting of ∼10 nm-thick alumina strands, spaced by ∼100 nm, and aligned parallel to the pendulum axis. Kinks in the development of the superfluid fraction (at various pressures) as the temperature is varied correspond to phase transitions. Two such transitions are seen in the superfluid state, and we identify the superfluid phase closest to T_c at low pressure as the polar state, a phase that is not seen in bulk ³He.

Anisotropic disorder is predicted to change the stability of the superfluid state in ³He and leads to new phases. Here, Zhelev et al. report signatures of the phase transitions in ³He confined in an extremely anisotropic ordered aerogel including a new polar phase.

Genetic and epigenetic profiling of CLL disease progression reveals limited somatic evolution and suggests a relationship to memory-cell development

We examined genetic and epigenetic changes that occur during disease progression from indolent to aggressive forms of chronic lymphocytic leukemia (CLL) using serial samples from 27 patients. Analysis of DNA mutations grouped the leukemia cases into three categories: evolving (26%), expanding (26%) and static (47%). Thus, approximately three-quarters of the CLL cases had little to no genetic subclonal evolution. However, we identified significant recurrent DNA methylation changes during progression at 4752 CpGs enriched for regions near Polycomb 2 repressive complex (PRC2) targets. Progression-associated CpGs near the PRC2 targets undergo methylation changes in the same direction during disease progression as during normal development from naive to memory B cells. Our study shows that CLL progression does not typically occur via subclonal evolution, but that certain CpG sites undergo recurrent methylation changes. Our results suggest CLL progression may involve developmental processes shared in common with the generation of normal memory B cells.

Evidence for the role of EPHX2 gene variants in anorexia nervosa

Anorexia nervosa (AN) and related eating disorders are complex, multifactorial neuropsychiatric conditions with likely rare and common genetic and environmental determinants. To identify genetic variants associated with AN, we pursued a series of sequencing and genotyping studies focusing on the coding regions and upstream sequence of 152 candidate genes in a total of 1205 AN cases and 1948 controls. We identified individual variant associations in the Estrogen Receptor-ß (ESR2) gene, as well as a set of rare and common variants in the Epoxide Hydrolase 2 (EPHX2) gene, in an initial sequencing study of 261 early-onset severe AN cases and 73 controls (P=0.0004). The association of EPHX2 variants was further delineated in: (1) a pooling-based replication study involving an additional 500 AN patients and 500 controls (replication set P=0.00000016); (2) single-locus studies in a cohort of 386 previously genotyped broadly defined AN cases and 295 female population controls from the Bogalusa Heart Study (BHS) and a cohort of 58 individuals with self-reported eating disturbances and 851 controls (combined smallest single locus P<0.01). As EPHX2 is known to influence cholesterol metabolism, and AN is often associated with elevated cholesterol levels, we also investigated the association of EPHX2 variants and longitudinal body mass index (BMI) and cholesterol in BHS female and male subjects (N=229) and found evidence for a modifying effect of a subset of variants on the relationship between cholesterol and BMI (P<0.01). These findings suggest a novel association of gene variants within EPHX2 to susceptibility to AN and provide a foundation for future study of this important yet poorly understood condition.

Enrichment of cis-regulatory gene expression SNPs and methylation quantitative trait loci among bipolar disorder susceptibility variants

We conducted a systematic study of top susceptibility variants from a genome-wide association (GWA) study of bipolar disorder to gain insight into the functional consequences of genetic variation influencing disease risk. We report here the results of experiments to explore the effects of these susceptibility variants on DNA methylation and mRNA expression in human cerebellum samples. Among the top susceptibility variants, we identified an enrichment of cis regulatory loci on mRNA expression (eQTLs), and a significant excess of quantitative trait loci for DNA CpG methylation, hereafter referred to as methylation quantitative trait loci (mQTLs). Bipolar disorder susceptibility variants that cis regulate both cerebellar expression and methylation of the same gene are a very small proportion of bipolar disorder susceptibility variants. This finding suggests that mQTLs and eQTLs provide orthogonal ways of functionally annotating genetic variation within the context of studies of pathophysiology in brain. No lymphocyte mQTL enrichment was found, suggesting that mQTL enrichment was specific to the cerebellum, in contrast to eQTLs. Separately, we found that using mQTL information to restrict the number of single-nucleotide polymorphisms studied enhances our ability to detect a significant association. With this restriction a priori informed by the observed functional enrichment, we identified a significant association (rs12618769, P(bonferroni)<0.05) from two other GWA studies (TGen+GAIN; 2191 cases and 1434 controls) of bipolar disorder, which we replicated in an independent GWA study (WTCCC). Collectively, our findings highlight the importance of integrating functional annotation of genetic variants for gene expression and DNA methylation to advance the biological understanding of bipolar disorder.

Common genetic variation near the connexin-43 gene is associated with resting heart rate in African Americans: a genome-wide association study of 13,372 participants

BACKGROUND

Genome-wide association studies have identified several genetic loci associated with variation in resting heart rate in European and Asian populations. No study has evaluated genetic variants associated with heart rate in African Americans.

OBJECTIVE

To identify novel genetic variants associated with resting heart rate in African Americans.

METHODS

Ten cohort studies participating in the Candidate-gene Association Resource and Continental Origins and Genetic Epidemiology Network consortia performed genome-wide genotyping of single nucleotide polymorphisms (SNPs) and imputed 2,954,965 SNPs using HapMap YRI and CEU panels in 13,372 participants of African ancestry. Each study measured the RR interval (ms) from 10-second resting 12-lead electrocardiograms and estimated RR-SNP associations using covariate-adjusted linear regression. Random-effects meta-analysis was used to combine cohort-specific measures of association and identify genome-wide significant loci (P≤2.5×10(-8)).

RESULTS

Fourteen SNPs on chromosome 6q22 exceeded the genome-wide significance threshold. The most significant association was for rs9320841 (+13 ms per minor allele; P = 4.98×10(-15)). This SNP was approximately 350 kb downstream of GJA1, a locus previously identified as harboring SNPs associated with heart rate in Europeans. Adjustment for rs9320841 also attenuated the association between the remaining 13 SNPs in this region and heart rate. In addition, SNPs in MYH6, which have been identified in European genome-wide association study, were associated with similar changes in the resting heart rate as this population of African Americans.

CONCLUSIONS

An intergenic region downstream of GJA1 (the gene encoding connexin 43, the major protein of the human myocardial gap junction) and an intragenic region within MYH6 are associated with variation in resting heart rate in African Americans as well as in populations of European and Asian origin.

Modification of the 3He phase diagram by anisotropic disorder

Motivated by the recent prediction that uniaxially compressed aerogel can stabilize the anisotropic A phase over the isotropic B phase, we measure the pressure dependent superfluid fraction of (3)He entrained in 10% axially compressed, 98% porous aerogel. We observe that a broad region of the temperature-pressure phase diagram is occupied by the metastable A phase. The reappearance of the A phase on warming from the B phase, before superfluidity is extinguished at T(c), is in contrast to its absence in uncompressed aerogel. The phase diagram is modified from that of pure (3)He, with the disappearance of the polycritical point (PCP) and the appearance of a region of A phase extending below the PCP of bulk (3)He, even in zero applied magnetic field. The expected alignment of the A phase texture by compression is not observed.

Generalized frequency coding: a method of preparing polymorphic multistate characters for phylogenetic analysis

A new method of coding polymorphic multiistate characters for phylogenetic analysis is presented. By dividing such characters into subcharacters, their frequency distributions can be represented with discrete states. Differential weighting is used to counter the effect of representing one character with multiple characters. The new method, generalized frequency coding (GFC), is potentially superior to previously used methods in that it incorporates more information and is applicable to both qualitative and quantitative characters. When applied to a previously published data set that includes both types of polymorphic multistate characters, the method performed well, as assessed with g1 and nonparametric bootstrap statistics and giving results congruent with those of other studies. The data set was also used to compare GFC with both gap-weighting and Manhattan distance step matrix coding. On these grounds and for philosophical reasons, we consider GFC to be a better estimator of phylogeny.

A new species of Osteocephalus (Anura: Hylidae) from Guyana

A new member of the genus Osteocephalus is described from the Pakaraima mountains of western Guyana. This species is the smallest known member of the genus and is probably closely related to O. subtilis. Both share a small size (less than 40 mm snout-vent length), large and bulgy eyes directed somewhat rostrally, green bones, smooth and brownish dorsal skin, relatively short and truncate snout, small tympanum, subgular and laterally expanded vocal sac, poorly developed subarticular and supernumerary tubercles, a supra-anal glandular ridge, and cream-white venter and subocular region. The new species can be distinguished from O. subtilis by the Buff iris (vs black), smaller overall size (32.7 vs 35.8-38.8 mm snout-vent length), relatively larger toe disks, and less developed foot webbing. The cranium of the new species is well ossified, relatively reduced in width between the orbits, without an exposed frontoparietal fontanelle and with the anterior arm of the squamosal extending to about half the distance to the maxillary. The vocal sac is subgularly poorly developed and possess lateral extensions to the area behind the jaw angles. Well developed supraocular and suprasquamosal cartilages give support to the enlarged eyes of this species.

A new species of arboreal pitviper from the Atlantic versant of northern Central America

A new species of green, prehensile-tailed pitviper of the genus Bothriechis is described from the Atlantic slopes of eastern Guatemala and western Honduras. This species appears to be most closely related to B. bicolor of the Pacific versant of Chiapas (Mexico) and Guatemala. Several other species of Bothriechis occur on the Atlantic versant of northern Central America, including two montane species, B. aurifer and B. marchi but, with one possible exception, these are not known to be sympatric with the new species and occur in different mountain ranges. The widespread B. schlegelii occurs up to at least 900 m on the Sierra de Caral, where the lowest elevation recorded for the new species is 885 m.

Physiological responses associated with feigned death in the American opossum

Heart rate, respiratory rate and body temperature of four free-ranging American opossums, Didelphis marsupialis of both sexes (2.47 +/- 0.27 kg; mean +/- SE), were monitored during mild provocation and during death feigning ('play possum'). Mild provocations, caused by the approach of either man or dog, elicited a freezing response. The behavioural response was accompanied by a 12% decrease in heart rate (218 +/- 11 to 192 +/- 10 beats X min-1; mean +/- SE) and a 31% reduction in respiratory rate (26.7 +/- 1.7 to 18.4 +/- 1.4 breaths X min-1) from pre-stimulation values. Death feigning was induced by vigorous tactile stimulation by either investigator or dog. The response was marked by immobility, prone position and stiffness of the body. Mouth was open and the animal showed no response to touch or pinching. Death feigning was always accompanied by salivation, urination, defaecation and erection of the penis (in males). Heart rate decreased 46% (222 +/- 10.6 to 120 +/- 17 beats X min-1) and respiratory rate was reduced 30% (27.4 +/- 1.5 to 19.2 +/- 2.3 breaths X min-1) from pre-stimulation values. Body temperature dropped from 34.8 +/- 0.2 to 34.2 +/- 0.3 degrees C. During death feigning the animal was fully conscious as was evident by heart rate reduction during the re-approach of the dog. Atropine treatment had no obvious effect on behaviour but abolished the bradycardia when compared to pre-stimulus condition.

Physiological thermoregulation of mature alligators

A 67.1 kg alligator (Alligator mississippiensis), tested in air, heated twice as fast as it cooled. The cooling thermal time constant was 425 min while alive. Warming and cooling thermal time constants were 421 min after death. The thermal time constant was not appropriate in describing warming in air of mature alligators. Surface and subdermal heat flow measurements of the 67.1 kg animal indicate greater blood flow in the skin during warming compared to cooling. Two mature alligators, 49.9 and 103 kg, were heated and cooled in water. Warming time constants were 67 and 110 min respectively. Cooling time constants were 180 and 246 min. Data from this study were combined with previously published thermal time constants for alligators providing regression equations for alligators ranging from 37 g to 103 kg. Regression equations for alligators tested in water are: tau w = 8.81 M050 tau c = 12.6 M0.62. Time constants (tau) are in minutes (w = warming, c = cooling) with all measurements in stirred water; mass, M, is in kg. Thermal conductance and metabolism data are combined to provide an estimate of the amount the body temperature of theoretical alligators ranging from 50 g to 1000 kg would be elevated by metabolism. A body temperature of 34.2 degrees C is predicted for a 1000 kg theoretical alligator in 30 degrees C water.

Effect of body temperature on ventilatory control in the alligator

Pulmonary ventilation and arterial blood acid-base balance were measured in six unanesthetized alligators, Alligator mississipiensis, at 15, 25, and 35 degree C. The animals exhibited pronounced ventilatory responses to hypercapnia at all temperatures studied. Arterial PCO2 increased and pH decreased with increases in body temperature during both normocapnia and hypercapnia. The fractional dissociation of imidazole (alpha Pr) remained constant with changes in body temperature during normocapnia, but increased with temperature during hypercapnia. Ventilatory sensitivity, defined as delta (VE/VO2/delta (alpha Pr), was independent of body temperature. We conclude that the control of breathing in the alligator is a physiological defense of alpha Pr and that ventilatory responses occur following nontemperature-induced changes in blood acid-base balance, which tend to return alpha Pr to a normal value.

Acute toxicity of methanol in the folate-deficient acatalasemic mouse

Formate acidosis is the chief measurable biochemical characteristic of acute methanol toxicity in man. Its marked elevation in the blood stream of primates has been proposed to account for their much greater susceptibility versus rodents to methanol poisoning. Therefore, a study was undertaken to assess whether folic acid deficient (FAD) mice which accumulate formate are much more sensitive to the lethal effects of this alcohol than folic acid sufficient (FAS) mice. Moreover, because some formate is oxidized by catalase-H2O2 in rodents, but not in primates, we also compared the urinary excretion and blood plasma accumulation of formate and the methanol sensitivity of acatalasemic mice. Methanol-dosed C57BL/6Csb (acatalasemic) mice exhibit slightly lower LD50S than CSa (normal catalase) mice, irrespective of their folate state. CSb-FAD mice excreted much more formate and developed higher plasma formate concentrations (11-17 mM) than identically dosed CSa-FAD animals (6 mM). However, in no instance did a folate deficiency produce a large reciprocal decrease in the oral or i.p. LD50 that would be expected from a huge increase (greater than 10-fold) in the 24-h blood plasma formate level. A low methionine (0.2%) intake did not decrease the oral methanol LD50 of CSb-FAD mice, although excess dietary methionine (1.8%) did lower it from 7.1 to 6.4 g/kg. Methanol treated (4 g/kg) Csb-FAD mice excreted 30.8-48.2% of the oral dose as urinary formate, depending on the level of dietary methionine. Csb-FAS and -FAD mice which were given 2 g/kg sodium formate orally (LD50 = 4.7 and 3.7 g/kg) cleared this dose from the blood within 24 h and excreted 58% and 76% of it, respectively, in the urine. Our results indicate that the plasma formate concentration does not correlate well with methanol lethality in Csb-FAS vs. -FAD mice. In addition, urinary excretion, not oxidation, is the primary means by which mice, and probably rats, eliminate high levels of blood formate. Since the Csb-FAD mouse attains high plasma formate levels and low blood pH-values similar to those which have been reported for methanol poisoned monkeys, it appears to be of value as an inexpensive small animal model for further studies of lethal methanol toxicity and the contribution of formate to this process.

Various pharmacokinetic parameters in relation to enzyme-inducing abilities of 1,2,4-trichlorobenzene and 1,2,4-tribromobenzene

1,2,4-Trichlorobenzene (TCB) and 1,2,4-tribromobenzene (TBB) were administered for 7 d to rats at a dose of 1 mmol/kg.d. The animals were sacrificed at various times to observe the decline in enzyme induction. Carbon 14-labeled TCB and TBB were administered and the disposition of the radioactivity was determined. The influence of starvation and phenobarbital on the inductive effects of TCB and TBB was observed. p-Nitroanisole demethylation and EPN (O-ethyl O-p-nitrophenyl phenylphosphonothionate) detoxification increases declined with time but were still elevated 16 d after the last dose of TBB. Cytochorme P-450 and NADPH-cytochrome c reductase were alsoinduced. Tissue analysis showed greater retention of TBB than of TCB, with highest levels in the fats. More TCB than TBB was excreted in the urine, and fecal excretion was only 5-10% of the dose. The highest enzyme levels were found after 4 d of starvation following the 7 d of treatment and 6 d of recovery. Starvation resulted in increased plasma, fat, and liver concentrations and increased urinary excretion of 14C after TBB dosing. Phenobarbital treatment decreased the levels of induction by the halogenated benzenes. The results demonstrate that, on an equimolar basis, TBB leads to higher levels of induction that are maintained for longer periods than does TCB. Treatments, such as starvation and phenobarbital, that after storage in fat of these materials change the decline with time of the level of induction.

Induction of xenobiotic metabolism in rat liver by chlorinated biphenyl ether isomers

Chlorinated diphenyl ether isomers were administered to rats at doses of 10 mumols/kg/day po for 3 days. Decachlorodiphenyl ether caused increases in EPN detoxification, NADPH cytochrome c reductase and cytochrome P-450 but did not alter aryl hydrocarbon hydroxylase (AHH). It caused a shift in P450 absorption to 448 nm. 2,4,5,2',4'-Pentachlorodiphenyl ether increased EPN detoxification and cytochrome P-450. 2,4,5,3',4'-Pentachlorodiphenyl ether increased AHH and cytochrome P-450 and caused a shift in the absorption maximum to 448 nm. 3,4,2',4'-Tetrachlorodiphenyl ether induced AHH. 2,4'-Dichlorodiphenyl ether, 4,4'-dichlorodiphenyl ether, 2,4,2'-trichlorodiphenyl ether, 2,4,4'-trichlorodiphenyl ether, 3,4,2'-trichlorodiphenyl ether and 3,4,2',4'-tetrachlorodiphenyl ether did not alter any of these parameters. The position and degree of chlorination are important in determining the extent of induction and pathways induced.

Cutaneous blood flow during heating and cooling in the American alligator

Nine alligators, Alligator mississippiensis, were injected with 133Xe and the clearance half times measured in response to heating and cooling. Mean half times for thermostable, heating, and cooling conditions were 12.2, 8.6, and 28.3 min, respectively, indicating cutaneous vasodilation in response to local heating and reduced blood flow during cooling. Alterations of cutaneous blood flow occurred before changes in body temperature or heart rate. Warming portions of the animal while shading the injection site resulted in reduced blood flow when heat loss occurred. Skin thickness (S in cm) was related to body mass (M in kg) as S = 0.08 M0.38. Cutaneous blood flow per unit area was found to increase with increasing body mass from approximately 0.0025 to 0.025 ml blood-cm-2 of skin-min-1 during warming and from 0.0018 to 0.0045 during cooling for the 0.18--8.6 kg animals, respectively.

Cutaneous heat flow during heating and cooling in Alligator mississipiensis

Direct in vivo measurement of heat flow across the skin of the American alligator (Alligator mississipiensis) showed increased heat flow during warming. Mean values at 25 degrees C during warming (15-35 degrees C) in air (airspeed 300 cm/s) were 17.9 +/- 92 SE cal/cm2 per h (mean alligator wt 3.27 kg). Cooling heat flow at the same temperature was 13.6 +/- 0.57 cal/cm2 per h. Subdermal heat flow was reduced during warming and was not significantly different from cutaneous heat flow during cooling. This indicated that the alligator was able to control its rate of heat exchange with the environment by altering cutaneous perfusion. Atropine, phenoxybenzamine, nitroglycerin, and Xylocaine did not affect cutaneous heat flow or heating and cooling rates. Atropine blocked bradycardia during cooling.

Multichannel subcarrier ECG, respiration, and temperature biotelemetry system

A three-channel biotelemetry system measuring ECG, respiration, and body temperature is described. The transmitter employs a 6-kHz subcarrier oscillator and is small enough for surgical implantation in animals the size of rats or larger. The frequency modulated 6-kHz tone from the reciver can be demodulated directly or recorded on an inexpensive cassette tape recorder for future analysis. The transmitter cost is approximately $35.00 and measures 3 times 1 cm. A battery life of several weeks and transmitter range of 10-100 m is typical. Transmission is on the FM broadcast band (88-108 MHz) and reception from an inexpensive FM portable receiver is possible.