Climate genomics-Geoscientists, ecologists, and geneticists must reinforce their collaborations to confront climate change

Geoscientists and ecologists alike must confront the impact of climate change on ecosystems and the services they provide. In the marine realm, major changes are projected in net primary and export production, with significant repercussions on food security, carbon storage, and climate system feedbacks. However, these projections do not include the potential for rapid linear evolution to facilitate adaptation to environmental change. Climate genomics confronts this challenge by assessing the vulnerability of ecosystem services to climate change. Because DNA is the primary biological repository of detectable environmentally selected mutations (showing evidence of change before impacts arise in morphological or metabolic patterns), genomics provides a window into selection in response to climate change, while also recording neutral processes deriving from stochastic mechanisms (Lowe et al., Trends in Ecology & Evolution, 2017; 32:141-152). Due to the revolution afforded by sequencing technology developments, genomics can now meet ecologists and climate scientists in a cross-disciplinary space fertile for collaborations. Collaboration between geoscientists, ecologists, and geneticists must be reinforced in order to combine modeling and genomics approaches at every scale to improve our understanding and the management of ecosystems under climate change. To this end, we present advances in climate genomics from plankton to larger vertebrates, stressing the interactions between modeling and genomics, and identifying future work needed to develop and expand the field of climate genomics.

Ocean-wide comparisons of mesopelagic planktonic community structures

For decades, marine plankton have been investigated for their capacity to modulate biogeochemical cycles and provide fishery resources. Between the sunlit (epipelagic) layer and the deep dark waters, lies a vast and heterogeneous part of the ocean: the mesopelagic zone. How plankton composition is shaped by environment has been well-explored in the epipelagic but much less in the mesopelagic ocean. Here, we conducted comparative analyses of trans-kingdom community assemblages thriving in the mesopelagic oxygen minimum zone (OMZ), mesopelagic oxic, and their epipelagic counterparts. We identified nine distinct types of intermediate water masses that correlate with variation in mesopelagic community composition. Furthermore, oxygen, NO3- and particle flux together appeared as the main drivers governing these communities. Novel taxonomic signatures emerged from OMZ while a global co-occurrence network analysis showed that about 70% of the abundance of mesopelagic plankton groups is organized into three community modules. One module gathers prokaryotes, pico-eukaryotes and Nucleo-Cytoplasmic Large DNA Viruses (NCLDV) from oxic regions, and the two other modules are enriched in OMZ prokaryotes and OMZ pico-eukaryotes, respectively. We hypothesize that OMZ conditions led to a diversification of ecological niches, and thus communities, due to selective pressure from limited resources. Our study further clarifies the interplay between environmental factors in the mesopelagic oxic and OMZ, and the compositional features of communities.

Plankton biogeography in the 21st century and impacts of climate change: advances through genomics

This article summarizes recent advances in our knowledge of plankton biogeography obtained by genomic approaches and the impacts of global warming on it. Large-scale comparison of the genomic content of samples of different plankton size fractions revealed a partitioning of the oceans into genomic provinces and the impact of major oceanic currents on them. By defining ecological niches, these provinces are extrapolated to all oceans, with the exception of the Arctic Ocean. By the end of the 21st century, a major restructuring of these provinces is projected in response to a high emission greenhouse gas scenario over 50% of the surface of the studied oceans. Such a restructuring could lead to a decrease in export production by 4%. Finally, obtaining assembled sequences of a large number of plankton genomes defining this biogeography has allowed to better characterize the genomic content of the provinces and to identify the species structuring them. These genomes similarly enabled a better description of potential future changes of plankton communities under climate change.

Genomic evidence for global ocean plankton biogeography shaped by large-scale current systems

Biogeographical studies have traditionally focused on readily visible organisms, but recent technological advances are enabling analyses of the large-scale distribution of microscopic organisms, whose biogeographical patterns have long been debated. Here we assessed the global structure of plankton geography and its relation to the biological, chemical, and physical context of the ocean (the ‘seascape’) by analyzing metagenomes of plankton communities sampled across oceans during the Tara Oceans expedition, in light of environmental data and ocean current transport. Using a consistent approach across organismal sizes that provides unprecedented resolution to measure changes in genomic composition between communities, we report a pan-ocean, size-dependent plankton biogeography overlying regional heterogeneity. We found robust evidence for a basin-scale impact of transport by ocean currents on plankton biogeography, and on a characteristic timescale of community dynamics going beyond simple seasonality or life history transitions of plankton.

Oceans are brimming with life invisible to our eyes, a myriad of species of bacteria, viruses and other microscopic organisms essential for the health of the planet. These ‘marine plankton’ are unable to swim against currents and should therefore be constantly on the move, yet previous studies have suggested that distinct species of plankton may in fact inhabit different oceanic regions. However, proving this theory has been challenging; collecting plankton is logistically difficult, and it is often impossible to distinguish between species simply by examining them under a microscope. However, within the last decade, a research schooner called Tara has travelled the globe to gather thousands of plankton samples. At the same time, advances in genomics have made it possible to identify species based only on fragments of their DNA sequence.

To understand the hidden geography of plankton communities in Earth’s oceans, Richter et al. pored over DNA from the Tara Oceans expedition. This revealed that, despite being unable to resist the flow of water, various planktonic species which live close to the surface manage to occupy distinct, stable provinces shaped by currents. Different sizes of plankton are distributed in different sized provinces, with the smallest organisms tending to inhabit the smallest areas. Comparing DNA similarities and speeds of currents at the ocean surface revealed how these might stretch and mix plankton communities.

Plankton play a critical role in the health of the ocean and the chemical cycles of planet Earth. These results could allow deeper investigation by marine modellers, ecologists, and evolutionary biologists. Meanwhile, work is already underway to investigate how climate change might impact this hidden geography.

Functional repertoire convergence of distantly related eukaryotic plankton lineages abundant in the sunlit ocean

Marine planktonic eukaryotes play critical roles in global biogeochemical cycles and climate. However, their poor representation in culture collections limits our understanding of the evolutionary history and genomic underpinnings of planktonic ecosystems. Here, we used 280 billion Tara Oceans metagenomic reads from polar, temperate, and tropical sunlit oceans to reconstruct and manually curate more than 700 abundant and widespread eukaryotic environmental genomes ranging from 10 Mbp to 1.3 Gbp. This genomic resource covers a wide range of poorly characterized eukaryotic lineages that complement long-standing contributions from culture collections while better representing plankton in the upper layer of the oceans. We performed the first, to our knowledge, comprehensive genome-wide functional classification of abundant unicellular eukaryotic plankton, revealing four major groups connecting distantly related lineages. Neither trophic modes of plankton nor its vertical evolutionary history could completely explain the functional repertoire convergence of major eukaryotic lineages that coexisted within oceanic currents for millions of years.

Universal and idiosyncratic characteristic lengths in bacterial genomes

In condensed matter physics, simplified descriptions are obtained by coarse-graining the features of a system at a certain characteristic length, defined as the typical length beyond which some properties are no longer correlated. From a physics standpoint, in vitro DNA has thus a characteristic length of 300 base pairs (bp), the Kuhn length of the molecule beyond which correlations in its orientations are typically lost. From a biology standpoint, in vivo DNA has a characteristic length of 1000 bp, the typical length of genes. Since bacteria live in very different physico-chemical conditions and since their genomes lack translational invariance, whether larger, universal characteristic lengths exist is a non-trivial question. Here, we examine this problem by leveraging the large number of fully sequenced genomes available in public databases. By analyzing GC content correlations and the evolutionary conservation of gene contexts (synteny) in hundreds of bacterial chromosomes, we conclude that a fundamental characteristic length around 10-20 kb can be defined. This characteristic length reflects elementary structures involved in the coordination of gene expression, which are present all along the genome of nearly all bacteria. Technically, reaching this conclusion required us to implement methods that are insensitive to the presence of large idiosyncratic genomic features, which may co-exist along these fundamental universal structures.

Diagnostic validity and triage concordance of a physiotherapist compared to physicians' diagnoses for common knee disorders

BACKGROUND

Emergence of more autonomous roles for physiotherapists warrants more evidence regarding their diagnostic capabilities. Therefore, we aimed to evaluate diagnostic and surgical triage concordance between a physiotherapist and expert physicians and to assess the diagnostic validity of the physiotherapist's musculoskeletal examination (ME) without imaging.

METHODS

This is a prospective diagnostic study where 179 consecutive participants consulting for any knee complaint were independently diagnosed and triaged by two evaluators: a physiotherapist and one expert physician (orthopaedic surgeons or sport medicine physicians). The physiotherapist completed only a ME, while the physicians also had access to imaging to make their diagnosis. Raw agreement proportions and Cohen's kappa (k) were calculated to assess inter-rater agreement. Sensitivity (Se) and specificity (Sp), as well as positive and negative likelihood ratios (LR+/-) were calculated to assess the validity of the ME compared to the physicians' composite diagnosis.

RESULTS

Primary knee diagnoses included anterior cruciate ligament injury (n = 8), meniscal injury (n = 36), patellofemoral pain (n = 45) and osteoarthritis (n = 79). Diagnostic inter-rater agreement between the physiotherapist and physicians was high (k = 0.89; 95% CI:0.83-0.94). Inter-rater agreement for triage recommendations of surgical candidates was good (k = 0.73; 95% CI:0.60-0.86). Se and Sp of the physiotherapist's ME ranged from 82.0 to 100.0% and 96.0 to 100.0% respectively and LR+/- ranged from 23.2 to 30.5 and from 0.03 to 0.09 respectively.

CONCLUSIONS

There was high diagnostic agreement and good triage concordance between the physiotherapist and physicians. The ME without imaging may be sufficient to diagnose or exclude common knee disorders for a large proportion of patients. Replication in a larger study will be required as well as further assessment of innovative multidisciplinary care trajectories to improve care of patients with common musculoskeletal disorders.

Efficacy of transcutaneous electrical nerve stimulation for rotator cuff tendinopathy: a systematic review

OBJECTIVE

To perform a systematic review on the efficacy of transcutaneous electrical nerve stimulation (TENS) for the treatment of rotator cuff tendinopathy in adults.

METHODS

A literature search was conducted in four databases (CINAHL, Embase, PubMed and PeDRO) for randomised controlled trials published from date of inception until April 2015, comparing the efficacy of TENS for the treatment of rotator cuff tendinopathy with placebo or any other intervention. Risk of bias was evaluated using the Cochrane risk of bias tool. Results were summarised qualitatively.

RESULTS

Six studies were included in this review. The mean methodological score was 49% (standard deviation 16%), indicating an overall high risk of bias. One placebo-controlled trial reported that a single TENS session provided immediate pain reduction for patients with rotator cuff tendinopathy, but did not follow the participants in the short, medium or long term. Two trials that compared ultrasound therapy with TENS reported discrepancy and contradictory results in terms of pain reduction and shoulder range of motion. Corticosteroid injections were found to be superior to TENS for pain reduction in the short term, but the differences were not clinically important. Other studies included in this review concluded that TENS was not superior to heat or pulsed radiofrequency.

CONCLUSION

Due to the limited number of studies and the overall high risk of bias of the studies included in this review, no conclusions can be drawn on the efficacy of TENS for the treatment of rotator cuff tendinopathy. More methodologically sound studies are needed to document the efficacy of TENS. Until then, clinicians should prefer other evidence-based rehabilitation interventions proven to be efficacious to treat patients with rotator cuff tendinopathy.

A systematic review of interventions promoting clinical information retrieval technology (CIRT) adoption by healthcare professionals

PURPOSE

This paper presents the evidence on the effectiveness of interventions promoting the use of clinical information retrieval technologies (CIRTs) by healthcare professionals.

METHODS

We electronically searched articles published between January 1990 and March 2008 using following inclusion criteria: (1) participants were healthcare professionals; (2) specific intervention promoted CIRT adoption; (3) studies were randomised controlled trials, controlled clinical trials, controlled before and after studies or interrupted time series analyses; and (4) they objectively reporting measured outcomes on CIRT use.

RESULTS

We found nine studies focusing on CIRT use. Main outcomes measured were searching skills and/or frequency of use of electronic databases by healthcare professionals. Three studies reported a positive effect of the intervention on CIRT use, one showed a positive impact post-intervention, and four studies failed to demonstrate significant intervention effect. The ninth study examined financial disincentives, and found a significant negative effect of introducing user fees for searching MEDLINE in clinical settings. A meta-analysis showed that educational meetings were the only type of interventions reporting consistent positive effects on CIRT adoption.

CONCLUSION

CIRT is an information and communication technology commonly used in healthcare settings. Interventions promoting CIRT adoption by healthcare professionals have shown some success in improving searching skills and use of electronic databases. However, the effectiveness of these interventions remains uncertain and more rigorous studies are needed.

[Evaluation of medical web sites. Interobserver and intraobserver reliability of an evaluation tool]

OBJECTIVE

To develop and test the reliability of a tool for rating websites that provide information on evidence-based medicine.

DESIGN

For each site, 60% of the score was given for content (eight criteria) and 40% was given for organization and presentation (nine criteria). Five of 10 randomly selected sites met the inclusion criteria and were used by three observers to test the accuracy of the tool. Each site was rated twice by each observer, with a 3-week interval between ratings.

SETTING

Laval University, Quebec city.

PARTICIPANTS

Three observers.

MAIN OUTCOME MEASURES

The intraclass correlation coefficient (ICC) was used to rate the reliability of the tool.

RESULTS

Average overall scores for the five sites were 40%, 79%, 83%, 88%, and 89%. All three observers rated the same two sites in fourth and fifth place and gave the top three ratings to the other three sites. The overall rating of the five sites by the three observers yielded an ICC of 0.93 to 0.97. An ICC of 0.87 was obtained for the two overall ratings conducted 3 weeks apart.

CONCLUSION

This new tool offers excellent intraobserver and interobserver measurement reliability and is an excellent means of distinguishing between medical websites of varying quality. For best results, we recommend that the tool be used simultaneously by two observers and that differences be resolved by consensus.

[Drug use in the elderly. Use of psychotropic drugs in the elderly: overuse or underuse?]

POORLY DEFINED USE: The first of three leading problems in the use of psychotropic drugs in elderly subjects is related to the overall situation of their use, often tainted by an ìideologicalî point of view. Prescribers are ìforî or ìagainstî psychotropic and justify their prescription by the need to take into account the general situation rather than strictly clinical arguments. Some prescriptions are written for the family or institutions. Even the definition of the elderly subject is extremely vague and is generally taken to include subjects over 65, a very heterogeneous group. Too few studies have been devoted to subjects over 80. NEED FOR GOOD CLINICAL ANALYSIS: The second type of problem is raised by the clinical expression of psychotic disorders in the elderly, too often considered to be limited to the classical signs of depression, dementia, and confusion. A careful clinical analysis is essential before prescription, with an adapted therapeutic response to each pathological situation. In addition, good clinical analysis would allow better diagnosis of depression, a condition largely underestimated and undertreated. BY THERAPEUTIC CLASS: It is now classical to denounce inappropriate use of neuroleptics and question their efficacy in controlling behavioral disorders in dementia. This attitude results from the impact of the adverse effects. Several authors have emphasized the contribution of new antipsychotic drugs but very few controlled studies have been reported. For antidepressors, the current consensus would suggest that prescription doses are generally insufficient and treatment durations too short. Finally, though it is widely accepted that use of benzodiazepines should be limited in dose and duration, data on drug use however show the contrary, emphasizing the difficulty in changing habits. New compounds including thymoregulators are increasingly used for elderly subjects but here again, like for antipsychotic drugs, too few studies have been published and many points remain to be elucidated.

Faculty evaluation in departments of family medicine: do our universities measure up?

Family medicine programmes at Canadian universities have expanded dramatically over the past several years. The development of effective means of faculty evaluation is a real concern for these departments as they strive to maintain the high quality of their teaching programmes in the face of rapid change. The literature on faculty evaluation, including reviews and articles discussing the application of faculty evaluations, is reviewed. The current state of faculty evaluation at three Canadian family medicine department has also been surveyed. Student evaluations were found to be valid, accurate and well studied. They are not perfect, however, and require the use of additional methods such as peer review or video review in conjunction in order to provide a comprehensive evaluation of all areas of faculty activity. Faculty evaluation in family medicine teaching units and community-based settings has not been well studied. Our survey of faculty evaluation at three Canadian universities shows much room for improvement, particularly in community-based settings where evaluation is almost non-existent. Expanding the use of faculty evaluations for formative means and linking evaluation to faculty development opportunities are essential if improvements to the currently used systems are to be successful and accepted by faculty. Special consideration must be given to community-based settings where systems designed for use in larger university settings will need to be modified substantially before they can be used effectively. Further research is required in this area.

Carbonic anhydrase in mouse skeletal muscle and its influence on contractility

Carbonic anhydrase III (EC 4.2.1.1) is the most abundant cytosolic protein in type I skeletal muscle fibers. Investigations of its physiological role have mostly been conducted with rat muscles, which sometimes are unsuitable for in vitro studies. The objective of the present study was to characterize the carbonic anhydrase in the mouse soleus muscle to verify if this muscle can be used as a model to further study the enzyme's function. Total carbonic anhydrase specific activity in the mouse soleus was comparable to the value for rat. However, 60% of the total carbonic anhydrase activity in the mouse was of the sulfonamide-sensitive type and, therefore, not related to carbonic anhydrase III. Electrophoretic analysis revealed the presence of a 29-kDa protein in total and cytosolic extracts of the mouse soleus. Immunoblotting with an antibody developed against rat carbonic anhydrase III showed that it was also specific for this 29-kDa peptide, which presumably is the mouse carbonic anhydrase III. Inhibition of the sulfonamide-sensitive activity had no effect on contractile and fatigue characteristics, whereas inhibition of the sulfonamide-resistant carbonic anhydrase III activity led to a significant increase in resistance to fatigue. We conclude that the mouse soleus may represent an excellent model to understand the contribution of different carbonic anhydrase isoforms to muscle physiology.

Effect of carbonic anhydrase III inhibition on substrate utilization and fatigue in rat soleus

Carbonic anhydrase III (CA III; EC 4.2.1.1) is the most abundant cytosolic enzyme in type I skeletal muscle fibers. We have previously shown that inhibiting the CA III activity of type I muscle can influence fatigability. Our goal was to test the hypothesis that the influence on fatigability of CA III inhibition is linked to an increased utilization of carbohydrates. Rat soleus muscles were incubated in vitro in a physiological solution with or without CA inhibitor (methazolamide, 1 mM) and submitted to a fatigue protocol. When the bathing solution contained glucose, the muscles incubated with methazolamide maintained a higher level of tension production than control muscles for the first 55-60 min of the test compared with 35-40 min when glucose was not added. Measurement of muscle glycogen content revealed that muscles incubated with CA inhibitor were utilizing their glycogen at a higher rate than control muscles over the first 45 min of the fatigue protocol. When glycolysis was inhibited with sodium iodoacetate, fatigability was not influenced by the addition of a CA inhibitor. These results further support the existence of a link between CA III activity and energy metabolism in type I skeletal muscle fibers.

Differential modulation of carbonic anhydrase (CA III) in slow- and fast-twitch skeletal muscles of rat following denervation and reinnervation

Carbonic anhydrase III (CA III) is influenced by neuronal factors in skeletal muscles of the rat. CA III protein and its mRNA levels were assessed in slow- and fast-twitch muscles after short-term denervation by ligature of the sciatic nerve and reinnervation following removal of the sheath tightly fixed around the nerve. Significant elevations in the CA III mRNA content of fast-twitch muscles were recorded after denervation, but they were cancelled following spontaneous muscle reinnervation. No such variations were observed in the slow-twitch soleus muscle. CA III specific activity or cytosolic CA III protein content increased in both types of muscles after denervation, while a decrease was solely observed in the soleus after reinnervation. These results suggest that neuronal mediators may be responsible for up and down variations in CA III gene expression and (or) mRNA stability in slow- and fast-twitch muscles exposed to identical stimuli. Variations of the mRNA and the protein probably reflect, in a time-related manner, the well-programmed changes in fiber type of the muscles in the context of the denervation-reinnervation model.

Fatigue and recovery of rat soleus muscle are influenced by inhibition of an intracellular carbonic anhydrase isoform

Carbonic anhydrase III (CA III; EC 4.2.1.1) is the most abundant cytosolic enzyme in type I skeletal muscle fibers. Methazolamide, a specific CA inhibitor, was used to characterize the effects of inhibiting CA III on the resistance to fatigue and recovery of the rat soleus muscle using a 60-min fatigue protocol performed in vitro at 25 degrees C. Incubation with 10(-3) M methazolamide resulted in a smaller decrease in tension production during the fatigue protocol, thereby increasing the total tension-time integral for the fatigue test. However, the rate and extent of recovery after the test were lower in the experimental group compared with the control group. A similar effect was observed at physiological temperature (35 degrees C). The results indicate that inhibition of CA III significantly influences tension production as early as 30 s into the stimulation protocol. Inhibition of CA III only during the recovery period did not influence the recovery profile, thereby indicating that the impaired recovery was related to the presence of methazolamide during the stimulation period.

Inhibition of carbonic anhydrases in type I muscle fibers influences contractility

We tested the effects of inhibiting the carbonic anhydrase activity of rat soleus and extensor digitorum longus muscles on the isometric contractile properties and the resistance to fatigue. SOL and EDL muscles from female rats were incubated in vitro in the presence of methazolamide, a specific inhibitor of carbonic anhydrase, before determining their contractile properties. Methazolamide had no effects on the contractile properties of the soleus muscle (10(-5) or 10(-3) M) and extensor digitorum longus (10(-3) M), except for the half-relaxation time of the soleus muscle which increased significantly. Values for half-relaxation time were significantly increased with both concentrations of the inhibitor. Muscles were then submitted to a fatigue protocol lasting 30 min. During the fatigue test, no significant difference was observed between control and 10(-5) M methazolamide soleus muscles. In presence of 10(-3) M methazolamide however, the soleus muscle showed a significantly increased resistance to fatigue compared with control preparations. No significant effect was observed with the extensor digitorum longus muscle exposed to 10(-3) M methazolamide. Results are discussed in terms of the presence of two different isoforms of carbonic anhydrase that may be associated with calcium uptake and energy metabolic processes, respectively.

Acetazolamide-sensitive and resistant carbonic anhydrase activity in rat and rabbit skeletal muscles of different fiber type composition

1. Acetazolamide (ACET)-resistant and -sensitive carbonic anhydrase (CA) activity was measured in post-mitochondrial supernatants from the soleus (SOL), deep vastus lateralis (DVL) and superficial vastus lateralis (SVL) muscles of rats and rabbits. 2. The relative total CA activity in the three muscles of both species can be summarized as SOL greater than DVL greater than SVL. 3. ACET-resistant CA activity was found in the SOL and DVL muscles of both species whereas a low level of ACET-sensitive CA activity was detected in the SVL muscle. 4. ACET-sensitive CA activity was also found in sarcoplasmic reticulum preparations from rat and rabbit SOL muscles.

Carbonic anhydrase III in skeletal muscle fibers: an immunocytochemical and biochemical study

The objectives of the present study were to determine if carbonic anhydrase III (CA III) demonstrated a specific association for any particular organelle or structure of the skeletal muscle cell and to quantify the activity and content of this enzyme in different types of skeletal muscle fibers. Ultrastructural localization of CA III in the soleus (SOL), deep vastus lateralis (DVL), and superficial vastus lateralis (SVL), composed of predominantly type I, IIa, and IIb fibers, respectively, was performed using a high-resolution immunocytochemical technique and antibody specific for CA III on ultra-thin sections of skeletal muscle embedded in the water-soluble medium polyvinyl alcohol (PVA). The results indicated a uniform distribution of CA III within the sarcomere. Mitochondria, nuclei, triads, Z-, and M-bands were not specifically labeled. Immunoblotting of washed myofibril preparations did not show any detectable CA III associated with this structure. In addition to quantification of the immunogold labeling, CA III activity and content were assayed in the post-mitochondrial supernatant of the three muscles. In the SOL, these values were found to be 3.6-7.6 times higher than in the DVL. The SVL showed a labeling intensity slightly higher than background level, while the enzyme activity and content were indistinguishable from background levels. We therefore conclude that CA III is randomly distributed in the cytoplasm of the three muscle fiber types and that the relative CA III content and activity in the three muscles studied is SOL greater than DVL greater than SVL approximately equal to 0.

Regulation of carbonic anhydrase III by thyroid hormone: opposite modulation in slow- and fast-twitch skeletal muscle

This laboratory previously reported that a major 30 kilodalton (kDa) protein of the soluble cytoplasmic fraction of the rat slow-twitch soleus muscle is modulated by thyroid hormone. This protein has been purified and a portion of the primary structure has been determined. The sequence analysis suggested that the 30-kDa protein is carbonic anhydrase III (CA III; EC 4.2.1.1). The reaction of the protein with a CA III specific antibody and the similar modulation of CA III by thyroid hormone also support this conclusion. Immunochemical quantification of CA III and measurement of CA activity were performed in skeletal muscles of defined fiber-type composition from rats that were rendered hyperthyroid by treatment with 3,3',5-triiodo-L-thyronine. These experiments revealed that CA activity and CA III content are deinduced in the soleus muscle (primarily type I fibers) and induced in the superficial vastus lateralis muscle (primarily type IIb), whereas no changes were detected in the tibialis anterior muscle (primary type IIa). These results show that the modulation of CA III by thyroid hormone in rat skeletal muscle is not limited to the slow-twitch soleus muscle and that the amplitude and direction of this modulation are directly related to the initial fiber-type composition of the skeletal muscle.

Recovery of biologically functional messenger RNA from agarose gels by passive elution

A general method for isolating biologically active messenger RNA (mRNA) from agarose gels is reported. Purified cellular RNA is resolved by preparative agarose gel electrophoresis and recovered in high yields (80%) by passive diffusion. Polyadenylated mRNA isolated from the eluted RNA is functionally intact based on the ability of the RNA to serve as a template in cell-free translation systems and complementary DNA synthesis reactions. The entire procedure is simple and rapid. A substantial purification of the mRNAs coding for skeletal muscle myosin heavy chain, light chain subunits and carbonic anhydrase III has been achieved employing this method.